Reaction of alkyl-3-nitro- and -3-bromo-3-nitroacrylates with 2-(2-nitroethenyl)furan

Article abstract of DOI:10.1134/S1070363208050216

The diene condensation of β-nitro and β-bromo-β- nitroacrylates with 2-(2-nitroethenyl)furan as 1,3-diene leads to a mixture of regioisomeric tetrahydrobenzofurans transforming under the reaction conditions into benzofurancarboxylates due to the easy dehydrohalogenation, denitration, and dehydration. In the case of a gem-bromonitroacrylate reaction takes two routes: diene synthesis and alkylation of the furan ring, the latter process prevailing. The structure of products formed was established by spectral methods. The investigation of geometry of 2-(1-methoxycarbonyl-2-nitroethenyl)- 5-(2-nitroethenyl)furan by XRD analysis showed that its vinyl fragments have the coplanar chelate-like structure with the cisoid orientation of the CO ₂Me and NO₂ groups. The ester group deviates from the plane of the the carbon-carbon multiple bond.

Full text of DOI:10.1134/S1070363208050216

ISSN 1070-3632, Russian Journal of General Chemistry, 2008, Vol. 78, No. 5, pp. 954–962. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © V.M. Berestovitskaya, N.A. Anisimova, O.N. Kataeva, G.A. Berkova, A. Jager, 2008, published in Zhurnal Obshchei Khimii, 2008,
Vol. 78, No. 5, pp. 811–819.
Reaction of Alkyl-3-nitro- and -3-Bromo-3-nitroacrylates
with 2-(2-Nitroethenyl)furan
V. M. Berestovitskayaa, N. A. Anisimovaa, O. N. Kataevab, G. A. Berkovaa, and A. Jagerc
a Hertzen Russian State Pedagogical University,
nab. r. Moiki 48, St. Petersburg, 191186 Russia
e-mail:kohrgpu@yandex.ru
bArbuzov Institute of Organic and Physical Chemistry, Kazan Research Center,
Russian Academy of Sciences, Tatarstan, Russia
c Technical University, Drezden, Germany
Received July 31, 2007
Abstract—The diene condensation of β-nitro and β-bromo-β-nitroacrylates with 2-(2-nitroethenyl)furan as 1,3-
diene leads to a mixture of regioisomeric tetrahydrobenzofurans transforming under the reaction conditions into
benzofurancarboxylates due to the easy dehydrohalogenation, denitration, and dehydration. In the case of a
gem-bromonitroacrylate reaction takes two routes: diene synthesis and alkylation of the furan ring, the latter
process prevailing. The structure of products formed was established by spectral methods. The investigation of
geometry of 2-(1-methoxycarbonyl-2-nitroethenyl)-5-(2-nitroethenyl)furan by XRD analysis showed that its
vinyl fragments have the coplanar chelate-like structure with the cisoid orientation of the CO2Me and NO2
groups. The ester group deviates from the plane of the the carbon–carbon multiple bond.
DOI: 10.1134/S1070363208050216
The interest to benzofuran derivatives is due to the
wide spread of this bicyclic framework in nature. It is
present in the structure of substances from vegetable
(carotinoids, alkaloids [1, 2]) and animal kingdoms
playing the role of plant growth regulators [3], enzyme
inhibitors [4, 5], etc. The benzofuran derivatives are
widely used in the cosmetics [6], in the agricultural
chemistry, and in the pharmacology [7–9]. The
benzofuran ring forms a basis of a series of drugs
structures like benzofurocaine (local anesthetic and
analgesic), amiodarone (antiarrhythmic), phenycabe-
ron, grizeofulvin, etc. [10].
We have for the first time investigated the reaction
of 3-nitro- and 3-bromo-3-nitroacrylates I–IV with 2-
(2-nitrovinyl)furan. It was found that 3-nitroacrylates
I, II enter the diene synthesis with 2-(2-nitrovinyl)
furan under boiling in p-xylene for 2 h in the presence
of aluminum chloride. At first the regioisomeric
tetrahydrobenzofurans Va, Vb, VIa, and VIb are
formed and under the conditions of diene synthesis
they undergo further transformations including the
elimination of both nitro groups or the simultaneous
dehydration and denitration to corresponding benzo-
furans having no nitro groups (compounds VIIa, VIIb,
VIIIa, and VIIIb) or to nitro derivatives IXa, IXb–
XIIa, XIIb.
According to published data one of the methods of
preparation of the benzofuran derivatives is Diels–
Alder reaction of β-furylnitroethene (the diene
component) with methyl acrylate or acrylonitrile (the
dienophiles) [1]. The reaction proceeds under rigid
conditions (100–140°C, pressure reactor) to give
disubstituted tetrahydrobenzofurans that under treating
with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ)
undergo aromatization to the corresponding benzo-
furans.
