Organophosphorus Chemistry

Organophosphorus Chemistry Volume 32

A Specialist Periodical Report

Organophosphorus Chemistry

Volume 32

A Review of the Literature Published between July 1999 and June 2000 Senior Reporters D.W. Allen, Sheffield Hallam University, Sheffield, UK J.C. Tebby, Staffordshire University, Stoke-on-Trent, UK Reporters N. Bricklebank, Sheffield HaIlam University, Sheffield, UK C.D. Hall, King's College, London, UK M. Migaud, The Queen's University of Belfast, UK J.C. van de Grampel, University of Groningen, The Netherlands

RSC ROYAL SOCIETY OF CHEMISTRY

ISBN 0-85404-334-9 ISSN 0306-0713

0The Royal Society of Chemistry 2002 All rights reserved Apart from any fair dealing for the purposes of research or private study, or criticism or review as permitted under the terms of the UK Copyright, Designs and Patents Act, 1988, this publication may not be reproduced, stored or transmitted, in any form or by any means, without the prior permission in writing of The Royal Society of Chemistry, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of the licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to The Royal Society of Chemistry at the address printed on this page. Published by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 OWF, UK Registered Charity Number 207890 For further information see our web site at www.rsc.org

Typeset by Computape (Pickering) Ltd, Pickering, North Yorkshire, UK Printed by Athenaeum Press Ltd, Gateshead, Tyne and Wear, UK

Introduction

The literature relating to the chemistry of organophosphorus compounds continues to grow. Our problem as Senior Reporters is to find authors who are willing to undertake the task of reviewing the various areas in a timely manner. The past year has been particularly difficult in this respect, and this volume lacks coverage of some areas that previously have been reviewed continuously over many years. Thus, this year, we are unable to provide a review of the chemistry of quinquevalent phosphorus acids, and the ‘Physical Methods’ chapter is also missing. The mononucleotide section of the normally extensive chapter on ‘Nucleotides and Nucleic Acids’ is provided by a new member of the team, Dr Marie Migaud (Queen’s, Belfast), but we have not been able to secure the usual coverage of polynucleotide and nucleic acid chemistry. On the credit side, we have a two-year review of the chemistry of tervalent phosphorus acid derivatives, making up for the absence of this topic in the previous Volume 31. We hope to remedy the deficiences of the present volume in a similar way next year. We would welcome approaches from potential authors, in particular for the ‘Physical Methods’ chapter, or specific sections thereof, as this topic requires an overview of the application of physical methods of all kinds across the whole of the organophosphorus area, and is a major undertaking. The synthesis of new chiral phosphines continues to be a major preoccupation, the main focus being applications in metal-catalysed processes. Interest in the synthesis and structural characterisation of metallo-organophosphide systems also continues to grow. In contrast, the volume of new work on lowcoordination number p,-bonded phosphorus compounds has declined, as the major features of this area have now become established, although much interesting new work continues to appear. The synthesis of new chiral ligand systems is also now a significant feature in the chemistry of tervalent phosphorus acid esters and amides, applications of such compounds in metalcatalysed processes hitherto having been neglected relative to those involving phosphine ligands. The past year has also seen continued interest in the structure of phosphonium ylides, with particular reference to gaining greater insight into their stability, electronic distributions and conformation, on which the reactivity of these systems depends. In the nucleotide field, the year has been marked by the development of new phosphorylation and chiral thiophosphorylation methods and by improvements in the formation of intramolecular pyrophosphate linkages. The year has seen yet another diminution in the number of publications dealing with hypervalent phosphorus chemistry but the quality of work V

vi

Introduction

remains high, relying heavily on the latest techniques in NMR spectroscopy and X-ray crystallography. Ample illustration of this is found in a study of cyclic phosphates, phosphonates and phosphonium salts containing sulfuryl groups. The work was designed to compare the coordinating ability of sulfur, reported earlier, with that of sulfuryl oxygen and in fact only one of a series of eight phosphates, phosphonates and phosphonium salts showed evidence of donor action towards phosphorus from phosphoryl oxygen, with a P-0 bond distance of 3.007 The keen interest in phosphazenes continues and many advances and further applications have been reported. There have been further studies of the azaWittig reaction, several of which focus on the synthesis of nitrogen heterocycles. Carbophosphazenes have been shown to ring-open tertiary bases, such as quinuclidine, to give amino-substituted derivatives. Several reports concern the preparation of ferrocenyl derivatives and much use has been made of silylated phosphazenes. Complexation with a wide range of metals has produced an interesting array of novel structures. Phosphazenes have been used as phase transfer catalysts and as strong bases, and crystals of a phenylenedioxide cyclotriphosphazene have been used to form inclusion compounds with various aromatics and polymers. Vinyl derivatives have been prepared, leading to fascinating dendritic architectures. A polyphosphazene derived from a chiral amine gave a large optical rotation assigned to the presence of a helical P = 3DN backbone. Applications as flame retardants abound and a polyphosphazene with pendant cyanate groups was cured to produce a novel cyclo-matrix with improved char yield. There has been much interest in polymers and copolymers, some being amphiphilic and capable of forming micelles. Platinum complexes with greater anticancer activity than Carboplatin have also been reported.

A.

D. W. Allen J. C. Tebby

Contents

Chapter 1

Phosphines and Phosphonium Salts By D. W.Allen

1

1 Phosphines 1.1 Preparation 1.1.1 From Halogenophosphines and Organometallic Reagents 1.1.2 Preparation of Phosphines from Metallated Phosphines 1.1.3 Preparation of Phosphines by Addition of P-H to Unsaturated Compounds 1.1.4 Preparation of Phosphines by Reduction 1.1.5 Miscellaneous Methods of Preparing Phosphines 1.2 Reactions of Phosphines 1.2.1 Nucleophilic Attack at Carbon 1.2.2 Nucleophilic Attack at Halogen 1.2.3 Nucleophilic Attack at Other Atoms 1.2.4 Miscellaneous Reactions of Phosphines

1 1

13 15 17 23 23 24 25 27

2 Phosphine Oxides 2.1 Preparation 2.2 Reactions 2.3 Structural and Physical Aspects 2.4 Phosphine Chalcogenides as Ligands

31 31 33 36 36

3 Phosphonium Salts 3.1 Preparation 3.2 Reactions

38 38 40

4 p,-Bonded Phosphorus Compounds

42

5 Phosphirenes, Phospholes and Phosphinines

47

6

53

References Chapter 2

1

Pentacoordinated and HexacoordinatedCompounds By C.D. Hall

74

1 Introduction

74

Organophosphorus Chemistry, Volume 32

0The Royal Society of Chemistry, 2002

vii

...

Contents

Vlll

2 Acyclic Phosphoranes

74

3 Monocyclic Phosphoranes

77

4 Bicyclic and Tricyclic Phosphoranes

79

5 Hexacoordinate Phosphorus Compounds

87

References Chapter 3

Tervalent Phosphorus Acid Derivatives By D. W.Allen

91

1 Introduction

91

2 Halogenopho sphines

91

3 Tervalent Phosphorus Esters 3.1 Phosphinites 3.2 Phosphonites 3.3 Phosphites

94 94 97 99

4 Tervalent Phosphorus Amides

Chapter 4

89

1.4 Aminophosphines 1.5 Phosphoramidites and Related Compounds

109 109 111

References

113

Nucleotides and Nucleic Acids By M. Migaud

120

1 Introduction

120

2 Mononucleotides 2.1 Nucleoside Acyclic Phosphates 2.1.1 Mononucleoside Phosphate Derivatives 2.1.2 Polynucleoside Monophosphate Derivatives 2.2 Nucleoside Pyrophosphates 2.2.1 Nucleoside Diphosphate Analogues 2.2.2 Nucleoside Diphosphosugars 2.2.3 Nucleoside Cyclic Pyrophosphates 2.2.4 Nucleoside Pyrophosphonates

120 120 120 133 139 139 139 140 141

3 Nucleoside Polyphosphates

141

References

153

ix

Contents Chapter 5

Ylides and Related Species By N. Bricklebank

157

1 Introduction

157

2 Phosphonium Ylides 2.1 Theoretical, Structural and Mechanistic Studies of Phosphorus Ylides and the Wittig Reaction 2.2 Synthesis and Characterisation of Phosphonium Ylides 2.3 Ylides Coordinated to Transition Metals 2.4 Reactions of Phosphonium Ylides 2.4.1 Reactions with Carbonyl Compounds 2.4.2 Miscellaneous Reactions 2.5 The Synthesis and Reactions of Aza-Wittig Reagents

157

3 Structure and Reactivity of Lithiated Phosphine Oxide Anions

180

4 Structure and Reactivity of Phosphonate Anions

180

References Chapter 6

Author Index

157 160 164 168 168 174 177

184

Phosphazenes By J. C. van de Grampel

188

1 Introduction

188

2 Linear Phosphazenes

188

3 Cyclophosphazenes

205

4 Polyphosphazenes

2 14

5

Crystal Structures of Phosphazenes and Related Compounds

222

References

23 1 24 1

Abbreviations

Benzamide adenine dinucleotide Cyclodiphospho D-glycerate Capillary electrophoresis Creatine kinase Controlled potential electrolysis 1-(2-chlorophenyl)-4-methoxylpiperidin-2-yl Cyclic voltammetry cv DETPA Di(2-ethylhexy1)thiophosphoric acid Dimethylacetylenedicarboxylate DMAD Dimethylformamide DMF DMPC Dimyristoylphosphatidylcholine DRAMA Dipolar restoration at the magic angle DSC Differential scanning calorimetry DTA Differential thermal analysis ERMS Energy resolved mass spectrometry ESI-MS Electrospray ionization mass spectrometry EXAFS Extended X-ray absorption fine structure FAB Fast atom bombardment 1-(2-fluorophenyl)-4-methoxylpiperidin-2-y1 FPmP High-performance liquid chromatography HPLC LA-FTICR Laser ablation Fourier Transform ion cyclotron resonance Matrix assisted laser desorption ionization MALDI Micellar electrokinetic chromatography MCE Mass-analysed ion kinetic energy MIKE Polycyclic aromatic hydrocarbons PAH Hydroquinone- 0,O’-diacetic acid QDA 9-[2-(phosphonomethoxy)ethyl]adenine PMEA S-acyl-2-thioethyl SATE Secondary ion mass spectrometry SIMS SSAT Spermidinelspermine-N1-acetyltransferase Static secondary ion mass spectrometry SSIMS TAD Thiazole-4-carboxamideadenine dinucleotide tert-Butyldimethylsilyl tBDMS Trifluoroacetic acid TFA Thermogravimetric analysis TGA Thin-layer chromatography TLC Time of flight TOF X-Ray absorption near edge spectroscopy XANES

BAD cDPG CE CK CPE CPmP

X

1

Phosphines and Phosphonium Salts BY D. W. ALLEN

1

Phosphines

1.1. Preparation. - 1.1.1. From Halogenophosphines and Organometallic Reagents. The use of organolithium reagents has once again dominated this approach in the past year, with few examples of the application of Grignard or other reagents being noted. An attempt to prepare the bulky triarylphosphine (1) from 2,4,6-tri(isopropyl)phenyllithium and phosphorus trichloride resulted in the formation of the P,P-diphosphine (2), which is unusually stable to further cleavage in the presence of the aryllithium reagent.' An improved route to ortho-substituted aryldichlorophosphines has been developed, enabling the synthesis of a wide range of new triarylphosphines (3).2 An improved route from o-dibromobenzene to the o-bromoarylphosphine (4) has enabled the ,pi

Pr'

Pr',

R

(3) R = SMe or OMe Ar = o-anisyl, p-CH3SC6H4, I-naphthyl or 9-anthtyl

(4)

synthesis of the o-dichlorophosphinoarylphosphine(9,from which a range of chiral o-phosphinoarylphosphite ligands has been ~ r e p a r e dA . ~wide variety of new phosphines has been described in the past year, the main focus being the synthesis of new ligands for application in metal-catalysed processes. Among simple ligands prepared by the above route are triarylphosphines bearing or tholpara-ether or thioether substituents, e.g. (6): the triarylphosphines (7), the bulky systems (S)6 and (9),7 and sterically-crowdedhomochiral ligands, e.g. (lo).' Phosphines bearing fluorinated substituents have attracted some interest, e.g. (11),9 (12)" and (13)." The phosphine (14) is the starting point of a new

'

Organophosphorus Chemistry, Volume 32 0The Royal Society of Chemistry, 2002 1

+

Organophosphorus Chemistry

2

PhXP@R]

Q-C

3-x

SMe

PBut2

(7) R = H, F or OMe

(6) Ar = p-anisyl

(8)

Ph

(9)R = H or Me F *

/

PhXP@] x )

c

F (11)x = 1 o r 2

3-x3

F

[

(

Ph

(10)

3-n

(12) R = o-Me, p F or H x =o Ir 2

phxpiQ

I

SX

CSF13 (13) x = 0, 1 or 2

approach for the synthesis of the perfluorotail-funtionalised triarylphosphines (1 5), involving the introduction of a silyl group bearing partially fluorinated alkyl substituents, enabling the attachment of 3-9 'remote' solubilising fluoroalkyl tails per phosphorus without compromising the donor properties of the phosphine.I2 A range of polyethyleneglycol-linked diphosphines (16) has also

1: Phosphines and Phosphonium Salts

3

been prepared, having application as reagents in synthesis, e.g. in Wittig reactions under aqueous conditions. The organolithium-halophosphine route has also been used in the synthesis of various heteroarylphosphines, e.g. the diphosphinoterpyridine (17),l 4 the chiral chelating pyridylphosphinocyclopentane (18),lS the atropisomeric bis(dibenzofurany1)diphosphine (19) (and a related sulfonated system),l 6 diphosphino-2,2’-dithienyls,e.g. (2O), l 7 and a range of simple monophosphino derivatives of thiophen, N-methylpyrrole and pyridine.l8 Improved routes to phosphinomethyloxazolines, e.g. (21), have also been described,l 9 and further examples of ‘wide-bite’ diphosphine (and related phosphine-arsine) ligands, e.g. (22),2c22 based on the xanthene backbone, have been prepared. There has been considerable interest in the prepara-

N

R2 Ar2P

PAr,

(21) R’ = H or Me

R2 = H or PPh2

tion of phosphines bearing alkynyl groups as part of the overall structure, not necessarily directly linked to phosphorus. Generation of 1,4-dilithiobutadiyne (from 1,4-bis(trimethylsilyI)butadiyne and methyllithium) followed by treatment with chlorodiphenylphosphine has given the diphosphine (23), of interest as a spacer ligand, used in the synthesis of macrocyclic complexes.23Various phosphadiynes, including the medium-sized heterocyclic systems (24), have been obtained from the reactions of propargyllithium reagents with halophosp h i n e ~Routes . ~ ~ to alkynylphosphines, e.g. (25), of interest for the synthesis of dendrimers, have also been explored.25An aryllithiumxhlorophosphine route has been described for the synthesis of the phosphine (26), which, on heating, or in solution in xylene, is converted into the strikingly red-coloured phosphorane (27), the structure of which was confirmed by an X-ray study.26 Phosphino-alkynylporphyrin systems have also been prepared and used as supramolecular building Full details of improved routes to the azofunctionalised phosphines (28) have now appeared.28 A classical diorganolithium-phenyldichlorophosphine cyclisation is the key step in the synthesis of the 1-benzophosphepines (29).29Metallation of an acetal of o-bromobenzaldehyde, followed by a reaction with trans- 1,2-bis(dichlorophosphino)cyclopentane, has given the diphosphine (30, R = CH(OMe)2), from which the related dialdehyde (30, R = CHO) has been obtained, this having considerable potential for the synthesis of new chiral ‘expanded’ phosphine ligands. Other related systems have also been prepared by this general a p p r ~ a c h . ~Routes ’ for

4

Organophosphorus Chemistry MeC’

O

0

1

Me

Ph (28) R = H, alkyl, NO2 or NMe2

(29) R = H or SiMe3

qR1

PR’R~

OMe

OH

(Me3Si)2CH ,p H

(31) R’ = Ph, Pr’ or But

4

R~ = Ph or P i R3 = But or F R4 = H, Me or But

N(CH2CH2NEt2)2

Me,NA./OR

o-””.

(33) R = H or Me

PPh2

(34)

the synthesis of o-phosphinophenols have undergone further development, and new examples described, e.g. (3 1),31 Treatment of o-methoxyaryllithium reagents with bis(trimethylsilyl)methyldichlorophosphine, followed by reduction of the intermediate monochlorophosphine, has given the new stericallydemanding secondary phosphines (32), from which new ytterbium-phosphido derivatives have been prepared.32 Routes to the amino-functional phosphines (33)33 and (34),34have also been described. Monofunctionalisation by trivalent phosphorus of the calix[4]arene upper-rim has been achieved by lithiation with butyllithium, followed by phosphination with chlor~diphenylphosphine.~~ Interest in the synthesis of chiral phosphinoferrocene systems has been maintained, and a considerable number of new systems described. Several reports of

I : Phosphines and Phosphonium Salts

5

f12 PPh2

Fe

Fe

(37)R = Me, Pr', NMe2 or N-pyrrolidinyl

(35) .PPh;! V

PPhp I h Fe

Fe

&.Me Ph (39) R = Me or Pr'

(40) Ar = Ph or o-anisyl

(41)

the synthesis of chiral oxazolinylferrocenylphosphines have appeared.3c38 Surprisingly, the C2-symmetric system (35) fragments to form the fulvene system (36) on protection of the phosphine as its sulfide.38Among new chiral phosphinoferrocenes described are (37),39 (38),40(39):l (40)42and (41).43The ortho-lithiation of 1,l'-dibromoferrocene, using lithium diisopropylamide has been reported for the first time, enabling access to a range of new phosphinoferrocenes, e.g. (42)44 and (43).45The organolithium-chlorophosphine route has also been applied in the synthesis of the new ferrocenophane systems (44)46947 and (45);' and in the synthesis of other phosphinometallocene systems based on chromi~m:~titanium5' and zirconium.51 Both organolithium and Grignard reagents have been employed in a stepwise synthesis of the chiral phosphine (46) from (-)menthy1 chloride. The PPhp

Fe

&Br

(42)

ie

&Br

(43)

R &p-R (44) R = (-)-menthy1

(-)-bornyl or NPt2

6

Organophosphorus Chemistry

.. (-)-Men'

( a v o : \

P AFI. ' Ph

Rn-P(CH2CH2(CF2)xCF3)3-n

(46) FI = fluorenyl

(-)-Men = (-)-menthy1

H

(48)

(47)

R = (-)-rnenthyl, cyclohexyl or Pr n = 1 or2 x = 5-7

H

H

H

H

(50)M = Si or Ge

diastereoisomers of (46) were obtained via fractional crystallisation of the borane adducts, followed by decomplexation, and shown to undergo an unusual crystallisation-induced asymmetric transformation upon slow evaporation from refluxing h e ~ t a n eGrignard .~~ reagents have also been employed in the synthesis of the diphosphine (47),53 and a series of alkylphosphines bearing partially perfluorinated substituents, e.g. (48).s4,ss The organozirconium reagent (49) is a key intermediate in the synthesis of bisphospholane systems, e.g. (50). s6 Organolithium, -magnesium and -sodium reagents have been used to prepare various new carboranylphosphines.s7-s9 1.1.2. Preparation of Phosphines from Metallated Phosphines. As in previous years, the use of lithiophosphide reagents continues to dominate this approach to phosphine synthesis. The 1-(9-anthracenyl)phosphirane ( 5 1) has been obtained in two steps by lithium aluminium hydride reduction of 9-anthryldichlorophosphine, and subsequent lithiation and cyclisation with 1,2-dichloroethane. This compound is quite stable, resisting attempts to form polymers by ring-opening of the phosphirane system.60The reactions of lithium diphenylphosphide with tosylate substrates have been used in an improved route to the chiral aminoalkylphosphine (52), derived from L-valine,61from which a series of new chiral phosphine ligands, e.g. (53), has been derived, and also to the phosphinoalkyloxazoline system (54).62 Stepwise substitution of a ditosylate

(54) R = Ph, I-adamantyl, But

or 3,5-But2C6H3

(55) R' = Me or I-naphthyl

R2 = Ph or p-anisyl

I : Phosphines and Phosphoniurn Salts

(59) n = 1 or 4-7 R = Pr' or Ph

7

(60) R =

or CgH19 n = 1-5, 11 or 13

derived from tartaric acid with lithium amide reagents, followed by lithium diphenylphosphide, has given a series of chiral aminoalkylphosphine ligands (55).63,64 The phosphinoarenetricarbonylchromium system (56) has been prepared by treatment of a related arylcarbamate substrate with lithium diphenylph~sphide.~~ Among new monophosphines prepared by the reactions of lithiophosphide reagents with chloroalkyl substrates are the phosphinomethylpyrazole (57),66 the mixed donor phosphines (5S),67 (59)68and (60),69 and the phosFhinoalkylcyclopentadienide system (6 1).70 Systems of the latter type have also been accessed by several groups via the ring-opening of spiro[2,4]hepta-4,6-dienes with lithium d i p h e n y l p h ~ s p h i d e . ~Among ~ - ~ ~ this series of anionic phosphine ligands is the indenyl system (62).74 One such system derived from potassium diphenylphosphide has been shown to involve coordination of a neutral phosphine functionality to the potassium ion.75 Phosphide-induced ring-opening of oxetanes has enabled the synthesis of functionalised neopentylphosphines, e.g. (63).76The generation of lithiophosphide reagents by cleavage of phenyl groups from a,o-bis(diphenylphosphin0)-

6..@ SR1 Pi

PhP-(C H2)n- PPh I I H H

'-OH PRg

PPh2

(62)

(63) R1 = lndenyl or fluorenyl R2 = Ph or Et

Ph

Ph.

'P

L

O

n =2or3 (66)

n =I-5 (64)

8

Organophosphorus Chemistry

alkanes on treatment with lithium in THF has received further study and optimised procedures developed, using low temperature conditions,7777g assisted by u l t r a ~ o u n dresulting ,~~ in improved routes to a,o-bis(pheny1phosphino) alkanes (64), and hence to new diphosphines, e.g. (65)79 and (66).80 Monolithiated a,o-bis(phosphin0) alkanes have been used in the synthesis of novel diblock copolymers bearing bidentate phosphine sites." A dilithiophosphide reagent derived from 1,2-bis(phenylphosphino)benzene has been used to prepare the chiral macrocyclic, atropisomeric binaphthyldiphosphines (67)-s2 Among other new diphosphines prepared via lithiophosphide agents are the atropisomeric C2-symmetric 3,3'-bisindolizine system (68),83 the pincer-system (69),84 the diphosphinoheptalene (70),85 a series of bis(phosphinoalky1) bipyridyls (7 1),86 and the bis(phosphinoaryl)calix-[4]-arenes (72), from which

Ar2P (67) R = H, Ph, 4-biphenyly1, 2-benzofuranyl or 2-naphthy1

(68) Ar = Ph or 0-tolyl

(69)

R' = H or OCH2Ph

R~ = cyclopentyl PPh2

I

PPh2

PPh2

PPh2

1 (70) R = Ph

(71) n = 1-3

OH (72) n = 1 or 2

novel water-soluble diphosphines have been prepared by multiple sulfonation under conditions that do not cause oxidation at phosph~rus.'~ The reactions of lithiophosphide reagents derived from 1,2-bis(phosphino)benzene with cyclic sulfate esters are the basis of the synthesis of various chelating diphosphines bearing chiral heterocyclic phosphine substituents, e.g. the 1,2bis(phosphetan0)benzene (73)," and a related series of 1,2-bis(phospholano)benzene^,^^-^^ e.g. (74).92In related work, the chiral phospholanes (75) have been prepared by sequential reactions of lithio(trimethylsily1)phosphide re-

1: Phosphines and Phosphonium Salts

9

R

&Ph

HO-

R (74) R = Me or Et

(73) R = PhCH2

(75) R = Me, Et or Pr‘

(77) R‘ = alkyl or Ph R2 = alkyl

agents with cyclic sulfate esters and subsequently employed in a lithiophosphide route with acyclic chiral tosylates to give a series of bisphospholanes having chiral back-bones, e.g. (76).93 Treatment of chiral cyclic sulfates with lithium diorganophosphides in a one-pot process has provided a direct route to the chiral diphosphines (77).94 Chiral 1,l’-bis(phosphetano)ferrocenes (78), have been prepared by two groups, using the lithiophosphide4yclic sulfate m e t h ~ d .Cyclooligophosphines, ~~?~~ (ArP),, (n = 4 6 ) , have been obtained by oxidation of monolithiated primary phosphines using benzophenone in THF at room t e m ~ e r a t u r e .The ~ ~ reactions of dilithiated primary silyphosphines with diorganodichlorosilanes, which give new organosilyl-phosphorus systems, have been reviewed.” The new sterically hindered tripod ligand (79) has been obtained from the reaction of lithium diphenylphosphide with a trifunctional bromo~ilylmethane.~~

@II

Fe

H

I

,p? R

I

c

Me2SizMe>SiMe2 Ph2P

I

PPh2

PPh2

R (78) R = alkyl

(79)

Sodio-organophosphine reagents have also found considerable use in the past years. Aminyl radicals, R2N, are involved in the photo-assisted radicalnucleophilic substitution reactions between sodium diphenylphosphide and Ncyclopropyl-N-ethyl-p-toluenesulfonamidein liquid ammonia, which after oxygenation, leads to the aminoalkyldiphosphine dioxide (80) as the principal product. loo The reactions of sodio-organophosphide reagents with chloroalkyl

Organophosphorus Chemistry

10

Me2PCH2CH2SR

(81) R = Me, Et or Ph

(83) R' = H or Me

R2 = Ph or Cy

substrates are the key steps in the synthesis of the thioethylphosphines (8 l), lo' and the new chiral diphosphine (82).'OZ A sodium diorganophosphide-tosylate or mesylate route has been employed in the synthesis of the chiral pyrrolidinophosphines (83)'03 and the chiral oxazolinyl system (84).lo4 Displacement of the chloride from a chloroarene is the key step in the synthesis of the chiral tetraphosphine (85). lo' Sodio-organophosphide reagents also promote ringopening of epoxides, enabling the synthesis of a range of chiral P-hydroxyet hylphosphines, 1oc108 e.g. (86) O7 and (87). O8

&$

Ph2P

I

Boc (84) R = Ph, P t or But

P h 5, P T O H R

OH

(86) R = Ph or Me

Potassium organophosphide reagents also continue to find applications in synthesis. Direct displacement of fluoride from fluoroaromatic substrates by potassium diphenylphosphide is the key step in the synthesis of the phosphinoarylsulfoxides (88),'09 water-soluble phosphino-amino acid systems, e.g. (89),"' and the chiral benzoxazine system (90)."' Related displacement of fluoride by potassium monophenylphosphide has been used to prepare a series of hydrophilic triarylphosphines, e.g. (9 1). l 2 Among new phosphines prepared by conventional displacement reactions by potassium diphenylphosphide on

I : Phosphines and Phosphonium Salts

11

0

Ph2P

PPh2

(88) R' = H or Me R2 = H or Me R3 = H or OMe

o-""" OMe

(91) X = COOH or NH2

t

(92)

pih

RiR2N

PPh2

(93) R' = Me or Ph R2 = Ph CI

Ph2P

PPh2 CI

(94)

(96)

(95)

alkyl halides or sulfonate esters are (92),' l 3 the chiral aminoalkylphosphines (93),'14 the chiral chelating diphosphines (94),'15 (95)'16 and (96),'17 and a diphenylphosphinoalkyl-functionalisedsilsesquioxane system. The reactions of potassio-phosphide reagents derived from primary (ortho-substituted)arylphosphines with cyclic sulfate esters have given the chiral phospholanes (97).'19 The heterocyclic system (98) is formed in the reaction of t-butylphosphonic dichloride with the dipotassium salt of the diphosphine ButPH.PHBu'. I2O Generation of metallophosphide reagents directly from red phosphorus in the presence of alkyl halides has been utilised in a two-step route to P-substituted alkylphosphines (99).'*' Interest in the isolation and structural characterisation of metallo-organophosphide systems continues to grow. Studies of the structures of alkali metal-

''

(97) X = H, OCH2Ph, CH20CH2Ph or CH20Me

(98)

(99)

Organophosphorus Chemistry

12

rich polyanionic phosphides have been reviewed,122 and new structural investigations of associations of bulky mono-organophosphide ions, RP2-, with lithium, sodium and copper(1) cations reported. 123 The solid state structure of a dioxane solvate of potassium diphenylphosphide involves a three-dimensional network involving anion-cation interactions. 124 The influence of donor solvents on the solid state molecular structure of KP(But)Ph has been studied.'25 Structural studies of crown ether adducts of caesium salts of bulky primary arylphosphines have been reported. 126 New lithiophosphide systems have been obtained from the reactions of lithium bis(trimethylsily1)phosphide with benzonitrile, and structurally characterised. 127 Magnesium organophosphide systems have been prepared by treatment of (triisopropylsily1)phosphine with dibutylmagnesium. 128 A lithiophosphide involving a silyl(bisbory1phosphide) anion has been characterised. 129 Further studies have been reported of the characterisation of phosphido derivatives of the heavier elements of main groups 13, 14130 and 15.131 The aluminium phosphide system ( B u ' ~ A ~ P H ~ ) ~ has been prepared and used as a mild phosphanylation reagent for the transfer of PH2 units to group 14 elements.132The application of zirconium organophosphide reagents in synthetic chemistry has been reviewed,133 and further studies of the reactivity of the zirconium-phosphorus bond have appeared. 347135 Applications in synthesis of phosphines metallated at carbon also continue to appear. The chemistry of metal cyclopentadienyl systems bearing pendant phosphorus donors has been reviewed. 36 The lithium diphosphinocyclopentadienide (100) is a key reagent for the synthesis of new polyphosphinoferroc e n e ~ Treatment . ~ ~ ~ of the ferrocenophane (44, R = Ph) with phenyllithium generates the C-lithiated ferrocenylphosphine (101), from which a range of new unsymmetrical diphosphorus donor systems has been prepared. 138 A study of the reactivity of the phosphinosilylcyclopentadienides (102) towards Me

Li+

@

Li

Me (102) R = Cy or Mes

zirconium tetrachloride has revealed unexpected P-Si and P-C bond cleavage p r o c e ~ s e s . 'Treatment ~~ of diphenyl(2-pyridylmethy1)phosphine with butyllithium results in metallation at the methylene group to form the reagent (103) from which the alkoxysilyl-terminated phosphine (104) has been prepared, this compound subsequently being tethered to a silica-supported palladium catalyst. 140 Lithiation of diphenyl(2-pyridy1)phosphine occurs at the 2-position of the pyridine ring; subsequent treatment with electrophilic reagents has given a range of new phosphines. 14' Lithiation of the (-)-menthy1 ester of 2-(dipheny1phosphino)propanoic acid, followed by alkylation with benzyl bromide,

1: Phosphines and Phosphonium Salts

13 CH2Ph I

O y H - P P h 2 Li

Q&pph2

\

Me-C-COOH PPh2 I

(CH2)3-Si(OMe)3

and ester cleavage, provides a route to the chiral system (105), isolated in 70% yield and >%YOenantiomeric excess as the (+)-lS-i~omer.'~~ Two reports of the deprotonation at carbon of methylphosphine-borane systems have appeared. Treatment of the chiral system (106) with secondary butyllithium, followed by addition of an epoxide, results in the formation of the chiral borane-complexed phosphino-alcohol(lO7), from which new chiral phosphitophosphino ligands have been prepared.143 Enantioselective deprotonation of the phosphine-boranes Ar(Me)2P(BH3with cyclopentyllithium in the presence of (-)sparteine, followed by treatment with benzophenone, has given the chiral system ( 108).14 Several solid state structural studies of phosphines

(106) R' = Ph, o-anisyl

(107) R2 = M e or Ph

or I-naphthyl

metallated at carbon have also a ~ p e a r e d . ' ~ ~ A-theoretical '~~ study of diphosphinomethamide systems coordinated to main group 14 elements in their +2 oxidation states has also been reported. 14* 1.1.3 Preparation of Phosphines by Addition of P-H to Unsaturated Compounds. A comprehensive review of addition reactions of P-H compounds of many types contains much that is relevant to this ~ e c t i 0 n . lAddition ~~ of secondary phosphines to aryl(diviny1)phosphines under base-catalysed or freeradical conditions has given a range of new triphosphines (109).'50 The polyether-functionalised diphosphines (1 10) have been obtained from the photochemically initiated addition of vinyl ethers to 1,3-(bisphosphino)propane.15' Addition of allyl alcohol and 1,4-pentadiene to the bis(phosphino)cyclopentane (1 11) has provided the new chiral diphosphines, (1 12) and (1 13), respectively. 52 Bis(2-phenylethy1)phosphines have been shown to react both chemo- and regio-selectively with phenylcyanoacetylene to give the Z-cyanovinylphosphines (1 14).153 Phosphinoalkyl-functionalised silsesquioxanes'54 and alkoxysilanes' 55 have also been obtained by addition of secondary phosphines to appropriate alkenyl-functionalised precursors. Metal ion-catalysed additions have also been reported. Cyclopentadienyl-lanthanum complexes have been shown to promote the intramolecular hydrophosphinationsyclisation of phosphinoalkenes and phosphinoalkynes. Thus, e.g. the phosphine (1 15) is converted to the phospholane (1 16).'56 Secondary phosphines bearing allyl

'

Organophosphorus Chemistry

14 RO CH2C H2PR2 Ar-P 'CH2CH2PR2

RO

OR

( 1 1 0 ) R = E t , Bu,Bu'otCy

GPH2 u. 'PH2 'PH2

(1 11)

(\/OH

(PhCHRCH&P-C(Ph)=CCN

(114) R = H or Me

substituents have been shown to undergo a cyclotrimerisation reaction at a cyclopentadienyl-iron template to form the triphosphorus macrocyclic system (1 17).157A macrocyclic polyphosphine involving 12 phosphorus atoms in a 36membered ring has been obtained from the radical-promoted reaction of phenylphosphine with phenyl(diviny1)phosphine complexed to a gold thiolate cluster. 58 A chiral platinum complex-catalysed asymmetric hydrophosphination of activated alkenes, e.g. acrylonitrile, with secondary phosphines of the type HPRPh has given the chiral phosphines (1 18) with control of stereochemx

P

R'PPh R2 (1 16)

(117) R = H or Ph

(118) R' = Pr', Cy, But, Me

o-anisyl or Mes R2 = H or alkyl X = CN or C02R

istry at phosphorus or carbon centres.159Hydroformylation of P-H bonds continues to find application in the synthesis of water-soluble phosphines, e.g. (1 19)l6' and (120),l6' the latter also capable of being anchored to a peptide via the carboxylic acid functionality. A series of water-soluble heterocyclic phosphino-amino acid salts (121), white, air-stable crystalline solids, has been obtained from the reactions of primary phosphines bearing bulky aryl groups with alkali metal glycinates and formaldehyde.'62 New 4-phosphino- 1,3,2dioxaborinanes (122) have been prepared from reactions of secondary phosphines with salicyaldehyde in the presence of phenylboronic acid esters.163 Examples of the addition of P-H bonds of phosphines to C=N have also been reported. 164-166 Thus, e.g. the chiral phosphino-functionalised chromocene system (123) has been obtained by addition of diphenylphosphine to an imine precursor. 166

1: Phosphines and Phosphonium Salts

15

wC02

cr

(HOCH2)2PvP(CH20H)2

'1

/- co2-

Ar-PrN)

HOH2C'I HOH2C

2M' L

p\

I

N

Lcop-

CH20H CH20H

(121) Ar = Ph, Mes or

(120)

M = Na or K

F:

co I co co (1 12) R = alkyl or Ph

(123) Y = Me, M e 0 or CI R = Me, CH,C02Me, p-anisyl or Ph

1.1.4 Preparation of Phosphines by Reduction. Trichlorosilane remains the most commonly used reagent for the reduction of phosphine oxides to phosphines, and has been widely applied in the synthesis of a range of new systems. A developing theme is the introduction of the diphenylphosphinyl group into an aromatic system by palladium-catalysed displacement of an aryl triflate functionality derived from a phenol, by diphenylphosphine oxide, followed by trichlorosilane reduction. Among new phosphines prepared in this way are the atropisomeric systems (124),'679'68(125),'69 (126; R = Ph)170 and (127).17' The biferrocenyldiphosphines (128) have been obtained by Ullmann coupling of o-iodoferrocenylphosphine oxides in the presence of copper,

Q

moMe PAr,

:Ph2 \

(124) Ar = Ph or p-CF&H4

PPhR

Fe 'PPhR Fe

(127) R = Ph, Pr'or CMe20SiMe2Bu' n = 1 or2

(128) R = 2-biphenylyl or 1-naphthyl

/

16

Organophosphorus Chemistry

Ph2P I

PPh2 I

Ph2P I

Ph2P

PPh2

PPh2 I

Ph2P

PPh2

(130)R = n-C6HI3

followed by final reduction with trichlorosilane and separation of enantiomers via borane complexation. 172 Palladium-catalysed Suzuki-coupling of the chiral diphosphine oxide (129) with p-dibromoarenes, followed by trichlorosilane reduction, has given a route to the rigid poly (BINAP) system (130).'73 Ullmann coupling of p-bromophenylphosphine oxides with perfluoroalkyl iodides has given the related p-perfluoroalkylphenylphosphine oxides, from which the phosphines (13 1) have been obtained on reduction with trichlorosilane in t01uene.l~~ Trichlorosilane has also been used in the final stage of the synthesis of a range of polyphosphines linked via alkyne bridges, e.g. the pincer-systems (132),'75 and related dendrimer core structures, e.g. (133).'76 Phosphine oxide groups attached to the lower rim of calixarene systems have been reduced by phenylsilane. 77 Hydrido-aluminium reagents have also attracted attention for the reduction of phosphine oxides, phosphonate esters, phosphinyl halides and halophosphines. The alane system, essentially AlH3 (from treatment of lithium aluminium hydride with concentrated sulfuric acid in THF), has been shown to be effective as a chemoselective reducing agent for phosphine oxides, enabling reduction to the related phosphines in the presence of other reactive groups (apart from aldehydes, ketones and disulfides).178 Reduction of alkylphosphonate esters to primary alkyl phosphines has been

1: Phosphines and Phosphonium Salts

(131) n = 1-3

17

(131) n = 1 o r 2

achieved with lithium aluminium hydride, enabling the isolation of the This bis(primary phosphines) (134) as air-stable, pale yellow solids.1617179 reagent has also been used to reduce chlorophosphines to form new secondary phosphines bearing perfluoroalkyl substituents, 180 and both phosphine oxide and phosphinyl chloride functionalities in the synthesis of the macrocyclic system (135).181 Reduction of chlorodiphenylphosphine with a variety of metals, followed by in-situ protonation of the intermediate metallophosphides, has also been reported. The use of activated zinc in THF was found to be the most effective system.182 Me

PH2 H2P

(134)n = O o r 1

Me (135)

1.1.5 Miscellaneous Methods of Preparing Phosphines. Approaches to the synthesis of specific types of organophosphine have been reviewed, covering phosphinoaryloxazolines, 83 trans-2,5-disubstituted phospholanes, 84 new chiral phosphines which have been reported since 1990,185 chiral hydroxyphosphines, 186 and phosphorus-sulfur donor ligands.187 The uses of phosphine (PH3) in the synthesis of organophosphines has also been reviewed.'88 A direct route for the synthesis of arylphosphines is offered by the reaction of

'

'

Organophosphorus Chemistry

18

Ph2P

R

\

ph2p%

(137) R = Ph, Pr' or But

(136)

diphenylphosphine with phenolic triflates, catalysed by nickel(I1)diphosphine complexes in the presence of a base in DMF at ca. 120". This approach has been applied in the synthesis of the atropisomeric system (126, R = Me or Ph), 89-19 the steroidal BINAP system (136),'92 and the hybrid donor system (1 37).193 A related reaction involving chlorodiphenylphosphine instead of diphenylphosphine has been used to prepare the diphosphine (138).'94 Direct phosphination of iodoarenes using diorganophosphines, catalysed by palladium acetate, has been used in the synthesis of the functionalised phosphines (139)'95 and ( 140).'96An even more straightforward route to arylphosphines is provided by the reaction of bromoarenes (bearing a wide variety of other functional groups) with triarylphosphines in DMF at 1lo", catalysed by palladium acetate. 197 A related reaction of triarylphosphines with aryl triflates has been used to prepare atropisomeric systems, e.g. (141).'98 The phosphinoarylboronic acid (142) has been shown to undergo palladium-promoted biaryl coupling to a dibromo-o-phenanthroline to give the polydentate hybrid ligand (143) (after dealkylation of the methyl ether group).'99 Enol triflates

' '

PR2

I

PPh2 PPh2

Me0

PhnP

3-n

M e J $ q o M e 0 (139)

n = 1or2

(140) R = Et or Ph

&&

PAr2

\

(141) Ar = Ph, ptolyl or

p-anisyl

/

PPh2

Ph2P (143)

1: Phosphines and Phosphonium Salts

19

Mel ,But Ph,

,BH3

OMe But

Me

have also been shown to undergo palladium-promoted phosphination with diphenylphosphine, enabling the synthesis of vinylphosphines from ketones bearing an a-hydrogen.200 Routes to chiral, borane-protected secondary phosphines (144) have been developed,201 ,202 enabling the synthesis of a range of new chiral tertiary phosphines, e.g. (145),202 via lithiophosphide routes. Sequential treatment of diastereoisomerically pure oxazaphospholidineboranes with different organolithium reagents provides a route to chiral phosphine-borane adducts, e.g. (146).203 Many new tertiary phosphines have been prepared by synthetic elaboration of simpler organophosphines which does not involve the phosphorus atom. Chiral phosphines bearing heterocyclic substituents have been obtained by elaboration of arylphosphines bearing amino, carboxaldehyde or nitrile groups, respectively, giving, e.g. the pyrrolidinyl system (147),204phosphinooxazolidines,205,206 e.g. (1419,~'~ phosphino-oxathianes, e.g. (149),207 phosphino-oxazines (150),208 and the phosphino-oxazolines (15 1).209Wittig reac-

(147) R = Me or Et

tions of p-diphenylphosphinobenzaldehyde with a,o-diphosphonium salts have given a series of bis(phosphinophenyl)polyenes, e.g. (152).2107211 Further examples of the synthesis of iminophosphine ligand systems by Schiff's base formation involving phosphinobenzaldehydes or phosphinoarylamines, have appeared,212-216 and this route has been extended into the organometallic area with the preparation of the benzenechromium tricarbonyl derivatives (153), which exhibit planar chirality.217New phosphinobenzenechromium tricar-

20

Organophosphorus Chemistry PPh2

Ar(CO),

'R3

(153) R' = Me or Ph

(152) n = 0-3

R2 = H, Me or Ph R3 = H or Me

bony1 and phosphinoferrocene systems, e.g. (154),218 (1 55)219 and (156),220 have also been prepared by side-chain elaboration. The macrocycle (157) has been obtained from a high dilution base-catalysed cyclocondensation of The phosphenyl bis(2-mercaptoethy1)phosphine and 1,2-di~hloroethane.~~~ phinoalkylthiourea (158) is formed in the reaction of 2-aminoethyldiphenyl-

0 (155) YR = OMe, OEt, OPr"

(156)

NHCH2CH20H

c5

or NH(CH2)30H

Ph

S

S I1

Ph2PCH2CH2NH-C-NHPh

WS

phosphine with phenylisothiocyanate.222Treatment of both cyclic and linear halogenophosphazenes with p-hydroxyphenyldiphenylphosphine in the presence of caesium carbonate has given phosphinoaryl-functionalised phosphaz e n e ~A . ~review ~ ~ of the synthesis of homogenised-heterogeneous catalyst systems includes coverage of the use of silane-functionalised phosphines for binding to silica surfaces,224and new approaches to this topic have been A combinatorial approach to the synthesis of phosphinefunctionalised peptides has been described, based on incorporation of the Nprotected phosphine sulfides (159), followed by d e ~ u l f u r i s a t i o nThe . ~ ~ ~chiral diphosphinopyrrolidine (160) has been coupled to a polyacrylic acid via nitrogen to give a new, water-soluble, polymeric ligand.228Amide formation involving a variety of amino-functional phosphines has been widely employed

1: Phosphines and Phosphonium Salts

(159) R

21

= Ph or Cy

(161) R = H or Me Pr' Y N H X

PPh2

0)-NbPPh2

a ($ P;'

(163)X =

,

or

7"'CH

3

in the synthesis of new systems, including ( 161),229air-stable primary phosand the C2-symmetric diphosphines (163).232Acylation phines, e.g. (162),2303231 of chiral hydroxyalkyl or hydroxyaryl phosphines with o-sulfobenzoic anhydride has given new water-soluble l i g a n d ~The . ~ ~reactions ~ of hydroxymethylphosphines with primary and secondary amines continue to find application in the synthesis of new aminomethylphosphines. In the past year, this approach has been used for the synthesis of dendrimeric water-soluble p h o ~ p h i n e s and ,~~~ new e.g. (164),238 used in the synthesis of macrocyclic dimetallo-complexes. A new route to (ferrocenylmethy1)diphenylphosphine is offered by the reaction of (hydroxymethy1)diphenylphosphine with (ferrocenylmethyl)trimethylammonium iodide.239The chiral phosphine (165) is formed similarly in the reaction of a related ammonium salt with tris(hydro~ymethy1)phosphine.~~~ An improved route to the phosphine (166)

Ph2P-N H

/O^o-H

has been developed, involving metallation of o-bromophenyldiphenylphosphine, followed by treatment with diethyl c h l o r ~ p h o s p h a t eThe . ~ ~ synthesis ~ of various water-soluble phosphines has been reported, including the wide-bite system (167),242 a disulfonated triphenylphosphine (free of phosphine oxide contaminant^),^^^ and the cationic phosphine (168) in an improved route.244

Organop hosphor us Chemistry

22

\

Ar = ~ O - ( C H 2 ) ,~ S 0 3 N a

/

Ar2P

PAr2 (167)

+

Ph2PCH2CH2NMe3 1 (168)

n =0,3or6 R2P-CH=N

+

Pr2’ X -

(169) R = Pr2’Nor Cy2N

R2P-CH 0 (170)

Treatment of the phosphino-iminium salts (169) with potassium hydroxide in THF affords the formylphosphines (170), which are remarkably stable in solution compared with the related phosphine Phosphines bearing aminoyl radical substituents, e.g. (171), have also been The phospha[3]triangulane, (172), has been obtained from the reaction of bicyclopropylidene with a metal complexed p h e n y l p h ~ s p h i n i d e n eThe .~~~ phosphinotrithiacyclophane (173) has been prepared by the base-promoted reaction of

kPPh I

0(171)

tris[(2-chloromethyl)phenyl]phosphine with 1,3,5-tris(mercaptornethyl)benzene. This system exhibits ‘in-out’ conformational isomerism, centred around pyramidal inversion at phosphorus. Inversion barriers and the reactivity of the conformers have also been s t ~ d i e d . ~Resolution ~ ~ , ~ ~ ’ of the 2,2’-biphospholene (174) has been achieved via chiral palladium complexes.251An electrochemical route to phosphines bearing heteroaryl substituents, e.g. pyridinyl, pyrimidyl and pyrazolyl systems, has been developed which entails a nickel complexcatalysed electroreduction of halogenophosphines in the presence of bromo (heter~)arenes.~’~ The single-electron reduction of phosphorus trichloride has been studied with a view to the generation of intermediate radical cation species for the synthesis of organophosphorus compounds.253 A photochemical route to tris(di-t-buty1phosphino)phosphine has been developed, this compound being shown to contain a planar central phosphorus atom.254

1:Phosphines and Phosphonium Salts

(174)

23

(175) R =Me or Ph X=HorF

Among new phosphines prepared via reactions of phosphines coordinated to metal ions are the diphosphinonaphthalenes (175),255and the iminophosphine (176).256 1.2 Reactions of Phosphines. - 1.2.1 Nucleophilic Attack at Carbon. Treatment of the unsaturated y-lactone (1 77) with tributylphosphine results in selective relacement of chlorine to form the phosphonium salt (178).257 Reactions of phosphines with alkynes have continued to attract interest. A palladium-catalysed addition of triphenylphosphine to unactivated terminal alkynes in the presence of methanesulfonic acid provides a route to the vinylphosphonium salts (179). This reaction fails with methyldiphenylphos-

RYx (179) R = alkyl

phine or tributylphosphine. Related reactions with fully substituted alkynes have also been explored, and provide novel routes to phosphonium salts.258 The generation of reactive zwitterionic intermediates by addition of phosphines to alkynes bearing electron-withdrawing groups has continued to be a useful synthetic approach, having been used in the preparation of functionalised ally1 c a r b ~ x y l a t e sand , ~ ~for ~ the generation of ylides which subsequently undergo intramolecular Wittig reactions, resulting in fused dihydrofurans,260 and highly electron-deficient 1,3-diene~.~~l Protonation of the zwitterion resulting from addition of triphenylphosphine to dimethyl acetylenedicarboxylate, by 2-hydroxyacetophenone, leads initially to a vinylphosphonium salt which undergoes an aromatic electrophilic substitution reaction with the conjugate base of the hydroxyacetophenone to give vinyl-substituted systems, together with 8-acetyl-4-methoxycarbonyl-2-chromone.262 Treatment of di-tbutyl acetylenedicarboxylate with triphenylphosphine in the presence of a series of heterocyclic N-H acids, e.g. imidazoles, triazoles or carbazoles, has given a series of highly hnctionalised stabilised ylides, e.g. (1 Related reactions in the presence of fluoropentane-2,4-dione result in the formation of the betaines (181),264 and, in the presence of c60, in a series of fullerenes containing phosphonium ylide f ~ n c t i o n a l i t y .Treatment ~~~ of a-zirconated phosphines, e.g. (182), with acetylenic reagents results in intramolecular coordination of the negative centre of the initially formed phosphonium zwitterion to the zirconium, acting as an electron-acceptor, to form cyclic

Organophosphorus Chemistry

24 0

0

HC-CO2R

Ph3P

I

HC-CO2R I

+PPh3 (181) R =Me, Et or But

systems, e.g. (183).266,267 The phosphine (184) is reported to be formed in the reaction of tributylphosphine with diphenylacetylene.268Tributylphosphine has been shown to catalyse the dimerisation of activated alkenes under ambient temperature and pressure conditions.269Dipolar adducts of triphenylphosphine with allenic esters undergo an unusual [8+2] annelation with tropone, leading to 8-oxabicyclo[5,3,0]-deca-l,3,5-trienes.270 The reactions of trialkylphosphines with methoxyallene have been investigated, with the identification of various betaine and ylide products.271The betaines (185), formed in the reactions of triphenylphosphine with polymer-bound 1,2-diaza-1,3-butadienes, undergo cleavage in methanol to provide a solid-phase synthesis of the heterocyclic stabilised ylides (186).272Tributylphosphine has been shown to catalyse the acylation of benzylic alcohol end-groups in rotaxane systems, in the presence of 3,5-dimethylbenzoic anhydride.273 0

1

Ph3P

0 +N

I

R

(186) R = H or COR

1.2.2 Nucleophilic Attack at Halogen. Two groups have reported studies of the adducts of trialkylphosphines with iodine. Both 1:1274 and 1:2274,275 phosphine-iodine combinations have been characterised, the former having an ion-pair structure whereas the latter are predominantly ionic, involving discrete R3PIf and I3- ions. Structural studies reveal weak iodine-iodine interactions between cation and anion in the latter type and also subtle structural variations depending on the nature of the substituents at phosphorus.27 The reactions of benzoin with the t riphenylphosphine-br omine adduct, under various conditions, have been investigated.276The mechanism of formation of diphenyltrichloromethylphosphine in the reaction between diphenylphosphine and carbon tetrachloride has been investigated, and shown to be multistep, involving the intermediacy of chlorodiphenylphosphine and

1: Phosphines and Phosphonium Salts

25

tetraphenyldipho~phine.~~~ A kinetic study of the reaction of tertiary alcohols with the triphenylphosphinexarbon tetrachloride system in various solvents has been reported, and pathways leading to both substitution and elimination products identified.278The triphenylphosphine-carbon tetrachloride system has also found use in the synthesis of 1,l-diheter~arylethylenes.~~~ A convenient route to dialkyl carbonates is provided by the reactions of primary alcohols with carbon dioxide, in the presence of a tributylphosphine-carbon tetrabromide-guanidine base system.280The reagent Ph3P(SCN)2 can be generated in situ from treatment of the triphenylphosphine-bromine system with ammonium thiocyanate in acetonitrile at room temperature, and has been used for the direct conversion of alcohols to alkyl thiocyanates in excellent yield, with very little contamination by the related isothiocyanates.281This reagent has also been used for the conversion of alkyl- and aryl-silyl ethers to the related thiocyanates.282A mild and efficient conversion of carboxylic acids to acid chlorides is offered by use of the cyanotrichloromethane-triphenylphosphine system.283The solid-state reaction between triphenylphosphine and chloramine has been studied by thermal analysis techniques, together with 31P NMR.284A combination of triphenylphosphine with N-halosuccinimides in refluxing dioxane offers a reagent for the conversion of hydroxyazines into the related heteroaryl chlorides.285The reactions of tritylphosphine (and secondary phosphines bearing a trityl group) with phosgene give the related, surprisingly stable, monochlorophosphines.286The iodotrimethylsilane-triphenylphosphine combination has been used to promote the facile dealkylation of Tris(perfluoroalky1)difluorobenzyl esters of cephalosporin carboxylic phosphoranes are formed in the electrochemical fluorination of trialkylphosphines.288 1.2.3 Nuckophilic Attack at Other Atoms. Phosphorus(II1)-bridged [ llferrocenophanes, e.g. (44, R = Ph), do not undergo transition metal-catalysed ringopening polymerisation. However, if the phosphorus lone pair is protected via formation of borane adducts, polymerisation can be achieved.289The reactivity of the boron-hydrogen bonds of phosphine-borane adducts has been reviewed.290The intermediacy of fluoroborane-phosphine adducts in the deprotection of borane-phosphine adducts using fluoroboric acid has now been confirmed by NMR studies.291A procedure has been developed for the oxidation of secondary and tertiary phosphines using oxygen (or air) in the presence of a catalytic amount of cobalt@) acetylacetonate, and 3-methylbutanal, which acts as a sacrificial aldehyde. A supported, re-usable catalyst for the oxidation of triphenylphosphine was also developed.292 A nickel(o) complex-catalysed oxidation of tertiary phosphines in the presence of nitrous oxide has been described, the key point being the activation of nitrous oxide in the coordination sphere of the Conversion of polykis(dipheny1phosphino)benzenes (Ph2P)&H6 --n [n = 2-41 to the related phosphine-sulfides and +elenides has been reported, together with 31Pand other NMR parameters.294 A kinetic study of the reactivity of a wide range of trivalent phosphorus compounds with elemental sulfur has been reported, together with related

26

Organophosphorus Chemistry

reactions involving carbon d i ~ u l f i d e Triphenylphosphine .~~~ has found use in the synthesis of nucleosides via cleavage of S , S - d i s ~ l f i d e s Cleavage .~~~ of selenium-selenium and tellurium-tellurium bonds on treatment of phenylselenium- and phenyltellurium-iodine adducts with triphenylphosphine has also been reported, giving rise to the charge-transfer complexes (187).297,298 Phosphine-induced cleavage of silicon-oxygen bonds is involved in the catalysis of the aldol reaction between ketene silyl acetals and aldehydes.299 Further studies of the involvement of radical species in Mitsunobu chemistry have appeared. Investigations of the reactions between a range of triarylphosphines and 1,1'-(azodicarbony1)dipiperidine indicate the formation of both triarylphosphonium radical cations and a radical anion derived from the azoester, via electron-transfer from the phosphine to the diazo function.300 Mitsunobu reagent systems continue to develop, and to find new applications. Tributylphosphine-azodicarboxamide combinations are more effective than the familiar triphenylphosphine-DEAD reagent for the one-pot cyanation of primary and some secondary alcohols.301 The stabilised ylide, Me,P+CH-CN, has now been used as a proton-abstracting agent in a modified Mitsunobu synthesis of C-alkylated arylmethylphenyl s ~ l f o n e s . ~Mitsunobu '~ chemistry is increasingly being adapted to solid phase systems, having been used in the past year for the intermolecular N-alkylation of aliphatic a m i n e ~ , ~the ' ~ synthesis of polyamine~,~'~ carbon-carbon bond formation in the C-alkylation of benzylic alcohols,305the N-alkylation of sulfonamides and alkylation of phenols, imides and carboxylic the synthesis of carbamates,307 and for the synthesis of tetrahydropyrazine-2-0nes.~'~Further conventional applications of Mitsunobu reagents have also appeared, including the synthesis of carbonyl compounds from 1,2-di0ls,~'~a one-pot regioselective and stereospecific azidation of 1,2- and 1,3-diols using trimethyl~ilylazide,~''and in hetero~yclic,~"and natural product chemistry.312 A Mitsunobu procedure for the synthesis of thioglycosides from 1-thiosugars and a series of alcohols has been developed, involving a combination of trimethylphosphine and 1,l '-azodicarbonyldipiperidine, the advantage being that trimethylphosphine oxide is easily removed on aqueous ~ o r k - u pl 3. ~Mitsunobu procedures for the synthesis of nucleosides from 1-thio- and l-seleno-glycosides have also been reported.314 Interest in the Staudinger reaction of phosphines with azides has also continued, and a theoretical treatment has a ~ p e a r e d . ~The ' reaction of an ortho-azidobenzamide with triphenylphosphine or methyldiphenylphosphine has allowed the isolation of the intermediate phosphazides (188) as crystalline solids, which, on heating in toluene, collapse to form the related phosphazenes which then undergo intramolecular aza-Wittig reactions.316Related dipolar species, e.g. (189) and (190), have been isolated from the reactions of the zirconaphosphine system (182) with a z i d e ~ . Various ~'~ monophosphino-phosphazenes, e.g. (191), have been isolated from the reactions of 0-substituted vinylazides with 2-1,2-bis(diphenylphosphino) ethene.3'8 The related reaction of a ferrocenylbisazide with 1,2bis(diphenylphosphin0) ethane has given the macrocyclic system (192).319 Monophosphino-phosphazenes have attracted the interest of the coordination

I : Phosphines and Phosphonium Salts

Ph3P + -Ph E-I -I

d:+J \

27

Me

N I -

kN I+

Ph2PR (187)

(188) R = Me or Ph

chemists and work in this area has been reviewed.320 The reactions of a z i d ~ t r i a z i n e sand ~ ~ ~tria~idopyridines~~~ with phosphines have also been explored. Staudinger reactions of acetylated glycopyranosylidene 1,l-diazides have given resonance-stabilised iminophosphoranes of 1 , 2 , 3 - t r i a ~ o l e Pro.~~~ tected glycosyl azides have been shown to react with acyl chlorides in the presence of triphenylphosphine to give glycosylamides in high yield at room temperature.324A simple route to carbamates is afforded by the reactions of trimethylphosphine with azides in THF at room temperature, followed by treatment with a chloroformate ester, work-up again being aided by the waterN-sulfonyltriphenylphosphinimines solubility of trimethylphosphine have been obtained by the reaction of triphenylphosphine under nitreneforming conditions with an N-sulfonyl iodonium imine.326 1.2.4 Miscellaneous Reactions of Phosphines. Procedures for the resolution of benzylcyclohexylphenylphosphine have been developed, involving adduct formation with cyclopalladated chiral amine complexes.3273328 A similar approach has also been used for the resolution of P-chiral secondary phosphines, e.g. (193).329Treatment of t-butyl(di-o-toly1)phosphinewith potassium tetrachloropalladate(I1) yields a cyclopalladated complex (194), involving chiral phos-

(1 93) R = CH2Ph or Me

28

Organophosphorus Chemistry

phorus, which was subsequently resolved.330The absolute configuration of the previously resolved chiral phosphine (195) has been determined by an X-ray study of the related borane complex.33' Phosphine radical cations have been generated via reactions of phosphines with the methylviologen dication, and their reactions with alkylpyridines A study of the thermal decomposition of cyclohexylphosphine has been reported.333 An example of the arylation of an unsymmetrical secondary phosphine has been reported, which involves treatment of a borane adduct of the secondary phosphine with copper(I), followed by an iodoarene in the presence of a palladium(I1) phosphine complex, providing a route to the borane adduct of a chiral tertiary p h o ~ p h i n eA . ~further ~ ~ example has appeared of the use of the o-diphenylphosphinobenzoate unit as a catalyst-directing structural unit for the stereoselective hydroformylation of chiral substrates.335 Photolysis of tetraphenylbisphosphine provides an initiator system for the bulk polymerisation of styrene and methyl m e t h a ~ r y l a t e . ~Fluoroalkylcopolymer-supported ~~ arylphosphines, useful in fluorous biphase catalysis, have been obtained via the copolymerisation of p-diphenylphosphinostyrene (196) and a fluoroalkyl acrylate ester.337 The first high molecular weight poly(phosphinoborane) (197), an 'inorganic' analogue of polystyrene, has been obtained from the borane adduct of phenylphosphine by rhodium-catalysed thermal d e h y d r o ~ o u p l i n g . The ~~~ aminoalkyl silylferrocenyldiphosphine (1 98) has been linked via the amino

r

PPh2

r

group to a cyclophosphazene core, forming a core dendrimer system with the chiral diphosphine units at the surface.339The cyclopolyphosphine (199) has been shown to undergo electron impact-induced fragmentation to form the neutral species P6, claimed as a new allotropic form of phosphorus.340 The diphosphinoketenimine (200) undergoes a reversible dimerisation on crystallisation at room temperature to form the dipolar system (201) by a novel [2+3] cycloaddition reaction.341 Photolysis of triarylphosphines in the presence of 9,lO-dicyanoanthracene in aqueous acetonitrile results in the formation of the

/s

P/p\P

\

/

CP* /p-p\cp*

pb=

h2

Ph2P

C NPh

Ph ,Ph Ph2PH'p+x Ph2P

pph2

Fh

NPh

I : Phosphines and Phosphonium Salts

29

related phosphine oxides via initial formation of the phosphine radical cation which then suffers nucleophilic attack by water to give an intermediate hydroxyphosphoranyl Triphenylphosphine has been shown to promote the cyclisation of 2-nitrophenylethenylketones to 2 - a ~ y l i n d o l e s . ~ ~ ~ Trichlorosilyldialkylphosphineshave been obtained by treatment of the related trimethylsilylphosphines with hexachl~rodisilane.~~ Tri-t-butylphosphine combined with caesium fluoride has been shown to facilitate carbon<arbon cross-linking of chloroarenes in the Stille reaction.345Aminolysis of a chromium carbene complex using the aminoalkylphosphine (202), followed by conventional N-methylation, has given the chiral chelate aminoalkylphosphine-carbene complex (203), the first of its type.346 The chemistry of phosphinocarbene systems has also developed significantly. The area has been reviewed.347Stable versions of transient push-pull phosphinocarbenes have been prepared, extending lifetimes from nanoseconds to weeks. Thus, e.g. the system (204) has been characterised by X-ray crystallography. Simpler systems, e.g. (205), have also been prepared, and are stable for a few days at - 30 "C in solution, but evaporation of the solution (even at - 50 "C) results in the formation of the dimers (206). The free phosphinocarbenes can be trapped by cycloaddition reactions with alkenes, to give phosphinocyclopropanes (207).348Another group of stable phosphinocarbenes are the silylated systems (208), which have been shown to act as electrophiles, reflecting the relatively

H2N

Ph

7

F3cp

R2P, C

PPh2

..

Ph

CF3 (204) R = Cy2N

R2px F3C

cF3 PR2

poor intramolecular donation from phosphorus into the vacant 2 orbital on carbon. With phosphine nucleophiles, the ylides (209) r e s u p The phosphinosilylcarbenes can also be trapped with electron-withdrawing a l k e n e ~ . ~The ~ ' electronic properties of diphosphinocarbenes (2 10) have received a theoretical study, which again confirms the relatively poor ndonor properties of p h o s p h ~ r u s . ~The ~ ' chemistry of the diradical species (211) has also been explored. On photolysis, it is converted into the previously unknown bicyclic system (2 12) which undergoes thermal conversion into a 1,4-dipho~phabutadiene.~~~ Treatment of (21 1) with a base generates the diradical carbene salt (213),a unique species.353A clean means of generating the ylide Ph3P=CI2 is afforded by the trapping of diiodocarbene (from iodoform and potassium t-butoxide) with triphenylph~sphine.~~~

30

Organophosphorus Chemistry R2P,

..C

,SiMe3

(208) R = Cy2N

x"' pY

Ar -

H

-Ar

(211) Ar = 2,4,6-But3C6H2

(208) R' = Cy2N R2 = Me or Ph

(2 10)

SiMe3 Ar-P#P-

-Ar

Ar

-pv .. P-Ar

,.

