Phosphines and phosphoranes

Lower symmetry than expected in some phosphines and phosphoranes... 

Halogenotrifluoromethyl-phosphines and -phosphoranes. The synthesis and stereochemistry of fluorophosphoranes RaPFj,-a (R = alkyl or aryl x — 1,2, or 3) have been extensively discussed, but comparatively little information is available on mixed halogenofluorophosphoranes of general formula... 

Even when chlorodiphenylphosphine is employed in excess, its reaction with 2,2 -biphenylenedilithium does not provide l,l-biphenyl-2,2 -diylbis(diphenylphosphine) (68) but 5-phenyl-5//-benzo[/)]phosphindole (67) ["9-phenyl-9-phosphafluorene"] instead (Scheme 1-47) Obviously, the ejection of phenyllithium from the monolithio intermediate 66 by intramolecular aryl/phenyl displacement occurs more rapidly than its combination with the second equivalent of chlorodiphenylphosphine. It is tempting to attribute the ease with which phosphines (and phosphoranes ) can undergo such intramolecular displacement processes to the intermediacy of ate complexes. However, all available evidence points instead at a still ill-defined SA/2-related mechanism ("spiraling backside attack"). 

Nucleophilic attack on phosphorus is not restricted to phosphonium salts, phosphines, and phosphoranes as Gottfried Markl has brilliantly demonstrated. Phenyllithium binds readily to the heteroelement of the faintly yellow 2,4,6-triphenyl-1-phosphabenzene (2,4,6-triphenylphosphorine). The resulting ate complex (69, Scheme 1-48) gives with methyl iodide the crystalline deep red 1-methyl-1,2,4,6-tetraphenyl-1 -phosphabenzene (76%). ... 

Ethyl (triphenylphosphoranylidene)acetate is available from FIuka AG and Trldom Chemical Inc. under the name (ethoxycarbonylmethylene)triphenyl-phosphorane and from Aldrich Chemical Company, Inc. under the name (carbethoxymethylene)triphenylphosphorane. The reagent may be prepared from triphenyl phosphine and ethyl bromoacetate by the following procedure. ... 

In the Wittig reaction an aldehyde or ketone is treated with a phosphorus ylid (also called a phosphorane) to give an alkene. Phosphorus ylids are usually prepared by treatment of a phosphonium salt with a base, and phosphonium salts are usually prepared from the phosphine and an alkyl halide (10-44) ... 

A novel route to indoles and quinolines has been developed by sequential Wiltig and Heck reactions <96CC2253>. Thus, treatment of o-bromo- or iodo-lV-lrifluoroaceiylanilines (86) with a stabilized phosphorane affords the corresponding enamines 87 as a mixture of isomers. Cyclization to 88 is effected by heating with palladium acetate, tri phenyl phosphine, and bu.se. 

The meta- and para-isomers of the phosphoranes (FC6H4)3P(OEt)2 have been prepared from the corresponding phosphines and diethyl peroxide. From their F chemical shifts it was concluded that the groups... 

The phosphoranes (4) and (5) have been obtained from the corresponding phosphines and diethyl peroxide. From the variable temperature n.m.r. spectrum of (5), below - 51 °C the phenyl group is locked in an equatorial position as in (5), between — 51 and 30 °C the pseudorotation (5) (6) is rapid on the n.m.r. time scale, and above 30 °C the pseudorotation (6) (7) is rapid. In the latter pseudorotation the strain involved in... 

A. Preparation.—Halogen displacement reactions have been used to prepare a number of new aminofluorophosphines. Aminodifluorophos-phine (1) has been prepared for the first time, from either bromodifluoro-phosphine or chlorodifluorophosphine, and ammonia. Studies of its n.m.r. spectrum have been made (see Chapter 11). The related NN-difluoroaminodifluorophosphine (2) has been prepared, from difluoroiodo-phosphine, and found to be explosive. Two syntheses of A-alkyl-amino-difluorophosphines have been reported, one of which was complicated by the subsequent formation of the phosphorane (3) and the bis-(A-alkylamino)fluorophosphine (4). 

