Intramolecular hydrogen bonds C-H⋯N in bisheterocyclic compounds according to 1H and 13C NMR data

Data of 1H and 13C NMR spectra show that in 2,2′-bipyridyl, 1-vinyl-2(2′-pyridyl)benzimidazole, 1-vinyl-3-vinylsulfanyl-5-(2-furyl)-1,2,4-triazole, and 1-vinyl-5-vinylsulfanyl-3-(2-furyl)-5-vinylthio-1,2,4-triazole exists a weak intramolecular hydrogen bond between the heterocyclic fragments. It causes a downfield shift of the bridging proton signal in the 1H NMR spectrum by 0.6–0.7 ppm and an increase in the corresponding direct coupling constant 13C-1H by 1.5–2.0 Hz. These variations in the spectral parameters can be efficiently used in the conformational analysis for establishing with the use of NMR method which conformers are predominantly populated in the heterocyclic compounds.