Phosphonium salts, vinylphosphonium ylide synthesis

The trimethylsilylated ylides (1), easily generated from trimethyl chlorosilane and ylides, react with aldehydes 2 to form vi-nylsilanes 3 (2,3). The vinylphosphonium silanolates 4 are also formed. Compounds 3 are versatile reagents for further reactions (4). The ylide J (with R1 =H) reacts with aldehydes 2 to give the dienes j). The oxidation of with the adduct 6, from triphenyl-phosphite and ozone, gives access to a generaT synthesis of acyl-silanes (trimethylsilylketones) (2). The silylated ylides react to form phosphonium salts 7 with halogen compounds. The salts 7.can be desilylated by fluorine ions. The disubstituted ylides JO Tormed can be converted in statu nascendi with aldehydes V[ into the tris-substituted olefin J2 (2,3). In the case of R3-I, vinyl... 

An alternative route to ylide synthesis via a-deprotonation is the abstraction of a proton from the y-po-sition of a vinylphosphonium salt (equation 10). Complications may arise, however, if the phosphonium salt carries a good leaving group in the P-position so that a vinylphosphonium salt may be formed, or if a P-proton is so acidic that a Hofmann elimination is favored. " ... 

Electrochemically-promoted reversible interconversion of alkyltriphenyl-phosphonium salts and the related ylides has been shown to occur in the presence of benzophenone oxime O-methyl ether as a mediator, providing an example of electrochromism. Nucleophilic addition to vinylphosphonium salts has again been widely used as a means of generating ylides, and for the synthesis of heterocyclic systems" New developments include the catalysis of addition of... 

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