3-nitro- and 3-bromo-3-nitroacrylates in reactions with phenyl azide

Article abstract of DOI:10.1134/S1070363207090113

1,3-Dipolar cycloaddition of alkyl 3-nitro-and 3-bromo-3-nitroacrylates to phenyl azide gives regioisomeric alkyl 5(4)-nitro-1-phenyl-4,5-dihydro-1H-1,2,3- triazole-4(5)-carboxylates, the corresponding triazoles both with and without nitro group, and alky

Full text of DOI:10.1134/S1070363207090113

ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 9, pp. 1567 1575.
Original Russian Text V.M. Berestovitskaya, N.A. Anisimova, O.N. Kataeva, N.G. Makarova, G.A. Berkova, 2007, published in Zhurnal Obshchei
Khimii, 2007, Vol. 77, No. 9, pp. 1493 1502.
Pleiades Publishing, Ltd., 2007.
3-Nitro- and 3-Bromo-3-nitroacrylates in Reactions
with Phenyl Azide
V. M. Berestovitskayaa, N. A. Anisimovaa, O. N. Kataevab,
N. G. Makarovaa, and G. A. Berkovaa
a Hertzen Russian State Pedagogical University,
nab. r. Moiki 48, St. Petersburg, 191186 Russia
e-mail: kohrgpu@yandex.ru
b Arbuzov Institute of Organic and Physical Chemistry, Kazan Research Center,
Russian Academy of Sciences, Kazan, Tatarstan, Russia
Received January 29, 2007
Abstract 1,3-Dipolar cycloaddition of alkyl 3-nitro- and 3-bromo-3-nitroacrylates to phenyl azide gives
regioisomeric alkyl 5(4)-nitro-1-phenyl-4,5-dihydro-1H-1,2,3-triazole-4(5)-carboxylates, the corresponding
triazoles both with and without nitro group, and alkyl 3-nitro-1-phenylaziridine-2-carboxylates. Nitrotriazole-
carboxylates were found to lose the ester moiety during chromatographic separation of the products on
1
aluminum oxide. The structure of the products was determined on the basis of IR, H NMR, and X-ray diffrac-
tion data.
DOI: 10.1134/S1070363207090113
Interest in 1,3-dipolar cycloadditions involving
nitroalkenes as dipolarophiles and azides as 1,3-di-
poles originates from the synthetic potential of these
reactions which lead to the formation of five-mem-
bered nitrogencontaining heterocycles, 1,2,3-triazoles.
Triazole derivatives are used as photosensitizers and
optical belaching agents, while nitrotriazoles exhibit
antiviral, antiphlogistic, and antifungal activity [1 3].
alkyl 5(4)-nitro-1-phenyl-1H-1,2,3-triazole-4(5)-
carboxylates VIa/VIb and VIIa/VIIb; (2) denitration
with formation of regioisomeric 1-phenyl-1H-1,2,3-
triazole-4(5)-carboxylates VIIIa/VIIIb and IXa/IXb;
and (3) elimination of nitrogen to give the correspond-
ing alkyl 3-nitro-1-phenylaziridine-2-carboxylates XI
and XII. The reactions of nitroalkenes I and II with
phenyl azide in boiling toluene (1.5 h) afforded
mainly triazoles VIIIa/VIIIb and IXa/IXb, whereas
nitrotriazoles VIa/VIb and VIIa/VIIb and aziridines
XI and XII were the minor products.
According to published data, -nitrostyrene reacts
with phenyl azide at 20 100 C (in the absence of a
solvent) to give only one regioisomeric triazole (or,
in rare cases, dihydrotriazole) [4 7]; a small amount
of another regioisomer was isolated only after pro-
longed heating (17 156 h) of the reactions mixture in
toluene or cyclohexane [6, 8].
Variation of the reaction conditions showed that,
regardless of the solvent nature (ethanol, benzene,
DMSO, toluene), raising the temperature from 20 to
110 C leads to complete transformation of dihydrotri-
azoles into triazoles via predominant elimination of
nitrous acid. In this case, the yields of triazoles VIIIa/
VIIIb and IXa/IXb containing no nitro group increase
from 15 17 to 48 54%, and the yields of aziridines
XI and XII increase from 7 8 to 20 25%.
In the present work we examined reactions of alkyl
3-nitro- and 3-bromo-3-nitroacrylates I IV with
phenyl azide under different conditions. Unlike model
-nitrostyrene containing no additional electron-
withdrawing groups, compounds I and II reacted with
phenyl azide in ethanol (18 20 C, 14 days) or ben-
zene (80 C, 2 h) at both reactive centers with forma-
tion of mixtures of regioisomeric alkyl 5(4)-nitro-1-
phenyl-4,5-dihydro-1H-1,2,3-triazole-4(5)-carboxyla-
tes Va and Vb which were isolated in a yield of 6 7%.
