Synthesis of 1,5,6,7-tetrahydro-4H-benzimidazol-4-one derivatives from 2,6-bis(hydroxyimino)cyclohexan-1-one

Article abstract of DOI:10.1134/S1070428017010122

The reaction of 2,6-bis(hydroxyimino)cyclohexan-1-one with aldehydes and ammonia afforded 2-substituted 4-hydroxyimino-4,5,6,7-tetrahydro-1H-benzimidazol-1-ols which were hydrolyzed to 1-hydroxy- 2-R-1,5,6,7-tetrahydro-4H-benzimidazol-4-ones. The N-hydroxy group in the latter can readily by removed by the action of chloroacetone in the presence of a base (potassium carbonate or triethylamine); as a result, 2-substituted 1,5,6,7-tetrahydro-4H-benzimidazol-4-ones were obtained.

Full text of DOI:10.1134/S1070428017010122

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2017, Vol. 53, No. 1, pp. 66–73. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © V.A. Samsonov, 2017, published in Zhurnal Organicheskoi Khimii, 2017, Vol. 53, No. 1, pp. 71–77.
Synthesis of 1,5,6,7-Tetrahydro-4H-benzimidazol-4-one
Derivatives from 2,6-Bis(hydroxyimino)cyclohexan-1-one
V. A. Samsonov
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 9, Novosibirsk, 630090 Russia
e-mail: samson@nioch.nsc.ru
Received June 22, 2016
Abstract—The reaction of 2,6-bis(hydroxyimino)cyclohexan-1-one with aldehydes and ammonia afforded
2-substituted 4-hydroxyimino-4,5,6,7-tetrahydro-1H-benzimidazol-1-ols which were hydrolyzed to 1-hydroxy-
2-R-1,5,6,7-tetrahydro-4H-benzimidazol-4-ones. The N-hydroxy group in the latter can readily by removed by
the action of chloroacetone in the presence of a base (potassium carbonate or triethylamine); as a result,
2-substituted 1,5,6,7-tetrahydro-4H-benzimidazol-4-ones were obtained.
DOI: 10.1134/S1070428017010122
Imidazole and benzimidazole derivatives are com-
ponents of natural substances, and they play an im-
portant role in biochemical processes occurring in
living organisms [1–6]. A number of natural and syn-
thetic derivatives of imidazole and benzimidazole are
used in medical practice for the treatment of various
diseases [7].
Transcription factor modulators [8–11] and urease
inhibitors [12] have been found among substituted
1,5,6,7-tetrahydro-4H-benzimidazol-4-ones. These
compounds were synthesized from 2-acylcyclohexane-
1,3-dione O-alkyloximes [13], from nitroso en-
aminones via condensation with benzylamine [14],
from halo ketones and amidines [15], from 2-amino-
dimedone hydrochloride and phenyl isothiocyanate
[16], from 2-nitrodimedone [17], from isonitroso
ketones, amines, and 4-oxo-4H-chromene-3-carbalde-
hyde [18], and from isonitroso ketones, aromatic
amines, and formaldehyde [19, 20].
from 1,2-dicarbonyl compounds with aldehydes in the
presence of amines. If ammonia is used as amine
component, 1-hydroxyimidazoles are formed. Removal
of the hydroxy group yields 1H-imidazoles [21].
Herein I report a simple procedure for the synthesis of
functionalized 1,5,6,7-tetrahydro-4H-benzimidazol-4-
one derivatives from an accessible ketone, cyclo-
hexanone, which is produced in Russia in an amount
of ~500000 tons annually.
The nitrosation of cyclohexanone gave 2,6-bis(hy-
droxyimino)cyclohexan-1-one (1) in a high yield [22].
Bis-oxime 1 reacted with aldehydes in the presence of
ammonia to produce 2-substituted 4-hydroxyimino-
4,5,6,7-tetrahydro-1H-benzimidazol-1-ols 2a–2i. Com-
pounds 2a–2c, 2e, and 2f were synthesized by reacting
the corresponding aldehydes with ketone 1 in ethanol
while passing gaseous ammonia through the reaction
mixture. Compounds 2d and 2h were obtained by
reaction of aldehydes with ketone 1 and ammonium
acetate in ethanol. The hydroxyimino group in 2a–2f
was readily hydrolyzed on heating in concentrated
The most widely known general synthesis of imid-
azoles is based on the reaction of monooximes derived
Scheme 1.
NOH
NOH
O
O
MeC(O)CH2Cl
NEt3
O
RCHO, NH3
N
N
HCl
N
N
N
R
R
R
N
H
NOH
OH
2a–2i
OH
3a–3i
1
4a–4i
R = Ph (a), 4-MeOC6H4 (b), 2-HOC6H4 (c), 3-O2NC6H4 (d), 4-ethylpyridin-2-yl (e), furan-2-yl (f), Me (g), H (h), i-Pr (i).
66

SYNTHESIS OF 1,5,6,7-TETRAHYDRO-4H-BENZIMIDAZOL-4-ONE DERIVATIVES
67
Scheme 2.
O
N
MeC(O)CH2Cl
R
O
NEt3
O
3a–3i
4a–4i +
N
Me
CHO
O
H+
Me
H
H
B–
A
aqueous HCl to afford ketones 3a–3f. The hydroxy-
imino group was removed from 2g–2i by treatment
with sodium nitrite in acid medium [23].
