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Autori: Alexandru C. Razus, Liviu Birzan, Oana Zaharia and Cristian Enache
Editorial: J. Heterocycl. Chem., 45, p.1139-48, 2008.
2-(Azulen-1-yl)-4,6-diphenyl substituted pyranylium salts, pyridinium salts and pyridines were efficiently synthesized and the new obtained compounds were completely characterized. Comparative structural analysis between these compounds and their corresponding isomers which contain azulen-1-yl moiety in the 4 position of the heterocycles were carried out. These studies are based on calculated dihedral angles formed between central heterocycle and the aromatic substituents and on the obtained electronic and NMR spectra. Due to the non-symmetrical substitution of the heterocycle moiety in the herein reported pyridinium salts, the substitution groups of the quaternary nitrogen atom are prochiral. This property leads to the non-equivalence of gem-protons or gem–methyl groups of N-substituents in the 1H-NMR spectra of the synthesized pyridinium salts.
Cuvinte cheie: azulene, nitrogen and oxygen heterocycles, prochirality, NMR spectroscopy