Synthesis, structures, and biological activities of new 1H-1,2,4-triazole derivatives containing pyridine unit

Article abstract of DOI:10.1002/hc.20308

Fourteen new 1H-1,2,4-triazole derivatives containing pyridine moiety were synthesized by condensation of 1-(pyridine-3-yl)-2-(1H-1,2,4-triazol1-yl) ethanone with aryl aldehydes, and their reaction conditions were studied. The title compounds were screened for their antibacterial and plant growth regulatory activities. The screening data revealed that most of the compounds showed some antifungal and plant growth regulatory activities.

Full text of DOI:10.1002/hc.20308

Heteroatom Chemistry
Volume 18, Number 4, 2007
S
ynthesis, Structures, and Biological Activities
of New 1H-1,2,4-Triazole Derivatives
Containing Pyridine Unit
Jian-Bing Liu, Wei-Feng Tao, Hong Dai, Zhong Jin,
and Jian-Xin Fang
State Key Laboratory of Elemento-organic Chemistry, Research Institute of Elemento-organic
Chemistry, Nankai University, Tianjin 300071, PR China
Received 10 November 2005; revised 11 July 2006
novel biologically active molecules. Compared with
ABSTRACT: Fourteen new 1H-1,2,4-triazole deriva-
the structurally complex natural compounds, these
molecules are easily synthesized and their structural
optimization usually leads to a feasible candidate
tives containing pyridine moiety were synthesized by
condensation of 1-(pyridine-3-yl)-2-(1H-1,2,4-triazol-
1-yl)ethanone with aryl aldehydes, and their reaction
compound. Of all the heterocyclic compounds, 1H-
,2,4-triazole derivatives due to their broad spec-
conditions were studied. The title compounds were
screened for their antibacterial and plant growth regu-
latory activities. The screening data revealed that most
of the compounds showed some antifungal and plant
growth regulatory activities. ꢀC 2007 Wiley Periodicals,
Inc. Heteroatom Chem 18:376–380, 2007; Published on-
line in Wiley InterScience (www.interscience.wiley.com).
DOI 10.1002/hc.20308
1
trum of biological activities, high activity, and
high selectivity had attracted the attention of many
chemists [5–9], and their various commercial com-
pounds had been widely used in plant protection and
medicines as fungicides triadimefon, triadimenol,
flusilazole, bitertanol, cyproconazole, etc. and as
clinical drugs fluconazole and itraconazole [10,11].
It is well known that pyridine unit is another im-
portant heterocyclic nucleus with regard to biolog-
ical activity [12]. Incorporating pyridine ring into
active compounds may usually improve their bio-
logical or physiological activities [13]. Many pyri-
dine derivatives, such as pioglitazone, rosiglita-
zone, zolpidem, frowncide, etc. [14–16], have played
an important role in agrochemistry and medical
chemistry.
INTRODUCTION
The considerable biological importance of hete-
rocyclic compounds has stimulated much work
on them [1–4]. Traditionally, small heterocyclic
molecules have been a reliable source for discovering
In our laboratory, various triazole derivatives
have been synthesized and were found to be effec-
tive in fungicidal and plant growth regulatory ac-
tivities [17,18]. To optimize them, we designed and
synthesized 14 new N-heterocyclic compounds by
incorporating pyridine ring into triazole compounds
Correspondence to: Jian-Xin Fang; e-mail: fjx@nankai.edu.
com.cn.
Contract grant sponsor: National Natural Science Foundation
of China.
Contract grant number: 29872022, 20172030.
Contract grant sponsor: Key Project of Chinese Ministry of
Education of PR China.
(Scheme 1), and evaluated their fungicidal and plant
Contract grant number: 105046.
ꢀ
c 2007 Wiley Periodicals, Inc.
growth regulatory activities.
