Chiral michael additions of acetamidomalonate to α-enones : Nuclear magnetic resonance and high-performance liquid chromatographic resolution of enantiomers

Abstract

Solid—liquid phase transfer catalysis without addition of solvent was used to induce asymmetric Michael addition. Determinations of enantiomer ratios by chiral liquid chromatography and by NMR chiral shifts using europium salts are compared. The effect of chiral phase transfer catalyst structure, addition of solvent and addition of molecular sieves are discussed. The best enantiomeric excess are obtained with N-benzyl-N-methylephedrinium salts in the absence of solvent and in the presence of molecular sieves.