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1 H and 13 C NMR spectral assignments of some novel 2,4,6,8‐tetraaryl‐3,7‐diazabicyclo[3.3.1]nonan‐9‐one derivatives
Author(s) -
Parthiban Paramasivam,
Ramachandran Rajamanickam,
Aridoss Gopalakrishnan,
Kabilan Senthamaraikannan
Publication year - 2008
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2243
Subject(s) - chemistry , aryl , proton nmr , molecule , chemical shift , cyclohexane conformation , nmr spectra database , stereochemistry , group (periodic table) , spectral line , carbon 13 nmr , crystallography , organic chemistry , hydrogen bond , alkyl , physics , astronomy
The 1 H and 13 C NMR spectra of 2,4,6,8‐tetraaryl‐3,7‐diazabicyclo[3.3.1]nonan‐9‐ones (1–2), oximes (3–8) and O ‐benzyl oximes (9–12) were recorded. The chemical shifts were unambiguously assigned using 1D and 2D NMR spectral data. The results clearly indicate that the compounds exist in chair‐boat conformation with equatorial and axial orientation of the aryl groups in the chair and boat forms, respectively. Since the molecules are flexible and dynamic in solution, the chair and boat forms are mutually interconvertible. In 3–12, because of the effect of oximation/oximination, all the protons in the heterobicyclic systems gave distinct signals except the benzylic protons of the boat form. In all synthesized compounds, the aryl group protons at C‐6,8 are shielded by the aryl groups at C‐2,4 and therefore appear in the lower frequency region than the aryl groups at C‐2,4. Copyright © 2008 John Wiley & Sons, Ltd.