Facile synthesis, characterization and pharmacological activities of 3,6-disubstituted 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles and 5,6-dihydro-3,6-disubstituted-1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles

Article abstract of DOI:10.1016/j.ejmech.2012.02.030

Two new series of compounds namely, 3,6-disubstituted-1,2,4-triazolo[3,4-b] [1,3,4]thiadizoles (5a-j) and 5,6-dihydro-3,6-disubstituted-1,2,4-triazolo[3,4- b][1,3,4]thiadizoles (7a-j) were prepared. In continuation of a previously reported study, the firs

Full text of DOI:10.1016/j.ejmech.2012.02.030

European Journal of Medicinal Chemistry 51 (2012) 124e136
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Facile synthesis, characterization and pharmacological activities
of 3,6-disubstituted 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles and
5,6-dihydro-3,6-disubstituted-1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles
,
,
a,
N. Chidananda a b, Boja Poojary a , V. Sumangala b, N. Suchetha Kumari c, Prashanth Shetty d,
*
T. Arulmoli b
a Department of Studies in Chemistry, Mangalore University, Mangalagangothri, Karnataka 574 199, India
b SeQuent Scientific Limited, No: 120 A & B, Industrial Area, Baikampady, New Mangalore, Karnataka 575 011, India
c Department of Biochemistry, K. S. Hegde Medical Academy, Deralakatte, Karnataka 574 162, India
d NGSM Institute of Pharmaceutical Sciences, Deralakatte, Mangalore, Karnataka 574 160, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Two new series of compounds namely, 3,6-disubstituted-1,2,4-triazolo[3,4-b][1,3,4]thiadizoles (5aej)
and 5,6-dihydro-3,6-disubstituted-1,2,4-triazolo[3,4-b][1,3,4]thiadizoles (7aej) were prepared. In
continuation of a previously reported study, the first series (5aej) were synthesized by the cyclo-
condensation of 4-amino-5-(2-bromo-5-methoxyphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (4)
with various substituted aromatic carboxylic acids in phosphorus oxychloride and the second series
(7aej) by the reaction of (4) with various substituted aromatic aldehydes in the presence of p-Toluene
sulfonic acid. Reaction of (4) with the aldehyde (9) afforded the Schiff’s base (10) and not the cyclised
product (11) on treatment with p-Toluene sulfonic acid. Synthesized compounds were structurally
confirmed by spectral analysis and studied for their anti-inflammatory, analgesic, anti-oxidant
and antimicrobial activities. Some of the tested compounds showed significant pharmacological
activities.
Received 26 October 2011
Received in revised form
15 February 2012
Accepted 16 February 2012
Available online 28 February 2012
Keywords:
Triazoles
Triazolo[3,4-b][1,3,4]thiadiazoles
Anti-inflammatory activity
Analgesic activity
Antioxidant activity
Anti-microbial activities
Ó 2012 Elsevier Masson SAS. All rights reserved.
1. Introduction
[8,9], antibacterial [10,11], antiviral [12], anthelmentic [13,14],
antitumour [15], analgesic [16] and anti-inflammatory activities
The recent literature is enriched with progressive findings
about the synthesis and pharmacological action of fused hetero-
cycles. Various 1,2,4-triazole and their fused heterocyclic deriva-
tives have received considerable attention due to their synthetic
and biological importance. For example, various 1,2,4-triazole
derivatives have been reported to possess versatile biological
properties such as antibacterial [1,2], anti-fungal [3], antiviral [4],
analgesic [5] and antimigraine [6] activities. The available thera-
peutically important medicines Terconazole, Itraconazole, Fluco-
nazole, Cefazoline, Ribavarin, Triazolam, Alprazolam, Etizolam and
Furacylin [7] are some of the examples which contain anyone of
these heterocyclic nucleuses. The fused 1,2,4-triazolo[3,4-b][1,3,4]
thiadiazole and 5,6-dihydro-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole
derivatives shows various biological properties such as anti-fungal
[17,18].
Severalmethodswerereportedforthesynthesisof1,2,4etriazolo-
[3,4-b][1,3,4]thiadiazole and 5,6-dihydro-1,2,4-triazolo[3,4-b][1,3,4]
thiadiazole derivatives and evaluated for their in vitro antimicrobial
and anti-inflammatory activities [19e21].
In terms of compounds of interest in medicinal chemistry the
most frequent cause of chirality results from the presence of a tet-
racoordinate carbon centre in a molecule to which four different
groups are attached. The presence of one such centre in a molecule
gives rise to a pair of enantiomers, the presence of n such centres
gives rise to 2n stereo isomers and half that number of pairs of
enantiomers [22].
Prompted by these observations and continuation of previously
reported [23,24] studies on heterocyclic derivatives of methyl 2-
bromo-5-methoxybenzoate (1), it was planned to investigate
a compositae system of bio labile components in a ring to give
a compact and planar structure like fused 1,2,4etriazolo-[3,4-b]
[1,3,4]thiadiazole and optically active 5,6-dihydro-1,2,4-triazolo
* Corresponding author. Tel.: þ91 824 2287262; fax: þ91 824 2287367.
E-mail address: bojapoojary@gmail.com (B. Poojary).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2012.02.030

N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
125
[3,4-b][1,3,4]thiadiazole derivatives and were screened for their
biological activities.
aromatic carboxylic acids in the presence of phosphorus oxy-
chloride at reflux temperature. Phosphorus oxychloride was
necessary for this condensation, which activate the carbonyl
group of aromatic acids and increases its electrophilicity to
enhance the addition of triazole to it.
2. Results and discussion
5,6-dihydro-3,6-disubstituted-1,2,4-triazolo[3,4-b][1,3,4]thia-
diazoles were also prepared by treating 4-amino-5-(2-bromo-5-
methoxyphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (4) with
different mono or disubstituted aromatic aldehydes in ethanol in
the presence of few drops of Conc. H2SO4. The Schiff’s base formed
was further cyclised by refluxing in DMF in the presence catalytic
amount of p-Toluene sulfonic acid. The reaction pathway is
summarized in Schemes 1 and 2.
2.1. Chemistry
The acid hydrazide (2) was prepared by esterification of 2-
bromo-5-methoxy benzoic acid followed by treatment with
hydrazine hydrate in absolute ethanol. 4-amino-5-(2-bromo-5-
methoxyphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (4) was
prepared by following the procedure of Reid and Heindel [25].
The acid hydrazide (2) was allowed to react with carbon disul-
phide in the presence of potassium hydroxide in ethanol to afford
the corresponding intermediate potassium dithiocarbazinate (3).
This salt underwent ring closure with an excess of 99% hydrazine
hydrate to give 4-amino-5-(2-bromo-5-methoxyphenyl)-2,4-
dihydro-3H-1,2,4-triazole-3-thione (4). The resultant triazole (4)
was further converted to 3,6-disubstituted-1,2,4-triazolo[3,4-b]
[1,3,4]thiadiazoles (5aej) through oneepot reaction by conden-
sation followed by cyclization with mono or disubstituted
The structure of 4-amino-5-(2-bromo-5-methoxyphenyl)-2,4-
dihydro-3H-1,2,4-triazole-3-thione (4) was confirmed by IR, NMR,
MASS spectral data and microanalyses. Compound (4) can exist in
two tautomeric forms, 4-amino-5-(2-bromo-5-methoxyphenyl)-4H-
1,2,4-triazole-3-thiol and 4-amino-5-(2-bromo-5-methoxyphenyl)-
2,4-dihydro-3H-1,2,4-triazole-3-thione. The spectral analysis shows
that it exists in the latter form, e.g., in the 1H-NMR spectra,
be only attributed to NHeC ¼ S rather than to SeH and in the IR
d 13.96 can
Br
O
H
N
Br
O
Br
O
-
+
S K
NH
N2H4.H2O/EtOH
CS2/KOH
2
N
H
N
H
OMe
S
78 oC
EtOH, 78 oC
MeO
MeO
MeO
(3)
(2)
(1)
100 oC, 4 h
N2H4.H2O
H
H
N
N
N
S
N
Br
N
N
Br
Br
S
N
S
R2-CHO, Con.H2SO4
N
PTSA
DMF, 152 oC
N
N
N
EtOH, 78 oC
H N
2
MeO
H
(4)
MeO
MeO
R2
(7a-j)
POCl3, 80 oC
R2
R1-CO2H
(6a-j)
N
N
H
N
Br
S
N
MeO
S
N
Br
N
Br
N
N
N
MeO
Cl
R1
(5a-j)
N
N
MeO
Cl
Cl
HN
S
Cl
(10)
Cl
(11)
Cl
Scheme 1. Synthetic route for the compounds 5aej, 7aej and 11.

126
N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
POCl3, DMF
Cl
Cl
O
Cl
O
60 oC
Cl
Cl
(9)
(8)
Scheme 2. Synthetic route for the compound 9.
spectrum, the SeH vibration band (2500 cmꢀ1) was absent. The 1H-
NMR spectrum showed singlet for NH2 group at 5.47 ppm.
cyclization. The 1H-NMR spectra of compounds (7aej) also showed
singlet in the region 5.46e5.52 ppm due to the presence C6
proton of thiadiazole ring. The NH proton of thiadiazole ring
resonated as broad singlet at 13.42e13.98 ppm. The IR, 1H NMR, 13
NMR, mass spectra and elemental analyses supported the structure
of various synthesized dihydro analogues of triazolo thiadiazoles.
d
d
The absence of signals due to NH2 and eN ¼ CeSH (eNHeC ¼ S
of the tautomer) protons in the compounds (5aej) confirmed the
cyclization of triazole (4) by reacting with COOH group of
substituted aromatic acids to afford triazolo-thiadiazoles (5aej).
An absorption band was observed for all the synthesized
compounds in the range of 3046.45e3096.83 cmꢀ1 may be
attributed for aromatic stretching vibration, while that seen at
1575.12e1615.02 cmꢀ1 corresponds to C]N linkage. Thus, the
formation of iminomethine functional group in the compound was
indicated.
On treatment of triazole (4) with the appropriate aromatic
aldehydes in refluxing ethanol afforded only open chain hydrazones
(6aej). The structures of compounds (6aej) were confirmed on the
basis of IR, 1H-NMR, 13C NMR and mass spectral data. The IR spectra
of these compounds showed common characteristic absorption
peaks at 3306.92e3317.24 cmꢀ1 (NH) and 3059.92e3090.46 cmꢀ1
(Ar CeH). The 1H-NMR spectra are characterized by the presence
C
We also prepared
a
new compound 1-Chloro-4-(3,4-
dichlorophenyl)-3,4-dihydronaphthalene-2-carbaldehyde (9) in
good yield by VilsmeiereHaack reaction of 4-(3,4-dichlorophenyl)-
3,4-dihydronaphthalen-1(2H)-one (8). The structure of the
compound (9) was confirmed by spectral and X-ray crystallographic
data [26,27]. The intermediate compound 4-(3,4-dichlorophenyl)-
3,4-dihydronaphthalen-1(2H)-one (8) was prepared by the previ-
ously reported procedure [28]. The above carbaldehyde further
reacted with 4-amino-5-(2-bromo-5-methoxyphenyl)-2,4-dihydro-
3H-1,2,4-triazole-3-thione (4) to give triazolo Schiff’s base (10).
Further we attempted intramolecular cyclization of (10) with p-
Toluene sulfonic acid in refluxing DMF to the respective 5,6-dihydro-
1,2,4-triazolo[3,4-b][1,3,4]thiadiazole (11) was unsuccessful under
conventional conditions.
The spectral values for all the compounds and C, H, N analyses
are given in the experimental part. Both analytical and spectral data
(IR, NMR, MS and elemental analysis) of all the synthesized
compounds were in full agreement with the proposed structure.
The physicochemical properties of synthesized compounds were
presented in Tables 1and 2.
of the CH]N proton appeared as a singlet at
while NH/tautomeric with SH proton appeared around
13.38e14.43 ppm. The 13C NMR spectra are characterized by the
presence of the CH]N carbon at 158.85e158.96 ppm.
d 9.43e10.59 ppm,
d
d
These hydrazones undergoes intramolecular Mannich reaction
in the presence of catalytic amount of p-Toluene sulfonic acid to
give corresponding 5,6-dihydro-1,2,4-triazolo[3,4-b][1,3,4]thia-
diazole derivatives (7aej). The compounds (7aej) contain one
stereocenter at C6, to which four different groups are attached.
Due to this chirality, the molecule can exist in two enantiomeric
forms. Hence the compounds (7aej) are optically active. The
IR spectra of the cyclized products (7aej) showed absorption
peaks at 3208.42e3220.04 cmꢀ1 (thiadiazole NH) and
3186.73e3194.89 cmꢀ1 (AreCeH). The absorption bands were
observed for all the synthesized compounds in the range of
1581.46e1591.61 cmꢀ1 attributed for C]N linkage. Thus, the
formation of iminomethine functional group in the compound was
indicated. In the 1H-NMR spectra, the absence of CH]N proton in
3. Pharmacological screening
3.1. Pharmacology
All newly synthesized compounds were evaluated for anti-
inflammatory and analgesic activities. The tested compounds
were administered in the form of a suspension (1% carboxy methyl
cellulose as vehicle). Anti-inflammatory and analgesic activities of
the tested compounds were measured with respect to the control
and compared with the standard drugs Diclo and pentazocine
respectively. All the pharmacological data are expressed as
the region
d 9.43e10.59 ppm confirms the intramolecular
Table 1
Characterization data of the compounds 2, 4 and 5aej.
Comp. no.
R1
Recryst. solvent
Mol. Formula (mol. wt.)
M.p. (ꢁC)
Yield (%)
2
4
e
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethyl acetate
Ethanol
Ethyl acetate
Ethyl acetate
Ethanol
C8H9BrN2O2 (245.07)
C9H9BrN4OS (301.16)
C17H13BrN4O2S (417.28)
C17H13BrN4OS (401.28)
C16H11BrN4OS (387.25)
C16H9BrCl2N4OS (456.14)
190e192
184e186
142e146
148e150
110e112
188e190
190e192
166e168
204e206
178e180
180e182
196e198
98
74
68
72
65
70
66
64
72
78
62
69
e
5a
5b
5c
5d
5e
5f
5g
5h
5i
4-methoxy phenyl
4-methyl phenyl
phenyl
3,5-dichlorophenyl
4-amino phenyl
3,5-dimethyl phenyl
4-nitro phenyl
3,5-dinitro phenyl
2-hydroxy-4-methyl phenyl
2,4-diiodo phenyl
C16H12BrN5OS (402.27)
C18H15BrN4OS (415.30)
C16H10BrN5O3S (432.25)
C16H9BrN6O5S (477.25)
C17H13BrN4O2S (417.28)
C16H9BrI2N4OS (639.04)
5j
Ethyl acetate

