Bis(4,5-dihydropyrazole) derivatives: Synthesis, characterization and antimicrobial-antioxidant evaluations

Article abstract of DOI:10.14233/ajchem.2018.21451

In the present work, five new bispyrazolines 3(a-e) have been prepared from the cyclization reaction of bischalcones 2(a-e) with phenyl hydrazine under alcoholic medium. The bischalcones 2(a-e) were synthesized by using the alkylation of chalcone 1 with a

Full text of DOI:10.14233/ajchem.2018.21451

Asian Journal of Chemistry; Vol. 30, No. 9 (2018), 2097-2102
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2018.21451
Bis(4,5-dihydropyrazole) Derivatives: Synthesis,
Characterization and Antimicrobial-Antioxidant Evaluations
*
MOHAMAD YUSUF and SALONI THAKUR
Department of Chemistry, Punjabi University, Patiala-147 002, India
*Corresponding author: E-mail: yusuf_sah04@yahoo.co.in
Received: 17 May 2018; Accepted: 4 June 2018;
Published online: 31 July 2018;
AJC-19027
In the present work, five new bispyrazolines 3(a-e) have been prepared from the cyclization reaction of bischalcones 2(a-e) with phenyl
hydrazine under alcoholic medium. The bischalcones 2(a-e) were synthesized by using the alkylation of chalcone 1 with appropriate
alkylating agents. The structures of the newly prepared products were confirmed by IR, 1H and 13C NMR and ESI-MS. The final products
were screened for their antimicrobial and antioxidant properties. The ortho-xylene linked bispyrazoline showed significant antimicrobial
action while the bischalcones proved themselves significant antioxidant.
Keywords: Bischalcone, Phenylhydrazine, Bispyrazolines, Biological activities.
regulatory activities [18]. Pyrazole scaffold is also found in
drugs such as celecobix [19], sildenefil [20] and rimonabant
[21]. Pyrazolines substituted with different functional groups
can be considered as cyclic benzylhydrazine moieties, endowed
with MAO inhibitory activity [22]. Synthesis of pyrazoline
compounds from α,β-unsaturated carbonyl compounds
(chalcones) is done by the cyclization with hydrazine hydrate
or substituted hydrazine. It is one of the most commonly used
method for the synthesis of pyrazoline compounds. Recently,
new catalysts are used for the synthesis such as glacial acetic
acid under heating or ultrasound irradiation, K2CO3 mediated
microwave irradiation [23], pyridine in refluxing ethanol [24]
Amberlyst [25] in toluene [26], hot propionic acid [27],
triethanolamine [28] and ethanolic sodium hydroxide [29] or
sodium acetate [30]. The presence of pyrazole cores in medici-
nally active molecules has stimulated the need for elegant and
efficient ways to make these heterocyclic compounds. Bispyra-
zolines are the heterocycles in which two pyrazoline moieties
are joined through the carbon chains of varying lengths and
structures. In continuation of our research work [31-36] upon
the bisheterocyclic compounds, we report herein the synthesis,
characterization, antimicrobial and antioxidant studies of five
new aromatic and rigid chain linked bis(4,5-dihydropyrazole)
derivatives. These bispyrazolines were synthesized through
the cyclization of bischalcones.
INTRODUCTION
Chalcones either natural or synthetic are associated with
various biological activities such as antiangiogenic [1,2],
cytotoxicity [3,4] and cholesterol-lowering activity [5]. These
are used in agrochemicals, pharmaceuticals, perfumes [6] and
as liquid crystalline polymer units [7]. The presence of a
reactive, unsaturated keto moiety in chalcones is responsible
for their biological behaviour, which may be altered depending
on the type and position of substituent on the rings [8]. It is
also an important precursor for the synthesis of a large number
of bioactive molecules, primarily the nitrogen containing hetero-
cyclics [9]. Invasive Fungal Infections (IFIs) are found in patients
especially with weak immune function [10].Azoles are termed
as antifungal agents and ketaconazole, an imidazole derivative
used as antifungal agent.
Pyrazoles are the structural isomers of imidazole and
pyrazolines are the reduced forms of the pyrazoles. Pyrazole
COX-2 inhibitor has highlighted the importance of these
heterocycles in pharmaceutical chemistry. These heterocycles
containing physiological activities such as antimicrobial [11],
antiamoebic [12], antidepressant [13], antinociceptive [14],
anticancer [15] and antiinflammatory [16]. Pyrazolines are
highly active insecticide towards coleopteran and lepidopteran
insects [17] and exhibited fungicidal and plant growth
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Synthesis of (2E,2E′)-3,3'-(4,4'-(1,4-phenylenebis(meth-
2098 Yusuf et al.
Asian J. Chem.
