One-Pot Synthesis of Highly Functionalized Piperidines

Significance

A one-pot, atom- and step-economical five-component condensation reaction for the synthesis of highly substituted piperidines in fair to good yields is reported. The trans stereo­chemistry of the 2,6-disubstituted piperidine product was confirmed by single crystal X-ray analysis. Reasonable yields of piperidines are obtained either by reaction of the enamine A with imine B and benzaldehyde or the β-keto ester C and imine D with aniline. Most convenient is the in situ formation of both enamine and the imine and their subsequent condensation/cyclization to the final product under InCl₃ catalysis.