Synthesis and antimicrobial evaluation of some fused heterocyclic [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives

Article abstract of DOI:10.1016/j.ejmech.2010.10.007

A series of fused 1,2,4-triazoles with diphenylsulfone moiety are prepared utilizing 4-amino-5-[4-(4-X-phenylsulfonyl)phenyl]-4H-1,2,4-triazole-3-thiol 1 (X = H, Br). The latter on reaction with aromatic isothiocyanate in DMF, aromatic acid in POCl₃ and CDI in dioxane gives five membered fused triazole derivatives 2a-c, 3a-c, 4a-g, 5a-g and 6a,b. The structures of newly synthesized compounds were confirmed on the basis of their elemental analysis and spectral data results (IR, ¹H-and ¹³C NMR). New synthesized compounds were screened for their antimicrobial activities. The preliminary results revealed that some of the compounds exhibited promising antimicrobial activities.

Full text of DOI:10.1016/j.ejmech.2010.10.007

European Journal of Medicinal Chemistry 45 (2010) 6139e6146
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Synthesis and antimicrobial evaluation of some fused heterocyclic [1,2,4]triazolo
[3,4-b][1,3,4]thiadiazole derivatives
,
a
b
a
Gabriela Laura Almajan a , Stefania-Felicia Barbuceanu , Gabriela Bancescu , Ioana Saramet ,
*
Gabriel Saramet c, Constantin Draghici d
a Organic Chemistry Department, Faculty of Pharmacy, Traian Vuia Street 6, Bucharest 020956, Romania
b Microbiology Department, Faculty of Dentistry, Calea Plevnei Street 19, Bucharest 050051, Romania
c Pharmaceutical Techniques and Drug Industry Department, Faculty of Pharmacy, Traian Vuia Street 6, Bucharest 020956, Romania
d C.D. Nenitescu Institute of Organic Chemistry, Romanian Academy, Splaiul Independentei 202B, Bucharest 060023, Romania
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of fused 1,2,4-triazoles with diphenylsulfone moiety are prepared utilizing 4-amino-5-[4-(4-X-
phenylsulfonyl)phenyl]-4H-1,2,4-triazole-3-thiol 1 (X ¼ H, Br). The latter on reaction with aromatic
isothiocyanate in DMF, aromatic acid in POCl3 and CDI in dioxane gives five membered fused triazole
derivatives 2a-c, 3a-c, 4a-g, 5a-g and 6a,b. The structures of newly synthesized compounds were
confirmed on the basis of their elemental analysis and spectral data results (IR, 1H-and 13C NMR). New
synthesized compounds were screened for their antimicrobial activities. The preliminary results revealed
that some of the compounds exhibited promising antimicrobial activities.
Received 30 July 2010
Received in revised form
2 October 2010
Accepted 9 October 2010
Available online 15 October 2010
Keywords:
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole
Cyclization
Ó 2010 Elsevier Masson SAS. All rights reserved.
Diphenylsulfone moiety
Antimicrobial activity
1. Introduction
together to give a compact and planar structure and evaluated
them for their antimicrobial profile after subtle structural
In the past decades, the problem of multidrug resistant micro-
organisms has reached on alarming level around the world, and the
synthesis of new anti-infective compounds has become an urgent
need for the treatment of microbial infections. The 1,2,4-triazole
nucleus has been incorporated into a wide variety of therapeuti-
cally important agents, which mainly displaying antimicrobial
activities [1e4]. Moreover, the chemistry of 1,2,4-triazoles and their
fused heterocyclic derivatives has received considerable attention
owing to their synthetic and effective biological importance. For
example, a triazolo-thiadiazole system may be viewed as a cyclic
analog of two very important components: thiosemicarbazide and
biguanide [5], which often display antimicrobial, anticancer, anti-
tubercular, antiinflammatory, analgesic or anticonvulsant activities
[6e11]. For this reason and in continuation to our efforts directed
toward the synthesis of new heterocyclic compounds with antici-
pated biological activities, in this paper we proposed to synthesized
a new series of this condensed system, which combine these two
biolabile components (1,2,4-triazole and 1,3,4-thiadiazole) in a ring
modification.
2. Chemistry
The ambient nucleophilic centers present in 3-substituted-4-
amino-5-mercapto-1,2,4-triazoles render them as useful synthons
for the synthesis of various N-bridged heterocycles. In this paper,
the
key
intermediates,
4-amino-5-[4-(4-X-phenylsulfonyl)
phenyl]-4H-1,2,4-triazole-3-thiols 1 (X ¼ H, Br) were prepared
from corresponding substituted benzoic acid hydrazides according
to literature [12].
The resulted triazoles 1 further converted to 3-[4-(4-X-phenyl-
sulfonyl)phenyl]-6-N-(substituted-phenyl)amino-[1,2,4]triazolo
[3,4-b][1,3,4]thiadiazoles 2a-c, 3a-c by reacting with aryl iso-
thiocyanates in the presence of DMF (Scheme 1).
Cyclocondensation of the SH and NH2 functions of 1 with
various substituted aromatic acids in the presence of phosphorus
oxychloride afforded a series of 3-[4-(4-X-phenylsulfonyl)phenyl]-
6-(substituted-phenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles
4aeg, 5aeg. The ring closure reaction with POCl3 as the cyclization
agent may have an esterification-addition-elimination mechanism
(Scheme 2). Phosphorus oxychloride activates the carbonyl group
* Corresponding author. Tel.: þ40 741 095490; fax: þ40 21 3180729.
E-mail address: laura.almajan@gmail.com (G.L. Almajan).
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.10.007

6140
G.L. Almajan et al. / European Journal of Medicinal Chemistry 45 (2010) 6139e6146
Scheme 1. Synthesis of the title compounds.
of intermediary (1.1) obtained by esterification of aromatic acid
with thiol group of triazole 1, which will be easier attacked by the
unshared pair of electrons of the amino-triazole group nitrogen.
Thus, an ionic intermediate (1.2) could be formed by the addition
reaction of POCl3 with the carbonyl group of compound (1.1), fol-
lowed by removal of a chloride anion. Subsequently, after removal
of a proton and the electron transfer, the leaving group ꢀOPOCl2
comes off with the electron pair from the CeO bond and the
reaction leading to the ring closure product 4/5.
An attempt to transform the triazole 1 into oxo-analog 6 by
fusion with urea at 250 ꢁC for 3h was unsuccessful because the
obtained reaction mixture was very complex and the components
could not be separated and identified. However, compound 6 was
obtained via the interaction of amino-triazole 1 with 1,10-carbon-
yldiimidazole (CDI) in dry dioxane.
All new compounds reported here were characterized by
elemental analysis, IR, 1H-and 13C NMR data. The physicochemical
properties of synthesized compounds are presented in Table 1.
3. Antibacterial activity
The synthesized compounds were tested for their in vitro anti-
microbial activity against the Gram-positive bacteria (Staphylo-
coccus aureus ATCC 25923; Staphylococcus epidermidis ATCC 14990;
Enterococcus faecalis ATCC 29212; Bacillus cereus ATCC 13061),
Gram-negative bacteria (Escherichia coli ATCC 25922; Enterobacter
cloacae ATCC 49141; Citrobacter freundii ATCC 8090; Acinetobacter
baumannii ATCC 19606; Pseudomonas aeruginosa ATCC 27853) and
Candida albicans ATCC 90028 as fungus, by using the broth dilution
Scheme 2. The proposed mechanism of the reaction in presence of POCl3.

