New bispyrazoline derivatives built around aliphatic chains: Synthesis, characterization and antimicrobial studies

Article abstract of DOI:10.1007/s12039-012-0355-9

The bispyrazolines 3a-3h built around the alkyl chains of varying lengths have been synthesized from the cyclization reactions of bischalcones with phenyl hydrazine. The bischalcones 2a-2h were obtained from the Claisen-Schmidt reactions of acetophenone w

Full text of DOI:10.1007/s12039-012-0355-9

c
J. Chem. Sci. Vol. 125, No. 1, January 2013, pp. 117–127. ꢀ Indian Academy of Sciences.
New bispyrazoline derivatives built around aliphatic chains: Synthesis,
characterization and antimicrobial studies
MOHAMAD YUSUF∗ and PAYAL JAIN
Department of Chemistry, Punjabi University, Patiala 147 002, India
e-mail: yusuf_sah04@yahoo.co.in
MS received 7 January 2012; revised 28 May 2012; accepted 28 June 2012
Abstract. The bispyrazolines 3a–3h built around the alkyl chains of varying lengths have been synthesized
from the cyclization reactions of bischalcones with phenyl hydrazine. The bischalcones 2a–2h were obtained
from the Claisen–Schmidt reactions of acetophenone with various bisaldehydes 1a–1h. The intermediate bis-
chalcones and final bisheterocyclic compounds have been characterized by means of IR, 1H-NMR, 13C-NMR,
Mass (ESI) and elemental analysis. The antibacterial and antifungal activities of the synthesized compounds
were also evaluated against the Klubsellia pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Staphylo-
coccus aureus, Bacillius subtilis and Aspergillius janus, Aspergillus niger and Pencillium glabrum, respectively.
The antimicrobial behaviour of the bispyrazolines 3a–3h is found to be dependent on the length of internal
spacer unit.
Keywords. Cyclization reactions; bischalcones; internal spacer; bispyrazolines; alkyl chains and
antimicrobial activity.
1. Introduction
subjected to the synthesis of many exotic heterocyclic
compounds. Bischalcones10,14–17 are the molecules
The study of heterocyclic systems has attracted the which are formed by joining two chalcone moieties
attention of organic chemists in the past decades together with the carbon chains of varying lengths and
because of their natural occurrence and large numbers structures. By keeping this aspect in view, the present
of their derivatives are essential to human life in vari- researches are focussed on the transformations of bis-
ous forms. Chalconoids are the natural compounds that chalcones 2a–2h to bispyrazolines 3a–3h built around
exhibit a wide spectrum of biological activity. The most the alkyl chains consisting of three to twelve methy-
common compounds among the chalconoid group are lene groups. The major interest behind this study was
the chalcones which are open chain molecule having to investigate the effect of the central spacer length on
two aromatic ring linked by the three carbon fragment. the formation and antimicrobial behaviour of the final
Many of these molecules show beneficial biologi- bispyrazolines.
cal activities like antiinflammatory1 and antiinvasive.2
These molecules are not only significant because of
their biological significances but also act as intermedi-
ate in the synthesis of pyrazolines and related hetero-
2. Experimental
cyclics. Pyrazolines have gained much interest because
Melting points reported are uncorrected. IR spec-
of wide range of applications in clinical and phar-
tra were scanned in KBr pellets on a Perkin Elmer
maceutical chemistry such as bacterial,3 depression,4
1
RXIFT Infrared spectrophotometer. H-NMR spectra
pyretic and antiinflammatory,1 and many industrial
were recorded on a 400 MHz Bruker spectrometer using
applications.5–9 Thus, chalcones10–13 are the valuable
TMS as the internal standard. The mass spectra have
synthones for the synthetic organic chemists and with
been scanned on the Waters Micromass Q-T of Micro
proper planning and designing these molecules can be
(ESI) spectrometer. UV-Vis spectra were recorded in
MeOH with Shimadzu UV-1800 Spectrophotometer.
TLC plates were coated with silica gel suspended in
MeOH–CHCl3 and iodine vapours were used as visua-
lizing agent. Bisaldehydes 1a–1h were prepared
∗For correspondence
according to the reported methods.18,19
117

118
Mohamad Yusuf and Payal Jain
2.1 Synthesis of (2E,2ꢁE)-3,3ꢁ-(4,4ꢁ-(ethane-1,2-
diylbis(oxy))bis(4,1-phenylene)) bis(1-phenylprop-2-
en-1-one) 2a
(0.816 g, 0.0068 mol) under the similar conditions as
used for 2a.
2c: White solid; Yield 80%; m.p.: 70–72◦C. UV-Vis
(MeOH) λmax(nm): 347, 245; IR (KBr) cm−1 2931,
2875 (methylene C-H), 1598 (C=C), 1659 (C=O); 1H-
NMR (400 MHz, CDCl3): δ 8.01 (4H, dd, Jo = 8.5,
1.1 Hz, H-2’, 6’), 7.78 (2H, d, Jtrans = 15.6 Hz, H-3),
7.57 (6H, m, H-3’, 4’, 5’), 7.47 (4H, m, H-2”, 6”), 7.41
(2H, d, Jtrans = 15.6 Hz, H-2), 6.92 (4H, d, Jo = 8.4 Hz,
H-3”, 5”), 4.10 (4H, t, Jvic = 5.3 Hz, OCH2CH2), 2.02
(4H, quintet, Jvic = 5.3 Hz, OCH2CH2); (MS-ESI):
m/z (M+H)+ 503. Anal. Calc. for C34O4H30: Calc. C,
81.20%; H, 5.97%; Found: C, 81.14%; H, 5.92%.
A mixture of acetophenone (0.910 g, 0.0072 mol),
bisaldehyde 1a (1.0 g, 0.0036 mol) and NaOH
(0.01 mol) in EtOH (25.0 ml) was stirred for 12 h at
room temperature. The reaction was monitored by TLC
and after the completion of reaction, the mixture was
poured into iced-HCl to provide a crude material which
was crystallized from CH3OH:CHCl3 (3:1) to yield a
pure compound 2a.
