Conformational analysis of 2,6-diarylpiperidin-4-one hydrazones by X-ray diffraction and NMR spectroscopy

A new series of 3t-alkyl-2r,6c-diarylpiperidin-4-one N-isonicotinoylhydrazones (12–22) derived from the condensation of 3t-alkyl-2r,6c-diarylpiperidin-4-ones with isoniazid (INH) is reported. Newly synthesized compounds have been characterized by using elemental analysis, IR, 1H, 13C and 2D NMR spectral analysis. Moreover, representative crystal structure of 3,3-dimethyl-2r,6c-diarylpiperidin-4-one N-isonicotinoylhydrazone has been determined by X-ray diffraction analysis. ta revealed that two geometrical isomers (E and Z) are formed in all cases, and the piperidine ring adopts chair conformation. Whereas in solid state the compounds have E configuration about the CN bond. These conclusions have also been confirmed by X-ray data of compound 16.