Carboxylation with CO2 via Brook rearrangement: preparation of α-hydroxy acid derivatives.

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