Facile regioselective synthesis of novel bioactive thiazolyl-pyrazoline derivatives via a three-component reaction and their antimicrobial activity

Article abstract of DOI:10.1016/j.bmcl.2012.11.024

A series of novel 2-(3,5-diphenyl-4,5-dihydro-1H-pyrazol-1-yl)-4- phenylthiazoles have been prepared by a three-component cyclo-condensation of various chalcones, thiosemicarbazide and phenacyl bromide. The easy work-up of the products, rapid reaction, and mild conditions are notable features of this protocol. The reaction was efficiently catalyzed in one-pot by a few drops of HCl in EtOH under reflux conditions providing the title compounds in moderate to high yields. The antibacterial activity of the selected products was examined. Some products exhibit promising activities.

Full text of DOI:10.1016/j.bmcl.2012.11.024

Bioorganic & Medicinal Chemistry Letters 23 (2013) 548–551
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Facile regioselective synthesis of novel bioactive thiazolyl-pyrazoline
derivatives via a three-component reaction and their antimicrobial activity
Bahman Sharifzadeh a, Nosrat O. Mahmoodi a, , Manouchehr Mamaghani a, Khalil Tabatabaeian a,
⇑
Alireza Salimi Chirani b, Iraj Nikokar c
a Department of Organic Chemistry, University of Guilan, PO Box 41335-1914, Rasht, Iran
b Department of Medical Microbiology, School of Medicine, Shahid Beheshti University of Medical Sciences, PO Box 19835-151, Tehran, Iran
c Laboratory of Microbiology and Immunology of Infectious Diseases, Paramedicine Faculty, Guilan University of Medical Sciences, PO Box 44715-1361, Guilan, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel 2-(3,5-diphenyl-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazoles have been prepared by
a three-component cyclo-condensation of various chalcones, thiosemicarbazide and phenacyl bromide.
The easy work-up of the products, rapid reaction, and mild conditions are notable features of this
protocol. The reaction was efficiently catalyzed in one-pot by a few drops of HCl in EtOH under reflux
conditions providing the title compounds in moderate to high yields. The antibacterial activity of the
selected products was examined. Some products exhibit promising activities.
Received 19 September 2012
Revised 5 November 2012
Accepted 7 November 2012
Available online 22 November 2012
Keywords:
Thiazolyl-pyrazoline
Chalcone
Ó 2012 Elsevier Ltd. All rights reserved.
Thiosemicarbazide
Three-component
Antibacterial activity
Chalcones are well known as intermediates for the synthesis of
various heterocyclic compounds, many of which have remarkable
synthesis of chemically and biologically medicinal heterocy-
cles22–26 we decided to explore the synthesis of these novel
thiazolyl-pyrazoline derivatives.
Herein, we report an efficient method for the regioselective
synthesis of new thiazolyl-pyrazoline derivatives (6a–i) via a
three-component reaction (Scheme 1). Due to the incorporation
of different pharmacophores into their structures these com-
pounds could display superior antibacterial properties.
Condensation of chalcones with thiosemicarbazide can lead to
two different pyrazolines 5 or 50 as shown in Scheme 2. The selec-
tivity that leads to the formation of intermediate 3 results from
1,2-addition of thiosemicarbazide to the carbonyl group of chal-
cone (2) and subsequent N–H intramolecular cycloaddition to the
double bond of (3). This occurs more readily than formation of
intermediate (30) resulting from 1,4-addition to provide (40). As a
result and in accordance with the currently accepted mechanism27
the formation of (6), instead of the regioisomer (60), is favored via
hydrazone formation (3). Under these reaction conditions, the
product structure is determined via steps 4 ? 5 rather than via
40 ? 50 where a regioselective enamine-imine tautomerism may
take place28 to form the more stable 2-pyrazoline (5).
biological activities and play
chemistry. The presence of the
a principal role in medicinal
a
,b-unsaturated carbonyl system
in chalcones makes them biologically attractive.1–3
The tetralone moiety plays an important role in diverse
biological activities and is a feature of some of the most interesting
and important classes of compounds. Many tetralones are pharma-
cologically active, functioning as antidepressants, anti-parkinson,
antifungals, antibacterials, COX-2 inhibitors, and anticonvul-
sants.4–9 Two tetralone-containing compounds, sertraline and
tametraline, have been used clinically as antidepression
agents.10,11 Finally, thiazolyl-pyrazoline derivatives were reported
to exhibit significant antimicrobial, antiviral and antihypertensive
activities.12–16
Our goal in this work was to incorporate these three indepen-
dently biologically active moieties into one molecule to generate
compounds with synergistic in vitro antimicrobial activities.
