Highly Enantioselective Phase-Transfer-Catalyzed Aza-Henry Reaction

Significance

A new catalytic enantioselective approach of the aza-Henry reaction between nitromethane and N-carbamoyl imines generated in situ from α-amido sulfones is described. This reaction proceeds in the presence of a chiral phase-transfer organocatalyst (the commercially available N-benzyl quininium chloride A) and a strong base (KOH). The phase-transfer catalyst has a dual function, first it reacts with the α-amido sulfone to form the imine in situ and then activates the nitromethane for asymmetric nucleophilic addition on the generated imine. Using this simple process optical active N-protected β-nitroamines were synthesized under mild reaction conditions with high yields and enantioselectivities and the first catalytic asymmetric aza-Henry reaction using N-carbamoyl imines derived from enolizable aldehydes has been developed.