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Conformational analysis. XXVII —A 1 H and 13 C NMR conformational study of cis ‐ and trans ‐annelated 2‐ p ‐nitrophenyl‐4,5‐ and ‐5,6‐tetramethyleneper‐hydro‐ and 2‐ p ‐chlorophenyl‐4,5‐ and ‐5,6‐tetramethylenedihydro‐1,3‐oxazines
Author(s) -
Pihlaja Kalevi,
Mattinen Jorma,
Bernáth Gábor,
Fülöp Ferenc
Publication year - 1986
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.1260240209
Subject(s) - vicinal , chemistry , coupling constant , chemical shift , nmr spectra database , spectral line , stereochemistry , cis–trans isomerism , crystallography , proton nmr , nuclear magnetic resonance spectroscopy , carbon 13 nmr , equilibrium constant , computational chemistry , organic chemistry , physics , particle physics , astronomy
The 400 MHz 1 H NMR spectra of cis ‐ and trans ‐annelated 2‐ p ‐nitrophenyl‐4,5‐ and ‐5,6‐tetramethyleneperhydro‐ and 2‐ p ‐chlorophenyl‐4,5‐ and ‐5,6‐tetramethylenedihydro‐1,3‐oxazines were recorded. The AMKX subspectra due to the protons at C‐4, C‐5 and C‐6 were analysed. Both cis ‐ and trans ‐annelated an equatorial 2‐ p ‐nitrophenyl group, as concluded from the values of their vicinal coupling constants and those in some simple model compounds, in agreement with the information given by 13 C NMR and low‐temperature experiements. Correspondingly, trans ‐2‐ p ‐chlorophenyl‐4,5‐ and ‐5,6‐tetramethylenedihydro‐1,3‐oxazines exist in anancomeric conformations; the cis isomers, however, are equilibrium mixtures of the N‐ or O‐eq and N‐ or O‐ax forms where the latter predominate, as shown by vicinal H, H coupling constants, 13 C chemical shifts and low‐temperature experiments.