Synthesis and Antimicrobial Activity of Some Novel Substituted 3 ...

Letters in Drug Design & Discovery

1316

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RESEARCH ARTICLE ISSN: 1570-1808 eISSN: 1875-628X

Synthesis and Antimicrobial Activity of Some Novel Substituted 3-(Thiophen-2-yl)pyrazole-based Heterocycles

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BENTHAM SCIENCE

Bakr F. Abdel-Wahaba,b,*, Abdelbasset A. Farahatc, Ghada E.A. Awadd and Gamal A. El-Hitie,* a

Applied Organic Chemistry Department, National Research Center, Dokki, 12622 Giza, Egypt; bDepartment of Chemistry, College of Science and Humanities, Shaqra University, Duwadimi, Saudi Arabia; cDepartment of Pharmaceutical Organic Chemistry, Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt; dDepartment of Chemistry of Natural and Microbial Products, National Research Center, Dokki, 12622 Giza, Egypt; eDepartment of Optometry, Cornea Research Chair, College of Applied Medical Sciences, King Saud University, P.O. Box 10219, Riyadh 11433, Saudi Arabia

A R T I C L E H I S T O R Y

Abstract: Background: A series of novel substituted 3-(thiophen-2-yl)pyrazoles was synthesized efficiently and in high yields using simple and convenient procedures starting from 1-phenyl-3(thiophen-2-yl)-1H-pyrazole-4-carbaldehyde.

Received: January 08, 2017 Revised: March 09, 2017 Accepted: March 19, 2017

Methods: The structures of the newly synthesized products were established and their antimicrobial activities were investigated against some bacteria and fungi.

DOI: 10.2174/1570180814666170327162447

Results and Conclusion: The products showed excellent antimicrobial activities against the tested microorganism compared to the standard antibacterial and antifungal drugs.

Keywords: Drug design, antimicrobial activity, microorganisms, 3-(thiophen-2-yl)pyrazoles, hydrazides, inhibition zone. 1. INTRODUCTION Compounds containing pyrazol-4-carbaldehydes core play a crucial role in material science and have been used in the synthesis of metal organic frameworks with extraordinary bases resistance [1]. Also, these classes of compounds are important building blocks for various pharmaceuticals application such as antimicrobial, antiinflammatory, antitubercular, antitumor, antiangiogenesis, anti-parasitic and antiviral [2-10]. The common methods for the synthesis of pyrazol-4-carbaldehydes are Vilsmeier-Haack reaction of hydrazones, Vilsmeier reaction of 1H-pyrazol-5(4H)-one and oxidation of pyrazole-4-carboxylic acids [11, 12]. Various 3(thiophen-2-yl)-4,5-dihydro-1H-pyrazoles have been synthesized and showed interesting biological applications [13-18]. In addition, pyrazolyl derivatives were found to be active against some bacteria and fungi [19, 20]. We utilized pyrazol-4-carbaldehydes in the synthesis of potentially active *Address correspondence to these authors at the Department of Chemistry, College of Science and Humanities, Shaqra University, Duwadimi, Saudi Arabia; E-mail: [email protected] and Department of Optometry, Cornea Research Chair, College of Applied Medical Sciences, King Saud University, P.O. Box 10219, Riyadh 11433, Saudi Arabia; Tel: 00966114693778; Fax: 00966114693536; E-mail: [email protected] 1570-1808/17 $58.00+.00

antimicrobial, antioxidant, anti-inflammatory and analgesic agents [21, 22]. Based on the biological activities of 3(thiophen-2-yl)pyrazoles, we became interested in the design and synthesis of novel derivatives as antimicrobial agents. Here we report simple and convenient processes for the synthesis of novel bioactive heterocycles as antimicrobial agents using pyrazole-4-carbaldehyde as a precursor as part of our interest in the synthesis and applications of heterocycles [23-28]. 2. EXPERIMENTAL 2.1. General Melting points were taken on Electrothermal IA 9000 series digital melting point apparatus. Elemental analytical data were obtained from the Microanalytical unit at the National Research Centre, Dokki, Giza, Egypt. The IR spectra (KBr discs) were recorded on a Shimadzu CVT-04 spectrophotometer. The NMR spectra were measured in DMSO-d6 on a JEOL ECA-500 MHz spectrometer using tetramethylsilane as internal standard. Chemical shift (δ) values are given in parts per million (ppm) and the coupling constants (J) are given in Hz. The electron-impact mass spectra were determined using a Varian MAT CH-5 spectrometer (70 eV). ©2017 Bentham Science Publishers

3-(Thiophen-2-yl)pyrazoles as Antimicrobial Agents

Crystallographic data for compound 6 has been deposited at the Cambridge Crystallographic Data Center (CCDC) as CCDC 1524401. Free copies of the crystallographic data can be obtained via www.ccdc.cam.ac.uk. Compounds 1 [29], 8a [30], 8b [31], 8c [32], 10a [33] and 10b [34] were synthesized according to the reported procedures.

