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Editors-in-Chief Professor Alan R. Katritzky, FRS University of Florida, Gainesville, FL, USA
Professor Richard J. K. Taylor University of York, York, UK
Editors-in-Chief Alan Katritzky, educated at Oxford, held faculty positions at Cambridge and East Anglia before migrating in 1980 to the University of Florida, where he is Kenan Professor and Director of the Center for Heterocyclic Compounds. He has trained some 800 graduate students and postdocs, and lectured and consulted worldwide. He led the team which produced Comprehensive Heterocyclic Chemistry and its sequel CHECII, has edited Advances in Heterocyclic Chemistry, Vols. 1 through 86 and conceived the plan for Comprehensive Organic Functional Group Transformations. He founded Arkat-USA, a nonprofit organization which publishes Archive for Organic Chemistry (ARKIVOC) electronic journal completely free to authors and readers at (www.arkat-usa.org). Honors include 11 honorary doctorates from eight countries and membership or foreign membership of the National Academies of Britain, Catalonia, India, Poland, Russia, and Slovenia.
Richard Taylor is currently Professor of Organic Chemistry at the University of York, where his research focuses on the development of novel synthetic methodology and the synthesis of natural products and related compounds of biological/medicinal interest. The methodology is concentrated primarily on organometallic, organosulfur, and oxidation processes, and the targets include amino acids, carbohydrates, prostaglandins, and polyene and polyoxygenated natural products, particularly with activity as antibiotics and anti-cancer agents. Richard Taylor is a graduate and postgraduate of the University of Sheffield. After his studies at Sheffield, he carried out postdoctoral research at Syntex, California (Dr. I. T. Harrison) and University College London (Professor F. Sondheimer). His first academic appointment was at the Open University in Milton Keynes. This post gave Professor Taylor the opportunity to contribute to Open University textbooks, radio programs and television productions on various aspects of organic chemistry. Professor Taylor then moved to UEA, Norwich, where he established his independent research program, before taking up his present position in York in 1993. Richard Taylor has just finished his term as President of the Organic Division of the Royal Society of Chemistry and was awarded the 1999 RSC Tilden Lectureship and the 1999 RSC Heterocyclic Prize. He is currently the UK Regional Editor of the international journal Tetrahedron.
Volume Editors EDITOR OF VOLUME 1 Janine Cossy did her undergraduate and graduate studies at the University of Reims. After a postdoctoral stay with Barry Trost, for two years (1980–1982) at the University of Wisconsin, she returned to Reims, where she became a Director of Research of the CNRS in 1990. In the same year she moved to Paris to become Professor of Organic Chemistry at the ESPCI (Ecole Supe´rieure de Physique et de Chimie Industrielles de la Ville de Paris). She is interested in synthetic methodologies (radicals, organometallics, photochemistry, thermal reactions, ring expansions, enantioselectivity, synthesis of heterocycles, synthesis of solid support) and in their applications to the synthesis of natural products and biologically active molecules.
EDITOR OF VOLUME 2 Chris Ramsden was born in Manchester, UK in 1946. He is a graduate of Sheffield University and received his Ph.D. (W. D. Ollis) in 1970 and D.Sc. in 1990. After postdoctoral work at the University of Texas (M. J. S. Dewar)(1971–1973) and University of East Anglia (A. R. Katritzky)(1973–1976), he worked in the pharmaceutical industry. He moved to Keele University as Professor of Organic Chemistry in 1992. His research interests are heterocycles and three-center bonds and applications of their chemistry to biological problems.
EDITOR OF VOLUME 3 Keith Jones was born in Manchester. He studied at Cambridge University for his B.A. in Natural Sciences (1976) and stayed to carry out research with Professor Sir Alan Battersby obtaining his Ph.D. in 1979. In 1979, he moved to a lectureship at King’s College London. In 1984, he caught up with his postdoctoral research by spending a year working with Professor Gilbert Stork at Columbia University, New York. After returning to King’s College, he became a reader in 1995. In 1998, he moved to a chair in organic and medicinal chemistry at Kingston University. His research interests cover natural product synthesis, heterocyclic chemistry and the use of radicals in synthesis. He has been a visiting professor at Neuchatel and Barcelona Universities as well as the Australian National University.
EDITOR OF VOLUME 4 Professor Gary Molander was born in Cedar Rapids, Iowa. He received his B.S. degree at Iowa State University and subsequently entered the graduate chemistry program at Purdue University in 1975, obtaining his Ph.D. degree in 1979 under the direction of Professor Herbert C. Brown. He joined Professor Barry Trost’s group at the University of Wisconsin, Madison 1980 as a postdoctoral research associate, and in 1981 he accepted an appointment at the University of Colorado, Boulder, as an Assistant Professor of chemistry, where he rose through the academic ranks. In 1999 he joined the faculty at the University of Pennsylvania, and in 2001 was appointed Allan Day Professor of Chemistry. Professor Molander’s research interests focus on the development of new synthetic methods for organic synthesis and natural product synthesis. A major focus of his research has been the application of organolanthanide reagents and catalysts to selective organic synthesis.
EDITOR OF VOLUME 5 Ray Jones started his chemistry career as an undergraduate and then completing a Ph.D. at Cambridge University under the supervision of Professor Sir Alan Battersby, in the area of alkaloid biosynthesis. After a year as an ICI Postdoctoral Fellow in the laboratories of Professor Albert Eschenmoser at the ETH Zurich, he was appointed as Lecturer in Organic Chemistry at University of Nottingham in 1974. He progressed to Senior Lecturer at Nottingham and then took up the Chair of Organic Chemistry at the Open University in 1995, before moving to the Chair of Organic and Biological Chemistry at Loughborough University in 2000. His research interests span heterocyclic and natural product chemistry, with over 100 publications. Example topics include the acyltetramic acids and pyridones, Mammea coumarins, spermine and spermidine alkaloids, imidazolines as templates for (asymmetric) synthesis, dipolar cycloadditions, and unusual amino acids and peptide mimetics.
EDITOR OF VOLUME 6 Eric F. V. Scriven is a native of Wales, UK. After working at BISRA and ESSO Ltd, he attended the University of Salford and graduated in 1965. He obtained his M.Sc. from the University of Guelph, and his Ph.D. from the University of East Anglia (with Professor A. R. Katritzky) in 1969. After postdoctoral years at the University of Alabama and University College London, he was appointed Lecturer in organic chemistry at the University of Salford. There, his research interests centered on the reactivity of azides and nitrenes. While at Salford, he spent two semesters on secondment at the University of Benin in Nigeria. He joined Reilly Industries Inc. in 1979 and was director of Research from 1991 to 2003. He is currently at the University of Florida. He edited Azides & Nitrenes (1984), and he and Professor H. Suschitzky were founding editors of Progress in Heterocyclic Chemistry, which has been published annually since 1989 by the International Society of Heterocyclic Chemistry. He also collaborated with Professors A. R. Katritzky and C. W. Rees as Editors-in-Chief of Comprehensive Heterocyclic Chemistry II (1997). His current research interests are in novel nitration reactions, ionic liquids, and applications of polymers in organic synthesis.
Preface Comprehensive Organic Functional Group Transformations (COFGT 1995) presented the vast subject of organic synthesis in terms of the introduction and interconversion of functional groups, according to a rigorous system, designed to cover all known and as yet unknown functional groups. Comprehensive Organic Functional Group Transformations II (COFGT-II), designed for specialist and nonspecialist chemists, active in academic, industrial, and government laboratories, now updates the developments of functional group transformations since the publication of the COFGT 1995. COFGT-II is structured in precisely the same manner as the original COFGT work, allowing truly comprehensive coverage of all organic functional group transformations. COFGT-II, in combination with COFGT 1995, provides an essential reference source for the all-important topic of methodologies for the interconversion of functional groups in organic compounds, and provides an efficient first point of entry into the key literature and background material for those planning any research involving the synthesis of new organic compounds. With the increase in our understanding of the way in which the chemical structure of compounds determines all physical, chemical, biological, and technological properties, targeted synthesis becomes ever more important. The making of compounds is germane not only to organic chemistry but also to future developments in all biological, medical, and materials sciences. The availability of the work in electronic format through ScienceDirect will greatly enhance its utility. The Editors-in-Chief would like to extend their warm thanks to the Volume Editors, the chapter authors, and the Elsevier staff for operating in such an efficient and professional manner. A. R. Katritzky R. J. K. Taylor
Introduction to Volume 6 Volume 6 is in four parts. Part I deals with tetracoordinate carbons bearing three heteroatoms. Part II covers tetracoordinate compounds bearing four heteroatoms, i.e., substituted methanes, and Part III deals with tricoordinate systems bearing three heteroatoms, i.e., where one heteroatom is attached to a double bond. Part IV is brief and deals with stabilized radicals, carbocations, and carbanions. Volume 6 covers a very broad area of chemistry and, even at the time of writing this second edition, many gaps in the development of organic chemistry still exist. The organization within the three parts not only follows the same broad logic developed in the previous volumes, but also has a structure unique to the multiheteroatom volume. According to the Latest Placement Principle, CF3C(NR2)3 appears in the chapter dealing with the carbons bearing three nitrogens (Chapter 6.5), not that dealing with carbons bearing three halogens (Chapter 6.1), while (CF3CH2O)2CO appears in Part III, not in Part I. In the chapter dealing with the iminocarbonyl function in Part III, the substituents on nitrogen are discussed in each appropriate subsection in the order outlined above.Thus, the RN = group would be first considered with R = H, then alkyl, alkenyl, aryl and hetaryl, alkynyl, and then heteroatom substituents in the usual order. Each chapter is divided into sections and subsections which follow the same numbering system that was used for the first edition. Where no significant new work has appeared in a specific area since the publication the first edition of Comprehensive Organic Functional Group Transformations in 1995, this is stated. This should allow readers to judge readily the scope and intensity of work outside their immediate area of expertise. Many growth areas are discussed, for example, the increase in the number and variety of methods for the introduction of a trifluoromethyl group into aromatic and aliphatic molecules (Chapter 6.1). Another instance is a metathesis reaction that involves the reaction of a metal or metalloid halide with a trimethyllithiomethane derivative such as (Me3Si)3CLi that promises general application for the synthesis of methanes that bear up to four metal or metalloid functions, many examples of which have yet to be made (Chapter 6.13). E. F. V. Scriven Florida, USA
Explanation of the reference system Throughout this work, references are designated by a number-lettering coding of which the first four numbers denote the year of publication, the next one to three letters denote the journal, and the final numbers denote the page. This code appears in the text each time a reference is quoted. This system has been used successfully in previous publications and enables the reader to go directly to the literature reference cited, without first having to consult the bibliography at the end of each chapter. The following additional notes apply: 1. A list of journal codes in alphabetical order, together with the journals to which they refer is given immediately following these notes. Journal names are abbreviated throughout using the CASSI ‘‘Chemical Abstracts Service Source Index’’ system. 2. The references cited in each chapter are given at the end of the individual chapters. 3. The list of references is arranged in order of (a) year, (b) journal in alphabetical order of journal code, (c) part letter or number if relevant, (d) volume number if relevant, and (e) page number. 4. In the reference list the code is followed by (a) the complete literature citation in the conventional manner and (b) the number(s) of the page(s) on which the reference appears, whether in the text or in tables, schemes, etc. 5. For non-twentieth-century references, the year is given in full in the code. 6. For journals which are published in separate parts, the part letter or number is given (when necessary) in parentheses immediately after the journal code letters. 7. Journal volume numbers are not included in the code numbers unless more than one volume was published in the year in question, in which case the volume number is included in parentheses immediately after the journal code letters. 8. Patents are assigned appropriate three-letter codes. 9. Frequently cited books are assigned codes. 10. Less common journals and books are given the code ‘‘MI’’ for miscellaneous with the whole code for books prefixed by the letter ‘‘B-’’. 11. Where journals have changed names, the same code is used throughout, e.g., CB refers to both Chem. Ber. and to Ber. Dtsch. Chem. Ges.
JOURNAL ABBREVIATIONS AAC ABC AC ACA AC(P) AC(R) ACH ACR ACS ACS(A) ACS(B) AF AFC AG AG(E) AHC AHCS AI AJC AK AKZ AM AMLS AMS ANC ANL ANY AOC AP APO APOC APS AQ AR AR(A) AR(B) ARP ASI ASIN AX AX(A) AX(B) B BAP BAU BBA BBR BCJ BEP BJ BJP BMC BMCL BOC BP BPJ BRP BSB BSF BSF(2) BSM C CA CAN CAR CAT CB CBR CC CCA CCC CCHT CCR CE CEJ CEN CHE CHECI CHECII CHIR CI(L) CI(M) CJC CJS CL
Antimicrob. Agents Chemother. Agric. Biol. Chem. Appl. Catal. Aldrichim. Acta Ann. Chim. (Paris) Ann. Chim. (Rome) Acta Chim. Acad. Sci. Hung. Acc. Chem. Res. Acta Chem. Scand. Acta Chem. Scand., Ser. A Acta Chem. Scand., Ser. B Arzneim.-Forsch. Adv. Fluorine Chem. Angew. Chem. Angew. Chem., Int. Ed. Engl. Adv. Heterocycl. Chem. Adv. Heterocycl. Chem. Supplement Anal. Instrum. Aust. J. Chem. Ark. Kemi Arm. Khim. Zh. Adv. Mater. (Weinheim, Ger.) Adv. Mol. Spectrosc. Adv. Mass Spectrom. Anal. Chem. Acad. Naz. Lincei Ann. N. Y. Acad. Sci. Adv. Organomet. Chem. Arch. Pharm. (Weinheim, Ger.) Adv. Phys. Org. Chem. Appl. Organomet. Chem. Adv. Polym. Sci. An. Quim. Annu. Rep. Prog. Chem. Annu. Rep. Prog. Chem., Sect. A Annu. Rep. Prog. Chem., Sect. B Annu. Rev. Phys. Chem. Acta Chim. Sin. Engl. Ed. Acta Chim. Sin. Acta Crystallogr. Acta Crystallogr., Part A Acta Crystallogr., Part B Biochemistry Bull. Acad. Pol. Sci., Ser. Sci. Chim. Bull. Acad. Sci. USSR, Div. Chem. Sci. Biochim. Biophys. Acta Biochem. Biophys. Res. Commun. Bull. Chem. Soc. Jpn. Belg. Pat. Biochem. J. Br. J. Pharmacol. Biorg. Med. Chem. Biorg. Med. Chem. Lett. Bioorg. Chem. Biochem. Biopharmacol. Br. Polym. J. Br. Pat. Bull. Soc. Chim. Belg. Bull. Soc. Chim. Fr. Bull. Soc. Chim. Fr., Part 2 Best Synthetic Methods Chimia Chem. Abstr. Cancer Carbohydr. Res. Chim. Acta Turc. Chem. Ber. Chem. Br. J. Chem. Soc., Chem. Commun. Croat. Chem. Acta Collect. Czech. Chem. Commun. Comb. Chem. High T. Scr. Coord. Chem. Rev. Chem. Express Chem. -Eur. J. Chem. Eng. News Chem. Heterocycl. Compd. (Engl. Transl.) Comp. Heterocycl. Chem., 1st edn. Comp. Heterocycl. Chem., 2nd edn. Chirality Chem. Ind. (London) Chem. Ind. (Milan) Can. J. Chem. Canadian J. Spectrosc. Chem. Lett.
CLY CM CMC COC COFGT COMCI CONAP COS CP CPB CPH CPL CR CR(A) CR(B) CR(C) CRAC CRV CS CSC CSR CT CUOC CZ CZP DIS DIS(B) DOK DOKC DP E EC EF EGP EJI EJM EJO EUP FCF FCR FES FOR FRP G GAK GC GEP GSM H HAC HC HCA HCO HOU HP IC ICA IEC IJ IJC IJC(A) IJC(B) IJM IJQ IJS IJS(A) IJS(B) IS IZV JA JAN JAP JAP(K) JBC JC JCA JCC JCO JCE JCED JCI JCP JCPB JCR(M) JCR(S)
Chem. Listy Chem. Mater. Comp. Med. Chem. Comp. Org. Chem. Comp. Org. Func. Group Transformations Comp. Organomet. Chem., 1st edn. Comp. Natural Products Chem. Comp. Org. Synth. Can. Pat. Chem. Pharm. Bull. Chem. Phys. Chem. Phys. Lett. C.R. Hebd. Seances Acad. Sci. C.R. Hebd. Seances Acad. Sci., Ser. A C.R. Hebd. Seances Acad. Sci., Ser. B C.R. Hebd. Seances Acad. Sci., Ser. C. Crit. Rev. Anal. Chem. Chem. Rev. Chem. Scr. Cryst. Struct. Commun. Chem. Soc. Rev. Chem. Tech. Curr. Org. Chem. Chem.-Ztg. Czech. Pat. Diss. Abstr. Diss. Abstr. Int. B Dokl. Akad. Nauk SSSR Dokl. Chem. (Engl. Transl.) Dyes Pigm. Experientia Educ. Chem. Energy Fuels Ger. (East) Pat. Eur. J. Inorg. Chem. Eur. J. Med. Chem. Eur. J. Org. Chem. Eur. Pat. Fortschr. Chem. Forsch. Fluorine Chem. Rev. Farmaco Ed. Sci. Fortschr. Chem. Org. Naturst. Fr. Pat. Gazz. Chim. Ital. Gummi Asbest Kunstst. Green Chem. Ger. Pat. Gen. Synth. Methods Heterocycles Heteroatom Chem. Chem. Heterocycl. Compd. [Weissberger-Taylor series] Helv. Chim. Acta Heterocycl. Commun. Methoden Org. Chem. (Houben-Weyl) Hydrocarbon Process Inorg. Chem. Inorg. Chim. Acta Ind. Eng. Chem. Res. Isr. J. Chem. Indian J. Chem. Indian J. Chem., Sect. A Indian J. Chem., Sect. B Int. J. Mass Spectrom. Ion Phys. Int. J. Quantum Chem. Int. J. Sulfur Chem. Int. J. Sulfur Chem., Part A Int. J. Sulfur Chem., Part B Inorg. Synth. Izv. Akad. Nauk SSSR, Ser. Khim. J. Am. Chem. Soc. J. Antibiot. Jpn. Pat. Jpn. Kokai J. Biol. Chem. J. Chromatogr. J. Catal. J. Coord. Chem. J. Comb. Chem. J. Chem. Ed. J. Chem. Eng. Data J. Chem. Inf. Comput. Sci. J. Chem. Phys. J. Chim. Phys. Physico-Chim. Biol. J. Chem. Res. (M) J. Chem. Res. (S)
JCS JCS(A) JCS(B) JCS(C) JCS(D) JCS(F1) JCS(F2) JCS(P1) JCS(P2) JCS(S2) JEC JEM JES JFA JFC JGU JHC JIC JINC JLC JMAC JMAS JMC JMOC JMR JMS JNP JOC JOM JOU JPC JPJ JPO JPP JPR JPS JPS(A) JPU JSC JSP JST K KFZ KGS KO KPS L LA LC LS M MC MCLC MI MIP MM MP MRC MS N NAT NEP NJC NJC NKK NKZ NMR NN NZJ OBC OCS OL OM OMR OMS OPP OPRD OR OS OSC P PA PAC PAS
J. Chem. Soc. J. Chem. Soc. (A) J. Chem. Soc. (B) J. Chem. Soc. (C) J. Chem. Soc., Dalton Trans. J. Chem. Soc., Faraday Trans. 1 J. Chem. Soc., Faraday Trans. 2 J. Chem. Soc., Perkin Trans. 1 J. Chem. Soc., Perkin Trans. 2 J. Chem. Soc., (Suppl. 2) J. Electroanal. Chem. Interfacial Electrochem. J. Energ. Mater. J. Electron Spectrosc. J. Sci. Food Agri. J. Fluorine Chem. J. Gen. Chem. USSR (Engl. Transl.) J. Heterocycl. Chem. J. Indian Chem. Soc. J. Inorg. Nucl. Chem. J. Liq. Chromatogr. J. Mater. Chem. J. Mater. Sci. J. Med. Chem. J. Mol. Catal. J. Magn. Reson. J. Mol. Sci. J. Nat. Prod. J. Org. Chem. J. Organomet. Chem. J. Org. Chem. USSR (Engl. Transl.) J. Phys. Chem. J. Pharm. Soc. Jpn. J. Phys. Org. Chem. J. Pharm. Pharmacol. J. Prakt. Chem. J. Pharm. Sci. J. Polym. Sci., Polym. Chem., Part A J. Phys. Chem. USSR (Engl. Transl.) J. Serbochem. Soc. J. Mol. Spectrosc. J. Mol. Struct. Kristallografiya Khim. Farm. Zh. Khim. Geterotsikl. Soedin. Kirk-Othmer Encyc. Khim. Prir. Soedin. Langmuir Liebigs Ann. Chem. Liq. Cryst. Life. Sci. Monatsh. Chem. Mendeleev Communications Mol. Cryst. Liq. Cryst. Miscellaneous [journal or B-yyyyMI for book] Miscellaneous Pat. Macromolecules Mol. Phys. Magn. Reson. Chem. Q. N. Porter and J. Baldas, ‘Mass Spectrometry of Heterocyclic Compounds’, Wiley, New York, 1971 Naturwissenschaften Nature Neth. Pat. Nouv. J. Chim. New J. Chem. Nippon Kagaku Kaishi (J. Chem. Soc. Jpn.) Nippon Kagaku Zasshi T. J. Batterham, ‘NMR Spectra of Simple Heterocycles’, Wiley, New York, 1973 Nucleosides & Nucleotides N. Z. J. Sci. Technol. Organic and Biomolecular Chemistry Organomet. Synth. Org. Lett. Organometallics Org. Magn. Reson. Org. Mass Spectrom. Org. Prep. Proced. lnt. Org. Process Res. Dev. Org. React. Org. Synth. Org. Synth., Coll. Vol. Phytochemistry Polym. Age Pure Appl. Chem. Pol. Acad. Sci.
PB PC PCS PH PHA PHC PIA PIA(A) PJC PJS PMH PNA POL PP PRS PS QR QRS QSAR RC RCB RCC RCM RCP RCR RHA RJ RJGC RJOC RP RRC RS RTC RZC S SA SA(A) SAP SC SCI SH SL SM SR SRC SRI SS SSR SST SUL SZP T T(S) TA TAL TCA TCC TCM TFS TH TL TS UK UKZ UP URP USP WOP YGK YZ ZAAC ZAK ZC ZN ZN(A) ZN(B) ZOB ZOR ZPC ZPK
Polym. Bull. Personal Communication Proc. Chem. Soc. ‘Photochemistry of Heterocyclic Compounds’, O. Buchardt, Ed.; Wiley, New York, 1976 Pharmazi Prog. Heterocycl. Chem. Proc. Indian Acad. Sci. Proc. Indian Acad. Sci., Sect. A Pol. J. Chem. Pak. J. Sci. Ind. Res. Phys. Methods Heterocycl. Chem. Proc. Natl. Acad. Sci. USA Polyhedron Polym. Prepr. Proceed. Roy. Soc. Phosphorus Sulfur (formerly); Phosphorus Sulfur Silicon (currently) Q. Rev., Chem. Soc. Quart. Rep. Sulfur Chem. Quant. Struct. Act. Relat. Rubber Chem. Technol. Russian Chemical Bull. Rodd’s Chemistry of Carbon Compounds Rapid Commun. Mass Spectrom. Rec. Chem. Prog. Russ. Chem. Rev. (Engl. Transl.) Rev. Heteroatom. Chem. Rubber J. Russ. J. Gen. Chem. (Engl. Transl.) Russ. J. Org. Chem. (Engl. Transl.) Rev. Polarogr. Rev. Roum. Chim. Ric. Sci. Recl. Trav. Chim. Pays-Bas Rocz. Chem. Synthesis Spectrochim. Acta Spectrochim. Acta, Part A S. Afr. Pat. Synth. Commun. Science W. L. F. Armarego, ‘Stereochemistry of Heterocyclic Compounds’, Wiley, New York, 1977, parts 1 and 2. Synlett Synth. Met. Sulfur Reports Supplements to Rodd’s Chemistry of Carbon Compounds Synth. React. Inorg. Metal-Org. Chem. Sch. Sci. Rev. Second Supplements to Rodd’s Chemistry of Carbon Compounds Org. Compd. Sulphur, Selenium, Tellurium [R. Soc. Chem. series] Sulfur Letters Swiss Pat. Tetrahedron Tetrahedron, Suppl. Tetrahedron Asymmetry Talanta Theor. Chim. Acta Top. Curr. Chem. Tetrahedron, Comp. Method Trans. Faraday Soc. Thesis Tetrahedron Lett. Top. Stereochem. Usp. Khim. Ukr. Khim. Zh. (Russ. Ed.) Unpublished Results USSR Pat. U.S. Pat. PCT Int. Appl. WO (World Intellectual Property Organization Pat. Appl.) Yuki Gosei Kagaku Kyokaishi Yakugaku Zasshi Z. Anorg. Allg. Chem. Zh. Anal. Khim. Z. Chem. Z. Naturforsch. Z. Naturforsch., Teil A Z. Naturforsch., Teil B Zh. Obshch. Khim. Zh. Org. Khim. Hoppe-Seyler’s Z. Physiol. Chem. Zh. Prikl. Khim.
List of Abbreviations TECHNIQUES/CONDITIONS 18-C-6 ))))) AAS AES AFM approx. aq. b.p. CD CIDNP CNDO conc. CT ee equiv. ESR EXAFS FVP g GC GLC h h HOMO HPLC h ICR INDO IR l LCAO LUMO MCD MD min MM MO MOCVD m.p. MS
18-crown-6 ultrasonic (sonochemistry) heat, reflux atomic absorption spectroscopy atomic emission spectroscopy atomic force microscopy approximately aqueous boiling point circular dichroism chemically induced dynamic nuclear polarization complete neglect of differential overlap concentrated charge transfer enantiomeric excess equivalent(s) electron spin resonance extended X-ray absorption fine structure flash vacuum pyrolysis gaseous gas chromatography gas–liquid chromatography Planck’s constant hour highest occupied molecular orbital high-performance liquid chromatography light (photochemistry) ion cyclotron resonance incomplete neglect of differential overlap infrared liquid linear combination of atomic orbitals lowest unoccupied molecular orbital magnetic circular dichroism molecular dynamics minute(s) molecular mechanics molecular orbital metal organic chemical vapor deposition melting point mass spectrometry
MW NMR NQR ORD PE ppm rt s SCF SET SN1 SN2 SNi STM TLC UV vol. wt.
molecular weight nuclear magnetic resonance nuclear quadrupole resonance optical rotatory dispersion photoelectron parts per million room temperature solid self-consistent field single electron transfer first-order nucleophilic substitution second-order nucleophilic substitution internal nucleophilic substitution scanning tunneling microscopy thin-layer chromatography ultraviolet volume weight
REAGENTS, SOLVENTS, ETC. Ac acac acam AcO AcOH AIBN Ans Ar ATP 9-BBN 9-BBN-H BEHP BHT binap bipy Bn t-BOC bpy BSA BSTFA Bt BTAF Bz Bzac CAN Cbz chalcogens CH2Cl2 COD COT Cp Cp* 18-crown-6 CSA CSI CTAB DABCO
acetyl CH3COacetylacetonato acetamide acetate acetic acid 2,20 -azobisisobutyronitrile ansyl aryl adenosine 50 -triphosphate 9-borabicyclo[3.3.1]nonyl 9-borabicyclo[3.3.1]nonane bis (2-ethylhexyl) phthalate 2,6-di-t-butyl-4-methylphenol (butyrated hydroxytoluene) 2,20 -bis(diphenylphosphino)-1,10 -binaphthyl 2,20 -bipyridyl benzyl C6H5CH2- (NB avoid confusion with Bz) t-butoxycarbonyl 2,20 -bipyridyl N,O-bis(trimethylsilyl)acetamide N,O-bis(trimethylsilyl)trifluoroacetamide benzotriazole benzyltrimethylammonium fluoride benzoyl C6H5CO- (NB avoid confusion with Bn) benzoylacetone ceric ammonium nitrate carbobenzoxy oxygen, sulfur, selenium, tellurium dichloromethane 1,5-cyclooctadiene cyclooctatetraene cyclopentadienyl pentamethylcyclopentadienyl 1,4,7,10,13,16-hexaoxacyclooctadecane camphorsulfonic acid chlorosulfonyl isocyanate cetyl trimethyl ammonium bromide 1,4-diazabicyclo[2.2.2]octane
DBA DBN DBU DCC DDQ DEAC DEAD DET DHP DIBAL-H diglyme dimsyl Na DIOP DIPT DMA DMAC DMAD DMAP DME DMF DMI DMN DMSO DMTSF DPPB DPPE DPPF DPPP Eþ EADC EDG EDTA EEDQ Et Et2O EtOH EtOAc EWG HMPA HMPT IpcBH2 Ipc2BH KAPA K-selectride LAH LDA LICA LITMP L-selectride LTA MAO MCPBA MCT Me MEM MEM-Cl MeOH MMA MMC MOM
dibenzylideneacetone 1,5-diazabicyclo[4.3.0]non-5-ene 1,5-diazabicyclo[5.4.0]undec-5-ene dicyclohexylcarbodiimide 2,3-dichloro-5,6-dicyano-1,4-benzoquinone diethylaluminum chloride diethyl azodicarboxylate diethyl tartrate (þ or ) dihydropyran diisobutylaluminum hydride diethylene glycol dimethyl ether sodium methylsulfinylmethide 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane diisopropyl tartrate (þ or ) dimethylacetamide dimethylaluminium chloride dimethyl acetylenedicarboxylate 4-dimethylaminopyridine dimethoxyethane dimethylformamide N,N0 -dimethylimidazolidinone diaminomaleonitrile dimethyl sulfoxide dimethyl(methylthio)sulfonium fluoroborate 1,2-bis(diphenylphosphino)butane 1,2-bis(diphenylphosphino)ethane 1,10 -bis(diphenylphosphino)ferrocene 1,2-bis(diphenylphosphino)propane electrophile ethylaluminium dichloride electron-donating group ethylenediaminetetraacetate N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline ethyl diethyl ether ethanol ethyl acetate electron-withdrawing group hexamethyl phosphoramide hexamethylphosphoric triamide isopinocampheylborane diisopinocampheylborane potassium 3-aminopropylamide potassium tri-s-butylborohydride lithium aluminium hydride lithium diisopropylamide lithium isopropyl cyclohexylamide lithium tetramethyl piperidide lithium tri-s-butyl borohydride lead tetraacetate monoamine oxidase 3-chloroperoxybenzoic acid mercury cadmium telluride methyl methoxyethoxymethyl methoxyethoxymethyl chloride methanol methyl methacrylate methylmagnesium carbonate methoxymethyl
Ms MSA MsCl MVK NBS NCS NMO NMP Nu PPA PCC PDC Ph phen Phth PPE PPO PPTS Pr Pyr Red-Al SDS SEM Sia2BH SM TAS TBAF TBDMS TBDMS-Cl TBDPS TBHP TCE TCNE TEA TES Tf TFA TFAA THF THP TIPBSCl TIPSCl TMEDA TMS TMSCl TMSCN Tol TosMIC TPP Tr Tris Ts TTFA TTMSS TTN X
methanesulfonyl (mesylate) methanesulfonic acid methanesulfonyl chloride methyl vinyl ketone N-bromosuccinimide N-chlorosuccinimide N-methylmorpholine N-oxide N-methyl-2-pyrrolidone nucleophile polyphosphoric acid pyridinium chlorochromate pyridinium dichromate phenyl 1,10-phenanthroline phthaloyl polyphosphate ester 2,5-diphenyloxazole pyridinium p-toluenesulfonate propyl pyridine sodium bis(methoxyethoxy)aluminum dihydride sodium dodecyl sulfate trimethylsilylethoxymethyl disiamylborane starting material tris(diethylamino)sulfonium tetra-n-butylammonium fluoride t-butyldimethylsilyl t-butyldimethylsilyl chloride t-butyldiphenylsilyl t-butyl hydroperoxide 2,2,2-trichloroethanol tetracyanoethylene tetraethylammonium triethylsilyl triflyl (trifluoromethanesulfonyl) trifluoroacetyl trifluoroacetic anhydride tetrahydrofuran tetrahydropyranyl 2,4,6-triisopropylbenzenesulfonyl chloride triisopropylsilyl chloride tetramethylethylenediamine [1,2-bis(dimethylamino)ethane] trimethylsilyl trimethylsilyl chloride trimethylsilyl cyanide tolyl C6H4(CH3)– tosylmethyl isocyanide meso-tetraphenylporphyrin trityl (triphenylmethyl) tris(hydroxymethyl)aminomethane 4-toluenesulfonyl (tosyl) thallium trifluroacetate tris(trimethylsilyl)silane thallium(III) nitrate halogen or leaving group
Volume 6: Synthesis: Carbon With Three or Four Attached Heteroatoms Part I: Tetracoordinated Carbon with Three Attached Heteroatoms RCX 1 X 2 X3 6.01 Trihalides, Pages 1-22, G. Sandford 6.02 Functions Containing Halogens and Any Other Elements, Pages 23-74, J. Suwi ński and K. Walczak 6.03 Functions Containing Three Chalcogens (and No Halogens), Pages 75-110, S. Rádl and S. Voltrová 6.04 Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen, Pages 111-159, A. M. Shestopalov 6.05 Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen), Pages 161-203, A. Güven 6.06 Functions Containing at Least One Metalloid (Si, Ge, or B) and No Halogen, Chalcogen, or Group 15 Elements; Also the Synthesis of Functions Containing Three Metals, Pages 205-242, V. D. Romanenko and V. L. Rudzevich Part II: Tetracoordinated Carbon with Four Attached Heteroatoms CX1 X 2 X 3 X4 6.07 Functions Containing Four Halogens or Three Halogens and One Other Heteroatom Substituent, Pages 243-269, A. Senning and J. Ø. Madsen 6.08 Functions Containing Two Halogens and Two Other Heteroatom Substituents, Pages 271-294, G. Varvounis and N. Karousis 6.09 Functions Containing One Halogen and Three Other Heteroatom Substituents, Pages 295-305, S. V. Yarlagadda and R. Murugan 6.10 Functions Containing Four or Three Chalcogens (and No Halogens), Pages 307-315, A. Senning and J. O. Madsen 6.11 Functions Containing Two or One Chalcogens (and No Halogens), Pages 317-353, W. Petz and F. Weller 6.12 Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen), Pages 355-379, S. Saba and J. A. Ciaccio 6.13 Functions Containing at Least One Metalloid (Si, Ge, or B) and No Halogen, Chalcogen, or Group 15 Element; Also Functions Containing Four Metals, Pages 381-408, P. D. Lickiss
Part III: Tricoordinated Carbon with Three Attached Heteroatoms Y=CX1 X 2 6.14 Functions Containing a Carbonyl Group and at Least One Halogen, Pages 409-427, R. Murugan and S. V. Yarlagadda 6.15 Functions Containing a Carbonyl Group and at Least One Chalcogen (but No Halogen), Pages 429-452, H. Eckert 6.16 Functions Containing a Carbonyl Group and Two Heteroatoms Other Than a Halogen or Chalcogen, Pages 453-493, O. V. Denisko 6.17 Functions Containing a Thiocarbonyl Group and at Least One Halogen; Also at Least One Chalcogen and No Halogen, Pages 495-544, E. Kleinpeter 6.18 Functions Containing a Thiocarbonyl Group Bearing Two Heteroatoms Other Than a Halogen or Chalcogen, Pages 545-572, J. Barluenga, E. Rubio and M. Tomás 6.19 Functions Containing a Selenocarbonyl or Tellurocarbonyl Group— SeC(X 1)X2 and TeC(X1)X2, Pages 573-594, L. J. Guziec and F. S. Guziec, Jr. 6.20 Functions Containing an Iminocarbonyl Group and at Least One Halogen; Also One Chalcogen and No Halogen, Pages 595-604, T. L. Gilchrist 6.21 Functions Containing an Iminocarbonyl Group and Any Elements Other Than a Halogen or Chalcogen, Pages 605-660, F. Sŕczewski ą 6.22 Functions Containing Doubly Bonded P, As, Sb, Bi, Si, Ge, B, or a Metal, Pages 661-711, V. D. Romanenko and V. L. Rudzevich 6.23 Tricoordinated Stabilized Cations, Anions, and Radicals, +CX1X2X3, - CX1X2X3, and CX1X2X3, Pages 713-727, M. Balasubramanian
.
6.01 Trihalides G. SANDFORD University of Durham, Durham, UK 6.01.1 GENERAL METHODS 6.01.1.1 The Addition of Halogens and Interhalogens to Fluoroalkenes 6.01.1.2 The Addition of Haloalkanes to Haloalkenes 6.01.1.2.1 Lewis acid-catalyzed addition of trihalomethyl cations to haloalkenes—the Prins reaction 6.01.1.2.2 Additions initiated by free radicals, heat, or radiation 6.01.1.2.3 Additions catalyzed by salts and complexes of transition metals 6.01.2 TRIFLUOROMETHYL DERIVATIVES, RCF3 6.01.2.1 General 6.01.2.2 Aryl Derivatives 6.01.2.2.1 Conversion of groups attached to an aromatic ring into the trifluoromethyl group 6.01.2.2.2 Substitution by trifluoromethyl radicals 6.01.2.2.3 Substitution of hydrogen by trifluoromethyl group acting as an electrophile 6.01.2.2.4 Substitution of halogens by trifluoromethyl group acting as a nucleophile 6.01.2.2.5 Substitution of halogen by trifluoromethyl group using derivatives of metals 6.01.2.3 Derivatives of Alkanes, Alkenes, Alkynes, and Other Unsaturated Compounds 6.01.2.3.1 Halogen exchange 6.01.2.3.2 Conversions of other groups to the trifluoromethyl group 6.01.2.3.3 Transfer of trifluoromethyl groups as radicals 6.01.2.3.4 Reactions involving trifluoromethyl derivatives of metals and metalloids 6.01.3 TRICHLOROMETHYL DERIVATIVES, RCCl3 6.01.3.1 Trichloromethyl Groups Attached to an Aliphatic Center 6.01.3.1.1 Conversion of groups attached to an aliphatic center into the trichloromethyl group 6.01.3.1.2 Transfer of the trichloromethyl group to an aliphatic center 6.01.3.2 Trichloromethyl Groups Attached to an Aromatic Ring 6.01.3.2.1 Conversion of groups attached to an aromatic ring into a trichloromethyl group 6.01.3.2.2 Transfer of trichloromethyl group to an aromatic ring 6.01.4 TRIBROMOMETHYL DERIVATIVES, RCBr3 6.01.5 MIXED SYSTEMS WITH FLUORINE, RCF2Hal AND RCFHal2 6.01.6 MIXED HALOFORMS, CHXY2 AND CHXYZ
6.01.1
1 2 2 2 2 4 5 5 5 5 6 6 7 7 8 8 9 10 11 16 16 16 16 17 17 17 17 18 18
GENERAL METHODS
There are several general methods that may be used for the synthesis of trihalomethyl compounds, and these were discussed in detail in COFGT (1995) <1995COFGT(6)1>. The experimental basis behind these established procedures remains valid; so in this chapter, a brief overview of addition reactions of halogens and haloalkenes to alkenes for the synthesis of systems bearing trihalomethyl groups is provided. Recent developments and further applications of these general processes are given where appropriate. 1
2 6.01.1.1
Trihalides The Addition of Halogens and Interhalogens to Fluoroalkenes
The addition of halogens and interhalogens to fluorinated alkenes is a well-established method for the synthesis of compounds bearing CHal3 groups and this area has recently been summarized <2000MI331, 2000MI234>. Many examples of such electrophilic addition processes, involving electrophilic halonium ion and nucleophilic fluoride ion, are given in COFGT (1995) and a few examples (Equations (1)–(3)) are shown below as an illustration <1978JFC(12)257, 1973ZOR673, 1961JCS3779>. CH2=CCl2
HF Hexachloromelamine 33%
CF2 CF CF3
Cl F, –10 °C 100%
CH2Cl CFCl2
CF3–CFCl–CF3
ð2Þ
CF3–CFI–CF3
ð3Þ
IF5, 2 I2
CF2 CF–CF3
ð1Þ
150 °C 99%
6.01.1.2
The Addition of Haloalkanes to Haloalkenes
The addition of haloalkanes to alkenes, catalyzed by either Lewis acids, free radical initiators, salts, and transition metal complexes, may be used for the synthesis of systems that bear trihalomethyl substituents, following the general scheme shown in Equation (4).
CY3–X +
6.01.1.2.1
CY3
X = Hal or H Y = Hal
X
ð4Þ
Lewis acid-catalyzed addition of trihalomethyl cations to haloalkenes—the Prins reaction
Trihalomethylation of alkenes by Lewis acid-catalyzed condensation with a tetrahalomethane, an adaptation of the Prins reaction, has been known for many years <1977FCR39>. Representative examples <1974CCC1330, 1971CCC1867> to illustrate these processes are shown below (Equations (5) and (6)), although this methodology has undergone limited recent development. F
H + CFCl3
F
F
F
0 °C, 7 h 65%
CF3
F CCl3
+
CF2Cl
CFCl2
ð5Þ
(70:30) F
F + CHFCl2
F
F
15 °C, 3 h 58%
F CF3
F
F
CHCl2
+
CF2Cl
F CHFCl
ð6Þ
(59:41)
6.01.1.2.2
Additions initiated by free radicals, heat, or radiation
Trihalomethyl radicals, generated by heat, peroxide, or UV initiation, react with alkenes to form an intermediate radical as shown below (Scheme 1). This radical may then react with further equivalent(s) of alkene to lead to oligomers and polymers or abstract a halogen atom from a molecule of the starting material to give a tetrahalogenated product.
3
Trihalides Initiation hν or heat
CY3 X or
RO–OR RO
CY3 +
X
2 RO
+ CY3 X
RO-X + CY3
+
Y3C
Propagation CY3 Chain transfer Y 3C
+ CY3–X
Y3C
X
Kharasch addition product
Oligomerization Y3C
n
+
Y 3C n
Termination + CY3–X
Y3C
Y3C
X
n
n
oligomers (n = 2–20) polymers (n = >20)
Scheme 1
The product distribution depends upon the relative rates of each of the stages outlined above. Generally, starting materials with weak carbonhalogen bonds (iodides) give predominantly lowmolecular-weight products, whilst systems with relatively strong carbonhalogen bonds give a higher proportion of oligomeric products. Furthermore, if the alkene is not easily polymerized under normal conditions (e.g., hexafluoropropene) the addition product is favored, while readily homopolymerized alkenes lead to polymeric systems. The addition of the halomethyl radicals is often regioselective due to a combination of steric and electronic factors <1982AG(E)401, 1996CRV1557, 1997TCC(192)97>. Since the initial report by Kharasch <1947JA1100> describing such radical chain addition processes, a substantial literature has developed <1963OR91, B-1992MI002, B-1986MI001>, detailing the syntheses of a great number of free-radical addition adducts, oligomers, and polymers all bearing trihalomethyl end groups. A selection of these processes is given below (Equations (7)–(11)) to illustrate some of the processes possible <1961JOC2089, 1955JA2783, 1953JCS1592, 1964JOC1198, 1981TL3405>.
OH + CF3I
F
+ CBr2F2
Cl
F
F
F
I
hν
F3C
50%
OH
Br
(PhCO)2O 100 °C 32%
+ CF3I
OEt + CBr2F2
F
Br F
F
hν 75%
hν 83%
F
F
I
F CF3
Cl
F F
Br
Br
ð7Þ
ð8Þ
ð9Þ
ð10Þ OEt
4
Trihalides
O
N + CF2BrCl
ð11Þ
CF2Cl
rt H2O 65%
The addition processes outlined above all lead to the formation of tetrahaloalkane systems in which trihalomethyl and halogen are added across a double bond. These reactions have, however, recently been adapted for the synthesis of trichloromethyl derivatives by the addition of an effective hydrogen atom donor (Equations (12) and (13)). Reaction of tetrachloromethane with alkenes in the presence of diethyl phosphite leads to good yields of trichloromethylated products because hydrogen is transferred to the intermediate radical, rather than halogen abstraction occurring <2001SL1719>. Cl (EtO)2P(O)H
+ CCl4
C6H13
(PhCO2)2
CCl3
C6H13
+
(55%)
OH
+ CCl4
(EtO)2P(O)H (PhCO2)2
CCl3
CCl3
C6H13
ð12Þ
(30%)
OH
+
CCl3
OH
ð13Þ
(44%)
(16%)
This methodology has been adapted to allow free-radical tandem trichloromethylation/cyclization processes (Equation (14)) which occur efficiently in the presence of diethyl phosphite <2001TL3137>.
CCl4, (EtO)2P(O)H
Cl3C
Cl
+
(PhCO2)2O Dioxane
N Tos
6.01.1.2.3
Cl3C N Tos
N Tos
(60%)
(4%)
ð14Þ
Additions catalyzed by salts and complexes of transition metals
The observation that thermally initiated addition processes involving reaction between carbon tetrachloride and acrylonitrile could be affected by the presence of metals or metal salts to give greater yields of the Kharasch addition product rather than oligomers prompted much research. Many different metals, metal salts, metal oxides, and transition metal complexes have been assessed for their effectiveness in such addition processes and are listed in COFGT (1995). Recently, Kharasch addition using ruthenium(II) complexes has been assessed <2000TL5347> and the process (Equation (15)) may be affected by changing the ligand on the ruthenium metal center <2000TL6071>. Cl O OMe
+ CCl4
RuCl(Cp*)(PPh3)2 40 °C
Cl3C
O
ð15Þ
OMe
Grubbs’ well-defined ruthenium catalyst, RuCl2(¼CHPh) (PR3)2 <1999JOC344>, and various diaminonickel (II) ‘‘pincer’’ complexes <1998ACR423> have also been used to promote both addition and polymerization reactions.
5
Trihalides 6.01.2
TRIFLUOROMETHYL DERIVATIVES, RCF3
6.01.2.1
General
The growing number of life science products that bear trifluoromethyl groups provides a continuing driving force for the development of effective methodology that enables both regio- and stereoselective introduction of trifluoromethyl groups into both aliphatic and aromatic systems. In more specific cases, the use of -trifluoromethyl ketones as potent enzyme inhibitors <2001MI755> and the synthesis of aliphatic cyclic systems that bear trifluoromethyl groups has been discussed <2000T3635>. In general, trifluoromethylating reagents which transfer trifluoromethyl groups directly onto a substrate by carboncarbon bond formation may be considered as either electrophilic (CF+ 3 ), radical (CF_3), or nucleophilic (CF3) trifluoromethylating systems. It is fair to say that in the 1990s many of the major developments in this area of synthetic chemistry have occurred in nucleophilic trifluoromethylation methodology, particularly in the use of Ruppert’s reagent, CF3SiMe3. This is reflected in the publication of major reviews detailing syntheses involving Ruppert’s reagent by Prakash <1997CRV757, 2001JFC(112)123> and Shreeve <2000T7613>, and more general nucleophilic trifluoromethylation by Langlois <2003S185>. Of course, functional group interconversion, resulting in the transformation of substituents, already located on a substrate, into a trifluoromethyl group upon reaction with a fluorinating reagent (carbonfluorine bond formation), is an alternative strategy.
6.01.2.2 6.01.2.2.1
Aryl Derivatives Conversion of groups attached to an aromatic ring into the trifluoromethyl group
Reaction of trichloromethyl and carboxylic acid groups with fluorinating agents, as discussed in COFGT (1995), continues to provide effective methodology for the synthesis of trifluoromethyl aromatic derivatives. Recent adaptations of this methodology are outlined below. Exchange of halogen for fluorine (Halex process) involving reaction of benzotrichloride derivatives with anhydrous hydrogen fluoride, antimony trifluoride, or hydrogen fluoride/antimony pentafluoride as fluorinating agents remains the most useful industrial process for the synthesis of aromatic trifluoromethyl derivatives. A one-step Friedel Crafts/Halex process is particularly efficient for the synthesis of various brominated <1981JFC(18)281> and acetanilide <2003TL1747> trifluoromethyl derivatives (Equations (16) and (17)). Br
CF3
CF3 Br
HF, CCl4
ð16Þ
+ Br
H
N
H
Ac
N
i. HF, CCl4 , SbF5 ii. HF.pyridine Cl
85%
Ac
ð17Þ CF3 Cl
There are now many examples of the transformation of carboxylic acid groups into trifluoromethyl groups using sulfur tetrafluoride, and this methodology continues to be used for the synthesis of poly trifluoromethyl aromatic systems <1997JFC(82)163> (Equation (18)). HO2C
CO2H CO2H
i. HF, SF4 ii. KOH 55%
F3C
CO2H CF3
ð18Þ
6 6.01.2.2.2
Trihalides Substitution by trifluoromethyl radicals
Electrophilic trifluoromethyl radicals, generated by electrolysis of potassium trifluoromethanesulfinate (Equation (19)) may be trapped by electron-rich aromatic systems <2002SL1697> (Equation (20)). –e–
CF3SO2
CF3SO2
–SO 2 OMe
OMe
CF3
CF3SO2K, DMF Et4NClO4 Electrolysis 32%
OMe
6.01.2.2.3
ð19Þ
CF3
ð20Þ OMe
Substitution of hydrogen by trifluoromethyl group acting as an electrophile
For electrophilic trifluoromethylating reagents, originally developed by Umemoto, the trifluoromethyl group is made highly susceptible toward nucleophilic attack by being attached to a very good leaving group, such as a sulfonium derivative (Equation (21)). +
Nuc
ð21Þ
Nuc CF3 + SR2
CF3 SR2
Intramolecular cyclization of trifluoromethyl sulfoxides provides efficient methodology for the synthesis of trifluoromethyl dibenzothiophenium salts (Equation (22)), which act as effective electrophilic trifluoromethylating reagents that are now commercially available but expensive <1998JFC(92)181, 1999JFC(98)75>.
60% SO3–H2SO4
NaOTf S CF3
S CF3 O
HSO4
S CF3
MeCN 92%
ð22Þ OTf
Variation of the chalcogen (S, Se, Te) and aromatic ring substituents lead to a series of related sulfur, selenium, and tellurium (trifluoromethyl)dibenzo-phenium triflates that can act as ‘‘power variable’’ trifluoromethylating reagents, in which the most powerful trifluoromethylating reagents are based on sulfonium systems with highly electron-withdrawing groups attached to both aromatic rings <1995JFC(74)77>. Electrophilic trifluoromethylation of anilines <1995JFC(74)77> (Equation (23)), for which related kinetic studies have been performed <1996JFC(80)163>, and zinc porphyrins <1999EJO2471>, which leads to the synthesis of longer-wavelength absorbing meso-substituted systems (Equation (24)), has been reported using the Umemoto reagents.
NH2
SO3
NO2
NH2
NH2
S+ CF3
CF3
ð23Þ
+ CF3 (18%)
(37%)
N
N Zn
N
CF3 S+
N
O2N
NO2 CF SO 3 3
N
N Zn
N
CF3 N
THF 16%
+ three other products
ð24Þ
7
Trihalides
New electrophilic trifluoromethylating reagents, based upon diaryl sulfides (Equation (25)), allow efficient trifluoromethylation of pyrroles <1998JOC2656>. O S
CF3
Benzene Tf2O
HNO3
OTf
S+ CF3
OTf NO2
S+ CF3
80%
N H
6.01.2.2.4
ð25Þ
N H
CF3
Substitution of halogens by trifluoromethyl group acting as a nucleophile
Only aromatic systems that are highly activated toward nucleophilic attack may be trifluoromethylated directly by nucleophilic aromatic substitution using trifluoromethyl anions generated by reaction of fluoride ion with Ruppert’s reagent <1990IZV169> (Equation (26)). CF3
F F
F
F
6.01.2.2.5
N
F
TMS–CF3 TAS–F
F
F
F
N
ð26Þ
F
Substitution of halogen by trifluoromethyl group using derivatives of metals
Trifluoromethylcopper, which may be generated in situ by various methods <1986JA832> including from either trifluoromethyl iodide and copper or sodium trifluoroacetate and copper(I) iodide, acts as a source of trifluoromethyl anion for the replacement of bromine and iodine, activated toward nucleophilic attack by the presence of copper ions, attached to activated aromatic rings. Syntheses of trifluoromethyl retinoial analogs <1999JFC(96)159> (Equation (27)), aromatics <2002T121, 1999JFC(96)159> (Equation (28)), and pyridine derivatives <2002EJO327> (Equations (29) and (30)) have been reported recently using these reagent systems. OMe
OMe O
Ph
O
CF3COONa CuI, DMF 84%
Br OMe Br
OMe CF3
ð28Þ
CuI
NO2
85% Br
TMSCF3 N
I
ð27Þ
CF3
FSO2CF2CO2Me
NO2
Ph
Br
KF, CuI
N
CF3
ð29Þ
69% I N
Cl
CF3
TMSCF3 KF, CuI 67%
ð30Þ N
Cl
8
Trihalides
6.01.2.3
Derivatives of Alkanes, Alkenes, Alkynes, and Other Unsaturated Compounds
Many of the reagents utilized for trifluoromethylation of aromatic systems have been applied to corresponding trifluoromethylation of aliphatic derivatives at both sp2 and sp3 carbon sites.
6.01.2.3.1
Halogen exchange
Halogen exchange (halex) processes, involving nucleophilic substitution of halogen by fluorine using a metal fluoride in combination with anhydrous hydrogen fluoride, continues to be very important for the industrial production of small fluorinated hydrocarbons such as the chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs). Since the establishment of the Montreal Protocol, effectively banning the use of CFCs in developed countries, manufacturing processes for the synthesis of HFCs have been rapidly implemented. Metal fluoride-effected substitution processes proceed via carbocation intermediates, (Scheme 2), as explained more fully in COFGT (1995). C Cl + MFx
C
HF
MFx–1Cl
C F
or C
Cl F
MFx–1
Scheme 2
Representative examples of this established and very important methodology are reiterated below for completeness (Equations (31) and (32)). Metal fluorides such as antimony pentafluoride and various chromia catalysts are most commonly used in conjunction with HF <1942JA3476, 1960USP2921099>. Cl
CCl3
Cl Br
SbF3, SbF3Cl2
Cl
ð31Þ
CF3
80%
Cl
Br
Cl H
F3C
HF, SbF3 42%
Br
Cl H
ð32Þ
Fluorinated chromia aerogel materials <2003JFC(121)83> (Equation (33)), alumina and aluminum(III) fluoride <2001JFC(110)181, 2001JFC(107)45>, and chromia impregnated with zinc <1999GC9> act as heterogeneous catalysts for the isomerization of various CFCs. CCl2F–CF2Cl
Chromia catalyst
ð33Þ
CF3–CCl3
Heat
The manufacture and current applications of HFCs and the current market situation regarding HFCs have been discussed <2001CI(M)83> and the process of phasing out CFCs has been addressed <2002JFC(114)237>. Various halogen exchange processes have been performed in which most, or all, of the usual aprotic solvent medium, such as sulfolane, was replaced by a perfluoroalkane fluid. In some cases, the products obtained using sulfolane/perfluoroalkane media were different from those found when using sulfolane alone. Hexachlorodiene, for example, gave hexafluorobut-2-yne, rather than heptafluorobutene, as the major product (Equation (34)) when carried out in a perfluoroalkanerich reaction medium because elimination of fluoride to give the alkyne occurs preferentially <1997JCS(P1)3623>. Cl
Cl Cl
Cl
KF, 190 °C Sulfolane, PFPHP
Cl
CF3
CF3
+
CF3
(75%)
ð34Þ
Via carbanion:
F
Cl
CF3
H CF3
(25%)
F
CF3
9
Trihalides 6.01.2.3.2
Conversions of other groups to the trifluoromethyl group
Bromine trifluoride, prepared from fluorine and bromine, converts aliphatic nitriles to the corresponding trifluoromethyl derivatives (Equation (35)) by a sequence of addition/elimination processes <2001JFC(111)161>. NC
CF3
CO2Et
CO2Et
BrF3
ð35Þ
35%
Fluorodesulfurization of unsaturated dithiolates (Equation (36)) mediated by sources of positively charged halonium and negative fluoride ion, give rise to various trifluoromethyl alkenes <1996SL1199>. S Ar
NIS Bu4NH2F3
SEt
CF3
Ar
ð36Þ
65%
Trifluoromethyl 1,3-diketone systems may be synthesized upon reaction of an electrophilic trifluoromethylation reagent with the corresponding carbanion precursor <1995JFC(74)77>, giving overall substitution of hydrogen by trifluoromethyl (Equation (37)). CH3 Na
O
O
A, DMF
CH3 O
CF3 A=
O
SO3
ð37Þ
S CF3
86%
Perfluorinated systems, that is, molecules in which all the hydrogen atoms have been replaced by fluorine, may be synthesized by a variety of techniques. Direct fluorination (Equations (38)–(40)) permits the synthesis of perfluorinated systems from the parent hydrocarbons <1979MI161, 1997TCC(193)1, 2003T437>. The concentration of fluorine and the reaction temperature are slowly increased over a period of several days to effect perfluorination, while minimizing substrate degradation. Many perfluorinated systems bearing trifluoromethyl groups have been synthesized by this technique and some examples are given <1997TCC(193)1> (Equations (38)–(40)). F2, N2 89%
CF3 CF3
CF3 F
CF3 F CFCF3 3
F
CH3
F
ð38Þ
CF3 F2, N2
F CH3
CF3
O
F
26%
F
ð39Þ
CF2CF3
ð40Þ
CF3
F
F2, N2, NaF hν
CF3
O
85%
Perfluorination of hydrocarbons by cobalt trifluoride continues to be used for the manufacture of a range of perfluorinated fluids. In particular, perfluorination of methyl-substituted aromatic substrates (Equation (41)) is very useful for the synthesis of trifluoromethylated perfluoroalkanes <1960AFC166>. CF3 CoF3, 360 °C 77%
ð41Þ F
10
Trihalides
Electrolysis of an organic substrate, dissolved in anhydrous hydrogen fluoride gives the corresponding perfluorinated derivatives by electrochemical fluorination (ECF). Starting materials that are soluble in HF are the most readily fluorinated and many perfluorinated amines (Equation (42)) and ethers have been efficiently synthesized by this methodology <1997TCC(193)197, 1988JFC(38)303>. HF, electrolysis
F
N
F
N
ð42Þ
CF3
6.01.2.3.3
Transfer of trifluoromethyl groups as radicals
Trifluoromethyl radicals may be generated from electrolysis or radiolysis of trifluoroacetic acid or related salts or thioesters or by homolytic cleavage of the weak carbonbromine bond in trifluoromethyl bromide. Irradiation of trifluoromethylthioacetates or trifluoromethane thiosulfonates gives trifluoromethyl radicals that react regioselectively with electron-rich alkenes at the least hindered site (Equation (43)). However, some reduction of the thiophenyl group is also obtained, leading to a mixture of products <2000TL3069>.
CF3–SO2–SPh +
SPh
hν , 40 °C
C9H19
+
CH2Cl2
C9H19
CF3
CF3
C9H19
ð43Þ
33%
49%
Trifluoromethyl radicals, generated by electrolysis of potassium trifluoromethane sulfinate, may be trapped by electron-rich alkenes and aromatic systems (Equation (44)) <2002SL1697>. C9H19
CF3SO2K, DMF
CF3
CF3
Et4NClO4 Electrolysis
CF3
ð44Þ
(69%), ratio 78:12:10
Radical trifluoromethylation, followed by nucleophilic cyclization in a tandem process (Equation (45)) gives rise to various trifluoromethyl carbohydrate derivatives <1998JFC(91)179>. S
O
CF3Br, HCO2Na
O
S HO
F3C S S O
NaHCO3, SO2
O
72%
H O O H
ð45Þ
O
Electrochemical trifluoromethylation of 3-sulfolene (Equation (46)) <1998JFC(87)179> and dimethyl acetylenedicarboxylate <1996JFC(78)193> in a trifluoroacetic acid/aqueous acetonitrile medium gives mixtures of products. However, radical addition of trifluoromethyl groups, followed by coupling of the intermediate radical derivatives, provides access to various bis-trifluoromethylated systems (Equation (47)) <1997T4437>.
S O
O
MeCN, H2O Electrolysis CN
CF3
CF3 CF3
CF3 CF3COOH
+ Six other products
+ O
O
O
MeCN, H2O Electrolysis
O CN
CF3COOH
25%
ð46Þ
S
S
CF3
CF3 CN
ð47Þ
11
Trihalides 6.01.2.3.4
Reactions involving trifluoromethyl derivatives of metals and metalloids
Trifluoromethyltrimethylsilane, CF3TMS, commonly referred to as Ruppert’s reagent <1984TL2195> and now commercially available, was first used for trifluoromethylation of carbonyl derivatives (Equation (48)) in 1989 by Prakash and co-workers <1989JA393>: O
CF3 OH Me3SiCF3
ð48Þ
TBAF 77%
Efficient trifluoromethylation occurs in the presence of a source of fluoride ion, such as caesium fluoride, TBAF, TBAT, or amberlite-fluoride resin <2002MI197> whereby fluoride ion attacks the silicon atom to release trifluoromethyl anions that are subsequently trapped by an electrophilic carbon site (Scheme 3): O R1
+ CF3 SiMe3
R2
Bu4 N
+
F
–
SiMe 3 F CF3
O – Bu4 N
R1
R2
+
CF3 SiMe 3
CF3 Me Si Me Me CF3 O R1
CF3
OSiMe3
R1
R2
H
+
CF3
OH
R1
R2
O
–
Bu4 N
R1
+
R2
R2
Scheme 3
Since the initial reports, the use of TMSCF3 for trifluoromethylation has been reviewed extensively <1997CRV757, 2000T7613, 2001JFC(112)123> and only representative examples of the large body of work that has been published are outlined here. Effective trifluoromethylation of many carbonyl containing systems, such as aldehydes (Equation (49)) <1998JFC(88)79>, ketones (Equation (50)) <1998TA213>, esters, ,-unsaturated ketones (Equations (51) and (52)) <2000JFC(101)199, 2000OL3173>, -keto esters (Equation (53)) <2000OL3173, 1991SL643>, and lactones (Equation (54)) <1993TL8241> have been described. O
O
N H Boc
Me3SiCF3 TBAF
N Boc
O O
ð49Þ
O O O
O
CF3 OH H
O
O
Me3SiCF3 O O
TBAF
O
HO
HO CF3
ð50Þ O O
CF3
CF3
i. TMSCF3, TBAF (cat.)
PCC
ii. TBAF (1 equiv.)
H2SO4
ð51Þ O
12
Trihalides H
CF3
i. TMSCF 3, CsF (cat.)
Ph
O
OH (90%)
Ph
ii. conc. HCl
i. O3, –78 °C ii. Me2S R1
R2
N
F3C
R1R2NH R3-B(OH)2
R3
OH H
OH
CF3 O
O
CF3 OH O
Me3SiCF3
O
TBAF 83%
O O
O
ð52Þ
O
ð53Þ
O
Me3SiCF3
OH
O
O
CF3
TBAF
O
ð54Þ
O
In attempts to synthesize enantiopure trifluoromethyl alcohols, chiral triaminosulfonium salts gave modestly enantioselective catalytic additions to carbonyl systems (Equation (55)) <1999TL8231, 2000MI1037>. OH * Ph CF3
Chiral catalyst 96%
PhCHO + TMS-CF3
52% ee
ð55Þ
Ph
Chiral catalyst =
Ph3SnF2
N S 3
Ph
Reaction of Ruppert’s reagent with methyl esters can lead to replacement of the methoxy group to furnish -trifluoromethyl ketones (Equation (56)) <1998AG(E)820, 1999JOC2873>: O
O OMe
O2N
TMSCF3 TBAF 81%
CF3
ð56Þ
O2N
In contrast, nucleophilic substitution of halides by trifluoromethyl anion is very difficult and only very highly reactive perfluoroalkenes (Equation (57)) <1993IC4802> and acid fluorides (Equation (58)) <1993IC5079> may be functionalized in this manner. CF3 N=CF 2
CF3
TMS–CF3 KF
CF3
N
CF3
ð57Þ
68% O
O
F F F
F F F
O
TMS–CF3 KF
F F CF3
CF3 F F
ð58Þ
O
Trifluoromethylation of ketones followed by Ritter reaction using acetonitrile in strong acid leads to a variety of trifluoromethylated amides in a one-pot procedure (Equations (59) and (60)) <1997SL1193>. O O Ph
TMS–CF3, TBAF (cat.) Ph
CH3CN, H2SO4 68%
H Ph
N Ph CF3
ð59Þ
13
Trihalides O
CF3 TMS–CF3, TBAF (cat.)
O
CH3CN, H2SO4 54%
ð60Þ
N H
Efficient trifluoromethylation of imines (Equation (61)) <1999TL5475> and other related systems including ,-unsaturated sulfonaldimines (Equation (62)) <2001SL77>, chiral sulfinimines (Equation (63)) <2001AG(E)589>, and azirines (Equation (64)) <1994TL3303>, in which the carbonnitrogen double bond is attacked by trifluoromethyl anion, has been established, giving various trifluoromethylated amine derivatives. In particular, stereoselective addition of trifluoromethyl groups to imines is possible in systems that possess chiral sulfoxide moieties adjacent to the carbonnitrogen double bond <2001AG(E)589>. R3 R1
N
R1 R2
i. TMSCF 3, TMS-imidazole, CsF, THF R2 ii. SiO2, 2 M HCl
N
SO2tol
TMSCF3 TBAT 87%
Cl
t-Bu
H N
N R3
H
ð61Þ
CF3
H
O S
CF3
TMSCF3
t-Bu
O S
N H
Cl
CF3 HCl, MeOH
N H
85%
97:3 diastereomers
Ph N
R1 R2
ð62Þ
CF3
TBAT
O
SO2tol
TMSCF3 TBAF
H3N
O
O
ð63Þ
Cl
Ph F3C
R1 R2
N SiMe3
ð64Þ
Nucleophilic trifluoromethylation by germanium reagents, which are analogous to the trimethylsilyl systems described above, also trifluoromethylate C¼N double bonds (Equation (65)) <1997TL3443, 1996SL1191>.
Ph
N
Ph
C6H5SCF3 Et3GeNa HMPA 96%
CF3 Ph
N H
Ph
ð65Þ
Whilst the use of Ruppert’s reagent is becoming widespread, the development of other sources of trifluoromethyl anion continues. Successful application of fluoroform (Equation (66)) <1998TL2973, 1999T275> and hemiaminals of fluoral, derived from either DMF <2000JOC8848, 2000TL8777> or morpholine (Equation (67)) <2000OL2101>, for analogous trifluoromethylations of ketones has been discussed by Langlois <2003S185, 2001EJO1467>.
O Ph
HCF3, ButOK H
DMF
CF3 OH Ph
H
ð66Þ
14
Trihalides CF3 N
O
OTMS +
O
R1
CF3 OTMS
TBAF
R1
R2
ð67Þ
R2
Addition of N,N-dimethyltrimethylsilylamine to trifluoroacetophenone gives a stable nucleophilic trifluoromethylating reagent (Equation (68)) that reacts with carbonyl derivatives upon catalysis by caesium fluoride <2002SL646>. Related reagents may also be derived from various trifluoromethylamides (Equations (69) and (70)) <2003SL230, 2003AG(E)3133> and sulfinates (Equation (71)) <2003SL233>: O O Ph
110 °C
CF3 + Me2N–SiMe3
Me2N
OTMS
Ph
R1
CF3
R2
HO
CF3
R1
R2
CSF
ð68Þ
O O CF3
N
+ Ph
N
Ph
ButOK
HO
CF3
DMF, THF
Ph
Ph
Bn
ð69Þ
100%
Ph O
Ph Me3SiO O
N
+
Ph
H
CF3
O Ot Bu
+ Ph N
Ph
ii. Bu 4NF 89%
CF3 O S
OH
i. CsF
ButOK
HO
THF
Ph
CF3
CF3
ð70Þ
ð71Þ
N
91%
A further nucleophilic trifluoromethylating reagent may be generated by a single-electron transfer process from the highly electron-rich alkene, tetrakis(dimethylamino)ethylene, to trifluoromethyl iodide. A complex between the TDAE dication and trifluoromethyl anion is thought to be the active reagent which may be used to synthesize -trifluoromethyl alcohols (Equation (72)) <2001OL4271>, trifluoromethyl alcohols (Equation (73)) <2002OL4671> and give bis-trifluoromethylation of acid halides, proceeding via the trifluoromethyl ketone (Equation (74)) <2002TL4317>: O O
S
O
Me2N
O
NMe2
THF
NMe2
55%
+ CF3I + Me2N
HO
CF3
ð72Þ
TDAE O Ph
H
+ CF3I + TDAE
DMF
HO
CF3
78%
Ph
H
ð73Þ
O O Ph
Cl
+ CF3I + TDAE
O
Et2O 98%
Ph
Ph
ð74Þ
CF3 CF3
A combination of an electron-rich phosphene and trifluoromethyl bromide may add to amides which are activated by a Lewis acid. Dehydration results in the formation of trifluoromethyl enamines (Equation (75)) <1995JFC(70)89>: O CH3
N CH3
P(NEt2)3, CF3Br CH3
BCl3 25%
CF3 CH3
N CH3
H H
ð75Þ
15
Trihalides
Trifluoromethylcopper may be generated from a variety of sources including reaction of either CF3I, CF3Br, or trifluoromethanesulfonyl chloride with copper powder in aprotic solvents or from sodium trifluoroacetate and copper(I) iodide <1995COFGT(6)1>. This trifluoromethylating reagent generated in situ is effective for the replacement of halogens attached to aromatic ring systems and also useful for the stereoselective transformation of haloalkenes into trifluoromethyl alkenes (Equations (76)–(78)) <1995JFC(72)241, 2001TL5929, 2001JFC(108)79, 2002JOC9421> such as in steroidal alkenyl bromides <1998JCS(P1)1139>.
NO2
CO2Et
NO2
FSO2CF2CO2Me
CO2Et 24/1 (E )/(Z )
CuI, DMF
Br
ð76Þ
CF3
91%
CO2Et
CO2Et FSO2CF2CO2Me
I O
O
O
F Ph
9/1 (Z )/(E )
CuI, DMF 81%
NaF, diglyme 82%
O
F
F
F
FSO2CF2CO2Me
FSO2CF2CO2Me
I
ð77Þ
CF3
Ph
ð78Þ
CuI, DMF
I
Ph
CF3
45%
Stereo- and regioselective replacement of terminal iodine atoms in 1,2-diiodoalkenes occurs upon treatment with trifluoromethylcopper. An excess of the trifluoromethylation system allows the synthesis of ditrifluoromethyl alkenes from di-iodoalkene precursors (Equations (79)–(81)) <1998JOC9486>:
I Ph
I
I
Ph
CuI, DMF 90%
Ph
I
CuI, DMF 88%
MeO2C
2.5 equiv. FSO2CF2CO2Me CuI, DMF
I
ð79Þ
CF3
I
FSO2CF2CO2Me
MeO2C
I
I
FSO2CF2CO2Me
ð80Þ
CF3
F3C Ph
ð81Þ
CF3
91%
Similar processes are effective in the presence of a palladium species which catalyzes insertion of trifluoromethyl group into carbonhalogen bonds (Equation (82)) <2001JFC(111)185>:
Br NO2
Br
CF3
FSO2CF2CO2Me CuI, Pd(PPh3)4 82%
NO2
CF3
ð82Þ
16
Trihalides
Allyl iodides are displaced by trifluoromethyl upon reaction with chlorodifluoroacetate and fluoride ion in the presence of copper(I) iodide (Equation (83)). The process probably occurs via carbene type mechanism, although this is not clear <1998TL3961>.
MeSO2
6.01.3
I
ClCF2CO2Me KF, CuI, DMF 43%
MeSO2
CF3
ð83Þ
TRICHLOROMETHYL DERIVATIVES, RCCl3
6.01.3.1 6.01.3.1.1
Trichloromethyl Groups Attached to an Aliphatic Center Conversion of groups attached to an aliphatic center into the trichloromethyl group
The most direct and industrially important method of introducing trichloromethyl groups into an aliphatic system remains sequential chlorination, in the presence of a Lewis acid, followed by dehydrochlorination (Equation (84)). Cl
6.01.3.1.2
Cl
Cl2
Cl
Cl
–HCl Cl
Cl
HCl Cl
Cl Cl
ð84Þ
Transfer of the trichloromethyl group to an aliphatic center
Trichloromethyl anions may be generated from chloroform/BuLi, chloroform/NaOH, or TMSCCl3/base, and react with various organic substrates that possess electrophilic carbon sites. However, trichloromethyl anion is relatively unstable and must be generated at low temperature (100 C) before loss of chloride ion, giving reactive dichlorocarbene, occurs as a competing process leading to the formation of unwanted side products. Nevertheless, some useful syntheses utilizing trichloromethyl anions have been developed. Michael-type addition processes (Equations (85) and (86)) to a range of electron-poor alkenes occur to give corresponding trichloromethyl adducts <1993JOC267, 1999OL2165> and -trichloromethyl alkanes may be prepared by reaction with sufficiently activated haloalkanes (Equation (87)) <1990JOC1281>. O
O OEt
O
TMSCl 75%
Et
I
OEt
ð85Þ
PPh3
O
CHCl3, BuLi
S N O
O
Cl3C
THF 90%
PPh3
O
O
CHCl3, BuLi
CCl3
S N O 55:45 ratio of diastereoisomers
ð86Þ
O
CHCl3, BuLi HMPA 68%
Et
CCl3
ð87Þ
Chloroform may be deprotonated by aqueous sodium hydroxide in the presence of a quaternary ammonium salt to give trichloromethyl anion which exists in equilibrium with dichlorocarbene. In general, for this reagent system, electron-rich alkenes react with dichlorocarbene, whereas electron-poor alkenes react by conjugate addition (Equation (88)). The reaction outcome is sensitive toward the type of ammonium salt present as the phase-transfer catalyst <1997T1053>. Lipophilic salts are more effective at promoting conjugate addition, rather than competing cyclopropanation involving dichlorocarbene addition. Indeed, catalysts may be
17
Trihalides
designed so that only products arising from Michael addition are obtained, providing a potentially useful solution to the problem of competing dichlorocarbene reactions <1999T6329, 2003PJC709>.
OCOPh
Cl
+
PTC
OCOPh
PTC = Me4NHSO4 BnEt3NCl
6.01.3.2
Cl
CCl3
CHCl3, 50% aq. NaOH
OCOPh 68% —
5% 65%
ð88Þ
Trichloromethyl Groups Attached to an Aromatic Ring
6.01.3.2.1
Conversion of groups attached to an aromatic ring into a trichloromethyl group
Free-radical chlorination, initiated by either heat or radiation, of methyl groups attached to aromatic and heteroaromatic rings bearing a range of functionalities are well established (Equation (89)), as discussed in COFGT (1995). Alternative methodologies to these industrially operated processes have not been generally developed:
CCl3
Cl2
ð89Þ
Heat or hν
6.01.3.2.2
Transfer of trichloromethyl group to an aromatic ring
Aromatic systems may be trichloromethylated by reaction with carbon tetrachloride and a Lewis acid, usually aluminum trichloride, by Friedel–Crafts process. Trichloromethyl derivatives are the major products but further Friedel–Crafts reaction of this system may take place to yield the corresponding diaryldichloromethane (Equation (90)) <1987JPR1131>. Carbocation rearrangements may occur in the highly acidic reaction medium, for example, durene gives exclusively a product arising from acid catalyzed rearrangement (Equation (91)) <1960JA4460>. Acid catalyzed oligomerization of 2,4-disubstituted thiophenes occurs upon reaction with the carbon tetrachloride/aluminum trichloride reagent system <1998CHE1276>.
Cl
CCl3
CCl4, AlCl3
CCl4, AlCl3
6.01.4
Cl
ð90Þ
+
CCl3
ð91Þ
TRIBROMOMETHYL DERIVATIVES, RCBr3
Methodologies for the synthesis of tribromomethylated derivatives are analogous to processes useful for the preparation of corresponding trichloromethyl systems. Tribromomethyl anions, generated from either decarboxylation of tribromoacetic acid <1967JOC2166> or tributyl (tribromomethyl)stannane <1975JOM(102)423>, react with electrophilic carbon centers, although development of this methodology remains very limited.
18 6.01.5
Trihalides MIXED SYSTEMS WITH FLUORINE, RCF2Hal AND RCFHal2
Many systems bearing CF2Hal and CFHal2 groups are synthesized as by-products of the various halex reactions described above. Other more general syntheses, involving either displacement of fluorine or the transfer of such groups onto organic substrates, are noted below. Transformation of -trifluoromethyl ketones to corresponding difluorohalo derivatives can be accomplished in two steps (Equations (92) and (93)) involving halogenation of the trimethylsilyl enol derivative of the starting ketone <2003JFC(121)239>. O Mg, TMS–Cl
CF3
THF
Cl
F
Cl
O
THF
F3C
F
F3C
I2 60%
OSiMe3 F
Mg, TMS–Cl
CF3
O
OSiMe3 F
CF2I
ð92Þ
CF2Br
ð93Þ
Cl O
Br2 87%
F3C
Various difluorobromo- and difluorochloromethyl-substituted derivatives may be formed upon condensation of bromodifluoroacetate (Equations (94) and (95)) <1999JFC(95)127> or difluorochloroacetic anhydride (Equation (96)) <2001SL821> with an appropriate nucleophile. NH2
O +
OH
BrCF2
OEt
N
H N
EtOAc Et3N
CF2Br i. PPA, 150 °C
OH
Ph
O
NH2
ð94Þ
O
73% Ph
Heat
+ BrCF2
N CF2Br
ii. NH3 (aq.)
O OH
35%
OEt
N O
N
ð95Þ
CF2Br NMe2
NMe2 N
N (ClCF2CO)2O Pyridine 75%
ð96Þ O
CF2Cl
Difluorochloromethyl groups may be introduced into organic systems by the use of a silicon reagent that is analogous to Ruppert’s reagent (Equations (97) and (98)). The difluorochloromethylating reagent is synthesized by reaction of trimethylsilyl chloride with difluorobromochloromethane in the presence of aluminum <1997JA1572>: O Ph
H
+ Me3SiCF2Cl
OH
THF, NMP TBAF
Ph
CF2Cl
ð97Þ
68% O Ph
6.01.6
H
+ Me3SiCF2Cl
THF, NMP TBAF 85%
OH Ph
CF2Cl
ð98Þ
MIXED HALOFORMS, CHXY2 AND CHXYZ
Recent interest in simple haloforms has concentrated upon the synthesis and spectroscopic measurement of enantiomerically pure samples of simple chiral systems such as CHClFI and CHFClBr. Decarboxylation of appropriate polyhalogenated acetic acids proceeds with retention of configuration allowing the isolation of pure enantiomers <2000MI429, 2003MI541>.
Trihalides
19
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20 1998JFC(91)179 1998JFC(92)181 1998JOC2656 1998JOC9486 1998TA213 1998TL2973 1998TL3961 1999EJO2471 1999GC9 1999JFC(95)127 1999JFC(96)159 1999JFC(98)75 1999JOC344 1999JOC2873 1999OL2165 1999T275 1999T6329 1999TL5475 1999TL8231 2000JFC(101)199 2000JOC8848 2000MI429 2000MI234 2000MI1037 2000MI331 2000OL2101 2000OL3173 2000T3635 2000T7613 2000TL3069 2000TL5347 2000TL6071 2000TL8777 2001AG(E)589 2001CI(M)83 2001EJO1467 2001JFC(107)45 2001JFC(108)79 2001JFC(110)181 2001JFC(111)161 2001JFC(111)185 2001JFC(112)123 2001MI755 2001OL4271 2001SL77 2001SL821 2001SL1719 2001TL3137 2001TL5929 2002EJO327 2002JFC(114)237 2002JOC9421 2002MI197 2002OL4671 2002SL646 2002SL1697 2002T121 2002TL4317 2003AG(E)3133 2003JFC(121)83 2003JFC(121)239 2003MI541 2003PJC709
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Trihalides 2003S185 2003SL230 2003SL233 2003T437 2003TL1747
21
B. R. Langlois, T. Billard, Synthesis 2003, 185. L. Jablonski, J. Joubert, T. Billard, B. R. Langlois, Synlett 2003, 230. D. Inschauspe, J. P. Sortais, T. Billard, B. R. Langlois, Synlett 2003, 233. G. Sandford, Tetrahedron 2003, 59, 437. S. Debarge, B. Violeau, N. Bendaoud, M. P. Jouannetaud, J. C. Jaquesy, Tetrahedron Lett. 2003, 44, 1747.
22
Trihalides Biographical sketch
Graham Sandford was born in Manchester. He studied at Durham University, where he obtained a B.Sc. in 1988 and his Ph.D. in 1991 under the direction of Professor R. D. Chambers. After spending 1992 in the laboratories of Professor G. A. Olah at USC, Los Angeles, he returned to Durham as a BNFL Postdoctoral Research Fellow. Subsequently, he was awarded a Royal Society University Research Fellowship in 1996 and took up his present position as Lecturer in Chemistry at Durham in March 2001. His scientific interests include all aspects of organofluorine chemistry, in particular, selective fluorination methodology, heterocyclic, free-radical and carbanion chemistry of fluorinated systems.
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Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 1–22
6.02 Functions Containing Halogens and Any Other Elements J. SUWIN´SKI and K. WALCZAK Silesian University of Technology, Gliwice, Poland 6.02.1 FUNCTIONS CONTAINING HALOGEN AND A CHALCOGEN 6.02.1.1 Halogen and Oxygen Derivatives (R1CHal2OR2 and R1CHal(OR2)2) 6.02.1.1.1 Tetracoordinated carbon atoms with two identical halogen and one oxygen function attached (R1CHal2OR2) 6.02.1.1.2 Tetracoordinated carbon atom bearing mixed halogens and one oxygen function (R1CHal2OR2) 6.02.1.1.3 Tetracoordinated carbon atom bearing one halogen and two oxygen functions (R1CHal(OR2)2) 6.02.1.2 Halogen and Sulfur Derivatives (R1CHal2SR2 and R1CHal(SR2)2) 6.02.1.2.1 Tetracoordinated carbon atoms with two identical halogen and one sulfur function attached (R1CHal2SR2) 6.02.1.2.2 Tetracoordinated carbon atoms bearing mixed halogens and one sulfur function (R1CHal2SR2) 6.02.1.2.3 Tetracoordinated carbon atoms bearing one halogen and two sulfur functions (R1CHal(SR2)2) 6.02.1.3 Halogen and Se or Te Derivatives (R1CHal2SeR2 or R1CHal2TeR2) 6.02.1.3.1 Tetracoordinated carbon atoms bearing two halogens and one selenium function (R1CHal2SeR2) 6.02.1.3.2 Tetracoordinated carbon atoms bearing two halogens and one tellurium function (R1CHal2TeR2) 6.02.1.4 Halogen and Mixed Chalcogen Derivatives (R1CHal(OR2)(SR3)) 6.02.2 FUNCTIONS CONTAINING HALOGEN AND A GROUP 15 ELEMENT AND POSSIBLY A CHALCOGEN 6.02.2.1 Halogen and Nitrogen Derivatives: General Considerations 6.02.2.1.1 Tetracoordinated carbon atoms bearing two halogens and one nitrogen function 6.02.2.1.2 Tetracoordinated carbon atoms bearing one halogen and two nitrogen functions 6.02.2.1.3 Tetracoordinated carbon atoms bearing one halogen, one nitrogen, and one oxygen function 6.02.2.1.4 Tetracoordinated carbon atoms bearing one halogen, one nitrogen, and one sulfur function 6.02.2.2 Halogen and Phosphorus Derivatives 6.02.2.2.1 Tetracoordinated carbon atoms bearing two halogens and one phosphorus function, and one halogen and two phosphorus functions 6.02.2.2.2 Tetracoordinated carbon atoms bearing one halogen, one oxygen function, and one phosphorus function 6.02.2.3 Halogen and Arsenic Derivatives 6.02.2.3.1 Tetracoordinated carbon atoms bearing two halogens and one arsenic function 6.02.3 FUNCTIONS CONTAINING HALOGEN AND A METALLOID AND POSSIBLY A CHALCOGEN AND/OR GROUP 15 ELEMENT 6.02.3.1 Halogen and Silicon Derivatives 6.02.3.1.1 Dichlorocarbene addition 6.02.3.1.2 Other additions to silanes 6.02.3.1.3 Substitution of silanes by haloalkyl derivatives 6.02.4 Halogen and Boron Derivatives 6.02.5 Halogen and Germanium Derivatives
23
24 24 24 32 33 33 34 49 50 50 50 52 52 53 53 53 59 61 62 62 62 63 63 63 64 64 64 64 64 65 65
24
Functions Containing Halogens and Any Other Elements
6.02.6 FUNCTIONS CONTAINING HALOGEN AND A METAL AND POSSIBLY A GROUP 15 ELEMENT, A CHALCOGEN OR A METALLOID 6.02.6.1 Halogen and Lithium Derivatives 6.02.6.2 Halogen and Magnesium Derivatives 6.02.6.3 Halogen and Copper Derivatives 6.02.6.4 Halogen and Silver Derivatives 6.02.6.5 Halogen and Zinc Derivatives 6.02.6.6 Halogen and Cadmium Derivatives 6.02.6.7 Halogen and Mercury Derivatives 6.02.6.8 Halogen and Tin Derivatives 6.02.6.9 Halogen and Lead Derivatives 6.02.6.10 Halogen and Ruthenium Derivatives 6.02.6.11 Halogen and Cobalt or Nickel Derivatives 6.02.6.12 Halogen and Palladium or Platinum Derivatives
6.02.1
65 65 65 66 66 66 66 67 67 68 68 68 69
FUNCTIONS CONTAINING HALOGEN AND A CHALCOGEN
Apart from broad overviews of haloalkyl systems relevant to this chapter and covering the literature up to 1984 <1985HOU(E5)> and up to 1994 <1995COFGT(6)35> no report of this type has ever been published. A few limited reviews which concentrated mainly on fluorinated oligo- and polymeric materials containing -(CF2O)n- or -(CF2S)n fragments were published. A review seeking to cover recent developments in the field of fluorinated elastomers was published in 2001 <2001MI105>. Heteroatom-containing fluoroelastomers were briefly summarized there (pp. 144–147). The following structures were discussed: -(CF2O)n-, -(CF2S)n-, -(N-OCF2CF2)n-. Also nitrile-containing fluoroelastomers (NC-(CF2)n-O-CF) were presented. A review on polymers (containing OCF2 fragments), which can be applied to a variety of surfaces and manufactured into thin films, has been recently published by Imae <2003MI(8)307>. Caminade et al. published a review on fluorinated dendrimers (some containing OCF2 fragments) and their applications in catalysis, material sciences, and biology <2003MI(8)282>. Application of several different perfluoroalkyl compounds, e.g., perfluoroethers in the biomedical field; in in vivo transport of O2, CO2, and NO was reviewed earlier <1998MI(80)489>.
6.02.1.1 6.02.1.1.1
Halogen and Oxygen Derivatives (R1CHal2OR2 and R1CHal(OR2)2) Tetracoordinated carbon atoms with two identical halogen and one oxygen function attached (R1CHal2OR2)
(i) From ethers Direct halogenation of ethers remains the simplest method for synthesis of perhalogenated compounds of this class. Fluorination of low-molecular weight ethers using elemental fluorine gives products with ratio being a function of the flow rate of fluorine and of carrier gas (usually helium). Direct fluorination of dioxane using elemental fluorine has afforded perfluorinated system in a moderate yield, whereas application of a mixture of sulfur tetrafluoride and hydrogen fluoride has led to the formation of 2,2,3-trifluorodioxane in a high yield. Electrochemical fluorination of ethers leads to perfluorinated products in moderate yields. Electrochemical fluorination of a range of oxanes also results in the formation of the corresponding perfluorinated products in only moderate yields <1995COFGT(6)35>. Combination of sodium fluoride and elemental fluorine has successfully been applied to fluorination of ethers in perhalogenated alkanes as the solvents. The appropriate perfluorinated ethers were obtained in high yields (Scheme 1) <1995JA4276, 1996SC375>. Fluorination of 5,7,9,11-tetraoxapentadecane using the same system has produced a mixture of perfluorinated ethers resulting from chain cleavage <1995JA4276, 1996SC375>. Fluorination of an alkoxyalkyl ester of perfluorinated acid using elemental fluorine at elevated pressure affords perfluorinated product in a moderate yield. It is worth mentioning that the ester function is preserved (Equation (1)) <2001JFC(112)109>.
25
Functions Containing Halogens and Any Other Elements F2, NaF, ClF2CCCl2F
O
75%
O
O
O
CF3
F F F2, NaF, ClF2CCCl2F
O
F F F F F F F F F F F3C
O 3
32%
F F
F F F F FF F3C
O
FF F F
O3
F F
CF3 F F
Scheme 1
O
O
F F F CF3
F2, C6H6, 20–40 °C, <1500 torr
R
F
75%
O
F
O
O
F F
R O
ð1Þ
R = –CF(CF3)OCF2CF2CF3
Electrochemical fluorination of N-(2-hydroxyethyl)morpholine leads to the corresponding acyl fluoride (Equation (2)) accompanied by a mixture of perfluorinated products resulting from the chain or ring cleavage and subsequent fluorination of the produced fragments <1999JFC(97)229>. Tetrahydrofuran, when treated with boron trichloride in the presence of bis(trifluoromethyl)cadmium-acetonitrile complex, undergoes ring-opening reaction followed by halogenation to produce 4-chlorobutyl difluoromethyl ether <1995JFC(73)229>. O
O
F N
HF, 7–8 °C, ~10 h
N
25% OH
F
ð2Þ F
O
F
Photochlorination of partially fluorinated ethers was also investigated; the appropriate chloroethers have been obtained in moderate yields <1995JOC1319>. Chlorination of p-methoxybenzoyl chloride using chlorine in the presence of phosphorus pentachloride affords p-(trichloromethoxy)benzoyl chloride in an excellent yield (Equation (3)) <2000JFC(103)81>. O MeO Cl
PCl5, Cl2, 200 °C 92%
O
ð3Þ
Cl3CO Cl
(ii) From mixed trihalomethanes No further advances have occurred in this area since the publication of <1995COFGT(6)35>.
(iii) From dihaloethers Selective further fluorinations of haloethers using manganese trifluoride or sodium fluoride have been reported (Scheme 2) <1996JFC(80)86, 1997JFC(85)111>. Treatment of haloethers, containing a mixed halogen function, with sevoflurane (1,1,1,3,3,3hexafluoro-2-(fluoromethoxy)propane) in the presence of antimony pentachloride <1998JFC(88)51, 2001JFC(111)11> or bromine trifluoride <2000JFC(102)363> results in halogen substitution. In the latter reaction respective fluorinated ethers have been obtained in moderate to good yields (Scheme 3). Substitution of a chlorine atom in trichloromethyl group using sevoflurane and antimony pentachloride was reported later <1999JFC(94)1>. A fluorine atom through a reaction with hydrogen fluoride in the presence of cobalt difluoride and porous aluminum trifluoride can substitute an -chlorine atom in mixed haloalkoxyalkanes (Scheme 3) <2001JFC(112)145>.
26
Functions Containing Halogens and Any Other Elements F
O
MnF3, 75 °C, 6 h
CF3
85%
F
O
F F3C
O
65%
F F Cl
F F
NaF, 85–95 °C, 6 h
CClF2
CF3
O
F3C
F F
MnF3, 50 °C, 5 h
O
Cl
O
45%
F
F
F F CH2F
F
Scheme 2
Cl F
Cl3C
CF3
O
SbCl5, sevoflurane, 5–10 °C, 1 h
Cl Cl
90%
CF3 F Cl F Cl
C F3 CF3
F
66%
CF3
O
F
SbCl5, sevoflurane
CF3
O
F
C F3 CF3
F F
CoF2, HF, AlF3, 200 °C, 1 h
O
O
F Cl
85%
F
O F
Scheme 3
Polyfluorinated ethers Rf CH2ORf react with fluoroethylenes in the presence of SbF5 catalyst under mild conditions. The reaction of CF3CH2OCF2CF2H with F2C¼CF2 results in the formation of CF3CH2OCF(C2F5)CF2H in a high yield. In contrast to that, the condensation of CF3CH2OCF2CF2H with F2C¼CFH affords CF3CH2OC(CHFCF3)CF2H as a major product (Scheme 4). A mechanism for the reactions was discussed <2001JFC(112)117>.
F F3C
F F H
O
F3C
F H
O
F3CHFC
F2C=CHF, 25 °C, 5 h
F
O
F3C
76%
F F
F
F2C=CF2, SbF5, 25 °C, 12 h
F3C
61%
F
O
CF2CF3 F H F CHFCF3 F H F
Scheme 4
A chlorine atom in polyfluorinated ether was exchanged by a fluorine one using trifluoroboride (Equation (4)) <1993JPS791>. F2HC
O
CF3 H Cl
BF3
F2HC
O
CF3 H
ð4Þ
F
Transformations of polyfluoroalkyl ethers have also been described <2002JFC(114)51>. Lubricating oils and greases for magnetic recording devices, containing partially esterified phosphates and phosphonates or salts of phosphate and phosphonate esters were prepared by reaction of mixed perfluoroalcohols or perfluorodiols with a phosphorus acid precursor i.e., phosphorus oxychloride in the presence of an amine acid scavenger <2003USP073588>.
27
Functions Containing Halogens and Any Other Elements (iv) From carbonyl derivatives
Several methods for conversion of carbonyl compounds into ethers perhalogenated in alkyl (cycloalkyl) groups have been described. Among others electrochemical fluorination of acyl chlorides and esters has been used. The sulfur tetrafluoride has been applied for conversion of a variety of anhydrides, esters, and formate esters into compounds with difluoromethyl groups. Aromatic o-diacids treated with sulfur tetrafluoride can form cyclic ethers in addition to perfluorination of other substituents <1995COFGT(6)35>. Phosphorous pentachloride, which reacts with a variety of formate esters to yield the corresponding ,-dichloro diethers <1995COFGT(6)35>, has recently been used successfully for the conversion (Scheme 5) of methyl formate <1996ZOR1186> and diphenyl carbonate <1996AJC1261>.
O H
PCl5 Me
OMe
O
Cl Cl
O PhO
Cl
PCl5, 180 °C, 24 h OPh
Cl
PhO
97%
OPh
Scheme 5
Acyl fluorides can be transformed in moderate yields into perfluoroalkyl methyl ethers using triethylamine–hydrogen fluoride complex (Equation (5)) <2002JFC(118)123>. Oxalyl difluoride treated with ethyl ester of trifluoromethanesulfonic acid has afforded ethoxy-difluoroacetyl fluoride in a moderate yield (Scheme 6) <2002JFC(113)97>. Oxalyl difluoride has also been used in reaction leading to the ring-opening in perfluorinated (methyl)oxiranes (Scheme 6) <1995JFC(75)163>. Perfluorinated (methyl)oxiranes when treated with several fluorinating agents gave appropriate derivatives of perfluorinated alkoxy acetyl fluorides in moderate-to-good yields (Scheme 7) <1996T9755, 2002JFC(114)51, 1999ZPK(72)425>. The use of ammonium- and phosphonium perfluorocyclobutane ylides, prepared with perfluorocyclobutene and tertiary amines or phosphines as a masked fluorine anion source, has been demonstrated in several reactions <1996T9755>. Et3N.3HF, EtOH
F F F3 C
O
(CH3O)2SO2 68%
F
O F
F
F F O
F F
F F O
O
71%
O
F3C
F
F O
F KF, 0 °C, 16 h 58%
ð5Þ
O
F3C
O S F3 C O O CsF, diglyme, 20 °C, 24 h
O
F
F F
O F
F F F CF3 O
F F F F
O
O F
Scheme 6
The reactions of oxalyl fluoride with electrophiles in the presence of alkali metal fluoride afford ,-difluoroethers. In the reaction with CF3CH2O3SCF3 or CH3CH2O3SCF3, synthesis of di-ether (ROCF2CF2OR) and mono-ether as a by-product (ROCF2COF) was achieved (Scheme 8) <2002JFC(113)97>.
28
Functions Containing Halogens and Any Other Elements F F3C
F F
O
F F3C
F F
O
O
F F
Et3NC4F7. BF4, MeCN, 2 h
O
F3C
82%
F
F F F CF3 F F F CF3
F F
CsF, various solv.
O
F3C
22%
O
O
F F F CF3
F
Scheme 7 F
O
F
O
F F
CF3CF2OTf, CsF, rt, 24 h F3C
Diglyme 56%
O
O
CF3
F F
Tetraglyme 63%
Scheme 8
A new synthetic procedure for the preparation of perfluoro(alkoxyalkanoyl) fluorides, precursors of perfluorinated vinyl ether monomers, from nonfluorinated alkoxyalcohols has been developed. The desired perfluoro(alkoxyalkanoyl) fluoride can be obtained from its hydrocarbon counterpart alcohol and an available perfluoroacyl fluoride as is shown (Scheme 9) <2001JFC(112)109>. Transformation of benzaldehydes to difluoromethoxybenzenes using xenon difluoride is enhanced by silicon tetrafluoride <1999JFC(98)163>. It was also found that a relatively new reagent namely bromine trifluoride converts aliphatic nitriles into trifluoromethyl group when a neighboring carboxylic moiety is present. In the case of ketonitrile, a participation of the internal nucleophilic oxygen in attacking the nitrile carbon was also observed <2001JFC(111)161–165>. F F3C
OC3F7 F O F
CF3 C3F7 O
F O
O R HO
O
F
99%
O
O
NaF (30 mol.%), 140 °C
O
RHOH C3F7
F CF3
F CF3
1,1,2-Trichlorotrifluoroethane 25–40 °C, 21–86%
O
C3F7 F CF3
O
20% F2/N2, 0.2 MPa C3F7
RHO
RFO
O
C3F7
F CF3
Scheme 9
(v) From alkoxyhaloalkenes Addition of fluorine to the double bond in alkoxyfluoroalkenes has not been reported in reviews yet. It can be achieved using some fluorinating agents like hydrogen fluoride, boron trifluoride, or cobalt trifluoride to afford products, in which former alkene substituents are perfluorated while alkoxy groups do not contain additional fluorine atoms. Yields of the products depend both on the fluorinating agent and reaction conditions (Scheme 10) <1996JOC9605, 2000MI(3)343>. Preparation of alkoxydi(tri or tetra)chloroalkanes by addition of dry hydrogen chloride or dry chlorine to alkoxychloroalkenes has already been discussed <1995COFGT(6)35>. More recent reports on chlorination or bromination of alkoxyhaloalkenes have not been located.
(vi) From haloalkenes The addition of primary alcohols to halogenated alkenes proceeds rapidly in the presence of metal alkoxides, giving the corresponding alkoxyhaloalkanes in high yields <1995JFC(74)273, 1997AG136, 2000JFC(102)363>. Also a variety of primary and tertiary alkyl hypohalides are added at low temperatures affording respective addition products in high yields <1995JFC(74)199>.
29
Functions Containing Halogens and Any Other Elements F
OCF3
F
F
F
O
F
F
F3C
F F
F
F F
CoF3, –196 to –20 °C, 0.5 h
F3C
45%
O F F
CoF3, –196 to –20 °C, 0.5 h
O
F3C
55%
F
F I
O
F3C
84%
O
F
F F
ICl, HF, BF3, 70 °C, 20 h
F F
Scheme 10
Perfluorinated vinyl ethers react smoothly with alcohols in the presence of deprotonating agents to give appropriate ethers in moderate yields (Scheme 11) <2000JFC(106)13, 2002JFC(117)149>. Addition of trifluoroethanol to the perfluorinated methyl vinyl ether has been accomplished using aqueous potassium hydroxide at an elevated temperature (Equation (6)) <1999JFC(95)5>. Also other compounds containing sufficiently acidic proton can be added to perfluoroalkenes in aprotic solvents in the presence of metal hydroxides (Scheme 12) <1998JCR(S)(4)192, 1998JMC1092, 2000JFC(101)91, 2000JFC(103)129, 2002JFC(117)149>. Addition of alcohols to perfluorinated alkoxyalkenes is also possible under photochemical conditions <1996JFC(80)135>. F F F3C
F
F F
F
O
O
F F F CF3
F
F3C
O
O
F
F3C
O O F F
F F F CF3 F
n-C6H13OH, BuLi, THF, 20 °C
F
F O
F3C
38%
F F F CF3 F
F
F F O
54%
F
F F
F F
MeOH, MeONa, 20 °C
O
F OC6H13
F F F CF3F
Scheme 11
F
F3C OH KOH, H2O, 100 °C, 20 h
F
F
OCF3
N OH
F
CF3 F DMF, NaOH,
O
F F CF3
N O
80%
F O
Me OH Me
ð6Þ
CF3
F
O
HO
O
O
92%
F O
F F F3C
F
F
F
CF3
KOH, DMSO, 60 °C, 5 h 92%
Scheme 12
F
F
F
Me
O CF3
F
F
F
O Me
CF3
30
Functions Containing Halogens and Any Other Elements
Epoxidation of chloroalkenes is a convenient route to ,-dichlorooxiranes—useful intermediates in the enantioselective synthesis of azido- and aminoacids. Perfluoroalkenes react with sulfur trioxide to give cyclic perfluoro-2--sulfones in excellent yields. Perfluoroalkenes also react with halogen monofluorosulfates to yield both 2-haloalkylfluoroalkyl fluorosulfates and vicinal bis(halosulfonyloxy)fluoroalkanes <1995COFGT(6)35>. A series of nucleophiles was treated with [1,1,2,4,4,5,7,7,8,8,9,9,9-tridecafluoromethyl3,6-dioxanon-1-ene] as a representative of perfluoro(alkyl vinyl ethers). All the reactions were completely regioselective with the nucleophilic attack on the terminal carbon atom. Reactions of hydroxy compounds, thiols, and sec-amines afford the desired products, while butyllithium, tributylphosphane, or complex hydrides cause displacement of vinylic fluorine (Scheme 13) <2002JFC(117)149>. CF3
CF3
NuH, BuLi, THF
F2C=CFOCF2CFO-CF2CF2CF3
–75 °C to rt, 5 days
NuF2CCHFOCF2CFO-CF2CF2CF3 NuH
Yield (%)
n-C6H13OH n-C16H31OH p-F3CSC6H4OH PhSH Et2NH (CH2)5NH
38 (unstable) 41 30 55 52 (unstable) 79 (unstable)
Scheme 13
(vii) From thiocarbonyl derivatives A novel, versatile route to difluoroalkoxyalkanes has been offered using bis(dimethoxyethylene)amino sulfur trifluoride in the presence of antimony trichloride. A number of thiocarbonyl methyl esters have been converted to the corresponding difluoroalkoxyalkanes in high yields (Equation (7)) <1999JOC7048, 2000JOC4830>. S R
O
Me
DAST, SbCl3, CH2Cl2, 20 °C, 4 h
F
F
R
O
Me
ð7Þ
R = Ph, 96%; cyclohexyl, 95%
S-Methyl thioxanthates, reacting with hydrogen fluoride or bromotrifluoride in the presence of DBH (1,3-dibromo-5,5-dimethyl)hydantoin), produce appropriate difluoroalkoxyalkanes. The latter reaction can be described as an oxidative desulfurization–oxidation process (Equation (8)) <1999JFC(97)75, 2000BCJ(73)471>. Sulfuryl chloride has been used for transformation of acetyl methoxy(thiocarbonyl)sulfide to the corresponding disulfenyl chloride <1997JMC864>. S RO
70% HF/pyridine, DBH, CH2Cl2, –78 to 0 °C, 1 h S
Me
F F R
R
= Decyln,
S
Me
ð8Þ
89%; p -BrC6H4, 62%
(viii) From mixed haloalkanes A halogen atom (Cl, Br, or I) at or position to a carbon atom bearing fluorine is easily substituted by the phenolate anion. In the presence of sodium hydroxide the reaction occurs easily in both protic and aprotic solvents. Substitution predominates over elimination and appropriate products are formed in moderate to good yields (Scheme 14) <1997KGS(33)967, 1998T4849, 1999KFZ(33)40, 2000JFC(102)369, 2000JFC(105)129, 2001JFC(107)89, 2001JMC2869, 2002T4077, 2002TL7353>. Sometimes pressure is necessary to accomplish the reaction, however, it does not help to prevent the elimination <2001JFC(107)89>.
31
Functions Containing Halogens and Any Other Elements F I
F
F
F
Cl F F
O
p-cresol, KOH, DMSO, 80 °C, 6 h
F
O
26%
F
F
F
Me O p -cresol, NaH, 1,4-dioxane, ∆, 3 h
O
100%
OH
OH
F O
F
Me
HO I F F
F
OEt KF, DMSO, 120–130 °C, 6 h
F
O
50%
F
F
F
O
F
OEt Phenol, KOH, H2O, 250 °C, 11 h
O
36–480 torr F 3C
Cl 72%
F I
OEt
i
I
F
F
OEt
F F
O
F
O
O
O
i. phenol, NaH, DMF, 20 °C, 4 h, 80%
Scheme 14
(ix) From trihaloalkyl derivatives Treatment of 2,2,2-trifluoroethyl chloride with alcohols or phenols and aqueous potassium hydroxide in an autoclave at 240–280 C gives the corresponding 2-chloro-1,1-difluoroethyl ethers in good yields (Scheme 15) <2002JFC(113)79>.
F
ROH, KOH, H2O F3 C
Cl
60–100 atm. 10–15 h, 250–285 °C
RO
F
ArOH, KOH, H2O F 3C
F
Cl
Cl
40–50 atm. 250 °C, 11 h
F Cl
ArO
R
(%)
Me Et Bun But MeCF2
55 67 42 0 70
Ar
(%)
Ph p-MeC6H4 o-MeC6H4 p-(But)C6H4
76 73 52 67
Scheme 15
(x) From other compounds Alcohols can be transformed into alkyl perfluoroethyl ethers using 2-trifluoromethyl-1,2-dithianylium triflate (Scheme 16) <2003TL5995>.
32
Functions Containing Halogens and Any Other Elements S +
i. NaH, ii .
CF3
– F3CSO3
S
RO
CF3
S
S
ROH
F
DBH, HF–Py RO
F F
F
83%; p-O2NC6H4O- 23%
54%;
R = c-C6H11–
F
Scheme 16
Fluorination of esters by gaseous fluorine leads to perfluorination of both alkyl groups without affecting the ester function (Equation (9)) <1998JA7117>. The same concerns fluorination of alkoxyesters (Scheme 17) <2001JFC(112)109>. O C11H23
O
F2, 25 °C
C11F23
F
O Cl
O
Cl
F C F 3 7 O CF3
ð9Þ
C4F9-t
C4H9-t
O
F
O
O
O
F
F F
i
F
F
F
F
O Cl
63%
F
F
Cl
CF3
F F
O
C3F7 O
CF3
i. F2, 20–40 °C, 0–1500 torr O C10H21
O
O
F2, 20–40 °C, 0–1500 torr
O
O C3F7 CF3
F2, 20–40 °C, 0–1500 torr
F
O
F
78%
O F 3C
CF3
F OC3F7 CF3
O
F F
F F
O
F
69%
F O
O
C10F21
O
O
F O
F F OC3F7 CF3
O C3F7 CF3
O CF3
Scheme 17
6.02.1.1.2
Tetracoordinated carbon atom bearing mixed halogens and one oxygen function (R1CHal2OR2)
Addition of chlorine to methyl perfluorovinyl ethers has been reported as a versatile route to chlorofluoroethers (Equation (10)) <1996JOC8024, 2001T4111, 1998JFC(88)51>. A highly selective exchange of chlorine by fluorine atom in trichloromethyl group of hexafluoroisopropyl trichloromethyl ether, using dichloroacetyl fluoride, has been observed. The use of antimony pentachloride in a similar process has also been reported <1999JFC(94)1>. Introducing four chlorine atoms into tetrafluoroethyl methyl ether has been achieved by photochemical chlorination using gaseous chlorine (Equation (11)) <1995JOC1319, 1999JFC(93)93>. F
OMe
F
F
Cl2, –196 to 20 °C, 5 min 97%
Cl F Cl
F OMe
F
ð10Þ
33
Functions Containing Halogens and Any Other Elements F
F Cl
Cl2, hν, 30 h
F3C
Me
O
F3C
74%
O
ð11Þ
CCl3
A synthesis of chiral enantiomerically pure chlorofluoromethyl tetrafluoroethyl ethers was described. The starting racemic trichloromethyl ether was subjected to fluorination with antimony trifluoride– bromine giving dichlorofluoromethyl ether in 51% yield. Irradiation of the latter with UV light in 2-propanol afforded racemic ether in 49% yield. Application of the above conditions to enantiomerically pure (R) and (S) ethers gave the target ethers respectively with only a very little erosion of the enantiomeric excess (ee). The importance of the latter result comes from the following: volatile halogenated chiral ethers are often used as anesthetics; in common with many other chiral pharmaceuticals, the optical antipodes can differ in pharmacological profile (Scheme 18) <1995JOC1319>. O Cl3C F
CF3
SbF3, Br2
H
45–56%
F Cl
O Cl
F
CF3
2-Propanol, hν 43–47%
H
F H
O Cl
F
CF3 H
Scheme 18
6.02.1.1.3
Tetracoordinated carbon atom bearing one halogen and two oxygen functions (R1CHal(OR2)2)
Compounds with a tetracoordinated carbon atom bearing one halogen and two oxygen atoms seem to be quite common and well known. Numerous examples of compounds of this class exist and their syntheses have been reviewed <1995COFGT(6)35>. The compounds are usually prepared either from 1,3-dioxolanes or from o-formates using a variety of halogenating agents. More recently one unusual example of the synthesis has been reported. Fluorosulfonic acid and sulfur dichloride reacting with trifluoromethyl trifluorovinyl ether yielded a product containing rests of both reagents added to the starting alkene. The products contain a tetracoordinated carbon atom bearing one halogen and two oxygen atoms (Scheme 19) <1996IZV(7)1745>. It appears that no further advances have occurred in this area since the publication of <1995COFGT(6)35>. SCl2, HSO3F, 30–35 °C
F
F
F
O CF3
F
F
O S O OF
33%
F Cl S O CF3
Scheme 19
6.02.1.2
Halogen and Sulfur Derivatives (R1CHal2SR2 and R1CHal(SR2)2)
The synthetic methods for preparing carbohydrates bearing a C-branched substituent of the type CF2-Y (e.g., n-CnF2n+1) where Y = heteroatom (O, S, P) were reviewed by Plantier and Portella. Examples of the syntheses are given in Scheme 20 <2000CAR119>. F
O
PhSH, AIBN F
(OR)3
PhH, ∆, 92%
F
O (OR)3
F
F
O F (OR)4
SPh
F
PhSH, AIBN
F
PhH, ∆, 79% (OR)4
Scheme 20
SPh
O
34 6.02.1.2.1
Functions Containing Halogens and Any Other Elements Tetracoordinated carbon atoms with two identical halogen and one sulfur function attached (R1CHal2SR2)
(i) From sulfides Halogenation of sulfides is the most popular method for the preparation of compounds described in this sub-chapter. Several new examples of fluorination of sulfides, containing other functional groups (not reported in <1995COFGT(6)35>) concern reactions under electrochemical conditions. The first reports on electrochemical difluorination of sulfides published by Fuchigami and co-workers appeared in 1995 (Scheme 21) <1995JOC3459, 1995JFC(73)121>.
i. Et3N–3HF, MeCN ii. aq. NH 4OH
F Ph
O
S
Et
F F Ph
O
S
Electrolysis, 57%
O
Et
O
Scheme 21
Carbonyl group or triple CC bond can serve in those fluorinations as activating groups (Scheme 22) <2001TL3009, 2002T5877>.
F F Ph
O
S
Ph
Et3N–3HF, MeCN
O
O
S O
Electrolysis, 11%
Et3N–5HF, MeO Ph
Ph
OMe
S
S
Electrolysis, 77% F
F
Scheme 22
Triethylamine–hydrogen fluoride complex was also used under electrochemical conditions for fluorination of sulfides in the -position to sulfur atom in compounds containing carboxyamide group (Equation (12)) <1999JFC(93)53>. O
O
Et3N–3HF, MeCN
Ph S NH2
Ph S
Electrolysis, 27% (not isolated)
ð12Þ
NH2
F
F
,-Difluorination of unactivated methylene group in sulfide was reported too (Scheme 23) <2001TL4861>.
Ph
S
O
O O
Et3N–3HF, MeO
OMe
Electrolysis, 40 °C, 68%
Scheme 23
F F Ph
S
O
O O
35
Functions Containing Halogens and Any Other Elements
Sulfides already containing one -fluoro atom can be fluorinated further to difluoro derivatives (Equation (13)) <1995T2605>.
F Ph S
F
Et3N–3HF MeCN, 2 h electrolysis
Ph F
Ph S
ð13Þ
Ph
F F
Fluorine atoms exchange with hydrogen in methylene group of sulfides, activated by carbonyl or cyano group linked to sulfur, in reactions with tetraethylammonium fluoride–hydrogen fluoride complex (Scheme 24) <1997JOC8579>.
n-C7H15 S
Et4NF–4HF
CO2Et
n-C7H15 S
MeCN, 50% electrolysis
Ph S
N
F
Et4NF–4HF
Ph S
MeCN, 50% electrolysis
CO2Et F
N
F F
Scheme 24
Electrochemical conditions have also been applied to difluorination of quinolin-2-yl propan2-on-1-yl sulfide (Equation (14)) <1999JOC138>.
Et4NF–3HF, MeO
O N
Electrolysis, 5% (not isolated)
S
O
OMe N
ð14Þ
S F
F
When the reaction of fluorination of sulfides is carried out in the presence of 1,3-dibromo5,5-dimethylhydantoin, fluorine atoms can substitute both hydrogen atom and carboxylic group attached to a methylene carbon atom (Scheme 25) <1998JFC(87)215>.
Ph S
CO2H C6H4-Cl-p
F
i 30%
Ph S
F
C6H4-Cl-p
i. Et3N–3HF, CH2Cl2, 1,3-dibromo-5,5-dimethylhydantoin, electrolysis
Scheme 25
Addition of pentafluoroiodine to triethylamine–hydrogen fluoride complex enables one to perform difluorination in hydrocarbon solvents without electrolysis. Usually improved (moderate or high) yields of products are obtained, though the reactions carried out at lower temperatures require a considerable length of time (Scheme 26) <2001CL222, 2002BCJ(75)1597>.
36
Functions Containing Halogens and Any Other Elements Ph
F F
Ph
S
IF5–Et3N–3HF, hexane, 63 °C, 4 h
O
Ph
S
45%
F Et
Ph
F
O F F F
IF5–Et3N–3HF, heptane, 74 °C, 1 h
Et
82%
S
S O
O Ph
O
S
S
C4H9
O
C4H9
F F
IF5–Et3N–3HF, hexane, 40 °C, 216 h
Et
Ph
F
F F Ph
36% F
O
S
Et
O F F F
IF5–Et3N–3HF, hexane, 40 °C, 4 h Et
80%
S
Et
O
IF5–Et3N–3HF, hexane, 40 °C, 216 h Et
O
S
O
Et
N
S
69%
O
F S
F F p-ClC6H4
36%
O
Ph
S O
IF5–Et3N–3HF, heptane, 80 °C,12 h
O
Ph
Ph
79%
N
S
Et
F F
IF5–Et 3N–3HF, heptane, 40 °C, 6 h
O Ph
O
S O
O
p-ClC6H4
Ph
59%
Ph
S
F F
IF5–Et3N–3HF, hexane, 63 °C, 4 h Et
O
Ph
F
F
S
O
O
Scheme 26
Rather recently a new fluorinating agent namely N-fluoro-2,4,6-trimethylpyridinium triflate has been shown to efficiently difluorinate several sulfides in the presence of zinc dibromide. The reaction occurs in chlorinated hydrocarbons at elevated temperatures affording products in high yields (Scheme 27) <2000CPB1097>. In another paper the same authors have reported even higher yields of the products (Scheme 28) <2001CPB173>.
O p-MeOC6H4
S
i 64%
O p-MeOC6H4
S F F
i. ZnBr2, N-fluoro-2,4,6-trimethylpyridinium triflate, Cl2HCCH2Cl, 100 °C, 1.5 h Ph
Ph
S O
i 76%
F F Ph
S
Ph
O i. ZnBr2, N-fluoro-2,4,6-trimethylpyridinium triflate, Cl2HCCH2Cl, 105 °C, 1.5 h
Scheme 27
37
Functions Containing Halogens and Any Other Elements F Et
F
F F F
i Et
85%
S
F
S
O
O
i. ZnBr2, N-fluoro-2,4,6-trimethylpyridinium triflate, Cl2HCCH2Cl Ph
Ph
S O
F F
i
Ph
82%
Ph
S O
i. ZnBr2, N-fluoro-2,4,6-trimethylpyridinium triflate, Cl2HCCH2Cl, 85–105 °C
Scheme 28
A high yield of difluorinated sulfide can be obtained by the treatment of ethyl -(phenylthio)acetate with difluoroiodotoluene in dichloromethane at a low temperature (Scheme 29) <2000TL4463>.
Ph
O
S
F F
Difluoroiodotoluene, CH2Cl2, 0 °C
Et
Ph
O
S
80%
O
Et
O
Scheme 29
Triethylamine–hydrogen fluoride in acetonitrile, in the presence of zinc dibromide, was used for difluorination of only one methylene group in 2,8-dioxa-5-thia-nonan-3,6-dione (Equation (15)) <2002SL996>. F F O
O
S O
Et3N–3HF, ZnBr2, MeCN
O
O
O
S O
ð15Þ
O
Moderate yields of -bromo-,-difluoro--methylthioketones are obtained from ,-dimethylthio-,-unsaturated ketones by treating them with hydrogen fluoride–pyridine in the presence of 1,3-dibromo-5,5-dimethylhydantoin (Scheme 30) <1998TL9651> or mercury trifluoroacetate (Equation (16)) <2000JFC(101)35> as catalysts.
O
S
O Pr
S
HF, pyridine, i, CH2Cl2, –78 °C, 2 h 39%
Et
S Et Br O
S
O
S
F F
Pr
HF, pyridine, i, CH2Cl2, –78 °C, 2 h
F F S Br
39% i = 1,3-dibromo-5,5-dimethylhydantoin
Scheme 30
O Ph
S
Pyridine–6HF, Hg(OCOCF3)2, CH2Cl2, 20 °C, 24 h S
76%
O
F F
Ph
S Et
ð16Þ
38
Functions Containing Halogens and Any Other Elements
Dichlorination of sulfides is a popular route to ,-dichloroalkyl sulfides and can be achieved easily using several chlorinating agents, e.g., sulfuryl dichloride. Pommelet and co-workers published several examples of such chlorination (Scheme 31) <1997T12565, 2002SL996, 1996TL2413>.
O
O Ph
SO2Cl2, CH2Cl2
S
Ph
S
72.5% O
S
Et
SO2Cl2, CH2Cl2 88.5%
O
Cl
Cl Cl
Cl O
Et
S O
O
O
S O
Ph
O
O
81.5% SO2Cl2, CH2Cl2, 20 °C, 2 h
O
S
Cl SO2Cl2, CH2Cl2
96.5%
O O
SO2Cl2, CH2Cl2
S
81%
Cl O
S O
O Cl
Cl Ph
O
S O
O S Cl Cl
Scheme 31
Partly fluorinated sulfides are dichlorinated in high yields using sulfuryl dichloride in chlorinated hydrocarbons (Scheme 32) <1997BSF697>. Under the conditions sulfuryl dichloride leaves the triple CC bond untouched (Equation (17)) <1997SC2993>.
F Ph
S
F F
F Ph
SO2Cl2, Cl2HCCH2Cl, ambient temp. 2 h
S Cl Cl
85%
F F
Cl Cl n-C3F7 S Pr
SO2Cl2, CH2Cl2, 2 h
n-C3F7
S Pr
S
88%
F
90%
F
Cl
Cl
SO2Cl2, CH2Cl2, 2 h
Et
F F
S
F
Et
F
Scheme 32
Ph S C6H13-n
SO2Cl2, CCl4, 0 °C, 30 min
Ph S Cl
C6H13-n
ð17Þ
Cl
Japanese chemists have reported an interesting dichlorination of enantiomerically pure chiral sulfide, not observing racemization at a carbon atom adjacent to the chlorinated one (Scheme 33) <2000TL4603>.
39
Functions Containing Halogens and Any Other Elements O
O O
O
SO2Cl2, CH2Cl2, 20 °C, 3 h
Ph S
F
Ph S
100%
F
Cl Cl F F
F F
Scheme 33
Gaseous chlorine was applied for ,-dichlorination of sulfide in methylene group activated by electron-withdrawing methanesulfonyl moiety <1997AJC683>. Gaseous chlorine is also easily added to ,-unsaturated sulfides. The addition can be followed by the replacement of a hydrogen atom (Scheme 34) <1998ZOR1792>, alkylthio- or alkyl-groups by additional chlorine atoms (Scheme 35) <2002IZV(6)948>.
Cl2, CCl4, 10 °C, 2.5 h
S
Cl
S Cl
68%
Cl Cl
Cl
Scheme 34
Bn S
Bn
Cl Cl S
Cl2, –78 to –50 °C, 29 h
S CO2–
Cl
CO–2 F3C Cl
49%
F3C
Scheme 35
Phosphorus pentachloride was used for unsymmetrical dichlorination of bis(benzoylmethyl)sulfide (Equation (18)) <1995ZOR1257>. Ph
Ph
S O
Cl
PCl5, CH2Cl2
Ph
43%
O
Cl Ph
S O
ð18Þ
O
Trifluoromethylation of organic halides with FO2SCF2CF2OCF2CO2K in DMF at 45 C was reported <1996JFC(78)177>. -Chlorinated--fluorinated sulfides are synthesized in good yields by nucleophilic fluorination of the corresponding dichlorosulfides. It can be achieved, e.g., with Et3N–3HF in refluxing acetonitrile <1996TL2413, 1997T12565>. Also chlorination of -fluorinated sulfides using SO2Cl2 leads to the formation of chloro--fluorosulfides, sometimes in very high yields (Schemes 36 and 37) (Table 1).
R S
CO2Me
2SO2Cl2
R
Cl S
Cl
PH2F3, CCl4
F S
CO2Me
2SO2Cl2 CO2Me
ca. 100%
R = Ph, Me, CO2Me
Scheme 36
R
Cl S
R = Ph 42%, Me 37%, CO2Me 75% R
R
Cl S
F CO2Me
F CO2Me
40
Functions Containing Halogens and Any Other Elements R R'
S
A
2SO2Cl2
R R'
Cl S
Cl
Et3N–3HF
A
R R'
Cl
F
S
A
Scheme 37
Table 1
Substituents and yields of products depicted in Scheme 37
R 25 C, 15–24 h Ph Me MeCO2 Ph Me Me Ph 180 C, 24–36 h Ph Me Ph Me Me Ph Me
R0
A
Yield (%)
H H H H H Me H
CO2Me CO2Me CO2Me COMe COPh COPh CN
67 78 56 41 67 54 0
H H H H Me H Me
CO2Me CO2Me COMe COPh COPh CN CO2Me
77 70 65 70 57 50 57
(ii) From halofluoroalkanes and derivatives The extensive studies on photochemical reaction of fluoroiodoalkanes with both methyl sulfide and dimethyl disulfide were reviewed earlier in <1995COFGT(6)35>. Photochemical substitution reaction of fluoroiodoalkane by thiole anion has recently been performed, leading to the corresponding sulfide in a high yield (Scheme 38) <1998SL1243, 2001JFC(108)95>.
n-C8F17I
RSH, liq. NH3, UV
n-C8F17 S
83% n-C6F13I
RSH, liq. NH3, UV 79%
RSH = HS
OEt O
n-C6F13 S
OEt O
OEt O
Scheme 38
Several recent reports bring examples of the nucleophilic substitution of 1-iodoperfluoroalkanes by thiols carried out in the absence of irradiation (Scheme 39) <1995JFC(74)123, 1998MI(8)1193, 1997JOC1457, 1995JOC6186>. Reactions of derivatives of ethyl difluoroiodoacetate with thiole anions either pre-generated or formed in situ are also known (Scheme 40) <2002TL2949>. Terminally iodinated perfluorohexane reacts with a derivative of 2-naphthothiol in dimethyl formamide in the presence of sodium ethanolate at room temperature to give the expected sulfide (Equation (19)) <1999CC2007, 2002JPCA3114>. S-(Perfluorooctyl) thioglycoside derivative can be obtained in a similar way under the different reaction conditions (Equation (20)) <1999JFC(98)55>.
Functions Containing Halogens and Any Other Elements
41
p-BrC6H4SH i. NaH, DMF, rt, 1 h n-C8F17I
p -BrC6H4-S-C8F17
ii. DMF, rt, 2 h p-MeC6H4SH NaH, DMF, rt, 24 h
n-C4F9I
p-MeC6H4-S-C4F9
77% p-HOC6H4SH NaH, DMF, rt, 24 h
n-C4F9I
n-C4F9-S-C6H4OH-p
30% p-MeC6H4SH, DBU benzene, rt, 15 h
n-C8F17I
n-C8F17-S-C6H4Me-p
60% PhSH, DBU benzene, rt
n-C8F17I
n-C8F17-S-Ph
50%
Scheme 39
O Et
F F
O F
F I
PriSH, Et3N DMF, 4 h, 30–40 °C
Pri
S O F F
O Et
Et
O
O F
ArSH, Et3N
F I
Et
DMF, 30–40 °C, 4 h
O
S
Ar
O
Ar = N
Scheme 40
n-C6F13I
ArSH, EtONa, DMF, rt, 24 h
ð19Þ
O Ar = O
n-C8F17I
n- C6F13-S-Ar
Pri O
RSH, NaHCO3, Na2S2O4 DMF, H2O, 20 °C, 1.5 h OAc
n-C8F17SR
ð20Þ
O R=
OAc AcO
OAc
Reaction of 1-iodoperfluorobutane with propane-1,3-dithiol occurs under very mild conditions. Both thiol groups react, affording a moderate yield of the corresponding sulfide (Scheme 41) <2000JFC(105)41>.
42
Functions Containing Halogens and Any Other Elements HS n-C4F9I
SH, Na3PO4
n-C4F9S
DMF, 15 min, 20 °C, 45%
SC4F9-n
Scheme 41
1,1-Difluoro-1,3-diiodoheptane in reaction with thiophenol, following its deprotonation by sodium hydride, behaved differently producing an unsaturated sulfide (Equation (21)) <2001JFC(107)89>. I
F
SPh
PhSH, NaH, DMF
I F
F
ð21Þ F
The respective sulfide was produced by the nucleophilic substitution of a bromine atom, in bromodifluoromethyl group attached to benzoxazole moiety, using 2-thiopyridone anion (Equation (22)) <2000JFC(102)369, 2001JFC(109)39>. HS N
N
F
O
F
N
, NaH
Br
N
ð22Þ
S DMF, rt, 23 h
F
O
F
Novel styrene and dimethylisophthalate monomers, with pendant lithium fluoroalkylsulfonate or sulfonimide functional groups and containing perfluoroalkyloxy substituents, were prepared from the corresponding phenolic intermediates. Necessary formation of CF2S fragment was achieved by substitution of bromine atom in a terminal CF2Br group by SO2Na anion (Scheme 42) <2000JFC(105)129>.
p-BrC6H4OCF2CF2Br
Na2S2O4, NaHCO3, DMF H2O, 75 °C, 3 h, 97%
p-BrC6H4OCF2CF2SO2Na
Scheme 42
(iii) From a,a-dichloroalkyl sulfides Dichloroalkyl sulfides are convenient starting materials for the preparation of chlorofluoroalkyl, bromofluoroalkyl, and difluoroalkyl sulfides <1995COFGT(6)35>. Fluorination of dichloroalkyl sulfides containing additional functional groups has been widely studied by Pommelet et al. They described the synthesis of alkylsulfanyldifluoroacetates and ketones by the Halex reaction. The remarkable reactivity of difluorothioacetate derivatives opened rapid access to the preparation of useful building blocks such as gem-difluoroketones and amides (Schemes 43 and 44) (Table 2) <2003TL5061>. Cl
R R'
S
A
R
2SO2Cl2
R'
S
Cl
R
Et3N–3HF
A
R'
Scheme 43 F PhS
F
RM, THF, rt CO2Me
–78 °C, 0.5 h
F R Me H2C= CH H2C= CH-CH2
M
Yield (%)
Li MgBr MgBr
80 70 82
Scheme 44
F
S
A
(b)
(a)
A = CO2Me, COMe, COPh
Cl
PhS
COR F
43
Functions Containing Halogens and Any Other Elements Table 2 Substituents and yields of products depicted in Scheme 43 R0
Product (a) yield (%)
Product (b) yield (%)
CO2Et CO2Me CO2Me CO2Me COPh COMe COMe COPh
52 70 75
70 52 75 80 61 72 68 54
R Ph Bz MeO2CCH2 AcO(CH2)2 Et Bz Ph Ph
70 65
An exchange of chlorine atom in ,-dichlorofluoropentyl benzyl sulfide using antimony pentafluoride in acetonitrile was reported (Scheme 45) <1998ZOR1012>. F
F F Cl
SbF5, MeCN, ∆,1 h
Cl
F
S
F
56%
Ph
F F F Cl
F
F F F F
S
Ph
F F F F
Scheme 45
(iv) From tri- or tetrahalomethanes Only a few examples of substitution of a chlorine atom in chlorodifluoromethane by thiols, using a variety of conditions, have been reported in <1995COFGT(6)35>. A mechanism of the substitution had been under discussion pointing to both a carbene and SN2 type character. Since then many new syntheses of dihaloalkyl sulfides have been published. Such methane derivatives like difluorodiiodomethane, chlorodifluoromethane, trifluoro-, and trichloromethanes were applied as starting materials. It appears from these reports that the carbene mechanism predominates. The treatment of difluorodiiodomethane with thiophenol in the presence of sodium hydride affords difluoromethyl phenyl sulfide in a low yield (Equation (23)) <2000JFC(102)105>. F F
I
PhSH, NaH, DMF, 20 °C
F
12%
F
I
SPh
ð23Þ
The majority of reported syntheses starts from chlorodifluoromethane. A high yield of the respective sulfide is obtained while treating chlorodifluoromethane with ethoxycarbonylmethylthiol in the presence of sodium ethanolate in ethanol (Scheme 46) <2000CPB509>. Also thiophenol reacts smoothly with chlorodifluoromethane, this time in the presence of sodium hydroxide in aqueous dioxane (Scheme 47) <1996IZV(45)162>. EtOCOCH2SH, EtONa F Cl F
EtOH, 1 h, heat
F
80%
F
SCH2CO2Et
Scheme 46
F Cl F
ArSH, NaOH dioxane, H2O, 45 °C, 3.3 h
F
89%
F
Ar = C6F5
Scheme 47
SAr
44
Functions Containing Halogens and Any Other Elements
Heteroaromatic thiols can substitute a chlorine atom in chlorodifluoromethane. An example of this type of reaction is reported to give the respective sulfide in a low yield (Scheme 48) <2001JFC(108)211>. A similar method was used for the preparation of a sulfide containing, beside difluoromethyl group, a large chiral substituent (Equation (24)) <1998JAN374>.
ArSH, KOH, DMF F Cl
DMF, 50–120 °C, 5 min
F
24%
F
F
SAr
N
Ar =
N
EtO
Scheme 48
F
F
RSH
Cl
SR
F
F Si O
ð24Þ SH N
RSH = O
O
C6H4NO2-p
Another enlarged substituent was introduced into a prepared sulfide in the presence of potassium t-butoxide. The reaction was carried out in tetrahydrofuran (Equation (25)) <1996JMC757>. F Cl
RSH, t-BuOK, THF, 0 °C, 30 min
F SR
F
F O
SH RSH =
ð25Þ
O
H
O
H O
Only one example of sulfide formation starting from trifluoromethane has been found. Dioctyl disulfide was used in the reaction as a precursor of an attacking S-nucleophile (Scheme 49) <2000JOC8848>.
n-C8H17SSC8H17-n
F F F
Me3SiSiMe3, DMF, THF
F n-C8H17S
F
–15 to –20 °C, 17.5 h 45%
Scheme 49
Also only one example of synthesis of sulfides starting from trichloromethane has been spotted. The reaction was performed under PTC conditions and doubtlessly followed the carbene mechanism resulting in insertion of dichloromethylene between sulfur atom and vinyl group (Scheme 50) <2000CHE201>.
45
Functions Containing Halogens and Any Other Elements H N
H N
S
Cl
N
Cl Cl
Cl
Cl
S
TBAB, NaOH aq. 50% 45–55 °C, 25 h 21%
N
Scheme 50
(v) From thioformates, thioesters, and ortho-trithioesters COFGT (1995) <1995COFGT(6)35> has brought only examples of dichlorination of alkyl thioformates yielding alkyl dichloromethyl sulfides. Since then several new approaches to the synthesis of dihaloalkyl sulfides have been designed starting with dithioesters or ortho-trithioesters. (a) From dithioesters. Thiocarbonyl group in dithioesters can be exchanged by difluoremethylene moiety using mercury(II) fluoride–potassium fluoride mixture in tetrahydrofuran in the presence of pyridinium hydrogen fluoride (Equation (26)) <1996TL3223>. S Ph
F F
HgF2, KF, THF S
HF–pyridine
Ph
ð26Þ
S
Similar results (the exchange of sulfur atom by two fluorine atoms) were achieved using tetrabutylammonium–hydrogen fluoride complex in the presence of N-iodosuccinimide (Scheme 51) <1999BCJ805> or by treating dithioester with bis(2-methoxyethyl)aminosulfur trifluoride in the presence of antimony(III) fluoride (Scheme 51) <2000JOC4830>. N-iodosuccinimide, Bu4n N–H2F3, CH2Cl 2
S p-Ph-C6H4
S
F p-Ph-C6H4
F S
86%
F
S S
N-iodosuccinimide,
Bu4nN–H2F3,
CH2Cl2
F S
52%
p-(t-Bu)C6H4
S
bis(2-methoxyethyl)aminosulfur trifluoride
S
SbCl3, CH2Cl2, 20 °C,1 h 74%
F p-(t-Bu)C6H4
F S
Scheme 51
(b) From ortho-trithioesters. In 1998, Japanese chemists published two papers on synthesis of ,-difluoroalkyl sulfides from ortho-trithioesters. The use of Et2SF3 led to the formation of the desired sulfide in a very low yield <1998BCJ2687>. In contrast to that, the same authors achieved very good results of difluorination, applying tetrabutylammonium–hydrogen fluoride complex in the presence of 1,3-dibromo-5,5-dimethylhydantoin (Scheme 52) <1998BCJ1939>.
(vi) From alkenes The first report on synthesis of dichloroalkyl sulfides via chloroalkenes was probably published in 1958. Since then additions of thiols or disulfides to alkenes have been reported several times <1995COFGT(6)35>. In the last few years haloalkenes became rather common substrates in syntheses of dihaloalkyl sulfides. Several haloalkenes such as tetrafluoroethene, chlorotrifluoroethene, alkoxytrifluoroethene, 1,1,2-trifluoroalkenes, 1,1-dichloro-2,2-difluoroethene, and 1,1-difluorethene were used in reactions with thiols, disulfides, or other sulfur compounds to yield difluoroalkyl sulfides.
46
Functions Containing Halogens and Any Other Elements S
Ph
F
Ph
Et2NSF3, CH2Cl2, 0 °C, 10 min
S S
13%
O
OH
S
Ph
F
Ph
Bu4N–H2F3, i. CH2Cl2, 10 min
S S
S F
51%
S F
O
O F S Ph
S Ph
Bu4N–H2F3, i. CH2Cl2, 20 min
S S
79%
S O
F Ph
51%
OH Ph
Br
Bu4N–H2F3, i. CH2Cl2, 10 min
S S
S F
O F
Ph
Bu4N–H2F3, i. CH2Cl2, 10 min
S S
S F
Ph
O
62%
S F
F
i = 1,3-dibromo-5,5-dimethylhydantoin
Scheme 52
Reaction of tetrafluoroethene with sulfur chloride leads to the formation of mixtures of compounds in proportions depending on the conditions used. One of the products is shown in Equation (27) <2001JFC(112)325>. F F
F F
S2Cl2, HF, BF3 40 °C, 12 h
F F F
F S
S
Cl
ð27Þ
F and others
Irradiated 1,1,2-trifluoro-1,4-pentadiene reacts smoothly with mercaptoacetic acid. A high yield of the addition of two molecules of the nucleophile to both double bonds is observed. When the reaction is conducted in the presence of azobisisobutylnitrile, an initiator of a radical process, the yield drops down (Scheme 53) <1998JFC(92)77>.
F
F
F F
O
F F
F
F
HO2CCH2SH, MeCN, PhCOPh
O
irradiation, 81%
HO
S
S
O
F F
HO2CCH2SH, AIBN, MeCN
O
80 °C, 7 h, 37%
HO
S
OH
S
OH
Scheme 53
Sodium thiophenolate is added easily though slowly to chlorotrifluoroethene in ethanol affording 2-chloro-1,1,2-trifluoroethyl phenyl sulfide <1997T17127, 1998TL6529>. At higher temperatures the reaction proceeds faster without affecting a yield (Scheme 54) <2000T3539>. Products distribution in reactions between chlorotrifluoroethene, 1,1-difluoroethene and ethylene thioglycol has been studied in detail. One of the major products is 2-chloro-1,1,2,4,4pentafluorobutyl 20 -hydroxyethyl sulfide (Scheme 55) <1995JFC(74)37>.
47
Functions Containing Halogens and Any Other Elements F
F
PhSNa, EtOH, 15 h
F
Cl
76%
F
F
F
F F Ph
Cl
S F
F F
PhSH, NaOH, 120 °C, 6 h
Ph
85%
Cl
Cl
S F
Scheme 54
F HOCH2CH2SH, Bz2O2
F F
F F HO
F
S
MeCN, 80 °C, 4 h
Cl
F
F Cl
F
Scheme 55
Chlorotrifluoroethene forms the respective chlorotrifluoroethyl phenyl sulfide in reaction with diphenyl disulfide under electrochemical conditions. The yield of the product is reasonable (Equation (28)) <1998CCC378>. F
F
F
Cl
F F
PhSSPh, MeCN Electrolysis, 30%
Ph
Cl
S
ð28Þ
F
Fluorosulfonic acid and sulfur dichloride reacting with trifluoromethyl trifluorovinyl ether yield a product containing fragments of both reagents added to the double bond in the starting ether (Equation (29)) <1996IZV(7)1745>. F F F
SCl2, HSO3F, 30–35 °C
F F
F
O
32.5%
F F
F
O
S O O F O F
S
Cl
ð29Þ
F F
Several new examples of addition of thiols to 1,1-dichloro-2,2-difluoroethene have been reported. The reaction is highly regiospecific, leading to the formation of ,-difluoro,-dichloroethyl sulfides usually in very good yields (Scheme 56) <1995JFC(73)27, 2000T3539>. When N-(t-butylcarboxy)-2-thiopyridone (instead of a thiole) is added to dichlorodifluoroethene, the reaction of addition is accompanied by migration of the N-substituent, and ,-difluoro-,-difluoroalkyl 2-pyridyl sulfides are obtained (Scheme 57) <1992TL3491, 1995T1903, 1997JOC7192>.
F
Cl
n-C6F13CH2CH2SH, MeCN
F
Cl
Butperpivalate, 70 °C, 4 h
F
Cl
PhSH, NaOH, 120 °C, 8 h
F
Cl
90%
Cl n-C6F13CH2CH2S
Cl Cl
Ph S F F
Scheme 56
Cl F F
48
Functions Containing Halogens and Any Other Elements F F
N Cl
i. MeCN, irr.
Cl
52%
Cl N
i=
O S
Cl But
S F
F
O But
F
Cl
i. CH2Cl2, irr. 5 h
F
Cl
35%
N Cl Cl S F F
i=
N
O O
S
Scheme 57
Novel sulfides, sulfones, and fluorovinyl ethers were prepared using tetrafluoroethylene as the only fluorinated substrate. Addition of thiole sodium salts and carbon dioxide to tetrafluoroethylene, followed by dimethylsulfate, provided corresponding methyl sulfide-esters. Reduction of the sulfide-esters by sodium borohydride gave sulfide-alcohols. Oxidation of the sulfide-esters with HOF in acetonitrile resulted in the formation of the corresponding sulfone-esters. Conversion of the sulfide-alcohols to their sodium salts with sodium hydride in diglyme, followed by the addition to tetrafluoroethylene, provided sulfidetrifluorovinyl ethers. The latter readily co-polymerized with tetrafluoroethylene to give higher molecular weight co-polymers (Scheme 58) <1999JFC(93)93>.
O F F R S O F F
HOF MeCN, 80%
F F
F F
F F
i. RSNa, CO2, DMSO ii. (MeO) 2SO2
F F
R = Me R = But F F
OH
RS F F
ii. F2C=CF2
O
EtOH
F F RS
O F F
NaBH4
80% 84%
i. NaH, diglyme R = Me, But
O
R S
O
OH
R S F F >90% >90%
OCF=CF2
F F ~60%
Scheme 58
(vii) From carbon disulfide Elemental fluorine reacting with carbon disulfide at 120 C affords fluorinated sulfide. No further advances have occurred in this area since the work of Shimp and Lagov <1977IC2974> cited in <1995COFGT(6)35>.
