Microwave-Assisted synthesis of nitroketene N, S-arylaminoacetals

Article abstract of DOI:10.1590/S0103-50532010000500005

In this paper we report the use of microwaves as heat source to promote the synthesis of a series of nitroketene N, S-acetals with good to excellent isolated yields. These compounds are very useful intermediates for synthesizing nitrogen-containing hetero

Full text of DOI:10.1590/S0103-50532010000500005

J. Braz. Chem. Soc., Vol. 21, No. 5, 795-799, 2010.
Printed in Brazil - ©2010 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
Diego P. Sangi and Arlene G. Corrêa*
Departamento de Química, Universidade Federal de São Carlos, 13565-905 São Carlos-SP, Brazil
Neste trabalho nós relatamos o uso de microondas como fonte de energia para promover
a síntese de uma série de nitroeteno N,S-acetais com bons rendimentos. Estes compostos são
intermediários muito úteis para a síntese de sistemas heterocíclicos nitrogenados.
In this paper we report the use of microwaves as heat source to promote the synthesis of a
series of nitroketene N,S-acetals with good to excellent isolated yields. These compounds are very
useful intermediates for synthesizing nitrogen-containing heterocycles.
Keywords: nitroketene N,S-arylaminoacetals, microwaves, quinoxalines
Introduction
Microwave-assisted organic synthesis has had a
profound impact on the way that chemists approach organic
and parallel synthesis. Clearly, reductions in reaction times,
improved yields and suppression of side products, relative
to conventional thermal heating, are some benefits of this
emerging technology.13-15
In this paper we report the use of microwaves as heat
source to promote the synthesis of a series of nitroketene
N,S-acetals with good to excellent isolated yields.
Nitroketene N,S-acetals are very useful intermediates
for synthesizing nitrogen-containing heterocycles,
such as 2-amino-3-nitro-4H-chromenes,1 4-imino-3,4-
dihydropyrimidin-2(1H)-ones,2 and quinoxalines.3,4
Substituted quinoxalines have displayed a large number
of biological activities including antiviral, antibacterial
and as kinase inhibitors.5,6 1-Methylamino-l-methylthio-
2-nitroethene is a crucial intermediate for the manufacture
of ranitidine.7
Results and Discussion
The synthesis of nitroketene N,S-acetals (3) are
usually performed by reaction of l,l-bis(methylthio)-2-
nitroethene (1) with one equivalent of several primary or
secondary amines (Scheme 1).1,8,9 A second approach to
the synthesis of nitroketene N,S-acetals is performed by
adding nitromethane anion to methyl isocyanate, followed
by S-methylation.8,10 In a different approach, nitromethane
has been condensed with bis(methylthio)methaneimine
in the presence of a rare-earth exchanged NaY zeolite.11
Nowadays, it is noteworthy to connect research in
chemistry and environmental protection. One of the
principles of green chemistry is energy efficiency, thus the
synthetic methods should be conducted whenever possible
at room temperature and pressure, to reduce the energy
spent during a chemical process. One option is to replace
the conventional heating by alternative energy sources such
as microwave.12
In a ongoing program towards the synthesis of
quinoxalines, we investigated the reaction of nitroethene 1
with aniline using ethanol as solvent and microwave (MW)
irradiation (Scheme 1). In our first trial, we obtained 43%
o
yield of the desired product after 30 min at 110 C and
70 W. We then performed a series of experiments in order
to optimize this result, which are summarized in Table 1.
We observed that the rate of conversion of reagents
increased with temperature and power of microwave
(entries 1 and 2); however when the temperature increased
o
up to 140 C and power to 150 W, by-products were
formed (entry 3). Thus, we decided to investigate the
time reaction by keeping temperature at 110 oC and power
at 70 W (entries 4, 5 and 6). The desired product was
obtained in 85% yield, gradually increasing the reaction
time, without formation of by-products after 90 min. We
confirmed the optimization with p-methoxyaniline, which
furnished higher yields in the same conditions.
*e-mail: agcorrea@ufscar.br