N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
127
Table 2
Characterization data of the compounds 6aej, 7aej, 9 and 10.
Comp. no.
R2
Recryst. solvent
Mol. Formula (mol. wt.)
16H12BrClN4OS (423.71)
C16H13BrN4OS (389.23)
C16H12BrClN4OS (423.71)
C16H12BrClN4OS (423.71)
C18H17BrN4O3S (449.32)
M.p. (ꢁC)
Yield (%)
6a
6b
6c
6d
6e
6f
6g
6h
6i
2-chloro phenyl
phenyl
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethyl acetate
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethyl acetate
Ethanol
Ethanol
Ethyl acetate
Ethanol
C
164e166
142e144
178e180
180e182
222e224
192e194
194e196
172e174
162e164
128e130
190e192
260e264
146e148
176e178
180e186
172e174
170e172
210e212
202e204
186e188
108e110
152e154
70
68
72
69
75
78
76
69
74
67
72
66
78
75
73
76
72
70
79
68
78
75
4-chloro phenyl
3-chloro phenyl
2,4-dimethoxy phenyl
4-methoxy phenyl
2-methoxy phenyl
4-nitro phenyl
biphenyl
4-methyl phenyl
2-chloro phenyl
phenyl
4-chloro phenyl
3-chloro phenyl
2,4-dimethoxy phenyl
4-methoxy phenyl
2-methoxy phenyl
4-nitro phenyl
biphenyl
C
17H15BrN4O2S (419.29)
C17H15BrN4O2S (419.29)
C16H12BrN5O3S (434.26)
C22H17BrN4OS (465.36)
C17H15BrN4OS (403.29)
C16H12BrClN4OS (423.71)
C16H13BrN4OS (389.23)
C16H12BrClN4OS (423.71)
6j
7a
7b
7c
7d
7e
7f
7g
7h
7i
C
16H12BrClN4OS (423.71)
C18H17BrN4O3S (449.32)
C17H15BrN4O2S (419.29)
C17H15BrN4O2S (419.29)
C16H12BrN5O3S (434.26)
C22H17BrN4OS (465.36)
C17H15BrN4OS (403.29)
C17H11Cl3O (337)
7j
9
10
4-methyl phenyl
e
e
C26H18BrCl3N4OS (620.77)
mean ꢂ SEM; statistical analysis was applied to determine the
significance of the difference between the control group and group
of animals tested with the tested compounds. The compounds
which showed potent anti-inflammatory and analgesic activities
also screened for their in vitro anti-oxidant activity by DPPH scav-
enging method. Ascorbic acid was used as a positive control and
measurements was run in triplicate. The percentage of scavenging
activity was calculated.
We investigated all the newly synthesized compounds for their
antibacterial activity against four bacterial strains, viz., Staphylo-
coccus aureus (ATTC-25923), Escherichia coli (ATTC-25922), Pseu-
domonas aeruginosa (ATTC-27853) and Klebsiella pneumoniae
(recultured). Newly synthesized compounds were also tested for
anti-fungal activity against Penicillium marneffei (recultred), Tri-
chophyton mentagrophytes (recultured), Aspergillus flavus (NICM
No.524) and Aspergillus fumigatus (NCIM No.902) fungal strains.
compared to a standard drug pentazocine. From the analgesic
study it was observed that the formation of thiadiazole ring
will not further enhanced the activity of synthesized compounds.
Like
4-amino-5-(2-bromo-5-methoxyphenyl)-2,4-dihydro-3H-
1,2,4-triazole-3-thione (4), the compounds 5d, 5e, 5g and 5h
showed potent activity compared to a standard drug pentazocine.
The good activity of these compounds are attributed in the pres-
ence of 3,5-dichlorophenyl, 4-amino phenyl, 4-nitro phenyl, 3,5-
dinitro phenyl groups. Similarly 5,6-dihydro-1,2,4-triazolo[3,4-b]
[1,3,4]thiadiazoles 7a, 7c, 7d, 7f and 7h containing 2-chloro phenyl,
4-chloro phenyl, 3-chloro phenyl, 4-methoxy phenyl and 4-nitro
phenyl respectively showed potent activity. The compounds 5a,
5b, 5i, 7b, 7e, 7f, 7g and 7j containing 4-methoxy phenyl, 4-methyl
phenyl, 2-hydroxy-4-methyl phenyl, phenyl, 2,4-dimethoxy
phenyl, 4-methoxy phenyl, 2-methoxy and 4-methyl phenyl
substituent’s respectively showed good analgesic activity. The
results were illustrated in Table 4.
3.2. Anti-inflammatory activity
3.4. Anti-oxidant activity
The 1,2,4-triazolo[3,4-b][1,3,4]thiadizoles 5d, 5e, 5g and 5h
containing 3,5-dichlorophenyl, 4-amino phenyl, 4-nitro phenyl, 3,5-
dinitro phenyl groups and 5,6-dihydro-1,2,4-triazolo[3,4-b][1,3,4]
thiadizoles 7a, 7c, 7d and 7h containing 2-chloro phenyl, 4-chloro
phenyl, 3-chloro phenyl and4-nitro phenyl groups respectively are
the most potent agents of this series against rat-foot inflammation.
According to the study, 1,2,4-triazole (4) itself showed good activity,
but it is observed that activity is further increased by the formation
of thiadiazole ring. Therefore according to structure activity rela-
tionship, the functional groups like chloro, nitro and amino are
responsible for the excellent activity against rat-foot inflammation.
The compounds 5a, 5b, 5i, 7e, 7f, 7g and 7j containing 4-methoxy
phenyl, 4-methyl phenyl, 2-hydroxy-4-methyl phenyl, 2,4-
dimethoxy phenyl, 4-methoxy phenyl, 2-methoxy and 4-methyl
phenyl substituent’s respectively showed good anti-inflammatory
activity. The results were presented in Table 3.
3.4.1. DPPH radical scavenging activity
The compounds having potent anti-inflammatory and analgesic
activity are also tested for their anti-oxidant activity. The
compounds 5e, 5g, 5h, 7h and 7f showed comparatively significant
anti-oxidant activities. The good activity of these compounds may
be due to the presence of strong electron withdrawing group (NO2)
or para substituted phenyl groups. The remaining compounds 4, 5d,
7a, 7c and 7d showed moderate activity compared to the positive
control ascorbic acid. These compounds contain chloro/methoxy
functional groups in their structure. The results were tabulated in
Table 5. Fig. 1 depicts the percentage of free radical scavenging
activity of tested compounds using DPPH method.
3.5. Antibacterial activity
The investigation of antibacterial screening data revealed
that all the tested compounds 4, 5aej and 7aej showed only
moderate activities. The compound 4-amino-5-(2-bromo-5-
methoxyphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione 4 alone
showed moderate activity against E. coli bacterial strain. The
3.3. Analgesic activity
The 4-amino-5-(2-bromo-5-methoxyphenyl)-2,4-dihydro-3H-
1,2,4-triazole-3-thione (4) itself showed potent analgesic activity

128
N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
Table 3
Anti-inflammatory activity of the compounds 4, 5aej and 7aej.
Compound
Dose (mg/kg)
60 min
120 min
180 min
Control
DICLO
4
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
7a
7b
7c
7d
7e
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
2.175 ꢂ 0.1797
0.6 ꢂ 0.04082***
1.491 ꢂ 0.1913*
1.605 ꢂ 0.1402*
1.576 ꢂ 0.1701*
1.88 ꢂ 0.1688
2.375 ꢂ 0.1436
0.625 ꢂ 0.04787***
1.64 ꢂ 0.1423**
1.70 ꢂ 0.0921**
1.66 ꢂ 0.1324**
1.985 ꢂ 0.1802
1.65 ꢂ 0.06455**
1.75 ꢂ 0.1936**
1.85 ꢂ 0.2041
1.8 ꢂ 0.108*
2.275 ꢂ 0.1181
0.625 ꢂ 0.04787***
1.72 ꢂ 0.1358*
1.73 ꢂ 0.1552*
1.77 ꢂ 0.1260*
2.035 ꢂ 0.0915
1.6 ꢂ 0.07071**
1.875 ꢂ 0.1315
2.055 ꢂ 0.1011
1.975 ꢂ 0.1109
1.899 ꢂ 0.1010
1.77 ꢂ 0.1263*
2.25 ꢂ 0.06455
1.9 ꢂ 0.1581
1.575 ꢂ 0.0677**
1.6 ꢂ 0.0778**
1.845 ꢂ 0.08739
1.45 ꢂ 0.06455**
1.51 ꢂ 0.06564**
1.577 ꢂ 0.1722*
2.15 ꢂ 0.09574
1.45 ꢂ 0.06455**
2 ꢂ 0.09129
1.78 ꢂ 0.106*
1.68 ꢂ 0.1383**
2.25 ꢂ 0.0866
1.75 ꢂ 0.1555**
2.05 ꢂ 0.0866
1.89 ꢂ 0.098
2.2 ꢂ 0.1213
1.515 ꢂ 0.1552**
1.525 ꢂ 0.1652**
1.545 ꢂ 0.2012*
1.581 ꢂ 0.1801*
1.585 ꢂ 0.1803*
1.45 ꢂ 0.1658**
2.125 ꢂ 0.06292
1.498 ꢂ 0.1692*
1.98 ꢂ 0.1743
1.95 ꢂ 0.1443
1.73 ꢂ 0.1451*
1.69 ꢂ 0.1336*
1.69 ꢂ 0.1828*
2.075 ꢂ 0.1548
1.9 ꢂ 0.178
1.9 ꢂ 0.108
1.68 ꢂ 0.1601**
1.59 ꢂ 0.0843**
1.59 ꢂ 0.1323**
1.875 ꢂ 0.1548
2.15 ꢂ 0.06455
1.60 ꢂ 0.1463**
7f
7g
7h
7i
7j
1.80 ꢂ 0.0154*
Results were expressed in mean ꢂ SE M. (n ¼ 6) significance levels *P < 0.05, **P < 0.01, ***P < 0.001 as compared with the respective control.
compound 5a showed moderate activity towards all the four
bacterial strains. This may be attributed because of the presence
of methoxy group in para position of the phenyl ring. The
compound 5b is moderately active towards Staphyllococcus
aureus, E. coli and K. pneumoniae bacterial strains. This
compound contains para-methyl phenyl substituent in their
structure. The compound 5h showed moderate activity against
Staphyllococcus aureus, E. coli and K. pneumoniae. The compounds
5d, 5f, 5i, 7c, 7e and 7j are moderately active towards three
bacterial strains namely, E. coli, Psedomonus Aeruginosa P. aeru-
ginosa and K. pneumoniae. All these compounds contain electron
releasing or electron withdrawing groups in their structure
either in 3,5 or para positions. The compound 5e is active against
E. coli and P. aeruginosa bacterial strains. The compound 7g
showed moderate activity towards E. coli bacterial strain
compared to the standard drug ampicillin. The compounds
5e and 7g contain electron emancipating groups like eNH2
or eOCH3 respectively. The compound 7h showed moderate
activity towards P. aeruginosa and K. pneumoniae bacterial
strains. The compounds 5h and 7h contain electron diminishing
eNO2 group in their structure. The compound 7i showed
moderate activity against K. pneumoniae bacterial strain. On after
going through structure activity relationship, it is observed that
the construction of the thiadiazole ring fused to the triazole
moiety widen the activity of the compound compared to 4-
amino-5-(2-bromo-5-methoxyphenyl)-2,4-dihydro-3H-1,2,4-
triazole-3-thione
Table 6.
4 alone. The results were summarized in
Table 4
Analgesic activity of the newly synthesized compounds 4, 5aej and 7aej.
Compound
Dose (mg/kg)
60 min
120 min
180 min
Control
Pentazocine
4
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
1.363 ꢂ 0.1297
7.075 ꢂ 0.1164***
3.463 ꢂ 0.3085**
2.379 ꢂ 0.09035*
2.384 ꢂ 0.08962*
1.963 ꢂ 0.2202
3.421 ꢂ 0.2653**
3.675 ꢂ 0.8125**
2.175 ꢂ 0.08539
3.375 ꢂ 0.4789**
3.675 ꢂ 0.8125**
2.388 ꢂ 0.08985*
2.038 ꢂ 0.07739
3.6 ꢂ 0.1242**
1.363 ꢂ 0.1297
6.863 ꢂ 0.1919***
3.388 ꢂ 0.2968**
2.674 ꢂ 0.2902**
2.681 ꢂ 0.2808**
2.125 ꢂ 0.09242
3.075 ꢂ 0.5622*
3.563 ꢂ 0.7031**
2.075 ꢂ 0.101
1.363 ꢂ 0.1297
7.025 ꢂ 0.2504***
2.338 ꢂ 0.1329**
2.440 ꢂ 0.0834
2.470 ꢂ 0.161
5a
5b
5c
5d
5e
5f
5g
5h
5i
2.5 ꢂ 0.1399
2.388 ꢂ 0.08985*
2.425 ꢂ 0.2385**
2.238 ꢂ 0.0875
2.663 ꢂ 0.2831**
2.425 ꢂ 0.2385**
3.121 ꢂ 0.1501
2.225 ꢂ 0.07773
2.938 ꢂ 0.1784*
3.391 ꢂ 0.2401
2.425 ꢂ 0.2385**
2.235 ꢂ 0.0485*
2.492 ꢂ 0.2342
2.841 ꢂ 0.4611*
2.501 ꢂ 0.1922
2.425 ꢂ 0.2385**
2.455 ꢂ 0.2616
2.438 ꢂ 0.1924
3.263 ꢂ 0.3243**
3.563 ꢂ 0.7031**
3.321 ꢂ 0.1603**
2.088 ꢂ 0.07739
3.25 ꢂ 0.1581*
5j
7a
7b
7c
7d
7e
7f
7g
7h
7i
3.181 ꢂ 0.6140*
3.675 ꢂ 0.8125**
3.546 ꢂ 0.6835**
2.390 ꢂ 0.09014*
3.468 ꢂ 0.5719**
2.387 ꢂ 0.0765*
3.675 ꢂ 0.8125**
2.102 ꢂ 0.0673
2.403 ꢂ 0.0902*
3.460 ꢂ 0.2710**
3.563 ꢂ 0.7031**
3.623 ꢂ 0.7631**
2.642 ꢂ 0.2730**
3.334 ꢂ 0.3953**
2.652 ꢂ 0.3436**
3.563 ꢂ 0.7031**
2.067 ꢂ 0.0803
2.643 ꢂ 0.2713**
7j
Results were expressed in mean ꢂ SE M. (n ¼ 6) significance levels *P < 0.05, **P < 0.01, ***P < 0.001 as compared with the respective control.