Alkyl 3-bromo-3-nitroacrylates III, IV react with
2-(2-nitrovilyl)furan (p-xylene, 138°C, 4 h) by two
competing pathways to give regioisomeric tetrahydro-
benzofurans XIIIa, XIIIb, XIVa, and XIVb, the
products of the diene synthesis, and 2,5-disubstituted
furans XVII, XVIII resulting from the alkylation with
nitroalkenes. Simultaneous proceeding of the Diels–
Alder reaction and the alkylation with the activated
954

REACTION OF ALKYL-3-NITRO- AND -3-BROMO-3-NITROACRYLATES
955
CO2R
H
H
H
C
C
+
O2N
O
NO2
H
I, II
138oC,
А
B
p-xylene, 2 h
NO2
CO2R
NO2
NO2
CO2R
NO2
4
5
4
3
2
3
2
5
6
7
6
1
O
1
7
O
Va, VIa
Vb, VIb
_H2, HNO2
_HNO2,H2
_2HNO2
_HNO2,H2
_2HNO2
_HNO2,H2
CO2R
CO2R
NO2
CO2R
CO2R
CO2R
NO2
CO2R
5
6
4
5
4
5
4
3
4
7
3
5
3
3
6
7
6
7
2
6
2
2
1
1
1
7
1
O
O
NO2
O
O
O
O
NO2
VIIa, VIIIa
IXa, Xa
XIа, XIIа
VIIb, VIIIb
XIb, XIIb
IXb, Xb
R = Me (I, Va, Vb, VIIа, VIIb, IXа, IXb, XIа, XIb), Et (II, VIа, VIb, VIIIа, VIIIb, Xа, Xb, XIIа, XIIb).
alkene while using vicinal β-bromo-β- nitroalkenes we
observed for the first time in reaction with furan [11].
The initially formed tetrahydro-benzofurans XIIIa,
XIIIb, XIVa, and XIVb because of the presence of
several electron-acceptor groups (CO2R,NO2, Br) easily
undergo aromatization to the corresponding regio-
isomeric mono- (IXa, IXb–XIIa, XIIb) and
dinitrobenzofurans XVa, XVb, XVIa, and XVIb.
The products XVII, XVIII under the reaction
conditions eliminate hydrogen bromide to give 2,5-di-
(nitrovinyl)furans XIX, XX. More rigid reaction
CO2R
H
Br
H
C
C
+
O
O2N
NO2
H
III, IV
138oC, p-xylene, 4 h
3
4
Br
Br
H
O2N
A'
5
H
CO2R
2
O
В
H
1
CO2R
NO2
B'
O2N
NO2
4
3
2
4
7
5
6
3
5
NO2
H
Br
6
CO2R
1
O
А
7
1
2
O
NO2
XVII, XVIII
XIIIa, XIVa
XIIIb, XIVb
_HBr
_HNO2, HBr
_HBr,H2
_HNO2, HBr
_HBr,H2
4
3
NO2
O2N
CO2R
RO2C
CO2R
5
2
CO2R
NO2
5
H
H
1
NO2
В
B'
3
NO2
4
7
4
7
5
6
O
3
2
O
1
O
6
H
NO2
1
А
O2N
CO2R
O
O
NO2
IXa, Xa
XVa, XVIa
IXb, Xb
XVb, XVIb
XIX, XX
R = Me (III, IXа, IXb, XIIIа, XIIIb, XVа, XVb, XVII, XIX), Et (IV, Xа, Xb, XIVа, XIVb, XVIа, XVIb, XVIII, XX).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 5 2008

956
BERESTOVITSKAYA et al.
Table 1. Yields, Rf, and elemental analyses of compounds Va, Vb–Xa, Xb, XIIIa, XIIIb–XVIa, XVIb, XIX, and XX
Found, %
Calculated, %
H N
Yield,
%
Rf,
a:b
Comp. no.
Formula
10.00, 10.03 С10Н10N2О7
(mp, °С)
ratio
С
H
–
N
С
13
30
7
0.52, 0.58
0.66, 0.71
0.60, 0.65
0.55, 0.65
8:1
9:1
1:3
1:2
–
–
–
10.37
9.86
–
Vа, Vb
46.28, 46.32
68.01, 68.03
69.51, 69.55
4.00, 4.11
4.43, 4.47
5.30, 5.31
9.77, 9.81
С11Н12N2О7
С10Н8О3
46.48
68.18
69.47
4.23
4.54
5.26
VIа, VIb
VIIа, VIIb
–
–
26
С11Н10О3
–
VIIIа,
VIIIb
16
9
0.64, 0.68
0.52, 0.56
0.61, 0.66
1:4
1:3
9:1
53.99, 54.10
56.22, 56.23
–
3.13, 3.17
4.23, 4.24
–
6.03, 6.09
5.78, 5.81
8.00, 8.05
С10Н7NО5
54.30
56.17
–
3.16
3.83
–
6.33
5.96
8.02
IXа, IXb
С11Н9NО5
Xа, Xb
8
С10Н9BrN2О7
XIIIа,
XIIIb
6
0.71, 0.65
7:1
36.89, 36.90
3.15, 3.35
7.32, 7.33
С11Н11BrN2О7
36.36
3.03
7.71
XIVа,
XIVb
7
9
(132–134)
0.65, 0.70
1:2
1:2
45.62, 45.64
–
2.62, 2.65 10.91, 10.95 С10Н6N2О7
45.11
–
2.26 10.53
10.00
XVа, XVb
–
9.81, 9.82
С11Н8N2О7
–
XVIа,
XVIb
XIX
40
38
(68–70)
0.53
–
–
44.52, 44.56
46.75, 46.78
2.64, 2.68
3.60, 3.61
10.61, 10.65 С10Н8N2О7
9.90, 9.95 С11Н10N2О7
44.77
46.81
2.98 10.45
3.55
9.93
XX
Table 2. 1H NMR and IR spectral data of tetrahydrobenzofurans Va, Vb, VIa, VIb, XIIIa, XIIIb, XIVa, and XIVb
1H NMR spectra, δ, ppm, J, Hz (CDCl3)
IR spectra, ν, cm–1 (CHCl3)
Comp.
no.
