ENANTIOSELECTIVE SYNTHESIS OF HIGHLY FUNCTIONALIZED 4-PIPERIDONES BY THE ASYMMETRIC IMINO-DIELS-ALDER REACTION OF CHIRAL 2-AMINO-1,3-BUTADIENES

Chiral 2-amino-1,3-butadienes 1 derived from commercially available (S )-2-methoxymethylpyrrolidine react with aromatic N-trimethylsilylaldim ines and phenylaldimines in the presence of ZnCl2 to give, after the r eaction workup. 4-piperidones 4 and 6, respectively, with moderate to very high enantiomeric excesses. In addition, the absolute configurati ons of derivatives of 4a and 4g were determined by circular dichroism and NMR spectroscopy on the Mosher ester, respectively.