162 JOURNAL OF CHEMICAL RESEARCH 2013
(NH), 1698 (C=O), 1605 (C=N) cm−1; 1H NMR (DMSO-d6): δ 2.08 (s,
3H, CH3), 2.20 (s, 3H, CH3), 8.50 (s, 1H, CH), 11.32 (s, 1H, NH); UV
[λmax, nm (ε × 10−3)]: 204 (2.09), 232 (1.50); Anal. Calcd for C5H8N4O:
C, 42.85; H, 5.75; N, 39.98. Found: C, 42.41; H, 5.77; N, 40.59%.
N-(3-Benzyl-4H-1,2,4-triazol-4-yl)acetamide (3b): Recrystallised
from ethyl acetate to yield 1.05 g (49%); m.p. 208 °C; IR (KBr): 3120
(NH), 1698 (C=O), 1590 (C=N) cm−1; 1H NMR (DMSO-d6): δ (ppm)
2.08 (s, 3H, CH3), 3.96 (s, 2H, CH2), 7.20 (bs, 5H, ArH), 8.48 (s, 1H,
CH), 11.34 (s, 1H, NH); UV [λmax, nm (ε × 10−3)]: 210 (8.72); Anal.
Calcd for C11H12N4O: C, 61.10; H, 5.59; N, 25.91. Found: C, 60.95; H,
5.50; N, 26.04%.
N-(3-p-Chlorobenzyl-4H-1,2,4-triazol-4-yl)acetamide(3c):Recrys-
tallised from ethyl acetate to yield 1.20 g (50%); m.p. 215 °C; IR
(KBr): 3115 (NH), 1725 (C=O), 1580 (C=N) cm−1; 1H NMR (DMSO-
d6): δ 2.00 (s, 3H, CH3), 4.00 (s, 2H, CH2), 7.24 (bs, 4H, ArH), 8.50 (s,
1H, CH), 11.28 (s, 1H, NH); UV [λmax, nm (ε × 10−3)]: 208 (7.64), 221
(8.90), 268 (0.07); Anal. Calcd for C11H11N4ClO: C, 52.70; H, 4.42; N,
22.35. Found: C, 53.02; H, 4.40; N, 21.70%.
4-Amino-3-p-chlorobenzyl-1H-1,2,4-triazol-5(4H)-one(7b):Recrys-
tallised from ethyl acetate to yield 1.05 g (45%); m.p. 181 °C; ref.23
180–181 °C, IR (KBr): 3330, 3230 (NH2, NH), 1735 (C=O), 1640
(C=N) cm−1.
4-Amino-3-methyl-1H-1,2,4-triazol-5(4H)-one (7c): Recrystallised
from ethyl acetate to yield 0.42 g (37%); m.p. 227 °C; ref.22 226–
227 °C, IR (KBr): 3320, 3220 (NH2, NH), 1695 (C=O), 1640 (C=N)
cm−1.
4-Amino-3-phenyl-1H-1,2,4-triazol-5(4H)-one (7d): Recrystallised
from ethyl acetate to yield 0.80 g (49%); m.p. 236 °C; ref.22 236–
237 °C, IR (KBr): 3345, 3205 (NH2, NH), 1725 (C=O), 1625 (C=N)
cm−1.
4-Amino-3-p-tolyl-1H-1,2,4-triazol-5(4H)-one (7e): Recrystallised
from ethyl acetate to yield 0.85 g (45%); m.p. 260 °C; ref.22 259–
260 °C, IR (KBr): 3325, 3185 (NH2, NH), 1705 (C=O), 1615 (C=N)
cm−1.
Synthesis of 8
N-(3-Methyl-4H-1,2,4-triazol-4-yl)isonicotinamide (3d): Recryst-
allised from ethyl acetate to yield 0.97 g (44%); m.p. 210 °C; IR
(KBr): 3110 (NH), 1708 (C=O), 1570 (C=N) cm−1; 1H NMR (DMSO-
d6): δ 2.36 (s, 3H, CH3), 7.84 (d, 2H, ArH), 8.66 (s, 1H, CH), 8.80 (d,
2H, ArH), 12.12 (s, 1H, NH); UV [λmax, nm (ε × 10−3)]: 217 (7.85), 267
(7.29); Anal. Calcd for C9H9N5O: C, 53.20; H, 4.46; N, 34.46. Found:
C, 53.01; H, 4.44; N, 34.77%.