EXPERIMENTAL
ylene))(oxy)bis(4,1phenylene)bis[(4-methoxy)-3-phenyl-
prop-2-en-1-one] (2b): The bischalcones 2b was synthesized
from the reaction of chalcone 1 (2.54 g, 0.01 mol), with α,α′-
dibromo-p-xylene (1.32 g, 0.005 mol) under the similar conditions
as described for compound 2a. Creamish solid: yield: 78 %;
m.p.: 152-154 ºC; IR (KBr, νmax, cm-1): 3098 (arom. C-H), 1720
(C=O) and 1261, 1032 (C-O); 1H NMR (400 MHz, DMSO-
d6): δ 8.01 (2H, d, Jtrans = 17.4 Hz, H-3), 7.98 (4H, d, Jo = 7.8
Hz, H-2′, 6′), 7.62 (4H, d, J = 7.4 Hz, H-2′′, 6′′), 7.52 (2H, d,
Jtrans =17.4 Hz, H-2), 7.14 (4H, d, Jo = 6.8 Hz, H-2′′′, 3′′′, 5′′′,
6′′′), 6.98 (4H, dd, Jo = 8.8 Hz, H-3′, 5′), 6.75 (4H, d, Jo = 8.3
Hz, H-3′′, 5′′), 5.35 (4H, s, OCH2) 3.75 (3H, s, OCH3); 13C
NMR (100 MHz, DMSO-d6): δ 192.16 (C=O), 145.91 (C-4′),
140.34 (C-4′′), 134.77 (C-3), 133.76 (C-1′′′, 4′′′), 132.18 (C-1′),
131.96 (C-1′′), 131.24 (C-2′′, 6′′), 129.93 (C-2′, 6′), 127.52
(C-2′′′, 3′′′, 5′′′, 6′′′), 121.77 (C-3′, 5′), 120.91 (C-3′′, 5′′),
120.69 (C-2), 64.43 (OCH2), 58.96 (OCH3); ESI-MS: m/z 634
(M+Na+1, 15 %), 611 (M+1, 75 %), 610 (M, 100 %);Anal. Calcd.
(%) for C40H34O6: C, 78.67; H, 5.61; Found: C, 78.38; H, 5.60.
Synthesis of (2E,2E′)-3,3′-(4,4′-(1,3-phenylenebis-
(methylene))(oxy)bis(4,1-phenylene)bis[(4-methoxy)-3-
phenylprop-2-en-1-one] (2c): The bischalcones 2c was
prepared from the reaction of chalcone 1 (2.54 g, 0.01 mol),
with α,α′-dibromo-m-xylene (1.32 g, 0.005 mol) under the
same protocol as given for compound 2a.Yellow solid: yield:
59 %; m.p.: 142-144 ºC; IR (KBr, νmax, cm-1): 3100 (arom. C-
H), 1717 (C=O) and 1258, 1029 (C-O); 1H NMR (400 MHz,
DMSO-d6): δ 7.96 (2H, d, Jtrans = 16.8 Hz, H-3), 7.93 (4H, d,
Jo = 8.0 Hz, H-2′, 6′), 7.78 (4H, d, J = 7.9 Hz, H-2′′, 6′′), 7.56
(1H, dd, J = 6.8, 2.4 Hz, H-5′′′), 7.49 (2H, d, Jtrans = 16.8 Hz,
H-2), 7.34 (2H, d, Jo = 6.9 Hz, H- 4′′′, 6′′′), 7.21 (1H, s, H-2′′′),
6.84 (4H, d, Jo = 7.4 Hz, H-3′, 5′), 6.79 (4H, d, Jo = 7.6 Hz, H-
3′′, 5′′), 5.25 (4H, s, OCH2) 3.81 (3H, s, OCH3); 13C NMR (100
MHz, DMSO-d6): δ 191.86 (C=O), 140.31 (C-4′), 137.74 (C-
4′′), 135.57 (C-3), 131.48 (C-1′), 130.79 (C-1′′), 129.88 (C-
2′′, 6′′), 129.33 (C-2′, 6′), 129.11 (C-1′′′, 3′′′) 127.97 (C-5′′′),
127.12 (C-4′′′, 6′′′), 124.87 (C-2′′′), 120.88 (C-3′, 5′), 119.98
(C-3′′, 5′′), 119.87 (C-2), 62.54 (OCH2), 57.32 (OCH3); ESI-
MS: m/z 611 (M+1, 25 %), 610 (M, 100 %); Anal. Calcd. (%)
for C40H34O6: C, 78.67; H, 5.61; Found: C, 78.69; H, 5.62.
Synthesis of (2E,2E′)-3,3′-(4,4′-(Z)-but-2-ene-(bis(meth-
ylene))(oxy)bis(4,1-phenylene)bis[(4-methoxy)-3-phenyl-
prop-2-en-1-one] (2d): The bischalcones 2d was obtained
from the reaction of chalcone 1 (2.54 g, 0.01 mol), with trans-
1,4-dibromo-2-butene (1.06 g, 0.005 mol) under the similar
conditions as mentioned for compound 2a. Off white solid:
yield: 72 %; m.p.: 126-128 ºC; IR (KBr, νmax, cm-1): 3111
All the chemicals were purchased from S.D. Fine Chem.
Ltd. and E. Merck. The melting points of the synthesized
heterocycles were determined through the open capillary. A
Perkin Elmer RXIFT Infrared spectrophotometer was used for
scanning the Infrared (IR) spectra through KBr pellets and a
400 MHz Bruker spectrophotometer was used to recorded 1H
and 13C NMR spectra in CDCl3/DMSO-d6 solvent. The progress
of reaction and after completion the purity of compounds was
checked by using thin layer chromatography.
