Catalytic direct cyclization of alkenyl thioester

Herein we report a one-step, catalytic, Markovnikov-selective, and scalable method for the synthesis of saturated sulfur het-erocycles, which are found in the structures of pharmaceuticals and natural products, from an alkenyl thioester. Unlike a po-tentially labile alkenyl thiol, an alkenyl thioester is stable and easy to prepare. Powerful catalysis via a cobalt hydride hydro-gen atom transfer and radical-polar crossover mechanism enabled simultaneous cyclization and deprotection. The substrate scope was expanded by extensive optimization of the reaction conditions and tuning of the thioester unit. This is a rare in-stance of thioesters showing nucleophilic behavior. This method was also applicable to alkenyl selenoesters.