Synthesis and anticonvulsant evaluation of 4-(4-alkoxylphenyl)-3-ethyl-4H-1,2,4-triazoles as open-chain analogues of 7-alkoxyl-4,5-dihydro[1,2,4]triazolo[4,3-a]quinolines

Article abstract of DOI:10.1016/j.bmc.2007.08.004

A series of 4-(4-alkoxylphenyl)-3-ethyl-4H-1,2,4-triazole derivatives was synthesized as open-chain analogues of 7-alkoxyl-4,5-dihydro[1,2,4]triazolo[4,3-a]quinolines. Their anticonvulsant activities were evaluated by the maximal electroshock test (MES te

Full text of DOI:10.1016/j.bmc.2007.08.004

Bioorganic & Medicinal Chemistry 15 (2007) 6775–6781
Synthesis and anticonvulsant evaluation of 4-(4-alkoxylphenyl)-
3-ethyl-4H-1,2,4-triazoles as open-chain analogues of
7-alkoxyl-4,5-dihydro[1,2,4]triazolo[4,3-a]quinolines
Jing Chen,a,b Xian-Yu Sun,b Kyu-Yun Chai,c Jin-Seok Lee,c
Mi-Sun Songc and Zhe-Shan Quana,b,
*
aKey Laboratory of Organism Functional Factors of the Changbai Mountain, Yanbian University, Ministry of Education,
Yanji, Jilin 133002, China
bCollege of Pharmacy, Yanbian University, Yanji, Jilin 133000, China
cDepartment of Chemistry, Wonkwang University, Iksan 570-749, Republic of Korea
Received 17 June 2007; revised 31 July 2007; accepted 1 August 2007
Available online 10 August 2007
Abstract—A series of 4-(4-alkoxylphenyl)-3-ethyl-4H-1,2,4-triazole derivatives was synthesized as open-chain analogues of 7-alk-
oxyl-4,5-dihydro[1,2,4]triazolo[4,3-a]quinolines. Their anticonvulsant activities were evaluated by the maximal electroshock test
(MES test) and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). MES test showed that 3-ethyl-4-(4-
octyloxyphenyl)-4H-1,2,4-triazole 3q was found to be the most potent with ED50 value of 8.3 mg/kg and protective index
(PI = TD50/ED50) value of 5.5, but compound 3r, 3-ethyl-4-(4-octyloxyphenyl)-4H-1,2,4-triazole, exhibited better PI value of
9.3, which was much greater than PI value of the prototype drug phenytoin. For explanation of the possible mechanism of
action, the compound 3r was tested in pentylenetetrazole test, isoniazid test, thiosemicarbazide test, 3-mercaptopropionic acid
and strychnine test.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
In our previous work, a series of derivatives of 6-alkoxy-
3,4-dihydro-1H-quinoline-2-ones were first found to
have anticonvulsant activities, among which 6-benzyl-
oxy-3,4-dihydro-1H-quinoline-2-one showed the stron-
gest activity with an ED50 value of 29.6 mg/kg in the
maximal electroshock test (MES) and a TD50 value
greater than 300 mg/kg.6 Introduction of triazole ring
to the first and second position of this 6-benzyloxy-
3,4-dihydro-1H-quinoline-2-one caused a remarkable
increase in the anticonvulsant activity, such as 7-benzyl-
Epilepsy, a ubiquitous disease characterized by recur-
rent seizures, inflicts more than 60 million people world-
wide according to epidemiological studies.1 For epilepsy
treatment, nearly 95% of clinically available drugs were
approved before 1985 and they could provide satisfac-
tory seizure control for 60–70% of patients. These drugs,
however, also cause notable adverse side effects such as
drowsiness, ataxia, gastrointestinal disturbance, hepato-
toxicity and megaloblastic anaemia,2–4 and even life-
threatening conditions.5 Research to find more effective
and safer antiepileptic drugs is, therefore, imperative
and challenging in medicinal chemistry.
oxyl-4,5-dihydro[1,2,4]triazolo[4,3-a]quinoline
(com-
pound 1a), which showed ED50 values of 17.3 and
24 mg/kg in the MES and the sc-PTZ tests, respectively.7
Another derivative in the group of 7-alkoxy-4,5-dihy-
dro[1,2,4]triazolo[4,3-a]quinoline,
7-(4-fluorobenzyl-
oxyl)-4,5-dihydro[1,2,4]triazolo[4,3-a]quinoline (compound
1b), showed ED50 values of 11.1 and 6.7 mg/kg,
protective index (PI = TD50/ED50) values of 4.6 and
8.1 in the MES and the pentylenetetrazole tests,
respectively, and thus demonstrated comparable
anticonvulsant potency to that of phenobarbital in the
corresponding tests.8
Keywords: 1,2,4-Triazole; Anticonvulsant activity; Open-chain ana-
logue; Maximal electroshock test; Neurotoxicity.
