Asymmetric Conjugate Addition of Malonate Esters to α,β-Unsaturated N-Sulfonyl Imines: An Expeditious Route to Chiral δ-Aminoesters and Piperidones

The asymmetric conjugate addition of malonate esters to alpha,beta-unsaturated N-sulfonyl imines is catalyzed by PyBOX/La(OTf)(3) complexes in the presence of 4 angstrom MS. The reaction gives the corresponding E enamines bearing a stereogenic center at the allylic position with good yields and enantiomeric ratios up to 97:3. This reaction provides a synthetic entry to chiral delta-aminoesters and piperidones.