δ 2.50 ppm, DMSO-d6, δC 39.50 ppm); when H2SO4
was used as solvent, CH2Cl2 was added as internal
standard (δ 5.33, δC 54.0 ppm). Multiplicities of
signals in the 13C NMR spectra were determined using
J modulation (JMOD) technique. The mass spectra
(electron impact, 70 eV) were obtained on a Thermo
Scientific DFS mass spectrometer with direct sample
admission into the ion source (ion source temperature
180°C); given below are ion peaks with an intensity
higher than 10%. The progress of reactions and the
purity of the isolated compounds were monitored by
TLC on Sorbfil UV-254 plates; spots were visualized
under UV light or by treatment with iodine vapor. The
melting points were determined on a Kofler micro hot
stage. The elemental analyses were obtained at the
Microanalysis Laboratory, Novosibirsk Institute of
Organic Chemistry, Siberian Branch, Russian
Academy of Sciences.
N-Hydroxyimidazoles can be converted into
1H-imidazoles by the action of reducing agents [16,
18, 21, 24]. Treatment of 3a–3i with chloroacetone in
the presence of a base (triethylamine or potassium
carbonate) readily afforded ketones 4a–4i (Scheme 1).
Removal of the N-hydroxy group from N-hydroxy-
indoles was accomplished in a similar way [25–27].
It was presumed that initial alkylation of the N-hy-
droxy group with chloroacetone gives intermediate A.
Proton abstraction from the CH2 group by base B
promotes electron density transfer to the oxygen atom
with simultaneous proton addition to the imidazole
nitrogen atom. As a result, ketone 4a–4i and methyl-
glyoxal are obtained (Scheme 2).
Oximes and ketones derived from tetrahydrobenz-
imidazole may be interesting as starting compounds
for the synthesis of benzimidazole derivatives.
Delyatitskaya and Strakov [28] reviewed numerous
examples of modification of the carbocyclic moiety of
ketones based on cyclohexene-fused heterocycles.
4-Hydroxyimino-2-phenyl-4,5,6,7-tetrahydro-
1H-benzimidazol-1-ol (2a). Gaseous ammonia was
passed at a moderate rate through a mixture of 78 g
(0.5 mol) of 2,6-bis(hydroxyimino)cyclohexan-1-one
(1) and 56 g (0.53 mol) of benzaldehyde in 500 mL of
methanol under stirring and cooling with cold water.
The mixture initially thickened, the precipitate dis-
solved, and a solid separated on further passing am-
monia. The mixture was stirred for 3 h and left over-
night at room temperature. The precipitate was filtered
off, washed with methanol on a filter, and dried. Yield
112 g (91%), white powder, mp 276–278°C (from
EtOH). UV spectrum, λmax, nm (logε): 253 (3.53), 312
EXPERIMENTAL
The analytical and spectral studies were performed
at the Joint Chemical Service Center, Siberian Branch,
Russian Academy of Sciences. The IR spectra were
recorded from samples pressed with KBr (concentra-
tion 0.25%) on a Bruker Vector spectrometer. The UV
spectra were measured in ethanol on a Specord M-40
1
(3.64). H NMR spectrum (DMSO-d6), δ, ppm: 1.80–
1
13
1.94 m (2H, CH2), 2.56–2.73 m (4H, CH2), 7.32–
7.52 m (3H, Harom), 7.97–8.12 m (2H, Harom), 10.48 br.s
(1H, OH), 11.91 br.s (1H, OH). 13C NMR spectrum
(H2SO4), δC, ppm: 16.77, 17.46, 22.54 (CH2); 126.95,
128.40, 134.00 (CHarom); 110.77, 116.10, 145.13,
145.56, 155.76. Mass spectrum, m/z (Irel, %): 243 (100)
[M]+, 227 (58), 209 (31), 208 (33), 196 (72), 182
(15), 105 (85). Found, %: C 64.20; H 5.40; N 17.27.
spectrophotometer. The H and C NMR spectra were
recorded at 25°C from 10% solutions in CDCl3,
DMSO-d6, or H2SO4 (chemically pure grade, GOST
4204-77) on a Bruker AV 400 spectrometer
1
(400.13 MHz for H and 100.61 MHz for 13C); the
chemical shifts were measured relative to the residual
proton and carbon signals of the deuterated solvent
(CHCl3, δ 7.24 ppm; CDCl3, δC 76.90 ppm; DMSO-d5,
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SAMSONOV
68
[M]+ 243.1000. C13H13N3O2. Calculated, %: C 64.18;
H 5.39; N 17.28. M 243.1002.
Found, %: C 54.23; H 4.18; N 19.44. [M]+ 288.0852.
C13H12N4O4. Calculated, %: C 54.16; H 4.20; N 19.44.
M 288.0853.
Compounds 2b–2g and 2i were synthesized
in a similar way.
2-(4-Ethylpyridin-2-yl)-4-hydroxyimino-4,5,6,7-
tetrahydro-1H-benzimidazol-1-ol (2e). Yield 86%,
yellow powder, mp 149‒152°C (from EtOH). UV
spectrum, λmax, nm (logε): 248 (3.45), 331 (3.87).
