Asymmetric Michael Addition Of Pyrazolin-5-ones To Nitroolefins Catalyzed By Chiral Bifunctional Glycosyl Thiourea

Recently, chiral thioureas are rapidly developed due to their versatility, high catalytic activity, excellent enantioselectivity and high functional group tolerance. Herein we report a new class of saccharide-substituted bifunctionaltertiary-amine thiourea catalyzed asymmetric Michael addition of Pyrazolin-5-ones to Nitroolefins. This experimentally simple process facilitates the access to various enantioenriched, multiply substituted pyrazolin-5-one derivatives, potential biologically active molecules, starting from readily available starting materials. Different parameters were tested to indicate the appropriate reaction conditions like catalyst loading, solvent, temperature and additives. Under the optimized condition, a wide variety of desired products were smoothly obtained in very good yields (up to > 99%) with excellent enantioselectivities (up to 98% ee). 16 adducts were separated and characterized by NMR, IR and MS.Many valuable optically active intermediates can be smoothly obtained by this conversion. On the other hand, Pyrazolinones are common motifs in natural products, medicines and pesticides. Therefore enanioselective construction of these compounds has potential meaning to drug synthesis.