One-pot synthesis of stable phosphorus ylides using aldehyde phenylhydrazone derivatives

Abstract

Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of phenylhydrazone derivatives, such as 1-benzylidene-2-phenylhydrazine, 1-(3-chlorobenzylidene)-2-phenylhydrazine, 1-(2,4-dinitrobenzylidene)-2-phenylhydrazine, 1-(4-nitrobenzylidene)-2-phenylhydrazine, 1-(2-fluorobenzylidene)-2-phenylhydrazine, 1-(4-fluorobenzylidene)-2-phenylhydrazine and 1-(2,4-dichlorobenzylidene)-2-phenylhydrazine. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of the restricted rotation around the carbon-carbon partial double bond resulting from the conjugation of the ylide moiety with the adjacent carbonyl group.