1320 Jain et al.
Asian J. Chem.
(C=N), 1472.3, 1441 (C-N and N-C str). 1H NMR (DMSO-d6,
400 MHz): δ 13.05 (s, 1H, SH), 7.99-8.75 (d, 4H, ArH), 7.68-
8.43 (d, 4H,ArH).Anal. calcd. (%) for C13H9N5O2S: C, 52.17;
H, 3.03; N, 23.40; O, 10.69; S, 10.71. Found (%): C, 52.22;
H, 3.10; N, 23.36; O, 10.65; S, 10.76.
4-(4-Methoxyphenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazole-
3-thiol (6h): m.p.: 282-284 °C. IR (KBr, νmax, cm–1): 3072 (Ar
CH), 2928.4 (aliphatic CH), 2578.2 (SH), 1531.6 (C=N), 1456,
1425.3 (C-N and N-C str). 1H NMR (DMSO-d6, 400 MHz): δ
13.05 (s, 1H, SH), 7.99-8.75 (d, 4H, ArH), 6.99-7.51 (d, 4H,
ArH), 3.83 (s, 3H, AlH). Anal. calcd. (%) for C14H12N4OS: C,
59.14; H, 4.25; N, 19.70; O, 5.63; S, 11.28. Found (%): C,
59.18; H, 4.28; N, 19.65; O, 5.68; S, 11.33.
4-(4-Fluorophenyl)-5-(pyridin-2-yl)-4H-1,2,4-triazole-
3-thiol (7a): m.p.: 263-265 °C. IR (KBr, νmax, cm–1): 3072.3
(Ar CH), 2556.5 (SH), 1555.5 (C=N), 1479, 1430 (C-N and
N-C str), 1243.6 (C-F str). 1H NMR (DMSO-d6, 400 MHz): δ
13.05 (s, 1H, SH), 7.34-8.65 (m, 4H, ArH), 7.0-7.2 (d, 4H,
ArH). Anal. calcd. (%) for C13H9N4SF: C, 57.34; H, 3.33; F,
6.98; N, 20.58; S, 11.78. Found (%): C, 57.50; H, 3.41; F,
6.86; N, 20.53; S, 11.72.
(d, 4H, ArH), 0.90-2.62 (s, 7H, AlH). Anal. calcd. (%) for
C16H16N4S: C, 64.84; H, 5.44; N, 18.90; S, 10.82. Found (%):
C, 64.80; H, 5.40; N, 18.95; S, 10.86.
4-(4-Nitrophenyl)-5-(pyridin-2-yl)-4H-1,2,4-triazole-3-
thiol (7g): m.p.: >320 °C. IR (KBr, νmax, cm–1): 3089.9 (Ar
CH), 2920 (aliphatic CH), 2570.6 (SH), 1530.5 (C=N), 1447.2,
1423 (C-N and N-C str). 1H NMR (DMSO-d6, 400 MHz): δ
13.05 (s, 1H, SH), 7.36-8.59 (s, 4H, ArH), 7.68-8.43 (d, 4H,
ArH). Anal. calcd. (%) for C13H9N5O2S: C, 52.17; H, 3.03; N,
23.40; O, 10.69; S, 10.71. Found (%): C, 52.20; H, 3.06; N,
23.38; O, 10.65; S, 10.68.
4-(4-Methoxyphenyl)-5-(pyridin-2-yl)-4H-1,2,4-triazole-
3-thiol (7h): m.p.: >320 °C. IR (KBr, νmax, cm–1): 3072 (Ar
CH), 2931 (aliphatic CH), 2568 (SH), 1550 (C=N), 1464, 1425
(C-N and N-C str). 1H NMR (DMSO-d6, 400 MHz): δ 13.05
(s, 1H, SH), 7.36-8.59 (s, 4H, ArH), 6.99-7.51(d, 4H, ArH),
3.83 (s, 3H, AlH). Anal. calcd. (%) for C14H12N4OS: C, 59.14;
H, 4.25; N, 19.70; O, 5.63; S, 11.28. Found (%): C, 59.17; H,
4.29; N, 19.67; O, 5.68; S, 11.34.
RESULTS AND DISCUSSION
The target molecules (6a-h and 7a-h) were synthesized
in four steps. 4-Substituted aniline (1a-1h), were treated with
carbon disulfide, methanol and then concentrated aqueous
ammonia to yield 2a-2h, which is stirred with lead nitrate yield
compounds 3a-3h which on further treatment with respective
pyridine carboxylic acid hydrazide hydrate in ethanol undergo
cyclization resulting in the formation of N-(4-substituted phenyl)-
2-(pyridin-2/4-ylcarbonyl) hydrazine carbothioamide (4a-h,
5a-h). Compounds (4a-4h, 5a-5h) were undergoing cycli-
zation with sodium hydroxide to form 6a-6h and 7a-6h, all
the target molecules were characterized by advanced spectro-
scopic data. The synthetic route for the target molecules was
depicted in Scheme-I and physical properties of synthesized
compounds shown in Table-1.