G.L. Almajan et al. / European Journal of Medicinal Chemistry 45 (2010) 6139e6146
6141
Table 1
Characterization data of the synthesized compounds.
Comp.
X
Y
Molecular formula
Molecular
M.p. (ꢁC)
Yield (%)
Elemental analysisa calc. (found)
weight (g/mol)
C
H
N
2a
2b
2c
3a
3b
3c
4a
4b
4c
4d
4e
4f
4g
5a
5b
5c
5d
5e
5f
H
H
H
Br
Br
Br
H
H
H
H
H
H
H
Br
Br
Br
Br
Br
Br
Br
H
Br
OCH3
CH3
Br
OCH3
CH3
4-Br
4-Cl
4-OCH3
4-NH2
4-CH2NH2
3,4,5-(OH)3
3-Br,4-Cl
4-Br
C21H14BrN5O2S2
C22H17N5O3S2
C22H17N5O2S2
C21H13Br2N5O2S2
C22H16N5O3S2
C22H16BrN5O2S2
C21H13BrN4O2S2
C21H13ClN4O2S2
C22H16N4O3S2
512.4
463.5
447.5
591.3
542.4
526.4
497.3
452.9
448.5
433.5
447.5
466.4
531.8
576.2
531.8
527.4
512.4
526.4
545.4
610.7
358.4
437.3
217e219
216e218
246e250
232e234
201e204
180e182
255e257
173e175
203e205
191e194
179e182
157e159
147e150
136e139
172e175
187e189
184e186
242e243
212e214
181e183
183e185
198e200
58
47
55
45
51
58
69
65
68
54
51
58
48
57
53
78
64
66
69
71
70
68
49.22 (49.18)
57.00 (56.96)
59.04 (59.01)
42.66 (42.62)
48.71 (48.69)
50.19 (50.16)
50.71 (50.67)
55.69 (55.64)
58.91 (58.89)
58.18 (58.15)
59.04 (59.01)
54.07 (54.04)
47.43 (47.40)
43.77 (43.74)
47.43 (47.46)
50.10 (50.06)
49.22 (49.19)
50.19 (50.22)
46.25 (46.22)
41.30 (41.27)
50.27 (50.24)
41.20 (41.17)
2.75 (2.71)
3.70 (3.65)
3.83 (3.79)
2.22 (2.17)
2.97 (2.93)
3.03 (3.03)
2.63 (2.59)
2.89 (2.84)
3.60 (3.57)
3.49 (3.52)
3.83 (3.79)
3.02 (2.98)
2.27 (2.23)
2.10 (2.04)
2.27 (2.23)
2.87 (2.85)
2.75 (2.73)
3.06 (3.08)
2.40 (2.37)
1.82 (1.80)
2.81 (2.79)
2.07 (2.10)
13.67 (13.63)
15.11 (15.09)
15.65 (15.62)
11.84 (11.78)
12.91 (12.88)
13.30 (13.28)
11.26 (11.22)
12.37 (12.41)
12.49 (12.47)
16.16 (16.12)
15.65 (15.62)
12.01 (12.05)
10.53 (10.49)
9.72 (9.75)
10.53 (10.50)
10.62 (10.59)
13.67 (13.64)
15.18 (15.22)
14.65 (14.60)
9.17 (9.14)
C21H15N5O2S3
C22H17N5O2S2
C21H14N4O5S2
C21H12BrClN4O2S2
C21H12Br2N4O2S2
C21H12BrClN4O2S2
C22H15BrN4O3S2
C21H14BrN5O2S2
C22H16BrN5O2S2
C21H13BrN4O5S2
C21H11Br2ClN4O2S2
C15H10N4O3S2
4-Cl
4-OCH3
4-NH2
4-CH2NH2
3,4,5-(OH)3
3-Br, 4-Cl
e
5g
6a
6b
15.63 (15.60)
12.81 (12.85)
Br
e
C15H9BrN4O3S2
a
elemental analysis value limit ¼ ꢂ0.4% of the theoretical value.
method [13,14] for determination of MIC. Ampicillin, aztreonam
and amphotericin were used as control drugs.
160.48e166.91 ppm and 154.76e160.16 ppm, respectively, while 13
C
signals derived from C-6 of triazolo-thiadiazole ring of compounds
4,5 were recorded at 150.32e158.81 ppm. The other signals present
in 13C NMR spectra of compounds 4,5 were recorded at the expected
chemical shifts. Moreover, elemental analyses are consistent with
the structures proposed for compounds 4,5 (Table 1).
4. Results and discussions
4.1. Chemistry
Analysis of spectral data for compounds 6, which were obtained
via the interaction of amino-triazole 1 with CDI, leads to the
conclusion that these compounds can exist in two tautomeric
forms: lactame form and lactime form. In the solid state, the stable
tautomeric state is lactim form. The IR spectra, recorded in KBr
pellets show a broad band at 3398 cmꢀ1 (for 6a) and 3405 cmꢀ1 (for
6b), which can be attributed to OH group and the new stretching
frequencies of N]C group formed by thiadiazole ring closure are
observed at 1260 cmꢀ1 in compound 6b and 1263 cmꢀ1 in
compound 6a. Most important is that there is no band in the
wavenumber range 1670e1780 cmꢀ1, where usually carbonyls give
a strong peak. The predominant tautomer of 6 was identified as
lactame form by means of NMR spectroscopy. Similar to previous
reports [23,24], the singlet signal at w 9 ppm in the 1H NMR can be
attributed to the NH-thiadiazolic proton, and the peaks at
175.26 ppm (for 6a) and 177.63 ppm (for 6b) in the 13C NMR spectra
can be assigned to carbon of carbonyl group in lactame form.
The build up of N-bridged condensed heterocycles, 2aec and
3aec from 1, is evidenced by its IR, 1H NMR, 13C NMR. Infrared
spectra of these compounds were in accordance with our structural
proposal: there is a broad band in 3108e3242 cmꢀ1 region,
assigned to NH group, new band appears in 1583e1620 cmꢀ1
region, which is attributed to stretching frequency of N]C group
formed by ring closure for all compounds and additional, for 2,3b,c,
asymmetric and symmetric stretching frequencies of CH3 group
appeared in 2858e2948 cmꢀ1 zone. In addition, the 1H NMR
spectra contain a characteristic singlet signal around 11 ppm due to
the NH proton and the new positive signal in 152e155 ppm region
in 13C NMR spectra corresponding to quaternary carbon of N]C
group.
