Synthesis and biological evaluation of some Schiff bases of 4-amino-5-(4-methylsulfonyl)benzyl-2,4-dihydro-3H-[1,2,4]-triazole-3-thione

Article abstract of DOI:10.1007/s00044-012-0294-5

The basic nucleus 4-amino-5-[4-(methylsulfonyl)benzyl]-2,4-dihydro-3H-[1,2, 4]-triazole-3-thione was prepared by cyclisation of potassium dithiocarbazinate with hydrazine hydrate using ethanol as solvent under reflux condition. The compound which has been

Full text of DOI:10.1007/s00044-012-0294-5

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-012-0294-5
ORIGINAL RESEARCH
Synthesis and biological evaluation of some Schiff bases of 4-
amino-5-(4-methylsulfonyl)benzyl-2,4-dihydro-3H-[1,2,4]-triazole-
3-thione
•
V. Sumangala Boja Poojary N. Chidananda
•
•
•
T. Arulmoli Shalini Shenoy
Received: 21 February 2012 / Accepted: 20 October 2012
Ó Springer Science+Business Media New York 2012
Abstract The basic nucleus 4-amino-5-[4-(methylsulfo-
nyl)benzyl]-2,4-dihydro-3H-[1,2,4]-triazole-3-thione was
prepared by cyclisation of potassium dithiocarbazinate
with hydrazine hydrate using ethanol as solvent under
reflux condition. The compound which has been synthe-
sized successfully was subjected to addition reaction with
different aldehydes to synthesize Schiff bases. The com-
pounds were confirmed by spectroscopic methods (IR,
NMR, and Mass). In order to ascertain the pharmaceutical
application, the selective pharmacological screening of the
derivatives was carried out according to the standard pro-
cedures. The compounds were screened for their cytotoxic
activity and antimicrobial activity.
considerable attention owing to their synthetic and effec-
tive biological importance. [1,2,4]-Triazole moieties have
been incorporated into variety of therapeutically interesting
drug candidates including antiviral (Ribavirin), anti
migraine (Rizatriptan), antifungal (Flucanazole), and anti-
anxiety compounds (Alprazolam). Moreover, sulfur con-
taining heterocyclic compounds represent an important
group of compounds that are promising on practical
application (Holla et al., 2003; Wu et al., 2007). The
pharmacological importance of heterocycles derived from
[1,2,4]-triazole paved the way toward active research in a
triazole chemistry. As a result, variety of new compounds
was being added to this field every year. A number
of attempts were made to improve the activity of the
compounds by varying the substituents on the triazole
nucleus (Ragenovic et al., 2001; Mathew et al., 2007;
Banachiewicz et al., 2004). Among these, the mercapto and
amino group substituted [1,2,4]-triazole ring system have
been reported for antituberculosis (Patole et al., 2006;
Hearn and Cynamon, 2004), anticancer (Ren et al., 2002;
Kuzmin et al., 2005), analgesic and anti-inflammatory
(Ronad et al., 2008; Bhandari et al., 2008), anticonvulsant
(Verma et al., 2004; Sridhar et al., 2002; Kaplan et al.
1980), and antibacterial and antifungal (Jarrahpour et al.,
2007; Shi et al., 2007) activities. The development of
antimicrobial resistance has increased in this century and
there is a need for synthesis of new antimicrobial agents
which will be more selective, potent, and less toxic com-
pared to the used drugs in clinical treatment. These
observations prompted us to synthesize and study the
cytotoxic activity and antimicrobial activity of some series
of Schiff bases containing [1,2,4]-triazole ring system on
the same molecule due to the importance of triazole and
Schiff bases in biological systems by means of antimicro-
bial activity.
Keywords Triazoles ꢀ Schiff base ꢀ Cytotoxicity ꢀ
Antimicrobial activity
Introduction
In the last two decades, the chemistry of [1,2,4]-triazole
and their fused heterocyclic derivatives have received
Electronic supplementary material The online version of this
article (doi:10.1007/s00044-012-0294-5) contains supplementary
material, which is available to authorized users.