Letters in Drug Design & Discovery, 2017, Vol. 14, No. 11 1317

2.2. Chemistry

8.38 (s, 1H, furyl-H), 9.17 (s, 1H, CH=C), 10.88 (s, exch., 1H, NH). 13C NMR δ: 14.4, 103.8, 111.1, 113.8, 114.6, 116.3, 118.6, 119.6, 119.9, 120.6, 121.8, 122.8, 124.1, 127.5, 127.7, 128.7, 129.4, 131.8, 136.6, 137.9, 140.2, 148.0, 155.8, 157.3, 164.4. IR (KBr) νmax/cm–1 1618 (C=O), 2198 (CN), 3199 (NH). EI-MS m/z (%): 478 (M+ + 1, 25), 477 (M+, 100); Anal. calcd for C27H19N5O2S (477.54): C 67.91, H 4.01, N 14.67; found: C 67.96, H 4.17, N 14.76.

2.2.1. Synthesis of 2-benzoyl-3-(1-phenyl-3-(thiophen-2-yl)1H-pyrazol-4-yl)acrylonitrile (3)

2-Cyano-3-(1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4-yl)N'-(1-(pyridin-2-yl)ethylidene)acrylohydrazide (9c)

A mixture of 1a (1.30 g, 5 mmol) and 2 (0.72 g, 5 mmol) in dry EtOH (30 mL) containing piperidine (0.3 mL) was refluxed for 5 h. The solid obtained was filtrated, dried and crystallized from EtOH to give pure 3 in 79% yield; Mp 182–184 °C. 1 H NMR δ: 7.21 (s, 1H, pyrazole-H), 7.42–8.11 (m, 13H, Ar-H), 9.26 (s, 1H, CH=C). 13C NMR δ: 108.6, 114.4, 117.0, 119.8, 126.2, 128.4, 128.6, 128.8, 129.0, 129.3, 130.0, 131.8, 134.5, 136.3, 139.9, 146.4, 149.4, 154.6, 189.6. IR (KBr) νmax/cm–1 1696 (C=O), 2220 (CN). EI-MS m/z (%): 382 (M+ + 1, 32), 191 (100). Anal. calcd for C23H15N3OS (381.45): C 72.42, H 3.96, N 11.02; found: C 72.64, H 4.27, N 11.36.

Yield 83%; Mp 246–247 °C. 1H NMR δ: 2.38 (s, 3H, CH3), 7.23 (s, 1H, pyrazole-H), 7.26–7.90 (m, 12H, Ar-H), 9.18 (s, 1H, CH=C), 10.91 (s, exch., 1H, NH). 13C NMR δ: 12.9, 103.8, 110.7, 111.5, 114.1, 116.1, 118.1, 119.2, 127.5, 127.6, 127.7, 128.9, 129.3, 131.9, 138.2, 139.9, 142.0, 144.0, 148.2, 151.3, 154.8, 162.7. IR (KBr) νmax/cm–1 1612 (C=O), 2223 (CN), 3287 (NH). EI-MS m/z (%): 478 (M+ + 1, 25), 477 (M+, 100). Anal. calcd for C27H19N5O2S (477.54): C 67.91, H 4.01, N 14.67; found: C 67.96, H 4.17, N 14.76.

2.2.2. Synthesis of methyl 2-cyano-3-(1-phenyl-3(thiophen-2-yl)-1H-pyrazol-4-yl)acrylate (6) A mixture of 3 (0.76 g, 2 mmol) and 4 (0.2 g, 2 mmol) in dry EtOH (30 mL) containing piperidine (0.3 mL) was refluxed for 5 h. The solid obtained was filtrated, dried and crystallized from DMF to give pure 6 in 64%; Mp 170-171 °C. 1 H NMR δ: 3.76 (s, 3H, CH3), 7.17 (s, 1H, pyrazole-H), 7.41–8.13 (m, 8H, Ar-H), 9.18 (s, 1H, CH=C). 13C NMR δ: 51.5, 104.0, 110.5, 113.6, 116.3, 119.0, 127.5, 127.6, 128.9, 129.3, 131.7, 137.9, 139.8, 140.2, 147.8, 161.9. IR (KBr) νmax/cm–1 1683 (C=O), 2228 (CN). EI-MS m/z (%): 335 (M+, 100). Anal. calcd for C18H13N3O2S (335.38): C 64.46, H 3.91, N 12.53; found: C 64.85, H 3.19, N 12.90. 2.2.3. Synthesis of 9 An equimolar mixture of 1a (2.54 g, 10 mmol) and 8 (10 mmol) in dry MeOH (20 mL) containing piperidine (0.50 mL) was refluxed for 1 h. The formed solid was collected by filtration and dried to give the pure products. 2-Cyano-3-(1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4-yl)N'-(1-(thiophen-2-yl)ethylidene)acrylohydrazide (9a) 1