*
Corresponding author. Tel.: +86 433 2660606; fax: +86 433
2660568; e-mail: zsquan@ybu.edu.cn
0968-0896/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2007.08.004

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J. Chen et al. / Bioorg. Med. Chem. 15 (2007) 6775–6781
F
O
O
R
O
O
R
B
A
N
N
N
N
N
N
N
N
C
N
N
N
N
1a
1b
1
3a-3s
Analyzing the relationship of anticonvulsant activity
and the structure of 7-alkoxyl-4,5-dihydro[1,2,4] triazol-
o[4,3-a]quinoline (1), it was found that triazole ring C
may be the main structure combined with receptor, aro-
matic ring A and 7-alkoxyl enhanced the hydrophobic
ability of target compounds, thus make them more per-
meable to the blood–brain barrier and enhance anticon-
vulsant activity. So we thought that the presence of A
and C ring was essential structure for the anticonvulsant
activity. In this paper, we designed and prepared a series
of 4-(4-alkoxylphenyl)-3-ethyl-4H-1,2,4-triazole deriva-
tives with ring B opened and pseudocycles’ structure
existing as open-chain analogue of 7-alkoxy-4,5-dihy-
dro[1,2,4]triazolo[4,3-a]quinoline. The hypothesis was
that a rotatable triazole ring may have higher affinity
for the receptor and enhance their anticonvulsant activ-
ity. The new compounds were evaluated as anticonvul-
sant agents in experimental epilepsy models, i.e.,
maximal electroshock (MES) induced seizure in mice.
The rotarod assay was performed in mice to evaluate
the neurotoxicity of the compounds. For explaining
the possible mechanism of action, the compound
3-ethyl-4-(4-octyloxyphenyl)-4H-1,2,4-triazole 3q was
tested in pentylenetetrazole, isoniazid, thiosemicarba-
zide, 3-Mercaptopropionic Acid and strychnine induced
test.
pounds exhibited anticonvulsant activity ED50 at a
dose of 30 mg/kg.
First, comparing the anticonvulsant activity of open-
chain analogues and the leading triazolo[4,3-a] quinoline
compounds, among these substituted-phenoxyl deriva-
tives we could see the following activity order, 1a > 3a,
1b > 3b and 1c > 3j; although the anticonvulsant activity
is comparatively weaker than the leading compound, the
open-chain analogues 3a–l possess lower neurotoxicity
ranging from 61.5 to 189.3 mg/kg than leading
compounds 1a–d ranging from 54.5 to 65.8 mg/kg.
Among these alkoxyl derivatives, the most potent com-
pound 3q (3-ethyl-4-(4-octyloxyphenyl)-4H-1,2,4-triaz-
oles) exhibited significantly enhanced activity with
ED50 value of 8.3 mg/kg than compound 1d with ED50
value of 13.5 mg/kg, especially, the alkoxyl open-chain
derivatives also possess remarkable lower neurotoxicity
than the leading compound.
Analyzing the activities of synthesized compounds 3a–s,
the following SAR was gained. The pharmacology result
revealed that atom Cl gave more contribution to the
anticonvulsant activity than atom F, and the position
of atom Cl on the phenyl ring greatly influenced the
anticonvulsant activity, the activity order being 2-
Cl > 2,6-Cl2 > 4-Cl > 3-Cl. The 4-Cl derivative 3f exhib-
ited weaker activity with ED50 value of 19.7 mg/kg than
2-Cl derivative 3 g with ED50 value of 13.2 mg/kg, but
compound 3f exhibited the lowest neurotoxicity with
TD50 value of 136.9 mg/kg, which was the safest among
all target compounds with PI value of 10.4 and better
than the reference drug phenytoin. But no visible differ-
ence was found between compounds with atom F substi-
tuted on different position of the phenyl ring.
Comparing the influence of electron–donor group to
anticonvulsant activity, their contribution order is
4-OCH3 > 3,4-OCH2O– > 4-CH3.
2. Results and discussion
2.1. Synthesis
There are many methods reported to synthesize triazole
derivatives. An efficient one-pot, three-component syn-
thesis of substituted-1,2,4-triazoles has been developed
by Michael,9 utilizing a wide range of substituted pri-
mary amines, acyl hydrazines and dimethylformamide
dimethyl acetal. In this paper, intermediate compound
2 was prepared by the Michael method, and then
compound 2 reacted with appropriate alkyl halide to
produce target compounds 4-(4-alkoxylphenyl)-3-ethyl-
4H-1,2,4-triazoles (3a–s) (Scheme 1).
Length of the alkyl chain appeared to have a direct
impact on anticonvulsant activity of the 4-alkyloxyl
derivatives. As shown in Table 1, derivative 3q was
the most active compound in seven alkoxyl-substituted
compounds, suggesting that appropriate length of the
alkyl chain at C-7 position, or appropriate lipophilic
property, was essential to the anticonvulsant activity
of these compounds. Compound 3q, with ED50 value
of 8.3 mg/kg, was better than Phenytoin in anti-MES
activity. In addition, compound 3r, with ED50 of
8.8 mg/kg and lower neurotoxicity and thus a high
PI value of 9.3, could also be considered a potentially
useful and safe therapeutic. And the anticonvulsant
activity decreased obviously when alkyl chain number
2.2. Pharmacology
The anticonvulsant activity against MES-induced sei-
zure and neurotoxicity TD50 of target compounds are
shown in Table 1, and also the anticonvulsant activities
and neurotoxicity of reference compounds 1a–e are list
to show the activity transformation tendency. As shown
in Table 1, all open-chain compounds exhibited strong
potency at a dose of 30 mg/kg against MES induced sei-
zure, but in the former paper,8 only five target com-

J. Chen et al. / Bioorg. Med. Chem. 15 (2007) 6775–6781
6777
RO
HO
HO
O
CMe
CMe
CH3CN
RX
N
+
NH2
+
°
C
min
50
N
N
N
N
N
NH2
N
H
N
2
3a-3s
Scheme 1. The synthesis route of compounds 3a–s.