Н2
Н3
Н4 (Н5)
Н6
Н7
СO2R
NO2
C=O
1750
C–O–C
7.05 d
6.95 d
4.40 m (4.45 m)
3.90 m (4.60 m)
4.36 m (4.43 m)
4.10 m
4.25 m
4.11 m
3.40–3.50 m
3.50–3.70 m
3.40–3.50 m
4.10 s
3.90 s
1.33 t
4.20 q
1.40 t
4.35 q
4.10 s
3.85 s
1.35 t
4.30 q
1.25 t
4.20 q
1360, 1565
1025, 1115
Va
J2,3 7.5
Vb
7.05 d
6.92 d
1360, 1565
1750
1025, 1115
VIa
J2,3 7.5
3.85 m (4.50 m)
4.15 m
3.45–3.60 m
VIb
7.10 d
6.95 d
6.97 d
(4.40 m)
4.30 m
4.80 m
5.20 m
4.75 m
3.50 m
3.80 m
3.50 m
1360, 1560
1375, 1560
1740
1730
1025, 1115
1035, 1128
XIIIа
XIIIb
XIVа
J2,3 7.5
7.10 d
(4.30 m)
J2,3 7.5
4.20 m
5.20 m
3.80 m
XIVb
conditions (boiling in p-xylene for 24 h without a
catalyst) favor the increase in the yield of the furan-
containing dinitrotetraenic derivatives XIX, XX from
20% to 40%.
The composition of compounds Va, Vb–Xa, Xb,
XIIIa, XIIIb–XVIa, XVIb, XIX, XX was confirmed
by elemental analyses (Table 1), and the structure of
all the compounds obtained was established by the
spectral methods including the regioisomeric attribu-
tion (Tables 2–4). For instance, the IR spectra contain
absorption bands at 1730–1750 cm–1 belonging to
ester carbonyl groups. The unconjugated nitro groups
of the compounds Va, Vb, VIa, VIb, XIIIa, XIIIb,
The chromatographic separation of tetrahydro-
benzofurans and benzofurans yielded mixtures of
regioisomers “a, b,” and the final alkylation products
XIX, XX were obtained as individual compounds.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 5 2008

REACTION OF ALKYL-3-NITRO- AND -3-BROMO-3-NITROACRYLATES
Table 3. H NMR and IR spectral data of benzofurans VIIa, VIIb–XIIa, XIIb, XVa, XVb, XVIa, XVIb
957
1
1H NMR spectra, δ, ppm, J, Hz (CDCl3)
IR spectra, ν, cm–1 (CHCl3)
Comp. no.
Н2
Н3
Н4 (Н5)
Н6
Н7
СO2R
NO2
–
C=O
1735
C–O–C
7.12 d
7.03 d
7.30–7.5 m
3.80 s
1030, 1110
1030, 1110
1025, 1120
VIIа
VIIb
VIIIа
VIIIb
IXа
J2,3 7.5
3.96 s
1.30 t, 4.40 q
1.40 t, 4.25 q
3.90 s
7.10 d
7.00 d
7.28–7.45 m
7.98 d
–
1735
1740
J2,3 7.5
7.15 d
7.05 d
–
7.50 d
1355, 1525
J6,7 7.9
J2,3 7.5
8.10 d
7.88 d
8.08 d
7.54 d
7.50 d
7.53 d
4.00 s
IXb
Xа
J6,7 8.1
J6,7 7.6
J6,7 8.0
7.15 d
7.05 d
–
–
1.30 t, 4.40 q
1.40 t, 4.25 q
1360, 1520
1740
1020, 1095
J2,3 7.5
Xb
7.15 d
7.10 d
7.55
–
–
8.52
3.80 s
3.75 s
–
–
–
–
–
–
XIa
XIb
J2,3 7.5
(7.70 d)
8.36 d
J5,7 1.47
8.38 d
8.34 d
J5,7 1.5
8.80 s
8.90 s
7.15 d
7.10 d
7.59
–
–
1.30 t, 4.40 q
1.25 t, 4.30 q
XIIа
J2,3 7.5
(7.68 d)
XIIb
XVаa
7.40 d
7.25 d
7.30 d
–
–
–
–
–
–
–
–
3.9 s
1360, 1525
1360, 1520
1740
1735
1020, 1095
1030, 1125
XVba
XVIаa
XVIba
J2,3 7.5
4.0 s
7.50 d
J2,3 7.5
8.70 s
8.90 s
1.40 t, 4.50 q
1.30 t, 4.25 q
a 1H NMR spectra of compounds XVa, XVb, XVIa, and XVIb were registered in DMSO-d6.
Table 4. 1H NMR spectral data of the furylnitroethene derivatives XVII-XX
1H NMR spectra, δ, ppm, J, Hz (CDCl3)
Comp. no.
Н3
Н4
НA
НВ
НВ' (НА')
СО2R
6.92 d
7.10 d
7.70 d
7.61 d
5.70 d (5.20 d)
3.90 s
1.30 t, 4.25 q
4.0 s
XVII
XVIII
XIX
JАВ 13.0
JАВ 13.0
JАВ 13.1
JАВ 12.6
6.70 d
6.91 d
6.85 d
6.95 d
7.00 d
6.95 d
7.60 d
7.75 d
7.65 d
7.45 d
7.63 d
7.60
5.50 d (5.10 d)
7.56 s
J3,4 3.4
J3,4 3.4
7.48 s
1.25 t, 4.30 q
XX
XIVa, XIVb are characterized by the bands at 1560–
1565 and 1360–1375 cm–1, while the bands of
conjugated nitro groups of compounds IXa, IXb–Xa,
Xb, XVa, XVb, XVIa, XVIb, XIX, XX appear at
1525–1535 and 1355–1360 cm–1.
ratio of the integral intensities indicating the formation
of adducts as a mixtures of regioisomers.
