1058 Nagarajan et al.
Asian J. Chem.
under anhydrous conditions unless otherwise indicated. Column
chromatography was performed with silica gel (200-400 mesh)
or neutral aluminium oxide. Chromatograms were visualized
by fluorescence quenching with UV light at 254 nm or by staining
using base solution of potassium permanganate or anisalde-
hyde or vanillin. Melting points were recorded in GUNA Melting
point apparatus and are uncorrected. NMR spectra were recorded
at room temperature on 300 or 500 MHz FT NMR Spectrometer
(Bruker). Chemical shift (δ) is reported in ppm, coupling cons-
tants (J) are given in Hz.
H]+ calcd. for C12H12N6O6 Calculated = 336.2603, found =
336.2601.
Methyl 1-((2,4-dinitrophenyl)amino)-5-methyl-1H-1,2,3-
triazole-4-carboxylate (b):Yellow powder, yield 90 %, m.p.
160 °C, IR (ν, cm-1): 3300, 2952, 1729, 1615, 1508, 1343,
1103, 524.1H NMR (300 MHz, CDCl3): δ 10.68 (s, 1H), 9.23
(s, 1H), 8.36 (dd, 1H, J = 6.9, 2.4 Hz), 6.30 (d, 1H, J = 9.3
Hz), 4.02 (s, 3H), 2.61 (s, 3H). 13CNMR (75 MHz, CDCl3): δ
161.13, 145.31, 141.11, 140.43, 135.85, 132.74, 130.86,
123.26, 114.89, 52.46, 8.63. HRMS (ESI): m/z [M + H]+ calcd.
for C11H10N6O6: Calculated = 322.2337, found = 322.2333.
Allyl 1-((2,4-dinitrophenyl)amino)-5-methyl-1H-1,2,3-
triazole-4-carboxylate (c): Light brown powder, yield 85 %,
m.p. 142 °C, IR (ν, cm-1): 3311, 3098, 1726, 1612, 1345, 1097,
925, 826, 734. 1H NMR (500 MHz, CDCl3): δ 10.92 (s, 1H),
9.17 (s, 1H), 8.33 (dd, 1H, J = 1.5, 2.5 Hz), 6.31 (d, 1H, J = 4
Hz), 6.02 (q, 1H, J = 1.5, 4.5 Hz), 5.41 (d, 1H, J = 1 Hz), 5.33
(d, 1H, J = 1 Hz), 4.87 (d, 2H, J = 1 Hz), 2.6 (s, 3H). 13CNMR
(125 MHz, CDCl3): δ 160.54, 145.48, 141.03, 140.76, 135.82,
132.80, 131.57, 130.96, 123.31, 119.53, 115.10, 66.19, 8.83.
HRMS (ESI): m/z [M + H]+ calcd. for C13H12N6O6. Calculated
= 342.2710, found = 342.2711.
tert-Butyl 1-((2,4-dinitrophenyl)amino)-5-methyl-1H-
1,2,3-triazole-4-carboxylate (d): Light brown powder, yield
76 %, m.p. 186 °C, IR (ν, cm-1): 3274, 2986, 1717, 1610, 1524,
1332, 1155, 828. 1H NMR (500 MHz, CDCl3): δ 9.20 (s, 1H),
8.28 (dd, 1H, J = 6.5, 2.5 Hz), 6.29 (d, 1H, J = 9 Hz), 4.10 (s,
1H), 2.57 (s, 3H), 1.64 (s, 9H). 13CNMR (125 MHz, CDCl3):
δ 160.11, 145.63, 141.17, 139.80, 137.33, 132.86, 130.96,
129.97, 123.39, 119.25, 115.14, 83.39, 28.45, 8.92. HRMS
(ESI): m/z [M + H]+ calcd. for C14H16N6O6 Calculated = 364.3134,
found = 364.3136.
Benzyl 1-((2,4-dinitrophenyl)amino)-5-methyl-1H-
1,2,3-triazole-4-carboxylate (e): Light yellow crystals, yield
83 %, m.p. 158 °C, IR (ν, cm-1): 3092, 1723, 1605, 1510, 1344,
1100, 833, 742.1H NMR (500 MHz, CDCl3): δ 10.76 (s, 1H),
9.17 (s, 1H), 8.31 (d, 1 H, J =9.5 Hz), 7.47 (d, 1H, J = 7.5 Hz),
7.38 (m, 5H, J = 7, 4.5 Hz), 5.42 (s, 2H), 2.56 (s, 3H). 13C
NMR (125 MHz, CDCl3): δ 160.73 145.48, 141.22, 140.73,
135.98, 135.36, 132.87, 130.98, 128.87, 128.80, 127.48,
123.39, 115.10, 67.37, 8.88. HRMS (ESI): m/z [M + H]+ calcd.
for C17H14N6O6. Calculated = 398.3297, found = 398.3302.