Synthesis of (2Z)-1-(4-hydroxyphenyl)-3-(4-methoxy-
phenyl)prop-2-en-1-one (1): A mixture of 4-hydroxyaceto-
phenone (1.36 g, 0.01 mol), anisaldehyde (1.36 g, 0.01 mol),
and NaOH (5.0 g, 0.024 mol) was dissolved in ethanol (20 mL)
and stirred for 6 h at 0 ºC. Reaction mixture was kept overnight
in refrigerator and resulting mass then put into acidic ice. A
yellow solid was separated out which was recrystallized from
methanol to yield a pure compound 1 (Scheme-I).Yellow solid:
yield: 81 %; m.p.: 162-164 ºC; IR (KBr, νmax, cm-1): 3280 (OH),
3094 (arom. C-H), 1653 (C=O) and 1258, 1077 (C-O); 1HNMR
(400 MHz, DMSO-d6): δ 12.89 (1H, s, OH), 7.59 (1H, d, Jtrans
=
15.6 Hz, H-3), 7.53 (2H, d, Jo = 8.0 Hz, H-2′, 6′), 7.48 (1H, d,
Jtrans = 15.6 Hz, H-2), 7.21 (2H, d, Jo = 8.0 Hz, H-2′′, 6′′), 7.01
(2H, d, Jo = 8.3 Hz, H-3′, 5′), 6.93 (2H, d, Jo = 8.6 Hz, H-3′′,
13
5′′), 3.82 (3H, s, OCH3); C NMR (100 MHz, DMSO-d6): δ
193.72 (C=O), 163.55 (C-4′), 158.53 (C-4′′), 131.81 (C-3), 129.77
(C-1′′), 129.61 (C-1′), 128.70 (C-2′′, 6′′), 120.03 (C-2′, 6′),
118.92 (C-2), 118.78 (C-3′, 5′), 118.55 (C-3′′, 5′′), 53.55
(OCH3); ESI-MS: m/z 255 (M+1, 25 %), 254 (M, 100 %);
Anal. Calcd. (%) for C16H14O3: C, 75.57; H, 5.55; Found: C,
75.26; H, 5.52.
Synthesis of (2E,2E′)-3,3′-(4,4′-(1,2-phenylenebis-
(methylene))(oxy)bis(4,1-phenylene)bis[(4-methoxy)-3-
phenylprop-2-en-1-one] (2a):A mixture of chalcone 1 (2.54
g, 0.01 mol), K2CO3 (2.0 g) with α,α′-dibromo-o-xylene (1.32 g,
0.005 mol) and tetrabutylammonium iodide (1.0 g) was disso-
lved in acetone and refluxed for 4 h with continuous stirring.
Thin layer chromatography was used to observe the completion
of reaction. On completion a colourless solid mass was separated
from acetonic part and poured in to acidic ice to provide a crude
solid. It was further recrystallized using methanol to yield a
pure compound 2a (Scheme-I). Off white solid: Yield: 72 %;
m.p.: 130-132 ºC; IR (KBr, νmax, cm-1): 3070 (aromatic C-H),
1
1711 (C = O) and 1257, 1030 (C-O); H NMR (400 MHz,
DMSO-d6): δ 7.78 (2H, d, Jtrans = 15.7 Hz, H-3), 7.60 (2H, dd,
J = 5.1, 2.0 Hz, H-5′′′), 7.54 (2H, dd, J = 6.0, 2.8 Hz, H-6′′′),
7.42 (2H, d, Jtrans = 15.7 Hz, H-2), 7.04 (4H, d, J = 2.2 Hz, H-2′,
6′), 7.02 (4H, dd, J = 2.5, 8.0 Hz, H-2′′, 6′′), 6.94 (4H, dd, J =
4.5, 2.0 Hz, H-3′, 5′), 6.85 (4H, d, J = 6.9, 2.0 Hz, 8.3 Hz, H-3'',
5''), 5.48 (4H, s, OCH2) 3.55 (3H, s, OCH3); 13C NMR (100 MHz,
DMSO-d6): δ 188.75 (C=O), 134.93 (C-4′), 134.54 (C-4′′),
131.75 (C-3), 130.77 (C-1′′′), 130.68 (C-1′), 130.16 (C-1′′),
129.95 (C-2′′, 6′′), 129.30 (C-2′, 6′), 128.88 (C-4′′′, 5′′′), 128.74
(C-3′′′, 6′′′), 127.75 (C-3′, 5′), 122.32 (C-3′′, 5′′), 119.43 (C-2),
68.26 (OCH2), 64.16 (OCH3); ESI-MS: m/z 611 (M+1, 55 %),
610 (M, 100 %); Anal. calcd. (%) for C40H34O6: C, 78.67; H,
5.61; Found: C, 78.35; H, 5.58.
