Synthesis and Transformations of 9-Substituted Imidazo[1,2-a]benzimidazole-2-carbaldehydes

Article abstract of DOI:10.1134/S1070428020070064

Abstract: Ethyl 2-formyl-9-methyl-9H-imidazo[1,2-a]benzimidazole-3-carboxylate was synthesized for the first time in a high yield by heating a solution of ethyl 2-(dibromomethyl)-9-methyl-9H-imidazo[1,2-a]benzimidazole-3-carboxylate in ethanol. Acid hydrolysis of the product gave less accessible 9-methylimidazobenzimidazole-2-carbaldehyde. Ethyl 2-formyl-9-methyl-9H-imidazo[1,2-a]benzimidazole-3-carboxylate underwent cyclization to fused oxopyridazine derivative by treatment with hydrazine hydrate, it reacted as a typical aldehyde with acetophenones, hydroxylamine hydrochloride, and malononitrile, and its reaction with acetylacetone and thiourea (Biginelli reaction) afforded the corresponding pyrimidine derivative.

Full text of DOI:10.1134/S1070428020070064

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2020, Vol. 56, No. 7, pp. 1160–1165. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Zhurnal Organicheskoi Khimii, 2020, Vol. 56, No. 7, pp. 1039–1045.
Synthesis and Transformations
of 9-Substituted Imidazo[1,2-a]benzimidazole-2-carbaldehydes
T. A. Kuzʼmenkoa, L. N. Divaevaa,*, and A. S. Morkovnika
a Research Institute of Physical and Organic Chemistry, Southern Federal University,
Rostov-on-Don, 344090 Russia
*e-mail: divaevaln@mail.ru
Received March 18, 2020; revised April 16, 2020; accepted April 20, 2020
Abstract—Ethyl 2-formyl-9-methyl-9H-imidazo[1,2-a]benzimidazole-3-carboxylate was synthesized for the
first time in a high yield by heating a solution of ethyl 2-(dibromomethyl)-9-methyl-9H-imidazo[1,2-a]benz-
imidazole-3-carboxylate in ethanol. Acid hydrolysis of the product gave less accessible 9-methylimidazo-
benzimidazole-2-carbaldehyde. Ethyl 2-formyl-9-methyl-9H-imidazo[1,2-a]benzimidazole-3-carboxylate
underwent cyclization to fused oxopyridazine derivative by treatment with hydrazine hydrate, it reacted as
a typical aldehyde with acetophenones, hydroxylamine hydrochloride, and malononitrile, and its reaction with
acetylacetone and thiourea (Biginelli reaction) afforded the corresponding pyrimidine derivative.
Keywords: ethyl 2-formyl-9-methyl-9H-imidazo[1,2-a]benzimidazole-3-carboxylate, 9-methyl-9H-imidazo-
[1,2-a]benzimidazole-2-carbaldehyde, 6-methyl-2H-pyridazino[4′,5′:4,5]imidazo[1,2-a]benzimidazol-1(6H)-
one, ethyl 2-cyano-9-methyl-9H-imidazo[1,2-a]benzimidazole-3-carboxylate, Biginelli reaction
DOI: 10.1134/S1070428020070064
2-Formylimidazo[1,2-a]benzimidazoles, unlike
their 3-formyl analogs, have been poorly studied.
While searching for new β-lactamase inhibitors,
Venkatesan et al. [1] described the synthesis of
9-methylimidazo[1,2-a]benzimidazole-2-carbaldehyde
which was characterized only by color (brown crystals)
and molecular weight. It was obtained by condensation
of 1-methyl-1H-benzimidazol-2-amine with ethyl
3-bromopyruvate, reduction of ethyl imidazo[1,2-a]-
benzimidazole-2-carboxylate thus formed to the corre-
sponding alcohl, and oxidation of the latter; the overall
yield did not exceed 16%.
dibromomethyl derivative 1 was successfully converted
to aldehyde 2 by heating in boiling ethanol (yield
~80%; Scheme 1). The acid hydrolysis of 2 was
accompanied by decarboxylation of intermediate
3-carboxylic acid to produce aldehyde 3. However, this
reaction involved considerable tar formation, especially
when the reaction solution was made alkaline in the
isolation stage, so that the yield of 3 decreased to 42%.
Presumably, the observed tar formation is related to
intermolecular addition of the unsubstituted C3 atom
(which possesses the largest negative charge in imid-
azobenzimidazoles) to the aldehyde carbonyl group.