1

K e 3

H (212)

(213)

Interest has continued in assessing the stereoelectronic properties of phosphines used as ligands in homogeneous catalyst systems and metal complexes in and a review of this area has appeared.357 The catalytic applications of pyridylphosphine and related heteroarylphosphines have also been reviewed.358 Intramolecular and supramolecular phenylphenyl interactions have now been explored for metal complexes of triphenylphosphine, and, as for other triphenylphosphorus systems, sixfold phenyl 'embraces' are frequently found in the solid state.359 Some interesting reactions of phosphines in the coordination sphere of metal ions have also been reported. Trans- 1,2-bis(diphenylphosphino)ethene undergoes photolytic dimerisation only in the presence of nickel, palladium or platinum acceptors to form the related complexes of the tetra kis(dipheny lpho sphino)cy clobutane (214).360 The perfluoroaryldiphosphine (2 15) undergoes regioselective C-F

bond replacement reactions on heating with a cyclopentadienylrhodium complex.361The reactivity of copper(1) complexes of vinylphosphines has been studied. The coordinated phosphines do not undergo hydroboration, but can be polymerised under Lewis acid conditions.362 A selective decomplexation procedure has enabled the characterisation by NiMR in solution of the first free 7h3-phosphanorbornadiene (216), liberated from its tungsten pentacarbonyl complex by stepwise treatment with iodine, followed by imidazole. It has not been possible to isolate the free phosphine since, at

1: Phosphines and Phosphonium Salts

31

room temperature, it is found to eliminate phenylphosphinidene and form a 5-meta~yclophane.~~~ The mechanism of the 2-vinylphosphirane (2 17)-+ 3phospholene (2 18) rearrangement has been studied using metal-complexed systems. A biradicaloid transition state is implied in the reactions of the tungsten complexes, but the mechanism shifts towards a concerted process in the presence of copper(^).^^^ Ring-chain rearrangements of triphosphirane have been studied from a theoretical ~ t a n d p o i n t . ~ ~ ’ 2

Phosphine Oxides

2.1 Preparation. - Supercritical nitrous oxide has been shown to oxidise phosphines to the related phosphine oxides under mild conditions, allowing a simple isolation of products.366 Oxidation of precursor phosphines by hydrogen peroxide is the final step in the synthesis of the chiral functionalised phosphine oxides (219)367and A novel resolution procedure for the preparation of P-stereogenic phosphine oxides is afforded by the reactions of racemic chiral tertiary phosphines with an optically pure camphorsulfonyl azide, followed by separation of the diastereoisomeric phosphazenes, and acid hydrolysis to liberate the resolved, chiral phosphine oxides.369 Protected primary phosphine oxides (221) have been obtained by treatment of (diethoxyPh

(221) R’ = H or Me R2 = Me, Bu

alky1)-phosphinates with Grignard or organolithium reagents. Subsequent metallation and alkylation at phosphorus affords the protected secondary phosphine oxides (222), from which chiral systems, e.g. (223), have been obtained.370 Among new phosphine oxides prepared by the reactions of organolithium or Grignard reagents with phosphinyl halides are the organometallic system (224),371the unsaturated system (225),372(which, in the presence of a cobalt carbonyl complex, undergoes intramolecular cycloaddition reactions to form (226)), and the alkadienylphosphine oxides (227).373 Phosphine oxides have also been prepared by treatment of diphenylphosphinyl chloride with organocerium reagents.374 Phosphine oxides metallated at carbon adjacent to phosphorus have been used in the synthesis of functionalised systems, including 2-hydroxy-2-arylethyldiphenylphosphineoxides (228) the diphenylphosphinyl(resolved via chromatography on a chiral enamide (229),376 and a series of unsymmetrical bis(phosphiny1)methanes (230).377The silylated allylphosphine oxide system (231) has been obtained via an Arbuzov reaction of methyl diphenylphosphinite with an allylic chloride

Organophosphorus Chemistry

32

0 II

4 3 /

R' I

(223) R = alkyl or aryl

(222) R3 = alkyl

~H

PPh2

R3 RI R ~ C =c' C ' =CH -PR;

PR2 COCP

CI/

II

0

(227) R'-R4 = alkyl

0 Ar I1 / Ph2P-CH2-CH OH

0

0 NLi II Ph2P-CHrC 'But

0 II

II

R:PYPR: k3

(230) R' = Ph or But R~ = H or Pr" R3 = Me, Bunor Ph

(229)

precursor.378 Calixarenes bearing phosphine oxide substituents have been prepared, and their ability to act as selective complexing agents for rare earth metals Classical and phase transfer-catalysed Williamson reactions have been used to prepare (po1y)alkoxymethylphosphine oxides from (po1y)hydroxymethyl- or (po1y)chloromethyl-phosphine oxides.38' The reactions of the ylide derived from the 1,l-diphenylphospholanium cation with a,0-unsaturated thioesters provides a route to a series of cycloheptenylphosphine oxides, (232).382Aminoalkylphosphine oxides, e.g. (233), have been obtained from the addition of secondary phosphine oxides to i m i n e ~ . ~ ' ~ Routes to phenylbis(0-oxocyc1opentyl)phosphine chalcogenides (234) have been developed from the reactions of phenyldichlorophosphine with 1-mor-

(232) R = alkyl or aryl

0 Ph2:

(233)

0

0

@)2

(234)

(235) R = t-CeH17 ,3,3-tetramethylbutyI or 1,I

33

1: Phosphines and Phosphonium Salts

pholino~yclopentene.~~~ Optically pure bis(phosphine oxides) (235) have been prepared by a Kolbe electrolytic coupling reaction of carboxylic acids bearing Interest has also continued in the synthesis of a chiral phosphinoyl the fire-retardant polymeric phosphine o ~ i d e s . ~ ’ ” ~ ~ ’ 2.2 Reactions. - Asymmetric hydrogenation of the bis(phosphinoy1)butadiene (236) using a chiral ruthenium catalyst has given the chiral bis(phosphine A novel access to oxide) (237), the immediate precursor of (S,S)-chiraph~s.~’~ alicyclic phosphine oxides is provided by rhodium-promoted ring-closing metathesis of the bis-unsaturated phosphine oxides (238), giving, e.g. (239).390 Further studies of the influence of bulky substituents at phosphorus on the reactivity of cyclic phosphine oxides have appeared. The presence of the 2,4,6tri(isopropy1)phenyl group at phosphorus in 3-phospholene oxides (240)

(236)

(237)

(238) n, m = 1 or 2

(239)

(240)

enables stereoselective cyclopropanation at the double bond to be achieved, the outcome depending on conditions. The bulky group also influences the stereochemical and regiochemical course of the subsequent ring-enlargement reactions undergone by the cyclopropano-fused systems, e.g. (241).391Such bulky substituents at phosphorus also promote unexpected [2+2]cycloaddition reactions involving the P=O bond of five- and six-membered heterocyclic phosphine oxides, forming oxaphosphetes involving pentacovalent phosphorus, e.g. (242), on treatment with dimethyl acetylenedicarboxylate.3g2~3g3 Treatment of the cyclic phosphine oxides (243) with maleic anhydride or Nphenylmaleimide results in Diels-Alder addition to form the new 2-phosphabicyclo[2,2,2]octene-2-oxides(244). X-ray studies show that these systems have a less strained framework than previously described phosphabicyclooctadienes. Consistent with this, the bicyclooctenes require more forcing thermal decomposition conditions to split out the 03-h5species (245), which can be subse-

(241)

(242)

(243) R’, R2 = H or Me

(244) X = 0 or NPh

(245)

quently trapped using h y d r o q ~ i n o n e In . ~ ~related ~ work, photolysis of the bicyclooctenes in the presence of primary or secondary amines has given phosphinamidates, again suggesting involvement of the intermediate (245).395

34

Organophosphorus Chemistry

Photolysis of (244) in the presence of alcohols likewise results in the formation of esters of methyl(pheny1)phosphinic acid. However, *O-isotopic labelling studies provide evidence of, at least, the partial involvement of a pentacovalent phosphorus intermediate in this reaction, and so the previous assumption of the intermediacy of (245) may not be the whole story.396The phosphole oxide dimers (246) have been shown to undergo regioselective reduction and complexation on treatment with the dimethylsulfide-borane adduct, to form the bicyclic system (247).397Treatment of the propadienylphosphine oxide

(246) R', R2 = H or Me

(247)

Ar = Ph, Mes or 2,4,6-But3C6H2

(248) with the phosphinylhydrazine (249) results in the formation of the phydrazonophosphine oxide (250), which has subsequently been transformed into the 3-phosphinylated- 1-aminopyrrole system (25 1).398Thermal decomposition in refluxing toluene of the azidovinylphosphine oxide (252) results in the formation of the 2H-azirinylphosphine oxide (253). This system can also be

= * iPh21,p 0 PPhT II II 0

-

+

Ph2P-NHNHp

I

PPh2

I1

0

N"

a

II PPh2

0

obtained by treatment of propadienylphosphine oxides (248) with hydroxylamine, followed by tosylation and base-promoted cyclisation. Borohydride reduction of the azirine system yields the related aziridines, subsequently isolated in chiral form.399 Treatment of the phosphine oxide (254) with Grignard or organolithium reagents results largely in displacement of the methoxymethyl group to form the phosphine oxides (255). In most cases, traces of other phosphine oxides arising from displacement of a phenyl anion were also dete~ted.~"Side-chain elaboration of alkyl- or vinyl-diphenylphos-

35

1 : Phosphines and Phosphonium Salts 0

0

II

II

Ph2PCH20Me (254)

Ph2PR (255) R = alkyl or aryl

phine oxides continues to be exploited by Warren's group, with particular reference to controlling stereochemistry at remote sites by the diphenylphosphinoyl This group has also demonstrated diastereoselective nucleophilic addition of cuprate and chiral amide reagents to vinylphosphine oxide^.^" Side-chain elaboration of bromoalkyl- and vinyl-diphenylphosphine oxides with monoaza-15-crown-5 has given a new type of hybrid donor lariat crown ether system, e.g. (256).406A series of N-substituted carbamoyl- or thiocarbamoyl-methylphosphine oxides (257) has been obtained via the reactions of aminomethyldimethylphosphine oxide with alkyl-isocyanates and -isothiocyanates, re~pectively.~'~ Photolysis of a range of substituted benzyldiphenylphosphine oxides has shown that the diphenylphosphinoyl and benzylic radicals are the primary photopr~ducts.~'~ Interest in hydrogen-bonded adducts of phosphine oxides has also continued. Complexes of triphenylphosphine oxide with 4-amin0-4'-nitrobiphenyl~'~ and triphenylmethan~l~~' have been characterised. Phosphonyl-hydroxyl hydrogen-bonding has also found application in promoting the miscibility of polymer blends.41 Hydrogen-bond formation is also central to a new procedure for resolution of the secondary phosphine oxide (258), using a chiral binaphthalenediol or (S)-mandelic acid. The resolved phosphine oxides were then converted into the corresponding enantiopure hydroxymethyl(phenyl)(t-buty1)phosphine oxide via treatment with f ~ r m a l d e h y d e .The ~ ' ~ trifunctional triarylphosphine oxide (259) has been used as a component triacid to form 2D-networks with various metal ionbipyridyl complexes.413 Relatively few papers have appeared describing the reactivity of phosphine sulfides and selenides. The P-aryl phosphetan sulfide (260) undergoes photolysis at 254 nm to form a variety of products, which are assumed to arise from low coordination p,-bonded intermediates (261).414Three separate groups

II Ph2P-CH2 CH2-N

(256)

0 II BU'-P-H

0 X II II Me2PCH2NH- C -NHR

I

Ph

(257)X = 0 or S

(258) Ar-P=S

.OMe hv \

OMe

36

Organophosphorus Chemistry

have reported studies of charge-transfer adducts of phosphine sulfides and selenides with halogens and inter halogen^.^^ 5417

2.3 Structural and Physical Aspects. - X-ray crystal structures of tris-pchlorophenylphosphine oxide and tris-p-methoxyphenylphosphineoxide have been reported, which enable further understanding of the nature of the phosphorus-oxygen bond. Both structural data and IR stretching frequencies for these triarylphosphine oxides support the interpretation of the phosphorus-oxygen bond as having substantial multiple bond character, with a bond order between 1.7 and 1.8. The para-substituents have an insignificant effect on the nature of the phosphorus-oxygen bond.418Studies of the various conformational isomers of the phosphine oxides (262) and (263) have been reported for both the crystalline state and in solution in solvents of different polarity.419 A theoretical study of anomeric effects in dithianephosphine oxides, e.g. (264), has also appeared.420X-ray absorption near-edge structure 0

dSL

II

::

0

CH2PPh2

0 I1 Ph-P-(CH,-C-OMe)

b(Phz

II

Ph2PCH2

(262)

CH2PPh2

(263)

(264)

(XANES) measurements of triorganophosphine chalcogenides have been reported and related to the effects of sub~tituents.~~' Triethylphosphine sulfide appears to offer some potential as a non-linear optical organic material, and a technique for growing it as bulk single crystals has been developed.422

2.4 Phosphine Chalcogenides as Ligands. - The complexation of lanthanide and actinide ions by phosphine oxide ligands remains an active area, and a theoretical assessment of the coordination of phosphine oxides (and phosphate esters) by trivalent lanthanide ions has appeared.423 Trivalent lanthanide complexes of the functionalised enol phosphine oxide (265), (and a related phosphonate), have been described.424Complexes of thorium(1v) with bis(diphenylphosphino) ethane dioxide and bis(diphenylphosphinoy1)amide have also been ~ h a r a c t e r i s e d .Calixarene ~~~ systems which bear phosphine oxide

2

1: Phosphines and Phosphonium Salts

37

functionalities at either the narrow or the wide rim, e.g. (266),426have been shown to be excellent extractants for trivalent lanthanide and actinide ions426,427 and also to bind alkali metal ions selectively.428Triphenylphosphine oxide coordinates to metal ions at the centre of metallophthalocyaninate complexes when the latter are dissolved in the molten phosphine oxide at 300 0C.429Long chain alkylphosphine oxides have found use as complexing agents for phase-transfer catalyst systems involving molybdenum-peroxo complexes.430Trioctylphosphine oxide has been used for the solvent extraction of chromium(Ir1) corn pound^.^^' The ability of the heterocyclic system (267) to complex metal ions has also been A series of new chiral titanium alkoxide-o-hydroxyarylphosphineoxide complexes has found use as catalysts in the asymmetric trimethylsilylcyanation of aromatic aldehydes.433Manganese@) complexes of the nitronyl-nitroxide-functionalisedphosphine oxide (268) have been characterised, these systems exhibiting both ferro- and antiferro-magnetic interactions in the solid state.434 Ph

Ph

Tributylphosphine sulfide has been used as a co-catalyst with dicobalt octacarbonyl for the Pawson-Khand reaction.435Thermolysis of a mixture of cadmium chloride and trioctylphosphine sulfide at 250°C has been used as a route to the formation of nanocrystalline cadmium A complex of triphenylphosphine sulfide with a silver-tungsten-iodine acceptor has been characterised by X-ray Ferrocenylphosphine chalcogenides have attracted considerable interest as ligands. Complexes of the monophosphinophosphine sulfide (269) with rhodium have been ~ h a r a c t e r i s e dThe . ~ ~ disulfide ~ (270) forms complexes with both gold(1) and gold(m) acceptors,439and a silver(1) complex of the diselenide (27 1) has been preparedeU0 S

Se (&P I h2

e

P

p

h

@PPh2

2 I

ie

Fe II

Fe

@PPh2 II

S

(270)

&PPh2

II

Se

Organophosphorus Chemistry

38

3

Phosphonium Salts

3.1 Preparation. - Quaternization of triphenylphosphine with a wide range of haloalkanes in various solvents has been achieved in only four minutes under sealed tube conditions with microwave heating, compared to reaction times of several hours under conventional heating.441Conventional quaternization procedures have been used in the synthesis of further examples of benzylic triphenylphosphonium-end-stopperrotaxane systems,442the tetrakisphosphoniobenzyl-substituted porphyrins (272)443and the salt (273).444The reactions of tertiary phosphines with alkylthio(chloro)acetylenes, RSC = CCl, have given the salts (274) as initial The phosphonioalkylphosphonates (275) have been prepared as analogues of the related trialkylammonio systems, well-known cationic phospholipid substances used for DNA transfection, and found to be more efficient transfection reagents and also to be less toxic than the ammonium salts.447The reaction of tetraphenyldiphosphine with pyridinium hydrochloride has given the diprotonated species (276)

+ Ph3PCF2Br Br(273)

+ R3P-CECSR

CI -

(274) R = Ph, CH=CHPh or CH2CH2Ph

(272) R = Ph or Bu

0

(275) R’ = alkyl

+ + Ph2 P-P Ph2 H H

2CI -

(276)

R2 = C14-18alkyl

as a pyridine-resistant colourless solid.448Various approaches to the synthesis of phosphonium-functionalised polymers have been described.4493450 Full details have appeared of the synthesis of arylphosphonium salts bearing acidic functional groups on the aryl substituent, e.g. (277), these promoting watersolubility and aiding the separation of related phosphine oxides from Wittig procedures.451The Horner nickel(I1)-catalysed formation of arylphosphonium salts from aryl halides and tertiary phosphines has been employed in the synthesis of a series of calix[4]resorcinolarenes bearing arylphosphonio substituents (278) on the lower rim,452 the phosphonioaryltosylimino betaine (279),453and the ‘push-pull’ systems (280) and (281), from which the phosphine oxides (282) have been obtained by alkaline hydrolysis.454The betaine

I: Phosphines and Phosphonium Salts

39 R

(278) R = Me or C6HI3

(277)

(279)

Br&6Ph3

Br-

Me2N

Ar (280) Ar = P-bh?zNC& ferrocenyl or 2-thienvl

(282) Ar = P-MezNC6H4 pMe2NC6H4CH=CH-, ferrocenyl or 2-thienyl

(279) and the salts (280) exhibit a modest degree of negative solvatochromism, whereas the related phosphine oxides show a small positive solvatochromic effect. Arylphosphonium salts, e.g. (283),455have also been formed in the reactions of phosphine-coordinated arylpalladium(I1) Phosphonium salts have been obtained from the reactions of phosphines with iodonium salts.457459Thus, e.g. treatment of diphenyliodonium triflate with 1fluorovinyldiphenylphosphine has given the salt (284),458and the salts (285) have been obtained from the reactions of alkenyl(pheny1)iodonium tetrafluoroborates with triphenylphosphine in the presence of ethyldiisopropylamine. The latter reaction is believed to involve the trapping of a vinylcarbene by the p h o ~ p h i n e Carbene . ~ ~ ~ intermediates also seem to be implicated in the formation of difluoromethylphosphonium salts in the reactions of phosphines with tris(trifluoromethy1)bismuth and aluminium chloride in a~etonitrile.~~' Electrochemical oxidation of tertiary phosphines in the presence of alkenes leads to the formation of phosphonium salts via the intermediacy of phosphine radical cations.461 Perhaps the structural surprise of the year is the tetrazirconacenylphosphonium salt (286), shown to have a pZanar tetracoordinate phosphorus atom, prepared from the Schwarz reagent [Cp2Zr(H)Cl] and a triphosphenium salt.463Not surprisingly, this has raised a number of issues, t462

t

+pph3 F

N=CHPh

OTfBFq-

40

Organophosphorus Chemistry

provoking comment.464A range of new iodophosphonium salts has been prepared from the reactions of diisopropyliodophosphine with alkyl halides.465 The structural dependence of iodophosphonium cations on the nature of the associated anion has been the subject of a review.466Interest in the synthesis of phosphonium salts involving unusual anions has also continued. A tetraphenylphosphonium salt containing a complex rhenium anion has been shown to undergo metallation by the anion at the m- and p-positions of the phenyl rings of the cation.467The first phosphonium salt bearing a calix[4]arene unit as the anion has been prepared.468A phosphonium salt containing a sulfide-functional dicarbaborane anion has been structurally ~ h a r a c t e r i s e dTetraphe.~~~ nylphosphonium thiocyanate has also been the subject of an X-ray The reaction of tetraphenylphosphonium azide with azidotrimethylsilane in the presence of water or ethanol results in the formation of the non-explosive salt Ph4P'[N3HN3]-, containing the hydrogen diazide anion, which has also been structurally ~haracterised.~~' Various benzyltriphenylphosphonium salts involving oxidising anions, e.g. peroxym~nosulfate,~~~ p e r o x ~ d i s u l f a t eand ~~~ d i ~ h r o m a t ehave , ~ ~been ~ ~ prepared ~~~ and used as selective oxidising agents in synthesis. Methyltriphenylphosphonium dichromate has also been prepared. An X-ray study shows that the dichromate anion modifies the usual crystal packing of the cations, resulting in a layer-type lattice with only weak phenylphenyl 'embrace' interactions.476In contrast, structural studies on a series of methyltriphenylphosphonium salts involving polyhalocuprate(I1) anions reveal that the attractive supramolecular multiple phenyl embraces influence the geometry of the anions.477Treatment of methyltriphenylphosphonium iodide with tellurium tetrachloride results in the formation of a bis(phosphonium) halotellurate, treatment of which with base yields related ylide complexes of tellurium tetrachloride, enabling a synthesis of di~inyltellurides.~~~ 3.2 Reactions. - The phosphonium salts (287) have been shown to undergo facile nucleophilic displacement of triphenylphosphine on treatment with a range of C , N and S-nucleophiles, giving a range of functional P-substituted silyl enol ethers.479The 4-phosphonio-oxazolones (288) undergo dephospho-

(287)n = 0 or 1

(288)

niation on treatment with hydrogen iodide in dichloromethane at room temperature, providing a route to N-acyl-a-aminoa~ids.~~~ Interest has continued in studies of the liquid crystalline and other properties of phosphonium salts bearing two or three long alkyl chain s u b s t i t ~ e n t sIndeed, . ~ ~ ~ the ~ ~ non~~ linear optical properties exhibited by the smectic phase formed by dimethyldi (long chain alky1)phosphonium salts have been attributed to non-centrosym-

1 :Phosphines and Phosphonium Salts

41

metry arising from a weak association of halide counterions with the phosphonium centre, an interaction not possible for the related tetra-alkylammonium salts.482Significant differences in self-organising ability between tetra-alkylammonium and -phosphonium salts, bearing one or two long alkyl chains, have been noted, and linked to comparative antimicrobial properties.483 Further developments in the chemistry of the t ribut ylphosphine-carbon disulfide adduct have been reported. Its reaction with alkynes furnishes ylide intermediates which, on treatment with aldehydes, provide a route to 2arylidene- or 2-alkylidene-1,3-dithiole~.~’~ The coordination chemistry of tertiary phosphinesarbon disulfide adducts and related dipolar compounds has been reviewed.485A semi-molten mixture of hexadecyltributylphosphonium bromide and potassium fluoride has been used to promote nucleophilic fluoride exchange with various organic halides.486Polymer-supported phosphonium salts have been used in conjunction with potassium fluoride to promote fluorination of 2,4-dinitrochlorobenzenes under solid-solid-liquid phase-transfer conditions.487 Kinetic and thermodynamic parameters have been obtained for the alkoxide decomposition of 3-bromopropyltriphenylphosphonium bromide in dioxane-ethanol mixtures.488Alkyl migrations have been observed in the alkaline hydrolysis of tributylstyrylphosphonium bromide, yielding dibutyl(1-butyl-2-phenylethy1)phosphineoxide (289) in addition to other products.489The ability of allylphosphonium salts to promote photochemically- and thermally-induced radical-promo ted cationic polymerisation reactions has been studied.490The carbonyl group of the phosphonioacetaldehyde system (290) has been shown to be strongly hydrated under aqueous conditions, leading to a low intrinsic reactivity of the aldehyde f ~ n c t i o n a l i t y Nevertheless, .~~~ such salts have been shown to undergo imine formation on treatment with primary aromatic amines, the imines subsequently tautomerising to form the salts (291).492The occurrence of ‘six-fold’ 0 II

Bu~P-CH-CH~P~ I

Bu (289)

Ph3kH2CHO

+

Ph3P-CH=CH-NHAr

X-

X(290)

(291)

multiple phenyl ‘embraces’ in the solid state of a wide range of triphenylphosphonio-systems, including triphenylphosphine-group 13 adducts, has been studied.493Interest has continued in the study of coordinative peri-interactions systems. Structural studies of a in 1-dimethylamino-8-phosphonionaphthalene range of new amino-phosphonionaphthalene systems, e.g. (292), reveal short N-P distances, implying the existence of a strong coordinative interaction between nitrogen and the phosphonium centre.494In contrast, Schiemenz and co-workers have argued that the short N-P distances in such peri-naphthalene systems arise naturally as a result of the structural constraints imposed by the 1,8-disubstituted naphthalene unit, and that just because the observed N-P distances are shorter than the sum of the Van der Waals radii, it does not necessarily follow that there is a hypervalent coordinative interaction, either in

42

Organophosphorus Chemistry

the phosphonium salts or in related 1-amino-8-naphthylphosphines. There is little support from 'H- and 31P-NMRdata for the existence of such interact i o n ~The . ~ previously ~~ reported X-ray study of the phosphine (293) (Corriu et al., Angew. Chem., Int. Ed. Engl., 1993, 32, 1430), has been revisited, and is now thought to be that of the phosphine hydrobromide salt (294). The authentic phosphine (293) has now been prepared, the key step being treatment of the crude product with alkali. Structural data for the authentic phosphine (293) are different to those of the Corriu material.496 +

(294)

4

p,-Bonded Phosphorus Compounds

A review of lone pair effects involving multiple bonds between heavier main group elements contains much of relevance to p,-bonded phosphorus systems.497The diphosphene (295) has been shown to undergo cycloaddition reactions with isocyanides, to give the iminodiphosphiranes (296).498 A thirtyfive-fold excess of methyl triflate is needed to convert the diphosphene (297) to the salt (298), which is unstable in non-polar solvents. Experimental data show that the P=P bond becomes stronger on alkylation as is the case for N=N compounds.499 (MeSi)&,

(MeSi)3C, P=P

/ C(SiMe&

7 NxR

(296) R = CH2CN or CH2CF3

(295) Mes*, P=P \

, C(SiMe3)3

p=$

Mes*

(297) Mes* = 2,4,6-But3C6H2

Mes*

/

Mes* \

OTf-

Me

(298)

Cyclic triphosphenium ions, e.g. (299), have been obtained from the reactions of bis(dipheny1phosphino)alkenes with phosphorus trichloride in the presence of tin(I1) chloride in dichloromethane.sOO The simple phospha-alkene (300) has been formed and stabilised as a molybdenum complex.s01A range of new phospha-alkenes bearing bulky groups has been prepared, including (301),'02 the functionalised C-fluorophospha-alkenes (302),'03 and the phosphoranyl-functionalised system (303).504The polycyclic oxa-bridged system (304) has also been prepared, and shown to undergo addition reactions at the P=C bond with alcohols in the presence of a base.s0sThe reactions of sterically

I : Phosphines and Phosphonium Salts

43 Ar

Ar

(301)Ar = Mes, pMeOC6HI4 or p-tolyl

R3E-P

=C

F NEt2

(302)R3E = Me3Si, Me3Ge, (CF3)sGe or Me3Sn

(303)

protected phospha-alkenes with boron hydride reagents have been studied.506 A study of the reactivity of the carbonyl-functional phospha-alkenes (305) has also been reportede507The triphospha-Dewar-benzene (306) has been shown to undergo cycloaddition reactions with alkynes to form the triphosphabishomoprismane system (307).'08 Cycloaddition of t-butylphospha-ethyne to the phosphatriafulvene (308) results in the formation of a single isomer of the diphosphaisobenzene (309), having an allene system within the ring. This 0 II

R- C-P= C( NMe&

*But\

Ph

&+ P

0

(304)

(305)

P

(306)

%

compound undergoes cycloaddition reactions with trimethylbenzonitrile oxide at the P=C bond to form the fused system (310) in which the internal allene unit is still intact.509Radical anions of various isomers of phenylene bis(phospha-alkenes) e.g. (311), and other systems, e.g. (312) and (313), have been generated by electrochemical and chemical reductions and studied by EPR techniques.510The reactivity of the bis(phospha-alkene) (3 14) towards alkyllithium reagents and lithium aluminum hydride has been explored.511Oxida-

44

Organophosphorus Chemistry

(310)

Ar-P H

.

;

(31 1) Ar = 2,4,6-But3C6H2

-

A

r

Ar-P

P-Ar

tive addition of water or methanol to the diphosphacyclobutadiene ligand in a series of cyclopentadienylmolydenum complexes has been observed.512Electrochemical reduction of the diphospha-allene (315) yields a radical anion which, on protonation, gives rise to the 1,3-diphospha-allyl radical (316), characH I

Ar-P=C=P-Ar

ArP
(315) Ar = 2,4,6-But3C6H2

(316)

terised by EPR.513A new phospha-aza-allene (317) has been prepared, and shown to undergo addition of a secondary phosphine to the C=N bond.514 Conjugation in phosphabutadienes and related aza-phosphabutadienes has been studied by computational techniques,515and an X-ray study of the 2-aza3-phosphabutadiene (3 18) has been reported.516Weber's group has reported a Me2N Mes*-P=C=N-Ar (317)

C=N-P=C Ph/ (318)

SiMe3 SiMe3

Mes" = 2,4,6-But3C6H2 Ar = p-CIC6H4

further series of studies of the reactivity of phospha-alkenes bearing a complexed metallo-substituent at p h o s p h ~ r u s17-520 , ~ and the topic has also been reviewed.521 Further studies of the chemistry of phospha-silenes and phospha-stannenes have also appeared. On heating in toluene, the phosphasilene (319) forms (320), treatment of which with butyllithium generates the new phosphasilene (321).522The phospha-stannene (322) undergoes a [2+2] cycloaddition reaction on treatment with benzaldehyde to afford the fourmembered ring system Phospha-alkyne systems have continued to attract interest. The phosphinophospha-alkyne (324) arises as a transient intermediate in the thermolysis of a phosphino-phosphiranyl-diazo system.524 A convenient synthetic route to substituted phosphavinyl Grignard reagents (325) is provided by the regio- and stereo-selective addition of Grignard reagents to the phospha-alkyne

45

1 :Phosphines and Phosphonium Salts

Ar2Sn-PMes*

I I

Ar2Sn=PMes*

O-CHPh

Whereas the latter phospha-alkyne does not react with sulfur or selenium, the related system Pr12NC= P yields the diphosphetene system (326). Also reported in this study is a slow cycloaddition of ButC=P with carbon disulfide, eventually yielding a 1-thia-2,4-dipho~phole.~~~ Interest in the dimer-

d (324)

p=c, MgX

(325) R = Cy, Cyclopentyl, Et or Mes

(326) X = S or Se

isation of phospha-alkynes in the presence of transition metal acceptors has ~ o n t i n u e d . The ~ ~ ~structure - ~ ~ ~ and energies of the various possible trimers of the phospha-alkyne HC = P have been compared, with phosphabenzene systems being the favoured products.530 The phospha-alkyne MesC = P has been shown to undergo an unprecedented pentamerisation in the coordination sphere of tungsten, to form (327).531The formation of phosphorus+arbon cage compounds by cyclo-oligomerisation of p h ~ s p h a - a l k y n e sand , ~ ~studies ~ of their reactivity,533have been reviewed. The reactivity of iminophosphenes has also received further study. Additions of alkyllithium reagents to the P=N bond have been documented,534and adducts of the P-functionalised iminophosphene (328) with triphenylphosphine, pyridine, and a carbene are described. The adducts (329) represent a new type of p,-system, involving a pyramidal three-coordinate phosphorus centre with a lone pair of electrons, and a distinctive N=P double bond.535

L

\

: P=N / \ E Mes* Mes (327)

(328) E = CI or OS02CF3 Mes* = 2,4,6-BUt&H2

(329) L = Ph3P, pyridine or R2C:

46

Organophosphorus Chemistry

The first aliphatic phosphenium cations involving a phosphorus-sulfur bond, e.g. (330) have been prepared and characterised.536t537 The stereochemistry, regioselectivity and mechanism of the insertion of the diisopropylamino (chloro) phosphenium cation into the phenylcyclopropane ring, to form phosphetanes, has been Ligand-exchange processes involving mono- and bis-adducts of phosphenium ions have received a theoretical treatment.539The coordination chemistry of the carbene adduct (331) of the + CI -

(330)

diphenylphosphenium ion has been in~estigated.'~'[2+2]-Cycloaddition of a complexed P-H functional phosphenium ion with alkylisothiocyanates has provided a series of metallocycles bearing P-H functionality.541 Interest has also continued in phosphinidene (RP:) chemistry. Evidence from mass spectrometry has led to the conclusion that phenylphosphinidene, PhP:, is a stable species in the gas phase.542The existence of p-phenylenebisphosphinidene (332) has been considered from a theoretical standpoint.543 The reactivity of coordinated phosphinidenes has received further study. The first examples of genuine 1,4-additions of the complex PhP=W(CO)S with 1,3dienes, giving phospholene complexes, e.g. (333), have been r e p ~ r t e d . ' ~ Phosphiranes are formed as intermediate species in the reactions of complexed phosphinidenes with chloro-alkenes, which lead ultimately to vinylphosphorus compounds (334), essentially insertion products of the phosphinidene into the

(332)

(333)

(334)

C-C1 bond.545Phosphirane intermediates are also involved in the reactions of the electrophilic phosphinidene complex (335) with a l l e n e ~The . ~ ~microwave ~ spectrum of the phosphinidene radical CH2P: has been recorded in the gas phase.547 Following earlier studies of the generation of reactive p,-bonded phosphorus compounds by the pyrolysis of arylphosphetan chalcogenide~?~~ it has now been shown that pyrolysis of the phosphirane chalcogenides (336) gives rise to the phosphinidene chalcogenides (337), which have carbene-like reactivity, having been trapped in reactions with dienes, diketones and other reagents.548 The main topic of interest in the chemistry of 03h5-p,-bonded systems in the past year has been their possible stabilisation by intramolecular coordination. Evidence of intramolecular coordination has been obtained for the dithioxo-

1: Phosphines and Phosphonium Salts

47

and diselenoxo-phosphorane systems (33 8)549~550and (339),551although such coordinative interactions are often the prelude to further reactivity at the phosphorus centre. Also reported is the synthesis of lithiated phosphoranylidene carbenoids involving 03h5-centres,e.g. (340).552 OMe

[ Pr‘2N-P=Fe(C0)4 ] \

OMe

OMe (336) X = 0 or S

(335)

(337) X = 0 or S

Mes*-P

E

//

\\C(x)Li

(338) D = SMe, SeMe or R2N

(339)

n = 0,i or 2

(340) X = F, CI, Br E = C(SiMe3)2

X = S or Se

or NMes*

5

Phosphirenes, Phospholes and Phosphinines

Trapping electrophilic phosphinidene complexes with alkynes has been used in the synthesis of the new phosphirene systems and (342).554In the latter, the phosphirene rings are coplanar and conjugated. The diphosphinines (343) are formed unexpectedly in a head to head dimerisation of 1H-phosphirPh, P&N\ R’

f

,W(C0)5

Fe(C0)4

AR2

(341) R’ = H, Me, Ph or SiMe3

R+’

-

Ph’

R’

P \W(CO)S

(342) R’ = But or SiMe3

R P-P / / Ph Ph (343) R = H, Ph or SiMe3

R2 = H, Me, Ph, SiMe3, C i C P h or C(Me)=CH2

enes (and their metal complexes) in the presence of nickel(I1) or palladium(o) catalysts.555 Further studies have been reported of the formation of 2Hazaphosphirenes (344) in the reactions of aminocarbene complexes with Phalofunctional phospha-alkenes (or their precursor halogenoph~sphines).~~~ Under thermal or photochemical conditions, 2H-azaphosphirenes undergo ring-opening to form nitrilium-phosphine ylide complexes, e.g. (349, which can then be trapped by alkynes or nitriles to form a variety of three- or fivemembered heterocyclic systems.557-559 Interest has continued in the chemistry of diphosphirenium salts (346) and diphosphirenylium salts (347), usually

48

Organophosphorus Chemistry

(344)

(345)

(346)

(347)

(348)X = NR2, F, CI, N3, OH or Ph

encountered in the form of complexes with a tungsten pentacarbonyl acceptor, and this area has been reviewed.560The coordination chemistry of the 1Hdiphosphirene system (348) has also received attention.5619562 The chemistry of the phosphole system, and that of related heterophospholes, has continued to be an active area. Treatment of unsymmetrical zirconacyclopentadiene reagents with phenyldichlorophosphine provides a route to the unsymmetrical phospholes (349).563Organozirconium intermediates have also been used in routes to electropolymerisable heteroaryl-substituted phospholes, e.g. (350),564and the bridged diphospholes (351)? Routes

Ph

vR1 & Ph

I

*'\(CHZ)~/'#

Ph

(349)R' = Me,Et or P s

(351)n = 1 or 2

(350)

to stable 1,3,4-triphenylphospholesystems (352) have been explored, and a wide range of compounds characterised, many of which have been obtained via the 2-lithiated system (352, X = Li). These compounds are unusually difficult to oxidise, and show little tendency to dimerise. The same is true of the related phosphole Treatment of 1,4-dilithiotetraphenylbutadiene with phosphorus tribromide in the presence of excess lithium metal results in the formation of the P,P-diphosphole (353), which exhibits a P-P bond length in the usual range.567An improved route to alkyldibenzophosphole oxides (354) has been developed, which enables the attachment of long alkyl chains to Ph

Ph Ph

ph*p-p$ Ph

Br

I Ph

(352)

Ph

Ph

(353)

Q-p R-CH~'

*o (354)

phosphorus.568The first 3H-phosphole, the 3H-phosphaindene (355), has been identified in the products of flash vacuum pyrolysis of 2,4,6-tris-t-butylphenyldichlorophosphine. As would be expected, it readily undergoes addition to the P=C bond.569An overview of the structure, stereochemistry and coordination chemistry of 2,2'- biphospholes (356) has appeared.570 Structure-property relationships in phosphole monomers have received a theoretical treatment.571

1: Phosphines and Phosphonium Salts

49

Interest has continued in the extent to which factors affecting the planarity of the trivalent phosphorus atom have a bearing on the aromaticity and other properties of the phosphole ring system, and a review has appeared.572A study of the coordination chemistry of phospholes bearing a sterically bulky substituent at phosphorus has shown that coordination to platinum results in increased pyramidality at phosphorus.573 In the same vein, an ab initio theoretical study of the triphosphole (357) has shown that the steric interac-

+

(357)

(356) R = Ph or CN

(355)

tions between the 2-t-butyl substituent of the triphosphole ring and the supermesityl system forces coplanarity about phosphorus, leading to the prediction that this compound will be fully aromatic.574The position of electrophilic halophosphination of the crowded phosphole (358) depends on the size of the substituents in the 1-aryl Further reports have appeared of studies of the Diels-Alder dimerisation and other addition reactions undergone by phospholes. A platinum complex of a chiral amine has been used to promote the dimerisation of 1-phenyl-3,4-dimethylphosphole to give the chiral diphosphine (359).576Two groups have described the use of a palladium complex of a chiral amine to promote the [4+2] addition of a range of functionalised alkenes to 1-phenyl-3,4-dimethylphosphole, resulting in a range of new chiral A theoretical consideration of the cyclodimerisation systems, e. g. (360).5779578 of 1-methylphosphole oxide predicts the specific formation of one of eight possible isomeric products.579 The cycloadduct (361) is formed as a single isomer in the reaction of pentaphenylphosphole oxide with benzyne.580 Ph P'..

R

(358)

(359)

(360) R = Ph, Ph2P

or CONMe2

(361)

The study of complexes of anionic phospholyl systems continues to develop. Heating 1-t-butyl-3,4-dimethylphospholein the presence of a pinene-fused cyclopentadienyl iron carbonyl complex results in the formation of the chiral

50

Organophosphorus Chemistry

Fe

phosphaferrocene (362).581Treatment of the phosphaferrocenylcyclopentadienide (363) with iron(I1) chloride gives the ferrocenyl bridged bis(phosphaferr0cene) system (364).582Phospholyl complexes of manganese,583cobalt, rhodium and and the heavier group 14 elements,585have also been described. The chemistry of the bis(phosphonio)benzophospholide (365) has also received further Interest in the synthesis and coordination chemistry of di- and tri-phosphacyclopentadienyl systems, notably that of 1,2,4- triphospholes and the related triphospholide anions, continues to grow. The triphenylstannyl system (366),589and related silicon and germanium + 7Ph3

+(

p-? ‘P

P’ I

SnPh3

are versatile starting materials for the synthesis of various polycyclic phosphorus cage compounds, and the general area of phosphorusxarbon cage compounds derived from di- and tri-phospholes has been reviewed.591 Studies of the coordination chemistry of 1,2,4-triphosphole systems have continued apace, with the characterisation of new polyp hosphametallocenes,592-596 and other compounds showing novel modes of coordination. 597 The chemistry of heterophosphole systems involving atoms such as oxygen, sulfur or nitrogen as a ring-member has also undergone significant development. The reactions of phospha-alkynes with a-diazo- 0-dicarbonyl and isomunchnones599provide new approaches to the synthesis of 1,3-oxaphospholes, e.g. (367). Both 1-thia-2,4- and 1-thia-3,4-diphospholes are among the products of the reactions of t-butylphosphaethyne with carbon disulfide. A platinum complex of the l-thia-3,4-diphosphole (368) was structurally characterised.600 The unsubstituted 1,3-thiaphosphole system (369) (and the related thiaarsole), have been characterised, spectroscopic studies indicating that these ring systems are aromatic.601 A simple approach to 1,2,4-selena- and telluradiphospholes (370) is provided by the reaction of phospha-alkynes with

51

1: Phosphines and Phosphonium Salts ,R3 Ri4>CO2R2 (367) R' = aryl R2 = Me or Et R3 = But or Pen'

selenium or tellurium.602 New synthetic routes to 1H-1,2-azaphospholes (37 1)603and 2H- 1,2-azaphosphindoles (372)604have been described. Further examples of fused 1,3-azaphospholes, e.g. (373), have been prepared.605The reactivity of 1,2,3-diazaphospholes in cycloaddition,606and general coordination chemistry,607has received attention. Two routes to the 1,2,4-azadiphosphole system (374) have been developed, and a structural study of (374, R = Ph) has revealed that the ring system is completely planar, consistent with aromatic character.608 Synthetic approaches to 2H- 1,3,2- and -1,4,2-diazaphospholes have been described,609 and the reactivity of 3H- 1,2,3,4-triazaphospholes explored.610

Q7ipR2

R.

P'

(370) R = But, CMe2Et or

R

R'

(371) R = But, I-Ad or Pr'

(372) R' = Ph or But

R' = But, CMe2Et or I - A d

1-adamantyl

X = Se or Te

R2 = NR2

R2 = H, Me or Ph R3 = Pr, PhCH2 or Ar

'C02R (373)

R (374) R = alkyl, cy or aryl

The chemistry of phosphinine systems has also received considerable attention. A synthetic approach to mixed phosphinine-phosphole systems, e.g. (379, has been developed,6" and this has been extended to the synthesis of macrocyclic systems involving phosphinines (and other aromatic ring systems such as thiophen and furan).612The coordination chemistry of tetraphosphinine-based macrocyclic systems is starting to develop, this ligand providing a suitable environment for the stabilisation of unusual oxidation states of noble metals, e.g. A u ( o ) . ~ ' ~Mixed donor ligands involving phosphinine donors have also been prepared, e.g. (376) and (377).614The coordination 57616 chemistry of 'simple' phosphinines has also seen some de~elopment.~' Reduction of 4,4', 5,5'- tetramethyl-2,2'-biphosphinine with alkali metals affords the corresponding dianion (37Q617subsequently used to form the first

52

qppp

Me Me2Siw S i M e 2 Me

SiMe3

4

Organophosphorus Chemistry

0

PPh2

SiMea

(377)

(375)

anionic complexes of phosphinines.61* Further study of the ligand properties of 2,2'-biphosphinines has also been reported.619The reactivity of the triphosphinine (379) has received further study. On treatment with potassium in toluene, it undergoes a remarkable transformation to form the diphospholide salt (380).620With alkynes, it undergoes various cycloaddition reactions to

+

+

form a range of new phosphorussarbon cage systems,621and on treatment with a stable silylene, it undergoes [1+4] addition to form the adduct (381).622 Theoretical studies, coupled with the results from photoelectron spectroscopy of n-bonded metal carbonyl complexes of the triphosphinine (379), reveal that this ring system has significant n-acceptor properties.623The first simple 0bonded metal complex of (379), a platinum(I1) adduct, has been characterised, and shown to undergo a remarkable addition of water to each of the formal P=C bonds.624A theoretical study has shown that the effect of replacing the CH adjacent to phosphorus in phosphinines by N, in the formation of 1,2azaphosphinines, is to reduce delocalisation and to induce a [ 1,4]-dipolar character through an increase in the positive charge at phosphorus. This does not happen in 1,3-aza- and 1,3,5-diazaphosphinine systems, which exhibit a poor dipolar character. This comparision therefore confirms the known high reactivity of 1,3,2-diazaphosphinines towards a l k y n e ~A. ~route ~ ~ to a heterofused 1,4-azaphosphinine system has been described.626Further progress has Me2N, ,NMe2 Np-N

'Si

,N-Np

1: Phosphines and Phosphonium Salts

53

been reported in the chemistry of AS- phosphinine systems.6273628 Among new compounds reported is the 2,2’-bipyridine ‘analogue’ (382), the structure of which has been confirmed by X-ray

References 1 2

3 4

5 6 7

8 9 10 11 12 13 14 15 16 17

18 19 20 21 22

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26 27 28 29 30 31 32

33 34 35

36 37 38 39 40 41 42 43 44 45 46 47 48

49 50 51

1: Phosphines and Phosphonium Salts 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67

68 69 70 71 72 73 74 75 76 77 78 79

80 81

82 83 84

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566 567 568 569 570 57 1 572 573 574 575 576 577 578 579 580 58 1

71

T. Baumgartner, D. Gudat, M. Nieger, E. Niecke and T. J. Schiffer, J. Am. Chem. SOC.,1999,121,5953. J. B. M. Wit, G. T. van Eijkel, M. Schakel and K. Lammertsma, Tetrahedron, 2000, 56, 137. N. H. T. Huy, L. Ricard and F. Mathey, J. Chem. SOC.,Dalton Trans., 1999, 2409. N. H. T. Huy, L. Ricard and F. Mathey, Chem. Commun.,2000, 1137. R. Streubel, S. Priemer, F. Ruthe and P. G. Jones, Eur. J. Org. Chem., 2000, 1253. R. Streubel, H. Wilkens and P. G. Jones, Chem. Commun., 1999,2127. R. Streubel, H. Wilkens, U. Rohde, A. Ostrowski, J. Jeske, F. Ruthe and P. G. Jones, Eur. J. Inorg. Chem., 1999, 1567. H. Wilkens, A. Ostrowski, J. Jeske, F. Ruthe, P. G. Jones and R. Streubel, Organometallics, 1999,18, 5627. D. Bourissou and G. Bertrand, Acc. Chem. Rex, 1999,32, 561. D. Bourissou, Y. Canac, H. Gornitzka, C. J. Marsden, A. Baceiredo and G. Bertrand, Eur. J. Inorg. Chem., 1999, 1479. D. Bourissou, Y. Canac, H. Gornitzka, A. Baceiredo and G. Bertrand, Chem. Commun., 1999,1535. J. Hydrio, M. Gouygou, F. Dallemer, J-C. Daran and G. G. A. Balavoine, . I Organomet. Chem., 2000,595,261. C. Hay, C. Frischmeister, M. Hissler, L. Toupet and R. RCau, Angew. Chem., Int. Ed., 2000,39, 1812. S. Doherty, G. R. Eastham, R. P. Touze, T. H. Scanlan, D. Williams, M. R. J. Elsegood and W. Clegg, Organometallics, 1999,18, 3558. T-A. Niemi, P. L. Coe and S. J. Till, J. Chem. Soc., Perkin Trans. I , 2000, 1519. J. K. Vohs, P. Wei, J. Su, B. C. Beck, S. D. Goodwin and G. H. Robinson, Chem. Commun.,2000,1037. E. Duran, D. Velasco and F. Lopez-Calahorra, J. Chem. SOC.,Perkin Trans. I , 2000,591. R. A. Aitken, P. N. Clasper and N. J. Wilson, Tetrahedron Lett., 1999,40, 5271. 0. Tissot, J. Hydrio, M. Gouygou, F. Dallemer, J-C. Daran and G. G. A. Balavoine, Tetrahedron, 2000,56, 85. D. Delaere, A. Dransfield, M. T. Nguyen and L. G. Vanquickborne, J. Org. Chem., 2000,65,2631. L. Nyulaszi, Tetrahedron, 2000,56,79. Z. Csok, G. Keglevich, G. Petocz and L. Kollar, J. Organomet. Chem., 1999,586, 79. L. Nyulaszi and J. F. Nixon, J. Organomet. Chem., 1999,588,28. G. Keglevich, T. Chuluunbaatar, A. Dobo and L. Toke, J. Chem. SOC.,Perkin Trans. I , 2000, 1495. G. He, Y. Qin, K. F. Mok and P-H. Leung, Chem. Commun.,2000, 167. P-H. Leung, G. He, H. Lang, A. Liu, S-K. Loh, S. Selvaratnam, K. F. Mok, A. J. P. White and D. J. Williams, Tetrahedron, 2000,56, 7. N. Giil and J. H. Nelson, Tetrahedron, 2000,56,71. G. M. Keseru and G. Keglevich, J. Organoment. Chem., 1999,586, 166. C. Gottardo, S. Fratpietro, A. N. Hughes and M. Stradiotto, Heteroatom Chem., 2000,11, 182. C. Pala, F. Podewils, A. Salzer, U. Englert and C. Ganter, Tetrahedron, 2000, 56, 17.

Organophosphorus Chemistry

72

C. Ganter, C. Kaulen and U. Englert, Organometallics, 1999, 18, 5444. B. Deschamps, L. Ricard and F. Mathey, Organometallics, 1999,18, 5688. K. Forissier, L. Ricard, D. Carmichel and F. Mathey, Urganometallics, 1999, 19, 954. 585 K. Forissier, L. Ricard, D. Carmichel and F. Mathey, Chem. Commun., 1999, 1273. 586 A. W. Holderberg, G. Schroder, D. Gudat, H-P. Schrodel and A. Schmidpeter, Tetrahedron, 2000,56,57. 587 D. Gudat, V. Bajorat, S. Hap, M. Nieger and G. Schroder, Eur. J. Inorg. Chem., 1999,1169. 588 D. Gudat, A. W. Holderberg, N. Korber, M. Nieger and M. Schrott, Z. Naturforsch., B: Chem. Sci., 1999,54, 1244. 589 A. Elvers, F. W. Heinemann, B. Wrackmeyer and U. Zenneck, Chem. Eur. J., 1999,5, 3143. 590 A. G. Avent, F. G. N. Cloke, M. D. Francis, P. B. Hitchcock and J. F. Nixon, Chem. Commun.,2000,879. 59 1 J. F. Nixon, Adv. Strained Interesting Org. Mol., 1999, (Suppl.l), 257. 592 C. S. J. Callaghan, P. B. Hitchcock and J. F. Nixon, J. Organomet. Chem., 1999,

582 583 584

584,87.

593 594 595 596 597 598 599 600 60 1 602 603 604 605 606 607 608 609 610 61 1

F. G. N. Cloke, J. R. Hanks, P. B. Hitchcock and J. F. Nixon, Chem. Commun., 1999,1731. J. J. Durkin, M. D. Francis, P. B. Hitchcock, C. Jones and J. F. Nixon, J. Chem. SOC.,Dalton Trans., 1999,4057. G. K. B. Clentsmith, F. G. N. Cloke, M. D. Francis, J. C. Green, P. B. Hitchcock, J. F. Nixon, J. L. Suter and D. M. Vickers, J. Chem. SOC.,Dalton Trans., 2000, 1715. T. Clark, A. Elvers, F. W. Heinemann, M. Henneman and M. Zeller, Angew. Chem., Int. Ed., 2000,39,2087. P. B. Hitchcock, J. F. Nixon and N. Sakarya, J. Organomet. Chem., 2000, 601, 335. S. G. Ruf, A. Mack, J. Steinbach, U. Bergstrasser and M. Regitz, Synthesis, 2000,360. S. G. Ruf, U. Bergstrasser and M. Regitz, Tetrahedron, 2000,56,63. S . E. d’Arbeloff-Wilson, P. B. Hitchcock, S. Krill, J. F. Nixon, L. Nyulaszi and M. Regitz, J. Am. Chem. Soc., 2000,122,4557. A. J. Ashe 111 and X. Fang, Chem. Commun., 1999,1283. S. M. F. Asmus, U. Bergstrasser and M. Regitz, Synthesis, 1999, 1642. C. Peters, F. Tabellion, M. Schroder, U. Bergstrasser, F. Preuss and M. Regitz, Synthesis, 2000,417. V. Cadierno, B. Donnadieu, A. Igau and J-P. Majoral, Eur. J. Inorg. Chem., 2000,417. R. K. Bansal, L. Hemrajani and N. Gupta, Heteroat. Chem., 1999, 10, 598. J. Kerth and G. Maas, Eur. J. Org. Chem., 1999,2633. M. D. Mikoluk, R. McDonald and R. G. Cavell, Inorg. Chem., 1999,38,4056. F. G. N. Cloke, P. B. Hitchcock, J. F. Nixon, D. J. Wilson, F. Tabellion, U. Fischbeck, F. Preuss, M. Regitz and L. Nyulaszi, Chem. Commun., 1999,2363. R. Streubel, H. Wilkens, F. Ruthe and P. G. Jones, Tetrahedron, 2000,56,21. J. Kerth, U. Werz and G. Maas, Tetrahedron, 2000,56, 35. X. Sava, N. Mezailles, N. Maigrot, F. Nief, L. Ricard, F. Mathey and P. Le Floch, Organometallics, 1999,18,4205.

1: Phosphines and Phosphonium Salts

612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629

73

N. Avarvari, N. Maigrot, L. Ricard, F. Mathey and P. Le Floch, Chem. Eur. J., 1999,5,2109. N. MCzailles, N. Avarvari, N. Maigrot, L. Ricard, F. Mathey, P. Le Floch, L. Cataldo, T. Berclaz and M. Geoffroy, Angew. Chem., Int. Ed., 1999,38, 3194. B. Breit, J. Mol. Catal. A: Chem., 1999, 143, 143. N. Mezailles, L. Ricard, F. Mathey and P. Le Floch, Eur. J. Inorg. Chem., 1999, 2233. M. T. Reetz, E. Bohres, R. Goddard, M. C . Holthausen and W. Thiel, Chem. Eur. J . , 1999,5,2101. P. Rosa, L. Ricard, F. Mathey and P. Le Floch, Organometallics, 1999,18, 3348. P. Rosa, N. MCzailles, L. Ricard, F. Mathey and P. Le Floch. Angew. Chem. Int. E d , 2000,39,1823. M. J. Bakker, F. W. Vergeer, F. Hartl, K. Goubitz, J. Fraanje, P. Rosa and P. Le Floch, Eur. J. Inorg. Chem., 2000, 843. F. G. N. Cloke, P. B. Hitchcock, J. F. Nixon and D. J. Wilson, Organometallics, 2000, 19,219. C. Peters, S. Stutzmann, H. Disteldorf, S. Werner, U. Bergstrasser, C. Kriiger, P. Binger and M. Regitz, Synthesis, 2000, 529. S . B. Clendenning, B. Gehrhus, P. B. Hitchcock and J. F. Nixon, Chem. Commun., 1999,2451. S. B. Clendenning, J. C . Green and J. F. Nixon, J. Chem. Soc., Dalton. Trans., 2000, 1507. S. B. Clendenning, P. B. Hitchcock and J. F. Nixon, Chem. Commun., 1999, 1377. G . Frison, A. Sevin, N. Avarvari, F. Mathey and P. Le Floch, J. Org. Chem., 1999, 5524. A. A. Tolmachev, S. I. Dovgopoly, A. N. Kostyuk, E. S. Kozlov, A. 0. Pushechnikov and W. Holzer, Heteroat. Chem., 1999,10, 391. C. Heckmann and E. Fluck, Z. Anorg. Allg. Chem., 2000,626, 1023. S. Plank, G. Heckmann, W. Schwarz, B. Neumiiller and E. Fluck, Z. Anorg. Allg. Chem., 1999,625,1712. G. Heckmann, S. Plank, E. Fluck, A. Dashti-Mommertz and B. Neumuller, Z. Naturforsch., B: Chem. Sci., 1999,54, 1478.

2

Pentacoordinated and Hexacoordinated Compounds BY C. D. HALL

1

Introduction

The year has seen yet another diminution in the number of publications dealing with hypervalent phosphorous chemistry but the quality of work remains high, relying heavily on the latest techniques in NMR spectroscopy and X-ray crystallography. Ample illustration of this is found in a study of cyclic phosphates, phosphonates and phosphonium salts containing sulfuryl groups.' The work was designed to compare the coordinating ability of sulfur, with that of sulfuryl oxygen and in fact only (1) of a series reported

of eight phosphates, phosphonates and phosphonium salts showed evidence of donor action towards phosphorus from phosphoryl oxygen with a P . . - Obond distance of 3.007

A.

2

Acyclic Phosphoranes

Phosphorus 1s photoabsorption spectra of a series of gaseous trivalent and pentavalent phosphorus compounds scanning coordination numbers 3,4 and 5 (e.g. PFs for the latter) have been measured using synchroton radiation.6 Chemical shifts of the main pre-edge peak positions relative to PH3 correlated with both the P-1s ionization potential and KLZL3 Auger shifts. Hence the photoabsorption transition energy can be regarded as an additional probe of the chemical environment of the phosphorus atom. Trifluorophosphoranes, (4a-c), were obtained by the oxidative addition of (2) to ( 3 a - ~ ) .At ~ room temperature only (4a) showed dynamic behaviour in solution but at - 5 "C pseudorotation was slow enough to detect 'J(PFaJ and 'J(PFa,) coupling by 31P NMR. X-ray crystallographic analysis of (4a-c) confirmed the expected tbp geometry with two axial fluorine substituents. All ~~

Organophosphorus Chemistry, Volume 32 0The Royal Society of Chemistry, 2002

74

~

75

2: Pentacoordinated and Hexacoordinated Compounds

three compounds were exceptionally stable towards hydrolysis and, for example, (4b) required heating with water at 60°C in the presence of triethylamine to generate (5). Complex reactions were observed with HCl and + RPF2 (3a-c)a, R = But b, R = Ph C, R = NEt2

Ph3CF (2)

0 II Ph3C-P-F

H20/NEt3 (4b)

Ph3C. RPF3 (4a-c)

60 "C, 18 h

I

Ph

HBr and reduction of (4b) with LiAlH4 gave either (6) or (7) according to the reaction conditions. An equilibrium exists between (4a) or (4b) and the starting materials as demonstrated by the trapping of (3a) with tetrachloro-o-benzoquinone (8) to form (9). Ph3CH +

+

(4a)

'*" LiAIH,, 7 (4b)

PhPH2

0

CI

-

H

LiAIH4

Et20TToluene

Ph3C-P, Ph

CI

Ph3CF

CI

F '

(9)

Pentacoordinate compounds of antimony and bismuth are becoming more prominent as illustrated by the work of Sharutin et al. For example, pentaarylantimony (10ab) and pentaphenylbismuth (16) arylate organotin halides (e.g. R3SnCl (1 1) and R2SnBr2 (13)) to form aryltin derivatives R3SnAr (12), R2SnArX (14) or R2SnAr2 (15), in 78-95% yields.' 4-

Ar&b

R3SnCI

R3SnAr

(1 1) R = Me,Et, Pr, Bu

(10ab) a, Ar = Ph b, Ar = pTol

+

(1Oab)

-

R2SnBr2

-

(12)

-

R2SnArBr

(16)

+

Bu3SnCI (11) R = Bu

(10ab)

Ph3Bi

+

PhCl

R2SnAr2 (15)

(14)

(13)

Ph5Bi

+

Bu3SnPh (12) R = Bu Ar = Ph

76

Organophosphorus Chemistry

A series of tetraarylantimony P-diketonates (18) have been prepared by the reaction of (1Oab) with P-diketones, P-ketoesters or diethyl malonate (wa-g).’ Furthermore, the reaction of (10ab) with phenols (19) and (21), gave pentacoordinate aryloxytetraarylantimony compounds (20) and (22), which were characterised by IR and X-ray crystallography.lo Both compounds were found to have the tbp configuration with the aryloxy groups in apical positions. (10ab)

+

R1COCH2COR2

PhCH3, RT

,COR’ Ar4SbCH,

D

CO R2

(17a-g) a, Ar = Ph, R‘ = Me, R2 = Ph b, Ar = Ph, R1, R2 = Ph c, Ar = Ph, R’ = Me, R2 = OEt d, Ar = Ph, R1, R2 = OEt e, Ar = pTol, R’, R2= Me f, Ar = p-Tol, R’ = Me, R2 = Ph g, Ar = pTol, R’ = Me,R2 = OEt

(18a-g)

OH

?H

p-T0l4Sb-0 Br

Reaction of (1Oa) with triphenylbismuth diacylates (23ab) gave good yields of (24ab) together with the disproportionation products (25ab) which in the case of (25a) decomposed to triphenyl bismuth and phenyl benzoate.” A crystallographic analysis of (23a) revealed a distorted tbp with the benzoate groups in apical positions as expected.

Ph3Bi (OOCOR)~ (23ab) a, R = Ph b, R = CC13

PhsSb

+

Ph4Sb (OCOR) (24ab)

+

[Ph4Bi (0-COR)]

I

(25) R = Ph

Ph3Bi + PhO-COPh

77

2: Pentacoordinated and Hexacoordinated Compounds

3

Monocyclic Phosphoranes

Heating a mixture of pentachlorophosphole (26) and phenylacetylene (27) gave the phosphorane (28) which, on the basis of variable temperature NMR, appeared to be in equilibrium with the phosphonium salt (29).12 The most CI

CI

CI

interesting aspect of this paper, however, is that X-ray crystallographic analysis of the product shows an almost regular tbp with two apical chlorine atoms and the five-membered ring in a diequatorial configuration. During a study of the reaction of a 02-1,2,3-diazaphosphole(30) with the trichlorophosphorane (31) Mironov et al. obtained a mixture of products (3235) which included a phosphorane (35) whose structure was assigned on the basis of 13Cand 31PNMR.13

+

The reaction of (36) with trimethyl phosphite in aprotic medium (hexane or benzene) leads to the formation of (38) as the sole product via a regiospecific [4 + 21 cycloaddition presumably involving (37) as an intermediate. Hydrolysis of (38) gave the ketophosphonate (40) apparently via an enol intermediate (39). l4 Three diazaphosphetidines (41a-c) have been studied by variable-temperature solid-state ”F, 31Pand 15N NMR. The NMR data depended upon the substituents at both N and P and although dynamic properties in the solid state were slowed relative to those in solution, they could still be investigated. Axial and equatorial fluorine atoms were distinguished by 19Fchemical shift, effective shielding anisotropies and isotropic JPFcoupling for (41b) at room

Organophosphorus Chemistry

78

*-

0

MeO’ ‘Me0

(37)

(36)

H20 -MeOH

M Z / P H p h ] Me0

(38)

-C F 3 n f P h MeO>v0 Me0

(41a-c)a,R‘ = Me, R2, R3 = Ph b, R’ = Me, R2 = Ph, R3 = F c,R’ = Ph, R2, R 3 = F

temperature and axiakquatorial exchange in (41c) was shown to be slow on the NMR time scale at low temperat~re.’~

xylene

95 “C

(43) I-\

t

X

QC=CJ3 Ph2P X = C(0)Me

Me

(46)

(45)

‘Ph

2: Pentacoordinated and Hexacoordinated Compounds

4

79

Bicyclic and Tricyclic Phosphoranes

In a complex series of reactions, Vedejs has shown that (42)rearranges to (43) on heating at 95 "C in xylene but that heating in ethanol gives the de-acetylated product (44)together with 43 in a ratio of 4.4:l(44:43).16The mechanism of the reaction leading to (43) is debatable but the authors prefer a route involving isomerisation of (42) to the P-acyl isomer (45)followed by intramolecular acetyl transfer to (46)and a subsequent [2 + 41 internal addition to generate (43). Reaction of PC15 with o-aminophenol (47) under controlled temperature conditions gave the spirophosphorane (48) but at higher temperatures a bisphosphorane (49) was isolated and characterised by X-ray crystallography.l7 CI

(47)

Multinuclear ('H, 13C,31Pand 15N) NMR studies have been reported for three hydrophosphoranes, (50a<), derived from o-aminophenols. * Selective heterodouble resonance experiments and 2-D "N/'H HETCOR nuclear 'H [' experiments enabled the determination of the signs of various coupling

(5Oa-c) a, R1, R2 = H b, R' = H, R2 = But c, R', R2 = But

80

Organophosphorus Chemistry

constants and the 'H-coupled 15N NMR spectrum recorded by the INEPT pulse sequence showed the splitting due to 1J(31P, "N) and 2J('5N, 31P,'H). Molecular modelling of 40 complexes derived from ten bicyclic phosphoranes (51-60), and the alkali cations, Li+, Na+ and K+ has been carried out using the Insight I1 V97 programme based on the ESFF force field." Calculations were

(57)

$4 OMe

+* OMe

2: Pentacoordinated and Hexacoordinated Compounds

81

performed for stoichiometries of 1:1, 2:l and 1:2 (1igand:cation) and were to some extent validated for ligands (51-57) by experimental structures2' and 13C NMR studies of the complexes.21 Reaction of (R)-2-aminobutan-l-01(61)with P(NEt2)3 gave a mixture of the diastereomeric phosphoranes (62ab) in a ratio of 3:7 (a:b). Multinuclear (13C, 31P, "N) NMR, IR and mass spectrometry studies were reported and X-ray crystallographic analysis of (62b) revealed a slightly distorted tbp with apical oxygen and equatorial nitrogen atoms.22

1,3,2h5-Oxazaphosphetidines(65a-c) have been synthesised by the reaction of iminophosphorane (63) with ketones (64a-c). The compounds were characterised by multinuclear NMR and in one case (65c), X-ray crystallographic analysis revealed a distorted tbp with two oxygen atoms in apical positions.23 Thermolysis of (65c) gave the cyclic phosphinate (66) and the corresponding imine (67) indicating that (65) is an intermediate in the aza-Wittig reaction.

-d T3 dCF3 +

Tip '!NPh

-/ (63)Tip =

@(

R'R2C = 0 (64a-c)

I

TiplgJ

,Ph

R1 R2

(65a-c) a, R' = Ph, R2 = H b, R' = Ph, R2 =CF3 c, R', R2 = CF3

The reaction of the P-H bond of spirophosphoranes (68) and (69) with long chain imines, (70a-h), occurs instantaneously at room temperature and leads to the formation of a-aminoalkyl spirophosphoranes (72a-h) and (73e), with a high degree of diastereoselectivity in most cases. With R2 = Ph the observed diastereoselectivity was between 80 and 90% as determined by 'H and 31P NMR but dropped to -65% for R2 = Me in (72g). The authors proposed a

a2

Organophosphorus Chemistry

+

0 (68) R‘ = Me (69) R’ = Ph

(70a-h) a, n = 10, R2 = Ph b, n = 12, R2 = Ph c, n = 14, R2 = Ph d, n = 16, R2 = Ph e, n = 18, R2 = Ph f, Me(CH2)7CH=CH(CH2)6, R2 = Ph g, n = 18, R2 = M e h, n = 18, R2 = (CH2)loMe

R’

*Io,

I *

P-CH-NH-(CH2),1Me

0 (72a-h) R’ = Me (73e) R’= Ph

mechanism involving a phosphoranide intermediate (71) as the source of the diastereoselectivity and showed that hydrolysis could lead to either (74a-h) or (75a-h) depending upon the conditions used.24

-r

0 R2

pathway A

P-CH-NH-(CH2),1CH3

H20

HO

0 (72a-h)

reflux pathway B

(74a-h)

R; ‘R’ HC1,,(20%) reflux

0 R2

I*

HO II,

/

I I

pathway C

P-CH-NH-(CH~)+ICH~

HO

(7 5a-h)

Nine chiral, tricyclic ‘triquinphosphoranes’ (77a-i), have been prepared from chiral enantiopure diamino diols (76a-i) and their 13U31P NMR data are consistent with a chiral SP structure or with a low energy. Berry pseudorotation process between the diastereomeric tbp structures, TBP (Rp) and TBP (Sp).25 Each triquinphosphorane reacted with borane to give two stable monoadducts (78a-i), with opposite configurations at the phosphorus centre which did not epimerise. The diastereomeric excess depended strongly upon the nature and position of the substituents with (78c) showing maximum selectivity at 90%. An X-ray crystallographic analysis of the major diastereomer of (78c) revealed the Sp configuration is close to an ideal tbp geometry. Semi-empirical AM1 MO calculations predicted a marked predo-

83

2: Pentacoordinated and Hexacoordinated Compounds

R3

::,:c:::I R3 Rx

8/).-R‘

R’

+ P(NMe2)3

0 - -p-N

reflux

R”~“-;,J.~~

R’

(76a-i) a, R2, R3 = H, R’ = Me b, R2, R3 = H, R1 = Et c, R2, R3 = H, R’ = Pr‘ d, R2, R3 = H, R‘ = Bu’ e, R2, R3 = H, R’ = Ph f, R2, R3 = H, R1 = Bn g, R1, R3 = H,R2 = (CH&h, R’, R3 = H, R2 = Ph i, R’, R2 = H, R3 = Ph

$

(77a-i)

IBH,SMe2

1BH3OSMe2

(78a-f) n.b. A similar set of structures may be written for (78a-i)

minance of the RP form for all the triquinphosphoranes except (77h) so the diastereomeric selectivity observed on borane addition to (77c) was rationalized in terms of a kinetically controlled process in which the minor isomer (Sp) reacted faster than the major one (Rp) to afford (78c) in the Sp configuration. Chiral, bicyclic phosphoranes incorporating a five- and an eight-membered ring have been prepared by selective P-N cleavage of triquinphosphoranes induced by dimethylzirconocene, Cp2ZrMe2 or diphenylzirconocene, For example, (79a-c) with Cp2ZrMe2gave (80a-c) and cleavage of the N-Zr bond of (80a) with acid regenerated (79a) in quantitative yield. In order to retain the open structure W(CO)5.THF was added to (8Oa) to give (8 1) which on treatment with methanol gave (82). Further studies in this area have shown that hydrophosphorane (83), as an equilibrium mixture of its Sp and R P forms, reacts with hexacarbonyl molybdenum to give (84) with a single absolute configuration (Sp) at tetrahedral p h o ~ p h o r u sX-ray . ~ ~ diffraction confirmed the structure of (84) with a virtually planar (sp2) nitrogen attached to phosphorus {PN = 1.699(3) A] and

84

Organophosphorus Chemistry

(79a-c)a, R = Et b, R = Pr' c, R = Bn

(80a-c)

.-Et H+

W(C0)sTHF

P

-5-3 P \

co,,

O I

co'

I

M";

,co

I co

PhPh

(83)TBP (Sp) 78%

Ph

(83)TBP (Rp) 22%

(84)

no transannular interaction between the second nitrogen atom and phosphorus at a P-N bond distance of 3.57 A. Diastereoselective ring opening of triquinphosphoranes (85a-d) to give enantiopure (87a-d) and (88a-d) was achieved by reaction with isocyanates, (86a-b).28 The Sp configuration at phosphorus was deduced by X-ray crystallography of the BH3 adduct of (88d) and the authors again proposed a mechanism involving equilibration of the RP and Sp forms coupled with kinetic control on reaction with isocyanate. Alkylthiylation of triquinphosphoranes has been achieved by reaction with disulfides either in the dark or under UV irradiation. Thus (89ab) on reaction with (90) in toluene gave (91ab) and in the case of (91b) the NMR data were consistent with either an enantiopure sp configuration or with diastereomeric trigonal bipyramids in fast e q ~ i l i b r i u r nThe . ~ ~ major product of the reaction of

2: Pentacoordinated and Hexacoordinated Compounds

(85a-d) a, R = Et. b, R = Pr’ c, R = Ph d,R=Bn

(85a-d)

R’NCO (86ab) a, R’ = Ph b, R =

85

d-,,

(88a-d) b, R’ =

Me

H

R,

N F N

‘‘k

‘0 ’0

//

F

(89ab) a, R = H b, R = Bn

R

A

+::,

(87a-d) a, R’ = Ph

Ph

Me

SMe

R

TBP (SP) MeSSMe (90) Toluene, RT

c

R’ TBP (Sp)

O>--R

TBP (Rp) (91ab)

I

t-butyl disulfide (92) with (89a) was the ring-opened thiophosphoramide (94) and isobutene, probably by elimination via (93). Reaction of triquinphosphorane (95) with BF3 etherate gave a mixture of two isomeric BF3 adducts (96ab), in which the hydrophosphorane structure was preserved. The products were characterised by mass spectrometry, elemental analysis, IR, multinuclear (llB, 13C, 19F, 31P) NMR and X-ray

7

I BF3

86

Organophosphorus Chemistry

photoelectron s p e c t r o s ~ o p y A . ~ ~similar study using ZnC12 gave (97) again with preservation of the hydrophosphorane structure and involving coordination of Zn2+to both the apical oxygen and apical nitrogen atoms. A comprehensive report of complexation between hydrophosphoranes and transition metal species includes (98) and (99) with [Rh(C0)2C1]2 and (100) with [Rh(C0)2C1], PdC12(COD) or PtC12(COD). All the products were characterised by laser-desorption MS, IR, multinuclear NMR and photoelectron spectroscopy.31 A correlation between Lewis basicity and coordination activity was reported for (98-loo), and (101) was shown to coordinate by means of its PI'' tautomer (102).

(98)

L=J (100)

i e

Oxidative addition of hexafluoroacetone to (103) gave (105) through elimination of methyl chloride from intermediate (104).32X-ray crystallographic analysis of (105) showed a slightly distorted tbp with one apical oxygen and the nitrogen at position 2 of the pyridine ring in the other apical position. Compounds (106a-c) also gave pentacoordinate structures (107a-c) on oxidative addition of hexafluoroacetone. Further work on the catalytic efficacy of (108) has shown that the compound is an efficient promoter for the reduction of aldehydes (92-96% yields) and most ketones (6695% yields) by poly(methy1hydrosiloxane)33 and also an efficient catalyst for the desilylation of t-butyldimethylsilyl ethers (68-94% yields).34

2: Pentacoordinated and Hexacoordinated Compounds

87

0

1+20

= WF3l2

-MeCi

*

ci (104)

61 (106a-c) a, X = N, R’ = Bn, R2 = M e b, X = N, R’ = o -CI-Bn, R2 = Me

(107 a-c)

c, X = CH, R’ = Me, R2 = Me

5

Me

Hexacoordinate Phosphorus Compounds

A hexacoordinated macro-ring structure (1 11) has been synthesised by the 2 + 2 condensation of (109) with (1 10) in THF and in the presence of diethylamine. The compound was characterized by MS, elemental analysis and multinuclear (‘H, 13C,31P)NMR.35 The nucleophilic carbene (1 12) has been shown to react with pnicogen pentafluorides (1 13a-c) to form adducts (1 14ac) with octahedral geomeotry at P (P-N = 1.898 A), As (As-N = 1.999 and Sb (Sb-N = 2.175 A). The structures are therefore those of internal zwitterions with an imidazolium cation and a pnictogen anion.36The strong nature of the bonds to the carbene

A)

88

Organophosphorus Chemistry

4-

6HNEtz

HO

Ph

Mes

Mes

Mes (1 12)

Mes (113 a-c) a, Pn = P b, Pn = As c, Pn = Bi

(1 14 a-c)

centre is evidenced by the upfield shifts of the carbene carbon (C,) from 220 ppm in the carbene (1 12) to 6 -1 60 ppm in (1 14a-c). Finally, Holmes et al. have reported the first authentic example of a heptacoordinate phosphorus compound (1 16) which is the hydrochloride salt of (1 15). The seven ligands comprise three carbon atoms, three nitrogen atoms and a proton, the P-H bond being confirmed by a J P H value of 691 Hz. X-ray crystallographic analysis of (1 16) reveals the phosphorus atom residing in .a tricapped tetrahedral geometry with P-N bond lengths averaging 2.8 13(6) A, somewhat larger than the sum of the P-N covalent radii (1.85 but The significantly shorter than the sum of the van der Waals radii (3.4 chloride ion is more than 6 away from any P-H contact.37 The X-ray crystallographic data is compared with an earlier report3' on the crystal structure of (1 15) and the comparison suggests that the earlier data belonged, in fact, to the hydrobromide salt of (1 15). In conclusion, the realm of hypervalent phosphorus chemistry is becoming ever more complicated as it expands into the chemistry of As, Sb and Bi and as the coordination of phosphoranes with Lewis Acids and transition metal elements adds another facet to the burgeoning field of asymmetric synthesis.