The signals of nitromethine protons H4,6 of the
isomer “a” in tetrahydrobenzofurans Va, Vb, VIa, and
VIb are located upfield (4.36–4.40 ppm and 4.10–
4.11 ppm, respectively) as compared to the analogous
protons H5,6 of the isomer “b” giving rise to signals at
1
The H NMR spectra of the products Va, Vb–
XVIa, XVIb contain two sets of signals with different
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 5 2008

958
BERESTOVITSKAYA et al.
4.43–4.60 ppm and 4.15–4.25 ppm (Table 2). Similar
approach permits to attribute the H5,4 protons at the
ester function (4.43–4.45 ppm for the compounds Va,
VIa and 3.85–3.90 ppm for the isomers Vb, VIb), and
also the protons of the cyclic methylene group (3.40–
3.50 ppm for the isomer “a” and 3.45–3.70 ppm for the
isomer “b”).
assignment of the structure of isomers because these
values depend on the mutual location of the proton and
the electron-acceptor nitro group [12–14]. Due to the
effect of the latter substituent the signals of the protons
1
H6,7 in the H NMR spectrum of compound IXb are
located downfield at 8.10 and 7.54 ppm respectively as
compared to location of the analogous protons (7.98
and 7.50 ppm) in the isomer IXa. Reciprocal location
of the aromatic protons in the molecules of
benzofurans IXa, IXb–XIIa, XIIb was determined on
the basis of values of the coupling constants of these
protons [15]. The coupling сonstants of the protons
H6,7 7.9 Hz in the compound IXa and 8.1 Hz in the
substance IXb indicate their ortho-location [15].
Analogously to [1] the signal of the ester methoxy
group at 4.0 ppm was attributed to product IXb, and
the signal at 3.9 ppm, to isomer IXa.
In the bromine-containing tetrahydrobenzofurans
XIIIa, XIIIb, XIVa, XIVb the signals of the cyclic
nitromethine protons H6 are evidently located down-
field (5.20 ppm for the isomers XIIIb, XIVb as
compared to 4.80 ppm for the compound XIIIa and
4.75 ppm for substance XIVa). Presence of the
electron-acceptor substituents from both sides leads to
the downfield position of signals of the protons H5
(4.40 ppm for the product XIIIa and 4.30 ppm for
substance XIVa) as compared to the protons H4 in the
isomers “b” (4.30 ppm for the product XIIIb and 4.20
ppm for compound XIVb).
The aromatic protons H5,7 of isomer XIb give
signals at 7.70 and 8.36 ppm with the characteristic
coupling constant 1.47 Hz showing their meta-loca-
tion. Spectral difference of ortho- and meta-isomers in
the series of structures under investigation is illustrated
Spectral characteristics of compounds VIIa, VIIIa
coincide with the published data for these compounds
prepared by another method [1] (Table 3). In our case
the signal of protons of the methoxycarbonyl group
1
by H NMR spectrum of a mixture of substances IXb
and XIb isolated by column chromatography (Fig.1).
1
in H NMR spectrum of a mixture of the products
VIIa, VIIb (the a:b ratio 1:3) is doubled (3.80 and
3.96 ppm), the downfield part belonging to the
isomer VIIb.
Chemical shifts of the aromatic protons H6,7 in
compounds IXa, IXb, Xa, and Xb and H4,5,7 in
substances XIa, XIb, XIIa, and XIIb were used for
Analogous rules are observed in the appearance of
signals of the protons H4–7 in nitrobenzofurans Xa, Xb,
XIIa, and XIIb (Table 3). Benzofurans XVa, XVb,
XVIa, and XVIb alongside the alkoxycarbonyl group
contain two nitro groups, and in the 1H NMR spectrum
the singlet of the aromatic proton H7 is observed at
8.80 ppm and 8.70 ppm for isomers XVa, XVIa, and
at 8.90 ppm for isomers XVb, XVIb.
1H NMR spectral data of compounds XVII, XVIII
correspond to the assumed structures. The coupling
constant values for the olefin protons of the nitrovinyl
fragment (13 Hz) show that they have E-configuration
(Table 4).
CO2CH3
NO2
CO2CH3
H
H
H
4
4
5
3
5
3
6
7
6
2
7
2 1
1
H
H
H
NO2
O
O
H
H
IXb
XIb
1
Analysis of the H NMR spectrum of compound
Fu (H2)
Fu (H3)
XIX (Fig. 2, Table 4) shows that the signal of the
proton HA is shifted downfield due to the cis-located
nitro group exhibiting the largest deshielding effect
[16]. The signal of the proton HA is doublet with the
IXb, XIb
H5
XIb
H7
XIb
IXb,
XIb
H7
IXb
H6
IXb
3
coupling constant JAB 13.1 Hz because of the inter-
action with the proton HB. These protons are trans-
located with respect to the C=C bond. The signal of
the proton HB' is a singlet at 7.56 ppm. Close values of
chemical shifts of the HB and HB' olefin protons show
that both of them are gem-located with respect to the
nitro group. The protons H3 and H4 of the furan ring
8.40 8.20 8.00 7.80 7.60 7.40 7.20
7.00
δ, ppm
1
Fig. 1. Fragment of the H NMR spectrum of a mixture of
4-methoxycarbonyl-5-nitro- and 4-methoxycarbonyl-6-
nitrobenzofurans IXb and XIb in CDCl3.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 5 2008

REACTION OF ALKYL-3-NITRO- AND -3-BROMO-3-NITROACRYLATES
CH3
959
C13
C4
O12
C5
4
3
5
2
HB'
HB
1
HB'
HB
C3
O11
O
C1
O2N
CO2Me HA
NO2
C11
C14
C15
HA
C6
O18
JAB
O2
N16
O17
H4 H3
C7
N8
O10
8.0 7.6 7.2 6.8 6.4 6.0 5.6 5.2 4.8 4.4 4.0
δ, ppm
Fig. 3. General view of the molecule of 2-(1-methoxy-
carbonyl-2-nitroethenyl)-5-(2-nitroethenyl)furan XIX ac-
cording to the XRD analysis.