376

Synthesis, Structures, and Biological Activities of New 1H-1,2,4-Triazole Derivatives 377
Synthesis of 3-Aryl-1-(pyridin-3-yl)-2-(1H-1,2,4-
triazol-1-yl)prop-2-en-1-one
Br2
H
O
O
N
O
N
N
HBr
N
Br
N
N
N
The reaction conditions for aldol condensation have
been well documented in literature, but the conden-
sation of substituted aryl aldehyde with the inter-
mediate 2 could not provide satisfactory results us-
ing these reported conditions. Traditionally, toluene,
benzene, or cyclohexane was used as solvent and
piperidine or piperidine and acetic acid as catalysts
in the aldol condensation reaction. When we synthe-
sized the title compounds 4a (X = H), 4h (X = 2-F-
4-Br), and 4n (X = 2-Cl) using the above conditions,
the yield of 4a is only 26.4%. Moreover, the yields of
Et3N
N
N
HBr
N
(
CH3)2CO
1
2
O
O
Piperidine
Chloroform
H
X
+
X
N
N
N
N
3
4
SCHEME 1
4
h and 4n were too low to be separated from the fi-
O
O
O−
nal products. Acetic anhydride both as a solvent and
a water acceptor and anhydrous potassium carbon-
ate as a catalyst were also investigated, but the yield
was still lower than 20%. Among the other solvents
investigated such as ethanol, acetonitrile, and chlo-
roform, chloroform was found to be the best solvent
in synthesizing the title compounds 4a–n, and by us-
ing piperidine as catalyst, their yield was more than
Br
Br
+
Base
1. Quaternization
2. +Base
N+
C
CH
−
HBr
N
HBr
N
n
5
SCHEME 2
30% (Table 1).
RESULTS AND DISCUSSION
Synthesis of 1-(Pyridin-3-yl)-2-(1H-1,2,4-triazol-
-yl)ethanone (2)
1
The Structures of Title Compounds
Condensation of 1H-1,2,4-triazole with compound 1
was performed in acetone using triethylamine (TEA)
as a base, and the yield can be improved by up to 10%
by refluxing a mixture of 1H-1,2,4-triazole, TEA, and
acetone for 30 minutes before the addition of inter-
mediate 1. The yield of this reaction is lower than the
similar reaction of 1H-1,2,4-triazole with 2-bromo-
All title compounds were colorless solids and their
1
structures were confirmed by H NMR (Table 2) and
elemental analyses (Table 1). The structure of com-
pound 4g was also confirmed by single crystal X-ray
diffraction analysis [21] (Fig. 1). In the crystal cell,
due to the bulkiness of pyridine ring, the substituted
aryl group is spatially repulsed and swerves to the
nearby triazole group.
1-arylethanone [19]; the reason may be due to the
conformation of aggregate 5 [20] (Scheme 2).
TABLE 1 Physical Properties and Elemental Analysis Data for Compounds 4a–n
Elementary Analysis (Calcd, %)
H
Yield
(%)
◦
X
mp ( C)
C
N
4
4
4
4
4
4
4
4
4
4
4
4
4
4
a
b
c
d
e
f
g
h
i
j
k
l
m
n
H
4-Cl
2-F
47.1
32.2
43.2
32.3
50.1
47.4
50.0
43.8
33.9
52.0
30.8
45.0
48.1
54.8
149–150
119–121
93–95
120–122
144–146
156–158
135–137
142–144
83–85
124–126
121–123
153–155
134–136
101–103
69.67 (69.55)
61.76 (61.84)
65.12 (65.30)
65.28 (65.30)
66.58 (66.66)
55.74 (55.67)
55.58 (55.67)
51.53 (51.50)
71.19 (71.04)
71.12 (71.04)
64.25 (64.28)
64.24 (64.28)
63.60 (63.75)
62.07 (61.84)
4.49 (4.38)
3.69 (3.57)
3.60 (3.77)
3.78 (3.77)
4.58 (4.61)
2.86 (2.92)
2.76 (2.92)
2.87 (2.70)
5.24 (5.30)
5.32 (5.30)
4.82 (4.79)
4.76 (4.79)
3.83 (3.78)
3.78 (3.57)
20.64 (20.28)
17.96 (18.03)
18.94 (19.04)
18.95 (19.04)
18.04 (18.29)
16.33 (16.23)
16.16 (16.23)
14.94 (15.01)
18.40 (18.41)
18.54 (18.41)
16.66 (16.66)
16.73 (16.66)
17.49 (17.49)
17.77 (18.03)
3-F
2-OMe
2,4-Cl2
2,6-Cl2
2-F-4-Br
2,4-Me2
3,4-Me2
2,4-(OMe)2
3,4-(OMe)2
3,4-( OCH O )
2
2-Cl
Heteroatom Chemistry DOI 10.1002/hc

