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