1
It is known that in the H NMR spectra of many
Another approach to 2-formylimidazobenzimid-
azoles has been proposed, and study of their reactivity
has been started, which seems important in view of
various pharmacological activities of imidazo[1,2-a]-
benzimidazole derivatives [2–5]. We used preparatively
accessible ethyl 2-(dibromomethyl)-9-methyl-9H-
imidazo[1,2-a]benzimidazole-3-carboxylate (1) as
starting material. The synthesis of analogous methyl
ester by the bromination of methyl 2,9-dimethylimid-
azo[1,2-a]benzimidazole with N-bromosuccinimide
was reported in [6]. Although the hydrolysis of geminal
dibromides to aldehydes is usually carried out in the
presence of silver nitrate or weakly alkaline reagents,
2,9-disubstituted imidazobenzimidazoles (CDCl3), the
3-H signal appears at a higher field (δ ~7 ppm) than the
signals from the other aromatic protons (5-H–8-H) [7].
In contrast, the 3-H proton of 3 appears as the most
downfield signal (δ 8.04 ppm) due to electron-with-
drawing effect and magnetic anisotropy of the neigh-
boring carbonyl group.
The condensation of 2-formylimidazobenzimid-
azoles 2 and 3 with acetophenones in ethanol in the
presence of sodium hydroxide gave chalcone analogs 4
and 5 which were assigned exclusively E configuration
1
on the basis of the H NMR data. Like most 9-sub-
1160

SYNTHESIS AND TRANSFORMATIONS OF 9-SUBSTITUTED IMIDAZO[1,2-a]...
1161
Scheme 1.
O
O
EtO
EtO
CHBr2
CHO
CHO
3
2
5
8
4N
N
N
N
N
H+, Δ
EtOH, Δ
6
7
N1
N
N
9
N
Me
Me
Me
1
2
3
ArC(O)Me
N2H4·H2O
N2H4·H2O
ArC(O)Me
O
Ar
O
EtO
R
N
O
Ar
N
H
N2H4·H2O
N
N
N
N
NH
N
N
N
N
N
Me
N
Me
4a–4c, 5a, 5b
Me
7
6
4, R = COOEt; 5, R = H; 4, 5, Ar = 4-O2NC6H4 (a), 1,1′-biphenyl-4-yl (b), naphthalen-1-yl (c); 6, Ar = 1,1′-biphenyl-4-yl.
stituted imidazobenzimidazoles having no substituent
on C3, compounds 5 formed electrostatically stabilized
complexes with DMSO [7]. Therefore, the 3-H signal
of, e.g., 5a shifted downfield by ~0.6 ppm in going
from CDCl3 to polar DMSO and was observed at
δ 8.29 ppm. Unlike many α,β-unsaturated ketones
which exhibit luminescence properties, imidazobenz-
imidazole 4 and 5 showed no luminescence. Chalcone
4b reacted with hydrazine hydrate in boiling ethanol to
give dihydropyrazole 6. The reaction of 2 or 1 with
hydrazine hydrate led to the formation of previously
unknown fused oxopyridazine derivative 7; compounds
structurally related to the latter were found to exhibit
cytotoxic and [8] and antimicrobial [9] activities.
Scheme 2.
S
O
O
NH
HN
EtO
EtO
CN
(1) NH2OH·HCl
(2) Ac2O
MeC(O)CH2C(O)Me
(H2N)2C=S
Me
Me
N
N
N
N
2
N
N
O
Me
Me
CH2(CN)2
8
11
C6H4-NO2-4
N
O
O
EtO
EtO
MeC(O)C6H4NO2-4
NH4OAc
CN
CN
NH2
CN
N
N
N
N
N
N
Me
Me
9
10
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 7 2020

KUZʼMENKO et al.
1162
Aldehyde 2 was converted to the corresponding
were visualized by treatment with iodine vapor in
a moist chamber.
oxime by treatment with hydroxylamine hydrochloride,
and subsequent dehydration by the action of acetic
anhydride on heating for a short time afforded 75% of
nitrile 8 (Scheme 2). According to the data of [10],
2-(imidazo[1,2-a]pyridin-2-ylmethylidene)malono-
nitrile is a good scaffold for the synthesis of various
2-hetaryl-substituted derivatives. Analogous nitrile 9
was obtained by us from aldehyde 2 and malononitrile
in nearly quantitative yield. However, fusion of 9 with
4-nitroacetophenone and ammonium acetate, which
was expected (by analogy with [10]) to furnish 2-pyr-
idinylimidazobenzimidazole 10, led to the formation of
a complex mixture of products which we failed to
separate and identify.
