210
X.-H. Zhao, Z.-W. Ye / Chinese Chemical Letters 25 (2014) 209–211
N
NH
H NN
NNH
2
2
O
O
2
a
N
N
b
N H
MnO
+
2
4
+
2
+
C
H Br
12 25
N
N
NH
NH
2
2
C
H
N
N
C
H
N
N
d
c
12 25
12 25
AgNO
NO
3
+
3
Br
Scheme 1. Synthesis of 1-amino-3-dodecyl-1,2,3-triazolium nitrate. Condition and reagent: (a) CH3OH, 70 8C; (b) CH3CN, 20 8C; (c) CH3COOCH2CH3, 80 8C; (d) CH3OH, 20 8C.
completed, the solution was distilled under high vacuum and the
yellow solid solidified at lower temperatures. Subsequently, the
solid was washed with isopropanol repeatedly and dried at 25 8C
for several hours in vacuo to give glyoxal bishydrazone as a white
3. Results and discussion
3.1. Optimal reaction conditions
crystal (7.92 g, 90.3%). 1H NMR (500 MHz, DMSO-d6):
d
6.58 (s, 4H,
In the general synthesis of 1-amino-3-dodecyl-1,2,3-triazolium
nitrate, cyclization of glyoxal bishydrazone and the use of MnO2
were critical. Thus, to optimize the conditions, the cyclization
reaction was investigated under different reaction conditions
(Table 1). We found that the increase of MnO2/glyoxal bishy-
drazone molar ratio and reaction time was beneficial to the
formation of 1-amino-1,2,3-triazole. Considering the effect of
increasing MnO2 and time on yields, we selected the molar ratio of
2:1 and reaction time of 3.0 h as the optimal values. Higher
temperatures were more favorable to intramolecular electron
transfer so promoted the decomposition of products, resulting in
decreased yields (entry 8, 9).
In the alkylation reaction of 1-amino-1,2,3-triazole and
bromododecane, reactants were highly soluble in acetonitrile,
dimethylformamide and ethyl acetate. Because of low volatility of
dimethylformamide and high toxicity of acetonitrile, we chose
ethyl acetate as the solvent in which the reaction proceeded well.
The reaction was further optimized under different conditions
(Table 2). The yield was less affected by the increase of molar ratio
bromododecane/1-amino-1,2,3-triazole, but it increased sharply at
increased temperatures until 80 8C. Thus, the reaction was carried
out with the molar ratio, temperature and time being 1.5:1, 80 8C
and 40 h, respectively. Longer time and higher temperatures led to
N–H), 7.40 (s, 2H, C–H); IR (neat, cmÀ1):
n 3329 (N–H), 3155 (C–H),
1574 (C55N), 917 (55C–H); MS (ESI): m/z 87.11 ([M+H]+).
2.3. Synthesis of 1-amino-1,2,3-triazole
To a solution of glyoxal bishydrazone (1.73 g, 20.0 mmol) in
acetonitrile (25.8 mL) was added activated MnO2 (3.43 g,
39.4 mmol) at 20 8C in batches, three fourths of which was added
over 0.5 h and the rest was added after 1.5 h. The reaction was
monitored by TLC (thin layer chromatography) analysis. Upon
completion, manganese dioxide was recovered by filtration.
Acetonitrile was easily removed under reduced pressure. A yellow
crystal was obtained at low temperatures, washed with a small
amount of chloroform and dried in vacuum to afford 1.49 g (88.2%)
of 1-amino-1,2,3-triazole. 1H NMR (500 MHz, DMSO-d6):
2H, NH2), 7.63 (s, 1H, C4-H), 7.89 (s, 1H, C5-H); IR (neat, cmÀ1):
d 6.98 (s,
n
3311 (N–H), 3142 (55C–H), 1639 (C55C), 1115 (C–N), 806 (N–H); MS
(EI): m/z 85.10 ([M+H]+), 107.04 ([M+Na]+), 123.02 ([M+K]+),
139.05 ([M+Na+CH3OH]+).