In the IR spectra of compounds 4,5 aeg, the absence of absorp-
tion bands due to eSH (eC¼S) and eNH2 stretching frequencies of
parent compounds
1 clearly indicated the fusing between
compounds 1 and aromatic acid in the presence of phosphorus
oxychloride. All the compounds show absorption peaks for NeN¼C
in the region of 1255e1269 cmꢀ1 and for CeSeC, in the region of
683e711 cmꢀ1. The new band which appears in 1602e1620 cmꢀ1
region is attributed to stretching frequency of N]C group of the
thiadiazole ring. These data were very similar to previous reports
[15e19]. The 1H NMR spectra of compounds 4,5c showed a singlet at
3.85e3.88 ppm integrating for three protons of the methyl group
and for compounds 4,5e displayed a singlet at 4.36e4.58 ppm cor-
responding to the methylene protons. The singlet signal observed at
8.57e8.68 ppm integrating for two protons was assigned to eNH2
group. The protons of the some group in 4,5d appear up field
(6.3e6.36 ppm). The other signals of the protons present in the
molecule appeared at 6.58e8.30 ppm as expected. As previous
reports [20e22], the 13C signals of triazole-C-3 and triazole-C-5
in newly synthesized compounds were observed around
4.2. Antibacterial activity
The newly synthesized compounds were tested for in vitro
antibacterial activities against five Gram-negative, four Gram-
positive bacterial strains and one fungus. Ampicillin, aztreonam
and amphotericin were used as reference drug molecules.
The data generated from this study (Table 2) showed that
compounds displayed low to moderate activity. The obtained
results can be attributed to quite bulky structure of the tested
compounds, to the nature of the fragments attached in different
positions to these molecules, but they may be associated with the
nature of tested bacterial species.
Thus, we can see that none of the tested compounds has
inhibitory action against E. cloacae, C. freundii, A. baumannii, B.
cereus, C. albicans. We can also notice that the exerted action on

6142
G.L. Almajan et al. / European Journal of Medicinal Chemistry 45 (2010) 6139e6146
Table 2
Antimicrobial activities of the title compounds as MIC values (
m
g/mL).
Compd.
X
Y
Gram-positive bacteriaa
Gram-negative bacteriab
Fungus
Sa
Se
512
Ef
Bc
Ec
Ebc
512
Cf
Ab
512
128
128
512
128
1024
1024
512
512
128
1024
1024
256
256
256
Pa
Ca
2a
H
Br
1024
1024
1024
512
512
512
512
256
256
512
512
512
256
256
128
128
256
512
256
64
1024
64
1024
256
256
256
256
128
256
256
512
512
512
256
256
256
128
256
128
256
256
256
128
64
1024
256
1024
1024
256
1024
1024
512
512
256
1024
1024
1024
128
512
512
512
1024
128
1024
512
256
512
256
512
512
256
512
512
512
256
256
256
128
128
256
512
512
512
128
128
32
1024
256
256
128
128
128
1024
512
512
256
512
512
512
128
1024
512
512
512
512
256
256
256
2b
2c
H
H
OCH3
CH3
128
512
512
128
1024
1024
512
512
64
512
512
128
64
128
512
512
1024
128
32
512
128
< 2
256
512
512
256
512
512
512
512
256
512
512
512
256
512
1024
1024
1024
256
256
256
256
512
128
128
512
1024
512
512
128
512
32
128
128
64
512
512
512
64
1024
1024
1024
1024
1024
1024
512
256
1024
256
256
1024
256
256
128
3a
3b
3c
4a
Br
Br
Br
H
Br
OCH3
CH3
4-Br
4b
H
4-Cl
4c
4d
4e
4f
4g
5a
5b
5c
5d
5e
5f
5g
H
H
H
H
4-OCH3
4-NH2
4-CH2NH2
3,4,5-(OH)3
3-Br,4-Cl
4-Br
H
Br
Br
Br
Br
Br
Br
Br
H
4-Cl
4-OCH3
4-NH2
4-CH2NH2
3,4,5(OH)3
3-Br,4-Cl
e
256
1024
1024
128
512
128
256
256
128
1024
1024
< 2
32
6a
256
256
< 2
128
64
< 2
256
256
512
256
6b
Br
e
256
Ampicillin
Aztreonam
Amphotericin
< 2
< 2
< 2
< 2
4
2
a
Sa (Staphylococcus aureus ATCC 25923); Se (Staphylococcus epidermidis ATCC 14990); Ef (Enterococcus faecalis ATCC 29212); Bc (Bacillus cereus ATCC 13061).
Ec (Escherichia coli ATCC 25922); Ebc (Enterobacter cloacae ATCC 49141); Cf (Citrobacter freundii ATCC 8090); Ab (Acinetobacter baumannii ATCC 19606); Pa (Pseu-
b
domonas aeruginosa ATCC 27853).
Gram-positive bacteria S. epidermidis and E. faecalis is better than
on Gram-negative strains.
Note that if the tested molecule has at least one halogen atom,
antibacterial action is significantly better than in its absence. Thus,
compounds in different series. Also, the presence of one or more
halogen atom in the structure has considerable increased the bio-
logical activity of the molecules. The best antibacterial effect has 6-
[(3-bromo-4-chloro)phenyl]-3-[4-(4-bromophenylsulfonyl)
the best antibacterial effect has compound 5g (MIC ¼ 64
m
g/mL
phenyl]-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 5g (MIC ¼ 64
m
g/mL
against S. aureus and E. coli, MIC ¼ 32
m
g/mL against S. epidermidis,
against S. aureus and E. coli, MIC ¼ 32
faecalis and P. aeruginosa).
mg/mL against S. epidermidis, E.
E. faecalis and P. aeruginosa) probably due to the cumulative elec-
tron-withdrawing effect of the chlorine and bromine atoms which
are directly attached to the phenyl ring of the thiadiazole, in
addition to the bromine atom attached to the diphenylsulfone
moiety. Compounds 5a and 5b have also a good antibacterial action
6. Experimental protocols
6.1. Chemistry
(MIC ¼ 64
mg/mL against S. epidermidis and E. faecalis, respectively).
In the serie of the derivatives with unsubstituted diphenylsulfone
Melting points were determined with Boetius apparatus and are
uncorrected. The IR spectra (in KBr pellets) were recorded on the
Vertex 70 Bruker apparatus. The NMR spectra (in DMSO-d6, at room
temperature) were registered on a Varian Gemini 300 BB apparatus
working at 300 MHz for 1H-and 75 MHz for 13C, using TMS as
internal standard. The content of C, H, and N were done with ECS-
40-10-Costeh micro-dosimeter, after drying the compounds at
105 ꢁC.
moiety, compounds 4d and 4f showed good activity against
S. epidermidis (MIC ¼ 64
mg/mL for 4d) and E. faecalis, (MIC ¼ 32
mg/
mL for 4f). This could possibly be due to the presence of the elec-
tron donor groups directly attached on condensed thiadiazole ring.
The presence of CH3, OCH3, CH2NH2 to the phenyl ring of the
thiadiazole was responsible for the decrease until disappearance of
antibacterial activity. From these results it is clear that substituents
affect the activity of compounds in different series. All the tested
compounds, which are considered active, are less effective than
drugs taken as a standard.
6.2. General procedure for synthesis of 3-[4-(4-X-phenylsulfonyl)
phenyl]-6-N-(substituted-phenyl)amino-[1,2,4]triazolo[3,4-b][1,3,4]
thiadiazoles 2a-c, 3a-c
5. Conclusions
Novel 3-[4-(4-X-phenylsulfonyl)phenyl]-6-(substituted-phenyl)/
An equimolar mixture (1 mmol) of 4-amino-5-[4-(4-X-phenyl-
sulfonyl)phenyl]-4H-1,2,4-triazole-3-thiol (X ¼ H, Br) 1 and aryl
isothiocyanate in dimethylformamide (10 mL) was refluxed for
20e22 h. The reaction mixture was cooled to room temperature
and then gradually poured on to crushed ice with stirring. The
mixture was allowed to stand overnight and the solid separated out
was filtered, and washed thoroughly with cold water. The
compound so obtained was dried and recrystallized from ethanol.
