Nucleophilic Attack at Other Atoms

Unsaturated monosaccharides [e.g. (91)] react with the Ph3P-DAD combination in the presence of phthalimide, with inversion of configuration of C-4, to form the phthalimido-derivatives (92).82 Treatment of carbohydrates having a free anomeric OH group with 6-chloropurine, DAD, and methyldiphenylphosphine gives the purine nucleosides (93).83 

The use of the triphenylphosphine-di(2-pyridyl) disulphide reagent for effecting condensation reactions has been reviewed.84 Combination of triphenylphosphine with bis(O-thiocarbonyl) disulphide gives a superior reagent compared to that mentioned above for the preparation of mixed diesters of phosphoric acid from monophosphate esters.86 

Further studies of the kinetics of reaction of disulphides with triphenylphosphine and water have been reported,86 87 supporting the previously suggested two-step mechanism.88 The reactions of -labelled acetyl aralkyl disulphides with triphenylphosphine have also been investigated.89 

The adducts (94) of triphenylphosphine and alkylphenyl-AT-p-tosylsulphilimines also act as dehydrating agents, and have been employed in the synthesis of acid anhydrides, esters, and amides.90-91 

The diphosphine monosulphides (95) rearrange on heating, the sulphur migrating to the more basic phosphorus centre.92 Benzyl methanesulphenate (96) reacts with 

Nucleophilic Attack at Other Atoms.— The formation of imino-phosphoranes from tetrazolopolyazines (50) and triphenylphosphine has been studied kinetically. Evidence was produced which indicated that the reaction occurred by nucleophilic attack of the phosphine on the tetrazolo-ring. An iminophosphorane was also formed when the diazocompound (51) was added to molten triphenylphosphine at 140 °C. 

Azobenzene reacts readily with triphenylphosphine in aqueous ethanol containing perchloric acid to yield a phosphonium salt (52). 

Tetracyclones react with phenylphosphine to yield /ra j-dihydrotetra-cyclones (53). The reaction is thought to proceed via initial attack at oxygen.  

For the reaction of triarylphosphines with radicals and related reactions see Chapter 10, Section 1. The reaction of several phosphines with diethylperoxide is described in Chapter 2. 

Miscellaneous.—Mislow has now found an example of a phosphine which does not obey the electronegativity rule for correlating energy barriers with pyramidal inversion in phosphines. The inversion barrier of the trimethoxysilylphosphine (54) is found to be 2 kcal mol lower than the 

Nucleophilic Attack at Other Atoms. A Lossen rearrangement occurs when aromatic hydroxamic acids are allowed to react with the triphenylphosphine-diethyl azodicarboxylate complex in the presence of ethanol, to give the hydroxamates (49). 

Attempted 1,3-dipolar additions of acetylenic phosphines to sodium azide gave only iminophosphoranes (50). No cyclic compounds were isolated. The 

Solvent effects on the oxidation of triphenylphosphine by perbenzoic acid have been reported. The second-order rate constants are directly proportional to the dielectric constant of the solvent. Oxidation of methylphenyl-propylphosphine with 3-chloroperbenzoic acid or ozone proceeds with retention of configuration. The reaction of alkyl- or aryl-phosphines with dialkyl peroxides or polyperoxides in aqueous solvents leads to the formation of alcohols or glycols, respectively.  

Desulphurization of / -keto-sulphides by tris(dimethylamino)phosphine is thought to proceed via a phosphonium salt intermediate, e.g. (52), which can collapse to give a variety of products depending upon the substrate used and the reaction conditions.  

Sulphimides (53) are reduced by the corresponding sulphides by triphenylphosphine in DMF. The kinetics of the reaction indicate that the initial 

Nucleophilic Attack at Other Atoms. The mechanism of reactions involving alcohols (or phenols) with the triphenylphosphine-diethyl azodicarboxylate (DAD) reagent (the Mitsunobu reaction) has now been reconsidered in the light of a number of spectroscopic and preparative studies in the past year. In an 

Further examples of the reactions of phosphines with azides have appeared.  

OndrejkoviSovd, V. Vancovi, and G. Ondrejovic, Collect. Czech. Chem. Common., 1983, 48, 254. 

