Radical Changes in Lewis Acid Catalysis: Matching Metal and Substrate

Whereas the stereochemical rigidity of the coordination sphere of boxmi/Cu-II catalysts is key to achieving high enantioselectivity in the electrophilic alkylation of beta-ketoesters, this pathway is outperformed by a radical process for the corresponding catalytic transformation of oxindoles, giving rise to racemic products. For the corresponding Zn-II catalysts, the selectivity in the latter process is outstanding despite the greater plasticity of the coordination shell. This reaction was thus developed into a highly useful synthetic method, which enabled the conversion of wide range of substrates with high yields and enantioselectivities.