Synthesis of New Thiazolo[3,2-b][1,2,4]triazole Derivatives and Preliminary Evaluation of Their Biological Activity

Article abstract of DOI:10.1134/S1070363219010067

Heterocyclization of 3-[(1H-1,2,4-triazol-3-yl)thio]pentane-2,4-dione afforded 1-(6-methylthiazolo[3,2-b][1,2,4]-triazol-5-yl)ethan-1-one, the reactions of which with hydroxylamine, hydrazincarboxamide, hydrazincarbothioamide, hydrazine hydrate and para-t

Full text of DOI:10.1134/S1070363219010067

ISSN 1070-3632, Russian Journal of General Chemistry, 2019, Vol. 89, No. 1, pp. 32–36. © Pleiades Publishing, Ltd., 2019.
Russian Text © A.P. Yengoyan, V.A. Pivazyan, E.A. Ghazaryan, R.S. Hakobyan, 2019, published in Zhurnal Obshchei Khimii, 2019, Vol. 89, No. 1,
pp. 39–44.
Synthesis of New Thiazolo[3,2-b][1,2,4]triazole Derivatives
and Preliminary Evaluation of Their Biological Activity
A. P. Yengoyana,b*, V. A. Pivazyanb, E. A. Chazaryanb, and R. S. Hakobyanb
a Russian-Armenian University, ul. H. Emina 123, Yerevan, 0051 Armenia
* e-mail: ayengoyan@mail.ru
b Pesticide Synthesis and Plant Protection Laboratory, National Agrarian University of Armenia, Yerevan, Armenia
Received July 5, 2018; revised July 5, 2018; accepted July 13, 2018
Heterocyclization of 3-[(1H-1,2,4-triazol-3-yl)thio]pentane-2,4-dione afforded 1-(6-methylthiazolo[3,2-b][1,2,4]-
triazol-5-yl)ethan-1-one, the reactions of which with hydroxylamine, hydrazincarboxamide, hydrazincarbo-
thioamide, hydrazine hydrate and para-toluenesulfonyl hydrazide resulted in the formation of the
corresponding derivatives. 1-(6-Methylthiazolo[3,2-b][1,2,4]triazol-5-yl)ethan-1-one oxime reacted with alkyl
halides and phenyl isocyanate to produce the corresponding O-alkyl- and O-phenylcarbamoyl derivatives. The
growth regulating activity of the compounds obtained was studied.
Keywords: thiazolo[3,2-b][1,2,4]triazoles, 1-(6-methylthiazolo[3,2-b][1,2,4]triazol-5-yl)ethan-1-one oxime, hetero-
cyclization, growth regulating activity
DOI: 10.1134/S1070363219010067
Derivatives of such nitrogen- and sulfur-containing
five-membered heterocycles, as 1,3-thiazole and 1,2,4-
triazole, have a broad spectrum of biological activity.
A large number of drugs contain 2-aminothiazole and
aminothiazole-2-thione fragments in their structure [1].
In recent years, much attention has been paid to the
synthesis of fused systems based on thiazole and 1,2,4-
triazole. Thus, bicyclic thiazolotriazoles have been
synthesized by the reaction of 5-phenyl-2,4-dihydro-
3H-1,2,4-triazole-3-thione with compounds containing
a cyanomethylene group [2]. 2,6-Diarylthiazolo[3,2-b]-
[1,2,4]triazoles with a similar structure were obtained
by reacting 3-aryl-1H-1,2,4-triazole-5-thiols with 2,2-
dibromo-1-arylethan-1-one [3]. Synthesis of 6-aryl-
thiazolo[3,2-b][1,2,4]triazoles by the reaction of 1,2,4-
triazole-5(1H)-thiol with 2-bromo-1-arylethan-1-ones
has been reported in [4 ]. One of the compounds ob-
tained, namely 6-(4-propoxyphenyl)thiazolo[3,2-b]-
[1,2,4]triazole, showed a higher activity than car-
bamazepine. Polyheterocyclic compounds with anti-
inflammatory and antiviral activity have been obtained
on the basis of 1,2,4-triazole thioethers [5]. Some of
the obtained derivatives based on 2-substituted 1-(6-
methylthiazolo[3,2-b][1,2,4]triazol-5-yl)ethan-1-one
showed antiviral and anti-mycobacterial activities [6, 7].
