Asymmetric Nitroaldol Reactions of Nitroalkanes with Isatins Catalyzed by Bifunctional Cinchona Alkaloid Derivatives

The enantioselective nitroaldol reactions of isatins with nitroalkanes were smoothly carried out by organocatalysis. A C6'-OH cinchona alkaloid derivative bearing a C9-OBn group exhibited outstanding catalytic efficiency as an acid-base bifunctional catalyst for the nitroaldol reaction of isatins with nitromethane, providing 3-hydroxy-3-(nitromethyl)indolin-2ones in good yields (90-98%) and with good to high enantiomeric excess values (72-95%). The resultant oxindole derivatives are highly important for the synthesis of related natural products and pharmaceutically active compounds.