N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
129
Table 5
methoxyphenyl)-6-(sustituted phenyl)-5,6-dihydro[1,2,4]triazolo
[3,4-b][1,3,4]thiadiazole (7aej) derivatives were successfully
synthesized in 62e79% yields. The newly synthesized compounds
are characterized by 1H NMR, 13C NMR, Mass spectrometry and IR
studies. The compounds 5d, 5e, 5g, 5h, 7a, 7c, 7d and 7h showed
potent anti-inflammatory activity. Whereas 4, 5d, 5e, 5g, 5h, 7a, 7c,
7d, 7f and 7h are potent analgesic compounds. Thus the anti-
inflammatory and analgesic study revealed that, the compounds
having strong electron withdrawing groups (NO2, Cl) in their
structures are potent anti-inflammatory and analgesic agents.
The anti-oxidant study results revealed that the compounds 5e,
5g, 5h, 7h and 7f are very good antioxidants. The significant activity
of these compounds may be attributed to the presence of strong
electron withdrawing group (NO2) or para substituted phenyl
groups. The remaining compounds 4, 5d, 7a, 7c and 7d showed
moderate activity when compared to the positive control ascorbic
acid. These compounds contain chloro/methoxy functional groups
in their structure.
The majority of synthesized compounds showed moderate
antibacterial activity compared to a standard drug ampicillin. On
the view of structure activity relationship, it is observed that the
construction of thiadiazole ring fused to triazole moiety widen the
activity of the compound compared to 4-amino-5-(2-bromo-5-
methoxyphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione 4 alone.
There is no considerable increase in the anti-fungal activity is
observed by the formation of thiadiazole ring fused to triazole
moiety compared to 4-amino-5-(2-bromo-5-methoxyphenyl)-2,4-
dihydro-3H-1,2,4-triazole-3-thione 4 alone.
DPPH radical scavenging assay for some selective derivatives.
Compounds
Concentration (ug/mL)
200
400
800
% inhibition
% inhibition
% inhibition
4
5d
5e
5g
5h
7a
7c
7d
52.67
49.75
60.32
62.91
58.55
47.96
42.30
35.85
53.24
40.56
87.57
56.84
54.29
67.98
68.14
68.40
51.81
48.06
44.72
72.42
65.87
94.97
67.45
66.82
75.92
71.86
78.01
62.73
63.39
62.55
82.65
77.92
96
7h
7f
Ascorbic acid
3.6. Antifungal activity
The anti-fungal screening data also revealed that all the newly
synthesized compounds were moderate anti-fungal agents. The
compounds 4, 5g and 7c showed moderate activity against all the
four fungal strains. The compound 5d showed moderate activity
against three fungal strains namely, P. marneffei, T. mentagrophytes
and A. fumigatus. The compounds 7b and 7f are active against P.
marneffei and A. fumigatus fungal strains. The compounds 5f, 5h, 5i
and 7g showed moderate activity towards T. mentagrophytes,
Aspergillus flavus and A. fumigatus fungal strains. The compound
7h moderately active against three fungal strains, P. marneffei,
Aspergillus flavus and A. fumigatus. The compounds 7a and 7j
showed moderate activity against Aspergillus flavus and A. fumi-
gatus fungal strains compared to a standard drug itraconozole. The
compound 5a showed moderate anti-fungal activity against T.
mentagrophytes and A. fumigatus. Similarly the compounds 5c, 5b
and 7i showed moderate activity against P. marneffei, T. menta-
grophytes and Aspergillus flavus respectively. The anti-fungal study
revealed that, the activities of triaolothiadiazoles are not enhanced
by the formation of thiadiazole ring fused to triazole moiety.
Results of anti-fungal studies are presented in Table 7.
5. Experimental section
5.1. Materials and methods
All solvents used were of analytical grade and the reagents were
used was purchased. DPPH was procured from SigmaeAldrich. All
melting points were determined by open capillary method and are
uncorrected. IR spectra were obtained in KBr disc on a Shimadzu
FT-IR 157 spectrometer. 1H NMR and 13C NMR spectra were recor-
ded either on a PerkineElmer EM-390 or on a Bruker WH-200
(400 MHz or 300 MHz) in CDCl3 or DMSO-d6 as a solvent, using
TMS as an internal standard and chemical shifts are expressed as
ppm. Mass spectra were determined on a Jeol SX 102/Da-600 mass
spectrometer/Data System using Argon/Xenon (6kv, 10 mA) as the
FAB gas. The accelerating voltage was 10 kV and spectra were
recorded at room temperature. The LCMS were recorded in
MDSSCIEX, API 4000 spectrometer. The elemental analyses (CHN)
were performed on CHNS-O-analyser Flash EA 1112 series. The
progress of the reaction was monitored by TLC on pre-coated silica
gel G plates.
4. Conclusion
Several 3-(2-bromo-5-methoxyphenyl)-6-(substituted)[1,2,4]-
triazolo [3,4-b][1,3,4]thiadiazole (5aej) and 3-(2-bromo-5-
All the spectral data’s of newly synthesized compounds are
consistent with proposed structure and microanalysis within ꢂ0.3
of the calculated values.
5.2. Conventional synthesis of 2-bromo-5-methoxy-benzoic acid
hydrazide (2)
A mixture of 2-bromo-5-methoxy-benzoic acid methyl ester (1)
(0.01 mol) in ethanol (10 mL) and hydrazine hydrate (0.01 mol) was
refluxed for 4 h. The completion of reaction was monitored by TLC.
After reaction completion the excess solvent was removed by
distillation. The reaction mass was then cooled to 5 ꢁC, the solid
separated was filtered, dried and recrystallized from ethanol.
Fig. 1. DPPH radical scavenging assay for some selective compounds. a) Concentrations
are given in mg/mL Blue-200 mg/mL Red-400 mg/mL Green-800 mg/mL b) Compound
numbers are shown in X-axis c) Radical scavenging activity was expressed as the
percentage of inhibition on Y-axis d) Ascorbic acid was used as a positive control. (For
interpretation of the references to color in this figure legend, the reader is referred to
the web version of this article.)
IR (KBr)
2845 (-OCH3), 1640.65 (>C]O stretch), 764 (>CeBr). 1H NMR:
(400 MHz, DMSO-d6): 3.77 (ss, 3H, eOCH3), 4.45 (ss, 2H, eNH2),
g
/cmꢀ1: 3352.4 (-NH2 Stretch), 3230.3 (>NH Stretch),
d

130
N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
Table 6
Antibacterial activity of the newly synthesized compounds 4, 5aej and 7aej.
Compounds
MIC (in mM) and zone of inhibition (mm) in parentheses
Staphylococcus
Escherichia
Pseudomonas
Klebsiella pneumoniae
aureus (ATTC-25923)
coli (ATTC-25922)
aeruginosa (ATTC-27853)
(recultured)
4
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
7a
7b
7c
7d
7e
41.50 (11e15)
14.97 (16e20)
15.75 (16e20)
32.27 (11e15)
27.40 (11e15)
31.07 (11e15)
30.09 (11e15)
28.92 (11e15)
13.09 (16e20)
29.95 (11e15)
19.56 (11e15)
14.75 (16e20)
32.11 (11e15)
29.50 (11e15)
29.50 (11e15)
27.81 (11e15)
29.81 (11e15)
29.81 (11e15)
28.78 (11e15)
26.86 (11e15)
30.99 (11e15)
4.46 (22e30)
20.75 (16e20)
14.97 (16e20)
15.75 (16e20)
32.27 (11e15)
13.70 (16e20)
31.07 (11e15)
15.05 (16e20)
28.92 (11e15)
13.09 (16e20)
14.97 (16e20)
19.56 (11e15)
29.50 (11e15)
16.05 (16e20)
14.75 (16e20)
29.50 (11e15)
13.90 (16e20)
29.81 (11e15)
14.90 (16e20)
28.78 (11e15)
26.86 (11e15)
15.49 (16e20)
17.88 (30e40)
41.50 (11e15)
14.97 (16e20)
31.15 (11e15)
32.27 (11e15)
13.70 (16e20)
15.53 (16e20)
15.05 (16e20)
28.92 (11e15)
26.19 (11e15)
14.97 (16e20)
19.56 (11e15)
29.50 (11e15)
32.11 (11e15)
14.75(16e20)
29.50 (11e15)
13.90 (16e20)
29.81 (11e15)
29.81 (11e15)
14.39 (16e20)
26.86 (11e15)
15.49 (16e20)
17.88 (25e33)
20.75 (16e20)
14.97 (16e20)
15.75 (16e20)
32.27 (11e15)
13.70 (16e20)
31.07 (11e15)
15.05 (16e20)
28.92 (11e15)
13.09 (16e20)
14.97 (16e20)
19.56 (11e15)
29.50 (11e15)
32.11 (11e15)
14.75 (16e20)
29.50 (11e15)
13.90 (16e20)
29.81 (11e15)
29.81 (11e15)
14.39 (16e20)
13.43 (16e20)
15.49 (16e20)
17.88 (23e27)
7f
7g
7h
7i
7j
Standard (Ampicillin)
6.89e6.92 (m, 1H, ArH), 6.94e6.95 (d, 1H, J ¼ 3.09 Hz, ArH),
7.49e7.52 (d, 1H, J ¼ 8.67 Hz, ArH), 9.52 (ss, 1H, NH); 13C NMR:
disulphide (0.013 mol) was added and the mixture was stirred at
ambient temperature for 10 h. The mixture was diluted with ether
(10 mL) and stirred for further 1 h. The potassium salt (3) separated
was filtered and washed with ether (5 mL). The potassium salt (3)
was used for the next stage without further purification. Hydrazine
hydrate (99%) (0.02 mol) was gradually added to the above potas-
sium salt (0.01 mol) dissolved in water (12 mL) with stirring and the
mixture was refluxed gently for 3 h during which hydrogen
sulphide evolved and the colour of the reaction mixture changed to
dark green colour. It was then cooled to 5 ꢁC and acidified with
Conc. HCl to pH 1.00. A yellow solid separated out was filtered,
washed with water and crystallized from ethanol to obtain pure
triazole (4).
(100 MHz, DMSO-d6): d 55.04 (OCH3 carbon), 113.73, 119.42, 121.91,
129.13, 131.39, 159.45, 166.32, 13C NMR-DEPT: (100 MHz, DMSO-
d6):
d
55.01(OCH3 carbon), 113.69, 119.39, 121.87; MS: m/z ¼ 246
(Mþ1); Anal. calcd. for C8H9BrN2O2: C, 39.28; H, 3.77; N, 11.48;
Found: C, 39.20; H, 3.70; N, 11.43%.
5.3. Conventional synthesis of 4-amino-5-(2-bromo-5-
methoxyphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (4)
The acid hydrazide (2) (0.01 mol) was added to absolute alcohol
(15 mL) containing KOH (1.6 g) at ambient temperature. Carbon
Table 7
Antifungal activity of the newly synthesized compounds 4, 5aej and 7aej.
Compounds
MIC (in mM) and zone of inhibition (mm) in parentheses
Penicillium marneffei
Trichophyton mentagrophytes
Aspergillus flavus
Aspergillus fumigatus
(recultured)
(recultured)
(NCIM No.524)
(NCIM No.902)
4
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
7a
7b
7c
7d
7e
20.75 (16e20)
29.95 (11e15)
31.15 (11e15)
16.13 (16e20)
13.70 (16e20)
31.07 (11e15)
30.09 (11e15)
14.46 (16e20)
26.19 (11e15)
29.95 (11e15)
19.56 (11e15)
29.50 (11e15)
6.25 (16e20)
16.05 (11e15)
29.50 (11e15)
13.90 (16e20)
14.90 (16e20)
29.87 (11e15)
14.39 (16e20)
26.86 (11e15)
30.99 (11e15)
2.21 (22e30)
20.75 (16e20)
14.97 (16e20)
15.75 (16e20)
32.27 (11e15)
13.70 (16e20)
15.53 (16e20)
15.05 (16e20)
14.46 (16e20)
13.09 (16e20)
14.97 (16e20)
19.56 (11e15)
29.50 (11e15)
12.5 (11e15)
16.05 (16e20)
29.50 (11e15)
27.81 (11e15)
29.81 (11e15)
14.90 (16e20)
28.78 (11e15)
26.86 (11e15)
30.99 (11e15)
8.86 (30e40)
20.75 (16e20)
29.95 (11e15)
31.15 (11e15)
32.27 (11e15)
27.40 (11e15)
31.07 (11e15)
15.05 (16e20)
14.46 (16e20)
13.09 (16e20)
14.97 (16e20)
19.56 (11e15)
14.75 (16e20)
12.5 (11e15)
16.05 (16e20)
29.50 (11e15)
27.81 (11e15)
29.81(11e15)
14.90 (16e20)
14.39 (16e20)
13.43 (16e20)
15.49 (16e20)
8.86 (25e33)
20.75 (16e20)
14.97 (16e20)
31.15 (11e15)
32.27 (11e15)
13.70 (16e20)
31.07 (11e15)
15.05 (16e20)
14.46 (16e20)
13.09 (16e20)
14.97 (16e20)
19.56 (11e15)
14.75 (16e20)
6.25 (16e20)
16.05 (16e20)
29.50 (11e15)
27.81 (11e15)
14.90 (16e20)
14.90 (16e20)
14.39 (16e20)
26.86 (11e15)
15.49 (16e20)
8.86 (23e27)
7f
7g
7h
7i
7j
Standard (Itraconozole)

