A general and mild strategy involving threecomponent carboarylation of unactivated alkenes with protic C(sp 3 )−H feedstocks via photoredox catalysis was reported. This catalytic system is compatible with a broad range of unactivated alkenes, cyano-substituted arenes, and diverse protic C(sp 3 )−H feedstocks. The synthetic value of this protocol was demonstrated by the late-stage functionalization of complex molecules and the synthesis of the antiallergies including pheniramine, chlorpheniramine, and brompheniramine.

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.