378 Liu et al.
TABLE 2 1H NMR Spectral Data for Compounds 4a–n
X
1H NMR spectral data (δ)
4a
4b
4c
4d
4e
H
9.05 (s, 1H, PyH), 8.85 (d, J = 3.3 Hz, 1H, PyH), 8.17 (s, 1H, TrH), 8.23 (s, 1H, TrH), 8.10 (d, J = 7.8
Hz, 1H, PyH), 7.64 (s, 1H, CH ), 7.45–7.49 (m, 1H, PyH), 7.33–7.45 (m, 3H, phH), 6.72 (d,
J = 7.2 Hz, 2H, phH)
4-Cl
2-F
9.02 (s, 1H, PyH), 8.84 (d, J = 3.6 Hz, 1H, PyH), 8.17 (s, 1H, TrH), 8.22 (s, 1H, TrH), 8.08 (d, J = 7.8
Hz, 1H, PyH), 7.58 (s, 1H, CH ), 7.47 (d d, J = 4.8 Hz, PyH), 7.30 (d, J = 8.4 Hz, 2H, phH), 6.88
(
d, J = 8.7 Hz, 2H, phH)
9.05 (d, J = 1.5 Hz, 1H, PyH), 8.84 (d d, J = 1.8 Hz, 1H, PyH), 8.17 (s, 1H, TrH), 8.20 (s, 1H, TrH),
8
7
.09–8.12 (m, 1H, PyH), 7.78 (s, 1H, CH ), 7.45–7.50 (m, 1H, PyH), 7.40–7.46 (m, 1H, phH),
.00–7.15 (m, 2H, phH), 6.58–6.64 (m, 1H, phH)
3-F
9.04 (s, 1H, PyH), 8.85 (d, J = 3.6 Hz, 1H, PyH), 8.18 (s, 1H, TrH), 8.23 (s, 1H, TrH), 8.09 (d, J = 7.8
Hz, 1H, PyH), 7.59 (s, 1H, CH ), 7.10–7.40 (m, 2H, PyH), 6.78 (d, J = 7.5 Hz, 1H, phH), 6.65 (d,
J = 9.6 Hz, 1H, phH)
2-OMe
9.03 (d, J = 2.1 Hz, 1H, PyH), 8.83 (d d, J = 1.6 Hz, 1H, PyH), 8.14 (s, 1H, TrH), 8.15 (s, 1H, TrH),
8
6
.10–8.12 (m, 1H, PyH), 7.98 (s, 1H, CH ), 7.44–7.49 (m, 1H, PyH), 7.40–7.41 (m, 1H, phH),
.91 (d, J = 8.4 Hz, 1H, phH), 6.79 (t, J = 7.8 Hz, phH), 6.55 (d d, J = 1.5 Hz, phH), 3.81 (s, 3H,
OCH )
3
4
4
4
4
4
4
4
4
4
f
2,4-Cl2
9.06 (d, J = 1.5 Hz, 1H, PyH), 8.83 (d, J = 1.2 Hz, 1H, PyH), 8.11(s, 1H, TrH), 8.20 (s, 1H, TrH), 8.14
(
t, J = 1.5 Hz, 1H, PyH), 7.76 (s, 1H, CH ), 7.46–7.50 (m, 2H, PyH, phH), 7.12 (d d, J = 2.1 Hz,
phH), 6.63 (d, J = 8.7 Hz, 1H, phH)
g
h
i
2,6-Cl2
9.20 (d, J = 1.8 Hz, 1H, PyH), 8.88 (d, J = 1.5 Hz, 1H, PyH), 8.28 (d, J = 8.1 Hz, 1H, PyH), 8.23 (s,
1
1
H, TrH), 7.90 (s, 1H, TrH), 7.51 (d d, J = 4.8 Hz, 1H, PyH), 7.37 (d, J = 2.4 Hz, 1H, phH), 7.34(s,
H, CH ), 7.24–7.30 (m, 2H, phH)
2-F-4-Br
2,4-Me2
3,4-Me2
2,4-(OMe)2
3,4-(OMe)2
3,4-
9.03 (s, 1H, PyH), 8.86 (d, J = 3.6 Hz, 1H, PyH), 8.23 (s, 1H, TrH), 8.17 (s, 1H, TrH), 8.10 (d, J = 3.6
Hz, 1H, PyH), 7.67 (s, 1H, CH ), 7.48 (d d, J = 4.8 Hz, 1H, PyH), 7.31 (t, J = 9.6 Hz, 1H, phH),
7
.20 (d, J = 8.4 Hz, 1H, phH), 7.31 (t, J = 7.8 Hz, 1H, phH)
