HETEROCYCLES

Paper | Regular issue | Vol. 89, No. 6, 2014, pp. 1393-1411
Received, 1st February, 2014, Accepted, 7th April, 2014, Published online, 16th April, 2014.
DOI: 10.3987/COM-14-12954

■ Synthesis and Antimicrobial Evaluation of Some Isoxazole Based Heterocycles

Elham S. Darwish, Khalid A. Atia, and Ahmad M. Farag*

Department of Chemistry, Faculty of Science, Cairo University, Giza 12613, Egypt

Abstract

The versatile hitherto unreported 2-cyano-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (3) was utilized for the synthesis of a variety of heterocycles incorporating sulfamoyl moiety. The 2-pyridone derivatives were obtained via reaction of cyanoacetamide with pentane-2,4-dione, arylidenes malononitrile, or terephthalaldehyde and malononitrile upon heating under reflux in the presence of a catalyst. Condensation of the cyanoacetamide 3 with salicylaldehyde furnished the corresponding chromene derivatives. Coupling of 3 with arene diazonium chlorides gave the hydrazone derivatives 13a-c, which upon treatment with hydrazine hydrate and ethyl chloroformate furnished the corresponding pyrazole and triazine derivatives, respectively. Reaction of 3 with carbon disulfide and 1,2-dibromoethane, 1,3-dibromopropane or dimethyl sulfate afforded 2-cyano-2-(1,3-dithiolan-2-ylidene)-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (18), 2-cyano-2-(1,3-dithian-2-ylidene)-N-4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (19), and 2-cyano-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)-3,3-bis(methylthio)acrylamide (20). The newly synthesized compounds were evaluated for their in vitro antibacterial and antifungal activities, and showed promising results.

INTRODUCTION
Cyanoacetamides are highly reactive bifunctional compounds. The carbonyl and the cyano functions of these compounds are suitably situated to enable reactions with common reagents to form a variety of heterocycles. Also, the active methylene of cyanoacetamide can take part in a variety of condensation and substitution reactions. Moreover, cyanoacetamides and their related heterocyclic derivatives have attracted great attention due to their interesting biological, therapeutic value and pharmaceutical activities such as antimicrobial,1,2 antifungal,3 insulin releasing,4 carbonic anhydrase inhibitory,5 anti-inflammatory,6 and antitumor properties.7 Some active sulfonamides as antibacterial are also known for their immune-modifying effects.8,9 In addition, pyrazole derivatives have attracted much more attention due to their utilities in the field of drug discovery and agricultural research.10-16 They are also known for their anticancer,17-22 antipyretic,23 anti-inflammatory,24 antimicrobial activities,25-27 antiviral,28 tranquillizing,29 antihypertensive,30 antidepressant,31 anti-arrhythmic,32 anticonvulsant,33 and antidiabetic activities.34 Moreover, some 2-pyridones are also reported to possess antitumor,35 antibacterial,36 elastase inhibitors37 and other biological activities.38,39 In view of these observations and in continuation of our previous work directed to the synthesis of novel heterocyclic compounds of potential biological and pharmacological activities,40-57 we report here the synthesis of some new pyridone, pyrazole and chromene derivatives incorporating sulfonamide moiety starting from 2-cyano-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (3) as an excellent building block for the synthesis of the target compounds.

RESULTS AND DISCUSSION
Cyanoacetamide 3 was synthesized by cyanoacetylation of 4-amino-N-(5-methylisoxazole-3-yl)benzenesulfonamide (sulfamethoxazole) (1) with 3,5-dimethyl-1-cyanoacetylpyrazole (2)58 as previously described (Scheme 1).

One pot reaction of the cyanoacetamide derivative 3 with terephthalaldehyde and malononitrile (1: 1: 2 molar ratio), at reflux temperature in the presence of catalytic amount of piperidine afforded the corresponding derivative 4 (Scheme 2). The mass spectrum of 4 showed a molecular ion peak at m/z 548 corresponding to a molecular formula C27H16N8O4S with a base peak at m/z 235 (100%). Knoevenagel condensation of the cyanoacetamide 3 with aromatic aldehydes viz. benzaldehyde, p-anisaldehyde, and p-chlorobenzaldehyde, furnished the corresponding arylidene derivatives 5a-c (Scheme 2). The IR spectrum of compound 5a, taken as a typical example of the series prepared, revealed absorption bands at 1678, 2219, 3304 and 3194 cm-1 corresponding to carbonyl, nitrile and NH functions, respectively. Its 1H NMR spectrum showed signals at δ 8.30, 10.77 and 11.35 (D2O-exchangeable) due to CH and 2NH protons in addition to aromatic protons at δ 7.62-8.00. Its mass spectrum showed a molecular ion peak at m/z 408. Pyridin-2(1H)-ones 7a-c were obtained through the reaction of the arylidene derivatives 5a-c with malononitrile in dioxane containing a catalytic amount of piperidine. 2-Pyridone derivatives 7a-c were also obtained via one-pot reactions of the cyanoacetamide derivative 3 with malononitrile and the same aldehydes (1:1:1 molar ratio) at reflux temperature in the presence of piperidine. On the other hand, the 2-pyridone derivatives 7a-c were also obtained via reaction of the cyanoacetamide 3 with arylidenemalononitrile viz. benzylidenemalononitrile, 2-(4-chlorobenzylidene)malononitrile, or 2-(4-methoxybenzylidene)malononitrile upon heating under reflux in the presence of piperidine as a catalyst. The spectroscopic data and elemental analyses of the obtained products were in complete agreement with the assigned structures 7a-c.

When the cyanoacetamide 3 was treated with pentane-2,4-dione, in dioxane in the presence of a catalytic amount of triethylamine, it afforded the corresponding 2-pyridinone derivative 10 (Scheme 2). It can be postulated that the reaction initially proceeds via a nucleophilic attack to form the Michael adduct which in turn underwent cyclization via elimination of two water molecules, affording the final product (Scheme 2).
Similarly, cyclocondensation of the cyanoacetamide 3 with salicylaldehyde, in dioxane and in the presence of a catalytic amount of piperidine afforded 2-iminochromene 11 (Scheme 3). On the other hand, reaction of 3 with salicylaldehyde in the presence of AcOH/AcONa afforded chromenone 12. The structure of compound 12 was further confirmed through its synthesis upon hydrolysis of 11 with ethanolic HCl. (Scheme 3). The IR spectrum of compound 11 revealed the disappearance of cyano absorption band and showed absorption bands at 1683, 3135, 3241 and 3301 cm-1 corresponding to carbonyl and three NH functions, respectively. Its 1H NMR spectrum showed three D2O-exchangeable signals at δ 9.29, 11.40 and 13.16 due to three NH protons, in addition to an aromatic multiplet in the region 7.31-7.91. Its mass spectrum showed a molecular ion peak at m/z 424 whereas the 1H NMR spectrum of compound 12 showed two D2O-exchangeable signal at δ 10.93 and 11.36 due to two NH protons.