The original one-step method for the synthesis of 5,6-
disubstituted thiazolo[3,2-b][1,2,4]triazoles based on
the reaction of unsaturated ketones with bis(1H-1,2,4-
triazolyl)sulfoxide has been proposed in [8]. The
reaction of 5-aryl-2,4-dihydro-1,2,4-triazol-3(3H)-thiones
with 2-bromo-1-phenylethan-1-one followed by cycliza-
tion of the resulting 1-phenyl-2-[(3-aryl-1H-1,2,4-tri-
azol-5-yl)thio]ethan-1-ones afforded 2-aryl-6-phenyl-
thiazolo[3,2-b][1,2,4] triazoles [9]. A similar approach
has been used to obtain naphthyridinyl-substituted thia-
zolotriazoles under the action of microwave irradiation
[10].
Among the synthesized compounds, substances
with antimicrobial [3], antibacterial [6, 9], anticon-
vulsant [4], antiviral [10] and anti-inflammatory [11]
activity were found. Some compounds were found to
be inhibitors of platelet aggregation [12] and were
similar in action to some well-known COX-2 inhi-
bitors [8].
Given the fact that 1,3-thiazole and 1,2,4-triazole
are the basic heterocycles of a large number of
pesticides and plant growth regulators, as well as great
interest in their fused bicyclic derivatives, herein we
reported effective methods for the synthesis of some
derivatives of fused bicyclic thiazolotriazoles and data
on preliminary evaluation of their biological activity in
32

SYNTHESIS OF NEW THIAZOLO[3,2-b][1,2,4]TRIAZOLE DERIVATIVES
33
Scheme 1.
CH3
CH3
O
O
CH3
O
N
N
N
NH
N
CH3
toluene, pTSA
125−130°C
S
S
N
1
O
NH2
NH2
NHNH2
S
H2NHN
CH3
CH3
N
N
CH3
N
S
N NH
O
CH3
NH
N
N
N
NH2
2
S
N
NH2
3
S
terms of finding new chemical plant protection agents
and plant growth regulators.
yl)ethan-1-one oxime 6 (Scheme 3). Heating the latter
with alkyl halides in DMF in the presence of KOH
afforded alkyl substituted oximes 7a and 7b. The
reaction of oxime 6 with phenyl isocyanate when
heated in toluene in the presence of catalytic amounts
of pyridine produced O-phenylcarbamoyloxime 8
(Scheme 3). For oxime 6 and its O-substituted deriva-
tives 7 and 8, E/Z isomerization at the C=N double
bond is possible (Scheme 4). Indeed, in the 1H and 13C
NMR spectra of these compounds, two sets of signals
corresponding to the E- and Z-isomers are observed in
a ratio of 1 : (3–4).
The starting 1-(6-methylthiazolo[3,2-b][1,2,4] triazol-
5-yl)ethan-1-one
1 was synthesized by hetero-
cyclization of the previously obtained 3-[(1H-1,2,4-
triazol-3-yl)thio]pentane-2,4-dione [13] when heated at
125–130°C in toluene for 8–10 h in the presence of
para-toluenesulfonic acid (pTSA). Further transforma-
tions of the obtained ketone 1 led to new fused bicyclic
derivatives (Scheme 1). Thus, 2-{1-(6-methylthiazolo-
[3,2-b][1,2,4]triazol-5-yl)ethylidene}hydrazine-1-car-
boxamide 2 and its corresponding thio-analogue 3 were
synthesized by reacting compound 1 with hydrazino-
carboxamide and hydrazinocarbothioamide, respectively.
For the study of herbicidal, fungicidal and growth-
regulating activities of the synthesized compounds,
laboratory and vegetation studies were conducted.
Oxime 6 and its derivatives 7a and 7b showed
moderate herbicidal activity (60–70%) at 3 kg/ha. At
the same time, almost all the studied compounds
demonstrated a stimulating effect on plant growth.
Experiments were performed on seeds and seedlings of
Phaseolus vulgaris L. The effect of aqueous
suspensions of compounds 1–8 and a solution of
The reaction of ketone 1 with hydrazine hydrate
and p-toluenesulfonyl hydrazide led to the formation
of 5-(1-hydrazonoethyl)-6-methylthiazolo[3,2-b][1,2,4]-
triazole 4 and 4-methyl-N'-{1-(6-methylthiazolo[3,2-b]-
[1,2,4]triazol-5-yl)ethylidene}benzenesulfonohydrazide
5, respectively (Scheme 2).