1
(arom. C-H), 1721 (C=O) and 1251, 1031 (C-O); H NMR
(400 MHz, DMSO-d6): δ 8.12 (4H, d, Jo = 7.3 Hz, H-2′′, 6′′),
7.91 (4H, d, Jo = 7.0 Hz, H-2′, 6′), 7.80 (2H, d, Jtrans = 15.5 Hz,
H-3), 7.72 (2H, d, Jtrans = 15.5 Hz, H-2), 7.07 (4H, d, Jo = 7.4
Hz, H-3′, 5′), 7.02 (4H, d, Jo = 7.3 Hz, H-3′′, 5′′), 6.10 (2H, t,
Jvic = 5.2 Hz, CH2CH=), Hz, 5.14 (4H, d, Jvic = 5.2 Hz, OCH2)
3.84 (3H, s, OCH3); 13C NMR (100 MHz, DMSO-d6): δ 187.14
(C=O), 139.01 (C-4), 135.14 (C-4′′), 130.59 (C-3), 129.19
(CH2CH=), 128.86 (C-1′), 128.29 (C-1′′), 128.08 (C-2′′, 6′′),
127.00 (C-2′, 6′), 121.81 (C-2), 116.86 (C-3′, 5′), 115.98 (C-

Vol. 30, No. 9 (2018)
Synthesis and Antimicrobial-Antioxidant Evaluations of Bis(4,5-dihydropyrazole) Derivatives 2099
OH
OCH3
HO
OCH3
a
+
O
O
CH3
O
H
1
b
H
C
H
H
C
H
OCH3
O
O
(X)
H3CO
2(a-e)
C
O
O
H
C
H
H
C
O
O
(X)
HM
N
H
HM
HA
HA
OCH3
H3CO
N
N
HX
N
HX
3(a-e)
H
C
(X) =
,
,
,
,
C
C
C
H
a
. NaOH, EtOH, 0 °C;
b. anhydrous K2CO3, dry acetone, PTC, BrCH2(X)CH2Br, c. PhNHNH2, dry ethanol, AcOH, ∆
Scheme-I
3′′, 5′′), 67.33 (OCH2), 55.19 (OCH3); ESI-MS: m/z 561 (M+1,
10 %), 560 (M, 90 %);Anal. Calcd. (%). for C36H32O6: C, 77.12;
H, 5.75; Found: C, 76.81; H, 5.72.
was confirmed with the help of TLC plates. The resulting reaction
mixture was concentrated and cooled in an ice bath to yield a
crude solid. The crude product was further crystallized from a
mixture of methanol and chloroform to provide pure product
3a (Scheme-I). Brown solid: yield: 68 %; m.p.: 116-118 ºC; IR
(KBr, νmax, cm-1): 3034 (arom. C-H), 2944, 2872 (methylene
C-H), 1598 (C=N); 1H NMR (400 MHz, DMSO-d6): δ 7.92 (2H,
d, Jo = 8.8 Hz, H-4′′′′, 5′′′′), 7.82 (2H, d, H-3′′′′, 6′′′′), 7.79
(4H, d, J = 3.7 Hz, H-2′, 6′), 7.64 (4H, d, J = 3.3 Hz, H-2′′, 6′′),
7.53 (4H, d, J = 3.2 Hz, H-2′′′, 6′′′), 7.38 (6H, m, H-3′′′, 4′′′, 5′′′),
7.00 (4H, d, Jo = 8.9 Hz, H-3′, 5′), 6.82 (4H, d, Jo = 7.0 Hz, H-3′′,
5′′), 5.87 (2H, dd, JXA = 3.0 Hz, JXM = 11.0 Hz, H-X), 5.28
(4H, s, OCH2), 3.81 (2H, dd, JMX = 11.9 Hz, JMA = 16.8 Hz, H-M),
3.10 (2H, dd, JAX = 3.2 Hz, JAM = 17.8 Hz, H-A), 3.77 (3H, s,
OCH3); 13C NMR (100 MHz, DMSO-d6): δ153.74 (C-4′), 143.39
(C-4′′), 140.48 (C-3), 137.11 (C-1′′), 135.02 (C-1′), 134.66
(C-1′′′), 131.41 (C-2′′, 6′′), 128.98 (C-2′, 6′), 125.91 (C-3′′′,
5′′′), 124.66 (C-4′′′), 120.73 (C-2′′′, 6′′′), 114.81 (C-3′, 5′), 113.60
(C-3′′, 5′′), 67.27 (OCH2), 63.11 (OCH3), 55.92 (C-5), 43.45
(C-4); ESI-MS: m/z 813 (M+Na, 14 %), 790 (M, 100 %);Anal.
Calcd. (%) for C52H46N4O4: C, 78.96.17; H, 5.86, N, 7.08;
Found: C, 78.64. H, 5.83, N, 7.05.
Synthesis of (2E,2E′)-3,3′-(4,4′-(Z)-but-2-yne-(bis(meth-
ylene))(oxy)bis(4,1-phenylene)bis[(4-methoxy)-3-phenyl-
prop-2-en-1-one] (2e): The bischalcones 2e was prepared on
treatment of chalcone 1 (2.54 g, 0.01 mol), with 1,4-dichloro-
2-butyne (0.64 g, 0.005 mol) under the same reaction condition
as given for compound 2a. Brown solid: yield: 58 %; m.p.:
140-142 ºC; IR (KBr, νmax, cm-1): 3104 (arom. C-H), 1737 (C=O)
and 1249, 1029 (C-O); 1H NMR (400 MHz, DMSO-d6): δ 7.97
(4H, d, Jo = 8.7 Hz, H-2′′, 6′′), 7.89 (4H, d, Jo = 8.4 Hz, H-2′, 6′),
7.80 (2H, d, Jtrans = 15.4 Hz, H-3), 7.32 (2H, d, Jtrans = 15.4 Hz,
H-2), 7.01 (4H, d, Jo = 7.8 Hz, H-3′, 5′), 6.96 (4H, d, Jo = 7.7
Hz, H-3′′, 5′′), 5.06 (4H, s, OCH2) 3.87 (3H, s, OCH3); 13C
NMR (100 MHz, DMSO-d6): δ 190.56 (C=O), 145.11 (C-4′),
137.21 (C-4′′), 130.54 (C-3), 129.25 (C-1′), 128.29 (C-1′′),
128.08 (C-2′′, 6′′), 126.44 (C-2′, 6′), 119.17 (C-2), 117.70
(C-3′, 5′), 114.49 (C-3′′, 5′′), 88.48 (C≡C) 65.49 (OCH2), 55.43
(OCH3); ESI-MS: m/z 559 (M+1, 100 %), 558 (M, 75 %);Anal.
