untitled European Journal of Chemistry 6 (2) (2015) 211‐218 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.6.2.211‐218.1251 European Journal of Chemistry Journal webpage: www.eurjchem.com Pyridazine and its related compounds: Part 32. Synthesis and antimicrobial evaluation of some 3‐substituted amino‐4,5,6‐triphenylpyridazine derivatives Ali Abdel Hamid Deeb 1,*, Fatma Abdel Rahman El‐Mariah 2 and Heba Kamal Abd El‐Mawgoud 2 1 Department of Chemistry, Faculty of Science, Zagazig University, Zagazig, 44519, Egypt 2 Department of Chemistry, College of Women for Arts, Science and Education, Ain Shams University, Cairo, 11753, 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.A. Deeb). ARTICLE INFORMATION ABSTRACT DOI: 10.5155/eurjchem.6.2.211‐218.1251 Received: 04 February 2015 Received in revised form: 25 April 2015 Accepted: 01 May 2015 Published online: 30 June 2015 Printed: 30 June 2015 3‐Amino‐4,5,6‐triphenylpyridazine was subjected to some selected reactions with nitrous acid, formic acid/dimethylformamide, acetic anhydride, benzoyl chloride, chloroacetyl chloride, acetaldehyde, diethyl malonate, malonic acid/phosphoryl chloride, diethyl oxalate, ethyl cyanoacetate, ethyl acetoacetate, and ethyl benzoylacetate to give new 3‐substituted aminopyridazine derivatives. A few sulfonamide derivatives (new) were also prepared. The structures of the synthesized compounds were proved by their infrared, mass spectra, 1H NMR, and elemental analysis. The antimicrobial activity of the compounds obtained was examined against some selected microorganisms. KEYWORDS 3‐Aminopyridazin Anti‐microbial activity Benzil monohydrazone Pyridazine sulfonamides Pyrimido[1,2‐b]pyridazines 3‐Substituted aminopyridazine Cite this: Eur. J. Chem. 2015, 6(2), 211‐218 1. Introduction The pyridazine nucleus is a very common component in many compounds of biological interest manifested in several fields of medicinal chemistry, such as phosphodiesterase type 4 inhibitors for inflammatory diseases [1], as endothelin‐A receptor antagonists [2], in the development of active compounds toward α1 and α2 adrenoceptors [3], as central analgesics and aldose reductose inhibitors [4]. The pyridazine derivatives are also used as analgesic [5], antibacterial [6], anti‐inflammatory [7], anti‐hypertensive [8], antihistaminic [9], antinociceptive agents [10], as well as platelet aggregation inhibitors [11]. They have a rapid systemic effect on the plants and are active at very low concentration. Some of the investigated pyridazine derivatives have chemical structures related to those of the phytohormones [12]. In addition, similar chemical structures occur in living cells, being involved in various biochemical reaction pathways. Some new synthesized pyridazine derivatives were used in many research fields due to their structure, stability, reactivity and their tendency to form stable derivatives with important biological properties. On the other hand, as a rule, a cytotoxic effect of higher concentrated compounds is correlated with their stimulation effect at lower concentrations [13]. Thus, due to this wide use of pyridazine based structures, great attention was paid to the development of different methods for the preparation of pyridazine and its functionalized derivatives. 2. Experimental 2.1. Instrumentation All melting points were determined in open glass capillaries and are uncorrected. Elemental analyses were carried out in the Micro Analytical Laboratory of the Faculty of Science, Cairo University. The IR spectra of compounds were recorded on a Nicolet 6700 FT‐IR (Thermo Scientific) as potassium bromide pellets and frequencies are reported in cm‐1. The mass spectra were recorded on a GC‐MS model Shimadzu Qp‐2010 plus EI 70 eV. The 1H NMR spectra were recorded on a Varian Gemini‐ 300 MHz NMR spectrometer and chemical shifts δ are in ppm relative to internal TMS. Reactions were routinely followed by thin layer chromatography (TLC) on silica gel; F254 aluminum sheets (Merck). The spots were detected by UV irradiation at 254‐365 nm. 212 Deeb et al. / European Journal of Chemistry 6 (2) (2015) 211‐218 Scheme 1 2.2. Synthesis 2.2.1. Synthesis of 4,5,6‐triphenylpyridazin‐3(2H)‐one (1) 4,5,6‐Triphenylpyridazin‐3(2H)‐one (1) was prepared according to the synthetic pathway starting from benzilmono hydrazine and ethyl phenylacetate as described in literature (Scheme 1) [14]. 