Heterocyclic system containing bridgehead nitrogen atom: synthesis and pharmacological activities of some substituted 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles

Article abstract of DOI:10.1016/j.ejmech.2006.03.018

Several 3,6-disubstituted-1,2,4-triazolo[3,4-b]-1,3,4-thiadizoles were prepared by the condensation of 4-amino-3-aryl/aralkyl substituted-5-mercapto-1,2,4-triazoles 3(a-c) with various substituted aromatic/hetero aromatic acids through a single step react

Full text of DOI:10.1016/j.ejmech.2006.03.018

European Journal of Medicinal Chemistry 41 (2006) 1048–1058
http://france.elsevier.com/direct/ejmech
Original article
Heterocyclic system containing bridgehead nitrogen atom:
synthesis and pharmacological activities of some substituted
1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles
a
b,
b
*
V. Mathew , J. Keshavayya , V.P. Vaidya
a Acharya and B.M. Reddy College of Pharmacy, Bangalore, Karnataka, India
b Department of Studies in Chemistry, Kuvempu University, Jnana Sahayadri, Shankaraghatta, 577451 Shimoga, Karnataka, India
Received in revised form 6 March 2006; accepted 9 March 2006
Available online 05 July 2006
Abstract
Several 3,6-disubstituted-1,2,4-triazolo[3,4-b]-1,3,4-thiadizoles were prepared by the condensation of 4-amino-3-aryl/aralkyl substituted-
5-mercapto-1,2,4-triazoles 3(a–c) with various substituted aromatic/hetero aromatic acids through a single step reaction. Elemental analysis, IR,
1H NMR and mass spectral data confirmed the structure of the newly synthesized compounds. Synthesized triazolo thiadiazoles investigated for
their antibacterial, antifungal, anti-inflammatory and analgesic activities. Some of the tested compounds showed moderate antimicrobial activity
against various tested bacterial and fungal strains. None of the synthesized compounds have significant anti-inflammatory and analgesic activ-
ities.
© 2006 Elsevier SAS. All rights reserved.
Keywords: 4-Amino triazoles; Triazolo thiadiazoles; Phosphorous oxychloride; Spectral characterization; Pharmacological activities
1. Introduction
nents in a ring together to give a compact and planar structure
and screened for their biological activities.
Prompted by these observations, we report herein the reac-
tion of 4-amino-3-aryl/aralkyl substituted-5-mercapto-1,2,4-
triazoles 3(a–c) with aromatic acids in the presence of phos-
phorous oxychloride to give 3,6-disubstituted-1,2,4-triazolo
[3,4-b]-1,3,4-thiadiazoles 4–11(a–c) and their biological activ-
ities (Scheme 2).
The recent literature is enriched with progressive findings
about the synthesis and pharmacological action of fused het-
erocycles. Heterocycles bearing a symmetrical triazole or
1,3,4-thiadiazole moiety are reported to show a broad spectrum
of pharmacological properties such as anti-inflammatory [1,2],
antiviral [3] and antibacterial [4,5] activities. A survey of lit-
erature revealed that s-triazolo[3,4-b]-1,3,4-thiadiazole rings,
have received much attention during recent years on account
of their prominent utilization as antifungal [6], anti-
inflammatory [7], antiviral, analgesic [8], anthelmintic [9] and
antibacterial agents [10].
Phosphorous oxychloride was necessary for this condensa-
tion, which activate the carbonyl group of aromatic acids and
increases its electrophilicity to enhance the addition of triazole
to it.
The
required
4-amino-3-aryl/aralkyl
substituted-
A triazolo thiadiazole system may be viewed as a cyclic
analogue of two very important components—thiosemicarba-
zide [11,12] and biguanide [13], which often display diverse
biological activities. Therefore it was planned to investigate a
composite system, which combine these two biolabile compo-
5-mercapto-1,2,4-triazoles 3(a–c) were prepared in good yield
through multi step reaction by using the method of Reid and
Heindel [14] with suitable modifications (Scheme 1). The
structure of the intermediate triazole derivatives was based on
their elemental analysis and other spectral data. The synthesis
of 3,6-disubstituted-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles was
accomplished in
a
single step by reacting 4-
* Corresponding author.
E-mail address: jkeshavayya@rediffmail.com (J. Keshavayya).
amino-3-aryl/aralkyl substituted-5-mercapto-1,2,4-triazoles 3
0223-5234/$ - see front matter © 2006 Elsevier SAS. All rights reserved.
doi:10.1016/j.ejmech.2006.03.018

V. Mathew et al. / European Journal of Medicinal Chemistry 41 (2006) 1048–1058
1049
Scheme 1. Heterocyclic system containing bridgehead nitrogen atom: synthesis and pharmacological activities of some substituted 1,2,4-triazolo [3,4-
b]-1,3,4-thiadiazoles.
Scheme 2.
(a–c) with various aromatic acids in the presence of phosphor-
ous oxychloride as per Scheme 2.
disappeared by the formation of the triazolo thiadiazoles (4–
11). Similarly the H NMR spectra of the synthesized triazoles
1
3(a–c) showed two characteristic broad signals at δ 5.5–5.7 and
the other at δ 13.8–13.95, due to NH2 and SH proton, respec-
tively, which were absent in the 1H NMR spectra of triazolothia-
diazoles. The absence of these absorptions due to SH and NH2
established that all the triazoles had converted to triazolo thia-
diazoles by reacting with the –COOH group of the various
acids. The H NMR, mass spectra, IR and elemental analysis
supported the structure of various synthesized triazolo thiadia-
zoles.
2. Chemistry
As depicted in scheme, in addition to triazolo thiadiazoles,
we have synthesized three substituted 1,2,4-triazoles through a
multiple step reaction (Scheme 1). Aromatic esters were hydra-
zinolysized to give aroyl hydrazides (1), which reacted with
carbon disulfide and potassium hydroxide in ethanol to yield
potassium dithiocarbazinate (2), which later cyclized to 4-
amino-5-mercapto-1,2,4-triazole 3(a–c) by reacting with hydra-
zine hydrate. The resulted triazoles 3(a–c) further converted to
triazolo thiadiazoles (4–11) by one pot reaction by the conden-
sation with aromatic/hetero aromatic acids in the presence of
phosphorous oxychloride (Scheme 2). This procedure afforded
various triazolo thiadiazoles in 50–65% yields. The infrared
spectra of the substituted-4-amino-5-mercapto-1,2,4-triazole
(3a–c) showed two characteristic absorption bands, one of
which appearing at 2585 cm–1, was attributed to SH and the
other at 3200–3300 cm−1, was assigned to NH2, which were
1
A slight modification has been done to the literature proce-
dure, which called for the removal of excess phosphorus oxy-
chloride under reduced pressure. This could result in damage to
the rotatory evaporator and vacuum pump due to the strong
acidity and high boiling point of phosphorus oxychloride.
Hence alternative method is suggested where in the reaction
mixture is poured into crushed ice with stirring. Some solid
potassium carbonate and required quantity of solid potassium
hydroxide were added till the pH of the reaction mixture was
raised to 8.

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V. Mathew et al. / European Journal of Medicinal Chemistry 41 (2006) 1048–1058
3. Biological results and discussion
dard showed 55% of inhibition. The animals were divided into
various groups and each group consisting of six animals. One
group served as control and received 0.1 ml of 1% gum acacia
suspension orally. Group II served as standard and received
phenylbutazone at the dose of 100 mg kg–1 as suspension in
gum acacia orally. One hour after the administration of test
compounds at the dose of 100 mg kg–1 as suspension in gum
acacia, 0.1 ml of 1% carrageenan in normal saline was given
subcutaneously to the sub plantar region of right hind paw. The
paw volume was measured immediately (‘0’ h) and after 1–4 h,
respectively, by using plethysmometer. The difference between
the paw volume at 4th and 0 h measurement was calculated
and taken as edema volume. Percentage inhibition in the paw
edema was calculated by using the formula, percentage
inhibition = 100 (1 – Vt/Vc), where Vt = mean increase in paw
volume of test, and Vc = mean increase in paw volume of con-
trol. Percentage inhibition shown by tested compounds is
recorded in Table 1.
The results of the antimicrobial effect of the newly synthe-
sized compounds were reported as minimum inhibition con-
centration (MIC) against Staphylococcus aureus, Bacillus sub-
tilis (gram-positive bacteria), Pseudomonas aeruginosa,
Escherichia coli (gram-negative bacteria) and two fungi Asper-
gillus niger (A.ߕniger) and Candida albicans (C.ߕalbicans).