Calcd. (%) for C36H32O6: C, 77.12; H, 5.75; Found: C, 76.81;
H, 5.72.
Synthesis of 1,2-bis[(4-(1-phenyl-4,5-dihydro-1H-
pyrazol-5-yl)(4-methoxy)-2-phenyl)phenoxy methyl)-
benzene] (3a):A mixture of bischalcone 2a (0.6 g, 0.001 mol)
and phenyl hydrazine (0.22 g, 0.002mol) in dry EtOH (25.0 mL)
was refluxed for 4 h in 100 mL round bottom flask using glacial
acetic acid as catalyst. The progress and completion of reaction
Synthesis of 1,4-bis[(4-(1-phenyl-4,5-dihydro-1H-pyrazol-
5-yl-)(4-methoxy)-2-phenyl)phenoxy methyl)benzene] (3b):
The bispyrazoline 3b was synthesized through refluxing of a
mixture of bischalcone 2b (0.6 g, 0.001 mol), phenyl hydrazine
(0.22 g, 0.002mol) and glacial acetic acid (5.0 mL) in dry
EtOH (25.0 mL) under the similar reaction condition as

2100 Yusuf et al.
Asian J. Chem.
described above for compound 3a. Brown solid: yield: 72 %;
m.p.: 124-126 ºC; IR (KBr, νmax, cm-1): 3034 (arom. C-H),
JMA = 17.2 Hz, H-M), 3.26 (2H, dd, JAX = 3.6 Hz, JAM = 17.8
Hz, H-A), 3.72 (3H, s, OCH3); 13C NMR (100 MHz, DMSO-
d6): δ 156.11 (C-4′), 147.63 (C-4′′), 141.88 (C-3), 135.81 (C-
1′′), 133.15 (C-1′), 129.51 (C-1′′′), 123.19 (C-2′′, 6′′), 121.33
(C-2′, 6v), 119.35 (C-3′′′, 5′′′), 117.66 (C-4′′′), 111.32 (C-2′′′,
6′′′), 109.95 (C-3′, 5′), 108.16 (C-3′′, 5′′), 67.73 (OCH2), 65.88
(OCH3), 53.48 (C-5), 43.53 (C-4); ESI-MS: m/z 741 (M+1,
25 %), 740 (M, 100 %); Anal. Calcd. (%) for C48H44N4O4: C,
77.81; H, 5.99, N, 7.56; Found: C, 77.49; H, 5.96; N, 7.52.
Synthesis of (Z)-1,4-bis[(4-(1-phenyl-4,5-dihydro-1H-
pyrazol-5-yl-)(4-methoxy)-2-phenyl)phenoxy]but-2-yne
(3e): The bispyrazoline 3e was prepared by refluxing a mixture
of bischalcone 2e (0.5 g, 0.001 mol) with phenyl hydrazine
(0.22 g, 0.002 mol) under the similar reaction conditions as
given above for compound 3a. Brown solid: yield: 58 %; m.p.:
104-106 ºC; IR (KBr, νmax, cm-1): 3022 (arom. C-H), 2989, 2873
(methylene C-H), 1594 (C=N); 1H NMR (400 MHz, DMSO-
d6): δ 7.68 (4H, d, Jo = 7.6 Hz, H-2′, 6′), 7.52 (4H, m, H-3′′′,
5′′′), 7.19 (4H, d, Jo = 7.1 Hz, H-2′′, 6′′), 7.01 (4H, d, Jo = 6.9
Hz, H-2′′′, 6′′′), 6.99 (1H, t, Jo = 6.8 Hz, H-4′′′), 6.93 (4H, d,
Jo = 8.0 Hz, H-3′, 5′), 6.91 (4H, d, Jo = 8.7 Hz, H-3′′, 5′′), 5.79
(2H, dd, JXA = 2.8 Hz, JXM = 11.8 Hz, H-X), 5.75 (4H, s, OCH2),
3.73 (2H, dd, JMX = 11.7 Hz, JMA = 16.9 Hz, H-M), 3.29 (2H,
dd, JAX = 2.8 Hz, JAM = 16.7 Hz, H-A), 3.69 (3H, s, OCH3); 13C
NMR (100 MHz, DMSO-d6): δ 148.11 (C-4′), 141.33 (C-4′′),
139.73 (C-3), 134.88 (C-1′′), 131.55 (C-1′), 128.59 (C-1′′′),
122.89 (C-2′′, 6′′), 121.36 (C-2′, 6′), 118.33 (C-3′′′, 5′′′), 116.96
(C-4′′′), 112.22 (C-2′′′, 6′′′), 110.95 (C-3′, 5′), 107.76 (C-3′′,
5′′), 88.48 (C≡C), 69.77 (OCH2), 66.81 (OCH3), 53.78 (C-5),
43.77 (C-4); ESI-MS: m/z 761 (M+Na, 15 %), 740 (M, 85 %);
Anal. Calcd. (%) for C48H44N4O4: C, 78.03; H, 5.73, N, 7.58;
Found: C, 77.71; H, 5.70; N, 7.54.