Fig. 2. 1H NMR spectrum of 2-(1-methoxycarbonyl-2-
nitroethenyl)-5-(2-nitroethenyl)furan XIX in CDCl3.
form the AB-system with the coupling constant 3.66 Hz,
their chemical shifts are 6.91 ppm and 7.00 ppm
respectively (Table 4).
ented in Fig. 3, and its geometric parameters in Tables
5–7. The nitrovinyl substituents located in the
positions 2 and 5 of the furan ring of compound XIX
have Z- and E-configuration respectively. The tetraene
conjugated system consisting of two endocyclic and
two exocyclic multiple bonds is practically coplanar. It
The crystals of compound XIX were analyzed by
XRD method. General view of the molecule is pres-
Table 5. Interatomic distances (d, Å) in the molecule of
compound XIX
Table 6. Bond angles (ω, deg) in the molecule of compound
XIX
Angle
ω
Angle
O9N8C7
O11С11O12
O11С11C16
O12С11C6
С11O12C13
O12С13H13A
O12С13H13B
O12С13H13C
H13AС13H13B
H13AС13H13C
H13BС13H13C
С15С14C3
ω
Bond
d
Bond
d
С5С1О2
С5С1C6
С5С1C6
С1O2C3
С4С3О2
С4С3C14
O2С3C14
С3С4C5
С3С4H4
С5С4H4
С1С5C4
С1С5H5
С4С5H5
С7С6C1
С7С6C11
С1С6C11
С6С7N8
С6С7H7
N8С7H7
O10N8O9
O10N8C7
110.13(12)
132.56(12)
132.56(12)
106.27(10)
110.07(12)
131.40(14)
118.43(12)
106.78(13)
126.6
119.58(12)
126.85(12)
122.44(13)
110.58(12)
115.65(13)
109.5
C1–C5
C1–O2
1.3593(19)
1.3657(15)
N8–O9
1.2216(16)
1.1915(18)
C11–O11
C1–C6
O2–C3
C3–C4
1.4387(19)
1.3708(16)
1.357(2)
C11–O12
O12–C13
C13–H13A
1.3172(18)
1.4518(18)
0.9600
109.5
109.5
C3–C14
C4–C5
C4–H4
1.4272(19)
1.406(2)
0.9300
C13–H13B
C13–H13C
C14–C15
0.9600
0.9600
1.321(2)
109.5
126.6
109.5
106.74(12)
126.6
109.5
124.57(13)
117.7
С15С14H14
С3С14H14
C5–H5
C6–C7
0.9300
C14–H14
C15–N16
0.9300
126.6
121.86(11)
123.13(12)
114.86(11)
121.96(12)
119.0
117.7
1.3327(19)
1.4325(17)
С14С15N16
С14С15H15
N16С15H15
O17N16O18
O17N16C15
O18N16O15
120.70(13)
119.7
C6–C11
C7–N8
C7–H7
N8–O10
1.5139(17)
1.4342(18)
0.9300
C15–H15
N16–O17
N16–O18
0.9300
119.7
1.2214(17)
1.2242(16)
122.73(13)
116.86(13)
120.39(12)
119.0
123.66(13)
116.75(12)
1.2183(16)
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 5 2008

960
BERESTOVITSKAYA et al.
Table 7. Torsion angles (τ, deg) in the molecule of com-
pound XIX
Table 8. Atomic coordinates of the structure XIX, their
equivalent temperature parameters (×104), and the
tropic parameters of hydrogen atoms (Å2 × 103)
iso-
Angle
τ
Angle
τ
С5С1О2С3
С6С1О2С3
С1O2С3С4
С1O2С3С14
O2C3С4С5
С14С3C4С5
O2C1С5С4
С6С1C5С4
С3С4C5С1
С5С1C6С7
O2C1С6С7
O2С1C6С11
С1С6C7N8
С11С6C7N8
0.47 (16)
С6С7N8O10
С6С7N8O9
–171.31 (14)
9.7 (2)
Atom
x
y
z
Ueq
C1
O2
C3
C4
C5
C6
C7
N8
2600 (1)
1785 (1)
1641 (1)
2339 (1)
2958 (1)
2916 (1)
2432 (1)
2732 (1)
3368 (1)
2313 (1)
3871 (1)
4617 (1)
3753 (1)
4630 (1)
864 (1)
–110 (1)
–80 (1)
–24 (2)
587 (1)
36 (1)
37 (1)
40 (1)
49 (1)
46 (1)
35 (1)
38 (1)
42 (1)
61 (1)
66 (1)
39 (1)
55 (1)
55 (1)
75 (1)
41 (1)
42 (1)
46 (1)
74 (1)
64 (1)
–179.44 (12)
–0.66 (16)
176.19 (12)
0.59 (18)
С7С6C11O11
С1С6C11O11
С7С6C11O12
С1С6C11O12
O11С11O12С13
С6С11O12O13
С4С3C14С15
O2С3C14С15
С3С14C15N16
75.30 (19)
–100.23 (17)
–108.57 (16)
75.90 (15)
–1.2 (2)
–1414 (1)
–2261 (2)
–1424 (1)
1182 (1)
2363 (1)
3645 (1)
3638 (1)
4693 (1)
1108 (2)
1484 (1)
508 (1)
1035 (2)
700 (2)
–179.71 (16)
–0.12 (17)
179.77 (15)
–0.29 (18)
179.22 (16)
–0.9 (2)
23 (2)
–575 (2)
–516 (2)
–1100 (1)
–1854 (2)
–822 (2)
–1104 (2)
–307 (1)
–2476 (1)
–3073 (2)
1810 (2)
2192 (2)
3034 (2)
3339 (2)
3395 (2)
–177.10 (14)
172.96 (17)
–3.1 (2)
O9
O10
C11
O11
O12
C13
C14
C15
N16
O17
O18
–177.08 (14)
174.70 (11)
–178.41 (12)
6.4 (2)
С14С15N16O17 –179.75 (16)
С14С15N16O18
–0.8 (2)
317 (3)
–1674 (1)
–706 (1)
–1056 (1)
–105 (1)
–2263 (1)
is confirmed by the values of torsion angles of the
main structural fragments of the molecule under study:
the C14C3C4C5 angle is –179.71°, the C6C1C5C6 angle
is 179.77°, the C3C4C5C1 angle is –0.29°, the
C5C1C6C7 angle is 179.22°. The values of the torsion
angles C1C6C7N8 (–177.41°) and C3C1C4C1C5N1N6
(–177.08°) show that both nitro groups of the vinyl
fragment have trans-orientation with respect to the
furan ring and are coplanar with it [C6C7N8O10 angle
(–171.77°), C6C7N8O9 angle (9.7°), C14C15N16O17
angle (–179.75°), C14C15N16O18 angle (–0.8°)]. It is
characteristic that the ester function having cis-location
to the nitro group and compelled to occupy the space
between the furan ring and the nitro group deviates
from the plain of the double bonds [C1C6C11O11 angle
(–100.23°), C1C6C11O12 angle (75.90°), C7C6C11O11
angle (75.30°), C7C6C11O12 angle (–108.57°)]. Hence,
in the molecule of compound XIX vinyl fragments
have the coplanar chelate-like structure. Its nitro and
methoxycarbonyl groups are cis-located with respect to
one another, and the ester function deviates from the
plain of the multiple carbon–carbon bond. In crystal
the hydrogen atoms of vinyl group are bound by weak
H-bonds with the oxygen atoms of nitro groups
belonging to the adjacent molecules.
292 (1)
–443 (1)
–946 (1)
–557 (1)
1
The H NMR spectra of compounds Va, Vb–XIVa,
XIVb, XVII–XX were registered on a Bruker AC-200
spectrometer (200 MHz) in CDCl3, and of
pounds XVa, XVb, XVIa, and XVIb in DMSO-d6,
external reference HMDS.
com-
X-ray diffraction analysis of compound (XIX).
The crystals of compound XIX are monoclinic, space
group P21/c. Unit cell parameters at 20°C are a fol-
lows: a 14.086(1), b 9.628(1), c 8.799(1) Å, β 104.04
(1)°, V 1167.1(3) Å3, Z 4, dcalc 1.526 g cm–3. Unit cell
parameters and the intensities of 45603 reflections
among which 2998 independent (Rint 0.037)
were
measured on an automatic Nonius KappaCCD X-ray
diffractometer (λMoKα irradiation, graphite
monochromator, θ < 30°) at room temperature using
the COLLECT (Nonius B.V., 1998), Dirax/Isl
(Duisenberg & Schreurs, 1989–2000) and EvalCCD
(Duisenberg & Schreurs 1990–2000) programs. The
extinction was accounted for empirically. The structure
was solved by the direct method using SHELXS-97
program [17] and refined with the help of the
SHELXL-97 program (G.M.Sheldrick, Universitat
EXPERIMENTAL
The IR spectra were obtained on an Infra-LYUM
FT-02 spectrometer in chloroform, c 0.1–0.001 mol l–1.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 5 2008

REACTION OF ALKYL-3-NITRO- AND -3-BROMO-3-NITROACRYLATES
961
Göttingen, 1997). Final values of the diversion factors
R 0.040, RW 0.095 by 2174 independent reflections
with F2 > 2σ.
ethoxycarbonylbenzofurans (Xa, Xb) and 6-nitro-
5(4)ethoxycarbonylbenzofurans (XIIa, XIIb). To a
solution of 0.70 g of ethyl 3-nitroacrylate II in 10 ml
of the anhydrous p-xylene were added 0.15 g of the
aluminum chloride and 0.67 g of 2-(2-nitroethenyl)
furan. The mixture obtained was refluxed for 2 h,
solvent was removed on a rotary evaporator, and the
residue was chromatographed on silica gel.
The separation and purification of the individual
compounds was carried out by column chromato-
graphy on the Chemapol (100/200 μm) silica gel and
on aluminum oxide. The reaction progress was
monitored by TLC on Silufol-254 plates, elution with
3:2 hexane-acetone, development with iodine vapour.
Initial β-nitro- and β-bromo-β-nitroacrylates I–IV were
prepared according to the procedures [18,19], and β -
furylnitroethylene, to the procedure [20].
Elution with carbon tetrachloride gave 0.15 g
(13%) of a mixture of compounds Xa, Xb, XIIa, and
XIIb, and elution with benzene yielded 1.20 g of a
mixture of tetrahydrobenzofurans VIa, VIb and
benzofurans VIIIa, VIIIb.
