Iodine-sodium acetate (I2-NaOAc) mediated oxidative dimerization of indolizines: An efficient method for the synthesis of biindolizines

Article abstract of DOI:10.1016/j.tetlet.2013.04.052

An I₂-NaOAc mediated one-pot process for the oxidative dimerization of indolizines under mild conditions is described. The reaction afforded a variety of products in good to excellent yields from indolizines with acceptor groups. Macrocyclic sy

Full text of DOI:10.1016/j.tetlet.2013.04.052

Accepted Manuscript
Iodine – Sodium Acetate (I –NaOAc) mediated oxidative dimerization of in‐
2
dolizines: an efficient method for the synthesis of biindolizines
Vakhid A. Mamedov, Aleksey A. Kalinin, Aida I. Samigullina, Ekaterina V.
Mironova, Dimitry B. Krivolapov, Aidar T. Gubaidullin, Il’dar K. Rizvanov
PII:
S0040-4039(13)00636-9
DOI:
http://dx.doi.org/10.1016/j.tetlet.2013.04.052
TETL 42820
Reference:
To appear in:
Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
2 March 2013
2 April 2013
12 April 2013
Please cite this article as: Mamedov, V.A., Kalinin, A.A., Samigullina, A.I., Mironova, E.V., Krivolapov, D.B.,
Gubaidullin, A.T., Rizvanov, I.K., Iodine – Sodium Acetate (I –NaOAc) mediated oxidative dimerization of
2
indolizines: an efficient method for the synthesis of biindolizines, Tetrahedron Letters (2013), doi: http://dx.doi.org/
10.1016/j.tetlet.2013.04.052
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Iodine – Sodium Acetate (I2–NaOAc) mediated oxidative dimerization of
indolizines: an efficient method for the synthesis of biindolizines
Vakhid A. Mamedov,* Aleksey A. Kalinin, Aida I. Samigullina, Ekaterina V. Mironova,
Dimitry B. Krivolapov, Aidar T. Gubaidullin, Il’dar K. Rizvanov
A.E. Arbuzov Institute of Organic and Physical Chemistry,
Kazan Research Center of the Russian Academy of Sciences,
Arbuzov str. 8, 420088 Kazan, Russian Federation
Tel.: +7 843 2727304; fax: +7 843 2732253. E-mail: mamedov@iopc.ru
Abstract: An I2–NaOAc mediated one-pot process for the oxidative dimerization of indolizines under
mild conditions is described. The reaction afforded a variety of products in good to excellent yields
from indolizines with acceptor groups. Macrocyclic systems with the biindolizine fragment(s) were
also synthesized from monoindolizinylquinoxaline podands under the same conditions.
Keywords: Indolizines, I2–NaOAc; Oxidative dimerization; 3,3′-Biindolizines; Indolizine macrocycles;
Quinoxaline macrocycles; X-ray analysis
3,3′-Biindolizines are reversible two-step redox systems of theoretical and practical interest,
which have attracted attention as an organic electroluminescent device,1 as a structural unit of
cyclophanes,2 as redox active and luminescent materials3 and as chiral ligands.4 Methods for the
synthesis of biindolizines have been developed only with substrates containing electron-donating
groups in good yields, using various agents including K3[Fe(CN)6],5 Pd/C,6 Pt/C6d and Fe (III)/O2.7
Indolizines with acceptor substituents either did not undergo oxidation,6d or the yields were very
low2a,6d,7 as in the cases with heteroaryl substitutents. A new method for the oxidative dimerization of
8
indolizines when exposed to Pd(OAc)2 was reported to produce high yields of biindolizines,
including examples with an acceptor substituent at position 1. Molecular iodine has received
considerable attention in organic synthesis because of its low cost and ready availability. The mild
Lewis acidity associated with iodine has enhanced its use in organic synthesis for performing several
organic transformations with stoichiometric to catalytic amounts.9 However, there are no examples in
which molecular iodine serves as a mild oxidant for the transformation of indolizine → biindolizine.
However, it should be noted that molecular iodine has been used as an excellent reagent-catalyst for
the synthesis of indolizine derivatives via 5-endo-dig cyclization.10 The application of molecular
iodine for the dehydrogenation of indolizines should, on the one hand, remove the need for a catalyst
or toxic reagents, while on the other hand, make it possible to carry out the desired reaction under
mild conditions, i.e. at room temperature and with easily removable solvents such as methylene
chloride.

