Chiral Squaramide-Catalyzed Highly Enantioselective Michael Addition of 2-Hydroxy-1,4-naphthoquinones to Nitroalkenes

A chiral squaramide-organocatalyzed, highly enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinones to nitroalkenes has been developed. This reaction afforded the chiral naphthoquinones in excellent yields (up to 99%) and excellent enantioselectivity (up to 98% ee) under very low catalyst loading (0.25 mol%). This organocatalytic asymmetric Michael addition provides an efficient alternative route toward the synthesis of chiral functionalized naphthoquinones.