A novel general method for preparation of α-fluoro-α-arylcarboxylic acid. Direct fluorination of silyl ketene acetals with Selectfluor®

The reaction of an α-arylcarboxylic acid with TBSCl and LiHMDS in THF yielded bis-silyl ketene acetal, which was directly fluorinated with inexpensive Selectfluor® to produce the corresponding α-fluoro-α-arylcarboxylic acid in high yield. Application of the methodology to the synthesis of α-fluorocarboxylic ester from the corresponding carboxylic ester is also described.