Highly Diastereo- and Enantioselective Michael Additions of 3-Substituted Oxindoles to Maleimides Catalyzed by Chiral Bifunctional Thiourea-Tertiary Amine

A highly diastereo- and enantioselective Michael addition reaction with respect to prochiral 3-substituted oxindoles and maleimides by a chiral bifunctional thiourea tertiary amine catalyst was investigated for the first time. The corresponding adducts, containing a quaternary center at the C3-position of the oxindole as well as a vicinal tertiary center, were generally obtained in good to high yields (up to 92%) with high to excellent diastereo- (up to 99:1 dr) and enantioselectivities (up to 99% ee).