A novel facile synthesis method of N-vinylpyrroles

Article abstract of DOI:10.1002/jhet.1102

A facile and effective synthesis of N-vinylpyrroles had been explored. The synthetic approach was practicable for preparation of N-vinylpyrroles for the mild reaction conditions and readily available materials, compared with previously inaccessible N-vinylpyrroles with electron-withdrawing groups, especially these pyrroles bearing alkaline sensitive substitution groups.

Full text of DOI:10.1002/jhet.1102

Month 2013
A Novel Facile Synthesis Method of N-Vinylpyrroles
*
Tian Lan, Xiaofen Chen, Zenglu Liu, and Zhenmin Mao
School of Pharmacy, Shanghai Jiaotong University, Shanghai, China
*
E-mail: zmmao@sjtu.edu.cn
Received June 11, 2011
DOI 10.1002/jhet.1102
Published online 00 Month 2013 in Wiley Online Library (wileyonlinelibrary.com).
A facile and effective synthesis of N-vinylpyrroles had been explored. The synthetic approach was
practicable for preparation of N-vinylpyrroles for the mild reaction conditions and readily available
materials, compared with previously inaccessible N-vinylpyrroles with electron-withdrawing groups, especially
these pyrroles bearing alkaline sensitive substitution groups.
J. Heterocyclic Chem., 00, 00 (2013).
INTRODUCTION
basic system (KOH-DMSO) was employed along with high
reaction temperature and high reaction pressure (Scheme 1)
[2,9]. Bogdal and Jaskot tried to prepare N-vinylpyrroles by
employing dichoroethane as vinyl formation agent with
slightly less alkaline conditions by using alcohols as solvent
instead of DMSO in Trofimov reaction, but the strong base,
KOH, still was used as the alkali for the reaction system. In
their report, only very limited samples of N-vinylpyrroles
were successful and with low yields [10].
N-Vinylpyrroles with diverse functional groups other
than alkyl groups are of great interest to researchers both
for better understanding of their chemical and physical
properties and their potential applications. Full investiga-
tion with N-vinylpyrroles requires mild synthetic approaches
in which those sensitive functional groups, such as esters,
carbonyl group and nitrile would survive.
The methods for synthesis of N-vinylpyrrole derivatives
with mild reaction conditions had been studied for some
time in our lab. A novel method had been developed to
solve the difficulties in the preparation of N-vinylpyrroles
with alkaline sensitive substitution groups. The mild
reaction conditions used potassium carbonate with mild
heating, and no high reaction pressure was required
(Scheme 2). N-Vinylpyrrole derivatives with alkaline
sensitive groups, such as CN, CHO, and COOEt, were
synthesized [11].
Pyrrole ring system, which widely existed in nature, is a
subunit of many natural products and pharmaceutical
agents, such as haem, chlorophylls, and vitamin B12. This
structure can also be found in functional polymers and
pigments. Substitutions and modifications at different
positions of the five-membered hetero ring further extend
number and types of its derivatives, and embedded many
major applications. Many substitutions and modifications
at all of its five positions of the ring system have been
widely explored [1]. However, among these substitutions
and modifications, the substitutions and modifications at
the nitrogen atom are less studied. N-vinylpyrrole, a vinyl
group conjugated with the hetero atom of the aromatic
ring, has been only studied in a very limited fraction,
mostly owing to the limited numbers of N-vinylpyrroles,
which are available by the current synthetic method. With
the increasing interests in pyrrole derivatives and their
great potential in many applications, such as conductive
polymers and pharmaceutical usage, more and more atten-
tion has been drawn all over the world from researchers.
N-Vinylpyrroles were first reported by Trofimov [2].
Chemistry involving N-vinylpyrroles was then developed
in several fields, such as synthetic chemistry [3,4], struc-
tural chemistry [5], and conductive polymer chemistry
[6–8]. However, restricted by the harsh reaction conditions
employed in Trofimov’s method, the preparations of
N-vinylpyrroles were limited to those pyrroles with alkyl
substituted on the ring carbon atoms. N-Vinylpyrroles with
substitution groups are unstable and sensitive to strong alka-
line conditions and high temperature; all these restrictions
lowered the feasibility of Trofimov reaction, in which strong
RESULTS AND DISCUSSION
Different with the Trofimov method in which the vinyl
group was formed along with the pyrrole ring system, our
approach took existing pyrroles as starting materials that
would make the synthesis of N-vinylpyrroles easier.