2
In accordance with our interest in developing indolizine chemistry,3b,c,11a,b herein we report
efficient and convenient approaches to the oxidative dimerization of indolizines, with acceptor
substituents such as a quinoxalin-3-yl fragment or an ester group at position 2, using both molecular
iodine and the binary system of molecular iodine and NaOAc (I2–NaOAc). These new methods are
applied for synthesizing macrocycles, which, owing to the biindolizine system in their structures are
promising redox switchable ligands and redox active materials.2,4
As can be seen from Table 1, the reactions of indolizines 1а,b11a containing a 1-
alkylquinoxalin-3-yl substituent at position 2, as an acceptor group, with a 1.5 fold excess of
molecular iodine for 20 hours led to the formation of biindolizines 2а,b in good yields. It should be
pointed out that independent of the reaction time (24 or 48 h) and the ratio of the reagents, a two or
three fold excess of molecular iodine was used; along with the desired biindolizines 2а,b, ~10-15% of
the starting material(s) remained in the reaction mixture. An appreciable increase in yields (~15%)
occurred when the binary system (I2–NaOAc) was used instead of molecular iodine alone.12
The most notable effect of the use of the binary system (I2–NaOAc) was achieved by the
oxidative dimerization of indolizine 1с possessing a bromodecyl fragment. Decomposition of
compound 1с occurred when it was stirred with molecular iodine at room temperature in CH2Cl2 for
20 hours, the desired product 2с being isolated in only a trace amount. When the binary system (I2–
NaOAc) was used, the desired product 2с was obtained in 80% yield after 30 minutes.13
The oxidative dimerization of 1-phenyl-2-ethoxycarbonylindolizine (1d), using the binary
oxidation system (I2 + NaOAc) gave a dimer 2d in 90% yield (Table 1). In contrast, it should be
emphasized that the presence of the ethoxycarbonyl group as an acceptor group in 1-ethoxycarbonyl-
2-phenylindolizine (which is the isomer of the indolizine 1d) did not lead to formation of the
corresponding dimer in the presence of Pd/C.6d The absence of a phenyl substituent at position 1 did
not prevent application of the I2-NaOAc system for the synthesis of 2,2-biindolizines with the free
1,1-CH groups. In the presence of a 1.5 fold excess of molecular iodine the predominant product of
the oxidation of compound 1e was tetramer 3, formed in 18% yield. In this case, the yield of dimer 2e
was 10%. On decreasing the excess of the molecular iodine to 1.1 equivalents there remained a
significant amount of unreacted indolizine 1e. The use of the binary oxidation system I2-NaOAc with
a 1.35 fold excess of iodine made it possible to obtain dimer 2e in 45% yield. The yield of the
tetramer 3 in this case was 4% (Table 1).
When exposed to the I2–NaOAc binary system, compounds with two indolizine fragments, 1f-
h11a successfully underwent intramolecular cyclization with the formation of macrocycles 2f-h12 in
high yields (Table 1). In addition, the macrocyclization of podands 1g,h gave products 2g,h in high
yields using molecular iodine. The use of molecular iodine for the oxidation of podand 1f gave

3
macrocycle 2f (of smaller size) in a moderate yield. In this case, there appeared to be products of
oligomerization in the reaction mixture and a significant amount of the starting substrate 1f remained.
Application of the binary system (I2–NaOAc) increased the yield of macrocycle 2f up to 60%, the
macrocyclic dimer 4 was obtained in a 24% yield. Decreasing the excess of molecular iodine from a
2.3-fold excess to a two fold excess in the case of a podand 1i, it was possible to synthesize the
macrocycle 2i with the free 1,1-CH groups, via the regioselective oxidative coupling of the 3,3-CH
groups of the 2,2-biindolizine system.
Table 1. Iodine-mediated oxidation of indolizines 1 to biindolizines 2
Yield of 2 (%)
Entry
1
Substrate
Product
mp (oC)
317-319
Rf
I2
I2-NaOAc
70
83
0.18d
2
3
303-305
172-174
73
5
92
0.40d
0.45e
80a
4
132-134
-
90
0.58e
0.55e
5
6
170-171
>360
-
45b
60c
35
0.12,f
0.48g

