Enantioselective Michael Addition of
N-Heterocycles to Nitroolefins

Significance

Exploration of asymmetric Michael additions has recently been of large interest in organocatalysis. In this report, cinchona alkaloid derived catalyst 1 is used to catalyze the Michael addition between several aliphatic and aromatic nitroolefins 3 and triazole 2. The N1 addition ­product 4 was formed selectively in good yields (67-90%) and enantioselectivities (57-94% ee) at -25 °C in one to four days. While tetrazoles and other triazoles can be employed in this reaction, purines did not give the products in reasonable yields. Also, both hydroxy groups in the catalyst are essential for high enantioselectivity. Urea and thiourea catalysts gave the same level of yields (79-88%), but diminished enantioselectivities (26-44% ee).