The reaction of compound 1 with hydroxylamine
furnished 1-(6-methylthiazolo[3,2-b][1,2,4]triazol-5-
Scheme 2.
O
NHNH2
S
CH3
CH3
CH3
CH3
O
CH3
CH3
O
N
N
N
N
CH3
H3C
N
N
N
N
N2H4
N
H
S
S
N NH2
S
N N S
O
O
1
4
5
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 89 No. 1 2019

34
YENGOYAN et al.
Scheme 3.
CH3
CH3
N
N
N
RHlg
S
N OR
7a, 7b
CH3
CH3
CH3
CH3
O
N
N
N
N
NH2OH
N
N
CH3
S
S
N OH
CH3
N O
O
6
N
1
N
C6H5−N=C=O
S
N
NH
8
R = C3H7 (a), CH2CH2OC6H5 (b).
heteroauxin as a reference in concentrations of 25 and
50 mg/L on seed viability, their germination and
seedling growth was studied. The activity of com-
pounds varied in the range of 65–87% compared with
heteroauxin (see the table). The substances that
showed the greatest activity in the experiment (1, 5, 6,
and 7a) were chosen for detailed study and further
field trials.
progress and individuality of the obtained compounds
were monitored by TLC on Silufol UV-254 plates;
eluting with acetone–hexane mixture (2 : 1). Melting
points were determined by the capillary method.
Plant growth regulating activity of compounds 1–8
Plant growth regulating
Compound
Heteroauxin
1
с, mg/L
activity compared
with heteroauxin, %
In conclusion, a simple and convenient method for
the synthesis of 1-(6-methylthiazolo[3,2-b][1,2,4]tri-
azol-5-yl)ethan-1-one was developed by hetero-
cyclization of 3-{(1H-1,2,4-triazol-3-yl)thio}pentane-
2,4-dione. As a result of its transformations, a number
of derivatives were obtained, which, with preliminary
biological screening, showed a stimulating effect on
plant growth. The results of the study indicate the
promise of finding new plant growth regulators in a
series of fused bicyclic thiazolotriazole derivatives.
25
50
100
100
25
50
81.2
82.1
2
3
25
50
64.9
65.7
25
50
63.3
63.1
EXPERIMENTAL
4
25
50
60.6
66.5
1H and 13C NMR spectra were recorded on a Varian
Mercury-300 NMR spectrometer (300 and 75 MHz,
respectively) from DMSO-d6 solutions. The reaction
5
25
50
84.8
65.0
6
25
50
86.1
87.0
Scheme 4.
7a
7b
8
25
50
74.7
–
CH3
CH3
CH3
CH3
N
N
N
N
N
N
N
25
50
65.7
66.1
S
S
N OR
25
50
69.1
60.7
RO
E
Z
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 89 No. 1 2019

SYNTHESIS OF NEW THIAZOLO[3,2-b][1,2,4]TRIAZOLE DERIVATIVES
35
1-(6-Methylthiazolo[3,2-b][1,2,4]triazol-5-yl)ethan-
1-one (1). A mixture of 3-{(1H-1,2,4-triazol-5-yl)thio}-
pentane-2,4-dione (0.01 mol) in 10 mL of toluene and
catalytic amount of p-toluenesulfonic acid was
refluxed for 10 h. After removal of toluene, the residue
was treated with water, filtered off and dried. Yield
78%, mp 138–140°C. 1H NMR spectrum, δ, ppm: 2.61
s (3H, 6-CH3), 2.91 s (3H, COCH3), 8.18 s (1H, CH).
13C NMR spectrum, δС, ppm: 12.56, 28.74, 126.60,
134.84, 154.57, 156.59, 189.39. Found, %: C 46.28; H
(5). A mixture of compound 1 (0.01 mol) and para-
toluenesulfonyl hydrazide (0.01 mol) in water (10 mL)
was stirred for 1 h at 60–70°C. The resulting pre-
cipitate was filtered off, washed with water and dried.
1
Yield 90%, mp 232–234°C. H NMR spectrum, δ,
ppm: 2.28 s (3H, CH3-tolyl), 2.38 s (3H, 6-CH3), 2.63
s (3H, N=C–CH3), 7.39–7.74 m (4H, C6H4), 8.28 s
(1H, CH), 10.78 s (1H, NH). 13C NMR spectrum, δС,
ppm: 12.24, 15.82, 20.77, 125.43, 127.49, 128.71,
129.28, 135.63, 143.39, 147.81, 153.23, 155.68. Found,
%: C 48.03; H 4.27; N 20.22; S 18.12. C14H15N5O2S2.