4
7
>360
69
92
0.18f
8
9
309-311
>360
75
86
50
0.07g
0.24g
-
a Reaction was carried out for 30 min with the addition of molecular I2 in three stages.13
b Along with the dimer 2е a tetramer 3 (Figure 1) was obtained in 4% yield, m.p. 214-216 оС, Rf 0.19.e
c Along with a macrocycle 2f, dimer 4 (Figure 1) was obtained in 24% yield, m.p. 265-267 оС, Rf 0.92.f
d EtOAc/hexane = 1:2; eEtOAc/hexane = 1:3; f EtOAc/hexane = 3:2; g EtOAc.
Figure 1. Compounds 3 and 4 – the products of the tetramerization and dimerization of
compounds 1е and 1f, respectively.
1
The absence of singlet signals for the H3 protons of the indolizine fragments in the H NMR
spectra at 7.8-8.5 ppm points to the fact that the oxidative dimerization had occurred with the
formation of dimers 2a-e in the cases of compounds 1a-e, and macrocycles 2f-i in cases of compounds

5
1f-i. In the latter cases the ring formation occurred at the C3-C3′ carbon atoms of the indolizines.12
The mass spectra (MALDI) of these compounds displayed ion peaks at appropriate [MH]+ values.12,13
The molecular structures of dimers 2d, 2e, tetramer 3 and macrocycle 2i were confirmed
unambiguously by single-crystal X-ray analyses (Figures 2-5).14-18
Figure 2. ORTEP plot of compound 2d and partial numbering scheme. Displacement
ellipsoids are drawn at the 30% probability level. H atoms are omitted for clarity.
Figure 3. ORTEP plot of compound 2e and partial numbering scheme. Displacement ellipsoids are
drawn at the 30% probability level. Hydrogen atoms are represented by circles of an arbitrary size.
Crystals of 2e appeared to be a solid solution. That is, two different molecules were present in the
crystal of 2e: one type with a hydrogen atom at the C(11) position (relative occupancy is 0.88), and
another type with a chlorine atom at the C(11) position (relative occupancy is 0.12). In this figure only
the molecule with a hydrogen atom at the C(11) position (with maximum occupancy 0.88) is shown.

6
Figure 4. ORTEP plot of compound 3 and partial numbering scheme. Displacement
ellipsoids are drawn at the 30% probability level. H atoms are omitted for clarity.
Figure 5. ORTEP plot of compound 2i and partial numbering scheme. Displacement
ellipsoids are drawn at the 30% probability level. H atoms are represented by circles of
arbitrary size.
In conclusion, we have reported a highly efficient method for the synthesis of biindolizines,
including macrocyclic systems with biindolizine fragment(s) from indolizines and
monoindolizinylquinoxaline podands with acceptor groups, using molecular iodine or the binary I2–
NaOAc reagent system. The present approach carried out under extremely mild conditions provides a
novel and efficient synthesis of biindolizine derivatives. The reagent employed for this process is

