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SPECTRAL AND QUANTUM-CHEMICAL STUDY OF NONEQUIVALENCE OF METHYLENE PROTONS IN 1,4-DIHYDROPYRIDINE DERIVATIVES

M. Петрова, Р. Мухамадеев, А. Чесноков, Б. Виганте, Б. Чекавичус, А. Плотниеце, Г. Дубурс, Э. Лиепиньш
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Abstract


Structural characteristics  of 1,4-dihydropyridines influencing the nonequivalence of the diastereotopic methylene protons in substituents at positions 2 and 6 were studied. The combined effect of magnetically anisotropic groups and intramolecular hydrogen bonds leads to a considerable difference in the chemical shifts of the methylene protons of the AB system. The unusual reversible temperature evolution of these proton signals in monocyclic 1,4-dihydropyridines is associated with two simultaneous conformational processes. It was estimated that the energetically most favorable conformations are stabilized by an intramolecular СН···О hydrogen bond.

How to Cite
Petrova, M.; Muhamadejev, R.; Chesnokov, A.; Vigante, B.; Cekavicus, B.; Plotniece, A.; Duburs, G.; Liepinsh, E. Chem. Heterocycl. Compd. 2014, 49, 1631. [Khim. Geterotsikl. Soedin. 2013, 1760.]

For this article in the English edition see DOI 10.1007/s10593-014-1414-6


Keywords


1,4-dihydropyridines; 1Н NMR spectroscopy; hydrogen bond; nonequivalence of methylene protons; quantum-chemical calculations

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