Acid-base properties of imidazo[2,1-b] tiazole and tiazolo[3,2- а] benzimidazole derivatives

For over 30 years, azomethine groups have been attracting significant research interest due to their high electrophilicity formed under the influence of strong electrophilic substituents. The combination of a polyhalidealkyl group and functional substitutes in close proximity to the azomethine bond reveals a wide range of possible chemical transformations, one of which is the production of heterocyclic derivatives. Since heterocyclic compounds are of interest in terms of their medical and synthetic prospects, research into the NH-acidity of these compounds is highly relevant. Information on the acid-base properties of such compounds is useful for predicting their reactivity and physical-chemical properties. The potentiometric titration method was used to determine the dissociation constants of the substances under study. As a result, titration curves with a different number of dissociation stages (their number was determined by the number of NH-groups) were obtained, which showed a clear jump in the potential of the indicating electrode. The experimental determination of the acid-base behaviour of the synthesized sulphonylamine-substituted imidazo[2,1-b]tiazoles and thiazolo[3,2-a]benzimidazoles was carried out in dimethylsulphoxide medium. The semi-neutralization potentials were determined using titration curves. A relationship between acidity constants (pK_A) and semi-neutralization potentials was determined. The pK_A =f (E^1/2) dependence allows the constants of NH-acidity for newly synthesized compounds in dimethylsulphoxide medium to be predicted. The statistical range of the conducted potentiometric titration was determined. The obtained dissociation constants showed a high level of intermediate precision. The variation coefficients ranged from 0.34 to 1.48%. The PASS software was used to calculate the potential of biological activity (Pa) of the compounds under study. The relationship between NH-acidity and biological potential is still ambiguous.

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