None of the synthesized compounds have important antimicro-
bial activities. While compounds 4a, 4b, 4c, 11a, 11b, and 11c
exhibit moderate inhibitory activities against the tested strains
of bacteria. Compounds 7a, 7b, and 7c exhibit moderate inhi-
bitory activity against P.ߕaeruginosa and E.ߕcoli. The other
compounds had no inhibitory activity. The results revealed
that compounds 11a, 11b and 11c exhibited the highest degree
of inhibition against various microbial strains. Moreover, the
biological activities of the other compounds against the tested
organisms are very weak. However, the activities of the tested
compounds are much less than those of standard antifungal and
antibacterial agents used.
4.1.2. Analgesic activity
Some of the tested compounds 9a, 9b, 9c, 11a, 11b and 11c
had shown weak anti-inflammatory and analgesic activity.
Other compounds had no anti-inflammatory and analgesic
activities. The anti-inflammatory and analgesic activity studies
indicated that compounds 11a, 11b and 11c exhibited the high-
est degree of anti-inflammatory and analgesic activity. How-
ever, the activities of the tested compounds are very much
less than those of standard agents used.
All the compounds were tested for their analgesic activity
by using Eddy’s hot plate technique [16] and exhibited weak
to moderate activity ranging from 6% to 32%. Mice (Swiss
strain) of either sex weighing between 25 and 35 g were used
for the experiment. Diclofenac sodium at the dose of
50 mg kg–1 body weight as suspension in 1% gum acacia
was used as standard, which showed percentage analgesic
activity of 52%. In this method heat is used as a source of
pain. Animals were individually placed on a hot plate main-
tained at constant temperature () and the reaction of animals,
such as paw licking or jump response (whichever appears first)
was taken as the end point. Tested compounds at the dose of
50 mg kg–1 body weight was given as suspension in 1% gum
acacia orally to animals and observed the reaction time of ani-
mals on the hot plate at 15, 30, 60, 90 and 120 min after the
compound administration. A cut off time of 15 s was taken as
maximum analgesic response to avoid injury to the paws. Per-
centage analgesic activity shown by the tested compounds is
recorded in Table 2.
4. Experimental protocols
Thin layer chromatography was used to reach the comple-
tion of the reaction and purity of the compounds synthesized.
Melting points were taken in open glass capillary tubes by
using Thiel’s tube containing liquid paraffin and were uncor-
rected. IR spectra in KBr were recorded on a Shimadzu-8400
1
FTIR spectrophotometer, H NMR spectra were recorded on
Brucker spectrophotometer (400 MHz) in DMSO-d6/CDCl3
using TMS as an internal standard (chemical shifts are
expressed in δ, ppm), mass spectra were recorded in Finnigan
MAT 8230 mass spectrophotometer and micro analysis were
recorded on Thermo Finnigan FLASH EA 1112 CHNS Analy-
zer. The purity of the compounds were checked on silica gel-G
coated plates by using ethyl acetate and petroleum ether (1:1)
as the eluent and observed in UV light. All the synthesized
compounds gave satisfactory elemental analyses.
4.1.3. Antibacterial and antifungal activities
The antibacterial activity of title compounds was determined
in vitro by using paper disc method against variety of patho-
genic micro organisms like E.ߕcoli, P.ߕaeruginosa (gram-
negative), S.ߕaureus, B.ߕsubtilis (gram-positive) at 25, 50,
100 μg ml–1 concentrations, respectively, in the nutrient agar
media by measuring the zone of inhibition in mm. The solu-
tions of required concentrations (25, 50, 100 μg ml–1) of test
compounds were prepared by dissolving the compounds in
DMF. Under identical conditions the standard antibiotics, ami-
kacin at 100 μg ml–1 showed zone of inhibition 36 mm for
E. coli, 43 mm for P. aeruginosa and vancomycin at
100 μg ml–1 showed zone of inhibition 41 mm for gram-
positive organism. Antibacterial activity shown by the com-
pounds towards various bacteria is recorded in Table 3.
4.1. Pharmacological evaluation
4.1.1. Anti-inflammatory activity
All the synthesized compounds were tested for their anti-
inflammatory activity using carrageenan induced rat hind paw
edema method of Winter et al. [15]. Albino rats (Wistar strain)
of either sex, weighing between 150 and 200 g, were used for
the experiment. Tested compounds showed weak to moderate
activity ranging from 6% to 32%, while phenylbutazone, stan-

V. Mathew et al. / European Journal of Medicinal Chemistry 41 (2006) 1048–1058
1051
Table 1
Anti-inflammatory activity of compounds (4–11)
Compounds
Change in paw volume (in ml) after ( S.E.)#
Percentage inhibition of edema volume after
1 h
2 h
3 h
4 h
1 h
2 h
3 h
4 h
4a
4b
4c
5a
5b
5c
6a
6b
6c
7a
7b
7c
8a
8b
8c
9a
9b
9c
10a
10b
10c
11a
11b
11c
0.84 0.02
0.82 0.02
0.86 0.03
0.76 0.03
0.76 0.02
0.77 0.03
0.76 0.03
0.75 0.03
0.76 0.03
0.74 0.04
0.73 0.03
0.75 0.03
0.57 0.02
0.57 0.02
0.58 0.04
0.82 0.03
0.81 0.02
0.84 0.03
0.57 0.02
0.57 0.02
0.56 0.02
0.81 0.04
0.80 0.02
0.79 0.03
1.17 0.02
1.13 0.03
1.21 0.03
1.03 0.02
1.05 0.02
1.07 0.03
1.08 0.04
1.06 0.02
1.09 0.03
1.05 0.03
1.04 0.03
1.07 0.04
0.83 0.03
1.83 0.02
0.84 0.03
1.12 0.02
1.11 0.03
1.12 0.04
0.81 0.06
0.82 0.05
0.82 0.04
1.06 0.06
1.04 0.03
1.08 0.02
0.92 0.03
1.61 0.05
1.54 0.03
1.67 0.06
1.50 0.02
1.55 0.07
1.56 0.02
1.57 0.02
1.55 0.02
1.58 0.02
1.55 0.04
1.50 0.03
1.57 0.04
1.29 0.02
1.30 0.04
1.30 0.02
1.42 0.02
1.44 0.02
1.45 0.03
1.21 0.04
1.21 0.02
1.22 0.02
1.35 0.02
1.37 0.02
1.43 0.05
0.97 0.04
1.90 0.03
1.85 0.02
1.98 0.05
1.70 0.02
1.74
6.6**
8.9***
4.5
5.0*
5.0*
3.8
5.0*
6.3*
5.0*
7.5**
8.8***
6.3*
5.0*
5.0*
8.6*
11.7**
5.5
12.0**
10.3*
8.6
7.7
9.4*
6.8
10.3*
11.2**
8.5*
5.8
5.4
10.6
14.4
7.2
14.3
11.6
10.9
10.3
11.4
9.7
11.4
14.3
10.3
6.5
15.6
17.8
12.0
17.5
15.5
13.6
13.1
12.1
11.6
17.9
16.9
12.6
8.9
1.78 0.03
1.80 0.03
1.82 0.02
1.83 0.05
1.70 0.04
1.72 0.05
1.81 0.02
1.75 0.02
1.74 0.02
1.80 0.02
1.60 0.03
1.65 0.02
1.70 0.03
1.60 0.03
1.62 0.02
1.66 0.03
1.54 0.04
1.58 0.04
1.64 0.04
1.00 0.03
5.8
5.8
9.4
6.3
3.4
4.9
8.9***
10.0***
6.7**
5.0*
12.5**
13.3**
12.5**
8.2
7.1
7.2
17.2***
18.8***
15.6***
17.9**
21.1*
20.0*
19.4*
12.5
12.5
11.7
25.0**
23.9*
20.6*
37.1***
28.9*
26.5*
24.4*
16.5
15.4
13.4
31.5**
29.9*
26.2*
55.6***
5.0*
6.7**
10.0***
11.1***
12.2***
10.0*
Phenyl butazone 0.72 0.03
# = Standard error; * = P < 0.05; ** = P < 0.01; *** = P < 0.001. For all other comparison P > 0.05.
Similarly, the antifungal screening of the compounds (4–11)
was carried out in vitro by paper disc method against two
fungi, A. niger and C. albicans by using griseofulvin
(100 μg ml–1) as the standard, which had shown (34 and
37 mm, respectively) as the zone of inhibition. Antifungal
activity shown by the compounds towards fungi is recorded
in Table 4. DMF was used, as the solvent control because the
tested compounds is freely soluble in DMF, for both antibac-
terial and antifungal activities.
constant stirring. The reaction mixture was agitated continu-
ously for a period of 15 h. It was then diluted with anhydrous
ether. The precipitated potassium dithiocarbazinate was col-
lected by filtration. The precipitate was further washed with
anhydrous ether (100 ml) and dried under vacuum. The potas-
sium salt thus obtained was in quantitative yield and was used
in the next step without further purification.
