Synthesis of new 1,2,4-triazole[3,4-b][1,3,4]thiadiazoles bearing pyrazole as potent antimicrobial agents

Article abstract of DOI:10.1248/cpb.58.1328

A new series of 6-(aryl/heteryl)-3-(5-methyl-1-phenyl-1H-4-pyrazolyl)[1,2, 4]triazolo[3,4-b][1,3,4]thiadiazoles (7a-j) has been synthesized by the reaction of 4-amino-5-(5-methyl-1-phenyl-1H-4-pyrazolyl)-4H-1,2,4-triazol-3-yl- hydrosulfide (6) with POCl₃ and the corresponding aryl/heteryl carboxylic acid, in ethanol at reflux temperature for 12 h. All the synthesized compounds were tested for in vitro activities against certain strains of bacteria such as Staphylococcus aureus, Bacillus subtilis, Escherichia coli and fungi such as Aspergillus niger, Aspergillus nodulans, Alternaria alternate. Compounds having 4-chlorophenyl (7d), 4-aminophenyl (7f), 4-nitrophenyl (7h) and 3-pyridyl (7i) substituents at 6-position of thiadiazole ring, showed marked inhibition of bacterial and fungal growth nearly equal to the standards. The other new compounds also showed appreciable activity against the test bacteria and fungi.

Full text of DOI:10.1248/cpb.58.1328

1328
Regular Article
Chem. Pharm. Bull. 58(10) 1328—1331 (2010)
Vol. 58, No. 10
Synthesis of New 1,2,4-Triazole[3,4-b][1,3,4]thiadiazoles Bearing Pyrazole
as Potent Antimicrobial Agents
b
Cherkupally SANJEEVA REDDY,*,a Lade SANJEEVA RAO,a Gaddam RAJESH KUMAR,a and Adki NAGARAJ
a Department of Chemistry, Kakatiya University; Warangal–506 009, India: and b Department of Pharmaceutical
Chemistry, Telangana University; Nizamabad–503 175, India.
Received March 14, 2010; accepted May 22, 2010; published online August 10, 2010
A new series of 6-(aryl/heteryl)-3-(5-methyl-1-phenyl-1H-4-pyrazolyl)[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles
(7a—j) has been synthesized by the reaction of 4-amino-5-(5-methyl-1-phenyl-1H-4-pyrazolyl)-4H-1,2,4-triazol-3-
yl-hydrosulfide (6) with POCl3 and the corresponding aryl/heteryl carboxylic acid, in ethanol at reflux tempera-
ture for 12 h. All the synthesized compounds were tested for in vitro activities against certain strains of bacteria
such as Staphylococcus aureus, Bacillus subtilis, Escherichia coli and fungi such as Aspergillus niger, Aspergillus
nodulans, Alternaria alternate. Compounds having 4-chlorophenyl (7d), 4-aminophenyl (7f), 4-nitrophenyl (7h)
and 3-pyridyl (7i) substituents at 6-position of thiadiazole ring, showed marked inhibition of bacterial and fungal
growth nearly equal to the standards. The other new compounds also showed appreciable activity against the test
bacteria and fungi.
Key words fused-triazole; antibacterial agent; antifungal agent; anfimicrobial agent
Pyrazole and its derivatives represent one of the most ac- drazinolysis of compound 3 with hydrazine hydrate. The hy-
tive classes of compounds possessing a wide spectrum of bi- drazide 4 on reaction with carbon disulfide and potassium
ological activities, including antibacterial,1) antifungal,2) her- hydroxide, in ethanol, followed by acidification gave 5-(5-
bicidal,3) insecticidal4) and other biological activities.5—7) methyl-1-phenyl-1H-4-pyrazolyl)-1,3,4-oxadiazol-2-yl-hy-
Similarly, the biological activities of various 1,2,4-triazole drosulfide (5) in 70% yield. Reaction of 5 with hydrazine hy-
derivatives and their N-bridged heterocyclic analogs have drate under reflux for 6 h resulted 4-amino-5-(5-methyl-1-
been widely investigated as antitumor,8) antiviral,9) anti-in- phenyl-1H-4-pyrazolyl)-4H-1,2,4-triazol-3-yl-hydrosulfide
flammatory,10) analgesic11) and antidepressant.12) 1,2,4-Tria- (6) in 69% yield. The final compounds, 6-(aryl/heteryl)-3-(5-
zole system is also an important starting material in the syn- methyl-1-phenyl-1H-4-pyrazolyl)[1,2,4]triazolo[3,4-b]
thesis of biologically active heterocycles, which constitute an [1,3,4]thiadiazole (7a—j), were synthesized in 66—78% via
important class of organic compounds with diverse biologi- the reaction of 6 with POCl3 and the corresponding aryl/het-
cal activities, including antiparasitic, analgesic, antibacterial eryl carboxylic acids, in ethanol at reflux temperature for
and anti-inflammatory activities.13—18) Further, triazole fused 12 h (Chart 1). The structures of all the newly synthesized
with other heterocyclic rings is also found to possess diverse compounds were confirmed by their elemental analyses, elec-
1
applications in the field of medicine.19—22) The commonly tron ionization (EI) mass, IR, H- and 13C-NMR spectral
known systems are triazolo-pyridines,19) triazolo-pyridazines,20) data.
