Dihydrothiophenes. III. Preparation of Some 3,4-Unsubstituted Examples

Using the reaction between four representative vinylphosphonium salts and three α-mercaptoaldehydes, 12 3,4-unsubstituted 2,5-dihydrothiophenes(1) were prepared. The reaction proceeds in excellent yields under mild conditions. The use of these compounds in the synthesis of dienes is indicated.