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Synthetic applications of N–N linked heterocycles. Part 18 —substituent effects on the 13 C NMR spectra in N ‐(4‐Aryliminio‐2,6‐dimethylpyridin‐1‐yl)pyridinium bistetra‐fluoroborates, and some variable‐temperature 1 H NMR measurements
Author(s) -
Sammes Michael P.,
Ho KingWah,
Katritzky Alan R.
Publication year - 1985
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.1260230908
Subject(s) - chemistry , substituent , isomerization , aryl , nmr spectra database , imine , deprotonation , pyridinium , chemical shift , medicinal chemistry , carbon 13 nmr , stereochemistry , ring (chemistry) , iminium , spectral line , organic chemistry , catalysis , ion , alkyl , physics , astronomy
The 13 C and 1 H NMR spectra have been recorded and fully interpreted for a series of N ‐(4‐Aryliminio‐2,6‐dimethylpyridin‐1‐yl)pyridinium bistetrafluoroborates having a variety of phenyl para substituents. Correlations between 13 C chemical shifts and both Hammett and Taft dual‐substituent parameters for the aryl substituents were found for C‐2, C‐6, C‐3 and C‐5 of the iminiopyridinyl ring (but not for C‐4), and also for the aryl carbon atom attached to the imino group. Data from variable‐temperature 1 H NMR spectra suggest that isomerization about the iminium CN bond is by the little known deprotonation‐imine isomerization‐reprotonation mechanism.