The synthesis of triazolothiadiazines and thiadiazoles from 1,2-bis-(4-amino-5-mercapto-1,2,4-triazol-3-yl)-ethanol and ethane

Article abstract of DOI:10.1080/10426500600634681

The reaction of DL-malic and succinic acids with thiocarbohydrazide afforded 1,2-bis[4-amino-5-mercapto-1,2,4-triazol-3-yl]-ethane derivatives 3a and 3b. The reaction of 3a,b with phenacyl bromide and benzoin afforded 1,2-bis-1,2,4-triazolo [3,4-b][1,3,4]thiadiazine derivatives 4 and 5. The carboethoxymethylation of 3a and 3b gave 6a and 6b, respectively, and their reactions with carbon disulfide and benzoylisothiocyanate gave the 1,2-bis-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole 7 and 9, and with p-nitrobenzaldehyde gave a Schiff's base and dihydrothiadiazole 8. The structures were confirmed by using ¹H and ¹³C NMR spectra. Selected members of these compounds were screened for antimicrobial activity. Copyright Taylor & Francis Group, LLC.

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The Synthesis of
Triazolothiadiazines and
Thiadiazoles From 1,2-Bis-
(4-amino-5-mercapto-1,2,4-
triazol-3-yl)- Ethanol and
Ethane
A. H. Moustafa a , R. A. Haggam a , M. E. Younes a
E. S. H. El Ashry b
&
a Chemistry Department, Zagazig University,
Zagazig, Egypt
b Chemistry Department, Alexandria University,
Alexandria, Egypt
Version of record first published: 22 Sep 2006.
To cite this article: A. H. Moustafa , R. A. Haggam , M. E. Younes & E. S. H. El Ashry
(2006): The Synthesis of Triazolothiadiazines and Thiadiazoles From 1,2-Bis-(4-
amino-5-mercapto-1,2,4-triazol-3-yl)- Ethanol and Ethane, Phosphorus, Sulfur, and
Silicon and the Related Elements, 181:10, 2361-2371
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Phosphorus, Sulfur, and Silicon, 181:2361–2371, 2006
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500600634681
The Synthesis of Triazolothiadiazines and Thiadiazoles
From 1,2-Bis-(4-amino-5-mercapto-1,2,4-triazol-3-yl)-
Ethanol and Ethane
A. H. Moustafa
R. A. Haggam
M. E. Younes
Chemistry Department, Zagazig University, Zagazig, Egypt
E. S. H. El Ashry
Chemistry Department, Alexandria University, Alexandria, Egypt
The reaction of DL-malic and succinic acids with thiocarbohydrazide afforded 1,2-
bis[4-amino-5-mercapto-1,2,4-triazol-3-yl]-ethane derivatives 3a and 3b. The re-
action of 3a,b with phenacyl bromide and benzoin afforded 1,2-bis-1,2,4-triazolo
[3,4-b][1,3,4]thiadiazine derivatives 4 and 5. The carboethoxymethylation of 3a and
3b gave 6a and 6b, respectively, and their reactions with carbon disulfide and ben-
zoylisothiocyanate gave the 1,2-bis-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole 7 and 9,
and with p-nitrobenzaldehyde gave a Schiff’s base and dihydrothiadiazole 8. The
1
13
structures were confirmed by using H and C NMR spectra. Selected members of
these compounds were screened for antimicrobial activity.
Keywords 1,2,4-triazole; antimicrobial activity; Malic acid; seco C-nucleosides; succinic
acid; triazolo[3,4-b][1,3,4]thiadiazine; triazolo[3,4-b][1,3,4]thiadiazole
INTRODUCTION
The biological activity of acyclic nucleosides has stimulated extensive
research for the synthesis of their analogues.1,2 The synthetic nucle-
oside ribavirin containing a 1,2,4-triazole ring has a broad spectrum
of activity against RNA and DNA viruses,3 and it has become a
unique drug, when combined with the pegylated interferon-α, for
Received December 9, 2005; accepted February 3, 2006.
We gratefully to Dr. Hasan Abd El-Salam, Assistant Prof. of Microbiology, Faculty of
Pharmacy, Zagazig University, Zagazig, Egypt, for performance of the biological assay. We
also gratefully for Konstanz University, Germany, for carring out all spectra and micro
analysis.
