Organophosphorus Chemistry: Volume 27 / Edition 1

by Christopher W Allen, R S Edmundson, O Dahl, C Dennis Hall, Jane A Grasby

Overview

Organophosphorus Chemistry provides a comprehensive annual review of the literature. Coverage includes phosphines and their chalcogenides, phosphonium salts, low coordination number phosphorus compounds, penta- and hexa-coordinated compounds, tervalent phosphorus acids, nucleotides and nucleic acids, ylides and related compounds, and phosphazenes. The series will be of value to research workers in universities, government and industrial research organisations, whose work involves the use of organophosphorus compounds. It provides a concise but comprehensive survey of a vast field of study with a wide variety of applications, enabling the reader to rapidly keep abreast of the latest developments in their specialist areas. Specialist Periodical Reports provide systematic and detailed review coverage of progress in the major areas of chemical research. Written by experts in their specialist fields the series creates a unique service for the active research chemist, supplying regular critical in-depth accounts of progress in particular areas of chemistry. For over 80 years the Royal Society of Chemistry and its predecessor, the Chemical Society, have been publishing reports charting developments in chemistry, which originally took the form of Annual Reports. However, by 1967 the whole spectrum of chemistry could no longer be contained within one volume and the series Specialist Periodical Reports was born. The Annual Reports themselves still existed but were divided into two, and subsequently three, volumes covering Inorganic, Organic and Physical Chemistry. For more general coverage of the highlights in chemistry they remain a 'must'. Since that time the SPR series has altered according to the fluctuating degree of activity in various fields of chemistry. Some titles have remained unchanged, while others have altered their emphasis along with their titles; some have been combined under a new name whereas others have had to be discontinued. The current list of Specialist Periodical Reports can be seen on the inside flap of this volume.

Product Details

ISBN-13:	9780854043095
Publisher:	RSC
Publication date:	12/03/1996
Series:	ISSN , #27
Edition description:	Edition. ed.
Pages:	408
Product dimensions:	5.43(w) x 8.50(h) x (d)

About the Author

Professor David Allen is Emeritus professor of chemistry at the University of Sheffield, UK. His main research interests are in phosphonium salts and related compounds. Current interests include the preparation of phosphonioalkyl derivatives of biologically active molecules, the phosphonioalkyl group facilitating the passage of the biologically active agent through cell membranes, and studies of the formation of biologically active surface-functionalised gold nanoparticles.

Read an Excerpt

Organophosphorus Chemistry Volume 27

A Review of the Recent Literature Published Between July 1994 and June 1995

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By D. W. Allen, B. J. Walker

The Royal Society of Chemistry

Copyright © 1996 The Royal Society of Chemistry
All rights reserved.
ISBN: 978-1-84755-447-5

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CHAPTER 1

Phosphines and Phosphonium Salts

BY D.W. ALLEN

1 Phosphines

1.1 Preparation

1.1.1 From Halogenophosphines and Organometallic Reagents. – Grignard reagents have been used to prepare a range of new chelating diphosphines (1) from 1,2-bis(dichlorophosphino)ethane, and also a series of phosphines (2) bearing mesityl groups. A new crystalline phase of trimesitylphosphine has been identified. However, as in previous years, the use of organolithium reagents continues to dominate this route to phosphines. The reaction of chlorodiphenylphosphine with 1,8-dilithionaphthalene offers a simple, high yield route to the diphosphine (3). The diphosphine (4) has been obtained in a similar way following direct dilithiation of 9,9-dimethylxanthene. There has been considerable interest in the synthesis of heteroarylphosphines. Tris-(2-benzofuryl)phosphine (5) has been prepared by direct lithiation of benzofuran followed by treatment with phosphorus tribromide. However, little success attended similar attempts to prepare tertiary phosphines from the reactions of 2-pyridyl-lithium, 2-quinolyl-lithium, and 2-benzothiazolyl-lithium reagents with phosphorus trichloride, the main product in each case being a biheteroarene coupling product. One exception was the synthesis of the pyridylphosphine (6), isolated in 72% yield. In contrast, the reactions of a series of 4-lithiopyridines, bearing chiral substituents in the 2,6-positions, with 1,2-bis(dichlorophosphino)ethane, have given the diphosphines (7), capable of acting as building blocks in the synthesis of dendrimer ligands. Metallation of 2-methylpyridine followed by treatment with chlorodiphenylphosphine at -78 °C has given an improved route to the pyridylmethylphosphine (8), which can be further functionalised at the methylene carbon to give, e.g., (9). Two groups have described the synthesis of imidazolylphosphines, e.g., (10) and (11) from the reactions of 2-lithioimidazoles with halogenophosphines. Organolithium-halogenophosphine procedures have also been employed in the synthesis of aminoalkylphosphines, e.g., (12) and (13), (the latter being subsequently quaternised selectively at nitrogen to give a new type of cationic phosphine ligand), and also in the synthesis of a series of chiral phosphinoaryloxazolines (14), starting from o-bromobenzonitrile.