Structural evaluations, properties, and synthetic routes to the
thiazolyl-pyrazoline skeleton have been reported in only limited
sources.17–21 A literature survey shows that thiazolyl-pyrazoline
derivatives containing a tetralone-derived moiety have not been
reported to date. Because of our interest in the design and
Pyrazoline formation is followed by the Hantzsch thiazole syn-
thesis. Initially, nucleophilic substitution of Br in phenacylbromide
by the S-atom of thioamide 5 generates the isothiourea, which
subsequently undergoes cyclocondensation and H2O elimination
give the thiazole ring of 6 (Scheme 2).
⇑
Corresponding author. Tel./fax: +98 131 3233262.
E-mail address: mahmoodi@guilan.ac.ir (N.O. Mahmoodi).
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.11.024

B. Sharifzadeh et al. / Bioorg. Med. Chem. Lett. 23 (2013) 548–551
549
O
O
Ar
Ar
or
R1
R1
2d-i
2a-c
O
+
+ NH2NHCSNH2
Br
con. HCl
/ EtOH
ref / 6-10 h
S
S
N
HX
N
N
N
N
N
Ar
Ar
HA
HB
HB
HA
R1
R1
6d-i
6a-c
Scheme 1. Synthesis of thiazolyl-pyrazolines (6a–i).
O
H2N
Ph
S
H
N
N
N
CSNH2
Ph
NHCSNH2
N
N
N
N
S
Br
-H+
NH2NHCSNH2
N
+H+
- H2O
via hydrazone
Ar
Ar
Ar
Ar'
Ar'
Ar
Ar'
formation
Ar
Ar'
Ph
3
5
4
6
O
O
H2N
N
S
Ar
Ar'
H2NSCHN
CSNH2
2
S
Ph
O
NH
HN
H
N
H
HN
N
HN
N
via michel
HO
Ar
Br
- H2O
Ar'
addition
Ar
NH2NHCSNH2
Ar'
- H2O
Ar'
Ar
Ar'
6'
3'
5'
4'
Scheme 2. Mechanism for addition of thiosemicarbazide to chalcone 2.
All of compounds described in Table 1 were characterized by
spectroscopic methods (IR, 1H NMR, 13C NMR) and elemental
analysis.29
diastromer is formed and recovered. In addition MM2 structural
minimize energy using Chem3D Ultra 8 (Cambridge soft) indicate
a trans bond of Hc and Hd structure as a most stable isomer for
6a–c (Scheme 3). However, cis isomer possesses more steric bulk
hindrance effects compare to the trans isomer.
The geminal methylene protons of the pyrazoline rings (HA and
HB in 6d–i) appear in the region of 3.11–3.2 ppm (JAB = 17.44 Hz,
JAX = 3.08 Hz, HA) and 3.83–3.9 ppm (JAB = 17.45 Hz, JBX = 11.13 Hz,
HB) as doublet of doublets. The CH (HX) protons appeared as dou-
blet of doublets in the region 5.99–6.11 ppm (JAX = 3.08 Hz,
JBX = 11.12 Hz, HX) due to vicinal coupling with the two nonequiv-
alent geminal protons of the adjacent carbon atom. Protons bound
to the aromatic ring were observed within the expected chemical
shift region and exhibited the expected integral values.
The IR spectra of thiazolyl-pyrazoline derivatives 6a–i reveal
the presence of thiocarboxamide amino stretching vibration bands
at
t
3482–3123 cmꢀ1, absorption bands in the 1509–1610 cmꢀ1 re-
gion corresponding to endocyclic C@N stretching bands, and peaks
in the regions 1355–1365 cmꢀ1 and 1055–1096 cmꢀ1 which
indicate the presence of C–S and C–N groups.
