Synthesis, Characterization and Antimicrobial Activities of Some Thiazole Derivatives E. M. Sharshira1, N. M. M. Hamada2,*
Department of Chemistry, Faculty of Science, Alexandria University, Alexandria, Egypt Department of Chemistry, Faculty of Education, Alexandria University, Alexandria, Egypt
2-hydrazinyl-N-(4-phenylthiazol-2-yl) acetamide 8a-c by treating with chalcones 3a-d. The structures of the newly synthesized compounds were determined on the basis of their elemental analyses and spectroscopic data such as IR and HNMR spectra.The antimicrobial activity of isolated heterocyclic compounds was evaluated against Gram-positive, Gram-negative bacteria and fungi. Most of the compounds showed a moderate degree of potent antimicrobial activity.
Abstract In this work a series of thiazoles 9a-l were prepared by incorporation of pyrazoline ring at position 2 of
Keywords Chalcones, Thiazoles, Pyrazolines, Antimicrobial
appropriately substituted benzaldehydes and cyclopropylmethyl ketone[16,30]. 2-aminothiazoles 6a-c[31,32], were obtained in good yields by cyclocondensation of appropriately substituted acetophenones with thiourea in presence of bromine as reported in the literature. Chloroacetamides 7a-c was obtained by reacting of 2-aminothiazoles 6a-c with chloroacetyl chloride in presence of pyridine. The IR of 7a-c showed the presence of bands characteristic for C=N at 1631-1642 cm-1 and an amide function at 1661-1671 (C=O) and 3160-3184 cm-1 (NH). The 1H NMR of 7a-c revealed a broad singlet at δ = 10.32-10.41 ppm characteristic for a secondary amine group, a multiplet at δ = 7.11-7.57 ppm for aromatic protons and a thiazolyl-C5-H proton as a singlet at 6.49-6.59 ppm. When chloroacetamides 7a-c were heated with hydrazine hydrate in ethanol, hydrazines 8a-c were obtained in a moderate to good yields. The structures of the isolated compounds were determined by spectral methods. The IR of 8a-c revealed characteristic bands for C=N at 1637-1641, C=O at 1664-1669, primary and secondary amines at 3224-3278 and 3166-3178 cm-1. The 1H NMR spectra showed the presence of three broad exchangeable singlets at δ = 9.24-9.29 ppm, δ = 10.31-10.33 ppm and δ = 11.45-11.77 ppm characteristic for -NH-NH2 and NH protons, while the thiazolyl-C5-H and O=C-CH2 protons appears at δ = 6.47-6.55 ppm and δ = 4.36-4.39 ppm, respectively. The aromatic protons of 8a-c appears as a multiplet at δ = 7.15-7.66 ppm. Finally, when chalcones 3a-d were heated with hydrazines 8a-c in dioxane containing few drops of acetic acid, pyrazoline derivatives 9a-l were obtained. The structures of 9a-l were determined by IR and NMR spectra its IR spectra showed the characteristic bands for C=N at 1631-1645 and amide function at 1659-1671 (C=O) and 3166-3182 cm-1 (NH). The 1H NMR of the pyrazole derivatives 9a-l showed the presence of one broad exchangeable singlet at δ = 10.31-10.47 ppm (NH), a multiplet at δ =
Thiazoles and pyrazoles have been reported to show pharmacological activities. Some of them are used as medicines. According to literature survey, thiazoles were reported to possess antimicrobial[2-5], analgesic, antiinflammatory, anticonvulsant, cardiotonic, anticancer[10,11], antitubercular and anthelmintic activities. Antimicrobial activities of some substituted thiazoles are well established because it posses (S-C=N) toxophoric unit. Thiazoles have enhanced lipid solubility with hydrophilicity. Thiazoles are easily metabolized by routine biochemical reactions and are non-carcinogenic in nature . In addition, pyrazoles are reported as antimicrobial[15-17], antiviral, antipyretic, anti-inflammatory, antidepressant, tranquillizing, anticancer[23,24], antihypertensive, antiarrhythmi, psychoanaleptic, anticonvulsant and antidiabetic activities.
2. Results and...