796
Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
Scheme 1. Synthesis of nitroketene N,S-arylaminoacetals (3).
After optimizing the reaction, we performed the
coupling of different amines possessing electron
donating and electron withdrawing groups to evaluate the
scope of this protocol. Good to excellent isolated yields
were obtained in most cases, excepting the reaction
with anilines 2k and 2n, probably due to the presence
of the strong electron withdrawing group. We have also
observed that groups in the 2-position may cause steric
hindrance effect, as for example for anilines 2d and 2g
(Table 2). The reaction with ciclohexylamine (4) was
performed (Scheme 2) and furnished the corresponding
N-[1-(methylthio)-2-nitroethenyl]-cyclohexanamine (5)
in 98% yield.
Table 1. Microwave-assisted reaction of nitroethene 1 with aniline and
p-methoxyaniline
Due to the failure of the methodology as a result of
the presence of strongly electron-withdrawing groups, we
performed further tests with the 4-trifluoromethylaniline
(Table 3). Therefore, we attempt the same procedure by
using higher power and temperature (entry 2). We have
also tested different solvents (entries 3 and 4). In general
a reaction medium with a high loss tangent (tan d) at the
standard operating frequency of a microwave synthesis
reactor (2.45 GHz) is required for good absorption and,
consequently, for efficient heating.13 However, even in this
Entry
time
(min)
Potency Temperature
(W)
3, yield (%)a
(oC)
R=H
R=4-OMe
1
2
3
4
5
6
30
30
30
45
60
90
20
70
80
35
43
40
61
73
85
53
64
110
140
110
110
110
150
70
35
84
70
94
70
100
aIsolated yield after purification. Purity was determined by GC-MS.
Table 2. Microwave-assisted reaction of nitroethene 1 with different anilines
Aniline 2
R1
OMe
OMe
OMe
OMe
H
R2
R3
R4
H
3, yield (%)a
mp (oC)
190 dec.
148-150
125-126
126-127
157-158
189 dec.
-
mp (oC) literature
a
b
c
d
e
f
OMe
OMe
80
87
-
H
OMe
H
142-143 3,4
122-123 3,4
121-1233,4
157-158 3,4
-
H
H
H
91
H
H
OMe
H
51
OMe
H
>99
89
H
OH
H
H
b
g
h
i
H
H
H
OH
H
-
-
H
F
H
98
traces
97
157-158
-
154-156 21
126-127 3,4
173-174 18
177-179 22
-
H
H
Br
F
H
j
H
H
H
174-175
-
b
k
l
H
NO2
H
H
-
H
–OCH2O–
H
–OCH2O–
H
93
85
151-152
152-153
-
m
H
H
H
H
152-153 18
b
n
H
CF3
H
-
-
a Isolated yield after purification; b No reaction was observed.