N-(3-Methyl-4H-1,2,4-triazol-4-yl)nicotinamide (3e): Recrystal-
lised from ethyl acetate to yield 0.70 g (35%); m.p. 185 °C; IR (KBr):
3115 (NH), 1700 (C=O), 1635, 1590 (C=N) cm−1; 1H NMR (DMSO-
d6): δ 2.26 (s, 3H, CH3), 7.40–7.76 (m, 1H, ArH), 8.10–8.40 (m, 2H,
ArH), 8.64 (s, 1H, CH), 9.00–9.60 (m, 1H, ArH), 12.12 (s, 1H, NH);
UV [λmax, nm (ε × 10−3)]: 213 (8.81), 266 (6.41); Anal. Calcd for
C9H9N5O: C, 53.20; H, 4.46; N, 34.46. Found: C, 53.74; H, 4.57; N,
34.63%.
The corresponding ester formylhydrazone 2 (0.01 mole) was heated
with m-nitrobenzaldehyde, p-chlorobenzaldehyde, o-chlorobenzalde-
hyde, o-hydroxybenzaldehyde, p-methylbenzaldehyde or p-nitroben-
zaldehyde in an oil bath at 160–165 °C for 1.5 h. After cooling, the
solid formed was recrystallised from an appropriate solvent to afford
the desired compound 8.
3-Methyl-4-m-nitrobenzylidenamino-1H-1,2,4-triazol-5(4H)-one
(8a): Recrystallised from ethanol to yield 2.00 g (81%); m.p. 243 °C;
IR (KBr): 3210, (NH), 1715 (C=O), 1610, 1595 (C=N) cm−1; 1H NMR
(DMSO-d6): δ (ppm) 2.36 (s, 3H, CH3), 7.52–7.88 (m, 1H, ArH),
8.00–8.40 (m, 2H, ArH), 8.70 (s, 1H, ArH), 9.80 (s, 1H, N=CH), 11.74
(s, 1H, NH); Anal. Calcd for C10H9N5O3: C, 48.59; H, 3.67; N, 28.33.
Found: C, 48.82; H, 3.58; N, 28.30%.
3-p-Chlorobenzyl-4-m-nitrobenzylidenamino-1H-1,2,4-triazol-
5(4H)-one (8b): Recrystallised from ethanol to yield 2.70 g (82%);
m.p. 232 °C; IR (KBr): 3200, (NH), 1712 (C=O), 1610, 1595 (C=N)
Synthesis of 4
1
cm−1; H NMR (DMSO-d6): δ (ppm) 4.08 (s, 2H, CH2), 7.30 (s, 4H,
The corresponding ester formylhydrazone 2 (0.01 mole) was heated
with isonicotinic acid hydrazide, nicotinic acid hydrazide or 4-
hydroxybenzoic acid hydrazide (0.01 mole) in an oil bath at 110–
120 °C for 1.5 h. After cooling to room temperature, 2–3 mL of ethyl
acetate was added to the viscous reaction mixture. On cooling the
mixture in a deep-freezer, a white solid appeared. This was recrystal-
lised from an appropriate solvent to give the desired compound.
2-p-Chlorobenzyl-5-(pyridine-4-yl)-1,3,4-oxadiazole (4a): Recrys-
tallised from acetone/water (1:1) to yield 1.50 g (55%); m.p. 135 °C;
IR (KBr):1610, 1555 (C=N) cm−1; 1H NMR (DMSO-d6): δ (ppm) 4.40
(s, 2H, CH2), 7.36 (s, 4H, ArH), 7.60 (d, 2H, ArH), 8.72 (d, 2H, ArH);
UV [λmax, nm (ε × 10−3)]: 221 (0.11), 245 (14.14); Anal. Calcd for
C14H10N3OCl: C, 61.88; H, 3.71; N, 15.46. Found: C, 61.62; H, 3.85;
N, 14.97%.
ArH), 7.60–8.40 (m, 3H,ArH), 8.52 (s, 1H,ArH), 9.80 (s, 1H, N=CH),
12.00 (s, 1H, NH); Anal. Calcd for C16H12N5O3Cl: C, 53.72; H, 3.38;
N, 19.58. Found: C, 53.95; H, 3.05; N, 19.60%.
3-Phenyl-4-o-chlorobenzylidenamino-1H-1,2,4-triazol-5(4H)-one
(8c): Recrystallised from ethyl acetate to yield 2.57 g (86%); m.p.
194 °C; IR (KBr): 3170, (NH), 1698 (C=O), 1592, 1550 (C=N) cm−1;
1H NMR (DMSO-d6): δ (ppm) 7.00–8.00 (m, 9H, ArH), 10.06 (s, 1H,
N=CH), 12.30 (s, 1H, NH); Anal. Calcd for C15H11N4OCl: C, 60.31;
H, 3.71; N, 18.75. Found: C, 60.92; H, 3.72; N, 18.74%.
