Synthesis and anticonvulsant activity of 3a,4-dihydro-3Hindeno[1,2-c]pyrazole-2-carboxamide/carbothioamide analogues

Article abstract of DOI:10.3109/14756366.2012.663364

A series of fourteen 3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide/carbothioamide analogues were synthesized and evaluated for anticonvulsant activity according to the Antiepileptic Drug Development Programme (ADD) protocol. Some of the synthesized compounds showed significant activity in minimal clonic seizure model (6 Hz psychomotor seizure test). 3-(4-Fluorophenyl)-N-(4-bromophenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c] pyrazole-2-carboxamide (4c) was found to be the most active compound of the series showing 75% (3/4, 0.25-2.0 h) and 50% (2/4, 4.0 h) protection against minimal clonic seizure at 100 mg/kg without any toxicity. 3-(Pyridin-4-yl)-N-(4-chlorophenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide (4f) showed protection in maximal electroshock (MES) seizure and subcutaneous metrazol (scMET) seizure at 300 mg/kg.

Full text of DOI:10.3109/14756366.2012.663364

Journal of Enzyme Inhibition and Medicinal Chemistry, 2013; 28(3): 644–650
© 2013 Informa UK, Ltd.
ISSN 1475-6366 print/ISSN 1475-6374 online
DOI: 10.3109/14756366.2012.663364
ShoRt CommunICatIon
Synthesis and anticonvulsant activity of 3a,4-dihydro-3H-
indeno[1,2-c]pyrazole-2-carboxamide/carbothioamide
analogues
Mohamed Jawed Ahsan1,2, Habibullah Khalilullah1, James P. Stables3, and Jeyabalan Govindasamy1
1Department of Pharmaceutical Chemistry, New Drug Discovery Research, Alwar Pharmacy College, Alwar, India,
2Department of Pharmaceutical Sciences, Nims University, Jaipur, India, and 3Preclinical Pharmacology Section,
Epilepsy Branch, National Institute of Health, Bethesda, MD, USA
abstract
A
series of fourteen 3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide/carbothioamide analogues were
synthesized and evaluated for anticonvulsant activity according to the Antiepileptic Drug Development Programme
(ADD) protocol. Some of the synthesized compounds showed significant activity in minimal clonic seizure model (6 Hz
psychomotor seizure test). 3-(4-Fluorophenyl)-N-(4-bromophenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]
pyrazole-2-carboxamide (4c) was found to be the most active compound of the series showing 75% (3/4, 0.25–2.0
h) and 50% (2/4, 4.0 h) protection against minimal clonic seizure at 100 mg/kg without any toxicity. 3-(Pyridin-4-yl)-
N-(4-chlorophenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide (4f) showed protection in
maximal electroshock (MES) seizure and subcutaneous metrazol (scMET) seizure at 300 mg/kg.
Keywords: Pyrazolines, 6 Hz psychomotor seizure test, maximal electroshock seizure test, subcutaneous metrazole
seizure test, neurotoxicity
Introduction
activities including antiamoebic, anticonvulsant, antican-
cer, antimicrobial, anti-inflammatory, antiviral, antiar-
rhythmic,antidepressant,antidiabetic,antitubercularand
more5–13. Hence, it is worth to synthesize such compounds.
In the present investigation, we have focussed on the anti-
convulsant screening of 3a,4-dihydro-3H-indeno[1,2-c]
pyrazole-2-carboxamide/carbothioamide analogues.
Earlier, we have reported the antitubercular activity of
pyrazoline analogues14–16. e proposed pharmacophore
model contains three binding site for interaction with a
macromolecular complex in vivo (Figure 1).
Epilepsy is a common neurological disorder, affecting
1–2% world’s population1. In recent years, several new
drugs such as oxcarbazepine, lamotrigine, topiramate,
gabapentine and vigabatrin have been added as thera-
peutic agents for the treatment of epilepsy. However,
there is a significant group of patients (up to 30%) who
are resistant to the available antiepileptic drugs (AEDs).
Also most of the AEDs have dose related toxicity and idio-
syncratic side effects2,3. Hence, there is an urgent need to
develop new AEDs that lead to substantial benefit to the
patient population in the form of increase seizure con-
trol, increase tolerability, and better safety and pharma-
cokinetic properties. CPP 115 and vigabatrin were found
to be effective in 6 Hz minimal clonic seizure test in mice
at both 32 mA and 44 mA stimuli (3 s).4
Results and discussion
Chemistry
e 3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carbox-
amide/carbothioamide analogues (4a–n) described
in this study are shown in Table 1 and the reaction
sequence for the synthesis is summarized in Scheme 1.