triazolo-pyrimidines,21) triazolo-pyrazines,22) triazolo-tri-
In the IR spectra of 7a—j, appearance of bands at 1610
azines21) and triazolo-thiadiazines.23) In addition, it has been (CϭC), 1520 (CϭN) cmϪ1 and the absence of NH2 and SH
reported that thiadiazoles exhibit a broad spectrum of biolog- stretching vibrations provided the evidence of ring closure,
ical effectiveness such as anti-parkinsonism,24) hypogly- involving –NH2 and SH groups. Similarly, the absence of sig-
caemic,25) anticancer,26) anti-inflammatory,27) anti-asthmatic28) nals for the –SH and –NH2 protons in the H-NMR spectra
1
and anti-hypertensive29) activities.
Inspired by the biological profile of pyrazole, triazole,
thiadiazole, and in continuation of our research on biologi-
cally active heterocycles,30—35) it was thought worthwhile to
synthesize some new heterocyclic compounds containing
pyrazole, triazole and thiadiazol rings in one molecular frame
work. We report herein the synthesis of a new series of 1,2,4-
triazole[3,4-b][1,3,4]thiadiazoles bearing pyrazole and their
antimicrobial activity.
Results and Discussion
Synthesis The starting material, (E)-2-acetyl-3-(di-
7: Arϭa) phenyl; b) 4-methylphenyl; c) 4-methoxyphenyl; d) 4-chlorophenyl;
e) 2-chloropheyl; f) 4-aminophenyl; g) 4-hydroxyphenyl; h) 4-nitrophenyl; i) 3-
methylamino)-2-propenoate (2), was obtained via conden-
pyridyl; j) 4-pyridyl.
sation of ethyl acetoacetate (1) with N,N-dimethyl-
Reagents and conditions: (i) Me2NCH(OMe)2; (ii) Ph–NH–NH2; (iii)
dimethoxymethanamine,36) which on cyclo-condensation
NH2–NH2H2O/EtOH, reflux, 72%; (iv) CS2/KOH/EtOH, reflux, 12 h,
70%; (v) NH2–NH2H2O/EtOH, reflux 6 h, 69%; (vi) Ar-COOH/POCl3/
EtOH, reflux 12 h, 66—78%.
with phenyl hydrazine resulted 5-methyl-1-phenyl-1H-4-pyra-
zolecarboxylate (3).36) The 5-methyl-1-phenyl-1H-4-pyra-
Chart 1
zolecarbohydrazide (4) was obtained in 72% yield via hy-
∗ To whom correspondence should be addressed. e-mail: chsrkuc@yahoo.co.in
© 2010 Pharmaceutical Society of Japan

October 2010
1329
followed by the presence of aromatic protons in the region of Table 1. Antimicrobial Activity of Compounds (7a—j)
d 7.60 and 7.92 ppm well support the structures. In the 13C-
Growth inhibition zone diameter (mm)
NMR spectra, the prominent signals corresponding to the
carbons of [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole ring for all
Antibacterial activity
Antifungal activity
Compound
the compounds, observed nearly at d 152.1, 144.3 and
134.9 ppm are proof of further evidence of their structures. In
summary all the newly synthesized compounds exhibited sat-
isfactory spectral data consistent with their molecular struc-
tures.
