Synthesis and Antimicrobial Activity of Novel Bis-1,2,3-triazol-1 H -4-yl-substituted Aryl Benzimidazole-2-thiol Derivat
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ynthesis and Antimicrobial Activity of Novel Bis-1,2,3-triazol-1H-4-yl-substituted Aryl Benzimidazole-2-thiol Derivatives Y. Aparnaa, G. Nirmalab, N. J. P. Subhashinib, L. N. Sharadab,*, and Sivan Sreekanthb a
b
Matrusri Engineering College, Saidabad, Telangana, Hyderabad, 500059 India Department of Chemistry, Osmania University, Telangana, Hyderabad, 500007 India *e-mail: [email protected] Received January 28, 2020; revised July 12, 2020; accepted August 1, 2020
Abstract—Novel bis-1,2,3-triazol-1H-4-yl-substituted aryl benzimidazole-2-thiol derivatives have been synthesized from 5-methoxy and 5-difluoromethoxy bis-propargyl substituted benzimidazole-2-thiols using the “click chemistry,” tested for their antimicrobial activity and subjected to molecular docking studies. Structures of the compounds have been elucidated from IR, NMR, and mass spectra. Keywords: benzimidazole-2-thiol, propargyl bromide, azide, click reaction, antimicrobial activity, molecular docking
DOI: 10.1134/S1070363220080186 INTRODUCTION 2-Mercapto benzimidazoles are well known as biologically and pharmacologically active compounds [1–4]. 1,2,3-Triazole derivatives [5–7] containing 2-mercapto benzimidazoles have been anticipated as promising pharmacophores. In the present study synthesis of such new derivatives was carried out by using the “click chemistry” [8]. The products were tested for their antimicrobial activity. RESULTS AND DISCUSSION Synthesis of 5-(difluoromethoxy)-1H-benzimidazole2-thiol and 5-methoxy-1H-benzo[d]imidazole-2-thiol was based on the known procedure [9, 10]. S- and N-bis propargylation of these compounds were also carried out according to the reported method [11]. The structures of bis propargylated compounds 3a, 3b were confirmed by 1H and 13C NMR and mass spectra. In 1H NMR spectrum of compound 3a the signal recorded at 3.72 ppm was attributed to the methylene group attached to sulfur atom and the singlet at 4.42 ppm corresponded to the methylene attached to nitrogen atom. Following coupling of semiproducts 3a, 3b with azides 4a–4f led to bis triazolyl-substituted arylbenzimidazole-2-thiol derivatives 5a–5l (Scheme 1) via the “click reaction” using 10 mol % of sodium ascorbate and 10 mol % CuSO4·5H2O as the catalysts.
Antimicrobial activity. Antimicrobial activity of the products was tested using the microtitre broth dilution method measuring zone of inhibition in mm. The newly synthesized compounds 5a–5l were tested in vitro at concentration of 10 μg/mL for their activity against Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, and Staphylococcus aureus. Standard antibacterial drug ciprofloxacin (10 μg/mL) was used as a standard. Each experiment was carried out in triplicates, and the average reading was recorded. The results of antibacterial activity are expressed in terms of zone of inhibition (Table 1). 90% Of growth inhibition was considered as MIC of the compound as per standard protocol. Triazole derivatives 5a–5l were dissolved in DMSO at 10 μg/mL concentration. The inhibition zones were meas
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