Synthesis of [1,3,4]thiadiazolo[2,3-C][1,2,4]triazin-4-ones using sulfuric acid supported onto silica gel in solventless system

Article abstract of DOI:10.1080/10426500490463835

[1,3,4]Thiadiazolo[2,3-c][1,2,4]triazin-4-ones were prepared by one pot condensation and cyclization of 4-amino-[1,2,4]triazine-3-thione-5-ones with, various aromatic carboxylic acids in the presence of silica gel sulfuric acid in solventless condition.

Full text of DOI:10.1080/10426500490463835

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SYNTHESIS OF [1,3,4]THIADIAZOLO[2,3-C]
[1,2,4]TRIAZIN-4-ONES USING SULFURIC ACID
SUPPORTED ONTO SILICA GEL IN SOLVENTLESS SYSTEM
a
b
b
c
Majid M. Heravi , Navid Ramezanian , Majid M. Sadeghi & Mitra Ghassemzadeh
a
Azzahra University , Vanak, Tehran, Iran
b
Azad University , Yazd, Iran
c
Chemistry & Chemical Engineering Research Center of Iran , Tehran, Iran
Published online: 16 Aug 2010.
To cite this article: Majid M. Heravi , Navid Ramezanian , Majid M. Sadeghi & Mitra Ghassemzadeh (2004) SYNTHESIS OF
1,3,4]THIADIAZOLO[2,3-C][1,2,4]TRIAZIN-4-ONES USING SULFURIC ACID SUPPORTED ONTO SILICA GEL IN SOLVENTLESS
[
SYSTEM, Phosphorus, Sulfur, and Silicon and the Related Elements, 179:8, 1469-1472, DOI: 10.1080/10426500490463835
To link to this article: http://dx.doi.org/10.1080/10426500490463835
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Phosphorus, Sulfur, and Silicon, 179:1469–1472, 2004
Copyright ꢀC Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490463835
SYNTHESIS OF
[
1,3,4]THIADIAZOLO[2,3-C][1,2,4]TRIAZIN-4-ONES
USING SULFURIC ACID SUPPORTED ONTO SILICA
GEL IN SOLVENTLESS SYSTEM
a
b
b
Majid M. Heravi, Navid Ramezanian, Majid M. Sadeghi,
c
and Mitra Ghassemzadeh
a
Azzahra University, Vanak, Tehran, Iran; Azad University,
b
Yazd, Iran; and Chemistry & Chemical Engineering Research
Center of Iran, Tehran, Iranc
(
Received November 25, 2003; accepted March 1, 2004)
[
1,3,4]Thiadiazolo[2,3-c][1,2,4]triazin-4-ones were prepared by one pot
condensation and cyclization of 4-amino-[1,2,4]triazine-3-thione-5-
ones with various aromatic carboxylic acids in the presence of silica
gel sulfuric acid in solventless condition.
Keywords: Carboxylic acid; silica gel sulfuric acid; solid state; solvent-
less conditions; thiadiazolotriazine
The preparation of fine chemicals following environmentally friendly
strategies represents a challenging goal in the field of synthetic or-
1
ganic chemistry. In the past 10 years this approach has had great
development, mainly due to the use of solid acids such as clays and
2
zeolites.
A number of [1,3,4]-thiadiaoles showed antibacterial properties
3
similar to those of well-known sulfonamide drugs. The thiadiazole
nucleus, which incorporates an N· · ·C· · ·S linkage, exhibits a large
4
number of biological activities. In view of possible pharmacological
activity of the new heterocyclic system containing [1,3,4]thiadiazoles,
the synthesis of a series of [1,3,4]thiadiazolo[2,3-c][1,2,4]triazines were
5
reported in the literature. We have recently reported a convenient
and general synthesis for 5H-[1,3,4]thiadiazolo[2,3-d][1,2,4]triazin-5-
6
ones. In continuation of our interest in developing selective and
Address correspondence to Majid M. Heravi, Department of Chemistry, School of Sci-
ences, Azzahra University, Vanak, Tehran, Iran. E-mail: mmheravi@azzahra.ac.ir
1
469

