1.3- dienylphosphonium salts

Isolated instances of 1,4-addition reactions of other hetero-nucleophiles to 4-en-2-ynoic acids and derivatives have been reported172-174. Thus, treatment of methyl 4-methyl-4-penten-2-ynoate with phenolate provided the 3-phenoxy-substituted conjugated dienoate (equation 71)172, and the 1,4-addition of water-soluble phosphines to 4-octen-2-ynoic acid afforded dienylphosphonium salts which were transformed into the corresponding phosphine oxides (equation 72)174. 

As expected, buta-l,3-dienylphosphonium salts add ketonic nucleophiles in the exposition792. A butadienylphosphonium salt is also the intermediate accounting for the... 

A new route to 1,3-dienes is provided by tandem nucleophilic addition to the dienylphosphonium salt (44) followed by reaction with aldehydes.2 6 An attempt to extend the reaction to provide a triene via the vinylogue of... 

A few examples of the reactions of a (trimethylsilyl)methylenephosphorane with carbonyl compounds have been reported. Reactions of the silylated phosphorus ylide 106 with a,/ -unsaturated aldehydes lead to the 1,3-dienylphosphonium salts 107 (Scheme 2.64) [170). These reactions show that the silyl group is eliminated faster than the phosphorus group. 

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