A novel method for the preparation of alpha,alpha'-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 BrF(3) to form the corresponding alpha,alpha-difluoro esters in 65-75% yield. Reaction conditions are very mild (1-2 min, 0 degrees C). The two sulfur atoms of the dithiane are essential for the reaction.