Vol. 21, No. 5, 2010
Sangi and Corrêa
797
Scheme 2. Synthesis of N-[1-(methylthio)-2-nitroethenyl]-cyclohexanamine (5).
Table 3. Microwave-assisted reaction of nitroethene 1 with
p-trifluoromethylaniline (2n)
Flash column chromatography was performed using
silica gel (Kieselgel 60, 230-400 mesh, E. Merck). Gas
chromatography was performed in a Shimadzu GC-17A
with N2 as carrier and using a DB-5 column. Melting points
were performed in Microquimica MQAPF - 301.
Entry
Solvent
EtOH
EtOH
DMF
Potency (W) Temperature (oC) Product 3n
a
1
2
3
4
70
150
70
110
140
110
110
-
traces
Typical experimental procedure: nitroethene 1 (30 mg
0.182 mmol), amine 2 (0.182 mmol) and ethanol (1 mL)
were placed in a glass tube, purged with oxygen-free
nitrogen during 10 min sealed and irradiated in during
90 min in a CEM Discovery® focused microwave oven
a
-
a
i-PrOH
70
-
a No reaction was observed and starting materials were recovered after
30 min of irradiation.
o
at 110 C and 70 W. The nitroketene N,S-acetals 3 were
case we have gotten just unreacted starting materials and
traces of the desired products.
purified by flash chromatography employing hexanes:ethyl
acetate (4:1 ratio) as eluent.
All products were characterized by 1H and 13C NMR,
infrared, GCMS spectra and melting point. The
spectroscopic data were identical with those described
in the literature.3,4,9,16-20 The geometry of the 1-aryl-1-
methylthio-nitroketenes are probably all E in which
orientation intramolecular hydrogen bonding is possible;
this was verified for 3e by the observation of an nOe
between the thiomethyl and the vinylic hydrogens.21
3,4,5-Trimethoxy-N-[1-(methylthio)-2-nitroethenyl]-
benzenamine (3a)17
1H NMR (400 MHz, CDCl3): d 2.39 (s, 3H), 3.86 (s,
6H), 3.87 (s, 3H), 6.52 (s, 2H), 6.68 (s, 1H), 11.82 (s,
1H). 13C NMR (100 MHz, CDCl3): d 14.77, 56.36, 60.98,
103.66, 107.82, 131.70, 153.65, 163.40, 170.87. IR (KBr)
ν
max/cm-1: 3159.67, 3066.59, 3008.73, 2947.01, 2842.87,
1595.01, 1548.73, 1415.65, 1330.79, 1234.35, 1126.35,
1004.84, 671.18. GC-MS (70 eV) m/z (%): 300 (M+, 10),
266 (80), 251 (100), 223 (33), 194 (37), 167 (20). (Found:
C, 47.34; H, 5.56; N, 9.17; S, 10.18. Calc. for C12H16N2O5S:
C, 47.99; H, 5.37; N, 9.33; S, 10.68%).
Conclusions
In summary, we have demonstrated that reactions
between amines and l,l-bis(methylthio)-2-nitroethene (1)
employing microwave heating is an advantage method since
desired products can be obtained in good yields and shorter
reaction time when compared to the conventional heating.
This protocol afforded a series of nitroketene N,S-acetals
(3) in with good to excellent yields.
3,5-Dimethoxy-N-[1-(methylthio)-2-nitroethenyl]-
benzenamine (3b)3,4
1H NMR (400 MHz, CDCl3): d 2.39 (s, 3H), 3.80 (s,
13
6H), 6.45-6.42 (m, 3H), 6.68 (s, 1H), 11.80 (s, 1H). C
NMR (100 MHz, CDCl3): d 14.81, 55.58, 100.11, 103.98,
108.08, 137.82, 161.32, 162.99. IR (KBr) νmax/cm-1:
3170.70, 3093.59, 2995.23, 2839.01, 1612.37, 1542.94,
1471.58, 1427.22, 1319.21, 1195.78, 1153.35, 1060.77,
972.05, 848.62, 690.47, 597.89. GC-MS (70 eV) m/z (%):
270 (M+, 12), 236 (52), 221 (100), 177 (66), 137 (93), 122
(70), 107 (45).
Experimental
Unless otherwise noted, all commercially available
reagents were purchased from Aldrich Chemical Co.
and used without purification. H and 13C NMR spectra
1
were recorded on a Bruker ARX-400 (400 and 100 MHz
respectively). The IR spectra refer to tablets in KBr and were
measured on a Bomem M102 spectrometer. Mass Spectra
were recorded on a Shimadzu GCMS-QP5000. Elemental
analyses were performed on a Fisons EA 1108 CHNS-O.
Analytical thin-layer chromatography was performed on a
0.25 mm film of silica gel containing fluorescent indicator
UV254 supported on an aluminum sheet (Sigma-Aldrich).
3-Methoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine
(3c)3,4
1H NMR (400 MHz, CDCl3): d 2.39 (s, 3H), 3.83 (s,
3H), 6.70 (s, 1H), 6.90 (t, 1H, J 2.15 Hz), 6.92-6.87 (m, 2H),
7.33 (t, 1H, J 8.26 Hz), 11.82 (s, 1H). 13C NMR (100 MHz,
CDCl3): d 14.71, 54.01, 111.44, 113.76, 117.89, 130.09,