Pyrazoline is an important class of heterocyclic
compounds, and were found to have various biological
Address for correspondence: Jeyabalan Govindasamy, New Drug Discovery Research, Department of Pharmaceutical Chemistry, Alwar
Pharmacy College, Alwar, Rajasthan 301 030, India. Tel: +91 8058790280. Fax: +91 144 5121120. E-mail: jeyabalan2001@gmail.com
(Received 01 December 2011; revised 31 December 2011; accepted 31 January 2012)
644

Synthesis and anticonvulsant activity of pyrazoline analogues 645
In the initial step, 5,6-dimethoxy-2,3-dihydro-1H-inden-
1-one (0.1 mol) and appropriate aromatic aldehydes (0.1
mol) in diluted methanolic sodium hydroxide solution
were stirred at room temperature giving the 2-substi-
tuted-5,6-dimethoxy-2,3-dihydro-1H-indene-1-one
derivatives (3a–f). In the subsequent step, 2-substituted-
the proposed structures. In general, the IR spectra of the
compounds afforded pyrazoline C=N stretching at 1560–
1573 cm−1, C-H deformation at 1362–1464 cm−1, C2-N1
stretching at 1135–1180 cm−1, and carbamoyl group N-H
stretching at 3330–3341 cm−1 and C=O stretching at 1645–
1681 cm−1 bands. In the Nuclear Magnetic Resonance
spectra (1H NMR), the signals of the respective protons
of the synthesized titled compounds were verified on the
basis of their chemical shift, multiplicities and coupling
constants in Dimethyl sulfoxide (DMSO) -d6. e spec-
tra showed multiplet at δ 3.03–3.35 ppm corresponding
to CH; a doublet at δ 3.33–3.45 ppm corresponding to
CH2 group; a singlet at δ 3.79–3.90 ppm corresponding
to OCH3 group; a doublet at 4.1–5.2 ppm corresponding
to CH; a broad singlet at δ 4.42–4.48 corresponding to
CONH2, a broad singlet at δ 4.92–4.96 corresponding to
5,6-dimethoxy-2,3-dihydro-1H-indene-1-one
deriva-
tives were treated with appropriate semicarbazides
furnishing the titled compounds (4a–n). e substituted
phenyl semicarbazides were synthesized as per the
reported method17. e yields of the titled compounds
were ranged from 66% to 84% after recrystallization with
absolute ethanol. e reactions were monitored by thin
layer chromatography (TLC) using benzene-acetone
(9:1) and the purity of the compounds was checked by
elemental analyses and mass spectroscopy. Both the
1
analytical and spectral data (IR, H NMR and MS) of all
the synthesized compounds were in full accordance with
Figure1. Suggestedpharmacophoremodelplayinganticonvulsant
activity.
Scheme 1. Synthetic protocol: (a) Reagents: MeOH/NaOH and
(b) Ar2NHCXNHNH2/AcOH.
Table 1. Physical constant of 3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide/carbothioamide.
+
Compound
Ar1
Ar2
Yield (%)
72
Mp (°C)
186
130
144
168
164
116
136
166
230
242
216
220
262
232
Rfa
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4-Pyridinyl-
4-Fluorophenyl-
0.56
0.79
0.71
0.45
0.54
0.81
0.88
0.85
0.55
0.69
0.68
0.52
0.55
0.67
2-Chlorophenyl-
4-Fluorophenyl-
3,4-Dimethoxyphenyl-
4-Methoxyphenyl-
4-Pyridinyl-
4-Bromophenyl-
68
4-Bromophenyl-
72
4-Bromophenyl-
88
4-Bromophenyl-
66
4-Chlorophenyl-
72
3,4-Dimethoxyphenyl-
Phenyl-
4-Chlorophenyl-
84
4-Chlorophenyl-
82
4-Pyridinyl-
3-Chloro-4-fluorophenyl-
72
2-Chlorophenyl-
3,4-Dimethoxyphenyl-
Phenyl-
H
H
H
H
H
68
78
72
3,4-Dimethoxyphenyl-
66
Phenyl-
76
aMobile phase: benzene-acetone (9:1).
