Synthesis of dihydrothiophenes or spirocyclic compounds by domino reactions of 1,3-thiazolidinedione.

The domino reactions of 1,3-thiazolidinedione, malononitrile, and aromatic aldehydes in the presence of different organic amines were studied. Secondary amines such as pyrrolidine, piperidine, morpholine, and dimethylamine and primary amines such as benzylamine yield dihydrothiophene derivatives through a domino ring-opening/recyclization reaction of 1,3-thiazolidinedione. Bulky diethylamine, diisopropylamine, and 1,4-diazabicyclo[2.2.2]octane give spirocyclohexano-1,3-thiazole through a double Michael addition/spirocyclization reaction.