A rapid and convergent synthesis of α,α-difluoro-β-hydroxyketones through regiospecific defluorinative alkylation reaction

Both the defluorinative alkylation reaction of trifluoroacetaldehyde N,O-acetals using alkyllithiums and the following C-C bond formation with carbonyls as electrophiles were accelerated by a suitable diamine additive such as (−)-sparteine to give α,α-difluoro-β-hydroxyketone N,O-acetal products in an excellent yield. We also found that N-benzyl-N,O-acetal group of the resultant products can be removed under palladium-catalyzed hydrogenolysis conditions giving rise to the corresponding α,α-difluoro-β-hydroxyketones. The present two-step procedure is a useful and novel synthetic approach for functionalized α,α-difluoroketones.