V. Sumangala ꢀ B. Poojary (&) ꢀ N. Chidananda
Department of Chemistry, Mangalore University,
Mangalagangothri 575199, Karnataka, India
e-mail: bojapoojary@gmail.com
V. Sumangala ꢀ T. Arulmoli
SeQuent Scientific Limited, 120 A & B Industrial Area
Baikampady, New Mangalore 575011, Karnataka, India
S. Shenoy
Department of Microbiology, KMC, Mangalore 575001,
Karnataka, India
123

Med Chem Res
Results and discussion
4H-[1,2,4]-triazole-3-thione (3e) showed the absence of
–NH2 stretching band thus indicating the Schiff base
formation. The other characteristic stretching vibrations
of the product were 3,224 cm-1 (N–H), 3,018 cm-1 (Ar–
H), 1,589 cm-1 (C=N), 1,421 cm-1 (S=O), 1,286 cm-1
(C=S), 1,142 cm-1 r (S=O), and 1,088 cm-1 (C–F). The
Synthetic strategy of the title compounds is outlined in
Scheme 1. The acid hydrazides (1) were treated with car-
bon disulfide and potassium hydroxide followed by
hydrazine hydrate to afford 4-amino-5-[4-(methylsulfo-
nyl)benzyl]-4H-[1,2,4]-triazole-3-thione (2). The resulting
triazole (2) was treated with different aldehydes to get
5-[4-(methylsulfonyl)benzyl]-4-{arylmethylene]amino}-
4H-[1,2,4]-triazole-3-thiones (3a–j). The formation of
Schiff bases (3) was evidenced by their elemental anal-
yses and spectral data. The characterization data of
synthesized compounds are presented in Table 1.
1
400 MHz H NMR spectrum showed prominent singlets
at d 3.16 and d 4.28 for its S–CH3 and CH2 protons,
respectively. Two characteristic singlets at d 13.93 and d
10.00 were due to N–H and N=CH protons of the triazole
ring and of the azomethine group, respectively. The four
protons of 4-fluorophenyl moiety appeared as two triplets
at d 7.39 and 7.94. The four protons of 4-methylsulfo-
nylphenyl moiety appeared as two doublets at d 7.57 and
7.86 (J = 8.0 Hz). The 100 MHz 13C NMR spectrum of
compound showed signals at d 30.91 (CH2), 43.98 (S–
CH3), 116.78, 117.00, 127.65, 129.23, 130.49, 131.58,
131.67, 139.94, 141.61, 150.20, 162.00, 162.40, and
166.38. The 13C NMR DEPT spectrum is also shown in
the figure. The Mass spectrum showed a protonated
molecular ion (M ? 1) peak at m/z 391.1, consistent with
its molecular formula C17H15FN4O2S2.
The structure of 4-amino-5-[4-(methylsulfonyl)benzyl]-
2,4-dihydro-3H-[1,2,4]-triazole-3-thione (2) was confirmed
1
by recording its IR, H NMR, and mass spectra. IR spec-
trum showed absorption bands at 3,315 and 3,177 cm-1
(NH), 3,091 cm-1 (Ar–H), 1,627 cm-1 (C=N), 1,494.9 and
1,144.3 cm-1 (SO2), and 1,290 cm-1 (C=S). The 400 MHz
1H NMR spectrum showed the down field broad singlet at d
13.61 for the NH proton due to tautomerization. This
compound also showed prominent singlets at d 3.20 and d
4.17 for its CH3 and CH2 protons, respectively. A singlet at
d 5.58 was also seen for its NH2 protons. The four protons
of 4-methylsulfonylphenyl moiety appeared as two distinct
doublets at d 7.56 and 7.88 (J = 8.0 Hz). The 100 MHz
13C NMR spectrum showed characteristic signals at 44.03
(CH2), d 30.55 (S–CH3), and 127.63, 130.35, 139.84,
141.94, 151.15, and 166.66 (C=S) thereby accounting for
the presence of ten different carbon atoms in the molecule.
The inverted signals at d 30.54 in the DEPT spectrum
confirmed the CH2 carbon. The quaternary carbon atom
signals disappeared in the DEPT spectrum. Further, mass
spectrum showed a (M ? 1) peak at m/z 285.1 corre-
sponding to its molecular formula, C10H12N4O2S2.
