Michael Addition of N-Unprotected 2-Oxindoles to Nitrostyrene Catalyzed by Bifunctional Tertiary Amines: Crucial Role of Dispersion Interactions

摘要

Bifunctional thiourea- or sulfonamide-derived tertiary amines catalyze the enantioselective nitro-Michael addition of N-unprotected 3-substituted 2-oxindoles to nitrostyrene in up to 99% yields, 94:6 er, and 87:13 dr. Overcoming the necessity to introduce and remove activating or protecting groups at the nitrogen moiety leads to a reduction of energy use, costs, and waste. Transition-state geometries for the formation of all possible stereoisomers in the nitro-Michael addition of N-unprotected 3-substituted 2-oxindole to nitrostyrene catalyzed by Takemoto's tertiary amine-thiourea are calculated. It is shown that the relative positions and binding patterns of the reactants and the catalyst molecule are largely determined by van der Waals interactions.