2a: Brown solid; Yield 64%; m.p.: 102–104◦C. UV-
Vis (MeOH) λmax(nm): 328, 250; IR (KBr) cm−1 2964,
2856 (methylene C-H), 1602 (C=C), 1657 (C=O); 1H-
NMR (400 MHz, CDCl3): δ 8.01 (4H, dd, Jp,o = 1.1,
8.8 Hz, H-2’, 6’), 7.73 (2H, d, Jtrans = 15.6 Hz, H-3),
7.52 (6H, m, H-3’, 4’, 5’), 7.42 (4H, td, Jp,o = 1.2,
8.8 Hz, H-2”, 6”), 7.39 (2H, d, Jtrans = 15.6 Hz, H-2),
2.4 Synthesis of (2E,2ꢁE)-3,3ꢁ-(4,4ꢁ-(pentane-1,5-
diylbis(oxy))bis(4,1-phenylene)) bis(1-phenylprop-2-
en-1-one) 2d
6.90 (4H, td, Jp,o = 1.2, 8.8 Hz, H-3”, 5”), 4.01 (4H, The bischalcone 2d was synthesized from the reaction
t, Jvic = 6.3 Hz, OCH2CH2); (MS-ESI): m/z (M+H)+ of bisaldehyde 1c (1.0 g, 0.0032 mol) with acetophe-
475. Anal. Calc. for C33O4H28: Calc. C, 81.01%; H, none (0.778 g, 0.0065 mol) under the similar conditions
5.48%; Found: C, 81.07%; H, 5.42%.
as used for 2a.
2d: Yellow solid; Yield 68%; m.p.: 120–122◦C. UV-
Vis (MeOH) λmax(nm): 312, 238; IR (KBr) cm−1 2945,
2860 (methylene C-H), 1597 (C=C), 1658 (C=O);
1H-NMR (400 MHz, CDCl3): δ 8.00 (4H, d, Jo =
7.2 Hz, H-2’, 6’), 7.78 (2H, d, Jtrans = 15.8 Hz, H-3),
7.58 (4H, d, Jo = 7.6 Hz, H-2”, 6”), 7.52 (6H, m,
H-3’, 4’, 5’), 7.40 (2H, d, Jtrans = 15.8 Hz, H-2),
6.92 (4H, d, Jo = 7.6 Hz, H-3”, 5”), 4.06 (4H, t,
Jvic = 6.3 Hz, OCH2CH2CH2), 1.87 (4H, quintet,
2.2 Synthesis of (2E,2ꢁE)-3,3ꢁ-(4,4ꢁ-(propane-1,3-
diylbis(oxy))bis(4,1-phenylene)) bis(1-phenylprop-2-
en-1-one) 2b
The bischalcone 2b was synthesized from the reaction
of bisaldehyde 1b (1.0 g, 0.0035 mol) with acetophe-
none (0.864 g, 0.0070 mol) under the similar conditions
as used for 2a.
2b: Brown solid; Yield 77%; m.p.: 156–158◦C. UV-
Vis (MeOH) λmax(nm): 353, 246; IR (KBr) cm−1 2960,
2850 (methylene C-H), 1600 (C=C), 1658 (C=O); 1H-
NMR (400 MHz, CDCl3): δ 8.00(4H, dd, Jp,o = 1.1,
8.8 Hz, H-2’, 6’), 7.78 (2H, d, Jtrans = 15.6 Hz, H-3),
7.58 (6H, m, H-3’, 4’, 5’), 7.49 (4H, td, Jp,o = 1.2,
8.8 Hz, H-2”, 6”), 7.41 (2H, d, Jtrans = 15.6 Hz, H-2),
6.94 (4H, td, Jp,o = 1.2, 8.8 Hz, H-3”, 5”), 4.23 (4H,
Jvic = 6.3 Hz, OCH2CH2CH2), 1.69 (2H, quintet, Jvic
=
6.3 Hz, OCH2CH2CH2); (MS-ESI): m/z (M+Na)+
539. Anal. Calc. for C35O4H32: Calc. C, 81.39%; H,
6.20%; Found: C, 81.32%; H, 6.26%.
2.5 Synthesis of (2E,2ꢁE)-3,3ꢁ-(4,4ꢁ-(hexane-1,6-
diylbis(oxy))bis(4,1-phenylene)) bis(1-phenylprop-2-
en-1-one) 2e
t, Jvic = 6.3 Hz, OCH2CH2), 2.31 (2H, quintet, Jvic
=
6.3 Hz, OCH2CH2); (MS-ESI): m/z (M+H)+ 489.
Anal. Calc. for C33O4H28: Calc. C, 81.14%; H, 5.73%;
Found: C, 81.20%; H, 5.78%.
The bischalcone 2e was obtained from the reaction of
bisaldehyde 1e (1.0 g, 0.0030 mol) with acetophenone
(0.744 g, 0.0062 mol) under the similar conditions as
described earlier for 2a.
2.3 Synthesis of (2E,2ꢁE)-3,3ꢁ-(4,4ꢁ-(butane-1,4-
diylbis(oxy))bis(4,1-phenylene)) bis(1-phenylprop-2-
en-1-one) 2c
2e: Brown solid; Yield 75%; m.p.: 80–82◦C. UV-Vis
(MeOH) λmax(nm): 320, 235; IR (KBr) cm−1 2938,
2863 (methylene C-H), 1593 (C=C), 1654 (C=O);
1H-NMR (400 MHz, CDCl3): δ 8.01 (4H, d, Jo =
7.3 Hz, H-2’, 6’), 7.78 (2H, d, Jtrans = 15.7 Hz, H-3),
The bischalcone 2c was prepared from the reaction of
bisaldehyde 1c (1.0 g, 0.0034 mol) with acetophenone

Synthesis of bispyrazolines
119
7.58 (4H, dd, Jp,o = 1.1, 8.8 Hz, H-2”, 6”), 7.50 (6H, Jvic = 5.4 Hz, OCH2CH2CH2CH2CH2), 1.40 (4H, t,
m, H-3’, 4’, 5’), 7.41 (2H, d, Jtrans = 15.7 Hz, H-2), Jvic = 5.6 Hz, OCH2CH2CH2CH2CH2), 1.20 (4H,
6.91 (4H, Jp,o = 1.1, 8.8 Hz, H-3”, 5”), 4.02 (4H, t, t, Jvic = 6.9 Hz, OCH2CH2CH2CH2CH2); (MS-ESI):
Jvic = 6.4 Hz, OCH2CH2CH2), 1.84 (4H, quintet,Jvic
=
m/z (M+Na)+ 609. Anal. Calc. for C40O4H42: Calc. C,
6.4 Hz, OCH2CH2CH2), 1.56 (4H, t, Jvic = 6.4 Hz, 83.04%; H, 7.26%; Found: C, 82.97%; H, 7.21%.
OCH2CH2CH2); (MS-ESI): m/z (M+H)+ 531. Anal.