Table 1. Quantitative anticonvulsant data in mice (test drug administered ip)
RO
O
R
B
A
N
N
N
N
C
N
N
1a-1e
3a-3s
a
b
Compound
R
MES, ED50
TD50
PI (TD50/ED50)
1a
1b
1c
–CH2C6H5
17.3 (14.8–20.4)c
11.8 (10.9–12.9)
20.5 (17.0–24.5)
13.5 (11.5–15.8)
20.8 (16.6–26.0)
22.8 (18.2–28.5)
21.2 (17.0–26.5)
22.8 (18.2–28.5)
15.8 (12.6–19.7)
19.7 (15.8–24.6)
13.2 (10.6–16.5)
27.4 (21.9–34.2)
15.8 (12.6–19.7)
25.5 (20.4–31.9)
15.8 (12.6–19.7)
20.1 (16.1–25.1)
>100
61.4 (51.4–73.3)
54.5 (46.1–64.5)
3.5
4.6
3.2
2.2
4.9
4.0
2.9
4.0
6.9
10.4
5.8
4.0
8.3
4.0
8.3
9.4
—
–CH2C6H5(p-F)
–CH2C6H5(p-CH3)
–n-C6H13
65.8 (55.6–77.7)
30.3 (25.5–36.0)
1d
3a
3b
3c
–CH2C6H5
101.8 (81.5–127.2)
91.3 (73.1–114.1)
61.5 (49.2–76.9)
–CH2C6H5(p-F)
–CH2C6H5(o-F)
–CH2C6H5(m-F)
–CH2C6H5(2,6-F2)
–CH2C6H5(p-Cl)
–CH2C6H5(o-Cl)
–CH2C6H5(m-Cl)
–CH2C6H5(2,6-Cl2)
–CH2C6H5(p-CH3)
–CH2C6H5(p-OCH3)
–CH2C6H5(3,4-OCH2O–)
–C2H5
3d
3e
91.2 (73.0–114.0)
109.0 (87.2–136.2)
136.9 (109.6–171.1)
76.1 (60.9–95.1)
3f
3g
3h
3i
109.5 (87.6–136.8)
131.5 (105.2–164.3)
101.0 (80.8–126.2)
131.5 (105.2–164.3)
189.3 (151.4–236.4)
3j
3k
3l
d
3m
3n
3o
3p
3q
3r
—
—
–n-C3H7
–n-C4H9
>100
>100
—
—
—
–n-C6H13
–n-C7H15
13.2 (10.6–16.5)
8.3 (6.6–10.4)
8.8 (7.04–11.0)
>100
62.1 (49.7–77.6)
45.6 (36.5–57.0)
82.2 (65.8–102.7)
—
4.7
5.5
9.3
—
–n-C8H17
–n-C12H25
3s
Phenytoin
9.5 (8.1–10.4)
65.5
6.9
a The dose measured in mg/kg.
b Minimal neurotoxicity was determined by the rotarod test 30 min after the tested compounds were administrated.
c The 95% confidence limits.
d Not tested.
lengthened to 12, even showing no activity at a dose
of 100 mg/kg.
against the seizures induced by pentylenetetrazole, isoni-
azid, 3-mercaptopropionic acid and thiosemicarbazide
with ED50 values of 26.4, 38.1, 31.7 and 22.8 mg/kg,
respectively.
As a result of first test, compound 3r showed strong
anticonvulsant activity and the best PI value in MES
test, so it was then selected for further investigations
against seizures induced by pentylenetetrazole, 3-merca-
ptopropionic acid, thiosemicarbazide, isoniazid and
strychnine to prove its anticonvulsant activity and spec-
ulate about the possible mechanism of anticonvulsant
action. As shown in Table 2, compound 3r was effective
Pentylenetetrazole and isoniazid have been reported to
produce seizures by inhibiting c-aminobutyric acid
(GABA) neurotransmission.10,11 GABA is the main
inhibitory neurotransmitter substance in the brain, and
is widely implicated in epilepsy. Inhibition of GABAer-
gic neurotransmission or activity has been shown to
Table 2. Anticonvulsant activity of compound 3r in chemically induced seizures tests
Compound
Pentylenetetrazole
Isoniazid
Thiosemicarbazide
3-Mercaptopropionic acid
22.8
Strychnine
a
—
3r
26.4
38.1
31.7
a Compound 3r failed to control the seizure induced by Strychnine at the dose of 300 mg/kg.

6778
J. Chen et al. / Bioorg. Med. Chem. 15 (2007) 6775–6781
promote and facilitate seizures,12 while enhancement of
GABAergic neurotransmission is known to inhibit or
attenuate seizures. The findings of the present study tend
to suggest that the derivatives in this study might have
inhibited or attenuated pentylenetetrazole-induced and
isoniazid-induced seizures in mice by enhancing GAB-
Aergic neurotransmission.
a reflux condenser. The reaction mixture was warmed to
50 ꢁC for 30 min and then p-aminophenol 5.45 g
(50 mmol) in acetonitrile (10 ml) was added and also
added acetic acid (3 ml) as a catalyst at the same time.
The reaction temperature was raised to 120 ꢁC for 3 h.
After being cooled and concentrated, the product was
recrystallized in ice-water. The precipitate was collected
through filtration and dried in a vacuum to produce the
crude product with a moderate yield and pure enough
for the next stage.
3-Mercaptopropionic acid and thiosemicarbazide were
seen as the competitive inhibitor of GABA synthesis en-
zyme glutamate decarboxylase (GAD), inhibiting the
synthesis of GABA to decrease the GABA level in the
brain.13,17 The moderate antagonism of 3-mercapto-
propionic acid-induced and thiosemicarbazide-induced
seizures suggests that the compound 3r might activate
GAD or inhibit aminotransferase (GABA-T) in the
brain.
