Convenient synthesis of some 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles and 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines bearing 3-methylthio{7H-1,2,4- triazolo[1,5-d]tetrazol-6-yl}moiety as possible antimicrobial activity

Article abstract of DOI:10.1080/10426500801967773

4-Amino-4H-3-methylthio{7H-1,2,4-triazolo[1,5-d]tetrazol-6-yl}-1,2, 4-triazole-5thi-ol (1) was condensed with various substituted aromatic aldehydes or acid chlorides to yield a series of arylideneamines 2 or aroylamines 3. These were easily cyclized to the corresponding 6-aryl-3-methylthio7H-1,2,4- triazolo[1,5-d]tetrazol-6-yl-1,2,4-triazolo [3,4-b]-1,3,4-thiadiazoles (4) on treatment with palladium-on-charcoal or phosphorus oxychloride. Compounds 4 were also prepared directly via the reaction of 1 with aromatic carboxylic acids in the presence of phosphorus oxychloride. Cyclocondensation of 1 with a variety of two-carbon cyclizing reagents, namely chloroacetone, pyruvic acid, benzoylformic acid, and benzoin led to the formation of 3-methylthio{7H-1,2,4- triazolo[1,5-d]tetrazol-6-yl}-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines (5-8). Some of the newly synthesized compounds were tested for their antibacterial and antifungal activity against a variety of microorganisms.

Full text of DOI:10.1080/10426500801967773

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Convenient Synthesis of
Some 1,2,4-triazolo[3,4-
b]-1,3,4-thiadiazoles and
1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazines Bearing 3-
Methylthio{7H-1,2,4-
triazolo[1,5-d]tetrazol-6-
yl}moiety as Possible
Antimicrobial Activity
Mamdouh A. M. Taha a
a Chemistry Department, Faculty of Science,
Faiyoum University, Faiyoum, Egypt
Version of record first published: 27 Sep 2008.
To cite this article: Mamdouh A. M. Taha (2008): Convenient Synthesis of Some 1,2,4-
triazolo[3,4-b]-1,3,4-thiadiazoles and 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines Bearing
3-Methylthio{7H-1,2,4-triazolo[1,5-d]tetrazol-6-yl}moiety as Possible Antimicrobial
Activity, Phosphorus, Sulfur, and Silicon and the Related Elements, 183:10, 2525-2533
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Phosphorus, Sulfur, and Silicon, 183:2525–2533, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500801967773
Convenient Synthesis of Some
1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles and
1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines Bearing
3-Methylthio{7H-1,2,4-triazolo[1,5-d]tetrazol-6-yl}moiety
as Possible Antimicrobial Activity
Mamdouh A. M. Taha
Chemistry Department, Faculty of Science, Faiyoum University,
Faiyoum, Egypt
4-Amino-4H-3-methylthio{7H-1,2,4-triazolo[1,5-d]tetrazol-6-yl}-1,2,4-triazole-5-
thi-ol (1) was condensed with various substituted aromatic aldehydes or acid
chlorides to yield a series of arylideneamines 2 or aroylamines 3. These were
easily cyclized to the corresponding 6-aryl-3-methylthio7H-1,2,4-triazolo[1,5-
d]tetrazol-6-yl-1,2,4-triazolo [3,4-b]-1,3,4-thiadiazoles (4) on treatment with
palladium-on-charcoal or phosphorus oxychloride. Compounds
4 were also
prepared directly via the reaction of 1 with aromatic carboxylic acids in the
presence of phosphorus oxychloride. Cyclocondensation of 1 with a variety of
two-carbon cyclizing reagents, namely chloroacetone, pyruvic acid, benzoylformic
acid, and benzoin led to the formation of 3-methylthio{7H-1,2,4-triazolo[1,5-
d]tetrazol-6-yl}-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines (5−8). Some of the newly
synthesized compounds were tested for their antibacterial and antifungal activity
against a variety of microorganisms.
Keywords Antimicrobial activity; triazole; triazolotetrazole; triazolothiadiazoles; tria-
zolothiadiazines
INTRODUCTION
A review2 reveals that publications dealing with the synthesis of con-
densed 1,2,4-triazolo-heterocycles are associated with a wide range of
diverse types of biological properties. A large number of triazoloth-
iadiazoles and triazolothiadiazines have recently been reported to
Received 24 October 2007; accepted 14 January 2008.
This article is Part IV of a series; for Part III, see Ref. 1.
Address correspondence to Mamdouh A. M. Taha, Chemistry Department, Faculty
of Science, Faiyoum University, Faiyoum 63514, Egypt. E-mail: mamdouhamtaha@
yahoo.com
2525