Monolithiation of 2,6-dibromo-4-t-butylanisole, followed by treatment with chlorodiphenylphosphine, has given the phosphine (15), an intermediate for the synthesis of the polydentate ligand (16). The acetal (17) undergoes regiospecific lithiation at the methyl carbon of the acetyl group on treatment with lithium bis(trimethylsilylamide). The subsequent reaction with chlorodiphenylphosphine provides the functionalised phosphine (18) from which a series of iminofunctionalised phosphines (19) has been prepared. A similar strategy was employed in the synthesis of the all cis-triphosphine (20).

Direct metallation of ferrocenes, followed by treatment with chlorodiphenylphosphine, continues to be a popular route for the synthesis of ferrocenylphosphines, e.g., (21), and (22). Treatment of the latter with secondary phosphines in acetic acid provides a route to new chiral diphosphines (23). This approach has also been applied to the introduction of the 9-phosphabicyclo[3,3,1]nonane group into such systems, the use of a large excess of crude bicyclic secondary phosphine allowing isolation of a pure product, free of traces of the isomeric 9-phospha[4,2,1]nonane system that always accompanies the former. Bistriptycylphosphines have been prepared from the reaction of triptycyl-lithium reagents with phosphorus trichloride, followed by reduction of the intermediate chlorodiorganophosphine with lithium aluminium hydride. A route to polyfunctional phosphines is provided by the reactions of functionalised organozinc reagents with halogenophosphines. Among the compounds described are (24) and (25).24 Treatment of the thallium reagent (26) with chlorodiphenylphosphine gives the phosphine (27) in much greater yield than in the related reaction using the corresponding organolithium reagent. In the presence of lithium tetramethylpiperidide, (27) is converted into the salt (28), capable of further elaboration.

1.1.2 Preparation of Phosphines from Metallated Phosphines. – Routes involving the use of metallophosphide reagents contine to dominate methods for phosphine synthesis. A solution NMR study of lithium diphenylphosphide has shown it to be dimeric in diethyl ether and monomeric in THF. A theoretical study has concluded that inversion barriers at phosphorus in metallophosphides are lower than in alkylphosphines. Interest in the generation of phosphide reagents from elemental phosphorus is growing, and a review has appeared. The cleavage of phosphorus-phosphorus bonds in both white and red phosphorus by lithium in liquid ammonia is assisted by addition of tertiary butanol. Subsequent alkylation of the lithium phosphide has given simple routes to primary and secondary alkylphosphines.

