Cobaloxime-catalysed regiodivergent hydrogen atom transfer for alkenyl and allylic carbamoylation with branched alkenes.

Abstract

Hydrogen atom transfer (HAT) represents a fundamental reaction in synthetic chemistry, with ongoing innovations aimed at improving its selectivity and efficiency. Leveraging the unique reactivity of cobaloxime, we developed a regioselective HAT process that enables divergent carbamoylation of branched alkenes. Through modulation of the electronic and steric properties of the ligands, this cobalt complex achieves precise discrimination between hydrogen atoms exhibiting minor differences in bond dissociation energies (BDEs), affording vinyl and allylic amides with predictable selectivity. This operationally simple method features a broad substrate scope, excellent functional group tolerance, and is applicable to the late-stage functionalization of natural products. The synthetic utility of this radical approach is highlighted by the asymmetric total synthesis of a lignan natural product (-)-arctigenin. Experimental and computational studies shed important light on the mechanism and the critical role of the cobaloxime catalyst in regiocontrol.