2526
M. A. M. Taha
possess CNS depressant, antibacterial, antifungal, antitumor, anti-
inflammatory, herbicidal, pesticidal, and insecticidal properties.3−12
Therefore, it was envisaged that chemical entities with both
1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles and 1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazines, bearing 3-methylthio {7H-1,2,4-triazolo[1,5-d]tetrazol-6-
yl} linkage would result in compounds of interesting antimicrobial
activity.
RESUTLS AND DISCUSSION
The syntheses of the title compounds were accomplished as shown in
Schemes 1 and 2. The reaction of 4-amino-4H-3-methylthio{7H-1,2,4-
triazolo[1,5-d] tetrazol-6-yl}-1,2,4-triazole-5-thiol1 (1) with aromatic
aldehydes gave the expected yellow arylideneamines (2) in excellent
1
yields. Their H NMR spectra revealed common characteristic signals
assignable to the methylenic ( N CH ) and aromatic protons. Their
MS showed the expected molecular ion peaks in agreement with the
assigned structures. Refluxing13 compound 1 with aromatic acid chlo-
rides afforded aroylamines 3. All products showed the presence of an
amide group ( N C O) through their absorption band in the IR spec-
tra. The MS of the aroylamines 3 revealed the expected molecular ions,
and their elemental analyses confirmed their formulas. The products
2 and 3 underwent cyclization into 6-aryl-3-methylthio{7H-1,2,4-
triazolo[1,5-d]tetrazol-6-yl}-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles
4, when their refluxed with 5% palladium-on-charcoal in ethanol
and phosphorus oxychloride, respectively. The formation of cyclized
compounds 4 were confirmed on the basis of spectral studies. The IR
spectrum of each product did not show any SH (2600−2545 cm−1
)
and amide absorption band; only NH absorption was present (tria-
SCHEME 1

1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles
2527
SCHEME 2
1
zolotetrazole). The H NMR spectra of the cyclized products showed
the disappearance of the signals assigned to methylenic and NH
(aroylamino) protons in the spectra of the parent compounds 2 and 3,
respectively. The characteristic proton signal (3.82−3.45 ppm) of the
1
SH group of the parent 2 and 3 was absent in H NMR spectra of the
cyclized products. Interestingly, compounds 4 can easily be obtained
directly from 1 with aromatic carboxylic acids in the presence of phos-
phorus oxychloride. These products were identical in all aspects to that
above described methods (m.p., mixed m.p., TLC, and IR). Recently, it
has been also reported3−5,13,14 that the same procedure by ring closure
of aminothiols using carboxylic acids. The physical constants and
spectral data of compounds (2–4) are listed in Tables I and II.
Furthermore, aminothiols can be considered3,15 as key starting
materials for the synthesis of diverse 1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazine compounds. Thus, the aminothiol 1 reacted in one-pot
with two-carbon cyclizing reagents, namely chloroacetone, pyruvic
acid, benzoylformic acid and benzoin, to construct 3-methylthio{7H-
1,2,4-triazolo[1,5-d]tetrazo-6-yl}-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazine
derivatives (5−8), respectively. The elemental and spectroscopic data
of these compounds are consistent with the assigned structures and
are given in the Experimental section.

