untitled European Journal of Chemistry 6 (1) (2015) 88‐92 European Journal of Chemistry ISSN 2153‐2249 (Print) / ISSN 2153‐2257 (Online)  2015 Atlanta Publishing House LLC ‐ All rights reserved ‐ Printed in the USA http://dx.doi.org/10.5155/eurjchem.6.1.88‐92.1166 European Journal of Chemistry Journal webpage: www.eurjchem.com Pyridazine and its related compounds. Part 35 [1]: Synthesis, characterization and antimicrobial activity of some novel pyridazine and triazolopyridazine containing sulfonamides Ali AbdelHamid Deeb 1,*, Wafaa Ibrahim El‐Eraky 2 and Sebaey Mahgoub Mohamed 3 1 Department of Chemistry, Faculty of Science, Zagazig University, Zagazig, 44519, Egypt 2 Department of Pharmacology, National Research Centre, Dokki, Cairo, 12622, Egypt 3 Research and Development Sector, Unipharma Company, El‐Obour City, 11828, Egypt * Corresponding author at: Department of Chemistry, Faculty of Science, Zagazig University, Zagazig, 44519, Egypt. Tel.: +20.55.2303252. Fax: +20.55.2308213. E‐mail address: dralideeb@hotmail.com (A. Deeb). ARTICLE INFORMATION ABSTRACT DOI: 10.5155/eurjchem.6.1.88‐92.1166 Received: 01 October 2014 Received in revised form: 02 November 2014 Accepted: 02 November 2014 Published online: 31 March 2015 Printed: 31 March 2015 The present study describes the chemical synthesis and antimicrobial evaluation of some new pyridazine and triazolopyridazine derivatives. The structure assignments of the new compounds are based on chemical and spectroscopic evidences. The Study results showed that derivatives 6a, 6b, 6g and 6i have promising inhibitory activity against (Micrococcus luteus). Compound 6i has also noticeable inhibition activity against (Escherichia coli) and compound 3g show remarkable activity against (Candida albicans). Rest of compounds showed moderate to low activity against the examined microorganisms. KEYWORDS Synthesis Pyridazine Sulfonamide Triazolopyridazine Antimicrobial activity Agar plate diffusion technique Cite this: Eur. J. Chem. 2015, 6(1), 88‐92 1. Introduction In recent years, there has been increasing interest in the chemistry of pyridazine family of heterocycles due to their diverse biological significance studied in large number of papers [1], this variety of biological activities includes anti‐HIV [2], anti‐tobacco mosaic virus Tobacco Mosaic Virus (TMV) [3], antidepressant [4], antiviral [5], anti‐cancer [6], analgesic, anti‐inflammatory [7], and selective CB2 agonists for the treatment of inflammatory pain [8]. Moreover, the chemistry of 1,2,4‐triazoles and their fused heterocyclic derivatives have received considerable attention owing to their synthetic and effective biological importance, such as antitumor, anti‐inflammatory, antimicrobial, anti‐ thrombotic and anticonvulsant activities [9], also a large number of triazole‐containing ring systems exhibit antifungal and antiviral properties [10]. Sulfonamide group forms the bioactive moiety of many therapeutic agents such as diuretics, antidiabetics, antibiotics, and antibacterials [11‐16]. So, our efforts were directed towards the synthesis of new heterocyclic compounds containing pyridazine moiety with anticipated biological activities. In this paper, the synthesis of new pyridazine and triazolopyridazine derivatives carrying sulfonamide groups is reported. These compounds were characterized by various spectroscopic methods. Antimicro‐ bial activities for some derivatives were assessed against representative Gram positive bacteria (Micrococcus luteus, Staphylococcus aureus), Gram negative bacteria (Escherichia coli) and fungi (Candida albicans). 