Biological Properties. Antibacterial Activity The
newly synthesized compounds 7a—j were tested for their in
vitro antibacterial activity against Staphylococcus aureus,
Bacillus subtilis and Escherichia coli by using the agar disc-
diffusion method.37) The results of the preliminary antimicro-
bial testing of the prepared compounds, the typical broad
spectrum of antibacterial drug ciprofloxacin are shown in
Table 1.
Among the tested compounds, four compounds showed
considerable activity almost equal to the activity of cipro-
floxacin. The other compounds were found to be moderate or
least effective. In order to get some meaningful results, the
structure–activity relationship was carried out. From the bac-
terial screening results it has been observed that the com-
pounds having 4-chlorophenyl (7d), 4-aminophenyl (7f), 4-
nitrophenyl (7h) and 3-pyridyl (7i) substituents at 6-position
of thiadiazole ring, showed marked inhibition of bacterial
growth. Compounds having phenyl (7a), 4-methylphenyl
(7b) and 4-methoxyphenyl (7c) substituents at 6-position of
thiadiazole ring showed least activity: whereas the com-
pounds having 2-chlorophenyl (7e), 4-hydroxyphenyl (7g)
and 4-pyridyl (7j) substituents at 6-position of thiadiazole
ring showed moderate effect on the growth of bacteria. The
comparison of growth inhibition zone diameter (mm) for the
selected compound 7 and standard drug against different bac-
teria is presented in Fig. 1.
A. nodu- A. alter-
S. aureus B. subtilis E. coli
A. niger
lans
nata
7a
7b
7c
7d
7e
7f
7g
7h
7i
12
9
8
8
9
8
6
—
11
18
14
21
13
20
18
16
—
20
6
9
6
8
16
20
15
23
12
23
22
18
10
21
14
24
14
23
24
13
22
—
12
19
13
23
15
19
27
16
25
—
10
19
7
12
19
8
24
13
14
20
15
—
23
22
16
16
22
16
—
20
7j
Ciprofloxacin 22
Amphotericin
B
—
The compounds 7a—j and the standards used were of 100 mg/8 mm discs.
Fig. 1. Comparison of Antibacterial Activity (Growth Inhibition Zone
Diameter, mm) of Selected Compounds with Ciprofloxacin (CF)
exposure to UV light or dipping in 1% aqueous potassium permanganate
solution. Melting points were determined through a Fisher–Johns apparatus
and are uncorrected. IR spectra were recorded using KBr disk on a Perkin–
Antifungal Activity All the newly synthesized com-
pounds 7a—j were also screened for their antifungal activity
against Aspergillus niger, Aspergillus nodulans and Al- Elmer FTIR spectrometer. The 1H- and 13C-NMR spectra were recorded on a
Varian Gemini spectrometer (300 MHz for H- and 75 MHz for 13C-NMR).
Chemical shifts are reported in d ppm units with respect to tetramethyl silane
(TMS) as internal standard and coupling constants (J) are reported in Hz
1
ternaria alternate by food poison technique.38) The results of
the preliminary antifungal testing of the prepared com-
pounds, the typical broad spectrum of the potent antifungal
units. Mass spectra were recorded on a VG micro mass 7070H spectrometer.
drug amphotericin B are shown in Table 1. The antifungal
activity data reveal that compounds containing 4-
chlorophenyl (7d), 4-aminophenyl (7f) and 3-pyridyl (7i)
substitutents at 6-position of thiadiazole ring, are showing
excellent activity against the test fungi and nearly equal to
the standard amphotericin B.
Elemental analyses (C, H, N), determined by means of a Perkin–Elmer 240
CHN elemental analyzer, were within Ϯ0.4% of theory.
Typical Procedure 5-Methyl-1-phenyl-1H-4-pyrazolecarbohydrazide
(4) A mixture of compound 3 (5 mmol) and hydrazine hydrate (5 mmol) in
ethanol (15 ml) was refluxed for 4 h, cooled to room temperature and fil-
tered. The crude product was recrystallized from ethanol to give new inter-
mediate 4 as white crystal. Yield 72%, mp 162—164 °C. IR (KBr) cmϪ1
:
3269, 3062, 2933, 1660, 1612, 1501. 1H-NMR (CDCl3) d: 2.61 (s, 3H,
CH3), 5.49 (s, 2H, NH2), 7.15—7.25 (m, 5H, Ar-H), 8.26 (s, 1H, Ar-H), 8.96
(s, 1H, NH). 13C-NMR (CDCl3) d: 15.6, 110.7, 124.9, 127.7, 128.3, 138.5,
139.6, 141.0, 165.1. MS m/z: 217 (Mϩϩ1). Anal. Calcd for C11H12N4O: C,
61.10; H, 5.59; N, 25.91. Found: C, 61.06; H, 5.65; N, 25.95.
