Synthesis, characterization stereochemistry and anti-bacterial evaluation of certain N-acyl-c-3,t-3-dimethyl-r-2,c-6-diphenylpiperidin-4-ones

• Five compounds have been synthesized and characterized using various NMR techniques.
• The energy barrier for N–CO rotation of one of the compounds has been determined.
• The N–CO function adopts coplanar orientation.
• N-Acyl compounds prefer distorted boat conformation rather than more common chair.
• Four of the compounds show significant antibacterial activity.

A new series of N-acyl-c-3,t-3-dimethyl-r-2,c-6-diphenylpiperidin-4-ones 2–6 has been synthesized and characterized using IR, mass, 1H, 13C, DEPT and 2D (COSY and HSQC) NMR spectral techniques. The NMR spectral data indicate that the N-acylpiperidin-4-ones 2–6 prefer to exist in a distorted boat conformation B1 with coplanar orientation of N–C=O moiety. The stereodynamics of these systems have been studied by recording the dynamic 1H NMR spectra of compound 4, and the energy barrier for N–CO rotation is determined to be 52.75 kJ/mol. Furthermore the compounds 1–5 show significant antibacterial activity.

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