Calculated, %: C 48.12; H 4.33; N 20.04; S 18.35.
3.79; N 23.30; S 17.48. C H7N3OS. Calculated, %: C
7
46.40; H 3.89; N 23.19; S 17.69.
1-(6-Methylthiazolo[3,2-b][1,2,4]triazol-5-yl)-
ethan-1-one oxime (6). To a solution of NaOH
(0.01 mol) in water (3 mL) at 0°C was added a
solution of hydroxylamine hydrochloride (0.01 mol) in
5 mL of water, compound 1 (0.01 mol) and ethanol
(5 mL). The mixture was kept at 20°C for 24 h, then
heated for 2 h at 50–60°C. After cooling, the pre-
cipitate was filtered off and dried. Yield 91%, mp 178–
2-{1-(6-Methylthiazolo[3,2-b][1,2,4]triazol-5-yl)-
ethylidene}hydrazine-1-carboxamide (2). A mixture
of hydrazincarboxamide hydrochloride (0.01 mol) and
compound 1 (0.01 mol) in water (15 mL) was stirred
for 4 h at 100°C. The resulting precipitate was filtered
1
off and dried. Yield 85%, mp 274–275°C. H NMR
spectrum, δ, ppm: 2.31 s (3H, 6-CH3), 2.71 s (3H,
N=C–CH3), 7.62 br. s and 8.27 br. s (2H, NH2), 9.09
br. s (1H, NH). 13C NMR spectrum, δС, ppm: 12.23,
15.20, 126.48, 127.04, 139.07, 152.97, 155.42, 156.21.
Found, %: C 40.19; H 4.15; N 35.45; S 13.60. C8H10N6OS.
Calculated, %: C 40.33; H 4.23; N 35.27; S 13.46.
1
180°C. H NMR spectrum, δ, ppm (Z:E = 3:1): 2.29
(Z) s and 2.31 (E) s (3H, 6-CH3), 2.65 (E) s and 2.71 (Z) s
(3H, N=C–CH3), 7.99 (Z) s and 8.01 (E) s (1H, CH),
11.50 (Z) s and 11.57 (E) s (1H, OH). 13C NMR spec-
trum, δС, ppm: 12.09 (Z), 12.86 (Z), 12.99 (E), 21.08
(E), 116.69 (E), 123.99 (Z), 126.16 (Z), 127.65 (E),
142.22 (E), 147.20 (Z), 152.89 (E), 154.76 (Z), 154.82
(Z), 155.04 (E). Found, %: C 42.74; H 4.02; N 28.22;
S 16.08. C7H8N4OS. Calculated, %: C 42.85; H 4.11;
N 28.55; S 16.34.
2-{1-(6-Methylthiazolo[3,2-b][1,2,4]triazol-5-yl)-
ethylidene}hydrazine-1-carbothioamide (3). Com-
pound 1 (0.01 mol) was added to a mixture of
hydrazincarbothioamide (0.01 mol) and a 36% aqueous
HCl solution (0.01 mol). The mixture was stirred for
4–5 h at 100°C. The resulting precipitate was filtered
1
Synthesis of compounds 7a, 7b. A mixture of
KOH (0.01 mol) and compound 6 (0.01 mol) in DMF
(10 mL) was stirred for 2 h until salt formation
completed, then 0.01 mol of propyl bromide or
2-phenoxyethyl bromide was added. The reaction
mixture was kept for 24 h at room temperature, then
heated for 2 h at 60–70°C until pH = 7 was adjusted.
DMF was removed and residue was treated with water.
Precipitate was filtered off and dried.
off and dried. Yield 90%, mp 267–268°C. H NMR
spectrum, δ, ppm: 2.43 s (3H, 6-CH3), 2.73 s (3H,
N=C–CH3), 7.41 br. s and 8.32 br. s (2H, NH2), 10.54
br. s (1H, NH). 13C NMR spectrum, δС, ppm: 12.49,
16.00, 125.87, 128.82, 142.95, 153.26, 155.70, 178.99.
Found, %: C 37.66; H 3.77; N 33.27; S 25.03. C8H10N6S2.
Calculated, %: C 37.78; H 3.96; N 33.04; S 25.21.