Yield 82%; Mp 225–226 °C. H NMR δ: 2.33 (s, 3H, CH3), 6.90 (s, 1H, pyrazole-H), 7.26–8.09 (m, 11H, Ar-H), 9.21 (s, 1H, CH=C), 11.25 (s, exch., 1H, NH). 13C NMR δ: 14.3, 103.4, 107.2, 113.8, 116.2, 119.2, 125.4, 126.1, 127.1, 127.6, 128.9, 129.4, 131.7, 137.9, 139.7, 140.8, 141.0, 142.1, 148.1, 151.3, 155.6, 164.1. . IR (KBr) νmax/cm–1 1621 (C=O), 2198 (CN), 3228 (NH). EI-MS m/z (%): 445 (M+ + 2, 10), 444 (M+ + 1, 20), 443 (M+, 100). Anal. calcd for C23H17N5OS2 (443.54): C 62.28, H 3.86, N 15.79; found: C 62.42, H 4.03, N 15.88. N'-(1-(Benzofuran-2-yl)ethylidene)-2-cyano-3-(1-phenyl-3(thiophen-2-yl)-1H-pyrazol-4-yl)acrylohydrazide (9b) Yield 79%; Mp 242–243 °C. 1H NMR δ: 2.41 (s, 3H, CH3), 7.18 (s, 1H, pyrazole-H),7.27–7.89 (m, 12H, Ar-H),

2.2.4. Synthesis of 11 In the solution of 10 (10 mmol) in dry EtOH (30 mL) containing two drops of glacial AcOH, 1a (0.25 g, 1 mmol) was added. The reaction mixture was refluxed for 1 h. The solid formed on cooling was collected by filtration and dried to give the pure products. 5-(4-Chlorophenyl)-1-phenyl-N'-((1-phenyl-3-(thiophen-2yl)-1H-pyrazol-4-yl)methylene)-1H-pyrazole-3carbohydrazide (11a) Yield 83%; Mp 240–242 °C. 1H NMR δ: 6.98 (s, 1H, pyrazole-H), 7.22 (s, 1H, pyrazole-H), 7.25–7.93 (m, 17H, Ar-H), 8.00 (s, 1H, CH=N), 12.18 (s, exch., 1H, NH). 13C NMR δ: 103.8, 106.3, 108.3, 110.8, 114.6, 119.3, 121.3, 122.9, 123.1, 124.5, 125.1, 126.2, 127.2, 127.3, 127.9, 128.5, 129.0, 129.4, 137.9, 139.8, 141.1, 144.2, 143.2, 147.4, 152.8, 154.0. EI-MS m/z (%): 550 (M37Cl+, 33), 548 (M35Cl+, 100). Anal. calcd for C30H21ClN6OS (549.04): C 65.63, H 3.86, N 15.31; found: C 66.01, H 4.02, N 15.76. 1-Phenyl-N'-((1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4yl)methylene)-1,4-dihydroindeno[1,2-c]pyrazole-3carbohydrazide (11b) Yield 79%; Mp 251–252 °C. 1H NMR δ: 3.91 (s, 2H, CH2), 7.21 (s, 1H, pyrazole-H), 7.27–7.91 (m, 17H, Ar-H), 8.88 (s, 1H, CH=N), 11.67 (s, exch., 1H, NH). 13C NMR δ: 28.7, 116.0, 118.2, 118.5, 122.6, 123.2, 126.2, 126.4, 126.5, 127.3, 127.5, 128.1, 128.2, 129.0, 129.1, 129.2, 130.2, 133.7, 137.6, 138.2, 138.6, 139.5, 140.1, 145.3, 148.5, 148.8, 157.0. EI-MS m/z (%): 527 (M+ + 1, 25), 426 (M+, 100). Anal. calcd for C31H22N6OS (526.61): C 70.70, H 4.21, N 15.96; found: C 70.96, H 4.37, N 16.12. 2.2.5. Synthesis of 2-cyano-N'-((1-phenyl-3-(thiophen-2yl)-1H-pyrazol-4-yl)methylene)acetohydrazide (13) To a solution of 12 (0.99 g, 10 mmol) in dry EtOH (30 mL) containing two drops of glacial AcOH, 1a (2.54 g, 10 mmol) was added. The reaction mixture was refluxed for 30 min and then left to cool to room temperature. The mixture

1318 Letters in Drug Design & Discovery, 2017, Vol. 14, No. 11

was poured onto ice/water mixture and the solid obtained was filtered and dried to give 13 in 88% yield; Mp 258– 260°C. 1H NMR δ: 3.89 (s, 2H, CH2), 7.21 (s, 1H, pyrazoleH), 7.45–8.40 (m, 8H, Ar-H), 9.08 (s, 1H, CH=N), 11.79 (s, exch., 1H, NH). 13C NMR δ: 24.3, 38.8, 115.4, 115.7, 118.1, 126.5, 126.6, 127.5, 128.1, 129.2, 133.3, 136.7, 138.2, 145.0, 163.8. IR (KBr) νmax/cm–1 1647 (C=O), 2198 (CN), 3218 (NH). EI-MS m/z (%): 336 (M+ + 1, 38), 191 (100). Anal. calcd for C17H13N5OS (335.38): C 60.88, H 3.91, N 20.88; found: C 61.04, H 4.06, N 20.96. 2.2.6. Synthesis of 14 and 16 An equimolar mixture of 13 (0.33 g, 0.01 mol) and appropriate aldehyde 1 (10 mmol) in dry MeOH (20 mL) containing piperidine (0.50 mL) was refluxed for 1 h. The formed solid was collected by filtration and dried to give the pure products. 2-Cyano-3-(1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4-yl)N'-((1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4-yl)methylene) acrylohydrazide (14a) Yield 74%; Mp 274–275 °C. 1H NMR δ: 6.93 (s, 1H, pyrazole-H), 7.14 (s, 1H, pyrazole-H), 7.23–7.84 (m, 16H, Ar-H), 8.61 (s, 1H, CH=N), 9.01 (s, 1H, CH=C), 11.17 (s, exch., 1H, NH). 13C NMR δ: 106.8, 115.8, 115.9, 119.8, 120.0, 121.7, 121.9, 122.7, 123.7, 124.1, 126.2, 127.6, 128.1, 128.3, 129.2, 130.5, 136.6, 136.6, 139.8, 141.1, 148.6, 150.4, 151.7, 158.0, 164.3, 167.8. IR (KBr) νmax/cm–1 1643 (C=O), 2218 (CN), 3291 (NH). EI-MS m/z (%): 572 (M+ + 1, 21), 191 (100); Anal. calcd for C31H21N7OS2 (571.67): C 65.13, H 3.70, N 17.15; found: C 65.32, H 3.89, N 17.36. Table 1.