Address correspondence to E. S. H. El Ashry, Chemistry Department, Faculty of
Science, Alexandria University, Alexendria, Egypt. E-mail: eelashry60@hotmail.com
2361

2362
A. H. Moustafa et al.
the treatment of hepatitis C virus infections.4 Consequently, various
approaches have been developed for the synthesis of its analogues
and for evaluating the biological activities of various 1,2,4-triazoles
and their fused ring systems.5,6 Those functionalized with amino and
mercapto groups have found a wide interest as precursors for fused
heterocyclic compounds and/or candidates for biological activities.7 We
have been interested in the acyclic nucleosides and their C-nucleoside
analogues.2 Recently, the syntheses of the seco C-nucleosides 4-
amino-3-(D-gluco- or D-galactopentitol-1-yl)-5-mercapto-1,2,4-triazoles
and the double headed acyclic nucleoside analogues8−11 have been
achieved. Surprisingly, the activity of the D-gluco analogue as an
inhibitor for glycosidase enzymes12−14 was found to be less than the
simple analogue 4-amino-5-mercapto-3-methyl-1,2,4-triazole.15 Such
results attracted our attention to synthesise the 4-amino-5-mercapto-
1,2,4-triazole ring linked to alkyl chains possessing a varied number of
hydroxy groups. In a former publication,16 we prepared 1,2-bis(1,2,4-
triazol-3-yl)ethane-1,2-diol. Continuing our work in this project, the
synthesis of 1,2-bis(triazolothiadiazinyl and thiadiazolyl)ethane and
ethanol analogues were prepared, and their reactivities toward various
cyclizing agents have been studied. Selected examples were screened
for antimicrobial activity.
INVESTIGATION, RESULTS, AND DISCUSSION
The synthesis of 1,2-bis-(4-amino-5-mercapto-4H-1,2,4-triazol-3-yl)
ethan-1-ol (3a) has been achieved by the dehydrative cyclization
of dl-malic acid (1a) with thiocarbohydrazide (2) in dry pyridine
(Scheme 1). Similarly, 1,2-bis-(4-amino-5-mercapto-4H-1,2,4-triazol-3-
yl)ethane (3b) was prepared from succinic acid (1b). Since compound
3b has a difference in m.p. from that reported in the literature,8
1
the structure which we obtained was confirmed by IR, H NMR, and
microanalysis.
The 1H NMR spectrum of 3a exhibited two multiplets at δ5.26 ppm
for CH, 3.28 ppm for CH2 and a doublet at δ5.96 ppm for the OH group,
respectively. This assignment was confirmed by the irradiation of the
CH signal at δ 5.26 ppm, whereby the multiplet at δ3.28 ppm became
two triplets, and the doublet of the OH became a singlet. Its 13C NMR
spectrum showed signals at δ29.4 and 60.8 ppm for CH2 and CHOH.
The 1H NMR spectrum of 3b showed at δ3.12 ppm a singlet due to the
2CH2 groups as a consequence of the symmetry in 3b.
The amino mercapto triazoles 3a and 3b were reacted with phenacyl
bromide under basic conditions to afford the triazolothiadiazine deriva-
1
tives 4a and 4b, respectively, in good yields. The H NMR spectra of

The Synthesis of Triazolothiadiazines and Thiadiazoles
2363
SCHEME 1
each of 4a and 4b showed a singlet in the range δ 4.31–4.33 ppm due
to the 2CH2S groups, but the 13C NMR spectra of 4a showed their
carbon signals at δ 28.9 and 30.2 ppm for the 2CH2S, whereas those of
4b appeared as a signal at δ 22.9 ppm for 4b.
The cycloaddition of compounds 3a and 3b with benzoin afforded the
triazolothiadiazine derivatives 5a and 5b, respectively. The IR spec-
trum of 5a showed bands at 3379 and 3415 cm−1 for NH and OH
stretching frequencies, and the 1H NMR spectra of 5a and 5b showed, in
addition to the expected signals, the presence of the aromatic protons
in the range δ 7.24–7.97 ppm and 2NH protons at δ8.01 and 8.03 ppm,
respectively.