During the process, compounds Va and Vb underwent
concurrent intramolecular transformations along three
paths: (1) dehydrogenation leading to regioisomeric
Compounds V IX, XI, and XII were isolated by
column chromatography on silica gel. Surprisingly,
chromatographic separation of the products on alu-
minum oxide was accompanied by transformation of
alkyl nitrotriazolecarboxylates VIa/Vb and VIIa/VIIb
into 5(4)-nitro-1-phenyl-1H-1,2,3-triazoles Xa/Xb as
a result of hydrolysis and decarboxylation. We suc-
ceeded in isolating individual isomers Xa and Xb by
1567

1568
BERESTOVITSKAYA et al.
X
CO2R
H
+ PhN3
C=C
O2N
I IV
CO2R
X
CO2R
O2N
X
CO2R
N
3
2
O2N
X
4 5
4
1
N15
N
1
N3
H
N
NO2
3
2
N
2
Ph
Ph
N
Ph
Va
I XIV
Vb
H
O2N
CO2R
CO2R
CO2R
H
O2N
CO2R
34N
H
O2N
H
34N
O2N
4
5
4
5
5
4
4
5
5
5
1N
N3
N3 1 N
N3
1 N
1
N3
N
N1
2
N
N1
2
N
2
2
N
2
N
2
N
Ph
Ph
Ph
N
Ph
Ph
Ph
Xa
VIa, VIIa
VIIIa, IXa
VIIIb, IXb
VIb, VIIb
Xb
R = Et: X = H (I, Va, Vb, VIa, VIb, VIIIa, VIIIb, XI, XIII), Br (III, XIII), R = Me (II, VIIa, VIIb, IXa, IXb, XII),
Br (IV, XIV).
repeated chromatography of their mixture, and isomer
Xb turned out to be identical in the melting point to
that reported in [9, 10]. By repeated chromatography
of regioisomer mixtures VIIa/VIIb, VIIIa/VIIIb, and
IXa/IXb were isolated pure isomers VIIa, VIIIa, IXa,
and IXb. Compounds VIIIa, IXa, IXb, and Xb were
identical in their physical constants and spectral
parameters to the corresponding samples described in
[11, 12], which were synthesized by different methods.
synthesized from alkenes I and II. Repeated chro-
matographic separation of regioisomer mixture VIIa/
VIIb gave pure nitrotriazole VIIa (18%).
The structure of products V XIV was proved by
the data of elemental analysis (Table 1) and IR and
1H NMR spectroscopy (Table 2), which were com-
pared with the corresponding data for structurally
related compounds reported in the literature (dihydro-
triazoles [13 15], triazoles [11, 12, 16, 17], and azir-
idines [18, 19]). The IR spectra of V XIV contained
absorption bands assignable to all functional groups
present in their molecules. The ester moiety was
characterized by strong absorption bands at 1745
Unlike halogen-free nitroalkenes I and II, alkyl
3-bromo-3-nitroacrylates III and IV reacted with
phenyl azide under more severe conditions, presumably
due to greater steric requirements of the dipolarophile.
Compounds III and IV failed to react with phenyl
azide at 20 C, and the reaction successfully occurred
only on heating in boiling benzene (2 h). Under these
conditions, dehydrobromination of the initially formed
halonitrotriazoles was faster than elimination of nitrous
acid therefrom; as a result, the nitro group was re-
tained in the triazole ring, and nitrotriazoles VIa/VIb
and VIIa/VIIb were isolated in 48 51% yield. In ad-
dition, as in the reactions with dipolarophiles I and II,
5 7% of aziridine derivatives XIII and XIV (as mix-
tures of diastereoisomers) and nitrotriazoles Xa and
Xb (after separation of the reaction mixture on alu-
minum oxide) was obtained. The products were iso-
lated by column chromatography on silica gel (VIa/
VIb, VIIa/VIIb) or aluminum oxide (Xa/Xb), and
their properties were identical to those of samples
1
1725 ( C=O) and 1190 1140 and 1025 1010 cm
(
C O C). Symmetric and antisymmetric stretching
vibrations of the conjugated nitro group in compounds
VIa, VIb, VIIa, VIIb, Xa, and Xb give rise to
1
absorption at 1360 1355 and 1560 1540 cm , res-
1
pectively, and bands at 1575 and 1365 cm were
assigned to the nonconjugated nitro group in dihydro-
triazoles Va and Vb.
