Chiral squaramide as multiple H-bond donor organocatalysts for the asymmetric Michael addition of 1,3-dicarbonyl compounds to nitroolefins

A series of chiral bifunctional squaramide multiple H-bond donor organocatalysts have been designed and synthesized by the rational assembly of chiral privileged scaffolds of indanol and cinchona alkaloids. In the presence of 1 mol % 1a, the asymmetric Michael addition reaction of 1,3-dicarbonyl compounds to nitroolefins proceeded to provide the product in high yields (up to 92%) and with good to high ee values (up to 96%). The additional H-bond in this squaramide system plays a crucial role in enhancing the enantioselectivity.

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