798
Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
137.19, 160.25, 163.28. IR (KBr) νmax/cm-1: 3159.17,
3070.45, 2995.23, 1602.73, 1546.80, 1465.79, 1417.58,
1330.79, 1269.07, 1222.78, 1157.20, 958.55, 848.62,
684.68, 570.89, 532.31. GC-MS (70 eV) m/z (%): 240
(M+, 12), 206 (41), 159 (38), 147 (64), 107 (100), 77 (99).
GC-MS (70 eV) m/z (%): 228 (M+, 7), 194 (11), 135 (54),
122 (45), 95 (100), 75 (47).
4-Bromo-N-[1-(methylthio)-2-nitroethenyl]-benzenamine
(3j)19
1H NMR (200 MHz, CDCl3): d 2.39 (s, 3H), 6.69 (s,
1H), 7.19 (d, 2H, J 8.77 Hz), 7.55 (d, 2H, J 8.77 Hz), 11.70
(s, 1H). 13C NMR (50 MHz, CDCl3): d 14.74, 108.32,
127.58, 131.06, 132.62, 135.30, 159.24. IR (KBr) νmax/cm-1:
3151.45, 3083.95, 3060.81, 1585.37, 1564.15, 1479.29,
1411.79, 1396.36, 1348.14, 1265.21, 1168.78, 1010.63,
910.33, 759.90, 678.89. GC-MS (70 eV) m/z (%): 290
(M+2, 5), 288 (M+, 6), 256 (16), 254 (16), 209 (44), 207
(44), 157 (68), 155 (69), 75 (100). (Found: C, 38.08; H,
3.49; N, 9.44; S, 10.44. Calc. for C9H9N2O2SBr: C, 37.38;
H, 3.14; N, 9.69; S, 11.09%).
2,5-Dimethoxy-N-[1-(methylthio)-2-nitroethenyl]-
benzenamine (3d)3,4
1H NMR (400 MHz, CDCl3): d 2.40 (s, 3H), 3.78 (s, 3H),
3.84 (s, 3H), 6.82 (dd, 1H, J1 9.27, J2 2.98 Hz), 6.90 (d, 1H, J
9.27 Hz), 7.01 (d, 1H, J 2.98 Hz), 6.71 (s, 1H), 11.79 (s, 1H).
13C NMR (100 MHz, CDCl3): d 14.86, 55.91, 56.33, 108.39,
112.33, 112.41, 113.13, 125.96, 147.24, 153.18, 162.78.
IR (KBr) νmax/cm-1: 3161.10, 3074.31, 2995.23, 1544.87,
1508.22, 1473.51, 1411.79, 1321.14, 1226.64, 1114.77,
1045.34, 802.33, 709.75. GC-MS (70 eV) m/z (%): 270
(M+, 19), 236 (69), 207 (56), 189 (55), 179 (100), 107 (55).
N-[1-(Methylthio)-2-nitroethenyl]-1,3-benzodioxol-5-
amine (3l)16
4-Methoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine
(3e)3,4
1H NMR (400 MHz, CDCl3): d 2.37 (s, 3H), 6.04 (s,
2H), 6.66 (s, 1H), 6.76-6.74 (m, 2H), 6.82 (d, 1H, J 8.08
Hz), 11.59 (s, 1H). 13C NMR (100 MHz, CDCl3): d 14.62,
107.82, 125.91, 128.10, 129.37, 138.18, 163.40. IR (KBr)
1H NMR (400 MHz, CDCl3): d 2.36 (s, 3H), 3.84 (s,
3H), 6.68 (s, 1H), 6.93 (d, 2H, J 8.64 Hz), 6.92-6.87 (d, 2H,
13
J 8.64 Hz), 11.64 (s, 1H). C NMR (100 MHz, CDCl3):
d 14.62, 55.51, 107.43, 127.72, 128.84, 159.43, 164.41.
IR (KBr) νmax/cm-1: 3145.67, 3001.02, 2960.52, 2839.01,
1606.59, 1510.15, 1467.72, 1427.22, 1334.64, 1247.85,
1182.28, 1157.20, 908.41, 825.47, 765.68, 684.68, 597.89,
532.31. GC-MS (70 eV) m/z (%): 240 (M+, 14), 206 (42),
159 (79), 134 (100), 107 (68), 77 (99).
ν
max/cm-1: 3139.88, 3024.16, 2908.44, 1610.44, 1566.08,
1504.37, 1473.51, 1336.57, 1174.56, 1029.91, 867.90,
761.83. GC-MS (70 eV) m/z (%): 254 (M+, 16), 220 (57),
207 (24), 173 (83), 121 (100), 65 (87). (Found: C, 47.04; H,
4.25; N, 10.80; S, 11.47. Calc. for C10H10N2O4S: C, 47.24;
H, 3.96; N, 11.02; S, 12.61%).
4-[[1-(Methylthio)-2-nitroethenyl]amino]-phenol (3f)16,17
1H NMR (400 MHz, MeOD): d 2.42 (s, 3H), 6.79 (s,
1H), 6.83 (d, 2H, J 9.24 Hz), 7.14 (d, 2H, J 9.24 Hz).
13C NMR (100 MHz, MeOD): d 14.91, 108.08, 117.04,
129.27, 129.49, 159.16, 167.98. IR (KBr) νmax/cm-1:
3199.67, 3164.95, 3055.02, 2931.58, 1610.44, 1552.58,
1517.87, 1442.65, 1425.29, 1313.43, 1271.00, 1230.49,
1168.78, 906.48, 509.17. GC-MS (70 eV) m/z (%): 226
(M+, 9), 192 (20), 145 (55), 133 (89), 119 (47), 93 (55), 65
(100). (Found: C, 47.16; H, 4.74; N, 12.23; S, 13.45. Calc.
for C9H10N2O3S: C, 47.78; H, 4.45; N, 12.38; S, 14.17%).
N-[1-(Methylthio)-2-nitroethenyl]-benzenamine
(3m)3,4,9,16-18
1H NMR (400 MHz, CDCl3): d 2.38 (s, 3H), 6.70 (s,
1H), 7.45-7.27 (m, 5H), 11.81 (s, 1H). 13C NMR (100 MHz,
CDCl3): d 14.67, 101.95, 107.54, 107.69, 108.35, 120.12,
129.94, 147.66, 148.29, 164.09. IR (KBr) νmax/cm-1:
3147.60, 2999.09, 1542.94, 1531.37, 1461.94, 1425.29,
1336.57, 1265.21, 1178.42, 896.83, 756.04, 690.47, 534.24.
GC-MS (70 eV) m/z (%): 210 (M+, 10), 176 (8), 163 (16),
117 (69), 77 (100).
N-[1-(Methylthio)-2-nitroethenyl]-cyclohexanamine (5)20
1H NMR (400 MHz, CDCl3): d 1.47-1.32 (m, 5H),
1.67-1.60 (m, 1H), 1.83 -1.74 (m, 2H), 2.05-1.95 (m,
2H), 2.44 (s, 3H), 3.67 (m, 1H), 6.56 (s, 1H), 10.59 (s,
1H). 13C NMR (100 MHz, CDCl3): d 14.34, 24.25, 25.07,
32.78, 53.79, 105.86, 163.29. IR (KBr) νmax/cm-1: 3136.02,
2993.30, 2927.73, 2852.51, 1564.15, 1461.94, 1423.36,
1348.14, 1315.36, 1218.92, 1081.99, 964.34, 852.47.
GC-MS (70 eV) m/z (%): 216 (M+, 1), 182 (1), 135 (17),
83 (79), 55 (100).
4-Fluoro-N-[1-(methylthio)-2-nitroethenyl]-benzenamine
(3h)9,16,17
1H NMR (400 MHz, CDCl3): d 2.40 (s, 3H), 6.70 (s,
1H), 7.16-7.12 (m, 2H), 7.33 – 7.29 (m, 2H,), 11.67 (s, 1H).
13C NMR (100 MHz, CDCl3): d 14.67, 107.90, 116.35 and
116.57 (C-F), 128.30 and 128.39 (C-F), 132.14, 160.82
and 163.89 (C-F), 163.29. IR (KBr) νmax/cm-1: 3161.10,
3051.16, 3016.45, 1577.66, 1512.08, 1477.36, 1415.65,
1361.64, 1274.85, 1188.06, 914.19, 837.04, 761.83, 684.68.

