Synthesis of 1, 3, 5-Trisubstituted Pyrazoline Nucleus Containing Compounds and Screening for Anti-Inflammatory Activity
Suneeti Rajput, Vikrant Jain, Sandeep Gangrade
Department of Chemistry, Faculty of Science & IT, Madhyanchal Professional University, Ratibad-462042, Bhopal, Madhya Pradesh, India.
*Corresponding Author E-mail: dr_vikrantjain@yahoo.in
ABSTRACT:
Pyrazolinenucleus is a privileged pharmacophore for various pharmacological activities, such as antimicrobial2-8, analgesic and anti-inflammatory9-12, antinociceptive13, antidepressant and anticonvulsant14-15and anti-amoebic16. Recently, 5-(substituted) aryl-3-(3-coumarinyl) -1-phenyl-2-pyrazolines have been utilized as versatile templates for synthesizing compounds that act as potential anti-inflammatory and analgesic agents17. Some pyrazoline derivatives have shown anticancer activity against leukemia, melanoma, lung, colon, CNS, ovarian, renal, prostate, and breast cancer cell lines18-20. Thus, pyrazoline moiety has attracted considerable interest in the development of biologically active compounds.
MATERIALS AND METHODS:
Chemistry:
All the chemicals used in this study were procured as LR grade reagents from S. D. Fine Chem. Ltd., Mumbai and Sigma–Aldrich Chemie, Germany. The melting points were determined by open capillary method and are uncorrected. Purity of the compounds was checked by TLC on precoated silica gelG-plates using chloroform: methanol, ethyl acetate: n-hexane and diethyl ether: n-hexane as solvent systems. The IR spectra were recorded on Shimadzu FTIR-8400S and Perkin Elmer Spectrum RX1 FTIR spectrophotometers. Mass spectra were recorded on JEOL-Accu TOF JMST100LC spectrometer and Micromass Quattro II triple quadrupole mass spectrometer. NMR spectra were recorded on Bruker DRX-300 spectrometer and elemental analysis was performed on Elemental Vario EL III analyzer from Central Drug Research Institute, Lucknow, India.
1-Naphthalen-1-yl-3-(4-nitro-phenyl)-propenone (3):
A solution of sodium hydroxide (0.5g, 0.012mol), water (5ml), and ethanol (3ml) was poured over 1-acetylnaphthalene (1.519 ml, 0.01mol) in a 50ml round bottom flask and the reaction mixture was stirred by a magnetic stirrer at room temperature. Then, 4-nitro benzaldehyde (1.51 g, 0.01mol) was added to the above mixture and a thick paste was formed after 6 h. The progress of the reaction was monitored by TLC. The reaction mixture was kept in a refrigerator overnight. The product was filtered and washed with cold water, followed by cold ethanol and recrystallized fromchloroform21 as pale-yellow solid (Scheme 1), yield 73.06%, melting range 114–118°C; IR (KBr) 1658.67, 1589.23, 1514.02, and 1340.43 cm-1; ms: m/z 304.10 (100).
General procedure for the synthesis of pyrazoline derivatives (5a–e):
An equimolar mixture of (3) and hydrazine derivatives in 4-6 ml of glacial acetic acid was refluxed for the respective time period as given in the Scheme 2. The progress of the reaction was monitored by TLC. The reaction mixture was cooled and poured into ice water. Crude product was filtered, washed with cold water and recrystallized with chloroform.
3-Naphthalen-1-yl-5-(4-nitro-phenyl)-4,5-dihydro-1Hpyrazole (5a):
A red solid, yield 47.35%, melting range 104–108°C; IR (KBr) 1660.60, 1514.02, 1344.29, and 1108.99 cm-1; 1HNMR (CDCl3, d, ppm): 7.26–8.25 (m, 11H), 7.0 (s, H), 4.02 (s, H) 2.54 (s, 2H); ms: m/z 360.09 (100). Anal.Calcd.for C19H15N3O2: C, 71.91; H, 4.76; N, 13.24. Found: C, 70.92; H, 4.82; N, 12.18.