(viii) From a-fluoroalkyl sulfoxides One example of Pummerer-type reaction was reported in <1995COFGT(6)35>. No further advances have occurred in this field since that publication.
49
Functions Containing Halogens and Any Other Elements (ix) From perfluoroalkanecarboxylic acid salts
Diphenyl disulfides react with potassium salts of perfluoroalkanecarboxylic acids at elevated temperatures affording moderate yields of perfluoroalkyl phenyl sulfides (Scheme 59) <2001JFC(107)311>.
n-C3F7COOK
PhSSPh, DMF, 130 °C, 6 h
PhSC3F7-n
29% C2F5COOK
PhSSPh, DMF, 145 °C, 5 h
PhSC2F5
42%
Scheme 59
6.02.1.2.2
Tetracoordinated carbon atoms bearing mixed halogens and one sulfur function (R1CHal2SR2)
Thiolate additions to mixed chlorofluoroalkenes under radical, ionic, or electrochemical conditions were employed to prepare mixed dihaloalkyl sulfides <1995COFGT(6)35>. As one can see from examples shown here (in equations and schemes), the reactions used resemble those described in the former section of this chapter. Fluorination of chloroalkyl sulfide has been reported too (Equation (30)) <1995JOC3459>. Et3N–3HF, MeCN, 20 °C
Cl Ph S
Cl F Ph S
Electrolysis, 66%
CO2Et
ð30Þ CO2Et
Pommelet et al. elaborated several reactions leading to mixed dihaloalkyl sulfides (Scheme 60) <1996TL2413>. Particularly interesting is the practically quantitative, highly regiospecific chlorination of methyl esters of -alkylthio--fluoroacetic acid, using sulfuryl dichloride. R S
2SO2Cl2
R
CO2Me
Cl
Cl
PH2F3
S
A
CCl4
R
Cl
F
S
A
R = Ph 42%, Me 37%, CO2Me 75% F
R S
2SO2Cl2
R
ca. 100%
CO2Me
Cl
F
S
A
R = Ph, Me, CO2Me F O O
O
S O
SbCl3, DAST, rt, 2–3 d
O
O
F Cl O
S O
O
S O
F O
O
SO2Cl2
O O
O
O
S O
Scheme 60
-Chlorinated--fluorinated sulfides were synthesized in good yields by the nucleophilic fluorination of the corresponding dichlorinated sulfides, formed in the first step of the reaction. It can be achieved with Et3N-3HF in refluxing acetonitrile. A number of examples are given in the scheme-explaining table (Scheme 37, Table 1) <1997T12565>. Addition of cysteine N-acetyl derivative to 1,2-dichloro-1,2-difluoroethene in the presence of sodium amide at 50 C occurred without racemization (Equation (31)) <1996MI1092>.
50
Functions Containing Halogens and Any Other Elements
F Cl
F Cl
RSH, NaNH2, liq. NH3, –50 °C
AcHN
CO2H H
F Cl
S CO2H RSH = AcHN H
F
Cl
ð31Þ
SH
6.02.1.2.3
Tetracoordinated carbon atoms bearing one halogen and two sulfur functions (R1CHal(SR2)2)
No further advances in the field of the title compounds synthesis have occurred since the publication of COFGT (1995) <1995COFGT(6)35>. Only an interesting transformation of a compound of this class was reported (Equation (32)) <1996CB1383>. Me3SiCl, 50 °C, 6 h (F3CS)2CBrCO2H
6.02.1.3 6.02.1.3.1
83%
(F3CS)2CBrCO2SiMe3
ð32Þ
Halogen and Se or Te Derivatives (R1CHal2SeR2 or R1CHal2TeR2) Tetracoordinated carbon atoms bearing two halogens and one selenium function (R1CHal2SeR2)
Several examples of compounds of the type reviewed in this section have been reported. Their preparation often involves transmetallation reactions of metal selenyl dihalomethyl derivatives. Also numerous examples of organoselenium metal complexes are known. In some cases almost quantitative yields of the products are obtained. Sometimes mixtures of organoselenium compounds are produced and neither the conditions of reactions nor yields are provided <1995COFGT(6)35>. Some advances that have occurred in this field since the publication of COFGT (1995) are presented here.
(i) From difluoroiodoalkane, bromodifluoroalkane, or chlorodifluoroalkane derivatives Twelve years ago Uneyama and Kitagawa reported shortly that butylphenyl selenide together with other products can be obtained by reaction of (nanofluorobutyl)iodide with diphenyl diselenide (Equation (33)) <1991TL375>. Ten years later the same method, under modified conditions, was applied for the preparation of perfluoroalkyl phenyl selenides in high yields (Scheme 61) <2001SL1260>.
C4F9I
NaBH4, PhSeSePh, EtOH, 0 °C, 15 min
C4F9SePh
rt, 2 h, 1-hexene
n-C4F9I
PhSeSePh, NaO2SCH2OH, DMF, H2O, 20 °C
n-C4F9SePh
57% n-C8F17I
MeSeSeMe, NaO2SCH2OH, DMF, H2O, 20 °C 79%
Scheme 61
n-C8F17SeMe
ð33Þ
51
Functions Containing Halogens and Any Other Elements
Bis(Pentafluoroethyl)selenide has also been formed from pentafluoroethyl iodide and selenium in the presence of copper metal (Equation (34)) <2000JFC(102)301>. C2F5I
Se, Cu, 220–230 °C, 15 h
ð34Þ
C2F5SeC2F5
Irradiation of mixtures of -chloro-,-difluorotoluene with sodium arylselenolates in dimethyl formamide results in the formation of aryl ,-difluorobenzyl selenium (Scheme 62) <1996BCJ2019>.
F
F
ArSeNa, EtOH, DMF, 100 °C
Ph
Cl
Ph
Irradiation
F
Se Ar F
Ar = Phenyl, 89%; naphthyl, 84%
Scheme 62
Reaction of N-allyl bromodifluoroacetamide with bis(phenyl)diselenide results in the substitution of a bromine atom by phenyl selenide group (Equation (35)) <1997TL7763>. O N H
O
PhSeSePh, NaBH4, THF, EtOH, 0 °C, 3 h
F Br
45%
F
F
N H
Se Ph
ð35Þ
F
(ii) From 1,1-difluoroalkene derivatives Chlorotrifluoroethene reacting with bis(phenyl)diselenide in acetonitrile under electrochemical conditions affords 2-chloro-1,1,2-trifluoroethyl phenyl selenide in a good yield (Equation (36)) <1998CCC378>. F
F
F
PhSeSePh, MeCN, electrolysis 57%
Cl
F
F
F
Cl
ð36Þ
Ph Se
Selenium compounds can be added to the double bond of 1,1-difluoroethene derivatives bearing a variety of additional substituents (Scheme 63) <2000TL7893, 2002CEJ2917>. EtO2C
F
p-MeOC6H4 N F SiMe3
EtO2C
F
p-MeOC6H4 N
F
PhSeF, CH2Cl2, –78 °C 64%
SePh
O
O F
N Ph
N
F
F
i. PhSeCl, TfOSiMe 3, hexane, THF, 20 h ii. H2O, hexane, THF, 1 h, 60%
N Ph
N
Se Ph F
Scheme 63
A mixture of reduced products containing ,-difluoromethyleneselenium moiety is obtained in the reaction of difluoromethyl phenyl selenoxide with dimethyl sulfide and acetic anhydride in dichloromethane. Similar reductions, unfortunately also leading to very low yields of difluoromethyl phenyl selenide, are observed in reactions of the selenoxide with mixtures of e.g., BuOBuAc2O, MeOCH2CH2OMeAc2O, (CH2)3OAc2O, (CH2)5OAc2O, etc. (Scheme 64) <1995JOC370>.
52
Functions Containing Halogens and Any Other Elements O Ph Se
F F
O Ph Se
F F
SMe2, Ac2O, CH2Cl2, ∆, 4 h
F Ph Se
6%
SMe2, Ac2O, CH2Cl2, ∆, 4 h
F F Ph Se
29%
S F
Scheme 64
6.02.1.3.2
Tetracoordinated carbon atoms bearing two halogens and one tellurium function (R1CHal2TeR2)
Among compounds described in this section only perfluoroalkyl tellurides and additionally ditellurides have been well known for more than ten years. Other compounds of this class have hardly been reported and without details of their preparation or yields obtained. The 1990s have brought about more details concerning preparations of difluoroalkyl tellurides. A general route to these compounds involves the reaction of dialkyl tellurides with bis(trifluoromethyl) cadmium or trifluoromethylzinc bromide performed in the presence of acetonitrile and boron trifluoride <1995COFGT(6)35>. Some advances that recently have occurred in this area are presented here. Unfortunately, the examples concern only syntheses of perfluoroalkyl derivatives of tellurium. Bis(pentafluoroethyl)telluride was obtained by the treatment of pentafluoroiodoethane with tellurium in the presence of copper metal at a very low pressure and an elevated temperature. Bis(pentafluoroethyl)ditellurid was prepared in a high yield under similar conditions using bis(pentafluoroethyl)mercury as the starting material (Scheme 65) <1996JCS(D)4463>.
C2F5I
Te, Cu,180 °C,36 h, 0.01 torr
C2F5TeC2F5
68% C2F5HgC2F5
Te, Cu, 200 °C, 15 h
C2F5TeTeC2F5
85%
Scheme 65
UV-irradiated bis(pentafluoroethyl)telluride is transformed into bis(pentafluoroethyl)ditelluride, which on treatment with silver cyanide gives (pentafluoroethyl)tellurium cyanide and with molecular iodine at low temperature yields (pentafluoroethyl)tellurium iodide (Scheme 66) <2000JCS(D)11>.
n-C3F7TeC3F7-n
Furan, 20 °C, 16 h, UV
n-C3F7TeTeC3F7-n
73% AgCN, 22 °C
n-C3F7TeTeC3F7-n
n-C3F7TeTeC3F7-n
92% I2, CHCl3, –196 to –20 °C
n-C3F7TeC N
n-C3F7TeI
100%
Scheme 66
6.02.1.4
Halogen and Mixed Chalcogen Derivatives (R1CHal(OR2)(SR3))
These compounds have been practically excluded from this section because the system is almost exclusively present in heterocycles, e.g., in oxathiolium salts covered by other reviews. Here only a couple of examples of compounds that can be described by the formula (R1CHal(OR2) (SR3)) are given.
53
Functions Containing Halogens and Any Other Elements
In 1995 Chande and Joshi published two papers describing bromination of extended ethanone derivatives, bearing C-, O-, S-linked large substituents and a hydrogen atom at the -carbon atom. Solutions of the starting material and molecular bromine in glacial acetic acid, when subjected to ultraviolet irradiation, afford products. Yields of the bromination products, depending on substituents in a substrate, vary from 50% to 95% (Scheme 67) <1995IJC(B)54, 1995IJC(B)147>.
Ph
O
N N
C6H4Cl-p Br2, MeCO2H, hν
S
N Ph N
N Ph N
O
N N
S
O C6H4Cl-p
C6H4Me-p O C6H4Cl-p
N N
Ph
S
O C6H4Cl-p
Br2, MeCO2H, hν
Br O C6H4Cl-p
O
N N
Ph
C6H4Me-p
H
90%
H
Br O C6H4Cl-p
H
S
N N
C6H4Cl-p
S
O
N N
90%
C6H4Me-p
O
N N
Ph
H
H
N Ph N
Ph S
50%
Br2, MeCO2H, hν S
O
N N
N N
C6H4Me-p Br O C6H4Cl-p
S H
Br2, MeCO2H, hν N N o-HOC6H4
N Ph N
O S
C6H4Me-p
95%
N N o-HOC6H4
O C6H4Cl-p
H
N Ph N
O S
H
C6H4Me-p Br O C6H4Cl-p
Scheme 67
6.02.2
FUNCTIONS CONTAINING HALOGEN AND A GROUP 15 ELEMENT AND POSSIBLY A CHALCOGEN
6.02.2.1
Halogen and Nitrogen Derivatives: General Considerations
Compounds of this class are somewhat unstable, being in equilibrium with the corresponding isomeric haloiminium salts. The equilibrium between isomeric forms depends on N-substituents. Electron-withdrawing substituents shift the equilibrium to haloalkylamines. This dynamic balance has been discussed in several papers and reviews <1995COFGT(6)35>.
6.02.2.1.1
Tetracoordinated carbon atoms bearing two halogens and one nitrogen function
Similar to COFGT (1995) <1995COFGT(6)35>, examples described here refer to compounds for which the equilibrium is probably shifted to covalent species. Probably the first compound reported as N-(dichloromethyl)-N,N-dimethylamine in US patent in 1955 did not satisfy these requirements <1955USP2854458>.
(i) From imines The addition of dihalocarbenes to imines was and still is a route of choice for synthesis of heterocycles like 2,2-dihaloaziridines. No further advances have been noticed in this field since the publication of COFGT (1995) <1995COFGT(6)35>.
54
Functions Containing Halogens and Any Other Elements
(ii) From amines or hydroxylamines Several halogenation methods have been applied to tertiary or secondary amines or alkylamino derivatives of other compounds. Only some of the routes lead to high yields of aminodihaloalkyl products. Just as superior fluorination involves the use of sulfur tetrafluoride, chlorination involves the use of molecular chlorine. The methods can be applied to perhalogenation of both tertiary and secondary amines. In the latter case the halogen atom also replaces N-hydrogen <1995COFGT(6)35>. Molecular fluorine was used for perfluorination of triethylamine at a low temperature (Equation (37)) <1999JFC(94)157>. F2, –35 to –20 °C, 14 h
Et3N
ð37Þ
(F3CF2C)3N
Some other methods sporadically give satisfying results. Displacement of chlorine by fluorine atoms is an effective approach to (difluoroalkyl)amino compounds. Using hydrogen fluoride in pentane at a low temperature allows replacement of four chlorine atoms by fluorine ones in N,N-di(dichloromethyl)aniline (Equation (38)) <1996JFC(76)95>. Cl Ph N
F Cl Cl
HF, pentane, –30 to –5 °C
F
Ph N 79%
ð38Þ
F
Cl
F
An unusual N-perfluoroalkylation of O-benzoyl sec-butylhydroxylamine, using bis-heptafluorobutyryl peroxide in perhalogenated ethane, leading to the formation of the corresponding amineoxy free radical, has recently been reported (Equation (39)) <2002JFC(116)109>.
N
O Bz
(C3F7CO2)2, Cl2FCCClF2
O N C3F7-n
20 °C
H
ð39Þ
A common electrochemical approach usually affords mixtures difficult to separate and leads to low yields of the desired compounds. Some exceptions to this general rule are known. While fluorination of N-ethyl-N-isopropyl amine under electrochemical conditions leads to a very low yield of the corresponding perfluorinated compound, N-(n-butyl)-N-methylamine under similar conditions affords a high yield of its perfluorinated derivative (Scheme 68) <2000JFC(106)35>. The same authors have reported moderate yields of perfluorinated products in electrochemical syntheses of other compounds too. An example is given (Equation (40)) <2001JFC(108)215>.
F H N
F F F F N F F F F
HF, 7–8 °C, 390 min, electrolysis 2.4%
H N
F
HF, 7–8 °C, 434 min, electrolysis
F
F F
F
F N
F F
high yield
F
F
F
F
F F F
Scheme 68
O
O N N
O
O
HF, 7–8 °C, 10 h, electrolysis 50%
F
F
F FF F O
N
F F
F
F F F
F
F F
ð40Þ
55
Functions Containing Halogens and Any Other Elements
As it was mentioned before, electrochemical methods usually afford mixtures. Low yields of fluorinated products are determined by chromatography. This can also be found out from the following schemes. Often yields are not reported at all and detailed synthetic procedures are not disclosed. Examples are given in Scheme 69 <1999JFC(97)229, 1999JFC(99)51, 2001JFC(108)21> and Scheme 70 <1996JCS(P1)915, 1997JFC(82)143, 1997JFC(83)1, 2002JFC(115)21>. OH
N
(C2F5)2N
8.7% (chromat.)
N H
N
F
F F
O
HF, 7–8 °C, 521 min, electrolysis
Si O
(F3C)2N
8.1%
F
F F
OH
N
HO
O
HF, 7–8 °C, 616 min, electrolysis
O
HF, 7–8 °C, 637 min, electrolysis
(C2F5)2N
5.9%
N
F
F F
Scheme 69
O O HF, electrolysis O
N
F F
F F
F
Not separated
F
N F
HF, electrolysis
N
F
F F F F
F
F F
F
n-C3F7N(C2F5)2
F N
HF, 0 °C, 24 h
N
Electrolysis
(F3C)3N
HF, electrolysis (n-C3H7)3N
(n-C3F7)3N
N HF, electrolysis N(C2F5)3
N
Scheme 70
(iii) From amides and thioamides Many of the compounds of this class have been prepared where electron-withdrawing groups limit the possibility of salt formation. A variety of approaches were successfully used in these cases for conversions of amides and thioamides. Some advances that have occurred in this area since the publication of <1995COFGT(6)35> are reported here. N,N-Dimethyl-,-difluorobenzylamine was prepared in a good yield from N,N-dimethylbenzthioamide by its fluorination with bis(2-methoxyethyl)aminosulfur trifluoride in the presence of antimonium trichloride (Scheme 71) <2000JOC4830>.
56
Functions Containing Halogens and Any Other Elements bis(2-methoxyethyl)aminosulfur trifluoride S
F
SbCl3, CH2Cl2, 20 °C, 48 h
Ph N
Ph
N
78%
F
Scheme 71
Very high yields of N,N-di(dichloromethyl)aniline and its p-chloro derivative are obtained from the corresponding N,N-diformylanilines while treating them with phosphorus pentachloride– phosphorus oxychloride mixture (Scheme 72) <1996JFC(76)95>.
O O
Ph N
Cl
PCl5, POCl3, 80 °C, 2 h
Cl
Ph N
92%
Cl Cl Cl
O O
p-Cl-C6H4-N
PCl5, POCl3, 80 °C, 2 h
p-Cl-C6H4-N
94%
Cl Cl
Cl
Scheme 72
The last decade has produced several examples of synthesis of N-(dihaloalkyl)sulfonamides from sulfonamides. The sulfonyl group obviously stabilizes the products. Cobalt trifluoride at a high temperature allows the displacement of four hydrogen atoms by fluorine ones in N,N-dimethylamide of fluorosulfonic acid (Equation (41)) <1995JFC(74)181>.
O F S N O
F O F F S N F O F
CoF3, 200–250 °C 38.5%
ð41Þ
Fluorination of N,N-dimethylamide of trifluoromethanesulfonic acid under electrochemical conditions affords the corresponding, additionally tetrafluorinated, sulfonamide in low to moderate yields. Other examples of halogenation under electrochemical conditions of either sulfonamides or amides were also reported (Scheme 73) <1995JFC(75)157, 1998JFC(87)157, 1997JFC(81)115, 2002JFC(113)201>.
F F F
O S N O
HF, electrolysis 27%
F O F S N F O F
F F F
F O F O N S S N O F O
HF, 0 °C, electrolysis
F F
F O F O F N S S N F O F O F F O
O n-C3F7
HF, –15 °C, electrolysis
F
n-C3F7 N
F
F
N
F
Scheme 73
57
Functions Containing Halogens and Any Other Elements
N-Alkylation of sulfonamide sodium salt by bromodifluoroalkene is another approach to the synthesis of an N-(,-difluoroalkyl)sulfonamide (Equation (42)) <2000CPB885>. The displacement of a sulfur atom by two fluorine ones in thioamide is shown in Equation (43) <1998SL1243>. F (PhNSO2Me)
F
Na
Br , Pd(OAc)2, PPh3, THF, 40 °C, 2 h
F F
S n-C7F15
F F
NBS, PPHF, CH2Cl2, 1 h
n-C7F15
N
Ph N
ð42Þ
SO2 Me
ð43Þ
N
(iv) From acyl halides Treatment of acyl fluorides with tetrafluorohydrazine under photolytic conditions resulting in the formation of corresponding perfluoroaminoalkane was reported earlier <1995COFGT(6)35>. A perhalogenated tertiary amine, containing apart from fluoro-substituents, one iodo-atom in -position was prepared by Abe et al. from the appropriate acyl fluoride by treating it with lithium iodide at an elevated temperature (Equation (44)) <1997JFC(83)117>. F (F3C)2N
F F O
F
F
LiI, 180 °C, 7.3 h
F
(F3C)2N
63%
F
F
ð44Þ
I
F
(v) From nitriles Chlorofluorination of primary alkyl cyanides, bearing electron-withdrawing groups, is a mild and convenient route for the preparation of N,N-dichloro- or N-chloro-N-fluoro-, -difluoroalkylamines. Yields are excellent. Other methods of synthesis of compounds of this class were also reported, being applied to particular cases <1995COFGT(6)35>. The treatment of acetonitrile with hydrogen bromide for 12 days has afforded N-(,-dibromoethyl)-acetamidine, probably as the result of electrophilic addition of two molecules of hydrogen bromide to cyano group, followed by nucleophilic addition of the intermediate dibromoethylamine to another molecule of acetonitrile (Equation (45)) <1998IZV(11)2274>.
N
HBr, 12 days
H N
Br
NH
ð45Þ
Br
Hydrogen fluoride is added to the double NS bond in a tetrafluorinated derivative of acetonitrile leaving the triple CN bond intact (Equation (46)) <1995CC1437>. F F F S N F N N H i = tris(dimethylamino)sulfonium difluorotrimethylsilicate F
F F S N F
i
F
ð46Þ
(vi) From haloiminium salts Haloiminium salts, by treating them with hydrogen halides at a low temperature, are easily converted to dihaloiminium species staying in equilibrium with dihaloalkylamines. Nothing is to be added since the publication of <1995COFGT(6)35>.
58
Functions Containing Halogens and Any Other Elements
(vii) From haloalkenes and haloalkanes The addition of secondary amines to perhalogenated ethenes results in the formation of the corresponding N,N-dialkyl-N-(tetrahalogenoethyl)amines <1995JFC(73)267, 1998JCR(M)301>. In a similar way, though under photochemical conditions, N-iodo derivatives of secondary amines react. The iodine atom is present in the products. Other, less general methods, were reported too in COFGT (1995) <1995COFGT(6)35>. Since then some new examples of known methods and new approaches to the synthesis of dihaloalkylamines from haloalkenes have been reported. For example: tetrafluoroethene reacts slowly with dimethylamine at room temperature to afford dimethyl-tetrafluoroethylamine in 90% yield (Equation (47)) <2001JFC(109)25>. F
F
F
Me2NH, 20 °C, 12 h
F
F
F
98%
F
F
ð47Þ
N
Secondary amines like diethylamine and di(n-butyl)amine are easily added to the double bond in an unsaturated perfluorated expanded diether in tetrahydrofuran at room temperature. Also in these cases yields of the addition products are high (Scheme 74) <1999ZPK(72)1345, 2000JFC(106)13>.
F F F F
O F
F F F
F F F F
O F
F F F
F
F F F F
O
F F
67%
F
F
F F
Et2NH, THF, 20 °C
O F F F
F
F
F
F F F F
O F
F F
82%
NEt2
F
F F F
F
F F
F
O F
F F F O
F F
Bun2NH, THF, 20 °C
F
F
F
F F F
F
O F
F
N(Bun)2
F
Scheme 74
Tetrafluoroethene reacting at 400 C with nitrogen trifluoride in the presence of caesium fluoride gave perfluorinated ethylamine in 10% yield only (Equation (48)) <2000JFC(101)15>. F
F
F
F
NF3, CsF, 400 °C, 1.5 h 10%
F F F
F N
F
ð48Þ
F F
A rather unexpected product was obtained from the reaction of partly fluorinated unsaturated tertiary amine with molecular fluorine. The reaction yielded a product, in which fluorine atoms displaced all hydrogen atoms in saturated N-alkyl groups while the former double bond was saturated by addition of two hydrogen atoms or stayed intact. No yield was given (Equation (49)) <1996JFC(76)139>. C2F5CF3 (F3C)2C-C NEt2 F F
F2
C2F5CF3 (F3C)2C-C N(C2F5)2 F F F
.
ð49Þ
Perhaloalkanes bearing an iodine atom in one terminal position react with nitrosobutane to yield the corresponding N-perhaloalkyl-N-(t-butyl)amineoxy free radicals (Scheme 75) <1995JFC(75)1>. N-(,-Difluoroalkyl)-N-(t-butyl)amineoxy free radical was also produced in the reaction of nitrosobutane with methoxycarbonyldifluoromethylsulfonyl azide (Equation (50)) <1995JFC(73)175>.
59
Functions Containing Halogens and Any Other Elements
F Cl F
ButNO, (NH4)2Ce(NO3)6, NaHSO3
F
aq. sulfonic acid, MeCN, H2O
F Cl F
F
F F F F Cl
I
I
ButNO, NaHCO3
F
Rongalite, DMF, H2O
F F F
O N Bu-t F
F
F F F F Cl
O N Bu-t F
F F F
Scheme 75
O
O
MeO2CCF2SO2N3
N
O N
O
CH2Cl2
ð50Þ
F F
Zhou et al. also reported other self-spin-probing reactions, in which products contained N-(,-difluoromethylene)amineoxy free radical grouping (Scheme 76) <1999JFC(98)61, 1986JA3132, 1999T2263>. (C2F5CO2)2, 20 °C NO2
C2F5
F2ClC–CFCl2
Na
C2F5NO2, CH2Cl2, (C2F5)2NO
N O
N O
N
NO2
.
O N C2F5
Cl2FCCFCl2
O
Scheme 76
(viii) Routes specific to dihalonitroalkanes and dihalonitrosoalkanes Jones and Matthews in their review <1995COFGT(6)35> describing routes to dihalonitroalkanes divided them into three approaches depending on the starting materials such as nitromethanes, haloalkenes, and nitro alcohols and gave examples of each approach. No further advances have been noted in this field since that publication. Indeed, treating of diazomethane with sodium hypochlorite afforded dichloronitromethane, but no yield was given (Equation (51)) <1998MI(32)3935>. H2C N N
NaOCl
Cl
H2O
Cl
NO2
ð51Þ
Halogenonitrosoalkanes were not reported in <1995COFGT(6)35>. The only example of a compound of this class found by the authors was reported in 1995. Perfluoronitrosopropane was obtained in a very high yield from 1,2-dimethoxyethane in reaction with bis(perfluoropropyl)cadmium and NOCl (Equation (52)) <1995JFC(73)273>. O
6.02.2.1.2
O
NOCl, (C3F7)2Cd
C3F7NO
ð52Þ
90%
Tetracoordinated carbon atoms bearing one halogen and two nitrogen functions
When the nitrogen functions are amino groups, compounds of this class are unstable and all attempts to prepare them end in the formation of corresponding haloiminium salts. Exceptions are halodiazirines. Many examples of synthesis of these compounds have recently been reported. All the examples employ amidines as starting materials. Yields of halodiazirines vary from low to high.
60
Functions Containing Halogens and Any Other Elements
Fluorodiazirines can be prepared directly from amidines (Equation (53)) <1996JA10307> or from the corresponding chloro- or bromodiazirines. The second approach seems to produce better yields of the fluoroderivatives (Scheme 77) <2001JA2628>. N
NH2 NH
12% aq. NaOCl, KF, LiF
N
NaOBr, NaBr, LiBr, 5 °C, 1 h DMSO, hexane, H2O
NH2 p-N3C6H4
NH
N
N
79%
Br N N
p-N3C6H4
40%
Br
N
p-N3C6H4
Bun4NF, MeCN, 25 °C, 4 h
N p-N3C6H4
ð53Þ
F
DMSO, pentane, 30–35 °C
F
Scheme 77
Usually chloro- or bromodiazirines are produced in higher yields than fluorodiazirines obtained by halooxidation of the same starting amidines. Preparation of benzylchloro- and benzylfluorodiazirines from benzylamidine can serve as an example <1997TL7049, 1998JOC3010>. In recent years the formation of chlorodiazirines with a variety of alkyl or arylalkyl substituents has been reported, mainly by Moss et al. Conditions of the reactions are disclosed in the schemes (Schemes 78 and 79) <2001TL8923, 1999TL5101, 1999CC467, 1997TL4379> and in the equations (Equation (54)–(57)) <1996TL279, 1996JA10307, 1999JA5940, 2001OL1439>. NH2 NH
N
HOCl, Graham oxidation
N 40%
Ph
NH2
Ph
NH
Cl
NaOCl
Ph
36%
NH2
NaOCl
NH
35%
Ph
NH
N
Cl N
N
Cl
AcOLi, NaOCl, AcONa, H2O NH2
N
N N Cl
pentane DMSO, 30–35 °C 40%
Scheme 78 H2N
NH
Cl
N N
NaOCl, Li, MeOH 75%
NH2 NH
N
Cl2, NaOH, MeOH, 20 °C, 40 min 56%
Scheme 79
Cl
N
61
Functions Containing Halogens and Any Other Elements NH2
N
12% aq. NaOCl, NaCl, LiCl
NH
N Cl
DMSO, pentane, 30–35 °C
N
NH2
12% aq. NaOCl
NH
NH2
12% aq. NaOCl NH2
NaOCl, H2O
NH
ð55Þ
N
ð56Þ
N
DMSO, pentane, 0 °C
NH
N Cl
DMSO, pentane, 0 °C
Me (CD3)2C
ð54Þ
Cl Me N (CD3)2C N Cl
ð57Þ
Slightly different procedures allowed Sheridan et al. to prepare 3-cycloalkyl or 3-aryl-3-chlorodiazirines in good yields (Scheme 79) <1999TL17, 1999JCS(P2)2257>. 3-Chloro-3-(p-azidophenyl)diazirine and 3-bromo-3-(20 -chloro-10 ,10 ,20 -trifluoroethyl)diazirine have recently been prepared in moderate yields in dimethylsulfoxide at temperatures ranging from 196 to 5 C (Scheme 80) <2001JA2628, 2002JMC1879>.
NH2 p-N3C6H4
F Cl
F F
NH
NH2 NH
NaOCl, NaCl, LiCl, 5 °C, 1 h DMSO, hexane, H2O
N N
p-N3C6H4
43%
Cl
NaOCl, NaBr, LiBr
F
DMSO, –196 to –40 °C
Cl
F
N
F
Br
N
Scheme 80
(i) Tetracoordinated carbon atoms bearing one halogen and two nitro groups (RCHal(NO2)2) The preparation of this type of compounds was widely reviewed and discussed. They can be synthesized by halogenation of salts of dinitroalkane anions using elemental halogens, perchloryl fluorine, or hydrogen halides. Anions of halogenodinitroalkanes easily undergo further transformations, e.g., addition to aldehydes. It seems that no further advances have occurred in this area since the publication of COFGT <1995COFGT(6)35>.
(ii) Tetracoordinated carbon atoms bearing one halogen, one nitro group, and one other nitrogen function Probably the only example of this class is ethyl azidobromocyanoacetate, already reported in <1995COFGT(6)35>.
6.02.2.1.3
Tetracoordinated carbon atoms bearing one halogen, one nitrogen, and one oxygen function
Stable compounds of this class probably do not exist. They are only formed as intermediates in, e.g., Vilsmeier alkylation. For a discussion of their shift to iminium halide salts see chapter 6.02 and the references cited therein <1995COFGT(6)35>.
62 6.02.2.1.4
Functions Containing Halogens and Any Other Elements Tetracoordinated carbon atoms bearing one halogen, one nitrogen, and one sulfur function
Like compounds described in the previous sub-chapter, also species with tetracoordinated carbon atoms bearing one halogen, one nitrogen, and one sulfur function, are nearly always found in the form of the corresponding iminium halide salts. The exceptions are nitrohalosulfides already reported in <1995COFGT(6)35>. There have not been any further advances in this field.
6.02.2.2 6.02.2.2.1
Halogen and Phosphorus Derivatives Tetracoordinated carbon atoms bearing two halogens and one phosphorus function, and one halogen and two phosphorus functions
The synthetic methods for preparing carbohydrates bearing a C-branched substituent of the type CF2-Y (e.g., n-CnF2n+1) where Y = heteroatom (O, S, P) were reviewed. Examples of the syntheses are given (Scheme 81) <2000CAR119>. O
S
O O O F EtO P Li OEt F
O
i. (OR)3 S ii. Ph
O
Cl
(OR)3
moderate-to-high yield
S F O
F P O EtO OEt
F
i. (RO) 2PH, octane, ∆
F
OPh F
F OR P OR S
O
ii. (ButO)2, 37% (OR)3
(OR)3
Scheme 81
(i) From haloalkenes The general approach to compounds of this class involves the addition of phosphines to halogenoalkenes. The reactions can be performed either under polar or photolytic conditions. Some examples were given in chapter 6.02 <1995COFGT(6)35>. No further advances have occurred in this area since that publication.
(ii) From haloalkanes The syntheses of compounds with tetracoordinated carbon atoms bearing two halogens and one phosphorus function involving reactions of haloalkanes with phosphorus derivatives were widely reviewed in chapter 6.02 <1995COFGT(6)35>. Another approach, consisting of the addition of lithium derivatives of dihalomethylphosphates to carbonyl compounds, was also reviewed previously in the work by Plantier–Royon and Portella already cited here <2000CAR119>. Among others lithiation of dibenzyl P-(difluoromethyl)thiophosphate was mentioned (Equation (58)) <1996TL2229>.
F F
S P OBn OBn
LiN(Pr i)2 Hexane, –78 °C
F Li F
S P OBn OBn
ð58Þ
63
Functions Containing Halogens and Any Other Elements
An interesting and effective reduction of phosphate to the corresponding dichloromethylphosphine using lithium aluminum hydride in the presence of aluminum brought about a paper by Guillemin et al. In this work one can also find a large quantity of data concerning phosphorus compounds (Scheme 82) <2001JOC7864>.
AlCl3, LiAlH4 O Cl O P O Cl
(MeOCH2)2O, –80 to –30 °C
Cl
91%
Cl
PH2
Scheme 82
6.02.2.2.2
Tetracoordinated carbon atoms bearing one halogen, one oxygen function, and one phosphorus function
Compounds of this class were not reviewed in chapter 6.02 <1995COFGT(6)35>. As shown by Cairns et al. they can be formed by halogenation of phosphates containing a secondary (or primary) P-alkyl substituent (Equation (59)) <1999PS385>. EtO EtO
O P OEt OEt
TiCl4
Cl
Et2O
EtO
O P OEt OEt
ð59Þ
Work by Chen et al. have indicated that -alkoxy--fluoroalkylphosphates undergo some transformations in which the -alkoxy--fluoroalkylphosphate group is preserved. Thus, the compounds containing hydroxy groups at the P-alkyl chain can be silylated, sulfonated, or can undergo Mitsunobu reaction (Scheme 83) <1996TL8975, 1998JCS(P1)3979>.
Si
O
O OEt P OEt
O
Dowex(H+), EtOH
F
HO
O OEt P OEt
O
HO
57%
i. DEAD, Ph3P, DMF 39%
F
O OEt P OEt
O F
i
O
O OEt P OEt
O F
NH2 N
i= N N
N H
Scheme 83
6.02.2.3 6.02.2.3.1
Halogen and Arsenic Derivatives Tetracoordinated carbon atoms bearing two halogens and one arsenic function
Two known examples of compounds of this class were already reported in COFGT (1995) <1995COFGT(6)35>. Their syntheses involve addition of organoarsenic derivatives to perfluorinated propene <1995COFGT(6)35>.
64 6.02.3
Functions Containing Halogens and Any Other Elements FUNCTIONS CONTAINING HALOGEN AND A METALLOID AND POSSIBLY A CHALCOGEN AND/OR GROUP 15 ELEMENT
6.02.3.1
Halogen and Silicon Derivatives
A variety of ,-dihaloalkyl silanes were prepared using different routes but only some of them are more general. A few more examples of the most common syntheses disclosing detailed conditions were reported in chapter 6.02 <1995COFGT(6)35>. A few years ago a review was published covering preparation and reactivity of perfluoroalkyl and difluoroalkyl silanes <1997CRV757>. Two following references cited there appertain to difluorosilanes <1995SL717, 1997JA1572>. 6.02.3.1.1
Dichlorocarbene addition
Dichlorocarbene generated from phenyl(bromodichloromethyl)mercury adds to a variety of silanes, giving the corresponding dichloromethyl silanes <1995COFGT(6)35>. 6.02.3.1.2
Other additions to silanes
Addition of bromine to alkynyl silanes results in an almost quantitative formation of tetrabromoalkyl silanes. Also addition of methylmagnesium bromide to trichlorosilyldichloromethane leads to the formation of trimethylsilyldichloromethane. Photochemical addition of the chlorosilylradical to tetrafluoroethene affords a very high yield of the corresponding adduct. Some of the reported examples concern syntheses of systems containing silicon, halogen, and chalcogen (oxygen or sulfur) at the same carbon atom. Such syntheses can be accomplished, for example, starting from (methylthiomethyl)trimethyl silane <1995COFGT(6)35>. 6.02.3.1.3
Substitution of silanes by haloalkyl derivatives
Electrochemical silylation of chlorodifluoromethyl enol ethers affords the new functionalized difluoromethyl allyl silanes on a preparative scale in good yields. These silanes react as difluoromethyl anion equivalents with electrophiles, e.g., aldehydes (Scheme 84) <1998TL3137>.
Cl CF2
4Me3SiCl, Bu4NBr DMF, Mg/Ni electrodes
EtO R
Si CF2 EtO R
R = Ph, 94% R = -(CH2)2Ph, 66%
Scheme 84
Petrov published a simple procedure for nucleophilic perfluoroalkylation of organic and inorganic substrates. A mixture of iodoperfluoroalkane and tetrakis(dimethylamino)ethylene is used for the nucleophilic perfluoroalkylation. The reaction of chlorotrimethyl silane and iodoperfluoroalkane/ tetrakis(dimethylamino)ethylene in diglyme results in the formation of perfluoroalkyltrimethyl silanes isolated in 55–81% yield. The interaction of this system with organic electrophiles, such as benzoyl and benzensulfonyl chlorides, aliphatic and aromatic aldehydes, or activated ketones, leads to the formation of the corresponding condensation products in 24–62% yield (Scheme 85) <2001TL3267>. (Me2N)2C=C(NMe2)2, ClSiMe3 RfI
Diglyme, –30 °C, 2 h, 55–81% Rf = C2F5, n-C3F7, n-C4F9
Scheme 85
RfSiMe3
Functions Containing Halogens and Any Other Elements 6.02.4
65
Halogen and Boron Derivatives
A review has recently appeared on perfluoroalkylborates as congeners of perfluoroalkanes <2001CCR243>. Apart from that review no interesting reports have been found in this area since the publication of chapter 6.02 <1995COFGT(6)35>. Compounds of this class are usually extremely unstable and probably due to this instability they have not found wider applications in organic synthesis.
6.02.5
Halogen and Germanium Derivatives
Jones and Matthews in chapter 6.02 <1995COFGT(6)35> reported several examples of efficient syntheses of compounds of this class. It seems that since then no advances in this area have been reported. The compounds can preferably be prepared either by addition of germane halogenides to chlorinated alkenes or by treating bis(perhaloalkyl)mercury compounds with germane halogenides. It is worth mentioning that trihalo(perfluoroalkyl)germanium derivatives are versatile synthetic intermediates in formation of alkyl(perfluoroalkyl)germanium products.
6.02.6
6.02.6.1
FUNCTIONS CONTAINING HALOGEN AND A METAL AND POSSIBLY A GROUP 15 ELEMENT, A CHALCOGEN OR A METALLOID Halogen and Lithium Derivatives
Haloalkyllithium compounds, due to their unusual reactivity and their ability to deliver halomethylene group to required acceptors, are commonly used in several syntheses. Very critical aspects of their use concern solvents and reaction temperatures. Metallation of terminal iodofluoroalkanes with methyllithium at 78 C in THF, followed by the addition of sulfur dioxide, results in the formation of a lithium difluoroalkylsulfinate via intermediate organolithium species chapter 6.02 <1995COFGT(6)35>. Rosnati, reviewing results achieved in fluoroorganic chemistry up to 1995, <1996T1> pointed to the addition of perfluoroalkyllithium to imines reported earlier by Uno et al. <1988CL729> and <1992JOC1504>. C-Lithiation of difluoromethyl group attached to phosphorus was reported by Piettre and Raboisson (Equation (60)) <1996TL2229>. F F
6.02.6.2
S P OBn OBn
LiN(Pri)2 Hexane, –78 °C
F Li F
S P OBn OBn
ð60Þ
Halogen and Magnesium Derivatives
Transmetallation reaction between Grignard reagents and perhalogenated systems is a versatile route to compounds of this class; e.g., arylmagnesium bromides react with 1-iodoperfluoroalkanes at low temperatures to produce perfluoroalkylmagnesium bromides, which can be used further without separation chapter 6.02 <1995COFGT(6)35>. Applications of perfluoroalkyl Grignard reagents (CnH2n+1MgX) in the synthesis of some fluorinated amines and diamines were reported by Katritzky et al. <1997TL7015>. Perfluoro-n-octylmagnesium bromide can be prepared with 1-bromo-1H-heptadecafluorooctane and hexylmagnesium bromide in THF at 60 C in 30 min <2001JOC1316>. The reaction of heptafluoropropylmagnesium bromide with sym-ketodibenzo-16-crown-5 at 78 to 20 C in Et2O produced the corresponding alcohol in 60% yield <2000JHC1337>. Perfluoroalkenyl ketones were obtained by reaction of perfluorometallic reagents with acyl silanes. Long-chain F-alkylations of sugar derivatives were carried out with F-organomagnesium bromides prepared in situ from F-alkyl iodides and ethylmagnesium bromide according to the method reported by Burton and Yang <1998T189>, or with F-alkyltrimethyl silane <1989PGE380554> in order to compare the influence of the method on the stereoselectivity. Examples are shown in the Scheme 86 <2002TL1677>.
66
Functions Containing Halogens and Any Other Elements EtMgBr, ether C4F9I
C4F9MgBr in situ
–45 °C, 0.5 h
Sugar
C4F9-sugar derivative
O CnF2n + 1CF2CF2Li or CnF2n + 1CF2CF2MgBr
O
RCSiMe3 lt – rt, 77–86%
F
R
CnF2n + 1 F
Scheme 86
DesMarteau and Creager presented, at the 226th National Meetings of the American Chemical Society, the paper describing applications of oligomeric bis[(perfluoroalkyl)sulfonyl]imide lithium salts as electrolytes for rechargeable lithium batteries <2003MI36>.
6.02.6.3
Halogen and Copper Derivatives
The reaction of copper metal with 1-iodoperfluoroalkanes at an elevated temperature is known to produce perfluoroalkylcopper(I). No further advances have occurred in this area since the publication of chapter 6.02 <1995COFGT(6)35>.
6.02.6.4
Halogen and Silver Derivatives
An equilibrium between the mixtures of di(perfluoroalkyl)cadmium(II) with silver nitrate and forming di(perfluoroalkyl)silver(I) anion was studied in dimethyl formamide and triethylamine at a low temperature (Equation (61)) <1997JOM79>. Equilibrium
Cd(CnF2n + 1)2 + AgNO3
DMF or Et3N, –30 °C
[Ag(CnF2n +1)2] –
ð61Þ
CnF2 n +1 = CF3, CF3CF2, CF3CF2CF2, (F3C)2CF
The formation of organometallic compounds, bearing ,-dihaloalkyl groups, in reactions of silver trifluoroacetate with perhalogenated ethene, promoted by caesium fluoride, was reported earlier. No further advances have occurred in this area since the publication of chapter 6.02 <1995COFGT(6)35>.
6.02.6.5
Halogen and Zinc Derivatives
A review on Reformatsky syntheses was published a few years ago <1999JOM215>. In this review the use of perfluoroalkylzinc by Kitazume and Ishikawa was mentioned <1985JA5186>. No further reports have been found in this area since the publication of chapter 6.02 <1995COFGT(6)35>.
6.02.6.6
Halogen and Cadmium Derivatives
Cadmium metal inserts rather easily between carbon and halogen atoms in haloalkanes to yield organocadmium reagents <1995COFGT(6)35>. The synthetic methods for preparing compounds bearing substituent such as CF2-Y were reviewed. Among others an example of the synthesis via cadmium intermediate was reported (Scheme 87) <2000CAR119>. Bis(perfluoroalkyl)cadmium reacts reversibly in organic solvents like dimethyl formamide or triethylamine at a low temperature with silver nitrate to yield bis(perfluoroalkyl)silver anion. An
Functions Containing Halogens and Any Other Elements
67
equilibrium of the reaction was studied (Equation (61)) <1997JOM79>. No further advances have occurred in this area since the publication of chapter 6.02 <1995COFGT(6)35>.
O F (EtO)2P Br F
Cd THF
O F (EtO)2P CdBr F
Br, rt
O F (EtO)2P F
62%
Scheme 87
6.02.6.7
Halogen and Mercury Derivatives
Mercuric fluoride adds readily to perhaloalkenes at elevated temperatures. Perhalodialkylmercury compounds are formed in the reaction. There have not been any further advances in this field since the publication of chapter 6.02 <1995COFGT(6)35>.
6.02.6.8
Halogen and Tin Derivatives
A few typical approaches to ,-dihaloalkyltin derivatives were reported earlier. They involve, for example, insertion of tin(II) chloride or fluoride into iodoperfluoroalkanes, the addition of dialkyltin hydrides to perfluorinated alkenes or transmetallation reactions <1995COFGT(6)65> Now some more recent examples of syntheses of ,-dihaloalkyltin derivatives are presented. The reaction of perfluoropropylmagnesium chloride (obtained from perfluoropropyl iodide and propylmagnesium chloride), with tin(IV) chloride was reported to give tetra(perfluoropropyl)stannane. In a similar manner perfluoropropylmagnesium chloride reacts with other tin(IV) derivatives. Yields of products are from poor to very good depending on the starting tin species (Scheme 88) <1995JOM131>.
PrMgCl, Et2O
C3F7I
–70 °C
C3F7MgCl
C3F7MgCl
SnCl4, Et2O, –70 to –30 °C
(C3F7)4Sn
19%
C3F7MgCl
MeSnCl3 11% MeSnCl3
C3F7MgCl
C3F7MgCl
49% H2C=CH-SnCl3 96% Me2SnBr2
C3F7MgCl
C3F7MgCl
82% (H2C=CH)2SnBr2 46%
Scheme 88
MeSn(C3F7)3
MeSn(C3F7)2Cl
H2C=CH-Sn(C3F7)2Cl
(C3F7)2Me2Sn
(H2C=CH)2Sn(C3F7)2
68 6.02.6.9
Functions Containing Halogens and Any Other Elements Halogen and Lead Derivatives
It was reported earlier that perfluoroalkyl iodides reacting with tetramethyllead at an elevated temperature afford perfluoroalkyltrimethyllead in low yields. No further advances have occurred in this area since the publication of chapter 6.02 <1995COFGT(6)35>.
6.02.6.10
Halogen and Ruthenium Derivatives
Compounds described here have not been reported in COFGT (1995) <1995COFGT(6)35>. In conjunction with two other independent minor reviews of organometallic main group fluorides <1997MI351> and f-block fluorides <1997JFC(86)121>, an extensive review appeared in 1997 on compounds containing carbonmetalfluorine fragments of d-block metals <1997CRV3425>. For the purpose of the reviews the term ‘‘organometallic fluoride’’ was used strictly to describe compounds containing fluorinemetal and carbonmetal bonds with the same metal atom. Nevertheless, at least a few examples included in the latter review refer to preparation of compounds, which contain such structural fragment as MCF2H where M is Ru <1997JA3185, 1994IC1476>. Me3SiCF3 reacts smoothly with RuHF(CO)(P(Bu-t)2Me) forming Me3SiF and a six-coordinated product where -F migration occurred in the proposed reaction intermediate. A fluoride atom abstraction using Me3SiOTf leads to an unusual rearrangement, in which coordinated hydride migrates to the carbene, forming CF2H fragment (Scheme 89). Experimental evidences suggest that this rearrangement occurs by a mechanism involving dissociation of one phosphine ligand. The CF2 group is readily converted to CO by the addition of water.
H L OC Ru F L
H L OC Ru F L
Me3SiOTf –Me 3SiF
Me3SiCF3 –Me 3SiF
L OC Ru F L F F
H L OC Ru F L F F
L OC Ru F L F F
THF
Scheme 89
6.02.6.11
Halogen and Cobalt or Nickel Derivatives
Compounds described here were not reported in <1995COFGT(6)35>. Perfluorometallacyclic compound Ni(PEt3)2(CF2)4 reacts irreversibly with BF3OEt2 complex affording unprecedented perfluorometallacycle with a phosphonium ylide structure. A reaction with sequence involving extraction of fluoride ions from the coordinated perfluorometallacycle followed by quenching the carbene species by migration of a phosphine ligand from the metal to carbon is likely (Equation (62)) <1988OM1642> acc. to <1997CRV3425>. +
F F F Et3P Ni Et3P F
F
F F F
BF3–OEt2
–
F
F4B Ni Et3P F
PEt3 F F
F
ð62Þ
F F
Fluoroalkylphosphine complexes of nickel(0) and cobalt(I) were also described. Treatment of (cod)2Ni with dfepe [(dfepe = (C2F5)2PCH2CH2P(C2F5)2, cod = 1,5-cyclooctadiene)] yields (dfepe)Ni(cod) and then (dfepe)Ni(bipy) (Scheme 90) <2003JOM65>.
Functions Containing Halogens and Any Other Elements
(acac)2Ni
(cod)2Ni
(CO)8Co
But3Al, butadiene
69
(dfspe)2Ni
dfepe excess, 82% dfepe
(dfepe)Ni(cod)
Toluene, 25 °C, 24 h, 80% LiEt3BH, THF (CO)4Co
i. dfepe, ii. HBF4, Me2O
(dfspe)(CO)2Co(H) stable up to –30 °C
Scheme 90
6.02.6.12
Halogen and Palladium or Platinum Derivatives
The first edition of COFGT (1995) <1995COFGT(6)35> reported neither examples of palladium nor platinum derivatives. The annual survey on transition metals in organic synthesis (covering 1993) brought, among others, an example of the reaction in which, in an intermediate, the PdCF2 bond is possibly formed (Equation (63)) <1995CCR153>. RCOCF2I
R' , L4Pd
RCOCF2 R
ð63Þ
I
Very recently it has been announced that the reaction of (1,5-cyclooctadiene = cod) (cod)PtMe2 with one molar equivalent of C4F9I in hexane, produces the stable perfluoroalkylplatinum (cod)PtMeC4F9 complex (Equation (64)) <2002POL2357>. C4F9I, N2, 12 h Pt
53%
Pt
C4F9
ð64Þ
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Rao, Tetrahedron 2000, 56, 3539–3546. M. F. Greaney, W. B. Motherwell, Tetrahedron Lett. 2000, 41, 4463–4466. Y. Kuroki, D. Asada, Y. Sakamaki, K. Iseki, Tetrahedron Lett. 2000, 41, 4603–4608. M. Mae, H. Amii, K. Uneyama, Tetrahedron Lett. 2000, 41, 7893–7896. G. Pawelke, H. Burger, Coord. Chem. Rev. 2001, 215, 243–266. N. Yoneda, T. Fukuhara, Chem. Lett. 2001, 3, 222–223. H. Eto, Y. Kaneko, S. Takeda, M. Tokizawa, S. Sato, K. Yoshida, S. Namiki, M. Ogawa, K. Maebashi, K. Ishida, M. Matsumoto, T. Asaoka, Chem. Pharm. Bull. 2001, 49, 173–182. A. Nicolaides, T. Enoyo, D. Miura, H. Tomioka, J. Am. Chem. Soc. 2001, 123, 2628–2636. Y. Guo, Q. Y. Chen, J. Fluorine Chem. 2001, 107, 89–96. N. Roques, J. Fluorine Chem. 2001, 107, 311–314. T. Abe, H. Baba, I. Soloshonok, J. Fluorine Chem. 2001, 108, 21–36. L. E. Kiss, I. Koevesdi, J. Rabai, J. Fluorine Chem. 2001, 108, 95–110. K. I. Petko, L. M. Yagupolskii, J. Fluorine Chem. 2001, 108, 211–214. T. Abe, H. Baba, I. Soloshonok, J. Fluorine Chem. 2001, 108, 215–228. V. A. Petrov, S. Swearingen, W. Hong, W. C. Petersen, J. Fluorine Chem. 2001, 109, 25–32. C. R. Burkholder, W. R. Dolbier, M. Medebielle, J. Fluorine Chem. 2001, 109, 39–48. L. V. Kudzma, Ch. G. Huang, R. A. Lessor, L. A. Rozov, S. Afrin, F. Kallashi, C. McCutcheon, K. Ramig, J. Fluorine Chem. 2001, 111, 11–16. S. Rozen, D. Rechavi, A. Hagooly, J. Fluorine Chem. 2001, 111, 161–165. T. Okazoe, K. Watanabe, M. Itoh, D. Shirakawa, S. Tatematsu, J. Fluorine Chem. 2001, 112, 109–116. V. Petrov, J. Fluorine Chem. 2001, 112, 117–121. A. Sekiya, H. Quan, M. Tamura, R. X. Gao, J. Murata, J. Fluorine Chem. 2001, 112, 145–148. V. A. Petrov, J. Fluorine Chem. 2001, 112, 325–328. G. Li, A. Graham, W. Potter, Z. D. Grossman, A. Oseroff, T. J. Dougherty, R. K. Pandey, J. Org. Chem. 2001, 66, 1316–1325. J. C. Guillemin, T. Janati, J. M. Denis, J. Org. Chem. 2001, 66, 7864–7868. Y. Gao, J. Voigt, H. Zhao, G. C. G. Pais, X. Zhang, L. Wu, Z. Y. Zhang, T. R. Burke, J. Med. Chem. 2001, 44, 2869–2878. B. A. Ameduri, B. Boutevin, G. Kostov, Progress in Polym. Sci. 2001, 26, 105–187. R. A. Moss, F. Zheng, K. Krogh-Jespersen, Org. Lett. 2001, 3, 1439–1442. E. Magnier, E. Vit, C. Wakselman, Syn. Lett. 2001, 8, 1260–1262. H. D. Quan, M. Tamura, R. Gao, A. Sekiya, Tetrahedron 2001, 57, 4111–4114.
Functions Containing Halogens and Any Other Elements 2001TL3009 2001TL3267 2001TL4861 2001TL8923 2002BCJ(75)1597 2002CEJ2917 2002IZV(6)948 2002JFC(113)79 2002JFC(113)97 2002JFC(113)201 2002JFC(114)51 2002JFC(115)21 2002JFC(116)109 2002JFC(117)149 2002JFC(118)123 2002JMC1879 2002JPCA3114 2002POL2357 2002SL996 2002T4077 2002T5877 2002TL1677 2002TL2949 2002TL7353 2003JOM65 2003MI(8)282 2003MI(8)307 2003MI36 2003TL5061 2003TL5995 2003USP073588
73
S. M. Riyadh, H. Ishii, T. Fuchigami, Tetrahedron Lett. 2001, 42, 3009–3012. V. A. Petrov, Tetrahedron Lett. 2001, 42, 3267–3269. K. Suzuki, H. Ishii, T. Fuchigami, Tetrahedron Lett. 2001, 42, 4861–4864. R. A. Moss, W. Ma, S. Yan, F. Zheng, Tetrahedron Lett. 2001, 42, 8923–8926. S. Ayuba, N. Yoneda, T. Fukuhara, S. Hara, Bull. Chem. Soc. Jpn. 2002, 75, 1597–1604. G. Blond, T. Billard, B. R. Langlois, Chem. Europ. J. 2002, 8, 2917–2922. A. N. Kovregin, A. Yu. Sizov, A. F. Ermolov, Izv. Akad. Nauk. Ser. Khim. 2002, 6, 948–950. (Chem. Abstr. 2003, 138, 136683). K. Wu, Q. Y. Chen, J. Fluorine Chem. 2002, 113, 79–83. J. Murata, M. Tamura, A. Sekiya, J. Fluorine Chem. 2002, 113, 97–100. N. V. Ignat’ev, M. Schmidt, U. Heider, A. Kucherina, P. Sartori, F. M. Helmy, J. Fluorine Chem. 2002, 113, 201–206. O. Paleta, J. Palecek, J. Michalek, J. Fluorine Chem. 2002, 114, 51–54. D. Velayutham, K. Jayaraman, M. Noel, S. Krishnamoorthy, P. Sartori, J. Fluorine Chem. 2002, 115, 21–26. C. H. Deng, C. J. Guan, M. H. Shen, C. X. Zhao, J. Fluorine Chem. 2002, 116, 109–116. I. Dlouha, J. Kvicala, O. Paleta, J. Fluorine Chem. 2002, 117, 149–160. Y. Cheburkov, G. J. Lillquist, J. Fluorine Chem. 2002, 118, 123–126. R. G. Eckenhoff, F. J. Knoll, E. P. Greenblatt, W. P. Dailey, J. Med. Chem. 2002, 45, 1879–1886. C. Clower, K. M. Solntsev, J. Kowalik, L. M. Tolbert, D. Huppert, J. Phys. Chem. A 2002, 106, 3114–3122. R. P. Hughes, J. S. Overby, K. C. Lam, C. D. Incarvito, A. R. Rheingold, Polyhedron 2002, 21, 2357–2360. S. Gouault, J. C. Pommelet, T. Lequeux, Syn. Lett. 2002, 6, 996–998. K. Wu, Q. Y. Chen, Tetrahedron 2002, 58, 4077–4084. S. M. Riyadh, H. Ishii, T. Fuchigami, Tetrahedron 2002, 58, 5877–5884. F. Chauteau, M. Essers, R. Plantier-Royon, G. Haufe, C. Portella, Tetrahedron Lett. 2002, 43, 1677–1680. A. V. Matsnev, N. V. Kondratenko, Yu. L. Yagupolskii, L. M. Yagupolskii, Tetrahedron Lett. 2002, 43, 2949–2952. A. Kamal, T. B. Pratap, K. V. Ramana, A. V. Ramana, A. H. Babu, Tetrahedron Lett. 2002, 43, 7353–7356. B. L. Bennett, S. White, B. Hodges, D. Rodgers, A. Lau, D. M. Roddick, J. Organomet. Chem. 2003, 679, 65–73. A. M. Caminade, C. O. Turrin, P. Sutra, J. P. Majoral, Current Opinion in Colloid and Interface Science 2003, 8, 282–295. T. Imae, Current Opinion in Colloid and Interface Science 2003, 8, 307–314. DesMarteau, D. D.; Creager, S. E. 2003, 226th National Meetings of the American Chemical Society, paper No. FLUO 36. S. Gouault, C. Guerin, L. Lemoux, T. Lequeux, J. C. Pommelet, Tetrahedron Lett. 2003, 44, 5061–5064. D. V. Sevenard, P. Kirsch, E. Lork, G. V. Roschenthaler, Tetrahedron Lett. 2003, 44, 5995–5998. J. L. Howell, E. W. Perez, US Patent 073588 (2003) (Chem. Abstr. 2003, 138, 323717).
74
Functions Containing Halogens and Any Other Elements Biographical sketch
Dr. Jerzy Suwin´ski, Prof. of Organic Chemistry, was born in 1939, graduated in 1961, obtained his Ph.D. in organic chemistry under Prof. C. Troszkiewicz’s supervision at Silesian University of Technology (Gliwice, Poland) in 1968. A few years later 1973/1974 he joined Prof. A. R. Katritzky’s research group as a postdoc. Back in Gliwice he received his D.Sc. degree in 1978 and later on in 1990 a position of Full Professor of Organic Chemistry. As a contract professor he lectured in Bologna, Italy (1986, 1991), Missouri Univ., USA (1994), Campinas, Brazil (1995), Poznan´, Poland (1997) and as visiting professor also in other countries. His main research interest is concerned with reaction mechanisms and nitrogen heterocycles. He is author or co-author of over 130 papers, books, and textbooks for students.
Dr. Krzysztof Walczak, Associate Professor of Organic Chemistry, was born in 1955, graduated in 1980, and obtained his Ph.D. degree in Organic Chemistry at the Silesian University of Technology (Gliwice, Poland) in 1988 under Professor J. Suwin´ski’s supervision. He continued his scientific education as a post-doctoral fellow (1989–1991) at the Odense University (Denmark) with Professor E. B. Pedersen. In 1996 he was granted a sixmonth fellowship founded by the Rectors Conference of Danish Universities and joined again Professor’s Pedersen research group at Odense University. In 1999 he received D.Sc. degree. Since then he remains at STU with exception of two sabbaticals: at the Utah State University in Logan (USA) with Professor Lance Seefeldt and in Nucleic Acids Centre of University of Southern Denmark as a contract professor. His current research activity is focused on the chemistry of heteroarenes including their sugar derivatives. He has published around 35 papers.
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Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 23–74
6.03 Functions Containing Three Chalcogens (and No Halogens) S. RA´DL Research Institute of Pharmacy and Biochemistry, Prague, Czech Republic and S. VOLTROVA´ Institute of Chemical Technology, Prague, Czech Republic 6.03.1 INTRODUCTION 6.03.2 FUNCTIONS BEARING THREE OXYGEN ATOMS 6.03.2.1 Methods for the Preparation of Carboxylic Ortho-esters and Related Compounds 6.03.2.1.1 Ortho-esters from 1,1,1-trihaloalkanes, ,-dihaloethers and -haloacetals 6.03.2.1.2 Ortho-esters from imidate ester salts 6.03.2.1.3 Ortho-esters from carboxylic acids and derivatives 6.03.2.1.4 Ortho-esters from dioxacarbenium salts 6.03.2.1.5 Ortho-esters from 1,1-dialkoxyalkenes 6.03.2.1.6 Ortho-esters from 1,1-dialkoxycyclopropanes and related compounds 6.03.2.1.7 Ortho-esters from acetals 6.03.2.1.8 Ortho-esters from ortho-carbonate esters and trialkoxyacetonitriles 6.03.2.2 Preparation of Carboxylic Ortho-esters from Other Ortho-esters 6.03.2.2.1 Trans-esterification reactions 6.03.2.2.2 Modification of R1 and R2 of R1C (OR2)3 6.03.3 FUNCTIONS BEARING THREE SULFUR ATOMS 6.03.3.1 Methods for the Preparation of Trithio-ortho-esters and Related Compounds 6.03.3.1.1 Trithio-ortho-esters from RC(X1)(X2)X3 6.03.3.1.2 Trithio-ortho-esters from thioimidate esters salts 6.03.3.1.3 Trithio-ortho-esters from carboxylic acids and derivatives 6.03.3.1.4 Trithio-ortho-esters from dithia- and trithiacarbenium salts 6.03.3.1.5 Trithio-ortho-esters from dithioacetals 6.03.3.1.6 Trithio-ortho-formates from trithiocarbonates 6.03.3.1.7 Trithio-ortho-formates from tetrathio-ortho-carbonates 6.03.3.1.8 Miscellaneous 6.03.3.2 Preparation of Trithio-ortho-esters from Other Trithio-ortho-esters 6.03.3.2.1 Higher trithio-ortho-esters from trithio-ortho-formate esters 6.03.3.2.2 Trans-esterification of trithio-ortho-esters 6.03.3.3 Methods for the Preparation of Oxidized Derivatives of Trithio-ortho-esters 6.03.3.3.1 Oxidized trithio-ortho-esters containing at least one sulfoxide group 6.03.3.3.2 Oxidized trithio-ortho-esters containing at least one sulfone group 6.03.3.3.3 Oxidized trithio-ortho-esters containing at least one sulfonate group 6.03.4 FUNCTIONS BEARING THREE SELENIUM ATOMS 6.03.4.1 Methods for the Preparation of Triseleno-ortho-esters 6.03.4.1.1 Triseleno-ortho-esters from triselenacarbenium salts 6.03.4.1.2 Triseleno-ortho-esters from diselenoacetals and related compounds
75
75 76 76 76 77 77 80 81 81 81 81 82 82 83 84 84 84 85 85 85 85 86 88 88 89 89 93 94 94 95 97 98 98 98 98
76
Functions Containing Three Chalcogens (and No Halogens)
6.03.5 MIXED CHALCOGEN FUNCTIONS INCLUDING OXYGEN 6.03.5.1 Methods for the Preparation of Functions R1C(OR2) (OR3)SR4 6.03.5.1.1 From R1C(X1)(X2)X3 6.03.5.1.2 Miscellaneous 6.03.5.2 Methods for the Preparation of Functions R1C(OR2) (SR3)SR4 6.03.5.2.1 From R1C(X1)(X2)X3 6.03.5.2.2 From dithiacarbenium salts 6.03.5.2.3 From dithioacetals and related compounds 6.03.5.2.4 From ketene dithioacetals 6.03.5.2.5 Miscellaneous 6.03.5.3 Methods for the Preparation of Functions R1C (OR2) (OR3)SeR4 6.03.6 MIXED SULFUR AND SELENIUM FUNCTIONS 6.03.6.1 Methods for the Preparation of Functions R1C(SR2) (SR3)SeR4 6.03.6.1.1 From dithioacetals 6.03.6.2 Methods for the Preparation of Functions R1C(SR2) (SeR3)SeR4 6.03.7 MIXED OXYGEN, SULFUR, AND SELENIUM FUNCTIONS
6.03.1
98 98 98 100 100 100 101 101 101 105 105 105 105 105 106 106
INTRODUCTION
As in COFGT (1995) <1995COFGT(6)67>, this chapter covers synthesis of compounds of general formula RC(X)(Y)Z where each of X, Y, and Z are independently linked through O, S, Se, and Te atoms. No compound of this type containing Te atoms has been reported in the literature, so only compounds containing O, S, and Se are discussed. In some cases older principal articles omitted in the basic work are included. Since 1993, no general review focused on preparation of the structural types covered by this chapter has appeared.
6.03.2
FUNCTIONS BEARING THREE OXYGEN ATOMS
6.03.2.1 6.03.2.1.1
Methods for the Preparation of Carboxylic Ortho-esters and Related Compounds Ortho-esters from 1,1,1-trihaloalkanes, a,a-dihaloethers and a-haloacetals
The extended Williamson synthesis of ortho-esters by nucleophilic displacement of three halogen atoms in 1,1,1-trihaloalkanes by sodium alkoxides has been used rarely owing to low yields <1995COFGT(6)67>. However, 3-chloro-2-trimethoxymethyl- or triethoxymethylpyrrole derivatives (2, R = Me, Et) have been prepared <1999T4133> from 3,3-dichloro-2-trichloromethyl-1-pyrroline 1 and 10 equiv. of the corresponding sodium alkoxide in 97% and 79% yields, respectively (Equation (1)). Cl N
Cl
Cl Cl
79–97% R = Me, Et
Cl
OR OR OR
H N
NaOR
ð1Þ
Cl 2
1
Nucleophilic displacement of the halogen atoms of ,-dihaloethers (e.g., 2,2-dichloro2-methoxyacetate <1995TL1827>) also gives ortho-esters. Thus, L-dimethyl tartrate was treated with phenylmagnesium bromide to give optically active tetraol 3, which reacted with the above mentioned dihaloether to afford the ortho-ester 4 used as a chiral auxiliary in the synthesis of -hydroxy acids (Equation (2)).
HO Ph
Ph
OH
OH 3
Ph + OH Ph
MeO
Cl Cl CO2Me
Py 90%
HO Ph
Ph O
O O MeO2C 4
Ph Ph
ð2Þ
77
Functions Containing Three Chalcogens (and No Halogens)
Reaction of bromomalonaldehyde tetraethylacetal 5 <1995T8623> with potassium t-butoxide afforded triethyl 3,3-diethoxy-ortho-propionate 6 via elimination of hydrogen bromide to diethoxymethylketene diethylacetal (Scheme 1), cf. Section 6.03.2.1.5 OEt OEt
OEt OEt
t-BuOK EtO
OEt
EtO
Br 5
EtOH
OEt
OEt OEt OEt EtO OEt 6
Scheme 1
6.03.2.1.2
Ortho-esters from imidate ester salts
Owing to the limited use of the Pinner method <1995T8623>, iminium salts were prepared from secondary or tertiary amides 7 <1997TL8499> by reaction with trifluoromethanesulfonic anhydride in the presence of pyridine at low temperatures. The resulting imino and iminium triflates afforded ortho-esters 8 by reaction with alcohols (Scheme 2, R1 = e.g., Ph(CH2)2, R2 and R3 = H or alkyl, R4 = alkyl). The yields of bridged ortho-ester 9 formed by reaction of suitable amides with 2,2-bis(hydroxymethyl)-propan-1-ol were 59–88%. O R1
N R3 7
R2 Tf2O, Py
OTf OR4 4 2 R4OH + R + R2 R OH R1 N R1 N R3 R3
OR4 4 OR R1 OR4 8
Scheme 2
O O O Ph 9
Sugar 1,2-cyclic ortho-esters 12 can be prepared <2000CAR(329)879> from the corresponding peracetylated trichloroacetimidate 10 and t-butyldimethylsilylated alcohol 11 under the action of usual promoters for trichloroacetimidate donors (0.1 equiv.): TMDMSOTf, BF3Et2O, TfOH, AgOTf, in dry dichloromethane using 4 A˚ molecular sieves (Scheme 3).
AcO AcO
O Ph O TBDMSO
OAc O +
AcO O
CCl3
O Ph O TBDMSO
O HO O
O
89%
NH 10
O
AcO AcO
11
O O
OO
AcO 12
Scheme 3
6.03.2.1.3
Ortho-esters from carboxylic acids and derivatives
Bicyclic ortho-esters reviewed in COFGT (1995) <1995COFGT(6)67> have been repeatedly used as suitable protecting groups for polyfunctionalized carboxylic acids. A new method of utilizing ortho-esters 15 both for protection and asymmetric synthesis has been developed <1997PAC639,
78
Functions Containing Three Chalcogens (and No Halogens)
1997T16575, 2003CC776>. The compounds can be prepared from oxiranes 13 using zirconocene and AgClO4 in CH2Cl2 at mild conditions (room temperature, 15 min). Mechanistically, this ortho-ester formation proceeds via dioxacarbenium ion intermediate 14 (Scheme 4).
R
O
O
Cp2(Cl)Zr-Cl
R
AgClO4
O
Zr+(Cl)Cp2 O O O
13
O
R
O
O
O
C(2)-attack
+ R O Zr(Cl)Cp2O
–Cp2(Cl)Zr+
15
14
Scheme 4
Ortho-pivalates, as sugar protecting groups were prepared by reaction of pivaloyl chloride and free sugar using an HF-supported procedure <1994LA965, 1999JPR41> or by intramolecular orthoesterification using dicyclohexylcarbodiimide (DCC) <1996MM6126, 2002CAR(337)951> or thiourea in pyridine <1998CAR(308)439>. The last procedure is exemplified in Scheme 5 by preparation of 18 from 16. During these procedures, dioxacarbenium ion intermediates, e.g., 17, are formed.
H
O OR
RO
Cl
NH2CSNH2
RO O MCA
80 °C, 6 h
OR
H RO
O MCA
16
RO
O
O
H
O+O
66 %
O O
O OR
17
18
MCA = ClCH2CO R = Me3CCO
Scheme 5
Similar conversion of a series of peracetylated sugars into the corresponding 1,2-ortho-esters via in situ generation of glycosyl iodides promoted by I2/Et3SiH followed by addition of the respective alcohol has also been reported <2003TL7863>. Formation of oleanolyl 1,2-O-ortho-acetates instead of expected glycosides was studied under the conditions of Ko¨nigs–Knorr glycosidation <2001M839>. Thus, acetobromo sugars with diphenylmethyl-oleanolate in the presence of drierite, Ag2O, and iodine in dry chloroform afforded ortho-esters 19, where R = OAc, peracetylated - or -D-glucopyranosyl, or -D-galactopyranosyl, in ca. 30% yields.
OAc
H O
O OAc R
O O O
H
O
Ph Ph
H 19
Oxidative cyclization–methoxycarbonylation of propargylic acetates 20 in the presence of (CH3CN)2PdCl2/p-benzoquinone <2002TL6587> in methanol at 0 C under CO atmosphere afforded (E)-cyclic ortho-esters 21 in moderate yields (Equation (3), R1 = Me, R2 = Bn, or R1R2 = (CH2CH2)2N-BOC).
Functions Containing Three Chalcogens (and No Halogens) R1
R 1 R2 AcO
i
O
79
R2 O
O O
ð3Þ
O 21
20
i. (MeCN)2PdCl2/p-benzoquinone, MeOH, CO, 0 °C
The mechanism proposed for this reaction includes formation of a vinyl palladium intermediate, which is subjected to nucleophilic attack of MeOH on the carbon atom of the acetyl group followed by CO insertion and methanolysis to provide the ortho-ester product 21 (Scheme 6).
R1 R 2 AcO 20
Hydroquinone Benzoquinone R1 R2 O
MeO
Pd2+
R1 R2 Pd2+ O
Pd(0)
O
CO2Me
O 21
MeOH O
R1 O
R1 2 R O + Pd+ O
R2
O H
COPd+ MeOH
H
CO
Scheme 6
Bis(trifluoroacetates) 22 react with bis(epoxides) 23 under the conditions of cycloaddition polymerization to form poly(cyclic ortho-esters) 24 (Equation (4), R1 =(CH2)4, CH2C6H4CH2, R2 =(CH2)2, C6H4C(CH3)2C6H4). The yields are generally between 75% and 96% depending on the catalysts (onium salts, e.g., TBABr, TBACl, TBAI, tetrabutylphosphonium bromide) or solvents (N-methyl-2-pyrrolidone (NMP), anisole, chlorobenzene, tetrahydrofuran (THF), sulfolane) used <1995MM3490>. O F3C
O O
R1
+
O
CF3
R2
O
O
O
O
23
22
O O
O
1
O
R CF3 F3C
O
O
R2
ð4Þ O
O n
24
Spiro-ortho-esters (SOE) of general formula 25, easily accessible from lactones by reaction with epibromohydrin (R = CH2Br) and further derivatization, undergo cationic polymerization. While at high temperatures (>100 C) a double ring-opening process to give poly(ether esters) 26 takes place, at low temperatures (<40 C) single ring opening of the ether ring to give poly(cyclic ortho-esters) (27) occurs (Scheme 7) <1994MM2380, 1997MI241, 1999JPS(A)2551>. This polymerization is reversible and the obtained polymers can be readily converted into the original monomers by treatment with acid catalysts at ambient temperature.
80
Functions Containing Three Chalcogens (and No Halogens) O O iii. >100 °C i, ii
n
n
O
O
O
O
n
R
iii. <40 °C
O O
m
26
R
O
n
25
O
O
i. Epibromohydrin; ii. derivatization; iii. cationic catalyst
R
m
27
Scheme 7
6.03.2.1.4
Ortho-esters from dioxacarbenium salts
Preparation of ortho-esters from carboxylic acid derivatives often proceeds via dioxacarbenium cation intermediates (cf. Section 6.03.2.1.3). The literature concerning dioxacarbenium tetrafluoroborates was duly reviewed in COFGT (1995) <1995COFGT(6)67>. Transformations requiring photoinduced electron transfer process involving dioxacarbenium ions will be discussed here. Electron transfer from acetonides, e.g., 2,2-dimethyl-1,3-dioxolane 28, to the singlet excited state of benzene 1,2,4,5-tetracarbonitrile followed by fragmentation of the donor radical cation gave methyl radical and dioxacarbenium cation 29 <1992JOC3051, 2001T555>, which by hydrolysis formed 2-hydroxyethyl acetate 31 via unstable ortho-acid 30. Methanolysis of 29 led to the formation of ortho-ester 32 (Scheme 8). This method was also applied for polyols and sugars <2001T555>.
O
NC
CN
NC
CN
+
O
MeCN hν
28
CN
O + + O CN–
NC
CN
29 H 2O MeOH
O
O
OH
O
O OH
O 31
O
O
30
32
Scheme 8
Compound 33, available in high yields from ninhydrin, was irradiated with fumarodinitrile in benzene for 5 h at 20 C to give racemic 6:7-benzo-anellated 4-oxaspiro[2.5]octane-trans-1,2-dicarbonitrile 34 in 32% yield <2002EJO2385>. The SOE 34 is the result of a cycloaddition of the dienophile with a dioxacarbenium ion intermediate (Equation (5)). CN O
O
CN O +
O O 33
NC
hν Benzene 32%
O
O CN O
O
O 34
ð5Þ
Functions Containing Three Chalcogens (and No Halogens) 6.03.2.1.5
81
Ortho-esters from 1,1-dialkoxyalkenes
Reaction of ketene dimethylacetal 36 with mono- and disaccharides led to cyclic ortho-esters at nonanomeric positions <1995CAR(267)227, 1998CAR(305)17>. For example 35 was transformed in 92% yield into 37 (Equation (6)). This sugar-protecting group can be selectively hydrolyzed under mild conditions. HO OH OH
O CH2=C(OMe)2
+
O OH
92%
OMe OH 35
MeO
PTSA, DMF
O
36
O OMe OH
ð6Þ
37
Substituted 2-alkoxyfurans 38 undergo dye-sensitized photo-oxygenation at low temperature (80 to 70 C) <1998SL17> to give 1-alkoxy-2,3,7-trioxabicyclo[2.2.1]hept-5-enes 39 (Equation (7)). R2
R3 R4
O
hν, –70 °C
R4
OR1
R2
R3 O O O 39
38
6.03.2.1.6
ð7Þ
OR1
Ortho-esters from 1,1-dialkoxycyclopropanes and related compounds
This method of ortho-esters preparation was completely reviewed in chapter 6.03 of COFGT (1995) <1995COFGT(6)67> and no substantial progress has been made since.
6.03.2.1.7
Ortho-esters from acetals
Reactive 2-phenylseleno acetals 40 (R1 = Bz, R2 = Ph or polystyrene), obtained from sugar glycosides by 1,2-selenium migration, can be transformed to ortho-esters 41 (path A comprising oxidative cleavage and ring closure, R3 = protecting group) and allyl ortho-esters 42 (path B including oxidative cleavage, ring closure, and Ferrier-type rearrangement, R3 = H) (Scheme 9) <2000AG(E)1089, 2000MI3149, 2000MI3166>.
O
O
OR1
SeR2 A O O
OR
B
3
40
O O
O
O R3O
R3O
42
41
Scheme 9
6.03.2.1.8
Ortho-esters from ortho-carbonate esters and trialkoxyacetonitriles
This method of ortho-esters preparation was completely reviewed in COFGT (1995) <1995COFGT(6)67> and no substantial progress has been reported since.
82 6.03.2.2 6.03.2.2.1
Functions Containing Three Chalcogens (and No Halogens) Preparation of Carboxylic Ortho-esters from Other Ortho-esters Trans-esterification reactions
Trans-ortho-esterification reactions with simple alcohols was duly reviewed in COFGT (1995) <1995COFGT(6)67> and only few improved methods have appeared since 1993. A series of chiral ortho-esters was prepared by re-esterification of triethyl ortho-acrylate with chiral substituted 1,2-diols in CH2Cl2 catalyzed by MgCl2 <1997TA139>. Similarly, 4,6-O(1-ethoxy-2-propenylidene)sucrose 43 was prepared from sucrose in anhydrous dimethlyformamide (DMF) in the presence of pyridinium p-toluenesulfonate (PPTS) at ambient temperature followed by acetylation of the crude reaction mixture <1993CAR(240)143>. 2-Ethoxymethyl- or 2-(2-methoxyethyl) propane-1,3-diol was heated with triethyl ortho-formate, -acetate, or -benzoate at 150 C to give 1,3-dioxane derivatives 44 <1994CJC2084>. OEt O O AcO AcO
O O
AcO O O AcO
R1
R2 OEt O
1
R = EtOCH2, MeOCH2CH2
OAc OAc
R2 = H, Me, Ph 44
43
Equilibrium polymerization reaction, as was shown in Section 6.03.2.1.3, can be also regarded as a trans-ortho-esterification reaction <1994MM2380, 1997MI241, 1999JPS(A)2551>. A further example of polymerization re-esterification is the reaction of 8-substituted 1,6,10-trioxaspiro[4.5]decane 45 in the presence of boron trifluoride diethyl etherate to give poly(cyclic orthoester) 46 as the intermediate (Scheme 10) during polymerization to the corresponding poly(ether esters) <1998JPS(A)2439>.
O O
BF3.Et 2O
R
R
O
O + O
O–
45
O O R
R
O O
O
O
O O O
O O
–
O
O
R
R
n
R
O + O
46
Scheme 10
Certain progress from 1993 is obvious in the chemistry of bicyclic ortho-esters of general formula 47 (e.g., OBO = 2,6,7-trioxabicyclo[2.2.2]octan-1-yl derivatives 47, R2 = H) and tricyclic ortho-esters 48, which are often used as alcohol or carboxyl protecting groups. R1
R2
O
O O
R1
O
47
O O 48
83
Functions Containing Three Chalcogens (and No Halogens)
Trans-ortho-esterification reactions of glycerol, 2-hydroxymethyl-2-methylpropane-1,3-diol, or 2,2-bis(hydroxymethyl)propane-1,3-diol with triethyl ortho-formate, -acetate, and -propionate were carried out at 100–140 C in the presence of an acid catalyst to obtain OBO derivatives <2002MI225>. The best result, a yield of about 90%, was obtained in the reaction of pentaerythritol with triethyl ortho-propionate in diglyme. The bulky OBO ester function has been shown to be a useful protecting group of amino acids e.g., aspartic or glutamic acid, for preventing epimerization at the -carbon and to induce good diastereoselectivities, e.g., in diazomethane cycloadditions <1999JOC8958, 2003MI36>. 1,2,5-Ortho-esters of D-arabinose <2002EJO3864> and a 1,2,6-ortho-ester of mannose <1999TL6423> have been described and their use in the glycosylation reaction has been studied. Tricyclic ortho-esters have been used for regioselective protection of polyalcohols <2000TL4185, 2002CAR(337)2399>. Thus, 4,6-di-O-benzyl-myo-inositol 50 was conveniently prepared via 1,3,5-ortho-ester 49, obtained by transesterification from ortho-formates or -acetates <2001CAR(330)409, 2002MI63> (Scheme 11).
R HO HO HO
OH
OH OH
i. DMF, RC(OEt)3 ii. Py, BzCl BzO R = H, Me
O
O O BzO 49
OH
i. DMF, Ag2O, BnBr ii. MeOH, i-BuNH2
R HO HO HO
O
TFA, H2O
OBn OH OBn
O O
HO BnO
50
OBn
Scheme 11
6.03.2.2.2
Modification of R1 and R2 of R1C (OR2)3
This method of ortho-ester preparation was completely reviewed in COFGT (1995) <1995COFGT(6)67>. 1,1,1-Triethoxypropyne 51 was prepared in 77% yield from trimethylsilylacetylene and triethoxycarbenium tetrafluoroborate in two steps <1997TL6803> (Scheme 12).
i. BuLi
OEt
–
TMS
ii. (EtO)3C+BF4
TMS
OEt OEt
i. BuLi ii. H2O
OEt OEt OEt 51
Scheme 12
As one example of the R2 modification, the radical addition of dithiols (R =(CH2)3, (CH2)6, or CH2C6H4CH2) to polymer 52, carried out at 20 C in the presence of 2,20 -azobisisobutyronitrile (AIBN) under ultraviolet (UV) irradiation in benzene for 4 h, affords the corresponding crosslinked poly(cyclic ortho-esters), which could be depolymerized to bifunctional monomers 53 (Scheme 13) <1997MI241>.
84
Functions Containing Three Chalcogens (and No Halogens) O 5O
HS-R-SH AIBN, hν
O 5O
O
O O O n
S R S
O
S R S
TFA, CH2Cl2
O
2n 52
O
O O
O
5O
53
n
Scheme 13
6.03.3
FUNCTIONS BEARING THREE SULFUR ATOMS
6.03.3.1
Methods for the Preparation of Trithio-ortho-esters and Related Compounds
6.03.3.1.1
Trithio-ortho-esters from RC(X1)(X2)X3
(i) From 1,1,1-trihaloalkanes This methodology using trihaloalkanes (X1 = X2 = X3 = halogen) was duly covered in COFGT (1995) <1995COFGT(6)67>. The reaction has been frequently used for preparation of both trialkyl and triaryl trithio-ortho-formates. Usually the reaction is done in the presence of a strong base. However, in the case of polyfluorothiophenol, extensive polymerization was observed under basic conditions. The reaction of pentafluorothiophenol 54 with iodoform in DMF was performed without any base providing tris(pentafluorophenylsulfanyl)methane 55, besides some polymeric products <1971TL2475>. Attempts to improve the reaction of 54 with chloroform and tetrachloromethane by the presence of AlCl3 led mainly to diarylated products 56, together with 57. Only small amounts of the expected triarylated compound 55 were formed <1999JFC(98)17> (Scheme 14). F F
CHI3, DMF
F
F
F
S F
F
F
CH 3
55
SH F
F
X-CCl3, AlCl3 X = H, Cl
54
F
F
F
F
S F
F
CXCl +
F
F F
2
+
S F
55
2
57
56
Scheme 14
(ii) From -halodithioacetals and ,-dihalothioethers -Chlorodithioacetal 58 treated with methanethiol provided the corresponding product 59 <1997AJC683> (Equation (8)). O Me
O
O S
S
SMe
MeSH
Me
O S
S
SMe
Cl 58
SMe
59
ð8Þ
Functions Containing Three Chalcogens (and No Halogens)
85
Similarly, alkylation of thiophenol with chloro derivative 61 generated in situ from 1,3-dithiane 60 gave 44% yield of 62 <1994SL547> (Scheme 15).
NCS S
S
S 60
S
PhSH 44 %
S
S
Cl
SPh
61
62
Scheme 15
Easily obtained dibromo derivative 63 treated with ethanethiol in the presence of silver triflate gave 91% yield of 64 <1996CAR(282)237> (Equation (9)). Br
S
S
Br OAc
AcO
EtSH, TfOAg 91%
ð9Þ
OAc
63
6.03.3.1.2
SEt OAc
AcO
OAc
SEt
64
Trithio-ortho-esters from thioimidate esters salts
This part covering reactions shown in Equation (10) was duly reviewed in chapter 6.03 in COFGT (1995) <1995COFGT(6)67> and no substantial progress has been achieved since. SR2 R1
R3SH + –
R1
NH2 X
6.03.3.1.3
SR3 SR3 SR3
ð10Þ
Trithio-ortho-esters from carboxylic acids and derivatives
As summarized in COFGT (1995) <1995COFGT(6)67>, acyl chlorides bearing no -hydrogen atom with thiols in the presence of suitable catalysts, e.g., ZnCl2 or AlCl3, provide acceptable yields of the corresponding trithio-ortho-esters. The method was used with various chlorides of aromatic carboxylic acids <1986TL4861, 1997JOC2917>.
6.03.3.1.4
Trithio-ortho-esters from dithia- and trithiacarbenium salts
Addition of thiols or other suitable sulfur nucleophiles to dithia- and trithiacarbenium salts was reviewed in COFGT (1995) <1995COFGT(6)67>. Regarding the reaction with dithiocarbenium salts, no progress has been made since. Trithiocarbenium salts are often generated from the corresponding trithiocarbonates and their reactions and progress in this field is covered in Section 6.03.3.1.6.
6.03.3.1.5
Trithio-ortho-esters from dithioacetals
The most common procedure converts dithioacetals by deprotonation with a strong base to a metallated intermediate, which upon treatment with a disulfide provides the final trithio-orthoesters. The procedure was summarized in COFGT (1995) <1995COFGT(6)67>. Similar conditions were also used for the preparation of tris(trifluoromethylsulfanyl)methyl cyanide 66 from 65 using either the corresponding sulfenyl chloride or disulfide <1994CB449> (Equation (11)). F3CS CN F3CS 65
i. NaH ii. CF3SCl or (CF3S–)2
F3CS SCF3 CN F3CS 66
ð11Þ
86
Functions Containing Three Chalcogens (and No Halogens)
Trimethylsilyl tetrathiophosphate 67 treated with dithioacetal 68 gave 69 <1994ZOB1333> (Equation (12)).
6.03.3.1.6
S P S SiMe3 EtS SEt
+ H2C(SEt)2
67
68
S P S EtS SEt
SEt
ð12Þ
SEt
69
Trithio-ortho-formates from trithiocarbonates
As reviewed in <1995COFGT(6)67>, trithiocarbonates treated with alkyllithiums at 78 C followed by quenching with an acid provided the corresponding trithio-ortho-formates. The methodology was later extended to the six-membered 1,3-dithiane 70 and compound 71 was prepared by this method (Scheme 16). When the intermediate anion was treated with an alkylating agent before the quenching, high yields (75–89%) of substituted analogs 72 were obtained. When the mixture was allowed to reach ambient temperature before the quenching, the corresponding thioacetals 73 and 74 were formed <1991CL1315>. i. BuLi, rt ii. H+
S
i. BuLi, –78 °C ii. H+
S
Bu
S i. BuLi, rt ii. RX, 0 °C iii. H+
S 73 S
Bu
S
R
S 70
S SBu
i. BuLi, –78 °C ii. RX iii. H+
S 71
R = Me, Et, Pr, i-Pr, Bu
74
S
SBu
S
R
72
Scheme 16
Compound 75, prepared by the above-mentioned method, was deprotonated with methyllithium and the formed anion 76 was treated with dithione 77 and then with an excess of iodomethane to give an acceptable yield of complex structure 78 <1996SM175> (Scheme 17).
BuS
BuS
S
S
SMe BuS
S 75
BuS
Li+ –
SMe
S 76
OMe S
S
S
S
i. S
S
55%
OMe 77
ii. MeI
SMe S
BuS
S
BuS
SMeS S
OMe SMe
S
SBu
S S MeS
SBu
S
OMe 78
Scheme 17
Fluorine ion-induced reaction of allyl and benzyl silanes with both linear and cyclic trithiocarbonates provided good yields of the corresponding trithio-ortho-esters <1994TL161> (Equations (13) and (14)).
87
Functions Containing Three Chalcogens (and No Halogens) S + Ph SPh
PhS
TBAF 67%
SiMe3
S PhS
S S
SiMe3
+
S
TBAF 71%
Ph
ð13Þ
SPh S
ð14Þ S
S
Readily available oxazolidinone derivative 79, as an equivalent of stabilized oxomethine ylide 80, reacted with trithiocarbonate 81 as dipolarophile giving cycloadduct 82 as a racemate and only the shown regioisomer was detected (Scheme 18). Derivatives of 79 bearing at C-6 t-butyldimethylsilyl (TBDMS)-protected (R)--hydroxyethyl substituent gave the corresponding cycloadduct in only 20% yield <1997JOC3438>. S H
MeS
O O
N O
MeCN 80 °C
O
N
+ –
CO2PNB
H
SMe
S
81
N
60%
O
SMe CO2PNB
CO2PNB 79
SMe
82
80
Scheme 18
One of the methods frequently used for the synthesis of 2-alkylsulfanyl-1,3-dithiole derivatives 85 is shown in Scheme 19. The method is based on reduction of alkylsulfanyl-1,3-dithiolium salts 84, easily obtained from the corresponding 1,3-dithiole-2-thiones 83 <1994JOC5324, 1994JOC6519, 1996JCS(P1)783, 1996SM175, 1997JOC1903, 1997S26, 1998CC361, 1998JMAC1185, 2001EJO933, 2001MI145, 2001SM97, 2002JMAC2137>. R1
S S
R2
R1
R3X
S
R2
83
– S X SR3 + S
R1
S
R2
S
SR3
84
85
Scheme 19
Alkylation of 83 is done with common alkylation agents, e.g., iodomethane <1994JOC6519>, dialkyl sulfate followed by tetrafluoroboric acid <1996JCS(P1)783, 1997S26, 2001MI145>, methyl triflate <1994JOC5324, 1997JOC1903, 1998CC361, 1998JMAC1185, 2001EJO933, 2001SM97, 2002JMAC2137>, or dimethoxycarbenium tetrafluoroborate formed in situ from ortho-formate and boron trifluoride diethyl etherate <1996SM175>. Yields of the corresponding dithiolium salts are frequently nearly quantitative. The reduction step is usually done with sodium borohydride and yields are also usually high, very often over 90%. Only very rarely did the borohydride reduction lead to decomposition and use of sodium cyanoborohydride was necessary <1994JOC5324, 2001EJO933>. Compounds 85 are of a great interest since they are intermediates of fulvane derivatives studied as perspective synthetic materials. Besides the mentioned references, there are many others using the same procedure without isolating the 2-alkylsulfanyl-1,3-dithiole intermediates. Some interesting structures, for example crown ether derivative 86 <2001EJO933> and [60]fullerene derivative 87 <2002JMAC2137> have been synthesized by this method. O O
S
S
S SMe
O
S
SMe
S
S
O 86
87
88
Functions Containing Three Chalcogens (and No Halogens)
Dithiolium salts, e.g., 88, can be reduced with zinc to give the corresponding dimeric products, e.g., 89 <1990KGS471> (Equation (15)). S X S
S + S
X– Zn
SEt
S
S SEt S
S
S
S EtS S
S
X
X
X = CO, O, S 88
ð15Þ
89
The triflate salt of 84 reacted with anions generated in situ from anthrone <1999OL2005> or cyclononatetraene <1994HCA1377> with lithium diisopropylcyclohexylamide (LDA) to give compounds 90 and 91, respectively. R1
R2
S
S SMe
S
S SMe
O 91
90
6.03.3.1.7
Trithio-ortho-formates from tetrathio-ortho-carbonates
Seebach has reported transformation of tetrathio-ortho-carbonate to trithio-ortho-formate by treatment with BuLi at low temperature followed by quenching with water <1967AG(E)443> and the method has been used several times since <1995COFGT(6)67>. Arsenic pentafluoride oxidized (F3CS)4C to the stable salt (F3CS)3C+AsF 6 92, which treated with halide ions provided good-to-excellent yields of the corresponding trithio-ortho-esters 93. Under the described reaction conditions using potassium iodide, the oxidation product 94 was obtained in 86% yield <1994CB597> (Scheme 20).
2 (F3CS)4C + 3AsF5
SO2
2 (F3CS)4C+ AsF–6 + AsF3 + F3CS-SCF3 92
X–
KI 86 %
F3CS F3CS F3CS
X
F3CS F3CS F3CS
SCF3 SCF3 SCF3
X = F, Cl, Br 93
94
Scheme 20
6.03.3.1.8
Miscellaneous
2-Methoxy-1,3-dithiolane 95 with silylated thymine did not provide the expected 1,3-dithiolan2-yl nucleoside but 1,2-bis(1,3-dithiolan-2-yl)dithioethane 96 was obtained in 92% yield instead <1996JOC3611> (Equation (16)). This compound can also be obtained from trialkyl orthoformates and ethanedithiol <1972HCA75>.
89
Functions Containing Three Chalcogens (and No Halogens) S
S 3
OMe S
2
92%
S
S S
ð16Þ
S
S
95
96
Addition of thiols to quinone methides 97 provided the corresponding trithio-ortho-esters 98 in yields between 44% and 99% <1995PS(107)119> (Equation (17)). OH
O Me
Me
Me R
Me
3SH
ð17Þ R1S
R1S
SR2
SR3
97
6.03.3.2 6.03.3.2.1
SR2
98
Preparation of Trithio-ortho-esters from Other Trithio-ortho-esters Higher trithio-ortho-esters from trithio-ortho-formate esters
Transformation of trithio-ortho-esters, mainly via the corresponding lithium salts, has become one of the most important methods of preparation of higher trithio-ortho-esters. The lithium salts are usually generated by BuLi at 78 C as described by Seebach <1967AG(E)443, 1969S17, 1972CB487, 1972CB3280>. Selected examples of utilization of such lithium salts are given below.
(i) Alkylation with alkyl halides or triflates Alkylation of LiC(SMe)3 with a wide range of alkyl halides provided good yields of the corresponding trithio-ortho-esters, which were used as intermediates of the synthesis of methyl thiolcarboxylates <1993JCS(P1)2075>. Alkylation of LiC(SMe)3 with 4-bromobutyric acid provided quantitative yield of 5-tris(methylsulfanyl)pentanoic acid <2000JOC235>. Similar alkylation with 1-azido-3-iodopropane led to 91% yield of the corresponding azido derivative, which was used in the synthesis of a reversed thioester analog of acetyl-coenzyme A <1998JA3275>. Nucleophilic displacement of allylic chloride 99 with LiC(SMe)3 at low temperature led to an excellent yield of alkylated trithio-ortho-ester 100, which was utilized as a carboxyl anion equivalent to the synthesis of ester 101 <1994JOC4853> (Scheme 21).
LiC(SMe)3 THP-O 99
Cl
97%
THP-O
C(SMe)3 100 55 %
THP-O
COOMe 101
Scheme 21
Similarly, high yields of sartane analog 102 <1994TL9391> as well as pyran derivative 103 <2002CEJ1670> were obtained by the reaction of suitable lithium salts with the corresponding iodo and triflate derivatives, respectively.
90
Functions Containing Three Chalcogens (and No Halogens) Cl N O-TBDMS
Bu
SMe SMe SMe
O
N Ar
S
O
SMe S
O
102
103
(ii) Reaction with aldehydes and ketones Tris(alkylsulfanyl)methyllithiums are known to react with a wide range of aldehydes from simple ones e.g., 3-hydroxy-2,2-dimethylpropionaldehyde <1999JOC2903>, 6-isopropyl-3-methylhept-6en-1-al <1996JCS(P1)349>, pentadec-5-en-1-al <1998TL3115>, to much more complex aldehydes derived from amino acids <1995BMC1063> or sugars <1999SC3841, 2000TL307>. Usually good-to-high yields of the respective hydroxy derivatives 104 are obtained. The formed hydroxy derivatives are either isolated, or in situ oxidized to the corresponding oxo derivatives 105 <2001JOC5822>, or alkylated to their O-alkyl derivatives 106 <1998TL3115>. Hydroxy trithio-ortho-esters 104 are often transformed to various carboxylic acid derivatives e.g., 107 or 108 (Scheme 22) in the following steps. O R
C(SMe)3 105 OMe
R
C(SMe)3 106
OH R-CHO + (MeS)3CLi R
OH
C(SMe)3 R
104
COOMe 107 OH
SMe
R O 108
R = CH2=CH-, HOCH2CMe2-, Me2CHC(=CH2)CH2CH2CHMeCH2-, Me(CH2)8CH=CH(CH2)3CHO
Scheme 22
In spite of the report on the 1,2-addition of LiC(SMe)3 on acrolein <2001JOC5822>, a different paper reported that reaction of LiC(SPh)3 with acrolein gave the 1,2- and 1,4-adducts in a 3:5 ratio <1995TL8925>. In the case of chiral compounds, the stereoselectivity of this reaction varies <1995BMC1063, 1996JOC6685, 1997JOC3880, 1999SC3841, 2000TL307> and only rarely is one stereoisomer obtained. This is the case when bulky LiC(SPh)3 reacted with protected aldehyde 109 where L-ido derivative 110 was obtained as the only isomer in 92% yield <2000TL307> (Equation (18)).
CHO OBn O O 109
LiC(SPh)3 O
C(SPh)3 OH OBn O
92%
O 110
O
ð18Þ
Functions Containing Three Chalcogens (and No Halogens)
91
In the case of ketone 111, the reaction is stereoselective even for LiC(SMe)3 giving 94% of the isomer 112 (Equation (19)). No 1,4-addition was observed <1996JOC6685>. High yield (78%) and similar stereoselectivity was also reported for the reaction of (S)-2-acetylpyrrolidine trifluoroacetate with an excess of LiC(SMe)3 <1997JA6984>. O
OBn
O
O
O LiC(MeS)3
OBn OH
O
C(SMe)3
94%
ð19Þ
O
O 111
112
(iii) Reaction with epoxides Terminal epoxides generally react with LiC(SPh)3 to give only low yields of -hydroxy trithioortho-formates <1967AG(E)443, 1972CB487>. However, a modification of this method using LiC(SMe)3 is reported to give good-to-excellent yields of 113, which can be easily converted to -hydroxyesters <1993SC811> (Equation (20)). O
OH
LiC(MeS)3
R
R
C(SMe)3
ð20Þ
113 R = Me, PhO, PhCH2O
(iv) Reaction with ,-unsaturated ketones or esters Addition of sulfur stabilized carbanions e.g., LiC(SPh)3, to unhindered ,-unsaturated ketones has been reported to produce high yields of the 1,4-addition products <1975CC216, 1977TL3549, 1990JOC1198, 1990JOC2132>. The ready availability of such adducts combined with the variety of possible transformations of the trithio-ortho-ester unit make the reaction potentially useful. The same reaction with exocyclic derivative 114 provided only 24% yield of the product. However, when the reaction was done in the presence of trimethylsilyl chloride (TMSCl), the yield was substantially improved and 75% yield of 115 was obtained (Equation (21)). The same modification was found useful also with noncyclic compounds 116 and the corresponding ketones or esters 117 were obtained in good yields <1995TL8925> (Equation (22)). C(SPh)3
TMSCl, LiC(SPh)3
O
75%
114
115
O
O
TMSCl, LiC(SPh)3
R 116
ð21Þ
O
R = Me, 96% R = OMe, 69%
(PhS)3C
R
ð22Þ
117
Cyclic ,-unsaturated lactones add lithiated trithio-ortho-esters to the ,-double bond to give the corresponding lithium salts 119. This reaction was described for several -angelicalactone derivatives 118, the formed lithium salts can be either quenched with aqueous solutions to give the corresponding saturated compounds 120 <1995JOC5628, 2003BMC357>, or further alkylated to 121 <1994TL4123, 1995JOC5628>, or transformed by reaction with tosyl azide to the corresponding azides 122 <1999JOC2657> (Scheme 23). Enantioselective synthesis of R-2-methyl-1,4-butanediol from 5R-(1-menthyloxy)-5-furan-2-one based on the Michael addition of LiC(SPh)3 and the following Raney nickel desulfuration has been reported <1992SC1367>.
92
Functions Containing Three Chalcogens (and No Halogens) (PhS)3C R (PhS)3C
Li
O 120
O
(PhS)3C
(PhS)3CLi R
O
O
R
118
O
O
R
119 R = Me, Bu, TBDPS-O
O 121
(PhS)3C R
O
N3 O
O
122
Scheme 23
Nucleophilic addition of LiC(SMe)3 to carbaldehyde-derived 2,3-dihydro-4H-pyran-4-one 123 yielded a mixture of both 1,2- and 1,4-addition products 124 and 125, respectively. Depending on the conformation on the C-2 atom, either 1,2- or 1,4-adducts were preferentially formed <1997T7867> (Equation (23)). O
BnO
HO BnO
LiC(SMe)3
BnO
BnO
O 123
O
C(SMe)3 BnO
+
BnO
O
124
O
C(SMe)3
ð23Þ
125
Tricyclic xanthone derivative 126 added LiC(SMe)3 in a 1,4-manner to give 35% of product 127 <1997JCS(P1)1819> (Equation (24)). O
O
O
OH
LiC(SMe)3
O 126
ð24Þ
35%
O
C(SMe)3
127
Addition of LiC(SMe)3 to methyl acrylate gave 40% yield of methyl 4,4,4-tris(methylsulfanyl)butyrate <2000JOC235>.
(v) Reaction with carboxylic derivatives Tris(alkylsulfanyl)methyllithiums are known to react with both aliphatic <1995JOC6017> and aromatic <1995JOC6017, 1996JOC9572, 1996S467, 2001TL8189, 2002S921> carboxylic acid esters to provide 128. The reports showed that the reaction should be optimized to suppress formation of side products to provide good yields of the desired products. In particular, aromatic derivatives are versatile intermediates in the synthesis of aryl bis(alkylsulfanyl)thioacetates 129 <1997JOC7228, 2002S921>, -ketothioesters 130 <1996S467, 2001TL8189> or -ketoacids 131 <2001TL8189> (Scheme 24). Similar reaction of LiC(SMe)3 with other carboxylic acid derivatives such as acyl chlorides, anhydrides, or thioesters leading to variable yields of identical products have also been described. The yields of the required products were substantially enhanced when N-(methylsulfanyl)phthalimide was used in the work-up procedure <1996JOC9572>.
93
Functions Containing Three Chalcogens (and No Halogens) RS
SR SR
Ar
O Ar
O
LiC(SR)3 Ar
OMe
O 129 O SR
Ar
C(SR)3 128
O 130 O Ar
COOH 131
Scheme 24
(vi) Miscellaneous Azulene treated with LiC(SMe)3 gave intermediate 132, which was oxidized with chloranil to provide practically quantitative yield of crude derivative 133 <2001S1346> (Scheme 25).
LiC(SMe)3
C(SMe)3
Chloranil quant.
C(SMe)3
132
133
Scheme 25
6.03.3.2.2
Trans-esterification of trithio-ortho-esters
No substantial achievements have been reported since COFGT (1995) <1995COFGT(6)67> was published.
(i) Modification of R1 and R2 of R1C (SR2)3 Bromine–lithium exchange of trithio-ortho-ester 134 was used to generate the corresponding lithium salt <1980JOC740>, which after the treatment with tris(perfluorodecylethyl)silyl bromide gave fluorous trithio-ortho-ester 135 <1997JOC2917> (Equation (25)). PrS
SPr SPr
PrS
i. BuLi ii. (C 10F21CH2CH2)3SiBr
SPr SPr
ð25Þ
(C10F21CH2CH2)3Si
Br 134
135
Various substituent modifications were done with cyano derivative 66, which can be prepared either from 65 (Section 6.03.3.1.5) or by alkylation of silver cyanide with bromo derivative 136. Acidic hydrolysis of 66 with sulfuric acid provided nearly quantitatively the corresponding amide 137. Its treatment with oxalyl chloride provided either 138 or 139, depending on the ratio of the reactants, while similar treatment with phosgene failed <1994CB449> (Scheme 26).
94
Functions Containing Three Chalcogens (and No Halogens) F3CS F3CS F3CS
O
F3CS F3CS F3CS
AgCN
Br
136
CN
H2SO4
F3CS F3CS
97 %
NH2 SCF3 137
66 0.5 equiv. (COCl)2
O F3CS F3CS
SCF3
O N H
70% 1 equiv. (COCl)2
60%
O
O SCF3 SCF3 SCF3
N H
F3CS F3CS
N C O SCF3
138
139
Scheme 26
6.03.3.3 6.03.3.3.1
Methods for the Preparation of Oxidized Derivatives of Trithio-ortho-esters Oxidized trithio-ortho-esters containing at least one sulfoxide group
Sulfoxide 140 treated with LDA and methyldisulfanylmethane provided 70% of 141 as the only isolated product <1998BMCL3331> (Equation (26)). MOM-O
MOM-O
O S
H2N
O S
LDA, MeSSMe
H2N
70%
Me
SMe
ð26Þ
SMe
140
141
Reaction of trithiocarbonates 142 with 3-chloroperoxybenzoic acid (MCPBA) afforded the corresponding S-oxides 143, which reacted with organolithium compounds, e.g., methyllithium, at low temperatures in a thiophilic manner to give carbanions 144 stabilized by three sulfur atoms <1997T1323>. Hydrolysis afforded trithio-ortho-ester oxides 145 which are unstable at ambient temperature. For unsymmetrical trithiocarbonates 142, a 1:1 mixture of both possible diastereoisomers was obtained. Carbanions 144 can also be trapped by other electrophiles, e.g., iodomethane in the presence of hexamethylphosphoramide (HMPA) provided 94% of 146. Addition of the anion to enones provided either unstable adducts 147 or directly their degradation products 148 (Scheme 27). S R1S
S
MCPBA SR2
R1S
142
O
MeLi
SR2
Me
R1S – SR2
143
144
MeCH=CH-CHO Me – R3SOH
R1S O R2S
Me 148
O
S
O Me S R1S
Me SR2
147
Me O
Me R1S
S
MeI
H2O
O Me SR2
Me
146
S
R1S
O SR2
145
Scheme 27
Generation of the corresponding bridgehead carbanion from 149 followed by treatment with iodoalkanes provided no expected substituted trithiolanes and the reaction led to unexpected products, the nature of which was strongly dependent on the electrophile added. When the anion was treated with iodomethane or iodoethane, compounds 150 were isolated and their structure was proved by X-ray crystallography. However, less reactive 2-bromopropane did not react at 78 C and at room temperature provided compound 151 <1999T10341> (Scheme 28).
95
Functions Containing Three Chalcogens (and No Halogens)
Ph
O S S
O i. LDA, THF, –78 °C S S S ii. 2-PrBr, rt S H S Ph
i. LDA, THF, –78 °C SR ii. RI, –78 °C Ph 79–90 %
150
149
S
O
151
Scheme 28
Silanes have also been successfully used as alternative nucleophiles for the thiophilic addition. S-Oxide 152 treated with allyl and benzyl trimethylsilane in the presence of tetrabutylammonium fluoride provided 38–41% yields of the respective products 153 <1997T1323> (Equation (27)). S S
R
O 38–41%
S
O
S
RSiMe3, TBAF
S
152
ð27Þ
S
153
Oxidation of triaryl trithio-ortho-esters with organic peroxy acids leading to triaryl sulfoxides is well known. Asymmetric oxidation of 2-phenylsulfanyl-1,3-dithiane 154 using modified Sharpless conditions led to 65% yield of the corresponding anti-R-oxide 155 but the enantiomeric excess (ee) achieved was poor (Equation (28)). No exocyclic oxidation was observed either for compound 154 or for the similar methylsulfanyl derivative <1996T2125>.
S
Ti(O-i Pr)4, DET, TBHP
S
S
S
+
65%
SPh
ð28Þ
SPh
154
6.03.3.3.2
–
O
155
Oxidized trithio-ortho-esters containing at least one sulfone group
Treatment of 2-lithium-1,3-dithiane 156 with tosyl azide gave no dimer 157 but instead low yield of the corresponding 2-tosyl derivative 158 was obtained, together with major amounts of unidentified products <1997T9269> (Scheme 29). S
S
S Li
S
S
S
157
TosN3
S
17%
S
156
Tos 158
Scheme 29
2,5-Norbornadiene 159a and 2,5-norbornene 159b were added in diffuse daylight C-sulfonyldithioformate 160 in a [2 +2] fashion to give 161a (92%) and 161b (80%), respectively (Equation (29)). The compounds in crystalline form are stable in the dark <1995SUL(19)29>. Similar treatment of 160 with hex-1-ene provided the corresponding ene-reaction product <1995SUL(19)59> 162. Thermal reaction of 160 with tetramethylallene provided more than 90% yields of the corresponding ene-products (Equation (30)). S + 159a,b
R1S
S
R2
O O 160
hν
S
80–92%
SO2R2 R1S 161a,b
ð29Þ
96
Functions Containing Three Chalcogens (and No Halogens)
S +
R1S
S O
S
hν 80%
R2
1
R S
O
R2
S O
ð30Þ
O
160
162
Sulfonyldithioformates 160 treated with dienes, e.g., cyclopentadiene or substituted butadienes, provided good yields of the corresponding adducts, e.g., 163 <1995SUL(18)215> (Equation (31)). S +
1
R S
R2
S O
R2O2S
O
R1S 163
160
ð31Þ
S
Allyldithiobenzoate 164 was oxidized by air oxygen to provide, beside the allyl thiobenzoate 166, also 1-phenyl-2,6,7-trithiabicyclo[2.2.1]heptane-2,2-oxide 165 at a rate of 7% a month (Equation (32)). The structure was proved by X-ray diffraction but the total yield achieved was not given <1995SUL(18)67, 1995T11503>. S Ph
S
air O2
S
S
+ S Ph O O Ph
164
165
O
ð32Þ
S 166
Bis(methanesulfonyl) (ethylsulfanyl)methane 168, also easily available from bis(methanesulfonyl)methane, was prepared in 87% yield by treatment of 167 with sodium ethanethiolate. Compound 168 treated with 2 equiv. of BuLi followed by iodopentane provided monoalkylation product 169 and dialkylation product 170 in 76% and 17% yields, respectively <2002TL1377> (Scheme 30). O OO O S S Me (CH2)5Me EtS H O OO O S S Me Me EtS SEt
O OO O S S Me Me EtS H
EtSNa, NaH 87%
167
i. 2equiv. BuLi ii. Me(CH2)4I
169 76% +
O OO O S S Me(CH2)5 (CH2)5Me EtS H 170 17%
168
Scheme 30
Though oxidation of hexathiaadamantane derivative 171 with 2 equiv. of MCPBA provided a complex mixture of mono-, bis-, and tris-S-oxides, the same reaction with 25 equiv. of MCPBA or MnO2 led to regioselective formation of 172, which was obtained in 69% and 60% yields as the only detectable product <2000JCS(P2)1777> (Equation (33)).
S S S
S S S
171
MCPBA, 69% MnO2, 60%
O2S S O 2S
SO2
ð33Þ
S SO2
172
Functions Containing Three Chalcogens (and No Halogens)
97
Sulfonylmethane derivative 173 treated with N-phenyltrifluoromethane sulfinimide in the presence of potassium bis(trimethylsilyl)amide provided 39% yield of 174 <1998JMC1092> (Equation (34)). O O S SMe
Cl
O OO O S S CF3 SMe
i. (Me3Si)2NK ii. PhN(SO2CF3)2 39%
Cl
173
ð34Þ
174
Trimethylsilylmethyllithium added smoothly to trifluoromethanesulfonyl, nonafluorobutanesulfonyl, tridecafluorohexanesulfonyl, and heptadecafluorooctanesulfonyl fluorides to provide the corresponding methane derivatives 175. Treatment of these compounds with 2 equiv. of BuLi followed by quenching of the generated dianions with one of the mentioned sulfonyl fluorides provided anion 176. The corresponding free acids 177 were obtained in high yields (72–95%) by vacuum sublimation from concentrated sulfuric acid (Scheme 31). A series of fluorous tris(perfluoroalkanesulfonyl)methanes was prepared in this way and catalytic activity of their lanthanide(III) salts was studied <1999JOC2910, 2000SL847, 2002T3835>.
i. 2 equiv. BuLi
O OO O S 1 1 S Rf Rf
2
ii. Rf SO2F
O OO O S S 1 – Rf + O S 2 Li Rf O 176
175
O OO O S S 1 Rf O S 2 Rf O 177
H2SO4
1
Rf
1 Rf
72–95%
Scheme 31
Reaction of 3 equiv. of nonafluorobutanesulfonyl fluoride with 4 equiv. of methylmagnesium chloride provided the corresponding magnesium salt 178 and its acidic hydrolysis gave 179 <1999SL1990> (Scheme 32).
C4F9SO2F
MeMgCl
(C4F9SO2)3CMgCl
O OO O S S C4F9 C4F9 O S C4F9 O
H2SO4
178
179
Scheme 32
The reaction of sulfinate anions with thiophosgene has been discovered <1980OPP229>. In the case of 1-adamantyl derivative 180, tris(adamantylsulfonyl)methane 181 was obtained in 39% yield <1992SUL(15)209> (Scheme 33).
AdSO2Na
CSCl2
(AdSO2)2CH-S-SO2Ad
180
–S 39%
O OO O S S Ad Ad O S Ad O 181
Scheme 33
6.03.3.3.3
Oxidized trithio-ortho-esters containing at least one sulfonate group
This was duly reviewed in COFGT (1995) <1995COFGT(6)67> and no substantial progress has appeared since its publication.
98 6.03.4
Functions Containing Three Chalcogens (and No Halogens) FUNCTIONS BEARING THREE SELENIUM ATOMS
6.03.4.1
Methods for the Preparation of Triseleno-ortho-esters
6.03.4.1.1
Triseleno-ortho-esters from triselenacarbenium salts
New examples documenting the usefulness of this method have been published <1996JOC2877>.
6.03.4.1.2
Triseleno-ortho-esters from diselenoacetals and related compounds
1,3-Diselenane 182 treated with BuLi and MeSeSeMe provided excellent yields of the corresponding triseleno-ortho-ester as a single cis-isomer 183 having the MeSe group in equatorial position. This compound treated with lithium diisopropylamide and then with MeOH or MeI provided good yields of the corresponding trans-derivatives 184 or 185 <1996TL8015> (Scheme 34). It was necessary to use potassium diisopropylamide (KDA) instead of BuLi to obtain similar PhSe derivative which was obtained in 92% as a mixture of cis-trans isomers in a ratio of 98:2 <1996TL2667>.
SeMe
Se Se
i. BuLi ii. MeSeSeMe 81%
182
i. LDA ii. MeOH
H Se SeMe Se 183
Se H Se
95%
184
i. LDA ii. MeI 93%
SeMe Se Me Se 185
Scheme 34
6.03.5
MIXED CHALCOGEN FUNCTIONS INCLUDING OXYGEN
6.03.5.1 6.03.5.1.1
Methods for the Preparation of Functions R1C(OR2) (OR3)SR4 From R1C(X1)(X2)X3
(i) From ortho-esters Treatment of partially protected mercaptodioles or mercaptotrioles 186 with methyl orthoformate in the presence of p-toluenesulfonic acid provided high yields (78–85%) of 187 <1996JOC3604, 1997JHC909> (Equation (35)). OMe
OH TBDMSO
R
O
(MeO)3CH 78–85 %
S
TBDMSO
SH 186
R = H, TBDMSOCH2
ð35Þ
R 187
Reactions of electrophilic carbenes with thiocarbonyl compounds are believed to occur through intermediate thiocarbonyl ylides <2000PJC1503>. Dimethoxycarbene formed by thermolysis of oxadiazoline 188 was trapped with adamantanethione 189 to provide 92% yield of the first 2,2-dialkoxythiirane described 190 <2001OL2455> (Equation (36)).
Functions Containing Three Chalcogens (and No Halogens) MeO OMe N N
S
+
O
188
99
S OMe Heat 92%
OMe
189
ð36Þ
190
(ii) From ,-dihalothioethers Acetylated dibromo derivative 63 treated with methanol, ethanol, or allyl alcohol in the presence of silver triflate provided good yields of the corresponding acetylated o-thiolactones 191 <1996CAR(282)237> (Equation (37)). S
Br Br OAc
AcO
OR
S ROH, TfOAg
OR OAc
AcO
OAc
OAc R Yield (%) 90 a Me 69 b Et Allyl 70 c
63
ð37Þ
191
Treatment of trichloro derivatives 192 with Na2CO3 in methanol led to selective replacement of both geminal chloro atoms to afford dimethoxy derivatives 193 <1994JOC6973> (Equation (38)). O
O SR Na2CO3–MeOH
Cl
Cl
SR
Cl
MeO OMe
Cl
192
ð38Þ
193
(iii) From thioesters Ozonolysis of 194 and 196 in CH2Cl2 at 78 C followed by reduction with Me2S gave good yields of cage compounds 195 and 197, respectively <1997T17653> (Equations (39) and (40)). OAc
O i. O3, CH2Cl2 ii. Me2S
O
60–65 %
O
O R 194
O
ð39Þ
O R 195
CHO
O R 196
SMe
O O
SMe
i. O3, CH2Cl2 ii. Me2S
SMe
80–85 %
CHO O
SMe
O O
ð40Þ
O R 197
(iv) From dithioesters Aromatic dithioesters 198, which are easily available either from the appropriate nitriles or from the corresponding Grignard reagents, were transformed in high yields to 201 by treatment with sodium methoxide followed by iodomethane. Intermediate formation of 199 and 200 was supposed <1997MI3691, 2001T1289> (Scheme 35).
100
Functions Containing Three Chalcogens (and No Halogens)
S
S SR2
MeONa
MeO MeONa
OMe
R1
S–Na+ OMe
R1
R1 198
199
200
MeI
R1 = Me, CH2 = CH–; R2 = Me, CH2COOH
MeO
SMe OMe
R1 201
Scheme 35
6.03.5.1.2
Miscellaneous
Protected bromopyranones, e.g., 202 <1994BMC1309, 1998CAR(308)287, 2001JA3369> and furanones 204, <1999OL1517>, treated with ethanethiol in the presence of 2,6-lutidine or collidine, usually in nitromethane, provided high yields of 203 and 205, respectively. The similar phenylsulfanyl analog of 205 was found to be unstable <1999OL1517> (Scheme 36).
O
Br
AcO
OAc
O EtSH 82%
AcO
OAc
O
SEt
203
O2CTol
O
Me
OAc
202
Br
O
EtSH
O
86%
O2CTol
O
EtS O
O2CTol
O2CTol
TolCO2
204
205
Scheme 36
6.03.5.2 6.03.5.2.1
Methods for the Preparation of Functions R1C(OR2) (SR3)SR4 From R1C(X1)(X2)X3
Good yields of 2-methoxy-1,3-dithiane were prepared from 1,3-dithiane 60 by its sequential treatment with N-chlorosuccinimide (NCS) and methanol <1994SL547> (Scheme 37).
NCS S
S 60
S
S
MeOH
S
S
70% Cl 61
Scheme 37
OMe
101
Functions Containing Three Chalcogens (and No Halogens) 6.03.5.2.2
From dithiacarbenium salts
Hexathiaadamantane 171 in superacid media (e.g., CF3SO3H, FSO3H-SbF5, or H2SO4SO3) formed carbodication 206, which treated with ice provided oxa derivative 207 <1999OL1771, 2000JCS(P2)1777> (Scheme 38).
S S S
+ S S S + S S
S S S
171
S S
H2O 30%
S
206
O S S
207
Scheme 38
6.03.5.2.3
From dithioacetals and related compounds
Acid 208 treated with lead tetraacetate provided 60% yield of 209 <1994S167> (Equation (41)). CF3
CF3
Pb(OAc)4
S S
COOH
60%
S O
ð41Þ O
209
208
6.03.5.2.4
S
From ketene dithioacetals
Intramolecular acid-catalyzed cycloaddition of hydroxysubstituted cyclic ketene dithioacetals was first described by Corey and Beames as a method of lactone protection <1973JA5829>. Though the methodology is undoubtedly important, it was not mentioned in the corresponding chapter of COFGT (1995) <1995COFGT(6)67>. Therefore, some principal older papers will be also reviewed here. Reviews on the ketene dithioacetals are also available <1977S357, 1990S171>. Several useful applications of this cyclization protocol have been described since <1986JA5221, 1992JCS(P1)1901, 1993TL1035, 1993TL1039, 1996S285, 1997JOC9107, 1998JCS(P1)9>. This reaction is a key step frequently used in the synthesis of a range of naturally occurring compounds. Transformation of mevinoline to its homolactone using ketene dithioacetal has been described <1982JOC4750>. This method was also used for the stereoselective synthesis of a range of -alkyl--butyrolactones 210 (Scheme 39). The method was also ˜ modified for the stereoselective synthesis of ,-bis-functionalized -butyrolactones <1993JOC2725>. OH S R
S
TFA–CH2Cl2 71–95 %
R
S O S
HgCl2–aq. MeCN
R O O 210
Scheme 39
Similarly, the cyclization can also be used for the synthesis of functionalized -lactones with remote asymmetric induction. Acid-catalyzed cyclization of ketene dithioacetals 211 by HCl/ CH2Cl2 gave predominantly the -isomers of the bicyclic dithio-ortho-esters 212 (Equation (42)). Hydrolysis (HgCl2, pH 7) then gave the corresponding lactones <1986JA5221, 1986TL3661>. High yield of spirocyclic compound 214 with acceptable diastereomeric ratio (12:1) was also obtained by acidic cyclization of 213 (Equation (43)). The compound was used as an intermediate of the salinomycin synthesis <1998JCS(P1)9>. A similar procedure was also used in the synthesis of a key synthetic fragment of rapamycin <1996SL903>.
102
Functions Containing Three Chalcogens (and No Halogens) OSiMe3 R
BOM S
R S
HCl–CH2Cl2 76% (R = H) 92% (R = Me)
S
BOM
H
211
O
ð42Þ
S
212
Et
HO
OH
HCl–CH2Cl2
HO S
S
81%
S
Et
H
213
ð43Þ
O
S
214
Even higher diastereoselection was reported in case of compound 215, where the stereocontrol was by bromine and oxazolidine moieties <1996S285> (Equation (44)).
S
S
Bn Br
S
S O
0 °C, 18 h
N
O
O
ð44Þ
N
H
O
OH O
O
47%
O
Br Bn 215
Lactols 216 and 218 on reaction with 2-lithio-2-trimethylsilyl-1,3-dithiane followed by acidic treatment afforded high yields of 217 <1994TA247> and 219 <1996SL925> (Equations (45) and (46)). MOMO BDPSO
OH
O OMOM
Me3Si
Li
S
S
+
MOMO BDPSO
OMOM
CSA, THF
O S
83%
216
ð45Þ S
217
COOEt OH
Me3Si
Li
S
S
+
COOEt HCl, dioxane
S
91%
O
O
218
ð46Þ
S
219
A similar reaction was also involved in transformation of lactol 220 into a 2:1 mixture of the corresponding aldehydes 221 and 222 <1998EJO275> (Equation (47)). OH O S S 220
CHO
CHO PPTS 99%
+
S
S
O S 221
O S
ð47Þ
222 2:1
Intramolecular nitrone cycloaddition reaction of 223 led stereoselectively to a high yield of 224 <2002OL1227> (Equation (48)).
103
Functions Containing Three Chalcogens (and No Halogens) O S S O
H [3 + 2]
H Bn
N+
O S S OO
ð48Þ
N H Bn
O– 223
224
As reported earlier <1993TL2649>, bis-sulfonyl derivative 225 can be easily oxidized to give stereoselectively oxirane 226 (Equation (49)). Similarly, enantiomerically and diastereomerically pure spirocyclic bis-sulfinyl oxiranes 228 (R = Ph, substituted Ph, cyclohexyl) were prepared by stereoselective nucleophilic epoxidation of ketene thioacetal dioxides 227 (Equation (50)). These novel epoxides represent potentially versatile chiral substrates for the preparation of a variety of heterosubstituted carbonyl compounds <1998JOC7128, 2002OL1227>. In these cases, the nucleophilic peroxide attacks the top face of the ketene dithioacetal, whereas the cycloaddition reaction of nitrone mentioned above attacks the opposite face. SO2Me Ph
O2S
Me
MCPBA 87%
H
O SO2Me
Ph O2S
225
O S S O
226
O S S O
H2O2 or TBHP R
ð49Þ
Me
70–98 %
O
R +
H Major
H 227
O S S O
O
H
ð50Þ
R Minor 228
Hetero Diels–Alder reaction of ketene dithioacetal 229 with 3-(benzenesulfonyl)-3-butene-2-one gave 91% yield of 230 <1991JOC4098> (Equation (51)). Similarly, 1-oxo-(E,E)-2,4hexadienephosphonate with ketene dithioacetal 231 gave 232 <1995PS(103)259> (Equation (52)). PhSO2 S
S +
CCl4, 25 °C O
91%
229
PhSO2 S O
ð51Þ
S
230
O S
S
+
P(O)(OMe)2
S (MeO)2(O)P
231
ð52Þ
O S 232
Similar hetero [4+2]-cycloaddition reaction of 233 and silylketene dithioacetal 234 proceeds at room temperature to give dihydropyran 235 in good yield <2002JOC7303>. Similarly, 233 with alkyne 236 provided 85% yield of the 2:1 adduct 237 as the only isolated product <2002JOC7303> (Scheme 40). It has been established that the ketene dithioacetal group influences the stereospecificity of anodic carbon–carbon bond formation. Earlier similar enol ether enol–ether coupling led to 1:1 mixtures of stereoisomers <1992JA1033>. Anodic oxidation of 238 in the presence of THF led to good yields of one stereoisomer of 239 (Equation (53)). In the case of five-membered product, only the trans-isomer was formed. Alternatively, the six-membered product was established as the cis-isomer. No rational explanation of this fact has been found <2001OL1729>. Bridged bicyclic product 241 was obtained in 75% yield by the same method from 240 <2001T5183>
104
Functions Containing Three Chalcogens (and No Halogens)
86%
EtS
SiMe3
EtS
EtS
O P(OEt)2
O P(OEt)2
Me3Si
EtS
O
O
EtS
EtS 234 O P(OEt)2 CHO 233
235
SiMe3
SMe 236
O P(OEt)2
Me3Si
236 85%
MeS
O (EtO)2P
O
SiMe3
O
O P(OEt)2
O SMe 237
Scheme 40
(Equation (54)). The suggested mechanism includes anodic oxidation leading to the formation of a radical cation from the ketene dithioacetal, which in turn is trapped by the side-chain enol ether. Following trapping by MeOH, loss of a second electron, and a second trapping with MeOH, finally afford the cyclization products with one dithio-ortho-ester group and one acetal group. OMe OMe S
n
S
MeOH–THF 8 mA, 2.2 F/mol
n
70–94 % n = 1, 2
MeO
MeOH–THF 8 mA, 2.2 F/mol 75%
S
ð53Þ
S 239
238
MeO S
OMe S
S S
240
OMe MeO OMe
ð54Þ
241
Similarly, the reactions where the initial cation radical is trapped with oxygen nucleophiles were studied. For example, anodic oxidation of ketene dithioacetal 242 in methanol led stereoselectively to 243. This methodology was used also for the synthesis of more substituted compounds 243 and preliminary results of the synthesis of -lactones 244 were mentioned without any data concerning the stereoselectivity <2001OL1729, 2002JA10101> (Equations (55) and (56)). HO
n
S
MeOH 8 mA, 2.2 F/mol
n
OMe
O
70–94 %
S
S
ð55Þ
S n = 1, 2 242
R
243
R N
MeOH 8 mA, 2.2 F/mol
O
S
30–67 %
O
Me OMe
O S
S 244
S
ð56Þ
105
Functions Containing Three Chalcogens (and No Halogens) 6.03.5.2.5
Miscellaneous
Deprotonation of sulfonyl oxirane 245 with butyllithium followed by addition of S-phenyl benzenethiosulfonate gave 69% yield of 246 <1998JCS(P1)4097> (Equation (57)). PhO2S
i. BuLi, THF, –100 °C O PhO2S ii. PhSSO2Ph
O O
69%
O
O
PhS
ð57Þ
O
245
246
Nitroethene derivatives 247 undergo fast intramolecular cyclization in CF3SO3H to give dications 248, which in the presence of MeOH provided good-to-excellent yields of the corresponding products 249 <2001EJO1525> (Scheme 41). RS
NO2
HO + H N
TfOH
nS
+ S
HO SR
N
S
n
247
SR
MeOH
OMe
n
248
249
R = Me, PhCH2CH2; n = 1– 4
Scheme 41
Selective protection of the hydroxyl groups in 2,3-dithiothreitol 250 as t-butyldimethylsilyl ethers followed by treatment with trimethyl ortho-formate in the presence of camphorsulfonic acid (CSA) gave 80% yield of 2-methoxy-1,3-dithiolane 251 <1996JOC3611> (Equation (58)). SH i, ii
HO OH
TBDMSO
OMe S
80%
S
TBDMSO
HS 250
ð58Þ
251
i. TBDMSCl, imidazole, DMF; ii. HC(OMe)3, CSA, CH2Cl2
Methods for the Preparation of Functions R1C (OR2) (OR3)SeR4
6.03.5.3
No further advances have occurred in this area since the publication of COFGT (1995) <1995COFGT(6)67>.
6.03.6
MIXED SULFUR AND SELENIUM FUNCTIONS
6.03.6.1 6.03.6.1.1
Methods for the Preparation of Functions R1C(SR2) (SR3)SeR4 From dithioacetals
While tris(trifluoromethylsulfanyl)methylcyanide 66 was obtained in good yields by alkylation of 65 (cf. Section 6.03.3.1.5), the corresponding seleno analog 252 was obtained only in 7% yield <1994CB449> (Equation (59)). F3CS CN F3CS 65
i. NaH ii. CF3SeCl 7%
F3CS SeCF3 CN F3CS 252
ð59Þ
106
Functions Containing Three Chalcogens (and No Halogens)
Trans-2-methylseleno-1,3-dithiane 253 was prepared in 90% yield as a single isomer with the methylseleno group in equatorial position. The compound can be transformed to the cis-isomer 254 similarly as described for the 2-methylseleno-1,3-diselenane 184 <1996TL8015> (Scheme 42).
S S
i. BuLi ii. MeSeSeMe
i. LDA ii. MeOH
H S
90%
S
SeMe
93%
253
SeMe S S
H
254
Scheme 42
6.03.6.2
Methods for the Preparation of Functions R1C(SR2) (SeR3)SeR4
No further advances have occurred in this area since the publication of COFGT (1995) <1995COFGT(6)67>.
6.03.7
MIXED OXYGEN, SULFUR, AND SELENIUM FUNCTIONS
Chloroform solutions of vinyl selenides 255 in the presence of catalytic amount of CF3COOH quickly cyclized to the corresponding 2-butylsulfanyl-1,3-oxaselenolanes; the major isomers 256 were indicated by nuclear magnetic resonance (NMR) techniques <1997CL545> (Equation (60)). R
Se
OH SBu
R CF3CO2H 77–88%
Se
O
ð60Þ
SBu 256
255
A new convenient synthesis of dialkyldiselenides by photolysis of Barton PTOC esters 257 in the presence of 258 provided adducts 259. Though the adducts were not isolated but hydrolyzed in situ with hydrochloric acid and then oxidized with air to the required diselenides, the structure of 259 was firmly established by 1H-, 13C-, and 77Se-NMR <1996T11163> (Scheme 43).
Se N R1COO 257
+ S
R2
OR3
258
N S R3O R2 SeR1
R1SeSeR1 + R3COOR2 +
N H
S
259
Scheme 43
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Functions Containing Three Chalcogens (and No Halogens) 1999SC3841 1999SL1990 1999T4133 1999T10341 1999TL6423 2000AG(E)1089 2000CAR(329)879 2000JCS(P2)1777 2000JOC235 2000MI3149 2000MI3166 2000PJC1503 2000SL847 2000TL307 2000TL4185 2001CAR(330)409 2001EJO933 2001EJO1525 2001JA3369 2001JOC5822 2001M839 2001MI145 2001OL1729 2001OL2455 2001S1346 2001SM97 2001T555 2001T1289 2001T5183 2001TL8189 2002CAR(337)951 2002CAR(337)2399 2002CEJ1670 2002EJO2385 2002EJO3864 2002JA10101 2002JMAC2137 2002JOC7303 2002MI225 2002MI63 2002OL1227 2002S921 2002T3835 2002TL1377 2002TL6587 2003BMC357 2003CC776 2003MI36 2003TL7863
109
K. M. K. Kutterer, G. Just, Synth. Commun. 1999, 29, 3841–3853. J. Nishikido, F. Yamamoto, H. Nakajima, Y. Mikami, Y. Matsumoto, K. Mikami, Synlett 1999, 1990–1992. K. A. Tehrani, D. Borremans, N. De Kimpe, Tetrahedron 1999, 55, 4133–4152. A. Ishii, T. Nakaniwa, K. Umezawa, J. Nakayama, Tetrahedron 1999, 55, 10341–10350. S. Hiranuma, O. Kanie, C. H. Wong, Tetrahedron Lett. 1999, 40, 6423–6426. K. C. Nicolaou, H. J. Mitchell, K. C. Fylaktakidou, H. Suzuki, R. M. Rodriguez, Angew. Chem., Int. Ed. Engl. 2000, 39, 1089–1093. Z. Yang, W. Lin, B. Yu, Carbohydr. Res. 2000, 329, 879–884. G. P. Miller, I. Jeon, A. N. Faix, J. P. Jasinski, A. J. Athans, M. C. Tetreau, J. Chem. Soc., Perkin Trans. 2 2000, 1777–1780. A. Padwa, A. G. Waterson, J. Org. Chem. 2000, 65, 235–244. K. C. Nicolaou, H. J. Mitchell, R. M. Rodriguez, K. C. Fylaktakidou, H. Suzuki, S. R. Conley, Chemistry-Eur. J. 2000, 6, 3149–3165. K. C. Nicolaou, K. C. Fylaktakidou, H. J. Mitchell, F. L. Van Delft, R. M. Rodriguez, S. R. Conley, Z. Jin, Chemistry-Eur. J. 2000, 6, 3166–3185. G. Mlston, H. Heimgartner, Pol. J. Chem. 2000, 74, 1503–1532. A. G. M. Barrett, D. C. Braddock, D. Catterick, D. Chadwick, J. P. Henschke, R. M. McKinnell, Synlett 2000, 847–849. A. Lubineau, O. Gavard, J. Alais, D. Bonnaffe, Tetrahedron Lett. 2000, 41, 307–311. K. M. Sureshan, M. S. Shashidhar, Tetrahedron Lett. 2000, 41, 4185–4188. T. Praveen, M. S. Shashidhar, Carbohydr. Res. 2001, 330, 409–411. M. R. Bryce, A. S. Batsanov, T. Finn, T. K. Hansen, A. J. Moore, J. A. K. Howard, M. Kamenjicki, I. K. Lednev, S. A. Asher, Eur. J. Org. Chem. 2001, 933–940. J. M. Coustard, Eur. J. Org. Chem. 2001, 1525–1531. W. Yu, Z. Jin, J. Am. Chem. Soc. 2001, 123, 3369–3370. S. Knapp, G. J. Morriello, S. R. Nandan, T. J. Emge, G. A. Doss, R. T. Mosley, L. Chen, J. Org. Chem. 2001, 66, 5822–5831. W. Seebacher, E. Haslinger, R. Weis, Monatsh. Chem. 2001, 132, 839–847. U. Jordis, K. Bhattacharya, P. Y. Boamah, V. J. Lee, Molecules 2001, 7, 145–154. Y. Sun, B. Liu, J. Kao, D. A. d’Avignon, K. D. Moeller, Org. Lett. 2001, 3, 1729–1732. M. Dawid, G. Mloston, J. Warkentin, Org. Lett. 2001, 3, 2455–2456. K. Kurotobi, K. Takakura, T. Murafuji, Y. Sugihara, Synthesis 2001, 1346–1350. S. Frenzel, M. Baumgarten, K. Mullen, Synth. Met. 2001, 118, 97–103. M. Mella, M. Fagnoni, A. Albini, Tetrahedron 2001, 57, 555–561. H. N. Tran, T. N. Pham, Tetrahedron 2001, 57, 1289–1295. S. H. K. Reddy, K. Chiba, Y. Sun, K. D. Moeller, Tetrahedron 2001, 57, 5183–5197. F. Zouhiri, D. Desmaele, J. d’Angelo, M. Ourevitch, J. F. Mouscadet, H. Leh, M. Le Bret, Tetrahedron Lett. 2001, 42, 8189–8192. M. Karakawa, F. Nakatsubo, Carbohydr. Res. 2002, 337, 951–954. K. M. Sureshan, M. S. Shashidhar, T. Praveen, R. G. Gonnade, M. M. Bhadbhade, Carbohydr. Res. 29-11-2002, 337, 2399–2410. P. Wipf, Y. Uto, S. Yoshimura, Chemistry-Eur. J. 2002, 8, 1670–1681. D. Leinweber, M. Schnebel, R. Wartchow, H. G. Wey, H. Butenschon, Eur. J. Org. Chem. 2002, 00, 2385–2390. S. Sanchez, T. Bamhaoud, J. Prandi, Eur. J. Org. Chem. 2002, 00, 3864–3873. B. Liu, S. Duan, A. C. Sutterer, K. D. Moeller, J. Am. Chem. Soc. 2002, 124, 10101–10111. D. Kreher, M. Cariou, S. G. Liu, E. Levillain, J. Veciana, C. Rovira, A. Gorgues, P. Hudhomme, J. Mater. Chem. 2002, 12, 2137–2159. S. Arimori, R. Kouno, T. Okauchi, T. Minami, J. Org. Chem. 2002, 67, 7303–7308. A. Noomen, Progr. Org. Coatings 2002, 45, 225–230. M. S. Shashidhar, ARKIVOC 2002, 63–75. V. K. Aggarwal, S. J. Roseblade, J. K. Barrell, R. Alexander, Org. Lett. 2002, 4, 1227–1229. M. Clericuzio, I. Degani, S. Dughera, R. Fochi, Synthesis 2002, 921–927. A. G. M. Barrett, N. Bouloc, D. Christopher Braddock, D. Catterick, D. Chadwick, A. J. P. White, D. J. Williams, Tetrahedron 2002, 58, 3835–3840. Y. Zhu, D. G. Drueckhammer, Tetrahedron Lett. 2002, 43, 1377–1379. K. Kato, Y. Yamamoto, H. Akita, Tetrahedron Lett. 2002, 43, 6587–6590. C. Mugnaini, M. Botta, M. Coletta, F. Corelli, F. Focher, S. Marini, M. L. Renzulli, A. Verri, Bioorg. Med. Chem. 2003, 11, 357–366. M. Oba, N. Nishiyama, K. Nishiyama, Chem. Commun. (Cambridge) 2003, 776–777. M. Mergler, F. Dick, B. Sax, P. Weiler, T. Vorherr, J. Pept. Sci. 2003, 9, 36–46. M. Adinolfi, A. Iadonisi, A. Ravida, M. Schiattarella, Tetrahedron Lett. 2003, 44, 7863–7866.
110
Functions Containing Three Chalcogens (and No Halogens) Biographical sketch
Stanislav Ra´dl was born in Pilsen, Czechoslovakia. After graduation from the Prague Institute of Chemical Technology in 1976 he joined the Research Institute of Pharmacy and Biochemistry in Prague. He received his Ph.D. in medicinal chemistry in 1984. From 1985 to 2003 his positions included: research scientist, senior research scientist, project leader and department head. He spent 1992–1993 as a visiting scientist at the Hoffmann-La Roche Research Center, Nutley, NJ. Besides medicinal chemistry, his research interests include mainly synthetic aspects of various nitrogen-containing heterocycles. He has coauthored many original articles on antibacterial quinolones, as well as several reviews on various aspects of this group of therapeutic agents. Dr. Ra´dl has also written three chapters of Adv. Heterocycl. Chem. and one chapter of Comp. Heterocycl. Chem. 2nd edn. He is an editor of Collect. Czech. Chem. Commun. and contributing editor of Drugs of the Future.