© 2013 Informa UK, Ltd.

646 M. J. Ahsan et al.
by rotorod test. Ten compounds were screened in 6 Hz
psychomotor seizure test to identify their anticonvulsant
activity at five different time points viz. 0.25 h, 0.5 h, 1.0 h,
2.0 h and 4.0 h after i.p. administration in mice. e results
are shown in Table 2. e MES, scMET and neurotoxicity
screening results of four compounds are given in Table
3. Two of the compounds (4f and 4j) were also evaluated
in the MES test and toxicity after oral administration to
rat at 30 mg/kg dose. e results are shown in Table 4.
ree compounds (4a, 4g and 4h) were also screened in
in vitro hippocampal slice culture neuroprotection assay
(NP). Only four of the title compounds (4f, 4g, 4h and 4i)
showed protection in MES and scMET screens but were
associated with toxicity while some of the compounds
showed promising activity in 6 Hz psychomotor seizure
test without any toxicity at five different time points, i.e.
0.25 h, 0.5 h, 1.0 h, 2.0 h and 4.0 h. Like the MES test, the
CSNH2, multiplet at δ 6.98–8.39 ppm corresponding to
aromatic protons; broad singlet at δ 8.89–10.05 ppm cor-
responding to CONH (D2O exchangeable). e elemen-
tal analysis results were within 0.4% of the theoretical
values.
Anticonvulsant screening
All the compounds were evaluated for their anticonvulsant
activity according to the Antiepileptic Drug Development
Programme (ADD) protocol reported elsewhere18–24
.
Initially, the compounds were administered i.p. at doses of
30, 100 and 300 mg/kg in mice and activity was established
using the maximal electroshock (MES) induced seizure
and subcutaneous metrazole (scMET) induced seizure
to identify their anticonvulsant activity at two intervals
(0.5 and 4.0 h). Neurotoxicity or toxicity was observed by
minimal motor impairment which was measured in mice
Table 2. 6 Hz psychomotor seizure test and neurotoxicity of 3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide/carbothioamide
analogues.
Intraperitoneal injection in mice
Time (h) to peak effect (N/F)a
Toxicityb
1.0
Compound
ADD no.
433042
434074
434075
434076
434078
439068
439071
439072
439063
434090
434092
434093
434098
434099
0.25
1/4
0/4
3/4
1/4
4/4
4/4
3/4
1/4
0/4
1/4
4/4
2/4
1/4
1/4
0.5
1.0
2.0
4.0
0.25
1/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0.5
2.0
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
1/4
2/4
3/4
0/4
3/4
2/4
3/4
1/4
0/4
1/4
1/4
2/4
2/4
3/4
0/4
1/4
3/4
0/4
2/4
3/4
4/4
2/4
0/4
2/4
2/4
3/4
1/4
1/4
0/4
0/4
3/4
0/4
0/4
1/4
2/4
0/4
0/4
1/4
2/4
2/4
1/4
1/4
0/4
0/4
2/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
1/4
1/4
0/4
0/4
0/4c
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
2/4c
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
ADD no., Antiepileptic Drug Development Number (National Institute of Neurodegenerative Disorders and Stroke, National Institute of
Health, USA).
aN/F, number of animals active or toxic over the number tested at a dose of 100 mg/kg.
bTime interval in hours.
cClonic seizure.
Table 3. Anticonvulsant activity of 3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide analogues.
MES
scMET
Toxicity
Compound
ADD no.
439068
439071
439072
439063
–
0.5 h
300
300
300
300
30
4.0 h
300
–
0.5 h
300
–
4.0 h
0.5 h
300a
300
300c
300
100
100
–
4.0 h
300b
–
4f
4g
4h
4i
300
–
–
300
–
–
–
300
30
–
–
Phenytoind
Carbamazepined
Sodium valproated
–
–
100
300
–
–
30
100
–
100
300
300
–
–
–
ADD no., Antiepileptic Drug Development Number (National Institute of Neurodegenerative Disorders and Stroke, National Institute of
Health, USA); MES, maximal electroshock; scMET, subcutaneous metrazol.
aLoss of righting reflex.
bRespiratory failure.
cDeath.
dActivity reported25.