2364
A. H. Moustafa et al.
Heating compounds 3a and 3b with ethyl bromoacetate under ba-
sic conditions gave the carboethoxymethylated 6a and 6b without
detecting their cyclized derivatives. The absorption bands in their IR
spectra showed bands at 1729 and 3325 cm−1 indicating the presence
of the ester carbonyl and NH2 groups, respectively. The 1H NMR spec-
trum of 6a showed the presence of the ethyl group at δ 1.17 (t) and 4.13
(q) ppm. Irradiation of the signal at δ1.17 ppm changed the quartet at
4.13 ppm to a singlet, and the irradiation at δ 3.34 ppm changed the
signal at 5.21 ppm to a singlet confirming the assigned. The 13C NMR
spectrum of 6a showed signals at δ 13.8, 13.9, 29.1, 61.0, 61.1, and
61.8 ppm for the unsymmetrical 2CH3, CH2, CH, and 2CH2O groups
(Scheme 1).
The reaction of 3a and 3b with carbon disulfide in the presence of
alcoholic KOH gave the corresponding triazolothiadiazole 7a and 7b.
1
Each of their H NMR spectra showed a singlet at δ 13.61 and 13.47
ppm for the SH group and compound 7a showed a doublet at δ 5.95
ppm for the OH group. The irradiation of the signal at δ 5.24 ppm
changed the multiplet at δ 3.19–3.32 ppm to a doublet of a doublet, thus
confirming the assigned structure. The 13C NMR spectrum of 7a showed
signals at δ 29.5 and 60.8 ppm characteristic for CH2 and CH groups,
respectively.
Treatment of triazoles 3a with p-nitrobenzaldehyde in acetic acid
1
or DMF gave the two geometric isomers of the schiff base 8a. Its H
NMR spectrum showed two signals at δ 10.29 and 10.41 ppm for CH N
of the syn and anti isomer and a broad signal at δ 13.9 ppm for the
two SH groups. The 1H NMR spectrum of the similar product 8b from
3b indicated its existence as dihydrothiadiazole as the major form in
addition to the Schiff base as a minor one in the ratio 1:0.25.
Thus, the spectrum showed signals at δ 5.56, 10.14, 11.27, and 13.49
ppm characteristic for SCHAr, CH N, NH, and SH groups (Scheme 2).
The reaction of 3b with benzoylisothiocyanate in DMF afforded tri-
azolothiadiazole 9. The reaction proceeded via the attack of aminotri-
azole to the electrophilic carbon of benzoylisothiocyanate to afford the
thiourea, which underwent cyclization with the elimination of the H2S
molecule. Its IR spectrum showed a band at 1684 cm−1 for the amidic
1
carbonyl group, and its H NMR spectrum showed a singlet at δ 2.96
and 11.8 ppm for the CH2 and NH group and the disappearance of the
SH group (Scheme 2).
The results of the antimicrobial activity of compounds 4a and 4b
showed interesting degrees of antibacterial activity. Pencillin was used
as a reference to evaluate the potency of the tested compounds. Com-
pounds 4a and 4b showed higher antibacterial activity than the stan-
dard drug (pencillin). Compound 6a did not show any activity against

The Synthesis of Triazolothiadiazines and Thiadiazoles
2365
TABLE I Antimicrobial Activity of Compounds 4 and 6 (Inhibition
Zones mm, Minimum Inhibitory Concentration µg/mL)
Compound
No.
S. aureus S. lutea B. subtilis P. aeruginosa K. peneumonie E. coli C. albicans
4a
4b
6a
6b
Pencillin
Nystatin
—
10
—
—
15
—
25
25
—
—
17
—
20
18
—
—
20
—
20
20
—
—
13
—
15
15
—
—
14
—
16
17
—
—
15
—
—
—
—
20
—
15
SCHEME 2

2366
A. H. Moustafa et al.
the tested microorganisms, while compound 6b showed higher ac-
tivity against C. albicans than the standard drug (Nystatin) and
was inactive against Gram +ve, and Gram −ve bacteria. The re-
sults of biological activities encourage further work on such a ring
system.
EXPERIMENTAL
Melting points were determined with a Melt-Temp apparatus and are
uncorrected. IR spectra were recorded with a Perkin-Elmer model 1600
FTIR spectrometer as KBr discs. 1H and 13C NMR spectra were deter-
mined with a JEOL-JNM-LA 400 and 100 MHz Spectrometer. Chemi-
cal shifts are expressed on the δ (ppm) scale using TMS as an internal
standard. Elemental analyses were determined on a Perkin-Elmer 240
(microanalysis).
