1,2,3-Triazolium-Tagged Prolines and Their Application in Asymmetric Aldol and Michael Reactions

Abstract

Novel 1,2,3-triazolium-tagged proline derivatives were synthesized by copper-catalyzed click-reaction of alkynes with azides and N-alkylation of the resulting 1,2,3-triazoles. They were applied as recyclable organocatalysts in direct asymmetric aldol and Michael reactions with high enantioselectivity and diastereoselectivity. These catalysts performed better than (S)-proline itself; that is to say, a synergistic effect of the triazolium and the proline moiety exists. The reactions could be carried out either in conventional solvents or in ionic liquids. The catalysts were easily recycled and reused several times.