2528
M. A. M. Taha
Antimicrobial Activities
Some of the prepared compounds were screened for their antimicrobial
activity (determined in Extension Laboratory, Faculty of Agriculture,
Alexandria University, Alexandria, Egypt) using Staphylococcus au-
reus (Gram- positive) and Escherichia coli (Gram-negative) bacteria, in
addition to a Candida albicans (fungus) microorganisms. The activities
of these compounds were used for the determination16,17 of antibacte-
rial and antifungal activity. Solutions of these compounds, ampicillin
trihydrate and clotrimazole were dissolved in DMSO at concentration
of 1600 mg/mL. The minimal inhibitory concentrations (MIC) were
measured in mg/mL (Table III) at the end of the incubation period
for 24 h to 48 h at 36◦C. Controls for the DMSO microorganisms and
media microorganisms were also undertaken. The results showed that
compounds 3a and 3c exhibited activity comparable 25% of the ampi-
cillin against S. aureus. While the effect of 3a and 3c were 50% of
the ampicillin against E. coli , the activity of 3a and both 2c and 3c
were 50% and 25% against C. albicans comparable to clotrimazole, re-
spectively. The remaining compounds showed lower activity than the
reference standards (ampicillin, clotrimazole) against the test organ-
isms. All these results are based on preliminary tests; more studies are
to be conducted to get conclusive results.
CONCLUSION
Thiadiazole and thiadiazine derivatives in this article have been syn-
thesized via the reaction of 1 with one/two-carbon cyclizing reagents
and were identified by microanalyses and spectral data. Furthermore,
some of the new synthesized compounds were screened for their an-
tibacterial and antifungal activities.
EXPERIMENTAL
Melting points were taken in open capillary tubes in a MEL-TEMP
II melting apparatus and are uncorrected. The purity of compounds
was confirmed by thin layer chromatography using plates precoated
with Silica Gel G (Merck: layer thickness 0.25 mm). All the spots were
detected by exposition to iodine vapour for a few minutes. The infrared
spectra (IR) were recorded on a Perkin-Elmer FT Paragon 1000 and
Pye-Unicam SP-300 spectrometers in KBr (νmax in cm−1). 1H NMR
spectra were recorded using a Varian Mercury VXR-3000 spectrometer
using tetramethylsilane (TMS) as internal standard. Mass spectra (MS)
were recorded on a Shimadzu GCMS-Q 1000 EX mass spectrometer at

1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles
2529
70eV. Microanalyses were performed by the Microanalytical Unit, Cairo
University, Giza, Egypt.
General Procedure for the Preparation of 4-arylideneamino-3-
methylthio{7H-1,2,4-triazolo[1,5-d]tetrazol-6-yl}-1,2,4-triazole-
5-thiols (2a−d)
A mixture of compound 11 (0.5 g, 1.85 mmol) and the appropri-
ate aromatic aldehyde (0.2 g, 1.85 mmol) namely: benzaldehyde,
p-tolualdehyde, p-chlorobenzaldehyde, and p-nitrobenzaldehyde in
ethanol (20 mL) was refluxed for 30 min. The solvent was evaporated
and the formed precipitate was filtered off and recrystallized from
ethanol to yield yellow crystals. The physical constants and spectral
data of compounds (2a−d) are given in Tables I and II.
TABLE I Physical Constants of Compounds (2−4)
Analysis (%) Calcd. /Found
Yield
(%)
M.p.
(◦C)
Molecular
formula
Compound
C
H
N
2a
86
84
85
88
65
71
75
74
170−172
180−182
186−188
190−192
184−186
189−190
196−198
200−202
190−191
195−196
C12H10N10S2
40.22
40.61
41.94
42.32
36.69
36.53
35.73
35.63
38.50
38.41
40.21
40.53
2.79
2.52
3.23
3.48
2.29
2.62
2.23
2.58
2.67
3.12
3.09
3.58
2.20
2.43
2.15
2.38
2.25
2.11
2.70
2.62
1.79
2.23
1.75
2.15
39.11
39.49
37.63
38.12
35.67
35.91
38.21
38.63
37.43
37.52
36.08
36.33
34.27
34.73
36.75
36.53
39.33
39.18
37.84
38.33
35.85
35.48
38.40
37.91
2b
2c
2d
3a
3b
3c
3d
4a
4b
4c
4d
C13H12N10S2
C
12H9ClN10S2
C12H9N11O2S2
C12H10N10OS2
C13H12N10OS2
C12H9ClN10OS2 35.25
34.91
C12H9N11O3S2
34.37
34.11
40.45
40.88
42.16
42.56
36.88
37.21
35.91
35.73
76 (A),
54(B), 56(C)
78(A),
C12H8N10S2
C13H10N10S2
59(B), 62(C) 210−211
C
12H7ClN10S2
77(A),
58(B), 61(C)
81(A),
61(B), 64(C)
218−219
C12H7N11O2S2

