TFA‐Promoted Intermolecular Friedel‐Crafts Alkylation of Arenes with 2,2,2‐Trifluoroethylaryl Sulfoxides

Abstract The classical Pummerer rearrangement of 2,2,2‐trifluoroethylaryl sulfoxide with trifluoracetic anhydride (TFAA) affords the S , O ‐acetal efficiently. In the presence of trifluoracetic acid (TFA) as the co‐solvent, the S , O ‐acetal can regenerate reactive thionium intermediate of Pummerer rearrangement. When employing arenes as nucleophiles, this strategy produces corresponding 1‐thiyl‐2,2,2‐trifluoroethyl arenes with excellent yields under metal‐free conditions.