The cyanoacetamide 3 coupled smoothly with arenediazonium salts, in pyridine to afford the respective hydrazones 13a-c (Scheme 4). The analytical and spectral data of the latter products are consistent with the proposed structures. The 1H NMR spectrum of 13a, taken as an example of the prepared series, displayed, besides an aromatic multiplet at 7.13-7.95 ppm, D2O exchangeable signals at 10.23, 11.32 and 12.02 ppm corresponding to 3 NH protons. Its IR spectrum showed bands at 3382, 3243, 3080, 2217 and 1684 cm-1 due to 3 NH, CN and CO groups, respectively. The latter hydrazones 13a-c underwent intramolecular cyclization upon treatment with hydrazine hydrate to give products identified as the 3-aminopyrazole derivatives 15a-c. The IR spectra of 15a-c showed, in each case, the absence of nitrile and carbonyl bands and revealed the appearance of three bands in the region 3460-3185 cm-1 due to NH2 and NH groups as depicted in Scheme 4. Their 1H NMR spectra displayed singlet in the region 6.05-6.07 and 9.97 and 10.82 ppm attributable to the NH2 and 2NH protons, respectively. Compounds 15a-c were alternatively obtained by reaction of the aminopyrazole derivative 14 with diazotized aromatic amines in pyridine. Compound 14 was prepared by the reaction of 3 with hydrazine hydrate in refluxing dioxane (Scheme 4).

Treatment of the hydrazones 13a-c with ethyl chloroformate in acetic acid, afforded the corresponding triazine derivatives 16a-c (Scheme 5). The structures of compounds 16a-c were established based on their elemental analyses and spectral data (see Experimental part).

When the cyanoacetamide 3 was treated with carbon disulfide, in the presence of potassium hydroxide in DMF followed by cycloalkylation with 1,2-dibromoethane or 1,3-dibromopropane, yielded 2-cyano-2-(1,3-dithiolan-2-ylidene)-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (18), and 2-cyano-2-(1,3-dithian-2-ylidene)-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)-acetamide (19), respectively in good yield (Scheme 6). Furthermore, reaction of 3 with CS2 in the presence of KOH and dimethyl sulfate afforded 2-cyano-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}-phenyl)-3,3-bis(methylthio)acrylamide (20) (Scheme 6). The IR spectra of compounds 18, 19 and 20 showed, in each case, bands corresponding to NH, CH-aliphatic, C≡N and C=O groups. The 1H NMR spectrum of the compound 18 showed signal at 3.95 (s, 4H, 2CH2-dithiolane). Its mass spectrum showed a molecular ion peak at m/z 422. The 1H NMR spectrum of compound 19 showed signals for dithiene moiety at 2.10 (m, 2H, J = 6.80 Hz, CH2), 3.03 (t, 2H, J = 6.6 Hz, CH2), 3.21 (t, 2H, J = 6.6 Hz, CH2). Its mass spectrum showed a molecular ion peak at m/z 436.

ANTIMICROBIAL ACTIVITY
The newly synthesized compounds 4, 5a, 5b, 7b, 10, 11, 14, 15a, 15b, 15c, 19, and 20 were evaluated for their in vitro antibacterial activity against Streptococcus pneumoniae (RCMB-010010) (SP) and Bacillis subtilis (RCMB-010067) (BS) as examples of Gram-positive bacteria and Pseudomonas aeruginosa (RCMB-010043) (PA) and Escherichia coli (RCMB-010052) (EC) as examples of Gram-negative bacteria. They were also evaluated for their in vitro antifungal activity against Aspergillus fumigatus (RCMB-02568) (AF), Syncephalastrum racemosum (RCMB-05922) (SR), Geotricum candidum (RCMB-05097) (GC) and Candida albicans (RCMB-05036) (CA) fungal strains. Inhibition zone diameter (IZD) in mm was used as criterion for the antimicrobial activity using the diffusion technique. The fungicide amphotericin B and the antibiotic sulfamethoxazole were used as references to evaluate the potency of the tested compounds under the same conditions. The results are depicted in Table 1. As it can be seen from the data present in Table 1, all the synthesized derivatives showed moderate to good activity against the tested microorganisms. The most active compounds were 15a,b,c and 7b which revealed strong inhibitory activity to the tested bacteria and fungi. The elevated activity of 15a,b,c and 7b is attributed to the presence of pharmacological pyrazole moiety in compound 15a,b,c and pyridone ring in 7b.