Journal of Enzyme Inhibition and Medicinal Chemistry

Synthesis and anticonvulsant activity of pyrazoline analogues 647
General procedure
Synthesis of 2-substituted-5,6-dimethoxy-2,3-dihydro-1H-
indene-1-one (3a–f)
Table 4. Evaluation of compound, 4f and 4j in the MES test and
toxicity after oral administration to rat.
Oral administration to rat (30 mg/kg)
Compound
MES (4f)
Toxicity
0.25 h
0/4
0.5 h
0/4
0/4
2/4
0/4
1.0 h
2/4
0/4
2/4
0/4
2.0 h
1/4
0/4
2/4
0/4
4.0 h
0/4
0/4
1/4
0/4
5,6-dimethoxy-2,3-dihydro-1H-inden-1-one (0.001
mol) with appropriate aldehyde (0.001 mol) in diluted
methanolic sodium hydroxide solution was stirred under
room temperature for 4 h. e resulting solution was
allowed to stand overnight and then the reaction mixture
was poured into cold water and neutralized with dilute
HCl. e solid was filtered, dried and recrystallized with
ethanol furnished the 2-substituted-5,6-dimethoxy-2,3-
dihydro-1H-indene-1-one (3a–f).
0/4
MES (4j)
Toxicity
1/4
0/4
MES, maximal electroshock.
minimal clonic seizure (6 Hz) test is used to assess a com-
pound’s efficacy against electrically induced seizures but
at a lower frequency (6 Hz) and longer duration of stimula-
tion (3 s) to identify potential AEDs, which are ineffective
in MES and scMET screen but still have anticonvulsant
activities in vivo. Among the title compounds 4k, 4l, 4e,
4f, 4g and 4c were found to have moderate to good activ-
ity in 6 Hz psychomotor seizure test. e compound, 4c
was found to be the most promising compound of the
series showing 75% (3/4, 0.25–2.0 h) and 50% (2/4, 4.0 h)
protection without any toxicity. e compound 4g showed
75% (3/4, 0.25–0.5 h), 100% (4/4, 1.0 h) and 50% (2/4, 2.0
h) protection. e compound 4f showed 100% (4/4, 0.25
h), 75% (3/4, 1.0 h) and 50% (2/4, 0.5 h) protection. e
compound 4e showed 100% (4/4, 0.25 h), 75% (3/4, 0.5 h)
and 50% (2/4, 1.0 h) protection. e compounds 4k and
4l were nearly equipotent. e compound 4h showed
25% (1/4 0.25–0.5 h) and 50% (2/4, 1.0 h) protection. e
compounds, 4a, 4d and 4i showed absence of activity in
50% mice population. e compound, 4j showed 50%
(2/4, 0.5–2.0 h) and 25% (0.25 and 4.0 h) protection while
compound 4f showed 50% (2/4, 1.0 h) and 25% (1/4, 2.0
h) in MES screen after oral administration in rat at dose 30
mg/kg without any toxicity. e in vitro hippocampal slice
culture neuroprotection assay (Test 76) of compounds 4a,
4g and 4h showed no neuroprotection against either kai-
nic acid (KA) or N-methyl-D-aspartate (NMDA) induced
cytotoxicity. We have observed that, the compound with
3-aryl substitution with 4-fluorophenyl, 3,4-dimethoxy-
phenyl, 4-pyridinyl, 4-methoxyphenyl and phenyl group
showed good to moderate activity.
Synthesis of 3-substituted-N-aryl-6,7-dimethoxy-3a,4-
dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide
analogues (4a–n)
2-substituted-5,6-dimethoxy-2,3-dihydro-1H-indene-1-
one (3a–g) (0.01 mol) and substituted phenyl semicarba-
zide (0.01 mol) were refluxed in 20 mL glacial acetic acid
for 12 h. e excess of solvent was removed under reduced
pressure and then the reaction mixture was poured into
the crushed ice. e solid mass was filtered dried and
recrystallized with ethanol furnished the 3-substituted-
N-aryl-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]
pyrazole-2-carboxamide analogues.
3-(Pyridin-4-yl)-N-(4-fluorophenyl)-6,7-dimethoxy-3-
a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide
(4a) IR: (KBr) cm−1: 3331 (NH), 1680 (C=O), 1563 (C=N),
1142 (C-N), 788 (C-F). 1H NMR (300MHz, DMSO-d6):
δ 3.29–3.33 (1H, m, CH), 3.42–3.45 (2H, d, J = 9.0 Hz,
CH2), 3.80 (3H, s, OCH3), 3.82 (3H, s, OCH3), 5.2 (1H, d, J
= 6.1 Hz, CH), 6.96–8.23 (10H, m, Ar), 8.91 (1H, s, CONH);
m/z = 432 (M+), 433 (M+1)+.