N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
131
IR (KBr)
g
/cmꢀ1
:
3171.36e3300.57 (NH2 stretch), 3071.36
5.4.3. 3-(2-Bromo-5-methoxyphenyl)-6-phenyl[1,2,4]triazolo[3,4-
b][1,3,4]thiadiazole (5c)
IR (KBr)
/cmꢀ1: 3096.83 (Ar CeH str), 2931.27 and 290.05
(aromatic CH stretching), 2939.95 (methyl CH stretch), 1611.23 (C]
N stretching), 1567.84, 1549.52 and 1428.03 (C]C ring stretching),
1472.38 (tautomeric C]S), 1337.39 (CeN stretching), 1223.61
g
(methyl CeH str), 1592.91 (C]N str), 1471.42 (C]C str), 862.98
(NeN ¼ C), 722.21(>CeBr); 1H NMR: (400 MHz, DMSO-d6):
d 3.76
(AreH bend) and 760.78 (CeBr); 1H NMR: (400 MHz, DMSO-d6):
(ss, 3H, eOCH3), 5.46 (ss, 2H, eNH2), 7.0580e7.1788 (m, 1H, ArH),
7.34e7.35 (d, 1H, J ¼ 2.96 Hz, ArH), 7.62e7.72 (dd, 1H, J ¼ 8.88 and
8.84 Hz, ArH), 13.95 (ss, 1H, SH); 13C NMR: (100 MHz, DMSO-d6):
d 3.78 (ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl), 7.48e7.60 and
7.02e7.423 (m, 5H, ArH), 7.423e7.429 (d, 1H, J ¼ 2.4 Hz, 2-Br-5-
OCH3 phenyl), 7.43e7.45 (d, 1H, J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl),
7.63e7.65 (d, 1H, J ¼ 7.6 Hz, 2-Br-5-OCH3 phenyl); MS: m/z ¼ 388
(Mþ1); Anal. calcd. for C16H11BrN4OS: C, 49.62; H, 2.86; N, 14.47;
Found: C, 49.59; H, 2.88; N, 14.50%.
d
56.31 (OCH3 carbon), 116.79, 118.74, 120.20, 128.43, 133.98,
150.23, 159.03, 166.96; 13C NMR-DEPT: (100 MHz, DMSO-d6):
d
56.32 (OCH3 carbon), 116.81, 118.74, 120.20; MS: m/z ¼ 303.1
(Mþ2); Anal. calcd. for C8H9BrN2O2: C, 35.89; H, 3.01; N, 18.60;
Found: C, 35.94; H, 3.06; N, 18.54%.
5.4.4. 3-(2-Bromo-5-methoxyphenyl)-6-(3,5-dichlorophenyl)[1,2,4]
triazolo[3,4-b][1,3,4] thiadiazole (5d)
IR (KBr)
str), 1597.32 (C]N str), 1472.79 (C]C str), 860.21 (AreH bend)
and 774.49 (CeBr); 1H NMR: (400 MHz, DMSO-d6):
3.86 (ss, 3H,
eOCH3 of 2-Br-5-OCH3 phenyl), 6.95e6.98 (dd, 1H, J ¼ 8.8 Hz and
2.9 Hz, 2-Br-5-OCH3 phenyl), 6.99e7.02 (m, 1H, 2-Br-5-OCH3
phenyl), 7.25 (s, 1H, 3,5-dichlorophenyl), 7.30 (s, 1H, 3,5-
g
/cmꢀ1: 3086.42 (Ar CeH str), 2838.24 (methyl CeH
5.4. General procedure for the conventional synthesis of 3-(2-
bromo-5-methoxyphenyl)-6-(substituted)[1,2,4]triazolo[3,4-b]
[1,3,4] thiadiazole (5aej)
d
An equimolar mixture of compound (4) (0.0035 mol) and
appropriate mono or disubstituted aromatic carboxylic acids
(0.0035 mol) in phosphorus oxychloride (15 mL) was refluxed for
5 h. The reaction mixture was cooled to room temperature and
poured onto crushed ice (50 g) with stirring. Finally, to remove the
excess of phosphorus oxychloride powdered potassium carbonate
and the required amount of potassium hydroxide were added till
the pH of the mixture was raised to 8. The solid was collected by
vacuum filtration, dried and recrystallized from appropriate
solvent.
dichlorophenyl), 7.60e7.62 (d, 1H,
phenyl), 7.74 (s, 1H, 3,5-dichlorophenyl); 13C NMR: (100 MHz,
DMSO-d6): 55.64 (-OCH3 of 2-Br-5-OCH3 phenyl), 112.98, 117.18,
117.94, 121.54, 122.53, 128.70, 130.42, 136.15, 141.57, 147.64, 159.92,
167.12; 13C NMR-DEPT: (100 MHz, DMSO-d6):
55.64 (-OCH3 of 2-
Br-5-OCH3 phenyl), 117.18, 117.94, 122.53, 128.70, 130.42, 136.15;
MS: m/z
J
¼
8.8 Hz, 2-Br-5-OCH3
d
d
¼
457.1 (Mþ1), 458.1 (Mþ2); Anal. calcd. for
C16H9BrCl2N4OS: C, 42.17; H, 2.03; N,12.30; Found: C, 42.13; H, 1.99;
N, 12.28%.
5.4.1. 3-(2-Bromo-5-methoxyphenyl)-6-(4-methoxyphenyl)[1,2,4]
5.4.5. 4-[3-(2-Bromo-5-methoxyphenyl)[1,2,4]triazolo[3,4-b][1,3,4]
triazolo[3,4-b][1,3,4] thiadiazole (5a)
g
/cmꢀ1: 3090.68 (Ar CeH str), 2943.83 and 2840.63
thiadiazol-6-yl]aniline (5e)
IR (KBr)
IR (KBr) g
/cmꢀ1:3286.00 (NH stretching), 3090.21 (Ar CeH str),
(methyl CeH str), 1605.45 (C]N str), 1475.28 (C]C str),
851.41(AreH bend) and 769.4 (CeBr); 1H NMR: (400 MHz, DMSO-
2942.90 (methyl CeH str), 1575.12 (C]N str), 1456.58 (C]C str),
859.41 (Ar CeH bend) and 781.78 (CeBr); 1H NMR: (400 MHz,
d6):
d 3.84 (ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl), 3.88 (ss, 3H,
DMSO-d6):
d 3.76 (ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl), 6.61 (bs,
eOCH3 of p-OCH3 phenyl), 7.26e7.28 (d, 1H, J ¼ 10.42 Hz, 2-Br-5-
OCH3 phenyl), 6.97e7.00 (m, 3H, ArH), 7.62e7.64 (d, 1H,
J ¼ 8.78 Hz, 2-Br-5-OCH3 phenyl), 7.80e7.83 (d, 2H, J ¼ 8.26, p-OCH3
2H, NH2 of p-amino phenyl), 6.92e6.94 (dd, 1H, J ¼ 8.8 Hz and
2.9 Hz, 2-Br-5-OCH3 phenyl), 7.13e7.25 (m, 4H, p-amino phenyl),
7.26 (d, 1H, J ¼ 2.49 Hz, 2-Br-5eOCH3ephenyl), 7.55e7.58 (d, 1H,
J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl); MS: m/z ¼ 403.27 (Mþ1), 404.29
(Mþ2); Anal. calcd. for C16H12BrN5OS: C, 47.75; H, 3.05; N, 17.44;
Found: C, 47.77; H, 3.01; N, 17.41%.
phenyl); 13C NMR: (100 MHz, DMSO-d6):
d 55.63 (-OCH3 of 2-Br-5-
OCH3 phenyl), 55.75 (OCH3 carbon of p-OCH3 phenyl), 113.48,
114.83, 117.27, 118.57, 121.81, 126.53, 127.83, 129.01, 134.37, 158.79,
163.22, 166.36, 167.01; 13C NMR-DEPT: (100 MHz, DMSO-d6):
d
55.63 (-OCH3 of 2-Br-5-OCH3 phenyl), 55.75 (OCH3 carbon of p-
5.4.6. 3-(2-Bromo-5-methoxyphenyl)-6-(3,5-dimethylphenyl)
OCH3 phenyl), 114.83, 117.27, 118.57, 129.01, 134.37; MS: m/z ¼ 418
(Mþ1); Anal. calcd. for C17H13BrN4O2S: C, 48.93; H, 3.14; N, 13.43;
Found: C, 48.96; H, 3.13; N, 13.46%.
[1,2,4]triazolo[3,4-b][1,3,4] thiadiazole (5f)
IR (KBr) g
/cmꢀ1: 3090.01 (Ar CeH str), 2940.89 and 2845.23
(methyl CeH str), 1594.03 (C]N str), 1482.08 (C]C str), 863.81
(AreH bend) and 780.35 (CeBr); 1H NMR: (400 MHz, DMSO-d6):
5.4.2. 3-(2-Bromo-5-methoxyphenyl)-6-(4-methylphenyl)[1,2,4]
triazolo[3,4-b][1,3,4] thiadiazole (5b)
d
2.45 (ss, 3H, eCH3 of 3,5-(CH3)2 phenyl), 2.50 (ss, 3H, eCH3 of
g
/cmꢀ1: 3081.65 (Ar CeH str), 2936.09 and 2840.63
3,5-(CH3)2 phenyl), 3.78 (ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl),
6.93e6.96 (dd, 1H, J ¼ 8.8 Hz and 2.9 Hz, 2-Br-5-OCH3 phenyl),
7.14 (s, 1H, 3,5-(CH3)2 phenyl), 7.24 (s, 1H, 3,5-(CH3)2 phenyl),
7.56e7.58 (d, 1H, J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl), 7.27 (d, 1H,
J ¼ 2.5 Hz, 2-Br-5eOCH3ephenyl), 7.70 (s, 1H, 3,5-(CH3)2 phenyl);
IR (KBr)
(methyl CeH str), 1595.81 (C]N str), 1474.31 (C]C str), 862.98
(AreH bend) and 775.24 (CeBr); 1H NMR: (400 MHz, DMSO-d6):
d
2.43 (ss, 3H, eCH3 of p-CH3 phenyl), 3.84 (ss, 3H, eOCH3 of 2-
Br-5-OCH3 phenyl), 6.97e7.00 (dd, 1H, J ¼ 8.8 Hz and 2.9 Hz, 2-
Br-5-OCH3 phenyl), 7.26e7.32 (m, 3H, ArH), 7.62e7.64 (d, 1H,
J ¼ 8.87 Hz, 2-Br-5-OCH3 phenyl), 7.76e7.78 (d, 2H, J ¼ 8.01, p-CH3
13C NMR: (100 MHz, DMSO-d6):
d 21.78 (CH3 carbon of3,5-(CH3)2
phenyl), 21.81 (CH3 carbon of3,5-(CH3)2 phenyl), 55.66 (-OCH3 of
2-Br-5-OCH3 phenyl), 112.98, 117.18, 117.94, 121.54, 122.53, 128.70,
130.42, 136.15, 141.57, 147.64, 159.92, 167.12; 13C NMR-DEPT:
phenyl); 13C NMR: (100 MHz, DMSO-d6):
d 21.72 (CH3 carbon of p-
CH3 phenyl), 55.78 (-OCH3 of 2-Br-5-OCH3 phenyl), 113.47, 117.28,
118.71, 126.53, 127.23, 127.57, 130.16, 134.41, 143.82, 146.46, 158.79,
(100 MHz, DMSO-d6):
d 21.78 (CH3 carbon of 3,5-(CH3)2
167.01; 13C NMR-DEPT: (100 MHz, DMSO-d6):
d 21.72 (-CH3 carbon
phenyl), 21.81 (CH3 carbon of3,5-(CH3)2 phenyl), 55.66 (-OCH3 of
2-Br-5-OCH3 phenyl), 117.34, 118.54, 127.98, 130.36, 134.25; MS:
of p-CH3 phenyl), 55.78 (-OCH3 of 2-Br-5-OCH3 phenyl), 117.28,
118.71, 127.24, 130.16, 134.41; MS: m/z ¼ 402 (Mþ1); Anal. calcd. for
C17H13BrN4OS: C, 50.88; H, 3.27; N, 13.96; Found: C, 50.84; H, 3.30;
N, 13.99%.
m/z
¼
416.31 (Mþ1), 417.30 (Mþ2); Anal. calcd. for
C18H15BrN4OS: C, 52.09; H, 3.68; N, 13.52; Found: C, 52.06; H,
3.64; N, 13.49%.