© 2013 HeteroCorporation

T. Lan, X. Chen, Z. Liu, and Z. Mao
Vol 000
Scheme 1. Synthesis of N-vinylpyrroles via Trofimov reaction.
Using the previous method, the desired alkylation of
nitrogen of pyrroles, the bifunctional reagents underwent
elimination of the hydrogen–halogen; a side reaction with
the loss of hydrogen–halogen would take place. This
decomposition of the 1,2-dihalogenethanes in the presence
of base forms vinyl halide would escape from the reaction
system. This was proved by the observation of formation
of a large amount of gas during the N-vinylation. The
decomposition of 1,2-dihalogenethanes occurred more
rapidly when strong bases were employed and when high
reaction temperatures were applied. Although the side
reaction and its volatile products, vinyl bromide, for
example, would not affect the N-vinylation of pyrroles as
long as there was sufficient 1,2-dibromoethane existing in
the reaction system. A suitable base for N-vinylation of
pyrroles should assure the N-alkylation step taking place
prior to the elimination step before the exhaustion of the
1,2-dibromoethane. The selection of a suitable base was laid
to the balance of its basicity. An appropriate base should
be strong enough to deprotonate the proton from pyrrole
nitrogen while its ability to elimination of hydrogen–
halogen of the haloethyl group should be softly allowing
the sufficient reaction time for the alkylation but still making
a tangible elimination subsequently. The bases studied in
the exploration were Na2CO3, NaHCO3, K2CO3, KHCO3,
Cs2CO3, NaOH, and KOH. Potassium carbonate gave the
best results among the bases studied (Table 1). The strong
bases, such as NaOH and KOH, led to rapid elimination
of hydrogen–halogen of the bifunctional reactants prior to
their alkylation to nitrogen of pyrroles. Sodium bicarbonate
and potassium bicarbonate were not reactive enough in
helping the alkylation of pyrrole nitrogen. Sodium carbonate
and cesium carbonate yield did not help in the formation of
the desired vinyl products. The organic bases, such as Et3N
and DBU (1,8-Diazabicyclo[5.4.0]undec-7-ene) (entries 10
and 11), led to the low yields and some undissolved dark
residue formed after the reaction.
Scheme 2. The novel synthesis of N-vinylpyrroles.
The mild N-vinylation reaction system involved mild
base, suitable solvents, and bifunctional reactants with
abilities to alkylation and elimination of its hydrogen–
halogen [12]. The reaction involves a possible two-step
mechanism (Scheme 3). In the first step, the bifunctional
reagent, 1,2-dibromoethane, for example, under the help of
K2CO3, alkylates the nitrogen of pyrroles, and then in the
subsequent step, was eliminated by the hydrogen bromide
to form the vinyl group.
Anhydrous DMSO, DMF, and THF were studied as
solvents in the N-vinylation. It was found that DMSO
interfered with the bifunctional reagents and THF led to very
poor yields of the N-vinylpyrroles. DMF as an excellent
solvent for alkylation reactions was found to be the solvent
of choice, in which N-vinylation occurred smoothly.
1,2-Dichloroethane, 1,2-bromochloroethane, and 1,2-
dibromoethane were explored as bifunctional reagents.
Among them, 1,2-dibromoethane gave the best yields
of N-vinylpyrroles, partially owing to the fact that 1,2-
dibromoethane has good abilities for both alkylation and
elimination. The chloride derivatives were found more
difficult in N-alkylation than that of bromide derivative
in this mild alkaline condition. 1,2-Dichloroethane required
much stronger alkaline condition to react as evidenced in a
previous report [10]. The use of KOH, as in Bogdal and
Jaskot’s study, could be harmful to these alkaline sensitive
substitution groups studied in this research, and therefore,
was not suitable for the N-vinylation of pyrroles with
alkaline sensitive substitution groups, such as CN, CHO,
and COOEt.
Table 1
The effects of bases and 1,2-dibromoethane in synthesis of diethyl
N-vinyl-3,4-pyrroledicarboxylate from 3,4-pyrroledicarboxylate.
Amounts
of basesa
Amounts of 1,2-
dibromoethanea
Yields
(%)
Entries
Bases
1
2
3
4
5
6
7
8
K2CO3
K2CO3
K2CO3
K2CO3
NaOH
KOH
Na2CO3
NaHCO3
Cs2CO3
Et3N
1
5
1
5
9
16
33
32
-
-
-
-
-
The optimum reaction temperature was 60–80ꢀC. When
it was below 60ꢀC, the reaction went very slowly. When it
was over 80ꢀC, decomposition of the bifunctional reagents
prevailed.
