2-Polyfluoroalkyl thiopyrylium salts: synthesis and reactions with nucleophiles

2-Polyfluoroalkylthiopyrylium salts have been synthesized by oxidative aromatization of 2-polyfluoroalkyl-2H-thiopyrans with triphenylmethane tetrafluoroborate. Nucleophilic addition of methanol, sodium azide, or urea to 2-trifluoromethylthiopyrylium tetrafluoroborate in a basic medium proceeds at the α-position to give the corresponding 2-substituted 6-trifluoromethyl-2H-thiopyrans whereas imidazoles, fluorine-containing 1,2,3-triazole, potassium thiolacetate, and sodium nitromethane afford mixtures of 2H- and 4H-thiopyrans. cis-Dihydroxylation of 6-trifluoromethyl-2-methoxy-2H-thiopyran affords the fluorine-containing thiohexenopyranoside derivative 8.