Site-Selective Defluorinative Functionalization of Unactivated Alkenes Enabled by Cobalt/Photoredox Relay Catalysis

We report a cobalt/photoredox relay catalytic system that integrates alkene isomerization with defluorinative functionalization, enabling remote and site-selective difluoroalkylation of unactivated alkenes. In this transformation, cobalt-mediated chain walking converts terminal alkenes into internal counterparts, which subsequently undergo photoinduced radical–polar crossover defluorinative alkylation with trifluoromethylarenes to selectively deliver branched gem-difluoroalkylated products under mild conditions. The method features a broad substrate scope and high functional group tolerance, accommodating terminal alkenes, trifluoromethylated aromatics, and amides, and can be further extended to difluoroalkylcarboxylation with CO2. Mechanistic studies support a sequential isomerization–defluorinative pathway mediated by cooperative cobalt and photoredox relay catalysis.