1
2944, 2872 (methylene C-H), 1592 (C=N); H NMR (400
MHz, DMSO-d6): δ 7.33 (4H, d, Jo = 7.8 Hz, H-2′′′′, 3′′′′, 5′′′′,
6′′′′), 7.19 (4H, d, Jo = 6.9 Hz, H-2′, 6′), 7.04 (4H, d, J = 3.6
Hz, H-2′′, 6′′), 7.03 (4H, d, Jo = 7.2 Hz, H-2′′′, 6′′′), 6.98 (6H,
m, H-3′′′, 4′′′, 5′′′), 6.93 (4H, d, Jo = 8.2 Hz, H-3′, 5′), 6.62
(4H, d, Jo = 7.8 Hz, H-3′′, 5′′), 5.98 (2H, dd, JXA = 2.6 Hz, JXM
= 11.7 Hz, H-X), 5.71 (4H, s, OCH2), 3.78 (2H, dd, JMX = 11.3
Hz, JMA = 17.3 Hz, H-M), 3.24 (2H, dd, JAX = 2.9 Hz, JAM
=
16.9 Hz, H-A), 3.53 (3H, s, OCH3); 13C NMR (100 MHz,
DMSO-d6): δ 149.94 (C-4′), 145.09 (C-4′′), 139.71 (C-3),
137.20 (C-1′′), 134.63 (C-1′), 130.23 (C-1′′′), 123.11 (C-2′′,
6′′), 121.93 (C-2′, 6′), 118.99 (C-3′′′, 5′′′), 116.86 (C-4′′′),
112.88 (C-2′′′, 6′′′), 109.55 (C-3′, 5′), 104.36 (C-3′′, 5′′), 68.17
(OCH2), 64.21 (OCH3), 54.99 (C-5), 44.85 (C-4); ESI-MS:
m/z 814 (M+Na+1, 35%), 790 (M, 100%); Anal. Calcd. (%)
for C52H46N4O4: C, 78.96.17; H, 5.86, N, 7.08; Found: C, 78.68;
H, 5.84; N, 7.06.
Synthesis of 1,3-bis[(4-(1-phenyl-4,5-dihydro-1H-pyrazol-
5-yl-)(4-methoxy)-2-phenyl)phenoxy methyl)benzene] (3c):
The compound 3c was prepared by treating a mixture of
bischalcone 2c (0.6 g, 0.001 mol), phenyl hydrazine (0.22 g,
0.002 mol), and glacial acetic acid (5.0 mL) in dry EtOH (25.0
mL) under the same conditions as described previously for
compound 3a. Yellow solid: yield: 63 %; m.p.: 110-112 ºC;
IR (KBr, νmax, cm-1: 3015 (arom. C-H), 2951, 2862 (methylene
1
C-H), 1591 (C=N); H NMR (400 MHz, DMSO-d6): δ 7.92
(4H, d, Jo = 7.3 Hz, H-2′, 6′), 7.53 (1H, dd, J = 3.6, 6.2 Hz, H-
5′′′′), 7.40 (2H, d, J = 3.8 Hz, H-4′′′′, 6′′′′), 7.35 (1H, s, H-
2′′′′), 7.22 (6H, m, H-3′′′, 4′′′, 5′′′), 7.08 (4H, d, Jo = 7.6 Hz,
H-2′′, 6′′), 6.99 (4H, d, Jo = 6.9 Hz, H-2′′′, 6′′′), 6.94 (4H, d, Jo
= 8.3 Hz, H-3′, 5′), 6.92 (4H, d, Jo = 8.0 Hz, H-3′′, 5′′), 5.91 (2H,
dd, JXA = 3.9 Hz, JXM = 12.3 Hz, H-X), 5.87 (4H, s, OCH2),
3.75 (2H, dd, JMX = 11.8 Hz, JMA = 17.7 Hz, H-M), 3.28 (2H,
dd, JAX = 3.3 Hz, JAM = 17.3 Hz, H-A), 3.61 (3H, s, OCH3); 13C
NMR (100 MHz, DMSO-d6): δ 154.91 (C-4′), 151.06 (C-4′′),
145.78 (C-3), 139.98 (C-1′′), 137.55 (C-1′), 132.43 (C-1′′′),
127.19 (C-2′′, 6′′), 125.13 (C-2′, 6′), 120.90 (C-3′′′, 5′′′), 115.86
(C-4′′′), 110.81 (C-2′′′, 6′′′), 108.15 (C-3′, 5′), 106.66 (C-3′′, 5′′),
69.19 (OCH2), 66.28 (OCH3), 52.98 (C-5), 43.95 (C-4); ESI-
MS: m/z 791 (M+1, 15 %), 790 (M, 100 %); Anal. Calcd. (%)
for C52H46N4O4: C, 78.96.17; H, 5.86, N, 7.08; Found: C, 78.70;
H, 5.87; N, 7.07.
RESULTS AND DISCUSSION
The bispyrazolines 3(a-e) were synthesized in the present
study. The compound 1 was synthesized through the conden-
sation reaction of 4-hydroxyacetophenone with anisaldehyde.
The O-alkylation of chalcone 1 with appropriate aromatic and
rigid linker using acetone as solvent in the presence of K2CO3
and tetrabutylammonium iodide provided bischalcones 2(a-e).
The cyclization of bischalcones with phenyl hydrazine in acidic
medium led to the formation of bispyrazolines 3(a-e). The phase
transfer catalysis (PTC) used in these synthesis was highly help-
ful to improve the yield of bischalcones. The structures of prep-
ared compounds 2(a-e) and 3(a-e) were analyzed on the basis
of their various spectral data (IR, 1H & 13C NMR and ESI-MS).