All reagents used were commercially available.
Ethyl 2-(dibromomethyl)-9-methyl-9H-imidazo-
[1,2-a]benzimidazole-3-carboxylate (1) was synthe-
sized according to the procedure reported in [6] for
analogous methyl ester. Yield 78%, colorless crystals,
mp 215–216°C. 1H NMR spectrum, δ, ppm: 1.50 t (3H,
CH2CH3, J = 7.0 Hz), 3.86 s (3H, CH3), 4.51 q (2H,
OCH2, J = 7.1 Hz), 7.22–7.41 m (3H, 6-H, 7-H, 8-H),
7.59 s (1H, CH), 8.12 d (1H, 5-H, J = 8.4 Hz).
Found, %: C 40.74; H 2.95; Br 38.24; N 10.30.
C14H13Br2N3O2. Calculated, %: C 40.51; H 3.16;
Br 38.50; N 10.12.
Ethyl 2-formyl-9-methyl-9H-imidazo[1,2-a]-
benzimidazole-3-carboxylate (2). A suspension of
4.15 g (0.01 mol) of compound 1 in 50 mL of ethanol
was refluxed for 1.5 h until complete dissolution and
for 0.5 h more (TLC (Rf 0.9 and 0.7 for 1 and 2,
respectively). The mixture was evaporated to 1/3 of the
initial volume and neutralized with 20% aqueous
sodium hydrogen carbonate, and the precipitate was
filtered off and washed with water. Yield 2.25 g (83%),
colorless crystals, mp 211–212°C (from EtOAc).
IR spectrum, ν, cm–1: 1695 s (C=O), 1681 s (C=O).
1H NMR spectrum, δ, ppm: 1.46 t (3H, CH2CH3, J =
7.1 Hz), 3.81 s (3H, CH3), 4.51 q (2H, OCH2, J =
7.1 Hz), 7.26 t (1H, 6-H or 7-H, J = 7.4 Hz), 7.29 d
(1H, 8-H, J = 8.0 Hz), 7.42 t (1H, 7-H or 6-H, J =
7.4 Hz), 8.52 d (1H, 5-H, J = 8.3 Hz), 10.51 s
(1H, CHO). Found, %: C 62.15; H 5.03; N 15.72.
C14H13N3O3. Calculated, %: C 61.99; H 4.83; N 15.49.
Taking into account a broad spectrum of pharmaco-
logical activity of 3,4-dihydropyrimidine-2-thione
derivatives, including anticancer activity [11, 12], we
synthesized pyrimidine derivative 11 by the three-
component Biginelly reaction of aldehyde 2 with
thiourea and acetylacetone (Scheme 2).
Thus, we have proposed a fairly convenient
procedure for the synthesis of previously unknown
ethyl 2-formyl-9-alkylimidazo[1,2-a]benzimidazole-3-
carboxylates. Acid hydrolysis of such esters provides
a more efficient synthetic route to 3-unsubstituted
imidazobenzimidazole-2-carbaldehydes than that de-
scribed in [1]. Nevertheless, these compounds still
remain difficult to obtain. 2-Formylimidazo[1,2-a]-
benzimidazoles have been shown to be promising for
the synthesis of new imidazo[1,2-a]benzimidazole
derivatives.
9-Methyl-9H-imidazo[1,2-a]benzimidazole-2-
carbaldehyde (3). A solution of 1.35 g (5 mmol) of
aldehyde 2 in 15 mL of concentrated aqueous HCl was
refluxed for 3.5 h. After completion of the reaction
(TLC), the mixture was neutralized with a 20% solu-
tion of sodium hydrogen carbonate, and the dark brown
mixture was extracted with chloroform (3×15 mL).