7
inexpensive, odorless and nontoxic, making this a practical protocol. Further investigations of the
scope and limitations of these reactions are in progress in our laboratory.
Acknowledgements
This work was supported by the Russian Foundation for Basic Research (grant №13-03-
00123-a) and the Federal Agency of Science and Innovation (state contract №8432).
References and notes
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Zabel, V. J. Org. Chem. 1996, 61, 710-714.
3 (a) Henry, J. B.; MacDonald, R. J.; Gibbad, H. S.; McNab, H.; Mount, A. R. Phys. Chem. Chem.
Phys. 2011, 13, 5235-5241; (b) Yanilkin, V. V.; Mamedov, V. A.; Toropchina, V. A.; Kalinin, A.
A.; Nastapova, N. V.; Morozov, V. I; Shekurov, R. P.; Isaikina, O. G. Russ. J. Electrochem. 2006,
42, 212-224; (c) Yanilkin, V. V.; Mamedov, V. A.; Nastapova, N. V.; Kalinin, A. A.; Morozov, V.
I; Isaikina, O. G. Russ. J. Electrochem. 2007, 43, 1127-1132.
4 (a) Theil, F.; Sonnenschein, H.; Kreher, T. Tetrahedron: Asymmetry. 1996, 7, 3365-3370; (b)
Sonnenschein, H.; Theil, F.; Kreher, T.; Kockritz, A. Chem. Commun. 1997, 551-552; (c) Kockritz,
A.; Sonnenschein, H.; Bischoff, S.; Theil, F.; Gloede, J. Phosphorus, Sulfur Silicon Relat. Elem.
1998, 132, 15-19.
5 (a) Hünig, S.; Linhart, F. Tetrahedron Lett. 1971, 1273-1276; (b) S. Hünig, F. Linhart. Liebigs
Ann. Chem. 1976, 317-335; (c); Leitner M. B., Kreher, T.; Sonnenschein, H.; Costisella, B.;
Springer, J. J. Chem. Soc., Perkin Trans. 2. 1997, 377-381.
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Kreher, T.; Sonnenschein, H.; Schmidt, L.; Hunig, S. Liebigs Ann. Chem. 1994, 1173-1176; (с)
Hunig, S.; J. Prakt. Chem. 1994, 38-42; (d) Sonnenshein, H.; Kosslick, H.; Tittelbach, F. Synthesis
1998, 1596-1598.
7 Andruzzi, R.; Cardellin, L.; Greci, L.; Stipa, P.; Poloni, M.; Trazza, A. J. Chem. Soc., Perkin
Trans. 1 1988, 3067-3070.
8 Xia, J. B.; Wang, X. Q.; You, S. L. J. Org. Chem. 2009, 74, 456-458.
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(a) Togo, H.; Iida, S. Synlett 2006, 2159-2175; (b) Lin, X.-F.; Cui, S.-L.; Wang, Y. G.
Tetrahedron Lett. 2006, 47, 4509-4512; (c) Chen, W.-Y.; Lu, J. Synlett 2005, 1337-1339; (d)
Royer, L.; De, S. K.; Gibbs, R. A. Tetrahedron Lett. 2005, 46, 4595-4997; (e) Banik, B. K.;
Fernandez, M.; Alvarez, C. Tetrahedron Lett. 2005, 46, 2479-2482; (f) Ko, S.; Sastry, M.N.V.;
Lin, C.; Yao, C.-F. Tetrahedron Lett. 2005, 46, 5771-5774; (g) Stavber, S.; Jereb, M.; Zupan, M.
Synthesis 2008, 1487-1513.
10 Kim, I.; Choi, J.; Won, H. K.; Lee, G. H. Tetrahedron Lett. 2007, 48, 6863-6867.
11 (a) Mamedov, V. A.; Kalinin, A. A.; Yanilkin, V. V.; Gubaidullin, A. T.; Latypov, Sh. K.;
Balandina, A. A.; Isaikina, O. G.; Nastapova N. V.; Iglamova N. A.; Litvinov, I. A. Russ. Chem.
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12 General procedure for the synthesis of 3,3-biindolizines (2a,b,d,e) and 21,31-diphenyl-12,42-dioxo-
1,4(3,1)-diquinoxalina-2(2,3),3(3,2)-diindolizinacycloalkaphanes (2f-i). A solution of I2 (0.12 g,
0.47 mmol) in CH2Cl2 (20 ml) at room temperature was added to a stirred mixture of the
appropriate indolizine 1 (0.32 mmol for a,b,d; 0.36 mmol for e; 0.2 mmol for f-h; 0.24 mmol for i)
and NaOAc (39 mg, 0.47 mmol) in CH2Cl2 (20 ml for a,b,d,e; 140 ml for f-i). After being stirred
for 20 h at rt, the reaction mixture was washed with aqueous NaHCO3 and Na2S2O3. The organic

