Molecules 2020, 25, 3188
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1H-NMR (400 MHz, CDCl3, ppm): 5.12 (1H, s, -NH), 7.08 (1H, d, J = 17 Hz, -CO-CH=), 7.68 (1H, d,
J = 17 Hz, =CH-Ar), 6.45–7.95 (6H, Ar-H).
(E)-1-(3,4-dichlorophenyl)-3-(thiophen-2-yl)prop-2-en-1-one (16): Yield 58%; m.p. 194 ◦C; FTIR (KBr, cm−1):
1661 (C=O), 1611 (C=C of Ar), 1519 (CH=CH), 628 (C-S), 823 (C-Cl); 1H-NMR (400 MHz, CDCl3, ppm):
7.14 (1H, d, J = 17 Hz, -CO-CH=), 7.72 (1H, d, J = 17 Hz, =CH-Ar), 6.69–8.14 (6H, Ar-H).
3.2.2. General Procedure for the Synthesis of Dihydropyrazoles (17–31)
Chalcones of 3,4-dichloroacetophenone (0.005 mol) and phenyl hydrazine hydrochloride
(0.005 mol) were dissolved in glacial acetic acid (10 mL). Later, the mixture was refluxed for 6–8 h,
the solvent was evaporated completely, and dried solid was obtained. The solid thus obtained was
purified by silica gel column chromatography using mixtures of ethyl acetate in n-hexane (5–75%) and
further recrystallized from chloroform.
3-(3,4-dichlorophenyl)-1-phenyl-5-(p-tolyl)-4,5-dihydro-1H-pyrazole (17): Yield 55%; m.p. 168 ◦C; FTIR (KBr,
cm−1): 1592 (C=N), 1120 (C-N), 1586 (C=C quadrant of Ar), 830 (C-Cl); 1H-NMR (400 MHz, CDCl3,
ppm): 3.28 (1H, d, HA), 3.72 (1H, d, HB), 5.45 (1H, d, Hx), 2.34 (3H, s, Ar-CH3), 6.75–7.91 (12H, Ar-H);
13C-NMR (100 MHz, CDCl3, ppm): 22.46 (-CH3), 66.54 (C-4), 45.50 (C-5), 152.50 (C-3), 133.95 (C-20 and
C-200), 143.51 (C-30 and C-300), 134.88 (C-40 and C-400), 112.12–145.96 (Ar-C’s); MS (m/z, %): 381.30 (M+),
383.30 (M + 2).
3-(3,4-dichlorophenyl)-1-phenyl-5-(4-fluorophenyl)-4,5-dihydro-1H-pyrazole (18): Yield 70%; m.p. 195 ◦C;
FTIR (KBr, cm−1): 1644 (C=N), 1099 (C-N), 1582 (C=C quadrant of Ar), 835 (C-Cl), 922 (C-F); 1H-NMR
(400 MHz, CDCl3, ppm): 3.29 (1H, d, HA), 3.75 (1H, d, HB), 5.33 (1H, d, HX), 6.65–7.65 (12H, Ar-H).
3-(3,4-dichlorophenyl)-1-phenyl-5-(2-fluorophenyl)-4,5-dihydro-1H-pyrazole (19): Yield 61%; m.p. 149 ◦C;
FTIR (KBr, cm−1): 1599 (C=N), 1105 (C-N), 1578 (C=C quadrant of Ar), 825 (C-Cl), 925 (C-F); 1H-NMR
(400 MHz, CDCl3, ppm): 3.26 (1H, d, HA), 3.72 (1H, d, HB), 5.46 (1H, d, HX), 6.66–7.55 (12H, Ar-H).
3-(3,4-dichlorophenyl)-1-phenyl-5-(4-chlorophenyl)-4,5-dihydro-1H-pyrazole (20): Yield 75%; m.p. 261 ◦C;
FTIR (KBr, cm−1): 1549 (C=N), 1091 (C-N), 1582 (C=C quadrant of Ar), 838 (C-Cl), 846 (C-Cl); 1H-NMR
(400 MHz, CDCl3, ppm): 3.28 (1H, d, HA), 3.77 (1H, d, HB), 5.49 (1H, d, HX), 6.56–7.39 (12H, Ar-H).
3-(3,4-dichlorophenyl)-1-phenyl-5-(2-chlorophenyl)-4,5-dihydro-1H-pyrazole (21): Yield 72%; m.p. 133 ◦C;
FTIR (KBr, cm−1): 1552 (C=O), 1591 (C=C quadrant of Ar), 832 (C-Cl), 838 (C-Cl); 1H-NMR (400 MHz,
CDCl3, ppm): 3.24 (1H, d, HA), 3.71 (1H, d, HB), 5.42 (1H, d, HX), 6.69–7.42 (12H, Ar-H).
3-(3,4-dichlorophenyl)-1-phenyl-5-(2,4-difluorophenyl)-4,5-dihydro-1H-pyrazole (22): Yield 81%; m.p. 291 ◦C;
FTIR (KBr, cm−1): 1526 (C=N), 1086 (C-N), 1588 (C=C quadrant of Ar), 831 (C-Cl), 921 (C-F); 1H-NMR
(400 MHz, CDCl3, ppm): 3.25 (1H, d, HA), 3.73 (1H, d, HB), 5.49 (1H, d, HX), 6.87–7.69 (11H, Ar-H).
3-(3,4-dichlorophenyl)-1-phenyl-5-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole (23): Yield 85%; m.p. 302 ◦C;
FTIR (KBr, cm−1): 1544 (C=N), 1081 (C-N), 1578 (C=C quadrant of Ar), 821 (C-Cl), 829 (C-Cl); 1H-NMR
(400 MHz, CDCl3, ppm): 3.26 (1H, d, HA), 3.81 (1H, d, HB), 5.52 (1H, d, HX), 6.82–7.77 (11H, Ar-H).
3-(3,4-dichlorophenyl)-1-phenyl-5-(4-trifluoromethylphenyl)-4,5-dihydro-1H-pyrazole (24): Yield 66%; m.p.
125 ◦C; FTIR (KBr, cm−1): 1641 (C=N), 1152 (C-N), 1568 (C=C quadrant of Ar), 818 (C-Cl), 926 (C-F);
1H-NMR (400 MHz, CDCl3, ppm): 3.28 (1H, d, HA), 3.76 (1H, d, HB), 5.50 (1H, d, HX), 6.61–7.81
(12H, Ar-H).
3-(3,4-dichlorophenyl)-1-phenyl-5-(benzo[d][1,3]dioxol-5-yl)-4,5-dihydro-1H-pyrazole (25): Yield 49%; m.p.
212 ◦C; FTIR (KBr, cm−1): 1595 (C=N), 1097 (C-N), 1576 (C=C quadrant of Ar), 1236 (O-CH2-O), 845
(C-Cl); 1H-NMR (400 MHz, CDCl3, ppm): 6.25 (2H,s,-O-CH2O-), 3.18 (1H, d, HA), 3.82 (1H, d, HB),
5.28 (1H, d, HX), 6.74–7.49 (11H, Ar-H).