Biological activity of the compounds: All the newly
synthesized compounds were assayed in vitro for antibacterial
and antifungal activity against a representative panel of bacterial
and fungal pathogens. In primary screening 500, 250 and 125
µg/mL concentrations of the synthesized compounds were
tested. The active compounds found in this primary screening
were further diluted and tested against the corresponding
microorganism to obtain their MICs, where the lowest
concentration that completely inhibited visible growth of the
organism was recorded as the minimal inhibitory concentration
(MIC, µg/mL).
Results (Table-2) revealed that all the synthesized com-
pounds exhibited potent antibacterial activities against both
Gram-positive strains. However few of them demonstrated
superior activity to that of standards tested. Compound 7g
showed MIC 11.7 µM against (Staphylococcus aureus) and
10.2 µM against (Bacillus subtilis) i.e. containing nitro group
at 4 position exhibited highest antimicrobial activity against
Gram-positive strain among the title compounds and compound
7f showed MIC 9.8 µM against (Pseudomonas aeruginosa)
and 10.2 µM against (Escherichia coli) i.e. containing propyl
group at 4 position exhibited highest antimicrobial activity
against Gram-negative strain among the title compounds, this
4-(4-Chlorophenyl)-5-(pyridin-2-yl)-4H-1,2,4-triazole-
3-thiol (7b): m.p.: 254-256 °C. IR (KBr, νmax, cm–1): 3075 (Ar
CH), 2559.2 (SH), 1559.1 (C=N), 1467.4, 1435 (C-N and N-
1
C str), 772.2 (C-Cl str). H NMR (DMSO-d6, 400 MHz): δ
13.05 (s, 1H, SH), 7.34-8.65 (m, 4H, ArH), 7.2-7.3 (d, 4H,
ArH). Anal. calcd. (%) for C13H9N4SCl: C, 54.07; H, 3.14; Cl,
12.28; N, 19.40; S, 11.10. Found (%): C, 54.11; H, 3.10; Cl,
12.21; N, 19.47; S, 11.06.
4-(4-Bromophenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazole-
3-thiol (7c): m.p.: 267-268 °C. IR (KBr, νmax, cm–1): 3077.3
(Ar CH), 2552.6 (SH), 1557.5 (C=N), 1475.6, 1430 (C-N and
N-C str), 575.2 (C-Br str). 1H NMR (DMSO-d6, 400 MHz): δ
13.05 (s, 1H, SH), 7.34-8.65 (m, 4H, ArH), 7.2-7.4 (d, 4H,
ArH). Anal. calcd. (%) for C13H9N4SBr: C, 46.86; H, 2.72; Br,
23.98; N, 16.81; S, 9.62. Found (%): C, 46.82; H, 2.78; Br,
23.92; N, 16.87; S, 9.55.
4-(4-Methylphenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazole-
3-thiol (7d): m.p.: 230-232 °C. IR (KBr, νmax, cm–1): 3075.3
(Ar CH), 2962.2 (Aliph. CH) 2555.2 (SH), 1550.5 (C=N),
1
1476.8, 1428 (C-N and N-C str). H NMR (DMSO-d6, 400
MHz): δ 13.05 (s, 1H, SH), 7.34-8.65 (m, 4H, ArH), 7.1 (d,
4H, ArH), 2.35 (s, 3H AlH). Anal. calcd. (%) for C14H12N4S:
C, 62.66; H, 4.51; N, 20.88; S, 11.95. Found (%): C, 62.61; H,
4.55; N, 20.80; S, 11.98.
4-(4-Ethylphenyl)-5-(pyridin-2-yl)-4H-1,2,4-triazole-
3-thiol (7e): m.p.: 244-246 °C. IR (KBr, νmax, cm–1): 3082 (Ar
CH), 2942.3 (aliphatic CH), 2533.2 (SH), 1580.5 (C=N),
1443.8, 1450.5 (C-N and N-C str). 1H NMR (DMSO-d6, 400
MHz): δ 13.05 (s, 1H, SH), 7.36-8.59 (s, 4H, ArH), 7.29-
7.31(d, 4H, ArH), 1.25-2.60 (s, 5H, AlH). Anal. calcd. (%) for
C15H14N4S: C, 63.80; H, 5.00; N, 19.84; S, 11.36. Found (%):
C, 63.77; H, 5.05; N, 19.80; S, 11.40.
4-(4-Propylphenyl)-5-(pyridin-2-yl)-4H-1,2,4-triazole-
3-thiol (7f): m.p.: 218-220 °C. IR (KBr, νmax, cm–1): 3070.8
(Ar CH), 2941.5 (aliphatic CH), 2573.2 (SH), 1561.6 (C=N),
1
1469.7, 1430 (C-N and N-C str). H NMR (DMSO-d6, 400
MHz): δ 13.05 (s, 1H, SH), 7.36-8.59 (s, 4H, ArH), 7.29-7.31