The hydrolysis of arylmethylenemalononitriles to α-cyanocinnamides in the presence of triphenylphosphine

Abstract

The reaction of triphenylphosphine with a series of arylmethylenemalononitriles in chloroform in the presence of aqueous hydrochloric acid gives the corresponding 1-aryl-2-carbamoyl-2-cyanoethyltriphenylphosphonium chlorides. Electron-withdrawing substituents on the malononitriles accelerate the reaction and give rise to higher yields. Heating the phosphonium salts under reflux in ethanol regenerates triphenylphosphine and gives the corresponding α-cyanocinnamides. The mechanisms of both reactions are discussed.