GEM-DIFLUOROALLYLATION OF ALDEHYDES AND KETONES AS A CONVENIENT ROUTE TO ALPHA,ALPHA-DIFLUOROHOMOALLYLIC ALCOHOLS

In the presence of zinc, 3-bromo-3,3-difluoropropene or 3-iodo-1,1-difluoropropene reacted with carbonyl compounds to give the corresponding alpha,alpha-difluorohomoallylic alcohols in good yields at 0-degrees-C to room temperature. The reaction is applicable to aliphatic and aromatic aldehydes, dialkyl ketones, and alkyl aryl ketones. Reaction with alpha,beta-unsaturated aldehydes and ketones yielded 1,2-adducts exclusively. However, the reaction could not be extended to esters and acyl chlorides. Other metals such as cadmium and tin could also be used to mediate gem-difluoroallylation. The regiochemistry of this reaction could be rationalized in terms of the more nucleophilic alpha-carbon of the gem-difluoroallyl intermediate.