A novel method for the preparation of α,α′ -difluoroesters and acids using BrF₃

Alkyl-, haloalkyl-, and ketoalkyl-2-ethoxycarbonyl-1,3-dithianes were easily made from the appropriate primary or secondary alkyl bromides, 1,3-dithiane, and ethyl chloroformate. They were reacted with BrF₃ to form the corresponding α,α-difluoro esters in 65-75% yield. Reaction conditions are very mild (1-2 min, 0 °C). The two sulfur atoms of the dithiane are essential for the reaction.