Enantioselective organocatalytic anti-Mannich-type reaction of N-unprotected 3-substituted 2-oxindoles with aromatic N-Ts-aldimines.

The modified cinchona alkaloid-catalyzed direct Mannich-type reaction of N-unprotected 2-oxindoles with N-Ts-imine was developed to afford anti-3,3-disubstituted 2-oxindoles with vicinal chiral quaternary and tertiary carbon centers in yields up to 90% with excellent diastereoselectivities (anti/syn up to 95:5) and good enantioselectivies (up to 89% ee). A transition model for the anti-diastereo- and enantioselectivity of the reaction was proposed.