Synthesis and anticancer activities of 1,4-bis(6-aryl-1,2,4-triazolo[3,4-b] -[1,3,4]thiadiazole-3-yl)benzene derivatives

Article abstract of DOI:10.1515/HC.2011.015

1,4-Bis(6-aryl-1,2,4-triazolo[3,4-b]-[1,3,4]thiadiazol-3-yl)-benzenes (3) were synthesized in high yields by reaction of bis(4-amino-5-mercapto-1,2,4- triazol-3-yl)benzene (1) with carboxylic acids 2 in the presence of POCl ₃ and tetrabutylammonium iodide as catalyst. The MTT assay indicated that compounds 3a-i possess inhibitory activity against the proliferation of HepG-2 (liver cancer), A549-1 (lung cancer) and 231-2 (breast cancer). Copyright by Walter de Gruyter Berlin Boston.

Full text of DOI:10.1515/HC.2011.015

Heterocycl. Commun., Vol. 17(1-2), pp. 69–71, 2011 • Copyright © by Walter de Gruyter • Berlin • Boston. DOI 10.1515/HC.2011.015
Synthesis and anticancer activities of 1,4-bis(6-aryl-1,2,4-
triazolo[3,4-b]-[1,3,4]thiadiazole-3-yl)benzene derivatives
Results and discussion
Hao-Yu Ding and De-Jiang Li*
Hubei Key Laboratory of Natural Products Research and
Development, China Three Gorges University, Yichang
443002, P.R. China
As shown in Scheme 1, terephthaloylhydrazide was prepared
by hydrazinolysis of dimethyl terephthalate. The reaction of
terephthaloylhydrazide with CS2 in the presence of KOH in
absolute ethanol gave potassium terephthaloyldithiocarbazate.
The reaction of this intermediate product with hydrazine hydrate
yielded bis(4-amino-5-mercapto-1,2,4-triazol-3-yl)benzene (1).
This four-step preparation of 1 has been described previously
(Li and Fu, 2007a,b, 2008).
*Corresponding author
e-mail: lidejiang999@yahoo.com.cn
Abstract
The desired 1,4-bis(6-aryl-1,2,4-triazolo[3,4-b]-[1,3,4]thi-
adiazol-3-yl)benzenes 3 were synthesized in good yields by
condensation of compound 1 with dicarboxylic acids in the
presence of POCl3 and tetrabutylammonium iodide as catalyst.
Because of poor solubility of 1 and carboxylic acids in POCl3,
the yields of products 3 were rather low for the reactions con-
ducted in the absence of the catalyst. For example, the yield
of 3a was 35%. However, in the presence of tetrabutylammo-
nium iodide as a phase transfer catalyst the desired product 3a
was obtained in 82% yield. The structures of all compounds 3
were established on the basis of elemental analysis and spec-
tral data. The IR spectra of compounds 3 show bands at 1621–
1630 cm-1, 1236–1253 cm-1, and 695–706 cm-1 due to the
presence of C=N, N-N=C, and C-S-C moieties, respectively.
The 1H NMR spectra of 3 exhibit multiple signals in the range
of δ 7.6–8.8 for protons of the aryl groups. The EI mass spec-
tra of compounds 3 exhibit molecular ion peaks. For example,
the spectrum of 3a shows a molecular ion peak at the expected
value m/z 478 with a 21% relative abundance.
1,4-Bis(6-aryl-1,2,4-triazolo[3,4-b]-[1,3,4]thiadiazol-3-yl)-
benzenes (3) were synthesized in high yields by reaction of
bis(4-amino-5-mercapto-1,2,4-triazol-3-yl)benzene (1) with
carboxylic acids 2 in the presence of POCl3 and tetrabutylam-
monium iodide as catalyst. The MTT assay indicated that
compounds 3a–i possess inhibitory activity against the pro-
liferation of HepG-2 (liver cancer), A549-1 (lung cancer) and
231-2 (breast cancer).
Keywords: anticancer activity; synthesis;
triazolothiadiazoles.
Introduction
Bis-1,2,4-triazolo[3,4-b]-[1,3,4]thiadiazoles have been
reported to possess antibacterial properties (Holla et
al., 1998) and anticancer activities against a panel of 60
cell lines derived from seven cancer types, namely lung,
colon, melanoma, renal, ovarian, and leukemia (Holla et
al., 2002). Pyridines containing a bis-1,2,4-triazolo[3,4-
b]-[1,3,4]-thiadiazole moiety (Li and Fu, 2006; Li et al.,
2006a,b) endowed with good fungicidal activities against
Cercospora beticola Sacc. have been reported from our
laboratory. Butanes and trans-ethenes containing the bis-
1,2,4-triazolo[3,4-b]-[1,3,4]thiadiazole moiety (Li et al.,
2006a,b, 2007) show significant antibacterial activities.
In a previous paper, we reported the synthesis of a series
of 1,2,4-triazolo[3,4-b]-[1,3,4]thiadiazoles by the reac-
tion of 3-aryl-4-amino-5-mercapto-1,2,4-triazoles with
dicarboxylic acids. Prompted by our previous results and
in continuation of our search for bioactive molecules,
we designed a facile method to prepare new 1,4-bis(6-
aryl-1,2,4-triazolo[3,4-b]-[1,3,4]thiadiazol-3-yl)benzene
derivatives 3 by cyclization of bis-(4-amino-5-mercapto-
1,2,4-triazol-3-yl)benzene (1) with carboxylic acids 2. The
synthesis, characterization, and the results of fungicidal
activity screening studies of the newly synthesized com-
pounds are presented in this paper.
The MTT assay indicated that compounds 3a–i possess
inhibitory activity against the proliferation of three cancer
cells, including HepG-2 (liver cancer), A549-1 (lung cancer)
and 231-2 (breast cancer). Compound 3d is highly active
against the HepG2 and 231-2 cells (Table 1).
Experimental
The IR spectra were recorded in the range of 4000–400 cm-1 on a
Nicolet Nexus 470 FT-IR spectrophotometer using KBr discs. 1H
NMR spectra were recorded at 400 MHz in CF3COOD on a Varian
Mercury-Plus 400 NMR spectrometer. The chemical shifts are re-
ported as parts per million relative to internal TMS. Electron impact
mass spectra were recorded on a Finnigan Trace GC-MS spectro-
meter. Elemental analyses were obtained on a Perkin-Elmer-2400-
CHN instrument.
General preparation of compounds 3a–i
A mixture of bis(4-amino-5-mercapto-1,2,4-triazol-3-yl)benzene (1,
2.2 mmol), carboxylic acid (2a–g, 1.0 mmol), tetrabutylammonium