6-N-(substituted-phenyl)
amino-[1,2,4]triazolo[3,4-b][1,3,4]thia-
diazoles were prepared and screened for their antimicrobial activi-
ties. The antibacterial data given for the compounds presented in this
paper allowed us to state that the variation of antimicrobial activity
may be associated with the nature of tested microorganisms and is
due to the chemical structure of the tested compounds. From the
obtained results it is clear that substituents affect the activity of

G.L. Almajan et al. / European Journal of Medicinal Chemistry 45 (2010) 6139e6146
6143
6.2.1. 3-[4-(phenylsulfonyl)phenyl]-6-N-(4-bromophenyl)amino-
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 2a
(DMSO-d6,
d
, ppm): 11.11 (s, 1H, NH); 8.00 (d, 2H, J ¼ 8.7 Hz,
aromatic protons); 7.97 (d, 2H, J ¼ 8.7 Hz, aromatic protons); 7.93
(d, 2H, J ¼ 8.7 Hz, aromatic protons); 7.86 (d, 2H, J ¼ 8.7 Hz,
aromatic proton); 7.83 (d, 2H, J ¼ 8.8 Hz; aromatic protons); 7.72
(d, 2H, J ¼ 8.8 Hz aromatic protons); 3.76 (s, 3H, OCH3); 13C NMR
IR (KBr, cmꢀ1): 3194 (NH); 3088 (aromatic CH); 1588, 1554, 1471
(C]N þ C]Caryl); 1324, 1292, 1156 (SO2); 1262 (NeN]C); 1011
(NeN); 689 (CeSeC); 575 (CeBr); 1H NMR (DMSO-d6,
d, ppm):
11.04 (s, 1H, NH); 8.21 (d, 2H, J ¼ 8.5 Hz, aromatic protons); 8.07
(d, 2H, J ¼ 8.5 Hz, aromatic protons); 7.93 (t, 1H, J ¼ 8.5 Hz, aromatic
proton); 7.70 (d, 2H, J ¼ 8.5 Hz; aromatic protons); 7-50-7.72
(m, 4H, aromatic protons); 13C NMR (DMSO-d6, d, ppm): 162.00 (C3-
triazole ring); 156.47 (C5-triazole ring); 153.13 (C]N-thiadiazole
ring); 143.03, 139.05, 138.96, 134.87, 116.72 (quaternary aromatic
ring carbons); 130.41, 130.06, 129.88, 129.13, 128.57, 128.35, 119.57
(CH-aromatic ring carbons).
(DMSO-d6, d, ppm): 159.53 (C3-triazole ring); 158.74 (C5-triazole
ring); 156.29 (C]N-thiadiazole ring); 155.21, 142.13, 139.82, 139.35,
129.70, 124.74 (quaternary aromatic ring carbons); 132.85, 129.28,
128.53, 128.25, 119.92, 115.53 (CH-aromatic ring carbons); 55.41
(OCH3).
6.2.6. 3-[4-(4-bromophenylsulfonyl)phenyl]-6-N-(4-methylphenyl)
amino-[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazole 3c
IR (KBr, cmꢀ1): 3242 (NH); 3089 (aromatic CH); 2920, 2858
(CH3); 1620, 1582, 1514 (C]N þ C]Caryl); 1328, 1288, 1160 (SO2);
1266 (NeN]C); 1008 (NeN); 694 (CeSeC); 577 (CeBr); 1H NMR
6.2.2. 3-[4-(phenylsulfonyl)phenyl]-6-N-(4-methoxyphenyl)amino-
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 2b
IR (KBr, cmꢀ1): 3208 (NH); 3061 (aromatic CH); 2933, 2841
(CH3); 1618, 1575, 1554, 1501 (C]N þ C]Caryl); 1326, 1294, 1158
(SO2); 1258 (NeN]C); 1009 (NeN); 691 (CeSeC); 1H NMR (DMSO-
(DMSO-d6,
d
, ppm): 11.18 (s, 1H, NH); 7.94 (d, 2H, J ¼ 8.0 Hz,
aromatic protons); 7.87 (d, 2H, J ¼ 8.0 Hz, aromatic protons); 7.72
(d, 2H, J ¼ 8.0 Hz, aromatic protons); 7.33 (d, 2H, J ¼ 8.3 Hz,
aromatic protons); 7.33 (d, 2H, J ¼ 8.3 Hz; aromatic protons); 7.24
(d, 2H, J ¼ 8.3 Hz; aromatic protons); 2.34 (s, 3H, CH3); 13C NMR
d6,
d
, ppm): 10.34 (s, 1H, NH); 8.18 (d, 2H, J ¼ 8.7 Hz, aromatic
protons); 8.10 (d, 2H, J ¼ 8.7 Hz, aromatic protons); 8.00 (dd, 2H,
J ¼ 8.1; 1.5 Hz, aromatic protons); 7.71 (t, 1H, J ¼ 8.1 Hz, aromatic
proton); 7.66 (d, 2H, J ¼ 8.7 Hz; aromatic protons); 7.56 (t, 2H,
J ¼ 8.1 Hz, aromatic protons); 7.10 (d, 2H, J ¼ 8.7 Hz; aromatic
(DMSO-d6, d, ppm): 159.84 (C3-triazole ring); 159.20 (C5-triazole
ring); 153.22 (C]N-thiadiazole ring); 141.86, 140.66, 137.54, 131.65,
129.86, 126.85 (quaternary aromatic ring carbons); 132.94, 130.85,
129.85, 129.33, 127.84, 120.31 (CH-aromatic ring carbons); 21.37
(CH3).
protons); 3.93 (s, 3H, OCH3); 13C NMR (DMSO-d6,
d, ppm): 160.03
(C3-triazole ring); 154.76 (C5-triazole ring); 152.75 (C]N-thia-
diazole ring); 153.31, 141.14, 139.03, 135.68, 132.81 (quaternary
aromatic ring carbons); 133.68, 128.81, 128.74, 128.62, 128.34,
121.72, 115.18 (CH-aromatic ring carbons); 55.82 (OCH3).
6.3. General procedure for synthesis of 3-[4-(4-X-phenylsulfonyl)
phenyl]-6-(substituted-phenyl)-[1,2,4]triazolo[3,4-b][1,3,4]
thiadiazoles 4aeg, 5aeg
6.2.3. 3-[4-(phenylsulfonyl)phenyl]-6-N-(4-methylphenyl)amino-
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 2c
A mixture of 4-amino-5-[4-(4-X-phenylsulfonyl)phenyl]-4H-
1,2,4-triazole-3-thiol (X ¼ H, Br) 1 (5 mmol) and aromatic acid
(5 mmol) in phosphoryl chloride (10 mL) was heated under reflux
until hydrogen chloride no longer evolved. The obtained mixture
was cooled to room temperature and the viscous material thus
formed was added in small portions to a mixture of 20 g of sodium
hydroxide, 50 mL of water, and 50 g of ice using a cooling bath. The
mixture was kept for 0.5 h at room temperature and adjusted to pH
8 by adding a 2M solution of sodium hydroxide. The obtained
precipitate was filtered off, washed on a filter with warm water,
dried in air and recrystallized from ethanol.