2.2.2. Synthesis of 3‐chloro‐4,5,6‐triphenylpyridazine (2) A mixture of compound 1 (0.5 g, 1.54 mmol) and phosphoryl chloride (10 mL) was refluxed for 3 hours, the reaction mixture was cooled and poured into ice cooled water (100 mL). The solid product was filtered off, washed with water, dried and recrystallized from ethanol. M.p.: 170‐172 °C (Scheme 1) [14]. 2.2.3. Synthesis of 6,7,8‐triphenyltetrazolo[1,5‐b]pyridazine (3) To a solution of compound 2 (0.5 g, 1.46 mmol) in dimethylformamide (10 mL) sodium azide (0.28 g, 4.38 mmol) was added. The reaction mixture was heated at 100 °C for 1 hour, the cooled reaction mixture was poured into water (100 mL), the solid product formed was filtered off, washed with water, dried and recrystallized from ethanol (Scheme 1). M.p.: 194‐196 °C [15,16]. 2.2.4. Synthesis of 4,5,6‐triphenyl‐N‐(triphenylphosphoran ylidene)pyridazine‐3‐amine (4) To a solution of compound 3 (0.5 g, 1.43 mmol) in o‐ dichlorobenzene (10 mL), triphenylphosphine (0.37 g, 1.43 mmol) was added. The reaction mixture was refluxed for 3 hours. The solvent was removed under reduced pressure; the residue was treated with diethyl ether (30 mL). The solid product was filtered off, dried and recrystallized from acetone similar to reported procedure (Scheme 1) [17]. Color: White. Yield: 83%. M.p.: 248‐250 °C. FT‐IR (KBr, ν, cm‐1): 3055‐3023 (CH arom.), 1597 (C=N), 1537 (P‐Ph), 1484, 1412 (C=C). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 7.93‐6.81 (m, 30H, 6Ph). MS (EI, m/z (%)): 583 (M+, 100). Anal. calcd. for C40H30N3P: C, 82.31; H, 5.18; N, 7.20. Found: C, 82.10; H, 5.00; N, 7.00%. 2.2.5. Synthesis of 3‐amino‐4,5,6‐triphenylpyridazine (5) A solution of compound 4 (0.5 g, 0.86 mmol) in AcOH (80 %, 10 mL) was heated under reflux for 1 h. After cooling, the reaction mixture was poured into water (100 mL). The precipitate that formed was filtered off, washed with water, dried, and recrystallized from methanol (Scheme 1). Color: White. Yield: 86.61 %. M.p.: 260‐262 °C. FT‐IR (KBr, ν, cm‐1): 3470‐3280 (NH2), 3059 (CH Arom.), 1629 (C=N). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 5.84 (s, 2H, NH2), 6.87‐7.62 (m, 15H, 3Ph). MS (EI, m/z (%)): 323([M]+, 58.23), 322 ([M‐1]+ (100)), 246 (3.82), 178 (15.05), 146 (2.10), 117 (36.06), 103 (1.31), 77 (5.93). Anal.calcd. for C22H17N3: C, 81.71; H, 5.30; N, 12.99. Found: C, 81.70; H 5.30; N 12.90%. 2.2.5.1. Reaction of compound 5 with nitrous acid Compound 5 (0.5 g,1.55 mmol) was dissolved in concentrated HCl (5 mL), cooled to 0‐5 °C in an ice bath, then a solution of NaNO2 (0.22 g, 3.1 mmol) in H2O (5 mL) was added drop by drop with stirring, keeping the temperature at 0‐5 °C. The mixture was stirred for further 1 h at room temperature. The solid product was filtered off, washed with water, dried and recrystallized from benzene to give compound 1, identical with that prepared from benzilmonohydrazone and ethyl phenyl acetate, according to reference (Scheme 1) [14] (M.p. and mixed m.p.). Yield: 0.43 g (85.66 %). 2.2.6. Synthesis of N‐(4,5,6‐triphenylpyridazin‐3‐yl) formamide (6a) A mixture of compound 5 (0.5 g, 1.55 mmol) and formic acid (0.1 mL, 1.55 mmol) in dimethylformamide (10 mL) was refluxed for 7 h. After cooling, the reaction mixture was poured into ice water (100 mL). The precipitate that formed was filtered off, washed with water, dried, and recrystallized from ethanol (Scheme 2). Color: White. Yield: 92 %. M.p.: 237‐ 238 °C. FT‐IR (KBr, ν, cm‐1): 3279 (NH), 3058 (CH arom.), 1697 (C=O), 1629 (C=N). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 5.78 (s, 1H, NH), 6.99‐7.09 (m, 15H, 3Ph), 7.14 (s, 1H, CHO). MS (EI, m/z (%)): 351 ([M]+, 2.37), 322 ([M‐29]+, 100), 246 (3.82), 178 (15.05), 146 (2.10), 117 (36.06), 103 (1.31). Anal. calcd. for C23H17N3O: C, 78.61; H, 4.88; N, 11.96. Found: C, 78.30; H 5.00; N 12.20%. Deeb et al. / European Journal of Chemistry 6 (2) (2015) 211‐218 213 Scheme 2 2.2.7. Synthesis of N‐(4,5,6‐triphenylpyridazin‐3‐yl) acetamide (6b) A solution of compound 5 (0.5 g, 1.55 mmol) in acetic anhydride (10 mL) was heated under reflux for 5 h. The solvent was evaporated under reduced pressure; the solid residue was collected and recrystallized from ethanol (Scheme 2). Color: White. Yield: 90.26 %. M.p.: 206‐208 °C. FT‐IR (KBr, ν, cm‐1): 3425 (NH), 3027(CH arom.), 2935 (CH aliph.), 1723 (C=O), 1629 (C=N). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 2.15 (s, 3H, CH3), 7.02‐7.39 (m, 15H, 3Ph), 7.40 (s, 1H, NH). MS (EI, m/z(%)): 365 ([M]+, 71.47), 364 ([M‐1]+, 100), 350 (66.80), 322 (61.66), 307 (4.84), 288 (7.68), 263 (6.65). Anal. calcd. for C24H19N3O: C, 78.88; H, 5.24; N, 11.50. Found: C, 79.10; H 5.10; N 11.20%. 2.2.8. Synthesis of N‐(4,5,6‐triphenylpyridazin‐3‐yl) benzamide (6c) A mixture of compound 5 (0.5 g, 1.55 mmol) and benzoyl chloride (0.18 mL, 1.55 mmol) in pyridine (10 mL) was refluxed for 7 h. After cooling, the reaction mixture was poured into ice water (100 mL), the precipitate that formed was filtered off, washed with water, dried and recrystallized from ethanol (Scheme 2). Color: White. Yield: 74.13 %. M.p.: 227‐229 °C. FT‐IR (KBr, ν, cm‐1): 3348 (NH amide), 3059, 3031 (CH‐Arom.), 1704 (C=O). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 7.13‐7.33 (m, 20H, 4Ph), 7.35 (s, 1H, NH). Anal. calcd. for C29H21N3O: C, 81.48; H 4.95; N, 9.83. Found: C 81.70; H 4.50; N 10.10%. 2.2.9. Synthesis of 2‐chloro‐N‐(4,5,6‐triphenylpyridazin‐3‐ yl)acetamide (6d) Chloroacetyl chloride (0.12 mL, 1.55 mmol) was added to a solution of compound 5 (0.5 g, 1.55 mmol) in pyridine (10 mL). The reaction mixture was stirred at room temperature for 2 h, poured into water (100 mL); the solid product that formed was filtered off, washed with water, dried and recrystallized from ethanol (Scheme 2). Color: White. Yield: 79.26 %. M.p.: 272‐274 °C. FT‐IR (KBr, ν, cm‐1): 3284 (NH amide), 3058 (CH‐Arom.), 1646 (C=O amide). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 4.20 (s, 2H, CH2), 6.93‐7.68 (m, 15H, 3Ph), 7.88 (s, 1H, NH). Anal. calcd. for C24H18ClN3O: C, 72.09; H, 4.54; N, 10.51. Found: C, 72.40; H, 4.80; N, 10.00%. 2.2.10. Synthesis of N‐ethylidene‐4,5,6‐triphenylpyridazin‐ 3‐amine (7) A mixture of compound 5 (0.5 g, 1.55 mmol) and acetaldehyde (0.1 mL, 1.55 mmol) was refluxed for 4 h, after cooling, the reaction mixture was treated with diethyl ether (50 mL). The solid product was filtered off, dried, and recrystallized from ethanol (Scheme 2). Color: Brown. Yield: 79.26 %. M.p.: 233‐235 °C. FT‐IR (KBr, ν, cm‐1): 3056, 3026 (CH Arom.), 2963, 2873 (CH aliph.), 1690 (C=N imino). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 1.80 (d, 3H, CH3), 7.18‐7.63 (m, 16H, 3Ph, =CH). Anal. calcd. for C24H19N3: C, 82.49; H, 5.48; N, 12.03. Found: C, 82.10; H, 5.40; N, 12.3%. 2.2.11. Synthesis of N,N‐bis(4,5,6‐triphenylpyridazin‐3‐yl) propanediamide (8) A mixture of compound 5 (0.5 g, 1.55 mmol) and diethyl malonate (0.24 g, 1.55 mmol) was heated under reflux for 3 h. After cooling, the reaction mixture was treated with diethyl ether (50 mL), and the solid product was filtered off,dried and recrystallized from dimethylformamide (Scheme 2). Color: White. Yield: 81.43 %. M.p.: 218‐220 °C. FT‐IR (KBr, ν, cm‐1): 3156 (NH amide), 3059, 3024 (CH Arom.), 2972, 2816 (CH Aliph.), 1698 (C=O amide). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 1.80 (s, 2H, CH2), 6.87‐7.31 (m, 30H, 6Ph), 10.23 (s, 2H, 2NH). 214 Deeb et al. / European Journal of Chemistry 6 (2) (2015) 211‐218 Scheme 3 MS (EI, m/z (%)): 714 ([M]+, 7.92), 658 (9.09), 406 (7.92), 363 (58.50), 322 (100). Anal. calcd. for C47H34N6O2: C, 78.97; H, 4.79; N, 11.67. Found: C 79.30; H, 4.69; N, 12.00%. 2.2.12. Synthesis of 7,8,9‐triphenyl‐2H‐pyrimido[1,2‐b] pyridazine‐2,4(3H)‐dione (9) A mixture of compound 5 (0.5 g, 1.55 mmol), malonic acid (0.16 g, 1.55 mmol) and phosphoryl chloride (10 mL) was heated under reflux for 1 h. The reaction mixture was cooled to room temperature and poured into ice cooled water (200 mL). The solid product was filtered off, washed with water, dried and recrystallized from ethanol (Scheme 2). Color: Yellow. Yield: 72.70%. M.p.: 188‐190 °C. FT‐IR (KBr, ν, cm‐1): 3057 (CH Arom.), 2923 (CH Aliph.), 1703 (C=O), 1636 (C=N). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 3.99 (s, 2H, CH2), 6.78‐ 7.65 (m, 15H, 3Ph). MS (EI, m/z (%)): 391 (M+, 72.07), 363 (11.24), 349 (10.60), 335 (5.41), 321 (16.82), 314 (4.59), 288 (3.35), 213 (3.30), 178 (25.40), 103 (4.85), 69 (100). Anal. calcd. for C25H17N3O2: C, 76.71; H, 4.38; N, 10.74. Found: C, 76.50; H, 4.20; N, 10.60%. 