Synthesis, characterisation, stereochemistry and biological activity of N-formylpiperidin-4-ones

A new series of N-formyl-2,6-bis(4-methoxyphenyl)piperidin-4-ones 5–8 has been synthesized and characterised using IR, mass and 1H, 13C, DEPT and 2D (COSY and HSQC) NMR spectral techniques. The NMR spectral data indicated that the N-formylpiperidin-4-ones 5–8 prefer to exist in a conformational equilibrium between a syn rotamer with a twist boat conformation (TB1) and an anti rotamer with a twist boat conformation (TB2) in solution. The stereodynamics of these systems have been studied by recording the dynamic 1H NMR spectra of compound 5, and the energy barrier for the N-CO rotation was determined to be 64.3 kJ/mol. All of the synthesized compounds (5–8) were screened for their biological activity.