70 H.-Y. Ding and D.-J. Li
O
C
O
C
.
NH2NH2 H2O
CH3OH
H2SO4
CH3O
OCH3
HOOC
COOH
C2H5OH
O
C
O
S
O
O
S
CS2/KOH
C2H5OH
S-K+
K+S-
H2NHN
C
NHNH2
C
C
NHNH
HNHN
C
C
N
N
N
N
N
N
N
N
N
N
.
NH2NH2 H2O
ArCOOH (2a-2g)
HS
SH
S
-
+
N
N
(
)
N I
4
n
C4H9
S
POCl
/
3
N
N
Ar
NH2
NH2
Ar
3a–3i
1
Cl
c: Ar =
a: Ar =
b: Ar =
;
;
;
Cl
CH3
d: Ar = Cl
;
e: Ar =
f: Ar =
;
;
CH3
h: Ar = CH3O
i: Ar = Br
g: Ar = CH3
;
;
Scheme 1 Synthesis of compounds 3a–i.
iodide (0.5 mmol), and POCl3 (8 ml) was stirred for 3 h at 55–60°C
and then heated under reflux for 10–14 h at 115–120°C. After cool-
ing, excess POCl3 was removed under reduced pressure. The con-
centrated mass was poured onto crushed ice, and the mixture was
neutralized with potassium carbonate. The separated solid was fil-
tered, washed with water, ethanol, and dried. The crude material was
crystallized from a mixture of ethanol and pyridine to yield pure title
compound 3a–i.
8.82–8.80 (m, 4H, Ar-H), 8.12–8.10 (m, 4H, Ar-H), 7.84–7.78 (m,
6H, Ar-H); IR: 1621, 1253, 698 cm-1; MS: m/z 478 (M+, 21%), 303
(18%), 121 (100%). Analysis calculated for C24H14N8S2: C, 60.24;
H, 2.95; N, 23.42. Found: C, 60.31; H, 2.87; N, 23.56.
1,4-Bis[6-(2-chlorophenyl)-1,2,4-triazolo[3,4-b]-[1,3,4]thiadi-
azol-3-yl]benzene (3b) Light yellow powder; yield 83%; 1H
NMR: δ 8.76–8.45 (m, 4H, Ar-H), 8.11–8.03 (m, 5H, Ar-H), 7.64–
7.29 (m, 3H, Ar-H); IR: 1623, 1257, 702 cm-1; MS: m/z 546 (M+,
12%), 548 (M++2, 6%), 137 (86%), 111 (100%). Analysis calculated
for C24H12N8S2Cl2: C, 52.66; H, 2.21; N, 20.47. Found: C, 52.72;
H, 2.31; N, 20.40.
1,4-Bis(6-phenyl-1,2,4-triazolo[3,4-b]-[1,3,4]thiadiazol-3-yl)-
benzene (3a) Light yellow powder; yield 82%; 1H NMR: δ
1,4-Bis[6-(3-chlorophenyl)-1,2,4-triazolo[3,4-b]-[1,3,4]thiadi-
azol-3-yl]benzene (3c) Yellow powder, yield 80%, H NMR: δ
Table 1 Inhibitory activities of compounds 3a–i against three types
of cancer cells.
1
8.49–8.38 (m, 5H, Ar-H), 8.07–8.01 (m, 3H, Ar-H), 7.56–7.31 (m,
4H, Ar-H); IR: 1627, 1246, 700 cm-1; MS-EI: m/z 546 (M+, 10%),
548 (M++2, 5%), 137 (90%), 111 (100%). Analysis calculated for
C24H12N8S2Cl2: C, 52.66; H, 2.21; N, 20.47. Found: C, 52.72; H,
2.25; N, 20.40.
Compound
IC50/(µg l-1)
HepG-2
A549-1
231-2
3a
3b
3c
3d
3e
3f
3g
3h
3i
35.61
30.28
31.2
25.8
36.2
37.3
35.1
30.4
29.1
40.2
39.5
38.2
36.1
42.1
43.5
46.1
4.08
45.3
39.2
33.5
33.6
23.1
42.3
43.5
40.6
42.3
40.1
1,4-Bis[6-(4-chlorophenyl)-1,2,4-triazolo[3,4-b]-[1,3,4]thiadi-
1
azol-3-yl]benzene (3d) Yellow powder, yield 85%, H NMR: δ
8.52–8.46 (m, 4H, Ar-H), 8.11–8.08 (m, 4H, Ar-H), 7.82–7.69 (m,
4H, Ar-H); IR: 1631, 1239, 705 cm-1; MS-EI: m/z 546 (M+, 20%),
548 (M++2, 8%), 137 (83%), 111 (100%). Analysis calculated for
C24H12N8S2Cl2: C, 52.66; H, 2.21; N, 20.47. Found: C, 52.501;
H, 2.27; N, 20.57.

