Microwave-Assisted Synthesis and Antimicrobial Activity of Novel Pyrazole–Indanone Hybrid Analogs

Article abstract of DOI:10.1134/S1070428020090213

Abstract: A simple and efficient microwave-assisted protocol has been developed for the synthetic of a series of novel pyrazole–indanone hybrid analogs. The target compounds have been synthesized by the Claisen–Schmidt condensation of different 1,3-diphenyl-1H-pyrazole-4-carbaldehydes with 2,3-dihydro-1H-inden-1-one in the presence of potassium hydroxide. The compounds were characterized by IR, ¹H and ¹³C NMR, and mass spectra and were found to exhibit potent antimicrobial activity in vitro.

Full text of DOI:10.1134/S1070428020090213

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2020, Vol. 56, No. 9, pp. 1635–1639. © Pleiades Publishing, Ltd., 2020.
Microwave-Assisted Synthesis and Antimicrobial Activity
of Novel Pyrazole–Indanone Hybrid Analogs
a
a
a
a,
N. Venkatesh , Sh. Sundergoud , M. Kumara Swamy , and P. Veerasomaiah *
a
Department of Chemistry, University College of Science, Osmania University, Hyderabad, 500007 India
*
e-mail: veerasomaiahp@gmail.com
Received March 25, 2020; revised March 30, 2020; accepted March 31, 2020
Abstract—A simple and efficient microwave-assisted protocol has been developed for the synthetic of a series
of novel pyrazole–indanone hybrid analogs. The target compounds have been synthesized by the Claisen–
Schmidt condensation of different 1,3-diphenyl-1H-pyrazole-4-carbaldehydes with 2,3-dihydro-1H-inden-1-one
1
13
in the presence of potassium hydroxide. The compounds were characterized by IR, H and C NMR, and mass
spectra and were found to exhibit potent antimicrobial activity in vitro.
Keywords: pyrazole, indan-1-one, chalcone, microwave irradiation, Vilsmeier–Haack reaction, Claisen–
Schmidt condensation, antimicrobial activity
DOI: 10.1134/S1070428020090213
INTRODUCTION
[22], and flavones [23]. On the other hand, microwave
irradiation method has gained attention of chemists
during the last decades due to its unique advantages
such as shorter reaction times, cleaner reaction
products, higher yields, and better selectivity, and
provided a valuable alternative to accomplish more
efficient syntheses of a variety of organic compounds
with much simpler operation and milder reaction
conditions. In addition, synthesis of hybrid heterocyclic
compounds has attracted much attention in recent
years. It is expected that combining features of more
than one biologically active fragments in a single mole-
cule may result in pronounced pharmacological activity
while retaining high diversity and biological relevance.
Owing to the above facts, we made an attempt to syn-
thesize (E)-2-[(1,3-diphenyl-1H-pyrazol-4-yl)methyli-
dene]-2,3-dihydro-1H-inden-1-one derivatives under
microwave irradiation.
Pyrazoles constitute one of the important classes of
nitrogen heterocycles and occupy a unique position in
medicinal chemistry due to their broad spectrum of
biological activities such as antimicrobial [1], anti-
inflammatory [2], anticancer [3], anticonvulsant [4],
and antipyretic [5] activities. Among the pyrazole
family, 1,3-diarylpyrazoles have gained much interest
in recent pharmacological applications. Indanone
derivatives are widely used in medicinal chemistry,
natural product synthesis, and agricultural products.
Indanone derivatives are associated with various
biological activities such as anti-inflammatory [6],
analgesic [7], antimicrobial [8], anticholinergic [9],
dopaminergic [10], anticancer [11], and antimalarial
[
12] activities. Indanone derivatives are very useful
synthons for various carbocyclic and heterocyclic
molecules as synthetic intermediates for several drugs
and natural products [13–15]. On the other hand,
chalcones are natural biocides and are well known
intermediates in the synthesis of various heterocyclic
compounds. Chalcone derivatives possess a wide
range of biological activities such as antimicrobial [16],
anti-inflammatory [17], and anticancer [18] activities.
Chalcones constitute an important class of natural
products belonging to the flavonoid family [19] and are
also key precursors in the synthesis of many bio-
logically important heterocycles such as benzothia-
zepines [20], dihydropyrazoles [21], 1,4-diketones
RESULTS AND DISCUSSION
Intermediate 1,3-diaryl-1H-pyrazole-4-carbalde-
hydes 4a–4l were prepared starting from commercially
available acetophenones 1a–1l and phenylhydrazine
(2) through intermediate hydrazones 3a–3l [24, 25].
