Histidine-based salt as an ionic tag for proline: application in enantioselective cross aldol reaction in ionic liquids

Abstract

A new ionic-liquid supported aminocatalyst was synthesized by the peptide coupling of proline on a ring-dialkylated histidine salt serving as ionic support. The catalytic activity and enantioselectivity of the obtained dipeptide catalyst were evaluated in the enantioselective cross aldol reaction of substituted benzaldehyde derivatives with acetone, in organic solvent and in ionic liquids, and both were found to be significantly higher in ionic liquids than in organic solvents. The [bmim][OTf] – catalyst system could be recycled for up to five cycles without any loss in activity.