1H NMR spectrum (DMSO-d6), δ, ppm: 1.20 t (3H,
CH3, J = 6.12 Hz), 1.63‒1.75 m (2H, CH2), 2.30‒
2.40 m (2H, CH2), 2.48‒2.54 m (2H, CH2), 2.56‒
2.68 m (2H, CH2), 6.17 br.s (1H, OH), 7.58 d.d (1H,
Py, J = 8.0, 1.8 Hz), 8.17 d (1H, Py, J = 8.0 Hz), 8.40 d
4-Hydroxyimino-2-(4-methoxyphenyl)-4,5,6,7-
tetrahydro-1H-benzimidazol-1-ol (2b). Yield 87%,
white powder, mp 267–269°C (from EtOH). IR spec-
trum: ν 1608 cm–1 (C=N). UV spectrum, λmax, nm
(logε): 241 (3.54), 317 (3.68). H NMR spectrum
(H2SO4), δ, ppm: 2.41 m (2H, CH2), 3.20 m (2H, CH2),
1
3.34 m (2H, CH2), 4.14 s (3H, OCH3), 7.36 d (2H,
Harom, J = 8.9 Hz), 8.17 d (2H, Harom, J = 8.9 Hz),
12.08 br.s (1H, OH), 12.34 br.s (1H, OH). 13C NMR
spectrum (H2SO4), δC, ppm: 17.55, 18.23, 23.29 (CH2);
56.15 (OCH3); 115.15, 130.37 (CH); 111.20, 111.28,
145.23, 146.44, 156.57, 161.44. Mass spectrum, m/z
(Irel, %): 273 (61) [M]+, 257 (100), 241 (66), 226 (90),
211 (72), 196 (16), 185 (16), 159 (17), 135 (76).
Found, %: C 61.48; H 5.35; N 15.43. [M]+ 273.1108.
C14H15N3O3. Calculated, %: C 61.53; H 5.33; N 15.38.
M 273.1104.
13
(1H, Py, J = 1.8 Hz). C NMR spectrum (DMSO-d6),
δC, ppm: 15.18 (CH3); 19.16, 21.51, 22.70, 25.17
(CH2); 121.37, 135.36, 148.64 (CHarom); 126.37,
132.33, 137.25, 139.58, 146.64, 149.32. Mass spec-
trum, m/z (Irel, %): 272 (55) [M]+, 255 (46), 225 (100),
210 (13), 149 (11), 133 (53). Found, %: C 61.80;
H 5.90; N 20.62. [M]+ 272.1274. C14H16N4O2. Cal-
culated, %: C 61.75; H 5.92; N 20.58. M 272.1274.
2-(Furan-2-yl)-4-hydroxyimino-4,5,6,7-tetra-
hydro-1H-benzimidazol-1-ol (2f). Yield 72%, yellow
powder, mp 265‒267°C (from EtOH). UV spectrum,
4-Hydroxyimino-2-(2-hydroxyphenyl)-4,5,6,7-
tetrahydro-1H-benzimidazol-1-ol (2c). Yield 84%,
white powder, mp 259–261°C (from EtOH). UV spec-
1
λmax, nm (logε): 248 (3.42), 322 (3.68). H NMR spec-
1
trum: λmax 322 nm (logε 3.46). H NMR spectrum
trum (DMSO-d6), δ, ppm: 1.77‒1.94 m (2H, CH2),
2.58‒2.74 m (4H, CH2), 5.48 br.s (1H, OH), 6.67 d.d
(1H, Fu, J = 3.4, 1.8 Hz), 7.09 d (1H, Fu, J = 3.4 Hz),
7.85 d (1H, Fu, J = 1.8 Hz), 10.85 br.s (1H, OH).
13C NMR spectrum (DMSO-d6), δC, ppm: 18.89,
21.02, 22.35 (CH2); 111.12, 111.87, 144.05 (CHarom);
122.47, 131.80, 133.58, 141.70, 147.68. Mass spec-
trum, m/z (Irel, %): 233 (33) [M]+, 217 (21), 199 (12),
186 (34), 162 (15), 149 (15), 121 (25), 95 (30),
91 (100). Found, %: C 56.70; H 4.77; N 17.93.
[M]+ 233.0797. C11H11N3O3. Calculated, %: C 56.65;
H 4.75; N 18.02. M 233.0795.
(DMSO-d6), δ, ppm: 1.84–2.01 m (2H, CH2), 2.62‒
2.78 m (4H, CH2), 6.81‒6.97 m (3H, Harom), 7.28–
7.41 m (1H, Harom), 7.79 br.s (1H, OH), 11.07 br.s (1H,
13
OH), 13.60 br.s (1H, OH). C NMR spectrum (D2O +
NaOH), δC, ppm: 22.03, 24.26, 25.56 (CH2); 115.63,
122.03, 132.85, 134.20 (CH); 122.43, 128.16, 132.35,
144.59, 155.70, 168.25. Mass spectrum, m/z (Irel, %):
259 (100) [M]+, 243 (36), 227 (63), 212 (80), 197
(29), 121 (77). Found, %: C 60.23; H 5.07; N 16.20.
[M]+ 259.0949. C13H13N3O3. Calculated, %: C 60.22;
H 5.05; N 16.21. M 259.0951.
4-Hydroxyimino-2-(3-nitrophenyl)-4,5,6,7-tetra-
hydro-1H-benzimidazol-1-ol (2d). Yield 76%, yellow
powder, mp 258°C (decomp., from EtOH). IR spec-
4-Hydroxyimino-2-methyl-4,5,6,7-tetrahydro-
1H-benzimidazol-1-ol (2g). Yield 64%, mp 168–
171°C (H2O). UV spectrum: λmax 268 nm (logε 3.68).
1H NMR spectrum (DMSO-d6), δ, ppm: 1.72–1.82 m
(2H, CH2), 2.14 s (3H, CH3), 2.43–2.50 m (2H, CH2),
2.50–2.58 m (2H, CH2), 5.48 br.s (1H, OH), 10.64 br.s
(1H, OH). 13C NMR spectrum (DMSO-d6), δC, ppm:
10.56 (CH3); 19.17, 21.69, 22.70 (CH2); 123.50,
130.48, 139.45, 148.08. Mass spectrum, m/z (Irel, %):
181 (100) [M]+, 165 (25), 146 (16), 134 (69), 122 (24).