3-Naphthalen-1-yl-5-(4-nitro-phenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (5b):
A yellow solid, yield 48.34%, melting range 132–136°C; IR (KBr) 1647.10, 1107.06, 1508.23, and 1340.43cm-1; 1HNMR (CDCl3, d, ppm): 6.5-8.4 (m, 16H), 4.4 (s, H), 1.25 (d, 2H); ms: m/z 393.10 (100). Anal. Calcd. For C25H19N3O2: C, 76.32; H, 4.87; N, 10.68. Found: C, 75.46; H, 4.50; N, 10.63.
3-Naphthalen-1-yl-1, 5-bis-(4-nitro-phenyl)-4,5-dihydro-1H-pyrazole (5c):
A dark brown solid, yield 13.74%, melting range 174–178°C; IR (KBr) 1593.09, 1517.87, 1342.36 and 1099.35 cm-1; 1HNMR (CDCl3, d, ppm): 7.40-8.45 (m, 16H), 2.06 (s, 2H), 2.74 (s, H); ms: m/z 438 (20). Anal. Calcd. for C25H18N4O4: C, 68.49; H, 4.14; N, 12.78. Found: C, 71.62; H, 3.95; N, 12.23.
3-Naphthalen-1-yl-5-(4-nitro-phenyl)-4,5-dihydropyrazole-1-carbothioic acid amide (5d):
A yellow solid, yield 57.84%, melting range 157–161°C; IR (KBr) 1660.90, 1517.90, 1343.40, and 1105.40 cm-1;1HNMR (CDCl3, d, ppm): 7.35–8.45 (m, 12H), 4.01 (s, H), 2.2 (s, 2H), 1.35 (s, H); ms: m/z 377 (20). Anal. Calcd. for C20H16N4O2S: C, 63.81; H, 4.28; N, 14.88. Found: C, 64.69; H, 3.93; N, 13.77.
1-(2,4-Dinitro-phenyl)-3-naphthalen-1-yl-5-(4-nitrophenyl)- 4,5-dihydro-1H-pyrazole (5e):
A yellow solid, yield 60.31%, melting range 204–208°C; IR (KBr) 1665.80, 1519.90, 1343.20, and 1106.30cm-1;1HNMR (CDCl3, d, ppm): 7.40–8.45 (m, 14H), 1.65 (s, 2H), 2.80 (s, H); ms: m/z 484 (10). Anal. Calcd. for C25H17N5O6: C, 62.11; H, 3.54; N, 14.49. Found: C, 60.04; H, 2.75; N, 11.76.
3-Naphthalen-1-yl-5-(4-nitro-phenyl)-4,5-dihydropyrazole- 1-carboxylic acid amide (5f):
Semicarbazide hydrochloride (0.111g, 0.001mol) was added to the suspension of 3 (0.303g, 0.001mol) and sodium hydroxide (0.01g, 0.0025mol) in ethanol (5 ml). The mixture was refluxed for 5-6 h. The progress of the reaction was monitored by TLC using the solvent system methanol: chloroform (1:99). The reaction mixture was cooled and poured on to crushed ice. Crude product was filtered, washed with cold water, and recrystallized with ethanol as black solid, yield 44.24%, melting range 173–176°C; IR (KBr) 3021.9, 2359.3, 1522, 1426, 1216, and 1027.2 cm-1; 1HNMR (CDCl3, d, ppm): 7.04-8.70 (m,12H), 5.45 (s, 2H), 4.94 (s, H), 1.30 (s, H); ms: m/z 360(50). Anal.Calcd.for C20H16N4O3: C, 66.66; H, 4.48; N, 15.55. Found: C, 65.85; H, 4.10; N, 15.12.
3-Naphthalen-1-yl-1-(2-nitro-phenyl)-5-(4-nitro-phenyl)-4,5-dihydro-1H-pyrazole (5g):
A mixture of the (3) (0.606g, 0.002mol) and 2-nitrophenylhydrazine (0.306g, 0.002mol) in 4-6ml of glacial acetic acid was refluxed for 8 h. The progress of the reaction was monitored by TLC using solvent system methanol: chloroform (1:99). The reaction mixture was cooled and poured into ice water. Crude product was filtered, washed with cold water and recrystallized with chloroform as red solid, yield 36.57%, melting range 183–187°C; IR (KBr) 3021.7, 2363.7, 1659.2, 1605.1,1516.1, 1342.1, 1220.2, 1138.7, and 1105.5 cm-1; 1HNMR (CDCl3, d, ppm): 6.81-8.40 (m, 15H), 2.75 (s, H), 1.65 (s,2H); ms: m/z 439 (60). Anal.Calcd. for C25H18N4O4: C,68.49; H, 4.14; N, 12.78. Found: C, 70.89; H, 3.68; N,11.34.
PHARMACOLOGICAL SCREENING:
Anti-Inflammatory Activity:
All the synthesized () compounds were tested for their ant-inflammatory activity using carrageenan-induced rat hind paw edema method of Winter et al. The protocol of animal experiments was approved by the Institutional Animal Ethics Committee (IAEC). The edema hind paw was induced by injection of 0.1mL of 1% carrageenan solution into subplanter region of right-hand paw. Diclofenac sodium was used as a reference anti-inflammatory drug and anti-inflammatory activity was calculated at hourly intervals up to 4h after injection and presented in Table 2 as the mean paw volume (mL) as well as the percentage anti-inflammatory activity (%AI). Most of the synthesized compounds showed appreciable inhibition of the edema size in comparison with diclofenac sodium. The pyrazoline derivatives 5a, 5b, 5c, and 5d showed good anti-inflammatory activity with a percent inhibition of 67.61, 66.90, 66.72, and 64.6 % respectively, the anti-inflammatory activity of 4a, 4b, 4c, and 4d showed least inhibition of the edema size in comparison with diclofenac sodium. The 1,3,4-thiadiazole derivatives 5a-d showed excellent protection against inflammation. The acetamide compounds 5a and 5b displayed consistently excellent anti-inflammatory activity (87.25 and 85.66 % inhibition, respectively) up to 4 h that was comparable to that of the standard drug diclofenac sodium, whereas N-phenylacetamide compounds 5c and 5d exhibit good systemic anti-inflammatory activity with percent inhibition of 73.45 and 74.33% respectively. A detail study of the results showed satisfactory anti-inflammatory activity of 5a, 5b, 5c, and 5d in second phase of the biphasic carrageenan induced edema assay demonstrating the capability of the tested compounds to inhibit prostaglandin synthesis1,31. This can be attributed to their ability to bind cyclooxygenase (COX) enzyme, which is responsible for the synthesis of prostaglandins. Consistently exhibited anti-inflammatory activity up to 4 h proposes that these compounds (5a-d) do not get easily metabolized in the system. Compounds 5a, 5b, 5c, and 5d were further evaluated for their inhibitory potency against COX-1 and COX-2.
In this study, chalcone (3) was synthesized by stirring 4-nitrobenzaldehyde with 1-acetyl naphthalene in the presence of ethanolic sodium hydroxide solution. Synthesis of intermediate-chalcone was confirmed on the basis of its IR and mass spectra. The IR spectra of chalcone displayed peak at1658.67 cm-1 indicating the presence of a conjugated carbonyl group (C=O). Mass spectra showed the [M+1] peak. The chalcone was then reacted with hydrazines (4a–g) to give2-pyrazoline derivatives (5a–g) (Scheme 2). This reaction probably takes place through modification of an appropriate α, β-unsaturated carbonyl group, which cyclizes to give pyrazoline compounds in the presence of a suitable cyclizing agent (glacial acetic acid) under prolonged refluxing condition. All the synthesized compounds were characterized by physical, spectral, and elemental analysis.
SCHEME 1: SYNTHESIS OF CHALCONE (3)
SCHEME 2 SYNTHESES OF PYRAZOLINE DERIVATIVES (5a-g)
RESULTS AND DISCUSSION:
The IR spectra in pyrazoline derivatives exhibited C=N stretching vibrations in the range of 1522–1665.8 cm-1. [M]+ or [M+1] peaks were observed for the various compounds synthesized. In all the 1H-NMR spectra, a multiplet indicating various naphthyl and aromatic protons appears at the δ values of ~6.5–8.5ppm.
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Received on 06.02.2022 Modified on 19.02.2022
Accepted on 10.03.2022 ©AJRC All right reserved
Asian J. Research Chem. 2022; 15(2):151-154.