Synthesis and structural study of 3t-isopropyl-2r,6c-diphenyl-4-oxopiperidinium nitrate and N-benzoyl-3t-isopropyl-2r,6c-diphenylpiperidin-4-one oxime

3t-Isopropyl-2r,6c-diphenyl-4-oxopiperidinium nitrate (2) and N-benzoyl-3t-isopropyl-2r,6c-diphenylpiperidin-4-one oxime (4) have been synthesized. The crystal structures of 2 and 4 have been determined. 1H NMR, 13C NMR, 1H–1H COSY and HSQC spectra also have been recorded for both the compounds. The piperidine ring in 2 adopts chair conformation in the solid state and in solution. In 4 the configuration about the CN bond is E. In the solid state the piperidine ring in 4 adopts boat conformation 4B2 with the phenyl group at C-2 in the flagpole position and the phenyl group at C-6 in the boat-equatorial position. The isopropyl group is in the boat-axial position. In solution alternative chair conformation 4CA with axial phenyl group may contribute to extent of 11% to 4.