Catalytic enantioselective aza-Henry reaction with broad substrate scope.J Am Chem Soc. 2005 Dec 21; 127(50):17622-3.JA
In situ generated azomethines from readily available precursors react with nitromethane in the presence of 120 mol % of CsOH.H2O and 12 mol % of quinine- and cinchonidine-derived quaternary ammonium chlorides to provide the corresponding aza-Henry adducts in good yields and very high selectivities. It represents the first general enantioselective aza-Henry method for azomethines derived from enolizable aldehydes, giving rise to enantiomeric excesses above 94%. In addition, the reactions with nitroethane afforded high diastereo- and enantioselectivities (syn:anti up to 95:5; up to 98% ee for syn).