Calc. for C36O4H34: Calc. C, 81.50%; H, 6.40%; Found:
C, 81.57%; H, 6.45%.
2.8 Synthesis of (2E,2ꢁE)-3,3ꢁ-(4,4ꢁ-(dodecane-1,12-
diylbis(oxy))bis(4,1-phenylene)) bis(1-phenylprop-2-
en-1-one) 2h
2.6 Synthesis of (2E,2ꢁE)-3,3ꢁ-(4,4ꢁ-(octane-1,8-
The bischalcone 2h was synthesized by reacting
bisaldehyde 1h (1.0 g, 0.0022 mol) with acetophenone
(0.617 g, 0.0054 mol) under the similar conditions as
diylbis(oxy))bis(4,1-phenylene)) bis(1-phenylprop-2-
en-1-one) 2f
The bischalcone 2f was prepared from the reaction of described earlier for 2a.
bisaldehyde 1f (1.0 g, 0.0026 mol) with acetophenone
2h: Brown solid; Yield 61%; m.p.: 86–88◦C. UV-Vis
(0.714 g, 0.0058 mol) under the similar conditions as
used for 2a.
(MeOH) λmax(nm): 314, 259; IR (KBr) cm−1 2918,
2849 (methylene C-H), 1596 (C=C), 1654 (C=O); 1H-
2f: Yellow solid; Yield 60%; m.p.: 64–66◦C. UV- NMR (400 MHz, CDCl3): δ 8.00 (4H, dd, Jp,o = 1.1,
Vis (MeOH) λmax(nm): 318, 253; IR (KBr) cm−1 8.2 Hz, H-2’, 6’), 7.75 (2H, d, Jtrans = 15.5 Hz, H-3),
2940, 2845 (methylene C-H), 1599 (C=C), 1655 7.54 (6H, m, H-3’, 4’, 5’), 7.42 (4H, d, Jo = 8.9 Hz,
1
(C=O); H-NMR (400 MHz, CDCl3): δ 8.00 (4H, dd, H-2”, 6”), 7.34 (2H, d, Jtrans = 15.5 Hz, H-2), 6.32
Jp,o = 1.1, 8.2 Hz, H-2’, 6’), 7.80 (2H, d, Jtrans
=
(4H, d, Jo = 8.8 Hz, H-3”, 5”), 3.96 (4H, t, Jvic =
15.5 Hz, H-3), 7.60 (6H, m, H-3’, 4’, 5’), 7.50 (4H, 6.9 Hz,OCH2CH2CH2CH2CH2CH2), 1.78 (4H, quintet,
m, H-2”, 6”), 7.41 (2H, d, Jtrans = 15.5 Hz, H-2), Jvic = 6.4 Hz, OCH2CH2CH2CH2CH2CH2), 1.48 (4H,
6.39 (4H, d, Jo = 8.8 Hz, H-3”, 5”), 4.00 (4H, t, t, Jvic =5.4 Hz, OCH2CH2CH2CH2CH2CH2), 1.38 (4H,
Jvic = 6.9 Hz, OCH2CH2CH2CH2), 1.81 (4H, quin- t, Jvic = 5.6 Hz, OCH2CH2CH2CH2CH2CH2), 1.15
tet, Jvic = 6.4 Hz, OCH2CH2CH2CH2), 1.48 (4H, t, (8H, t, Jvic = 6.9 Hz, OCH2CH2CH2CH2CH2CH2);
Jvic = 5.4 Hz, OCH2CH2CH2CH2), 1.41 (4H, t, Jvic
=
(MS-ESI): m/z (M+Na)+ 637. Anal. Calc. for
5.6 Hz, OCH2CH2CH2CH2); (MS-ESI): m/z (M+H)+ C42O4H46: Calc. C, 83.21%; H, 7.49%; Found: C,
559. Anal. Calc. for C38O4H38: Calc. C, 82.31%; H, 83.29%; H, 7.54%.
6.85%; Found: C, 82.36%; H, 6.89%.
2.9 Synthesis of 1,2-bis(4-(1,3-diphenyl-4,5-dihydro-
1H-pyrazol-5-yl) phenoxy)ethane 3a
2.7 Synthesis of (2E,2ꢁE)-3,3ꢁ-(4,4ꢁ-(decane-1,10-
diylbis(oxy))bis(4,1-phenylene)) bis(1-phenylprop-2-
en-1-one) 2g
A mixture of bischalcone 2a (1.0 g, 0.0020 mol), phenyl
hydrazine (0.4426 g, 0.0040 mol) and glacial AcOH
The bischalcone 2g was synthesized by reacting (5 ml) in dry EtOH (30 ml) was refluxed for 8 h. The
bisaldehyde 1g (1.0 g, 0.0024 mol) with acetophenone progress of reaction was monitored by TLC. The result-
(0.650 g, 0.0056 mol) under the similar conditions as ing reaction mixture was concentrated under vacuum
described earlier for 2a.
to obtain a solid product which was crystallized from
CHCl3:CH3OH (1:3) to yield pure bispyrazoline 3a.
