Asymmetric Michael addition reactions of aldehydes with nitrostyrenes catalyzed by functionalized chiral ionic liquids

A new class of pyrrolidine-based functionalized chiral ionic liquids (FCILs) has been developed and shown to be effective and reusable catalysts for the asymmetric Michael addition reactions. For the Michael addition reaction involving various aldehydes and nitrostyrenes, FCIL 6, in combination with trifluoroacetic acid as an additive, was found to be a very effective catalyst, compared to FCIL 3, which varied slightly in structure. Excellent yields (up to 99%), good enantioselectivities (up to 85% ee), and high diastereoselectivities (syn/anti ratio up to 97:3) were obtained for these reactions. The FCIL catalysts were easily recycled and reused for at least five times without significantly losing their ability to affect the outcome of the asymmetric reactions. (C) 2008 Elsevier Ltd. All rights reserved.