Ethyl 1-((2,4-dinitrophenyl)amino)-5-phenyl-1H-1,2,3-
triazole-4-carboxylate (f): Orange colour powder, yield 88
%, m.p. 130 °C, IR (ν, cm-1): 3484, 2116, 1693, 1614, 1506,
1334, 1138, 1088, 754. 1H NMR (500 MHz, CDCl3): δ 11.51
(s, 1H), 9.13 (s, 1H), 8.64 (dd, 1H, J = 7, 2.5 Hz), 8.11 (d, 2H,
J = 5 Hz), 7.91 (t, 1H, J = 4 Hz), 7.76 (t, 2H, J = 2, 3.5 Hz),
7.52 (s, 1H), 4.43 (q, 2H, J = 7, 7.5 Hz), 1.37 (t, 3H, J = 7, 7
Hz). 13CNMR (125 MHz, CDCl3): δ 163.03, 144.56, 139.12,
138.84, 134.34, 131.20, 130.57, 130.41, 130.06, 129.01,
128.09, 123.45, 117.21, 62.82, 14.58. HRMS (ESI): m/z [M +
H]+ calcd. for C17H14N6O6. Calculated = 398.3297, found =
398.3294.
General procedure for 1-arylamino 1,2,3-triazole: A
two neck round bottom flask was charged with β-keto ester (5
mmol), 2,4-dinitro phenyl hydrazine (5.5 mmol), ethanol (15
mL), few drops of conc. HCl and heated at 50 °C for 1 h. After
confirming the formation of hydrazone by TLC, ice cooled
water or ice cubes are added in to the reaction mixture. The
product will form as yellow precipitate, that precipitate has
been filtered by normal filter paper. In second step hydrazone
(3 mmol), DBU (3.3 mmol) and a solution imidazole sulfonyl
azide (3.3 mmol) in CH3CN (10 mL) was added and the reaction
mixture was cooled to -20 to 25 °C.After 2 h, the reaction was
quenched with water, diluted with CH2Cl2 washed with water,
brine, dried over anhydrous Na2SO4. The organic layer was
concentrated under reduced pressure to get the crude product,
which was purified by column chromatography (silica gel) using
petroleum ether/ethyl acetate (85:15) to get pure compound.
General procedure for reductive cleavage of N-N bond
from 1-arylamino 1,2,3-triazole: A two neck round bottom
flask was charged with 1-arylamino-1,2,3-triazole (1 mmol),
methanol (5 mL) this mixture was kept under hydrogen gas
atmosphere. In this atmosphere we have to add Pd/C (100 mg)
powder carefully. This reaction mixture allowed to run under
room temperature for overnight, after completion of the
reaction we have to filter using celite powder. The organic layer
was concentrated under reduced pressure to get the crude pro-
duct which was purified by column chromatography (silica gel)
using petroleum ether/ethyl acetate (65:35) to get pure compound
(Scheme-I).
NO
2
EtO C
2
N
N
Imid-SO N ,
O
O
2
3
N
2,4-DNPH
NO
DBU,CH CN,
3
2
OEt
NH
NH
NO
Con. HCl, EtOH
-20 to 25 ºC,
3 h
N
2
CO Et
2
O N
2
Scheme-I: Synthesis of 1-arylamino-1,2,3-triazole
Spectroscopic data for 1-arylamino-1,2,3-triazole
Ethyl 1-((2,4-dinitrophenyl)amino)-5-methyl-1H-1,2,3-
triazole-4-carboxylate (a): Light brown solid, yield 92 %,
m.p. 104 °C, IR (ν, cm-1): 3359, 3260, 1725, 1613, 1532, 1344,
1307, 1158, 1095, 906, 817. 1H NMR (300 MHz, CDCl3): δ
10.89 (brs, 1H), 9.19 (s, 1H), 8.35 (dd, 1H, J = 6.9, 2.4 Hz),
6.31 (d, 1H, J = 9.3 Hz), 4.49 (q, 2H, J = 6.9, 7.2 Hz), 2.60 (s,
3H), 1.41 (m, 3H, J = 7.2, 5.4 Hz). 13CNMR (75 MHz, CDCl3):
δ 160.48, 145.11, 140.30, 140.26, 135.44, 132.16, 130.52,
122.83, 114.70, 61.23, 13.89, 8.37. HRMS (ESI): m/z [M +
1-(1-((2,4-Dinitrophenyl)amino)-5-methyl-1H-1,2,3-
triazol-4-yl)ethanone (g): Dark brown solid, yield 93 %, m.p.
116 °C, IR (ν, cm-1): 3446, 3126, 1610, 1533, 1346, 1124,
904, 843, 735. 1H NMR (500 MHz, CDCl3): δ 8.77 (s, 1H),