2g: Brown solid; Yield 69%; m.p.: 96–98◦C. UV-Vis
(MeOH) λmax(nm): 320, 246; IR (KBr) cm−1 2920, 3a: Brown solid; Yield 70%; m.p.: 90–92◦C. UV-Vis
2835 (methylene C-H), 1603 (C=C), 1665 (C=O); (MeOH) λmax(nm): 355, 252, 230; IR (KBr) cm−1 1590,
1
1H-NMR (400 MHz, CDCl3): δ 8.02 (4H, dd, Jp,o
=
1505 (C=N, C=C), 2922, 2846 (methylene C-H); H-
1.1, 8.2 Hz, H-2’, 6’), 7.78 (2H, d, Jtrans = 15.5 Hz, NMR (400 MHz, CDCl3): δ 7.67 (4H, dd, Jp,o = 1.1,
H-3), 7.56 (6H, m, H-3’, 4’, 5’), 7.47 (4H, d, Jo = 8.8 Hz, H-2”, 6”), 7.36 (6H, m, H-3”, 4”, 5”), 7.25 (4H,
8.9 Hz, H-2”, 6”), 7.39 (2H, d, Jtrans = 15.5 Hz, H- m, H-2’, 6’), 7.18 (6H, m, H-3’, 4’, 5’), 7.12 (4H, dd,
2), 6.36 (4H, d, Jo = 8.8 Hz, H-3”, 5”), 3.99 (4H, t, Jp,o = 1.1, 8.8 Hz, H-2”’, 6”’), 6.80 (4H, dd, Jp,o = 1.1,
Jvic = 6.9 Hz,OCH2CH2CH2CH2CH2), 1.80 (4H, quin- 8.8 Hz, H-5”’, 3”’), 5.23 (2H, dd, JXA = 7.1, JXM
=
tet, Jvic = 6.4 Hz, OCH2CH2CH2CH2CH2), 1.46 (4H, t, 12.1 Hz, HX), 4.00 (4H, t, Jvic = 6.3 Hz, OCH2CH2),

120
Mohamad Yusuf and Payal Jain
3.76 (2H, dd, JAM = 17.0, JMX = 12.00 Hz, HM), 3.10 Calc. C, 80.93%; H, 6.15%; N, 8.21%; Found: C,
(2H, dd, JAX = 7.1,JAM = 17.2 Hz, HA); (MS-ESI): 80.88%; H, 6.10%; N, 8.15%.
m/z (M+H)+655. Anal. Calc. for C45O2N4H40: Calc.
C, 80.73%; H, 5.81%; N, 8.56%; Found: C, 80.78%; H,
5.88%; N, 8.49%.
2.12 Synthesis of 1,5-bis(4-(1,3-diphenyl-4,5-dihydro-
1H-pyrazol-5-yl) phenoxy)pentane 3d
The bispyrazoline 3d was prepared by reacting bis-
chalcone 2d (1.0 g, 0.00192 mol) with phenyl hydrazine
(0.4186 g, 0.003874 mol) under the similar conditions
as described earlier for 3a.
2.10 Synthesis of 1,3-bis(4-(1,3-diphenyl-4,5-dihydro-
1H-pyrazol-5-yl) phenoxy)propane 3b
The bispyrazoline 3b was obtained from the reaction
of bischalcone 2b (1.0 g, 0.00200 mol) with phenyl
hydrazine (0.443 g, 0.00400 mol) under the similar con-
ditions as described earlier for 3a.
3d: Yellow solid; Yield 73%; m.p. 125–127◦C. UV-Vis
(MeOH) λmax(nm): 356, 240, 212; IR (KBr) cm−1 1598,
1
1508 (C=N, C=C), 2946, 2830 (methylene C-H); H-
NMR (400 MHz, CDCl3): δ 7.72 (4H, d, Jo = 7.8 Hz,
H-2”, 6”), 7.37 (4H, dd, Jp,o = 1.1, 8.8 Hz, H-2”’, 6”’),
7.30 (6H, m, H-3”, 4”, 5”), 7.20 (6H, m, H-3’, 4’, 5’),
7.11 (4H, m, H-2’, 6’), 6.85 (4H, dd, Jp,o = 1.1, 8.8 Hz,
H-3”’, 5”’), 5.22 (2H, dd, JXA = 7.1, JXM = 1.1 Hz,
HX), 3.95 (4H, t, Jvic = 6.3 Hz, OCH2CH2CH2), 3.80
(2H, dd, JMX = 1.1, JMA = 16.2 Hz, HM), 3.11 (2H,
dd, JAX = 7.1, JAM = 16.2 Hz, HA), 1.82 (4H, quin-
tet, Jvic = 6.3 Hz, OCH2CH2CH2), 1.64 (2H, quintet,
Jvic = 6.3 Hz, OCH2CH2CH2); (MS-ESI): m/z (M)+
696. Anal. Calc. for C47O2N4H44: Calc. C, 81.10%; H,
6.32%; N, 8.04%; Found: C, 81.15%; H, 6.26%; N,
8.00%.
3b: Mustard brown solid; Yield 75%; m.p.: 95–97◦C.
UV-Vis (MeOH) λmax(nm): 356, 253, 218; IR (KBr)
cm−1 1597, 1503 (C=N, C=C), 2926, 2849 (methylene
1
C-H); H-NMR (400 MHz, CDCl3): δ 7.70 (4H, dd,
Jp,o = 1.1, 8.8 Hz, H-2”, 6”), 7.38 (6H, m, H-3”, 4”, 5”),
7.30 (4H, m, H-2’, 6’), 7.20 (6H, m, H-3’, 4’, 5’), 7.08
(4H, dd, Jp,o = 1.1, 8.8 Hz, H-2”’, 6”’), 6.85 (4H, dd,
Jp,o = 1.1, 8.8 Hz, H-5”’, 3”’), 5.20 (2H, dd, JXA
=
7.1, JXM = 12.1 Hz, HX), 4.08 (4H, t, Jvic = 6.3 Hz,
OCH2CH2), 3.78 (2H, dd, JAM = 17.0, JMX = 12.00 Hz,
HM), 3.08 (2H, dd, JAX = 7.1,JAM = 17.2 Hz, HA), 2.20
(2H, quintet, Jvic = 6.3 Hz, OCH2CH2); (MS-ESI): m/z
(M+H)+ 669. Anal. Calc. for C45O2N4H40: Calc. C,
80.51%; H, 5.98%; N, 8.38%; Found: C, 80.56%; H,
5.93%; N, 8.44%.
2.13 Synthesis of 1,6-bis(4-(1,3-diphenyl-4,5-dihydro-
1H-pyrazol-5-yl) phenoxy)hexane 3e
The bispyrazoline 3e was prepared from the treatment
of bischalcone 2e (1.0 g, 0.00188 mol) with phenyl
hydrazine (0.4074 g, 0.003773 mol) under the same
conditions as used earlier for 3a.
2.11 Synthesis of 1,4-bis(4-(1,3-diphenyl-4,5-dihydro-
1H-pyrazol-5-yl) phenoxy)butane 3c
The bispyrazoline 3c was obtained from the reaction
of bischalcone 2c (1.0 g, 0.00198 mol) with phenyl
hydrazine (0.430 g, 0.00398 mol) under the similar con-
ditions as described earlier for 3a.