Found, %: C 53.00; H 6.08; N 23.22. [M]+ 181.0847.
C8H11N3O2. Calculated, %: C 53.03; H 6.12; N 23.19.
M 181.0846.
trum, ν, cm–1: 1348, 1529 (NO2). UV spectrum, λmax
,
1
nm (logε): 253 (3.52), 316 (3.68). H NMR spectrum
(DMSO-d6), δ, ppm: 1.81–1.93 m (2H, CH2), 2.58‒
2.70 m (4H, CH2), 7.73 m (1H, CH), 8.19 d.d (1H, CH,
J = 8.2, 2.4 Hz), 8.45 d (1H, CH, J = 8.2 Hz), 8.86 m
(1H, CH), 10.61 br.s (1H, OH), 12.48 br.s (1H, OH).
13C NMR spectrum (H2SO4), δC, ppm: 17.69, 18.26,
23.52 (CH2); 123.52, 129.00, 131.36, 135.08 (CHarom);
112.59, 119.10, 142.92, 146.13, 146.70, 156.20. Mass
spectrum, m/z (Irel, %): 288 (100) [M]+, 272 (70), 254
(34), 241 (62), 208 (34), 195 (26), 180 (18), 150 (96).
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SYNTHESIS OF 1,5,6,7-TETRAHYDRO-4H-BENZIMIDAZOL-4-ONE DERIVATIVES
69
1
(3.30), 293 (3.30), 316 (3.30). H NMR spectrum
(DMSO-d6), δ, ppm: 2.00‒2.15 m (2H, CH2), 2.38‒
2.48 m (2H, CH2), 2.80‒2.90 m (2H, CH2), 7.40‒
7.55 m (3H, Harom), 7.98‒8.10 m (2H, Harom), 12.3 br.s
(1H, OH). 13C NMR spectrum (DMSO-d6), δC, ppm:
19.96, 23.08, 38.49 (CH2); 127.51, 128.93, 129.52
(CH); 128.83, 129.95, 143.07, 143.59, 190.68 (C=O).
Mass spectrum, m/z (Irel, %): 228 (14) [M]+, 212 (55),
184 (19), 155 (9), 105 (34), 104 (100). Found, %:
C 68.43; H 5.39; N 12.43. [M]+ 228.0892. C13H12N3O2.
Calculated, %: C 68.41; H 5.30; N 12.27. M 228.0893.
4-Hydroxyimino-4,5,6,7-tetrahydro-1H-benz-
imidazol-1-ol (2h). A mixture of 15.6 g (0.1 mol) of
compound 1, 3.1 g (0.103 mol) of paraformaldehyde,
and 8.0 g (0.104 mol) of ammonium acetate in 200 mL
of methanol was heated to the boiling point with
stirring. The heating bath was removed; when the exo-
thermic reaction was over, the mixture was stirred for
1.5 h maintaining it slightly boiling and cooled, and
the precipitate was filtered off, washed with methanol,
and dried. Yield 11.3 g (68%), white powder,
mp 225°C (decomp., from EtOH). UV spectrum:
1
λmax 261 nm (log ε 3.57). H NMR spectrum
Compounds 3b–3f were synthesized in a similar
(DMSO-d6), δ, ppm: 1.76‒1.84 m (2H, CH2), 2.52‒
2.60 m (4H, CH2), 7.68 s (1H, CH), 10.47 br.s (1H,
OH), 12.05 br.s (1H, OH). 13C NMR spectrum
(DMSO-d6), δC, ppm: 18.76, 21.40, 22.40 (CH2);
132.19 (CH); 126.77, 129.88, 148.58. Mass spectrum,
m/z (Irel, %): 167 (100) [M]+, 151 (25), 132 (29), 119
(67), 106 (23). Found, %: C 50.32; H 5.45; N 25.15.
[M]+ 167.0691. C7H9N3O2. Calculated, %: C 50.29;
H 5.43; N 25.14. M 167.0689.
way.
1-Hydroxy-2-(4-methoxyphenyl)-1,5,6,7-tetra-
hydro-4H-benzimidazol-4-one (3b). Yield 74%,
white powder, mp 246–249°C (from EtOH). IR spec-
trum: ν 1666 cm–1 (C=O). UV spectrum, λmax, nm
1
(logε): 267 (3.40), 324 (3.60). H NMR spectrum
(DMSO-d6), δ, ppm: 2.03–2.14 m (2H, CH2), 2.37–
2.46 m (2H, CH2), 2.78–2.86 m (2H, CH2), 3.82 s (3H,
OCH3), 7.05 d (2H, Harom, J = 8.9 Hz), 7.98 d (2H,
H
arom, J = 8.9 Hz), 12.17 br.s (1H, OH). 13C NMR
4-Hydroxyimino-2-(propan-2-yl)-4,5,6,7-tetra-
hydro-1H-benzimidazol-1-ol (2i). Yield 74%, white
powder, mp 240–242°C (from EtOH). UV spectrum:
spectrum (H2SO4), δC, ppm: 18.91, 20.28, 33.06 (CH2);
56.83 (OCH3); 115.95, 132.03 (CH); 110.98, 118.21,
149.27, 157.02, 163.33, 198.20 (C=O). Mass spectrum,
m/z (Irel, %): 258 (8) [M]+, 242 (76), 212 (16), 149
(14), 134 (100). Found, %: C 65.12; H 5.50; N 10.90.
