Heterocyclic Betaines. 19. Unconventional Extended .pi.-Systems Containing Pyridinium and Benzimidazolate Subunits. Synthesis and Characterization
摘要:
A convenient synthesis and characterization of several examples of (E)-2- [2-(1-alkyl-3-pyridinio): vinyl] benzimidazolate inner salts and (E)-1-alkyl-2(or 4)-[2- (benzimidazol-2-ylidene)ethylidene]-dihydropyridines with a betaine character is reported. Their structural aspects are discussed mainly on the basis of the H-1 NMR data and experimental dipole moment values (11.6-13.0 D). The experimental information available for (E)-1-alkyl-2(or 4)- [2- (benzimidazol-2-ylidene)ethylidene] dihydrepyridines (A <-> B) is consistent with a betaine character, and the dipolar form (B) has been shown to make an important contribution to the ground state.
An Advantageous Synthesis of 2-Substituted Benzimidazoles Using Polyphosphoric Acid. 2-(Pyridyl)-1H-benzimidazoles, 1-Alkyl-(1H-benzimidazol-2-yl)pyridinium Salts, their Homologues and Vinylogues