A

A) A).

2: Pentacoordinated and Hexacoordinated Compounds

89

References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

A. Chandrasekaran, R.O. Day, P. Sood, N.V. Timosheva, D.J. Sherlock and R.R. Holmes, Phosphorus, Sulfur, Silicon Relat. Elem., 2000,160, 1. A. Chandrasekaran, P. Sood, R.O. Day and R.R. Holmes, Inorg. Chem., 1999, 38, 3369. P. Sood, A. Chandrasekaran, R.O. Day and R.R. Holmes, Inorg. Chem., 1998, 37, 6329. P. Sood, A. Chandrasekaran, R.O. Day and R.R. Holmes, Inorg. Chem., 1998, 37,3747. D.J. Sherlock, A. Chandrasekaran, R.O. Day and R.R. Holmes, Inorg. Chem., 1997,36,5082. R.G. Cave11 and A. Jurgensen, J. Electron Spectroscopy and Related Phenomena, 1999,101-103,125. V. Plack, J.R. Goerlich, H. Thonnessen, P.G. Jones and R. Schmutzler, 2. Anorg. Allg. Chem., 1999,625, 1278. V.V. Sharutin, O K . Sharutina, V.S. Senchurin, T.A. Kovaleva, V.I. Shcherbakov and E.N. Gladyshev. Russ. J. Gen. Chem., 2000,70(1), 64. V.V. Sharutin, O K . Sharutina, O.P. Zadachina, V.S. Senchurin, E.V. Gukhman, V.A. Reutov and N.P. Shapkin, Russ. J. Gen. Chem., 2000,70(5), 696. V.V. Sharutin, O.K. Sharutina, P.E. Osipov, E.B. Vorob’eva, D.V. Muslin and V.K. Bel’skii, Russ. J. Gen. Chem., 2000, 70(6), 867. V.V. Sharutin, O K . Sharutina, I.V. Egorova, V.S. Senchurin,, LA. Ivashchik and V.K. Bel’skii, Russ. J. Gen. Chem., 2000,70(6), 873. V.F. Mironov, I.A. Litvinov, A.A. Shtyrlina, F.F. Alekseev, T.A. Gubaidullin and A.I. Konovalov, Russ. J. Gen. Chem., 2000,70(4), 648. V.F. Mironov, M.G. Khusainova, G.R. Reshetkova, T.A. Zyablikova and R.A. Cherkasov, Russ. J. Gen. Chem., 2000,70(6), 984. V.G. Ratner, E. Lork, K.I. Pashkevich and G.-V. Roschenthaler, J. Fluorine Chem., 2000,102,73. R.K. Harris and L.A. Crowe, J. Chem. SOC.,Dalton Trans., 1999,4315. E. Vedejs and P.L. Steck, Angew. Chem. Int. Ed., 1999,38(18),2788. B.M. Anand, R. Bains and P. Venugopalan, Indian J. Chem., 1999,38A, 874. J. Hernandez-Diaz, R. Contreras and B. Wrackmeyer, Heteroatom Chemistry, 2000, 11(1), 11. D. Houalla, L. Moureau and C. Vidal, Phosphorus, Sulfur, Silicon, Relat. Elem., 2000,156, 8 1. D. Houalla, L. Moureau and C. Vidal, Phosphorus, Sulfur, Silicon, Relat. Elern., 1997, 123, 359. D. Houalla and L. Moureau, Phosphorus, Sulfur, Silicon, Relat. Elem., 1996, 114, 51. A.I. Polosukhin, A. Yu Kovalevsky, A.V. Korostylev, V.A. Davankov and K.N. Gavrilov, Phosphorus, Sulfur, Silicon, Relat. Elem., 2000, 159, 69. N. Kano, X. Jia Hua, S. Kawa and T. Kawashima, Tetrahedron Lett., 2000, 41, 5237. K. Vercruysse, C. Dkjugnat, A. Munoz and G. Etemad-Moghadam, Eur. J. Org. Chem., 2000,281. C. Marchi, F. Fotiadu and G. Buono, Organometallics, 1999, 18 ( 5 ) 916. C. Marchi, A. Igau, J.P. Majoral and G. Buono, J. Organomet. Chem., 2000,599, 304.

90

Organophosphorus Chemistry

27 28

C. Marchi and G. Buono, Inorg. Chem., 2000,39,2951. Chem. C. Marchi, G. Delapierre, F. Fotiadu and G. Buono, J. Chem. SOC., Comm., 2000,2227. C. Marchi and G. Buono, Tetrahedron Lett., 2000,41, 3073. K.N. Gavrilov, A.V. Korostylev, P.V. Petrovskiy, A. Yu. Kovalevsky and V.A. Davankov, Phosphorus, Sulfur, Silicon, Relat. Elem., 1999,155, 15. K.N. Gavrilov, A.V. Korostylev, A.E. Polosukhin, O.G. Bondarev, A. Yu. Kovalevsky and V.A. Davankov, J. Organomet. Chem., 2000,613,148. R. Sonnenburg, I. Neda, H. Thonnessen, P.G. Jones and R. Schmutzler, 2. Anorg. Allg. Chem., 2000,626,412. Z. Wang, A.E. Wroblewski and J.G. Verkade, J. Org. Chem., 1999,64,8021. Z. Yu and J.G. Verkade, J. Org. Chem., 2000,65,2065. S. Richelme, C. Claparols, E. Leroy, A.-M. Caminade and A. Munoz, Phosphorus, Sulfur, Silicon, Relat. Elem., 2000, 161, 143. A.J. Arduengo 111, F. Davidson, R. Krafczyk, W.J. Marshall and R. Schmutzler, Monatscheftefur Chemie, 2000, 131,251. A. Chandrasekaran, N.V. Timosheva, R.O. Day and R.R. Holmes, Inorg. Chem., 2000,39,1338. C. Chuit, R.J.P. Corriu, P. Monforte, C. Reye, J.-P. Declercq and A. Dubourg, Angew. Chem. Int. Ed. Engl., 1993,32, 1430.

29 30 31 32 33 34 35 36 37 38

3

Tervalent Phosphorus Acid Derivatives ~~

~~

BY D. W. ALLEN

1

Introduction

As this area was not covered in Volume 31, the present chapter provides an overview of the literature published over the two years between July 1998 and June 2000. The report is structured in terms of the principal classes of tervalent phosphorus acid derivatives, viz halogenophosphines, tervalent phosphorus esters, and amides. Attempts have been made to minimise the extent of overlap with other chapters, in particular those concerned with the synthesis of nucleic acids and nucleotides to which the chemistry of tervalent phosphorus esters and amides contributes significantly (see Chapter 4), the use of known halogenophosphines as reagents for the synthesis of phosphines (see Chapter l), and the reactions of dialkyl- and diaryl-phosphite esters, in which the contribution of the phosphonate tautomer, (R0)2P(0)H, is the dominant aspect. 2

Halogenophosphines

An improved route to ortho-substituted aryldichlorophosphinesis provided by the reactions of organozinc halides with phosphorus trichloride, and this has been applied to the synthesis of the new aryldichlorophosphine,2-thioanisyldichlorophosphine (1, X = S), and its 2-anisyl analogue (1, X = 0),both of which have found use for the preparation of a family of multidenate 0substituted triarylphosphine ligands. The pr opargyldibromophosphine (2) has been obtained in 73% yield from the reaction of allenyltributylstannane with phosphorus tribromide. Surprisingly, the related reaction of propargyltriphenylstannane gave the allenyldibromophosphine (3) but in only 23% yield. It would seem that the propargylic system (2) rearranges to the thermodynamically more stable allenyl system (3).2 A route to phenyl(viny1)chlorophosphines MeX

(2)

(1) X = S or 0

Organophosphorus Chemistry, Volume 32 0The Royal Society of Chemistry, 2002 91

(3)

92

Organophosphorus Chemistry

is provided by the reaction of the transient terminal phosphinidene complex [PhP-W(CO)5] with chloroalkenes, involving insertion of the phosphorus unit into the C-Cl bond with retention of alkene stereochemistry to form intermediate phosphiranes, e.g. (4), which then rearrange to form the complexed chlorophosphines (5).3 The surprisingly stable tritylchlorophosphine (6) has been obtained from the reaction of tritylphosphine, Ph3C-PH2, with phosgene, and can be converted into the related fluoro- and bromo-phosphines. Corresponding reactions of the secondary phosphines Ph$(R)PH (R = Ph or But) with phosgene gave the secondary chlorophosphines (7), although in the case

of (7, R = But), the product was contaminated with t-butyldichlorophosphine, arising from cleavage of the trityl-phosphorus bond.4 The reactions of (6) (and the related fluorophosphine) with tetrachloro-ortho-benzoquinonehave also been studied, and shown to lead to a variety of product^.^ Interest in the synthesis of halogenophosphines by the direct C-halogenophosphination of reactive heterocyclic systems has continued. Phosphorus trihalides react with 2,5-dimethyl-N-arylpyrroles in the presence of a base to form the dihalogenophosphines (8), and the monobromophosphines (9), from which numerous

Q R

(8) R = Me or Br

X = CI or Br

Q R

(9) R = Me or Br

derivatives have been prepared by established procedures.6 In related work, this approach has been applied to a series of bis(pyrroly1) systems, leading to the formation of heterocyclic halogenophosphines, e.g. (I 0),7,8 and extended further in the synthesis of other heterocyclic nitrogen-phosphorus systems and heteroaryl-halogenophosphines, e.g. (1 1)9 and (12).lo N-Ethylcarbazole has also been shown to undergo electrophilic halophosphination by phosphorus tribromide to give the dibromophosphine (13), but under more forcing conditions than for pyrrole and indole systems.l1 Direct halogenophosphination of 5-substituted- 2-furaldehyde dimethylhydrazones and 2-phenyl-l,3,4oxadiazole has also been reported, yielding the dihalogenophosphines (14) l2?l3

93

3: Tervalent Phosphorus Acid Derivatives Me Me

Me

Br

Me

(10) Ar

= ptolyl

Me

Br

Me

(11) Ar = plC6H4

Et

(14) X = CI or Br R = Et2N or Me

and (15), l4 respectively. An improved route to the dichlorophosphino-diazaphosphole (16) has also been developed, enabling the synthesis of a wide range of phosphino-substituted diazaphosphole systems. A number of 'non-routine' reactions of halogenophosphines are worthy of note. The first aliphatic phosphenium cation featuring a phosphorus-sulfur bond (17) has been obtained by treatment of the chlorophosphine (18) with aluminium trichloride in dichloromethane solution. l 6 A new synthesis of acyclic chiral t-phosphines has been developed which employs selective, sequential alkylation of the chloro(amino) phosphines (19) by Grignard and organolithium reagents. The key intermediates (19) are readily prepared by the MeS,, /P: Me2N (17)

MeS, /P-CI Me2N (18 )

,NMePh R-P, CI (19) R = Ph or Et

reaction of organodichlorophosphines with LiNMePh, and have been shown to undergo selective reaction at the P-C1 bond with Grignard reagents, forming aminophosphines in good yield. Treatment of the latter with organolithium reagents results in cleavage of the P-N bond, with formation of the unsymmetrical t-phosphines.l 7 The chemistry of pyridinium- and phosphonium-ylides bearing chlorophosphino-substituentsat the ylidic carbon has seen further development. Reduction of the ylide (20) has given the cyclic system (21). The reactions of ylidyl chlorophosphines with trimethylsilylphosphines, and various bis(phosphine) systems have also been investigated, yielding new

'*

94

Organophosphorus Chemistry P\h

/Ph

Ph~P==(~-~bPl’h3 P-P / \ Ph Ph (22) R’ = Me or Et R2 = Ph or Ph2P R3 = Ph, SiMe3 or CH2PPh2

ylidyl di-and tri-phosphines, e.g. (22).l 9 N-Pyridinium dichlorophosphinomethylides (23) have now been shown to disproportionate to form a bis(pyridiniumylidy1)phosphenium chloride which undergoes a 1,5-electrocyclisation to form the 2-phosphaindolizine system (24), enabling a one-pot synthesis of 2phosphaindolizines from N-(alkoxycarbonylmethy1)pyridinium bromide, on treatment with phosphorus trichloride in the presence of triethylamine.20A route to unsymmetrical bis(diphosphin0)methanes is provided by the reactions of the stannylated phosphines (25) with a diorganochlorophosphine in the R2

R2

R3

R2PCH2SnPh3

@R4 R’-d-

I

PClp (23) R’ = C02Me R2, R3, R4 = H or Me

R <\’

P

)-R’

(24)

absence of a solvent, via elimination of chlorotriphenylstannane.21The reactions of halogenophosphines with hetero- 1,3-dienes, which often result in the formation of heterocyclic phosphorus compounds, have been reviewed.22 Protonation of the metal diphenylphosphide formed by the reaction of chlorodiphenylphosphine with a range of metals, e.g. magnesium, aluminium, zinc, tin and some transition metals, e.g. manganese, provides a satisfactory route to diphenylphosphine. Dicyclohexyl- and di-t-butyl-phosphine can also be prepared in this way from the corresponding dialkylchlorophosphines. 23

3

Tervalent Phosphorus Esters

3.1 Phosphinites. - Most of the interest in this area has centred around the synthesis of new ligand systems for use in homogeneous catalysis, in which phosphinite donor centres either replace or complement conventional phosphino donor groups in previously designed systems, many of which are chiral. In most cases, the phosphinite centre is introduced via the reaction of an alcohol or phenol with a chlorophosphorus(II1) precursor, in the presence of a base. A useful review of the application of borane-protected trivalent

3: Tervalent Phosphorus Acid Derivatives

95

organophosphorus compounds in ligand synthesis contains much that is relevant to the synthesis of phosphinite l i g a n d ~A . ~series ~ of mixed alkyl- or aryl-phosphinite compounds (26) has been prepared from the perfluorinated alcohol and the appropriate diorganochlorophosphine in the presence of base. A bidentate phosphonito analogue (27) was prepared in a similar

manner from 1,2-bis(dichlorophosphino)ethane.Infrared and solution calorimetry studies of a series of rhodium(1) (ch1oro)carbonyl complexes of these fluoroalkylphosphorus(II1) esters have enabled comparisons of their donor strength to be made.25 The same synthetic approach has been used for the preparation of the a,o-bis(phosphinite) (28),26 and phosphinite systems derived from cycl~dextrins~~ and ~alix[4]arenes.~* An unusual approach to a chiral bicyclic phosphinite is provided by base-promoted addition of alcohols to the P=C bond of the bicyclic phospha-alkene (29), giving the esters (30), as a mixture of diastereois~mers.~~ The hydrogenation of acetoacetanilide in the presence of a chiral ruthenium catalyst yields 3-hydroxy-N-phenylbutanamide, which can then be phosphinylated with chlorodiphenylphosphine to form the chiral, amido-phosphinite ligand (31).30A series of chiral phosphinite-imino-nitrogen donor ligands (32) has been prepared from D-glucosa-

H (311

I R

(32) R = Me, P i , But, Bunor Ph

mine, and used to promote homogeneous catalytic asymmetric arylation of alkenes and allylic substitution reaction^.^ 1-33 The reaction of chiral diols with chloroorganophosphines in the presence of base has provided a series of chiral diphosphinites, again of interest as ligands in homogeneous catalyst systems. Included in this category are the diphosphinites (33),34 (34)35 and (35)36 and more complex systems derived from carbohydrates, e.g. (36),36

96

Organophosphorus Chemistry

(34) R = Et, Cy, Ph or Mes

p Ar2P0 h a

A r 2 P O q 0PAr2

6

I PhpP

O

p

h

OPAr2

'0 I PPh2 (37)

~

\O*Ph (38)

(39) R = Ph, Cp or Cy

(37),37(38),38 and (39).39There has also been much interest in the synthesis of phosphinites, and related aminophosphine-phosphinite systems derived from P-aminoalcohols, and similar compounds. A review of the synthesis and coordination chemistry of these compounds has a~peared.~' Chiral phosphinites, e.g. (40):l and also aminophosphine-phosphinites, e.g. (41),42943have been prepared from (R,S)-ephidrine. Among other related compounds preparedM7 are (42),45 and (43), derived from the chiral p-blocker Propra-

(40)

(41) R', R2 = alkyl or aryl

Also described are the N-phosphinoamide phosphinites (44),48 chiral aminophosphine-carboxyphosphinites (45),49 and the bicyclic system (46) derived from a chiral y-aminoalcohol.50Phosphinite esters derived from the heavier chalcogens have also attracted attention. The reaction of the diphosphine (47) with the dichalcogens RX-XR (X = S, Se or Te), provides a route to the esters (48).51

97

3: Tervalent Phosphorus Acid Derivatives

\/

(44) R = Ph, Cy, 2-fury1or 3,5-Me2C6H4, R2P = 5H-dibenzophospholyl ( 3c)2p(47)

(cF3)2

(45)

(CF&P-XR (48) X = S, Se or Te

3.2 Phosphonites. - As for the above phosphinite esters, the main area of activity in phosphonite ester chemistry has been the synthesis of new chiral ligand systems, which often involve other types of trivalent phosphorus donor. have described routes to the o-diphenylphosphinoaryldichloroTwo phosphine (49) which has then been used to prepare a range of new chiral systems, including the phosphinoarylphosphonites (50)-(52), and the ephidrine-based phosphinoarylphosphonamidite (53). A similar strategy has been

(51) R = Me02C or Ph

based on the phosphinoferrocenyldichlorophosphine (54), which has been converted into phosphonito derivatives, e.g. (59, via its reactions with phenol, binaphthol and ethanedi01,~~ and also on the bis(dich1orophosphino)ferrocene (56) from which the bis(phosphonite) (57) has been prepared.55 The chiral diphosphonites (58)55>56 and (59)56have been prepared, and their abilities as ligands in asymmetric hydrogenation catalysis compared with that of the related chiral monophosphonites, e.g. (60). Surprisingly, in this context, the latter are superior to the former in promoting higher e e ~A. route ~ ~ to the 0dichlorophosphinoaryl phosphorodichloridite (61) has been developed, which has enabled the synthesis of the chiral phosphonite-phosphite system (62).57

98

Organophosphorus Chemistry

gpL

\

\

\

-R

/

\

2

(58)

o

(59)

(60) R = Me, Ph or But

Other chiral monophosphonito-systems, e.g. (63) have also been prepared, and their role in catalysis explored.58The vinylphosphonite (64) has been shown to suffer cleavage of the phosphorus-carbon bond in protic solvent systems containing potassium ~ a r b o n a t e . ~ ~

@-@ a'"''

0-P

\

0

OR'

0-PC12

& p ' 0O- P / o p

Br-CH=C-P,

Ph I

,OEt

OEt

(63)R' = H or Me R2 = Me0 or But

3: Tervalent Phosphorus Acid Derivatives

99

3.3 Phosphites. - Di(hydroxyary1)phosphites are formed together with other products on bubbling phosphine-argon mixtures into a dioxan solution of 1,4benzoquinone, which also contains mercuric chloride. In aqueous solution, only the diarylphosphite is formed.60Dialkyl phosphites are formed, together with trialkylphosphates, in the transition metal-catalysed oxidation of white phosphorus in toluene-alcohol solutions.61 The phosphoramidite route to phosphites has been used to prepare phospholipid analogues, e.g. (65), possessing biocompatible properties. Modifications to established methodology include the use of 4,5-dichloroimidazole as an alternative acid catalyst, instead of the thermally unstable tetrazole, and also the use of trimethylamine-N-oxide for the conversion of phosphite esters into the corresponding phosphates.62A series of allylic polyprenyl phosphites has been prepared by the tetrazolepromoted phosphoramidite route.63 The reactions of chlorophosphites with alcohols have been used in the preparation of a glucopyranoside-derived phosphitea (66), which functions as an efficient glycosyl unit donor for the synthesis of di~accharides,~~ the bisindolizinyl system (67)66and various chiral diphosphites, e.g. (68), derived from a series of diphenols and diols. Surprisingly, compound (68) displays a degree of chiral self-recognition, which is not

observed in other members of the series.67 This route has also been used extensively for the synthesis of new chiral ligands involving phosphito-centres (and often other donors) of interest in homogeneous catalyst systems. Among new chiral ligands noted are a series of phosphite-oxazolines,6876g e.g. (69),69 cyclic phosphites (70) derived from ( - )-TADDOL (easily accessible from tartaric acid),70 bulky phosphites derived from ribo- and xylo-furanose, e.g. (71),71972the codeine-phosphite (72),73the diphosphites (73),74 and the phosphino-phosphites (74).75 Routes to a range of triaryl phosphites, e.g. (75),

100

Organophosphorus Chemistry R2

R1%R2

P-OR

7-O (69) R = H, Me, Ph, Mes, 4-biphenylyl or 3,5-But2C6H3

R’

(70) R = e.g. OMe, OCy, OBu‘ OMenthyl or OPh

R2 (71) R1 = R2 = H R’ = Bu‘, R2 = OMe R’ = R2 = But

(RO)2P-0

Bu‘

(73) (R0)2P = e.g.

But R’\ p - . A o - p Ph’

J+oBut ‘

Bu‘

(74) R1 = Ph, o-An, I-Naphthyl

R2 = Me or Ph

bearing perfluoroalkyl substituents, have been developed. Such ligands aid the formation of fluorocarbon-soluble complexes for use in ~ a t a l y s i s . ~In~ ’ ~ ~ related work, the fluoroalkyl-functionalised phosphino-phosphite (76) forms catalytically-active rhodium complexes that are soluble in supercritical carbon dioxide.78Holmes et al. have reported the synthesis of a series of new cyclic phosphites containing pentafluorophenoxy or salicylate groups, e.g. (77) and (78). Structural studies on a number of the pentafluorophenoxy compounds reveal significant intramolecular coordination from sulfur or oxygen to phosphorus within the eight-membered ring when X = S or SO2, the geometry

3: Tervalent Phosphorus Acid Derivatives

101

R f d : ] : (75) Rf = C8FI7 or C7HI5CO

(76) A r =

‘I

O

F

I

D/ F F F

(77) X = CH2, S or SO2

(78) X = CH2, S or So2

R = Me or Bu‘

R = Me or But

about phosphorus approaching that of a quasi-trigonal bipyramid having an equatorial lone pair. These interactions are even more evident in pentaaryloxyphosphoranes derived from the phosphites, the geometry at phosphorus becoming essentially ~ctahedral.~”’~ Holmes has argued that such hypervalent interactions may be of relevance in biological systems, possibly assisting in nucleophilic attack at phosphorus in causing a general weakening of P-0 bonds undergoing cleavage to form products via a hexacoordinate transition state. Previously, only pentacoordinate intermediates have been invoked in nucleophilic displacement reactions of phosphoryl transfer enzyme^.'^ Routes to calix[4] arene-based monophosphites (79),84-86and the calix[6]arene-derived diphosphite (80)87 have been developed, and their coordination chemistry explored. Similar macrocyclic phosphito-systems derived from calix[4]resorcinarenes*’ and other polyphenolic substratess9 have also been described. A series of chiral dialkyl phosphites based on (-)-menthol and (-)-nopol have been prepared, and used as carriers for the transport of aromatic aminoacids through supported liquid membranes.” Treatment of trialkyl phosphites with dimethyl acetylenedicarboxylate in toluene at 80 “C in the presence of the fullerene, c 6 0 , results in the formation of the stabilised phosphite-ylides (8 l), involving a cyclopropane ring on the fullerene unit. These ylides readily undergo hydrolysis with hydrobromic acid to give the phosphonates (82) in good yield.” Protonation of the initial adducts of trimethyl phosphite and dialkyl acetylenedicarboxylates by indane1,3-dione leads to the formation of vinyltrimethoxyphosphonium cations,

Organophosphorus Chemistry

102 R'

(79) R' = H or But R2 = alkyl, COMe or COPh

R

R

R

R (80) R = But

which then add the enolate anion of the dione to give functionalised phosphonates (83).92 Nucleophilic attack at the carbonyl carbon is the likely initial step in the conversion of the tetrabenzoylthiopyran-4-chalcogenones(84)into the bisannelated furans (85) on treatment with triethyl p h ~ s p h i t e Michael-type .~~ addition of trimethyl phosphite to (E)-l,l,1-trifluoro-4-phenyl-but-2-en-4-one

@

C02Me Me

'

\ /

\

I +P(W3

(81) R = Me, Et or Bun

II

C02R M e 0 I

(Me0)2P-CH-CH

\

I

R02C

0 (83) R = Me, Et or But

'

(82)

O P

h

Ph

X x

0 P

S 0

h P(OEt)3, 80°C, Ih, Ph

0 (84)

:%i Ph

X=OorS

(85)

leads to the formation of the oxaphospholene (86) as the sole product, which, upon hydrolysis, is converted to the y-ketophosphonate (87).94 Irradiation of cyclic enones in the presence of dialkyl(trimethylsily1) phosphites results in an SET process in which the triplet enone initially accepts an electron from the phosphite, leading eventually to cycloalkylphosphonates, e.g. (88).95 Trimethyl 0

3: Tervalent Phosphorus Acid Derivatives

103

phosphite has been shown to act as a co-initiator of the ring-opening iodonium-induced cationic photopolymerisation of cyclohexene oxide.96 Trialkyl phosphites have been widely employed in promoting the formation of C=C dimers from 1,3-dithio1-2-ones(and the related dithiol-thiones), presumably via initial attack at the carbonyl- or thiocarbonyl-group, with eventual elimination of the trialkyl-phosphate or -thi~phosphate.~~-"~ Thus, e.g. heating the dithiol-one (89) in the presence of trimethyl phosphite gives the bis(ethy1enethio)tetrathiafulvalene (90), a useful n-electron donor system.98 The diferrocenyl system (9 1) has been prepared similarly.99Related phosphite-

QSXSfl s s promoted homo-coupling reactions between dithiol-thiones have been used to give the symmetrical tetrathiafulvalenes (92)'" and (93). lo' Unsymmetrical systems, e.g. (94) have also been prepared by coupling of a dithiol-one with a dithiol-thione bearing different substituents.lo2 Unexpectedly, treatment of the dithiol-thione (95) with triethyl phosphite resulted in the formation of (96), rather than a homo-coupled product. lo3 The Michaelis-Arbuzov reaction continues to be widely employed in synth-

Cl (92) X = 0 or S

S

RXs)+sXsx R

S

'

S

S

H

X

(93)

4%) Et

Et

#

\

(94) R = SMe X = CH2CH2CN or CH2C6H40Ac-p

H s

Me

(95)

s

Me

104

Organophosphorus Chemistry

esis. The bromoethyl phosphonate (97, X = Br) has been prepared in a conventional reaction between 1,2-dibromoethane and triethyl phosphite, and converted into the related 1-thioethyl derivative (97, X = SEt), of interest for the fire-proofing of polyurethanes. The reactions of trimethylsilyl-protected 11-bromoundecanol with triethyl phosphite has given the phosphonate (98), used as an intermediate in the synthesis of a suicide inhibitor for the directed molecular evolution of lipolytic enzymes.lo5 The reaction of 1-iodoalkylboronates with trimethyl phosphite proceeds smoothly to give the phosphonoboronates (99). The absence of alkene formation is attributed to prior 0 11

XCH*CH2P\'

OEt

OEt

(97)

(98)

(99) R = H, C3H7, CSHq1,C6HI3, PhCH2 or But

complexation of the phosphite with the boron centre, as observed by "B NMR. lo6 The complexation of trialkyl phosphite esters by trivalent boron acceptors has also been studied independently.lo7 Michaelis-Arbuzov procedures have also been used to prepare polymer-bound phosphonate ester and related phosphonic acid systems.lo8,lo9 The reaction of 3-( 1-bromobenzyl)coumarin with trialkyl phosphites has given the phosphonates (100). The best yields of the esters (100, R = Me or Et) were obtained by conducting the reactions in toluene under reflux rather than in the presence of the neat phosphite. Not surprisingly, when triphenyl phosphite was used as the solvent, no phosphonate was formed. However, when the reaction with triphenyl phosphite was conducted under reflux in xylene, the phosphonate (100, R = Ph) was obtained in 22% yield. This compound was subsequently isolated in 65% yield when the reaction was carried out in the absence of solvent but under reduced pressure. The related reactions of 3-(o-bromoacetyl)coumarin with phosphite triesters also provided some surprises. The reactions with trimethyl and triethyl phosphite gave only the Perkow vinylphosphate products (lOl), whereas with triphenyl phosphite in refluxing toluene or xylene, the Michaelis-Arbuzov product (102) was isolated in 4 6 6 5 % yield.' l o Another group has reported the unconventional formation of phosphonato derivatives of coumarin by treatment of 3-acetylcoumarin with trialkyl phosphites, the CH-P< Ph I 0 II OR

a O - ! ( OCH2 R ) 2

0 II ~ c o c H 2 p ~ o p h ~ z 0

(100) R = Me or Et

(101) R = Me or Et

(102)

3: Tervalent Phosphorus Acid Derivatives

105

reactions proceeding via initial Michael addition of the phosphite to the apunsaturated ketone to give the betaine (103), which subsequently undergoes intramolecular dealkylation to give the phosphonates (104).l1 The reaction of 1-bromo- 1-nitroalkanes with trialkyl phosphites has been revisited, and a procedure developed which leads directly to the formation of (1-hydroxyiminoalky1)phosphonates (105). l2 Treatment of P-phthalimido acid chlorides

'

RO,

RO I ,OR

RO

P=O OR

&Me

/

m /

0

OR

\ /

0M

0

0 =P ( 0R2)*

e

RIAN-oH

0 (104) R = Me, Et or Pr'

(105) R' = Me, Et, P i or BU R2 = Me or Et

with triethyl phosphite has given the crude phosphonates (106),"371l4 which have been subsequently reduced to give the P-phthalimido-a-hydroxyalkylphosphonates (107), as two diastereoisomers. l4 The butenolide (108) has been shown to react sequentially with triethyl phosphite to give the fluorovinylphosphonate (109) as the initial product, followed by displacement of fluorine to give the diphosphonate (1 lo)."' Phosphite displacement of carbon-fluorine

bonds has also been reported in the reactions of perfluoroalkenes and perfluoroalkylketones with trimethylsilyl phosphites, with the formation of phosphonate derivative^."^" l 7 A study of the reactions of mucochloric acid with trialkyl phosphites has provided a new method for the synthesis of phosphorylated furanones. Michaelis-Arbuzov procedures involving the initial displacement of groups other than halide ions have also been reported. Routes involving displacement of acetate (in the synthesis of thiazolylketosephosphonates, e.g. (1 1I)' 19), and mesylate (in the synthesis of phosphonic acid derivatives of anti-inflammatory drugs, e.g. (1 12),120 and carboranylphosphonates12'), have been described. Displacement of benzotriazolyl anion is the key step in the synthesis of the phosphonate( 11 3),122 and the reactions of phosphite esters with phenolic Mannich base methiodides have been used to prepare the azoarylphenolic phosphonates (1 14).123 Photo-Arbuzov rearrangements of phosphite esters have also been studied. Ultraviolet irradiation of dimethyl(benzyl) phosphite yields the phosphonate (1 15) as the predominant photoArbuzov product, whereas irradiation of dimethyl@-acetylbenzyl)phosphite yields the photo-Arbuzov product (1 16) as only a minor product, the course of

'

106

Organophosphorus Chemistry P(O)(OMe)2

I

UNH

c'-b"'

) -Q O BnO ""

R'

0 (114)R'=HorMe R2 Et, Pr' or Bu X = H, Me, CI, NO2 or OMe

the reaction being dominated by the formation of radical diffusion products including dimethyl phosphite, p-acetyltoluene, and the p-acetylbenzyl radical dimer.'24 The stereochemistry at the migratory benzylic carbon has been studied in the conversion of the phosphite (1 17) to the phosphonate (118), which proceeds with predominant retention of c~nfiguration.'~~ The SETPh

I

induced photo-conversion of the cyclic phosphite (119) to the phosphonate (120) has been shown to proceed with complete retention of configuration of phosphorus. 126 The transition metal-catalysed reaction of trialkyl phosphites with aryl halides (the Tavs reaction) has found further application. Treatment

of carboxylic amides of o-bromoaniline with triethyl phosphite in the presence of nickel(I1) chloride results in a smooth conversion to the acylamidophosphonates (121), which have been shown to undergo subsequent reductive cyclisation on treatment with lithium aluminium hydride to give the 1,3-

107

3: Tervalent Phosphorus Acid Derivatives 0

(121) R = Me,But or Ph

(122)

benzazaphospholes (122). The Tavs reactions fails with the free o-bromoaniline, 127 which also fails to undergo palladium(0)-promoted phosphonation with diethyl phosphite. However, phosphonation can be achieved under basepromoted photochemical conditions, giving a general route to unprotected aminoarylphosphonates. 28 Reactions of phosphites at centres other than carbon have also been reported. Treatment of the azide (123) with triethyl phosphite in toluene initially yields the Staudinger product (124), which undergoes an unexpected ethyl migration to form the amidophosphate (125). This reaction can be

F

SAC

Yt

FO"

N=P,

F,OEt

SAC

SAC

suppressed on addition of aqueous acid, which ultimately yields the amine hydrolysis product from the phosphazene (124). 29 Attack of phosphorus at nitrogen is also involved in the reaction of the naphthoquinone imide (126) with trimethyl phosphite, which proceeds via the zwitterion (127) to form the oxazole (128) as the sole product.13' The reactions of trialkyl phosphites with 0

/

/

2-thioxo-4-thiazolidinones have also been studied.13' A further report of the formation of pentacovalent oxyphosphoranes from the reactions of cyclic phosphites with diketones, and with related diol/N-chlorodiisopropylamine systems, has appeared. 132 Phosphites continue to find application for deoxygenation reactions. Recent examples include the reduction of sulfonyl chlorides under solid state conditions, supported on silica gel, leading to the formation

108

Organophosphorus Chemistry

of chiral sulfinite esters,133 and the reduction of heterocycli~-N-oxides.~~~~~~~ The interaction between trialkyl phosphites and the aminoxyl radical 2,2,6,6,tetramethylpiperidine-1-oxyl (TEMPO) has been studied to shed light on antagonistic effects attending their joint use in polymer stabilisation. Main products from TEMPO and triethyl or triisopropyl phosphite in decane at 150°C are the salts (129), and dialkylphosphate, arising from the initial formation of the phosphoranyl species (130).136 The hydroperoxide-decomposing ability and hydrolytic stability of phosphite esters containing hindered amine moieties, e.g. (131), have also been investigated in connection with their

(129)R = Et or Pr'

(130)

role in polymer stabilisation.137 The ozone-triphenyl phosphite system has been re-examined, with particular reference to the origin of triphenyl phosphate at low temperatures. 13* Dimethyldioxirane has been used as a reagent for the mild oxidation of cytidine-sialic acid phosphite derivatives.139 The reactions of various trialkyl phosphites bearing benzylic substituents with tbutyl hypochlorite have been investigated with particular reference to the mechanism of decomposition of the initially formed phosphonium chloride intermediate (132) to give phosphates, isobutene, alkyl chlorides and benzylic chlorides.140 The thiophilic properties of trialkyl phosphites have been utilised in an intramolecular macrocyclisation of 5-methylthio-1,2-dithiol-3-ones with triethyl phosphite, forming various thioxodesaurine systems e.g. (133).14' The reaction of selenothioic acid S-esters (134) with trialkyl phosphites proceeds smoothly with the extrusion of selenium atoms to afford a-phosphoryl sulfides (135) in good yield.1429143 Alkaneselenyl halides have been shown to react with

c""? n

(133)

/R

R

.SR

S-BU

(134)R = alkyl

dialkyl phosphites to give the corresponding 0,O-diethylselenoalkyl selenophosphates (136). 144 A combination of dimethyl phosphite and triethylamine provides a reagent system that selectively reduces 1,l-dibromoalkenes to the corresponding vinyl bromides.145 Combination of dialkyl phosphite with carbon tetrachloride gives a reagent system useful for the preparation of esters and amides from carboxylic acids.146 The halophilic reactivity of triethyl

109

3: Tervalent Phosphorus Acid Derivatives

phosphite towards carbon tetrachloride and diethyl trichloromethylphosphonates has been ~ 0 m p a r e d . lThe ~ ~ reactions of tertiary aryl phosphites with diiodine have been studied under ambient temperature conditions, tetraiodine adducts (137) being isolated regardless of stoichiometry used. Solid state structures show a dependence on the nature of the aryl

#-

Nucleotide-based phosphite methodology has been adapted in a new approach to the synthesis of stereospecific sphingomyelin.14' Various groups have reported the use of sugar phosphite esters as intermediates for the formation of glycoside linkages.1 5 ~ 1 5 3Improved routes to a-aminophosphonates have been described involving the use of phosphite triesters as effective in situ sources of secondary phosphites, which formally undergo addition to C=N bonds.154-157 Related addition to C=C bonds have also been described.15* Phosphite triesters have been shown to act as ligands for the efficient catalysis of Heck reactions. '51 Arylphosphite esters have been shown to undergo orthopalladation, 160-162 the complexes behaving as highly active catalysts in biaryl coupling161and Heck reactions.162 The fate of tris-(2,4-di-t-butylpheny1)phosphite (138) in the environment has been studied, using a 14C-labelled compound.163 Combination of triethyl phosphite with p-dimethylaminopyridine provides a reagent system for the direct synthesis of amides from carboxylic acids and amines.164 Trialkyl phosphites have been shown to convert 4-hydroxycoumarin into the related 0-alkyl ethers.165 Studies of the reactions of phosphite triesters with phosphinyl chlorides have also been reported.166 4

Tervalent Phosphorus Amides

4.1 Aminophosphines. - The bis(N-pyrrolidiny1)phosphines ( 139), prepared conventionally by treatment of the appropriate organodichlorophosphine with an excess of pyrrolidine, have proved to be unusually electron-rich o-donor ligands when compared to either tris(N-pyrrolidinyl)phosphine, or trialkyland triaryl-phosphines.167 Full details of a route to the polycylic aminophosphirane systems (140) have now appeared. 168 The bis(aminophosphine) (141) has been prepared and used in the synthesis of macrocyclic metal c o m p l e x e ~ . ' ~ ~ Two new chiral aminophosphine systems (142) and (143) have been prepared by transamidation of related aryl bis(dimethy1amino)phosphines with a chiral amine.17' The chiral aminophosphine (144) has been obtained from the reaction of chlorodiphenylphosphine with the methyl ester of alanine.17' A range of ether-functionalised aminophosphines (145) has also been prepared,

110

Organophosphorus Chemistry

R- P ,

3

PhpPHN

(139) R = Me, Bu'

NHPPhp

or Ph

(142) R

= Me or PhCH2

(143)

0 II

Me0-C -CH-NHPPh2

Ph p PNHR

I

Me (145)

(144)

R = CH2CH20Me, CH2CH(OMe)2, CH2CH2CH20Me, or o-MeOC6H4

and their coordination chemistry with palladium(I1) and platinum(I1) described.172Treatment of the heterocyclic bisamino chlorophosphine (146) with a lithiated (trimethylsily1)diazomethane reagent affords the diazomethylphosphine carbene precursor (147), which is converted into the new phosphino-

+

+ N

Me2Si< ;P-Cl

(146)

+ N

-c

Mepsi< lP-C-SiMe3 II

(147)

N2

+

+

N Mepsi< ;P-$

,SiMe3

(148)

silylcarbene (148) on photolysis.173 Chiral aminophosphines, e.g. (149), have been used for the enantioselective conversion of meso-cyclic disulfides to chiral cyclic sulfides.174 The chemistry of the bicyclic aminophosphines (150) continues to attract interest, these compounds proving to be versatile reagents and catalysts for an increasing number of organic transformations as a result of the extraordinary basicity and low nucleophilicity of the phosphorus atom. 175 The reactivity of the phosphazanes (15 1) has received further study, and a range of new systems developed.176 Surprisingly, the reactions of the methylenebis(aminophosphines) (152) with hexafluoroacetone do not lead to the expected dioxaphospholane heterocycles, but yield the carbodiphosphoranes ( 153). 177In addition to the study of the reactivity of 3-acetylcoumarins towards trialkyl

3: Tervalent Phosphorus Acid Derivatives

(149) R = Ph or Me2N

111

(151) R = H, Me3Si or PhP(CI)

phosphites noted earlier,' '' the same paper also describes the related reactions with tris(dimethylamino)phosphine, which lead to the ylides (154), described as water-sensitive,yellow solids.

Phosphoramidites and Related Compounds. - Stepwise reactions between rescorcinol and tris(dialky1amino)phosphines have been used to build up intermediates which have undergone ultimate cyclisation to form macrocyclic aminophosphites, e.g. (155), of interest as analogues of crown ether l i g a n d ~ . ' ~ ~

4.2

(155) R = Me or Et

A range of new chiral phosphoramidite ligands (156) and (157) has been prepared by metallation of quinolines with butyl-lithium, followed by treatment with appropriate phosphorochloridites. '799180 A wide range of new chiral phosphoramidites (158) has been obtained from the reactions of the related 2,2'-binaphthol phosphorochloridite with appropriate amines in the presence of triethylamine.18' Phosphoramidites such as the above are attracting increasing interest as ligands for homogeneous catalysis applications, being relatively little studied in this context in comparison to related phosphines and phosphites. Heterocyclic phosphoramidites involving indolyl- and imidazolyl moieties, e.g. (159) and (160), have been prepared and used as intermediates for the synthesis of dinucleotide phosphorothioates and related com-

Organophosphorus Chemistry

112

OMe (1 56) R = CI or PAr2

(157) R

= CI or PAr2

g P ' O R (160) X = OR,alkyl or aryl

(1 59)

Phosphoramidites derived from high molecular mass poly(ethy1ene glycol) systems have been prepared, and used in the synthesis of oligonucleotides. 84 Phosphoramidites derived from 1,2-thiazetidine 1,l-dioxides have also been characterised.lS5 Fundamental aspects of the reaction between phosphoramidites and alcohols continue to be studied. The kinetics and mechanism of the tetrazolecatalysed alcoholysis of phosphoramidites has been investigated by 31P NMR.ls6 A similar study of the alcoholysis of some cyclic phosphoramidites, e.g. (161), has revealed the involvement of phosphorane intermediate^.'^^ Problems inherent in the reactivity of phosphoramidites derived from tertiary alcohols have also been explored. Such compounds are found to give phosphites in good yield with tetrazole catalysis when the coupling time with alcohols is prolonged. Low yields of phosphotriesters result from the elimination of the tertiary alkyl group during the subsequent oxidation of the phosphite with aqueous iodine systems, and this problem can be avoided by the use of t-butyl hydroperoxide as the oxidant.'88 The reaction of ferrocenylmethanol with P-cyanoethyl-N,N-diisopropylchlorophosphoramidite in dichloromethane surprisingly yields the Michaelis-Arbuzov rearrangement product (162), as the isolable product. The related reaction with benzyl alcohol proceeds normally to give the expected phosphoramidite. 189 Exchange reactions between amines and phosphoramidites have been applied in the synthesis of N-phosphorylated amino acid systems190and also of related oligopep-

&

E, N Pi2

c H2-P,

I /

\

(161) n = 0-2

OCH2CHzCN

3: Tervalent Phosphorus Acid Derivatives

113

tides.19' Oligonucleotide phosphoramidite methodology has also been adapted in a new approach to the synthesis of stereospecific ~phingomyelin'~~ and for the synthesis of sialyltransferase inhibitors based on CMP-quinic acid'93 and phosphorylated myo-in~sitols.'~~ Electrospray mass spectrometry of phosphoramidites has been shown to have significant advantages over the other mass spectrometry techniques, and affords a powerful tool for identification of these labile compounds.19' Several pentacoordinated phosphoranes have been obtained from oxidative addition reactions of cyclic phosphoramidites with either o-quinones or catechols in the presence of chlorodiisopropylamine,and the products characterised by X-ray crystallography.196

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49

Organophosphorus Chemistry

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3: Tervalent Phosphorus Acid Derivatives 50 51 52 53 54 55

56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81

115

X. S. Li, R. L. Lou, C. H. Yeung, A. S. C. Chan and W. K. Wong, TetrahedronAsymmetry,2000,11,2077. J. Grobe and J. Vetter, 2. Anorg. Allg. Chem., 1999,625,2085. T. L. Schull and D. A. Knight, Tetrahedron-Asymmetry, 1999,10,207. M. T. Reetz and A. Gosberg, Tetrahedron-Asymmetry, 1999,10,2129. M. Laly, R. Broussier and B. Gautheron, Tetrahedron Lett., 2000,41, 1 183. M. T. Reetz, A. Gosberg, R. Goddard and S. H. Kyung, Chem. Commun., 1998, 2077. C. Claver, E. Fernandez, A. Gillon, K. Heslop, D. J. Hyett, A. Martorell, A. G. Orpen and P. G. Pringle, Chem. Commun., 2000,961. M. T. Reetz and M. Pasto, Tetrahedron Lett., 2000,41,3315. D. Selent, K. D. Wiese, D. Rottger and A. Borner, Angew. Chem. Int. Ed., 2000, 39, 1639. A. A. Sivakov, A. Y. Platonov, V. N. Chistokletov and E. D. Maiorova, Zh. Obshch. Khim., 1999,69, 162. Y. A. Dorfman, G. S. Polimbetova, M. M. Aleshkova and A. K. Borangazieva, Russ. J. Phys. Chem., 1999,73, 1788. R. R. Abdreimova, D. N. Akbayeva, G. S. Polimbetova, A. M. Caminade and J. P. Majoral, Phosphorus, Suljiu, Silicon, Relat. Elem., 2000,156,239. J. E. Browne, M. J. Driver, J. C. Russell and P. G. Sammes. J. Chem. SOC., Perkin Trans. I , 2000,653. C. L. Branch, G. Burton and S. F. Moss, Synth. Comrnun., 1999,29,2639. J. J. Hu, Y. Ju and Y. F. Zhao, Chin. Chem. Lett., 1999,10,457. M. Reiner and R. R. Schmidt, Tetrahedron-Asymmetry, 2000,11, 319. A. Kockritz, H. Sonnenschein, S. Bischoff, F. Theil and J. Gloede, Phosphorus, Su@r, Silicon, Relat. Elem., 1998,132, 15. A. C. Dros, A. Meetsma and R. M. Kellogg, Tetrahedron, 1999,55, 3071. R. Hilgraf and A. Pfaltz, Synlett, 1999, 1814. I. H. Escher and A. Pfaltz, Tetrahedron, 2000,56,2879. A. Alexakis, J. Vastra, J. Burton, C. Benhaim and P. Mangeney, Tetrahedron Lett., 1998,39, 7869. 0.Pamies, G. Net, A. Ruiz and C. Claver, Tetrahedron-Asymmetry, 1999,10,2007. 0. Pamies, M. Dieguez, G. Net, A. Ruiz and C. Claver, Organometallics, 2000, 19, 1488. K. N. Gavrilov, A. V. Korostylev, 0. G. Bondarev, A. I. Polosukhin and V. A. Davankov, J. Organomet. Chem., 1999,585,290. M. T. Reetz and T. Neugebauer, Angewandte Chem. Int. Ed., 1999,38,179. S. Deerenberg, P. C. J. Kamer and P. W. N. M. van Leeuwen, Organometallics, 2000,19,2065. T. Mathivet, E. Monflier, Y. Castanet, A. Mortreux and J. L. Couturier, Tetrahedron Lett., 1998,39,9411. T. Mathivet, E. Monflier, Y. Castanet, A. Mortreux and J. L. Couturier, Tetrahedron Lett., 1999,40, 3885. G. Francio and W. Leitner, Chem. Commun., 1999, 1663. P. Sood, A. Chandrasekaran, R. 0. Day and R. R. Holmes, Inorg. Chem., 1998, 37, 3747. N. V. Timosheva, A. Chandrasekaran, R. 0. Day and R. R. Holmes, Inorg. Chem., 1998,37,3862. P. Sood, A. Chandrasekaran, R. 0. Day and R. R. Holmes, Inorg. Chem., 1998, 37, 6329.

116

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82

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83 84 85 86 87 88

89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110

3: Tervalent Phosphorus Acid Derivatives

117

111 W. M. Abdou and A. A. Sediek, Tetrahedron, 1999,55, 14777. 112 K. S. Kim, E. Y. Hurh, J. N. Youn and J. I. Park, J. Org. Chem., 1999,64,9272. 113 A. Barco, S. Benetti, P. Bergamini, C. De Risi, P. Marchetti, G. P. Pollini and V. Zanirato, Tetrahedron Lett., 1999,40,7705. 114 Z. Ziora, A. Maly, B. Lejczak, P. Kafarski, J. Holband and G. Wojcik, Heteroat. Chem., 2000,11,232. 115 0 .Paleta, A. Volkov and J. Hetflejs, J. Fluorine Chem., 2000, 102, 147. 116 M. Gorg, R. M. Schoth, I. Szekely and G . V. Roschenthaler, Phosphorus, Sulfur, Silicon, Relat. Elem., 1999, 146, 667. 117 V. G. Ratner, E. Lork, K. I. Pashkevich and G. V. Roschenthaler, Heteroat. Chem., 1999,10,632. 118 R. A. Cherkasov, N. A. Polezhaeva and V. I. Galkin, Phosphorus, Sulfur, Silicon, Relat. Elem., 1999, 146, 333. 119 A. Dondoni and A. Marra, Chem. Commun., 1999,2133. 120 B. Mugrage, C. Diefenbacher, J. Somers, D. T. Parker and T. Parker, Tetrahedron Lett., 2000,41,2047. 121 A. A. Semioshkin, S. G. Inyushin, L. V. Ermanson, P. V. Petrovskii, P. Lernmen and V. 1. Bregadze, Russ. Chem. Bull., 1998,47, 1985. 122 A. R. Katritzky, G. F. Qiu, H. Y. He and B. Z. Yang, J. Org. Chem., 2000, 65, 3683. 123 J. Pernak, R. Kmiecik and J. Weglewski, Synth. Commun., 2000,30, 1535. 124 S . Ganapathy, B. B. V. S. Sekhar, S. M. Cairns, K. Akutagawa and W. G. Bentrude, J. Amer. Chem. SOC.,1999,121, 2085. 125 W. Bhanthumnavin, A. Arif and W. G. Bentrude, J. Org. Chem., 1998,63,7753. 126 D. C. Hager, A. E. Sopchik and W. G. Bentrude, J. Org. Chem., 2000,65,2778. 127 R. K. Bansal, N. Gupta, J. Heinicke, G. N. Nikonov, F. Saguitova and D. C. Sharma, Synthesis, 1999,264. 128 N. Defacqz, B. de Bueger, R. Touillaux, A. Cordi and J. Marchand-Brynaert, Synthesis, 1999, 1368. 129 P. Bitha, T. W. Strohmeyer, Z. Li and Y. I. Lin, Synth. Commun., 2000,30, 1233. 130 M. H. N. Arsanious, Monatshefte Fur Chemie, 1999,130,921. 131 L. S . Boulos and M. H. N. Arsanious, Heteroat. Chem., 1999,10, 337. 132 K. C. K. Swamy, C. Muthiah, S. Kumaraswamy and M. A. Said, Proc. Ind. Acad. Sci., Chem. Sci., 1999, 111,489. 133 A. Hajipour and F. Islami, Ind. J. Chem. B-Org. Chem. Med. Chem., 1999, 38, 461. 134 M. Barbieux-Flammang, S. Vandevoorde, R. Flammang, M. W. Wong, H. Bibas, C. H. L. Kennard and C. Wentrup, J. Chem. SOC.Perkin Trans. 2, 2000, 473. 135 S. Canestrari, A. Mar’in, P. Sgarabotto, L. Righi and L. Greci, J. Chem. SOC., Perkin Trans. 2,2000, 833. 136 A. Mar’in, E. Damiani, S. Canestrari, P. Dubs and L. Greci, J. Chem. SOC., Perkin Trans. 2, 1999, 1363. 137 I. Bauer, S. Korner, B. Pawelke, S. Al-Malaika and W. D. Habicher, Polymer Degradation and Stability, 1998,62, 175. 138 G. D. Mendenhall and D. B. Priddy, J. Org. Chem., 1999,64,5783. 139 M. D. Chappell and R. L. Halcomb, Tetrahedron Lett., 1999,40, 1. 140 S . S. Kim, Y. Zhu, I. S. Oh and C. G . Lim, Canad. J. Chem., 1998,76,836. 141 S . Rudershausen, H. J. Holdt, H. Reinke, H. J. Drexler, M. Michalik and J. Teller, Chem. Commun., 1998, 1653.

118

Organophosphorus Chemistry

142 T. Murai, C. Izumi and S. Kato, Chem Lett., 1999, 105. 143 T. Murai, C. Izumi, T. Itoh and S. Kata, J. Chem. SOC.,Perkin Trans. I , 2000, 917. 144 V. A. Potapov, A. A. Starkova, S. V. Amosova, A. I. Albanov and B. V. Petrov, Russ. Chem. Bull., 1998,47,2042. 145 S. Abbas, C. J. Hayes and S. Worden, Tetrahedron Lett., 2000,41, 3215. 146 Z. M. Jaszay, I. Petnehazy and L. Toke, Synth. Commun., 1998,28,2761. 147 S. Bakkas, A. Mouzdahir, L. Khamliche, M. Julliard, E. Peralez and M. Chanon, Phosphorus, Sulfur, Silicon, Relat. Elem., 2000, 157, 21 1. 148 S. M. Godfrey, C. A. McAuliffe, A. T. Peaker and R. G. Pritchard, J. Chem. SOC.,Dalton Trans., 2000,8, 1287. 149 A. L. Weis, Chem. Phys. Lipids, 1999,102, 3. 150 R. R. Schmidt, J. C. Castro-Palomino and 0. Retz, Pure Applied Chem., 1999, 71, 729. 151 H. Tanaka, H. Sakamoto, A. Sano, S. Nakamura, M. Nakajima and S. Hashimoto, Chem. Commun., 1999, 1259. 152 H. Schene and H. Waldmann, Synthesis, 1999, 1411. 153 C. Gege, J. Vogel, G. Bendas, U. Rothe and R. R. Schmidt, Chem. Eur. J., 2000, 6, 111. 154 S. M. Lu and R. Y. Chen, Synth. Commun., 1999,29,3443. 155 K. Manabe and S. Kobayashi, Chem. Commun.,2000,669. 156 A. Fade1 and N. Tesson, Eur. J. Org. Chem., 2000,2153. 157 B. Boduszek and M. Uher, Synth. Commun.,2000,30, 1749. 158 N. A. Ganoub, Phosphorus, Sulfur, Silicon, Relat. Elem., 1999,148,21. 159 M. Beller and A. Zapf, Synlett, 1998, 792. 160. V. I. Sokolov, L. A. Bulygina, 0. Y. Borbulevych and 0. V. Shishkin, J. Organomet. Chem., 1999,582,246. 161 D. A. Albisson, R. B. Bedford, S. E. Lawrence and P. N. Scully, Chem. Commun., 1998,2095. 162 D. A. Albisson, R. B. Bedford and P. N. Scully, Tetrahedron Lett., 1998,39,9793. 163 K. Fischer, S. von Norman and D. Freitag, Chemosphere, 1999,39,611. 164 C. I. Chiriac, M. Onciu, F. Tanasa, C. Badarau and I. Truscan, Revue Roumaine De Chimie, 1998,43,971. 165 N. A. Ganoub and M. R. H. Mahran, Heteroat. Chem., 1998,9,427. 166 M. A. Pudovik, G. M. Saakyan, S. A. Terent’ev, V. K. Khairullin and A. N. Pudovik, Russ. J. Gen. Chem., 1999,69, 1712. 167 M. L. Clarke. D. J. Cole-Hamilton, A. M. Z. Slawin and J. D. Woollins, Chern. Commun., 2000,2065. 168 J. Liedtke, S. Loss. C. Widauer and H. Grutzmacher, Tetrahedron, 2000,56, 143. 169 E. Lindner, M. Mohr, C. Nachtigal, R. Fawzi and G. Henkel, J. Org. Chem., 2000,595, 166. 170 S. Breeden and M. Wills, J. Org. Chem., 1999,64,9735. 171 A. M. Z. Slawin, J. D. Woollins and Q . Z. Zhang, Inorg. Chem. Commun., 1999, 2, 386. 172 A. D. Burrows, M. F. Mahon and M. T. Palmer, J. Chem. SOC.,Dalton Trans., 2000, 1669. 173 T. Kato, H. Gornitzka, A. Baceiredo, A. Savin and G. Bertrand, J. Am. Chem. SOC.,2000,122, 998. 174 Y. Miyake, H. Takada, K. Ohe and S. Uemura, J. Chem. SOC.,Perkin Trans. I , 2000, 1595.

3: Tervalent Phosphorus Acid Derivatives

119

175 P. Kisanga, D. McLeod, X. D. Liu, Z. K. Yu, P. Ilankumaran, Z. G. Wang, P. A. McLaughlin and J. G. Verkade, Phosphorus, Sulfur, Silicon, Relat. Elem., 1999,146,101. 176 R. M. Hands, M. Helm, B. No11 and A. D. Norman, Phosphorus, Sulfur, Silicon, Relat. Elem., 1997,125,285. 177 I. Shevchenko, R. Mikolenko, S. Loss and H. Grutzmacher, Eur. J. Inorg. Chem., 1999,1665. 178 E. E. Nifantyev, E. N. Rasadkina, I. V. Yankovich, V. K. Belsky and A. I. Stash, Heteroatom Chem., 2000, 129. 179 G. Francio, C. G. Arena, F. Faraone, C. Graiff, M. Lanfranchi and A. Tiripicchio, Eur. J. Inorg. Chem., 1999, 1219. 180 G. Francio, F. Faraone and W. Leitner, Angew. Chem. Int. Ed., 2000,39, 1428. 181 L. A. Arnold, R. Imbos, A. Mandoli, A. H. M. de Vries, R. Naasz and B. L. Feringa, Tetrahedron, 2000,56,2865. 182 J. C. Wang and G. Just, J. Org. Chem., 1999,64,8090. 183 Y. X. Lu and G. Just, Tetrahedron, 2000,56,4355. 184 G. Pace, F. M. Veronese and G. M. Bonora, Reactive and Functional Polymers, 1999,41, 141. 185 G. Mielniczak and A. Lopusinski, Heteroat. Chem., 1999,10,61. 186 E. J. Nurminen, J. K. Mattinen and H. Lonnberg, J. Chem. Soc., Perkin Trans 2, 1998, 1621. 187 Y. Watanabe and S. Maehara, Heterocycles, 2000,52,799. 188 C. Scheuer-Larsen, B. M. Dahl, J. Wengel and 0. Dahl, Tetrahedron Lett., 1998, 39, 8361. 189 C. J. Isaac, M. R. J. Elsegood, W. Clegg, N. H. Rees, B. R. Horrocks and A. Houlton, Polyhedron, 1998, 17, 3817. 190 C. P. Chow and C. E. Berkman, Tetrahedron Lett., 1998,39,7471. 191 Y. M. Li, Y. F. Zhao and H. Waldmann, Chin. Chem. Lett., 1998,9, 1075. 192 A. L. Weis, Chem. Phys. Lipids, 1999,102, 3. 193 C. Schaub, B. Muller and R. R. Schmidt, Eur. J. Org. Chem., 2000, 1745. 194 L. Schmitt, B. Spiess and G. Schlewer, Tetrahedron Lett., 1998,39,4817. 195 Z. Kele, Z. Kupihar, L. Kovacs, T. Janaky and P. T. Szabo, J. Mass. Spectrometry, 1999,34, 1317. 196 C. Muthiah, M. A. Said, M. Pulm, R. Herbst-Inner and K. C. K. Swamy, Polyhedron, 2000, 19,63.

4

Nucleotides and Nucleic Acids BY M. MIGAUD

1

Introduction

In this year’s review, it has only been possible to provide extensive coverage of the mononucleotide area. We hope to include a two-year review of oligo- and poly-nucleotide chemistry and nucleic acid structures in the next volume. The past year has been marked by the development of new phosphorylation and chiral thiophosphorylation methods and by improvements in the formation of intramolecular pyrophosphate linkages. A novel efficient phosphorylating agent, a derivative of 2,2’ sulfonyldiethanol, has been developed to prepare dinucleotide systems. Novel phenyl-substituted chiral N-acylphosphoramidites, derivatives of deoxyribonucleosides, have been elaborated for the P-stereospecific synthesis of oligodeoxyribonucleoside phosphorothioates in solution and on solid supports. In the field of nucleotide derivatives involved in intracellular signalling, Matsuda’s contribution has been extensive. Elegant routes to numerous adenophostin and cyclic adenosine diphosphate ribose analogues have been reported, together with a general methodology for the efficient construction of pyrophosphate linkages. Finally a novel method that combines chemical and enzymatic steps for the large-scale production of short RNA strands containing the labelled cap structure m7GpppA has been described. 2

Mononucleotides

2.1 Nucleoside Acyclic Phosphates. - 2.1.1 Mononucleoside Phosphate Derivatives. Selective phosphorylation at the primary hydroxyl group of O-unprotected nucleosides has been described. Slow addition of dibenzyldiisopropylphosphoramidite to a solution of the nucleoside and 5-@-nitrophenyl)-1 Htetrazole in acetonitrile yielded the 5’-phosphite triester, which was subsequently oxidised in situ by tert-butyl hydroperoxide. A novel phosphorylating agent, 2-O-(4,4’-dimethoxytrityl) ethylsulfonylethan-2’-yl-phosphate( 1) has been utilised (Scheme 1) in the phosphorylation of primary and secondary alcohols of nucleosides ( 2 ) in the presence of the coupling reagent TPS-TAZ. The product of this phosphorylation could undergo selective phosphate deprotection and overcome difficulties encountered in monitoring the reaction2 Organophosphorus Chemistry, Volume 32 0The Royal Society of Chemistry, 2002 120

4: Nucleotides and Nucleic Acids

121 0)(0Na)2

i, DMTrO,s02,0P( (1) TPS-TAZ, Py

*

ii, 1 M NaOHIPylEtOH

R’O

R’O

(2) R = H, R’ = Ac R = DMTr, R1 = H

(3) R = DMTrOCH2SO2CH20P(0)(ONa),R’ = Ac R = DMTr, R1 = DMTrOCH2S02CH20P(0)(ONa

Scheme 1

Some lipophilic pronucleotides are thought to be capable of releasing their phosphorylated nucleoside congeners inside the cell and not require the intervention of phosphodiesterase(s), hence potentiating the antiretroviral activity. This aspect is particularly important when the analogues do not incorporate the structural features required for enzyme-catalysed phosphodiester hydrolysis. The lipophilic phosphoralaninate derivatives of methylenecyclopropane purine nucleosides (4a+) have been prepared using methylchlorophosphoryl P-N-L-alaninate and evaluated for their antiviral properties3 The E-series was found to be active against HIV-1, HBV and EBV and non-cytotoxic while the 2-series were potent inhibitors against HCMV, HSV-1, HSV-2, HHV-6, EBV, VZV, HIV-1 and HBV, but were also cytotoxic. The 2-diaminopurine analogue (Z-4e) was the most potent inhibitor of HIV and HBV replication. 0 II

C6H50-P-o AH I

&fy;

Me/c’COOMe

0 II

R2

I

R2

Me”

HC00Me

(4a) R’ = NH2, R2 = H

(5a) R’ = NH2, R2 = H

(4b) R’ = OH, R2 = NH2

(5b) R’ = OH, R2 = NH2

(4c) R’ = NH(CH2)3, R = H (4d) R’ = NH2, R2 = OMe (4e) R’ = NH2, R2 = NH2

The spiropentane mimics of 2’-deoxyadenosine and 2’-deoxyguanosine(5a,b) have also been synthesised as putative antiviral and anti-tumour agent^.^ They were modest inhibitors of viral replication but could be activated by their conversion to lipophilic phosphoramidate pronucleosides, thus bypassing the first phosphorylation step required by their mode of action. However, the increase in potency was compromised by the amplification of their cytoxicity. Membrane permeant substituted-aryl phosphoralaninate derivatives (6) of the anti-HIV drug d4T have been ~ynthesised.~ All of the derivatives were significantly more potent than d4T against HIV in cell culture; however steric and electronic effects altered only slightly the inhibitor potency while the position of the mono-substituent had no obvious effect.

Organophosphorus Chemistry

122

0

Il

0-P-0. I

O> \

/O (6a) X = p-NO2 (6b) X = p-CN (6c) X = pCOOMe (6d) X = p-CI (6e) X = p-F (60 X = p-Br

(6g) X = p-l (6h) X = p-Me (6i) X = p-OMe (6j) X = pOCF, (6k) X = p-CF3 (61) X = rn-COMe

(6m) X = rn-F (6n) X = rn-CI (60) X = rn-Br (6p) X = rn-l (6q) X = m-CF3 (6r) X = 0-CI (6s) X = 3,4-c12

0

0

?

?

. :N , N o

(7a) R‘ = CH2CH2Br,R2 = Me (7b) R’ = R2 = (CH2)5

bNo2

(8a) R’ = CH2CH2Br,R2 = Me, X = 0 (8b) R1 = CH2CH2Br,R2 = Me, X = NH ( 8 ~ R1, ) R2 = (CH2)5, X = 0 (8d) R’, R2 = (CH2)5, X = NH

A new approach to the design of lipophilic nucleoside prodrugs (7) and (8) exploited the reactivity of the nucleoside haloethyl 5’-phosphoramidates towards intracellular activation and formation of the phosphoramidate anion. This intermediate rapidly liberated the corresponding nucleotide via P-N bond hydrolysis.6 The activation mechanism was closely investigated using 31P-NMR, and was shown to implicate a highly electrophilic aziridinium ion intermediate, which was then hydrolysed to release the free phosphate nucleoside m ~ n o e s t e r .The ~ observations that support this mechanism differed from those made for the piperidyl nucleoside phosphoramidate analogues (7b, 8c, 8d) in which the intracellular hydrolysis was found to involve an endogenous phosphoramidase. Acyclovir-5’-(phenylmethoxyalaniny1)-phosphoramidate (9) has been synthesised and evaluated as a lipophilic, membrane-soluble prodrug of the free nucleotide, acyclovir.* Biological evaluations against a range of viruses indicated the poor intracellular phosphate delivery. Another prodrug form of acyclovir, 1-O-hexadecylpropanediol-3-phosphate-acyclovir (lo), an orally bio-available lipid prodrug, has been synthesised from acyclovir using 2-chlorophenyldichlorophosphate in a phosphotriester approach and evaluated in vitro and in vivo against HSV-1.

4: Nucleotides and Nucleic Acids

123

While the prodrug was less potent than acyclovir in in vivo assays, it was 2.4 times more active orally than its parent nucleoside.' A library of novel partially protected nucleotides (1 1) has been prepared using solid-phase synthesis.lo These building blocks were derived from deoxyand ribonucleosides and the phosphate moiety was substituted with groups (1 1) B = A,C,T,G 2 = H,OMe ROH = Open-Chain Alcohols

Cyclic Primary Alcohols

Cyclic Secondary Alcohols

-OH 3

O

H

Aromatic Alcohols

0, OH

bMe

A I

Ton

T

O

OOH

H

%OH

OMe

0""doH I

T

O

H

\

OH

Me0&OH

HCi

O *H

P

O

H

/

Organophosphorus Chemistry

124

E:? Eo3

(12d) n = 2, R = -Cj6H33 (12e) n = 2, R = -0C16H33

(12a) n = 1, R =-OCl6H33 (12b)n=1, R =

(12c) n = 1, R =

0

F

O-cl6H33

(129n=2,~=

E 3 Eoi

16H33

o-cl 6H33

O-CH2-C F3

(129) n = 2, R =

0-C16H33

O-CH2-CF3

R2

F

(14) R2 = OH (15) R2 = NH2

derived from 25 primary and secondary alcohols, each with differing degrees of hydrophobicity as well as steric and electronic properties. The R group was coupled to the nucleoside units via a phosphorothioate linkage that insured stability against nuclease-mediated degradation and imparted aqueous solubility to the compounds. Several phospholipid-adducts of %P-~-arabinofuranosyl-2-fluoroadenine (12), have been prepared. The biological activities were shown to depend strongly on the chemical structure of the lipid component, as the phospholipid adducts were more potent against solid tumour cell lines while the parent nucleoside was more effective against leukemic cell lines.” Novel analogues of p-D- and 13-L-enantiomers of uracyl and cytosine 2‘,3’dideoxypentofuranosyl nucleosides and the respective bis-(S-pivaloyl-2thioethyl) phosphotriester derivatives (12, 13) have been synthesised and evaluated for the inhibition of HIV and HBV replication.12 In contrast to the 3’-dideoxy-5-chloro-uracyl( 1 3), P-~-3’-fluoro-2’, 3’-dideoxy-5P-~-3’-fluoro-2’, chloro-uracyl (14) and cytidine congener (15 ) were devoid of significant antiHIV effects. The use of S-acyl-2-thioethyl labile phosphate protecting groups resulted in the intracellular delivery of the parent 5’-nucleotide, thus circumventing the first anabolic phosphorylation step, Nucleotide delivery systems based upon pH-driven selective chemical hydrolysis have been extended to 2’,3’-dideoxy-adenosinemonophosphate (ddAMP) protected as the lipophilic cyclosaligenyl diester. The syntheses, lipophilic

125

4: Nucleotides and Nucleic Acids

(16b) X = 5-OMe (16c) X = 3-Me (16d) X = 3,5-Me2

(17b) X = 5-OMe (17c) X = 3-Me (17d) X = 3,5-Me2

and hydrolytic properties and biological activities of cycZoSal-2’,3’-dideoxyadenosine monophosphate (16) and cycloSal-2’,3’-dideoxydidehydro-adenosine monophosphate (17) have been reported. The cycZoSal-monophosphate residues were introduced stepwise by reaction of the appropriate chlorophosphoranes with the unprotected nucleosides, followed by a TBHP-mediated oxidation. In hydrolysis studies, the cycZoSal-ddAMP and cycloSal-d4AMP decomposed under mild basic conditions, releasing solely the phosphate monoester and the alcohol, while a marked increase in stability was detected under acidic conditions with respect to the glycosidic bond. The phosphotriesters exhibited antiviral activities against wild type HIV- 1 and HIV-2 that were 100- and 600-fold higher than those of the corresponding nucleoside and were not substrates for enzymatic deactivation by deaminases. The unstable aminoacyl adenylates (18) and the amino-adenylate analogues (19) in which the 5’-phosphoryl oxygen has been replaced by a sulfur or a methylene moiety have been synthesised and their chemical properties have been investigated using 31P-NMR.l 4 The aminoacylation of 5’-AMP proceeded to completion when DCC was used as condensing reagent under anhydrous conditions. Phosphidosine A (20a), a novel antitumour agent isolated from Streptomyces sp. has been synthesised from the 5’-0-phosphoramidate precursor and a prolinamide derivative via 5-(3,5-dinitrophenyl)-lff-tetrazolecatalysed N-acyl phosphoramidate bond formation. Two new putative inhibitors of adenosine 5’-monophosphate deaminase

R 1 H N - iR2 r0

R_,

0 -p‘T

w fN

HO

I2 / )N

OH

(18a) X = 0, Y = 0, R’ = H, R2 = H

(18b) X = 0, Y = 0, R’ = CH2Ph, R2 = H

(18c) X = 0, Y = 0, R’ = CH2Ph, R2 = CBz (18d) X = 0, Y = 0, R’ = (CH2)2SMe,R2 = CBz (18e) X = 0, Y = 0, R’ = CH(Me)*, R2 = CBz (180 X = CH2, Y = 0, R’ = (CH2)$3Me, R2 = CBz (19) X = 0, Y = S , R’ = (CH2)$3Me, R2 = CBz

\ 0

ywoz&

-O

HO (20a) R = H (20b) R = Ac

OH

Organophosphorus Chemistry

126

have been prepared from aristeromycin and formycin via N6-deamination followed by enzymatic phosphorylation. While the aristeromycin phosphate ester (21) was a poor inhibitor of adenosine monophosphate deaminase, the deaminoformycin derivative (22) was a very potent inhibitor of this enzyme and displayed potent herbicidal activities.