In the IR spectrum of the compound 5-[4-(methylsulfo-
nyl)benzyl]-4-({[4-(methylthio)phenyl]methylene}amino)-
2,4-dihydro-3H-1,2,4-triazole-3-thione (3h), the absence of
–NH2 stretching band thus indicates the Schiff base for-
mation. The other characteristic stretching vibrations of the
product were at 3,101 cm-1 (N–H), 3,057 cm-1 (Ar–H),
1,585 cm-1 (C=N), 1,426 cm-1 (S=O), 1,285 cm-1 (C=S),
1
and 1,142 cm-1 (S=O). The 400 MHz H NMR spectrum
showed prominent singlets at d 2.52, 3.15, and d 4.25 for its
S–CH3, SO2–CH3, and CH2 protons, respectively. Two
characteristic singlets at d 13.90 and d 9.89 each integrat-
ing for protons of the N–H and N=CH protons of the tri-
azole ring and of the azomethine group were also seen in
the spectrum. The four protons of 4-(methylthio)phenyl
moiety appeared as two doublets at d 7.37 and 7.75
The IR spectrum of the compound 4-{[(4-fluoro-
phenyl)methylene]amino}-5-[4-(methylsulfonyl)benzyl]-
H
H
N
N
O
N
N
H
N
S
2
S
N
N
H
N
N
1.CS2/KOH, RT
H
2
N
Acetic acid
2. N2H4. H2O
Ethanol, 80°C
R
1
R -CHO
1
O
O
O
Ethanol, 80°C
O
S
2
S
1
S
H
C
O
3
H
C
H
C
3
O
(3a-j)
3
R1= 4-C6H5-C6H4, 2-Thienyl, 4-Cl-C6H4, 2-Cl-C6H4, 3-pyridyl, 4-F-C6H4, 2-F-C6H4, 2-Cl-6-F-C6H3, 4-CH3S-C6H4, 6-CH3O-2-naphthyl.
Scheme 1 Formation of [1,2,4]-triazoles
123

Med Chem Res
Table 1 Characterization data of compounds 3a–j
Compd
Ar
Mol. formulae
Mol. wt
m.p (oC)
Yield (%)
Analysis (%) (calculated) found
C
H
N
3a
3b
3c
3d
3e
3f
2-Cl–C6H4
C17H15ClN4O2S2
16H15N5O2S2
406.9
210–212
225–227
242–244
215–128
233–236
223–225
208–211
216–218
231–233
225–227
85
85
85
82
86
89
86
88
89
90
(50.18) 50.16
(51.46) 51.42
(50.18) 50.16
(52.29) 50.25
(52.29) 50.25
(48.05) 48.00
(61.59) 61.54
(51.65) 51.62
(47.60) 47.60
(58.39) 58.40
(3.72) 3.70
(4.05) 4.00
(3.72) 3.70
(3.87) 3.85
(3.87) 3.85
(3.32) 3.30
(4.49) 4.49
(4.33) 4.30
(3.73) 3.70
(4.45) 4.43
(13.77) 13.72
(18.75) 18.72
(13.77) 13.72
(14.35) 14.33
(14.35) 14.33
(13.19) 13.15
(12.49) 12.43
(13.39) 13.35
(14.80) 14.76
(12.38) 12.35
3-pyridyl
C
373.45
406.9
4-Cl–C6H4
C17H15ClN4O2S2
C17H15FN4O2S2
C17H15FN4O2S2
C17H14ClFN4O2S2
C23H20N4O2S2
C18H18N4O2S3
2-F-C6H4
390.45
390.45
424.9
4-F-C6H4
2-Cl-6-F-C6H3
4-C6H5–C6H4
4-CH3–S–C6H4
2-thienyl
3g
3h
3i
448.56
418.55
378.49
452.54
C
C
15H14N4O2S3
22H20N4O3S3
3j
6-methoxy-2-naphthyl
(J = 8.3 Hz). The four protons of 4-methylsulfonylphenyl
moiety appeared as two doublet at d 7.55 and 7.85
(J = 8.1 Hz). The 100 MHz 13C NMR spectrum of com-
pound showed characteristic signals at d 14.48 (S–CH3),
30.95 (CH2), 43.98 (SO2–CH3), 125.93, 127.65, 128.62,
129.37, 130.49, 139.90, 141.64, 145.26, 150.13, 161.97,
and 163.09 thereby accounting for the presence of different
kinds of carbon atoms in the molecule.
Molecular devices). The % cell death is calculated by the
formula
AbsorbanceðDMSOÞ ꢁ AbsorbanceðsampleÞ
% cell death ¼
AbsorbanceðDMSOÞ
ꢂ 100
The EC50 value is obtained based on the % cell death
value.
The Table 2 contains the cytotoxicity data of the syn-
thesized compounds (3a–j). The results of the MTT assay
on HeLa cells (human epithelial cervical cancer) showed
that compound 3f having substituent 2-chloro-6-fluoro,
showed EC50 value 25 lM which was better than the rest
of the compounds. But this value is far below the standard
doxorubicin (2.5 lM). The better EC50 value of compound
3f than rest of the compounds may be due to the presence
of two electron withdrawing groups in the molecule. The
compounds 3c, 3g, 3h, and 3j having the substituents
4-chloro, biphenyl, 4-(methylthio)phenyl, and 6-methoxy-
2-naphthyl have showed moderate EC50 value (50 lM).
