Reaction of ethyl 3-nitroacrylate with phenyl azide

Full text of DOI:10.1007/s11178-005-0272-1

Russian Journal of Organic Chemistry, Vol. 41, No. 6, 2005, pp. 941–943. Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005,
pp. 957–958.
Original Russian Text Copyright © 2005 by Makarova, Anisimova, Berkova, Deiko, Berestovitskaya.
SHORT
COMMUNICATIONS
Reaction of Ethyl 3-Nitroacrylate with Phenyl Azide
N. G. Makarova, N. A. Anisimova, G. A. Berkova, L. I. Deiko, and V. M. Berestovitskaya
Hertzen Russian State Pedagogical University, nab. r. Moiki 48, St. Petersburg, 191186 Russia
e-mail: kohrgpu@yandex.ru
Received December 1, 2004
Nitrogen-containing heterocycles are known to
exhibit a broad spectrum of practically useful prop-
erties [1–5]. In particular, triazole rings are structural
fragments of a number of medicines possessing anti-
fungal, antiphlogistic, and tuberculostatic properties
[1, 2]. Dihydrotriazoles are used in manufacture of
photostabilizers, optical bleaching agents, and incom-
bustible materials [3–5].
Nitro-substituted 1,2,3-triazoles and dihydro-1,2,3-
triazoles can be obtained by 1,3-dipolar cycloaddition
of phenyl azide to nitroalkenes. As shown previously,
nitroethenes having alkyl or aryl substituents in the
β-position with respect to the nitro group slowly react
with phenyl azide in polar solvents at room tempera-
ture; the reaction is regioselective, and the products
are the corresponding 4,5-dihydro-1,2,3-triazoles. At
elevated temperature (up to 130°C), these reactions are
accompanied by denitration or dehydrogenation to
produce the corresponding 1,2,3-triazoles [6, 7].
ethanol at room temperature takes 14 days. The proc-
ess involves two concurrent pathways and finally leads
to formation of a mixture of regioisomeric ethyl
5-nitro-1-phenyl-4,5-dihydro-1H-1,2,3-triazole-4-car-
boxylate (IIa) and ethyl 4-nitro-1-phenyl-4,5-dihydro-
1H-1,2,3-5-carboxylate (IIb), nitrotriazoles IIIa and
IIIb, triazoles IVa and IVb, and aziridine V. The latter
was isolated as a mixture of diastereoisomers. Regio-
isomers IIIa and IVa were isolated as individual prod-
ucts. Compounds IIIa, IIIb, IVa, and IVb are likely
to result from intramolecular transformations of di-
hydrotriazoles IIa and IIb via dehydrogentation or
elimination of nitrous acid molecule, respectively.
Aziridine V can be formed either from dihydrotriazole
IIa/IIb or directly by reaction of I with phenyl azide
with elimination of nitrogen.
The structure of the products was confirmed by
spectral methods. Their IR spectra contained absorp-
tion bands at 1750–1735 cm–1 due to stretching vibra-
tions of the ester carbonyl group; nonconjugated nitro
groups in molecules IIa, IIb, and V give rise to
absorption bands at 1560–1545 and 1390 cm–1, and
We were the first to study the reaction of ethyl
3-nitroacrylate (I) with phenyl azide. We found that
the cycloaddition of phenyl azide to nitroalkene I in
O2N
COOEt
N
N
–H2
N
O2N
COOEt
Ph
IIIa, IIIb
COOEt
N
N
N
H
Ph
IIa, IIb
O2N
H
COOEt
H
N
N
PhN3
–HNO2
N
–N2
Ph
IVa, IVb
I
H
COOEt
O2N
H
N
–N2
Ph
V
1070-4280/05/4106-0941 © 2005 MAIK “Nauka/Interperiodica”

