Domino synthetic strategy for tetrahydrothiophene derivatives from 2-acetylfuran/2-acetylthiophene,benzaldehydes, and sulfur powder

A domino reaction from 2-acetylfuran/2-acetylthiophene, benzaldehydes and sulfur powder has been developed to synthesize a series of tetrahydrothiophene derivatives. The reaction proceeds well to construct five new bonds and a tetrahydrothiophene ring by one-pot. A possible mechanism was proposed, involving a stepwise of Aldol/double Michael addition/internal S_N2 cascaded reaction with sulfur powder acts as a source of sulfur. This method is characterized by mild reaction conditions, commercially available starting materials and transition-metal-free.