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

•Four new compounds are characterised using IR, mass and advanced NMR techniques.•Compounds showed doubling of all the signals due to syn and anti rotamers at RT.•The energy barrier for N-CO rotation of one of the compounds was determined.•The equilibrium observed between the syn rotamer of TB1 and anti rotamer of TB2.•All the compounds were screened for their antibacterial & antifungal activities.

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.

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