[M]+ 258.1002. C14H14N2O3. Calculated, %: C 65.10;
H 5.46; N 10.85. M 258.0999.
1
λmax 267 nm (log ε 3.70). H NMR spectrum
(DMSO-d6), δ, ppm: 1.18 d (6H, CH3, J = 7.6 Hz),
1.71‒1.82 m (2H, CH2), 2.41–2.58 m (4H, CH2), 3.00‒
3.14 m (1H, CH), 3.42 br.s (1H, OH), 10.39 br.s (1H,
13
OH). C NMR spectrum (DMSO-d6), δC, ppm: 20.36
(CH3), 24.57 (CH); 18.84, 21.34, 22.36 (CH2); 123.89,
130.03, 147.18, 148.20. Mass spectrum, m/z (Irel, %):
209 (25) [M]+, 193 (11), 178 (11), 162 (23), 149
(43), 105 (100). Found, %: C 57.35; H 7.23; N 20.12.
[M]+ 209.1237. C10H15N3O2. Calculated, %: C 57.40;
H 7.23; N 20.08. M 209.1159.
1-Hydroxy-2-(2-hydroxyphenyl)-1,5,6,7-tetra-
hydro-4H-benzimidazol-4-one (3c). Yield 68%, white
powder, mp 248–251°C (from EtOH). IR spectrum:
ν 1685 cm–1 (C=O). UV spectrum, λmax, nm (logε): 321
1
(3.48), 263 (3.67). H NMR spectrum (DMSO-d6), δ,
ppm: 2.07–2.18 m (2H, CH2), 2.45–2.53 m (2H, CH2),
2.81–2.90 m (2H, CH2), 6.91–6.98 m (2H, Harom),
7.32–7.40 m (1H, Harom), 7.49–8.09 m (1H, Harom),
1-Hydroxy-2-phenyl-1,5,6,7-tetrahydro-4H-
benzimidazol-4-one (3a). Compound 2a, 122 g
(0.5 mol), was added to 600 mL of concentrated aque-
ous HCl, and the mixture was heated to 80°C with
stirring. Compound 2 dissolved, and then 3a hydro-
chloride separated. The mixture was stirred for 30 min
at 80°C, left to stand for 4 h at room temperature, and
cooled to 5°C. The precipitate was filtered off, washed
with ~50 mL of concentrated aqueous HCl, dried, and
dissolved in 450 mL of 10% sodium hydroxide. The
solution was carefully acidified to pH 6 with
10% aqueous HCl, and the precipitate was filtered off,
washed with water, and dried. Yield 90 g (79%), white
powder, mp 259‒262°C (from EtOH). IR spectrum:
ν 1670 cm–1 (C=O). UV spectrum, λmax, nm (logε): 269
13
11.18 br.s (1H, OH). C NMR spectrum (DMSO-d6),
δC, ppm: 19.38, 22.63, 37.83 (CH2); 118.12, 119.06,
127.64, 132.13 (CH); 111.99, 126.34, 142.14, 142.67,
158.05, 189.44 (C=O). Mass spectrum, m/z (Irel, %):
244 (97) [M]+, 228 (100), 199 (27), 172 (28), 121 (76).
Found, %: C 63.89; H 5.05; N 11.55. [M]+ 244.0849.
C13H12N2O3. Calculated, %: C 63.92; H 4.95; N 11.47.
M 244.0842.
1-Hydroxy-2-(3-nitrophenyl)-1,5,6,7-tetrahydro-
4H-benzimidazol-4-one (3d). Yield 56%, yellow
powder, mp 265–267°C (from EtOH). IR spectrum, ν,
cm–1: 1670 (C=O), 1350, 1510 (NO2). UV spectrum,
1
λ
max, nm (logε): 268 (3.63), 319 (3.60). H NMR spec-
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SAMSONOV
70
trum (DMSO-d6), δ, ppm: 2.05–2.18 m (2H, CH2),
2.40–2.53 m (2H, CH2), 2.82–2.94 m (2H, CH2),
compound 2g in a mixture of 800 mL of water and
35 mL (0.41 mol) of concentrated aqueous HCl, main-
taining the temperature at 28–30°C by cooling with
water over a period of 1 h. The mixture was stirred for
1 h at room temperature and evaporated to dryness
under reduced pressure (20 mm). The residue was
dissolved on heating in 200 mL of propan-2-ol, the
solution was filtered, the filtrate was treated with char-
coal, evaporated to a volume of ~50 mL, and cooled,
and the precipitate was filtered off. Yield 31.2 g (47%),
white powder, mp 222–225°C (decomp.). IR spectrum:
ν 1672 cm–1 (C=O). UV spectrum: λmax 285 nm
7.81 d.d (1H, Harom, J = 7.9, 7.9 Hz), 8.29 d (1H, Harom
,
J = 8.6 Hz), 8.49 d (1H, Harom, J = 7.9 Hz), 8.87 m
(1H, Harom), 12.61 br.s (1H, OH). 13C NMR spectrum
(DMSO-d6), δC, ppm: 19.65, 22.68, 38.20 (CH2);
121.19, 123.63, 130.48, 132.91 (CHarom); 129.97,
130.20, 140.50, 143.72, 147.97, 190.50 (C=O). Mass
spectrum, m/z (Irel, %): 273 (54) [M]+, 257 (100), 229
(22), 218 (23), 200 (29), 150 (67). Found, %: C 57.20;
H 4.10; N 15.44. [M]+ 273.0742. C13H11N3O4. Calcu-
lated, %: C 57.14; H 4.06; N 15.38. M 273.0744.
