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Proton and carbon-13 nuclear magnetic resonance studies of substituted pyrimidines. V13C, 1H coupling contsants for some methyl- and aminopyrimidines

✍ Scribed by Jacques Riand; Marie-Thérèse Chenon

Publisher
John Wiley and Sons
Year
1981
Tongue
English
Weight
356 KB
Volume
15
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

J(^13^C^1^H) coupling constants for some methyl‐ and aminopyrimidines have been determined by ^13^C NMR. Both the one‐bond and long‐bond and long‐range coupling constants follow general trends which can be summarized in a few simple rules. In particular, the ^3^J(C‐i,H) coupling constants between a ring carbon C‐i and the ring protons are larger than the ^2^J(C‐i,H) coupling constants. The opposite is observed for the couplings between the ring carbons and the methyl protons: ^3^J(C,Me). These general rules are very useful for the assignment of resonances in complex ^13^C spectra of pyrimidines and seem to be valid for other 6‐membered aromatic nitrogen heterocycles. Furthermore, the additivity of substituent effects on ^1^J (CH) for monosubstituted pyrimidines allows the estimation of ^1^J (CH) for polysubstituted pyrimidines with a very good accuracy.

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