Hydrogen-Evolution Allylic C(sp3)–H Alkylation with Protic C(sp3)–H Bonds via Triplet Synergistic Brønsted Base/Cobalt/Photoredox Catalysis

Transition-metal-catalyzed allylic C(sp3)–H alkylation with carbon-center nucleophiles is a straightforward approach to C(sp3)–C(sp3) bond formation, which has found widespread application in organic synthesis. However, stoichiometric oxidants are typically required to realize the transformation. Herein, by the triplet synergistic merger of Brønsted base/cobalt/photoredox catalysis, a mild protocol for the hydrogen-evolution allylic C(sp3)–H alkylation with protic C(sp3)–H feedstocks was developed in an oxidant-free manner. This operationally simple method enables direct allylic C(sp3)–H alkylation of a wide range of branched α-olefins with diverse protic C(sp3)–H feedstocks. The synthetic robustness of this strategy was further demonstrated by the late-stage functionalization of complex molecules and the synthesis of the natural product dihydropallescensin D.