5-Fluoropropynyl-dUMP (23), a novel mechanism based inhibitor of the iVs,N1o-methylenetetrahydrofolate-dependentenzyme thymidylate synthase, has been synthesised. This 5-fluoropropynyl-dUMP caused rapid, irreversible inactivation of thymidylate synthase both in the presence and in the absence of the c ~ f a c t o r . ' ~ F

0

N

,OH

(24a) R = H (24b) R = Me

Several novel 5-substituted ~-hydroxy-2'-deoxycytidine5'-phosphates (24) with substituents of different electronic, hydrophobic and steric properties at the 5-position were synthesised chemoenzymatically with the aid of the wheat shoot phosphotransferase system and evaluated as putative inhibitors of thymidylate synthase. All @-hydroxy-dCMP (24a) and dUMP analogues (24b) were competitive inhibitors of the enzyme-catalysed dUMP methylation. The inhibitory activity was attributed to the rare trans-rotamer ( p - O H pointing towards CS), and therefore weaker slow-binding inhibitors were detected when unfavourable 04C5-substituent steric interactions were present. A new series of 5-carboranyl-substituted-2'-deoxyuridine(25a) and deoxythymidine (25b) derivatives containing a range of alkyl spacers has been prepared to access a more effective use of boron neutron capture therapy.'' Evaluation of these derivatives as substrates for the human thymidine kinases TK1 and TK2 showed that a decrease in the length of the spacer (from 8 methylene units to 4) between the carborane moiety and the pyrimidine base resulted in better substrate characteristics.

4: Nucleotides and Nucleic Acids

127

/

wBioHio

H d

HO

R=

0 II

HO-P-0-R I OH

PMEA

n = 4, 5, 6, 7

0 II

O=S-0-R I

NH2 Pa)

Chemically stable analogues of acyclovir (26) have been synthesised in an attempt to attain appreciable activity against herpes virus type- 1 while allowing their cellular internalisation and bypassing the intracellular activation of acyclovir to its triphosphate derivative required for activity. These compounds are bio-isosteres of acyclovir monophosphate and diphosphate, but are devoid of any appreciable antiviral activity on both HSV- 1 and HIV- 1. The 2’-deoxy-purineand pyrimidine derivatives (27), bearing a 5’-methylene-

DMT~O’ (27)

0

Organophosphorus Chemistry

128

phosphonate with a 4-methoxy- 1-oxide-2-picolyl function as an intramolecular nucleophile catalytic group, have been prepared.20 This particular protecting group can assist in the coupling of the 5’-methylenephosphonate building blocks to a receptor molecule and therefore facilitate incorporation of the methylenephosphonate function into various biomolecules. Abramov nucleophilic addition of various phosphorus acid esters to nucleoside aldehyde derivatives yielded the phosphonate-based iso-polar, non-isosteric 5’-nucleotide analogues (28) containing a geminal hydroxy phosphonate moiety on the 5’-carbon of the pentofuranose ring.21 The enantiomerically pure D- and L- 2’,3’,5’-trideoxy-4’-[(ethoxyphosphoryl) difluoromethyl] thymidine analogues(29) have been synthesized from (Rs)-(E)-2-methyl- 5-(4-methylphenyl-sulfinyl)pent-2-ene and ethyl 2-(diethoxyphosphoryl)-2,2-difluoroacetate in 45% overall yield over seven steps.22 To identify motifs that are effective for the inhibition of human purine nucleoside phosphorylase, Shibuya et al. have prepared numerous conformationally restricted nucleotides (30) and ( 3 l) that act as ‘multi-substrate analogue’ inhibitors for PNP.23-25 Preliminary results demonstrated that difluoro (( 1S*, 2S*)-2-[(1S*)- l-(6-0~0-l,6-1,6-dihydr0-9H-purin-9-yl)ethyl]cyclopropy1)methylphosphonic acid (3 1a) was a potent inhibitor with a Ki of 19.6 nM for PNP-catalysed phosphorylation of inosine in the presence of 100 mM o r t h ~ p h o s p h a t e . ~ ~

(30a) n = 1, 2

(31a) R = Me, X = H (31b)R=Me, H = M e (31c) R = Ph, X = Me (31d) R = CH2Ph, X = Me (31e) R = CH2(C6Hll), X = Me

Novel congeners of 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA, 32), the dialkyl esters of purine and pyrimidine N-[2-(phosphonomethoxy)ethyl] derivatives substituted at position 2, 6 or 8 of the purine base (33) or position 2, 4 or 5 of the pyrimidine base (34), were prepared by alkylation of the appropriate heterocyclic base with 2-chloroethoxymethylphosphonate diester.26Except for the 5-bromo-cytosine derivative (34a), no activity against DNA viruses or retroviruses was observed for the novel pyrimidine analogues. However, modifications to the purine led to compounds highly active against HSV-1 and -2, VZV, CMV, W, MSV and HIV. Non-racemic amino alcohols derived from common amino acids have been employed to prepare acyclic nucleotide analogues (35) with controlled absolute stereochemistry, as structural hybrids of PMEA and PMPA, the propyl homologue of PMEA.27 L-threonine and L-alanine were used as precursors in

129

4: Nucleotides and Nucleic Acids 0

(32a) R = iC3H7 (32b) R = iC8H17 ( 3 2 ~R ) = C2H5

+ R

(33a) R' = H, NH2, F, CI, OH R2 = H, Br

(33e)

R' = H, NH2 X = CH, N; Y = CH, N

H2N

-1R

(33b) R' = H, Me

(33c) R' = Me, SH, SMe

(334

?\

H2N\

"r" R

5'

R' \

H2N \

"r" R

(339) R' = H, Br

(339

(33N

0

the synthesis of (1R,2R)-9-[1-hydroxymethyl-2-hydroxypropyl]adenine, its bisphosphonomethoxy derivative (35a) and (R)- and (S)-9[1-methyl-2-phosphonomethoxyethyl] adenine (35b) respectively. Cyclic phosphonate analogues of PMEA (36) have been obtained after stereoselective cyclisation of an acyclic phosphonyl intermediate to the phosphonyltetrahydrofuran nucleoside derivative.28A series of cyclopropylphosphonate analogues (37) has been synthesised stereoselectively via intramolecular epoxide opening reaction of y,ti-epoxyalkanephosphonates with subsequent Mitsunobu coupling reaction to purine bases.29 Acyclic phosphonate derivatives of thymine (3843) have been prepared and evaluated as multisubstrate analogue inhibitors of Escherichia coli thymidine phosphor-

130

N; ; & ! E

0 II

X

a12

(R) (36) B = A, T, G ,C

(37a) X = NH2, R1 = H (37b) X = NH2, R' = Me (37c) X = CI, R1 = H (37d) X = CI, R' = Me

ylase3' Only the molecules possessing an unsubstituted flexible linker (38a,b), (40), (41a-d) and (42) inhibited the phosphorylase, acting as multisubstrateadduct inhibitors. A novel one-pot procedure, from which potentially explosive activators such as tetrazole have been eliminated, has been described. It allowed largescale production of nucleoside 3'-phosphoramidite derivatives and employed

0

Meexo

OH (38a) R1 = R2 = H, n = 1 (38b) R' = R2 = H, n = 2 (38c) R' = R2 = OH, n = 1 (38d) R' = R2 = OH, n = 2

(41a) n = 6 (41b) n = 7 (41c) n = 8 (41d) n = 9

(39a) n = 1 (39b) n = 2

4: Nucleotides and Nucleic Acids DMTrO

131 DMTrO

DMTrO

I i

I

/.k

/P\ Pr2N N’Pr2 ’

‘Pr2N

0-Pg

PgOH = pNO2C6H4CH2OH, CNCH2CH20H

Scheme 2

DMTrowB 0 I

npeO/ p\ NiPr2 (44) B = npeoc and npe-N6-protected Adenine, N2-protected Guanine,

N3-protected Thymine, N4-protected Cytosine

bis-(diisopropy1amino)-chlorophosphine as phosphitylating agent (Scheme 3.31

2-(4-Nitrophenyl)ethyl (npe) and 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) groups have been presented as versatile protecting groups that could be removed under aprotic conditions by p-elimination. A large number of npe and npeoc protected 2’-deoxynucleoside phosphoramidite thymidine and guanosine derivatives (44)have been synthesised as potential building blocks for oligonucleotide synthesis.32 3’-Phosphoramidite nucleoside analogues (45) that incorporate a hydrocarbon or oligothiophene fluorophore at the Cl of the deoxyribose moiety have been prepared by reacting the Grignard derivative of the aromatic precursor with 2-deoxy-3,5-di-O-(p-toloyl)-~-ribosyl chloride in the presence of a Lewis acid. The terphenyl, stilbene, terthiophene, benzothiophene and pyrene nucleoside analogues, present in the a-D-form were subsequently deprotected, selectively protected at the 5’-hydroxyl position and treated with 2-cyanoethyl-diisopropyl phosphoramidochloride to yield the phosphoramidite nucleoside analogues.33 The protected hydrogen phosphonate of a 2’-deoxyadenosine tetracyclic analogue, (46) has been synthesised via the Stille biaryl coupling reaction of N(tert-butoxycarbonyl)-2-(trimethylstannyl)-anilineon a protected 6-chloro-7deaza-7-iodopurine-2’-deoxyribose, followed by cyclisation. After subsequent deprotection and 5’-O-protection, the nucleoside analogue was treated with 2chloro-4H- 1,3,2-benzodioxaphosphorin-4-one in the presence of ~ y r i d i n e . ~ ~ A versatile synthetic route to stereochemically pure 2’-deoxyguanosine-3’phosphate adducts of cyclopenta[cdJpyrene, applicable to other nucleosides, has been described to gain access to site-specificallymodified oligomers as well as to access chromatographic standards to definitely identify stereochemical

Organophosphorus Chemistry

132

DMTrO,

(45a) R = (terthiophen)-yl (45b) R = (benzoterthi0phen)-yI (45c) R = (pterpheny1)-yl (45d) R = pyrenyl (45e) R = stibenyl (450 R = cyclohexenyl

0

NH

10

HO-P=O

I OH

I

configurations of DNA adducts. Stereochemically pure nucleotide pyrene adducts (47) were obtained by condensation of racemic trans 3-amino-4hydroxy-cyclopenta[cdlpyrene with 2-fluoro-2’-deoxyinosine-3’-H-phosphonate derivatives, followed by oxidation to the corresponding 3’-phosphate and reverse phase separation of the diastereomeric mixture.35 2’-0-modified 3’-phosphoramidite nucleosides (48) have been prepared via alkylation of the 2’-position of a protected nucleoside using 1,3,2-dioxathiolane-2,2-dioxide and 1,3,2-dioxathiane 2,2-dioxide, followed by a further nucleophilic displacement of sulfate ion.36 Further modifications of the ribose moiety of nucleotides were sought to access conformationally restricted oligomers with the synthesis of D-altritol phosphoramidite nucleoside derivatives. Adenine and uracil derivatives were obtained by nucleophilic opening of the epoxide ring of 1,5:2,3-dianhydro-4,60-benzylidene-D-allitol using the sodium salt of the purine or pyrimidine base. The cytosine congener was prepared from the uracil derivative while protection of the 06-function of guanine with 2-trimethylsilylethyl was required to access the guanosine nucleoside. Further treatment with 2-cyanoethyl-diisopropylaminochlorophosphoramidate yielded the phosphoramidite nucleoside analogues ( 4 9 1 . ~ ~ Precursors to thymidine-3’-O-(S-aryl methanephosphothionate) (50) have been prepared and treated with triphenylphosphine to provide access to novel dinucleotide 3’,5’-methanephosphonate analogues (Scheme 3). The reaction of

4: Nucleotides and Nucleic Acids

133 R

DMTrO, NC

1 0 , /p ‘Pr2N

NMe2 (49W

(494

NHBz

LI

NHBz

I

5’-TBDMS-0-protected 2’-deoxy-thymidine methanephosphonothioic acid with p-nitrophenylsulfenyl chloride yielded the mixed disulfide (50). (50) was then treated with triphenylphosphine to yield the symmetric pyrophosphonothionate ( 5 1) and the 3’-0-(S-aryl methanephosphonothionate) nucleoside (52) when an excess of p-nitrophenylsulfenyl chloride was present .38 Baker has described a novel rearrangement of 3’-a-diethylphosphono-3’-P0-methane-sulfonyl 2’,5’-TBDMS-0-uridine (53) in the presence of fluoride anion, leading to the corresponding 2’-phosphate (54) (Scheme 4).39 An efficient synthesis of adenophostin (55a) analogues (55b-f) from Dxylose has been rep~rted.~’ The C-glycosidic analogue of adenophostin A and its uracil congener (56a,b) have also been prepared via a temporary silicontethered radical coupling reaction as the key step.41742 Introduction of a fluoride at the 3-position of neuraminic acid yielded a compound (57) that was a competitive inhibitor of the a-(2,6)-sialyl-transf e r a ~ eBase . ~ ~ and sugar-modified analogues of CMP-Neu5Ac have also been prepared to investigate the tolerance of a-(2,6)-sialyl-transferase to base exchange (58) and modification of the 5-, 8- or 9-position of neuraminic acid (59), (60).44While base-exchange was not tolerated, modifications of the acid moiety yielded compounds that were substrates for the enzyme. 2.1.2 Polynucleoside Monophosphate Derivatives. Amphiphilic heterodinucleoside derivatives (6 1, 62), specifically the I@-palmitoylated2’,3’-dideoxycytidine linked to AZT or ddI via a (5’,5’)-phosphate diester linkage have been prepared to compare their activity as anti-HIV agents to the activity of their hydrophilic heterodimer ~ o u n t e r p a r t The . ~ ~ dimers exhibited strong activity against HIV wild type and an AZT-resistant virus variant.

Organophosphorus Chemistry

134 0

0

-

TBDMSO PPh3 /

Me-P=O

0

TBDMSO


Me-P=S

Scheme 3

Hoktxo

GNA0

TBDMSO

MsO

TBAF

MsO

____)

EtO-P=O

I OEt

OTBS

0 I EtO-P=O I OEt

(53)

(54)

Scheme 4

Symmetrical dinucleoside phosphoramidates and N-substituted phosphoramidates (63) and (64) were obtained after oxidative coupling of the symmee.~~ trical H-phosphonate diester of AZT with the appropriate a m i ~ ~Biological evaluation on HIV-infected TK-deficient cell lines suggested that such dinucleoside phosphoramidates could not be regarded as pronucleotides, as they were unable to deliver the corresponding 5’-nucleotide inside the cells.

135

4: Nucleotides and Nucleic Acids

2-03p0&x2 - ~ 3

~

~

- JOH

2-~P 3 0’

(55a) X = 0 (56a) X = CH2

Me0 (55d) X = 0

(59a) x = N H ~ + (59b) X = ‘BuCONH

( 5 9 ~X) = +H3NCH2CONH (59d) X = EtOCONH

B

(55b) X = 0 (56b) X = CH2

N ‘

I

VJ,

(55e) X = 0

(rJ L

N

(55c) x = 0

(1

L

(559 x = 0

(60a) R’ = Me, R2 = H (60b) R’ = H, R2 = HO(0)PO-

136

Organophosphorus Chemistry

0

0 (64b) R =

(64c) R =

N3 N3

0

(63) R = H (64a) R = Bu

A facile, one-pot synthetic method, employing phosphorus trichloride to synthesise phosphorothioate dimers (65), has been described47 Dinucleoside phosphite triesters were obtained from the 1,2,4-triazole-catalysedcoupling of a protected nucleoside bearing free 5’-OH and a protected nucleoside bearing free 3’-OH in the presence of PC13. Their subsequent in situ sulfurisation yielded (65). A simple and straightforward synthesis of the pyrimidine 2’-deoxyribonucleoside cyclic N-acylphosphoramidites Rp (66) and Sp (67) has offered the possibility of preparing the dinucleoside phosphotriesters and phosphorothioates (68, 69), with total P-stereospecificity. The dinucleotides were obtained from the reaction between the appropriate cyclic N-acylphosphoramidite and 3’-O-acetylthymidine in the presence of N,N,N’,N’-tetramethylguanidine(Scheme 5), followed by oxidat i ~ n . ~Stereoselective * synthesis of protected 3’,5’-dithymidine phosphorothioate analogues (70) has been accomplished using a dichlorophosphorus compound incorporating a chiral auxiliary group derived from L-tryptophan. The protected dimer was obtained in high yield and was diastereomerically pure. However, removal of the chiral auxiliary resulted in a complete loss of chirality due to two competing inter and intra-molecular deprotect ion mechanisms .49 The first synthesis of a dinucleotide analogue combining phosphorothioate and boranophosphate features has been reported.” To prepare dithymidine boranophosphorothioate (7 l), Fmoc-protected thymidine was phosphitylated by bis(diisopropy1amino)-chlorophosphine in the presence of DMAP. The resulting phosphoramidite was treated in situ with a 3’-protected thymidine and tetrazole and was then converted to a phosphite triester with nitrophenol. The phosphite triester was subsequently treated with BH3.SMe2 followed by LiS2 in the presence of 18-crown-6 to yield (71). This novel type of dinucleoside

4: Nucleotides and Nucleic Acids DMTrO

137

w’

0

0

HO

I,O npeOYP\

+

RO

3-

0 H0’

(65a) B’ = T, B2 = T

(66a) R’ = H, Rp

(68a) R’ = H, X = 0

(65b) B’ = T, B2 = CBz

(66b) R’ = Me, Rp

(6%) B’ = GBu,B2 = T

(67a) R’ = H, Sp (67b) R‘ = Me, Sp

(68b) R‘ = Me, X = 0 (69a) R1 = H, X = S

(65d) B’ = GBu,B2 = CBz

(69b) R’ = Me, X = S

(65e) B’ = ABz, B2 = T (659 6’ = ABz, B2 = CBz

Scheme 5

(659) B’ = T, B2 = GB” (65h) B’ = mCBZ,B2 = T

R = H, P(Onpe)(NiPr2)

(70) T3’,T5’, Thymidine

monophosphate analogue displays the same stability towards nucleosidases as the parent species and also possesses higher lipophilicity. Dinucleoside monophosphates containing an anti-conformationally constrained acyclic thymidine (72) have been prepared to improve on the loss of entropy observed in unconstrained oligonucleotide system^.'^ These analogues possessed excellent enzymatic stability towards nucleases and phosphodiesterases. Novel non-natural dinucleoside and dinucleotide analogues (73) have been synthesised in several steps from (S,S)-isodeoxyadenosine, a structural analogue of natural 2’-deoxyadenosine, which was treated with the bifunctional phosphorylating agent 2-chlorophenylphosphoro-bis-triazolidein the first step of the synthesis.52The internucleotide coupling was carried out with triisopropyl benzenesulfonyl tetrazolide to yield the protected dinucleotide. Selective phosphorylation of the 5’-hydroxyl of the fully deprotected dinucleotides using 2-cyanoethylphosphate in the presence of DCC offered the 5’phosphorylated dinucleotide after deprotection with NH40H. These novel dinucleotide analogues have been reported to be stable to 3’ and 5’-exonucleases and sequence specific inhibitors of HIV-integrase.

138

Organophosphorus Chemistry NH2

I

HO

.Me

HO

HO

HO

(72) B = T, ABZ,CBz, Gi-Bu

(71)

(73a) R = H (73b) R H203P

While the introduction of heteroatoms at non-bridging positions of the phosphodiester bond can be easily achieved, modifications involving bridging positions of the phosphorus centre often require elaborated chemical approaches. A novel P3’-+N5’dinucleotide linkage (74) has now been described. Thymidine-3’-N-(thymidine-5’-yl)-H-phosphonamidate(74a) was synthesised by reacting the appropriately protected 3’-aryl H-phosphonate derivative of in the presence of pivaloyl thymidine with the 3’-protected-S-amino-thyrnidine chloride. The phosphonamidate was subsequently oxidised to yield the dinucleoside phosphoramidate (74b) and dinucleoside phosphoramidothioate derivatives ( 7 4 ~ 1 . ~ ~ The preparation of a phosphate diester hydrolysing-hammerhead ribozyme substrate analogue containing an amide linkage in place of the normal phosphate diester linkage (75) has been reported. The dinucleoside analogue was incorporated in a dodecamer, which displayed high affinity for the ribozyme but did not act as a substrate.54 NHBz

0

DMTrO

I

TBDMSO (74a) Y = H (74b) Y = S (74c) Y = 0

O-CN

(75)

4: Nucleotides and Nucleic Acids

139

Novel masked phosphorylated derivatives of d4T-(CH&TSAO, which incorporated linkers of different conformational freedom and different anchorage location, have been prepared. Among these novel phosphate masked heterodimers, several had particularly high efficiency against HIV-RT.55 2.2 Nucleoside Pyrophosphates. - 2.2.1 Nucleoside Diphosphate Analogues. The enzymatic regeneration of 3’-phosphoadenosine-5’-phosphosulfate(76) catalysed by the rat liver sulfotransferase IV enzyme has been reported to provide useful quantities of the cofactor for enzyme kinetic experiment^.'^ The first thio-nucleotide analogues of adenosine 5’-phosphosulfate (77a) and of 3’phosphoadenosine 5’-phosphosulfate (77b) have been synthesised in enantiomerically pure forms. Using these novel analogues, the sulfuryl transfer reaction to adenosine 5’-triphosphatewas shown to proceed with inversion of configuration at the a - p h o s p h ~ r u s . ~ ~ H2N,

0 t

OH

o=p-o-

0-

HO

OH

(77a) R = H (77b) R = P03H2

2.2.2 Nucleoside Diphosphosugars. UDP-C-D-Galactofuranose (78) has been synthesised from the fully benzoylated P-D-galactofuranoside and was found to act as a potent competitive inhibitor of UDP-galactopyranose mutase. This analogue has been further employed in the studies of the mutase by X-ray crystallography experiment^.^^ The enzymatic synthesis of novel UDP-(3deoxy-3-fluoro)-~-galactopyranose(79a) and UDP-(2-deoxy-2-fluoro)-~-galactopyranose (79b) offered species that displayed a similar Michaelis constant as the substrate, UDP-galactopyranose, with a much lower Kcatvalues.59

txo

HO 10--

pLi’o\:!o~Ao

HO

OH I

0 II

F

HO

N

OH

H

R

2

qO-p0 OH O ,Il l,

:’

0 0 OH

HO (79a) R’ = F, R~ = OH (79b) R’ = OH, R2 = F

OH

140

Organophosphorus Chemistry

A reliable chemical synthesis of UDP-galactofuranose has been described as an alternative approach to the less efficient mutase conversion of UDPgalactopyranose. UDP-galactofuranose was obtained by coupling of a - ~ galactofuranosyl phosphate, prepared from methyl a,P-D-galactofuranoside and uridine 5’-monophosphate, which had been activated to the phosphoimidazolidate using carbonyldiimidazole in DMF.60 The mechanism of UDP-galactopyranosyl transferase has been investigated using C-glycosidic UDP-Gal and amido derivatives (80) acting as transition state-based enzyme inhibitors.61 A similar transferase, the cytidylyltransferase, has been used to synthesise 4-(cytidine 5’-diphospho)-2-C-methyl-~-erythritol (8 1) from 2-C-methyl-~-erythritol4-phosphatein the presence of CTP.62

&

0

R’HO

O H 0

K i

7 4OH

HO

,O,Il

HO=

0 P’ I

OH

0, / 0, P’

OH

(80a) R’ = OH, R2 = H, R3 = OH (80b) R’ = NHAc, R2 = OH, R3 = H (80c) R’ = NHAc, R2 = H, R3 = OH

II

0

(81)

Ho

oH

A general synthetic method using base-unprotected nucleosides and 2cyanoethyl tetraisopropylphosphorodiamiditehas been described to prepare enantiomerically pure ADP and GDP analogues containing a non-bridging borano moiety at the a-phosphorus atom.63 Further application of this methodology was applied to prepare a variety of nucleoside diphosphate sugars and coenzymes that incorporated the a-P-borano group in place of the non-bridging oxygen of the phosphate, such as the adenosine derivative (82).@

HO

OH

2.2.3 Nucleoside Cyclic Pyrophosphates. Extensive work has been carried out by Matsuda et al. in their efforts to synthesise chemically stable cyclic adenosine diphosphate ribose (cADPR) analogues. The carbocyclic inosine analogue (83) was first prepared through an efficient cyclisation of an 8bromo-N- 1-[5”-(phosphoryl)carbocyclic-ribosyl]inosine S-phenylthiophos-

141

4: Nucleotides and Nucleic Acids

phate derivative mediated by iodine.65 The formation of the intramolecular pyrophosphate linkage was favoured by a conformational restriction approach in which formation of the syn-form was encouraged using a halogen substitution at the 8-position of the adenine ring. The intramolecular pyrophosphate linkage was accomplished using modified Hata-condensation conditions.66 Finally, the first true precursor to a stable cADPR analogue (84) has been prepared from the treatment of the N- 1-carbocyclic-8-chloroadenosine5’3’diphosphate derivative with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.67

0x0 (83a) R = H (83b) R = Br

2.2.4 Nucleoside Pyrophosphonates. Rosenberg et al. have reported that treatment of the geminal hydroxyphosphonate moiety of 2’-thymidine-3’-Cphosphonate with acetic anhydride yielded the phosphonate anhydride derivative (85a), the cyclic dinucleoside diphosphonate (85b) and the tetranucleoside diphosphonate ( 8 5 ~ ) . ~ * 3

Nucleoside Polyphosphates

In order to increase the chemical stability of ATP derivatives that possess long thioether tethers, the 1-thiotriphosphate analogues (86) have been prepared from 2-thio-adenosine. These compounds were fourfold more stable to pig pancreas type I ATPDase than ATP. They were also more potent than ATP at stimulating intracellular response and were established as new insulin secretag~gues.~~ ATP analogues substituted at the C2 (87) or C8 (88) positions with electrondonating groups such as ethers, thioethers or amines have been synthesised and evaluated for their potency at inducing P2Y 1 receptor mediated activation of the phospholipase C and subsequent intracellular Ca2+ release.70 These analogues were also evaluated for their chemical stability to the hydrolytic nucleoside triphosphate diphosphohydrolase enzyme^.^' Adenine derivatives

142

Organophosphorus Chemistry 0

0

0

I

OH

f0 NH

/

\

0-P-0-P-0

0

I

OH

0

R= HO

"'j=,

-0,1

0-

r r

0

0,I

b N

4M' 0-

0

0,I

0-

F's

0

tN?+++sR

H d

'OH

(86a) R = (CH2)5Me (86b) R = C H ~ C H ~ ( C G H ~ ) N O ~ ( 8 6 ~R ) = CH2Ph

(87a) R = -O(CH2)3Me,n = 1 (87b) R = -S(CH2)3Me, n = 1 (87c) R = -O(CH2)3Me, n = 3 (87d) R = -S(CH2)3Me,n = 3

(88a) R = -O(CH2)3Me,n = 1 (88b) R = -S(CH2)3Me,n = 1 (88c) R = -O(CH2)3Me, n = 3 (88d) R = -S(CH2)3Me,n = 3

that contained two symmetrical phosphate or phosphonate groups and incorporated diverse side-chains (89-9 1) have been prepared and evaluated as P2Y 1 antagonist^.^^ Numerous bisphosphate derivatives of known constrained carbocyclic 2'-deoxyadenosine analogues and non-glycosyl linkage containing

143

4: Nucleotides and Nucleic Acids MeHN

MeHN

H203P0 H203P0

H N v c H 2 p 0 3 H :

CH2P03H2 (89a) R = R’ = H, X = (CH2)2

(91)

(90)

(89b) R = H, R’ = CI, X = (CH2)2

(89c) R = Me,R’ = H, X = (CH2)2 (89d) R = Me, R’ = CI,X = (CH&

(89e) R = Me, R’ = H, X = (CH2)2 (899 R = Me, R’ = H, X = (CH2)3 (899) R = Me, R’ = H, X = (CH2)4 (89h) R = Me, R’ = H, X = (CH2)S (891) R = Me, R’ = H, X = CH2CH=CHCH2 (89j) R = Me, R’ = H, X = CH2CH=CHCH2

MeHN R=

I

(NHc)$-O gP3O

(929 R = H, n = 1 (929) R = H, n = 2 (92h) R = H, n = 3

(921)

144

Organophosphorus Chemistry

nucleoside analogues (92) have also been synthesised in order to explore the role of sugar puckering in P2Y receptor r e ~ o g n i t i o n . ~ ~ Two conformationally locked ‘cyclonucleotides’ with fixed glycosidic bond linkages (93), (94) have been synthesised in an attempt to determine whether purino-receptors display conformation-based selectivity to ATP with regard to the orientation of the purine ring in relation to the ribose residue.74Selective agonists of the P2X receptor have been synthesised as prototypes of selective drugs for cardiac disorders mediated by P2 receptors. Their structure was based on a ‘mini-nucleotide’ scaffold that is lacking the ribose moiety and possesses a modified purine ring, (95). These molecules are the first non-ATP based P2X receptor agonists to be reported.75 The syntheses of the 5’-phosphoramidates and 5’-diphosphates of 2’4-allylfl-D-arabinofuranosyl-uracyl, -cytosine and adenine (96) have been described. 0

-0

HO/

(93)

(94)

Me

(95a) R = H, n = 2,m = 1 (95b) R = SPh, n = 2, m = 1 (9%) R = H, n = 3, m = 1 (95d) R = SPh, n = 3, m = 1 (95e) R = H, n = 2, m = 3 (959 R = SPh, n = 2, m = 3 (959) R = H, n = 3, m = 3 (95h) R = SPh, n = 3, m = 3

(95) R = OEt, m = 1 (95j) R = SPh, m = 1 (95k) R = CI,m = 1 (951) R = OEt, m = 3 (95m) R = CI, m = 3

These nucleotide analogues have been evaluated for inhibition of the nucleotide reductase enzymes but exhibited no activity.76 In order to develop a purification procedure of thymidine 5’-diphosphateglucose-4,6-dehydratase based on affinity chromatography, novel activated thymidine diphosphate analogues that display high affinity for the dehydratase have been synthesised. These diphosphate analogues have been derived from

4: Nucleotides and Nucleic Acids

145 R1

(974

Me

R2

0 rc FP-0 O-Li+

R3

oo-

H

H

R30 H

thymidine (97), 2-deoxy-uridine (98) and -cytidine (99), and in some cases the pyrophosphate moiety was either replaced by a methylene diphosphonate (97b) or phosphoryl hydroxyacetic acid (97a) moiety. These modified nucleotides were acting as inhibitors of the dehydratase and displayed similar affinity for the enzyme as thymidine 5’-diphosphate itself.77 Novel fluorescent ATP analogues where the two tertiary carbons of the etheno-moiety of N1,N6-ethenoadenosine have been modified by the introduction of a p-nitro or a p-amino-phenyl group and a hydroxy moiety (100) have been prepared via a Kornblum oxidation reaction and imidazole formation. These compounds exhibited relative stability towards type I1 A T P D ~ s ~ . ~ ~ The N6-modified adenosine and CS-modified uridine triphosphate derivatives (101) and (102) containing a highly reactive aminooxy moiety have been

Organophosphorus Chemistry

146 R

HO

OH

(100a) R = NO2, n = 1 , 2, 3 (100b) R = NO2, NH2, n = 1, 2, 3

incorporated into a 330mer fragment, which was then labelled by reaction with an aldehyde fluorophore derived from fluorescein thiourea. 79 The same research group synthesised two other nucleoside triphosphates bearing a similar linker incorporating a terminal methyl ketone group (103). These novel compounds have been used for enzymatic incorporation into RNA fragments and selective post-labelling by a fluorescein derivative containing an aminooxy group. The nucleoside triphosphates were labelled with fluorescein to evaluate the coupling reaction between the methyl ketone and aminooxy fluorescein derivative ( 104).80 Novel 2’,3’-deoxy fluorescent 3’Gbranched thymidine 5’-triphosphate analogues have been prepared and employed as potential terminators in DNAsequencing reactions. The amino-nucleotide derivatives (109, (106) have been dye-labelled at the aliphatic amino-group with the oxazine dye JA242.*’ The 3’-thioamido-modified 2’,3’-deoxy-nucleoside triphosphates (107) and the dye-linked congeners (108) have been synthesised from protected AZT using Lawesson’s reagent, but failed as chain terminators in DNA sequen3’-deoxy-3’-isothiocyacing.82Unlike (107)’ 3’-deoxy-3’-isocyanato-thymidine, natothymidine and their JA242-dye derivatives (109), prepared from AZT using solid supports have been successful reagents in DNA incorporation. Similarly, d-dye-labelled dideoxycytidine 5’-triphosphate (1 10) has been synthesised and used as substrate by DNA sequencing enzymes.83 The dye-labelled analogue of dideoxyadenosine triphosphate, (1 11) has been synthesised and shown to terminate the syntheses of DNA when catalysed by terminal transferases and DNA polymerases, thus allowing DNA detection by time-resolved fluore~cence.~~ Treatment of 5’-O-TBDMS-2’,3’-dideoxyadenosine with phenoxycarbonyltetrazole followed by N-trifluoroacetyl-1,6-diaminohexane yielded the 6-N-carbamoyl derivative, which was then deprotected, phosphorylated and finally dye-labelled at the aliphatic amino group with the fluorescent dye JA242. Two series of modified AZT polyphosphate metabolites (1 12) and (1 13) have been synthesised in order to raise specific antibodies for the development of highly sensitive titration kits for the intracellular metabo-

4: Nucleotides and Nucleic Acids

147

; ; ;&NLt

0-

0-

0-

-0,III ,o, III /O\III ,o

HO

o \0~ / o0, p \ ~0-/ o y & II

0

I1

0

ANY

-0,1

0 HO’

OH

& I s &Iyy 0-

0-

O\I,O,I

0-

0

HO

(103b) B =

0

HO

OH

I

0

OH

Organophosphorus Chemistry

148

0

p3012-Y i R1

R

(105a) R = N3

(106a) R’ = -(CH2)3CONH(CH2)6NH2

(105b) R = NH2

(106b) R1 = -(CH2)3CONHCH2CH2NH2

( 1 0 5 ~R ) = NHR~

(106c) R1 = -(CH2)3CONH(CH2)6NHR2 (106d) R’ = -(CH2)3CONHCH2CH2NHR2

0

p30

R (107a) R = ‘Pr (107b) R = F ~ O C N H ( C H ~ ) ~ ( 1 0 7 ~R ) = (CH2)5NH2

p30104-w (109a) X = 0 (109b) X = S

(IlOa)n=l (110b)n=3

4: Nucleotides and Nucleic Acids

149

lites of AZT. A methylenebis-phosphonate group mimicked the pyrophosphate moiety in AZT-DP and AZT-TP analogues. An amino-linker was introduced on the base to facilitate anchoring of the compounds to carrier proteins prior to immunisation and to promote an immune response specific to the phosphate mimic moiety and the non-natural sugar. Novel mimics of nucleoside 5’-triphosphate modified at the glycone and at all three phosphate residues (1 14) have been synthesised and studied for their stability in blood serum, properties towards DNA polymerases and potential antiviral activities. These compounds only bear an enzymatically labile anhydride bond between the a and the P-phosphorus atoms. Their synthesis has been reported to employ phosphorylphosphonate key intermediates prepared by reacting the appropriate phenyl or methyl isopropyl chlorophosphonates with diethyl difluoromethylphosphonate and LDA. All compounds demonstrated high biological stability and the guanosine derivative (1 14e) acted as potent reverse transcriptase inhibitor^.^^ Novel 2’-modified nucleoside triphosphate derivatives incorporating imidazole, amino or carboxylate pendant groups attached to the 5-position of pyrimidine base through alkynyl and alkyl spacers (1 15) have been synthesised. In one reported procedure, the appropriately protected modified nucleoside was phosphorylated with P0Cl3 in triethylphosphate in the presence of 1,8bis(dimethy1amino)naphthalene. The phosphorochloridate intermediate was then condensed in situ with tri-n-butylammonium pyrophosphate to yield the protected triphosphate analogue that was then deprotected. In another

Organophosphorus Chemistry

150 R1

R,I

OH

OH

OH

P’

P II 0

0

II

X,I,O,I

0

P-0

II

(114a) R’ = NH2, R2 = H, X = CF2, R = OH (1 14b) R’ = NH2, R2 = H, X = 0, R = Ph (114c) R’ = NH2, R2 = H, X = CH2, R = Ph (1 14d) R’ = OH, R2 = NH2, X = CF2, R = Me (114e) R1 = OH, R2 = NH2, X = CF2, R = Ph

(115a) R = -CCCH2NH2, R1 = OMe (1 15b) R = -CCCH2NH2, R’ = F (115c) R = -(CH2)3NH2,R’ = OMe (115d) R = -(CH2)3NH2,R’ = F (115e) R = -CCCH2NHlmmAA, R’ = OMe (1 159 R = -CCCH2NHlmmAA, R’ = F (1 15g) R = -(CH2)3NHlmmAA, R’ = OMe (1 15h) R = -(CH2)3NHlmmAA, R1 = F (115i) R = -CCCH2NHlmmAADPC,R’ = OMe (115j) R = -CCCH2NHlmmAADPC,R’ = F (1 15k) R = -(CH2)3NHlmmAADPC,R’ = OMe (1 151) R = -(CH2)3NHlmmAADPC,R1 = F (115m) R = -(CH2)3NHCOCH(NH2)CH2COOH,R’ = F (1 1511) R = -CH=CHCOOH, R = F

HOOCd

N

I

H

HO (1150)

F

HO

F

(1’5P)

reported procedure, phosphorylation carried out using 2-chloro-4H- 1,3,2benzodioxaphosphorin-4-onewas followed by pyrophosphate addition and oxidation to afford the desired triphosphate esters.86 A non-enzymatic RNA-capping reagent has been described. Its synthesis

4: Nucleotides and Nucleic Acids

151 R’

L

HO

N

OH

(116a) R’ = NH2, R2 = H, n = 0 (116b) R’ = NH2, R2 = H, n = 1 (116c) R’ = OH, R2 = NH2, n = 0 (116d) R’ = OH, R2 = NH2, n = 1

0 HO,

,OH

i-\

H2N&N,

0-

OO ,, I, O . I0,\ OI\I P

19II ..

Me Me

HO,

000- 0 0I 0 0,

P’

‘fPNH2

‘P’

L’I I ‘p’0I I ..

0

0

0

0

..

0

GHO HO

N

OH‘ OH

,OH \

,

used adenosine and 7-methylguanosine 5’-diphosphate imidazolides prepared from imidazole and the corresponding nucleoside diphosphates. The phosphorimidazolide derivatives (1 16) were then reacted with 7-methylguanosineor adenosine- monophosphate in neutral aqueous conditions in the presence of Mn2+ to yield (1 17) and (1 18) respectively. Unlike chemoenzymatic synthesis, this synthesis is carried out in neutral aqueous solution, thus avoiding the complicated procedure to solubilise the reagents in anhydrous organic solvent~.~~ Phosphorothioate and boranophosphate linkages introduced into DNA or RNA using nucleoside 5’-[a-thioltriphosphates and nucleoside 5’-[a-borano]triphosphates are more resistant to exo- and endonucleases than normal 3’3’ phosphodiester linkages. Combination of the two modifications yielded a novel non-bridging-disubstituted chiral a-triphosphate nucleoside, namely the thymidine 5’-[a-P-borano, a-P-thio] triphosphate (1 19).” The synthesis was the modification of a procedure developed for the synthesis of nucleoside triphosphates and previously reported by the group. Novel bases for the genetic alphabet have been synthesised and evaluated

Me-c;z

Organophosphorus Chemistry

152

HO-P-0-P-0-P-0 0 II 0 II I

I

OH

OH

s II

AH3-Y HO

for pairing capabilities. Two of these bases are the triphosphates of 2’deoxyisoguanosine (1 20) and 2’-deoxy-5-methylisocytidine (12 1). The introduction of a methyl group at the 5-position of 2’-deoxyisocytidine remarkably improved on the triphosphate’s stability.89 The triphosphate ester of 2’deoxyribosyl-4-methylpyridine-2-one(122), in which the amino group of 3deaza-cytidine has been substituted with a methyl group, has also been prepared and evaluated for base-pairing ability.” Finally, the 5’-triphosphate2’-deoxyribosyl derivative of 2-aminopurine (123) has been synthesised and examined for its utility in mutagenesis.’’ HZN

\

(121a) R = H (121b) R = Me

4-09P30

A novel class of non-isopolar but isosteric analogues of diadenosine polyphosphates (1 24) has been prepared from N6,N6, 02’, 03’-tetrabenzoylade03’nosine 3’-0-(2-thiono-1,3,2-oxathiaphospholane) and from @,I@, 02’, tetrabenz~yladenosine.~~ Treatment of the appropriate polyo1 with N6,N6,02’, 03’-tetrabenzoyladenosine 3’-O-(2-thiono-l,3,2-oxathiaphospholane) in the presence of DBU yielded (1 24). Alternatively, phosphorothioylation of the polyol using 2-chloro- 1,3,2-0xathiaphospholane followed by sulfurisation yielded an intermediate that was then condensed with N6,N6,02’,03’-tetrabenzoyladenosine in the presence of DBU to yield the isosteric ApnA mimics. Only preliminary evaluations of these novel analogues

4: Nucleotides and Nucleic Acids

153

R=

(124a) RCH2CH(OH)CH2R (124b) RCH2CH(OP(0)OS2-)CH2R (12 4 ~ RCH2CH(OP(0)OS23CH2R ) (124d) C(CH2R)d (124e) RCH2CHRCH2R (1249 (RCH2)&CH20P(0)OS2(1249) (RCH2)2C(CH20P(0)OS2-)2 (124h) [(RCH2)(OP(0)OS2-)CHk (124i) RCH2P(0)O-CH2R

as potential inhibitors of Ap3A and Ap,A hydrolases and as inhibitors of platelet aggregation have been reported. References 1 2 3 4 5

6 7 8 9 10 11 12 13

S. M. Graham and S. C. Pope, Org. Lett., 1999, 1,733. M. Taktakishvili and V. Nair, Tetrahedron Lett., 2000,41, 7173. Y. L. Qiu, R. G. Ptak, J. M. Breitenbach, J. S. Lin, Y. C. Cheng, J. C. Drach, E. R. Kern and J. Zemlicka, Antiviral Res., 1999,43, 37. H. P. Guan, M. B. Ksebati, Y. C. Cheng, J. C. Drach, E. R. Kern and J. Zemlicka, J. Org. Chem., 2000,65, 1280. A. Q. Siddiqui, C. McGuigan, C. Ballatore, F. Zuccotto, I. H. Gilbert, E. De Clercq and J. Balzarini, J. Med. Chem., 1999,42,4122. C. L. F. Meyers, L. P. Hong, C. Joswig and R. F. Borch, J. Med. Chem., 2000, 43,4313. C. L. F. Meyers and R. F. Borch, J. Med. Chem., 2000,43,43 19. C. McGuigan, M. J. Slater, N. R. Parry, A. Perry and S. Harris, Bioorg. Med. Chem. Lett., 2000, 10, 645. J. R. Beadle, G. D. Kini, K. A. Aldern, M. F. Gardner, K. N. Wright, R. J. Rybak, E. R. Kern and K. Y. Hostetler, Nucleosides, Nucleotides and Nucleic Acids, 2000,19,471. W. Q. Zhou, S. Upendran, A. Roland, Y. Jin and R. P. Iyer, Biourg. Med. Chem. Lett., 2000, 10, 1249. H. Brachwitz, J. Bergmann, Y. Thomas, T. Wollny and P. Langen, Biuorg. Med. Chem., 1999,7,1195. C. Pierra, J. L. Imbach, E. De Clercq, J. Balzarini, A. Van Aerschot, P. Herdewijn, A. Faraj, A. G. Loi, J. P. Sommadossi and G. Gosselin, Antiviral Res., 2000,45, 169. C. Meier, T. Knispel, E. De Clercq and J. Balzarini, J. Med. Chem., 1999, 42, 1604.

154 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

Organophosphorus Chemistry

T. Moriguchi, T. Yanagi, T. Wada and M. Sekine, J. Chem. SOC.,Perkin Trans. I , 1999, 1859. T. Moriguchi, N. Asai, T. Wada, K. Seio, T. Sasaki and M. Sekine, Tetrahedron Lett., 2000,41, 5881. S. D. Lindell, B. A. Moloney, B. D. Hewitt, C. G. Earnshaw, P. J. Dudfield and J. E. Dancer, Bioorg. Med. Chem. Lett., 1999,9, 1985. T. I. Kalman, Z. Nie and A. Kamat, Bioorg. Med. Chem. Lett., 2000,10, 391. K. Felczak, A. Miazga, J. Poznanski, M. Bretner, T. Kulikowski, J. M. Dzik, B. Golos, Z. Zielinski, J. Ciesla and W. Rode, J. Med. Chem., 2000,43,4647. A. J. Lunato, J. H. Wang, J. E. Woollard, A. K. M. Anisuzzaman, W. H. Ji, F. G. Rong, S. Ikeda, A. H. Soloway, S. Eriksson, D. H. Ives, T. E. Blue and W. Tjarks, J. Med. Chem., 1999,42, 3378. A. Kers, T. Szabo and J. Stawinski, J. Chem. SOC.,Perkin Trans. I , 1999,2585. S. Kralikova, M. Budesinsky, M. Masojidkova and I. Rosenberg, Tetrahedron Lett., 2000,41, 955. A. Arnone, P. Bravo, M. Frigerio, A. Mele, B. Vergani and F. Viani, Eur. J. Org. Chem., 1999,2149. T. Yokomatsu, Y. Hayakawa, K. Suemune, T. Kihara, S. Soeda, H. Shimeno and S. Shibuya, Bioorg. Med. Chem. Lett., 1999,9,2833. T. Yokomatsu, Y. Hayakawa, T. Kihara, S. Koyanagi, S. Soeda, H. Shimeno and S. Shibuya, Bioorg. Med. Chem., 2000,8,2571. T. Yokomatsu, T. Yamagishi, K. Suemune, H. Abe, T. Kihara, S. Soeda, H. Shimeno and S. Shibuya, Tetrahedron, 2000, 56,7099. A. Holy, J. Gunter, H. Dvorakova, M. Masojidkova, G. Andrei, R. Snoeck, J. Balzarini and E. De Clercq, J. Med. Chem., 1999,42,2064. A. L. Jeffery, J. H. Kim and D. F. Wiemer, Tetrahedron, 2000,56,5077. X. P. Zheng and V. Nair, Tetrahedron, 1999,55, 11803. J. H. Hah, J. M. Gil and D. Y. Oh, Tetrahedron Lett., 1999,40, 8235. A. Esteban-Gamboa, J. Balzarini, R. Esnouf, E. De Clercq, M. J. Camarasa and M. J. Perez-Perez, J. Med. Chem., 2000,43,971. A. Eleuteri, D. C. Capaldi, D. L. Cole and V. T. Ravikumar, Nucleosides and Nucleotides, 1999, 18, 1879. H. Lang, M. Gottlieb, M. Schwarz, S. Farkas, B. S. Schulz, F. Himmelsbach, R. Charubala and W. Pfleiderer, Helv. Chim. Acta, 1999,82,2172. C. Strassler, N. E. Davis and E. T. Kool, Helv. Chim. Acta, 1999,82,2160. C. A. Buhr, M. D. Matteucci and B. C. Froehler, Tetrahedron Lett., 1999, 40, 8969. C. M. Prusiewicz, R. Sangaiah, A. Gold and L. M. Ball, Polycyclic Aromatic Compd., 1999,17, 11. T. P. Prakash, M. Manoharan, A. N. Kawasaki, E. A. Lesnik, S. R. Owens and G. Vasquez, Org. Lett., 2000, 2, 3995. B. Allart, R. Busson, J. Rozenski, A. Van Aerschot and P. Herdewijn, Tetrahedron, 1999,55,6527. A. Chworos, L. A. Wozniak and W. J. Stec, Tetrahedron Lett., 2000,41, 1219. T. J. Baker and D. F. Wiemer, Tetrahedron, 2000,56,3127. R. D. Marwood, S. Shuto, D. J. Jenkins and B. V. L. Potter, Chem. Commun., 2000,2 19. H. Abe, S. Shuto and A. Matsuda, J. Org. Chem., 2000,65,4315. H. Abe, S. Shuto and A. Matsuda, Tetrahedron Lett., 2000,41,2391. M. D. Burkart, S. P. Vincent and C. H. Wong, Chem. Commun., 1999, 1525.

4: Nucleotides and Nucleic Acids

44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

60 61 62 63 64 65 66 67 68 69 70 71 72 73

155

G. Dufner, R. Schworer, B. Muller and R. R. Schmidt, Eur. J. Org. Chem., 2000, 1467. H. Schott, P. S. Ludwig, A. Immelmann and R. A. Schwendener, Eur. J. Med. Chem., 1999,34,343. I. Kers, J. Stawinski, J. L. Girardet, J. L. Imbach, C. Perigaud, G. Gosselin and A. M. Aubertin, Nucleosides and Nucleotides, 1999,18, 2317. T. Miyashita, K. Yamada, K. Kondo, K. Mori and K. Shinozuka, Nucleosides, Nucleotides and Nucleic Acids, 2000, 19, 955. A. Wilk, A. Grajkowski, L. R. Phillips and S. L. Beaucage, J. Am. Chem. Soc., 2000,122,2149. Y. X. Lu and G. Just, Tetrahedron, 2000,56,4355. J. L. Lin and B. R. Shaw, Chem. Commun., 1999, 1517. L. Y. Hsu and K. T. Yang, Nucleosides and Nucleotides, 1999,18,2031. M. Taktakishvili, N. Neamati, Y. Pommier, S. Pal and V. Nair, J. Am. Chem. SOC.,2000,122, 5671. I. Kers, J. Stawinski and A. Kraszewski, Tetrahedron, 1999,55, 11579. F. Burlina, A. Favre, J. L. Fourrey and M. Thomas, Eur. J. Org. Chem., 2000, 633. S. Velazquez, V. Tunon, M. L. Jimeno, C. Chamorro, E. De Clercq, J. Balzarini and M. J. Camarasa, J. Med. Chem., 1999,42, 5188. M. D. Burkart, M. Izumi and C. H. Wong, Angew. Chem. Int. Ed., 1999, 38, 2747. H. P. Zhang and T. S. Leyh, J. Am. Chem. SOC.,1999,121,8692. J. Kovensky, M. McNeil and P. Sinay, J. Org. Chem., 1999,64,6202. J. N. Barlow and J. S. Blanchard, Carbohydr. Res., 2000,328,473. Y. E. Tsvetkov and A. V. Nikolaev, J. Chem. Soc., Perkin Trans. I , 2000, 889. A. Schafer and J. Thiem, J. Org. Chem., 2000,65,24. T. Kuzuyama, M. Takagi, K. Kaneda, T. Dairi and H. Seto, Tetrahedron Lett., 2000,41,703. J. L. Lin, K. Z. He and B. R. Shaw, Helv. Chim. Acta, 2000,83, 1392. J. L. Lin and B. R. Shaw, Tetrahedron Lett., 2000,41,6701. M. Fukuoka, S. Shuto, N. Minakawa, Y. Ueno and A. Matsuda, Tetrahedron Lett., 1999,40, 5361. M. Fukuoka, S. Shuto, N. Minakawa, Y. Ueno and A. Matsuda, J. Org. Chem., 2000,65,5238. Y. Sumita, M. Shirato, Y. Ueno, A. Matsuda and S. Shuto, Nucleosides, Nucleotides and Nucleic Acids, 2000, 19, 175. S. Kralikova, M. Budesinsky, M. Masojidkova and I. Rosenberg, Nucleosides, Nucleotides and Nucleic Acids, 2000, 19, 1159. B. Fischer, A. Chulkin, J. L. Boyer, K. T. Harden, F. P. Gendron, A. R. Beaudoin, J. Chapal, D. Hillaire-Buys and P. Petit, J. Med. Chem., 1999,42,3636. E. Halbfinger, D. T. Major, M. Ritzmann, J. Ubl, G. Reiser, J. L. Boyer, K. T. Harden and B. Fischer, J. Med. Chem., 1999,42,5325. F. P. Gendron, E. Halbfinger, B. Fischer, M. Duval, P. D’Orleans-Juste and A. R. Beaudoin, J. Med. Chem., 2000,43,2239. Y. C. Kim, C. Gallo-Rodriguez, S. Y. Jang, E. Nandanan, M. Adams, T. K. Harden, J. L. Boyer and K. A. Jacobson, J. Med. Chem., 2000,43,746. E. Nandanan, S. Y. Jang, S. Moro, H. 0. Kim, M. A. Siddiqui, P. Russ, V. E. Marquez, R. Busson, P. Herdewijn, T. K. Harden, J. L. Boyer and K. A. Jacobson, J. Med. Chem., 2000,43,829.

156 74 75 76 77 78 79 80

81 82 83 84 85

86 87 88 89 90 91 92

Organophosphorus Chemistry

G. Tusa and J. K. Reed, Nucleosides Nucleotides and Nucleic Acids, 2000,19, 805. B. Fischer, R. Yefidoff, D. T. Major, I. Rutman-Halili, V. Shneyvays, T. Zinman, K. A. Jacobson and A. Shainberg, J. Med. Chem., 1999,42,2685. S. Manfredini, P. G. Baraldi, E. Durini, S. Vertuani, J. Balzarini, E. De Clercq, A. Karlsson, V. Buzzoni and L. Thelander, J. Med. Chem., 1999,42, 3243. A. Naundorf and W. Klaffke, Carbohydr. Res., 1999,318,38. B. Fischer, E. Kabha, F. P. Gendron and A. R. Beaudoin, Nucleosides, Nucleotides and Nucleic Acids, 2000,19, 1033. E. Trevisiol, E. Defrancq, J. Lhomme, A. Laayoun and P. Cros, Eur. J. Org. Chem., 2000,21 1 . E. Trevisiol, E. Defrancq, J. Lhomme, A. Laayoun and P. Cros, Tetrahedron, 2000,56,6501. T. Schoetzau, U. Koert and J. W. Engels, Synthesis - Stuttgart, 2000, 707. C. Wojczewski, K. Schwarzer and J. W. Engels, Helv. Chim. Acta, 2000,83, 1268. K. Stolze, U. Koert, S. Klingel, G. Sagner, B. Wartbichler and J. W. Engels, Helv. Chim. Acta, 1999,82, 131 1. T. Schoetzau, S. Klingel, R. Wartbichler, U. Koert and J. W. Engels, J. Chem. SOC.,Perkin Trans. I , 2000,9, 141 1. A. V. Shipitsin, L. S. Victorova, E. A. Shirokova, N. B. Dyatkina, L. E. Goryunova, R. S. Beabealashvilli, C. J. Hamilton, S. M. Roberts and A. Krayevsky, J. Chem. Soc., Perkin Trans. 1, 1999, 1039. J. Matulic-Adamic, A. T. Daniher, A. Karpeisky, P. Haeberli, D. Sweedler and L. Beigelman, Bioorg. Med. Chem. Lett., 2000, 10, 1299. H. Sawai, H. Wakai and A. Nakamura-Ozaki, J. Org. Chem., 1999,64,5836. J. L. Lin and B. R. Shaw, Chem. Commun.,2000,2115. S. C. Jurczyk, J. T. Kodra, J. H. Park, S. A. Benner and T. R. Battersby, Helv. Chim. Acta, 1999,82, 1005. I. Hirao, T. Ohtsuki, T. Mitsui and S. Yokoyama, J. Am. Chem. Soc., 2000, 122, 61 18. F. Hill, I. R. Felix, M. G. McDougall, S. Kumar, D. Loakes and D. M. Brown, Nucleosides and Nucleotides, 1999,18,2677. J. Baraniak, E. Wasilewska, D. Korczynski and W. J. Stec, Tetrahedron Lett., 1999,40,8603.

5

Ylides and Related Species BY N. BRICKLEBANK

1

Introduction

The past year has seen continued interest in the structural nature of phosphorus ylides with the aim of gaining greater insight into their stabilities, electronic distributions and conformations, which ultimately affect the reactivities of these species. However, there have been fewer mechanistic studies of the Wittig reaction itself although several studies into the closely related azaWittig and Horner-Wadsworth-Emmons modifications have appeared. An interesting new route to ylides, with clear synthetic potential, utilises the reaction of stable phosphanylcarbenes with phosphines, and a novel route to fullerene derivatives of ylides involves the reaction of C60 with tertiary phosphines and electron deficient acetylenes. Investigations into the coordination chemistry of ylides and iminophosphoranes continue apace, an interesting development being the use of iminophosphorane fragments as the pendant arms on new ‘pincer’ ligands which help to stabilise unusual samarium and zirconium carbene complexes. Parallel kinetic resolution is a developing area of asymmetric synthesis which facilitates the simultaneous conversion of both enantiomers of a racemic mixture into useful products. Pedersen and co-workers have recently reported the first Horner-Wadsworth-Emmons procedure that allows the parallel kinetic resolution of racemic aldehydes. Lastly, it is unusual for us to report new advances in teaching practice in this chapter, but we can do so now as Chymol and Eastes have developed a Wittig reaction as a high schoollundergraduate experiment using microchemistry techniques. This and the other discoveries highlighted here are discussed in greater detail in the relevant sections below. 2

Phosphonium Ylides

2.1 Theoretical, Structural and Mechanistic Studies of Phosphorus Ylides and the Wittig Reaction. - In contrast to previous years there are no significant new theoretical or mechanistic studies to report. However, investigations into the structural nature of ylides continue to provide much of interest. Although the crystal structures of many phosphorus ylides have been Organophosphorus Chemistry, Volume 32 0The Royal Society of Chemistry, 2002 157

Organophosphorus Chemistry

158

determined crystallographically over the years, there have been far fewer studies of the charge-density distribution which can be used to provide an insight into the bonding in ylides. With this in mind, Yufit et al. have reported a topological analysis of the charge density distribution in triphenylphosphonium benzylide (l).' The analysis provides an understanding of the role of the phenyl groups bonded to the phosphorus in delocalising the positive charge, and how the inter- and intra-molecular contacts are responsible for the confirmation and solid state packing of the molecules. It is well established that phosphorus ylides containing a carbonyl group are stabilised significantly, and this can be attributed to the delocalisation of the negative charge on the ylidic carbon atom onto the carbonyl function resulting in the formation of enolate species (2) and (3). Moreover, such delocalisation can lead to the formation of distinct geometrical isomers. The most effective delocalisation is achieved when the P-C and C-0 moieties are planar but the adoption of a syn (2) or anti (3) conformation depends on the other R groups bonded to the phosphorus and carbon atoms. Aitken et al. have carried out a detailed study of the solid state conformation of 0x0 stabilised ylides and have reported the structures of four ylides (4), (9,(6) and (7) (the synthesis of which OMe "-0

ph3p54 P

0

h

3

Ph3P P

c

p h 3 p 3 P P h 3

Me

Ph

Me0

ph-s

PPh:

0

have been reported previously), that contain linear arrays of contiguous P=C and C=O functions.2 Trioxo ylide (4) has the ylide and carbonyl functions in a syn conformation, whereas (9,which is stabilised by two identical 1,2-diketone groups, has one of the carbonyl groups syn to the ylide function and the other anti. Nonetheless, the extent of delocalisation towards the two carbonyl functions in (9,as measured by the bond lengths is equal and thus appears to be independent of the conformation. The structure of bis ylide (6) has one of the ylide functions with both adjacent carbonyls syn whereas the other ylide function has one syn and one anti carbonyl. Bis ylide (7) contained two molecules in the unit cell; one molecule has one ylide function with two syn carbonyls and the other with one syn and one anti carbonyl. In contrast, the second molecule has both ylide functions with all syn carbonyls. The overall

5: Ylides and Related Species

159

“‘eMe +

- O w p

Me

I

Et

(9)a R = 4-MeC6H4bR=Ph

conclusion of the study was that crystal-packing forces are often sufficient to over-ride the normal preference for syn conformation. Other stabilised ylides that have been structurally characterised recently and (9a). Carboninclude (8), which also adopts a syn enolate conf~rmation,~ 13 NMR analysis of (9a) and (9b) show extensive delocalisation of the negative ~harge.~ As might be expected, the X-ray crystal structure of triphenylphosphoranylidene-2-propanone (10) reveals the formation of a web of intra- and intermolecular hydrogen bonds. An EPR/ENDOR study of X-irradiated single crystals of (10) shows that upon radiolysis the molecules undergo a drastic reorientation about the ylidic P-C bond as radical cation (11) is f ~ r m e d . ~ HO Ph

Me

X-ray irradiation

.

D

Phosphorus-3 1 and carbon- 13 CPMAS NMR spectroscopy together with ab initio calculations at the hf/6-31g* levels have been used to provide information on the structure and electronic distribution of imino(tripheny1)phosphorane (12).6 In an attempt to increase the reactivities of diarylmethylene(tripheny1)phosphorane ylides, compounds (13) and (14) have been prepared and studied by

160

Organophosphorus Chemistry

combinations of 31PNMR spectroscopy and MO calculation^.^ It was hoped that by tethering the phenyl rings together in (13) and (14) that delocalisation of the ylidic negative charge onto the phenyl rings would be suppressed. However, the Wittig reactivity of (13) and (14) was still limited, primarily because the electron density at the ylidic carbon is still too low. The synthesis, structures and reactivity of a series of silicon-containing organophosphorus betaines which have a P-C-Si-S or P-C-C-S skeleton have been reported and the changes in the geometric parameters of the betaines depending on the substituents at the phosphorus, carbon and silicon atoms analy~ed.~'~ 2.2 The Synthesis and Characterisation of Phosphonium Ylides. - Bertrand and co-workers have reported the instantaneous quantitative formation of phosphorus ylides (15 ) when stable phosphanylcarbenes are treated with phosphines (Scheme 1).lo Ylides (15 ) are very readily oxidised by atmospheric

PhMe, Ar

..