Svatava Voltrova´ was born in Bohumı´ n, she studied at Prague Institute of Chemical Technology, where she obtained an M.Sc. in 1985 under the direction of Professor O. Cˇervinka and Ph.D. in 1989 under the supervision of Professor J. Kuthan. After spending 1991–1992 at the Dyson Perrins Laboratory, University of Oxford under the direction of Professor J. E. Baldwin, she returned to Prague and took up her present position as Assistant Professor at the Prague Institute of Chemical Technology. Her scientific interests include chemistry of heterocyclic compounds, especially aminopyridines, and amidiniumcarboxylates.
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Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 75–110
6.04 Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen A. M. SHESTOPALOV N. D. Zelinsky Institute of Organic Chemistry, Moscow, Russia 6.04.1 FUNCTIONS CONTAINING CHALCOGEN AND A GROUP 15 ELEMENT 6.04.1.1 Functions Bearing Chalcogen and Nitrogen 6.04.1.1.1 Functions bearing oxygen and nitrogen 6.04.1.1.2 Functions bearing sulfur and nitrogen 6.04.1.1.3 Functions bearing selenium and nitrogen substituent 6.04.1.2 Functions Bearing Chalcogen and P, As, Sb, or Bi 6.04.1.2.1 Functions bearing oxygen and P, As, Sb, or Bi 6.04.1.2.2 Functions bearing sulfur and P, As, Sb, or Bi 6.04.1.2.3 Functions bearing selenium and phosphorus substituent 6.04.2 FUNCTIONS CONTAINING CHALCOGEN AND A METALLOID AND POSSIBLY A GROUP 15 ELEMENT 6.04.2.1 Functions Bearing Chalcogen and Boron 6.04.2.2 Functions Bearing Chalcogen and Silicon 6.04.2.2.1 Functions bearing oxygen and silicon 6.04.2.2.2 Functions bearing sulfur and silicon 6.04.2.2.3 Functions bearing selenium and silicon 6.04.2.3 Functions Bearing Chalcogen and Germanium 6.04.2.3.1 Functions bearing two oxygen and one germanium substituents 6.04.2.3.2 Functions bearing one oxygen, one sulfur, and one germanium substituents 6.04.3 FUNCTIONS CONTAINING CHALCOGEN AND A METAL AND POSSIBLY A GROUP 15 ELEMENT OR A METALLOID 6.04.3.1 Functions Bearing Oxygen and a Metal 6.04.3.1.1 Functions bearing two oxygens and a metal 6.04.3.1.2 Functions bearing oxygen, silicon, and a metal 6.04.3.1.3 Functions bearing oxygen and two metals 6.04.3.2 Functions Bearing Sulfur and a Metal 6.04.3.2.1 Functions bearing sulfur, oxygen, and a metal 6.04.3.2.2 Functions bearing two sulfurs and a metal 6.04.3.2.3 Functions bearing sulfur, boron, and a metal 6.04.3.2.4 Functions bearing sulfur, silicon, and a metal 6.04.3.2.5 Functions bearing sulfur and two metals 6.04.3.3 Functions Bearing Selenium and a Metal
6.04.1
111 112 112 124 131 132 132 139 143 144 144 144 144 148 151 151 151 151 152 152 152 152 152 152 152 153 154 154 154 154
FUNCTIONS CONTAINING CHALCOGEN AND A GROUP 15 ELEMENT
Compounds of this class were described previously in reviews <1969ZC201, B-1970MI001, 1971S16, 1977UK685, B-1979MI002, 1979T1675, 1985HOU(E5)3, 1995COFGT(6)103>. 111
112
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
6.04.1.1
Functions Bearing Chalcogen and Nitrogen
Functional groups bearing chalcogen and nitrogen are available by modification of precursors, which contain sp3- or sp2-carbon atoms, via cycloadditions or by other miscellaneous methods. This general order is adhered to throughout this section.
6.04.1.1.1
Functions bearing oxygen and nitrogen
(i) Functions bearing two oxygen and one nitrogen substituent The functional groups containing two ether groups and one nitrogen atom bonded to an sp3carbon atom are named acetalamides. They can be classified as acyclic acetalamides and cyclic acetalamides. This is a large class of organic compounds that is widely used in organic synthesis. (a) From sp3-carbon compounds. Ethyl orthoformate reacts with benzotriazole 1 to give (benzotriazol-1-yl)diethoxymethane 2 in 90% yield <1995H131> (Scheme 1). Diacetalamides such as 2 have been reported as convenient reagents for the syntheses of various organic compounds <1998CR409>. N
(EtO)3CH, performance fluid
N N
90% N
EtO 2
N N H
O
1
OEt, PF5080, ∆
O
OEt
N N
75%
N O
O
3
Scheme 1
A general method for the masked formylation by the electrophilic reagent, viz., 1-(1,3-dioxolanyl-2-yl)-1H-1,2,3-benzotriazole 3, has been reported <2000JOC1886>. Similarly to benzotriazole, imidazole 4 has been demonstrated to react with ethyl orthoformate to give diethylacetal 5, which was used for the synthesis of quaternized diethylacetal 6 (Scheme 2) <2002JAP2002105058>.
N
N
(EtO)3CH
N H 4
N + N
EtI, AcOEt
N EtO
OEt 5
EtO
Et I–
OEt 6
Scheme 2
Treatment of lactams such as 7 with CH(OEt)3 leads to the formation of N-diethoxymethylsubstituted derivatives such as 8 (Scheme 3) <1995S168, 1996S1196>. Similarly, ergoline-active analogs 10 were obtained from substituted indole derivatives 9 <1995AP609>. Building units 13 have been produced by the reaction of compounds 11 and 12. This reaction takes place in the presence of TsOH in 1,4-dioxane at 20 C (Equation (1)) <2002S274>.
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
113
CHOEt (EtO)3CH O
O
N H
N
7
EtO
OEt 8
R1
R2
N H
(EtO)3CH
R1
R2
R
R
N
OEt
EtO 9
10
Scheme 3
R2
R2 OH
EtO
+
R1
N
O
OEt
OH
R1
N O
12
11
O
ð1Þ
O 13 1
2
R = COOEt, CN, CHO, CH(CN)2; R = H, Br, I
A similar reaction has been used for the synthesis of indole derivatives <2000SL125, 2000JMC4563>. Pyrrolidone-2 and valerolactone diethoxyacetal 15 have been obtained in 60–70% yield by the treatment of compounds 14 with ethyl orthoformate (Equation (2)) <2002DOK61>. ( )n
(EtO)3CH, TsOH
( )n
O
N H
N EtO
O
ð2Þ
OEt 15
14 n = 1, 2
In the presence of MeONa or MeOLi in methanol, trichloropyrrole dimethylacetal 16 will react to give pyrrolidin-2-one 17. The reaction is driven to completion by the elimination of three chlorine atoms (Equation (3)) <2001TL4573>. Cl Cl O
N Bn 16
Cl
Me
MeONa or MeOLi, MeOH
OMe O
N OMe Bn
ð3Þ
17
Hydroxymethyldioxolanylfluorouracil 18 and other novel classes of 1,3-dioxolane nucleosides were synthesized by a coupling reaction. Thus, 2-methoxy-4[[(t-butyldiphenylsilyl)oxy]methyl]-1,3dioxolane or 2-methyl-1,3-dioxolane have been demonstrated to react with silylated 5-fluorouracil, thymine, cytosine, and 5-chlorocytosine in the presence of TMSOTf to give the corresponding 1,3-dioxolane nucleosides <1995JOC1546>.
114
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen O F
NH N
O OH O
O 18
A new type of Morinclaparvin A 20 has been obtained from 1,2-dihydroxyanthraquinone 19 (Equation (4)) <1995MI218>. R1
O
R1
O
R1
O
R1
O
OH
O
OH
ð4Þ
O NR2
19
20 R = H, Me; R1 = H, OH
Stereoselective electrophilic addition (bromo-pivaloyloxylation) to 1-[3,5-bis-O-(t-butyldimethylsilyl)-2-deoxy-D-erythro-pent-1-enofuranosyl]uracil has been used to produce 10 -C-branched uracil nucleosides such as 21 (R = O-Piv) and, when combined with nucleophilic substitution using organo-aluminum reagents, provides a new CC bond forming method at the anomeric position to give compounds such as 21 (R = CH2CH¼CH2) <1995MI417>. It was found that substituted pyrimidine nucleosides 22 exhibit a wide spectrum of biological activities, for instance they have been proposed as antitumor drugs <1995JAP07109289>. R1
O R2
NH N
NH
O
O
N R 5O
TBDMSO
O Br
O Br R
OR3 4
TBDMSO
R O 21
22
(b) From sp2-carbon compounds. Anilide 23 has been used for the synthesis of cyclic acetals. Primarily the oxygen in compound 23 was methylated on treatment with TfOMe to yield salt 24, which has been converted to diacetal 25 on further reaction with MeONa, which has been demonstrated to react with dimethyl-L-tartrate to give a mixture of atropoisomers of cyclic diacetal 26 (Scheme 4) <2001JA5130>. COOMe
MeOOC O
OMe N
Me
+
N But
23
O
Me But
TfOMe
O Me N
25
Scheme 4
N
Me But
But
MeONa MeOH
24
O
O
26
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
115
Ethylene 27 was converted into aziridine diacetal 28 on treatment with tosylazide at room temperature in acetonitrile. However, in this case acyclic compounds were also obtained along with aziridine 28 <2001T3909>. Similarly, the corresponding aziridines, containing RFSO2 group, were obtained from unsaturated compounds such as 27 on treatment with RFSO2N3 (Equation (5)) <2001T669>. Me
OTMS + TsN3
Me
Me
CH3CN, rt
OTMS
Me
OMe 27
N OMe Ts
ð5Þ
28
Azaadamantane diacetal 30 was synthesized using the traditional method by the reaction of azaadamantane 29 with propane-1,3-diol in benzene in the presence of TsOH (Equation (6)) <2001JCS(P2)522>. N
O
N
HO(CH2)3OH, TsOH, benzene, ∆, 48 h
Me
O O
Me Me
ð6Þ
Me
Me
Me 29
30
(c) Cycloaddition methods. The Vilsmeier reagents, generated from N,N-dimethylformamide and oxalylchloride, have been demonstrated to react with N-phenacylacetylanthranilic acid 31 to give compound 32, which contains the diacetalamino fragment as a part of the bicyclic system (Equation (7)) <1996T753>. O COOH N Ac
O Ph
Ph
N
O
O
31
ð7Þ
O O
32
1,3-Dipolar cycloaddition of nitrones such as 33 to dihydropyrrolediones such as 34 leads to the formation of diastereomers such as 35 and 36 (Equation (8)) <1996JCR(S)466>. Ar EtOOC ArCH=N-Ph
+ MeO
O
33
H
O N Ph
O
Ph N O N MeO Ph
34
O
Ar
O
H
O
+ Ph N O
O
35
N
ð8Þ
OMePh
36
The -diazocompounds 37 were transformed into isomu¨nchnone derivatives of (5(S))-phenyloxazin3-one and -2,3-dione (38 and 39), by treatment with aldehyde in the presence of rhodium(II) acetate (1 mol.%) with high diastereofacial selectivity and exo-selectivity though in comparatively moderate yields (Equation (9)) <1997TL4521>. OMe NO2
H O H Ph
N2 OH
N O
4-R-C6H4-CHO, O Rh2(OAc)4 (1 mol.%) O H CH2Cl2, rt Ph N O
X
37
X = C=O, CH2; R = NO2, OMe
O
HO O
or
Ph
H
H N
O OH
X exo-II 38
O 39
ð9Þ
116
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
Under Rh2(OAc)4 catalysis, substituted 2-amino-3-cyano-4,5-dihydrofurans will react with 3 equiv. of (PhCO)2C¼N¼N to give furo[2,3-b]pyrans 40 (Equation (10)) <1998JPR51>.
R1 3(PhCO)2C=N=N
R1 NC O
CN
+
Ph
R2
R2
O
O
NR2
Ph
O NR2
ð10Þ
40
The cycloaddition of 2-aza-1,3-dienes 41, which are readily available from carboxylic acids, gives 1,3-oxazinones 42 in good yields (Equation (11)) <1999TL7079, 2002S2043>. R1 OSi(CH3)2CMe3 R
1
R2
O +
i N CHOPr
R2CHO
HN
ð11Þ
O OPri
41
42
The Diels–Alder reaction of unsaturated compound 43 with azobutadiene 44 leads to the formation of tetrahydropyridine diacetal 45, which is the key compound in the synthesis of ent-Fredericamycin A (Equation (12)) <1995JA11839>. i. 25 °C, 20 h, CH2Cl2
EtOOC
EtOOC
ii. MeSO2Cl, Et3N +
EtO
OEt
N OH
43
EtO EtO
COOEt 44
N COOEt SO2Me
ð12Þ
45
Thermal hetero-[3+2]-cycloaddition of dipolar trimethylenemethanes (46 Ð 47), to N-acyl- or N-tosylimines 48 gives -methylene--pyrrolidone acetals 49 in high yields (Equation (13)) <1999CL879>.
N O
Heat
O
O
R2
O
R3
R1
48
O
δ R1
R2
δ
R1
46
N O R3
ð13Þ
49
47
Pyrrolidone acetal 53 has been obtained by the reaction of unsaturated isocyanate 52 and dimethoxycarbene 51, which was generated from oxadiazoline 50 <1996JA12848>. Besides, oxadiazoline 50 has been demonstrated to react with azide 54 to give the indole acetal 55, which was used in the synthesis of alkaloid ()-Tazettine (Scheme 5) <1998JA3664>. The reaction of piperidinecarboxylic acid 56 with carboxylic anhydrides afforded spiropiperidineoxazolines 57, which have been used in the synthesis of opioid agonists (Equation (14)) <1999SL1923>.
117
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
MeO N N
MeO
OMe
∆
O
MeO
OMe
NCO 52
OMe
O
N 51
50
MeO
OMe 53 O
THPO O
TO 50
O
O
+
O
O
OMe OMe
O N
O
CON3
O
MeO OMe
54
55
Scheme 5 R O PhHN
COOH
R
O O
Ph N
+ (RCO)2O N Bn
O
ð14Þ
N Bn
56
57
Nucleosides such as 58 undergo intramolecular cyclization by the action of [Pb(OAc)4/I2/h] or [(diacetoxyiodo)benzene (DIB)/I2/h] to give a mixture of anomers of spirouracil nucleosides such as 59 and 60, containing the diacetalamide fragment (Equation (15)) <1997TL6421>. O
O R1
N
O R4O
R5O
O
O
R4O
R4O
N
O
R2
R1 O
R R3O
R2
HN
HN
3O
R
R
R2
R1
O O
+
N R
3O
R O
59
O
ð15Þ
NH
60
58
Under base catalysis, O-glycosyltrichloroacetimidates 62, themselves obtained from protected glucose 61 and trichloroacetonitrile, undergo ring closure to give cyclic diacetals 63 (Scheme 6) <1994SL84>.
Y X RO
OR O OH 61
Y
CH2Cl2, CCl3CN, DBU OH
RO
OR O
X
HO O HN CCl3 62
Scheme 6
Y
OR O
X RO
O H2N 63
O CCl3
118
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
Tetrahydroquinoline diacetal 66 was synthesized by the reaction of compound 64 with unsaturated compound 65 (Equation (16)) <1999AG(E)1928>. Cl +
t
Bu O
OMe TBSO
NH
OMe
N
65
O
t
O
Bu O
64
ð16Þ
OTBS
66
Under the action of Bu3S4H and AlBN in toluene, oxazolines such as 67 undergo stereoselective reductive ring closure to give compounds 68 (Equation (17)) <2002TL6911>. SePh TBSO O
OTBS
O
Ph N
R
Ph
ð17Þ
R
N O
O 68
67
Spirocyclic diacetal 71, obtained via Scheme 7 from chiral compound 69, has been used in the synthesis of the rennin inhibitor SPP-100 <2000TL10091, 2001TL4819, 2002EUP1215201A2>. Other epoxides similar to diacetals 71 are available from oxazolyloxiranes <2002OL1551>.
Ph O Ph
i, ii
N
O Ph
78%
iii
N
N O
60%
OH
OH
O
Br 69
71
70
i. LDA, LiCl, THF, 0 °C; ii. allyl bromide, 0 °C; iii. NBS, DME-H2O, 0 °C
Scheme 7
The general method for synthesis of cyclic diacetals is exemplified by the transformation of compounds 72. Lactam acetals 73 were obtained by the isomerization of phthalimidomethyleneoxiranes 72 in the presence of Lewis acid. The reaction is driven to completion by the treatment of the reaction mixture with Et3N resulting in the formation of lactam diacetals in 73–96% yields (Equation (18)) <1997S1077, 1998CC43>. O
R2
i. Lewis acid, PhCl, 120–130 °C ii. Excess, Et3N
O N
O N O
R1 R2
O
R1
O
ð18Þ 73
72 O R1 =
,
,
,
;
R2 = N O
The reaction of -hydroxyiminonitriles 74 with 2 equiv. of resorcinol or phluoroglucinol 75 occurs in the presence of HCl and leads to the formation of benzofuro[2,3-b]benzofurans 76 containing the diacetalamino fragment (Equation (19)) <1999S751>.
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
119
R1
N
OH CN
OH +
74
R2
ð19Þ
2 R2
R1
R2
i. HCl, Et2O, 0 °C ii. NaOH aq. HO
OH
O
O NH2
OH
75 76
R2 = H or OH
(ii) Functions bearing one oxygen and two nitrogen substituents Functions bearing two nitrogen and one oxygen substituents are known commonly as ester aminals. The main methods for synthesis of ester aminals are described in COFGT (1995) <1995COFGT(6)103>, and almost no new publications in this area have appeared since. Oxazoloisoindole 79, containing the aminyl fragment, can be obtained in a mixture with phthalimide derivative 80 by the treatment of compound 77 with t-butyl-2-aminoacetate 78. In the same manner, compound 77 gives a mixture of oxazoloisoindol 82 and compound 83 on the reaction with chiral N1,N2,N2-trisubstituted-1,2-propanediamine 81 (Scheme 8) <1995JOC6987>.
O
O H2N N
N
OTf
O
COOBut +
H N
N
78 HN
O 77
O
But OOC ButOOC
COOBut
O 80
79 N
ButOOC
NH
COOBut
81 O N N But OOC
O N(COOBut)2
O +
N
COOBut N
O
N(COOBut)2 83
82
Scheme 8
(iii) Functions bearing one oxygen, one sulfur, and one nitrogen substituent Functional groups bearing oxygen, sulfur, and nitrogen are nonsymmetrical, and this reduces the number of synthetic routes available for their preparation compared to their symmetrical analogs. (a) From sp2-carbon compounds. Alkenes 85 were obtained from the aldehydes by condensation with [(4-methylphenyl)thio]nitromethane 84. The treatment of the electron-deficient alkenes 85 with lithium t-butyl peroxide in THF at 78 C according to a previously reported method <1990T7429> resulted in rapid epoxidation to give 2-(tolylthio)-2-nitrooxiranes 86 in good yields (Scheme 9) <1995JOC6431, 1999JCS(P1)937>. A ring-intact oxazoloisoindole derivative was obtained through the reaction of triflate 87 with an excess of benzylmercaptan producing equal amounts of diastereomers 88 and 89 in 86% yield and the ring-open product 90 in 9% yield (Scheme 10) <1995JOC6987>. Under SnCl4 catalysis, thiophenol has been demonstrated to react with 1,2-unsaturated nucleosides 91 in the presence of N-bromosuccinamide to give substituted nucleosides 92 (Equation (20)) <2002JOC6124>.
120
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen i, ii +
RCHO
TolS
iii
NO2
NO2
R
O R
STol
84
85
NO2 STol
86
i. But OK, ii. MeSO2Cl, Pr2i NEt, iii. ButOOLi
O
Me
Me
R = Ar,
,
Me
O
Me
O
OH O,
O
R
(R1 = Me, Pri, Ph)
1
OMe
Scheme 9 O
O OTf –
N
N
OTf O 87
O
BnSH Pr2i NEt
O
O
N
N
O N SBn
BnS
O
BnS
88
O
O
89
90
Scheme 10 O HN
O NH
O
N
RO
O
O
RO
N
ð20Þ
O
RO
SPh RO 91 92
The reaction of compound 93 with 94 gave cyanine dyes 95 (Equation (21)) <2002DP143>. Z I–
Cl
Z
N OH R
N R
N R
Z Me
+
i 94
93
Z I–
N O
Z = O, S, Se; R = (CH2)nCH3
ð21Þ
R Z N R
N R
i. pyridine, reflu x
n = 1, 4, 9
Z Me
95
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
121
(b) Cycloaddition methods. 1,2-Diaza-1,3-butadienes and 2-thiooxazolines or 2-thiothiazolines have been used in the synthesis of spiroheterocyclic compounds. At room temperature in THF, compounds 96 react with 2-thiooxazoline 97 to give spiroheterocycles (98, x = 0). Under the same conditions, adducts 100 can be accessed by the reaction of compounds 96 with 2-thiothiazoline 99. The subsequent ring closure of adducts 100 occurs on heating in THF or DMSO to give spiroheterocycles (98, x = 0) (Scheme 11) <2000SL1464>.
S S O R1O
N 96
THF, rt
99
R2
N
NH R1OOC
O
S
S
N H
H N
R O
N
O
S
i
NH
100
THF, rt
97
R1OOC S X
i. THF, ∆ ; or DMSO, 65–70 °C X = O, S
O N N H NH
R2
98
Scheme 11
2-Thiobenzooxazolines 101 and alkenes 102 on photolysis undergo [2+2]-cycloaddition to give the spiroadducts 103. In the case of compound 104, containing the vinyl fragment (R = CH¼CH2), photocyclization affords the tetracyclic compound 105 (Scheme 12) <2002HCA2383, 1999JCS(P1)1151>.
O S
+
R2
N OR
hν
R3
R1
R4
R4
N OR
102
O
R2 R3
R1 O
O
101
103 O S
hν
N
O S N
O
O
O
O 104
105
Scheme 12
Under Lewis catalysis by SnCl2 at 78 C, spirocompound 106 stereoselectively reacts with oxirane 107 to give compound 108. Under these conditions, the trans-dimethyl fragment of oxirane 107 undergoes inversion to the cis-dimethyl fragment (Equation (22)) <2000HCA3163>.
122
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen S
N
H
+
SnCl4, –78 °C
O
O
S O
Ph
S
N Ph
H
106
107
H H
S O
ð22Þ
108
Spiroheterocycles 111 are available from the reaction of phthaloyl chloride 109 with 1,5-bisnucleophiles 110 (Equation (23)) <1998CC1459>. O COCl
S +
COCl
R
Ph O R N
H N S
SEt 109
ð23Þ
O
R
110
111
(iv) Functions bearing one oxygen, one selenium, and one nitrogen substituent Sodium selenocyanate stereoselectively reacts with D-glucopyranose 112 to give cis-1,2-fused gluco-oxazolidine-2-selenone 113 as a single product. Also, gluco-oxazolidine-2-selenone 113 was obtained with high stereoselectivity from compounds 114 and 115 (Scheme 13) <2000CAL397>.
Ph
O
O
H O
Ph
O
O Ph
O
H
OHC Ph
KSeCN, AcNMe2
O O
O O
O
Ph
O
Ph
i. OsO4, Me-morpholineoxide, H2O, Me2CO
O
Ph
OH
114
112
Ph
Ph
OH O
S O
KSeCN, THF, AcNMe2
O
H H N Se
Ph
ii. KSeCN, THF, AcNMe2
Ph
Ph
O
O O
H
113
115
Scheme 13
Elemental selenium has been demonstrated to react with 1,2-dinitrobenzene 116 to give a mixture of benzoselenazole 117 and benzimidazole 118 on further reaction with carbon monoxide (Equation (24)) <1996KTK374>. NO2
i. Se, H2O, Et3N, THF
H N
N O
NO2 116
ii. CO
Se
O
+ N
41%
22%
117
118
ð24Þ
5-Alkylideneselenazolin-2-ones 120 were obtained by the reaction of 3-aminoalkynes 119 with elemental selenium and CO. Similarly, six-membered ring heterocycle 122 has been obtained from homopropargylamine 121 (Scheme 14).
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
123
O Se
Se, CO, DBU, THF
NHR
R1
R1
rt, 1.5 h
119
NR
120 O
Se (2 mmol.), CO (1 atm)
NHBu
CuI (2 mmol.)
Se
NBu
reflux
DBU, THF, rt
121
122
Scheme 14
Under the basic conditions, the reaction of alcohol 123 with elemental selenium leads to the formation of 1,3-oxazine-2-selenone in high yield 124 (Equation (25)) <1997PS335>. OH H 3C
Se, Et3N, THF NC
NH
80%
O
ð25Þ
Se
124
123
2-Oxoselenazolidine-4((R))carboxylic acid 127 has been reported as a stable seleno-containing physiologically active compounds. It was obtained in 40% yield from selenocysteine 126 and 1,10 -carbonylldiimidazole (CDI). Selenocysteine 126 was generated in the reaction mixture by the reduction of diselenide 125 with NaBH4 (Scheme 15). Se HOOC
Se
NH2 H2N
HSe
NaBH4
COOH
H2N
125
Se
CDI
O
COOH 126
N H
COOH
127
Scheme 15
Complex of LiAlHSeH has been widely used for the synthesis of different seleno-containing compounds, including synthesis of Se-methyl-N-phenylcarbamate 129. LiAlHSeH 128 has been obtained by the reaction of lithium aluminum hydride with black selenium powder (Equation (26)) <2001JA8408>.
LiAlHSeH
i. PhNCO ii. CH3I
O Ph
128
N H
SeCH3
ð26Þ
129
Selenocarboxylic acid was found to readily react with aryl-, acyl-, and arenesulfonyl isocyanates to give the acylcarbamoyl selenides 130 <2001HAC250>. O R1
O Se
NHR2
130 R1 = CH3, C4H9i , 1-Adamantyl, Ar R2 = C6H5, C6H4CO, 4-CH3C6H4SO2
2-Methylbenzselenazole was used for the synthesis of heptamethinecyanine dyes 131 <2002DP143>.
124
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
N R CH3 Se
Se O
Se
I– N R
N R 131 R = (CH2)nCH3 n = 1, 4, 9
10 --Phenylselenouridines (132 and 133) have been obtained by the reaction of 20 -ketouridine derivatives with PhSeCl in the presence of a base, or by addition of PhSeH to the corresponding nucleoside, containing unsaturated dihydrofuranic cycle <2000TL3643, 2001CEJ2332, 2002JOC6124, 2002JOC7706>. Phenylselenonucleosides (132 and 133) are potentially useful precursors for the synthesis of a variety of 10 -modified nucleosides. O
O NH
O
N
O
SePh
O TIPDS O
NH O
RO
O
N
O
SePh RO
O 133
132
TIPDS - 1,1,3,3-tetraizopropyldisiloxane-1,3-diyl
6.04.1.1.2
Functions bearing sulfur and nitrogen
(i) Functions bearing two sulfur and one nitrogen substituent(s) Literature examples of acetalthioamides synthesis are much rarer than those of acetalamides. However, the methods for synthesis of acetalthioamides and acetalamides resemble each other in many cases and sometimes are described in the same articles. (a) From sp3-carbon compounds. A complex of quinuclidine and BF3 134 has been deprotonated on treatment with BuLi/ButOK to give quinuclidine-2,2-diphenyl sulfide 136 in 52% yield on further reaction of the intermediate 135 with diphenyl disulfide (Scheme 16) <1999CC1927>.
BF3 Et2O N
BuLi, ButOK
(PhS)2 +
+
SPh
N – BF3
N M – BF3
N
134
135
136
SPh
Scheme 16
(b) From sp2-carbon compounds. 2-(Dimethylamino)-2H-1,3-dithiolene 138 has been obtained by the reduction of the 4-S-alkyl-1,3-dithiolium salt 137 with NaBH4 in EtOH. Compound 138 has been shown to be a useful precursor for the synthesis of tetrathiafulvalenes (Equation (27)) <1994JOC5877>.
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen EtOOC
S COOEt Me
137
S S
125
Me – PF6 N Me
NaBH4, EtOH EtOOC
S COOEt Me
ð27Þ
Me N Me S S
H
138
Dithialenes, containing the piperidine fragment, were obtained similarly <1997S407>. Bis(alkylthio)carbene has been demonstrated as a novel convenient reagent for organic synthesis <2000T10101>. Bis(alklylthio)carbene 140 was generated from oxadiazoline 139 on heating, similar to dimethoxycarbene 51 generated from 2,2-dimethoxyoxadiazoline 50. Further rapid reaction of bis(alklylthio)carbene 140 with isocyanate 52 leads to the formation of pyrrolin2-one tetrathioacetals 141 (Scheme 17).
RS N N
SR SR
SR Heat
RS
O
NCO 52
SR
N 140
RS
139
140 N3
O
O
SR 141
142
Scheme 17
Compounds 141 can also be accessed from acyl azides 142 and bis(alkylthio)carbene 140. By this methodology, various substituted pyrrolidines (143–148), including spirocondensed analogs, were obtained from the corresponding acylazides or isocyanates and bis(alkylthio)carbene <1999TL6891, 1999JOC1766>. PrS
SPr O SR
PrS
O
146
S
SPr O N SPr
SPr
PrS 145
PrS
N
N
PrS
O
Ph S
S
S
O
144
143
S
O
N
N RS
SPr SPr
Ph
S
O
O
O
SPr O N SPr
S
S
PrS
147
148
The formation of heterocycles 151 and 154 can be exemplified by the reactions of the in situ generated nitrilium phosphane ylide complex 149, which leads to either 1,2,3-thiazaphosphole 151 via [3+2]-cycloaddition or to sulfanyl-1,2-thiaphosphiran-3-amine 154 via an
126
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
intersystem-transylidation-type reaction giving the 1,3-dipolar complex 152 that undergoes ring closure to form intermediate 153 and subsequent decomplexation to give sulfanyl-1,2-thiaphosphiran-3-amine 154 as the final product (Scheme 18) <1999CC499>.
N [W] Ph
R N
CN
[W]
[W]
+
[W] PhC N P + R +
+ PhC N P R
–PhCN
149
S
[W]
+
P
R N
N C N P R
149
N Ph
150
N 151
+ PhCH2CS(CH3)2N)C=S
[W] R Me2N P S PhH2CS
Ph S
[W]
+
S P R
Me2N
–[W]
SCH2Ph
153
152
H P S
Me2N
154
[W] = W(CO)5
Scheme 18
A mixture of diastereomeric -lactams 157 is obtained by the reaction of thioketals 155 with the complex 156 (Equation (28)) <1994JOC7934>. O Ph
SMe +
R N
N
SMe
Ph SMe
N
ð28Þ
SMe
CO, 2 atm
(OC)5Cr
155
O
Et2O, hν
N
O
156
R
157
Under zirconium catalysis, compounds 158 undergo stereoselective assymetrical intramolecular [3+2]-cyclization to give hydrogenated pyrazolines containing the dithioacetal fragment 159 (Equation (29)) <2002JA13678>. R1
MeS
R2
NO2 Chiral Zn cat.
NO2
N HN S
R R
1
2
H H N HS
158
N S
ð29Þ
159
Under acid catalysis, compounds 160 undergo intramolecular ring closure to give hexahydropyrimidines containing a dithioacetal fragment 161 in 99% yield (Equation (30)) <1995TL6257>. S R2HN
O
O N H MeS 160
R1 SMe
R1
HN S
SMe N SMe R2
ð30Þ
161
Pyrrolidine dithioacetals 164 were obtained by the [3+2]-cycloaddition of ylides 162 to ethylenes 163 (Scheme 19) <1995TL9409, 1996TL711, 1996TL3915>.
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen R1 S S
+
N Me
CsF
SiMe3 Hal
–
S
+
S
N CH3
CH2
127
R1
R2 163
R2
S S N Me 164
162
Scheme 19
At room temperature, compounds 165 undergo intramolecular ring closure to give 1,2-dihydroazeto[2,1-b]quinazolines 166 (Equation (31)) <1997T13449, 2000JOC7512>. H SMe
R
N
N
SMe
C
Me
R
25 °C, 1 h
H N N
Ph
SMe SMe Me
ð31Þ
Ph
166
165
The cycloaddition of dithioesters 167 to acids 168 using triphosgene as an activator gave 4,4-bismethylsulfanylazetidin-2-ones 169 in good yields (Equation (32)) <2002T2215>. MeS
Et3N, triphosgene, 0 °C, 12 h N R1 + R 2
COOH
MeS
O
58–68% 167
R2
168
SMe SMe N 1 R
ð32Þ
169
R1 = Ph, CH2Ph, CH2COOMe, CH(Me)COOMe; R2 = OMe, OPh
(ii) Functions bearing one sulfur and two nitrogen substituents (a) From sp3-carbon compounds. Tris(azolyl) methylthiolates 170 have been obtained by the reaction of the corresponding trimethylsilylazoles with [CF3S(NMe2)2]+[CF3S] <2001AG(E)1247>. –
X
N C S N
+
CF3S(NMe2)2
3
170 X = CH, N
Pyrimidine 171 reacts with benzyl bromide to give benzyl-substituted imidazo[1,5-a]-1,3,5triazine 172. The reaction proceeds via intramolecular ring closure at the sulfur atom and leads to the formation of the imidazole ring <1995JMC3558>. Compound 172 is also accessible by the reaction of imidazotriazine 173 with benzyl bromide (Scheme 20). Similarly, S-alkylquinazoline is obtained from benzopyrimidinethione and -dimethylamino-1chloroethane in the presence of a base <2002MI335>. (b) From sp2-carbon compounds. Nitration of compounds 174 and 175 with 55% HNO3 yielded 2,2,4-trinitro-3-chloro-3-thiolene-1,1-dioxide 176 but its yield did not exceed 8% (Scheme 21) <2002MI1111>. 2-Hydrazino-2,3-dihydrobenzothiazoline 177 is widely used for the syntheses of heterocycles, azomethines, and other compounds containing the benzothiazoline fragment (178–182). This compound reacts in the same way as monosubstituted hydrazines (Scheme 22) <1999MI325, 2001MI129>.
128
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
S
N
i. Me3SiCl, (Me3Si)2NH, Py ii. K2CO3, MeOH
NH2 Me
HN O
Br
NHCHO
O
Me
171
HN
N
S
N
N Me
O HN S
N
Me
K2CO3, MeOH
N
N H
172
Me 173
Scheme 20
Cl
Cl
NO2 55% HNO3 O
S
NO2
Cl
O2N
O
NO2
55% HNO3
O2N
HON
S O
O
176
174
S O
O
175
Scheme 21
Me N
Me N
H HO N N
NH S
H N C
178
Me N
OH
S Ar
HO
179
i
O
N S
O
H N
S
OH
H2N iii
180
Me N NHNH2 S 177 i, iv
ii
Ar
Me N
N
S
NHNHCH2NH S
N Me 182
N 181 N
i. ArCHO, AcOH, EtOH; ii. N iii. CH2(CN)COOEt, EtO, K2CO3;
, HCHO, HCl, H2O; NH2
iv. HSCH2COOH, Dioxan
Scheme 22
S N N H O
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
129
Similar to 2-hydrazino-2,3-dihydrobenzothiazoline 177, imidazothiazoline hydrazide 183 has also been demonstrated to react with aromatic aldehydes to give substituted hydrazones <2002UKZ46>.
NHNH2
N S
N H
O
183
5-Aminothiadiazolines 184 were obtained by the reaction of substituted thiosemicarbazide with tetracyanoethylene (Equation (33)) <1998PS141>.
S RNHCNHNH2
+
NC
CN
NC
CN
N N
EtOAc 20–23%
RHN
S
CN
ð33Þ
CN
184
Heterocycles 186 and 187 have been obtained from dithiosemicarbazide 185, which was produced by the reaction of 1,4-dichlorophthalazine with thiosemicarbazide. Besides, compounds 186 and 187 can be accessed directly from 1,4-dichlorophthalazine and thiosemicarbazide in one step without isolation of compound 185 (Scheme 23) <2001IJC(B)500>.
O
S S N N C NH2 H NH N NHNHC NH2 S
S
N
CS2
NH N N
KOH, EtOH N
S
NH
S
N
S
N
NAOH, H2O N
N S
186
N
ClCH2COOH
HN
185
S N
HN
S
O 187
Scheme 23
The intramolecular 1,3-dipolar cycloaddition of the o-allenylaryl fragment to the betaine fragment of thienopyrimidine 188 occurs on heating and affords framework compounds 189. Similarly, the intermolecular cycloaddition of maleineamide to thienopyrimidines 190 leads to the formation of adducts 191 containing the bridging sulfur atom (Scheme 24) <1997JOC3109>. 3,3,6,6-Tetramethyl-1-thia-4-cycloheptane 192 reacts with isothiocyanates 193 in a ratio of 1:3 on heating in an autoclave without solvent to form adducts 194 in 17–60% yield. The formation of the compound 194 can most plausibly be explained by a concerted [3+2]-cycloaddition (Scheme 25) <2000JOC8940>. The highly reactive 4-phenyl-1,2,4-thiazoline-3,5-dione 195 has been demonstrated to interact with 4-phenyl-1,2,4-triazoline-3,5-dione 196 as a dipolarophile to give cycloadducts 197 in excellent yields (Equation (34)) <1995T6651>.
130
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
( )n R1OOC Me
–
O
+
N N PG
S
Deprotection
R
Me
188
Ph R1OOC Me
O
–
O
+
N N Me
S
63%
Me
O
190
O
N N H 189
S
Ph
O
R1OOC
Toluene, ∆
N Me
+ Ph
( )n
R1OOC
∆
N
R
Ph H
S
N Me H O
O N Me
191
PG = protecting group, n = 1, 2
Scheme 24
+
S
R
N C S
120 °C
R S C N
S S N
17–60%
R 192
193
+
S
R S C N
S
S
–
N R
S S S
N R
R N
N N R R
S
194
R = Me, Ph
Scheme 25
O Me
S Me Me
N N
+ N ( )n 195
O
O
N Ph 196
Ph O O
Me O O S N
N N
Me
N
( )n
ð34Þ 197
n = 1, 2
The reaction of 1,2-diaza-1,3-butadienes 198 with 2-thiooxazoline 199 in THF at 20 C leads to the formation of the spiroheterocycle 200 containing the CNNS-fragment (Equation (35)) <2000SL1464>.
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
131
O O R1O
N
R2
N
S
+ N H
O 198
HN H R2 N N
THF, 20 °C
O
ð35Þ
S O
R1OOC
200
199
(iii) Functions bearing one selenium, one sulfur, and one nitrogen substituent (a) From sp2-carbon compounds. N-Methylbenzoselenazole-2-thiones such as 201 have been alkylated at the exocyclic sulfur atom by the strong alkylating agents such as diethoxycarbonium tetrafluoroborate, which was generated in situ from BF3Et2O and triethylorthoformate, to afford compounds such as 202 on further electrochemical reaction (Equation (36)) <2002JCS(P1)1568, 2000MI92>. Me N S
Me Electrochem N S + Et Se
CH(OEt)3, BF3·Et2O reflux
Se
S Et
Se
BF4–
201
6.04.1.1.3
Me N
ð36Þ
202
Functions bearing selenium and nitrogen substituent
The salt 203 obtained via Scheme 26 has been used for the synthesis of methyltetraselenafulvalene <2001MI1035>.
13
C-labeled tetra-
Cl NH
580–600 °C
Se O N
Se *CSe2
*CH2Cl2 + 2Se
i. H2SO4 ii. HPF6
* Se
N
+
N
Se * Se
* Se
PF6–
O
+
H 2N
i. H2Se, EtOH ii. (EtO)3P/ toluene
Se * Se
Se * Se
203
Scheme 26
Spiroselenoamide 205 has been obtained in a mixture with compound 206 by the treatment of compound 204 with AgBF4 (Equation (37)) <2001CC1336>. Me N Se
204
Se N Me
AgBF4, toluene, ∆
Me N Se
Me N +
Se N Me 205
+
Se +
Se
206
N Me
·2BF4–
ð37Þ
132
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
6.04.1.2
Functions Bearing Chalcogen and P, As, Sb, or Bi
6.04.1.2.1
Functions bearing oxygen and P, As, Sb, or Bi
(i) Functions bearing two oxygen and one phosphorus substituent 1,1-Diethoxyethylphosphinates and phosphonites have been demonstrated to be convenient reagents for the synthesis of different functionally substituted phosphoric acids and phosphinates. Some reactions of the synthons (207–209) are outlined below (Table 1). Final ketal-protected phosphorus acids can be deprotonated on further treatment with 1–2 equiv. of trimethylsilylchloride in CH2Cl2, containing up to 5% weight of ethanol, and stirring of the reaction mixture for several hours under argon at room temperature <1995TL9385>.
R O (EtO)2C PH OEt
R OSiMe3 (EtO)2C P OEt
R O (EtO)2C P Me OEt
207
208
209
R = H, Me
Table 1 Synthesis of functional phosphorus acids Reactant
Condition
Bn N Bn
N
N
Toluene 100 C, 1 h, 60% Bn
Product O Me Bn-NH-CH2 P OEt OEt OEt
Na, toluene 5–20 C, 3 h, 80%
Na, toluene 0–20 C, 3 h, 60%
NH Cl
EtOOC
THF 60 C, 3 h, 95%
O P H OEt
NH Cl
Cl
O Me P OEt OEt OEt
EtOOC
O Me P OEt OEt OEt
NO2 H2N
i. BuLi, THF, 78!0 C, 1 h, 60% ii. Ni.H2, EtOH, rt, 90% Cl Cl
O P H OEt
O Me P OEt OEt OEt
CH2Cl
Cl
O Bn-NH-CH2 P H OEt
O Me P OEt OEt OEt
Br
Deprotected product
NH Cl
Cl
O P H OEt
EtOOC
O P H OEt
H2N
Cl
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
133
1,3-Dioxalanes 210 have been phosphorylated by treatment with diethyl chlorophosphite. The reaction proceeds through oxidation of the phosphorus atom (PIII ! PV) in the presence of an orthoester and carboxylic acids to give a mixture of exo- and endo-isomers of nucleosides 211 and 212 (Equation (38)) <1996TL3497>. TBDPSO
O B
TBDPSO
O B
TBDPSO
(EtO)2PCl, CH3CN O R
O B
+
O
O
OEt
O
R
O
P(O)(OEt)2
(EtO)2(O)P
ð38Þ
R
endo-isomer
exo-isomer
210
O
211
212
R = H, Me, Ph; B = T, U, CBz, GBz, ABz
Alkylation of the hypophosphorus acid derivative 213 with 4-iodobenzyl bromide has been used to obtain compound 214, which was used in the synthesis of aminocarboxylic acid 215 (Scheme 27) <2000BMCL2343>.
Br, i O P H OEt
EtO EtO
EtO EtO
I
O
O OEt P OEt OEt
ii, iii
P OEt
213
I
214
R1HN
R1 = Boc, Z; R2 = Me, Bn
COOR2 215
i. NaH, THF, –10 °C to rt; ii. BOC-iodoAla-OMe, Zn, BrCH2Br, TMSCl; iii. (2-furyl)3P, Pd2dba3, DMA–THF, 60 °C
Scheme 27
The phosphorylated analog of sialic acid was obtained from N-acetyl--D-mannosamine 216. Initially compound 216 has been phosphorylated by dimethyl[1-(bromomethyl)ethyl]phosphonate 217 in the presence of indium to give the threo product 218, which undergoes subsequent ozonolysis to give - and -sialoside acid mixture in a ratio of 5:1 (Scheme 28) <1996JOC9538>. O
OMe P
HO HO HO
NHAc O + OH Br O 216
O P OMe OMe
OMe
CH2 OH
i 81%
217
ii, iii 90%
AcHN HO
OH OH
HO
AcHN
OH OH OH 218
OH
O P OMe HO MeO O
219
i. In, EtOH, H2O, 6 days; ii. O3, MeOH, –78 °C; iii. Me2S, MeOH, –78 °C to rt
Scheme 28
Dialkoxymethyl(diphenyl)phosphine oxides 220 and aldehydes 221 undergo the Horner–Wittig reaction to give asymmetrical -hydroxy carboxylic esters 224. The reaction proceeds through intermediates 222 and 223 (Scheme 29) <1999MI2270>.
134
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen RO OR
O OR R1 O Ph P + H Ph OR 220
R1
221
Ph ROK or ROLi R1 P Ph H OH O 222
OR
AD
OR
71–92%
R1 * COOR OH
223
224
AD-mix α[(DHQ)2PHAL] config. (S ) AD-mix β[(DHQ)2PHAL] config. (R )
Scheme 29
Synthesis of the 50 -homologated H-phosphinate 228 was achieved as follows. The 50 -homologated phosphinate 225 was made available from boron trifluoride-catalyzed oxetane ring opening with a phosphinate-stabilized carbanion. Subsequent hydrolysis of the 30 -benzoate followed by silylation yielded 226. Selective removal of the orthoester protecting group from 226 liberated the ethylH-phosphinate 227. Hydrolysis with triethylamine, water, and ethanol produced the corresponding H-phosphinic acid, which was re-esterified with allyl alcohol, using DCC as the condensing agent, to produce the allyl-H-phosphinate 228 (Scheme 30) <2001SL467>.
O O
+
T
EtO Me EtO
O P Me OEt
EtO Me EtO
O P
i, ii
EtO BzO
O
T
225 EtO Me EtO
O H P
O P iii
EtO
TBDPSO
O
O H P iv, v
EtO TBDPSO
T
226
O
O TBDPSO
T
227
O
T
228
i. NaOMe, MeOH, rt, 85%; ii. TBDPS-Cl, imidazole, DMF, rt, 91%; iii. Me3SiCl, EtOH, CHCl3, rt, 71%; iv. Et3N, EtOH, H2O, rt, 95–98%; v. allyl alcohol, DCC, 2 mol.% DMAP, THF, rt, 69–73%
Scheme 30
Compound 229 has been used for the synthesis of inhibitors of the bacterial cell-wall biosynthesis enzyme MurC <2001BMCL1451>. Hypophosphorus acid synthons 230 were used for the synthesis of phosphorylated oligonucleotides <1995SL703, 1998SL283>, carbohydrates <2001SL473>, and other organic compounds <1999SL1633, 2002SL525>.
EtO EtO
R2 O P H R1O OR1
O O S O P O OEt
R1O
229 1
R = Me, Et, Ph;
230 R2
= H, CH3
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
135
(ii) Functions bearing one oxygen and two phosphorus substituents Tris(trimethylsilyl)phosphite 232 reacts with acyl halides 231 to produce 1-hydroxymethylene1,1-bisphosphonic acids 233 on subsequent hydrolysis of the intermediates (Equation (39)) <2001PIAWO0109146, 2001TL8475>. i. THF, 25 °C ii. MeOH, 25 °C, 1 h
O R
Cl 231
OH O OH R P OH O P HO OH
+ n-P(OSiMe3)3 61–98% 232
ð39Þ
233 R = Me, C5H11, C11H23, Ph, PhCH2, 4-MeOPh, 4-NO2Ph, 3-Py n = 2–6
A one-pot synthesis of methyl(benzyl)hydroxylbisphosphonic esters was achieved without a protic reagent which removes the unusual -ketophosphonate step. Thus, reaction of P(OCH2Ph)3 with RCOCl (R = Me, Ph, Bu, CH2OMe) in MeOH or AcOH gave (PhOCH2)2P(O)C(R)(OH)P(O) (OCH2Ph)2 <1996PS295>. Synthesis of compounds 234 (R1 = H, NO2, halo, amino, C1–6-alkyl, C1–6-alkoxy, aryl, heteroaryl; 2 R = H, halo, amino, C1–6-alkyl, C1–6-alkoxy, aryl, heteroaryl; Y = O, S, NH, etc.; Z = C1–5-alkylene, aminoalkylene, m, n = 0–1) has been reported <2002GEP10114352>. Thus, chlorination of 4-RC6H4CH2CH2CH2COOH with oxalylchloride followed by treatment with P(OSiMe3)3 produced 4-RC6H4CH2CH2CH2C(OSiMe3)[P(O)(OSiMe3)2]2. Hydrolysis of the latter followed by treatment with NaOAc afforded 4-RC6H4CH2CH2CH2C(OH)[P(O)(ONa)(OH)][P(O)(OH)2] (R = N(CH2CH2Cl)2).
R1 Yn Zm R2
PO3H2 OH PO3H2
234
Every so often, directly carboxylic and aminocarboxylic acids can be used for synthesis of 1-hydroxy-1,1-diphosphorus compounds instead of acyl halides. In these cases PCl3, POCl3, and PCl5 can act as chlorination agents and H3PO4 as a reagent for phosphorylation <2002PIAWO0290367, 2002JMC2185, 2000USP6143923, 2000JAP281690, 2003USP3013918, 2001MIP2173321, 2002MIP2178793, 1998BRP2316945, 1998PIAWO9834940, 1998GEP(O)19737923, 1997PIAWO9739004, 1995JOC8310>. A typical example of such reaction is presented below (Equation (40)).
H2N
COOH
i. H3PO3 ii. PCl3 iii. H2O
O HO
57%
OH P
OH P OH O OH
ð40Þ
H2N
A method of synthesis of radioiodinated aminobisphosphonates 235 (X = 125I, 211At; Y = CH, N) has been described with active esters N-succinimidyl-3-(trimethylstannyl)benzoate and N-succinimidyl-5-(trimethylstannyl)3-pyridinecarboxylate as precursors. The isolated and purified radiolabeled intermediates were coupled to give 3-amino-1-hydroxypropylidene1,1-bisphosphonate [H2NCH2CH2C(PO3HNa)2OH] in high yields ranging from 60% to 97% <1999MI397>.
136
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen O
HO ONa HO P O
RO O RO P
P O HO ONa
RO P O RO
N H
Y
Y
235
O
236 R = Me, Et, iPr
1-Hydroxybisphosphonates [(R1O)2P(O)]2C(OH)R3 (R1, R2 = H, straight or branched C1–6 alkyl, benzyl, aryl, Na, Ca, Li, K; R3 = C1–10 straight chain or branched alkyl, Ph, benzyl, aryl, amido, organothio, alkoxy) and substituted hydroxybisphosphonates were obtained by the reaction of anions of dialkyl phosphites with acid halides. It is preferred that this reaction takes place at a low temperature in the presence of a base so that rearrangement to dialkyl(dialkoxyphosphinyl)phosphates is minimized. Thus, KN(SiMe3)2-mediated reaction of (EtO)2P(O)H with hydrocinnamoyl chloride produced 60% of [(EtO)2P(O)]2C(OH)CH2CH2Ph along with 9% of [(EtO)2P(O)]2CHCH2CH2Ph, and 3% of ester <1996PIAWO9633199>. The feasibility of synthesizing -hydroxy -alkyl-/aryl methylenebisphosphonates via Grignard addition to tetraalkyl carbonylbisphosphonates was shown; and some current and potential therapeutic uses of bisphosphonates and phosphonocarboxylates were summarized <1999PS313>. Synthesis of acylaminoalkanediphosphonates 239 with 41–87% yields was achieved by the reaction of acyl halides 237 with aminoalkyldiphosphonates 238 <2002MIP1333210>. It was shown that mono-, di-, and trisodium salts of compounds 239 can be obtained depending upon the pH of the media (Equation (41)). O Cl
+
HO ( )n
R
O OH P OH P OH
i. NaOH, H2O ii. HCl, H2O
( )n
O OH P OH P OH
NH
O OH
HO
NH2 O OH 237
ð41Þ
O
238
R 239
n = 2, 3, 5
1-Hydroxyethylidene-1,1-bisphosphonic esters 240 were used as a precursor for selective synthesis of mono- or disalts of these esters (241 and 242) (Scheme 31). <2000S633>.
HO Me
O OR P OR P OR O OK 241
KI
HO
R = Me, Et
Me
O OR P OR P OR O OR 240
NaI
HO
R = Me
Me
O OR P ONa P OR O ONa 242
Scheme 31
Arylcarbonylphosphonates 243 react with 2-isocyanato-4H-1,3,2-benzodioxaphosphorin-4-one 244 to give bicyclic aryl bisphosphonates 247. Probably, this reaction proceeds through intermediates 245 and 246 (Scheme 32) <2002MI980>. 1,2-Dihydro-1,3-diphosphinine 248 and mesitylnitrileoxide 249 undergo chemo-, regio-, and stereoselective 1,3-dipolar cycloaddition to give cyclic allene 250 (Equation (42)) <2000AG(E)1261>.
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen O Ar
O
OR P OR O
+
P O
Benzene, 80 °C NCO 8 h, argon
O
O 243 O
O
Ar
OR P OR O
Ar O
–
N O + P O
NCO O–
+
P O
O 245
244
O O P N
O
OR P OR Ar O
60–70%
137
P O
OR OR
O
O 247
246 R = Me, Et; Ar = 4-ClPh, 1-naphthyl
Scheme 32
But P
But
But
P
But
C N O Me
Me
But
+
P
77%
But
P
But O N
Me
ð42Þ
But
Me
Me 249
248
Me
250
(iii) Functions bearing one oxygen, one nitrogen, and one phosphorus substituent Synthesis of the compound 253 was achieved by the reaction of diisopropylammonium salt 251 with bis(diisopropylamino)(trimethylstannyl)phosphine 252 in the presence of MeONa in methylene chloride (Equation (43)) <1998EJI1539>.
+
– (Pri)2N=CHClPO2Cl2
+
SnMe3 P N(Pri)2 N(Pri)2
i. CH2Cl2 ii. THF, MeONa
MeO (Pri) 2N
90%
252
251
P
N(Pri)2 N(Pri)2
ð43Þ
253
[3+2]-Cycloaddition of diazoketones 254 to compounds 255 leads to the formation of 5-alkylidene-4,5-dihydro-3H-1,2,4-diazaphospholes 256 (Equation (44)) <1996T10053>.
(Pri)3Si
O C C Bui N2 254
+
O SiMe3 X Bui P 255
But 81–83%
Me3SiO
N N P X
O Si(Pri)3 But
ð44Þ
256
X = Cl, SiMe3
Atimicine A undergoes selective phosphorylation along formylamino group with hydrophosphoryl compounds 258. The reaction is driven to completion by the elimination of the formyl group resulting in the formation of compounds 259 containing NHCH(OH)P fragment (Equation (45)) <1996KFZ31>.
138
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen Prn
Prn O O Me(H2C)5
Me O O
O
Me
O
O
O O O MeOH H P OR Me(H2C)5 58–81% OR 258 O NHCHO
+
N H
Me O O Me
O
O OH
N H OH
OH
N H
OR P OR O
ð45Þ
259
257 R = Et, Ph, H
Phosphorylated oxazoloisoindole 262 has been obtained by the reaction of phthalimide 260 with diethylphosphonate 261 (Scheme 33) <2000PS107>.
O
O Br
N
O + H P OEt OEt
O
i, ii, iii N 86% O P O EtO OEt
261
260
262 NH2
iv, v, vi N
OH
Pri
93%
Pri
O P O Ph Ph
263
264 i. NaTHF; ii. THF; iii. NH4Cl, H2O; iv. Phthalic anhydride, xylene; v. TsCl, CH2Cl2, Py; vi. Ph 2PH, KH, THF
Scheme 33
Similar phosphorylated oxazoloisoindole 264 can be accessed by the enantioselective reaction of aminoalcohol 263, phthalic anhydride, and Ph2PH <2001TA923>.
(iv) Functions bearing one oxygen, one sulfur, and one phosphorus substituent Derivative of pulegone 265 gives compound 266, containing oxygen, sulfur, and phosphorus at an sp3-carbon atom, on the chain of subsequent reactions with BuLi, ClPPh2, and BH3SMe2 <2000JA10242>. Reaction occurs stereoselectively with retention of configuration of the starting reagent 265 (Equation (46)).
i. BusLi, –78 °C ii. ClPPh2, –78 °C to rt iii. BH3·SMe2
Me
O Me Me
S
265
81%
Me
O Me Me
S 266
Ph P Ph BH3
ð46Þ
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen 6.04.1.2.2
139
Functions bearing sulfur and P, As, Sb, or Bi
(i) Functions bearing two sulfur and one phosphorus substituent The reaction of complex 267 with ylides 268 or with phosphine R3P and carbon disulfide yielded the salt 269, which was acylated with acetyl chloride to produce tributylphosphonium salt 270 (Scheme 34) <1996JOC9585>. S R3P 268
S Me
[Cp2ZrHCl]n
i. CS2; ii. R3P
267
R3P
S
H
S
+
ZrCp2Cl
S
Bu3P S
O O
Cl
–
Me
269 270
R = Me, Bu.
Scheme 34
Dithioacetal formylphosphonates 273 have been obtained by the reaction of disulfides 272 with -phosphorylcarbenes, generated from the corresponding diazocompounds 271 <1996S1232>. Cyclic dithioformylphosphonates 274 and 275 were made available by the introduction of the cyclic disulfides in this reaction (Equation (47)). O (R1O)
2PCHN2
+
R-S-S-R
BF3·Et2O, CH2Cl2, 25 °C
O SR R1O P OR1 SR
4–93% 272
271
ð47Þ
273
R1 = Me, Et; R = Me, Et, Pr, Ph, 4-MePh, COOEt
O MeO P
S
OMe
O MeO P
S
S S
S
S
OMe
274
275
General methods for the synthesis of optically active -phosphoryl sulfoxides 277 have been reported. Compounds 276 have been subjected to lithiation and methylsulfonation with MeSO2SMe at P- and S-linked carbon atom to give -phosphoryl sulfoxides 277 (Equation (48)) <1997T2959>.
O R1O
P R1O
S O
R2
i. BunLi ii. MeS(O)2SMe
SMe
O R1O
P R1O
S O
R2
ð48Þ
277
276 R1 = Me, Et; R2 = Me, Ph, 4-MePh
Phosphonate bisdisulfoxide 278 can be accessed by the recently developed method. This reagent can be used for asymmetric synthesis of -aminoamides <1998JOC7128, 1999PS337>. Compound 278 was obtained as shown in Scheme 35.
140
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen i. Chlorosuccinimide ii. P(OEt)3 S
S
[O] S
S
O
43–58%
S
S
O
O P OEt OEt
O P OEt OEt
278
Scheme 35
Compounds 280 and 281 were obtained in high yields by hetero-Diels–Alder reaction of phosphonodithioformate 279 with cyclic dienes <2000TL7327> (Scheme 36).
Cyclopentadiene
S OPri P MeS O
OPr
CH2Cl2
i
O S PriO P C SMe OPri
Me
CH2:CMeCMe:CH2,
S OPri
THF
Me
P MeS
279
280
OPri
O
281
Scheme 36
Phosphorylated crown ethers 286 have been obtained by the reaction of compounds 282–285 and triethoxyphosphine. Ethers 286 are convenient reagents for the synthesis of crown ethers of tetrathiofulvalenes (Scheme 37) <2001EJO933>.
O S
S
S
S
O O
S
S
S
S
O
S O O
75%
282
i, ii, iii
O (OEt)2P
iii
O O
75%
285
O S
S
H S
S
CF3SO3–
O O O 286
ii, iii
O S
S
75%
75%
ii, iii
O
MeS
O S
S
S
S
O
MeS S
S
O
O
O
O
283
284 i. CF3SO3Me, CH2Cl2, EtOH; ii. CF3SO2H, MeCN; iii. P(OEt)3, MeCN
Scheme 37
Reaction of 2-alkoxy-1,3-benzodithiolene 287 or 1,3-benzodithiolylium fluoroborate 288 with P(OMe)3 takes place in acetonitrile in the presence of NaI to give 2-dimethoxyphosphinyl-1,3benzodithiole 289 in high yield (Scheme 38) <2002M1055>.
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
S
O
Me
S
Me
i, ii, iii
S
82%
S
O OMe P OMe
iii
S
82%
S
289
287
141
BF4–
288
i. HBF4, Ac2O; ii. Et2O; iii. P(OMe)3, NaI, MeCN
Scheme 38
Phosphorylated 1,3-dithiolenes 291 have been isolated as side products in the synthesis of tetrathiafulvalene derivatives 292 from acetylenes 290, CS2, and P(OMe)3 (Equation (49)) <2002JHC691>. i. CS2 ii. P(OMe)3 iii. MeOH Ph
R
S P
R Ph 290
S
OMe OMe
R
S
S
Ph
Ph
S
S
R
+
291
ð49Þ
292
36 –37%
R = H, COOMe
Thiphosphirane 154, containing a CPNS fragment, can be prepared by the method shown in Scheme 18.
(ii) Functions bearing one sulfur and two phosphorus substituents A methanediphosphonic ester, containing 4-MeSC6H4-S group 295, has been prepared by recently developed method, which is based on the reaction of compound 293 with disulfide 294 in the presence of ButOK <1998JAP10130284>. Salt 296 has been obtained on further hydrolysis of the ester 295 (Scheme 39) <1999JAP11080176>.
O ( PrOi)2P
O P(OPri)2 293
ButOK, PhMe
S S
S (PriO)2P O 295
+ MeS
O (PriO)2P
SMe 294
SMe
i. MeOH, HCl ii. NaOH, H2O PO3HNa MeS
S PO3HNa 296
Scheme 39
Initial exploratory results on the [4+2]-cycloaddition potential of the hetero-1,3-diene system of 297 were provided by the reactions between the heterocyclic compounds 297 and the phosphoalkynes 298. It was shown that the intermediate 299 reacts with one more molecule of RCP to form compound 300, which then reacts with elemental sulfur to give compound 301 in high yield (Scheme 40) <2002EJO1664>.
142
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
P
S
+ RC P P
P P
86–92%
R 297
298
RC P
R
P
R P
P
R
R
P P
299
R 300
1/8, S8, Et3N, toluene, 25 °C
81%
S
But But P S P R = But, Me2CEt, Me-c-Hex
S
R
S
R
Toluene, 100 °C
R
P
But
P But 301
Scheme 40
(iii) Functions bearing one sulfur, one nitrogen, and one phosphorus substituent The reaction of the unsaturated compound 302 with dimethyl diazomethane 303 leads to the formation of pyrazoline 304 stereoselectively, which has been used in cyclopropane synthesis (Equation (50)) <1999T14791>. O O EtO P EtO
O S
O EtO P EtO
Et2O, rt, 6 h + Me2CN2
S
Tol-p N N
ð50Þ
Me
Tol-p
Me
303 302
304
Isothiazolylphosphonate 305 has been demonstrated to react with an ethereal solution of diazomethane to give a mixture of the two tautomers of 1- and 2-pyrazolines 306 and 307 (Equation (51)) <2001T5455>.
Ar
NEt2 Et2O
EtO
N
S EtO P O O O
OEt O P O N S O N N
EtO
+ CH2N2
85% total yield
Ar
305
+
OEt EtO O P O H N S O N N Ar
NEt2
306
NEt2
ð51Þ
307
Ar = 4-MeOPh
1,4,2-Oxazaphospholine 309 has been prepared by the [4+1]-cycloaddition reaction of heterodiene 308 with 4-chlorobenzenethiol and triethyl phosphite (Equation (52)) <1995ZOB948>.
O
Cl
F3C S N
i, ii Ph
Ph
N 308
CF3
O P OEt EtO OEt 309
i. 4-Cl-C6H4SH, KOH; ii. P(OEt)3, CH2Cl2
Cl
ð52Þ
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen 6.04.1.2.3
143
Functions bearing selenium and phosphorus substituent
(i) Functions bearing two selenium and one phosphorus substituent Triselenocarbonate 310 has been used in the synthesis of 2-triphenylphosphino-1,3-diselenole trifluoroborate 311. Compound 311 has been prepared by a one-pot reaction (Scheme 41) <1996JOC2877>.
E
Se Se
E
CF3SO3Me
Se
+
E
Se
E
Se
SeMe
NaCNBH3
E
Se SeMe
E
Se H
i. HBF4, Et2O ii. Ph3P
E E
310
+
Se PPh3 – Se H BF4
311
Scheme 41
Similar to sulfur-containing compounds 273, seleno-containing analogs 313 were obtained from diazocompounds 271 and diselenides 312 (Equation (53)) <1996S1232>. O (R1O)
BF3·Et2O, CH2Cl2, 25 °C
2PCHN2
+
O SeR R1O P OR1 SeR
R–Se–Se–R
271
312
ð53Þ
313 –
–
R1 = Me; R = Ph; –R-R– = –CH2CMe2CH2, –CH2CH(But)CH2
(ii) Functions bearing one selenium and two phosphorus substituents 1,2,4-Selenodiphospholes 314, RCP and elemental Se were used as precursors for the synthesis of 5-seleno-1,4,7,8-tetraphosphatetracyclo[4.3.0.02,4.03.7]non-8-enes 315 (Equation (54)) <1999S1642, 2000CC1745, 2001HAC406>. But But P P
But P P
+ Se
But
Bu
tC
P + Se
314
Se P
But
P 315
ð54Þ
But
(iii) Functions bearing one selenium, one sulfur, and one phosphorus substituent Phosphonates, containing sulfur and selenium atoms 317, have been obtained by the reaction of -phosphoryl sulfoxides 316 with phenyl selenobromide <1995TL2871, 1997T2959>. As in the case of the sulfuric analogs <1997T2959>, this reaction occurs stereoselectively (Equation (55)). Me
R (R1O)
2P
O
S O 316
i. BuLi, THF ii. PhSeBr
PhSe (R1O)
2P
O
R S O 317
Me
ð55Þ
144
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
6.04.2
FUNCTIONS CONTAINING CHALCOGEN AND A METALLOID AND POSSIBLY A GROUP 15 ELEMENT
6.04.2.1
Functions Bearing Chalcogen and Boron
Only one example of the synthesis of compounds bearing two boron atoms and one oxygen has appeared in the literature since COFGT (1995). The reaction of 1,2-bis(diisopropylamino)-2,5dihydro-1H-1,2-diborole 318 with carbon monoxide leads to the formation of the product 319. Similarly, compound 321 can be obtained from unsaturated 1,2-diborole 320 (Scheme 42) <1998EJI459>. N(Pri)2 (Pri)2N CH2 B O B
N(Pri)
2
(Pri)2N
B
B
CH2
CO, THF 44%
B O B CH2 N(Pri )2 N(Pri)2
318
319
N(Pri)2 B B
N(Pri )2
CO, THF
N(Pri)2
50%
N(Pri)2 O B B B B O (Pri)2N
320
N(Pri)2 321
Scheme 42
6.04.2.2 6.04.2.2.1
Functions Bearing Chalcogen and Silicon Functions bearing oxygen and silicon
(i) Functions bearing two oxygen and one silicon substituent(s) [(3-Benzyltetrahydro-2-furanyl)(dimethoxy)methyl](trimethyl)silane 323 has been obtained from compound 322, Ph3P+CH2OMeCl, and Me3SiCl by the electrochemical reaction. Also compound 323 was synthesized using acyclic monomers. This reaction occurs stereoselectively (Equation (56)) <2002JA10101>. Ph O
O 322
i
ii
iii 80%
O
Ph OMe OMe SiMe3
ð56Þ
323
i. Ph3P+CH2OMeCl–; ii. Me3SiCl; iii. 0.5 M Et4NOTs, MeOH, 8 mA, 2.0 F/mol
In the presence of tertiary amine, compound 324 undergoes nucleophilic substitution by phenol or benzylalcohol at a bromine-linked carbon atom to give asymmetric trimethylsilyl acetals 325, which are also accessible directly from silyl methyl ether 326 without preliminary isolation of compound 324 <2001TL4557>. Furthermore, compounds 325 can be obtained from 1-octanole (Scheme 43) <1999MI469>.
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen ROH, EtN(Pri )2
Br MeO
SiMe3
OR MeO
84%
324
i. Br2 ii. ROH, EtN(Pri)2
MeO
84%
SiMe3
145
SiMe3
326
325
R = Ph, Bu, 1-octane
Scheme 43
1-Substituted-1-alkoxy-1,3-diene 327 has been brominated by N-bromosuccinimide to give compound 328 on subsequent washing of the reaction mixture with sodium bicarbonate solution (Equation (57)) <1999SL1841>. i. MeOH, bromosuccinimide, THF ii. NaHCO3, H2O iii. Et2O
EtO Me3Si
OMe Me3Si
CH2
Br
ð57Þ
OMe
327
328
Mg-promoted cross-coupling reactions of aromatic carbonyl compounds 329 with trimethylsilyl chloride in DMF at room temperature bring about reductive carbon–silicon bond formation to give the corresponding -trimethylsilyl alkyltrimethylsilyl ethers 330 selectively in good yields (Equation (58)) <1995CL829>. O Ph
Me3SiCl, Mg, DMF OEt
Ph EtO
56%
329
O SiMe3 SiMe3
ð58Þ
330
(ii) Functions bearing one oxygen and two silicon substituents Epoxide 331 selectively reacts with Me3SiCl in the presence of BusLi to yield di-(trimethylsilyl)epoxide 332 (Equation (59)) <2002PIAWO2002053549>. i. Me3SiCl, BusLi, hexane ii. THF iii. HCl, H2O
O (CH2)9-Me
O
Me3Si
ð59Þ (CH2)9-Me
Me3Si
52%
331
332
Silylation of epoxide 333 by Me3SiCl also selectively leads to the formation of 1,1-disilyl epoxide 334 (Equation (60)) <2002SL553>.
O But Me
CH2
i. TMEDA, BusLi, Et2O, cyclohexane ii. Me3SiCl 58%
Me 333
O
Me3Si But Me
CH2
Si
ð60Þ
Me 334
Allyl ether 337 can be accessed by the electrochemical reaction of compounds 335 and 336 (Equation (61)) <2001JEC55>.
146
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
Me3Si
OMe Sn(Bun) SiMe3
Bu4N+BF4– , CH2Cl2
OMe
H2C CHCH2SiMe3
+
98%
335
CH2
Me3Si SiMe3
ð61Þ
337
336
Substituted benzotriazole 340 containing the bis(trimethylsilyl)phenoxymethylene group has been obtained by the reaction of 1-(phenoxymethyl)-1H-1,2,3-benzotriazole 338 with 2 equiv. of Me3SiCl (Scheme 44) <1999T11903>.
OH
N N
+
N CH2Cl
N
NaH, DMF
N N CH2OPh
85%
338
N N
i. LiN(Pri )2, THF ii. Me3SiCl, THF
N
86%
N
N CH2OPh
N
Me3Si
i. LiN(Pri )2, THF ii. Me3SiCl, THF
N
36%
N
N Me3Si
OPh SiMe3 340
OPh
339
338
Scheme 44
The reaction of complex 341 with pivaldehyde afforded the di(hypersilyl)compound 342 (Equation (62)) <1997CB1709>. SiMe3 Me3Si Si SiMe3 + ButCHO O Li O O
Pentane
(Me3Si)3Si
OH Si(SiMe)3 342
ð62Þ
341
Oxidation of the unsaturated compound 343 by MCPBA in dichloroethane leads to the formation of epoxide 344 (Equation (63)) <1997JCS(P1)2279>. Me3Si
(CH2)4COOMe
Me3Si
MCPBA, CH2Cl2
Me3Si
97%
Me3Si
343
O (CH2)4COOMe
ð63Þ
344
Benzyl-N,N-diethylcarbamate 345 reacts with BuLi and trimethylsilyl chloride to give bissilylated product 346 (Equation (64)) <1995SC3347>. O Et2N
O
Ph
BuLi, THF Me3SiCl 60%
345
Ph Me3Si
O SiMe3
O NEt2
ð64Þ
346
(iii) Functions bearing one oxygen, one sulfur, and one silicon substituent The reaction of benzoquinones 347 or 348 with chloromethylenesulfinic acid 349 and subsequent silylation of the reaction mixture yielded benzoxathiole 1,1-dioxides 350 (Scheme 45) <1996AP361>.
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
147
O F
O
O
F 347
O i, ii, iii, iv, v + ClH2C S OH 72%
F
Me Si But S O Me
O
MeO
O
349
F
i, ii, iii, iv, vi
+ 349
72% O 348
350
i. HCl, H2O; ii. NaOH, H2O; iii. Me2SO4; iv. Li(Pri)2, THF; v. ButSiMe2Cl, HHF; vi. ButSiMe2Cl
Scheme 45
Substituted trimethylsilylmethane 352 has been obtained by consecutive reactions of the ether 351 with ButLi, trimethylgermyl bromide, and trimethylsilyl chloride in THF (Equation (65)) <2000JCS(P1)2677>. PhSCH2OMe
i, ii, iii, iv
Me3Ge
90% 351
OMe SPh SiMe3
ð65Þ
352
i. ButLi, THF; ii. Me3GeBr, THF; iii. ButLi, THF; iv. Me3SiCl
(iv) Functions bearing one oxygen, one silicon, and one nitrogen substituent 1-(Chloromethyl)benzotriazole 353 has been lithiated by LDA to give 3,3-disubstituted-1-oxiranylbenzotriazoles such as 354 on further reaction with ketones, which have been silylated by trimethylsilyl chloride to yield substituted oxiranylbenzotriazoles such as 355 bearing oxygen, silicon, and nitrogen at an sp3-carbon atom (Scheme 46) <2003JOC407>.
N
N
i, ii, iii
N
iv, v
N
69%
N
N
N
N CH2Cl 353
N O Et
Et
Et
354
SiMe3 O
Et 355
i. 3-pentanone, LiN(Pr-i)2, THF; ii. BuLi; iii. Me3SiCl; iv. BuLi, THF; v. Me3SiCl
Scheme 46
Trimethylsilyl allylbenzotriazole 357, obtained by the silylation of the substituted benzotriazole 356, has been demonstrated as a convenient reagent for the synthesis of carbonyl compounds (Equation (66)) <1995JOC7589>. N N N EtO 356
Me3SiCl, BuLi, THF
N N N Me3Si EtO
ð66Þ
357
Some other benzotriazoles substituted with a trimethylsilyl group 358 have been obtained by the reaction of methoxymethyl benzotriazole with alcohols and trimethylsilyl chloride <1999T11903>.
148
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen N N N RO
SiMe3
358 R = Ph, 4-MeOPh, Et, Me, But
The reaction of O-allenyl--D-xylofuranoses with Me3SiCl and ClSO2NCO afforded silyl derivatives of -D-xylofuranose 359 with high yields <2000TA3131>.
Me O Me
H O OR
O H O Me3Si HN
CH2
O 359
6.04.2.2.2
Functions bearing sulfur and silicon
(i) Functions bearing two sulfur and one silicon substituent(s) 2-Trimethylsilyl-1,3-dithiane 360 chemoselectively reacts with vinyl epoxides 361 to give compounds 362 (Equation (67)) <2002JA14516>. CH2 O
S S 360
+ SiMe3
R
CH2
i, ii, iii 76–88%
R HO
S
SiMe3 S
ð67Þ
361 362 i. HMPT, ButLi, THF, hexane; ii. THF; iii. NH4Cl, H2O R = CH2OCHPh, CH2OSiBuPh2, cyclohexyl
Substituted 2-silyl-1,3-dithianes have been obtained by various methods: the reaction of 2,4dithiacyanopentanes with sodium in liquid ammonia and phenoxymethoxytrimethylsilylmethane <2002SL1447>, treatment of octanal with 1,3-dimercaptopropane and Me3SeCl <2002TA1825>, from 1,3-dithiane with diphenylfluorosilyl ether <2002JA7363>, by the reaction of 2-trimethyl1,3-dithiane with triphenylsilyl ether of iodoethane <2002OL1787>, by silylation of 2-substituted 1,3-dithianes with Alk3SiCl or disilylic ethers <2002OL2957, 2002S552, 2001CL476, 2000TL321>, from 2-trimethylsilyl-1,3-dithianes with azulenes <2001S1346>, by the reaction of 2-triphenylsilyl-1,3-dithianes with 5-bromopentanal acetal <2001JOC8983>, by the condensation of aromatic aldehydes with 1,3-dimercapropropane and subsequent silylation of the reaction mixture with Me3SiCl <2000JOM220>. Substituted 2-silyl-1,3-dithianes, obtained by these methods, have been used for the synthesis of different derivatives of carbonyl compounds, including natural products. 2-Trimethylsilyl-1,3-dithiolane 366 has been obtained by the reaction of compounds 363, 364, or 365 with 1,2-dimercaptoethanol (Scheme 47) <2001TL4557>. 2-Acetylthiotetrahydropyran gives silylated 2-phenylthiomethylthiotetrahydropyran in 67% yield on reaction with chloromethylthiobenzene and Me3SiCl in THF <2002PS709>. The reaction of disilane 367 with diphenyldithiomethane 368 leads to the formation of bis(disilyl)ether 369 (Equation (68)) <2000JOM12>.
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
149
i, ii, iii
Me3SiCH2OMe 363 Br
S
ii, iii
MeOCHSiMe3 364
SiMe3 88%
S 366
OMe iii
Me3SiCHOBun 365
i. Br2; ii. BuOH, EtN(Pri)2; iii. HSCH2CH2SH, BF3-Et2O
Scheme 47
PhS
Cl Me Si Me Me Si Me Cl
+
Bu, THF
2PhSCH2SPh
SPh
Me Si Me Me Si Me
368
PhS
367
ð68Þ
SPh 369
1,3-Disilacyclohexanes 371 and 373 are formed by silylation of bis(alkylthio)methyllithium with chloro(chloromethyl)dimethylsilane 370 and 372 followed by ring closure in the presence of a base. The spiro-fused disilacyclohexane ring 373 is structurally strain free, like cyclohexane. The proposed reaction mechanism involves a silacyclopropane intermediate (Scheme 48) <1999ICA231>.
CH2Cl Me Si Me MeS
MeS
Me Si Me MeS SMe Si SMe Me Me 371
LiN(Pri)2, THF
SMe 370
Me Me S S
Me Si CH2Cl Me 372
LiN(Pri)2, THF
S
Si S
S
Si S Me Me 373
Scheme 48
Norbor-5-en-2,3-dicarboximide 374 reacts with thiophenol and 2-methylsilyl-1,3-dithiane to give compound 375 (Equation (69)) <1998T12361>. OMe
H O N
OMe
+
374
I
S
+
I N
S H O
OMe
H O
SH
SiMe3
OMe
H HO
S Me3Si 375
S
ð69Þ
150
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
(ii) Functions bearing one sulfur and two silicon substituents Bis(trimethylsilyl)methane sulfonamide 377 has been obtained by the reaction of tris(trimethylsilyl)methanesulfonyl chloride 376 with H2O, PCl5, and piperidine (Equation (70)) <2000CJC1642>.
Cl
i. H2O, THF ii. PCl5, Et2O iii. Piperidine, CH2Cl2
O SiMe3 S SiMe3 O SiMe3
O N S O
376
SiMe3
ð70Þ SiMe3
377
Reductive lithiation of (PhS)2CH(SiMe2)3CH(SPh)2 378 or deprotonation of PhSCH2(SiMe2)3CH2SPh 380 has been used to afford PhSCHLi(SiMe2)3CHLiSPh, which was silylated with Me2SiCl2 or (SiMe2Cl)2 to give the tetrasilacyclohexane 381 or pentasilacycloheptane 379 (Scheme 49) <1999SL1772, 2000JOM12>. Me PhS Me Si PhS Me Si Me SPh Me Si SPh Me
Cl Me Si Me Me Si Me Cl
+
Me Me Me Si Si Me PhS Si Me Me Si Me Me Si SPh Me Me
(4-ButC6H4)2.Li, THF
378
379 Me SPh Me Si Me Si Me Me Si Me SPh
Me2SiCl2,
PhS
Me Si Si Me Me Me Si Si SPh Me Me Me Me
BusLi
380
381
Scheme 49
(iii) Functions bearing one sulfur, one silicon, and one nitrogen substituent The lithiation site of 2-trimethylsilyl-N-BOC-pyrrolidine 382 is strictly dependent on the reaction temperature; at 78 C the anion of 382 reacts with dimethyl disulfide to give in solely 2,2disubstituted product 383 (Equation (71)) <1999JPC455>. i. BusLi, TMEDA ii. Me2S2 (–78 °C to rt) SiMe3 N BOC
SMe
ð71Þ
N SiMe 3 BOC
76%
382
383
Nonregioselective reaction of 1-chloromethylbenzotriazole 384 with ButSH and Me3SiCl leads to the formation of the mixture of compounds 385 and 386 (Equation (72)) <1999T11903>. SH
N N N CH2Cl 384
+
Me
Me
SiMe3
(1) i, ii, iii (2) iv, v, vi
N
N N
+
N
N
Me Me3Si
80% 385
N SBut
Me3Si
SBut
10% 386
i. NaH, DMF; ii. H2O; iii. CH2Cl2; iv. LiN(Pri)2, THF; v. Me3SiCl, THF; vi. NH4Cl, H2O, Et2O
ð72Þ
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen 6.04.2.2.3
151
Functions bearing selenium and silicon
No new examples of the synthesis of the functional groups bearing selenium and silicon have appeared in the literature since COFGT (1995) <1995COFGT(6)103>.
6.04.2.3 6.04.2.3.1
Functions Bearing Chalcogen and Germanium Functions bearing two oxygen and one germanium substituents
Since 1994 only two examples of a functional group of such type have been reported. Reaction of the diazagermylenes 387 with dichlorocarbene leads to the formation of the mixture of compounds 388 and 389 (Equation (73)) <1998MI729>. SiMe3 N Ge N SiMe3
SiMe3 N Cl Ge OBut N Cl SiMe3
CHCl3, ButOK, hexane, pentane
SiMe3 N Cl Ge OBut N OBut SiMe3
+
388
387
ð73Þ
389
Unsaturated ether 390 reacts with tri-2-furylgermane to give t-butyldimethylsilyl acetal 391 (Equation (74)) <2001MI461>. OSiMe2But
R
+ O
OMe
3
O
GeH
3
R
Ge OSiMe2But
ð74Þ
OMe
390
391
6.04.2.3.2
Functions bearing one oxygen, one sulfur, and one germanium substituents
Compound 393, bearing oxygen, sulfur, and germanium, has been obtained in several steps by the reaction of ether 392 with Me3GeBr and in one step from compound 394 (Scheme 50) <2000JCS(P1)2677>.
PhS-CH2-OMe
i, ii
i, ii, iii
OMe Me3Ge C SPh GeMe3
392
i, ii, iii
OMe Me3Ge C SPh H
92%
(Step 1)
393
394
i. ButLi, THF; ii. Me3GeBr, THF; iii. NH4Cl, H2O
Scheme 50
Compound 395 has been obtained in a similar way to the above-mentioned methods from ethers 392 and 394 (Scheme 51) <2000JCS(P1)2677>.
PhS-CH2-OMe
i, ii
i, iii, iv
OMe Me3Ge C SPh SiMe3
i, iii, iv
OMe Me3Ge C SPh H
392
(Step 1) 395 90% 394 i. ButLi, THF; ii. Me3GeBr, THF; iii. Me3SiCl, THF; iv. NH4Cl, H2O
Scheme 51
152
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
6.04.3
FUNCTIONS CONTAINING CHALCOGEN AND A METAL AND POSSIBLY A GROUP 15 ELEMENT OR A METALLOID
6.04.3.1 6.04.3.1.1
Functions Bearing Oxygen and a Metal Functions bearing two oxygens and a metal
No new examples of the synthesis of the functional groups bearing two oxygens and a metal have appeared in the literature since COFGT (1995) <1995COFGT(6)103>.
6.04.3.1.2
Functions bearing oxygen, silicon, and a metal
Methoxymethyltrimethyl silane 396 on treatment with BuLi undergoes regioselective lithiation to give in good yield 397 metallated at the methylene carbon (Equation (75)) <2000JOM87>. Li MeOCH2SiMe3
BuLi, THF
MeOCHSiMe3
ð75Þ
95% 396
6.04.3.1.3
397
Functions bearing oxygen and two metals
No new examples of the synthesis of the functional groups bearing oxygen and two metals have appeared in the literature since COFGT (1995) <1995COFGT(6)103>.
6.04.3.2 6.04.3.2.1
Functions Bearing Sulfur and a Metal Functions bearing sulfur, oxygen, and a metal
Compounds such as 399, bearing functional groups of this type, have been obtained by the reaction of trimethylsilyl ethers such as 398 with BuLi. Germanium-containing analogs such as 401 were generated directly in the reaction mixture to give bisdigermenyl ethers such as 402 on further reaction with Me3GeBr or to give silylated compounds such as 403 on treatment with Me3SiCl (Scheme 52) <2000JCS(P1)2677>.
Me3Si
OMe C SPh H
BuLi, THF
398
OMe Me3Ge C SPh H 400
ButLi, THF
OMe Me3Ge C SPh Li 401 90%
Me3Si
Li C SPh OMe 399
Me3GeBr 92%
OMe Me3Ge C SPh GeMe3 402
MeSiCl
OMe Me3Ge C SPh SiMe3 403
Scheme 52
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen 6.04.3.2.2
153
Functions bearing two sulfurs and a metal
Compound 407, which can be used for the synthesis of macrolide antibiotic Roflamycoin, has been obtained by the reaction of compounds 404–406 with BuLi (Equation (76)) <1997JA2058>.
S S
O
H O
SnBu3 + SnBu3
404
BuLi +
LiCH2OCH2Ph
S
56%
S
406
OH OH O
SnBu3
405
Ph
ð76Þ
407
Besides, 1,3-dithiane 404 has been converted into 2-deuterated-1,3-dithiane 408 bearing one Bu3Sn group <2001TL5001>.
S SnBu3 S
D 408
Dithioacetals such as 409 have been demonstrated to react with Bu3SnCl to give tributylstannylthioacetals such as 410, which can be used for the synthesis of ,-unsaturated ketones (Equation (77)) <1995T2515>.
SPh PhS C H
i. BuLi, THF, hexane ii. Bu3SnCl Ph
97%
SPh (Bun)3Sn C SPh
409
Ph
ð77Þ
410
Trimethylstannylthioacetal 411 undergoes Michael addition to 2-cyclohexenone to yield the ketone 412 (Equation (78)) <2000AG(E)414>.
SMe MeS C SnMe3 H 411
2-cyclohexenone HMPT, THF 77%
SMe O
C MeS
SnMe3
ð78Þ
412
By the reaction of pentadiene 413 with 2-methylene-1,3-dithiane 414, compound 415 has been generated in the reaction mixture and then alkylated to produce different dithiane polyenes 416 and 417, which have been demonstrated to be convenient reagents for the stereoselective synthesis of decahydronaphthalenes (Scheme 53) <1995TL3473>. Li-N,N-diisopropyl-3-amino-1,3-benzothiaborolide 418 has been prepared by the multistep synthesis starting from thioanisole (Equation (79)) <1998JOM2379>.
154
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
Me
Br
i, ii
Me
413
Li
415
Me
S
S
S
S 416
Br SnBu3 SnBu3 Me
S S 417 S 414
i. BuLi, THF; ii. S
Scheme 53 Me S Ph
i, ii
iii, iv
v
S Li B N(Pri )2 418
ð79Þ
i. BuLi, hexane; ii. Bu2SnCl2, pentane, hexane; iii. BCl3, pentane; iv. Pr2i NH, CH2Cl2; v. ButLi, THF
6.04.3.2.3
Functions bearing sulfur, boron, and a metal
No new examples of the synthesis of the functional groups bearing sulfur, boron, and a metal have appeared in the literature since COFGT (1995) <1995COFGT(6)103>.
6.04.3.2.4
Functions bearing sulfur, silicon, and a metal
No new examples of the synthesis of the functional groups bearing sulfur, silicon, and a metal have appeared in the literature since COFGT (1995) <1995COFGT(6)103>.
6.04.3.2.5
Functions bearing sulfur and two metals
No new examples of the synthesis of the functional groups bearing sulfur and two metals have appeared in the literature since COFGT (1995) <1995COFGT(6)103>.
6.04.3.3
Functions Bearing Selenium and a Metal
No new examples of the synthesis of the functional groups bearing selenium and a metal have appeared in the literature since COFGT (1995) <1995COFGT(6)103>.
REFERENCES 1969ZC201 1971S16 1977UK685
J. Gloede, L. Haasse, H. Gros, Zeitschrift fuer Chemie 1969, 9, 201–213. R. Feinauer, Synthesis 1971, 16–26. V. G. Granik, A. M. Zhidkova, R. G. Glushkov, Usp. Khim. 1977, 46, 685–711. (Chem. Abstr. 1977, 87, 21650).
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2001TL4819 2001TL5001 2001TL8475
A. Dondoni, G. Lathauwer, D. Perrone, Tetrahedron lett. 2001, 42, 4819–4824. J.-C. P. Cintrat, F. Pillon, B. Rousseau, Tetrahedron Lett. 2001, 42, 5001–5003. M. Lecouvey, I. Mallard, T. Bailly, R. Burgada, Y. Leroux, Tetrahedron Lett. 2001, 42, 8475–8478. 2002DOK61 A. B. Koldobskii, V. E. Vakhmistrov, E. V. Solodova, O. S. Shilova, V. N. Kalinin, Doklady Akademii Nauk 2002, 387, 61–64. (Chem. Abstr. 2003, 138, 304131). 2002DP143 S. S. Ramos, P. F. Santos, L. V. Reis, P. Almeida, Dyes Pigm. 2002, 53, 143–152. 2002EJO1664 J. Dietz, T. Schmidt, J. Renner, U. Bergstrasser, F. Tabellion, F. Preuss, P. Binger, H. Heydt, M. Regitz, Eur. J. Org. Chem. 2002, 1664–1676. 2002EUP1215201A2 Bellus, D.; Dondoni, A. Eur. Pat., 1215201A2 (2002) (Chem. Abstr., 2002, 137, 33135). 2002GEP10114352 Blum, H.; Pustovit, Y.; Greb, W.; Roeschenthaler, G.-V. Ger. Pat. 10114352 (2002) (Chem. Abstr., 2002, 136, 310034). 2002HCA2383 T. Nishio, K. Shiwa, M. Sakamoto, Helv. Chim. Acta 2002, 85, 2383–2393. 2002JA10101 B. Liu, S. Duan, A. C. Sutterer, K. D. Moeller, Journal Am. Chem. Soc. 2002, 124, 10101–10111. 2002JA13678 S. Kobayashi, H. Shimizu, Y. Yamashita, H. Ishitani, J. Kobayashi, J. Am. Chem. Soc. 2002, 124, 13678–13679. 2002JA14516 A. B. Smith III, M. S. Pitram, M. J. Gaunt, S. A. Kozmin, J. Amer. Chem. Soc. 2002, 124, 14516–14517. 2002JA7363 M. W. Mutahi, T. Nittoli, L. Guo, S. Luxuan, M. Scott, J. Am. Chem. Soc. 2002, 124, 7363–7375. 2002JAP2002105058 Ono, M.; Sen, M. Japan Patent 2002, 2002105058 (Chem. Abstr., 2002, 137, 200977). 2002JCS(P1)1568 Z. Casar, I. Leban, A. M. Marechal, D. Lorcy, J. Chem. Soc., Perkin Trans. 1 2002, 1568–1573. 2002JHC691 W. A. O. Sarhan, M. Murakami, T. Izumi, J. Heterocycl. Chem. 2002, 39, 691–694. 2002JMC2185 C. M. Szabo, Y. Matsumura, S. Fukura, M. B. Martin, J. M. Sanders, S. Sengupta, J. A. Cieslak, T. C. Laftus, C. R. Lea, H.-J. Lee, A. Koohang, R. M. Coates, H. Sagami, E. Oldfield, J. Med. Chem. 2002, 45, 2185–2196. 2002JOC6124 H. Kumamoto, M. Murasaki, K. Haraguchi, A. Anamyra, H. Tanaka, J. Org. Chem. 2002, 67, 6124–6130. 2002JOC7706 K. Tetsuya, S. Satoshi, M. Akira, J. Org. Chem. 2002, 67, 7706–7715. 2002M1055 W. A. O. Sarhan, M. Murakami, T. Izumi, Monatsh. Chem. 2002, 133, 1055–1066. 2002MI1111 V. M. Berestovitskaya, I. A. Litvinov, I. E. Efremova, L. V. Lapshina, D. B. Krivolapov, A. T. Gubaidullin, Russian J. General Chem. 2002, 72, 1111–1118. 2002MI335 B. P. Sharma, Indian Journal Heterocyclic Chem. 2002, 11, 335–336. 2002MI980 L. M. Burnaeva, V. F. Mironov, N. M. Azancheev, I. V. Konovalova, G. A. Ivkova, O. V. Yashagina, A. N. Pudovik, Russian J. General Chem. 2002, 72, 980–981. 2002MIP1333210 Xie, Y.; Li, Q.; Xie, Y.; Yan, X.; Qin, X. Chinise Patent 1333210 (2002) (Chem. Abstr., 2003, 138, 221705). 2002MIP2178793 Badmaev, A. V.; Mudryi, F. V.; Suchkov, A. V.; Milgotin, I. M.; Bogach, E. V.; Kuznetsov, A. A.; Bolshova, I. V. Russia Patent 2178793 (2002) (Chem. Abstr., 2003, 138, 221706). 2002OL1551 V. Capriati, L. Degennaro, R. Favia, S. Florio, R. Luisi, Org. Lett. 2002, 4, 1551–1554. 2002OL1787 P. Wipf, M. J. Soth, Organic Lett. 2002, 4, 1787–1790. 2002OL2957 L. Xin, D. A. Nicewicz, J. S. Johnson, Org. Lett. 2002, 4, 2957–2960. 2002PIAWO0290367 H. Dabak, A. E. Zarslan, F. Sahbaz, T. Aslan, PCT Int. Appl. WO 0290367 (2002). (Chem. Abstr. 2002, 137, 353175). 2002PIAWO2002053549 D. M. Hodgson, S. L. M. Norsikiun, I. D. Cameron, E. Gras, PCT Int. Appl. WO 2002053549 (2002). (Chem. Abstr. 2002, 137, 93678). 2002PS709 K. Sipia, T. Hase, J. Koskimies, J. Matikainen, J. Kansikas, Phosphorus, Sulfur, Silicon and the Related Elements 2002, 177, 709–727. 2002S2043 D. Ntirampebura, L. Ghosez, Synthesis 2002, 2043–2052. 2002S274 M. Berganer, P. Gmeiner, Synthesis 2002, 274–278. 2002S552 J.-P. Bouillon, F. Huguenot, C. Portella, Synthesis 2002, 552–556. 2002SL1447 A. Capperucci, V. Care, A. Degllnnocenti, T. Nacenthini, S. Pollicino, Synlett 2002, 1447–14450. 2002SL525 M. Monenschein, M. Brunjes, A. Krischning, Synlett 2002, 525–527. 2002SL553 J.-C. Marie, C. Courillon, M. Malacria, Synlett 2002, 553–556. 2002T2215 D. Krishnaswamy, V. V. Govande, V. K. Gumaste, B. M. Bhawal, A. R. A. S. Deshmukh, Tetrahedron 2002, 58, 2215–2226. 2002TA1825 A. Battaglia, E. Baldelli, G. Barbaro, P. Giorgianni, A. Guerrini, M. Monari, S. Selva, Tetrahedron: Asymmetry 2002, 13, 1825–1832. 2002TL6911 Y. Omata, A. Kakehi, M. Shirai, A. Kamimura, Tetrahedron Lett. 2002, 43, 6911–6914. 2002UKZ46 M. K. Bratenko, V. O. Chornous, M. V. Vovk, Ukr. Khim. Zh. 2002, 68, 46–51. (Chem. Abstr. 2003, 138, 89723). 2003JOC407 A. R. Katritzky, K. Mauju, P. J. Steel, J. Org. Chem. 2003, 68, 407–411. 2003USP3013918 Cowan, J. M.; Christopher, C. J.; Michael, J. US Patent 2003013918 (2003) (Chem. Abstr., 2003, 138, 8921). B-1970MI001 R. H. De Wolfe, in Carboxylic Ortho Acid Derivatives, Academic Press, New York, 1970, pp. 420. B-1979MI002 S. Patai, Ed., The Chemistry of Acid Derivatives, Supplement B, Interscience, New York, 1979.
Functions Containing a Chalcogen and Any Other Heteroatoms Other Than a Halogen
159
Biographical sketch
Anatoliy M. Shestopalov was born in Khmel’nyts’kyy, Ukraine, in 1954. He studied chemistry and biology at the Lugansk Pedagogical Institute, where he received his M.Sc. in chemistry and biology in 1979. In 1985 he graduated with a Ph.D. (Development of the methods of synthesis, and investigation of chemical properties and biological activities of 3-cyanopyridine-2(1H)-thiones and products of their transformation) from the Institute of Chemical Aids of Plant Protection in Moscow, Russia. After a postdoctoral stay at the Zelinsky Institute of Organic Chemistry in Moscow, he received his ‘‘Doctor of Science’’ degree in chemistry (Quaternized azines in the synthesis of carbo- and heterocyclic compounds) in 1991 at the Zelinsky Institute of Organic Chemistry. He is now a chief scientist and head of the scientific group at the Zelinsky Institute of Organic Chemistry. His research interests include regio- and stereoselective synthesis of carbo- and heterocyclic compounds, multicomponent reactions, chemistry of N-, O-, S-, Se-containing heterocycles and chemistry of physiologically active compounds. He is an author of more then 200 scientific publications.
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Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 111–159
6.05 Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) A. GU¨VEN Anadolu University, Eskis¸ ehir, Turkey 6.05.1 FUNCTIONS CONTAINING THREE GROUP 15 ELEMENTS 6.05.1.1 Functions Bearing Three Nitrogen Atoms 6.05.1.1.1 1,1,1-Triaminoalkanes 6.05.1.1.2 1,1,1-Trinitroalkanes 6.05.1.1.3 1-Amino-1,1-dinitroalkanes 6.05.1.2 Functions Bearing Three Phosphorus Atoms 6.05.1.3 Functions Bearing Three Arsenic Atoms 6.05.1.4 Functions Bearing Group 15 Elements 6.05.1.4.1 Functions bearing two nitrogen atoms and phosphorus atom 6.05.1.4.2 Functions bearing two nitrogen atoms and one arsenic atom 6.05.1.4.3 Functions bearing two nitrogen atoms and one antimony atom 6.05.1.4.4 Functions bearing two phosphorus atoms and one nitrogen atom 6.05.1.4.5 Functions bearing two phosphorus atoms and one arsenic atom 6.05.1.4.6 Functions bearing two phosphorus atoms and one antimony atom 6.05.1.4.7 Functions bearing two antimony atoms and one phosphorus atom 6.05.2 FUNCTIONS CONTAINING TWO GROUP 15 ELEMENTS AND ONE GROUP 13 OR 14 ELEMENTS 6.05.2.1 Functions Containing Two Group 15 Elements and One Group 13 Elements 6.05.2.1.1 Functions bearing two nitrogen atoms and one boron atom 6.05.2.1.2 Functions bearing two nitrogen atoms and one gallium atom 6.05.2.1.3 Functions bearing two nitrogen atoms and one indium atom 6.05.2.1.4 Functions bearing two nitrogen atoms and one thallium atom 6.05.2.1.5 Functions two phosphorus atoms and one gallium atom 6.05.2.1.6 Functions bearing two phosphorus atoms and one indium atom 6.05.2.1.7 Functions bearing one phosphorus, one nitrogen, and one boron atom 6.05.2.2 Functions Containing Two Group 15 Elements and One Group 14 Element 6.05.2.2.1 Functions bearing two nitrogen atoms and one silicon atom 6.05.2.2.2 Functions bearing two nitrogen atoms and one germanium atom 6.05.2.2.3 Functions bearing two phosphorus atoms and one silicon atom 6.05.2.2.4 Functions bearing two phosphorus atoms and one germanium atom 6.05.2.2.5 Functions bearing two phosphorus atoms and one tin atom 6.05.2.2.6 Functions bearing two antimony atoms and one silicon atom 6.05.2.2.7 Functions bearing one nitrogen atom, one phosphorus atom, and one silicon atom 6.05.2.2.8 Functions bearing one phosphorus atom, one antimony atom, and one silicon atom 6.05.3 FUNCTIONS CONTAINING ONLY ONE GROUP 15 ELEMENT 6.05.3.1 Functions Bearing One Nitrogen Atom and Two Silicon Atoms 6.05.3.2 Functions Bearing One Phosphorus Atom and Two Silicon Atoms 6.05.3.3 Functions Bearing One Arsenic Atom and Two Silicon Atoms 6.05.3.4 Functions Bearing One Antimony Atom and Two Silicon Atoms 6.05.3.5 Functions Bearing One Bismuth Atom and Two Silicon Atoms 6.05.3.6 Functions Bearing One Antimony Atom, One Gallium Atom, and One Silicon Atom
161
162 162 162 166 168 171 175 176 176 176 177 177 180 180 181 181 181 181 184 184 187 187 188 189 189 189 189 190 191 192 193 193 194 194 194 195 197 197 199 199
162
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
6.05.1
FUNCTIONS CONTAINING THREE GROUP 15 ELEMENTS
6.05.1.1
Functions Bearing Three Nitrogen Atoms
6.05.1.1.1
1,1,1-Triaminoalkanes
The use of a 2.1 molar ratio between conjugated azoalkenes 1 and diethylcyanomethylphosphonate 2 in tetrahydrofuran (THF) at room temperature with a catalytic amount of sodium hydride led to the direct formation of diethyl phosphonopyrrolo[2,3-b]pyrroles 4, via two sequential 1,4-addition reactions 3 (Scheme 1) <1994S181>.
R
Me
Me
Me
H
O CN NaH EtO N NHR1 1 + EtO P C N N R THF O P OEt N NHR1 H 44–77% EtO R 1 H 2 Me R1 = CO2Me, CO2But, 3 CONHPh, CO2Et, CONH2 R = CO2Me
MeO2C
N
R
N NHR1 NH2 N NHR1
EtO O P EtO R
Me 4
Scheme 1
Reactions of 1-aryl-2-methylthio-4-(N-arylamino)-4-phenyl-1,3-diazabuta-1,3-dienes 7 with -nitrosostyrenes 6, generated from -chlorooximes 5 in the presence of sodium carbonate, resulted in the formation of a mixture of products which are easily separated, and characterized as 1,4-diaryl-2-[N-arylamino(phenyl)methyleneamino]imidazole-3-oxide 8 and 1,4-diaryl2-[N-arylamino(phenyl)methyleneamino]imidazole 9 (Scheme 2) <1999(JCS(P1)615>. C6H4-p-R3
Cl
C6H4-p-R3
Na2CO3
OH
O
N
R3 = H, Cl, Me 6
5
Ph
N
C6H4-p-R1
Ph
NHC6H4-p-R2
N
N
SMe
Ph
+ p-R1-C6H4
NH O–
R1 = H, Me R2 = H, OMe, Cl
6
C6H4-p-R2 N
N
NC6H4-p-R2 SMe
7
Ph
C6H4-p-R1
NH
N+ C6H4-p-R3
p-R1-C6H4
44–53% 8
C6H4-p-R2 N
N NH
N C6H4-p-R3
31–38% 9
Scheme 2
Tris(alkylpyrazolyl)methanes 11 were prepared from the corresponding pyrazoles 10 under phase transfer conditions in 35–67% yields (Scheme 3) <2000JOM120>. The reaction of tris(pyrazolyl)methane 11 (R1 = R2 = H) with KOBut and paraformaldehyde followed by quenching with water yielded 12, which was then reacted with [Mn(CO)5SO3CF3], prepared in situ from Mn(CO)5Br and Ag(SO3)CF3, to afford complex 13 <2000JOM120>. The rhenium complexes of tris(alkylpyrazolyl)methanes 14 were prepared in refluxing toluene from the corresponding tris(alkylpyrazolyl)methanes 11 and Re(CO)5Br or Re(CO)5BF4 in 63–91% yield (Scheme 3) <2002JOM50>.
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
163
R1 R2 N
R2 N N H
R1
10 1 = H,
R
Na2CO3, Bun4NBr
R2
N
N
H2O, CHCl3 1 rt then reflux, 3 days R 35–67%
H
N
N
N
R2
R1
Me, Ph, Pri, But
11
R2 = H, Me
11
+
R1 = R2 = H
Bu4NBr, Na2CO3, H2O CHCl3, Et2O HCHO, ButOK
O C + N N Mn C O C O N N O – F3C S O O 13
N N
N N
Mn(CO)5Br N N AgO SCF 3 3 78%
HOCH2
HOCH2
N N 12 R2
11 +
Toluene, reflux Re(CO)5Br or Re(CO)5BF4 63–91%
R1 = H, Me, Ph, Pri R2 = H, Me, Pri
H R2
R1 O N N C + N N Re C O X– C X = Br–, BF4– R1 O N N R1
R2 14
Scheme 3
[4+1]-Cycloaddition reaction of N-heterocyclic carbene, generated by thermal decomposition of 2trichloromethyl-1,3-imidazolidines 15, which is readily available from the condensation of the vicinal diamines and chloral, with isocyanates (16 and 17), obtained in situ via thermolysis of the readily available acyl azides, afforded compounds (18–20) in 70–71% yields (Scheme 4) <2002MI4289>.
O N
N
Ph N N O Ph 18 H N Ph
16 N C O 71%
Ph N CCl3 N H Ph 15
18 1 = 19 0.6
Ph N
∆ xylene
OH O
80 °C, 2 h then reflux 16 h
N H 19
[4 + 1]-cycloaddition 17
O
N C O 70%
N
N
Ph N N O Ph 20
Scheme 4
164
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
Phenyl isocyanide reacted with the N,N-(dimethylamino)benzotriazolylcarbene 22, which was generated from benzotriazol-1-ylmethylene-dimethyl-ammonium chloride 21, in a [1+2+2]cycloaddition, and then with nucleophiles to generate various hydantoins 23 in a one-pot procedure (Scheme 5) <1996JHC1935>.
N
Me
N N
N
+ Ph N C O Et3N, benzene morpholine Me 48% N Me
N + Me N Cl– Me
H 21
Me N
N
O
Ph
N
N
O
N Ph
O 23
22
Scheme 5
The methyl ester 27 was obtained in 80% yield in the presence of N-ethyldiisopropylamine (Hu¨nig’s base) 26 from the reaction of phenyl isocyanide with salt 25, 1-amino-5-methoxycarbonyl2,3-dimethyl-3H-imidazol-1-ium mesitylenesulfonate, which was prepared by direct amination of the 1,2-dimethyl-1H-imidazole-4-carboxylic acid methyl ester 24 with mesitylenesulfonylhydroxylamine (MSH) <1977S1> as the aminating agent (Scheme 6) <2001JOC8528>. MeO2C
N Me
MSH
NH2 – MSTSH N Me N Me MSTS = mesitylenesulfonate
+
MeO2C
CH2Cl2, rt 93%
N Me 24
25 –
Pr 25 +
Et
i
N Pri 26
MeCN 20 h, rt
MeO2C
NH N
+
Me Ph N C O
N Me
Me Me Ph N N
MeO2C
N N H
Ph N C O Et 80%
O
Pri N Pri
Me Me Ph N N N
O O
MeO2C
H N Ph
27
Scheme 6
The cycloadducts tetrahydro-1H-[1,3,5]triazino[1,2-a]quiazoline-1,3-(2H)-diones 29 were obtained from the reaction of 3,4-dihydroquinazoline 28 with phenyl isocyanate under mild conditions. When the reaction was carried out at temperatures above 110 C in 1,2-dichlorobenzene containing excess of phenyl isocyanide afforded 30 in 53% yield (Scheme 7) <2000MI2105>. The reactions of perfluoro-5-azanon-4-ene 31 with 2 equiv. of aniline and derivatives 32 in the presence of Et3N afforded the corresponding quinazolines 33 in 67–72% yields. The treatment of 31 with 2,6-dimethylaniline in a 1:1 stoichiometry afforded a six-membered heterocycle—the dihydroquinazoline derivative 34 in 61% yield. The reactions 31 with 1 equiv. of 2-nitro-, 4nitro-, or pentafluoroaniline 35 produced the diazetine derivatives 36. The fluorine atom in C-4 of 36 was substituted by the N-nucleophile to yield the compounds 37 in 57–68% yields (Scheme 8) <2000JFC263>.
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) R1 N H Ph N O N N O Ph
Et2O, 0 °C R2
48–83% R2
N
165
R1 + Ph N C O
29
N 28
110 °C, reflu x 1,2-Cl2C6H4
R1= Me, 4-Me-C6H4 R2 = H, Me
O
R2
NR1 N Ph N O
53%
N Ph
O R1 = 4-Me-C6H4 R2 = Me
30
Scheme 7
CF2CF2CF3
F
NH2 N C4F9 + 2 equiv.
F3CF2CF2C
N
MeCN, Et3N 40 °C, 3 h 67–72%
R
31
32
CF2CF2CF3 N
NH
R
R = H, F, OMe
CF2CF2CF3 Me N CF2CF2CF3 N NH Me Me
NH2 31 +
Me MeCN, Et3N
Me
61%
R 33
34 F 31 + ArNH2 35
Et3N MeCN
CF2CF2CF3
N N F3CF2CF2C
Ar = 2-NO2-C6H4, Ar = 4-NO2-C6H4, C6F5
Ar 36
ArNH2 57–68% F CF CF C 3 2 2
N
NHAr CF2CF2CF3 N Ar 37
Scheme 8
The reaction of bis(dimethylamino)difluoromethane 40, which was produced from tetramethylchloroformamidinium chloride 39 and tetramethylammonium fluoride 38 in high yield, with dimethylaminotrimethylsilane, provided a rapid and facile access to hexamethylguanidinium fluoride 41 in 95% yield. 1,1,1-Trifluoro-2,2,2-tris(dimethylamino)ethane 42 was prepared from 41 and Me3SiCF3 in Et2O at 50 C in 96% yield (Scheme 9) <2000JFC159>. Orthoamide 45 was obtained from guanidininium chloride 43 and appropriate carbanion 44 in high yield (Scheme 9) <2002ZN(B)399>. The 1,3-dipolar cycloaddition reaction of various N-aryl-C-ethoxycarbonylnitrilimines 47, generated in situ from ethylhydrazono--bromoglyoxylate 48, with 1,3,4-benzotriazepin-5-ones 46 in the presence of Et3N regio- and chemoselectively afforded [1,2,4]triazolo[1,3,4]benzotriazepines 49 in 18–44% yields (Scheme 10) <2002MI1545>.
166
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) Me Me Cl N – Me Me N Me F + N Me Me + Me 38 Cl– 39
Me
+
N Me Cl
N Me
–
N Me Me 43
N
F Me N Me Me 40 0 °C, 2.5 h Me2NSiMe3 95% MeCN
Me Me N CF3 Me N N Me Me Me 42
Me
F
Me
CH2Cl2 0–5 °C, 5 h 95%
+
Me Me3SiCF3 –50 °C Et2O 96%
Me
+
N Me F
N Me
–
N Me Me 41
Me Me Et Et N Me NaH, THF + Et C C C H Et C C C C N 94% Me SiO Me OSiMe3 N 3 Me Me 44 45
Scheme 9
O
O Me N N H
N
O
+ EtO2C
Me
R1 = H,
–
R2
N N 47
R1
R1 Ph
1 week, rt 18–44%
Me CO2Et N N N N R1 H N
In situ
R2
N N N H
+
Et3N benzene
N H
N
R2
CO2Et
Br 48 R2 = Me, Cl, NO2
46
O
Me N CO2Et N
N N 1 N H R
R2 49
Scheme 10
6.05.1.1.2
1,1,1-Trinitroalkanes
The photolysis of tetranitromethane (TNM) 51 with 4-chloroanisole 50 in CH2Cl2 led to the formation of mainly 4-chloro-2-trinitromethylanisole 52 in 40–50% yields (Scheme 11) <1993ACS925>, with 1-methyl-4-propenylbenzene 53 to 1-methyl-4-(2-nitro-1-trinitromethylpropyl)benzene 54 <1998ACS745>, with 2,8-dimethyldibenzofuran 55 to mainly (50%) 2,8dimethyl-3-trinitromethyldibenzofuran 56 <1997ACS476>, with 1,4-dimethoxynaphthalene 57
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) OMe NO2 O2N NO2 NO2
+
OMe NO2 NO2 + NO2
CH2Cl2 hν
Cl
Cl 51
50
51
+
CH2Cl2 Me hν 29%
Me
O
40% 52 O2N
Me
NO2 NO2 NO2 OMe
Cl ON
NO2 NO2 Me
O2N 54
53
Me
Me NO2 NO2 NO2
50% O Me
56
Me +
51
CH2Cl2 19% Me
Me
hν
NO2
O
O
55
5%
Me
Me
O
OMe NO2 NO2 NO2
OMe
NO2 OMe
O2N +
OMe 18%
OMe +
167
51
CH2Cl2 hν
OMe 33%
58 O2N NO2 MeO NO2
57
NO2
MeO +
OH NO2 NO2 NO2
OMe
OMe
6%
14%
59
60
Scheme 11
to 1,4-dimethoxy-2-trinitromethylnaphthalene 58, 1,4-dimethoxy-2-nitro-1-trinitromethyl-1,2dihydronaphthalene 59, and 1,4-dimethoxy-2-trinitromethyl-1,2-dihydro-naphthalen-1-ol 60 (Scheme 11) <1997ACS1066>. The reaction of ,-unsaturated ketones of the adamantanes, 1-adamantan-1-yl-3-phenyl-propenone 62 and 1-adamantan-1-yl-4-phenyl-but-3-en-2-one 63 with trinitromethane 61 afforded the corresponding trinitroketones, 1-adamantan-1-yl-4,4,4-trinitro-3-phenyl-butan-1-one 64 and 1-adamantan-1-yl-5,5,5-trinitro-4-phenyl-pentan-2-one 65 in 61% and 93% yields, respectively (Scheme 12) <2001ZOR1872>. The destructive nitration of polynitrocarbonyl compounds 66 with HNO3–H2SO4 at 0 C yielded hexanitroethane 67 in 18–80% yields. Yield increased with electron-donor groups on 66 (Scheme 13) <1994ZOR29>. The compound 5,5-dinitro-6-(4-nitrophenyl)hexan-2-one 68 was also subjected to nitration with HNO3–H2SO4 to yield 1-nitro-4-(2,2,3,3,3-pentanitro-propyl)benzene 69 in 19% yield (Scheme 13) <1994ZOR1521>.
168
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) Ph O
O2N NO 2 NO2
62
O2N
NO2 Dioxane H rt NO2
Ph
O 64
61%
O Ph
61
Ph
O
63
NO2 NO2 NO2
93% 65
Scheme 12
O
O2N O2N
R2 NO2 R1 66
HNO3 H2SO4
NO2 O2N O2N C C NO2 NO2 O2N 67
NO2
O
HNO3 Me H SO 2 4 19%
O2N NO2
O2N
68
1 2 R = H, R = Me 1 R = H, R2 = Et 1 2 t R = H, R = Bu 1 2 R = H, R = CH2CH2CO2H 1 2 R = H, R = 3-NO2-C6H4 1 R = Me, R2 = Me
NO2 NO2 O2N NO2 O2N 69
Scheme 13
The addition of weakly nucleophilic alcohols even to unactivated alkenes was made feasible under mild reaction conditions by the simple use of BF3Et2O catalyst. The 2-(2,2,2-trinitro-ethoxy)-bicyclo[2.2.1]heptane (2-alkoxynorbornane) 72 was prepared from bicyclo[2.2.1]hept-2-ene (norbornene) 70 and 2,2,2-trinitroethanol 71 at room temperature in 31% yield (Scheme 14) <1997S1056>.
+ O2N 70
NO2 CH2Cl2 CH2OH rt, 15 min NO2 31% 71
O 72
NO2 NO2 NO2
Scheme 14
The condensation of the dialkyl aminomalonates 73 with 2,2,2-trinitroethanol 71 gave the corresponding Mannich bases, 2-(2,2,2-trinitroethylamino)malonates 74 in 70% and 82% yields, which were nitrated with HNO3–H2SO4 to give dialkyl 2-nitro-2[N-nitro-N-(2,2,2-trinitroethyl)amino]malonates 75 in 80% and 86% yields (Scheme 15) <2001ZOR207>. The treatment of acetonitrile N-oxide 76 with trinitroacetonitrile 77 afforded 3-methyl-5-trinitromethyl[1,2,4]oxadiazole 78 in 39% yield (Scheme 16) <2002ZOR1269>.
6.05.1.1.3
1-Amino-1,1-dinitroalkanes
The difluoroamines 81 were obtained in 20–70% yields from the reaction of dinitrocarbanions 79 with difluoroaminating reagent 80 (Scheme 17) <1996DOK358>. The 1,3-dicarbanion 82 generated from 1,1,3,3-tetranitropropane was also difluoroaminated by 83 to afford the geminal(difluoroamino)tetranitro compound 84 in 65% yield (Scheme 17) <1996IZV2689>.
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
O2N
NO2 CH2OH + H2N NO2 71
CO2R CO2R 73
R = Me, Et
pH = 4 MeCO2Na
O2N
rt R = Me, 70% R = Et, 82%
NO2 H N
O2N
169
CO2R CO2R
74 HNO3–H2SO4 0–5 °C, 1 h
NO2 NO2 N CO2R O2N O N CO R
O2N
2
2
75
Scheme 15
+
–
Me C N O 76
NO2 NO2 1,3-Dipolar O2N O C N + O2N N O2N 39% NO2 N 77 Me 78
Scheme 16
R
NO2 Na+ + NO2 7
–
O NO2 MeCN F S NF2 R NF2 20–70% O NO2 80 81
R = CN, CONH2 NO2 NO2 O2N
–
–
Li+ Li+ 82
NO2
O + F S O NF2 O 83
MeCN CH2Cl2 65%
NO2 NO2 NF2 F2N NO2 NO2 84
Scheme 17
The photochemical reaction of TNM 51 in CH2Cl2 or MeCN with styrene (R = H), 4-methylstyrene (R = Me), 4-chlorostyrene (R = Cl), and 4-acetoxystyrene (R = OAc) 85 afforded two stereo isoxazolidines, 5-(4-R-phenyl)-2-[1-(4-R-phenyl)-2-nitro-ethoxy]-3,3-dinitroisoxazolidines 88, 3-nitro-5R-phenyl-4,5-dihydroisoxazole 2-oxides 87, and 1-(4-R-phenyl)-2-nitroethanones 86 (Scheme 18) <1998ACS751>. The selection of the olefin to form the nitronic ester 91 in the reaction with TNM 2 is a crucial factor in the synthesis of isoxazolidines (92, 94, and 96). Bicyclobutylidene 89 is the compound for this purpose. The compound 89 reacts with TNM even at 0 C; the reaction initially gives a charge transfer complex, which can be transformed into nitronic ester 91, which does not enter into 1,3dipolar cycloaddition with a second molecule of olefin 89 at low temperatures (0–5 C). Only keeping of the reaction mixture at room temperature resulted in 3,3-dinitroisoxazolidines 92 (Scheme 19) <2002DOK210>. The reaction of TNM 51 and bicyclobutylidene 89 with methylenecyclobutane 93 (R = H) or methylenecyanocyclobutane 5 (R = CN) afforded the corresponding isoxazolidines 94 in 46% and 66% yields, respectively. The olefins 95 containing electronwithdrawing groups were also reacted with 91 to yield the 3,3-dinitroisoxazolidines 96 in 24–59% yields (Scheme 19) <2002DOK210>. The aryl-O N,N-azoxy-,-dinitroalkanes 98 were prepared by nitration of the corresponding N-phenyl-N0 -(-hydroxyiminoalkyl)diazene N-oxides 97 in 60% yields (Scheme 20) <1994MI226>.
170
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) O NO2
6–27% R
86 –
O O N +
NO2 NO2 + O 2N NO2 51
R 85
NO2
CH2Cl2 4 –11%
hν
R 87
R = H, Me, Cl, OAc O2N R 18 –31%
R O
O N O 2N
NO2
88
Scheme 18
+ O 2N 89
NO2 Hexane NO2 0 °C NO2 30 min
NO2 O
O2N
51
+
N O–
1
NO2
O2N
rt 24 h
O2N O N O
91 92
91
O2N O N O
rt O2N 24 h 46–66%
+ R R = H, CN 93
NO2
94 R 1
R1 91
+
H2C
R2
95
rt O2N 24 h 24–59%
O2N O N O 96
R2
NO2 R1
2 R = H, R = CN 1 R = Me, R2 = CO2Me 1 2 R = H, R = CH(OEt)2 1 R = H, R2 = Ph R1 = H, R2 = 4-pyridyl
Scheme 19
–
O N +
N N
OH
–
i. NH4NO3–HNO3 R
ii. N2O4, ClCH2CH2Cl 60%
O N +
98
97 R = CO2Et, Me, CH2Cl, CH2N3, CH2N(NO2)Me
Scheme 20
NO2 N
R NO2
NO2
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) 6.05.1.2
171
Functions Bearing Three Phosphorus Atoms
When the phosphaalkynes 99 were heated at 130 C, or at 180 C in a Schlenk pressure tube, in the absence of a solvent, complex mixtures of products were formed from which the respective tetraphosphacubanes 100 could be isolated in modest yields (8% and 2%) (Scheme 21) <1994S1337>. At higher temperatures for the cyclooligomerization, 101 were formed in 7% and 2% yields, respectively. Tetraphosphacubanes 100 could also be prepared from the zirconecene complexes 102, obtained from 103 and 99, in higher yields (50–80%) (Scheme 21) <1994S1337>.
∆
R C P
P
R
Schlenk pressure tube R = But, 180 °C, 6 h, 7% R = Pet, 200 °C, 3–5 h, 2%
P P R P R
R 101
99 ∆ Schlenk pressure tube R = But, 130 °C, 65 h, 8% R = Pet, 180 °C, 3.5 h, 2%
R
P
R R
P P
P 100
R
[2+2]-Cycloaddition 50–80% R
R R Hetero-Diels–Alders
P P
P R
P P
P
R
R
Toluene 2Cl CCCl 3 3 25 °C
R
= But,
Pet,
1-Me-Cp, 1-Me-Cy R
n
Zr Cl Cl
+ R C P
THF, Bu Li –78 °C then rt
103
Zr
P
P
R 102
Scheme 21
The treatment of t-butylphosphaalkynes with bis(cyclooctatetraene)zirconium 104 and hafnium complexes 105 afforded 106 <1995AG(E)81> and 107 <1995AG(E)2227> in 81% yield, which were then demetallated with hexachloroethane to give 1,3,5,7-tetraphosphabarrelene 108 in 88% yield (Scheme 22) <1995AG(E)81, 1995AG(E)2227>. Tetraphosphabarrelenes 110 were formed nearly quantitatively by heating a pentane solution of 2,4,6-tri-t-butyl-1,3,5-triphosphabenzene with phosphaacetylenes. Analogous reaction of triphosphabenzene with di(isopropylamino)phosphaacetylene 109 led to an unexpected product 111 in quantitative yield (Scheme 23) <1998MI2071>. The compound 109 reacted with the sterically highly substituted t-butylacetylene only at temperatures above 100 C to yield tricyclic compound 112 in 76% yield (Scheme 23) <2000S529>. The unusual reaction of t-butylphosphaalkyne with diethyl phosphite 113 at room temperature in the absence of solvent produced the primary phosphine 114 (Scheme 24) <1996ZOB522>. The phosphaalkynes undergo spirocyclotrimerization with incorporation of the corresponding Lewis acid to form the betaines 115, which was then treated with dimethyl sulfoxide (DMSO) in the presence of t-butylphosphaacetylene as a trapping reagent to afford two isomeric phosphaalkynecyclotetramers having cage structures 118 and 119 (Scheme 25) <1996CB489>. The reaction most probably proceeds by way of the triphosphabenzenes 116 and 117, which cannot be isolated as such but can only be trapped by a homo-Diels–Alder reaction. When, however, the spirocyclic zwitterion 115 was treated in the absence of a trapping reagent with an excess of DMSO at 78 C, the tetra(t-butyl)hexaphosphadecadiene 121 could be isolated in 22% yield
172
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) 81%
But But P But
Zr 104
But C P
P
P
But
But
But
Cl3CCCl3
P M
88%
P
P But
P
But
P 108
R
R 106, M = Zr, R = H 107, M = Hf, R = H, SiMe3
R
R Hf R = H, SiMe3 105
Scheme 22
R R C P 25 °C, 12 h
But
P
P But
But
But
P P
P But
Pr i Pr
i
P
But
P 110
R = But, 98% R = Pent, 96%
But
109 N C P
P
–20 °C <10 min 95%
P P N Pr
But
Pr i
P
But
i
111 But
2 equiv. But
H
Toluene, –20 °C, 5 days 76%
But
But
P But P
P
112
Scheme 23
t
Bu
O Na C P + EtO P OEt 1 week H 113
H H EtO P OEt O P P O EtO But OEt 114
Scheme 24
<2002MI2622>. Compound 121 can be viewed as a dimer of the initially formed spirodiphosphete 120, which undergoes elimination of one molecule of di-t-butylacetylene. Tetracyclic compound 121 was formed more efficiently by reaction utilizing triphosphoryl metal complexes such as trimethylstannyltriphosphole 122 <1999MI3143>. The compound 118 was also prepared from the reaction of t-butylphosphaacetylene with 116 in Et2O in high yield (96%)
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
But
Cl – Cl Al Cl P But DMSO + P CH2Cl2 P But 37% But 115
C P + AlCl3
Et2O 10 min 96%
116
But
But 22%
–78 °C then rt
But
P
But P
P
P
P
But But P
117
P
P
+ But
But But P
P But
But 119
120
P
THF CrCl3(THF)3 –40 °C then rt 31%
PPP P
But
But
But
P
118
But
P P
But
P P
But But
But
+ P P 116 But C P
DMSO
118
P
173
But
But
SnMe3 P P + But P t Bu 122
121
But 116 + R2
R1
Et2O 0 °C, 0.5 h
But
But
P
P
P
R1
R2
123
1 2 R = H, R = CO2Me, 71% 1 2 R = R = CO2Me, 82% R1 = R2 = H, 85% 1 2 R = H, R = Ph, 78% R1 = R2 = Me, 88% R1 = R2 = Ph, 85% R1 = R2 = SiMe3, 80% R1 = Ph, R2 = SiMe3, 70%
Scheme 25
<1997JOM215>. [2+2+2]-Cycloaddition reaction of 116 with numerous alkynes under mild conditions afforded cycloadducts 123 in high yields (Scheme 25) <1997JOM215, 1999S1363>. The treatment of 1-stannyl-3,5-di-t-butyl-1,2,4-triphospholes 124, which could be obtained from Na[3,5-di-t-butyl-1,2,4-triphospholyl] 125 and R3SnCl, with t-butylphosphaalkyne afforded 126 in 80% yield (Scheme 26) <1999MI3143>. SnR3 P But C P P P [4+2]-cycloaddition t R = Ph 124 Bu 70 °C, 12 h
R3Sn
But
SnR3Cl –30 °C
R = Me, 98% R = Ph, 87% R = Bun, 90%
But [Na(THF)x]
But
P
But
C P [2+2+2]-cycloaddition
SnR3 But P P P P P
P But
But
P
But
P P
P
P
But But
125
126
Scheme 26
174
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
The co-condensation of electron beam generated titanium atoms with an excess of t-butylphosphaacetylene afforded the hexaphosphatitanocene complex 127. The complex 128 was formed as a result of an unusual [2+2]-cycloaddition with a P¼C bond of one of 127 (Scheme 27) <1999CC1731>. But
P
But
P
P
Ti
But
+ But
P P
But C P
P
But
But But
P
But
P
P P P Ti
P
127
P But 128
Scheme 27
The Lewis base adducts of imidovanadium(V) compound 129 underwent chemoselective cyclooligomerizatiom reactions with the phosphaalkynes to afford the corresponding azatetraphosphaquadriccyclanes 130 (Scheme 28) <2001ZN(B)951>. R1 Me N O Cl 2 1 P V N R + R2 C P Toluene R O Cl P P P Me R2 = But, Pent, 1-Ad, R2 1-Me-Cp, 1-Me-Cy 129 130 R1 = But, 1-Ad
Scheme 28 Se R1 C P + Sex Toluene Et3N 25–70 °C R1 = But, Pent, 1-Ad, 15–89%
R1
P P Se
R1
R1
R2 C P [4 + 2]
131
P P R1 P
R2
2 t t R2 C P R = Bu , Pen , 1-Ad, [2 + 2 +2]
1-Me-Cp, Mes
Se R1
P
P R1 P P
Se R2
R1 +
R2
R2
132 Toluene 150 °C, 4 days Et3P 1 2 t 82% R = R = Bu 135 11 = 3 134 P
But
P 135 But
But
But
But
P
P
P +
134
But
P
But P
But
P But
25 °C, 14 days
Scheme 29
P But P
P But P But
P P R1 P P 133
R2
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
175
The reaction of the selenodiphospholes 131, which could be obtained from the treatment of phosphaalkynes with an excess of elemental selenium in toluene in the presence of an equimolar of Et3N, with phosphaalkynes led to the formation of a pair of regioisomers 132 and 133. The removal of the selenium from the cage afforded a mixture of the tetraphosphabisprismane 135, and the valance isomeric tetraphosphasemibullvalane 134 in a ratio of 11:3 (Scheme 29) <2001HAC406>. 134 undergoes a slow and thermal isomerization leading to the bisprismane 135. Triphosphabicyclo[1.1.1]pentane 138 was obtained in 36% yield from the reaction of phosphavinyl Grignard reagent 136 with PCl3 in a 3:1 stoichiometry. This is presumably formed via the bisphosphavinyl phosphorus intermediate 137, which undergoes facile phosphavinyl coupling reaction to give the bicyclic product 138 <2002MI1209>. The analogous reaction of 136 with PCl3 in 1:1 stoichiometry afforded the bicyclic product 139 (Scheme 30) <2002MI1209>.
Cl Et 1/3 equiv. PCl3 Mg O C Et Et 2O But 36% 136 1 equiv. PCl3 Et2O 15%
P
P
Cl
P
But
But P
P But
But
P P Cl
138
137
But
P P
Cl P
P
Cl
But 139
Scheme 30
6.05.1.3
Functions Bearing Three Arsenic Atoms
There are only two reports related to this functional group since 1993. The reaction of arsaalkene 141 with the lithium salt of tri(trimethylsilyl)phosphine 142 in the presence of CoCl2 gave tetraarsanecubane 140a (M¼As) in 35% yield, which on reaction with Fe2(CO)9 in THF afforded 140b (M¼As+-Fe(CO)4) in 46% yield <1993AG86, 1993AG(E)83>. The arsacubane 140a reacts at room temperature with ethyl triflate to give the As-ethylated arsonium salt 140c. A similar reaction of 140a with benzyl triflate, generated in situ via PhCH2Cl/AgOTf, gave 140d, the As-benzylated salt of 140a. Low-temperature protonation of 140a with FSO3H/SO2 produces a mixture of arsonium ions 140e, resulting from mono- and diprotonation (Scheme 31) <1994HAC503>.
OTMS TMS As Bu
t
(TMS)2PLi
But
As
CoCl2
142
But
As
But
As But
M
As
141
But 140
140a, M = As 140b, M = As+–Fe(CO)4 140c, M = As+ –Et 140d, M = As+–CH2Ph 140e, M = As+HFSO–3
Scheme 31
176
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
6.05.1.4 6.05.1.4.1
Functions Bearing Group 15 Elements Functions bearing two nitrogen atoms and phosphorus atom
N-benzoyl- and N-methoxycarbonyltrifluoroacetamidophosphonates 145, which could be prepared from the reactions of imidoyl chlorides 143 with trialkylphosphites 144, reacted with dimethylcyanamide 146 in a [4 + 2]-cycloaddition to give 147 in 48–88% yields (Scheme 32) <2002HAC22>.
CF3 O
Et2O, rt, 2 days
Me
R1O R1O P N O 145
R2
+
N C N Me 146
5–10 °C 3h CF3 O Cl
N
O OR1 P OR1 N N
F3C
Reflux, 6 h R2 = Ph 44–88%
Me
143
O
R2
147
2 1 n i R = Ph, R = Me, Et, Pr , Pr 2 1 i R = OMe, R = Pr
R1O P OR1 OR1
+ R2
N Me
144
Scheme 32
When 4,5-dichloro-1,3-dimesitylimidazol-2-ylidene 148 was allowed to react with phosphorus pentafluoride in toluene, 1,3-dimesityl-4,5-dichloroimidazolium-2-pentafluorophosphate 149 was obtained in 58% yield (Scheme 33) <2000M251>.
Cl
Mes N
Cl
F F P F F F
+
N Mes 148
Mes + N F F – P F N F F Mes
Cl Toluene –198 °C
Cl
58%
149
Mes = 1-(2,4,6-mesityl)
Scheme 33
6.05.1.4.2
Functions bearing two nitrogen atoms and one arsenic atom
The reaction of the 4,5-dichloro-1,3-dimesitylimidazol-2-ylidene 148 with arsenic pentafluoride in 1,3-bis(trifluoromethyl)benzene furnished the 1,3-dimesityl-4,5-dichloroimidazolium-2-pentafluoroarsenate 150 in 65% yield (Scheme 34) <2000M251>.
Cl Cl
Cl
Mes N N Mes 148
+
F 1,3-(CF3)2C6H4 F As F –198 °C F F 65%
Cl
Mes + N F F – As F N F F Mes 150
Mes = 1-(2,4,6-mesityl)
Scheme 34
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) 6.05.1.4.3
177
Functions bearing two nitrogen atoms and one antimony atom
The reaction of the 4,5-dichloro-1,3-dimesitylimidazol-2-ylidene 148 with antimony pentafluoride in 1,3-bis(trifluoromethyl)benzene furnished the 1,3-dimesityl-4,5-dichloroimidazolium-2-pentafluoroantimonate 151 in 75% yield (Scheme 35) <2000M251>.
Cl Cl
Mes + N F F – Sb F N F F Mes
Cl
Mes N
F 1,3-(CF3)2C6H4 F Sb F F 77% F
+
N Mes 148
Cl
151
Mes = 1-(2,4,6-mesityl)
Scheme 35
6.05.1.4.4
Functions bearing two phosphorus atoms and one nitrogen atom
The reaction of imidoyl chloride 153, which can be obtained from 152 and PCl5, with diphenyl phosphite 154 in the presence of triethylamine gave a mixture of 155 and tetraphenyl 2-fluoro-1trichloroacetamido-1,1-ethylidenebis-phosphonate 156 in 35% yield (Scheme 36) <2002JFC107>.
F
Reflux O O hexane N CCl3 6 h H PCl5 152
F Cl
Et3N Et2O
O N 153
1h O PhO P OPh H
CCl3
F PhO PhO P O
O PhO P OPh O F
O N H 155
CCl3 + PhO N P H O OPh 156
CCl3
35%
154
Scheme 36
G. Olive and co-workers prepared the tetraethyl(pyrrolidine-2,2-diyl)bisphosphonate 158 from the reaction of pyrrolidine 157, triethylphosphite, and phosphorus oxychloride in 58% yield (Scheme 37) <1998JOC9095, 2001MI275>.
O N H
OEt O + EtO P + Cl P Cl OEt Cl
157
–8 °C 1h 58%
O OEt P OEt OEt N P H O OEt 158
Scheme 37
1-Arylidineamino-1,1-diphosphonoethanes 161 were obtained by Shmarov and co-workers from the reaction of aromatic aldehydes 160 with tetrasodium salt of 1-aminoethane-1,1-diphosphonic acid 159 in 25–60% yields (Scheme 38) <2000JGU521>. The reaction of triethyl phosphite with the various types of Vilsmeier reagents 162 prepared from the N,N-disubstituted formamides, acetylamides, benzoylamides, phenylacetamides, and phosphorus oxychloride afforded the tetraethyldialkylaminomethylenediphosphanates 163 in 30–78% yields. The carbanion 164, generated from 163 by deprotonation with NaH, reacted with benzyl chloride in THF to give the C-benzylated bis-phosphanate 165 in 32% yield (Scheme 39) <1999HAC271>.
178
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) R2
O HO P OH H2N Me + HO P OH R1 O 159
O HO P OH Me N P HO OH O
O R2 H
Water–EtOH 25–60% R1
R3
R3
160a, R2 = R3 = H, R1 = OH, Et2N, NO2 1
2
161
3
160b, R = H, R = OH, R = NO2
Scheme 38
O R2 + Cl P Cl N Cl R3 162 1 R = H, Me, Ph, CH2Ph R2 = Me, Et, Pr R3 = Me, Et, Pr, Ph
O OEt P R2 1 N 3 R R P EtO OEt O EtO
O
O 2EtO P OEt + R1 H
CH2Cl2 10 h 30–78%
163 THF R1 = H NaH R2 = R3 = Me
O OEt P Me PhH2C N Me P EtO OEt O 165
O OEt P Me +– N Na Me P EtO OEt O EtO
EtO
PhCH2Cl THF 32%
164
Scheme 39
The Wittig rearrangement of the ammonium ylides 169 derived from N-allylic ammonium salts 168, prepared by quaternization of the tetraethyldimethylaminomethylene-bis-phosphanate 166, <1968AG(E)391, 1976JPR116, 1982SC415, 1999HAC271> with various allylic halides 167 resulted in the formation of tetraethyl bisphosphanates 170 in 35–85% yields (Scheme 40) <1999HAC281>. O OEt P Me H N Me P EtO OEt O EtO
166
R1 +
X
R
3
MeCN, AgBF4 reflux, 3–5 h
R2 167
X=Cl, Br, I R1 = R2 = R3 = H
O OEt R1 EtO P + Me N R3 – H BF4 Me 2 EtO P R O OEt 168
R1 = R2 = H, R3 = Me R1 = Me, R2 = R3 = H R1 = R2 = H, R3 = Ph R1 = H, R2 = R3 = Me O OEt EtO R3 P R1 Me N 2 Me R P EtO OEt O 170
[2,3]-Wittig rearrang. 35– 85%
NaH THF rt 2h
O OEt R1 + Me EtO P N EtO P Me O OEt 169
Scheme 40
R3
–
R2
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
179
[4+1]-Cycloaddition reaction of heterodienes 171 with triethyl phosphite gave the 5-phenyl-3trifluoromethyl-2,3-dihydro-25-[1,4,2]oxazaphosphol-3-yl)phosphonic acid diethyl ester derivatives 172 (Scheme 41) <1995ZOB948>. O Ph
CF3 N
Cl
+
OEt EtO P OEt
Ph
CCl4 84%
171
O OEt P OEt O P 2CF3 R1 2 R R1 = F, Cl, EtO, PhO R R2 = EtO, PhO 172 N
Scheme 41
Beckmann rearrangement of oximes 173, in the presence of phosphorus nucleophiles, e.g., dior triethyl phosphites, afforded the corresponding aminomethylene gem-diphosphanates 174 in moderate yields (30–60%). The method is applicable to the synthesis of conformationally restricted analogs. The diphosphanate 174 (R1 = Ph, R2 = Me) was converted to diphosphonic acid 175 with TMSBr in CH2Cl2 in 59% yield (Scheme 42) <1994JOC7562>. N R1
OR Beckmann R1 N C R 2
R2
+
rearrangement
173
CH2Cl2, POCl3 Pnu 30–60%
EtO OEt P O R1
N
R1
R = H, Ms OEt O Pnu phosphorus nucleophiles (Pnu) = EtO P , EtO P OEt OEt H
R1 = R2 = –(CH4)– R1 = R2 = –(CH5)– R1 = Ph, R2 = Me
R1 O OEt HN P OEt R2 P OEt O OEt
R1 = Ph, R2 = Et R1 = 4-MeO–C6H4, R2 = Me
R1 = Ph R2 = Me TMSBr, CH2Cl2 25 °C, 12 h 59%
Ph O OH HN P OH Me P OH O OH 175
174
Scheme 42
Nurgent and co-workers prepared the pyrazoline bis-phosphonates 179 and 180 from the reaction of vinylidenephosphonic acid tetraethyl ester, 177, which was obtained from the tetraethylmethylenebisphosphonate 176 and formaldehyde, with diazomethane, diazoacetate 178 (R = OEt), and diazoketones 178 (R = Ph, Et, etc.) in ether at room temperature in 30–92% yields (Scheme 43) <1993JMC134>. O O P P EtO OEt OEt OEt
O + H
H
p-TSA, MeOH NHEt2 O
176 N2CH 178 EtO O OEt P EtO O P EtO N N H 180
O R
R = OEt, Ph, Et, But, 2-F-C6H4, 3-F-C6H4, 2-Me-C6H4, 3-Me-C6H4, 4-Me-C6H4
Scheme 43
O EtO P EtO
O P OEt OEt CH2
177 R rt, 18 h Et2O
Et2O
CH2N2, 32 0 °C
EtO O OEt P EtO O P EtO N N H 179
180
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
6.05.1.4.5
Functions bearing two phosphorus atoms and one arsenic atom
Arsadiphosphabicyclo[1.1.1]pentane 182 was obtained in 41% yield from the reaction of phosphavinyl Grignard reagent 136 with AsCl3. This is presumably formed via the bisphosphavinyl phosphorus intermediate 181, which undergoes facile phosphavinyl coupling reaction to give the bicyclic product 182 (Scheme 44) <2002MI1209>.
