The synthesis of benzimidazole derivatives, similar to dibazole, was carried out using two methods. According to the first, 1, 2-Phenylenediamine condensed with excess quantity of 2-chlorophenylacetic acid in the presence of orthoboric acid at a temperature of 150 °C. After treatment and crystallization, the yield of 2-(2-chlorobenzyl)-1H-benzimidazole was 36 %. In the second method, 1, 2-phenylenediamine was reacted with an excess of phenoxyacetic acid and 1-naphthylacetic acid in the presence of orthoboric acid in an o-xylene solvent at boiling point. Thus, 2-(phenoxymethyl)-1H-benzimidazole was obtained in 93 % yield, and 2-(1-naphthylmethyl)-1H-benzimidazole in 35 % yield. The structure of all obtained benzimidazoles was confirmed by 1H-NMR spectroscopy. In the spectra of 2-(phenoxymethyl)-1H-benzimidazole and 2-(2-chlorobenzyl)-1H-benzimidazole signals of protons of the methyl group were identified in the form of a singlet with a chemical shift of 5.28 and 4.35 ppm. Multiplets of eight and nine aromatic protons are in the region of 6.94–7.51 and 6.23–7.62 ppm. The aromatic amine proton singlet has a chemical shift of 12.61 and 12.32 ppm. respectively. Similar signals confirmed the structure of 2-(1-naphthylmethyl)-1H-benzimidazole. Potential antiviral activity by PASSOnline program for 2-(phenylmethyl)-1H-benzimidazole (dibazole), 2-(phenoxymethyl)-1H-benzimidazole, 2-(2-chlorophenylmethyl)-1H-benzimidazole, 2-(1-naphthylmethyl)-1H-benzimidazole was 0.704, 0.667, 0.629, and 0.613, respectively. The range of potential psychotropic activity differs and decreases in the following order: 2-(phenoxymethyl)-1H-benzimidazole 0.833, 2-(phenylmethyl)-1H-benzimidazole 0.758, 2-(1-naphthylmethyl)-1H-benzimidazole 0.687, 2-(2-chlorobenzyl)-1H-benzimidazole 0.621.
dibazole, benzimidazole, condensation, antiviral activity, PASSOnline.
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