1
Yield, 93%, mp 206–208 ꢁC. H NMR (CDCl3) d: 1.27
(t, J = 7.5 Hz, 3H, –CH3), 2.74 (q, J = 7.5 Hz, 2H,
–CH2), 7.00 (d, 2H, J = 8.5 Hz, Ar-H),7.10 (d, 2H,
J = 8.5 Hz, Ar-H), 8.40 (s, 1H, triazole-H). IR (KBr)
cmÀ1: 3405 (OH), 1593 (C@N), 1286 (CAN), 1190
(NAN). MS m/z: 190 (M+1). Anal. Calcd for
C17H17N3O: C, 63.48; H, 5.86; N, 22.21. Found: C,
63.27; H, 6.08; N, 21.95.
As shown in Table 2, compound 3r failed to protect ani-
mals from seizure induced by Strychnine at the dose of
300 mg/kg. It is known that Strychnine directly antago-
nizes the inhibitory spinal reflexes of glycine,14 so the re-
sult suggesting that compound 3r could not influence
glycine system.
4.1.2. General procedure for the synthesis of 4-(4-
alkoxylphenyl)-3-ethyl-4H-1,2,4-triazoles (3a–s). A mix-
ture of compound 2 1.9 g (10 mmol) and alkyl halide
(11 mmol) in 50 ml anhydrous ethanol was refluxed for
4 h in the presence of NaOH 0.4 g (10 mmol). After
the solvent was removed, the residue was dissolved in
dichloromethane (60 ml) and washed with water (2·
30 ml), the dichloromethane layer was dried over
MgSO4, and then the solvent was removed under re-
duced pressure. A pale yellow solid or oil was obtained
after being purified by silica gel chromatography (ethyl
acetate/methanol, 10:1). The yield, melting point and
spectral data of each compound are given below.
3. Conclusions
In conclusion, 4-alkoxyl-3-ethyl-4-H-1,2,4-triazoles, the
open-chain analogues of 7-alkoxyl-4,5-dihydro-[1,2,4]-
triazolo[4,3-a]quinolines, exhibited remarkable anticon-
vulsant activity and lower neurotoxicity. Especially,
compound 3r produced significant antagonism activity
against seizures induced by pentylenetetrazole, 3-merca-
ptopropionic acid, thiosemicarbazide and Isoniazid,
suggested that the compound 3r might have effects on
GABAergic neurotransmission and activate glutamate
decarboxylase (GAD) or inhibit (GABA)–a-oxoglutar-
ate aminotransferase (GABA-T) in the brain.
4.1.2.1. 3-Ethyl-4-(4-benzyloxyphenyl)-4H-1,2,4-tria-
zole (3a). Yield = 78.8%, mp 102–105 ꢁC. 1H NMR
(CDCl3) d: 1.19 (t, J = 7.5 HZ, 3H, –CH3), 2.67 (q,
J = 7.5 Hz, 2H, –CH2), 5.11 (s, 2H, OCH2), 7.15 (d,
2H, J = 8.3 Hz, Ar-H), 7.29–7.37 (m, 5H, Ar-H), 7.43
(d, 2H, J = 8.3 Hz, Ar-H), 8.45 (s, 1H, triazol-H). IR
(KBr) cmÀ1: 1606 (C@N), 1292 (CAN), 1242, 1031
(CAOAC), 1176 (NAN). MS m/z 280: (M+1); Anal.
Calcd for C17H17N3O: C, 73.10; H, 6.13; N, 15.04.
Found: C, 73.07; H, 6.08; N, 14.95.
4. Experimental
4.1. Chemistry
Melting points were determined in open capillary tubes
and are uncorrected. IR spectra were recorded (in KBr)
on a FT-IR1730. H NMR spectra were measured on
4.1.2.2.
3-Ethyl-4-(4-fluorobenzyloxyphenyl)-4H-
1,2,4-triazole (3b). Yield = 66.3%, mp 95–98 ꢁC. 1H
NMR (CDCl3) d: 1.22 (t, J = 7.5 Hz, 3H, – CH3), 2.71
(q, J = 7.5 Hz, 2H, –CH2CH3), 5.14 (s, 2H, –OCH2–),
6.90 (d, 2H, J = 8.7 Hz, Ar-H), 7.24 (d, 2H,
J = 8.7 Hz, Ar-H), 7.35–7.50 (m, 4H, Ar-H), 8.50 (s,
1H, triazol-H). IR (KBr) cmÀ1: 1602 (C@N), 1282
(CAN), 1238, 1072 (CAOAC), 1170 (NAN). MS: m/z
298 (M+1); Anal. Calcd for C17H16FN3O: C, 68.67; H,
5.42; N, 14.13. Found: C, 68.42; H, 5.25; N, 14.05.
1
AV-300 (Bruker, Switzerland), and all chemical shifts
were given in ppm relative to tetramethysilane. Mass
spectra were measured on an HP1100LC (Agilent Tech-
nologies, USA). Elemental analyses were performed on
a 204Q CHN (Perkin-Elmer, USA). Microanalyses of
C, N, and H were performed using a Heraeus CHN Ra-
pid Analyzer. The major chemicals were purchased from
Aldrich Chemical Corporation. All other chemicals were
of analytical grade.
4.1.2.3.