Metallophosphide reagents have continued to be widely used in the synthesis of polyphosphorus compounds, and further consideration has been given to structural rules for the assembly of cyclopolyphosphorus compounds. Tetra-alkylammonium ions have been employed as stereospecific alkylating agents in the stepwise alkylation of the cyclopolyphosphide anion P73- (29), leading to the neutral species (30). The generation of lithium di(2-pyridyl)phosphide from the lithium-promoted cleavage of tri(2-pyridyl)phosphine in THF is also accompanied by the formation of 2,2'-bipyridyl. Protonation of the pyridylphosphide provides a route to di(2-pyridyl)phosphine. The related tri(2-pyridyl)arsine also undergoes a similar cleavage. Nucleophilic ring-opening of epoxides by lithium diphenylphosphide has given a series of chiral hydroxyalkylphosphines, e.g., (31), (derived from (+)-trans-limonene oxide). The new tripodal hydroxyalkyldiphosphine ligand (32) has been obtained via phosphide-induced ring cleavage of an oxetane precursor. A lithiophosphide route to the chiral hydroxyethyldiphosphine (33) has been developed, starting from L-ascorbic acid. Lithium dicyclohexylphosphide is reported to be unstable in THF solution, but can be used in the conventional way in diethylether, in which it forms a yellow chemiluminescent solution. With the lithium salt of 2-fluorobenzoic acid, it gives rise to the phosphinocarboxylic acid (34), which exists as the phosphorane (35) (δ31P + 2.3 ppm; JP-H 277Hz). In the presence of base, the latter generates the phosphino carboxylate (36), and not the related phosphoranide anion. A mixture of isomeric cyclopentadienylphosphines, e.g., (37), has been isolated from the reaction of lithium t-butylphosphide and 1,2,3,4-tetramethylfulvene. The reaction of lithiumdiphenylphosphide with 3-chloropropylamine is the initial step in the synthesis of the guanadinium-functionalised phosphine (38), one of a new series of water-soluble phosphines which are less susceptible to oxidation than the more familiar sulfonated arylphosphines. The addition of lithium diphenylphosphide to a vinylphosphine-borane adduct is the key step in a route to the new chelating diphosphine (39), having a single stereogenic phosphorus atom. The phosphazeno-phosphine (40) has been prepared by the reaction of lithium diphenylphosphide with the related 3-chloropropylphosphazene. Among other new diphosphines prepared via the reactions of lithium diphenylphosphide with chloroalkyl or alkyltosylate substrates are the ferrocenyl system (41), the sulfoxide (42), the diphosphinoalkylthiophen (43), and the chiral systems (44). Lithiophosphide reagents have also been used in the synthesis of the new chiral mixed donor polydentate ligand (45), and the macrocyclic systems (46) and (47). Lithiation of primary and secondary phosphines coordinated to a metal acceptor, (followed by treatment with carbon dioxide), is the key step in the synthesis of phosphinoformic acids (48). These compounds only appear to be stable in the coordinated state.

Interest has continued in the participation of SRN1 pathways in the photo-stimulated reactions of phosphide ions with halogenoadamantanes in liquid ammonia. A series of lithio- and sodio-organosilylphosphide cluster systems has been prepared and characterised. The propellane-like cyclosilaphosphine (49) has been obtained from the reaction of lithium cyclohexylphosphide with t-butyl(fluoro)dichlorosilane. Treatment of cyclohexylphosphine with butyl-sodium in the presence of pentamethyldiethylenetriamine has given a crystalline complex containing the sodio-cyclohexylphosphide moiety, the first simple sodio-organophosphide to be structurally characterised. Routes to potassium silylphosphides have also been developed. Sodium diphenylphosphide has been used in the synthesis of the new chiral diphosphine (50) and of the cyanoalkylphosphines (51), subsequently converted into cyclic aminophosphonium salts following reduction of the cyano group. Sodium- and potassium-diorganophosphide reagents figure prominently in a review of synthetic approaches to tripodal phosphines, e.g., (52). Potassium diarylphosphide reagents have also been used in the synthesis of another range of tripodal phosphines (53) bearing different donor groups on the neopentyl backbone, the new chiral diphosphine (54), lower rim 1,3-diphosphinocalix[4]arenes, and a range of chiral aminoalkylphosphines, e.g., (55).

A route to simple cycloalkylphosphines, e.g., 1-phenyl-phosphetane, phospholane, -phosphorinane, and -phosphepane is provided by the reactions of phenylphosphine, coordinated to a metal, with α,ω-dihaloalkenes in the presence of potassium t-butoxide. The generation of phosphide reagents under super-base conditions (DMSO-KOH) continues to attract interest. Under these conditions, alkylation and arylation of phosphine (PH3) is possible. Thus, e.g., with potassium p-fluorophenylsulfonate, the water-soluble arylphosphine (56) is formed, and with ω-chloroalkylamines, a range of primary and secondary (aminoalkyl)phosphines, e.g., (57) is accessible. Such compounds can be selectively alkylated at nitrogen to give the related, water-soluble aminoalkylphosphines. Further alkylation at phosphorus can be achieved by conventional phosphide routes, to give, e.g., the tertiary phosphine (58), also capable of conversion into water-soluble N-alkylammonium derivatives. The reactions of diphenylphosphine with 1,1- and 1,2-dichloroethylenes under super-basic condition have given 1,2-bis(diphenylphosphino)ethylene. A new route to the chiral BINAP system (59) is provided by the reaction of the related chiral bistriflate of the 1,1'-binaphthol system with diphenylphosphine in the presence of DABCO, the reaction being catalysed by a diphosphine-nickel chloride complex.

