Sustainable Organocatalyzed Enantioselective Catalytic Michael Additions in Betaine-Derived Deep Eutectic Solvents

Abstract

The catalyst cinchonidine-squaramide was immobilized within three different deep eutectic solvents (DES): (Betaine: D-Sorbitol: Water), (Betaine: D-Xylitol: Water) and (Betaine: D-Mannitol: Water) and evaluated in a well-known asymmetric Michael addition. These reactions provided excellent yields (up to 99%) and enantioselectivities (up to 98%) using only 1 mol% of catalyst. It was also possible to achieve 9 cycles in reactions with DES (Betaine: D-Sorbitol: Water), proving the high recyclability of this system. In the reactions realized with only 0.5 mol% of catalyst, it was possible to achieve 5 cycles and the products were obtained with high yields (up to 95%) and excellent enantioselectivities (up to 94%), using DES (Betaine: D-Sorbitol: Water).