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

Abstract

Data of 1 Н and 13 С 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 downfi eld shift of the bridging proton signal in the 1 Н NMR spectrum by 0.6-0.7 ppm and an increase in the corresponding direct coupling constant 13 С-1 Н by 1.5-2.0 Hz. These variations in the spectral parameters can be effi ciently used in the conformational analysis for establishing with the use of NMR method which conformers are predominantly populated in the heterocyclic compounds.