Organocatalysis in Ionic Liquids: Highly Efficient L-Proline-Catalyzed Direct Asymmetric Mannich Reactions Involving Ketone and Aldehyde Nucleophiles

Abstract

Proline-catalyzed direct asymmetric Mannich reactions of N-PMP protected α-imino ethyl glyoxylate with various aldehydes and ketones in ionic liquids afforded both α- and β-amino acid derivatives with excellent yields and enantioselectivities, providing facile product isolation, catalyst recycling, and significantly improved reaction rates, ca 4- to 50-fold. Three component Mannich reactions involving other imines also worked well in ionic liquids. Significant advantages and limitations of ionic liquid solvents in this reaction have been revealed.