1,2-Bis-(4-amino-5-mercapto-4H-1,2,4-triazol-3-yl)-ethane
derivatives (3): General Procedure
A mixture of 1a and 1b (10 mmol) and 2 (20 mmol) in dry pyridine
(10 mL) was heated under reflux for 6 h. The reaction mixture was
cooled and poured into cold water. The product was filtered, washed
with water, and crystallized from hot water to give colorless crystals.
1,2-Bis-(4-amino-5-mercapto-4H-1,2,4-triazol-3-yl)-ethan-1-ol
(3a)
56% yield; m.p. 224–225◦C. IR (cm−1): 1633 (C N), 3166 (NH2), 3257
(OH).1H NMR (400 MHz. DMSO-d6), (δ ppm): δ = 3.28 (m, 2 H, CH2),
5.26 (t, 1 H, J = 6.1 Hz, CH), 5.52, 5.55 (2 s, 4 H, 2 NH2), 5.96 (d, 1 H,
J = 6.1 Hz, OH), 13.48, 13.61 (2 br s, 2 H, 2 SH). Irradiation at δ 5.26
changed the multiplet at δ 3.20–3.35 to two triplets and the doublet at
δ 5.96 to a singlet. 13C NMR (100 MHz. DMSO-d6), (δ ppm): δ = 29.4
(CH2), 60.8 (CH), 148.8, 152.1, 165.6, 166.1 (4 C N). Anal. calcd. for
C6H10N8OS2 (274.3): C, 26.27; H, 3.67; N, 40.85. Found: C, 26.23; H,
3.53; N, 40.75.
1,2-Bis-(4-amino-5-mercapto-4H-1,2,4-triazol-3-yl)-ethane (3b)
60% yield; m.p. 234–235◦C (lit.8 m.p. 242–244, 220–222◦C). IR
(cm−1): 1614 (C N), 3156 (NH2). 1H NMR (400 MHz. DMSO-d6),
(δ ppm): δ = 3.12 (s, 4 H, 2 CH2), 5.33 (s, 4 H, 2 NH2), 13.12 (br s,
2 H, 2 SH). Anal. calcd. for C6H10N8S2 (258.3): C, 27.90; H, 3.88; N,
43.38. Found: C, 27.92; H, 3.72; N, 43.30.

The Synthesis of Triazolothiadiazines and Thiadiazoles
2367
1,2-Bis-[6-phenyl-1,2,4-triazolo[3,4-b][1,3,4]thiadiazin-3-yl]-
ethane derivatives (4): General Procedure
A solution of phenacyl bromide (20 mmol) in ethanol (10 mL) was added
dropwise to a solution of 3a or 3b (10 mmol) and three drops of triethy-
lamine in ethanol (10 mL). The mixture was heated under reflux for 6 h
and then cooled. The precipitate was crystallized from DMF.
1,2-Bis-[6-phenyl-1,2,4-triazolo[3,4-b][1,3,4]thiadiazin-3-yl]-
ethan-1-ol (4a)
80% yield; m.p. 265–266◦C. 1H NMR (400 MHz. DMSO-d6), (δ ppm):
δ = 3.65 (d, 2 H, J = 6.7 Hz, CH2), 4.33 (s, 4 H, 2 CH2S), 4.35 (d, 1
H, J = 6.1 Hz, OH), 5.59 (t, 1 H, J = 6.7 Hz, CH), 7.49–7.80 (m, 6 H,
Ar-H), 8.01 (d, 4 H, J = 7.2 Hz, Ar-H). 13C NMR (100 MHz. DMSO-d6),
(δ ppm): δ = 22.8 (CH2), 28.9, 30.2 (2 CH2S), 61.6 (CH), 127.3, 127.4,
128.8, 128.9, 131.7, 131.8, 133.3, 133.4, (Ar-C), 151.0, 151.1, 153.2,
153.3, 154.5, 164.6, (6 C N). Anal. calcd. for C22H18N8OS2 n(474.6):
C, 55.68; H, 3.82; N, 23.61. Found: C, 55.60; H, 3.79; N, 23.50.