8
layer was dried over Na2SO4, filtered, and evaporated under reduced pressure. The residue was
purified by flash column chromatography (hexanes-СH2Cl2 = 7:3→СH2Cl2-EtOH = 50:1) to give
1
compound 2. Compound 2h: H NMR (400 MHz, CDCl3)  3.20-3.45 (m, 16H), 3.80-3.92 (m,
2H), 3.92-4.04 (m, 2H), 6.64 (2H, ddd, J = 7.2, 6.8, 0.9 Hz, Н6-ind), 6.86 (2H, ddd, J = 8.9, 6.8,
0.7 Hz, Н7-ind), 7.05-7.42 (18H, m, ArH), 7.62 (2H, d, J = 6.8 Hz, Н5-ind), 7.70 (2H, d, J = 9.2
13
Hz, Н8-ind). C NMR (100.6 MHz, CDCl3)  42.00, 67.79, 70.32, 70.86, 70.88, 111.79, 114.17,
114.36, 115.29, 118.40, 118.92, 122.50, 124.35, 125.37, 125.96, 128.04, 129.26, 129.59, 130.09,
130.99, 133.19, 133.58, 135.57, 153.61, 153.68. IR (max, cm-1, KBr): 3072, 2923, 2868, 1654,
1602, 1583, 1529, 1520, 1488, 1444, 1363, 1347, 1308, 1278, 1424, 1125, 768, 727, 700, 608,
560, 507, 434 cm-1. MS (MALDI) 875 (МН)+, 897 (M+Na)+, 913 (M+K)+. Found: C, 74.04; H,
5.17; N, 9.65. C54H46N6O6 requires: C, 74.13; H, 5.30; N, 9.60.
13 Procedure for the synthesis of 1,1-diphenyl-2,2-di[5-(10-bromodecyl)quinoxalin-2-on-3-yl]-3,3-
biindolizine (2c): A solution of I2 (0.40 g 1.6 mmol) in CH2Cl2 (9 ml) at room temperature was
added to a stirred suspension of the indolizine 1c (0.62 g, 1.1 mmol) and NaOAc (0.18 g, 2.2
mmol) in CH2Cl2 (30 ml) 20 min, in three times every 10 min per 3 mL. The reaction mixture was
stirred 10 min at this temperature and then was washed with aqueous 5% NaHCO3 (10 mL) and
5% Na2S2O3 (10 mL). The organic layer was dried over Na2SO4, filtered, and evaporated under
reduced pressure. The residue was purified by flash column chromatography with 3:1→2:1 hexane
: CH2Cl2 to give compound 2c. Yellow powder, mp 172-174 оС. IR (max, cm-1, Nujol mull): 1653,
1
1602, 1585, 1548, 1348, 1307, 1279, 1159, 1103, 1075, 972, 74, 722. H NMR (400.1 MHz,
CDCl3):  = 1.15-1.30 (20Н, m, CH2), 1.35-1.45 (8Н, m, CH2), 1.80-1.90 (4Н, m, CH2), 3.40 (4Н,
t, J = 6.9 Hz, CH2Br), 3.62-3.72 (2Н, m, NCH2), 3.90-4.00 (2Н, m, NCH2), 6.61-6.68 (2Н, m, Н6-
ind), 6.82-6.89 (2Н, m, Н7-ind), 6.94 (2Н, dd, J = 7.6, 7.2 Hz, Н6-quin), 7.00 (2Н, d, J = 7.4 Hz,
Н5-quin), 7.07 (2Н, dd, J = 8.4 Hz, Н8-quin), 7.11 (2Н, dd, J = 7.5, 7.5 Hz, p-Ph), 7.22 (4Н, dd, J
= 7.8, 7.5 Hz, m-Ph), 7.32 (2Н, d, J = 8.4, 6.9, 1.7 Hz, Н7-qui), 7.40 (4Н, d, J = 7.5 Hz, о-Ph),
13
7.64-7.70 (4Н, m, Н5,8-ind). C NMR (100.6 MHz, CDCl3)  27.05, 27.22, 28.52, 29.05, 29.50,
29.63, 29.72, 33.19, 34.33, 42.28, 112.18, 113.37, 115.11, 115.71, 118.78, 119.19, 122.91, 124.93,
125.78, 125.90, 128.29, 129.68, 130.23, 130.31, 131.55, 132.92, 133.37, 135.75, 153.76, 154.00.
MS (MALDI TOF) = 1113, 1111, 1109 (MH)+. Found: C, 69.07; H, 5.90; N, 7.57; Br, 14.28.
C64H66N6O2Br2 requires: C, 69.19; H, 5.99; N, 7.56; Br, 14.38.
14 The X-ray diffraction data for crystals of 2d were collected on a Bruker AXS Smart APEX II
CCD diffractometer at 296 K. Crystallographic data for 2d. С34H28N2O4, colorless prisms,
formula weight 528.58, monoclinic, P 21/c, a = 14.296(1) Å, b = 34.083(4) Å, c = 16.876(2) Å, β
= 93.291(2)º, V = 8209(1) Å3, Z = 12 (three independent molecules), ρcalc = 1.283 g cm–3,
μ(λMoKα) = 0.84 cm–1, F(000) = 3336, reflections collected = 62140, unique = 16100, R(int)
=
0.1110, full matrix least squares on F2, parameters = 1088, restraints = 0. Final indices R1 =
0.0569, wR2 = 0.1057 for 8765 reflections with I > 2σ(I); R1 = 0.1265, wR2 = 0.1327 for all data,
goodness-of-fit on F2 = 0.974, largest difference in peak and hole (0.260 and –0.273 eÅ–3).
15 The X-ray diffraction data for crystals of 2e was collected on a Bruker AXS Smart APEX II CCD
diffractometer at 296 K. Crystallographic data for 2e. С22H21N2O4(88%) · С22H20ClN2O4(12%),
colorless prisms, formula weight 376.40, monoclinic, P 21/c, a = 10.534(2) Å, b = 15.189(2) Å, c
= 14.744(2) Å, β = 128.322(7)º, V = 1851.0(5) Å3, Z = 4, ρcalc = 1.351 g cm–3, μ(λMoKα) = 0.94
cm–1, F(000) = 792, reflections collected = 13659, unique = 3631, R(int) = 0.0255, full matrix least
squares on F2, parameters = 269, restraints = 0. Final indices R1 = 0.0532, wR2 = 0.1219 for 3270
reflections with I > 2σ(I); R1 = 0.0583, wR2 = 0.1244 for all data, goodness-of-fit on F2 = 1.153,
largest difference in peak and hole (0.765 and – 0.503 eÅ–3).
16 The X-ray diffraction data for crystals of 3 were collected on a Smart Apex II CCD diffractometer
at 100(2) K. Crystallographic data for 3. C44H38N4O8, colourless plate crystals, formula weight
750.78, triclinic, P-1, a = 7.932(4), b = 14.747(6), c = 17.614(8)Å, α = 66.632(5),  = 86.199(5),
γ = 83.562(6), V = 1879(1) Å3, Z = 2, calc = 1.327 gcm-3, μ(λMo Kα)= 0.092 mm−1. F(000) =
788, reflections collected = 15249, unique = 7610, R(int) = 0.0839, full-matrix least-squares on F2,