Vol. 21, No. 5, 2010
Sangi and Corrêa
799
Supplementary Information
9. Kearney, T.; Joule, J. A.; Jackson, A.; Heterocycles 1992, 33,
757.
Supplementary information is available free of charge
at http://jbcs.org.br, as PDF file.
10. Seager, J.F.; Dansey, R.; GB 2 160 204A, 1985.
11. Deshmukh, A. R. A. S.; Reddy, T. I.; Bhawal, B.M.; Shiralkar,
V. P.; Rajappa, S.; J. Chem. Soc., Perkin Trans. I 1990, 1217.
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Soc. 2008, 19, 1264.
Acknowledgments
We acknowledge CAPES, FAPESP, CNPq and
INBEQMeDI – INCT Program for financial support and
fellowships.
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Takeo, H.; WO 2000016766, 2000.
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J. Braz. Chem. Soc., Vol. 21, No. 5, S1-S20, 2010.
Printed in Brazil - ©2010 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
Diego P. Sangi and Arlene G. Corrêa*
Departamento de Química, Universidade Federal de São Carlos, 13565-905 São Carlos-SP, Brazil
Experimental
1H and 13C NMR spectra were recorded on a BrukerARX-400 (400 and 100 MHz respectively). The IR spectra refer
to tablets in KBr and were measured on a Bomem M102 spectrometer. Mass Spectra were recorded on a Shimadzu
GCMS-QP5000.
Figure S1. Representative graphic of the reaction of aniline with nitroethene 1 irradiated during 90 min in a CEM Discovery® focused microwave oven
at 110 ºC and 70 W.
*e-mail: agcorrea@ufscar.br