P
Cl Et Mg O C Et But
Cl As
P
AsCl3 Et2O 41%
But
But P P
P But
But
As Cl
136
182
181
Scheme 44
6.05.1.4.6
Functions bearing two phosphorus atoms and one antimony atom
Two equivalents of the diphosphastibolyl ring anion 183 reacted with FeCl3 to produce an antimony containing cage compound 184 via an oxidative coupling mechanism (Scheme 37) The mechanism for the formation of 184 presumably involves an initial coupling reaction to give the intermediate 185, which then undergoes a [4+2]-cycloaddition reaction affording 184 <1997JCS(D)4321, 1997CC305>. The compound 184 was also obtained from the reaction of 183 with PbCl2 in 1,2-DME at 45 C (Scheme 45) <1999JCS(D)4057>.
But But
P P Sb
But
FeCl3 1,2-DME 18 h
P Sb
183
P P Sb But
But
[4 + 2]-cycloaddition
P
65%
Bu
t
P But
But
Sb P Sb
But P
P
184
But
185
Scheme 45
The reaction of 2 equiv. of 186, which could be prepared from the reaction of 188 and 189, with SiMeCl2 afforded hexahetero-cage compound 187 in moderate yield (41%) (Scheme 46) <2001JOM61>.
Me3Si
188
SiMe3 Sb + KOBut 1,2-DME –78 °C SiMe3
But –78 °C then rt P C 13% OSiMe3 189
+ Me3Si
But
Me3Si Sb K Me3Si 188
rt
P
But But
P SbH
(DME) P K P SbH
K (DME) 186
But
SiMeCl2 THF
P But
P
–78 °C then rt 41% But
P
But Sb But
P 187
Scheme 46
Me Si Me
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) 6.05.1.4.7
181
Functions bearing two antimony atoms and one phosphorus atom
The reaction of phosphavinyl Grignard reagent 136 with SbCl3 led to an unusual heterocyclic compound 190, which quantitatively decomposes in solution to yield the known 1,2-dihydro-1,2diphosphete 192. Although no intermediate was observed in this reaction, it seems likely that the phosphaalkene 191 initially forms (Scheme 47) <2002MI1209>.
Cl Cl Sb
Et Cl
O Mg
P
Et + Cl
But
Cl
Cl Et2O Sb 66% Cl
Cl Sb
P But
136
But Sb Cl
P Solution
P
P P
Cl But
But
But 190
192
191
Scheme 47
6.05.2
FUNCTIONS CONTAINING TWO GROUP 15 ELEMENTS AND ONE GROUP 13 OR 14 ELEMENTS
6.05.2.1 6.05.2.1.1
Functions Containing Two Group 15 Elements and One Group 13 Elements Functions bearing two nitrogen atoms and one boron atom
Stable imidazol-2-ylidene-borane adducts 194 were obtained from the reaction of imidazol-2ylidene 193 with Me2SBH3 or Et2OBF3 (R1 = Me and R2 = Me, Et, i-Pr) (Scheme 48) and (R1 = H, Cl and R2 = Mes) (Scheme 48) <2000M251>.
R1 N R1
N R2 193
H + – S B H Me H or Et + F – O B F Et F Me
R2 +
R1 THF or Et2O
R2 N
R1
+
N R2
X – B X X
194 X = H, F
R1 = Me, R2 = Me, Et, Pri R1 = H, R2 = Mes R1 = Cl, R2 = Mes Mes = 2,4,6-mesityl
Scheme 48
The silylation of lithium 3,5-dimethyl-1-(dimethylamino)boratabenzene 195 <1999OM5496> with chlorotrimethylsilane afforded 196 in 86% yield, which was then treated with BCl3 to give the highly reactive chloro-compound 197. When a toluene solution of imidazol-2-ylidene was added to a solution of 197 at room temperature, the adduct 198 formed immediately in high yield (80%) (Scheme 49) <2000OM3751>. The reaction of (E)-2-chlorodimethylstannyl-3-diethylboryl-2-pentene 199 <1986ZNB890>, which could be obtained via 1,1-organoboration of 1-alkynyl compounds 202, with the C-lithiated imidazoles gave a mixture of 200 and 201, which are present in the beginning as a 1:1 mixture (Scheme 50) <1995JOM197>. The borolylimidazolium salts 205 were prepared from the reactions of the appropriate 1,3-dialkyl-4,5-dimethylimidazol-2-ylidenes with 2-bromo-2,3-dihydro-1H-1,3,2-diazaboroles 204, which were synthesized by cyclocondensation reaction of the corresponding dilithiation of compounds 203 with BBr3 in hexane (Scheme 51) <1997CB705>.
182
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) Me
Me
Me
B– Li+ N Me Me 195
Me + Me Si Cl Me
Me
Me
Me
BCl3
THF 2 h, rt 86%
–
Me
B N +
SiMe3
B Cl
91%
Me
SiMe3 197
196 Me
Me N
Me
N Me
Me
Me N
Me
N Me
Toluene 83%
Me B–
+
Me
198
Scheme 49
Cl Me Sn Me Me
Et B Et
N
+
Cl Me Sn Me 202
Me N
N +
–
N Me
Et 199 Et
Me
Me Li+
Me N Sn Me
B
Me
Et
Et
–
+
Sn
B
Me Me
Et
Et Et
Et 201
200
Et B Et
+ –
N
Me
Me
Scheme 50
R3
Me N R2 N
R1 + Br
R1
N R2
B
Br Hexane Br
203 R1 = H, R2 = But
R1
R1
R2 N B N R2 Br 204
R1 = H, R2 = 2,6-Me2-C6H3
Me
N R3
R3 = Me, Pri
R1 R1
R2 N B N R2
R3 Br– + Me N N R3
Me
205
R1 = Me, R2 = Pent
Scheme 51
Treatment of 1,4,5-trimethylimidazole with triethylborane at 0 C led to 3-(triethylborane)-1,4,5trimethylimidazole 206 in quantitative yield. The treatment of 206 with n-BuLi was expected to yield a carbene 207, surprisingly the rearranged compound lithium triethyl(1,4,5-trimethylimidazolyl)borate 208 was obtained in 77% yield (Scheme 52) <1998MI843>. Methylation of 208 with MeI was carried out in THF at 30 C affording 209 in 69% yield. The reaction of 1,4,5-trimethylimidazole with BH3THF at 0 C afforded the air-sensitive compound 3-borane-1,4,5-trimethylimidazole 210, which was deprotonated with n-BuLi to give 3-borane-1,4,5-trimethylimidazol-2-ylidene 211. The reaction of 211 with chlorobis(dimethylamino)borane 212a, 2-bromo-1,3-di(t-butyl)-1,3,2-diazaboroline 212b, and triethylborane 212c led to 3-borane-2-[bis(dimethylamino)boryl]-1,4,5-trimethylimidazoline 213a
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
183
in 72% yield <1998MI843>, 2-(1-borane-3,4,5,trimethylimidazoloyl)-1,3-di(t-butyl)-1,3,2-diazaboroline 213b in 32% yield <1999MI789>, and 3-borane-1,4,5-trimethyl-2-(triethylborane)imidazoline 213c in 96% yield, respectively (Scheme 52) <1999MI789>.
Et Et
Et
Me Et 0 °C, 2 h B toluene Et 99%
N +
Me
Me
Et
N Me
N+
Me
Me Me
B
77%
N+ N Me
H H BunLi –78 °C
H
B– Li N H
Me Me
Me
+
+
N Me 208
N Me Et
Et + – Li B Et
N
Me
N Me
210
Et – N B Et Me Et
MeI, THF –30 °C, 1 h 69%
209
211 H
Me Me Me N 211 B Cl Me N Me 212a
Me
H
N Me
Me
H –
N
Me 207
BunLi –78 °C
THF H B H
Me
X
Et
N Me
206
H
B–
Et B– Et
N
Me
H
H Me H B H – N But
But
B –
H Me N N B Me Me N Me Me 213a
N B Br N But
+
211 Me
Me
+
N
B N
N
But
212b
213b
Et Et
B
H
Me 211
N Me
Et 212c
H B –
+
H Et B Et Et
N Me 213c
Scheme 52
Martinez and co-workers prepared the 1,5-dimethyl-4,4,8,8-tetrahydroimidazaboles 215a (Scheme 53) <1994CB343> and 1,5-dibenzyl-4,4,8,8-tetrahydroimidazaboles 215b (Scheme 53) <1998MI1547> from N-methylimidazole-N-borane 214a and N-benzylimidazole-N-borane 214b.
H +
–
N
B
H H
H I2,270 °C
32% N R 214a R = Me 214b R = CH2Ph
N
H B –
+
R N
– N N + B R H H
215a R = Me 215b R = CH2Ph
Scheme 53
The treatment of 1-alkynyl(chloro)dimethylsilane 216 with tetraethyldiborane or 9-borabicyclo[3.3.1]nonane dimer, (9-BBN)2, afforded the (Z)-1-chloro-dimethylsilyl-1-diethylboryl-alkenes 217 <1999JOM98> and (Z)-1-chloro(dimethyl)silyl-1-(9-borabicyclo[3.3.1]non-9-yl)-3,3-dimethylbut-1-ene 218 <2000JOM45>, respectively, which were reacted with 2-lithio-1-methylimidazole to
184
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
give 219–222. The treatment of 1 equiv. of B(C6F5)3 223 with 2-lithio-1-methylimidazole yields 224 in 63% yield (Scheme 54) <2002MI2015>. Et H Et2BH But Me Si Cl Me
But
But Me Me Si + N
N B Et
Li
N Me
Me Si Me Cl 217
But Me Me Si
H Et –
B
+ Et
Me 219, 80%
Et –B
N+ Et
Me N
N
H
221, 20%
N
216
B
H 9-BBN
But
Li
N Me
Me Si Me Cl
But Me Me Si + N
218
But Me Me Si
H B– N
+
+
Me N
F
F F
F B
N N Me
F F
Li
F
F
F
Li+ –
63% F
FF
F
F F 223
F
F B
F
B–
222, 7%
F
F F
N
Me
220, 93% F
H
FF
N Me F
F
F
N
F F
F
224
Scheme 54
6.05.2.1.2
Functions bearing two nitrogen atoms and one gallium atom
The gallium compound 227 was obtained from the reaction of complex 226 <1963IC1039>, which was prepared from lithium gallium hydride and trimethylammonium chloride, with imidazol-2-ylidene in 40% yield (Scheme 55) <1998JCS(D)3249>. The treatment of 1,3-bis(2,4,6trimethylphenyl)imidazol-2-ylidene with an equimolar amount of LiGaH4 in Et2O afforded the gallium complex 228 in 89% yield (Scheme 55) <2000OM4852>. The treatment of the potentially chelating reagent bis-carbene 1,2-ethylene-3,30 -di-t-butyl-diimidazol-2,20 -diylidene 225 with GaH3NMe3 in a 1:1 or 1:2 stoichiometry led to the 2:1 adduct 229, which is moderately thermally stable compound (Scheme 55) <2002JCS(D)1992>. The unusual reaction of 230 with 1,3,4,5-tetramethylimidazol-2-ylidene in toluene gave complex 233 in 54% yield (Scheme 56) <2002JOM487>. A possible mechanism for the formation of 233 involves the initial displacement of a [C5H5] and formation of an unstable adduct of the decamethylgallocenium cation 231, which undergoes reaction with the [C5H5] counter ion via hydride transfer to form tetramethylfulvane 232 and 233.
6.05.2.1.3
Functions bearing two nitrogen atoms and one indium atom
The reaction of imidazole-2-ylidene with InX3 (X = Cl, Br) yielded 1:1 234 or 1:2 235 complexes depending on the stoichiometry employed (Scheme 57) <1997JCS(D)4313>. Treatment to an ethereal solution of InH3NMe3, generated in situ from LiInH4 with 2 equiv. of imidazol-2-ylidene at 30 C led to a moderate yield (42%) of 236, which is an extremely air sensitive material (Scheme 57) <1998CC869, 1998JCS(D)3249>. The treatment of LiInH4 with 2 equiv. of imidazol-2-ylidenes also gave 236 in 38% yield.
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) Me H Et2O + H Ga– H Li+ + Me N H Cl – –30 °C Me H 3h Et2O Mes –78 °C N rt 89%
H Me 40% – + H Ga N Me –78 °C, Et2O H Me Pri Me N 226 But N
N Mes
+
H Ga H H
–
N Pri 227
Me
N Pri
Me Et2O –50 °C
N 225
Mes H N – + Ga H N H Mes 228
Pri N
Me
185
59% N N But H – H Ga H
Mes = 2,4,6-mesityl
But N
+
N
N
N But
+
–
H Ga H H
229
Scheme 55
Me Me
Me Me Me Me Me
Me
Me Me Me Ga Me Me Me
Me Me
Me + Me
Me N Toluene –78 °C N Me
Me
Me Me Me
rt 54%
Me Me
Me Me Me
Me
–
Me
N Me Me
Me
230
Me
Me Me N Ga +
Me
231
Me Me
Me Me
+ Me
Me
Me
Me Me Me 232 Me
–
Me Me N
Ga H Me
Me
+
Me
N Me Me
233
Scheme 56
Treatment of an ethereal solution of either LiInH4 or InH3NMe3 with 1 equiv. of the 1,3dimesitylimidazol-2-ylidene 237 at 78 C resulted in the formation of indium trihydride complex 238 in high yield (Scheme 58) <2000OM4852>. Compound 238 displays a remarkable thermal stability. In solution the products of decomposition depends on the solvent used. In toluene decomposition results in liberation of the free carbene and deposition of indium metal, in CH2Cl2, chloride abstraction occurs from the solvent to yield 240. The reaction of InH2ClNMe3 with an equimolar amount of 237 afforded 239 in 65% yield. The reaction of 0.5 or 1 equiv. of the 1,3dimesitylimidazol-2-ylidene 237 with InBr in toluene at 25 C led to the deposition of indium metal
186
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
and formation of the thermally robust carbene–indium complex 241 in 54% yield (Scheme 58) <2002CC1196>. The treatment of 1,3-dimesitylimidazol-2-yliden 237 with InBr3 and Et2O with carefully resublimed InBr3 afforded 1:1 adduct 242 in 88% yield (Scheme 58) <2002JOM203>.
1:1 X X In X
Pri X N – + In X N X Pri
Me Me
THF 20 °C 3h
X = Cl 74% X = Br 43% 234
1:2 X
Me
Pri N
Me
N Pri
X In X
Pri Me Pri N X N + + In Me N N X X i Pr Pri
Me Me
THF 20 °C 3h H Me – + H In N Me H Me –30 °C 2 h, 42% H – H In H H Et2O –30 °C 5 h, 38%
X = Cl, 38% X = Br, 69% 235 Me Me
Pri H N – + In H N H Pri 236
Scheme 57
Mes LiInH4 Mes Mes Mes + InBr H N Br Br N 86% N N – toluene – – + In H + In In N 25 °C H N N N Br Br InH3NMe3 54% Mes Mes Mes Mes 238 54% 237 241 Et2O InH2ClNM3 CH2Cl2 –50 °C, then rt InBr3 65% Et2O 67% 2h –50 °C 88% Mes + Mes Mes Br N – + + Cl N – H N In Br – In Cl In Cl N Br N N H Cl Mes Mes Mes 242 239 240
Scheme 58
Treatment of bis-carbene, 1,2-ethylene-3,30 -di-t-butyldiimidazol-2,20 -diylidene 225, with LiInH4 or InH3NMe3 in a 1:1 or 1:2 stoichiometry led to good yields of the indium-rich 2:1 adduct 243. In contrast, the 1:1 or 1:2 reaction of 243 with InBr3 yielded the 1:1 adduct 244 in 41% yield (Scheme 59) <2002JCS(D)1992>.
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
187
Et2O, –50 °C, 48%
But N 225
N
N
N But
But N
+
N
N
N But
+
H In H
Et2O, –78 °C, 58% H H In– H Li+ H 2 equiv.
N
+
But
H – H In H
–
InBr3 –78 °C then rt THF 41% Br N In + N Br Br N
H Me – + H In N Me H Me
H
243
But
244
Scheme 59
6.05.2.1.4
Functions bearing two nitrogen atoms and one thallium atom
Treatment of bis-carbene, 1,2-ethylene-3,30 -di-t-butyl-diimidazol-2,20 -diylidene 225, with 2 equiv. of TlCl3 in THF yielded the 1:1 adduct 245 in 92% yield (Scheme 60) <2002JCS(D)1992>.
But N
N
N
Cl N But + Tl 2 Cl Cl
225
Cl N Tl + N Cl Cl N N
THF –78 °C then rt 92%
+
But
But
245
Scheme 60
6.05.2.1.5
Functions two phosphorus atoms and one gallium atom
Phosphaalkyne (R = t-Bu) underwent spirocyclotrimerization structure 246 in high yield (95%) (Scheme 61) <1996CB489>. with 3 equiv. of phosphaalkyne (R = t-Bu and 1-Ad) in Et2O in moderate yield (43–49%) (Scheme 61) <1998MI1597>. coordinated at a phosphorus atom of the polycyclic system. Cl Cl Ga Cl CH2Cl2 95%
R C P
Et Et Ga Et Et2O 48 h, rt
with GaCl3 to form the betaine When triethylgallium was reacted at room temperature yielded 247 Exocyclic triethylgallium unit is
R P R
P+
246 R = But Et – Ga Et Et + P Et R Et +P – R Ga P Et R 247 R = But R = 1-Ad
Scheme 61
Cl Cl Ga – Cl
49% 43%
188
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
Lithiation of 248 with 1 equiv. of n-butyllithium in THF gave the monolithium salt of the product 249 in 78% yield, which was then reacted with GaCl3 to furnish the compound 250 in 68% yield (Scheme 62) <1999JA2939>. Me Ph Ph Me Si N P Me Ph P Me Ph N Si Me Me 248
Bun THF 78%
Me Ph Li+ Me Si N P – Ph Me Ph P Me Ph N Si Me Me Cl 249 Ga Cl Cl Benzene 68%
Cl Ph Ga Cl Me Si N P Ph Ph P Me Me Ph N Si Me Me 250 Me
Scheme 62
The reaction of 3 equiv. of 136 with gallium(III) chloride in toluene led to the formation of diphosphagalliumbicyclo[1.1.1]pentane complex 253 in low yield (15%) (Scheme 63) <2001JOM109>. The mechanism of this reaction is not determined as the reaction proceeds too rapidly to observe any intermediate by 31P-NMR spectroscopy. However, it is believed that the gallium chloride initially reacts with 2 equiv. of 136 to give the intermediate 251, which then undergoes intramolecular phosphavinyl coupling reaction to afford 252, which reacts with a third equivalent of 136 to yield 253.
Cl Ga
But P
P
But But
P
Ga Cl But
251
P 252
Cl
Cl Ga
Toluene 136 15%
Cl
But P
Cl Mg Et O Et
P But
Ga But
3 equiv. 136
P
P But
253
Scheme 63
6.05.2.1.6
Functions bearing two phosphorus atoms and one indium atom
The reaction of 3 equiv. of 136 with indium(III) chloride in toluene led to the formation of diphosphaindiumbicyclo[1.1.1]pentane complex 256 in (42%) yield (Scheme 64) <2001JOM109>. The mechanism of this reaction is not determined as the reaction proceeds too rapidly to observe any intermediate by 31P-NMR spectroscopy. However, it is believed that the indium chloride initially reacts with 2 equiv. of 136 to give the intermediate 254, which then
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
189
undergoes intramolecular phosphavinyl coupling reaction to afford 255, which reacts with a third equivalent of 136 to yield 256.
Cl In
But
P
But
P
But
P 254
Cl
Cl In
In
Cl
But P Toluene
255
136
42%
Cl
But P
Cl Mg Et O Et
P But
In But P
3 equiv. 136
P But
256
Scheme 64
6.05.2.1.7
Functions bearing one phosphorus, one nitrogen, and one boron atom
The reaction of 257 with BF3OEt2 or BH3THF afforded 258, which was then treated with ,-unsaturated esters to yield pyrazolines 259 (Scheme 65) <1991AG(E)1154>.
Pri
Pri
N + – Cl P C N N N Pri Pri 257
BF3OEt2 or BH3THF
Pri i + N Pr N N Cl P C – Pri N B X X Pri X 258
Pri
O Cl
OMe R R = H, CO2Me
X = H, F
Pri
N P +
Pri N N
CO2Me N – Pri X B X R X X=F 259
Scheme 65
6.05.2.2 6.05.2.2.1
Functions Containing Two Group 15 Elements and One Group 14 Element Functions bearing two nitrogen atoms and one silicon atom
Photolysis of a benzene solution of (1-methyl-2,3,4,5-tetraphenyl-1-silacyclopentadienyl) diazomethane 260 in an excess of methanol yielded (1-methyl-2,3,4,5-tetraphenyl-1-silacyclopentadienyl)diazirine 261 and other side products 262–264 (Scheme 66) <1985OM584>.
6.05.2.2.2
Functions bearing two nitrogen atoms and one germanium atom
Triphenylgermyl-bis(3,5-dimethylpyrazol-1-yl)methane 267 could be prepared by the reaction of bis(3,5-dimethylpyrazol-1-yl)methyllithium 266, which was generated from 265 and n-BuLi in THF, with triphenylgermanium bromide in moderate yield (48%) (Scheme 67) <2002JOM198>. The treatment of 267 with W(CO)5THF prepared in situ afforded complex 268 in 43% yield.
190
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) Ph
Ph Ph
Ph
Si
CHN2
Me
Ph
Ph hν Benzene MeOH
Ph
Ph +
Si Me N
260
Ph
Ph
+ Ph
Si Me
19% 262
48% 261
Ph
Ph
+
OMe
Et
N
Ph Ph
Si
Ph
Ph
Ph
Ph
Ph OMe
Si Me
7% 263
OMe
8% 264
Scheme 66
Me
Me N N
N N
N N
–78 °C, 1 h Me
Me
Me
Me BunLi
–
Li+ 266
Me
265
N N Me
Ph THF Ph Ge Br 48% Ph OC CO Me OC W CO N N N N
Me
Me
Me
Me N N
W(CO)5THF 43%
Me Ge Ph Ph Ph 268
Me Ph
N N Me Ge Ph Ph 267
Scheme 67
6.05.2.2.3
Functions bearing two phosphorus atoms and one silicon atom
The reaction of 2 equiv. of t-butylphosphaalkyne with silene 270, which was obtained thermally from the disilacyclobutane 269 by [2+2]-cycloreversion, afforded diphosphatricyclobenzoheptane 271 in 75% yield (Scheme 68) <1994JOM41>.
Me3Si SiMe3 Me3Si Si Si SiMe3 Me3SiO
∆
OSiMe3
Me3Si Si Me3Si
Ph Ph
OSiMe3 Ph
Toluene But C P 75%
Me3Si Me3SiO Si Me3Si P
270
269
But
P But 271
Scheme 68
Hydrostannylation of phosphaalkene 272 with tributyltin hydride in pentane or petroleum ether gave 1,3-diphosphacyclobutane 273 in low yield (7%) (Scheme 69) <1998HAC453>.
SiMe3 Cl
P C Ph 272
+
Bu3SnH
Petroleum ether 20 °C, 1 days 7%
Scheme 69
Me3Si Ph
H P
Ph
P SiMe3 H 273
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
191
1,3-Diphosphacyclobutane-2,4-diyl 275, which can be obtained from 1,3-diphosphacyclobutane2,4-diyl 274 by selective Cl/SiMe3 exchange, can be transformed into the protonated form 276 with n-BuLi and subsequent t-BuOH addition. Where 276 is thermally stable, irradiation induced a rapid conversion of 276 into the 1,3-diphosphabicyclo[1.1.0]butane 277, which can be transformed into the 1,4-diphosphabutadiene 278 in 68% yield by heating 277 (Scheme 70) <1999AG(E)3028>. Cl Mes P
Cl Hg(SiMe3)2
P Mes
Mes P
H P Mes
71% Cl 274
SiMe3
BunLi
Mes P
ButOH 97%
276
P Mes SiMe3
275 hν 90%
Mes = 2,4,6-Bu3t C6H2 H Me3Si 278
Mes P P Mes
H ∆ 68%
Mes P 277
P Mes SiMe3
Scheme 70
The reaction of trimethylsilylphosphaacetylene, which can be prepared from dichloro(trimethylsilyl)methylphosphane 279 in 70% yield <1991AG(E)196>, with an excess of the buta-1,3-dienes (R=H, Me) produced in a 2:1 stoichiometry the phosphatricyclooctenes 282 in 50–55% yields (Scheme 71) <1999MI363>. The Diels–Alder adduct 280 as well as the product 281 of a phosphaene reaction are assumed to be formed as intermediates prior to the intramolecular [4+2]cycloaddition leading to the polycyclic product 282. R Cl Cl
TMS
350 °C
P H
TMS C P
H R
R [4 + 2] rt, 2 h R = H, Me
H 279
TMS P
R
280 TMS C P ene reaction
R
TMS
R R
P P TMS
[4 + 2] Intramolecular 50–55%
282
R
TMS P H
TMS
281
Scheme 71
The stable bis(amino)silylenes 283 underwent smooth [1+4]-cycloaddition with 2,4,6-tri-tbutyl-1,3,5-triphosphabenzene 284 to furnish 285 in 66% and 80% yields, respectively (Scheme 72) <2002JCS(D)484>.
6.05.2.2.4
Functions bearing two phosphorus atoms and one germanium atom
The compound 287 was prepared in high yield (80%) from the reaction of 286 with 1 equiv. of GeCl2. The compound 287 was then treated with carbanion 289 to yield 288 in 75% yield (Scheme 73) <1999OM389>.
192
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) [NN] t
P
Bu [NNSi]
+
Si
But
But
Benzene P
283
P
66–80%
P
P t Bu
But 284
285 But
CH2But N and Si N CH2But
[NNSi] =
But
P
N Si N But
Scheme 72
Li+
Ph – HC P Ph P Ph Ph Et2O 75%
289 N Me3Si
SiMe3
Ge
Me3Si
SiMe3
N
Et2O GeCl2 dioxane 80%
SiMe3 N Ge Cl
SiMe3
287
SiMe3 N Ge Ph
SiMe3
Ph P P Ph Ph 288
286
Scheme 73
The metallation of bis(iminophosphorano)methane 290 with n-BuLi in THF gave the monolithium salt 291, which was then reacted with 0.5 equiv. of GeCl2 to produce bis(germavinylidene) 292 in 42% yield (Scheme 74) <2001AG(E)2501>. The reaction of 292 with W(CO)5 and Cr(CO)5 in THF afforded 293 in moderate yields (37% and 43%) (Scheme 74) <2003CC248>.
Ph Ph P N SiMe 3 Ph P N SiMe3 Ph 290
THF n-BuLi
Ph Ph Ph N SiMe3 N P P 1/2 equiv. GeCl2 Me3Si Ph N Ge Li+ – Ge Et2O, dioxane P N SiMe 3 Ph Ph P 42% Ph P Ph Ph 291 Ph N SiMe3 292 M(CO)5THF M(CO)5 M = W, 37% Me3Si N Ge M(CO) M = Cr, 43% 3 Ph P Ph Ph P N SiMe 3 Ph 293 Ph Ph P N SiMe 3
Me3Si
Scheme 74
6.05.2.2.5
Functions bearing two phosphorus atoms and one tin atom
Reactions of the tin hydrides with an excess of the phosphaalkynes at room temperature for 2 weeks gave the 2-stannyl-substituted 1,2-dihydro-1,3-diphosphetes 294 in 22–74% yields depending on substituents. Reactions of the phosphaalkyne (R = But) with chlorodiorganotin hydrides proceed much less selectively than those with the triorganotin hydrides. In addition to the
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
193
1,2-dihydro-1,3-diphosphetes 295 formed as main product with the yield (85%), numerous side products were formed (Scheme 75) <1998MI235>.
R13SnH
+ R2 C P
R1 = n-Bu, Ph
R2 C P H R13 Sn
n-Pentane 2 weeks
R2 = t-Bu, t-Pent, 1-Ad
R12ClSnH + R2 R1 = n-Pr, n-Bu
n-Pentane C P 2 weeks
R2 C P H R12ClSn
R2 C P
R2
[2 + 2]-cycloaddition 22–74%
R2 C P [2 + 2]-cycloaddition
294
R2
85%
R2 = But
SnR13 P P
R2
SnClR12 P P R2 295
Scheme 75
6.05.2.2.6
Functions bearing two antimony atoms and one silicon atom
The chloro-bridged polymeric C-centered geminal distibine 298 was obtained in 63% yield by the thermolysis of the doubly bonded intermediate species 297, which could be prepared from 296 and SbCl3 (Scheme 76) <1998CC575>.
THF –78 °C then rt 3 days
N
Me N
Me
SiMe3 Cl Li SiMe + Cl Sb 3 N Me Cl Me 296
N 297
SiMe3 Cl 63%
Cl
Toluene 50 °C 4h
Cl Sb
SiMe3
Et2O
N
–78 °C
SiMe3
N
Me3Si
Cl Sb SiMe3 Cl
Sb
Cl
N
298
Scheme 76
6.05.2.2.7
Functions bearing one nitrogen atom, one phosphorus atom, and one silicon atom
[1+2]-Cycloaddition reaction of [bis(dicyclohexylamino)phosphino]trimethylsilylcarbene 299 with benzonitrile in toluene afforded 2-phosphino-2H-azirine 300 in 85% yield (Scheme 77) <1995AG(E)1246, 1997MI1757>.
N
SiMe3 P
N
+ Ph C N
Toluene 85%
Ph
N
N P
N
Me3Si
300 299
Scheme 77
194
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
6.05.2.2.8
Functions bearing one phosphorus atom, one antimony atom, and one silicon atom
See compound 187 in Scheme 46 in Section 6.05.1.4.6.
6.05.3 6.05.3.1
FUNCTIONS CONTAINING ONLY ONE GROUP 15 ELEMENT Functions Bearing One Nitrogen Atom and Two Silicon Atoms
The functionalization of imines 302, which were prepared from the reactions of bis(trimethylsilyl)methylamine (BSMA) 301 and aldehydes, with electrophilic reagents through the formation of an intermediate 2-azaallylmetallic derivative 303 by hydrogen–metal exchange was carried out by A. Ricci and co-workers (Scheme 78) <1994SL955>. A very good control of the regioselectivity occurs in the deprotonation of imino derivatives of 301 followed by quenching with electrophiles. Functionalization at C-1 or C-3 takes place selectively depending on the nature of electrophile and base used (304 and 305).
Me3Si Me3Si
O NH2 +
R
301
Mol. sieve H benzene 0 °C then rt
Me3Si
R N
Me3Si
Base H THF
302
R = Ph, Me3Si–CH=CH, Et–CH=CH Me3Si E Me3Si
R H 304
R = Ph Base = MeLi E+ = MeI 63% yield
M+ – Me3Si
R N H
303 Me3Si
+
N
Me3Si
R N
Me3Si
E H
E+
Me3Si
R N
Me3Si
–
M+
H
305 R = Ph Base = MeLi E+ = Me3SiCl 60% yield
Scheme 78
Bis(trimethylsilyl)methyl-isocyanate 309 and bis(trimethylsilyl)methyl-isothiocyanate 310 were obtained from the reactions of [[bis(trimethylsilyl)methyl]imino]triphenylphosphorane 308, which was prepared from bis(trimethylsilyl)methyl azide 307 generated from bis(trimethylsilyl)methyl chloride 306, with PPh3 in 81% and 83% yields, respectively (Scheme 79) <1995JOC6032>. The symmetrically substituted bis(trimethylsilyl)methyl carbodiimide 311 could be prepared in 76% yield via a Wittig-type reaction of 308 with 309. The synthesis of the unsymmetrically substituted carbodiimide 312 was performed by using two different procedures. The compound 312 was obtained in a 2.5:1 mixture with the symmetrically substituted N,N0 -diphenylcarbodiimide 313 from the reaction of 308 with phenyl isocyanate or by the reaction of N-phenyltriphenylphosphinimine 314 with 309 in 82% yield (Scheme 79) <1995JOC6032>. [Bis(trimethylsilyl)methyl]sulfinylamine 315 was prepared by the reaction of BSMA with thionyl chloride in 65% yield. Mono- and bis(trimethylsilyl)benzyl isothiocyanates 316 and 317 were synthesized via lithiated benzyl isothiocyanates and chlorotrimethylsilane in 88% and 91% yields, respectively (Scheme 80) <1997MI232>. The reaction of N-BOC-2-trimethylsilylpyrrolidine 318 with chlorotrimethylsilane in the presence of TMEDA afforded a mixture of N-BOC-2,2-bis(trimethylsilyl)pyrrolidine 319 and NBOC-2,5-bis(trimethylsilyl)pyrrolidine 320 in 71% yield (Scheme 81) <2001MI1061>. The use of HMPA in place of TMEDA resulted in the formation of completely regioselective product 320 in 87% yield (Scheme 81) <2002JA14824>. The transient silenes 322, which are strongly influenced by reverse Si¼C bond polarization, were formed upon heating of tris(trimethylsilyl)silylamides 321. The silenes were trapped with
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
Me3Si Cl
NaN3
Me3Si N3 Me3Si
Me3Si
307
306
PPh3 THF 25 °C 2h
Me3Si N PPh3
Me3Si CO2 Et2O 81% Me3Si 25 °C 5 min
+
308
N C O 309
Me3Si 308
CS2 Me3Si 83% Me3Si
308
195
Me3Si
+ 309 Benzene reflux 1h 76%
N C S 310
SiMe3 N C N SiMe3 311
Me3Si
Benzene Me3Si Ph N C O N C N Ph Ph N C N Ph Ph N C O reflux Si Me 3 3h 312 313 56% 82% 309 312:313 = 2.5:1 Ph Ph N P Ph Ph 314 Me3Si NH2 +
SOCl2
Me3Si
Et2O
Me3Si
Et3N 65%
Me3Si
N S O 315
Scheme 79
1 equiv. Me3SiCl PhH2C N C S
LDA, Et2O–hexane
88% 2 equiv. Me3SiCl 91%
Ph Me3Si 316
N C S H Ph
Me3Si 317
N C S SiMe3
Scheme 80
i. BusLi, Et2O, TMEDA COOBut
Me3Si
ii. Me3SiCl, 71%
N SiMe3 318
COOBut N SiMe3
+
319 i. BusLi, Et2O, HMPA
COOBut N SiMe3 SiMe3 320
320
ii. Me3SiCl, 87%
Scheme 81
2,3-dimethyl-1,3-butadiene to afford a quantitative yield of only one of the possible diastereomers of the functionalized cyclic allyl silanes 323 (Scheme 82) <2002MI1915>.
6.05.3.2
Functions Bearing One Phosphorus Atom and Two Silicon Atoms
The P-metallophosphiranes 325 could be prepared from the reaction of 324 <1986OM593> with aryl isocyanides in moderate yields (56–69%) (Scheme 83) <1993OM4653>.
196
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) +
O ∆ TMS R1 Si N benzene 2 TMS TMS R
TMS
O
–
Si TMS
TMS N R2
O
R1
TMS
–
Si TMS
TMS +
N R2
R1
322
321
Me
Me
Me
Me
1 = R2 = Ph,
97% R R1 = R2 = Me, 88% R1 = Me, R2 = Ph, 95%
TMS Si TMSO
NR1R2 TMS
323
Scheme 82
+ Ar
+
–
N C
OC
P SiMe3 Fe C OC SiMe3 324
Benzene
SiMe3
20 °C, 2 h
OC Fe P CO
SiMe3
Ar = Ph, 56% Ar = 2-MeC6H4, 67% Ar = 2,6-(Me)2C6H3, 69%
N Ar
325
Scheme 83
The reaction of P-chloro-bis(trimethylsilyl)methylenephosphane 326 with diisopropyl(trichlorosilyl)phosphane 327 afforded 1-bis(trimethyl)methylidene-2,2-diisopropyldiphosphane 328 in 82% yield (Scheme 84) <1998ZAAC1447>. The P¼C double bond in 328 could be protected reversibly by a [2+4]-cycloaddition with cyclopentadiene resulting in the formation of a P-phosphanyl phosphannorbornene 329, with 2,3-dimethylbutadiene produced the cyclic diphosphane 330, and with selenium gave 331 which was then treated with cyclopentadiene to furnish 332.
Me3Si P Cl Me3Si
+
Pri P SiCl3 Pri
326 Pentane 20 °C 74%
328 +
+
Me3Si
82%
Me3Si
Me3Si
Pri Me
Pri
328 +
SiMe3 329
Se Me3Si
+ SiCl4 Pri
328 Pri
P P
Pri P P
327
Me3Si 328
CH2Cl2
Me 91%
Me
Se P Se P Pri Pri 331
70%
Me3Si
Me
P Pri SiMe3
SiMe3 330
Se i P Se P Pr i Pr SiMe3 332
Scheme 84
P
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
197
The deprotonation of 6-methyl-2-bis(trimethylsilyl)methylpyridine 333 with n-BuLi in Et2O or THF gave 334, which was then treated with PCl3 at 78 C in Et2O to give the [6-methyl-2bis(trimethylsilyl)methylpyridine]-phosphorus dichloride 335 in 66% yield (Scheme 85) <2000JOM213>. The reaction of 335 with LiAlH4 in THF afforded 336 in 42% yield <2000CC1961>. When the reaction was carried out in Et2O, the compound 337 was obtained and not the expected dihydride species <1998CC547>. As seen in Scheme 85, the choice of solvent is crucial.
Me
N
SiMe3 SiMe3
Li+
BunLi THF, 0 °C
Me
–
N
SiMe3
SiMe3
333
PCl3, Et2O –78 °C, 6 h 66%
SiMe3 Me
N
SiMe3
P Cl
334
Cl 335
THF
Me3Si
–78 °C
SiMe3 Me P H H Al N Al N H H P Me Me3Si
335 + LiAlH4
SiMe3
336
Et2O –78 °C
Me
Me3Si SiMe 3 H N P P N H Me3Si SiMe3
Me
337
Scheme 85
The LiBr-phosphoranylidine carbenoid 339 was obtained by treatment of dibromo species 338 <1999JA5953> with 1 equiv. of n-BuLi at 78 C. In typical carbanion fashion, 339 reacted with water to give the bis(methylene)phosphorane 341 (Scheme 86) <2002OM4919>. The reaction of the dibromo compound 338 with 2 equiv. of n-BuLi afforded 340, which was then quenched with water or MeI to furnish the product 342 in 96% yield. The dimethylated bis(methylene)phosphorane 342b was not stable and rearranged within days to form vinyl-substituted phosphane 343 in 69% yield (Scheme 86) <2002OM4919>.
6.05.3.3
Functions Bearing One Arsenic Atom and Two Silicon Atoms
The deprotonation of 6-methyl-2-bis(trimethylsilyl)methylpyridine 333 with n-BuLi in Et2O or THF gave 334, which was then treated with AsCl3 at 78 C in Et2O to give the [6-methyl-2bis(trimethylsilyl)methylpyridine]-arsenic dichloride 344 in 68% yield (Scheme 87) <2000JOM213>. The reaction of 344 with LiAlH4 in THF afforded 345 in 35% yield. When the reaction was carried out in Et2O, the dihydride species 346 was obtained in 60% yield <2000CC1961>.
6.05.3.4
Functions Bearing One Antimony Atom and Two Silicon Atoms
The monochloride species 347 was obtained from the 2:1 reaction of 296 with SbCl3. The compound 347 is not stable and Me3SiCl elimination at room temperature occurs giving 348,
198
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
which was then reacted with AlMe3 in THF to afford 349 in 32% yield (Scheme 88) <1997CC1183>, with Et3In in hexane at 78 C to give 350 in 63% yield <1999OM4247>, and with Me3Ga either in THF–hexane at 78 C to produce 351 in 73% yield <2000OM1277> or in hexane at room temperature to furnish 352 in 34% yield, which was also prepared by warming a hexane–toluene solution of 351 to 60 C for 4 h and allowing it to cool to room temperature, followed by refrigeration at 4 C <2000OM1277>.
SiMe3 Me3Si
1 equiv. BuLi
P
SiMe3
Br 2 equiv. BuLi
Me3Si
338
Li P
Mes
Li
340
SiMe3 Me3Si
CH2 P
Mes
Me3Si
Me 343
Br P
97%
Li Mes 339
Br
Mes
H 2O
P
Bus Me3Si
SiMe3
Br
H Mes 341
SiMe3 H2O or R Me3Si MeI P 96% R Mes 342a R = H 342b R = Me Pentane 4 weeks –25 °C R = Me 69%
Scheme 86
Me
N 333
SiMe3
BunLi THF, 0 °C
Li+ Me
N
SiMe3
334
THF –78 °C 35%
–
–78 °C, 6 h 68%
SiMe3
SiMe3 Me As H H Al N Al N H H As Me Me3Si 345
Me3Si
344 + LiAlH4 Et2O –78 °C 60%
AsCl3, Et2O
SiMe3
SiMe3 Me
N Cl
SiMe3 As Cl 344
SiMe3
SiMe3 Me
N
SiMe3 As
H
H 346
Scheme 87
The deprotonation of 6-methyl-2-bis(trimethylsilyl)methylpyridine 333 with n-BuLi in Et2O or THF gave 334, which was then treated with SbCl3 at 78 C in Et2O to give the [6-methyl-2bis(trimethylsilyl)methylpyridine]antimony dichloride 353 in 74% yield. When the reaction was run in THF at 78 C, 354 was obtained in 58% yield (Scheme 89) <2000JOM213>.
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
N Me Li Me N
–
SiMe3
SiMe3
+
N Me Me
Cl Sb
Cl
SiMe3 SiMe3
N Et2O
Cl Sb
Cl –78 °C
Me3Si
Me3Si 348
+ 2.5 equiv. AlMe3
THF –78 °C
Sb
SiMe3
Me3Si
Me
N
348
SiMe3
N Sb
32%
SiMe3 SiMe3
N
347
296
N
199
Me N
Al SiMe3 Me 349
SiMe3 SiMe3 Sb Et SiMe3
N
+
348
Et3In
Hexane –78 °C
Et
63%
In
Et
N 350 Me3Si
+ 1.5 equiv. Me3Ga.THF
348
THF–Hexane –78 °C
SiMe3
N Sb
73% 351
Me N
Me Ga SiMe3 Me
Hexane Toluene 60 °C 4h
N Me Si Ga Me Me3Si Sb Me
348
+
Me3Ga.THF
Hexane rt
N
SiMe3
Me 352
Scheme 88
6.05.3.5
Functions Bearing One Bismuth Atom and Two Silicon Atoms
The treatment of a THF solution of 1-aza-allyllithium salt 355 <1999OM2256> with BiBr3 in toluene afforded the mono(1-aza-allyl)bismuth dibromide 356 in 69% yield, which is not stable in solution, and slowly decomposes even under inert atmosphere (Scheme 90) <2000POL471>.
6.05.3.6
Functions Bearing One Antimony Atom, One Gallium Atom, and One Silicon Atom
See compounds 351 and 352 in Scheme 88 in Section 6.05.3.4.
200
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
SiMe3
N
Me
+ SbCl3
+ SbCl3
334
Me
N
SiMe3
333
334
Li+
BunLi THF, 0 °C
–
SiMe3
334 SiMe3
SbCl3, Et2O –78 °C, 6 h 74%
SiMe3 Me
SbCl3, THF –78 °C, 6 h 58%
N Cl Sb Cl 353 SiMe3
SiMe3
Me Cl
N
Cl Sb N Cl Cl Sb
Me SiMe3 354
Scheme 89
SiMe3 N
Ph –
Me3Si
SiMe3
Ph
Br THF–toluene + Bi Li+ –78 °C then rt Br Br SiMe3 20 h
355
N
Me3Si Me3Si
Bi Br Br
356
Scheme 90
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202
Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
1999MI3143 1999OM389
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Wrackmeyer, H. Maisel, W. Milius, A. Badshah, E. Molla, A. Mottalib, J. Organomet. Chem. 2000, 602, 45–50. 2000JOM120 D. L. Regel, T. C. Grattan, K. J. Brown, C. A. Little, J. J. S. Lamba, A. L. Rheingold, R. D. Sommer, J. Organomet. Chem. 2000, 607, 120–128. 2000JOM213 T. R. Ancker, P. C. Andrews, S. J. King, J. E. McGrady, C. L. Raston, B. A. Roberts, B. W. Skelton, A. H. White, J. Organomet. Chem. 2000, 607, 213–221. 2000M251 A. J. Arduengo, IIIF. Davidson, R. Krafczyk, W. J. Marshall, R. Schmutzler, Monatsh. Chem. 2000, 131, 251–265. 2000MI2105 H. Tietz, O. Rademacher, G. Zahn, Eur. J. Org. Chem. 2000, 2105–2112. 2000OM1277 P. C. Andrews, P. J. Nichols, Organometallics 2000, 19, 1277–1281. 2000OM3751 X. Zheng, G. E. Herberich, Organometallics 2000, 19, 3751–3753. 2000OM4852 C. D. Abernethy, M. L. Cole, C. Jones, Organometallics 2000, 19, 4852–4857. 2000POL471 C. Cui, H. Hao, M. Noltemeyer, H. G. Schmidt, H. W. Roesky, Polyhedron 2000, 19, 471–474. 2000S529 P. Christoph, S. Stutzmann, H. Disteldorf, S. Werner, U. Bergstra¨ßer, C. Kruger, P. Binger, M. Regitz, Synthesis 2000, 529–536. 2001AG(E)2501 W. P. Leung, Z. X. Wang, H. W. Li, T. C. W. Mak, Angew. Chem., Int., Ed. Engl. 2001, 40, 2501–2503. 2001HAC406 S. M. F. Asmus, G. Seeber, U. Bergstra¨ßer, M. Regitz, Heteroatom Chem. 2001, 12, 406–413. 2001JOC8528 J. Valenciano, E. S. Pavo´n, A. M. Cuadro, J. J. Vaquero, J. A. Builla, J. Org. Chem. 2001, 66, 8528–8536. 2001JOM61 C. Jones, R. C. Thomas, J. Organomet. Chem. 2001, 622, 61–65. 2001JOM109 C. Jones, A. F. Richards, J. Orgamomet. Chem. 2001, 629, 109–113. 2001MI275 G. Olive, A. Jacques, Molecules 2001, 6, 275. 2001MI1061 J. C. Dong, R. T. Li, T. M. Cheng, Chinese Chem. Lett. 2001, 12, 1061–1064. CAN 136:263192. 2001ZN(B)951 P. Christoph, F. Tabellion, A. Nachbauer, U. Fischbeck, F. Preuss, M. Regitz, Z. Naturforsch., Teil B. 2001, 56, 951–962. 2001ZOR207 M. A. Ishchenko, V. D. Nikolaev, A. A. Sokolov, S. V. Nikolaeva, Zh. Org. Khim. 2001, 37, 207–210. 2001ZOR1872 A. A. Pimenov, N. V. Makarova, I. K. Moiseev, M. N. Zemtsova, Zh. Org. Khim. 2001, 37, 1872–1873 (Chem. Abstr. 137, 20062). 2002CC1196 R. J. Baker, R. D. Farley, C. Jones, M. Kloth, D. M. Murphy, J. Chem. Soc., Chem. Commun. 2002, 1196–1197. 2002DOK210 E. M. Budynina, E. B. Averina, O. A. Ivanova, Y. K. Grishin, T. S. Kuznetsova, N. S. Zefirov, Dokl. Akad. Nauk 2002, 382, 210–213 (Chem. Abstr., 138, 4478). 2002HAC22 P. P. Onys’ko, A. A. Sinitsa, V. V. Pirozhenlo, A. N. Chernega, Heteroatom Chem. 2002, 13, 22–26. 2002JA14824 S. Suga, M. Watanabe, J. Yoshida, J. Am. Chem. Soc. 2002, 124, 14824–14825. 2002JCS(D)484 S. C. Clendenning, B. Gehrhus, P. B. Hitchcock, D. F. Moser, J. F. Nixon, R. West, J. Chem. Soc., Dalton Trans. 2002, 484–490. 2002JCS(D)1992 R. J. Baker, M. L. Cole, C. Jones, M. F. Mahon, J. Chem. Soc., Dalton Trans. 2002, 1992–1996. 2002JFC107 Y. V. Rassukana, K. O. Davydova, P. P. Onys’ko, A. D. Sinitsa, J. 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Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)
203
Biographical sketch
Alaettin Gu¨ven is currently Associate Professor of organic chemistry at Chemistry Department at Anadolu University, Eskis¸ ehir, Turkey. He was born in Eskis¸ ehir-Turkey, received a B.Sc. in chemical engineering in 1976 and M.Sc. in Chemistry in 1987 from Anadolu University. He obtained a Ph.D. in 1992 under the direction of Dr. R. Alan Jones at UEA in Norwich, England. He held postdoctoral position from 2002 to 2003 in the laboratories of Professor Alan R. Katritzky at UFL in Gainesville, Florida. His scientific interests are computational chemistry, acidity, conformation, and tautomerism in heterocyclic systems.
# 2005, Elsevier Ltd. All Rights Reserved No part of this publication may be reproduced, stored in any retrieval system or transmitted in any form or by any means electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without permission in writing from the publishers
Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 161–203
6.06 Functions Containing at Least One Metalloid (Si, Ge, or B) and No Halogen, Chalcogen, or Group 15 Elements; Also the Synthesis of Functions Containing Three Metals V. D. ROMANENKO and V. L. RUDZEVICH National Academy of Sciences of Ukraine, Kiev, Ukraine 6.06.1 INTRODUCTION 6.06.2 FUNCTIONS CONTAINING AT LEAST ONE METALLOID FUNCTION (AND NO HALOGEN, CHALCOGEN, OR GROUP 15 ELEMENTS) 6.06.2.1 Synthesis of Functions Containing Three Metalloids 6.06.2.1.1 Functions bearing three silicons 6.06.2.1.2 Functions bearing three borons 6.06.2.1.3 Functions bearing three germaniums 6.06.2.1.4 Functions bearing mixed metalloids 6.06.2.2 Functions Containing Metalloids and Metals 6.06.2.2.1 Functions bearing silicon(s) and metal(s) 6.06.2.2.2 Functions bearing boron(s) and metal(s) 6.06.2.2.3 Functions bearing germanium(s) and metal(s) 6.06.2.2.4 Functions bearing mixed metalloid(s) and metal(s) 6.06.3 FUNCTIONS CONTAINING THREE METALS 6.06.3.1 Three Similar Metals 6.06.3.2 Three Dissimilar Metals
6.06.1
205 206 206 206 214 220 221 226 226 232 232 232 235 235 237
INTRODUCTION
This chapter outlines the synthesis and reactions of compounds of the general formula (XmE)n(LkM)3nCR (R = H or organyl; E = Si, Ge, or B; M = metal; X, L = any substituents; n = 0–3) having three heteroatoms (E, M) bonded to the same carbon. Much of the important pioneering work on these species was carried out in the 1970s and 1980s; COFGT (1995) covers the field up to 1994 <1995COFGT(6)171>. Use of the tris(trimethylsilyl)methyl (trisyl) group, (TMS)3C, in organometallic chemistry began with the demonstration that this function can be attached to a wide range of elements by simple ligand transfer from the lithium reagent (TMS)3CLi <1970JOM(24)529>. Since that time, numerous studies have shown that organometallic compounds containing the bulky ‘‘trisyl’’ group adopt a range of unprecedented structures and are 205
206
Functions Containing at Least One Metalloid (Si, Ge, or B)
much more chemically and thermally stable than analogous derivatives with smaller alkyl groups. This topic has been summarized in review articles <1996CCR125, 1995JOM(500)89>, both of which emphasize the progress made between 1985 and 1995, a period in which the use of trisilylmethanes in organic synthesis really began to grow. Within the period 1993–2003, functionalized trisilylmethanes and related compounds have emerged as uniquely useful ligand precursors <1999MI267>. It has been shown that the range of isolable organometallic compounds can be considerably extended by the use of ligands (XMe2Si)n(TMS)3nCH (n = 1–3) in which lone pairs from groups X can occupy sites in the metal coordination sphere. Moreover, the introduction of tripodal amino ligands of the type (RNHMe2Si)3CH into coordination chemistry has enabled the stabilization of new types of organometallic species with novel structural and reactivity patterns. In this chapter emphasis will be placed on the rapid and continuing developments, in the period 1993–2003, in the field of synthesis and reactions of the above compounds although most of that part of their chemistry which is concerned with the synthesis of C-hetero-substituted derivatives will be covered in Chapter 6.13. Whereas much information has been published about functions containing three metalloids, relatively little attention has been paid to functions bearing three metals. Nevertheless, despite the relative infancy of investigations directed to the use of these species in organic synthesis, attempts have been made to summarize and classify various compounds of the general formula (MLk)3CR. To eliminate complications introduced by the kind of E and M, the consideration is restricted here to compounds (EXm)n(MLk)3nCR, where C/E and C/M are bound via a -bond. Carboranes, metal clusters, and -metal complexes, of course, will not be treated.
6.06.2
FUNCTIONS CONTAINING AT LEAST ONE METALLOID FUNCTION (AND NO HALOGEN, CHALCOGEN, OR GROUP 15 ELEMENTS)
6.06.2.1 6.06.2.1.1
Synthesis of Functions Containing Three Metalloids Functions bearing three silicons
The various methods available for the formation of 1,1,1-trisilylalkanes can be divided into four categories. (i) ‘‘Direct synthesis’’ in the gas phase involving insertion of elemental silicon into a carbonhalogen bond of polychlorinated alkane such as chloroform (Equation (1)). Cl Cl
Cl
SiCl2X
Cu (cat.)
+ Si
XCl2Si
SiCl2X
H +
SiCl2Y + Others
Cl3Si SiCl2X
n
ð1Þ
X = H or Cl; Y = CH2SiCl2X; n = 1–3
(ii) Reductive silylation of trihalomethanes (the Merker–Scott procedure) (Equation (2)). SiR3
X X
X
+ nM + 3 SiX3R
R3Si
SiR3
ð2Þ
X = Cl, Br; R = alk; M = Li (n = 6), Mg (n = 3)
(iii) Reactions of organometallic carbon nucleophiles such as a Grignard reagent or an organolithium compound with halo- or alkoxy-silanes (Equations (3)). R13Si
–
SiR33 SiR23
+
R33SiX
–X–
R13Si
SiR23
ð3Þ
X = Cl, Br, OAlk; R = Alk, Ar
(iv) Derivatization and rearrangement of the compounds already containing polysilylated carbon or silicon units.
207
Functions Containing at Least One Metalloid (Si, Ge, or B)
When applicable, the Merker–Scott procedure is usually by far the most convenient and is therefore the method of choice. However, reactions of organometallic carbon nucleophiles with halosilanes probably represent the most general approach, which has provided various routes to trisilylmethanes not readily accessible by other methods.
(i) Trisilylmethanes and their linear C-organyl derivatives, (X3Si)3CR Direct reaction of elemental silicon with a mixture of CHCl3 and HCl has been studied in the presence of a copper catalyst at various temperatures in the range 280–340 C <1997OM93>. Tris(chlorosilyl)methanes with SiH bonds were obtained as the major products along with bis(chlorosilyl)methanes, derived from the reaction of silicon with CH2Cl2 formed by the decomposition of CHCl3 (Scheme 1). A related preparation of the compounds Cl3nMenSiCH(SiHCl2)2 and Cl3nMenSiCH(SiCl3)2 (n = 0–3) has been described starting from the dichloromethylsilanes Cl3nMenSiCHCl2 <1994USP5332849, 1995USP5399740, 2000MI1020>. Cu/Cd 300 °C
CHCl3 + HCl + Si
SiH2Cl
SiHCl2
SiHCl2
Cl2HSi
+
Cl2HSi
6%
SiHCl2 Cl3Si
SiHCl2
SiCl3 +
Cl2HSi
SiHCl2
+
16%
45%
SiCl3
SiCl3
+
Cl3Si
3%
SiCl3
+ High boilers + Bis(chlorosilyl)methanes 12%
trace
17%
Scheme 1
Tris(trichloromethylsilyl)methane 1 has been obtained by the one-step synthesis presented in Scheme 2. When CHCl3, SiHCl3, and Bun3N are allowed to react in the ratio 1:4.5:3, (Cl3Si)2CH2 is obtained in 90% yield; however, if a large excess (9 equiv.) of SiHCl3 is introduced in the reaction medium, the compound 1 is preferentially formed, isolated in ca. 30% yield as tris(ethoxysilyl) derivative 2 after ethanolysis. The latter could then be metallated on the central carbon atom and trapped with MeI. With CO2, insertion and rearrangement afforded the stable ketene, [(EtO)3Si]2C¼C¼O <1998JOM(562)79>. Cl Cl
+ 3SiHCl3 + 3Bun3N
Cl
SiCl3
i Cl3Si
SiCl3
ii 30%
1 Si(OEt)3 (EtO)3Si
Si(OEt)3
Si(OEt)3
iii
–
(EtO)3Si
Si(OEt)3
iv 95%
[(EtO)3Si]3CMe
2 i. MeCN, –40 °C; ii. EtOH, –40 °C; iii. ButLi, THF, –80 °C; iv. MeI, THF, –80 °C
Scheme 2
Interest in 1,1,1-tris(organylsilyl)alkanes has also continued. Tris(trimethylsilyl)methane, (TMS)3CH, and related compounds have been intensively studied in the late 1990s and early 2000s in respect of their molecular geometry, ionization potentials, conformational structure, and molecular dynamics <1999CEJ3501, 1999MI219, 1997OM5218, 2000JCS(D)4312, 1994JCS(P2)2555>. Determination of the solution acidity of (TMS)3CH supports earlier findings <1994JA8304> that this compound is a significantly weaker acid (pK 36.8) than the corresponding silicon analog (TMS)3SiH (pK 29.4) <2002OM3157>. Consequently, (TMS)3CLi is a significantly stronger base than (TMS)3SiLi. This suggests that silicon accommodates a negative charge
208
Functions Containing at Least One Metalloid (Si, Ge, or B)
much more effectively than carbon, despite its lower electronegativity (C 2.5, Si 1.7). Reich and co-workers have prepared 13C-labeled tris(TMS)methane from commercially available 13C-paraformaldehyde (Scheme 3). This synthesis involves several in situ electrophilic traps, which take advantage of the differing reactivities of the starting materials, products, and electrophiles toward metallating agents <1998MRC118>.
(C13H2O)n + PhSeH
i 100% crude yield
PhSe
ii 81%
C13H2 PhSe
TMS C13 TMS SePh
iv 90%
TMS C13 PhSe SePh
iii 97%
TMS C13 TMS TMS
i. BF3·OEt2,CHCl3, 0 °C, 4 days; ii. TMS–Cl, LDA, THF, –78 °C, 2 h; iii. BunLi, THF, –78 to –20 °C, TMS–Cl
Scheme 3
A modification of the Merker–Scott procedure, involving the reaction between CHBr3, R3SiCl, and BunLi has been extended to numerous sterically crowded tris(organyl)chlorosilanes; an example is the preparation of the tris(i-propyldimethylsilyl)methane (Equation (4)). The latter can be used to attach the bulky trisilylmethyl group to a metalloid or metal center, was demonstrated by treating the lithium reagent, (PriMe2Si)3CLi, with Me2HSiCl to give a 77% yield of (PriMe2Si)3CSiMe2H <1995JOM(489)181>. Other examples relate to trisilylmethanes (RMe2Si)3CH (R = o-Tol, Et) <1996JOM(510)117, 1998JOM(555)263>. Metallation of (o-TolMe2Si)3CH by MeLi in tetrahydrofuran (THF) was shown to be much slower than that of (PhMe2Si)3CH. The lithium salt reacts with MeI to give (o-TolMe2Si)3CMe, but neither with Me2SiHCl nor with a range of other organosilicon halides <1996JOM(510)117>. A further extension of this type of chemistry was the development of arene-catalyzed lithiation of polychlorinated compounds under the Merker–Scott conditions. The reaction of 1,1,1-trichloroalkanes with a large excess of lithium metal (1:20 molar ratio) in THF in the presence of chlorotrimethylsilane and a catalytic amount of 4,40 -di-t-butylbiphenyl (DTBB) was found to produce 1,1,1-trisilylalkanes in good yield (Equation (5)). Conditions for preparing the monoand disilylated compounds have also been described <1996T1797>. Br Br
Br
+
Cl3CR
3PriMe
2SiCl
+
3BunLi
SiMe2Pri
–78 °C, THF 60%
TMS–Cl, Li (1:20), DTBB (5 mol.%) 51–93%
PriMe2Si
SiMe2Pri
ð4Þ
(TMS)3CR
ð5Þ
R = H, D, Me, Ph DTBB = 4,4'-di-t-butylbiphenyl
The obvious thought of using combination of the Merker–Scott procedure and the reaction of an organolithium compound with the corresponding halosilane for the synthesis of trisilylmethanes with different silyl groups attached to the carbon atom was realized for the compounds 4 and 5 <1997OM4728>. Treatment of CHBr3 at low temperature with 3 equiv. of BunLi in the presence of 3 equiv. of Me2PhSiCl gave trisilylmethane (PhMe2Si)3CH. When 2 equiv. of Me2PhSiCl/BunLi was used, the product was bromodisilylmethane 3, and this was converted into trisilylmethane 4 by treatment with BunLi/TMS-Cl. In the same way, the compound 5 was obtained by use of 2 equiv. of TMS-Cl/BunLi in the first step and 1 equiv. of BunLi/Me2PhSiCl in the second step (Scheme 4). Good yields could be obtained at each stage, provided the temperature was rigorously controlled. The attachment of the very bulky (PhMe2Si)3C ligand or of the closely related (TMS) (Me2PhSi)2C and (TMS)2(Me2PhSi)C ligands to a metal center made possible the isolation of a number of metal derivatives (TMS)3n(Me2PhSi)nCM: n = 1, M = Li(tetramethylethylenediamine [1,2-bis(dimethylamino)ethane] (TMEDA)), Li(Et2O), Na(TMEDA); n = 2, M = Li(THF)2, Li(TMEDA), K; n = 3,
209
Functions Containing at Least One Metalloid (Si, Ge, or B)
M = Rb or Cs <1997OM4728>. For further details of this subject, readers are referred to the following articles and references therein <1998JOM(564)215, 1997OM5653, 1996JOM(510)143>. Eaborn and co-workers have subsequently introduced the closely related dicarbanionic ligand [C(TMS)2SiMe2CH2CH2Me2Si(TMS)2C] (R-R) <1999OM2342>. Its precursor HR-RH 6 was prepared by the reaction shown in Scheme 5 <1996OM1651>. The compound 6 was metallated with MeLi in THF in the presence of TMEDA to give the chelated salt 7. If no TMEDA is added, a solid compound, assumed to be [(R-R)Li], may be isolated in 80% yield from diethyl ether/hexane. The lithium salt can be used to make cyclic derivatives of mercury <1996OM1651>, lead <1997OM5621>, potassium, zinc, ytterbium, tin <1999OM2342>, manganese, and cesium <2000OM1190>. The structurally related disiloxane [(TMS)2CHMe2Si]2O has also been prepared, and shown to undergo metallation reaction leading to a novel molecular species incorporating a cyclic organolithate anion and disiloxane-solvated lithium cation <1998CC1277>. Br Br
Br
i Br
Li
ii SiMe2Ph
PhMe2Si
PhMe2Si
TMS
iii SiMe2Ph
Br
iv TMS
SiMe2Ph
PhMe2Si
3
4
Li
ii TMS
TMS
SiMe2Ph
v TMS
TMS
TMS 5
i. 2PhMe2SiCl/2BunLi, THF, –80 °C; ii. BunLi, Et2O, –78 °C; iii. TMS–Cl, Et2O, –78 °C; iv. 2TMS–Cl/2BunLi, THF, –80 °C; v. PhMe2SiCl, Et2O, –78 °C
Scheme 4
TMS Li + ClMe2Si
2
SiMe2Cl
THF, reflux, 4 h 82%
TMS
SiMe2 Me2Si TMS TMS TMS TMS 6
MeLi/ TMEDA THF, 6 h, 20 °C 69%
Me2Si TMS TMS
SiMe2 [Li(TMEDA)2]+ TMS Li TMS 7
Scheme 5
The reaction of (TMS)2CHLi with hexachlorodisilane has been explored as a means of synthesizing tetrachlorodisilane 8 <2001IC3766>. Starting from 8 a wide variety of 1,2-bis[bis(TMS)methyl]substituted disilanes were prepared (Scheme 6). A reduction of 8 with LiAlH4 resulted in the formation of the disilane 9 and the metathesis with Me3SnF yielded the tetrafluorodisilane 10. The interaction of 8 with a solution of sodium in liquid ammonia at 78 C affords the tetraaminodisilane 11. In turn, treatment of 11 with reagents containing acidic protons (HBr, HI, or H2O) leads under elimination of NH3 to the tetrabromo- 12, tetraiodo- 13, and tetrahydroxydisilane 14. The siliconsilicon bonds were not cleaved under these conditions. The disilane 14 can also be obtained directly from the reaction of tetrachlorodisilane 8 with a mixture of H2O2/H2O. However, in contrast to 8, the tetraaminodisilane 11 reacted under the same conditions to yield the trihydroxycyclotrisiloxane 15 <2002OM3671>. The synthetic utility of 11 has also been demonstrated by the reaction with liquid H2S at 70 C leading to the formation of a S4Si4 cage compound 16 <2001OM1282>. The driving force for the crossover arrangement of the sulfur atoms is most likely the formation of the four five-membered rings. Finally, a somewhat similar chemistry was performed with (TMS)2CHSiCl3. The ammonolysis of this compound with ammonia which was not predried with sodium yielded the trihydroxycyclotrisilazane 17 while the reaction with sodium in predried ammonia gave the acyclic tetraaminodisilazane 18 <2000EJI827>.
210
Functions Containing at Least One Metalloid (Si, Ge, or B) TMS Li
+ Si2Cl6
TMS
i 53%
Cl Cl Si Si Cl Cl
TMS TMS
TMS TMS
ii 85%
TMS TMS
TMS TMS
H H Si Si H H
76%
TMS
TMS
TMS
TMS
TMS TMS
10
8 ii
F F Si Si F F
iv 82% NH2 NH2 TMS Si Si NH2 NH2 TMS
9
v–vii 74–86%
11
TMS TMS
X X Si Si X X
TMS TMS
12, X = Br 13, X = I 14, X = OH
i. toluene, reflux, 6 h; ii. LiAlH4, THF, –78 °C; iii. Me3SnF, toluene, reflux, 15 min; iv. Na /NH3, –78 °C; v. HBr, toluene, 20 °C, 30 min; vi. HI, toluene, 20 °C, 30 min; vii. H2O, THF, reflux, 20 h
Scheme 6
OH R Si O R O Si HO Si O OH R 15
R R
S Si S
Si
R
Si S Si R S 16
OH Si NH R HN Si Si NH OH HO R 17 R
H N H2N NH2 Si Si R R NH2 NH2 18
R = (TMS)2CH
(ii) Functionalized trisilylmethanes containing an ‘‘active’’ ligand framework The extreme exploitation of the steric demand of an Si3C function is a common feature of most of the early reports on trisilylmethane chemistry <1996CCR125, 1995JOM(500)89>. The emphasis in studies on trisilylmethane derivatives has moved toward polydentate compounds of the type (XMe2Si)3n(TMS)nCH, n = 0–2, in which the trisilylmethyl ligands have bulk similar to that of the (TMS)3C, but contain groups X bearing heteroatoms with lone pairs capable of coordinating intra- or intermolecularly to the metal. The most prominent example of the versatility of this concept is the structural chemistry and chemical reactivity of a series of compounds studied by Eaborn and co-workers. Those include functionalized trisilylmethanes (Me2NMe2Si)(TMS)2CH <1999OM45>, (Me2NMe2Si)3CH <1996CC741, 1997OM503, 1998OM3135>, (MeOMe2Si) (TMS)2CH <1996JOM(521)113, 1996OM4783, 1997AG(E)2815, 1997OM5653, 1998OM4322>, (MeOMe2Si)3CH <1992JCS(D)1015>. Typically the compounds (XMe2Si)3n(TMS)nCH are obtained in several steps via the corresponding bromosilanes. Representative examples are given in Scheme 7 <1999JCS(D)3267>. Interestingly, the reaction between compound 19 and BunLi proceeded much faster than the corresponding reaction with (TMS)3CH suggesting that it is facilitated by initial coordination of Me2N to lithium. The compound 20 reacted with MeLi at 0 C to give a complex mixture that, after aqueous work-up, was found to contain (MeOMe2Si) (TMS)2CH, indicating that MeLi had attacked SiOMe as well as CH bonds. However, the reaction between 20 and Pri2NLi proceeded smoothly at 60 C and the lithium compound (MeOMe2Si)2(TMS)CLi was isolated in good yield. The symmetrically substituted tris(aminosilyl)methanes (RNHMe2Si)3CH are available from the reaction of (BrMe2Si)3CH 21 with 3 equiv. of a primary amine in the presence of an excess of triethylamine as auxiliary base. The facile accessibility of these compounds along with the possibility of preparing enantiomerically pure derivatives provided the motivation for the synthesis of an extensive series of novel trisilylmethane-derived tripodal amines and the corresponding trilithium triamides (Scheme 8). A comprehensive study into the coordination chemistry of
211
Functions Containing at Least One Metalloid (Si, Ge, or B)
these ligands has been carried out by Glade and co-workers <2002JCS(D)2608, 2001CEJ2563, 2001EJI1425>. Interestingly, the tris(aminosilyl)methanes were found to be in equilibrium in solution with the cyclic diamines, which are generated upon ejection of one molecule of the primary amine. Reaction of these equilibrium mixtures with 3 equiv. of BunLi affords the trilithium triamides. It is notable that the result of the metallation is the same whether the reaction is carried out with the essentially pure tripodal amine or with a mixture of the triamine and the cyclic product in the presence of the dissociated primary amine (Scheme 9) <2001CEJ2563, 2001MI191,1994IC3064>. TMS
TMS
i
SiMe2Ph
PhMe2Si
BrMe2Si
TMS
ii or iii
SiMe2Br
XMe2Si
4
SiMe2X
19, X = Me2N 20, X = MeO
i. Br2/Al, petroleum, 2 h, 0 °C; ii. Me2NH, petroleum, –60 °C, 84%; iii. MeOH/Et3N, petroleum, 20 °C, 83%
Scheme 7
H
Mg
HCBr3 + 3Me2Si(H)Cl
THF
H
3Br2
Me2Si SiMe2 SiMe2 H H H H
3RNH2, 3Et3N
Me2Si SiMe2 SiMe2 Br Br Br
Me2Si SiMe2 SiMe2 NH NH NH R R R
21 R = But <1993IC2308>, Ph <1994IC3064>, 2-FC6H4 <1995IC4062>, 4-FC6H4, 2-MeC6H4, 3-MeC6H4, 4-MeC6H4 <1994IC3064>, 2-MeOC6H4 <2002EJI1968>, 4-methyl-2-pyridyl, 4,6-dimethyl-2-pyridyl <1997OM5585>, (S)-Ph(Me)CH <1994IC3064, 1996OM3637, 2001CEJ2563>, (R)-4-MeOC6H4(Me)CH <2001MI191>, (R)-1-tetralenyl <2001JCS(D)964>, (S)-But(Me)CH <2001EJI1425>, (S)-1-(1-naphthyl)ethyl <2002PO629>, (R)-1-indanyl <2001CEJ2563>
Scheme 8
H Me2Si
H Me2Si SiMe2 SiMe2 NH NH NH R R R
R
SiMe2
N +
SiMe2 NH R
RNH2
H BunLi
Me2Si
SiMe2 SiMe2 Li N N N R Li Li R R
R = (S)-Ph(Me)CH, (R)-1-indaryl, (R)-4-MeOC6H4(Me)CH
Scheme 9
Tris(diphenylphosphinodimethylsilyl)methane 22 has been prepared from the reaction of 21 and Ph2PLi (yield 62%) <1999CJC1931> or Ph2PK (89%) <1999JCS(D)831>. The compound 22 reacted with [Mo(CO)6] to give the complex cis-23, in which two phosphine groups are coordinated to molybdenum and one is free and with BunLi in the presence of TMEDA to give [Li(TMEDA)2][(Ph2PMe2Si)3C] which contains discrete planar carbanions and no LiP coordination
212
Functions Containing at Least One Metalloid (Si, Ge, or B)
<1999JCS(D)831>. The susceptibility of 22 to cleavage of the PSi bonds by protic reagents has also been described <1999CJC1931>. Hydrolysis of the PSi bond in 22 produces principally the alcohol 24. In the presence of excess of methanol, the compound 22 is cleanly converted to the trisilylmethane 25. Bubbling oxygen through solutions of 22 for 15 min gives only trace amounts of the oxidation product 26 (Scheme 10).
H Me2Si Ph2P
SiMe2 PPh2
H SiMe2
Mo(CO)6
PPh2
Toluene, reflux 90%
Me2Si Ph2P
SiMe2 PPh2
SiMe2 PPh2
(OC)4Mo
22
23 H HX or O2 Toluene, 20 °C
Me2Si X
SiMe2
SiMe2 X
X
24, X = OH 25, X = OMe 26, X = OP(O)Ph2
Scheme 10
Other examples of this type of functionalized trisilylmethanes are (Ph2PCH2Me2Si)3CH, (Ph2PCH2Me2Si)2(TMS)CH, and (Ph2PCH2Me2Si)(TMS)2CH <2000JCS(D)2183>. The conversion of triphosphino derivative to the corresponding lithium salt was affected by MeLi in ether. The anionic ligand in compound (Ph2PCH2Me2Si)3CLi shows a close skeletal resemblance to the tripodal ligands in silatranes, but the coordination to the metal center is provided by the lone pair of electrons of the carbanion rather than by that of the nitrogen atom. The [dimethyl(2-pyridyl)silyl]-bis(TMS)methane, (2-PyMe2Si)(TMS)2CH, containing a nitrogen atom in its ligand periphery was synthesized by reaction of (BrCH2Me2Si)(TMS)2CH with 2-lithiopyridine (yield 61%). This ligand precursor reacts with MeLi in THF to give the lithium derivative, which could be used to obtain compounds of a wide range of metals (K, Mg, Cr, Mn, Co, Ni) <2000OM3224, 2000CC691>. Synthesis of more sophisticated trisilylmethane-based polydentate species is shown in Scheme 11. Preparation of the compound 27 was readily achieved by reaction of 3 equiv. of propynyl lithium with 1 equiv. of 21. Reaction of this precursor with an excess of the 4,6-di-t-butyl-1,3,2-diazaphosphinine yields intermediate 28. In a subsequent step, 28 was reacted with trimethylsilylacetylene to give the desired ligand 29. Complex of 29 with [Mo(CO)5(THF)] has also been characterized <2000EJI2565>.
(iii) Compounds with an Si3C function as part of one or more ring systems Tris(aminosilyl)methanes, HC(SiMe2NHR)3, have been shown to be valuable starting materials to build up compounds in which the trisilylmethane unit is part of a hetero-bicyclo[2.2.2]octane system. After lithiation with n-butyllithium, these amines react with early transition metals (Y <1995IC4062>, Ti <1997OM5585, 2001CEJ2563>, Zr <1995IC4062, 1999JOM(591)71, 2000OM963, 2001EJI1425>, Hf <1999JOM(591)71>, Nb <1997OM5585>) as well as groups 13 (Tl <2001CC899>, Sn and Pb <1995IC4069, 1995CB29, 1998POL737, 2001ZAAC(627)1417>) and 15 (Sb, Bi <2000IC3931>) metals to form complexes with tripodal amido ligands. Some examples taken from the studies by Gade and co-workers are shown in Scheme 12. Related hetero-bicyclo[2.2.2]octanes containing chalcogens instead of the nitrogen atoms are formed in a smooth reaction from easily available HC(SiMe2Cl)3, RMCl3 (M = Si, Ge, or Sn), and a suspension of Li2E (E = S or Se) in THF (Scheme 13) <2002JOM(660)27>. A new synthetic approach toward hexasilabicyclo[2.2.2]octane system, in which three SiSi linkages are aligned in parallel between two bridgehead carbons, is conceptually based on triple silylation of two molecules of a trilithiomethane equivalent with three molecules of dichlorodisilanes
213
Functions Containing at Least One Metalloid (Si, Ge, or B) H i. 3Me2SiHCl, Mg, THF
HCBr3
Me2Si
ii. Br2, benzene
Br
THF, –78 °C
Br
Br
Li
3Me
SiMe2
SiMe2
21
Me2Si
SiMe2
But
But
H
3
SiMe2
N
H
N
P
Me2Si
Me
Toluene, 100 °C, 3 h Me
Me
P
SiMe2
P P N N
N
–3ButCN
Me
SiMe2
But
Me
But
But
27
28 H Me
Me2Si
3TMS Toluene, ∆
SiMe2
P
–3ButCN
SiMe2
Me
P
P
TMS TMS
TMS 29
Scheme 11
H Me2Si
SiMe2 SiMe2 Li N N N R Li Li R R
ZrCl4
TlCl3
Me2Si N R
SiMe2 N
R
H
H
H SiMe2
Me2Si N
N R
R
Tl
R Cl
SiMe2 N
MCl3
MCl2
SiMe2
Me2Si
SiMe2
N
N R
R
Zr
R
Cl Li (OEt ) 2 2
H SiMe2
Me2Si
N
N M
N R
–
Li(THF)n+
M = Sn, Pb
R
R
SiMe2
SiMe2 N
N
R
M
M = Sb, Bi
Scheme 12
TMS TMS
TMS
SiMe2Cl
3MeCOCl/AlCl3 Hexane, 0 °C 82%
ClMe2Si
SiMe2Cl
H R-MCl3/3Li2E Hexane, rt 45–70%
M = Si, Ge, Sn; E = S, Se; R = Me, Ph, H2C=CH–
Scheme 13
Me2Si
SiMe2
E E M R
SiMe2 E
214
Functions Containing at Least One Metalloid (Si, Ge, or B)
as illustrated in Scheme 14. Commercially available bis(phenylthio)methane was selected for a trilithiomethane equivalent because the phenylthio group facilitates deprotonation and stabilizes the anionic center. Moreover, the group is readily removed by metallation to give rise to the lithium derivative. Reduction of the disilane 30 with lithium radical anion and its silylation with (ClSiMe2)2 lead to 1,2,4,5-tetrasilacyclohexane 31 as a stereoisomeric mixture (cis:trans = 1:1). Final ring formation for hexasilabicyclo[2.2.2]octane 32 was attained by reduction of 31 and subsequent silylation with (ClSiMe2)2 <1998CL1145>.
PhS 2 PhS
PhS
BuLi
2
THF, 0 °C
Li PhS
PhS
SPh
(ClSiMe2)2
PhS
–78 °C to rt 94%
PhS
Li
Si Si PhS
82%
Li
SPh
LDBB THF, –78 °C
30
(ClSiMe2)2
Si Si
SPh Si Si
SPh
LDBB
Si Si 31 (1/1 cis/trans)
Si Si Li
Li
Si Si H Si Si Si Si H
(ClSiMe2)2
Si Si
73%
32 Li+
LDBB =
Scheme 14
Functionalization of 32 at bridgehead carbon was achieved by treatment with BunLi-ButOK followed by a reaction with electrophile (Scheme 15). It is noteworthy that only monosilylation occurs. Probably through-space or through-bond electrostatic interaction prevented the formation of a bridgehead dianion. Nevertheless, a stepwise procedure involving deprotonation of 32 followed by electrophilic quenching allowed preparation of symmetrically or dissymmetrically disubstituted derivatives <2000JOM(611)12, 2001CL1090>. Further extension of this synthetic strategy is illustrated in Scheme 16. Synthesis of cage compounds 36 and 37 containing a trisilane linkage was achieved starting from the acyclic trisilane 33. Reduction of 1,3,4,5-tetrasilacyclohexane 34 with lithium radical anion effectively produced 1,3-dimetallic reagent 35 which, upon quenching with Me2SiCl2, gave pentasilabicyclo[3.1.1]heptane 36. Silylation of 35 with Cl(SiMe2)2Cl also proceeded successfully, giving rise to 2,3,4,6,7,8-hexasilabicyclo[3.2.1]octane 37 <2000JOM(611)12>. The reaction of tris[dimethyl(ethynyl)silyl]methane with triethylborane was reported to proceed via a threefold 1,1-ethylboration to give a bicyclic compound incorporating trisilylmethane unit <1995CC399>.
6.06.2.1.2
Functions bearing three borons
The first synthesis of triborylmethane derivatives was reported in 1968, by Matteson and Castle who obtained tris(dimethoxyboryl)methane, CH[B(OMe)2]3, by treatment of (MeO)2BCl and CCl4 with
215
Functions Containing at Least One Metalloid (Si, Ge, or B) Si Si H Si Si Si Si H
Si Si H Si Si
BunLi-ButOK THF, –42 °C
Si
Si Si H Si Si Si Si R
RX
Si M
32
i. BunLi-ButOK ii. MeI
Si Si Me Si Si Si Si
Si Si H Si Si Si Si
TMS
TMS
RX, R, yield: MeI, Me, 97%; CH2=CHCH2Br, CH2=CH–CH2, 94%; PhCH2Br, PhCH2, 85%; Me2PhSiCl, Me2PhSi, 90%; Me2[Cl(CH2)3]SiCl, SiMe2[(CH2)2Cl], 86%; Bu3SnCl, Bu3Sn, 88%; (PhS)2, PhS, 62%; I2, I, 77%
Scheme 15
Si
Si
i. BuLi-ButOK ii. Me2SiCl2
Si
PhS
SPh
THF, –78 °C
33
Si PhS
Si
Si
Si
Si
LDBB SPh
THF, –78 °C
34
Si
Si Li
35
Me2SiCl2 63%, –40 °C
Cl(SiMe2)2Cl
Si
–40 °C, 62%
Si H
Si Si Si H
Li
Si
H Si Si Si H
Si
36
Si Si
37 Li+
LDBB =
Scheme 16
lithium in THF <1968JA2194>. Subsequently, tris(dichloroboryl)methane, CH(BCl2)3, was synthesized by an exchange reaction of tris(dimethoxyboryl)methane with boron trichloride <1973IC2472, 1995COFGT(6)171>. Siebert and co-workers have reported the synthesis of 1,1,1-tris(dichloroboryl)alkanes and tris(boronate)esters via hydroboration of alkynylboronates using in situ generated HBCl2 <2001EJI373, 2002EJI1293>. In addition, Marder and co-workers have described a catalytic route to the tris(boronate)esters in a single step from readily accessible vinylboronates <2002JOM(652)77>. New acyclic systems bearing three dialkylboryl groups on a single carbon atom have also been prepared <1998AG(E)1245>.
216
Functions Containing at Least One Metalloid (Si, Ge, or B)
(i) 1,1,1-Tris(dihaloboryl)alkanes 1,1,1-Tris(dichloroboryl)-3,3-dimethylbutane 38 is now readily available on a large scale by lithiation of 3,3-dimethyl-1-butyne by n-butyllithium, followed by boron/lithium exchange with BCl3 and a double hydroboration of the boryl alkyne with dichloroborane (HBCl2) prepared in situ (Scheme 17). This reaction sequence afforded a 42% yield of 38 <2002EJI1293>. Treatment of trimethylsilylacetylene with BunLi, BCl3, and 2 equiv. of HBCl2 provided 1,1-bis(dichloroboryl)2-trimethylsilylethene 40 and isomeric products 41–43 (Scheme 18) <2002EJI1293>. Presumably, the hydroboration of 39 occurs regioselectively to give bis(dichloroboryl) derivative 40. Dichloroborane then hydroborates 40 in both directions, giving rise to the compounds 41 and 42, with the former being favored. The mechanism of the formation of 43 is unclear.
BCl2
i, ii
BCl2 BCl2 BCl2
iii 42%
38
i. BunLi, pentane, –15 °C; ii. BCl3, pentane, –78 °C; iii. BCl3/Me3SiH (2 equiv.), pentane, –30 °C
Scheme 17
i. BuLi ii. BCl3
TMS
TMS
–LiCl
BCl2
2HBCl2
BCl2
+
39
BCl2 BCl2 BCl2
TMS
BCl2
TMS 40
Cl2B
BCl2 +
+ TMS
BCl2
Cl2B Cl2B TMS
42
41
BCl2
43
Scheme 18
(ii) Methanetriboronic esters The preparation of tris(ethylenedioxyboryl)methane 45, a reagent for the homologation of aldehydes and ketones under nonacidic conditions, was improved by avoiding the isolation of the intermediate tris(dimethoxyboryl)methane. The compound 45 is best prepared from the dimethoxyboron chloride, chloroform, and lithium dispersion by transesterification of crude methyl ester 44 with ethylene glycol and subsequent crystallization of the product from hot THF (Scheme 19) <1995T11219>.
MeO
Cl Cl
Cl
+ 3ClB(OMe)2
+
MeO
6Li –30 to 20 °C
B
OMe B B OMe OMe 44
Scheme 19
O
OMe HO
OH
THF, 0 to 70 °C 16%
O
B
B O
O B O
45
O
217
Functions Containing at Least One Metalloid (Si, Ge, or B)
Knowledge of the versatile reactions of boranes with unsaturated compounds prompted an investigation into the synthesis of methanetriboronic esters via alkynes. Siebert and co-workers have shown that the interaction of the catechol-substituted monoborylacetylene 46 with an excess of 1,3,2-benzodioxaborole (catecholborane) leads to a mixture of 1,1-bis(1,3,2-benzodioxaborol-2-yl)ethene 47 and a small amount of trans-1,2-bis(1,3,2-benzodioxaborol-2-yl)ethene 48. In contrast with catecholborane, dichloroborane adds to 47 affording triborylethane 49, which was identified as a catechol ester 50. The direct hydroboration of 46 with 2 equiv. of HBCl2 and subsequent reaction with catechol also affords 50 in 83% yield (Scheme 20) <2001EJI373>.
Bcat
O
O +
B
HB O
O
+
80 °C
Bcat
46
48
47
2HBCl2
HBCl2
OH
OH Me
Bcat catB
Bcat BCl2 BCl2
2 OH –4HCl
Me
Bcat Bcat Bcat
OH –2HCl
Me
Bcat BCl2 Bcat
78% 50
49
O Bcat = –B O
Scheme 20
The transition metal-promoted catalytic diboronation of diborylacetylenes offers another new route to compounds containing a B3C function <1999EJI1693>. Thus in refluxing toluene, the platinum complexes [Pt(PPh3)2(C2H4)] or [Pt(PPh3)4] catalyze the double diboronation of the diborylacetylene 51 with the catechol-substituted diborane 52 to give the hexaborylethane 53 (Scheme 21). Reaction conditions were found to be critical; the formation of tetraborylethane 54 instead of hexaborylethane occurs by catalysis with [Pt(PPh3)2(C2H4)] or [Pt(PPh3)4] in THF at 55 C. Moreover, the tetraborylethene 55 is obtained from 51 and 52 with the base-free platinum complex [Pt(COD)2] under mild conditions in toluene. At temperatures above 40 C 55 adds 52 to form hexaborylethane 53. Hexaborylethane derivatives have also been obtained from the diborylacetylene 56 and the diborane 52. However, the reaction leads to a mixture of naphthalene- and benzo-1,3-dioxa-2-borol-2-ylethanes, in which between five and two boryl substituents of 52 and between one and four substituents of 56 are incorporated. It is unclear whether the exchange occurs before or after the formation of the hexaborylethanes. The route employing transition metal-catalyzed diboration of borylalkenes appeared to be a general method for synthesizing tris(boronate)esters, as further examples demonstrate. Diboration of the styrylboronate esters 57 with diborane 52 in the presence of a variety of rhodium phosphine catalysts gives predominantly either 58, which contains three boronate ester groups on the carbon atom, or its isomer 59. Wilkinson’s catalyst, [Ph(PPh3)3Cl], gave the highest yield of 58, 75% and 71% for 58a and 58b, respectively, with the reactions essentially going to completion (Equation (6)). The formation of 58 apparently involves regiospecific insertion of the vinylboronates into a RhB bond followed by -hydride
218
Functions Containing at Least One Metalloid (Si, Ge, or B)
elimination, another regiospecific insertion of the 2,2-vinyl bis(boronate) into the remaining RhB bond followed by CH reductive elimination leading to 2,2-diboration and a 2,1-hydrogen shift <2002JOM(652)77>. O
O B
B
O
O 51
catB catB catB
(Ph3P)2Pt(C2H4)
+ O
Toluene, reflux, 24 h
O
71%
B B O
Bcat Bcat Bcat
O 53
52
52 >40 °C (Ph3P)2Pt(C2H4)
Pt(COD)2
catB
Bcat
55 °C, 24 h
Toluene, 40 °C, 48 h 70%
catB
Bcat 55
Bcat
H catB catB
O
O
Bcat
B
B
O
H
O 56
54 O Bcat = –B O
Scheme 21
O
Bcat
O +
B B O
O 52
Rh(PPh3)3Cl (1 mol.%) THF, 58 °C, 12 h
Ar
Ar
Bcat Bcat Bcat 58
57
catB
Bcat
Ar
Bcat
+
59
ð6Þ
O Ar = Ph (a), 4-MeOC6H4 (b); Bcat = –B O
(iii) Tris(boryl)alkanes and boracycloalkanes involving a B3C function 1,1,1-Tris(diethylboryl)alkanes have been postulated and evidenced in many reactions of borylacetylenes with diethylborane <1994AG(E)2296, 1995CC1691, 1998AG(E)1245>. For example, hydroboration of trimethyl(propyn-1-yl)silane with Et2BH under ‘‘hydride bath’’ conditions (i.e., with a large excess of diethylborane) leads to the 1-carba-arachno-pentaborane(10) derivative 64. The reaction proceeds via intermediate formation of compounds 60–63. In the hydride bath, exchange reactions between in situ generated 1,1,1-tris(diethylboryl)propane 62 and geminal bis(diethylboryl)alkane 63, take place until the carborane skeleton 64 is formed (Scheme 22) <1997CCC1254>. A thermally stable tris(boryl)ethane has been derived from the interaction of 50 with t-butyllithium. This reaction results in the formation of 1,1,1-tris[di(t-butyl)boryl]ethane 65, which does not form any closo-C2B3 carborane by elimination of trisorganoboranes (Equation (7)) <2001EJI373>.
219
Functions Containing at Least One Metalloid (Si, Ge, or B) TMS
Me
TMS
Et2BH
+
Me +
Et2B
Me
Et2B 60
61 Et2BH
Et2B Et2B Et2B
Et
+
Et2B
TMS
Et2B
Et 63
62 3Et2BH
–4BEt 3
Et Et B Et Me2HSi
B BH B
Et H
Et
H Et
64
Scheme 22 catB catB
6ButLi Me
catB
–3C6H4O2Li2
50
Bu2t B Bu2t B
Me
Bu2t B
ð7Þ
65 O
Bcat = –B O
Siebert and co-workers also found that cyclic tetraborylmethane 67 is formed in excellent yield upon addition of B2Cl4 to a solution of boriranylideneborane 66 in hexane at low temperature. The substitution of the chlorine atoms of 67 by amino groups yields the triamino derivatives 68 with unexpected cleavage of one of the exocyclic CB bonds (Scheme 23) <2001EJI387>. HNEt2 or Bu TMS
t
B
B
But
TMS
B2Cl4 Hexane, –85 °C
TMS
92%
But B Cl
TMS–NMe2 or 2LiN(CH2)4
TMS
B Cl
B Cl But
Hexane, –30 °C 32–48%
TMS
67
66 R2N = Me2N, Et2N,
TMS
Cl B
NR2 But B B NR
2
B H NR2 68
N
Scheme 23
A route to boracycloalkanes possessing closo-C2B3 carborane structure, which may be described as midway between classical and nonclassical, uses thermolysis of the triborylalkane 38. On heating neat 38 at 170 C, elimination of BCl3 occurred with formation of the compound 69.
220
Functions Containing at Least One Metalloid (Si, Ge, or B)
Methylation of 38 with Al2Me6 gave 70, which, on heating, was transformed into 71. The latter was also formed by direct methylation of 69 with MeLi or Al2Me6. Treatment of 69 with 3,3-dimethylbutynellithium and 2-phenylethynyllithium afforded 72a and 72b, respectively (Scheme 24). Attempts to substitute the chloro atoms with OH, OMe, OBut, and catechol groups were unsuccessful. With sterically demanding lithium, reagents such as ButLi, Pri2NLi, BunLi, and PhLi only product mixtures were obtained <2002EJI1293>. But
But R
BCl2 BCl2 BCl2
But
–BCl3 170 °C, 2 h; 25%
Cl
Cl B B
R
B
Cl
Li
Hexane, –78 °C 62–67%
B
R But
69
Al2Me6
hexane, –78 °C 83%
B
R
But
38
B
72a,b
MeLi or
Et2O, –70 °C
Al2Me6
75%
R = But (a), Ph (b)
But BMe2 BMe2 BMe2
But
Me –BMe3 Me toluene, reflux, 2 h
B
B
B
Me
But
70
71
Scheme 24
6.06.2.1.3
Functions bearing three germaniums
Traditionally, trigermylmethane derivatives are synthesized either via condensation of the polylithiated hydrocarbons with chlorotrimethylgermane or via stepwise base-assisted introduction of an R3Ge group into compounds containing an activated methyl group <1995COFGT(6)171>. Kouvetakis and co-workers have utilized the high reactivity of dihalogermylenes toward CHal bonds to develop probably the most general and effective synthesis of simple trigermylmethanes <1995IC5103, 1996CM2491, 1998JA6738>. They found that the germylene complexes GeX2.dioxane (X = Cl, Br) undergo complete insertion into the CBr bonds of CBr4 to give the tetrakis(trihalogermyl)methanes 73 and 74, in 79% and 94% yields, respectively. Reduction of 73 with LiAlH4 in a very high boiling solvent (C30H50 squalene) in a two-phase system with a phase transfer catalyst leads to the tetrakis(germyl)methane 75 in 20% yield. A substantial quantity (18% yield) of 76, the tris(germyl) analog, is also obtained as a by-product. The reduction of 74 with LiAlH4, under conditions similar to those for the reduction of 73, leads to compounds 75 and 76 in 1:1 molar ratio in approximately 12% yield each (Scheme 25) <1998JA6738>.
CBr4
GeX2Br
4GeX2·diox Toluene
BrX2Ge
GeH3
LiAlH4
GeX2Br GeX2Br
73, X = Cl
H3Ge
GeH3 GeH3 75
74, X = Br
Scheme 25
GeH3 +
H GeH3
H3Ge 76
221
Functions Containing at Least One Metalloid (Si, Ge, or B)
A more attractive synthesis of the trigermylmethane 76 is based on the direct reduction of tris(tribromogermyl)methane. The bromide 77 in turn is prepared by direct insertion of GeBr2 into the CBr bonds of bromoform (Scheme 26) <1996CM2491>. Br Br
GeBr3
3GeBr2.diox Br
Toluene, 85 °C
Br3Ge
GeH3
LiAlH4
GeBr3
H3Ge
15%
GeH3
89% 77
76
Scheme 26
Trigermylmethane 76 is a stable, colorless liquid, and its relatively high volatility makes it highly suitable for low-pressure chemical vapor deposition experiments <1999MI958>. The structure of this compound was determined by electron diffraction and density functional theory calculations <1999JST29>.
6.06.2.1.4
Functions bearing mixed metalloids
There are several methods for the production of compounds of the general structure RC(E1Xm) (E2Xn) (E3Xmn), where E1, E2, and E3 = Si, B, or Ge, but three groups of reactions are most important: (i) synthesis based on -silyl-, boryl, or germyl-substituted organometallics; (ii) synthesis based on p-bonded low-coordinate boron and germanium derivatives; and (iii intermolecular C–H insertions and cyclization reactions involving a stable germylene.
(i) Synthesis based on a-silyl-, boryl-, or germyl-substituted organometallics This approach has been extensively studied and seems to be most general for preparing functions bearing mixed metalloids <1995COFGT(6)171>. An example provided in Equation (8) illustrates the application of this strategy for the synthesis of base-stabilized germylene containing a Si2(GeII)C function <1997OM2116, 1999OM389>.
N Li
TMS TMS
GeCl2.diox Et2O, –78 °C 53%
TMS TMS
N
ð8Þ
Ge TMS TMS
N
Wiberg and co-workers have investigated the reaction of (Me3Ge)2CHLi with But2Si(H)F, which gives the sterically overloaded digermylsilylmethane 78 <1996JOM(511)239>. With bromine, 78 reacts, as do hydrosilanes, to form bromosilyl derivative 79. Coupling reaction between 79 and MeLi followed by the treatment of a lithium intermediate 80 with MeOH lead to the silyldigermylmethane 81 (Scheme 27). Li Me3Ge
GeMe3
Bu2t SiHF
Me3Ge
12 h, 130 °C
Me3Ge
But Si But H
77%
Br2
Me3Ge
CCl4, 0 °C 95%
Me3Ge
78
MeLi THF, –78 °C
Me3Ge Me3Ge Li
But Si But Me
But Si But Br 79
SiMeBut2
MeOH 95%
Me3Ge
GeMe3 81
80
Scheme 27
222
Functions Containing at Least One Metalloid (Si, Ge, or B)
Silylation of 2-trimethylsilylboratabenzene salt 83 affords compounds 84 and 85 as a slowly interconverting equilibrium mixture of isomers (Scheme 28). When this reaction was run in THF, a mixture of the monosilylated compound 82, the expected bis(trimethylsilyl) derivatives, and more highly silylated species were formed. When pentane was used as the reaction medium, the chemoselectivity was much improved. The product obtained was essentially an equilibrium mixture of the isomers 84 and 85 in a 4:3 ratio with some 82 (10–20%) <1997OM926>.
B Me
LDA THF, 1 h,
TMS
92%
82
TMS
TMS B TMS Me
TMS–Cl
Li B Me
Pentane, rt 72%
83
+
TMS
B Me
TMS
85
84
Scheme 28
Structurally related 1-chloro-1,2-dihydroborinines 88 and 89 were prepared according to the pathway outlined in Scheme 29. Treatment of stannacyclohexadiene 86 with lithium diisopropylamide (LDA) followed by chlorotrimethylsilane affords stannacycle 87 in excellent yield. Transmetallation through reaction of 87 with BCl3 then provides boracyclohexadienes 88 and 89 <1997JOC8286>. TMS
i. LDA
TMS
ii.TMS– Cl
BCl3
90%
–Bu2SnCl2
Sn Bu
TMS
Sn Bu
Bu 86
TMS B Cl
55–60%
Bu
+ TMS
TMS
88
87
B Cl
TMS
89
Scheme 29
(ii) Synthesis based on p-bonded low-coordinate boron and germanium derivatives The scope of these reactions is restricted to the preparation of specific polyfunctional compounds. Thus, reaction of methyleneborane 90 with trimethylstannylethyne 91 affords the spiro cyclic compound 92, which upon isomerization followed by rearrangement gave compound 93. Lithium exchange of the latter with ButLi followed by treatment with chlorotrimethylsilane result in the formation of the cyclic compound 94 containing an B2SiC function (Scheme 30) <1994AG(E)2064>.
Dur TMS
B
B
Dur +
Me3Sn
Ar
TMS –20 °C
91
TMS
Dur B
TMS Me3Sn
90
Dur B Ar
92
TMS C
Dur B SnMe3 B Ar Dur
TMS
Bu
tLi
Dur B Li
TMS C TMS
93
B Ar Dur
TMS–Cl
Dur B TMS
TMS C
B Ar Dur
TMS
94
Ar = 3,5-Bu2t C6H3, Dur = 2,3,5,6-Me4C6H
Scheme 30
Functions Containing at Least One Metalloid (Si, Ge, or B)
223
The tetracoordinate germanium derivative 96 is reported to be formed by intramolecular cyclization of 1-germaallene 95 (Equation (9)) <1998CL811>.
H TMS
Tbt Ge C Tbt
Benzene, 80 °C
Ge
TMS
Tbt
ð9Þ
CH(TMS)2 (TMS)2HC
95
96 Tbt = 2,4,6-[(TMS)2CH]3C6H2
Diels–Alder and ene reactions of the germaethene Me2Ge = C(TMS)2 generated as a reaction intermediate by thermolysis of Me2GeCl-CLi(TMS)2 <1996ZN(B)838> or cycloadduct of the germaethene and anthracene <2000CJC1412> lead to various cyclic compounds containing an Si2GeC function <1996ZN(B)838>. Similarly, thermolysis of But2SiF-CLi(GeMe3)2 at 100 C in benzene and in the presence of propene, isobutene, butadiene, or 2,3-dimethylbutadiene leads to ene reaction products and/or [4+2]-cycloadducts of the germaethene Me2Ge = C(GeMe3) (SiMe2But2) 97 which contain a SiGe2C unit (Scheme 31) <1996JOM(519)107>. Me Me Ge
GeMe3 SiMe2But H
Me Ge Me
89%
GeMe3 SiMe2But
77%
Me GeMe3 Me Ge SiMe2But
97
Me Me Ge
GeMe3 SiMe2But H
97 73%
Me Me Me Me Me3Ge Ge Ge GeMe3 Bu2t MeSi
SiMe2But2
Scheme 31
(iii) Intermolecular CH insertions and cyclization reactions involving a stable germylene A great deal of chemical research has focused upon CH and CHal insertions and cyclization reactions involving divalent germylenes in the hope of developing general methods for introducing functionality into a variety of organic molecules <1996OM741, 1997AG(E)2514, 1996JOM(521)387, 1999JA4229>. Banaszak Holl and co-workers demonstrated that bis[bis(trimethylsilyl)methyl]germylene 98 inserts into the -CH bond of acetonitrile in the presence of THF and LiCl, MgCl2, or LiBr to yield 99 quantitatively as monitored by nuclear magnetic resonance (NMR) spectroscopy. Similar reactivity was observed for propionitrile, phenyl acetonitrile, and succinonitrile (Scheme 32). The presence of THF and specific salts was essential for the insertion reactions. For acetonitrile, no reaction occurred over the period of a week at 20 C when benzene, diethyl ether, or 1,4-dioxane were used as solvents in the absence of added salts. However, when 0.5 equiv. of THF was added to the reaction mixture in benzene, the reaction slowly proceeded to 5% completion after 3 days at 20 C. The reaction rate was dramatically affected by added salt. In THF solvent, the reaction is complete with 2 min and 20 min, respectively, if 0.2 equiv. of MgCl2 or LiCl are added <2001JA982>. It has also been found that by the reaction of germylene 98 with an excess of trans-1,2dichloroethene, cis-1,2-dichloroethene, or 1,1-dichloroethene, the [(TMS)2CH]2ClGe-functionalized ethenes 100, 102, and 104 can be obtained in quantitative yields <1996JOM(521)387>. The stereochemistry of the starting material was retained in the product, showing that these reactions proceeded stereospecifically. When 2 molar equiv. of 98 were used with 1,2-dichloroethenes, the reactions gave the double germylene insertion products 101 and 103 (Scheme 33).
224
Functions Containing at Least One Metalloid (Si, Ge, or B) TMS
TMS H
TMS Ge TMS
TMS
TMS
PhCH2CN
Ge
Ge
TMS
CN
H
TMS
MeCN
TMS
CN
TMS
TMS Ph
TMS 99
98
NC(CH2)2CN
MeCH2CN
TMS
TMS H
TMS
H
TMS
Ge TMS TMS
Ge TMS
CN CN
CN TMS Me
Scheme 32 TMS Cl
R2Ge Cl
Cl
TMS
rt Cl
Ge
TMS TMS
R2Ge
TMS TMS
Reflux
Ge
Cl
rt
Cl
Cl
TMS TMS
101
TMS R2Ge
Ge
TMS
100
Cl
TMS
TMS
TMS
Cl
Cl
TMS TMS
Ge
TMS 102
R2Ge Reflux
TMS TMS
TMS TMS Cl Cl Ge Ge TMS
TMS TMS TMS
103
TMS Cl Cl
R2Ge rt
Cl
TMS TMS
Ge
TMS 104 R = CH(TMS)2
Scheme 33
A stable digermacyclobutane 106 bearing (TMS)2CH groups at germanium atoms was obtained by the interaction of 98 with ethylene (Scheme 34). This reaction presumably runs via the germirane intermediate 105. An attempt to prepare the corresponding digermacyclobutanes by the reaction between 98 and propene or 2-butene was unsuccessful. Nevertheless, the digermacyclobutane 106 is a useful synthon for novel organogermanium compounds. For example, photolysis of 106 in carbon tetrachloride afforded 1,4-digerma-1,4-dichlorobutane 107 quantitatively, and photolysis in 2,3-dimethylbutadiene yielded 1-germacyclopent-3-ene 108 <1995OM2139>. The photolysis of 106 in a toluene solution of C60 provided the germylene and germacyclopropane adducts of C60, respectively. The former is possibly the first example of a closed [6,5]bridged derivative of germacyclopropane, while the latter is a closed [6,6]-bridged fullerene derivative of germacyclopentane <2001JOM(636)82>. Heterocyclic GeIVO species including a conjugated triene system and Si2CHGe functions have been obtained from the reaction of 98 with phenones. For example, germylene 98 reacts with benzophenone in THF at ambient temperature to produce compound 109. A number of other phenone species yield products similar to 98 and benzophenone. The reaction occurs with both weakly electron-withdrawing and releasing groups present on the rings. Moreover, the pattern of
225
Functions Containing at Least One Metalloid (Si, Ge, or B) TMS
TMS TMS
H Ge
TMS TMS
H
98
+
TMS
H
TMS TMS
TMS
H
Ge
TMS
TMS TMS Ge Ge TMS
TMS
TMS 105
106
98
TMS TMS TMS
Cl Ge
Ge Cl TMS TMS
TMS
TMS
TMS TMS CCl4
TMS TMS
106
TMS
hν
hν
Ge
TMS
–H2C=CH2 108
107
Scheme 34
reactivity of the 4,40 -dichlorobenzophenone and benzophenone imine resembles that of the benzophenone. In each case, rather than undergoing insertion, the germylene instead exclusively activates the aromatic ring, forming compounds 110 and 111 (Scheme 35) <2002OM457>.
TMS TMS
TMS TMS
PhCOPh
Ge
TMS O
Ge TMS
TMS
Ph
TMS 98
109 Cl
C O
Cl
PhC(=NH)Ph
TMS TMS
TMS Ge
TMS
NH Ph
TMS TMS
TMS Ge
O
TMS
Cl
Cl 111
110
Scheme 35
(iv) Miscellaneous The exhaustive hydroboration of the (CC)-groups in dimethyl-di-1-propynylsilane by adding Et2BH at room temperature is presumed to lead initially to the formation of a mixture of the threo- and erythro-3,3,5,6-tetrakis(diethylboryl)-4,4-dimethyl-4-silaheptanes 112. The erythro-112 reacts further by borane catalyzed intermolecular condensation to substituted disilatetraboratricyclo[6.2.16,9]dodecane 113. In contrast, the erythro-112 undergoes intramolecular, thermal elimination of Et3B to give the 1,2-diethyl-2,4-bis(diethylboryl)-3,3,5-trimethyl-3-silaborolane 114 (Scheme 36) <1995ZN(B)439>. Thermolysis of the silole 115 in a sealed evacuated tube without solvent at 175 C quickly and quantitatively resulted in the formation of the 2,4-disila-1-germatricyclo[2.1.0.02.5]pentane 116. The tricyclic skeleton of 116 incorporates the two fused three-membered ring comprising all different group 14 elements: C, Si, and Ge (Equation (10)) <2002JA9962>.
226
Functions Containing at Least One Metalloid (Si, Ge, or B) Me
Me Si
Me
SiMe2R BEt2
H Et2B
Me
+
H
Et2B
Me
Et Me
Et B
Me
–4Et3B
Si
B
Me
BH
Me
Et2B Me
B
Et H H Et Si Me Me
Et
B H
113
R = Et(Et2B)2C
–Et3B
Me Me Si H BEt2
H H
Et B Et
H Me
erythro -112
threo -112
BH
SiMe2R H
Et2B
Et
114
Scheme 36
R R Si
R
R Si 175 °C, 10 mm
Ge
H Si R
R Si Ge
Ph
R 115
Ph
R
ð10Þ
116
R = ButMe2Si
6.06.2.2
Functions Containing Metalloids and Metals
The work on functions RC(EXm)n(MLk)3n (E = Si, Ge, or B; M = metal; R = H or organyl; X = any substituent; n = 1 or 2) up to 1994 has been reviewed <1995COFGT(6)171>, and an account up to 1996 on compounds of elements of groups 11–13 containing (TMS)3C, (PhMe2Si)3C, and related ligands can be found <1996CCR125>. A review of the synthesis and reactions of compounds [(TMS)2CH]2E-E[CH(TMS)2]2 (E = Al, Ga, or In) contains much that is relevant to this chapter <1997CCR1>. Thus, this section considers in general, besides a number of fundamentals, the literature for 1997–2003.
6.06.2.2.1
Functions bearing silicon(s) and metal(s)
Synthesis of compounds of the general formula RC(SiX3)n(MLk)3n, where n = 2 or 1, is made by one of the following methods, which are mainly based on the standard synthetic procedures developed for the preparation of organometallic species: (i) metal–hydrogen exchange reactions of silylmethanes with basic metal-containing reagents; (ii) metal–halogen exchange reactions or oxidative metallation of halo(silyl)methanes; (iii) organometallic addition to vinyl silanes; (iv) synthesis via (cyclo)addition to stannaethenes; and (v) transmetallation of an already -metalated organosilanes. Most of the work in the decade 1993–2003 in this area has centered on the synthesis of specific organometallic derivatives, often with the goal of preparing new kinetically stabilized species.
227
Functions Containing at Least One Metalloid (Si, Ge, or B) (i) Metal–hydrogen exchange
In order to assess the potential utility of various possible metallating reagents, Seyferth and Lang carried out studies of the metallation of Me3SiCH2SiMe3, (Me3SiCH2)2SiMe2, (Me3Si)2CHSiMe2CH2SiMe3, and cyclo-(Me2SiCH2)3, using several strong organometallic bases such as ButLi/TMEDA, BusLi/TMEDA, BunLi/ButOK, and BunLi/ButOK/TMEDA <1991OM551>. BunLi/ButOK was found to be the most effective metallation reagent for CH2 groups in an SiCH2Si environment. The yields of monolithium derivatives in these reactions are very good, but further metallation did not occur even when a fivefold excess of the reagent was used. The bis(triethoxysilyl)methyl lithium 117 is simply prepared by treatment with t-butyllithium of the corresponding disilylmethane (Equation (11)). This compound is a very convenient starting material for a variety of common disilylmethane derivatives <1998JOM(562)79>. ButLi
Si(OEt)3
Si(OEt)3 Li
THF, –65 °C
Si(OEt)3
Si(OEt)3
ð11Þ
117
The 1,8-silanonaphthalene 118 has been used to generate uniquely the lithiodisilylmethane 120 as indicated in Scheme 37. The addition of MeLi to 118 presumably affords ring-opened 1-(8-silylnaphthyl)lithium 119, which undergoes proton migration leading to 120, a useful anion synthon <2000OM5582>.
TMS
Si
TMS
TMS
MeLi THF, rt
TMS Me Si Li
TMS
TMS
Me Si
118
Li
TMS TMS–Cl 46%
TMS
Me Si
TMS
120 119
Scheme 37
Lithiation of 2-[bis(trimethylsilyl)methyl]-6-methylpyridine with n-butyllithium yields lithiocarbanion 121, which reacts readily with chlorosilanes such as HSiCl3, MeSiCl3, Me2SiCl2, and Me3SiCl to form the corresponding hypervalent five-coordinate silicon species 122 (Scheme 38) <2000OM4437>.
Me
N
TMS
BunLi THF, 0 °C
Me
N Li
TMS
TMS TMS
121
XYZSi–Cl –78 °C
Me
N Y Si X Z
TMS TMS
122a–d a, X = H, Y = Z = Cl (79%) b, X = Me,Y = Z = Cl (72%) c, X = Y = Me, Z = Cl (94%) d, X = Y = Z = Me (78%)
Scheme 38
(ii) Metal–halogen exchange Bis(dimethylphenylsilyl)bromomethane, (Me2PhSi)2HCBr, has been reported to react with n-butyllithium in ether to give (Me2PhSi)2HCLi. The compound was isolated as solvent-free crystals and studied by multinuclear NMR and X-ray crystallography <1997OM4728>.
228
Functions Containing at Least One Metalloid (Si, Ge, or B)
By analogy with the preparation of bis(iodozincio)methane from diodomethane and zinc, the reaction of silyl-substituted dibromomethanes, RMe2SiCHBr2 (R = Me, Ph, p-MeOC6H4), with zinc dust in the presence of a catalytic amount of lead in THF provides route to silyl-substituted bis(bromozincio)methanes, RMe2CH(ZnBr)2 (72–80% yield) <1998SL1315>. Yet another example of the diversity of the original reagents, which may be used to synthesize lithiodisilylmethanes by metal–halogen reactions is the interaction of polysilacyclohexanes containing pseudohalogen (PhS) groups with lithio radical anion (see Schemes 14 and 16) <2000JOM(611)12>.
(iii) Organometallic addition to vinyl silanes The reactivity of 1,1-bis(trimethylsilyl)ethane 123 toward lithium metal has been re-investigated by Maercker and co-workers <1998EJO1455>. In THF, the exclusive formation of the product of reductive dimerization 124 was observed. When hexane or diethyl ether was used as solvent, an almost quantitative yield of a 1:1 mixture of the two lithio derivatives 124 and 126 was isolated. Lithium hydride elimination from the 1,4-dilithioalkane 124 can be ruled out since mixtures of 124 and 126, once synthesized, were found to be stable. Presumably, 123 adds to 125, which may be generated as a by-product, with formation of 126. In contrast to 123, 1,1-bis(trimethylsilyl)3,3-dimethyl-1-butene 127a reacted with lithium metal to give the 1,1-bis(trimethylsilyl)-1,2-dilithioalkane 128a, which shows no tendency to form a dimer product. The general reaction pathway was the same when the t-butyl group at the -position was replaced with a phenyl group (Scheme 39). TMS
2Li THF
TMS
Li TMS TMS
Li
123
2Li –LiH
124
–LiH
Hexane or Et2O
TMS
123
Li TMS
Li
TMS
TMS TMS
TMS
125
126
TMS TMS
TMS TMS
2Li R
THF
TMS TMS Li
127a
R Li
128a
127b
128b R = But (a), Ph (b)
Scheme 39
(iv) Synthesis via (cyclo)addition to stannaethenes The scope of these reactions, being investigated mainly by Wiberg and co-workers, has not yet been well delineated. Even so, the following useful procedures have been developed. Lithium organils (RLi) act as very active trapping reagents for Me2Sn = C(TMS)2 with formation of the adducts Me2Sn(R)-C(Li)(TMS)2. The insertion reactivity of RLi decreases when the bulkiness of R increases (decreasing reactivity in the order MeLi>BunLi>PhLi>ButLi; MeLi>(TMS)2CHLi>(TMS)3CLi). The influence of electronic effects is obviously smaller than
229
Functions Containing at Least One Metalloid (Si, Ge, or B)
those of steric effects (decreasing reactivity in the order (TMS)2(Me2ClSi)CLi>(TMS)2(Me2BrSi)CLi>(TMS)3CLi) <2000JOM(598)292>. Reactions of the stannaethene 129 with butadiene and propene as well as their methyl and phenyl derivatives afford Diels–Alder adducts and ene products containing an SnC(TMS)2 unit (Scheme 40). The reactions are accelerated by an increasing tendency of substituents in butadiene or propene to donate electrons and retarded by increasing bulkiness of substituents in 1,4- or 1,3positions. It is concluded that Diels–Alder and ene reactions of 129 occur in a concerted way and are orbital controlled <1998CEJ2571, 2000CJC1412>. Me TMS Me Sn TMS
100 °C, 2 days
Me Sn Me
Me TMS Me Sn TMS
TMS 100 °C, 3 days
TMS
129 Me TMS Me Sn TMS
100 °C, 2 days
Me TMS Sn Me TMS
+ 84:16
Scheme 40
(v) Transmetallation reactions A convenient route to bis(trimethylsilyl)methyl-substituted organoaluminum compounds is via transmetallation reactions starting from [(TMS)2CH]2Zn and aluminum halides. For example, compound 130 was prepared in high yield from the reaction depicted in Scheme 41. Compound 130 was reacted with Na/K alloy, which results immediately in the formation of organoalanes 131 and 132 due to a disproportion reaction <2001MI225>.
TMS
TMS +
Zn TMS
TMS Cl Cl Al Al Cl Cl TMS TMS
TMS 2AlCl3 Hexane, rt, 48 h
TMS
72%
130
Na /K
TMS TMS
TMS Al
TMS
TMS TMS 131
TMS + Cl
TMS Al Cl Cl
K +
Al
132
Scheme 41
The alkyl transferring properties of [(TMS)2CH]2Zn toward transition metal halides have also been studied. The monosubstituted tantalum halides, (TMS)2CHTaX4 (X = Cl, Br), were prepared by the reaction of TaX5 with [(TMS)2CH]2Zn in hexane <1999OM832>. Compounds
230
Functions Containing at Least One Metalloid (Si, Ge, or B)
(TMS)2CHTiCl3, (TMS)2CHNbCl4, and (TMS)2CHNbBr4 have been isolated, respectively, from reacting TiCl4, NbCl5, and NbBr5. In addition, the fluoride derivative (TMS)2CHNbF4 was prepared via chlorine–fluorine metathesis employing Me3SnF as a fluorinating reagent. The crystal structure of (TMS)2CHNbCl4 was determined by single-crystal X-ray diffraction <2001JOM(621)310>. The first bis(trimethylsilyl)methyl-substituted organogallium compound containing a GaGa single bond, 133, was synthesized by Uhl and co-workers according to Scheme 42 <1989JOM(364)289>. Remarkably, this compound reacted with tropolone by replacement of two (TMS)2CH groups and retention of its GaGa single bond <2002ZN(B)141>. As a starting compound for the synthesis of an alkylgallium-bridged [1,1]-ferrocenophane 135 Uhl and co-workers employed the trichloroalkylgallate 134, which is easily available by the reaction of GaCl3 with (TMS)2CHLi in THF (Scheme 43). Treatment of the adduct 134 with 1,10 -dilithioferrocene in hexane afforded the orange-red compound 135 in 47% yield <2001JOM(637/639)300>.
TMS
Li Ga2Br4.2 diox +
TMS
TMS O TMS O TMS TMS OH O Ga Ga O Ga Ga TMS TMS Pentane, –70 °C TMS O TMS 83% TMS TMS TMS
TMS
133
Scheme 42
GaCl3
+
(TMS)2CHLi
THF/Et2O, –10 °C 62%
[Cl3Ga-CH(TMS)2] [Li(THF)] 134
Fe[CpLi(TMEDA)]2 THF, –80 °C
TMS
TMS Ga Fe
Fe Ga TMS
TMS 135
Scheme 43
The transmetallation of the bridged ditin compound 136 with (TMS)2CHLi afforded a new organotin derivative 137, which was converted into its tetrachloro derivative 138 by stepwise reaction with Me2SnCl2 and SnCl4 (Scheme 44) <1998OM4096>. Along with this, the di- and trimethylene-bridged ditin compounds, 140 and 141, were prepared by reaction of 139 with (TMS)2CHLi followed by treatment with mercuric chloride (Scheme 45) <1998OM4096>. The synthetic potential of lithium bis(trimethylsilyl)methanide in transmetallation reactions is also illustrated by the synthesis of electron-deficient monocyclopentadienylvanadium(III) dialkyl 142 <1993OM2268> and vanadium(III) hydrocarbyl 143 <1999JCS(D)3345> (Equations (12) and (13)). These results provide a further demonstration that the bulky (TMS)2CH ligand may stabilize unusual metal complexes.
231
Functions Containing at Least One Metalloid (Si, Ge, or B) Me Me Me Cl Sn Sn Cl Me Me Me
Me Me TMS TMS Me 2Me2SnCl2 Sn Sn 110–120 °C, 30 h TMS Me Me Me TMS
2(TMS)2CHLi Pentane, 20 °C 82%
136
TMS TMS
137 Cl Me Cl TMS Sn Sn Me Me Me TMS
SnCl4
TMS
60–70 °C, 12 h
TMS
Cl Me Cl Sn Sn Cl Me Cl
TMS TMS
74% 138
Scheme 44
TMS
TMS F
TMS
TMS SnPh2
X SnPh2
SnPh2
2(TMS)2CHLi Pentane, 20 °C
F
SnCl2
4HgCl2
X
X
73–87%
SnPh2
SnCl2 TMS
TMS
TMS
TMS
139
141
140 X = (CH2)n; n = 2 or 3
Scheme 45
CpVCl2(PMe3)2
+
TMS
2 (TMS)2CHLi Et2O, 0 °C 90%
TMS
TMS TMS N Li N Cl N V V + 2 TMS TMS N Cl N N TMS TMS TMS
V
ð12Þ
TMS TMS 142
TMS Toluene, –78 °C 60%
TMS
TMS N TMS N V N TMS TMS
ð13Þ
143
Neutral alkyl derivative lanthanides, stabilized by bis(trimethylsilyl)groups, are, of course, known and interpretation of their stability in terms of steric protection appears to be generally accepted <1994CC2691, 1995JCS(D)3933>. Alkyl lanthanide complexes are the precursors of organolanthanide hydrides by hydrogenolysis of the lanthanidecarbon -bond. Bis(trimethylsilyl)methyl lanthanides are especially often used because they are usually hydrocarbon-soluble unsolvated species that can be straightforwardly obtained by reaction of organolanthanide halides with (TMS)2CHLi. The synthesis of 146 and 147 illustrates this. The crude products from the reaction of [LnCl3(THF)x] (Ln = Nd, Sm) with 2,3,4,5-tetramethylphospholylpotassium, 144 and 145, reacted smoothly with (TMS)2CHLi to give bis(trimethylsilyl)methyl derivatives 146 and 147 in fair-to-good yields (Scheme 46). [(C4Me4P)2LaCH(TMS)2] was also obtained by the same procedure, but the yields were very low and inconsistent <1999EJI1041>. Lanthanide metallocene cation [(C5Me5)2Sm][BPh4], which may be prepared from (C5Me5)2Sm and AgBPh4, reacts with (TMS)2CHLi in benzene to produce (C5Me5)2SmCH(TMS)2 in over 96% yield. [(C5Me5)2Nd][BPh4] similarly reacts with (TMS)2CHLi to produce (C5Me5)2NdCH(TMS)2 in quantitative yield <1998JA6745>.
232
Functions Containing at Least One Metalloid (Si, Ge, or B)
[LnCl3(THF)x]
2C4Me4PK
[(C4Me4P)2LnCl2K]
THF/Et2O
(TMS)2CHLi 53–67%
P Ln P
TMS TMS
144, Ln = Sm
146, Ln = Sm
145, Ln = Nd
147, Ln = Nd
Scheme 46
6.06.2.2.2
Functions bearing boron(s) and metal(s)
Important methods for the preparation of polyheteroatom species of the general formula RC(BX2)n(MLm)3n, where n = 1 or 2, M is metal, and R = H, alkyl, or aryl, along with some representatives examples, are summarized in Scheme 47. These comprise reactions: (i) via metal– hydrogen exchange (deprotonation of diorganoboranes and related compounds); (ii) via transmetallation; (iii) via cleavage of 1,1-diboryl- and 1,1,1-triboryl compounds; and (iv) via addition to vinyl boranes and methyleneboranes. During the years from the publication of chapter 6.06, COFGT (1995) to the end of 2003, little further effort was given to expanding this chemistry. Readers are referred to the reference <1995COFGT(6)171> and review <1991COS(1)487> for more detailed information concerning synthetic potential of the mentioned methods. A unique method for the synthesis of compounds containing a BSn2C function utilizes the reaction of the bicyclic N-pyrrolylborane 148 with bis(trimethylstannyl)ethyne <1997JOM(545/546)297>. The interaction of 148 with 2 equiv. of Me3SnCCSnMe3 proceeds selectively to give 149, in which the five-membered ring in 148 has been extended by two carbon atoms (Scheme 48).
6.06.2.2.3
Functions bearing germanium(s) and metal(s)
In contrast to the numerous reactions involving metallation of CH2 groups in an SiCH2Si environment, the metal–hydrogen exchange reactions have met with very limited success when applied to the corresponding germyl analogs <1995COFGT(6)171>. The metal–halogen exchange reactions seem to be less limited than the direct metallation of organogermanes. Thus, Wiberg and co-workers have described an efficient route to lithium bis(trimethylgermyl)methide 151 starting from bromoform (Scheme 49). This approach permits access to bis(trimethylgermyl)bromomethane 150, which is difficult to obtain by other methods and produces salt-free reagent 151 in good yield. The ease with which the latter is prepared makes it a particularly attractive starting material for a variety of organic and inorganic applications. The reactivity of 151 appears roughly comparable to that of (TMS)2CHLi <1996JOM(511)239>. Triethylgermyl-substituted bis(bromozincio)methane, Et3GeCH(ZnBr)2, has been prepared from the corresponding dibromide by Pb-catalyzed reaction with zinc dust in THF (30–40% yield) <2000SL495>.
6.06.2.2.4
Functions bearing mixed metalloid(s) and metal(s)
Very few species with this special ligand arrangement around the carbon atom have been reported up to the end of 2003. In practice, they can be prepared by multiple-step procedures involving reactions described in Sections 6.06.2.2.1–6.06.2.2.3. In particular, if mixed compounds such as XnE1CH2E2Ym or XnE1CH(Hal)E2Ym are available then metal–hydrogen or metal–halogen exchange reactions seem to be the most practical route to metallated derivatives. Another attractive and potentially general route to functions with mixed metalloid(s) and metal(s) is provided by the reactions of heteroalkenes with organometallics. Some examples taken from the literature are illustrated by Equations (14)–(17).
233
Functions Containing at Least One Metalloid (Si, Ge, or B) Approaches to Forming Stable RC(BX2)n(MLm)3–n Species Via metal–hydrogen exchange
Mes2B
BMes2
K
KH THF
Mes2B
BMes2
<1982JCR(S)132>
Via transmetallation reaction Li B O O
O B O
PbPh3
Ph3PbCl
B O O
O B O
THF/ether
<1976JOM(110)25
Via cleavage of 1,1-diboryl- or 1,1,1-triboryl compounds
SnPh3 B O O
O B O
SnPh3
MeLi O B O
THF, –78 °C
Li
<1976JOM(110)25>
O
B
O B O O
O B O
Li
MeLi
B O O
O B O
THF, –70 °C <1973JA5096>
Via addition to vinylboranes and methyleneboranes But
But TMS
Cl
TMS
Cl
TMS TMS K
K /Na THF
But
But K
<1985AG(E)788>
Mes
Mes Li+ C B TMS TMS
2ButLi
Mes
Mes 2Li+ B C B t t Bu Bu –
–
<1988AG(E)1370>
Scheme 47
Li CpH
But
But B B Mes Mes
234
Functions Containing at Least One Metalloid (Si, Ge, or B) Me3SnC SnMe3 N B
Me3SnC SnMe3
C6D6, rt
B
Et
Et
Me3Sn
148
SnMe3
B
Et Me3Sn
B Et Me3Sn
SnMe3 SnMe3 SnMe3
SnMe3
SnMe3
Me3Sn 149
Scheme 48
Br Br
Br
Me3GeCl, 2BunLi Br
THF, –78 °C 85%
Me3Ge
Li
BunLi GeMe3
Et2O, –78 °C
Me3Ge
150
GeMe3 151
Scheme 49
Li But Si But H
But Si But H
MeLi THF
GeMe3
GeMe3
ð14Þ
<1996JOM(511)239> Li TMS
B O
LiTMP THF
O
TMS
B O
O
ð15Þ
<1983OM230, 1991COS(1)487>
Li+
– B Me
TMS
Me3SnCl
SnMe3 B TMS Me
Pentane, rt
+
Me3Sn
B Me
TMS
ð16Þ
<1997OM926> BMes2 TMS
RM
R
M BMes2 TMS
ð17Þ R = Bun, But, Ph, (R1S)2CH, ButO2CCH2, CH2=CH(CH2)4, Bu2nCu(CN) <1987JA931, 1991COS(1)487>
235
Functions Containing at Least One Metalloid (Si, Ge, or B) 6.06.3
FUNCTIONS CONTAINING THREE METALS
In contrast to sp2- <2000CRV2887> and sp3-1,1-bismetallic derivatives <1996CRV3241>, which have been intensively studied in the late 1990s and early 2000s, the chemistry of functions RC(MLk)(M1Ll) (M2Lm) (M, M1, M2 = metal) featuring three -bonds between carbon and metal atoms is in its infancy. Although several structural types of sp3-geminated trismetallics are known, information about these compounds remains sparse. Little further effort has been given to expanding this chemistry since the publication of COFGT (1995). This chapter therefore presents an illustrative summary of the methods used for the preparation of 1,1,1-trismetallic derivatives. Methods for preparing specific types of compounds were discussed previously <1995COFGT(6)171>.
6.06.3.1
Three Similar Metals
Isolable compounds of the type RC(MLm)3 (M = metal) are known with M = Li, Hg, Al, Sn, and Pb. Table 1 outlines the synthetic approaches to these species with an example from each major method. The limits of the methods have certainly not been fully explored and, up to the end of 2003, comparatively little has been published on work devoted to the use of trimetallomethanes as reagents for organic synthesis.
Table 1 Preparation of organometallic species of the type RC(MLm)3
Method From halides: 1
2
From active C–H compounds: 3 4 From unsaturated compounds: 5
From organometallics: 6 7 8
Description Reductive metallation with lithium vapor Reductive displacement of halogen by metallate anions Lithium–hydrogen exchange Electrophilic mercuration Hydrometallation (M = Al, Sn)
Oxidative–reductive transmetallation Boron–mercury exchange Pyrolysis reactions
General equation
Preparation equation number
RCX3 + 6Li ! RCLi3 + 3LiX
(18)
RCX3 + 3ML m ! 3RC(MLm)3 +3X
(19)
FG-RCH3 + 3MR1 ! FG-RCLi3 +3R1H
(20)
FG-RCH3 + HgX2 ! FG-RC(HgX)3 + 3HX
(21)
+ 3MH
M M M
(22), (23)
RCM3 + 3M1 ! RCM13 + 3M
(24)
RC(BX2)3 + 3HgY2 ! RC(HgY)3 +3BX2Y
(25)
CHnLi4n ! CHLi3 + (n = 0–3)
(26)
The following tentative generalizations may be useful. (i) Direct halogen–metal exchange in polyhaloalkanes by treatment with reactive metal, such as Li or Mg, is only of limited value for the preparation of polymetalated methanes due to -elimination of metal halide after the first step being faster than the halogen–metal exchange. However, these difficulties can be overcome by high-temperature reaction of polyhaloalkanes with
236
Functions Containing at Least One Metalloid (Si, Ge, or B)
metal vapor (the Lagow procedure). This technique is especially suited for the preparation of organometallics of readily ionizable metals (Equation (18)).
Cl
Li
Li
Cl Cl
+ 6Li(g)
750 °C
Li
+
Li
Li
Li
+ Li
Li Li
Li 40%
16%
Li
+ 19%
ð18Þ
20%
<1983JOM(249)1>
(ii) The coupling reactions between chloroform and organostannyl- and organoplumbylmetallic compounds of the type R3MLi is the valuable route to the corresponding trimetallomethanes (Equation (19)). It is known that the metallate anions containing transition metals are among the strongest nucleophiles known to chemists. However, the synthetic potential of reactions between polyhaloalkanes and metallate anions of transition metals is not clear.
Cl Cl
PbPh3
Ph3PbLi Cl
THF, –60 °C 91%
Ph3Pb
PbPh3
ð19Þ
<1985CB380>
(iii) Much more easily accessible than the 1,1,1-trilithioalkanes are certain perlithioalkynes, for example perlithiopropyne (C3Li4), since alkyllithium reagents can abstract quantitatively not only the hydrogen atoms on sp-hybridized carbon atom, but also those of the adjacent methyl group (Equation (20)). Unlike alkynes, linear and branched alkenes upon treatment with organolithium reagents form only mono- and dilithiated derivatives. Typical saturated hydrocarbons are not acidic enough to form the polylithiated species by metal–hydrogen exchange with basic reagents. 4BunLi Hexane 75%
Li Li Li
Li
ð20Þ
<1984AG(E)995>
(iv) Metal–hydrogen exchange with Lewis acidic reagents, such as Hg(OAc)2, represents one of the most direct and convenient routes to 1,1,1-trimercurioalkane derivatives (Equation (21)). The method tends to fail, however, in cases where the CH bonds are not sufficiently acidic. Hg(OAc)2
MeCN
150 °C, 20 h
NC
HgOAc HgOAc HgOAc
93%
ð21Þ
<1974JPR557>
(v) The best way to 1,1,1-trialuminioalkanes involves bishydroalumination of alkynylalanes derived from the reaction of alkali metal acetylides with dialkylaluminum chlorides (Equation (22)).
Bun
2Et2AlH AlEt2
70 °C <1963BSF1462>
Bun
AlEt2 AlEt2 AlEt2
ð22Þ
237
Functions Containing at Least One Metalloid (Si, Ge, or B)
(vi) Transmetallation reactions with other elements of the periodic table for example boron/ mercury exchange (Equation (23)) can also be used for the synthesis of sp3 geminated trismetallics but the limits of the method have not been fully explored. B(OMe)2 (MeO)2B
HgCl
3HgCl2
B(OMe)2
ClHg
THF, rt 62%
HgCl
ð23Þ
<1983JOM(243)245>
(vii) A general route to 1,1,1-tristannylalkanes involves the hydrostannation of 1,1-distannyl1-alkenes (Equation (24)).
R
SnMe3
Me3SnH
SnMe3
52–80%
SnMe3 SnMe3 SnMe3
R
ð24Þ
R = Me, Bun, Ph, PhCH2, MeOCH2, PhOCH2, PhO <1985OM1044>
(viii) In practice, mercury–lithium exchange reactions represent one of the most effective routes to the trilithiomethanes (Equation (25)). Reactions using tin–lithium exchange would be even better than mercury–lithium exchange, but tris(trimethylstannyl)methanes are not easily available. HgCl ClHg
Li
Li THF, 20 °C
HgCl
Li
ð25Þ
Li
<1982MI47>
(ix) As a preparative method to be used in practical organic synthesis, pyrolysis reactions do not yet provide advantages over conventional methods. It shows high promise, however, as a method for preparing otherwise inaccessible species (Equation (26)). 225 °C CLi4
CLi4
8 min
20%
+
C3Li4
+
40%
C2Li4 30%
+
C2Li2
ð26Þ
10%
<1985JA5313>
6.06.3.2
Three Dissimilar Metals
A few of the compounds of the general formula HC(MLk)2(M1Lm) have been prepared by metallation or transmetallation reactions and examples are described in COFGT (1995) <1995COFGT(6)171>. The readily available trismetallics 152–155 <1983IZV636, 1980TCC109> may prove useful in the synthesis of other compounds having three dissimilar metals bonded to the same carbon; however, the synthetic potential of these species in transmetallation reactions remains unexplored. Li Ph3Sn
SnPh3 152
SnMe3
Li Ph3Pb
PbPh3 153
Ph3Pb
AlEt2 AlEt2 AlEt2
PbPh3 154
155
238
Functions Containing at Least One Metalloid (Si, Ge, or B)
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Functions Containing at Least One Metalloid (Si, Ge, or B) Biographical sketch
Vadim D. Romanenko was born in Lugansk, Ukraine, in 1946. He studied at the Institute of Chemical Technology, Dnepropetrovsk, Ukraine and received his Ph.D. degree there under the direction of Professor S. I. Burmistrov. Since 1975 he has been working at the National Academy of Sciences of Ukraine from which he earned his Doctor of Chemistry degree in 1988. He became a full professor in 1991. He has been a visiting scientist at the Centre of Molecular and Macromolecular Studies, Lodz, Poland, the Shanghai Institute of Organic Chemistry, China, the University of Pau & des Pays de l’Adour, France, the University Paul Sabatier, Toulouse, France, the University California Riverside, USA. His research interests include a wide range of topics at the border between organic and inorganic chemistry, in particular the chemistry of multiple bonded heavy main group elements. He is the author of approximately 260 papers on organoelement chemistry. He is also author of numerous reviews and two monographs on low-coordinated phosphorus compounds.
Valentyn Rudzevich was born in Kazatin, Ukraine, in 1968. He received his Diploma degree in 1992 from Taras Shevchenko Kiev State University, Ukraine. Since 1992 he has been working at the Institute of Organic Chemistry of National Academy of Science of Ukraine, from which he received his Ph.D. degree under the supervision of Professor V. D. Romanenko in 1997. Afterwards, he carried out postdoctoral studies at the Universite´ Paul Sabatier, Toulouse, France, University of California Riverside, USA and the Johannes Gutenberg University, Germany. On his return to Kiev, he joined the Institute of Organic Chemistry where he is presently a Scientist Researcher. His research interests are focused on organoelement compounds, short-lived intermediates, and coordination chemistry.
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Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 205–242
6.07 Functions Containing Four Halogens or Three Halogens and One Other Heteroatom Substituent A. SENNING and J. Ø. MADSEN Technical University of Denmark, Kgs. Lyngby, Denmark 6.07.1 TETRAHALOMETHANES, C(Hal)4 6.07.1.1 Four Similar Halogens 6.07.1.1.1 Tetrafluoromethane 6.07.1.1.2 Tetrachloromethane 6.07.1.1.3 Tetrabromomethane 6.07.1.1.4 Tetraiodomethane 6.07.1.2 Three Similar Halogens and One Different Halogen 6.07.1.2.1 Trifluoromethyl halides 6.07.1.2.2 Trichloromethyl halides 6.07.1.2.3 Tribromomethyl halides 6.07.1.2.4 Triiodomethyl halides 6.07.1.3 Two Similar Halogens 6.07.1.3.1 Difluoromethylene dihalides 6.07.1.3.2 Dichloromethylene dihalides 6.07.1.3.3 Dibromomethylene dihalides 6.07.1.3.4 Diiodomethylene dihalides 6.07.1.4 Bromochlorofluoroiodomethane 6.07.2 METHANES BEARING THREE HALOGENS 6.07.2.1 Three Halogens and a Chalcogen 6.07.2.1.1 Three halogens and an oxygen function 6.07.2.1.2 Three halogens and a sulfur function 6.07.2.1.3 Three halogens and an Se or Te function 6.07.2.2 Three Halogens and a Group 15 Element 6.07.2.2.1 Three halogens and a nitrogen function 6.07.2.2.2 Three halogens and a phosphorus function 6.07.2.2.3 Three halogens and an As, Sb, or Bi function 6.07.2.3 Three Halogens and a Metalloid 6.07.2.3.1 Three halogens and a silicon function 6.07.2.3.2 Three halogens and a boron function 6.07.2.3.3 Three halogens and a germanium function 6.07.2.4 Three Halogens and a Metal Function 6.07.2.4.1 Trihalomethyl alkali and earth alkali metals, CHal3M (M = Li, Na, K, Cs, Mg) 6.07.2.4.2 (Trihalomethyl)aluminum, -gallium, -indium, and -thallium compounds, CHal3MRn (M = Al, Ga, In, Tl) 6.07.2.4.3 (Trihalomethyl)tin and -lead compounds, CHal3MRn (M = Sn(II), Sn(IV), Pb(IV)) 6.07.2.4.4 (Trihalomethyl)zinc, -cadmium, and -mercury compounds, CHal3MR (M = Zn, Cd,Hg(II)) 6.07.2.4.5 (Trihalomethyl)copper, -silver, and -gold compounds, CHal3MRn (M = Cu(I), Cu(III), Ag(I), Ag(III), Au(I), Au(III)) 6.07.2.4.6 Miscellaneous trihalomethyl transition metal compounds, CHal3MRn (M = transition metal)
243
244 244 244 244 244 244 244 244 245 245 246 246 246 246 247 247 248 248 248 248 251 257 258 258 260 261 261 261 262 262 263 263 263 263 263 264 264
244 6.07.1
Functions Containing Four Halogens or Three Halogens TETRAHALOMETHANES, C(Hal)4
6.07.1.1
Four Similar Halogens
All four compounds CF4, CCl4, CBr4, and CI4 are commercially available.
6.07.1.1.1
Tetrafluoromethane
Two Russian patents deal with the industrial preparation of CF4 by fluorination of activated carbon <2002RUP2181351> and of trifluoromethane <2002RUP2181352> with F2. According to a US patent, CF4 can be prepared by vapor-phase chlorofluorination of methane with Cl2 and HF in the presence of a catalyst such as CrO3 <1995USP5446218>. A similar process (fixed-bed reactor, reaction temperature 449 C) with trichloromethane as the starting material yields CF4 with 99.8% conversion and 29.1% selectivity <1997JAP09020695>.
6.07.1.1.2
Tetrachloromethane
The formation of CCl4 by chlorination of methane with Cl2 is catalyzed by nanocrystalline MgO or nanocrystalline CaO <2000JA5587>.
6.07.1.1.3
Tetrabromomethane
No further advances have occurred in this area since the publication of chapter 6.07.1.1.3 in <1995COFGT(6)211>.
6.07.1.1.4
Tetraiodomethane
No further advances have occurred in this area since the publication of chapter 6.07.1.1.4 in <1995COFGT(6)211>.