Conclusion
In conclusion, a new series of 1,2,4-triazole[3,4-b][1,3,4]-
thiadiazoles bearing pyrazoles 7a—j has been synthesized
and evaluated for their antimicrobial activity. Most of the
new compounds showed appreciable antimicrobial activity.
Among them, the compounds having 4-chlorophenyl (7d), 4-
aminophenyl (7f), 4-nitrophenyl (7h) substituents at 6-posi-
tion of thiadiazole ring showed marked inhibition of bacterial
and fungal growth nearly equal to the standards.
Typical Procedure 5-(5-Methyl-1-phenyl-1H-4-pyrazolyl)-1,3,4-oxadi-
azol-2-yl-hydrosulfide (5) A mixture of compound 4 (5 mmol), potassium
hydroxide (5 mmol) and carbon disulfide (7.5 mmol), in ethanol (100 ml)
was heated under reflux with stirring for 12 h and the solvent was distilled in
vacuo, the residual mass was poured over crushed ice and neutralized the al-
kaline solution with 10% hydrochloric acid. The precipitated crude product
was filtered, washed with water, dried and recrystallized from ethanol to give
pure compound 5. Yield 70%, mp 136—138 °C. IR (KBr) cmϪ1: 3162,
2914, 2845, 1612, 1604, 1504, 1343, 1266. 1H-NMR (DMSO-d6) d: 2.52 (s,
3H, CH3), 7.15—7.28 (m, 5H, Ar-H), 8.21 (s, 1H, Ar-H). 11.61 (s, 1H,
Experimental
General All the reagents used were of commercial grade. Reactions
were monitored by thin-layer chromatography (TLC) on pre-coated silica gel NH/SH). 13C-NMR (DMSO-d6) d: 13.7, 124.0, 125.1, 127.5, 128.7, 136.7,
F254 plates obtained from Merck and the compounds visualized either by 138.5, 139.7, 157.8, 170.0. MS m/z: 258 (Mϩ). Anal. Calcd for C12H10N4O5:

1330
Vol. 58, No. 10
C, 55.80; H, 3.90; N, 21.69. Found: C, 55.86; H, 3.82; N, 21.64.
(1.365 g) with 4-aminobenzoic acid (0.685 g) as described in the typical pro-
Typical Procedure 4-Amino-5-(5-methyl-1-phenyl-1H-4-pyrazolyl)- cedure. Yield 68%, mp 142—144 °C. IR (KBr) cmϪ1: 3320, 3034, 2928,
1
4H-1,2,4-triazol-3-yl-hydrosulfide (6) To a warm solution of compound 5 1612, 1514, 1510. H-NMR (DMSO-d6) d: 2.51 (s, 3H, CH3), 6.63 (d, Jϭ
(5 mmol) in ethanol (50 ml), 80% hydrazine hydrate (7.5 mmol) was added 8.4 Hz, 2H, Ar-H), 7.20—7.30 (m, 5H, Ar-H), 7.80 (d, Jϭ8.4 Hz, 2H, Ar-
drop wise and the reaction mixture was heated under reflux for 6 h. The sol- H), 8.04 (s, 1H, Ar-H). 13C-NMR (DMSO-d6) d: 14.3, 113.5, 116.2, 124.7,
vent was distilled in vacuo, cooled and the crystals separated were filtered, 126.9, 128.0, 128.9, 129.5, 134.5, 135.4, 137.4, 140.3, 144.0, 152.0, 152.7.
washed with cold ethanol and recrystallized from chloroform to give pure MS m/z: 374 (Mϩϩ1). Anal. Calcd for C19H15N7S: C, 61.11; H, 4.05; N,
compound 6. Yield 69%, mp 142—143 °C. IR (KBr) cmϪ1: 3300, 3145, 26.26. Found: C, 61.15; H, 4.00; N, 26.27.