Other compounds showed marginal EC50 value
(C100 lM).
Biological activity
Cytotoxic study
Procedure for MTT assay
RAW 264.7 (murine macrophage cell line) and HT-29
(human colonic epithelial cell lines) cell lines were seeded
at a density of 1 9 104 cells (cell viability was determined
by Trypan blue exclusion dye method) (Mosmann, 1983)
per each well in 100 lL of DMEM (Dulbeccos modified
Eagles Medium) supplemented with 10 % FBS (Fetal
bovine serum). 12 h after seeding, the above media was
replaced with fresh DMEM supplemented with 10 % FBS,
then 20 lL samples from the above stock solutions were
added to each well in triplicates which gives final con-
centration of 100, 50, 25, and 10 lg/well. The above cells
were incubated for 48 h at 37 °C with 5 % CO2. After 48 h
incubation, the above media was replaced with 100 lL
of fresh DMEM without FBS and to this 10 lL of MTT
[3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium
bromide] (5 mg dissolved in 1 mL of FBS) was added and
incubated for 3 h at 37 °C with 5 % CO2. After 3 h of
incubation the above media was removed with a multi
channel pipette, then 200 lL of DMSO was added to each
well, and then incubated at 37 °C for 15 min. Finally, the
plate was read at 570 nm using spectrometer (Spectra-Max,
Antimicrobial activity
The newly synthesized [1,2,4]-triazoles (3a–j) were
screened for their in vitro antibacterial and antifungal
activity. For antibacterial studies microorganisms
employed were Staphylococcus aureus, Escherichia coli,
Pseudomonas aeruginosa, and Bacillus cereus. For anti-
fungal screening, Candida albicans strain was used. Both
microbial studies were assessed by minimum inhibitory
concentration (MIC) by serial dilution method (Mackie and
McCartney, 1989). For this, the compound whose MIC has
to be determined was dissolved in serially diluted DMF.
Then a standard drop of the culture prepared for the assay
123

Med Chem Res
respectively. In order to ensure that the solvent had no
effect on bacterial growth, a negative control test was also
performed for media containing inoculated broth supple-
mented with only DMF at the same dilution used in our
experiment and found to be inactive in culture media. Three
replicates were made for each analysis. The MIC values
were evaluated at concentration range 0.024–50 lg/mL.
The MIC was noted by seeing the lowest concentration of
the drug at which there was no visible growth. The figures
in the tables show the MIC values in lg/mL.
From the MIC value it is clear that all the tested com-
pounds were active in the concentration range of
1.562–12.5 lg/mL which is comparatively more than the
stds Penicillin and Flucanazole and hence have less anti-
microbial activity compared to the stds. Among the
screened samples, compounds 3d, 3g, and 3i in Table 3
(lg/mL) may show good antibacterial activity (3.125
lg/mL) against E. Coli due to the substituents 2-fluorophenyl,
biphenyl, and 2-thienyl, respectively. Similarly compounds
3a and 3f with 2-chlorophenyl and 2-chloro-6-fluorophenyl
substituents, respectively, showed good (3.125 lg/mL)
activity against P. aeruginosa as shown in antibacterial
activity Table 3. Another set of compound that shows good
antibacterial activity against B. cereus (3.125 lg/mL) are
compounds 3d and 3f with substituents 2-fluorophenyl and
2-chloro-6-fluorophenyl, respectively. Only compound 3h is
active against all the above four microorganisms even at
concentration of 3.125 lg/mL. The enhanced activity may be
due to the presence of 4-(methylthio)phenyl group.