6.07.1.2 6.07.1.2.1
Three Similar Halogens and One Different Halogen Trifluoromethyl halides
(i) Chlorotrifluoromethane According to a US patent, the commercially available CClF3 is one of the products of the vaporphase chlorofluorination of methane with Cl2 and HF in the presence of a catalyst such as CrO3 <1995USP5446218>.
(ii) Bromotrifluoromethane The boiling point of CBrF3 is 59.0 C <2001MI897>. An industrial high-temperature process for the preparation of CBrF3 involves the treatment of CHF3 with Br2 in the presence of Cl2 <1995SUP1381923>. Bromotrifluoromethane, commercially known as Halon 1301, is being phased out as a consequence of the Montreal Protocol <1995MI8>.
Functions Containing Four Halogens or Three Halogens
245
(iii) Trifluoroiodomethane This compound is commercially available. A method for the preparation of CF3I is based on the treatment of solvated (trifluoromethyl)zinc bromide CF3ZnBr with ICl. The yield is 70% and complications with the onus of heavy metal containing wastes, typical of earlier methods, is also avoided <1994JFC(67)91>. A patented procedure for the preparation of CF3I calls for the interaction of pentafluoroethane with I2 in the presence of alkali metal or earth alkali metal salts <2000FRP2794456>. A flow reactor process carried out at 400 C in the presence of CuI converts a 1:1 iodine–trifluoroacetic acid mixture to CF3I <2001MI144>.
6.07.1.2.2
Trichloromethyl halides
(i) Trichlorofluoromethane This compound is commercially available. The fluorination of tetrachloromethane with HF in the presence of NH4AlF4 and -Al2O3 in a high-temperature reactor yields CCl3F as the main product <1990GE(E)P278473>. The cited patent is the latest in a series of closely related patents. Both trichloromethane and tetrachloromethane react slowly with XeF2 to form, inter alia, CCl3F <1993JFC(62)293>.
(ii) Bromotrichloromethane This compound is commercially available. It can be prepared with 45% yield from CHCl3 and CBr2F2 in the presence of Bu4NHSO4 and KOH <1998PLP173916>. The air labile cubic fullerene solvate C6012CBrCl3 and the air stable hexagonal solvate C6012CBrCl3 have been prepared as potential superconductors <2003CM288>.
(iii) Trichloroiodomethane No further advances have occurred in this area since the publication of chapter 6.07.1.2.2 in <1995COFGT(6)211>.
6.07.1.2.3
Tribromomethyl halides
(i) Tribromofluoromethane This compound is commercially available. No further advances have occurred in this area since the publication of chapter 6.07.1.2.3 in <1995COFGT(6)211>.
(ii) Tribromochloromethane A 43% yield of the commercially available CBr3Cl is obtained in the reaction of CBr2F2 with CHBr2Cl in the presence of benzyltriethylammonium chloride and KOH <1998PLP173916>.
(iii) Tribromoiodomethane No further advances have occurred in this area since the publication of chapter 6.07.1.2.3 in <1995COFGT(6)211>.
246 6.07.1.2.4
Functions Containing Four Halogens or Three Halogens Triiodomethyl halides
(i) Fluorotriiodomethane No further advances have occurred in this area since the publication of chapter 6.07.1.2.4 in <1995COFGT(6)211>.
(ii) Chlorotriiodomethane No further advances have occurred in this area since the publication of chapter 6.07.1.2.4 in <1995COFGT(6)211>.
(iii) Bromotriiodomethane No further advances have occurred in this area since the publication of chapter 6.07.1.2.4 in <1995COFGT(6)211>.
6.07.1.3 6.07.1.3.1
Two Similar Halogens Difluoromethylene dihalides
(i) Bromochlorodifluoromethane No further advances have occurred in this area since the publication of chapter 6.07.1.3.1 in <1995COFGT(6)211>. Bromochlorodifluoromethane, formerly commercially available as Halon 1211, is being phased out as a consequence of the Montreal Protocol <1995MI8>.
(ii) Chlorodifluoroiodomethane A 9% yield of CClF2I (b.p. 31–34 C) is obtained (in admixture with other products) in the nickel catalyzed high-temperature reaction of commercially avavailable 2,2,3-trifluoro-3-(trifluoromethyl)oxirane (a convenient source of CF2 by thermally induced loss of (CF3)2C(¼O)) with ICl <1996JA8140>.
(iii) Bromodifluoroiodomethane A 9% yield of CBrF2I is obtained in the nickel catalyzed high-temperature reaction of 2,2,3trifluoro-3-(trifluoromethyl)oxirane with IBr <1996JA8140>.
6.07.1.3.2
Dichloromethylene dihalides
(i) Dichlorodifluoromethane Dichlorodifluoromethane (b.p. 28.0 C, <2001MI897>) is one of the minor products of the nickel catalyzed high-temperature reaction of 2,2,3-trifluoro-3-(trifluoromethyl)oxirane with ICl <1996JA8140>. Both CHCl3 and CCl4 react with XeF2 to form CCl2F2 <1993JFC(62)293>. The reaction of CCl4 with HF in the presence of an NH4AlF4 catalyst yields CCl2F2 as the minor product with CCl3F as the major product <1990GE(E)P278473>. The cited patent is the latest in a series of closely related patents.
Functions Containing Four Halogens or Three Halogens
247
(ii) Bromodichlorofluoromethane The b.p. of CBrCl2F is 52.5 C <2001MI897>. No synthetic advances have occurred in this area since the publication of chapter 6.07.1.3.1 in <1995COFGT(6)211>.
(iii) Dichlorofluoroiodomethane Dichlorofluoroiodomethane can be obtained by reaction of (dichlorofluoromethyl)tris(dimethylamino)phosphonium chloride [(Me2N)3P(CCl2F)]Cl with I2 or ICl <1982JFC(20)89>.
(iv) Bromodichloroiodomethane No further advances have occurred in this area since the publication of chapter 6.07.1.3.2 in <1995COFGT(6)211>.
6.07.1.3.3
Dibromomethylene dihalides
(i) Dibromodifluoromethane This compound is commercially available. A 68% yield of CBr2F2 (b.p. 25.0 C <2001MI897>) is obtained in the nickel catalyzed high-temperature reaction of 2,2,3-trifluoro-3-(trifluoromethyl)oxirane with Br2 <1996JA8140>. Dibromomethane reacts with XeF2 to form CBr2F2 <1993JFC(62)293>.
(ii) Dibromodichloromethane This compound is commercially available. A 51% yield of CBr2Cl2 is obtained in the reaction of CHBrCl2 with CBr2F2 in the presence of Bu4NBr and NaOH <1998PLP173916>.
(iii) Dibromochlorofluoromethane This compound is commercially available. No further advances have occurred in this area since the publication of chapter 6.07.1.3.3 in <1995COFGT(6)211>.
(iv) Dibromofluoroiodomethane No further advances have occurred in this area since the publication of chapter 6.07.1.3.3 in <1995COFGT(6)211>.
(v) Dibromochloroiodomethane No further advances have occurred in this area since the publication of chapter 6.07.1.3.3 in <1995COFGT(6)211>.
6.07.1.3.4
Diiodomethylene dihalides
(i) Difluorodiiodomethane Up to 78% yield of the commercially available CF2I2 is obtained in the nickel catalyzed high temperature reaction of 2,2,3-trifluoro-3-(trifluoromethyl)oxirane with I2, IBr, or ICl, respectively <1996JA8140>.
248
Functions Containing Four Halogens or Three Halogens
(ii) Dichlorodiiodomethane No further advances have occurred in this area since the publication of chapter 6.07.1.3.4 in <1995COFGT(6)211>.
(iii) Bromofluorodiiodomethane No further advances have occurred in this area since the publication of chapter 6.07.1.3.4 in <1995COFGT(6)211>.
(iv) Dibromodiiodomethane This compound is still unknown.
(v) Chlorofluorodiiodomethane This compound is still unknown.
(vi) Bromochlorodiiodomethane This compound is still unknown.
6.07.1.4
Bromochlorofluoroiodomethane
Both the racemic compound and the two enantiomers of bromochlorofluoroiodomethane CBrClFI have been considered in theoretical work <2000MI3811>, but no syntheses have been reported so far.
6.07.2
METHANES BEARING THREE HALOGENS
6.07.2.1 6.07.2.1.1
Three Halogens and a Chalcogen Three halogens and an oxygen function
(i) Trihalomethanols, CHal3OH (a) Trifluoromethanol. No new preparative procedures for CF3OH have become known. In an ion flow tube study, it was shown that CF3OH is formed from (trifluoromethyl)sulfur pentafluoride CF3SF5 and hydroxide anions <2003MI(223-224)403>. In the environment CF3OH appears to be formed in the upper atmosphere from trifluoromethoxy radicals and ambient hydrogen donors <2001CPL(345)435>. (b) Trichloromethanol. UV irradiation of methanolchlorinenitrogen gas mixtures generates, inter alia, CCl3OH, which again decomposes to C(¼O)Cl2 and HCl <2000CPL(322)97>. (c) Tribromomethanol. The acidity of the unknown CBr3OH has been investigated by quantum chemical methods <1995JPC12151>. All other CAS references to CBr3OH appear to be in error due to confusion with 2,2,2-tribromoethanol. (d) Dichlorofluoromethanol. Transient CCl2FOH is formed by insertion of 1D oxygen atoms into the CH bond of CHCl2F <1972JPC1425>. (e) Chlorodifluoromethanol. Transient CClF2OH is formed by insertion of 1D oxygen atoms into the CH bond of CHClF2 <1972JPC1425>.
Functions Containing Four Halogens or Three Halogens
249
(ii) Trihalomethyl ethers, CHal3OR 4-Amino- and 4-nitrophenol can be converted in 52–90% yield into the corresponding trifluoromethyl ethers CF3OAr by reaction with CCl4 or CCl3F in the presence of HF and one or several of the following catalysts: KF, NaF, SbCl3, SbCl5, SnCl4 TaCl5, TiCl4 <2001GEP10030090>. This is by and large a rediscovery of earlier findings along the same lines <1982JFC(19)553>. The aliphatic trifluoromethyl ethers CF3OCH2CF3 and CF3OCH(CF3)2 have been prepared by treatment of the corresponding alcohols with CCl4 and HF in the presence of a Lewis acid catalyst. The mixed trihalomethyl ethers CF2ClOCH(CF3)2 and CCl2FOCH(CF3)2 were also among the products <1995USP5382704>. 2-Methoxyaniline has been converted into 2-(trifluoromethoxy)aniline by protection of the amino group as an isocyanate (by treatment with C(¼O)Cl2), AIBN catalyzed chlorination of 2-methoxyphenyl isocyanate to 2-(trichloromethoxy)phenyl isocyanate (90% yield), halogen exchange with liquid HF at 100 C, and hydrolysis of 2-(CF3O)C6H4N¼C¼O to 2-(CF3O)C6H4NH2 <1998FRP2763940>. A particularly convenient and general method for the preparation of aliphatic and aromatic trifluoromethyl ethers CF3OR 8 has been found in the shape of the conversion of alcohols or phenols ROH 1 to the corresponding dithiocarbonates ROC(¼S)SMe 2, which in turn are converted into trifluoromethyl ethers CF3OR 8 by treatment with an N-halo imide such as 1,3dibromo-5,5-dimethylhydantoin and the commercially available 70% HF/pyridine reagent (Olah’s reagent), cf. Scheme 1. In the case of R = secondary or tertiary alkyl or ArCH2, the milder 50% HF/ pyridine reagent is required to prevent the formation of the corresponding fluoride RF. Typical examples of 8 thus prepared are 2-benzyloxy-1-bromo-3-(trifluoromethoxy)benzene 1-Br-3(CF3O)C6H4 (56% yield), methyl 3-(trifluoromethoxy)benzoate 3-(CF3O)C6H4C(¼O)OMe (76% yield), 4-acetoxy-40 -(trifluoromethoxy)biphenyl 4-[MeC(¼O)O]C6H4C6H4(OCF3)-40 (80% yield), and hexadecyl trifluoromethyl ether CF3O(CH2)15Me (95% yield). The cited papers also review earlier methods for the preparation of trifluoromethyl ethers 8 <2000BCJ471, 2001JOC1061, 2001MI815>. With 14CS2, correspondingly labeled RO14CF3 can be obtained <2001MI815>. Fluorination of a methoxy to a trifluoromethoxy group takes place in the synthesis of the ester CF3CF2CF2OCF(CF3)C(¼O)OCF2CF(OCF3)CClFCClF2 from the acid fluoride CF3CF2CF2OCF(CF3)C(¼O)F, the ester CF3CF2CF2OCF(CF3)C(¼O)OCH2CH(OMe)CHClCH2Cl, and F2 <2002WOP2002026688>.
ROH
ii. CS2 iii. MeI
1
RO
RO
X+
RO
SMe 6
SMe 3
X2S F
X+
RO
SMe
F–
SMe
–SX2
5
4
F F
S
RO
SMe 2
XS F
F–
X
S
i. NaH
X+
F F RO
X
S Me
F– –MeSX
ROCF3 8
7
Scheme 1
Chlorodifluoromethyl ethers (CClF2)OR are converted into trifluoromethyl ethers CF3OR in excellent yield and purity by treatment with BrF3 <2000JFC(102)363>. Aryl chlorodifluoromethyl ethers (CClF2)OAr are available both by condensation of the corresponding sodium phenoxide with CCl2F2 and by halogen exchange between the corresponding trichloromethyl ether CCl3OAr and liquid HF <2000JFC(103)81, 2001MI191>.
250
Functions Containing Four Halogens or Three Halogens
The selectivity of the photochlorination of aryl methyl ethers ArOMe with Cl2 to aryl trichloromethyl ethers CCl3OAr is improved by the removal of traces of the phenol ArOH in the starting material <2000WOP2000012456>. Photochlorination of the chiral methyl 1,2,2,2-tetrafluoroethyl ethers CF3CHFOMe yields the corresponding chiral trichloromethyl ethers CCl3OCHFCF3 <1995JOC1319>. Reaction of 2,2,3-trifluoro-2-(trifluoromethyl)oxirane with C(¼O)F2 leads to 2,3,3,3-tetrafluoro-3-(trifluoromethoxy)propanoyl fluoride CF3CF(OCF3)C(¼O)F, which, after hydrolysis and decarboxylation, gives trifluoroethenyl trifluoromethyl ether CF3OCF¼CF2 <1997JOC6160>. Upon treatment with C(¼O)F2 and KF (the synthetic equivalent of potassium trifluoromethoxide CF3OK) 2,2,2-trifluoroethyl trifluoromethanesulfonate CF3S(¼O)2OCH2CF3 yields 56% 2,2,2-trifluoroethyl trifluoromethyl ether CF3OCH2CF3 <1995JAP07179385>; cf. <1995JAP07179386>. Dichlorofluoromethyl ethers (CCl2F)OR have been prepared by treatment of trichloromethyl ethers CCl3OR with SbF3 and Br2 <1995JOC1319>. Upon treatment with catalytic SbCl5 and an equimolar amount of dichloroacetyl fluoride CHCl2C(¼O)F as the fluoride donor, trichloromethyl 2,2,2-trifluoro-1-(trifluoromethyl)ethyl ether CCl3OCH(CF3)2 is converted into the corresponding dichlorofluoromethyl ether (CCl2F)OCH(CF3)2 <1999JFC(94)1>. A similar procedure with fluoromethyl 2,2,2-trifluoro-1-(trifluoromethyl)ethyl ether (commercially available as sevofluran) as the fluoride donor allows the conversion of trichloromethyl ethers CCl3OR to dichlorofluoromethyl ethers (CCl2F)OR and to chlorodifluoromethyl ethers (CClF2)OR, of dichlorofluoromethyl ethers (CCl2F)OR to chlorodifluoromethyl ethers (CClF2)OR, and of chlorodifluoromethyl ethers (CClF2)OR to trifluoromethyl ethers CF3OR <1998JFC(88)51>. Chlorodifluoromethyl 1,2,2-trichloro-1,2-difluoroethyl ether (CClF2)OCClFCCl2F, among other products, has been obtained by photochlorination of 2-chloro-1,2-difluoroethyl difluoromethyl ether CHClFCHFO(CHF2) (mixture of diastereomers). Minor products of the same reaction were difluoromethyl 1,1,2,2-tetrachloro-2-fluoroethyl ether (CHF2)OCCl2CCl2F, dichlorofluoromethyl 2,2,2-trichloro-1,1-difluoroethyl ether (CCl2F)OCF2CCl3, and 1,2,2-trichloro-1,2-difluoroethyl trichloromethyl ether CCl3OCClFCCl2F <1997JFC(82)9>. Aryl bromodifluoromethyl ethers (CBrF2)OAr have been obtained from sodium arenoxides ArONa and CBr2F2 <2001MI191>. A series of aryl difluoroiodomethyl ethers (CF2I)OAr have been prepared in modest yields by treatment of CF2I2 with alkyl-, methoxy-, or halo-substituted phenoxides <2000JFC(102)105>.
(iii) Trihalomethyl esters Trichloromethyl chloroformate CCl3OC(¼O)Cl (the commercially available ‘‘diphosgene’’) has been made by exhaustive photochlorination of methyl formate HC(¼ O)OMe or methyl chloroformate ClC(¼O)OMe <1998CNP1172102>. A manufacturing concept for bis(trichloromethyl)carbonate CCl3O(C¼O)OCCl3 9 (the commercially available ‘‘triphosgene’’) converts 9 and methanol to dimethylcarbonate MeOC(¼O)OMe which is then photochlorinated to 9 of >99% purity. This reaction generates 3 mol. 9 per mol. 9 originally consumed <2002CNP1336361>. Another patent describes the photochlorination of dimethylcarbonate to 9 in 99% yield <1998JAP10007623>. The ester peroxides CF3OC(¼O)OOC(¼O)OCF3 and CF3OC(¼O)OOOC(¼O)OCF3 are formed by photolysis of a mixture of TFAA, CO, and O2. Thermal decomposition of CF3OC(¼O)OOOC(¼O)OCF3 also furnishes, inter alia, CF3OC(¼O)OOC(¼O)OCF3 <2000IC1195, 2002MI1>. Trifluoromethylnitrite CF3ONO (presumably formed in the reaction of trifluoromethoxy radicals with NO) decomposes at room temperature to C(¼O)F2 and FNO. The somewhat labile trifluoromethylnitrate CF3ONO2 has been prepared in 15% yield in a pressure reaction between CF3OF and NO2. It is also formed by rearrangement of the unstable trifluoromethyl peroxynitrite CF3OONO <2001ZAAC(627)655>.
(iv) Trihalomethyl hypohalites, CHal13OHal2 Three patents disclose new approaches to the synthesis of the commercially available trifluoromethyl hypofluorite CF3OF. It can be obtained from C(¼O)F2 and F2 in the presence of metal fluorides such as KF and CsF <2003JAP2003081919> and from CO2 and F2 in the presence of CsF <2002JAP2002003451>.
Functions Containing Four Halogens or Three Halogens
251
Dichlorofluoromethyl hypofluorite (CCl2F)OF and chlorodifluoromethyl hypofluorite (CClF2)OF have been prepared from bis(1-chloro-2,2-difluoroethenyl) ether (CF2¼CCl)2O and OF2. Chlorodifluoromethyl hypofluorite is also formed in the photolysis of a mixture of OF2 and 1,3-dichloro-1,1,3,3-tetrafluoropropan-2-one <1968ZOB1410>. Trifluoromethyl hypochlorite CF3OCl, decomposing rapidly above 78 C, is formed by interaction of C(¼O)F2 with ClF in the presence of CsF <1986IS58>. Trifluoromethyl hypobromite CF3OBr, only observable at low pressure and temperature, has been obtained from CF3OCl and Bu4NBr3 in unspecified yield <1997IC2147>. Trifluoromethyl hypoiodite CF3OI has been observed as a product of the photochemical decomposition of the complex between CF3I and O3 <1985IC4234>. The hypothetical trichloromethyl hypochlorite CCl3OCl has been the subject of quantum chemical calculations <2000JPC(A)9581>. The fluorosulfenate CF3OSF has been prepared by UV irradiation of the isomeric sulfinyl fluoride CF3S(¼O)F <1988IC2706>.
(v) O-Trihalomethyl peroxides, CHal3OOR Bis(trifluoromethyl) peroxide CF3OOCF3 is commercially available. Difluorodioxirane CF2O2 reacts with C(¼O)F2 and CsF to form trifluoromethyl fluoroperformate FC(¼O)OOCF3 as well as oligomers of the type CF3O(OCF2O)nOC(¼O)F. The detailed reaction mechanism has been elucidated by 13C labeling <1999CC1671>. Trifluoromethyl peroxynitrite CF3OONO is a possible transient product of the photoreaction between CF3NO and O2 in an argon matrix <1987JPC3650>. Trifluoromethyl peroxynitrate CF3OONO2 (b.p. 0.9 C) has been obtained in 30–70% yield by photolysis of a mixture of CF3I, NO2, and O2 and removal of by-products by subsequent treatment with O3 <1998IC6208>; cf. <2001ZAAC(627)655>. Bis(trifluoromethyl) trioxide CF3OOOCF3 (m.p. 138 C) is most conveniently prepared in up to 87% yield by a pressure reaction of CsF, C(¼O)F2, and OF2 cf. <2001ZAAC(627)655>. The possible chemistry of the hypothetical bis(trifluoromethyl) tetroxide CF3OOOOCF3 has been considered theoretically <1997JCS(F)379>. The peroxide CF3OOC(¼O)OCF3 is one of the products of the photolysis of a mixture of [CF3C(¼O)]2O, CO2, and O2 <2000IC1195>.
(vi) Trihalomethyl sulfonates, CHal3OS(¼O)2R Trichloromethyl trifluoromethanesulfonate CF3S(¼O)2OCCl3 has been prepared in 90% yield from the mixed anhydride [CF3S(¼O)2O]3B and CFCl3 <1995JFC(73)17>.
(vii) N-Trihalomethoxy compounds, CHal3ON(¼O)nR No further advances have occurred in this area since the publication of chapter 6.07.2.1.1 in <1995COFGT(6)211>.
(viii) Metal trihalomethoxides, CHal3OM No further advances have occurred in this area since the publication of chapter 6.07.2.1.1 in <1995COFGT(6)211>.
6.07.2.1.2
Three halogens and a sulfur function
(i) Trihalomethanethiols, CHal3SH Trifluoromethanethiol CF3SH is formed upon irradiation of trifluoromethanethioic acid CF3C(¼O)SH in an inert gas matrix <1997JST(407)171>. The reactivity of the hypothetical trichloromethanethiol CCl3SH has been investigated in depth by quantum chemical methods <2002JPC(A)11581>.
252
Functions Containing Four Halogens or Three Halogens
(ii) Trihalomethyl sulfides, CHal3SR 2-Biphenylyl trifluoromethyl sulfide CF3SC6H4Ph-2 has been prepared from the corresponding methyl sulfide MeSC6H4Ph-2 by the standard sequence of photochlorination (to give CCl3SC6H4Ph-2) (in 82% yield) and subsequent halogen exchange with HF (86% yield) <1999JAP11049742>. The syntheses of a large number of geminal bis[(trifluoromethyl)sulfanyl] compounds derived from the ketene 2,2-bis[(trifluoromethyl)sulfanyl]ethenone (CF3S)2C¼C¼O have been described <1998JFC(89)9>. Sodium hydroxymethanesulfinate (rongalite) HOCH2SO2Na is a useful auxiliary in the preparation of alkyl trifluoromethyl sulfides CF3SAlk from aliphatic thiols AlkSH and CBrF3 in that it suppresses the competing formation of disulfides AlkSSAlk <2000JFC(105)41>. Trifluoromethyl sulfides CF3SAr and CF3SR have been prepared in a pressure reaction of CF3CO2K with diaryl disulfides ArSSAr and thiocyanates RSCN, respectively <2001JFC(107)311, 2002USP2002042542>. Aryl trifluoromethyl sulfides CF3SAr such as 2-chloro-5-nitrophenyl trifluoromethyl sulfide are available by heating of the corresponding diaryl disulfides ArSSAr with CF3CO2K in boiling tetrahydrothiophene 1,1-dioxide (sulfolane) <1999EP962450>. A 70% yield of 2-thiazolyl trifluoromethyl sulfide was obtained when 2-(trimethylsilyl)thiazole was treated with CF3SCl. The alternative reaction between 2-bromothiazole and CF3SCu was unsatisfactory <2002PS(177)2465>. Activated aromatic ring positions such as an unsubstituted 4-position of a pyrazole can be trifluoromethylsulfenylated to the corresponding sulfide CF3SAr with S-(trifluoromethyl) trifluoromethanethiosulfonate CF3S(¼O)2SCF3 <2002JAP2002338547>. O-(Trimethylsilyl)2,2,2-trifluoroethanal hemiaminals CF3CH(OSiMe3)NR2, together with tetrabutylammonium difluorotriphenylsilicate (De Shong’s reagent) [Bu4N][Ph3SiF2], convert disulfides RSSR to the corresponding trifluoromethyl sulfides CF3SR in good yields <2001TL2473>. A modest yield of benzhydryl and 4,40 -disubstituted benzhydryl trifluoromethyl sulfides CF3SCHAr2 is obtained in the reaction between thiobenzophenone and 4,40 -disubstituted thiobenzophenones, respectively, and commercial trimethyl(trifluoromethyl)silane CF3SiMe3 (Ruppert’s compound) in the presence of TBAF <2002HCA1644>. Trimethyl(trifluoromethyl)silane CF3SiMe3 neatly reacts with thiocyanates RSCN (with TBAF catalysis) <1997TL65> and arenesulfenyl chlorides ArSCl (with TASF, i.e., tris(dimethylamino)sulfonium difluorotrimethylsilicate, catalysis) <1995JFC(70)255> to form the corresponding trifluoromethyl sulfides CF3SR (30–87% yield) and aryl trifluoromethyl sulfides CF3SAr (59–72% yield), respectively. The photolysis of mixtures of disulfides RSSR and the corresponding trifluorothioacetate CF3C(¼O)SR (available from TFAA and the corresponding thiol RSH) or trifluoromethanethiosulfonate CF3S(¼O)2SR (available from CF3SO2Na, RSSR, and Br2), dissolved in MeCN, constitutes a mild method for the generation of trifluoromethyl sulfides CF3SR. In this way a highly functionalized trifluoromethyl sulfide such as methyl N-(trifluoroacetyl)-S-(trifluoromethyl)-L-cysteinate could be obtained in 60% yield. The reaction fails with aromatic substrates (R = Ar) <1999JOC3813>. Aromatic diazonium tetrafluoroborates ArN2BF4 react with CF3SCu to give the corresponding aryl trifluoromethyl sulfides CF3SAr in high yields. The reaction fails when the aryl group is donor substituted <2000CC987>. Activation of CF3SAg, CF3SCu, or (SCF3)2Hg with inorganic iodides was found to promote the formation of aryl trifluoromethyl sulfides CF3SAr in their reactions with halonitroarenes. Quantitative yields can be achieved <2000JOC1456>. Especially active salts like CF3SM (M = K, Me4N) 10, cf. Scheme 2, can be employed in this reaction <1999JFC(95)171>. S Cl
MF Cl
MeCN
CF3 S
M + 2MCl
10
M = K, Me4N
Scheme 2
A number of derivatives (such as esters and acid halides) of 2,2-bis[(trifluoromethyl)sulfanyl]ethanoic acid (CF3S)2CHCO2H, of 2-bromo-2,2-bis[(trifluoromethyl)sulfanyl]ethanoic acid (CF3S)2CBrCO2H, and of 2,2,2-tris[(trifluoromethyl)sulfanyl]ethanoic acid (CF3S)3CCO2H have been prepared by standard methods <1996CB1383>.
253
Functions Containing Four Halogens or Three Halogens
Mixed trihalomethyl sulfides and related compounds such as CF3SSCF3, CF3SSSCF3, CF3SCH2I, CF3SCH2SCF3, (CCl2F)SCF3, (CBrClF)SCF3, and CF3SCH2CN have been obtained from copper(I) trifluoromethanethiolate CF3SCu and various halomethanes. Also, S-(trifluoromethyl) thiocarbonates and thio-ortho-carbonates are formed <1996JFC(76)7>. Trifluoromethanide anion, generated by treatment of CHF3 with t-BuOK at 30 C, can be sulfenylated to the corresponding aryl trifluoromethyl sulfides CF3SAr by treatment with ArSSAr, ArSCl, or PhS(¼O)2SAr in yields ranging from 60% to 90% <1998T13771, 2000JOC8848>. Tetracoordinate sulfur intermediates, formed in situ by addition of potassium t-butoxide to CF3S(¼O)OR or CF3S(¼O)NR2, decompose with formation of CF3, which in turn converts aliphatic and aromatic disulfides RSSR to the corresponding sulfides CF3SR in modest yields <2003SL233>. 1-(1-Pyrrolidino)cyclopentene and 1-(1-pyrrolidino)cyclohexene react with N-[(trifluoromethyl)sulfanyl]phthalimide to yield the corresponding -[(trifluoromethyl)sulfanyl]cycloalkanones <2000SC2847> ,-Bis[(trifluoromethyl)sulfanyl]enamines such as (CF3S)2C¼CHNEt2 are formed in a complicated reaction sequence starting from CF3SCl and certain tertiary ethylamines EtNR1R2 <1995JFC(70)45>. Trimethylsilyl enol ethers R2C¼C(R)OSiMe3 react with CF3SCl to yield the corresponding -[(trifluoromethyl)sulfanyl]alkanones CF3SCR2C(¼O)R <2002PS(177)1021>. Aryl dichlorofluoromethyl sulfides (CCl2F)SAr have been prepared in a pressure reaction from the corresponding disulfides ArSSAr, sodium hydroxymethanesulfinate HOCH2SO2Na, and CCl3F <2001JOC643>.
(iii) Trihalomethyl sulfoxides and trihalomethyl sulfones, CHal3S(¼O)nR Different stereoisomers of 3,4-dimethylhexa-1,5-diyne-3,4-diol 11 react with CCl3SCl to give, via the corresponding bissulfenates 12, the corresponding 1,2-dimethyl-3,4-bis[(trichloromethylsulfinyl)methylene]cyclobutenes 13 with full stereochemical control, cf. Scheme 3 <2000TL6923>. 9-Fluorenyl trichloromethyl sulfoxide CCl3S(¼O)R (R = 9-fluorenyl) has been obtained by baseinduced rearrangement of 9-fluorenyl trichloromethanesulfenate CCl3SOR (R = 9-fluorenyl). Prop-2-enyl trichloromethyl sulfoxide CCl3S(¼O)CH2CH¼CH2 and 2-methylprop-2-enyl trichloromethyl sulfoxide CCl3S(¼O)CH2C(Me)¼CH2 can be rearranged to (E )-prop-1-enyl trichloromethyl sulfoxide (E)-CCl3S(¼O)CH¼CHMe and 2-methylprop-1-enyl trichloromethyl sulfoxide CCl3S(¼O)CH¼CMe2, respectively <1997T13933>. The phosphonate (MeO)2P(¼O)CH¼C¼CMe2 can be converted into the sulfoxide (MeO)2P(¼O)C(¼C¼CMe2)S(¼O)CCl3 by treatment with LDA and CCl3S(¼O)Cl <2000PS(166)265>.
Me R C C C OH HO C C C R Me
CCl3SCl –HCl
Me S CCl3 R C C C O O C C C R Me CCl3 S
11
12
O CCl3 S Me C R C R CCl3 S O 13
Me
Scheme 3
While the oxidation of 1,2-bis[(trifluoromethyl)sulfanyl]benzene 1,2-(CF3S)2C6H4 to the corresponding bissulfoxide 1,2-[CF3S(¼O)]2C6H4 is readily achieved with MCPBA the corresponding oxidation of the 1,4-isomer apparently requires a different oxidant, i.e., SELECTFLUOR, [1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)], a source of electrophilic fluorine <2001USP6215021>. The insecticidal GABA-gated chloride channel blocker fipronil, 5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazole-3-carbonitrile 14 is an important commercial trifluoromethyl sulfoxide. Its industrial preparation by oxidation of the corresponding sulfide with trifluoroperacetic acid CF3CO3H has been fine tuned <2001WOP0130760>.
254
Functions Containing Four Halogens or Three Halogens
5-Amino-3-methyl-1-phenylpyrazole can be trifluoromethylsulfinylated in the 4-position by treatment with N-[(trifluoromethyl)sulfinyl]succinimide which in turn is obtained from N-lithiosuccinimide and CF3S(¼O)Cl <2003EUP1331222>.
CF3 NC N
S O N
Cl
NH2 Cl
CF3 14
Protonated trifluoromethanesulfinic acid [CF3SO2H2]+ appears to be the reactive species in the CF3SO2Na(K)CF3SO3H mixture which converts arenes ArH with o,p-directing substituents to the corresponding sulfoxides CF3S(¼O)Ar with predominant p-substitution. Yields range from 55% to 82%. In the absence of activating substituents in the substrate, i.e., with benzene, only 24% yield can be achieved. With CF3OPh as ArH only one product, 1,4(CF3O)C6H4[S(¼O)CF3] is formed <2001SL550>. 1-Methylpyrrole could be trifluoromethylsulfinylated in the 2-position with an in situ reagent [equivalent to [CF3S(¼O)]+] prepared from CF3SO2Na and Cl3P(¼O) <1999T7243>. Trimethyl(trifluoromethyl)silane CF3SiMe3, in the presence of catalytic amounts of TBAF, neatly reacts with arenesulfinyl chlorides ArS(¼O)Cl to form the corresponding trifluoromethyl sulfoxides CF3S(¼O)Ar (53–61% yield) <1995JFC(70)255>. Tolyl trifluoromethyl sulfone CF3S(¼O)2C6H4Me-4 has been prepared in 83% yield from 4-MeC6H4S(¼O)2F, CF3SiMe3, and TASF <1995JFC(70)255>. Contrary to all other (mostly aromatic) sulfides tested, oxidation of phenyl trifluoromethyl sulfide CF3SPh with methyl(trifluoromethyl)dioxirane Me(CF3)CO2 is >99% selective towards the formation of the corresponding sulfoxide CF3S(¼O)Ph and no trace of the sulfone is formed <2002JA9154>. Bis(trifluoromethyl) sulfoxide CF3S(¼O)CF3 and phenyl trifluoromethyl sulfoxide CF3S(¼O)Ph have been prepared by reaction of dimethyl sulfite (MeO)2S(¼O) and methyl benzenesulfinate PhS(¼O)OMe, respectively, with CsF and CF3SiMe3 <1999JOC2873>. Dichlorofluoromethyl phenyl sulfone (CCl2F)S(¼O)2Ph is the major product (90% yield) of the oxidation of the sulfide (CCl2F)SPh with excess H2O2 in AcOH with the corresponding sulfoxide (CCl2F)S(¼O)Ph as the minor product (5% yield) <2001JOC643>. Methyl methanesulfonate MeS(¼O)2OMe and methyl benzenesulfonate PhS(¼O)2OMe, give methyl trifluoromethyl sulfone CF3S(¼O)2Me and phenyl trifluoromethyl sulfone CF3S(¼O)2Ph, respectively, when treated with CsF and CF3SiMe3 <1999JOC2873>. The extremely volatile sulfone [CF3S(¼O)2]3CF has been made from the corresponding lithium salt [CF3S(¼O)2]3CLi and F2. Contrary to expectation, it does not constitute a source of F+ <2003JFC(122)233>.
(iv) S-Trihalomethyl thio- and dithioesters, CHal3SC(¼Z)R (Z = O or S) An S-(trifluoromethyl) androstane-17-carbothioate RC(¼O)SCF3 has been prepared by trifluoromethylation of the corresponding carbothioic acid RC(¼O)SH with CBrF3 or CClF3 <1998ILP109656>. The S-thioester (CF3S)2CHC(¼O)SCF3 has been obtained by addition of CF3SH to the ketene (CF3S)2C¼C¼O <1998JFC(89)9>.
(v) Trihalomethanesulfenyl, -sulfinyl, and -sulfonyl halides, CHal13S(¼O)nHal2 The known compounds are listed in Tables 1–3.
Functions Containing Four Halogens or Three Halogens
255
Table 1 Trihalomethanesulfenyl halides CHal3SHal CAS RN
CHal3
References
Trihalomethanesulfenyl fluorides CHal3SF [17742-04-0] [17742-03-9] [17742-02-8] [2712-94-9]
CF3 CClF2 CCl2F CCl3
<1993JST(301)65> <1993JST(301)65> <1993JST(301)65> <1981MI399>
Trihalomethanesulfenyl chlorides CHal3SCl CF3 CClF2 CCl2F CCl3 CCl3 (35S labeled)
[421-17-0] [993-38-4] [2712-93-8] [594-42-3] [244082-02-8]
commercially available <1964AG807> <1993JST(301)65> commercially available <1999MI225>
Trihalomethanesulfenyl bromides CHal3SBr [753-92-4] [993-37-3] [993-36-2] [993-35-1] [993-34-0] [993-32-8] [993-33-9] [993–31-7] [753-91-3] [993-30-6]
CF3 CClF2 CCl2F CCl3 CBrF2 CBr2F CBrCl2 CBr2Cl CBrClF CBr3
<1964AG807> <1964AG807> <1964AG807> <1964AG807> <1964AG807> <1964AG807> <1964AG807> <1964AG807> <1964AG807> <1964AG807>
Trihalomethanesulfenyl iodides CHal3SI CF3
[102127-62-8]
<1992ZAAC(611)114>
Table 2 Trihalomethanesulfinyl halides CHal3S(¼O)Hal CAS RN
CHal3
References
Trihalomethanesulfinyl fluorides CHal3S(¼O)F CF3 CF3 (13C labeled) CF3 (18O labeled) CClF2
[812-12-4] [115095-68-6] [115095-69-7] [63177-65-1]
<1968JA5403> <1968JA5403> <1968JA5403> <1977JFC(9)233>
Trihalomethanesulfinyl chlorides CHal3S(¼O)Cl CF3 CCl2F CCl3
[20621-29-9] [156904-01-7] [25004-95-9]
<2001USP6316636> <1992IC492> commercially available
Trihalomethanesulfinyl bromides CHal3S(¼O)Br CF3 CCl3
[20621-30-1] [503844-33-5]
<1988ZAAC(537)169> <1968ACS3256>
Trihalomethanesulfinyl iodides CHal3S(¼O)I CF3
[108863-76-9]
<1988ZAAC(537)169>
Trifluoromethanesulfinyl chloride CF3S(¼O)Cl can be prepared in situ from the commercially available trifluoromethanesulfonyl chloride CF3S(¼O)2Cl and trimethyl phosphite (MeO)3P <2001TL1391>. An improved synthesis of trifluoromethanesulfonyl fluoride CF3S(¼O)2F, useful in lithium battery technology, has been achieved by fluorination of MeS(¼O)2F with F2 in perfluoro-2-methylpentane <2003JFC(120)105>. A low yield (18%) synthesis of
256
Functions Containing Four Halogens or Three Halogens Table 3 Trihalomethanesulfonyl halides CHal3S(¼O)2Hal CAS RN
CHal3
References
Trihalomethanesulfonyl fluorides CHal3S(¼O)2F CF3 CClF2 CBrF2 CF2I CCl3
[335-05-7] [64544-26-9] [73043-96-6] [73043-97-7] [1495-34-7]
<1994IC3281> <1979S972> <1979S972> <1979S972> <1970MI795>
Trihalomethanesulfonyl chlorides CHal3S(¼O)2Cl CF3 CClF2 CCl2F CCl3 CCl3 (35S labeled) CBrF2
[421-83-0] [1495-29-0] [1495-33-6] [2547-61-7] [244082-03-9] [146691-88-5]
commercially available <1993IC5007> <1993IC5007> commercially available <1999MI225> <1992MI274>
Trihalomethanesulfonyl bromides CHal3S(¼O)2Br CF3 CBrF2 CCl3
[15458-53-4] [146691-81-8] [993-51-1]
<2001WOP0127076> <1992MI274> <1997JCR(S)6>
(CClF2)S(¼O)2Cl has been achieved by reaction of zinc hydroxymethanesulfinate (HOCH2 SO2)2Zn with CBrClF2 and subsequent chlorination of the intermediate (CClF2)SO2H salt with Cl2 <1989JOC2452>.
(vi) Trihalomethanesulfenic, -sulfinic, and -sulfonic derivatives, CHal3S(¼O)nZR Benzyl trifluoromethansulfenate CF3SOCH2Ph has been prepared in a one-pot reaction by oxidation of benzyl trifluoromethyl sulfide CF3SCH2Ph with H2O2 <2001USP6316636>. Trifluoromethanesulfinates CF3S(¼O)OR and trifluoromethanesulfinamides CF3S(¼O)NR1R2 are available by reaction of the corresponding precursors ROH and R1R2NH, respectively, with an in situ reagent (equivalent to [CF3S(¼O)]+) prepared from CF3SO2Na and Cl3P(¼O) <1999T7243>. 9-Fluorenyl trichloromethanesulfenate CCl3SOR (R = 9-fluorenyl) has been prepared in 86% yield by the standard method <1997T13933>. Potassium trifluoromethanesulfinate CF3SO2K, an important synthetic intermediate, is available from a pressure reaction between CF3CO2K and SO2 <2002USP2002042542>. Propargylic alcohols HCCCR1R2OH react with trifluoromethanesulfinyl chloride CF3S(¼O)Cl to give the corresponding sulfinates CF3S(¼O)OCR1R2CCH which in turn can be further converted by rearrangement into the corresponding allenyl sulfones CF3S(¼O)2CH¼C¼CR1R2 <2001TL1391>. In situ generation of trifluoromethanesulfinyl chloride CF3S(¼O)Cl from CF3S(¼O)2Cl and (MeO)3P allows the convenient conversion of the appropriate amines RNH2 to the trifluoromethanesulfinamides CF3S(¼O)NHR <1998SUL63>. Sodium trifluoromethanesulfinate CF3SO3Na, useful as intermediate in the synthesis of CF3S(¼O)Cl, has been obtained by the treatment of 2-chlorocyclohexyl trifluoromethyl sulfone with NaOH <2001USP6316636>. Trifluoromethanesulfinamides CF3S(¼O)NHR are also formed by the interaction of N-sulfinylamines R-N¼S¼O with CF3SiMe3 and Me4NF (75–85% yield) <2002TL3029>. Treatment of trifluoromethoxy substituted aliphatic ethers with a mixture of commercially available trifluoromethanesulfonic anhydride Tf2O and CF3SO3H leads to trifluoromethoxy substituted trifluoromethanesulfonic esters such as CF3S(¼O)2O(CH2)2OCF3 useful as alkylating agents <2001JOC1061>. Trifluoromethanethiosulfonic acid S-esters CF3S(¼O)2SR, including CF3S(¼O)2SCCl3, have been prepared from CF3SO2Na and the appropriate sulfenyl chlorides RSCl (or bromides RSBr). Trifluoromethaneselenosulfonic acid Se-esters CF3S(¼O)2SeR are accessible with the corresponding selenyl chlorides RSeCl (or bromides RSeBr) as starting materials. Yields range from 50% to 95% <1996JOC7545>.
Functions Containing Four Halogens or Three Halogens
257
N-[(Trifluoromethyl)sulfinyl]trifluoromethanesulfonamide CF3S(¼O)2NHS(¼O)CF3 has been prepared in a lengthy procedure starting from bis(trifluoromethyl) disulfide CF3SSCF3, N,N-dichlorotrifluoromethanesulfonamide CF3S(¼O)2NCl2, and trifluoromethanesulfinyl chloride CF3S(¼O)Cl <2002JFC(115)129>. The chemistry and the materials science aspects of the commercially available trifluoromethanesulfonimide [CF3S(¼O)2]2NH have been reviewed <2002JCS(P1)1887>. S,S-Dimethyl-N-[(trifluoromethyl)sulfonyl]iminodithiocarbonate CF3S(¼O)2N¼C(SMe)2, a useful intermediate for the preparation of N-[(trifluoromethyl)sulfonyl]ureas and -guanidines, has been obtained in 85% yield by treatment of S,S-dimethyl iminodithiocarbonate HN¼C(SMe)2 with Tf2O <2003JFC(124)151>. N-Sulfinyltrichloromethanesulfonamide CCl3SO2N¼S¼O has been prepared by treatment of the corresponding sulfonamide with SOCl2 <1982LA545>. The compound CCl3S(¼O)N[S(¼O)2Me]2 has been prepared by trichloromethanesulfinylation of silver(I) trifluoromethanesulfonimidate [MeS(O)2]2NAg with CCl3S(¼O)Cl <1998ZN(B)734>.
(vii) Metal trihalomethanethiolates, CHal3SM Particularly nucleophilic salts of trifluoromethanethiol 10 can be obtained by reaction in MeCN of thiophosgene C(¼S)Cl2 with anhydrous KF or Me4NF, cf. Scheme 2 <1999JFC(95)171>. The preparation of the trifluoromethanethiolates of copper(I), CF3SCu (commercially available), silver(I), CF3SAg, and mercury(II), (CF3S)2Hg (commercially available) and their use for the introduction of CF3S groups into organic compounds have been reviewed <1996JFC(76)7>. The important synthetic intermediate CF3SCu has been prepared in 98% yield from CS2, AgF, and CuBr <2001USP6215021>. Bis(trifluoromethyl) disulfide CF3SSCF3 reacts with tetrakis(dimethylamino)ethene (Me2N)2C¼C(NMe2)2 to form the salt (Me2N)2C+– C+(NMe2)22CF3S the anion of which can be alkylated or arylated to give trifluoromethyl sulfides such as CF3SCH2Ph, CF3SC5NF4, and CF3SC6H3(NO2)2-2,4 in 80–95% isolated yield <2000JCS(P1)2183>.
6.07.2.1.3
Three halogens and an Se or Te function
(i) (Trihalomethyl) selenium compounds, CHal3SeR Tetramethylammonium trifluoromethaneselenolate [Me4N][CF3Se], a useful synthetic intermediate, is available in 65% yield from red selenium, CF3SiMe3, and Me4NF <2003JFC(123)183>. The syntheses of a large number of geminal bis[(trifluoromethyl)selanyl] compounds derived from the ketene 2,2-bis[(trifluoromethyl)selanyl]ethenone (CF3Se)2C¼C¼O have been described <1998JFC(89)9>. O-(Trimethylsilyl)-2,2,2-trifluoroethanal hemiaminals CF3CH(OSiMe3)NR2, together with tetrabutylammonium difluorotriphenylsilicate [Bu4N][Ph3SiF2], convert aromatic diselenides ArSeSeAr to the corresponding trifluoromethyl selenides CF3SeR in good yields <2001TL2473>. Trifluoromethanide anions, generated from CHF3 in different ways, react with diphenyl diselenide PhSeSePh to give phenyl trifluoromethyl selenide CF3SePh in fair yield <2000JOC8848>. Trimethyl(trifluoromethyl)silane CF3SiMe3, in the presence of catalytic amounts of TBAF, neatly trifluoromethylates selenocyanates RSeCN to the corresponding trifluoromethyl selenides CF3SeR (58–75% yield) <1997TL65>. A large number of new trifluoromethylselanyl compounds such as (CF3Se)3CF, (CF3Se)3CCl, (CF3Se)3CBr, (CF3Se)3CC(SeCF3)3, and (CF3Se)2C¼C(SeCF3)2 have been obtained from tris[(trifluoromethyl)selanyl]methylium hexafluoroarsenate [(CF3Se)3C][AsF6] as the common precursor <1996CB1383>. N-[(Trifluoromethyl)selanyl]succinimide has been prepared from trifluoromethaneselenyl chloride CF3SeCl and silver(I) succinimidate <1996CB1383>. A particularly mild method for the preparation of phenyl trifluoromethyl selenide CF3SePh in 58% yield consists of the photolysis of Se-phenyl trifluoromethanselenosulfonate CF3S(¼O)2SePh (prepared from CF3SO2Na, PhSeSePh, and Br2) in the presence of equimolar PhSeSePh <1999JOC3813>. Bis(trifluoromethyl) selenoxide CF3Se(¼O)CF3 has been prepared in 84% yield from dimethyl selenite (MeO)2Se(¼O), CsF, and CF3SiMe3 <1999JOC2873>. The same selenoxide CF3Se(¼O)CF3 has also been prepared from bis(trifluoromethyl) selenide CF3SeCF3 and hypofluorous acid HOF <2000JFC(102)301>.
258
Functions Containing Four Halogens or Three Halogens
(ii) (Trihalomethyl)tellurium compounds, CHal3TeR The chemistry of (trifluoromethyl)tellurium compounds has been reviewed. The key compounds described as useful intermediates are CF3TeCF3, CF3TeTeCF3, CF3TeI, and (CF3Te)2Hg <2001PS(171-172)113>. Aromatic Te-(trifluoromethyl) tellurocarboxylates ArC(¼O)TeCF3 are available by reaction of the corresponding acyl chlorides ArC(¼O)Cl with trifluoromethyl trimethylstannyl telluride CF3TeSnMe3. This same tellurium reagent replaces two of the three chlorine atoms of 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride) with (trifluoromethyl)telluranyl groups. The reaction between CBr4 and CF3TeSnMe3 is assumed to give tetrakis(trifluoromethyl)tellurium (CF3)4Te which decomposes spontaneously to bis(trifluoromethyl) ditelluride CF3TeTeCF3 and tetrakis[(trifluoromethyl)telluranyl]ethene (CF3Te)2C¼C(TeCF3)2 <1999JFC(94)195>. Bis(trifluoromethyl)tellurium dichloride (CF3)2TeCl2 reacts with AgNSO to yield the labile tellurium compound (CF3)2Te(NSO)2 <2000JFC(102)301>.
6.07.2.2 6.07.2.2.1
Three Halogens and a Group 15 Element Three halogens and a nitrogen function
(i) Trihalomethylamines, CHal3NR2 (a) Primary trihalomethylamines. No further advances have occurred in this area since the publication of chapter 6.07.2.2.1 in <1995COFGT(6)211>. (b) Secondary trihalomethylamines. The serendipitous formation of a secondary trifluoromethylamine was observed when the attempted simple halogen exchange of 2-(trichloromethyl)phenyl isocyanate 15 with HF yielded 2-[(trifluoromethyl)amino]benzoyl fluoride 16 rather than the expected 2-(trifluoromethyl)phenyl isocyanate 17 <1982JFC(19)553>. O C N
CF3 NH
HF
C F
CCl3 15
O
16 HF
O C N CF3 17
(c) Tertiary trihalomethylamines. Electrochemical fluorination of methyl 2-methyl-3-(dimethylamino)propanoate leads to 2% of the perfluorinated product (CF3)2NCF2CF(CF3)C(¼O)OCF3, together with, inter alia, 36% (CF3)2NCF2CF(CF3)C(¼O)F and 5% (CF3)2NC3F7. Similar results were seen in the electrofluorination of methyl 3-(dimethylamino)butanoate <1994JFC(66)193>. Solution-phase fluorination with F2 of TMEDA in the presence of NaF gives a 20% yield of the perfluorinated product (CF3)2NCF2CF2N(CF3)2 <2003JFC(123)233>. Secondary amines R1R2NH can be converted into the corresponding tertiary trifluoromethylamines CF3NR1R2 by treatment with BuLi, CS2, and MeI, and subsequent fluorination of the resulting methyl dithiocarbamate with [Bu4N][H2F3] and 1,3-dibromo-5,5-dimethylhydantoin. Labeled compounds 14CF3NR1R2 are obtained with 14CS2 <2001MI815>. A large number of tertiary trifluoromethylamines such as perfluoro-1,4-dimethylpiperazine CF3N(CF2CF2)2NCF3
Functions Containing Four Halogens or Three Halogens
259
have been obtained by electrofluorination of 1-[2-(methoxycarbonyl)ethyl]-4-methylpiperazine MeN(CH2CH2)2NCH2CH2C(¼O)OMe and related compounds <2001JFC(108)21>. Hexakis(trifluoromethyl)tetrazane (CF3)2NN(CF3)N(CF3)N(CF3)2 is formed in 90% yield upon photolysis of N-chloro-N,N0 ,N0 -tris(trifluoromethyl)hydrazine (CF3)2NN(Cl)CF3 <1995AG(E)586>.
(ii) N-(Trihalomethyl)amides, CHal3NRC(¼O)R The imines CF3N¼CF(CF3) and CF3N¼CF(C2F5) react with AcOH with loss of acetyl fluoride to yield the N-(trifluoromethyl)amides (CF3)NHC(¼O)CF3 and (CF3)NHC(¼O)C2F5, respectively <1988IZV833>.
(iii) Trihalomethyl isocyanates, CHal3N¼C¼O; trihalomethyl isocyanide dihalides, CHal3N¼CHal2 and N-(trihalomethyl)carbodiimides, CHal3N¼C¼NR All known trihalomethyl isocyanates CHal3N¼C¼O (Hal¼F, Cl, Br) have been shown to exist in equilibrium with their halotropic isomers, the halocarbonyl isocyanide dihalides CHal2¼NC(¼O)Hal with the latter strongly predominating <1996ZOB1715>. (a) Trifluoromethyl isocyanate. No further advances have occurred in this area since the publication of chapter 6.07.2.2.1 in <1995COFGT(6)211>. (b) Trichloromethyl isocyanate. This compound is listed in the 2003–2004 Aldrich catalog. However, early as well as more recent work has shown that its equilibrium with chlorocarbonyl isocyanide dichloride Cl2C¼NC(¼O)Cl lies completely to the right <1996ZOB1715>. (c) Tribromomethyl isocyanate. No further advances have occurred in this area since the publication of chapter 6.07.2.2.1 in <1995COFGT(6)211>. (d) Triiodomethyl isocyanate. There is no record of this compound. (e) Fluorodichloromethyl isocyanate. The isomeric fluorocarbonyl isocyanide dichloride Cl2C¼NC(¼O)F is available from Cl2C¼NC(¼O)Cl and AgF <1968AG(E)630>. (f) Bromodifluoromethyl isocyanate. Photochemical insertion of CO into the NBr bond of CF2¼NBr gives a 55% yield of (CBrF2)N¼C¼O. No halotropic equilibrium with CF2¼NC(¼O)Br or other isomers has been reported <1988JOC4443>. (g) Trifluoromethyl isocyanide difluoride. Pyrolysis of alkali metal 2-[bis(trifluoromethyl)amino]-2,2-difluoroethanoates such as (CF3)2NCF2CO2Na gives, among other products, difluoro-N-(trifluoromethyl)methanimine CF3N¼CF2 <1999JFC(95)161>. The defluorination of CF3N¼CF2 with Ph3P proceeds smoothly to yield 80%–90% trifluoromethyl isocyanide CF3NC <1995IC3114>.
(iv) N-Halo(trihalomethyl)amines, CHal13NRHal2 N,N-Dichlorotrifluoromethylamine CF3NCl2 is available by addition of ClF to ClCN in the presence of catalytic CsF <1991IC2699>. Addition of ClF to the hydrazone (CF3)2NN¼CF2 produces N-chloro-N,N0 ,N0 -tris(trifluoromethyl)hydrazine (CF3)2NN(Cl)CF3 <1995AG(E)586>.
(v) N-(Trihalomethyl)hydroxylamines, CHal3NR1OR2; trihalonitrosomethanes CHal3NO, trihalonitromethanes, CHal3NO2, and related compounds N,N-Bis(trifluoromethyl)-O-fluorohydroxylamine (CF3)2NOF is available from difluoro-N(trifluoromethyl)methanimine CF3N¼CF2 and OF2 in the presence of CsF, but decomposes spontaneously to trifluoronitrosomethane CF3NO and CF4. If the same reagents are used in the ratio 2:1 the hydroxylamine derivative 1,1,3,3-tetrakis(trifluoromethyl)-2,1,3-oxadiazane (CF3)2NON(CF3)2 is formed in 77% yield <1999JFC(99)145>. In the presence of CsF trimethyl(trifluoromethyl)silane CF3SiMe3 reacts with NOCl to form trifluoronitrosomethane CF3NO in 92% yield and with excellent purity <2002CC1818>. Another possibility for the preparation of CF3NO is the reaction of (CF3)2Cd with NOCl (yield 98%) <1995JFC(73)273>. Trichloronitrosomethane CCl3NO can be prepared on a commercial scale by photonitrozation of CHCl3 with NOCl <2001JAP2001002625>.
260
Functions Containing Four Halogens or Three Halogens
Tribromonitrosomethane CBr3NO and the mixed trihalonitrosomethanes CClF2NO, CCl2FNO, CBrCl2NO, and CBr2ClNO are on record in the older literature (with the extremely hazardous mercury(II) fulminate as the most common ultimate synthetic precursor) <1980SA(A)75> as is CBrF2NO <1953JCS2075>. A substantially simplified synthesis of trifluoronitromethane CF3NO2 has been achieved in the shape of the photoreaction of CF3I with NO2 (35% yield; only highly volatile by-products are formed which can be readily removed by treatment with excess CsF). This method could also be used to prepare the labeled CF15 3 NO2 <2002JFC(117)181>. A yield of 47% CF3NO2 is achieved in the reaction of isopropyl nitrate Me2CHONO2 with (trifluoromethyl)zinc bromide CF3ZnBr and AlCl3 <1995JFC(73)273>. Trichloronitromethane (chloropicrin) CCl3NO2 is commercially available as a versatile C1 reagent. Tribromonitromethane (bromopicrin), along with bromonitromethane and dibromonitromethane, has been obtained by bromination of nitromethane with t-butyl hypobromite Me3COBr in the presence of hex-1-ene (yield 71%) <1976JOC1285>. Treatment of nitromethane with a Br2/Cl2 mixture in the presence of water and NaOH yields 33% CBrCl2NO2, 35% CBr2ClNO2, 13% CCl3NO2, and 18% CBr3NO2 <1964USP3159686>. Neither triiodonitrosomethane CI3NO nor triiodonitromethane CI3NO2 are known except for a theoretical treatment of CI3NO2 <1972JST321>. Chlorodifluoronitromethane CClF2NO2 has been prepared by oxidation of chlorodifluoronitrosomethane CClF2NO <1953JCS2075>. The compounds CClF2NO2 and CBrF2NO2, respectively, have been obtained by treatment of difluoronitroethanoic acid with XeF2 and Cl2 or Br2. Corresponding treatment of chlorofluoronitroethanoic acid with XeF2, Cl2 and Br2, respectively, gives CCl2FNO2 and CBrClFNO2 <1988IZV2639>. The compounds CCl2INO2 and CF2INO2 have been considered theoretically <1972JST321>.
(vi) N-(Trihalomethyl)sulfenamides, CHal3SNR1R2 Simple trifluoromethanesulfenamides CF3SNR1R2 have been prepared from CF3SCl and secondary aliphatic amines <1995JFC(70)45>. Several imide type heterocycles have been N-sulfenylated with CCl3SCl <2000PS(161)213>.
(vii) Metal (trihalomethyl)amides, CHal3NRM No further advances have occurred in this area since the publication of chapter 6.07.2.2.1 in <1995COFGT(6)211>.
(viii) Miscellaneous compounds Trifluoromethyl azoxy compounds have been reviewed. In the case of (Z)-1-fluoro-2-(trifluoromethyl)diazene 2-oxide (Z)-CF3N(¼O)¼NF, obtained from the reaction of trifluoronitrosomethane CF3NO with tetrafluorohydrazine N2F4, the structure could be confirmed by gas-phase electron diffraction although quantum chemical calculations showed the corresponding 1-oxide to be more stable by 12 kcal mol1. Apparently, the energy of activation for the corresponding isomerization is of considerable magnitude <2002IC6125>.
6.07.2.2.2
Three halogens and a phosphorus function
When triphenyl phosphite (PhO)3P is treated with excess CBrF3 and (Et2N)3P, an 85% yield of tris(trifluoromethyl)phosphine (CF3)3P is obtained <1996JFC(79)103>. Dichlorophosphines RPCl2 react with equivalent amounts of CBrF3 and tris(diethylamino)phosphine (Et2N)3P to give the corresponding bis(trifluoromethyl)phosphines (CF3)2PR 18, which upon further elaboration yield bis(trifluoromethyl)-substituted phosphoranes. The phosphines 18 can be methylated with methyl trifluoromethanesulfonate CF3S(¼O)2OMe to give the corresponding phosphonium sulfonates [(CF3)2P(R)Me][CF3SO3] <2002HAC650>. When bis(trifluoromethyl)phosphine (CF3)2PH is treated with tetraethylammonium cyanide Et4NCN, the bis(trifluoromethyl)phosphanide anion
Functions Containing Four Halogens or Three Halogens
261
[(CF3)2P] 19 is formed (with evolution of HCN). The phosphanide anion 19 is only stable below 30 C, but can be considerably stabilized as a CS2 adduct, [(CF3)2PCS2] <2002IC2260>. Alkylation of 19 with ethylene ditosylate 4-MeC6H4S(¼O)2OCH2CH2OS(¼O)2C6H4Me-4 leads to the bisphosphine (CF3)2PCH2CH2P(CF3)2 <2001IC3113>. Solution-phase perfluorination of 1,2-bis(dimethylphosphino)ethane Me2PCH2CH2PMe2 affords the bisphosphorane (CF3)2P(F2)CF2CF2P(F2)(CF3)2 <2000JFC(102)333>. A poor yield (15%) of 1,2-bis[bis(trifluoromethyl)phosphino)]ethane (CF3)2PCH2CH2P(CF3)2 has been obtained upon treatment of 1,2-bis(dichlorophosphino)ethane Cl2PCH2CH2PCl2 with CBrF3 and (Et2N)3P <1992TL7601>. Both the tetraphosphetane [(CF3)P]4 and the pentaphospholane [(CF3)P]5 decompose to bis(trifluoromethyl)diphosphene (CF3)P¼P(CF3) which can be trapped in cycloadditions with alka-1,3-dienes <1995ZN(B)189>. The bis(trichloromethyl)phosphine 2,4,6-Me3C6H4P(CCl3)2 can be prepared in good yield by reaction of the phosphorane 2,4,6-Me3C6H4P¼CCl2 with CCl4 and (Et2N)3P <1992ZOB948>.
6.07.2.2.3
Three halogens and an As, Sb, or Bi function
Trihalomethylarsines such as (CF3)3As, (CF3)2As(CClF2), and CF3As(CF2Cl)2 can be obtained from solvent-free (CF3)2Cd and AsCl3. Also the corresponding dihaloarsoranes R1R2R3AsHal1Hal2 are formed <1995JOM(503)C51>. Trifluoronitrosomethane CF3NO reacts with trifluoromethylarsine (CF3)AsH2 to form the hydroxylamine derivative (CF3)As[ONH(CF3)]2 and with bis(trifluoromethyl)arsine (CF3)2AsH to give the analogous (CF3)2AsONH(CF3). The latter reacts with bis(trifluoromethyl)nitroxyl radicals (CF3)2NO to give, inter alia, (CF3)2AsON(CF3)2 <1996JFC(79)111>. The metal complex (CF3)2AsMn(CO)5 can be made from tetrakis(trifluoromethyl)diarsane (CF3)2AsAs(CF3)2 and pentacarbonylmanganese(I) iodide Mn(CO)5I <2002ZAAC(628)2523>. The cycloarsanes [(CF3)As]4.5 decompose to bis(trifluoromethyl)diarsene (CF3)As¼As(CF3) which can be trapped in cycloadditions with alka-1,3-dienes <1995ZN(B)189>. Tris(trifluoromethyl)antimony (CF3)3Sb has been prepared in 61% yield from (CF3)PbPh3 and SbI3 <2000OM2603>. Ligand exchange of the bismuthane compounds ArBiBr2 and Ar2BiCl with (CF3)2Cd yields (CF3)2BiAr and (CF3)BiAr2, respectively. The former rapidly disproportionates to (CF3)BiAr2 and (CF3)3Bi <1994JFC(69)219>. Tris(trifluoromethyl)bismutane (CF3)3Bi and copper(II) acetate react with each other to form (CF3)2BiOAc and CF3Bi(OAc)2. This mixture can be used in trifluoromethylations, for instance of [Bu4N][SPh], where CF3SPh is formed in undetermined yield <2000JFC(106)217>.
6.07.2.3 6.07.2.3.1
Three Halogens and a Metalloid Three halogens and a silicon function
Trimethyl(trifluoromethyl)silane (CF3)SiMe3, trimethyl(trichloromethyl)silane (CCl3)SiMe3, and trichloro(trichloromethyl)silane (CCl3)SiCl3 are commercially available. The silanes (CClF2)SiMe3 and (CBrF2)SiMe3 are available by interaction of CBrClF2 and CBr2F2, respectively, with aluminum and Me3SiCl <1997JA1572>. Catalytic thermal decarboxylation of silyl trichloroacetates CCl3C(¼O)OSiMe2R gives the corresponding trichloromethylsilanes (CCl3)SiMe2R <1995IZV150>. Insertion of diaminosilylenes (R1R2N)2Si into a CCl bond of CCl4 gives the corresponding amino-substituted 1-chloro-2-(trichloromethyl)disilanes (R1R2N)2Si(CCl3)Si(Cl)(NR1R2)2 <2002JA4186>. A minuscule yield (3%) of 2,2-dibromo-1,1,3,3,5-pentamethyl-5-(tribromomethyl)-1,3,5-(trisilacyclohexane) 21 has been obtained by photobromination of 1,1,3,3,5,5-hexamethyl-1,3,5-trisilacyclohexane 20 <2000CJC1388>. Br Me2Si
SiMe2
SiMe2 20
Br2
Br SiMe2
Me2Si
hν Me
Si 21
CBr3
262 6.07.2.3.2
Functions Containing Four Halogens or Three Halogens Three halogens and a boron function
Potassium tetrakis(trifluoromethyl)borate K[B(CF3)4] is available via treatment of ammonium tetracyanoborate NH4[B(CN)4], dissolved in liquid HF, with ClF3 or ClF. The primary step in this conversion is assumed to be an addition to the CN triple bond, cf. Scheme 4 <2001CEJ4696>. As a rule of thumb trifluoromethyl derivatives of tricoordinate boron are unstable while those of tetracoordinate boron are much more accessible. Thus, while tris(trifluoromethyl)borane (CF3)3B still eludes its isolation and characterization, its impressively stable adduct with carbon monoxide (CF3)3BCO (m.p. 9 C) has been prepared by partial hydrolysis of the salt K[B(CF3)4]. When (CF3)3BCO is dissolved in CD3CN at room temperature CO is evolved and the acetonitrile adduct (CF3)3BNCCD3 is formed <2002JA15385>. (Dimethylamino)bis(trifluoromethyl)borane (CF3)2BNMe2 22 reacts with N-sulfinylcarboxamides RC(¼O)N¼S¼O by [2+4]-cycloaddition leading to 23 and with N-sulfinylcarbamates ROC(¼O)N¼S¼O by concomitant [2+4]- and [2+2]-cycloaddition leading to 24 and 25, respectively, cf. Scheme 5 <2002ZAAC(628)2299>.
ClF
NH4[B(CN)4]
R C N
ClF
HF
K[B(CF3)4] HF
NCl2 R CF2
R CF3 + HNCl2
Scheme 4
O N RC(=O)N=S=O
R
S
NMe2 B(CF3)2
O 23
(CF3)2BNMe2 22
ROC(=O)N=S=O
O N RO
S O 24
O NMe2 B(CF3)2
S +
NMe2
N B(CF3)2 ROC(=O) 25
Scheme 5
6.07.2.3.3
Three halogens and a germanium function
Iodotris(trifluoromethyl)germane (CF3)3GeI is commercially available. The compound (CF3)GePh3 has been prepared from Ph3GeCl and (CF3)2Cdglyme <2000OM2603>. When CF3I is heated with GeBr4 and copper bronze at 180 C, tribromo(trifluoromethyl)germane (CF3)GeBr3 is formed <2001MI765>. The phosphaethene HP¼C(F)NEt2 has been converted into (CF3)3GeP¼C(F)NEt2 by treatment with (CF3)3GeI and Et3N <2000ZAAC(626)1141>. Displacement reactions of (CF3)3GeI and (CF3)2GeI2 with Hg(NSO)2 lead to (CF3)3GeNSO 26 and (CF3)2Ge(NSO)2 27, respectively. Compound 26 suffers loss of SO2 with formation of sulfur diimide (CF3)3GeN¼S¼NGe(CF3)3 28. The corresponding condensation of 27 leads to the medium sized heterocycle (CF3)2Ge(N¼S¼N)2Ge(CF3)2 29, cf. Scheme 6 <1999JFC(96)147>.
Functions Containing Four Halogens or Three Halogens
(CF3)3GeI
Hg(NSO)2
263
(CF3)3GeN=S=O 26
(CF3)2GeI2
Hg(NSO)2
CF3 S O N Ge N CF3 O S 27
(CF3)3GeN=S=O 26 CF3 S O N Ge N O S CF3
(CF3)3GeN=S=NGe(CF3)3 –SO2
–SO2
27
28
CF3 N S N CF3 Ge Ge CF3 N S N CF3 29
Scheme 6
6.07.2.4 6.07.2.4.1
Three Halogens and a Metal Function Trihalomethyl alkali and earth alkali metals, CHal3M (M = Li, Na, K, Cs, Mg)
A transient species, tentatively identified as (triiodomethyl)magnesium chloride (CI3)MgCl, has been observed in the reaction system triiodomethane–isopropylmagnesium chloride <2001OM5310>.
6.07.2.4.2
(Trihalomethyl)aluminum, -gallium, -indium, and -thallium compounds, CHal3MRn (M = Al, Ga, In, Tl)
Tris(trifluoromethyl)indium(III) (CF3)3In is available by cocondensation of trifluoromethyl radicals with indium vapor <1986MI701>. Phenylbis(trifluoromethyl)thallium(III) (CF3)2TlPh and bis(trifluoromethyl)thallium(III) acetate (CF3)2Tl(OAc) have been prepared from (CF3)2Cdglyme and PhTl(OAc)2 and Tl(OAc)3, respectively <1989IC2816>.
6.07.2.4.3
(Trihalomethyl)tin and -lead compounds, CHal3MRn (M = Sn(II), Sn(IV), Pb(IV))
The reaction of trimethyltin chloride Me3SnCl with solvent-free (CF3)2Cd gives a 90% yield of (CF2Cl)SnMe3 and (CF3)SnMe3 in a 2:1 ratio <1995JOM(503)C51>. The compounds (CF3)SnPh3, (CF3)2SnPh2, (CF3)PbPh3, (CF3)2PbPh2, and (CF3)3PbPh are available by treatment of the corresponding halo(phenyl)metal compounds with (CF3)2Cdglyme <2000OM2603>.
6.07.2.4.4 (Trihalomethyl)zinc, -cadmium, and -mercury compounds, CHal3MR (M = Zn, Cd,Hg(II)) The chemistry of (trifluoromethyl)zinc bromide (CF3)ZnBr, especially with regard to the preparation and utilization of complexes, has been reviewed <1996JPR(338)283>. Donor-free bis(trifluoromethyl)cadmium (CF3)2Cd is formed in quantitative yield from Et2Cd and CF3I <1995JOM(503)C51>. The mercury(I) compound CF3HgHgCF3 has not been observed yet in keeping with its theoretically predicted instability. Apparently other factors counteract the expectedly stabilizing effect of the strongly electronegative CF3 groups on the strength of the HgHg bond <1995JST(358)195>.
264 6.07.2.4.5
Functions Containing Four Halogens or Three Halogens (Trihalomethyl)copper, -silver, and -gold compounds, CHal3MRn (M = Cu(I), Cu(III), Ag(I), Ag(III), Au(I), Au(III))
Tris(trifluoromethyl)silver(III) (CF3)3Ag has been used as a starting material for heteroleptic argentates(III) containing trifluoromethyl groups. The anions tetrakis(trifluoromethyl)cuprate(III) [Cu(CF3)4], tetrakis(trifluoromethyl)argentate(III) [Ag(CF3)4], and tetrakis(trifluoromethyl)aurate(III) [Au(CF3)4], available by oxidation of lower-valency (trifluoromethyl)metal compounds, have been employed in the construction of superconducting BEDT-TTF salts <1999CCR(190192)781>. (Trifluoromethyl)gold(I) phosphine complexes (CF3)AuPR3 have been prepared from CF3SiMe3 and the corresponding alkoxides Au[OCH(CF3)2]PR3. The analogous reaction with CCl3SiMe3 leads to the corresponding labile products (CCl3)AuPR3. Starting from the gold(III) compound (CF3)Me2Au(OPh), CF3SiMe3, and a ligand PR3 the gold(III) complexes (CF3)Me2AuPR3 are obtained <2000ICA(309)151>.
6.07.2.4.6 Miscellaneous trihalomethyl transition metal compounds, CHal3MRn (M = transition metal) Attempts at oxidative addition of CCl4, CBr4, and CI4 to the Rh(I) complex RhCl(CO)(PPh3)(HNEt2) failed to yield the corresponding trichloromethyl-, tribromomethyl-, and triiodomethylsubstituted Rh(III) complexes, halogenation being observed instead <1998OM4966>.
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Functions Containing Four Halogens or Three Halogens 1993JFC(62)293 1993IC5007 1993JST(301)65 1994IC3281 1994JFC(66)193 1994JFC(67)91 1994JFC(69)219 1995AG(E)586 1995COFGT(6)211 1995IC3114 1995IZV150 1995JAP07179385
1995JAP07179386
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269
Biographical sketch
Alexander Senning Born 1936 in Riga, Latvia, Alexander Senning studied chemistry in Munich, Germany (1954–1959) and Uppsala, Sweden (1960–1962). He obtained a Ph.D. in organic chemistry from Uppsala University 1962, joined the Department of Chemistry, Aarhus University, Denmark as assistant professor (1962–1965) and served as associate professor during 1965–1993. During a sabbatical leave (1973–1975), he was head of the research laboratory of the drug company A/S Alfred Benzon, Copenhagen, Denmark. He joined the Danish Engineering Academy (DIA), Lyngby, Denmark, later part of The Technical University of Denmark (DTU), Lyngby, Denmark, as professor of organic chemistry in 1993, until his retirement in 2003. Research interests: organic sulfur chemistry, medicinal chemistry. Extensive activities as book and journal editor. A detailed chemical autobiography is available in Sulfur Rep., 2003, 24, 191–253.
Jørgen Øgaard Madsen Born 1940 in Aars, Denmark, Jørgen Øgaard Madsen studied chemistry in Aarhus, Denmark (1962–1971) and received an M.Sc. (1967) and a Ph.D. (1972) in organic chemistry from Aarhus University, Denmark. He held an assistant professorship at the Department of Chemistry, Aarhus University, Denmark (1967–1971) and joined the Department of Organic Chemistry (later Department of Chemistry) of the Technical University of Denmark (DTU) as associate professor (1972 to present). Research interests: heterocyclic enamines, stereospecific syntheses with baker’s yeast, natural product chemistry, analytical organic chemistry (HPLC, MS).
# 2005, Elsevier Ltd. All Rights Reserved No part of this publication may be reproduced, stored in any retrieval system or transmitted in any form or by any means electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without permission in writing from the publishers
Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 243–269
6.08 Functions Containing Two Halogens and Two Other Heteroatom Substituents G. VARVOUNIS and N. KAROUSIS University of Ioannina, Ioannina, Greece 6.08.1 INTRODUCTION 6.08.2 TWO HALOGENS AND TWO CHALCOGEN FUNCTIONS 6.08.2.1 Two Halogens and Two Oxygen Functions 6.08.2.1.1 Difluoro compounds 6.08.2.1.2 Dichloro and dibromo compounds 6.08.2.2 Two Halogens and Two Sulfur Functions 6.08.2.2.1 Difluoro compounds 6.08.2.2.2 Dichloro, dibromo, and diiodo compounds 6.08.2.3 Two Halogens, an Oxygen, and a Sulfur Function 6.08.2.4 Two Halogens and Other Chalcogen Functions 6.08.3 TWO HALOGENS AND ONE CHALCOGEN FUNCTION 6.08.3.1 Two Halogens, a Chalcogen, and a Nitrogen Function 6.08.3.1.1 Oxygen compounds 6.08.3.1.2 Sulfur compounds 6.08.3.2 Two Halogens, a Chalcogen, and Other Functions 6.08.4 TWO HALOGENS AND TWO GROUP V ELEMENT FUNCTIONS 6.08.4.1 Two Halogens and Two Nitrogen Functions 6.08.4.1.1 Diamines and their derivatives 6.08.4.1.2 Cyclic compounds 6.08.4.2 Two Halogens and Two Phosphorus Functions 6.08.4.2.1 Bis(phosphonates) 6.08.4.2.2 Cyclic compounds 6.08.4.2.3 Miscellaneous compounds 6.08.4.3 Two Halogens, a Nitrogen, and a Phosphorus Function 6.08.5 TWO HALOGENS AND ONE GROUP V ELEMENT FUNCTION 6.08.5.1 Two Halogens, a Phosphorus, and a Metalloid or Metal Function 6.08.5.2 Two Halogens, a Nitrogen, and a Metalloid Function 6.08.6 TWO HALOGENS AND TWO METALLOID FUNCTIONS 6.08.6.1 Two Halogens and Two Silicon Functions 6.08.6.1.1 Linear carbosilanes 6.08.6.1.2 Cyclic carbosilanes 6.08.7 TWO HALOGENS AND TWO METAL FUNCTIONS
271
272 272 272 272 274 274 274 277 278 278 279 279 279 280 280 281 281 281 281 282 282 284 285 287 288 288 289 290 290 290 291 292
272 6.08.1
Functions Containing Two Halogens and Two Other Heteroatom Substituents INTRODUCTION
Compounds or functionalities that consist of a central carbon atom attached to two halogens and two other heteroatoms that include chalcogens (O, S, Se, or Te), group V elements (N, P, As, Sb, Bi, B, Si, or Ge), main group metals (Sn, Pb, Al, Ga, In, Tl, Be, Mg, Ca, Sr, Ba, Li, Na, K, Rb, or Cs), and transition metals (Cu, Ag, Au, Zn, Cd, Hg, Ti, Zr, Hf, Cr, Mo, W, Mn, Fe, Co, Ni, Pd, or Pt) are generally rare. The most frequently encountered halogen is by far fluorine, with chlorine in the second place. One example of a mixed halogen is known whereas mixed heteroatoms are quite common. The most common heteroatom combinations are two oxygen, two phosphorus, and two sulfur atoms.
6.08.2
TWO HALOGENS AND TWO CHALCOGEN FUNCTIONS
6.08.2.1
Two Halogens and Two Oxygen Functions
6.08.2.1.1
Difluoro compounds
Fluorocarbonylhypofluorite, FC(O)OF, is a relatively unstable product prepared in low yield from the UV irradiation of a mixture of F2 and bis(fluoroformyl)peroxide. The reactions of FC(O)OF have been limited to the preparation of difluorodioxirane, bis(fluoroxy)difluoromethane, and chloroxyfluoroxydifluoromethane <1995COFGT(6)249>. The yield of FC(O)OF was greatly improved by using a 12 W low-pressure UV lamp in place of a 350 W mediumpressure Hg lamp, as reported in the literature. Furthermore in the reaction of FC(O)OF with ClF, the yield of chloroxyfluoroxydifluoromethane was improved by using CsF doped with H2O instead of dry CsF <1995IC6221>. The chemistry of this compound has not yet been investigated. Difluorodioxirane is one of the most stable dioxiranes known. It was originally prepared by passing a 1:1 (v/v) mixture of FC(O)OF and ClF over a CsF catalyst <1995COFGT(6)249>. An improvement over this method has been achieved by using Cl2 and the new catalyst KHF2; difluorodioxirane was obtained in moderate but higher yields <1999CC1671>. The OO bond length in difluorodioxirane is 157.6 pm, and is the longest OO bond ever calculated and measured. This theoretically explains why it is a powerful oxidant and can readily undergo reactions that are typical of dioxiranes. It transfers oxygen to alkenes, forming epoxides and COF2 in high yield. Its reaction with 13COF2 in the presence of CsF was used to show that it reacts by ring opening of the OO bond (Equation (1)). A reasonable mechanistic proposal (Scheme 1) predicts trifluoromethoxy anion attack on the dioxirane peroxide bond to give CF3OOCF2O, which loses fluoride to form 1 or reacts further with dioxirane to form new oligomeric peroxides 2–4. The 13C distribution makes it clear that the predominant reaction is attack of CF3O on the dioxirane at oxygen and not at the more electropositive carbon.
F F
O O
+
13COF
CsF 3
70% 13C
–50 °C, 16 h
13CF
3OOC(O)F
67% 13C 10% 13C 1
+
13CF
3O(OCF2O)nOC(O)F
67% 13C
ð1Þ 7% 13C
2–4 (n = 1–3)
Bis(fluoroxy)difluoromethane reacts with tetrafluoroethylene and trans-1,2-dichloroethylene to give bisethers of formula (RO)2CF2. Bis(fluoroxy)difluoromethane also reacts thermally and photochemically with perfluoro Dewar benzene; the reaction products were mainly complex copolymer mixtures, whereas a structure containing 1,1-difluoro-1,3-dioxolane was isolated in 6% yield <1995COFGT(6)249>. Previous preparations of halogenated 2,2-difluoro-1,3-dioxolanes used multistep processes but often in low or inconsistent yields <1976USP3978030>. Later the addition of bis(fluoroxy)difluoromethane to halogenated alkenes (CX2¼CX2) gave a better yield of 2,2-difluoro-1,3-dioxolanes <1995COFGT(6)249>. This method was further improved by carrying out the reaction of bis(fluoroxy)difluoromethane with halogenated alkenes (CF2¼CFCF3, CF2¼CFOCF2CF3, CF2¼CHCF3, CF3CF¼CFCl, CFBr¼CFBr,
273
Functions Containing Two Halogens and Two Other Heteroatom Substituents
CCl2¼CCl2, CHCl¼CHCl, CH2¼CHCl, CF2¼CFCl, (CF3)2CFCF¼CFCF3, CF2¼CFBr, and CF2¼CF2) in the presence of halogenated inert solvents (CF2Cl2, CFCl3, and perfluoropolyethers) as well as in neat olefin. The halogenated 2,2-difluoro-1,3-dioxolanes were obtained in 43–95% yields, together with 1,2-difluorotetrahalogenoethanes as side products. Continuous, semicontinuous or batch procedures were used depending on the physicochemical properties of the olefin <1995JFC(71)111>.
13COF
13CF
2
– 3O
13CF
+ F–
O O
F
3O
–
13CF
–F–
–
3OOCF2O
13CF
3OOC(O)F
F
1 O n F OF 13CF
–F–
–
3(OCF2O)nOCF2O
13
CF3(OCF2O)nOC(O)F 2–4 (n = 1–3)
Scheme 1
4-(2,2-Difluoro-1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile 5 is a fungicide which is metabolized by poultry into the N-hydroxy derivative. The latter has been synthesized in seven steps and 23% overall yield from 2,2-difluoro-1,3-benzodioxole-4-carboxylic acid 6 <1989EUP333685>. The 2,2-difluoro-1,3-benzodioxole ring remains intact throughout the synthesis <1995JOC4302>. 6,6-Difluoro-1,3-dioxolo[4,5-f]benzimidazole-2-thione 7 was converted into the 2-chlorodioxolobenzimidazole 8 by chlorine (Scheme 2) <2001GEP10005277>. Apparently 8 was also prepared by heating dioxobenzimidazol-2-one 9 with phosphoryl chloride under HCl. Compound 9 is an intermediate for the preparation of compounds with fungicidal activity <2001GEP10005277>. H N NC
CO2H O
F
O
F
H N
O
S F
N H
O 7
F
O
F
6
5
F
O
Cl2, MeOH, 0 °C
F
O
N
96%
F
O
N H
Cl 8
POCl3, HCl, ∆
F
O
85%
F
O
H N O N H 9
Scheme 2
2,2-Difluorobenzo[1,3]dioxole-4-carbaldehyde 13 (Scheme 3) was prepared in three steps from 4-methylbenzo[1,3]dioxole 10. The latter and 2,20 -azobisisobutyronitrile (AIBN) were heated with chlorine at 70 C and then at 150 C to induce chlorination to both C-2 and the methyl group. 4-Dichloromethyl-2,2-dichlorobenzo[1,3]dioxole 11 thus obtained was fluorinated by HF at 15 C to give 2,2-difluoro derivative 12, in high yield. Conversion of the CHCl2 group in 12 into an aldehyde group in 13 required heating in formic acid <1997EUP759433>.
274
Functions Containing Two Halogens and Two Other Heteroatom Substituents CHCl2
Me O
AIBN, Cl2
O
70 °C then 150 °C
CHCl2
O
Cl
O
Cl
Anhyd. HF, –15 °C
F
O
F
12
11
10
O
HCO2H 100 °C CHO O
F
O
F
13
Scheme 3
A process for producing fluorinated alkyl ethers 15 from fluorinated alcohols 14, by the action of HF in the presence of BF3, is claimed in a patent (Equation (2)) <1995USP5382704>. H R C OH R 14
R
HF, BF3, CCl4
R
C
H F H R C C O O R F 15
ð2Þ
R = CF2CF3, (CF2)2CF3, or (CF2)3CF3
6.08.2.1.2
Dichloro and dibromo compounds
The synthesis and reactions of these compounds remains an area very little investigated. Interest was focused in developing more efficient methods to synthesize dichlorodiphenoxymethane 17 and dichloroformals 19 <1995COFGT(6)249>. It has been claimed in a patent that the yield of 17 may be increased over the previous methods, by heating 16 in a mixture of PCl3 and POCl3 at 160–175 C, while passing chlorine into the reaction mixture (Equation (3)) <1998JAP10182538>. Another patent claims that TiCl4 as catalyst in the reaction between thionocarbonates 18 and SO2Cl2 increases the efficiency in the synthesis of dichloroformal derivatives 19, where R is CCl3, CF3, C(NO2)3, C(NO2)2Me, CF(NO2)2, CF2CF3, CF2NO2, or CCl(NO2)2 (Equation (4)) <1997USP5631406>. Ph O + PCl3 + POCl3
Cl2, 160–175 °C
PhO
Cl
91%
PhO
Cl
Ph
17
16 RCH2O S
+
SO2Cl2
RCH2O 18
6.08.2.2 6.08.2.2.1
ð3Þ
TiCl4
RCH2O
Cl
RCH2O
Cl
ð4Þ
19
Two Halogens and Two Sulfur Functions Difluoro compounds
Bis(trifluorothio)difluoromethane was first observed as a by-product in electrochemical fluorination (ECF) of carbon disulfide. Later it was shown that this compound could be prepared in high purity by direct fluorination of CS2. Oxidative additions to the SF3 groups and controlled BF3catalyzed solvolysis in liquid SO2 to give difluoromethanedisulfinyldifluoride 20 have been described. The chemistry of the latter with nitrogen nucleophiles has been investigated in detail
Functions Containing Two Halogens and Two Other Heteroatom Substituents
275
<1995COFGT(6)249>. This work has been extended to the preparation of difluoromethanebis(sulfinic acid) 21 by allowing moist air to come into contact with 20 for 3 weeks (Equation (5)). In this reaction no detectable amounts of the anhydride 23, expected as an intermediate, were found. Single crystals of the anhydride 23 were isolated after salt 22 was hydrolyzed slowly by traces of moisture while stored at 8 C (Equation (6)) <1998JFC(89)55>. O S F F S F O 20 F
–78 °C, 3 weeks
+
Cs [F2C(SF3)2F]
–
O S OH F S OH O 21 F
Moist air
Traces of moisture
F
8 °C, 2–3 weeks
F
ð5Þ
O S O
22
ð6Þ
S O 23
While ECF in anhydrous HF was used to prepare bis(fluorosulfonyl)difluoromethane from CH2(SO2F)2 <1997JFC(83)145>, the preparation of F2C(SO2Ph)2 required first the reaction of PhSO2CHF2 and NaOH in a two-phase system to give PhSO2CF2SPh, and second oxidation of the latter with H2O2 <1995COFGT(6)249>. Recently, F2C(SO2Ph)2 was prepared from PhSCHF2 by reaction with PhSO2Cl in the presence of aqueous NaOH, followed by oxidation of the product PhSO2CF2SPh with H2O2 <2002IC6118>. Bis(trifluoromethylsulfonyl)methane 24 was first prepared by reacting methylmagnesium halides with trifluoromethanesulfonylfluoride in Et2O <1956JCS173>. Later the synthesis was improved by simply replacing Et2O by THF. ECF of 24 in anhydrous HF gave difluoromethyl derivative 25 in 25% yield, together with 5% of CF3SO2F (Equation (7)) <1998JFC(91)9>. Compound 25 was first obtained in traces by the treatment of 26 with elemental fluorine <1994JFC(67)27>. Anhyd. HF, e–
H2C(SO2CF3)2
F2C(SO2CF3)2 + CF3SO2F
ECF
25 (25%)
24 O O S
ð7Þ
5%
O S O S
O
O 26
The condensation of BrCF2Cl with sodium thiophenoxides 27 gave bis(thiophenol)difluoromethanes 28 in good yields. The authors postulated an ionic mechanism for the reaction (Equations (8) and (9)) <1981TL1997>. 4-XC6H4SNa + BrCF2Cl
DMF, –40 °C
F
SC6H4X-4
X = Cl or NO2
F
SC6H4X-4
27
ð8Þ
28 –
4-XC6H4SCF2
+
28
4-XC6H4SBr X = Cl or NO2
ð9Þ
The related reaction of sodium thiophenoxide with BrCF2Cl in dimethyl formamide (DMF) at 40 C gave four products, the bromo and hydrogenated derivatives 29 and 30 and the chloro and bis(thiophenol)difluoromethane derivatives 31 and 32, in 60% overall yield (Equation (10)). Repetition of this reaction in the presence of nitrobenzene, a known inhibitor of electron-transfer processes, greatly reduced the yield of 32 (Equation (11)). This result indicates that 32 is formed through a radical chain mechanism. The condensation between dichlorodifluoromethane CF2Cl2
276
Functions Containing Two Halogens and Two Other Heteroatom Substituents
and sodium thiophenoxide under UV irradiation produced three products, 30 and 31 as minor products with 32 as the major product (Equation (12)). These facts strongly indicate that the reactions leading to 32 occur through a radical mechanism as depicted in Scheme 4 <1983JOC1979>. DMF
PhSNa + BrCF2Cl
–40 °C
29 (9%)
30 (3%) DMF
PhSNa + BrCF2C + PhNO2
+
PhSCF2Cl
CF2Cl2
DMF, –40 °C hν
–
–
31 (5%)
F
SPh
2%
32 (43%)
2%
ð11Þ
5%
30 + 31 + 32 6%
6%
ð10Þ
ð12Þ
22%
PhSCF2 + Cl–
PhSCF2 + PhS– PhSCF2SPh
SPh
29 + 30 + 31 + 32
–40 °C
52% PhSNa
F PhSCF2Br + PhSCF2H + PhSCF2Cl +
PhSCF2SPh
+ BrCF2Cl
–
PhSCF2SPh + BrCF2Cl
–
32
Scheme 4
The reaction of CF2Cl2 with PhSK 33a and 4-MeC6H4SK 33b in DMF under 2 atm pressure gave sulfides 34 as major products while 35 and difluoromethylbis(arylsulphides) 36 as minor products (Equation (13)) <1984CC793>. ArSK + CF2Cl2 33
DMF, 2 atm a, Ar = Ph b, Ar = 4-MeC6H4
ArSCF2Cl + ArSCF2H + 34a (62%) 34b (44%)
35a (8%) 35b (8%)
F
SAr
F
SAr
ð13Þ
36a (7%) 36b (6%)
The work on the reactivity of dichlorodihalomethanes with thionate anions has been extended to CF2I2. Sodium 4-chlorothiophenoxide 37 and CF2I2 react in a 2:1 ratio in diglyme at room temperature to afford bis(4-chlorothiophenol)difluoromethane 38 in 43% yield (Equation (14)). Repeating the reaction by changing the molar ratio of 37 to CF2I2 into 1:2 resulted in a drastic drop of the yield of 38 to 9% and the formation of two major products disulfide 39 and difluoromethane 40 (Equation (15)). Even better, 38 was formed in 60% yield by the action of 37 on 4-ClC6H4SCF2I in DMF <2000JFC(102)105>. 4-ClC6H4SNa + CF2I2 37
Diglyme
F
SC6H4Cl-4
ratio 2:1 43%
F
SC6H4Cl-4
ð14Þ
38 37 + CF2I2
Diglyme ratio 1:2
4-ClC6H4SSC6H4Cl-4 + 4-ClC6H4SCF2I + 38 39 (28%)
40 (35%)
ð15Þ
9%
Halogen exchange reactions occur when bis(pentafluorothiophenol)dichloromethane 41 is heated with SbF3, SbF5, or CsF. Reaction of 41 with an excess of SbF3 at 150 C gave dithiocarbonate 43 as the main product and small amounts of bis(pentafluorothiophenol)difluoromethane 44 and disulfide 42 (Equation (16)). The reaction of 41 with SbF5 at 90 C resulted in an increase in the formation of difluoromethyl derivative 44 but the main product was the disulfide 42. (C6F5S)2CClF, C6F5SCF3, and dithiocarbonate 43 were also identified among the
Functions Containing Two Halogens and Two Other Heteroatom Substituents
277
reaction products. At 225 C the reaction of 41 with excess anhydrous CsF without solvent gave difluoromethane 44 and polysulfides 46 as major products together with disulfide 42 and chlorofluoromethane 45 as minor products (Equation (17)). All these compounds were difficult to obtain pure so were identified by 19F-NMR and GC-MS data <1999JFC(98)17>. SbF3
(C6F5S)2CCl2
(C6F5S)2 + (C6F5S)2CO +
150 °C
41 41
42 (6%)
CsF
42 + 44
225 °C
+
43 (75%)
F
SC6F5
Cl
SC6H5
6.08.2.2.2
SC6F5
F
SC6H5
ð16Þ
44 (16%) F
SC6F5
X
S(C6F4S)nC6H5
+ 46
45
F
ð17Þ
X = Cl or F n = 1, 2, or 3
Dichloro, dibromo, and diiodo compounds
In this category of compounds, the major interest has been the synthesis and reactions of halogenated 1,1,3,3-tetraoxo-1,3-dithietanes, halogenated 1,1,3,3,5,5-hexaoxo-1,3,5-trithianes, halogenated [1,3]dithioles, [1,3]dithiole-1,1-dioxides, and [1,3]dithiole-1,1,3,3-tetraoxides, dichloromethanedisulfenyl chloride, and bis(alkyl or arylsulfonyl)dihalogenomethanes <1995COFGT(6)249>. An interesting rearrangement of chloromethylsulfenylchloride 47 into 1-adamantylsulfonyl dichloromethyl pentachlorophenyl disulfide 48 occurred when 47 was left in CHCl3 for a few days (Equation (18)). In addition, refluxing an ethereal solution of 47 led to a quantitative yield of thiosulfonate 49 (Equation (19)). These reactions are postulated to occur via concerted mechanisms supported by AM1 calculations and from an experimental point of view, as the reactions take place in solvents of low polarity <1994JCS(P1)1251>. O O R1 R1 S S CHCl , 5 d Cl 3 O Cl O C C S Cl S Cl S S R2 R2 48 47 R1 = 1-adamantyl, R2 = C6Cl5 O R1 S Cl O C S S R2 Cl
Et2O, ∆, 40 min
47
Cl
ð18Þ
Cl
O O S S S R2 R1 C
ð19Þ
49 R1 = 1-adamantyl, R2 = C6Cl5
Bis(substitutedsulfonyl)dihalogenomethanes for all four halogens have been known for over hundred years. Methods of synthesis include direct chlorination or bromination of gem-disulfones, halogenation of potassium salts of monohalogenated gem-disulfones, and the halogenation of benzeneiodonium ylides with halosuccinimides <1995COFGT(6)249>. An improved synthesis of bis(trifluoromethylsulfonyl)methane 50 was accomplished by the action of methylmagnesium chloride on trifluoromethanesulfonylfluoride. The reaction of N-chlorosuccinimide (NCS), N-bromosuccinimide (NBS), and N-iodosuccinimide (NIS) in carbon tetrachloride with 50 leads to the formation of the corresponding dihalogenomethanes 51 (Equation (20)) <1998JFC(91)9>. O H H
SO2CF3 SO2CF3
+ 2
N X
CCl4
X
SO2CF3
X = Cl, Br or I
X
SO2CF3
O 50
51a, X = Cl 76% 51b, X = Br 78% 51c, X = I 39%
ð20Þ
278
Functions Containing Two Halogens and Two Other Heteroatom Substituents
A study of the interaction of pentafluorothiophenol 52 and CCl4 in the presence of AlCl3 led to the conclusion that at room temperature, 60 C, or 80 C and irrespective of the amount of CCl4 and AlCl3 used, dichloromethane 53 was formed as the main product together with minor products chloromethane 54 and disulfide 55 (Equation (21)). The origin of observed products is depicted in Scheme 5. The stability of compound 53 toward hydrolysis or further reaction with starting material and compound 54 is attributed to the inefficient stabilization of the adjacent carbocationic center that is involved in these reactions <1999JFC(98)17>. C6F5SH
AlCl3, CCl4
Cl
SC6F5
Cl
SC6F5
52
+ (C6H5S)3CCl + (C6F5S)2
53
δ– δ+ C6F5SH + [CCl3...Cl...AlCl3]
C6F5SCCl3
AlCl3
ð21Þ
55
54
δ+ δ– C6F5SCCl2...Cl...AlCl3
Cl–
52 52
AlCl3
(C6F5S)2CCl2
δ– δ+ (C6F5S)2CCl...Cl...AlCl3
52
(C6F5S)3CCl
Cl–
53
54
Scheme 5
6.08.2.3
Two Halogens, an Oxygen, and a Sulfur Function
Earlier work on this category of compounds is represented only by MeOCCl2SCl synthesized by the addition of chlorine to either MeOC(S)SMe or MeOC(S)SSC(S)OMe or MeOC(S)SSC(S)OMe <1995COFGT(6)249>. Treatment of phenols or alcohols ROH with NaH, CS2, and then with MeI led to high yields of dithiocarbonates 55. Oxidative desulfurization–fluorination of dithiocarbonates 55 was carried out using tetrabutylammonium dihydrogentrifluoride (TBAH2F3) with NBS in CH2Cl2 to afford difluoro(methylthio)methylethers 56 (Scheme 6). Methyl ethers 56 were converted readily into trifluoromethyl ethers ROCF3 by reaction with 70% HF in pyridine and 1,3-dibromo-5,5dimethylhydantoin <2000BCJ471>. S R
O
F
TBAH2F3 SMe
NBS, CH2Cl2
55
R 4-MeC6H4 4-PrnC6H4 4-BrC6H4CH2CH2 PhCH2CH2CH2 n-C16H33 4-PhC6H4 4-(4-BrC6H4)C6H4
F
R O
SMe 56
Yield (%) 64 58 19 15 9 23 28
R 4-n-C6H13C6H4 4-MeOC6H4 4-PhCH2OC6H4 4-PrnOC(O)C6H4 3-MeOC(O)C6H4 4-BrC6H4
Yield (%) 36 33 43 42 32 43
Scheme 6
6.08.2.4
Two Halogens and Other Chalcogen Functions
Tetrahalogeno 1,3-diselenetanes, 1,3-ditelluretanes, and 1,3-selenatelluretanes are known, most common being the tetrafluoro derivatives. Iodo derivatives are unknown <1995COFGT(6)249>. Several difluoro(phenylseleno)methylethers 60 have recently been reported. Difluoromethylbenzene selenide 57 was prepared by the treatment of diphenyl diselenide with NaBH4 in a 2:1 ratio of
Functions Containing Two Halogens and Two Other Heteroatom Substituents
279
EtOH/DMF and then with CF2Br2. Oxidation of 57 led to the formation of oxide 58 (Scheme 7). Compound 58 was reacted with acetic anhydride in the presence of cyclic ethers 59 in refluxing CH2Cl2 to give difluoro(phenylseleno)methyl compounds 60 (Equation (22)). The reaction of selenoxide 58 with Ac2O and (4-MeOC6H4Se)2 in THF provided AcOCH2CH2CH2CH2OCF2SePh and AcOCH2CH2CH2CH2OCF2SeC6H4Me-4 <1995JOC370>.
(PhSe)2
i. NaBH4, EtOH, DMF
F2HCSePh
ii. CF2Br
O
H2O2, CH2Cl2
F2HCSePh
57
58
Scheme 7
Z 58 +
R
Ac2O, CH2Cl2
n
H 59
6.08.3
F
Z(CH2)nCH(R)OAc
F
SePh 60
R
Z
n
Yield (%)
Me H H Me H H
O O O O O S
1 2 3 3 4 3
34 60 87 56 74 53
ð22Þ
TWO HALOGENS AND ONE CHALCOGEN FUNCTION
6.08.3.1
Two Halogens, a Chalcogen, and a Nitrogen Function
6.08.3.1.1
Oxygen compounds
Several compounds of the general formula X2C¼N-R (where X is F or Cl and R = F, Cl, CF3, or CF2CFClY where Y is F, Cl, or Br) proved to be good electrophiles. They reacted with substrates such as FSO2OX, F5SOCl, and F3CO2H to give the corresponding addition products FSO2OCF2NFX, F5SOCCl2NCl2, F3COOCF2NHCF3, and F3COOCF2NHCF2CF2CFClX (where X = F, Cl, or Br). The synthesis and reactions of 3,3-difluoro-3-(trifluoromethyl or pentafluorothio)oxaziridines have also been described <1995COFGT(6)249>. The difluorocarbimide double bond in 61 is saturated in 20 min at room temperature by SF6OCl to give difluoromethane derivative 62 (Scheme 8). The reaction of difluorocarbimide 64 with (CF3)3COCl is much slower and requires 1 day to give difluoromethane derivative 65 (Scheme 9). Irradiation of 62 and 65 gives rise to tetrazanes 63 and 66, respectively <1995IC5049>.
CF3(C3F7)NN=CF2 + SF5OCl
OSF5 Cl F N N F3C CF3
20 min
61
OSF5 C3H7 N N CF3 F N OSF5 F3C N C F C3H7 F F
F
hν
62
63
Scheme 8
1 day (CF3)2NN=CF2 + (CF3)3COCl 64
OC(CF3)3 Cl F N N F3C CF3 65
Scheme 9
OC(CF3)3 CF3 N N F CF3 N C OC(CF3)3 F3C N F F F3C F
F
hν
66
280
Functions Containing Two Halogens and Two Other Heteroatom Substituents
6.08.3.1.2
Sulfur compounds
Representatives of this category of compounds are F5SCF2NF2, FSCF2NF2, Et3N+CF2SO2, R+CF2SCF2SO2 (where R is quinucidine), and FCl(SCl)NCS <1995COFGT(6)249>. Isocyanatodifluoromethanesulfonyl fluoride 69 was prepared in good yield from azidocarbonyldifluoromethanesulfonyl fluoride 68, which was obtained by the reaction of sodium azide with chloroformyldifluoromethanesulfonylfluoride 67 (Scheme 10). Compound 69 is extremely sensitive to moisture. Autocatalytic fragmentation is observed with water (Scheme 11) <1997JFC(84)135>. Cl O
CCF2SO2F
NaN3
N3 O
67
∆
CCF2SO2F
F
N=C=O
F
SO2F 69
68
Scheme 10
69
HOOCNHCF2SO2F
–CO2 –HF
HN=CFSO2F
N C OS
N CSO2F
–HF
F O
Scheme 11
6.08.3.2
Two Halogens, a Chalcogen, and Other Functions
Generally, work on this category of compounds is very limited. Most of it is focused on difluoromethanes (such as F3CPHCF2OMe and C2F5PHCF2OMe) derived respectively from F3CP¼CF2 and C2F5P¼CF2 by the addition of methanol. Sulfinic salt (EtO)2P(O)CF2SO2Na was formed from (EtO)2P(O)CF2Br and sodium sulfite or sodium dithionite, and PhSO2CX2HgPh was synthesized by the addition of the anion of halogenated sulfones PhSO2CHX2 to PhHgCl (where X is Cl or Br) <1995COFGT(6)249>. Recently, the reaction of polyfluorinated ether 70 with hexaethylphosphorus triamide (HEPT) and chlorotrimethylsilane in benzonitrile as solvent was described to give the stable silane 71, in a reaction where the silyl ether was used as a transfer reagent (Equation (23)) <1995IC13>. PhCN
C6F5OCF2Br + HEPT + Me3SiCl
F
OC6F5
F
SiMe3
ð23Þ
70 71
Phenyl(trimethylsilyl)difluoromethyl sulfide 73 can be prepared in 85% yield by the reaction of bromodifluoromethylphenyl sulfide 72 with magnesium metal and Et3SiCl in DMF at 0 C. Sulfide 73 was oxidized with 3-chloroperoxybenzoic acid (m-CPBA) in dichloromethane to afford sulfone 74 (Scheme 12) <2003JOC4457>. PhSCF2Br + Me3SiCl
Mg
F
SPh
DMF
F
SiMe3
72
+ PhSSPh 73 85% m-CPBA CH2Cl2, 0 °C 51% F
SO2Ph
F
SiMe3 74
Scheme 12
Functions Containing Two Halogens and Two Other Heteroatom Substituents 6.08.4
281
TWO HALOGENS AND TWO GROUP V ELEMENT FUNCTIONS
6.08.4.1 6.08.4.1.1
Two Halogens and Two Nitrogen Functions Diamines and their derivatives
Representatives of this class of compounds are quite large in number. Difluoromethyldiamines, RNCF2NR1, were prepared by the addition of fluorine and cesium fluoride or chlorine to the nitrile function of cyanamides R3NCN. Addition of SF4, F4SO, Br2, and HgF2 or Cl2 and HgF2 to the latter has produced sulfur containing amine derivatives. Dihalogenodinitromethanes CX2(NO2)2 are derived from the treatment of PhI¼C(NO2)2 with Cl2, Br2, NCS or NBS, difluorodiazirine with N2O4 under UV irradiation, and Br2C(NO2)2 by reaction with ammonia and then with chlorine. UV irradiation of polyhalogenated diamines such as (CF3)2NCF2R produced the corresponding difluoromethylene gem-diamines. (Me2N)2CF2 was prepared by fluorinating tetramethylchloroformaimidinium chloride with KF in CH3CN. Bis(dialkylamino)difluoromethanes, (R2N)2CF2, are easily available via chlorination of tetraalkyl urea derivatives with oxalyl chloride followed by the fluorination of (R2N)2CCl+Cl salts with KF in CH3CN or 1,3dimethyl-2-imidazinone solutions <1995COFGT(6)249>. Recently, bis(dialkylamino)difluoromethanes have been used as precursors for fluorinated hexaalkylguanidinium salts. For example, the reaction of (Me2N)2CF2 75 with (dimethyl- or diethylamino)trimethylsilanes in CH3CN afforded the salts 76 (Equation (24)) <1999EUPO949226, 2002IC6118>. F F
NMe2
R2NSiMe3
NMe2
R = Me or Et
+
[(Me2N)2CNR2] [Me3SiF2]
–
ð24Þ
76
75
Previously 75 was formed by treating tetramethyl urea with COF2 in the presence of NaF <1995COFGT(6)249>. Recently a high-yield preparation of 75 involved the straightforward fluorination of salt 77 using anhydrous Me4NF in dichloromethane (Equation (25)). Compound 75 reacts with Me2NSiMe3 in CH3CN to give hexamethylguanidinium chloride, (Me2N)3C+F, which in turn reacts with Me3SiCF3 in monoglyme to provide easy access to (Me2N)3CCF3 <2000JFC(103)159>. (Me2N)2CCl+ Cl–
+
M4NF
CH2Cl2, 0 oC
F
NMe2
95%
F
NMe2
77
6.08.4.1.2
ð25Þ
75
Cyclic compounds
In this category of compounds three-, five-, and six-membered halogenated azirine, 1,3-diazolidine, and 1,3,5-triazolinane derivatives are known. Difluoroazirine, for example, was prepared by the reaction of Bu4N+I on F2C(NF2)2 <1995COFGT(6)249>. Halogen exchange between 2-chloro-1,3-dimethylimidazolinium chloride 78 and NaF in CH3CN gives the difluoroimidazolidine 79 in 77% yield (Equation (26)) <1999EUP895991>. A similar preparation of 79 uses KF and 1,3-dimethyl-2-imidazinone as solvent in the reaction with 78 (Equation (26)) <1999EUP895991, 1999EUPO949226, 2000JAP(K)200053650, 2002IC6118>. Me N H N Cl.HCl Me 78
NaF, MeCN, 80 °C
Me N F
Me N
N F Me
or KF,
O, 85 °C N Me
79
ð26Þ
282
Functions Containing Two Halogens and Two Other Heteroatom Substituents
Difluoroimidazolidine 81 was prepared from 1,3-bis(2-methoxyethyl)-2-imidazolidinone 80 upon reaction with oxalyl chloride at 40 C, followed by AgF in CH3CN at 50 C (Equation (27)) <2002JAP(K)2002322156>. O O
N
i. (COCl)2, 40 °C
N
O
ii. AgF, MeCN, 50 °C
HO
F
F
N
N
80
OH
ð27Þ
81
2-Chloro-1,3-dimethyl-2,3-dihydro-1H-benzoimidazole 82 was converted into the difluoro derivative 83 with KF at 85 C (Equation (28)). Compound 83 is an efficient fluorinating agent used to transform benzyl alcohol, at ambient temperature, into benzyl fluoride in 54% yield <2001JAP(K)2001322984>. Me N Cl
Me N F
KF, 85 °C
N F Me
N H Me
ð28Þ
83
82
Cyclic difluoro gem-diamines 79 and 81 are efficient fluorinating agents. Compound 79 was used in the fluorination of cyclohexanone into 1,1-difluorocyclohexane (20%) and 1-fluorocyclohexane (68%) <2002PCT0266409>, of thioester PhCS(OMe) into the a,a-difluoroether PhCF2(OMe) in 89% yield <2002JAP(K)200215015>, and of 2-trimethylsiloxyoctane into 2-fluorooctane in 91% yield <2002JAP(K)2002104999>. Furthermore, compound 81 converted 1-octanol into n-octylfluoride in 81% yield <2001JAP(K)2002322156>. Difluoromethane 79 when reacted with (dimethyl- or diethylamino)trimethylsilane in CH3CN at 30 C gave (2-dialkylamino)-1,3dimethylimidazolinium trimethyldifluorosiliconates 84 in high yield (Equation (29)) <2002IC6118>. Me N F N Me
F
79
6.08.4.2 6.08.4.2.1
R2NSiMe3 MeCN, –30 °C R = Me or Et
Me N +
NR2[Me3SiF2]–
N Me
ð29Þ
84
Two Halogens and Two Phosphorus Functions Bis(phosphonates)
The interest in this category of compounds rests upon (dichlorophosphonomethyl)phosphonic acid Cl2C(PO3H2)2, a substance used in the treatment of increased bone resorption and malignant hypercalcemia, and also upon the diverse biological properties of ATP analogs. A general route to (dihalogenophosphonomethyl)phosphonic acids X2C(PO3H2)2 is halogenation of appropriate tetraesters H2C(PO3R2)2 to give (dihalogenophosphonomethyl)tetraesters X2C(PO3R2)2. Although for the hydrolysis step heating in concentrated hydrochloric acid was widely used, conversion of tetraesters X2C(PO3R2)2 into silyl derivatives X2C(PO3-TMS2)2, and hydrolysis with water was more convenient. Mixed tetraesters containing silyl esters were also synthesized in order to selectively hydrolyze the silyl ester groups. However, little is known about selective preparation of partial methylbis(phosphonate esters), due to the difficulties in obtaining pure compounds having exactly one, two, or three ester substituents. Nucleoside analogs have resulted from the coupling of X2C(PO3H2)2 with 50 -phosphoromorpholidate of adenosine. By an analogous manner, the CF2 analog of 30 -azido-3-deoxythymidine triphosphate was obtained. Several other nucleoside analogs were reported <1995COFGT(6)249, 1995T6805>. A general and selective method for the synthesis of dichloromethylbis(phosphonic acid) partial alkylesters 86 and 87 from tetraesters 85 makes use of tertiary or secondary amines as dealkylating reagents (Scheme 13) <1996TL3533>. The degree of demethylation was found to depend on
Functions Containing Two Halogens and Two Other Heteroatom Substituents
283
the type of amine and the length of the alkyl chains in the amine used. Treatment of tetraesters 85 (where R1 = R2 = R3 = R4 = Me and R1 = R2 = Pri, R3 = R4 = Me) with Bu3N at 50 C led to the formation of the corresponding partial esters 86 (where Z+ is Bu3N+Me) in quantitative yield. Treatment of tetraesters 85 (where R1 = R2 = R3 = R4 = Et, Pri, or Hex) with pyridine at 115–120 C afforded the respective partial esters 86 (where Z+ is C5H5N+Et, C5H5N+Pri, or C5H5N+(n-C6H14)) in 80–85% yield. Reaction of tetraesters 85 (where R1 = R2 = R3 = R4 = Me, Et, or allyl, and R1 = R2 = Bu or Et, R3 = R4 = Pri or Me) with piperidine at 105–110 C resulted in the formation of the corresponding partial esters 87 (where Z+ is C5H10N+H) in yields ranging from 36% to 100%. When tetraesters 85 (where R1 = R2 = R3 = R4 = Me, Et, Pri, n-C5H12, cyclopentane, or n-C6H14) were heated at 105–110 C with morpholine, the corresponding partial esters 87 (where Z+ is O(CH2CH2)2N+H) were formed in 20–80% yields. The mechanism of the reaction can be understood by considering that the tetraester acts as an N-alkylating agent (Equation (30)).
O Cl
OR1 P
OR2 OR3
C Cl O
O
P
O–
Z
R3N
Cl
MeCN
Cl
OR1 P
OR2 OR3
C O
+
86
O
P
R2NH
Cl
MeCN
Cl
OR1 P
C O
OR4 85
P
O– Z+ OR3 O– Z+
87
Scheme 13
O OR3 P O R4
R N R R'
O– OR3 P O
MeCN
+
R + R4 N R R'
ð30Þ
The synthesis of partial esters 91 uses tetraalkylesters 88 as starting materials (Scheme 14). Tetraester 88 (where R is Me) was treated with Bu3N while the other three were treated with pyridine to give ammonium salts 89. The latter are converted into the corresponding sulfonic mixed ‘‘anhydrides’’ 90 by reaction with mesyl chloride, and then treated with aqueous base in acetone to precipitate partial esters 91. The reaction mechanism of these products can be tentatively rationalized as depicted in Scheme 15. The obtained ammonium cation, R3N+R0 , possesses a very powerful election-withdrawing effect that probably attracts the chlorine of MsCl thus facilating sulfonation at PO. In the resulting intermediate, the POR bond is additionally weakened by the MeSO2-moeity allowing easy cleavage of the POR bond by the chlorine anion of the ammonium salt that leads to the product <1996TL3533>.
O Cl
OR P
C Cl O
P
OR OR
O Bu3N
Cl
OR P
C
or pyridine
Cl O
OR
88
P
O MeSO2Cl
OR OR
O
O– Z+ R
O Cl
or NaOH, H2O
Cl
P
OR OSO2Me O– Z+R
90
OR P
OR O–Na+
C O
OR P
C Cl
89
NaHCO3, H2O
Cl
P
O– Na+ 91
+
+
+
+
+
R = Me, Et, Pri, or n-C6H14; Z R = Bu3N Me, C5H5N Et, C5H5N Pri, or C5H5N n-C6H14
Scheme 14
284
Functions Containing Two Halogens and Two Other Heteroatom Substituents O Me S Cl R O – O + O R N R P R' O R
O Me O S O O P R + O R Cl– R N R R'
O Me S O O O R P + R N R O– R'
–RCl
Scheme 15
Two nonnucleoside triphosphate analogs 96 and 97 were synthesized as substrates for terminal deoxynucleotidyl transferase. Their preparation required activation of fluorenylmethoxycarbonylaminoethylphosphonic acid (Fmoc–aminoethyl–phosphonic acid) 92 by 1,10 -carbonyldi(1,2,4-triazole) 93 in DMF and then addition of MeOH followed by bis(tri-n-butylammonium)difluoromethylenediphosphate 94 to give ammonium salt 96 or bis(tri-n-butylammonium)dibromo-ethylenediphosphate 95 to give ammonium salt 97 (Scheme 16) <2000MI1787>. O N i.
N N
N
N N , DMF
93 ii. MeOH FmocNHCH2CH2P(OH)2 O 92
O– O– iii. [Bu3NH]2[F2CHOP O POH] 94 O O O– O– + or [Bu3NH]2[Br2CHOP O POH] 95 O O +
OH OH O– + FmocNHCH2CH2P O P X P O– [Bu3NH]2 O O O 96, X = F2C (15%) 97, X = Br2C (16%)
Scheme 16
6.08.4.2.2
Cyclic compounds
Diphosphiranes (X2CP(R)P(R)) were produced by reacting ylides (Ph3P+CX2) with Ph3P, and by reacting trans-diphosphene (ArPPAr) with dichloro and dibromocarbenes (CHX3) in the presence of KOH. 1,3-Diphosphetanes X2CP(R)P(R)CX2 have been prepared by treating Cl2PCHCl2 with Et3N; by thermolysis of Me3SnP(CF3)2 gave, along with 1,3-diphosphetane F2CP(CF3)P(CF3)CF2, the trimer 2,4,6-tris(trifluoromethyl)-1,3,5-triphosphorin; and by heating Me2NP(SnMe3)CF3 at 500–600 C at 0.001 torr. 1-t-Butyl-2,4-dichloro-3,3-difluoro[1,2,4]azadiphosphetidine was prepared from the reaction of Cl2P(S)CF2P(S)Cl2 and butylamine <1995COFGT(6)249>. 1,2-Dihydro-1,3-diphosphetes 99 were formed as formal [2+2]-cycloaddition products by the reaction of perfluoro-2-phosphapropene 98 with phosphalkynes of the type RCP. Instead of the not isolable aminophosphalkynes Me2NCP and Et2NCP, the precursors HP¼C(F)NR2 were successfully used as synthetic equivalents (Equation (31)) <1997JOM(529)177>. F F
PCF3
+
RC P or HP C(F)R
F –78 °C
F
P P
R
98
99 R
= But,
Me2N, Et2N, or
CF3
Pr2i N
ð31Þ
Functions Containing Two Halogens and Two Other Heteroatom Substituents
285
Treatment of dichloromethane derivative 100 with 1 equiv. of N,N0 -dimethyl-N,N0 -bis(trimethylsilyl)urea 101 at low temperature led to the formation of 1,5-diaza-2,4-diphosphorinane6-one 102 (Equation (32)). Further reaction of 102 with another equivalent of 101 resulted in the formation of a mixture of symmetric bicyclic products 103 and 104. It was found that compound 103 rearranges slowly into thermodynamically more stable 104 (Scheme 17) <1993HAC565>.
O
O Cl
PCl2
Cl
Me
Me N SiMe3
N Me3Si
+
PCl2
–15 °C
Cl
N P
N P
Cl
Cl
101
100
–2Me3SiCl 20 °C Me
Me
ð32Þ
Cl
102
N Me 102 + 101
–2Me3SiCl
Me
Me
N O P Cl P N Cl N
O Me Rearrangement Me
Me
Me N N P Cl P N Cl N
Me
O
O 103
104
Scheme 17
The substitution of the chlorine atoms bonded to phosphorus in 102 by fluorine, alkoxy, or phenoxy groups could be realized with the formation of the corresponding P,P0 -disubstituted derivatives 105 (Equation (33)) <1993HAC565>. O Me Cl
O
N P
N P
Cl
Cl
Me Cl
Me R
N P
N P
Cl
Cl
102
Me R
ð33Þ
105 R = F, MeO, EtO, PriO, or PhO
When compound 102 was allowed to react with catechol, 2,3-dihydroxynaphthalene, tetrabromocatechol, resorcinol, saligenin, or 3,5-di-t-butylcatechol in the presence of Et3N, bridged compounds 106 to 110 were formed (Scheme 18). Whereas the catechol derivative 106, the naphthol derivative 107, and the tetrabromocatechol derivative 108 could be easily obtained, the saligenin derivative 109 and the 3,5-di-t-butylcatechol derivative 110 were found to be stable only in solution. The reaction of 102 with 1,2,4,5-tetrahydroxybenzene led to the pentacyclic derivative 111. In addition, reaction of hydroquinone with 102 afforded the polycyclic structure 112 (Scheme 18) <1997HAC165>. During the first hours, reaction between 113 and 101 produced a mixture of products 114 and 115 that were found by NMR spectroscopy to be in the ratio 10:1. Isomer 114 rearranged after 6 days into isomer 115 (Scheme 19) <2002ZAAC(628)1903>.
6.08.4.2.3
Miscellaneous compounds
In this category the phosphorus atoms of linear compounds R-PCX2P-R are substituted by various atoms or groups. For example, Cl2P(S)CF2P(S)Cl2 was treated with PriOH, SbF3, TMSNMe2, and PhPCl2 to afford the corresponding derivatives (PriO)2P(S)CF2P(S)(OPri)2,
286
Functions Containing Two Halogens and Two Other Heteroatom Substituents O Me O
O
N P
N P
Cl
Cl
Me
Me
O
N N P P O Cl Cl O
Me Me O P N
Cl Cl
O Me
Cl
Cl
P N
P N
OH
106
O
OH
OH
OH
Me
O 112
Br
OH
Br Br
OH
HO
OH
Br
OH OH
Br Br Br
O Me
Me
OH
OH
OH
Me
O Me
Me
O O P P Cl Cl N N
O
OH
But
O
O P N Me
108
But
N N P P OCl Cl O
Me O P N Cl Cl
Br
102 HO
O
O P N Me 107
OH
N N P P OCl Cl O
N N P P O Cl Cl O
Me
Me 109
Me But
O 111
But 110
Scheme 18
N Cl
Cl
Cl
P Cl
O
P Cl
Cl
+
Me
Me Me
N Me3Si
N SiMe3
–2Me3SiCl
N P
O P
Cl Cl
113
O Me Rearrangement Cl
Cl 114
101
Me N P
Cl
N P
Me Cl
Cl
Cl 115
Scheme 19
F2PCF2PF2, (Me2N)2PCF2P(NMe)2, and Cl2PCF2PCl2. Dialkylphosphines R2PH reacted with monomeric F2C¼PCF3 to give R2PHCF2PHCF3 derivatives, which upon heating with elemental sulfur afforded R2P(S)CF2PHCF3 derivatives <1995COFGT(6)249>. Trifluoromethyl-1,3-diphosphane 117 is formed regioselectively in almost quantitative yield by the addition of t-butylphosphane to perfluoro-2-phosphapropene 116 as a mixture of two diastereoisomers (Scheme 20). Compound 117 reacts with nickel tetracarbonyl to give the binuclear complex 118 as the only isolable product. The mixture contains four of the eight possible isomers. One of them was isolated in pure form by crystallization from n-pentane and its structure deciphered by X-ray crystallography (Equation (34)) <1993ZN1203>.
Functions Containing Two Halogens and Two Other Heteroatom Substituents F3CP=CF2 + ButPH2
287
But(H)PCF2P(H)CF3
116
117 But
Bu
t
F
P H
F
P H
F
P H
F
P H
F3C
F3C
But
But
F
P H
F
P H
F
P H
F
P H
F3C
F3C (S ),(R )/(R ),(S )-racemate
(R ),(R )/(S ),(S )-racemate
Scheme 20
117
Ni(CO)4 –2CO
F FH F 3C P Ni(CO)2 H P P H (OC)2Ni CF3 P F HF
ð34Þ
118
Reaction of compound 100 with catechol and Et3N led to the formation of compound 119 involving two benzodioxaphospholane rings connected via a CCl2 group (Equation (35)).
Cl Cl
OH
PCl2 PCl2 100
+ OH
Et3N
Cl O P C P O Cl O O
ð35Þ
119
Reaction of 119 with 1 equiv. of tetrachloroorthobenzoquinone 120, led to the formation of a mixture of 121, 122, and 123. The insolubility of isomer mixture 122/123 enabled easy separation from 121, but neither of the two structures could be assigned unambiguously to one isomer (Scheme 21) <1997CB1479>.
6.08.4.3
Two Halogens, a Nitrogen, and a Phosphorus Function
(E)/(Z)-2,2,4,4-Tetrafluoro-1,3-bis-trifluoromethyl[1,3]diarsetane and 2,2,4,4,6,6-hexafluoro-1,3,5tris-trifluoromethyl[1,3,5]triarsinane were two compounds obtained when Me3SnAs(CF3)2 was thermolyzed <1995COFGT(6)249>. Reductive debromination of N-bromodifluoromethyl4-dimethylaminopyridinium bromide 124 with tetrakis(dimethylamino)ethene (TDAE) lead to carbanionic species 125, which in the presence of Ph2PCl and Me3SiOTf provided the water soluble 1-(difluorodiphenylphosphanylmethyl)-4-dimethylaminopyridinium triflate 126 in 67% yield (Scheme 22). The imidazole-N-difluoromethylanion 128 was generated in situ from 1-bromodifluoromethylimidazole 127 using (Et2N)3P under Marchenko–Ruppert reaction conditions and trapped in the presence of Ph2PCl to afford (imidazol-1-yl)difluoromethyldiphenylphosphine 129 in 78% yield (Scheme 23) <2001JFC(109)173>.
288
Functions Containing Two Halogens and Two Other Heteroatom Substituents Cl
Cl
Cl Cl Cl
O Cl O O P C P O O O Cl
O
Cl Cl
O Cl
121
120
119
Cl
Cl
Cl Cl
Cl
Cl
Cl
Cl O O O O P C P O O O Cl O
Cl O O Cl O O P C P O O Cl O O
or Cl
Cl
Cl Cl
Cl
Cl Cl
Cl 123
122
Scheme 21
+
Me2N
NCF2Br
TDAE
+
–
Me2N
N CF2
Br– 124
i. Ph2PCl, TDAE
+
Me2N
ii. Me3SiOTf
NCF2PPh2
–OTf
126
125
Scheme 22
N N CF2Br 127
P(NEt2)3
N
–
N CF2 128
Ph2PCl
N N CF2PPh2 129
Scheme 23
6.08.5 6.08.5.1
TWO HALOGENS AND ONE GROUP V ELEMENT FUNCTION Two Halogens, a Phosphorus, and a Metalloid or Metal Function
In this category, various phosphonates and their salts such as Cl2C(TMS)P(O)(OEt)2, (TMS)(Cl or F)2CP(O)(OEt)2, (Bu3Sn)F2CP(O)(OEt)2 PhHgCF2P(O)(OEt)2, (Li+ or BrCd+)CX2P(O) (OEt)2, (BrCd+ or BrZn+)CF2P(O)(OEt)2, and (Cd2+)[CF2P(O)(OEt)2]2 have been synthesized <1995COFGT(6)249>. The silylated phosphonate (Me3Si)CF2P(O)(OEt)2 132 was readily prepared in 92% yield by direct silylation of (Br)CF2P(O)(OEt)2 130 using n-BuLi and Me3SiCl in THF at 78 C <1996T165>. Under similar reaction conditions, 130 was treated at low temperature in THF with PriMgCl (Scheme 24). This magnesium–bromine exchange reaction gave organomagnesium compound 131 that was stable for several days at low temperature. Compound 131 is more stable than the organolithium analog (Li+)F2CP(O)(OEt)2 133, when by contrast the organocadmium (BrCd+)CF2P(O)(OEt)2 134 and the organozinc (BrZn+)CF2P(O)(OEt)2 135
Functions Containing Two Halogens and Two Other Heteroatom Substituents
289
compounds are stable even at room temperature. With Me3SiCl, magnesium reagent 131 was converted into the silylated compound 132 in 90% yield <1997JOM(529)267>. Compound 132 was prepared less efficiently by electrochemical reduction of 130 in DMF and Me3SiCl, using a zinc anode at a current density of 10 mA cm2 <1997JFC(85)127>.
Br
F C P(OEt)2 F O
PriMgCl THF, –78 °C
F ClMg C P(OEt)2 F O 131
130
Me3SiCl, THF –78 °C
90% Zn anode, 2e, Me3SiCl, DMF 40%
Me3Si
F C P(OEt)2 F O 132
Scheme 24
Salt (Li+)CF2P(O)(OEt)2 133 was used on route to prepare (a,a-difluoroalkyl)phosphonates <1993JOC6174>, 50 -deoxy-50 -difluoromethylphosphonate nucleotide analogs <1995JOC2563>, and 1,1,6,6-tetrafluorohexane-1,6-bisphosphonic acid <2000HAC470>. Salt (BrCd+)CF2P(O)(OEt)2 134 underwent CuCl coupling with aryl iodides to give (a,a-difluorobenzylic)phosphonates <1996TL2745>. Mimetic L-4-[diethylphosphono(difluoromethyl)]phenylalanine derivatives were prepared from appropriately protected L-4-iodophenylalanine by esterification with diazomethane followed by a CuCl-mediated coupling with 134 <1997T11171>. Salt (BrZn+)CF2P(O)(OEt)2 135 was regioselectively cross coupled in a CuBr-mediated medium with methyl 2,5-diiodobenzoate <1999BMCL3109>, with various iodobenzene derivatives but with sonication <2000JCS(P1)2591>, and with -halo-,-unsaturated carboxylic acid derivatives <2000JOC4888>.
6.08.5.2
Two Halogens, a Nitrogen, and a Metalloid Function
Me3SiCl was able to trap intermediate 125 followed by the exchange of fluoride for triflate as counterion providing water-soluble 1-(difluorotrimethylsilylmethyl)-4-dimethylaminopyridinium triflate 136. The latter was reacted with benzaldehyde to give pyridinium triflate 137 (Scheme 25). The imidazol-N-difluoromethyl anion 129 and 2-methyl-1-difluoromethylbenziimidazole anion 141 were generated using (Et2N)3P in CH2Cl2 at 70 C under Marchenko–Ruppert reaction conditions from 127 and 1-difluoromethyl-2-methylbenzimidazole 140, and then trapped by Me3SiCl to yield imidazol-1-yltrimethylsilane 138 and benzimidazol-1-yltrimethylsilane 142 derivatives. Compounds 138 and 142 were also produced from 127 and 140 by the Grobe method, that is, using Al powder in N-methylpyrrolidinone (NMP) at 2040 C to generate the anions 129 and 141 followed by trapping with Me3SiCl. The heteroaryl-N-difluoromethyltrimethylsilanes 138 and 142 were quantitatively converted into their respective heteroarylium derivatives 139 and 143 (Scheme 26) <2001JFC(109)173, 2001SL374>.
+
i. Me3SiCl 125
ii. Me3SiOTf
+
NCF2SiMe3
Me2N
PhCHO +
Me4NF–
–OTf
+
Me2N F–
O– NMe4 NCF2C Ph H 137
136
Scheme 25
290
Functions Containing Two Halogens and Two Other Heteroatom Substituents N
(Et2N)3P, CH2Cl2, –70 °C
N R N CF2Br
R N CF2
or Al, NMP, 20–40 °C R = H or Ph
129
127
+
N
Me3SiCl
R N CF2SiMe3
MeOTf pentane
Me N CF2Br
–OTf
R N CF2SiMe3
138
N
Me
N
139
(Et2N)3P, CH2Cl2, –70 °C
N Me
or Al, NMP, 20 – 40 °C
N CF2
140
141
N
Me3SiCl
Me N CF2SiMe3
Me N+ –OTf Me N CF2SiMe3
MeOTf Pentane
142
143
Scheme 26
6.08.6
TWO HALOGENS AND TWO METALLOID FUNCTIONS
6.08.6.1 6.08.6.1.1
Two Halogens and Two Silicon Functions Linear carbosilanes
Perchloro-1,3-disilapropane Cl2C(SiCl3)2, prepared by photochlorination of Cl3SiCH2SiCl3, was converted into Cl2C(SiF3)2, reduced to Cl2C(SiH3)2, and transformed into Cl2C(SiCl3) (SiMeCl2). Several other compounds in this category, for example, Cl2C(TMS)2, Cl2C(TMS) (SiMe2Cl), Cl2C(TMS) (SiMeCl2), Cl2Si(CCl2SiCl3)2, Cl2Si(CCl2SiF3)2, Cl2C(SiCl3) (SiMeCl2), F3SiCCl2SiF2CH2SiF3, and F3SiCCl2SiF2CHClSiF3, have been prepared by various methods. Dihalo and dimethoxycarbosilanes of the general formula (XMe2Si)2 reacted with difluorocarbene to give difluoromethylsilane derivatives F2C(SiMe2X)2. Further reactions of F2C(SiMe2F)2 with Grignard and organolithium compounds have been reported <1995COFGT(6)249>. Reaction of 1,1,1,2,2-pentamethyl-2-chloromethyldisilane 144 with AlCl3 in pentane led to the rearrangement product 145 in 65% yield (Equation (36)) <1996IZV1511>. The dibromide, Br2C(SiMe3)2, was prepared on a multigram scale and in near quantitative yield by the addition of methylene dibromide to lithium diisopropylamide in the presence of Me3SiCl at 110 C. The use of excess Me3SiCl may prevent decomposition of the presumed intermediate carbenoids [LiCHBr2 and BrLiC(SiMe3)2] before silylation and/or prevent CC formation between BrLiC(SiMe3)2 and Br2C(SiMe3)2. Compound 145 was used in the chromium(II)-mediated transformation of a variety of aldehydes into vinylbis(silanes), RCH¼(SiMe3)2 <1997JCS(P1)2279>. Me Me3Si Si CCl3 Me 144
AlCl3, pentane 65%
Me3Si
Cl Me C Si Cl Cl Me
145
ð36Þ
291
Functions Containing Two Halogens and Two Other Heteroatom Substituents
Electroreduction of a mixture of ClF2C(SiMe3)2 and Me3SiCl in the THF/hexamethylphosphoramide (HMPA) solvent system and in the presence of Bu4NBr as an electrolyte support, resulted in the formation of Me3SiCF2SiMe3 148 (anion-derived product), as major product, and Me3SiCF2CF2SiMe3 147 (radical-derived product), as minor product. Compound 148 difluoro2 methylates aldehydes through the action of a difluoromethylene dianion, CF3 , equivalent <1997JA1572>. Difluoromethylbis(phenyl sulfone) 146, obtained by the oxidation of PhSO2CF2SPh with H2O2, and sulfone 74 reacts with Mg and TMSCl in DMF to produce 147 as the major product together with 148 as the minor product (Equation (37)) <2003JOC4457>. 25% 74
70%
Mg, TMSiCl
Me3SiCF2CF2SiMe3
DMF (PhSO2)2CF2
F
SiMe3
F
SiMe3 8%
+
79% 147
146
ð37Þ
148
Methylene dibromide reacts with lithium aluminum hydride (LDA) in THF at 78 C and then with diphenylmethylsilyl chloride 150 gave, via the lithium salt 149, the dibromosilylmethane 151. The latter was deprotonated by LDA under the same conditions and the resulting lithium salt 152 was silylated with Me3SiCl to yield the dibromodisilylmethane 153 (Scheme 27). By a similar type of reaction, CB4 and silyl chloride 150 reacted in the presence of 2 equiv. of n-BuLi to yield Br2C(SiMePh2)2 in 75% yield <2001CL956>.
Br
H
LDA, THF
Br
Br
H
–78 °C
Br
–Li+
Ph2MeSiCl 150
Br
SiMePh2
85%
Br
H
H
151
149
LDA, THF
SiMePh2
Br
–78 °C
Me3SiCl
–Li+
Br
Br
SiMePh2
Br
SiMe3 153
152
Scheme 27
6.08.6.1.2
Cyclic carbosilanes
In this category, representative compounds are five-membered rings 1,1,2,2,3,3,4,4,5,5decachloro[1,3]disilolane and 1,1,2,2,3,3,4-heptachloro-5-trimethylsilanyl-2,3-dihydro-1H-[1,3]disilole and the six-membered ring 1,1,2,2,3,3,4,4,5,5,6,6-dodecachloro[1,3,5]trisilinane. Several derivatives of these compounds have been synthesized and their chemistry explored <1995COFGT(6)249>. Photobromination of trisilacyclohexane 154 with NBS in CCl4 led to the formation of a mixture containing trisilacyclohexanes 155 and 156 in a ratio of 1:1 and about 10% of compound 157. Isolation of 155 and further photobromination afforded 156 in 90% yield (Scheme 28). Compound 157 was obtained in 70% yield by reacting 155 with ICl and treating the intermediate 158 with LiCBr3 (Scheme 29) <2000CJC1388>. Me
Me
Me Si Me
Si Me Me 154
Me
O
Si +
N Br O
CCl4 hν
Me
Me
Me Si Si Me Me Me Br Br 155
Scheme 28
Me Si
Si +
Br Br Si Me
Me Si Me Me Br Br 156
Me
CBr3 Si
+ Me Si Si Me Me Me Br Br 157
292
Functions Containing Two Halogens and Two Other Heteroatom Substituents Me
Cl Si
ICl 155
LiCBr3
Me Si Si Me Me Me Br Br
70%
157
158
Scheme 29
6.08.7
TWO HALOGENS AND TWO METAL FUNCTIONS
Several compounds in this category are represented by the general formula X2C(SnR3)2 and are prepared by the insertion of dichlorocarbene into tin derivatives R3Sn–SnR3. However, compound Br2C(SnMe3)2 could also be prepared by coupling of Me3SnCBr2TMS with Me3SnCBr2MgCl <1995COFGT(6)249>. The reaction of Na2[Fe2(CO)8] with Br2CF2 in pentane generates (CO)3Fe(-CO)2(CF2)Fe(CO)3 159. Compound 159 reacts with PPh3 with replacement of two CO ligands to form Fe2(CO)6(-CF2)(PPh3)2 160. Both complexes 159 and 160 were characterized by single crystal X-ray diffraction. A simplified structure of 159 and 160 extracted from the molecular structure is depicted below <2001ZAAC(627)1859>. O C F OC CO OC Fe C Fe CO CO OC F C O
F F PPh3 OC OC Fe Fe CO CO OC PPh CO 3 160
159
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294
Functions Containing Two Halogens and Two Other Heteroatom Substituents Biographical sketch
George Varvounis was born in Alexandria, Egypt, in 1953. He received his B.Sc. degree in chemistry and biochemistry in 1977 at the Polytechnic of Central London, UK, his M.Sc. degree in applied heterocyclic chemistry in 1979 and Ph.D. degree in organic chemistry in 1982 at the University of Salford, UK. He became a Lecturer at the University of Ioannina, Greece in 1982, an Assistant Professor in 1990, and an Associate Professor in 2001. He spent several short periods on sabbatical leave working with Dr. G. W. H. Cheeseman at Queen Elizabeth College, University of London in 1983–1987, with Professor H. Suschitzky and Dr. B. J. Wakefield at the University of Salford, and, with Professor J. A. S. Smith and Dr. C. W. Bird at King’s College London, University of London in 1988–1994. His research interests include the synthesis and properties of heterocyclic compounds, especially benzo- and naphtho-fused tricycles containing nitrogen, nitrogen and oxygen, or nitrogen and sulfur.
Nikolaos Karousis was born in Athens, Greece, in 1971. He received his B.Sc. degree in chemistry in 1995 and his Ph.D. degree in organic chemistry in 2003 under the supervision of Associate Professor Varvounis. During the period 2000–2002 he served in the Greek army. He is now working as postdoctoral fellow on the synthesis of analogs of the pyrrolo[2,1-c][1,4]benzodiazepine group of antitumor antibiotics.
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Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 271–294
6.09 Functions Containing One Halogen and Three Other Heteroatom Substituents S. V. YARLAGADDA and R. MURUGAN Reilly Industries Inc., Indianapolis, IN, USA 6.09.1 INTRODUCTION 6.09.2 ONE HALOGEN AND THREE CHALCOGENS 6.09.2.1 One Halogen and Three Oxygen Functions 6.09.2.2 One Halogen, Sulfur, and Oxygen Function 6.09.2.2.1 One halogen and three sulfur functions 6.09.2.2.2 One halogen, two sulfurs, and one oxygen function 6.09.2.3 One Halogen, Selenium, and Sulfur Function 6.09.3 ONE HALOGEN AND TWO CHALCOGENS 6.09.3.1 One Halogen, Two Chalcogens, and a Nitrogen 6.09.3.2 One Halogen, Two Sulfurs, and a Phosphorus Function 6.09.3.3 One Halogen, Two Sulfurs, and a Metal Function 6.09.4 ONE HALOGEN AND ONE CHALCOGEN 6.09.4.1 One Halogen, One Chalcogen, and Two Group 15 Elements 6.09.4.1.1 One halogen, one oxygen, and two nitrogen functions 6.09.4.1.2 One halogen, one sulfur, and two nitrogen functions 6.09.4.1.3 One halogen, one chalcogen, and two phosphorus functions 6.09.4.2 One Halogen, One Sulfur, and Two Silicon Functions 6.09.5 ONE HALOGEN AND THREE GROUP 15 ELEMENTS 6.09.5.1 One Halogen and Three Nitrogen Functions 6.09.5.1.1 Halonitromethanes 6.09.5.1.2 Miscellaneous halonitromethanes 6.09.5.1.3 Halotriaminomethanes 6.09.5.1.4 (Difluoroamino)fluorodiazirine 6.09.5.1.5 Fluorine-containing diaziridines 6.09.5.2 One Halogen, One Nitrogen, and Two Phosphorus Functions 6.09.5.3 One Halogen and Three Phosphorus Functions 6.09.6 ONE HALOGEN AND TWO GROUP 15 ELEMENTS 6.09.6.1 Metal Halodinitromethides 6.09.6.2 Metal Bis(phosphonyl) Halomethides 6.09.7 ONE HALOGEN AND ONE GROUP 15 ELEMENT 6.09.8 ONE HALOGEN AND METALLOID FUNCTION (THREE, TWO, OR ONE, TOGETHER WITH METALS) 6.09.8.1 One Halogen and Three Metalloid Functions 6.09.8.1.1 Three silicon functions 6.09.8.1.2 Two silicons and a germanium function 6.09.8.1.3 Two silicons and a boron function 6.09.8.1.4 Three boron functions or two borons and a metal function 6.09.8.2 One Halogen, Two Metalloids, and One Metal Function
295
296 296 296 296 296 298 298 298 298 298 299 299 299 299 299 300 300 300 300 300 300 301 301 301 301 301 302 302 302 302 302 302 302 303 303 303 303
296 6.09.1
Functions Containing One Halogen and Three Other Heteroatom Substituents INTRODUCTION
The literature search done for this chapter showed that little work has been done in this area. Many subsections of the corresponding chapter in COFGT (1995) <1995COFGT(6)271> had no relevant work done during the period 1993–2003 as shown by a literature search and confirmed by a search of authors, whose groups were researching in this area. Where no literature was found, a summary of the work reported in the corresponding sections of COFGT (1995) <1995COFGT(6)271> is provided. In addition, we have included a summary for a better comparison of the functional group transformations. Chalcogens is a term used for group 16 elements or the oxygen family.
