Tertiary Amine-Derived Ionic Liquid-Supported Squaramide as a Recyclable Organocatalyst for Noncovalent “On Water” Catalysis

Chiral tertiary amine-derived ionic liquid-supported squaramide was synthesized from available precursors and applied as an efficient organocatalyst for asymmetric Michael additions of β-dicarbonyl compounds to α-nitroolefins in the presence of water. Corresponding Michael adducts were generated under proposed conditions in nearly quantitative yield with high enantioselectivity (up to 99% ee). Useful precursors to pharmaceutically important chiral β-amino acids and anticonvulsant Pregabalin were conveniently prepared using the developed “on water” protocol. The catalyst is readily recoverable and reusable over 30 times without a significant decrease of catalytic reaction activity and selectivity.