Synthesis, Structure Elucidation and Determination of Acid Dissociation Constant, Tautomerism of Pyrido [1,2-a] benzimidazole-2,4-dione
It has been seen that keto form is dominated when the spectral data from IR and NMR techniques for identification studies was taken into consideration. The results of IR spectrums showed two carbonyl peaks and no hydroxyl peaks in addition to the results of 1 H-NMR spectrums explained that there are methylene peak between two carbonyls and the other methylene peak and no aromatic proton peaks for pyridine ring causing as a result of tautomerism. The results of 13C-NMR spectrums showed also two peaks of carbons from carbonyls and no aromatic carbons peaks from the pyridine ring as well. The acidity constant study ended up using by UV spectrophotometer shows, the possible form as keto form. In this pronounced study, benzimidazole results were employed to compare the compound, 7. On the other hand, the results of Gaussian 03 program were utilized to support this situation. When the tautomerism tests that performed in there mediums which are acidic, basic and neutral were searched, the keto form was decided as predominant. All of these results have proved that the compound, 7, recrystallized as keto form. It has been reported that some pyrido[1,2-a]benzimidazolone derivatives existed on keto forms6 . This situation has supported our study and results as well.
ACTA PHARMACEUTICA SCIENCIA Dergisi 54/3. Sayısı İçin Tıklayınız.