1,2-Bis-[6-phenyl-1,2,4-triazolo[3,4-b][1,3,4]thiadiazin-3-yl]-
ethane (4b)
1
83% yield; m.p. 244–245◦C. IR (cm−1): 1620 (C N). H NMR (400
MHz. DMSO-d6), (δ ppm): δ = 3.41 (s, 4 H, 2 CH2), 4.31 (s, 4 H, 2 CH2S),
7.48–7.97 (m, 6 H, Ar-H), 8.17 (d, 4 H, J = 7.2 Hz, Ar-H). 13C NMR
(100 MHz. DMSO-d6), (δ ppm): δ = 21.7, 22.9 (CH2 and CH2S), 127.3
128.9, 131.8, 133.3 (Ar-C), 140.3, 152.1, 154.6 (3 C N). Anal. calcd. for
C22H18N8S2(458.6): C, 57.62; H, 3.96; N, 24.43. Found: C, 57.14; H, 3.98;
N, 24.09.
1,2-Bis-[6,7-diphenyl-1,2,4-triazolo[3,4-b][1,3,4]thiadiazin-3-yl]-
ethane derivatives (5): General Procedure
A mixture of 3a or 3b (10 mmol), benzoin (20 mmol), and 1N aqueous
potassium hydroxide (5 mL) in ethanol (10 mL) was boiled under reflux
for 4 h. The reaction mixture was cooled and poured into ice-cold water.
The precipitate was filtered off, washed with water, and crystallized
from ethanol.
1,2-Bis-[6,7-diphenyl-1,2,4-triazolo[3,4-b][1,3,4]thiadiazin-3-yl]-
ethan-1-ol (5a)
1
50% yield; m.p. 274–275◦C. IR (cm−1): 3379 (NH), 3415 (OH). H
NMR (400 MHz. DMSO-d6), (δ ppm): δ = 3.38 (d, 2 H, J = 6.7 Hz, CH2),
5.31 (d, 1 H, J = 6.1 Hz, OH), 6.02 (s, 2 H, 2NH), 6.09 (t, 1 H, J = 6.7 Hz,

2368
A. H. Moustafa et al.
CH), 7.24–7.59 (m, 12 H, Ar-H), 8.01 (d, 8 H, J = 7.2 Hz, Ar-H). Anal.
calcd. for C34H26N8OS2 (626.8): C, 65.15; H, 4.18; N, 17.88. Found: C,
65.02; H, 4.10; N, 17.60.
1,2-Bis-[6,7-diphenyl-1,2,4-triazolo[3,4-b][1,3,4]thiadiazin-3-yl]-
ethane (5b)
66% yield; m.p. 259–260◦C. IR (cm−1): 3416 (NH). 1H NMR (400 MHz.
DMSO-d6), (δ ppm): δ = 3.54 (s, 4 H, 2CH2), 5.95 (br s, 2 H, 2 NH),
7.26–7.97 (m, 20 H, Ar-H). Anal. calcd. for C34H26N8S2 (610.8): C, 66.86;
H, 4.29; N, 18.35. Found: C, 66.80; H, 4.24; N, 18.15.
1,2-Bis-[4-amino-5-carboethoxymethylthio-4H-(1,2,4-triazol-3-
yl)]-ethane Derivatives (6): General Procedure
A solution of 3a or 3b (10 mmol) in anhydrous ethanol (10 mL) was
treated with anhydrous sodium acetate (2 mmol) and ethyl bromoac-
etate (40 mmol). The reaction mixture was heated under reflux for
8 h and then cooled. The product was filtered, washed with water and
ethanol, and then crystallized from ethanol, to give a colorless crystal.