4.2.3. General method for the synthesis
of 3-substituted-4-amino-5-mercapto-1,2,4-triazole 3(a–c)
A suspension of potassium dithiocarbazinate of respective
aromatic esters (2), (0.1 M) in water (5 ml) and hydrazine
hydrate (15 ml, 0.3 M) was refluxed for 6–7 h with occasional
shaking. The color of the reaction mixture changed to green
with the evolution of hydrogen sulfide gas (lead acetate paper
and odor). A homogenous reaction mixture was obtained dur-
ing the reaction process. The reaction mixture was cooled to
room temperature and diluted with water (100 ml). On acidifi-
cation with concentrated hydrochloric acid, the required tria-
zole was precipitated. It was filtered, washed thoroughly with
cold water and recrystallized from ethanol. The completion of
the reaction was monitored on TLC by using silica gel-G
coated plates by using ethyl acetate and petroleum ether (1:1)
as the eluent and observed in UV light.
4.2. Preparation
4.2.1. General method for the synthesis of aryl acid hydrazide
(1)
Dissolved the esters of substituted aromatic acids (0.1 M),
in 30 ml of ethanol and hydrazine hydrate (0.1 M) was added
drop wise to the mixture with stirring. The resulting mixture
was allowed to reflux for 6 h. Excess ethanol was distilled
out and the contents were allowed to cool. The crystals formed
was filtered, washed thoroughly with water and dried. The
completion of the reaction was monitored on TLC by using
silica gel-G coated plates by using ethyl acetate and petroleum
ether (1:1) as the eluent and observed in UV light.
4.2.2. General method for the synthesis of potassium
dithiocarbazinate (2)
Potassium hydroxide (0.15 M) was dissolved in absolute
ethanol (200 ml). To the above solution, aryl acid hydrazide
(0.1 M) was added and cooled the solution in ice. To this,
carbon disulfide (0.15 M) was added in small portions with
4.2.4. 4-Amino-3-[4-(N,N-dimethyl amino) phenyl]-
5-mercapto-1,2,4-triazole (3a)
M.p.: 248°C yield (%): 60%; IR (KBr) n (cm−1): 3313 (NH
stretching), 1608 (C=N stretching); 3131 (aromatic CH stretch-
ing), 2586 (SH), 2978, 2813 (methyl CH stretch), 1232 (N–

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V. Mathew et al. / European Journal of Medicinal Chemistry 41 (2006) 1048–1058
Table 2
Analgesic activity of compounds (4–11)
Compounds
Reaction time (s) after drug administration
30 min S.E.# 90 min S.E.#
Percent increase in reaction time
60 min S.E.#
5.84 0.55
8.24 0.60
8.17 0.34
7.12 0.37
6.00 0.17
7.67 0.45
8.83 0.48
6.50 0.43
4.92 0.55
5.24 0.48
8.24 0.60
4.60 0.26
8.53 0.48
8.24 0.60
8.67 0.48
7.15 0.56
5.78 0.55
5.24 0.43
6.36 0.26
8.83 0.43
6.67 0.43
4.92 0.42
7.67 0.50
7.33 0.33
6.50 0.43
30 min
4.4
5.4
4.6
7.6
6.0
5.6
4.9
4.5
4.2
5.6
5.0
4.3
3.1
2.8
–
60 min
7.4
9.1
8.4
11.7
8.9
6.6
8.7
8.4
6.1
90 min
4a
4b
4c
5a
5b
5c
6a
6b
6c
7a
7b
7c
8a
8b
8c
9a
9b
9c
10a
10b
10c
11a
11b
11c
5.20 0.33
5.87 0.33
7.22 0.31
6.44 0.34
5.50 0.48
6.41 0.55
8.17 0.31
6.00 0.73
4.46 0.34
4.56 0.43
7.84 0.33
4.02 0.42
8.17 0.31
7.45 0.33
–
6.17 0.34
5.12 0.33
4.34 0.37
5.87 0.58
8.17 0.43
5.83 0.37
4.46 0.34
5.54 0.56
6.33 0.43
5.67 0.50
6.71 0.45
9.17 0.31
9.63 0.31
8.08 0.21
7.45 0.55
8.17 0.61
9.83 0.17
7.50 0.35
5.36 0.48
6.04 0.21
9.17 0.31
5.83 0.31
9.00 0.17
9.17 0.31
9.17 0.55
8.55 0.37
6.48 0.45
8.00 0.31
7.64 0.31
9.83 0.21
7.33 0.31
6.14 0.34
8.45 0.61
8.76 0.22
7.33 0.21
12.6
13.2
11.1
14.0
13.6
10.0
13.9
12.6
10.3
12.0
11.3
9.4
9.1
7.3
5.8
4.5
6.9
4.0
6.2
3.2
5.8
10.3
11.8
9.3
4.6
5.2
19.2*
21.7*
19.5*
7.8
6.6
7.3
20.3*
20.8*
19.4*
37.2***
29.8*
29.4*
25.9*
13.2
12.3
10.5
31.9*
28.9*
26.5*
52.3***
4.7
11.8
10.5
9.2
Diclofenac sodium
26.2***
# = Standard error; * = P < 0.05; *** = P < 0.001. For all other comparison P > 0.05.
N=C), 1564, 1542, 1470, 1434 (C=C ring stretching), 1322
(C–N stretching); 1H NMR: 13.65 (s, 1H, SH), 6.8, 7.9 (d, 4H,
Ar-H), 5.73 (s, 2H, NH2), 2.99 (s, 6H, N (CH3)2); MS m/z [%
rel. int.]: 235 [24] (M+). Calcd. (%) for C10H13N5S: C; 51.04,
H; 5.57, N; 29.76, S; 13.63. Found: C; 50.96, H; 5.56, N;
29.75, S; 13.63.
Calcd. (%) for C13H12N4S: C; 60.91, H; 4.72, N; 21.86, S;
12.51. Found: C; 60.86, H; 4.73, N; 21.84, S; 12.52.
4.2.7. Synthesis of 3-aryl/aralkyl substituted-
6-(2-methyl/2-phenyl-4-quinolinyl)-1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazoles 4 and 5(a–c)
An equimolar mixture of respective triazole 3(a–c)
(0.02 M), 2-methyl/2-phenyl-quinoline-4-carboxylic acid
(0.02 M) in dry phosphorous oxy chloride (10 ml) was
refluxed for 7 h. The reaction mixture was cooled to room
temperature and then gradually poured onto crushed ice with
stirring. Finely powdered potassium carbonate and the required
amount of solid potassium hydroxide were added till the pH of
the mixture was raised to 8, to remove the excess of phosphor-
ous oxychloride. The mixture was allowed to stand overnight
and solid was separated. It was filtered, washed thoroughly
with cold water, dried and recrystallized from hot ethanol.
4.2.5. 4-Amino-3-[2-(N-methyl amino) phenyl]-
5-mercapto-1,2,4-triazole (3b)
M.p.: 221°C yield (%): 60%; IR (KBr) n (cm−1): 3355,
3300 (NH stretching), 1610 (C=N stretching), 3110 (aromatic
CH stretching), 1579, 1510, 1467, 1428 (C=C ring stretching),
2587 (SH), 2940, 2837 (methyl CH stretching), 1286 (N–
1
N=C), 1316 (C–N stretching); H NMR: 13.89 (s, 1H, SH),
7.3 (d, 1H of Ar), 7.7 (d, 1H of Ar), 6.6–6.7 (m, 2H of Ar),
5.6 (s, 2H, NH2), 6.18 (q, 1H, NH in NH–CH3), 2.8 (d, 3H,
CH3 in NH–CH3); MS m/z [% rel. int.]: 221 [38] (M+). Calcd.
(%) for C9H11N5S: C; 48.85, H; 5.01, N; 31.65, S; 14.49.
Found: C; 48.90, H; 5.01, N; 31.62, S; 14.49.
4.2.8. 3-[4-(N,N-dimethyl amino) phenyl]-
6-(2-phenyl-4-quinolinyl)-1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazole (4a)
4.2.6. 4-Amino-3-(1-naphthyl methyl)-
M.p.: 224°C yield (%): 58%; IR (KBr) n (cm−1): 3050 (aro-
matic CH stretching), 1618 (C=N stretching), 1594, 1480,
1464 (C=C ring stretch), 2932, 2875 (methyl CH stretch),
5-mercapto-1,2,4-triazole (3c)
M.p.: 210°C yield (%): 70%; IR (KBr) n (cm−1): 3269 (NH
stretching), 1625 (C=N stretching), 3162, 3044 (aromatic CH
stretching), 1596, 1570, 1495, 1425 (C=C ring stretching),
2600 (SH), 2929 (methyl CH stretch), 1254 (N–N=C); 1H
NMR: 13.48 (s, 1H, SH), 7.3–8.1 (m, 7H, Ar-H), 5.67 (s, 2H,
NH2), 4.5 (s, 2H, CH2); MS m/z [% rel. int.]: 256 [26] (M+).