6.09.2
ONE HALOGEN AND THREE CHALCOGENS
6.09.2.1
One Halogen and Three Oxygen Functions
These functional groups are called halo orthoformates. In COFGT (1995) <1995COFGT(6)271>, halo orthoformates were made by halogenation of orthoformates or carbonates, and by displacement by substituted oxygen nucleophilies on carbon tetrachloride. Halogen exchange on a halo orthoformate has also been used in preparing such compounds. Huang and DesMarteau have reported an interesting work on fluorination and reactions of a few fluoro compounds to give the fluoro orthoformates <2001JFC363, 1999CC1671>. The reaction of bis(fluoroformyl) peroxide with fluorine in the presence of cesium fluoride or potassium fluoride produces FOCF2OOC(O)F in 60% yield along with a small amount of FOCF2OOCF2OF. The hydrolysis of difluorofluoroxymethyl fluoroperformate gave FOCF2OOC(O)OOCF2OF, which on fluorination gave the corresponding fluoro orthoformate (Equation (1)). O O FOF2C
6.09.2.2 6.09.2.2.1
O O
O
CF2OF
F2
O FOF2C
F O
OF O O
ð1Þ CF2OF
One Halogen, Sulfur, and Oxygen Function One halogen and three sulfur functions
The approaches to halo thioorthoformate derivatives are very similar to those used for the corresponding oxygen compounds, halo orthoformates as shown in COFGT (1995) <1995COFGT(6)271>. However, sulfur can show more than two valencies and this leads to different types of halo thioorthoformates. Halo thioorthoformates can be acyclic or cyclic and the sulfur can be in sulfide, sulfoxide, or sulfone oxidation states. Halogenation of thiocarbonates either with halogens or with sulfenyl halides leads to halo thioorthoformates. Halogen exchange can also convert one halo thioorthoformate into another halo thioorthoformate. During the decade 1993–2003, little work was reported in this category. Senning and co-workers described the reactions of sulfenyl chlorides, in particular, chloro[(4-methylphenyl)sulfonyl] (phenylthio)-methanesulfenyl chloride 1, and chloro[(4-chlorophenyl)sulfonyl] [(1-methylethyl)thio]methanesulfenyl chloride 2 <1998SUL19, 1999SUL73, 1994PS(86)239> with thiobenzoic acid, 4-amino-ethylbenzene, and aniline. Compound 1 is dehalogenated by potassium iodide to a trithiocarbonate derivative (Equation (2)).
PhS
O ClS C S Cl O Me 1
Functions Containing One Halogen and Three Other Heteroatom Substituents
297
O SPr-i S C SCl O Cl Cl 2 Ph S O ClS C S Cl O
S O PhS C S O
KI, MeCN
ð2Þ
Me
Me
1
Tris(perfluoroorganochalcogenyl)methyl compounds are useful starting materials in organic chemistry. Thus (F3CS)3CCN easily undergoes hydrolysis in the presence of H2SO4 to the corresponding amide and reacts with oxalyl chloride to give the tris(trifluoromethylthio)methyl isocyanate. A number of methods are available for the synthesis of (F3CS)3CCN, however, the nucleophilic substitution of bromide in (CF3S)3CBr with silver cyanide is the most simple and convenient of them all (Equation (3)) <1994CB449>. AgCN (CF3S)3CCN
(CF3S)3CBr
ð3Þ
Tris(trifluoromethylselenyl or sulfuryl)carbenium, (CF3Z)3C+, (Z = Se or S) moieties are suitable synthons for the preparation of (CF3Z)3C halides <1996CB1383>. The carbenium ions prepared by the reaction of (CF3Se)3CF with arsenic pentafluoride in liquid SO2 medium on treatment with potassium halides provide (CF3Se)CX, (X = F, Cl, Br). The same approach is not extendable to the iodo analog as it gives the diseleno derivative and other olefinic compounds. Arsenic pentafluoride oxidizes tetra(trifluoromethylthio)methane, (F3CS)4C, to yield a stable salt, (F3CS)3C+ AsF6. This salt reacts with halide ions to form halo tris(trifluoromethylthio)methane, (F3CS)3CX (X = F, Cl, Br) as mentioned above for the equivalent selenium compound. In the case of iodide, it is oxidized to iodine with the formation of (F3CS)3CC(SCF3)3 <1994CB597, 1996JFC7>. Tris(trifluoromethylthio)carbonium arsenic hexafluoride, (F3CS)3C+ AsF6, easily abstracts a fluorine from 2,2,4-trifluoro-4-(trifluoromethylthio)1,3-dithietane to give (F3CS)3CF and 2,2-difluoro-4-(trifluoromethylthio)-1,3-dithietane hexafluoroarsenate (Equation (4)). F F S
F
F
(F3CS)3C+ AsF 6–
S
F3CS SCF3 + F3CS
SCF3 F
F
S S + SCF3 AsF6–
ð4Þ
Cyclic diaryliodonium salts fall under this category of halo thioorthoformate where all three sulfurs are in the sulfone form. These compounds showed generally poor reactivity towards nucleophilic substitution reactions. This surprisingly poor reactivity of cyclic diaryliodonium salts with nucleophiles was solved, shedding light on its mechanism <2000CSR315>. Bozopoulos and co-workers have determined the crystal structure of 2,20 -biphenyleneiodonium (methylsulfonyl) bis(phenylsulfonyl) methylide 3 <1994MI528>. The crystal structure of 3 showed that the two iodine carbon bonds and the two iodine oxygen secondary bonds to different sulfonyl groups, form a distorted planar tetragonal co-ordination around the iodine atom. Another feature of interest is the delocalization occurring in the carbanion and its planarity. O O S Me O O Ph S C S Ph O I O
3
298
Functions Containing One Halogen and Three Other Heteroatom Substituents
El-Sayed and co-workers have studied the effect of reaction conditions on the chlorotropic rearrangement of (1-adamantylsulfonyl) (pentachlorophenylthio)chloromethanesulfenyl chloride <1994JCS(P1)1251> (Scheme 1). The starting sulfenyl chloride gives (1-admantylsulfonyl)dichloromethyl pentachlorophenyl disulfide if left in CHCl3 for a few days, whereas it forms S-[(pentachlorophenylthio) dichloromethyl] adamantane-1-thiosulfonate when refluxed in ether or left standing in CHCl3 for a much longer time. O O S
R1
CHCl3, 5 days rt
Cl C
O O S
S S Cl R2
R1 Cl C
Cl
96%
CHCl3 Ether
S S R2
longer time rt
Reflux Cl
Cl
O O S S S 1 R 2 R C
R1 = 1-Ad R2 = C6Cl5
98%
Scheme 1
6.09.2.2.2
One halogen, two sulfurs, and one oxygen function
Halo dithioorthoformates have been obtained by the halogenation of dithiocarbonates <1995COFGT(6)271>. No new reports on the preparation of these halo dithioorthoformates for the review period 1993–2003 were found.
6.09.2.3
One Halogen, Selenium, and Sulfur Function
Halo selenothioorthoformates have been obtained by halogenation of diselenothiocarbonate and by the reaction of either selenyl or sulfenyl chloride with selenothiocarbonates <1995COFGT(6)271>. No new synthetic approach has been reported during the period 1993–2003 on this class of halo selenothioorthoformates.
6.09.3 6.09.3.1
ONE HALOGEN AND TWO CHALCOGENS One Halogen, Two Chalcogens, and a Nitrogen
These compounds, referred to as substituted halomethane derivatives, in COFGT (1995) <1995COFGT(6)271> are made by the addition of peroxides to cyanogen chloride, and by either addition of diazonium salts, or adding a nitration mixture to halo diarylsulfonylmethanes. The nitrogen part of this functional group can also be an azide. Crawford and co-workers have synthesized the interpseudohalogen, ClCS2N3, by chlorination of cyclic pseudohalogen (CS2N3)2 (Equation (5)) <1999ICA68>. S S C C S S N3 N 3
6.09.3.2
Cl2
Cl
ð5Þ
S S
N3
One Halogen, Two Sulfurs, and a Phosphorus Function
No new preparative methods were reported under this category in the decade 1993–2003. In COFGT (1995) <1995COFGT(6)271>, the synthesis of halodisulfonylmethyl phosphonates by halogenation of phosphonium salts, like triethoxyphosphonium bis(diphenylsulfonyl)methylide, was described. These phosphonates have also been prepared by nucleophilic displacement with a sulfur nucleophile on trihalomethylphosphonate ester.
Functions Containing One Halogen and Three Other Heteroatom Substituents 6.09.3.3
299
One Halogen, Two Sulfurs, and a Metal Function
No new preparative methods for this class of compounds have appeared in the period after 1999–2003 The metallo halo disulfonylmethanes reported in COFGT (1995) <1995COFGT(6)271> were prepared from bis(sulfonyl)halomethanes by treatment with either sodium hydroxide or by other strong bases like alkyllithiums.
6.09.4
ONE HALOGEN AND ONE CHALCOGEN
6.09.4.1
One Halogen, One Chalcogen, and Two Group 15 Elements
No preparations have been reported in the period 1993–2003 for this class of compounds, where the two group 15 elements are phosphorus and the chalcogen is sulfur.
6.09.4.1.1
One halogen, one oxygen, and two nitrogen functions
The most cited compounds in this category are oxaziridines. In general, the oxaziridines are prepared by the oxidation of perfluoroimines with aromatic peroxides or hydrogen peroxide. The reaction of polynitrohalomethane with t-butyl-1-adamantane carboxylate gave an oxaziridine derivative (Equation (6)) <1994ZOR704>. O
X O2N O2N NO2
+
X
37–39%
t-BuO
O N O
O2N
ð6Þ
X = -F -Cl
Moss and co-workers have reported the improved synthesis of alkoxychlorodiazirines <2002JPC12280> by a procedure similar to one reported by Smith and Stevens mentioned in COFGT (1995) (Scheme 2) <1995COFGT(6)271>. A mixture of octanol, cyanamide, and anhydrous trifluoromethanesulfonic acid was heated in chloroform under nitrogen, to give octyloxyisouronium trifluoromethane sulfonate (Step 1). This was then treated with LiCl in dimethyl sulfoxide and pentane as solvent, and subsequently with sodium hypochlorite to give the octyloxychlorodiazirine (Step 2).
Cyanamide HO-(CH2)7-Me
CF3SO3H
NH H2N C O (CH2)7 Me
. CF3SO3H
Step 1 LiCl, DMSO, pentane Step 2
NaOCl
N Cl N O (CH2)7 Me
Scheme 2
6.09.4.1.2
One halogen, one sulfur, and two nitrogen functions
No synthetic method has been reported in the decade 1993–2003 for this class of compounds. Compounds reported so far in this class are either 1-chloro-1,1-dinitromethyl sulfides or sulfones. They have been prepared by chlorination of the potassium salts of dinitromethyl sulfides or dinitromethyl sulfones <1995COFGT(6)271>.
300
Functions Containing One Halogen and Three Other Heteroatom Substituents
6.09.4.1.3
One halogen, one chalcogen, and two phosphorus functions
This class of compounds has been made by the Michaelis-Arbuzov reaction, between triethylphosphite and trichloromethyl phenyl ether <1995COFGT(6)271>. Halogenation of alkoxymethylene (or alkylthiomethylene) bisphosphonates also leads to this class of compounds <1995COFGT(6)271>. No new reports were found in the period 1993–2003.
6.09.4.2
One Halogen, One Sulfur, and Two Silicon Functions
There have not been any reports of the synthesis of this class of compounds in the period 1993–2003. Some examples were made previously by halogenation of bis(trimethylsilyl)methyl sulfides as reported in COFGT (1995) <1995COFGT(6)271>.
6.09.5
ONE HALOGEN AND THREE GROUP 15 ELEMENTS
6.09.5.1 6.09.5.1.1
One Halogen and Three Nitrogen Functions Halonitromethanes
Halonitromethanes (one halogen and three nitro groups) are widely used as oxidants in monopropellant fuels and in bipropellant systems with hypergolic fuels and their synthesis has been thoroughly covered in COFGT (1995) <1995COFGT(6)271>. The simplest synthetic route for halonitromethanes is the halogenation of trinitromethane potassium salt <1994ZOR704>. Fluoro--azidodinitromethane was prepared (Equation (7)) by reacting -(difluroamino)trinitromethane with sodium azide (NaN3) in the presence of dimethylformamide (DMF) and CH2Cl2 to give 37% yield of the desired product <1997MI324>. NO2 O2N C O N NF2
F O2N C O2N N3
NaN3, DMF, CH 2Cl 2 37%
2
ð7Þ
Reaction of difluoroaminotrinitromethane with metal fluorides (KF and CsF) in DMF yields a fluorodifluoroaminodinitromethane (Scheme 3). The reaction of F2NC(NO3)3 with LiBr in ethanol or DMF affords Br(O2N)C = NF rather than the expected bromo derivative, BrF2NC(NO2)2 <2001MI736>. F
NF2 O 2N O2N
i
NO2 ii
O2N O2N
NO2
ii Br
Br(O2N)C=NF i. KF, CsF, DMF ii. LiBr, DMF
O2N O2N
NF2
Scheme 3
6.09.5.1.2
Miscellaneous halonitromethanes
Halo compounds with two nitro groups and one amino group are reported under this category. The preparation of these compounds is thoroughly covered in COFGT (1995) <1995COFGT(6)271>. Compound, FC(NO2)2NF2 behaves similarly to FC(NO2)3, with respect to stability and decomposition. The Arrhenius parameters were determined for the decomposition rates controlled by rupture of a CNO2 bond in both the gaseous and the liquid states <1995IZV649, 2000MI234>.
Functions Containing One Halogen and Three Other Heteroatom Substituents 6.09.5.1.3
301
Halotriaminomethanes
Poly(fluoroamino)halomethanes come under this category and are used as bleaching and pyrotechnic agents. Several patents were known on these compounds, however, in the early 2000s only a few reports were available in academic journals <1995COFGT(6)271>.
6.09.5.1.4
(Difluoroamino)fluorodiazirine
No new reports have been available for the preparation of this class of compounds in the review period 1993–2003. This compound was reported in COFGT (1995) <1995COFGT(6)271>.
6.09.5.1.5
Fluorine-containing diaziridines
These compounds have been reported in COFGT (1995) <1995COFGT(6)271> to be made either by rearrangement of fluorinated guanidines or by reductive defluorination cyclization sequence as discussed earlier for (difluoroamino)-fluorodiazirine. No new reports were found for the preparation of these fluorine-containing diaziridines in the decade 1993–2003.
6.09.5.2
One Halogen, One Nitrogen, and Two Phosphorus Functions
No new reports have been available in the period 1993–2003 for the preparation of these compounds. Compounds in this class of this with two phophoryl groups and the nitrogen in the form of either an isocyanato group or an ammonium group were reported in COFGT (1995) <1995COFGT(6)271>. The halo diphosphonylmethyl isocyanate compounds have been made by double nucleophilic displacement with trialkylphosphites on trichloromethyl isocyanate. The corresponding ammonium compound has been made by chlorination of diphosphonylmethyl trimethyl ammonium salt.
6.09.5.3
One Halogen and Three Phosphorus Functions
Blackburn and co-workers <1998CC2619, 1999PS(144)541> described the preparation of halogenated methanetriyl trisphosphonic acids and their esters for incorporation into analogs of adenosine 50 -triphosphate <1999AG(E)1244>. They envisaged that multiplicity of anionic charge is a major factor in protein affinity. Tetraisopropyl methylenebisphosphonate was reacted with diethyl chlorophosphite in the presence of NaHMDS (sodium hexamethyl disilazane), followed by oxidation with iodine to give methanetriyl trisphosphonic ester (Scheme 4). The resultant ester was treated with NaOCl to give chloromethane trisphosphonate ester, treatment with FClO3 gives the fluoro derivative (Scheme 5). Both the haloesters are hydrolyzed by trimethylsilyl bromide and Bu3N to afford the corresponding halo-substituted acids, which are good in ligation of calcium ion and useful as potential bone affinity agents.
OPri PriO P P i Pr O i O O OPr
i
EtO
P
O
OEt
PriO OPri P P i Pr O i O O OPr i: NaHMDS, (EtO)2PCl, toluene.
Scheme 4
ii
OEt P OEt
OPri PriO P P PriO i O O OPr ii: 0.5 M I2 solution in Py-THF-H2O
302
Functions Containing One Halogen and Three Other Heteroatom Substituents
O
OEt P OEt
PriO OPri P P i Pr O i O O OPr
i
OEt O P OEt Cl PriO OPri P P PriO i O O OPr
O
iii
F
ii
OEt P OEt
OPri PriO P P i Pr O i O O OPr
OH O O– Cl P HO OH P –O P – O O O
OH P O– OH HO P –O P – O O O O
ii
F
i. 20%NaOCl, NaHCO3, 0 °C, 1.5 h ii. TMSBr, Bu3N, CH2Cl2, reflux, overnight iii. FClO3, NaHMDS, THF, -75 °C
Scheme 5
6.09.6
ONE HALOGEN AND TWO GROUP 15 ELEMENTS
6.09.6.1
Metal Halodinitromethides
New preparations of this class of compounds have not been reported for the period 1993–2003. Carbanions have been made from halodinitromethanes and halotrinitromethane with metals such as potassium, silver, and mercury <1995COFGT(6)271>.
6.09.6.2
Metal Bis(phosphonyl) Halomethides
Alkali metal salts of alkylidenebis(phosphonic acid) or esters have been widely used in laundry detergents, and have some biological applications. Little progress has been made in the decade, 1993–2003, on these compounds since they were covered fully in COFGT (1995) <1995COFGT(6)271>. They are usually made from the dichloromethylene bis(phosphonic acid) ester and either a metal base or an amino base <2001WOP0121629, 1999WOP9920634>.
6.09.7
ONE HALOGEN AND ONE GROUP 15 ELEMENT
Compounds of this class were well documented in COFGT (1995) <1995COFGT(6)271>. During the decade 1993–2003 no reports were found in the literature for this class of compounds.
6.09.8
ONE HALOGEN AND METALLOID FUNCTION (THREE, TWO, OR ONE, TOGETHER WITH METALS)
6.09.8.1 6.09.8.1.1
One Halogen and Three Metalloid Functions Three silicon functions
This class of compounds, organosilanes was thoroughly covered in COFGT (1995) <1995COFGT(6)271>. A widely used procedure is the halogenation of the corresponding active dialkylmagnesium compound. For instance, the reaction of I2 and Br2 with Mg(Tsi)2 (Tsi = (Me3Si)3C) gives TsiI and TsiBr, respectively. Mg(Tsi)2 was obtained by heating the lithium magnesate [Li(THF)2(-Br)2Mg(Tsi) (THF)] in vacuum. Whereas, the TsiCl was prepared by reacting the dialkylmagnesium with benzenesulfonyl chloride (Scheme 6) <1994JOM(480)199>.
Functions Containing One Halogen and Three Other Heteroatom Substituents PhSO2Cl Mg(Tsi)2
303
Tsi Cl
Br2 Tsi Br
I2
TMS Tsi = C TMS TMS
Tsi I
Scheme 6
Halo tris(substituted dimethylsilyl)methane reacts with magnesium metal to form the Grignard reagent. Interestingly, the reaction of iodotris(dimethylamino-dimethylsilyl)methane with magnesium gives the planar carbanionic center 4, without the C–Mg covalent bond <1997OM503>.
C Me2Si
SiMe2
Me2Si NMe2
Me2N
Mg
NMe2
I 4
6.09.8.1.2
Two silicons and a germanium function
No publication was found under this category in the review period 1993–2003. These compounds have been reported in COFGT (1995) <1995COFGT(6)271> to be made from dihalo di(trimethylsilyl)methane and organo germanium halide with butyl lithium as the coupling agent.
6.09.8.1.3
Two silicons and a boron function
The only compound reported in COFGT (1995) was bromo[bromobis(isopropyl)aminoboryl]bis(trimethylsilyl)methane. This compound was made by the addition of bromine to the respective methylidene bis(isopropyl)aminoborane <1995COFGT(6)271>. No work was reported for this class of compounds in the decade 1993–2003.
6.09.8.1.4
Three boron functions or two borons and a metal function
There have not been any reports of the preparation of this class of compounds since COFGT (1995) <1995COFGT(6)271> was published. These compounds can be prepared from tetraborylmethanes by the following methods: tetraborylmethanes are converted into triborylmethides on treatment with alkyl lithiums, which on further halogenation leads to the expected final products. A similar approach was used to make the metal function containing class of compounds. Triborylmethyl halides on treatment with alkyl lithium followed by organometal halides leads to the expected products, diborylhaloorganometallomethanes.
6.09.8.2
One Halogen, Two Metalloids, and One Metal Function
No reports have been found for this class of compounds since the publication of COFGT (1995) <1995COFGT(6)271>. These compounds have been prepared from dihalobis(trimethylsilyl)methanes, which on reaction with alkyl lithium generates halobis(trimethylsilyl)methides. The lithium in these methides could be exchanged with other metals leading to the final products.
304
Functions Containing One Halogen and Three Other Heteroatom Substituents
REFERENCES 1994CB449 1994CB597 1994JCS(P1)1251 1994JOM(480)199 1994PS(86)239 1994MI528 1994ZOR704 1995COFGT(6)271 1995IZV649 1996CB1383 1996JFC7 1997OM503 1997MI324 1998CC2619 1998SUL19 1999AG(E)1244 1999CC1671 1999ICA68 1999PS(144)541 1999SUL73 1999WOP9920634 2000CSR315 2000MI234 2001JFC363 2001MI736 2001WOP0121629 2002JPC12280
R. Boese, A. Haas, M. Lieb, U. Roeske, Chem. Ber. 1994, 127, 449–455. R. Boese, A. Haas, C. Krueger, G. Moeller, A. Waterfeld, Chem. Ber. 1994, 127, 597–603. I. El-Sayed, V. K. Belsky, V. E. Zavodnik, K. A. Jorgensen, A. Senning, J. Chem. Soc., Perkin Trans. 1994, 1, 1251–1252. S. S. Al-Juaid, C. Eaborn, P. B. Hitchcock, K. Kundu, C. A. McGeary, J. D. Smith, J. Organomet. Chem. 1994, 480, 199–203. I. El-Sayed, M. F. Abdel-Megeed, S. M. Yassin, A. Senning, Phosporus Sulfur Silicon Relat. Elem. 1994, 86, 239–257. A. P. Bozopoulos, C. A. Kavounis, G. A. Stergioudis, P. J. Rentzeperis, A. Varvoglis, Z. Kristal. 1994, 209, 528–530. V. L. Medzhinski, E. L. Golod, Zh. Org. Khim. 1994, 30, 704–706. A. Marinetti, P. Savignac, Functions containing one hologen and three other heteroatom substituents, in Comprehensive Organic Functional Group Transformations, A. R. Katritzky, O. Meth-Cohn, C. W. Rees, Eds., Elsevier, Oxford, 1995, Vol. 6, pp. 271–294. V. N. Grebennikov, G. M. Nazin, G. B. Manelis, Izv. Akad. Nauk SSSR, Ser. Khim. 1995, 4, 649–651. H. Alois, M. Guido, Chem. Ber. 1996, 129, 1383–1388. S. Munavalli, D. I. Rossman, D. K. Rohrbaugh, C. P. Ferguson, H. D. Durst, J. Fluorine Chem. 1996, 76, 7–13. C. Eaborn, A. Farook, P. B. Hitchcock, J. D. Smith, Organometallics 1997, 16, 503–504. G. Kh. Khisamutdinov, V. I. Slovetsky, Yu. M. Golub, S. A. Shevelev, A. A. Fainzil’berg, Russ. Chem. Bull. 1997, 46, 324–327. X. Liu, H. Adams, G. M. Blackburn, J. Chem. Soc., Chem. Commn. 1998, 2619–2620. F. A. G. El-Essawy, S. M. Yassin, I. A. El-Sakka, A. F. Khattab, I. Sotofte, J. O. Madsen, A. Senning, Sulfur Lett. 1998, 22, 19–32. L. Xiaohai, B. Charles, G. Andrzej, S. Elzbieta, G. M. Blackburn, Angew. Chem. Int. Ed. Engl. 1999, 389, 1244–1247. Q. Huang, D. D. DesMarteau, J. Chem. Soc., Chem. Commn. 1999, 17, 1671–1672. M. J. Crawford, T. M. Klapotke, Inorg. Chim. Acta 1999, 294, 68–72. X. Liu, X. R. Zhang, G. M. Blackburn, Phosphorus Sulfur Silicon Relat. Elem. 1999, 144, 541–544. F. A. G. El-Essawy, A. F. Khattab, S. M. Yassin, I. A. El-Sakka, J. O. Madsen, A. Senning, Sulfur Lett. 1999, 22, 73–84. E. Pohjala, J. Vepsalainen, H. Nupponen, J. Kahkonen, L. Lauren, R. Hannuniemi, T. Jarvinen, M. Ahlmark, PCT Int. Appl. WO (World Intellectual Property Organization Pat. Appl.) WO 99/ 20634. V. V. Grushin, Chem. Soc. Rev. 2000, 29, 315–324. G. M. Nazin, V. G. Prokudin, G. B. Manelis, Russ. Chem. Bull. 2000, 49, 234–237. Q. Huang, D. D. DesMarteau, J. Fluorine Chem. 2001, 112, 363–368. G. Kh. Khisamutdinov, S. A. Shevelev, Russ. Chem. Bull. 2001, 50, 736–737. M. Purdie, PCT Int. Appl. WO (World Intellectual Property Organization Pat.) WO 01/21629. R. A. Moss, Y. Ma, F. Zheng, R. R. Sauers, T. Bally, A. Maltsev, J. P. Toscano, B. M. Sharalter, J. Phys. Chem. 2002, 106, 12280–12291.
Functions Containing One Halogen and Three Other Heteroatom Substituents
305
Biographical sketch
Subbarao Yarlagadda received his M.Sc. in organic chemistry from Andhra University, Waltair, India. He obtained his Ph.D. in 1991 from the Indian Institute of Chemical Technology (IICT), Hyderabad, India. His doctoral work was chiefly on selective organic transformations by using a new class of heterogenised homogeneous catalysts. Later, he joined, as a postdoctoral fellow, Professor M. Graziani at the University of Trieste, Italy under the UNIDO program, and worked on polydentate ligands and their metal complexes for an oxidative amination reaction. From 1992 to 1996, he was a staff scientist in Dr. A.V. Ramarao’s group at IICT, India, and worked on the synthesis of fine and specialty chemicals, pharmaceutical intermediates by using zeolite catalysts. In 1996, he joined Professor P. A. Jacobs at the Catholic University of Louvain, Belgium and worked on mesoporous zeolites and homogeneous catalysts for the synthesis of specialty chemicals. Since July 1998, he has worked at Reilly Industries, Indianapolis, IN, USA as a Research Associate. His current interests include: the process development, invention of new routes for the existing products, synthesis of fine and specialty chemicals, development of new catalysts for the synthesis of pharmaceutical and agrochemical intermediates, and vitamins.
Ramiah Murugan: Born in Madurai, India, he obtained his B.Sc. in 1975 from American College and M.Sc. in 1977 from Madurai University. After four years of working as a Junior Scientist at Madurai University, he joined Professor A. R. Katritzky’s group at the University of Florida, USA and obtained his Ph.D. in 1987. He continued there for two more years doing postdoctoral work in the area of high temperature aqueous organic chemistry. He joined Reilly Industries Inc., Indianapolis, IN, USA in 1989 and is currently a Senior Research Associate. His research interests include: synthesis of intermediates for pharmaceuticals, agrochemical products, and performance products; mechanistic studies; catalysis; polymer chemistry; and process development.
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Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 295–305
6.10 Functions Containing Four or Three Chalcogens (and No Halogens) A. SENNING and J. Ø. MADSEN Technical University of Denmark, Kgs. Lyngby, Denmark 6.10.1 TETRACHALCOGENOMETHANES 6.10.1.1 Four Similar Chalcogens 6.10.1.1.1 Four oxygen functions 6.10.1.1.2 Four sulfur functions 6.10.1.1.3 Four selenium functions 6.10.1.1.4 Four tellurium functions 6.10.1.2 Three Similar and One Different Chalcogen 6.10.1.2.1 Trioxygen-substituted methyl chalcogens 6.10.1.2.2 Trisulfur-substituted methyl chalcogens 6.10.1.2.3 Triselenium- or tritellurium-substituted methyl chalcogens 6.10.1.3 Two Similar and Two Different Chalcogens 6.10.1.3.1 Dioxygen-substituted methylene dichalcogens 6.10.1.3.2 Disulfur-substituted methylene dichalcogens 6.10.1.3.3 Diselenium- or ditellurium-substituted methylene dichalcogens 6.10.2 TRICHALCOGENOMETHANES 6.10.2.1 Methanes Bearing Three Oxygens and a Group 15 Element, Metalloid, or Metal Function 6.10.2.2 Methanes Bearing Three Sulfurs and a Group 15 Element, Metalloid, or Metal Function 6.10.2.3 Methanes Bearing Three Seleniums or Three Telluriums and a Group 15 Element, Metalloid, or Metal Function 6.10.2.4 Methanes Bearing Three Dissimilar Chalcogens and a Group 15 Element, Metalloid, or Metal Function
6.10.1
307 307 307 309 310 311 311 311 311 311 312 312 312 312 312 312 313 313 313
TETRACHALCOGENOMETHANES
6.10.1.1 6.10.1.1.1
Four Similar Chalcogens Four oxygen functions
The traditional approaches to ortho-carbonates (RO)4C using chloropicrin CCl3NO2, trichloroacetonitrile CCl3CN, cf. references <2002EUP1207147> and <2002GEP10121116>, trichloromethanesulfenyl chloride CCl3SCl, or N-(trichloromethyl)imidocarbonyl dichloride (CCl3)N¼CCl2 as C1 donor in ortho-carbonate syntheses have been supplemented by a procedure using CS2. Monovalent and divalent alcohols (or phenols) react with CS2 in the presence of stoichiometric amounts of CF3CO2Ag and excess Et3N to form ortho-carbonates (RO)4C in excellent yields (Equation (1)). Tetraethyl ortho-carbonate (EtO)4C is formed in 61% yield, tetraphenyl orthocarbonate (PhO)4C in 68% yield, and the spiro compounds 1–4 in 33%, 75%, 31%, and 20% yield, respectively <1998H(48)461>. 307
308
Functions Containing Four or Three Chalcogens CF3COOAg
CS2 + 4 ROH
Ph
O O
Ph
Ph
O O
Ph
NEt3
ð1Þ
C(OR)4
O O O O 2
1
O O
O O
O
O O
O
O O
3
4
Heating of O,O-bis(4-chlorophenyl)iminocarbonate (4-ClC6H4O)2C(¼NH) to 180 C gives a very low yield of tetrakis(4-chlorophenyl) ortho-carbonate (4-ClC6H4O)4C <1992JPR(334)95>. 2,2-Diphenoxy-1,3-dioxan has been prepared in 80% yield from 1,3-propanediol and dichlorodiphenoxymethane (PhO)2CCl2 <1999AJC657>. Dialkoxydichloromethanes react with alcohols in the presence of FeCl3 to yield the corresponding ortho-carbonater <1991IZV198>. Propylene carbonate 5 adds epichlorohydrin 6 in the presence of BF3 to form 2-(chloromethyl)8-methyl-1,4,6,9-tetraoxaspiro[4.4]nonane 7 as a mixture of stereoisomers (Scheme 1) which upon treatment with EtONa 7 forms the corresponding methylene derivative 8 <2002MI588>. A spirooligomer 9 is formed when pentaerythritol C(CH2OH)4 is treated with (EtO)4C at 260 C for 12 h <2002JA4942>. Other bis(hydroxymethyl) compounds form spirocyclic ortho-carbonates upon heating with (MeO)4C and acid <1992JAP04164085>. Spirocycli ortho-carbonates are also avialable from cyclic carbonates and oxiranes in the presence of 1-alkylpyridinium salts <1990CL2019>.
Me O
O
+
BF3.OEt2
Cl
Me
O O
O
O O
6
O 5
7 –HCl
Me
O O O O 8
Scheme 1
HO
O O
HO
O O n
9
O O
OH
O O
OH
Cl
309
Functions Containing Four or Three Chalcogens
Symmetrical tetrasilyl ortho-carbonates have been prepared by heating of alkene-1,1-disilanols, such as CH2¼C(SiMe2OH)2 and (MeO)4C, in the presence of p-toluenesulfonic acid <1992JAP04169592>. Chlorination of a solution of O,O-bis(2,2,2-trifluoroethyl)thiocarbonate (CF3CH2O)2C(¼S) and 2,2,2-trinitroethanol (O2N)3CCH2OH in 1,2-dichloroethane gives 90% yield of bis(2,2,2trinitroethyl) bis(2,2,2-trifluoroethyl) ortho-carbonate [(O2N)3CCH2O]2C(OCH2CF3)2 <1998USP5783732>. Divinyl-substituted ortho-carbonates can be converted to the corresponding diepoxides with MCPBA <1999JAP11158182>.
6.10.1.1.2
Four sulfur functions
Spiro compounds continue to dominate the portfolio of available tetrathio-ortho-carbonates (RS)4C. Dibenzo[3,4;10,11]-1,6,8,13-tetrathiaspiro[6.6]tridecane 10 has been prepared in quantitative yield by heating (MeS)4C (the synthesis of which was accomplished by a modified and somewhat improved Backer procedure involving N,N0 -dinitrosoisothioureas as key intermediates) and benzene-1,2-dimethanethiol 1,2-C6H4(CH2SH)2 with acid catalysis <1997MM6721>.
S
S
S
S
10
2-Methylenepropane-1,3-dithiol HSCH2C(¼CH2)CH2SH reacts with dichlorodiphenoxymethane (PhO)2CCl2 in the ratio 2:1 to form the tetrathio-ortho-carbonate 3,9-bis(methylene)1,5,7,11-tetrathiaspiro[5.5]undecane <1996AJC1261>. The tetrathio-ortho-carbonates 13a–13d have been prepared from the zinc complexes 11 and the trissulfanylcarbenium salts 12 as shown in Equation (2) <1999SM(102)1617>. 2– RS + 2NMe4
RS
S S
S S
S S Zn S S
RS
S
S
R1 +
S
S
+
S
RS
RS
–
SMe BF4
12
11
RS
S
S
S
S
S
S S
S
R1
ð2Þ
S
13 13a, R = Me, R1 = H 13b, R = R1 = Me 13c, R, R = CH2CH2; R1 = H 13d, R, R = CH2CH2; R1 = Me
Tetrakis(trifluoromethyl)tetrathio-ortho-carbonate (CF3S)4C has been obtained in 61% yield from CBr2Cl2 and (CF3)SCu <1996JFC(76)7>. Spirocyclic 1,4,6,9-tetrathiaspiro[4.4]nonanes are formed in very low yields (4–5%) when 1,3-dithiolan-2-ones are treated with thiiranes <1996JCS(P1)289>. A particularly neat high-yielding access to spirocyclic tetrathio-ortho-carbonates such as 16 has been found in the reaction between 2H-benzo[b]thiete 14 and cyclic trithiocarbonates such as 15 (cf. Equation (3)) <1997LA1603>.
310
Functions Containing Four or Three Chalcogens S
S
S
+
S
S
ð3Þ
S
S 15
14
S
16
The unexpectedly stable tetrathio-ortho-carbonate 18, i.e., 4,7-dichloro-2-isopropylsulfanyl-2sulfanyl-1,3-dithiolo[4,5-c]pyridine-6-carbonitrile, was obtained (22% yield) from the reaction between 3,4,5,6-tetrachloropyridine-2-carbonitrile 17 and potassium isopropyltrithiocarbonate (cf. Equation (4)) <1998MI297>. Cl Cl Cl
Cl N
HS Me2CHSC(=S)SK
S
SCHMe2 S Cl
EtO S +
SCHMe2 S Cl
EtOH
CN
Cl
N
CN
Cl
17
N
ð4Þ
CN
19
18
Following an established procedure, bis(methylsulfonyl)methane (MeSO2)2CH2 can be disulfenylated with N-(ethylsulfanyl)phthalimide 1,2-C6H4[C(¼O)]2NSEt to yield bis(ethylsulfanyl)bis(methylsulfonyl)methane (EtS)2C(SO2Me)2 <2002TL1377>. The unexpected unsymmetrical dimerization of the thiocarbonyl ylide 20, formed in situ from PhS(¼O)2C(¼S)SC6H4Cl-4 and Me3SiCHN2, leads to tetrathio-ortho-carbonate 21, cf. Equation (5) <2003EJO813>. Me3Si 4-ClC6H4S
CHSiMe3 4-ClC6H4S
C S PhSO2
SiMe3
+
– C S
S
ð5Þ
PhSO2
20
SO2Ph
4-ClC6H4S 21
6.10.1.1.3
Four selenium functions
Two new tetraseleno-ortho-carbonates (RSe)4C, both spiroheterocycles, have been reported. 2,3,7,8-Tetramethyl-1,4,6,9-tetraselenaspiro[5.5]nona-2,7-diene 22 is formed in low yield from 4,5-dimethyl-1,3-diselenole-2-selone, 4,5-methylenedithio-1,3-dithiol-2-one, and (MeO)3P <1994ZOR1009>. The structure of 22 was proven by X-ray crystallography <1995DOK(340)62>.
Me
Se Se
Me
Me
Se Se
Me
22
The reaction between the ring-strained alkyne cyclooctyne and CSe2 yields, among other products, 3.3% of the yellow 4,4,5,5,6,6,7,7,8,8,9,9-dodecahydro-2,20 -spirobi[cycloocta-1,3-diselenole] 25, the main products being the triselenocarbonate 23 and the tetraselanylethene 24 (cf. Equation (6)) <2000JOC8940>.
311
Functions Containing Four or Three Chalcogens Se Se
+ CSe2
+
Se 23
Se
Se
Se
Se
+
Se Se 25
24
6.10.1.1.4
ð6Þ
Se Se
Four tellurium functions
Tetratelluro-ortho-carbonates (RTe)4C are still unknown.
6.10.1.2
Three Similar and One Different Chalcogen
6.10.1.2.1
Trioxygen-substituted methyl chalcogens
Cyclic thio-ortho-carbonates (RO)3CSR have been prepared from dichlorodiphenoxymethane (PhO)2CCl2 and ,!-mercaptoalkanols <1999AJC657>. No seleno-ortho-carbonates (RO)3CSeR or telluro-ortho-carbonates (RO)3CTeR are on record.
6.10.1.2.2
Trisulfur-substituted methyl chalcogens
The trissulfanylcarbenium salt 26, when treated with NaBH4 in EtOH, gives a mixture of the trithio-ortho-carbonate 27 and the trithio-ortho-formate 28 (cf. Equation (7)) <2001MI145>. Me
Me
BF4–
+
S
NaBH4
SMe
EtO2C
EtO2C
S
SMe
SMe
EtO2C
S OEt
S
EtOH
S
S
Me S
27
26
S
S
ð7Þ
28
Good yields of 1-oxa-4,6,9-trithiaspiro[4.4]nonanes 31 are obtained from the appropriate 1,3-dithiolane-2-thiones 29 and oxiranes 30 (cf. Equation (8)) <1996JCS(P1)289>. 1
2
R
R
S
S S
R3
R4
+ O 30
HBF4.Et2O PhCl
R1 2
R
S
S
R3(R4)
S
O
R (R )
4
3
ð8Þ
31
29
The trithio-ortho-carbonate 19, i.e., 4,7-dichloro-2-ethoxy-2-isopropylsulfanyl-1,3-dithiolo[4,5-c]pyridine-6-carbonitrile, has been obtained according to Equation (4) <1998MI297>. Seleno-trithio-ortho-carbonates (RS)3CSeR and telluro-trithio-ortho-carbonates (RS)3CTeR are unknown.
6.10.1.2.3
Triselenium- or tritellurium-substituted methyl chalcogens
None of the hypothetical compound classes (RSe)3COR, (RSe)3CSR, (RSe)3CTeR, (RTe)3COR, (RTe)3CSR, or (RTe)3CSeR have been reported.
312
Functions Containing Four or Three Chalcogens
6.10.1.3
Two Similar and Two Different Chalcogens
6.10.1.3.1
Dioxygen-substituted methylene dichalcogens
A modest yield of 1,6-dioxa-4,9-dithiaspiro[4.4]nonane 32 has been obtained in the reaction between 2-mercaptoethanol and (PhO)2CCl2. The higher homolog 1,5-dioxa-7,11-dithiaspiro[5.5]undecane 33 can be made from 2,2-diphenoxy-1,3-dioxan and propane-1,3-dithiol (62% yield) or from 2,2-diphenoxy-1,3-dithian and propane-1,3-diol (37% yield). Either reactant may also carry a methylene substituent to give the corresponding methylene-substituted spiro-ortho esters <1999AJC657>.
O O
O S
S
O S
S 32
6.10.1.3.2
33
Disulfur-substituted methylene dichalcogens
No further advances have occurred in this area since the publication of chapter 6.10.1.3.2 in <1995COFGT(6)295>.
6.10.1.3.3
Diselenium- or ditellurium-substituted methylene dichalcogens
Treatment of dimethyl 2-selenoxo-1,3-thiaselenole-4,5-dicarboxylate 34 with Ph3P leads to a mixture of the (E )- and (Z )-diselenadithiafulvalenes 35 (cf. Equation (9)) <1980JOC2632>.
MeO2C
S Se
MeO2C
Ph3P
Se 34
ð9Þ MeO2C
Se
Se
CO2Me
MeO2C
S
Se
CO2Me
MeO2C
Se
S
CO2Me
+ MeO2C
S
S
CO2Me
(Z )-35
6.10.2 6.10.2.1
(E )-35
TRICHALCOGENOMETHANES Methanes Bearing Three Oxygens and a Group 15 Element, Metalloid, or Metal Function
3,4-Dihydro-2,2-dimethoxy-5,5-dimethyl-1,3,4-oxadiazole 38, useful as a source of dimethoxycarbene upon pyrolysis, has been prepared from acetone methoxycarbonylhydrazone 36 via the intermediate 37 as shown in Equation (10) <1994JA1161>. The analogous spiro compound 39 has been obtained along similar lines <2002CJC1187>.
313
Functions Containing Four or Three Chalcogens
Me Me
OMe NH C C N O
Me N N
LTA AcOH
O
Me
36
OMe OAc
37 Me N N
MeOH
Me
O
ð10Þ OMe OMe
38 LTA = Pb(MeCO2)4
Ph O
O
N O N Me Me 39
Tris(fluorosulfinyloxy)methyllithium [[FS(¼O)O]3C]Li has been prepared for use in lithium batteries <1996FRP2730988>.
6.10.2.2
Methanes Bearing Three Sulfurs and a Group 15 Element, Metalloid, or Metal Function
2,3-Dihydro-9a-(methylsulfanyl)-7-(trifluoromethoxy)thiazolo[2,3-b]benzothiazole 41 has been prepared in three simple steps from benzothiazole 40 (cf. Equation (11)) <1999JMC2828>. N
N Cl
S
CF3O 40
CF3O
S
S SMe
ð11Þ
41
Nitrotris[(trifluoromethyl)sulfanyl]methane (CF3S)3CNO2 is formed in 45% yield upon treatment of bis[tris[(trifluoromethyl)sulfanyl]methyl] disulfide (CF3S)3CSSC(SCF3)3 with NO2 <1994CB597>. Tris[(trifluoromethyl)sulfonyl]methyllithium [(CF3SO2)3C]Li has been prepared as starting material for the corresponding fluorine compound (CF3SO2)CF <2003GEP10258577>. The corresponding caesium salt [(CF3SO2)3C]Cs has also been prepared <1993WOP9309092>.
6.10.2.3
Methanes Bearing Three Seleniums or Three Telluriums and a Group 15 Element, Metalloid, or Metal Function
The salt [(CF3Se)3C][AsF6] is available, inter alia, from tetrakis(trifluoromethyl) tetraselenoortho-carbonate (CF3Se)4C and AsF5 <1996CB1383>.
6.10.2.4
Methanes Bearing Three Dissimilar Chalcogens and a Group 15 Element, Metalloid, or Metal Function
No further advances have occurred in this area since the publication of chapter 6.10.2.4 in <1995COFGT(6)295>.
314
Functions Containing Four or Three Chalcogens
REFERENCES 1980JOC2632 1990CL2019 1991IZV198 1992JAP04164085 1992JAP04169592 1992JPR(334)95 1993WOP9309092 1994CB597 1994JA1161 1994ZOR1009 1995COFGT(6)295 1995DOK(340)62 1996AJC1261 1996CB1383 1996FRP2730988 1996JCS(P1)289 1996JFC(76)7 1997LA1603 1997MM6721 1998H(48)461 1998MI297 1998USP5783732 1999AJC657 1999JAP11158182 1999JMC2828
1999SM(102)1617 2000JOC8940 2001MI145 2002CJC1187 2002EUP1207147 2002GEP10121116 2002JA4942 2002MI588 2002TL1377 2003EJO813 2003GEP10258577
M. V. Lakshmikantham, M. P. Cava, J. Org. Chem. 1980, 45, 2632–2636. S. B. Lee, T. Takata, T. Endo, Chem. Lett. 1990, 2019–2022. I. T. Eremenko, G. V. Oreshko, M. A. Fadeev, Izv. Akad. Nauk SSSR, Ser. Khim. 1991, 198–200. Higashiura, M.; Nishino, H.; Kodera Y., (Toyobo Co., Ltd., Japan), Jpn. Patent JP 04 164 085, 1992 (Chem. Abstr. 1992, 117, 191857). Nishino, H.; Higashiura, M.; Ohashi, H.; Kodera, Y, (Toyobo Co., Ltd., Japan), Jpn. Patent JP 04 169 592, 1992 (Chem. Abstr. 1993, 118, 7186). M. Bauer, D. Janietz, G. Reck, B. Schulz, J. Prakt. Chem.-Chem.-Ztg. 1992, 334, 95–97. Armand, M.; Benrabah, D.; Sanchez, J. Y., (Centre National de la Recherche Scientifique CNRS, France), PCT Int. Appl. WO 9 309 092, 1993 (Chem. Abstr., 1994, 120, 180111). R. Boese, A. Haas, C. Kru¨ger, G. Mo¨ller, A. Waterfeld, Chem. Ber. 1994, 127, 597–603. K. Kassam, D. L. Pole, M. El-Saidi, J. Warkentin, J. Am. Chem. Soc. 1994, 116, 1161–1162. M. L. Petrov, I. K. Rubtsova, Zh. Org. Khim. 1994, 30, 1009–1011. A. H. Gouliaev, A. Senning, Functions containing four or three chalcogens (and no halogens), in Comprehensive Organic Functional Group Transformations, A. R. Katritzky, O. Meth-Cohn, C. W. Rees, Eds., Elsevier, Oxford, 1995, Vol. 6, pp. 295–318. Yu. E. Ovchinnikov, K. A. Potekhin, V. Panov, Yu. T. Struchkov, Dokl. Akad. Nauk 1995, 340, 62–66. M. K. Bromley, S. J. Gason, A. G. Jhingran, M. G. Looney, D. H. Solomon, Aust. J. Chem. 1996, 49, 1261–1262. A. Haas, G. Mo¨ller, Chem. Ber. 1996, 129, 1383–1388. Guyomard, D.; Piffard, Y.; Leroux, F.; Tournoux, M., (Centre National de la Recherche Scientifique CNRS, France), Fr. Demande 2 730 988 (1996) (Chem. Abstr., 1997, 126, 77446). M. Barbero, I. Degani, S. Dughera, R. Fochi, L. Piscopo, J. Chem. Soc., Perkin Trans. 1 1996, 289–294. S. Munavalli, D. I. Rossman, D. K. Rohrbaugh, C. P. Ferguson, H. D. Durst, J. Fluorine Chem. 1996, 76, 7–13. H. Meier, D. Gro¨schl, R. Beckert, D. Weiß, Liebigs Ann. Chem./Recueil 1997, 1603–1605. T. Takata, M. Kanamaru, T. Endo, Macromolecules 1997, 30, 6721–6726. I. Shibuya, Y. Gama, M. Shimizu, Heterocycles 1998, 48, 461–464. A. M. Sipyagin, V. V. Kolchanov, Z. G. Aliev, N. K. Karakhanova, A. T. Lebedev, Chem. Heterocycl. Compd. 1998, 34, 297–307. Gilligan W. H., (United States Dept. of the Navy, USA), U.S. Patent 5 783 732, 1998 (Chem. Abstr. 1998, 129, 148765). M. K. Bromley, S. J. Gason, M. G. Looney, D. H. Solomon, Aust. J. Chem. 1999, 52, 657–661. Takazaki, T.; Endo, T., (Zaidan Hojin Kagaku Gijutsu Senryaku Suishin Kiko, Japan), Jpn. Patent JP 11 158 182, 1999 (Chem. Abstr. 1999, 131, 31946). P. Jimonet, F. Audiau, M. Barreau, J. C. Blanchard, Y. Boireau, A. Bour, M. A. Cole´no, A. Doble, G. Doerflinger, C. Do Huu, M. H. Donat, J. M. Duchesne, P. Ganil, C. Gue´re´my, E. Honore´, B. Just, R. Kerphirique, S. Gontier, P. Hubert, P. M. Laduron, J. Le Blevec, M. Meunier, J. M. Miquet, C. Nemecek, M. Pasquet, O. Piot, J. Pratt, J. Rataud, M. Reibaud, J. M. Stutzmann, S. Mignani, J. Med. Chem. 1999, 42, 2828–2843. M. Iwamatsu, K. Ueda, T. Sugimoto, H. Fujita, Synth. Met. 1999, 102, 1617–1618. J. Fabian, A. Krebs, D. Scho¨nemann, W. Schaefer, J. Org. Chem. 2000, 65, 8940–8947. U. Jordis, K. Bhattacharya, P. Y. Boamah, V. J. Lee, Molecules 2001, 7, 145–154. N. Merkley, J. Warkentin, Can. J. Chem. 2002, 80, 1187–1195. Fries, G.; Kirchhoff, J., (Degussa A.G., Germany), Eur. Patent EP 1 207 147, 2002 (Chem. Abstr. 2002, 136, 385875). Fries, G.; Theis, C.; Kirchhoff, J., (Degussa A.G., Germany), Ger. Patent DE 10 121 116, 2002 (Chem. Abstr. 2002, 137, 325164). D. T. Vodak, M. Braun, L. Iordanidis, J. Plevert, M. Stevens, L. Beck, J. C. H. Spence, M. O’Keeffe, O. M. Yaghi, J. Am. Chem. Soc. 2002, 124, 4942–4943. V. V. Zaitseva, T. G. Tyurina, S. Yu. Suikov, S. L. Bogza, S. P. Kobzev, Russ. J. Org. Chem. 2002, 38, 588–590. Y. Zhu, D. G. Drueckhammer, Tetrahedron Lett. 2002, 43, 1377–1379. I. El-Sayed, R. G. Hazell, J. Ø. Madsen, P. O. Norrby, A. Senning, Eur. J. Org. Chem. 2003, 813–815. Kirsch, P.; Hahn, A., (Merck Patent G.m.b.H., Germany), Ger. Patent DE 10 258 577 2003 (Chem. Abstr., 2003, 139, 133074).
Functions Containing Four or Three Chalcogens
315
Biographical sketch
Alexander Senning was born in 1936 in Riga, Latvia. He studied chemistry in Munich, Germany (1954–1959) and Uppsala, Sweden (1960–1962). He obtained a Ph.D. in organic chemistry from Uppsala University in 1962. He joined the Department of Chemistry, Aarhus University, Denmark as assistant professor (1962–1965) and associate professor (1965–1993). During a sabbatical leave (1973–1975), he was head of the research laboratory of the drug company A/S Alfred Benzon, Copenhagen, Denmark. He joined the Danish Engineering Academy (DIA), Lyngby, Denmark, later part of The Technical University of Denmark (DTU), Lyngby, Denmark as professor of organic chemistry in 1993 until his retirement in 2003. Research interests: organic sulfur chemistry, medicinal chemistry. Extensive activities as book and journal editor. A detailed chemical autobiography is available in Sulfur Rep., 2003, 24, 191–253.
Jørgen Øgaard Madsen was born in 1940 in Aars, Denmark. He studied chemistry in Aarhus, Denmark (1962–1971) and received an M.Sc. (1967) and a Ph.D. (1972) in organic chemistry from Aarhus University, Denmark. He held an assistant professorship at the Department of Chemistry, Aarhus University, Denmark (1967–1971) and joined the Department of Organic Chemistry (later Department of Chemistry) of the Technical University of Denmark (DTU) as associate professor (1972 to present). Research interests: heterocyclic enamines, stereospecific syntheses with baker’s yeast, natural product chemistry, analytical organic chemistry (HPLC, MS).
# 2005, Elsevier Ltd. All Rights Reserved No part of this publication may be reproduced, stored in any retrieval system or transmitted in any form or by any means electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without permission in writing from the publishers
Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 307–315
6.11 Functions Containing Two or One Chalcogens (and No Halogens) W. PETZ and F. WELLER Universita¨t Marburg, Marburg, Germany 6.11.1 INTRODUCTION 6.11.2 DICHALCOGENOMETHANES 6.11.2.1 Methanes Bearing Two Similar Chalcogens 6.11.2.1.1 Two oxygens and a group V (15) element and/or a metalloid and/or a metal function 6.11.2.1.2 Two sulfurs and a group V (15) element and/or a metalloid and/or a metal function 6.11.2.1.3 Two seleniums or two telluriums and a group V (15) element and/or a metalloid and/or a metal function 6.11.2.2 Methanes Bearing Two Dissimilar Chalcogens 6.11.2.2.1 Oxygen, sulfur, and two functions derived from a group V (15) element, metalloid, and/or a metal 6.11.2.2.2 Oxygen and selenium, or oxygen and tellurium, and two functions derived from a group V (15) element, metalloid, and/or a metal 6.11.2.2.3 Sulfur and selenium, or sulfur and tellurium, and two functions derived from a group V (15) element, metalloid, and/or a metal 6.11.3 MONOCHALCOGENOMETHANES 6.11.3.1 Methanes Bearing One Oxygen Function and Three Functions Derived from the Group V (15) Element, Metalloid, and/or a Metal 6.11.3.1.1 Compounds with the OCN3 core 6.11.3.1.2 Compounds with the OCNP2 core 6.11.3.1.3 Compounds with the OCNSi2 core 6.11.3.1.4 Compounds with the OCNSiTa core 6.11.3.1.5 Compounds with the OCNB2 core 6.11.3.1.6 Compounds with the OCPSiTa core 6.11.3.1.7 Compounds with the OCFe3 core 6.11.3.1.8 Compounds with the OCCo3 core 6.11.3.1.9 Compounds with the OCNi3 core 6.11.3.1.10 Compounds with the OCW3 core 6.11.3.1.11 Compounds with the OCRu3 core 6.11.3.1.12 Compounds with the OCOs3 core 6.11.3.1.13 Compounds with the OCFe2Ni core 6.11.3.1.14 Compounds with the OCFe2Co core 6.11.3.1.15 Compounds with the OCFe2Rh core 6.11.3.1.16 Compounds with the OCFe2Mn core 6.11.3.1.17 Compounds with the OCRu2W core 6.11.3.1.18 Compounds with the OCW2Ru core 6.11.3.2 Methanes Bearing One Sulfur Function and Three Functions Derived from the Group V (15) Element, Metalloid, and/or a Metal 6.11.3.2.1 Compounds with the SCN3 core 6.11.3.2.2 Compounds with the SCNSi2 core 6.11.3.2.3 Compounds with the SCPFe2 core 6.11.3.2.4 Compounds with the SCPNi2 core 6.11.3.2.5 Compounds with the SCPMnRe core 6.11.3.2.6 Compounds with the SCSi3 core 6.11.3.2.7 Compounds with the SCSi2P core
317
318 318 318 318 320 332 333 333 334 334 335 335 335 336 337 337 338 338 338 338 339 340 340 340 341 341 341 342 342 342 342 342 344 345 345 345 346 346
318
Functions Containing Two or One Chalcogens (and No Halogens)
6.11.3.2.8 Compounds with the SCPSiLi core 6.11.3.2.9 Compounds with the SCSi2Li core 6.11.3.2.10 Compounds with the SCN2Fe core 6.11.3.2.11 Compounds with the SCNSnPt core 6.11.3.2.12 Compounds with the SCSiSnLi core 6.11.3.2.13 Compounds with the SCFe3 core 6.11.3.2.14 Compounds with the SCRu3 core 6.11.3.2.15 Compounds with the SCOs3 core 6.11.3.2.16 Compounds with the SCCo3 core 6.11.3.2.17 Compounds with the SCAu3 core 6.11.3.2.18 Compounds with the SCFe2Co core 6.11.3.2.19 Compounds with the SCFeCo2 core 6.11.3.2.20 Compounds with the SCCo2W core 6.11.3.3 Methanes Bearing One Selenium or One Tellurium Function and Three Functions Derived from the Group V (15) Element, Metalloid, and/or a Metal 6.11.3.3.1 Compounds with the SeCN3 core 6.11.3.3.2 Compounds with the SeCSi3 core 6.11.3.3.3 Compounds with the TeCSi3 core
6.11.1
346 347 347 347 347 347 347 348 348 348 348 348 349 349 349 350 350
INTRODUCTION
This chapter is arranged in a manner identical with that of the corresponding chapter in COFGT (1995). At first those compounds are discussed with a group V (15) element at the carbon atom followed by compounds with metalloids (other main group elements), and finally by transition metal functionality. Compounds with dissimilar atoms at the carbon atom are arranged after compounds with similar atoms.
6.11.2
DICHALCOGENOMETHANES
6.11.2.1
Methanes Bearing Two Similar Chalcogens
Dichalcogenomethanes with similar chalcogens and further atoms other than chalcogens or halogens have only been described with O2C, S2C, and Se2C; compounds with the Te2C unit had not been found up to the end of 2003.
6.11.2.1.1
Two oxygens and a group V (15) element and/or a metalloid and/or a metal function
Until 2003, compounds with the (RO)2C unit bonded to group V (15) elements other than N were not described. Further compounds were found in which this unit is connected to silicon (O2CSi2 core) and boron (O2CB2 core).
(i) Compounds with the O2CN2 core One group of compounds with this core are urea acetals; however, the majority are spiro compounds and have been reviewed earlier by Kantlehner and co-workers in COFGT (1995). The reaction of [C(NMe2)3]BF4 with the system NaH/H2NMe2/B(OMe)3 produces (NMe2)2C(OEt)2 1 along with (NMe2)C(OEt)3, (NMe2)3C(OEt) (see OCN3 core), and Me2NCOOEt as a nonseparable mixture <2000JPR256>.
Me2N NMe2 EtO OEt 1
319
Functions Containing Two or One Chalcogens (and No Halogens)
A series of spiro fused oxaziridines 2 and 3 were synthesized by reacting the corresponding semicarbazone R2C¼NNHC(O)NR0 (CH2)nOH (n = 2, 3) with PhI(OAc)2 in CH2Cl2 or CH3OH; the compounds were separated and purified by chromatography followed by bulb-to-bulb distillation; the individual compounds are collected in Table 1 <1996JA4214, 1997CJC1264, 1997CJC1281>. Theoretical studies have been done on these oxaziridines <1999CJC1340>. Table 1 R and R0 of the compounds 2 and 3 2 R
R
Sl. no
R
R0
Me Me Me Me Me Me Me Me Me Me Me
H Me C(O)H C(O)Me C(O)C(Me)¼CH2 C(O)Ph C(O)C6H4(2-OMe) C(O)C6H4(4-OMe) C(O)C6H4(4-NO2) C(O)Me SO2Ph
a b c d e
Me (CH2)5 (CH2)5 Me (CH2)5
H H Me C(O)Ph C(O)Ph
Sl. no a b c d e f g h i j k
3 0
The compound 4 is an intermediate during the photosensitized oxidation of corresponding isotopelabeled imidazole and has been characterized by low-temperature NMR spectroscopy <2002JA9629>. The spirocyclic compounds 5 and 6 were obtained by silver(I) ion-mediated desulfuration– condensation reactions of carbon disulfide with the corresponding hydroxyl compounds as colorless compounds with yields of about 75% <1998H461>.
O
N
N N
O
O
R'
R
O N R N R
3
2
R
Ph
Ph
N
N
HO
OH
4
Ph O N N O Ph
5
N
N
O
O
O
Ph
Ph
N R'
O
6
Further spiro compounds with the O2CN2 core have been reported <1997RCB(46)126, 1999RCB(48)2136>. The diazirine 7 was obtained as a solution in pentane in 70% yield in dimethylformamide (DMF) at 0 C for 1 h (Scheme 1) <1995JFC101>.
C7F15CH2O Br
N N
C7F15CH2ONa
C7F15CH2O C7F15CH2O 7
Scheme 1
N N
320
Functions Containing Two or One Chalcogens (and No Halogens)
(ii) Compounds with the O2CSi2 core The only example of a compound with this core was described recently. The reaction of (Me2PhSi)2C(SMe)2 (compound 18 with the S2CS2 core) with I2 in ethyleneglycol–acetonitrile generates the acetal 8 in 78% yield <1996CL841>. O O
SiMe3 SiMe3 8
(iii) Compounds with the O2CB2 core Only one compound with this core is reported. The reaction of the dibromobis(tetramethylethylenedioxboryl)methane with anhydrous NaAc in methylenechloride leads to the formation of the compound 9 in 25% yield <1974JOM(69)45>.
O B O AcO O B AcO O 9
6.11.2.1.2
Two sulfurs and a group V (15) element and/or a metalloid and/or a metal function
The majority of compounds in this section involve the coordination chemistry of the adduct S2CPR3 in which the two S atoms and the C atom interact with a mononuclear or dinuclear transition metal fragment in an allyl-like manner. In addition to the earlier described compounds with the S2CPMo, S2CPW, and S2CPMn core, compounds with the cores S2CPFe and S2CPCo are also now available. The coordination mode of the S2CPR3 ligand was studied earlier.
(i) Compounds with the S2CN2 core There are only a few compounds described in the literature with the S2CN2 core, and because of the different nature of the compounds a common method of preparation for these compounds cannot be formulated. The spirocyclic compounds (10a–10e) were obtained by intramolecular ring-closure by heating the appropriate starting material in tetrahydrofuran (THF) or dimethyl sulfoxide (DMSO) as shown in Scheme 2; yields and melting points are shown in Table 2 <2000SL1464>. The similar spirocyclic compound 11 was obtained in 53% yield by the reaction of N-phenylbenzohydrazonoyl chloride with the 5-benzylidene-3-phenyl derivative of rhodamine in CHCl3 in the presence of NEt3; the structure was confirmed by an X-ray analysis (Scheme 3) <1999AX1877>.
O
O R1O S
N H
H N
R2
THF, ∆
R1O O S
O
S
S N
N
N NH H 10
Scheme 2
R2
Functions Containing Two or One Chalcogens (and No Halogens)
321
Table 2 Yields and melting points of the compounds 10a–10e Nr 10
R1
R2
Yield (%)
m.p. ( C)
a b c d e
Me Me Me Me Et
OMe OC(Me)3 OBz NH2 NHPh
85 66 77 67 68
78–81 80–83 96–99 185–188 134–137
Ph
Ph
Ph S
HN
+
O
Ph N N
Et3N
S
N
S
Ph
Ph
N S Ph
O
Cl
Ph
11
Scheme 3
Condensation between the 2-methylsulfanylthiazolium iodide and p-phenetidine in the presence of NEt3 in CH2Cl2 produces the compound 12 in about 26% yield as shown in Scheme 4 <2000JPR554>.
– F3C
S + N
I
F3C
S
p -Phenetidine
S
OEt
HN
N
S
12
Scheme 4
As shown in Scheme 5 the thiouracil reacts with P(OR)3 to produce the dithiaspirodione 13 <1996PS(119)225>.
S N
N
P(OR)3
O
N
S
N
N
S
N
O
O 13
Scheme 5
Various nitrilimines cycloadd to the C¼S bond of 3-phenyl-5-arylmethylene-2-thioxothiazolidine-4-one to give the corresponding spiro cycloadducts 14 (Ar = 4-MeOC6H4, 4-MeC6H4; R = Ph, PhC2H2, PhCO, 2-naphthoyl, 2-thienoyl, Ac, EtOCO, PhNHCO) <1996PS(113)53>. The related spiro compounds 15 were formed from the nitrilimines RCN2R1 and 3-phenyl-5phenylmethylene-2-thioxothiazolidine-4-one (R = EtCOO, Ph, Bz, 2-thenoyl, PhNHCO, styryl, 2-naphthoyl, Ac, R1 = Ph, 2-thienyl) <1995JPS205>.
322
Functions Containing Two or One Chalcogens (and No Halogens) Ar S N N
Ar O
N S Ph
O R
PhHC
15
R1 S N N S Ph
R
14
(ii) Compounds with the S2CP2 core The spiro compound 16 was reported by a Chinese working group. The compound was obtained in excellent yield by refluxing a mixture of 1-(2-bromoethyl)-2,3-dihydro-3-propyl-1,3,2-benzodiazaphosphorin-4(1H)-one-2-oxid with CS2 in benzene <2002CCL125>.
O N
P
R
N R O S
S P O N
N O
R = CH2COOEt
16
A complex with this core was also prepared as shown in Scheme 6. Starting from the appropriate Cp2Zr complex, reaction with CS2 in toluene at 40 C gave the complex 17 in 72% yield <1999OM1882>.
Zr P Ph S S Ph P Zr
CS2 Zr
P Ph
Zr = ZrCp2 17
Scheme 6
(iii) Compounds with the S2CSi2 core The general method is the reaction of the corresponding (RS)2CH2 with BuLi followed by addition of R3SiCl to give first (RS)2CH(SiR3), which is again treated with BuLi/R3SiCl to generate the bis(dimethylphenylsilyl) ketone dithioacetal 18 in 60% yield <1996CL841>.
MeS
SiPhMe2
MeS
SiPhMe2 18
A series of spiro compounds with this core containing SiPd and SiPt bonds have been described. The reaction of 2,2-bis(disilanyl)dithiane 19 with Pd(CNBut)2 at room temperature or Pt3(CNBut)6 in refluxing benzene produces the Pd complex 20 and the Pt complex 21, respectively, in 27% yield as shown in Scheme 7; 21 was characterized by an X-ray analysis <1996JOM(521)405>. The Pd
Functions Containing Two or One Chalcogens (and No Halogens) S S S Si SiMe2Ph S Si SiMe2Ph
S
19
S
Me2 CNBut Si Pd Si CNBut Me2
20
t Me2 CNBu SiMe2Ph Si Pt SiMe2Ph Si Me2 CNBut
21
323
Scheme 7
complex 20 was also described in <1996BCJ(69)289>. Cyclic organosilicon compounds 22 (R = Ph, SiMe3; R1 = H) were obtained upon bis-sylilation of RCCR1 compounds with cyclic bis(organosilyl)palladium intermediates <1996BCJ(69)289>.
Me2 R S Si 1 S Si Me2 R
22
(iv) Compounds with the S2CSiSn2 core Only one compound with this core was described. Compound 23 was prepared by adding butyllithium to a stirred solution of 2-trimethylsilyl-1,3-dithiane in THF; then a THF solution of Sn(3-C5H5)(-N¼C(NMe2)2) was added. Yellow crystalline blocks were obtained in 29% yield. The compound is dimeric containing a four-membered SnNSnN ring and was characterized by an X-ray analysis <1995JCS(D)1587>.
S
Me3Si
S NMe2
Me2N
Sn
N
N
Sn
NMe2
Me2N S SiMe3
S 23
(v) Compounds with the S2CGe2 core Related to the heterocycles with the S2CSi2 core, 20 and 21, the corresponding Ge-derivatives have been prepared in a similar procedure as shown in Scheme 8. Thus, the corresponding compound 24 reacts with Pd(CNBut)2 at room temperature to produce quantitatively the Pd complex 25. With Pt3(CNBut)6 in refluxing benzene the Pt complex 26 was formed in 30% yield along with 27 as a by-product; the compounds 25 and 27 were characterized by X-ray analyses <1996JOM(521)405>.
324
Functions Containing Two or One Chalcogens (and No Halogens) S S S Ge SiMe2Ph S Ge SiMe2Ph
S
24
S S L = CNBut
S
Me2 L Ge Pd L Ge Me2
25
Me2 L SiMe2Ph Ge Pt SiMe2Ph Ge Me2 L
26
Me2 L Ge Pt Ge Me2 L
27
Me2 Ge S Ge S Me2
Scheme 8
(vi) Compounds with the S2CSn2 core Two more compounds of this type are described in the literature. Compound 28 was prepared according to Scheme 9 in 94% yield by insertion of the corresponding dithiacarbene (prepared in situ) into the tintin bond of Me6Sn2; the compound was characterized by an X-ray structure analysis. The related compound 29 was obtained in 48% yield by the reaction of the appropriate carbanion with Me3SnCl <1996PAC853>. S C: S
S SnMe 3
Me6Sn2
S – SnMe3
28
S SnMe3
Me3SnCl
S
S SnMe3 SnMe3 S
29
Scheme 9
(vii) Compounds with the S2CNa2 core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.2 (vi)).
(viii) Compounds with the S2CNSi core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.2 (vii)).
(ix) Compounds with the S2CNP core A [3 + 2]-cycloaddition of an in situ generated nitrilium phosphane ylide complex with benzyl N,N-dimethyl dithiocarbamate ester generates the thiaphosphirane 30 as a pale yellow oil in 13% yield as shown in Scheme 10; R denotes ubiquitous organic substituents <1999CC499>.
Functions Containing Two or One Chalcogens (and No Halogens)
W(CO)5 pip C N P R
BzS(NMe2)CS –pipCN, –W(CO)5
Me2N
325
R P S
BzS 30
Scheme 10
(x) Compounds with the S2CPSi core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.2 (viii)).
(xi) Compounds with the S2CSiGe core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.2 (ix)).
(xii) Compounds with the S2CSiLi core In addition to the compounds with this core reported earlier, the solution ion pair structure of 2-lithio-1,3-dithianes in THF and THF–HMPTA were studied. From low-temperature multiNMR studies, it was found that in THF the compounds are contact ion pair species and become separated ions with excess HMPTA. The compounds 31 (R = Me, Ph) were obtained from the appropriate substituted 1,3-dithianes and BuLi <1994T5869>. S
Li
S
SiMe2R 31
(xiii) Compounds with the S2CSnLi core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.2 (xi)).
(xiv) Compounds with the S2CPCr core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.2 (xii)).
(xv) Compounds with the S2CPMo core The coordination chemistry of the adduct S2CPR3 (R = Me, Et, Cy) and various molybdenum compounds has been explored by Miguel and co-workers. This ligand coordinates in an 3-pseudoallylic manner to one or two transition metals or to one transition metal and a main group element with formation of an S2CPM core. Molecular orbital (MO) analysis of the fluxional behavior of M(S2CPMe3)(CO)2(PMe3)2 complexes (M = Mo, W) was studied in <1996IC2406>. The Br-bridged complex of the general formula (CO)3M0 (-Br)(-S2CPR3)M(CO)3 (where M0 = Re and M = Mo) was a starting complex for various other species. The complex 32 (Scheme 11, R = Cy) can be reduced with Na/Hg at 78 C in THF to an anionic species, which by subsequent addition of Ph3SnCl gives the yellow complex 33; on warming to room temperature, 33 is reversibly converted into the red compound 34 and an equilibrium of 4/5 of both complexes is reached at room
326
Functions Containing Two or One Chalcogens (and No Halogens)
temperature; both compounds were studied by X-ray analyses <1999OM490>. Reduction of 35 with Na/Hg in THF produces the anion 36 with formation of an MoMn bond (Scheme 12). The addition of ClSnPh3 causes migration of the central carbon atom of the S2CPR3 ligand from Mo to Mn to give compounds 37 with the S2CPMn core, which are converted into 38a–38d on addition of the ligands dmpm or tedip. The same reaction sequence occurs, if two CO groups are replaced in 35 by the chelating ligands dmpm or tedip to give 39a–39d and 40a–40d (see Table 3) <1995JOM(492)23>. Further, 35 reacts with NaCCPh and NaCCH to give the acetylene-bridged derivatives 41 and 42, respectively, in high yields (Scheme 13), which were characterized by X-ray analyses <1998JA417>. The Br-bridged complex 43a (M = Mo) is shown in Scheme 14; the Mo complex (see also compound 43b with S2CPW core) was obtained with Mo(CO)3(NCMe)3 in 90% yield. The complex 43a with the MoBrMo arrangement reacts with monodentate ligands to give nearly quantitatively the related complexes 44 or with chelating ligands to produce the complexes 45 in 60% and 80% yields, respectively. The crystal structure of 44 (L = PEt3) is shown <1997JOM(545-546)327>. PR3
S S
Mo(CO)3
(OC)3Re
i. Na[Hg] ii. Ph3SnCl
Br 32 PR3
S
S
Ph3Sn
(OC)3Re
PR3
S
S
(OC)2Re
Mo(CO)3
Mo(CO)3 C
SnPh3
O
33 34
Scheme 11
– PR3
S S
Mo(CO)3
(OC)3Mn 36
S
ClSnPh3
Na[Hg]
(OC)3Mn
–
OC CO 37
PR3
S S
L–L
Mo
(OC)3Mn PR3
S
L
S
Br L
Mn(CO)3
OC
Br 35
(OC)2Mn
Ph3Sn
S Mo
Mo(CO)3
Mo
PR3
S
PR3
S
CO CO
L–L
CO CO L
Na[Hg] 40
ClSnPh3 S OC Ph3Sn OC
L L
L = dmpm, tedip
39
Scheme 12
PR3
S
CO
Mo
Mn
L
L
CO 38
Functions Containing Two or One Chalcogens (and No Halogens)
327
Table 3 R and chelating ligand of the compounds 38, 39, and 40a–40d 38, 39, 40
R
L–L
a b c d
Cy Pri Cy Pri
tedip tedip dmpm dmpm
PR3
S S (OC)3Mn
PR3
S
Mo(CO)3
S
Br 35
NaCCH (OC)3Mn NaCCPh
C C
PR3
S
Mo(CO)3
S
Mn(CO)3
(OC)3Mo
(OC)3Mn
Mo(CO)3
S S
R3P
C
R = Cy
CPh 41
42
Scheme 13
OC
S
M(CO)3(NCMe)3
S Mo
OC
PCy3
S
NO PCy3
M(CO)3
(ON)(OC)2Mo
S
Br
Br
43 (a, M = Mo; b, M = W) L–L
L
PCy3
S PR3
S
S
S Mo
(ON)(OC)2Mo (ON)(OC)2Mo
Mo(CO)2L Br L
Br L = PEt3 L = P(OMe)3
CO CO L
L–L = Me2PCH2PMe2 L–L = Ph2PCH2PPh2
44
45
Scheme 14
Reactions of 35 with Br bridge replacement are depicted in Scheme 15. The reaction of 35 with NaOMe in methylenechloride generates 46 in about 80% yield containing an OMe bridge instead of a Br bridge. The OMe bridge can easily be replaced by carbon acids to produce the related complexes 47 in yields between 30% and 60%, while the action of ethanolamine generates
328
Functions Containing Two or One Chalcogens (and No Halogens)
48 in 46% yield. The S-bridged complex 49 was obtained by the reaction of 35 with the salt [HSCH2CH(COOMe)NH3]Cl in 41% yield; most of the complexes were studied by X-ray analysis <2002OM2979>. PCy3
S
PCy3
S
S
S NaOMe
46
Mo(CO)3
(OC)3Mn
Mo(CO)3
(OC)3Mn
Br
O Me
35
PCy3
S
PCy3
S
S (OC)3Mn
Mo(CO)2
PCy3
S
S
S Mo(CO)2
(OC)3Mn
O
R2
R
H
Me
H
H
Ph
H
H
Bz
H
Me
Me
H
H
H
Me
Mo(CO)2
(OC)3Mn SH
O NR2
R1
NH2
NH2
O R1
R2
COOMe
47
48
49
Scheme 15
Replacement of the Br bridge by other ligands starting from the dinuclear complex 35 (R = Pri) is also shown in Scheme 16. Thus, Na/Hg reduction generates the anion 36, which can be converted with PhSeI in THF into red crystals of 50 (82% yield, crystal structure). Similarly, with –
PR3
S
S
S
S
Na[Hg] Mo(CO)3
(OC)3Mn
PR3
(OC)3Mn
Br
Mo(CO)3 36
35
PhSeI
Ph2PCl
PR3
S
PR3
S S
S
Ph3SnCl (OC)3Mn
Mo(CO)3
Mo(CO)3
(OC)3Mn P
Se Ph
Ph
50
Ph 51
PR3
S S
CH2Cl2, reflux
S
PR3
S Mn(CO)3
(OC)3Mn Ph
Mn(CO)3
(OC)3Mo
P Ph
Ph3Sn
52
Scheme 16
53
Functions Containing Two or One Chalcogens (and No Halogens)
329
Ph2PCl, brown crystals of 51 (76% yield) were obtained which on heating rearrange and give 52 with the S2CPMn core in 86% yield. Heating of 36 and addition of Ph3SnCl rearranged to give 53, which was confirmed by an X-ray analysis <1994OM4667>.
(xvi) Compounds with the S2CPW core MO analysis of the fluxional behavior of M(S2CPMe3)(CO)2(PMe3)2 complexes (54, M = Mo, W) was studied in <1996IC2406>. PMe3
S S M OC
PMe3 PMe3
CO
54
The dinuclear nitrosyl complex 43b (M = W) with an MoBrW arrangement was obtained in 86% yield by the reaction of (CO)2(NO)BrMo(S2CPPCy3) with W(CO)3(NCMe)3 in THF as shown in Scheme 14; for the related Mo complex, see compounds with the S2CPMo core <1997JOM(545-546)327>. Cationic carbyne complexes with this core are also described. As shown in Scheme 17, two CO groups and MeCN are replaced in the starting carbyne complexes (n = 1, 4) by the reaction with S2CPCy3 for 24 h in MeOH at room temperature; the compounds 55 were obtained in 90% yield; the complex with n = 1 was characterized by an X-ray analysis <1997OM4099>.
CO CO MeCN W P P C
H
PCy3
S S
[BF4]
[BF4]
W S2CPCy3
(CH2)n
P
P
C
H
(CH2)n 55
Scheme 17
(xvii) Compounds with the S2CPMn core Compounds with this core are only known with the S2CPR3 ligand bonded in an 3-manner and bridging two transition metals. As depicted in Scheme 18, the neutral complexes 56 (M = Mn) and 57 (M = Re) can be reduced with Na[Hg] to produce anionic species (structure not reported), which undergo protonation reactions <1998OM3448>. For further compounds with an S2CPMn core, see migration of the central carbon atom from Mo to Mn to give 37 and 38 as shown in Scheme 12 <1995JOM(492)23> and the compounds 52 and 53 in Scheme 16 <1994OM4667>.
(xviii) Compounds with the S2CPRe core For an Re complex with this core, see also compound 57 in Scheme 18. The complexes 58 (R = Cy, Pri) were obtained in about 55% yield by heating the appropriate S2CPR3 bridged
330
Functions Containing Two or One Chalcogens (and No Halogens) PR3
S S
Na[Hg]
(OC)3M
[M2(CO)6(S2CPR3]2–
M(CO)3
M R 56, Mn Cy 56, Mn Pri 57, Re Cy
Scheme 18
dinuclear octacarbonyl compounds in octane or toluene at reflux temperature during conversion of the ligand from an 2- into an 3-coordination, as shown in Scheme 19; the cyclohexyl derivative was confirmed by an X-ray analysis <1997CB1507>. The preference of 3-Mn coordination over 3-Re coordination in an MRe(CO)6(3-S2CPR3) complex has been studied <1999OM490>. PR3 PR3
S S
Toluene, reflux
S
S
Re
Re
(OC)3Re
Re = Re(CO)4
Re(CO)3
58
Scheme 19
(xix) Compounds with the S2CPFe core Mononuclear complexes with this core have been described by Miguel and co-workers as depicted in Scheme 20. The complex 59 (R = Cy, Pri) could be obtained in 40% yield by reacting Fe(BDA)(CO)3 with S2CPR3 in CH2Cl2 solution. The complex with R = Cy was characterized by an X-ray structure analysis. Alkylation with CF3SO3Me produced the corresponding cationic complexes 60; a crystal structure of 60 (R = Cy) was obtained <1996OM2735>. Me S Ph
O
S2CPR3
S
Fe OC
+
Me PR3
S CF3SO3Me
S
Fe CO
CO
OC
PR3
Fe CO
CO
59
OC
CO CO
60
Scheme 20
(xx) Compounds with the S2CPCo core The first compounds with an S2CPCo core are reported (Schemes 21 and 22). Starting from various Mn or Re complexes with the chelating S2CPR3 ligand, with Co2(CO)8 or Na[Co(CO)4] a variety of mixed dinuclear complexes (61a–61d) with CoMn and CoRe bonds are obtained in about 80% yield; an X-ray analysis was performed on 61 (M = Mn, R = Cy). The preparation of the complexes 62 with an allylic ligand and MoCo and WCo bonds from the related mononuclear complexes and Co2(CO)8 are depicted in Scheme 22; the structure of the complex 62 with M = Mo and R = Cy was confirmed by an X-ray analysis <1994OM2330>.
Functions Containing Two or One Chalcogens (and No Halogens)
331
Br OC
S PR3
M OC M Mn Mn Re Re
S
Co2(CO)8
CO
R Cy Pri Cy Pri
PR3
S S (OC)3M
Br OC
S Re
Na[Co(CO)4]
PR3
OC
Co(CO)2 61
S CO
a b c d
M Mn Mn Re Re
R Cy Pri Cy Pri
Scheme 21
PR3
S Br Co2(CO)8
S M OC
S
PR3
M
S
OC
CO
Co(CO)2
CO 62
a b c d
M Mo Mo W W
R Cy Pri Cy Pri
Scheme 22
(xxi) Compounds with the S2CPNi core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.2.(xvi)).
(xxii) Compounds with the S2CPPt core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.2.(xvii)).
(xxiii) Compounds with the S2CFe2 core The reaction of the cationic complex cis-[Cp2Fe2(-CS)(-CSMe)(CO)2]+ with Na[S2CNMe2] affords the dithiocarbene complex 63 along with a carbyne complex <2002JOM(659)15>. With nucleophiles RS (R = Me, Ph, CH2Ph), the related -carbene complexes 64 were obtained <1989OM521>. MeS
NMe2
S
Fe
Cp(OC)Fe
S Cp
C S 63
332
Functions Containing Two or One Chalcogens (and No Halogens)
MeS
SR
Cp(OC)Fe
Fe(CO)Cp C O 64
(xxiv) Compounds with the S2CFeCo core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.2.(xix)).
(xxv) Compounds with the S2CCoRu core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.2.(xx)).
6.11.2.1.3
Two seleniums or two telluriums and a group V (15) element and/or a metalloid and/or a metal function
(i) Compounds with the Se2CSi2 core A series of bicyclic compounds containing SeSe bonds have been described, which were obtained by the reaction of bis(silyldiazamethyl)polysilanes with elemental Se. Thus, Se-bridged six-membered rings (65a–65b) and seven-membered rings (66a–66c) were reported <1996G147>. SiMe3
SiMe3
Se
Me2Si
Se
Me2Si
Se Me2Si
Se Me2Si
Se
Se
65a
SiMe3
65b
SiMe2Ph
SiMe2
Se Se
SiMe2Ph
Se
SiMe2
Se
SiMe2
Se
Se
SiMe2
66a
SiMe2
SiMe3
SiMe2
Se Se
Se
SiMe2 PhMe2Si
SiMe2 SiMe2
Me3Si
66b
66c
(ii) Compounds with the Se2CSiLi core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.3.(ii)).
Functions Containing Two or One Chalcogens (and No Halogens)
333
(iii) Compounds with the Se2CPPd core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.1.3.(iii)).
6.11.2.2
Methanes Bearing Two Dissimilar Chalcogens
Dichalcogenomethanes with dissimilar chalcogens and further atoms other than chalcogens or halogens are known with the OSC and SSeC units.
6.11.2.2.1
Oxygen, sulfur, and two functions derived from a group V (15) element, metalloid, and/or a metal
(i) Compounds with the OSCN2 core The spirocyclic compounds (67a–67e) were obtained via a one-flask reaction of the corresponding 1,2-diaza-1,3-butadienes with oxazolidine-2-thion in THF at room temperature as shown in Scheme 23; yields and melting points are shown in Table 4 <2000SL1464>.
S OR1
O
O
O NH
R1O O S
N N
O
R2
N
N NH H
R2
O 67
Scheme 23
Table 4 Yields and melting points of the compounds 67a–67e Nr 67
R1
R2
Yield (%)
m.p. ( C)
a b c d e
Me Me Me Me Et
OMe OC(Me)3 OBz NH2 NHPh
69 78 67 79 80
147–150 126–128 105–108 180–185 145–148
(ii) Compounds with the OSCSi2 core The O,S-acetal (Me3Si)2C(OMe)(SPh) 68 was obtained by reacting methoxy(phenylthio)methane with BusLi in THF in the presence of TMEDA followed by addition of Me3SiCl <1986JOC879>; reactions of the compound are described in <1998SC1415, 1998ACS1141>. MeS
SiMe3
MeO
SiMe3
68
The preparation of this fluoro-substituted benzoxathiol–1,1-dioxide 69 was described in <1996AP(329)361>.
334
Functions Containing Two or One Chalcogens (and No Halogens) O O S SiMe3
MeO
O
F
SiMe3
69
(iii) Compounds with the OSCSiGe core Treatment of HC(SPh)(GeMe3)(OMe) with BuLi in THF solution at 78 C followed by addition of Me3SiCl in THF produced the compound (Me3Si)C(SPh)(GeMe3)(OMe) 70 in 90% yield <2000JCS(P1)2677>.
PhS
GeMe3
MeO
SiMe3
70
(iv) Compounds with the OSCGe2 core Treatment of HC(SPh)(GeMe3)(OMe) with BuLi in THF solution at 78 C followed by addition of Me3GeCl in THF produced the compound C(SPh)(GeMe3)2(OMe) 71 in 46% yield; the use of Me3GeBr increased the yield to 92% <2000JCS(P1)2677>.
PhS
GeMe3
MeO
GeMe3
71
(v) Compounds with the OSCSiLi core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.2.1.(iii)).
6.11.2.2.2
Oxygen and selenium, or oxygen and tellurium, and two functions derived from a group V (15) element, metalloid, and/or a metal
Compounds with OSeC or OTeC fragments with adjacent group V elements, metalloids or transition metals have not yet been described and no further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.2.2).
6.11.2.2.3
Sulfur and selenium, or sulfur and tellurium, and two functions derived from a group V (15) element, metalloid, and/or a metal
(i) Compounds with the SSeCSiLi core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.2.3.(i)).
Functions Containing Two or One Chalcogens (and No Halogens)
335
(ii) Compounds with the SSeCFe2 core The only compound in this series is reported by Angelici and co-workers and it contains the carbene ligand CSR(SeR0 ) coordinated at a metal in a bridged manner. Thus, the reaction of the chemically generated radical [Fe2Cp2(CO)2(-CSMe)]_ with PhSeSePh in THF solution at 20 C produced the carbene complex 72 in 31% yield <1986JA3688>. The complex is also obtained by reacting the cationic complex [Fe2Cp2(CO)2(-CSMe)]_+ with the nucleophile PhSe; see also compounds with the S2CFe2 core <1989OM521>. MeS
SePh
Cp(OC)Fe
Fe(CO)Cp C O 72
(iii) Compounds with the SSeCPPd core No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.2.2.3.(ii)).
6.11.3
MONOCHALCOGENOMETHANES
The majority of compounds in this section contain a 3-CER carbyne ligand (E = chalcogen) bridging a triangular face of a transition metal cluster compound. R can also be a 16- or 17-electron transition metal fragment, e.g., C5H5Fe(CO)2, Mn(CO)5, etc. In this case the CE unit can be considered as 4-bridging. Not included are cluster compounds in which only the 16-electron ligand CE coordinates at an appropriate trinuclear cluster in a 3-manner. The bonding of a CER fragment to the main group elements is restricted to a few examples bearing mainly the OCN3 core. The compounds are arranged in a manner that the CER fragment (E = chalcogen) is bonded to three identical main group elements, mixed main group elements, mixed main group transition metal elements, three identical transition metal elements, and different transition metal elements.
6.11.3.1
6.11.3.1.1
Methanes Bearing One Oxygen Function and Three Functions Derived from the Group V (15) Element, Metalloid, and/or a Metal Compounds with the OCN3 core
The reaction of [C(NMe2)3]BF4 with the system NaH/H2NMe2/B(OMe)3 produces (NMe2)3C(OEt) 73 along with (NMe2)2C(OEt)2 1, (NMe2)3C(OEt) and Me2NCOOEt as a nonseparable mixture; similar for (NMe2)3C(OEt) 74 <2000JPR256>. Me2N NMe2 EtO NMe2
73
Me2N NMe2 MeO NMe2
74
The compound 75 was obtained in 90% yield by the reaction of the related ionic triazole derivative with methanol in the presence of K2CO3; the related compound 76 was detected during
336
Functions Containing Two or One Chalcogens (and No Halogens)
the thermolysis of CF3C(O)N¼C(NPri2)OCOCF3 and characterized by NMR studies; see Scheme 24 <1997JOC9070>.
NPr2i N
NPr2i
MeO
N
N
N 75
NPr2i
Pr2N + N SO2CF3
NPr2i N SO2CF3
Pr2N
SO2CF3– NPr2i
F3COCO O F3C
OCOCF3
N
NPr2i
N
N CF3
O
F3C
76
Scheme 24
The compounds 77 (R = H, Ac) were obtained from hydrolysis of the corresponding imidazolones as shown in Scheme 25 <1996JCS(P2)371>. The compound 77 (R = H) was also obtained in 18% yield from a photosensitized oxidation process of the corresponding guanidine compound <1999EJOC49>; see also <1998JA10283>.
H N
O
N O
NH
HN
RO
H2N H2N RO
RO
O
O
N O
NH
RO 77
Scheme 25
The preparation of various heterocyclic compounds were reported; the compounds 78 were obtained by the reaction of the appropriate nitrone with RCNX compounds in CH2Cl2 in 70–90% yield (X = O; R = ClCH2CH2, a-naphthyl; X = S, R = Ph) <2001RCB882>. The triazine 79 was obtained as a by-product (15% yield) during the reaction of [C(NH2)3]Cl with C3F7CF¼NC4F9 in MeCN in the presence of NEt3 <2001RCB476>.
N O
Ph N
O
C3F7
X
N R
78
6.11.3.1.2
N N
OH N N
C3F7 N
C3F7 C3F7
79
Compounds with the OCNP2 core
The phosphonic acid derivative 80 was used as a biochemical inhibitor; no preparation was given <2001BBR(287)468, 1999BJ(337)373>. The related compounds 81 were used as compounds interacting with HIV-1 reverse transcriptase <2001MB(35)717>.
Functions Containing Two or One Chalcogens (and No Halogens) R (HO)2OP HO
H N
337
O
O N (HO)2P H N HO P(OH)2 OH O
SPh
PO(OH)2 80
81 R = PO(OH)2, H
6.11.3.1.3
Compounds with the OCNSi2 core
Compounds with this core are shown in Scheme 26 and have been obtained from the appropriate benzotriazole in various yields together with other products by the reaction with lithium diisopropylamide (LDA) and trimethylsilyl chloride at 78 C. Exhaustive silylation leads to 82 with yields up to 86%. Silylation of 83 produces 82 in high yields <1999T11903>; the preparation of 83 was also described in an earlier report <1995TL6321>.
N N N
83
R Me3Si
SiMe3
N N
LDA, TMSCl
N
LDA, TMSCl
R SiMe3 N N
82
N Me3Si
R SiMe3
R = OMe, OCD3, OPh, OC2D5
Scheme 26
The four-membered ring compound 84 was obtained in 52% yield by the photochemically induced addition of MeOH on the corresponding trisilacyclobutanimine (Scheme 27) <1992JOM(441)185>.
R2 Si SiR2 R2Si
MeOH
NPh
OMe Ph NH R2Si R2Si SiR2
84
R = But
Scheme 27
6.11.3.1.4
Compounds with the OCNSiTa core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.1.2).
338 6.11.3.1.5
Functions Containing Two or One Chalcogens (and No Halogens) Compounds with the OCNB2 core
Only one compound with this core is described. The reaction of the three-membered ring compound NB2R3 (R = But) at 78 C with CO produces the tricyclic spiro compound 85 as depicted in Scheme 28 <2002ZAAC1631>.
RN BR RB
RB RN
CO
O BR RB O
NR BR
85
R = But
Scheme 28
6.11.3.1.6
Compounds with the OCPSiTa core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.1.3).
6.11.3.1.7
Compounds with the OCFe3 core
The related section in chapter 6.11.3.1.4 in COFGT (1995) includes compounds in which the 3-bonded COR group bridges the face of a triangular cluster or one face of a tetrahedral cluster, contributing three electrons to the number of 48 or 60 CVE, respectively. Only one new example of a triangular cluster has been described. The trinuclear complex 86 (NR2 = NBut(SiMe3), X = Cl) was obtained in 62% yield by the reaction of [Fe3(CO)11]2 with Cl2BNBut(SiMe3) in benzene <1999EJIC2277>. X B
NR2
O
Fe(CO)3
(OC)3Fe
Fe(CO)3
O R2N
B X 86
6.11.3.1.8
Compounds with the OCCo3 core
This section contains compounds that are based on the trinuclear cluster Co3(CO)9(3-COR), in which R represents various organic substituents including main group or transition metal elements. Starting materials are mainly Co2(CO)8, MCo(CO)4, or the covalent trinuclear cluster Co3(CO)9(3-COLi). Thus, the reaction of NaCo(CO)4 with (acac)3ZrCl in toluene generates the complex [(acac)3Zr-OCCo3(CO)9] 87 in 60% yield <2000JOM(604)68>. The similar reaction with AlCl3 in benzene gave [(THF)3AlOCCo3(CO)9{Co4(CO)13}] 88 <1994ZN(B)1549>. The mixed salt
Functions Containing Two or One Chalcogens (and No Halogens)
339
[Et4N][Cl2SiOCCo3(CO)9{Co4(CO)11}] 89 was prepared as a minor compound during the reaction of Si2[Co2(CO)7]2 with [Et4N][Co(CO)4] <1992AX(C)1204>. All the compounds were characterized by X-ray analyses. Zr(acac)3 O
Co
Co
Co = Co(CO)3
Co
87
Co Co
THF O THF Al THF
Co
O
Co
O
Co
Co
Co = Co(CO)3
Co 88
Co1
Cl Cl
Si
-
O
Co
Co
Co = Co(CO)3 Co1 = Co4(CO)11
Co
89
6.11.3.1.9
Compounds with the OCNi3 core
The reaction of K[CpNiCO] in toluene with a series of boron compounds of the type ClB(NR2)X leads to the trinuclear Ni cluster compounds 90 (a: NR2 = NBut(SiMe3), X = Cl; b: NR2 = N(SiMe3)2, X = Cl; c: NR2 = NMe2, X = BNMe2Cl) in low yields of about 15% <1999EJIC2277>. X B
NR2
O
NiCp
CpNi
NiCp C O
90
340 6.11.3.1.10
Functions Containing Two or One Chalcogens (and No Halogens) Compounds with the OCW3 core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.1.6).
6.11.3.1.11
Compounds with the OCRu3 core
Two new compounds with this core were prepared. Starting from [Ru3H3(CO)9(3-COMe)], addition of the appropriate Au complexes [Au{-Ph2P(CH2)nPPh2}Me2] (n = 1, 5) in ether gave the mixed-metal cluster complexes 91 and in about 30–40% yield; both compounds were characterized by X-ray analyses <1998JCS(D)1107>.
O OC
Ru Ru H Ru Au
OC P
Au P 91
Ru = Ru(CO)3 P
P = PPh2(CH2)nPPh2; n = 1, 5
In <1995OM481> the tetranuclear cluster [Ru3Pt(-H)(3-COMe)(CO)10(PR3)] 92 is described, obtained from the reaction of [Ru3(-H)(-COMe)(CO)10] with PtPR3(nb)2 (R = Cy, Pri), but according to the crystal structure, the carbyne group COMe is asymmetrically bonded directing to a -bridging group (two short RuC bonds, 199 and 197 pm and one long bond, 260 pm).
O
Ru
Ru
Ru
H
Pt CO
R3P
Ru = Ru(CO)3 92
6.11.3.1.12
Compounds with the OCOs3 core
The anionic complex 93 was obtained as yellow crystals from the reaction of [Os3H3(CO)9(3-COMe)] with 1,5-diazabicyclo[5.4.0]undec-5-ene (DBU) in CH2Cl2 in 87% yield. Further reaction with [AuPPh3]Cl/TlPF6 gave the cluster compound 94 in 85% yield as depicted in Scheme 29 <1992JCS(D)1701>. The hexanuclear cluster 95 was obtained in 32% yield from the reaction of [Os6(CO)16(MeCN)2] with 1 equiv. of pyridine in
Functions Containing Two or One Chalcogens (and No Halogens)
341
CH2Cl2 solution at room temperature; the cluster was characterized by an X-ray analysis <1997JCS(D)4357>.
O
O
– H Os H
H Os H
Os Os
H
Os Os
93
O
H Os H
Os = Os(CO)3 Os AuPh3
Os 94
Scheme 29
Os(CO)2(py)2
O
Os(CO)2
py(OC)2Os
Os Os
Os
Os = Os(CO)3
95
6.11.3.1.13
Compounds with the OCFe2Ni core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.1.9).
6.11.3.1.14
Compounds with the OCFe2Co core
The cluster 96 was obtained in 62% yield by addition of HgPh2 to a solution of Fe2Co(H)(-COMe)(CO)7Cp in toluene; the compound was characterized by an X-ray analysis <1992OM540>.
6.11.3.1.15
Compounds with the OCFe2Rh core
For the structure of the Rh cluster 97 with this core, see the related Co cluster 96. The cluster was obtained in 55% yield by addition of HgPh2 to a solution of Fe2Rh(H)(-COMe)(CO)7Cp in toluene; the compound was characterized by an X-ray analysis <1992OM540>.
342
Functions Containing Two or One Chalcogens (and No Halogens)
O
O
Fe
(OC)CpM
Fe
Fe Hg
MCp(CO)
Fe
Fe = Fe(CO)3 96 (M = Co) 97 (M = Rh)
6.11.3.1.16
Compounds with the OCFe2Mn core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.1.12).
6.11.3.1.17
Compounds with the OCRu2W core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.1.13).
6.11.3.1.18
Compounds with the OCW2Ru core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.1.14).
6.11.3.2
Methanes Bearing One Sulfur Function and Three Functions Derived from the Group V (15) Element, Metalloid, and/or a Metal
The compounds in which two or three different elements are attached to the SC carbon atom are rare and only realized in some examples. Main group compounds concentrate with few exceptions on species with the SC(SiMe3)3 fragment. The majority of samples in this section, however, are based on M3 cluster compounds with a 3-C¼S ligand or similar clusters in which one or two Co atoms are replaced by other transition metals; addition of an electrophile at the C¼S sulfur atom gives a 3-methylidine ligand, which contributes three electrons to the cluster.
6.11.3.2.1
Compounds with the SCN3 core
A series of heterocyclic compounds with this core were prepared recently. The reaction of N-[(trimethylsilyl)methyl]imminium triflate with various imines in the presence of CsF gave the compounds 98 in 40% to 70% yields as depicted in Scheme 30. Similarly, the reaction of the triflate with diethyl azodicarboxylate generated the compounds 99 in yields between 20% and 74% <2001H243>. A new series of transition metal complexes was prepared containing the tris(pyrazoly)methansulfonato ligand 100 (Tpms). Toward transition metals, Tpms can act as a bidentate or, tridentate ligand. This new ligand was prepared as the Tl salt by adding excess of Tl2CO3 to an aqueous solution of LiTpms. Recrystallization from methanol gave 60% yield <2000AG2464, 2001EJIC1415>. The complex 101 was obtained from the reaction of TlTpms with [Rh(CO)2Cl]2 under 2–3 atm CO in THF is quantitative yield; without a positive CO pressure,
343
Functions Containing Two or One Chalcogens (and No Halogens) Ar HC N
H N Ts
98
NHPh
N
Ar
Me3Si
SMe
Ts
N SMe
E
PhHN
N N E
H N E
SMe 99
NHPh
N N E
Ar = Ph, p -ClC6H4, p -NO2C6H4 E = COOEt
Scheme 30
the dinuclear complex 102 was formed quantitatively. If the reaction was carried out with [Rh(cod)Cl]2 in CH2Cl2, the complex 103 (dien = cod) was obtained. Similarly, the reaction of TlTpms with [Rh(nbd)Cl]2 in dichloromethane generated the complex 104 (dien = nbd). Addition of PPh3, PMe3, or PCy3 to 101 produced the complexes 105a–105c (PR3 = PPh3, PMe3, PCy3). With potassium diphenyl(sulfonatophenyl)phosphane 106 was obtained in 40% yield. Most of the complexes have been characterized by X-ray analyses <2001EJIC1415>. The complex 105 (R = PMe3) activated benzene upon irradiation to form 107, which was carbonylated with CO to give 108; the reactions are collected in Scheme 31 <2001EJIC3113>. Treatment of CuCl in EtOH/ MeCN with LiTpms and PPh2C6H4COOH-4 produced the complex 109 in 76% yield <2003JIB(94)348>.
N
N S
S
N Rh
N
N
CO
S
N
N
N N Rh
N
PR3
S
_
N N
PPh2PhSO3
Rh(dien)
CO
CO 105
104
106 N
C6H6 S
103 CO
N N
PMe3 Rh
Ph
N N
S N
108
107
SO3 N N
N N
= S
PMe3 Rh
COPh H
H
–
N
Rh
N
Rh
S
N
102
N
N
C O C O
K[PPh2PhSO3]
PR3
N
Rh
CO
101
S
N O C
N
N N
N
100 = Tpms
Scheme 31
344
Functions Containing Two or One Chalcogens (and No Halogens) COOH N S
N
S
S N
N N N
N
N N PPh2 N Cu PPh2
N COOH 109
111
The compounds 110 in Scheme 32 contain the MFe3S4 cluster and are obtained as the [Me4N]2[VFe3S4R4] salts. The chloro derivative 110 (R = Cl) was obtained in 38% yield from the DMF complex by reacting with LiTpms in acetonitrile followed by addition of Me4NCl. Further reaction with NaSR compounds generates 110 (R = SEt) and 110 (R = S-Tol-p) in 48% yield; similarly, the action of NaO-Tol-p produces the complex 110 (R = O-tol-p) <2002IC958>.
R Fe S
DMF
S
R S
Fe
Fe S Fe
V
DMF
R
R
Fe S Fe
S R
S
V
N N
DMF
S
R
N
S
110
–SO 3 N N
N
N
N N
= S
N N
N
100
Scheme 32
The formation of the compound 111 was mentioned in <2001AG1247>.
6.11.3.2.2
Compounds with the SCNSi2 core
The reaction of BtCHSMe(SiMe3) with BuLi followed by subsequent addition of Me3SiCl afforded the compound 112 according to Scheme 33 <2000JOC9206>.
N
N
N
BuLi, Me3SiCl
N
N
N Me3Si
Me3Si
SMe
SMe SiMe3
112
Scheme 33
Functions Containing Two or One Chalcogens (and No Halogens) 6.11.3.2.3
345
Compounds with the SCPFe2 core
The cationic complex [Cp2Fe2(CO)2(-CSMe)]+ was allowed to react with ButP(H)SiMe3/DBU in MeCN to give the unstable complex 113, which loses CO to produce finally black 114 in 36% yield, which was characterized by an X-ray analysis as depicted in Scheme 34 <1997ZN(B)655>. Me
Me
PHBut
S
PHBut
S
Cp(OC)Fe
–CO
Fe(CO)Cp
CpFe
Fe(CO)Cp C O
C O
114
113
Scheme 34
6.11.3.2.4
Compounds with the SCPNi2 core
The dinuclear nickel complex 115 was prepared in 36% yield from the reaction of [Ni(cod)(PMe3)2] with thiophosgene in toluene at 78 C and characterized by an X-ray analysis <1998AG2385>. PMe3
S Ni
Me3P
Ni
Cl
Cl PMe3
115
6.11.3.2.5
Compounds with the SCPMnRe core
The complexes with the SCPMnR core were prepared according to Scheme 35. Thus, Na2[MnRe(CO)6(S2CPR3)] (R = Pri, Cy) reacts with MeI in THF to give 116 and with Pt(cod)Cl2 to produce 117 with a dimetallacyclopentadienyl ring in 53% yield. Addition of PEt3 to 116 generates the complex 118 in 82% yield <2002AG3034>. [MnRe(CO)6(S2CPR3)]2–
PR3
PR3
S S (OC)3Re
Mn(CO)3
(cod)Pt
S PR3 S
116
Et3P(OC)2Re
Mn(CO)3 C O
118 a, R = Pri, b, R = Cy
Scheme 35
S Mn (CO)3 117
Re(CO)3
346 6.11.3.2.6
Functions Containing Two or One Chalcogens (and No Halogens) Compounds with the SCSi3 core
New compounds with this core are collected in Schemes 36 and 37. The Si-methylated hexasilabicyclo[2,2,2]octane 119 was prepared in 62% yield from the monolithio derivative (obtained from the H derivative and the superbase BuLi/ButOK) and (PhS)2 in THF at 42 C (Scheme 36) <2000JOM(611)12>. (Me3Si)3CSO2Li 120 was obtained from the reaction between (Me3Si)3CLi (from (Me3Si)3CH and MeLi in ether/THF) and SO2 at 78 C; addition of Cl2 at this temperature yields (Me3Si)3CSO2Cl 121 in 71% yield (m.p. 131 C) <2000CJC1642>.
Si
Si
Si
Si
BuLi, (PhS)2
Si
Si
Si
Si
Si
Si
Si PhS
H
Si
Si = SiMe3
119
Scheme 36
LiO2S
SiMe3
Me3Si
SiMe3
ClO2S
SiMe3
Me3Si
SiMe3
120
121
The starting compound for a series of complexes is LiSC(SiMe3)3 (see chapter 6.11.3.2.2 in COFGT (1995)), which exists in a tetrameric form in hexane consisting of an Li4S4 cubane skeleton. A further complex was obtained by the reaction with YbCl3 in the presence of TMEDA generating [Li(TMEDA)][YbCl3{SC(SiMe3)3(TMEDA)}] 122; both compounds were characterized by an X-ray analysis and the anion is shown in Scheme 37 <1995KID(26)242>.
S Li S
Li
Me2 N Cl
Li S
YbCl3 S
Li
TMEDA
S = SC(SiMe3)3
SiMe3 S
Yb
SiMe3 SiMe3
N Cl Cl Me2
122
Scheme 37
6.11.3.2.7
Compounds with the SCSi2P core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.2.3).
6.11.3.2.8
Compounds with the SCPSiLi core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.2.4).
Functions Containing Two or One Chalcogens (and No Halogens) 6.11.3.2.9
347
Compounds with the SCSi2Li core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.2.5).
6.11.3.2.10
Compounds with the SCN2Fe core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.2.6).
6.11.3.2.11
Compounds with the SCNSnPt core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.2.7).
6.11.3.2.12
Compounds with the SCSiSnLi core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.2.8).
6.11.3.2.13
Compounds with the SCFe3 core
The reaction of the in situ generated radical complex [Fe2(-CSR)(-CO)(CO)2Cp2] with [Fe2(CO)4Cp2] under UV photolysis leads to the novel 3-carbyne complex 123 (a, R = Me; b, R = Et) in 30% yield; the methyl derivative was characterized by an X-ray analysis. Alkylation of this complex with MeSO3CF3 afforded the cationic complex 124, as shown in Scheme 38; all CO groups are bridging ones <1993G703>.
R
Me
S
Me S +
MeSO3CF3 FeCp(CO)
(OC)CpFe
FeCp(CO)
(OC)CpFe
FeCp(CO)
FeCp(CO)
123
124
Scheme 38
6.11.3.2.14
Compounds with the SCRu3 core
The cluster 125 was obtained in 63% yield by stirring a solution of the complex [Ru3(CO)4(-PCy2)(-dppm)] in CS2 for 2 days. The cluster was characterized by an X-ray analysis <2002ZAAC2247>.
348
Functions Containing Two or One Chalcogens (and No Halogens) X S S
S
S Cy2P
Ru
Ru Cy2P
Ru S
PPh2
H (OC)3Os H
P Ph2
125
6.11.3.2.15
Os(CO)3 Os(CO)3 126
Compounds with the SCOs3 core
The neutral clusters 126 (X = CH2, S) were synthesized in 50% yield by the reaction of the corresponding Cl-cluster Os3H3(CO)9CCl with 1 equiv. of DBU and a 10-fold excess of thiane or 1,4-dithiane <1995JCS(D)2735>.
6.11.3.2.16
Compounds with the SCCo3 core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.2.10).
6.11.3.2.17
Compounds with the SCAu3 core
The only known complex with the SCAu3 core was obtained by the reaction of [Au(acac)PPh3] with [Me3SO]ClO4, which generated the trinuclear cationic Au complex 127 <1996JA699>. O S +
AuPPh3
Ph3PAu
AuPPh3 127
6.11.3.2.18
Compounds with the SCFe2Co core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.2.11).
6.11.3.2.19
Compounds with the SCFeCo2 core
A series of cationic compounds (128a–128h) was prepared in 70% to 80% yields by alkylation of the corresponding 3-CS complex (L = PPh3, P(OMe)3, or P(OPh)3) with the appropriate RX salt (Scheme 39, Table 5); the crystal structure of 128a is reported <1998JOM(551)139>. The complex 129 was obtained according to Scheme 40 in 75% yield in refluxing CS2 (12 h) <1998CC1577>.
349
Functions Containing Two or One Chalcogens (and No Halogens) S
SR
+
CO Fe
RX
CO
CpCo CoCp
CO Fe
CO
CpCo
L
CoCp
S
X–
L
S 128a–h
Scheme 39 Table 5 R, L, and X for the compounds 128a–128h Nr 128 a b c d e f g h
L
R
X
PPh3 PPh3 PPh3 PPh3 P(OPh)3 P(OPh)3 P(OMe)3 P(OMe)3
Me Et Allyl HgCl Me Et Me Et
SO3CF3 I I HgCl BPh4 BPh4 BPh4 BPh4
S S
S CO Fe
CpCo CoCp
S CS2
CO
Fe CpCo
PPh3
CoCp
S
CO PPh3
S 129
Scheme 40
6.11.3.2.20
Compounds with the SCCo2W core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.2.12).
6.11.3.3
Methanes Bearing One Selenium or One Tellurium Function and Three Functions Derived from the Group V (15) Element, Metalloid, and/or a Metal
The compounds bearing the SeC or TeC unit, with few exceptions, are restricted to examples with the SiMe3 group and the resulting trimethylsilylmethyl group (Me3Si)3C is generally abbreviated as TSi.
6.11.3.3.1
Compounds with the SeCN3 core
No further advances have occurred in this area since the publication of COFGT (1995) (chapter 6.11.3.3.1).
350 6.11.3.3.2
Functions Containing Two or One Chalcogens (and No Halogens) Compounds with the SeCSi3 core
This section contains compounds of the general type (Me3Si)3CSeX(TsiX) in which the Se atom is further bonded to other groups including transition metals. Reaction of TsiSeI with the corresponding thiocarbonyl derivatives (a, R = Me; b, R = Prn) in toluene forms the compounds 130 in 85% yield, as shown in Scheme 41 <2001AG2486>. If the compound TsiSeLi(DME) was treated with InCl3 in hexane, the compound (TsiSe)3In was formed in 31% yield and characterized by an X-ray analysis <1995IC4854>. Treatment of TsiSeLi(DME) with CuCl (in DME solution) or Cu(PCy3)2BF4 (in ether) leads to the complexes CuSeTsi (31% yield) and Cu(PCy3)SeTsi (35% yield), respectively; Cu(PCy3)SeTsi is dimeric with an SeCuSeCu four-membered ring and characterized by an X-ray analysis. The similar reaction with AgNO3 or AgBr(PCy3)2 produced the complexes AgSeTsi (56% yield) and Ag(PCy3)SeTsi (30% yield), respectively. The first one is tetrameric with an AgSeAgSeAgSeAgSe eightmembered ring and also characterized by an X-ray analysis. If the reaction with CuCl was carried out in benzene, the salt [Li(DME)2]{Cu[SeTsi]2} was obtained in 23% yield <1994IC1797>. O TSi
Se
I
O
HN +
N
S
TSi HN R Me3Si Me3Si Me3Si
Se
S
130 HN R
Se = SeTSi
Scheme 41
6.11.3.3.3
Compounds with the TeCSi3 core
Most of the compounds that have been described with the SeCSi3 core are also known with the TeCSi3 core and similarly to the selenium derivatives, only compounds with the SiMe3 group are known. Thus, compounds of the general type (Me3Si)3CTeX in which the Te atom is further bonded to other groups including transition metals have been prepared by the same working groups as reported for the corresponding selenium compounds. The (Me3Si)3C group is abbreviated as Tsi. A solution of (THF)LiTeC(SiMe3)3 in toluene was added to a solution of Cu(PCy3)BF4 to produce the complex Cu(TeTsi)PCy3 in 51% yield; see also compounds with the SeCSi3 core <1994IC1797>.
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Lanfranchi, A. Tiripicchio, Organometallics 1997, 16, 4099–4108. 1998AG2385 H.-F. Klein, A. Schmidt, U. Flo¨rke, H.-J. Haupt, Angew. Chem., Int. Ed. Engl. 1998, 37, 2385–2387. 1998CC1577 A. R. Manning, A. J. Palmer, J. McAdam, B. H. Robinsin, J. Simpson, Chem. Commun. 1998, 1577–1578. 1998JOM(551)139 A. R. Manning, L. O’Dwyer, P. A. McArdle, D. Cunningham, J. Organomet. Chem. 1998, 551, 139–149. 1998ACS1141 M. Pan, T. Benneche, Acta Chem. Scand. 1998, 52, 1141–1143. 1998JA417 D. Miguel, M. Moreno, J. Perez, V. Riera, J. Am. Chem. Soc. 1998, 120, 417–418. 1998JA10283 D. Gasparutto, J.-L. Ravanat, O. Gerot, J. Cadet, J. Am. Chem. Soc. 1998, 120, 10283–10286. 1998OM3448 J. Li, D. Miguel, M. D. Morales, V. Riera, S. Garcia-Granda, Organometallics 1998, 17, 3448–3453. 1998H461 I. Shibuya, Y. Gama, M. Shimizu, Heterocycles 1998, 48, 461–464. 1998JCS(D)1107 C. A. Collins, I. D. Salter, V. Sik, S. A. Willams, T. Adatia, J. Chem. Soc., Dalton Trans. 1998, 1107–1114. 1998SC1415 M. Pan, T. Benneche, Synth. Commun. 1998, 28, 1415–1419. 1999BJ(337)373 R. Gordon-Week, S. Parmar, T. G. E. Davies, R. A. Leigh, Biochem. J. 1999, 337, 373–377. 1999T11903 D. P. M. Pleynet, J. K. Dutton, A. P. Johnson, Tetrahedron 1999, 55, 11903–11926. 1999CC499 R. Streubel, C. Neumann, Chem. Commun. 1999, 499–500. 1999AX1877 A. Linden, E. M. A. H. Awad, H. Heimgartner, Acta Cryst. 1999, C55, 1877–1881. 1999OM490 E. M. Lopez, D. Miguel, J. Perez, V. Riera, C. Bois, Y. Jeannin, Organometallics 1999, 18, 490–494. 1999OM1882 V. Cadierno, M. Zablocka, B. Donnadieu, A. Igau, J.-P. Majoral, Organometallics 1999, 18, 1882–1886. 1999CJC1340 A. D. Bain, P. Hazendonk, P. Couture, Can. J. Chem. 1999, 77, 1340–1348. 1999EJOC49 A. Romieu, D. Gasparutto, D. Molko, J.-L. Ravanat, J. Cadet, Eur. J. Org. Chem. 1999, 49–56. 1999EJIC2277 H. Braunschweig, C. Kollan, M. Coster, U. Englert, M. Mu¨ller, Eur. J. Inorg. Chem. 1999, 2277–2281. 1999RCB(48)2136 S. M. Bakunova, I. A. Grigorev, I. A. Kirilyuk, L. B. 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Functions Containing Two or One Chalcogens (and No Halogens)
353
Biographical sketch
Wolfgang Petz was born in Munich. He studied at the University of Munich, where he obtained his diploma in 1966 and his Ph.D. at the University of Marburg in 1969 under the direction of Professor Heinrich No¨th. After 2 years as scientific assistant he was appointed to Dozent auf Zeit at the University of Marburg, where he finished his Habilitation in 1979. In 1982 he moved to the Gmelin Institut of the Max-Planck-Society where he was author and editor of many organometallic volumes and in 1990 he became chief editor of the organometallic division. After closure of the Gmelin Institut in 1998 he moved to the MPI for Bioinorganic Chemistry in Mu¨lheim and took up his present position as apl. Professor at the University of Marburg. His scientific interests are on the field of organometallic chemistry, in particular carbene, difluorocarbene, and thiocarbonyl compounds including carbanion chemistry of transition metal carbonyl compounds.
Frank Weller was born in Stuttgart, Germany. He studied at the local University and got his Diploma in 1968. Having worked out a doctoral thesis with Professor K. Dehnicke in Marburg, Germany by 1971, he stayed there, and did some work mainly in the fields of vibrational spectroscopy and, later on, crystallography. Except for his early stage, when he was dealing with methylmercuric species, his scientific interests were, according to his mainly methodic activities, spread over a wide range of fields.
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Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 317–353
6.12 Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen) S. SABA and J. A. CIACCIO Fordham University, New York, NY, USA 6.12.1 METHANES BEARING FOUR GROUP 15 ELEMENTS 6.12.1.1 Four Similar Group 15 Element Functions 6.12.1.1.1 Four nitrogen functions 6.12.1.1.2 Four phosphorus functions 6.12.1.2 Three Similar and One Different Group 15 Element Functions 6.12.1.2.1 Three arsenic functions 6.12.1.3 Two Similar and Two Different Group 15 Element Functions 6.12.2 METHANES BEARING THREE GROUP 15 ELEMENTS AND A METALLOID OR A METAL FUNCTION 6.12.2.1 Three Similar Group 15 Elements 6.12.2.1.1 Three nitrogen functions 6.12.2.1.2 Three phosphorus functions 6.12.3 METHANES BEARING TWO GROUP 15 ELEMENTS AND METALLOID AND/OR METAL FUNCTIONS 6.12.3.1 Two Similar Group 15 Elements 6.12.3.1.1 Two nitrogen functions 6.12.3.1.2 Two phosphorus functions 6.12.3.1.3 One phosphorus, two silicon, and one arsenic functions 6.12.4 METHANES BEARING ONE GROUP 15 ELEMENT AND METALLOID AND/OR METAL FUNCTIONS 6.12.4.1 Nitrogen Functions 6.12.4.1.1 One nitrogen and three boron functions 6.12.4.1.2 One nitrogen and three silicon functions 6.12.4.1.3 One nitrogen, two silicon, and one metal functions 6.12.4.1.4 One nitrogen and three metal functions 6.12.4.2 Phosphorus Functions 6.12.4.2.1 One phosphorus and three metalloid functions 6.12.4.2.2 One phosphorus and three metal functions 6.12.4.2.3 One phosphorus, one silicon, and two metal functions
355
356 356 356 358 359 359 359 359 359 360 360 360 360 360 361 366 367 367 367 367 369 369 372 372 374 376
356 6.12.1
Functions Containing at Least One Group 15 Element METHANES BEARING FOUR GROUP 15 ELEMENTS
6.12.1.1 6.12.1.1.1
Four Similar Group 15 Element Functions Four nitrogen functions
Several reasonably general methods for the construction of molecules bearing this function have been previously described <1995COFGT(12)359>. These include (i) nucleophilic exchange of chlorine atoms with amine functions, (ii) addition of amine functions to carbon–nitrogen double bonds, (iii) addition of nitrogen-bearing carbons to nitrogen–nitrogen double bonds, and (iv) exchange of a nitrogen-bearing group with a nitrogen-bearing carbanion. A few cyclic and acyclic compounds featuring four nitrogen functions have been reported since 1995. These include structures with two, three, or four similar nitrogen functions. While some of these compounds were prepared by adaptation of previously developed methods, a few were generated by miscellaneous syntheses. These preparations are described below.
(i) By nucleophilic exchange of chlorine atoms (a) From tetraalkylchloroformamidinium chlorides. A few tetrakis(dialkylamino)methanes were synthesized by adaptation of the method previously described for preparation of tetrakis(dimethylamino)methane from reaction of a tetraalkylchloroformadinium chloride with lithium dialkylamides (Equation (1) and Table 1); yields were low to moderate. Single-crystal structural studies on tetrakis(dimethylamino)methane and tetra(pyrrolidinyl)methane, as well as reactivity studies on hydrolysis of the former compound, have also been reported <1997CB(130)1739>. +
R2N Cl
2 LiNR2
Cl–
R2N
R2N
NR2 NR2 NR2
ð1Þ
Table 1 Nucleophilic exchange of chlorine and addition of dialkylamides R
Yield (%)
References
54 25 49 12
<1997CB(130)1739> <1997CB(130)1739> <1997CB(130)1739> <1997CB(130)1739>
Me Et (CH2)4 (CH2)5
(b) From pentacarbonyl(trichloromethylisocyanide)chromium(0). Reaction of pentacarbonyl(trichloromethylisocyanide)chromium(0) with imidazole afforded a 70% yield of the electron-deficient isocyanide complex pentacarbonyl[tris(imidazol-1-yl)methylisocyanide]chromium(0) (Equation (2)) <1995JOM(489)27>. N (OC)5Cr
C N CCl3 + N
N H
CH2Cl2, rt, 6 h 70%
N (OC)5Cr
C N
N N
N
ð2Þ
N
(ii) By nucleophilic addition to guanidinium salts N,N,N0 ,N0 ,N00 ,N00 -Hexamethylguanidinium chloride, when reacted with sodium hydride/dimethylamine in the presence of trimethyl borate, produced a mixture of tetrakis(dimethylamino)methane and tri(dimethylamino)orthoformamide (Equation (3)). The reaction was conducted in anhydrous THF affording, after crystallization from acetonitrile, colorless crystals of tetrakis(dimethylamino)methane in 11% yield <2000JPR(342)256>.
357
Functions Containing at Least One Group 15 Element +
Me2N NMe2 Me2N
NaH, HNMe2, B(OMe)3
Cl–
Me2N
THF, 11%
NMe2 NMe2 NMe2
+
NMe2 NMe2 NMe2
H
ð3Þ
Similarly, as part of a general preparative scheme for selective N-monoalkylation and 1,4N,N-dialkylation of 1,4,7,10-tetraazacyclododecane, 1, octahydro-2a,4a,6a,8a-tetraazapentaleno[1,6-cd]pentalene, 3, was obtained in higher than 95% yield from guanidinium chloride 2 upon reaction with 1M NaOH at 20 C (Scheme 1). The reagents and reaction conditions for conversion of 3 to its N-monoalkyl and 1,4-N,N-dialkyl derivatives were also reported <1998ACS1247>.
NH HN NH HN
i. 37% HCl EtOH, 20 °C
NH +
N
ii. C(OEt)4 EtOH, 78 °C, 19 h
N
N
1
Cl–
1M NaOH 20 °C, 1 h
2
N
N
N
N 3
Scheme 1
(iii) Miscellaneous syntheses A few isolated reactions leading to methanes bearing four nitrogen functions have also appeared in the literature since 1995. (a) The high activation of the CF bond in the anions of salts 4 and 5 was utilized in the interaction of these salts with silylated azoles. Tetrapyrrolemethane was prepared in 90% yield by treatment of salts 4 and 5 with trimethylsilylpyrrole. Salt 4 reacted readily at 10 C while salt 5 required 24 h at room temperature (Equations (4) and (5)) <2001AG(E)1247>. [CF3S(NMe2)2]+ [CF3S]–
+ 4
N TMS
N
4
[(Me2N)2CC(NMe2)2]2+ [CF3S– ]2 + 8
2
N TMS
C + 3TMSF + . . . 4
N
C + 6TMSF + . . . 4
ð4Þ
ð5Þ
5
(b) An NMR and GC-MS study of thermolysis fragments from the 1:1 adduct obtained by reaction of diisopropylcyanamide and trifluoroacetic anhydride led to detection of a compound with mass 431. The structure suggested for this compound was that for 4-(diisopropylamino)4-(trifluoroacetoxy)-2,6-bis(trifluoromethyl)-4H-1,3,5-oxadiazine, 6. Another compound produced from reaction of compound 6 and N,N-diisopropyl-N0 ,N0 -bis(trifluoroacetyl)urea, 7, had a mass of 418 and was characterized as 4,4-bis(diisopropylamino)-2,6-bis(trifluoromethyl)-4H1,3,5-oxadiazine, 8 (Equation (6)). The former compound is the principal component in the original adduct <1997JOC9070>; however, the expected by-product shown in Equation (6) was never detected. (Pri)2N N F3C
OCOCF3 O N + (Pri)2N C N(COCF3)2 O CF3 6
7
(Pri)2N N F3C
N(Pri)2 N O
CF3
O O + F3C C O C N(COCF3)2
ð6Þ
8
(c) Tetrapyrazolylmethane (Cpz4) was used for the synthesis of the binuclear adduct [{CpMo(CO)2}(-Cpz4){Re(Cl)O3}][BF4] (81% yield) formed between the high oxidation state rhenium complex ClReO3 and a molybdenum-based organometallic ligand bearing a bridge with nitrogen donors like Cpz4 <1998POL1091>.
358
Functions Containing at Least One Group 15 Element
(d) In a study of some properties of N-polynitromethyl derivatives of fused benzotriazoles, 2,6bis(trinitromethyl)benzo[1,2-d;4,5-d0 ]ditriazole-4,8-dione, 11, was prepared by nitration of 2,6-bis(dinitromethyl)benzo[1,2-d;4,5-d0 ]ditriazole-4,8-dione, 9, and its sodium or potassium salts, 10, with conc. HNO3 (Scheme 2). Treatment of 11 with hydroxylamine afforded a chemically unstable dioxime that gradually decomposed to 11 <1993IZV1623>. O
O N
N
(NO2)2HC N
HNO3
N CH(NO2)2 N
O 9 M = Na+, K+
N
N
N
(NO2)3C N
60 °C , 24 h 44%
N
N
N C(NO2)3 O 11
MOAc O
HNO3
N
N
N
N
(NO2)2MC N
N CM(NO2)2 O 10
Scheme 2
(e) Nucleophilic displacement of a nitro group with an azido group was shown to occur in polynitromethanes. It was found that reaction of tetranitromethane with NaN3 in DMSO-CH2Cl2 afforded azidotrinitromethane in 20–24% yield (Equation (7)). When this reaction was carried out in pure DMSO or DMF, the yields were 10–14%. In aqueous acetone, this reaction produced a mixture of azidotrinitromethane and diazidodinitromethane (identified by GLC) that were difficult to separate. Pure diazidodinitromethane was obtained in 12% yield by the reaction of teranitromethane with excess NaN3 in aqueous ethanol at 5–10 C. Diazidodinitromethane was also detected by GLC in the reaction of the monoazide with NaN3 in aqueous ethanol <1997IZV338>. NaN3
C(NO2)4
ð7Þ
C(NO2)3N3
20–24%
(f) In the course of syntheses of condensed pyrazolo derivatives, reaction of 5-amino-3-arylamino-1H-pyrazole-4-carbonitrile, 12, with dicyandiamide in refluxing ethanol afforded compounds for which Structure 13 was suggested (Equation (8)) <1997CCA1039>. These structures were based on spectral and elemental analyses of the products; however, only MS data for compound 13 (Ar = C6H4CH3m) were reported. NC ArHN
NH2 N
NH
NH2 +
NC N
12
NH2
NC
NH2
EtOH, 78 °C, 4 h 65–70%
ArHN
N
N
CN NH NH2 NH2
ð8Þ
13
Ar = C 6H4-CH3-m Ar = C 6H4-F-p
6.12.1.1.2
Four phosphorus functions
Only two reports describing the preparation of compounds of this class have appeared in the literature since 1995. Treatment of bis(trimethylsilyl)methylidene triphenylphosphorane, 14, with a phosphorus trihalide gave the corresponding dihalophosphanyl ylides, 15, which self-condensed in pyridine (X = Cl) or a mixture of benzene and pyridine (X = Br) to selectively afford tetramers having cations with a tetraphosphabicyclo[2.2.2]octane (1,3,5,7-tetraphosphabarrelane) structure, 16 (Scheme 3) <1995AG(E)1853>. The chloride salt was formed as a complex with pyridine in 43% yield; no yield was reported for the bromide salt. Reaction of the tetraphosphabarrelane chloride with either aluminum trichloride or gallium trichloride converted the singly charged
359
Functions Containing at Least One Group 15 Element
cation to a tetracation having a cubane structure (17; 20% yield for M = Al, and 50% yield for M = Ga), whereas treatment with antimony pentachloride afforded a mixture of dications, one with the barrelane structure preserved, 18, and a minor amount of a dication with a tetraphosphabicyclo[3.3.0]octane structure <1998ZN(B)1285>. (MCl4– )4 PPh3 MCl3
PPh3 Ph3P C(TMS)2
PX3 (–TMSX)
14
TMS
Ph3P
X = Cl, Br
X Ph3P
PX2
PP
PPP Ph3P
16
PPh P PPh3 3 17
PPh3
X P P X Ph3P X–
15
CH2Cl2
PPh3 SbCl5 X = Cl
Cl Cl PPh3 Ph3P P P Cl P P Cl Ph3P 2– SbCl5 18
Scheme 3
6.12.1.2
Three Similar and One Different Group 15 Element Functions
6.12.1.2.1
Three arsenic functions
In a reaction analogous to the synthesis of a 1,3,5,7-tetraphosphabarrelane cation described in Section 6.12.1.1.2, treatment of 14 with arsenic trichloride afforded a 1,3,5,7-tetraarsabarrelane cation, 20, along with minor amounts of 1,3-diarsetane and 1,3,5-triarsinane cations (Scheme 4) <2000CEJ3531>. The reaction proceeded via the intermediacy of a dichloroarsanyl trimethylsilyl ylide, 19 that tetramerized to 20 over a period of weeks. X-ray analysis of the crystalline cation 20 disclosed average AsCl bond lengths of 249 pm, reported to be by far the longest to be observed at a three-coordinate, pyramidal arsenic atom. PPh3 Ph3P C(TMS)2
AsCl3, Pyr
Cl As Ph3P As
TMS Ph3P
AsCl2
(–TMSCl ) 14
19
62%
Cl
PPh3
As As Cl Ph3P AsCl4– 20
Scheme 4
6.12.1.3
Two Similar and Two Different Group 15 Element Functions
No further advances have occurred in this area since the publication of chapter 6.12.1.3 in <1995COFGT(12)359>.
6.12.2
6.12.2.1
METHANES BEARING THREE GROUP 15 ELEMENTS AND A METALLOID OR A METAL FUNCTION Three Similar Group 15 Elements
Two reports have appeared in the literature since 1995 featuring compounds of this class; each describing structures containing a carbon that bears one metal function and either three nitrogen or three phosphorus functions.
360
Functions Containing at Least One Group 15 Element
6.12.2.1.1
Three nitrogen functions
In the course of studies on preparation of anionic tris(3,5-dimethylpyrazolyl)-containing ligands in transition metal chemistry, it was stated that deprotonation of HC(Me2Pz)3 (Pz = pyrazolyl) occurred cleanly without prior complexation to a metal center by reaction with MeLi in THF to form LiC(Me2Pz)3 in quantitative yield. The use of this compound as a reagent was established toward the preparation of a titanium-containing zwitterionic complex displaying a naked sp3-hybridized carbanion <2001CC705>.
6.12.2.1.2
Three phosphorus functions
Treatment of tris(diphenylphosphanyl)methane, 21, with an acetylacetonato (acac) gold(I) complex, 22, led to the formation of a neutral gold(I) complex, 23, with the gold atom linearly bound to both triphenylphosphine and the carbon of the methanide ligand, an unprecedented coordination type for tris(phosphanoyl)methanide and its derivatives (Equation (9)) <1996CB585>.
CH[PPh2(O)]3
+
Ph3P Au
Au(acac)PPh3 79%
21
6.12.3
23
22
PPh2O PPh2O PPh2O
+
acacH
ð9Þ
METHANES BEARING TWO GROUP 15 ELEMENTS AND METALLOID AND/OR METAL FUNCTIONS
6.12.3.1 6.12.3.1.1
Two Similar Group 15 Elements Two nitrogen functions
Only two compounds featuring a carbon attached to two nitrogen functions and two metal functions have been described since 1995. Both compounds exhibit carbene metal interactions and the nitrogens are part of five-membered heterocycles. Deprotonation of 3-borane-1,4,5-trimethylimidazole, 24, with BunLi afforded lithium 3-borane1,4,5-trimethylimidazol-2-ylidene, 25 (Equation (10)). An X-ray diffraction study on a single crystal of this salt grown from a THP solution at 4 C revealed dimeric units of two carbene anions connected by two lithium cations. The nitrogen-flanked carbene carbons have a shorter (2.169 A˚) and a longer (2.339 A˚) contact with the lithium cations <1998EJI843>.
-BH Me Me
-BH
3
N+
BunLi
N Me
THF-hexane, –40 °C
24
Me Me
N N Me
3
Li+
ð10Þ
25
The reaction of 2,6-bis(imidazolmethyl)pyridine, 26, and 1-methyl-2,5-bis(trimethylaminomethyl)pyrrole diiodide, 27, in nitromethane produced the cyclophane diiodide 28 (Equation (11)). Treatment of an aqueous solution of 28 with NH4PF6 afforded the dihexafluorophosphate salt which, upon deprotonation with Ag2O in DMSO at 55 C, afforded a dimeric silver N-heterocyclic carbene complex with composition [Ag4(28*)2][PF6]4, where 28* represents the deprotonated 28. Both the 13C NMR and X-ray diffraction data on the carbene complex indicated that each carbene is interacting with two different silver atoms via -bonding and -bonding interactions <2001CC1780>.
361
Functions Containing at Least One Group 15 Element + Me3N
N
N N
+
N
N + N
2I–
MeNO2
Me N
N
N
2I–
N + N
Me3N +
26
Me N
27
28
ð11Þ
N
N
Me N
N N
N 28*
6.12.3.1.2
Two phosphorus functions
(i) Two phosphorus and two silicon functions Only three practical syntheses of compounds of this class, all leading to the formation of diphosphirane functionality, have been reported since 1995. The first involved protonation of the lithium salt of a persilylated 2,3,4-triphosphapentadienide, 29, the first of its kind reported, leading to a bicyclic diphosphirane, 31 (no yield reported). The latter most likely arose from a valence isomerization of intermediate 30 (Scheme 5) <1996AG(E)313>.
TMS P Cl
+
2 LiP(TMS)2(THF)x
TMS
–LiCl –P(TMS)3
Li+(DME)3 TMS
P
P
TMS
TMS TMS
76%
58%
TMS
P
TMS P
P
Li+(DME)
TMS 3
29 H
H+ TMS TMS
TMS P
P
P
TMS
H TMS TMS
30
TMS P
P
TMS
P 31
Scheme 5
The same research group subsequently reported a reaction between dilithioferrocenylphosphanide and dichlorobis(trimethylsilanyl)methane, leading to a mixture of a diferrocenyldiphosphirane, 34 (65% yield), and a minor amount of a bis(methylene)phosphorane, 35. The authors explained the formation of these products by assuming an initial lithium–halogen exchange, affording a phosphenoid and carbenoid that immediately dimerized with elimination of LiCl; further reaction of the dimer with either the phosphenoid or carbenoid led to 34 and 35, respectively. The predominance of the diphosphorane suggests an increased stability of the phosphenoid compared to the carbenoid under these conditions (Scheme 6) <1997JOM(541)237>. The third report described a reaction between a 1,2-dihydro-1,2-phosphasilete, 36, and [bis(trimethylsilyl)methylene]chlorophosphane that led to a phosphaalkene-substituted phosphasilete, 37, in 93% yield, which then underwent a thermal isomerization to afford bicyclic diphosphirane 38 in 80% yield (Scheme 7) <1999CEJ1581>.
362
Functions Containing at Least One Group 15 Element PLi2 Fe
Cl +
Cl
PClLi
0 °C, ether
TMS
Fe
Li
TMS
+
TMS
Cl
TMS 33
32
TMS TMS –2 LiCl
P
P
TMS 32, –LiCl
Fe
Fe
TMS P
C(TMS)2
P +
C(TMS)2
Fe
65% 34
Fe
35
33, –LiCl
Scheme 6
But
Ph
TMS P Si TMS TMS
+
ClP
TMS –TMSCl TMS
93%
TMS
TMS
But
P P TMS Si TMS TMS
Ph
But
180 °C, 2 h
P P Ph Si TMS TMS
80%
37
36
TMS
38
Scheme 7
(ii) Two phosphorus and two metal functions A number of compounds of this class have been reported since 1995, the majority bearing two gold functions, in addition to a few compounds bearing two aluminum, chromium, lead, tin, or nickel functions. (a) Two phosphorus and two gold functions. All but one of the recently reported syntheses of compounds bearing two phosphorus and two gold functions involved carbon metallation by the use of basic acetylacetonato (acac) gold complexes, hydroxide, or hydride for deprotonation of a methylene or methine group bearing two phosphorus functions. The reaction of trinuclear gold complex 39 with a fourfold excess of [Au(acac)PPh3] gave heptanuclear gold complex 40 in which bis(diphenylphosphino)methanediide [bis(dppm)] bonds to four gold atoms as an eight-electron donor ligand (Equation (12)) <1995OM2918>. Ph3PAu AuPPh3 Ph2P (C6F5)3Au
PPh2 ClO4 Au Au(C6F5)3 4 [Au(acac)PPh3] PPh2 Ph2P CH2Cl2, 48 h, 80%
Ph2P (C6F5)3Au
PPh2 Au Au(C6F5)3 PPh2 Ph2P
Ph3PAu
ClO4
ð12Þ
AuPPh3
40
39
In a similar fashion, a cyclic, linearly coordinated tetranuclear gold complex 41 with tridentate bis(dppm) ligands was treated with 2 equiv. of [Au(PPh3)2]ClO4, leading to deprotonation of the CH groups and the formation of the hexanuclear complex 42 in 75% yield (Equation (13)) <1995CB121>. Ph3PAu AuPPh3
(acac)Au H Ph2P Au Ph2P
PPh2 Au PPh2
H Au(acac) 41
2 [Au(PPh3)2]ClO4, 8 h –2 acacH, 75%
Ph2P Au Ph2P
PPh2 Au PPh2
Ph3PAu AuPPh3 42
(ClO4)2
ð13Þ
363
Functions Containing at Least One Group 15 Element
With the aim of developing controlled syntheses of heterometallic species of high nuclearity, Ruiz and co-workers <1997OM3388> investigated the chemistry of bis(dppm) derivatives of ruthenium and manganese. Treatment of the bis(dppm) derivative 43 (M = Mn, L = CO) with one molar equivalent of [AuCl(PPh3)] and excess KOH gave a mixture of dinuclear and trinuclear, 44, complexes in a 6:4 molar ratio; however, the trinuclear, 44 (90% yield), tetranuclear, 45 (83% yield), and pentanuclear, 46 (81% yield), complexes were selectively obtained in the presence of excess KOH by treatment of the same bis(dppm) derivative with two, three, and four molar equivalents of [AuCl(PPh3)], respectively. By contrast, partial metallation of the bis(dppm) derivative, 43 (M = Ru and L = CNBut or CNPh), was not possible, and only the corresponding pentanuclear complex, 46, could be isolated in pure form (L = CNBut, 78% yield; L = CNPh, 81% yield) (Scheme 8 and Table 2).