(15 )

(16a) R' = Me, R = cHex2N

CP(CO)~MO,~/MO(CO)~CP / p\

..P

(17)

R = cHex2N; R'3 = Me3, Et3, Me2Ph, MePh2, Ph3

Scheme 1

oxygen resulting in the formation of ylide-phosphine oxide (16). The structure of (16a) was determined by X-ray crystallography. The reaction of the phosphorus lone pairs in the P2-containing complex (1 7) with stable carbenes leads to p-q'-q3-diphosphene complexes (18), which can be considered as containing an ylidic four 7c electron, four-membered, heterocycle. This new route to ylides, and ylidyl-heterocycles clearly has exciting potential. Schmidpeter and co-workers continue to report their thorough studies into the reactions of ylidyl phosphines and chlorophosphines with trimethylsilylphosphines. Some of their more significant results are summarised in Scheme 2. Generally, treatment of ylidyl chlorophosphines (19) with trimethylsilylphosphines proceeds with the elimination of chlorotrimethylsilane to yield ylidyl diphosphines (20) and (21). The reaction of (19) with lithium diphos-

5: Ylides and Related Species

161 Ph PhsPAP-

PPh2

R = Ph

PPh2

(20)

R Ph3P

R = Ph

A’

+R2R3PSiMe3

Apf R

b

R2 I R ,3‘

Ph3P

A’ ,

(1

R = Ph

\

R2 = R3 = Ph, SiMe3

+LiCH(PPh2)2

R‘ = Me, Et CH2Cl

k’ (22) R’ = Me, Et, CH2CI

A

R’ = CH2CI

+

Ph3P

pTiph2 I

R’

Ph

(25) R = Me, R’ = Ph R = Ph, R’ = Me

Scheme 2

phinyl amide or lithium diphosphinyl methanide results in the formation of ylidyl diphosphinimines (22) or ylidyl diphosphonium ylides (23) respectively. Diphosphinimine (22) (R’ = CH2Cl) undergoes cyclisation to give the 1,2,3,5azatriphosphole (24), whereas compounds (23) rearrange to give ylidyl triphosphinyl methanes (25). 1,2,4,5-Tetraphosphinine(26) and 1,2,3,5,6-azatetraphosphinine derivatives (27) and (28) were obtained from the treatment of ylidyl bis(ch1orophosphines) with lithium diphosphinyl amide. The same workers have also investigated the interaction of ylides with phosphorus, arsenic and antimony trihalides. The ylides Ph3P=CH2 and Ph3P=CHMe form 1:1 adducts with all three of these trihalides, which differ in their structural nature depending on the identity of both the parent ylide and the pnicogen

162

Organophosphorus Chemistry

Me Ph3PA

Me SiMe3

AsCI3, C6H6, 0 “C,Ar -Me3SiCI

Ph3PAAsCIz

(30)

(29)

atom. l 2 Treatment of trimethylsilyl ylide (29) with arsenic trichloride results in the formation of dichloroarsanyl ylide (30).l 3 Similarly arsanyl ylides (32) and (33) are obtained from (31) in a stepwise process (Scheme 3). Single crystal structures of compounds (30) and (33) show a transfer of charge from the ylidic moiety to one of the As-Cl bonds, which is significantly longer than the other As-Cl bond, with a concomitant shortening of the As-C bond indicating partial multiple bonding character. Upon prolonged standing, solutions of arsanyl ylide (32) deposited crystals of several oligomers; dimer (34), trimer (35) and tetramer (36). Dimer (34) has a 1,3-diarsetane structure. HCl adds readily to it, without ring-opening, yielding (37). The trimer and tetramer are

+ Ph3P

PPh3 CI-


H

Scheme 3

163

5: Ylides and Related Species

both ionic, the counterion in both cases being AsC14-. The cation of trimer (35) forms a six-membered ring with a delocalised arseniudphosphonium charge. The cation of the tetramer forms a barrelane cage with a phosphonio substituent. The triflic acid-promoted hydrolysis of bis-triphenylphosphonio-isophosphindolide cation (38) has been followed using NMR spectro~copy.'~ No evidence was found for direct phosphorus protonation or alkylation which had previously been postulated. Hanamoto and co-workers have published a detailed report on the synthesis and reactivity of a-fluorovinylphosphonium salt (39), which they had first described in a previous communication. Ylides derived from (39) have been

Q$ +

+

h3

+'PPh3

OTf-

(38)

+

4pPh3*0Tf F -

utilised in the formation of alkenes through subsequent reactions with carbonyl compounds. Triphenylvinylphosphonium salts have been prepared by treating hydroxyalkyltriphenylphosphonium salts with acetyl chloride or oxalyl chloride, Alternatively, the same compounds were obtained in a one-pot procedure from triphenylphosphine, epoxide and acetyl chloride. l 6 Schobert et al. have utilised ketenylidenetriphenylphosphorane(Scheme 4) for the C-acylation of CH-active dicarbonyl compounds including unprotected tetronic acids, 4-hydroxycoumarins, pyrazol-5-ones and P-ketoesters.l 7 The structures of the resulting ylides ( 4 0 4 ) have been thoroughly investigated by NMR and X-ray crystallography. The structure-reactivity interdependencies of these new ylides are also discussed; it was found that those ylides with a widespread conjugation of the n-system such as (40) and (42) do not readily undergo Wittig olefination, whereas those with separated P-keto moieties, e.g. (41), react normally. Cheng and co-workers have reported a unique method for the synthesis of fullerene derivatives of ylides (45) from the reaction of C60 with tertiary phosphines and electron deficient acetylenes.18 All four new ylides show temperature dependent NMR spectra that can be rationalised on the basis of the interchange between two E, 2 isomers. The structure of compound (45a) was determined crystallographically. Other ylides which have been reported include (46), which undergoes

164

Organophosphorus Chemistry

Me Et Et Me Ph Et

(41) n = 1,2

(44) R’

R2

Me Me Ph H Ph Me Ph Ph CH2C02Me Me Scheme 4

cyclocondensations with carboxylic acid chlorides, carbon disulfide and acyl isothio~yanates,~~ and (47) which have been used to prepare pyrazole and thiophene derivatives.20 2.3 Ylides Coordinated to Transition Metals. - Complexes of a-keto-stabilised ylides with early transition metals have been reported by Spannenberg et aL21 The reaction of tetrakis(dimethylamino)titanium(IV) and benzoyltriphenylphosphonium bromide (48) produces complex (49) (Scheme 5) whose structure

5: Ylides and Related Species

+

165

PR'3

PhMe, rt

R Me Me Et Me

(45)a

b

c d

R' Ph C6D5 Ph p-MeC&

(47) R = C02Et, CN, COMe, COPh

(46)

0 (48)

THF, 1 hour, Ph3P-'

H

,Ti-0 Me2N I Br

Scheme 5

was determined crystallographically. Bromination of the titanium occurs simultaneously with the complexation. The ylide coordinates through the carbonyl oxygen and adopts a cisoid arrangement. The P-C bond in (49) is elongated compared to the uncoordinated ylide consistent with the localization of the positive charge on the phosphorus atom. Complexes containing ylides coordinated to early transition metals are found to be very unstable, undergoing complex decompositions in which a dimethylamino group migrates from the starting metal complex to the ylide. For example, the new ylide (50) and phosphine oxide ( 5 1) were obtained from the reaction of acetyltriphenylphosphorane with tetrakis(dimethylamino)titanium(IV) and benzoyltriphenylphosH Ph3P=ClC+CH2 I

U

II

PhZPCH=C:

NMe2 Ph

166

Organophosphorus Chemistry

Ph3P=C:

CH2C12, 2 days, Ar

H ,R

C II

0

Ph (52)a R = Ph bR=Me

Scheme 6

phorane with tetrakis( dimethylamino)zirconium(IV) respectively. Niobium complexes of acet yltr ipheny lphosphor ane and benzoy 1t ripheny1phosphor ane (52), were obtained from the reaction of these ylides with [ 1-phenyl-2(trimethylsilyl)acetylene]niobium(III) chloride (Scheme 6). The binuclear structure of compound (52a) was confirmed by X-ray crystallography which showed that the ylide moieties adopt a transoid conformation. The intramolecular migration of ylide coordinated to iron to a phosphenium centre bonded to the same metal atom has been described.22 As outlined in previous volumes, the chemistry of ylides coordinated to noble metals, particularly palladium, platinum and gold continues to attract most attention. Refluxing (dppm)palladium(II) dichloride [dppm = bis(diphenylphosphino)methane] with alkynes in mixtures of 172-dichloroethane/174-dioxane provides a novel route to palladium-bound alkenyl phosphorus ylide complexes (53) (Scheme 7).23 The reaction represents the

Scheme 7

insertion of an alkyne into a palladium phosphine bond. The choice of solvent for this reaction appears critical, use of non-coordinating polar solvents resulting in no reaction. The mechanism suggested by the authors is nucleophilic attack on a coordinated alkyne by a dangling phosphine group of the dppm molecule. 175-Cyclooctadiene complexes of palladium and platinum undergo nucleophilic attack by carbonyl-stabilised ylides in an exo manner (Scheme S), yielding complexes (54) which are best described as metallated phosphonium salts.24 Mono- and bis-ylide complexes of platinum(II), (55) and (56) respectively, have been obtained from

5: Ylides and Related Species

::

acetone, 24 h,

M Pt Pd Pd

R Ph Ph Tolyl

167

R3P< R ,‘/, CH I

R’ OMe, OEt, NMe, OMe, OEt OMe, OEt

Scheme 8

the reactions of Zeise’s salt or [ (PtC12(C2H4)}2 ] with ketenylidenetriphenylphosph~rane.~~ As part of a wider study of the chemistry of ferrocene derivatives containing organophosphorus groups, Laguna and co-workers have prepared and structurally characterised ylide complex (57).26 Other gold complexes containing coordinated ylides reported include mononuclear species (58), (59) and dinuclear complex (60) which were obtained from the reactions of the ylides or

(57)

(60) L = PPh3; R = Ph, tolyl L = P(C6H4-4-OMe)3;R = tolyl L = AsPh3; R = tolyl

their parent phosphonium salts with a several gold(1) compounds including [AuCl(tht)] (tht = tetrahydrothiophene) and [Au(a~ac)(PR3)].~~ Several new complexes of iminophosphoranes have been reported by Cave11 and co-workers (Scheme 9). Reaction of dimethyl zinc with bis- { trimethylsilylimino-dipheny1phosphorano)methane (6 1) yields zinc complex (62) via elimination of methane.28 Complex (62) did not react with adamantyl nitrile or isonitrile but does undergo nucleophilic addition reactions with hetereroallenes such as carbodiimides and isocyanates. Thus, treatment of (62) with adamantyl isocyanate produces the novel tripodal alkyl zinc complex (63). Iminophosphorane (61) reacts with [ S ~ ( N C Y ~ ) ~ ( T H and F )tetrakis(benzyl)zirconium(IV) ]

Organophosphorus Chemistry

168

Ph2 /SiMe3 P-N, $!n-Me P-N Ph2 ‘SiMe3

ZnMe2 Ar, PhMe, rt, 24 h

I

(62)

H2 C Ph2P’ ‘PPh2 II II N N, SiMe3 Me3Si’

Ph2 /SiMe3 ,P=N,

(611

t

PhMe, Ar, rt, 24 h, then 80 “C, 20 m

Ph

Ph’

SiMe3

AdNCO Ar, PhMe, rt, 24 h

Ph2

\

\

‘SiMe3

(63) Ad = Adamantyl

SiMe3

Ph

Scheme 9

producing the unusual iminophosphorane-carbene complexes (64) and (65) The ‘pincer’ arrangement of the chelating iminophosphorane fragments helps to stabilise the carbene moiety. 2.4 Reactions of Phosphonium Ylides. - 2.4.1 Reactions with Carbonyl Compounds. Standard Wittig olefination procedures continue to provide an invaluable route to alkenes and other unsaturated species. An interesting report by Chemmol and Eastes describes the development of a rapid Wittig reaction between benzyltriphenylphosphonium chloride and 9-anthraldehyde, using microchemistry techniques, for use as a high schoolhndergraduate teaching experiment. Several other developments of the Wittig reaction have been reported. Ochiai and co-workers have previously reported that unstabilised monocarbony1 iodonium ylides can be generated from (2)-(2-acetoxyalk- 1-enyl)phenylh3-iodanes (66) (Scheme 10). The monocarbonyl iodonium ylides are moderately nucleophilic and were found to react with aldehydes to give epoxides exclusively. Thus, the reaction of (66) with aldehydes in THF, in the presence of lithium ethoxide, gives a,P-epoxyketones in good yields, with no formation of Wittig olefination products. These workers have now reported a modification of this procedure which allows the reaction to follow a standard Wittig

5: Ylidesand Related Species

169 MeOH,

R

BF4-

TAcOMe

0

R

&;Ph

-

+

Et3NHBF4-

0

Ji-PPh3 Phl

Ph3PO

0

Scheme 10

olefination pathway, by adding two molar equivalents of triphenylphosphine, changing the reaction solvent to methanol and using triethylamine as the base.32 The authors propose a mechanism (Scheme 10) which involves the in situ conversion of the iodonium ylide into a phosphonium ylide which then reacts with the aldehyde creating the olefin. In an attempt to improve the environmental credentials of Wittig olefination, Russell and Warren have described the synthesis of a range of water/ aqueous base soluble phosphonium salts (67-7 1) and assessed their reactivity towards carbonyl compounds.33The use of D20 as a solvent for the reaction between stable ylides and carbonyl compounds leads to a-deuterated a, 0unsaturated carbonyl compounds.34 A new Wittig protocol involves the simultaneous in situ formation of aldehydes, generated from the spontaneous decomposition of a-amino alcohols, and ylides, formed by deprotonation of alkyltriphenylphosphonium salts, which react together affording 01efins.~~

Organophosphorus Chemistry

170 Ph

Ph

JYkR Ph

Ph

H 0 2 Cy J + R

HO

(67) R = Ph, Pr

Ph3P=/

n

(68) R = Ph, Pr

Te k p P h 3

2RCHo

Ph

R

Te

(69) R = Ph, Pr

R

R'

Ph3P<'. C 0 2 E t EPh

Ph

HORQ ,,\

/

R *<0 ;2Et

0 "C, 1 h

E = S, Se; R = H, R' = Me; R = Me, R' = H, Me R = Bun, R' = H, Me

Scheme 11

Silveira et al. continue to report their work into the synthesis of vinylic chalcogenides using Wittig chemistry; treatment of tellurium phosphorane derivative (72) with aldehydes provides a route to symmetrical divinyl tellurides (73),36and ethyl 2-(triphenylphosphoranylidene)acetate or propionate have been used to convert a-chalcogeno acid chlorides (74) into chalcogeno allenic esters (75) (Scheme 1l).37 Ruthenium-bound ylide alkynyl complexes (76) (Scheme 12)' generated from the corresponding phosphonioalkynyl ruthenium complexes, react with aldehydes and ketones yielding ruthenium(I1) complexes containing highly unsaturated a-alkynyl and vinylidene derivatives.3x Homoconjugated or 'skipped' trienes are vital components of natural products such as fatty acids, leucotrienes and insect pheromones. Pohnert and Boland have reported a detailed discussion of the synthesis of these molecules using a one-pot Wittig approach which employs bis(y1ides) (77)' (78) and (79) New one-pot Wittig procedures have also been as key building developed for the synthesis of alkynes and bromoalkynes (Scheme 13)40 and iodoalkynes (Scheme 14).41 The latter process utilises diiodomethyltriphenylphosphorane (80)' which is generated in situ from triphenylphosphine, iodoform and potassium butoxide. Tandem Michael-intramolecular Wittig reactions of cyclic-ylide (8 1) with

5: Ylidesand Related Species

171

1

R\ ,H [Ru]-C EC -C; PR3

LiBu", THF

pF6-

-20 "C

R' b

I

[Ru]- C FC -C\'

PR3

(76) R' = Ph, R = Me R' = H, R = Ph

t R'

HBF4

I

THF, -20 "C

[Ru] -C EC -C ,,

7-R3 R2

R' Ph Ph

[Rul= Ph3P'

A

.Ru PPh3

Ph H H

R2 R3 -CH2(CH2)3CH2H Me Ph Ph -CH2(CH&CH*Me H

Scheme 12

Ph3P--V--V-pPh3 Ph3P=v=pPh3 P h 3 P e P P h (77)

(78)

3

(79)

a,P-unsaturated thioesters were used to prepared cycloheptane derivatives (82)

and hydroazulenes (83) (Scheme 15).42 The more extreme conditions employed in flash-vacuum pyrolysis experiments are required to facilitate the intramolecular Wittig reaction of stable ylides (84), producing cyclobutenes which, under the harsh conditions employed, rapidly ring-open affording functionalised b u t a d i e n e ~ . ~ ~ The reaction between 1,3-diphenyl-2-(phenyImethylene)-1,3-propanedione (85a) and ylides (86) has been shown to result in the formation of Michael adducts (87). In contrast, under identical conditions 1,3-diphenyl-2-(phenylimino)- 1,3-propanedione (85b) undergoes Wittig olefination yielding alkenes

(S8).44

Wittig reactions have been used to prepare a variety of heterocyclic compounds including pyridin~phanes,~~ benzoylindole~,~~ substituted-porp h y r i n ~ , and ~ ~ , fur ~ ~an^;^^ the latter were unexpectedly obtained from the reaction of cis-2,3-bis(trimethylsilyl)cyclopropanone and P-ketophosphorus ylides (Scheme 16). Natural products prepared using Wittig reactions include (+)-Saponaceolide B, a potent anticancer agent which shows activity against sixty human cancer cell lines,50 the antibacterial agent plaunotol, and its thiourea derivatives, which utilised ylide (89),51 the C44-C51 side chain of

172

Organophosphorus Chemistry i.

i Ph3PCHBr2 Br-, t-BuOK, THF

RCHO

* R-R’

ii t-BuOK

R

R‘

R

R

H, Br

H, Br I

Boc & = +M *e H, Br

+f--?-

w

H

Bn

H

H

H

H, Br

H

Scheme 13

RCHO + Ph3P=C”

1-“ \

I

t-BUOK RII

I

BoC Scheme 14

Altohyrtin C, which involved the synthesis of ylide (90) that contains the said side chain,52and Xerulin, which inhibits the biosynthesis of cholesterol, which required the use of ylide (91).53Wittig reactions are also useful reagents for the synthesis of polymeric materials, for example fluorene ylide (92) has been used to generate light emitting polymers.54 Attansai et al. have reported the first general protocol for the preparation of polymer-bound 1,2-diaza-1,3-butadienes (93) and demonstrated their utility in the solid state synthesis of 4-triphenylphosphoranylidene-4,5-dihydropyrazol5-ones (94) (Scheme 17).55

5: Ylides and Related Species

173

Q

0

Ph’

‘Ph

A, THF

0 (83) R = c-C6HI3, ‘Bu

Scheme 15

0

0

(84) R = Me, Et; R‘ = Me, Et

H P

h

R q

P

h

(85)a R = CHPh b R=NPh

A

SiMe3 +

Ph3P%

(86)

R’

R’ = C02Ph, C02Me, C02Bu‘

N

P h t H Ph3P=C-R

Me3Si

+

I

Ph

P h 3 P q R2

Reflux * M e 3 S i X 1 PhMe

R’ R’ = H, R2 = Me, Et, Ph, p-N02-C6H4,E-CH=CHPh R’ = Me, R2 = Me Y = H, SiMe3

Scheme 16

R2

174

Organophosphorus Chemistry SjMe2CMe3

Me P

h

d

’

o,

d

cF--J

SiMe3Bu‘

Meo2 / Ph3P

(90)

(89)

ph3p-Q0

(91)

(92) R = fCH2)gMe

0

(93)

phv prB +

0

~

reflux MeOH 10-1 2 h

Y’H

I

COR (94)

R = OMe, OEt, OBu‘, NH2, NHPh

Scheme 17

2.4.2 Miscellaneous Reactions. So-called ‘Oxidation-Wittig conditions’, where a primary alcohol is oxidised using manganese dioxide in the presence of a stabilised ylide, have been applied for the first time to unactivated alcohols, producing a,P-unsaturated esters in high yields (Scheme 18).56 FluorenylRCH20H

Mn02, PhMe or CHCI,, A PhsPCHC02Et

RCHZCHC02Et

Scheme 18

substituted ylides (99, which are normally considered to be extremely stable, have been converted into dimethyl fluorenylideneoxalacetate (96) by photoirradiation in acetonitrile solution in the presence of 9-fluorenone which acts as a photo~ensitiser.~~ Aromatic nitriles are readily converted into the corresponding a-methoxyacetophenones upon treatment with a stabilised ylide in the presence of lithium chloride (Scheme 19); it has been suggested that the

5: Ylidesand Related Species

175

C02Me /

hv p350 nm)

02,9-Fluorenone MeCN

@-hco2Me PR3

*

(95)

ocN

R);

/

Ph3P=CHOMe LiCI, THF *

H-C< I

'PPh3

;Li Me

R = H, p-Me, p-MeO, p-CI, m-CI, p-CF3, P F Scheme 19

Lewis acid activates the nitrile function in the intermediate (97), which yields the product upon hydrolysis.58 Treatment of 3-(aryliminomethy1)-chromones (98) with ylides results in the formation of phosphorane-adducts (99).59

0 (99) R = CI, OMe

(98) R = CI, OMe

Vinylphosphonium salts, formed as intermediates during the reactions of acetylenedicarboxylate derivatives and triphenylphosphine continue to provide useful routes to new heterocyclic species.60t6'For example, treatment of ybutyrolactones with triphenylphosphine and dimethyl acetylenedicarboxylate yields fused dihydrofurans (Scheme 20).62 Cyanomethylenetriphenylphos,-(OH

PPh,, CH3O2CC_CCO2Me dioxane, 0 "C, 1 h then reflux 3 h

H H fi0yC02Me C02Me

Scheme 20

phorane (100) has been found to act as a powerful reagent for the conversion of carboxylic acid derivatives such as esters, lactones and imides, into the corresponding 01efins.~~ The need for new classes of strong non-ionic, non-nucleophilic bases has led Palacios and co-workers to investigate ylide (101) and its polymer-supported analogue (102) in this capacity.@ It was found that ylides (101) and (102) acted as versatile bases for selective N-alkylation reactions of p-amino phosphine

Organophosphorus Chemistry

176

oxides and a-amino acids and the C-alkylation of enamines and benzophenone imines derived from glycine ethyl ester. Ylide (101) was also found useful as a base in the Wittig-Horner reaction of phosphine oxide anions and the HornerWadsworth-Emmons type olefination of phosphonate anions. Pentacoordinate 1,2-thiaphosphetenes (103) are obtained when ylide (104), which contains a Martin ligand, is treated with aryl isothi~cyanates.~~ A series of stabilised ylides (105) has been studied as thermally latent catalysts for

Ph3PYR 0

\

NHAr

curing epoxy resins.66 It was found that the catalytic activity of the ylide increased with increasing electron acceptor character of the acyl group. Two series of oxoylides, (106) and (107), have been prepared from the reaction of ylides with acid chlorides.67The thermal decomposition of these compounds, under flash vacuum pyrolysis conditons (500 "C, l o A 2Torr), was also reported; such oxoylides should make useful precursors for the formation of conjugated polyalkynes.

Ph3PH0 AHR 0

(106) A = I,4-C6H4-; R = Ph, PhC-C-,

~ - C I C H ~ C G Hm-CI-C6H4~-, A = Biphenyl-4,4'-diyl; R = Ph

PPh3

(107) A = I,4-C6H4-; R = Ph, p-MeC&, C02Et A = thiophene-2,5-diyl; R = Ph, 2-thieny1, C02Et

A = biphenyl-4,4'-diyl; R = Ph, C02Et A = I,3-C6H4-; R = C02Et

The interaction of triphenylmethylenephosphoranes (108) with tertiary butyl lithium has been studied by proton and lithium-7 NMR.68 It was found that treatment of simple ylides such as (108a) and (108b) with one equivalent of the butyl lithium resulted in ortho-metallation of one of the phenyl rings

5: Ylides and Related Species

177 H

Ph3P=C,

'BuLi, THF/Hexane

,H

-78 "C

R (108)a R = H b R=Me c R=SiMe3

Scheme 21

(Scheme 21). However, when a sterically demanding, electron-withdrawing, trimethylsilyl group is present as a substituent on the ylidic carbon (108c) then no metallation was observed, possibly because ortho-metallation is strongly dependent upon pre-coordination of the lithium ion to the ylide function.

2.5 The Synthesis and Reactions of Aza-Wittig Reagents. - A computational study of the aza-Wittig reaction, by means of ab initio calculations, has been published.69 It has been reported that microwave irradiation can greatly reduce the time needed to prepare aza-Wittig reagents.70 Molina and co-workers continue to develop their work on the synthesis of nitrogen-containing heterocycles using the aza-Wittig reaction. Recent developments, include studies into the synthesis and reactivity of phosphazides (109) (Scheme 22) which were obtained from the Staudinger reaction of an NR3P, Et2O Me

I

NaN

+'

PR3

(109) R3 = Ph3, Ph2Me

Scheme 22

substituted o-azidobenzamide with tertiary p h ~ s p h i n e sThe . ~ ~ Staudinger reaction between ferrocenyl azide (1 10) and triphenylphosphine leads to the formation of iminophosphoranes (1 11) (Scheme 23).72Bisiminophosphoranes (112) and (113) were obtained when azide (110) was treated with bisphosphines. Iminophosphorane (1 14) was similarly obtained from the reaction of the corresponding azide and triphenylphosphine. Compounds (1 11) and (1 14) were shown to be useful precursors for the formation of ferrocene-substituted quinolines and quinazolinones. ha-Wittig chemistry has also played a role in the synthesis of ferrocene-substituted o x a ~ o l e s and , ~ ~ in the synthesis of the alkaloids cryptotackieine and cryptosangyinolentine, which show antiplasmodial activity.74 Iminophosphoranes (115), prepared from 3-azidobenzothiophene, have been utilised in the synthesis of benzo[b]thienopyridines through

Organophosphorus Chemistry

178

/

&yJ Fe

Ph &h

N=P-P=N

&Yhb

(ii)

\

\

ire

Reagents: (i) PPh3, Ch2C12,O "C; (ii) Ph2P -(-CH2+PPh2,

0 "C, CH2C12;

(iii) 1,l'bis(diphenylphosphino)ferrocene,CH2C12, 0 "C

Scheme 23

their reactions with carbonyl corn pound^.^^ Condensation of ylide (1 16) with alicyclic and heterocyclic aldehydes has been used to prepare pyrimidines and dihydropyrimidines in a one-pot p r ~ c e d u r e . ~ ~ Iminophosphoranes (1 17), (1 18) and their polymer-supported analogues (1 19), (120) (Scheme 24) have been found to catalyse the acylation of primary alcohols with enol esters with high yields and selectivities. Moreover, these ylide based catalysts appear more tolerant of sensitive functional groups than alternative Lewis base reagents.77 It has been shown that lithium diaminophosphonium diazaylides (121) are

5: Ylides and Related Species

179

Ph3P=N, C=N-H I

Ph Fe

(115)

R1 = R 2 = Ph, R 3 = Me R1 = Ph, R2 = R3 = Me R’ = R2 = R3 = Me

Ph

I

Q

NaN3, DMf, b

70 “C, 24 h

Scheme 24

(1 16)

Organophosphorus Chemistry

180 H +

Ph2P(

N-R N-R I H

2Bu"Li t THF, -50 "C

N-R Ph2P<,-N-R

Li'

(121) R = Bu", P i , But, CH2Ph,

Ph, CH2CH =CH2,

C(0)Ph

useful synthons for the production of diphenyl-N-(substituted)ketenimines through their reactions with diphenylacetyl chloride.78 3

Structure and Reactivity of Lithiated Phosphine Oxide Anions

Warren and co-workers continue to develop the use of phosphine oxides, and the Horner-Wittig elimination, to control the stereoselectivity of organic reactions. 79-82 The Wittig-Horner reaction between C-metallated a-phosphoryl sulfides and carbonyl compounds provides a common route to a,P-unsaturated sulfides, but one which usually results in poor yields of the desired product when enolisable ketones are used. Stephan et al. have investigated the role of boron trifluoride in promoting the Wittig-Horner reaction of enolisable ketones, which usually follows a two-step process; the initial condensation of the anion followed by an elimination step. It was found that when the second step occurred at a slow rate then addition of boron triflouride was necessary for c o r n p l e t i ~ n . ~ ~ 4

Structure and Reactivity of Phosphonate Anions

The Horner-Wadsworth-Emmons modification of the Wittig reaction continues to be widely employed as a key method for the synthesis of a,Punsaturated esters. A predominant feature of this reaction is the formation of trans-olefins. Over the past twelve months, two new mechanistic studies have appeared in the literature. A combined theoretical and experimental study into the 2-selectivity indicates that steric effects in the oxaphosphetane transition state are of greater importance in determining the selectivity than electronic effect^.'^ An ab initio (RHF/6-3l+G*) study of the reaction between the lithium enolate of trimethyl phosphonacetate and acetaldehyde shows that the process begins with the addition of the lithium enolate to the aldehyde, followed by oxaphosphetane formation, pseudorotation and finally P-C bond cleavage and then 0-C bond cleavage. It was found that the transition state leading to the trans-olefin is more stable than that leading to the ~ i s - o l e f i n . ~ ~ Several new phosphonates bearing the 2,2,2-trifluoroethyl group have been described for the first time including (122) which, upon treatment with aldehydes in the presence of base, is converted into (2)-vinylic phosphonates (123). The latter can be converted into the corresponding (9-allylic phospho-

5: Ylides and Related Species 0

0

II

(CF&H20)2P,

181

II

P(OCH2CF3)2

RCHO

(122)

H

L

f P(OCH2CF3)2

(123) R = Ph, PhCH,, PhCH=CH-, n-C6H13,'Pr

(124) R = H, Me

nates by treatment with potassium tertiary butoxide.86 Phosphonate (124), has been used to prepare di- and tri-substituted a,P-unsaturated ketones,87 and methyl bis(2,2,2-trifluoroethoxy)bromophosphonoacetate(125) was designed for the efficient synthesis of (a-a-bromoacrylates (126), which are themselves useful precursors for a variety of carbon-carbon bond formations.88 Other 0 II

\ OCH2CF3 Me02cY Br

(i)BU'OK, 18-crown-6 THF, -78 "C

p-O C H , ~ ~ (ii) RCHO, -78 "C

* Br

(125)

new phosphonates include polymer-supported (127), ring-opening metathesis polymers or ROMPGELS,89 and a family of a- C-glycosidic phosphonates (128), useful synthons for the formation of complex sugars, which were synthesised by the addition of pyranosidic and furanosidic radicals to aphosphonoacrylates.90

0 I

O=PCH2R

(OAC

(128)R =

I

OEt '3C-sO

(127) R = C02Et, CN

Me

Of course, the main interest in the Horner-Wadsworth-Emmons reaction is its application in synthesis. New biologically active molecules synthesised include endothelin receptor antagonist S-0 139, which requires phosphonate

Organophosphorus Chemistry

182

(129),91 adenosine A1 receptor antagonist FR 166124,92 seco-D-15,19-bisnorla,25-dihydroxyvitamin D analogues,93 and (k)-desepoxy-4,5-dehydroxomethylenomycin A methyl ester, phosphonate (130) being a key reagent in the synthesis of this compound.94 Polymeric materials prepared using this methodology include phenylene vinylene polymers95and d e n d r i m e r ~both , ~ ~ of which are of interest because of their potential as light-emitting materials for use in electronic displays, and organic donor molecules containing stable TEMPO free radicals (Scheme 25).97 A new method for preparing olefins bearing

Reagents: (i) LDA, THF, -78

“C,15 m (ii) P(OEQ3,75 “C,45 m Scheme 25

donor-acceptor groups requires phosphonate (13 1).98Other classes of compound prepared include vinyl s ~ l f o n e sunsaturated ,~~ esters of the adamantane series,loo and phosphono-substituted oxadiazines. l o ’ A new strategy for accessing cylohexenes and related ring structures devised by Chollerton et al. involves an intramolecular radical addition to an unactivated olefin in conjunction with an intramolecular Horner-Wadsworth-

5: Ylides and Related Species

183

R'

COzEt R = Me; R' = X = H; n = 1 R = Me; R ' = H,X = SCSOEt; n = 1 R = R ' = )( = H; n = 2 R = R = M e ; X = H; n = 1 Reagents: (i) lauroyl peroxide (0.1-0.2 equiv.),l ,Zdichloroethane,reflux; (ii) BuaSnH (AIBN), PhMe, reflux; (iii) K2C03/18-crownd, PhMe, reflux; (iv) NaH. THF

Scheme 26

Emmons reaction (Scheme 26). lo2 Horner-Wadsworth-Emmons reactions also feature in new routes to (dipheny1phosphono)acetic acid esterslo3 and alkenes.lo4 The latter involve combining the Horner-Wadsworth-Emmons procedure with a Heck coupling reaction for the synthesis of tri-substituted alkenes. The development of new methodologies for asymmetric synthesis is of crucial importance and in this context the new strategy of parallel kinetic resolution (PKR), whereby both enantiomers of a racemic mixture can be converted to useful products via simultaneous reaction with two different chiral reagents, is particularly promising. Pedersen and co-workers have recently reported the first asymmetric Horner-Wadsworth-Emmons procedure that allows the parallel kinetic resolution of racemic aldehydes. These workers have used two alternative approaches. In the first approach (Scheme 27) the racemic aldehyde is allowed to react with two phosphonate reagents (132) and (133) that contain different chiral auxiliaries. The alkene products obtained are separated by chromatography. In the second approach (Scheme 28), the aldehyde is treated with two phosphonates (134), one (@-selective and one (2)-selective, that contain the exact same auxiliary. This approach relies on the observation that (Q- or (2)-selective phosphonates generally react with opposite enantiotopic group preference affording one (@- and one (2)product with opposite absolute configuration at the allylic stereocentre. Both PKR routes described offer the potential to increase material throughput and selectivity compared with conventional kinetic resolution, which will surely lead to further reports on this topic in the future.

184

Organophosphorus Chemistry

(132) R* = (IR,2S,SR)-b-Phenylmenthyl

= (R,R)-I,2-Diphenylaziridine

(133) a NR;

b N R i = (S,S)-1,2-Diphenylaziridine NaHMDS -78 "C 2-6 h

&NT-ph +

h PJ. - ' - ; (

Ts

I

Ph

Ph Scheme 27

f\

0

18-crown-6, KHMDS, -78°C THF 2-5h

0

A

A

II

(134) a R = CF3CH2

b R = 'Pr

R = (IR,2S,5R)-8-Phenylmenthyl

Scheme 28

References 1 2 3 4 5 6

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5: Ylidesand Related Species

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186 39 40 41 42 43

44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71

Organophosphorus Chemistry

G. Pohnert and W. Boland, Eur. J. Org. Chem., 2000, 1821. P. Michel, D. Gennet and A. Rassat, Tetrahedron Lett., 1999,40,8575. P. Michel and A. Rassat, Tetrahedron Lett., 1999,40,8579. N. Kishimoto, T. Fujimoto and I. Yamamoto, J. Org. Chem., 1999, 64, 5988. R.A. Aitken, M.E. Balkovich, H.J. Bestmann, 0. Clem, S.E. Gibson and T. Roder, Synlett. 1999, 1235. L.S. Boulos, R. Shabana and Y.M. Shaker, Heteroatom Chem., 2000,11, 57. H. Yamamoto, M. Yuasa and M. Nitta, Heterocycles, 1999,51,2991. R.S. Mali, S.G. Tilve and V.G. Desai, J. Chem., Res., Synop., 2000, 150. T. Shigeoka, Y. Kuwahara, K. Watanabe, K. Sato, M. Omote, K. Ando and I. Kumadaki, Heterocycles, 2000, 52, 383. G. Zheng, M. Shibata, T.J. Dougherty and R.K. Pandey, J. Org. Chem., 2000, 65, 543. T. Takanami, A. Ogawa and K. Suda, Tetrahedron Lett., 2000,41,3399. B.M. Trost and J.R. Corte, Angew. Chem. Int. Ed., 1999,38,3664. H. Kogen, K. Tago, M. Arai, E. Minami, K. Masuda and T. Akiyama, Biorg. Med. Chem. Lett., 1999,9, 1347. G.R. Ott and C.H. Heathcock, Org. Lett., 1999,1, 1475. K. Siege1and R. Bruckner, Synlett., 1999, 1227. J.K. Kim, J.W. Yu, J.M. Hong, H.N. Cho, D.Y. Kim and C.Y. Kim, J. Mater. Chem., 1999,2171. O.A. Attanasi, P. Filippone, B.Guidi, T. Hippe, F. Mantellini and L.F. Tietze, Tetrahedron Lett., 1999,40, 9277. L. Blackburn, X. Wei and R.J.K. Taylor, Chem. Commun., 1999, 1337. Y. Kawamura, Y. Sato, M. Arai, T. Horie and M. Tsukayama, Phosphorus, Sulfur, Silicon Relat. Elem., 1999,149, 1. B. Camuzat-Dedenis, 0. Provot, H. Moskowitz and J. Mayrargue, Synthesis, 1999, 1558. M.D. Khidre, H.M. Abdou-Yousef and M.R.H. Mahran, Phosphorus, Sulfur, Silicon Relat. Elem., 1998, 140, 147. I. Yavari, H. Djahaniani, M.T. Maghsoodlou and N. Hazeri, J. Chem. Res. ( S ) , 1999,382. I. Yavari and F. Nourmohammadian, J. Chem. Res. ( S ) , 1999,512. L. Heys, P.J. Murphy, S.J. Coles, T. Gelbrich and M.B. Hursthouse, Tetrahedron Lett., 1999,40,7151. T. Tsunoda, H. Takagi, D. Takaba, H. Kaku and S. Ito, Tetrahedron Lett., 2000, 41,235. F. Palacios, D. Aparicio, J.M. de 10s Santos, A. Baceiredo and Guy Bertrand, Tetrahedron, 2000, 56, 663. T. Kawashima, T. Iijima, H. Kikuchi and R. Okazaki, Phosphorus, Sulfur, Silicon Relat. Elem., 1999, 1 6 1 4 6 , 149. M. Kobayashi, F. Sanda and T. Endo, Macromolecules, 1999,32,4751. R.A. Aitken, M.J. Drysdale, L. Hill, K.W. Lumbard, J.R. MacCallum and S. Seth, Tetrahedron, 1999,55, 11039. K. Korth and J. Sundermeyer, Tetrahedron Lett., 2000,41,5461. W.C. Lu, C.C. Sun, Q.J. Zang and C.B. Liu, Chem. Phys. Lett., 1999,311,491. M. Chen, G. Yuan and S. Yang, Synth. Commun., 2000,30,1287. M.D. Velasco, P. Molina, P.M. Fresneda, and M.A. Sanz, Tetrahedron, 2000, 56, 4079.

5: Ylides and Related Species 72 73 74 75 76 77 78 79 80 81 82 83 84

85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105

187

P. Molina, A. Tarraga, J.L. Lbpez and J.C. Martinez, J. Organomet. Chem.,

1999,584,147. A. Tarraga, P. Molina, D. Curiel, J.L. Lopez and M.D. Velasco, Tetrahedron, 1999,55, 14701. P.M. Fresneda, P. Molina and S. Delgado, Tetrahedron Lett., 1999,40,7275. C. Bonini, L. Chiummiento, M. Funicello and P. Spagnolo, Tetrahedron, 2000, 56, 1517. E. Rossi, G. Abbiati and E. Pini, Synlett., 1999, 1265. P. Ilankumaran and J.G. Verkade, J. Org. Chem., 1999,64,9063. H.-J. Christau, I. Jouanin and M. Taillefer, J. Organomet. Chem., 1999,584, 68. A. Nelson and S. Warren, J. Chem. Soc., Perkin Trans. I , 1999, 1963. A. Nelson and S. Warren, J. Chem. Soc., Perkin Trans. I , 1999, 1983. N. Feeder, G. Hutton, A. Nelson and S. Warren, J. Chem. Soc., Perkin Trans. I , 1999,3413. A. Nelson and S . Warren, J. Chem. Soc., Perkin Trans. I , 1999,3425. E. StCphan, A. Olaru and G. Jaouen, Tetrahedron Lett., 1999,40,8571. K. Kokin, K.-I. Iitake, Y. Takaguchi, H. Aoyama and S. Hayashi, Phosphorus, Sulfur, Silicon and Rel. Elem., 1998,133, 21. K. Ando, J. Org. Chem., 1999,64,6815. J. Kiddle, A.A. Davis and J.J. Rosen, Phosphorus, Sulfur, Silicon Relat. Elem., 1999,144-146,68 1. W. Yu, M. Su and Z. Jin, Tetrahedron Lett., 1999,40, 6725. K. Tag0 and H. Kogen, Org. Lett., 2000,2, 1975. A.G.M. Barrett, S.M. Cramp, R.S. Roberts and F.J. Zecri, Org. Lett., 1999, 1, 579. H.-D. Junker, N. Phung and W.-D. Fessner, Tetrahedron Lett., 1999,40, 7063. T. Konoike, K. Oda, M. Uenaka and K. Takahashi, Org. Process Rex Dev., 1999,3, 347. S. Kuroda, A. Akahane, H. Itani, S. Nishimura, K. Durkin, T. Kinoshita, I. Nakanishi and K. Sakane, Tetrahedron, 1999,55, 10351. X. Zhou, G.-D. Zhu, D. Van Haver, M. Vandewalle, P.J. De Clercq, A. Verstuyf and R. Bouillon, J. Med. Chem., 1999,42, 3539. P. Balczewski and M. Mikolajczyk, Org. Lett., 2000, 1153. J.-Y. Pu, T. Minoru, E. Tsuchida and H. Nishide, J. Polym. Sci., Part A: Polym. Chem., 2000,38,4119. J.N.G. Pillow, P.L. Burn, I.D.W. Samuel and M. Halim, Synth. Met., 102, 1468. H. Fujiwara and H. Kobayashi, Chem. Commun., 1999,2417. E.N. Durantini, Synth. Cornmun., 1999,29,4201. J.W. Lee, J. C.-W. Lee, J. J. Hang, D.Y. Oh, Synth. Commun., 2000,30,279. N.I. Miryan, S.D. Isaev, S.A. Kovleva, N.V. Petukh, E.V. Dvornikova, E.V. Kardakova and A.G. Yurchenko, Russ. J. Org. Chem., 1999,35,857. W.M. Abdou and A.F. Ganoub, Heteroat. Chem., 2000,11,196. N. Chollerton, I. Gauthier-Gillaizeau, Y. Six and S.Z. Zard, Chem. Commun., 2000,535. K. Ando, J. Org,. Chem., 1999,64, 8406. K. Bodman, S . Hans-Becker and 0. Reiser, Phosphorus, Sulfur, Silicon Relat. Elem., 1999,144146,173. T.M. Pedersen, J.F. Jensen, R.E. Humble, T. Rein, D. Tanner, K. Bodmann and 0. Reiser, Org. Lett., 2000,2, 535.

6

Phosphazenes BY J. C. VAN DE GRAMPEL

1

Introduction

This review covers phosphazene literature over the period June 1999 to June 2000 (Chemical Abstracts Vols. 131 and 132) and discusses linear phosphazenes including compounds derived thereof (Section 2), cyclophosphazenes (Section 3) and polyphosphazenes (Section 4). Structural data have been summarized in Section 5. 2

Linear Phosphazenes

The role of the phosphorus-nitrogen double bond in synthetic organic chemistry is well-understood. An important strategy to incorporate this reactive centre in a reagent is the application of the Staudinger procedure - the reaction of an azide RN3 and a phosphine PR’3, yielding RN=PR’3 after elimination of a nitrogen molecule. The reaction intermediate RN=N-N=PR’3, that has been isolated in some cases, can adopt a cis and a trans configuration. Ab initio calculations on the model system HN=N-N=PH3 predict the cis-isomer to be more stable than the trans-form.1’2However, the former isomer reacts very easily via a cyclic intermediate that decomposes with evolution of nitrogen to give a phosphoranimine. The trans-form is only stable in presence of suitable substituents. Calculations show that the decomposition of the cis-isomer can be inhibited by intramolecular donor-acceptor interactions, as proven by the isolation of the cis-isomer (1). Compound (1) decomposes to the phosphazene (2) at 110 “C,however, without evolution of nitrogen. Me /c N,

PhN3

dl*c

CI

CI

;Me

?

CI

Organophosphorus Chemistry, Volume 32 0The Royal Society of Chemistry, 2002 188

O0

189

6: Phosphazenes

The Staudinger reaction forrns a part of several organic-synthetic procedures, as for example, conversion of glycosyl azides into N-glycoside derivat i v e ~ ,synthesis ~ of sugar pho~phoranimines,~ synthesis of P-stereogenic phosphine oxide^,^ reaction with bornanylene(dimethy1phosphino)methylimine,6 synthesis of estradiol derivative^,^ synthesis of isothiocyanophosphonates.* In addition to Na[Ph2P(NCN)2], published before, other diphenyldiaminophosphonium diylides Na[Ph2P(NR)2] with R = COAr or So2C6H4Mehave been prepared by a Staudinger reaction involving Ph2PNa and RN3.9 The reaction of PPh3 with 2,4,6-triazidopyridine takes place exclusively at N3 group in 4-position to give 2,6-diazido-4-phosphoraniminatopyridine.lo Investigations into the scope of dendrimers with PNP moieties, reactions of phosphines PR‘R”R”’ and azides (3) have been claimed to yield N-thiophosphorylated and N-phosphorylated phosphoranimines R’R”R”’P=NP(X)(OC6H4Y-4)2. Analogous reactions have been carried out with the ferrocenyl derivatives, yielding (4). The P=N-P(X) linkage can be easily alkylated on the X atom by means of methyl or isopropyl triflate to yield compounds ( 5 ) with a [P(Ph2)NP(XAlk)]’ group, Treatment of [P(Ph2)NP(SAlk)]’ with P(NMe2)3leads to desulfurization and formation of a PV=N-P1I1 linkage, which offers the possibility for

(3a) (3b)

X=O,Y=H X = S, Y = CHO 4

X

2

Ph

X = 0, Y = H X = S, Y = CHO

(4a) (4b)

MeOS(02)CF3

/

Ph

Me

2[cF3sO31-

Me (5a) (5b)

X=O,Y = H X = S, Y = CHO

190 Ph HzC=CH-P I Ph

+

X

(3a) (3b) (3~) (3d)

6b

(

N3-P II 0

a' )

Organophosphorus Chemistry

Ph

2

X = 0 ,Y = H X = S, Y = CHO-4 X = S, Y = CN-4 X = S, Y = MezN-3

Ph HzC=CH-P=N-P I

HzNNMeP(S)Cl2 c

Ph

(6a) (6b) (6~) (6d)

X

2

X=O,Y=H X = S, Y = CHO-4 X = S, Y = CN-4 X = S, Y = Me2N-3

Me S

0 +i=N-h-F:$

2

(7)

i, NaOC6H4CHO-4 ii, H,NNMeP(S)CI, iii, NaOC6H4CHO-4 iv, H2NNMeP(S)Cl2

further reactions at the reactive PI" centre, for instance, a Staudinger reaction. Examples involving some ferrocenyl derivatives are shown below. The preparation of vinyl compounds (6) according to the Staudinger procedure has been described. The conversion of the formyl directive (6b) to (8b) occurs via a fine step procedure of which the formation of (7) is the first step. The third generation dendron (8) has 16 chorine atoms at the surface and a reactive vinyl group at the core. It has been shown that suitable derivatization of (8) both at the core and the surface provides reactive blocks that can lead to fascinating dendritic architectures by core-core, core-surface or corecore-surface-core reactions. The azidophenoxyphosphinothione N3P(S)(OPh)OC6H4PPh2-4 or its BH3 adduct, has been described as precursor for the preparation of linear polymers (9) with NP entities. Hyperbranched polymers have been claimed from the reaction of N3P(S){OC6H4[P(BH3)Ph2-4]}2 and NEt3.I5 The -N(Me)P(=S)C12 site in the 3714

6: Phosphazenes

191 OPh

N3-P-O It

S

OPh N3-P-O II

S

third generation dendrimer (10) has been used for grafting of tetraazamacrocycles at the surface of dendrimers.16 The reaction of phosphoranimines with carbonyl compounds (aza-Wittig reaction) has been subjected to ab initio calculations with the geometries optimised at the HF/6-31G level of theory. It has been shown that the model reaction of X3P=NH (X = H, C1, Me) and O=CHC02H to yield X3P0 and HN=C02H occurs via two transition states, one corresponding with the formation of a four-membered cyclic intermediate, the other with its decomposition. The energy barriers are influenced by the substituent X and decrease in the order C1 > H > Me.17 A similar theoretical study describes the azaWittig reaction of H3P=NH and O=CH2,leading to analogous results. l8 The aza-Wittig reaction, whether or not preceded by a Staudinger reaction, forms a well-known tool for the preparation of a wide range of organic compounds, such as the preparation of 1,4-benzodiazepin-2,5diones,lg thieno[3,2-~]pyridines,~~ pyrrolidine C-nucleosides,21pyrazino[2,1b]quinaz~linediones~~ and alkaloids.23Ferrocenylazide ketones have proven to be excellent precursors for the preparation of ferrocenyl-substituted azaheterocycles. As examples, compounds (11) and (13) react via a Staudinger reaction with Ph3P=N, followed by an aza-Wittig reaction with isocyanates and internal cyclization to quinazoline (12) and quinoline derivatives (14), re~pectively.~~ An oxazole derivative (16) can be obtained by sequential treatment of (15) with PPh3, ArNCO and finally by a base-promoted cy~lization.~~ Examples of ferrocenylazide ketones as building blocks for the preparation of macrocycles and cryptants are compounds (17) and (19). The Staudinger reaction of (17) with PBu"3 and a subsequent intramolecular aza-Wittig

Organophosphorus Chemistry

192

0

N3

ArHN,-! i, PPh3 ii, ArNCO iii, cyclization

O

0

H

e E L c H ' C n

e

i, PPh3

N3

ii, ArNCO iii, cyclization

!? i, PPh3 ii, ArNCO iii, cyclization with RNH2

b

reaction yields the cryptant (1S), whereas the Staudinger reaction of (19) and PhzPCH2CH2PPhZoffers the macrocycle (20).26 The aza-Wittig reaction of N-vinylic phosphoranimines Ph3P=NC(R)=CHC02R' or MePh2P=N-C(R)=CHC02R' (R = H, R' =Et; R = R' = Me;

f

? -C'CH,z a

Fe

c

PBu"~ m

I1

0

+H, .

intramolecular aza-Wittig

2

N3

193

6: Phosphazenes

R = Ph, R' = Et) and arylaldehydes ArCHO has been reported to yield azadienes with general formula ArC=N-C(R)=CHC02R'. These azadienes appear to be very useful as starting materials for the preparation of nitrogen heterocycle^.^^ An easy one-pot synthesis of dihydropyrimidines from NH=C(Ph)N=PPh3 and a,P-unsaturated aldehydes has been described. The reaction is supposed to proceed via an aza-Wittigmechanism followed by ring closure.28 Treatment of the silylated phosphoranimine Me3SiN=P(Ph2)CH2SiMe3 with LiBu" and subsequent recrystallization of the reaction product from diethyl ether has been described to yield compound (21), that can be converted at low pressure into a bicyclic dilithio compound (22). A new silylated phosphoranimine (23) has been obtained from the reaction (22) with Me3SiOS(02)CF3.The reaction of Et2NSi(Mez)Cl and Li[CH2P(Ph2)=NSiMe3]affords another silylated phosphoranimine (24).29 Ph2

, p, 'N-SiMe3

Me3Si-C

H2

LiBu"

Ph2 P )N-SiMe3

H Me3Si-C(

Et20

,Li\ Et2O OEt2

Me3Si,

Ph2

Me3SiS(02)CF3

H C H Ph2P' 'Li-C-SiMe3 I I I Me3Si-N, Li,,N--PPh2 Me3Si

Ph2 Hfi
Et2NSi(Me2)CI

Ph2 Et2N-Si-ClpQN-SiMe3 Me\ Me/

H2

Donor-acceptor complexes of silylated phosphoranimines Me3SiN=PR3 with a large variety of metal salts have been a continuous subject of investigations. Reactions of Me3SiN=PR3 [R = Pr', Cy (cyclohexyl), Ph] and AlC13, A1MeCl2, A1Me2Cl and AlMe3 have been described to yield complexes with general formula R3P=N-A1(C13--Me,). Similar reactions have been carried out with the non-silylated phosphoranimines HN=PR3 (R = But, Cy, Ph). It is worthy to note that Me3SiN=PBut3 does not react with the aluminum compounds A1Me3-,ClX due to the steric hindrance exerted by But groups. The adduct Me3A1NH=PBut3can be converted into the dimer (25), when heating the reaction mixture at 80 0C.30

Organophosphorus Chemistry

194 But3P=NH

+

AIMe3

-*

But3PNH-AIMe3

8o oC +

Me2AI--NPBut3

I 1

Bd3PN-AIMe2

The phosphoraniminato complex [FeC1(N=PEt3)l4(26) can be prepared by the reaction of Me3SiN=PEt3and FeC12 in the presence of KF. X-ray analysis showed a heterocubane structure with Fe and N atoms at the corners of the cube with short non-bonded Fe.--Fe distances [mean value 272.9(1) ~ m ] . ~ ~ Compounds [Fe(C(CR)(N=PEt3)I4 (R = CMe3 or SiMe3) are formed by reaction of (26) with the appropriate lithiated acetylenes. During this substitution reaction the heterocubane is preserved. On the contrary, reaction of Me3SiNP(NMe2)3and FeCl2 in presence of KF leads to the formation of a mixed valence Fe(II)/Fe(III) cluster (27), in which the central structure consists of an incomplete cubane skeleton. Heterocubane structures have also been found for [MnBr(NPEt3)I4and (28) (M = Mn, Co) were prepared by the reaction of the anhydrous metal dibromides' with Me3SiN=PR3 (R = Et, NMe2). Whereas compound [MnBr(NPEt3)I4has a [MnNI4 cubane structure, the cubane unit in compound (28) has the composition Mn4N3Br, which means a nitrogen corner is replaced by a bromine.32

(28a) (28b)

M=Mn M=Co

Phosphoraniminato-acetato complexes [M(N=PEt3)(02CMe)14(M = Co, Cd) are formed by the reaction of the appropriate anhydrous metal acetates M(02CMe)2 with Me3SiN=PEt3.The molecular structure consists of a metalnitrogen heterocubane unit with the acetato groups coordinated to the metal atoms.33A chain structure has been found for [Zn(02CMe)2(HN=PEt3)](29) in which zinc atoms are bridged by the oxygens of an acetato group. The other acetato group and the phosphoraniminato group are bonded terminally.34A more complicated structure has been found for the copper compound (30), which consists of [Cu3(02CMe)6(HN=PPh3)]and [ C U ~ ( O ~ C Munits, ~ ) ~ ]connected to each other by acetato groups thus forming three crystallographic independent chains. Whereas compound (30) can be isolated from an 1:l reaction mixture of C U ( O ~ C M and ~ ) ~ Me3SiN=PEt3 in CH2C12, the 1:2 reaction mixture yields the simpler complex (31). In this compound the Cu atom is coordinated to two oxygen and two nitrogen atoms in a square-planar coordination. Four-membered metal-nitrogen rings, formed either from metal halides and Me3SiN=PEt3 or from neat metals and IN=PPh3, have been reported for the

6: Phosphazenes

195 0

0

MeC

+Zn/O

/

Et3PNH

Me

Me

CMe

'oco/

O\Zn

Me

PEt3

Me

Me

oco

EtSPNH

\ cu/ /

\ HNPEt3

ocoMe

Me

PEt3

\

HNPEtS

Me

oco Me Me

structures [A1C12(N=PEt3)]2,35 [Ga12(N=PEt3)]2,35 [Ga12(N=PPh3)]2,35 [BiF2(N=PEt3)(HN=PEt3)]2,37[Bi2(N=P[SnI(N=PPh3)I2 (32),36 Ph3)4]2'[I] - [I3]- ,37 [Sm21(N=PPh3)5DME](DME = 1,2-dimetho~yethane)~~ and vb21(thf)2(N=PPh3)4.39 Oxidation of the divalent tin compound [SnI(N=PPh3)I2(32) with I2 leads to the formation of the tetravalent tin hexaiodide (33) in which tin has a trigonal-bipyrimidal coordination. A mixed divalent-tetravalent tin compound [Sn213(N=PPh3)3] (34) can be obtained by treating (32) with Na in thf.40

In vb12(HN=PPh3)(DME)2], prepared from ytterbium powder and IN=PPh3 in DME as solvent, the metal atom is coordinated by two iodine, one nitrogen and three oxygens atoms, forming a pentagonal-bipyramid with the two iodine atoms in trans position.39The reaction of YbCp2Cl with LiN=PPh3 in boiling toluene yields vb2Cp3(N=PPh3)3].The structure of this compound is characterized by a four-membered Yb2N2 ring with two NPPh3 bridges. The

196

Organophosphorus Chemistry

remaining NPPh3 group is terminally bonded to one of the two Yb atoms. The Cp groups complete the four-coordination of the metal atoms.41 Borane donor-acceptor complexes (35a, R = Et; 35b, R = Ph) are formed by the reaction of Me3SiN=PR3 with BH3-SMe2. The reaction of Me3SiN=PEt3 with BHBr2.SMe2 yields [B3H3(N=PEt3)3Br2]Br,which in a CC14/CH2C12 solution converts into borazine (36).42 R3P,

N-BH3

r

1'

Me3Si'

(35a) R = Et (35b) R = P h

L CI: B r = 1 . 8 5 : 0 . 1 5

(36)

A quantum-mechanical study of the model compounds TiC13N=PH3and Re03N=PH3 reveals that the metal-ligand bond dissociates homolytically. Variation of the metal-nitrogen-phosphorus angle influences the potential energy surface only to a small extent.43 It has been shown that cyclometallation of PhN=PPh3 with PhCH2M(CO)5 (M = Mn, Re) proceeds smoothly to give the complexes (37a, M = Mn) and (37b, M = Re).&

(37a) M = M n (37b) M = R e

The chemistry of metal complexes of diphosphorus imines has been reviewed.45 Chiral 1,2-phosphoranediimines have been prepared via the Kirsanov route, viz. reaction of diamines (38) or (39) with phosphine dibromides followed by treatment with NaH. The P-dimethylamino-substituted products (41a) and (41b) are reasonably stable in contrast with the phenoxy analogues (42a) and (42b), which are very water- and air-sensiti~e.~~ Palladium complexes (43) and (44) have been obtained from the reaction of [Pd(q3-C3H5)C1]2with (41b) and (42b), respectively, in presence of AgBF4. Complexes (47a,b) and (48a,b) have been prepared in a similar way starting from the P-phenyl-substituted 1,2 phosphoranediimines (45) or (46) in presence of either silver tetrafluoroborate or silver trifluoromethanesulfonate. All complexes exhibit a good stability, which is in line with the capability of the 1,2-phosphoranediimidesto stabilize Pdo centres in catalytic processes. It has been shown that (45) induces the highest enantioselectivity in a Pd-catalysed

197

6: Phosphazenes H

+

R H ,

2 Br-

R/2”N-PH(NMe2)3 H + (38)

NaH

yk

N=P(NMe2)3

W a ) , (40b)

or

a R----R = -(CH,J4b R=Ph

r

+

P(OPh)3 -

+ BF4-

BF4

II P(OPh):, (44)

PPh3 (47a) R = H (47b) R = P h

C I Ph/?,N II PPh3

L

PPh3 I1

LPh3

I Ph H ,N ,

R

-

(45)

+

+

BFd-

TfO-

-

(48a) R = H (48b) R = P h

allylic alkylation, when compared with the activity of (41a, b), (42a,b) and (46) Also, the silylated phosphoranediimine CH2[P(Ph2)=NSiMe3I2(49) acts as a powerful ligand with two nitrogens as donor sites. The 1:l molar ratio reaction of AlMe3 with (49) has been reported to yield a cyclic complex (50) via elimination of methane. A bimetallic complex can be obtained either by the reaction of (SO) and one equivalent of AlMe3 or by the reaction of (49) and two equivalents of The equimolar reaction of (49) and ZnMe2 leads to the formation of *

Organophosphorus Chemistry

198 Ph2 P=N-SiMe3 H2C\

Ph2 ?‘Me3 P-N H( >IMe2 P-N Ph2 \

AIMe3

P=N-SiMe3 Ph2

51me3

(50)

(49)

\

/

a1me3

2 AIMe3

Ph2

Me2

Me2

Ph2

complex (52) in which zinc has an unusual three-coordinated environment. Nucleophilic addition to the carbon in adamantylisocyanate results in complex (53) with a novel tripodal four-coordinated zinc atom.48 The samarium complex (54) has been formed by the reaction of (49) with one equivalent of samarium t ris(dicyclohexylamino).th f [Sm(NCyJ 3. thf 1. Two methy lene protons are removed followed by the elimination of dicyclohexylamine, resulting in a samarium complex with a C-Sm double bond.49 A similar Ph2 P=

Ph2 ,!3Me3 H(

P-N

\&Me f

P-N Ph2

\

AdNCO

/

HC,-c-

oe

b

P= Ph2

SiMe3

(52) Ad = adamantyl Ph2 P=N-

SiMe3

H2C\

Sm(N C ~ ~ ) ~ . t h f D

P= N- SiMe3 Ph2

(49) Zr(CH2Ph)l

Ph2 ,SiMe3 P=N CH2Ph \ \ / C= Zr

Cy = cyclohexyl

,SiMe3 N,

I

N- Zn- Me >Ad N,

SiMe3

(53)

Ph2 ,SiMe3 thf P=N \ \ / C= Sm f \ P=N NCy2 Ph2 ‘SiMe3

(54)

199

6: Phosphazenes

zirconium complex (55) arises from treatment of diimine (49) with Zr(CH2Ph)4. Deprotonation and elimination of toluene lead to the formation of a C-Zr double bond.50 Due to their acidic character the methylene protons in (49) can easily be replaced by lithium atoms. Treatment of (49) with one equivalent of Bu"Li in thf affords the monolithium derivative (56).51 Dilithiation succeeds with an excess of MeLi in benzene51 or two moles of MeLi or PhLi in toluene.52The X-ray structure of dimer (57) shows the core that can be described as an octahedron with four lithium atoms in a square plane and two carbon atoms in axial position. The lithium atoms are intramolecularly solvated by the imine groups, preventing solvation by solvent molecule^.^^ 252 Ph2 PEN- SiMe3 H2C, P=N-SiMe3 Ph2

-

Ph2 P=N-SiMe3 LiH( P=N-SiMe3 Ph2

Ph2 P=N -SiMe3 Li2C, P=N-SiMe3 Ph2

.

Ph2 Ph2 molecular structure of dimer of (57)

The monolithiated compound diimine (56) smoothly reacts with the metal trichlorides AlC13, GaC13 and hC13 to yield the complexes (58a), (58b) and (58c), re~pectively.~~ Treatment of (56) with A1Me2Cl gives the complex already described as reaction product of CH2[P(Ph2)=NSiMe3I2and A1Me3.47 Metal chloride complexes (59) with structures analogous to that of the samarium complex (50) have been obtained by the reaction of (57) with titanium or zirconium tetrachlorides via elimination of LiC1.53 Equimolar reaction of (57) and CrC12(thf), has been shown to yield binuclear chromium complex (60), whilst reaction with a twofold excess of CrCl,(thf), affords a partially substituted tetranuclear complex (6 1).54 The coordination chemistry of the inorganic ligands with general formula [R2P(E)NP(E')PRZ]- (E, E' = 0, S, Se) still attracts broad attention. These ligands can be readily deprotonated to form stable metal-phosphazene heterocycles, exhibiting different binding modes. Preparation of Pr12P(E)NHP(E)Pr12 (E = E = Se; E = Se, E' = S; E = S, E' = 0; E = E' = 0) and complexes

200

Organophosphorus Chemistry Ph2 P= N- SiMe3 LiH( P=NPh2

SiMe3

-

Ph2 /SiMe3 P-N

MCI3

Hc:

1mc12

P-N Ph2

f \

51me3

(58a) M = Al (58b) M = G a (58c) M = In

P-N HC\

\AIMe2

f

P-N Ph2 \SiMe3

P=N-SiMe3 Ph2

(57)

P=N’ Ph2 ‘SiMe3

(59a) M = Z r (59b) M = T i

CrClz(thf);!

51me3 Ph2

Ph2

51me3

M[Pri2P(E)NP(E’)Pri2-E,El2with M = Zn2+, Cd2+, Pd2+ and Pt2+have been described.55 TetrabutylimidodithiophosphinatesR2P(S)NHP(S)RI2(R = Bun, Bus, Bu’; R’ = Bun, Bus, Bu’) have been prepared by the reaction of R2P(S)NH2 and R’2P(S)Br. Complexation reactions of these butylimidodithiophosphinates with ZnCl2, PdCl2-cod and PtCl2.cod (cod = cycloocta-1,5-diene) in presence of KOBut have been reported.56 Preparation and characterization of new manganese57 and cobalt5* complexes, (62), (63), as Mn[Me2P(O)NP(S>Ph2-O,Sl2, well as Mn[Ph2P(O)NP(S)Me,-O,s ] 2 , C O [ P ~ ~ P ( S ) N P ( S ) P ~ ~ - S , CO[P~’~P(S)NP(S)P~’~-S,S’]~, .S]~, Co[Ph2P(Se)NP (Se)Ph&, Se’12, Co[Pr12P(Se)NP(Se)Pr’2-Se,Se’]2 have been reported. X-ray

6: Phosphazenes

20 1

analysis reveals that compound (62) and all cobalt complexes have the bicyclicspiro structure (E,E-coordination), whereas complex (63) has a dimeric structure. Trinuclear Cu' complexes (64-66) have been obtained from the reaction of CuCl or CuC12 with R2P(S)NHP(S)R'2 (R = R' = Pr'; R = Pr' , R' = Ph; R = Pr' , R' = OPh) and KOBut in methanol solution. In case of CuC12, reduction to Cu(1) takes place via the solvent.59 and From the reaction mixture of [(Me3Si)2CH]2Ga-Ga[CH(SiMe3)2]2 Ph2P(0)NHP(O)Ph2 two gallium complexes can be isolated, one in which the Ga-Ga bond has been cleaved to yield the complex [(Me3Si)2CH]2Ga[Ph2P(O)NP(O)Ph2-O,0'12 (67), the other (68) in which the metal-metal bond remains intact.60 Ligand exchange between di~is(trimethylsily1)methyl di(pdiacetato)digallium and [Ph2P(S)NP(S)Ph2]Li results in a tetraphenylimidodithiophosphinato complex (69), in which the ligands no longer adopt a bridging position across the Ga-Ga bond. Yttrium complexes (70, E = S; 71, E = Se) have been prepared from Y[N(SiMe3)2]3and Ph2P(E)NHP(E)Ph2.In the sulfur containing complex the metal atom is nine-coordinated by three nitrogen and six sulfur atoms, whereas in the selenium analogue a seven-coordinate yttrium centre is present surrounded by one nitrogen and six selenium atoms. In the latter case steric effects do not allow for more than one q3-bonded imidodiselenophosphinate ligand.61Replacement of six bromo ligands in by three tetraphenylimidodichalcogenidophosphinate ligands yields complex (72) (E = S, Se).62 Ruthenium complexes with [Ph2P(S)NP(S)Ph2]- or [Pr$P(S)NP(S)Pri2]ligands exhibit metal-ligand bonding through sulfur, thus forming six-membered metallo-heterocyclic entities. Complex Ru[Ph2P(S)NP(S)Ph2S, S']2[PPh3], that has an 'unsaturated' coordination around the metal atom, is

202

Organophosphorus Chemistry (Me3Si)2HC,

,Ga-Ga’: (Me3Si)2HC

CH(SiMe3)2 CH(SiMe3)2

Ph2P(O)NHP(0)Ph2

1 Ph,P/

I

I

I

0, 0 ,Ga’ (Me3Si)2HC ‘CH(SiMe&

+

O,

(Me3S i)2HCG,-

-

o N/ PPh2

I

(Me3Si)z HC

p p

[Ph2P(S)NP(S)Ph2]Li

(Me3S i)2C -Ga -Ga - CH(SiMe3)

0,

I

I) a - G7 CH(SiMe3)2

h2P\

Me

I

\PPh2

Y

(67)

H

’

Ph2P

“pPh2

t

\

/o C

Me

Ph2P,y

N

/PPh2 /

,P-s\ Ph2 ,s-P, Ph2 N\ Ga-Ga N

&‘I

\

/

h;2 -‘

CH(SiMe3)2

+ Ph2 P Y N \ P Ph;!