The extract was evaporated, and the residue was
subjected to column chromatography on alumina using
chloroform as eluent; a fraction with Rf 0.6 was col-
lected. Yield 0.42 g (42%), off-white crystals, mp 138–
EXPERIMENTAL
The 1H NMR spectra of compounds 1, 3, 5b, 6, and
9 were recorded on a Varian Unity-300 spectrometer at
300 MHz, and of the other compounds, on a Bruker
Avance 600 spectrometer at 600 MHz; samples were
dissolved in DMSO-d6 (6, 7, 4c, 11) or CDCl3 (all
other compounds); the chemical shifts were measured
relative to the residual proton signal of the solvent. The
IR spectra were recorded in mineral oil on a Varian
Excalibur 3100 FT-IR spectrometer. The melting points
were determined with a Fisher–Johns melting point
apparatus. Elemental analysis was performed by
classical micro analysis methods [13]. The progress of
reactions and the purity of the isolated compounds
were monitored by TLC on alumina plates (Brockmann
activity grade III) using chloroform as eluent; spots
1
139°C (from isooctane–toluene, 9:1). H NMR spec-
trum, δ, ppm: 3.83 s (3H, CH3), 7.23–7.43 m (2H, 6-H,
7-H), 7.44 d (1H, 8-H, J = 8.0 Hz), 7.64 d (1H, 5-H,
J = 8.1 Hz), 8.04 s (1H, 3-H), 9.93 s (1H, CHO).
Found, %: C 66.12; H 4.28; N 21.30. C11H9N3O. Cal-
culated, %: C 66.32; H 4.55; N 21.09.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 7 2020

SYNTHESIS AND TRANSFORMATIONS OF 9-SUBSTITUTED IMIDAZO[1,2-a]...
1163
Chalcones 4 and 5 (general procedure). A solution
of 2 mmol of aldehyde 2 or 3 and 2 mmol of the
corresponding ketone in 5 mL of ethanol containing
a catalytic amount of 40% aqueous sodium hydroxide
was refluxed for 5–7 min. After cooling, the precipitate
was filtered off and washed with ethanol and diethyl
ether.
(3H, CH3), 7.22 t (1H, 6-H or 7-H, J = 7.8 Hz), 7.29 d
(1H, 8-H, J = 8.0 Hz), 7.36 t (1H, 7-H or 6-H, J =
7.9 Hz), 7.54 d (1H, 5-H, J = 8.0 Hz), 7.66 s (1H, 3-H),
7.76 d and 7.85 d (1H each, CH=CH, J = 14.9 Hz),
8.22 d and 8.32 d (2H each, C6H4NO2, J = 8.5 Hz); in
DMSO-d6: 3.74 s (3H, CH3), 7.22 t (1H, 6-H or 7-H,
J = 7.8 Hz), 7.36 t (1H, 7-H or 6-H, J = 7.8 Hz), 7.54 d
(1H, 8-H, J = 8.1 Hz), 7.65 d and 7.78 d (1H each,
CH=CH, J = 14.9 Hz), 7.81 d (1H, 5-H, J = 7.9 Hz),
8.23 d (2H, C6H4NO2, J = 8.7 Hz), 8.29 s (1H, 3-H),
8.36 d (2H, C6H4NO2, J = 8.7 Hz). Found, %: C 66.12;
H 4.27; N 16.40. C19H14N4O3. Calculated, %: C 65.89;
H 4.07; N 16.18.
Ethyl 9-methyl-2-[(E)-3-(4-nitrophenyl)-3-oxo-
prop-1-en-1-yl]-9H-imidazo[1,2-a]benzimidazole-3-
carboxylate (4a). Yield 0.69 g (83%), orange crystals,
1
mp 226–227°C (from DMF). H NMR spectrum, δ,
ppm: 1.48 t (3H, CH2CH3, J = 7.1 Hz), 3.84 s (3H,
CH3), 4.49 q (2H, OCH2, J = 7.1 Hz), 7.26 t (1H, 6-H
or 7-H, J = 8.1 Hz), 7.30 d (1H, 8-H, J = 7.9 Hz), 7.39 t
(1H, 7-H or 6-H, J = 7.9 Hz), 7.93 d (1H, CH=, J =
15.2 Hz), 8.19 d and 8.31 d (2H each, C6H4NO2, J =
8.9 Hz), 8.51 d (1H, CH=, J = 15.2 Hz), 8.54 d (1H,
5-H, J = 7.9 Hz). Found, %: C 63.37; H 4.12; N 13.52.
C22H18N4O5. Calculated, %: C 63.15; H 4.34; N 13.39.
(E)-1-(1,1′-Biphenyl-4-yl)-3-(9-methyl-9H-imid-
azo[1,2-a]benzimidazol-2-yl)prop-2-en-1-one (5b).