EXPERIMENTAL
Melting points were determined in open glass capillaries with a Gallenkamp apparatus. The IR spectra were recorded using KBr disks on a Pye Unicam SP 3-300 or a Shimadzu FTIR 8101 PC IR spectrophotometer. The NMR spectra were recorded with a Varian Mercury VXR-300 NMR spectrometer at 300 and 75 MHz (1H and 13C NMR spectra, respectively) using CDCl3 and DMSO-d6 as solvents. Chemical shifts were related to that of the solvent. Mass spectra (EI) were obtained at 70 eV with a Shimadzu GCMQP 1000 EX spectrometer. Elemental analyses were carried out at the Micro-analytical Center of Cairo University, Giza, Egypt. The biological evaluation of the products was carried out in the Medical Mycology Laboratory of the Regional Center for Mycology and Biotechnology of Al-Azhar University, Cairo, Egypt.
2-Cyano-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (3). A mixture of 4-amino- N-(5-methylisoxazole-3-yl)benzenesulfonamide (1) (5.06 g, 20 mmol) and 3,5-dimetyl-1- cyanoacetylpyrazole (2) (3.26 g, 20 mmol) in dioxane (20 mL) was refluxed for 3 h. The reaction mixture was poured into crushed ice and the resulting precipitate was filtrated off, washed with EtOH, dried, and finally crystallized from DMF/MeOH (1:3) to give 3. Yield (80%), mp 220-222 ºC (from DMF/MeOH); IR (KBr) νmax/ cm-1: 3329, 3277 (2NH), 2964, 2861 (aliphatic CH), 2262 (C≡N), 1691 (C=O); 1H NMR (DMSO-d6) δ 2.29 (s, 3H, CH3), 3.94 (s, 2H, CH2), 6.11 (s, 1H, isoxazole-H-4), 7.71 (d, 2H, J = 9 Hz, ArH), 7.83 (d, 2H, J = 9 Hz, ArH), 10.67 (s, 1H, D2O-exchangeable, NH), 11.32 (s, 1H, D2O-exchangeable, NH); 13C NMR (DMSO-d6) δ 11.9, 26.9, 66.3, 95.3, 119.1, 128.1, 133.9, 142.5, 157.4, 161.8, 170.2; MS (m/z, %): 322 (M++2, 2.7), 321 (M++1, 2.9), 320 (M+, 4.1), 256 (8.2), 238 (2.9), 223 (11.7), 186 (80.1), 159 (62.9), 132 (41.3), 97 (6.2), 82 (3.1), 68 (100). Anal. Calcd for C13H12N4O4S (320.32): C, 48.74; H, 3.78; N, 17.49; S, 10.01. Found: C, 48.70; H, 3.72; N, 17.43; S, 9.88%.
6-Amino-4-(4-(2,2-dicyanovinyl)phenyl)-1-(N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile (4). To a mixture of the acetamide 3 (0.01 mol), terephthalaledehyde (0.01 mol) and malononitrile (0.02 mol) in EtOH (30 mL), few drop of piperidine was added. The reaction mixture was heated under reflux for 3 h. The formed solid product while hot, was filtrated off, washed with EtOH, dried, and finally crystallized from dioxane to give 4 as white crystals. Yield (80%), mp > 300 ºC (from dioxane); IR (KBr) νmax/cm-1: 3435, 3148 (NH, NH2), 2959 (aliphatic-H), 2214 (C≡N), 1639 (C=O); 1H NMR (DMSO-d6) δ 2.20 (s, 3H, CH3), 6.00 (s, 1H, isoxazole-H-4), 7.39 (m, 4H, Ar-H), 7.44 (s, 1H, D2O-exchangeable, NH), 7.74 (s, 1H, olefinic-H), 7.91 (m, 4H, ArH), 8.40 (s, 2H, D2O-exchangeable NH2); 13C-NMR (DMSO-d6) δ 12.2, 43.6, 66.3, 75.3, 87.8, 96.6, 112.0, 114.0, 115.4, 116.0, 127.9, 128.3, 128.7, 129.5, 135.3, 136.2, 146.9, 157.0, 159.4, 160.2, 163.9, 167.1; MS (m/z, %): 549 (M++1, 78.1), 548 (M+, 89.5), 474 (66.7), 466 (54.3), 451 (67.6), 331 (59.1), 235 (100), 215 (49.5), 153 (70.5), 77 (59.1). Anal. Calcd for C27H16N8O4S (548.53): C, 59.12; H, 2.94; N, 20.43; S, 5.85. Found: C, 59.01; H, 2.90; N, 20.39; S, 5.80%.
N-[4-(Aminosulfonyl)phenyl]-3-aryl-2-cyanoacrylamide (5a-c).
General Procedure: To a solution of the cyanoacetamide 3 (0.320 g, 1 mmol) and the appropriate aromatic aldehydes (1 mmol) in dioxane (20 mL), was added few drops of piperidine and the reaction mixture was refluxed for 6 h. The formed solid product was filtered off, washed with EtOH, dried, and finally recrystallized from proper solvent to give 5a-c.
2-Cyano-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)-3-phenylacrylamide (5a). Yield (80%), mp 282-284 ºC (from dioxane); IR (KBr) νmax/cm-1: 3304, 3194 (2NH), 2892, 2838 (aliphatic CH), 2219 (C≡N), 1678 (C=O); 1H NMR (DMSO-d6) δ 2.30 (s, 3H, CH3), 6.13 (s, 1H, isoxazole-H-4), 7.62 (d, 2H, J = 9 Hz, ArH), 7.84-7.86 (m, 5H, ArH), 8.00 (d, 2H, J = 9 Hz, ArH), 8.30 (s, 1H, olefinic-H), 10.77 (s, 1H, D2O-exchangeable, NH), 11.35 (s, 1H, D2O-exchangeable, NH). MS (m/z, %): 410(M++2, 5.5), 409 (M++1, 5.5), 408 (M+, 7.3), 326 (4.6), 311 (3.2), 236 (4.0), 171 (5.5), 156 (96.3), 128 (100), 101 (39.1), 77 (77.0). Anal. Calcd for C20H16N4O4S (408.43): C, 58.81; H, 3.95; N, 13.72; S, 7.85. Found: C, 58.78; H, 3.88; N, 13.70; S, 7.80%.