3-(2-Chlorophenyl)-N-(4-bromophenyl)-6,7-dime-
thoxy-3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-car-
boxamide (4b) IR: (KBr) cm−1: 3335 (NH), 1685 (C=O),
1
1567 (C=N), 1151 (C-N), 767 (C-Cl). H NMR (300MHz,
DMSO-d6): δ 3.03–3.05 (1H, m, CH), 3.33–3.35 (2H, d, J =
6.0 Hz, CH2), 3.84 (3H, s, OCH3), 3.90 (3H, s, OCH3), 4.04
(1H, d, J = 6.4 Hz, CH), 7.23–7.81 (10H, m, Ar), 10.06 (1H,
s, CONH); m/z = 526 (M+), 527 (M+1)+.
3-(4-Fluorophenyl)-N-(4-bromophenyl)-6,7-
dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-
carboxamide (4c) IR: (KBr) cm−1: 3341 (NH), 1645 (C=O),
Experimental
All chemicals were supplied by E. Merck (Darmstadt,
Germany) and S. D. Fine Chemicals (Mumbai, India).
Melting points were determined by open tube capillary
method and are uncorrected. e completion of the reac-
tions was monitored by TLC plates (silica gel G) using
eluants benzene-acetone (9:1), the spots were identified
by iodine vapours or UV light. IR spectra were obtained
on a Schimadzu 8201 PC, FT-IR spectrometer (KBr pel-
1
1573 (C=N), 1381 (CH), 1180 (C-N), 786 (C-F). H NMR
(300MHz, DMSO-d6): δ 3.23–3.31 (1H, m, CH), 3.39–3.43
(2H, d, J = 12.0 Hz, CH2), 3.81 (6H, s, OCH3), 5.2 (1H, d,
J = 6.1 Hz, CH), 7.02–8.39 (10H, m, Ar), 8.96 (1H, s, CONH);
m/z = 510 (M+), 511 (M+1)+.
3-(3,4-Dimethoxyphenyl)-N-(4-bromophenyl)-6,7-
dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-
carboxamide (4d) IR: (KBr) cm−1: 3339 (NH), 1678 (C=O),
1556 (C=N), 1141 (C-N). 1H NMR (300MHz, DMSO-d6): δ
3.04–3.07 (1H, m, CH), 3.35–3.36 (2H, d, J = 3.0 Hz, CH2),
3.83 (6H, s, OCH3), 3.91 (6H, s, OCH3), 4.02 (1H, d, J = 6.4
Hz, CH), 7.06–7.56 (9H, m, Ar), 10.06 (1H, s, CONH); m/z
= 552 (M+), 553 (M+1)+.
1
lets). H NMR spectra were recorded on a Bruker AC
300 MHz spectrometer using tetramethylsilane (TMS) as
internal standard in DMSO. Mass spectra were recorded
on a Bruker Esquire LCMS using ESI and elemental anal-
yses were performed on Perkin-Elmer 2400 Elemental
Analyzer.
© 2013 Informa UK, Ltd.

648 M. J. Ahsan et al.
3-(4-Methoxyphenyl)-N-(4-bromophenyl)-6,7-dime-
thoxy-3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carbox-
amide (4e) IR: (KBr) cm−1: 3334 (NH), 1681 (C=O), 1561
(C=N), 1151 (C-N). 1H NMR (300MHz, DMSO-d6): δ
3.03–3.05 (1H, m, CH), 3.33–3.34 (2H, d, J = 6.2 Hz, CH2),
3.83 (6H, s, OCH3), 3.90 (3H, s, OCH3), 3.96 (1H, d, J = 6.4
Hz, CH), 5.2 (1H, d, J = 6.1 Hz, CH), 7.05–7.73 (10H, m,
Ar), 10.05 (1H, s, CONH); m/z = 522 (M+), 523 (M+1)+.
