Phosphorus ylid

Notice that sulphur ylids behave quite differently from phosphorus ylids, which would of course do the Wittig reaction (ftames 41-43). 

An extensive chemistry is developing of dinuclear gold(III) complexes with phosphorus ylid ligands (Figure 4.41). As mentioned in section 4.19, gold(I) compounds can undergo one- or two-electron oxidative additions,... 

Although the phosphorus ylid shown has three R groups on the phosphorus atom, other phosphorus ylids are known where other atoms (e.g., oxygen) replace one or more of these R groups. When the three groups are all alkyl or aryl, the phosphorus ylid is also called a phosphorane. 

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) ... 

Phosphorus ylids also react in a similar manner with the C=0 bonds of ketenes/ isocyanates, and certain anhydrides and imides, the N=0 of nitroso groups, and the C=N of imines, for example. 

Phosphorus ylids react with carbon dioxide to give the isolable salts (48), which can be hydrolyzed to the carboxylic acids (49) (thus achieving the conversion RR CHX RR CHCOOH) or (if neither R nor R is hydrogen) dimerized to... 

Although phosphorus ylids are most commonly used to alkenylation reactions, nitrogen ylids can occasionally be used. As an example, the reaction of A-benzyl-A-phenylpiperidinium bromide with base generated a A-ylid, which reacted with benzaldehyde to form styrene. ... 

Phosphorus ylids do not give this reaction, but give 16-47 instead. 

Although phosphorus ylids also react with esters, that reaction is too slow to interfere Greenwald, R. Chaykovsky, M. Corey, E.J. J. Org. Chem., 1963, 28, 1128. 

Phosphorus ylids are quite common (see 16-47) and keto-phosphorus ylids (RCOCH=PPh3) are also known. When these compounds are heating (flash vacuum pyrolysis, FVP) to great than >500°C, alkynes are formed. Simple alkynes can... 

Reaction between phosphorus ylids and aldehydes or ketones... 

This reaction involves Michael addition of (28) to the enone followed by cycllsation (29) with displacement of DMSO, Sulphur y,llds react in these ways rather than removing oxygen, as phosphorus ylids do, because the SO bond is weaker than the PO bond and the lower valency states of sulphur more stable than those of phosphorus. 

With acyl and alkoxycarbonyl azides, 2 -triazoles are isolated, although the l.ff-isomers are detected as intermediates. The reaction is not very general it fails with the corresponding sulfonium ylids, and fairly minor changes in substituents on the phosphorus ylid result in the formation of diazoketones rather than triazoles. ... 

Isuclectronic with the phosphine oxides are the phosphorus ylids, R,PCH2. As for the oxides, two resonance forms... 

To our knowledge, amides failed to react with phosphorus ylids... 

Complexes of nickel constitute a distinct group of homogeneous alkylalumi-nium-free catalysts for olefin polymerisation. An efficient catalyst for ethylene polymerisation is formed in the reaction of bis(cycloocta-l,5-diene)nickel(0) [Ni(Cod)2] with phosphorus-ylid and triphenylphosphine in toluene solvent [181] ... 

In their search for less complex pentaalkylphosphoranes114), Schmidbaur and coworkers could provide convincing evidence for the intermediate occurence of monocyclic pentaalkylphosphoranes of type 104 in reactions of phosphorus ylids with silacyclobutanes. Isolation of such phosphoranes 104 was, however, never possible 115). 

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