1
(logε 3.87). H NMR spectrum (DMSO-d6), δ, ppm:
2-(4-Ethylpyridin-2-yl)-1-hydroxy-1,5,6,7-tetra-
hydro-4H-benzimidazol-4-one (3e). Yield 52%, white
powder, mp 144–146°C (from EtOH). IR spectrum:
ν 1670 cm–1 (C=O). UV spectrum: λmax 318 nm
1.98–2.07 m (2H, CH2), 2.25 s (3H, CH3), 2.31–2.37 m
(2H, CH2), 2.70–2.76 m (2H, CH2), 11.97 br.s (1H,
13
OH). C NMR spectrum (DMSO-d6), δC, ppm: 19.51,
1
(logε 3.76). H NMR spectrum (DMSO-d6), δ, ppm:
22.92, 37.98 (CH2); 11.23 (CH3); 128.52, 141.43,
142.56; 189.81 (C=O). Mass spectrum, m/z (Irel, %):
166 (28) [M]+, 150 (100), 128 (32), 122 (46), 110
(13), 94 (30). Found, %: C 57.86; H 5.96; N 16.80.
[M]+ 166.0737. C8H10N2O2. Calculated, %: C 57.82;
H 6.07; N 16.86. M 166.0740.
1.23 t (3H, CH3, J = 8.3 Hz), 2.11–2.20 m (2H, CH2),
2.50–2.56 m (2H, CH2), 2.61–2.70 m (2H, CH2), 2.84–
2.90 m (2H, CH2), 7.70 d.d (1H, Py, J = 8.4, 2.1 Hz),
8.17 d (1H, Py, J = 8.2 Hz), 8.25 d (1H, Py, J =
2.1 Hz), 14.16 br.s (1H, OH). 13C NMR spectrum
(DMSO-d6), δC, ppm: 14.66 (CH3); 19.50, 22.85,
25.83, 38.17 (CH2); 120.51, 138.12, 144.89 (CHarom);
130.30, 135.21, 138.84, 140.01, 146.66, 191.27 (C=O).
Mass spectrum, m/z (Irel, %): 257 (83) [M]+, 241 (60),
213 (19), 201 (12), 185 (10), 149 (34), 133 (100).
Found, %: C 65.30; H 5.90; N 16.38. [M]+ 257.1156.
C14H15N3O2. Calculated, %: C 65.35; H 5.88; N 16.33.
M 257.1159.
Compounds 3h and 3i were synthesized in a simi-
lar way.
1-Hydroxy-1,5,6,7-tetrahydro-4H-benzimidazol-
4-one (3h). Yield 58%, white powder, mp 185–186°C.
IR spectrum, ν, cm–1: 1656, 1679 (C=O). UV spec-
1
trum: λmax 262 nm (logε 3.80). H NMR spectrum
(H2SO4), δ, ppm: 2.12–2.28 m (2H, CH2), 2.72–2.89 m
(2H, CH2), 2.90–3.00 m (2H, CH2), 8.69 s (1H, CH),
12.15 s (1H, OH). 13C NMR spectrum (H2SO4), δC,
ppm: 15.99, 18.83, 32.46 (CH2); 134.73, 118.71,
147.40, 195.56 (C=O). Mass spectrum, m/z (Irel, %):
152 (59) [M]+, 136 (100), 124 (48), 108 (62), 96
(43), 80 (61). Found, %: C 55.34; H 5.36; N 18.49.
[M]+ 152.0582. C7H8N2O2. Calculated, %: C 55.25;
H 5.30; N 18.41. M 152.0580.
2-(Furan-2-yl)-1-hydroxy-1,5,6,7-tetrahydro-4H-
benzimidazol-4-one (3f). Yield 68%, yellow powder,
mp 271–272°C (decomp., from EtOH). IR spectrum:
ν 1664 cm–1 (C=O). UV spectrum, λmax, nm (logε): 230
1
(3.40), 275 (3.60), 303 (3.78), 314 (3.80). H NMR
spectrum (DMSO-d6), δ, ppm: 2.04–2.14 m (2H, CH2),
2.37–2.47 m (2H, CH2), 2.78–2.86 m (2H, CH2),
6.67 d.d (1H, Fu, J = 3.5, 1.8 Hz), 7.07 d (1H, Fu, J =
3.4 Hz), 7.86 d (1H, Fu, J = 1.8 Hz), 12.30 br.s (1H,
1-Hydroxy-2-(propan-2-yl)-1,5,6,7-tetrahydro-
4H-benzimidazol-4-one (3i). Yield 66%, white
powder, mp 241–244°C. IR spectrum: ν 1668 cm–1
(C=O). UV spectrum: λmax 267 nm (log ε 3.86).
1H NMR spectrum (CDCl3), δ, ppm: 1.24 d (6H, CH3,
J = 7.6 Hz), 2.00–2.10 m (2H, CH2), 2.33–2.39 m (2H,
CH2), 2.67–2.74 m (2H, CH2), 3.23–3.33 m (1H, CH),
13
OH). C NMR spectrum (DMSO-d6), δC, ppm: 19.47,
22.68, 38.16 (CH2); 110.85, 111.70, 144.10 (CHarom);
129.92, 136.35, 142.63, 142.70, 190.30 (C=O). Mass
spectrum, m/z (Irel, %): 218 (12) [M]+, 202 (49), 174
(10), 149 (51), 104 (18), 94 (78), 85 (100). Found, %:
C 60.50; H 4.60; N 12.82. [M]+ 218.0685. C11H10N2O3.
