Pyridinium azolate inner salts

Heterocyclic Betaines Pyridinium (Imidazolium) Azolate Inner Salts with Several Interannular Linkages ... 

Methods of synthesis leading to pyridinium (imidazolium) azolate inner salts and related compounds with a betaine character 1 can be varied. In almost all cases, their protonated compounds azolylpyridinium (imidazolium) salts with several interannular linkages 2 are useful as synthetic intermediates (Scheme 1). These quaternary salts of nitrogen heteroaromatic compounds 2 allow us to deepen the study of classical reactions and seek suitable alternatives for their preparation. 

Pyridinium(imidazolium) inner azolate salts and molecules with a betaine character of general type 1 are attractive substrates from the viewpoint of structural chemistry, as mentioned in the Introduction. This ensemble of compounds offers the possibility of two terminal heterocyclic rings, joined through several spacers, with extreme characteristics within heteroaromatic systems a 7r-deficient nucleus (cation) and a 7r-excessive nucleus (anion). The high dipolar character is the distinctive feature offered by these compounds and has a powerful influence on their physical and chemical properties. 

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