2 [AuClPPh3]
Ph2 L P M P Ph L
Ph3PAu H
KOH, CH2Cl2
2
Ph2 AuPPh3 P H P Ph2
n
[AuClPPh3] KOH, CH2Cl2
44
Ph2 L P M P Ph2 L 43
Ph2 P P Ph2
Ph3PAu H
4 [AuClPPh3] KOH, CH2Cl2
Ph2 L P M P Ph L
Ph3PAu Ph3PAu
2
Ph2 L P M P Ph2 L 45
Ph2 P AuPPh3 P AuPPh3 Ph2
n
n Ph2 [AuClPPh3] P AuPPh3 P AuPPh3 KOH, CH2Cl2 Ph2
46
Scheme 8
Table 2 Controlled syntheses of heterometallic species of high nuclearity Compound
M
L
n
Yield (%)
References
44 45 46 46 46
Mn Mn Mn Ru Ru
CO CO CO CNBut CNPh
1+ 1+ 1+ 2+ 2+
90 83 81 78 81
<1997OM3388> <1997OM3388> <1997OM3388> <1997OM3388> <1997OM3388>
Treatment of bis(pentafluorophenyl)gold(III) methanide complex 47 (Scheme 9) and tris(pentafluorophenyl)gold(III) methanide complex 50 (Equation (14)) with [Au(acac)L] afforded the corresponding disubstituted products (80% [L = PPh3] and 74% [L = AsPh3] for the metallacycle 47; 71% [L = PPh3] for the acyclic compound). When complex 47 was treated sequentially with NaH and [Au(acac)PPh3] a four-membered methanide complex was afforded in 53% yield (Scheme 9) <1998POL2029>.
S C6F5 Au PPh2 C6F5 Ph3PAu PPh2 S 48
i. NaH ii. [Au(acac)PPh3] 53%
C6F5 S PPh2 ClO4 2 [Au(acac)L] Au C6F5 S PPh2 CH2Cl2, 2 h 47
Scheme 9
C6F5 C6F5
S PPh2 ClO4 AuL AuL S PPh2
Au
49
364
Functions Containing at Least One Group 15 Element (C6F5)3Au S PPh2
2 [Au(acac)]PPh3, CH2Cl2, 1 h 71%
Ph2P S
(C6F5)3Au S PPh2 AuPPh3 Ph2P AuPPh3 S
ð14Þ
50
In a report on the synthesis of a family of cyclic palladium complexes containing N,P-diphosphinomonoimine ligands, exposure to two molar equivalents of [Au(acac)PPh3] led to double deprotonation and functionalization of a palladium complex having an acidic methylene group (Equation (15)) <1998OM4544>.
Tol
N
Tol
Pd N
Ph3PAu AuPPh3 Ph2P
OTf
Ph2P PPh2
2 [Au(acac)PPh3], CH2Cl2, 36 h 88%
N
OTf
PPh2
Tol
N
Tol
Pd N N
ð15Þ
In another report detailing a synthesis of this class of compound by deprotonation and metallation of an acidic methylene or methine, gold ferrocenyl methanide derivative 52 was prepared in 86% yield when 51 was treated with [O(AuPPh3)3]ClO4 (Equation (16)) <1999ICA60>.
Fe
P Ph2
PPh2
(ClO4)2
Ph3PAu AuPPh3
ClO4 [O(AuPPh3)3]ClO4, CH2Cl2, 2 h
Fe
P Ph2
86%
51
PPh2 AuPPh3
ð16Þ
52
Finally, a dinuclear complex 53 with a carbon bearing two gold functions and two phosphorus functions was prepared in 70% yield from the reaction of the diylide C(PPh3)2 with AuCltetrahydrothiophene (tht) complex in a 1:2 molar ratio (Equation (17)) <2002OM5887>.
2 AuCl(tht)
C(PPh3)2, THF, 1 h 70%
Cl Au Au Cl
PPh3
ð17Þ
PPh3 53
(b) Two phosphorus and two aluminum functions. Since the mid-1990s, a notable amount of interest has focused on the development of nitrogen donor complexes as alternatives to cyclopentadienyl groups on metals, with impact on homogeneous catalysis. One study investigating bis(iminophosphorano)methane chemistry led to the synthesis of novel aluminum complex 55 (67% yield) by both single and double, stepwise deprotonation of the ligand’s methylene backbone (Scheme 10) <1999OM4241>. A patent also appeared that describes the preparation of derivatives of the aluminum complex with various groups attached to nitrogen, phosphorus, and aluminum, and it outlines processes for polymerizing various alkenes using the various complexes <1999USP6235919B1>.
Ph2P N Ph2P N
TMS AlMe3, PhMe, 20 °C 68% TMS
TMS Ph2P N Me Al Me Ph2P N TMS
AlMe3, PhMe, 120 °C
Ph2 Me2 Al P TMS N N TMS Al P Me2 Ph2 55
54 2 AlMe3, PhMe, 120 °C 67%
Scheme 10
365
Functions Containing at Least One Group 15 Element
(c) Two phosphorus and two tin, lead, or chromium functions. Disilylated bis(iminophosphorano)methane, 54, was reported to lead to 1,3-dimetallacyclobutanes (56–58) upon monodeprotonation with BunLi and treatment with PbCl2 <2001AG(E)2501> (Equation (18)), double deprotonation with BunLi and treatment with CrCl2(THF)2 (Equation (19)) <1999CC1993>, and direct treatment with M[N(TMS)2]2 (M = Sn, 70% yield; Pb, 80% yield, Equation (20)), <2001AG(E)2501>. TMS TMS Ph2P N
TMS Ph2P N
BunLi, THF
PbCl2, Et2O,18 h
Li Ph2P N
Ph2P N
TMS
54
84%
Ph2P
TMS N
Ph2P N
N Pb TMS
TMS
PPh2
Pb
PPh2
ð18Þ
N TMS
56 TMS
TMS Ph2P N Ph2P N
2 BunLi, THF
Li Li
Ph2P N Ph2P N
TMS
TMS CrCl2(THF)2, THF, 2 days
Ph2 Ph2 TMS N P P N Cr
56% TMS
TMS
54
Cr
N P P N TMS Ph2 Ph2
ð19Þ
57 TMS TMS Ph2P N Ph2P N
Ph2P
54
PPh2
M
M[N(TMS)2]2, PhMe, M = Pb, Sn TMS
TMS N
Ph2P N
N M TMS
ð20Þ
PPh2 N TMS
58 n
Double deprotonation of 54 with Bu Li and then treatment with 2 equiv. of CrCl2(THF)2 was reported to lead to partially substituted tetranuclear complex 59 (Equation (21)) <1999CC1993>. TMS N
TMS Ph2P N Ph2P N
i. 2 BunLi, THF; ii. 2 CrCl 2(THF)2 ,THF, 1 day 61% TMS
54
Cl Ph2P Cr Cl Li(THF)2 N TMS Ph2P Cr Cl Cr PPh2 Cl TMS N Cl PPh 2 (THF)2Li Cr Cl N TMS 59
ð21Þ
The dimetallacyclobutane 57 is the first example of a bridging chromium carbene without the usual carbonyl or cyclopentadienyl ligands, and it is also the first example of a chromium carbene complex that contains two phosphorus functions on the carbene carbon. (d) Two phosphorus and two nickel functions. In a study of oxidative addition reactions of dichlorophosphaalkene 60 with Ni(0) complexes, Konze and co-workers isolated the first example of a complex 61 (59–74% yield) with a mixed 2,4-diphosphaallene ligand that is bridged between two nickel atoms forming a fused, bicyclic heterocycle (Equation (22)) <1998OM1569>.
2 Ni(PPh3)2L + Cl2C=PN(TMS)2 60
PhMe, –50 °C to rt, 1 h
Cl Ph3P Ni
L = (C2H4), 74%; (COD), 69%; (PPh3)2, 59%
Cl Ni PPh3 P
PPh3
ð22Þ
(TMS)2N 61
Treatment of the bicyclic complex 61 with 2 equiv. of triethylphosphine at 40 C led to substitution of the PPh3 groups on nickel by PEt3, but the newly formed complex 62 was unstable and could not be isolated (Equation (23)).
366
Functions Containing at Least One Group 15 Element
61
3 PEt3, THF, –78 to –40 °C, 15 min
Cl Et3P Ni
Cl Ni PEt3 PPh3
P
Not isolated
ð23Þ
(TMS)2N 62
(iii) Two phosphorus, one metal, and one silicon functions In a study similar to that described in Section 6.12.3.1.2.(i).(c), Konze and co-workers <1998OM5275> treated dichlorophosphaalkene 60 with a Pd(0) complex and isolated the first example of a complex, 63, with a phosphinio-methylene(imino)metallophosphorane ligand 2-coordinated to one palladium center and 1-coordinated to another in a dinuclear complex (Equation (24)).
2Pd(PEt 3)4
+
60
Hexanes, 0 °C to rt, 15 min 57%
Et3P Cl Pd PEt3 Pd TMS P Et3P NTMS Cl
ð24Þ
63
Treatment of complex 63 with 3 equiv. of either iodomethane or sodium iodide afforded a similar complex, 64, in 24% yield. Hydrolysis of complex 63 afforded another novel, threemembered heterocycle, 65 (Scheme 11). TMS Cl Pd Et3P
PEt3
H2O, THF, rt, 5 min
P
82%
O NHTMS
3 MeI, THF, rt, 24 h 63
24%
Et3P I Pd PEt3 Pd P TMS Et3P NTMS I
65
64
Scheme 11
The only recent synthesis of a compound with a carbon bearing one phosphorus, one lithium, and one silicon function was that of the first coligand-free diphosphinomethanide, 67, afforded in crystalline form, by the reaction of silyl substituted phosphinomethane 66 with BunLi (Equation (25)) . The crystal structure of this trimeric compound showed each lithium atom surrounded by two phosphorus atoms and one carbon atom, with two of the lithium atoms displaying weak lithium–phenyl contacts. Me2P PhMe2Si Me2P
H
BunLi –BuH
1/3
66
6.12.3.1.3
Me2P PhMe2Si Me2P
Li
ð25Þ
3
67
One phosphorus, two silicon, and one arsenic functions
Only two compounds of this description were prepared recently; both are phosphaarsiranes. Treatment of metalloarsane (5-C5Me5)(CO2)FeAs(TMS)2, 68, with 1 equiv. of [bis(trimethylsilyl)methylene]chlorophosphane gave 1-metallo-1-arsa-2-phosphapropene 69 and a few crystals of dimetallophosphaarsirane 70 (Equation (26)) <1996CB219>.
+ ClP C(TMS)2 OC Fe OC As(TMS)2 68
C(TMS)2 [Fe]
THF, –15 °C to rt, overnight 69, 88%; 70, trace
OC Fe As P OC TMS
[Fe] = [(η 5-C5Me5)(CO)2Fe]
69
[Fe] P As
+
TMS
TMS 70
ð26Þ
367
Functions Containing at Least One Group 15 Element
The 1-arsa-2-phosphapropene 69 was treated with an excess of [(Z)-cyclooctene]Cr(CO)5 and the resulting product was purified by chromatography on Florisil followed by crystallization to afford crystalline phosphaarsirane 71 in 17% yield (Equation (27)). 69
i. [(Z )-cyclooctene]Cr(CO)5, n -pentane, 20 °C, 2 days; ii. SiO2/H2O
[Fe] As
TMS H P
17% TMS Cr(CO5)
ð27Þ
71
6.12.4
METHANES BEARING ONE GROUP 15 ELEMENT AND METALLOID AND/OR METAL FUNCTIONS
6.12.4.1 6.12.4.1.1
Nitrogen Functions One nitrogen and three boron functions
Since 1995, only one report has appeared that describes the preparation of compounds bearing nitrogen and three boron functions. By reacting sterically hindered isocyanide ButNC with [anti-B18H22] in benzene, cluster carbonatom insertion occurred yielding macropolyhedral carbaboranes [7-(ButMeHN)-(anti)-B18H20] and [9-(ButNH2)-(anti)-9-B17H19-8-(CN)] in 6% and 12% yields, respectively <1995CC2407>. These compounds were characterized by MS and NMR spectroscopy; the latter compound was further characterized by single-crystal X-ray diffraction analysis.
6.12.4.1.2
One nitrogen and three silicon functions
A few compounds with a carbon bearing nitrogen and three silicon functions have appeared since 1995. All feature trimethylsilyl substituents with the nitrogen as part of an isothiocyanate moiety or a heterocyclic system. As a promising building block for heterocyclic syntheses, tris(trimethylsilyl)methyl isothiocyanate was prepared in 95% yield by a novel, direct lithiation of methyl isothiocyanate at 95 C using LDA and trapping of the carbanion intermediate with excess TMSCl/THF (Equation (28)) <1997S423>. The product was characterized by its melting point as well as IR and 1H NMR spectra. MeN C S
+ 3TMSCl
LDA (3 equiv.) THF, Et2O, hexane, –95 °C
(TMS)3C N C S
ð28Þ
95%
As part of a synthetic exploration of the Peterson olefination route to 1-(1-alkenyl)benzotriazoles, 1-(trimethylsilylmethyl)benzotriazole, 72, was lithiated at the -carbon using LDA, and the resulting lithiated species was trapped with TMSCl affording 1-bis(trimethylsilyl)methyl-1H-benzotriazole, 73, in 83% yield (Scheme 12). Further treatment of the latter compound with LDA and trapping with TMSCl afforded 1-tris(trimethylsilyl)methyl-1H-benzotriazole, 74, and 4-trimethylsilyl-1-tris(trimethylsilyl)methyl-1H-benzotriazole, 75, as crystalline compounds in 44% and 41% yields, respectively. These compounds were characterized by elemental analysis and NMR spectroscopy (1H, 13C). While Peterson olefination on other silylated benzotriazole derivatives was carried out, no further exploration on compounds 74 and 75 was reported <1999T11903>. Photolysis of 1,3-bis(trimethylsilyldiazomethyl)-1,1,3,3-tetramethyl-2,2-diphenyltrisilane, 76, in cyclohexane with a high-pressure mercury lamp at 0 C afforded the five-membered heterocycle 79 in 11% yield (Scheme 13). The structure of this compound was established spectroscopically (1H, 13C, 29Si NMR) as well as by elemental analysis, exact mass determination by high-resolution mass spectrometry (HRMS), and X-ray crystallographic analysis. It was suggested that this heterocycle is the hydrolysis product of the bicyclic azo compound 78 produced from intramolecular [2+3]-cycloaddition of diazosilene 77. Photolysis of
368
Functions Containing at Least One Group 15 Element N N
LDA / TMSCl, –78 °C
N
83%
N
N
LDA / TMSCl, –78 °C
N
TMS
TMS
72
TMS 73
TMS
N
N
N N TMS
N
+
N
TMS TMS
TMS
74
TMS TMS 75
Scheme 12
TMS N2 TMS
Ph2 N2 Si Si Si TMS Me2 Me2
hν Cyclohexane, 4 h
Ph2Si Me2Si TMS
76
SiMe2 N
Me2(HO)Si
Ph2Si Me2Si
N 77
TMS N N TMS 78
H2O
TMS N HN
Me2 Si
[2 + 3]
SiMe2 TMS SiPh2
TMS H2O
SiMe2 TMS
N
N Me2Si SiPh2
79
Scheme 13
1,4-bis(dimethylphenylsilyldiazomethyl)-1,1,2,2,3,3,4,4-octamethyltetrasilane, 80, in cyclohexane afforded compound 82 in 25% yield, and is believed to have formed from nitrogen extrusion of the bicyclic azo compound 81 (Scheme 14) <1995JOM(499)99>.
N2 PhMe2Si
SiMe2Ph
N2 (SiMe2)4 80
hν
SiMe2Ph
Me2Si Me2Si Me2Si PhMe2Si
SiMe2 N
N
[2 + 3]
PhMe2Si Me2Si Me2Si
Me2 Si N
N Si Me2 SiHMe2Ph 81 –N2
Me2 Si SiMe2 Me2Si Si PhMe2Si Me2 82
PhMe2Si
Scheme 14
Silaethene Ph2Si¼C(TMS)2, 83, a product of thermal elimination of LiX (X = Br, F) from Ph2SiXCLi(TMS)2 and its rearranged form 84, produced upon interaction of 83 with LiBr, underwent [3 + 2]-cycloaddition with azidodi-t-butylmethylsilane as well as azidotri-t-butylsilane in diethyl ether at 78 C affording cycloadducts 85–87 (Scheme 15) <1995CB1231>.
369
Functions Containing at Least One Group 15 Element
Ph2Si
C(TMS)2
+ LiBr _
83 . LiBr
TMS Me2Si
83
+ LiBr _
TMS
. LiBr
Me2Si
SiMePh2
84
Bu3t SiN3
Bu2t MeSiN3
Ph2Si C(TMS)2 N N Bu2t MeSi N
SiMePh2
Bu3t SiN3
TMS Ph2Si SiMePh2 N N Bu3t Si N
Ph2Si C(TMS)2 N N Bu3t Si N
85
86
87
Scheme 15
6.12.4.1.3
One nitrogen, two silicon, and one metal functions
There is a single report of such a compound since 1995. [3+2]-Cycloaddition of the labile stannaethene 88 with But2MeSiN3 at 78 C afforded the triazoline cycloadduct 89 (Scheme 16) . This compound is a suitable source of the thermolabile stannaimine Me2Sn¼NSiBut2Me.
Me2Sn C(TMS)2 PhLi Br Br
TMS Me TMS Me Sn N N But2MeSi N 89
Bu2t MeSiN3 Me2Sn C(TMS)2 –LiBr Me2Sn C(TMS)2 Br Li –78 °C 88
Scheme 16
6.12.4.1.4
One nitrogen and three metal functions
(i) One nitrogen and three chromium functions There appears to be only one report of a compound belonging to this class since 1995. Cothermolysis of the thiocarbenoid complex CpCr(CO)2(SCNMe)2, 90, with [CpCr(CO)3]2 afforded a four-component mixture which, after column chromatography on silica gel, yielded a dark brown solid, Cp4Cr4S2(CO)(CNMe2), in 36% yield as a highly air-sensitive compound. This compound was characterized by 1H NMR and IR spectroscopy, MS, and single-crystal X-ray diffraction analysis revealing it as a 3-aminocarbyne cubane complex 91 (Equation (29)) <2002OM4408>. All six CrCr bonds in compound 91 are not shown for clarity. CO CO 2 OC Cr
O +
Toluene, 110 °C, 3 h Cr S OC OC 36% N Me H Me 90
Cr S
Cr
S
Cr
Cr
Me N Me
+ ...
ð29Þ
91
(ii) One nitrogen and three ruthenium functions Two reports on compounds bearing one nitrogen and three ruthenium functions have appeared since 1995. The organometallic cluster H3Ru3(CNMeBz)(CO)6(PPh3)3 was prepared in 77% yield by treatment of a cyclohexane solution of HRu3(CNMeBz)(CO)10 with PPh3 and heating the mixture in the presence of hydrogen gas bubbled through the solution. Chemical oxidation of this cluster with Ag+ or ferricenium produced the 47-electron cation [H3Ru3(CNMeBz)(CO)6(PPh3)3]1+ which was
370
Functions Containing at Least One Group 15 Element
characterized spectroscopically (EPR, 1H, 31P NMR, IR). An account of cyclic voltammetric experiments on this cluster has been detailed <1998OM872>. An investigation on the mechanistic decomposition of the 47-electron cationic cluster, generated by chemical or electrochemical oxidation of the 48-electron precursor, has also been reported. In connection with this study, several clusters featuring a tetracoordinated carbon bearing nitrogen and three ruthenium functions were prepared <2001JOM(633)51>. These included H3Ru3(CNMeBz)6L3 (L = PPh3, SbPh3), prepared by previously published procedures <1998OM872, 1990IS196>, and H3Ru3(CNEtBz)6(PPh3)3, H3Ru3(CNMeBz)6(PPh3)2(CNBz), prepared using analogous procedures by substitution of appropriate ligands on the parent carbonyls. No further preparative details were provided, but IR and 1H NMR data for the latter compounds were reported.
(iii) One nitrogen, two cobalt, and one iron functions A few compounds having this structural unit have been described since 1995. Clusters of the type 93 were generated upon cleavage of the 2-isothiocyanate ligand in [Fe(PPh3)2(CO)2(2-SCNR)], 92, by 2 equiv. of [Co(-Cp)(PPh3)2] (Equation (30)) <1999JOM(573)109>. While the cluster with R = MeC(O) decomposed during reaction work-up, others were obtained in good yields. R OC
PPh3 Fe
+ 2
S
OC PPh3
N
N R Benzene, 5 h
Co
65–70%
Co
Fe
Co Ph3P
PHPh3
S
92
CO CO
ð30Þ
PPh3
93 R = Ac, PhC(O), Me2N– C6H4–C(O)
Except when R = Me2NC6H4C(O), reaction of clusters 93 with CF3SO2OMe afforded salts 94 in which the CNFeCo2 moiety was retained. All the clusters were characterized by their IR and 1 H NMR spectra. The crystal structure of cluster 94 with R = PhC(CO) was also studied by X-ray diffraction analysis.
R + Me N Co Fe Co S
CO CO
PPh3
94
(iv) One nitrogen and three osmium functions Numerous reports describing the preparation, reactivity, and crystal structures of various triosmium clusters having a carbon bearing one nitrogen and three osmium functions have appeared in the literature since 1995. All clusters described contain a triosmium alkylidyne metal core linked to a nitrogen function at an apical position. Triosmium alkylidyne cluster 96 was synthesized by the reaction of 95 with 1 equiv. of DBU in the presence of a 10-fold excess of 4-vinylpyridine (Equation (31)) <1995MI311>. Treatment of cluster 96 with a slight excess of [Os3(CO)10(NMe)2] in refluxing n-hexane for 8 h produced the homonuclearly linked cluster 97 in 34% yield, while reaction of 96 in refluxing CH2Cl2 with traces of water, using stoichiometric amounts of Wilkinson’s catalyst RhCl(PPh3)3, afforded a 29% yield of 98 <1995JOM(493)229>.
371
Functions Containing at Least One Group 15 Element
Cl N
H
Os
H
CH2Cl2, 0 °C, 0.5 h 69%
Os
Os
ð31Þ
4-Vinylpyridine, DBU
H
H
Os
H Os
Os
95 96
Os Os
Os H
H
Me
H
N
N
H
Os
H
H
Os
H Os
Os
Os
Os
O
98
97
Following the same methodology as that used for the preparation of 96, reaction of 95 with pyridine-containing ligands 99, 100 <1995JCS(D)1379>, 101, 102 <1995ICA(234)5, 1995JCS(D)3995>, 103, 104 <1996JCS(D)1853>, 105 <1996JCS(D)2293>, 106, 107, and 108 <1999JOM(584)48> afforded moderate-to-good yields of structurally similar complexes.
N N Fe
N
99
N N
Fe
100
N
N
101
102
OC16H33
N
N
N
N
103
104
105
372
Functions Containing at Least One Group 15 Element
R
OMe O 2N
N
N
N
106
107
N 108
R = H, CMe3, NH2, NMe2, SMe, OMe, OC6H13, OC7H15, OC9H19, Br, Cl
Treatment of an ethereal solution of the triosmium cluster 109 with an excess of diazomethane afforded the diazomethylidyne complex 110 (Equation (32)). The structure of this compound was established based on its analytical and spectroscopic data and was further characterized by singlecrystal X-ray crystallography <2000OM5623>. Ph P
Ph
N
Os
CH2N2, Et2O
P Ph Os Ph
Os
Os
40%
ð32Þ
H
CH2Cl2, –10 °C, 1 h
H
P Ph Os Ph
Os H 110
109
6.12.4.2
Ph P
N
Phosphorus Functions
By far, the greatest number of reports since 1995 of compounds possessing a carbon bearing one phosphorus and three metalloid and/or metal functions is for those with one phosphorus and three silicon functions. A few examples have been reported of compounds with a carbon bearing one phosphorus and either three transition metals, or one silicon and two metal functions.
6.12.4.2.1
One phosphorus and three metalloid functions
(i) By nucleophilic exchange of chlorine atoms on a silicon atom Two equivalents of phosphinomethanide 111 reacted with various chlorosilanes generating phosphorus ylides 112 with a tetraheteroatom-substituted methane functionality . When the reaction was carried out in a 1:1 ratio where R = Ph and R0 = Cl, phosphorus ylide 112 was obtained in an impure form along with tetraheteroatom-substituted methane 113 resulting from monosubstitution on silicon (Equation (33)) <1995JOM(501)167>.
R Cl Si Cl + n {Li[C(PMe2)(TMS)2]}2.TMEDA R1
111
R1 R TMS Me2P Si P TMS + PhCl2Si TMS TMS Me Me 112
R = R1 = Me; R = R1 = Cl; R = Ph, R1 = Cl
PMe2 TMS TMS 113
ð33Þ
373
Functions Containing at Least One Group 15 Element (ii) By nucleophilic exchange of chlorine atoms on a phosphorus atom
Tris(trimethylsilyl)methyllithium was reported to effect nucleophilic displacement of chlorine on the phosphorus atoms of chloro-substituted iminophosphane 114 <1997CC293> and 1-chloro-1Hphosphirene 115 <1997CB711>, affording the corresponding products 116 and 117 in 76% and 90% yields, respectively (Scheme 17).
ClP N 114 THF, –78 °C, 76% TMS TMS TMS
TMS TMS
P N TMS 116
Li
But Cl
P TMS TMS TMS
115 Ph Et2O, 90%
But P Ph 117
Scheme 17
The first reports outlining the preparation of diphosphenes (TMS)3CP¼PC(TMS)3 <1982TL4941> and (2,4,6-But)C6H2P¼PC(TMS)3 <1983JA1655> by reductive coupling of the corresponding alkyldichlorophosphines appeared in the early 1980s, but more recent reports describe further transformations at the phosphorus–phosphorus double bond, including [2 + 1] cycloadditions with dichlorocarbene and isonitriles <1998JFC(89)73, 1999ZAAC1934>; each of these transformations left the tetrasubstituted carbon atom unchanged.
(iii) By reaction of carbon–phosphorus double bonds P-Halogeno-, P-phenyl-, and P-phosphanyl-substituted 2,2-bis(trimethylsilyl)-1-phosphaethenes, 118, have been reported to react with C¼P cleavage to afford compounds possessing a carbon bearing one phosphorus and three silicon functions, or a carbon bearing one phosphorus, one germanium, and two silicon functions. When a phosphanyl-substituted phosphaethene (118; X = (5-1,3-But2C5H3)(CO)2Fe P(TMS)) was treated with an excess of [(Z)-cyclooctene]Cr(CO)5, the 1,2-diphosphaferrocene pentacarbonylchromium adduct 121 was obtained in low yield along with the butterfly complex 119 and the metallodiphosphene 120, the latter two being too unstable to isolate and only identified by 31 P-NMR data in comparison with those of related compounds (Equation (34)) <1995CB665>.
XP C(TMS)2
118
LCr(CO)5
[Fe]
TMSO
P P C(TMS)3 + [Fe] + P P Cr C(TMS)3 (CO)4 But 119
120
OTMS OTMS P P Fe Cr(CO)5 But 121
ð34Þ
X = (η 5-1,3-Bu2t C5H3)(CO)2Fe–P(TMS) L = (Z )-cyclooctene [Fe] = (h5-1,3-Bu2t C5H3)(CO)2Fe
Treatment of P-halogenophosphaethenes (118; X = Cl, Br, I) with an equimolar amount of hexadichlorosilane effected C¼P cleavage and P¼P formation, giving diphosphene 122 in 71% yield when X = Cl . By following the reaction by 31P-NMR, the authors postulated the intermediacy of the phosphaalkene (TMS)2C¼PSiCl3, which then
374
Functions Containing at Least One Group 15 Element
dimerizes by 1,2-addition of the PSi bond of one molecule to the C¼P bond of another to give (TMS)2C¼P-P(SiCl3)C(TMS)2SiCl3, followed by a 1,2-trichlorosilyl shift from phosphorus to carbon, thereby affording diphosphene 122 (Equation (35)). Si2Cl6, hexanes, 60 °C, 8 days; X = Cl XP=C(TMS)2
Cl3Si(TMS)2C
71%
P P
C(TMS)2SiCl3
ð35Þ
122
118
In their studies of group 14 carbene analogs and their reactions with P-phosphanyl phosphaalkenes, du Mont and co-workers observed a similar type of transformation when phosphaethene 122 (X = PPri2) was converted to diphosphene 123 (83% yield) upon treatment with the silylene SiCl2; the latter was generated in situ by an -elimination of Me3GeCl from Me3GeSiCl3, induced by the dialkylphosphanyl group within phosphaethene 118 (Equation (36)) <2002AG(E)3829>. The same research group also investigated the reactivity of phosphaethene 118 (X = PPri2) with GeCl2-dioxane, observing the formation of diphosphene 124 by 31P-NMR and isolating a crystal suitable for low-temperature X-ray diffraction analysis; however, the major isolated product was the fused bicyclic heterocycle 125, which possesses two carbons that each bear one phosphorus, one germanium, and two silicon functions (50% yield) (Equation (37)) <2001MI609>. i
Me3GeSiCl3; X = PPr 2
Pr 2i P Cl2Si
XP=C(TMS)2 83% 118
(TMS)2C SiCl2 PPr 2i P P
ð36Þ
C(TMS)2 123
XP=C(TMS)2 118
GeCl2; X = PPr 2i –(Pr 2i P)2GeCl2
i (TMS)2C GeCl2PPr 2
P P Cl3Ge C(TMS)2
–Pr2i PCl 50%
124
Cl2Ge P C(TMS) 2 (TMS)2C P Ge Cl2 125
ð37Þ
In another recent study of the reaction of silylenes and germylenes with phosphaalkenes, Kimel et al. <2001MC85> described the reaction of phosphaethene 118 (X = Ph) with MMe2 (M = Si, Ge) affording the corresponding unstable phosphasilacyclopropane (126, M = Si) and phosphogermacyclopropane (126, M = Ge), respectively; the former generated as part of a gross mixture of other phosphorus-containing products and identified only by a 31P-NMR signal at 132.4; the latter obtained cleanly and characterized by 1H, 13C, 31P, and 29Si NMR analysis. Further reaction of 126 (M = Ge) with GeMe2 gave the 2,3-digerma-1-phosphacyclobutane 127 (Equation (38)) <2002MI1568>. XP=C(TMS)2 118
MMe2
TMS
X =Ph; M = Si, Ge
TMS
PPh MMe2 126
6.12.4.2.2
GeMe2; M = Ge
TMS TMS PPh Me2Ge GeMe2
ð38Þ
127
One phosphorus and three metal functions
The only reports since 1995 of compounds of this description involve organometallic complexes with carbons bearing, in addition to one phosphorus function, either three osmium functions or three cobalt functions. All of the reported syntheses of the former complexes involve CP bond formation upon displacement of chlorine from carbon bearing three osmium functions, and the sole reported synthesis of the latter involves CCo bond formation by displacement of chlorine from a carbon bearing one phosphorus function. The reaction of the triosmium alkylidene cluster [Os3(-H)3(CO)9(3-CCl)], 128, with various bidentate diphosphine ligands is outlined in Scheme 18. Cluster 128 reacted with an excess of butyldiphenylphosphine in the presence of a stoichiometric amount of DBU to give the expected complex 129 in 30% yield. A similar reaction was observed with the optically active diphosphine 130, affording a mixture of isomeric complexes 131 and 132 in 15% and 20% yields, respectively. Complex 131 decarbonylated at room temperature after 24 h to give an octacarbonyl homometallic
375
Functions Containing at Least One Group 15 Element
cluster 133 in 50% yield. The isomeric complex 132 failed to cyclize under similar conditions, perhaps due to potentially unfavorable steric interactions in the corresponding six-membered ring <1995JCS(D)2831> (Scheme 18). PPh2Bu
Os
Os
H Os BuPPh2, DBU
Ph2P
30%
Os
Os H
Me Ph3P Os
H Os
Ph Me H
Os
Os
H Os
PPh2 130
Ph P
H Me
129
Cl H
PPh2
H
PPh2
Os
H Os
H
H
, DBU 132
134
131, 15%; 132, 20%
H
H
Me
PPh2
Me Ph2P
Ph2P
128
Os
CH2Cl2, 24 h
Os
H Os
Os
50%
H
H Os
H Os
PPh2
H
133
131
Scheme 18
Complexes 135 (45% yield) and 136 (50% yield) were formed in a similar way from the reaction of 128 with the bidentate ligands Ph2PCH2PPh2 and Ph2PCH2CH2PPh2, respectively, (Scheme 19) <1996JOM(518)227>. Both subsequently decarbonylated and cyclized to form five- and six-membered osmacyclic complexes 137 (60% yield) and 138 (40% yield), respectively, whereas treatment of cluster 128 with the homologous ligand Ph2PCH2CH2CH2PPh2 led to an acyclic, linking complex 139. PPh2CH2PPh2 Ph2PCH2PPh2, DBU 45%
Ph2P
CH2Cl2, 2 days
Os
Os
H Os
Os 60%
H
Os
H Os 137
135
PPh2CH2CH2PPh2 Ph2PCH2CH2PPh2, DBU
Ph2P
CH2Cl2, 2 days
Os
128 50%
Os
H Os
Os 40%
H
Os
H Os
136
138
PPh2
PPh2
Ph2PCH2CH2CH2PPh2, DBU
Os 40%
PPh2
H
H Os
Os
Os
H
H Os 139
Scheme 19
Os H
H
PPh2
376
Functions Containing at Least One Group 15 Element
The ferrocenyl-phosphine cluster derivative 140 was prepared in a similar fashion by the reaction of cluster 128 with 1,10 -bis(diphenylphosphino)ferrocene (Equation (39)) <1995JCS(D)1379>. Ph2P
Ph2P 128
+
Fe
DBU, CH2Cl2, 30 min
Fe
32%
PPh2
Os H Ph2 P
Os
ð39Þ
Os H
140
The formation of a tricobalt carbonyl cluster (141; R = Et) was accomplished by treatment of [Co2(CO)8] with Cl3CP(O)(OEt)2 (Equation (40)) <1997JOM(541)417>. A similar complex (141; R = TMS) was also prepared either by treatment of [Co2(CO)8] with Cl3CP(O) (OTMS)2 or by reaction of 141 (R = Et) with TMSBr (in 15% yield for the latter). The Lewis donor ability of the P¼O function of cluster 141 (R = Et) was used to assemble early-late metal systems by reaction with [Cp2MCl]+ (M = Ti, Zr). O (RO)2P O (RO)2P Cl
Cl
THF, 50 °C, 3 h
+ Co2(CO)8
(OC)3Co
28%, R = Et; 23%, R = TMS
Cl
Co(CO)3
ð40Þ
Co (CO)3 141
6.12.4.2.3
One phosphorus, one silicon, and two metal functions
Two reports describing the preparation of compounds of this type have appeared since 1995; one describing a symmetrical complex with two carbons each bonded to one phosphorus atom, one silicon atom and two rhodium atoms, and a second outlining a structural investigation of a dilithiated phosphonate with a carbon bonded to one phosphorus atom, one silicon atom and two lithium atoms. Photolysis of rhodium-substituted triethylsilyldiazomethyl complex 142 led to the dimer 143, most likely via the intermediacy of a transient rhodium-stabilized carbene (Equation (41)) <1996OM1166>.
(Et3P)3Rh
N2 TMS
Benzene, 25 °C, 90 min, hν = 330 nm Unstable > –20 °C
TMS PEt3 PEt3 Et3P Rh Rh Et3P PEt3 Et3P TMS
ð41Þ
142 143
Treatment of a solution of dimethyl(trimethylsilylmethyl)phosphonate in TMEDA at 78 C with 2.5 equiv. of BunLi gave the crystalline dilithiated phosphonate 144, whose X-ray crystal structure revealed a highly aggregated species that is characterized by a LiOLiO fourmembered ring at its core (Equation (42)) <1999AG(E)92>. O (MeO)2P
TMS
i. 2.5 BunLi, TMEDA, –78 °C; ii. rt, 24 h
O (MeO)2P Li
+. . – TMS . N(Me)2 . (Li (TMEDA)2) (TMEDA) Li 2 3 2
144
ð42Þ
Functions Containing at Least One Group 15 Element
377
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1998POL2029
Functions Containing at Least One Group 15 Element
379
Biographical sketch
Shahrokh Saba was born in Tehran, Iran, studied at the American University of Beirut, in Lebanon where he obtained his B.S. in 1970. He continued his education at the University of East Anglia and received his Ph.D. in 1974 under the direction of Professor A. R. Katritzky. During 1975–1979 he taught as an Assistant Professor at Azad University in Tehran. He moved to the United Stated in 1980 and after postdoctoral fellowships in 1980 (Professor R. Breslow, Columbia University), 1981 (Professor W. C. Agosta, Rockefeller University), and 1982–1983 (Professor N. O. Smith, Fordham University) assumed a teaching position at Kean College, New Jersey in 1984. He returned to Fordham University in 1986 and took up his present position, and is currently an Associate Professor of chemistry. His scientific interests include all aspects of heterocyclic chemistry, and new uses of simple ammonium salts in organic synthesis.
James A. Ciaccio was born in Newburgh, NY, studied at SUNY, Oneonta where he obtained a B.S. in chemistry. His graduate studies in organic chemistry were conducted at SUNY, Stony Brook, where he obtained a Ph.D. under the direction of Professor T. W. Bell. In 1989 he was awarded a Camille and Henry Dreyfus Postdoctoral Teaching and Research Fellowship at Bucknell University, where he was Visiting Assistant Professor of Chemistry while working in the laboratories of Prof. H. W. Heine. During 1989–1990 he taught as Visiting Assistant Professor of Chemistry at Bard College, after which he took up his present position at Fordham University, where he is currently Associate Professor of Chemistry and Director of the General Science Program. His scientific interests fall in the general area of organic synthetic methods with emphasis on reactions and synthesis of epoxides and other heterocycles. He has also published several novel undergraduate organic laboratory experiments that combine synthesis and mechanistic discovery.
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Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 355–379
6.13 Functions Containing at Least One Metalloid (Si, Ge, or B) and No Halogen, Chalcogen, or Group 15 Element; Also Functions Containing Four Metals P. D. LICKISS Imperial College London, London, UK 6.13.1 METHANES CONTAINING AT LEAST ONE METALLOID (AND NO HALOGEN, CHALCOGEN, OR GROUP 15 ELEMENT) 6.13.1.1 Methanes Bearing Four Metalloid Functions 6.13.1.1.1 Four similar metalloid functions 6.13.1.1.2 Three similar and one different metalloid functions 6.13.1.1.3 Two similar and two different metalloid functions 6.13.1.2 Methanes Bearing Three Metalloid Functions and a Metal Function 6.13.1.2.1 Three similar metalloid functions 6.13.1.2.2 Other mixed metalloid functions 6.13.1.3 Methanes Bearing Two Metalloid and Two Metal Functions 6.13.1.3.1 Two Si and two metal functions 6.13.1.3.2 Two Ge and two metal functions 6.13.1.3.3 Two B and two metal functions 6.13.1.3.4 Other combinations of two metalloids and two metal functions 6.13.1.4 Methanes Bearing One Metalloid and Three Metal Functions 6.13.1.4.1 One Si and three metal functions 6.13.1.4.2 One Ge and three metal functions 6.13.1.4.3 One B and three metal functions 6.13.2 METHANES BEARING FOUR METAL FUNCTIONS 6.13.2.1 Methanes Bearing Four Similar Metals 6.13.2.2 Methanes Bearing Three Similar and One Different Metal Functions 6.13.2.3 Methanes Bearing Two Similar and Two Different Metal Functions 6.13.2.4 Methanes Bearing Four Different Metal Functions 6.13.3 METHANES BEARING MORE THAN FOUR METALLOID OR METAL FUNCTIONS
381
382 382 382 387 388 389 389 401 402 402 402 402 403 403 403 403 403 403 403 403 404 404 404
382 6.13.1
Functions Containing at Least One Metalloid (Si, Ge, or B) METHANES CONTAINING AT LEAST ONE METALLOID (AND NO HALOGEN, CHALCOGEN, OR GROUP 15 ELEMENT)
The structure of this chapter is based closely on the corresponding one in COFGT (1995), where it was noted that for the 47 different elements (i.e., not the elements specifically excluded in the title of the section, the lanthanides, the actinides, and Fr, Ra, and Tc) that were to be considered as substituents at a quaternary carbon, there are 230 300 different possible combinations of the metal substituents (not including a further 178 365 optical isomers generated by having four different elements as substituents). The number of these possible combinations discussed later is still below 0.1% of those possible thus indicating that there is still tremendous scope for the synthesis of such organometallic compounds. For the case of methanes bearing four metal substituents, it has been necessary to make some judgment about whether the species may be of interest to organic chemists. For example, compounds where the carbon is part of a metal carbide have been excluded.
6.13.1.1
Methanes Bearing Four Metalloid Functions
There are hundreds of compounds known containing a carbon substituted by four silyl groups. The many methods to prepare them have not developed much beyond those described in COFGT (1995), but some new variations of reagents and experimental conditions mean that yields are often improved. The surprising lack of compounds with no tetragermyl substitution at carbon was noted in COFGT (1995). Although this is no longer the case, very few compounds of this type are known even now. This is still presumably due to a lack of synthetic effort as many of the methods available for tetrasilylmethane synthesis should be suitable for the preparation of tetragermylmethanes. A small number of methanes substituted by four boron functions have been prepared and there are an increasing range of compounds containing either a variety of metalloid functions or mixed metalloid and metal functions.
6.13.1.1.1
Four similar metalloid functions
(i) Four Si functions (a) Tetrasilylmethanes from in situ coupling reactions. Symmetrical compounds containing the Si4C function may be prepared by in situ coupling reactions involving CCl4 or CBr4 and a group 1 or 2 metal. These reactions are discussed in more detail in <1995COFGT(6)377>. A few new examples have been reported recently; for example, the use of 4,40 -di-t-butylbiphenyl as a catalyst in the reaction of CCl4 with lithium powder at low temperature gives an 80% yield of (Me3Si)4C <1996T1797>, which is much better than that without the catalyst. The in situ method has also been used in the preparation of the spirocyclic compound 1 in 25% yield (Equation (1)) <1999CL317>. These syntheses rely on the relatively slow coupling reactions to form disilanes using Li or Mg and should be applicable to a wider range of silanes as long as the substituents are not too bulky. SiMe2Cl + SiMe2Cl
CCl4
+
Mg
Me2 Si C Si Me2
Me2 Si Si Me2
ð1Þ
1
(b) Formation by reaction between a trisilyllithiomethane and a halosilane. The reactions between trisilyllithiomethanes (for their synthesis, see Section 6.13.1.2.1 below) and halosilanes have been used to prepare a wide range of tetrasilylmethanes in which there are at least two different silyl substituents on the carbon. Such compounds are not accessible via the in situ coupling reaction, which produces only symmetrical compounds. This method is thus more general and often gives good yields. The only potential difficulty with these reactions is that the Si3CLi-substituted precursor may require stringent low-temperature conditions for its preparation.
Functions Containing at Least One Metalloid (Si, Ge, or B)
383
The bulk of a trisilyllithiomethane derivative together with the low-temperature preparations means that it is possible to prepare reagents containing functional groups that would not normally be compatible in simpler compounds. For example, reagents containing both SiH and CLi groups are accessible and can be used to give a range of compounds containing SiH groups that can then be used as precursors to many other tetrasilylmethanes. The range of trisilylithium reagents available for these reactions, together with the products available, is given in Table 1. As would be expected from simple metathesis reactions, the yields for this method are usually good. The order in which the silyl substituents are attached to the central carbon may be important if the groups are particularly bulky, and it seems best if the most bulky silyl substituent is not the one to be attached last. It should also be noted that addition of more than 1 equiv. of a trisilylmethyllithium reagent to a polyhalosilane does not result in more than monosubstitution at silicon; presumably this is due to the steric crowding at the relatively small silicon center. The reaction of (HMe2Si)3CLi with SiCl4 gives several products (see Table 1), the main one being the cyclic species 2, in approximately 38% yield <1999OM1804>. The generation of compounds containing more complicated tetrasilylmethane centers by this general route is exemplified by the syntheses of the bicyclic compounds 5 and 6 shown in Scheme 1 <1998CL1145, 2000JOM(611)12>. In this case, the intermediate organometallic reagent, 4, derived from the trisilylmethane derivative 3, is probably the potassium derivative in THF solution. In a related reaction to those described above, the treatment of the Grignard-like species [Mg(OEt)2{C(SiMe3)3}I]2 with Me3SiCl gives (Me3Si)4C in 23% yield <2001JOM(631)76>.
Me2 Si (HMe2Si)2C C(SiMe2H)2 Si Me2 2 Me2 Si Me2Si
H
Me2Si
C
BuLi/ButOK
SiMe2
Me2Si Me2Si
Me2 Si
H 3
Si Me2
SiMe2
Me2Si
THF, – 40 °C
C
M C
C H
Me2Si 4
Si Me2
RMe2SiCl Me2 Si Me2Si
Me2 Si
SiMe3 C SiMe2
Me2Si C
Me2Si Me3Si
Me2Si
R = Me
Si Me2
i. BuLi/ButOK ii. Me 3SiCl
C
SiMe2
Me2Si Me2Si
C H
98%
6
SiMe2R
Si Me2
R = Me, 82% R = Ph, 90 % R = CH2CH2CH2Cl, 86 %
5
Scheme 1
(c) Formation via addition reactions of silenes. The dimerization of silenes, Si¼C containing compounds, occurs readily at room temperature and usually gives head–tail dimers. If there are two silyl substituents at the unsaturated carbon center, then the resulting dimers contain two tetrasilylmethane centers. The silenes (Ph2MeSi)(Me3Si)C¼SiMe2 <1996JOM(524)147> and (Me3Si)2C¼SiPh2 <1995CB1241> undergo Ph and Me group migrations to give a mixture of isomeric silenes that dimerize in the head-to-tail fashion to give the disilacyclobutanes 7–10 in varying yields depending on the nature of the silene starting material. The silene (Me3Si)2C¼SiMe2 dimerizes in a similar manner <2000JOM(598)292>.
Table 1 Lithiomethane
Tetrasilylmethanes from the reaction of miscellaneous trisilyllithiomethanes with halosilanes
Halosilane
Product
R2C(SiMe2Ph)Li R2C(SiPh2Me)Lia
PhMeHSiCl Me2SiHCl
R2C(SiMe2Ph)(SiPhMeH) R2C(SiPh2Me)(SiMe2H)
R2C(SiPh2Me)Li R3CLi R3CLi
Me3SiCl EtSiCl3 BunSiCl3
R3CSiPh2Me R3CSiEtCl2 R3CSi(Bun)Cl2
R3CLi R3CLi R3CLi R3CLi R3CLi R3CLi R3CLi R3CLi
(p-MeOC6H4)SiCl3 (p-MeOC6H4)MeSiF2 (p-MeOC6H4)2SiF2 Si2Cl6 Me3SiCl Me2SiHCl CH2¼CHMeSiCl2 (p-MeOC6H4)2SiMeHCl
R3CSi(p-MeOC6H4)Cl2 R3CSiMe(p-MeOC6H4)F R3CSi(p-MeOC6H4)2F R3CSi2Cl4CR3 R4C R3CSiMe2H R3CSiMeClCH¼CH2 R3CSi(p-MeOC6H4)MeH
R3CLi
(p-MeC6H4)2SiMeHCl
R3CSi(p-MeC6H4)MeH
R3CLi R2C(SiMe2H)Li
Ph2SiF2 Me3SiCl
R3CSiPh2F R3CSiMe2H
R2C(SiMe2H)Li R2C(SiMe2H)Li R2C(SiMe2OPh)Li R2C(SiMe2SPh)li R2C(SiMe2SMe)Li (HMe2Si)3CLi (HMe2Si)3CLi (HMe2Si)3CLi (HMe2Si)3CLi (HMe2Si)3CLi (HMe2Si)3CLi (HMe2Si)3CLi (HMe2Si)3CLi (HMe2Si)3CLi (HMe2Si)3CLi (PriMe2Si)3CLi
Me2SiHCl Me2PhSiCl Me2SiHCl Me2SiHCl Me2SiHCl Me3SiCl MeSiHCl2 HSiCl3 MeSiCl3 SiCl4 SiCl4 CH2¼CHMe2SiCl CH2¼CHMeSiCl2 CH2¼CHCH2MeSiCl2 [CH2¼CH(CH2)4]Me2SiCl Me2SiHCl
R2C(SiMe2H)2 R2C(SiMe2Ph)(SiMe2H) R2C(SiMe2OPh)(SiMe2H) R2C(SiMe2SPh)(SiMe2H) R2C(SiMe2SMe)(SiMe2H) (HMe2Si)3CR (HMe2Si)3CSiMeHCl (HMe2Si)3CSiHCl2 (HMe2Si)3CSiMeCl2 (HMe2Si)3CSiHCl2b (HMe2Si)3CSiMe2CH(SiMe2H)2b (HMe2Si)3CSiMe2CH¼CH2 (HMe2Si)3CSiMeClCH¼CH2 (HMe2Si)3CSiMeClCH2CH¼CH2 (HMe2Si)3CSiMe2[(CH2)4CH¼CH2] (PriMe2Si)3CSiMe2H
Yield (%)
References
40 40
<1998JOM(560)41> <1995BSF517> <2001EJI481> <2001EJI481> <1996JCS(P2)163> <2000JOM(598)222> <2000PS(158)97> <2000PS(158)97> <2000PS(158)97> <1997JOM(545–546)61> <2001IC3766> <2001EJI481> <2001EJI481> <2000JOM(598)222> <2000JOM(598)222> <1999PS(149)229> <2000JOM(598)222> <1999PS(149)229> <2000JOM(598)222> <2000OM374> <2001JOM(640)29> <2001JOM(640)29> <2001JOM(640)29> <2001JOM(640)29> <2001JOM(640)29> <2001JOM(640)29> <1999OM1804> <1999OM1804> <1999OM1804> <1999OM1804> <1999OM1804> <1999OM1804> <2001JOM(620)127> <2001JOM(620)127> <2001JOM(620)127> <2001JOM(620)127> <1995JOM(489)181>
48 60 70 62 72 82 82 40 45
a
R ¼ Me3Si.
b
Formed as a mixture, together with compound 2.
30 63 69 64 47 43 31 98 91 20 96 26 8 89 85 87 92 77
385
Functions Containing at Least One Metalloid (Si, Ge, or B) Me2 Si
Me3Si C
SiMe3 C
SiMe2
R2 C
R2
R2
Me2 Si
SiMe3 C
SiMe2
R1 C
R2
Me2 Si
SiMe3 C
SiMe2
R1 C
R2
R1
Me3Si 7
Me2 Si
R1 C
SiMe2
R1
R1 9
8
10
R1 = SiMe2Ph R2 = SiMePh2
Photolysis or thermolysis of diazomethane precursors gives rise to the silenes 11, which undergo intramolecular head-to-tail additions to give the cyclic species 12 in low yield as components of complicated product mixtures (Equation (2)) <1995JOM(499)99>. Reaction of PhSiCl3 with {Li[C(PMe2)(SiMe3)2]}2xTMEDA occurs to give the phospha-alkene 13, which on prolonged reaction times or on storage gives 14 via a complicated mechanism thought to involve loss of PMe2Cl, formation of a silene intermediate, and both Me and SiMe3 migrations (Equation (3)) <1995JOM(501)167>.
Me2Si PhMe2Si
Me2 Me 2 Si Si
SiMe2
(
Si Me2
)
PhMe2Si
SiMe2Ph
C SiMe2Ph
C
n
( SiMe )
11
2
ð2Þ
n
n = 1 or 2 12 Ph Me Si SiMe3 (Me3Si)2C Me2Si PMe2
Me3Si Ph Me3Si Si P C(SiMe3)2 Me2 P Cl Me2 13
ð3Þ
14
Addition of Me3SiN3 to the THF adduct of the silene (But2MeSi)(Me3Si)C¼SiMe2 leads not to a cycloaddition but the formation (But2MeSi)(Me3Si)2CSiMe2N3 in 15% yield together with diazo-containing products <1996CB471>. Addition of a lithium reagent to a silene can also occur, thus reaction of TsiLi(Tsi=(Me3Si)3C) with the silene (Me3Si)2C¼SiMe2, at 95 C followed by warming to room temperature and work-up in the air affords (Me3Si)2CHSiMe2Tsi <2000JOM(598)292>. (d) Thermolytic or photolytic methods. Interest in the thermolysis of low-molecular-weight silanes to give complicated cyclic compounds has waned in recent years but the thermolysis of (Cl3Si)2CCl2 in a fluidized bed of Si/Cu has been revisited and shown to afford (Cl3Si)4C and the cyclic compounds 15 and 16 <1994ZAAC(620)136>. Similarly, thermolysis of the trisilacyclohexane derivative 17 over Si/Cu gives compounds 18 and 19 (Equation (4)) <1994ZAAC(620)1253>. Cl2Si
SiCl2 Cl2 Si C C Si SiCl3 Cl3Si Cl2
Cl2 Si Cl3Si C C Cl3Si Si Cl2
16 n = 0, 1, or 2
15
Cl2Si
SiCl2 Si Cl2 17
330 °C Si/Cu
Cl2 Si SiCl3 C Si n SiCl3 Cl2
Cl2Si
SiCl2 C SiCl3 Si SiCl3 Cl2 18
Cl2 Si +
Cl2Si
Cl2 Si C C Si Si Cl2 Cl2 19
Cl2 Si SiCl2 Si Cl2
ð4Þ
386
Functions Containing at Least One Metalloid (Si, Ge, or B)
(e) Other methods. No recent examples of transition metal catalyzed syntheses or carbosilane rearrangements catalyzed by AlBr3 as methods for preparing tetrasilylmethanes seem to have been published. These methods are discussed in <1995COFGT(6)377>. The reaction between Me3GeSiCl3 and phosphaalkenes 20 led to an unusual P¼C bond cleavage and the formation of the cyclic species 21 (Equation (5)) <2002AG(E)3829>. Me3Si
P
Me3Si
PPriR1
Cl2 Si Me3Si C P PPriR1 Me3Si Si Cl2
Toluene 2 h, rt
20
ð5Þ
21
R1 = Pri or But
(ii) Four Ge functions The surprising absence of tetragermylmethane derivatives was noted in the reference <1995COFGT(6)377> and was attributed to a lack of synthetic effort in this area rather than to any inherent instability of such compounds. More recently, a need for the synthesis of tetragermylmethanes has been generated by the semiconductor and chemical vapor deposition community and this has led to the preparation of a small number of these compounds. The synthesis of (BrCl2Ge)4C and (Br3Ge)4C can be achieved in 80% and 95% yields, respectively, via the insertion of GeX2dioxane (where X = Cl or Br, respectively) into the CBr bonds of CBr4 <1998JA6738, 1995IC5103>. Reduction of these perhalo compounds with LiAlH4 gives (H3Ge)4C in 20% yield, which has been used as a precursor to various semiconductor materials via thermal decomposition .
(iii) Four B functions Compounds containing the CB4 grouping in which the CB bonds are simple two-center twoelectron bonds are rare, much more common are the polyhedral carboranes where multicenter bonding predominates. This chapter will not discuss carboranes, more information about them can be found in several reviews <2002CCR(232)173, 2002CCC869, 2000JOM(614)10, 1999CCC895>. One of the very few preparations of a tetraboramethane derivative is shown in Equation (6), in which a boriranylideneborane, 22, reacts with tetrahalodiboranes. If the substituents at boron are aryl rather than alkyl, then products containing the CB2Si2 grouping are formed (see Section 6.13.1.1.3) <2001EJI387>. But B
B
But
Hexane
+ B2X4 (Me3Si)2C
–85 °C
C 22
X But Me3Si B B X C C Me3Si B X B X But
ð6Þ
X = Cl, 92%; X = Br, 82%
Despite the lack of synthetic interest in simple compounds containing the CB4 grouping, there has been theoretical interest as the computational search for species containing planar four-coordinate carbon reveals that the ‘‘boraplane’’ 23 does have a D4h arrangement at the central carbon. An experimental confirmation of this planarity does not seem to have been carried out <2001JA994>.
B
B C
B
B
23
387
Functions Containing at Least One Metalloid (Si, Ge, or B) 6.13.1.1.2
Three similar and one different metalloid functions
(i) Three Si functions and one Ge function The ready availability of trisilyllithiomethane derivatives (see Section 6.13.1.2.(i).(a) below) would suggest that the easiest route to Si3GeC compounds is the reaction of a germyl halide with an Si3CLi derivative. The reaction of (Me3Si)3CLi with GeCl4 in THF gives the expected (Me3Si)3CGeCl3 <1997T12215>, and the reaction of 1 equiv. of (Me3Si)3CLi with GeBr4 in toluene solution affords (Me3Si)3CGeBr3 but use of a 2:1 ratio of reagents does not give rise to [(Me3Si)3C]2GeBr2 but rather to (Me3Si)3C(PhCH2)GeBr2 in 64% yield. This is thought to be due to a loss of Tsi from the initially formed [(Me3Si)3C]2GeBr2 followed by formation of PhCH2 from the solvent and radical recombination of PhCH2 and (Me3Si)3CGeBr2 <1999ZAAC(625)1807>. Reaction of (Me3Si)3CLi with GeCl2 dioxane in THF solution gives the germylene [(Me3Si)3C]ClGe:LiCl3THF in 41% yield, which undergoes ready reaction with alkenes or with phenyl acetylene to give Ge(IV) products 24 and 25 resulting from (2+1)-cycloadditions (Scheme 2). A novel bicyclic digermane, 26, is formed on reduction of 25a with Mg/MgBr2 (Scheme 2) <1996OM3103>. Reaction of (Me3Si)2(2-NC5H4Me2Si)CLi with GeCl2 dioxane gives the monomeric organogermanium(II) chloride 27 in 72% yield <2001OM1223>. As in the case of [(Me3Si)3C]ClGe:LiCl3THF, the usual dimerization expected for such species is prevented by the steric protection afforded by the three bulky silyl substituents, intramolecular coordination via the pyridyl nitrogen also prevents an increase in coordination number at the Ge atom. The first structurally characterized organometallic ate complex of Ge(II), 28, has been prepared in 40% yield from the reaction of (Me3Si)3CLi with Ge(SBun)2 <2002OM4005>.
Ph
Cl Cl Tsi Ge Ge Tsi
H
Ph
Tsi Ge:.LiCl.THF Cl
Tsi = (Me3Si)3C
R1 R2
H
24
Cl Cl Tsi Ge Ge Tsi
H R3
R1
R2
H
R3
Mg/MgBr2 Ethylene, 25a
Tsi Ge
Ge Tsi
26, 68%
25a, R1 = R2 = R3 = H b, R1 = R2 = H, R3 = Me c, R1 = R2 = H, R3 = Ph d, R1 = R2 = Me, R3 = H
Scheme 2
Me2Si Me3Si C Me3Si
BuS Me3Si SBu THF Me3Si C Ge Li S THF Me3Si S
N Ge Cl
27
28
(ii) Three Si functions and one B function Relatively few new syntheses of compounds containing the Si3BC grouping were reported in the 1990s; most of the recent chemistry of such compounds deriving from compounds prepared before COFGT (1995) was published. The most obvious route to Si3BC-containing compounds is to treat a boron trihalide with a trisilyllithium reagent. Thus, the reaction between (Me3Si)3CLi and BCl3 gives the expected monosubstituted product (Me3Si)3CBCl2. Substitutions at the BCl bonds may then be carried out to generate further compounds containing the Si3BC grouping <1997JOM(536)361>. A more complicated route has been found to be the addition of a silylene
388
Functions Containing at Least One Metalloid (Si, Ge, or B)
to an unsaturated species. Thus, addition of Me2Si: to MeB¼C(SiMe3)2 is thought to lead initially to a three-membered ring, which undergoes further reaction with a second equivalent of MeB¼C(SiMe3)2 to give ring expansion and the formation of 29 in 77% yield <1995OM1507>. Me2 Si C(SiMe3)2 (Me3Si)2C B B Me Me 29
(iii) Three Ge functions and one Si or B function; also three B functions and one Si or Ge function Considering the dearth of compounds containing the CGe4 function, it is, perhaps, not surprising that there are a few trigermylmethyl derivatives known. Only one compound, (Me3Ge)3CSiBut2F, containing the CGe3Si grouping seems to have been prepared. It can be made in 20% yield by reaction of (Me3Ge)2(FBut2Si)CLi2THF with Me3GeCl <1996JOM(511)239>. No doubt many other derivatives could be prepared in a similar way. No compounds with the CGe3B grouping seem to be known. Again, this lack of compounds is not likely to be due to a problem of inherent instability of such species but rather a lack of interest in their synthesis. Apart from the silyl- and germyl-substituted carboranes, there is a lack of CB3Si or CB3Ge functions, which is surprising when one considers that several compounds containing the CB4 function are known (see Section 6.13.1.1.1). However, the first triboracyclobutane 30 can be prepared according to Equation (7) from the triboracyclobutanide 31 in 50% yield <2003AG(E)669, 2003AG(E)671>. The synthesis of these mixed metalloid compounds could probably be easily achieved in a manner similar to those already known, i.e., via metathetical reactions between a metalloid-substituted methyllithium derivative and an element halide. SiMe3 Me3Si
Dur
C B B B Dur 31
6.13.1.1.3
CH2SiMe3 +
Li
Cl2BCH2SiMe3
–LiCl
C Dur
B
Me3SiCH2 B Cl Dur = duryl, 2,3,5,6-Me4C6H
B
Dur
B
ð7Þ
CH2SiMe3 30
Two similar and two different metalloid functions
(i) Two Si and two Ge functions When one considers that there are a large number of compounds containing the CSi4 function and a few CGe4 function known, it might be expected that there will only be a handful of compounds known that contain the CSi2Ge2 function. This is indeed the case. Such compounds have been prepared using methods that have been widely used for the synthesis of CSi4 functions and many more species could no doubt be prepared in similar ways. Little work has been done with these compounds since that reported in <1995COFGT(6)377>, but more examples of the elimination of LiX from XMe2GeCLi(SiMe3)2 compounds (where X = F, Br, OMe, or OPh) to give Me2Ge¼C(SiMe3)2, which dimerizes to give the head-to-tail dimer [Me2GeC(SiMe3)2]2, have been reported <2000JOM(598)292, 2000JOM(598)304>.
(ii) Two Si, one Ge, and one B functions Compounds containing the CSi2GeB function do not appear to be known. They are likely, however, to be readily available from the reaction of one of the several known CSi2GeLi containing compounds with a boron halide or B(OMe)3.
389
Functions Containing at Least One Metalloid (Si, Ge, or B) (iii) Two Si and two B functions
There are very few compounds known containing the CSi2B2 grouping but two such compounds have been prepared using addition reactions to unsaturated boranes. Thus reaction of methylideneborane 32 with the three-membered species 33 gives the five-membered species 34 in 81% yield (Equation (8)) <1995OM1507> and the borataalkyne 35 reacts with Me2SiHCl to give the bicyclo[1.1.1]pentane derivative 36 in 73% yield (Equation (9)) <1995AG(E)657>. But N Me B C(SiMe3)2
Bu
But N
t
B
+ But
32
B
B
But
Me
B
B
But
C SiMe 3 SiMe3
33
ð8Þ
34 Me mes – – B C B mes Me3Si 2 Li+ SiMe3
–2 LiCl + 2Me2SiHCl
–Me2SiH2
Me3Si
C
Me Si B B
C SiMe3 mes
ð9Þ
mes
35
36
The boriranylideneboranes 37 react with B2Cl4 to give the unsaturated species 38 (Equation (10)). If the substituent on boron is But rather than the aromatic group, then B4C-containing species are produced, see Section 6.13.1.1.1 <2001EJI387>. Ar
Ar
Ar B
B
Hexane +
(Me3Si)2C
C
B2Cl4
–85 °C
Cl
Me3Si Me3Si C B Cl2B
Cl Ar
ð10Þ
37 38, Ar = C6Me4H, 50% Ar = C6Me3H2, 33%
(iv) Two Ge and two B functions; two Ge, one Si, and one B functions; and two B, one Si, and one Ge functions As might be expected from the paucity of CSi2Ge2 and CSi2B2 containing species, there appear to have been no compounds prepared containing the CGe2B2, CGe2SiB, or CB2SiGe functions. Again, there is unlikely to be any good reason why such compounds should not be made. Reactions between appropriately substituted lithiomethanes and halometalloids should readily afford the required functions.
6.13.1.2 6.13.1.2.1
Methanes Bearing Three Metalloid Functions and a Metal Function Three similar metalloid functions
(i) Three Si functions (a) Three Si and one group 1 metal functions. There has been a surge of interest in the preparation and use of trisilyllithiomethane derivatives because of the previous widespread application of (Me3Si)3CLi and (PhMe2Si)3CLi as bulky alkyl group transfer reagents popularized by Eaborn and Smith <2001JCS(D)1541, 2001JCS(D)3397>. The chemistry and structures of compounds containing these bulky groups have been reviewed. Table 2 gives details of how many of the trisilyllithium lithium reagents available may be prepared. Several general points can be made. There are two main
Table 2 Trisilyllithiomethanes from the reactions of trisilylmethane derivatives and various metallating agents Trisilylmethane derivative R3CH R3CH R3CCl (HMe2Si)3CH (PriMe2Si)3CH (Ph2PCH2Me2Si)3CH (Ph2PMe2Si)3CH (Me2NMe2Si)3CH (o-MeC6H4Me2Si)3CH [(EtO)3Si]3CH R2(CyMe2Si)CH R2(PhMe2Si)CH R2(PhMe2Si)CH R2(PhMe2Si)CH R2(PhMe2Si)CH R2(Ph2MeSi)CH R2(2-C5H4NMe2Si)CH R2(MeOMe2Si)CCl R(MeOMe2Si)2CH R(MeOMe2Si)2CH R2(BrMe2Si)CBr R(FMe2Si)(But3Si)CBr R(TfOMe2Si)(But3Si)CBr R2(Ph2PMe2Si)CH R2(Ph2PCH2Me2Si)CH R2(Me2NMe2Si)CCl R2(Me2NMe2Si)CH R(Me2NMe2Si)2CH [(Me3Si)2CHSiMe2]2O [HCR2SiMe2CH2]2 [HCR2SiMe2CH2]2 a R = Me3Si. examples.
b
a
Metallating agent and conditions
Trisilyllithiomethane product
MeLi, THF/Et2O BunLi, hexane Li, toluene, 85–90 C LDA, THF MeLi, THF, 48 h reflux MeLi BuLi, hexane, TMEDA MeLi, THF BuLi, petroleum, TMEDA ButLi, THF, –65 C MeLi, THF MeLi, Et2O MeLi, THF/TMEDA MeLi, THF MeLi, petroleum/TMEDA MeLi, THF/Et2O, 4 h reflux, MeLi, THF BuLi, THF, 78 C MeLi LDA PhLi, low temp. 2 PhLi 2 BunLi MeLi MeLi BuLi, THF, –78 C MeLi, THF BuLi MeLi, THF MeLi, THF/TMEDA MeLi, THF
R3CLi R3CLi, base-free R3CLi, base-free (HMe2Si)3CLi (PriMe2Si)3CLi 41 [Li(TMEDA)2][(Ph2PMe2Si)3C] [(Me2NMe2Si)2CLi]1 [Li(TMEDA)2][(o-MeC6H4Me2Si)3CLi] [(EtO)3Si]3CLi R2(CyMe2Si)CLiTHF R2(PhMe2Si)CLiEt2O R2(PhMe2Si)CLiTMEDA R2(PhMe2Si)CLi2THF R2(PhMe2Si)CLiTMEDA R2(Ph2MeSi)CH 39 R2(MeOMe2Si)CLi2THF mixtureb R(MeOMe2Si)2CLi R2(BrMe2Si)CLic R(PhMe2Si)(But3Si)CLi R(BuMe2Si)(But3Si)CLi R2(Ph2PMe2Si)CLi2THF 42 40 40 R(Me2NMe2Si)2CLi 43 [Li(TMEDA)2]+ salt of 44 [Li(THF)4]+ salt of 44
Reaction occurs at both the methine CH and at SiOMe bonds.
c
Yield (%)
86 66 65 84 92 54 54
67 90
75 ca. 90 87 59 53 90 79 43
References <1999MI813> <1997JOM(536–537)361> <1997ZAAC(623)1455> <1999OM1804> <1995JOM(489)181> <2000JCS(D)2183> <1999JCS(D)831> <1996CC741> <1997OM6035> <1998JOM(562)79> <2001MI(162)225> <1997OM4728> <1997OM4728> <1997OM4728> <1997OM4728> <1995BSf517> <2000OM3224> <1998OM4322> <1999JCS(D)3267> <1999JCS(D)3267> <2000CJC1412> <1997JOM(531)47> <1997JOM(531)47> <2000JCS(D)2183> <2000JCS(D)2183> <1999OM45> <1999OM45> <1999JCS(D)3267> <1998CC1277> <1996OM1651> <1996OM1651>
This lithium species eliminates LiBr at room temperature to give the silene (Me3Si)2C¼SiMe2, see text for other related
391
Functions Containing at Least One Metalloid (Si, Ge, or B)
synthetic routes, metallation of an Si3CH substituted carbon, usually by MeLi or BuLi, and treatment of an Si3CX (X = Cl or Br) substituted carbon with lithium metal. The first method is more common as it is often easier to make the Si3CH grouping compared to the corresponding Si3CX and complications arising from the incorporation of LiX into reactions following the preparation of the trisilylmethyllithium reagent are avoided. The yields given in Table 2 are for lithium reagents isolated as solids and fully characterized. The yield of those species without an entry in the yield column can be determined indirectly from the yields of derivatives from subsequent reactions. There has been interest in recent years in the preparation of ‘‘base-free’’ trisilylmethyllithium reagents, i.e., not containing coordinated solvent such as THF or Et2O that can either react or be incorporated into products in further reactions. Such syntheses are carried out in alkane or aromatic solvents and the reagent formed usually contains no solvent, the lithium atoms being coordinated by alkyl or aryl groups within the trisilylmethyl substituent. Another extension to this area has been the preparation of reagents containing one or more potentially reactive or coordinating groups within the trisilylmethyl group. Thus, groups such as (RMe2Si)(Me3Si)2C, where R = OMe, NMe2, 2-pyridyl, or PPh2, can be transferred via their lithium derivatives to a range of transition metal centers where intramolecular coordination by the group R promotes monomer formation and discourages formation of oligomeric species. This synthetically useful range of reagents will no doubt be expanded in the future to include other more complicated ligating groups. A recent example, (Me3Si)2(HMe2Si)CLi(THF)2, containing a reactive SiH group can be prepared by treating (Me3Si)2(HMe2Si)CH with MeLi <2004JOM(689)1238>. The various methods for the preparation of TsiLi, the most popular of the trisilyllithium reagents, have been described in <1995COFGT(6)377>, but some new variations are included in Table 2. Sublimation of TsiLi2THF gives a small amount of TsiLi1.5THF while reaction of base-free TsiLi with O2 in toluene gives (Me3Si)2C¼O, which forms a 1:1 adduct with TsiLi to give TsiLiO¼C(SiMe3)2 <2000ZAAC(626)2040>. Solid-state 7Li NMR studies of base-free TsiLi and some of its adducts have also been carried out in order to investigate further the range of structures adopted by this useful reagent <2000JA9858>. The presence of coordinating groups in the trisilylmethyl substituent leads to species in which intramolecular coordination occurs to give monomeric species such as 39–41 (see Table 2 for details of the syntheses) in which some or all of the coordinating solvent is excluded. Despite the wide variety of structures that have found to be adopted by these species in the solid state, they all act as simple trisilylmethyl derivative transfer agents in solution. The use of these reagents in the synthesis of trisilylmetallamethane derivatives is detailed extensively in following sections. If two readily metallated carbons are present in a molecule, then a double metallation can occur as shown by compounds 42–44. Compound 43 is a molecular species containing an unusual interaction between the relatively low-basicity siloxane oxygen and a lithium, and the [Li(TMEDA)2]+ salt of anion 44 can be used to make a range of divalent organometallic complexes as detailed in the following sections.
N Me2Si Me3Si C Li THF Me3Si 39 Me2 Li(THF)2 Si Me3Si C PPh2 Me3Si Li THF
Me2Si
40
Me2Si (THF)2Li O Me2Si
Ph2 P Ph2 Li P C
Ph2 P
Me2Si NMe2 Me3Si C Li(THF)2 Me3Si
41
SiMe3 C SiMe3 Li C SiMe 3
Me2Si (Me3Si)2C
SiMe2
SiMe2 SiMe2 C(SiMe3)2
Li
SiMe3 42
43
44
Although few examples of polycyclic trisilyllithiomethanes have been reported recently (compared to the many described in <1995COFGT(6)377>), the bicyclic species 3 can be monometallated, then derivatized and then metallated at the second methine center and further derivatized as shown in Scheme 1 above. A further series of trisilyllithiomethanes that have received detailed study are of the general form (XR2Si)CLi(SiMe3)2 where R is an alkyl or aryl group and X is an electronegative function such as halide or alkoxide. As might be expected, these compounds need to be prepared at low temperature as they readily eliminate LiX (at different temperatures depending on the nature of X) to give silenes R2Si¼C(SiMe3)2. For example,
392
Functions Containing at Least One Metalloid (Si, Ge, or B)
reaction between (XPh2Si)(Me3Si)2CBr (X = F or Br) with BuLi or PhLi at 78 C in Et2O gives (XPh2Si)(Me3Si)2CLi, which then generate Ph2Si¼C(SiMe3)2 <1995CB1231, 1995CB1241> and (XMe2Si)(Me3Si)2CBr (X = alkoxide or halide) react with BuLi or PhLi at low temperature to give (XMe2Si)(Me3Si)2Cli, which can then be used to generate Me2Si¼C(SiMe3)2 <2000CJC1412, 2000JOM(598)292, 2000JOM(598)304>. Trisilyllithiomethane derivatives sometimes result unexpectedly from complicated reactions and rearrangements, the relative stability of trisilylmethyl anions perhaps being a driving force for this. For example, (Me3Si)2(HMe2Si)CLi is found to be an intermediate in the reaction between MeLi and Me3SiSiMe3 <2000OM374>, and the disilylmethane derivative (MeOMe2Si)2CH2 reacts with ButLi in pentane at 78 C to give (MeOMe2Si)2CHLi, which undergoes a remarkable skeletal rearrangement to give the previously prepared dimer 45 (intra- and intermolecular coordination of Li in [{LiC(SiMe2OMe)3}2]; methyl groups have been omitted for clarity) in 64% yield <2003OM2505>. O
Si
O
Si
Li
O Si
C Si Si
O O
C Li
Si O
45
The popular synthetic use of trisilylmethyllithium derivatives, particularly in transition metal chemistry, has prompted the synthesis of similar species incorporating heavier group 1 metals. Clearly, such compounds are likely to be more difficult to prepare being intolerant of ether solvents, and will be more difficult to handle because of their sensitivity toward water and oxygen. Despite these problems there are now well-characterized sodium, potassium, rubidium, and caesium derivatives of trisilylmethanes, some of which have been shown to be synthetically useful. Sodium derivatives can be prepared in a similar way to some of their lithium analogs, for example, (PhMe2Si)(Me3Si)2CH reacts with MeNa in petroleum containing TMEDA to give (PhMe2Si)(Me3Si)2CNaTMEDA in 34% yield <1997OM4728>. Alkali metal exchange may also be a useful synthetic route in preparing sodium compounds; thus, reaction of (Ph2PMe2Si)(Me3Si)2CLi2THF reacts with ButONa to give (Ph2PMe2Si)(Me3Si)2CNa in which the sodium is coordinated to both the carbanionic center and to a phenyl group <2000JCS(D)2183>. In the search for stable silenes, even more bulky trisilylmethane derivatives have been prepared, e.g., treatment of (FMe2Si)(But3Si)(Me3Si)CBr with But3SiNa affords (FMe2Si)(But3Si)(Me3Si)CNa, which can then potentially eliminate NaF <1997JOM(531)47>. Trisilylmethylpotassium derivatives can be prepared in a similar manner to the analogous lithium compounds. Thus, reaction of TsiH with MeK in Et2O in the presence of TMEDA gives TsiKTMEDA in 34% yield, (Me3Si)2(PhMe2Si)CH reacts with MeK in Et2O at 20 C to give (Me3Si)2(PhMe2Si)CK in 60% yield <1997OM4728>, and (MeOMe2Si)2(Me3Si)CH reacts with MeK to give (MeOMe2Si)2(Me3Si)CK cleanly <1999JCS(D)3267>. If (Me3Si)2(PhMe2Si)CK is crystallized from benzene, orange crystals of the potassate [K(C6H6)][K{C(SiMe3)2(SiPhMe2)}2] may be isolated <1995AG(E)2679>. The reactivity of the potassium compounds can be shown from the reaction of the vinyl derivative, (Me3Si)2(CH2¼CHMe2Si)CK (prepared from (Me3Si)2(CH2¼CHMe2Si)CH and MeK) with adventitious silicone grease in its container over a period of 4 weeks to give [K(SiMe2O)7][K{C(SiMe3)2(SiMe2CH2¼CH)}2] <1995AG(E)2679>. Alkali-metal exchange may also be useful as a synthetic route, species 39 reacts with ButOK to give the potassium analog (2-C5H4NMe2Si)(Me3Si)2CK which contains no solvent, the potassium being coordinated as shown in 46 in a polymeric structure <2000OM3224>.
Me2Si C
N Me2Si
N
K
K
C
Me3Si SiMe3 Me3Si SiMe3 46
Functions Containing at Least One Metalloid (Si, Ge, or B)
393
The [Li(THF)4]+ salt of 44 can also be used in the preparation of the dipotassium species 47, or a benzene solvate of the same species, 48 can be prepared directly from 49 as shown in Scheme 3 <1999OM2342>. The dicaesium compound 50 can be prepared in a similar manner <2000OM1190>.
[Li(THF)4] 44
MeLi, THF
ButOK, THF
CH2Me2Si(Me3Si)2CK(THF)2 CH2Me2Si(Me3Si)2CK(THF)2
CH2Me2Si(Me3Si)2CH CH2Me2Si(Me3Si)2CH 49 MeK, C6H6
i. MeCs, Et2O ii. Cryst. from C6H6
CH2Me2Si(Me3Si)2CK(C6H6) CH2Me2Si(Me3Si)2CK(C6H6)
47
CH2Me2Si(Me3Si)2CCs(C6H6) CH2Me2Si(Me3Si)2CCs(C6H6) 50
48
Scheme 3
Rare examples of structurally characterized alkylrubidium and caesium derivatives can be made using the reaction between MeM (M = Rb or Cs), prepared in situ from MeLi and the corresponding alkali-metal-2-ethylhexoxide, and TsiH. Thus, TsiRb is prepared in 64% yield and comprises an infinite chain of alternating planar Tsi anions and Rb+ cations, and TsiCs crystallizes from benzene to give TsiCs3.5C6H6 in which the Cs is coordinated to both the carbanion center and three benzene molecules <1995AG(E)687>. Similar reactions but using (PhMe2Si)3CH as starting material give (PhMe2Si)3CRb and (PhMe2Si)3CCs in yields of 74 and 66%, respectively <1997OM4728>. The structure of the rubidium species shows that the rubidium is coordinated by the aromatic groups of the trisilylmethyl substituent. The uses of these Na, K, Rb, and Cs derivatives of trisilylmethanes are largely unexplored but the widespread use of the Li analogs suggests that they may well have significant potential, particularly in organometallic chemistry. (b) Three Si and one group 2 metal functions. The reaction of (Me2NMe2Si)3CI with Mg in Et2O gives (Me2NMe2Si)3CMgI in 54% yield. Although it has the general Grignard reagent formula of RMgX, a structural study has shown that the central carbanionic carbon has a planar environment and that there is in fact no significant CMg interaction, the coordination sphere of the Mg comprising three nitrogen and one iodide ligand <1997OM503>. The reaction of (MeOMe2Si)(Me3Si)2CI with Mg in Et2O is thought to give the Grignard reagent (MeOMe2Si)(Me3Si)2CMgI, which decomposes to give the dialkylmagnesium species Mg{C(SiMe3)2(SiMe2OMe)}2 in 50% yield together with MgI2(OEt2)2. The Grignard compound can however be isolated in 80% yield from the reaction between (MeOMe2Si)(Me3Si)2CI and Mg in toluene solution <1996JOM(521)113>. A variety of other more complicated organomagnesium complexes containing solvent are also available from similar preparative routes. Thus, reaction of reagent 39 (see Section 6.13.1.2.1 above) with MgBr2 gives 51 <2000OM3224> but with [MgBr2(OEt2)2] the Li is retained to give complex 52 <2001JOM(631)76>. The ate complex, [Li(TMEDA)2][Li{C(SiMe3)2(SiMe2Ph)}2], reacts with MgBr2 in THF solution to give 53 in poor yield <2001JOM(631)76>. Grignard reagents 54 are formed when R3CI species (R = Me3Si or PhMe2Si) react with activated magnesium and an unusual, unsymmetrical dialkylmagnesium compound, 55, is obtained in 95% yield from the reaction between [MgBr2(OEt2)2] and the lithium reagent formed from BuLi and (Me2NMe2Si)(Me3Si)2CI in Et2O with <2001JOM(631)76>.
N Me2Si Me3Si C Mg THF Me3Si Br 51
Me2 THF Br N N Me2Si Mg Li (PhMe2Si)(Me3Si)2C Me3Si C Mg Br Br N Me3Si Me2 Br Li(THF)3 53 52 NMe2
Me2Si
R3C I OEt2 Mg Mg Et2O CR3 I
Me3Si C Mg OEt 2 Me3Si Bu
54, R = Me3Si or PhMe2Si
55
394
Functions Containing at Least One Metalloid (Si, Ge, or B)
The steric protection afforded by the Tsi group is seen clearly in the isolation of Tsi2Ca, the first solvent-free dialkylcalcium compound to be structurally characterized and which is obtained from the reaction between 2 equiv. of TsiK and 1 equiv. of CaI2 in 87% yield <1997CC1961>. Use of a bulky trisilyllithium reagent containing a group capable of intramolecular coordination allows the preparation of simple, monomeric dialkyl derivatives of strontium and barium. Thus, reaction of 2 equiv. of (MeOMe2Si)(Me3Si)2CK with MI2 (M = Sr or Ba) in THF affords [(MeOMe2Si)(Me3Si)2C]2M(THF)n, which when crystallized from methylcyclohexane, for M = Sr, gives [(MeOMe2Si)(Me3Si)2C]2Sr(THF) in 72% yield, and when crystallized from (Me2SiO)3/DME, for M = Ba, gives [(MeOMe2Si)(Me3Si)2C]2Ba(DME) in 68% yield <2003JA7534>. (c) Three Si and one group 12 metal functions. Reaction between TsiLi and ZnCl2 affords TsiZnCl in 26% yield as an isolated product after sublimation of the initially formed [Li(THF)4] [(TsiZn)2Cl3] <1998EJI1175, 1999JOM(572)249>. This is presumably also an intermediate in the sequential treatment of ZnCl2 with TsiLi followed by LiP(SiMe3)2 to give TsiZnP(SiMe3)2 in 60% yield <1995ZAAC(621)287>. Reaction of the trisilyllithiomethane derivative 39 containing a potentially chelating group with ZnBr2 or CdCl2 gives the halide-bridged dimers 56 and 57 in 67% and 69% yields respectively <2002JCS(D)2467> and reaction of reagent 40 with ZnBr2 affords an analogous cyclic dimer <2004JOM(689)1718>. The monomeric species 58 M = Zn is formed in 60% yield from the reaction of the [Li(TMEDA)2] salt of the diorganolithiate ion 44 with ZnCl2 <1999OM2342>. A series of crowded diorganomercury compounds have been prepared by metathesis reactions. Thus, TsiHgR compounds can be prepared by reaction of TsiHgBr with RMgX (R = Me, Pri, Bun, But, or Ph) and (PhMe2Si)3CHgR compounds from (PhMe2Si)3CHgCl and RLi (R = Me, Pri, Bun, But, or Ph). Treatment of (PhMe2Si)3CHgCl with TsiLi gives the extremely bulky (PhMe2Si)3CHgTsi in 21% yield. The symmetrical dialkylmercury derivative [(Me3Si)2(HMe2Si)C]2Hg is obtained in 16% yield from the reaction between HgCl2 and (Me3Si)2(HMe2Si)CLi at 110 C <1996JOM(510)143>. Other congested organomercury compounds containing potentially chelating groups can also be prepared by simple metathesis reactions. Thus, reaction between (MeOMe2Si)2Me3SiCK and HgBr2 gives (MeOMe2Si)2Me3SiCHgBr in 31% yield <1999JCS(D)3267>, reaction of 40 with HgBr2 gives [(Me2NMe2Si)(Me3Si)2C]2Hg in 51% yield <1999OM45>, reaction of 39 with HgCl2 gives 59 in 62% yield <2002JCS(D)2467>, and reaction of the [Li(TMEDA)2] salt of the diorganolithiate ion 44 with HgBr2 gives a 91% yield of 60 <1996OM1651>.
N Me2Si Me3Si C M X SiMe3 Me3Si X M C SiMe3 N SiMe2
SiMe2 C(SiMe3)2
Me2Si (Me3Si)2C M
58, M = Zn 60, M = Hg
N Me2Si Me3Si C Hg Cl Me3Si 59
56, M = Zn, X = Br 57, M = Cd, X = Cl
(d) Three Si and one group 13 metal functions. There has been increasing interest in compounds containing a Si3MC grouping (where M = Al, Ga, In, or Tl) and several such compounds have been found to be useful precursors to a wide range of novel organometallic compounds. The synthesis of these compounds relies largely on metathesis reactions between a bulky trisilyllithium reagent [for their synthesis see Section 6.13.1.2.1.(i).(a)] and a metal halide. One potential problem with this synthetic method is that coordinating solvents, such as THF or Et2O that are convenient to use in the synthesis of the organolithium reagent, may be cleaved by strong Lewis acidic group 13 compounds. For example, the reaction of TsiLi with BX3 (X = F, Cl, or Br) in Et2O affords TsiOEt and not TsiBX2 species <1995OM3098>. This problem can be avoided by the use of base-free trisilyllithium reagents [for their synthesis see Section 6.13.1.2.1.(i).(a)]. The reactions between bulky trisilyllithium reagents and aluminum halides give the products expected from metathesis reactions. For example, TsiAlMe2THF is formed in 85% yield from the reaction between TsiLi2THF and Me2AlCl in THF <1997CEJ1783> and the solventfree TsiAlMe2 is formed in 68% yield when base-free TsiLi in toluene is used <1997ZAAC(623)1455>. Similarly, reaction of (CyMe2Si)(Me3Si)2CLiTHF (Cy = cyclohexyl) with Me2AlCl gives (CyMe2Si)(Me3Si)2CAlMe2THF in 88% yield and which has been used to
Functions Containing at Least One Metalloid (Si, Ge, or B)
395
prepare a range of other (CyMe2Si)(Me3Si)2CAlX2 derivatives <2001MI(162)225>. The dimethyl derivative TsiAlMe2THF is also a useful precursor to other crowded alanes. For example, the reaction with Me3SnX (X = F or Cl) gives TsiAlX2THF, and with Br2 or I2 gives TsiAlBr2THF and TsiAlI2THF, respectively <1998OM2249>. Reduction of TsiAlI2THF by NaK alloy gives the tetrahedrane [TsiAl]4, analogous to the tetrahedranes of Ga, In, and Tl described below <1998AG(E)1952>. Base-free TsiLi reacts with AlCl3 at 78 C in a 1:1 ratio to give Li[TsiAlCl3] in 83% yield <1997ZAAC(623)1455> but if 2 equiv. of TsiLi are used then a methylation occurs to give TsiAlMeCl <2001ZAAC(627)715>. If a coordinating group is present in the trisilyllithium reagent or the aluminum halide, then solvent may be excluded from the coordination sphere of the aluminum in the product. For example, reaction of 40 with AlCl3 generates 61 in 91% yield <1999OM45>, reaction of (Me2NMe2Si)3CLi with AlCl3 in toluene containing THF gives 62 as a colorless solid in almost quantitative yield <1998OM3135>, and the product, 63, in Equation (11) is formed in 50% yield in THF solution <1995CB493>. However, the weaker basic OMe site in 64, derived from the reaction of (Me3Si)2(MeOMe2Si)CLi2THF with AlCl3 in 62% yield, does not prevent THF from coordinating to the Al <1998OM4322>. Me2Si NMe2 Me3Si C Al Cl Me3Si Cl
Me2 Me2NMe2Si Si NMe2 C Me2NMe2Si Al Cl2
61
(Me3Si)3CLi
62
+
NMe2
Cl Me3Si Me3Si C Al Cl MeOMe2Si THF 64
THF, –78 °C
NMe2 Al
Al Cl2
Cl
C(SiMe3)3
ð11Þ
63
Bulky trisilyllithium reagents have also been used to prepare sterically hindered aluminum hydrides, which are often monomeric in contrast to species containing less sterically demanding substituents. For example, the treatment of TsiLi with H3AlNMe3 readily affords TsiAlH2THF in 86% yield <2001OM2047>. Several trisilyllithium reagents, (RMe2Si)(Me3Si)2CLi (where R = Me, Ph, or NMe2), react with LiAlH4 in THF to give cyclic dimers 65 <1994OM4143, 2000JOM(597)3>. These structures all incorporate THF, excluding, in the case where R = NMe2, coordination of aluminum by the nitrogen. Treatment of the dimers where R = Me or Ph with Me3SiCl gives the simple hydrides (RMe2Si)(Me3Si)2CAlH2THF in 40% and 50% yields, respectively <2000JOM(597)3>. Reaction of 65, where R = Me, with 4 equiv. of 2,6-Pri2C6H3OH gives the diaryloxo species 66 in 75% yield and with Ph3SiOH the monomeric 67 is formed in 98% yield <2002JCS(D)3971>. The trisilyllithium reagent (MeOMe2Si)(Me3Si)2CLi2THF reacts with LiAlH4 in THF to give 68 in which the weakly basic SiOMe group does coordinate to the Li to exclude coordination by a second THF molecule <1998OM4322>. (The structure of 68 was later found to be dimeric <2000JOM(597)3>.) The reaction of (MeOMe2Si)2(Me3Si)CLi with LiAlH4 gives [Li(THF)4][(MeOMe2Si)2(Me3Si)CAlH3] <1999JCS(D)3267>.
H (RMe2Si)(Me3Si)2C Al H H
(THF)2 Li H H Al H C(SiMe3)2(SiMe2R) Li (THF)2 R = Me, 64% 65 R = Ph, 56% R = NMe2, 95%
OSiPh3 (Me3Si)3C Al OSiPh3 THF 67
R
R THF Li O O Al H Tsi R R R = Pri 66 Me3Si Me3Si
C
Al H2 Me2Si 68
H O Li Me THF
396
Functions Containing at Least One Metalloid (Si, Ge, or B)
Some remarkable polymetallic compounds have been isolated from the reaction between TsiLi and the gallium(I) halide GaBr. Thus, the reaction in toluene/THF at 78 C affords the lithium salt of the anion [Ga19Tsi6] in 30% yield <2000JA9178> and a small amount of the fused tetrahedrane derivative 69 <2001AG(E)1241>. The [Ga19Tsi6] anion contains a central Ga13 metal core surrounded by six Tsi–Ga substituents. Use of the simpler, related tetrahedrane [TsiGa]4, as a source of the monomer TsiGa for the preparation of a wide variety of organometallic compounds containing TsiGa as a ligand has been demonstrated (see, e.g., <2001IC750, 2000JCS(D)3133>). C(SiMe3)3 C(SiMe3)3 Ga Ga Ga Ga Ga C(SiMe3)3 (Me3Si)3C Ga Ga Ga C(SiMe3)3 C(SiMe3)3
(Me3Si)3C
Br
Li(THF)3
In (Me3Si)3C In Br In C(SiMe3)3 Br
69
71
The reaction of base-free TsiLi and GaX3 (X = Cl or I) at 78 C in a 1:1 ratio gives Li[TsiGaX3], but if 2 equiv. of TsiLi are used then a methylation occurs to give TsiGaMeCl <2001ZAAC(627)715>. Reaction of GaCl3 with (EtMe2Si)3CLi gives [Li(THF)4][(EtMe2Si)3CGaCl3] in 49% yield. Both this species and the (Me3Si)3C analog can be reduced by magnesium to give the corresponding tetragallium tetrahedranes <1998JOM(555)263>. The THF adduct, TsiGaMe2THF, can be isolated in 90% yield from the reaction between TsiLi2THF and Me2GaCl in THF. When the adduct is sublimed the THF is lost to give the solvent-free TsiGaMe2 <1997CEJ1783>, which can also be prepared in 58% yield from the reaction between base-free TsiLi and Me2GaCl <1997ZAAC(623)1455>. If a coordinating group is present in the trisilyllithium substituent, then solvent is excluded from the product; thus, reaction of 40 with GaCl3 generates the gallium analog of 61 in 58% yield <1999OM45>. The reactions between InBr and trisilyllithium reagents as shown in Equation (12) afford oligomers of (RR1MeSi)3CIn, 70 <1995JOM(493)C1, 1998OM5009>. For RR1 = Me2, EtMe, and BunMe the compounds are tetrameric in benzene solution, while for the larger cases of RR1 = MePri and MePh the compounds are monomers in solution. For RR1 = Et2 there is a monomer–dimer equilibrium in solution. In the solid state when RR1 = Me2, EtMe, Et2, or MePri, the compounds are tetrameric, having a near perfect tetrahedral arrangement of indium atoms, similar to the tetrahedral gallium species described previously <1995COFGT(6)377>. In the reaction of TsiLi with InBr an unusual species 71 is also formed in 24% yield, which contains a chain of three indium atoms <2002ZAAC(628)1963>. The tetrahedrane [TsiIn]4 has been used as a convenient source of the monomer TsiIn for the preparation of a variety of organometallic compounds containing TsiIn (see, e.g., <2003OM2705, 2001CEJ4216, 2001IC750, 2000ZAAC(626)2043>). InBr + (RR1MeSi)3C-Li
Toluene, –40 °C
[(RR1MeSi)3CIn]n
70 R = Me, R1 = Me, 69%; R = Me, R1 = Et, 47% R = Me, R1 = Bun, 57%; R = Me, R1 = Pri, 64% R = Me, R1 = Ph, 66%; R = Et, R1 = Et, 56%
ð12Þ
The reaction of In(III) compounds with bulky lithium reagents has also continued to be of interest. Thus, the reaction of InBr3 with TsiLi in THF/Et2O gives a 60% yield of [Li(THF)4][TsiInBr3] <1998ZAAC(624)4> and the reaction of TsiLi with Me2InCl in Et2O gives TsiInMe2 in 65% yield <1997ZAAC(623)1455>. The reaction of base-free TsiLi and InX3 (X = Cl, Br, or I) at 78 C in a 1:1 ratio gives Li[TsiInX3] but if 2 equiv. of TsiLi are used then a methylation occurs to give TsiInMeCl, and if 3 equiv. of TsiLi are used then two methylations occur to give TsiInMe2 together with the 1,3-disilacyclobutane [Me2SiC(SiMe3)2]2 <2001ZAAC(627)715>. If moisture is present in the reaction between TsiLi and Prn2InBr, an unusual hydroxide-bridged trimer, 72, is formed in 28% yield, presumably via hydrolysis of the initially formed TsiInPr2n <1999ZAAC(625)547>. Some of the chemistry described above for gallium and indium can be extended to thallium. The reaction of TsiLi with the thallium(I) organometallic TlCp in a 1:1 ratio gives the deep red-violet TsiTl, which is tetrameric in the solid state having a slightly distorted tetrahedron of thallium atoms similar to that described above for the gallium and indium analogs <1997AG(E)64>.
Functions Containing at Least One Metalloid (Si, Ge, or B) (Me3Si)3C HO (Me3Si)3C In
397
OH In
H Prn O
C(SiMe3)3 In Prn
Prn 72
(e) Three Si and one group 14 metal functions. Compounds containing the Si3MC grouping where M = Sn or Pb are usually made by simple metathesis reactions between trisilyllithium reagents and metal halides. For example, reaction between SnX4 and TsiLi in Et2O at 78 C affords the expected TsiSnX3 compounds in excellent yields, 91% for X = Cl <2002AG(E)1365> and 89% for X = Br <1999EJI869>. However, reaction between (Me3Si)3CLi and SnX4 (where X = Cl, Br, or I) in a 2:1 ratio in toluene solution gives (Me3Si)3C(PhCH2)SnX2 in 58%, 72%, and 76% yields respectively for X = Cl, Br, or I, apparently via a radical mechanism similar to that found in the germanium analog described in Section 6.13.1.1.2 <1999ZAAC(625)1807>. The related bulky reagent, (PhMe2Si)3CLi, reacts with SnCl4 in THF to give only a 25% yield of (PhMe2Si)3CSnCl3 along with (PhMe2Si)3CCl as the main product but it reacts more cleanly with Me2SnCl2 to give (PhMe2Si)3CSnMe2Cl, which reacts readily with EtOH to give the final product (PhMe2Si)3CSnMe2OEt in 76% yield <1998JOM(564)215>. Related reagents that contain substituents capable of intramolecular coordination to the tin atom also undergo similar metathesis reactions. Thus reaction of 40 with SnCl4 gives (Me2NMe2Si)(Me3Si)2CSnCl3, which probably has intramolecular SnN coordination, in 78% yield <1999OM45>, and treatment of (Me2NMe2Si)2(Me3Si)CLi with Me3SnCl gives (Me2NMe2Si)2(Me3Si)CSnMe3 (along with the precursor (Me2NMe2Si)2(Me3Si)CH) <1999JCS(D)3267>. Derivatization using Bu3SnCl of the organometallic reagent formed by metallation of 3 affords a derivative of 5 in which a Bu3Sn group has replaced the SiMe2R group <1998CL1145>. It is likely that a second metallation and further reaction with a tin halide would give a further range of compounds containing two Si3SnC substituted centers. Introduction of two tin atoms occurs in the reaction of the [Li(TMEDA)2] salt of 44 with Me2SnCl2 or the [Li(THF)4] salt of 44 with SnCl4 to afford [ClR2SnC(SiMe3)2SiMe2CH2]2 in 79% and 47% yields, respectively for R = Me and Cl <1999OM2342>. The Si3SnC grouping has also been prepared by using the reaction between a disilylstannyllithium reagent and a silyl chloride. Thus, (Me3Si)2(PhMe2Sn)CLi reacts with Me2SiCl2 to furnish (Me3Si)2(PhMe2Sn)CSiMe2Cl in 76% yield <1998JOM(564)215>. Reactions of (Me3Si)2(PhMe2Sn)CLi (for its synthesis, see Section 6.13.1.3.1) with a range of other metal halides would, no doubt, allow convenient preparation of many new Si2SnMC groupings. The high degree of steric protection afforded by an (R3Si)3C substituent at a group 14 metal center has prompted investigation into the stabilization of M(II) species where M = Sn or Pb by such substituents. Reaction of (Me3Si)2(2-NC5H4Me2Si)CLi with SnCl2 or PbCl2 gives monomeric organotin- and organolead(II) chlorides in 74% and 47% yields, respectively, which have structures analogous to that of the related germanium compound 27 <2001OM1223>. The bis-methoxy species (MeOMe2Si)2Me3SiCLi reacts with SnCl2 to give (MeOMe2Si)2Me3SiCSnCl in 65% yield <1999JCS(D)3267>. The first structurally characterized organometallic ate complex of Sn(II), has a structure similar to that of the germanium analog, 28, and has been prepared in 60% yield from the reaction of (Me3Si)3CLi with Sn(SBun)2 <2002OM4005>. Treatment of the K(THF)2 salt of [CH2(SiMe2)(Me3Si)2C]2 2 (see Section 6.13.1.2.1(a)) with SnCl2 in Et2O at 78 C gives a mixture of dialkyl Sn(II) compounds 73 (M = Sn) and 74, both of which readily undergo oxidative addition reactions to give Sn(IV) compounds <1997OM5621, 2000OM49, 2002OM2183, 2002OM2430>. Chlorobridged dimers 75 are formed from the reaction of (PhMe2Si)3CLi and MCl2 in THF <1995CC1829, 1997OM5653>. The lead species is a yellow-orange solid and is the first monoorganolead(II) derivative to be characterized. In contrast, if the smaller reagent TsiLi reacts with PbCl2 in THF then a chloro-bridged trimer 76 is produced in 85% yield <1997OM5653>. When the organolithium reagent (MeOMe2Si)(Me3Si)2CLi reacts with MCl2, where M = Sn or Pb, intramolecular coordination of the OMe group to the metal occurs to give the four-coordinate M(II) species 77 <1997OM5653>. Treatment of the [Li(TMEDA)2] salt of 44 with PbCl2 gives the Pb(II) organometallic species 73 (M = Pb) as dark blue crystals in 85% yield <1997OM5621>.
398
Functions Containing at Least One Metalloid (Si, Ge, or B) Me2Si (Me3Si)2C
SiMe2 C(SiMe3)2
CH2Me2Si(Me3Si)2CSnCl CH2Me2Si(Me3Si)2CSnCl
M
M (PhMe2Si)3C
74
73, M = Sn or Pb
(Me3Si)3C
Pb Cl
76
Cl
Pb Cl
C(SiMe3)3
Pb C(SiMe3)3
Cl C(SiMe2Ph)3 M Cl
75, M = Sn or Pb SiMe3 Me Me3Si Cl O C SiMe2 M M Me2Si Cl C O SiMe3 Me Me3Si 77, M = Sn, 93%; M = Pb, 60%
(f) Three Si and one transition metal functions. The reaction of lithium reagent 39 with CrCl2 gives a 40% yield of 78 having a square-planar geometry at Cr, together with a small amount of 79 <2000OM3224>. Reaction of TsiLi2THF with CrCl2 is reported to give Tsi2Cr, but no details have been given <2002USP00334829>.
N Me2Si SiMe3 Me3Si C Cr C SiMe3 Me3Si SiMe2 N
N Me2Si Me3Si C Cr Cl SiMe3 Me3Si Cl Cr C SiMe3 N SiMe2
78
79
Reaction of the lithium reagent 39 with MnCl2 gives the manganese complex 80 in 41% yield <2000OM3224>. Similarly, the lithium reagent 40 reacts with 1 equiv. of MnCl2 to give a 95% yield of 81 X = Cl, and with 0.5 equiv. of MnCl2 to give [(Me2NMe2Si)(Me3Si)2C]2Mn in 72% yield together with a small amount of the Mn(III) complex 81 X = O (presumably formed via oxidation by adventitious air) <2002JOM(649)121>. Reaction of the related reagent containing a chelating methoxy group (see Table 2) with MnCl2 gives 82 in 63% yield <2002JOM(649)121> while the use of the chelated dialkyllithium reagent 44 affords the chloride-bridged, high-spin manganese complex 83 in 60% yield <2000OM1190>.
N Me2Si Me3Si C Mn Cl Me3Si Cl
Li(THF)3
80 THF Me (Me3Si)2 C Cl O Me2Si Mn Mn SiMe2 O Cl C (SiMe3)2 Me THF 82
Me2Si NMe2 Me3Si C Mn X SiMe3 Me3Si X Mn C SiMe3 Me2N SiMe2 81, X = Cl, X = O Me2Si (Me3Si)2C
SiMe2 C(SiMe3)2 Mn Cl Li(THF)3 83
Reaction of base-free TsiLi with FeCl3 leads to reduction and formation of the Fe(II) compound Tsi2Fe in 68% yield <2001ZAAC(627)715>. If coordinated THF is present in the lithium reagent, TsiLi2THF, then reaction with FeCl2 at 35 C in THF solution also occurs to give red blocks of Tsi2Fe in 44% yield <2003ICA(345)359, 2002USP00334829>.
399
Functions Containing at Least One Metalloid (Si, Ge, or B)
Reaction of the lithium reagent 39 with CoBr2 gives the halide-bridged ate complex 84 in 56% yield <2000OM3224>. Similarly, lithium reagent 40 containing a dimethylamino substituent capable of acting as a ligand, reacts with CoBr2 to give 85 in 50% yield <2002JOM(649)121>. The simple diorganocobalt compound Tsi2Co has been reported to be formed as dark-green, plate-like crystals from the reaction between CoCl2 and TsiLi2THF but no spectroscopic details are available <2002USP00334829>.
N Me2Si Me3Si C Co Br Me3Si Br Li(THF)2
Me2Si NMe2 Me3Si C Co Br SiMe3 Me3Si Br Co C SiMe3 Me2N SiMe2
84
85
The first -bonded organonickel(I) compound 86 is obtained in 30% yield from the reaction shown in Scheme 4. Trace amounts of hydroxide present in the starting material are thought to be responsible for the formation of complex 87 as a minor by-product. In contrast, reaction of [PdCl2(PPh3)2] gave the chloro-bridged dimer 88 as a pale yellow solid in 53% yield <2000CC691>.
2 [PdCl2(PPh3)2]
N Me2Si Me3Si C Li THF Me3Si
[NiCl2(PPh3)2] THF, –78 °C trace H2O
THF, –78 °C
N
Me3Si
SiMe3 C
SiMe2 Cl Pd Pd Cl C N SiMe3 Me3Si
Me2Si
N Me2Si Me3Si C Ni PPh3 Me3Si 86
88
Me2 SiMe 3 Si C N O SiMe2 Ni Ni O N Me2Si C Si Me3Si Me2 87
Scheme 4
Reaction of 39 with CuI or AuClSMe2 gives dimeric products 89 M = Cu or Au in 62% and 37% yields, respectively <2002JCS(D)2467>. Me2 (Me3Si)2C Si M N M N Si C(SiMe3)2 Me2
89, M = Cu or Au
The reactions between group I metal derivatives of trisilylmethanes and CuCN can give a variety of products. Thus, treatment of CuCN with (PhMe2Si)3CM (M = Li or Na) in THF solution affords the monomeric species (PhMe2Si)3CCuCNM(THF)3 which, when crystallized from toluene, gives the dimeric species 90 <2000OM5780>. Similar dimers, 91 and 92, are formed, in 65% and 41% yield, respectively, directly from reactions with (RMe2Si)(Me3Si)2CLi (R = Me or NMe2) while (MeOMe2Si)2(Me3Si)CLi gives 93 <2002JCS(D)3975>. Crystallization of the product formed from the potassium reagent (PhMe2Si)3CK and CuCN gives the tetramer 94 in 43% yield <2000OM5780>.
400
Functions Containing at Least One Metalloid (Si, Ge, or B) SiMe3
THF Li
THF
THF Li RCu CN NC CuR Li THF THF
Cu
CN
SiMe2
OMe
MeO
Me2Si Me2Si
90, R = (PhMe2Si)3C 91, R = (Me3Si)3C 92, R = (Me2NMe2)(Me3Si)2C
C SiMe2
MeO OMe C
Cu
CN
Me3Si
Li THF
93
K RCu
C
N
K C
RCu
N
N
K
K
C
CuR
94, R = (PhMe2Si)3C
N C CuR
(g) Three Si and one lanthanide or actinide functions. The first structurally characterized -bonded organosamarium(II) complex [Sm{C(SiMe3)2(SiMe2OMe)}2THF] was obtained from the reaction between K{C(SiMe3)2(SiMe2OMe)} and [SmI2(THF)2]. The compound is isolated as deep green-black, air-sensitive crystals in 71% yield and should inspire further work into alkyl, rather than the more well-known cyclopentadienyl, derivatives of samarium <1997AG(E)2815>. Reaction of a range of alkylpotassium species with YbI2 (Equation (13)) in benzene solution gives simple, monomeric dialkylytterbium compounds 95 <1994JA12071, 1996OM4783> including the solvent-free dialkyl lanthanide compound Tsi2Yb as an orange solid in 85% yield which, despite the steric encumbrance of the Tsi groups, is bent at Yb (CYbC angle 137 ) and can act as a polymerization catalyst for methylmethacrylate <2002JOM(647)128, 2003T10409>. A similar metathetical reaction occurs between TsiK and EuI2 to give the bent species Tsi2Eu in 65% yield <1996OM4783>. Grignard-like complexes [RYbIEt2O]2, 96, are formed from the reaction between RI and elemental Yb in Et2O (Equation (14)) <1994JA12071, 1996OM4783>. Reaction of the dipotassium compound 48 with YbI2 in benzene solution affords 97 in 45% yield <1999OM2342>. In contrast to the reactions carried out in benzene as a solvent, reaction between TsiK and YbI2 in Et2O in either a 2:1 or a 1:1 ratio gives the centrosymmetric dimer 98 as orange-red crystals in 63% yield. It is not clear how the EtO group is generated, but possibly by the Lewis acid character of initially formed Tsi2Yb or TsiK cleaving the solvent <1994CC2691, 1995JCS(D)3933>. YbI2 +
2(Me3Si)2(Me2RSi)CK
C6H6
[(Me3Si)2(Me2RSi)C]2Yb + 2KI 95, R = Me, 85% R = CH2=CH, 80% R = EtOCH2CH2, 70%
(Me3Si)2(Me2RSi)CI + Ybpowder
Et2O
Et2O
Yb
(RMe2Si)(Me3Si)2C
C(SiMe3)2(SiMe2R) I Yb I OEt2
96, R = Me R = OMe, 65%
Me2Si (Me3Si)2C
SiMe2 C(SiMe3)2 Yb 97
Et O C(SiMe3)3 Yb Yb O (Me3Si)3C OEt2 Et Et2O
98
No trisilylmethyl derivatives of the actinide elements seem to have been prepared.
ð13Þ
ð14Þ
401
Functions Containing at Least One Metalloid (Si, Ge, or B) (ii) Three Ge and one metal functions
As has been seen in sections above there is a general lack of compounds containing several germanium atoms attached to the same carbon and there do not appear to be any compounds containing the Ge3MC grouping known. Such compounds should be readily available via the routes used to prepare the many analogous Si3MC containing functions as described above.
(iii) Three B functions As has been described above, there are few compounds containing several boron atoms attached to carbon apart from carboranes and other compounds with multicenter bonding. See reference <1995COFGT(6)377> for early work in this field.
6.13.1.2.2
Other mixed metalloid functions
(i) Two Si, one Ge, and one metal functions Treatment of XMe2GeCBr(SiMe3)2 with PhLi (for X = Br) or Bun (for X = OPh) at low temperature gives XMe2GeCLi(SiMe3)2 species which, on warming, eliminates LiX to give the unsaturated Me2Ge¼C(SiMe3)2 <2000CJC1412, 2000JOM(598)304>.
(ii) Two Si, one B, and one metal functions The products obtained from the reaction between boriranylideboranes and [CoCp(C2H4)2] depend on the substituents at boron. For R = duryl (2,3,5,6-Me4C6H) or mesityl the dinuclear metal complexes 99 are formed (in 46% and 19% yields, respectively) but for R = But the mononuclear complex 100 is formed (Scheme 5) in 11% yield <1998CEJ44>. R
R
B B
Me3Si
C
C
Me3Si 2[CoCp(C2H4)2]
2[CoCp(C2H4)2] R = mesityl or duryl Co Me3Si Me3Si
C
R = But
R C B
B
Co Me3Si
Men
Me3Si
Co 99
C
B
But
B But 100
Scheme 5
(iii) One Si, one Ge, one B, and one metal functions. Also two Ge, one Si, and one metal functions. Also two Ge, one B, and one metal functions. Also Two B, one Si, and one metal functions. Also two B, one Ge, and one metal functions Very few examples of compounds containing these functions seem to have been prepared. Compounds containing such functions should, however, be available from synthetic routes described above in this section. In particular, such functions should be available from the reactions between suitably substituted lithium reagents and appropriate metal halides.
402
Functions Containing at Least One Metalloid (Si, Ge, or B)
As would be expected from the ready metallations of trisilylmethane derivatives the digermylsilylmethane (Me3Ge)2(FBut2Si)CH reacts with MeLi in THF/Et2O to give (Me3Ge)2(FBuFBut2Si)CLi, which, when treated with Me3SnCl, affords (Me3Ge)2(FBut2Si)CSnMe3 in 51% yield <1996JOM(511)239>.
6.13.1.3 6.13.1.3.1
Methanes Bearing Two Metalloid and Two Metal Functions Two Si and two metal functions
Metallation of BrMe2SnCBr(SiMe3)2 by PhLi affords BrMe2SnCLi(SiMe3)2 which, when warmed, eliminates LiBr to give first a stannene and then a cyclic dimer, 101, as shown in Scheme 6 <2000JOM(598)292, 2000JOM(598)304>. A related bulky methyllithium derivative (Me3Si)2(PhMe2Sn)CLi was readily prepared via SnC bond cleavage of (Me3Si)2(PhMe2Sn)2C by MeLi in THF/Et2O <1998JOM(564)215>.
Me2Sn C(SiMe3)2 + PhLi Br Br
Et2O
Me2Sn C(SiMe3)2 Br Li
low temp.
Warm
Me2Sn C(SiMe3)2
–LiBr x2 Me2Sn C(SiMe3)2 (Me3Si)2C SnMe2 101
Scheme 6
Attempts have been made to prepare (Me3Si)2CLi2 by the pyrolysis of either the ate complex [Li(THF)4][Tsi2Li] or the solvent-free [TsiLi]2 (a method that works in the synthesis of (Me3Si)2SiLi2 from (Me3Si)3SiLi) but they fail and give instead oligomeric products <1998MI222>.
6.13.1.3.2
Two Ge and two metal functions
There do not appear to be any compounds containing this function but they could, doubtless, be prepared in similar ways to the analogous Si2M2C-containing species described above in Section 6.13.1.3.1.
6.13.1.3.3
Two B and two metal functions
Compounds containing this grouping are relatively rare (see <1995COFGT(6)377> for early work in the area). A range of diboraallenes, 102, containing a four-coordinate planar carbon can be prepared according to Equation (15) from the anions 103 <2001AG(E)2662>. Synthetic approaches to planar carbon atoms have often involved the preparation of compounds containing carbons heavily substituted by metalloids or metals and this work has been reviewed in <1999CSR367>.
R1
– B C B R1
+
2 R2Li
–(Me3Si)2CHLi
(Me3Si)2CH 103
R1 R2
R1 = R2 = mesityl R1 = R2 = 2,3,5,6-Me4C6H R1 = R2 = 2,6,-Me24-ButC6H2 R1 = mesityl, R2 = But
OEt2 Li – R1 – B C B R2 Li OEt2 102
ð15Þ
Functions Containing at Least One Metalloid (Si, Ge, or B) 6.13.1.3.4
403
Other combinations of two metalloids and two metal functions
There are very few compounds known containing mixed metalloids and two metal functions. They should, however, be available by the routes described above for related compounds containing two of the same metalloid. One notable example of this type of compound is racemic (Me3Pb)(Me3Sn)(Me3Ge)(Me3Si)C, a molecule containing all the elements of group 14 connected together, which can be obtained from a series of metathesis reactions .
6.13.1.4
Methanes Bearing One Metalloid and Three Metal Functions
6.13.1.4.1
One Si and three metal functions
Relatively few new compounds of this type have been prepared since those described in <1995COFGT(6)377>. The bulky dialkyltitanium complex 104 reacts with AlMe3 (Equation (16)) to give the four-coordinate carbide complex 105 in 78% yield <2001OM1175>.
Cp Me3 Si
Ti
N
PPr3i
SiMe3
PPr3i 3AlMe3 –3CH4
Cp Me
104
6.13.1.4.2
Ti
N AlMe2 C
+ AlMe2CH2SiMe3
ð16Þ
Al SiMe3 Me2 105
One Ge and three metal functions
No new compounds containing this grouping seem to have been prepared since those described in <1995COFGT(6)377>.
6.13.1.4.3
One B and three metal functions
There seem to be few, if any, compounds of this type known. It may be possible to prepare such species by the reaction of a methylidyne cluster with a borane, R2BH, in a manner similar to that used in the preparation of silyl-substituted alkylidyne complexes.
6.13.2 6.13.2.1
METHANES BEARING FOUR METAL FUNCTIONS Methanes Bearing Four Similar Metals
A slightly modified method for the preparation of (Me3Sn)4C from CCl4, Li, and Me3SnCl has been reported together with new spectroscopic data <1995JOM(496)241>. This compound does not seem to have been of use in synthesis but has been the subject of several detailed structural studies (see, e.g., <1999MI385>). A method for obtaining very pure Hofmann’s base, [CHg4O(OH)2OH2]n, has been described <1996JOM(522)297>. The pure base can be used in the preparation of C(HgNO3)4 and C(HgSO4)2(HgOH2)2.
6.13.2.2
Methanes Bearing Three Similar and One Different Metal Functions
Treatment of phosphinimide complexes 106 with excess AlMe3 leads to multiple CH bond activation and formation of the carbide complexes 107 in good yield (Equation (17)) <2001OM1175>. (For the products from the analogous reaction with bulky alkyl substituents at Ti see Section 6.13.1.4.1, and for their behavior in solution see Section 6.13.3.)
404
Functions Containing at Least One Metalloid (Si, Ge, or B) PR3 PR3 N Cp1 Ti Me Me
Cp1
3AlMe3
AlMe2
ð17Þ
C
Al AlMe2 Me2
1 i 106, Cp = Cp; R = Cy or Pr Cp1 = indenyl; R = Pri
6.13.2.3
Ti
Me
–3CH4
N
107
Methanes Bearing Two Similar and Two Different Metal Functions
Compounds containing this type of grouping seem to be very rare although carbons coordinated by different metals may well occur in metal carbides, these are outside the scope of this chapter.
6.13.2.4
Methanes Bearing Four Different Metal Functions
Although there are a potential 135 751 different combinations (and their optical isomers) of 43 different metals at a tetrahedral carbon center, very few seem to have been prepared. A comprehensive search of the literature for such a large number of functional groups is clearly very difficult to carry out and it is quite possible that many such groupings have been missed in compiling this article. It is hoped that any omissions of such groupings will not be serious for the organic chemist.
6.13.3
METHANES BEARING MORE THAN FOUR METALLOID OR METAL FUNCTIONS
Polyhedral metallacarboranes in which carbon is bonded to more than four metalloid or metal centers via multicenter interactions are numerous but beyond the scope of this article. Reviews of metallacarborane chemistry can be found in <2002CCC728, 2002CCR(231)23, 2000MCLC(342)7, 1999JOM(581)1>. Variable temperature NMR studies show that the four-coordinate carbide complexes, 107 (see Section 6.13.2.2), are in equilibrium (Equation (18)) with five-coordinate complexes 108 in the presence of AlMe3 <2000AG(E)3263>. Cp
PR3 Cp
Ti
Me
N AlMe2
C Al AlMe2 Me2
AlMe3 –AlMe3
Me Me2Al
PR3 Me2 N Al
Ti C
Me
ð18Þ
Al Me2
107 R = Pri or Ph
AlMe2
108
ACKNOWLEDGMENTS This chapter is dedicated to Professor C. Eaborn, FRS, who died in February 2004. Much of the chemistry described above was initiated in the Eaborn group and the versatility of reagents, such as (Me3Si)3CLi, that have now become popular across a wide range of organometallic chemistry was demonstrated first in the research laboratories at Sussex University.
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Schno¨ckel, J. Am. Chem. Soc. 2000, 122, 9178. A. Pepels, H. Guenther, J.-P. Amoureux, C. Fernandez, J. Am. Chem. Soc. 2000, 122, 9858. A. G. Avent, D. Bonafoux, C. Eaborn, M. S. Hill, P. B. Hitchcock, J. D. Smith, J. Chem. Soc., Dalton Trans. 2000, 2183. W. Uhl, M. Benter, J. Chem. Soc., Dalton Trans. 2000, 3133. C. Eaborn, S. M. El-Hamruni, M. S. Hill, P. B. Hitchcock, A. LeGouic, J. D. Smith, J. Organomet. Chem. 2000, 597, 3. K. D. Safa, M. G. Asadi, A. Abri, A. Mohammadpour, H. Kiae, J. Organomet. Chem. 2000, 598, 222. N. Wiberg, T. Passler, S. Wagner, K. Polborn, J. Organomet. Chem. 2000, 598, 292. N. Wiberg, T. Passler, S. Wagner, J. Organomet. Chem. 2000, 598, 304. M. Shimizu, T. Hiyama, M. Matsubara, T. Yamabe, J. Organomet. Chem. 2000, 611, 12. N. S. Hosmane, J. A. Maguire, J. Organomet. Chem. 2000, 614, 10. R. N. Grimes, Mol. Cryst. Liq. Cryst. 2000, 342, 7. C. Eaborn, M. S. Hill, P. B. Hitchcock, D. Patel, J. D. Smith, S. Zhang, Organometallics 2000, 19, 49. L.-K. Liu, L.-S. Luh, Organometallics 2000, 19, 374. C. Eaborn, P. B. Hitchcock, J. D. Smith, S. Zhang, W. Clegg, K. Izod, P. O’Shaughnessy, Organometallics 2000, 19, 1190. S. S. Al-Juaid, C. Eaborn, P. B. Hitchcock, M. S. Hill, J. D. Smith, Organometallics 2000, 19, 3224. C. Eaborn, M. S. Hill, P. B. Hitchcock, J. D. Smith, Organometallics 2000, 19, 5780. K. D. Safa, A. R. Koushki, M. G. Asadi, Phos. Sulf. Silicon 2000, 158, 97. T. Viefhaus, A. Walz, M. Niemeyer, W. Schwarz, J. Weidlein, Z. Anorg. Allg. Chem. 2000, 626, 2040. W. Uhl, S. Melle, Z. Anorg. Allg. Chem. 2000, 626, 2043. A. Schnepf, R. Ko¨ppe, H. Schno¨ckel, Angew. Chem., Int. Ed. Engl. 2001, 40, 1241. Y. Sahnin, M. Hartmann, G. Geiseler, D. Swiekart, C. Balzerit, G. Frenking, W. Massa, A. Berndt, Angew. Chem., Int. Ed. Engl. 2001, 40, 2662. W. Uhl, S. Melle, Chem. -Eur. J. 2001, 7, 4216. A. Ziegler, H. Pritzkow, W. Siebert, Eur. J. Inorg. Chem. 2001, 387. K. Schmohl, H. Reinke, H. Oeme, Eur. J. Inorg. Chem. 2001, 481. W. Uhl, S. Melle, G. Frenking, M. Hartmann, Inorg. Chem. 2001, 40, 750. C. Ackerhans, P. Bottcher, P. Muller, H. W. Roesky, I. Uson, H.-G. Schmidt, M. Noltemeyer, Inorg. Chem. 2001, 40, 3766.
Functions Containing at Least One Metalloid (Si, Ge, or B) 2001JA994 2001JCS(D)1541 2001JCS(D)3397 2001JOM(620)127 2001JOM(631)76 2001JOM(640)29 2001MI(162)225 2001OM1175 2001OM1223 2001OM2047 2001ZAAC(627)715 2002AG(E)1365 2002AG(E)3829 2002CCC728 2002CCC869 2002CCR(231)23 2002CCR(232)173 2002JCS(D)2467 2002JCS(D)3971 2002JCS(D)3975 2002JOM(647)128 2002JOM(649)121 2002OM2183 2002OM2430 2002OM4005 2002USP00334829 2002ZAAC(628)1963 2003AG(E)669 2003AG(E)671 2003ICA(345)359 2003JA7534 2003OM2505 2003OM2705 2003T10409 2004JOM(689)1238 2004JOM(689)1718
407
Z.-X. Wang, P. v. R. Schleyer, J. Am. Chem. Soc. 2001, 123, 994. C. Eaborn, J. D. Smith, J. Chem. Soc., Dalton Trans. 2001, 1541. C. Eaborn, J. Chem. Soc., Dalton Trans. 2001, 3397. E. J. Hawrelak, D. Sata, F. T. Lapido, J. Organomet. Chem. 2001, 620, 127. S. S. Al-Juaid, A. G. Avent, C. Eaborn, S. M. El-Hamruni, S. A. Hawkes, M. S. Hill, M. Hopman, P. B. Hitchcock, J. D. Smith, J. Organomet. Chem. 2001, 631, 76. C. Eaborn, A. Kowalewska, J. D. Smith, W. A. Stan´czyk, J. Organomet. Chem. 2001, 640, 29. M. Schormann, K. S. Klimek, H. Hatop, S. P. Varkey, H. W. Roesky, C. Lehman, C. Ro¨pken, R. Herbst-Irmer, M. Noltemeyer, J. Solid State Chem. 2001, 162, 225. J. E. Kickham, F. Gue´rin, J. C. Stewart, E. Urbanska, D. W. Stephan, Organometallics 2001, 20, 1175. S. S. Al-Juaid, A. G. Avent, C. Eaborn, M. S. Hill, P. B. Hitchcock, D. J. Patel, J. D. Smith, Organometallics 2001, 20, 1223. K. S. Klimek, J. Prust, H. W. Roesky, M. Noltemeyer, H.-G. Schmidt, Organometallics 2001, 20, 2047. T. Viefhaus, W. Schwarz, K. Hubler, K. Locke, J. Weidlein, Z. Anorg. Allg. Chem. 2001, 627, 715. J. Janssen, J. Magull, H. W. Roesky, Angew. Chem., Int. Ed. Engl. 2002, 41, 1365. W. W. du Mont, T. Gust, E. Seppa¨la¨, C. Wismach, P. G. Jones, L. Ernst, J. Grunenberg, H. C. Marsmann, Angew. Chem., Int. Ed. Engl. 2002, 41, 3829. R. N. Grimes, Coll. Czech. Chem. 2002, 67, 728. A. Franken, C. A. Kilner, M. Thornton-Pett, J. D. Kennedy, Coll. Czech. Chem. 2002, 67, 869. Z. Xie, Coord. Chem. Rev. 2002, 231, 23. J. F. Valliant, K. J. Guenther, A. S. King, P. Morel, P. Schaffer, O. O. Sogbein, K. A. Stephenson, Coord. Chem. Rev. 2002, 232, 173. C. Eaborn, M. S. Hill, P. B. Hitchcock, J. D. Smith, J. Chem. Soc., Dalton Trans. 2002, 2467. A. G. Avent, C. Eaborn, I. B. Gorrell, P. B. Hitchcock, J. D. Smith, J. Chem. Soc., Dalton Trans. 2002, 3971. C. Eaborn, S. M. El-Hamruni, M. S. Hill, P. B. Hitchcock, J. D. Smith, J. Chem. Soc., Dalton Trans. 2002, 3975. H. Yasuda, J. Organomet. Chem. 2002, 647, 128. S. S. Al-Juaid, C. Eaborn, S. M. El-Hamruni, P. B. Hitchcock, J. D. Smith, S. E. So¨zerli, J. Organomet. Chem. 2002, 649, 121. A. Asadi, A. G. Avent, C. Eaborn, M. S. Hill, P. B. Hitchcock, M. M. Meehan, J. D. Smith, Organometallics 2002, 21, 2183. A. Asadi, C. Eaborn, M. S. Hill, P. B. Hitchcock, M. M. Meehan, J. D. Smith, Organometallics 2002, 21, 2430. I. V. Borisova, C. Eaborn, M. S. Hill, V. N. Khrustalev, M. G. Kuznetzova, J. D. Smith, Y. A. Ustynyuk, V. V. Lunin, N. N. Zemlyansky, Organometallics 2002, 21, 4005. Hall, K.; Murphy, V.; Lapointe, A. M.; Van Beek, J. A. M.; Diamond, G. M. U.S. Patent 200200334829; CAN 136, 263 599. W. Uhl, F. Schmock, G. Gieseler, Z, Anorg. Allg. Chem. 2002, 628, 1963. Y. Sahin, C. Prasang, P. Amseis, M. Hofmann, G. Geiseler, W. Massa, A. Berndt, Angew. Chem., Int. Ed. Engl. 2003, 42, 669. Y. Sahin, C. Prasang, M. Hofmann, G. Subramaniam, G. Geiseler, W. Massa, A. Berndt, Angew. Chem., Int. Ed. Engl. 2003, 42, 671. A. M. LaPointe, Inorg. Chim. Acta 2003, 345, 359. K. Izod, S. T. Liddle, W. Clegg, J. Am. Chem. Soc. 2003, 125, 7534. F. Antolini, P. B. Hitchcock, M. F. Lappert, X.-H. Wei, Organometallics 2003, 22, 2505. C. Gemel, T. Steinke, D. Weiss, M. Cokoja, M. Winter, R. A. Fischer, Organometallics 2003, 22, 2705. G. Qi, Y. Nitto, A. Saiki, T. Tomohiro, Y. Nakayama, H. Yasuda, Tetrahedron 2003, 59, 10409. A. Asadi, A. G. Avent, M. P. Coles, C. Eaborn, P. B. Hitchcock, J. D. Smith, J. Organomet. Chem. 2004, 689, 1238. D. Azarifar, M. P. Coles, S. M. Al-Hamruni, C. Eaborn, P. B. Hitchcock, J. D. Smith, J. Organomet. Chem. 2004, 689, 1718.
408
Functions Containing at Least One Metalloid (Si, Ge, or B) Biographical sketch
Paul D. Lickiss was born in Kent, the Garden of England, studied at The University of Sussex, where he obtained a B.Sc. degree in 1980 and his D.Phil. in 1983 under the supervision of Professor C. Eaborn, FRS. After staying at the University of Toronto with Professor Adrian Brook from 1983 to 1984, he returned to Sussex and took up a position as a Royal Society 1983 University Research Fellow in 1985. In 1989 he resigned his Fellowship to take up a position as a lecturer in the University of Salford where he stayed for four years. From the 1990s, he has been a Lecturer, Senior Lecturer, and now Reader in organometallic chemistry in the Synthesis Section in the Chemistry Department at Imperial College, London. His research interests are mainly in the field of organosilicon chemistry, particularly the synthesis of low-coordinate compounds such as silyl cations and the use of bulky groups to stabilize unusual compounds. He is also interested in the synthesis and uses of organosilanols, especially those containing several Si–OH groups. The use of ultrasound for synthesis is also actively pursued.
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Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 381–408
6.14 Functions Containing a Carbonyl Group and at Least One Halogen R. MURUGAN and S. V. YARLAGADDA Reilly Industries Inc., Indianapolis, IN, USA 6.14.1 INTRODUCTION 6.14.2 CARBONYL HALIDES WITH TWO SIMILAR HALOGENS 6.14.2.1 Carbonic Difluoride 6.14.2.2 Carbonic Dichloride 6.14.2.2.1 Preparation of phosgene 6.14.2.2.2 Phosgene alternatives 6.14.2.3 Carbonic Dibromide 6.14.2.4 Carbonic Diiodide 6.14.3 CARBONYL HALIDES WITH TWO DISSIMILAR HALOGENS 6.14.3.1 One Fluorine and Chlorine, Bromine, or Iodine 6.14.3.1.1 Carbonic chloride fluoride 6.14.3.1.2 Carbonic bromide fluoride 6.14.3.1.3 Carbonic fluoride iodide 6.14.3.2 One Chlorine and Bromine or Iodine 6.14.3.2.1 Carbonic bromide chloride 6.14.3.2.2 Carbonic chloride iodide 6.14.3.3 One Bromine and Iodine 6.14.3.3.1 Carbonic bromide iodide 6.14.4 CARBONYL HALIDES WITH ONE HALOGEN AND ONE OTHER HETEROATOM 6.14.4.1 One Halogen and One Oxygen 6.14.4.1.1 Fluoroformate esters 6.14.4.1.2 Chloroformate esters 6.14.4.1.3 Bromoformate esters 6.14.4.1.4 Iodoformate esters 6.14.4.2 One Halogen and One Sulfur 6.14.4.2.1 Fluorothiolformate esters 6.14.4.2.2 Chlorothiolformate esters 6.14.4.2.3 Bromothiolformate esters 6.14.4.2.4 Iodothiolformate esters 6.14.4.3 One Halogen and One Nitrogen 6.14.4.3.1 Carbamoyl fluorides 6.14.4.3.2 Carbamoyl chlorides 6.14.4.3.3 Carbamoyl bromides 6.14.4.3.4 Carbamoyl iodides 6.14.4.4 One Halogen and One Phosphorus 6.14.4.4.1 Chlorocarbonyl derivatives of phosphorus(III) 6.14.4.4.2 Chlorocarbonyl derivatives of phosphorus(V) 6.14.4.5 One Halogen and One Arsenic, Antimony, or Bismuth 6.14.4.6 One Halogen and One Metalloid (Boron, Silicon, or Germanium) 6.14.4.7 One Halogen and One Metal 6.14.4.7.1 Halocarbonyl complexes of first transition metal series (iron and chromium) 6.14.4.7.2 Halocarbonyl complexes of second transition metal series (ruthenium and rhodium) 6.14.4.7.3 Halocarbonyl complexes of third transition metal series (rhenium and iridium)
409
410 410 410 411 411 411 412 412 413 413 413 413 414 414 414 414 414 414 414 414 415 415 419 419 419 419 420 420 420 420 421 421 422 422 422 422 423 423 423 424 424 424 424
410 6.14.1
Functions Containing a Carbonyl Group and at Least One Halogen INTRODUCTION
The literature search was done using the general term carbonyl halides and other specific compounds such as carbonyl difluoride, phosgene, chloroformates, etc., discussed by name in this chapter. As observed by the authors, of COFGT (1995) <1995COFGT(6)407>, the present authors observed more literature on those compounds, when the halogen is chlorine. For example, there are more references on carbonyl dichloride than those on carbonyl difluoride, carbonyl dibromide, and carbonyl diiodide combined. Similarly in the case of halo formate derivatives there are more references on chloro formates than those on, fluoro-, bromo-, or iodo-formates. The arrangement of sections and subsections is similar to that of COFGT (1995) <1995COFGT(6)407>, except some sections are not repeated as not much has changed between then and the end of 2003. For example, the section on toxicity and handling of phosgene is not repeated here. In the decade up to 2003, the trend has been towards the ‘‘green chemistry’’ concept of alternative synthetic approaches for the titled functional groups that would replace toxic substances like carbon monoxide and phosgene with other relatively less/nontoxic chemicals like carbon dioxide.
6.14.2
CARBONYL HALIDES WITH TWO SIMILAR HALOGENS
The general preparations reported in <1995COFGT(6)407> on these carbonyl difluoride, dichloride, dibromide, and diiodide are summarized in Scheme 1. There are three general synthetic routes for these compounds. One of the methods is by halogen exchange reaction on carbonyl chloride or phosgene using a halide source. The other two methods start from carbon monoxide and halogen (carbon monoxide insertion into halogens works well for carbonyl difluoride and dichloride), and oxidation of a perhalogenated organic compound with an oxygen oxidant (works well for carbonyl dibromide). X2
CO
COX2
Oxidant
CX4
2X– COCl2
Scheme 1
6.14.2.1
Carbonic Difluoride
A novel approach to making carbonyl difluoride has been to react carbon dioxide and fluorine gas (Equation (1)). This method does not use toxic compounds such as phosgene and carbon monoxide. Carbon dioxide and fluorine are allowed to react with each other in the gaseous state, to produce carbonyl difluoride, at a preferred temperature range of 150–250 C with a mole ratio of 0.5:2, and near atmospheric pressure in a fluorine resistant metal, such as stainless steel, under anhydrous conditions <1999JAP11116216>. CO2
+
F2
COF2
ð1Þ
Carbonyl difluoride has been used in the synthesis of fluorinated methyl ethers <1995USP5382704> of the formula R2CHOCF2A where A is Cl or F, and each R is H, (CF2)nCl, (CF2)nF, or (CF2)nH (where n = 1–10). Dry etching of high-melting-point metals has been achieved by using carbonyl compounds, specifically that of carbonyl difluoride <1995JAP07221074>. This process has been useful for forming electrodes, circuits, etc.
Functions Containing a Carbonyl Group and at Least One Halogen 6.14.2.2
411
Carbonic Dichloride
Carbonic dichloride or carbonyl dichloride or phosgene is the most important of all the functional compounds mentioned in this chapter. It is made commercially in large quantities and almost all the other functional groups mentioned in this chapter could be obtained by chemical transformations on phosgene. Phosgene is also a highly toxic and very reactive compound. It is an industrially important compound, as it is used in the preparation of polyurethanes and polycarbonates. Hence, it is the most studied of all the functional groups mentioned in this chapter. In the early 2000s, there is an awareness that phosgene should be replaced by other less toxic chemicals in the synthesis of polyurethanes and polycarbonates.
6.14.2.2.1
Preparation of phosgene
In general, phosgene has been prepared in three ways: the classical synthesis of insertion of carbon monoxide to chlorine; the chemical as well as photochemical oxidation of perchlorinated compounds; and the decomposition of other phosgene derivatives such as chloroformates and carbonates which are also used as phosgene alternatives. All these methods have been discussed in COFGT (1995) <1995COFGT(6)407>. Phosgene is also produced as one of the products in the photocatalytic degradation of perhalogenated hydrocarbons on porous titanium oxide <2001AC(B)109, 2002MI412>. A report on the synthesis of phosgene from triphosgene or bis(trichloromethyl)carbonate, along with the comparison of the reactivity of phosgene with that of diphosgene and triphosgene with methanol, has been published <2000JOC8224>. Phosgene can be manufactured from diphosgene and triphosgene using deactivated amines as the catalysts. The amine catalysts are selected from poly(2-vinylpyridine), phenanthridine, phthalocyanines, and metallophthalocyanines free and on a polymer support, and poly(N,N-dimethylaminomethylstyrene) <1999GEP19740577>. There are a few reports of carbon labeled phosgene synthesis, which were also discussed in COFGT (1995) <1995COFGT(6)407>. Even in the preparation of 11C-labeled phosgene to make 11C-labeled ureas and isocyanates, alternatives like 11C-labeled carbon dioxide have been used <1999MI537>. Another example of the use of 11C-carbon monoxide in place of labeled phosgene is in the preparation of 11C-carbamoyl compounds using selenium <2002JOC3687>. 11 C-Phosgene, a useful precursor for labeling several radiopharmaceuticals, is generally made by catalytic oxidation of 11C-carbon tetrachloride over iron granules, although in low yields or with poor reproducibility. Chlorination of 11C-methane followed by reaction with a stream of 98:2 nitrogen/oxygen over iron has provided 11C-phosgene <2001MI785>. The yield of 11C-phosgene was significantly increased by using iron oxide along with iron granules <2002MI345>. A simple review of the history, preparation, and uses of phosgene was done by Senet <1998MI12>. A modified production of phosgene from carbon monoxide and chlorine has been patented. This patent claims the use of a metal halide catalyst preferably selected from group III metals like aluminum and gallium <1999GEP19916856>. An improved method for the preparation of phosgene in the laboratory has been reported. In this approach phosgene was prepared by addition of 95–98% sulfuric acid to a mixture of phosphorus pentoxide and carbon tetrachloride <1998MI123>. An interesting way to address the toxicity and safety issues associated with phosgene is the use of a microfabricated reactor for its manufacture. This is an example of the potential for safe on-site/on-demand production of a hazardous compound, in this case phosgene. Complete conversion of chlorine is observed for a 1:1 feed at 8 cc/min, which gives a projected productivity of approximately 100 kg/year from a 10-channel microreactor, with the opportunity to produce significant quantities by operating many reactors in parallel <2001MI1639>.
6.14.2.2.2
Phosgene alternatives
Because of the toxicity and the high reactivity of phosgene, many alternatives have been made and used as phosgene equivalents. Interestingly, most of them are made from phosgene but are easier to handle than phosgene itself. The most common phosgene alternatives mentioned in COFGT (1995) <1995COFGT(6)407> are summarized in Scheme 2.
412
Functions Containing a Carbonyl Group and at Least One Halogen N O
N N
Imidazole
COCl2
Methanol
Phosgene
CH3OCOCl
Methanol CH3OCOOCH3 Cl2
Cl2
N CCl3OCOCl
CCl3OCOOCCl3
Diphosgene
Triphosgene
Scheme 2
Ureas have been traditionally synthesized by methodologies mainly based on the use of dangerous reagents such as phosgene and isocyanates. However, in the late 1990s and early 2000s, these reagents have been increasingly substituted by cleaner and inherently safer compounds, referred to as phosgene substitutes, such as bis(4-nitrophenyl)carbonate, triphosgene, di-t-butyl-dicarbonate, 1,1-carbonylbisimidazole, 1,1-carbonylbisbenzotriazole, S,S-dimethyl dithiocarbonate, and trihaloacetyl chlorides. These safer reagents could be stored and handled without special precautions <2000GC140>. Phosgene has been replaced with carbon dioxide in the synthesis of alkyl carbonates. Mixed or symmetrical dialkyl carbonates were generated in high yields (53–97%) from alcohols, carbon dioxide, and alkyl chlorides in apolar aprotic solvents using guanidine bases under mild conditions <1995JOC6205>.
(i) Prepared from phosgene The common phosgene alternatives are usually made from phosgene, replacing either one or both of the chlorine atoms with a leaving group, and thus making the whole compound more stable and easier to handle. There are also reviews on the use of these phosgene alternatives. For example, the use of bis(trichloromethyl)carbonate or triphosgene in organic synthesis as a substitute for phosgene is well reviewed <1996S553, 1994MI357>. The preparation of N,N0 -carbonyldiimidazole has been reported, starting from imidazole and phosgene. Reaction of imidazole with phosgene in toluene in the presence of tributylamine gave 76% yield of N,N0 -carbonyldiimidazole <2001MI33>.