1,3-Diaryl-1H-pyrazole-4-carbaldehydes 4a–4l were
condensed with 2,3-dihydro-1H-inden-1-one (5) in the
presence of potassium hydroxide in methanol under
microwave irradiation to yield the corresponding pyra-
zole–indanone conjugates 6a–6l (Scheme 1). Initially,
1
635

1636
VENKATESH et al.
Scheme 1.
O
H
Me
H
N
Ph
N
i
ii
R
Ph
NH2
N
Ph
N
Me
+
N
H
O
R
R
1
a–1l
2
3a–3l
4a–4l
Ph
N
Ph
Ph
N
N
N
N
N
iii
S
N
O
O
O
R
6
a–6j
6k
6l
R = H (a), 4-Me (b), 4-MeO (c), 4-Br (d), 4-Cl (e), 4-F (f), 4-HO (g), 4-O N (h), 3-MeO (i), 2,4-Cl (j).
2
2
i: Glacial acetic acid, MeOH, heating; ii: DMF (3 equiv), POCl (7 equiv), 0–5°C, 90°C, 8 h;
3
iii: indan-1-one (5), KOH, MeOH, MW, 320 W, 4–5 min.
the model condensation of 1,3-diphenyl-1H-pyrazole-
-carbaldehyde (1a) with indanone 6 was carried
drug. The activity was determined using cup plate agar
diffusion method by measuring the zone of inhibition
in mm at a concentration of 500 μg/mL in DMSO.
Compounds 6f, 6j, and 6l showed a good activity
against the tested fungi, and the remaining compounds
showed low to moderate antifungal activity.
4
out in the presence of piperidine at room temperature
for 8 h to obtain 58% of 6a. The yield did not increase
to an appreciable extent when pyrrolidine was used
instead of piperidine, other conditions being equal.
Using sodium hydroxide as a base, the product yield
was improved to 67%, but the best result (72% yield)
was obtained in the presence of potassium hydroxide.
The reaction was then carried out under different
temperature conditions, but the yield did not vary
significantly with temperature. Finally, the reaction
was conducted under microwave irradiation, which
significantly increased the yield up to 92% with
shorter reaction time. The structure of compounds 6a–
EXPERIMENTAL
The purity of the compounds was checked by TLC
using precoated silica gel 60 F254 plates (Merck). The
IR spectra were recorded in KBr on a Shimadzu FT-IR-
1
13
8
400s spectrometer. The H NMR and C NMR
spectra were recorded on a Bruker Avance II 400 MHz
spectrometer using tetramethylsilane as an internal
standard. The mass spectra were recorded on
a Shimadzu GCMS-QP 1000 EX mass spectrometer.
6
l was established by different spectroscopic methods
1
13
such as IR, H and C NMR and mass spectrometry.
General procedure for the synthesis of
Compounds 6a–6l were tested for their in vitro
antibacterial activity against four bacterial strains,
namely B. faecalis, S. aureus, K. pneumoniae, and
E. coli, using ampicillin as standard drug. The activity
was determined using cup plate agar diffusion method
by measuring the zone of inhibition in mm at a con-
centration of 100μg/mL in DMSO. Compounds 6e, 6f,
and 6k showed a good activity against the tested bac-
terial organisms and the remaining compounds showed
low to moderate activity compared with the standard
drug ampicillin.
(
2
E)-2-[(1,3-diphenyl-1H-pyrazol-4-yl)methylidene]-
,3-dihydro-1H-inden-1-ones 6a–6l. A quartz tube
inserted into a screw-capped Teflon vial was charged
with a mixture of 1,3-diphenyl-1H-pyrazole-4-carbal-
dehyde 4a–4l (1 mmol), 2,3-dihydro-1H-inden-1-one
(
5, 1 mmol), and potassium hydroxide (2 mmol) in
methanol (10 mL). The mixture was subjected to
microwave irradiation at 320 W for 4–5 min, and the
progress of the reaction was monitored by TLC. After
completion of the reaction, the mixture was poured into
ice-cold water and neutralized with dilute hydrochloric
acid to obtain solid product. The product was washed
with water, dried, and purified by column chromatog-
raphy using n-hexane–ethyl acetate as eluent.
The antifungal activity of compounds 6a–6l was
evaluated in vitro against Aspergillus niger and
Candida metapsilosis using griseofulvin as standard
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 9 2020

MICROWAVE-ASSISTED SYNTHESIS AND ANTIMICROBIAL ACTIVITY
1637
(
E)-2-[(1,3-Diphenyl-1H-pyrazol-4-yl)methyli-
(E)-2-{[3-(4-Fluorophenyl)-1-phenyl-1H-pyrazol-
4-yl]methylidene}-2,3-dihydro-1H-inden-1-one (6f).
