, 2001, 11(6), 230–232
The rearrangement of prepared compounds 6 into 4-acetyl-
amino-2-aryl-5-nitro-2H-1,2,3-triazoles 9 was initially examined
by the example of 4-acetylamino-3-(4-methoxyphenylazo)furoxan
6a. Attempts to perform its thermal rearrangement (boiling in
ethyl acetate, dioxane or toluene) by analogy with that described
in ref. 9 were unsuccessful. In all cases, thermal degradation
with the liberation of initial compound 6a was observed. The
rearrangement was successfully performed only under conditions
of basic catalysis in water at room temperature for 20 min. The
reaction conditions were found suitable for the rearrangement
of other prepared acetylamino derivatives 6. Target nitrotriasoles
9 were precipitated after neutralising the reaction mixture with
hydrochloric acid, and the precipitates were filtered off.†,¶ In all
cases, the yields of nitrotriasoles were higher than 50% (54–62%).
By analogy with ref. 8, we may believe that compounds 9 are
formed via two successive (cascade) rearrangements. As a result
of the first rearrangement via intermediate 7, 1,2,4-oxadiazole
derivatives 8 are formed, which are rearranged into final 4-acetyl-
amino-2-aryl-5-nitro-2H-1,2,3-triazoles 9 under reaction condi-
tions in accordance with Scheme 2.
The formation of nitrotriazoles 9 was supported by the
appearance of a signal due to the nitro group in the 14N NMR
spectra and a peak due to the molecular ion in the mass spectra
(note that the fragment ions [M+ – NO] and [M+ – 2NO], which
are typical of furoxans, are absent). Moreover, upfield signals
(110–130 ppm), which correspond to the C-3 atom of a furoxan
ring, are absent from the 13C NMR spectrum. To provide an
§
4-Acetylamino-3-(4-methoxyphenylazo)furoxan 6a: 82% yield, mp 130–
132 °C, Rf 0.25 (eluent: CHCl3). 1H NMR ([2H6]DMSO) d: 2.20 (s, 3H,
3
MeCO), 3.95 (s, 3H, MeO), 7.10, 7.90 (4H, AA'BB', J 7.3 Hz), 10.50
(br. s, 1H, NH). IR (n/cm–1): 3304 (NH), 1728 (CO), 1616, 1584, 1576,
1568, 1544, 1504, 1496, 1464, 1416, 1368, 1312, 1264, 1240, 1220, 1148,
1016, 1000, 848.
4-Acetylamino-3-(4-ethoxyphenylazo)furoxan 6b: 80% yield, mp 137–
139 °C, Rf 0.20 (eluent: CHCl3). 1H NMR ([2H6]DMSO) d: 1.45 (t, 3H,
Me), 2.13, 2.21 (2s, 3H, MeCO), 4.19 (q, 2H, CH2), 7.10, 7.90 (4H,
3
AA'BB', J 7.4 Hz), 10.50, 10.85 (2br. s, 1H, NH). IR (n/cm–1): 3288
‡
All new compounds exhibited satisfactory elemental analyses, and their
(NH), 2984, 1704 (CO), 1616, 1584, 1568, 1532, 1480, 1472, 1460, 1448,
1432, 1424, 1372, 1328, 1304, 1288, 1256, 1192, 1144, 1128, 1040, 1000,
952, 840.
structures were confirmed by IR and NMR spectroscopy and mass
1
spectrometry. Spectroscopic data: H NMR (250, 300 MHz), 13C NMR
(75.47 MHz) standard TMS; 14N NMR (21.6 MHz), internal standard
MeNO2 (Bruker WM-250 and Bruker AM-300 spectrometers). Compounds
3 were characterised by only spectral methods owing to their capacity to
explode. Mass spectra were measured on a Finnigan MAT INCOS-50
spectrometer. IR spectra were recorded on a UR-20 spectrometer.
3-Azidocarbonyl-4-(4-methoxyphenylazo)furoxan 3a: 86% yield, mp 85–
87 °C (lit.,10 85–87 °C).