2.2.13. Synthesis of ethyl oxo[(4,5,6‐triphenylpyridazin‐3‐ yl)amino]acetate (10a) A mixture of compound 5 (0.5 g, 1.55 mmol) and diethyl oxalate (0.16 mL, 1.55 mmol) was heated under reflux for 3 h. After cooling, the reaction mixture was treated with diethyl ether (50 mL), and the solid product formed was filtered off, dried, and recrystallized from ethanol (Scheme 3). Color: Yellow. Yield: 80.92 %. M.p.: 217‐219 °C. FT‐IR (KBr, ν, cm‐1): 3425 (NH amide), 3059 (CH Arom.), 2976, 2933 (CH Aliph.), 1729 (C=O ester), 1682 (C=O amide), 1226 (C‐O). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 1.26 (t, J = 7.5 Hz, 3H, CH3), 3.91 (q, 2H, CH2), 6.99‐7.62 (m, 15H, 3Ph), 7.86 (s, 1H, NH). MS (EI, m/z (%)): 423 (M+, 6.77), 422 ([M‐1]+, 10.68), 378 (14.28), 350 (100), 322 (3.48), 307 (5.11), 206 (0.64), 178 (9.14), 77 (10.57), 76 (2.03). Anal. calcd. for C26H21N3O3: C, 73.74; H, 5.00; N, 9.92. Found: C 74.10; H, 5.40; N, 10.10%. 2.2.14. Synthesis of 2‐cyano‐N‐(4,5,6‐triphenylpyridazin‐3‐ yl)acetamide (10b) A mixture of compound 5 (0.5 g, 1.55 mmol) and ethyl cyanoacetate (0.16 mL, 1.55 mmol) was heated under reflux for 1 h. The cooled reaction mixture was treated with diethyl ether (50 mL). The solid product was filtered off, dried and recrystallized from ethanol (Scheme 3). Color: Brown. Yield: 79.51 %. M.p.: 178‐180 °C. FT‐IR (KBr, ν, cm‐1): 3184 (NH Amide), 3060 (CH Arom.), 2985 (CH Aliph.), 2204 (C≡N), 1658 (C=O amide). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 3.58 (s, 2H, CH2), 6.51 (s, 1H, NH), 6.97‐7.42 (m, 15H, 3Ph). MS (EI, m/z (%)): 390 (M+, 79.96), 373 (12.58), 364 (5.13), 362 (11.96), 322 (100), 313 (12.83), 307 (20.20), 287 (25.24), 178 (30.92), 77 (42.05), 68 (71.96). Anal. calcd. for C25H18N4O: C, 76.91; H, 4.65; N, 14.35. Found: C: 77.30; H, 4.90; N, 14.70%. 2.2.15. Synthesis of 4‐amino‐7,8,9‐triphenyl‐2H‐pyrimido [1,2‐b]pyridazin‐2‐one (11a) A mixture of compound 5 (0.5 g, 1.55 mmol), ethyl cyanoacetate (0.16 mL, 1.55 mmol), and excess polyphosp‐ horic acid (1 g) was heated at 110 °C for 6 h with stirring. The cooled mixture was poured into ice water (200 mL), and the solution was neutralised with NaOH (10 %). The solid product was filtered off, washed with water, dried and recrystallized from ethanol (Scheme 3). Color: Pale brown. Yield: 76.16 %. M.p.: 196‐198 °C. FT‐IR (KBr, ν, cm‐1): 3431, 3389 (NH2), 3058 (CH Arom.), 1645 (C=O Amide). Deeb et al. / European Journal of Chemistry 6 (2) (2015) 211‐218 215 Scheme 4 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 5.49 (s, 1H, CH), 5.80 (s, 2H, NH2), 6.89‐7.63 (m, 15H, 3Ph). MS (EI, m/z (%)): 390 (M+, 70.87), 350 (67.96), 347 (64.08), 335 (52.43), 312 (7.77), 271 (58.25), 246 (52.43), 236 (58.25), 204 (81.55), 161 (66.02), 103 (64.08), 79 (100), 77 (83.50), 76 (53.40). Anal. calcd. for C25H18N4O: C, 76.91; H, 4.65; N, 14.35. Found: C, 77.40; H, 4.90; N, 14.70%. 2.2.16. Synthesis of 4‐acetylamino‐7,8,9‐triphenyl‐2H‐ pyrimido[1,2‐b]pyridazin‐2‐one (11b) A solution of compound 11a (0.5 g, 1.28 mmol) in acetic anhydride (10 mL) was refluxed for 3 h. The solvent was then evaporated under reduced pressure; the solid product was collected and recrystallized from acetone (Scheme 3). Color: Dark brown. Yield: 79.57 %. M.p.: > 300 °C. FT‐IR (KBr, ν, cm‐ 1): 3357 (NH Amide), 3059 (CH Arom.), 2979, 2932 (CH Aliph.), 1700 (C=O cyclic), 1634 (C=O amide). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 1.80 (s, 3H, CH3), 6.56 (s, 1H, H‐3), 7.70 (d, 1H, NH), 7.29‐7.98 (m, 15H, 3Ph). MS (EI, m/z (%)):432 (M+, 14.40), 377 (23.25), 372 (12.96), 353 (11.73), 350 (13.37), 328 (12.76), 314 (11.32), 305 (10.70), 227 (16.87), 205 (23.87), 125 (11.73), 117 (16.05), 102 (14.61), 84 (14.61), 80 (100), 59 (14.40), 53 (16.67). Anal. calcd. for C27H20N4O2: C, 74.98; H, 4.66; N, 12.95. Found: C, 74.70; H, 4.60; N, 12.70%. 2.2.17. Synthesis of ethyl 3‐[(4,5,6‐triphenylpyridazin‐3‐yl) imino]butanoate (12a) A mixture of compound 5 (0.5 g, 1.55 mmol) and ethyl acetoacetate (0.2 mL, 1.55 mmol) was heated under reflux for 3 h. After cooling, the reaction mixture was treated with diethyl ether (50 mL), and the solid product formed was filtered off, dried and recrystallized from ethanol (Scheme 3). Color: Brown. Yield: 77.22 %. M.p.: 216‐218 °C. FT‐IR (KBr, ν, cm‐1): 3057 (CH Arom.), 2977, 2927 (CH Aliph.), 1718 (C=O ester), 1650 (C=N imino), 1231 (C‐O acetate). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 2.8 (t, J = 7.5 Hz, 3H, CH2CH3), 1.91 (s, 3H, CH3C=N), 2.60 (s, 2H, CH2CO), 3.83 (q, 2H, CH2CH3), 6.95‐ 7.63 (m, 15H, 3Ph). MS (EI, m/z (%)): 435 (M+, 23.09), 390 (44.86), 361 (17.00), 358 (19.57), 349 (22.15), 322 (52.64), 307 (52.67), 256 (13.28), 229 (13.43), 206 (49.44), 178 (18.91), 176 (100), 128 (29.51), 98 (8.46), 87 (26.46), 74 (22.10). Anal. calcd. for C28H25N3O2: C, 77.22; H, 5.79; N, 9.65. Found: C, 77.60; H, 6.00; N, 10.00%. 2.2.18. Synthesis of 3‐[(4,5,6‐triphenylpyridazin‐3‐yl)imino] butanoic acid (12b) Compound 12a (0.5 g, 1.15 mmol) was added to a solution of potassium hydroxide (1 g) in ethanol (10 mL), then the reaction mixture was heated under reflux for 2 h. After cooling, the reaction mixture was poured into ice water (100 mL), and neutralized with hydrochloric acid. The solid product was filtered off, washed with water, dried and recrystallized from ethanol (Scheme 3). Color: Dark brown. Yield: 81.20 %. M.p.: > 300 °C. FT‐IR (KBr, ν, cm‐1): 3384 (OH acid), 3059 (CH Arom.), 2922, 2852 (CH Aliph.), 1714 (C=O acid). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 1.95 (s, 3H, CH3), 2.71(s, 2H, CH2), 7.41‐7.79 (m, 15H, 3Ph) 11.03 (s, 1H, COOH). MS (EI, m/z (%)): 407 (M+, 38.30), 392 (39.01), 379 (41.13), 361 (43.97), 348 (48.23), 307 (46.10), 303 (40.43), 267 (44.68), 141 (52.48), 104 (11.35), 100 (42.55), 58 (8.51), 57 (100). Anal. calcd. for C26H21N3O2: C, 76.64; H, 5.19; N, 10.31.Found: C, 76.90; H, 5.40; N, 10.50%. 2.2.19. Synthesis of N‐(4,5,6‐triphenylpyridazin‐3‐yl) benzoylacetamide (13) A mixture of compound 5 (0.5 g, 1.55 mmol) and ethyl benzoylacetate (0.27 mL, 1.55 mmol) was heated under reflux for 1 h. after cooling, the reaction mixture was treated with diethyl ether (50 mL), and the solid product was filtered off , dried and recrystallized from ethanol (Scheme 3). Color: Dark brown. Yield: 68.87 %. M.p.: 190‐192 °C. FT‐IR (KBr, ν, cm‐1): 3429 (NH amide), 3058 (CH arom.), 2925 (CH aliph.), 1723 (C=O ketone), 1677 (C=O, amide). 1H NMR (300 MHz, DMSO‐ d6, δ, ppm): 3.31 (s, 2H, CH2), 7.11‐7.82 (m, 20H, 4Ph), 7.97 (s, 1H, NH). MS (EI, m/z (%)): 469 (M+, 4.09), 363 (3.21), 350 (4.94), 322 (5.34), 291 (11.45), 263 (5.51), 206 (4.12), 177 (5.60), 163 (4.32), 105 (89.44), 103 (7.46), 77 (100). Anal. calcd. for C31H23N3O2: C, 79.30; H, 4.94; N, 8.95. Found: C, 79.60; H, 5.10; N, 8.50%. 2.2.20. General procedure for the reaction of 3‐chloro‐4,5,6‐ triphenylpyridazine (2) with 4‐aminobenzenesulfonamide derivatives (14a‐g) A mixture of compound 2 (0.5 g, 1.46 mmol) and 4‐ aminobenzenesulfonamide derivatives 14a‐g (1.46 mmol) in n‐butanol (10 mL) was refluxed for 5 h, cooled to room temperature, and the separated solid was filtered off, washed with water, dried, and recrystallised from ethanol to givecompounds 15a‐g (Scheme 4). 4‐[(4, 5, 6‐Triphenylpyridazin‐3‐yl)amino]benzenesulfon amide (15a): Color: White. Yield: 81.66 %. M.p.: 216‐218 °C. FT‐IR (KBr, ν, cm‐1): 3369, 3294, 3214 (NH, NH2), 3078 (CH arom.), 1328 (SO2 asym.), 1156 (SO2 sym.). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 7.21 (s, 2H, NH2), 7.70‐7.76 (m, 19H, Ar‐H), 10.25 (s, 1H, NH). MS (EI, m/z (%)): 478 (M+, 25.09), 463 (21.91), 373 (18.37), 361 (18.37), 322 (19.08), 305 (21.20), 178 (33.57), 172 (100), 118 (8.13), 103 (3.89). Anal. calcd. for C28H22N4O2S: C, 70.27; H, 4.63; N, 11.71. Found: C, 70.50; H, 4.70; N, 11.40%. N‐Benzyl‐4‐[(4, 5, 6‐triphenylpyridazin‐3‐yl)amino]benzene sulfonamide (15b): Color: White. Yield: 90.43 %. M.p.: 118‐120 °C. FT‐IR (KBr, ν, cm‐1): 3379, 3292 (2NH), 3064 (CH arom.), 2931, 2877 (CH aliph.), 1311 (SO2, asym.), 1154 (SO2, sym.). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 3.87 (s, 2H, CH2), 5.91 (s, 1H, NHSO2), 6.58‐7.61 (m, 24H, Ar ‐ H), 7.63 (s, 1H, NH). MS (EI, m/z (%)): 567 ([M‐1]+, 48.86), 477 (3.41), 466 (37.50), 216 Deeb et al. / European Journal of Chemistry 6 (2) (2015) 211‐218 452 (29.55), 390 (34.09), 362 (35.23), 341 (11.93), 305 (31.25), 288 (37.50), 260 (47.73), 234 (52.27), 179(43.18), 170 (31.25), 116 (36.93), 106 (69.89), 103 (44.89), 93 (100), 91 (32.39), 77 (16.48). Anal. calcd. for C35H28N4O2S: C, 73.92; H, 4.96; N, 9.85.Found: C, 73.60; H, 4.80; N, 10.10%. N‐Phenyl‐4‐[(4, 5, 6‐triphenylpyridazin‐3‐yl)amino]benzene sulfonamide (15c): Color: White. Yield: 80.35 %. M.p.: 191‐193 °C. FT‐IR (KBr, ν, cm‐1): 3349, 3247 (2NH), 3068 (CH arom.), 1318 (SO2 asym.), 1154 (SO2 sym.). 