Yield 90%. H NMR spectrum, δ, ppm: 4.11 s (2H,
dene]-2,3-dihydro-1H-inden-1-one (6a). Yield 90%.
H NMR spectrum, δ, ppm: 4.12 s (2H, CH ), 7.40–
1
1
2
7
7
.44 t (1H, Harom), 7.46–7.51 m (3H, Harom), 7.53–
.60 m (4H, Harom), 7.66–7.74 m (4H, Harom), 7.76 d
CH ), 7.28 d (2H, Harom), 7.42–7.45 m (1H, Harom),
2
7.65–7.61 m (4H, Harom), 7.69–7.75 m (3H, Harom),
7.76–7.80 m (2H, Harom), 8.05 d (2H, Harom), 8.96 s
(
1H, Harom), 8.06 d (2H, Harom), 8.98 s (1H, Harom).
1
3
13
C NMR spectrum, δ , ppm: 31.8, 116.6, 119.1, 122.2,
(1H, Harom). C NMR spectrum, δC, ppm: 31.8, 114.6,
C
1
1
23.5, 126.3, 127.2, 127.5, 129.0, 129.5, 130.5, 131.0,
118.9, 121.5, 123.4, 125.9, 126.9, 127.5, 128.6, 128.9,
31.8, 134.2, 134.7, 137.7, 138.8, 149.3, 152.6, 192.5.
129.3, 131.7, 133.8, 134.5, 137.5, 138.5, 149.2, 153.9,
+
+
1
92.4. Mass spectrum: m/z 381 [M + H] .
Mass spectrum: m/z 363 [M + H] .
(
E)-2-{[3-(4-Hydroxyphenyl)-1-phenyl-1H-pyra-
(
E)-2-{[3-(4-Methylphenyl)-1-phenyl-1H-pyr-
zol-4-yl]methylidene}-2,3-dihydro-1H-inden-1-one
(6g). Yield 87%. H NMR spectrum, δ, ppm: 4.11 s
2H, CH ), 7.09 d (2H, Harom), 7.38–7.47 m (3H,
Harom), 7.55–7.59 m (3H, Harom), 7.65–7.75 m (5H,
arom), 8.05 d (2H, Harom), 8.96 s (1H, Harom).
C NMR spectrum, δ , ppm: 31.8, 104.3, 116.3, 118.5,
22.0, 122.5, 125.7, 126.0, 126.5, 127.3, 127.6, 128.2,
28.5, 129.4, 131.1, 133.5, 134.2, 136.3, 149.0, 153.0,
azol-4-yl]methylidene}-2,3-dihydro-1H-inden-1-one
6b). Yield 92%. H NMR spectrum, δ, ppm: 2.45 s
3H, OCH ), 4.11 s (2H, CH ), 7.26 d (2H, Harom),
.41–7.51 m (3H, Harom), 7.56–7.61 m (3H, Harom),
.66–7.78 m (4H, Harom), 8.05 d (2H, Harom), 8.96 s
1H, Harom). C NMR spectrum, δ , ppm: 31.8, 24.5,
15.9, 121.3, 123.4, 125.9, 127.1, 127.4, 128.9, 129.4,
30.2, 130.9, 132.0, 133.9, 134.5, 137.5, 138.6, 149.2,
52.5, 192.4. Mass spectrum: m/z 377 [M + H] .
1
1
(
(
7
7
(
1
1
1
(
2
3
2
H
1
3
13
C
C
1
1
+
+
192.2. Mass spectrum: m/z 379 [M + H] .
(
E)-2-{[3-(4-Nitrophenyl)-1-phenyl-1H-pyrazol-
(
E)-2-{[3-(4-Methoxyphenyl)-1-phenyl-1H-pyr-
4
-yl]methylidene]-2,3-dihydro-1H-inden-1-one (6h).
Yield 85%. H NMR spectrum, δ, ppm: 4.17 s (2H,
azol-4-yl]methylidene}-2,3-dihydro-1H-inden-1-one
6c). Yield 92%. H NMR spectrum, δ, ppm: 3.85 s
3H, OCH ), 4.13 s (2H, CH ), 7.14 d (2H, Harom),
.39–7.50 m (3H, Harom), 7.57–7.60 m (3H, Harom),
.67–7.78 m (4H, Harom), 8.05 d (2H, Harom), 8.97 s
1H, Harom). C NMR spectrum, δ , ppm: 31.8, 55.6,
08.5, 116.5, 118.8, 122.4, 123.1, 125.9, 126.8, 127.3,
28.4, 128.9, 129.5, 131.3, 133.9, 134.5, 136.8, 149.1,
1
1
(
(
7
7
(
1
1
1
CH ), 7.42–7.47 m (3H, Harom), 7.61–7.90 m (5H,
2
3
2
Harom), 8.09 d (2H, Harom), 8.13–8.15 m (3H, Harom),
.38 d (2H, Harom), 9.06 s (1H, Harom). C NMR spec-
trum, δ , ppm: 31.8, 117.1, 119.2, 122.5, 123.3, 125.9,
26.9, 127.4, 127.9, 129.0, 129.4, 129.9, 130.2, 130.6,
36.9, 138.9, 142.3, 145.3, 149.5, 152.3, 192.4. Mass
spectrum: m/z 408 [M + H] .