Interest has been maintained in the synthesis and characterisation of organophosphido derivatives of other metallic elements, notably aluminium, gallium, titanium, zirconium, tin, and zinc. Reviews have appeared of the chemistry of bis(cyclopentadienyl)zirconium- and hafnium-organophosphides, and of metallo-organic routes to phosphide semiconductor meterials. Organophosphido derivatives of strontium and thulium have also been characterised.

The chemistry of phosphines metallated at carbon also continues to attract attention. In particular, Karsch et al have continued to develop the chemistry of phosphinomethanide systems. Several structural studies of C-metallated phosphines have appeared. The bis(diphenylphosphino)methanide ion is oxidised by iodine to form the P-C coupling product (60).

1.1.3 Preparation of Phosphines by Addition of P-H to Unsaturated Compounds. – Interest has continued in the generation of phosphine from red phosphorus under superbasic conditions (KOH in DMSO), and its subsequent addition to unsaturated systems. Thus, addition of PH3 to aryl- and heteroaryl-ethynes provides an efficient route to tris-(2-substitutedvinyl)phosphines (61). A similar addition to alkenes has provided a route to secondary phosphines, e.g., (62). A range of phosphorus, nitrogen-hybrid donor ligands containing 2-pyridyl groups has been prepared by the base-catalysed addition of primary and secondary phosphines to 2-vinylpyridine. The addition of 1,2-bis(phosphino)-benzene (63) to optically-active ester- and amide-derivatives of acrylic acid has given a series of optically-active "expanded" phosphines, e.g., (64). The 1,5,9-triphosphacyclododecane (65, R = H), in the form of a metal carbonyl complex, has been shown to add to allylamine to give (65, R = (CH2)3NH2). Subsequent reactions of this coordinated cyclopolyphosphine were also explored. Addition of secondary phosphines to allylethers has provided a series of phosphino-ethers (66). Diastereoisomerically-pure forms of the phosphine (67), (protected as the borane complex) undergo addition of diphenylphosphine to form two epimers of the new chiral system (68). Addition of diphenylphosphine to the butadiynyldiphosphine (69) has given the tetraphosphinobutadiene (70). Subsequent cyclopropanation of the double bonds of the latter has also been explored.

1.1.4 Preparation of Phosphines by Reduction. – The use of trichlorosilane, usually in combination with triethylamine, remains the most popular approach for the reduction of phosphine oxides, usually in the final step of a synthetic route. Among new chiral phosphines prepared in this way are a series of new partially hydrogenated BINAP ligands, e.g. (71) and (72), the bis(benzothienyl)diphosphine (73), the P,S-binaphthyl system (74), the conformationally rigid C2-symmetrical diphosphine (75), and the chiral phosphetan system (76). Combination of either trichlorosilane or dichloro(methyl)silane with tributylamine has been employed in the synthesis of the chiral system (77), subsequently resolved via a chiral palladium complex. The enantiomers of (77) do not racemise in solution, even up to a temperature of 207 °C. Catalytic reduction of diphenylphosphinyl to the related dicyclohexylphosphinyl units, and subsequent reduction with trichlorosilane have been employed as key steps in the synthesis of a range of chiral pyrrolidine bisphosphines (78) bearing two different types of phosphino groups. Phenylsilane has been employed as reducing agent in the final stage of the synthesis of a series of calix[4]arene systems, e.g., (79), bearing phosphine and other donor groups. The ferrocenyldiphosphine (80) has been obtained via reduction of a related ferrocenyldiphosphonate ester using a combination of lithium aluminium hydride and trimethylchlorosilane, and converted subsequently into the new chiral system (81). Reduction of arenephosphonate esters using lithium aluminium hydride is also the key step in the synthesis of a series of α-functionalised 2-methylphenylphosphines (82).