1
1331 (C–N stretching), 1261 (N–N=C); H NMR δ: 6.8–8.7
(m, Ar-H), 3.1 (s, 6H, N (CH3)2); MS m/z [% rel. int.]: 449
[24] (M+). Calcd. (%) for C26H20N6S: C; 69.62, H; 4.49, N;
18.74, S; 7.15. Found: C; 69.59, H; 4.49, N; 18.75, S; 7.15.

V. Mathew et al. / European Journal of Medicinal Chemistry 41 (2006) 1048–1058
1053
Table 3
Antibacterial activity of compounds# (3–11)
1
2
3
E. coli
P. aeruginosa
B. subtilis
S. aureus4
Com-
pounds
25 μg ml–1 50 μg ml–1 100 μg ml–1 25 μg ml–1 50 μg ml–1 100 μg ml–1 25 μg ml–1 50 μg ml–1 100 μg ml–1 25 μg ml–1 50 μg ml–1 100 μg ml–1
S.D.*
3.00
1.00
3.33
1.16
3.00
0.58
7.33
1.16
7.00
1.73
7.00
1.73
6.67
1.16
8.00
1.00
5.33
0.58
6.67
1.16
5.00
1.00
5.67
0.58
4.33
0.58
7.33
0.58
6.00
0.00
3.67
1.16
4.67
1.16
4.00
0.00
6.00
0.00
3.67
1.16
2.00
0.00
4.67
1.16
3.33
0.58
3.67
0.58
8.00
1.00
7.33
0.58
8.33
0.58
S.D.*
6.67
0.58
7.67
0.58
7.67
S.D.*
10.33
0.58
11.33
0.58
11.00
0.58
17.67
0.58
17.00
2.65
15.67
2.89
16.33
2.52
16.33
0.58
14.67
1.53
15.00
0.00
14.33
1.53
14.00
1.73
18.67
0.58
17.67
1.16
15.33
1.16
12.33
0.58
13.00
0.00
10.67
2.68
12.67
0.58
11.67
0.58
7.67
1.16
13.00
1.00
7.33
1.16
9.00
1.00
17.67
1.16
17.00
1.00
17.33
1.16
S.D.*
2.00
0.00
4.67
1.16
6.33
0.58
6.33
0.58
5.33
1.16
4.67
1.16
6.67
0.58
7.67
0.58
6.67
0.58
8.33
0.58
8.67
1.16
9.00
1.00
7.33
0.58
6.67
1.16
4.67
1.16
3.67
0.58
4.00
0.00
1.33
0.58
3.00
1.00
3.33
0.58
0.33
0.58
1.67
0.58
0.67
0.58
1.33
0.58
7.33
1.53
8.00
1.00
6.67
1.16
S.D.*
5.33
1.16
7.33
S.D.*
9.33
0.58
13.67
0.58
13.00
1.00
17.00
1.00
16.33
0.58
14.67
0.58
17.33
0.58
17.33
1.16
15.33
1.16
16.33
0.58
15.67
1.53
15.33
0.58
18.67
0.58
18.00
1.73
14.67
0.58
11.67
1.53
11.33
2.31
10.67
1.16
12.33
0.58
12.67
1.53
7.00
1.73
11.33
0.58
7.33
0.58
8.00
1.00
18.33
0.58
17.33
1.53
17.67
1.16
S.D.*
1.67
0.58
2.00
0.00
1.33
0.58
6.00
1.00
6.00
0.00
4.67
0.58
6.33
0.58
5.33
1.16
7.33
1.16
4.67
1.16
5.33
1.16
5.33
0.58
4.33
1.53
6.33
1.16
7.67
1.16
6.00
1.00
3.33
1.53
1.67
0.58
2.33
0.58
4.00
0.00
1.33
0.58
3.00
1.00
1.67
0.58
1.67
0.58
8.33
1.16
6.67
0.58
5.33
0.58
S.D.*
5.67
0.58
6.00
1.00
4.67
S.D.*
11.33
1.53
12.67
1.16
10.33
1.16
17.33
0.58
17.33
1.53
15.33
0.58
17.00
1.00
16.67
0.58
18.00
1.73
15.33
0.58
15.00
1.00
16.33
1.53
18.00
1.00
17.33
1.53
18.00
2.00
15.00
1.00
10.67
0.58
9.00
0.00
10.67
0.58
12.00
0.00
8.33
1.53
11.33
0.58
10.67
0.58
8.33
1.53
19.00
1.73
16.67
0.58
16.33
0.58
41.00
3.00
–
S.D.*
2.67
0.58
3.00
0.00
1.67
0.57
5.67
0.58
5.33
0.58
5.33
0.58
4.33
0.58
5.33
0.58
6.33
0.58
4.33
0.58
5.33
0.58
6.00
0.00
4.00
0.00
3.33
0.58
4.33
0.58
2.67
0.58
2.33
0.58
2.33
0.58
3.33
0.58
2.00
0.00
1.33
0.58
2.67
0.58
2.67
0.58
1.33
0.58
6.33
0.58
6.33
0.58
6.67
0.58
S.D.*
5.67
0.58
5.33
0.58
4.67
S.D.*
11.33
0.58
11.00
1.00
10.33
1.53
18.33
1.53
17.33
0.58
16.33
1.16
15.67
0.58
17.00
1.00
16.67
0.58
14.67
0.58
17.00
1.00
16.67
0.58
14.67
0.58
14.33
0.58
16.00
1.00
12.33
0.58
11.33
1.16
11.00
1.00
12.67
0.58
9.67
1.16
6.33
0.58
12.33
0.58
10.67
1.53
8.33
0.58
17.67
0.58
17.00
1.00
18.33
0.58
40.67
1.53
–
3a
3b
3c
0.58
11.67
0.58
11.67
0.58
10.33
0.58
9.33
0.58
10.67
0.58
11.67
0.58
10.33
0.58
11.67
1.16
11.67
0.58
11.67
1.53
12.33
0.58
10.67
0.58
8.67
0.58
6.67
1.16
6.00
1.73
4.67
1.16
7.33
0.58
6.67
0.58
2.67
0.58
5.33
0.58
3.67
0.58
4.33
0.58
12.67
0.58
11.67
0.58
12.33
0.58
–
1.16
12.33
1.53
10.33
2.52
10.33
2.52
10.33
1.53
11.67
0.58
10.67
0.58
10.00
0.00
8.33
1.16
8.33
1.16
9.00
1.00
12.33
0.58
10.33
0.58
8.67
1.53
8.33
1.16
6.67
1.16
8.67
1.16
6.67
1.16
4.33
0.58
7.67
0.58
6.33
0.58
6.67
0.58
12.33
1.16
11.67
1.16
12.33
0.58
–
1.16
12.30
1.53
11.67
1.16
8.33
0.58
11.67
1.16
10.67
0.58
12.33
0.58
9.33
0.58
8.67
0.58
9.67
0.58
8.33
0.58
11.33
1.16
12.33
0.58
9.67
1.16
6.33
0.58
4.00
0.00
5.33
0.58
6.33
0.58
5.33
0.58
5.67
0.58
4.67
1.16
4.00
0.00
13.33
1.16
11.67
0.58
10.67
0.58
20.33
1.53
–
0.58
12.33
0.58
10.67
0.58
10.67
0.58
9.33
1.16
12.33
0.58
11.33
0.58
8.33
0.58
10.33
0.58
10.67
0.58
8.67
1.16
6.67
0.58
7.33
0.58
6.00
1.00
6.33
0.58
5.33
0.58
6.33
0.58
4.67
0.58
3.33
0.58
5.67
0.58
5.33
0.58
4.33
0.58
11.67
0.58
11.33
0.58
12.33
0.58
22.33
0.58
–
4a
4b
4c
5a
5b
5c
6a
6b
6c
7a
7b
7c
8a
8b
8c
9a
9b
9c
10a
10b
10c
11a
11b
11c
Vanco-
mycin
Amikacin
–
–
–
–
–
–
–
21.67
0.58
36.00
1.00
–
24.00
2.65
43.00
1.00
–
–
1 = Escherichia coli; 2 = Pseudomonas aeruginosa; 3 = Staphylococcus aureus; 4 = Bacillus subtilis; *S.D. = standard deviation; # = zone of inhibition in mm.