10
15
10
10
10
10
10
10
10
10
15
10
10
10
10
10
10
10
Scheme 3. The two steps of synthesis of N-vinylpyrroles.
9
10
11
11
17
DBU
aMolar ratios to 3,4-pyrroledicarboxylate
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2013
The Mild and Simple Synthesis Method of N-Vinylpyrrole Using DMF-K2CO3 System
To overcome the side effects caused by the competing
side reaction, which consumes the bifunctional reagents
as well, excessive bifunctional reagents were needed to
bring up the yield of the desired N-vinyl products. A 10
times in molar ratio of the bifunctional reagents vs the
pyrroles was found to be necessary to achieve a reasonable
yield of N-vinylation products. When less amount of the
bifunctional reagents would be used in the reaction, it
would result in poor N-vinylation products caused by the
decomposition. However, when the molar ratios of the
bifunctional reagents were over 10 times, no improvement
of the yields of N-vinylation was found. Equal molar
amount of anhydrous base to the dihalogenethanes was
required in the reaction.
were sensitive to alkaline owing to possible hydrolysis
or condensation.
It was observed that the substitution groups on the
pyrrole ring played important roles in the reaction (Table
2). In general, stronger electron-withdrawing groups
(R3) helped with the higher yields. The yields rose suc-
cessively from COOEt, COCH3 to NO2 (entries 1–3 in
Table 2) as their increased electron-withdrawing effects.
The similar trend was also noticed in other trial in which
disubstitutions of pyrroles were employed (entries 4–12
in Table 2).
Electron-withdrawing substitutions at a and/or b posi-
tions of pyrroles ring had similar effects for N-vinylation
(entry 13 in Table 2). No reactions were going on with
substitutions only with non-electron-withdrawing groups
or electron-donating groups on the pyrrole ring (entry 14
in Table 2). To enable the N-vinylation, the existence of
electron-withdrawing group on the pyrrole ring is
necessary. The similar yields were obtained when the
benzene substituted by different steric groups (entries 9–12),
it was indicated that the steric effect was much less than that
of electron-withdrawing effect for the reaction.
The N-vinylation reactions used take from 4 to 8 h to
complete. After this improvement, the most of bifunctional
reagents would be depleted out as evidenced by the cease
of gas emission. Extending the reaction time beyond 8 h
would not make any sense.
The reaction conditions were relatively mild that most
alkaline sensitive substitution groups could survive, and a
number of N-vinylpyrrole derivatives were able to be
prepared from their corresponding pyrroles (Table 2).
As the first step, in which the N-vinylation was
carried out, the alkylation of nitrogen of pyrroles must
go prior to the elimination of hydrogen–halogen. The
acidity of nitrogen proton of the pyrrole rings was
crucial for the alkylation. Electron-drawing substitutions
at the pyrrole ring would increase the acidity of the
nitrogen protons of pyrroles, therefore, would facilitate the
alkylation of pyrrole nitrogen. The electron-withdrawing
groups, which promote the N-alkylation, include nitro,
carbonyl, esters and nitrile groups. Among them, many
CONCLUSIONS
A facile and effective method for synthesis of N-
vinylpyrrole derivatives with mild reaction conditions has
been developed. The use of mild base instead of strong
base like KOH as used in Trofimov and Bogdal’s methods
was noteworthy for the achievement of N-vinylation of
alkaline sensitive pyrroles. The presence of electron-
withdrawing groups at the pyrrole ring is necessary for
the N-vinylation. The stronger the electron-withdrawing
effect the substitution group brings, the easier the reaction
runs. Similarly, the more electron-withdrawing groups
present at the pyrrole ring, the easier the reaction is carried
on and the higher reaction yield it obtained. Presumably,
substitution by other electron-withdrawing groups, such as
sulphonyl and trifluoromethyl groups would also help the
reaction. Further exploration of functional applications of
these novel N-vinylpyrroles would be very interesting.
Table 2
Several N-vinylpyrroles obtained by the novel method from their
corresponding pyrroles.
