Conformational Studies of Some t(4)-Acetoxy-r(2),c(6)-diphenyl-N-acetylpiperidines Using 1H NMR Spectra. Evidence for Contribution of Boat Forms with a Substituent in the Flagpole Position
✍ Scribed by K. Pandiarajan; A. Manimekalai; N. Kalaiselvi
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 368 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
The NOESY spectrum and vicinal coupling constants of t(4)-acetoxy-3,3-dimethyl-r(2),c(6)-diphenyl-Nacetylpiperidine suggest that the compound adopts a chair conformation with axial phenyl groups. The vicinal coupling constants of t(4)-acetoxy-r(2),c(6)-diphenyl-N-acetylpiperidine could be accounted for by an equilibrium mixture of the chair conformation with axial phenyl groups and a boat conformation with one phenyl group in the Ñagpole position. The vicinal coupling constants suggest that in the case of t(4)-acetoxy-t(3)-methyl-r(2),c(6)diphenyl-N-acetylpiperidine another boat conformation with the acetoxyl group in the Ñagpole position also makes some contribution andt(4)-acetoxy-t(3),t(5)-dimethyl-r(2),c(6)-diphenyl-N-acetylpiperidine exists largely in a boat conformation with the acetoxyl group in the Ñagpole position. The Ñattened chair conformation, proposed earlier for the piperidine ring in N-acetylsolasodine, has been shown to be incorrect and a boat conformation without allylic strain is assigned. The earlier interpretation of spectral results on N-nitroso-2a-methyldecahydroquinoline is also re-examined.