The 1H NMR spectra of thiazolyl-pyrazolines 6a–i showed a
sharp singlet at d 7–8 ppm due to the thiazole ring proton. The vic-
inal protons of the adjacent carbon atom in the pyrazole ring of com-
pounds 6a–c appear in the region of 3.91–4.2 and 5.91–6.05 ppm.
The reaction for compounds 6a–c generates one diastromer as pair
of enantiomer. The 1H NMR spectrum of thiazolyl-pyrazoline 6a–c
showed only one precipitate indicating that chemoselectively one
The in vitro antibacterial activities of compounds 6a–i were
evaluated against gram-positive and gram-negative bacteria using

550
B. Sharifzadeh et al. / Bioorg. Med. Chem. Lett. 23 (2013) 548–551
Table 1
Characterization of synthesized compounds
Entry
Compound
R1
Ar
Yield (%)
1
2
3
6a
6b
6c
H
H
H
4-H3COC6H4
4-ClC6H4
2-Thienyl
75
76
75
S
N
N
N
Hc
Ar
HA
HB
Hd
R1
4
5
6d
6e
H
H
2-Thienyl
4-H3COC6H4
78
78
S
N
HX
6
7
8
9
6f
OCH3
OCH3
CH3
4-H3COC6H4
4-H3CC6H4
4-H3CC6H4
4-H3COC6H4
76
79
76
78
N
N
6g
6h
6i
Ar
CH3
HB
HA
R1
compounds 6b, 6c, 6f, 6h and 6i have moderate growth-inhibiting
activity against Escherichia coli. Among these substances, 6a, 6d, 6e,
6g and 6h show moderate growth-inhibiting effects on Staphylo-
coccus aureus. The results are shown in Table 2.
In conclusion, this three-component, one-pot protocol provides
a regioselective, fast, and practical method for the preparation of
novel
2-(3,5-diphenyl-4,5-dihydro-1H-pyrazol-1-yl)-4-phenyl
thiazoles from a variety of chalcones, thiosemicarbazide, and
phenacyl bromide in good yields. This allows the rapid assessment
of pharmacological activities of these novel thiazolyl-pyrazoline
derivatives. The simplicity, high atom economy, easy execution,
simple workup, and good yields, together with the use of inexpen-
sive starting materials and an environmentally friendly procedure,
are features of this procedure. Most of the compounds prepared as
part of this study exhibited good antibacterial activity against
Pseudomonas aeruginosa.
Acknowledgments
Scheme 3. MM2 structural minimize energy indicate a trans bond of Hc and Hd for
6a–c.
The authors are grateful to the Research Council of University of
Guilan for financial support of this research work. We also
acknowledge the useful suggestions made by Douglas Fry of
Ricerca Biosciences, USA.
Table 2
Antimicrobial activity of the compounds (6a–i)
Entry Compound Conc. of
compound
Antimicrobial activity (zone of inhibition in
mm)
References and notes
in DMSO
Staphylococcus Escherichia Pseudomonas
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2
3
4
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6a
6b
6c
6d
6e
6f
6g
6h
6i
100
100
100
100
100
100
100
100
100
8
—
7
8
—
—
8
—
7
9
9
—
—
9
6
—
7
16
19
7
18
17
16
19
21
—
7
9
10
11
—
23
—
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22
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the cultures of three different standard microorganisms:
Escherichia coli (E. coli) ATCC 25922 and Pseudomonas aeruginosa
ATCC 27853 as gram-negative models, and Staphylococcus aureus
(S. aureus) ATCC 29213 as a gram-positive model.30
Compounds 6c, 6d and 6f–i exhibited good antibacterial activity
against Pseudomonas aeruginosa that may be due to the incorpora-
tion of thiophene ring (6c and 6d) and electron-donating groups
like –OCH3 and –CH3 (6f–i). Also the results indicate that

B. Sharifzadeh et al. / Bioorg. Med. Chem. Lett. 23 (2013) 548–551
551
17. Peng-Cheng, L. V.; Dong-Dong, L.; Qing-Shan, L.; Xiang, L.; Zhu-Ping, X.; Hai-
Liang, Z. Bioorg. Med. Chem. Lett. 2011, 21, 5374.