IR (KBr, cmꢀ1): 3216 (NH); 3085 (aromatic CH); 2948, 2917
(CH3); 1614, 1578, 1504 (C]N þ C]Caryl); 1326, 1286, 1158 (SO2);
1264 (NeN]C); 1005 (NeN); 695 (CeSeC); 1H NMR (DMSO-d6, d
,
ppm): 10.85 (s, 1H, NH); 8.03 (d, 2H, J ¼ 8.5 Hz, aromatic protons);
7.96 (d, 2H, J ¼ 8.5 Hz, aromatic protons); 7.89 (d, 2H, J ¼ 8.5 Hz,
aromatic protons); 7.68 (d, 2H, J ¼ 8.3 Hz, aromatic protons);
7.52e7.68 (m, 3H, aromatic protons); 2.38 (s, 3H, CH3); 13C NMR
(DMSO-d6, d, ppm): 159.87 (C3-triazole ring); 154.52 (C5-triazole
ring); 153.68 (C]N-thiadiazole ring); 143.08, 140.41, 137.24, 136.84,
131.24 (quaternary aromatic ring carbons); 133.14, 129.61, 128.79,
128.14, 127.95, 127.88, 120.68 (CH-aromatic ring carbons); 20.45
(CH3).
6.3.1. 6-(4-bromophenyl)-3-[4-(phenylsulfonyl)phenyl]-[1,2,4]
triazolo[3,4-b][1,3,4]thiadiazole 4a
6.2.4. 3-[4-(4-bromophenylsulfonyl)phenyl]-6-N-(4-bromophenyl)
amino-[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazole 3a
IR (KBr, cmꢀ1): 3088 (aromatic CH); 1602, 1587, 1567, 1520 (C]
N þ C]Caryl); 1319, 1290, 1156 (SO2); 1267 (NeN]C); 1008 (NeN);
685 (CeSeC); 568 (CeBr); 1H NMR (DMSO-d6, d, ppm): 8.05 (d, 2H,
J ¼ 8.5 Hz, aromatic protons); 8.01 (d, 2H, J ¼ 8.5 Hz, aromatic
protons); 7.95 (t, 2H, J ¼ 8.0 Hz, aromatic protons); 7.72 (d, 2H,
J ¼ 8.2 Hz, aromatic protons); 7.65 (d, 2H, J ¼ 8.2 Hz; aromatic
protons); 7.62 (tt, 1H, J ¼ 8.0; 1.8 Hz aromatic proton); 7.50 (t, 2H,
J ¼ 8.0 Hz; aromatic protons); 13C NMR (DMSO-d6, d, ppm): 163.45
(C3-triazole ring); 155.28 (C5-triazole ring); 152.68 (C¼N-thiadia-
zole ring); 141.93, 140.26, 143.14, 132.45, 128.53 (quaternary
aromatic ring carbons); 132.90, 132.65, 129.53, 128.78, 127.84,
127.13, 126.43 (CH-aromatic ring carbons).
IR (KBr, cmꢀ1): 3108 (NH); 3095 (aromatic CH); 1583, 1534, 1473
(C]N þ C]Caryl); 1322, 1290, 1159 (SO2); 1261 (NeN]C); 1012
(NeN); 693 (CeSeC); 574 (CeBr); 1H NMR (DMSO-d6, d, ppm): 11.14
(s, 1H, NH); 8.08 (d, 2H, J ¼ 8.8 Hz, aromatic protons); 8.02 (d, 2H,
J ¼ 8.8 Hz, aromatic protons); 7.96 (d, 2H, J ¼ 8.8 Hz, aromatic
protons); 7.80 (d, 2H, J ¼ 8.8 Hz, aromatic protons); 7.61 (d, 2H,
J ¼ 8.5 Hz; aromatic protons); 7.44 (d, 2H, J ¼ 8.5 Hz, aromatic
protons); 13C NMR (DMSO-d6,
d, ppm): 159.90 (C3-triazole ring);
159.16 (C5-triazole ring); 154.31 (C]N-thiadiazole ring); 141.10,
141.00, 139.47, 129.40, 127.99, 114.63 (quaternary aromatic ring
carbons); 133.60, 131.95, 130.20, 129.12, 127.58, 122.25 (CH-
aromatic ring carbons).
6.3.2. 6-(4-chlorophenyl)-3-[4-(phenylsulfonyl)phenyl]-[1,2,4]
triazolo[3,4-b][1,3,4]thiadiazole 4b
6.2.5. 3-[4-(4-bromophenylsulfonyl)phenyl]-6-N-(4-
IR (KBr, cmꢀ1): 3087 (aromatic CH); 1604, 1582, 1569, 1543 (C]
N þ C]Caryl); 1320, 1289, 1160 (SO2); 1267 (NeN]C); 1007 (NeN);
766 (CeCl); 687 (CeSeC); 1H NMR (DMSO-d6, d, ppm): 8.27 (d, 2H,
J ¼ 8.7 Hz, aromatic protons); 8.17 (d, 2H, J ¼ 8.7 Hz, aromatic
protons); 8.00 (dd, 2H, J ¼ 8.4; 1.6 Hz, aromatic protons); 7.91 (t, 1H,
methoxyphenyl)amino-[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazole 3b
IR (KBr, cmꢀ1): 3166 (NH); 3078 (aromatic CH); 2928, 2864
(CH3); 1619, 1579, 1502 (C]N þ C]Caryl); 1328, 1292, 1156 (SO2);
1261 (NeN]C); 1007 (NeN); 690 (CeSeC); 576 (CeBr); 1H NMR

6144
G.L. Almajan et al. / European Journal of Medicinal Chemistry 45 (2010) 6139e6146
J ¼ 8.5 Hz; aromatic protons); 7.55 (d, 2H, J ¼ 8.5 Hz; aromatic
protons); 7.51e7.85 (m, 4H, aromatic protons); 13C NMR (DMSO-d6,
carbons); 130.12,129.63,128.65,127.73,127.58,111.53 (CH-aromatic
ring carbons).
d, ppm): 160.48 (C3-triazole ring); 158.78 (C5-triazole ring); 150.32
(C]N-thiadiazole ring); 143.47, 139.13, 138.04, 131.56, 130.20
(quaternary aromatic ring carbons); 133.99, 133.19, 129.30, 128.89,
128.37, 127.72, 127.58 (CH-aromatic ring carbons).
