Assembly of functionalized gem-difluoroalkenes via photocatalytic defluorocyanoalkylation and defluoroacylation of α-CF3 styrenes with oxime esters†

Abstract

We report an efficient photocatalytic protocol for the defluorocyanoalkylation and defluoroacylation of α-trifluoromethyl styrenes by utilizing oxime esters as radical donors, allowing for the preparation of diverse gem-difluoroalkenes. The treatment of α-trifluoromethyl styrenes with cyclobutanone oxime esters led to the formation of distal cyano group-anchored gem-difluoroalkenes. Notably, adding K₂CO₃ as an inorganic base to the photocatalytic system afforded γ,γ-difluoroallylic ketones by utilizing acyl oxime esters as the acylating agents. Preliminary mechanistic investigations into this reaction pathway revealed the involvement of single-electron reduction, C–C bond cleavage initiated by iminyl radicals, radical addition, and β-fluoride elimination steps.