The IR spectra of compounds 2(a-e) showed carbonyl (C=O)
and aromatic (C-H) stretching absorptions at 1737-1711 and
1602-1594 cm-1, respectively. The proton spectra of bischal-
cones exhibited the doublets at δ 8.01-7.78 and 7.52-7.32 could
be assigned to H-3 and H-2 protons and these protons are trans
to each other confirmed through coupling value of 17.4-15.4
Hz. The H-2′, 6′ and H-3′, 5′' could produce suitable doublet
which were easily centered at δ 7.98-7.89 (Jo = 8.4-7.8 Hz) and
7.07-6.84 (Jo = 8.8-7.4 Hz), respectively. The protons belonging
to intermediate chain (OCH2) generated appropriate singlet at
5.48-5.06. In 13C NMR spectra of compounds 2(a-e), OCH2
groups were resonating at δ 68.26-62.54 which suggest their
Synthesis of (Z)-1,4-bis[(4-(1-phenyl-4,5-dihydro-1H-
pyrazol-5-yl-)(4-methoxy)-2-phenyl)phenoxy]but-2-ene
(3d): The compound 3d was synthesized by treating a mixture
of bischalcone 2d (0.5 g, 0.001 mol) with phenyl hydrazine
(0.22 g, 0.002mol) under the similar reaction conditions as
given above for compound 3a. Brown solid: yield: 72 %; m.p.:
104-106 ºC; IR (KBr, νmax, cm-1): 3033 (arom. C-H), 2990,
1
2880 (methylene C-H), 1595 (C=N); H NMR (400 MHz,
DMSO-d6): δ 7.80 (4H, d, Jo = 8.4 Hz, H-2′, 6′), 7.48 (6H, m,
H-3′′′, 4′′′, 5′′′), 7.11 (4 H, d, Jo = 7.8 Hz, H-2′′, 6′′), 7.01 (4H, d,
Jo = 7.1 Hz, H-2′′′, 6′′′), 6.98 (4H, d, Jo = 8.8 Hz, H-3′, 5′),
6.94 (4H, d, Jo = 8.3 Hz, H-3′′, 5′′), 5.83 (2H, dd, JXA = 3.6
Hz, JXM = 12.6 Hz, H-X), 6.07 (2H, t, Jvic = 6.4 Hz, OCH2CH=)
5.81 (4H, d, Jvic = 6.4 Hz, OCH2), 3.71 (2H, dd, JMX = 11.3 Hz,

Vol. 30, No. 9 (2018)
Synthesis and Antimicrobial-Antioxidant Evaluations of Bis(4,5-dihydropyrazole) Derivatives 2101
placement near an electronegative oxygen atom. The signals
of carbon atom C-2 and C-3 found to be placed at δ 121.81-
119.17 and 139.77-130.54, respectively while carbonyl carbon
atoms resonated at the most downfield positions at δ 192.16-
187.14. IR spectra of bispyrazolines 3(a-e) did not reveal any
absorption in the region of 1737-1711 cm-1, which confirmed
the absence of C=O group and the major bands were observed
in the region at 1598-1591 cm-1 due to C=N group. In 1H NMR
spectra of compounds 3(a-e) signals corresponding to H-2 and
H-3 at δ 8.01-7.78 and 7.52-7.32 present in compounds 2(a-e)
were found to be absent which confirmed the involvement of
enone moiety during the cyclization reactions. The pyrazoline
ring protons H-X, H-M and H-A generated well defined dd at
δ 5.98-5.79 (2H, dd), 3.81-3.71 (2H, dd) and 3.29-3.10 (2H,
dd), respectively.
The stereochemical features of bispyrazolines 3(a-e) were
studied from the considerations of coupling constants (J) of
H-X, H-M and H-A. The vicinal coupling constant 12.7-11.6
Hz, between H-X and H-M confirmed that these hydrogens are
cis- to each other, whereas H-X and H-A are trans- to each other
with coupling value of JXA = 2.6-3.9Hz and JMA = 17.8-16.9
Hz. H-M and H-A are geminally placed at C-4 and the phenyl
groups placed at N-1 and C-2 are trans to each other and avoid
any intramolecular repulsion.
The remaining aromatic protons of compounds 3(a-e) were
absorbed at appropriate positions. 13C NMR spectra of comp-
ounds 3(a-e) did not exhibit any signals in the carbonyl group
region which proved that these group reacted during the trans-
formation of chalcone moiety. The bispyrazoline ring carbon
atoms C-3, C-4 and C-5 were resonating at δ 145.78-139.71,
44.45-43.45 and 55.92-52.98, respectively. The remaining
aromatic and OCH2 carbon group carbon atoms were charact-
erized through their respective signals at appropriate δ values.
Antimicrobial activity: The bischalcones 2(a-e) and bis-
pyrazolines 3(a-e) were tested against bacterial and fungal
species namely Staphylococcus aureus, Escherichia coli,
Bacillius subtilis, Klebsiella pneumoniae, Pseudomonas
aeruginosa and Aspergillius janus, Fusarium oxysporum, Penici-
llium glabrum, Aspergillus niger, Aspergillus sclerotum, respec-
tively to evaluate their antibacterial and antifungal activities.
