13C and 1H NMR Spectral Studies of Some t-3-Carboxyethyl-r-2,c-6-diphenylpiperidine Derivatives

1H and 13C NMR spectra were recorded for six t-3-carboxyethyl-r-2,c-6-diphenylpiperidine derivatives 5–10 in CDCl3 and analysed. For t-3-carboxyethyl-r-2,c-6- diphenylpiperidin-4-one (5) difference NOE spectra, SEFT and H-C COSY spectra were also recorded. Contrary to the shielding magnitude expected for the nearby axial proton by the introduction of vicinal equatorial substituent, considerable deshielding magnitude is observed on H(2) in 5 and 6 due to the presence of equatorial carboxyethyl group at C-3. Substituent parameters for equatorial COOEt group were also derived and analysed. The effect of varying the nature of substituent at C-4 and nitrogen on the chemical shifts was also discussed.