2-Cyano-3-(4-methoxyphenyl)-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acrylamide (5b).59 Yield (80%), mp 260-262 ºC (from dioxane); IR (KBr) νmax/cm-1: 3322, 3091 (2NH), 2993, 2843 (aliphatic CH), 2215 (C≡N), 1685 (C=O); 1H NMR (DMSO-d6) δ 2.29 (s, 3H, CH3), 3.87 (s, 3H, OCH3), 6.14 (s, 1H, isoxazole-H-4), 7.19 (d, 2H, J = 9 Hz, ArH), 7.85-7.89 (m, 4H, ArH), 8.04 (d, 2H, J = 9 Hz, ArH), 8.23 (s, 1H, olefinic-H), 10.64 (s, 1H, D2O-exchangeable, NH), 11.35 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 439 (M++1, 4.7), 438 (M+, 6.2), 412 (6.2), 341 (4.2), 304 (10.6), 279 (6.7), 206 (4.1), 186 (100), 158 (26.5), 97 (14.3); Anal. Calcd for C21H18N4O5S (438.45): C, 57.53; H, 4.14; N, 12.78; S, 7.31. Found: C, 57.50; H, 4.09; N, 12.72; S, 7.28%.
3-(4-Chlorophenyl)-2-cyano-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acrylamide (5c).
Yield (60%), mp 275-277 ºC (from dioxane); IR (KBr) νmax/cm-1: 3300, 3087 (2NH), 2988, 2898 (aliphatic CH), 2220 (C≡N), 1682 (C=O); 1H NMR (DMSO-d6) δ 2.29 (s, 3H, CH3), 6.14 (s, 1H, isoxazole-H-4), 7.80 (d, 2H, ArH), 7.84 (d, 2H, Ar-H), 7.88 (d, 2H, J = 9 Hz, ArH), 7.95 (d, 2H, J = 9 Hz, ArH), 9.93 (s, 1H, olefinic-H), 10.76 (s, 1H, D2O-exchangeable, NH), 11.34 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 444 (M++2, 4.8), 443 (M++1, 5.8), 442 (M+, 6.3), 363 (15.4), 345 (9.5), 308 (36.9), 281 (21.9), 254 (5.7), 237 (4.1), 206 (8.8), 190 (100), 161 (45.0), 97 (13.4); Anal. Calcd for C20H15ClN4O4S (442.87): C, 54.24; H, 3.41; Cl, 8.01; N, 12.65; S, 7.24. Found: C, 54.20; H, 3.36; Cl, 8.00; N, 12.62; S, 7.20%.
Synthesis of the pyridones 7a–c.
Method A: A mixture of 5 (10 mmol) and malononitrile (0.66 g, 10 mmol) in dioxane (30 mL) containing piperidine (0.5 mL) was heated under reflux for 3 h, then left to cool. The solid product was filtered off, washed with EtOH, dried, and finally recrystallized from the proper solvent to give 7a-c.
Method B: Equimolar amounts of 3 (10 mmol) and the appropriate 2-(arylidene)malononitrile (10 mmol) in dioxane (30 mL) was added piperidine (0.5 mL) and the reaction mixture was heated under reflux for 3 h, then left to cool. The solid product was filtered off, washed with EtOH, dried, and finally recrystallized from the proper solvent to give 7a-c.
Method C: A mixture of 3 (10 mmol), the appropriate aromatic aldehyde (10 mmol), piperidine (0.85 mmol), and malononitrile (0.66 g, 10 mmol) in dioxane (30 mL) was heated under reflux for 3 h, then left to cool. The solid product was filtered off, washed with EtOH, dried, and finally recrystallized from the proper solvent to give 7a-c.
4-(6-Amino-3,5-dicyano-2-oxo-4-phenylpyridin-1(2H)-yl)-N-(5-methylisoxazol-3-yl)benzenesulfonamide (7a). Yield (54%), mp > 300 ºC (from dioxane); IR (KBr) νmax/cm-1: 3362, 3316, 3217 (NH, NH2), 2970, 2889 (aliphatic CH), 2217 (C≡ N), 1629 (C=O); 1HNMR (DMSO-d6) δ 2.33 (s, 3H, CH3), 4.31 (br., 2H, D2O-exchangeable, NH2), 6.22 (s, 1H, isoxazole-H-4), 7.51-7.57 (m, 5H, ArH), 7.67 (d, 2H, J = 9 Hz, ArH), 8.06 (d, 2H, J = 9 Hz, ArH), 11.60 (s, 1H, D2O-exchangeable, NH); 13C NMR (DMSO-d6) δ 12.0, 66.3, 75.5, 87.9, 95.4, 116.0, 127.8, 128.6, 128.8, 130.0, 130.3, 134.5, 138.0, 141.1, 156.8, 157.4, 159.3, 161.5, 170.3; MS (m/z, %): 473 (M++1, 42.3), 472 (M+, 69.2), 397 (54.6), 390 (66.9), 373 (46.2), 283 (68.5), 235 (50.0), 175 (60.0), 157 (43.9), 80 (100). Anal. Calcd for C23H16N6O4S (472.47): C, 58.47; H, 3.41; N, 17.79; S, 6.79. Found: C, 58.42; H, 3.38; N, 17.75; S, 6.74%.
4-[6-Amino-4-(4-methoxyphenyl)-3,5-dicyano-2-oxopyridin-1(2H)-yl]-N-(5-methylisoxazol-3-yl)benzenesulfonamide (7b). Yield (56%), mp > 300 ºC (from dioxane); IR (KBr) νmax/cm-1: 3324, 3280, 3191 (NH, NH2), 2985, 2846 (aliphatic CH), 2215 (C≡N), 1688 (C=O); 1H NMR (DMSO-d6) δ 2.32 (s, 3H, CH3), 3.85 (s, 3H, OCH3), 4.9 (br., 2H, NH2), 6.23 (s, 1H, isoxazole-H-4), 7.14 (d, 2H, Ar-H), 7.51 (d, 2H, Ar-H), 7.67 (d, 2H, ArH), 8.05 (d, 2H, ArH), 11.75 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 503 (M++1, 10.1), 502 (M+, 16.3), 419 (11.0), 404 (7.7), 267 (14.9), 186 (100), 158 (27.2), 106 (11.0), 97 (15.8). Anal. Calcd for C24H18N6O5S (502.50): C, 57.36; H, 3.61; N, 16.72; S, 6.38. Found: C, 57.33; H, 3.58; N, 16.70; S, 6.36%.
4-4-[6-Amino-4-(4-chlorophenyl)-3,5-dicyano-2-oxopyridin-1(2H)-yl]-N-(5-methylisoxazol-3-yl)benzenesulfonamide (7c). Yield (40%), mp > 300 ºC (from dioxane); IR (KBr) νmax/cm-1: 3324, 3204, 3093 (NH, NH2), 2993, 2892 (aliphatic CH), 2220 (C≡N), 1654 (C=O); 1H NMR (DMSO-d6) δ 2.33 (s, 3H, CH3), 4.31 (br., 2H, D2O-exchangeable, NH2), 6.22 (s, 1H, isoxazole-H-4), 7.57 (d, 2H, J = 9 Hz, ArH), 7.58-7.74 (m, 4H, ArH), 8.06 (d, 2H, J = 9 Hz, ArH), 11.60 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 507 (M++1, 69.3), 506 (M+, 94.7), 409 (76.3), 295 (73.7), 264 (59.7), 221 (47.4), 157 (57.9), 137 (100), 111 (45.6). Anal. Calcd for C23H15ClN6O4S (506.92): C, 54.49; H, 2.98; Cl, 6.99; N, 16.58; S, 6.33. Found: C, 54.45; H, 2.93; Cl, 6.94; N, 16.56; S, 6.30%.