Table 2 Cytotoxic activity data of compounds 3a–j
Compound name Conc. (lM) % Cell death SE
EC50(lM)
Doxorubicin
2.5
12.5
25
78.2
2.5
2.5
3a
34.65
36.26
42.65
76.53
16.89
19.36
14.00
45.10
44.73
47.51
53.99
57.04
16.48
14.03
21.90
28.08
2.80
2.79
1.77
2.83
5.66
50
100
12.5
25
3b
3c
3d
3e
3f
2.13 [100
2.58
50
3.33
100
12.5
25
1.59
1.59 50
3.93
50
1.94
100
12.5
25
4.62
3.53 [100
2.42
50
4.27
100
12.5
25
0.97
2.80 100
Not effective 4.61
50
26.25
57.79
49.84
55.32
70.55
77.28
30.44
37.32
61.56
69.54
27.94
32.66
57.50
71.86
28.69
33.33
48.59
61.09
43.71
42.01
54.13
64.60
8.54
100
12.5
25
3.68
2.78 25
1.90
50
6.12
100
12.5
25
2.05
3g
3h
3i
4.63 50
2.26
The antifungal activity of the derivatives have much
better results for compounds like 3a, 3c, 3d, 3e, 3f, 3h, and
3i as in Table 4. The compound 3c (1.562 lg/mL) has
shown good antifungal activity compared to others due to
the 4-chlorophenyl substituent. Remaining compounds 3a,
50
2.32
100
12.5
25
0.75
2.44 50
1.07
50
3.42
Table 3 Antibacterial activity data of compounds (3a–j)
100
12.5
25
3.81
Compound
MIC in lg/mL
2.17 100
0.43
E. coli
S. aureus P. aeruginosa B. cereus
50
5.20
3a
6.25
6.25
12.5
6.25
3.125
6.25
6.25
6.25
6.25
3.125
6.25
3.125
6.25
6.25
–
6.25
12.5
100
12.5
25
4.32
3b
3j
3.17 50
3.94
3c
12.5
6.25
6.25
6.25
3d
3.125
6.25
3.125
6.25
50
7.76
3e
12.5
100
1.95
3f
6.25
6.25
6.25
3.125
3.125
6.25
3g
3.125
3.125
3h
3.125
is added to each of the dilutions, and incubated for 16–18 h
at 37 °C. MIC is the highest dilution of the compound,
which shows clear fluid with no development of turbidity.
The antimicrobial activity data are presented in Tables 3
and 4. Penicillin and Flucanazole were used as reference
standards for antibacterial and antifungal activity,
3i
3.125 12.5
12.5
3j
6.25
–
6.25
6.25
–
Control (DMF)
Penicillin
–
0.097
0.097
0.097
0.097
MIC minimum inhibitory concentrations
123

Med Chem Res
disulfide and potassium hydroxide followed by hydrazine
hydrate to afford the 4-amino-5-[4-(methylsulfonyl)
benzyl]-4H-[1,2,4]-triazole-3-thione (2). The resulting
triazole (2) was treated with different aldehydes to get
5-[4-(methylsulfonyl)benzyl]-4-{arylmethylene]amino}-
4H-[1,2,4]-triazole-3-thiones (3). The formation of
Schiff’s bases (3) was evidenced by their elemental
analyses and spectral data.
Table 4 Antifungal activity data of compounds (3a–j)
Compound
MIC in lg/mL
C. albicans
3a
3.125
6.25
3b
3c
1.562
3.125
3.125
3.125
6.25
3d
3e
3f
3g
Procedure for the synthesis of 4-amino-
5-[4-(methylsulfonyl)benzyl]-2,4-dihydro-
3H-[1,2,4]-triazole-3-thione (2)
3h
3.125
3.125
6.25
3i
3j
Control (DMF)
Flucanazole
–
The acid hydrazide (1) (2.28 g, 0.01 mol) was added to
absolute alcohol containing KOH (0.85 g, 0.011 mol) at
room temperature followed by carbon disulfide (0.729 g,
0.013 mol) and the resulting mixture was stirred at room
temperature for 10 h. The mixture was diluted with ether
and stirred for further 1 h. The potassium salt was fil-
tered and washed with ether. The salt was taken in two
volume of ethanol and treated with hydrazine hydrate
(0.69 g, 0.015 mol). Reaction mixture was refluxed
gently for 3 h during which hydrogen sulfide was
evolved and the color of the reaction mixture changed to
a dark green. It was then cooled to 5 °C and acidified
with concentrated HCl to pH 2.5. A yellow solid sepa-
rated out was filtered, washed with water, and recrys-
tallized from ethanol to get pure product (2). Yield
89 %; mp 237–239 °C.
0.78
MIC minimum inhibitory concentrations
3d, 3e, 3f, 3h, and 3i (3.125 lg/mL) have the substituents
2-chlorophenyl, 2-fluorophenyl, 4-fluorophenyl, 2-chloro-
6-fluorophenyl, 4-(methylthio)phenyl, and 2-thienyl,
respectively. The screening studies have demonstrated that
the newly synthesized compounds have promising anti-
bacterial and antifungal properties. Therefore, it was con-
cluded that there exists better scope for further study on
this class of compounds.