3-(Pyridin-4-yl)-N-(4-chlorophenyl)-6,7-dimethoxy-
3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide
(4f) IR: (KBr) cm−1: 3334 (NH), 1680 (C=O), 1563 (C=N),
(2H, d, J = 6.0 Hz, CH2), 3.80 (3H, s, OCH3), 3.82 (3H, s,
OCH3), 5.1 (1H, d, J = 6.2 Hz, CH), 5.48 (2H, s, CONH2),
7.08–7.72 (7H, m, Ar); m/z = 337 (M+).
3-(3,4-Dimethoxyphenyl)-6,7-dimethoxy-3a,4-di-
hydro-3H-indeno[1,2-c]pyrazole-2-carbothioamide (4m)
IR: (KBr) cm−1: 3334 (NH), 1563 (C=N), 1271 (C=S), 1135
(C-N). 1H NMR (300MHz, DMSO-d6): δ 3.23–3.24 (1H, m,
CH), 3.36–3.38 (2H, d, J = 6.0 Hz, CH2), 3.81 (6H, s, OCH3),
3.83 (6H, s, OCH3), 5.2 (1H, d, J = 6.2 Hz, CH), 5.89 (2H, s,
CSNH2), 7.12–7.76 (5H, m, Ar); m/z = 413 (M+).
3 - P h e ny l - 6 , 7 - d i m e t h ox y - 3 a , 4 - d i hy d ro - 3 H-
indeno[1,2-c]pyrazole-2-carbothioamide (4n) IR: (KBr)
cm−1: 3336 (NH), 1562 (C=N), 1270 (C=S), 1135 (C-N).
1H NMR (300MHz, DMSO-d6): δ 3.21–3.23 (1H, m, CH),
3.34–3.36 (2H, d, J = 6.0 Hz, CH2), 3.79 (3H, s, OCH3),
3.81 (3H, s, OCH3), 5.1 (1H, d, J = 6.1 Hz, CH), 5.90 (2H, s,
CONH2), 7.18–7.82 (7H, m, Ar); m/z = 453 (M+).
1
1144 (C-N), 767 (C-Cl). H NMR (300MHz, DMSO-d6): δ
3.29–3.35 (1H, m, CH), 3.41–3.43 (2H, d, J = 6.0 Hz, CH2),
3.81 (3H, s, OCH3), 3.83 (3H, s, OCH3), 5.1 (1H, d, J = 6.4
Hz, CH), 6.98–8.31 (10H, m, Ar), 8.89 (1H, s, CONH); m/z
= 448 (M+), 449 (M+1)+.
3-(3,4-Dimethoxyphenyl)-N-(4-chlorophenyl)-6,7-
dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-
carboxamide (4g) IR: (KBr) cm−1: 3336 (NH), 1685 (C=O),
Biology
MES seizure
1
1565 (C=N), 1174 (C-N). H NMR (300 MHz, DMSO-d6):
δ 3.29–3.33 (1H, t, CH), 3.40–3.44 (2H, d, J = 6.7 Hz, CH2),
3.80 (6H, s, OCH3), 3.83 (6H, s, OCH3), 5.2 (1H, d, J = 6.4
Hz, CH), 6.78–8.19 (9H, m, Ar), 9.39 (1H, s, CONH); m/z =
437 (M+), 438 (M+1)+.
e anticonvulsant evaluations were undertaken by the
National Institute of Health, using their reported proce-
dures. For all tests based on MES convulsions, 60Hz of
alternating current (50 mA in mice and 150 mA in rat) was
delivered for 0.2 s by corneal electrodes which have been
primed with an electrolyte solution containing anaes-
thetic agent (0.5% tetracaine HCl). e mice were tested
at various (0.5 and 4 h) intervals following doses of 30, 100
and 300 mg/kg of test compound given by i.p. injection
of a volume of 0.01 mL/g. An animal is considered “pro-
tected” from MES-induced seizures upon abolition of the
hind limb tonic extensor component of the seizure.
3-Phenyl-N-(4-chlorophenyl)-6,7-dimethoxy-3a,4-
dihydro-3H-indeno[1,2-c]pyrazole-2-carboxamide (4h)
IR: (KBr) cm−1: 3331 (NH), 1681 (C=O), 1565 (C=N),
1
1144 (C-N), 766 (C-Cl). H NMR (300MHz, DMSO-d6): δ
3.27–3.31 (1H, m, CH), 3.41–3.43 (2H, d, J = 6.0 Hz, CH2),
3.81 (3H, s, OCH3), 3.83 (3H, s, OCH3), 5.1 (1H, d, J = 6.3
Hz, CH), 6.98–8.33 (11H, m, Ar), 9.49 (1H, s, CONH); m/z
= m/z = 447 (M+), 448 (M+1)+.