4-(3-Cyano-4,6-dimethyl-2-oxopyridin-1(2H)-yl)-N-(5-methylisoxazol-3-yl)benzenesulfonamide (10).
To a mixture of the cyanoacetamide 3 (1.60 g, 5 mmol) and pentane-2,4-dione (0.50 g, 5 mmol) in dioxane (20 mL), triethylamine (0.5 mL) was added and the reaction mixture was refluxed for 8 h. On cooling, the separated solid was filtered, washed with EtOH, dried, and finally crystallized from DMF to afford the corresponding sulfonamide (10). Yield (64%), mp 295-297 ºC (from dioxane); IR (KBr) νmax/cm-1: 3082 (NH), 2983, 2870 (aliphatic CH), 2217 (C≡N), 1651 (C=O); 1H NMR (DMSO-d6) δ 2.01 (s, 3H, CH3), 2.26 (s, 3H, CH3), 2.39 (s, 3H, CH3), 6.20 (s, 1H, isoxazole-H-4), 6.48 (s, 1H, pyridine-H), 7.63 (d, 2H, J = 9 Hz, ArH), 8.03 (d, 2H, J = 9 Hz, ArH), 11.60 (s, 1H, D2O-exchangeable, NH); 13C-NMR (DMSO-d6) δ 12.0, 20.6, 21.3, 95.4, 100.0, 109.1, 115.5, 128.0, 129.4, 140.2, 141.3, 151.4, 157.3, 160.0, 160.2, 170.5; MS (m/z, %): 384 (M+, 13.2), 321 (15.5), 288 (17.2), 239 (15.5), 222 (18.9), 148 (20.8), 97 (19.6), 79 (100). Anal. Calcd for C18H16N4O4S (384.41): C, 56.24; H, 4.20; N, 14.57; S, 8.34. Found: C, 56.20; H, 4.16; N, 14.52; S, 8.30%.
2-Imino-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)-2H-chromene-3-carboxamide (11).
A mixture of equimolar amounts of the cyanoacetamide 3 (1.60 g, 5 mmol) and salicylaldehyde (0.61 g, 5 mmol) in dioxane (25 mL) containing a catalytic amount of piperidine was heated under reflux for 2 h, then left to cool. The solid product formed was filtrated off, washed with EtOH, dried, and finally crystallized from dioxane to give 11. Yield (60%), mp 255-257 ºC (from dioxane); IR (KBr) νmax: 3301, 3241, 3135 (3NH), 2926, 2888 (aliphatic CH), 1683 (C=O) cm-1; 1H NMR (DMSO-d6) δ 2.29 (s, 3H, CH3), 6.13 (s, 1H, isoxazole-H-4), 7.31 (d, 2H, Ar-H), 7.60 (s, 2H, Ar-H), 7.62 (s, 1H, CH), 7.80-7.91 (m, 3H, Ar-H), 8.56 (s, 1H, CH), 9.29 (br., 1H, D2O-exchangeable, NH), 11.40 (br., 1H, D2O-exchangeable, NH), 13.16 (br., 1H, D2O-exchangeable, NH); MS (m/z, %): 425 (M++1, 8.4), 424 (M+, 17.9), 343 (4.8), 328 (4.4), 279 (19.8), 253 (4.8), 236 (4.4), 187 (5.4), 172 (100), 145 (54.2), 97 (6.3), 83 (11.2). Anal. Calcd for C20H16N4O5S (424.43): C, 56.60; H, 3.80; N, 13.20; S, 7.56. Found: C, 56.57; H, 3.78; N, 13.18; S, 7.53%.
N-(4-{[(5-Methylisoxazol-3-yl)amino]sulfonyl}phenyl)-2-oxo-2H-chromene-3-carboxamide (12).60
Method A: To a solution of 3 (1.60 g, 5 mmol) in acetic acid (30 mL) containing 0.5 g of fused sodium acetate, salicylaldehyde (0.61 g, 5 mmol) was added. The mixture was heated under reflux for 2 h. After cooling, the formed product was filtrated off, washed with EtOH, dried, and finally crystallized from DMF to give 12.
Method B: The iminochromene derivatives 11 (1.06 g, 2.5 mmol) was dissolved in dioxane (40 mL) and treated with HCl (5 mL). The reaction mixture was heated under reflux for 2 h, left to cool. The obtained solid product was filtered off, washed with cold water, dried, and finally crystallized from dioxane. Yield (50%), mp > 300 ºC (from dioxane); IR (KBr) νmax/cm-1: 3212, 3127 (2NH), 2960, 2867 (aliphatic CH), 1708 (C=O), 1669 (C=O); 1H NMR (DMSO-d6) δ 2.30 (s, 3H, CH3), 6.13 (s, 1H, isoxazole-H-4), 7.56 (d, 2H, J = 9 Hz, ArH), 7.75-7.91 (m, 4H, ArH), 8.02 (d, 2H, J = 9 Hz, ArH), 8.90 (s, 1H, CH), 10.93 (s, 1H, D2O-exchangeable, NH), 11.36 (s, 1H, D2O-exchangeable, NH); 13C NMR (DMSO-d6) δ 11.9, 66.3, 95.3, 116.2, 118.3, 119.6, 125.2, 128.1, 130.3, 134.2, 134.4, 142.0, 147.7, 153.9, 157.4, 160.1, 160.5, 170.2; MS (m/z, %): 426 (M++1, 6.7), 425 (M+, 14.5), 353 (11.0), 328 (11.8), 278 (9.5), 253 (9.7), 188 (14.8), 173 (100), 145 (11.8), 101 (37.1), 82 (10.5). Anal. Calcd for C20H15N3O6S (425.41): C, 56.47; H, 3.55; N, 9.88; S, 7.54. Found: C, 56.43; H, 3.51; N, 9.85; S, 7.50%.
Coupling of 2-cyano-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (3) with arenediazonium salts. Formation of the hydrazones 13a-c.
General procedure: To a cold solution of the cyanoacetamide 3 (1.60 g, 5 mmol) in pyridine (20 mL), was added the appropriate diazonium salt of the appropriate aromatic amine (aniline, 4-methoxyaniline and 4-chloroaniline) (5 mmol), prepared according to literature procedures.61 The addition was carried out portionwise with stirring at 0-5 oC over a period of 30 min. After complete addition, the reaction mixture was stirred for further 4 h then kept in an ice chest for 12 h and finally diluted with water. The precipitated solid was collected by filtration, washed with water, dried and finally recrystallized from the proper solvent to afford the corresponding hydrazones 13a-c.