BrPh2P

PPh2 Ph2

Ph2

capable of hydrogenation of alkenes in presence of a base. A conversion of 90% has been observed for the hydrogenation of styrene to ethylbenzene with 10 mol% of the ruthenium complex in presence of Et3N.63Indium”’ bis(imidodichalcogenidophosphinate) complexes InC1[R2P(E)NP(E)R2-E,E‘l2(R = Ph, Pr’, E = S, Se) are easily accessible by an 1:2 molar ratio reaction of InC13 and K[R2P(E)NP(E)R2.64 Reactions of InC13 with the asymmetric ligands Ph2P(E)NHP(E’)Ph, afford In[Ph2P(O)NP(S)Ph2-0,s ] 3 and InCl[Ph2P(S)NP(Se)R2-S,Se]2.65 Rare-earth complexes with general formula Cp2Ln[Ph2P(Se)NP(Se)Ph2](Ln = La, Gd, Er, Yb) have been prepared from Cp3Ln and Ph2P(Se)NHP(Se)Ph2.All complexes show q3-bonded imidodiselenophosphinate ligands through two selenium atoms and one nitrogen atom, except for Ln = Yb where q2-bonding (Se, Se) is observed. In compound Cp2Yb[Ph2P(S)NP(S)Ph2], where selenium has been replaced by the smaller sulfur, again q3-bonding occurs.66 The iridium complexes Cp*Ir[Ph2P(S)NP(S)Ph2-S,SIC1 and Cp*Ir[Ph2P(Se)NP(Se)Ph2-S,S]Cl, which

203

6: Phosphazenes

are synthesized from c~*IrCl(p-Cl)~ and [Ph2P(E)NHP(E)Ph2](E = S or Se), allow for further derivatization by metathetic exchange of the chloro ligand for a thiocyanato or selenocyanato ligand.67Different modes of complexation of the unsymmetrical ligand [Ph2P(0)NP(E)Ph2]- (E = S, Se) have been illustrated by the reaction of its potassium salt with late-transition metal complexes. Reaction with [M(o-Ph2PC6H4NH2-P, N)2]C12 (M = Pt, Pd) affords compounds (73), in which the imidophosphinate group acts as counter ion. It is noteworthy that during formation of these ionic complexes one of the Ph2PC6H4NH2ligands has been deprotonated by [Ph2P(0)NP(E)Ph2]- .68 a similar deprotonation has been observed for the reaction of the symmetric ligand K[Ph2P(S)NP(S)Ph2]and [Pt(o-Ph2PC6H4NH2Ph2-P, N)2]Cl2 affording compound (74).69 Next to the formation of (73c) also 0,s-chelation is observed leading to (75).68The reaction of [Ph2P(O)NP(E)Ph2]- (E = S, Se) with [Pt(X)Cl(o-Ph2PC6H4NH2-P,N)](X = C1, Me) gives compounds (76), which are complexes with E-monodentate [Ph2P(0)NP(E)Ph2]- ligands. Emonodentate coordination is also found for gold complexes (77).78 +

i

Ph2 P’II .. O

N

N Ph2P’ -‘PPh2 II II

‘PPh2 .I I. E

s

s

(73a) M = Pt, E S (73b) M = Pt, E = Se (73c) M = Pd, E = S H

Ph2

p s-P Ph2 Ph2 (75)

(77) E = S, L = o - C ~ H ~ P ( P ~ ~ ) N H ~

(76a) (76b) (76c) (76d)

E = S, X = Me E = Se, X = Me E = S , X = CI E = Se, X = CI

(78a) E = S (78b) E = S e

Platinum complexes (78) have been obtained by transmetallation of K[Ph2P(E)NP(E)PPh2] with ci~-Ptcl*(HL)~. 31P NMR shows the two PI1’ centres to be identical, pointing to a fast proton exchange between the nitrogen

204

Organophosphorus Chemistry

atoms of HL and L. Chlorine metathesis of [AuC1(Ph2PNHP(0)PPh2-P)]with K[Ph2P(E)NP(E)PPh2](E = S, Se) affords complexes Au[ { Ph2P(E)NP(E)PPh2-

E,E’){Ph2PNHP(0)PPh2-P)].70

In contrast to alkali metals or transition metals, complexation of [R2P(E)NP(E)PR’2]- with main group elements is less well documented. Syntheses and structures of a number of tellurium complexes Te[R2P(E)NP(E’)PR’2]2(E = S, Se) have been reported. It has been argued that electronic rather than steric effects control the geometry around the central tellurium atom. As examples: four-coordination in (79) and two-coordination in (80).71

(79) R = R ’ = C y

(80)

Linear chlorophosphazenes catalyst mixtures have been synthesized by reaction of a mixture of PC15 and Me3SiN(H)SiMe3 in CH2C12, followed by reaction in a siloxane medium72or in trimethylsiloxy-terminatedpolydimethyl~ i l o x a n e Linear . ~ ~ phosphazenes [C13P=N-(PC12=N),-PC13]+PC16, [C13P=N(PC12=N),-PC13]+SbC16 or phosphorylphosphazenes [C13P=N-(PC12=N),POC12 can be applied in the equilibration and/or condensation of organosiloxanes.7477 Nucleophilic substitution of chlorine atoms in C13P=N-POC12 by sodium phenoxides in a 1:2 molar ratio has shown to take place at the PC13 centre, affording geminal substituted compounds C1P(OR)2=N-PC120with R = C6H2(But3-2,4,6) or C G H ~ ( M ~ - ~ ) ( B UProtonation ~ ~ - ~ , ~ ) . of ~ ~C13P=NR with sulfonic acids has been proven to be strongly dependent on the nature of the substituent R.79 Neutral phosphazene bases as [(Me2N)3P=N]3P=NBu‘ (But-P4) are wellknown base catalysts for the ring opening polymerization of cyclosiloxanes. It has been found that their catalytic capacity can be enhanced by the presence of small amounts of water, which results in the case of But-P4 to the formation of the active ion-pair catalyst ([(Me2N)3P=N]3P-NHBut}+OH-. For the ring opening polymerisation of (Me2Si0)4 this leads to high molecular weight polysiloxanes at low catalyst concentration with short reaction times.80 Polymerisation of mixtures containing octamethylcyclotetrasiloxane and dimethylvinylsilyl-terminated polydimethylsiloxane in presence of But-P4 has been reported.8c83 Ring opening polymerization of 1-(hydroxydimethylsiloxy)pentamethylcyclotrisiloxane 84-86 or 1-hydroxypentamethylcyclotrisiloxane87 with But-P4 leads to hyperbranched polysiloxanes. The phosphazene base was shown to be more effective for the preparation of high molecular weight hyperbranched polysiloxanes than the conventional lithium silanolates. Successful applications of the strong bases Et-P2 and But-P4 in organic synthetic procedures have been de~cribed.~~-~’ The compound

6: Phosphazenes

205

[Ph3PNPPh3]+Br- has been used as phase-transfer catalyst for the preparation of polycarbonate from bisphenol A and COe91Phosphazene bases Bu'N=PPyr3 (Pyr = pyrrolidinyl) and Bu'N=P(NEt2)N(Me)CH2CH2CH2N(Me)have been applied in the enantioselective preparation of a-amino acid derivative^.'^ A large number of patents covers the ring opening polymerisation of epoxides in presence of [(MezN)3P=N]3P=093or { [(Me2N)3P=N]4P}+OH-.94 X-ray structure determinations of some miscellaneous linear compounds containing a N=P entity are summarized in Section 5.41395-106

3

Cyclophosphazenes

The number of reviews about cyclophosphazenes is limited. Cyclocarbaphosphazenes have been reviewed,1073108 as well as applications of cyclophosphazenes.log Calculations show that 1,2-azaphosphinines and 1,3,2diazaphophinines possess a higher reactivity as compared to their 1,3-aza and 1,3,5-diaza isomers as a consequence of larger electrophilic character of the phosphorus atom.' lo Thermodynamic functions for (NPC12)3 and NPC12)4 have been determined in the temperature range of T = 0 4 5 0 K. '11 The electrochemical behaviour of N3P3[(OC6H4(N=NC6H5-4)I6has been discussed, including a reduction mechanism of the azo-group.' l 2 Conductivity measurements have shown that protonation of N3P3(NH2)6leads to the formation of a compound with a high capacitance, suitable for fast-ion conduction. l 3 IR and Raman spectra of the compounds N3P3C14(02C12H8)2, N3P3C12(02C12H8)2 and N3P3(02C12H8)3 (O2C12H8 = 2,2'-dioxybiphenyl) have been reported and compared with the spectra calculated at the 3-21G level of theory.' l 4 Ultraviolet photoelectron spectral (UPS) data of a number of alkenyl and alkynylfluorocyclophosphazenes have been shown to be consistent with a model in which phosphazene substituent effects are exclusively transmitted through polarization of the endocyclic and exocyclic 0-bonds.' l 5 The UPS data of the vinyloxy derivatives N3P3C15(OCH=CH2)and N3P3F,(OCH=CH2)6-, (n = 2-5) reveal a strong electron-withdrawing effect of the phosphazene ring on the olefinic moiety. A linear relation has been found between the p 13Cand the 31Pchemical shifts of the =P(X)OCH=CH2 moiety of compounds (NPX2)2NP(X)OCH=CH2(X = F, C1, OCH2CF3, OMe, NMe2). A model, based on the relative donoracceptor properties of the substituents, has been proposed to explain this relation. An explanation has been given for the preferential formation of cisNPC12[NPC1(OCH=CH2)I2 during the second substition step. l 6 The kinetics of the phenolysis of (NPCl& by phenol under three-phase (water-solidorganic solvent) catalytic conditions along with mass transfer phenomena during the substitution reaction have been studied.' l7 Three mechanisms has been put forward for the reaction of (NPC12)3 with pyridine-N-oxide derivatives. A novel preparation of [NP(CF3)2]3 from (NPF2)3 and Me3SiCF3 in the

'

206

Organophosphorus Chemistry

presence of CsF has been described together with X-ray structures of cyclic starting material and end product.' l9 Only a limited number of papers deals with amino substituted cyclophosphazenes. Dicarboxylic amino acid ester derivatives N3P3{NHCH[(CH2)xC02R]C02R}6(x = 0, R = Et; x = 1, 2, R = Me) have been synthesized, including their corresponding sodium and barium salts.I2O Treatment of (81) Cy = cyclohexyl by strong organometallic bases Me3Al and Et2Zn have shown to lead to complete deprotonation of the NH moiety and formation of metal phosphazene complexes (82) after recrystallization from thf and (83), respectively. Incomplete deprotonation takes place, when (84) is reacted with Et2Zn to give (85). All three compounds have complex structures, in which coordination of the metal centres by the endocyclic and exocyclic nitrogen donor sites can be described by five coordination modes (a-f).12'

a

b

d

C

e

coordination modes found in (82), (83) and (85) N3P3(NC~)~(thfAlMe)(AlMe~)~ modes a, b, c

CyHN, ,NHCy N""N

CyHN

NHCy

(82) excess

Et2Zn

N3P3(NCy)6(ZnEf)6

(81)

modes b, d, e (83)

CyHN, ,NHCy ,P=N, ,NHCy

'YHN\P F\NHCy CyHNO'\ N 7 \/ N CyHN

NHCy

excess Et2Zn

*

N4P4(NHCy)2(NCy)6(ZnEt)6

modes b, d, e

Protonation of the [N~P~(NCY)$-anion of [ N ~ P ~ ( N C Y ) by ~ ] Lthree ~~ equivalents of Bu"0H has been found to take place exclusively at the axial exocyclic nitrogen atoms of the chair-shaped phosphazene ring, yielding cis complex (86). Deprotonation of p3P3(NHC6H&]Li6 by three equivalents of Bu"Li gives the cis-isomer of cyclotriphosphazene (87), in which also the protonated amino ligands possess an axial position. Compound (86) crystallizes as a dimer, whereas the chemical composition of (87) appears to be IN3P3(NHC6H5)3(NC6HS)3]Li3.6thf, when recrystallised from thf.'22

6: Phosphazenes

207

NHCy

coordination mode of only one Li is given

Treatment of (NPC12)3 and (NPC12)4with one equivalent of triethyleneglycol bis(2-aminophenyl ether) in MeCN have been reported to give the corresponding ansa derivatives (88) and (89) in low yields and, in the case of (NPC12)3, also a compound with two bridged phosphazene rings (90).'23

n0n0n0

n0n0n0

0

a

H/ N

YP,N* H CI'II

0

D

a

FCI NXp//N

N,/ H

/N H

D

"I$/ \

C12P\ N '

CI2

(88)

II

,PC12

(89)

n0n0n0

0

Reactions of (NPC12)3 and pP(OPh)2]2NPC10Ph with N,N,N',"-tetramethylguanidine have shown to yield a monosubstituted product (91) and a geminal tetrasubstituted product (92), respectively. Replacement of all chlorine atoms in (NPC12)3appears to be impossible, even when using a large excess of amine. Complexes of (92) with CuC12 (93) and PdC12 (94) have been r e ~ 0 r t e d . lA~ binuclear ~ cobalt complex (95) has formed by the reaction of NP(OPh)2[NP(NHCH2CH2(C5H4N-2)I2 and CoCl2. One cobalt is coordinated by one chlorine, two pyridyl nitrogen of two cis-vicinal pyridylethylamino

Organophosphorus Chemistry

208 NMe2 PhO, N , Nyp+N

/,C-NMe2

NMe2 cI2 NMe2 I N"%N I Me2N-C , /,C-NMe2 N# , I/N Me2N-Cl'/

N/ \N//p,

NMe2

NMe2 I

NMe2

cI2

Me2N-C+ N"*N C12Pd::N>#\N5P,

NMe2

(93)

NMe2 I

+C-NMe2 I ,N. :PdCI2 N' *C -NMe2

t~le~N-C'/~ NMe2

N ,C-NMe2

I

I

NMe2

NMe2

(94)

groups and a ring nitrogen, the other cobalt is coordinated by three chlorine atoms and one pyridyl nitrogen.'25 Tungsten carbonyl complexes N3P3Am6W(C0)3 and N4P,&ngW(C0)4 have been prepared from the corresponding amino derivatives (Am = NC4H@, NC5HI0, HNC6H11, HNCgH17) and W(CO)6.126A study of the reactivity of (NPC12)3 and (NPC12)4 towards diamines and diols has shown that the formation of spiro compounds is preferred.127 In contrast to the amino-substituted cyclophosphazenes, many papers have appeared concerning alkoxy and aryloxy substituted phosphazenes. A one-pot procedure based on phase-transfer catalysis has been developed for the preparation of N3P3 (OC&I~[C(O)H-4]} 6 and N3P3 { OC6H4[C(O)Me-4])6. 12* Insertion of [NP(OPh)2]2NP(OPh)N3 into C&t5(C&)@e via a nitrene intermediate has been observed at 280 "C, yielding mP(OPh)2]2N-

6: Phosphazenes

209

P(OPh)NHC6H4(CH2)8Me.Photolytic insertion (UV light 254-300 nm) of [NP(OCH2CF3)2]2NP(OCH2CF3)N3 into cyclohexane leads to the formation of pP(OCH2CF&]2NP(OCH2CF3)NHCy.12’ An improved synthesis of N3P3[OC6H3(But-3)(OH-4)]6 has been described.130 Novel inorganic-organic cyclomatrix polymers have been obtained by the reaction of N3P3[0C6H3(But3)(OH-4)I6 with dicarboxylic acid chlorides.13’ A novel CuC12-bridged dimer with overall composition { C U ~ [ N ~ P ~ ( ~ C ~ H(cu&) ~ N - ~ )(96) ~ ] has C ~been ~) prepared by the reaction of hexakis(2-pyridyloxy)cyclotriphosphazene with cuc12. 32

As a part of the study of cyclolinear polymers with cyclophosphazenes as cyclic groups, the stereochemistry of the substitution reaction of (NPC12)3with two equivalents of the biphenolate anions of 2,2’-dihydroxy-1,1’-biphenyl and 2’,2’’-dihydroxy-1,l”-binaphtyl has been analysed. A speculative mechanism has been put forward to explain the formation of different stereoisomers in subsequent phenolysis of the remaining PC12 group by NaOC6H40Me-4.133 Tris(bipyridiny1) spiro derivatives have been prepared by the reaction of and 2,2’-dihydroxy-3,3’-bipyri(NPC12)3 with 3,3’-dihydrox~-2,2’-bipyridine dine. Only the 3,3’-dioxy-2,2’ bipyridinyl derivative gives trinuclear cobalt complexes, when reacting with C0~(C0)~3,5-dbbq (3,5-di-tert-butyl-o-benzoquinone or Co~(C0)83,6-dbbq (3,6-di-tert-butyl-o-benzoquinone).Steric reasons have been put forward to explain this difference.134 Compounds N ~ P ~ A ~ ( O C S Hand ~ NN3P3A(OCSH4N-4)4 -~)~ (A = 2,2’-dioxy-1,l ’-biphenyl) reacts with W(MeOH)(CO)Sto give mixtures of polymetallic complexes, which are unstable in solution. 35 Alternatively, the phosphine derivatives N$3(OC6H4PPh2-4)6 and (NPA)2NP(OC6H4PPh2-4)2 react to the well-defined complexes N3P3 {OC6H4[PPh2.W(CO)S-4116 and (NPA)2NP { OC6H4[PPh2.W(CO)S-4])2,respectively, in which the metal atoms are coThe compounds [NP(OC6H4Butordinated to phosphine. 136 4)2]2NP(OC6H4But-4)(Oc6H4Ch2CN-4) 37 and [NPA]2NP(OC6H4Ch2CN-4)2 (A = 2,2’-dioxy-1,l’-biphenyl)13’ have been used as starting materials for the preparation of iron and ruthenium complexes. Electrochemical and spectro-

210

Organophosphorus Chemistry

scopic data show no influence of the phosphazene ring on the coordinating capacity of the CN group, due to the insulating effect of the spacer between the phosphazene ring and the nitrile group. 1379138 A number of cyclophosphazenes with chromophoric substituents and obeying the general formula N3P3[OC6H4(CH=NAr-4)]6, N3P3[0C6H4(N=CHAr-4)l6 and N3P3[OC6H4(N=NAr-4)]6 have been synthesized and fully characterized by spectroscopic methods.139y140 Crystals of tris(o-pheny1enedioxyde)cyclotriphosphazene (97) can act as hosts for the inclusion of a number of organic polymers, e.g. cis- 1,4-polybutadiene, trans- 1,4-polyisoprene, polyethylene (PE), poly(ethy1ene oxide) (PEO) and polytetrahydrofuran. X-ray studies of the PE and PEO inclusion compounds show that the polymer chains are extended along the tunnel-like voids of the host lattice. The formation of clathrates appears to be limited by the tunnel dimension of the host crystal lattice. The melting points of the inclusion adducts appear to be higher than those of either the pure host or the pure guest.141A similar observation has been made for inclusion compounds of (97) with the n-alkanes C12H25,C16H33, C19H39, C24H49, C36H73 and C54H109.142 Inclusion compounds of (97) with benzene and p-xylene 143 and poly(ethy1ene oxide)lMhave been investigated with 13Cand 31PMAS NMR. Also host-guest inclusion adducts have been synthesized using the related compound, tris(3,6dimethylpheny1enedioxyde)cyclotriphosphazene(98), as a host. 145

Q

M

e

Me

e

M

e

Me'

Studies of the reactivity of 1,3-ansa-oxy(tetraethyleneoxy) derivative (99) have been extended to reactions with alkylene diamines. Substitution takes place at the PCl centre as a consequence of the interaction between the incoming nucleophile and the crown ether ligand already present, yielding compounds (loo), (101) and (102). Only for H2N(CH2)3NH2 was the l~~ of (99) with formation of a spiro derivative (103) was 0 b ~ e r v e d .Treatment an excess of nucleophilic reagents leads to substitution of all chlorine atoms.147 A very interesting series of dendrimers with a cyclophosphazene core and with protonated -CHZCHZN+(H)Et2or methylated -CH2CH2N+(Me)Et2tenninal tertiary amines has been developed. These dendrimers appear to act as DNA transfecting agents, their capability depending on the size (generation) of the dendrimer and the terminal tertiary amino group.14* First generation

6: Phosphazenes

21 1

'R

f

/

(99)

(103)

R = (CH2)"; n = 2-6, 8 , 10, 12

dendrimers with (NP)3 or a (NP)4 ring as core and with chiral ferrocenyl end groups have been r e ~ 0 r t e d . l ~ ~ Ring opening metathesis polymerization (ROMP) of norborenes with a cyclophosphazene side group (104) in presence of the ruthenium catalyst (PCy3)2Ru(C12)CHPh has shown to yield organic polymers with a cyclophosphazene as pendant group (1O5).l5O

Organophosphorus Chemistry

212

\ NH4CI

Two new procedures have been developed for the preparation of aryl and hetero aryl substituted cyclophosphazenes with a direct P-C bond, viz. via the reaction of 9,9,9-trichloro-9-phosphafluorene with NH&l in refluxing C6H5Cl yielding (106), or via treatment of H2NP(0)Ar2 (Ar = aryl residue) with Appel’s reagent (PPh3, EtN3, CC14).151 In contrast to cyclophosphazenes, chlorocyclocarbophosphazenes are capable of C-N bond cleavage of tertiary amines followed by a regiospecific substitution reaction at the ring carbon atom. Dialkylaminomethylferrocenes react with the dealkylating compound NPC12(NCC1)2 (107) to yield the corresponding bis(P-dialkylamino) derivatives together with ferrocenyltetraalkylammonium halide. 52 Ring opening involving C-N bond cleavage of bicyclic tertiary amines, such as 1,4-diazabicyclo[2,2,2]octaneand quinuclidine, by (107) leads to the formation of amino-substituted carbophosphazenes (lOS), (109) and (1 P-spirocyclic ferrocenyl derivatives [NPOCH2P(S)RCH20][NC(NR’2)2]2 (R = CH2C5H4FeC5H5)have been synthesised from [NPC12][NC(NR’,),], by a nucleophilic substitution at the phosphorus centre.154 Studies of the application of cyclophosphazene derivatives find a broad interest and comprise many areas, such as multifunctional initiators, biological materials, lubricants and flame-retardants. Controlled radical polymerization of styrene has been carried out in the presence of cyclophosphazene derivatives of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1 -one (4-hydroxy-TEMPO).lS5 Hexafunctional compounds, and N3P3[OC6H4(CH2Br-4)]6, N3P3 { oC6H,[CH,oC(o)CH(Me)Br-4]) 6 16, have been applied as multifunctional N3P3{ OC6H4[CH20C(0)CMe2Br-4] initiators in atomic transfer radical polymerizations (ATRP). Hexa(ally1amino)cyclotriphosphazene has been applied as a coupling agent during the extrusion of polypropylene (PP) in the presence of a radical initiator, improving the mechanical properties of PP above these of PP extruded with the initiator alone.’58 Compounds N3P3[0CH2(CH20CH2),CH2OR]6 (n = 2, R = Bun; n = 3, R = C12H25; n = 19, R = C16H33) have been used for the preparation of vesicles in I

,

I

6: Phosphazenes

213

\

i, NR2R

RR"'

the presence of cholesterol and dicetylphosphate. In the vesicles formed both hydrophilic and lipophilic can be entra~ped.'~'Several studies deal with the application of N3P3(0C6H4F-4)2(0C6H4cF~-4)4(x-1P) as lubricant or as additive in perfluoropolyether lubricants.16c163 Partial replacement of OC6H4F-4 groups by OC6H4[0(Ch2)20h-3]results in a lower tribological performance.la A novel flame-retardant compound (1 12) could be obtained by the reaction of the phosphoryloxyphenoxy derivative (1 11) with epichloro-

214

Organophosphorus Chemistry

hydrin. Treatment with diamines lead to the formation of epoxy polymers. Their high char yields and their limiting oxygen index (LOI) values indicate that these polymers possess good flame retardant properties. 165 The thermal behaviour of copolymers (1 13) with pendant phosphazene groups, prepared by copolymerization of [NP(OPh)2]NP(OPh)[OC6H3(OH)23,5], C6H4(OH)2-1,3 and OCN(CH2)6NC0, have been investigated. An enhancement of the char yield has been observed with increasing phosphazene content.'66 The related cyclolinear polymer will be discussed in Section 4.

Hexamethoxycyclotriphosphazene has been used as component in a flameretardant formulation for lithium batteries. 167 Flame retardant cotton could be obtained by treatment of cotton with N3P3(NhCH20H)6. Cyclophosphazene-containing flame retardant formulations have been described. 69-175 as well as the use of cyclic and polymeric phosphazenes in processing of silver halide photographic materials. 1767177 X-ray structure determinations of some miscellaneous cyclic compounds containing a N=P entity are summarized in Section 5.'7g-'82

'

4

Polyphosphazenes

The interest in polyphosphazenes may be reflected by the number of papers that have appeared on this subject. Review papers deal with general features of p o l y p h o ~ p h a z e n e s or ' ~ ~describe ~ ~ ~ ~ a specific subject, as application of polyphosphazenes to form ceramic materials through the sol-gel technique,' 85 medical a p p l i ~ a t i o n ' and ~ ~ ~polyphosphazene '~~ electrolytes.lS8 Short reviews have been presented as contributions for symposia or conferences.lS9-l9' Molecular dynamics calculations have been carried out to simulate a conformational mode11g2 and vibrational spectra of poly(dich1orophosphazenes).193 Molecular dynamics similations for [NP(OCH2CF3)2], and the isomers [NP(0Bun)2],, [NP(OBus)2], and [NP(OBut)2], show a reasonable agreement between the calculated and experimental values of density and glass transition t e m p e r a t ~ r e 'as ~ ~well as for gas transport parameters in these polymers.195 Small molecule models have been used for a theoretical approach of poly(thiony1phosphazenes). 96 There has been a continuation of the study of the polymer-salt complex poly(ethy1ene oxide) (PEO)/LiCF3S03,in which the morphology and conduc-

6: Phosphazenes

215

tivity of the system ~~~/~~~~~/po~y[(octafluoropentoxy)(tr~fluoroethoxy phosphazene] (PPz) has been investigated in relation to the addition of the ceramic filler y-LiA102and the plasticizer propylene carbonate. 1977198 Rheological properties of copolymers { NP(OCH2CF3)2-x[OCH2(CF2)5CHF2)]x},'99have been investigated as well as the rheology of blends of [NP(OCH2CF3)2], and copolymers { NP(OCH2CF3)2-x[OCH2(CF2)5CHF2)],},.200 Mutual diffusion and solubility phenomena of partly fluorinated polydialkoxyphosphazenes, including WP(OCH2CF3)2], and/or copolymers { NP(OCH2CF3)2- ,[OCH2(CF2)5CHF2>],}. have been studied.201 Phase transitions of mP(OCH2CF3)2], have been analysed in relation to preparation and thermal history of the samples.202The study of dilute solutions of copolymers bearing 2,2'-dioxybiphenyl groups and having the formula [NP(02C12H8)]o.351NP(oc6H4R-4)2]o.6with 5 R = COPh, COMe, CN and Br shows the copolymers in the high molecular range behave as random coil chains.203 Solution properties of [NPC12],, [NP(OBun2], and [NP(OCH2C6H5)2]nhave been investigated.204 A number of structural investigations of polyorganophosphazenes has been carried out. Poly(dipropy1phosphazene) can be characterized by one ordered crystalline phase and a thermotropic mesophase. The crystalline phase has a monoclinic symmetry with polymer chains with a nearly planar cis-trans conformation of the polymer backbone, in which the PNP angle is about 10" larger than in the cyclic trimer.205 Thermal analysis of poly(diphenoxyphosphazene) films (from xylene solution) has shown a phase transition from a three-dimensional ordered structure and a two-dimensional ordered structure, which has been confirmed by X-ray diffraction Annealing above the transition temperature leads to a more ordered crystal structure.206Energy-dispersive X-ray diffraction (EDXD) in combination with molecular modelling studies point to a planar cis-trans conformation for the backbone chain of the monoclinic a-form of [NP(OC6H5)2]n.207 The high-temperature behaviour of [NP(OCH2CF3)2], has been investigated by various techniques.208 Electrical properties of {NP(NHBu")[N(CH2CH=CH2)2]},have been described.209The ionic conductivity of complexes of polymers { NP[O(CH2CH20)2Me]x[NH(CH2),Me]2-x}n (rn = 2-5) with various amounts of LiC104 has been studied. The system {NP[(CH2CH20)2Me]o,8[NH(CH2)4Me] 1.2)~LiC104 with a molar ratio LiC104:NP = 0.25 appears to possess the highest conductivity and can be considered as a potential polymer electrolyte for rechargeable batteries.210Comparison of electron beam cross-linking data and glass transition temperatures of a number of fluoroalkoxy, methoxyethoxyethoxy and substituted phenoxy polyphosphazenes suggests that the increase of the glass transition temperature (T,) of { NP[(OCH2CH2)20Me]2} ,upon complexation with LiC104 may be ascribed to coordination of lithium at the nitrogen sites on the polymer backbone.21 New methods have been put forward for the preparation of the basic polyphosphazene (NPC12),. A one-pot reaction of PC15 and (NH4)2S04 (molar ratio about 4.5: 1) delivers linear (NPC12), without significant cross-linking.

216

Organophosphorus Chemistry

The reaction pathway consists of two stages, viz. the formation of C13PNPOC12 at 165°C' followed by thermal decomposition of the linear phosphazene at about 225 0C.212,213 The preparation of (NPClz), at low temperature by thermal decomposition of C13PNPOC12 in a dry and oxygen-rich atmosphere air has been The living polymer (1 14), prepared by the well-known cationic PC15-induced polymerization of C13P=NSiMe3,will form a diblock copolymer upon treatment with another phosphoranimine C12P(Ph)=NSiMe3.Substitution of the chlorine atoms by O(CH2CH20)2Megroups yields an amphiphilic copolymer (1 15) capable of self aggregation in an aqueous medium to form m i c e l ~ . A ~'~ novel phosphazene-siloxane triblock copolymer (1 16) has been synthesized by the reaction of (1 14) with the polysiloxane Me(CH2)3[Si(Me2)0],Si(Me2) (CH2)30(CH2)20P(OCH2CF3)z=NSiMe3, followed by treatment with NaOCH2CF3.2'6 The analogeous reaction with ((CF3CH20)3P=N[P(Cl2)=N],-PCl3>'PCl6- yields a diblock

[

+ [ PC16 ]

Cl3P=N-&NkPCl3]

-

i, PhC12P=NSiMe3 ii, NaOR

{pNj;;klNk OR

Ph (1 15)

(114)

0R' 0 R'

ii,

NaOR'

1

I

Me (1 16)

R = (CH2CH20)2Me R' = CH2CF3

Ditelechelic polyphosphazenes (1 17) have been prepared by quenching the living polymer (1 14) with two equivalents of an amino phosphoranimine. Monotelechelic polymers (1 18) could be obtained by cationic polymerization as initiator.217 of C13P=NSiMe3 with [RN(H)P(OCH2CF3)2=NPC13]+PC16PC15-inducedcationic polymerisation of BrP(Ph)(R)=NSiMe3 (R = CF3, Me) leads to stereoregular polymers [N=P(Ph)(R)]n.218The syntheses of poly(organophosphazenes) with Schiff's base linkages,219cinnamyloxy groups220and carbazolylethoxy groups22 have been described. Phosphazene terpolymers (1 19) with a varying ratio of 2-(2-methoxyethoxy)ethoxy and diacetone Dglucofuranosyl substituents have been prepared. Glass transition temperatures of these polymers increase with an increasing content of diacetone D-glucofuranosyl groups obeying the Fox equation.222 Graft copolymerization of 2-methyl-2-oxazoline onto pP(OC6H4Me-

6: Phosphazenes

217 OR' I i, 2 RN(H)-P=NSiMe3 I 0R'

(1 14)

t

ii, NaOR (117)

1

-8",- I

0R'

RN(H)

PC13

]+

[ pc16] -

i, CI3P=NSiMe3 ii, NaOR'

(119)

c

t& OR'

RN(H)

P=N

(OR)2

I P-OR'

'H

4)x(OC6H4CH2Br)2yields copolymer (I 20). Micelle formation of this copolymer in water has been The acid-base reaction of the polyphosphazene [NP(OC6H4C02H-4)2]nand the optically active amine (R)-C6H5CH(Me)NH2at 65 "C has been reported to yield a polyphosphazene with a large negative optical rotation, possibly arising from a preferred one-handed helical conformation of the phosphazene backbone during the reaction.224 Phosphorylated polyphosphazenes { NP(0c~H~[oP(o)(OR)2-4]}2}40 (R = Et, Ph) have been prepared by the reaction of [NP(OC6H40H-4)2]40and ClP(0)(OR)2. Despite their high thermal stability, the phosphorylated polymers do not exhibit a high flame resistance.225 Studies of membranes based on polyphosphazenes, bearing groups other that substituted phenoxy groups, have been continued, in particular to develop Ion-exchange membranes of crossmaterials for specific linked and non-crosslinked sulfonated [NP(OC6H4Me-3)2],229have been

Organophosphorus Chemistry

218

studied with respect to their behaviour towards NaCl solutions in water.230 The sorption isotherms and permeability for vapours of water and ethanol in membranes consisting of [NP(OCH2CF3)2], have been investigated in a temperature range of 25-55 "C. The permeability for both compounds appear to increase with increasing vapour activity, whereas the sorption isotherms obey Henry's law.23' Hybrid polyphosphazene-silica gels have been prepared by acid hydrolysis of a mixture of Si(OEt), and [NP(OC6H40H-4)2], and casted onto ceramic supports to form membranes.232A sol-gel precursor (121) for the preparation of phosphazene-silica networks has been obtained by the use of a silylated alkyl is0 cyanate. Acid hydrolysis of polymer (121) yields a phosphazene-silica network with reactive -0-C(0)-NH- sides, which in their turn can be used for further (grafting) reactions.233

IN=!

1

OCH~CHPOCH~CH~OC(O)NH(CH~)~S~(OE~)~ H+, H 2 0 OCH2CH20CH2CH20C(0)NH(CH2)3Si(OEt)3

1

phosphazene-silica network

KOH- or LiF-catalysed hydrolysis of a mixture of (NP[(OCH2CH2)20Me]2},and Si(OEt), yields rubbery and highly adhesive nanocomposites, whereas acid (HCl/NaCl) hydrolysis leads to more glassy composites.234 Novel cyclomatrix phosphazene-triazine polymers have been prepared by curing of the cyanophenyl derivatives (122) or (123) at 250°C. The cyanate groups undergo cyclotrimerisation to form triazine rings, by which process a phosphazene-triazine network is formed. The cyclomatrix phosphazene-triazine systems exhibit an improved char yield and flame resistance, compared to the phosphazene-free system obtained by curing of bisphenol-A d i ~ y a n a t e . ~ ~ ~ Analogous to the preparation of copolymer (1 11) (Section 3), a cyclolinear phosphazene-urethane copolymer (124) can be obtained by the reaction of a geminal bis(4-hydroxyphenoxy)cyclophosphazene, 3,3'-(ethy1enedioxy)diphenol and hexamethylene-1,6-diisocyanate.166 Blends of polyurethane with [NP(OC6H4C02H)2In have been prepared under conditions which enable reactions of the carboxylic group with the isocyanate group. Loadings of 20 wt% phosphazene or more induce a significant increase in flame resistance.2369237 This finding corresponds with the

219

6: Phosphazenes OCN

CMe2

OCN

OCN

behaviour of polyurethane-[NP(OPrn)2In blends238where loading of phosphazene increases flame retardan~y.~~' Crystallization kinetics and thermal degradation behaviour of polyethylene-[NP(OPr")21nblends have been reported.240 Thermal characterization of blends of poly(ethy1ene oxide) (PEO) and the copolymer with overall composition [NP[(OCH2CH2)20Me] { OC6H4 [C(O)C6H5-4]}], has shown an increasing glass transition temperature with increasing polyphosphazene content. Irradiation of these blends by U V light at wave lengths longer than 250 nm, excites the benzophenone chromophore resulting in grafting of PEO onto the polyphosphazene together with crosslinking reactions.241 It is well-known that fluoroalkoxy-substituted polyphosphazenes can be used for the preparation of dental soft liners, due to their permanent softness, energy absorbance, bonding to poly(methy1 methacrylate) (PMMA) liners, and fungus resistance.242The temperature dependency of the viscoelasticity of polyphosphazene liners has been as well as their ageing characteristics.244In comparison to other liner materials fluoroalkoxy polyphosphazenes show a low adsorption to proteins.245

220

Organophosphorus Chemistry

OCN(CH&NCO

1 c

0

0 1

Preparation and investigations of the antitumour activity of polyphosphazenes bearing biologically active groups have been continued. Methoxydiethyleneglycol and methoxypoly(ethy1ene glycol) diamineplatinum(I1) derivatives with aspartate (q = 1) and L-glutamate (q = 2) spacers (125) have been prepared according to well-known procedures. The in vivo activity of some of these polymers against the L1210 cell line appears to be higher than that of cisplatin or ~ a r b o p l a t i nIn . ~ a~ ~parallel study polyphosphazenes (126) with two active groups are considered, in which the platinum group is incorporated next to doxorubicin, a known cytostatic for solid tumours. It has been found that at a given doxorubine content the in vivo antitumour activity against L 1210 increases with increasing platinum content, reaching T/C values higher than C i ~ p l a t i n . ~ ~ ~ The hydrolytic degradation of polyphosphazenes bearing amino ester and MPEG groups can be directed in aqueous solution by the nature of the amino esters, the molar ratio of the substituents, pH and the temperature of the buffer s o ht ion.248 The polyelectrolyte [NP(OC6H4C02H-4)2]n(PCPP) can be hydrophobically modified by replacing some of the carboxylic acid groups by propyl ester moieties. These modified PCPP require a higher NaCl concentration for coacervation in aqueous solution, the higher the ester content the higher the salt c ~ n c e n t r a t i o nIonic . ~ ~ ~crosslinking of coacervated microdroplets of PCPP by aluminum lactate leads to the formation of microspheres, stable for at least one month in a phosphate buffer (pH 7.4).250It has been claimed that influenza virus present in an aqueous medium of PCPP and monophosphoryl Lipid A induces a higher anti-influenza response than present in either a PCPP medium or a lipid medium alone.25'

22 1

6: Phosphazenes

(125) p = 2,7;q = 1 ; z = 0 p = 2,7,16;q = 2;z # 0

OMe

OMe

OMe

I

I

(fH2)6

I

(YH2)6

(:H2)6

o=c

o=c I

I NHCHC02H(R)

NHCHC02H(Na) I

CH2CH2C02Na(H)

o=c

I

CH2CH2C02R(H) (126)

R=

Me0

0

Me& Ho

OH

0 I II NHCHCO-Pt, I

CH2CH2Cd

6

H2

0

I

doxorubicin substituent

The mechanical properties of polypyrrole can be improved by electropolymerization of pyrrole onto a cast film of mP(OPh)2], (PBPP), yielding a PBPP-polypyrrole composite.252 Polyphosphazenes with general formula INP[O(CH2CH20),C6H4R-4]2}~,in which R is a hydrophobic branched alkyl group, have been used as one of the components of the cathode liquid in a reactive metal-water battery.253 Polymers [NP(Me)Ph],[NP( Ph)CH2RIy with small amounts of R = CH2CF3 or CH2C6F5are under investigation as possible coatings.254Poly(ferroceny1aminophosphazenes) have been applied for polyphosphazene modified carbon past electrodes as electron transfer mediat01-s.~~~ Poly(aminothionylphosphazene)-b-poly(tetrahydrofuran) block copolymers ~=P(Am2)-N=P(Am2)-N=S(0)Am],-[OCH~CH2CH2CH2],, with methylamino or n-butylamino substituents have used as polymeric matrixes for oxygen sensor applications.256

222

Organophosphorus Chemistry

Organo-substituted polyphosphazenes have been used in photographic applications257y258 and as flame retardants.259 Crystal Structures of Phosphazenes and Related Compounds

5

The following compounds have been examined by diffraction methods. Distances are given in picometers and angles in degrees. Standard deviations are given in parentheses.

Compound

Comments

(1)

N( l)P( 1) 162.6(6) N( 1)P(2) 181.2(5) mean NP(1) 161.7(5) mean NP(2) 175.8(4)

MeXMe NP 158.0(3)

ReJ:

2

5

MeVMe

NP 160.8(8)

NP 169(1) NP(Ph2) 156.8(2), NP(0) 157.8(2) LPNP 136.8(1) NP(Ph2) 155.9(4), NP(S) 156.9(4) LPNP 137.2(3) NP(Ph2) 158.3(4), NP(0) 153.5(4) LPNP 137.5(3) NP(Ph2) 160(1) NP(X) 153(1) LPNP 140.7(6) two independent mols. in unit cell

6

13 11 11 11 11

13

223

6: Phosphazenes

(7) (21) (22) C13A1N(SiMe3)=PPri3 MeCl2A1N(SiMe3)=PPh3 Me2ClAlN(SiMe3)=PPh3 Me3AlN(SiMe3)=PPr'3 Me2ClAlNH=PCy3 Me3AlNH=PCy3 (25) But3PNA1(C12)N(PBu'3)kl(C12) (50) (58b) (26) [Fe(C = CSiMe3)(N=PEt3)]4 (27) [MnBr(NPEt3)I4.CH2Cl2 (28a).2CH2C12

.

[BiF2(NPEt3)(HNPEt3)I2 [Bi2(NPPh3)4]2t

[Sm21(NPPh3),(DME)].2DME

DME = 1,2-dimethoxyrnethane mb2I(thf )2(NPPh3)4.2thf

mean NP(Ph2) 157.2(2) NP(S) 156.9(4), 159.0(4) LPNP 132.4(2), 135.4(2) NP(Ph2) 159.1(4) NP(S) 157.9(4) LPNP 127.4(2) NP 159.2(2) mean NP 161.3(5) NP 164.6(2) NP 158(2) NP 161.2(2) NP 160.6(6) NP 162.3(2) two independent mols. in the unit cell; mean NP 152.0(5) mean NP 160.4(2) mean NP 162.5(4) mean NP 163.9(2) mean NP 163.8(1) mean NP 158.9(2) mean NP 157.0(6) mean NP 158.2(7) mean N(Me2)P 163.4(5) mean NP 159.4(6) mean NP 158.0(6) N(Me2)P 155.8(10)-169.2(8) mean NP 160.3(9) N(Me2)P 161.3(9)-164.9(11) mean NP 158.0(4) mean NP 158.6(4) NP 157.0(7) NP 164.9(5) NP 159.4(2) NP 159.2(2) NP 159.5(4) NP 159.7(6) NP 158.0(3) NP 160.2(9) mean NP (p-NPPh3) 162.3(7) NP (term. NPPh3) 159.6(8) mean NP 157.4(4) mean NP 157.8(5) mean NP (p-NPPh3) 157.0(3) mean NP (term. NPPh3) 153.9(3) mean NP (p-NPPh3) 154(2) NP (term. NPPh3) 148(2), 155(2)

13 29 29 30 30 30 30 30 30 30 30 30 30 31 31 31 32 32 32 33 33 34 34 34 35 35 35 36 36 40 37 37 38 39

224

(35b) (36).CC14 (37a) (C2/c);

Pri2P(0)NHP(O)Pri2 Cd[Pr 2P(Se)N P(Se)Pr 2-Se,Se']2 Pt[Pri2P(Se)NP(Se)Pri2-Se,Sell2

Bus2P(S)NHP(S)Bui2

Organophosphorus Chemistry

NP 158.7(5) mean NP (p-NPPh3) 155.3(4) NP (term. NPPh3) 150.3(6) N(Si)P 159.4(5) N(Y)P 154.9(6) N(Si)P 158.0(4) mean N(Y)P 152.9(3) N(Si)P 156.7(3) mean N(Sm)P 154.1(2) two independent mols. in unit cell; mean NP 161.1(4) NP 159.8(3) mean NP 165.2(8) two independent mols. in unit cell; mean NP 160.1(3) NP 159.4(4) mean NP 158.5(9) mean NP 159.4(5) NP 158.2(3), 159.3(3) mean NP 162.7(2) mean NP 161.4(2) NP 158.5(3), 160.0(3) mean NP 157.5(2) mean NP 162.9(3) mean NP 165.0(2) mean NP 163.O( 3) mean NP 162.1(2) mean NP 162.1(2) mean NP 160.6(2) mean NP 160.3(2) mean NP 169.0(4) LPNP 131.2(2) mean NP 167.0(1) LPNP 130.0(2) NP 156(1)-160( 1) mean LPNP 143.5(9) NP 160.3(5), 162.3( 5 ) LPNP 127.6(3) mean NP 168.4(2) LPNP 132.1(2) mean NP169.1(5) LPNP 133.1(2) NP 165.7(5), 170.6(6) LPNP 133.0(4) mean NP 158.1(4) LPNP 134.2(6), 136.1(5)

39 41 41 41 41 42 42 42 44 44 46 46 46 47 47 48 48 49 50 51 52 53 54 54 55 55

55 55 56 56 56 57

6: Phosphazenes

mean NP 158.6(4) LPNP 123.5(6)-133.8(6) mean NP 158.9(1) mean LPNP 130.3(1) molecule on special position S’I2 Co[Pri2P(S)NP(S)Pri2-S, NP 158.4(2) LPNP 138.3(4) mean NP 158.9(1) Co[Ph2P(Se)NP(Se)Phz-Se,Se’l2 mean LPNP 131.8(2) mean NP 159.5(1) Co[Pri2P(Se)NP(Se)Pri2-Se,Se’]2 mean LPNP 137.9(1) NP 156.9(4)-159.3(4) LPNP 137.9(3), 140.3(3) two independent mols. in the unit cell; NP 157.2(3)-160.0(3) LPNP 138.1(2)-142.1(2) NP 155.0(3)-159.0(3) LPNP 136.1(2), 144.2(2) mean NP 158.3(2) LPNP 131.9(2), 135.7(2) mean NP 159.2(2) LPNP 130.1(2), 131.8(2) NP 161.0(2) LPNP 147.7(3) NP 158.9(4)-163.4(3) (7 1).CH2C12 LP(q2-N)P128.0(2), 135.0(2) LP(q 3-N)P 140.9(2) NP 159.1(5)-162.8(5) LP(q2-N)P129.4(4), 130.8(3) LP(q3-N)P 139.3(3) NP 159.0(4) IPNP 133.8(3)-135.1(4) mean NP 159.7(2) Ru{[PhzP(S)NP(S)Phz-S,S’12PPh3). LPNP 126.4(2), 129.6(2) CH2C12 mean NP 158.6(5) Ru { [Pr12P(S)NP(S)Pri2-S,S12PPh3) LPNP 127.8(4), 135.4(4) mean NP 160.1(4) trans-Ru { [Pri2P(S)NP(S)Pri2-S,S]2 LPNP 128.3(2) (Bu“C)21 mean NP 160.0(7) Ru{[Ph2P(S)NP(S)Ph2-S,S]3. 120.6(9-1 29.4(6) LPNP OSMeCN NP 158.5(3)-160.8(3) Ru { [Pri2P(S)NP(S)Pri2-S,S‘]2SO} LPNP 125.6(2), 136.1(2) NP 155(1)-162( 1) C~S-RU { [Ph2P(S)NP(S)Ph2-S,9 1 2 LPNP 125.0(8), 134.5(8) -(PPh,)(SO2)) .CH2C12 mean NP 158.6(4) { Ru[Pri2P(S)NP(S)Pr’z-S,S’] LPNP 135.7(4) (PPh3))2(@04)2

(63)

225

57 58 58

58

58 59 59 59 60 60 61 61 61 62 63 63 63 63 63 63 63

226

Organophosphorus Chemistry

mean NP 158.7(2) LPNP 138.0(2) mean NP 159.1(2) InC1[Pri2P(Se)NP(Se)Pri2-Se,Sell2 LPNP 139.4(2) mean NP 159.7(3) InC1[Pri2P(Se)NP(Se)Pri2-Se,Se’I2. CH2C12 LPNP 127.1(2), 130.7(2) sJ3.0.75C6H6 NP 156.6(2)-159.4(6) In[Ph2P(O)NP(S)Ph2-0, LPNP 128.8(3), 133.6(4) mean NP 159.3(5) InC1[Ph2P(S)NP(Se)Ph2-S,Se]2 LPNP 127.7(6), 130.9(6) mean NP 162.3(3) Cp2La[Ph2P(Se)nP(Se)Ph2] LPNP 141.1(1) mean NP 162.7(2) CpzGd[Ph2P(Se)nP(Se)Ph2] LPNP 140.0(2) mean NP 162.8(3) Cp2Er[Ph2P(Se)nP(Se)Ph2] LPNP 139.0(2) Cp2Yb[Ph2P(Se)nP(Se)Ph2-Se,Se‘] two independent mols. in unit cell; mean NP 159.2(2) LPNP 135.0(2), 138.0(2) mean NP 162.5(1) LPNP 141.9(1) Cp*IrC1[Ph2P(S)NP(S)Ph2-S, S’]. NP 158.3(3), 160.1(3) CHC13 LPNP 133.2(2) Cp*IrCl[Ph2P(Se)NP(Se)Ph2-Se,Se’]. mean NP 159.4(3) CHC13 LPNP 134.1(3) Cp*Ir(SCN)[Ph2P(S)NP(S)Ph2-S, S’] NP 157.3(3), 159.0(3) LPNP 131.7(2) Cp*Ir(SCN)[Ph2P(Se)NP(Se) mean NP 158.0(5) PhZ-Se,Se’] LPNP 133.7(4) Cp*Ir(SeCN)[Ph2P(S)NP(S)Ph2-S,S ] mean NP 158.9(4) LPNP 132.2(4) Cp*Ir(SeCN)[Ph2P(Se)NP(Se) NP 157.5(6), 158.9(6) Ph2-Se,Se’] LPNP 133.7(4) Cp*Irph2P(S)NP(S)Ph2-S,S’] NP 158.2(4), 159.5(4) LPNP 125.9(3) NP = 156.8(5) LPNP 149.9(4) in SPNPS unit (74) NP 159.9(2) LPNP 133.3(3) mean NP 160.0(4) (75) LPNP 127.8(3) mean NP 158.2(7) LPNP 135.5(4) (77), E = S, L = o - C ~ H ~ P ( P ~ ~ ) NNP H ~157.9(6), 161.5(7) LPNP 132.3(4)

InC1[Pri2P(S)NP(S)Pri2-S,S’I2

64

64 64 65 65 66 66 66 66 66 67 67 67 67 67 67 67 68 69 68 68 68

6: Phosphazenes

in SePNPSe unit NP 156.3(9), 160.5(9) LPNP 123.8(6) Au [Ph2P(Se)NP(Se)PPhZ-Se,Se'] mean NP 161(1) [Ph2PNHP(O)PPh,-P] 1 LPNP 134(1) Te[Pri2P(S)NP(S)Pri2-S,SI2 mean NP 158.4(1) LPNP 142.9(1) Te[Cy2P(S)NP(S)Cy2-S,SIl2.1.5CHC13 mean NP 158.9(5) LPNP 145.3(3) NP 155.8(3)-158.0(3) Te[Et 2P(S)NP(S)(OPh)2- S, SI2 LPNP 142.2(2) Te[Pri2P(S)NP(S)Ph2-S, S'I2 mean NP 159.1(4) LPNP 138.8(8) mean NP 158.4(5) Te[Pri2P(Se)NP(Se)Pri2-Se,Se'I2 LPNP 145.1(2) Te(C6H40Me-4)[Pri2P(S)NP(S) mean NP 158.0(2) Pri2-S,~ ' 1 ~ 1 ~ LPNP 144.3(2) Te(C6H4OMe-4)[Prl2P( S)NP(S) NP 155.8(9), 159.9(9) PhZ-S,SIC12 LPNP 139.0(6) 155.8(3)-158.0(3) (80) LPNP 142.2(2) NP 151.1(5), 155.0(5) LPNP 158.0(3) NP 161.2(3) NP 157.6(3) mean NP 159.3(6) NP 158.9(7) NP 160.0(4) NP 161.2(8) mean NP 156.8(2) mean NP 159.1(4) NP(F2) 151.4(2) N(Me)P 166.4(2) NP[(NMe2)2] 159.2(6) N(Me)P 166.9(6) mean N(Me2)P 164.8(5) NP 162.4(6) mean NP 157.7(4) LPNP = 144.7(4) NP (in segment PNP) for three diff. compds.: 157.6)2)-163.8(2) LNPN 100.5(2)- 12 1.8(2) LPNP 129.1(1)-133.7(2) [Os(NPPh3)L]'CT NP 156(1) L = salophen [Ph3PNPPh3]+ mean NP 158.4(2) (78b)

227

69 70 71 71 71 71 71 71 71 71 78 95 96 96 97 97 97 98 99 100 100 101 102 103

104 105

228

Na[Ph2P(S)NP(S)Ph2-S,S‘]L L = triglyme Na[Ph2P(S)NP(S)Ph2-S,S’]L L = tetraglyme (NPF2)3

Organophosphorus Chemistry

LPNP 137.4(2) mean NP 158.5(2) LPNP 133.7(2) mean NP 159.6(3) LPNP 129.6(1) mean NP 156.7(2) LNPN 119.1(1) LPNP 121.2(2) mean NP 158.0(2) LNPN 119.7(3) LPNP 120.0(2) mean endocycl. NP 158.8(4) mean exocycl. NP 164.7(8) endocycl. LNPN 116.1(3) mean LPNP 122.3(3) mean endocycl. NP 159.9(2) mean exocycl. NP 165.0(4) mean endocycl. LNPN 116.3(1) mean LPNP 123.6(2) endocycl. NP 162.1(6)-168.0(6) exocycl. NP 160.0(6)-170.8(6) endocycl. LNPN 106.8(3)-108,2( 3) LPNP 116.6(3)-127.0(4) endocycl. NP 162(1)-168( 1) exocycl. NP 159(1)-167( 1) endocycl. LNPN 105.8(6)-110.2(6) LPNP 112.6(7) - 116.6(8) endocycl. NP 161(1)-167( 1) exocycl. NP 161(1)-165(1) endocycl. LNPN 107.9(6)-114.4(6) LPNP 122.4(6)-130.8(7) endocycl. NP 161.7(5)-164.6(5) mean exocycl. NP(eq) 161.5(3) exocycl. NP(ax) 165.4(6)-1673 5 ) mean endocycl. LNPN 112.1(5) LPNP 119.8(3)-123.5(3) mean endocycl. NP 161.8(3) exocycl. NP(ax) 170.8(4) exocycl. NP(eq) 159.2(3) endocycl. LNPN 114.7(2) LPNP 119.8(2) endocycl. NP 1.54(3)- 164(3) mean exocycl. NP 162(2) endocycl. LNP(C12)N 119.0(1)-120.0(2) LNP(N,Cl)N 110.0(1)-115.0(1)

106 106 119 119 120

122

121

121

121

122

122

123

229

6: Phosphazenes

LPNP 118.0(2)-126.0(2) in segment P(O2)NP(N,O) mean NP(N,O) 159.8(1) mean NP(02) 156.7(1) in segment P(O2)NP(o2) mean NP 157.7(3) exocycl. NP 159.1(2) LNPN 115.2(1)-11931) LPNP 120.8(1)-123.3(1) in segment P(C12)NP(N2) mean NP(C12) 155(1) mean NP(N2) 164(1) in segment P(N2)NP(N2) mean NP 159(1) mean exocycl. NP 164(1) mean LNP(N2)N 112.5(4) LNP(C12)N 122.8(5) LP(NZ)NP(N2) 129.4(6) mean LP(C12)NP(N2) 120.9(4)

(91)

(93)

mean endocycl. NP 155(4) LNPN 118.9(5)-123.2(5) LPNP 131.4(6)-141.9(5) \

/I

C12P\ 'N ,PCh

But

124

124

I27

.O.SC4H&12

(NPC12)3NP[N(Pri)(CH2)3N(Pri)]endocycl. NP 150.6(4)-157.7(3)

127 mean exocycl. NP 162.6(5) endocycl. mean LNP(C12)N 122.1(2) endocycl. LNP(N2)N 111.3(2) LPNP 130.8(3)- 160.9(3) (NPC12)2(NP[r;J(Pri)(CH2)3N(Pri)]}2 endocycl. NP 156.9(5)-160.3(5) 127 exocycl. NP 162.4(5)- 164.2(5) 1,4-isomer endocycl. LNPN 113.0(3)-125.9(3) LPNP 131.5(3)-15 1.3(4) (NPC12)2NP[N(Pri)(CH2)3N(Pri)] in segment P(N2)NP(C12) 127 mean NP(N2) 162.3(6) mean NP(c12) 154.8(3) in segment P(C12)NP(C12) mean NP 158.0(6) endocycl. LNP(N2)N 110.4(2) mean endocycl. LNP(C12)N 120.7(3) mean LP(C12)NP(N2) 125.0(1) LP(Cl2)NP(Cl2) 117.1(2)

230

Organophosphorus Chemistry

155.8(2), NP 160.(3) LPNP 140.5(2)

(96)

127

in segment N(Cu)PN 132 mean N(Cu)P 160.0(3) mean NP(02) 156.6(2) mean remaining NP 158.4(2) mean LNPN(Cu) 116.3(1) remaining LNPN 118.6(1) LPN(Cu)P 123.4(2) remaining LPNP 120.6(2)-122.2(2) NPC12(NPA)2 in segment P(C12)NP(02) 133a A = 2,2’-dioxy-1,1’-biphenyl mean NP(A) 158.4(5) mean NP(C12) 156.9(5) in segment P(A)NP(A) mean NP 156.4(4) mean LNP(A)N 117.3(2) LNP(C12)N 119.8(3) mean LP(C12)NP(A)120.9(3) LP(A)NP(A) 123.8(4) NP(OC6H40Me-4)2(NPA)2 NP 156.1(3)-157.8(3) 133a A = 2,2’-dioxy-1,l’-biphenyl mean LNPN 117.9(1) mean LPNP 121.8(1) NP(OC6H40Me-4)2(NPA’’) NP 153.9(10)-158.1(8) 133a A ’ = 2,2”-dioxy-l’,1”-binaphthyl LNPN 116.0(5)-118.7(5) LPNP 120.5(6)- 124.3(6) N3P3A’’3.CH2C12.C6H5Me mean NP 157.0(4) 134 A”’ = 3,3’-dioxy-2,2’-bipyrimidyl mean LNPN 117.9(2) mean LPNP 112.1(3) N3P3(OC6H40)3-PEadduct mean NP 158.0(3) 141 PE = polyethylene LNPN 117.4(3) LPNP 122.6(3) N3P3(OC6H40)3-PEOadduct mean NP 158.2(2) 141 PEO = poly(ethy1ene oxide) LNPN 117.4(1) LPNP 122.6(1) NPC121NC(NMe2)12 NP 157.6(3) 152 LNPN 117.3(2) (108), R = R = Me mean NP 158.1(3) 153 LNPN 116.6(1) pPOCH2P(S)RCH20]pC(NMe2)2]2 NP 157.4(2), 158.2(2) 154 R = CH2C5H4FeCSH5 LNPN 115.7(1) I

I

23 1

6: Phosphazenes

(NPC12)2NPC1[OC6H2(But2-2,6)(Me-4] NP 156.3(3)-158.1(3) LPNP 119.9(2)-122.5(2) mean LNP(C12)N 1 18.9(1) LNP(Cl0rg)N 1 15.1 (1) NP(endocyc1.) 157.7(2)-159.2(2) (NPPip2)2[NP(NHEt)Pip]z Pip = piperidinyl NP(exocyc1.) 165.1(2)-l68.9(2) mean LPNP 130.0(1)

178 179

LNPN (endocycl.) 117.9(1), 122.0(1) mean NP 157.6(1) 180 LPNP 119.9(2)-120.9(2) LNPN 117.0(2jl18.2(2) NP 1 53.9(8)-160.2(9) LPNP 120.1(5)-122.5( 5) LNPN 1 16.0(4)-117.8(4) NP 156.0(3) mean NP 159.9(2) mean LPNP 122.4( 1) mean LNPN 116.8(3) NP 159.0 LPNP 132.6 LNPN 114.2

181

182 205 205

References 1 2 3 4 5

6 7 8 9

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6: Phosphazenes 38 39 40 41 42 43

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234 71 72 73 74 75

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76 77 78 79 80 81 82 83 84 85 86 87 88

89

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90 91 92 93

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94

Y. Matsuzaka, T. Haseyama, T. Nobori, U. Takagi, S. Yamazaki and T. Izukawa, Jpn. Kokai Tokkyo Koho, JP 11181275 (Chem. Abstr., 1999, 131, 74156); S. Yamazaki, Y. Hara, T. Noboru, U. Takagi, F. Yamazaki and S . Izukawa, Jpn. Kokai Tokkyo Koho, JP 11315138 (Chem. Abstr., 2000, 132, 337540); S. Yamazaki, H. Watanabe, T. Noboi, U. Takagi, Y. Hara and T. Izukawa, Jpn. Kokai Tokkyo Koho, JP 11302352 (Chem. Abstr., 2000, 132, 323366); S. Yamazaki, Y. Hara, F. Yamazaki and S . Izukawa, Jpn. Kokai Tokkyo Koho, JP 2000038443 (Chem. Abstr., 2000,132, 137834); S . Yamazaki, S. Akimoto, T. Kunihiro and T. Izukawa, Jpn. Kokai Tokkyo Koho, JP 2000017040 (Chem. Abstr., 2000, 132, 109022); S. Yamasaki, Y. Hara, T. Kunihiro, F. Yamazaki, M. Matsufuji, A. Nishikawa, S. Matsumoto, T. Izukawa, M. Isobe, K. Ohkubo and K. Ueno, PCT Int. Appl., WO 2000023500 A;

6: Phosphazenes

95 96 97 98 99 100 101 102 103 1 04 105 106 107 108 109 110

111 112 113 114 115 116 117 118

119 120 121 1 22 123 124 125

235

T. Nobori, T. Hayashi, A. Hara, S. Kiyono, A. Shibahara, K. Funaki, K. Mizutani and U. Takagi, Jpn. Kokai Tokkyo Koho, JP 2000128830 (Chem. Abstr., 2000,132, 308061). R. T. Paine, W. Koestle, T. T. Borek, G. L. Wood, E. A. Pruss, E. N. Duesler and M. A. Hiskey, Inorg. Chem., 1999,38, 3738. A. Dietrich, B. Neumuller and K. Dehnicke, 2. Anorg. Allg. Chem., 1999, 625, 1321. S. Schlecht, D. V. Deubel, G. Frenking, G. Geiseler, K. Harms, J. Magull and K. Dehnicke, 2. Anorg. Allg. Chem., 1999,625, 887. K. Weber, K. Korn, M. Schulz, K. Korth and J. Sundermeyer, Z. Anorg. Allg. Chem., 1999,625, 1315. U. Siemeling, B. Neumann, H.-G. Stammler and 0. Kuhnert, 2. Anorg. Allg. Chem., 2000,626,825. M. D. Mikoluk, R. McDonald and R. G. Cavell, Inorg. Chem., 1999,38,2791. J.-S. Fan, F.-Y. Lee, C.-C. Chiang, H.-C. Chen, S.-H. Liu, Y.-S. Wen, C.-C. Chang, S.-Y. Li, K.-M. Chi and K.-L. Lu, J. Organomet. Chew., 1999,580, 82. T. S. Cameron and M. E. Peach, J. Chem. Crystallogr., 1998,28,919. K. Landskron and W. Shcnick, 2. Naturforsch. B: Chem. Sci., 1999,54, 1363. T.-W. Wong, T.-C. Lau and W.-T. Wong, Inorg. Chem., 1999,38,6181. U. Geiser, M. L. Mercuri and J. P. Parakka, Acta Crystallogr. Sect. C: Cryst. Struct. Commun., 1999, C55, 1253. A. J. Blake, J. A. Darr, S. M. Howdle, M. Poliakoff, W. S. Li and P. B. Webb, J. Chem. Crystallogr., 1999,29, 547. A. J. Elias, M. Jain and D. Reddy, Phosphorus, Sulfur, Silicon Relat. Elem., 1998, 140,203. A. J. Elias, N. D. Reddy and T. V. V. Ramakrishna, Proc. - Indian Acad. Sci. Chem. Sci., 1999,111,453. R. E. Singler and F. J. Gomba, Chem. Ind. (Dekker), 1999,77,297. G. Frison, A. Sevin, N. Avarvari, F. Mathey and P. L. Floch, J. Org. Chem., 1999,64,5524. B. V. Lebedev and T. G. Kulagina, J. Chem. Thermodynamics, 1999,31.697. N. Menek, G. Turgut and M. Odabawglu, Turk. J. Chem., 1999,23,423. M. B. Sayed, Solid State Ionics, 2000,128, 191. J. R. Menendez, G. A. Carriedo, F. J. Garcia-Alonso, E. Clavijo, M. Nazri and R. Aroca, J. Raman Spectrosc., 1999,30, 1 121. C. W. Allen and S. D. Worley, Inorg. Chem., 1999,38, 5187. C. W. Allen, D. E. Brown and S. D. Worley, Inorg. Chem., 2000,39,810. H. S. Wu and S . S . Meng, Can. J. Chem. Eng., 1999,77,1146. V. V. Vapirov, A. E. Shumeiko and N. V. Khobotova, Russ. J. Gen. Chem., 1999, 69, 1008. R. P. Singh, A. Vij, R. L. Kirchmeier and J. M. Shreeve, Inorg. Chem., 2000, 39, 375. Y. Cho, H. Baek and Y. S. Sohn, Polyhedron, 1999,18, 1799. G . T. Lawson, C. Jacob and A. Steiner, Eur. J. Inorg. Chem., 1999,1881. G. T. Lawson, F. Rivals, M. Tascher, C. Jacob, J. F. Bickley and A. Steiner, Chem. Commun., 2000,341. M. Yildiz, Z. Kilig and T. Hokelek, J. Mol. Struct., 1999,510, 227. M. Bloy and U. Diefenbach, 2. Anorg. Allg. Chem., 2000,626, 885. U. Diefenbach, M. Bloy and B. Stromburg, Phosphorus, Sulfur, Silicon Relat. Elem., 1999,144-146, 65.

236

Organophosphorus Chemistry

126 A. K. Shrimal, 2. Naturforsch., 1999, 54b, 1543. 127 S. Kumaraswamy, M. Vijjulatha, C. Muthiah, K. C. Kumara Swamy and U. Engelhardt, J. Chem. SOC.Dalton Trans. , 1999, 891. 128 K. N. Ludwig and R. B. Moore, Synth. Commun.,2000,30, 1227. 129 H. R. Allcock, M. B. McIntosh and T. J. Hartle, Inorg. Chem., 1999, 38, 5535; T. J. Hartle, M. B. McIntosh and H. R. Allcock, Polym. Prepr. (Am. Chern. SOC. Div. Polym. Chem.), 1999,40(2), 908. 130 F. F. Stewart and M. K. Harrup, J. Appl. Polym. Sci., 1999,72, 1085. 131 F. F. Stewart, T. A. Luther, M. K. Harrup and R. P. Lash, Polym. Prepr. (Am. Chem. SOC.Div. Polym. Chem.) , 2000,41(1), 576. 132 E. W. Ainscough, A. M. Brodie and C. V. Depree, J. Chem. SOC.Dalton Trans., 1999,4123. 133 I. Dez, J. Levalois-Mitjaville, H. Grutzmacher, V. Gramlich and R. De Jaeger, Eur. J. Inorg. Chem., 1999, 1673; I. Dez, J. Levalois-Mitjaville, H. Grutzmacher, V. Gramlich and R. De Jaeger, Phosphorus Res. Bull., 1999,10,720. 134 0.S. Jung, Y. T. Kim, Y.-A. Lee, Y. J. Kim and H. K. Chae, Inorg. Chem., 1999, 38, 5457. 135 G. A. Carriedo, F. J. Garcia Alonso, J. L. Garcia, R. J. Carbajo and F. Lopez Ortiz, Eur. J. Inorg. Chem., 1999, 1015. 136 G. A. Carriedo, F. J. Garcia Alonso, P. A. Gonzalez and P. Gomez-Elipe, Polyhedron, 1999,18,2853. 137 V. Diaz and G. Izquierdo, Polyhedron, 1999,18, 1479. 138 C. Diaz, I. Izquierdo, F. Mendiziibal and N. Yutronic, Inorg. Chim. Acta, 1999, 294, 20. 139 M. Odabawglu, G. Turgut and H. Kocaokutgen, Phosphorus, Sulfur, Silicon Relat. Elem., 1999, 152, 9. 140 M. Odabawglu, G. Turgut and H. Kocaokutgen, Phosphorus, Sulfur, Silicon Relat. Elem., 1999, 152, 27. 141 H. R. Allcock, A. P. Primrose, N. J. Sunderland, A. L. Rheingold, I. A. Guzei and M. Parvez, Chem. Mater., 1999, 11, 1243; N. J. Sunderland and H. R. Allcock, Polym. Prepr. (Am. Chem. SOC.Div. Polym. Chem.), 1999,40(2), 750. 142 A. Comotti, R. Simonutti, G. Catel and P. Sozzani, Chem. Mater., 1999, 11, 1476. 143 A. Comotti, R. Simonutti, S . Stramare and P. Sozzani, Nanotechnology, 1999,10, 70. 144 R. Simonutti, P. Sozzani, S. Bracco and A. Comotti, Polym. Mater. Sci. Eng., 2000, 82, 161. 145 H. R. Allcock, N. J. Sunderland, A. P. Primrose, A. L. Rheingold, I. A. Guzei and M. Parvez, Chem. Mater., 1999,11,2478. 146 K. Brandt, I. Porwolik-Czomperlik, M. Siwy, T. Kupka, R. A. Shaw, S. Ture, A. Clayton, D. B. Davies, M. B. Hursthouse and G. D. Sykara, J. Org. Chem., 1999,64,7299. 147 K. Brandt, I. Ponvolik-Czomperlik, M. Siwy, T. Kupka, R. A. Shaw, D. B. Davies and R. A. Bartsch, J. Inclusion Phenom. Macrocyclic Chem., 1999, 35, 281. 148 C. Loup, M.-A. Zanta, A.-M. Caminade, J.-P. Majoral and B. Meunier, Chem. Eur. J . , 5, 1999,3644. 149 R. Schneider, C. Kollner, I. Weber and A. Togni, Chem. Commun., 1999,2415. 150 H. R. Allcock, W. R. Laredo, C. R. deDenus and J. P. Taylor, Macromolecules, 1999,32,7719.

6: Phosphazenes 151

152 153 154 155 156 157 158

159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178

179 180

23 7

M. Taillefer, F. Plenat, C. Chamalet-Combes, V. Vicente and H. J. Cristau, Phosphorus Res. Bull., 1999,10,696. N. D. Reddy, A. J. Elias and A. Vij, J. Organomet. Chem., 1999,580,41. N. D. Reddy, A. J. Elias and A. Vij, J. Chem. SOC.,Dalton Trans., 1999, 1515. N. D. Reddy, A. J. Elias and A. Vij, Inorg. Chem. Commun., 2000,3,29. E. Yoshida and T. Terazono, Polym. J., 1999,31, 621. K. Matyjaszewski, P. J. Miller, J. Pyun, G. Kickelbick and S. Diamanti, Macromolecules, 1999,32,6526. G. Kickelbick, P. J. Miller and K. Matyjaszewski, Mater. Res. SOC.Symp. Proc., 1999,576,129. K. N. Ludwig and R. B. Moore, Annu. Tech. Conf: - SOC.Plast. Eng., 1999,57th, 1844. B. Baroli, G. Delogu, A. M. Fadda, G. Podda and C. Cinico, Int. J. Pharm., 1999,183,101. Z. Zhao and B. Bhushan, Tribol. Lett., 1999,6, 129. Z. Zhao, B. Bhushan and C. Kajdas, Tribol. Lett., 1999,6, 141. C. L. Jiaa and Y. Liu, Tribol. Lett., 1999,7, 1 1 . H. J. Kang, D. J. Perettie and F. E. Talke, IEEE Trans. Magn., 1999, 35, 2385. Q. Zhao, H. J. Kang, L. Fu, F. E. Talke, D. J. Perettie and T. A. Morgan, Lubr. Eng., 1999, 55, 16. Y. W. Chen-Yang, H. F. Lee and C . Y. Yuan, J. Polym. Sci. Part A: Polym. Chem., 2000,38,972. I. Dez, N. Henry and R. De Jaeger, Polym. Degrad. Stab., 1999,64,433. C. W. Lee, R. Venkatachalapathy and J. Prakash, Electrochem. Solid-state Lett., 2000,3, 63. A. Hebeish, A. Waly and A. M. Abou-Okeil, Fire Mater., 1999,23, 117. M. Ikeyama and J. Amano, Jpn. Kokai Tokkyo Koho, JP 11189977 (Chem. Abstr., 1999,131, 103485); M. Ikeyama and J. Amano, Jpn. Kokai TokkyoKoho, JP 11 189978 (Chem. Abstr., 1999,131, 103486). Y. Tada, Y . Nishioka, T. Yabuhara, T. Kameshima, and S . Nakano, PCT Int. Appl., WO 9946314 A (Chem. Abstr., 1999,131,214782). N. Fukuoka and H. Yasuda, Jpn. Kokai Tokkyo Koho, JP 11263885 (Chem. Abstr., 1999,131, 2441 14). M. Zobel, T. Eckel and D. Wittmann, Ger. Offen., DE 19828541. H. Tsujimoto, S. Ishikuro, T. Yonezawa, and T. Watanuki, Jpn. Kokai Tokkyo Koho, JP 2000017574 (Chem. Abstr., 2000,132,109336). Y. Tada, T. Yabuhara, S . Nakano, T. Kameshima, Y. Nishioka, and H. Takase, Jpn. Kokai TokkyoKoho, JP 2000063564 (Chem. Abstr., 2000,132,195239). K. Tendo, H. Sue, and S . Hagiwara, Jpn. Kokai Tokkyo Koho, JP 2000103939 (Chem. Abstr., 2000,132,266141). W. Ishikawa and N. Fukuwatari, Eur. Pat. Appl., EP 0921432 A. H. Komatsu, Jpn. Kokai Tokkyo Koho, JP 200001969 (Chem. Abstr., 2000, 132, 115156). T. Hokelek, A. Kilig, S. Begeg and Z. Kiliq, Acta Crystallogr. Sect. C: Cryst. Struct. Commun., 1999, C55, 783. T. Hokelek, E. Kilig and Z. Kilig, Acta Crystallogr. Sect. C: Cryst. Struct. Commun., 1999, C55,983. T. Hokelek, N. Akduran, M. Yildiz, H. Dal and Z. Kiliq, Acta Crystallogr. Sect. C: Cryst. Struct. Commun., 2000, C56,90.

238 181 182 183 184 185 186 187 188 189 190 191

192 193 194 195 196 197 198 199 200 20 1 202 20 3 204 205

206 207 208 209 210

Organophosphorus Chemistry

T. Hokelek, N. Akduran, A. Kilig, S. Begeg and Z . Kilic, Anal. Sci., 2000, 16, 101. T. Uchiyama, T. Fujimoto, A. Kakehi and I. Yamamoto, J. Chem. SOC.Perkin Trans. I , 1999, 1577. M. L. Turner, Ann. Rep. Prog. Chem. Sect. A: Inorg. Chem., 1999,95,453. M. Gleria, Phosphorus Res. Bull., 1999, 10, 55. M. Guglielmi, G. Brusatin, G. Facchin and M. Gleria, Appl. Orgunomet. Chem., 1999, 13, 339. H. R. Allcock, Macromol. Symp., 1999, 144, 33. L. Qiu and K. Zhu, Gongneng Guofenzi Xuebuo, 1999, 12, 115 (Chem. Abstr., 1999,131, 35704). V. Chandrasekhar, S. Nagendran and A. Athimoolam, Main Group Chem. News, 1999,7,4. H. R. Allcock, Phosphorus, Sulfur, Silicon Relat. Elem., 1999, 144146,61. G. A. Carriedo, F. J. Garcia Alonso, P. A. Gonzalez, J. L. Garcia and P. GomezElipe, Phosphorus, Sulfur, Silicon Relut. Elem., 1999, 144146, 73. M. Gleria, F. Minto, A. Galeazzi, R. Po, N. Cardi, L. Fiocca and S. Spera, Phosphorus, Sulfur, Silicon Relut. Elem., 1999, 144146, 201; M. Gleria, F. Minto, R. Bertani, B. Tiso, R. Po, L. Fiocca, E. Lucchelli, G. Giannotta and N. Cardi, Phosphorus Res. Bull., 1999, 10,730. M. P. Tarazona and E. Saiz, Polymer, 2000,41, 3337. D. Dumont and D. Bougeard, Comput. Theor. Polym. Sci., 1999,9,89. J. R. Fried and P. Ren, Comput. Theor. Polym. Sci., 1999,9, 1 11. P. Ren and J. R. Fried, Polym. Muter. Sci. Eng., 1999, 81, 535. A. V. Raja and J. B. Lagowski, J. Mol. Struct. THEOCHEM, 1999,465,93. E. Morales, I. Villarreal and J. L. Acosta, J. Appl. Polym. Sci., 1999, 73, 1023. I. Villarreal, E. Morales and J. L. Acosta, Angew. Mukromol. Chem., 1999, 266, 24. V. G. Kulichikhin, S. A. Kuptsov and D. R. Tur, Vysokomol.Soedin. Ser. A Ser. B, 1998,40, 1823 (Chem. Abstr., 1999,131, 116764). E. K. Borisenkova, G. B. Vasil’ev, V. G. Kulichikhin and D. R. Tur, Vysokomol. Soedin. Ser. A Ser. B, 1998,40, 1809 (Chem. Ahstr., 1999,131, 117015). N. N. Avdeev, D. K. Novikova, G. B. Vasil’ev, V. G. Kulichikhin and D. R. Tur, Vysokomol. Soedin. Ser. A Ser. B, 1998, 40, 1757 (Chem. Abstr., 1999, 131, 116817). A. T. Kalashnik, S. P. Papkov and D. R. Tur, Fibre Chem., 1998,30, 308. J. Burdalo, M. P. Tarazona, G. Carriedo, F. J. G. Alonso and P. Gonzalez, Polymer, 1999,40,4251. W. W. Sulkowski, V. Kireev, A. Sulkowska, B. Makarucha and Z. Zinovitch, Phosphorus Res. Bull., 1999, 10, 764. E. Corradi, A. Farina, M. C. Gallazzi, S. Briickner and S. V. Meille, Polymer, 1999,40,4473. H. Tang and P. N. Pintauro, Eur. Polym. J., 1999,35, 1023. R. Caminiti, M. Gleria, K. B. Lipkowitz, G. M. Lombard0 and G. C. Pappalardo, Chem. Muter., 1999,11, 1492. H. Nakamura, T. Masuko, M. Kojima and J. H. Magill, Mucromol. Chem. Phys., 1999,200,2519. T. Kimura and M. Kajiwara, J. Muter. Sci., 1998,33,2955. Y. W. Chen-Yang, J. J. Hwang and A. Y. Huang, Macromolecules, 2000, 33, 1237.