4-Acetylamino-3-(2,4,6-trimethylphenylazo)furoxan 6c: 80% yield,
mp 119–120 °C, Rf 0.52 (eluent: CHCl3). 1H NMR ([2H6]DMSO) d:
2.00 (s, 3H, MeCO), 2.10 (s, 3H, 4-Me), 2.35 (s, 6H, 2-Me), 7.10 (s,
2H, CH), 10.50, 10.85 (2br. s, 1H, NH). 13C NMR ([2H6]DMSO) d:
16.41 (MeCO), 20.45 (4-Me), 22.55 (2,6-Me), 129.09 (C-3 fur. ring),
128.92, 134.45, 135.51, 140.47 (Ar), 147.90 (C-4 fur. ring), 168.33
(CO). IR (n/cm–1): 3320 (NH), 1728 (CO), 1604, 1568, 1528, 1456, 1440,
1372, 1304, 1296, 1288, 1280, 1272, 1208, 1152, 992.
3-Azidocarbonyl-4-(4-ethoxyphenylazo)furoxan 3b: yield 100%, mp 71–
1
73 °C, Rf 0.35 (eluent: CHCl3). H NMR (CDCl3) d: 1.50 (t, 3H, Me),
4-Acetylamino-3-(2,4-dimethylphenylazo)furoxan 6d: 85% yield, mp 145–
3
1
4.20 (q, 2H, CH2), 7.03, 8.05 (4H, AA'BB', J 7.2 Hz). IR (n/cm–1):
147 °C, Rf 0.12 (eluent: CHCl3). H NMR ([2H6]DMSO) d: 2.08, 2.15
2176 (N3), 2144 (N3), 1688 (CO), 1616, 1600 (fur. ring), 1488 (N=N),
1388, 1268, 1196, 1040, 868, 800.
(2s, 3H, MeCO), 2.35 (s, 3H, 4-Me), 2.60 (s, 3H, 2-Me), 7.20, 7.60 (2H,
3J 7.2 Hz), 7.30 (s, 1H, CH), 10.70, 11.05 (2br. s, 1H, NH). IR (n/cm–1):
3280 (NH), 2928, 1700 (CO), 1616, 1592, 1372, 1308, 1232, 1176,
1000, 832.
3-Azidocarbonyl-4-(2,4,6-trimethylphenylazo)furoxan 3c: 100% yield,
1
mp 82–84 °C, Rf 0.65 (eluent: CHCl3). H NMR ([2H6]DMSO) d: 2.40
(s, 3H, 4-Me), 2.55 (s, 6H, 2,6-Me), 7.10 (s, 2H, CH). IR (n/cm–1): 2928
(CH), 2184 (N3), 2136 (N3), 1700 (CO), 1608 (fur. ring), 1488 (N=N),
1432, 1392, 1332, 1304, 1288, 1200, 1120, 1080, 984, 864, 808, 752,
720, 704.
4-Acetylamino-2-(4-methoxyphenyl)-5-nitro-2H-1,2,3-triazole 9a: 54%
¶
yield, mp 143–145 °C, Rf 0.22 (eluent: CHCl3). 1H NMR ([2H6]DMSO)
d: 2.15 (s, 3H, MeCO), 3.85 (s, 3H, MeO), 7.15, 7.95 (4H, AA'BB', 3J
7.2 Hz), 10.95 (s, 1H, NH). 13C NMR ([2H6]DMSO) d: 22.63 (MeCO),
55.47 (MeO), 114.82 (m-Ar), 120.53 (o-Ar), 131.32 (ipso-Ar), 138.27
(C–NH), 144.80 (C–NO2), 159.88 (p-Ar), 168.38 (CO). 14N NMR (CDCl3)
d: –26.83 (NO2). IR (n/cm–1): 3240 (NH), 3212 (NH), 3202(NH), 2978,
1690 (CO), 1554, 1514, 1442, 1178, 1124, 1088, 920, 670. MS, m/z:
278 (M+ + 1), 277 (M+), 247 (M+ – NO), 236, 235 (M+ – CH2CO), 205
(M+ – NO2 – CN), 190, 189, 135 (MeOPhN2), 107 (MeOPh).