2-Cyano-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)-2-(phenylhydrazono)acetamide (13a). Yield (60%), mp 272-274 oC (from dioxane); IR (KBr) νmax/cm-1: 3382, 3243, 3080 (3NH), 2992, 2890 (aliphatic CH), 2217 (C≡N), 1684 (C=O); 1H NMR (DMSO-d6) δ 2.30 (s, 3H, CH3), 6.14 (s, 1H, isoxazole-H-4), 7.13-7.43 (m, 5H, ArH), 7.82 (d, 2H, J = 9 Hz, ArH), 7.95 (d, 2H, J = 9 Hz, ArH), 10.23 (s, 1H, D2O-exchangeable, NH), 11.32 (s, 1H, D2O-exchangeable, NH), 12.02 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 425 (M++1, 6.0), 424 (M+, 9.5), 326 (10.12), 290 (30.9), 279 (14.9), 252 (2.2), 187 (3.1), 172 (19.1), 97 (14.6), 92 (96.2), 77 (100). Anal. Calcd for C19H16N6O4S (424.43): C, 53.77; H, 3.80; N, 19.80; S, 7.55. Found: C, 53.75; H, 3.79; N, 19.78; S, 7.50%.
2-Cyano-2-[(4-methoxyphenyl)hydrazono]-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (13b). Yield (70%), mp 283-295 oC (from dioxane); IR (KBr) νmax/cm-1: 3375, 3240, 3084 (3NH), 2993, 2896 (aliphatic CH), 2212 (C≡N), 1680 (C=O); 1H NMR (DMSO-d6) δ 2.29 (s, 3H, CH3), 3.76 (s, 3H, OCH3), 6.14 (s, 1H, isoxazole-H-4), 6.99 (d, 2H, J = 7.8 Hz, ArH), 7.68 (d, 2H, J = 7.8 Hz, ArH), 7.84 (d, 2H, J = 9 Hz, ArH), 7.95 (d, 2H, J = 9 Hz, ArH), 10.16 (s, 1H, D2O-exchangeable, NH), 11.32 (s, 1H, D2O-exchangeable, NH), 11.98 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 455 (M++1, 7.1), 454 (M+, 11.8), 372 (2.6), 357 (1.2), 319 (5.1), 292 (16.1), 217 (1.2), 201 (4.2), 155 (24.4), 135 (21.9), 122 (100), 107 (72.6), 97 (20.9). Anal. Calcd for C20H18N6O5S (454.46): C, 52.86; H, 3.99; N, 18.49; S, 7.06. Found: C, 52.83; H, 3.96; N, 18.45; S, 7.05%.
2-[(4-Chlorophenyl)hydrazono]-2-cyano-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (13c). Yield (70%), mp 290-292 oC (from dioxane); IR (KBr) νmax/cm-1: 3384, 3258, 3079 (3NH), 2981, 2887 (aliphatic CH), 2216 (C≡N), 1686 (C=O); 1H NMR (DMSO-d6) δ 2.29 (s, 3H, CH3), 6.13 (s, 1H isoxazole-H-4), 7.46 (d, 2H, J = 8.7 Hz, ArH), 7.74 (d, 2H, J = 8.7 Hz, ArH), 7.85 (d, 2H, J = 9 Hz, ArH), 7.94 (d, 2H, J = 9 Hz, ArH), 10.27 (s, 1H, D2O-exchangeable, NH), 11.32 (s, 1H, D2O-exchangeable, NH), 12.15 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 459 (M++1, 23.0), 458 (M+, 11.6), 360 (10.4), 325 (7.2), 303 (0.3), 296 (33.8), 279 (20.1), 205 (10.6), 155 (20.8), 140 (19.9), 126 (66.4), 111 (100), 97 (30.3). Anal. Calcd for C19H15ClN6O4S (458.87): C, 49.73; H, 3.29; Cl, 7.73; N, 18.31; S, 6.99. Found: C, 49.71; H, 3.27; Cl, 7.70; N, 18.30; S, 6.96%.
4-[(5-Amino-1H-pyrazol-3-yl)amino]-N-(5-methylisoxazol-3-yl)benzenesulfonamide (14). To a solution of the compound 3 (1.60 g, 5 mmol) in dioxane (20 mL), hydrazine hydrate (80%, 1.0 mL) was added and the reaction mixture was refluxed for 6 h and then allowed to cool. The solid product was filtered, washed with EtOH and dried. Recrystallized from dioxane afforded 14. Yield (50%), mp 245-246 oC (from dioxane); IR (KBr) νmax/cm-1: 3476, 3372, 3266 (NH, NH2), 1629 (C=O); 1H NMR (DMSO-d6) δ 2.03 (s, 3H, CH3), 4.15 (br., 2H, D2O-exchangeable, NH2), 5.77 (s, 1H, isoxazole-H-4), 6.30 (s, 1H, CH), 6.60 (d, 2H, J = 9 Hz, ArH), 6.85 (s, 1H, D2O-exchangeable, NH), 7.48 (d, 2H, J = 9 Hz, ArH), 7.84 (s, 1H, D2O-exchangeable, NH), 10.45 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 335 (M++1, 3.9), 334 (M+, 5.3), 272 (5.5), 253 (4.6), 236 (4.1), 172 (67.4), 156 (58.4), 108 (69.8), 92 (85.4), 80 (40.6), 65 (100). Anal. Calcd for C13H14N6O3S (334.35): C, 46.70; H, 4.22; N, 25.14; S, 9.59. Found: C, 46.67; H, 4.20; N, 25.10; S, 9.55%.
Synthesis of aminopyrazole derivatives 15a-c.
Method A: To a solution of the appropriate hydrazone 13 (5 mmol) in dioxane (20 mL) was added hydrazine hydrate (5 mmol). The reaction mixture was refluxed for 6 h, and then left to cool. The solid product was collected, washed with EtOH, dried and finally recrystallized from dioxane to afford the corresponding 4-arylazopyrazole derivatives 15a-c, respectively.
Method B: To a stirred cold solution of the pyrazole derivative 14 (1.67 g, 5 mmol) in pyridine (30 mL) was added the appropriate arenediazonium chloride61 (5 mmol) portionwise over a period of 30 min at 0-5 °C. After complete addition, the reaction mixture was stirred for further 3 h at 0-5 °C. The solid product was collected, washed with water, dried, and finally recrystallization from dioxane afforded the corresponding aminopyrazoles 15a-c.