6: Phosphazenes 21 1 212 213 214 215 216 217 218 219 220 22 1 222 223 224 225 226 227 228 229 230 23 1 232 233 234 235 236 237 238 239

239

F. F. Stewart, R. E. Singler, M. K. Harrup, E. S. Peterson and R. P. Lash, J. Appl. Polym. Sci., 2000, 76, 55. C. W. Allen and A. S. Hneihen, Phosphorus, Surur, Silicon Relat. Elem., 1999, 16146,213. C. W. Allen, A. S. Hneihen, and E. S. Peterson, PCT Int. Appl., WO 0004074 A. N. Kajiwara and T. Tsuchiya, Jpn. Kokai Tokkyo Koho, JP 11 172004 (Chem. Abstr., 1999, 131, 88347). C. Kim, Y. Chang, S. C. Lee, H. R. Allcock and S. D. Reeves, Polym. Prepr. (Am. Chem. SOC.),2000,41(1), 609. R. Prange and H. R. Allcock, Macromolecules, 1999,32, 6390. C. R. de Denus, H. R. Allcock and R. Prange, Polym. Prepr. (Am. Chem. SOC. Div. Polym. Chem.), 2000, 41(1), 554; H. R. Allcock, J. M. Nelson, R. Prange, C. A. Crane and C. R. de Denus, Macromolecules, 1999,32, 5736. H. R. Allcock, C. R. de Denus, R. Prange and J. M. Nelson, Macromolecules, 1999,32,7999. K. H. Lee and D. C. Lee, Polym. Bull. (Berlin), 1999,42 , 543. Y. S. Choung, K. H. Lee and D. C. Lee, Polym. Eng. Sci., 1999,39,1153. Z. Li, M. Zhan and J. G. Qin, Chin. Chem. Lett., 2000,11, 103 F. F. Stewart, M. K. Harrup, R. P. Lash and M. N. Tsang, Polym. Int. , 2000,49, 57. J. Y. Chang, P. J. Park and M. J. Han, Macromolecules, 2000, 33, 321; J. Y. Chang, P. J. Park, M. J. Han and T. Chang, Phosphorus, Sulfur, Silicon Relat. Elem., 1999, 1 6 1 4 6 , 1 9 7 . E. Yashima, K. Maeda and T. Yamanaka, Polym. Prepr. (Am. Chem. SOC.Div. Polym. Chem.), 2000,41(1), 890. J. P. Taylor and H. R. Allcock, Polym. Prepr. (Am. Chem. SOC. Div. Polym. Chem.) , 1999,40(2), 9 10. E. S. Peterson, F. F. Stewart, M. L. Stone, M. K. Harrup, L. A. Polson and C. J. Orme, Phosphorus, Sulfur, Silicon Relat. Elem., 1999, 144-146, 225. M. L. Stone, E. S. Peterson, F. F. Stewart, M. N. Tsang, C. J. Orme and L. Polson, Sep. Sci. Technol., 1999, 34, 1243. F. F. Stewart, M. K. Harrup, E. S. Peterson, M. L. Stone, C. J. Orme and L. A. Polson, Polym. Muter. Sci. Eng., 1999,81, 539. Q. Guo, H. Tang, P. N. Pintauro and S. O’Connor, A C S Symp. Ser., 2000, 744, 162. L. Jones, P. N. Pintauro and H. Tang, J. Membr. Sci., 1999, 162, 135. Y. M. Sun, C. H. Wu and A. Lin, J. Polym. Res., 1999,6,91. G . Golemne, G. Facchin, M. Gleria and E. Drioli, Phosphorus Rex Bull., 1999, 10, 736. S. Park, J. S. Kim, Y . Chang, S. C. Lee and C. Kim, J. Inorg. Organomet. Polym., 1998, 8,205. M. K. Harrup, A. K. Wertsching and F. F. Stewart, Polym. Muter. Sci. Eng., 2000, 82, 307. D. Mathew, C. P. R. Nair and K. N. Ninan, Polym. Int., 2000,49,48. C. S. Reed, J. P. Taylor, K. S . Guigley, M. M. Coleman and H. R. Allcock, Polym. Eng. Sci., 2000,40,465. H. R. Allcock, M. M. Coleman, C. S. Reed and K. S. Guigley, US, US 5965627. W.-Y. Chiu, P.-S. Wang and T.-M. Don, Polym. Degrad. Stab., 1999,66,233. P.-S. Wang, W.-Y. Chiu, L.-W. Chen, B.-L. Denq, T.-M. Don and Y.-S. Chiu, Polym. Degrad. Stab., 1999,66, 307.

240

Organophosphorus Chemistry

240

W.-Y. Chiu, F.-T. Wang, L.-W. Chen, T.-M. Don and C.-Y. Lee, Polym. Degrad. Stab., 2000,67,223. F. Minto, M. Gleria, A. Pegoretti and L. Fambri, Macromolecules, 2000, 33, 1173; F. Minto, A. Pegoretti, L. Fambri and M. Gleria, Phosphorus Res. Bull., 1999, 10, 752. L. Gettleman, Phosphorus, Sulfur, Silicon Relat. Elem., 1999, 144-146,205. K. Saber-Sheikh, R. L. Clarke and M. Braden, Biomaterials, 1999,20, 817. K. Saber-Sheikh, R. L. Clarke and M. Braden, Biomaterials, 1999,20,2055. Y. Imai and Y. Tamaki, J. Prosthet. Dent., 1999,82, 348. S. B. Lee, S.-C. Song, J.-I. Jin and Y. S. Sohn, Polym. J. (Tokyo), 1999, 31,

24 1 242 243 244 245 246

1247.

247 248 249 250 25 1 252 253 254 255 256

257 258 259

S.-C. Song, C. 0. Lee and Y . S. Sohn, Polym. Int., 1999,48, 627. S. B. Lee, S.-C. Song, J.-I. Jin and Y. S. Sohn, Macromolecules, 1999,32, 7820. A. K. Andrianov, Y. Y. Svirkin, J. Chen and B. E. Roberts, Polym. Prepr. (Am. Chem. Soc. Div. Polym. Chem.), 1999,40(2), 293. A. K. Andrianov, J. Chen and S. S. Sule, Polym. Prepr. (Am. Chem. SOC.Div. Polym. Chem.), 1999,40(1), 355. A. K. Andnanov, S. S. Jenkins, J.R. Loebelenz, B. E. Roberts, PCT Int. Appl., WO 0025815 A. M. A. de la Plaza, M. C. Izquierdo, E. Sanchez de la Blanca and F. Hernandez Fuentes, Synth. Met., 1999, 106, 121. M. K. Harrup, E. S. Peterson, and F. F. Stewart, P C T Int. Appl., WO 2000028609 A. I. 1. Selvaraj, R. L. Kirchmeier and J. M. Shreeve, Polym. Prepr. (Am. Chem. SOC.Div. Polym. Chem.), 2000, 41(1), 556. C. N. Myer and C. W. Allen, Polym. Prepr. (Am. Chem. SOC. Div. Polyrn. Chem.), 2000,41(1), 558. R. Ruffolo, C. E. B. Evans, X.-H. Liu, Y. Ni, Z . Pang, P. Park, A. R.McWi1liams, X. Gu, X. Lu, A. Yekta, M. A. Winnik and I. Manners, Anal. Chem., 2000, 72, 1894; Y. Ni, M. A. Winnik, I. Manners, Z . Pang and X. Gu, Can. Pat. Appl., CA 22043 19. H. Shimizu and N. Fukuwatari, Jpn. Kokai Tokkyo Koho, J P 11143029 (Chem. Abstr., 1999, 131, 2571 1). H. Komatsu, Jpn. Kokai Tokkyo Koho, JP 1 1 338095 (Chem. Abstr., 2000, 132, 42754). T. Yabuhara, Y. Tada, T. Kameshima, S. Nakano, Y. Nishioka, and H. Takase, Jpn. Kokai TokkyoKoho, J P 2000026741 (Chem. Abstr., 2000,132, 123416).

Author Index

In this index the number in parenlhesis is the Chapter number of the citation and this is followed by rite reference number or numbers ofthe relevant cilations within lhal Chapter.

Abad, J.A. (1) 455 Abbas, S. (3) 145 Abbiati, G. (5) 76; (6) 28 Abdallah, D.J. (1) 481 Abdou, W.M. (3) 111; (5) 101 Abdou-Yousec H.M. (5) 59 Abdreimova, R.R. (3) 61 Abe, H. (4) 25,41,42 Abe, I. (1) 109 Abe, J. (1) 482 Abou-Okeil, A.M. (6) 168 About-Jaudet, E. (3) 104 Abram, U. (1) 425 Ackermann, H. (6) 33,34 Acosta, J.L. (6) 197, 198 Adams, M. (4) 72 Adibi, H. (1) 472 Agbossou, F. (3) 39, 40, 44, 59 Aggawal, M.D. (1) 422 Aguirre, G.(1) 66 Ahlrichs, R. (1) 254 Ahn, K.H. (1) 37, 193 Ainscough, E.W. (6) 132 Aitken, R.A. (1) 569; (5) 2,4, 43,67

Akahane, A. (5) 92 Akbayeva, D.N. (3) 61 Akduran, N. (6) 180, 181 Akimoto, S.(6) 94 Akiyama, T. (5) 51 Akutagawa, K. (3) 124 Alajarin, M. (1) 3 15; (6) 1 Albanov, A.I. (1) 164; (3) 144 Albert, J. (1) 327-329 Alberti, A. (1) 513 Albinati, A. (1) 209 Albisson, D.A. (3) 161, 162 Alder, M.J. (1) 28

Aldern, K.A. (4) 9 Alekseev, F.F. (2) 12 Aleshkova, M.M. (3) 60 Alexakis, A. (3) 70 Ali, M.A. (3) 39 Allart, B. (4) 37 Allcock, H.R. (6) 129, 141,

145, 150, 186, 189,215218,225,236,237 Allen, A., Jr. (5) 23 Allen, C.W. (6) 115, 116, 212, 213,255 Allen, D.W. (1) 453,454 Al-Malaika, S. (3) 137 Al-Masum, M. (1) 334 Alonso, F.J.G. (1) 223; (6) 203 Alvarez-Ibarra, C. (1) 259 Alvarez-Manzaneda, E.J. (1) 3 09 Amano, J. (6) 169 Amosova, S.V.(3) 144 Amsallem, D. (1) 245 Anand, B.M.(2) 17 Andersen, N.G. (6) 5 Anderson, C. (1) 34,228; Anderson, J.C. (1) 114 Anderson, N.G. (1) 194,369 Ando, K. (5) 47, 85, 103 Andrei, G. (4) 26 Andrews, C.D. (1) 5 12 Andrianov, A.K. (6) 249-25 1 Andrieu, J. (1) 166 Anfang, S.(6) 35,41 Angelici, R.J. (1) 140, 158 Angel], C.A. (6) 79 Anishchenko, A.A. (3) 12, 13 Anisuuaman, A.K.M. (4) 19 Anselme, G. (1) 523 24 1

Anzenbacher, P. (1) 443 Aoyama, H. (5) 84 Aparicio, D. (1) 398; (5) 64 Aparna, K. (6) 47,49 Aragaki, M. (3) 102 Arai, M.(5) 51,57 Arasi, H.N. (1) 264 Arbuzova, S.N.(1) 106, 121, 153, 188,445

Arca, M. (1) 416 Arduengo, A.J., III (2) 36 Arduini, A. (1) 426 Arena, C.G. (3) 179 Argay, G. (1) 323; (6) 4 Arif, A. (3) 125 Arifin, A. (1) 371 Arisawa, M. (1) 258 Ariza, X. (1) 325 Arnold, L.A. (3) 18 1 Arnone, A. (4) 22 Arnoud-New, F. (1) 380 Aroca, R. (6) 114 Arques, A. (1) 3 18 Arsanious, M.H.N. (3) 130, 13 1

Arya, P.(1) 234 Asai, M. (6) 91 Asai, N. (4) 15 Asghari, S. (1) 26 1 Ashe, A.J., III (1) 601 Asmus, S.M.F. (1) 602 Athimoolam, A. (6) 188 Atmaca, L. (1) 490 Attanasi, O.A. (1) 272; (5) 55 Atwood, J.D. (1) 244 Aubert, C. (1) 372 Aubertin, A.M. (4) 46 Audoux, J. (1) 170

242

Baroli, B. (6) 159 Barranco, E.M. (5) 26 Barrero, A.F. (1) 309 Barrett, A.G.M. (5) 89 Barsegyan, S.K. ( I ) 268,489 (6) 110 Bartels, B. (1) 405 Avdeev, N.N. (6) 201 Barth, D. (3) 21 Avendaiio, C. (6) 22 Bartoli, G. (1) 374 Avent, A.G. (1) 145, 590 Bartsch, R.A. (6) 147 Ayers, T.A. (3) 36 Batsanov, A.S. (3) 103 Batterby, T.R. (4) 89 Baudler, M. (1) 120 Baaden, M. (1) 427,428 Babu, R.P.K. (5) 30; (6) 50, 52, Baumann, A. (1) 155 Baumann, W. (5) 21 53 Baurngartner, T.(1) 552 Baceiredo, A. (1) 245, 349, Bautista, D. (1) 3 18; (5) 24 350, 561, 562; (3) 173; (5) Bayon, J.C. (1) 115 10,64 Bazhanova, Z.G.(1) 419 Bachmann, C. (1) 360 Beabealashvilli, R.S. (4) 85 Badarau, C. (3) 164 Beadle, J.R. (4) 9 Badri, A.A. (1) 5 10 Beatty, A.M. (1) 548 Bae, S.K. (1) 144 Beaucage, S.L. (4) 48 Baek, H. (6) 120 Beaudoin, A.R. (4) 69, 71,78 Bains, R. (2) 17 Becher, J. (3) 93 Bajorat, V. (1) 587 Beck, B.C. (1) 567 Baker, T.J. (4) 39 Becker, G. (1) 127 Bakkas, S . (3) 147 Bedford, R.B. (3) 161, 162 Bakker, M.J. (1) 619 Begq, S. (6) 78, 178, 181 Bako, P. (1) 406 Balavoine, G.G.A. (1) 563, 570 Beghetto, V. (1) 389 Bei, X. (1) 7 Balazs, G. (6) 57 Beigelman, L. (4) 86 Balczewski, P. (5) 94 Beletskaya, I.P. (1) 175, 176, Baldoli, C. (1) 166, 346 465 Baldridge, K.K.(I) 250 Beller, M. (1) 236; (3) 159 Balkovich, M.E. (5) 43 Belogorlova, N.A. (1) 164 Ball, L.M. (4) 35 Bel'skii, V.K. (2) 10, 11; (3) Ballatore, C. (4) 5 89, 178 Balueva, A. (1) 25, 163 Benaglia, M. (1) 5 13 Balzarini, J. (4) 5, 12, 13,26, Benakki, R. (1) 469 30, 55, 76 Bendas, G. (3) 153 Bampos, N. (1) 27 Bender, C. (1) 444 Bandoli, G. (1) 440 Benetti, S.(3) 113 Bansal, R.K. (1) 605; (3) 20, Benhaim, C. (3) 70 127 Benincori, T. (1) 17 Baraldi, P.G. (4) 76 Benndorf, G. (1) 333 Baraniak, J. (4) 92 Benner, S.A. (4) 89 Barboso, S. (1) 380 Bennett, M.A. (1) 255 Barco, A. (3) 113 Bentabet, E. (1) 137 Barkallah, S.(1) 384 Bentrude, W.G. (3) 95, 124Barlow, J.N. (4) 59 126 Barnaro, P. (1) 116 Berberova, N.T.(1) 253 Barndsma, L. (1) 121 Berclaz, T. (1) 613; (5) 5 Barnieux-Flammang, M. (3) BCreau, V. (6) 62 134

Auer, F. (1) 224 Aunon, D. (1) 3 18 Aust, J. (1) 463 Avarvari, N. (1) 612, 613,625;

I

OrganophosphorusChemistry Berens, U. (1) 96; (3) 34 Bergamini, P. (3) 113 Bergbreiter, D.E. (1) 84 Bergerhoff, G. (1) 432 Bergman, J. (1) 3 1 1 Bergmann, J. (4) 11 Bergot, J. (1) 305 Bergstrasser, U. ( I ) 505, 509, 598, 599, 602, 603, 621; (3) 29 Berkman, C.E. (3) 190 Bernarinelli, G. (5) 5 Bertagnolli, H. (1) 155 Bertani, R. (5) 25; (6) 191 Bertrand, G. (1) 245, 347-350, 524, 560-562; (3) 173; (5) 10,64 Beskrylaya, E.A. (1) 445 Bestmann, H.J. (5) 43 Beswick, M.A. (1) 13 1 Bhaduty, P.S. (1) 486 Bhanthumnavin, W. (3) 125 Bhattacharyya, P. (1) 216 Bhushan, B. (6) 160, 161 Bianchini, C. (1) 116 Bibas, H. (3) 134 Bickelhaupt, E.M. (6) 43 Bickelhaupt, F. (1) 363, 364, 544 Bickley, J.F. (6) 122 Bieler, N.H. (1) 2 18 Bienewald, F. (1) 25 1 Bijanzadeh, H.R. (1) 264 Binger, P. ( I ) 508, 62 1 Birdsall, D.J.(6) 55, 59, 7 1 Bischof€, S. (1) 83; (3) 66 Bitha, P. (3) 129 Bittman, R. (1) 3 10 Blackbum, L. (5) 56 Blacque, 0. (1) 137 Blake, A.J. (1) 371; (6) 106 Blanchard, J.S. (4) 59 Blaser, D. (1) 507 Blaurock, S. (1) 134, 139 Blowe, P.J.(1) 221 Bloy, M. (6) 124, 125 Blue, T.E. (4) 19 Bocskei, Z. (i) 394 Bodmann, K. (5) 104, 105 Boduszek, B. (3) 157 Boeck, P. (1) 478; (5) 36,37 Boehmer, V. (1) 380,426,427 BBmer, A. (1) 61, 89, 186, 233;

243

Author Index (3) 24, 58 Boese, R.(1) 4 10, 507 Bohnen, F.M. (1) 180 Bohres, E. (1) 616 Bojilova, A. (3) 110 Boland, W. ( 5 ) 39 Bolm, C. (1) 73 Bol'shakova, M.Y. (1) 8 1 Bonafoux, D.(1) 145 Bondarenko, N.A. (1) 149 Bondarev, O.G.(2) 3 1; (3) 73 Bonfada, E. (1) 425 Bonini, C. ( 5 ) 75 Bonn, G. (3) 109 Bonora, G.M. (3) 184 Boon, J.A. (1) 500 Bootle-Wilbraham, A. (1) 178 Borangazieva, A.K. (3) 60 Borbulevych, O.Y.(3) 160 Borch, R.F.(4) 6, 7 Borchert, T.V. (3) 105 Borek, T.T.(6) 95 Borisenkova, E.K. (6) 200 Borisova, I.V.( 5 ) 8 Borkenhagen, F.(6) 6 Borodkin, S.A. (1) 492 Bonov, M.V. (1) 71 Bougeard, D. (6) 193 Bouillon, R. ( 5 ) 93 Boukraa, M. (1) 384 Boullanger, P.(1) 324 Boulos, L.S. (3) 131; ( 5 ) 44 BOUT~SSOU, D.(1) 347, 524, 560-562 Boyer, J.L. (4) 69,70,72,73 Boyer, P. (1) 137 Boyle, P.D. ( I ) 297, 298 Bracco, S. (6) 144 Brachwitz, H. (4) 11 Braden, M. (6) 243,244 Brady, F.J. (1) 1 Braga, A.L. (1) 478; ( 5 ) 36,37 Branch, C.L.(3) 63 Brandsma, L. (1) 106, 164 Brandt, K. (6) 146, 147 Brauer, D.J. (1) 107, 110 Brauge, L. (6) 15 Braunstein, P. (1) 19 Bravo, P. (4) 22 Breeden, S.(3) 170 Bregadze, V.I.(3) 121 Breinholt, J. (3) 105 Breit, B. (1) 335,614

Breitenbach, J.M. (4) 3 Breitkopf, C. (1) 120 Breitsameter, F. (3) 18, 19; ( 5 ) 11-13 Bretner, M. (4) 18 Breuning, M. (1) 169 Breyhan, T. (6) 32 Bringmann, G. (1) 169,430 Brodie, A.M. (6) 132 Broger, E.A. (3) 48 Bronstein, L.M. (1) 8 1 Broussier, R. (1) 137, 138,438; (3) 54 Brown, D.E. (6) 116 Brown, D.M. (4) 91 Brown, S.M. (1) 243 Browne, J.E. (3) 62 Bruckner, R. ( 5 ) 53 Briickner, S. (6) 205 Bruegeller, P.(1) 360 Bruneau, C. (3) 30 Brunel, J.-M. (1) 433 Brunett, J.J. (3) 41 Brunner, H. (1) 30, 47 Brusatin, G. (6) 185 Bryce, M.R. (3) 103 Buchmeiser, M.R. (3) 109 Buchwald, S.L.(1) 6 Budesinsky, M. (4) 21,68 Budnikova, Y.G. (1) 252 Biichele, J. (1) 225 Buenzli, J.-C.G. (1) 379 Buhr, C.A. (4) 34 Bukowski, R. (1) 495 Bulygina, L.A. (3) 160 Bunel, C. (3) 104 Buono, G. (1) 433; (2) 25-29 Biudalo, J. (6) 203 Burford, N. (1) 535 Burgard, M. (1) 428 Burgess, K. (1) 62 Burilov, A.R. (1) 452; (3) 88 Burk, M.J. (1) 93,96, 184; (3) 34 Burkart, M.D. (4) 43, 56 Burkart, W. (3) 48 Burkus, F.S., I1 (6) 72,73 Burlina, F. (4) 54 Burn, P.L. ( 5 ) 96 Buron, C. (1) 348 Burrows, A.D. (1) 512; (3) 172 Burton, G. (3) 63 Burton; J. (3j 7 0

Buschmann, J. (1) 498 Busson, R. (4) 37, 73 Butenschon, H. (1) 136 Butler, l.R. (1) 44,45,79 Butt, A. (1) 50 Buzzoni, V. (4) 76 Bycroft, B.W. (1) 304 Byers, H.L. (1) 500 Byrn, R.W. (1) 5 Byun, H.-S. (1) 3 10 Cabasso, I. (3) 108 Cadena, J.M. (1) 327-329 Cadietno, V. (1) 256, 266, 267, 3 17, 604; ( 5 ) 38 Cahill, J.P. (1) 204 Cai, R.-F. (1) 5 14 (3) 124 Cairns, S.M. Calabrese, J.C. (3) 36 Callaghan, C.S.J. (I) 592 Camarasa, M.J. (4) 30, 55 Cameron, T.S. (1) 535; (6) 102 Caminade, A.-M. (1) 25,23 5; (2) 35; (3) 61; (6) 11-16, 148 Caminiti, R. (6) 207 Camuzat-Dedenis,B. ( 5 ) 58 Canac, Y.(1) 561,562 Canestrari, S.(3) 135, 136 Cantrill, S.J. (1) 442 Cao, RZ. (1) 484 Capaldi, D.C. (4) 3 1 Carbajo, R.J. (6) 135 Cardellicchio, C. (1) 400 Cardi, N. (6) 191 Cardin, C.J.(1) 1 Cardin, D.J. (1) 1 Carmichel, D.(1) 584,585 Carpentier, J.F. (3) 40 (1) 494 Carrk, F.H. Carrera, A.G. (1) 380 Carriedo, G.A. (1) 223; (6) 114, 135, 136, 190,203 Carroll, M.A. (1) 38,43 Casalnuovo, A.L. (3) 36 Casarin, M. ( 5 ) 25 Cassidy, P.E. (1) 386 Castanet, Y.(3) 76, 77 Castillon, S.(1) 3 14 Castro-Palomino,J.C. (3) 150 Cataldo, L. (1) 613 Catel, G. (6) 142

244

Cauzzi, D. (1) 222 Cavell, K.J. (1) 67 Cavell, R.G. (1) 320,607; (2)

6; (3) 15; (5) 28-30; (6) 45, 47-50, 52-54, 100 Cea-Olivares, R. (6) 65 Cesario, M. (1) 14 Cesarotti, E. (1) 17 Cha, K.H.(1) 287 Chadwick, A.V. (1) 22 1 Chae, H.K. (6) 134 Chahboun, R. (1) 309 Chaikovskaya, A.A. (3) 6 Chamalet-Combes, C. (6) 15 1 Chamorro, C. (4) 55 Chan, A.S.C. (3) 38,45, 50 Chan, J. (6) 63 Chan, K.S.(1) 197, 198 Chandrasekaran, A. (1) 496; (2) 1-5,37; (3) 79-82 Chandrasekhar, V. (6) 188 Chang, C.-C. (6) 101 Chang, J.Y. (6) 223 Chang, T. (6) 223 Chang, W . 4 . (1) 144 Chang, Y.(6) 215 Chanon, M. (3) 147 Chantson, J. (1) 18 Chapal, J. (4) 69 Chapouland, V.G. (1) 170 Chappell, M.D. (3) 139 Chapyshev, S.V.(1) 322; (6) 10 Charubala, R. (4) 32 Chaseau, D. (1) 434 Chatterjee, S. (1) 105 Chaturvedi, S. (1) 305 Chauvin, R. (3) 41 Che, D. (1) 194, 369; (6) 5 Chen, D.-W. (1) 457; (5) 32 Chen, H. (1) 229 Chen, H.-C. (6) 101 Chen, J. (6) 249, 250 Chen, K.S. (1) 199 Chen, L.-W. (6) 239,240 Chen, M. (5) 70 Chen, R.-Y. (1) 537; (3) 154 Chen, T. (1) 129 Chen, W. (1) 174,337 Chen, X.D. (1) 484 Chen, Y.T.(1) 250 Chen, Y.X.(3) 38 Chen, Z.-C. (1) 326

Cheng, C.-H. (1) 265; (3) 91; (5) 18

Cheng, L . 4 . (1) 213 Cheng, S.-h. (1) 212 Cheng, S.-W. (1) 226 Cheng, Y.C. (4) 3,4 Chen-Yang, Y.W. (6) 165,210 Cherkasov, R.A. (2) 13; (3) 118

Chernega, A.N. (1) 5 16 Chernyshev, E.A. (5) 8 , 9 Cherryman, J.C. (5) 6 Chhabra, S.R.(1) 304 Chi, K.-M. (6) 101 Chiang, (2.42. (6) 101 Chiba, K. (1) 280 Chicote, M.-T. (5) 24, 27 Chifie, J. (3) 41 Chim, J.L.C. (6) 63 Chiriac, C.I. (3) 164 Chistokletov, V.V. (3) 59 Chitsaz, S . (6) 36, 37, 40 Chiu, W.-Y. (6) 238-240 Chiu, Y . 4 . (6) 239 Chiummiento, L. (5) 75 Cho, C.-W. (1) 37 Cho, D.O.(1) 287 Cho, H.N. (5) 54 Cho, M. (1) 479 Cho, M.H.(1) 214 Cho, S.-I. (1) 58 Cho, Y. (6) 120 Choi, J. (1) 422 Choi, M.C.K. (3) 38 Choi, M.J. (1) 300 Choi, N. (1) 131 Chollerton, N. (5) 102 Chop, Y.-J. (1) 38 Choung, Y.S.(6) 220 Chow, C.P. (3) 190 Christov, V.C. (1) 373 Chuang, S.-C. (1) 265; (3) 91; (5) 18

Chuchurjukin, A.V. (1) 175, 176

Chuit, C. (1) 494; (2) 38 Chulkin, A. (4) 69 Chuluunbaatar, T. (1) 397, 575 Chung, B.Y.(6) 2 1 Chung, K.G. (3) 33 Chung, Y.K. (1) 49,217 Churakov, A.V. (1) 71 Churchill, M.R.(1) 244

OrganophosphorusChentisfry Chworos, A. (1) 296; (4) 38 Chymol, N. (5) 3 1 Ciesla, J. (4) 18 Cieslik, M.(1) 432 Cinico, C. (6) 159 Ciruelos, S. (1) 73 Clade, J. (1) 421 Claparols, C. (2) 35 Clark, T. (1) 596 Clarke, M.L. (3) 167 Clarke, R.L. (6) 243,244 Clasper, P.N. (1) 569 Claver, C. (3) 56, 71, 72 Clavijo, E. (6) 114 Clayden, J. (1) 405 Clayton, A. (6) 146 Cledera, P. (6) 22 Clegg, W.(1) 32, 146, 147, 376, 565; (3) 189; (5) 3 Clem, 0. (5) 43 Clement, J.-C. (1) 447 Clendenning, S.B.(1) 622-624 Clentsmith, G.K.B. (1) 595 Cloke, F.G.N. (1) 590,593, 595,608,620

Cobley, C.J. (1) 255; (3) 84, 86 Coe, P.L. (1) 566 Coessens, V. (1) 449 Cole, D.L. (4) 3 1 Cole-Hamilton, D.J. (3) 167 Coleman, M.M. (6) 236, 237 Coles, S.J. (1) 79,260, 362, 453; (5) 62

Combs, D. (1) 66 Comotti, A. (6) 142-144 Concolino, T.E. (1) 535 Conesa, C. (1) 3 15; (6) 1 Contreras, R. (2) 18 Coppens, P. (1) 409 Corcoran, C. (1) 9 Cordi, A. (3) 128 Cornelissen, U. (1) 249 Corona, D. (6) 20 Coronado, E. (1) 4 13 Corradi, E. (6) 205 Corriu, R.J.P. (1) 226,494; (2) 38

Corte, J.R. (5) 50 Costa, M. (1) 222 Couturier, J.L. (3) 76, 77 Craig, D.C. (1) 476, 477 Cramp, S.M.(5) 89 Crane, C.A. (6) 2 17

A ti thor Index Creve, S.(1) 527 Cristau, H.-J. (1) 376, 381; (5) 78; (6) 9, 15 1

Cros, P. (4) 79, 80 Crosby, J. (1) 243 Cross, R.J.(1) 142, 367 Cross, W.I. (1) 28, 275, 298, 415

Crowe, L.A. (2) 15 Cruz-Almanza, R. (6) 20 Csaky, A.G. (1) 259 Csok, Z. (1) 573; (3) 28 Cubbon, R.J. (1) 114 Cucci, N. (1) 222 Cuevas, G. (1) 420 Cunneen, D. (1) 204 Cunningham, D. (1) 10 Cunskis, S.(1) 76 Cupertino, D. (6) 55, 56 Curiel, D. (5) 73; (6) 25 Currie, J. (6) 81-83 Curry, K. (1) 422 Czira, G. (3) 28 Dabbagh, A.H. (1) 278 Dahl, B.M. (3) 188 Dahl, 0. (3) 188 Dahlenburg, L. (1) 152 Dai, L.-X.(1) 36 Dairi, T. (4) 62 Dal, A. (1) 3 1 Dal, H. (6) 180 Dallemer, F. (1) 563, 570 Dalpozzo, R. (1) 374 Damiani, E. (3) 136 Dance, I.G. (1) 359,476,477 Dancer, J.E. (4) 16 Danielsen, S. (3) 105 Daniher, A.T. (4) 86 Daran, J.-C. (1) 563, 570 &Arbeloff-Wilson, S.E.(1) 600 Darcel, C. (3) 42 Darling, S.L. (1) 27 Dan-, J.A. (6) 106 Darwin, K. (6) 64 Dashti-Mommertz, A. (1) 629; (6) 42

Dauber, M. (1) 335 Davankov, V.A. (2) 22,30, 3 1; (3) 73

Davidson, F. (2) 36 Davidson. M.G. (5) 1.6

24 5

Davies, D.B. (6) 146, 147 Davies, J.E. (1) 501 Davies, R.P. (1) 376 d'Avignon, D.A. (1) 548 Davis, A.A. (5) 86 Davis, N.E. (4) 33 Davlet-Schina, G.R. (3) 88 Day, R.O. (1) 496; (2) 1-5, 37; (3) 79-82

de Arellano, M.C.R. (1) 455 de Bueger, B. (3) 128 Decker, S.A. (5) 30; (6) 50 Declercq, J.-P. (2) 38; (5) 93 De Clerq, E. (4) 5, 12, 13,26, 30, 55, 76

deDenus, C.R. (6) 150,2 17, 218

Dee, R.F. (1) 244 Deelman, B.-J. (1) 12 Deerenberg, S. (1) 143; (3) 75 Defacqz, N. (3) 128 Defrancq, E. (4) 79,80 Dehnicke, K. (1) 471; (6) 3 142, 96, 97

De Jaeger, R. (6) 133, 166 Dejugnat, C. (2) 24 de Kanter, F.J.J. (1) 363,364, 544, 546

Delaere, D. (1) 571 Delapierre, G. (2) 28 de la Plaza, M.A. (6) 252 Delbecq, F. (1) 64 Delgado, F. (6) 92 Delgado, S. (5) 74; (6) 23 Dell, S.(1) 249 Delmau, L. (1) 426 Delogu, G. (6) 159 de 10s Santos, J.M. (1) 398; (5) 64

Demarcq, M.C. (1) 295 Demartin, F. (1) 4 16 Deng, J.G. (3) 45 Deng, W.-P. (1) 36 Deng, Y.-H. (1) 437 De Nino, A. (1) 374 Denq, B.-L. (6) 239 Deplano, P. (1) 274 Depree, C.V.(6) 132 De Riai, C. (3) 113 Derrien, N. (3) 34 des Abbayes, H. (1) 447 Desai, V.G. (1) 343; (5) 46 Deschamm B. (1) 583

Descotes, G. (1) 323; (6) 4 Deshpande, R.M. (3) 27 Desiraju, G.R. (1) 4 10 Desreux, J.-F. (1) 426, 427 Deubel, D.V. (6) 97 Deubzer, B. (6) 77 Deussen, H.J. (3) 105 Devillanova, F.A. (1) 416 de Vries, A.H.M. (3) 18 1 de Vries, J.G. (1) 241 de Wolf, E. (1) 12 de Wolf, W.H. (1) 363, 364, 544

Dez, I. (6) 133, 166 Diamanti, S.(6) 156 Diaz, M.R. (1) 341 Din, V. (6) 137, 138 Diaz-Torres, E. (6) 20 Dickson, R.S. (1) 78, 529 Diefenbach, A. (6) 43 Diefenbach, U. (6) 124, 125 Diefenbacher, C. (3) 120 Dieguez, M. (3) 72 Dielemann, C.B. (1) 177 Dietrich, A. (6) 96 Dijkstra, H.P. (1) 175, 176 Dillon, K.B. (1) 500 Dilworth, J.R. (1) 187 Disteldorf, H. (1) 621 Dixneuf, P.H. (3) 30 Djahaniani, H. (1) 263; (5) 60 Dobler, C. (3) 46 Dobo, A. (1) 575 Dogan, J. ( I ) 77 Doherty, S.(1) 565 Dolenko, G.N. (1) 446 Don, T.-M. (6) 238-240 Donde, Y.(1) 52 Dondoni, A. (3) 119 Donnadieu, B. (1) 235,256, 266, 3 17, 604; (3) 4 1; (6) 11, 13, 16 Dorfman, Y.A. (3) 60 D'Orleans-Juste, P. (4) 71 Dorn, H. (1) 338 Douce, L. (1) 14 Dougherty, T.J. (5) 48 Douglas, W.E.(1) 494 Douglas, M.R. (1) 156 Dousson, C.B. (3) 34 Dovgopoly, S.I. (1) 626 Doyle, R. (1) 105 D o A , J.-F. (1) 380,426

246

Drabowicz, J. (1) 412 Drach, B.S. (5) 19 Drach, J.C. (4) 3,4 Drake, J.E. (6) 57 Dransfield, A. (1) 365, 571 Drew, M.G.B. (1) 45 Drexler, H.J. (3) 141 Driess, M. (1) 98, 122, 132,

Ehrenberg, B. ( I ) 443 Eilers, J. (3) 44 Eisentrager, F. (1) 209 EI-Baky, C.A. (1) 541 El-Batouti, M. ( I ) 488 Eleuteri, A. (4) 3 1 Elhabiri, M. (1) 379 Elias, A.J. (1) 240; (6) 107,

Drioli, E. (6) 232 Driver, M.J. (3) 62 Dros, A.C. (3) 67 Drouin, M. (1) 35 Drysdale, M.J. (5) 67 Dubo, A. (1) 395 Dubourg, A. (2) 38 Dubs, P. (3) 136 Dudfield, P.J. (4) 16 Duesler, E.N. (1) 129; (6) 95 Duffner, G. (4) 44 Dumont, D. (6) 193 du Mont, W.-W. (1) 274,344,

El-Khoshnieh, Y.O. (1) 321 Ellis, D.D. ( I ) 241; (3) 84, 86 Elmes, P.S.(1) 78 Elsegood, M.R.J. (1) 565; (3)

463, 522

108, 152-154

189

Dunbar, L. (1) 376 Dunina, V.V. (1) 330 Duran, E. (1) 568 Durantini, E.N. (5) 98 Durini, E. (4) 76 Durkin, J.J. (1) 594 Durkin, K. (5) 92 Dutoi, A.D. (1) 418 Duval, M. (4) 71 Dvorakova, H. (4) 26 Dvornikova, E.V. (5) 100 D'yachkova, S.G.(1) 445,446 Dyatkina, N.B. (4) 85 Dzik, J.M.(4) 18 Dzygiel, P. (3) 90

Elvers, A. (1) 589, 596 Enders, D. (1) 40 Endo, T. (5) 66 Enev, V. (1) 192 Engelhardt, U. (6) 127 Engels, J.W. (4) 81-84 Engemann, C. (1) 421 Englert, U. (1) 73, 581, 582 Ensling, J. (6) 32 Erhart, V. (1) 423 Eriksson, S. (4) 19 Ermanson, L.V. (3) 121 Ermolaeva, L.V.(3) 88 Ertel, T.S. (1) 155 Escher, I.H. (3) 69 Escudie, J. (1) 502, 523 Esnouf, R. (4) 30 Espinet, P. (1) 358 Esteban-Gamboa, A. (4) 30 Etemad-Moghadam, G. (2) 24 Evans, C.E.B. (1) 289; (6) 256 Ewalds, R. (3) 43 Ewin, R.A. (1) 371 Ezpeleta, J.M. (1) 399

Eaborn, C. (1) 145 Earnshaw, C.G. (4) 16 Eastes, R.-E. (5) 3 1 Eastham, G.R. (1) 565 Eath, N.P. (1) 414 Eckel, T. (6) 172 Eckholtz, L. (1) 495 Edelmann, F.T. (1) 180 Edwards, P.G. (1) 67, 157 Eggeling, E.B. (3) 43 Egold, H. (1) 467 Egorova, I.V. (2) 11 Ehlers, A.W. (1) 248, 546

Facchin, G. (6) 185,232 Fadda, A.M. (6) 159 Fadel, A. (3) 156 Faghihi, K. (1) 278 Fahl, J. (1) 448 Falconer, R.A. (1) 3 13 Fambri, L. (6) 241 Fan, J.-S. (6) 101 Fang, X. (1) 601 Fanghanel, E. (3) 100 Fanwick, P.E. (1) 60 Faraj, A. (4) 12 Faraone, F. (3) 179, 180

417,466

OrganophosphorusChemistry Farcas, S.I. (6) 57 Farina, A. (6) 205 Farkas, S. (4) 32 Farrugia, L.J. (1) 142 Faulds, P. (1) 362 Favre, A. (4) 54 Fawcett, J. (1) 9, 237 Fawzi, R. (1) 151, 238; (3) 169 Faza, N. (6) 32, 35 Feeder, N. (1) 27, 376, 403; (5) 81

Felczak, K. (4) 18 Felix, I.R. (4) 91 Feng, M.Q. (1) 199 Fenske, D. (1) 123 Fdrec, C. (1) 447 Ferguson, M. (5) 29; (6) 47,49 Feringa, B.L. (3) 18 1 Fernandez, A.L. (1) 355,356 Fernandez, E. (3) 56 Fernandez-Baeza, J. (5) 24 Fessner, W.-D. (5) 90 Fettinger, J.C. (1) 4 18 Fey, N. (1) 10 Fey, 0. (1) 541 Fickert, C. (1) 430 Filippone, P. (1) 272; (5) 55 Fingerhuth, M. (1) 432 Finn, T. (3) 103 Fiocca, L. (6) 191 Firouzabadi, H. (1) 28 1, 282 Fischbeck, U. (1) 608 Fischer, A. (I) 286; (3) 4 Fischer, B. (4) 69-71,75, 78 Fischer, C. (3) 47 Fischer, K. (3) 163 Fitch, J.W. (1) 386 Fitzjohn, S. (1) 243 Fitzner, A. (1) 460 Flammang, R. (3) 134 Floch, P.L. (6) 110 Floch, V. (1) 447 Flock, M. (1) 543 Flor, T. (1) 1 15 Flores, J.C.(1) 50 Florke, U. (1) 3 1,467 Flower, K.R. (1) 28 Fluck, E. (1) 627-629 Font-Bardia, M. (1) 328 Foray, G.S. (1) 100 Foreman, M.R.St.J. (1) 413 Forintos, H. (1) 391-393 Forissier, K. (1) 584, 585

A uthor Index ForniCs-Cimer, J. (6)46 Fort, Y.(1) 141 Fotiadu, F. (2)25,28 Fourrey, J.L. (4) 54 Fraanje, J. (1) 80;(3) 85 Fracchiolla, G. (1) 400 Francio, G. (3) 78, 179,180 Francis, M.D. (1) 529,590, 594,595 Franke, R.(1) 421 Frankland, A.D. (1) 455 Franzheld, R.(1) 333 Fratpietro, S.(1) 580 Frazier, D.O. (1) 422 Freitag, D. (1) 51; (3) 163 Frenking, G. (6)97 Frenzel, C.(1) 97 Fresneda, P.M. (1) 316;(5) 71, 74;(6)23 Fried, J.R. (6) 194, 195 Friedrichs, S.(1) 9 Fries, G. (1) 94;(3) 21 Friesen, D.M. (1) 99 Frigerio, M.(4)22 Frischmeister, C.(1) 564 Frison, G. (1) 625;(6) 110 Fritz, G. (1) 254 Froehler, B.C.(4)34 Fruchier, A.(1) 376 Fryzuk, M.D.(1) 19 Fu, F.M. (3) 45 Fu, G.C. (1) 345 Fu, Z.(1) 200 Fuchs, A.(1) 352,353 Fuentes, A.(6)20 Fujimoto, T.(1) 382;(5) 42; (6) 182 Fujita, K. (1) 33 1 Fujiwara, H.(5) 97 Fukamachi, S.(1) 280 Fukuoka, A. (3) 27 Fukuoka, M. (4) 65,66 Fukuoka, N. (6) 171 Fukuwatari, N. (6) 176,257 Funaki, K.(6) 93,94 Funicello, M. (5) 75 Furukawa, 1. (1) 276 Gabbutt, C.D. (5) 3 Gagnon, J. (1) 35 Gaillard, N. (1) 63 Gais, H.J. (1) 218

Gajda, T. (6)8 Galeazzi, A. (6) 191 Gali, H.(1) 161, 179,230,231 Galimov, R.D.(3) 88 Galindo, A. (1) 485 Galkin, V.I. (3) 118 Gallazzi, M.C. (6)205 Gallo-Rodriguez, C. (4)72 Gamasa, M.P. (5) 38 Ganapathy, S.(3) 124 Ganis, P. (5) 25 Ganoub, A.F. (5) 101 Ganoub, N.A. (3) 158, 165 Ganter, C.(1) 581, 582 Gao, H.(1) 140 Gao, J.-X. (1) 212 Garau, A. (1) 416 Garcia, J.L. (6) 135, 190 Garcia-Alonso, F.J. (6) 114, 135, 136, 190 Garcia-Granda, S.(1) 341 Garcia-Lbpez, J.J. (6)3 Garcia-Montalvo, V.(6)65 Garci-Carrera, M.A. (1) 426 Gardner, M.F.(4)9 Gaspar, P.P.(1) 414,548 Gautheron, B.(1) 137,138, 438;(3) 54 Gauthier-Gillaizeau, I. (5) 102 Gavrilov, K.N. (2)22,30,31; (3) 73 Gavrilova, E.L. (1) 452 Gawdzik, B.(1) 378 Gege, C. (3) 153 Gehrhus, B.(1) 622 Geiseler, G. (6)34,97 Geiser, U.(6) 105 Gelbrich, T.(1) 260;(5) 62 Gelpke, A.E.S. (1) 16 Gendron, F.P. (4) 69,71,78 Genet, J.-P. (1) 88,95 Gennet, D. (5) 40 Geofioy, M.(1) 510,613;(5) 5 Georgiev, 1.0.(1) 162 Geprags, M.(1) 160 Gerhards, F. (1) 218 Gerlach, A. (1) 96 Gettleman, L.(6) 242 Giannotta, G. (6) 19 1 Gibson, S.E.(5) 43 Giering, W.P. (1) 355, 356 Gil, J.I. (1) 399

247 Gil, J.M. (4)29 Gilbert, I.H. (4)5 Gilbertson, S.R. (1) 104,200, 227 Gilby, L.M. (6)58,64 Gillon, A. (3) 56 GimCnez-Martinez,J.J. (6)3 Gimeno, J. (5) 38 Gimeno, M.C. (1) 439;(5) 26 Girardet, J.L. (4)46 Gladyshev, E.N. (2)8 Gladysz, J.A. (1) 55 Gleiter, R. (1) 24 Gleria, M. (6) 184, 185,191, 207,232,241 Gloede, J. (1) 83;(3) 66 Glueck, D.S. (1) 159 Gnanou, Y.(6)15 Goddard, R.(1) 189,616;(3) 55 Godfrey, S.M. (1) 275,297, 298,415;(3) 148 Goedheijt, M.S. (1) 242 Gohner, M.(1) 540 Goerlich, J.R. (I) 286;(2) 7; (3) 4, 5 Goeta, A.E.(1) 500 Gold, A. (4)35 Goldner, M.(1) 249 Goldschmidt, Z.(1) 10 Golemne, G. (6)232 Golhen, S.(1) 246 Golos, B.(4) 18 Gomba, F.J. (6) 109 Gomez, M. (1) 80 G6mez-Bengoa, E. (6) 89 Gomez de la Oliva, C. (1) 259 G6mez-Elipe, P. (1) 223;(6) 136, 190 Gomez-Garcia, C.J. (1) 413 Gong, M.-S. (1) 450 Gonzalez, P.A. (1) 223;(6) 136, 190,203 Goodwin, N.J. (1) 239 Goodwin, S.D.(1) 567 Gorg, M. (3) 116 Gorls, H.(1) I8 Gornitzka, H.(1) 245, 348-350, 561,562;(3) 173;(5) 10 Gorunova, O.N. (1) 330 Goryunova, L.E. (4)85 Gosberg, A. (1) 3; (3) 53, 55 Gosselin, G. (4) 12,46

248

Gottardo, C. (1) 580 Gottlieb, H.E. (1) 10 Gottlieb, M. (4) 32 Gottschalch, V. (1) 333 Gotze, L. (1) 186, 233 Goubitz, K. (1) 80, 619; (3) 85 Goumri-Magnet, S. (1) 349, 350; (5) 10

Gouverneur, V. (1) 390 Gouygou, M. (1) 563,570 Goyal, M. (6) 91 Graf, C.-D. (1) 8 Graf, V.W. (1) 75 Graham, S.M. (4) 1 Graiff, C. (1) 222, 346; (3) 179 Grajkowski, A. (4) 48 Gramlich, V. (6) 2, 133 Grandi, F.(I) 222 Granell, J. (1) 327-329 Gray, G.M. (1) 248; (3) 26 Greatrex, R. (1) 59 Grebe, J. (6) 35 Greci, L. (3) 135, 136 Green, J.C. (1) 595, 623 Green, M.J. (1) 67, 5 12 Greenwell, C.H. (1) 45 Greiner, A. (6) 41 Grewal, N.S. (1) 159 Grifith, P. (6) 81-83 Grigor'ev, A.N. (1) 452 Grishin, Y.K.(1) 330 Grobe, J. (1) 503, 526; (3) 51 Grob, T. (6) 38,39,41 Grondey, H. (1) 289 Gros, P. (1) 141 Grossheimann, G. (1) 39 Grotjahn, D.B.(1) 66 Griin, K.(1) 54 1 Griitzmacher, H. (1) 499; (3) 168, 177; (6) 2, 133

Grushin, V.V. (1) 456 Gu, X. (6) 256 Guan, H.P. (4) 4 Gubaidullin, T.A. (2) 12 Gudat, D. (1) 552, 586-588; (5) 14

Giil, N. (1) 578 GuCnin, E. (1) 447 Giinther, K. (1) 508 Guerra, M. (1) 513 Gutlich, P. (6) 32 Guglielmi, M. (6) 185 Guidi, B. (1) 272; (5) 55

Guigley, K.S. (6) 236,237 Guillemin, J.C.(3) 2 Guionneau, P. (1) 434 Guiry, P.J. ( I ) 189-191, 204 Gukhman, E.V. (2) 9 Gunter, J. (4) 26 Guo, Q. (6) 229 Gupta, N. (1) 605; (3) 20, 127 Guram, A.S. (1) 7 Gusarova, N.K. (1) 106, 121, 153, 164, 188,445,446

Guy, D.M.H. (1) 494 Guzei, I.A. (1) 125, 159; (6) 141, 145

Ha, K.M. (1) 300 Haar, C.M. (1) 355,356; (3) 25 Habicher, W.D. (3) 89, 137 Habimana, J. (6) 76 Habu, H. (1) 280 Haeberli, P. (4) 86 Hap, S.(1) 587 Hagenau, U. (1) 1 13 Hager, D.C. (3) 126 Hagiwara, S. (6) 175 Hah, J.H. (4) 29 Haid, R. (1) 360 Haiduc, I. (6) 57 Hajipour, A.R. (1) 472-475; (3) 133

Halbfinger, E. (4) 70, 71 Halcomb, R.L. (3) 139 Halim, M. (5) 96 Hall, R.G.(1) 370 Hamashima, Y. (1) 368 Hamilton, C.J.(4) 85 Hampel, F. (5) 17 Han, 1.4. (1) 479 Han, J.W. (1) 49,217 Han, M.J. (6) 223 Hanamoto, T. (1) 458; (5) 15 Hands, R.M. (3) 176 Hang, J.J. (5) 99 Hanks, J.R. (1) 593 Hans-Becker, S. (5) 104 Hansen, H.-J. (1) 85, 203 Hanson, B.E. (1) 242 Hapiot, F. (3) 40 Hara, A. (6) 94 Hara, I. (6) 93 Hara, Y.(6) 93, 94 Harden, K.T. (4) 69,70,72,73

OrgatiophosphorusCheniistry Hariharasarma, M. (3) 26 Harling, J.D.(1) 114 Harms, K. (1) 8, 335; (6) 3 1, 32, 34, 37, 4 1, 97

Harnisch, J.J. (1) 158 Harre, M. (1) 192 Harriman, A. (1) 177 Harris, R.K. (2) 15; (5) 6 Harris, S. (4) 8 Harrison, G. (1) 24 1 Harrup, M.K. (6) 130, 13 1,

2 1 1, 222, 226, 228, 234, 253 Hartl, F. (1) 619 Hartle, T.J. (6) 129 Hartley, R.C. (6) 90 Hartmann, E. (1) 421 Harvey, P.D.(1) 35 Haseyama, T. (6) 94 Hashimoto, K.(1) 293 Hashimoto, S. (1) 457; (3) 15 1; (5) 32 Hashimoto, Y. (1) 435 Hashimme, T. (1) 108; (3) 3133,37 Haukka, M. (1) 2, 4; (3) 1 Haupt, E.T.K.(1) 424 Haupt, H.-J. (1) 3 1 Hauptman, E. (3) 35 Hausen, H.-D. (1) 130 Hausler, T. (1) 110 Hay, C. (1) 564 Hayakawa, Y.(4) 23, 24 Hayashi, M. (1) 435 Hayashi, S. (5) 84 Hayashi, T. (1) 167, 168; (6) 93,94 Hayes, C.J. (3) 145 Hazeri, N. (1) 263; (5) 60 He, F.-H. (1) 538 He, G. (1) 25 1,576,577 He, H.Y. (3) 122 He, K.Z.(4) 63 He, L. (1) 310 He, M. (1) 3 1 Head, S. (1) 178 Heathcock, C.H. (5) 52 Hebeish, A. (6) 168 Heck, J.R. (1) 113, 127 Heckmann, G. (1) 130,627629 Hegedus, L. (1) 393 Heikkinen, V. (1) 2; (3) 1

Author Index Heinemann, F.W. (1) 589, 596 Heinicke, J. (1) 3 1; (3) 127 Heise, H. (1) 125 Hekmat-Shoar, R.(1) 262 Heller, D.(1) 89 Helm, M.(3) 176 Helmchen, G.(1) 183 Hemrajani, L.(1) 605 Hems, W. (1) 96 Hendan, B.J. (1) 118 Henderson, W. (1) 239 Henkel, G.(1) 238,540;(3) 169 Henneman, M. (1) 596 Hennig, M. (3) 48 Henry, N.(6) 166 Henschel, P.(1) 169 Hepworth, J.D. (5) 3 Her, Y.(1) 279 Herberhold, M.(1) 46 Herbst-Inner, R.(1) 180;(3) 196 Herdewijn, P.(4) 12, 37, 73 Herdtweck, E.(1) 195 Hernandez, R. (1) 50,366 Hedndez-Diaz, J. (2) 18 Hernandez Fuentes, F. (6)252 Hernindez-Ortega, S.(6)65 Heron, M.B. (5) 3 Herran, E.(6)27 Herrmann, W.A.(1) 117 Herron, W.(6)81-83 Hertel, F. (1) 46 Hervk, A.-C. (1) 447 Herzig, C.(6)77 Heslop, K. (3)56 Hetche, 0.(1) 3 1 Hetflejs, J. (1) 257;(3) 115 Hewat, A.C.(3) 43 Hewitt, B.D. (4) 16 Hey-Hawkins, E.(1) 72,97, 124, 134, 135, 139, 162 Heys, L.(1) 260;(5) 62 Hibbs, D.E. (1) 525,529 Hiemstra, H.(1) 16 Hilfiker, M.A. (1) 65 Hilgraf, R. (3) 68 Hill, F. (4)91 Hill, L. (5) 67 Hill, M.S.(1) 145 Hillaire-Buys, D.(4)69 Himmelsbach, F. (4)32 Hippe, T. (1) 272;(5) 55

Hirai, C. (1) 87 Hirao, I. (4)90 Hiroi, K. (1) 109 Hiskey, M.A. (6)95 Hissler, M.(1) 564 Hitchcock, P.B.(1) 145,590, 592-595,597,600,608, 620,622,624;(6)29 Hneihen, A.S. (6)212,213 Ho, D.M. (1) 249,250 Hoarau, C.(1) 226 Hockless, D.C.R. (1) 105 Hodge, P.R.(6)64 Hofman, M.A.(1) 509, 530 Hokelek, T. (6)78, 123, 178181 Holband, J. (3) 114 Holderberg, A.W. (1) 586,588; (5) 14 Holdt, H.J. (3) 141 Holloway, J.H.(1) 9 Holmes, R.R.(1) 496;(2) 1-5, 37;(3) 79-83 Holody, W.(1) 400 Holthausen, M.C.(1) 616 Holub, J. (1) 59 Holy, A. (4)26 Holz, J. (1) 61,89, 186,233 Holzer, W.(1) 626 Homborg, H. (1) 249 Hon, S.-Y. (5) 34 Hong, B.(1) 23 Hong, C.-I. (1) 287 Hong, J.M. (5) 54 Hong, L.P.(4)6 Hongo, H. (1) 206,207 Hooijdonk,M.C.J.M. (1) 106 Hope, E.G.(1) 9, 1 1 Hopkins, A.D. (1) 13 1 Horie, T.(5) 7,57 Hormes, J. (1) 421 Horn, C.(I) 477 Horrocks, B.R.(3) 189 Hostetler, K.Y. (4)9 HOU,D.-R. (1) 62 HOU,X.-L. ( I ) 36 Houalla, D.(2) 19-21 Houlton, A. (3) 189 Howard, J.A.K. (1) 438;(3) 103;(5) 1 Howdle, S.M.(6) 106 Howell, J.A.S. (1) 10 HSU,F.-L. (1) 3 12

249 HSU,H.-F. (1) 481 Hsu, L.Y. (4)51 Hu, J.J. (3) 64 Hu, Q.-S. (1) 173 Hu, W.H. (3) 45 Hu, X.(1) 229 Huang, A.Y. (6)210 Huang, J. (3) 25 Huang, T.-B. (1) 536-538;(3) 16,97 Huang, W.-F. (1) 536,537;(3) 16

Huang, Z . 4 . (1) 5 14 Hubler, U. (1) 127 Huc, V.(1) 25 Huckstadt, H. (1) 249 Hudson, A. (1) 5 13 Huffman, J.C. (1) 5 Hughes, A.N. (1) 580 Huguet, S.(3) 41 Humble, R.E.(5) 105 Hung, J.-T. (1) 248 Hupfield, P.C.(6)80 Hurh, E.Y. (3) 112 Hursthouse, M.B. (1) 10,79, 260,362,453,529;(5) 62; (6) 146 Huttner, G. (1) 76 Hutton, G.(1) 403;(5) 81 Huy, N.H.T. (1) 545,554,555; (3) 3 Hwang, J.J. (6) 210 Hydrio, J. (1) 563,570 Hyett, D.J. (3) 56 Ibers, J.A. (6)61,62,66 Ichikawa, M.(3) 27 Igau, A. (1) 256,266,267, 3 17, 604;(2)26 Ignat'ev, N.(1) 288 lijima, T.(1) 487;(5) 65 litake, K.-I. (5) 84 Ikariya, T. ( 1) 2 12 Ikeda, I. (1) 219 Ikeda, S.(4) 19 lkeda, T.(1) 482,483 Ikeno, T. (1) 293 Ikeyama, M.(6) 169 Ilankumaran, P. (3) 175;(5) 77 Imai, Y. (6)245 Imamoto, T. (1) 185,299 Imbach, J.L. (4) 12.46

250

Imbos, R. (3) 18 1 Immel, F. (1) 526 Immelmann, A. (4) 45 Imre, T. (1) 406 Inagaki, M. (1) 366 Inamoto, T. (1) 201,202 Incarvito, C.D. (1) 126, 159 Indzhikyan, M.G. (1) 268,271, 489

Inguimbert, M. (6) 9 Inoue, T. (1) 276 Inyushin, S.G. (3) 121 Iranpoor, N. (1) 281, 282 Ireland, T. (1) 39, 41 Isaac, C.J. (3) 189 Isaev, S.D. (5) 100 Isaia, F. ( 1) 4 16 Isarno, T. (6) 88 Ishar, M.P.S. (1) 270 Ishikawa, W. (6) 176 Ishikuro, S. (6) 173 Ishiyama, T. (5) 22 Ishmaeva, E.A. (1) 419,504 Islami, F. (3) 133 Isobe, M. (6) 94 Itani, H. (5) 92 Ito, K. (1) 171 Ito, S. (1) 301, 302,511; (5) 63 Itoh, T. (3) 143 Ivashchik, I.A. (2) 11 Ives, D.H. (4) 19 Ivonin, S.P. (3) 6-9, 11-13 Iwano, Y. (5) 7 Iwasaki, K. (1) 171 Iwato, Y.(1) 74 Iyer, R.P.(4) 10 Izod, K. (1) 32, 146, 147 Izquierdo, G. (6) 137, 138 Izquierdo, M.C.(6) 252 Izukawa, S. (6) 93 Izukawa, T. (6) 94 Izumi, C. (3) 142, 143 Izumi, M. (4) 56 Jaaskalainen, S. (1) 4 Jablonkai, I. (1) 3 13 Jackson, S.L. (1) 415 Jackson, W.R. (1) 78 Jacob, C. (6) 121, 122 Jacobson, K.A. (4) 72,73,75 Jacques, V. (1) 427 Jlger, L. (6) 9

Jain, M. (6) 107 Jaiswal, D.K. (1) 486 James, B.R. (1) 15 Janaky, T. (3) 195 Janda, K.D. (1) 13 Jang, D.O. (1) 283 Jang, H.-Y. (1) 49,217 Jang, S.Y. (4) 72, 73 Jankins, D.J. (4) 40 Jankowski, K. (6) 20 Jankowski, S. (1) 396 Jansat, S. (1) 80 Jansen, A. (1) 68 Jansen, M. (1) 42 1 Jaouen, C.(1) 429 Jaouen, G. (5) 83 Jaszay, Z.M. (3) 146 Jeffery, A.L. (4) 27 Jeffery, J.C. (1) 221 Jeges, G. (1) 48 Jenkins, S.S. (6) 251 Jenner, G. (1) 269 Jensen, J.F. (5) 105 Jeppesen, J.O. (3) 93 Jeske, J. (1) 417, 558, 559 Jessop, P.G.(1) 366 Jetti, R.K.R. (1) 410 Ji, Q. (1) 41 1 Ji, W.H. (4) 19 Jiaa, C.L. (6) 162 Jia Hua, X. (2) 23 Jiang, Q. (1) 150 Jiang, Y.Z.(3) 45 Jim, Q.-H. (1) 437 Jimenez, J. (1) 70 Jimeno, M.L. (4) 55 Jin, J. (1) 119 Jin, J.4. (6) 246, 248 Jin, K.Y. (1) 287 Jin, M.-J. (1) 205 Jin, Y. (4) 10 Jin, Z. (5) 87 Johal, K.U. (1) 534 Johannsen, M. (1) 42 Johansson, M. (1) 34 Jones, A.M. (5) 3 Jones, C. (1) 512, 525, 529, 5 94

Jones, L. (6) 230 Jones, N.D. (1) 15 Jones, P.G.(1) 274,4 17,439, 468, 556-559, 609; (2) 7, 32; (3) 5; (6) 6

OrganophosphorusChemistry Jones, W.D. (3) 21 Jonsson, J.A. (3) 90 Joswig, C. (4) 6 Jouaiti, A. ( I ) 510 Jouanin, 1. (5) 78; (6) 9 Ju, Y.(3) 64 Jiirgensen, A. (2) 6 Juge, S. (3) 42 Julliard, M. (3) 147 Jun, J.-G. (1) 279 Jung, J.-A. (1) 205 Jung, 0,s. (6) 134 Junk, P.C.(1) 529 Junker, H.-D. (5) 90 Jurczyk, S.C. (4) 89 Juriskova, K. (1) 443 Jus, S. (1) 88 Just, G. (3) 107, 182, 183; (4) 49

Jutzi, P.(1) 340 Kabachii, Y.A. (1) 81 Kabachnik, M.M. (1) 465 Kabha, E. (4) 78 Kadokawa, J. (1) 280 Kadyrov, R. (1) 233 Kafarski, P. (3) 90, 114 Kahn, 0. (1) 246,247,434 Kaifer, E. (1) 76 Kajdas, C. (6) 161 Kajiwara, M. (6) 209 Kajiwara, N. (6) 214 Kajtar-Peredy, M. (1) 323; (6) 4

Kaku, H. (1) 301,302; (5) 63 Kalashnik, A.T. (6) 202 Kalck, P. (1) 438 Kilmin, A. (1) 323; (6) 4 Kalman, T.I. (4) 17 Kamat, A. (4) 17 Kamer, P.C.J. (1) 20-22, 80, 143, 172, 242; (3) 43, 75, 85, 87 Kameshima, T. (6) 170, 174, 259 Kamijo, K. (1) 549, 550 Kanai, M. (1) 368 Kanazawa, A. (1) 482,483 Kaneda, K. (4) 62 Kang, H.J. (6) 163, 164 Kang, S.O. (1) 58,214 Kang, T.W.(1) 287

Author Index Kang, Y. (1) 214 Kano, N. (2) 23 Kao, J.L.-F. (1) 548 Kapur, A. (1) 270 Karasik, A.A. (1) 162 Karasu, M. (1) 280 Kardakova, E.V. (5) 100 Kargin, Y.M. (1) 252 Karim, A. (3) 39 Karlsson, A. (4) 76 Karlsson, M. (1) 34 Karodia, N. (5) 2 Karpeisky, A. (4) 86 Karra, S.R. (1) 161, 179 Karsch, H.H. (1) 75 Kasani, A. (5) 28, 29; (6) 48, 52-54

Kashik, T.V. (1) 445 Kashiwabara, K. (1) 101 Kashiwagi, R. (1) 171 Kataev, A.V. (1) 419 Kataev, V.E. (1) 419 Kataoka, Y. (1) 74 Kato, S. (3) 142, 143 Kato, T. (1) 350; (3) 173 Katritzky, A.R. (3) 122 Katsuki, T. (1) 171 Katti, K.V. (1) 161, 179,230, 23 1

Kaulen, C. (1) 582 Kawa, S. (2) 23 Kawagishi, R. (1) 109 Kawaguchi, H. (1) 101 Kawamura, M. (1) 30 1 Kawamura, Y. (5) 7,57 Kawasaki, A.N. (4) 36 Kawasaki, H. (1) 273 Kawashima, M. (1) 182; (3) 23 Kawashima, T. (2) 23; (5) 65 Kawatsura, M. (1) 168 Kayihan, I. (1) 490 Kazakova, E.K. (3) 88 Keay, B.A. (1) 194,369; (6) 5 Keck, H. (1) 407,542 Keeven, P.K. (1) 21,22 Kegl, T. (1) 48 Keglevich, G. (1) 391-397, 406, 573,575, 579

Keim, W. (1) 31 Kekehi, A. (6) 182 Kele, Z. (3) 195 Kellogg, R.M. (3) 67 Kelly, D.G. (1) 362

25 1

Kelly, W.M. ( I ) 5 1 Kemmitt, R.D.W. (1) 11,237 Kenard, C.H.L. (3) 134 Kennedy, J.D. (1) 59 Kern, E.R. (4) 3,4, 9 Kers, I. (4) 20, 46, 53 Kerth, J. (1) 606,610 Keseru, G.M. (1) 391,393, 394,579

Keyte, R.W. (6) 56 Khairullin, V.K.(3) 166 Khamliche, L. (3) 147 Khan, A.N. (1) 304 Kheradmandan, S. (1) 125 Khidre, M.D. (5) 59 Khobotova, N.V. (6) 118 Khodak, A.A. (1) 284 Khomutova, Yu.A. (1) 465 Khrustalev, I.V. (5) 9 Khusainova, M.G. (2) 13 Kibardin, A.M. (3) 22 Kickelbick, G. (6) 156, 157 Kida, T. (1) 219 Kiddle, J.J. (1) 441; (5) 86 Kiefer, W. ( I ) 430 Kiener, C. (3) 85, 87 Kiewel, K. (1) 84 Kiguchi, Y. (1) 458; (5) 15 Kihara, N. (1) 273 Kihara, T. (4) 23-25 Kikuchi, H. (5) 65 Kikuchi, S . ( I ) 202 Kiliq, A. (6) 78, 178, 179, 181 Kiliq, Z. (6) 78, 123, 178-181 Kim, C. (6) 215,233 Kim, C.Y.(5) 54 Kim, D.C. (6) 21 Kim, D.-H. (1) 58 Kim, D.Y. (5) 54 Kim, H.O. (4) 73 Kim, J. (1) 283 Kim, J.H. (4) 27 Kim, J.K. (5) 54 Kim, J.S. (6) 233 Kim, J.-W. (I) 287 Kim, K.S. (3) 112 Kim, K.-W. (1) 287 Kim, S. (1) 479 Kim, S.-G.(1) 193 Kim, S.-H. (1) 205 Kim, S.S. (3) 140 Kim, Y.C. (4) 72 Kim, Y.J. (6) 134

Kim, Y.T. (1) 387; (6) 134 Kimura, T. (6) 209 Kimura, Y. (1) 487 Kincaid, S. (1) 306 King, P.-P. (1) 308 Kini, G.D.(4) 9 Kinoshita, T. (5) 92 Kintzinger, J.-P. (1) 177 Kircher, P. (1) 76 Kirchmeier, R.L. (6) 119, 254 Kireev, V. (6) 203 Kirij, N.V. (1) 460 Kirmse, R. (1) 139 Kirsano, R.R. (1) 7 1 Kisanga, P. (3) 175 Kishimoto, N. (1) 382; (5) 42 Kishishita, M. (5) 22 Kishore, P.N. (1) 23 1 Kivekas, R. (1) 57,469 Kiyono, S. (6) 93, 94 KlafTke, W. (4) 77 Klankermeyer, J. (1) 47 Klein, H.-F. (1) 3 1 Kleinbekel, S. (1) 520 Kleinhenz, D. (1) 430 Kliava, J. (1) 434 Klimchuk, E.G. (1) 284 Klingel, S. (4) 83, 84 Klobukowski, M. (5) 30; (6) 50 Klose, A. (1) 55 Klyba, L.A. (1) 164 Kmiecik, R. (3) 123 Knight, D.A. (3) 52 Knispel, T. (4) 13 Knizek, J. (1) 123, 128; (3) 18 Knochel, P. (1) 8, 39,41; (6) 32

KO, J. ( I ) 58, 214 Kobayashi, H. (5) 97 Kobayashi, M. (5) 66 Kobayashi, S. (3) 155 Kocaokutgen, H. (6) 139, 140 Koch, T. (1) 72, 139 Kockerling, M. (1) 470 Kodra, J.T. (4) 89 Kockritz, A. (1) 83; (3) 66 Kijllner, C. (1) 339; (6) 149 Koenig, M. (1) 56 Korner, S . (3) 137 Koert, U. (4) 8 1, 83, 84 Koestle, W. (6) 95 Kogan, V.A. (1) 492 Kogen, H. (5) 5 1, 88

Organophosphorus Chemistry

252

Kojima, M. (6) 208 Kokin, K. (5) 84 Kollar, L. (1) 48, 573; (3) 28 Komatsu, H. (6) 177, 258 Kondo, K. (4) 47 Kondo, M. (1) 458; (5) 15 Konoike, T. (5) 91 Konovalov, A.I. ( I ) 452; (2) 12; (3) 88

Kooijman, H.(1) 16; (3) 87 Kool, E.T. (4) 33 Kopacka, H.(1) 360 Kopteva, S.D. (3) 11 Korber, N. (1) 588 Korczynski, D. (4) 92 Kom, K. (6) 98 Korostylev, A.V. (2) 22, 30, 3 1; (3) 73

Korth, K. (5) 68; (6) 98 Kosachev, I.P. (1) 462 Koskinen, A.M.P. (1) 2; (3) 1 Kostas, I.D. (1) 33 Kostyuk, A.N. (1) 626; (3) 9 Kovacik, J. (1) 159 Kovacs, J. (1) 323; (6) 4 Kovacs, L. (3) 195 Kovaleva, T.A. (2) 8 Kovalevsky, A.Yu. (2) 22, 30, 31

Kovensky, J. (4) 58 Kovleva, S.A. (5) 100 Koyanagi, S. (4) 24 Kozlov, E.S. (1) 626 Kozminykh, E.N.(5) 4 Kozminykh, V. (5) 4 Kraatz, H.-B. ( I ) 196 Krafczyk, R. (2) 36 Kral, V. (1) 443 Kralikova, S. (4) 21,68 Kramkowski, F. (1) 53 1 Krasil'nikova, E.A. (1) 452 Kraszewski, A. (4) 53 Krause, H.W. (3) 46,47 Krauter, J.G.E. (1) 236 Krautscheid, H. (1) 254 Krayevsky, A. (4) 85 Krebs, B. (1) 154, 503, 526 Kreuzfeld, H.J. (3) 46 Krill, S. (1) 600 Krotko, D.G. (3) 9 Kriiger, C. (1) 621 Krut'ko, D.P.(1) 7 1 Ksebati, M.B.(4) 4

Ksenofontov, V. (6) 32 Kubat, P. (1) 443 Kubiak, C.P.(1) 60 Kubicki, M.M. (1) 137 Kuchen, W. (1) 542 Kuchinke, J. ( I ) 154, 526 Kudyra, T.N.(3) 6 Kuhl, 0. (1) 124 Kuhn, N. (1) 448,540 Kuhnert, 0. (6) 99 Kulagina, T.G.(6) 111 Kulichikhin, V.G. (6) 199-201 Kulikowski, T. (4) 18 Kumadaki, I. (5) 47 Kumar, K. (1) 270 Kumar, S. (4) 91 Kumaraswamy, K.C. (6) 127 Kumaraswamy, S. (3) 132; (6) 127