1
470
M. M. Heravi et al.
preparatively useful methodology based on solid acids promoters in
7
solventless system for the synthesis of fine chemical and heterocyclic
8
compounds, in this communication we wish to report the synthesis
of [1,3,4]thiadiazolo[2,3-c][1,2,4]triazines using sulfuric acid supported
onto silica gel. In recent years it has been shown that sulfuric acid ad-
9
sorbed on silica gel can be used as a multipurpose acid catalyst. We
1
0
have recently used this catalyst for tetrahydropyranylation of alcohols
and acetylation of alcohols and phenols.1 Armed with these experi-
1
ences for the present work 6-methyl-4-amino-3-thio-[1,2,4]triazin-5-
1
2
one was condensed and cyclized in a one-pot reaction with various
aromatic carboxylic acids using sulfuric acid supported onto silica gel
(
Scheme 1).
SCHEME 1 Formation of title compounds was confirmed by physical and spec-
troscopic data.
However, it is noteworthy to mention that in the case of using
aliphatic carboxylic acid. this reaction failed and only proceeded to ob-
tain the amide of triazione, which could not be cyclized by prolonged
reaction time.
In conclusion, in comparison with the presently available synthetic
methods for the synthesis of [1,3,4]thiadiazolo[2,3-c][1,2,4]triazin-4-
ones, which uses neat sulfuric acid5b and phosphorus oxychloride5a,c
and shows, drawback from the standpoint of yield, price, and its haz-
ardous, nature the efficiency of the present work is apparent from the
availability of inexpensive sulfuric acid and high yields. Also, due to the
lack of solvent the workup procedure is easy.

Thiadiazolotriazines
1471
EXPERIMENTAL
Melting points were taken in open capillary tubes and are uncorrected.
Infrared (IR) spectra on KBr disc were recorded on Schimadzu-470
1
spectrophotometer. HNMR spectra were recorded in d6-DMSO on a
Brucker Ac80 spectrometer, with tetramethylsilane as an internal stan-
dard. Purity of the compounds was checked by thin-layer chromatog-
raphy using toluene/methanol (8:2) solvent system. 6-Methyl-4-amino-
3
-thio-[1,2,4]-triazin-5-one (1) was prepared according to the reported
1
2
method.
Adsorption of Sulfuric Acid on Slica Gel
A solution of concentrated sulfuric acid (2 ml) in acetone (20 ml) is added
to a solution of silica gel (100 g, Merck, 60,70-230) in acetone (200 ml)
at room temperature for 1 h. The solvent is removed under reduced
pressure. A yellowish brown powder is obtained, which can be stored
in a desiccator for long period of times without any appreciable loss of
activity.
Synthesis of [1,3,4]thiadiazolo[3,2-c][1,2,4]triazin-5-one
General Procedure
Compound 1 (0.158 g, 1 mmol) and an appropriate carboxylic acid
(
3 mmol) were mixed with sulfuric acid supported onto silica gel (0.1 g)
◦
using a spatula. This mixture was kept at 120 C for 3 h. Water (15 ml)
was added and extracted to the residue with CHCl3. The organic layer
was evaporated to dryness, the crude was directly subjected to col-
umn chromatography using CHCl3: EtOAc 70:30 to afford to the title
compound.
◦
◦
5a
Selected data for 2a. Yield 91%; m.p.: 265–266 C (lit. 265 C),
1
HNMR, δ(CDCl3) 2.62 (s, 3H, Me), 7.49–7.53 (m, 3H, aromatic pro-
tons), 8.0–8.1 (m, 2H, aromatic protons); IR v˜ (KBr disc) 1692 cm
−
1
(
C O).
◦
1
Selected data for 2b. Yield 81%; m.p.: 226–227 C, HNMR, δ(CDCl3)
.46 (s, 3H, Me), 4.46 (s, 2H, CH2), 7.32–7.54 (s, 5H, Ph); IR v˜ (KBr disc)
695 cm (C O).
2
1
−1
◦
1
Selected data for 2c. Yield 84%; m.p.: 246–247 C, HNMR, δ(CDCl3)
2
(
.44 (s, 3H, Me), 2.61 (s, 3H, Me), 7.26 (d, 2H, aromatic protons), 7.98
−
1
d, 2H, aromatic protons); IR v˜ (KBr disc) 1674 cm (C O).

1
472
M. M. Heravi et al.
Selected data for 2d. Yield 86%; m.p.: 239–240 C, 1HNMR, δ(d6-
◦
DMSO) 2.47 (s, 3H, Me), 7.85–8.01 (m, 4H, aromatic protons); IR v˜ (KBr
−
1
disc) 1696 cm (C O).
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