6.3.7. 6-[(3-bromo-4-chloro)phenyl]-3-[4-(phenylsulfonyl)phenyl]-
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 4g
IR (KBr, cmꢀ1): 3095 (aromatic CH); 1609, 1596, 1454 (C]
N þ C]Caryl); 1322, 1290, 1158 (SO2); 1269 (NeN]C); 1015 (NeN);
766 (CeCl); 699 (CeSeC); 575 (CeBr); 1H NMR (DMSO-d6, d, ppm):
8.13 (d, 2H, J ¼ 8.6 Hz, aromatic protons); 7.95 (dd, 2H, J ¼ 8.7;
1.6 Hz, aromatic protons); 7.86 (d, 1H, J ¼ 8.5 Hz, aromatic proton);
7.78 (d, 1H, J ¼ 8.5 Hz, aromatic proton); 7.61 (t, 2H, J ¼ 8.7 Hz;
aromatic protons); 7.57 (d, 2H, J ¼ 8.6 Hz, aromatic protons); 7.42
6.3.3. 6-(4-methoxyphenyl)-3-[4-(phenylsulfonyl)phenyl]-[1,2,4]
triazolo[3,4-b][1,3,4]thiadiazole 4c
IR (KBr, cmꢀ1): 3087 (aromatic CH); 2930, 2867 (CH3); 1602,
1592, 1518 (C]N þ C]Caryl); 1313, 1290, 1159 (SO2); 1264 (NeN]
C); 1005 (NeN); 684 (CeSeC); 1H NMR (DMSO-d6, d, ppm): 8.01 (d,
2H, J ¼ 8.7 Hz, aromatic protons); 7.95 (d, 2H, J ¼ 8.7 Hz, aromatic
protons); 7.86 (d, 2H, J ¼ 8.5, aromatic protons); 7.78 (t, 2H,
J ¼ 8.5 Hz, aromatic proton); 7.57 (tt, 1H, J ¼ 8.7; 1.6 Hz; aromatic
proton); 7.50 (d, 2H, J ¼ 8.8 Hz, aromatic protons); 7.12 (d, 2H,
J ¼ 8.8 Hz; aromatic protons); 3.85 (s, 3H, OCH3); 13C NMR (DMSO-
(dd, 1H, J ¼ 8.5; 2.4 Hz, aromatic proton); 13C NMR (DMSO-d6,
d,
ppm): 165.66 (C3-triazole ring); 158.94 (C5-triazole ring); 154.68
(C]N-thiadiazole ring); 143.10, 140.29, 138.17, 135.78, 134.40,
122.93 (quaternary aromatic ring carbons); 133.33, 128.87, 128.34,
127.93, 127.58, 127.17, 127.02, 126.93 (CH-aromatic ring carbons).
d6, d, ppm): 166.28 (C3-triazole ring); 159.26 (C5-triazole ring);
154.94 (C]N-thiadiazole ring); 157.31, 142.13, 141.30, 135.78,
132.69 (quaternary aromatic ring carbons); 133.61, 129.53, 129.12,
127.58, 127.12, 126.44, 115.26 (CH-aromatic ring carbons); 55.61
(OCH3).
6.3.8. 6-(4-bromophenyl)-3-[4-(4-bromophenylsulfonyl)phenyl]-
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 5a
IR (KBr, cmꢀ1): 3086 (aromatic CH); 1619, 1599, 1573, 1548 (C]
N þ C]Caryl); 1327, 1291, 1159 (SO2); 1259 (NeN]C); 1010 (NeN);
698 (CeSeC); 575 (CeBr); 1H NMR (DMSO-d6, d, ppm): 7.98 (s, 2H,
aromatic protons); 0.7.82 (d, 2H, J ¼ 8.3 Hz, aromatic protons); 7.61
(d, 2H, J ¼ 8.3 Hz, aromatic protons); 7.65 (d, 2H, J ¼ 8.2 Hz;
aromatic protons); 7.50e7.58 (m, 4H; aromatic protons); 13C NMR
6.3.4. 6-(4-aminophenyl)-3-[4-(phenylsulfonyl)phenyl]-[1,2,4]
triazolo[3,4-b][1,3,4]thiadiazole 4d
IR (KBr, cmꢀ1): 3384, 3188 (NH2); 3088 (aromatic CH); 1619,
1599, 1585, 1548 (C]N þ C]Caryl); 1326, 1288, 1159 (SO2); 1263
(NeN]C); 1012 (NeN); 707 (CeSeC); 1H NMR (DMSO-d6, d, ppm):
6.27 (s, 2H, NH2); 8.03 (d, 2H, J ¼ 8.7 Hz, aromatic protons); 7.96
(d, 2H, J ¼ 8.7 Hz, aromatic protons); 7.89 (dd, 2H, J ¼ 8.6; 1.8 Hz,
aromatic protons); 7.76 (d, 2H, J ¼ 8.2 Hz; aromatic protons); 7.71
(t, 2H, J ¼ 8.6 Hz, aromatic protons); 7.57 (t, 1H, J ¼ 8.2 Hz, aromatic
proton); 6.66 (d, 2H, J ¼ 8.2 Hz; aromatic protons); 13C NMR
(DMSO-d6, d, ppm): 164.78 (C3-triazole ring); 154.76 (C5-triazole
ring); 153.94 (C]N-thiadiazole ring); 141.30, 139.47, 135.17, 132.45,
129.53, 127.66 (quaternary aromatic ring carbons); 133.79, 133.62,
132.72, 130.20, 129.40, 128.16 (CH-aromatic ring carbons).
6.3.9. 6-(4-chlorophenyl)-3-[4-(4-bromophenylsulfonyl)phenyl]-
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 5b
(DMSO-d6,
d
, ppm): 166.17 (C3-triazole ring); 159.16 (C5-triazole
IR (KBr, cmꢀ1): 3084 (aromatic CH); 1610, 1588, 1574 (C]
N þ C]Caryl); 1313, 1291, 1160 (SO2); 1263 (NeN]C); 1005 (NeN);
768 (CeCl); 683 (CeSeC); 572 (CeBr); 1H NMR (DMSO-d6, d, ppm):
8.30 (d, 2H, J ¼ 8.3 Hz, aromatic protons); 8.16 (d, 2H, J ¼ 8.3 Hz,
aromatic protons); 7.95 (d, 2H, J ¼ 8.1 Hz, aromatic protons); 7.92 (d,
2H, J ¼ 8.4 Hz; aromatic protons); 7.60 (d, 2H, J ¼ 8.1 Hz; aromatic
protons); 7.59 (d, 2H, J ¼ 8.4 Hz; aromatic protons); 13C NMR
ring); 154.31 (C]N-thiadiazole ring); 151.22, 141.43, 140.66, 135.62,
132.76 (quaternary aromatic ring carbons); 133.59, 129.48, 128.77,
128.53, 128.34, 127.68, 115.10 (CH-aromatic ring carbons).
6.3.5. 6-[(4-aminomethyl)phenyl]-3-[4-(phenylsulfonyl)phenyl]-
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 4e
IR (KBr, cmꢀ1): 3375, 3118 (NH); 3085 (aromatic CH); 2960, 2884
(CH2); 1619, 1599, 1585 (C]N þ C]Caryl); 1327, 1291, 1159 (SO2);
(DMSO-d6, d, ppm): 161.89 (C3-triazole ring); 156.66 (C5-triazole
ring); 151.16 (C]N-thiadiazole ring); 141.54, 139.40, 138.63, 134.74,
134.18, 128.31 (quaternary aromatic ring carbons); 133.00, 132.48,
129.31, 128.82, 127.71, 127.52 (CH-aromatic ring carbons).