13
8
13
C
C
1
1
+
+
52.5, 153.5, 192.3. Mass spectrum: m/z 393 [M + H] .
(
E)-2-{[3-(3-Methoxyphenyl)-1-phenyl-1H-pyra-
(
E)-2-{[3-(4-Bromophenyl)-1-phenyl-1H-pyra-
zol-4-yl]methylidene]-2,3-dihydro-1H-inden-1-one
6i). Yield 88%. H NMR spectrum, δ, ppm: 3.84 s
3H, OCH ), 4.11 s (2H, CH ), 7.11 d (1H, Harom),
.28 d (1H, Harom), 7.42–7.49 m (3H, Harom), 7.56–
.62 m (4H, Harom), 7.67–7.75 m (3H, Harom), 8.05 d
(2H, Harom
ppm: 31.7, 111.7, 113.2, 116.5, 119.1, 123.1, 126.6,
27.5, 128.5, 129.1, 129.5, 130.0, 131.3, 133.9, 137.5,
zol-4-yl]methylidene}-2,3-dihydro-1H-inden-1-one
6d). Yield 90%. H NMR spectrum, δ, ppm: 4.11 s
2H, CH ), 7.42–7.47 m (3H, Harom), 7.66–7.62 m (3H,
Harom), 7.67–7.71 m (3H, Harom), 7.75–7.78 m (3H,
arom), 8.04 d (2H, Harom), 8.97 s (1H, Harom).
C NMR spectrum, δ , ppm: 31.8, 116.6, 119.0, 122.6,
23.4, 126.4, 127.1, 127.5, 128.7, 128.8, 128.9, 129.5,
31.8, 134.0, 134.7, 137.8, 138.9, 149.4, 153.9, 192.6.
1
(
(
7
7
1
(
(
3
2
2
H
13
), 8.96 s (1H, Harom). C NMR spectrum, δ ,
C
1
3
C
1
1
1
1
38.5, 149.5, 152.4, 153.6, 192.5. Mass spectrum:
m/z 393 [M + H] .
+
Mass spectrum: m/z 441 [M + H] .
+
(
E)-2-{[3-(4-Chlorophenyl)-1-phenyl-1H-pyra-
(
E)-2-{[3-(2,4-Dichlorophenyl)-1-phenyl-1H-pyr-
zol-4-yl]methylidene}-2,3-dihydro-1H-inden-1-one
6e). Yield 89%. H NMR spectrum, δ, ppm: 4.11 s
2H, CH ), 7.40–7.47 m (3H, Harom), 7.66–7.63 m (2H,
Harom), 7.65–7.72 m (6H, Harom), 7.76 d (1H, Harom),
.04 d (2H, Harom), 8.97 s (1H, Harom). C NMR spec-
trum, δ , ppm: 31.8, 116.5, 119.0, 122.5, 123.3, 126.5,
azol-4-yl]methylidene}-2,3-dihydro-1H-inden-1-one
(6j). Yield 87%. H NMR spectrum, δ, ppm: 4.11 s
(2H, CH ), 7.38–7.45 m (2H, Harom), 7.47–7.50 m (1H,
Harom), 7.61–7.66 m (3H, Harom), 7.65–7.71 m (4H,
Harom), 7.75 d (1H, Harom), 8.04 d (2H, Harom), 8.96 s
1
1
(
(
2
2
1
3
8
1
3
C
(1H, Harom). C NMR spectrum, δ , ppm: 31.8, 116.3,
C
1
1
26.9, 127.4, 128.8, 129.0, 129.3, 129.7, 131.5, 134.2,
118.8, 121.5, 123.3, 125.2, 126.5, 1296.9, 127.3, 128.6,
129.5, 130.2, 130.5, 133.4, 134.6, 136.7, 137.4, 139.1,
149.5, 153.2, 192.4. Mass spectrum: m/z 431 [M + H] .