1054
V. Mathew et al. / European Journal of Medicinal Chemistry 41 (2006) 1048–1058
Table 4
#
Antifungal activities of compounds (3–11)
Compounds
C. albicans1
50 (μg ml–1
A. niger2
50 (μg ml–1
25 (μg ml–1
S.D.*
)
)
100 (μg ml–1
S.D.*
)
25 (μg ml–1
S.D.*
)
)
100 (μg ml–1
S.D.*
)
S.D.*
S.D.*
3a
3b
3c
4a
4b
4c
5a
5b
5c
6a
6b
6c
7a
7b
7c
8a
2.33 0.58
2.33 0.58
2.00 1.00
6.00 1.00
6.33 0.58
4.67 1.16
5.33 1.16
4.67 0.58
4.00 1.00
4.67 0.58
3.33 0.58
4.67 0.58
4.67 0.58
4.67 0.58
5.00 0.00
2.33 0.58
2.67 0.58
1.67 0.58
1.33 0.58
2.33 0.58
–
5.33 0.58
5.33 1.16
5.00 1.00
10.33 0.58
11.00 1.00
11.33 0.58
16.33 1.53
17.00 1.00
13.33 1.16
16.33 0.58
16.33 1.16
14.33 0.58
15.00 1.00
14.33 0.58
15.67 0.58
16.00 0.00
16.33 1.53
16.33 0.58
11.33 0.58
13.33 0.58
10.33 0.58
10.33 1.16
11.33 1.53
5.33 0.58
11.33 1.53
11.00 2.00
8.67 0.58
18.33 1.16
17.67 1.16
17.33 0.58
34.67 1.16
2.33 0.58
1.67 0.58
2.33 0.58
3.33 0.58
5.67 0.58
6.33 0.58
4.67 0.58
5.67 0.58
5.33 0.58
5.67 0.58
5.33 0.58
4.33 0.58
4.67 0.58
7.33 0.58
12.33 0.58
10.67 1.53
10.33 0.58
16.33 1.16
15.67 1.16
16.33 0.58
14.67 0.58
17.00 1.00
16.33 0.58
17.33 0.58
17.00 0.00
16.00 1.00
16.33 2.08
16.33 1.16
17.67 1.16
10.67 1.16
11.33 0.58
9.33 1.16
12.00 1.73
12.67 0.58
5.33 1.53
12.33 0.58
9.33 1.53
9.00 1.00
18.33 2.08
18.33 1.53
16.00 1.73
37.00 2.00
10.33 1.16
10.67 0.58
8.33 0.58
9.33 0.58
9.33 0.58
6.67 0.58
7.33 0.58
6.33 0.58
7.67 0.58
7.67 0.58
7.33 0.58
7.67 0.58
5.67 0.58
5.67 0.58
4.33 0.58
4.00 0.00
5.00 1.00
2.33 0.58
4.67 0.58
4.33 0.58
4.33 0.58
13.33 1.16
11.67 0.58
10.67 0.58
20.33 0.58
10.00 1.00
10.67 0.58
8.67 0.58
10.33 0.58
9.67 0.58
10.33 0.58
10.00 0.00
9.33 0.58
9.67 0.58
9.67 1.16
10.67 0.58
5.67 0.58
5.33 0.58
4.67 0.58
5.67 0.58
6.00 0.00
2.67 1.16
5.67 0.58
4.33 0.58
4.67 0.58
13.33 1.16
12.67 1.16
9.67 1.16
21.67 2.08
4.67 0.58
5.33 0.58
5.33 1.16
6.33 0.58
1.67 0.58
1.33 0.58
1.33 0.58
2.33 0.58
3.33 0.58
–
2.33 0.58
1.67 0.58
1.67 0.58
6.67 0.58
6.67 0.58
4.67 0.58
–
8b
8c
9a
9b
9c
10a
10b
10c
11a
11b
11c
Griseofulvin
1.67 0.58
1.33 0.58
1.33 0.58
6.33 0.58
5.67 0.58
5.33 0.58
–
*S.D. = standard deviation; 1 = Candida albicans; 2 = Aspergillus niger.
4.2.9. 3-[2-(N-methyl amino) phenyl]-
6-(2-phenyl-4-quinolinyl)-1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazole (4b)
4.2.11. 3-[4-(N,N-dimethyl amino) phenyl]-
6-(2-methyl-4-quinolinyl)-1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazole (5a)
M.p.: 184°C yield (%): 58%; IR (KBr) n (cm−1): 3050 (aro-
matic CH stretching), 1618 (C=N stretching), 1594, 1480,
1464 (C=C ring stretch), 2932, 2875 (methyl CH stretch),
M.p.: 208°C yield (%): 60%; IR (KBr) n (cm−1): 3329 (NH
stretching), 1610 (C=N stretching), 3090 (aromatic CH stretch-
ing), 1579, 1510, 1467, 1428 (C=C ring stretching), 2980,
2837 (methyl CH stretching), 1280 (N–N=C), 1320 (C–N
1
1331 (C–N stretching), 1261 (N–N=C); H NMR δ: 6.8–8.2
1
(m, Ar-H), 3.1 (s, 6H, N (CH3)2), 2.46 (s, 2H, CH3); MS m/z
[% rel. int.]: 386 [32] (M+). Calcd. (%) for C21H18N6S: C;
65.26, H; 4.69, N; 21.75, S; 8.30. Found: C; 65.31, H; 4.69, N;
21.73, S; 8.30.
stretching); H NMR δ: 7.3–8.5 (m, Ar-H), 6.6–6.7 (m, 2H of
Ar), 6.42 (q, 1H, NH in NH–CH3), 2.9 (d, 3H, CH3 in
NH–CH3); MS m/z [% rel. int.]: 434 [18] (M+). Calcd. (%) for
C25H18N6S: C; 69.10, H; 4.18, N; 19.34, S; 7.38. Found: C;
69.06, H; 4.18, N; 19.35, S; 7.38.
4.2.12. 3-[2-(N-methyl amino) phenyl]-
6-(2-methyl-4-quinolinyl)-1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazole (5b)
4.2.10. 3-(1-Naphthyl methyl)-
6-(2-phenyl-4-quinolinyl)-1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazole (4c)
M.p.: 200°C yield (%): 56%; IR (KBr) n (cm−1): 3329 (NH
stretching), 1610 (C=N stretching), 3090 (aromatic CH stretch-
ing), 1579, 1510, 1467, 1428 (C=C ring stretching), 2980,
2837 (methyl CH stretching), 1280 (N–N=C), 1320 (C–N
M.p.: 198°C yield (%): 60%; IR (KBr) n (cm−1): 3080 (aro-
matic CH stretching), 1612 (C=N stretching), 1518, 1483
(C=C ring stretching), 2930, 2850 (methyl CH stretch), 1280
1
stretching); H NMR δ: 7.3–8.3 (m, Ar-H), 6.6–6.7 (m, 2H of
1
(N–N=C); H NMR δ: 7.2–8.4 (m, Ar-H), 5.02 (s, 2H, CH2);
Ar), 6.40 (q, 1H, NH in NH–CH3), 2.94 (d, 3H, CH3 in
NH–CH3), 2.44 (s, 2H, CH3); MS m/z [% rel. int.]: 372 [36]
(M+). Calcd. (%) for C20H16N6S: C; 64.50, H; 4.33, N; 22.56,
S; 8.61. Found: C; 64.43, H; 4.33, N; 22.58, S; 8.61.
MS m/z [% rel. int.]: 469 [24] (M+). Calcd. (%) for
C29H19N5S: C; 74.18, H; 4.08, N; 14.91, S; 6.83. Found: C;
74.09, H; 4.06, N; 14.92, S; 6.83.

V. Mathew et al. / European Journal of Medicinal Chemistry 41 (2006) 1048–1058
1055
4.2.13. 3-(1-Naphthyl methyl)-
4.2.17. 3-(1-Naphthyl methyl)-
6-(2-methyl-4-quinolinyl)-1,2,4-triazolo[3,4-b]-1,3,4-
6-(2,6-dihydroxy-4-pyridinyl)-1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazole (5c)
thiadiazole (6c)
M.p.: 196°C yield (%): 60%; IR (KBr) n (cm−1): 3080 (aro-
matic CH stretching), 1612 (C=N stretching), 1518, 1483
(C=C ring stretching), 2930, 2850 (methyl CH stretch), 1280
M.p.: 284°C yield (%): 50%; IR (KBr) n (cm−1): 3456 (OH
stretching), 3045 (aromatic CH stretching), 1610 (C=N stretch-
ing), 1572, 1484, 1458 (C=C ring stretch), 2970, 2920 (methyl
1
1
(N–N=C); H NMR δ: 7.2–8.2 (m, Ar-H), 5.0 (s, 2H, CH2),
CH stretch), 1239 (C–O stretching), 1280 (N–N=C); H NMR
2.44 (s, 2H, CH3); MS m/z [% rel. int.]: 407 [32] (M+).