Through serial dilution technique the minimum inhibitory
concentrations of the intermediate 2(a-e) and final product
3(a-e) were determined. Minimum inhibitory concentration (MIC)
is that minimum concentration which is required to prevent the
growth of both bacterial and fungal strains [37]. The standard
drugs used were amoxycillin and fluconazole and all the tubes
were introduced with the bacterial and fungal strains. Nutrient
broth as food for bacterial strain and malt extract as food for
fungal strain were added to each tube for their successive
growth. Different dilutions of the concerned bisheterocycles
at the concentration 100, 50, 25, 12.5, 6.25, 3.12, 1.56 µg/mL
were introduced against above said microorganisms. Table-1
represented the MIC values of bischalcones 2(a-e) and bispyra-
zolines 3(a-e). The resutls in Table-1 indicated that compounds
2(a-e) exhibited the moderate antimicrobial action against
the tested strains. The compounds 2a exhibited good activity
against bacterial strains Escherichia coli and Bacillius subtilis
and against fungal strain Penicillium glabrum at the MIC
of 12.5 µg/mL. Similarly, compound 2d revealed its potent
behaviour against bacterial strains Escherichia coli, Pseudo-
monas aeruginosa and fungal strains Aspergillius janus, Penici-
llium glabrum and Aspergillus niger at the similar MIC values.
The bischalcones 2b and 2c exhibited the MIC value of 25
µg/mL against Escherichia coli, Pseudomonas aeruginosa,
Aspergillus Janus and Pencillium glabrum. In Table-1. bispyrano-
pyrazole 3a showed a significant antimicrobial action against
Escherichia coli, Klebsiella pneumoniae, Pseudomonas aerug-
inosa and Penicillium glabrum at the MIC of 6.25 µg/mL and
excellent result against Klebsiella pneumoniae at the MIC of
3.12 µg/mL, which is equivalent to the standard drug fluconazole.
The compounds 3b and 3c were found to be moderately active
at the MIC value of 12.5 mg/mL while compound 3d is found
to be active Klebsiella pneumoniae, Penicillium glabrum and
Aspergillus niger at the MIC of 6.25 µg/mL. It is evaluated
from the data that the bispyrazolines 3(a-e) are found to be
more biological significant as compare to the corresponding
bischalcones 3(a-e).
Antioxidant activity: The bisheterocycles 2(a-e) and 3(a-e)
were also screened for their antioxidant evaluation. The free
radical scavenging activity of the prepared bischalcones and
bispyrazolines were measured in terms of radical scavenging
ability to become as diamagnetic compound [38,39]. Three
different concentrations 50, 75 and 100 µg/mL of the sample
solutions were prepared and 1.5 mL solution of both DPPH (1
mM) and prepared compounds 2(a-e) and 3(a-e) was mixed.
At room temperature the sample solutions were left for 30 min
for incubation in the dark. The absorbance of the blank solution
and prepared samples was noticed at 517 nm in UV spectrophoto-
meter. The antioxidant capacity [40] was calculated by the
following equation:
TABLE-1
MIC (µg/mL) DATA OF BISCHALCONES 2(a-e) AND BISPYRAZOLINES 3(a-e)
Compounds
Amoxicillin Fluconazole
2a
12.5
25
25
25
12.5
50
12.5
25
25
50
3a
2b
25
50
25
50
50
25
25
50
50
50
3b
25
25
12.5
25
12.5
25
12.5
25
12.5
12.5
2c
25
50
25
50
50
25
25
50
50
50
3c
12.5
25
12.5
12.5
12.5
25
25
12.5
25
2d
25
25
12.5
25
25
12.5
12.5
12.5
50
3d
2e
25
50
25
25
50
12.5
25
50
25
3e
25
25
12.5
50
12.5
25
25
12.5
25
E. coli
6.25
3.12
6.25
12.5
12.5
25
6.25
25
12.5
12.5
12.5
6.25
12.5
25
12.5
6.25
6.25
25
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
3.12
Gram-
negative
K. pneumonia
P. aeruginosa
S. aureus
B. subtilis
A. janus
P. glabrum
A. niger
F. oxysporum
A. sclerotiorum
Gram-
positive
Fungi
12.5
12.5
12.5
25
25
12.5

2102 Yusuf et al.
Asian J. Chem.
TABLE-2
PERCENTAGE SCAVENGING AT DIFFERENT CONCENTRATIONS OF BISCHALCONES 2(a-e) AND BISPYRAZOLINES 3(a-e)
Conc.
(µg/mL)
Compounds
Ascorbic
acid
2a
3a
2b
3b
2c
3c
2d
3d
2e
3e
50
75
100
38.3
42.1
49.9
42.3
51.1
63.9
37.6
40.8
44.3
38.3
43.4
48.6
35.9
39.3
42.6
39.6
47.3
51.3
41.8
48.1
51.9
41.8
49.9
57.9
40.5
45.7
48.5
40.5
48.7
53.5
53.8
67.5
75.4
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The radical scavenging abilities of bischalcones 2(a-e)
and bispyazolines 3(a-e) have been represented in Table-2.
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moderate to significant radical scavenging activity.The compound
3a could prove itself a potential antioxidant as compared to
other bispyrazoline derivatives.
Conclusion
In this study, we have synthesized the bispyrazoline linked
through aromatic and rigid chain linkers. The o-xylene linked
bispyrazoline showed significant antimicrobial action while
the bischalcones proved themselves significant antioxidant.
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The authors declare that there is no conflict of interests
regarding the publication of this article.
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