Materials and methods
IR (KBr, cmax, cm-1): 3,315, 3,177 (NH2), 3,091
(Ar–H), 2,944 (C–H), 1,627 (C=N), 1,564 (C=C), 1,494.9
Melting points were determined by the open capillary
method and are uncorrected. The IR spectra (in KBr pel-
lets) were recorded on a Shimadzu FT-IR 4100 type A
spectrophotometer. H NMR and 13C NMR spectra were
1
(S=O), 1,290 (C=S), 1,144.3 (S=O); H NMR: (400 MHz,
1
DMSO-d6): 3.20 (s, 3H, S–CH3), 4.17 (s, 2H, CH2), 5.58 (s,
2H, NH2), 7.56 (d, 2H, J = 8.0 Hz), 7.88 (d, 2H,
J = 8.0 Hz,), 13.61(s, 1H, NH); 13C NMR: (100 MHz,
DMSO-d6): 44.03 (S–CH3), 30.55 (CH2), 127.63, 130.35,
139.84, 141.94, 151.15, 166.66; DEPT (100 MHz, DMSO-
d6): CH, CH3: 44.03 (S–CH3), 127.64, 130.35, CH2:
-30.54; MS (m/z): 285.1 (M ? 1); Anal. calcd. for
C10H12N4O2S2: C, 42.24; H, 4.25; N, 19.70; Found: C,
42.21; H, 4.23; N, 19.72.
recorded on a Varian 400 MHz NMR spectrometer/Perkin-
Elmer EM300 MHz spectrometer using TMS as an internal
standard. The mass spectra were recorded on a MDS
SCIEX/API 4000 spectrophotometer. Elemental analysis
was carried out using Flash EA 1112 Series, CHNSO
Analyzer (Thermo). The progress of the reaction was
monitored by thin layer chromatography (TLC) on pre-
coated silica gel G plates.
Materials
General procedure for the synthesis of Schiff base (3a-j)
All the reagents and solvents are from Spectrochem and
Aldrich and they were used as received without further
purification.
A
mixture of 4-amino-5-[4-(methylsulfonyl)benzyl]-
2,4-dihydro-3H-[1,2,4]-triazole-3-thione (2) (0.01 mol)
and substituted aldehydes (0.01 mol) in absolute ethanol
in the presence of catalytic amount of acetic acid was
refluxed for 4 h. After cooling, the precipitated product
was filtered, washed with water, and dried. The solid
product obtained was recrystallized from ethanol.
Experimental
Synthetic strategy of the title compounds is outlined in
Scheme 1. The acid hydrazide (1) was treated with carbon
123

Med Chem Res
4-{[(2-Chlorophenyl)methylene]amino}-5-[4-(methylsul-
fonyl)benzyl]-2,4-dihydro-3H-[1,2,4]-triazole-3-thione
(3a) IR (KBr, cmax, cm-1): 3,221 (NH), 3,012 (Ar–H),
2,930 (C–H), 1,583 (C=N), 1,420 (S=O), 1,288 (C=S),
1,142(S=O), 768 (C–Cl); 1H NMR: (400 MHz, DMSO-d6):
3.15 (s, 3H, S–CH3), 4.27 (s, 2H, CH2), 7.14–7.40 (m, 3H),
7.55 (d, 2H, J = 8.0 Hz), 7.85 (d, 2H, J = 8.0 Hz); 8.10
(d, 1H, J = 8.0),10.03 (s, 1H, N = CH), 13.89 (s, 1H,
NH); MS (m/z): 408.2 (M ? 1); Anal. calcd. for
C17H15ClN4O2S2, C, 50.18; H, 3.72; N, 13.77; Found: C,
50.16; H, 3.70; N, 13.72.