6.14.2.3
Carbonic Dibromide
Carbon monoxide and bromine are reacted over activated carbon to give carbonyl dibromide (Equation (2)). Like phosgene, carbonyl dibromide is also used in the synthesis of compounds such as diaryl carbonates <1992EUP520238>. In the application on the use of carbonyl dibromide in the preparation of diaryl carbonates, aluminum trifluoride has been used as the catalyst <1992EUP516355>. Carbonyl dibromide is also used in the synthesis of metal bromides and their bromide oxides <1997JCS(D)257>. This reaction of carbonyl bromide with metal oxides is further discussed in Section 6.14.4.7 on the halocarbonyl metal compounds. Activated “C” CO
6.14.2.4
+
Br2
COBr2
ð2Þ
Carbonic Diiodide
This compound was not reported in COFGT (1995) <1995COFGT(6)407> and many attempts to make this compound have failed. It was suggested that this may be due to its poor stability. However, it has been found that heating carbon tetraiodide in a stream of oxygen results in the formation of carbonyl diiodide, and this has been confirmed from its infrared (IR) spectrum (Equation (3)) <1995CPL594>. Carbonyl diiodide, which is similar to carbonyl difluoride, has
Functions Containing a Carbonyl Group and at Least One Halogen
413
been used in the decontamination of metal surfaces that are contaminated by metal oxides of U, Pu, Np, Tc, etc. The metal oxides are converted into their iodides or carbonyl complexes, which are volatile and hence removed by vacuum <2001JAP153996>. CI4
6.14.3
O2
+
ð3Þ
COI2
CARBONYL HALIDES WITH TWO DISSIMILAR HALOGENS
The general syntheses of these compounds mentioned in COFGT (1995) are summarized in Scheme 3 <1995COFGT(6)407>. The two major approaches are: the insertion of carbon monoxide with the mixed halogen compound, and halogen exchange with a halide ion source on a carbonyl dihalide with a different halogen. X1X2
X1–
COX1X2
CO
COCl2
–Cl–
Scheme 3
6.14.3.1 6.14.3.1.1
One Fluorine and Chlorine, Bromine, or Iodine Carbonic chloride fluoride
An improved method for the synthesis of carbonyl chloride fluoride under mild conditions has been reported. Pure carbonyl chloride fluoride can be isolated in essentially quantitative yield from the decomposition of the oxygen-bridged COCl2SbF5 donor–acceptor adduct at room temperature (rt) in a dynamic vacuum <1999JFC(94)107> (Equation (4)). These adducts along with that of carbonyl chloride fluoride and penta fluoro compounds have been studied using vibrational spectroscopy, nuclear magnetic resonance (NMR), mass spectra, and theoretical calculations <1997JCS(D)251, 1999IC3143>. COCI2.SbF5
+
COClF
O2
ð4Þ
Carbonyl chloride fluoride is formed by thermal decomposition of chlorofluoro carbons like CCl2F2 with titanium dioxide catalyst <1995JCA394> (Equation (5)), as well as by dielectric discharge <1999MI627>. They are also formed by the oxidation of chlorofluoro carbons with ozone <1992JPC8069> (Equation (6)). CF2Cl2
+
TiO2
O2
CFCl3
+
COFCl
+
O3
Other products
ð5Þ
COFCl
ð6Þ
Carbonyl chloride fluoride is also formed in the oxidation of hydrofluorocarbons with either chlorine <1993MI179> or other oxidants <1993MI(66)97> (Equation (7)). CHFCl2
6.14.3.1.2
+
Cl.
Air
COFCl
Air
Cl.
+
H3CCFCl2
ð7Þ
Carbonic bromide fluoride
Photooxidation of tribromofluoromethane in an oxygen atmosphere containing ozone showed the formation of carbonyl bromide fluoride (Equation (8)) <1996JPC9271>. This compound like other different carbonyl dihalides has been spectroscopically studied, specifically its NMR and mass spectra <1997JCS(D)251>.
414
Functions Containing a Carbonyl Group and at Least One Halogen CFBr3
6.14.3.1.3
O3
+
ð8Þ
COFBr
Carbonic fluoride iodide
The synthesis of carbonic fluoride iodide was reported in COFGT (1995) <1995COFGT(6)407> by a reaction of iodine pentafluoride with carbon monoxide under pressure, and no new synthetic methods for this compound have been reported, up to 2003.
6.14.3.2
One Chlorine and Bromine or Iodine
6.14.3.2.1
Carbonic bromide chloride
Carbonyl bromide chloride has been prepared by the insertion reaction of carbon monoxide with bromine chloride <1993USP5235000>, a readily available brominating reagent (Equation (9)) <1999JPC2624>. BrCl
+
CO
ð9Þ
COBrCl
Carbonyl bromide chloride has also been prepared by the photochemical oxidation of bromochlorohydrocarbons such as, dibromochloromethane and bromodichloromethane, with ozone (Equation (10)) <1999JCS(D)73, 1997JPC2074>. HCBr2Cl + O3
COBrCl + Others
O3 + H2CBrCl
ð10Þ
Like other carbonyl dihalides, carbonyl bromide chloride has been studied for its spectral behavior, like that of NMR and mass spectra <1997JCS(D)251>.
6.14.3.2.2
Carbonic chloride iodide
As was the case in COFGT (1995) <1995COFGT(6)407>, carbonic chloride iodide has not yet (in late 2003) been reported.
6.14.3.3
One Bromine and Iodine
6.14.3.3.1
Carbonic bromide iodide
As in COFGT (1995) <1995COFGT(6)407>, no synthetic method for this compound, carbonic bromide iodide, has been reported, up to the end of 2003.
6.14.4
6.14.4.1
CARBONYL HALIDES WITH ONE HALOGEN AND ONE OTHER HETEROATOM One Halogen and One Oxygen
The general methods used for the syntheses of these haloformate esters, reported in COFGT (1995), are summarized in Scheme 4 <1995COFGT(6)407>. The three possible approaches are: first, the nucleophilic displacement of one of the halogen of a dihalo carbonyl with an alcohol to give the haloformates; second, the insertion of carbon monoxide on organo hypohalites; and third, the halogen exchange reaction of one haloformate ester to another haloformate ester by using a halide ion source.
Functions Containing a Carbonyl Group and at Least One Halogen COX2
ROH
ROCl
ROCOX
–HX
415
CO
X1–
ROCOX1 +
X–
Scheme 4
6.14.4.1.1
Fluoroformate esters
A method for the production of aliphatic fluoroformates, where carbonyl fluoride is esterified with aliphatic alcohols (e.g., t-butanol) in an ether at 20 C to +50 C, is described. The method is carried out using carbonyl fluoride obtained by reacting phosgene with surplus powdered sodium fluoride whose granules have a specific surface of 0.1 m2 g1 and/or an average diameter of 20 mm. This method enables the preparation of unstable fluoroformates (e.g., t-Bu fluoroformate) in excellent yields (Equation (11)) <2000WOP0059859>.
OH
+
COCl2
NaF
ð11Þ OCOF
One of the fluoroformates, 9-fluorenylmethyl fluoroformate, is a useful reagent for the largescale synthesis of dipeptide-free Fmoc (9-fluorenylmethoxycarbonyl) amino acids. 9-Fluorenylmethyl fluoroformate (Fmoc-F) is an inexpensive and effective reagent, which is available in large quantities for the synthesis of Fmoc-amino acids <1998MI244>.
6.14.4.1.2
Chloroformate esters
Next to phosgene, chloroformate esters are the most important industrial compounds considered in this chapter. Significant research has been done on the transformation of these compounds into other compounds. Chloroformates are much easier to handle than phosgene and the difference in reactivity of the two leaving groups has been exploited in its chemistry. Diphosgene or trichloromethyl chloroformate, a versatile reagent in organic synthesis, is reviewed. Its reactions with amines, alcohols, and others have been discussed <1992MI230>. Similarly, another chloroformate, methyl chloroformate, has been reviewed for its chemistry as well as its hazardous nature <1994MI181>. As mentioned earlier, because of its importance as an industrial chemical, procedures for the storage and transport of chloroformate esters with reduced decomposition are well documented and regulated. For example, using polymer surface coatings of polyethylene for storage vessels as well as transport pipes decreases the decomposition of ethyl chloroformate <2002GEP10102807>. Chloroformates with the simplest alkyls, such as methyl, ethyl, or isobutyl, are used as general derivatizing agents in gas chromatography. The use of chloroformates in this regard in various disciplines has been reviewed <1998JC57>. The preparation and application of chloroformates, for the immobilization of enzymes, have been described <1995ANY391>.
(i) From phenols and phosgene A continuous process is reported for the preparation of monofunctional aromatic chloroformates. Thus para-cumylphenol in methylene chloride reacted with phosgene in the presence of excess of aqueous sodium hydroxide gave a very good yield of the chloroformate with trace amounts of the diaryl carbonate impurity <2000WOP0058259> (Equation (12)). Other similar approaches are also known <2001WOP0132598, 1994JAP06135900, 1994USP5332841, 1993RUP1240016, 1993RUP1235148, 1996EUP743298, 2000WOP0051964>.
416
Functions Containing a Carbonyl Group and at Least One Halogen O OH Cl
O
NaOH
ð12Þ
COCl2
+
Synthesis and application of 3,5-di-t-butylbenzyl chloroformate for the protection of amino functions and the improvement of solubility in polyurethane synthesis have been reported <1999JPR29> (Equation (13)). O OH +
COCl2
NaOH
O
Cl
ð13Þ
Arylene bis(chloroformates), precursors for cyclic oligomeric carbonate monomers, are prepared by three methods: using PhNEt2 to scavenge HCl, by low pH, low-temperature interfacial condensation of bisphenols with phosgene, and using Ca(OH)2 in interfacial condensation with phosgene <1995MI179> (Equation (14)). O OH
Cl
O +
2COCl2
OH
AIBN
ð14Þ O
Cl O
Chiral resolution of 1,10 -binaphthalene-2,20 -diol and its ()-menthyl chloroformate derivatives by high-performance liquid chromatography has been reported using the urea derivative as a chiral stationary phase <2002MI217>.
(ii) From alcohols and phosgene Chloroformates are prepared by dissolution of water-soluble alcohols having a melting point 20 C in H2O and reaction with phosgene. Trimethylolpropane reacted with phosgene in H2O under ice cooling for 1 h to give 72% trimethylolpropane trischloroformate <2000JAP273066> (Equation (15)). CH2OH CH2OH CH2OH
CH2OCOCl +
3COCl2
CH2OCOCl CH2OCOCl
ð15Þ
Chloroformates are prepared by treating alcohols with molecular sieves followed by reaction with phosgene. Thus, s-butyl alcohol was treated with molecular sieves at room temprature for 15 h, and reacted with phosgene to give 96% s-butyl chloroformate <1999JAP11302230> (Equation (16)). + OH
ð16Þ
COCl2 OCOCl
Chloroformates have also been prepared by phosgenation of alcohols under pressure <1999WOP9911597>, under reduced pressure <2002EUP1216983>, as well as in the presence of activated carbon <1999GEP19737329>. Under the reduced pressure conditions, phosgene has been replaced by either diphosgene or triphosgene <2002EUP1216983>.
Functions Containing a Carbonyl Group and at Least One Halogen
417
Hydroxyalkyl (meth)acrylate chloroformates are prepared by reaction of hydroxyalkylated acrylate or methacrylate esters with chloroformylation agents in the presence of H2O. 2-Hydroxyethyl methacrylate was treated with COCl2 in the presence of H2O at 0 C for 2 h to give 78% chloroformate <1998JAP10130205> (Equation (17)). CH3 +
O
COCl2
OH
O
CH3
NaOH
O O
ð17Þ OCOCl
Purification of methacryloyl-terminated chloroformates is done in high yields by mixing them with hydrocarbon solvents and removing polymerized product by filtration <2001JAP288145>. A convenient process for the synthesis of glyoxylate-derived chloroformates has been developed. The approach involves the reaction of glyoxylate esters with triphosgene and pyridine in various solvent systems. These novel glyoxylate-derived chloroformates are multifunctional, possessing a chloroformate, ester, and haloalkyl moiety <2002S365>. The synthesis of benzyl chloroformate from benzyl alcohol and phosgene was studied. The application of benzyl chloroformate in polypeptide synthesis has been introduced <2001MI35>.
(iii) Chlorination of carbonate Trichloromethyl chloroformate is prepared from methyl formate or methyl chlorocarbonate in reactor under stirring using an ultraviolet (UV) high-pressure mercury lamp <1998PRP1172102> (Equation (18)). +
CH3OCOOCH3
Cl2
Cl3COCOCl
ð18Þ
(iv) Preparation of -halogenated chloroformates from aldehyde and phosgene -Chlorinated chloroformates, useful as pharmaceutical intermediates, are prepared by the reaction of phosgene with an aldehyde in the presence of a catalyst comprising alkyl-substituted guanidines, hexa-substituted guanidinium chlorides, or bromides. Thus, acetaldehyde reacted with phosgene in the presence of pentabutylguanidine, producing 1-chloroethyl chloroformate in 88.9% yield <1998USP5712407> (Equation (19)). Similarly, benzaldehyde-derived chloroformates have also been made and used in the synthesis of novel insecticides <2001TL7751>. H + O
COCl2
O
Cl
ð19Þ O
Cl
(v) Preparation of -halogenated chloroformates by halogenation of chloroformates An improved process for concurrently preparing 1-chloroethyl chloroformate and 2-chloroethyl chloroformate with improved selectivity, was achieved by chlorination of ethyl chloroformate, optionally in presence of a free radical initiator. Ethyl chloroformate was chlorinated with chlorine gas in the presence of a free radical initiator 2,2-azobis(2-methylpropanenitrile) to give a mixture of 1-chloroethyl- and 2-chloroethyl-chloroformate <1994USP5298646>. Preparation of trichloromethyl chloroformate has been achieved by a photochemical chlorination process of methyl chloroformates. For example, this process comprises adding PCl5 to methyl chloroformate and heating to 30–50 C under light, treating with chlorine for 70–80 h while absorbing HCl with lime water <1998PRP1192434> (Equation (20)). CH3OCOCl
+
PCl5
Cl3COCOCl
ð20Þ
Preparation of chloromethyl chloroformate was done by free radical chlorination, using sulfuryl chloride and 2,20 -azobisiobutyronitrile (AIBN), of methyl chloroformate. The product, chloromethyl chloroformate, thus obtained was reacted with alcohols to give alkoxycarbonyloxymethyl
418
Functions Containing a Carbonyl Group and at Least One Halogen
chlorides as intermediates for pharmaceuticals <1996JAP08040986> (Equation (21)). Chloromethyl chloroformate has also been used in the synthesis of trichloroacryloyl chloride <1993MI001>. CH3OCOCl
+
SO2Cl2
ð21Þ
ClCH2OCOCl
(vi) Nonphosgene methods Chloroformate esters are prepared by treating 1 mol of HCl or nitrosyl chloride with 0.1–100 mol of nitrite esters and CO in the presence of Pt-group metal catalysts. A mixture of HCl, CO, MeONO, NO, and MeOH (0.6:6:7:2:8) was passed through PdCl2/alumina at 60 C to give 100% ClCO2Me <1994JAP06306017> (Equation (22)).
HCl
+ CO
+
MeONO +
NO +
MeOH
PdCl2/Al2O3
MeOCOCl
ð22Þ
Chloroformate esters are also prepared by treating 1 mol of chlorine with 0.1–100 mol of nitrite esters and CO in the presence of supported Pt-group metal catalysts. A mixture of chlorine, CO, MeONO, NO, and MeOH (1:7:6:2:6) was passed through PdCl2/alumina at 120 C to give 18% ClCO2Me (based on chlorine) <1994JAP06306016>. Similar preparations are reported for the synthesis of alkyl chloroformate where the methyl nitrite has been replaced with alkyl nitrite ester <1994BCJ2554>. Methyl chloroformate has been synthesized via direct interaction of palladium bis(methoxycarbonyl) complexes with CuCl2 <1993JOM243> (Equation (23)). ClCOOMe has been obtained in 80% yield by reaction of [PdL2(COOMe)2] [L2 = 2,20 -bipyridine (bipy) or 1,10-phenanthroline (phen)] with CuCl2. [Pd (bipy) (COOMe)2]
+
4CuCl2
THF
ð23Þ
MeOCOCl
Benzyl chloroformate synthesis using carbon monoxide as a carbonyl source has been reported <2002T10011>. A novel nonphosgene synthetic method for benzyl chloroformate has been established. SMe O–benzyl carbonothioates were prepared by the carbonylation of benzyl alcohols with carbon monoxide and sulfur (or carbonyl sulfide) in the presence of 1,5-diazabicyclo[5.4.0]undec-5-ene (DBU) followed by esterification using methyl iodide in good yields. Then, the benzyl chloroformates were successfully synthesized by the chlorination of SMe O–benzyl carbonothioates using sulfuryl chloride in excellent yields (Equation (24)). CH2OH +
CO
S/DBU
CH2OCOSMe
SCl2
CH2OCOCl
ð24Þ
A novel synthetic method for benzyl chloroformate using carbon monoxide or carbonyl sulfide as a carbonyl source has been established. Benzyl chloroformate was successfully synthesized by the chlorination using sulfuryl chloride of PhCH2O2CSMe, which was prepared by the carbonylation of benzyl alcohol with carbon monoxide and sulfur (or carbonyl sulfide) in the presence of DBU (1,5-diazabicyclo[5.4.0]undec-5-ene) followed by esterification using methyl iodide <2002TL7765>.
(vii) Other chloroformates An oxime of an estradiene derivative was reacted with phosgene or diphosgene to give a chloroformate derivative <2002GEP10056677> (Equation (25)).
419
Functions Containing a Carbonyl Group and at Least One Halogen HO
O
Cl
N
N
O OR
H Me
OR
H CH2OR
Me
COCl2
CH2OR
ð25Þ
H
H O
O
Methyl 11C-labeled methyl chloroformate, a novel 11C-acylating agent, was formed by the reaction of 11C-labeled methanol and phosgene <1995MI365>.
6.14.4.1.3
Bromoformate esters
From COFGT (1995) <1995COFGT(6)407> it is known that these compounds, bromoformate ester, are prepared by two approaches. One using the reaction of alcohols with carbonyl dibromide, and two using the bromide exchange reaction on the chloroformates. Up until the end of 2003, no new approaches have been reported for making bromoformate esters.
6.14.4.1.4
Iodoformate esters
Stable iodoformates were reported in COFGT (1995) <1995COFGT(6)407>. The first iodoformate, 9-triptycyl iodoformate, was made photochemically from its 9-triptycyl monoester of oxalic acid. Iodoformates have also been synthesized by using the iodide exchange reaction on chloroformates. Up until the end of 2003, there have not been any new approaches to the synthesis of iodoformates.
6.14.4.2
One Halogen and One Sulfur
Similar to the oxygen system of haloformate esters, here again in the halothiolformate esters the synthetic methods mentioned in COFGT (1995) <1995COFGT(6)407> are summarized in Scheme 5. The insertion of carbon monoxide to sulfenyl halide, the nucleophilic displacement of one of the halogen in carbonyl dihalide with a thiol, and the halogen exchange on a halothiolformate are the three general routes to halothiolformate esters. COX2
RSH –HX
RSCOX
RSCl
CO
X1–
RSCOX1 + X–
Scheme 5
Structures and conformations of (fluorocarbonyl)trifluoromethylsulfane and that of (chlorocarbonyl)trifluoromethylsulfane have been determined by gas electron diffraction, vibrational spectroscopy, and theoretical calculations <1997JPC2173>.
6.14.4.2.1
Fluorothiolformate esters
The preparation of fluorocarbonyl sulfenyl bromide from fluorocarbonyl sulfenyl chloride and trimethylsilyl bromide was described in COFGT (1995) <1995COFGT(6)407>. A photochemical
420
Functions Containing a Carbonyl Group and at Least One Halogen
study has been done with this compound. Under photochemical conditions, this fluorothiolformate ester eliminates carbon monoxide to give sulfur bromide fluoride <1993IC948>.
6.14.4.2.2
Chlorothiolformate esters
Here one should be careful not to confuse the thiono formates, with sulfur in the thiocarbonyl group (C¼S), with that of thiol formates, with sulfur in the thiol group (CS). In some cases the thiono formates could rearrange to thiol formates as seen with the allylic thiono chloroformates.
(i) From phosgene and thiols Thiochloroformates are manufactured with reduced amount of by-products by reacting thiols with phosgene in the presence of ureas as a catalyst. For example, phosgene and n-octanethiol with N,N-dimethylpropyleneurea as the catalyst, gave mainly n-octylthio chloroformate with very small amounts of thiocarbonate and disulfide as impurities <1999GEP19737619>.
(ii) By rearrangement of allylic thionochloroformates Treatment of allylic alcohols with thiophosgene and pyridine gives thiolo chloroformates directly at rt, presumably via a very rapid [3,3]-sigmatropic rearrangements of thionochloroformates. Synthesis of allyl thionochloroformate from allyl alcohols sodium hydride and thiophosgene at low temperature and warming up to rt supports this finding <1999TL8059>. Thiophosgene, as seen above, has been used in the synthesis of thiochloroformates. General reviews on the industrial synthesis of thiophosgene and derivatives are available <1998MI252, 1997OPRD240>.
6.14.4.2.3
Bromothiolformate esters
These compounds, bromothiolformate esters, have rarely been reported <1995COFGT(6)407>. Bromide exchange on a fluorothiolformate has been reported to make trifluoromethyl bromothiolformate and carbon monoxide insertion on methylsulfenyl bromide has been used to make methyl bromothiolformate. Up until the end of 2003, new methods for the synthesis of bromothiolformate esters were not found in the literature.
6.14.4.2.4
Iodothiolformate esters
Similarly to what was reported in COFGT (1995) <1995COFGT(6)407>, the present authors did not find any reference to this class of compounds in the period up to 2003.
6.14.4.3
One Halogen and One Nitrogen
The general methods reported in COFGT (1995) <1995COFGT(6)407> for the preparation of the above-mentioned compounds are summarized in Scheme 6. The reaction of carbonyl dihalide with primary, secondary, and tertiary amines leads to carbamoyl halides, which in the case of a primary amine could further be converted into isocyanates, an important industrial compound. The secondary amine carbamoyl halides could also be synthesized from either carbon monoxide insertion into dialkyl haloamines, or halogenation of N,N-dialkyl formamides. Halo cyanato and halo thiocyanato carbonyl compounds are made by nucleophilic displacement of the corresponding anions source with a carbonyl dihalide.
421
Functions Containing a Carbonyl Group and at Least One Halogen SCNCOCl SCN– R1R2R3N
R1R2R3N+COCl Cl
RNH2
COCl2
HCl
RNHCOCl
RNCO
–
NCO–
R1R2NH R1R2NCl
OCNCOCl
R1R2NCOCl
CO
Cl2 R1R2NCOH
Scheme 6
6.14.4.3.1
Carbamoyl fluorides
Carbamoyl fluorides formed by the addition of hydrogen fluoride on to an isocyanate are used as fluorinating agents, specifically for converting a chloride into a fluoride. For example, para(trifluoromethyl)phenyl isocyanate is prepared from para-(trichloromethyl)phenyl isocyanate and hydrogen fluoride in the presence of tin tetrachloride. A carbamoyl fluoride is suggested as the intermediate in this reaction, which is isolated in small amounts from the reaction mixture <2002WOP0255487> (Scheme 7).
O C
O C
O HN
N +
HF
F
HN
N
SnCl4
CCl3
O F
+
CCl3
CF3 97%
CF3 3%
Scheme 7
Experimental and theoretical investigations of the geometry and conformation of fluorocarbonyl isocyanate and fluorocarbonyl azide were carried out. These were compared with that of their corresponding precursors, formyl isocyanate and formyl azide, respectively. The present authors warn that fluorocarbonyl azide is an explosive and should be handled only with proper safety precautions and in millimolar quantities <1993JST197>. N-fluoroformyliminotrifluoromethylsulfur fluoride, FCON¼S(F)CF3, has been studied using vibration spectroscopy and theoretical calculations <2000MI881>.
6.14.4.3.2
Carbamoyl chlorides
Carbamoyl chlorides have also been made using the phosgene substitute, trichloromethyl carbonate or triphosgene. The effects of solvent, reaction time and temperature, feed ratio, and dosage of nucleophile on the yield have been discussed <2000MI16>. Solid-phase synthesis of ureas of secondary amines via carbamoyl chloride has been reported. Secondary amines attached to a solid support such as the Wang resin can be converted to the corresponding carbamoyl chlorides by treatment with phosgene or triphosgene <1997TL1895>.
422
Functions Containing a Carbonyl Group and at Least One Halogen
A novel synthesis of 3-substituted 1-chlorocarbonylimidazolidin-2-ones using triphosgene or bis(trichloromethyl)carbonate has been reported. The yields and purity of the products obtained are better than those obtained by a conventional method using phosgene <2000JCR(S)440, 2000OPP498>. New and efficient palladium-catalyzed routes to carbamoyl chlorides have been reported. The palladium-based catalytic system is very active and operates in two steps, avoiding the synthesis of phosgene, but making use of carbon monoxide and chlorine as in phosgene chemistry. Primary amines lead directly to isocyanates and the secondary amines lead to carbamoyl chlorides <2000OM3879>.
6.14.4.3.3
Carbamoyl bromides
Carbamoyl bromides or N-bromocarbonyl compounds have been made as reported in COFGT (1995) <1995COFGT(6)407> using the general methods used for the preparations of carbamoyl halides. The addition of hydrogen bromide to an isocyanate or the exchange of chloride in carbamoyl chlorides with a bromide source are the two common approaches to the synthesis of carbamoyl bromides. Up until the end of 2003, new methods for the synthesis of carbamoyl bromides have not been seen in the literature.
6.14.4.3.4
Carbamoyl iodides
These compounds are suggested to be not very stable according to COFGT (1995) <1995COFGT(6)407>. Only one approach, that of addition of hydrogen iodide to an isocyanate, has been reported for the synthesis of carbamoyl iodides. There have been no new reports on the synthesis of this class of compounds, up to the end of 2003.
6.14.4.4
One Halogen and One Phosphorus
Synthesis of compounds belonging to this section, mentioned in COFGT (1995) <1995COFGT(6)407>, is summarized in Scheme 8. The trivalent phosphorus compounds could further react either by elimination of CO to give phosphorus halide, or by elimination of hydrogen halide to give phosphaketene. The reaction of trisalkoxy phosphorus with carbonyl dihalide gives alkyl halide and (dialkoxyphosphinyl)formyl halide, a pentavalent phosphorus compound (Arbuzov reaction).
R1R2PSiMe3
COCl2
R1R2PCOCl
R1R2PCl
R2 = H
R1P=C=O (RO)2POCOCl + RCl
(RO)3P + COCl2
Scheme 8
6.14.4.4.1
Chlorocarbonyl derivatives of phosphorus(III)
The reaction of triphenylmethyl-substituted primary and secondary phosphines with phosgene has been studied. The nature of the product with the trityl-substituted primary phosphine depends on the nature of the solvent. In toluene, the initially formed chlorocarbonyl phosphorus compound is stable, but it loses CO in methylene chloride to give a chlorophosphine, and loses HCl in ether
Functions Containing a Carbonyl Group and at Least One Halogen
423
solvent to give a phosphaketene, which dimerizes. In the case of the trityl-substituted secondary phosphine, the nature of the product depends on the nature of the second substituent on phosphorus. When the substituent was phenyl, the initial adduct, chlorocarbonyl phosphorus compound, was very stable, and when the substituent was a t-butyl the initial adduct readily lost the CO to give the corresponding chlorophosphine compound <1999ZAAC1979>. In the same paper the reaction of diphosphine with phosgene was reported. It was found to be inert in the absence of hydrogen chloride. In the presence of HCl the PP bond was cleaved to give the primary phosphine and the chlorophosphine as the products <1999ZAAC1979>. All these reactions are summarized in Scheme 9. COCl2/ether
COCl2/CH2Cl2
Ph3CPHCOCl
Ph3CPH2
Ph3CPHCOCl –CO
COCl2/ toluene
Ph3PHCl
–HCl
(Ph3CPCO)2
Ph3CPHCOCl
Ph3CPCl2 + Ph3CPRCl
(Ph3CPH)2
COCl2 R
= But
COCl2
Ph3CPRH
COCl2 HCl
Ph3CPRCOCl
R = Ph
Ph3CPH2 + Ph3CPHCl
Scheme 9
Another way these chlorocarbonyl phosphorus compounds have been made is via anhydrous HCl hydrolysis of phospha–urea compound, where the cleavage of a PCO bond occurs leading to a phosphine and a chlorocarbonyl phosphorus compound. This reaction is depicted in Scheme 10 <1999ZAAC919>.
HCl (Ph3CPH)2CO
Ph3CPH2
+
Ph3CPHCOCl
Scheme 10
6.14.4.4.2
Chlorocarbonyl derivatives of phosphorus(V)
A facile one-pot preparation of phosphonothiolformates, useful reagents for the synthesis of carbamoylphosphonates, was accomplished by sequential reaction of phosgene solution with alkane thiols, to form the chlorothiolformates, followed by Arbuzov reaction with trialkylphosphites <2000SL815>.
6.14.4.5
One Halogen and One Arsenic, Antimony, or Bismuth
As in COFGT (1995) <1995COFGT(6)407> any reports on these compounds were not seen.
6.14.4.6
One Halogen and One Metalloid (Boron, Silicon, or Germanium)
Preparation of this class of compounds has not been reported, in the period up to 2003, as was similarly observed in COFGT (1995) <1995COFGT(6)407>.
424 6.14.4.7
Functions Containing a Carbonyl Group and at Least One Halogen One Halogen and One Metal
The organometal carbonyls reactions with halogens are known to give organometal carbonyl halides <1995COFGT(6)407>. These compounds could further lose carbon monoxide to give organometal halides. The synthesis of metal bromides and their bromide oxides by the use of carbonyl dibromide must have gone through bromocarbonyl metal intermediates. Carbonyl dibromide reacted with a wide selection of d- and f-block transition-metal oxides to form either the metal bromide or bromide oxide. The reaction was done, by heating the metal oxides at 125 C for 10 days with excess carbonyl dibromide in a sealed tube. Under these conditions V2O5, MoO2, Re2O7, Sm2O3, and UO3 were converted into VOBr2, MoO2Br2, ReOBr4, SmBr3, and UOBr3, respectively <1997JCS(D)257>. No new synthetic method for this class of compounds has been seen in the period 1993–2003. All the references were to complexes with halogens and carbonyls attached directly to the metals, which are beyond the scope of this chapter.
6.14.4.7.1
Halocarbonyl complexes of first transition metal series (iron and chromium)
No new synthetic methods for this class of compounds have been reported in the period 1993–2003, other than those mentioned in COFGT (1995) <1995COFGT(6)407>.
6.14.4.7.2
Halocarbonyl complexes of second transition metal series (ruthenium and rhodium)
No new synthetic methods for this class of compounds have been reported in the period 1993–2002, other than those reported in COFGT (1995) <1995COFGT(6)407>.
6.14.4.7.3
Halocarbonyl complexes of third transition metal series (rhenium and iridium)
No new synthetic method for this class of compounds have been reported, other than those mentioned in COFGT (1995) <1995COFGT(6)407>, briefly discussed above.
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Functions Containing a Carbonyl Group and at Least One Halogen
427
Biographical sketch
Ramiah Murugan was born in Madurai, India. He obtained B.Sc. in chemistry in 1975 from American College, Madurai, Tamil Nadu, India and an M.Sc. in chemistry in 1977 from Madurai University. After four years of Junior Scientist work at Madurai University, he joined Professor A. R. Katritzky’s group at the University of Florida, USA and obtained his Ph.D. in 1987. He stayed there for two more years doing postdoctoral work in the area of high-temperature aqueous organic chemistry. He joined Reilly Industries in 1989 and is currently a Senior Research Associate. His research interests include synthesis of intermediates for pharmaceuticals, agrochemical products, and performance products; mechanistic studies; catalysis; polymer chemistry; and process development.
Subbarao Yarlagadda received his M.Sc. in organic chemistry from Andhra University, Waltair, India. He obtained his Ph.D. in 1991 from the Indian Institute of Chemical Technology (IICT), Hyderabad, India. His doctoral work was chiefly on selective organic transformations by using a new class of heterogenized homogeneous catalysts. Later, he joined as a postdoctoral fellow with Professor M. Graziani at the University of Trieste, Italy under the UNIDO program, and worked on polydentate ligands and their metal complexes for an oxidative amination reaction. From 1992 to 1996, he was a staff scientist in Dr. A.V. Ramarao’s group at IICT, India, and worked on the synthesis of fine and specialty chemicals, pharmaceutical intermediates by using zeolite catalysts. In 1996, he joined Professor P. A. Jacobs at the Katholieke University of Leuven, Belgium and worked on Mesoporous zeolites and homogeneous catalysts for the synthesis of specialty chemicals. Since July 1998, he has been with Reilly Industries, Indianapolis, IN, USA as a Research Associate. His current interests include the process development, invention of new routes for the existing products, synthesis of fine and specialty chemicals, development of new catalysts for the synthesis of pharmaceutical and agrochemical intermediates, and vitamins.
# 2005, Elsevier Ltd. All Rights Reserved No part of this publication may be reproduced, stored in any retrieval system or transmitted in any form or by any means electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without permission in writing from the publishers
Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 409–427
6.15 Functions Containing a Carbonyl Group and at Least One Chalcogen (but No Halogen) H. ECKERT Technical University Munich, Garching, Germany 6.15.1 CARBONYL CHALCOGENIDES WITH TWO SIMILAR CHALCOGEN FUNCTIONS 6.15.1.1 Two Oxygen Functions 6.15.1.1.1 Carbonates from phosgene and substitutes, chloroformates 6.15.1.1.2 Carbonates from carbon oxides and carbonate salts 6.15.1.1.3 Carbonates from ureas 6.15.1.1.4 Cyclic carbonates and transesterification 6.15.1.1.5 Acylcarbonates 6.15.1.1.6 Carbonates by iodolactonization 6.15.1.1.7 Polycarbonates 6.15.1.2 Two Sulfur Functions 6.15.1.2.1 Dithiocarbonates by [3,3]-sigmatropic rearrangement 6.15.1.2.2 1,3-Dithiol-2-ones by xanthogen disulfide-alkyne cycloaddition 6.15.1.2.3 Mixed methods 6.15.1.3 Two Selenium Functions 6.15.2 CARBONYL CHALCOGENIDES WITH TWO DISSIMILAR CHALCOGENIDE ATOM FUNCTIONS 6.15.2.1 Oxygen and Sulfur Functions 6.15.2.1.1 Thiocarbonates from activated carbonates 6.15.2.1.2 Thiocarbonates from alkoxycarbonylsulfenyl chlorides 6.15.2.1.3 Thiocarbonates from carbonothioic acid salts 6.15.2.1.4 Other methods 6.15.2.2 Other Dissimilar Chalcogenide Functions 6.15.2.2.1 Oxygen and selenium functions 6.15.2.2.2 Oxygen and tellurium functions 6.15.2.2.3 Sulfur and selenium functions 6.15.3 CARBONYL CHALCOGENIDES WITH A CHALCOGEN FUNCTION AND ONE OTHER HETEROATOM FUNCTION 6.15.3.1 Oxygen and Nitrogen Functions 6.15.3.1.1 Carbamates from chloroformates or phosgene equivalents 6.15.3.1.2 Carbamates from isocyanates 6.15.3.1.3 Carbamates from N,N0 -carbonyldiimidazole (CDI) 6.15.3.1.4 Carbamates from carbonates or dicarbonates 6.15.3.1.5 Carbamates from carbon oxides 6.15.3.1.6 Carbazates 6.15.3.1.7 Azidoformates 6.15.3.2 Oxygen and Phosphorus Functions 6.15.3.2.1 Phosphinecarboxylates by the Arbuzov reaction and related methods 6.15.3.3 Oxygen and Other Heteroatom Functions 6.15.3.3.1 Oxygen and boron functions
429
430 430 430 432 433 433 434 434 435 435 435 435 436 436 436 436 436 437 437 438 438 438 439 440 440 440 440 441 441 442 443 444 444 444 444 445 445
430
Functions Containing a Carbonyl Group and at Least One Chalcogen
6.15.3.4 Sulfur and Nitrogen Functions 6.15.3.4.1 Thiocarbamates from chlorothioformates and amines 6.15.3.4.2 Thiocarbamates from carbamoyl chlorides and thiols 6.15.3.4.3 Thiocarbamates from isothiocyanates and alcohols 6.15.3.4.4 Thiocarbamates from alkylamide salts, carbon monoxide, and sulfur 6.15.3.4.5 Thiocarbamates from [3,3]-sigmatropic rearrangement 6.15.3.4.6 Thiocarbamates from trichloroacetyl chloride, thiols, and amines 6.15.3.5 Sulfur and Phosphorus Functions 6.15.3.5.1 Phosphonothioformates 6.15.3.6 Other Mixed Systems 6.15.3.6.1 Selenium and nitrogen functions 6.15.3.6.2 Tellurium and nitrogen functions
6.15.1
445 445 445 446 446 446 447 447 447 447 447 449
CARBONYL CHALCOGENIDES WITH TWO SIMILAR CHALCOGEN FUNCTIONS
An overview on all functional group transformations, which can be accomplished by use of phosgene as well as by use of about 70 phosgene substitutes and equivalents, has been presented in 2003 by Cotarca and Eckert in Phosgenations—A Handbook .
6.15.1.1
Two Oxygen Functions
Carbonic acid is principally a difunctional carboxylic acid; therefore, manifold preparative accesses for a great variety of its organic derivatives exist, which differ widely in rate and selectivity of reactions and reagents. Some reviews have been published .
6.15.1.1.1
Carbonates from phosgene and substitutes, chloroformates
Phosgene, as the formal carboxylic acid dichloride of carbonic acid, is a highly reactive reagent, which affords high turnovers and good yields. Thus, both symmetrical and unsymmetrical dicarbonates, the latter via chloroformates, can easily be produced. A key intermediate of the decalin part of azadirachtin, an antifeedant, insect growth regulatory, and reproductive effective substance from the Neem tree Azadirachta indica, has been prepared by carbonylation of the alcohol with methyl chloroformate, affording the carbonate (Equation (1)) <2000S1878>. O
TBDMS O
O
O
TBDMS O
O
Cl-CO2Me
OH O
O
ð1Þ
Pyridine, DCM 0 °C, 70 min, then, rt, 40 min 70%
O O
OMe
O O
During a nice enantioselective total synthesis of epothilone A using multifunctional asymmetric catalysis (Suzuki cross-coupling of fragment A with fragment C, followed by Yamaguchi lactonization), the reaction of the aldehyde with TMS-acetylide affords an alcohol, which is methoxycarbonylated with methyl chloroformate resulting the carbonate (Equation (2)) <2000JA10521>. _
Li + THF, –78 °C 40 min
i. TMSS N CHO OTBS
O
S N
O
ð2Þ
O
ii. MeOCOCl 30 min, 79%
OTBS
TMS
431
Functions Containing a Carbonyl Group and at Least One Chalcogen
A carbonate intermediate for the synthesis of functionalized ‘‘pyridoindoles,’’ which have attracted great interest by virtue of their cytotoxic activity toward leukemia cells, has been prepared by using ethyl chloroformate <2001T4787>. Phenyl chloroformate has been employed in the cyclocarbonylation reaction to prepare an intermediate in synthesis of solanoeclepin A <2000CC1463>. Functionalization of taxol, which is a powerful anticancer drug, in the position 2, is an important pharmaceutical tool. This can be achieved advantageously by cyclocarbonylation of the 1,2-diol at 13-deoxy-7-TES baccatin III with phosgene yielding 95% of the corresponding 1,2-cyclocarbonate (Equation (3)), which will further be reacted with alkyllithium compounds to afford 2-acylbaccatin derivatives under ring opening of the 1,2-cyclocarbonate <1994CC295>. AcO
O
AcO
OTES
O
OTES
COCl2 1
2
H
HO
OH
Pyridine 25 °C, 30 min 95%
O OAc
1
2
H
O
O
ð3Þ
O OAc
O
A highly interesting synthetic route for preparing intermediates of ‘‘retinal’’ comprises a palladium-catalyzed transformation of an ‘‘yne-carbonate’’ into an ‘‘allenyl enal.’’ The carbonate is prepared by unsymmetrical carbonylation of propargylic alcohol and silyl enol ether with phosgene, each step with 90% yield (Scheme 1) <1994TL7383>. Ph
Ph
Cat. Pd(PPh3)4
i. BuLi O
OH ii. COCl2
Ph
O
CHO
–CO2
O
90%
iii. TMSO MeLi 90%
Scheme 1
In all reactions previously described phosgene is the basic chemical for the preparation of carbonates in a direct way as well in the synthesis of the chloroformates. Phosgene itself is a poisonous gas which was discovered in 1812 by Davy from the action of sunlight on carbon monoxide and chlorine. Extensive safety precautions are required to prevent exposure to phosgene during handling. In order to avoid the difficulties associated with the toxicity of phosgene gas, equivalents and substitutes for phosgene as well as the ‘‘safety phosgenation’’ have been developed . Another often used phosgene equivalent to accomplish carbonylation reactions is the solid 1,10 -carbonyldiimidazole (CDI). The conversion of (RS)-sec-phenethyl alcohol to its 2,2,2-trifluoroethylcarbonate, which is needed for the resolution of ‘‘chiral alcohols,’’ by using CDI in good yield has been described (Scheme 2) <2000TA1279>. O
O O
OH
N N
O
N
CDI
N
N
O
N CF3
OH
10% DMAP DCM, rt, 24 h 85%
DCM, rt, 2 h 98%
Scheme 2
O
CF3
432 6.15.1.1.2
Functions Containing a Carbonyl Group and at Least One Chalcogen Carbonates from carbon oxides and carbonate salts
The bulk chemical diphenyl carbonate (DPhC), which is an important reagent in the manufacture of polycarbonates, has been produced by the oxidative carbonylation of phenol with carbon monoxide (CO) and air-oxygen catalyzed by Pd dinuclear complexes and redox catalyst (Equation (4)) <1999JMOC(148)289, 2000JMOC(154)243>. Reaction proceeds smoothly on a Pd dinuclear complex bridged with a pyridylphosphine ligand [Pd2(Ph2Ppy)2X2] and redox catalyst along with ammonium halide in the presence of CO and air at 100 C and the TOF reaches 19.21 (mol-DPhC/mol-Pd h). OH CO, O2
O H2O
+
2 Pd2(Ph3PPy)2Cl2 Redox catalyst
ð4Þ
O
O
DPhC
NH4Cl, 100 °C
Dialkylcarbonates have been prepared from CO2 and alkanols under Appel conditions by using tri-(1-butyl)-phosphane, tetrabromomethane, and cyclohexyl tetramethylguanidine (CyTMG). This strong, hindered, and non-nucleophilic base is more effective than other bases such as DBU. DMF is the solvent of choice (Equation (5)) <1996CL825>. Yields of dialkyl carbonates derived from various primary alkanols are 54–91%; from secondary alkanols they are 14–22%. + 2ROH
+
n-Bu3P
CyTMG
CBr4
DMF 54–91%
CO2 +
+
O OR
n-Bu3P=O
ð5Þ
OR +
CHBr 3
A three-component coupling system of aliphatic alcohol/CO2/alkyl halide under a pressure of 160 psig CO2 and in the presence of a peralkylated guanidine has been applied to prepare dialkylcarbonates <1995JOC6205>. Thus, di-1-butylcarbonate is obtained in 73% yield (by GC). An approach to synthesize ‘‘mixed’’ dialkylcarbonates employs the above three-component coupling system aliphatic alcohols/CO2/alkyl halides in the presence of Cs2CO3 and without pressure of CO2 (Scheme 3). This method shows a great variety in use of alcohols and alkyl halides (Table 1), reaction times are 2.5–23 h, yields of the resulting mixed dialkylcarbonates are 91–98% <1999JOC4578>.
Ph
OH
Ph
OBu
O O
Cs2CO3 TBAI
DMF 23 °C, 3.5 h
_
Ph
O
Cs +
1-BuBr CO2
92% _
Ph
O
O
Cs +
O
Scheme 3
One of the most attractive synthetic goals starting from CO2 is the bulk chemical dimethylcarbonate (DMC). An approach is the organostannane-catalyzed reaction of dehydrated derivatives of methanol (ortho-ester and acetals) with ‘‘supercritical’’ CO2 <1999JA3793, 1998JOC7095, 2000POL573>. The reaction of acetals is especially attractive because the starting material is much less expensive compared with ortho-esters, and the co-produced acetone can be recycled (Scheme 4).
Functions Containing a Carbonyl Group and at Least One Chalcogen
433
Dialkyl carbonate formation using alcohols, halides, and CO2 in the presence of Cs2CO3
Table 1
Alcohol (ROH)
Halide (R0 -X)
4-Phenylbutanol
t-Butyl 2-bromoacetate Benzyl chloride Allyl bromide s-Butyl bromide n-Butyl bromide t-Butyl 2-bromoacetate Benzyl chloride n-Butyl bromide MPMCl
2-Phenylpropanol
Time (h)
Yield (%)
5 2.5 4 23 4.5 5 3 5 3
95 94 91 98 92 96 98 96 92
Source: <1999JOC4578>.
O
O
Supercritical CO2 MeO cat. Me2Sn(OMe)2
O
O + OMe
+2 MeOH –H2O
Scheme 4
6.15.1.1.3
Carbonates from ureas
Processes to produce DMC in high yield are of great interest. There is a need for low-cost DMC, because it becomes more and more important in fuel application as a gasoline additive. DMC has many desirable properties: almost 3 times the oxygen content of methyl t-butyl ether (MTBE), good octane for blending (RON of 130), lower volatility than MTBE, and biodegradability. Reaction of methanol with urea to give DMC is a well-known low-yield synthesis, but the use of triethylene glycol dimethyl ether (triglyme) as a solvent, in conjunction with tin catalysts, affords high yields of DMC to be realized (Scheme 5) <1999USP5902894, 1998JAP10259165>. More details on this process are also described in . O
O H2N
NH2 + 2MeOH
NH2
H2N
2NH3 + CO2 Diglyme tin-cat. 180 °C
+ H2O
O OMe + 2NH3
MeO
O 2MeOH +
CO2
98% MeO
OMe
+ H2O
DMC
Scheme 5
6.15.1.1.4
Cyclic carbonates and transesterification
Transesterification is used industrially to produce DMC and diethylcarbonate as shown in recent patents. Dowex MSA 1, CoYO, and Y2O3 are used as catalysts (Equation (6)) <1992JAP04198141, 1997JAP09040616, 2001JAP2001316332>.
434
Functions Containing a Carbonyl Group and at Least One Chalcogen O
O
Cat. O
O
+ 2MeOH
OMe
MeO
+
OH
HO
ð6Þ
DMC
The above-presented process with CoYO as catalyst is also employed in the production of diphenyl carbonate (DPhC) in 95% yield from ethylene carbonate (EC) (Equation (7)) <1997JAP09040616>. It is a continuous process using a fixed bed reactor at 130 C, a pressure of 9 kg cm2, and an LHSV of 3 h1. O O
i. MeOH ii. PhOH O
O
Cat., 130 °C 95%
O
+
OH
HO
ð7Þ
O
DPhC
(i) Enzyme catalysis In a transesterification process by selective alkoxycarbonylation using enzymes in organic solvents as catalysts, the A-Ring precursor of vitamin D3 has been prepared. Candida antarctica lipase (CAL) is found to be the best catalyst in toluene (Equation (8)). Other enzymes are PSL and CVL, other solvents are THF and 1,4-dioxane, yields of alkoxycarbonylation products depend strongly on conditions and are 17–100%. Regioselective alkoxycarbonylation occurs only at the C-5-(R) hydroxy group <1997JOC4358, 2001JOC4227>.
Enzyme Cal Toluene
O + HO
O
O
N
30 °C, 4 h 100%
OH
ð8Þ
O O
O
OH
Enzymatic acylation in organic solvents has also been employed to synthesize water-soluble Paclitaxel derivatives. Thus, potential new ‘‘prodrugs’’ can be generated possessing high solubility in water. The approach involves an enzymatic acylation of ‘‘paclitaxel’’ with a bifunctional acylating reagent, catalyzed by enzyme ‘‘thermolysin’’ (from ‘‘bacillus thermoproteolyticus rokko’’) to give an activated carbonate dervative (conversion 83%) <1997JA11554>.
6.15.1.1.5
Acylcarbonates
A detailed review on di-t-butyldicarbonate (BOC2O), a widely used standard reagent for the introduction of the BOC-group, in its reactions with alcohols in the presence of DMAP is given by Hassner and Basel <2000JOC6368>. Many general procedures for reactions of BOC2O with common alcohols affording O-BOC-derivatives and/or symmetrical carbonates are described (Equation (9)). O
O ROH +
But O
O
O But
BOC2O
6.15.1.1.6
MeCN
O
O
DMAP RO
OBut
+ RO
OR
ð9Þ
Carbonates
Carbonates by iodolactonization
An intermediate carbonate 1 for an iodolactonization reaction has been accomplished by using the acylcarbonate BOC2O in excellent yield of 98% <1999JOC3798>.
Functions Containing a Carbonyl Group and at Least One Chalcogen
435
O-But H
O
O C6H11 1
6.15.1.1.7
Polycarbonates
For polycarbonates there is a huge and fast-growing market. They are excellent engineering thermoplastics and substitutes for metals and glass because of their good impact strength, heat resistance, and transparency, which makes it an ideal material for optical data-storage devices. A number of synthetic routes for producing polycarbonates have been described. During this process phenol is removed by distillation and recycled by transesterification with DMC to afford DPhC which is employed again in the polycarbonate production process <1994CBR970, 1996PAC367, B-2003MI615-05>.
6.15.1.2 6.15.1.2.1
Two Sulfur Functions Dithiocarbonates by [3,3]-sigmatropic rearrangement
Alkylxanthate undergoes a thermal [3,3]-sigmatropic rearrangement to form the dithiocarbonate, which is the starting material for a novel rearrangement of allylic thionitrites to thioepoxides (Equation (10)) <2002CC2394>. R1
S R3
6.15.1.2.2
S
ð10Þ
SMe
Reflux, 7 h
R2
R1
R3
THF
SMe
O
R2 O
1,3-Dithiol-2-ones by xanthogen disulfide-alkyne cycloaddition
1,3-Dithiol-2-ones (cyclic dithiocarbonates) have been prepared in a single-step synthesis from diisopropylxanthogen disulfide and an alkyne in a radical cycloaddition reaction <1995CC1429, 1998H2003, 2003OBC129>. The method is versatile and provides good yields; in particular, with arene-substituted alkynes, starting materials are commercially available. The radical cyclization is initiated by AIBN <1995CC1429> (Scheme 6). The scope of the reaction can be extended to some alkenes such as bornene and norbornene <1998H2003>. S S
O
S
AIBN
O
S
2
Heat
O
S
.
S R
.
O S +
R
. S
R
R=
*
*
O
S
76–82% S
MeO
* CO2Me
Scheme 6
* HO
*
436
Functions Containing a Carbonyl Group and at Least One Chalcogen
This proven method has been applied to the preparation of an intermediate of molybdopterin, where the needed alkynes are disubstituted, yields are similar to those reactions with monosubstituted alkynes (Equation (11)) <2003OBC129>. For work-up only flash chromatography is necessary. O O O
S
H
N
AIBN Toluene
N
S
H
N
2 x 1.5 h Reflux 77%
+ S O
S
ð11Þ
O
N
O
O
S S
6.15.1.2.3
Mixed methods
Besides these classical methods some less common synthetic approaches have been published. Benzo-1,3-dithiol-2-ones are important precursors for tetrathiofulvalenes (TTFs) which have been successfully used as building blocks for low-dimensional organic conductors and superconductors. They have been prepared from benzo-1,3-dithiol-2-thiones (Equation (12)) <2003AG(E)2765>. By the same method a 1,3-dithiol-2-one intermediate has been prepared for the synthesis of a zinc(II) phthalocyanine derivative functionalized with four peripheral substituted TTF units <2002JHC1071>. OTBDPS
OTBDPS
S
Hg(OAc)2
S
DCM, AcOH 85%
S
S S OTBDPS
6.15.1.3
O
ð12Þ
OTBDPS
Two Selenium Functions
An unusal synthesis of Se,Se0 -diphenyldiselenocarbonate has been accomplished by the reaction of dipotassium nitroacetate with benzeneselenyl bromide in 19% yield (Equation (13)) <2001CC1390>. The product is thermally unstable. K+ _ KO2C
6.15.2
O NO2
+ 2PhSeBr
ð13Þ
MeOH 1 h, 19%
PhSe
SePh
CARBONYL CHALCOGENIDES WITH TWO DISSIMILAR CHALCOGENIDE ATOM FUNCTIONS
6.15.2.1 6.15.2.1.1
Oxygen and Sulfur Functions Thiocarbonates from activated carbonates
A simple and efficient procedure has been developed for a one-pot synthesis of substituted benzothiazine-2,4-diones from thiosalicylic acid and amines. Both functional groups of thiosalicylic acid are reacted and activated, recpectively, with ethyl chloroformate affording the intermediate thiocarbonate in 62% yield (Scheme 7) <2003H115>.
Functions Containing a Carbonyl Group and at Least One Chalcogen O
O CO2H + 2ClCO2Et SH
2Et3N
OEt
O
CHCl3
437
S O
H2N
OEt
62%
O N H S O
OEt
+ CO2 + EtOH
Scheme 7
An alkyl chloroformate has also been employed to form thiocarbonates from thiols for the ‘‘desymmetrization’’ of 2,20 ,6,60 -tetramethoxybiphenyl by a regioselective sulfenylation reaction <2001TA3313>. This provides an access to C2-symmetric sulfur derivatives. Resolution of 2,20 ,6,60 -tetramethoxy-3,30 -dimercapto1,10 -biphenyl was achieved by conversion to the corresponding dithiocarbonate diastereomers. During the synthesis of potential plant protecting compounds on basis of 2,3-didehydrothiazole2-thione, isobutyl chloroformate has been used to acylate the tautomeric form of the thione catalyzed by lead nitrate affording the corresponding thiocarbonate in 89% yield (Equation (14)) <2000JPR554>. But
H N
S S
6.15.2.1.2
+ ClCO 2Bui
Cat. Pb(NO3)2
But
N S
DCM, Et3N 89%
OBui
S
ð14Þ
O
Thiocarbonates from alkoxycarbonylsulfenyl chlorides
For synthesis of the two conformationally different ‘‘tetrathiacyclododecino tetraindoles’’ the intermediate 3,30 -bis(methoxycarbonylsulfenyl)-2,20 -biindolyl has been prepared from 2,20 bisindolyl- and methoxycarbonylsulfenyl chloride in excellent yield of 94% (Equation (15)) <2002EJO1392>. Reaction occurs at rt within 2 h and needs no Friedel–Crafts catalyst. OMe O H N N H
S
MeO2CSCl DCM, rt, 2 h 94%
H N
ð15Þ N H
S
O
MeO
6.15.2.1.3
Thiocarbonates from carbonothioic acid salts
As described above, S-methyl O-benzyl carbonothioates with substituted phenyl groups have been prepared by carbonylation of benzyl alcohols with carbon monoxide and sulfur (or carbonyl sulfide) in the presence of DBU followed by esterification using methyl iodide in good yields (Equation (16)) <2002T10011>.
438
Functions Containing a Carbonyl Group and at Least One Chalcogen
OH
+ CO + S
O
i. DBU, THF 1 MPa CO 80 °C, 6 h
S
O
ð16Þ
ii. MeI 20 °C, 16 h 89%
6.15.2.1.4
Other methods
Benzimidazo[1,2-c]quinazoline-6(5H)-thiones were prepared by cyclization of 1,2-diaminobenzene with dimethyl 2-isothiocyanatoterephthalate and acylated with ethyl chloroformate according to Equation (17) affording thiocarbonate in 70% yield <2002MI615-01>. O OEt S
N=C=S CO2Me
NH2 + NH2
MeO2C
N i. PriOH
N
ii. ClCO2Et DMF, Et3N 70%
N
ð17Þ
CO2Me
A convenient process for the synthesis of highly functionalized glyoxylic acid derivatives has been accomplished by reaction of n-butylglyoxylate with triphosgene, sodium thioethylate, and benzoic acid, to provide the acetal containing a thiocarbonate moiety with excellent yield of 91% (Equation (18)) <2002S365>. i. (Cl3CO)2CO THF, pyridine ii. NaSEt, Et 2O
O BunO O
iii. Ph-CO 2H THF, DIPEA 91%
O
SEt
O O
BunO
ð18Þ Ph
O O
According to Equation (19) a thiocarbonate is quantitatively formed from methyl 2-thioxo3H-benzoxazole-3-carboxylate with 1,6-dimethyl-2,4-hexadiene in a photochemical reaction <2002HCA2383>. O O S N
OMe S
O
6.15.2.2 6.15.2.2.1
N Photochem. Benzene, 100%
OMe
ð19Þ
O
Other Dissimilar Chalcogenide Functions Oxygen and selenium functions
During the synthesis of ‘‘mucocin,’’ a powerful antitumor ‘‘acetogenin,’’ the 4-hydroxybutenolide terminus is a key intermediate. Its precursor, the selenocarbonate, has been prepared according to Scheme 8 in a yield of 89% <1998TL9627>. Total synthesis of mucocin was achieved in an analogous way for preparing the selenocarbonate 2 (yield 78%) by using TBDPS protective group and triphosgene instead of phosgene as a carbonyl source <2002JOC5739>. In the synthesis of ‘‘(+)-juruenolide C,’’ a 5-exo-digonal radical cyclization has been applied with a selenocarbonate intermediate 3, which has been prepared in 74% yield in a similar way as described above by using carbonyldiimidazole (CDI) as a carbonyl source <2001JOC4841>.
439
Functions Containing a Carbonyl Group and at Least One Chalcogen O TBDMSO
+ TBDMSO
Se
O BuLi THF
PhSeH 89% Pyridine
O Cl
Cl TBDMSO
Ph
O
TBDMSO
Et3N
Cl
O
OH TBDMS = t-butyl dimethyl silyl
O
Scheme 8 O Se
O
Ph
TBDPSO TBDPS = t-butyl diphenyl silyl
MeO
O
OMe
O 2
O Ph
Se
O O
t Bu2SiH
O O
3
Preparation of 5-selenopentopyranose sugars from pentose starting materials by samarium(II) iodide or (phenylseleno)formate-mediated ring closures is described <2000T3995>. Selenocarbonates have been prepared by insertion of selenium into the zinc–carbon bond of arylzinc halides forming corresponding zinc selenoates which react with acyl halides in the presence of HMPA providing selenocarbonates in good yields (Equation (20)) <2002MI615-02>. O MgBr
i. ZnCl 2, THF ii. Se
Se
OMe
ð20Þ
iii. ClCO2Me HMPT 70%
6.15.2.2.2
Oxygen and tellurium functions
Alkyl aryl tellurocarbonates, which are effective precursors of oxyacyl, primary, and secondary alkyl radicals, have been prepared from diphenyl ditelluride and alkyl chloroformate in good yields (Equation (21)) <1996JOC5754>. The same tellurocarbonates can be obtained in yields of 60–96% by palladium-mediated reactions of chloroformates with aryltellurotris(trimethylsilyl)silane (Equation (22)) <1998JOC5713>.
Ph
Te
Te
Ph
i. NaBH4 MeOH, THF ii. ClCO2Me THF, 91%
O MeO
Te
Ph
ð21Þ
440
Functions Containing a Carbonyl Group and at Least One Chalcogen SiMe3 SiMe3
Si Te Ph
+ ClCO 2Me
MeO
Benzene 80%
SiMe3
6.15.2.2.3
O
Pd(PPh3)4
Te
Ph
ð22Þ
Sulfur and selenium functions
A thioselenocarbonate precursor for the synthesis of thioselenofulvalenes, which are strong electron donors, has been prepared in several steps according to the overall Equation (23) <2002JOC4218>. KCNS +
O
+ Cl-Mg
+ Se + EtSCN + CS2 + Tol-SO 2Cl 83%
O
ð23Þ I
S
S
S
Se
O
6.15.3
CARBONYL CHALCOGENIDES WITH A CHALCOGEN FUNCTION AND ONE OTHER HETEROATOM FUNCTION
6.15.3.1
Oxygen and Nitrogen Functions
Carbamates are carbonic acid derivatives containing a carbonyl function directly connected to an alkoxy function and an amino function. They are important for producing pharmaceuticals and polymers, and therefore many preparative methods exist. A review is given in . The formal constitution allows a great deal of variety in the alkoxy component as well as the basic amino function. In general, two synthetic approaches to carbamates can be distinguished: the first method involves a carbonic acid derivative of an alcohol or of a phenol reacting with ammonia or amine and the second one involves carbonic acid derivatives of ammonia or an amine reacting with an alcohol or a phenol.
6.15.3.1.1
Carbamates from chloroformates or phosgene equivalents
Chloroformates are easily prepared using phosgene or phosgene equivalents such as the readily available triphosgene (bis(trichloromethyl)carbonate) <1987AG(E)894, 1996S553>. 2-Methyl-2-propyl-1,3-propanediol dicarbamate (Meprobamate), a general sedative, is synthesized by the low-temperature phosgenation of the substituted 1,3-propanediol in an inert medium in the presence of a tertiary amine, followed by conversion of the bischloroformate derivative to the dicarbamate by ammoniation with gaseous NH3. Antipyrine gave consistently higher yields than other tertiary amines (Equation (24)) . i. COCl2 Antipyrine Toluene, CHCl3 OH
OH
ii. NH3 (g)
H2N
O O
O
NH2
ð24Þ
O
2-Cyclohexenyloxycarbonyl chloride has been reacted with 2-hydroxymethylaniline to provide the corresponding carbamate in 76% yield (Equation (25)) <1999AG(E)1928>.
Functions Containing a Carbonyl Group and at Least One Chalcogen H
Cl
O
OH
+
O
NH2
441
OH
Pyridine DCM
ð25Þ
NH
0 °C to rt 2 h, 76%
O
O
H
(4R,5S)-4,5-diphenyl-2-oxazolidinone has been prepared from (1S,2R)-(+)-2-amino1,2-diphenylethanol and triphosgene (Equation (26)) <1998OS45>. It is used for the synthesis of optically active amines because of its high stereoselectivity and easy deprotection by hydrogenolysis after the reaction <1993TL289>. The procedure can also be used for preparing 2-oxazolidinones from various 2-aminoethanol derivatives.
+ Ph
H2N
DCM Et3N
O
Ph
HO
Cl3CO
OCCl3
O
Ph
N H
Ph
ð26Þ
O
<10 °C, 3 h 99%
Triphosgene (1/3 equivalent) has also been employed advantageously in the preparation of 6-methoxy-2-oxo-2,3-dihydrobenzoxazole (MBOA), in yield of 75%, from 2-amino-5-methoxyphenol (Equation (27)) <1989S875>. With the exception of CDI, approaches by using other reagents—such as phosgene, urea, or potassium cyanate—employed in the reaction provide substantially lower yields of MBOA . MeO
0.33 equiv. (Cl3CO)2CO
OH
O O
2 equiv. Et3N THF, rt 30 min, 75%
NH2
6.15.3.1.2
MeO
N H
ð27Þ
Carbamates from isocyanates
Highly functionalized carbamate intermediates suitable for potential elaboration to ‘‘esperamicinone’’ have been prepared by Nicolaou employing phenyl isocyanate to react with an epoxyalcohol in excellent yield (99%) (Equation (28)) <1994T11391>. O-benzyl N-vinyl carbamate has been prepared from vinyl isocyanate and benzyl alcohol <2002OPRD74>.
O
Ph-N=C=O
O
O OH O
O
O
O
OTBDMS
DCM, Et3N 25 °C, 1 h 99%
Ph
ð28Þ
H N
O
O
OTBDMS
O
TBDMS = ButMe2Si
The first ‘‘molecular motor,’’ which consists of just ‘‘78 atoms,’’ was developed by Kelly and gets rotational energy from forming a cyclic carbamate which causes a directed movement of the rotor as shown in Scheme 9. The carbamate results from the addition reaction of the isocyanate (at the rotor) with the alcohol function (connected over a propoxy linker to the base plate) <2000JA6935, 1999NAT(401)150>.
6.15.3.1.3
Carbamates from N,N0 -carbonyldiimidazole (CDI)
CDI is widely used in the preparation of oxazolidinones. It has been employed in the synthesis of (4S,5R)-5-[(E)-dec-1-en-1-yl]-4-methyl-2-oxazolidinone (Equation (29)) <1999JOC6147, 1992JOC5469>. Further similar applications of CDI on oxazolidinones are given <2000T8643, 1998S627>.
442
Functions Containing a Carbonyl Group and at Least One Chalcogen
Me
rotor
Me
Me Baseplate
Rotation over Eact –25 kcal O
O
H N O
O
N
N
C OH O
O
O
H O
Scheme 9 O C 8 H 17
H 2N
N
N
C 8 H 17 N
N
ð29Þ
THF, 20 °C 2 h, 70%
OH
O
HN O
An elegant method for formation of N-imidazole carbamates is the reaction of alcohols with CDI which in this case is an aminocarbonylating reagent. Thus, 2,6-dimethylphenol has been reacted with CDI to result in the formation of the carbamate in good yield of 91% (Equation (30)) <2002S29>. Me
Me
6.15.3.1.4
OH
CDI
Me
DCM, reflux 5 h, 91%
O
N
N
ð30Þ
O Me
Carbamates from carbonates or dicarbonates
Diethylcarbonate is employed for the cyclocarbamation of various aminoalcohols. The reaction is catalyzed by basic substances, such as sodium methoxide, magnesium methoxide, potassium hydroxide, or sodium or potassium carbonate. Sodium methylate in xylene <1996S719>, potassium or sodium carbonate under reflux <1993TA2513, 1999EJO2965> are the preferred reaction conditions. The reaction has wide scope and synthetic utility. 4,4-Dimethyl-2-oxazolidone has been prepared with diethylcarbonate in excellent yield (98%) (Equation (31)) <1991T2801>. OH H3C NH2
H3C
O
(EtO)2CO
H 3C
K2CO3, 120 °C 2 h, 98%
O N H
H 3C
ð31Þ
Preparation of t-butyl carbamates with BOC2O from amines (and their one-pot conversion to amides with acyl halide–methanol mixture) in mostly quantitative yields has been described (Equation (32)) <2002S203>. A review on reactions of BOC2O with amines forming carbamates has appeared <2000JOC6368>.
R
1
BOC 2 O NH 2
R1 = PhCH2 (92%) n-C 8 H 17 (100%) PriOC(O)CH2 (100%) BOC = ButOCO
O Bu t
O
N H
R1
ð32Þ
443
Functions Containing a Carbonyl Group and at Least One Chalcogen
t-Butoxycarbonylation of an amidic nitrogen with BOC2O, in acetonitrile at room temperature, as part of an efficient and regioselective method for the exchange of the N-benzoyl group in Paclitaxel (Taxol1) 4 to 10-acetyldocetaxel and to Docetaxel 5 has been reported (Equation (33)) <1999TL189>. Paclitaxel1 4 and its semisynthetic analog Docetaxel (Taxotere1) 5 are among the most important new antitumoral agents of the 1990s. R2O
O
OH
O R1
NH
O
Ph
H
O
OHO AcO COPh
OH
O
4 Paclitaxel R1 = Ph, R2 = Ac 5 Docetaxel R1 = But O, R2 = H
AcO
O
O Ph
NH
OSiEt3 BOC2O, DMAP
O
Ph
O O
O
O
O
H OH O AcO
MeCN, rt, 24 h 61%
Ph Ph
O
O
OSiEt3
H
O O AcO Bn
O
O
6.15.3.1.5
O O
COPh
Bn
AcO
OtBu CO N O
Ph
O
ð33Þ
OtBu
Carbamates from carbon oxides
Carbamates can be obtained from carbon monoxide (CO) or carbon dioxide (CO2) as outlined in . A review on converting carbon dioxide into carbamato derivatives has been reported treating mainly carbamato metal complexes and their reactions <2003CRV3857>. Carbon dioxide (CO2) can be reacted with amines and alkyl halides in the presence of bases (Scheme 10) <1995JOC2820>. Use of sterically hindered guanidine bases gives best results, i.e., 80–99% yield with virtually 100% selectivity. But the need for stoichiometric amounts of base causes serious limitation to the large-scale application of the process. O
O Guanidine
R1HN
R1NH2 + CO 2
O
_
Hal-R2
R1HN
O R2 + GuanidineHHal
GuanidineH +
Scheme 10
The transformation of vicinal aminoalcohols with CO2 to the corresponding carbamates in a catalytic process that occurs in good yields has been described (Equation (34)) <2002SL307>. The catalyst is commercially available n-Bu2SnO in powder form, which is stable in air. R2 R1HN
R3 + CO2 OH
10 mol.% n Bu2SnO NMP 180 °C, 16 h
O
R3
N R1
R2
O
ð34Þ R1 = Me, R2 = R3 = H, 94% R1 = Et, R2 = R3 = H, 76% R1 = R2 = R3 = H, 53% R1 = R2 = H, R3 = Me, 73% R1 = H, R2 = R3 = Me, 85%
444 6.15.3.1.6
Functions Containing a Carbonyl Group and at Least One Chalcogen Carbazates
Generally carbazates can be divided into two groups: monoacylated and bisacylated derivatives. They are obtained simply by reacting alkyl- or aryl chloroformates with hydrazine hydrate, or with alkyl- or arylhydrazine derivatives. Chloroformate as an intermediate is employed in the reaction of 3-chlorophenol, diphosgene, and hydrazine (Equation (35)) <1998CCC793>. OH
Cl
H N
O
Cl
i. Cl 3COCO–Cl
NH2
ð35Þ
O
ii. N 2H4, Et2O 88%
Instead of chloroformates, unsymmetrically substituted O-alkyl O0 -phenylcarbonates can be used; the phenoxy group activates the carbonate ester <1968HCA622, 1984CJC574> (Equation (36)). In special cases, dialkylcarbonates, particularly the symmetrical ones, have been employed to achieve carbazates in good yields (Equation (37)) <2002CJC1187, 2000GEP19837070>. H N NH2
O Ph O
ð36Þ
O
H2NNH2
O
O O O
6.15.3.1.7
N H
O
HO
DCM 77%
Ph
O
Ph
H2NNH2
O
NH2
ð37Þ
Azidoformates
The chloroformates to be used for the synthesis of azidoformates can be generated in situ from an alcohol and phosgene <1991JCS(P1)37> or a phosgene equivalent such as diphosgene <2001JOC6585> or triphosgene <2003T8233, 2002SL1455>. A synthesis of fused 2-pyrrolines via thermolysis of 6-substituted 3,5-hexadienylazidoformates is described <2001JOC6585>. During a total synthesis of a penicillin N analog the intermediate azidoformate has been prepared by using triphosgene as shown in Equation (38) <2003T8233>. i. (Cl3CO)2CO Pyridine CCl4, 50 °C
S HO
6.15.3.2 6.15.3.2.1
H
ii. NaN3, DMF 50 °C, 67%
CO2Et
S N3
ð38Þ O
O
H
CO2Et
Oxygen and Phosphorus Functions Phosphinecarboxylates by the Arbuzov reaction and related methods
Alkyldialkyloxyphosphinecarboxylate oxides are prepared by reacting alkyl chloroformates and trialkyl phosphites in a typical Arbuzov reaction (Equation (39)) <1998T12233>. O
O (EtO)3P +
Cl
OEt
91%
EtO EtO P
OEt
+ EtCl
ð39Þ
O
Alkoxycarbonyl-substituted t-butylmethylboranes have been synthesized from the reaction of t-butylphosphine with an alkyl chloroformate, methyl iodide, and borane/THF in yields of 61–85% (Equation (40)) <2002BCJ1359>. Also disubstituted derivatives have been prepared in yields of 86–99%.
Functions Containing a Carbonyl Group and at Least One Chalcogen
445
O But-PH2 +
BH3-THF
+
MeI
+ Cl
O
67%
BuLi, THF Hexane
ð40Þ O H3B P
But
6.15.3.3 6.15.3.3.1
O
Oxygen and Other Heteroatom Functions Oxygen and boron functions
Tricyclohexylphosphine(methoxycarbonyl)borane has been prepared from the reaction tricyclohexylphosphine-iodoborane with DMC as carboxylating reagent (Equation (41)) <2000JA6329>. i. (p-But-C6H4)2*Li TMEDA, THF
c-Hex3 P I + Me2CO3 (i)
H B H
c-Hex3 P Br
O
ð41Þ
B
ii. Br 2, MeOH
OMe
H
As a synthon for novel ‘‘carboranyl peptides,’’ water-soluble icosahedral carboranyl anions have been synthesized by the above methods <2002CCC1095>.
6.15.3.4 6.15.3.4.1
Sulfur and Nitrogen Functions Thiocarbamates from chlorothioformates and amines
A simple and efficient procedure has been developed for a one-pot synthesis of benzothiazine2,4-diones directly from thiosalicylic acid and amines; the reagent for supply of the carbonyl group is ethyl chloroformate (Equation (42)) <2003H115>. NH2 CO2H
O
+
+
SH
6.15.3.4.2
OEt
Cl
O CHCl3
Ph
N
Et3N 66%
S
ð42Þ
O
Thiocarbamates from carbamoyl chlorides and thiols
A synthesis of S-2-cyclohexenyl N-dialkyl thiocarbamates is described (Equation (43)) <2002OL4217>. SH
O
i. NaH, THF
+ Cl
Ni-Pr2
ii. H2O, 82%
Ni-Pr2
S
ð43Þ O
Thiocarbamates can also be prepared from carbamoyl chlorides and disulfides which are reductively acylated in the presence of Yb metal and a catalytic amount of MeI (Equation (44)) <2002JCR(S)442>.
446
Functions Containing a Carbonyl Group and at Least One Chalcogen O O S
O
N
O S
Br
N
S
O N
Yb Cat. MeI
Cl
N
HMPT THF 83%
S
+
O
Br
ð44Þ
O S
O Br
6.15.3.4.3
Thiocarbamates from isothiocyanates and alcohols
An example for the synthesis of a thiocarbamate by reaction of an isothiocyanate with an alcohol is given <2002JGU1146>. The primary generated thioncarbamate undergoes thione–thiol (Newman–Kwast) rearrangement providing the thiocarbamate. According to Scheme 11 this immediately reacts intramolecularly to afford the 4-phospha-1,3-thiazolidin-2-one. S
EtOH
S
H N
S=C=N P OPh
Rearr.
S P
OEt
OPh
S P
S
Et
Cl
Cl
H N
O
27%
OPh
H N
O
–EtCl
Cl
S P
S
OPh
Scheme 11
6.15.3.4.4
Thiocarbamates from alkylamide salts, carbon monoxide, and sulfur
1,3-Thiazolidin-2-one has been prepared from 2-aminoethanethiol, elemental sulfur, and carbon monoxide in good yield of 87% (Equation (45)) <2002T7805>.
SH
H2N
6.15.3.4.5
S8, K2CO3 DMF, O2
H N
87%
ð45Þ
O
+ CO S
Thiocarbamates from [3,3]-sigmatropic rearrangement
2-Cyclohexenol reacts with methyl isothiocyanate via Newman–Kwast rearrangement to form S-2-cyclohexenyl N-methyl thiocarbamate (Equation (46)) <2002EJO2970>. OH
NHMe
S
i. NaH, THF
+ Me-N=C=S O
ii. NaHCO3 H2O, 80%
ð46Þ
A series of isothiocyanate-substituted allenes has been prepared by [3,3]-sigmatropic rearrangement of the corresponding propargyl thiocyanates. Further reaction of the isothiocyanate allenes provides a substituted 1,3-thiazolin-2-ones; an example is given in Equation (47) <2002S1423>. S=C=N
MeOH H2O 32%
S=C=N
OMe
H N
O
ð47Þ
S Et
Functions Containing a Carbonyl Group and at Least One Chalcogen 6.15.3.4.6
447
Thiocarbamates from trichloroacetyl chloride, thiols, and amines
It has been found that the carbonyl group in trichloroacetic acid esters behaves like one in carbonic acid ester, i.e., it can be reacted twice with nucleophiles. This is exploited for a simple two-step synthesis of thiocarbamates from trichloroacetyl chloride, thiol, and amine <2003JOC3733>. Either trichloroacetyl chloride can be reacted first with an amine and then with a thiol, or first with a thiol and then with an amine (Scheme 12). The latter method provides significantly better yields of 83–100% for thiocarbamates.
O
Cl3CCOCl
R1-SH
R1
HNR2R3
CCl3
S
83–100%
O R1
O
N
R3
1
Cl3CCOCl
Et2NH
R2 S
54–63% R -SH NEt2
CCl3
R1 = n-Hex, Ph, p-ClBn R2 = H, Et R3 = H, Et, But
Scheme 12
6.15.3.5 6.15.3.5.1
Sulfur and Phosphorus Functions Phosphonothioformates
Trialkylphosphonothioformates have been prepared in a mild one-pot reaction by sequential reaction of phosgene with alkanethiols, and subsequent Arbuzov reaction with trialkyl phosphites in good yields (Equation (48)) <2000SL815>. i. Toluene n-PrSH Et3N, DCM
O Cl
6.15.3.6 6.15.3.6.1
Cl
O +
P(OEt)2
S
ii. P(OEt)3 Toluene 84%
ð48Þ
EtCl
O
Other Mixed Systems Selenium and nitrogen functions
A ring-closure reaction has been performed using elemental selenium, carbon monoxide, and alkyl(prop-2-ynyl)amines resulting 5-alkylideneselenazolin-2-ones stereoselectively via cycloaddition of the in situ generated carbamoselenoates to the carbon–carbon triple bond <2002JOC6275>. Yields are 58–95% of product (Equation (49)). Butyl(but-3-ynyl)amine affords the corresponding six-membered selenium-containing heterocycle (69% yield) with the aid of CuI <2002JOC6275>. HN Se + CO +
R
O i. DBU, THF rt, 1.5 h ii. Sat. NH4Claq rt, 5 min
Se
N
R
R
Me Pri Bu c-Hex
Product yield (%)
78 58 95 76
ð49Þ
448
Functions Containing a Carbonyl Group and at Least One Chalcogen
Also N-heterocyclic carbamoyl chlorides have been employed in the synthesis of carbamates. Thus, N-(phenylselenocarbonyl)oxazolidin-2-one has been prepared with 85% yield by treatment of the Li salt of oxazolidinone with triphosgene, followed by addition of PhSeH <1999SL1657> (Scheme 13). Cl
O H N
i. BuLi
O
N
ii. (Cl3CO)2C=O
O
N
O 85%
O
SePh
O
PhSeH Pyridine
O O
Scheme 13
The samarium-iodide-mediated reaction of N-chlorocarbonyl-imidazolidin-2-one-N0 -methansolfonamide with dinaphthyl diselenide provides the corresponding naphthylselenocarbamate in 82% yield via the samarium selenolate RSeSmI2 <2002JCR(S)168> (Equation (50)).
O
O S
N
O
O Cl
N
+
Se
Se
SmI2 THF
O
O
O S
O
N
N
Se
ð50Þ
82%
An easy access to benzoselenazine-2,4-diones has been described <1995AJC1221>. N-butylbenzamide has been reacted with dibenzyl diselenide to provide 2-benzylseleno(butyl)benzamide, which has been treated with trimethylsilyl triflate. Resulting N-TMS-benzamide is further reacted with phosgene to afford 3-butyl-2H-1,3-benzoselenazin-2,4(3H)-dione in 80% yield (Scheme 14). O
O i. BuLi
N H
N H
ii. (BnSe) 2
Se Bn rt, overnight
TMS-Tf O N Se
O
COCl2 rt, 12 h O
N Se TMS
80%
Bn
Scheme 14
A rather exceptional access to selenocarbamates with potential antiviral properties is the treatment of an isocyanate with LiAlHSeH and the alkylation of the resulting selenide by an alkyl halide <2002JOC486>. Thus, Se-methyl N-phenylselenocarbamate has been prepared in 70% yield (Equation (51)).
Ph
i. LiAlHSeH THF, rt, 1 h N=C=O ii. MeI, rt, 2 h 70%
O Ph
N H
Se–Me
ð51Þ
Functions Containing a Carbonyl Group and at Least One Chalcogen 6.15.3.6.2
449
Tellurium and nitrogen functions
A method using very simple starting materials for the preparation of tellurocarbamates employs elemental tellurium and carbon monoxide together with amines and alkyl halides <1993HAC471>. Thereby the corresponding lithium amides react with tellurium under atmospheric pressure of carbon monoxide to yield carbamotellurates, which are trapped with alkyl halides to obtain the tellurocarbamates (Scheme 15). Satisfactory yields of above 60% can only be achieved, if the correct order of reaction steps is maintained
NH BuLi THF –78 °C
NLi
i. Te ii. CO (1 atm), 2 h iii. EtBr, 1 h
O N
Te
THF –78 °C 65%
Scheme 15
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452
Functions Containing a Carbonyl Group and at Least One Chalcogen Biographical sketch
Heiner Eckert was born in Munich, Germany, where he did his diploma in chemistry at the Technical University of Munich (TUM) in 1973, and received his Ph.D. with ‘‘summa cum laude’’ under Prof. Ugi three years later. In 1977 he founded ‘‘Dr. Eckert GmbH,’’ a company specializing in developing fine chemicals and processes for chemical production (phosgenations). At present he is working as an Academic Director at the TUM, with his research focused on new methods in organic syntheses development. Dr. Eckert has published numerous scientific papers and patents (natural product syntheses, metal phthalocyanines as reagents and catalysts), and indeed the ‘‘Eckert hydrogenation catalysts’’ are named after him. In 2003, he published the voluminous book Phosgenations–A Handbook.
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Comprehensive Organic Functional Group Transformations 2 ISBN (set): 0-08-044256-0 Volume 6, (ISBN 0-08-044258-7); pp 429–452
6.16 Functions Containing a Carbonyl Group and Two Heteroatoms Other Than a Halogen or Chalcogen O. V. DENISKO Chemical Abstracts Service, Columbus, OH, USA 6.16.1 FUNCTIONS CONTAINING AT LEAST ONE NITROGEN FUNCTION (AND NO HALOGENS OR CHALCOGENS) 6.16.1.1 Carbonyl Derivatives with Two Nitrogen Functions 6.16.1.1.1 Reactions with isocyanates 6.16.1.1.2 Reactions with metal cyanates 6.16.1.1.3 Carbonylation of amines 6.16.1.1.4 Substitution reactions of amines with phosgene and its equivalents 6.16.1.1.5 Oxidation of thioureas and related compounds 6.16.1.1.6 Reactions of amines with amides and other carboxylic acid derivatives 6.16.1.1.7 Miscellaneous reactions 6.16.1.1.8 Preparation of carbamoyl azides 6.16.1.2 Carbonyl Derivatives with One Nitrogen and One P, As, Sb or Bi Function 6.16.1.2.1 Carbonyl derivatives with one nitrogen and one phosphorus(III) function 6.16.1.2.2 Carbonyl derivatives with one nitrogen and one phosphorus(V) function 6.16.1.2.3 Carbonyl derivatives with one nitrogen and one arsenic function (carbamoyl arsines) 6.16.1.2.4 Carbonyl derivatives with one nitrogen and one antimony function 6.16.1.2.5 Carbonyl derivatives with one nitrogen and one bismuth function 6.16.1.3 Carbonyl Derivatives with One Nitrogen and One Metalloid (B, Si, Ge) Function 6.16.1.3.1 Carbonyl derivatives with one nitrogen and one boron function 6.16.1.3.2 Carbonyl derivatives with one nitrogen function and one silicon function (carbamoyl silanes) 6.16.1.3.3 Carbonyl derivatives with one nitrogen and one germanium function (carbamoyl germanes) 6.16.1.4 Carbonyl Derivatives with One Nitrogen and One Metal Function 6.16.1.4.1 Carbon monoxide insertion reactions 6.16.1.4.2 Aminative carbonylation 6.16.1.4.3 Amination 6.16.1.4.4 Reactions with heterocumulenes (isocyanates, ketenimines, azides, carbodiimides) 6.16.1.4.5 Miscellaneous reactions 6.16.2 FUNCTIONS CONTAINING AT LEAST ONE PHOSPHORUS, ARSENIC, ANTIMONY, OR BISMUTH FUNCTION (AND NO HALOGEN, CHALCOGEN, OR NITROGEN FUNCTIONS) 6.16.2.1 Carbonyl Derivatives with Two P, As, Sb, or Bi Functions 6.16.2.2 Carbonyl Derivatives with One Phosphorus and One Metal Function 6.16.2.3 Carbonyl Derivatives with One B, As, Sb, or Bi Function, and One Metal Function 6.16.3 FUNCTIONS CONTAINING AT LEAST ONE METALLOID FUNCTION (AND NO HALOGEN, CHALCOGEN, OR GROUP 5 ELEMENT FUNCTIONS) 6.16.3.1 Carbonyl Derivatives with Two Silicon Functions 6.16.3.2 Other Carbonyl Derivatives with Two Metalloid Functions 6.16.3.3 Carbonyl Derivatives with One Metalloid and One Metal Function 6.16.4 CARBONYL DERIVATIVES CONTAINING TWO METAL FUNCTIONS
453
454 454 454 460 460 461 466 466 467 468 468 468 469 470 471 471 471 471 472 473 473 473 474 474 475 476 476 476 478 479 479 479 480 480 481
454 6.16.1
Functions Containing a Carbonyl Group and Two Heteroatoms FUNCTIONS CONTAINING AT LEAST ONE NITROGEN FUNCTION (AND NO HALOGENS OR CHALCOGENS)
6.16.1.1 6.16.1.1.1
Carbonyl Derivatives with Two Nitrogen Functions Reactions with isocyanates
(i) Additions of amines to isocyanates with formation of acyclic ureas (a) Starting materials. The addition of various amines to isocyanates (Equation (1)) represents the most widely used approach to the preparation of mono-, di-, and trisubstituted ureas and their functionalized derivatives, especially if the starting isocyanates are readily available. R1 N C O
O +
2 3
R R NH
R1
N H
N R3
R2
ð1Þ
As an amine component, ammonia <1994S56>, primary aliphatic amines <1999JOC2835, 2001MI351, 2003TL2065>, secondary aliphatic amines <2002PS(177)1303> and their silylated <1996JGU349> and labeled <1993MI655> analogs, cycloalkyl <2001JCO171> and cycloalkenylamines <2001CPB391>, polyaza macrocycles <2001EJO1943>, hydroxyalkyl amines <2001JMC2344, 2001MI191>, N-hydroxylamines <2000MI115723> and their O-alkyl derivatives <1992BAU1920, 1996TL5835>, amino acids <1997TL4603, 2000TL1487>, allylic amines <1993SC2065>, benzylic amines <1998TL1121, 1999JOC2835, 2000PHA490, 2003TL2065>, arylamines <1996JMC1243, 1997SL1184, 1999JOC2835, 2003MI425>, heteroaryl amines <1995JHC13, 2000BAU1202, 2001CPB391, 2001JCS(P1)2012, 2002CPB1379, 2002JMC2994>, heterocyclic saturated <1996SC3685, 1997HCA966, 1998JCS(P1)3127, 2002HCA2458> and partially hydrogenated amines <1992JHC1189, 2003SC1449>, azaheteroaromatics <1995SL605>, heterocyclic ammonium and aminophosphonium salts <1993H(35)1237, 1994JOC7144, 2002JOC5527>, aminophosphonates <1993PS(85)161, 1994OPP357, 2002PS(177)1303>, diamines <2001PHA361, 2002MI81, 2002ZN(B)937, 2003JMC1112>, polyamines <1995CL759>, amino-substituted calixarenes <1995JOC6448, 2000MI1152, 2002T7207>, steroidal amines <2002OL4639>, amino sugars <1993T2655, 1993T2676, 2002SL1779>, nucleosides <1995BSB411>, amino borabicyclononanes <1992HAC245>, cyano imines <2002JOC5546>, sulfimines <1999H(51)2035>, metalated acrylamides <2001JGU1953>, N-arylsulfonyl sulfenamides <2001JOU1611>, sulfonamides <1994AP819, 1998EUP879816, 2001MI127, 2001MI404>, hydrazines <1994H(38)235, 1994JOC6487, 1996SC2941, 2001JMC1475, 2001MI42>, N-amino indoles <2001SL222>, hydrazides <1994AP469, 2000PHA490, 2001JMC1475, 2001MI180>, carbamates <1999TL6545>, isoureas <1995AP393>, isothioureas <1996TL1945, 2002JCO285>, thiourethanes <1992JOU1635>, guanidines <2002H(57)1799>, triazenes <2000JCO710>, and even amino ligands of organometallic complexes <1994JOM(465)297> were used successfully. Along with amines, isocyanates could also be used to introduce one or more functional groups in the urea molecule. Due to the mild reaction conditions generally used, the reaction is tolerant to a wide variety of functionalities, and urea preparation from ammonium isocyanate <1993GEP4127562>, alicyclic <1995BSB411>, N-acyl <1993JGU1675, 1996SC2941> and unsaturated acyl isocyanates <1994H(38)235>, polyfluorinated <2000BAU1202>, polyunsaturated <1994S56, 2003JOC5512>, azido- and diazine-substituted isocyanates <1993MI655>, glucosyl and glucopyranosyl <1994SL919, 1995JCS(P1)377, 2000SL1253, 2001JOC4200, 2002SL1779>, phosphoryl and thiophosphoryl isocyanates <1996JGU349>, radiolabeled <2002MI785>, chlorinated <1992JOU1635, 2001MI351>, chlorosulfonyl <1996JHC943, 1996JMC1243>, arylsulfonyl isocyanates <2001WOP23368>, and isocyanato-substituted carboranes <1996POL4355, 1997IC4753> has been reported. Reaction of disubstituted silaazacyclohexanes with isocyanate-terminated polyurethane prepolymer afforded oligomeric silylureas useful as sealants <1994WOP14820>. The addition of bulky 4-(triphenylmethyl)aniline to linear isocyanates at 40 C in the presence of a macrocyclic host allowed for the preparation of nonpolymeric rotaxanes with urea-containing axles <1997SL1184>.
455
Functions Containing a Carbonyl Group and Two Heteroatoms
(b) Chemo-, regio-, and stereoselectivity of the addition. The chemoselectivity of the CuClcatalyzed carbamoylation of ergoline carboxamide 1 (Figure 1), bearing two reactive nitrogen atoms is determined by the nature of the ligand used <1995SL605>. Thus, the best ligand for carbamoylation of the indole nitrogen was found to be triethyl phosphite, whereas the chemoselectivity was reversed in the presence of 2,20 -bipyridyl. O
H N
H NMe2 N H
H
N
1
Figure 1 Ergoline carboxamide: two reactive nitrogen atoms.
3-Amino-1H-1,2,4-triazole, also having two potential reaction sites, reacts with substituted benzylic isocyanates exclusively at the ring nitrogen with the amino substituent remaining intact <2002MI109>. A similar trend was observed on carbamoylation of 2-arylaminothiadiazolidinium chloride <1993H(35)1237>. 2-Substituted 1-methylperhydropyrimidines 2 (R1 = Me, Et, i-Pr, Ph), existing in equilibrium with minor, but more reactive open-chain tautomers, N-[3-(methylamino)propyl]imines, react with isocyanates R2NCO (R2 = t-Bu, Ph, Bn) producing either ureas 3 or 4 (Scheme 1) <1997HCA966>. The chemoselectivity depends mostly on the bulkiness of the R1 substituent with smaller R1 substituents favoring the cyclic products 3. R2NCO
Me
N
N R1
NHR
R2NCO
2
N
Me
N
R2HN
H
O
3
N
N Me
R1
R1
O
2
4
Scheme 1
The reactions of isocyanates with ,-unsaturated amines bearing -hydrogen, such as 2,2-diamino acrylonitriles <1994JHC329> or N-monosubstituted -aminovinyl trifluoromethyl ketones 5 (Scheme 2) <2000TL10141, 2003T1731>, give either C-addition products e.g., 6, or ureas e.g., 7, with the nature of the predominating product depending both on the reactant substitution and the reaction conditions. Generally, the increase in the steric hindrance caused by N-substituents or those in the -position to the amino group or higher reaction temperatures favor the formation of the C-addition products, whereas the use of more polar solvents and addition of nucleophilic catalysts (pyridine, triethylamine) shifts the equilibrium toward the ureas. The effect of isocyanate component variation is less pronounced. Ts NH
O R2
H N
TsNCO CF3
2
R
H N
CF3 1
R1
O 6
Ts NH
O TsNCO
O
R
5
R2
N
CF3 R1
O
7
R1 = H, Me, Ph; R2 = H, Me, t-Bu, PhCH2, etc.
Scheme 2
The similar effect of the N-substituents was observed in reactions of acyl or phosphoryl isocyanates with 2-amino-1-propenyl phosphonates <1993JGU1675>.
456
Functions Containing a Carbonyl Group and Two Heteroatoms
When optically active amines or isocyanates are used, the reaction proceeds without racemization affording optically active ureas and their derivatives <1994JOC6487, 2000M463, 2001JOC4200>. (c) Experimental techniques and solid-phase synthesis. A series of 1,3-diaryl ureas was conveniently prepared in 80–93% yields by addition of anilines to 2-nitrophenyl isocyanate under microwave irradiation conditions <2003MI425>. An automated solution-phase parallel synthesis approach has been successfully implemented for the preparation of numerous urea libraries. To eliminate the major problem of this approach, time-consuming work-up and purification, a series of scavengers, both small-molecule and on a solid support, has been developed. Thus, excess of an isocyanate could be effectively quenched using a fluoro-tagged primary amine <1999JOC2835>, aminomethyl polystyrene <1998JCS(P1)3127> or microgel-supported tris(2-aminoethyl)amine <2002JCO436> and removed from the reaction medium by simple phase-separation or filtration, respectively. On the other side, the excess of an amine could be readily removed with fluoroalkyl-substituted isatoic anhydride or isocyanate <2003TL2065>, while the control over the unwanted amine presence could be carried out using ‘‘self-indicating’’ resins with pH-dependent color <2003JCO632>. Lately, solid-phase synthesis has become the major approach to the preparation of urea libraries and several procedures based on either the resin-bound isocyanate <1999TL2749, 1999TL4501, 2002MI81> or the resin-bound amine component <2000JCO710, 2001JCO189, 2001SL697, 2001TL1973, 2002JCO285, 2002OL597, 2002OL4033, 2003TL811> have been developed. m- and p-Ureido-substituted arylboronic acids were readily synthesized in 65–92% yields and with >95% purity via the preliminary deactivation of the acid functionality by condensation of an aminophenylboronic acid with resin-bound diethanolamine followed by treatment of the polymer-supported boronate thus prepared with an isocyanate and mild acidic cleavage from the solid support <2002JOC3>.
(ii) Additions of amines to isocyanates with formation of cyclic ureas (a) Solution-phase reactions. Reactions of isocyanates with amines, bearing a suitably located additional functional group sensitive to nucleophilic attack, are often followed by the intramolecular reactions of the nitrogen atom of the newly formed urea fragment with formation of five- or six-membered cyclic ureas. These ring closure reactions could be further subdivided into substitution and addition reactions, the former being more widely exploited. This isocyanate addition/intramolecular substitution approach generally uses - or -amino acids and esters as amine components, and the ring closure step includes intramolecular acylation of the newly formed urea fragment (e.g., Scheme 3). This procedure is most commonly applied to the preparation of fused polyheterocyclic systems <1993JHC897, 1993S111, 1994CPB2108, 1994JHC77, 1994JHC1569, 1994JOC1583, 1996TL5835, 1997WOP47626, 2002CPB1379, 2002JHC417, 2003JMC113>, but was also used for the synthesis of monocyclic substituted tetrahydropyrimidinediones <2000TL4307>, chiral hydantoins <2003OL2555>, and 5-alkoxyhydantoins <1997JOC3230>.
COOH
HO
COOH
HO R2NCO
NH N H
R1
N reflux acetone/DMSO 30–82%
N H
R1
NHR2 O
O
H
HO
2 N R
N N H
O R1
R1 = H, Me; R2 = Me, Et, n-Pr, Ph
Scheme 3
Ethoxycarbonylhydrazones 8 of aromatic aldehydes and ketones react with 2 equiv. of an isocyanate in triethylamine with formation of intermediates 9, which immediately undergo intramolecular N-acylation/ring closure to give imino-substituted triazinetriones 10 (Scheme 4) <1998JHC261>.
457
Functions Containing a Carbonyl Group and Two Heteroatoms O
EtO R2 R1
N
R3NCO (2 equiv.)
H N
OEt
N
Et3N, rt
O
15–79%
R1
N O R2
8
O
R3 N
NHR
R1
3
N R2
O
9
O
N
N N R3
R3 O
10 R1 = Me, Ph, 4-ClC6H4, 4-MeC6H4; R2 = H, Me
Scheme 4
On carbamoylation of 2-methylimidazoline, three equivalents of an aryl isocyanate are consumed affording hexahydroimidazo[1,2-c]pyrimidine-5,7-diones in good yields <1994BAU1430>. Intramolecular addition reactions, realized as a second step in one-pot preparation of cyclic ureas, include: (a) addition to a carbonyl group <2003JOC754>; (b) addition to a thiocarbonyl group followed by H2S elimination <2002HAC199>; (c) addition to a carboncarbon double bond of enamines <1998S967>; (d) addition to a carbonnitrogen double bond of imines <1998PHA607, 2001JCS(P1)1241>, isothiocyanates <1993IJC(B)779>, oximes <1999T475>, diazo compounds <2002JMC5448> or methyleneamines, generated in situ by retro-Mannich reaction of hexahydro-1,3,5-triazines <1995JHC995>; (e) addition to a carboncarbon <1995JHC1141> or carbonnitrogen <2000PS(160)141, 2001EJO1695> triple bond. The latter could further be followed by another cyclization reaction <1994AP469> or rearrangement <2001JCS(P1)1241> thus providing access to highly substituted polyheterocyclic systems. (b) Solid-phase synthesis. There are two major approaches to the solid-phase synthesis of heterocycles with a urea fragment. The first is based on the direct construction of the desired heterocyclic ring on the solid support using the isocyanate addition/cyclization procedures, described above for solution-phase synthesis, followed by simple cleavage from the resin. The representative examples of this approach include: preparation of quinazoline-2,4-diones from resin-bound 2-aminobenzoates <1996TL4439>, 1,3-disubstituted uracils <2000TL1487> and 1,3,5-triazine-2,4,6-triones <2002JCO484> from -amino esters, 1,3,5-triazine-2,4-diones from resin-bound guanidines <2001JCO278>, and trisubstituted triazinobenzimidazolediones from polymer-supported 2-iminobenzimidazoles <2002JCO345>. In the second approach, the acyclic urea fragment is constructed while on a solid support. The subsequent cleavage from the resin releases a reactive functional group (most commonly, carboxylic group), which intramolecularly reacts with the nitrogen atom of the urea unit affording the corresponding cyclic ureas. This approach was successfully used for synthesis of functionalized hydantoins <1996TL5835, 1997TL4603, 1998MI129, 1999TL5841, 2000TL7409, 2001TL1973>, spiro-hydantoins <2001JCO171>, tetrahydrouracils <1998MI139>, and 1,2,4-trisubstituted urazoles <2002JCO491>.
(iii) Self-condensation and cycloaddition reactions of isocyanates (a) Dimerization and trimerization reactions. Catalytic cyclodimerization and cyclotrimerization reactions of isocyanates with formation of symmetrical 1,3-diazetidine-2,4-diones 11 or isocyanurates 12, respectively, are well known (Scheme 5). The direction of the cyclocondensation depends predominantly on the catalyst and the reaction conditions used.
O
O R R N
N R
RNCO O
O 11
Scheme 5
N
N N R 12
R O
458
Functions Containing a Carbonyl Group and Two Heteroatoms
A wide variety of catalysts for high-yielding trimerization of isocyanates includes fluoride salts <1993JOC1932>, tricyclic proazaphosphatrane and its derivatives <1993AG(E)896, 1994JOC4931>, potassium or sodium piperidinedithiocarbamate under conventional or microwave heating <2000JCR(S)145>, sodium p-toluenesulfinate <2002BCJ851>, trialkyl amines <1994NKK146>, tetrasulfido tin complexes <1999OM4700>, and transition metal complexes e.g., CpCo(PPh3)Me2, in supercritical carbon dioxide <2001JOM(626)227>. Even minor changes in the catalyst composition can affect the product distribution: thus, self-condensation of PhNCO in the presence of the oxoniobocene complex [Cp*2Nb(O)OMe] resulted in exclusive formation of triphenyl isocyanurate, whereas the [Cp*2Nb(O)H]-catalyzed reaction gave a mixture of dimerization and trimerization products with the former predominating <2001JOM(634)47>. The exclusive or predominant formation of 1,3-diazetidine-2,4-diones 11 occurs either on heating without a catalyst <2001JOU1747> or under catalysis with pyridine or 2- or 4-picolines under high pressure <1994NKK146>. In the latter case, the selectivity of the dimerization increases with the increase in pressure or in amount of the pyridine catalyst, whereas polar solvents, such as acetonitrile, favor the trimeric product. The predominant dimerization of phenyl isocyanate was also observed when 1,5-diazabicyclo[5.4.0]undec-5-ene (DBU) was used as a catalyst <1994JOC4931>. The reaction of tungsten hexachloride with excess of ethyl isocyanate in dichloroethane led to insertion of three isocyanate molecules into one of the tungstenchlorine bonds furnishing the tungsten complex WCl4[(EtNCO)3Cl], which on hydrolysis gave isocyanurate 12 (R = Et) <2002MI673>. Self-condensation of isocyanates under aqueous (aq.) basic conditions affords acyclic symmetrical ureas. Thus, heating 3-alkoxyphenyl isocyanates in aq. NaOH gave the corresponding N,N0 -bis(3-alkoxyphenyl)ureas in 72–83% yields <1994CCC495>. Aromatic isocyanates were readily converted into symmetrical 1,3-diaryl ureas in 85–95% yields in aq. pyridine at 20 C <1999S1907>. (b) Other cycloaddition reactions of isocyanates. SbCl5-Catalyzed 1,3-dipolar cycloaddition of isocyanates with -chloro-substituted azo compound 13 afforded the corresponding triazolonium hexachloroantimonates 14 in moderate yields (Equation (2)) (where TMSNCO indicates trimethylsilyl isocyanate) <1993T9973>, whereas 1,3-dipolar cycloaddition of isoquinolinium arylimides, generated in situ from N-(arylamino)isoquinolinium halides, gave the corresponding triazoloisoquinolones in 87–99% yields <1998EJO379>.
Me Cl
i. SbCl 5, CH2Cl2,
Me N
N
–60 °C
Ar
Me
+ Me N N N Ar R
ii. RNCO 42–68%
–
SbCl6
ð2Þ
O 14
13
R = H (from TMSNCO), t-Bu, Ph
Ar = 2,4,6-Cl3C6H2
Heating phenyl isocyanate with nonsymmetrical azines 15 in xylene triggered two consecutive 1,3-dipolar cycloaddition reactions yielding heterocycles 16 with three fused five-membered rings (Equation (3)) <2002TL6431>. 1,3-Dipolar cycloaddition of phenyl isocyanate to -imino thioamides occurs with sulfur elimination affording 4-amino-1,3-dihydroimidazol-2-ones <1997BSF623>. O
Ph R H2C
N
OMe
C
N Me Me 15
N
PhNCO Xylene Reflux
N N
Me Me
OMe
ð3Þ
R 16 R = Me (64%), Et (68%)
The in situ 1,3-dipole generation via thermal or palladium-catalyzed ring opening of threemembered heterocycles, such as functionalized aziridines <1995JA4700, 2000JOC5887>, bicyclic aziridines <2000SL1779>, or oxaziridines <2001TL9131>, in the presence of isocyanates
459
Functions Containing a Carbonyl Group and Two Heteroatoms
presented a convenient method for regioselective preparation of substituted imidazolin-2-ones, pyrazolo[1,2-a][1,2,4]triazolones and 1,2,4-oxadiazolidin-3-ones, respectively. A similar azetidine ring opening/isocyanate cycloaddition of 2-vinyl azetidines under palladium catalysis <2001SL914> or of 2-azabicyclo[2.2.0]hex-5-enes <2003JOC1626> afforded the corresponding vinylic or azetidine-fused tetrahydropyrimidin-2-ones in moderate to excellent yields. Chiral 2-alkenyl dihydrooxazoles 17 (X = O) react with 2 equiv. of aryl and arylsulfonyl isocyanates to give nonracemic dihydropyrimidone derivatives 18 (Scheme 6) via asymmetric hetero-Diels–Alder reaction followed by the addition of a second molecule of the isocyanate to the cycloadduct <1997CC2311>. The thia analogs 18 (X = S) were obtained in the similar reactions of 17 (X = S) with tosyl isocyanate; however, cycloaddition with less reactive phenyl isocyanate afforded 1:1 adduct 19 as the sole product <1999SL1379>.
O
R1
R1
R3HN
N X
R3
2R3NCO
N
X
R2
R2
(X = S, R1 = Ph, R2 = H)
R1
= Me, Et, Ph;
R2
Ph O
N
S
55%
17
18 X = O;
N
PhNCO
25–94%
O
N
Ph
19
= Et;
X = S; R1 = Ph; R2 = H, (i-Pr)3SiOCH 2 R3 = Ph, 4-BrC6H4, Ts, etc.
Scheme 6
Other examples of hetero-Diels–Alder cycloaddition reactions with isocyanates include the preparation of benzimidazolotriazinones and benzothiazolotriazinones from the corresponding N-(2-heteroaryl) arylimines <1993SC1427> and of imidazo[5,1-d]-1,2,3,5-tetrazin-4-one (temozolomide) and analogs from 5-diazoimidazole-4-carboxamide <1995JCS(P1)2783, 2002JMC5448>. [2+2+2]-Cycloadditions of N-trimethylsilyl imine 20 with various isocyanates afforded unsymmetrical 1,3,5-triazine-2,4-diones 21 (Scheme 7) in 75–96% yields <1995S1529>. Importantly, two different isocyanates could be added stepwise allowing for introduction of different substituents on N-1 and N-3 atoms of the cycloadducts. Analogous [2+2+2]-cycloaddition of 3-aryl-3,4-dihydroquinazolines with 2 equiv. of phenyl isocyanate gave the corresponding quinazolinotriazinediones <2000EJO2105>. CH2OTBDMS
CH2OTBDMS
CH2OTBDMS CH2OTBDMS
R2NCO
R1NCO
N
TMS
R1
N
N
N O TMS
O N TMS
20
75–96%
R1
HN O
N N R1
R2 O
21
Scheme 7
Benzotriazolyl-substituted iminium chloride undergoes [1+2+2]-cycloaddition with 2 equiv. of phenyl isocyanate to give, after quenching with an appropriate nucleophile, functionalized hydantoins in moderate yields <1996JHC1935>. Conjugated heteroarylvinyl iminophosphoranes react with alkyl or phenyl isocyanates via the azaWittig-type reaction and formation of carbodiimide intermediates to afford heteroarylmethylidenesubstituted imidazoline-2,4-diones in moderate yields <1994JOC6413>. A similar approach was used for the solid-phase synthesis of 2-imino-4-oxo-1,3,5-triazino[1,2-a]benzimidazoles from resin-bound 2-benzimidazolyl iminophosphoranes <2003JCO155>.
460 6.16.1.1.2
Functions Containing a Carbonyl Group and Two Heteroatoms Reactions with metal cyanates
Reactions of primary amines with sodium or potassium cyanates (Equation (4)) represent the most common method for the preparation of monosubstituted ureas. As an amine component, benzylic amines <2002JOC8827>, anilines <2000EJM879>, sterically constrained primary amines <1994TL8891>, -amino acids <2001JCS(P2)1247, 2001MC32, 2002JOC8827>, -amino acids <2001MC32>, and amino sugars <2002JCS(P1)1982> were successfully used. The kinetics of N-carbamoylation of -amino acids with potassium cyanate were studied in detail <2001JCS(P2)1247>. O RNH2
+
R
MOCN
N H
(M = K, Na)
ð4Þ
NH2
Secondary aromatic amines <2003JOC754>, hydroxylamines <1994TL6017>, and even azaheterocycles, such as 4,5-disubstituted 2,4-dihydro-1,2,4-triazol-3-ones <1995GEP4343595>, were also reacted with potassium cyanate to afford the corresponding urea derivatives. When the amine component has a suitably located carbonyl group, the latter undergoes intramolecular condensation with the newly formed urea fragment <2002JOC5527, 2003JOC754>. The reaction of KOCN with haloalkyl acrylates and methacrylates 22 gave the corresponding symmetrical ureas 23 (Equation (5)) <1993TL3857>. The presence of water is required to suppress the trimerization of the intermediate isocyanates. R
R
KOCN
O(CH2)nX
H2C O
O(CH2)nNH
H2C
aq. MeCN
O
Bu4 NBr
22
69–85%
CO 2
ð5Þ
23 R = H, Me; n = 6, 8; X = Cl, Br
Treatment of acyl or sulfenyl chlorides with silver cyanate in ether or aromatic solvents is a convenient approach to in situ generation of isocyanates which are unstable and/or not readily available. The subsequent addition of amines <1995TL6257>, N-alkoxyamines <1995JHC1625>, or hydrazines <1995PHA379> allows for the preparation of the corresponding functionalized ureas and sulfenyl carbazides.
6.16.1.1.3
Carbonylation of amines
A convenient approach to the conversion of primary and secondary amines into symmetrical ureas is the catalytic oxidative carbonylation of the amines with CO/O2 (Equation (6)). A wide variety of catalysts has been found effective for this reaction, including selenium compounds <2000MI355, 2000USP6127575>, manganese-based catalysts <1993JCA631>, resin-immobilized gold <2002JCA548>, Pd/H2SO4-modified ZrO2 <2001TL2161>, sulfur <1993HAC455>, polymersupported palladiumcopper catalyst <2000MI55>, PdI2/KI catalytic system <2003CC486>, and palladium methoxycarbonyl complexes in the presence of CuCl2 <1994JOM(470)249>. Electrocatalysis has also been applied <2001MI799>. Primary aromatic amines and secondary aliphatic amines are generally less reactive than primary alkylamines, allowing for the preparation of unsymmetrical ureas by oxidative carbonylation of primary alkylamines in the presence of excess of a less reactive amine <2001TL2161, 2003CC486>. R1R2NH
+
R3R4NH
CO Catalyst or ∆
O R1
N R2
N R4
R3
ð6Þ
High-pressure Se-catalyzed carbonylation of amines and diamines with [11C] carbon monoxide provided access to 11C-labeled cyclic and symmetrical acyclic ureas <2002JOC3687>. Treatment of N,N0 -di(t-butyl)diaziridinone with Ni(CO)4 under CO atmosphere resulted in CO insertion into the NN bond giving the ring expansion product, symmetrical N,N0 -di(t-butyl)diazetidinedione, in 75% yield <1999H(50)67>.
Functions Containing a Carbonyl Group and Two Heteroatoms
461
Instead of oxygen, iodine could be used as an oxidant. Thus, tungsten-catalyzed carbonylation of aliphatic primary and secondary amines and diamines in the presence of iodine furnished a series of acyclic <2000JMOC(A)11, 2000JOC5216> and cyclic ureas <1999OL961, 2002JOC4086, 2003JOC1615>. This reaction is compatible with acid-sensitive and fluoride-sensitive functional groups. A nitroarene, such as 3-(trifluoromethyl)nitrobenzene, was also used as an oxidant for Se-mediated conversion of primary alkylamines into symmetrical 1,3-dialkyl ureas <1995JGU88>. The ability of carbon monoxide to reduce nitroarenes to the corresponding anilines has been exploited in the preparation of 1,3-diaryl- <1993USP5198582, 2002JCA255, 2003JMOC(A)135> and 1-aryl-3-cycloalkyl ureas <2003JMOC(A)135>. Selenium is the most common catalyst for this process, although a polymer-supported rhodium catalyst has also been applied <2002JCA255>. In these reactions the nitro compound acts as both the reagent and an oxidant. The use of toxic carbon monoxide could be avoided by replacing it with CO2. Thus, 1,3-dialkyl ureas and 2-imidazolinones were successfully prepared from the corresponding amines or diamines and CO2 at 80 C using the Ph3SbO/P4S10 catalytic system <1992JOC7339>. Trisubstituted ureas were also synthesized under these conditions in moderate yields, but the attempts to prepare a tetrasubstituted urea, other than tetramethylurea, failed. This shortcoming was later overcome by carrying out the reaction in the presence of carbon tetrachloride and 1,8-bis(dimethylamino)naphthalene <2002JOC9070>. Purging CO2 into a mixture of a primary aromatic amine and DBU in pyridine or tetrahydrofuran (THF) followed by addition of the trimethylamine–sulfur trioxide complex as a dehydrating agent gave the corresponding 1,3-diaryl ureas in 23–87% yields <1995SC2467>. The analogous reaction of ammonia with carbon dioxide with removal of water using water-selective membranes allowed for the large-scale preparation of unsubstituted urea <2001WOP04085>. Heating primary aromatic or aliphatic amines with ethyl acetoacetate at 180 C in the presence of the commercially available zeolite, HSZ-360, led to carbonylative dimerization of the amines affording symmetrical 1,3-diaryl or 1,3-dialkyl ureas as the sole reaction products <1998CC513, 1999JOC1004>. The reaction presumably occurs via the intermediate formation of the corresponding acetoacetamide, which undergoes CC bond cleavage on further reaction with an amine.
6.16.1.1.4
Substitution reactions of amines with phosgene and its equivalents
(i) Reactions of amines with phosgene Despite its toxicity, phosgene is still utilized, although to a lesser degree than other carbonic acid derivatives, for the conversion of amines into ureas (Equation (7)). The reaction generally takes place in inert solvents (toluene, dichloromethane, THF) at 0–5 C in the presence of a base (aq. NaHCO3, aq. NaOH, triethylamine, etc.). O R1R2NH
+
R3R4NH
+
COCl2
R1
N R2
N R4
R3
ð7Þ
The reactions of phosgene with 2 equiv. of an amine were used for the synthesis of a variety of symmetrical ureas, including N,N0 -carbonylbis(azoles) <1996EUP692476, 1997JOC4155, 2000GEP19830556, 2002GEP10035011> and cyclic ureas, such as 4,5-diaminoimidazol-2-ones <1998EJO183>, imidazolidin-2-ones and their fused analogs <1993T4419>, tetrahydropyrimidin2-ones <2002HCA1999>, and hexahydroazepin-2-ones <1997JOC5380, 1998JOC9252>. More useful, however, is the synthesis of unsymmetrical ureas by consecutive treatment of phosgene with two different amines with in situ formation of an isocyanate intermediate. A combination of two aromatic amines <2002WOP83642>, two amino acids <2001OL2313>, or an aromatic or heterocyclic amine and O-alkyl hydroxylamine <1996TL2361, 2000CCA569> were all successfully used. 14C-Labeled phenylureas bearing photoactive azido and diazine groups were also prepared by this procedure <1993MI655>. The reaction with phosgene was also employed in the solid-phase synthesis of functionalized N-carbamoyl indolines <2000JA2966>.
462
Functions Containing a Carbonyl Group and Two Heteroatoms
(ii) Reactions of amines with carbamoyl chlorides Reactions of carbamoyl chlorides with amines (Equation (8)) are comparatively seldom used for the urea synthesis, probably due to a limited range of available carbamoyl chlorides. O R1R2NH
+
R1
R3R4NCOCl
N R2
N R4
R3
ð8Þ
Dialkyl and alkyl aryl carbamoyl chlorides were successfully used for carbamoylation of azaheterocycles, such as triazoles <2002BCJ567>, oxazolidinones <2002JA9060> and tetrazolinones <1995EUP646577>, arylhydrazines <1994S782>, and O,O0 -polyoxyethylene bis(hydroxylamine)s <1993JOU1464>, the latter being dicarbamoylated. In contrast, treatment of O,O0 -polyoxyethylene bis(hydroxylamine) with N-carbazolylcarbonyl chloride gave exclusively the monocarbamoylation product, albeit in a moderate yield <2001SL682>. Carbamoylation of pyridines affords the corresponding N-carbamoylpyridinium halides <1996EUP692473>; however, when -chloroformyl arylhydrazines 24 are used as the reactants, further attack of the free amino group at the 2-position of the pyridine ring occurs to afford [1,2,4]triazolo[4,3-a]pyridine-3-ones 25 (Equation (9)) <2001MI1135>. The analogous cyclization reaction was observed with isoquinoline and pyridazine <2002MI239>. Pyrimidine, however, was unreactive under the reaction conditions, whereas 1,3,5-triazine, thiazole, and 1,4,5,6-tetrahydropyrimidine underwent ring opening of the original heterocycle to afford functionalized 2,4-dihydro-1,2,4-triazol-3-ones in good yields. O Ar
100 °C
+
N Cl NH2
N
12 h
N
75–84%
excess
24
N Ar
N
ð9Þ
O 25
Ar = Ph, 4-ClC6H4, 4-MeC6H4
Carbamoylation of N-alkyl hydroxylamines with N-cyano-N-arylcarbamoyl chlorides followed by intramolecular addition of the N-hydroxy group to the nitrile furnished the corresponding 1,2,4-oxadiazol-3-ones in 93–98% yields <2002SC803>. Analogous tandem carbamoylation/intramolecular cyclization procedure was used for preparation of thiatetraazaindenones and -fluorenones from mercapto-substituted triazoles and benzimidazoles, respectively <2000M953>.
(iii) Reactions of amines with chloroformates Chloroformates, bearing two good leaving groups of different nucleofugicity, represent convenient reagents for step-by-step CO-linking of different amines (Scheme 8) and preparation of unsymmetrical ureas without isolation of the intermediate carbamates.
O
O 1 2
R R NH
+
Cl
R1 OR3
N R2
R4R5NH
OR3
O R1
N R2
N R5
R4
Scheme 8
The most widely used are phenyl and 4-nitrophenyl chloroformates, although some alkyl and chloroalkyl chloroformates are also applied. This approach was successfully used for the preparation of di- and trisubstituted ureas <1996SC4253, 2002JAP(K)212160>, N-carbamoyl amino esters <1996OPP173, 1997TL5335>, and N-arylcarbamoyl aminopyrazoles <2002WOP66442> and indolines <2000SC1937>. The procedure was also applied to solidphase synthesis of functionalized ureas <1994TL4055, 1996TL4439>.
Functions Containing a Carbonyl Group and Two Heteroatoms
463
When a substrate molecule has two amino groups of different reactivity, intramolecular cyclization can occur. Thus, heating pyrazolyl hydrazides 26 with trichloromethyl chloroformate gave pyrazolotriazinediones 27 (Equation (10)) <1999S453>, whereas condensation of -hydrazono selenamide with methyl chloroformate afforded selenated 1,2,4-triazine-3-one in 49% yield <2000PS(164)161>.
R O
R H N
N N H
O
+
N H
O
Cl
Ar
CCl3
Toluene
N
Reflux, 1 h 53–68%
O
O
N
26
N Ar
NH
ð10Þ
27
R = H, Cl, Br, NO2 Ar = Ph, 2-MeC6H4, 3-ClC6H4
(iv) Reactions of amines with carbamates and thiocarbamates Carbamates represent the carbonic acid derivatives most widely used in the urea synthesis and are generally prepared by partial aminolysis of chloroformates (see Scheme 8). O-Phenyl and O-tbutyl carbamates are the most popular, the latter being readily available from amines and (BOC)2O. Aminolysis of carbamates (Equation (11)) usually requires the presence of a base (triethylamine, DBU, NaHCO3, etc.) and, when necessary, can be promoted by addition of chlorosilanes <1998JOC8515, 2000JOC3239> or by heating over -Al2O3 <2000TL6347>. O R1R2NH
+
R3
N R4
O X
R5
R1
N R2
N R4
R3
ð11Þ
X = O, S
The reaction is tolerant to a wide variety of the functional groups on both the carbamate and the amine reactants allowing for the preparation of multiply functionalized ureas, including: acryloyl ureas <1993EUP556841>, hydroxy-substituted ureas <1997S1189, 2001TL1445>, polyfluorinated ureas <2000JOC1549>, arylsulfonyl <2001WOP05354> and heteroarylsulfonyl ureas <1995WOP00509, 2001MI404>, carbamoyl diamino acids <1994EUP629612>, N-carbamoyl nucleosides <1994HCA1267>, carbamoylamino glycosides <2000OL2113, 2001TL1445> and N-carbamoyl piperidines <1997S1189, 2000JOC1549>, piperazines <1996SL507>, indolines <2001JHC451, 2002TL6649>, dihydroquinolines <2000TL6387>, and dihydrophthalazines <2002JHC989>. The groups sensitive to the transformation include some amino protecting groups, such as N-benzoate <2000MI405> and N-phenoxycarboxylate <1992JOC5020>. The carbamate aminolysis has also been applied to the solid-phase preparation of N-carbamoyl dihydroquinolinones <2000SL45>, N-carbamoyl guanidines <1999JCO361>, oligoureas <2000TL1553>, and libraries of di- and trisubstituted ureas <1998JOC4802, 2002MI81>. On treatment with amines, cyclic carbamates, such as 2-oxazolidinones <1996TL1217> or 1H-thieno[2,3-d][1,3]oxazine-2,4-diones <1998T10789>, undergo aminative ring opening to afford hydroxy- or carboxy-functionalized ureas, respectively. When a reactive amino or imino function is already present in the carbamate or activated in situ by deprotection, the intramolecular carbamoylation can occur allowing for access to variously substituted hydantoins <1997TL2065, 1998CC2703, 2000T3697>, optically active polycyclic ureas <1996T8581>, triazinediones <2002HCO123>, and fused tetrazinones <2002JCS(P1)1877>. Cyclic ureas could also be prepared by intermolecular carbamoylation if the carbamate and/ or amine component have additional reactive functional groups. Thus, hydantoins 29 (Equation (12)) and their dehydro derivatives were prepared by condensation of N-BOC amines 28 having the
464
Functions Containing a Carbonyl Group and Two Heteroatoms
activated -position with imines <1996JOC428, 2001JOC2858, 2002EJO301> and nitriles <1994JHC1689>, respectively. Cyclocondensation of ,-unsaturated -amino acids or their esters with carbamates afforded uracil derivatives <1995JAP(K)0761975, 1998USP5817814>, whereas the reaction of dihydrobenzodiazepinethione with ethyl carbazate gave fused triazolobenzodiazepinones in moderate yields <2003JMC3758>. Pyrazolo[1,5-d][1,2,4]triazinones were prepared via the analogous cyclocondensation of 5-acylpyrazolyl-1-carboxylates with phenylhydrazine <2002JOU602>. R1 R R2
OMe
1
N
+
BOC
R3
s-BuLi THF or Et2O
N
–78 °C 22–92%
28
R2
R3
N
N OMe
O
ð12Þ
29
R1 = Ph, R2 = 4-MeOC6H4 R1 = benzotriazol-1-yl, R2 = PhCH2 R3 = Ph, 4-MeOC6H4, 2-furyl, etc.
Aminolysis of S-methyl alkylthiocarbamates with primary or secondary alkyl and cycloalkyl amines in acetonitrile <1998TL3609>, or with primary sulfonamides in toluene in the presence of DBU <2000SC3081>, gave the corresponding ureas and sulfonylureas in 60–89% yields without racemization. Although benzamide and thiobenzamide were unreactive under these conditions, aryl-substituted ureas were prepared in 81–100% yields by treatment of thiocarbamates with generated in situ aniline carbanions <2000SC1675>. Aminolysis of S-allyl N-acylthiocarbamates with a variety of amines in benzene-water twophase system <1993CCC575> or with phenylhydrazine in benzene <1993MI64> afforded the corresponding acyl ureas and acyl semicarbazides, respectively. Thermolysis of N-aryl carbamates at 230–240 C produces the corresponding symmetrical 1,3-diarylureas in 42–97% yields <1994RRC397>.
(v) Reactions of amines with ureas (a) Preparation of acyclic ureas via disubstitution of symmetric ureas with amines. Microwave irradiation of a mixture of an aromatic amine or phenylhydrazine with unsubstituted urea afforded the corresponding symmetrical ureas in moderate-to-good yields (Equation (13)) <1999JCR(S)710>. The addition of a suitable energy-transfer solvent, such as N,N-dimethyl acetamide, to the reaction mixture resulted in significant improvement in the product yields <2000MI24>. Primary aliphatic amines <2000MI24> and 2-aminopyridines <2001HCO233> reacted in a similar manner. O RNH2
H2N
O
Microwave
+
NH2
40–90%
RHN
NHR
ð13Þ
R = alkyl, aryl, 2-pyridyl, PhNH
However, of all the symmetrical ureas, commercially available, easily handled, crystalline N,N0 -carbonyldiimidazole (CDI) is the most widely used as a phosgene equivalent. Significantly lower reactivity of an N-carbamoylimidazole, formed after substitution of one imidazolyl group with an amine, compared to CDI itself allows one to carry out the disubstitution consecutively using two different amines or their analogs. This approach was applied in the solution-phase synthesis of optically active dipeptides <1997TL5335, 2002JA9356>, N-carbamoyltetrahydropapaverines <2002CPB1223> and 4-hydroxysemicarbazides <2000HCO55, 2002HCO321>, and in the solid-phase synthesis of unsymmetrical polyfunctional 1,3-diaryl ureas <1997BOC277>. Although N-carbamoyl imidazoles, formed from secondary amines and CDI, were found to be unreactive toward coupling with secondary amines, these intermediates could be activated by their conversion into the corresponding imidazolium salts <1998TL6267>, thus making this approach suitable for the preparation of tetrasubstituted ureas.
465
Functions Containing a Carbonyl Group and Two Heteroatoms
Instead of CDI, 1,10 -carbonylbis(benzotriazole) was used for preparation of tetrasubstituted ureas (no activation is required in this case) <1997JOC4155> and for solution- and solid-phase synthesis of dipeptides <1998TL7811>. (b) Preparation of acyclic ureas via monosubstitution of ureas with amines. Condensation of unsubstituted urea with a sterically hindered secondary amine in a strongly acidic medium <2000CHE837> or with a heteroaromatic amine, such as pyrazole, under thermal conditions <1992EUP508191> results in substitution of only one of the urea amino groups providing products of the general formula R1R2NCONH2. On treatment of N-phenylurea with a variety of amines, the unsubstituted amino group of the urea is cleaved, thus allowing access to a series of 1,3-di- and trisubstituted ureas <1992M607, 1995GEP4405056>. The same products could be prepared by reaction of 1,3-diphenylurea with amines <1993OPP600>. Analogously to the second step of the CDI aminolysis, reaction of independently prepared N-carbamoyl imidazoles with amines leads to the substitution of the imidazolyl moiety with the amino group <1994WOP06825>. Similarly, heating resin-bound 1-carbamoyl-1,2,3-benzotriazole with primary or secondary amines results in the nucleophilic displacement of the benzotriazole moiety releasing the newly formed unsymmetrical urea in the solution <2001JCO354>. (c) Preparation of cyclic ureas. The most widely used procedure for the preparation of cyclic ureas via the substitution pathway is the condensation of urea or its derivatives with diamines. Unsubstituted urea or CDI are generally used as phosgene equivalents. This approach was applied to the preparation of 2-imidazolidinones <1993T4419>, 2-benzimidazolones <2002JCO320>, tetrahydropyrimidin-2-ones <2002HCA1999>, hexahydroazepin-2-ones <1996USP5508400, 2002OL4673>, hexahydro-1,3,6-triazocin-2-one <1995EUP670316>, and macrocyclic ureas <1993USP5206362>. A series of functionalized hydantoins were synthesized from the corresponding resin-bound 1,2-diamines <1997TL931, 2001JCO68, 2002JCO175>. Instead of two amino groups, their analogs, such as amide <1993TL7953>, hydrazine <1999HCO473, 2001JHC1097>, or amidrazone <2002JMC2942> moieties, can participate in the reaction. If a second amine, used for the double aminolysis of CDI, features a suitably located carboxylic group, the in situ intramolecular cyclization of the newly formed urea can occur giving, for example, fused imidazolidinediones <1994JHC1235, 2002JHC417>. The similar intramolecular cyclization after formation of the urea fragment was used for solution-phase <2000TL1159> and solid-phase <2000TL1165> synthesis of 3-aminohydantoins and 3-aminodihydrouracils.
(vi) Reactions of amines with carbonates and thiocarbonates (a) Preparation of acyclic ureas. Similarly to reactions of ureas with amines, aminolysis of carbonates (Scheme 9) could be carried out by consecutive introduction of two different amines or their analogs allowing for access to unsymmetrical ureas and their derivatives. O
O R1R2NH
+
R3X
R1 XR3
N R2
R4R5NH
XR 3
O R1
N R2
N R5
R4
X = O, S
Scheme 9
Bis(trichloromethyl) carbonate, or triphosgene, is the most widely exploited. Using the coupling reaction with triphosgene, ureas derived from two different amino acids <1994JOC1937, 1999TL2895>, as well as 1-aryl-3,3-dialkyl ureas <1998JCR(S)442>, glucopyranosylureas <2001JOC4200>, -ureido alkylphosphonates <2000PS(160)51, 2001JCR(S)470, 2001HAC68>, carborane-substituted ureas <2000TL7065, 2001TL5913, 2002JOM(657)48>, ureapeptoid peptidomimetics <1997TL5335>, and urea-functionalized porphyrins <1998JOC2424> were all successfully prepared. This approach has also been applied to the solution-phase synthesis of tri- and tetrasubstituted ureas from polyethylene glycol-bound amines <2001BMCL271> and to solid-phase synthesis of peptide C-terminal semicarbazones <1999TL6121>.
466
Functions Containing a Carbonyl Group and Two Heteroatoms
Other symmetrical carbonates, such as dimethyl carbonate <2002GC269>, diphenyl carbonate <2001JAP(K)302640>, cyclic ethylene carbonate <1998EUP846679> and bis(1-cyclohexenyl) carbonate <1995JAP(K)06239805>, as well as unsymmetrical diaryl carbonates <1996SC331> were also used. Nitrophenyl carbonates were applied in the solid-phase synthesis of various ureas <1998TL3631> and azapeptides <2000TL3983>. Although di(t-butyl) carbonate is known to react with amines directly to give N-BOC-protected derivatives, under catalysis with 4-(dimethylamino)pyridine (DMAP) it reacts with a second equivalent of an amine to give the corresponding ureas. This procedure was successfully applied to primary aromatic <1996SL502, 2000JOC6368>, primary aliphatic amines and resin-bound anilines <1999TL8563>; however, with secondary amines only N-BOC protection was observed <2000JOC6368>. The condensation of primary alkylamines with S,S-dimethyl dithiocarbonate in methanol or without solvent at 60 C gave 1,3-dialkyl ureas <1996JOC4175>. Aromatic and sterically hindered alkylamines are unreactive, whereas dialkylamines give only monosubstituted products i.e., thiocarbamates. (b) Preparation of cyclic ureas. Condensation of carbonates with diamines leads to the formation of cyclic ureas if the diamine structure allows for nonconstrained ring closure. This procedure has been used for the preparation of benzimidazolones in solution <2001JCA91> and on the solid support <1998TL179>, quinazoline-2,4-diones <2002M1067>, and macrocyclic carborane-substituted ureas <2001TL5913>. Low-valent titanium-induced carbonylative dimerization of aryl imines in the presence of triphosgene gave substituted imidazolin-2-ones <2002SC2613>, which were also prepared via DMAP-catalyzed carbonylative cyclization of 1,2-diamines with BOC2O <2000JOC6368>. Condensation of S,S-dimethyl dithiocarbonate with appropriate diamines afforded a series of imidazolin-2-ones, tetrahydropyrimidin-2-ones, and 2-quinazolinone in moderate to good yields <1996JOC4175>.
6.16.1.1.5
Oxidation of thioureas and related compounds
Both acyclic and cyclic thioureas were readily converted into the corresponding ureas (Equation (14)) on treatment with bismuth nitrate pentahydrate in acetonitrile at reflux <2003TL591> or in phosphate buffer at 20 C <2000MI285>. The reaction is chemoselective: although thioamides are also oxidized, thiono esters and thioketones are essentially unreactive. Inexpensive, stable, and commercially available Oxone could also be used as an oxidant <2003PS(178)61>; however, in this case the excess of the reagent is required and a poorer chemoselectivity is observed. S R1
N R2
N R4
R3
Oxidant
O R1
N R2
N R4
R3
ð14Þ
Oxidation of 1,3-di- and trisubstituted thioureas was also carried out using sodium metaperiodate, sodium chlorite, and ammonium persulfate in water <1997SC2357>, whereas N-aroyl ureas were prepared via the oxidation of thioureas with bromine in chloroform (Hugershoff reaction) <1994CCC2663>. Potassium iodate (KIO3) was found to be a convenient reagent for the preparation of N-aroyl ureas <2000SC2635>, N-acylated bis(urea)s <2002SC3373>, and N,N0 -diacyl semicarbazides <2000SC3405, 2000SC4543, 2001SC1433> from the corresponding thiocarbonyl analogs. Trisubstituted glucopyranosyl thioureas were readily oxidized with excess of yellow HgO <2002TL4313>; the disubstituted analogs, however, gave exclusively bicyclic isoureas. There are few procedures specific for oxidation of cyclic thioureas. These include oxidation with mercury(II) acetate, used for the preparation of 1,3-diacylimidazolidin-2-ones <1993T4419>, and oxidation with 30% hydrogen peroxide in aq. NaOH, used in synthesis of six-membered cyclic ureas <1994JHC1569, 1999JHC1327>. Tetrazolinethiones were oxidized to tetrazolinones using unsubstituted oxirane or 2-alkyl epoxides as oxidants <1995EUP643049>.
6.16.1.1.6
Reactions of amines with amides and other carboxylic acid derivatives
Ruthenium-catalyzed carbamoylation of dialkylamines <1992USP5155267> or primary aromatic amines <1997OM2562> with formanilides at 165 C give the corresponding unsymmetrical diand trisubstituted ureas in high yields. For reaction with anilines, unsubstituted formamide could
467
Functions Containing a Carbonyl Group and Two Heteroatoms
also be used. Although simple alkyl and cycloalkyl amides are unreactive, -polychloro- or -polynitro-substituted aliphatic amides readily undergo -elimination to give intermediate isocyanates, which on trapping with ammonia or primary amines afford mono- and disubstituted ureas, respectively (Scheme 10) <1992BAU891, 1994BAU821, 1994CL2299, 1994OPP357, 1999TL3235>. O
O R1
N H
R3R4NH
∆
R2
R2
R2NCO
N H
–R1H
N R4
R3
R1 = CCl3, O2NCCl2, MeC(NO2)2
Scheme 10
Curtius rearrangement of acyl azides also produces the intermediate isocyanates as urea precursors. The starting acyl azides are usually generated in situ by one of the following methods: (i) reaction of a carboxylic acid with diphenylphosphoryl azide in the presence of a base <2001MI133, 2002MI109, 2002T4225>; (ii) from acyl chlorides and sodium azide <1999S943, 2000JHC1247>; or (iii) oxidation of acyl hydrazides with HNO2 <1998JCS(P1)2377>. This approach has also been applied to the synthesis of N,N0 -disubstituted ureas from heterocyclic and aliphatic carboxylic acids and resin-bound amines <2000OL3309>.
6.16.1.1.7
Miscellaneous reactions
(i) From carbodiimides Hydrolysis of carbodiimides produces the corresponding ureas <2000CAR161>, whereas their heterocyclization with diaryl nitrones <1998SC3665> or 2-(bromomethyl)acrylic acid <1996JHC1259> yields polysubstituted 1,2,4-triazolin-3-ones and 5-methylidenetetrahydropyrimidine-2,4-diones, respectively.
(ii) Heterocycle ring–ring interconversions Variously substituted 1,2,4-triazol-3-ones were prepared by ring opening/recyclization of 2-amino-1,3,4-oxadiazoles <2002JCR(S)213> or 5-amino-1,2,4-oxadiazoles (Equation (15)) <1996JOC8397> in the presence of a primary amine. The rearrangement of arylhydrazones of 3-benzoyl-5-amino-1,2,4-oxadiazoles, however, occurs differently with formation of ureidosubstituted 1,2,3-triazoles <2002JOC8010>. Ph
H
N R1
O
N
+
R2NH2
R1 = NH2, NHMe, NMe2
MeOH 57–60%
Ph N
hν
O
N R2
N
ð15Þ
R2 = H, Me, n-Pr, n-Bu, NH2
Heating 3-(2-oxopropyl)benzothiazol-2-ones with excess of a primary amine in HClO4 affords 1-(2-mercaptoaryl)imidazolin-2-ones, readily oxidizable in air to the corresponding disulfides <2000PS(158)67>. Oxidative rearrangement of 3-arylimino-2-indolinones occurs with the ring expansion to give quinazoline-2,4-diones <2000TL5265>.
(iii) Oxidation Purines and xanthines are readily oxidized to the corresponding 8-oxo derivatives with dimethyldioxirane <1995TL2665> or bacteria <1999JCS(P1)677>, whereas oxidation of benzimidazolium salts and their N,N0 -polymethylene-bridged analogs in air affords the relevant benzimidazolones
468
Functions Containing a Carbonyl Group and Two Heteroatoms
in high yields <1994TL33, 1995TL2741>. Treatment of amidines with (diacetoxyiodo)benzene yields either 1,3-disubstituted ureas or trisubstituted acylureas depending on the reaction conditions <1997JCS(P1)2319>.
6.16.1.1.8
Preparation of carbamoyl azides
The early review on carbamoyl azides <1965CRV377> indicated three preparation methods, which are still the ones most commonly used: (a) reaction of carbamoyl chlorides with sodium azide; (b) addition of hydrazoic acids to isocyanates; and (c) oxidation of semicarbazides with HNO2. Since this review, only few reports on synthesis of the title compounds have appeared. The reaction of carbamoyl chlorides with sodium azide usually occurs under very mild conditions (aq. acetone, 0–20 C) with carbamoyl chlorides being used as such <1987GEP252824> or prepared in situ from the corresponding amine and phosgene <1995JOC321>. Treatment of chloroformyl <1985JOU1436> and -chloroalkyl isocyanates <1976JOU1140> with excess of hydrazoic acid resulted in both addition to the isocyanate moiety and substitution of the chlorine atom with the azido group affording the corresponding diazido compounds, whereas with -chloro-functionalized isocyanates no substitution reaction was observed <1985RRC317>. The isocyanate reactant can also be generated in situ by addition of hydrazoic acid to acyl ketenes accompanied by nitrogen elimination <1981JOC147, 1981JOC153> or by Curtius rearrangement of acyl azides <1986JHC1103, 1990JOC5017>. Instead of unstable hydrazoic acid, its derivatives, such as trimethylsilyl azide <1980JOC5130> or triarylbismuth diazides <1992JCR(S)34> could be used; however, in these reactions the mixtures of products are usually obtained with the product distribution depending on the reaction conditions. Other methods for synthesis of carbamoyl azides include oxidation of aldehydes with pyridinium chloroformate in the presence of sodium azide <1988SC545> and reaction of carboxylic acids with the Vilsmeier salt followed by treatment with sodium azide <1994TL2729>. The latter approach is high-yielding and applicable to the preparation of a wide variety of carbamoyl azides, including optically active substrates.
6.16.1.2 6.16.1.2.1
Carbonyl Derivatives with One Nitrogen and One P, As, Sb or Bi Function Carbonyl derivatives with one nitrogen and one phosphorus(III) function
The most common procedure for the preparation of carbamoyl phosphines is based on the phosphine addition to alkyl or aryl isocyanates (Equation (16)) <1995COFGT(6)499>. The reaction is tolerant to the presence of thiol <1973JPR471>, alkylthio <1988JGU1310>, and keto <1970JPR366> groups, and is applicable both to secondary and primary phosphines. In the latter case, however, double carbamoylation of the phosphine occurs <1988JGU28>, even for sterically hindered phosphines. R1 P H R2
+
R3 N C O
O R1
P R2
N H
R3
ð16Þ
The bulky analog of PH3, tris(trimethylsilyl)phosphine (tris(TMS)phosphine), gives with isopropyl isocyanate exclusively 1:1 adduct 30, which exists in equilibrium with its (siloxy)imine tautomer 31 (Equation (17)) <1989AG(E)53>. Under mild conditions, isocyanates readily insert into the ZrP bond of PH-functionalized zirconocene complexes 32 to afford the corresponding (phosphinoamidato)zirconocenes 33 in 81–85% yields (Equation (18)). The presence of a bulky ligand, such as R1 = 5-C5EtMe4, favors the formation of complexes 33 exclusively as endoisomers (shown), whereas products 33 with less sterically hindered ligands e.g., R1 = 5C5MeH4, were formed as mixtures of endo- and exo-isomers, with exo-isomers predominating <2000OM2445>. To our knowledge, up to the early 2000s, this reaction represents the only procedure for the preparation of a secondary carbamoyl phosphine in acceptable yields.
469
Functions Containin