4,6(5,6)-Dinitro-5(4)-methoxycarbonyl-4,5,6,7-
tetrahydrobenzofurans (Va, Vb), 5(4)-methoxy-
carbonylbenzofurans (VIIa, VIIb), 5(4)-methoxy-
carbonyl-4(5)nitrobenzofurans (IXa, IXb), and 5
(4)-methoxycarbonyl-6-nitrobenzofurans (XIa,
XIb). To a solution of 0.68 g of methyl 3-nitroacrylate
I in 10 ml of anhydrous p-xylene were added 0.15 g of
aluminum chloride and 0.70 g of 2-(2-nitroethenyl)
furan. The reaction mixture was refluxed for 2 h,
solvent was removed on a rotary evaporator, and the
residue was subjected to chromatography on silica gel.
Repeated chromatography of
a
mixture of
compounds VIa, VIb, VIIa, and VIIb gave the
benzene-eluted fraction containing 0.24 g (26%) of a
mixture of benzofurans VIIIa, VIIIb in 1:2 ratio, Rf
0.55 and 0.65. Elution with chloroform gave 0.41 g
(30%) of oil containing tetrahydrobenzofurans VIa,
VIb in 9:1 ratio, Rf 0.66 and 0.71.
Repeated chromatography of a mixture of com-
pounds Xa, Xb, XIIa, XIIb (elution with benzene)
gave 0.1 g (9%) of a mixture of compounds Xa, Xb in
1:3 ratio, Rf 0.52 and 0.56 respectively.
Elution with carbon tetrachloride permitted
isolation of 0.66 g of a mixture of nitrobenzofurans
IXa, IXb, XIa, and XIb, and by elution with benzene
0.5 g of a mixture of tetrahydrobenzofurans Va, Vb
and benzofurans VIIa, VIIb was obtained.
5-(4)-Methoxycarbonyl-4(5)-nitrobenzofurans
(IXa, IXb), 4(5)-bromo-4,6(5,6)-dinitro-5(4)-
methoxycarbonyltetrahydrobenzofurans (XIIIa,
XIIIb),4,6(5,6)-dinitro-5(4)-methoxycarbonyl-
benzofurans (XVa, XVb), 2-(2-bromo-1-methoxy-
carbonyl-2-nitroethyl)-5-(2-nitroethenyl)furan
(XVII), 2-(1-methoxycarbonyl-2-nitroethenyl)-5-(2-
nitroethenyl)furan (XIX). To a solution of 0.73 g of
methyl 3-bromo-3-nitroacrylate III in 10 ml of p-
xylene were added 0.15 g of aluminum chloride and
0.48 g of 2-(2-nitrovinyl)furan. The reaction mixture
was boiled for 4 h, solvent was evaporated on a rotary
evaporator, and the residue was subjected to chro-
matography on silica gel. Elution with benzene gave
0.94 g of a mixture of compounds IXa, IXb, XVa,
XVb, XVII, and XIX, and elution with chloroform
yielded 0.1 g (8%) of regioisomeric tetrahydro-
benzofurans XIIIa, XIIIb, Rf 0.61 and 0.66 respec-
tively. According to 1H NMR data the ratio of
compounds XIIIa, XIIIb was 9:1.
By repeated chromatography of a mixture of
compounds IXa, IXb, XIa, and XIb elution with
carbon tetrachloride gave 0.39 g (35%) of a mixture of
isomeric benzofurans IXb and XIb in 1:1 ratio, Rf 0.64
and 0.72 respectively. Elution with benzene (first
portion ~200 ml) gave 0.03 g (3%) of a mixture of
compounds IXb, XIa, and XIb, Rf 0.64, 0.72, and
0.75. The second portion of benzene (~200 ml) gave
0.06 g (6%) of a mixture of compounds IXa and IXb
in 1:4 ratio, Rf 0.64 and 0.68 respectively.
By repeated chromatography of a mixture of
compounds Va, Vb, VIIa, and VIIb elution with
benzene gave 0.06 g (7%) of benzofurans VIIa and
VIIb in 1:3 ratio, Rf 0.60 and 0.65. The fraction eluted
with chloroform gave 0.18 g (13%) of oil consisting of
tetrahydrobenzofurans Va, Vb in 1:8 ratio, Rf 0.52 and
0.58.
A mixture of compounds IXa, IXb, XVa, XVb,
XVII, and XIX was washed with benzene, and the
crystals were filtered off to give 0.065 g (7%) of
dinitrobenzofurans XVa, XVb in 1:2 ratio, mp 132–
4,6(5,6)-Dinitro-5(4)-ethoxycarbonyl-4,5,6,7-
tetrahydrobenzofurans (VIa, VIb), 5(4)-ethoxy-
carbonylbenzofurans (VIIIa, VIIIb), 4(5)nitro-5(4)-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 5 2008

962
BERESTOVITSKAYA et al.
134°C. The filtrate was evaporated and subjected to
chromatography on silica gel. The first portion of
benzene eluate (~150 ml) gave 0.63 g of a mixture of
compounds XVII, XIX in 1:8 ratio as a brown oil, Rf
0.60 and 0.68 respectively. The chloroform eluate gave
0.05 g (16%) of mononitrobenzofurans IXa, IXb in
1:4 ratio, Rf 0.64 and 0.68 respectively.
REFERENCES
1. Kusurkar, R.S. and Bhosale, D.K., Synth. Commun.,
1990, vol. 20, no. 1, p. 101.
2. Gilkrist, T., Khimiya geterotsiklicheskikh soedinenii
(Chemistry of Heterocyclic Compounds), Moscow: Mir,
1966, p. 280.
3. Baralti, P.G., Romagnoli, R., Beria, J., Cozzi, P., and
Geroni, C., J. Med. Chem., 2000, vol. 43, no. 14, p. 2675.
