Microwave Assisted Synthesis and Antibacterial Activity of New 1,3,4-Thiadiazoles and 1,2,4-Triazoles Derived from 2-{2-
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icrowave Assisted Synthesis and Antibacterial Activity of New 1,3,4-Thiadiazoles and 1,2,4-Triazoles Derived from 2-{2-[2-(4-Fluorophenyl)-4-methylthiazol-5-yl]1H-benzo[d]imidazol-1-yl}acetohydrazide N. R. Darekara,b, B. K. Karalea, H. N. Akolkara, and A. S. Burungaleb,* a P.G.
and Research, Department of Chemistry, Rayat Shikshan Sanstha’s Radhabai Kale Mahila Mahavidyalaya, Maharashtra, Ahmednagar, 414001 India b P.G. and Research, Department of Chemistry, Rayat Shikshan Sanstha’s S. M. Joshi College, Hadapsar, Maharashtra, Pune, 411028 India *e-mail: [email protected] Received July 7, 2020; revised August 18, 2020; accepted August 31, 2020
Abstract—A series of novel derivatives of 1-(2-{2-[2-(4-fluorophenyl)-4-methylthiazol-5-yl]-1H-benzo[d]imidazol1-yl}acetyl)-4-phenylthiosemicarbazide, 5-({2-[2-(4-fluorophenyl)-4-methylthiazol-5-yl]-1H-benzo[d]imidazol1-yl}methyl)-4-phenyl-4H-1,2,4-triazole-3-thiol and 5-({2-[2-(4-fluorophenyl)-4-methylthiazol-5-yl]-1H-benzo[d]imidazol-1-yl}methyl)-N-phenyl-1,3,4-thiadiazol-2-amine have been synthesized by the conventional method as well as using MW irradiation. All newly synthesized compounds have been tested for antibacterial activity. Several products have demonstrated moderate activity against gram positive and gram negative bacterial strains. Keywords: 1,3,4-thiadiazole, 1,2,4-triazole, microwave irradiation, antibacterial activity
DOI: 10.1134/S1070363220090200 Antimycobacterial and antimicrobial activities have been well established and studied in depth for benzimidazole [1, 2], thiazole [3, 4], 1,3,4-thiadiazole [5–7], and 1,2,4-triazole [8, 9] derivatives. Pharmacological importance associated with those compounds inspired us to synthesize novel benzimidazole and thiazole containing 1,3,4-thiadiazoles and 1,2,4triazoles under conventional and MW irradiation. All newly synthesized compounds were evaluated for their antibacterial activity. RESULTS AND DISCUSSION Synthesis of 2-{2-[2-(4-fluorophenyl)-4-methylthiazol-5-yl]-1H-benzo[d]imidazol-1-yl}acetohydrazide 6 was carried out by the known method (Scheme 1) [10–12]. A novel series of 1-(2-{2-[2-(4-fluorophenyl)-4methylthiazol-5-yl]-1H-benzo[d]imidazol-1-yl}acetyl)4-phenylthiosemicarbazide 7a–7e was synthesized from the intermediate 6 and substituted aryl isothiocyanates by conventional method and under MW irradiation [10, 13]. Their molecular structures were supported by
IR, 1H and 13C NMR spectra. Reaction of compounds 7a–7e in presence of NaOH under conventional conditions or MW irradiation gave 1,2,4-triazole derivatives 8a–8e [10, 13]. In IR spectra of the products 8a–8e no bands at ca. 3100 cm–1 characteristic for –NH group were recorded. In 1H NMR spectra of those compounds characteristic singlets of S–H were recorded at ca. 14.00 ppm. Similar reaction of compounds 7a–7e in acidic media under conventional conditions or MW irradiation gave 1,3,4-thiadiazoles 9a–9e [10, 13]. The NH group of compound 9a was recorded in IR spectrum by the band at 3201 cm–1 and in 1H NMR spectrum by a singlet at 9.50 ppm. The
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