Catalytic Direct Cyclization of Alkenyl Thioester

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Herein we report a one-step, catalytic, Markovnikov-selective, and scalable method for the synthesis of saturated sulfur heterocycles, which are found in the structures of pharmaceuticals and natural products, from an alkenyl thioester. Unlike a potentially labile alkenyl thiol, an alkenyl thioester is stable and easy to prepare. Powerful catalysis via a cobalt hydride hydrogen 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 instance of thioesters showing nucleophilic behavior. This method was also applicable to alkenyl selenoesters.