Yield 0.51 g (69%), bright yellow crystals, mp 223–
1
224°C (from BuOH). H NMR spectrum, δ, ppm:
3.84 s (3H, CH3), 7.21–7.69 m (10H, 3-H, 5-H, 6-H,
7-H, 8-H, C6H5), 7.73 d (2H, 2′-H, 6′-H, J = 8.4 Hz),
7.86 d and 7.90 d (1H each, CH=CH, J = 15.0 Hz),
8.22 d (2H, 3′-H, 5′-H, J = 8.4 Hz). Found, %: C 79.73;
H 4.80; N 11.42. C25H19N3O. Calculated, %: C 79.55;
H 5.07; N 11.13.
Ethyl 2-[(E)-3-(1,1′-biphenyl-4-yl)-3-oxoprop-1-
en-1-yl]-9-methyl-9H-imidazo[1,2-a]benzimidazole-
3-carboxylate (4b). Yield 0.65 g (72%), pale yellow
1
crystals, mp 239–241°C (from DMF). H NMR spec-
trum, δ, ppm: 1.50 t (3H, CH2CH3, J = 7.1 Hz), 3.84 s
(3H, CH3), 4.49 q (2H, OCH2, J = 7.1 Hz), 7.25–
7.47 m (6H, 6-H or 7-H, C6H5), 7.63–7.65 m (2H, 7-H
or 6-H, 8-H), 7.71 d (2H, 2′-H, 6′-H, J = 8.4 Hz), 8.04 d
(1H, CH=, J = 15.2 Hz), 8.16 d (2H, 3′-H, 5′-H, J =
8.4 Hz), 8.50 d (1H, CH=, J = 15.2 Hz), 8.55 d (1H,
5-H, J = 8.0 Hz). Found, %: C 74.98; H 5.03; N 9.57.
C28H23N3O3. Calculated, %: C 74.82; H 5.16; N 9.35.
Ethyl 2-{3-[(1,1′-biphenyl)-4-yl]-4,5-dihydro-1H-
pyrazol-5-yl}-9-methyl-9H-imidazo[1,2-a]benzimid-
azole-3-carboxylate (6). A solution of 0.45 g (1 mmol)
of 4b and 0.2 mL of hydrazine hydrate in 10 mL of
ethanol was refluxed for 45 min. After cooling, the
colorless solid was filtered off and washed with
acetone. Yield 0.32 g (69%), mp 187–189°C (from
1
i-PrOH). H NMR spectrum, δ, ppm: 1.52 t (3H,
CH2CH3, J = 7.0 Hz), 3.51–3.55 m and 3.68–3.74 m
(1H each, 4′-H), 3.81 s (3H, CH3), 4.52 q (2H, OCH2,
J = 7.0 Hz), 5.59–5.66 m (1H, 5′-H), 6.58 br.s (1H,
NH), 7.26–7.82 (12H, Harom), 8.50 d (1H, 5-H, J =
8.1 Hz). Found, %: C 72.68; H 5.27; N 14.88.
C28H25N5O2. Calculated, %: C 72.55; H 5.44; N 15.11.
Ethyl 9-methyl-2-[(E)-3-(naphthalen-1-yl)-3-oxo-
prop-1-en-1-yl]-9H-imidazo[1,2-a]benzimidazole-3-
carboxylate (4c). Yield 0.60 g (70%), yellow crystals,
1
mp 196–197°C (from BuOH). H NMR spectrum, δ,
ppm: 1.41 t (3H, CH2CH3, J = 7.1 Hz), 3.78 s (3H,
CH3), 4.28 q (2H, OCH2, J = 7.1 Hz), 7.28 t (1H, 6-H
or 7-H, J = 7.4 Hz], 7.42 t.d (1H, 7-H or 6-H, J = 7.4,
1.2 Hz), 7.57 d (1H, CH=, J = 15.5 Hz), 7.59–7.66 m
(4H, 3′-H, 5′-H, 6′-H, 7′-H), 7.84 d.d (1H, 8-H, J = 7.0,
1.2 Hz), 8.02–8.04 m (1H, 4′-H), 8.09 d (1H, CH=, J =
15.5 Hz), 8.13 d (8′-H, J = 8.3 Hz), 8.20–8.22 m (1H,
2′-H), 8.34 d (1H, 5-H, J = 8.1 Hz). Found, %: C 73.52;
H 5.23; N 10.18. C26H21N3O3. Calculated, %: C 73.74;
H 5.00; N 9.92
6-Methyl-2H-pyridazino[4′,5′:4,5]imidazo-
[1,2-a]benzimidazol-1(6H)-one (7). A solution of
0.42 g (1 mmol) of 1 in 5 mL of hydrazine hydrate was
refluxed for 0.5 h. After cooling, the precipitate was
filtered off and washed with water. Yield 0.21 g (88%),
1
colorless crystals, mp > 300°C (from DMF). H NMR
spectrum, δ, ppm: 3.85 s (3H, CH3), 7.37 t and 7.40 t
(1H, 8-H, 9-H, J = 7.1 Hz), 7.70 d (1H, 7-H, J =
8.1 Hz), 8.25 d (1H, 10-H, J = 8.0 Hz), 8.40 s
(1H, 4-H), 12.90 s (1H, NH). Found, %: C 60.12.15;
H 3.95; N 29.17. C12H9N5O. Calculated, %: C 60.25;
H 3.79; N 29.27.