Entries
R1
R2
R3
R4
Yields (%)a
b
1
2
3
4
5
6
7
8
H
H
H
H
H
H
H
H
H
H
H
H
CN
H
H
H
H
COOEt
COCH3
NO2
COOEt
COOEt
COCH3
COCH3
NO2
NO2
NO2
NO2
NO2
H
H
H
H
H
H
H
H
H
H
H
H
H
-
23
56
33
EXPERIMENTAL
COOEt
p-MeOPh
p-FPh
p-MeOPh
p-BrPh
p-MePh
p-MeOPh
p-FPh
b
-
1 H NMR and 13 C NMR spectra were characterized by a
Varian 300 MHz Spectrophotometer in CDCl3 solutions, and
chemical shift values are expressed in d values (ppm) relative to
tetramethylsilane (TMS) as internal standard, MS spectra were
carried out on a MicroMass GCT. Reaction progress was moni-
tored by analytical thin-layer chromatography (TLC) on pre-
coated glass plates (Silica gel 60 F254-plate). Melting points were
not corrected.
8
30
33
42
48
52
43
35
9
10
11
12
13
14
o-ClPh
H
CH3
H
H
b
CH3
-
General procedure for synthesis of 1-ethenylpyrroles. To
a solution of corresponding pyrroles (1 mM) in DMF(10 mL),
K2CO3 (1.4 g, 10 mM) and 1,2-dibromoethane (2.3 g, 10 mM)
aIsolated yields
bNo desired product formed
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

T. Lan, X. Chen, Z. Liu, and Z. Mao
Vol 000
were added. The mixtures were stirred at 80ꢀC under nitrogen
atmosphere for 8 h, and then, were poured into 50 mL water,
extracted with CH2Cl2 (3 Â 20 mL). The combined organic layer
was washed with saturated brine, dried over anhydrous Na2SO4,
filtered, and then the solvent was removed in vacuum. The
crude products were purified by column chromatography on
silica gel with ethyl acetate/hexanes as eluents to afford the
N-vinylpyrroles.
105.2. MS (m/z): 291 [M+]. Anal. Calcd. for C12H9N2O2Br
(%): C, 49.17; H, 3.09; N, 9.56; O, 10.92; Br, 27.26. Found: C,
49.08; H, 3.11; N, 9.53.
3-nitro-4-(4-methylphenyl)-1-ethenylpyrrole (9).
Oil; IR
(cmÀ1, KBr): 3104, 1743, 1559, 1564, 1442, 1083. 1HNMR
(300 MHz, CDCl3), d (ppm): 7.78 (1 H, m), 7.34 (1 H, d,
J = 7.5 Hz), 7.21 (2 H, d, J = 7.5 Hz), 6.83 (1 H, m), 6.82 (1 H,
dd, J = 9.0, 15.6 Hz), 5.38 (1 H, dd, J = 15.6, 1.5 Hz), 5.02 (1 H,
dd, J = 9.0, 1.5 Hz), 2.37 (3 H, s). 13CNMR (75 MHz, CDCl3), d
(ppm): 139.5, 135.2, 133.7, 130.6, 127.7, 125.9, 123.4, 120.7,
111.8, 108.5, 23.7. MS (m/z): 227 [M+-1]. Anal. Calcd. for
C13H12N2O2 (%): C, 68.41; H, 5.30; N, 12.27; O, 14.02. Found:
C, 68.38; H, 5.28; N, 12.30.
3-acetyl-1-ethenylpyrrole (2).
Oil; IR (cmÀ1, KBr): 3193,
2917, 1652, 1633, 1507, 1435, 1335. 1HNMR (300 MHz,
CDCl3), d (ppm): 7.45 (1 H, s), 6.88 (1 H, s), 6.81 (1 H, dd,
J = 9, 15.6 Hz), 6.66 (1 H, s), 5.26 (1 H, d, J = 15.6 Hz), 4.85
(1 H, d, J = 9 Hz), 2.38 (3 H, s). 13CNMR (75 MHz, CDCl3), d
(ppm): 193.6, 132.6, 127.3, 123.7, 120.1, 110.7, 100.7, 21.4.
MS (m/z): 134 [M+-1]. Anal. Calcd. for C8H9NO (%): C, 71.09;
H, 6.71; N, 10.36; O, 11.84. Found: C, 71.12; H, 6.78; N, 10.33.
3-nitro-4-(4-methoxyphenyl)- 1-ethenylpyrrole (10). Yellow
solid, m.p: 127–128 0 C; IR (cmÀ1, KBr): 2912, 2850, 1718,
1
1603, 1513, 1487,1132. HNMR (300 MHz, CDCl3), d (ppm):
3-nitro-1-ethenylpyrrole (3).