2.4. Synthesis of 1-amino-3-dodecyl-1,2,3-triazolium bromide
1-Amino-1,2,3-triazole (0.569 g, 6.50 mmol) was dissolved in
ethyl acetate (30 mL) followed by the addition of bromododecane
(3.7 mL) in the darkness. The reaction mixture was stirred under
reflux for 40 h at 80 8C. At the end of the reaction, the solution was
cooled to room temperature and washed with ethyl acetate.
Thereafter, the solvent was removed by evaporation in vacuo. The
residue was dried to afford 1.46 g (64.5%) of 1-amino-1,2,3-
Table 1
Optimization of reaction conditions on the synthesis of 1-amino-1,2,3-triazole.
Entry
Ma
Temperature (8C)
Time (h)
Yield (%)
1
2
1.0:1
1.0:1
1.0:1
1.5:1
1.5:1
2.0:1
2.0:1
2.0:1
2.0:1
2.5:1
2.5:1
20
20
20
20
20
20
20
25
30
20
20
2.5
3.0
3.5
3.0
3.5
3.0
3.5
3.0
3.0
3.0
3.5
43.4
61.2
81.4
76.1
87.7
88.2
88.6
73.4
60.7
88.3
88.5
3
triazolium bromide as
DMSO-d6): 0.86 (3H, CH3), 1.2 (18H, CH2), 1.88 (2H, C–H), 4.53
(2H, C–H), 8.30 (2H, N–H), 8.64 (1H, C5-H), 8.86 (1H, C4-H); IR
(neat, cmÀ1):
3119 (N–H), 3071 (55C–H), 2962 (–CH3), 1634
a
white crystal. 1H NMR (500 MHz,
4
5
d
6
7
n
8
(C55C), 1371 (–CH3), 1466 (C–H), 1216 (C–N), 823 (N–H), 718
(C–H), 666 (C–H); MS (EI): m/z 53.06 ([M+]), 85.03 ([MÀ]).
9
10
11
a
2.5. Synthesis of 1-amino-3-dodecyl-1,2,3-triazolium nitrate
Molar ratio (MnO2/glyoxal bishydrazone).
Table 2
A solution of AgNO3 (0.297 g, 1.70 mmol) in water (5 mL) was
slowly added to a solution of 1-amino-3-dodecyl-1,2,3-triazolium
bromide (0.439 g, 1.30 mmol) in methanol (20 mL) at 20 8C in the
darkness. The reaction mixture was stirred for 3.5 h. Silver bromide
was filtered off and the filtrate was dried over anhydrous CaCl2. The
solvent was evaporated under reduced pressure to give 0.353 g
(80.4%) of 1-amino-3-dodecyl-1,2,3-triazolium nitrate a the white
Optimization of reaction conditions on the synthesis of 1-amino-3-dodecyl-1,2,3-
triazolium bromide.
Entry
Ma
Temperature (8C)
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
9
1.5:1
1.5:1
1.5:1
1.5:1
1.5:1
1.5:1
1.5:1
2.0:1
2.5:1
50
60
70
80
85
80
80
80
80
40
40
40
40
40
45
50
40
40
–
10.9
32.5
64.5
37.6
53.2
–
powder. 1H NMR (500 MHz, DMSO-d6):
CH2), 1.88 (2H, C–H), 4.53 (2H, C–H), 8.30 (2H, N–H), 8.64 (1H, C–
H), 8.86 (1H, C–H); IR (neat, cmÀ1):
3126 (N–H), 3059 (55C–H),
d 0.86 (3H, CH3), 1.2 (18H,
n
64.7
66.1
2915 (–CH3), 1647 (C55C), 1373 (–CH3), 1467 (C–H), 1254 (C–N),
828 (N–H), 718 (C–H), 623 (C–H); MS (EI): m/z 253.17 ([M+]), 62.09
([MÀ]).
a
Molar ratio (bromododecane/1-amino-1,2,3-triazole).