3-p-Tolyl-4-o-hydroxybenzylidenamino-1H-1,2,4-triazol-5(4H)-
one (8d): Recrystallised from ethanol to yield 2.45 g (83%); m.p.
238 °C; IR (KBr):3210, 3180 (NH, OH), 1717 (C=O), 1620, 1588
(C=N) cm−1; 1H NMR (DMSO-d6): δ (ppm) 2.40 (s, 3H, CH3), 7.80–
7.92 (m, 8H, ArH), 9.84 (s, 1H, N=CH), 10.30 (s, 1H, OH), 12.16 (s,
1H, NH); Anal. Calcd for C16H14N4O2: C, 65.30; H, 4.79; N, 19.04.
Found: C, 65.72; H, 4.52; N, 18.95%.
2-Phenyl-5-(pyridine-4-yl)-1,3,4-oxadiazole (4b): Recrystallised
from cyclohexane to yield 1.07 g (48%); m.p. 152 °C; lit.18 152–
155 °C, IR (KBr): 1610, 1572 (C=N) cm−1.
3-p-Tolyl-4-p-methylbenzylidenamino-1H-1,2,4-triazol-5(4H)-one
(8e): Recrystallised from ethanol to yield 2.30 g (79%); m.p. 203 °C;
IR (KBr): 3170, (NH), 1705 (C=O), 1605, 1586 (C=N) cm−1; 1H NMR
(DMSO-d6): δ (ppm) 2.40 (s, 6H, 2CH3), 7.20–7.92 (m, 8H, ArH),
9.56 (s, 1H, N=CH), 12.04 (s, 1H, NH); Elemental Anal. Calcd For
C17H16N4O: C, 69.85; H, 5.52; N, 19.16. Found: C, 69.70; H, 5.65; N,
19.23%.
3-p-Tolyl-4-p-nitrobenzylidenamino-1H-1,2,4-triazol-5(4H)-one
(8f): Recrystallised from ethanol to yield 2.50 g (78%); m.p. 240 °C;
IR (KBr): 3190, (NH), 1705 (C=O), 1600, 1580 (C=N) cm−1; 1H NMR
(DMSO-d6): δ (ppm) 2.40 (s, 3H, CH3), 7.20 (d, 2H, ArH), 7.56–8.40
(m, 6H, ArH), 9.76 (s, 1H, N=CH), 12.24 (s, 1H, NH); Anal. Calcd for
C16H13N5O3: C, 59.44; H, 4.05; N, 21.66. Found: C, 59.11; H, 4.32; N,
21.74%.
2-p-Tolyl-5-(pyridine-4-yl)-1,3,4-oxadiazole (4c): Recrystallised
from acetone/water (1:1) to yield 1.20 g (51%); m.p. 125 °C; lit.19
120–123 °C, IR (KBr): 1610, 1572 (C=N) cm−1.
2-Phenyl-5-(pyridine-3-yl)-1,3,4-oxadiazole (4d): Recrystallised
from acetone/water (1:3) to yield 1.06 g (48%); m.p. 116 °C; lit.20
112–114 °C, IR (KBr): 1608, 1580 (C=N) cm−1.
2-p-Tolyl-5-(pyridine-3-yl)-1,3,4-oxadiazole (4e): Recrystallised
from acetone/water (1:3) to yield 1.06 g (48%); m.p. 103 °C; lit.20
102–104 °C, IR (KBr):1602, 1585 (C=N) cm−1.
2-Phenyl-5-(p-hydroxyphenyl)-1,3,4-oxadiazole (4f): Recrystal-
lised from acetone/water (1:2) to yield 1.05 g (44%); m.p. 253 °C;
lit.21 253 °C, IR (KBr): 3120 (OH), 1610 (C=N) cm−1.
Synthesis of 7
A solution of the corresponding compound 2 (0.01 mol) in water was
refluxed with carbohydrazide (0.01 mol) for 8 h. The solvent was
removed under reduced pressure and the gummy residue was crystal-
lised from an appropriate solvent to give the desired compound.
4-Amino-3-benzyl-1H-1,2,4-triazol-5(4H)-one (7a): Recrystallised
from ethyl acetate to yield 0.82 g (44%); m.p. 168 °C; ref.22 167–
168 °C, IR (KBr): 3340, 3220 (NH2, NH), 1730 (C=O), 1640 (C=N)
cm−1.
We thank Aykut Ikizler (Professor emeritus) for his valuable
scientific contribution to the work.
Received 22 October 2012; accepted 7 January 2013
Paper 1201586 doi: 10.3184/174751913X13603559594859
Published online: 12 March 2013