Calcd. (%) for C24H17N5S: C; 70.74, H; 4.21, N; 17.19, S;
7.87. Found: C; 70.68, H; 4.21, N; 17.20, S; 7.87.
δ: 7.4–8.2 (m, Ar-H), 6.3 (s, 2H, OH), 4.8 (s, 2H, CH2); MS m/
z [% rel. int.]: 375 [36] (M+). Calcd. (%) for C19H13N5O2S: C;
60.79, H; 3.49, N; 18.66, S; 8.54. Found: C; 60.71, H; 3.49, N;
18.70, S; 8.54.
4.2.14. Synthesis of 3-aryl/aralkyl substituted-
6-(2-chloro/2,6-dihydroxy-4-pyridinyl)-1,2,4-triazolo[3,4-b]-
1,3,4-thiadiazoles 6 and 7(a–c)
4.2.18. 3-[4-(N,N-dimethyl amino) phenyl]-
6-(2-chloro-4-pyridinyl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole
(7a)
M.p.: 276°C yield (%): 62%; IR (KBr) n (cm−1): 3045,
3010 (aromatic CH stretching), 1601 (C=N stretching), 1541,
1494, 1455 (C=C ring stretch), 2919, 2847 (methyl CH
Equimolar proportions of respective triazole 3(a–c)
(0.02 M) and 2-chloro/2,6-dihydroxy-pyridinyl-4-carboxylic
acid (0.02 M), were dissolved in 10 ml of dry phosphorous
oxy chloride and the resulting solution was refluxed for 10 h.
Cooled the reaction mixture to room temperature and then gra-
dually poured onto crushed ice with stirring. Finely powdered
potassium carbonate and the required amount of solid potas-
sium hydroxide were added to the solution with stirring till
the pH of the mixture was raised to 8, to remove the excess
of phosphorous oxychloride. On allowing the reaction mixture
to stand overnight, solid was separated. It was filtered, washed
thoroughly with cold water, dried and recrystallized from aqu-
eous DMF.
1
stretch), 1329 (C–N stretching), 1275 (N–N=C); H NMR δ:
6.82, 7.86 (2d, 4H of Ar), 7.34 (s, 1H of pyridine), 7.62 (d,
1H of pyridine), 8.12 (d, 1H of pyridine); MS m/z [% rel.
int.]: 356 [34] (M+), 358 [12] (M + 2). Calcd. (%) for
C16H13N6SCl: C; 53.85, H; 3.67, N; 23.55, S; 8.99. Found: C;
53.90, H; 3.67, N; 23.56, S; 9.00.
4.2.19. 3-[2-(N-methyl amino) phenyl]-
6-(2-chloro-4-pyridinyl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole
(7b)
M.p.: 292°C yield (%): 58%; IR (KBr) n (cm−1): 3317 (NH
stretching), 3076, 3034 (aromatic CH stretching), 1607 (C=N
stretching), 1590, 1538, 1478, 1448 (C=C ring stretch), 2970,
2934 (methyl CH stretch), 1331 (C–N stretching), 1275 (N–
4.2.15. 3-[4-(N,N-dimethyl amino) phenyl]-
6-(2,6-dihydroxy-4-pyridinyl)-1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazole (6a)
M.p.: 288°C yield (%): 55%; IR (KBr) n (cm−1): 3423 (OH
stretching), 3045, 3010 (aromatic CH stretching), 1601 (C=N
stretching), 1541, 1494, 1455 (C=C ring stretch), 2919, 2847
(methyl CH stretch), 1275 (N–N=C), 1328 (C–N stretching),
1
N=C); H NMR δ: 7.24, 7.68 (2d, 2H of Ar), 6.7–6.8 (m, 2H
of Ar), 7.40 (s, 1H of pyridine), 7.54 (d, 1H of pyridine), 8.18
(d, 1H of pyridine), 6.38 (q, 1H, NH in NH–CH3), 2.64 (d, 3H,
CH3 in NH–CH3); MS m/z [% rel. int.]: 342 [45] (M+), 344
[14] (M + 2). Calcd. (%) for C15H11N6SCl: C; 52.55, H; 3.23,
N; 24.52, S; 9.35. Found: C; 52.50, H; 3.23, N; 24.50, S; 9.35.
1
1225 (C–O stretching); H NMR δ: 6.78, 7.86 (2d, 4H of Ar),
8.05 (s, 2H of pyridine), 6.32 (s, 2H, OH); MS m/z [% rel. int.]:
354 [40] (M+). Calcd. (%) for C16H14N6O2S: C; 54.23, H;
3.98, N; 23.71, S; 9.05. Found: C; 54.19, H; 3.98, N; 23.74, S;
9.04.
4.2.20. 3-(1-Naphthyl methyl)-
6-(2-chloro-4-pyridinyl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole
(7c)
4.2.16. 3-[2-(N-methyl amino) phenyl]-
6-(2,6-dihydroxy-4-pyridinyl)-1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazole (6b)
M.p.: 284°C yield (%): 59%; IR (KBr) n (cm−1): 3045 (aro-
matic CH stretching), 1610 (C=N stretching), 1572, 1484, 1458
(C=C ring stretch), 2970, 2920 (methyl CH stretch), 1239 (C–O
M.p.: 292°C yield (%): 55%; IR (KBr) n (cm−1): 3443 (OH
stretching), 3317 (NH stretching), 3076, 3034 (aromatic CH
stretching), 1607 (C=N stretching), 1590, 1538, 1478, 1448
(C=C ring stretch), 2970, 2934 (methyl CH stretch), 1334
(C–N stretching), 1262 (asymmetric C–O stretching), 1075
1
stretching), 1280 (N–N=C); H NMR δ: 7.4–8.12 (m, Ar-H),
4.64 (s, 2H, CH2); MS m/z [% rel. int.]: 377 [36] (M+), 379
[12] (M + 2). Calcd. (%) for C19H12N5SCl: C; 60.40, H; 3.20,
N; 18.53, S; 8.49. Found: C; 60.36, H; 3.20, N; 18.53, S; 8.49.
1
(symmetric C–O stretching), 1275 (N–N=C); H NMR δ: 7.3,
4.2.21. Synthesis of 3-aryl/aralkyl substituted-
6-(4-hydroxy-3-methoxy cinnamyl)-
1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles 8(a–c)
Respective triazole 3(a–c), (0.02 M) and 4-
hydroxy-3-methoxy cinnamic acid (0.02 M) was added to
7.8 (2d, 2H of Ar), 6.7–6.8 (m, 2H of Ar), 8.33 (d, 2H of Ar′),
6.05 (s, 2H, OH), 6.42 (q, 1H, NH in NH–CH3), 2.94 (d, 3H,
CH3 in NH–CH3); MS m/z [% rel. int.]: 340 [26] (M+). Calcd.
(%) for C15H12N6O2S: C; 52.93, H; 3.55, N; 24.69, S; 9.42.
Found: C; 52.89, H; 3.55, N; 24.71, S; 9.42.

1056
V. Mathew et al. / European Journal of Medicinal Chemistry 41 (2006) 1048–1058
10 ml of dry phosphorous oxy chloride and the solution was
refluxed for 5 h. The reaction mixture was cooled to room
temperature and then gradually poured onto crushed ice with
stirring. Finely powdered potassium carbonate and the required
amount of solid potassium hydroxide were added till the pH of
the mixture was raised to 8, to remove the excess of phosphor-
ous oxychloride. The mixture was allowed to stand overnight
and solid was separated. It was filtered, washed thoroughly
with cold water, dried and recrystallized from hot ethanol.
4.2.25. Synthesis of 3-aryl/aralkyl substituted-
6-(2-amino-3,5-dibromo phenyl)-1,2,4-triazolo[3,4-b]-1,3,4-
thiadiazoles 9(a–c)
Respective triazole 3(a–c) (0.02 M) was dissolved in dry
phosphorous oxy chloride (10 ml) and to the above solution,
added 2-amino-3, 5-dibromo benzoic acid (0.02 M). The
resulted mixture was refluxed for 5 h. The reaction mixture
was cooled to room temperature and the mixture was gradually
poured onto crushed ice with stirring. Finely powdered potas-
sium carbonate and the required amount of solid potassium
hydroxide were added until the pH of the mixture was raised
to 8, to remove the excess of phosphorous oxychloride. Solid
was separated on allowing the mixture to stand overnight. It
was filtered, washed thoroughly with cold water, dried and
recrystallized from aqueous DMF.