Abdel-Wahab et al.

2-Cyano-3-(4-fluorophenyl)-N'-((1-phenyl-3-(thiophen-2yl)-1H-pyrazol-4-yl)methylene)acrylohydrazide (14b) Yield 79%; Mp 248–250 °C. 1H NM, δ: 6.91 (s, 1H, pyrazole-H), 7.23–7.83 (m, 12H, Ar-H), 8.56 (s, 1H, CH=N), 8.68 (s, 1H, CH=C), 10.16 (s, exch., 1H, NH). 13C NM, δ: 103.8, 106.3, 110.8, 114.6, 119.3, 121.3, 122.9, 123.1, 125.1, 127.2, 127.3, 127.9, 129.0, 129.4, 137.9, 144.2, 147.4, 152.8, 160.0, 169.0. IR (KBr) νmax/cm–1 1667 (C=O), 2218 (CN), 3198 (NH). MS m/z (%): 442 (M+ + 1, 46), 191 (100); Anal. calcd for C24H16FN5OS (441.48): C 65.29, H 3.65, N 15.86; found: C 65.79, H 3.96, N 15.07. 2-Imino-N'-((1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4yl)methylene)-2H-chromene-3-carbohydrazide (16) Yield 72%; Mp 240–242 °C. 1H NMR δ: 6.93 (s, 1H, pyrazole-H), 7.23–7.83 (m, 12H, Ar-H), 8.05 (s, 1H, pyranCH), 9.13 (s, 1H, CH=N), 10.11 (s, exch., 1H, NH), 10.20 (s, exch., 1H, NH). 13C NM, δ: 106.8, 107.8, 110.8, 115.4, 115.5, 121.2, 121.3, 122.9, 123.5, 125.3, 125.5, 127.3, 127.4, 139.8, 140.6, 143.8, 152.7, 152.7, 154.0, 154.1, 159.1, 165.3. IR (KBr) νmax/cm–1 1648 (C=O), 3340 (NH). EI-MS m/z (%): 440 (M+ + 1, 23), 191 (100). Anal. calcd for C24H17N5O2S (439.49): C 65.59, H 3.90, N 15.94; found: C 65.72, H 3.16, N 16.07. 2.3. Antimicrobial Activity The synthesized products were individually tested against several gram positive and gram negative bacteria, yeast and fungi. Antibacterial tests were carried out on nutrient agar using the agar well diffusion method [35]. Suspension of

The inhibition zone diameter (mm) for the synthesized products against the tested microorganisms based on the well diffusion assay (N = 3).

Product

Gram Positive Bacteria

Gram Negative Bacteria

Yeast

S. aureus

B. subtilis

B. megaterium

K. peneumoniae

P. aeruginosa

E. coli

S. cerevisiae

C. albicans

3

22

22

26

20

20

22

28

26

6

25

27

27

27

27

25

28

28

9a

14

14

14

14

13

13

17

15

9b

17

14

14

14

13

13

17

15

9c

20

17

20

20

20.

20

28

25

11a

20

22

25

24

23

24

23

19

11b

20

22

27

23

22

22

26

22

14a

17

20

20

20

21

13

17

15

14b

14

14

14

22

22

20

17

15

16

17

22

24

22

22

20

27

24

Ciprofloxacin

20

22

24

25

24

23

NA

NA

Ketoconazole

NA

NA

NA

NA

NA

NA

23

22


Table 2.


The minimum inhibitory concentration (µg/mL) of the synthesized compounds against the tested microorganisms based on the two fold serial dilution technique (N = 3).