34.8, 137.5, 138.7, 149.2, 153.5, 192.4. Mass spec-
+
+
trum: m/z 397 [M + H] .
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 9 2020

1638
VENKATESH et al.
(
E)-2-{[1-Phenyl-3-(pyridin-3-yl)-1H-pyrazol-4-
4. Palaska, E., Aytemir, M., Uzbay, I.T., and Erol, D., Eur.
J. Med. Chem., 2001, vol. 36, p. 539.
https://doi.org/10.1016/S0223-5234(01)01243-0
yl]methylidene}-2,3-dihydro-1H-inden-1-one (6k).
Yield 85%. H NMR spectrum, δ, ppm: 4.10 s (2H,
1
5
6
. Sener, A., Kasэmogullar, R., Sener, M.K., Bildirici, I.,
and Akcamur, Y., J. Heterocycl. Chem., 2002, vol. 39,
p. 869.
https://doi.org/10.1002/jhet.5570390503
. Tang, M.L., Zhong, C., Liu, Z.Y., Peng, P., and Sun, X.,
Eur. J. Med. Chem., 2016, vol. 113, p. 63.
CH ), 7.40–7.42 m (2H, Harom), 7.62–7.77 m (9H,
2
Harom), 7.96 d (1H, Harom), 8.06 d (1H, Harom), 8.11 d
1H, Harom), 8.96 s (1H, Harom). C NMR spectrum, δ ,
ppm: 31.7, 116.5, 118.9, 122.2, 123.2, 1245.5, 126.6,
27.3, 128.5, 129.5, 129.9, 130.5, 131.4, 133.6, 134.2,
35.7, 137.8, 140.5, 149.5, 153.1, 192.4. Mass spec-
trum: m/z 364 [M + H] .
1
3
(
C
1
1
https://doi.org/10.1016/j.ejmech.2016.02.02
+
7
8
. Hammen, P.D. and Milne, G.M., US Patent no. 4164514,
1979.
. Finkieisztein, L.M., Castro, E.F., Fabian, L.E., Mol-
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(
E)-2-{[1-Phenyl-3-(thiophen-2-yl)-1H-pyrazol-
4
-yl]methylidene}-2,3-dihydro-1H-inden-1-one (6l).
Yield 90%. H NMR spectrum, δ, ppm: 4.11 s (2H,
1
CH ), 7.10–7.12 m (1H, Harom), 7.38–7.42 m (2H,
2
Harom), 7.66–7.63 m (2H, Harom), 7.65–7.72 m (6H,
Harom), 7.76 d (1H, Harom), 7.91 d (1H, Harom), 8.96 s
1H, Harom). C NMR spectrum, δ , ppm: 31.7, 115.5,
16.3, 118.2, 122.5, 123.1, 125.7, 126.8, 128.5, 129.3,
29.6, 129.9, 131.2, 133.8, 136.9, 138.5, 140.2, 149.1,
9. Sheng, R., Xu, Y., Hu, Ch., Zhang, J., Lin, X., Li, J.,
Yang, B., He, Q. and Hu, Y., Eur. J. Med. Chem., 2009,
vol. 44, p. 7.
13
(
1
1
1
C
https://doi.org/10.1016/j.ejmech.2008.03.003
+
10. Sindelar, R.D., Mott, J., Barfknecht, C.F., Arneric, S.P.,
Flynn, J.R., Long, J.P., and Bhatnagar, R.K., J. Med.
Chem., 1982, vol. 25, p. 858.
52.2, 192.3. Mass spectrum: m/z 369 [M + H] .
ACKNOWLEDGMENTS
https://doi.org/10.1021/jm00349a019
1
1. Gomez, N., Santos, D., Vazquez, R., Suescun, L.,
The authors are thankful to the Head, Department of
Mombru, A., Vermeulen, M., Finkielsztein, L.,
Shayo, C., Moglioni, A., Gambino, D., and Davio, C.,
ChemMedChem, 2011, vol. 6, p. 1485.
Chemistry for providing laboratory facilities. The authors
are also thankful to the Director, Central Facilities for
Research and Development (CFRD), Osmania University,
for providing IR and NMR spectral analysis.
https://doi.org/10.1002/cmdc.201100060
1
2. Charris, J.E., Lobo, G.M., Camacho, J., Ferrer, R.,
Barazarte, A., Domínguez, J.N., Gamboa, N.,
Rodrigues, J.R., and Angel, J.E., Lett. Drug Des.
Discovery, 2007, vol. 4, p. 49.
FUNDING
Financial assistance from DRS-SAP program to carry out
this work is highly appreciated.
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CONFLICT OF INTEREST
The authors declare that they have no conflict of interest.
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