3-Azidocarbonyl-4-(2,4-dimethylphenylazo)furoxan 3d: 82% yield,
mp 94–95 °C, Rf 0.18 (eluent: CHCl3). 1H NMR (CDCl3) d: 2.45 (s, 3H,
4-Me), 2.67 (s, 3H, 2-Me), 7.15, 7.75 (2H, 3J 7.4 Hz), 7.25 (s, 1H, CH).
IR (n/cm–1): 2184 (N3), 2136 (N3), 1692 (CO), 1608 (fur. ring), 1484
(N=N), 1392, 1328, 1180, 808, 712.
3-Azidocarbonyl-4-(2-hydroxy-1-naphthylazo)furoxan 3e: 100% yield,
mp 100–101 °C, Rf 0.30 (eluent: CHCl3). 1H NMR ([2H6]DMSO) d: 5.0
(br. s, 1H, OH), 7.10–7.80 (m, 6H, naphth.). IR (n/cm–1): 3072 (OH),
2168 (N3), 1712, 1672 (CO), 1616, 1592 (fur. ring), 1584, 1576, 1560,
1536, 1508, 1464 (N=N), 1456, 1400, 1312, 1256, 1192, 1136, 1096,
984, 968, 848, 776, 736. MS, m/z: 325 (M+), 255 (M+ – N3CO), 224
(M+ – N3CO – NO – 1), 194 (M+ – N3CO – 2NO – 1), 171 (M+ – N3CO –
– fur), 143 (M+ – N3CO – fur – N=N).
4-Acetylamino-2-(4-ethoxyphenyl)-5-nitro-2H-1,2,3-triazole 9b: 60%
yield, mp 189–191 °C, Rf 0.25 (eluent: CHCl3). 1H NMR ([2H6]DMSO)
d: 1.35 (t, 3H, Me), 2.15 (s, 3H, MeCO), 4.15 (q, 2H, CH2), 7.15, 7.95
(4H, AA'BB', 3J 7.2 Hz), 11.05 (br. s, 1H, NH). 14N NMR ([2H6]acetone)
d: –25.82 (NO2). IR (n/cm–1): 3248 (NH), 3208 (NH), 3204 (NH), 3064,
2976, 1692 (CO), 1544, 1512, 1448, 1252, 1176, 1120, 1084, 920, 672.
4-Acetylamino-5-nitro-2-(2,4,6-trimethylphenyl)-2H-1,2,3-triazole 9c:
57% yield, mp 145–147 °C, Rf 0.22 (eluent: CHCl3). 1H NMR ([2H6]DMSO)
d: 2.15 (s, 3H, MeCO), 2.35 (s, 3H, 4-Me), 2.63 (s, 6H, 2,6-Me), 7.10
(s, 2H, CH), 10.80 (br. s, 1H, NH). 14N NMR ([2H6]acetone) d: –25.69
(NO2). IR (n/cm–1): 3184 (NH), 2976, 1680 (CO), 1576, 1540, 1524,
1404, 1376, 1368, 1360, 1340, 1320, 1304, 1288, 1272, 1200, 1176, 1036,
1016, 976, 856, 804, 736. MS, m/z: 289(M+), 272 (M+ – OH), 247 (M+ –
– CH2CO), 230 (M+ – NO2COMe), 147 (Me3PhN2), 119 (Me3Ph).
4-Acetylamino-2-(2,4-dimethylphenyl)-5-nitro-2H-1,2,3-triazole 9d:
4-Amino-3-(4-methoxyphenylazo)furoxan 5a: 65% yield, mp 161–163 °C,
1
Rf 0.18 (eluent: CHCl3). H NMR ([2H6]DMSO) d: 3.90 (s, 3H, MeO),
3
6.75 (br. s, 2H, NH2), 7.15, 8.10 (4H, AA'BB', J 7.2 Hz). IR (n/cm–1):
3431, 3322 (NH), 1632, 1625 (NH), 1588, 1194.