Product

Gram Positive Bacteria

Gram Negative Bacteria

Yeast

S. aureus

B. subtilis

B. megaterium

K. peneumoniae

P. aeruginosa

E. coli

S. cerevisiae

C. albicans

3

250

250

250

500

500

500

125

125

6

65

65

65

65

65

65

65

65

9a

⎯

⎯

⎯

⎯

⎯

⎯

500

⎯

9b

⎯

⎯

⎯

⎯

⎯

⎯

500

⎯

9c

⎯

⎯

⎯

250

250

500

500

⎯

11a

250

250

250

125

125

125

250

500

11b

65

65

65

125

125

125

65

125

14a

500

250

250

250

250

⎯

500

⎯

14b

125

125

125

125

125

125

65

65

16

500

250

125

125

125

250

125

125

Ciprofloxacin

65

65

65

65

65

65

NA

NA

Ketoconazole

NA

NA

NA

NA

NA

NA

65

65

tested bacteria (100 µL; 1 × 108 CFU/mL) were used. The antifungal tests were carried out on Sabourand dextrose agar using suspension of fungi (100 µL containing 1 × 106 CFU/mL). After the media had cooled and solidified, wells (10 mm in diameter) were made in the solidified agar and loaded with a solution of the synthesized products (100 µL; 100 mg/mL of dimethyl sulfoxide, DMSO). The plates were incubated for 24 h at 37 °C for bacteria and 48 h at 28 °C for fungi. DMSO was used as a negative control. Ciprofloxacin and Ketoconazole were used as antibacterial and antifungal standards, respectively. After incubation time, the zone of inhibition in millimeters (mm) was measured. Each experiment was carried out in triplicate and the average zone of inhibition was calculated (Table 1).

Michael addition of methyl 2-cyanoacetate (4) to 3 in anhydrous ethanol in the presence of piperidine as a catalyst afforded the unexpected product, methyl 2-cyano-3-(1-phenyl3-(thiophen-2-yl)-1H-pyrazol-4-yl)acrylate (6), in 64% yield (Scheme 1). None of the expected products, 2-oxo-6-phenyl4-(1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4-yl)-2H-pyran3,5-dicarbonitrile (5; Scheme 1) was obtained.

The bacteriostatic activity of the synthesized heterocycles was evaluated using the two fold serial dilution technique [36]. Two fold serial dilutions of the tested compounds were prepared using the proper nutrient broth. The final concentration of the solutions was 500, 250, 125 and 65 µg/mL. Each 5 mL received 0.1 mL of the inoculum and incubated at 37 °C for 24 h. all experiments were carried out in triplicate and the lowest concentration showing no growth was taken as the minimum inhibitory concentration (MIC; Table 2).

A proposed mechanism for the formation of 6 could involve a nucleophilic addition of the methyl 2-cyanoacetate anion of 4 at the electrophilic center of the double bond in 3 to furnish the intermediate 7 which gave 6 on the elimination of 2 (Scheme 2).

3. RESULTS AND DISCUSSION 3.1. Chemistry Reaction of 1-phenyl-3-(thiophen-2-yl)-1H-pyrazole-4carbaldehyde (1a) [29] with a molar equivalent of 3-oxo-3phenylpropanenitrile (2) in anhydrous ethanol, in the presence of a catalytic amount of piperidine under reflux condition for 5 h, afforded 2-benzoyl-3-(1-phenyl-3-(thiophen-2yl)-1H-pyrazol-4-yl)acrylonitrile 3 in 79% yield (Scheme 1).

The structure of compound 6 was confirmed by IR, NMR, MS and microanalytical data. For example, its IR spectrum shows the absorption band corresponding to the nitrile group at 2228 cm-1. Also, the 1H NMR spectrum of 6 shows a singlet corresponding to the methyl protons that resonates at 3.76 ppm. The structure of 6 was confirmed further by the x-ray crystallography (Fig. 1).

Treatment of 1a with 2-cyano-N'-(1-(heterocycl) ethylidene)acetohydrazides 8 (Ar = heteroaromatic) in methanol containing piperidine as a catalyst under reflux for 1 h gave the corresponding 2-cyano-N'-(1-(heterocycl) ethylidene)-3-(1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4-yl) acrylohydrazides 9a-c in 79–83% yields (Scheme 3). The 1 H NMR spectra of 9 showed the presence of the methyl protons as singlet signals that resonate at δ = 2.33–2.41 ppm region. Also, the IR spectra of 9 exhibited a characteristic band that resonates at 2198–2223 cm–1 region corresponding to the nitrile group. Reaction of 1a with acid hydrazides 10, in ethanol in the presence of acetic acid under reflux for 1 h, gave N'-((1-


Abdel-Wahab et al.

O

O

CN

O

CN

2 S

N

N

EtOH/piperidine reflux, 5 h

S

N

N

3 (79%)

1a

O

MeO

CN

4 EtOH/piperidine reflux, 5 h

N N

S

N N

CN MeO

O

S NC O

6 (64%)

CN O 5

Scheme 1. Synthesis of acrylate derivative 6.

phenyl-3-(thiophen-2-yl)-1H-pyrazol-4-yl)methylene)hydrazides 11a, b (Scheme 4) in 83 and 79% yields, respectively. The 1 H NMR spectra of 11 showed the presence of an exchangeable singlet that resonates at 11.67–12.18 ppm region corresponding to the NH proton. Reaction of 1a and 2-cyanoacetohydrazide (12) in anhydrous ethanol in the presence of traces of acetic acid for 2 h under reflux afforded acetohydrazide 13 in 88% yield (Scheme 5). The 1H NMR spectrum of 13 shows a singlet signal that resonates at 3.89 ppm corresponding to the CH 2 protons and an exchangeable singlet signal (11.79 ppm) due