1259 (NeN]C); 1010 (NeN); 710 (CeSeC); 1H NMR (DMSO-d6,
d,
ppm): 8.68 (s, 2H, NH2); 8.09 (d, 2H, J ¼ 8.6 Hz, aromatic protons);
8.01 (d, 2H, J ¼ 8.6 Hz, aromatic protons); 7.95 (dd, 2H, J ¼ 8.4;
1.8 Hz, aromatic protons); 7.68e7.86 (m, 3H, aromatic protons);
7.50 (d, 2H, J ¼ 8.2 Hz; aromatic protons); 7.28 (d, 2H, J ¼ 8.2 Hz;
6.3.10. 6-(4-methoxyphenyl)-3-[4-(4-bromophenylsulfonyl)
phenyl]-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 5c
aromatic protons); 4.36 (s, 2H, CH2); 13C NMR (DMSO-d6,
d, ppm):
IR (KBr, cmꢀ1): 3088 (aromatic CH); 2937, 2840 (CH3); 1605,
1589, 1512 (C]N þ C]Caryl); 1312, 1288, 1158 (SO2); 1269 (NeN]
165.45 (C3-triazole ring); 160.16 (C5-triazole ring); 155.28 (C]N-
thiadiazole ring); 143.31, 141.61, 141.13, 134.24, 131.35 (quaternary
aromatic ring carbons); 134.13, 129.73, 128.43, 128.03, 126.94,
123.17, 116.65 (CH-aromatic ring carbons); 45.93 (CH2).
C); 1007 (NeN); 687 (CeSeC); 581 (CeBr); 1H NMR (DMSO-d6,
d,
ppm): 8.06 (d, 2H, J ¼ 8.5 Hz, aromatic protons); 7.98 (d, 2H,
J ¼ 8.5 Hz, aromatic protons); 7.76 (dd, 2H, J ¼ 8.5, aromatic
protons); 7.66 (d, 2H, J ¼ 8.2 Hz, aromatic protons); 7.52 (d, 2H,
J ¼ 8.7 Hz; aromatic protons); 7.15 (d, 2H, J ¼ 8.2 Hz, aromatic
6.3.6. 6-[(3,4,5-trihydroxyphenyl)]-3-[4-(phenylsulfonyl)phenyl]-
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 4f
proton); 3.88 (s, 3H, OCH3); 13C NMR (DMSO-d6,
d, ppm): 165.89
IR (KBr, cmꢀ1): 3384 (OH); 3089 (aromatic CH); 1618, 1593, 1574
(C]N þ C]Caryl); 1326, 1291, 1159 (SO2); 1265 (NeN]C); 1009
(C3-triazole ring); 158.92 (C5-triazole ring); 153.94 (C]N-thia-
diazole ring); 155.87, 140.66, 140.40, 137.03, 133.07, 128.53
(quaternary aromatic ring carbons); 133.48, 129.04, 128.61, 126.98,
125.88, 114.74 (CH-aromatic ring carbons); 55.38 (OCH3).
(NeN); 700 (CeSeC); 1H NMR (DMSO-d6,
d, ppm): 8.03 (d, 2H,
J ¼ 8.2 Hz, aromatic protons); 7.96 (d, 2H, J ¼ 8.2 Hz, aromatic
protons); 7.89 (d, 2H, J ¼ 8.2 Hz, aromatic protons); 7.72 (t, 1H,
J ¼ 8.2 Hz, aromatic proton); 7.51 (dd, 2H, J ¼ 8.2; 1.2 Hz; aromatic
protons); 6,76 (d, 2H, J ¼ 8.1 Hz; aromatic protons); 5.35 (s, 3H, OH);
6.3.11. 6-(4-aminophenyl)-3-[4-(4-bromophenylsulfonyl)phenyl]-
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 5d
13C NMR (DMSO-d6,
d, ppm): 166.48 (C3-triazole ring); 158.81
IR (KBr, cmꢀ1): 3368, 3220 (NH2); 3063 (aromatic CH); 1608,
1579, 1541 (C]N þ C]Caryl); 1325, 1290, 1158 (SO2); 1255 (NeN]
(C5-triazole ring); 158.75 (C]N-thiadiazole ring); 147.08, 142.12,
139.33, 134.78, 134.23, 134.17, 133.72, (quaternary aromatic ring
C); 1012 (NeN); 705 (CeSeC); 580 (CeBr); 1H NMR (DMSO-d6,
d,

G.L. Almajan et al. / European Journal of Medicinal Chemistry 45 (2010) 6139e6146
6145
ppm): 6.13 (s, 2H, NH2); 7.94 (d, 2H, J ¼ 8.8 Hz, aromatic protons);
6.4.1. 3-[4-(phenylsulfonyl)phenyl]-[1,2,4]triazolo[3,4-b][1,3,4]
thiadiazol-6(5H)-one 6a
7.87 (d, 2H, J ¼ 8.8 Hz, aromatic protons); 7.77 (d, 2H, J ¼ 8.8 Hz,
aromatic protons); 7.71 (d, 2H, J ¼ 8.8 Hz; aromatic protons); 7.64
(d, 2H, J ¼ 8.6 Hz, aromatic protons); 6.58 (d, 2H, J ¼ 8.6 Hz;
aromatic protons); 13C NMR (DMSO-d6, d, ppm): 165.89 (C3-triazole
ring); 159.34 (C5-triazole ring); 154.94 (C]N-thiadiazole ring);
145.88, 142.13, 141.00, 137.60, 131.75, 129.48 (quaternary aromatic
ring carbons); 132.72, 130.20, 129.67, 129.12, 128.82, 114.38 (CH-
aromatic ring carbons).
IR (KBr, cmꢀ1): 3398 (OH), 3089 (aromatic CH); 1616, 1572, 1489
(C]N þ C]Caryl); 1324, 1291, 1159 (SO2); 1263 (NeN]C); 1009
(NeN); 700 (CeSeC); 1H NMR (DMSO-d6, d, ppm): 9.08 (s, 1H, NH);
8.27 (d, 2H, J ¼ 8.5 Hz, aromatic protons); 8.11 (d, 2H, J ¼ 7.8 Hz,
aromatic proton); 8.00 (d, 2H, J ¼ 8.5 Hz, aromatic proton); 7.70 (tt,
1H, J ¼ 7.8; 1.5 Hz, aromatic proton); 7.63 (t, 2H, J ¼ 7.8 Hz; aromatic
protons); 13C NMR (DMSO-d6,
d, ppm): 175.26 (C]O); 158.75 (C3-
triazole ring); 157.89 (C5-triazole ring); 143.51, 139.56, 133.84
(quaternary aromatic ring carbons); 133.97, 129.87, 128.62, 127.57,
124.47 (CH-aromatic ring carbons).