3e: Brown solid; Yield 60%; m.p.: 160–162◦C. UV-Vis
(MeOH) λmax(nm): 357, 238, 214; IR (KBr) cm−1 1588,
1
1501 (C=N, C=C), 2932, 2846 (methylene C-H); H-
3c: Pale yellow solid; Yield 70%; m.p.: 110–112◦C.
UV-Vis (MeOH) λmax(nm): 368, 246, 220; IR (KBr)
cm−1 1590, 1513 (C=N, C=C), 2930, 2850 (methylene
NMR (400 MHz, CDCl3): δ 7.64 (4H, dd, Jp,o = 1.2,
8.6 Hz, H-2”, 6”), 7.32 (4H, m, H-3”, 5”), 7.20 (2H, m,
H-4”), 7.14 (8H, m, H-2’, 3’, 5’, 6’), 7.00 (4H, dt, Jp,o
=
1
C-H); H-NMR (400 MHz, CDCl3): δ 7.65 (4H, dd,
1.1, 8.4 Hz, H-2”’, 6”’), 6.78 (4H, dt, Jp,o = 1.1, 8.4 Hz,
H-3”’, 5”’), 6.67 (2H, td, Jm,o = 2.4, 4.8 Hz, H-4’), 5.15
(2H, dd, JXA = 7.2, JXM = 12.24 Hz, HX), 3.84 (4H,
Jp,o = 1.4, 8.5 Hz, H-2”, 6”), 7.30 (4H, m, H-3”, 5”),
7.22 (2H, m, H-4”), 7.10 (8H, m, H-2’, 3’, 5’, 6’), 7.00
(4H, dt, Jp,o = 1.1, 8.5 Hz, H-2”’, 6”’), 6.74 (4H, dt,
Jp,o = 1.1, 8.6 Hz, H-3”’, 5”’), 6.68 (2H, dt, Jm,o = 2.6,
4.6 Hz, H-4’), 5.14 (2H, dd, JXM = 12.2, JXA = 7.04 Hz,
t, Jvic = 6.4 Hz, OCH2CH2CH2), 3.73 (2H, dd, JMX
=
12.2, JMA = 17.1 Hz, HM), 3.04 (2H, dd, JAX = 7.2,
JAM = 17.1 Hz, HA), 1.70 (4H, quintet, Jvic = 6.1 Hz,
OCH2CH2CH2), 1.45 (4H, m, OCH2CH2CH2); (MS-
ESI): m/z (M+Na)+ 733. Anal. Calc. for C48O2N4H46:
Calc. C, 81.12%; H, 6.47%; N, 7.88%; Found: C,
81.07%; H, 6.41%; N, 7.93%.
HX), 3.73 (4H, brs, OCH2CH2), 3.69 (2H, dd, JXM
=
12.2, JMA = 17.6 Hz, HM), 3.04 (2H, dd, JAX = 7.2,
JAM = 17.0 Hz, HA), 1.85 (4H, brs, OCH2CH2); (MS-
ESI): m/z (M+Na)+ 705. Anal. Calc. for C46O2N4H42:

Synthesis of bispyrazolines
121
O
CH (CH ) CH
2 2 n 2
O
OHC
CHO
1a−1h
a
3'
6'
2''
3''
5''
2'
1'
4'
5'
4''
2
1''
O
CH (CH ) CH
2 2 n 2
O
3
1
6''
O
2a−2h
O
b
3''
6''
4''
5''
2''
H
A
H
1''
3
A
4
H
M
3'''
2'''
6'''
H
1'''
M
4'''
N
5
2 N
O
CH (CH ) CH
2 2 n 2
O
N
H
X
1 N
H
5'''
X
1'
6'
5'
2 '
3a−3h
3'
4'
n=0, 1, 2, 3, 4, 6, 8, 10
Reaction Conditions: a) NaOH/EtOH/PhCOCH3 ; b) EtOH/AcOH/PhNHNH2/ Δ
Scheme 1. Synthesis of bispyrazolines 3a–3h.
2.14 Synthesis of 1,8-bis(4-(1,3-diphenyl-4,5-dihydro- hydrazine (0.387 g, 0.003584 mol) under the similar
1H-pyrazol-5-yl) phenoxy)octane 3f conditions as described above for 3a.
The bispyrazoline 3f was obtained from the reaction 3f: Brown solid; Yield 67%; m.p.: 175–177◦C. UV-
of bischalcone 2f (1.0 g, 0.00178 mol) with phenyl Vis (MeOH) λmax(nm): 370, 243, 225; IR (KBr) cm−1
Figure 1. 1H-NMR (400 MHz) spectrum of bischalcone 3c.

122
Mohamad Yusuf and Payal Jain
1596, 1502 (C=N, C=C), 2925, 2852 (methylene C-
1
H); H-NMR (400 MHz, CDCl3): δ 7.62 (4H, dd,
J,p,o = 1.0, 8.7 Hz, H-2”, 6”), 7.32 (4H, m, H-3”, 5”),
7.20 (2H, m, H-4”), 7.10 (8H, m, H-2’, 3’, 5’, 6’), 7.02
(4H, dt, Jp,o = 1.0, 8.4 Hz, H-2”’, 6”’), 6.76 (4H, dt,
Jp,o = 1.0, 8.4 Hz, H-3”’, 5”’), 6.68 (2H, td, Jm,o = 2.6,
4.8 Hz, H-4’), 5.12 (2H, dd, JXA = 7.2, JXM = 12.2 Hz,
HX), 3.81 (4H, t, Jvic = 6.4 Hz, OCH2CH2CH2CH2),
3.70 (2H, dd, JMX = 12.3, JMA = 17.0 Hz, HM),
3.02 (2H, dd, JAX = 7.2, JAM = 17.0 Hz, HA),
1.66 (4H, quintet, Jvic = 6.0 Hz, OCH2CH2CH2CH2),
1.35 (4H, m, OCH2CH2CH2CH2), 1.28 (4H, m,
OCH2CH2CH2CH2); (MS-ESI): m/z (M)+ 738. Anal.
Calc. for C49O2N4H48: Calc. C, 81.21%; H, 6.62%; N,
7.73%; Found: C, 81.15%; H, 6.58%; N, 7.68%.
