Construction of Fluorinated Benzoxathiin Skeleton by Successive Perfluorophenylthiolation/Cyclization of Activated α-Methylene Ketones by Perfluorophenyl Diethylaminosulfur Difluoride.

Pharmaceutically attractive fluorinated benzoxathiin (thiaflavan) skeleton 4 was directly constructed by the reaction of activated α-methylene ketones 1 such as β-keto esters, 1,3-diketone, and β-keto sulfones with a perfluorophenyl analogue of diethylaminosulfur trifluoride, C6F5-DAST, in high yields via successive perfluorophenylthiolation/cyclization reaction.