4-({5-Amino-4-[phenyldiazenyl]-1H-pyrazol-3-yl}amino)-N-(5-methylisoxazol-3-yl)benzenesulfonamide (15a). Yield (40%), mp 248-250 oC (from dioxane); IR (KBr) νmax/cm-1: 3431, 3367 (NH, NH2), 2921 (aliphatic CH); 1H NMR (DMSO-d6) δ 2.28 (s, 3H, CH3), 6.05 (s, 2H, D2O-exchangeabl, NH2), 6.14 (s, 1H, isoxazole-H-4), 6.59 (d, 2H, ArH), 7.18 (d, 2H, J = 9 Hz, ArH), 7.47 (d, 3H, ArH), 7.84 (d, 2H, J = 9 Hz, ArH), 7.92 (s, 1H, D2O-exchangeable, NH), 10.20 (s, 1H, D2O-exchangeable, NH), 10.82 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 439 (M++1, 27.9), 438 (M+, 37.6), 424 (39.3), 356 (58.1), 333 (38.2), 314 (50.6), 251 (40.9), 238 (29.0), 203 (53.8), 186 (29.6), 105 (33.9), 92 (100), 77 (59.7). Anal. Calcd for C19H18N8O3S (438.46): C, 52.05; H, 4.14; N, 25.56; S, 7.31. Found: C, 52.00; H, 4.10; N, 25.53; S, 7.30%.
4-({5-Amino-4-[(4-methoxyphenyl)diazenyl]-1H-pyrazol-3-yl}amino)-N-(5-methylisoxazol-3-yl)ben-zenesulfonamide (15b). Yield (72%), mp 234-236 oC (from dioxane); IR (KBr) νmax/cm-1: 3345, 3219 (NH, NH2), 2970, 2857 (aliphatic CH); 1H NMR (DMSO-d6) δ 2.29 (s, 3H, CH3), 3.39 (s, 3H, OCH3), 6.05 (s, 2H, D2O-exchangeable, NH2), 6.13 (s, 1H, isoxazole-H-4), 7.09 (d, 2H, J = 7.8 Hz, ArH), 7.37 (d, 2H, J = 9 Hz, ArH), 7.51 (d, 2H, J = 7.8 Hz, ArH), 7.87 (d, 2H, J = 9 Hz, ArH), 7.93 (s, 1H, D2O-exchangeable, NH), 9.97 (s, 1H, D2O-exchangeable, NH), 10.40 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 469 (M++1, 12.2), 468 (M+, 10.6), 458 (10.8), 437 (10.2), 368 (16.9), 255 (13.3), 206 (10.8), 156 (34.1), 135 (10.2), 119 (43.7), 108 (58.8), 92 (100). Anal. Calcd for C20H20N8O4S (468.49): C, 51.27; H, 4.30; N, 23.92; S, 6.84. Found: C, 51.24; H, 4.28; N, 23.90; S, 6.82%.
4-({5-Amino-4-[(4-chlorophenyl)diazenyl]-1H-pyrazol-3-yl}amino)-N-(5-methylisoxazol-3-yl)benzensulfonamide (15c). Yield (75%), mp 250-252 oC (from dioxane); IR (KBr) νmax/cm-1: 3460, 3369, 3185 (NH, NH2), 2922, 2856 (aliphatic CH); 1H NMR (DMSO-d6) δ 2.28 (s, 3H, CH3), 5.83 (s, 1H, isoxazole-H-4), 6.07 (s, 2H, D2O-exchangeable, NH2), 6.59 (d, 2H, J = 8.7 Hz, ArH), 7.47 (d, 2H, J = 9 Hz, ArH), 7.59 (d, 2H, J = 8.7 Hz, ArH), 7.84 (d, 2H, J = 9 Hz, ArH), 7.95 (s, 1H, D2O-exchangeable, NH), 10.52 (s, 2H, D2O-exchangeable, 2NH); MS (m/z, %): 473 (M++1, 47.5), 472 (M+, 71.3), 440 (72.9), 292 (60.7), 237 (100), 219 (59.8), 152 (50.8), 111 (46.7), 98 (47.5), 82 (60.7). Anal. Calcd for C19H17ClN8O3S (472.90): C, 48.26; H, 3.62; Cl, 7.50; N, 23.69; S, 6.78. Found: C, 48.24; H, 3.60; Cl, 7.48; N, 23.66; S, 6.76%.
Reaction of hydrazones 13a-c with ethyl chloroformate. Formation of the triazine derivatives 16a-c.
To a solution of the hydrazone 13a-c (1 mmol) in acetic acid (20 mL), ethyl chloroformate (1 mmol) was added and the reaction mixture was refluxed for 8 h, then left to cool. The solid product was filtered off, washed with EtOH, dried, and finally recrystallized from dioxane afforded the corresponding triazine derivatives 16a-c.
4-(6-Cyano-3,5-dioxo-2-phenyl-2,5-dihydro-1,2,4-triazin-4(3H)-yl)-N-(5-methylisoxazol-3-yl)benzenesulfonamide (16a). Yield (70%), mp > 300 ºC (from dioxane); IR (KBr) νmax/cm-1: 3383 (NH), 2992, 2894 (aliphatic CH), 2219 (C≡N), 1682 (C=O); 1H NMR (DMSO-d6) δ 2.30 (s, 3H, CH3), 6.14 (s, 1H, isoxazole-H-4), 7.18 (s, 1H, ArH), 7.43 (d, 2H, J = 9 Hz, ArH), 7.73 (s, 2H, ArH), 7.85 (s, 2H, ArH), 8.06 (d, 2H, J = 9 Hz, ArH), 10.23 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 450 (M+, 38.0), 416 (52.8), 368 (42.9), 355 (44.8), 337 (33.1), 284 (47.9), 268 (50.3), 213 (60.1), 136 (45.4), 77 (86.5), 65 (100). Anal. Calcd for C20H14N6O5S (450.42): C, 53.33; H, 3.13; N, 18.66; S, 7.12. Found: C, 53.31; H, 3.11; N, 18.63; S, 7.09%.
4-[6-Cyano-2-(4-methoxyphenyl)-3,5-dioxo-2,5-dihydro-1,2,4-triazin-4(3H)-yl]-N-(5-methylisoxazol-3-yl)benzenesulfonamide (16b). Yield (75%), mp 292-294 oC (from dioxane); IR (KBr) νmax/cm-1 3381 (NH), 2991, 2896 (aliphatic CH), 2214 (C≡ N), 1682 (C=O); 1H NMR (DMSO-d6) δ 2.32 (s, 3H, CH3), 3.85 (s, 3H, OCH3), 6.23 (s, 1H, isoxazole-H-4), 7.14 (d, 2H, J = 9 Hz, ArH), 7.51 (d, 2H, J = 8.7 Hz, ArH), 7.67 (d, 2H, J = 8.7 Hz, ArH), 8.05 (d, 2H, J = 9 Hz, ArH), 11.60 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 481 (M++1, 23.7), 480 (M+, 18.1), 457 (16.7), 397 (19.0), 375 (16.9), 307 (18.4), 240 (16.7), 237 (16.1), 215 (20.8), 133 (20.5), 111 (18.1), 107 (16.9), 97 (60.6), 92 (16.1), 80 (100). Anal. Calcd for C21H16N6O6S (480.45): C, 52.50; H, 3.36; N, 17.49; S, 6.67. Found: C, 52.48; H, 3.33; N, 17.46; S, 6.65%.