9.01 (s, 1H, PyH), 8.83 (d, J = 3.9 Hz, 1H, PyH), 8.23 (s, 1H, TrH), 8.15 (s, 1H, TrH), 8.07 (d, J = 7.8
Hz, 1H, PyH), 7.60 (s, 1H, CH ), 7.46 (d d, J = 4.8 Hz, 1H, PyH), 7.07 (d, J = 8.1 Hz, 1H, phH),
7
.05 (s, 1H, phH), 6.85 (d, J = 7.8 Hz, 1H, phH), 6.49 (d, J = 7.8 Hz, 1H, phH), 2.30 (s, 6H, CH )
3
j
9.02 (s, 1H, PyH), 8.81 (d, J = 4.5 Hz, 1H, PyH), 8.11 (s, 1H, TrH), 8.08 (t, J = 1.8 Hz, 1H, PyH),
8
.06 (s, 1H, TrH), 7.76 (s, 1H, CH ), 7.44 (d d, J = 4.8 Hz, 1H, PyH), 7.07 (s, 1H, phH), 6.85 (d,
J = 7.8 Hz, 1H, phH), 6.61 (d, J = 7.8 Hz, 1H, phH), 2.25 (s, 6H, CH ).
3
k
l
9.01 (d, J = 1.8 Hz, 1H, PyH), 8.10 (d d, J = 1.5 Hz, 1H, PyH), 8.20 (s, 1H, TrH), 8.16 (s, 1H, TrH),
8
.05–8.10 (m, 1H, PyH), 8.04 (s, 1H, CH ), 7.45 (d d, J = 4.8 Hz, 1H, PyH), 6.30–6.41(m, 3H,
phH), 3.79 (s, 3H, OCH ), 3.81 (s, 3H, OCH ).
3
3
9.03 (s, 1H, PyH), 8.83 (d, J = 3.6 Hz, 1H, PyH), 8.27 (s, 1H, TrH), 8.21 (s, 1H, TrH), 8.08 (d, J = 7.5
Hz, 1H, PyH), 7.63 (s, 1H, CH ), 7.46 (d d, J = 4.2 Hz, 1H, PyH), 6.81 (d, J = 8.1 Hz, 1H, phH),
6
.75 (d, J = 8.4 Hz, 1H, phH), 6.14 (s, 1H, phH), 3.90 (s, 3H, OCH ), 3.64 (s, 3H, OCH )
3
3
m
n
8.99 (d, J = 1.5 Hz, 1H, PyH), 8.82 (d, J = 4.2 Hz, 1H, PyH), 8.25 (s, 1H, TrH), 8.18 (s, 1H, TrH),
(
OCH O )
8.05 (d, J = 7.8 Hz, 1H, PyH), 7.58 (s, 1H, CH ), 7.46 (d d, J = 4.8 Hz, 1H, PyH), 6.78 (d, J = 8.1
2
Hz, 1H, phH), 6.71(d, J = 8.1 Hz, 1H, phH), 6.01 (s, 1H, phH), 2.41 (s, 2H, OCH O)
2
2-Cl
9.08 (d, J = 1.5 Hz, 1H, PyH), 8.86 (d d, J = 1.8 Hz, 1H, PyH), 8.13–8.18 (m, 2H, PyH, TrH), 8.11 (s,
1
H, TrH), 7.84 (s, 1H, CH ), 7.45–7.51 (m, 2H, PyH, phH), 7.31–7.36 (m, 1H, phH), 7.10–7.16
(
m, 1H, phH), 6.70 (d d, J = 1.2 Hz, 1H, phH)
Biological Activities
edge, a linkage between the triazole ring and sub-
stituted aryl group via no more than two single or
double bonds is essential for their fungicidal activ-
ities, and an extended carbon backbone linking the
triazole ring and aryl group in an almost linear fash-
ion possesses higher activity than a distorted one
[18]. Because the triazole ring and aryl groups of
the compounds 4a–n are connected in a distorted
fashion, they do not display predominant fungicidal
activity.