The bis-(o-formylphenyl)phosphine (108) undergoes a mechanistically intriguing acid-catalysed reaction with water to form (109). This appears to be closely related to the previously observed hydration of u-(phenylethynyl)phenyl-phosphines. Reactions of the latter with iron carbonyls have now been shown to involve transformation of the acetylenic units to form the cyclopentadienone structure (110), isolated as the phosphine oxide.  

Interest continues in metallation reactions undergone by phosphines when co-ordinated to a transition metal. Platinum(n) and iridium(m) complexes of cyclopropylmethylphosphines undergo intramolecular metallation involving the 

3 Nucleophilic Attack at Other Atoms.- Interest has continued in the synthesis of phosphine-borane adducts. Complexes of tetramethyldiphosphine with borane and various halogenoboranes have been used to generate a series of open-chain and cyclic phosphino-boranes. Adducts of 1,3,5-diazaphosphorinanes involving two 

An unstable adduct between triphenylphosphine and a photochemically-generated dimethylgermylene has been characterised spectrophotometrically.The first 2,3-dihydro-l,3,2-X -benzodiazaphospholes (73) have been formed in the reactions of triphenylphosphine with g-benzoquinone di-imines stabilised by coordination.A complex of phenylnitrene with a tungsten pentacarbonyl acceptor has been trapped using triphenylphosphine. A kinetic study of the reactions of diazoalkanes with triphenylphosphine, leading to the phosphazenes (74), indicates a biphilic mechanism, the dominant interaction in the transition state involving the diazoalkane as a net electron donor, 

The air-induced oxidation of trimethylphosphine has been followed in Y-type zeolites using solid state P n.m.r. techniques.The known chiral triphosphines (76) have been transformed into their monoxides and monosulphides via protection of the diphosphinoethane moiety by coordination.- A more detailed study of the reactivity of 1,3,5-triaza-7-phospha-adamantane (77) has revealed that whereas protonation and 

3 Nucleophilic Attack at Other Atoms.- The reaction of tertiary 

Diethoxytriphenylphosphorane (the product of insertion of triphenylphosphine into diethyl peroxide) finds use as a mild, neutral reagent which initiates cyclodehydration of N- and C-substituted g-aminoalcohols to form aziridines in excellent yield, 

Second order kinetics have been observed for oxygen transfer from 

3 Nucleophilic Attack at Other Atoms. - The chemistry of phosphine-borane adducts continues to develop. The diphenylphosphine-borane adduct has been employed in the synthesis of linear systems having a skeleton consisting of alternating phosphorus and boron atoms, e.g., (73). Unusual salt-like systems, e.g., (74), have been isolated from the reactions of trialkylphosphines with the dimethylsulphide adduct of dibromoborane. 

The mechanism of the Mitsunobu reaction is proving to be more complex than previously recognised. Evidence has been presented for the irreversibility of betaine formation between triphenylphosphine and azodicarboxyl ate esters. The course of the subsequent reaction of the betaine with m-chloroperoxybenzoic 

Mitsunobu reaction has also found use for the synthesis of nucleoside analogues. The reactions of diphosphines with cyanamide or sulphamide in the presence of diethyl azodicarboxyl ate have given bis-azenes, e.g.,(76). In a similar manner tris-X -azenes have been obtained from triphosphines Bis(diphenyl-phosphino)methane reacts cleanly with trimethylsilylazide to give, initially, one isomeric form of the silylated monophosphazene (77) 

A kinetic study of the oxidation of triphenylphosphine by hydrogen peroxide has revealed a second order rate law consistent with the initial formation of the phosphonium species (78). A further 

Nucleophilic attack by phosphorus at sulphur is involved in the triphenylphosphine-induced cleavage of 1,2,4-thiadiazol-3-ones, in the reactions of methylideneaminophosphines with carbon disulphide, which gives the unstable four-membered ring system (81) as the initial product,and in the reaction with sulphur of the acetylenic phosphine (82) which results in the 

3 Nucleophilic Attack at Other Atoms. - Trifluoromethanesulfonyloxyboron derivatives of tricyclohexylphosphine-borane have been prepared. Two enantiomerically pure borane complexes of chiral dihydrobenzazaphosphole systems, e.g., (128), have been structurally characterised. The synthesis of phosphinoboranes bearing an L-menthyloxy group is a key strategy in the synthesis of chiral phosphines, e.g., (129). Treatment of the phosphines 

