Deacylative SN2'-Type Alkylation of Monochloro- and gem-Dichlorocyclobutenones Mediated by Pro-aromatic Intermediates.

We report a mild, redox-neutral deacylative SN2'-type alkylation of monochloro- and gem-dichlorocyclobutenones with pro-aromatic ketone-derived dihydroquinazolinones enabled by visible light photocatalysis. The method uniquely combines the C-C bond cleavage of unstrained aliphatic ketones with concurrent C-C bond formation via α-selective radical addition to the enone moiety of gem-dichlorocyclobutenones, contrasting β-selective radical addition in Giese-type addition. This base- and oxidant-free method provides efficient access to highly functionalized 4-alkylated α-chlorocyclobutenones. Furthermore, aldehyde-derived pro-aromatic 4-alkyl-1,4-dihydropyrides served as C-radical precursors, enabling the synthesis of 4-alkylated α-chlorocyclobutenones under similar reaction conditions.