to the NH proton. The IR spectrum shows a characteristic absorption band that resonates at 2198 cm–1 due to the CN group. Condensation of 13 with equimolar quantities of 1a and 4-flourobenzaldehyde (1b), in anhydrous methanol in the presence of few drops of piperidine under reflux for 1 h, gave 2-cyano-3-(1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4-yl)N'-((1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4-yl)methylene) acrylohydrazide (14a) and 2-cyano-3-(4-fluorophenyl)-N'((1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4-yl)methylene) acrylohydrazide (14b) in 74 and 79% yields, respectively (Scheme 6). The mass spectra of 14a and 14b show pseudo molecular ion (MH+) peaks at m/z 572 and 442, respectively. Finally, condensation of 13 with a molar equivalent of salicylaldehyde (1c) gave 2-imino-2H-chromene-3-carbohydrazides (16) in 72% yield (Scheme 7). The formation of 16 possibly occurs via reaction of the carbonyl group of 1c with the active methylene of 13 to form the intermediate 15. The nucleophilic attack of the hydroxyl group on the CN residue in 15 ultimately gave 16 (Scheme 7). The IR spectrum of 16 showed the absence of the CN group which indicates the cyclization process. 3.2. Antimicrobial Activity

Fig. (1). The X-ray structures for compound 6.

The antibacterial activities of the new products were investigated against three Gram positive bacteria, Staphylococcus aureus (ATCC29213), Bacillus subtilis (ATCC6633)



Ph O

O

CN

N

S

N

NC

CN

O

NC

4

N N

S

O

O

Ph

H

OMe

Ph

OMe

OMe

O

CN

CN

- Ph 2

N

S

Ph

7

3

6

Scheme 2. Proposed mechanism for the formation of 6. Ar O

O

Ar

N

N H

Me N

S

NC

CN

NH O

8

N

Me

N

MeOH/piperidine

S

N N

1a Ar = 2-thienyl, 2-benzofuryl, 2-pyridyl

9a-c (79-83%)

Scheme 3. Synthesis of 9. O O

O Ar N

S

N H

N NH

NH2

10

N

EtOH/AcOH

N

S

Ar

N

11 (79-83%)

1a

N N Ar =

or

N N Cl

Scheme 4. Synthesis of 11.

H2N

O

O

H N

HN N

CN O

S

N 1a

Scheme 5. Synthesis of acetohydrazide 13.

N

12 MeOH

S

N 13 (88%)

N

CN

N

Ph


Abdel-Wahab et al.

O HN N

O HN N

CN

CN

1a,b, MeOH S

N

N

Ar

piperidine

S

N

N

14 (74-79%)

13

Ar = 1-phenyl-3-(thiophen-2-yl)-1H-pyrazol-4-yl, 4-FC6H4

Scheme 6. Synthesis of pyrazolylthiphenes 14. HO

HN N

O

O

O

N NH

CN

N NH

CN

1c, MeOH

S

N

N

piperidine

13

S

N

O HN

N S

15

N

N

16 (72%)

Scheme 7. Synthesis of thiophenylchromene 16.

and Bacillus megaterium (ATCC9885) and three Gram negative bacteria, Klebseilla peneumoniae (ATCC13883), Pseudomonas aeruginosa (ATCC27953) and Escherichia coli (ATCC25922). Also, Saccharomyces cerevisiae and Candida albicans (NRRL Y-477) as yeasts were tested. Ciprofloxacin was used as a standard antibiotic and Ketoconazole was used as a standard antifungal agent. Each experiment was carried out in triplicate and the average zone of inhibition was calculated. The results obtained are recorded in Tables 1 and 2. The products showed good antimicrobial activity against the tested microorganisms. Compound 3, 6, 11a and 11b were found to exhibit the highest activity against the tested bacteria in which the inhibition zones varied from 20 to 28 mm. Other compounds show less reactivity as antibacterial agents compared to Ciprofloxacin. On the other hand, compound 3, 6, 9c and 16 were the most active against the tested fungi in which the inhibition zones varied from 24 to 28 mm. Other derivatives were less active as antifungal agents compared to Ketoconazole. Compound 6 shows a minimum inhibitory concentration (MIC) at 65 µg/mL. The structureantimicrobial activity relationship of the synthesized heterocycles against the tested microorganisms indicated that a combination of various functional groups and heterocyclic rings could be the reason that some compounds have high activity towards the tested microorganisms compared to the others. For example, compounds 3 and 6 contain αketonitrile moiety, while, compounds and 11a and 11b contain carbohydrazide moiety. Also, the 3-(thiophen-2-yl)4,5-dihydro-1H-pyrazole nucleus could increase the potency. Various heterocycles contain thiophene and pyrazole ring

and pyrazole ring systems show antimicrobial activity against bacteria and fungi [17-20]. CONCLUSION A facile synthesis of novel 3-(thiophen-2-yl)-1Hpyrazole derivatives in high yields was reported. The synthesized products can be used as pressures for the production of more complex heterocycles that can be used in various applications. The synthesized products showed good antimicrobial activities against the tested microorganisms compared to the standard drugs. CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The authors declare no conflict of interest, financial or otherwise. ACKNOWLEDGEMENTS The project was supported by King Saud University, Deanship of Scientific Research, Research Chair. REFERENCES [1]

Wang, K.; Lv, X.L.; Feng, D.; Li, J.; Chen, S.; Sun, J.; Song, L.; Xie, Y.; Li, J.R.; Zhou, H.C. Pyrazolate-based porphyrinic metalorganic framework with extraordinary base-resistance. J. Am. Chem. Soc., 2016, 138, 914-919.