2849, 2915, 1614, 1510, 1340. 1H-NMR (CDCl3) d: 1.30 (s, 2H, NH2), 2.49
4-[3-(5-Methyl-1-phenyl-1H-4-pyrazolyl)[1,2,4]triazolo[3,4-
b][1,3,4]thiadiazol-6-yl]phenol (7g) This was obtained by reacting 6
(s, 3H, CH3), 7.15—7.25 (m, 5H, Ar-H), 8.05 (s, 1H, Ar-H), 12.20 (s, 1H,
NH/SH). 13C-NMR (CDCl3) d: 14.7, 119.8, 125.1, 127.9, 129.0, 134.2, (1.365 g) with 4-hydroxy acid (0.69 g) as described in the typical procedure.
137.6, 138.6, 142.0, 146.9. MS m/z: 273 (Mϩ). Anal. Calcd for C12H12N6S2: Yield 76%, mp 140—142 °C. IR (KBr) cmϪ1: 3400, 3030, 2960, 1615,
1
C, 52.93; H, 4.44; N, 30.86. Found: C, 52.90; H, 4.50; N, 30.80.
1520, 1512. H-NMR (DMSO-d6) d: 2.52 (s, 3H, CH3), 5.20 (s, 1H, OH),
Typical Procedure 6-(Aryl/Heteryl)-3-(5-methyl-1-phenyl-1H-4-pyra- 6.76 (d, Jϭ8.4 Hz, 2H, Ar-H), 7.20—7.30 (m, 7H, Ar-H), 8.04 (s, 1H, Ar-
zolyl)[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (7a—j) To a solution of H). 13C-NMR (DMSO-d6) d: 14.2, 113.7, 117.0, 124.6, 127.5, 128.3, 129.4,
compound 6 (5 mmol) in POCl3 (10 ml), a solution of aryl/heteryl carboxylic
134.4, 134.9, 135.4, 137.3, 140.1, 144.3, 152.0, 161.1. MS m/z: 374 (Mϩ).
acid (5 mmol) in ethanol (15 ml) was added and the reaction mixture was Anal. Calcd for C19H14N6OS: C, 60.95; H, 3.77; N, 22.43. Found: C, 60.89;
heated under reflux for 12 h under anhydrous conditions. The solvent was H, 3.72; N, 22.41.
distilled in vacuo, the residual mass was poured over crushed ice and the
3-(5-Methyl-1-phenyl-1H-4-pyrazolyl)-6-(4-nitrophenyl)[1,2,4]tria-
excess POCl3 was neutralized with 10% sodium bicarbonate solution. The zolo[3,4-b][1,3,4]thiadiazole (7h) This was obtained by reacting
6
solid thus separated was filtered, washed with 10% sodium bicarbonate solu- (1.365 g) with 4-nitrobenzoic acid (0.835 g) as described in the typical pro-
tion and finally with water, dried and recrystallized from ethanol to give pure cedure. Yield 71%, mp 167—169 °C. IR (KBr) cmϪ1: 3062, 2971, 1620,
compounds.
1555, 1520, 1510, 1370. 1H-NMR (DMSO-d6) d: 2.54 (s, 3H, CH3), 7.20—
3-(5-Methyl-1-phenyl-1H-4-pyrazolyl)-6-phenyl[1,2,4]triazolo[3,4- 7.30 (m, 5H, Ar-H), 8.00—8.10 (m, 3H, Ar-H), 8.27 (d, Jϭ8.4 Hz, 2H, Ar-
b][1,3,4]thiadiazole (7a) This was obtained by reacting compound 6 H). 13C-NMR (DMSO-d6) d: 14.3, 113.5, 120.1, 124.3, 124.8, 128.3, 129.4,
(1.365 g) with benzoic acid (0.61 g) as described in the typical procedure.
134.6, 135.4, 137.2, 140.4, 140.9, 144.4, 149.0, 152.1. MS m/z: 403 (Mϩ).
Yield 66%, mp 137—139 °C. IR (KBr) cmϪ1: 3035, 2922, 1610, 1520, Anal. Calcd for C18H13N7O2S: C, 56.57; H, 3.25; N, 24.30. Found: C, 56.53;
1515. 1H-NMR (DMSO-d6) d: 2.51 (s, 3H, CH3), 7.20—7.30 (m, 7H, Ar-H), H, 3.21; N, 24.26.