4-{[(4-Fluorophenyl)methylene]amino}-5-[4-(methylsul-
fonyl)benzyl]-2,4-dihydro-3H-[1,2,4]-triazole-3-thione
(3e) IR (KBr, cmax, cm-1): 3,224 (NH), 3,018 (Ar–H),
2,958 (C–H), 1,589 (C=N), 1,421 (S=O), 1,286 (C=S),
1
1,142 (S=O), 1,088 (C–F); H NMR (400 MHz, DMSO-
d6): 3.16 (s, 3H, S–CH3), 4.28 (s, 2H, CH2), 7.39 (t, 1H),
7.57 (d, 2H, J = 8.0 Hz,), 7.86 (d, 2H, J = 8.0 Hz), 7.94
(t, 1H), 10.00 (s, 1H, N=CH), 13.93 (s, 1H, NH); 13C NMR
(100 MHz, DMSO-d6, d ppm): 30.91 (CH2), 43.98
(S–CH3), 116.78, 117.00, 127.65, 129.23, 130.49, 131.58,
131.67, 139.94, 141.61, 150.20, 162.00, 162.40, 166.38;
DEPT (100 MHz, DMSO-d6, d ppm): CH2: -30.90, CH,
CH3: 43.98, 116.78, 117.00, 127.65, 130.49, 131.58,
131.67; MS (m/z): 391.1 (M?); Anal. calcd. for
C17H15FN4O2S2, C, 52.29; H, 3.87; N, 14.35; Found: C,
50.25; H, 3.85; N, 14.33.
5-[4-(Methylsulfonyl)benzyl]-4-{[(pyridin-3-yl)methylene]
amino}-2,4-dihydro-3H-[1,2,4]-triazole-3-thione (3b) IR
(KBr, cmax, cm-1): 3,222 (NH), 3,014 (Ar–H), 2,943 (C–
H), 1,588 (C=N), 1,432 (S=O), 1,293 (C=S), 1,135 (S=O);
1H NMR: (400 MHz, CDCl3): 3.16 (s, 3H, S–CH3), 4.29 (s,
2H, CH2), 7.45–7.50 (m, 2H), 7.56 (s, 1H), 7.59 (d, 2H,
J = 8.0 Hz), 7.84 (d, 2H, J = 8.0 Hz), 8.15 (d, 1H,
J = 6.0 Hz), 10.08 (s, 1H, N = CH), 13.94 (s, 1H, NH);
MS (m/z): 374.4 (M ? 1); Anal. calcd. for C16H15N5O2S2,
C, 51.46; H, 4.05; N, 18.75; Found: C, 51.44; H, 4.03; N,
18.72.
4-{[(2-Chloro-6-fluorophenyl)methylene]amino}-5-[4-(meth-
ylsulfonyl)benzyl]-2,4-dihydro-3H-[1,2,4]-triazole-3-thione
(3f) IR (KBr, cmax, cm-1): 3,222 (NH), 3,017 (Ar–H),
2,950 (C–H), 1,587 (C=N), 1,425 (S=O), 1,292 (C=S),
1,142 (S=O), 1,080 (C–F); 745 (C–Cl); 1H NMR
(400 MHz, DMSO-d6): 3.16 (s, 3H, S–CH3), 4.25 (s, 2H,
CH2), 7.40 (t, 1H, J = 7.9 Hz), 7.49 (d, 1H, J = 8.0 Hz),
7.55 (d, 2H, J = 8.0 Hz,), 7.62 (t, 1H, J = 7.9 Hz), 7.84
(d, 2H, J = 8.0 Hz), 10.80 (s, 1H, N=CH), 14.03 (s, 1H,
NH); 13C NMR (100 MHz, DMSO-d6): 30.78 (CH2), 43.99
(S–CH3), 116.39, 116.60, 119.18, 119.30, 127.12, 127.63,
130.39, 134.54, 134.64, 135.57, 139.94, 141.53, 150.60,
154.90, 160.12, 161.70, 162.72; DEPT (100 MHz, DMSO-
d6): CH2: -30.78, CH, CH3: 43.99, 116.39, 116.61, 127.15,
127.63, 130.39, 134.54, 134.64, 154.90; MS (m/z): 426
(M ? 1); Anal. calcd. for C17H14 Cl FN4O2S2, C, 48.05; H,
3.32; N, 13.19; Found: C, 48.00; H, 3.30; N, 13.15.
4-{[(4-Chlorophenyl)methylene]amino}-5-[4-(methylsul-
fonyl)benzyl]-2,4-dihydro-3H-[1,2,4]-triazole-3-thione
(3c) IR (KBr, cmax, cm-1): 3,220 (NH), 3,015 (Ar–H),
2,945 (C–H), 1,585 (C=N), 1,420 (S=O), 1,289 (C=S),
1
1,138 (S=O), 760 (C–Cl); H NMR: (400 MHz, DMSO-
d6): 3.15 (s, 3H, S–CH3), 4.27 (s, 2H, CH2), 7.55 (d, 2H,
J = 8.4 Hz), 7.59 (d, 2H, J = 8.0 Hz), 7.80 (d, 2H,
J = 8.4 Hz); 7.84 (d, 4H, J = 8.0 Hz); 10.08 (s, 1H,
N=CH), 13.94 (s, 1H, NH); 13C NMR: (100 MHz, DMSO-
d6): 30.90 (CH2), 43.97 (S–CH3), 127.65, 129.82, 130.50,
130.68, 131.5, 137.76, 139.93, 141.58, 150.27, 161.74,
162.00; DEPT (100 MHz, DMSO-d6): CH2: -30.90, CH,
CH3: 43.96, 127.66, 129.82, 130.50, 130.68, 161.74; MS
(m/z): 408 (M ? 1); Anal. calcd. for C17H15ClN4O2S2, C,
50.18; H, 3.72; N, 13.77; Found: C, 50.16; H, 3.70; N,
13.72.