Kundig, E.P. (1) 1 11 Kunihiro, T. (6) 94 Kupihar, 2. (3) 195 Kupka, T. (6) 146, 147 Kuptsov, S.A. (6) 199 Kurita, J. (1) 29 Kurochkin, A.F. (3) 12, 13 Kuroda, S. (5) 92 Kurth, V. (1) 152 Kusakabe, S.(1) 431 Kuwahara, Y. (5) 47 Kuz'mina, L.G. (1) 330,438 Kuzuyama, T. (4) 62 Kwong, F.Y. (1) 197, 198 Kwong, H.-L. (1) 213 Kyritsakas, N. (1) 177 Kyung, S.H. (3) 5 5 Laali, K.K. (1) 517, 533 Laayoun, A. (4) 79,80 Labahn, D. (1) 180 Labrue, F. (1) 95 Lacey, P.M. (1) 190 Lachkova, V. (1) 407 Liige, M. (1) 503,526 Lafont, D. (1) 324 Lagowski, J.B. (6) 196 Laguna, A. (1) 439; (5) 26 Lagunas, M.-C. (5) 27 Lahoz, F.I. (1) 3 18 Laitinen, R.H. (1) 2,4; (3) 1 Lake, C.H. (1) 244; (3) 26 Lal, R.B. (1) 422

Laly, M. (1) 138, 438; (3) 54 Lam, F. (1) 199 Lam, K.-C. (1) 126, 535 Lambert, B. (1) 426,427 Lammertsma, K. (1) 248,363, 364,544, 546,553

Landis, C.R.( I ) 220 Landskron, K. (6) 103 Landuyt, L. (1) 365 Lanfranchi, M. (3) 179 Lang, H.(1) 577; (4) 32 Lang, K. (1) 443 Langen, P. (4) 11 Langes, C. (1) 360 Lappert, M.A. (6) 29 Laredo, W.R. (6) 150 Larrb, C. (6) 11, 12 Lash, R.P. (6) 131,211, 222 Lau, S.Y.W. (1) 194 Lau, T.-C. (6) 104 Laurent, R. (1) 235; (6) 13, 14 Lauterbach, C. (1) 42 1 Lawrance, N.J. (1) 375 Lawrence, S.E. (3) 161 Lawson, G.T.(6) 121, 122 Lawson, Y.G. ( I ) 131 Lazell, M. (1) 436 Lebbe, T. (1) 181 Lebedev, B.V. (6) 111 Le Blanc, D.J. (1) 535 LeDall, M. (1) 19 Lee, C. (1) 214 Lee, C.-F. (5) 34 Lee, C.I. (1) 387 Lee, C.O. (6) 247 Lee, C.S.(3) 99 Lee, C.-W. (1) 450; (6) 167 Lee, C.-Y. (6) 240 Lee, D.C. (6) 219,220 Lee, D.D. (3) 91 Lee, F.-Y. (6) 101 Lee, H.F. (6) 165 Lee, H.J.(3) 99 Lee, H.-S. (1) 58 Lee, H.-W. (1) 287 Lee, J.C.-W. (5) 99 Lee, J.W. (5) 99 Lee, K.H. (6) 2 19,220 Lee, K.-J. (1) 279 Lee, P.H. (1) 479 Lee, S. (1) 37 Lee, S.B.(6) 246,248 Lee, S.C. (6) 21 5,233

Author Index Lee, T.Y. (1) 355, 356 Lee, W . 4 . (1) 213 Lee, Y.-A. (6) 134 Leeson, M.A. (6) 44 Le Floch, P. (1) 524, 61 1-613, 615, 617-619, 625 Le Gendre, P. (3) 30 Leglaye, P. (3) 41 Legrand, 0.(1) 433 Leitner, W. (3) 78, 180 Lejczak, B. (3) 114 Lemmen, P.(3) 121 Lentz, D. (1) 498 Leo, R. (6) 33,34 Leroy, E. (2) 35 Le Saulnier, L. (1) 379 Lesnik, A.N. (4) 36 Leung, P.-H. (1) 25 1, 576, 577 Leung, W.-H. (6) 63 Levalois-Mitjaville, J. (6) 133 Le Van, D. (1) 503,526 Levina, E.Y. (3) 22 Lewis, E. (1) 45 Leyh, T.S. (4) 57 Leznoff, D.B. (1) 246,247,434 Lhomme, J. (4) 79,80 Li, S.-Y. (6) 101 Li, W. (1) 91,92 Li, W.-S. (1) 371; (6) 106 Li, X.S.(3) 38, 50 Li, Y.M.(3) 191 Li, Z. (3) 129; (6) 221 Liable-Sands, L.M. (1) 93, 125, 126 Licandro, E.(1) 346 Licence, P. (1) 79 Liddle, S.T. (1) 32, 376 Liedtke, J. (3) 168 Liek, C. (1) 112 Light, M.E. (1) 10 Lightfoot, P. (5) 2,4 Lim, C.G. (3) 140 Lin, A. (6) 231 Lin, C.-H. (1) 265; (5) 18 Lin, J.L. (4) 50, 63, 64, 88 Lin, J.S.(4) 3 Lin, P.-Y. (1) 312 Lin, S. (3) 108 Lin, W. (5) 23 Lin, Y.I. (3) 129 Lindell, S.D. (4) 16 Linden, A. (1) 203 Lindner, E. (1) 86, 15 1, 155,

253

160,224,238; (3) 169

Lindner, J. (1) 432 Lipkowitz, K.B. (6) 207 Lippolis, V. (1) 416 Littke, A.F. (1) 345 Litvinov, I.A. (1) 163; (2) 12 Liu, A. (1) 577 Liu, C.B. (5) 69; (6) 17 Liu, L.-F. (1) 536-538; (3) 16, 97

Liu, L.Z. (1) 484 Liu, S. (1) 208 Liu, S.-H. (6) 101 Liu, X.D. (3) 175 Liu, X.-H. (6) 256 Liu, X.M. (3) 101 Liu, X.-P. (1) 537 Liu, Y. (1) 84; (6) 162 Liu, Y.X.(1) 484 Livantsov, M.V. (1) 330 Livinghouse, T. (1) 334 Loakes, D. (4) 91 Lochtman, R. (1) 40 Loebelenz, J.R. (6) 25 1 Loh, S.-K. (1) 577 Loi, A.G. (4) 12 Loisel, S. (1) 447 Lombardo, G.M. (6) 207 Longato, B. (1) 440 Longbottom, D.A. (1) 500 Longstaffe, J. (1) 178 Lonnberg, H. (3) 186 Lcjpez, J.L. (1) 319; (5) 72, 73; (6) 24-26

Gpez, R. (6) 89 Lopez-Calahorra, F. (1) 568 Lcjpez-Castaiiares,R. (6) 20 Lcjpez-Ortiz, F. (6) 135 Lopusinski, A. (3) 185 Lorenzo, S.(1) 476,477 Lork, E. (2) 14; (3) 94, 117 Loss, S.(1) 499; (3) 168, 177 Lotz, M. (1) 41 Lotz, s. (1) 18 Lou, R.G. (3) 45 Lou, R.L. (3) 50 Lough, A.J. (1) 289,338 Loup, C. (6) 148 Lovatt, J.D. (1) 10 Loza, M.L. (1) 216 Lu, K.-L. (6) 101 Lu, S.M. (3) 154 Lu, W. (6) 18

Lu, W.C.(5) 69; (6) 17 Lu, X. (6) 256 Lu, Y.(6) 18 Lu, Y.X.(3) 183; (4) 49 Lucchelli, E. (6) 191 Ludanyi, C. (1) 391, 397,406 Ludwig, K.N. (6) 128, 158 Ludwig, P.S.(4) 45 Luecke, S. (1) 154 Lukes, I. (1) 165, 383 Lumbard, K.W.(5) 67 Lunato, A.J. (4) 19 Luther, T.A. (6) 131 Lutz, M. ( I ) 172, 544, 546; (3) 85

Lynam, J.M. (1) 5 12 Lyzwa, P. (1) 412 Maas, G. (1) 606,6 10 McArdle, P. (1) 10 McAuliffe, C.A. (1) 275, 297, 298,415; (3) 148

MacBeath, C. (5) 24 McCarthy, M. (1) 189, 191 Maccato, C. (5) 25 Macciantelli, D. (1) 513 MacCullum, J.R. (5) 67 McDonald, R. (1) 99, 607; (5) 28, 30; (6) 47,48, 50, 5254, loo McDonnell, C.M. (1) 190 McDougall, M.G. (4) 91 McFarlane, H.C.E. ( I ) 294 MacFarlane, K.S.(1) 15 MacFarlane, W. (1) 147, 294 McGrath, J.E. (1) 4 11 McGuigan, C. (4) 5, 8 Machnitzki, P.(1) 107, 112, 181, 195 Mclntosh, M.B. (6) 129 Mack, A. (1) 532, 598 McKearns, P. (6) 30 McKinstry, L. (1) 29 1 McLaughlin, P.A. (3) 175 McLeod, D. (3) 175 McNeil, M. (4) 58 McPartlin, M. (1) 13 1 McWilliams, A.R. (6) 256 Madrigal, L.G. (1) 210, 21 1 Maeda, K. (6) 224 Maehara, S. (3) 187 Maghsoodlou, M.T. (1) 263;

254 ( 5 ) 60

Magill, J.H. (6) 208 Magull, J. (6) 35, 97 Mahon, M.F. (1) 5 12; (3) 172 Mahran, M.R.H. (3) 165; (5) 59

Maigrot, M. (1) 61 1-613 Maiorana, S. (1) 166, 346 Maiorova, E.D. (3) 59 Maischak, A. (1) 73 Majewski, P. (1) 277 Majima, T. (1) 342 Major, D.T. (4) 70, 75 Majoral, J.-P. (1) 25, 235, 256,

266, 267, 3 17, 604; (2) 26; (3) 61; (6) 11-16, 148 Makarova, N.A. (3) 88 Makarucha, B. (6) 203 Malacria, M. (1) 372 Malagu, K. (3) 2 Malan, C. (1) 8 Mali, R.S. (1) 343; (5) 46 Malisch, W. (1) 541 Mal'kina, A.G. (1) 153 Mallakpour, S.E. (1) 472, 473, 475 Malmstrom, T. (1) 228 Maly, A. (3) 114 Malysheva, S.F. (1) 153, 164, 446 Mamaseva, T.V. (1) 446

Mamdani, H.T. (6) 90 Manabe, K. (3) 155 Mandoli, A. (3) 181 Manfredini, S.(4) 76 Mangeney, P. (3) 70 Manger, M. (3) 21 Manners, I. (1) 289,338; (6) 256

Manoharan, M. (4) 36 Mantellini, F. (1) 272; (5) 55 Manuel, G. (1) 56 Maraval, V. (1) 235; (6) 13, 14 Marchand-Brynaert, J. (3) 128 Marchetti, P. (3) 113 Marchi, C. (2) 25-29 Marlin, A. (3) 135, 136 Marinetti, A. (1) 88, 95 Marks, T.J. (1) 156 Marosi, G. (1) 394 Marquez, V.E. (4) 73 Marquinez, F. (1) 341 Marra, A. (3) 119

Marschall, C. (1) 333 Marsden, C.J. (1) 349, 561; (5) 10

Marshall, W.J. (2) 36; (3) 35 Marsmann, H.C. (1) 1 18 Marsol, C. (1) 177 Martens, J. (3) 44 Martens, R. (1) 344 Martin, C.G. (1) 405 Martin, J.A. (1) 93 Martinez, F. (1) 3 18 Martinez, J.C. (5) 72; (6) 24 Martorell, A. (3) 56 Marwood, R.D. (4) 40 Masojidkova, M. (4) 21, 26, 68 Massa, W. (6) 32-35,38, 39, 41,42

Massey, J.A. (1) 338 Mastrodli, P. (1) 292 Masuda, K. (5) 51 Masuko, T. (6) 208 Matern, E. (1) 254 Mathew, D. (6) 235 Mathey, F. ( I ) 25 1, 524, 545,

554, 555, 583-585, 61 1613, 615, 617, 618, 625; (3) 3; (6) 110 Mathieu, R. (1) 69 Mathivet, T. (3) 76, 77 Matsuda, A. (4) 41,42, 65-67 Matsuhji, M. (6) 94 Matsukawa, S. (1) 20 1,299 Matsumoto, K. (1) 103 Matsumoto, S. (6) 94 Matsuoka, M. (1) 458; (5) 15 Matsuzaka, Y.(6) 94 Matt, D. (1) 177,428 Matteoli, U. (1) 389 Matteucci, M.D. (4) 34 Mattheis, C. (1) 70 Matthews, S.E. (1) 380,427 Mattinen, J.K.(3) 186 Matulic-Adamic, J. (4) 86 Matyjaszewski, K. (1) 449; (6) 156, 157 Maulitz, A.H. (1) 503 Maunier, V. (1) 324 Mauzac, M. (1) 235; (6) 13 Mayer, H.A. (1) 155,224,225 Mayer, P. (5) 11 Mayrargue, J. (5) 58 Mays, M.J. ( I ) 501 Mazurkiewicz, R. (1) 480

Organophosphorus Cheniistry Meetsma, A. (3) 67 Mehdi, A. (1) 226 Meidine, M.F. (1) 528 Meier, C. (4) 13 Meier, P. (1) 111 Meille, S.V. (6) 205 Meisel, M. (1) 444 Mele, A. (4) 22 Mellet, P. (1) 137 Mendenhall, G.D. (3) 138 Mendizibal, F. (6) 138 Menek, N. (6) 112 Menendez, J.C. (6) 22 Menendez, J.R. (6) 114 Meng, S.S. (6) 117 Mercier, F. (1) 25 1 Mercuri, M.L. (1) 274; (6) 105 Merdivan, M. (3) 109 Mereiter, K. (1) 48, 172 Merino, S. (6) 15 Merz, K. (1) 463, 522 Merzhanov, E.G. (1) 284 Merzweiler, K. (1) 70 Metz, W.A. (1) 13 Meunier, B. (6) 148 Meyer, P. (3) 19 Meyers, C.L.F. (4) 6, 7 Mbzailles, N. (1) 6 11,6 13, 615,618

Mi, A.Q. (3) 45 Miazga, A. (4) 18 Michalik, M. (3) 47, 141 Michel, P. (1) 354; (5) 40,41 Miele, D. (1) 374 Mielniczak, G. (3) 185 Miffiin, J.P. (1) 454 Miguel, D. (1) 485 Miki, M. (1) 342 Mikolajczyk, M. (1) 412; (5) 94

Mikolenko, R. (3) 177 Mikoluk, M.D. (1) 607; (3) 15; (6) 100

Milewska, M. (3) 90 Milius, W. (1) 46; (5) 17 Miller, P.J. (6) 156, 157 Minakawa, N. (4) 65,66 Minami, E. (5) 51 Minami, T. (1) 33 1 Minasyan, G.G. (1) 271 Minoru, T. (5) 95 Minto, F. (6) 191, 241 Miquel, Y.(1) 266

Author Index Miranda, L.D. (6)20 Mironov, V.F. (1) 504;(2) 12,

13 Miryan, N.I. (5) 100 Misaki, Y.(3) 102 Mitsui, T.(4)90 Miura, T.(1) 202 Miyajima, F.(1) 487 Miyake, Y.(3) 174 Miyashita, T.(4)47 Miyoshi, K. (5) 22 ' Mizutani, K.(6)93,94 Moehlen, M. (6)35,42 Mohamed, N.R. (5) 20 Mohammadpoor-Baltork, I. (1) 474 Mohler, P. (1) 85 Mohr, J.T. (1) 192 Mohr, M.(1) 238;(3) 169 Mok, K.F.(1) 25 1, 576, 577 Molina, P.(1)316, 318,319; (5) 71-74;(6)23-26 Moloney, B.A. (4) 16 Momchilova, S.(1) 424 Monflier, E.(3) 76,77 Monforte, P.(2)38 Monk, C.(1) 132 Montahaei, A.R. (3) 92 Moore, A.J. (3) 103 Moore, R.B.(6) 128, 158 Morales, E.(6) 197, 198 Moreno-Maiias, M. (6) 16 Morgan, T.A. (6) 164 M o ~K. , (3) 3 1-33,37;(4)47 Mori, M. (1) 285 Mori, T.(3) 102 Moriguchi, T.(4) 14, 15 Morimoto, T. (1) 232 Moro, S.(4)73 Mortreux, A. (3) 39,40,44,59, 76,77 Moskowitz, H.(5) 58 Moss, S.F.(3) 63 Mosslemin, M.H. (3) 92 Mothes, E.(3) 41 Mouchet, P.(1) 376 Mouth, D.(3) 42 Moureau, L.(2) 19-21 Moutiers, G.(1) 491 Mouzdahir, A. (3) 147 M'rabet, H.(1) 384 Miiller, C.(6)42 Miiller, J.F.K. (1) 208

Mugrage, B. (3) 120 Mullen, G.E.D. (1) 221 Muller, B.(3) 193;(4)44 Muller, G.(1) 80,327,329 Muller, L.(1) 344 Mulvey, R.E.(1) 376 Muneer, R. (3) 96 Munoz, A. (2)24,35 Murai, T.(3) 142,143 Murakami, N. (6)75 Murphy, P.J. (1) 260;(5) 62 Muscio, F. (1) 292 Musigmann, C. (1) 426 Musina, E.I. (1) 163 Muslin, D.V.(2) 10 Mussig, S.(1) 44,45 Mustafina, A.R. (3) 88 Muthiah, C. (3) 132, 196;(6) I27 Muxworthy, J.P. (1) 243 Myer, C.N. (6)255 Naasz, R. (3) 181 Nachtigal, C.(1) 86, 15 1, 160, 238;(3) 169 Nagahata, R.(6)91 Nagata, K.(1) 201 Nagendran, S. (6) 188 Nagino, C.(1) 301 Nagy, 2.(1) 395 Naili, S.(3)39,59 Nair, C.P.R. (6)235 Nair, V. (4)2,28,52 Nakagawa, Y.(1) 103 Nakajima, K.(1) 101 Nakajima, M. (3) 151 Nakamoto, T. (5) 22 Nakamura, H.(6)208 Nakamura, M. (1) 342 Nakamura, N. (5) 22 Nakamura, S.(3) 151 Nakamura-Ozaki, A. (4)87 Nakanishi, I. (5) 92 Nakano, H.(1) 206,207 Nakano, S.(6) 170, 174,259 Nakatsuji, Y.(1) 219 Nakazawa, H.(5) 22 Nakazawa, M.(1) 551 Nalli, T.W. (3) 96 Nandanan, E.(4)72, 73 Nandi, M.(1) 1 19 Nangia, A. (1) 410

255 Naso, F.(1) 400 Naud, F. (1) 19 Nauer, I. (3) 137 Naumann, D.(1) 460 Naundorf, A. (4)77 Nazri, M. (6) 114 Neamati, N. (4)52 Neckers, D.C.(1) 408 Neda, I. (1) 468;(2)32;(6)6 Nedolya, N.A. (1) 164 Nelson, A. (1) 401-405;(5) 7982 Nelson, J.H. (1) 578 Nelson, J.M. (6)217, 218 Nelson, S.G. (1) 65 Net, G.(3) 71,72 Nettekoven, U.(1) 172 Neuburger, M. (1) 208 Neugebauer, T.(3) 74 Neumann, B. (1) 507,517, 5 18, 520;(6)99 Neumueller, B. (1) 471,628, 629;(6)33,35-37,40,42, 96 Newman, P.D. (1) 142,367 Nguefack, C.(1) 64 Nguyen, M.T. (1) 365, 527, 543,571 Ni, Y.(6)256 Nicastro, P.J. (1) 4 18 Nicholas, K.M. (3) 17 Nicholson, B.K.(1) 239;(6)44 Nickel, T.(1) 107, 1 I2 Nickisch, K. (1) 192 Nie, Z.(4) 17 Niecke, E.(1) 352,353, 552 Nief, F. (1) 61 1 Nieger, M. (1) 352,353,552, 587,588 Niemi, T.-A. (1) 566 Nieuwenhuyzen, M. (1) 361; ( 5 ) 17

Nifant'ev, E.E. (3) 89, I78 Nifant'ev, I.E. (1) 438 Nijbacker, T. (1) 364 Nikitin, E.V.(1) 461,462 Nikitin, M.V.(1) 121, 153, 445,446 Niknam, K. (1) 474 Nikolaev, A.V. (4)60 Nikolaeva, I.L. (3) 88 Nikolova, R.(3) 1 10 Nikonov, G.N. (1) 163;(3) 127

256 Ninan, K.N. (6) 235 Nishi, Y. (1) 457; (5) 32 Nishide, H. (5) 95 Nishikawa, A. (6) 94 Nishikawa, M. (6) 93 Nishimura, S. (5) 92 Nishioka, Y. (6) 170, 174, 259 Nishitani, J. (1) 457; (5) 32 Nitta, M. (5) 45 Nixon, J.F. (1) 528, 574, 590595, 597, 600, 608, 620, 622-624 Nobile, C.F.(1) 292 Nobori, T. (6) 93,94 Nocera, D.G. ( I ) 53 Noda, R. (1) 459 NMh, H. (1) 123, 128, 129; (3) 18; ( 5 ) 12, 13 Noh, D.Y. (3) 99 Nohira, H. (1) 385 Nolan, S.P. (1) 54, 355, 356; (3) 25 Noll, B. (3) 176 Norman, A.D. (3) 176 Nourmohammadian, F. (5) 61 Novak, T.(1) 395,406 Novikova, D.K. (6) 201 Novosad, J.46) 65, 71 Nunez, R. (1) 57 Nurminen, E.J. (3) 186 Nyuiaszi, L.(1) 509, 572,574, 600,608

Oba, G. (1) 56 Oberhauser, W. (1) 360 OBrien, P. ( I ) 436 Ochiai, M. (1) 457,459; (5) 32 Ochoa de Retana, A.M. (1) 399 O'Connor, S.(6) 229 Oda, K. (5) 91 Odabwglu, M. (6) 112, 139, 140 O'Donnell, M.J. (6) 92 Oehme, G. (3) 47 Oevering, H. (1) 241 Offenbecher, M. (3) 30 Ogasawara, M. (1) 168 Ogawa, A. ( 5 ) 49 Oh, D.Y. (4) 29; (5) 99 Oh, I.S. (3) 140 Ohe, K.(1) 108; (3) 31-33,37, 174

Ohff, M.(3) 24,34 Ohkubo, K. (6) 94 Ohlmeyer, M.H.J. (6) 19 Ohno, A. (1) 332 Ohshima, S. (1) 33 1 Ohtaguro, T. (1) 33 1 Ohtani, T. (1) 302 Ohtsuki, T.(4) 90 Oiarbide, M. (6) 89 Okano, N. (1) 299 Okauchi, T.(1) 33 1 Okazaki, R.(5) 65 Okuda, J. (1) 50 Okuma, K. (5) 16 Okuyama, Y.(1) 206,207 Olaru, A. (5) 83 Olkowska, J.W. (1) 254 Olsen, M.R.(6) 44 Omelanczuk, J. (1) 412 Ornote, M. (5) 47 Onciu, M. (3) 164 Ong, C.M. (6) 30, 51 Orme, C.J. (6) 226-228 Ormsby, D.L. (1) 59 Orpen, A.G. (1) 241; (3) 56, 84,86 Ortega, F. (1) 66 Ortner, K.(1) 86 OShaughnessy, P. (1) 32, 146, 147 Osipov, P.E. (2) 10 Ostrowski, A. (1) 558, 559 Otoguro, A. (1) 550 Ott, G.R. ( 5 ) 52 Otteson, K. (1) 305 Ou, W. (1) 326 Ouahab, L. (1) 246 Ovakimyan, M.Zh. (1) 268, 271,489 Overberg, J.J. (1) 29 1 Owens, S.R.(4) 36 Pace, G. (3) 184 Padberg, H.J. (1) 432 Paige, D.R. (1) 11 Paine, R.T. (1) 129; (6) 95 Pakkanen, T.A. (1) 4 Pal, S. (4) 52 Pala, C. (1) 58 1 Palacios, F. (1) 398, 399; (5) 64;(6) 27 Paleta, 0. (1) 257; (3) 115

Organophosphorus Chenristry Palmer, M.T.(3) 172 Palomo, C. (6) 89 Pamies, 0. (3) 71,72 Panchishin, S.Ya. ( 5 ) 19 Pandey, R.K. ( 5 ) 48 Pandolfo, L. ( 5 ) 25 Pang, Z. (6) 256 Panyella, D. (1) 80, 327, 329 Papagni, A. (1) 346 Papathomas, P.M. (1) 344 Papkov, S.P. (6) 202 Pappalardo, G.C. (6) 207 Parakka, J.P. (6) 105 Park, D.J. (1) 283 Park, J. (1) 37 Park, J.H. (4) 89 Park, J.I. (3) 112 Park, K. (1) 58 Park, P.J. (6) 223, 256 Park, S . (6) 233 Park, S.-W. (1) 193; (6) 21 Park, Y.H. (1) 387 Park, Y.Y.(1) 144 Parker, D.T. (3) 120 Parker, T. (3) 120 Parlevliet, F.J. (3) 85, 87 Parr, J. (1) 215, 216; (6) 67 Parry, N.R. (4) 8 Parsons, S. (3) 101 Parvez, M. (1) 194,369; (6) 5, 141, 145 Pascal, R.A. (1) 249,250 Pasenok, S.V.(1) 460 Pashkevich, K.I. (2) 14; (3) 94, 117 Pasquier, C. (3) 44 Pasto, M. (3) 57 Patsanovskii, 1.1. (1) 504 Paulasaari, J.K. (6) 84-87 Paulsen, C. (1) 247 Pawelke, B. (3) 137 Peach, M.E.(6) 102 Peacock, R.D. (1) 142,367 Peaker, A.T. (3) 148 Pebler, J. (6) 31 Pedersen, T.M.(5) 105 Pederson, H.L. (1) 42 Pegoretti, A. (6) 241 Peignieux, A. (1) 491 Pelletier, J.C. (1) 306 Peiieiiory, A.B. (1) 100 Peng, Y.X. (1) 49 1 Penn, B.G.(1) 422

Author hidex Peraleq E. (3) 147 Perdicchia, D. (1) 346 Perea, J.J.A. (1) 4 1 Perettie, D.J. (6) 163, 164 Perez, J. (1) 485 Perez-Benitez, A. (3) 98 Perez-Perez, M.J. (4) 30 Pergament, I. (3) 106 Perigaud, C. (4) 46 Perin, G. (1) 478; (5) 36 Pernak, J. (3) 123 Pernin, C.G. (6) 6 1,62,66 Perron, P. (1) 438 Perry, A. (4) 8 Perry, R.J. (6) 74 Peters, C. (1) 603, 621 Peters, E.-M. (1) 169 Peters, K. (1) 169 Peters, R. (1) 40 Petersen, J.L. (1) 7; (3) 25 Peterson, E.S. (6) 21 1, 213, 226-228,253

Petit, P. (4) 69 Petnehazy, I. (3) 146 Petiicz, G. (1) 48,573 Petragnani, N. (1) 478; (5) 36 Petrov, B.V. (3) 144 Petrova, J. (1) 424 Petrovskii, P.V. (1) 268, 271; (2) 30; (3) 121

Petrusevich, K.M. (1) 4 19 Petukh, N.V. (5) 100 Pfaltz, A. (1) 183; (3) 68, 69 Pfeiffer, M. (1) 94 Pfitzner, A. (1) 128 Pfleiderer, W. (4) 32 Phetmung, H. (1) 241 Phillips, A.D. (1) 535 Phillips, L.R. (4) 48 Phok, S.(1) 56 Phung, N. (5) 90 Piccolo, 0. (1) 17 Pickaert, G. (1) 14 Pierloot, K.(1) 543 Pierra, C. (4) 12 Piers, W.E.(1) 290 Pierwocha, A. (1) 480 Pietrusiewicz, K.M. (1) 400, 412

Piggott, B. (6) 58, 64 Pikies, J. (1) 254 Pillarsetty, N. (1) 230 Pilloni, G. (1) 440

257

Pillow, J.N.G. (5) 96 Pinchuk, A.M. (3) 6, 14 Pini, E. (5) 76; (6) 28 Pink, M. (1) 247 Pintauro, P.N. (6) 206, 229, 230

PintCr, I. (1) 323; (6) 4 Pistorio, B.J. (1) 53 Pitter, S. (1) 68 Pizzano, A. (1) 93 Plack, V. (1) 286; (2) 7; (3) 4, 5

Plank, S. (1) 628,629 Plater, M.J. (1) 413 Plath, M. (1) 44, 45 Platonov, A.Y. (3) 59 PIC, N. (1) 170 Plenat, F. (6) 15 1 Pletsch, A. (1) 196 Po, R. (6) 191 Pochini, A. (1) 426 Podda, G. (6) 159 Podewils, F. (1) 581 Poh, S . (1) 366 Pohlmeyer, T. (1) 526 Pohnert, G. (5) 39 Poirer, D. (6) 7 Polborn, K. (1) 123 Polezhaeva, N.A. (3) 118 Poli, R. (1) 166 PoliakoK M. (6) 106 Polimbetova, G.S. (3) 60, 61 Polishchuk, 0. (1) 349; (5) 10 Poljansek, I.D.(1) 336 Pollini, G.P. (3) 113 Polosukhin, A.I. (2) 22,3 1; (3) 73

Polson, L.A. (6) 226-228 Pombeiro, A.J.L. (1) 528 Pommier, Y.(4) 52 Poopeiko, N. (1) 3 14 Pope, S.C. (4) 1 Popova, E.V. (1) 504 Popp, R. (1) 24 Porwolik-Czomperlik,I. (6) 146, 147

Potapov, V.A.(3) 144 Potter, B.V.L. (4) 40 Pottorf, R.S.(6) 92 Pouet, M.J. (1) 49 1 Povolotskii, M.I. (1) 515, 516 Powell, A.K. (1) 221 Power, P.P. (1) 497

Poznanski, J. (4) I8 Prabhu, K.R. (1) 179,230,23 1 Prakash, J. (6) 167 Prakash, T.P. (4) 36 Praly, J.-P. (1) 323; (6) 4 Prange, R. (6) 216-218 Predieri, G. (1) 222 Pregosin, P.S. (1) 209 Preuss, F. (1) 603,608 PrkvM, D. (6) 16 Price, A.J. (1) 157 Price, R.D. (5) 6 Priddy, D.B.(3) 138 Priemer, S.(1) 556 Primrose, A.P. (6) 141, 145 Pringle, P.G. (1) 241; (3) 56, 84, 86

Pritchard, R.G.(1) 28,275, 297,298,4 15; (3) 148

Prock, A. (1) 355,356 Provot, 0. (5) 58 Prusiewicz, C.M. (4) 35 Pruss, E.A. (6) 95 Ptak, R.G. (4) 3 Pu, J.-Y. (5) 95 Pu, L. (1) 173 Pucknat, H. (1) 526 Pudovik, A.N. (3) 166 Pudovik, M.A. (1) 452; (3) 88, 166

Puerta, C. (1) 327 Pulm, M. (3) 196 Pursiainen, J. (1) 2,4; (3) 1 Pushechnikov, A.O. (1) 626; (3) 8, 9

Pyun, J. (6) 156 Qian, H. (1) 414, 548 Qian, X.H.(3) 97 Qin, J.G. (6) 221 Qin, Y. (1) 576; (3) 45 Qiu, G.F.(3) 122 Qiu, L. (6) 187 Qiu, Y.L. (4) 3 Quan, Z. (1) 37 QuCguiner, G. (1) 170 Queisser, J.A. (1) 160 Quirmbach, M. (1) 61, 186; (3) 24

Rube, G. (I) 40

258

Ramakrishna, T.V.V. (1) 240;

Retker, C. (1) 333 Rettig, S.J. (1) 15, 19, 246, 247 Retz, 0. (3) 150 Reutov, V.A. (2) 9 Reye, C. (1) 226, 494; (2) 3 8 Reyes, C. (1) 355,356 Reznik, V.S. (3) 88 Rhee, H.-W. (1) 450 Rheingold, A.L. (1) 93, 125,

Ramf, F.A. (1) 117 Ramsden, P.D. (1) 369; (6) 5 Ranaivonjatova, H. (1) 502,

Ribblett, J.W. (1) 5 Ribera, E. (3) 98 Ricard, L. (1) 88, 251, 554,

Rabe, G.W. (1) 125, 126 Radetich, B. (3) 36 Radom, L. (1) 539 Rae, A.D. (1) 255 Raithby, P.R. (1) 501 Raja, A.V. (6) 196 RajanBabu, T.V. (1) 90, 119; (3) 36

(6) 108

523

126, 159, 535; (6) 141, 145

555, 583-585, 61 1-613,

615,617,618 Rancurel, C. (1) 246, 247,434 Richard, P. (1) 166 Rankin, D.W.H. (1) 344 Richards, A.F. (1) 525, 529 Rao, G. (5) 5 Richelme, S. (2) 35 Rao, N.A. (1) 234 Richter, B. (1) 12 Raper, E.S. (5) 3 Riebli, P. (1) 370 Rasadkina, E.N. (3) 178 Rieder, A. (1) 360 Rassat, A. (1) 354; (5) 40,41 Riera, V. (1) 34 1 Rath, N.P. (1) 548 Ratner, V.G. (2) 14; (3) 94, 117 Riese, U. (6) 31, 32 Righi, L. (3) 135 Ravadits, 1. (1) 394 Rigon, L. (1) 502 Ravikumar, V.T. (4) 3 1 Riihimaki, H. (1) 4 Raza, S.K. (1) 486 Rippert, A.J. (1) 85,203 Riau, R. (1) 564; (6) 46 Reddy, N.D. (6) 107, 108, 152- Ritschl, F. (1) 444 Ritzmann, M. (4) 70 154 Rivals, F. (6) 122 Reddy, V.S. (1) 161,386 Robert, F. (1) 63, 64 Reed, C.S. (6) 236,237 Roberts, B.E. (6) 249,25 1 Reed, J.K.(4) 74 Roberts, R.S. (5) 89 Reed, N.N. (1) 13 Roberts, S.M. (3) 34; (4) 85 Reek, J.N.H. (1) 242 Robertson, A. (1) 48 1 Rees, N.H. (3) 189 Robertson, E.H. (1) 344 Reetz, M.T. (1) 3,616; (3) 53, Robertson, N. (3) 101 55,57, 74 Robins, K.A. (1) 291 Reeves, S.D. (6) 215 Robinson, G.H. (1) 567 Regitz, M. (1) 505, 508, 509, Rode, W. (4) 18 530, 532, 598-600, 602, Roder, T. (5) 43 603,608,621; (3) 29 Rodi, A.K. (1) 523 Reiher, M. (1) 148,340 Rodios, N.A. (3) 110 Rein, T. (5) 105 Roschenthaler, G.-V. (2) 14; Reiner, M. (3) 65 (3) 94, 116, 117 Reiners, I. (3) 44 Roesky, H.W. (1) 180 Reinke, H. (3) 141 Rottger, M. (1) 498 Reinoehl, U. (1) 155 Rohde, U. (1) 558 Reis, G.J. (1) 509 Reiser, G. (4) 70 Rohovec, J. (1) 165,383 Reiser, 0. (5) 104 Rojas-Lima, S. (5) 12 Reisky, M. (1) 75 Roje, M. (6) 88 Roland, A. (4) 10 Rell, S. (1) 522 Romain, J.K.( I ) 5 Ren, P. (6) 194, 195

OrganophosphorusCheniistty Romakhin, A. S. (1) 46 1,462 Romanenko, E.A. (5) 19 Romanenko, V. ( I ) 348 Rominger, F. (1) 24 Rominger, R.L. (1) 244 Rong, F.G. (4) 19 Rosa, P. (1) 6 17-6 19 Rosen, J.J. (5) 86 Rosenberg, I. (4) 21, 68 Rosenberg, L. (1) 99 Rosenthal, U.(5) 21 Rossenbach, S. (1) 110 Rossi, E. (5) 76; (6) 28 Rossi, R.A. (1) 100 Rothe, U. (3) 153 Rothenberger, A. (1) 13 1 Rottger, D. (3) 58 Rovira, C. (3) 98 Rowan, S.J. (1) 442 Royo, P. (1) 50 Rozenski, J. (4) 37 Rozhenko, A. (1) 148, 5 15 Rshetkova, G.R. (2) 13 Rubuales, G. (6) 27 Rudershausen, S. (3) 141 Rudzinski, J. (1) 396 Ruegger, H. (1) 150 Ruhlicke, A. (1) 520 Ruf, S.G. (1) 505, 598, 599; (3) 29

Ruffolo, R. (6) 256 Ruiz, A. (3) 71, 72 Ruiz, J.L. (1) 1 15, 34 1 Rummey, C. (1) 430 Rusanov, E.B. (1) 5 16 Russ, P. (4) 73 Russell, D.R. (1) 9, 237 Russell, J.C. (3) 62 Russell, M.G. (1) 405,45 1; (5) 33

Ruthe, F. (1) 274, 4 17,466, 556, 558, 559,609

Rutman-Halili, I. (4) 75 Rutsch, P. (1) 76 Rybak, R.J. (4) 9 Rzepa, H.S. (1) 315; (6) 1 Saadioui, M. (1) 380 Saak, W. (6) 60 Saakyan, G.M. (3) 166 Saber-Sheikh, K. (6) 243,244 Sadeh, E. (1) 10

Author Index Sadighe, J.P. (1) 6 Safaryan, G.P. (1) 492 Sagner, G. (4) 83 Saguitova, F. (3) 127 Said, M.A. (3) 132, 196 Saigo, K. (1) 435 Saito, S. (1) 547 Saitoh, A. (1) 232 Saiz, E. (6) 192 Sakamoto, H. (3) 15 1 Sakane, K. (5) 92 Sakarya, N. (1) 597 Salek, S.N. (1) 221 Salem, G. (1) 105 Salzer, A. (1) 73, 218, 581 Sammes, P.G. (3) 62 Samuel, I.D.W. (5) 96 Sdnchez de la Blanca, E. (6) 252

Sanda, F. (5) 66 Sanders, J.K.M. (1) 27 Sangaiah, R. (4) 35 Sannicolo, F. (1) 17 Sano, A. (3) 15 1 Santhosh, K.C. (1) 265; (3) 91; ( 5 ) 18 Santoyo-Godlez, F. (6) 3 Sanudo, C.(1) 327,329 Sam, M.A. (1) 3 16; (5) 71 Sarapulova, G.I.(1) 164 Sargent, J.R. (6) 86 Sarroca, C. (1) 439 Sarwar, S. (1) 298 Sasaki, M. (1) 276 Sasaki, T.(4) 15 Sasaki, Y. (1) 87 Sato, K. (5) 47 Sato, T. (1) 55 1 Sato, Y. (5) 57 Satori, P. (1) 288 Saunders, G.C. (1) 9, 361 Sauthier, M. (6) 46 Sava, X.(1) 61 1 Savin, A. (3) 173 Sawai, H. (4) 87 Sawye, R.A. (1) 220 Sayed, M.B. (6) 113 Scalone, M. (3) 48 Scanlan, T.H.(1) 565 Scapacci, G. (1) 116 Schafer, A. (4) 61 Schaffner, S.(1) 208 Schakel, M. (1) 546,553

259

Schaller, A. (1) 130 Schapman,F. (3) 104 Schaub, C. (3) 193 Scheer, M. (1) 53 1 Scheffer, M.H. (1) 5 17-5 19 Scheider, M. (1) 192 Scheller, T.(1) 224 Schene, H. (3) 152 Schenk, S. (1) 110, 112 Scheuer-Larsen,C. (3) 188 Schiemenz,G.P. (1) 495 Schiffer, T.J. (1) 552 Schlecht, S. (6) 97 Schlewer,G. (3) 194 Schleyer, P.von R.(1) 365, 530 Schlosser, M. (5) 35 Schmick, W. (6) 103 Schmid, M. (1) 151, 160 Schmid, R.(3) 48 Schmidpeter, A. (1) 586; (3) 18, 19; (5) 11-14 Schmidt, 0. (1) 353 Schmidt, R.R.(3) 65, 150, 153, 193; (4) 44

Schmidt, U.(3) 21,46,47 Schmitt, L. (3) 194 Schmock,F. (1) 471 Schmutzler, R.(1) 286,468;

(2) 7, 32, 36; (3) 4, 5; (6) 6

Schneider, R. (1) 339; (6) 149 Schneiderbauer,S.(1) 128 Schobert, R. (5) 17 Schoeller, W.W.(1) 148, 351, 353,507,515,517

Schoetzau,T. (4) 81, 84 Schorm, A. (1) 430 Schoth, R.M. (3) 116 Schott, H. (4) 45 Schraa, M. (1) 467 Schroder, D. (1) 340 Schroder, M. (1) 603 Schriidel, H.-P. (1) 586; (5) 12, 14

Schrader, G. (1) 586, 587; (5) 14

Schrott, M. (1) 588 Schull, T.L. (3) 52 Schulte, J.B. (1) 77 Schulz, B.S. (4) 32 Schulz, M. (6) 98 Schulz-Lang, E. (1) 425 Schumann,H. (1) 333 Schurhammer,R. (1) 423

Schutte, R.P.(1) 15 Schwarz, H. (1) 340 Schwarz, M. (4) 32 Schwarz, W. (1) 127, 130,628 Schwarzer, K. (4) 82 Schwendener, R.A. (4) 45 Schwing-Weill,M.-J. (1) 380 Schworer, R.(4) 44 Scopelliti, R.(1) 379 Screttas, C.G. (1) 33 Scrivanti, A. (1) 389 Scudder, M. (1) 359,476,477 Scully, P.N. (3) 161, 162 Sebastian, R.-M. (1) 25 Sebenik, A. (1) 336 Sediek, A.A. (3) 11 1 Segerer, U. (1) 134, 135 Seio, K. (4) 15 Sekhar, B.B.V.S. (3) 95, 124 Sekhri, L. (1) 375 Sekine, M. (4) 14, 15 Selent, D.(3) 58 Selke, R. (1) 233 Selvakumar, K.(1) 209 Selvaraj, 1.1. (6)254 Selvaratnam, S.(1) 577 Semioshkin, A.A. (3) 121 Senchurin, V.S. (2) 8,9, 11 Seo, H. (1) 217 Seppala, E. (1) 4 17 Serindag, 0. (1) 237 Seth, S. (5) 67 Seto, H. (4) 62 Sevin, A. (1) 625; (6) 110 Seybert, G. (6) 38, 39,41 Sgarabotto, P. (3) 135 Shaabani, A. (1) 264 Shabana, R.(5) 44 Shainberg, A. (4) 75 Shaker, Y.M. (5) 44 Shapiro, R (3) 35 Shapkin, N.P. (2) 9 Sharma, D.C.(3) 127 Sharutin, V.V. (2) 8-1 1 Sharutina, O.K.(2) 8-1 1 Shaterian, H.R.(1) 281, 282 Shaw, B.R. (4) 50,63,64,88 Shaw, R.A. (6)146, 147 Shcherbakov, V.I. (2) 8 Shefield, J.M. (1) 32,275, 297,298

Sheldrick, W.S.(1) 110, 181 Shelzer, 0. (1) 195

260

Sherlock, D.J. (2) 1, 5 Shestakova, A.K. (5) 8 Sheu, T.-R.(5) 34 Shevchenko, I. (3) 177; (6) 2 Shi, S.-J. (1) 312 Shibahara, A. (6) 93 Shibasaki, M. (1) 368 Shibata, M. (5) 48 Shibuya, S. (4) 23-25 Shigeoka, T. (5) 47 Shimanuki, T. (1) 219 Shimeno, H. (4) 23-25 Shimizu, H. (6) 257 Shimizu, S. (1) 87 Shin, J. (1) 287 Shindo, K. (1) 458; (5) 15 Shinozuka, K. (4) 47 Shioji, K. (1) 332 Shipitsin, A.V. (4) 85 Shirakawa, S. (1) 87 Shirato, M. (4) 67 Shiratori, S. (1) 29 Shiro, M. (1) 459 Shirokova, E.A. (4) 85 Shishkin, O.V. (3) 160 Shivanyuk, A. (1) 426,427 Shneyvays, V. (4) 75 Shon, J.-I. (I) 58 Shreeve, J.M. (6) 119,254 Shrimal, A.K. (6) 126 Shtyrlina, A.A. (2) 12 Shultz, A.R. (1) 41 1 Shumieko, A.E. (6) 118 Shuto, S. (4) 40-42,65-67 Shvets, A.A. (1) 492 S h y , S.G.(1) 226 Siddiqui, A.Q. (4) 5 Siddiqui, M.A. (4) 73 Sieber, F. (1) 13 Siedentop, T. (1) 468 Siege], K. (5) 53 Siegfried, S.(5) 17 Sieler, J. (1) 124, 134, 135 Siemeling, U. (6) 99 Sievers, H. (1) 340 Sikora, D. (6) 8 Sillanpaa, R.(1) 57,469 Silveira, C.C.(1) 478; (5) 36, 37

Silvestru, C. (6) 57 Simard, J. (6) 7 Simonutti, R. (6) 142-144 Simpkins, N.S. (1) 371

Sinay, P. (4) 58 Sinegovskaya, L.M. (1) 446 Singh, R.A. (1) 338 Singh, R.P. (6) 119 Singh, S. (3) 17 Singkonrat, J. (1) 234 Singler, R.E. (6) 109, 21 1 Sinou, D. (1) 63, 64 Sinyashin, O.G. (1) 162, 252 Sivakov, A.A. (3) 59 Siwy, M. (6) 146, 147 Six, Y.(5) 102 Skabara, P.J. (1) 454 Skowronska, A. (1) 256,267, 3 17

Slater, M.J. (4) 8 Slawin, A.M.Z. (1) 215, 216, 413; (3) 167, 171; (6) 55, 56, 59, 67-71 Slowinski, F. (1) 372 Smart, B.A. (1) 344 Smith, D.C. (1) 54 Smith, J.D. (1) 145 Smith, M.B. (1) 15; (6) 67-70 Smith, R.J. (1) 221 Smolii, O.B.(5) 19 Snaith, R. (1) 376 Snoeck, R. (4) 26 Snyder, R.D. (1) 5 Soeda, S.(4) 23-25 Sohn, Y.S.(6) 120,246-248 Sokolov, V.I. (3) 160 Solans, X. (1) 328 SolladiC-Cavallo, A. (6) 88 Sslling, T.I.(1) 539 Soloway, A.H. (4) 19 Somers, J. (3) 120 Sommadossi, J.P. (4) 12 Somoza, F.B.(1) 139 Somsook, E. (1) 220 Son, J.-H. (1) 193 Song, G.H. (3) 97 Song, S.-C. (6) 246-248 Sonnenburg, R. (2) 32 Sonnenschein, H. (1) 83; (3) 66 Sood, P. (2) 1-4; (3) 79, 81, 82 Sopchik, A.E. (3) 126 Soubra-Ghaoui, C.( I ) 29 1 Soulantica, K.(1) 358 Sozzani, P. (6) 142-144 Spagnolo, P. (5) 75 Spangler, C.W. ( I ) 210,211 Spaniol, T.P. (1) 50

OrganophosphorusChemistry Spannenberg, A. (5) 21 Speiser, F. (1) 19 Spek, A.L. (1) 16, 172, 544, 546; (3) 85, 87

Spera, S. (6) 191 Spiegler, M. (1) 117 Spies, T. (6) 60 Spiess, B. (3) 194 Srebnik, M. (3) 106 Stalke, D. (1) 94, 13 1, 180 Stammler, A. (1) 519 Stammler, H.-G. (1) 507, 5 17520; (6) 99

Stampf, T. (1) 360 Starkey, G.W. (1) 200 Starkova, A.A. (3) 144 Starzewski, K.A.O. (1) 5 1 Stash, A.I. (3) 178 Stasi, L. (3) 107 Stawinski, J. (4) 20, 46, 53 Stec, W.J. (1) 296; (4) 38,92 Steck, P.L. (1) 26; (2) 16 Stefaniak, S. (1) 30 Steimann, M. (1) 86, 151 Steinbach, J. (1) 598 Steiner, A. (6) 121, 122 Steiner, T. (1) 493 Steinhauser, K. (1) 394 Stelzer, 0. (1) 107, 110, 112, 181

Stephan, D.W. (1) 133,464; (6) 30, 51

Stephan, E. (5) 83 Stephenson, H. (1) 303,307 Stevens, E.D.(1) 54 Stewart, F.F. (6) 130, 13 1, 21 1, 222,226-228,234,253

Stibr, B. (1) 59 Stirling, D. (1) 142, 367 Stoddart, J.F. (1) 442 Stoke, K. (4) 83 Stone, M.L.(6) 226-228 Stoppek-Langner, K. ( 1) 154 Storhoff, B.N. ( I ) 5 Stowasser, R. (1) 430 Stradiotto, M. (1) 580 Stramare, S. (6) 143 Strassler, C.(4) 33 Streubel, R. (1) 556-559, 609 Strohmeyer, T.W. (3) 129 Stromburg, B. (6) 125 Stuart, A.M. (1) 9, 1 1 Stiirmer, R. (1) 89.2 18

Author Index Stulz, E. (1) 27 Stumpf, A. (1) 51 Sturm, T. (1) 48 Stutzmann, S.(1) 621 Su, J. (1) 567 Su, M. (5) 87 Suades, J. (1) 69 Suda, K. (5) 49 Sue, H. (6) 175 Sueda, T. (1) 459 Suemune, K. (4) 23,25 Sugimoto, K. (6) 93 Sugimoto, 0. (1) 285 Sugiya, M.(1) 385 Sugiyarna, J. (6) 91 Suisse, I. (3) 39,40 Sule, S.S.(6) 250 Sulikowski, G.A. (1) 84 Sulkowska, A. (6) 203 Sulkowski, W.W.(6) 203 Sumita, Y.(4) 67 Sumtsova, E.A. (3) 9 Sun, C.C.(5) 69; (6) 17 Sun, Y.M.(6) 23 1 Sunderland, N.J. (6) 141, 145 Sundermann, A. (1) 148,s 17 Sundermeyer, J. (1) 430; (5) 68; (6) 98

Sung, D.D. (1) 300 Sunjic, V. (6) 88 Surana, A. (3) 20 Suranna, G.P. (1) 292 Suter, L. (1) 595 Sutter, J.-P. (1) 246, 247, 434 Suzuki, K. (1) 293; (6) 93 Suzuki, Y.(1) 109 Svirkin, Y.Y.(6) 249 Swamy, K.C.K. (3) 132, 196 Swayze, E. (1) 308 Sweedler, D. (4) 86 Swiegers, G.F.(1) 77 Sykara, G.D. (6) 146 Szabo, P.T. (3) 195 Szabo, T. (4) 20 Szalontai, G. (3) 28 Szekely, I. (3) 116; (6) 57 Szelke, H. (1) 395,396 Szewczyk, J. (1) 45 Sziillosy, A. (1) 391, 392 Tabellion, F. (1) 603,608 Tada, Y. (6) 170, 174,259

26 1

Tagarelli, A. (1) 374 Tagaya, H. (1) 280 Tago, K. (5) 51, 88 Taguchi, N. (1) 101 Taillefer, M.(5) 78; (6) 9, 15 1 Tajima, T. (6) 93 Takaba, D. (5) 63 Takada, H. (3) 174 Takagi, H. (5) 63 Takagi, M.(4) 62 Takagi, U. (6) 94 Takaguchi, Y.(5) 84 Takahashi, H. (1) 506 Takahashi, K. (5) 91 Takaki, U. (6) 93 Takanami, T. (5) 49 Takase, H. (6) 174,259 Takata, T. (1) 273 Takeuchi, K. (6) 91 Taktakishvili,M. (4) 2,52 Takuma, K. (6) 93 Talke, F.E. (6) 163, 164 Tamaki, Y.(6) 245 Tanaka, H. (3) 151 Tanaka, K. (3) 102 Tanasa, F. (3) 164 Tancic, Z. (5) 5 Tang, H. (6) 206,229,230 Tani, K. (1) 74 Tanji, K.4. (1) 285 Tanner, D. (5) 105 Tao, Z.F.(3) 97 Tararov, V.I. (1) 61 Tarazona, M.P. (6) 192,203 Tirraga, A. (1) 319; (5) 72, 73; (6) 24-26

Tarres, J. (3) 98 Tascher, M. (6) 122 Taton, D. (6) 15 Tatsumi, K. (1) 101 Taylor, J.P. (6) 150, 225, 236 Taylor, R. (6) 80-83 Taylor, R.J.K. (5) 56 Tchatchoua, C.N. (1) 41 1 Teimouri, M.B. (1) 264 Teixidor, F. (1) 57 Teleshev, A.T. (3) 89 Teller, J. (3) 141 Tendo, K. (6) 175 Tepper, M. (1) 110, 112, 195 Terazono, T. (6) 155 Terenin, V.I. (3) 9 Terent'ev, S.A. (3) 166

Terikovska, T.E. (3) 6 Terlouw, J.K. (1) 542 Terrier, F. (1) 491 Tesson, N. (3) 156 Thalladi, V.R.( I ) 410 Theil, F.(1) 83; (3) 66 Thelander, L. (4) 76 Thiel, W. (1) 616 Thiem, J. (4) 61 Thonnessen, H. (1) 468; (2) 7, 32; (3) 5; (6) 6

Tholander, J. (1) 3 11 Thomas, M. (4) 54 Thomas, Y. (4) 11 Thompson, G.M. (1) 275 Thorpe, T. (1) 243 Thorup, N. (3) 93 Tietze, L.F. (1) 272; (5) 55 Till, S.J. (1) 566 Tilve, S.G.(1) 343; (5) 46 Tirnosheva, N.V. (1) 496; (2) 1, 37; (3) 80

Tiripicchio, A. (1) 222,346; (3) 179

Tiso, B.(6) 191 Tissot, 0. (1) 570 Tjarks, W. (4) 19 Togni, A. (1) 218,339; (6) 149 Toke, L.(1) 391-395, 397,406, 575; (3) 146

Toker, J.D.(1) 13 Tolmachev, A.A. (1) 626; (3) 6, 8, 9, 11-14

Tomioka, K.(1) 103 Tommes, P. (1) 542 Tomoi, M.(1) 487 Tomori, H. (1) 6 Toner, A.J. (1) 362 Tong, S.K.(3) 38 Tortoella, P. (1) 400 Toscano, R.A. (6) 65 Tosheva, T. (1) 407 Toth, I. (1) 313 Toto, J.L. (1) 291 Toto, T.T. (1) 291 Touillaux, R. (3) 128 Toupet, L. (1) 564; (6) 46 Touze, R.P. (1) 565 Toyota, K. (1) 506,5 1 1,549551

Tremblay, M.R. (6) 7 Trevisiol, E. (4) 79, 80 Trevitt, M. (1) 390

262

Trinkhaus, S.(1) 233 Trofimov, B.A. (1) 106, 121, 153, 164, 188,445,446

Trost, B.M. ( 5 ) 50 Troxler, L. (1) 423 Truscan, I. (3) 164 Trzeciak, A.M. (1) 357 Tsai, K.-r. (1) 212

Tsang, M.N.(6) 222,227 Tsuchida, E. (5) 95

Tsuchimoto, Y.(1) 457; (5) 32 Tsuchiya, T. (1) 29; (6) 214 Tsujimoto, H. (6) 173 Tsujimoto, M.(1) 332 Tsukayama, M.(5) 7, 57 Tsunoda, T. (1) 301,302; (5) 63

Tsvetkov, Y.E.(4) 60 Tunayar, A. (1) 427 Tunon, V. (4) 55 Tur, D.R. (6) 199-202 Turck, A. (1) 170 Ture, S.(6) 146 Turgut, G. (6) 112, 139, 140 Turner, H.W. (1) 7 Turner, M.I. (6) 183 Tumn, C.-0. (6) 12 Tusa, G. (4) 74 Tutass, A. (1) 249 Tyrra, W. (1) 460 TZOU,D.-L. (1) 226 Ubl, J. (4) 70 Uchiyama, T. (6) 182 Uda, T. (1) 232 Ueda, M. (6) 91 Uemoto, K.(1) 301, 302 Uemura, S.(1) 108; (3) 31-33, 37, 174

Uenaka, M. (5) 91 Ueno, K. (6) 94 Ueno, Y.(4) 65-67 Ugozzoli, F. (1) 426 Uher, M. (3) 157 Uhl, W. (6) 60 Uhm, T.S.(1) 300 Uiterweerd, P.G.K. (6) 29 Ujszaszy, K. (1) 394,406 Ullrich, A. (3) 100 Underhill, A.E. (3) 99 Uozumi, Y.(1) 168 Upendran, S. (4) 10

Urakami, T. (6) 93 Urpi, F. (1) 325 Ustynyuk, Y.A. (5) 8, 9 Usuki, J. (1) 435 Uthmann, S. (1) 507 Vakul'skaya, T.I. (1) 153 Valentini, M. (1) 209 Valerga, P. (1) 327 Valetsky, P.M. (1) 8 1 Valls, E. (1) 69 Van, S.(1) 66 Van Aerschot, A. (4) 12,37 van Calsteren, M.R. (6) 20 van der Kerk, A.H.T.M. (1) 106

Van der Veen, L.A. (1) 20-22 van der Zeijden, A.A.H. (1) 70 Vandevoorde, S. (3) 134 Vandewalle, M.(5) 93 van Eijkel, G.T. (1) 546,553 van Eis, M.J. (1) 363, 364 Van Haver, D. (5) 93 van Klink, G.P.N. (1) 175, 176 van Koten, G. (1) 12, 175, 176 van Leeuwen, P.W.N.M. (1)

20-22, 80, 143, 172,242; (3) 43, 75, 85, 87 Vanquickenborne, L.G. (1) 365, 527,543,571 van Wullen, C. (1) 463 Vapirov, V.V. (6) 118 Varbanov, S. (1) 379,407 Vargas-Berenguel, A. (6) 3 Varnskuhler, B. (1) 495 Vasen, D. (1) 218 Vasil'ev, G.B.(6) 200,201 Vasisht, S.K.(1) 534 Vasquez, G. (4) 36 Vastra, J. (3) 70 Vatsadze, S.Zh. (3) 9 Vechorek, V. (1) 419 Veciana, J. (3) 98 Vedejs, E. (1) 26,52; (2) 16 Veigel, R. (1) 86 Veksler, EN.(1) 71 Velasco, M.D. (1) 3 16, 3 18, 568; (5) 71,73; (6) 25 Velazquez, S.(4) 55 Venanzi, L.M.(1) 150 Venkatachalapathy, R. (6) 167 Venugopalan, P. (2) 17

OrganophosphorusChemistry Venzo, A. (5) 25 Verani, G. (1) 4 16 Vercruysse, K. (2) 24 Vereshchagina, Y.A. (1) 4 19 Vergani, B. (4) 22 Vergeer, F.W. (1) 619 Verkade, J.G. (2) 33, 34; (3) 175; (5) 77

Veronese, F.M. (3) 184 Verstuyf, A. (5) 93 Vertuani, S. (4) 76 Vetter, J. (3) 5 1 Vezina, M. (1) 35 Viani, F. (4) 22 Vicente, J. (5) 24 Vicente, V. (6) 151 Vicic, D.A. (3) 21 Vickers, D.M. (1) 595 Victorova, L.S. (4) 85 Vidal, C. (2) 19,20 Vij, A. (1) 240; (6) 119, 152154

Vijjulatha, M. (6) 127 Vilaplana, M.J.(1) 3 18 Vilarrasa, J. (1) 325 Villarreal, I. (6) 197, 198 Villeneuve, K. (1) 35 Vinas, C. (1) 57,469 Vincent, S.P. (4) 43 Vincente, J. (1) 455; (5) 27 Vinkovic, V. (6) 88 Virieux, D. ( I ) 376, 381 Viso, A. (1) 3 14 Vittadini, A. (5) 25 Vivanco, M. (1) 34 1 Voelker, H. (1) 180 Vogel, J. (3) 153 Vogelgesang, J. (1) 76 Vogt, D. (3) 43 Vogt, H. (1) 444 Vohs, J.K. (1) 567 Voigt, A. (1) 139 Vojtisek, P. (1) 165, 383 Volkov, A. (1) 257; (3) 115 von Eis, M.J.(1) 544 von Norman, S. (3) 163 Vorob'eva, E.B. (2) 10 Vukojevic, S . (3) 101 Wada, T. (4) 14, 15 Wagner, C. (1) 70; (3) 100 Wakai, H. (4) 87

263

Author Index

Wald, J. (1) 160 Waldmann, H. (3) 152, 191 Wall, G. (1) 430 Walsh, D.S. (1) 291 Waly, A. (6) 168 Wan, H . 4 . (1) 212 Wang, B. (1) 248 Wang, F.-T. (6) 240 Wang, J.C.(3) 182 Wang, J.H. (4) 19 Wang, K. (1) 536-538; (3) 16, 97

Wang, P . 4 . (6) 238, 239 Wang, Q.(5) 35 Wang, S.-L. (1) 265; (5) 18 Wang, W.S. (1) 422 Wang, X. (1) 227 Wang, 2. (2) 33 Wang, 2.-G. (1) 326; (3) 175 Wang, Z.-X. (6) 29 Wanunu, M. (1) 3 10 Warren, S.(1) 40 1-405,45 1; (5) 33, 79-82 Wartbichler, B. (4) 83, 84 Wasilewska, E. (4) 92 Wassermann, B.C. (1) 333 Watanabe, H. (6) 94 Watanabe, K. (5) 47 Watanabe, N. (5) 7 Watanabe, Y. (3) 187 Watanuki, T. (6) 173 Watkins, C.L. (3) 26 Watt, J.C. (1) 548 Wawrzenczyk, C. (1) 378 Webb, P.B. (6) 106 Weber, A. (1) 155 Weber, D. (3) 89 Weber, I. (1) 339; (6) 149 Weber, K. (6) 98 Weber, L. (1) 507, 5 17-521 Weber, R. (1) 432 Weber, W.P.(6) 84-87 Weberndorfer, B. (3) 2 1 Weglewski, J. (3) 123 Wegner, P. (1) 15 1, 160 Wei, H.-X. (5) 35 Wei, P. (1) 567 Wei, X. (5) 56 Weidlein, J. (1) 130 Weinberg, W.H. (1) 7 Weis, A.L. (3) 149, 192 Weiss, H.-C. (1) 410 Weiss, R.G. (1) 481

Weissensteiner, W. (1) 48 Weller, A S . (1) 512 Weller, F. (6) 34 Wen, Y.-S. (6) 101 Weng, L.-H. (1) 5 14 Weng,S. (1)411 Wengel, J. (3) 188 Wenger, E. (1) 255 Went, M.J. (1) 22 1 Wentrup, C. (3) 134 Wentworth, A.D. (1) 13 Wentworth, P. (1) 13 Wenz, K. (1) 195 Werner, H. (1) 94; (3) 21 Werner, S.(1) 62 1 Wertsching, A.K. (6) 234 Wen;, U. (1) 610 Westerhausen, M. (1) 128 Wheatley, A.E.H. (1) 131,376 Wheatley, N. (1) 187 Wheeler, J.W. ( I ) 388 White, A.J.P. (1) 38, 43,442, 577

White, M.L. (6) 72 Wiberg, N. (1) 123 Wicht, D.K. (1) 159 Widauer, C. (1) 499; (3) 168; (6) 2

Widdowson, D.A. (1) 38,43 Widhalm, M. (1) 82, 172 Wieczorek, P. (3) 90 Wielandt, W. (1) 155 Wiemer, D.F. (4) 27, 39 Wiese, K.D. (3) 58 Wieser-Jeunesse, C. (1) 39 Wilcock, D.J. (1) 1 Wild, S.B. (1) 77, 539 Wilk, A. (4) 48 Wilkens, H. (1) 557-559,609 Willems, J.B. (1) 470 Willemsen, S.(1) 498 Williams, D. (1) 565 Williams, D.J. (1) 38, 43,442, 577

Williams, I.D. (6) 63 Williams, J.M.J. (1) 243 Willis, A.C. (1) 105, 255 Wills, M. (3) 170 Wilson, D.J. (1) 608, 620 Wilson, N.J. (1) 569 Winnemoller, J. ( I ) 503 Winnik, M.A. (6) 256 Wipff, G. (1) 423,427,428

Wit, J.B.M. (1) 546, 553 Wittmann, D. (6) 172 Worner, A. (1) 123 Wohlfahrt, G.A. (1) 386 Wojcik, G. (3) 114 Wojczewski, C. (4) 82 Wolf, J. (1) 94; (3) 21 Wolfe, J.P. (1) 6 Wollny, T. (4) 11 Wong, C.H. (4) 43,56 Wong, M.W. (3) 134 Wong, T.-W. (6) 104 Wong, W.K. (3) 50 Wong, W.-T. (6) 63, 104 Wood, D.R.W. (1) 1 1 Wood, G.L. (6) 95 Woods, A.D. (1) 501 Woollard, J.E. (4) 19 Woollins, J.D. (3) 167, 171; (6) 55, 56, 59, 70, 71

Worden, S. (3) 145 Worley, S.D. (6) 115, 116 Wozniak, L.A. (1) 296; (4) 38 Wrackmeyer, B. (1) 46, 589; (2) 18

Wright, D.S.(1) 13 1 Wright, K.N.(4) 9 Wroblewski, A.E. (2) 33 Wu, C.H. (6) 231 Wu, H.S. (6) 117 WU, Q.-J. (I) 5 14 Wulf, M. (1) 340 Wulff-Molder, D. (1) 444 Wuzik, A. (1) 169 Wyatt, P. (1) 178 Xia, W. (1) 36 Xiao, D. (1) 91, 92, 102 Xiao, J. (1) 174,337 Xie, D. (1) 104 Xin, X.-L. (1) 437 Xu, D.(1) 23 Xu, K. (6) 79 x u , L. (1) 337 x u , P.-p. (1) 212 XU, X.-L. (1) 536, 537; (3) 16 Xue, M. (1) 484 Yabuhara, T. (6) 170, 174, 259 Yaftian, M.R. (1) 428 Yagci, Y.(1) 490

264

Yagupolskii, Yu.L. (1) 460 Yamabe, T. (3) 102 Yamada, H. (1) 202 Yamada, K. (4) 47 Yamada, T. (1) 293 Yamagata, T. (1) 74 Yamagishi, T. (4) 25 Yamaguchi, M. (1) 258 Yamamoto, H. (5) 45 Yamamoto, I. (1) 382; (5) 42; (6) 182

Yamamoto, S.(1) 547 Yamamoto, Y.(1) 435 Yamanaka, T. (6) 224 Yamanoi, Y. (1) 185 Yamazaki, F.(6) 94 Yamazaki, S.(6) 93,94 Yan, Y.-Y. (1) 82,90 Yanagi,'T. (4) 14 Yang, B.Z. (3) 122 Yang, C.-b. (1) 212 Yang, F. (1) 60 Yang, H. (1) 140 Yang, K.T. (4) 51 Yang, S.(5) 70 Yankovich, I.V. (3) 178 Yaouane, J.-J. (1) 447 Yashima, E.(6) 224 Yasuda, H.(6) 171 Yasui, S. (1) 332 Yasuike, S.(1) 29 Yates, P.C. (1) 10 Yavari, I. (1) 261-264; (3) 92; (5) 60, 61

Yefidoff, R. (4) 75 Yekta, A. (6) 256 Yellowlees, L.J. (3) 101 Yeung, C.H.(3) 50 Yi, X.-d. (1) 212 Yildiz, M. (6) 123, 180 Yin, S. (1) 6 Yokomatsu, T. (4) 23-25 Yokoyama, S.(4) 90 Yonehara, K. (1) 108; (3) 3133,37

Yonezawa, T. (6) 173

Yoo, J.W. (1) 214 Yoo, K.H.(6) 21 Yoshida, E. (6) 155 Yoshifbji, M. (1) 506, 5 11,

Orgartophosphortrs Chemistry

Zarudnitskii, E.V.(3) 14 Zdravkova, Z. (1) 424

Zecri, F.J. (5) 89 Zehnder, M. (1) 208 Zeller, M. (1) 596 549-5 5 1 Zemlicka, J. (4) 3,4 You, K.K. (3) 36 Zemlyanskii, N.N. (5) 8, 9 Youn, J.N. (3) 112 Zenneck, U. (1) 589 YounQ-Millot, C.B. (1) 141 Zhan, M. (6) 221 Youngman, P.W.(1) 386 Zhang, H. (1) 212 Youssef, B. (3) 104 Zhang, H.P. (4) 57 Yu, H.-B. (1) 173 Zhang, J.-L. (1) 537 Yu, J.W. (5) 54 Zhang, L.-B. (1) 5 14 Yu, K.-B. (1) 437 Zhang, Q.Z. (3) 171 Yu, W. (5) 87 Zhang, W. (1) 219 Yu, X.-M. (1) 537 Zhang, X.(1) 9 1,92, 102,229 Yu, Y.-H. (1) 36 Zhang, Y. (1) 409 Yu, z. (2) 34 Zhang, Z. (1) 91,92, 102 Yu, Z.K. (3) 175 Zhao, N. (1) 408 Yuan, C.Y. (6) 165 Zhao, Q. (6) 164 Yuan, G. (5) 70 Zhao, Y.F. (3) 64, 191 Yuasa, M. (5) 45 Zhao, Z. (6) 160, 161 Yufit, D.S. (5) 1 Zhdanov, A.A. (3) 89 Yurchenko, A.A. (3) 14 Zheng, G. (5) 48 Yurchenko, A.G. (5) 100 Zheng, H. (6) 63 Yutronic, N. (6) 138 Zheng, X.P. (4) 28 Zhou, W.Q. (4) 10 Zhou, X.(5) 93 Zabel, M. (1) 30,47 Zablocka, M. (1) 256,267,3 17 Zhou, X.-G. (1) 514 Zhu, G.-D. (5) 93 Zabska, A. (1) 480 Zhu, K. (6) 187 Zadachina, O.P.(2) 9 Zhu, Y. (3) 140 Zagumennov, V.A. (1) 46 1, Zielinski, Z. (4) 18 462 Ziessel, R. (1) 14 Zang, Q. (6) 18 Zilkowski, J.J. (1) 357 Zang, Q.J. (5) 69; (6) 17 Ziller, J.W. (1) 418 Zanirato, V. (3) 113 Zinman, T. (4) 75 Zano, R.A.(1) 425 Zinov'eva, V.P. (1) 164 Zanobi, F.(1) 116 Zinovitch, Z. (6) 203 Zanoni, R. (1) 222 Ziora, Z. (3) 114 Zanotto, L. (5) 25 Zobel, M.(6) 172 Zanta, M.-A. (6) 148 Zuccotto, F. (4) 5 Zantous, H. (1) 384 Zuideveld, M.A. (3) 87 Zapf, A. (3) 159 Zyablikova, T.A. (2) 13 Zappy, H. (1) 363 Zygo, K. (1) 419 Zaragoza, F. (1) 303, 307 Zyk, N.V. (3) Zard, S.Z. (5) 102