Finally, a reaction should be mentioned in which a nucleophile gives support to another reacting species without appearing in the final product. Diphenyl cyclopropenone interacts with 2,6-dimethyl phenyl isocyanide only in the presence of tri-phenylphosphine with expansion of the three-ring to the imine 344 of cyclobutene-dione-1,2229,230 Addition of the isocyanide is preceded by formation of the ketene phosphorane 343, which can be isolated in pure formss 231 it is decomposed by methanol to triphenyl phosphine and the ester 52. 

The phosphoranes (81),64 (82),65 and (83),68 each containing a hydrogen ligand, have been prepared by the now standard procedure from amino-phosphines and amino-alcohols. A similar reaction of the amino-alcohol (84) gave oxazaphosphol-idine derivatives (85).6 7... 

Includes bibliographical references and indexes. Contents v. 1. Primary, secondary, and tertiary phosphines, polyphosphines, and heterocyclic organo-phosphorus(III) compounds—v. 2. Phosphine oxides, sulphides, selenides, and tellurides—v. 3. Phosphonium salts, ylides, and phosphoranes. 

Peptides. A new amide or peptide synthesis is based on the formation of iminophosphoranes, R N=PR3, from the reaction of azides with a tertiary phosphine. These phosphoranes react with carboxylic acids to form amides.1 Ethyl diphenylphosphinite is more useful than a triarylphosphine because the by-product is hydrolyzed to diphenylphosphinic acid, which can be readily removed. The iminophosphorane 2, derived from 1 and ethyl azidoacetate, reacts with CboGly-L-Phe-OH to give optically pure 3 in 70% yield.2... 

There have been extensive studies on the reaction of dioxetanes and dioxetanones with nucleophiles (C, N, P, and S) and the reader is directed to CHEC-II(1996) for an exhaustive list up to 1996. The most common reactions of dioxetanes have been with phosphorus nucleophiles. The phosphines and phosphites first insert into the 0-0 bond. The phosphorane intermediate then collapses to afford phosphine oxide or the trialkylphosphate and the corresponding epoxide (Scheme 6). The same is true for the treatment of a-peroxy lactones with phosphines and phosphites except that the so-formed a-lactone intermediate undergoes decarboxylation and ultimately furnishes a ketone <1997JOC1623>. 

Polymer-supported Wittig reagents were first prepared more than 20 years ago [32]. It has been shown that the success of the reaction depends strongly upon (i) the preparation of the reagent by bromination and phosphination of cross-linked polystyrene rather than by co-polymerization using styryldi-phenyl phosphine, and (ii) the generation of the phosphorane with a base/ solvent system that swells the phosphonium sites in the polymer network (Scheme 6) [33]. Thus, bromination of polystyrene 1 yielded phenyl bromide 32, and this was followed by phosphination with n-butyUithium and chlor-odiphenylphosphine or with Hthium diphenylphosphide to give 33, a compound which is commercially available (Scheme 6). 

A detailed study of the interaction of dimethyl phenylphosphonite (62 R = Ph) and ( )-63 (R = Pr ) initially showed that, at -50 °C only traces of unsaturated phosphinate and dimethyl phenylphosphonate are formed, and that the phosphorane 66 (R = Ph, R = Pr ) is the main produc In outline, the system of observed reactions resembles that observed for trimethyl phosphite, with the formation of the dipolar species 65 in equilibrium with the phosphorane 66 and with the ylide 67 the last acts as the immediate precursor to the methyl [(alk-2-enyl)phenyl]phosphinates 68 (R = Ph). Although hydrolysis of the phosphorane could be expected to yield the methyl [(nitroalkyl)phenyl]phosphinates... 

Amongst the carbophosphynes (6.3) only those of types (6.3a) (methylidyne phosphines) and types (6.3d) (methylidyne phosphoranes) are at present well established. 

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