2. Experimental 2.1. Chemistry All melting points were determined in open glass capillaries and are uncorrected. IR spectra were recorded on a Bruker Vector 22 Germany spectrometer (KBr). 1H NMR spectra were recorded on Varian Gemini 200 MHz spectrometer and 13C NMR spectra on JMS‐AX500 (125 MHz), using tetramethylsilane (TMS) as an internal reference. The electron impact mass spectra were obtained at 70 eV using Shimadzu QP‐2010 Plus mass spectrometer. Reactions were monitored by thin layer chromatography (TLC) on silica gel 60F254 aluminum sheets (Merck) and pots were detected by Deeb et al. / European Journal of Chemistry 6 (1) (2015) 88‐92 89 Scheme 1 UV lamp at 254‐365 nm. The synthesis of 4,5,6‐triphenyl pyridazine‐3(2H)‐thione (1) [17], 6,7,8‐triphenyl‐[1,2,4] triazolo[4,3‐b]pyridazine‐3‐thiol (4) [18] and their corres‐ ponding sulfonylchloride derivatives 2 and 5 were performed according to known procedure [19]. 2.2. Antimicrobial activity Antimicrobial activity study was performed using standard cultures of Micrococcus luteus (ATCC10240), Staphylococcus aureus (ATCC6538P), Escherichia coli (ATCC10536) and Candida albicans (ATCC2091). Micrococcus luteus, Staphylococcus aureus Staphylococcus aureus and E. coli cultures were incubated in Nutrient Broth (NB) (Difco), while Candida albicans was incubated in Sabouraud Dextrose Broth (SDB) (Difco), dimethylformamide was used as a solvent for tested compounds. A blank disc impregnated with dimethylformamide followed by drying off was used as a negative control. Sulfadoxine, sulfadimidine and nystatin at concentration of 0.4 mg/0.1 mL in dimethylformamide were used as positive control (Table 1). 2.3. Synthesis 2.3.1. Preparation of 4,5,6‐triphenylpyridazine‐3‐sulfonyl chloride (2) In a solution of 3‐mercapto derivative 1 (2.9 mmol) in acetic acid (19 mL) and water (1 mL), chlorine gas was bubbled at 0 °C for 1 h. The reaction mixture was poured into water (250 mL) portion‐wise with stirring; the precipitate was filtered, washed with water several times and dried to give 3‐ sulfonylchloride derivative 2 in 92% yield. The respective crude sulfonylchloride was used in the next step without further purification (Scheme 1). 2.3.2. Preparation of 4,5,6‐triphenylpyridazine‐3‐ sulfonamide derivatives (3a‐i) To a solution of sulfonylchloride derivative 2 (2.46 mmol) in benzene (20 mL), substituted amine was added (2.46 mmol), the reaction mixture was refluxed for 3 hours, the solvent was evaporated in vacuo, the solid product was collected and recrystallized from ethanol (Scheme 1). 4,5,6‐Triphenylpyridazine‐3‐sulfonohydrazide (3a): Prepa‐ red from hydrazine hydrate. Color: White crystals. Yield: 85%. M.p.: 295‐298 °C. FT‐IR (KBr, ν, cm‐1): 3390 (NH), 3230, 3150 (NH2), 1617 (C=N), 1350, 1160 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.10 (s, 1H, NH), 7.89‐7.42 (m, 15H, Ar‐H), 2.80 (s, 2H, NH2). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 158.9 (C‐6), 157.9 (C‐3), 137.4 (C‐4), 136.7 (C‐5), 135.7 (C‐5), 134 (C‐4), 130.2‐128.5 (3Ph). MS (m/z (%)): 402 (M+, 7.87), 338 (M+‐SO2, 100, F1), 322 (F1‐NH2, 39.29, F2), 296 (F2 ‐CH2=NH, 2.81), 236 (F2 –Ph, 3.47). Anal. calcd. for C22H18N4O2S: C, 65.65; H, 4.51; N, 13.92. Found: C, 65.50; H, 4.35; N, 13.76%. N‐(2‐Hydroxyethyl)‐4, 5, 6‐triphenylpyridazine‐3‐sulfon amide (3b): Prepared from ethanolamine. Color: White crystals. Yield: 75.4%. M.p.: 285‐287 °C. FT‐IR (KBr, ν, cm‐1): 3420 (OH), 3285 (NH), 2921 (CHaliph), 1639 (C=N), 1368, 1167 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.30 (s, 1H, NH), 7.89‐7.42 (m, 15H, Ar‐H), 2.90 (t, 2H, CH2NH), 3.50 (t, 2H, CH2OH), 3.75 (s, 1H, OH). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 157.9 (C‐6), 156.9 (C‐3), 136.4 (C‐4), 135.7(C‐5), 134.7 (C‐5), 133 (C‐4), 129.2‐127.5 (Ar‐C), 61.1 (C‐OH), 46.5 (C‐NH). MS (m/z (%)): 431 (M+, 8.02), 386 (M+‐CH2CH2OH, 7.39, F1), 371 (F1‐NH2, 8.56, F2), 346 (F2‐N2, 9.18, F3), 271 (F3‐Ph, 7.62, F4). Anal. calcd. for C24H21N3O3S: C, 66.80; H, 4.91; N, 9.74. Found: C, 66.65; H, 4.76; N, 9.60%. 4‐((4,5,6‐Triphenylpyridazin‐3‐yl)sulfonyl)morpholine (3c): Prepared from morpholine. Color: White crystals. Yield: 80.3%. M.p.: 188‐190 °C. FT‐IR (KBr, ν, cm‐1): 3057 (CHarom), 2915 (CHaliph), 1624 (C=N), 1351, 1158 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 7.89‐7.42 (m, 15H, Ar‐H), 2.98 (t, 4H, CH2NCH2), 3.85 (t, 4H, CH2OCH2). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 158.4 (C‐6), 157.4 (C‐3), 136.9 (C‐4), 136.2 (C‐5), 135.2 (C‐5), 134.0 (C‐4), 130.1‐128.2 (Ar‐C), 67.3 (C‐O‐C), 49.2 (C‐N‐C). MS (m/z (%)): 455 (M+‐2, 0.62), 393 (M+ ‐SO2, 4.54, F1), 308 (F1 ‐NC4H8O, 88.63, F2), 280 (F2 ‐N2, 4.40). Anal. calcd. for C26H23N3O3S: C, 68.25; H, 5.07; N, 9.18. Found: C, 68.10; H, 4.90; N, 9.01%. N‐Benzyl‐4, 5, 6‐triphenylpyridazine‐3‐sulfonamide (3d): Prepared from benzyl amine. Color: White crystals. Yield: 76.9%. M.p.: 275 ‐277 °C. FT‐IR (KBr, ν, cm‐1): 3381 (NH), 2890 (CHaliph), 1636 (C=N), 1377, 1146 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.54 (s, 1H, NH), 7.31‐7.10 (m, 15H, Ar‐H), 7.08‐7.05 (m, 5H, Ar‐H), 4.10 (s, 2H, CH2). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 157.9 (C‐6), 156.9 (C‐3), 136.4 (C‐4), 135.7 (C‐5), 134.7 (C‐5), 133.0 (C‐4), 129.2‐126.7 (Ar‐C), 48.5 (C‐ NH). MS (m/z (%)): 478 (M++1, 17.29), 341 (100). Anal. calcd. for C29H23N3O2S: C, 72.93; H, 4.85; N, 8.80. Found: C, 72.79; H, 4.70; N, 8.65% N, 4, 5, 6‐Tetraphenylpyridazine‐3‐sulfonamide (3e): Prepa‐ red from aniline. Color: White crystals. Yield: 92.6%. M.p.: 290‐ 292 °C. FT‐IR (KBr, ν, cm‐1): 3316 (NH), 3036 (CHarom), 1644 (C=N), 1354, 1222 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.10 (s, 1H, NH), 7.89‐6.82 (m, 20H, Ar‐H). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 158.9 (C‐6), 157.9 (C‐3), 137.4 (C‐4), 136.7 (C‐5), 135.7 (C‐5), 134.0 (C‐4), 129.2‐119.4 (Ar‐C). MS (m/z (%)): 464 (M+, 30.6), 370 (M+‐NHPh, 0.72, F1), 308 (F1‐SO2, 1.14, F2), 2804 (F2‐N2, 3.75, F3). Anal. calcd. for C28H21N3O2S: C, 72.55; H, 4.57; N, 9.06. Found: C, 72.40; H, 4.41; N, 8.83%. 90 Deeb et al. / European Journal of Chemistry 6 (1) (2015) 88‐92 Scheme 2 4,5,6‐Triphenyl‐N‐(o‐tolyl)pyridazine‐3‐sulfonamide (3f): Prepared from o‐tolidine. Color: White crystals. Yield: 81.1%. M.p.: 280‐282 °C. FT‐IR (KBr, ν, cm‐1): 3350 (NH), 2915 (CHaliph), 1640 (C=N), 1304, 1137 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 9.10 (s, 1H, NH), 7.94‐7.42 (m, 19H, Ar‐H), 3.1 (s, 3H, CH3). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 158.9 (C‐6), 157.9 (C‐3), 137.4 (C‐4), 136.7 (C‐5), 135.7 (C‐5), 134.0 (C‐4), 130.2‐128.5 (Ar‐H), 19.3 (CH3). MS (m/z (%)): 477 (M+, 37.82), 308 (M+‐SO2NHC6H4CH3, 7.64, F1), 280 (F1‐N2, 7.64, F2), 204 (F2‐Ph, 16.77, F3), 106 (F3‐C8H8, 100, F4). Anal. calcd. for C29H23N3O2S: C, 72.93; H, 4.85; N, 8.80. Found: C, 72.88; H, 4.70; N, 8.65%. 4,5,6‐Triphenyl‐N‐(m‐tolyl)pyridazine‐3‐sulfonamide (3g): Prepared from m‐tolidine. Color: White crystals. Yield: 76.9%. M.p.: 218‐220 °C. FT‐IR (KBr, ν, cm‐1): 3279 (NH), 3107 (CHarom), 2918 (CHaliph), 1636 (C=N), 1365, 1163 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 9.10 (s, 1H, NH), 7.94‐6.70 (m, 19H, Ar‐H), 3.20 (s, 3H, CH3). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 159.9 (C‐6), 158.9 (C‐3), 138.4 (C‐4), 137.7 (C‐5), 136.7 (C‐5), 135.0 (C‐4), 129.2‐119.4 (Ar‐C), 22.5 (CH3). MS (m/z (%)): 477 (M+, 1.96), 387 (M+‐C6H4CH3, 0.4, F1), 323 (F1‐SO2, 100, F2), 308 (F2‐NH2, 0.92, F3), 280 (F3‐N2, 3.82, F4), 204 (F4‐ Ph, 8.01, F5), 106 (F5‐C8H8, 0.67, F6). Anal. calcd. for C29H23N3O2S: C, 72.93; H, 4.85; N, 8.80. Found: C, 72.90; H, 4.72; N, 8.63%. N‐(2‐Chlorobenzyl)‐4,5,6‐triphenylpyridazine‐3‐sulfonamide (3h): Prepared from 2‐chlorobenzylamine. Color: White crystals. Yield: 79.3%. M.p.: 211‐213 °C. FT‐IR (KBr, ν, cm‐1): 3390 (NH), 2885 (CHaliph), 1642 (C=N), 1376, 1105 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.54 (s, 1H, NH), 7.64‐7.51 (m, 15H, Ar‐H), 7.43‐7.40 (m, 4H, Ar‐H), 4.10 (s, 2H, CH2). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 159.9 (C‐6), 158.9 (C‐3), 138.4 (C‐4), 137.7 (C‐5), 136.7 (C‐5), 134.0 (C‐4), 129.2‐126.6 (4Ph), 43.2 (C‐NH). MS (m/z (%)): 512 (M+, 11.56), 476 (M+‐ HCl, 100, F1), 387 (F1‐CH2Ph, 15.34, F2), 370 (F2‐NH2, 14.36, F3), 307 (F3‐SO2, 20.42, F4), 323 (F2‐SO2, 57.84, F5), 308 (F5‐ NH2, 0.92, F6). Anal. calcd. for C29H22ClN3O2S: C, 68.03; H, 4.33; N, 8.21. Found: C, 67.86; H, 4.15; N, 8.04%. N‐(Naphthalen‐1‐yl)‐4, 5, 6‐triphenylpyridazine‐3‐sulfon amide (3i): Prepared from α‐naphthylamine. Color: White crystals. Yield: 86.09%. M.p.: 228‐230 °C. FT‐IR (KBr, ν, cm‐1): 3350 (NH), 3034 (CHarom), 1628 (C=N), 1391, 1120 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 10.10 (s, 1H, NH), 8.20‐7.41 (m, 22H, Ar‐H). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 157.9 (C‐6), 156.9 (C‐3), 142 (C‐1), 136.4 (C‐4), 135.7 (C‐5), 134.7 (C‐5), 133.0 (C‐4), 129.2‐127.5 (Ar‐C), 127‐109 (1‐Naphthyl‐ C). MS (m/z (%)): 513 (M+, 26.59), 449 (M+‐SO2, 16.12, F1), 323 (F1‐C10H7, 27.74, F2), 307 (F2‐NH2, 9.51, F3), 280 (F3‐N2, 7.71, F4). Anal. calcd. for C32H23N3O2S: C, 74.83; H, 4.51; N, 8.18. Found: C, 74.68; H, 4.36; N, 8.03%. 2.3.3. 6,7,8‐Triphenyl‐[1,2,4]triazolo[4,3‐b]pyridazine‐3‐ sulfonyl chloride (5) To a solution of 3‐mercapto derivative 4 (2.6 mmol) in acetic acid (19 mL) and water (1 mL), chlorine gas was bubbled at 0 °C for 1 h. The reaction mixture was poured into water (250 mL) portion‐wise with stirring; the precipitate was filtered, washed with water several times and dried to give 3‐ sulfonylchloride derivative 5 yield 90.5%. The respective crude sulfonylchloride was used in the next step without further purification. Color: White crystals. Yield: 90.5%. M.p.: 130‐132 °C (Scheme 2). 2.3.4. 