An organocatalytic enantioselective N-nitroso-aldol reaction of 2-oxindoles promoted by a cinchona alkaloid catalyst has been developed. The reaction shows exclusively N-selectivity, affording corresponding products with good to excellent yields (up to 100%) and moderate enantioselectivity. The regioselectivity of nitroso-aldol reaction being controlled by different cinchona catalysts was also observed. (C) 2010 Elsevier Ltd. All rights reserved.
Enantioselective organocatalytic oxyamination of unprotected 3-substituted oxindoles
An enantioselective α-oxyamination of unprotected 3-substituted oxindoles with nitrosobenzene catalyzed by tertiary amine–thiourea bifunctional organocatalysts has been developed and affords the corresponding 3-amino-2-oxindole derivatives in good yields and with moderate to excellent enantioselectivities (up to > 99.9 : 0.1 er when the product is isolated by direct filtration from the reaction mixture)