СТРУКТУРА САЛІЦИЛ ГІДРАЗОНУ 2-(5-АМІНО-4-ФЕНІЛ- 1,2,4-ТРИАЗОЛ-3-ІЛСУЛЬФАНІЛ)АЦЕТОГІДРАЗИДУ

Abstract

Polysubstituted functional derivatives of 1,2,4-triazole have been widely used for the treatment of a wide variety of diseases. In experimental studies, several derivatives of triazoles with a hydrazide fragment have been shown to exhibit anti-tuberculosis properties. Based on this, in our previous work, we have described the synthesis of 2-(5-amino-4-phenyl-1,2,4-triazol-3-ylsulfanyl) acetohydrazide which has a high similarity to the known antitubercular agent – isoniazid. In order to modify this compound, a condensation reaction was carried out with a salicylic aldehyde to form the corresponding Schiff base. The present study was devoted to a detailed analysis of the structural peculiarities of the Schiff base product of the reaction. The reaction with salicylic aldehyde was carried out in the acetic acid medium. It was found that in this case, the condensation product is formed selectively through the hydrazide group, while the amino group in position 5 of the 1,2,4-triazole cycle does not react. Such a low reactivity of the amino group of the triazole can be explained by the electron-acceptor effect of the 1,2,4-triazole moiety, which leads to decreasing the electron density over the amino group and, consequently, to the decreasing the nucleophilic properties. The 1H-NMR spectrum of the Schiff base was obtained and carefully examined to explain the molecule structure. The signal splitting is due to the formation of anti- and syn-forms of the hydrazone. In addition, the presence of the phenyl moiety hydroxyl group causes the possibility of the existence of additional isomeric structures through the hydrogen bonding. A significant difference in the chemical shifts of the S-methylene group, depending on the type of isomer, was found and explained in terms of E/Z-geometric isomers of azomethine group. The singlet at 3.77 ppm corresponds to the anti-isomer, and the singlet at 4.13 ppm corresponds to the syn-isomer. The analysis of the integral intensity of these two signals indicates the ratio of isomers anti: syn equals 55:45(%). The signals of the amino group form two singlets at 5.76 and 5.79 ppm. In the area from 6.84 ppm to 7.70 ppm, there are signals of aromatic protons.