9
parameters = 510, restraints = 0. Final indices R1 = 0.0816, wR2 = 0.1863 for 3475 reflections with
I>2σ(I); R1 = 0.1884, wR2 = 0.2348 for all data, goodness-of-fit on F2 = 0.977, largest difference
in peak and hole (2.128 and -0.082e Å−3).
17 The X-ray diffraction data for crystals of 2i were collected on a Smart Apex II CCD diffractometer
at 150(2) K. Crystallographic data for 2i.. C40H34N6O5, red prismatic crystals, formula weight
678.73, monoclinic, P 21/n, a = 14.999(3), b = 15.213(3), c = 15.854(4)Å,  = 112.988(3), V =
3330(1) Å3, Z = 4, calc = 1.354 gcm-3, μ(λMo Kα)= 0.091 mm−1. F(000) = 1424, reflections
collected = 49480, unique = 7988, R(int) = 0.0669, full-matrix least-squares on F2, parameters =
650, restraints = 38. Final indices R1 = 0.0578, wR2 = 0.1160 for 5055 reflections with I>2σ(I); R1
= 0.1054, wR2 = 0.1336 for all data, goodness-of-fit on F2 = 1.038, largest difference in peak and
hole (0.250 and -0.247e Å−3).
18 Crystallographic data (excluding structure factors) for have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication numbers CCDC 923523, 923524,
922447 and 922448 (compounds 2d, 2e, 3 and 2i, respectively). Copies of the data can be
obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK,
(fax: +44-(0)1223-336033 or e-mail: deposit@ccdc.cam.ac.uk).

Graphical abstract
Iodine – Sodium Acetate (I2–NaOAc) mediated oxidative dimerization of
indolizines: an efficient method for the synthesis of biindolizines
Vakhid A. Mamedov,* Aleksey A. Kalinin, Aida I. Samigullina, Ekaterina V. Mironova,
Dimitry B. Krivolapov, Aidar T. Gubaidullin, Il’dar K. Rizvanov