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NMR spectra and stereochemistry of perhydrooxazolo[3,4‐ a ]pyridines
Author(s) -
Crabb Trevor A.,
Trethewey Andrew N.,
Takeuchi Yoshito
Publication year - 1988
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.1260260413
Subject(s) - conformational isomerism , chemistry , epimer , isopropyl , pyridine , alkyl , equilibrium constant , spectral line , cis–trans isomerism , stereochemistry , nuclear magnetic resonance spectroscopy , nmr spectra database , proton nmr , medicinal chemistry , molecule , organic chemistry , physics , astronomy
Low‐temperature 13 C and 1 H NMR spectra show perhydrooxazolo[3,4]‐ a pyridine to exist in CDCl 3 CFCl 3 solution at 183 K as an equilibrium between 73% trans ‐fused and 27% O ‐inside cis ‐fused conformers. cis ‐(H‐1, H‐8a)‐1‐Alkylperhydrooxazolo‐[3,4‐ a ]pyridines (alkyl = methyl, ethyl, isopropyl) adopt equilibria heavily biased towards the trans ‐fused conformers, whereas the epimers adopt 18% O ‐inside cis ‐fused = 82% trans ‐fused comformational equilibria at 183 K in CDCl 3 CFCl 3 . At 190 K in CDCl 3 cis ‐(H‐6, H‐8a)‐6‐ethylperhydrooxazolo[3,4‐ a ]pyridine adopts an equilibrium containing ca 3% trans ‐fused conformer in equilibrium with 97% O ‐inside cis ‐fused conformer.