3‐Sustituted sulfamoyl‐6,7,8‐triphenyl [1,2,4]triazolo [4,3‐b]pyridazine (6a‐i) To a solution of sulfonyl chloride derivative 5 (2.20 mmol) in benzene (20 mL), substituted amine was added (2.20 mmol), the reaction mixture was refluxed for 3 hours, the solvent was concentrated, the solid product was collected and recrystallized from ethanol (Scheme 2). 6,7 , 8‐Triphenyl [1, 2, 4]triazolo[4, 3‐b]pyridazine‐3‐sulfono hydrazide (6a): Prepared from hydrazine hydrate. Color: White crystals. Yield: 80.7%. M.p.: 260‐262 °C. FT‐IR (KBr, ν, cm‐1): 3350 (NH), 1621 (C=N), 1322, 1171 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.20 (s, 1H, NH), 7.80‐7.41 (m, 15H, Ar‐H), 2.9 (s, 2H, NH2). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 155.7 (C‐8), 150.1 (C‐5), 147.0 (C‐3), 135.4 (C‐6), 135.0 (C‐6), 134.4 (C‐7), 133.7 (C‐7), 132.0 (C‐8), 128.2‐126.5 (Ar‐C). MS (m/z (%)): 442 (M+, 3.17), 426 (M+‐NH2, 1.67, F1), 411 (F1‐NH2, 3.44, F2). Anal. calcd. for C23H18N6O2S: C, 62.43; H, 4.10; N, 18.99. Found: C, 62.28; H, 3.93; N, 18.82% N‐(2‐Hydroxyethyl)‐6, 7, 8‐triphenyl [1, 2, 4]triazolo[4, 3‐b] pyridazine‐3‐sulfonamide (6b): Prepared from ethanolamine. Color: White crystals. Yield: 55.2%. M.p.: 148‐150 °C. FT‐IR (KBr, ν, cm‐1): 3416 (OH), 3325 (NH), 2914 (CHaliph), 1640 (C=N), 1302, 1100 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.20 (s, 1H, NH), 7.80‐7.41 (m, 15H, Ar‐H), 4.10 (t, 2H, CH2OH), 3.80 (s, 1H, OH), 2.9 (t, 2H, CH2NH). 13C NMR (125 MHz, DMSO‐ d6, δ, ppm): 155.7 (C‐8), 150.1 (C‐5), 147 (C‐3), 135.4 (C‐6), 135.0 (C‐6), 134.4 (C‐7), 133.7 (C‐7), 132.0 (C‐8), 128.2‐126.5 (Ar‐C), 59.1 (C‐OH), 44.5 (C‐NH). MS (m/z (%)): 472 (M++1, 4.27), 347 (M+‐SO2NHCH2CH2OH, 4.81, F1), 348 (F1‐C4H8NO, 59.56, F2), 324 (F2‐N2, 4.40, F3). Anal. calcd. for C25H21N5O3S: C, 63.68; H, 4.49; N, 14.85. Found: C, 63.50; H, 4.31; N, 14.70%. 4‐((6, 7, 8‐Triphenyl‐[1, 2, 4]triazolo[4, 3‐b]pyridazin‐3‐yl) sulfonyl)morpholine (6c): Prepared from morpholine. Color: White crystals. Yield: 84.1%. M.p.: 223‐225 °C. FT‐IR (KBr, ν, cm‐1): 2920 (CHaliph), 1622 (C=N), 1309, 1115 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 7.80‐7.41 (m, 15H, Ar‐H), 4.10 (t, 4H, CH2‐O‐CH2), 3.50 (t, 4H, CH2‐N‐CH2). Deeb et al. / European Journal of Chemistry 6 (1) (2015) 88‐92 91 Table 1. Anti‐microbial activity of synthesized compounds *. Compound Micrococcus luteus Staphylococcus aureus Escherichia coli Candida albicans 3a +++ ++ +++ +++ 3b +++ ++ +++ +++ 3c +++ ++ +++ +++ 3d ++ +++ ++ +++ 3e +++ ++ ++ +++ 3f +++ ++ ++ +++ 3g +++ ++ ++ +++ 3h +++ ++ ++ +++ 3i +++ ++ ++ +++ 6a ++++ +++ +++ +++ 6b ++++ ++ ++ +++ 6c + ++ + +++ 6d ++ ++ +++ +++ 6e +++ + ++ +++ 6f + ++ + ++ 6g ++++ + + ++++ 6h ++ + + +++ 6i ++++ ++ ++++ +++ DMF ‐ ‐ ‐ ‐ Sulfadoxine +++ +++ ++ +++ Sulfadimidine +++ +++ ++ +++ Nystatin ‐ ‐ ‐ ++++ * Values are mean inhibition zone (mm) of two replicates, 25‐35 mm = ++++, 18‐24 mm = +++, 11‐16 mm = ++, ≤10 mm = +, ‐ = negative inhibition. 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 155.7 (C‐8), 150.1 (C‐5), 147.0 (C‐3), 135.4 (C‐6), 135.0 (C‐6), 134.4 (C‐7), 133.7 (C‐7), 132.0 (C‐8), 128.2‐126.5 (Ar‐C), 64.3 (C‐O‐C), 46.2 (C‐N‐ C). MS (m/z (%)): 497 (M+, 0.75), 433 (M+‐SO2, 2.72, F1), 348 (F1‐C4H8NO, 59.56, F2), 324 (F2‐N2, 4.40, F3). Anal. calcd. for C27H23N5O3S: C, 65.17; H, 4.66; N, 14.08. Found: C, 65.01; H, 4.50; N, 13.92%. N‐Benzyl‐6, 7, 8‐triphenyl‐[1, 2, 4]triazolo[4, 3‐b]pyridazine‐ 3‐sulfonamide (6d): Prepared from benzylamine. Color: White crystals. Yield: 69.5%. M.p.: 237‐239 °C. FT‐IR (KBr, ν, cm‐1): 3390 (NH), 2891 (CHaliph), 1624 (C=N), 1312, 1151 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.20 (s, 1H, NH), 7.80‐7.41 (m, 15H, Ar‐H), 7.35‐7.25 (m, 5H, Ar‐H), 3.50 (s, 2H, CH2). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 157.7 (C‐8), 152.1 (C‐5), 149.0 (C‐3), 137.4 (C‐6), 137.0 (C‐6), 136.4 (C‐7), 135.7 (C‐7), 134.0 (C‐8), 130.2‐127.7 (Ar‐C), 47.2 (C‐NH). MS (m/z (%)): 516 (M+‐1, 3.32), 425 (M+‐CH2C6H5, 3.23). Anal. calcd. for C30H23N5O2S: C, 69.61; H, 4.48; N, 13.53. Found: C, 69.44; H, 4.30; N, 13.37%. N, 6, 7, 8‐Tetraphenyl‐[1, 2, 4]triazolo[4, 3‐b]pyridazine‐3‐ sulfonamide (6e): Prepared from aniline. Color: White crystals. Yield: 62.5%. M.p.: 261‐263 °C. FT‐IR (KBr, ν, cm‐1): 3360 (NH), 3054 (CHarom), 1640 (C=N), 1360, 1161 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.40 (s, 1H, NH), 7.31‐7.10 (m, 15H, Ar‐H), 7.08‐7.05 (m, 5H, Ar‐H). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 157.7 (C‐8), 152.1 (C‐5), 149.0 (C‐3), 137.5 (C‐6), 137.0 (C‐6), 136.4 (C‐7), 135.7 (C‐7), 134.0 (C‐8), 129.5‐119.4 (Ar‐C). MS (m/z (%)): 503 (M+, 19.27), 439 (M+‐SO2, 50.47, F1), 348 (F1‐NHPh, 14.31, F2). Anal. calcd. for C29H21N5O2S: C, 69.17; H, 4.20; N, 13.91. Found: C, 69.00; H, 4.03; N, 13.76%. 6,7,8‐Triphenyl‐N‐(o‐tolyl)‐[1,2,4]triazolo[4, 3‐b]pyridazine‐ 3‐sulfonamide (6f): Prepared from o‐toluidine. Color: White crystals. Yield: 67.2%. M.p.: 268‐270 °C. FT‐IR (KBr, ν, cm‐1): 3396 (NH), 2962 (CHaliph), 1635 (C=N), 1342, 1165 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.30 (s, 1H, NH), 7.32‐7.22 (m, 15H, Ar‐H), 6.90‐6.80 (m, 4H, Ar‐H), 2.28 (s, 3H, CH3). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 157.7 (C‐8), 152.1 (C‐5), 149.0 (C‐3), 137.5 (C‐6), 137.0 (C‐6), 136.4 (C‐7), 135.7 (C‐7), 134.0 (C‐8), 129.5‐123.7 (Ar‐C), 18.3 (CH3). MS (m/z (%)): 517 (M+, 33.45), 453 (M+‐SO2, 58.90, F1), 438 (F1‐NH2, 5.48, F2), 348 (F2‐C6H4CH3, 1.20, F3), 324 (F3‐N2, 1.60, F4). Anal. calcd. for C30H23N5O2S: C, 69.61; H, 4.48; N, 13.53. Found: C, 69.44; H, 4.30; N, 13.36%. 6,7,8‐Triphenyl‐N‐(m‐tolyl)‐[1,2,4]triazolo[4,3‐b]pyridazine‐ 3‐sulfonamide (6g): Prepared from m‐toluidine. Color: White crystals. Yield: 76.3%. M.p.: 210‐212 °C. FT‐IR (KBr, ν, cm‐1): 3270 (NH), 2916 (CHaliph), 1638 (C=N), 1381, 1161 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.20 (s, 1H, NH), 7.32‐7.22 (m, 15H, Ar‐H), 6.90‐6.80 (m, 4H, Ar‐H), 2.38 (s, 3H, CH3). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 157.7 (C‐8), 152.1 (C‐5), 149.0 (C‐3), 137.5 (C‐6), 137.0 (C‐6), 136.4 (C‐7), 135.7 (C‐7), 134.0 (C‐8), 129.5‐117.4 (Ar‐C), 12.3 (CH3). MS (m/z (%)): 517 (M+, 37.78), 453 (M+‐SO2, 19.79, F1), 348 (F1‐NHC6H4CH3, 19.93, F2). Anal. calcd. for C30H23N5O2S: C, 69.61; H, 4.48; N, 13.53. Found: C, 69.45; H, 4.31; N, 13.35%. N‐(2‐Chlorobenzyl)‐6, 7, 8‐triphenyl‐[1, 2, 4]triazolo[4, 3‐b] pyridazine‐3‐sulfonamide (6h): Prepared from 2‐chlorobenzyl amine. Color: White crystals. Yield: 75%. M.p.: 218‐220 °C. FT‐ IR (KBr, ν, cm‐1): 3330 (NH), 2891 (CHaliph), 1588 (C=N), 1322, 1109 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.20 (s, 1H, NH), 7.80‐7.41 (m, 15H, Ar‐H), 7.30‐7.10 (m, 4H, Ar‐H), 3.60 (s, 2H, CH2). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 157.7 (C‐8), 152.1 (C‐5), 149.0 (C‐3), 137.5 (C‐6), 137.0 (C‐6), 136.4 (C‐7), 135.7 (C‐7), 134.0 (C‐8), 130.2‐127.4 (Ar‐C), 43.1 (C‐NH). MS (m/z (%)): 552 (M+, 38.06), 106 (100). Anal. calcd. for C30H22ClN5O2S: C, 65.27; H, 4.02; N, 12.69. Found: C, 65.10; H, 3.88; N, 12.51%. N', 6, 7, 8‐Tetraphenyl‐[1, 2, 4]triazolo[4, 3‐b]pyridazine‐3‐ sulfonohydrazide (6i): Prepared from phenyl hydrazine. Color: White crystals. Yield: 60.3%. M.p.: 188‐190 °C. FT‐IR (KBr, ν, cm‐1): 3337, 3202 (2NH), 3033 (CHarom), 1640 (C=N), 1306, 1159 (SO2). 1H NMR (200 MHz, DMSO‐d6, δ, ppm): 8.0 (s, 1H, NH), 7.80‐7.41 (m, 15H, Ar‐H), 7.37‐6.90 (m, 5H, Ar‐H), 4.20 (s, 1H, NHPh). 13C NMR (125 MHz, DMSO‐d6, δ, ppm): 157.7 (C‐8), 152.1 (C‐5), 149.0 (C‐3), 137.5 (C‐6), 137.0 (C‐6), 136.4 (C‐7), 135.7 (C‐7), 134.0 (C‐8), 130.2‐115.4 (Ar‐C). MS (m/z (%)): 514 (M+‐4, 9.59), 105 (100). Anal. calcd. for C29H22N6O2S: C, 67.17; H, 4.28; N, 16.21. Found: C, 67.00; H, 4.11; N, 16.04%. 3. Results and discussion 3.1. Synthesis The sulfonamide derivatives as the target compounds depicted in (Scheme 1 and 2) were obtained by allowing the pyridazinethiol derivatives 1 [17] and triazolopyridazinethiol 4 [18] to oxidatively chlorinate with chlorine gas in presence of 90% acetic acid at 0 °C, the corresponding sulfonyl chlorides 2 and 5 were obtained [19]. Because of the instability of sulfonyl chlorides, the crude products of sulfonyl chloride derivatives 2 and 5 were converted directly to the more stable sulfonamides 3 and 6 by amidation. The sulfonyl chloride derivatives 2 and 5 were identified by their corresponding sulfonamides. The IR spectra 92 Deeb et al. / European Journal of Chemistry 6 (1) (2015) 88‐92 of compounds 3a‐i and 6a‐i are characterized by bands at 3300‐3200 cm‐1 (NH), and characteristic absorption bands in the regions of 1134‐1152 and 1358‐1377 cm‐1 corresponding to symmetrical and asymmetrical vibrations of SO2 group. Moreover, for SAR study, we aimed to synthesize a new series of sulfonamides 3a‐i and 6a‐i to investigate the effect of attaching triazole ring (of the known pharmacological activity) to pyridazine nucleus upon the required activity as antimicrobial agents. The synthesized compounds were characterized by various spectroscopic methods such as IR, 1H NMR, 13C NMR and MS, elemental and spectral analyses of all prepared compounds described are consistent with the assigned structures. 3.2. Antimicrobial activity Applying the agar plate diffusion technique [20], the newly synthesized sulfonamide derivatives were screened in vitro for antimicrobial activity against Gram positive bacteria (Staphylococcus aureus and Micrococcus luteus), Gram negative bacteria (Escherichia coli) and yeast (Candida albicans). In this method, a standard 5 mm diameter sterilized filter paper disc impregnated with the compounds (0.4 mg/0.1 mL of dimethylformamide) was placed on the agar plates which had previously been inoculated with the above organisms; The petri dishes were left at 4 °C for 2 h, then the injected plates with bacteria were incubated at 37±0.1 °C for 24 h, and those inoculated with fungi were incubated at 25±0.1 °C for 48 h. At the end of the period, diameter of inhibition zones were measured in mm, these studies were performed in two replicates. The screening results given in Table 1 indicated that all the compounds exhibited antimicrobial activity against all the test organisms. 