2.15 Synthesis of 1,10-bis(4-(1,3-diphenyl-4,5-
dihydro-1H-pyrazol-5-yl)phenoxy)decane 3g
The bispyrazoline 3g was synthesized by reacting
bischalcone 2g (1.0 g, 0.0017064 mol) with phenyl
hydrazine (0.3686 g, 0.003412 mol) under the similar
conditions as used earlier for 3a.
3g: Brown solid; Yield 62%; m.p.: 240–242◦C. UV-Vis
(MeOH) λmax(nm): 362, 247, 218; IR (KBr) cm−1 1602,
1
1509 (C=N, C=C), 2925, 2854 (methylene C-H); H-
NMR (400 MHz, CDCl3): δ 7.60 (4H, dd, Jp,o = 1.0,
8.7 Hz, H-2”, 6”), 7.29 (4H, m, H-3”, 5”), 7.21 (2H,
m, H-4”), 7.15 (8H, m, H-2’, 3’, 5’, 6’), 7.02 (4H, dt,
Jp,o = 1.0, 8.9 Hz, H-2”’, 6”’), 6.75 (4H, dt, Jp,o = 1.0,
8.9 Hz, H-3”’, 5”’), 6.63 (2H, td, Jm,o = 2.6, 4.9 Hz,
H-4’), 4.88 (2H, dd, JXA = 7.2, JXM = 12.0 Hz, HX),
3.84 (4H, t, Jvic = 6.2 Hz, OCH2CH2CH2CH2CH2),
3.70 (2H, dd, JMX = 12.1, JMA = 17.0 Hz, HM),
3.30 (2H, dd, JAX = 7.2, JAM = 17.2 Hz, HA), 1.67
(4H, quintet, Jvic = 6.4 Hz, OCH2CH2CH2CH2CH2),
1.36 (4H, m, OCH2CH2CH2CH2CH2), 1.24 (4H, m,
OCH2CH2CH2CH2CH2), 1.10 (4H, quintet, Jvic
=
6.3 Hz, OCH2CH2CH2CH2CH2); (MS-ESI): m/z
(M+H)+ 767. Anal. Calc. for C50O2N4H50: Calc. C,
81.30%; H, 6.77%; N, 7.58%; Found: C, 81.36%; H,
6.82%; N, 7.63%.
2.16 Synthesis of 1,12-bis(4-(1,3-diphenyl-4,5-
dihydro-1H-pyrazol-5-yl)phenoxy) dodecane 3h
The bispyrazoline 3h was synthesized by reacting bis-
chalcone 2h (1.0 g, 0.00167 mol) with phenyl hydrazine
(0.3482 g, 0.003387 mol) under the similar conditions
as used earlier for 3a.
3h: Brown solid; Yield 60%; m.p.: 150–152◦C. UV-Vis
(MeOH) λmax(nm): 359, 243, 216; IR (KBr) cm−1 1603,

Synthesis of bispyrazolines
123
1
1505 (C=N, C=C), 2920, 2850 (methylene C-H); H- 1h were obtained in good yields from the O-
NMR (400 MHz, CDCl3): δ 7.62 (4H, dd, Jp,o = 1.0, alkylation of 4-hydroxybenzaldehyde with suitable 1,
8.7 Hz, H-2”, 6”), 7.25 (4H, m, H-3”, 5”), 7.19 (2H, m, ω-dibromoalkanes in the presence of KOH/EtOH/
H-4”), 7.12 (8H, m, H-2’, 3’, 5’, 6’), 7.00 (4H, dt, Jp,o
=
DMF (scheme 1). The structures of prepared com-
1.0, 8.9 Hz, H-2”’, 6”’), 6.72 (4H, dt, Jp,o = 1.0, 8.9 Hz, pounds (2a–2h and 3a–3h) were analysed from the rigo-
H-3”’, 5”’), 6.61 (2H, td, Jm,o = 2.6, 4.9 Hz, H-4’), 4.85 rous analysis of their IR, UV-Vis, 1H-NMR, 13C-NMR
(2H, dd, JXA = 7.2, JXM = 12.0 Hz, HX), 3.80 (4H, t, and Mass spectral data.
Jvic = 6.2 Hz, OCH2CH2CH2CH2CH2CH2), 3.72 (2H,
The electronic spectra (MeOH) of the bischalcones
dd, JMX = 12.1, JMA = 17.0 Hz, HM), 3.28 (2H, dd, 2a–2h had two major absorptions at 353–312 and 259–
JAX = 7.2, JAM = 17.2 Hz, HA), 1.63 (4H, quin- 235 nm. The later band may be ascribed to the π→π*
tet, Jvic = 6.4 Hz, OCH2CH2CH2CH2CH2CH2), 1.32 transitions of the conjugated double bond while the for-
(4H, m, OCH2CH2CH2CH2CH2CH2), 1.20 (4H, m, mer band could be given by the n→ π* transition of
OCH2CH2CH2CH2CH2CH2), 1.12 (8H, quintet, Jvic
=
the C=O group of the chalcone moiety. In the IR spec-
6.3 Hz, OCH2CH2CH2CH2CH2CH2); (MS-ESI): m/z tra of compounds 2a–2h, strong bands were observed
(M+Na)+ 817. Anal. Calc. for C52O2N4H54: Calc. C, at 1665–1654 cm−1 which may be attributed to the con-
81.41%; H, 6.82%; N, 7.40%; Found: C, 81.47%; H, jugated C=O group and other significant absorptions
6.87%; N, 7.34%.
were found at 2964–2835 (methylene C-H), 1603–1593
1
(C=C) and cm−1. The major feature of the H-NMR
spectra of 2a–2h was the two broad doublets centred at δ
7.80–7.73 and δ 7.41–7.34 which could be generated
by H-3 and H-2 protons, respectively. The coupling
value of 15.8 Hz between theses hydrogens describes
the trans geometry around the C-2 and C-3 double
3. Results and discussion
3.1 Chemistry
The bispyrazolines 3a–3h needed for the present bond. The downfield resonance of the H-3 as com-
investigations were synthesized starting from the pared to H-2 could be ascribed to the electron defi-
Claisen–Schmidt reactions20 of acetophenone with va- cient nature of the β-carbon (H-3) in the enone moiety
rious bisaldehydes18,19 1a–1h which yielded bischal- (figure 1). Other significant signals in the aromatic
cones 2a–2h. The cyclizations10 of later with phenyl region appeared at δ 7.58–7.42 (H-2ꢁꢁ, 6ꢁꢁ) and 6.94–
hydrazine under alcoholic medium led to the forma- 6.32 (H-3ꢁꢁ, 5ꢁꢁ) having coupling value of 8.4 Hz (Jo);
tion of bispyrazolines 3a–3h which were crystallized the electron releasing effect of the C-4ꢁ alkoxy group
from CHCl3:CH3OH (1:3) to give pure compounds causes the upfield resonance of the later hydrogens.
in moderate yields. The starting bisaldehydes 1a– The signal for internal chain OCH2 protons were found
Figure 2. Partial 400 MHz 1H-NMR spectrum of HX, HM and HA in bispyrazoline 4c.