132
N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
5.4.7. 3-(2-Bromo-5-methoxyphenyl)-6-(4-nitrophenyl)[1,2,4]
5.5.1. 5-(2-Bromo-5-methoxyphenyl)-4-{[(2-chlorophenyl)
triazolo[3,4-b][1,3,4] thiadiazole (5g)
methylene]amino}-4H-1,2,4-triazole-3-thiol (6a)
IR (KBr)
g
/cmꢀ1: 3092.01 (Ar CeH str), 2938.98 (methyl CeH
IR (KBr) g
/cmꢀ1: 3307.32 (NH tautomeric with SH), 3065.3 (Ar
str), 1576.42 (C]N str), 1455.80 (C]C str), 860.65 (Ar CeH
CeH str), 2960.2 and 2830.03 (methyl CeH str), 1591.95 (C]N
str), 1475.28 (C]C str), 860.09 (AreH bend) and 752.10 (CeBr);
bend) and 778.48 (CeBr); 1H NMR: (400 MHz, DMSO-d6):
d
3.78 (ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl), 6.91e6.93 (dd,
1H, J ¼ 8.79 Hz and 2.88 Hz, 2-Br-5-OCH3 phenyl), 7.12e7.23 (m,
4H, p-nitro phenyl), 7.24 (d, 1H, 2.5 Hz, 2-Br-
5eOCH3ephenyl), 7.53e7.56 (d, 1H, J ¼ 8.8 Hz, 2-Br-5-OCH3
phenyl); MS: m/z
1H NMR: (400 MHz, DMSO-d6):
d 3.74 (ss, 3H, eOCH3 of 2-Br-
5-OCH3 phenyl), 7.07e7.10 (dd, 1H, J ¼ 8.8 Hz and 2.6 Hz, 2-Br-5-
OCH3 phenyl), 7.271e7.277 (d, 1H, J ¼ 2.49 Hz, 2-Br-5-OCH3
phenyl), 7.37e7.40 (t, 1H, J ¼ 6.9, 2-Cl-phenyl), 7.63e7.66 (d, 1H,
J ¼ 8.84 Hz, 2-Br-5eOCH3ephenyl), 7.52e7.58 (m, 2H, 2-Cl-
phenyl), 7.71e7.73 (d, 1H, J ¼ 7.59, 2-Cl-phenyl), 10.59 (ss, 1H,
CH]N), 14.43 (bs, NH/tautomeric with SH); 13C NMR: (100 MHz,
J
¼
¼
433.25 (M þ1); Anal. calcd. for
C16H10BrN5O3S: C, 44.48; H, 2.36; N, 16.22; Found: C, 44.46; H,
2.33; N, 16.20%.
DMSO-d6):
d 56.20 (-OCH3 of 2-Br-5-OCH3 phenyl), 113.43,
5.4.8. 3-(2-Bromo-5-methoxyphenyl)-6-(3,5-dinitrophenyl)[1,2,4]
118.83, 119.18, 126.49, 127.28, 127.75, 128.43, 130.71, 134.06,
triazolo[3,4-b][1,3,4] thiadiazole (5h)
134.56, 143.92, 146.76, 158.71(CH]N), 158.76, 167.08; 13C NMR-
IR (KBr)
str), 1580.23 (C]N str), 1455.78 (C]C str), 861.58 (Ar CeH bend)
and 779.78 (CeBr); 1H NMR: (400 MHz, DMSO-d6):
3.78 (ss, 3H,
g
/cmꢀ1: 3088.91 (Ar CeH str), 2945.42 (methyl CeH
DEPT: (100 MHz, DMSO-d6):
phenyl), 118.83, 119.18, 127.75, 128.43, 130.77, 134.06, 134.56,
158.71 (CH]N); MS: m/z
d 56.3 (-OCH3 of 2-Br-5-OCH3
d
¼ 424 (Mþ1); Anal. calcd. for
eOCH3 of 2-Br-5-OCH3 phenyl), 6.93 (dd, 1H, J ¼ 8.8 Hz and 2.9 Hz,
2-Br-5-OCH3 phenyl), 7.11e7.24 (m, 4H, 3,5-(NO2)2 phenyl), 7.25 (d,
1H, J ¼ 2.48 Hz, 2-Br-5eOCH3ephenyl), 7.54e7.56 (d, 1H, J ¼ 8.8 Hz,
2-Br-5-OCH3 phenyl); MS: m/z ¼ 478.3 (Mþ1); Anal. calcd. for
C16H9BrN6O5S: C, 40.30; H, 2.01; N, 17.63; Found: C, 40.27; H, 1.90;
N, 17.61%.
C16H12BrClN4OS: C, 45.35; H, 2.85; N, 13.22; Found: C, 45.38; H,
2.83; N, 13.25%.
5.5.2. 5-(2-Bromo-5-methoxyphenyl)-4-{[(phenyl)methylene]
amino}-4H-1,2,4-triazole-3-thiol (6b)
IR (KBr) g
/cmꢀ1: 3310.42 (NH tautomeric with SH), 3090.46(Ar
CeH str), 2958.4 and 2835.63 (methyl CeH str), 1586.45 (C]N str),
5.4.9. 2-[3-(2-Bromo-5-methoxyphenyl)[1,2,4]triazolo[3,4-b][1,3,4]
1465.99 (C]C str), 859.93 (AreH bend) and 765.03 (CeBr); 1H
thiadiazol-6-yl]-5-methylphenol (5i)
NMR: (400 MHz, DMSO-d6): d 3.78 (ss, 3H, eOCH3 of 2-Br-5-OCH3
IR (KBr)
g
/cmꢀ1: 3454.23 (OH stretching), 3046.45 (aromatic
phenyl), 7.03e7.06 (dd, 1H, J ¼ 8.8 Hz and 2.44 Hz, 2-Br-5-OCH3
phenyl), 7.19e7.20 (d, 1H, J ¼ 2.46 Hz, 2-Br-5eOCH3ephenyl),
7.63e7.65 (d, 1H, J ¼ 8.79 Hz, 2-Br-5eOCH3ephenyl), 7.66e7.68 and
7.5e7.6 (m, 5H, phenyl ring), 9.43 (ss, 1H, CH]N), 13.73 (bs, NH/
CH stretching), 1615.02 (C]N stretching), 1573.12, 1485.36,
1457.75 (C]C ring stretch), 2972.54, 2921.75 (methyl CH stretch),
1240.34 (CeO stretching), 1278.47 (NeN ¼ C); 1H NMR: (400 MHz,
DMSO-d6):
d
2.64 (s, 3H, CH3 of 2eOHe4eCH3ephenyl), 3.78
tautomeric with SH); 13C NMR: (100 MHz, DMSO-d6):
d 56.22
(ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl), 6.3 (s, 1H, OH of
2eOHe4eCH3ephenyl), 6.88e6.90 (dd, 1H, J ¼ 8.8 Hz and 2.9 Hz,
2-Br-5-OCH3 phenyl), 7.01e7.20 (m, 4H, 2eOHe4eCH3ephenyl),
7.30 (d, 1H, J ¼ 2.49 Hz, 2-Br-5eOCH3ephenyl), 7.53e7.55 (d, 1H,
J ¼ 8.8 Hz2-Br-5-OCH3 phenyl); MS: m/z ¼ 418.3 (Mþ1), 419.29
(Mþ2); Anal. calcd. for C17H13BrN4O2S: C, 48.96; H, 3.17; N, 13.47;
Found: C, 48.93; H, 3.14; N, 13.43%.
(-OCH3 of 2-Br-5-OCH3 phenyl), 112.10, 117.32, 118.91, 126.54,
127.42, 128.25, 130.96, 134.86, 143.86, 146.72, 149.74, 158.96 (CH]
N), 166.99; 13C NMR-DEPT: (100 MHz, DMSO-d6):
d 56.22 (-OCH3 of
2-Br-5eOCH3ephenyl), 117.32, 118.91, 127.42, 128.25, 130.96,
134.86, 158.96 (CH]N); MS: m/z ¼ 390 (Mþ1); Anal. calcd. for
C16H13BrN4OS: C, 49.37; H, 3.37; N, 14.39; Found: C, 49.40; H, 3.35;
N, 14.42%.
5.4.10. 3-(2-Bromo-5-methoxyphenyl)-6-(2,4-diiodophenyl)[1,2,4]
5.5.3. 5-(2-Bromo-5-methoxyphenyl)-4-{[(4-chlorophenyl)
triazolo[3,4-b][1,3,4] thiadiazole (5j)
methylene]amino}-4H-1,2,4-triazole-3-thiol (6c)
IR (KBr)
g
/cmꢀ1: 3050.89 (aromatic CH stretching), 1620.78
IR (KBr) g
/cmꢀ1: 3306.92 (NH tautomeric with SH), 3092.64 (Ar
(C]N stretching), 1574.56, 1482.56, 1453.43 (C]C ring stretch),
CeH str), 2958.42 and 2848.85 (methyl CeH str), 1586.55 (C]N
2980.43, 2925.76 (methyl CH stretch), 1269.21 (NeN ¼ C); 1H
str), 1480.73 (C]C str), 875.65 (AreH bend) and 757.98 (CeBr); 1H
NMR: (400 MHz, DMSO-d6):
d
3.78 (ss, 3H, eOCH3 of 2-Br-5-
NMR: (400 MHz, DMSO-d6): d 3.75 (ss, 3H, eOCH3 of 2-Br-5-OCH3
OCH3 phenyl), 6.90e6.92 (dd, 1H, J ¼ 8.8 Hz and 2.9 Hz, 2-Br-5-
OCH3 phenyl), 7.08e7.14 (m, 3H, 2,4-(I)2 phenyl), 7.24 (d, 1H,
J ¼ 2.5 Hz, 2-Br-5eOCH3ephenyl), 7.53e7.55 (d, 1H, J ¼ 8.78 Hz,
2-Br-5-OCH3 phenyl); MS: m/z ¼ 640.04 (Mþ1); Anal. calcd. for
C16H9BrI2N4OS: C, 30.10; H, 1.44; N, 8.80; Found: C, 30.07; H, 1.42;
N, 8.77%.
phenyl), 7.08e7.10 (d, 1H, J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl),
7.24e7.25 (d, 1H,J ¼ 2.8 Hz, 2-Br-5eOCH3ephenyl), 7.54e7.56
(m, 2H, 4-Cl-phenyl), 7.62e7.64 (d, 1H,J
¼
8.8 Hz, 2-Br-
5eOCH3ephenyl), 7.71e7.73 (d, 2H, J ¼ 8.0, 4-Cl-phenyl), 9.91 (ss,
1H, CH]N), 13.90 (bs, NH/tautomeric with SH); LC MS: m/z ¼ 424
(Mþ1); Anal. calcd. for C16H12BrClN4OS: C, 45.35; H, 2.85; N, 13.22;
Found: C, 45.32; H, 2.84; N, 13.24%.
5.5. General procedure for the conventional synthesis of 5-(2-
bromo-5-methoxyphenyl)-4-{[(substituted)methylene]amino}-4H-
1,2,4-triazole-3-thiol (6aeh) and (10)
5.5.4. 5-(2-Bromo-5-methoxyphenyl)-4-{[(3-chlorophenyl)
methylene] amino}-4H-1,2,4-triazole-3-thiol (6d)
IR (KBr) g
/cmꢀ1: 3310.28 (NH tautomeric with SH), 3064.25 (Ar
Equimolar mixture of compound (4) (0.003 mol) and
substituted aromatic aldehydes/(9) (0.003 mol) in ethanol (15 mL)
along with few drops Conc. H2SO4 (0.1 mL) was refluxed for 4 h. The
completion of reaction was monitored by TLC. After reaction
completion, the reaction mass was cooled to 30 ꢁC. The solid
separated was filtered off, washed with ethanol (8 mL) and dried.
Recrystallization was done using appropriate solvent to obtain
(6aeh) and (10).
CeH str), 2956.22 and 2828.32 (methyl CeH str), 1588.89 (C]N
str), 1480.82 (C]C str), 861.29 (AreH bend) and 751.20 (CeBr); 1H
NMR: (400 MHz, DMSO-d6):
d 3.73 (ss, 3H, eOCH3 of 2-Br-5-OCH3
phenyl), 7.04e7.08 (dd, 1H, J ¼ 8.8 Hz and 2.6 Hz, 2-Br-5-OCH3
phenyl), 7.27e7.28 (d, 1H, J ¼ 2.49 Hz, 2-Br-5eOCH3ephenyl),
7.32e7.37 (t, 1H, J ¼ 6.9, 3-Cl-phenyl), 7.59e7.61 (d, 1H, J ¼ 8.84 Hz,
2-Br-5eOCH3ephenyl), 7.50e7.54 (m, 2H, 3-Cl-phenyl), 7.68e7.72
(d, 1H, J ¼ 7.59, 3-Cl-phenyl), 10.55 (ss, 1H, CH]N), 14.42 (bs, NH/