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20. Supriya, D.; Beedkara, C. N.; Khobragadea; Santosh, S.; Chobeb, B. S.; Dawaneb,
O. S.; Yemul, B. Int. J. Biol. Macromol. 2012, 50, 947.
6.90–7.82 (m, 14H, Ar–H), 6.85(S, 1H, H5 of thiazole), 5.66–5.70 (dd, 1H, Hx,
JAX = 6.6 Hz, JBX = 12 Hz), 3.88–3.95 (dd, 1H, HB, JBX = 12 Hz, JAB = 17.4 Hz), 3.82
(s, 3H, substituted-OCH3), 3.34–3.40 (dd, 1H, HA, JAX = 6.6 Hz, JAB = 17.4 Hz),13
C
NMR (100 MHz, CDCl3) (d/ppm): 164.93 (S-C@N), 159.60 (Ar–C–O), 153.14
(C@N of pyrazole), 150.92 (C–N of thiazole), 114.33–135.04 (Ar–C), 104.43 (C5
of thiazole), 64.02 (C5 of pyrazole), 55.82 (substituted-OCH3), 43.66 (C4 of
pyrazole), molecular weight: 411.52, Anal. Calcd. for C25H21N3OS: C, 72.97; H,
5.14; N, 10.21%. Found C, 72.96; H, 5.12; N, 10.20%.
21. Shoman, M. E.; Abdel-Aziz, M.; Aly, O. M.; Farag, H. H.; Morsy, M. A. Eur. J. Med.
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Arch. Pharm. 2007, 340, 409.
23. Mahmoodi, N. O.; Khodaee, Z. Arkivoc 2007, 29.
2-(3,5-Bis(4-methoxyphenyl)-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazole (6f).
Yellow solid; yield 76%; mp 201–205 °C; IR (KBr) (m
max/cmꢀ1): 3056, 2932,
1655, 1610, 1549, 1070; 1H NMR (400 MHz, CDCl3): 6.92–7.76 (m, 13H, Ar–H),
7.30 (S, 1H, H5 of thiazole), 5.59–5.64 (dd, 1H, Hx, JAX = 6 Hz, JBX = 11.6 Hz),
3.96–4.04 (dd, 1H, HB, JBX = 11.6 Hz, JAB = 17.6 Hz), 3.83 (s, 3H, substituted-
OCH3), 3.72 (s, 3H, substituted-OCH3), 3.30–3.36 (dd, 1H, HA, JAX = 6 Hz,
JAB = 17.6 Hz),13C NMR (100 MHz, CDCl3) (d/ppm): 164.93 (S–C@N), 161.17
(Ar–C–O), 159.06 (Ar–C–O), 153.14 (C@N of pyrazole), 150.92 (C–N of
thiazole), 114.33–135.04 (Ar–C), 104.43 (C5 of thiazole), 64.02 (C5 of
pyrazole), 55.82 (substituted-OCH3), 55.51 (substituted-OCH3), 43.66 (C4 of
pyrazole), molecular weight: 441.54, Anal. Calcd. for C26H23N3O2S: C, 70.72; H,
5.25; N, 9.52%. Found C, 70.69; H, 5.24; N, 9.55%.
24. Mahmoodi, N. O.; Khodaee, Z. Mendeleev Commun. 2004, 14, 304.
25. Mahmoodi, N. O.; Emadi, S. Russ. J. Org. Chem. 2004, 40, 377.
26. Mahmoodi, N. O. Phosphorus Sulfur Silicon Relat. Elem. 2002, 177, 2887.
27. Wiley, R. H.; Jarboe, C. H.; Hayes, F. N.; Hansbury, E.; Nielsen, J. T.; Callahan, P.
X.; Sellars, M. C. J. Org. Chem. 1958, 23, 732.