4-[2-(4-Chlorophenyl)-6-cyano-3,5-dioxo-2,5-dihydro-1,2,4-triazin-4(3H)-yl]-N-(5-methylisoxazol-3-yl)benzenesulfonamide (16c). Yield (65%), mp > 300 ºC (from dioxane); IR (KBr) νmax/cm-1: 3427 (NH), 2927 (aliphatic CH), 2197 (C≡N), 1628 (C=O); 1H NMR (DMSO-d6) δ 2.28 (s, 3H, CH3), 6.02 (s, 1H, isoxazole-H-4), 7.74-7.77 (m, 4H, ArH), 7.82 (d, 2H, ArH), 8.25 (s, 2H, ArH), 10.65 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 485 (M++1, 5.2), 484 (M+, 83.2), 450 (61.1), 402 (66.3), 373 (61.1), 347 (57.9), 278 (82.1), 249 (80.0), 237 (54.7), 138 (90.5), 110 (65.3), 98 (100). Anal. Calcd for C20H13ClN6O5S (484.87): C, 49.54; H, 2.70; Cl, 7.31; N, 17.33; S, 6.61. Found: C, 49.51; H, 2.68; Cl, 7.29; N, 17.31; S, 6.59%.
Synthesis of compounds 18, 19 and 20.
General procedure:
To a stirred suspension of finely powdered potassium hydroxide (0.26 g, 5 mmol) in dry DMF (20 mL) cyanoacetamide 3 (1.60 g, 5 mmole) was added. The resulting mixture was cooled at 10 oC in an ice bath, then carbon disulfide (5 mmol) was added slowly over the course of 10 min. After complete addition, stirring was continued for additional 2 h, then dibromoethane or dibromopropane or dimethyl sulfate (5 mmol) was added to the mixture while cooling (~15 oC) and stirring for 1 h. then poured into crushed ice, the resulting precipitate was filtrated off, dried, and finally crystallized from the proper solvent to give 18-20.
2-Cyano-2-(1,3-dithiolan-2-ylidene)-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (18). Yield (70%), mp 200-202 oC (from dioxane); IR (KBr) νmax/cm-1: 3327, 3277 (2NH), 2962 (aliphatic CH), 2190 (C≡N), 1692 (C=O); 1H NMR (DMSO-d6) δ 2.28 (s, 3H, CH3), 3.95 (s, 4H, 2CH2), 6.11 (s, 1H, isoxazole-H-4), 7.72 (d, 2H, J = 9 Hz), 7.84 (d, 2H, J = 9 Hz), 10.69 (s, 1H, D2O-exchangeable, NH), 11.32 (s, 1H, D2O-exchangeable, NH); 13C NMR (DMSO-d6) δ 11.9, 29.9, 95.3, 112.5, 115.5, 119.0, 128.1, 133.8, 142.5, 153.2, 157.4, 161.8, 170.2; MS (m/z, %): 422 (M+, 35.7), 353 (54.1), 338 (44.3), 326 (33.5), 284 (36.8), 252 (37.8), 238 (35.1), 186 (100), 169 (28.1), Anal. Calcd for C16H14N4O4S3 (422.50): C, 45.48; H, 3.34; N, 13.26; S, 22.77. Found: C, 45.46; H, 3.31; N, 13.24; S, 22.75%.
2-Cyano-2-(1,3-dithian-2-ylidene)-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)acetamide (19). Yield (50%), mp 205-207 oC (from dioxane); IR (KBr) νmax/cm-1: 3324, 3277 (2NH), 2960 (aliphatic CH), 2208 (C≡N), 1691 (C=O); 1H NMR (DMSO-d6) δ 2.10 (m, 2H, J = 6.80 Hz, CH2), 2.29 (s, 3H, CH3), 3.03 (t, 2H, J = 6.6 Hz, CH2), 3.21 (t, 2H, J = 6.6 Hz, CH2), 6.11 (s, 1H, isoxazole-H-4), 7.74 (d, 2H, J = 9 Hz, ArH), 7.83 (d, 2H, J = 9 Hz, ArH), 10.68 (s, 1H, D2O-exchangeable, NH), 11.32 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 436 (M+, 9.4), 356 (8.4), 335 (12.3), 280 (11.8), 255 (17.2), 253 (8.4), 238 (13.1), 200 (16.2), 186 (98.7), 155 (16.5), 97 (15.4), 68 (100). Anal. Calcd for C17H16N4O4S3 (436.53): C, 46.77; H, 3.69; N, 12.83; S, 22.04. Found: C, 46.75; H, 3.66; N, 12.80; S, 22.00%.
2-Cyano-N-(4-{[(5-methylisoxazol-3-yl)amino]sulfonyl}phenyl)-3,3-bis(methylthio)acrylamide (20).
Yield (90%), mp 180-182 oC (from EtOH); IR (KBr) νmax/cm-1: 3325, 3275 (2NH), 2969 (aliphatic CH), 2186 (C≡N), 1640 (C=O); 1H NMR (DMSO-d6) δ 2.29 (s, 3H, CH3), 2.44 (s, 3H, CH3), 2.49 (s, 3H, CH3), 6.14 (s, 1H, isoxazole-H-4), 7.80 (d, 2H, J = 9 Hz, ArH), 7.95 (d, 2H, J = 9 Hz, ArH), 10.68 (s, 1H, D2O-exchangeable, NH), 11.34 (s, 1H, D2O-exchangeable, NH); MS (m/z, %): 425 (M++1, 28.5), 424 (M+, 42.5), 392 (41.9), 342 (38.3), 327 (30.1), 236 (40.4), 186 (33.7), 171 (41.9), 144 (27.9), 99 (34.2), 82 (49.2), 64 (100). Anal. Calcd for C16H16N4O4S3 (424.52): C, 45.27; H, 3.80; N, 13.20; S, 22.66. Found: C, 45.25; H, 3.78; N, 13.17; S, 22.64%.

Antimicrobial Evaluation
The antibacterial and antifungal activity assays were carried out in the Medical Mycology Laboratory of the Regional Center for Mycology and Biotechnology of Al-Azhar University, Cairo, Egypt. Using the diffusion plate method.62-64 A bottomless cylinder containing a measured quantity (1 mL, mg/mL) of the sample is placed on a plate (9 cm diameter) containing a solid bacterial medium (nutrient agar broth) or fungal medium, which has been heavily seeded with a spore suspension of the test organism. After incubation (24 h for bacteria and 5 days for fungi), the diameter of the clear zone of inhibition surrounding the sample is taken as measure of the inhibitory power of the sample against the particular test organism. The solvent used was DMSO and the concentration of the sample used is 100 μg/mL. The results of antimicrobial activity are summarized in Table 1.

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