4.2.22. 3-[4-(N,N-dimethyl amino) phenyl]-
6-(4-hydroxy-3-methoxy cinnamyl)-
1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (8a)
M.p.: 206°C yield (%): 60%; IR (KBr) n (cm−1): 3448 (OH
stretching), 3075 (aromatic CH stretching), 1609 (C=N stretch-
ing), 1578, 1540, 1481, 1450 (C=C ring stretch), 2970, 2860
(methyl CH stretch), 1260 (asymmetric C–O–C stretching),
1021 (symmetric C–O–C stretching), 1286 (N–N=C), 1360
4.2.26. 3-[4-(N,N-dimethyl amino) phenyl]-
6-(2-amino-3,5-dibromo phenyl)-
1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (9a)
1
(C–N stretching); H NMR δ: 6.85, 8.1 (2d, 2H of Ar), 7.1,
M.p.: 224°C yield (%): 55%; IR (KBr) n (cm−1): 3280 (NH
stretching), 3080, (aromatic CH stretching), 1611 (C=N
stretching), 1587, 1510, 1467 (C=C ring stretch), 2970, 2838
(methyl CH stretch), 1316 (C–N stretching), 1285 (N–N=C);
1H NMR δ: 6.9, 8.0 (2d, 2H of Ar), 7.7, 7.9 (2s, 2H of Ar′),
6.7 (s, 2H, NH2), 3.0 (s, 6H, N (CH3)2); MS m/z [% rel. int.]:
494 [28] (M+), 496[36] (M + 2), 498 [26] (M + 4). Calcd. (%)
for C17H14N6SBr2: C; 41.32, H; 2.86, N; 17.01, S; 6.49.
Found: C; 41.37, H; 2.86, N; 16.99, S; 6.50.
7.82 (2d, 2H of Ar′), 7.52 (s, 1H of Ar′), 3.0 (s, 6H, N
(CH3)2), 3.89 (d, 3H, OCH3), 6.8 (d, 1H, CH), 6.3 (d, 1H, CH),
6.1 (s, 1H, OH); MS m/z [% rel. int.]: 393 [44] (M+). Calcd.
(%) for C20H19N5O2S: C; 61.05, H; 4.88, N; 17.80, S; 8.15.
Found: C; 60.97, H; 4.88, N; 17.78, S; 8.14.
4.2.23. 3-[2-(N-methyl amino) phenyl]-
6-(4-hydroxy-3-methoxy cinnamyl)-1,2,4-triazolo[3,4-b] 1,3,4-
thiadiazole (8b)
M.p.: 170°C yield (%): 56%; IR (KBr) n (cm−1): 3444 (OH
stretching), 3312 (NH stretching), 3090 (aromatic CH stretch-
ing), 1612 (C=N stretching), 1590, 1560, 1485, 1460 (C=C
ring stretch), 2985, 2840 (methyl CH stretch), 1264 (asym-
metric C–O–C stretching), 1021 (symmetric C–O–C stretch-
4.2.27. 3-[2-(N-Methyl amino) phenyl]-
6-(2-amino-3,5-dibromo phenyl)-
1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (9b)
M.p.: 218°C yield (%): 58%; IR (KBr) n (cm−1): 3298 (NH
stretching), 3086 (aromatic CH stretching), 1614 (C=N stretch-
ing), 1582, 1475, 1456 (C=C ring stretch), 2976, 2845 (methyl
1
ing), 1286 (N–N=C), 1360 (C–N stretching); H NMR δ: 7.3,
7.7 (2d, 2H of Ar), 6.8–6.9 (m, 2H of Ar), 7.02, 7.86 (2d, 2H
of Ar′), 7.50 (s, 1H of Ar′), 3.9 (d, 3H, OCH3 of Ar′), 6.44 (q,
1H, NH in NH–CH3), 2.88 (d, 3H, CH3 in NH–CH3), 6.62 (d,
1H, CH), 5.82 (d, 1H, CH), 6.12 (s, 1H, OH); MS m/z [% rel.
int.]: 379 [38] (M+). Calcd. (%) for C19H17N5O2S: C; 60.14,
H; 4.52, N; 18.46, S; 8.45. Found: C; 60.06, H; 4.52, N; 18.45,
S; 8.44.
1
CH stretch), 1280 (N–N=C), 1328 (C–N stretching); H NMR
δ: 7.3, 7.7 (2d, 2H of Ar), 6.8–6.9 (m, 2H of Ar), 7.63, 7.9 (2s,
2H of Ar′), 6.44 (q, 1H, NH in NH–CH3), 2.88 (d, 3H, CH3 in
NH–CH3), 6.62 (s, 2H, NH2), MS m/z [% rel. int.]: 480 [28]
(M+), 482 [38] (M + 2), 484 [24] (M + 4). Calcd. (%) for
C16H12N6SBr2: C; 40.02, H; 2.52, N; 17.50, S; 6.68. Found: C;
39.99, H; 2.52, N; 17.53, S; 6.68.
4.2.24. 3-(1-Naphthyl methyl)-6-(4-hydroxy-3-methoxy
cinnamyl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (8c)
4.2.28. 3-(1-Naphthyl methyl)-6-(2-amino-3,5-dibromo
M.p.: 188°C yield (%): 56%; IR (KBr) n (cm−1): 3438 (OH
stretching), 3060 (aromatic CH stretching), 1606 (C=N stretch-
ing), 1544, 1478, 1453 (C=C ring stretch), 2950, 2920 (methyl
CH stretch), 1235 (asymmetric C–O–C stretching), 1070 (sym-
metric C–O–C stretching), 1288 (N–N=C); 1H NMR δ: 7.4–7.7
(m, 7H, Ar-H), 7.98, 7.88, 8.3 (m, 3H of Ar), 3.85 (d, 3H,
OCH3), 4.84 (s, 2H, CH2), 6.8 (d, 1H, CH), 6.32 (d, 1H,CH),
6.1 (s, 1H, OH); MS m/z [% rel. int.]: 414 [26] (M+). Calcd.
(%) for C23H18N4O2S: C; 66.65, H; 4.38, N; 13.52, S; 7.74.
Found: C; 66.56, H; 4.38, N; 13.53, S; 7.74.
phenyl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (9c)
M.p.: 210°C yield (%): 56%; IR (KBr) n (cm−1): 3273 (NH
stretching), 3090, 3047 (aromatic CH stretching), 1612 (C=N
stretching), 1585, 1575, 1484, 1436 (C=C ring stretch), 2964
1
(methylene CH stretch), 1290 (N–N=C); H NMR δ: 7.3–7.6
(m, 4H of Ar), 7.7–7.9 (m, 4H, Ar-H), 8.3 (1d, 1H of Ar), 5.78
(s, 2H, NH2), 4.93 (s, 2H, CH2); MS m/z [% rel. int.]: 515 [20]
(M+), 517 [28] (M + 2), 519 [18] (M + 4). Calcd. (%) for
C20H13N5SBr2: C; 46.62, H; 2.54, N; 13.59, S; 6.22. Found: C;
46.70, H; 2.54, N; 13.58, S; 6.23.

V. Mathew et al. / European Journal of Medicinal Chemistry 41 (2006) 1048–1058
1057
4.2.29. Synthesis of 3-aryl/aralkyl substituted-
6-(2-methyl-4-nitro phenyl)1,2,4-
triazolo[3,4-b]-1,3,4-thiadiazoles 10(a–c)
4.2.33. Synthesis of 3-aryl/aralkyl substituted-
6-[2-(2,4-dichloro phenoxy) ethyl] 1,2,4-
triazolo[3,4-b]-1,34-thiadiazoles 11(a–c)
An equimolar mixture of respective triazole 3(a–c)
(0.02 M), 2-methyl-4-nitro benzoic acid (0.02 M) in dry phos-
phorous oxy chloride (10 ml) was refluxed for 4 h. The reac-
tion mixture was cooled to room temperature and then gradu-
ally poured onto crushed ice with stirring. Finely powdered
potassium carbonate and the required amount of solid potas-
sium hydroxide were added till the pH of the mixture was
raised to 8, to remove the excess of phosphorous oxychloride.
The mixture was allowed to stand overnight and solid was
separated. It was filtered, washed thoroughly with cold water,
dried and recrystallized from hot ethanol.
To the equimolar proportions of respective triazole 3(a–c),
(0.02 M) and 2-(2,4-dichloro phenoxy) propionic acid
(0.02 M), 10 ml of dry phosphorous oxy chloride was added.