1,4-Bis(6-aryl-1,2,4-triazolo[3,4-b]-[1,3,4]thiadiazol-3-yl)benzene 71
1,4-Bis[6-(2-methylphenyl)-1,2,4-triazolo[3,4-b]-[1,3,4]thia-
Acknowledgements
diazol-3-yl]benzene (3e) Light yellow powder; yield 79%; 1H
NMR: δ 8.35–8.32 (m, 5H, Ar-H), 8.27–8.21 (m, 3H, Ar-H), 7.71–
7.62 (m, 4H, Ar-H), 2.46 (s, 6H, 2CH3); IR: 1621, 1236, 700 cm-1;
MS: m/z 506 (M+, 8%), 135 (92%), 117 (100%). Analysis calculated
for C26H18N8S2: C, 61.64; H, 3.58; N, 22.12. Found: C, 61.52; H,
3.63; N, 22.01.
We gratefully acknowledge financial support of this work by the
Science Foundation of Hubei Province Education Department, China
(Project no. C2010027).
References
1,4-Bis[6-(3-methylphenyl)-1,2,4-triazolo[3,4-b]-[1,3,4]thia-
diazol-3-yl]benzene (3f) Light yellow powder; yield 80%; 1H
NMR: δ 8.35–8.32 (m, 5H, Ar-H), 8.31–8.25 (m, 3H, Ar-H), 7.81–
7.76 (m, 4H, Ar-H), 7.71–7.63 (m, 4H, Ar-H), 2.51 (s, 6H, 2CH3);
IR: 1628, 1241, 700 cm-1; MS: m/z 506 (M+, 8%), 135 (92%), 117
(100%). Analysis calculated for C26H18N8S2: C, 61.64; H, 3.58; N,
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1,4-Bis[6-(4-methylphenyl)-1,2,4-triazolo[3,4-b]-[1,3,4]thia-
diazol-3-yl]benzene (3g) Light yellow powder; yield 83%; 1H
NMR: δ 8.35–8.32 (m, 8H, Ar-H), 7.58–7.52 (m, 4H, Ar-H), 2.56 (s,
6H, 2CH3); IR: 1630, 1236, 707 cm-1; MS: m/z 506 (M+, 15%), 135
(83%), 117 (100%). Analysis calculated for C26H18N8S2: C, 61.64;
H, 3.58; N, 22.12. Found: C, 61.56; H, 3.60; N, 22.03.
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1,4-Bis[6-(4-methoxyphenyl)-1,2,4-triazolo[3,4-b]-[1,3,4]thia-
diazol-3-yl]benzene (3h) Light yellow powder; yield 84%; 1H
NMR: δ 8.45–8.31 (m, 8H, Ar-H), 7.38–7.32 (m, 4H, Ar-H), 4.03 (s,
6H, 2OCH3); IR: 1627, 1236, 700 cm-1; MS: m/z 538 (M+, 8%), 151
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1,4-Bis[6-(4-bromophenyl)-1,2,4-triazolo[3,4-b]-[1,3,4]thiadi-
azol-3-yl]benzene (3i) Yellow powder; yield 77%; H NMR: δ
8.37–8.29 (m, 8H, Ar-H), 7.91–7.78 (m, 4H, Ar-H), 3.91 (s, 6H,
2OCH3); IR: 1626, 1231, 706 cm-1; MS: m/z 634 (M+, 5%), 636
(M++2, 4%), 181 (70%), 155 (100%). Analysis calculated for
C24H12N8S2Br2: C, 45.31; H, 1.90; N, 17.61. Found: C, 45.41;
H, 2.10; N, 17.41.
1
Received April 19, 2011; accepted May 26, 2011

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