2530
M. A. M. Taha
TABLE II Spectral Data of Compounds (2−4)
Compound
Spectral Data
2a
IR : ν = 3235 (NH), 2555 (SH) cm−1
.
1HNMR (DMSO-d6): δ =
12.70 (s, 1H, NH), 8.30−7.52 (m, 5H, ArH), 7.33 (s, 1H,
N
CH), 4.20 (s, 2H, CH2), 3.82 (s, 1H, SH) ppm. MS: m/z
(%) = 359 (M++ 1, 17).
2b
2c
IR : ν = 3200 (NH), 2570 (SH) cm−1
.
1HNMR (DMSO-d6): δ =
12.60 (s, 1H, NH), 7.92−7.63 (m, 4H, ArH), 7.13 (s, 1H,
N
CH), 4.15 (s, 2H, CH2), 3.75 (s, 1H, SH) 2.91 (s, 3H, CH3)
ppm. MS: m/z (%) = 372 (M+ , 25).
IR : ν = 3195 (NH), 2590 (SH) cm−1
.
1HNMR (DMSO-d6): δ =
11.92 (s, 1H, NH), 8.22−7.66 (m, 4H, ArH), 7.22 (s, 1H,
N
CH), 4.12 (s, 2H, CH2), 3.80 (s, 1H, SH) ppm. MS: m/z
(%) = 392 (M+ , 28).
2d
3a
IR : ν = 3230 (NH), 2600 (SH) cm−1
.
1HNMR (DMSO-d6): δ =
12.65 (s, 1H, NH), 8.22−7.52 (m, 5H, 4ArH +
N CH), 4.15
(s, 2H, CH2), 3.75 (s, 1H, SH) ppm.
IR : ν = 3325 (NH), 2550 (SH) 1670 (NCO) cm−1
.
1HNMR
(DMSO-d6): δ = 12.62, 11.25 (2s, 1H each, 2NH), 8.20−7.28
(m, 5H, ArH), 4.15 (s, 2H, CH2), 3.74 (s, 1H, SH) ppm. MS:
m/z (%) = 374 (M+ , 12).
3b
3c
3d
IR : ν = 3290 (NH), 2600 (SH) 1660 (NCO) cm−1
.
1HNMR
(DMSO-d6): δ = 12.51, 11.81 (2s, 1H each, 2NH), 8.15−7.62
(m, 4H, ArH), 4.22 (s, 2H, CH2), 3.74(s, 1H, SH), 2.53(s, 3H,
CH3) ppm. MS: m/z(%) = 388 (M+, 19).
IR : ν = 3280 (NH), 2550 (SH) 1665 (NCO) cm−1
.
1HNMR
(DMSO-d6): δ = 11.91, 11.62 (2s, 1H each, 2NH), 8.24−7.14
(m, 4H, ArH), 4.18 (s, 2H, CH2), 3.71 (s, 1H, SH) ppm. MS:
m/z (%) = 408 (M+ , 25).
IR : ν = 3300 (NH), 2545 (SH) 1671 (NCO) cm−1
.
1HNMR
(DMSO-d6): δ = 12.51, 11.81 (2s, 1H each, 2NH), 8.21−7.63
(m, 4H, ArH), 4.25 (s, 2H, CH2), 3.64 (s, 1H, SH) ppm. MS:
m/z (%) = 420 (M++ 1, 30).
4a
4b
IR : ν = 3225 (NH), cm−1
.
1HNMR (DMSO-d6): δ = 12.65, (s, 1H,
NH), 8.25−7.44 (m, 5H, ArH), 4.15 (s, 2H, CH2) ppm.
IR : ν = 3220 (NH), cm−1
.
1HNMR (DMSO-d6): δ = 11.92 (s, 1H,
NH), 8.46−7.29 (m, 4H, ArH), 4.15 (s, 2H, CH2), 2.41 (s, 3H,
CH3) ppm. MS: m/z (%) = 370 (M+, 27).
4c
4d
IR : ν = 3220 (NH), cm−1
.
1HNMR (DMSO-d6): δ = 12.22 (s, 1H,
NH), 8.24−7.44 (m, 4H, ArH), 4.25 (s, 2H, CH2) ppm. MS: m/z
(%) = 390 (M+, 9.8).
IR : ν = 3125 (NH), cm−1
.
1HNMR (DMSO-d6): δ = 12.43 (s, 1H,
NH), 8.11−7.45 (m, 4H, ArH), 4.18 (s, 2H, CH2) ppm.