1.1.5 Miscellaneous Methods of Preparing Phosphines. – The synthesis of phosphorus heterocycles from a-hydroxyalkylphosphines and vinylphosphines has been reviewed. A review has also appeared of synthetic approaches for the preparation of scalemic chiral phosphines (i.e. those in which one enantiomer is present in excess). Optically pure forms of the bicyclic diphosphine (83) have been obtained via the cycloaddition of diphenylvinylphosphine and 3,4-dimethyl-1-phenylphosphole in the presence of a palladium(II) complex of a chiral amine. The commercially available linear tetraphosphine (84) has been separated into its diastereoisomers, one of which has been resolved by the use of a chiral metal complex. The diphosphine (85) has been resolved in a similar manner. Further examples of functionalised chiral diphosphines, e.g., (86), have been prepared by side chain elaboration of the bicyclic system. Treatment of the chiral phosphine (87) with sodium dimethylarsenide has given the chiral phosphino-arsine (88), subsequently resolved via a chiral metal complex. A further example of imine formation from the functionalised phosphine (89) has appeared, the reaction with 2-(2-pyridyl)ethylamine giving the new multifunctional ligand (90). In a similar vein, a wide range of imino-functionalised phosphine ligands, e.g., (91), (92) has been prepared via the reactions of aminoalkyl- and related-phosphines with carbonyl compounds. Catalysis by amines of the hydroxymethylation of phosphine, to form trishydroxymethylphosphine, has been explored. Mannich-type reactions of diphenylhydroxymethylphosphine with chitosan, a readily available naturally occurring polymeric aminosugar, have given a new type of chiral, immobilised phosphine system (93). Coupling of functionalised arylphosphines, e.g., (94), to polyacrylic acid and polyethyleneimine provides a new route to water-soluble phosphine ligands, which have been used to prepare water-soluble cobalt carbonyl complexes. A route to tris(perfluoroalkyl)phosphines, not the most easily accessible of substances, is provided by initial fluorination of alkylphosphines in solution in FREON, giving the tris(perfluoroalkyl)difluorophosphoranes which are then reduced to the related phosphines on treatment with tris(trimethylsilyl)phosphine. The reaction of tris(trimethylsilyl)phosphine with tropylium bromide in polar solvents gives good yields of tris-(l-cyclohepta-2,4,6-trienyl)-phosphine (95), together with the related tetra(cycloalkenyl)phosphonium salt, from which the phosphine can be regenerated using lithium aluminium hydride. The phosphine behaves normally in reactions with oxygen, sulfur, and selenium. The palladium(II)-catalysed reaction of diorgano(trimethylsilyl)phosphines with substituted vinyl bromides provides a route to 2-alkenylphosphines. The related reactions of mono-organo(trimethylsilyl)phosphines with 1-alkoxy-1-bromo alkenes afford the secondary phosphines (96) which partially isomerise by 1,3-sigmatropic hydrogen migration to form the phosphaalkenes (97). Heating the 1,2,4-diazaphospholes (98) in boiling toluene results in extrusion of nitrogen with the formation of the alkylidenephosphirane system (99) as the major product, together with some of the vinylphosphine (100). In the presence of secondary phosphines, metal complexes of alkynylcarbenes are transformed into phosphinonaphthalenes, e.g., (101), and phosphinoindenes, e.g., (102). An improved route to a diphenylphosphino-dicarbaborane system has been reported.

(Continues...)

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Excerpted from Organophosphorus Chemistry Volume 27 by D. W. Allen, B. J. Walker. Copyright © 1996 The Royal Society of Chemistry. Excerpted by permission of The Royal Society of Chemistry.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents

Contents

Chapter 1 Phosphines and Phosphonium Salts By D. W. Allen, 1,
Chapter 2 Pentaco-ordinated and Hexaco-ordinated Compounds By C. D. Hall, 62,
Chapter 3 Tervalent Phosphorus Acid Derivatives By O. Dahl, 78,
Chapter 4 Quinquevalent Phosphorus Acids By R. S. Edmundson, 100,
Chapter 5 Nucleotides and Nucleic Acids By J. A. Grasby and D. M. Williams, 177,
Chapter 6 Ylides and Related Compounds By B. J. Walker, 264,
Chapter 7 Phosphazenes By C. W. Allen, 308,
Author Index, 352,