Silylated phosphonium ylides synthesis

In addition to the generation of phosphonium ylides from phosphonium salts by deprotonation with bases in some instances ylides may result from pyrolysis of phosphonium salts, especially silylated salts (equation 17). Similar fluoride ion induced desilylation (equation 18) of phosphonium salts proved to be a very useful alternative for the synthesis of ylides which are difficult to synthesize by the conventional salt method (as in the case of R, R = alkyl). - The most effective fluoride source is cesium fluoride and the reaction proceeds at room temperature. 

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... 

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