3-Ethyl-4-(2-fluorobenzyloxyphenyl)-4H-
1,2,4-triazole (3c). Yield = 73.5%, mp 104–105 ꢁC. 1H
NMR (CDCl3) d: 1.22 (t, J = 7.5 Hz, 3H, –CH3), 2.73
(q, J = 7.5 Hz, 2H, –CH2CH3), 5.21 (s, 2H, –OCH2–),
7.19 (d, 2H, J = 8.64 Hz, Ar-H), 7.51–7.56 (m, 4H, Ar-
H), 7.38 (d, 2H, J = 8.64 Hz, Ar-H), 8.52 (s, 1H, tria-
zol-H). IR (KBr) cmÀ1: 1604 (C@N), 1297 (CAN),
4.1.1. Synthesis of 4-(4-hydroxyphenyl)-3-ethyl-4 H-
1,2,4-triazole (2). Dimethoxy-N,N-dimethylmethanam-
inel 6.5 g (55 mmol) was added to a solution of
propionohydrazide 4.8 g (55 mmol) in acetonitrile
(20 ml) in a 100-ml round-bottomed flask equipped with

J. Chen et al. / Bioorg. Med. Chem. 15 (2007) 6775–6781
6779
1240, 1061(CAOAC), 1147 (NAN). MS m/z: 298
(M+1); Anal. Calcd for C17H16FN3O: C, 68.67; H,
5.42; N, 14.13. Found: C, 68.53; H, 5.36; N, 13.82.
7.24 (d, 2H, J = 8.76 Hz, Ar-H), 7.37 (d, 2H,
J = 8.76 Hz, Ar-H), 7.40–7.49 (m, 3H, Ar-H), 8.55
(s, 1H, triazol-H). IR (KBr) cmÀ1: 1608 (C@N), 1287
(CAN), 1229, 1018 (CAOAC), 1183 (NAN). MS:
m/z 348 (M+1); Anal. Calcd for C17H15Cl2N3O: C,
58.63; H, 4.34; N, 12.07. Found: C, 58.42; H, 4.16; N,
11.91.
4.1.2.4.
3-Ethyl-4-(3-fluorobenzyloxyphenyl)-4H-
1,2,4-triazole (3d). Yield = 75.7%, mp 76–78 ꢁC. 1H
NMR (CDCl3) d: 1.27 (t, J = 7.5 Hz, 3H, –CH3), 2.71
(q, J = 7.5 Hz, 2H, –CH2CH3), 5.12 (s, 2H, –OCH2–),
7.08 (d, 2H, J = 7.38 Hz, Ar-H), 7.38–7.69 (m, 4H, Ar-
H), 7.35 (d, 2H, J = 7.38 Hz, Ar-H), 8.16 (s, 1H, tria-
zol-H). IR (KBr) cmÀ1: 1608 (C@N), 1287 (CAN),
1237, 1071 (CAOAC), 1175 (NAN). MS: m/z 298
(M+1); Anal. Calcd for C17H16FN3O: C, 68.67; H,
5.42; N, 14.13. Found: C, 68.51; H, 5.38; N, 13.81.
4.1.2.10. 3-Ethyl-4-(4-methanebenzyloxyphenyl)-4H-
1,2,4-triazole (3j). Yield = 93.8%, mp 113–114 ꢁC. 1H
NMR (CDCl3) d: 1.22 (t, J = 7.5 Hz, 3H, –CH3), 2.33
(s, 3H, Ar-CH3), 2.70 (q, J = 7.5 Hz, 2H, –CH2CH3),
5.10 (s, 2H, –OCH2–), 7.15 (d, 2H, J = 8.52 Hz, Ar-
H), 7.34 (d, 2H, J = 8.52 Hz, Ar-H), 7.12-7.31 (m, 4H,
Ar-H), 8.49 (s, 1H, triazol-H). IR (KBr) cmÀ1: 1604
(C@N), 1247 (CAN), 1242, 1012(CAOAC), 1180
(NAN). MS: m/z 294 (M+1); Anal. Calcd for
C18H19N3O: C,73.69; H, 6.53; N, 14.32. Found: C,
73.65; H, 6.41; N, 14.05.
4.1.2.5. 3-Ethyl-4-(2,6-difluorobenzyloxy)phenyl-4H-
1,2,4-triazole (3e). Yield = 82.5%, mp 144–145 ꢁC. 1H
NMR (CDCl3) d: 1.23 (t, J = 7.5 Hz, 3H, –CH3), 2.74
(q, J = 7.5 Hz, 2H, –CH2CH3), 5.22 (s, 2H, –OCH2–),
7.21 (d, 2H, J = 8.70 Hz, Ar-H), 7.42 (d, 2H,
J = 8.70 Hz, Ar-H), 7.01–7.51 (m, 3H, Ar-H), 8.53 (s,
1H, triazol-H). IR (KBr) cmÀ1: 1608 (C@N), 1285
(CAN), 1248, 1072 (CAOAC), 1168 (NAN). MS: m/z
316(M+1); Anal. Calcd for C17H15F2N3O: C, 64.75;
H, 4.79; N, 13.33. Found: C, 64.51; H, 4.65; N, 13.15.
4.1.2.11. 3-Ethyl-4-(4-methoxybenzyloxyphenyl)-4H-
1,2,4-triazole (3k). Yield = 76.9%, mp 93–95 ꢁC. 1H
NMR (CDCl3) d: 1.22 (t, J = 7.5 Hz, 3H, –CH3), 2.72
(q, J = 7.5 Hz, 2H, –CH2CH3), 3.33 (s, 3H, CH3O–),
5.08 (s, 2H, –OCH2–), 7.16 (d, 2H, J = 2.22 Hz, Ar-
H), 7.35 (d, 2H, J = 2.22 Hz, Ar-H), 7.37–7.39 (m, 4H,
Ar-H), 8.52 (s, 1H, triazol-H). IR (KBr) cmÀ1: 1610
(C@N), 1296 (CAN), 1246, 1020 (CAOAC), 1168
(NAN). MS: m/z 310 (M+1); Anal. Calcd for
C18H19N3O2: C, 69.88; H, 6.19; N, 13.58. Found: C,
69.64; H, 6.02; N, 13.35.