4. Conclusion In summary, we have developed a novel class of sulfonamide derivatives substituted with pyridazine and triazolopyridazine derivatives as potential antimicrobial agents and the following was concluded: compounds 6a, b and 6g, i with triazole ring fused with pyridazine nucleus showed a remarkable antimicrobial activity against Micrococcus luteus greater than that of the non‐condensed pyridazine nucleus in case of compounds 3a, b and 3g, i. This in turn reveals that there’s a significant relation between activity and nature of the pyridazine nucleus, Rest of the compounds showed moderate to low activity against the examined micro‐organisms. Acknowledgements The authors are grateful for financial support of this work by the Academy of Scientific Research and Technology, Cairo, Egypt, through a research grant no. 293/2005 titled “Synthesis of Biologically Active Organic Compounds”. References [1]. Buonora, P. T.; Zhang, Q.; Sawko, J.; Westrum, L. J. Tetrahedron‐ Asymm. 2008, 19(1), 27‐30. [2]. Sweeney, Z. K.; Dunn, J. P.; Li, Y.; Heilek, G.; Dunten, P.; Elworthy, T. R.; Han, X. C.; Harris, S. F.; Hirschfeld, D. R.; Hogg, J. H.; Huber, W.; Kaiser, A. C.; Kertesz, D. J.; Kim, W.; Mirzadegan, T.; Roepel, M. G.; Saito, Y. D.; Silva, T. M. P. C.; Swallow, S.; Tracy, J. L.; Villasenor, A.; Vora, H.; Zhou, A. S.; Klumpp, K. Bioorg. Med. Chem. Lett. 2008, 18, 4352‐4354. [3]. Zou, X. J.; Jin, G. Y. Chin. J. Org. Chem. 2003, 23, 62‐65. [4]. Coelho, A.; Sotelo, E.; Ravina, E. Tetrahedron 2003, 59, 2477‐2484. [5]. Wang, Z.; Wang, M.; Yao, X.; Li, Y.; Tan, J.; Wang, L.; Qiao, W.; Geng, Y.; Liu, Y.; Wang, Q. Eur. J. Med. Chem. 2012, 54, 33‐41. [6]. Jiang, J. K.; Boxer, M. B.; Vander Heiden, M. G.; Shen, M.; Skoumbourdis, A. P.; Southall, N.; Veith, H.; Leister, W.; Austin, C. P.; Park, H. W.; Inglese, J.; Cantley, L. C.; Auld, D. S.; Thomas, C. Bioorg. Med. Chem. Lett. 2010, 20, 3387‐3393. [7]. Refaat, H. M.; Khalil, O. M.; Kadry, H. H. Arch. Pharm. Res. 2008, 30(7), 803‐811. [8]. Gleave, R. J.; Beswick, P. J.; Brown, A. J.; Giblin, G. M. P.; Goldsmith, P.; Haslam, C. P.; Mitchell, W. L.; Nicholson, N. H.; Page, L. W.; Patel, S.; Roomans, S.; Slingsby, B. P.; Swarbrick, M. E. Bioorg. Med. Chem. Lett. 2010, 20, 465‐468. [9]. Xie, Z. F.; Chai, K. Y.; Piao, H. R.; Kwak, K. C.; Quan, Z. S. Bioorg. Med. Chem. Lett. 2005, 15, 4803‐4805. [10]. Kritsanida, M.; Mouroutsou, A.; Marakos, P.; Pouli, N.; Papakonstantinou‐Garoufalias, S.; Annecouque, C.; Witvrouw, M.; Clercq, E. D. Il Farmaco 2002, 57, 253‐257. [11]. Lednicer, D.; Mitscher, L. A.; Georg, G. I. The organic chemistry of drug synthesis, Vol. 4, Wiley, New York, 1990. [12]. El‐Gaby, M. S. A.; Micky, J. A.; Taha, N. M; El‐Sharief, M. A. M. S. J. Chin. Chem. Soc. 2002, 49, 407‐ 414. [13]. El‐Emary, T. I.; Al‐Muaikel, N.; Moustafa, O. S. Phosphorus Sulfur 2002, 177, 195‐210. [14]. Deeb, A.; Mahgoub, S. Med. Chem. Res. 2014, 23, 4559‐4569. [15]. Hosny, M.; El‐Mariah, F.; Deeb, A. Phosphorus Sulfur 2007, 182, 1475‐ 1482. [16]. El‐Mariah, F.; Nassar, E.; Hosny, M.; Deeb, A. Phosphorus Sulfur 2008, 184, 92‐102. [17]. Deeb, A.; Said, S. Collect. Czech. Chem. Commun. 1990, 55, 2795‐2799. [18]. Deeb, A.; Hassaneen, M.; Kotb, M. Heteroatom. Chem. 2005, 12, 278‐ 282. [19]. Deeb, A.; El‐Eraky, W.; El‐Awdan, S.; Mahgoub, S. Med. Chem. Res. 2014, 23, 34‐41. [20]. Bauer, A. W.; Kirby, M. D. K.; Sherries, J. C.; Turck, M. Am. J. Clin. Pathol. 1966, 45, 493‐496.