Repeated chromatography of a mixture of com-
pounds XVII, XIX (elution with benzene) gave 0.38 g
(40%) of compound XIX, mp 68–70°C.
4. Bertinano, P., Blize, A.E., Bronk, B.S., and Cheng, H.,
PCT Int. Appl. WO 032,533,2002; C.A., 2003, vol. 138,
no. 73533d.
5. Lombaert, S., Blanchard, L., Stamford, L., and Tan, J.,
J. Med. Chem., 2000, vol. 43, no. 3, p. 488.
4(5)-Nitro-5(4)ethoxycarbonylbenzofurans
(Xa, Xb), 4(5)-bromo-4,6(5,6)-dinitro-5(4)-ethoxy-
carbonylbenzofurans (XIVa, XIVb), 4,6(5,6)-di-
nitro-5(4)ethoxycarbonyltetrahydrobenzofurans
(XIVa, XIVb), 4,6(5,6)-dinitro-5(4)-ethoxycar-
bonylbenzofurans (XVIa, XVIb), 2-(2-bromo-2-
nitro-1-ethoxycarbonylethyl)-5-(2-nitroethenyl)
furan (XVIII), 2-(2-nitro-1-ethoxycarbonyl-
ethenyl)-5-(2-nitroethenyl)furan (XX). To a solution
of 0.7 g of ethyl 3-bromo-3-nitroacrylate IV in 10 ml
of p-xylene was added 0.4 g of 2-(2-nitroethenyl)furan.
The reaction mixture was refluxed for 4 h, solvent was
removed on a rotary evaporator and subjected to
chromatography on aluminum oxide.
6. Leung, A.Y. and Foster, S., Encyclopedia of Common
Natural Ingredients Used in Food, Drugs, and
Cosmetics, New York: Wiley, 1996, p. 268.
7. Joule, J. and Mills, K., Khimiya geterotsiklicheskikh
soedinenii (Chemistry of Heterocyclic Compounds),
Moscow: Mir, 2004, p. 479.
8. Boger, D.L., Fink, B.E., and Hetrick, M.P., J. Am.
Chem. Soc., 2000, vol. 122, no. 27, p. 6382.
9. Walker, D.P., Piotrowski, D.W., and Jacobson, E.J.,
PCT Int. Appl. WO 03 70,731,2003; C.A., 2003, vol. 139,
no. 214612x.
10. Mashkovskii, M.D., Lekarstvennye sredstva (Pharma-
ceuticals), Moscow: Meditsina, vol. 1, pp. 381, 481,
517; vol 2, p. 427.
The hexane eluate gave 0.46 g of a mixture of
compounds Xa, Xb, XVIa, and XVIb, and the
benzene one yielded 0.60 g of a mixture of compounds
XIVa, XIVb, XVIII, and XX.
11. Anisimova, N.A., Kuzhaeva, A.A., Berkova, G.A.,
Berestovitskaya, V.M., and Deiko, L.I., Zh. Obshch.
Khim., 2005, vol. 75, no. 11, p. 1833.
12. Suzuki, T., Bull. Chem. Soc. Japan, 1985, vol. 58, no. 10,
Repeated chromatography of a mixture of com-
pounds Xa, Xb, XVIa, and XVIb (elution with
benzene) gave 0.13 g (7%) of isomeric mononitro-
benzofurans Xa, Xb in 2:3 ratio as an orange oil, Rf
0.52 and 0.56 respectively. Elution with chloroform
yielded 0.08 g (9%) of dinitrobenzofurans XVIa,
XVIb in 1:2 ratio, Rf 0.65 and 0.70 respectively.
p. 821.
13. Tromelin, A., Demerseman, P., and Royer, R., Synth.,
1985, vol. 11, p. 1074.
14. Einhorn, J., Demerseman, P., and Royer, R., Can. J.
Chem., 1983, vol. 61, no. 10, p. 2287.
15. Ionin, B.I., Ershov, B.A., and Kol’tsov, A.I., YaMR
spektroskopiya v organicheskoi khimii NMR (Spectro-
scopy in Organic Chemistry), Leningrad: Khimiya,
1983.
Repeated chromatography of a mixture of com-
pounds XIVa, XIVb, XVIII, and XX (elution with
chloroform) gave 0.25 g of a mixture of compounds
XVIII, XX in 1:6 ratio, Rf 0.48 and 0.53
respectively. The ether eluate yielded 0.07 g (6%) of
tetrahydrobenzofurans XIVa, XIVb in 7:1 ratio, Rf
0.71 and 0.65 respectively.
16. Trukhin, E.V., Makarenko, S.V., and Berestovitskaya, V.M.,
Zh. Org. Khim., 1998, vol. 34, no. 1, p. 72.
17. Sheldrick, G.M., Acta Cryst., 1990, vol. 46, p. 467.
18. Shechter, H. and Conrad, F., J. Am. Chem. Soc., 1953,
vol. 75, no. 22, p. 5610.
19. Sarkisyan, Z.M., Sadikov, K.D., Smirnov, A.S., Maka-
renko, S.V., Anisimova, N.A., Kuzhaeva, A.A., and Be-
restovitskaya, V.M., Zh. Org. Khim., 2004, vol. 40, no. 6,
p. 944.
Additional chromatography of a mixture of com-
pounds XVIII, XX gave in the first portion of
chloroform eluate (~200 ml) 0.32 g (38%) of com-
pound XX, Rf 0.53.
20. Dornow, A. and Frese, C.D., Lieb. Ann., 1953, p. 211.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 5 2008