Enantioselective 1,6-Michael addition of anthrone to 3-methyl-4-nitro-5-alkenyl-isoxazoles catalyzed by bifunctional thiourea-tertiary amines

A simple and efficient method for the enantioselective 1,6-Michael addition reaction of anthrone to a series of 3-methyl-4-nitro-5-alkenyl-isoxazoles with a bifunctional thiourea-tertiary amine as catalyst is described. This transformation proceeds smoothly with 10 mol % catalyst and provides a series of Michael adducts bearing 3-methyl-4-nitro-isoxazole and anthrone units with good to high enantioselectivities (up to 96% ee) and in very high yields (up to 99%). (C) 2011 Elsevier Ltd. All rights reserved.