The most useful information on the structure of all
compounds of the above series was derived from their
1H NMR spectra. The isomer structure was deter-
mined on the basis of the signal intensity ratios and
3
chemical shifts of the Csp H (dihydrotriazoles, azir-
idines) and olefinic CH= protons (triazoles). Different
effects of functional groups, N=N and C=N bonds,
neighboring endocyclic nitrogen atom, and magne-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 9 2007

3-NITRO- AND 3-BROMO-3-NITROACRYLATES IN REACTIONS
Table 1. Elemental analyses of compounds V XIV
1569
Found, %
H
Calculated, %
H
Comp. no.
Formula
C
N
C
N
Va, Vb
21.60
21.64
C11H12N4O4
C11H10N4O4
C10H8N4O4
C11H11N3O2
21.21
21.37
22.58
19.35
VIa, VIb
VIIa, VIIb
VIIIa, VIIIb
50.29
50.30
4.00
4.02
21.40
21.41
50.38
48.39
60.83
3.82
3.23
5.07
48.34
60.85
3.26
5.28
22.50
19.65
60.81
60.85
5.27
5.28
19.69
19.65
IXa, IXb
Xa, Xb
XI
59.17
59.18
50.66
50.71
55.78
55.69
54.18
54.18
4.65
4.63
3.19
3.15
4.97
4.94
4.69
4.70
20.57
20.52
29.39
29.37
11.76
11.89
12.71
12.65
8.87
C10H9N3O2
C8H6N4O2
59.11
50.53
55.93
54.05
4.43
3.16
5.08
4.50
20.69
29.47
11.86
12.61
8.89
C11H12N2O4
C10H10N2O4
C11H11BrN2O4
C10H9BrN2O4
XII
XIII
8.88
9.40
XIV
9.30
Table 2. IR and 1H NMR spectra of compounds V X
1
1H NMR spectrum (CDCl3), , ppm
CO2R
IR spectrum (CHCl3), , cm
Comp.
no.
C4H
C5H
OCH2
CH3
Ph
NO2
(C=O)
1745
(OCH3)
Va
Vb
4.47 d
5.12 d
4.35 d
4.30 q
4.20 q
1.30 t
1.26 t
7.00 7.70 m
1575
1365
3J4,5 4.0 Hz
5.24 d
3J4,5 6.0 Hz
VIa
4.45 q
4.30 q
1.30 t
1.40 t
7.65 m
7.60 m
1540
1360
1540
1360
1740
1745
1735
1740
VIb
VIIa
VIIb
VIIIa
VIIIb
IXa
(3.95 s)
(3.90 s)
7.40 7.70 m
8.50 s
8.50
4.40 q
4.20 q
1.15 t
1.35 t
7.35 7.80 m
7.40 7.80 m
7.60 7.80 m
8.18 s
(4.00 s)
(3.80 s)
IXb
Xa
8.25
8.70
1540
1355
Xb
8.82
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 9 2007

1570
BERESTOVITSKAYA et al.
Ph
CH3
VIIIa
OCH2
VIIIa
CH3
VIIIb
OCH2
VIIIb
H5
VIIIa
H4
VIIIb
8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0
, ppm
1
Fig. 1. H NMR spectrum of a mixture of regioisomeric ethyl 1-phenyl-1H-1,2,3-triazole-4(5)-carboxylates VIIIa and VIIIb
in CDCl .
3
CH3
Ph
OCH2
H5
8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5
, ppm
1
Fig. 2. H NMR spectrum of ethyl 1-phenyl-1H-1,2,3-triazole-4-carboxylate (VIIIa) in CDCl .
3
tically anisotropic properties of the benzene ring (in
molecules VI X) were taken into account [16, 17].
The effect of the phenyl group in dihydrotriazoles Va
and Vb on proton chemical shifts is likely to be in-
significant (Table 2; Figs. 1, 2).
nyl group to the ester moiety: the Ph and COOR
substituents in series a regioisomers are the most
distant from each other, whereas the corresponding
groups in series b isomers are attached to the neigh-
1
boring atoms. Their H NMR spectra contain two sets
of signals characterized by different intensity rations.
In the 1H NMR spectrum of regioisomer mixture
Va/Vb, the 4-H proton of Vb resonates in a weaker
Regioisomers a and b of dihydrotriazoles V and
triazoles VI X differ by the distance from the 1-phe-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 9 2007

3-NITRO- AND 3-BROMO-3-NITROACRYLATES IN REACTIONS
1571
field ( 5.24 ppm) relative to the corresponding signal
from 5-H in isomer Va ( 5.12 ppm) due to joint
effect of the electron-withdrawing double N=N bond
and nitro group. The second methine proton in Vb
(5-H) gives a more upfield signal ( 4.35 ppm), as
compared to that of 4-H in Va ( 4.47 ppm). Thus,
the 4-H and 5-H signals in the spectrum of isomer b
are most distant from each other ( 5.24 and 4.35 ppm;
= 0.89 ppm), whereas the corresponding signals in
larger chemical shift ( 4.40 ppm) than those in mo-
lecule VIIIb ( 4.20 ppm) due to effect of the endo-
cyclic N=N bond (Figs. 1, 2). However, another factor
is also important here: planar arrangement of the
benzene and triazole rings in molecule VIIIb is hardly
probable because of steric hindrances created by the
ester substituent on C5. As a result, protons in the
ester group falls into the shielding cone of the benzene
ring, which leads to upfield shift of the methylene
proton signal. It should be noted that the effect on the
cyclic proton of the N=N bond constituting a part of
the -electron system of the aromatic triazole heteror-
ing is likely to be weaker than the through-space
effect of the benzene ring.