7.60 (d, Jϭ7.7 Hz, 1H, Ar-H), 7.92 (d, Jϭ7.6 Hz, 2H, ArH), 8.06 (s, 1H, Ar-
H). 13C-NMR (DMSO-d6) d: 14.1, 113.0, 124.6, 126.8, 128.0, 129.7, 131.2, b][1,3,4]thiadiazole (7i) This was obtained by reacting 6 (1.365 g) with
132.0, 133.2, 134.9, 135.8, 137.4, 140.5, 144.3, 152.1. MS m/z: 358 (Mϩ).
nicotinic acid (0.615 g) as described in the typical procedure. Yield 74%, mp
Anal. Calcd for C19H14N6S: C, 63.67; H, 3.94; N, 23.45. Found: C, 63.70; H, 153—155 °C. IR (KBr) cmϪ1: 3034, 2961, 1618, 1522, 1520, 1510. 1H-
3.88; N, 23.47. NMR (DMSO-d6) d: 2.52 (s, 3H, CH3), 7.20—7.30 (m, 6H, Ar-H), 7.90 (d,
3-(5-Methyl-1-phenyl-1H-4-pyrazolyl)-6-(3-pyridyl)[1,2,4]triazolo[3,4-
6-(4-Methylphenyl)-3-(5-methyl-1-phenyl-1H-4-pyrazolyl)[1,2,4]tria- Jϭ5.7 Hz, 2H, Ar-H), 8.05 (s, 1H, Ar-H), 8.86 (d, Jϭ5.7 Hz, 2H, Ar-H).
zolo[3,4-b][1,3,4]thiadiazol (7b) This was obtained by reacting
6
13C-NMR (DMSO-d6) d: 14.3, 113.4, 124.6, 125.9, 128.0, 129.5, 134.5,
135.2, 135.8, 136.5, 137.3, 140.0, 144.3, 150.3, 152.3, 153.1. MS m/z: 360
(1.365 g) with 4-methylbenzoic acid (0.68 g) as described in the typical pro-
cedure. Yield 68%, mp 126—128 °C. IR (KBr) cmϪ1: 3032, 2928, 1615, (Mϩϩ1). Anal. Calcd for C18H13N7S: C, 60.15; H, 3.65; N, 2728. Found: C,
1
1520, 1510. H-NMR (DMSO-d6) d: 2.37 (s, 3H, CH3), 2.54 (s, 3H, CH3), 60.10; H, 3.62; N, 27.32.
7.20—7.30 (m, 7H, Ar-H), 8.00—8.05 (m, 2H, Ar-H). 13C-NMR (DMSO-
3-(5-Methyl-1-phenyl-1H-4-pyrazolyl)-6-(4-pyridyl)[1,2,4]triazolo[3,4-
d6) d: 14.2, 23.1, 113.4, 124.5, 128.0, 129.6, 130.9, 132.9, 133.7, 134.6, b][1,3,4]thiadiazole (7j) This was obtained by reacting 6 (1.365 g) with
135.5, 137.3, 139.0, 140.1, 144.2, 151.9. MS m/z: 373 (Mϩ). Anal. Calcd for isonicotinic acid (0.615 g) as described in the typical procedure. Yield 70%,
1
C20H16N6S: C, 64.50; H, 4.33; N, 22.56. Found: C, 64.42; H, 4.30; N, 22.52.
mp 157—159 °C. IR (KBr) cmϪ1: 3036, 2961, 1621, 1520, 1515, 1510. H-
6-(4-Methoxyphenyl)-3-(5-methyl-1-phenyl-1H-4-pyrazolyl)[1,2,4]tria- NMR (DMSO-d6) d: 2.52 (s, 3H, CH3), 7.20—7.30 (m, 5H, Ar-H), 7.90 (d,
zolo[3,4-b][1,3,4]thiadizole (7c) This was obtained by reacting 6 (1.365 g)
Jϭ6.1 Hz, 2H, Ar-H), 8.04 (s, 1H, Ar-H), 8.87 (d, Jϭ6.1 Hz, 2H, Ar-H).
with 4-methoxybenzoic acid (0.76 g) as described in the typical procedure.
13C-NMR (DMSO-d6) d: 14.3, 113.5, 123.4, 124.5, 128.1, 129.4, 134.5,
Yield 67%, mp 130—132 °C. IR (KBr) cmϪ1: 3035, 2930, 1612, 1522, 135.3, 137.1, 140.1, 141.7, 144.4, 152.4, 154.1. MS m/z: 360 (Mϩϩ1). Anal.
