Photocatalytic S _N 2′-Type Mono-, Di-, and Trifluoromethylation of <i>gem</i> -Dichlorocyclobutenones

We report a metal-free photocatalytic S_N2'-type trifluoromethylation of both β-alkyl- and β-aryl-<i>gem</i>-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.