28. Gokhan, N.; Yesilada, A.; Ucar, G.; Erol, K. Arch. Pharm. 2003, 336, 362.
29. General: IR absorption band maxima were measured with a Shimadzu UV-
2100 spectrophotometer. Chemicals were purchased from Fluka, Merck, and
Aldrich. Melting points are uncorrected and determined using a Mettler Fp5
melting point apparatus. All NMR data were recorded in CDCl3 using a Bruker
Avance 400-MHz spectrometer. Chemical shifts are reported in ppm (d) using
deuterated solvents as internal references. Elemental analyses were made by a
Carlo–Erba EA1110 CNNO-S analyzer and agreed with the calculated values
General procedure for the synthesis of 2-(3,5-diphenyl-4,5-dihydro-1H-pyrazol-1-
2-(3-(4-Methoxyphenyl)-5-p-tolyl-4,5-dihydro-1H-pyrazol-1-yl)-4-
phenylthiazole (6g). Yellow solid; yield 79%; mp 195–198 °C; IR (KBr) (mmax
/
cmꢀ1): 3057, 2933, 1664, 1623, 1548, 1073; 1H NMR (400 MHz, CDCl3): 7.03–
7.75 (m, 13H, Ar–H), 7.30(S, 1H, H5 of thiazole), 5.60–5.64 (dd, 1H, Hx,
JAX = 6 Hz, JBX = 11.6 Hz), 3.98–4.05 (dd, 1H, HB, JBX = 11.6 Hz, JAB = 6 Hz), 3.82
(s, 3H, substituted-OCH3), 3.27–3.33 (dd, 1H, HA, JAX = 6 Hz, JAB = 17.6 Hz), 2.26
(s, 3H, substituted-CH3),13C NMR (100 MHz, CDCl3) (d/ppm): 164.89 (S–C@N),
161.19 (Ar–C–O), 153.15 (C@N of pyrazole), 150.89 (C–N of thiazole), 114.78–
139.49 (Ar–C), 104.45 (C5 of thiazole), 64.23 (C5 of pyrazole), 55.83
(substituted-OCH3), 43.75 (C4 of pyrazole), 21.15 (substituted-CH3),
molecular weight: 425.55, Anal. Calcd. for C26H23N3OS: C, 73.38; H, 5.45; N,
9.87%. Found C, 73.36; H, 5.44; N, 9.86%.
yl)-4-phenylthiazole derivatives (6a–i):
A mixture of chalcone (0.01 mol),
thiosemicarbazide (0.01 mol), phenacyl bromide derivatives (0.01 mol) and a
few drops of HCl were refluxed in dry ethanol (25 mL) for 8 h. After cooling, the
solid which precipitated was recrystallized from ethanol
2-(3-(4-Methoxyphenyl)-3,3a,4,5-tetrahydro-2H-benzo[g]indazol-2-yl)-4-
phenylthiazole (6a). Yellow solid; yield 75%; mp 211–214 °C; IR (KBr) (mmax
/
cmꢀ1): 3060, 2924, 1653, 1610, 1541, 1095; 1H NMR (400 MHz, CDCl3): 6.96–
7.799 (m, 13H, Ar-H), 7.29 (S, 1H, H5 of thiazole), 5.89–5.92 (d, 1H, H3 of
pyrazole, J = 10.8 Hz), 3.90–3.97 (m, 1H, H3a of pyrazole), 3.67 (s, 3H,
substituted-OCH3), 2.82–2.94 (m, 2H, H5),1.77–1.80 (m, 1H, HA), 0.92–0.97
(m, 1H, HB) 13C NMR (100 MHz, CDCl3) (d/ppm): 164.37 (S–C@N), 158.97 (Ar–
C–O), 154.00 (C@N of pyrazole), 151.12 (C–N of thiazole), 114.30–139.73 (Ar–
C), 104.16 (C5 of thiazole), 70.27 (C3 of pyrazole), 67.00 (C3a of pyrazole), 55.37
(substituted-OCH3), 29.17 (CH2), 24.03 (CH2), molecular weight: 437.56, Anal.
Calcd. for C27H23N3OS: C, 74.11; H, 5.30; N, 9.60%. Found C, 74.08; H, 5.29; N,
9.59%.
