Difluoromethylation of Carboxylic Acids via the Addition of Difluorinated Phosphorus Ylide to Acyl Chlorides.

A one-step protocol for the difluoromethylation of carboxylic acids is described. The reaction involves the interaction of intermediate acyl chlorides with in situ generated difluorinated phosphorus ylide PhP═CF. Aromatic acids can be selectively transformed within one step either to bis-difluoromethylated alcohols or to difluorinated ketones depending on the particular reaction conditions. For bulky α-branched carboxylic acids, only ketones are produced.