α,α-Diarylprolinol-derived chiral ionic liquids: recoverable organocatalysts for the domino reaction between α,β-enals and N-protected hydroxylamines

Chiral ionic liquids bearing alpha alpha-diarylprolinol units were synthesized and applied for the first time as organocatalysts for the domino reaction between alpha beta-enals and N-protected hydroxylamines involving aza-Michael and intramolecular acetalization steps Corresponding 5-hydroxy-3-arylisoxazolidines with either an (S)- or (R)-configuration at C-3 were obtained in excellent yields (up to 94%) and with moderate to high enantioselectivities (64 to >99% ee) The ionic liquid supported catalyst can be easily recycled and reused for at least four times without a significant loss of chemical yield or enantioselectivity (C) 2010 Elsevier Ltd All rights reserved