Basic chiral ionic liquids: A novel strategy for acid-free organocatalysis

We present design, synthesis and application of basic chiral ionic liquids based on commercially available (S)-proline. This new set of chiral ionic liquids was specifically designed to replace trifluoroacetic acid in enamine-based organocatalysis for asymmetric Csingle bondC bond formation. Based on their permanent charge, these chiral ionic liquids could be applied as organocatalysts in asymmetric aldol reaction of 4-nitrobenzaldehyde and acetone, and good yields and selectivities up to 80%ee could be obtained without additional acid.