Asymmetric Michael Addition of Ketones to Nitroolefins Catalyzed by a Novel Chiral Pyrrolidine-Thiourea in the Ionic Liquid

A novel chiral pyrrolidine-thiourea has been developed and successfully applied to the asymmetric Michael addition of ketones with nitroolefins in ionic liquid. The corresponding products could be obtained in good yields with good enantio- and diastereoselectivities of products. In addition, the chiral catalytic system could be reused with comparable catalytic activity and stereoselectivity. Further studies are under way to expand the synthetic utility of this new reaction, as well as the application of this catalytic system in other asymmetric transformations. Organocatalytic asymmetric reactions have proved to be efficient and powerful tools in organic synthesis. Among them, the asymmetric Michael reaction of nitroolefins with carbon nucleophiles is widely recognized as one of the most important and versatile processes for the synthesis of enantioselective C-C and C-X bonds; for the nitroolefins are of special interest as excellent Michael acceptors, and the nitro functionality can be easily transformed into an amine, nitrile oxide, ketone, carboxylic acid, hydrogen, etc., providing a wide range of synthetically interesting compounds