[2]

ity evaluation in leukemia cell lines. J. Braz. Chem. Soc., 2017, 28, 217-224. Mathew, B.; Suresh, J.; Anbazhagan, S. Synthesis, in silico preclinical evaluation, antidepressant potential of 5-substituted phenyl3-(thiophen-2-yl)-4,5-dihydro-1H-pyrazole-1-carboxamides. Biomed. Aging Pathol., 2014, 4, 327-333. Bekhit, A.A.; Ashour, H.M.A.; Guemei, A.A. Novel pyrazole derivatives as potential promising anti-inflammatory antimicrobial agents. Arch. Pharm., 2005, 338, 167-174. Vijesha, A.M.; Isloor, A.M.; Shetty, P.; Sundershan, S.; Fun, H.K. New pyrazole derivatives containing 1,2,4-triazoles and benzoxazoles as potent antimicrobial and analgesic agents. Eur J. Med. Chem., 2013, 62, 410-415. Abdel-Wahab, B.F.; Sediek, A.; Mohamed, H.A.; Awad, G.E.A. Novel 2-pyrazolin-1-ylthiazoles as potential antimicrobial agents. Lett. Drug Des. Discov., 2013, 10, 111-118. Khidre, R.E., Abdel-Wahab, B.F., Badria, F.A. New quinolinebased compounds for analgesic and anti-inflammatory evaluation. Lett. Drug Des. Discov., 2011, 8, 640-648. Bekheit, M.S.; Farahat, A.A.; Abdel-Wahab, B.F. Synthetic routes to thiazoloquinazolines. Chem. Heterocycl. Compds., 2016, 52, 766-772. Baashen, M.A.; Abdel-Wahab, B.F.; El-Hiti, G.A. Syntheses of triazoloquinoxalines. Heterocycles, 2016, 92, 1931-1952. Smith, K.; El-Hiti, G.A.; Hegazy, A.S. Directed lithiation and substitution of pyridine derivatives. Heterocycles, 2015, 91, 479-504. Smith, K.; El-Hiti, G.A.; Fekri, A.; Alshammari, M.B. Side-chain lithiation of 2- and 4-substituted pyridines: Synthesis of more complex substituted pyridines. Heterocycles, 2012, 86, 391-410. Metwally, M.A.; Abdel-Wahab, B.F.; El-Hiti, G.A. 2Acetylbenzofurans: Synthesis, reactions and applications. Curr. Org. Chem., 2010, 14, 48-64. Metwally, M.A.; Shaaban, S.; Abdel-Wahab, B.F.; El-Hiti, G.A. 3Acetylindoles: Synthesis, reactions and biological activities. Curr. Org. Chem., 2009, 13, 1475-1496. Bratenko, M.K.; Panimarchuk, O.I.; Chornous, V.A.; Vovk, M.V. 4-Functionally substituted 3-heterylpyrazoles: XIV N-benzyl-N-[3aryl(heteryl)-4-pyrazolylmethylene]amines and their derivatives. Russ. J. Org. Chem., 2005, 41, 98-102. Mohareb, R.M.; El-Arab, E.E.; El-Sharkawy, K.A. The Reaction of cyanoacetic acid hydrazide with 2-acetylfuran: Synthesis of coumarin, pyridine, thiophene and thiazole derivatives with potential antimicrobial activities. Sci. Pharm., 2009, 77, 355-366. Rida, S.M.; El-Hawash, S.A.M.; Fahmy, H.T.Y.; Hazza, A.A.; ElMeligy, M.M. Synthesis and in vitro evaluation of some novel benzofuran derivatives as potential anti-HIV-1, anticancer, and antimicrobial agents. Arch. Pharm. Res., 2006, 29, 16-25. Zhang, X.-Y.; Han, X.-L.; Qian, Z.-B. 2-Cyano-N′-[1-(pyridin-2yl)ethylidene]acetohydrazide. Acta Cryst., 2012, 68, 3203. Dawood, K.M.; Abdel-Gawad, H.; Mohamed, H.A.; Badria, F.A. Synthesis, anti-HSV-1, and cytotoxic activities of some new pyrazole- and isoxazole-based heterocycles. Med. Chem. Res., 2011, 20, 912-919. Hegazi, B.; Mohamed, H.A.; Dawood, K.M.; Badria, F.A. Cytotoxicity and utility of 1-indanone in the synthesis of some new heterocycles. Chem Pharm. Bull., 2011, 58, 479-483. Balouiri, M.; Sadiki, M.; Ibnsouda, S.K. Methods for in vitro evaluating antimicrobial activity: A review. J. Pharm. Anal., 2016, 6, 71-79. Scott, A.C. In: Laboratory control of antimicrobial therapy. Collee, J.G.; Duguid, J.P.; Fraser A.G.; Marmion, B.P. Eds.; mackie and McCartney practical medical microbiology. 13th ed: Churchill Livingstone, London 1989, 2, pp. 161-181.