4.1.2.6.
3-Ethyl-4-(4-chlorobenzyloxyphenyl)-4H-
1,2,4-triazole (3f). Yield = 75.7%, mp 104–105 ꢁC. 1H
NMR (CDCl3) d: 1.18 (t, J = 7.5 Hz, 3H, –CH3), 2.45
(q, J = 7.5 Hz, 2H, –CH2CH3), 5.02 (s, 2H, –OCH2–),
7.01 (d, 2H, J = 7.82 Hz, Ar-H), 7.15 (d, 2H,
J = 8.67 Hz, Ar-H), 7.26–7.32 (m, 4H, Ar-H), 8.11 (s,
1H, triazol-H). IR (KBr) cmÀ1: 1604 (C@N), 1247
(CAN), 1242, 1012 (CAOAC), 1180 (NAN). MS: m/z
314 (M+1); Anal. Calcd for C17H16ClN3O: C, 65.07;
H, 5.14; N, 13.39. Found: C, 64.96; H, 5.08; N, 13.18.
4.1.2.12. 3-Ethyl-4-(3,4-methylenediooxybenzyloxy-
phenzol)-4H-1,2,4-triazole (3l). Yield = 78.8%, mp
1
89–90 ꢁC. H NMR (CDCl3) d: 1.21 (t, J = 7.5 Hz, 3H,
–CH3), 2.71 (q, J = 7.5 Hz, 2H, –CH2CH3), 5.05 (s,
2H, –OCH2–), 5.93 (s, 2H, –OCH2–O–), 6.98–6.95 (m,
3H, Ar-H), 7.15 (d, 2H, J = 8.78 Hz, Ar-H), 7.34 (d,
2H, J = 8.78 Hz, Ar-H), 8.48 (s, 1H, triazol-H). IR
(KBr) cmÀ1: 1606 (C@N), 1288 (CAN), 1246, 1031
(CAOAC), 1176 (NAN). MS: m/z 324 (M+1); Anal.
Calcd for C18H17N3O3: C, 66.86; H, 5.30; N, 13.00.
Found: C, 66.65; H, 5.16; N, 12.88.
4.1.2.7.
3-Ethyl-4-(2-chlorobenzyloxyphenyl)-4H-
1,2,4-triazole (3g). Yield = 81.0%, mp 118–120 ꢁC. 1H
NMR (CDCl3) d: 1.24 (t, J = 7.5 Hz, 3H, –CH3), 2.75
(q, J = 7.5 Hz, 2H, –CH2CH3), 5.26 (s, 2H, –OCH2–),
7.36 (d, 2H, J = 3.57 Hz, Ar-H), 7.47 (d, 2H,
J = 3.57 Hz, Ar-H), 7.57–7.60 (m, 4H, Ar-H), 8.54 (s,
1H, triazol-H). IR (KBr) cmÀ1: 1605 (C@N), 1252
(CAN), 1242, 1008 (CAOAC), 1176 (NAN). MS: m/z
314 (M+1); Anal. Calcd for C17H16ClN3O: C, 65.07;
H, 5.14; N, 13.39. Found: C, 64.89; H, 5.07; N, 13.16.
4.1.2.13. 3-Ethyl-4-(4-ethoxyphenyl)-4H-1,2,4-triazole
1
(3m). Yield = 77.5%, oil. H NMR (CDCl3) d: 0.80 (t,
J = 6.8 Hz, 3H, –CH3), 1.19 (t, J = 7.5 Hz, 3H, –CH3),
2.66 (q, J = 7.5 Hz, 2H, –CH2CH3), 3.89 (t, J = 6.4 Hz,
2H, –CH–O–), 7.06 (d, 2H, J = 8.4 Hz, Ar-H), 7.53 (d,
2H, J = 8.4 Hz, Ar-H), 8.18 (s, 1H, triazol-H). IR
(KBr) cmÀ1: 1610 (C@N), 1290 (CAN), 1256, 1036
(CAOAC), 1174 (NAN). MS: m/z 218 (M+1); Anal.
Calcd for C12H15N3O: C, 66.34; H, 6.96; N, 19.34.
Found: C, 66.12; H, 6.75; N, 19.14.
4.1.2.8.
3-Ethyl-4-(3-chlorobenzyloxyphenyl)-4H-
1,2,4-triazole (3h). Yield = 79.8%, mp 102–104 ꢁC. 1H
NMR (CDCl3) d: 1.28 (t, J = 7.5 Hz, 3H, –CH3), 2.71
(q, J = 7.5 Hz, 2H, –CH2CH3), 5.10 (s, 2H, –OCH2–),
7.10 (d, 2H, J = 7.92 Hz, Ar-H), 7.21 (d, 2H,
J = 7.92 Hz, Ar-H), 7.27–7.54 (m, 4H, Ar-H), 8.16 (s,
1H, triazol-H). IR (KBr) cmÀ1: 1607 (C@N), 1272
(CAN), 1232, 1028 (CAOAC), 1175 (NAN). MS: m/z
314 (M+1); Anal. Calcd for C17H16ClN3O: C,65.07; H,
5.14; N, 13.39. Found: C, 64.86; H, 5.06; N, 13.17.
