Chemoselective allylic addition of allyltrichlorosilane to α-oxocarboxylic acids: synthesis of tertiary α-hydroxy carboxylic acids

Allyltrichlorosilane can add to α-oxocarboxylic acids in the presence of DMF and HMPA. The α-carboxylic substituent exerts a remarkable neighboring group effect on the reaction. The reaction presumably proceeds in an intramolecular fashion through a ‘rigid’ bicyclic transition state assembly involving a hypervalent silicate species, which produces the chemoselectivity approaching 100%.