4-{[(2-Fluorophenyl)methylene]amino}-5-[4-(methylsulfo-
nyl)benzyl]-2,4-dihydro-3H-[1,2,4]-triazole-3-thione
(3g) IR (KBr, cmax, cm-1): 3,225 (NH), 3,011 (Ar–H),
2,935 (C–H), 1,580 (C=N), 1,422 (S=O), 1,280 (C=S),
1
1,139 (S=O), 1,060 (C–F); H NMR: (400 MHz, DMSO-
d6): 3.18 (s, 3H, S–CH3), 4.29 (s, 2H, CH2), 7.16–7.43 (m,
3H), 7.58 (d, 2H, J = 8.0 Hz), 7.86 (d, 2H, J = 8.0 Hz);
8.20 (t, 1H, J = 7.8),10.06 (s, 1H, N=CH), 13.99 (s, 1H,
NH); MS (m/z): 391.5 (M ? 1); Anal. calcd. for
C17H15FN4O2S2, C, 52.29; H, 3.87; N, 14.35; Found: C,
50.25; H, 3.85; N, 14.33.
4-{[(2-Fluorophenyl)methylene]amino}-5-[4-(methylsul-
fonyl)benzyl]-2,4-dihydro-3H-[1,2,4]-triazole-3-thione
(3d) IR (KBr, cmax, cm-1): 3,225 (NH), 3,011 (Ar–H),
2,935 (C–H), 1,580 (C=N), 1,422 (S=O), 1,280 (C=S),
1
1,139 (S=O), 1,060 (C–F); H NMR: (400 MHz, DMSO-
d6): 3.18 (s, 3H, S–CH3), 4.29 (s, 2H, CH2), 7.16–7.43 (m,
3H), 7.58 (d, 2H, J = 8.0 Hz), 7.86 (d, 2H, J = 8.0 Hz);
8.20 (t, 1H, J = 8.0), 10.06 (s, 1H, N=CH), 13.99 (s, 1H,
NH); MS (m/z): 391.5 (M ? 1); Anal. calcd. for
C17H15FN4O2S2, C, 52.29; H, 3.87; N, 14.35; Found: C,
50.25; H, 3.85; N, 14.33.
5-[4-(Methylsulfonyl)benzyl]-4-({[4-(methylthio)phenyl]meth-
ylene}amino)-2,4-dihydro-3H-[1,2,4]-triazole-3-thione
(3h) IR (KBr, cmax, cm-1): 3,201 (NH), 3,057 (Ar–H),
2,950 (C–H), 1,585 (C=N), 1,426 (S=O), 1,285 (C=S),
1
1,142 (S=O); H NMR: (400 MHz, DMSO-d6): 2.52 (s,
3H, S–CH3), 3.15 (s, 3H, SO2CH3), 4.25 (s, 2H, CH2), 7.37
123

Med Chem Res
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1
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Conclusions
The research study reports the successful synthesis of
5-[4-(methylsulfonyl)benzyl]-4-{(arylmethylene)amino}-
4H-[1,2,4]-triazole-3-thiones from 4-amino-3-substituted-5-
mercapto-[1,2,4]-triazoles in good yields. All the synthe-
sized compounds have been characterized by analytical and
spectral data. The cytotoxic study and antimicrobial activity
evaluation of these compounds were done. Many of the
synthesized traizoles have good cytotoxicity and antimi-
crobial activity.
Acknowledgments We are grateful to the Management, SeQuent
Scientific Ltd., New Mangalore. The authors are also thankful to Prof.
A. Srikrishna, Department of Organic Chemistry, IISc, Bangalore for
providing 1H NMR and 13C NMR spectral facilities. The authors also
thank the Department of Pharmacology, Manipal College of Pharma
science, Manipal University for the analysis of cytotoxicity.
123

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123