4.1.2.14. 3-Ethyl-4-(4-propoxyphenyl)-4H-1,2,4-tria-
1
zole (3n). Yield = 77.5%, oil. H NMR (CDCl3) d: 0.80
(t, J = 6.8 Hz, 3H, –CH3), 1.00 (t, J = 7.5 Hz, 3H,
–CH3), 1.39 (m, 2H, –CH2–), 2.45 (q, J = 7.5 Hz, 2H,
–CH2CH3), 3.72 (t, J = 6.4 Hz, 2H, –CH–O–), 6.78 (d,
2H, J = 3.46 Hz, Ar-H), 6.98 (d, 2H, J = 3.46 Hz, Ar-
H), 7.91 (s, 1H, triazol-H). IR (KBr) cmÀ1: 1611
(C@N), 1292 (CAN), 1246, 1038 (CAOAC), 1176
4.1.2.9. 3-Ethyl-4-(2,6-dichlorobenzyloxyphenyl)-4H-
1,2,4-triazole (3i). Yield = 82.2%, mp 141–142 ꢁC. 1H
NMR (CDCl3) d: 1.25 (t, J = 7.5 Hz, 3H, –CH3), 2.76
(q, J = 7.5 Hz, 2H, –CH2CH3), 5.38 (s, 2H, –OCH2–),

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J. Chen et al. / Bioorg. Med. Chem. 15 (2007) 6775–6781
(NAN). MS: m/z 232 (M+1); Anal. Calcd for
C13H17N3O: C, 67.51; H, 7.41; N, 18.17. Found: C,
67.31; H, 7.35; N, 18.02.
4.2. Pharmacology
The MES test, scMet test and rotarod test were carried
out by the standard described in the Antiepileptic Drug
Development Program (ADD) of the National Institutes
of Health following previously described testing proce-
dures (USA).15,16 All compounds, which were dissolved
in polyethylene glycol-400, were evaluated for anticon-
vulsant activities with C57B/6 mice in the 18–25 g weight
range. Groups of 10 mice were given a range of intra-
peritoneal doses of the test drug until at least three
points were established in the range of 10–90% seizure
protection or minimal observed neurotoxicity. From
the plots of these data, the respective ED50 and TD50
values, 95% confidence intervals, slopes of the regression
line and the standard error of the slopes were calculated
by means of a computer program written by the Na-
tional Institute of Neurological Disorders and Stroke.
4.1.2.15. 3-Ethyl-4-(4-butoxyphenyl)-4H-1,2,4-triazole
1
(3o). Yield = 79.3%, oil. H NMR (CDCl3) d: 0.84 (t,
J = 6.8 Hz, 3H, –CH3), 1.12 (t, J = 7.5 Hz, 3H, –CH3),
1.37 (m, 2H, –CH2–), 1.66 (m, 2H, –CH2–), 2.57 (q,
J = 7.5 Hz, 2H, –CH2CH3), 3.87 (t, J = 6.4 Hz, 2H,
–CH–O–), 6.89 (d, 2H, J = 8.5 Hz, Ar-H), 7.08 (d, 2H,
J = 8.5 Hz, Ar-H), 8.02 (s, 1H, triazol-H). IR (KBr)
cmÀ1: 1611 (C@N), 1292 (CAN), 1246, 1038 (CAOAC),
1176 (NAN). MS: m/z 246 (M+1); Anal. Calcd for
C14H19N3O: C, 68.54; H, 7.81; N, 17.13. Found: C,
68.32; H, 7.65; N, 17.01.
4.1.2.16. 3-Ethyl-4-(4-hexyloxyphenyl)-4H-1,2,4-tria-
1
zole (3p). Yield = 87.5%, oil. H NMR (CDCl3) d: 0.82
(t, J = 6.8 Hz, 3H, –CH3), 1.27 (t, J = 7.5 Hz, 3H,
–CH3), 1.34 (m, 4H, –(CH2)2–), 1.77 (m, 2H, –CH2–),
2.77 (q, J = 7.5 Hz, 2H, –CH2CH3), 4.01 (t, J = 6.4 Hz,
2H, –CH–O–), 7.01 (d, 2H, J = 7.45 Hz, Ar-H), 7.22
(d, 2H, J = 7.45 Hz, Ar-H), 8.29 (s, 1H, triazol-H). IR
(KBr) cmÀ1: 1613 (C@N), 1295 (CAN), 1249, 1036
(CAOAC), 1178 (NAN). MS: m/z 274 (M+1); Anal.
Calcd for C16H23N3O: C, 70.30; H, 8.48; N, 15.37.
Found: C, 70.10; H, 8.25; N, 15.15.
4.2.1. Maximal electroshock seizure. Seizures were elic-
ited with a 60-Hz alternating current of 50 mA intensity
in mice. The current was applied via corneal electrodes
for 0.2 s. Protection against the spread of MES-induced
seizures was defined as the abolition of the hind leg and
tonic maximal extension component of the seizure. At
30 min after the administration of the compounds, the
activities were evaluated in MES test.
4.1.2.17. 3-Ethyl-4-(4-heptyloxyphenyl)-4H-1,2,4-tria-
zole (3q). Yield = 86.3%, oil. H NMR (CDCl3) d: 0.91
4.2.2. Pentylenetetrazole-induced seizures.15,16 At 30 min
after the administration of the compounds, the animals’
sc dose of pentylenetetrazole (85 mg/kg) at which 100%
of the animals showed convulsive reaction was deter-
mined by a dose–percent effect curve. This dose was then
administered to animals 30 min after different treat-
ments, latency and duration of convulsions as well as la-
tency and percentage of lethality were recorded during
the 1 h following pentylenetetrazole administration.
The doses were calculated which prevented 50% of the
treated animals from tonic convulsions (ED50).