Solid, m.p. 64 ~ 66 0 C; IR
7.78 (1 H, m), 7.37 (2 H, d, J = 8.7 Hz), 6.93 (2 H, d, J = 8.7 Hz),
6.82 (1 H, m), 6.79 (1 H, dd, J = 9.0, 15.6 Hz), 5.38 (1 H,
dd, J = 15.6, 2.1 Hz), 4.86 (1 H, dd, J = 9.0, 2.1 Hz), 3.84
(3 H, s). 13CNMR (75 MHz, CDCl3), d (ppm): 159.5, 133.9,
131.8, 130.9, 130.7, 124.0, 121.3, 117.9, 113.8, 102.9, 55.5.
MS (m/z): 244 [M+]. Anal. Calcd. for C13H12N2O3 (%): C,
63.93; H, 4.95; N, 11.47; O, 19.65. Found: C, 63.90; H, 4.98;
N, 11.47.
3-nitro-4-(4-fluorophenyl)-1-ethenylpyrrole (11). Solid, m.p:
77–79 0 C; IR (cmÀ1, KBr): 2987, 2876, 1658, 1603,1576, 1446.
1HNMR (300 MHz, CDCl3), d (ppm): 7.80 (1H, s), 7.41 (2H,
m,), 7.08 (2H, m), 6.84 (1H, s), 6.79 (1H, dd, J = 9.0, 15.6 Hz),
5.41 (1H, dd, J = 15.6, 2.1 Hz), 5.03 (1 H, dd, J = 9.0, 2.1 Hz).
13CNMR (75 MHz, CDCl3), d (ppm): 163.9, 161.5, 131.8, 131.3,
122.3, 121.4, 118.4, 115.4, 115.2, 103.3. MS (m/z): 232 [M+].
Anal. Calcd. for C12H9N2O2F (%): C, 62.07; H, 3.91; N, 12.06;
O, 13.78; F, 8.18. Found: C, 62.10; H, 3.91; N, 12.02.
(cmÀ1, KBr): 3281, 2954, 1687, 1655, 1506, 1327. 1HNMR
(300 MHz, CDCl3), d (ppm): 7.70 (1 H, m), 6.84 (1 H, m), 6.80
(1 H, dd, J = 9, 15.6 Hz), 6.75 (1 H, s), 5.33 (1 H, dd, J = 15.6,
2.1 Hz), 4.98 (1 H, dd, J = 9, 2.1 Hz). 13 C NMR (75 MHz,
CDCl3), d (ppm): 132.1, 119.3, 106.9, 103.0, 77.7, 77.3, 76.8.
MS (m/z): 137 [M+-1]. Anal. Calcd. for C6H6N2O2(%): C,
52.17; H, 4.38; N, 20.28; O, 23.17. Found: C, 52.20; H, 4.31;
N, 20.15.
Diethyl 1-ethenylpyrrole-3,4,-dicarboxylate (4).
Yellow
solid, m.p. 89 ~ 91 0 C; IR (cmÀ1, KBr): 3142, 1716, 1508,
1
1485. HNMR (400 MHz, CDCl3), d (ppm): 7.37 (2 H, s), 6.74
(1 H, dd, J = 15.7, 8.7 Hz), 5.31 (1 H, dd, J = 15.7, 2.0 Hz), 4.91
(1 H, dd, J = 8.8, 2.0 Hz), 4.27 (4 H, m, J = 7.2 Hz), 1.27 (6 H, t,
J = 6.9 Hz); 13CNMR (75 MHz, CDCl3), d (ppm): 163.4, 131.9,
125.0, 117.7, 102.4, 60.6, 14.5. MS (m/z): 237 [M+]. Anal.
Calcd. for C12H15NO4(%): C, 60.75; H, 6.37; N, 5.90; O,
26.97. Found: C, 60.50; H, 6.99; N, 5.84.
3-nitro-4-(2-chlorophenyl)- 1-ethenylpyrrole (12).
Solid,
3-acetyl-4-(4-fluorophenyl)-1-ethenyl pyrrole (6).
Oil; IR
m.p: 68–70 0 C; IR (cmÀ1, KBr): 2991, 2855, 1590, 1543,
1507, 1474. 1HNMR (300 MHz, CDCl3), d (ppm): 7.74 (1 H,
d, J = 2.4 Hz), 7.44 (1 H, m), 7.38 (3 H, m), 6.88 (1 H, dd,
J = 15.9, 8.7 Hz), 6.76 (1 H, d, J = 2.4 Hz), 5.29 (1 H, dd,
J = 15.9, 2.1 Hz), 4.89 (1 H, dd, J = 8.7, 2.1 Hz). 13CNMR
(75 MHz, CDCl3), d (ppm):140.2, 137.5, 132.1, 129.9, 129.5,
129.0, 127.9, 127.5, 122.8, 121.6, 115.5, 100.4. MS (m/z):
248 [M+]. Anal. Calcd. for C12H9N2O2Cl (%): C, 57.96; H,
3.65; N, 11.27; O, 12.87; Cl, 14.26. Found: C, 57.92; H, 3.66;
N, 11.23.
