Synthesis and structure of indole-, pyridine-, and benzimidazole-containing nitroethenes

Article abstract of DOI:10.1023/B:RUGC.0000045874.46434.ea

Previously unknown 2-(1,2-dimethylindol-3-yl)-1-nitroethene was synthesized, and procedures for preparing 2-(1-methylbenzimidazol-2-yl)- and 2-(3-pyridyl)-1-nitroethens were improved. The structures of the products were determined by spectroscopic methods and from their dipole moments. According to single crystal X-ray diffraction data, the (E)-2-(1-methylbenzimidazol-2-yl)-1- nitroethene molecules are virtually planar and are packed in stacks in the crystal lattice, with appreciable stacking interaction.

Full text of DOI:10.1023/B:RUGC.0000045874.46434.ea

Russian Journal of General Chemistry, Vol. 74, No. 7, 2004, pp. 1108 1114. Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 7, 2004,
pp. 1198 1205.
Original Russian Text Copyright
Aleksandrova.
2004 by Berestovitskaya, Ishmaeva, Litvinov, Vasil’eva, Vereshchagina, Ostroglyadov, Fattakhova, Beskrovnyi,
Synthesis and Structure of Indole-, Pyridine-,
and Benzimidazole-Containing Nitroethenes
V. M. Berestovitskaya, E. A. Ishmaeva, I. A. Litvinov,
O. S. Vasil’eva, Ya. A. Vereshchagina, E. S. Ostroglyadov,
G. R. Fattakhova, D. V. Beskrovnyi, and S. M. Aleksandrova
Herzen Russian State Pedagogical University, St. Petersburg, Russia
Kazan State University, Kazan, Tatarstan, Russia
Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center,
Russian Academy of Sciences, Kazan, Tatarstan, Russia
Kazan State University of Technology, Kazan, Tatarstan, Russia
Received June 24, 2003
Abstract Previously unknown 2-(1,2-dimethylindol-3-yl)-1-nitroethene was synthesized, and procedures
for preparing 2-(1-methylbenzimidazol-2-yl)- and 2-(3-pyridyl)-1-nitroethens were improved. The structures of
the products were determined by spectroscopic methods and from their dipole moments. According to single
crystal X-ray diffraction data, the (E)-2-(1-methylbenzimidazol-2-yl)-1-nitroethene molecules are virtually
planar and are packed in stacks in the crystal lattice, with appreciable stacking interaction.
Compounds containing indole, pyridine, and benz-
imidazole fragments show biological activity [1] and
widely occur in the nature. In particular, these frag-
ments are present in molecules of many drugs: Indo-
pan, Diazoline, Cordiamin, Dibasol, Furodazol, etc.
proved this general procedure by adding methanol
to the hot reaction mixture after the reaction comple-
tion and then slowly cooling the mixture to room
temperature with stirring. As a result, high-purity
nitroalkenes I and II were isolated.
[
2]. Convenient synthetic precursors of compounds
1
-Nitro-2-(3-pyridyl)ethene III was prepared by
containing these pharmacophoric heterocycles are the
corresponding 2-heteryl-1-nitroethenes. For example,
aspidophytin alkaloid [3] and staurosporin, an active
substance of some fungi [4], were prepared from indo-
lylnitroethenes. 1-Nitro-2-(3-pyridyl)ethene and 1-ni-
tro-2-(6-chloro-3-pyridyl)ethene are used in synthesis
of pyrrolyzidine alkaloids [5], epibatidine alkaloid,
and its analogs [6 9]. Indolylnitroethenes not only
are interesting as synthetic precursors, but also exhibit
amebicidal and fungicidal activity themselves [10,
condensation of nicotinaldehyde with nitromethane in
the presence of methylamine [15, 16]. Modification
of the procedures from [15, 16] (replacement of anhy-
drous ethanol by methanol) allowed the yield of the
target product III to be increased from 55 to 73%,
with high quality of the product.
2
-(1-Methylbenzimidazol-2-yl)-1-nitroethene V
was prepared according to [17]. In the first step, the
reaction of 1-methyl-2-formylbenzimidazole with
nitromethane in aqueous-alcoholic solution of NaOH
afforded 2-(1-methylbenzimidazol-2-yl)-2-hydroxy-1-
nitroethane IV in 65% yield. We obtained the first
spectroscopic data for IV (see Experimental). The
subsequent acylation of nitro alcohol IV with freshly
distilled acetic anhydride under heating on a water
bath for 3 min is accompanied by simultaneous de-
acylation and formation of the desired nitroethene V.
However, when performed under these conditions
(corresponding to the published protocol [17]), the
mixture sometimes undergoes tarring, and no desired
nitroalkene V is obtained. We improved this step of
preparation of V from IV by changing the order of
1
1]. Therefore, optimization of the synthesis and
study of structure and properties of the above-men-
tioned 2-heteryl-1-nitroethenes are urgent problems.
Unsaturated nitroalkanes are commonly prepared
by reactions of nitroalkanes with aldehydes in the
presence of base catalysts [12, 13]. We used this pro-
cedure to prepare 2-(indol-3-yl)- (I), 2-(1,2-dimethyl-
indol-3-yl)- (II), 2-(3-pyridyl)- (III), and 2-(1-methyl-
benzimidazol-2-yl)-1-nitroethenes (V). In particular,
compound I was prepared following the published
protocol [14]; previously unknown compound II was
prepared by the same procedure. However, we im-
1
070-3632/04/7407-1108 2004 MAIK Nauka/Interperiodica

SYNTHESIS AND STRUCTURE OF INDOLE-, PYRIDINE-...
O
1109
+
3
CH NO2
Ht C
H
N
Ht =
CH COONH
Ht =
CH NH
3 2
3
4
Ht =
NaOH
N
R
R
N
N
CH3
NO2
H
H
NO2
H
N
C=C
C=C
R
H
CH CH NO
2
2
N
N
OH
N
R
CH3
IV
I, II
III
H
N
NO2
(
CH CO) O
3 2
C=C
H
N
CH3
V
adding the reactants and by stirring the reaction mix-
ture both in the course of heating and for 2 h after
adding water to the reaction mixture. In this case, the
tarring of V is prevented, and nitroalkene V is ob-
tained in a reproducibly high yield, no less than 74%.
All the heterylnitroethenes I III and V are colored
crystalline substances with well-defined melting points.
with the published data for 2-(indol-3-yl)-1-nitroeth-
ene I [5, 18 23] and 1-nitro-2-(3-pyridyl)ethene III
1
[5, 15], respectively (Table 1). For example, in the H
NMR spectrum of II, the vicinal olefinic protons give
an AB pattern with the signal centers at 7.75 (H ) and
8.32 ppm (H ) and coupling constant of 13.4 Hz, typi-
cal of trans-protons. The indole ring protons in II give
signals at 7.69 7.65 (1H), 7.32 (2H), and 7.28 ppm
The structure of 2-(indol-3-yl)-1-nitroethene I was
2
(
1H); the methyl groups at C and indole nitrogen
1
13
characterized [5, 18 23] by H and C NMR, IR, and
UV spectroscopy, and also by single crystal X-ray dif-
fraction, which allowed us to use this compound as
reference. 1-Nitro-2-(3-pyridyl)ethene III was charac-
atom give singlets at 2.57 and 3.77 ppm, respectively.
1
In the H NMR spectrum of 2-(1-methylbenzimidazol-
2
-yl)-1-nitroethene V, the olefinic protons also give
an AB pattern with the signal centers at 7.97 (H ) and
.15 ppm (H ) and coupling constant of 13 Hz. The
1
terized by H NMR spectroscopy, and the bond ener-
8
gies in its molecule were calculated in [15].
benzimidazole ring protons give two groups of low-
field signals at 7.79 (1H) and 7.39 ppm (3H); the
methyl protons give a singlet at 3.92 ppm (Table 1).
1
The characteristics of the H NMR spectra of II
and V, measured for the first time, are well consistent
Table 1. 1H NMR and electronic absorptiona spectra of 2-heteryl-1-nitroethenes II, III, and V
1H NMR spectrum (CDCl3), , ppm
Het
Electronic absorption spectrum
Comp.
no.
H
H
NCH (CCH )
max, nm
3
3
4
7
II
7.75 d 8.32 d 7.69 7.65 m (1H, H ), 7.28 s (1H, H ), 7.32 s
(
3.77 s
(2.57 s)
225
283
20600
9700
3
5
6
5 3
JAB 13.4 Hz) (2H, H , H ), 7.42 d.d (1H, H , J 4.8, 7.7 Hz)
4
15
20200
16700
19200
16700
17200
7.80 d 8.03 d 7.88 m (1H, H ), 8.73 d.d (1H, H , 4+3J 1.6,
(
4
6
219
294
212
361
III
V
3
2 4
JAB 13.8 Hz) 4.8 Hz), 8.80 d (1H, H , J 2.1 Hz)
7.97 d 8.15 d 7.39 s (3H), 7.79 m (1H)
3.92 s
3
(
JAB 13 Hz)
a
Solvent: II, acetonitrile; III, IV, methanol.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 7 2004

1
110
BERESTOVITSKAYA et al.
25 27], contains no bands of covalently bound nitro
1
Table 2. IR data ( , cm ) for III and V
group but contains strong bands at 1310 1286 and
NO2
CH=CH
1284 1250 cm 1 assignable to the ionic nitro group
Comp.
no.
1
and at 1500 1620 cm , probably belonging to the
system of conjugated multiple bonds with the preva-
lent contribution from C=N [28 32]. The nicely con-
as
s
CH
+
CH Cl
1348 s
1344 vs
Mineral oil
1352 s
sistent IR spectra of indolylnitroethenes I and II con-
firm the similarity of the fine structure of their mole-
cules, and the specific features of the IR spectra re-
flect the high degree of polarization of the electron
density in the indolylnitroethene moiety. This conclu-
sion is consistent with the electronic absorption spec-
trum of II, containing a strong long-wave maximum
at about 415 nm (Table 1), similar to that in the spec-
2
2
III
V
1528 s
1528 vs
1640 m
1644 s
972 m
972 s
III
V
1518 s
1526 s
1634 m
1646 s
976 m
974 s
1344 s
1
1
1
The H NMR spectra of heterylnitroethenes I III and
V show that these compounds are stereochemically
uniform and exist as E isomers. The medium-intensity
IR bands at 972 (II) and 972 976 cm 1 (III, V), as-
signable to the CH out-of-plane bending vibrations in
the CH=CH group, also suggest the trans orientation
of the substituents in the molecules [24] (Table 2).
trum of I ( max 393 nm, 19429 l mol cm ) [23];
hence, compound II is a highly conjugated system
with a significant contribution of the bipolar structure.
Such features of the IR and UV spectra of indole-
containing nitroethenes I and II, compared to com-
pounds III and V, are apparently due to more pro-
nounced redistribution of the electron density in I
and II, compared to pyridyl- and benzimidazolylnitro-
ethenes III and V.
The IR spectra of I III and V were taken from
solid samples (mulls in mineral oil) and solutions in
CH Cl and CHCl . As seen from Table 2, in the
2
2
3
The same conclusion follows from the experimen-
tal dipole moments of heterylnitroalkenes I III and V
(Table 3). For example, the dipole moment of II,
measured in dioxane, is higher than that of V by
2.22 D (Table 3).
spectra of III and V the absorption frequencies of the
1
C=C bonds (1644 1634 cm ) and nitro groups (
as
1
1
528 1518,
1352 1344 cm ) are typical of nitro-
s
ethenes [18, 24].
The IR spectrum of II, as well as that of I [18, 23,
Furthermore, for indole-substituted nitroethenes I
H
NO2
H
H
NOO
H
C=C
R
C C
R
+
N
N
R
R
I, II
R = H (I), CH3 (II).
Table 3. Coefficients of calculation equations, orientation polarizations, and calculated and experimental dipole moments
of I III and V
calc,
D
Comp.
no.
Solvent
P , cm3
exp, D
or
E isomer
Z isomer
I
II
Benzene
26.010
26.802
33.844
10.547
14.824
18.371
1.451
0.787
0.797
0.353
2.471
0.796
868.023
1056.637
1173.830
287.536
299.357
586.721
6.52
7.19
7.58
3.75
3.83
5.36
4.18
4.63
3.30
3.20
Dioxane
Benzene
Dioxane
III
V
4.32
6.15
3.27
3.32
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 7 2004

SYNTHESIS AND STRUCTURE OF INDOLE-, PYRIDINE-...
1111
c
C12
O42
C6
N1
C2
C5
C11
C7
C10
O41
C9
N4
N3
C4
C8
Fig. 1. Geometry of the molecule of V in the crystal.
and II,
between the experimental (in benzene) and
calculated (for E isomers) dipole moments is 2.34 and
b
2
.56 D, respectively, which also suggests significant
O41
redistribution of the electron density in molecules of
N C9
C4
C5
3
0
indolylnitroethenes I and II between the donor hetero-
11
C8
C7
C
1
0
cycle and acceptor nitro group. For III and V,
is
C
N4
O42
considerably smaller (0.49 and 0.79 D) and has differ-
ent sign, which also suggests considerably weaker
polarization of molecules of nitroethenes III and V,
compared to I and II.
C2
N1
C6
C12
Fig. 2. Unit cell of the crystal of V.
When calculating the dipole moments, we used the
following moments of bonds and groups: m(H Csp
.7 [33], m(Csp NO ) 2.81 D {calculated from
exp(CH =CHNO ) [34]}. The group moment of the
2
)
0
2
2
2
2
pyridine ring (1.51 D) was calculated from
of
exp
pyridine [34]; that of the indole ring (1.37 D), from
of indole [34]; that of the 1,2-dimethylindole
exp
ring (1.82 D), from
and that of the 1-methylbenzimidazole ring (3.34 D),
from of N-methylbenzimidazole [34]. The direc-
tion of the group moments of nitrogen-containing
heterocycles is from the heterocycle to Csp . In cal-
of 1,2-dimethylindole [34];
exp
exp
2
culations, we used the bond angles determined in a
single crystal X-ray diffraction study of 2-(1-methyl-
1
benzimidazol-2-yl)-1-nitroethene V ( C=CH 118 ,
2
C=CH 117 , NO C=C 121 , C=CC 122 ).
2
According to single crystal X-ray diffraction data,
the 2-(1-methylbenzimidazol-2-yl)-1-nitroethene mol-
ecule in the crystal is virtually planar, with the trans
configuration at the double bond (Fig. 1). The steric
structure of V is shown in Figs. 1 3, and the atomic
coordinates and geometric parameters are listed in
Tables 4 and 5. The oxygen atoms of the nitro group
show the largest deviation from the least-squares plane
of the molecules [maximal deviation 0.145(5) ].
Without considering the oxygen atoms of the nitro
group and the methyl carbon atom, the molecule is
planar to within 0.027(5) . Thus, the double bond
and the benzimidazole fragment can form a common
conjugated system. The bond length distribution is
consistent with this assumption. The molecules in the
crystal are packed in stacks in the antiparallel fashion
Fig. 3. Molecular packing of V in the crystal.
(Figs. 2, 3). A short contact of 3.31
between the
planes of the benzimidazole fragment in the stacks
suggests the occurrence of stacking interaction in the
crystal.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 7 2004

1112
BERESTOVITSKAYA et al.
Table 4. Atomic coordinates in the structure of V,
equivalent isotropic temperature factors of nonhydrogen
Table 5. Principal geometric parameters of the structure
of V: bond lengths (d, ), bond angles ( , deg), and
torsion angles ( , deg)
3
3
atoms B = 4/3
(a a )B(i, j) ( 2), and isotropic
i j
i=1 j=1
2)
Bond
d
Bond
d
temperature factors of hydrogen atoms Biso
(
O4 N4
1
1.228(6)
1.220(6)
1.328(6)
1.382(6)
1.466(7)
1.341(6)
1.358(5)
1.433(6)
C C
2
10
5
1.451(7)
1.412(7)
1.405(7)
1.360(7)
1.426(9)
1.42(1)
Atom
x
y
z
Biso
42
1
4
4
O
N
C C
2
4
9
O4
1
N C
C C
0.9646(4) 0.6275(6) 1.2627(3)
1.0302(4) 0.5289(7) 1.1246(3)
0.5842(4) 0.2649(5) 0.9570(3)
0.5247(4) 0.3333(5) 1.1102(3)
0.9410(4) 0.5511(5) 1.1810(3)
0.6235(5) 0.3351(6) 1.0474(4)
0.4158(4) 0.2552(6) 1.0538(3)
0.4487(5) 0.2087(5) 0.9563(4)
0.3606(6) 0.1266(7) 0.8840(5)
0.2275(7) 0.0890(7) 0.9143(6)
0.1930(6) 0.1402(8) 1.0110(5)
0.2818(5) 0.2206(8) 1.0789(4)
0.7629(5) 0.4038(6) 1.0712(3)
0.8031(5) 0.4827(7) 1.1592(4)
0.6607(6) 0.2552(9) 0.8682(4)
7.6(1)
8.0(1)
3.69(7)
3.89(8)
4.48(9)
3.72(9)
3.56(8)
4.1(1)
5.6(1)
7.8(2)
6.3(1)
5.5(1)
4.4(1)
4.4(1)
6.5(1)
7(3)
10(2)
8(4)
8(4)
5(3)
5(3)
9(4)
8(4)
9(4)
1
5
5
6
4
2
N C
N C
N C
N C
C C
O
N
N
N
1
12
2
6
7
1
3
4
C C
3
7
8
C C
3
4
8
9
C C
1.321(8)
1.331(7)
4
11
10
C11
2
4
5
6
7
8
9
1
1
1
N C
C
C
C
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
Angle
Angle
2
1
5
3 4 9
C N C
107.6(4)
N C C
129.3(4)
2
1
12
12
4
5
4
9
4
C N C
128.8(4)
123.4(4)
103.3(4)
122.3(4)
115.0(4)
122.6(4)
113.9(4)
120.2(4)
125.8(4)
111.7(4)
C C C
119.0(4)
103.5(4)
131.8(5)
124.8(5)
114.1(6)
121.2(5)
122.7(6)
118.2(5)
121.6(5)
120.8(5)
5
1
1 5
C N C
N C C
2
3
1 5 6
0
1
2
C N C
N C C
4
1
4
42
4
5
6
7
8
9
8
O N O
O N C
C C C
4
1
4
11
11
5 6
C C C
4
2
4
6 7
6
7
8
9
1
1
1
1
1
O N C
C C C
0.390(9)
0.164(6)
0.10(1)
0.09(1)
0.032(9) 0.856(5)
0.815(8)
1
2
3
7 8
N C N
C C C
1
2
10
10
5
4 9
N C C
C C C
0.12(2)
0.25(3)
0.39(1)
0.49(1)
0.294(6) 0.868(4)
0.13(3) 0.84(2)
0.321(9) 0.806(6)
1.02(1)
1.15(2)
1.022(7)
1.207(6)
3
2
2 10 11
N C C
C C C
0.26(2)
3
4
4
11 10
0
N C C
N C C
0.830(9)
0.734(7)
0.747(5)
0.65(2)
1
21
22
23
Angle
Angle
5
1
2
3
41 4 11 10
C N C N
0.5(5)
179.1(4)
175.5(5)
5.0(7)
O N C C
177.1(5)
5.8(7)
176.6(4)
3.9(7)
0.604(7)
5
1
2
10
3
42 4 11 10
C N C C
O N C C
1
2
1
2
1 2 10 11
C N C N
N C C C
1
2
1
2
10
3 2 10 11
C N C C
N C C C
Comparative analysis of the single crystal X-ray
diffraction data for V (this work) and I [23] confirms
the above conclusions. In particular, the C NO2
2
1
5
4
6
3 4 5 1
C N C C
0.5(5)
N C C N
0.4(5)
2
1
5
3
4
5
6
1
C N C C
179.0(5)
175.7(4)
4.8(8)
0.2(5)
179.4(4)
0.2(5)
N C C C
179.1(4)
178.4(4)
2.1(7)
179.2(5)
179.4(5)
179.5(4)
12
1
5
4
6
9 4 5
C N C C
C C C N
(
1.433 ) and C Ht (1.451 ) bonds in V are appreci-
1
2
1
5
9
4
5
6
8
C N C C
C C C C
ably longer than in I (1.424 and 1.422 , respective-
ly), suggesting weaker conjugation in V.
4
3
2
1
3 4 9
C N C N
C N C C
C N C C
C N C C
N C C C
4
3
2
10
5
1 5 6 7
N C C C
2
3
4
2 10 11 4
Thus, we have prepared previously unknown 2(1,2-
dimethylindol-3-yl)-1-nitroethene and optimized the
procedures for preparing its pyridine- and 1-methyl-
benzimidazole-containing analogs. The fine structure
of these molecules was studied by the method of
C C C N
2
3
4
9
178.5(5)
to single crystal X-ray diffraction, the molecules of
(E)-2-(1-methylbenzimidazol-2-yl)-1-nitroethene are
virtually planar and are packed in stacks in the crystal,
with the stacking interaction.
1
dipole moments, H NMR, IR, and UV spectroscopy,
and single crystal X-ray diffraction. Comparative
analysis of the physicochemical characteristics de-
scribed for the reference compound, 1-(indol-3-yl)-2-
nitroethene I, with those obtained for heterylnitro-
ethenes II, III, and V suggests that all these nitro-
ethenes are E isomers; indole-containing nitroethenes
I and II are highly conjugated systems with a signifi-
cant contribution of the bipolar structure. According
EXPERIMENTAL
1
The H NMR spectra were recorded on a Bruker
AC-200 spectrometer (200 MHz) in chloroform-d (II,
III, V) or acetonitrile-d3 (IV), internal reference
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 7 2004

SYNTHESIS AND STRUCTURE OF INDOLE-, PYRIDINE-...
1113
HMDS. The IR spectra were recorded on a Specord
M-80 spectrophotometer [mulls in mineral oil (I III,
V), solutions in dichloromethane (I III, V), or KBr
pellets (IV). The electronic absorption spectra were
measured on an SF-121 spectrophotometer in aceto-
nitrile (I, II) or methanol (III, V).
1-Nitro-2-(3-pyridyl)ethene III. To a mixture of
10 ml of methanol and 15 ml of nitromethane, we
added with stirring 0.4 g of methylamine hydrochlo-
ride, 0.2 g of sodium hydrogen carbonate, and 10.7 ml
of nicotinaldehyde. The mixture was stirred for 72 h.
The precipitate was filtered off and washed with a
small amount of methanol. Yield of III 11 g (73%);
mp 138 140 C (from methanol) (published data: mp
Crystals of 2-(1-methylbenzimidazol-2-yl)-1-nitro-
ethene V, C N N O , are monoclinic. The unit cell
1
0
9
3
2
140 C [16]). Found, %: C 56.55, 56.55; H 4.52, 4.51;
parameters at 20 C are as follows: a 9.715(4), b
3
N 18.41, 18.39. C H N O . Calculated, %: C 56.00;
7
6
2
2
7
.632(3), c 13.261(9)
;
96.65(5) , V 976.6(9)
,
3
H 4.00; N 18.67.
Z 4, dcalc 1.38 g cm , space group P2 /c. The unit
1
cell parameters and intensities of 2278 reflections,
including 1037 reflections with I 3 , were measured
on an Enraf Nonius CAD-4 automatic four-circle dif-
fractometer ( CuK radiation, graphite monochro-
2-(1-Methylbenzimidazol-2-yl)-2-hydroxy-1-
nitroethane IV was prepared according to [17]. IR
1
spectrum (KBr), , cm : 1384, 1560 (NO ); 3650
2
1
3300 (OH). H NMR spectrum (CD CN), , ppm:
3
mator, /2 scanning,
76.9 ). No decrease in the
5.15 4.96 m (CH ), 5.69 5.63 m (CH), 7.61 d (1H-
2
intensity of three check reflections within the time of
Bz), 7.48 d (1H-Bz), 7.34 7.19 m (2H-Bz), 3.85 s
(NCH3).
measurements was observed. The absorption ( Cu
1
7
.91 cm ) was not taken into account. The structure
2
-(1-Methylbenzimidazol-2-yl)-1-nitroethene V.
To 5 ml of acetic anhydride, we added with stirring
.2 g of 2-(1-methylbenzimidazol-2-yl)-2-hydroxy-1-
was solved by the direct method using the SIR prog-
ram [35] and refined first in the isotropic and then in
the anisotropic approximation. The methyl hydrogen
atoms were revealed from the differential electron
density syntheses, and the other hydrogen atoms were
placed in the calculated positions. Their contribution
to the structural amplitudes was taken into account
with fixed positional and isotropic thermal parameters.
2
nitroethane IV. The mixture was heated on a boiling
water bath until the precipitate fully dissolved (3
4
min). Then 40 ml of ice-cold water was added, and
the mixture was stirred for 2 h. The yellow crystalline
product was filtered off and washed on the filter with
water, alcohol, and ether. Yield of V 1.5 g (74%), mp
137 139 C (from methanol) {published data: mp
The final divergence factors were R 0.069, R 0.074
W
2
for 686 unique reflections with F 3 . All the calcu-
1
5
39 140 C (methanol) [17]}. Found, %: C 59.15,
9.18; H 4.53; 4.50; N 20.70; 20.63. C H N O .
lations were performed on an AlphaStation-200 com-
puter using MolEN program package [36]. The inter-
molecular interactions were analyzed and the struc-
tures plotted with the PLATON program [37].
1
0
9
3
2
Calculated, %: C 59.11; H 4.46; N 20.68.
ACKNOWLEDGMENTS
The dipole moments of I III were determined in
benzene, and those of II, III, and V, in dioxane at
Ya.A. Vereshchagina, E.A. Ishmaeva, and G.R. Fat-
takhova performed the study within the framework of
the programs Support of the Leading Scientific
Schools of Russia and Universities of Russia (pro-
ject no. UR.05.01.016); G.R. Fattakhova is grateful to
the Scientific and Educational Center of the Kazan
State University Materials and Processes of XXI
Century (grant for young researchers within the
framework of the Joint Russia US Program Basic
Research and Higher Education, REC-007).
2
5 C with an IDM-2 device according to [38]. The
orientation polarizations and coefficients of the calcu-
lation equations are given in Table 3.
1-Methylbenzimidazole-2-carbaldehyde was pre-
pared according to [39], and 2-(indol-3-yl)-1-nitro-
ethene I, by the modified procedure in [14]. Commer-
cial nicotinaldehyde was used.
2
-(1,2-Dimethylindol-3-yl)-1-nitroethene II.
A mixture of 20 ml of nitromethane, 1.54 g of ammo-
nium acetate, and 7 g of 1,2-dimethylindole-3-carbal-
dehyde was refluxed with continuous stirring for
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