Carboxylation with CO2 via Brook Rearrangement: Preparation of α-Hydroxy Acid Derivatives

In the presence of CsF, a wide range of alpha-substituted alpha-siloxy silanes were carboxylated under a CO2 atmosphere (1 atm) via Brook rearrangement. A variety of alpha-substituents including aryl, alkenyl, and alkyl groups were tolerated to afford alpha-hydroxy acids in moderate-to-high yields. One-pot synthesis from aldehydes using PhMe2SiLi and CO2 was also possible, providing alpha-hydroxy acids without the isolation of an alpha-hydroxy silane.