Indian Journal of Chemistry Vol. 44B,December 2005, pp. 2614-2617 Note Synthesis and antimicrobial activity of some 3-alkyl-4-(arylmethyleneamino)-4,5-dihydro- 1H-1,2,4-triazol-5-ones Bahittin Kahveci* a , Olcay Bekircan b & Şengül Alpay Karaoğlu c a Department of Chemistry, Faculty of Arts and Sciences, Karadeniz Technical Universty, 53100 Rize, Turkey b Department of Chemistry, Faculty of Arts and Sciences, Karadeniz Technical Universty, 28049 Giresun, Turkey c Department of Biology, Faculty of Arts and Sciences, Karadeniz Technical Universty, 53100 Rize, Turkey Received 13 April 2004;accepted (revised) 2 March 2005 Eight new ethyl N ı -(3-methyl-4-arylmethyleneamino-4,5-di- hydro-1H-1,2,4-triazolyl-5-one)acetates 2 and N ı -(3-methyl-4- arylmethyleneamino-4,5-dihydro-1H-1,2,4-triazolyl-5-one)acetyl- hydrazines 3 have been synthesized. The structures of the compounds have been confirmed by IR and 1 H NMR spectra and microanalysis. The compounds show some antimicrobial activities. Compound 2a shows antibacterial activity against B. subtilis. Compounds 3a, 3b and 3d have antifungal activity against Candida species. Keywords: Antimicrobial activity, B. subtilis, Candida species, 1,2,4-triazolone, triazolyl acetates, acetylhydrazines IPC: Int.Cl. 7 C 07 D Some 4-amino-4,5-dihydro-1,2,4-triazol-5-ones were reported by Ikizler et al. 1 . In recent years, the reactions of these amino compounds with certain aldehydes and the formation of benzylidenamino compounds were studied. The reduction of benzylidenamino compounds leads to the formation of 3-alkyl-4-(arylmethyleneamino)-4,5-dihydro-1H- 1,2,4-triazol-5-ones 1. Most of these compounds have significant biological and antitumour effects 2,3 . Furthermore, a number of studies involving the antibacterial activity of some 4,5-dihiydro-1H-1,2,4- triazol-5-ones have been reported 4,5 . Thus, in the present study, ethyl N ı -(3-methyl-4- arylmethyleneamino-4, 5-dihydro-1H-1, 2,4-triazolyl- 5-one)acetates 2 were synthesized from the reaction of compounds 1 with bromoethyl acetate using the literature methods 6-9 . Compounds 2 were then converted to compounds 3 by treating with hydrazine hydrate 10,11 (Scheme I). The antimicrobial properties of all the compounds synthesized were investigated by using the minimal inhibition concentration method 12 . Experimental Section All chemicals were supplied from Aldrich, Merck and Fluka Co. Melting points were taken in open capillary tubes and are uncorrected. IR spectra in KBr pellets were recorded on a Perkin-Elmer 1600 FTIR spectrophotometer; and 1 H NMR in CDCl 3 on a Varian 200 A spectrometer using TMS as an internal standard. All compounds gave satisfactory C, H and N analysis. 3-Alkyl-4-(arylmethylenamino)-4, 5-dihydro-1H- 1,2,4-triazol-5-ones 1a-d were synthesized by the reported method 2,3 . Synthesis of 2a-d. General method. Compounds 1a-d (0.005 mole) were dissolved in 30 mL of absolute ethanol and treated with an ethanolic sodium ethoxide solution [obtained by dissolving sodium (0.005 mole) in 50 mL of absolute ethanol]. After refluxing for 2 hr, the mixture was cooled to 35-40ºC and 0.55 mL of bromoethyl acetate were added. After the addition, the mixture was refluxed for 8 hr and evaporated at 30-35ºC under reduced pressure. The crude products 2a-d were purified by recrystallization from the appropriate solvents.Their characterization data are given in Table I. Synthesis of 3a-d. General method. Compounds 2a-d (0.005 mole) and hydrazine hydrate (0.006 mole) in absolute ethanol (10 mL) were refluxed for 4 hr and cooled. The crystals thus formed were filtered and recrystallized from appropriate solvent to afford 3a-d. Their characterization data are given in Table I Biological activity 12 The compounds were tested against some Gram- positive and Gram-negative bacteria and some yeast like fungi. All microorganisms tested were obtained from the Hifzissihha Institute of Refik Saydam Ankara, Turkey. The microorganisms used are Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, Enterococcus faecalis ATCC 29212,