5-(1-Hydrazonoethyl)-6-methylthiazolo[3,2-b]-
[1,2,4]triazole (4). A mixture of compound 1
(0.01 mol), hydrazine hydrochloride (0.01 mol) and
water (10 mL) was stirred for 3-4 h at 80–90°C. The
resulting precipitate was filtered off, washed with
1-(6-Methylthiazolo[3,2-b][1,2,4]triazol-5-yl)ethan-
1-one O-propyloxime (7a). Yield 85%, mp 48–50°C.
1H NMR spectrum, δ, ppm (Z:E = 3:1): 0.98 (Z) t and
0.99 (E) t (3H, CH3-propyl, J = 6.9 Hz), 1.73 m (2H,
CH2), 2.30 (Z) s and 2.33 (E) s (3H, 6-CH3), 2.67 (E) s
and 2.72 (Z) s (3H, N=C–CH3), 4.09 (E) t and 4.12 (Z)
t (2H, OCH2, J = 6.7 Гц), 8.01 (Z) s and 8.04 (E) s
(1H, CH). 13C NMR spectrum, δС, ppm: 9.89 (Z), 10.09
(E), 12.22 (Z), 13.03 (E), 13.62 (Z), 21.10 (E), 21.64
(E), 21.78 (Z), 75.41 (Z), 75.58 (E), 116.24 (E), 122.46
(Z), 127.09 (Z), 128.52 (E), 143.23 (E), 147.85 (Z),
1
water and dried. Yield 88%, mp 270–272°C. H NMR
spectrum, δ, ppm: 2.62 s (3H, 6-CH3), 2.88 br. s (2H,
NH2), 2.92 s (3H, N=C–CH3), 8.18 s (1H, CH). Found,
%: C 43.12; H 4.71; N 35.60; S 16.19. C7H9N5S.
Calculated, %: C 43.06; H 4.65; N 35.87; S 16.42.
4-Methyl-N'-[1-(6-methyl[1,3]thiazolo[3,2-b][1,2,4]-
triazol-5-yl)ethylidene]benzenesulfonohydrazide
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 89 No. 1 2019

36
YENGOYAN et al.
153.01, 154.96 (Z), 155.27 (E). Found, %: C 50.52; H
5.90; N 23.70; S 13.62. C10H14N4OS. Calculated, %: C
50.40; H 5.92; N 23.51; S 13.46.
CONFLICT OF INTEREST
No conflict of interest was declared by the authors.
REFERENCES
1-(6-Methylthiazolo[3,2-b][1,2,4]triazol-5-yl)-
ethan-1-one O-(2-phenoxyethyl)oxime (7b). Yield
97%, mp 70–72°C. 1H NMR spectrum, δ, ppm (Z : E =
3.5 : 1): 2.32 (Z) s and 2.33 (E) s (3H, 6-CH3), 2.62 (E)
s and 2.73 (Z) s (3H, N=C–CH3), 4.26 m (2H, NO–
CH2), 4.48 m (2H, C6H5OCH2), 6.85–7.26 m (5H,
C6H5), 8.03 (Z) s and 8.04 (E) s (1H, CH). 13C NMR
spectrum, δС, ppm: 12.25 (Z), 12.97 (E), 13.91 (Z),
21.17 (E), 65.22 (E), 65.43 (Z), 71.98 (E), 72.42 (Z),
113.98 (E), 114.02 (Z), 116.05, 120.16 (Z), 122.05 (E),
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Found, %: C 56.81; H 5.02; N 17.51; S 10.33.
C15H16N4O2S. Calculated, %: C 56.94; H 5.10; N
17.71; S 10.14.
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(Z : E = 4 : 1): 2.52 (Z) s and 2.53 (E) s (3H, 6-CH3),
2.63 (E) s and 2.83 (Z) s (3H, N=C–CH3), 6.96–7.58 m
(5H, C6H5), 8.10 (Z) s and 8.14 (E) s (1H, CH), 9.47
(E) s and 9.58 (Z) s (1H, NH). 13C NMR spectrum, δС,
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118.50 (Z), 121.23, 122.41 (Z), 128.02 (E), 128.12 (Z),
129.98 (E), 138.06 (Z), 150.16 (E), 153.48 (E), 154.54
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S 10.31. C14H13N5O2S. Calculated, %: C 53.32; H
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FUNDING
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This work was financially supported by the Russian-
Armenian University and the Ministry of Education
and Science of of Russia.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 89 No. 1 2019