A simple synthesis of alkylated and acylated dihydrothiopyrans

The reaction of β-mercaptoaldehydes and ketones with vinylphosphonium salts results in the ready formation of 3,6-dihydro-(2H)thiopyrans. The presence of an α-substituent on the salt blocks this reaction. It has also been shown that both α- and β-mercaptoaldehydes can be condensed with conjugated aldehydes to give 5,6-dihydro-(2H)thiopyran-3-carboxaldehydes ( 13 - 15 ) or 2,5-dihydrothiophene-3-carboxyaldehydes ( 16 , 17 ). The potential synthetic application of these reactions to stereospecific olefin synthesis is indicated.