6.3.12. 6-[(4-aminomethyl)phenyl]-3-[4-(4-bromophenylsulfonyl)
phenyl]-[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazole 5e
IR (KBr, cmꢀ1): 3316, 3228 (NH); 3091 (aromatic CH); 2925,
2837 (CH2); 1620, 1599, 1573 (C]N þ C]Caryl); 1326, 1288, 1159
(SO2); 1263 (NeN]C); 1012 (NeN); 711 (CeSeC); 575 (CeBr); 1H
NMR (DMSO-d6, d, ppm): 8.68 (s, 2H, NH2); 8.09 (d, 2H, J ¼ 8.6 Hz,
aromatic protons); 8.01 (d, 2H, J ¼ 8.6 Hz, aromatic protons); 7.95
(dd, 2H, J ¼ 8.4; 1.8 Hz, aromatic protons); 7.68e7.86 (m, 3H,
aromatic protons); 7.50 (d, 2H, J ¼ 8.2 Hz; aromatic protons); 7.28
(d, 2H, J ¼ 8.2 Hz; aromatic protons); 4.36 (s, 2H, CH2); 13C NMR
6.4.2. 3-[4-(4-bromophenylsulfonyl)phenyl]-[1,2,4]triazolo[3,4-b]
[1,3,4]thiadiazol-6(5H)-one 6b
IR (KBr, cmꢀ1): 3405 (OH), 3091 (aromatic CH); 1617, 1573, 1471
(C]N þ C]Caryl); 1326, 1292, 1158 (SO2); 1260 (NeN]C); 1009
(NeN); 692 (CeSeC); 577 (CeBr); 1H NMR (DMSO-d6, d, ppm): 9.09
(s, 1H, NH); 8.15 (d, 2H, J ¼ 8.5 Hz, aromatic protons); 8.09 (d, 2H,
J ¼ 8.5 Hz, aromatic protons); 7.94 (d, 2H, J ¼ 8.8 Hz, aromatic
proton); 7.87 (d, 2H, J ¼ 8.8 Hz, aromatic proton); 13C NMR (DMSO-
(DMSO-d6, d, ppm): 166.91 (C3-triazole ring); 159.92 (C5-triazole
ring); 153.89 (C]N-thiadiazole ring); 143.91, 142.78, 141.40, 135.60,
132.57,128.14 (quaternary aromatic ring carbons); 133.60, 130.53,
129.33, 127.30, 126.94, 126.89 (CH-aromatic ring carbons); 46.13
(CH2).
d6, d, ppm): 177.63 (C]O); 159.10 (C3-triazole ring); 158.35 (C5-
triazole ring); 143.13, 140.68, 134.35 (quaternary aromatic ring
carbons); 133.05, 129.60, 128.45, 127.92 (CH-aromatic ring
carbons).
6.3.13. 6-[(3,4,5-trihydroxyphenyl)]-3-[4-(4-bromophenylsulfonyl)
phenyl]-[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazole 5f
6.5. Antibacterial activity
IR (KBr, cmꢀ1): 3373 (OH); 3088 (aromatic CH); 1620,1595,1573,
1552 (C]N þ C]Caryl); 1326, 1288, 1158 (SO2); 1267 (NeN]C);
1010 (NeN); 702 (CeSeC); 573 (CeBr); 1H NMR (DMSO-d6, d, ppm):
7.92 (d, 2H, J ¼ 8.5 Hz, aromatic protons); 7.87 (d, 2H, J ¼ 8.5 Hz,
aromatic protons); 7.77 (d, 2H, J ¼ 8.5 Hz, aromatic protons); 7.71
(d, 2H, J ¼ 8.5 Hz, aromatic protons); 6,71 (d, 2H, J ¼ 8.2 Hz;
Determination of minimum inhibitory concentration (MIC, mg/
mL) was done using the serial dilutions in liquid broth method.
Tests were performed in 96-well round bottom sterile culture
plates. Antibacterial and antifungal assays were performed in
Mueller-Hinton broth (Merck) and Sabouraud dextrose agar (Difco),
respectively. Ampicillin and Aztreonam for bacteria and Ampho-
tericine for the yeast C. albicans were used as standard drugs.
For inoculum preparation microbial suspensions of reference
strains in saline were made. They were adjusted to the turbidity of
0.5 McFarland standard and were diluted 1:100 in Mueller-Hinton
aromatic protons); 5.42 (s, 3H, OH); 13C NMR (DMSO-d6,
d, ppm):
167.62 (C3-triazole ring); 157.93 (C5-triazole ring); 157.72 (C¼N-
thiadiazole ring); 146.75, 143.15, 142.87, 139.54, 135.28, 134.35,
133.69, 127.28 (quaternary aromatic ring carbons); 133.08, 129.65,
128.49, 127.44, 114.67 (CH-aromatic ring carbons).
broth/Sabouraud dextrose agar for achieving
mL of the diluted inoculum were
added to each well containing the tested compounds and in the
a
density of
1 ꢃ 106 CFU/mL. Aliquots of 50
6.3.14. 6-[(3-bromo-4-chloro)phenyl]-3-[4-(4-bromophenylsulfonyl)
phenyl]-[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazole 5g
positive growth control well, filled already with 50
mL broth
IR (KBr, cmꢀ1): 3068 (aromatic CH); 1613, 1592, 1449 (C]
N þ C]Caryl); 1324, 1287, 1158 (SO2); 1264 (NeN]C); 1013 (NeN);
762 (CeCl); 697 (CeSeC); 579 (CeBr); 1H NMR (DMSO-d6, d, ppm):
8.09 (s, 4H, aromatic protons); 8.00 (dd, 2H, J ¼ 8.5; 1.6 Hz, aromatic
protons); 7.74 (d, 1H, J ¼ 8.8 Hz, aromatic proton); 7.64 (dd, 2H,
J ¼ 8.5; 1.6 Hz, aromatic protons); 7.34 (dd, 1H, J ¼ 8.8; 2.2 Hz;
aromatic proton); 7.58 (d, 1H, J ¼ 8.8 Hz, aromatic protons); 13C
without compound. The sterility control well contained only
compound-free broth. The final liquid volume in each well was of
100
mL.
All the test compounds were dissolved in DMSO (2048
mg/mL).
Further dilutions of the compounds in the test medium were fur-
nished at the required quantities of the broth used. Ten different
dilutions of the test compounds between 1024 and 2 mg/mL were
prepared in microplates by serial dilutions from top to bottom.
Then all the wells except the 12th wells (positive control) were
NMR (DMSO-d6,
d, ppm): 165.31 (C3-triazole ring); 159.04
(C5-triazole ring); 154.12 (C]N-thiadiazole ring); 142.84, 140.66,
136.14, 135.07, 133.89, 131.79, 128.53 (quaternary aromatic ring
carbons); 134.82, 133.60, 129.88, 128.61, 128.12, 122.95, 121.05 (CH-
aromatic ring carbons).
filled with 50
mL of the standardized strains. These plates were
incubated at 37 ꢁC for 18e20 h for bacterial strains and 48 h for C.
albicans. The lowest concentration of the test compounds inhibiting
visible growth of microorganisms was taken as the MIC value. Tests
using DMSO as negative control were carried out in parallel and it
was determined that the solvent had no antimicrobial activity
against any of the test microorganisms. Because the MIC values are
not spectacular, no statistical calculations were made.
6.4. General procedure for synthesis of 3-[4-(4-X-phenylsulfonyl)
phenyl]-[1,2,4] triazolo[3,4-b][1,3,4]thiadiazol-6(5H)-one 6a,b
A mixture of 4-amino-5-[4-(4-X-phenylsulfonyl)phenyl]-4H-
1,2,4-triazole-3-thiol 1 (0.36 mmol) and N,N0-carbonyldiimidazole
(0.54 mmol) in dry dioxane (10 mL) was heated under reflux for 4 h.
After cooling, the solvent was removed under reduced pressure and
the solid product obtained was washed with water, filtered and
recrystallized from ethanol.
Acknowledgements
This work was supported by CNCSIS eUEFISCSU Romania,
project number 301, PNII e IDEI 226/2007.

6146
G.L. Almajan et al. / European Journal of Medicinal Chemistry 45 (2010) 6139e6146
[12] G.L. Almajan, S.F. Barbuceanu, I. Saramet, C. Draghici, Rev. Chim. (Bucharest)
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