Studies on some 5-chloro-2-benzoxazolinone thiosemicarbazide, 1,3,4-thiadiazole ve 1,2,4-triazole-5-thione derivates

Studies on Some 5-Chloro-2-benzoxazolinone Thiosemicarbazide, 1,3,4-Thiadiazole ve 1,2,4-Triazole-5-thione Derivates, Hacettepe University, Institute of Health Sciences, MS Thesis in Pharmaceutical Chemistry, Ankara 2018. In this study, nineteen new compounds which have 1-[2-(5-chloro-2-benzoxazolinone-3-yl)acetyl]-4-substitutedthiosemicarbazide, 3-[(5-chloro-2-benzoxazolinone-3-yl)methyl]-4-substituted-1H-1,2,4-triazole-5(4H)-thione, 2-substitutedamino-5-[(5-chloro-2-benzoxazolinone-3-yl)methyl]-1,3,4-thiadiazole and 3-[(5-chloro-2-benzoxazolinone-3-yl)methyl]-4-substituted-5-methylthio-1H-1,2,4-triazole structures were synthesized and screened for their antimicrobial activities. Starting compound, 2-(5-chloro-2-benzoxazolinone-3-yl)acetylhydrazine was obtained by the reaction of 5-chloro-2-benzoxazolinone with ethyl bromoacetate followed by hydrazine hydrate. This compound was reacted with methyl, ethyl, allyl, cyclohexyl and phenyl isothiocyanates to obtained 1-[2-(5-chloro-2-benzoxazolinone-3-yl)acetyl]-4-substituted thiosemicarbazides (Compounds 1-5). Compounds 1-5 were cyclized into 3-[(5-chloro-2-benzoxazolinone-3-yl)methyl]-4-substituted-1H-1,2,4-triazole-5(4H)-thiones (Compounds 6-10) and 2-substitutedamino-5-[(5-chloro-2-benzoxazolinone-3-yl)methyl]-1,3,4-thiadiazole (Compounds 15-19) in alkaline and acidic medium respectively. 3-[(5-Chloro-2-benzoxazolinone-3-yl)methyl]-4-substituted-5-methylthio-1H-1,2,4-triazoles (Compounds 11-14) were prepared by reaction of compounds 6-10 with methyl iodide in alkali medium. The physical properties of the synthesized compounds were determined. Their structures have been elucidated by spectral methods (IR, 1H-NMR, 13C-NMR, ESI-MS) and elemental analyses. Their antimicrobial activities were investigated by microdilution method against some bacteria such as Enterococcus faecalis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa and some fungi such as Candida albicans, C. krusei and C. parapsilosis. The synthesized compounds do not show strong antimicrobial activity but it has been found that antifungal activities are higher than their antibacterial activities. Keywords: Thiosemicarbazide, 1,2,4-triazol-5-thione, 1,3,4-thiadiazole, 5-methylmercapto-1,2,4-triazol, antimicrobial activity