The resulted mixture was further refluxed continously for 4 h
on a water bath. The reaction mixture was cooled to room tem-
perature and then gradually poured onto crushed ice with stir-
ring. Finely powdered potassium carbonate and the required
amount of solid potassium hydroxide were added till the pH
of the mixture was raised to 8, to remove the excess of phos-
phorous oxychloride. The mixture was allowed to stand over-
night and solid was separated. It was filtered, washed thor-
oughly with cold water, dried and recrystallized from
petroleum ether.
4.2.30. 3-[4-(N,N-dimethyl amino) phenyl]-6-(2-nitro-4-methyl
phenyl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (10a)
4.2.34. 3-[4-(N,N-dimethyl amino) phenyl]-6-[2-(2,4-dichloro
phenoxy) ethyl]-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (11a)
M.p.: 184°C yield (%): 62%; IR (KBr) n (cm−1): 3084 (aro-
matic CH stretching), 1606 (C=N stretching), 1587, 1556,
1475, 1451 (C=C ring stretch), 2956, 2845 (methyl CH
stretch), 1284 (N–N=C), 1535 (asymmetric Ar–NO2 stretch),
1339 (symmetric Ar–NO2 stretch); 1H NMR δ: 6.82, 7.94
(2d, 4H of Ar), 7.74, 8.1 (d, 2H of Ar′), 7.80 (s, 1H of Ar′),
2.62 (s, 3H, CH3); MS m/z [% rel. int.]: 380 [34] (M+). Calcd.
(%) for C18H16N6O2S: C; 56.83, H; 4.24, N; 22.09, S; 8.43.
Found: C; 56.79, H; 4.24, N; 22.11, S; 8.44.
M.p.: 114°C yield (%): 65%; IR (KBr) n (cm−1): 3085 (aro-
matic CH stretching), 1611 (C=N stretching), 1584, 1543,
1484, 1452 (C=C ring stretch), 2954, 2842 (methyl CH
1
stretch), 1278 (N–N=C), 1357 (C–N stretching); H NMR δ:
6.8, 8.1 (2d, 4H of Ar), 6.98, 7.42 (2d, 2H of Ar′), 7.16 (s,
1H of Ar′), 5.64 (q, 1H, CH in –CH–CH3), 3.0 (s, 6H, N
(CH3)2), 1.9 (d, 1H, CH3 in CH–CH3); MS m/z [% rel. int.]:
434 [40] (M+), 436[32] (M + 2), 438 [14] (M + 4). Calcd. (%)
for C19H17N5OCl2S: C; 52.54, H; 3.95, N; 16.12, S; 7.38.
Found: C; 52.48, H; 3.95, N; 16.10, S; 7.38.
4.2.31. 3-[2-(N-methyl amino) phenyl]-6-(2-nitro-4-methyl
phenyl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (10b)
M.p.: 180°C yield (%): 60%; IR (KBr) n (cm−1): 3298 (NH
stretching), 3086 (aromatic CH stretching), 1614 (C=N stretch-
ing), 1582, 1546, 1479, 1456 (C=C ring stretch), 2976, 2845
(methyl CH stretch), 1280 (N–N=C), 1530 (asymmetric
4.2.35. 3-[2-(N-methyl amino) phenyl]-6-[2-(2,4-dichloro
phenoxy) ethyl]-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (11b)
M.p.: 92°C yield (%): 64%; IR (KBr) n (cm−1): 3086 (aro-
matic CH stretching), 3308 (NH stretching), 1614 (C=N
stretching), 1575, 1549, 1477, 1446 (C=C ring stretch), 2948,
2832 (methyl CH stretch), 1283 (N–N=C), 1361 (C–N
1
Ar–NO2 stretch), 1330 (symmetric Ar–NO2 stretch); H NMR
δ: 7.3, 7.7 (2d, 2H of Ar), 6.7–6.8 (m, 2H of Ar), 7.8, 8.1 (d,
2H of Ar′), 7.88 (s, 1H of Ar′), 6.42 (q, 1H, NH in NH–CH3),
1.86 (d, 3H, CH3 in NH–CH3), 2.64 (s, 3H, CH3); MS m/z [%
rel. int.]: 366 [40] (M+). Calcd. (%) for C17H14N6O2S: C;
55.73, H; 3.85, N; 22.94, S; 8.75. Found: C; 55.68, H; 3.85, N;
22.93, S; 8.75.
1
stretching); H NMR δ: 7.3, 7.7 (2d, 2H of Ar), 8.3, 8.4, 8.8
(3d, 3H of Ar′), 6.7–6.8 (m, 2H of Ar), 5.7 (q, 1H, NH in
NH–CH3), 4.8 (q, 1H, CH in CH–CH3), 1.9 (d, 3H, CH3 in
CH–CH3), 1.7 (d, 3H, CH3 in NH–CH3); MS m/z [% rel.
int.]: 420 [38] (M+), 422 [26] (M + 2), 424 [12] (M + 4).
Calcd. (%) for C18H15N5OCl2S: C; 51.44, H; 3.60, N; 16.66,
S; 7.63. Found: C; 51.52, H; 3.60, N; 16.67, S; 7.64.
4.2.32. 3-(1-Naphthyl methyl)-6-(2-nitro-4-methyl phenyl)-
1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (10c)
M.p.: 156°C yield (%): 65%; IR (KBr) n (cm−1): 3069 (aro-
matic CH stretching), 1608 (C=N stretching), 1587, 1545,
1463, 1431 (C=C ring stretch), 2916, 2848 (methyl CH
stretch), 1525 (asymmetric Ar–NO2 stretch), 1340 (symmetric
4.2.36. 3-(1-Naphthyl methyl)-6-[2-(2,4-dichloro phenoxy)
ethyl]-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (11c)
M.p.: 86°C yield (%): 55%; IR (KBr) n (cm−1): 3070 (aro-
matic CH stretching), 1607 (C=N stretching), 1586, 1538,
1477 (C=C ring stretch), 2982, 2929 (methylene CH stretch),
1
Ar–NO2 stretch); H NMR δ: 7.3–7.6 (m, 4H of Ar), 7.8–7.9
1
(m, 4H, Ar-H), 8.3 (1d, 1H of Ar), 8.10 (d, 1H of Ar′), 2.68
(2s, 6H, CH3), 4.9 (s, 2H, CH3); MS (m/z, %): 401 (M+); MS
m/z [% rel. int.]: 401 [38] (M+). Calcd. (%) for C21H15N5O2S:
C; 62.83, H; 3.77, N; 17.45, S; 7.99. Found: C; 62.78, H; 3.77,
N; 17.46, S; 7.99.
1284 (N–N=C); H NMR δ: 6.8, 7.05 (2d, 2H of Ar′), 7.1 (s,
1H of Ar′), 7.3–7.6 (m, 4H of Ar), 7.8, 7.9, 8.3 (3d, 3H of Ar),
5.5 (q, 1H, CH in CH–CH3), 1.78 (d, 3H, CH3 in CH–CH3),
4.9 (s, 2H, CH2); MS m/z [% rel. int.]: 455 [44] (M+), 457 [36]
(M + 2), 459 [14] (M + 4). Calcd. (%) for C22H16N4OCl2S: C;

1058
V. Mathew et al. / European Journal of Medicinal Chemistry 41 (2006) 1048–1058
[4] H. Saad, Indian J. Chem. 35B (1996) 980.
58.03, H; 3.54, N; 12.30, S; 7.04. Found: C; 57.96, H; 3.54, N;
12.31, S; 7.04.
[5] X.P. Hui, C.H. Zang, Q. Wang, Q. Zhang, Indian J. Chem. 41B (2002)
2176.
[6] N. Tiwari, B. Chaturvedi, Nizamuddin, Agric. Biol. Chem. 52 (1988)
1229.
Acknowledgements
[7] A.R. Prasad, T. Ramlingam, A. Bhaskar Rao, P.V. Diwan, P.B. Sattur,
Indian J. Chem. 25B (1986) 566.
The authors are thankful to IISc, Bangalore, IIT, Chennai
and STIC, Cochin, for the Spectral analysis. The authors are
also thankful to the Chairman, Department of Chemistry,
Kuvempu University, for providing laboratory facilities.
[8] V. Srivastava, S. Sen, R. Shekar, Indian J. Chem. 33B (1994) 344.
[9] M. Imtiaz Hussain, V. Kumar, Indian J. Chem. 31B (1992) 673.
[10] Z.Y. Zhang, X.W. Sun, C.H. Chu, L. Zhao, J. Chin. Chem. Soc. 44
(1997) 535.
[11] K.C. Joshi, S. Giri, J. Indian Chem. Soc. 40 (1963) 42.
[12] M.C. Goldsworthy, Phytopath 32 (1942) 498.
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