1H and 13C NMR conformational study of N-substituted hexahydrocyclopent[e][1,3]-oxazin-4-ones and hexahydro-2H-1,3-benzoxazin-4-ones

A 1H and 13C NMR conformational study of four cis‐fused N‐substituted hexahydrocyclopent[e][1,3]oxazin‐4‐ones and four cis‐fused hexahydro‐2H‐1,3‐benzoxazin‐4‐ones at various temperatures revealed several dynamic conformational processes to be in effect. These included a clear conformational equilib...

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Bibliographic Details
Published in:Magnetic resonance in chemistry 2001-03, Vol.39 (3), p.141-146
Main Authors: Shaikhutdinov, Roustem A., Klika, Karel D., Fülöp, Ferenc, Pihlaja, Kalevi
Format: Article
Language:English
Subjects:
13C NMR
1H NMR
conformational analysis
heterocycles
hydrogen bonding
NMR
restricted rotation
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Summary:A 1H and 13C NMR conformational study of four cis‐fused N‐substituted hexahydrocyclopent[e][1,3]oxazin‐4‐ones and four cis‐fused hexahydro‐2H‐1,3‐benzoxazin‐4‐ones at various temperatures revealed several dynamic conformational processes to be in effect. These included a clear conformational equilibrium between the O‐in (major conformer) and O‐out ring forms in the hexahydro‐2H‐1,3‐benzoxazin‐4‐ones, an equilibrium consisting of two intramolecularly hydrogen bonded forms (between the hydroxyl proton and the carbonyl oxygen attached to C4 or the ethereal oxygen) and a non‐hydrogen bonded form in two compounds, and a restricted rotation about the amide C N bond in the CH2OCONHC6H4X‐p substituents (X = H, Cl) in three other compounds. Copyright © 2001 John Wiley & Sons, Ltd.
ISSN:0749-1581
1097-458X
DOI:10.1002/mrc.816