The assessment of in vitro fungicidal activities
for compounds 4a–n were performed against six
selected fungi including G. zeae, A. solani, P.
asparagi, P. piricola, C. rachidicola, and C. cucumer-
inum. Their relative inhibitory ratios (%) were deter-
mined, and the results of such studies are listed in
Table 3.
The screening data revealed that most of the
compounds 4a–n showed some degree of antifun-
gal activities. But the relative inhibitory ratio was
present on the low side. To the best of our knowl-
The plant growth regulator activities of com-
pounds 4a–n were also tested by wheat coleoptile
and cucumber cotyledon tests at a concentration
Heteroatom Chemistry DOI 10.1002/hc

Synthesis, Structures, and Biological Activities of New 1H-1,2,4-Triazole Derivatives 379
EXPERIMENTAL
All reactions were carried out under nitrogen and
1
monitored by thin-layer chromatography. The H
NMR spectra were measured on a Bruker AC
300, using tetramethylsilane and deuterochloro-
form as the internal standard and solvent, respec-
tively. Elemental analyses were determined with
a Yanaco CHN Corder MT-3 elemental analyzer.
Melting points were determined with X-4 digi-
tal melting point apparatus, and the thermome-
ter was uncorrected. The intermediate compound
1
was synthesized according to the literature [22],
and was used in the next step without further
purification.
FIGURE 1 Molecular structure and crystallographic number-
˚
ing for compound 4g. Selected bond lengths (A): Cl (1) C (1)
.7292 (17); Cl (2) C (5) 1.7373 (17); O (1) C (11) 1.212
1
(
(
2); N (1) C (10) 1.339 (2); N (1) N (2) 1.3608 (19); N (1) C
8) 1.418 (2); N (3) C (10) 1.306 (2); N (4) C (13) 1.330 (2);
Synthesis of 1-(Pyridin-3-yl)-2-(1H-1,2,4-triazol-
1-yl)ethanone (2)
C (5) C (6) 1.392 (2); C (6) C (7) 1.475 (2); C (7) C (8)
1
(
1
(
(
(
(
◦
.328 (2). Selected angles ( ): O (1) C (11) C(8) 120.44
To a vigorous stirred suspension of 1H-1,2,4-triazole
4.08 g, 0.059 mol) in 80 mL acetone, TEA (11.38 g,
.112 mol) was added in a single portion. The mix-
ture was refluxed for 30 minutes, and then cooled to
15); O (1) C (11) C (12) 120.06 (15); C (12) C (11) C (8)
19.49 (14); C (7) C (8) N (1) 121.81 (15); C (7) C (8) C
11) 123.08 (15); N (1) C (8) C (11) 114.82 (13); C (6) C
7) C (8) 126.28 (15); C (10) N (1) N (2) 108.82 (14); C
10) N (1) C (8) 129.33 (14); N (2) N (1) C (8) 121.83
13); C (10) N (3) C (9) 101.71 (15); C (13) N (4) C (14)
(
0
◦
◦
room temperature. After cooling to −5 C to −10 C
in an ice–salt bath, the intermediate compound 1
1
16.31 (16); N (4) C (14) C (15) 124.48 (18).