2-(3,5-Dip-tolyl-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazole (6h). Yellow
solid; yield 76%; mp 192–195 °C; IR (KBr) (m
max/cmꢀ1): 3059, 2938, 1659,
1630, 1543, 1078; 1H NMR (400 MHz, CDCl3): 7.16–7.75 (m, 13H, Ar-H), 7.30
(S, 1H, H5 of thiazole), 5.63–5.67 (dd, 1H, Hx, JAX = 6 Hz, JBX = 12 Hz), 3.99–4.07
(dd, 1H, HB, JBX = 12 Hz, JAB = 6 Hz), 3.29–3.35 (dd, 1H, HA, JAX = 6 Hz,
JAB = 18 Hz), 2.38 (s, 3H, substituted-CH3), 2.27 (s, 3H, substituted-CH3),13
C
NMR (100 MHz, CDCl3) (d/ppm): 164.78 (S–C@N), 153.28 (C@N of pyrazole),
150.91 (C–N of thiazole), 125.97–140.24 (Ar–C), 104.60 (C5 of thiazole), 64.27
(C5 of pyrazole), 43.62 (C4 of pyrazole), 21.52 (substituted-CH3), 21.16
(substituted-CH3), molecular weight: 409.55, Anal. Calcd. for C26H23N3S: C,
76.25; H, 5.66; N, 10.26%. Found C, 76.23; H, 5.65; N, 10.26%.
2-(3-(4-Chlorophenyl)-3,3a,4,5-tetrahydro-2H-benzo[g]indazol-2-yl)-4-
phenylthiazole (6b). Yellow solid; yield 76%; mp 229–231 °C; IR (KBr) (mmax
/
cmꢀ1): 3056, 2908, 1649, 1608, 1544, 1107; 1H NMR (400 MHz, CDCl3): 7.14–
7.97 (m, 13H, Ar–H), 7.32(S, 1H, H5 of thiazole), 5.96–5.99 (d, 1H, H3 of
pyrazole, J = 10.8 Hz), 3.93–4.01 (m, 1H, H3a of pyrazole), 3.06–3.08 (m, 2H,
H5),1.78–1.81 (m, 1H, HA), 0.88–0.92 (m, 1H, HB) 13C NMR (100 MHz, CDCl3) (d/
ppm): 164.21 (S–C@N), 154.19 (C@N of pyrazole), 150.99 (C–N of thiazole),
132.17 (Ar–C–Cl), 124.17–143.90 (Ar–C), 104.36 (C5 of thiazole), 66.60 (C3 of
pyrazole), 66.13 (C3a of pyrazole), 29.14 (CH2), 24.16 (CH2), molecular weight:
441.98, Anal. Calcd. for C26H20ClN3S: C, 70.66; H, 4.56; N, 9.51%. Found C,
70.62; H, 4.52; N, 9.48%.
2-(5-(4-Methoxyphenyl)-3-p-tolyl-4,5-dihydro-1H-pyrazol-1-yl)-4-
phenylthiazole (6i). Yellow solid; yield 78%; mp 197–201 °C; IR (KBr) (mmax
/
cmꢀ1): 3056, 2933, 1665, 1623, 1547, 1074; 1H NMR (400 MHz, CDCl3): 6.92–
7.72 (m, 13H, Ar–H), 7.30(S, 1H, H5 of thiazole), 5.61–5.66 (dd, 1H, Hx,
JAX = 6.4 Hz, JBX = 12 Hz), 3.98–4.05 (dd, 1H, HB, JBX = 12 Hz, JAB = 6.4 Hz), 3.72
(s, 3H, substituted-OCH3), 3.31–3.37 (dd, 1H, HA, JAX = 6 Hz, JAB = 17.6 Hz), 2.38
(s, 3H, substituted-CH3),13C NMR (100 MHz, CDCl3) (d/ppm): 164.81 (S–C@N),
159.08 (Ar–C–O), 153.28 (C@N of pyrazole), 150.93 (C–N of thiazole), 114.34–
140.23 (Ar–C), 104.59 (C5 of thiazole), 64.07 (C5 of pyrazole), 55.51
(substituted-OCH3), 43.54 (C4 of pyrazole), 21.52 (substituted-CH3),
molecular weight: 425.55, Anal. Calcd. for C26H23N3OS: C, 73.38; H, 5.45; N,
9.87%. Found C, 73.37; H, 5.42; N, 9.87%.
