Highly Enantioselective Michael Addition of Nitroalkanes to Chalcones Using Chiral Squaramides as Hydrogen Bonding Organocatalysts

A series of squaramide-based organocatalysts were facilely synthesized and applied as hydrogen bonding organocatalysts in the enantioselective Michael addition of nitroalkanes to chalcones. These organocatalysts promoted the Michael addition with low catalyst loading under high temperature. (80 degrees C), affording the desired R or S enantiomers of the products flexibly in high yields with excellent enantioselectivities (93-96% ee) by the appropriate choice of organocatalysts.