Eco-friendly synthesis, structural elucidation, computational investigation and in vitro antioxidant activity of a new N-tosylated benzimidazole derivative

Abstract

Synthesis of 2-(diethoxymethyl)-1-tosyl-1H-benzo[d]imidazole 5 in excellent yield was achieved from 2-(1-ethoxypropyl)-1H-benzo[d]imidazole by ionic liquid supported eco-friendly green protocol. The precursor, 2-(diethoxymethyl)-1H-benzo[d]imidazole was prepared from o-phenylenediamine in good yield. The compound 5 was characterized by 1H, 13C and mass spectroscopic analyses. Also, its structure was further confirmed by X-ray single crystal analysis. From Hirshfeld calculations, it was clear that the H…H (51.1 %), H…C (21.6 %), O…H (18.9 %) and N…H (6.3 %) interactions were the most dominant in the solid-state structure of compound 5. The crystal stability was controlled by the short distance of O3…H7 (2.556 Å), N2…H6 (2.555 Å) and H11C…H11C (1.964 Å). Natural bond orbital (NBO) calculations were used to calculate the different intramolecular charge transfer interactions in the synthesized benzimidazole molecule 5. In addition, the DFT calculations were used to predict its electronic and reactivity descriptors. Furthermore, the synthesized compound was examined for its antioxidant properties and it was found that the compound 5 exhibited potent antioxidant activity (IC50 value of 42.32 µM) when compared to the standard drug butylated hydroxyanisole (BHA) (IC50 value of 58.6 µM). In addition, the compound 5 showed significant tuberculosis activity (3.12 µg/mL) against Mycobacterium tuberculosis H37Rv when compared to the standard drug, ethambutol (1.56 µg/mL). The docking simulation was also performed for compound 5 which correlated well with the in vitro findings.