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.
Keywords: Friedel-Crafts alkylation; Pummerer reaction; Sulfoxide; Thionium; Trifluoroethyl.
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