the spectrum of isomer a ( 5.12 and 4.47 ppm;
0.65 ppm) appear closer to each other.
=
An analogous approach was applied by Huisgen et
al. [13] to identify the structure of regioisomeric N-
phenyldihydrotriazoles. The authors noted an upfield
shift (by 0.2 ppm) of the methine proton signal of
structures like a relative to the signal of regioisomers
like b.
The above assignment is consistent with the ob-
served signal intensity ratio for regioisomers VIIIa
and VIIIb (2:1; Fig. 1). Presumably, isomer VIIIa is
less sterically strained than VIIIb, and planar struc-
ture of the former ensures effective conjugation be-
tween the benzene and triazole rings. Following an
analogous approach, we have distinguished regio-
isomeric triazoles IXa and IXb and Xa and Xb. The
structure of triazoles VIIIa, Xb, IXa, and IXb is also
confirmed by similarity of their spectral parameters
and identity of their melting points to those reported
in the literature [9 12].
The spectra of phenyltriazoles VI X were analyzed
with account taken of the aromatic character of the
planar triazole ring and specific effect of the phenyl
substituent. It is known that a benzene ring is mag-
netically anisotropic, and its effect (shielding or
deshielding) depends on the orientation of the benzene
ring plane with respect to a given proton [20]. If the
benzene ring is oriented by its plane toward an ole-
finic proton or protons of a functional group, the latter
fall into the shielding cone, and the NMR signal shifts
upfield. If the benzene is oriented by its edge toward
an olefinic proton or functional group (deshielding
area), the signal shifts downfield.
Convincing proofs for the fine structure of the iso-
lated triazoles were obtained by X-ray analysis of a
single crystal of individual regioisomer VIIIa (Fig. 3).
It is seen that the Ph and CO2Et substituents in mo-
lecule VIIIa are attached to N1 and C4, respectively,
and are therefore most distant from each other. Tables
3 5 contain the geometric parameters (torsion and
bond angles and bond lengths) of molecule VIIIa in
crystal. The torsion angles involving atoms of the tri-
azole ring (C5N1N2N3, N1N2N3C4, N2N3C4C5, and
N3C4C5N1) range from 0.05 to 0.13 , indicating that
the triazole ring is virtually planar. The torsion angles
N2N1C10C11 and C5N1C10C15 are 6.3(2) and 4.2(2) ,
respectively; i.e., the triazole and benzene rings lie
almost in one plane. Their orientation favors effective
electronic interaction between the rings, as follows
from the length of the C10 N1 bond (1.4294 ); it is
The molecules of isomeric triazoles VIIIa/VIIIb
and IXa/IXb differ by the distance between the ole-
finic proton and double N=N and by the presence or
absence of benzene ring in the vicinity of that proton.
Undoubtedly, combined effect of the above factors on
the olefinic proton chemical shifts must be taken into
account while distinguishing the isomers. The benzene
ring and triazole ring in molecule VIIIa are likely to
lie in one plane since the olefinic proton on C5 does
not create steric hindrances to their planar arrangement.
H
N15
CO2Et
H
N15
CO2Et
4
4
3
3
N
N
shorter than standard ordinary C N bond (1.472
but longer than standard double C=N bond (1.339
[6].
)
)
2
2
N
N
VIIIa
VIIIb
In this case, the 5-H signal should appear in a
weaker field ( 8.50.ppm) due to deshielding effect of
the benzene ring. Contrastingly, the 4-H proton in
regioisomer VIIIb is remote from the benzene ring,
and its signal is located in a stronger field (
8.18 ppm). Methylene protons in the ester group
[C(O)OCH2CH3] of VIIIa are characterized by a
The ester carbonyl group and the endocyclic C4=C5
bond form diene fragment C5=C4 C6=O6 having s-cis
conformation with respect to the single C4 C6 bond.
The latter (C4 C6, 1.461 ) is appreciably shortened,
which is typical of conjugated diene systems. The
geometric parameters of the ethoxycarbonyl group do
not differ from the corresponding standard values.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 9 2007

1572
BERESTOVITSKAYA et al.
N3
N2
C11
C12
C4
C9
C10
C13
N1
C6
C5
C8
C15
C14
O6
Fig. 3. Molecular geometry of 1-phenyl-1H-1,2,3-triazole-4(5)-carboxylates (VIIIa).
Due to asymmetric substitution pattern, aziridines
of the 2-H signal to 3.50 3.85 ppm relative to the
corresponding signals from compounds XI and XII.
XI XIV possess chiral centers; therefore, they can be
formed as mixtures of diastereoisomers. In fact, com-
1
plicated character of their H NMR spectra (Table 6)
EXPERIMENTAL
is consistent with the presence of different stereo-
isomers. However, we failed to distinguish signals
from particular stereoisomers, and it seemed more
reasonable to assign signals to specific groups of
protons on the basis of general relations and com-
parison of chemical shifts with those reported for
The IR spectra were recorded from solutions in
chloroform (c = 0.1 0.001 M) on an InfraLYuM FT-
1
02 spectrometer. The H NMR spectra were measured
on a Bruker AC-200 spectrometer at 200 MHz in
chloroform-d or acetone-d6; the chemical shifts were
determined relative to hexamethyldisiloxane as ex-
ternal reference with an accuracy of 0.5 Hz. The
isomer ratios were determined from the corresponding
1
known analogs [18 22]. In the H NMR of aziridine
derivatives XI and XII, the most downfield were
signals from the O2NCH proton ( 4.40 4.85 ppm)
due to electron-withdrawing effect of the neighboring
nitro group. The CH proton adjacent to less electro-
withdrawing ester group resonated in a stronger field,
at 2.75 3.30 ppm. The presence of a bromine atom
in molecules XIII and XIV leads to a downfield shift
1
signal intensities in the H NMR spectra of samples
isolated by column chromatography.
X-Ray diffraction data for compound VIIIa.
Monoclinic crystals, C11H11N3O2, space group
Table 3. Torsion angles in the molecule of ethyl 1-phe-
nyl-1H-1,2,3-triazole-4-carboxylate (VIIIa)
Table 4. Bond angles in the molecule of ethyl 1-phenyl-
1H-1,2,3-triazole-4-carboxylate (VIIIa)
Angle
Angle
Angle
Angle
C5N1N2N3
0.05 (18) C4C6O7C8
178.97 (16)
167.74 (18)
4.2 (2)
173.09 (15)
176.50 (16)
6.3 (2)
0.8 (3)
178.50 (16)
0.6 (3)
C5N1N2
C5N1C10
N2N1C10
N3N2N1
N2N3C4
N3C4C5
N3C4C6
C5C4C6
N1C5C4
O6C6O7
O6C6C4
109.67 (13)
129.84 (13)
120.45 (12)
107.61 (13)
108.83 (13)
108.27 (14)
124.63 (14)
127.10 (15)
105.63 (14)
124.02 (16)
122.80 (15)
O7C6C4
C6O7C8
O7C8C9
113.17 (15)
116.04 (15)
108.4 (2)
C10N1N2N3 177.70 (14) C6O7C8C9
N1N2N3C4
N2N3C4C5
0.13 (19) C5N1C10C15
0.16 (19) N2N1C10C15
C15C10C11
C15C10N1
C11C10N1
C12C11C10
C11C12C13
C12C13C14
C15C14C13
C14C15C10
120.56 (15)
119.64 (13)
119.80 (14)
119.11 (17)
121.12 (18)
119.22 (18)
120.40 (17)
119.58 (16)
N2N3C4C6 179.59 (15) C5N1C10C11
N2N1C5C4
0.05 (17) N2N1C10C11
C10N1C5C4 177.53 (14) C15C10C11C12
N3C4C5N1
C6C4C5N1
0.13 (18) N1C10C11C12
179.54 (15) C10C11C12C13
N3C4C6O6 175.02 (17) C11C12C13C14
0.2 (3)
0.2 (3)
0.0 (3)
0.5 (3)
C5C4C6O6
N3C4C6O7
C5C4C6O7
O6C6O7C8
5.7 (3)
4.5 (2)
C12C13C14C15
C13C14C15C10
174.87 (15) C11C10C15C14
0.5 (3)
N1C10C15C14
178.80 (15)
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 9 2007

3-NITRO- AND 3-BROMO-3-NITROACRYLATES IN REACTIONS
1573
P21/c. Unit cell parameters (20 C): a = 11.674(1), b =
Table 5. Bond lengths d in the molecule of ethyl 1-phenyl-
1H-1,2,3-triazole-4-carboxylate (VIIIa)
11.273(1), c = 9.068(1)
;
= 111.82(1) ; V =
3
1107.7(2) 3; Z = 4; dcalc = 1.302 g cm . The unit
call parameters and intensities of 14832 reflections
(2346 of which were independent, Rint = 0.0418) were
measured on a Nonius KappaCCD automatic X-ray
diffractometer ( MoK irradiation, graphite mono-
Bond
d
Bond
d
N1 C5
N1 N2
N1 C10
N2 N3
N3 C4
C4 C5
C4 C6
C6 O6
C6 O7
1.3371(19)
1.3607(18)
1.4294(19)
1.299(2)
1.359(2)
1.361(2)
1.461(2)
1.203(2)
1.3281(19)
O7 C8
1.450(2)
1.475(3)
1.377(2)
1.378(2)
1.373(3)
1.373(3)
1.379(3)
1.375(2)
C8 C9
chromator,
27.99 ) at room temperature using
C10 C15
C10 C11
C11 C12
C12 C13
C13 C14
C14 C15
COLLECT (Nonius B.V., 1998), Dirax/lsq (Duisen-
berg & Schreurs, 1989 2000), and EvalCCD prog-
rams (Duisenberg & Schreurs 1990 2000). An em-
pirical correction for absorption was introduced. The
structure was solved by the direct method using
SHELXS-97 program [23] and was refined using
SHELXL-97 software (G.M. Sheldrick, Universitat
Gottingen, 1997). The final divergence factors were
R = 0.045, RW = 0.111 (from 1590 independent reflec-
(VIa/VIb), ethyl 1-phenyl-1H-1,2,3-triazole-4(5)-
carboxylates (VIIIa/VIIIb), and ethyl 3-nitro-1-
phenylaziridine-2-carboxylate (XI). a. Ethyl 3-nitro-
acrylate (I), 0.7 g, was dissolved in 20 ml of an-
hydrous ethanol, 1.14 g of phenyl azide was added,
and the mixture was kept for 14 days at 18 20 C, ap-
plied to silica gel, and subjected to column chromato-
graphy. Elution with hexane gave 0.57 g (45%) of a
mixture of regioisomeric triazoles VIa and VIb at a
ratio of 4:1 (Rf 0.77 and 0.71, respectively). Elution
with carbon tetrachloride gave 0.3 g of a mixture of
compounds Va, Vb, and XI at a ratio of 5:2:7. From
the benzene fraction we isolated 0.16 g (15%) of a
mixture of regioisomeric triazoles VIIIa and VIIIb at
a ratio of 7:2 (Rf 0.73 and 0.65, respectively). Re-
tions with F2
2 ).
Individual compounds were isolated and purified
by column chromatography on silica gel (100 200 m,
Chemapol) or aluminum oxide using eluotropic sol-
vent series [24]. The progress of reactions and the
purity of products were monitored by thin-layer
chromatography on Silufol UV-254 plates (hexane
acetone, 3:2; development with iodine vapor).
Initial 3-nitroacrylates I and II were synthesized
by an improved procedure [25], and 3-bromo-3-nitro-
acrylates III and IV were obtained as described in
[26].
Ethyl 5(4)-nitro-1-phenyl-4,5-dihydro-1H-1,2,3-
triazole-4(5)-carboxylates (Va/Vb), ethyl 5(4)-
nitro-1-phenyl-1H-1,2,3-triazole-4(5)-carboxylates
peated chromatographic separation of the Va/Vb/XI
mixture gave 0.08 g (7%) of aziridine XI (a mixture
of diastereoisomers, Rf 0.64, 0.42; elution with carbon
Table 6. Yields, Rf values, and IR and 1H NMR spectra of aziridines XI XIV
CO2R
H
(Br)H
NO2
3
2
1
N
Ph
1
IR spectrum (CHCl3), , cm
1H NMR spectrum (CDCl3), , ppm
Comp. Yield,
Rf
no.
%
NO2
C=O
1750
1740
1750
1745
COC
C2H
C3H
R
Ph
XI
7
22
7
0.64, 0.42
0.68, 0.63
0.30, 0.24
0.61, 0.42
1550
1370
1550
1370
1595
1390
1585
1385
1160 2.75 3.16 m 4.40 4.70 m 4.25 q, 1.25 t 7.20 7.70 m
1015
XII
XIII
XIV
1155 2.60 3.30 m 4.50 4.85 m 3.50 3.70 m 7.30 7.70 m
1020
1165
1020
1165
1015
3.50 m
4.45 q, 1.25 t
7.70 m
7
3.85 m
3.90 s
7.20 7.70 m
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 9 2007

1574
BERESTOVITSKAYA et al.
tetrachloride) and 0.09 g (7%) of a mixture of dihydro-
triazoles Va and Vb at a ratio of 5:2 (Rf 0.56 and
0.52, respectively; elution with benzene). Repeated
chromatography of regioisomer mixture VIa/VIb gave
0.30 g (24%) of nitrotriazole VIa (elution with carbon
tetrachloride) as an oily substance (Rf 0.77) which
crystallized on storage, mp 33 35 C.
3-nitro-1-phenylaziridine-2-carboxylate (XII).
a. Phenyl azide, 0.63 g, was added to a solution of
0.7 g of methyl 3-nitroacrylate (II) in 20 ml of an-
hydrous toluene. The mixture was heated for 1.5 h
under reflux (110 C), the solvent was removed on a
rotary evaporator, and the residue was subjected to
chromatography on silica gel. From the hexane frac-
tion we isolated 0.07 g (5%) of a mixture of triazoles
VIIa and VIIb at a ratio of 4:1 (Rf 0.76, 0.70). From
By repeated chromatography of regioisomer mix-
ture VIIIa/VIIIb using benzene as eluent we isolated
0.08 g (8%) of triazole VIIIa as yellow crystals with
mp 75 76 C, Rf 0.73; published data [11]: mp 76
77 C.
the benzene fraction we isolated 0.54 g (50%) of a
mixture of triazoles IXa and IXb at a ratio of 9:2 (Rf
0.60, 0.54). From the chloroform fraction we isolated
0.26 g (22%) of aziridine XII as a mixture of dia-
stereoisomers (Rf 0.68, 0.63) with mp 90 92 C. By
repeated chromatography of regioisomer mixture IXa
and IXb using carbon tetrachloride as eluent we iso-
lated 0.37 g (35%) of triazole IXa as light yellow
crystals with mp 119 120 C; published data [12]: mp
120 121.5 C.
b. Phenyl azide, 1.14 g, was added to a solution of
0.7 g of ethyl 3-nitroacrylate (I) in 20 ml of DMSO.
The mixture was heated for 5 min at 60 C and applied
to silica gel, and the solvent was evaporated at room
temperature. By column chromatography we isolated
0.42 g (33%) of a mixture of nitrotriazoles VIa and
VIb at a ratio of 4:1 (elution with hexane; Rf 0.77,
0.71), 0.14 g (12%) of aziridine XI (a mixture of dia-
stereoisomers; elution with carbon tetrachloride; Rf
0.64, 0.42), and 0.29 g (28%) of triazole mixture
VIIIa/VIIIb (ratio 7:2; elution with benzene; Rf 0.73,
0.65).
b. The procedure was the same as in a, but the oily
residue was subjected to chromatography on alu-
minum oxide. Elution with benzene gave 0.49 g
(45%) of triazole mixture IXa/IXb (5:1, Rf 0.60,
0.54). Elution with chloroform gave 0.30 g (25%) of
aziridine XII (a mixture of diastereoisomers) as
orange crystals with mp 90 92 C. Elution with
acetone gave 0.18 g (18%) of triazole mixture Xa/Xb
(1:2, Rf 0.86, 0.80). Elution with diethyl ether gave
0.05 g (5%) of triazole Xa with mp 120 122 C. By
repeated chromatography of triazole mixture Xa/Xb
using acetone as eluent we isolated isomer Xb with
mp 132 134 C; published data [9, 10]: mp 134 C.
c. Phenyl azide, 1.14 g, was added to a solution of
0.7 g of ethyl 3-nitroacrylate (I) in 20 ml of an-
hydrous benzene, and the mixture was heated for 2 h
under reflux. The solvent was removed on a rotary
evaporator, and the oily residue was subjected to
chromatography on silica gel. Elution with hexane
gave 0.13 g (10%) of triazole mixture VIa/VIb (5:1).
Elution with carbon tetrachloride gave 0.25 g (22%)
of aziridine XI (mixture of diastereoisomers, Rf 0.64,
Ethyl 5(4)-nitro-1-phenyl-1H-1,2,3-triazole-4(5)-
carboxylates (VIa/VIb) and ethyl 3-bromo-3-nitro-
1-phenylaziridine-2-carboxylate (XIII). Phenyl
azide, 0.37 g, was added to a solution of 0.7 g of ethyl
3-bromo-3-nitroacrylate (III) in 20 ml of anhydrous
benzene. The mixture was heated for 2 h under reflux,
the solvent was removed on a rotary evaporator, and
the residue was subjected to chromatography on silica
gel. From the hexane fraction we isolated 0.39 g
(48%) of a mixture of triazoles VIa and VIb at a ratio
of 4:1 (Rf 0.77, 0.71). From the acetone fraction we
isolated 0.07 g (7%) of aziridine XIII as a mixture of
diastereoisomers (Rf 0.30, 0.24).
0.42). Elution with benzene gave 0.48 g (46%) of tri-
azole mixture VIIIa/VIIIb (9:2, Rf 0.73, 0.65).
d. Phenyl azide, 0.6 g, was added to a solution of
0.7 g of ethyl 3-nitroacrylate (I) in 20 ml of an-
hydrous toluene, and the mixture was heated for 1.5 h
under reflux (110 C). The solvent was removed on a
rotary evaporator, and the oily residue was subjected
to chromatography on silica gel. From the hexane
fraction we isolated 0.06 g (5%) of a mixture of nitro-
triazoles VIa and VIb at a ratio of 5:1 (Rf 0.77 and
0.71, respectively). From the carbon tetrachloride frac-
tion we isolated 0.28 g (25%) of aziridine XI as a
mixture of diastereoisomers (Rf 0.64, 0.42). From the
benzene fraction we isolated 0.56 g (54%) of triazole
mixture VIIIa/VIIIb.
Methyl 5(4)-nitro-1-phenyl-1H-1,2,3-triazole-
4(5)-carboxylates (VIIa/VIIb), 5(4)-nitro-1-phenyl-
1H-1,2,3-triazoles (Xa/Xb), and methyl 3-bromo-3-
nitro-1-phenylaziridine-2-carboxylate (XIV).
a. Phenyl azide, 0.39 g, was added to a solution of
0.7 g of methyl 3-bromo-3-nitroacrylate (IV) in 20 ml
of anhydrous benzene. The mixture was heated for 2 h
Methyl 5(4)-nitro-1-phenyl-1H-1,2,3-triazole-
4(5)-carboxylates (VIIa/VIIb), methyl 1-phenyl-1H-
1,2,3-triazole-4(5)-carboxylates (IXa/IXb), 5(4)-nit-
ro-1-phenyl-1H-1,2,3-triazoles (Xa/Xb), and methyl
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 9 2007

3-NITRO- AND 3-BROMO-3-NITROACRYLATES IN REACTIONS
1575
under reflux and evaporated on a rotary evaporator,
and the residue was subjected to chromatography on
silica gel. Elution with hexane gave 0.41 g (50%) of
a mixture of nitrotriazoles VIIa and VIIb at a ratio of
4:1 (Rf 0.76, 0.70). Elution with chloroform gave
0.07 g (7%) of aziridine XIV as a mixture of dia-
stereoisomers (Rf 0.61, 0.42). By repeated chromato-
graphy of isomer mixture VIIa/VIIb using hexane as
eluent we isolated 0.15 g (18%) of nitrotriazole VIIa
as a crystalline substance with mp 70 72 C.
8. Callagham, P.D. and Gibson, M.S., Chem. Commun.
(London), 1967, vol. 18, nos. 8 9, p. 918.
9. Maiorana, S., Pocar, O., and Croce, P.D., Tetra-
hedron Lett., 1966, vol. 7, no. 48, p. 6043.
10. Pocar, O., Maiorana, S., and Croce, P.D., Gazz. Chim.
Ital., 1968, vol. 98, nos. 8 9, p. 949.
11. Abu-Orabi, S.T., Atfah, M.A., and Jibril, I., J. Hetero-
cycl. Chem., 1989, vol. 26, no. 5, p. 1461.
12. Huisgen, R., Knorr, R., Mobius, L., and Szeimies, G.,
Chem. Ber., 1965, vol. 98, no. 12, p. 4014.
b. The procedure was the same as in a (benzene,
80 C), but the oily product mixture was separated by
column chromatography on aluminum oxide. From
the chloroform fraction we isolated 0.07 g (7%) of
aziridine XIV as a mixture of diastereoisomers (Rf
0.61, 0.42). From the acetone fraction we isolated
0.28 g (45%) of a mixture of nitrotriazoles Xa and Xb
at a ratio of 4:1 (Rf 0.86, 0.80).
13. Huisgen, R., Szeimies, G., and Mobius, L., Chem. Ber.,
1966, vol. 99, no. 2, p. 475.
14. Makarova, N.G., Anisimova, N.A., Berkova, G.A.,
Deiko, L.I., and Berestovitskaya, V.M., Russ. J. Org.
Chem., 2005, vol. 41, no. 6, p. 941.
15. Makarova, N.G., Anisimova, N.A., Berkova, G.A.,
Deiko, L.I., and Berestovitskaya, V.M., Russ. J. Gen.
Chem., 2005, vol. 75, no. 9, p. 1495.
ACKNOWLEDGMENTS
16. Holzer, W., Tetrahedron, 1991, vol. 47, no. 47,
p. 9783.
The authors are grateful to Prof. P. Metz for pro-
viding the possibility for performing X-ray diffraction
experiment at the Technical University of Dresden
(Technische Universitat Dresden).
17. Barlin, G.B. and Batterham, T.J., J. Chem. Soc. B,
1967, no. 4, p. 516.
18. Nagel, D.L., Woller, P.B., and Cromwell, N.H.,
J. Org. Chem., 1971, vol. 36, no. 25, p. 3911.
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