1510, 1070. 1H-NMR (DMSO-d6) d: 2.52 (s, 3H, CH3), 3.67 (s, 3H, OCH3),
6.82 (d, Jϭ8.4 Hz, 2H, Ar-H), 7.15—7.20 (m, 5H, Ar-H), 7.40 (d, Jϭ8.4 Hz,
2H, Ar-H), 8.05 (s, 1H, Ar-H). 13C-NMR (DMSO-d6) d: 14.3, 56.7, 113.4,
Calcd for C18H13N7S: C, 60.15; H, 3.65; N, 27.28 Found: C, 60.20; H, 3.60;
N, 27.29.
Antibacterial Assay For the antimicrobial assay standard inoculums
116.0, 124.5, 128.1, 128.5, 129.4, 132.9, 134.3, 135.6, 137.2, 140.0, 143.9, were introduced on to the surface of sterile agar plates, and a sterile glass
152.1, 157.4. MS m/z: 388 (Mϩ). Anal. Calcd for C20H16N6OS: C, 61.84; H, spreader was used for even distribution of the inoculums. The discs measur-
4.15; N, 21.63. Found: C, 61.80; H, 4.20; N, 21.58.
ing 8.0 mm in diameter were prepared from Whattman no. 1 filter paper and
6-(4-Chlorophenyl)-3-(5-methyl-1-phenyl-1H-4-pyrazolyl)[1,2,4]tria- sterilized by dry heat at 120 °C for 1 h. The sterile discs previously soaked in
zolo[3,4-b][1,3,4]thiadiazole (7d) This was obtained by reacting
(1.365 g) with 4-chlorobenzoid acid (0.775 g) as described in the typical pro-
6
a known concentration (100 mg/8 mm disc) of the test compounds were
placed in nutrient agar medium. The plates were inverted and incubated for
cedure. Yield 70%, mp 141—143 °C. IR (KBr) cmϪ1: 3062, 2942, 1610, 24 h at 37 °C. The inhibition zones were measured and compared with the
1515, 1512, 685. 1H-NMR (DMSO-d6) d: 2.52 (s, 3H, CH3), 7.15—7.20 (m, standard. The antimicrobial activity data of the test compounds are pre-
5H, Ar-H), 7.37 (d, Jϭ8.5 Hz, 2H, Ar-H), 7.80 (d, Jϭ8.5 Hz, 2H, Ar-H), sented in Table 1.
8.06 (s, 1H, ArH). 13C-NMR (DMSO-d6) d: 14.0, 113.1, 124.5, 128.1,
128.9, 129.2, 130.9, 134.0, 134.7, 135.0, 135.4, 137.1, 140.2, 143.8, 152.3.
Acknowledgements The authors are grateful to the Director, Indian In-
MS m/z: 392 (Mϩ). Anal. Calcd for C19H13ClN6S: C, 58.09; H, 3.34; N, stitute of Chemical Technology, Hyderabad, India, for providing NMR and
21.39. Found: C, 58.12; H, 3.30; N, 21.44. Mass spectral data. Financial assistance from the UGC SAP (Phase-I)-DRS
6-(2-Chlorophenyl)-3-(5-methyl-1-phenyl-1H-4-pyrazolyl)[1,2,4]tria- Programme, New Delhi, India, is greatly acknowledged.
zolo[3,4-b][1,3,4]thiadiazole (7e) This was obtained by reacting
6
(1.365 g) with 2-chlorobenzoic acid (0.775 g) as described in the typical pro-
cedure. Yield 72%, mp 136—138 °C. IR (KBr) cmϪ1: 3061, 2939, 1611,
1515, 1510, 686. 1H-NMR (DMSO-d6) d: 2.53 (s, 3H, CH3), 7.00—7.10 (m,
2H, Ar-H), 7.20—7.30 (m, 5H, ArH), 7.40—7.50 (m, 2H, ArH), 8.03 (s, 1H,
Ar-H). 13C-NMR (DMSO-d6) d: 14.5, 113.2, 124.3, 127.3, 128.4, 129.3,
130.4, 132.0, 132.4, 134.1, 134.6, 135.0, 135.5, 137.2, 140.1, 142.7, 152.2.
MS m/z: 392 (Mϩ). Anal. Calcd for C19H13ClN6S: C, 58.09; H, 3.34; N,
21.39. Found: C, 58.05; H, 3.30; N, 21.33.
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