Elemental sulfur-promoted one-pot synthesis of 2-(2,2,2-trifluoroethyl)benzoxazoles and their derivatives

A novel and direct strategy has been developed for the synthesis of 2-(2,2,2-trifluoroethyl)benzoxazoles by reaction of o-aminophenols and 2-bromo-3,3,3-trifluoropropene in the presence of elemental sulfur under metal-free conditions. The scope of this methodology was further extended to the synthesis of the trifluoroethylated benzothiazole and benzoimidazole derivatives. A plausible mechanism was proposed on the basis of isolation and characterization of a thioamide intermediate.