1H NMR (300 MHz, DMSO‐ d6, δ, ppm): 5.94 (s, 1H, NH), 6.51‐7.39 (m, 24H, Ar‐H), 9.82 (s, 1H, NHSO2). MS (EI, m/z (%)): 554 (M+, 22.10), 462 (25.21), 399 (4.53), 376 (15.58), 350 (20.96), 326 (19.83), 306 (17.56), 245 (16.43), 206 (18.41), 178 (12.18), 154 (18.13), 129 (7.65), 107 (100). Anal. calcd. for C34H26N4O2S: C, 73.62; H, 4.72; N, 10.10. Found: C, 73.90; H, 4.90; N, 9.80%. N‐4‐Tolyl‐4‐[(4, 5, 6‐triphenylpyridazin‐3‐yl)amino]benzene sulfonamide (15d): Color: White. Yield: 84.4 %. M.p.: 188‐190 °C. FT‐IR (KBr, ν, cm‐1): 3344, 3128 (2NH), 3064 (CH arom.), 2918, 2857 (CH aliph.), 1320 (SO2 asym.), 1152 (SO2 sym.). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 2.17 (s, 3H, CH3), 5.91 (s, 1H, NH), 6.49‐7.37 (m, 23H, Ar‐H), 9.64 (s, 1H, NHSO2). MS (EI, m/z (%)): 568 (M+, 74.00), 540 (54.00), 526 (65.00), 477 (65.00), 450 (84.00), 435 (84.00), 401 (100), 399 (58.00), 388 (54.00), 312 (55.00), 308 (57.00), 279 (6.00), 261 (71.00), 169 (78.00), 105 (57.00), 76 (82.00). Anal. calcd. for C35H28N4O2S: C, 73.92; H, 4.96; N, 9.85. Found: C, 73.60; H, 5.10; N, 9.60%. N‐(4‐Methoxyphenyl)‐4‐[(4, 5, 6‐triphenylpyridazin‐3‐yl) amino]benzenesulfonamide (15e): Color: White. Yield: 86.75 %. M.p.: 198‐200 °C. FT‐IR (KBr, ν, cm‐1): 3388, 3282 (2 NH), 3074 (CH arom.), 2957, 2835 (CH aliph.), 1310 (SO2 asym.), 1252 (C– O), 1148 (SO2, sym,). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 3.66 (s, 3H, CH3), 5.90 (s, 1H, NH), 6.48‐7.32 (m, 23H, Ar‐H), 9.43 (s, 1H, NHSO2). MS (EI, m/z (%)): 584 (M+, 44.78), 554 (41.79), 508 (28.86), 478 (28.36), 463 (25.87), 406 (41.79), 398 (33.83), 377 (26.87), 321 (28.36), 262 (41.79), 206 (34.83), 186 (28.36), 179 (29.85), 123 (32.34), 107 (80.10), 106 (100), 77 (42.79). Anal. calcd. for C35H28N4O3S: C, 71.90; H, 4.83; N, 9.58. Found: C, 71.50; H, 4.90; N, 9.30%. N‐(4‐Chlorophenyl)‐4‐[(4, 5, 6‐triphenylpyridazin‐3‐yl) amino]benzenesulfonamide (15f): Color: White. Yield: 87.3 %. M.p.: 193‐195 °C. FT‐IR (KBr, ν, cm‐1): 3414, 3347 (2NH), 3056 (CH aomr.), 1316 (SO2 asym.), 1153 (SO2 sym.). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 5.98 (s, 1H, NH), 6.51‐7.40 (m, 23H, Ar‐H), 9.98 (s, 1H, NHSO2). MS (EI, m/z (%)): 590.5 (M++2, 0.60), 588.5 (M+, 2.87), 486 (3.08), 477 (3.63), 396 (2.41), 282 (45.14), 156 (100), 155 (19.51), 127 (17.78). Anal. calcd. for C34H25ClN4O2S: C, 69.32; H, 4.28; N, 9.51. Found: C, 69.64; H, 4.20; N, 9.78%. N‐(4‐Nitrophenyl)‐4‐[(4,5,6‐triphenylpyridazin‐3‐yl) amino] benzenesulfonamide (15g): Color: White. Yield: 91.43 %. M.p.: 208‐210 °C. FT‐IR (KBr, ν, cm‐1): 3389, 3342 (2NH), 3061 (CH arom.), 1528 (NO2 asym.), 1348 (NO2 sym.), 1317 (SO2 asym.), 1152 (SO2 sym.). 1H NMR (300 MHz, DMSO‐d6, δ, ppm): 6.05 (s, 1H, NH), 6.53‐6.92 (m, 23H, Ar‐H), 10.49 (s, 1H, NHSO2). MS (EI, m/z (%)): 599 (M+, 16.40), 554 (8.84), 479 (10.13), 422 (11.25), 407 (4.02), 395 (9.97), 371 (8.84), 323 (4.82), 293 (27.33), 277 (18.17), 206 (10.61), 202 (2.73), 191 (8.36), 178 (7.72), 138 (38.26), 92 (100). Anal. calcd. for C34H25N5O4S: C, 68.10; H, 4.20; N, 11.68. Found: C, 68.40; H, 4.10; N, 11.9%. 2.3. Antimicrobial activity Applying the agar plate diffusion technique [18], the newly synthesised compounds were screened for their antimicrobial activity against some Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa), yeast (Candida albicans), and fungi (Aspergillus niger). In this method, a standard 5 mm sterilised filter paper disk impregnated with the compound (0.3 mg in 0.1 mL of dimethylformamide) was placed on agar plate seeded with the tested organism. The plates were incubated for 24 h at 37 °C for bacteria, and for four days at 28 °C for fungi. The inhibition zone of bacteria and fungi growth around the disk were determined. 3. Results and discussion 3.1. Synthesis During a study of the synthesis of pyridazine derivatives, 3‐aminopyridazine (5) was selected as an ideal starting material for our purpose. Its preparation was accomplished via the classical Staudinger reaction [17]. Tetrazolopyridazine (3) was reduced to the corresponding aminopyridazine 5 via formation of phosphazene intermediate (4), as depicted in (Scheme 1). 