[3]

[4] [5]

[6]

[7] [8]

[9]

[10]

[11] [12] [13]

[14]

[15] [16]

[17]

Thumar, N.J.; Patel, M.P. Synthesis and in vitro antimicrobial evaluation of 4H-pyrazolopyran, -benzopyran and naphthopyran derivatives of 1H-pyrazole. Arkivoc, 2009, xiii, 363-380. Damljanović, I.; Vukicević, M.; Radulović, N.; Palić, R.; Ellmerer, E.; Ratković, Z.; Joksović, M.D.; Vukicević, R.D. Synthesis and antimicrobial activity of some new pyrazole derivatives containing a ferrocene unit. Bioorg. Med. Chem. Lett., 2009, 19, 1093-1095. Prakash, O.; Kumar, R.; Sehrawat, R. Synthesis and antibacterial activity of some new 2,3-dimethoxy-3-hydroxy-2-(1-phenyl-3-aryl4-pyrazolyl)chromanones. Eur. J. Med. Chem., 2009, 44, 1763-1767. Bekhit, A.A.; Ashour, H.M.A.; Ghany, Y.S.A.; Bekhit, A.E.A.; Baraka, A.M. Synthesis and biological evaluation of some thiazolyl and thiadiazolyl derivatives of 1H-pyrazole as anti-inflammatory antimicrobial agents. Eur. J. Med. Chem., 2008, 43, 456-463. Bekhit, A.A.; Fahmy, H.T.Y.; Rostom, S.A.F.; Baraka, A.M. Design and synthesis of some substituted 1H-pyrazolyl-thiazolo[4,5d]pyrimidines as anti-inflammatory-antimicrobial Agents. Eur. J. Med. Chem., 2003, 38, 27-36. Abadi, A.H.; Eissa, A.A.H.; Hassan, G.S. Synthesis of novel 1,3,4trisubstituted pyrazole derivatives and their evaluation as antitumor and antiangiogenic agents. Chem. Pharm. Bull., 2003, 51, 838-844. Rathelot, P.; Azas, N.; El-Kashef, H.; Delmas, F.; Giorgio, C.D.; Timon-David, P.; Maldonado, J.; Vanelle, P. How a single inversion of configuration leads to a reversal of the binding mode: proposal of a novel arrangement of CCK2 ligands in their receptor, and contribution to the development of peptidomimetic or non-peptide CCK2 ligands. Eur. J. Med. Chem., 2002, 37, 671-686. Hashem, A.I.; Youssef, A.S.A.; Kandeel, K.A.; Abou-Elmagd, W. S.I. Conversion of some 2(3H)-furanones bearing a pyrazolyl group into other heterocyclic systems with a study of their antiviral activity. Eur. J. Med. Chem., 2007, 42, 934-939. Joshi, N.S.; Shaikh, A.A.; Deshpande, A.P.; Karale, B.K.; Bhirud, S.B.; Gill, C.H. Synthesis, characterization and antimicrobial activities of some fluorine containing 2-(1-phenyl-3-aryl-1Hpyrazol-4-yl)-3-chlorochromones, 2-(1-phenyl-3-aryl-1H-pyrazol4-yl)chromones and 5-(1-phenyl-3-aryl-1H-pyrazol-4-yl)-3-(2hydroxyphenyl)-4,5-dihydropyrazolines. Ind. J. Chem., 2005, 44B, 422-425. Abdel-Wahab, B.F.; Khidre, R.E.; Farahat, A.A. Pyrazole-3(4)carbaldehyde: Synthesis, reactions and biological activity. Arkivoc, 2011, i, 196-245. Gouda, M.A.; Abu-Hashem, A.A.; Saad, H.H.; Elattar, K.M. 5Chloropyrazole-4-carboxaldehydes as synthon in heterocyclic synthesis. Res. Chem. Intermed., 2016, 42, 2119-2162. Fahmy, H.H.; Khalifa, N.M.; Ismail, M.M.; El-Sahrawy, H.M.; Nossier, E.S. Biological validation of novel polysubstituted pyrazole candidates with in vitro anticancer activities. Molecules, 2016, 21, 271. Gomha, S.M.; Edrees, M.M.; Altalbawy, F.M.A. Synthesis and characterization of some new bis-pyrazolyl-thiazoles incorporating the thiophene moiety as potent anti-tumor agents. Int. J. Mol. Sci., 2016, 17, 1499. Ghorab, M.M.; El-Gazzar, M.G.; Alsaid, M.S. Synthesis, characterization and anti-breast cancer activity of new 4-aminoantipyrinebased heterocycles. Int. J. Mol. Sci., 2014, 15, 7539-7553. Raghavendra, K.R.; Girish, Y.R.; Ajay Kumar, K.; Shashikanth, S. Regioselective synthesis of N-formohydrazide and formyl pyrazole analogs as potent antimicrobial agents. J. Chem. Pharm. Res., 2015, 7, 361-366. Dos Santos, E.F.S.; Do Nascimento, T.A.; Casagrande, G.A; Pizzuti, L.; Cury, N.M.; Yunes, J.A.; Raminelli, C.; Pereira, C.M.P.; Simionatto, E. Ultrasound-promoted synthesis of 3-(thiophen-2-yl)4,5-dihydro-1H-pyrazole-1-carboximidamides and anticancer activ-

[18]

[19] [20]

[21] [22] [23] [24] [25] [26] [27] [28] [29]

[30]

[31]

[32] [33]

[34] [35] [36]