1,2-Bis-[4-amino-5-carboethoxymethylthio-4H-(1,2,4-triazol-3-
yl)]-ethan-1-ol (6a)
90% yield; m.p. 150–151◦C. IR (cm−1): 1729 (C O, ester), 3323 (NH2),
1
3439 (OH). H NMR (400 MHz. DMSO-d6), (δ ppm): δ = 1.17 (t, 6 H,
J = 2.1 Hz, 2 CH3), 3.34 (dd, 2 H, J = 11.6, 11.7 Hz, CH2), 4.00 (2 s, 4 H,
2 CH2S), 4.08 (d, 1 H, J = 6.1 Hz, OH), 4.13 (q, 4 H, J = 2.1 Hz, 2 CH2O),
5.21 (m, 1 H, J = 6.7 Hz, CH), 6.96, 6.04 (2 s, 4 H, 2 NH2). 13C NMR
(100 MHz. DMSO-d6), (δ ppm): δ = 13.8, 13.9 (2 CH3), 29.1 (CH2), 32.5,
32.6 (2 CH2S), 61.0,61.1 (2 CH2O), 61.8 (CH), 150.4, 151.6, 153.5, 156.8
(4 C N), 168.3, 168.4 (2 C O). Anal. calcd. for C14H22N8O5S2 (446.5):
C, 37.66; H, 4.97; N, 25.09. Found: C, 37.38; H, 4.58; N, 24.89.
1,2-Bis-[4-amino-5-carboethoxymethylthio-4H-(1,2,4-triazol-3-
yl)]-ethane (6b)
85% yield; m.p. 175–176◦C. IR (cm−1): 1614 (C N), 1729 (C O, ester),
1
3325 (NH2). H NMR (400 MHz. DMSO-d6), (δ ppm): δ = 1.14 (t, 6 H,
J = 2.1 Hz, 2 CH3), 3.35 (s, 4 H, 2 CH2), 3.98 (s, 4 H, CH2S), 4.15 (q, 4 H,
J = 2.1 Hz, 2 CH2O), 6.08 (s, 4 H, 2 NH2). Anal. calcd. for C14H22N8O4S2
(430.5): C, 39.06; H, 5.15; N, 26.03. Found: C, 38.95; H, 5.01; N, 25.89.
1,2-Bis-[6-mercapto-4H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazol-3-
yl]-ethane Derivatives (7): General Procedure
To a stirred solution of potassium hydroxide (15 mmol) in ethanol
(20 mL) was added 3a or 3b (10 mmol) followed by carbon disulfide

The Synthesis of Triazolothiadiazines and Thiadiazoles
2369
(50 mL). The reaction mixture was refluxed for 24 h, cooled, poured
into ice-cold water, and then acidified with acetic acid. The precipitate
was collected by filtration and crystallized from aqueous ethanol.
1,2-Bis-[6-mercapto-4H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazol-3-
yl]-ethan-1-ol (7a)
60% yield; m.p. 245–246◦C. 1H NMR (400 MHz. DMSO-d6), (δ ppm):
δ = 3.19–3.32 (m, 2 H, CH2), 5.24 (t, 1 H, J = 6.6 Hz, CH), 5.95 (d, 1 H,
J = 6.1 Hz, OH), 13.61 (s, 2 H, 2 SH). 13C NMR (100 MHz. DMSO-d6),
(δ ppm): δ = 29.5 (CH2), 60.8 (CH), 148.8, 148.9, 152.1, 152.2, 165.6,
166.2 (6 C N). Anal. calcd. for C8H6N8OS4 (358.5): C, 26.80; H, 1.69;
N, 31.26. Found: C, 26.56; H, 1.82; N, 31.52.
1,2-Bis-[6-mercapto-4H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazol-3-
yl]-ethane (7b)
59% yield; m.p. 248–249◦C. 1H NMR (400 MHz. DMSO-d6), (δ ppm):
δ = 3.06 (s, 4 H, 2 CH2), 13.47 (s, 2 H, 2 SH). 13C NMR (100 MHz.
DMSO-d6), (δ ppm): δ = 20.7 (CH2), 150.3, 150.5, 165.9 (3 C N). Anal.
calcd. for C8H6N8S4 (342.5): C, 28.05; H, 1.77; N, 32.72. Found: C, 27.87;
H, 1.68; N, 32.82.
The Reaction of p-nitrobenzaldehyde with 3a: (1,2-Bis-
[4-p-nitrobenzylideneamino-5-mercapto-1,2,4-triazol-3-yl]-
ethan-1-ol)
A mixture of 3a (10 mmol) and p-nitrobenzaldehyde (20 mmol) in DMF
(20 mL) was refluxed for 8 h, cooled, and then poured into ice-cold water.