3-(Pyridin-4-yl)-N-(3-chloro-4-fluorophenyl)-6,7-
dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]pyrazole-2-
carboxamide (4i) IR: (KBr) cm−1: 3331 (NH), 1678 (C=O),
1560 (C=N), 1144 (C-N), 789 (C-F), 789 (C-F), 766 (C-Cl).
1H NMR (300MHz, DMSO-d6): δ 3.18–3.21 (1H, m, CH),
3.33–3.35 (2H, d, J = 6.0 Hz, CH2), 3.81 (3H, s, OCH3), 3.83
(3H, s, OCH3), 4.02 (1H, d, J = 6.7 Hz, CH), 7.22–7.99 (9H,
m, Ar), 10.03 (1H, s, CONH); m/z = 467 (M+), 468 (M+1)+.
3-(2-Chlorophenyl)-6,7-dimethoxy-3a,4-dihydro-3H-
indeno[1,2-c]pyrazole-2-carboxamide (4j) IR: (KBr) cm−1:
3337 (NH), 1685 (C=O), 1561 (C=N), 1151 (C-N). 1H NMR
(300MHz, DMSO-d6): δ 3.22–3.24 (1H, m, CH), 3.33–3.35
(2H, d, J = 6.0 Hz, CH2), 3.80 (3H, s, OCH3), 3.82 (3H, s,
OCH3), 4.9 (1H, d, J = 6.3 Hz, CH), 5.46 (2H, s, CONH2),
7.08–7.68 (6H, m, Ar); m/z = 372 (M+), 373 (M+1)+.
Subcutaneous metrazole-induced seizure (scMET)
Subcutaneous injection of the convulsant metrazol pro-
duces clonic seizures in laboratory animals. e scMET
test detects the ability of a test compound to raise the
seizure threshold of an animal and thus protect it from
exhibiting a clonic seizure. Animals were pretreated with
various doses of the test compound (in a similar man-
ner to the MES test, although a dose of 50 mg/kg (p.o.) is
the standard for scMET). An animal is considered “pro-
tected” from scMET induced seizures upon absence of
episode of clonic spasms, approximately 3–5 s, of the fore
and/or hindlimbs, jaws or vibrissae.
6 Hz psychomotor seizure test
Some clinically useful AEDs are ineffective in the stan-
dard MES and scMET tests but still have anticonvulsant
activities in vivo. In order to identify potential AEDs
with this profile, compounds were tested in the 6 Hz or
“psychomotor” test (minimal clonic seizure). e title
compounds were tested in the minimal clonic seizure
test at dose of 100 mg/kg to four mice. Like the MES test,
the minimal clonic seizure (6 Hz) test is used to assess a
compound’s efficacy against electrically induced seizures
but uses a lower frequency (6 Hz) and longer duration of
stimulation (3 s).
3-(3,4-Dimethoxyphenyl)-6,7-dimethoxy-3a,4-di-
hydro-3H-indeno[1,2-c]pyrazole-2-carboxamide (4k) IR:
(KBr) cm−1: 3330 (NH), 1678 (C=O), 1565 (C=N), 1135
(C-N). 1H NMR (300MHz, DMSO-d6): δ 3.22–3.25 (1H, m,
CH), 3.33–3.35 (2H, d, J = 6.0 Hz, CH2), 3.79 (6H, s, OCH3),
3.83 (6H, s, OCH3), 5.2 (1H, d, J = 6.3 Hz, CH), 5.44 (2H, s,
CONH2), 7.09–7.62 (5H, m, Ar); m/z = 497 (M+).
3 - P h e ny l - 6 , 7 - d i m e t h ox y - 3 a , 4 - d i hy d ro - 3 H-
indeno[1,2-c]pyrazole-2-carboxamide (4l) IR: (KBr) cm−1:
3333 (NH), 1675 (C=O), 1564 (C=N), 1135 (C-N). 1H NMR
(300MHz, DMSO-d6): δ 3.22–3.24 (1H, m, CH), 3.34–3.36
Journal of Enzyme Inhibition and Medicinal Chemistry

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Declaration of interest
e authors declare no conflict of interest.
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