Deracemizing α-Branched Carboxylic Acids by Catalytic Asymmetric Protonation of bis-Silyl Ketene Acetals with Water or Methanol.

We report a highly enantioselective catalytic protonation of bis-silyl ketene acetals. Our method delivers alpha-branched carboxylic acids, including nonsteroidal anti-inflammatory arylpropionic acids such as Ibuprofen, in high enantiomeric purity and high yields. The process can be incorporated in an overall deracemization of alpha-branched carboxylic acids, involving a double deprotonation and silylation followed by the catalytic asymmetric protonation.