Ring-Retentive S N 2′-Type Alkylation of gem -Dichlorocyclobutenones Enabled by an In Situ Alkene-to-Radical Relay

A photocatalyst-free radical S N 2′-type alkylation of gem -dichlorocyclobutenones with unactivated alkenes is enabled by visible-light-induced C–Zr bond homolysis. Alkylzirconium intermediates generated in situ from terminal or internal alkenes serve as alkyl radical precursors and undergo radical addition/β-fragmentation with gem -dichlorocyclobutenones to afford ring-retained α-chlorocyclobutenones. This protocol avoids preformed radical donors and external photocatalysts, proceeds under mild conditions, tolerates structurally complex substrates, and furnishes multifunctional α-chlorocyclobutenones suitable for further diversification.