N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
133
tautomeric with SH); MS: m/z ¼ 424 (Mþ1); Anal. calcd. for
C16H12BrClN4OS: C, 45.35; H, 2.85; N, 13.22; Found: C, 45.37; H,
2.85; N, 13.21%.
1480.34 (C]C str), 858.38 (AreH bend) and 762.49 (CeBr); 1H
NMR: (400 MHz, DMSO-d6): 3.78 (ss, 3H, eOCH3 of 2-Br-5-OCH3
d
phenyl), 7.04e7.08 (dd, 1H, J ¼ 8.8 Hz and 2.44 Hz, 2-Br-5-OCH3
phenyl), 7.12e7.21 (d, 1H, J ¼ 2.46 Hz, 2-Br-5eOCH3ephenyl),
7.60e7.63 (d, 1H, J ¼ 8.79 Hz, 2-Br-5eOCH3ephenyl), 7.64e7.69 and
7.70e7.74 (m, 9H, biphenyl ring), 9.82 (ss, 1H, CH]N), 13.96 (bs,
NH/tautomeric with SH); MS: m/z ¼ 466 (Mþ1); Anal. calcd. for
C22H17BrN4OS: C, 56.78; H, 3.68; N, 12.04; Found: C, 56.75; H, 3.70;
N, 12.01%.
5.5.5. 5-(2-Bromo-5-methoxyphenyl)-4-{[(2,4-dimethoxyphenyl)
methylene]amino}-4H-1,2,4-triazole-3-thiol (6e)
IR (KBr)
g
/cmꢀ1: 3314.58 (NH tautomeric with SH), 3068.82
(Ar CeH str), 2960.4 and 2830.20 (methyl CeH str), 1584.35 (C]N
str), 1478.79 (C]C str), 868.42 (AreH bend) and 754.94 (CeBr);
1H NMR: (400 MHz, DMSO-d6):
d 3.82 (s, 3H, eOCH3 of 2,4-
(OCH3)2 phenyl), 3.84 (ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl),
3.85 (s, 3H, eOCH3 of 2,4-(OCH3)2 phenyl), 7.10e7.12 (d, 1H,
J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl), 7.25e7.27 (d, 1H, J ¼ 2.49 Hz, 2-
Br-5eOCH3ephenyl), 7.31 (s, 1H, 2,4-(OCH3)2 phenyl), 7.60e7.61
(d, 1H, J ¼ 8.84 Hz, 2-Br-5eOCH3ephenyl), 7.62e7.69 (m, 2H,
2,4-(OCH3)2 phenyl), 10.48 (ss, 1H, CH]N), 13.38 (bs, NH/tauto-
5.5.10. 5-(2-Bromo-5-methoxyphenyl)-4-{[(4-methylphenyl)
methylene]amino}-4H-1,2,4-triazole-3-thiol (6j)
IR (KBr) g
/cmꢀ1: 3317.24 (NH tautomeric with SH), 3070.31 (Ar
CeH str), 2961.06 and 2834.83 (methyl CeH str), 1594.14 (C]N str),
1480.32 (C]C str), 857.38 (AreH bend) and 762.48 (CeBr); 1H
NMR: (400 MHz, DMSO-d6):
d 2.25 (ss, 3H, 4-methyl phenyl), 3.78
meric with SH); MS: m/z
C18H17BrN4O3S: C, 48.12; H, 3.81; N, 12.47; Found: C, 48.14; H,
3.84; N, 12.50%.
¼
450 (Mþ1); Anal. calcd. for
(ss, 3H, eOCH3), 6.90e6.92 (d,1H, J ¼ 8.79 Hz, 2-Br-5-OCH3 phenyl),
7.14e7.19 (m, 4H, 4-methyl phenyl), 7.24 (d, 1H, J ¼ 2.5 Hz, 2-Br-
5eOCH3ephenyl), 7.52e7.56 (d, 1H, J ¼ 8.8 Hz, 2-Br-5-OCH3
phenyl), 10.42 (ss, 1H, CH]N), 14.01 (bs, NH/tautomeric with SH);
MS: m/z ¼ 404 (Mþ1); Anal. calcd. for C17H15BrN4OS: C, 50.63; H,
3.75; N, 13.89; Found: C, 50.60; H, 3.77; N, 13.90%.
5.5.6. 5-(2-Bromo-5-methoxyphenyl)-4-{[(4-methoxyphenyl)
methylene]amino}-4H-1,2,4-triazole-3-thiol (6f)
IR (KBr) g
/cmꢀ1: 3309.94 (NH tautomeric with SH), 3062.92 (Ar
CeH str), 2964.8 and 2827.43 (methyl CeH str), 1590.43 (C]N str),
5.5.11. 5-(2-Bromo-5-methoxyphenyl)-4-{[1-chloro-4-(3,4-
dichlorophenyl)-3,4-dihydronaphthalen-2-yl]amino}-4H-1,2,4-
triazole-3-thiol (10)
1474.42 (C]C str), 860.49 (AreH bend) and 758.46 (CeBr); 1H
NMR: (400 MHz, DMSO-d6):
d 3.65 (s, 3H, eOCH3 of 4-OCH3
phenyl), 3.77 (ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl), 7.09e7.12 (d,
1H, J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl), 7.22e7.24 (d,1H, J ¼ 2.49 Hz, 2-
IR (KBr) g/cm-1: 3322.28 (NH tautomeric with SH), 3078.25 (Ar
CeH str), 2958.26 and 2842.53 (methyl CeH str), 1592.44 (C]N
str), 1482.02 (C]C str), 856.28 (AreH bend), 838.883 (CeCl)and
Br-5eOCH3ephenyl), 7.61e7.62 (d, 1H,
J
¼
8.84 Hz, 2-Br-
5eOCH3ephenyl), 7.63e7.70 (m, 3H, 4-OCH3 phenyl), 10.41 (ss, 1H,
CH]N), 14.04 (bs, NH/tautomeric with SH); MS: m/z ¼ 420 (Mþ1),
421 (Mþ2); Anal. calcd. for C17H15BrN4O2S: C, 48.70; H, 3.61; N,
13.36; Found: C, 48.72; H, 3.64; N, 13.38%.
762.48 (C-Br); 1H NMR: (400 MHz, DMSO-d6):
d 3.70e3.72(d, 2H,
J ¼ 6.84 Hz, eCH2 proton of fused cyclohexene ring), 3.80 (ss, 3H,
eOCH3), 4.11 (m,1H, eCH proton of fused cyclohexene ring), 6.84 (s,
1H, CH of dichlorophenyl ring), 7.34e7.45 (m, 3H, Benzene ring),
7.18e7.19 (d, J ¼ 2.1 Hz, 1H, Dichlorophenyl ring), 6.93e7.78 (m, 1H,
Dichloro phenyl ring), 7.84 (s, 1H, Benzene ring), 8.18 (s, 1H,
Benzene ring), 8.48 (ss, 1H, ¼CH proton), 10.67 (NH/tautomeric
5.5.7. 5-(2-Bromo-5-methoxyphenyl)-4-{[(2-methoxyphenyl)
methylene]amino}-4H-1,2,4-triazole-3-thiol (6g)
IR (KBr)
g
/cmꢀ1: 3312.86 (NH tautomeric with SH), 3059.47 (Ar
with SH); 13C NMR: (100 MHz, DMSO-d6):
d 29.70 (CH2 carbon of
CeH str), 2958.84 and 2834.03 (methyl CeH str), 1592.94 (C]N
fused cyclohexene ring), 41.68 (CH carbon of fused cyclohexene
ring), 55.86 (-OCH3 of 2-Br-5-OCH3 phenyl), 113.35, 117.30, 118.97,
126.62, 126.74, 127.48, 127.82, 127.87, 128.00, 128.16, 128.24, 130.07,
130.13, 31.52, 132.76, 134.23, 142.02, 142.27, 149.52, 158.60, 158.85
(CH]N), 159.12, 159.29; MS: m/z ¼ 621 (Mþ1); Anal. calcd. for
C26H18BrCl3N4OS: C, 50.30; H, 2.92; N, 9.03; Found: C, 50.28; H,
2.94; N, 9.06%.
str), 1472.52 (C]C str), 861.50 (AreH bend) and 760.06 (CeBr); 1H
NMR: (400 MHz, DMSO-d6):
d 3.62 (s, 3H, eOCH3 of 2-OCH3
phenyl), 3.78 (ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl), 7.10e7.12 (d,
1H, J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl), 7.21e7.25 (d,1H, J ¼ 2.49 Hz, 2-
Br-5eOCH3ephenyl), 7.60e7.61 (d, 1H,
J
¼
8.84 Hz, 2-Br-
5eOCH3ephenyl), 7.62e7.69 (m, 3H, 2-OCH3 phenyl), 10.42 (ss, 1H,
CH]N), 13.99 (bs, NH/tautomeric with SH); MS: m/z ¼ 420 (Mþ1);
Anal. calcd. for C17H15BrN4O2S: C, 48.70; H, 3.61; N, 13.36; Found: C,
48.73; H, 3.59; N, 13.34%.
5.6. General procedure for the conventional synthesis of 3-(2-
bromo-5-methoxyphenyl)-6-sustituted phenyl-5,6-dihydro[1,2,4]
triazolo[3,4-b][1,3,4]thiadiazole (7aej)
5.5.8. 5-(2-Bromo-5-methoxyphenyl)-4-{[(4-nitrophenyl)
methylene]amino}-4H-1,2,4-triazole-3-thiol (6h)
The compounds (6aej) (0.002 mol), a catalytic amount of p-
Toluene sulfonic acid (0.025 g) and DMF (12 mL) were taken in
a round bottom flask. The reaction mixture was refluxed for about
10e12 h. The reaction mixture was concentrated to half of its
volume and cooled to room temperature. Poured the cooled mixture
gradually into crushed ice cubes (30 g) with stirring. Allowed the
mixture to stand till solid separated. It was filtered, washed thor-
oughly with cold water, dried and recrystallized from hot ethanol.
IR (KBr) g
/cmꢀ1: 3310.76 (NH tautomeric with SH), 3065.24 (Ar
CeH str), 2960.56 and 2835.13 (methyl CeH str),1590.04 (C]N str),
1475.92 (C]C str), 859.98 (Ar-H bend) and 761.56 (CeBr); 1H NMR:
(400 MHz, DMSO-d6):
d 3.84 (ss, 3H, eOCH3 of 2-Br-5-OCH3
phenyl), 6.92e6.94 (dd, 1H, J ¼ 8.79 Hz and 2.88 Hz, 2-Br-5-OCH3
phenyl), 7.13e7.22 (m, 4H, p-nitro phenyl), 7.23 (d, 1H, J ¼ 2.5 Hz, 2-
Br-5eOCH3ephenyl), 7.54e7.58 (d, 1H, J ¼ 8.8 Hz, 2-Br-5-OCH3
phenyl), 10.44 (ss, 1H, CH]N), 14.05 (bs, NH/tautomeric with SH);
MS: m/z ¼ 435 (Mþ1), 436 (Mþ2); Anal. calcd. forC16H12BrN5O3S: C,
44.25; H, 2.79; N, 16.13; Found: C, 44.23; H, 2.76; N, 16.11%.
5.6.1. 3-(2-Bromo-5-methoxyphenyl)-6-(2-chlorophenyl)-5,6-
dihydro[1,2,4]triazolo[3,4-b ][1,3,4]thiadiazole (7a)
IR (KBr) g
/cmꢀ1: 3307.32 (NH), 3065.30, 2987.20, 2960.20 (Ar
5.5.9. 4-{[Biphenyl-4-ylmethylene]amino}-5-(2-bromo-5-
CeH str), 2937.06 and 2830.03 (methyl CeH str), 1591.95 (C]N str),
1475.28 (C]C str), 860.09 (AreH bend), 752.10 (CeBr) and 616.14
methoxyphenyl)-4H-1,2,4-triazole-3-thiol (6i)
IR (KBr)
g
/cmꢀ1: 3316.09 (NH tautomeric with SH), 3070.14 (Ar
(CeSeC); 1H NMR: (400 MHz, DMSO-d6):
d
3.74 (ss, 3H, eOCH3 of
CeH str), 2964.63 and 2840.28 (methyl CeH str),1593.14 (C]N str),
2-Br-5-OCH3 phenyl), 7.08e7.11 (dd, 1H, J ¼ 8.8 Hz and 2.6 Hz, 2-Br-