4-Amino-3-(4-ethoxyphenylazo)furoxan 5b: 78% yield, mp 160–162 °C,
1
Rf 0.11 (eluent: CHCl3). H NMR ([2H6]DMSO) d: 1.42 (t, 3H, Me),
3
4.19 (q, 2H, CH2), 6.75 (br. s, 2H, NH2), 7.10, 8.00 (4H, AA'BB', J
7.4 Hz). 13C NMR ([2H6]DMSO) d: 15.90 (Me), 64.10 (CH2), 114.4
(m-Ar), 121.58 (C-3 fur. ring), 125.55 (o-Ar), 125.70 (ipso-Ar), 151.30
(C-4 fur. ring), 160.60 (p-Ar). IR (n/cm–1): 3424 (NH2), 3304 (NH2),
3008, 1604, 1592, 1556, 1524, 1480, 1432, 1392, 1360, 1336, 1316, 1304,
1248, 1204, 1192, 1164, 1148, 1128, 1112, 1068, 1024, 1016, 920, 872,
840. MS, m/z: 249 (M+), 233(M+ – O), 219 (M+ – NO), 189 (M+ – 2NO),
149 (M+ – fur – NH2 – 1), 121 (M+ – N=N – fur – NH2 – 1).
1
62% yield, mp 139–141 °C, Rf 0.19 (eluent: CHCl3–isooctane 1:1). H
NMR ([2H6]DMSO) d: 2.15 (s, 3H, MeCO), 2.30 (s, 3H, 4-Me), 2.38 (s,
3
3H, 2-Me), 7.25, 7.55 (2H, J 7.6 Hz), 7.31 (s, 1H, CH), 10.90 (br. s,
1H, NH). 14N NMR (CDCl3) d: –27.26 (NO2). IR (n/cm–1): 3360 (NH),
3200 (NH), 3080, 3056, 1692 (CO), 1568, 1496, 1324, 1240, 1176, 968,
832, 804.
4-Amino-3-(2,4,6-trimethylphenylazo)furoxan 5c: 56% yield, mp 119–
120 °C, Rf 0.70 (eluent: CHCl3). 1H NMR ([2H6]DMSO) d: 2.35 (s, 3H,
Me), 2.55 (s, 6H, 2Me), 6.85 (br. s, 2H, NH2), 7.10 (s, 2H, CH). IR
(n/cm–1): 3425 (NH2), 3316 (NH2), 1655, 1600, 1542, 1524, 1494, 1395,
1385, 1324, 1282, 1210, 1196, 999, 872, 868, 706.
4-Amino-2-(4-ethoxyphenyl)-5-nitro-2H-1,2,3-triazole 10b: 68% yield,
mp 133–135 °C, Rf 0.17 (eluent: CHCl3). 1H NMR ([2H6]DMSO) d:
1.47 (t, 3H, Me), 4.13 (q, 2H, CH2), 6.74 (br. s, 2H, NH2), 7.05, 7.90
(4H, AA'BB', 3J 7.4 Hz). 13C NMR ([2H6]acetone) d: 15.16 (Me), 64.90
(OCH2), 116.16 (m-Ar), 121.50 (o-Ar), 133.15 (ipso-Ar), 140.55 (C–NO2),
150.30 (C–NH2), 160.70 (p-Ar). 14N NMR ([2H6]acetone) d: –23.18
(NO2), –139.34 (N-2 tr. ring), –342.60 (NH2). IR (n/cm–1): 3480 (NH),
3368 (NH), 2992 (CH), 2944 (CH), 1640, 1600, 1568, 1512, 1476, 1396,
1324, 1248, 920, 832. MS, m/z: 249 (M+), 221 (M+ – C2H4), 203 (M+ –
– NO2), 121 (M+ – NH2 – tr-NO2 – 1), 93 (PhO).
4-Amino-3-(2,4-dimethylphenylazo)furoxan 5d: 77% yield, mp 151–
153 °C, Rf 0.21 (eluent: CHCl3). 1H NMR ([2H6]DMSO) d: 2.35 (s, 3H,
3
4-Me), 2.60 (s, 3H, 2-Me), 6.70 (br. s, 2H, NH2), 7.15, 7.55 (2H, J
7.4 Hz), 7.25 (s, 1H, CH). IR (n/cm–1): 3464 (NH2), 3336 (NH2), 2960,
1592, 1192, 1008, 864, 824, 712.
– 231 –