1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles
2531
TABLE III Antimicrobial Activity Data of the Prepared Compounds
(MIC in µg/mL)
Compound
S. aureus
E. Coli
C. albicans
2a
2c
3a
> 200
100
50
100
100
50
100
50
25
3c
50
50
50
4a
6
100
> 200
12.5
—
>200
100
25
>200
100
—
Ampicillin
Clotrimazole
—
12.5
General Procedure for the Preparation of 4-aroylamino-3-
methylthio{7H-1,2,4-triazolo[1,5-d]tetrazol-6-yl}-1,2,4-triazole-
5-thiols (3a−d)
A mixture of 1 (0.5 g, 1.85 mmol) and the suitable aromatic acid chlo-
ride (0.3 g, 1.85 mmol) in pyridine (2 mL) was heated under reflux at
100◦C for 1 h. After attaining room temperature, ice-water (20 mL)
was added to the reaction mixture and then extracted with chloroform.
The chloroform extract was washed with aqueous sodium bicarbonate
solution and water, dried and evaporated. The collected residue was
crystallized from ethanol. The physical constants and spectral data of
compounds (3a−d) are given in Tables I and II.
General Procedure for the Preparation of
6-aryl-3-methylthio{7H-1,2,4-triazolo[1,5-d]tetrazol-6-yl}-1,2,4-
triazolo[3,4-b]-1,3,4-thiadiazoles (4a−d)
Method (A)
A solution of the respective 2a−d (0.5 g) in ethanol (15 mL) was
treated with 5% palladium-on-charcoal (0.2 g) and heated under reflux
for 2 h. The catalyst was filtered off and the filtrate evaporated. The
obtained product was crystallized from ethanol.
Method (B)
A mixture the appropriate 3a−d (0.5 g) and phosphorus oxychloride
(10 mL) was heated under reflux for 1 h. and then allowed to cool at
room temperature. The reaction mixture was poured onto a diluted
aqueous solution of sodium bicarbonate. The precipitated solid product
was filtered and washed with cold water. The collected solid was dried
and crystallized from ethanol.