124
Mohamad Yusuf and Payal Jain
resonating at δ 4.23–3.96 as triplet and for {(CH2)n} it
appeared at δ 2.31–1.15. In the 13C-NMR spectra of 2a–
2h, the internal chain methylene groups were resonating
at δ 67.58–63.45 (OCH2) and δ 29.12–11.21 {(CH2)n};
the downfield resonance of the former suggests its
placement near an electronegative oxygen atom. Other
major signals were located at δ 200–190, 119–112 and
144–142 which could be very well attributed to C-1,
C-2 and C-3 of the enone moiety (see table 1).
The UV-Vis (MeOH) spectra of the pyrazoline
derivatives 3a–3h exhibited two major absorption bands
in the UV region of the spectra. The band at 370–
355 nm may be assigned to the n →π* transition of
C=N moiety while absorption bands at 253–238 nm
may be resulted by π → π* transition of phenyl ring.
IR spectra of 3a–3h did not have any absorption in the
region of 1665–1654 cm−1 which describes the absence
1
of C=O group in these compounds. In the H-NMR
spectra of these compounds, the signals corresponding
to the double bond hydrogens (H-2 and 3) at δ 7.80–
7.73 and 7.41–7.34 in the bischalcones 2a–2h were
found missing altogether which indicates the involve-
ment of the enone moiety in the cyclization reactions.
The pyrazoline ring protons HX, HM and HA produced
resonances at δ 5.23–4.85 (dd), 3.80–3.70 (dd) and
3.30–3.02 (dd), respectively. The vicinal coupling con-
stant (3 J) between HX and HM was found to be 12.1 Hz
which reflects that these hydrogens are cis to each
other while coupling value JXA = 6.8 Hz and JMA
=
17.7 Hz describes the trans relationship between HX
and HA while HM and HA are geminally placed at C-4ꢁ
(figure 2). In the 13C-NMR spectra, signals corres-
ponding to C=O group of bischalcones at δ 200–190
were not present which also corroborate the transforma-
tion of this functionality in the formation of pyrazoline
moiety. The pyrazoline ring carbons C-3, C-4 and C-5
were very well placed at δ 159–158, 43–41 and 67–66,
respectively (see table 2).
3.2 Antimicrobial activity
The newly prepared compounds were screened for their
antibacterial and antifungal activity using paper disc
method21 in vitro against Escherichia coli, Klubsellia
pneumeniae, Bacillius subtilis, Staphylococcus aureus
and Pseudomonas aeruginosa and Aspergillius janus,
Aspergillius niger and Pencillium glabrum at conc.
100 μg/ml. In this method, the standard 5 mm dia-
meter sterilized filter paper discs impregnated with the
prepared compounds (2a–2h and 3a–3h) were placed
on an agar plate seeded with the test organisms. The
plates were incubated for 24 h at 37◦C for bacteria and

Synthesis of bispyrazolines
125
Table 3. In vitro MIC (μg/mL) of bischalcones 2a–2h.
Gram (−ve) bacteria
Compound Escherichia Klubsellia Pseudomonas Staphylococcus Bacillius Aspergillus Pencilluim Aspergillus
Gram (+ve) bacteria
Fungi
No.
coli
pneumoniae aeruginosa
aureus
subtilis
janus
glabrum
niger
2a
2b
2c
2d
2e
2f
2g
2h
16
16
32
16
4
8
8
8
16
16
8
8
8
16
8
2
8
16
16
8
8
8
16
8
2
16
16
8
8
8
8
16
8
32
8
8
16
16
16
8
16
2
16
8
8
8
8
16
16
16
8
8
8
16
4
4
32
32
16
8
8
16
4
8
4
8
2
8
Amoxicillin
Fluconazole
2
1
1
1
at 28◦C for fungi. The minimum inhibitory concentra- was also observed in 2f, 2h and 2g against the strain
tion (MIC-μg/mL) of the studied compounds were also Pencilluim glabrum and Aspergillus niger, respectively.
determined by using serial tube dilution method22 at Among the bispyrazolines, significant results (MIC:
conc. 128, 64, 32, 16, 8, 4, 2, 1 μg/mL and the observed 4 μg/mL) were observed in 3c, 3e and 3f against Klub-
MIC values are given in tables 3 and 4 (figures 3 and 4). ssila pneumoniae and 3d also revealed the activity of
Compounds 2e, 2h, 2g, 3c, 3d, 3e and 3f showed sig- same order against Staphylococcus aureus.
nificant activity against the tested microorganisms. The
It is evident from the above MIC data that bischal-
zones of inhibitions of bacteria and fungi growth around cones linked through the internal chain of six, eight
the discs were observed. DMSO was used as a con- and twelve carbon atoms were more active in the
trol and it did not show any activity against the strains present investigations. Similarly, the bispyrazolines
of microorganisms used. The results are recorded as built around four, six and eight methylene spacer units
average diameter of inhibition zone in mm (figures 5 also provided significant results. Thus, compounds
and 6).
involving longer internal chain consisting of even num-
In vitro antimicrobial MIC results of the bischalcones ber of carbon atoms seem to be better antimicrobial
2a–2h and bispyrazolines 3a–3h have been presented products. The importance of this work lies in the
in tables 3 and 4, respectively. Most of the compounds possibility that the new compounds might be more
showed good activities against the tested microorga- efficacious derivatives against the strains for which
nisms (MIC: 8–16 μg/mL). The compound 2e showed investigation regarding the more biological studies
significant activity against Escherichia coli and Pen- could be helpful in designing the potent antimicrobial
cilluim glabrum (MIC: 4 μg/mL) and similar activity agents.
