Palladium-Catalyzed Allylic Alkylation via Photocatalytic Nucleophile Generation

The rapid assembly of an easily accessible terminal alkene, an aliphatic C(sp3)–H coupling partner, and allyl carbonate has been established by merging hydrogen atom transfer photocatalyst-mediated nucleophile generation and palladium-catalyzed allylic alkylation. The synthetic utility of this strategy is embodied by a concise synthesis of (±)-mesembrine. Mechanistic studies suggest that this protocol proceeds via a radical/ionic relay process, and a carbanionic species serves as a key intermediate for nucleophile attack on π-allylpalladium through a classic two-electron allylation pathway. This protocol showcases an atom-economic and environmentally friendly method to generate a nonstabilized nucleophile for transition-metal catalysis.