(cmÀ1, KBr): 3024, 2940, 1605, 1563, 1527, 1415, 1253, 1194.
1HNMR (300 MHz, CDCl3), d (ppm): 7.54 (1 H, m), 7.39 (2 H,
m), 7.03 (2 H, m), 6.88 (1 H, s), 6.84 (1 H, dd, J = 9, 15.6 Hz),
5.28 (1 H, dd, J = 15.6, 2.1 Hz), 4.88 (1 H, dd, J = 9, 2.1 Hz),
2.33 (3 H, s). 13CNMR (75 MHz, CDCl3), d (ppm): 194.2,
160.9, 131.1, 128.7, 125.7, 125.3, 119.5, 119.2, 115.0, 114.7,
104.3, 28.7. MS (m/z): 229 [M+]. Anal. Calcd. for C14H12NOF
(%): C, 73.35; H, 5.28; N, 6.11; O, 6.98; F, 8.29. Found: C,
83.22; H, 5.29; N, 6.05.
3-acetyl-4-(4-methoxyphenyl)- 1-ethenylpyrrole (7). Yellow
2-cyano-1-ethenyl pyrrole (13). Oil, IR (cmÀ1, KBr):3178,
solid, m.p: 113–115 0 C; IR (cmÀ1, KBr): 2925, 1716, 1648,
2226, 1517, 1357, 1242. HNMR (300 MHz, CDCl3), d (ppm):
1
1
1516, 1246, 1179, 1079, 1034. HNMR (300 MHz, CDCl3), d
7.16 (1 H, s), 7.04 (1 H, s), 6.86 (1 H, s), 6.28 (1 H, s), 5.40
(1 H, dd, J = 15.6, 2.1 Hz), 4.98 (1 H, dd, J = 8.8, 2.1 Hz).
13CNMR (75 MHz, CDCl3), d (ppm): 129.5, 117.9, 116.8,
115.3, 105.6, 101.7. MS (m/z): 91 [M+-27]. Anal. Calcd. for
C7H6N2 (%): C, 71.17; H, 5.12; N, 23.71. Found: C, 71.21; H,
5.11; N, 23.68.
(ppm): 7.45 (1 H, s), 7.35 (2 H, d, J = 8.4 Hz), 6.90 (2 H, d,
J = 8.4 Hz), 6.88 (1 H, s), 6.80 (1 H, dd, J = 9, 15.6 Hz), 5.27
(1 H, d, J = 15.6 Hz), 4.86 (1 H, d, J = 9 Hz), 3.83 (3 H, s), 2.30
(3 H, s). 13CNMR (75 MHz, CDCl3), d (ppm): 198.7, 161.8,
132.0, 130.6, 125.4, 123.1, 119.8, 110.9, 110.8, 107.2, 101.1,
56.2, 27.4, . MS (m/z): 241 [M+]. Anal. Calcd. for C15H15NO2
(%): C, 74.67; H, 6.27; N, 5.81; O, 13.26. Found: C, 74.65; H,
6.32; N, 5.87.
Acknowledgments. The authors are indebted to Shanghai Zhongke
Qiaochang Crop Protection Inc. For the NMR spectral measurements.
3-nitro-4-(4-bromophenyl)- 1-ethenylpyrrole (8). Oil; IR (cmÀ1
,
KBr): 3077, 2864, 1867, 1621, 1543, 1508, 1218. 1HNMR
(300 MHz, CDCl3), d (ppm): 7.81 (1 H, m), 7.52 (1 H, d,
J = 8.4 Hz), 7.31 (2 H, d, J = 8.4 Hz), 6.85 (1 H, m), 6.81
(1 H, dd, J = 9.0, 15.6 Hz), 5.42 (1 H, dd, J = 15.6, 1.5 Hz), 5.05
(1 H, dd, J = 9.0, 1.5 Hz). 13CNMR (75 MHz, CDCl3), d (ppm):
137.5, 132.1, 130.0, 128.7, 126.8, 121.4, 119.4, 117.4, 117.1,
REFERENCES AND NOTES
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2013
The Mild and Simple Synthesis Method of N-Vinylpyrrole Using DMF-K2CO3 System
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet