Five-membered 2,3-dioxo heterocycles: LXIII. Cascade recyclization of isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates with cyclic enamines. Crystalline and molecular structure of 1′-benzyl-6′,6′-dimethyl-3-[(Z)-phenyl(phen

Article abstract of DOI:10.1134/S1070428009010163

Title Full: Five-membered 2,3-dioxo heterocycles: LXIII. Cascade recyclization of isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates with cyclic enamines. Crystalline and molecular structure of 1′-benzyl-6′,6′-dimethyl-3-[(Z)

Full text of DOI:10.1134/S1070428009010163

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 1, pp. 126–130. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © P.S. Silaichev, Z.G. Aliev, A.N. Maslivets, 2009, published in Zhurnal Organicheskoi Khimii, 2009, Vol. 45, No. 1, pp. 130–133.
Five-Membered 2,3-Dioxo Heterocycles: LXIII.* Cascade
Recyclization of Isopropyl 2-(1-Aryl-4,5-dioxo-2-phenyl-4,5-
dihydro-1H-pyrrol-3-yl)-2-oxoacetates with Cyclic Enamines.
Crystalline and Molecular Structure of 1′-Benzyl-6′,6′-dimethyl-
3-[(Z)-phenyl(phenylamino)methylidene]-6′,7′-dihydro-
3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone
P. S. Silaicheva, Z. G. Alievb, and A. N. Maslivetsa
a Perm State University, ul. Bukireva 15, Perm, 614990 Russia
e-mail: koh2@psu.ru
b Institute of Chemical Physics Problems, Russian Academy of Sciences, Chernogolovka, Moscow oblast, Russia
Received March 12, 2008
Abstract—Isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates reacted with
N-substituted 3-amino-5,5-dimethylcyclohex-2-en-1-ones to give the corresponding 1′-substituted (Z)-6′,6′-di-
methyl-3-[phenyl(arylamino)methylidene]-6′,7′-dihydro-3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-
tetraones. The structure of 1′-benzyl-6′,6′-dimethyl-3-[(Z)-phenyl(phenylamino)methylidene]-6′,7′-dihydro-3H-
spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone was proved by X-ray analysis.
DOI: 10.1134/S1070428009010163
We previously described reactions of new mono-
cyclic 1H-pyrrole-2,3-diones [isopropyl 2-(4,5-dioxo-
1,2-diphenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoace-
tates] with o-phenylenediamine and o-aminobenzene-
thiol, which involved successive nucleophilic attacks
on the C5 atom in the pyrrole ring and ketone carbonyl
carbon atom in the substituent on C3 and resulted in the
formation of substituted pyrrolo[2,3-b][1,5]benzodi-
azepines [2] and pyrrolo[2,3-b][1,5]benzothiazepines
[3], respectively. Reactions of analogous 1H-pyrrole-
2,3-diones with 1,3-binucleophiles were not studied.
chloroform using equimolar amounts of the reactants;
the reaction mixtures were kept for 8–10 h at 20–22°C,
the progress of the reaction being monitored by chro-
matography. As a result, we isolated in good yields the
corresponding 1′-R-6′,6′-dimethyl-3-[(Z)-phenyl(aryl-
amino)methylidene]-6′,7′-dihydro-3H-spiro[furan-2,3′-
indole]-2′,4,4′,5(1′H,5′H)-tetraones IIIa–IIIk. The
structure of compound IIIb was proved by X-ray
analysis.
Compounds IIIa–IIIk are bright yellow crystalline
substances which are readily soluble in DMSO and
DMF, poorly soluble in other common organic sol-
vents, and insoluble in saturated hydrocarbons and
water. They showed a negative test for enolic hydroxy
group with an alcoholic solution of iron(III) chloride.
The IR spectra of IIIa–IIIk contained absorption
bands due to stretching vibrations of the NH group
(a broad band at 3158–3183 cm–1), lactone carbonyl
group (C5=O, 1781–1793 cm–1), lactam carbonyl group
(C2′=O, 1752–1764 cm–1), and ketone carbonyl groups
(C4=O, C4′=O; one or two peaks in the region 1637–
In continuation of our studies on nucleophilic recy-
clizations of monocyclic 1H-pyrrole-2,3-diones, in the
present work we examined reactions of isopropyl
2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-
yl)-2-oxoacetates Ia–Ic with cyclic enamino ketones,
N-substituted 3-amino-5,5-dimethylcyclohex-2-en-1-
ones IIa–IIf. Substituent on the nitrogen atom in
enamines II was varied over a wide range with a view
to estimate its effect on the reaction course.
The reactions of compounds Ia–Ic with cyclic
enamines IIa–IIf were carried out in anhydrous
1
1660 cm–1). In the H NMR spectra of IIIa–IIIk, we
observed signals from protons in the aliphatic substit-
* For communication LXII, see [1].
126

FIVE-MEMBERED 2,3-DIOXO HETEROCYCLES: LXIII.
127
Scheme 1.
O
Me Me
O
O
i-PrO
O
O
i-PrO
O
O
+
Ph
Me
Me
N
R
O
Ph
O
NHR
N
NH
O
Ar
Ar
Ia–Ic
IIa–IIf
i-PrO
O
O
O
5
4
O
NHAr
O
O
NHAr
Ph
HO
O1
3
2
4'
7'
3'
–i-PrOH
Ph
5'
6'
2'
O
O
1'
Me
Me
Me
N
N
Me
R
R
A
IIIa–IIIk
I, Ar = Ph (a), 4-MeOC6H4 (b), 4-MeC6H4 (c); II, R = CH2=CHCH2 (a), PhCH2 (b), Ph (c), 4-MeC6H4 (d), 4-MeOC6H4 (e),
1-naphthyl (f); III, Ar = Ph, R = CH2=CHCH2 (a), PhCH2 (b), Ph (c), 4-MeC6H4 (d), 4-MeOC6H4 (e), 1-naphthyl (f); Ar =
4-MeOC6H4, R = PhCH2 (g), Ph (h), 4-MeOC6H4 (i), 1-naphthyl (j); Ar = 4-MeC6H4, R = PhCH2 (k).
uents, aromatic rings, and substituents in the latter.
Two methyl groups gave two singlets in the region
δ 0.80–0.95 ppm, four nonequivalent protons in the C5′
H2 and C7′H2 methylene groups resonated as doublets
at δ 1.56–2.25 ppm with coupling constants J of 16.0–
18.8 Hz, and the NH signal appeared as a broadened
singlet in the region δ 12.65–12.78 ppm.
Variation of substituent on the nitrogen atom in
enamines IIa–IIf does not affect the direction of their
reaction with pyrrolediones Ia–Ic, and the rate of the
process also changes insignificantly. For example, we
performed in parallel two control reactions of N-benzyl
and N-phenyl enamino ketones IIb and IIc with the
same pyrroledione Ia under similar conditions; accord-
The structure of molecule IIIb is shown in figure.
The configuration of the phenylamino group is fixed
by strong intramolecular hydrogen bond N2–H2 ···O2
with the following parameters: N2–H2 0.90(3), H2···O2
1.93(3), N2 ···O2 2.690(3) Å; ∠N2H2O2 141(3)°. The
formation of intramolecular hydrogen bond affected
the C3=O2 bond length (1.236 Å). All other bond
lengths and bond angles did not differ from the
corresponding standard values. Neither intermolecular
hydrogen bonds nor shortened contacts were found in
crystal.
C32
C31
C30
C33
C28
C29
C24
C23
C6
C14
C25
N1
C10
C9
C11
C26
C7
C15
C12
C13
O5
C8
O1
C4
C22
O4
C27
C17
C5
C1
Presumably, compounds IIIa–IIIk are formed by
initial addition of the activated NH group in enamines
IIa–IIf at the C5 carbon atom of pyrrolediones Ia–Ic.
Next follows cleavage of the pyrrole ring at the N1–C5
bond and closure of new pyrrole ring via intramolec-
ular nucleophilic addition of the β-CH group in en-
amine II at the ketone carbonyl group in I. The hemi-
acetal hydroxy group thus formed (structure A) attacks
the ester carbonyl carbon atom, leading to the forma-
tion of furan ring and elimination of propan-2-ol.
C18
C19
N2
H2
C2
C3
C16
O3
C20
O2
C21
Structure of the molecule of 1′-benzyl-6′,6′-dimethyl-3-[(Z)-
phenyl(phenylamino)methylidene]-6′,7′-dihydro-3H-spiro-
[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone (IIIb) accord-
ing to the X-ray diffraction data.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 1 2009

SILAICHEV et al.
128
ing to the TLC data, the reactions were complete
almost simultaneously.
18.5 Hz), 1.89 d and 1.99 d (1H each, 5′-H, J =
16.0 Hz), 4.33 d and 4.70 d (1H each, CH2Ph, J =
16.0 Hz), 6.97–7.43 m (15H, Harom), 12.67 br.s
(1H, NH). 13C NMR spectrum (DMSO-d6), δC, ppm:
25.93 and 29.50 (Me), 32.82 (C6′), 35.00 (C7′), 43.24
(CH2Ph), 49.99 (C5′), 79.93 (C3′), 110.64–135.54
(Carom, C3a′, C3=C), 162.18 (C7a′), 164.23 (C5), 165.93
(C2′), 174.65 (C4), 189.50 (C4′). Found, %: C 74.36;
H 5.27; N 5.23. C33H28N2O5. Calculated, %: C 74.42;
H 5.30; N 5.26.
It should be noted that the described reaction is
a rare example of cascade recyclization of monocyclic
1H-pyrrole-2,3-diones by the action of 1,3-difunctional
nucleophiles, which gives rise to difficultly accessible
spiro[furan-2,3′-indole] system with various substit-
uents in several positions of both heterorings.
EXPERIMENTAL
6′,6′-Dimethyl-1′-phenyl-3-[(Z)-phenyl(phenyl-
amino)methylidene]-6′,7′-dihydro-3H-spiro[furan-
2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone (IIIc). Yield
71%, mp 181–182°C (from ethyl acetate). IR spectrum,
ν, cm–1: 3158 br (NH), 1786 (C5=O), 1764 (C2′=O),
The IR spectra were recorded on an FSM-1201
spectrophotometer from samples dispersed in mineral
1
oil. The H and 13C NMR spectra were measured on
1
a Bruker AM-400 spectrometer (400 MHz for H)
1
1658 (C4′=O), 1643 (C4=O). H NMR spectrum, δ,
using DMSO-d6 as solvent and tetramethylsilane as
internal reference. The purity of the isolated com-
pounds was checked by TLC on Silufol plates using
benzene–ethyl acetate (5:1) or ethyl acetate as eluent.
ppm: 0.91 s (6H, Me), 1.81 d and 2.06 d (1H each,
7′-H, J = 18.8 Hz), 2.09 d and 2.11 d (1H each, 5′-H,
J = 16.8 Hz), 6.96–7.56 m (15H, Harom), 12.74 br.s (1H,
NH). Found, %: C 74.05; H 5.03; N 5.36. C32H26N2O5.
Calculated, %: C 74.12; H 5.05; N 5.40.
1′-Allyl-6′,6′-dimethyl-3-[(Z)-phenyl(phenyl-
amino)methylen]-6′,7′-dihydro-3H-spiro[furan-2,3′-
indole]-2′,4,4′,5(1′H,5′H)-tetraone (IIIa). A solution
of 1.0 mmol of compound Ia and 1.0 mmol of enamine
IIa in 15 ml of anhydrous chloroform was kept for 8 h
at 20°C (until the initial pyrroledione disappeared ac-
cording to the TLC data). The solvent was removed,
and the residue was ground with hexane. Yield 72%,
mp 148–149°C (from ethyl acetate). IR spectrum, ν,
cm–1: 3172 br (NH), 1788 (C5=O), 1753 (C2′=O), 1649
6′,6′-Dimethyl-1′-(4-methylphenyl)-3-[(Z)-phenyl-
(phenylamino)methylidene]-6′,7′-dihydro-3H-spiro-
[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone
(IIId). Yield 74%, mp 168–170°C (from ethyl acetate).
IR spectrum, ν, cm–1: 3171 br (NH), 1788 (C5=O),
1
1752 (C2′=O), 1660 (C4′=O), 1641 (C4=O). H NMR
spectrum, δ, ppm: 0.90 s (6H, Me), 1.78 d and 2.04 d
(1H each, 7′-H, J = 18.4 Hz), 2.08 d and 2.10 d (1H
each, 5′-H, J = 16.8 Hz), 2.35 s (3H, Me), 6.91–7.54 m
(14H, Harom), 12.74 br.s (1H, NH). Found, %: C 74.37;
H 5.26; N 5.24. C33H28N2O5. Calculated, %: C 74.42;
H 5.30; N 5.26.
1
(C4=O, C4′=O). H NMR spectrum, δ, ppm: 0.89 s and
0.95 s (3H each, Me), 1.77 d and 2.24 d (1H each,
7′-H, J = 18.4 Hz), 1.99 d and 2.01 d (1H each, 5′-H,
J = 16.8 Hz), 3.66 d.d and 4.06 d.d (1H each,
CH2CH=CH2, J = 16.8, J = 5.0 Hz), 5.01 d (1H,
CH2CH=CH2, J = 17.6 Hz), 5.17 d (1H, CH2CH=CH2,
J = 10.0 Hz), 5.74 m (1H, CH2CH=CH2), 6.95–7.44 m
(10H, Harom), 12.65 br.s (1H, NH). Found, %: C 74.13;
H 5.41; N 5.77. C29H26N2O5. Calculated, %: C 74.18;
H 5.43; N 5.81.
1′-(4-Methoxyphenyl)-6′,6′-dimethyl-3-[(Z)-
phenyl(phenylamino)methylidene]-6′,7′-dihydro-
3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetra-
one (IIIe). Yield 73%, mp 174–175°C (from chloro-
form–ethyl acetate, 1:3). IR spectrum, ν, cm–1: 3160 br
(NH), 1793 (C5=O), 1754 (C2′=O), 1655 (C4′=O), 1649
1
(C4=O). H NMR spectrum, δ, ppm: 0.90 s and 0.91 s
Compounds IIIb–IIIk were synthesized in a simi-
lar way.
(3H each, Me), 1.76 d and 2.03 d (1H each, 7′-H, J =
18.3 Hz), 2.08 d and 2.11 d (1H each, 5′-H, J =
16.8 Hz), 3.80 s (3H, OMe), 6.95–7.22 m (14H, Harom),
12.76 br.s (1H, NH). 13C NMR spectrum (DMSO-d6),
δC, ppm: 26.14 and 29.21 (Me), 33.04 (C6′), 35.68
(C7′), 50.29 (C5′), 55.37 (OMe), 79.99 (C3′), 111.08–
130.77 (Carom, C3a′, C3=C), 159.27 (C4″), 162.36 (C7a′),
164.21 (C5), 165.49 (C2′), 173.49 (C4), 190.11 (C4′).
Found, %: C 72.20; H 5.11; N 5.09. C33H28N2O6. Cal-
culated, %: C 72.25; H 5.14; N 5.11.
1′-Benzyl-6′,6′-dimethyl-3-[(Z)-phenyl(phenyl-
amino)methylidene]-6′,7′-dihydro-3H-spiro[furan-
2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone (IIIb). Yield
77%, mp 152–153°C (from acetone–ethyl acetate–
acetonitrile, 1:1:1). IR spectrum, ν, cm–1: 3183 br
(NH), 1781 (C5=O), 1751 (C2′=O), 1651 (C4′=O), 1637
1
(C4=O). H NMR spectrum, δ, ppm: 0.81 s and 0.90 s
(3H each, Me), 1.78 d and 2.25 d (1H each, 7′-H, J =
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 1 2009

FIVE-MEMBERED 2,3-DIOXO HETEROCYCLES: LXIII.
129
6′,6′-Dimethyl-1′-(1-naphthyl)-3-[(Z)-phenyl
(phenylamino)methylidene]-6′,7′-dihydro-3H-spiro-
[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone (IIIf).
Yield 68%, mp 185–186°C (from ethyl acetate). IR
spectrum, ν, cm–1: 3178 br (NH), 1793 (C5=O), 1759
tetraone (IIIj). Yield 71%, mp 186–187°C (from ethyl
acetate). IR spectrum, ν, cm–1: 3173 br (NH), 1783
(C5=O), 1764 (C2′=O), 1657 (C4′=O), 1639 (C4=O).
1H NMR spectrum, δ, ppm: 0.84 s (6H, Me), 1.56 d
and 1.76 d (1H each, 7′-H, J = 18.4 Hz), 2.10 d and
2.14 d (1H each, 5′-H, J = 16.0 Hz), 3.67 s (3H, OMe),
6.75–8.17 m (16H, Harom), 12.78 br.s (1H, NH). Found,
%: C 74.18; H 5.03; N 4.67. C37H30N2O6. Calculated,
%: C 74.23; H 5.05; N 4.68.
1
(C2′=O), 1656 (C4′=O), 1651 (C4=O). H NMR spec-
trum, δ, ppm: 0.85 s (6H, Me), 1.58 d and 1.78 d (1H
each, 7′-H, J = 18.8 Hz), 2.11 d and 2.14 d (2H, 5′-H,
J = 16.8 Hz), 7.03–8.17 m (17H, Harom), 12.77 br.s (1H,
NH). Found, %: C 76.00; H 4.94; N 4.90. C36H28N2O5.
Calculated, %: C 76.04; H 4.96; N 4.93.
1′-Benzyl-6′,6′-dimethyl-3-[(Z)-(4-methylphenyl)-
(phenyl)methylidene]-6′,7′-dihydro-3H-spiro[furan-
2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone (IIIk). Yield
76%, mp 152–153°C (from ethyl acetate). IR spec-
trum, ν, cm–1: 3160 br (NH), 1781 (C5=O), 1753
1′-Benzyl-3-[(Z)-(4-methoxyphenylamino)-
(phenyl)methylidene]-6′,6′-dimethyl-6′,7′-dihydro-
3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetra-
one (IIIg). Yield 80%, mp 152–153°C (from ethyl
acetate). IR spectrum, ν, cm–1: 3174 br (NH), 1785
(C5=O), 1754 (C2′=O), 1655 (C4′=O), 1639 (C4=O).
1H NMR spectrum, δ, ppm: 0.80 s and 0.90 s (3H each,
Me), 1.76 d and 2.23 d (1H each, 7′-H, J = 18.8 Hz),
1.89 d and 1.97 d (1H each, 5′-H, J = 16.4 Hz), 3.65 s
(3H, OMe), 4.31 d and 4.69 d (1H each, CH2Ph, J =
16.0 Hz), 6.73–7.43 m (14H, Harom), 12.67 br.s (1H,
NH). Found, %: C 72.54; H 5.34; N 4.95. C34H30N2O6.
Calculated, %: C 72.58; H 5.37; N 4.98.
1
(C2′=O), 1650 (C4=O, C4′=O). H NMR spectrum, δ,
ppm: 0.80 s and 0.90 s (3H each, Me), 1.77 d and
2.24 d (1H each, 7′-H, J = 18.4 Hz), 1.89 d and 1.97 d
(1H each, 5′-H, J = 16.4 Hz), 2.17 s (3H, Me), 4.32 d
and 4.69 d (1H each, CH2Ph, J = 16.0 Hz), 6.87–
7.43 m (14H, Harom), 12.69 br.s (1H, NH). Found, %:
C 74.66; H 5.51; N 5.09. C34H30N2O5. Calculated, %:
C 74.71; H 5.53; N 5.12.
X-Ray diffraction data for compound IIIb.
Yellow well-defined crystals, C33H28N2O8, rhombic
crystal system; unit cell parameters: a = 9.890(2), b =
14.607(3), c = 18.947(4) Å; V = 2737.1(10) Å3;
M 532.57; dcalc = 1.292 g/cm3; Z = 4; space group
P212121. The set of experimental reflections was
acquired on a KM-4 (KUMA Diffraction) automatic
four-circle diffractometer with χ-geometry (mono-
chromatized MoKα irradiation, ω/2Θ scanning, 2Θ ≤
50.5°). Total of 2559 independent reflections (91.1%
of possible ones) were measured with no correction for
absorption (μ = 0.087 mm–1). The structure was solved
by the direct method using SIR92 program [4],
followed by calculation of electron density maps. The
positions of all hydrogen atoms (except for H2) were
set on the basis of geometry considerations and were
refined by the riding model. Full-matrix anisotropic
approximation (for non-hydrogen atoms) by the least-
squares procedure was performed using SHELXL-97
software [5] and was complete at R1 = 0.0380, wR2 =
0.1003 [for 2241 reflections with I ≥ 2σ(I)] and R1 =
0.0473, wR2 = 0.1041 (for all reflections); number of
refined parameters 364, goodness of fit 1.064. Friedel
pairs of reflections were not measured, and the abso-
lute structure of molecule IIIb was not determined.
3-[(Z)-(4-Methoxyphenylamino)(phenyl)meth-
ylidene]-6′,6′-dimethyl-1′-phenyl-6′,7′-dihydro-3H-
spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone
(IIIh). Yield 75%, mp 180–181°C (from ethyl acetate).
IR spectrum, ν, cm–1: 3168 br (NH), 1785 (C5=O),
1
1765 (C2′=O), 1649 (C4=O, C4′=O). H NMR spec-
trum, δ, ppm: 0.91 s (6H, Me), 1.80 d and 2.03 d (1H
each, 7′-H, J = 18.4 Hz), 2.07 d and 2.12 d (1H each,
5′-H, J = 16.4 Hz), 3.65 s (3H, OMe), 6.73–7.56 m
(14H, Harom), 12.76 br.s (1H, NH). Found, %: C 72.19;
H 5.12; N 5.08. C33H28N2O6. Calculated, %: C 72.25;
H 5.14; N 5.11.
1′-(4-Methoxyphenyl)-6′,6′-dimethyl-6′,7′-dihy-
dro-3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-
tetraone (IIIi). Yield 72%, mp 163–164°C (from ethyl
acetate). IR spectrum, ν, cm–1: 3173 br (NH), 1785
(C5=O), 1758 (C2′=O), 1660 (C4′=O), 1649 (C4=O).
1H NMR spectrum, δ, ppm: 0.90 s (6H, Me), 1.74 d
and 2.00 d (1H each, 7′-H, J = 18.8 Hz), 2.06 d and
2,10 d (1H each, 5′-H, J = 16.4 Hz), 3.65 s and 3.80 s
(3H each, OMe), 6.72–7.55 m (13H, Harom), 12.76 br.s
(1H, NH). Found, %: C 70.53; H 5.21; N 4.81.
C34H30N2O7. Calculated, %: C 70.58; H 5.23; N 4.84.
3-[(Z)-(4-Methoxyphenylamino)(phenyl)meth-
ylidene]-6′,6′-dimethyl-1′-(1-naphthyl)-6′,7′-dihy-
dro-3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 07-03-96036).
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SILAICHEV et al.
3. Maslivets, A.N., Smirnova, L.I., Ivanenko, O.I., and
130
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