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Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
Figure S2. GC-MS of 3,4,5-Trimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3a).
Figure S3. 1H NMR of 3,4,5-Trimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3a).

Vol. 21, No. 5, 2010
Sangi and Corrêa
S3
Figure S4. 13C NMR of 3,4,5-Trimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3a).
Figure S5. IR of 3,4,5-Trimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3a)

S4
Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
Figure S6. GC-MS of 3,5-Dimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3b).
Figure S7. 1H NMR of 3,5-Dimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3b)

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Figure S8. 13C NMR of 3,5-Dimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3b).
Figure S9. IR of 3,5-Dimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3b)

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Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
Figure S10. GC-MS of 3-Methoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3c).
Figure S11. 1H NMR of 3-Methoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3c).

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Figure S12. IR of 3-Methoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3c).
Figure S13. GC-MS of 2,5-Dimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3d).

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Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
Figure S14. 1H NMR of 2,5-Dimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3d).
Figure S15. 13C NMR of 2,5-Dimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3d).

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Figure S16. IR of 2,5-Dimethoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3d).
Figure S17. GC-MS of 4-Methoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3e).

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Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
Figure S18. 1H NMR of 4-Methoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3e).
Figure S19. 1H NMR- NOE of 4-Methoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3e).

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Figure S20. 13C NMR of 4-Methoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3e).
Figure S21. IR of 4-Methoxy-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3e).

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Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
Figure S22. GC-MS of 4-[[1-(methylthio)-2-nitroethenyl]amino]-phenol (3f).
Figure S23. 1H NMR of 4-[[1-(methylthio)-2-nitroethenyl]amino]-phenol (3f).

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Figure S24. IR of 4-[[1-(methylthio)-2-nitroethenyl]amino]-phenol (3f).
Figure S25. GC-MS of 4-Fluoro-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3h).

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Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
Figure S26. 1H NMR of 4-Fluoro-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3h).
Figure S27. 13C NMR of 4-Fluoro-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3h).

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Figure S28. IR of 4-Fluoro-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3h).
Figure S29. GC-MS of 4-Bromo-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3j).

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Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
Figure S30. 1H NMR of 4-Bromo-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3j).
Figure S31. IR of 4-Bromo-N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3j).

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Figure S32. GC-MS of N-[1-(methylthio)-2-nitroethenyl]-1,3-benzodioxol-5-amine (3l).
Figure S33. 1H NMR of N-[1-(methylthio)-2-nitroethenyl]-1,3-benzodioxol-5-amine (3l).

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Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
Figure S34. 13C NMR of N-[1-(methylthio)-2-nitroethenyl]-1,3-benzodioxol-5-amine (3l).
Figure S35. IR of N-[1-(methylthio)-2-nitroethenyl]-1,3-benzodioxol-5-amine (3l).

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Figure S36. GC-MS of N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3m).
Figure S37. 1H NMR of N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3m).

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Microwave-Assisted Synthesis of Nitroketene N,S-Arylaminoacetals
J. Braz. Chem. Soc.
Figure S38. 13C NMR of N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3m).
Figure S39. IR of N-[1-(methylthio)-2-nitroethenyl]-benzenamine (3m).