134
N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
5-OCH3 phenyl), 5.48 (s, 1H, eCHeNH), 7.27e7.28 (d, 1H,
J ¼ 2.49 Hz, 2-Br-5eOCH3ephenyl), 7.37e7.41 (t, 1H, J ¼ 6.9, 2-Cl-
phenyl), 7.64e7.66 (d, 1H, J ¼ 8.84 Hz, 2-Br-5eOCH3ephenyl),
7.52e7.58 (m, 2H, 2-Cl-phenyl), 7.72e7.74 (d, 1H, J ¼ 7.59, 2-Cl-
phenyl), 13.73 (bs, NHeCHe); 13C NMR: (100 MHz, DMSO-d6):
5.6.5. 3-(2-Bromo-5-methoxyphenyl)-6-(2,4-dimethoxyphenyl)-
5,6-dihydro[1,2,4]triazolo [3,4-b][1,3,4]thiadiazole (7e)
IR (KBr) g
/cmꢀ1: 3210.58 (NH), 3186.73 (Ar CeH str), 2961.59
and 2840.12 (methyl CeH str), 1581.46 (C]N str), 1480.92 (C]C
str), 859.54 (AreH bend), 756.66 (CeBr) and 612.62 (CeSeC); 1H
d
56.20 (-OCH3 of 2-Br-5-OCH3 phenyl), 60.24 (CHeNH), 67.08,
NMR: (400 MHz, DMSO-d6): d 3.82 (s, 3H, eOCH3 of 2,4-(OCH3)2
113.43, 118.83, 119.18, 126.49, 127.28, 127.75, 128.43, 130.71, 134.06,
phenyl), 3.84 (ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl), 3.85 (s, 3H,
eOCH3 of 2,4-(OCH3)2 phenyl), 5.48 (s, 1H, eCHeNH), 7.11e7.12 (d,
1H, J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl), 7.25e7.26 (d,1H, J ¼ 2.49 Hz, 2-
Br-5eOCH3ephenyl), 7.30 (s, 1H, 2,4-(OCH3)2 phenyl), 7.61e7.62 (d,
1H, J ¼ 8.84 Hz, 2-Br-5eOCH3ephenyl), 7.62e7.70 (m, 2H, 2,4-
(OCH3)2 phenyl), 13.42 (bs, NHeCHe); MS: m/z ¼ 450 (Mþ1); Anal.
calcd. for C18H17BrN4O3S: C, 48.12; H, 3.81; N, 12.47; Found: C,
48.12; H, 3.79; N, 12.45%.
134.56, 143.92, 146.76, 158.76; 13C NMR-DEPT: (100 MHz, DMSO-
d6):
d 56.3 (-OCH3 of 2-Br-5-OCH3 phenyl), 60.24 (CHeNH),
118.83, 119.18, 127.75, 128.43, 130.77, 134.06, 134.56; MS: m/
z ¼ 424 (Mþ1); Anal. calcd. For C16H12BrClN4OS: C, 45.35; H, 2.85;
N, 13.22; Found: C, 45.35; H, 2.82; N, 13.19%.
5.6.2. 3-(2-Bromo-5-methoxyphenyl)-6-(phenyl)-5,6-dihydro
[1,2,4]triazolo[3,4-b][1,3,4] thiadiazole (7b)
IR (KBr)
(C]N str), 1477.21 (C]C str), 868.77 (AreH bend), 728.96 (CeBr)
and 627.71 (CeSeC); 1H NMR: (400 MHz, DMSO-d6):
3.78 (ss,
g
/cmꢀ1:3094.23 (NH), 2921.28 (Ar CeH str), 1583.27
5.6.6. 3-(2-Bromo-5-methoxyphenyl)-6-(4-methoxyphenyl)-5,6-
dihydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (7f)
d
IR (KBr) g
/cmꢀ1: 3212.38 (NH), 3190.24 (Ar CeH str), 2960.03
3H, eOCH3 of 2-Br-5-OCH3 phenyl), 5.52 (s, 1H, eCHeNH-),
7.04e7.06 (dd, 1H, J ¼ 8.8 Hz and 2.44 Hz, 2-Br-5-OCH3 phenyl),
7.24 (d, 1H, J ¼ 2.46 Hz, 2-Br-5eOCH3ephenyl), 7.64e7.66 (d, 1H,
J ¼ 8.79 Hz, 2-Br-5eOCH3ephenyl), 7.62e7.68 and 7.52e7.68 (m,
5H, phenyl ring), 13.66 (bs, NH); 13C NMR: (100 MHz, DMSO-d6):
and 2841.88 (methyl CeH str),1582.26 (C]N str),1484.62 (C]C str),
861.95 (AreH bend), 752.36 (CeBr) and 616.11 (CeSeC); 1H NMR:
(400 MHz, DMSO-d6): d 3.64 (s, 3H, eOCH3 of 4-OCH3 phenyl), 3.78
(ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl), 5.51 (s, IH, eCHeNH),
7.11e7.12 (d, 1H, J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl), 7.21e7.23 (d, 1H,
J ¼ 2.49 Hz, 2-Br-5eOCH3ephenyl), 7.60e7.62 (d, 1H, J ¼ 8.84 Hz, 2-
Br-5eOCH3ephenyl), 7.63e7.69 (m, 3H, 4-OCH3 phenyl), 13.86 (bs,
NHeCHe); MS: m/z ¼ 420 (Mþ1); Anal. calcd. for C17H15BrN4O2S: C,
48.70; H, 3.61; N, 13.36; Found: C, 48.68; H, 3.59; N, 13.37%.
d
56.22 (-OCH3 of 2-Br-5-OCH3 phenyl), 59.90 (eCHeNH-), 112.10,
117.32, 118.91, 126.54, 127.42, 128.25, 130.96, 134.86, 143.86, 146.72,
149.74, 166.99; 13C-NMR-DEPT-135: (100 MHz, DMSO-d6), 56.22
(-OCH3 of 2-Br-5eOCH3ephenyl), 59.90 (eCHeNH-), 117.32, 118.91,
127.42, 128.25, 130.96, 134.86; MS: m/z ¼ 390 (Mþ1); Anal. calcd.
for C16H13BrN4OS: C, 49.37; H, 3.37; N, 14.39; Found: C, 49.38; H,
3.39; N, 14.40%.
5.6.7. 3-(2-Bromo-5-methoxyphenyl)-6-(2-methoxyphenyl)-5,6-
dihydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (7g)
IR (KBr) g
/cmꢀ1: 3210.97 (NH), 3191.48 (Ar CeH str), 2968.76 and
5.6.3. 3-(2-Bromo-5-methoxyphenyl)-6-(4-chlorophenyl)-5,6-
2846.28 (methyl CeH str), 1585.32 (C]N str), 1480.25 (C]C str),
dihydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (7c)
858.69 (AreH bend), 756.93 (CeBr) and 610.24 (CeSeC); 1H NMR:
IR (KBr)
g
/cmꢀ1: 3208.42 (NH), 3191.32 (Ar CeH str), 2960.65
(400 MHz, DMSO-d6): d 3.63 (s, 3H, eOCH3 of 2-OCH3 phenyl), 3.78
and 2840.67 (methyl CeH str), 1588.44 (C]N str), 1481.42 (C]C
(ss, 3H, eOCH3 of 2-Br-5-OCH3 phenyl), 5.46 (s, IH, eCHeNH),
7.11e7.12 (d, 1H, J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl), 7.22e7.23 (d, 1H,
J ¼ 2.49 Hz, 2-Br-5eOCH3ephenyl), 7.59e7.60 (d, 1H, J ¼ 8.84 Hz, 2-
Br-5eOCH3ephenyl), 7.61e7.68 (m, 3H, 2-OCH3 phenyl), 13.78 (bs,
NHeCHe); MS: m/z ¼ 420 (Mþ1); Anal. calcd. for C17H15BrN4O2S: C,
48.70; H, 3.61; N, 13.36; Found: C, 48.71; H, 3.63; N, 13.35%.
str), 863.04 (AreH bend), 752.81 (CeBr) and 613 (CeSeC); 1H NMR:
(400 MHz, DMSO-d6):
d 3.78 (ss, 3H, eOCH3 of 2-Br-5-OCH3
phenyl), 7.10e7.12 (dd, 1H, J ¼ 8.8 Hz and 2.6 Hz, 2-Br-5-OCH3
phenyl), 5.46 (s, IH, eCHeNH), 7.24e7.27 (d, 1H, J ¼ 2.49 Hz, 2-Br-
5eOCH3ephenyl), 7.34e7.38 (t, 1H, J ¼ 6.9, 4-Cl-phenyl), 7.63e7.65
(d, 1H, J ¼ 8.84 Hz, 2-Br-5eOCH3ephenyl), 7.50e7.56 (m, 2H, 4-Cl-
phenyl), 7.70e7.72 (d, 1H, J ¼ 7.59, 4-Cl-phenyl), 13.92 (bs,
5.6.8. 3-(2-Bromo-5-methoxyphenyl)-6-(4-nitrophenyl)-5,6-
NHeCHe); 13C NMR: (100 MHz, DMSO-d6):
d
56.21 (-OCH3 of 2-Br-
dihydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (7h)
5-OCH3 phenyl), 60.42 (CHeNH), 69.12, 113.13, 118.53, 119.72,
IR (KBr) g
/cmꢀ1: 3220.04 (NH), 3194.89 (Ar CeH str), 2965.61
126.53, 127.30, 127.82, 128.81, 130.93, 134.28, 134.87, 143.87, 146.05,
and 2848.14 (methyl CeH str), 1585.32 (C]N str), 1481.65 (C]C
159.06; 13C NMR-DEPT: (100 MHz, DMSO-d6):
d 56.21 (-OCH3 of 2-
str), 856.87 (AreH bend), 751.86 (CeBr) and 612.84 (CeSeC); 1H
Br-5-OCH3 phenyl), 60.42 (CHeNH), 118.53, 119.72, 127.82, 128.81,
130.93, 134.28, 134.87; MS: m/z ¼ 424 (Mþ1), 425 (Mþ2); Anal.
calcd. for C16H12BrClN4OS: C, 45.35; H, 2.85; N, 13.22; Found: C,
45.34; H, 2.88; N, 13.20%.
NMR: (400 MHz, DMSO-d6): d 3.84 (ss, 3H, eOCH3 of 2-Br-5-OCH3
phenyl), 5.52 (s, IH, eCHeNH), 6.91e6.93 (dd, 1H, J ¼ 8.79 Hz and
2.88 Hz, 2-Br-5-OCH3 phenyl), 7.14e7.21 (m, 4H, p-nitro phenyl),
7.22 (d, 1H, J ¼ 2.5 Hz, 2-Br-5eOCH3ephenyl), 7.53e7.56 (d, 1H,
J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl), 13.95 (bs, NHeCHe); MS: m/
z ¼ 435 (M þ1), 436 (M þ2); Anal. calcd. for C16H12BrN5O3S: C,
44.25; H, 2.79; N, 16.13; Found: C, 44.22; H, 2.75; N, 16.15%.
5.6.4. 3-(2-Bromo-5-methoxyphenyl)-6-(3-chlorophenyl)-5,6-
dihydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (7d)
IR (KBr) g
/cmꢀ1: 3214.85 (NH), 3194.06 (Ar CeH str), 2962.64
and 2838.17 (methyl CeH str), 1582.53 (C]N str), 1478.82 (C]C
5.6.9. 6-Biphenyl-4-yl-3-(2-bromo-5-methoxyphenyl)-5,6-dihydro
str), 861.14 (AreH bend), 750.94 (CeBr) and 614.98 (CeSeC); 1H
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (7i)
NMR: (400 MHz, DMSO-d6):
d
3.84 (ss, 3H, eOCH3 of 2-Br-5-OCH3
IR (KBr) g
/cmꢀ1: 3216.87 (NH), 3192.76 (Ar CeH str), 2963.74
phenyl), 7.08e7.10 (dd, 1H, J ¼ 8.8 Hz and 2.6 Hz, 2-Br-5-OCH3
and 2852.98 (methyl CeH str), 1582.78 (C]N str), 1486.24 (C]C
phenyl), 5.51 (s, IH, eCHeNH), 7.21e7.23 (d, 1H, J ¼ 2.49 Hz, 2-Br-
str), 854.64 (AreH bend), 756.36 (CeBr) and 614.77 (CeSeC); 1H
5eOCH3ephenyl), 7.32e7.35 (t, 1H,
J
¼
6.9, 3-Cl-phenyl),
NMR: (400 MHz, DMSO-d6): d 3.78 (ss, 3H, eOCH3 of 2-Br-5-OCH3
7.65e7.68 (d, 1H, J ¼ 8.84 Hz, 2-Br-5eOCH3ephenyl), 7.51e7.58 (m,
phenyl), 5.49 (s, IH, eCHeNH), 7.06e7.08 (dd, 1H, 2-Br-5-OCH3
phenyl, J ¼ 8.8 Hz and 2.44 Hz), 7.14e7.16 (d, 1H, J ¼ 2.46 Hz, 2-
2H, 3-Cl-phenyl), 7.68e7.70 (d, 1H, J ¼ 7.59, 3-Cl-phenyl), 13.80
(bs, NHeCHe); MS: m/z
¼
424 (Mþ1); Anal. calcd. for
Br-5eOCH3ephenyl), 7.61e7.63 (d, 1H,
5eOCH3ephenyl), 7.66e7.69 and 7.71e7.78 (m, 9H, biphenyl ring),
13.96 (bs, NHeCHe); MS: m/z ¼ 466 (Mþ1), 467 (Mþ2); Anal.
J
¼
8.79 Hz, 2-Br-
C16H12BrClN4OS: C, 45.35; H, 2.85; N, 13.22; Found: C, 45.38; H,
2.83; N, 13.24%.