Calculated, %: C 60.54; H 4.62; N 12.84. M 218.0686.
13
14.13 br.s (1H, OH). C NMR spectrum (CDCl3), δC,
ppm: 19.57, 22.93, 37.75 (CH2); 19.78 (CH3), 25.18
(CH), 125.83, 142.10, 151.50, 189.19 (C=O). Mass
spectrum, m/z (Irel, %): 194 (29) [M]+, 177 (9), 163
(16), 149 (8), 121 (15), 71 (16). Found, %: C 61.79;
1-Hydroxy-2-methyl-1,5,6,7-tetrahydro-4H-
benzimidazol-4-one (3g). A solution of 28.0 g
(0.406 mol) of sodium nitrite in 50 mL of water was
added dropwise to a solution of 72.4 g (0.4 mol) of
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SYNTHESIS OF 1,5,6,7-TETRAHYDRO-4H-BENZIMIDAZOL-4-ONE DERIVATIVES
71
H 7.32; N 14.40. [M]+ 194.1053. C10H14N2O2. Calcu-
lated, %: C 61.83; H 7.27; N 14.42. M 194.1050.
2-(2-Hydroxyphenyl)-1,5,6,7-tetrahydro-4H-
benzimidazol-4-one (4c). Yield 78%, white powder,
mp 264–266°C (from EtOH). IR spectrum: ν 1652 cm–1
(C=O). UV spectrum, λmax, nm (logε): 323 (3.76), 294
2-Phenyl-1,5,6,7-tetrahydro-4H-benzimidazol-4-
one (4a). a. Compound 3a, 1.14 g (0.005 mol), was
dissolved in 10 mL of acetone, 0.54 g (0.0065 mol) of
chloroacetone and 1.30 g (0.0125 mol) of triethyl-
amine were added, and the mixture was kept for
24 h at room temperature. The solvent was distilled
off, the residue was dispersed in water, and the precip-
itate was filtered off, washed with water, and dried.
Yield 0.90 g (89%).
1
(3.40). H NMR spectrum (DMSO-d6), δ, ppm: 2.07–
2.18 m (2H, CH2), 2.45–2.53 m (2H, CH2), 2.81–
2.90 m (2H, CH2), 6.91–6.98 m (2H, Harom), 7.32–
7.40 m (1H, Harom), 7.49–8.09 m (1H, Harom), 10.35 br.s
and 12.35 br.s (1H each, OH, NH). 13C NMR spectrum
(DMSO-d6),1 δC, ppm: 22.93, 23.64, 37.67 (CH2);
116.83, 118.56, 125.78, 130.36 (CH); 113.83, 129.90,
150.24, 150.71, 157.64, 188.71 (C=O). Mass spectrum,
m/z (Irel, %): 228 (100) [M]+, 172 (18), 120 (53).
Found, %: C 68.35; H 5.35; N 12.32. [M]+ 228.0892.
C13H12N2O2. Calculated, %: C 68.41; H 5.30; N 12.27.
M 228.0893.
b. Compound 3a, 1.14 g (0.005 mol), was dissolved
in 10 mL of dimethylformamide, 0.54 g (0.0065 mol)
of chloroacetone and 2.80 g (0.02 mol) of potassium
carbonate were added, and the mixture was stirred for
24 h at room temperature. The precipitate was filtered
off, the solvent was distilled off under reduced
pressure, the residue was dispersed in water, and the
precipitate was filtered off, washed with water, and
dried. Yield 0.85 g (88%), white powder, mp 220–
223°C (from EtOH). IR spectrum: ν 1665 cm–1 (C=O).
UV spectrum: λmax 298 nm (logε 3.87). 1H NMR spec-
trum (DMSO-d6), δ, ppm: 2.01–2.14 m (2H, CH2),
2.40–2.48 m (2H, CH2), 2.73–2.90 m (2H, CH2), 7.37–
7.51 m (3H, Harom), 7.93–8.17 m (2H, Harom), 12.30 br.s
(1H, NH). 13C NMR spectrum (H2SO4), δC, ppm:
20.85, 21.50, 33.11 (CH2); 128.18, 130.49, 136.87
(CH); 118.33, 123.15, 152.94, 160.25, 199.45 (C=O).
Mass spectrum, m/z (Irel, %): 212 (88) [M]+, 184 (26),
156 (8), 104 (100). Found, %: C 75.57; H 5.70;
N 13.30. [M]+ 212.0939. C13H12N2O. Calculated, %:
C 75.56; H 5.70; N 13.20. M 212.0944.
2-(3-Nitrophenyl)-1,5,6,7-tetrahydro-4H-benz-
imidazol-4-one (4d). Yield 66%, white powder,
mp 295°C (decomp., from EtOH). IR spectrum, ν,
cm–1: 1637 (C=O); 1350, 1516 (NO2). UV spectrum:
1
λmax 296 nm (logε 3.74). H NMR spectrum (H2SO4),
δ, ppm: 1.67–1.86 m (2H, CH2), 2.42–2.55 m (2H,
CH2), 2.55–2.67 m (2H, CH2), 7.30 t (1H, Harom, J =
7.6 Hz), 7.67 d (1H, Harom, J = 7.6 Hz), 7.98 d (1H,
H
arom, J = 8.1 Hz), 8.25 s (1H, Harom), 12.06 s and
12.27 s (1H, NH). 13C NMR spectrum (H2SO4), δC,
ppm: 20.00, 20.89, 33.19 (CH2); 122.91, 129.52,
131.78, 134.18 (CHarom); 120.20, 123.46, 147.07,
148.50, 156.96, 199.10 (C=O). Mass spectrum, m/z
(Irel, %): 257 (100) [M]+, 229 (13.5), 211 (8), 149 (32).