Further studies have been reported of the intramolecular transfer of oxygen from nitrogen or sulfur to phosphorus in o-diarylphosphino-nitrones, -acetylhy-droxylamines, and -sulfoxides. Thus, e.g., the phosphino-nitrone (132) rearranges on heating in toluene for a prolonged period to form the iminophosphine oxide 

Nucleophilic attack at nitrogen has also been identified in a study of the reactions of triarylphosphines with tetracyanoethylene in aqueous acetonitrile. In contrast, the related reactions with tetracyanoquinodimethane (TCNQ) involve one electron transfer from phosphorus to the TCNQ molecule. Full details of the reactions of tertiary and ditertiary phosphines with bromophenyldiazirines have now appeared. Interest in the Staudinger reaction of tertiary phosphines with azides has also been maintained. A spectroscopic study has shown that the sequence of addition of reactants alters the course of the Staudinger reaction of azides in the presence of acyl derivatives. The Staudinger reaction of a-azidophenylacetonitrile with triphenylphosphine unexpectedly results in the formation of the salt (135). Applications of the Staudinger reaction in synthesis 

Thioamides are conveniently transformed into nitriles by addition to DAD to form the intermediates (89), which decompose when subsequently treated with triphenyl-phosphine.  

The reaction of thiobenzophenone with tri-n-butylphosphine at 100 °C gives 1,1,2,2-tetraphenylethane, tetraphenylethylene, and the phosphine sulphide. A similar reaction occurs with dibenzocyclopentadienethione.  

Aryl thiocyanates react with primary alcohols in the presence of triphenyl-phosphine to give alkyl aryl sulphides in high yield. It has been suggested that the products arise from the collapse of a triphenyloxythiophosphorane (90) resulting from attack of the alcohol on the initially formed arylthiotriphenylphosphonium cyanide.  

The reaction of triphenylphosphine with A -arylsulphonylsulphimides in DMF gives a sulphide and a phosphinimine via a 1,3-dipolar sulphurane intermediate (91).  

Nucleophilic attack of tertiary phosphines at tellurium (and iodine) is indicated by 

Recent advances in the Staudinger reaction of tertiary phosphines with azido compounds have been reviewed.The reaction of the alkynylphosphine (88) with phenylazide yields the unstable intermediate (89), which in the presence of protic substances undergoes nucleophilic addition to the triple bond. The reactivity of the nitrogen-silicon bond of the phosphinimine derived from triphenylphosphine and trimethylsilylazide has been exploited in reactions with chloroformyl reagents to generate new functionalised phosphinimines, e.g., (90).  

Treatment of solutions of lithium aluminium hydride in ether with the hydrochloride salts of bulky trialkylphosphines provides a route to stable tertiary phosphine adducts of alane, AlH,.  

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Nucleophilic Attack at Other Atoms. A highly efficient general synthesis of secondary- and tertiary- phosphine-borane adducts is afforded by treatment of the phosphine with sodium borohydride in the presence of acetic acid in THF. Any carbonyl groups present in the phosphine undergo concomitant... 

Nucleophilic Attack at Other Atoms. - Routes for the preparation of borane adducts of polyfunctional phosphines have been developed. The bicyclic base DABCO is recommended... 

Nucleophilic attack at other atoms. The chemistry of phosphine-borane adducts has continued to generate interest. Simple borane adducts of primary vinyl-, ethynyl- and allenyl-phosphines have been prepared and studied by a range of spectroscopic and theoretical techniques. The same group has also shown that attachment of the BH3 unit to a variety of primary phosphines results in a substantial increase in the intrinsic acidity of the system in the gas-phase. Group III halide adducts of the type Bu 2PH EX3 (E = B, Al, Ga or In X = Cl or Br) are accessible from the reactions of the secondary phosphine with the trihalides at room temperature. The solid state structure and reactivity of these adducts was also reported. Treatment of l,8-bis(diphenylphosphino)naphthalene with the borane-dimethylsulfide complex in ether solvents affords a simple monoborane adduct of the diphosphine irrespective of the molar ratio of the... 

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