N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
135
calcd. for C22H17BrN4OS: C, 56.78; H, 3.68; N,12.04; Found: C, 56.80;
H, 3.64; N, 12.07%.
administration of compounds. A cut off point of 10 s was observed
to prevent the tail damage.
5.6.10. 3-(2-Bromo-5-methoxyphenyl)-6-(4-methylphenyl)-5,6-
5.10. Anti-oxidant activity
dihydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (7j)
IR (KBr) g
/cmꢀ1: 3214.82 (NH), 3190.34 (Ar CeH str), 2958.15
5.10.1. DPPH radical scavenging activity
and 2860.91 (methyl CeH str), 1584.88 (C]N str), 1482.24 (C]C
1,1-Diphenyl-2-picrylhydrazyl (DPPH) is a stable free radical
which has maximum optical absorbance at 517 nm. The reaction of
DPPH with free radical scavenger causes decline in the absorbance
value at 517 nm [31]. The newly synthesized compounds were
dissolved in methylene dichloride at 200, 400 and 800 ug/mL
concentrations and 4 mL of 0.1 mM methanolic solution of DPPH
was added. The test tubes were kept at an ambient temperature for
20 min and the absorbances were measured at 517 nm against
control. Ascorbic acid was used as a positive control. These
measurements were run in triplicate. The percentage of scavenging
activity was calculated as follows:
str), 852.61 (AreH bend), 752.35 (CeBr) and 612.76 (CeSeC); 1H
NMR: (400 MHz, DMSO-d6):
d 2.26 (ss, 3H, 4-methyl phenyl), 3.78
(ss, 3H, eOCH3), 5.48 (s, IH, eCHeNH), 6.90e6.92 (d, 1H,
J ¼ 8.79 Hz, 2-Br-5-OCH3 phenyl), 7.14e7.17 (m, 4H, 4-methyl
phenyl), 7.22 (d, 1H, J ¼ 2.5 Hz, 2-Br-5eOCH3ephenyl), 7.53e7.54
(d, 1H, J ¼ 8.8 Hz, 2-Br-5-OCH3 phenyl), 13.98 (bs, NHeCHe); MS:
m/z ¼ 404 (Mþ1), 405 (Mþ2); Anal. calcd. for C17H15BrN4OS: C,
50.63; H, 3.75; N, 13.89; Found: C, 50.61; H, 3.76; N, 13.91%.
5.7. Synthesis of 1-chloro-4-(3,4-dichlorophenyl)-3,4-
dihydronaphthalene-2-carbaldehyde (9)
Scavenging activityð% of inhibitionÞð%Þ
¼ ½ðADPPH ꢀ ATESTÞ=ADPPHꢃ ꢄ 100
To the VilsmeiereHaack complex prepared from DMF (0.12 mol)
and POCl3 (0.03 mol) at 0 ꢁC, the compound (8) (0.01 mol) was
added and the reaction mixture was stirred at 65 ꢁC for 4 h. The
reaction completion was monitored by TLC. The contents were
cooled, poured in to ice-cold water and neutralized using Na2CO3
solution in water. The solid product that separated was filtered,
washed with cold water and dried. The crude product was recrys-
tallized from ethyl acetate.
Where ADPPH is the absorbance of DPPH without test sample
(control) and A<SUB>TEST</SUB> is the absorbance of DPPH in
the presence of test sample.
5.11. Antibacterial activity
g
/cmꢀ1: 3443.28 (-CHO), 1662.34 (C]O of aldehyde),
All the newly synthesized compounds were screened for their
antibacterial activity against four bacterial strains, viz., Staph-
yllococcus aureus (ATTC-25923), E. coli (ATTC-25922), P. aeruginosa
(ATTC-27853) and K. pneumoniae (recultured) by disc diffusion
method [32,33]. Serial dilutions of the drug in Muller-Hinton broth
were taken in tubes and their pH was adjusted to 5.0 using
a phosphate buffer. A standardized suspension of the test bacte-
rium was inoculated and incubated for 16e18 h at 37 ꢁC. The
minimum inhibitory concentration (MIC) was noted by seeing the
lowest concentration of the drug at which there was no conspic-
uous growth.
IR (KBr)
1595.81 (C]C, aromatic),838.88 (CeCl), 1255.43 (CeH stretch).1H
NMR (400 MHz, DMSO-d6): 2.86e3.01(m, 2H, eCH2 proton of
d
fused cyclohexene ring), 4.13 (t, 1H, J ¼ 7.5 Hz, eCH proton of fused
cyclohexene ring), 6.92e6.98 (m, 1H of dichloro phenyl ring and 1H
of benzene ring), 7.34e7.45 (m, 3H, Benzene ring), 7.18e7.19 (d,1H,
J ¼ 2.1 Hz, Dichloro phenyl ring), 7.96e8.00 (m, 1H, Dichloro phenyl
ring), 10.33 (s, 1H, eCHO); MS: m/z ¼ 337 (Mþ); Anal. calcd. for
C17H11Cl3O: C, 60.48; H, 3.28; Found: C, 60.49; H, 3.28%.
5.8. Anti-inflammatory activity
A number of antibacterial discs were placed on the agar for the
sole purpose of producing zone of inhibition in the bacterial lawn.
Twenty millilitres of agar media was poured into each Petri dish.
The excess of suspension was decanted and plates were dried by
placing in an incubator at 37 ꢁC for an h. Using a punch, wells were
made on these seeded agar plates and minimum inhibitory
concentrations of the test compounds in dimethyl sulfoxide
(DMSO) was added into each labelled well. A control was also
prepared for the plates in the same way using DMSO as a solvent.
The Petri dishes were prepared in triplicate and maintained at 37 ꢁC
for 3e4 days. Antibacterial activity was determined by measuring
the diameter of inhibition zone. Activity of each compound was
compared with taking ampicillin as standard.
The anti-inflammatory activity of newly synthesized 3,6-
disubstituted-1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles (5aej) and
5,6-dihydro-3,6-disubstituted-1,2,4-triazolo[3,4-b][1,3,4]thiadia-
zoles (7aej) were evaluated by applying carrageenan-induced paw
oedema bioassay in rats of either sex (100-140 g) by following the
method of Winter et al. [29] using Diclo as a reference standard.
Rats were selected by random sampling technique. The test
compounds were administrated at dose level of 100 mg/kg orally
30 min prior to the administration of carrageenan in the right hind
paw of the rats. The paw thickness was measured using vernier
callipers at regular intervals of 60, 120 and 180 min after carra-
geenan administration.
5.9. Analgesic activity
5.12. Antifungal activity
The analgesic activity of the above mentioned derivatives were
also evaluated by applying tail flick method [30] using pentazocine
as a standard reference. Wistar albino mice of either sex (20-30 g)
in the groups of six animals each one was selected by random
sampling technique. The test compounds at dose level of 100 mg/kg
were administered orally by intragastric tube. The animals were
held in position by a suitable restrained the tail extending out and
the tail (up to 5 cm) was then dipped in a beaker of water main-
tained at 50e55 ꢁC. The time in seconds taken to withdraw the tail
clearly out of water was taken as the reaction time. The reading was
recorded at regular intervals of 60, 80 and 120 min after
All those compounds screened for antibacterial activity were
also tested for their anti-fungal activity against P. marneffei (recul-
tred), T. mentagrophytes (recultured), Aspergillus flavus (NICM
No.524) and A. fumigatus (NCIM No.902) by serial plate dilution
method [34]. Sabourands agar media was prepared by dissolving
peptone (1 g), D-glucose (4 g) and agar (2 g) in distilled water
(100 mL) and adjusting pH to 5.7. Normal saline was used to make
a suspension of sore of fungal strains for lawning. A loopful of
particular fungal strain was transferred to 3 mL saline to get
a suspension of the corresponding species. Twenty mL of agar
media was poured in to each petri dish. The excess of suspension

136
N. Chidananda et al. / European Journal of Medicinal Chemistry 51 (2012) 124e136
[8] T. Karabasanagouda, A.V. Adhikari, N. Suchetha shettey, Eur. J. Med. Chem. 42
(2007) 521e529.
[9] V. Mathew, J. Keshavayya, V.P. Vaidya, Eur. J. Med. Chem. 41 (2006)
1048e1058.
[10] N. Demirbas, A. Demibras, S.A. Karaoglu, E. Celik, Arkivoc 1 (2005) 75e91.
[11] Z.Y. Zhang, X.W. Sun, C.H. Chu, L. Zhao, J. Chin. Chem. Soc. 44 (1997) 535.
[12] F.P. Invidiata, D. Simoni, F. Scintu, N. Pinna, Farmaco 51 (1996) 659e664.
[13] M. ImtiazHussain, V. Kumar, Indian J. Chem. 31B (1992) 673.
[14] S.M. El Khawass, M.A. Khalli, A.A. Hazza, A. Bassiouny, N.F. Loutfy, Farmaco 44
(1989) 703e709.
was decanted and the plates were dried by placing in an incubator
at 37 ꢁC for 1hr. Using a punch, wells were made on these seeded
agar plates. Minimum inhibitory concentrations of the test
compounds in DMSO were added into each labelled well. A control
was also prepared in triplicate and maintained at 37 ꢁC for 3e4
days. Activity of each compound was compared with itraconozole
as standard. Itraconozole has a MIC value of 0.04e22.67 mM. The
minimum inhibitory concentrations of each compound were
determined.
[15] W. Rzeski, J. Matysiak, M. Kandefer-Szerszen, Bioorg. Med. Chem. 15 (2007)
3201e3207.
[16] V. Srivastava, S. Sen, R. Shekar, Indian J. Chem. 33B (1994) 344.
[17] M. Amir, K. Harish, S.A. Javed, Eur. J. Med. Chem. 43 (2008) 2056e2066.
[18] A.R. Prasad, T. Ramlingam, A. Bhaskar Rao, P.V. Diwan, P.B. Sattur, Indian J.
Chem. 25B (1986) 566.
Acknowledgements
[19] Shi Haijian, Wang Zhongyi, Shi Haoxin, Syn. Comm. 28 (1998) 3973e3982.
[20] Dushyant H. Purohit, Bhavesh L. Dodiya, Renish M. Ghetiya, Piyush
B. Vekariya, Hitendra S. Joshi, Acta Chim. Slov. 58 (2011) 53e59.
[21] Arunkumar Subramani, Ilango Kaliapan, Ravindar Bairam, N. Ramalakshmi,
Der Pharma Chemica. 1 (2009) 70e77.
[22] A.J. Hutf, J.O. Grady, J. Antimicrob. Chemother. 37 (1996) 7e32.
[23] K.K. Vijaya Raj, B. Narayana, B.V. Ashalatha, K.N. Suchetha, Eur. J. Med. Chem.
42 (2007) 425e429.
[24] K.K. Vijaya Raj, B. Narayana, Phosphorus, Sulfur, Silicon Relat. Elem. 181
(2006) 1971e1981.
[25] J.R. Reid, N.D. Heindel, J. Heterocyclic Chem. 13 (1976) 925.
[26] H.C. Devarajegowda, P. Nagendra, S. Jeyaseelan, N. Chidananda, Boja Poojary,
Acta Cryst. E67 (2011) o378.
One of the authors, N. Chidananda, is grateful to the manage-
ment of SeQuent Scientific Ltd., New Mangalore, India for encour-
aging research work. N. Chidananda is also thankful to Prof. A.
Srikrishna, Department of Organic Chemistry, IISc, Bangalore for
providing 1H NMR and 13C NMR spectral facilities. We are also
thankful to Smt. Ashwini Srinivas, Department of Bioscience,
Mangalore University for her sincere help during the anti-oxidant
study. Thanks are also due to CDRI-Lucknow and Punjab University
Chandigarh for providing 1H NMR and MS spectral data.
[27] CCDC 811335 contains the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre viawww.ccdc.cam.ac.uk/ data_request/cif
[28] T.P. Jerussi, Q.K. Fang, M.G. Currie, PCT Int. Appl. (2004) WO 2004042669 A1,
200440325.
[29] C.A. Winter, E.A. Risley, G.N. Nuss, Proc. Soc. Exp. Biol. 111 (1962) 544e547.
[30] D.M. Kar, S.K. Sahu, P.K. Misro, Indian Drug 40 (2003) 261e266.
[31] R.P. Singh, C.K.N. Murthy, K. Jayaprakash, J. Agric. Food Chem. 50 (2002)
81e86.
[32] R. Cruickshank, J.P. Duguid, B. Marmion, R.H.A. Swain, Med. Microbiol. 11
(1975) 190.
[33] S. Lemriss, B. Marquet, H. Ginestet, L. lefeuvre, A. Fassouane, P. Boiron,
J. Mycol. Med. 13 (2003) 189e192.
References
[1] M.I. Sahar Badr, Rasha M. Barwa, Bioorg. Med. Chem. 19 (2011) 4506e4512.
[2] B.N. Goswami, J.C.S. Kattaky, J.N. Baruah, J. Hetercyclic. Chem. 21 (1984)
1225e1229.
[3] B.S. Holla, K.A. Poojary, B. Kalluraya II, Farmaco 51 (1996) 793e799.
[4] S.S. Papakonstantinou-Garoufalias, E. Tani, O. Todoulou, A. Papadaki-Valiraki,
E. Filippatos, E. De Clercq, P.N. Kourounakis, J. Pharm. Pharmacol. 50 (1998)
117e124.
[5] G. Turan-Zitouni, Z.A. Kaplancikli, K. Erol, F.S. Kilic, Farmaco 54 (1999) 218e223.
[6] C. Hart, Am. Chem. Soc. 2 (1999) 20e31.
[7] W.A. David, L.L. Thomas, Foye’s Princ. of Med. Chem. fifth ed.., Lippincott
Williams & Wilkins. London.
[34] Z.K. Khan, Proceeding Int. workshop UNIDO-CDRI, (1997) 210e211.