MAKAROVA et al.
942
stretching vibrations of conjugated nitro groups in IIIa
and IIIb appear at 1540 and 1360 cm–1.
Found, %: C 50.29, 50.30; H 4.00, 4.02; N 21.40,
21.41. C11H10N4O4. Calculated, %: C 50.38; H 3.82;
N 21.37. Pure isomer IIIa was isolated in 35% by
repeated chromatographic separation of a mixture of
compounds IIIa and IIIb using carbon tetrachloride as
eluent. Rf 0.77, mp 33–35°C.
1
The H NMR spectral parameters of the isolated
compounds are consistent with the assumed structures
and are analogous to the spectra of structurally related
model compounds [8–10]. The spectra contain two set
of signals with different signal intensity ratios. The
main criteria for the structure of isomer a or b were the
chemical shifts of the CH (olefinic) and ethyl protons
in the ester group. These groups in isomers a and b
appear at different distances from the phenyl group.
The phenyl and ethoxycarbonyl groups in isomers b
are attached to the neighboring atoms, while the corre-
sponding groups in isomers a are more distant from
each other. Due to effect of the benzene ring, the 5-H
proton in the spectrum of IVa resonates in a weaker
field (δ 8.50 ppm) than the corresponding proton in
IVb (δ 8.18 ppm). The CH2 protons of the ester group
in molecule IVb are located below the benzene ring
plane (i.e., they fall into the area shielded by the ben-
zene ring), and their signal appears in a stronger field
(δ 4.20 ppm) relative to the corresponding signal of
isomer IVa (δ 4.40 ppm) [11, 12]. Likewise, we dis-
tinguished between regioisomeric dihydrotriazoles IIa
and IIb and triazoles IIIa and IIIb.
Ethyl 1-phenyl-1H-1,2,3-triazole-4-carboxylate
(IVa) and ethyl 1-phenyl-1H-1,2,3-triazole-5-car-
boxylate (IVb). Yield 15% (from benzene fraction),
Rf 0.73, 0.65; ratio IVa:IVb = 7:2. IR spectrum, ν,
1
cm–1: 1735 (C=O). H NMR spectrum, δ, ppm: IVa:
1.15 t (3H, CH3), 4.40 q (2H, OCH2), 7.60 m and
7.80 m (5H, C6H5), 8.50 s (1H, 5-H); IVb: 1.40 t (3H,
CH3), 4.20 q (2H, OCH2), 7.30–7.60 m (5H, C6H5),
8.18 s (1H, 4-H). Found, %: C 60.41, 60.45; H 5.27,
5.28; N 19.69, 19.65. C11H11N3O2. Calculated, %:
C 60.83; H 5.07; N 19.35. Pure isomer IVa was isolat-
ed in 10% yield by repeated chromatography of a mix-
ture of isomers IVa and IVb using benzene as eluent.
Rf 0.73, mp 75–77°C.
Ethyl 2-nitro-1-phenylaziridine-3-carboxylate
(V) was isolated in 7% yield as an inseparable mixture
of diastereoisomers (by repeated chromatographic
separation of a mixture of compounds IIa, IIb, and V
using carbon tetrachloride as eluent), Rf 0.64, 0.42.
IR spectrum, ν, cm–1: 1750 (C=O); 1550, 1385 (NO2).
1H NMR spectrum, δ, ppm: 1.25 t (3H, CH3), 4.25 q
(2H, OCH2), 2.75–3.16 m (1H, 2-H), 4.45–4.80 m (1H,
3-H), 7.20–7.70 m (5H, C6H5). Found, %: C 55.78,
55.69; H 4.84, 4.87; N 11.76, 11.89. C11H12N2O4. Cal-
culated, %: C 55.93; H 5.08; N 11.86.
The IR spectra were recorded on an InfraLYuM
FT-02 spectrometer from solutions in chloroform (c =
0.1–0.001 M). The 1H NMR spectra were measured on
a Bruker AC-200 instrument (200 MHz) using chloro-
form-d as solvent. The chemical shifts were measured
relative to hexamethyldisiloxane (external reference)
with an accuracy of ±0.5 Hz. The products were isolat-
ed and purified by column chromatography on silica
gel (Chemapol, 100/200 μm) using the Trappe solvent
series. The purity of the products was checked, and
the progress of the reaction was monitored, by thin-
layer chromatography on Silufol UV-254 plates using
hexane–acetone (3:2) as eluent; development with
iodine vapor.
Initial nitroalkene I was synthesized by improved
procedure [13], and phenyl azide was prepared as
described in [14].
Ethyl 5-nitro-1-phenyl-4,5-dihydro-1H-1,2,3-tri-
azole-4-carboxylate (IIa) and ethyl 4-nitro-1-phe-
nyl-4,5-dihydro-1H-1,2,3-triazole-5-carboxylate
(IIb). Yield 7%. Isomer mixture IIa/IIb was isolated
by repeated chromatographic separation of a mixture
of compounds IIa, IIb, and V using benzene as eluent.
Rf 0.56, 0.52; ratio IIa:IIb = 5:2. IR spectrum, ν, cm–1:
1745 (C=O); 1545, 1390 (NO2). 1H NMR spectrum, δ,
ppm: IIa: 1.26 t (3H, CH3), 4.30 q (2H, OCH2), 5.24 m
(1H, 5-H, J4,5 = 4.0 Hz), 4.41 m (1H, 4-H, J4,5
4.0 Hz), 7.20–7.60 m (5H, C6H5); IIb: 1.30 t (3H,
CH3), 4.20 q (2H, OCH2), 4.47 m (1H, 5-H, J4,5
=
=
6.0 Hz), 5.12 m (1H, 4-H, J4,5 = 6.0 Hz), 7.20–7.60 m
(5H, C6H5). Found, %: N 21.60, 21.64. C11H12N4O4.
Calculated, %: N 21.21.
Ethyl 5-nitro-1-phenyl-1H-1,2,3-triazole-4-car-
boxylate (IIIa) and ethyl 4-nitro-1-phenyl-1H-1,2,3-
triazole-5-carboxylate (IIIb). Yield 45% (eluent
hexane), Rf 0.77, 0.71; ratio IIIa:IIIb = 4:1. IR spec-
trum, ν, cm–1: 1740 (C=O); 1540, 1360 (NO2).
1H NMR spectrum, δ, ppm: IIIa: 1.30 t (3H, CH3),
4.45 q (2H, OCH2), 7.65 m (5H, C6H5); IIIb: 1.40 t
(3H, CH3), 4.30 q (2H, OCH2), 7.60 m (5H, C6H5).
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