3‐Chloro‐4, 5, 6‐triphenylpyridazine (2) was obtained by treatment of 4,5,6‐triphenylpyridazin‐3(2H)‐ one(1) with phosphoryl chloride at refluxing temperature. Azidation of compound 2 with sodium azide in dimethyl formamide at 100 °C gave the corresponding tetrazolo[1,5‐ b]pyridazine, 3 [15,16]. Refluxing the latter compound with one equivalent of triphenylphosphine in 1,2‐dichlorobenzene for 3 hours yielded 4,5,6‐triphenyl‐N‐(triphenylphosphanyli‐ dene)pyridazin‐3‐amine (4) [17]. Subsequent acid hydrolysis of compound 4 with a mixture of acetic acid: water (4:1, v:v) provided the corresponding 3‐aminopyridazine intermediate 5, in 86% yield. The structure of compound 5 was established by the presence of stretching absorption bands at 3473 and 3280 cm‐1 in the IR spectrum due to NH2 group. It was also supported by the presence of D2O exchangeable broad singlet band due to the NH2 protons at 5.80 ppm in 1H NMR. In addition, the mass spectrum showed the molecular ion peak M+ at m/z = 323, which was in agreement with the calculated molecular weight (C22H17N3).Treatment of compound 5with hydrochloric acid/sodium nitrite solution, carried out at low temperature, gave a single product obtained from the diazonium ion, which was generated as an intermediate followed by ultimate hydroxylation. The isolated product was found to be identical with the authentic sample 1 (M.p., mixed m.p. and identical IR spectra), which was synthesized according to method A [14] (Scheme 1). Formylation, acetylation, and benzoylation of the amino group in compound 5 were achieved successfully by heating with formic acid/ dimethylformamide, acetic anhydride, and benzoyl chloride/ pyridine at refluxing temperature to afford N‐(4,5,6‐triphenyl pyridazin‐3‐yl)formamide 6a, N‐(4,5,6‐triphenylpyridazin‐3‐ yl)acetamide 6b and N‐(4,5,6‐triphenylpyridazin‐3‐yl)benza‐ mide 6c, respectively. Furthermore, reaction of compound 5 with chloroacetyl chloride in pyridine at room temperature yielded 2‐chloro‐N‐ (4,5,6‐triphenylpyridazin‐3‐yl)acetamide 6d (Scheme 2). The structures of compounds 6a‐d were confirmed on the basis of spectroscopic data (IR, Mass, and1H NMR spectra) and elemen‐ tal analysis as described in the experimental part. Reaction of the 3‐aminopyridazine(5) with aromatic aldehydes under different reaction conditions did not produce the arylidene amino derivatives, but led only to the recovery of the starting material, possibly owing to steric hindrance of the bulky phenyl group in position four, and the electronic effect of sp2 cyclic nitrogen atom. On the other hand, refluxing compound 5 with little excess of acetaldehyde for 4 hours afforded N‐ ethylidene‐4,5,6‐triphenylpyridazin‐3‐amine (7) (Scheme 2), as proved by the disappearance of NH2 bands of the starting material in IR and 1H NMR spectra. The reaction of compound 5 with active methylene compoundswas investigated, such as diethyl malonate at refluxing temperature for 3 hours gave the dimeric structure 8 (Scheme 2) as indicated from elemental analysis and spectral data (IR, Mass, and 1H NMR spectra). On the other hand, reaction of compound 5 with malonic acid in presence of phosphoryl chloride at refluxing tempe‐ rature for 1 hour afforded 7,8,9‐triphenyl‐2H‐pyrimido[1,2‐ b]pyridazine‐2,4(3H)‐dione (9) in good yield. Deeb et al. / European Journal of Chemistry 6 (2) (2015) 211‐218 217 Table 1. Antimicrobial activity of the prepared compounds *. Zone of inhibition Compound Aspergillus niger Candida albicans Pseudomonas aeruginosa (G‐) Escherichia coli (G‐) Bacillus Subtilis (G+) Staphylococcus Aureus (G+) ‐ ‐+++++ +++++ 5 ++ ++ +++++‐ + 6b +++ ++ ++++++++ ++ 9 +++ ++ +++++++++ ++ 11a +++ ++ ‐‐+ ++ 15a +++ ++ ++ +++ + ++ 15b +++++ +++ ++ + ++ ++ 15c +++++ ++ ++ +++ +++ ++ 15d ‐ ‐+++++++++ +++ 15e +++++ ++ ++ +++ +++ + 15f ‐ ‐++++++ +++++ 15g ‐ ‐ ++++ +++ ++++ ++++ Septrin D.S. ++++ ++++ ‐ ‐ ‐ ‐ Fungistatin * The concentration ofthe all synthesised compounds and the two references was 0.30 mg in 0.10 mL of dimethylformamide. Zone of inhibition: + = < 15 mm; ++ = 15‐24 mm; +++ = 25‐34 mm; ++++ = 35‐44 mm; +++++ = 45‐54 mm, ‐ = no inhibition. However, when compound 5was refluxed in diethyl oxalate, a