Chiral Ionic Liquids Based on L-Cysteine Derivatives for Asymmetric Aldol Reaction

Structure, and consequently properties, of ionic liquids can be easily tailored by changing cation/anion combinations and/or attaching functional groups. By grafting enantiopure moieties to the framework liquid it is possible prepare bioinspired chiral molecules that serve as a reaction medium, additive or even asymmetric catalyst. In this context, new (CILs), based on biomolecules, such aminoacids (L-cysteine derivatives), have been synthesised tested in aldol condensation aldehydes ketones. The best results were obtained for CILs composed S-methyl-L-cysteine cation bis(trifluoromethane)sulfonimide anion, 2- 4-nitrobenzaldehyde with acetone cyclohexanone, giving product moderate yields 70–76% high ee values (up 96%).