4-Phenyl-2-(3-(thiophen-2-yl)-3,3a,4,5-tetrahydro-2H-benzo[g]indazol-2-
yl)thiazole (6c). Deep yellow solid; yield 75%; mp 181 -183 °C; IR (KBr) (mmax
/
cmꢀ1): 3057, 2908, 2835, 1649, 1691, 1608, 1544, 1107; 1H NMR (400 MHz,
CDCl3): 6.95–7.96 (m, 12H, Ar–H), 7.39 (S, 1H, H5 of thiazole), 6.18–6.21 (d, 1H,
H3 of pyrazole, J = 10.4 Hz), 3.91–3.97 (m, 1H, H3a of pyrazole), 3.02–3.05 (m,
2H, H5),1.89–1.92 (m, 1H, HA), 1.14–1.25 (m, 1H, HB) 13C NMR (100 MHz,
CDCl3) (d/ppm): 164.91 (S–C@N), 153.55 (C@N of pyrazole), 150.96 (C–N of
thiazole), 126.01–144.40 (Ar–C), 105.21 (C5 of thiazole), 67.00 (C3 of pyrazole),
64.03 (C3a of pyrazole), 29.17 (CH2), 24.03 (CH2), molecular weight: 413.56,
Anal. Calcd. for C24H19N3S2: C, 69.70; H, 4.63; N, 10.16%. Found C, 69.66; H,
4.60; N, 10.14%.
30. Determination of antimicrobial activity: a sterilized glass tube (5 mm diameter)
was used aseptically to make wells on plates. The antibacterial activity of
compounds was assayed biologically using the Agar well-diffusion method. A
colony of each standard test organism was sub-cultured in order to obtain
fresh bacteria on the nutrient agar plates at 37 °C for 18 h. To preparations of
suspensions of microorganisms (0.5 McFarland), one to two colonies from each
plate was dissolved in isotonic saline solution. Then Mueller–Hinton agar
(Merck) plates were prepared according to manufacturers’ instructions in
order to evaluate the antibacterial activities of compounds. The sterile
Mueller–Hinton agar plates were inoculated with the bacteria.
4-Phenyl-2-(3-phenyl-5-(thiophen-2-yl)-4,5-dihydro-1H-pyrazol-1-yl)thiazole
(6d). Deep yellow solid; yield 78%; mp 155–157 °C; IR (KBr) (m
max/cmꢀ1): 3057,
2914, 1663, 1619, 1539, 1099; 1H NMR (400 MHz, CDCl3): 7.00–7.86 (m, 13H,
Ar–H), 7.47–746(d, 1H, H5 of thiazole J = 0.8 Hz), 6.01–6.06 (dd, 1H, Hx,
JAX = 5.6 Hz, JBX = 11.6 Hz), 4.04–4.11 (dd, 1H, HB, JBX = 11.6 Hz, JAB = 18 Hz),
3.55–3.60 (dd, 1H, HA, JAX = 5.6 Hz, JAB = 18 Hz), 13C NMR (100 MHz, CDCl3) (d/
ppm): 164.91 (S–C@N), 153.55 (C@N of pyrazole), 150.96 (C–N of thiazole),
126.01–144.40 (Ar–C), 105.21 (C5 of thiazole), 60.18 (C5 of pyrazole), 43.26 (C4
of pyrazole), molecular weight: 387.52, Anal. Calcd. for C22H17N3S2: C, 68.19; H,
4.42; N, 10.84%. Found C, 68.14; H, 4.40; N, 10.80%.
0.01 g of test samples was dissolved in 1 mL dimethyl sulfoxide (DMSO) to
obtain a stock solution. A concentration of 1 mg/mL or 100 lg/0.1 mL of each
sample was prepared. 0.1 mL of prepared samples was dropped into each
respective labeled well aseptically. The inoculated plates were left on the table
for 1 h to allow the each sample to diffuse into the agar. For comparison,
Gentamycin was used as a positive control and DMSO as a negative control.
Test organism growth may be affected by the inhibitory action of the test
compound and so, a clear zone around the disc appeared as an indication of the
inhibition of the test organism growth. The results of our tests were presented
as the inhibition zones, given in millimeters (mm). Measurements were
obtained after 24 h for bacteria.
2-(5-(4-Methoxyphenyl)-3-phenyl-4,5-dihydro-1H-pyrazol-1-yl)-4-
phenylthiazole (6e). Pale yellow solid; yield 78%; mp 185–187 °C; IR (KBr)
(m
max/cmꢀ1): 3061, 2928, 1656, 1614, 1543, 1099; 1H NMR (400 MHz, CDCl3):