Synthesis of Cyclopropane and Spirocyclic γ-Lactams via Relay Reduction and Radical–Polar Crossover Cyclization

A RPCC/RPCCC cascade cyclization strategy has been successfully established for the continuous reduction of electrophilic aldehydes and imines through a CO₂• ⁻-mediated off-cycle photocatalytic cycle approach. This represents the first application of the SET-HAT-SET relay process in cyclopropane synthesis. This mild method exhibits a broad substrate scope, enabling the efficient synthesis of β-hydroxycyclopropanes and spirocyclopropane-γ-lactams. This strategy offers a viable approach for introducing 3D framework moieties into complex compounds.