product was isolated in 80% yield, which was proved to be ethyl oxo[(4,5,6‐triphenylpyridazin‐3‐yl) amino]acetate, 10a (Scheme 3) on the basis of elemental and spectral data. Refluxing compound 5 with ethyl cyanoacetate produced 2‐cyano‐N‐(4,5,6‐triphenyl pyridazin‐3‐yl) acet‐ amide 10b (Scheme 3), as proved by the presence of cyano group at 2204 cm‐1 and amide carbonyl group at 1658 cm‐1, and the disappearance of the NH2 bands in the IR spectrum. On the other hand, heating equimolar amounts of compound 5 and ethyl cyanoacetate in polyphosphoric acid at 110 °C for 6 hours, quenching the reaction mixture with water, and neutralizing with 10% sodium hydroxide, yielding 4‐amino‐7, 8, 9‐triphenyl‐2H‐pyrimido[1,2‐b]pyridazin‐2‐one (11a), which was identified on the basis of elemental analysis and spectral data. The reaction of the 4‐aminopyrimidopyridazine11a with acetic anhydride produced the corresponding 4‐acetylamino derivative 11b (Scheme 3), which affords a further evidence for the structure of the compound 11a. Fusion of the 3‐aminopyridazine derivative 5 with ethyl acetoacetate was found to proceed steadily to give the condensation product 12a (Scheme 3). The IR spectrum of compound 12a showed the presence of ester carbonyl group at 1718 cm‐1, C=N imino group at 1650 cm‐1, and the disappearance of the NH2 bands. The mass spectrum showed the molecular ion peak M+ at m/z435. Further evidence for the structure of compound 12a was obtained by hydrolysis of the latter compound in boiling ethanolic potassium hydroxide to yield the corresponding carboxylic acid 12b. However, fusion of compound 5 with ethyl benzoylacetate produced N‐(4,5,6‐ triphenylpyridazin‐3‐yl)benzoylacetamide, 13 (Scheme 3), as proved by IR spectrum showing absorption bands at 3429 (NH, amide), 1723(C=O, ketone) and 1677 cm‐1 (C=O, amide). The mass spectrum revealed the molecular ion peak M+ at m/z469.The study was also extended to prepare some sulfonamide derivatives containing the pyridazine nucleus with the aim to compare the antimicrobial activity relative to the systems prepared earlier [18]. When 3‐chloropyridazine derivative 2 reacted with N1‐unsubstituted 4‐aminobenzene sulfonamides 14a, and N 1‐substituted 4‐aminobenzenesulfon amides 14b‐g, N1‐4‐[(4, 5, 6‐triphenylpyridzin‐3‐yl)amino] benzenesulfonamide, 15a‐g were produced (Scheme 4). The structure of the latter compounds was established on the basis of elemental analysis, IR, Mass, 1H NMR spectra. The sulfonamide derivatives 14a‐g was prepared using a previously described method [19]. 3.2. Antimicrobial activity bioassay The results (Table 1) indicated that two synthesized compounds 5 and 15ginhibited the growth of the Gram positive bacteria Staphylococcus aureus completely, while compound 15e showed relatively very high antimicrobial activity against Bacillus subtilis. On the other hand, the latter compound 15e; as well as compounds 15d and 15f showed high activity against both Staphylococcus aureus and Bacillus subtilis, respectively. Compounds 9, 11a, 15a, 15b, 15c and 15d possessed moderate activity against Staphylococcus aureus, while compounds 9, 11a, 15c and 15g showed moderate inhibition of Bacillus subtilis. Only compounds 9, 11a and 15c showed moderate antimicrobial activity against both examined Staphylococcus aureus and Bacillus subtilis. On the other hand, compound 11a showed relatively very high antimicrobial activity against Escherichia coli. In addition, compounds 9, 15b, 15d and 15f; and compounds 6b, 9, 11a and 15e possessed high activity against Escherichia coli and Pseudomonas aeruginosa, respectively. Compound 9 was highlyactive against both Escherichia coli and Pseudomonas aeruginosa. Also, the results indicated thatcompounds 5, 6b, 15e and 15g; and compounds 5, 15b, 15c, 15d, 15f and 15g showed moderate activity against Escherichia coli and Pseudomonas aeruginosa, respectively. Compounds 5 and 15g were moderate active against both Escherichia coli and Pseudomonas aeruginosa. The results revealed that compounds 15c, 15d and 15f showed complete inhibition for the growth of Aspergillus niger. In addition, compound 15c; as well as compounds 9, 11a, 15a and 15b were highly active against Candida albicans and Aspergillus niger, respectively. 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