The yellow precipitate was crystallized from DMF/ethanol; 75% yield;
m.p. 254–256◦C. IR (cm−1): 1638 (C N), 3427 (OH). 1H NMR (400 MHz.
DMSO-d6), (δ ppm): δ = 3.46 (d, 2 H, J = 6.6 Hz, CH2), 5.38 (t, 1 H,
J = 6.7 Hz, CH), 6.29 (d, 1 H, J = 6.1 Hz, OH), 7.90–8.47 (m, 8 H,
Ar-H), 10.29, 10.41 (2 s, 2 H, 2 HC N, syn and anti), 13.9 (br s, 2 H, 2
SH). Anal. calcd. for C20H16N10O5S2 (540.5): C, 44.44; H, 2.99; N, 25.91.
Found: C, 44.14; H, 2.95; N, 26.12.
The Reaction of p-Nitrobenzaldehyde with 3b: (1,2-Bis-[5,6-
dihydro-p-nitrophenyl-1,2,4-triazolo[3,4-b][1,3,4]thiadiazol-3-
yl]-ethane)
A mixture of 3b (10 mmol) and p-nitrobenzaldehyde (20 mmol) in DMF
(20 mL) was refluxed for 8 h, cooled, and then poured into ice-cold water.
The yellow precipitate was crystallized from DMF/ethanol; 85% yield
in ratio 1:0.25%; m.p. 258–259◦C. IR (cm−1): 1607 (C N), 3157–3220

2370
A. H. Moustafa et al.
1
(br, NH). H NMR (400 MHz. DMSO-d6), (δ ppm): δ = 3.34 (s, 4 H, 2
CH2), 5.56 (s, 1.5 H, 2 HCNS), 7.89–8.50 (m, 8 H, Ar-H), 10.14 (s, 0.5 H,
2 HC N), 11.27 (br s, 1.5 H, 2 NH), 13.49 (s, 0.5 H, 2 SH). Anal. calcd.
for C20H16N10O4S2 (524.5): C, 45.80; H, 3.07; N, 26.71. Found: C, 45.50;
H, 3.00; N, 26.50.
1,2-Bis-[6-benzoylamino-1,2,4-triazolo[3,4-b][1,3,4]thiadiazol-
3-yl]-ethane (9)
A mixture of benzoyl chloride (10 mmol) and ammonium thiocyanate
(10 mmol) in dry DMF (20 mL) was refluxed for 30 min. The mixture
was filtered off, and the filtrate was collected. Compound 3b (10 mmol)
in DMF (10 mL) was added to the filtrate, and the mixture was refluxed
4 h; the reaction mixture was concentrated and then cooled. The solid
product was filtered and crystallized from DMF to give yellow crystals;
65% yield; m.p. 284–285◦C. IR (cm−1): 1684 (C O), 3163 (NH). 1H NMR
(400 MHz. DMSO-d6), (δ ppm): δ = 2.96 (s, 4 H, 2 CH2), 7.05–7.98 (m, 6
H, Ar-H), 7.97 (d, 4 H, J = 7.6 Hz, Ar-H), 11.8 (s, 2 H, 2 NH). 13C NMR
(100 MHz. DMSO-d6), (δ ppm): δ = 20.4 (CH2), 127.8, 128.5, 128.6,
130.7, 132.9, 151.1, 165.5, 167.4 (Ar-C, 3 C N and C O). Anal. calcd.
for C22H16N10O2S2 (516.6): C, 51.15; H, 3.12; N, 27.11. Found: C, 50.92;
H, 3.00; N, 26.95.
ANTIMICROBIAL ACTIVITY
The antimicrobial activities of some newly synthesized compounds
were screened for their antibacterial and antifungal activity against
six species of bacteria and one fungi, namely Stophylococcus aureus,
Sarcina lutea, and Bacillus subtilis as Gramm +ve; Pseudomonas ar-
reuginosa, Klebseilla pneumonie, and Eschericia coli as Gram −ve; and
Candida albicans as fungi, using a cup plate agar diffusion method.17
The tested compounds were dissolved in DMF to get a solution of 1
mg/mL concentration. The inhibition zones were measured in mm at
the end of an incubation period of 48 h at 37◦C. Dimethylformamide
showed no inhibition zones. The fungi cultures were maintained on a
dextrose agar medium. Penicillin and Nystatin were used as a refer-
ence.
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