(15.02 g, 0.053 mol) was added in portions. The mix-
ture was reacted for another 6 h at this tempera-
ture, and then refluxed for 30 minutes. The reac-
tion mixture was cooled to room temperature and
filtered, and the filtrate was evaporated under re-
duced pressure. The residue was purified by column
chromatography on silica gel (100–200 mesh) with
petroleum ether/ethyl acetate (1:1 v/v) as eluant to
of 10 mg/L. All of the compounds exhibited low
inhibitory activities on the growth of wheat coleop-
tile and cucumber cotyledon, and the inhibitory ratio
(
%) are listed in Table 4.
TABLE 3 Fungicidal Activities of Compounds 4a–n (50 mg/L, Relative Inhibitory Ratio %)
Ratio (%)
4
a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
G. zeae
A. solani
28.6 34.3 17.8 26.9 35.7 22.9 43.5 34.3 26.6 33.3 35.1 22.2
6.1
54.5
19.5 41.5 31.7 35.2 18.1 43.9 22.9 48.7 33.1
7.9 34.1 18.4 15.2 34.9
P. asparagi
P. p i r i c o l a
C. rachidicola
C. cucumerinum
13.0 34.8 11.9 28.4 32.7 39.1 28.4 39.1 29.8 31.7 41.0 19.7 24.6 15.9
0
25.0
43.6 25.8 19.5 41.9 12.8 35.1 35.3 28.7 25.7 31.9 38.1 29.8 28.6
5.0 18.1 25.6 27.9 7.5 21.7 28.1 25.7 18.9 18.8 34.8 19.5 25.3
15.0 15.0 26.8 28.6 35.7 25.0 33.3 30.0 42.6 19.4 29.5 34.1 41.9 29.1
TABLE 4 Plant Growth Regulator Activities of Compounds 4a–n (10 mg/L)
Ratio a
4
a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
Growth of wheat coleoptile
−18.9 −26.7 −2.9 −36.7 −38.9 −40.5 −55.6 −51.8 −28.9 −36.7 −46.8 −48.9 −16.8 −28.8
Growth of cucumber cotyledon −33.9 −60.9 −25.6 −19.8 −19.1 −9.1 −36.4 −37.9 −38.1 −45.5 −29.7 −19.1 −9.1 −18.9
a
:
inhibition %.
Heteroatom Chemistry DOI 10.1002/hc

380 Liu et al.
afford 6.39 g yellow solid (yield 63.5%), mp 114–
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◦
1
1
16 C; H NMR (CDCl , 300 MHz) δ: 9.17 (s, 1H,
3
[
[
[
[
[
[
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2
); for C
9
H
8
N O
4
anal, calcd: C 57.44, H 4.28, N 29.77; found: C 57.52,
H 4.15, N 29.38.
General Procedure for the Synthesis of Title
Compounds 4a–n
To a stirred solution of 1-(pyridin-3-yl)-2-(1H-1,2,4-
triazol-1-yl)ethanone (1.00 g, 3.83 mmol), 4.60 mmol
aryl aldehyde, and 30 ml dry chloroform, a few drops
of piperidine was added at room temperature un-
der nitrogen. The mixture was then heated under
reflux for 4 h. The solvent was evaporated under re-
duced pressure, and then the residue was purified
by column chromatography on silica gel (200–300
mesh) with the solvent system petroleum ether/ethyl
acetate (4:1 v/v) to get the desired compounds 4a–n
in various yields.
[8] Gasztonyi, M.; Josepovits, G. Pestic Sci 1984, 15, 48.
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9] Moreno-Manas, M.; Arredondo, Y.; Pleixats, R.;
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[
The title compounds 4a–n were screened for their
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2
[
(%) against these fungi are listed in Table 3. The
2
plant growth regulatory activities of the title com-
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Heteroatom Chemistry DOI 10.1002/hc