Table 4. In vitro MIC (μg/mL) for bispyrazolines 3a–3h.
Gram (−ve) bacteria
Gram (+ve) bacteria
Fungi
Compound Escherichia Klubsellia Pseudomonas Staphylococcus Bacillius Aspergillus Pencilluim Aspergillus
No.
coli
pneumoniae aeruginosa
aureus
subtilis
janus
glabrum
niger
3a
3b
3c
3d
3e
3f
3g
3h
16
16
16
32
16
16
16
32
2
16
8
4
32
4
4
8
8
2
16
8
16
8
16
32
8
4
8
16
16
8
16
32
16
32
16
8
16
32
2
16
8
16
8
16
8
8
8
16
8
16
8
16
16
16
16
16
6
32
16
16
32
8
8
16
32
32
2
16
Amoxicillin
Fluconazole
2
1
1
1

126
Mohamad Yusuf and Payal Jain
In vitro MIC of compounds 2a-2h
35
30
25
20
15
10
5
E. coli
K. pneumoniae
P. aeruginosa
S. aureus
B. subtilis
A. janus
0
2f
2a
2b
2c
2d
2e
2g
2h
Amoxicillin
P. glabrum
A. niger
Fluconazole
Compounds
Figure 3. In vitro MIC (μg/mL) of compounds 2a–2h.
In vitro MIC of compounds 3a-3h
35
30
25
20
15
10
5
E. coli
K.pneumoniae
P.aeruginosa
S.aureus
0
B. subtilis
A. janus
3f
3a 3b
3c 3d 3e
3g 3h
Amoxicillin
Fluconazole
P. glabrum
A. niger
Compounds
Figure 4. In vitro MIC (μg/mL) of compounds 3a–3h.
In vitro zone of inhibition of compounds 2a−2h
30
25
20
15
10
5
E. coli
S. aureus
K. pneumoniae
P. aeruginosa
B. subtilis
0
Aspergillius janus
Pencillium glabrum
Aspergillius niger.
compounds
Figure 5. Zone of inhibition (mm) of compounds 2a–2h.
In vitro zone of inhibition of compounds 3a−3h
30
25
20
15
10
5
E. coli
S. aureus
K. pneumoniae
P. aeruginosa
B. subtilis
0
Aspergillius janus
Pencillium glabrum
Aspergillius niger
compounds
Figure 6. Zone of inhibition (mm) of compounds 3a–3h.

Synthesis of bispyrazolines
127
4. Conclusion
8. Modzelewska A, Pettit C, Achanta G, Davidson E N,
Huang P and Khan R S 2006 Bioorg. Med. Chem. 14
3491
9. Bhat R A, Athar F and Azam A 2009 Eur. J. Med. Chem.
44 426
10. Elwahy H M A 1999 J. Chem. Res. (S) 602
11. Azarifar D and Ghasemnejad H 2003 Molecules 8
642
12. Padmavathi V, Radhalakshmi T, Mahesh K and Mohan
N V A 2008 Indian J. Chem. 47B 1707
13. Ram J V, Saxena S A, Srivastava S and Chandra S 2000
Bioorg. Med. Chem. Lett. 10 2159
14. Barsoum F F, Hosni H M and Girgis A S 2006 Bioorg.
Med. Chem. 14 3929
15. Insuasty B, Martinez H, Quiroga J, Abonia R, Nogueras
M and Cobo J 2008 J. Heterocyclic Chem. 45 1521
16. Bhat A R, Athar F and Azam A 2009 Eur. J. Med. Chem.
44 426
It may be concluded that this study describe the gen-
eral method for the synthesis of new bispyrazolines
linked through the alkyl chains under the normal condi-
tions. The significant antimicrobial activities were pro-
vided by the bischalcones and bispyrazolines linked
through the intermediate chain containing even number
of methylene groups
Acknowledgements
Authors are thankful to the Department of Science
and Technology (DST), New Delhi (SERB, Fast Track
Scheme no. SR/FT/CS-041/2010) for providing the
financial support for this research work.
17. Barsoum F F and Girgis A S 2009 Eur. J. Med. Chem.
44 2172
18. Abdelhamid A O and El-Shaity F H H 1988 Phosphorus,
sulfur silicon 39 45
References
1. Won S J, Liu C T, Tsao L T, Weng J R, Ko H H, Wang 19. Yusuf M and Jain P 2012 Arab. J. Chem. 5 93
J P and Lin C N 2005 Eur. J. Med. Chem. 40 103
2. Mukherjee S, Kumar V, Prasad A K, Raj H G, Bracke
M E, Olsen C E, Jain S C and Parmar V S 2001 Bioorg.
Med. Chem. 9 337
3. Holla B S, Akbrali P M and Shivanada M K 2000 IL
Farmaco 55 256
4. Prassad Y R, Rao A L, Prasoona L, Murali K and Kumar
P R 2005 Bioorg. Med Chem. Lett. 15 5030
5. Azarifar D and Shaebanzadeh M 2002 Molecules 7 885
20. (a) Gennari C 1991 In Comprehensive organic syn-
thesis, B M Trost and I Fleming (eds) Pergamon:
Oxford, vol. 2, p. 629; (b) Mahrwald R, ed., Mod-
ern aldol reactions; Wiley-VCH: Weinheim, Germany,
2004 1 & 2; (c) Mukaiyama T 1982 Organic reactions;
W G Dauben ed., J. Wiley & Sons: New York, NY,
USA, 28, 203; (d) Healthcock C H 1991 In Comprehen-
sive organic synthesis, B M Trost and I Fleming (eds)
Oxford, UK: Pergamon, vol. 2, p. 133.
6. Solankee A, Lad S, Solankee S and Patel G 2009 Indian 21. Baurer A W, Kirby M M, Sherris J C and Turck M 1966
J. Chem. 48B 1442 Am. J. Clin. Pathol. 45 493
7. Padmavathi V, Reddy V K, Padmaja A and Reddy 22. Pandey K S and Khan N, 2008 Arch. Pharm. Chem. Life
Bhaskar D 2002 Syn. Commun. 32(8) 1227 Sci. 341 418