1
(t, J = 6.8 Hz, 3H, –CH3), 1.23 (t, J = 7.5 Hz, 3H,
–CH3), 1.44 (m, 6H, –(CH2)3–), 1.82 (m, 2H, –CH2–),
2.74 (q, J = 7.5 Hz, 2H, –CH2CH3), 4.05 (t, J = 6.4 Hz,
2H, –CH–O–), 7.51 (d, 2H, J = 8.7 Hz, Ar-H), 7.36 (d,
2H, J = 8.7 Hz, Ar-H), 8.52 (s, 1H, triazol-H). IR
(KBr) cmÀ1: 1615 (C@N), 1298 (CAN), 1251, 1042
(CAOAC), 1182 (NAN). MS; m/z 288 (M+1); Anal.
Calcd for C17H25N3O: C, 71.04; H, 8.77; N, 14.62.
Found: C, 70.86; H, 8.59; N, 14.35.
4.1.2.18. 3-Ethyl-4-(4-octyloxyphenyl)-4H-1,2,4-tria-
zole (3r). Yield = 87.5%, oil. H NMR (CDCl3) d: 0.81
4.2.3. Isoniazid-induced seizures.17 At 30 min after the
administration of the compounds, the animals’ ip dose
of Isoniazid (250 mg/kg) at which 100% of the animals
showed convulsive reaction was determined by a dose–
percent effect curve. The mice were placed in individual
cages and observed for 1 h. The doses were calculated
which prevented 50% of the treated animals from tonic
convulsions (ED50).
1
(t, J = 6.8 Hz, 3H, –CH3), 1.19 (t, J = 7.5 Hz, 3H,
–CH3), 1.39 (m, 8H, –(CH2)4–), 1.76 (m, 2H, –CH2–),
2.63 (q, J = 7.5 Hz, 2H, –CH2CH3), 3.93 (t, J = 6.4 Hz,
2H, –CH–O–), 6.94 (d, 2H, J = 8.5 Hz, Ar-H), 7.12 (d,
2H, J = 8.5 Hz, Ar-H), 8.08 (s, 1H, triazol-H). IR
(KBr) cmÀ1: 1617 (C@N), 1296 (CAN), 1249, 1039
(CAOAC), 1178 (NAN). MS: m/z 302 (M+1); Anal.
Calcd for C18H27N3O: C, 71.72; H, 9.03; N, 13.94.
Found: C, 71.56; H, 8.97; N, 13.78.
4.2.4. Thiosemicarbazide-induced seizures.18 At 30 min
after the administration of the compounds, the animals’
ip dose of thiosemicarbazide (50 mg/kg) at which 100%
of the animals showed convulsive reaction was deter-
mined by a dose–percent effect curve. This dose was then
administered to animals 1 h after different treatments,
latency and duration of convulsions as well as latency
and percentage of lethality were recorded during the
2 h 30 min following thiosemicarbazide administration.
The doses were calculated which prevented 50% of the
treated animals from tonic convulsions (ED50).
4.1.2.19. 3-Ethyl-4-(4-dodecyloxyphenyl)-4H-1,2,4-tri-
azole (3s). Yield = 92.5%, mp 58–60 ꢁC. 1H NMR
(CDCl3) d: 0.91 (t, J = 6.8 Hz, 3H, –CH3), 1.24 (t,
J = 7.5 Hz, 3H, –CH3), 1.42 (m, 14H, –(CH2)7–), 1.82
(m, 2H, –CH2–), 2.75 (q, J = 7.5 Hz, 2H, –CH2CH3),
4.06 (t, J = 6.4 Hz, 2H, –CH–O–), 7.12 (d, 2H,
J = 1.86 Hz, Ar-H),7.38 (d, 2H, J = 1.86 Hz, Ar-H),
8.54 (s, 1H, triazol-H). IR (KBr) cmÀ1: 1619 (C@N),
1298 (CAN), 1247, 1041 (C–O–C), 1181 (NAN). MS:
m/z 358 (M+1); Anal. Calcd for C22H35N3O: C, 73.91;
H, 9.87; N, 11.75. Found: C, 73.75; H, 9.67; N, 11.54.
4.2.5. 3-Mercaptopropionic acid-induced seizures.19 At
30 min after the administration of the compounds,

J. Chen et al. / Bioorg. Med. Chem. 15 (2007) 6775–6781
2. Leppik, I. E. Epilepsia 1994, 35, 29.
6781
40 mg/kg 3-mercaptopropionic acid in saline solution was
injected sc. This dose was then administered to animals 1 h
after different treatments, latency and duration of convul-
sions as well as latency and percentage of lethality were re-
corded during the 1h following 3-mercaptopropionic acid
administration.Thedoseswerecalculatedwhichprevented
50% of the treated animals from tonic convulsions (ED50).
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at which 100% of the animals showed convulsive reac-
tion was determined by a dose–percent effect curve.
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for 30 min. The time of onset of the seizure, the number
of tonic seizures and the lethality were recorded.
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of the compounds, the animals were tested on a 1-in.
diameter, knurled plastic rod rotating at 6 rpm for
1 min. Neurotoxicity was indicated by the inability of
an animal to maintain equilibrium in each of three trials.
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Acknowledgments
This work was supported by the National Natural
Science Foundation of China (No. 30460151) and
Important Item Foundation of Ministry of Education
P.R. China (No. 20070422029).
20. Geurts, M.; Poupaert, J. H.; Scriba, G. K.; Lambert, D.
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References and notes
21. Sun, X. Y.; Jin, Y. Z.; Li, F. N.; Li, G.; Chai, K. Y.; Quan,
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