Photocatalytic S N 2′-Type Mono-, Di-, and Trifluoromethylation of gem -Dichlorocyclobutenones

We report a metal-free photocatalytic SN2'-type trifluoromethylation of both β-alkyl- and β-aryl-gem-dichlorocyclobutenones using commercially available sodium trifluoromethylsulfinate. This mild and scalable method enables efficient access to highly functionalized 4-trifluoromethylated α-chlorocyclobutenones, showcasing late-stage functionalization. The mild protocol can be readily extended to di- and monofluoromethylation using di- and monofluoromethylsulfinate, respectively. Mechanistic studies indicate a radical-mediated pathway, contrasting a conventional nucleophile-driven process.