(E)-3-(9-Methyl-9H-imidazo[1,2-a]benzimidazol-
2-yl)-1-(4-nitrophenyl)prop-2-en-1-one (5a). Yield
0.52 g (75%), orange crystals, mp 237–238°C (from
1
BuOH). H NMR spectrum, δ, ppm: in CDCl3: 3.81 s
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 7 2020

KUZʼMENKO et al.
1164
Ethyl 2-cyano-9-methyl-9H-imidazo[1,2-a]benz-
J = 7.8 Hz) and 7.38 t (1H, J = 7.9 Hz) (6-H, 7-H),
7.57 d (1H, 8-H, J = 8.2 Hz), 8.33 d (1H, 5-H, J =
8.3 Hz), 9.39 s (1H, NH), 10.16 s (1H, NH). Found, %:
C 58.59; H 5.27; N 16.85; S 7.51. C20H21N5O3S.
Calculated, %: C 58.38; H 5.14; N 17.02; S 7.79.
imidazole-3-carboxylate (8). A solution of 0.27 g
(1 mmol) of aldehyde 2 and 0.14 g (2 mmol) of
hydroxylamine hydrochloride in 3 mL of glacial acetic
acid containing 0.17 g (2 mmol) of anhydrous sodium
acetate was refluxed for 30 min. The mixture was
cooled and diluted with 15 mL of water, and the
precipitate (oxime) was filtered off, washed with water,
and dried. Yield 0.24 g (84%). The product was
dissolved in 2 mL of acetic anhydride, and the solution
was refluxed for 30 min. The mixture was treated with
7 mL of water to decompose excess acetic anhydride,
and the precipitate was filtered off and washed with
water. Yield 0.2 g (75%, based on the initial alde-
hyde 2), colorless crystals, mp 177–178°C (from
EtOAc). IR spectrum, ν, cm–1: 2237 s (C≡N), 1712 s
ACKNOWLEDGMENTS
This study was performed using the equipment of the
joint center of Southern Federal University.
FUNDING
This study was performed under financial support by the
Ministry of Science and HIgher Education of the Russian
Federation in the framework of state assignment no. BAZ
0110.20-3-11IKh (YuFU).
1
(C=O). H NMR spectrum, δ, ppm: 1.46 t (3H,
CH2CH3, J = 7.1 Hz), 3.79 s (3H, CH3), 4.46 q (2H,
OCH2, J = 7.1 Hz), 7.27 t (1H, 6-H or 7-H, J = 7.4 Hz),
7.32 d (1H, 8-H, J = 8.1 Hz), 7.42 t (1H, 7-H or 6-H,
J = 7.4 Hz), 8.47 d (1H, 5-H, J = 8.3 Hz). Found, %:
C 62.51; H 4.67; N 20.75. C14H12N4O2. Calculated, %:
C 62.68; H 4.51; N 20.88.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
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1
1.50 g (94%), mp 264–265°C (from BuOH). H NMR
spectrum, δ, ppm: 1.55 t (3H, CH2CH3, J 7.2 Hz),
3.88 s (3H, CH3), 4.57 q (2H, OCH2, J = 7.2 Hz), 7.31 t
(1H, 6-H or 7-H, J = 7.4 Hz), 7.38 d (1H, 8-H, J =
8.2 Hz), 7.48 t (1H, 6-H or 7-H, J = 7.5 Hz), 8.46 s
(1H, CH=), 8.54 d (1H, 5-H, J = 8.1 Hz). Found, %:
C 63.72; H 4.27; N 22.18. C17H13N5O2. Calculated, %:
C 63.94; H 4.10; N 21.93.