2532
M. A. M. Taha
Method (C)
A mixture of aminothiol 1 (0.5 g, 1.85 mmol), and suitable aromatic
carboxylic acid (0.23 g, 1.85 mmol) solubilized in phosphorus oxychlo-
ride (15 mL) was refluxed for 3 h. After cooling, the reaction mixture
was poured onto cold sodium bicarbonate solution. The resulting solid
product that formed filtered off, washed with water and crystallized
from ethanol.
The physical constants and spectral data of compounds (4a−d) are
given in Tables I and II.
Synthesis of Compounds 5–8—General Procedure
A mixture of compound 1 (0.5 g, 1.85 mmol) and the appropriate
reagents, namely: chloroacetone (0.17 g, 1.85 mmol), pyruvic acid (0.16
g, 1.85 mmol), benzoylformic acid (0.28 g, 1.85 mmol), and benzoin (0.39
g, 1.85 mmol) in phosphorus oxychloride (10 mL) was refluxed for 2−3
h, slowly quenched onto crushed ice with stirring and it was neutralized
with solid sodium bicarbonate. The solid which separated was filtered
and crystallized from ethanol.
The characterization data of these compounds follow.
6-Methyl-7H-3-methylthio{7H-1,2,4-triazolo[1,5-d]tetrazol-6-
yl}-1,2,4-triazolo[3,4-bi b]-1,3,4-thiadiazine (5)
Yield: 58%; m.p. 220−221◦C; : ν = 3250 (NH)cm−1. 1H NMR (DMSO-
d6): δ = 12.60 (s, 1H, NH), 4.15, 4.05 (2s, 2H each, 2CH2), 2.30 (s, 3H,
CH3) ppm. MS: m/z (%) = 309 (M++ 1, 28).
Anal. calcd. for C8H8N10S2 : C, 31.17; H, 2.60; N, 45.46%. Found : C,
31.51; H, 3.09; N, 45.91%.
6-Methyl-3-methylthio{7H-1,2,4-triazolo[1,5-d]tetrazol-6-yl}-
1,2,4-triazolo [3,4-b]-1,3,4-thiadiazin-7-one (6)
Yield: 65%; m.p. 195–197◦C; IR : ν = 3230 (NH), 1730 (CO) cm−1. 1H
NMR (DMSO-d6) : δ = 12.55 (s, 1H, NH), 4.10 (s, 2H, CH2), 2.15 (s, 3H,
CH3) ppm.
Anal. calcd. for C8H6N10OS2 : C, 29.81; H, 1.86; N, 43.48%. Found:
C, 30.22; H, 1.52; N, 43.63% .
3-Methylthio{7H-1,2,4-triazolo[1,5-d]tetrazol-6-yl}-6-phenyl-
1,2,4-triazolo [3,4-bi b]-1,3,4-thiadiazin-7-one (7)
Yield: 71%; m.p. 180−182◦C; IR : ν =3235 (NH), 1740 (CO) cm−1
.
MS: m/z (%) = 385 (M++ 1, 32).

1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles
2533
Anal. Calcd. For C13H8N10OS2 : C, 40.63; H, 2.08; N, 36.46%. Found:
C, 40.13; H, 2.52; N, 36.13% .
6,7-Diphenyl-3-methylthio{7H-1,2,4-triazolo[1,5-d]tetrazol-6-
yl}-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazine (8)
Yield: 60%; m.p. 224−226◦C; IR : ν =3200 (NH) cm−1
.
1H NMR
(DMSO-d6) : δ = 12.10 (s, 1H, NH), 8.30–7.55 (m, 10H, ArH), 7.25 (s,
1H, CH); 4.25 (s, 2H, CH2) ppm. MS: m/z (%) 446 (M+ , 16).
Anal. calcd. for C19H14N10S2: C, 51.12; H, 3.14; N, 31.39%. Found: C,
51.22; H, 3.44; N, 31.83% .
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[1] M. A. M. Taha and S. M. El-Badry, Phosphorus, Sulfur, and Silicon, 182, 1011
(2007).
[2] M. A. E. Shaban and A. Z. Nasr, Advances in Heterocyclic Chemistry, A. R. Katritzky,
Ed. (Academic Press Inc, New York, 1990), Vol. 49, p. 277.
[3] T. Karabasanagouda, A. V. Adhikari, and N. S. Shetty, Eur. J. Med. Chem., 42, 521
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