K₂S₂O₈-Mediated Selective Trifluoromethylacylation and Trifluoromethylarylation of Alkenes under Transition-Metal-Free Conditions: Synthetic Scope and Mechanistic Studies

Abstract

A practical and efficient method for selective intramolecular radical trifluoromethylacylation and -arylation of alkenes with inexpensive CF₃SO₂Na and K₂S₂O₈ in aqueous media has been developed, respectively, affording the highly chemoselective synthesis of CF₃-functionalized chroman-4-ones and chromanes in satisfactory yields. Control experiments and DFT calculations indicate that the CF₃SO₂Na/K₂S₂O₈ system is capable of trifluoromethylating the substrate of alkenes without a transition metal catalyst and the oxidation of CF₃SO₂Na to ·CF₃ by K₂S₂O₈ is involved in the rate-determining step.