https://doi.org/10.1016/ j.bmcl.2005.06.02
3. Spasov, A.A., Vassiliev, P.M., Lenskaya, K.V., Kosola-
pov, V.A., Babkov, D.A., Anisimova, V.A., Kuzmen-
ko, T.A., and Morkovnik, A.S., Pure Appl. Chem., 2017,
vol. 89, p. 1007.
https://doi.org/10.1515/pac-2016-1024
4. Spasov, A.A., Grechko, O.Yu., Shtareva, D.M.,
Rashchenko, A.I., Eliseeva, N.V., and Anisimova, V.A.,
J. Clin. Health Sci., 2018, vol. 3, p. 13.
Ethyl 2-(5-acetyl-6-methyl-2-sulfanylidene-
1,2,3,4-tetrahydropyrimidin-4-yl)-9-methyl-9H-
imidazo[1,2-a]benzimidazole-3-carboxylate (11).
A suspension of 0.54 g (2 mmol) of aldehyde 2, 0.23 g
(3 mmol) of thiourea, and 0.2 mL (2 mmol) of
acetylacetone in 10 mL of ethanol was heated to the
boiling point, and the resulting solution was heated at
50°C for 8 h. The precipitate was filtered off and
washed with ethanol. Yield 0.49 g (60%), colorless
https://doi.org/10.24191/ jchs.v3i2.7275
5. Spasov, A.A., Yakovlev, D.S., Maltsev, D.V.,
Zhukovskaya, O.N., Anisimova, V.A., Kovalev, G.I.,
Zimin, I.A., and Morkovina, Y.V., Russ. J. Bioorg. Chem.,
2016, vol. 42, p. 397.
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6. Anisimova, V.A. and Lukova, O.A., Chem. Heterocycl.
Compd., 1994, vol. 30, p. 325.
https://doi.org/10.1007/BF01165699
1
crystals, mp 284–285°C (from DMF). H NMR spec-
7. Kuzʼmenko, T.A., Divaeva, L.N., Morkovnik, A.S.,
Anisimova, V.A., Borodkin, G.S., and Kuzʼmenko, V.V.,
Russ. J. Org. Chem., 2014, vol. 50, p. 716.
trum, δ, ppm: 1.41 t (3H, CH2CH3, J = 7.1 Hz), 2.09 s
(3H, 6′-CH3), 2.31 s (3H, COCH3), 3.71 s (3H, 9-CH3),
4.38–4.45 m (2H, OCH2), 6.18 s (1H, 4′-H), 7.25 t (1H,
https://doi.org/10.1134/S1070428014050169
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 7 2020

SYNTHESIS AND TRANSFORMATIONS OF 9-SUBSTITUTED IMIDAZO[1,2-a]...
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8. Murineddu, G., Cignarella, G., Chelucci, G., Loriga, G.,
and Pinna, G.A., Chem. Pharm. Bull., 2002, vol. 50,
p. 754.
11. Kulakov, I.V., Talipov, S.A., Shulgau, Z.T., and
Seilkhanov, T.M., Chem. Heterocycl. Compd., 2015,
vol. 50, p. 1478.
https://doi.org/10.1248/cpb.50.754
https://doi.org/10.1007/s10593-014-1613-1
9. Avan, I., Guven, A., and Guven, K., Turk. J. Chem.,
2013, vol. 37, p. 271.
12. Cheng, Q., Wang, Q., Tan, T., Chen, N., and Shuai, M.,
J. Heterocycl. Chem., 2012, vol. 49, p. 1352.
https://doi.org/10.1002/jhet.978
https://doi.org/10.3906/kim-1210-22
10. Haouchine, A.-L., Kabri, Y., Bakhta, S., Curti, Ch.,
Nedjar-Kolli, B., and Vanelle, P., Synth. Commun., 2018,
vol. 48, p. 2159.
13. Gel’man, N.E., Terent’eva, E.A., Shanina, T.M., and
Kiparenko, L.M., Metody kolichestvennogo organi-
cheskogo elementnogo analiza (Methods of Quantitative
Organic Elemental Analysis), Moscow: Khimiya, 1987.
https://doi.org/10.1080/00397911.2018.1479759
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 7 2020