Found, %: C 60.67; H 4.28; N 16.32. [M]+ 257.0791.
C13H11N3O3. Calculated, %: C 60.69; H 4.31; N 16.34.
M 257.0795.
Compounds 4b–4i were synthesized in a simi-
lar way.
2-(4-Ethylpyridin-2-yl)-1,5,6,7-tetrahydro-4H-
benzimidazol-4-one (4e). Yield 72%, mp 170–172°C
(from EtOH). IR spectrum: ν 1664 cm–1 (C=O). UV
2-(4-Methoxyphenyl)-1,5,6,7-tetrahydro-4H-
benzimidazol-4-one (4b). Yield 76%, white powder,
mp 247–249°C (from EtOH). IR spectrum: ν 1633 cm–1
(C=O). UV spectrum, λmax, nm (logε): 312 (3.87), 246
1
spectrum: λmax 303 nm (logε 3.86). H NMR spectrum
(DMSO-d6), δ, ppm: 1.21 t (3H, CH3, J = 7.3 Hz),
2.12–2.20 m (2H, CH2), 2.50–2.56 m (2H, CH2), 2.58–
2.67 m (2H, CH2), 2.84–2.89 m (2H, CH2), 7.58 d (1H,
Py, J = 7.8 Hz), 8.11 d (1H, Py, J = 7.8 Hz), 8.32 s
(1H, Py), 11.23 br.s (1H, NH). 13C NMR spectrum
(H2SO4), δC, ppm: 11.52 (CH3); 19.46, 20.51, 24.87,
35.55 (CH2); 127.54, 143.13, 147.63 (CHarom); 125.75,
127.92, 136.89, 149.90, 150.88, 195.45 (C=O). Mass
spectrum, m/z (Irel, %): 241 (51) [M]+, 213 (10), 185
(4), 133 (100). Found, %: C 69.73; H 6.30; N 17.54.
1
(3.40). H NMR spectrum (DMSO-d6), δ, ppm: 2.00–
2.12 m (2H, CH2), 2.37–2.47 m (2H, CH2), 2.71–
2.84 m (2H, CH2), 3.80 s (3H, OCH3), 7.02 d (2H,
H
arom, J = 9.35 Hz), 8.06 br.s (2H, Harom), 12.83 br.s
and 13.10 br.s (1H, NH). 13C NMR spectrum
(DMSO-d6), δC, ppm: 23.54, 24.10, 37.54 (CH2); 55.23
(OCH3), 114.20, 127.93 (CH); 121.99, 126.85, 149.97,
156.07, 160.40, 187.45 (C=O). Mass spectrum, m/z
(Irel, %): 242 (98) [M]+, 227 (10), 214 (10), 186 (9),
134 (100). Found, %: C 69.34; H 5.65; N 11.43. [M]+
242.1048. C14H14N2O2. Calculated, %: C 69.40;
H 5.83; N 11.56. M 242.1050.
1
With addition of ~5% of triethylamine; otherwise signals at
δC 150.24 and 129.90 ppm were not observed because of strong
broadening.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 53 No. 1 2017

SAMSONOV
72
[M]+ 241.1208. C14H15N3O. Calculated, %: C 69.69;
H 6.27; N 17.42. M 241.1211.
ppm: 23.27, 24.02, 37.15 (CH2); 20.86 (CH3), 28.26
(CH), 126.05, 156.91, 159.97, 189.26 (C=O). Mass
spectrum, m/z (Irel, %): 178 (34) [M]+, 163 (100),
135 (7). Found, %: C 67.42; H 8.05; N 15.68.
[M]+ 178.1096. C10H14N2O. Calculated, %: C 67.38;
H 7.92; N 15.72. M 178.1101.
2-(Furan-2-yl)-1,5,6,7-tetrahydro-4H-benzimid-
azol-4-one (4f). Yield 76%, white powder, mp 279–
281°C (from EtOH). IR spectrum: ν 1664 cm–1 (C=O).
UV spectrum, λmax, nm (logε): 275 (3.60), 303 (3.85),
1
314 (3.86). H NMR spectrum (DMSO-d6), δ, ppm:
REFERENCES
1.89–2.16 m (2H, CH2), 2.34–2.57 m (2H, CH2), 2.64–
2.95 m (2H, CH2), 6.64 s (1H, Fu), 7.09 s (1H, Fu),
13
1. Grimmett, M.R., Comprehensive Heterocyclic Chem-
istry, Katritzky, A.R., Rees, C.W., and Potts, K.T., Eds.,
Oxford: Pergamon, 1984, vol. 5, p. 345.
7.81 s (1H, Fu), 13.30 br.s (1H, NH). C NMR spec-
trum (H2SO4), δC, ppm: 20.72, 21.10, 32.32 (CH2);
115.20, 124.59, 152.59 (CHarom); 121.96, 134.40,
142.42, 161.56, 198.24 (C=O). Mass spectrum, m/z
(Irel, %): 202 (100) [M]+, 174 (20), 146 (24), 94 (72).
Found, %: C 65.28; H 5.05; N 13.95. [M]+ 202.0736.
C11H10N2O2. Calculated, %: C 65.33; H 4.98; N 13.86.
M 202.0737.
2. Bradley, R.A. and Wilkins, D.J., Progress in Hetero-
cyclic Chemistry, Gribble, G.W. and Gilchrist, T.L.,
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vol. 106, p. 1.
2-Methyl-1,5,6,7-tetrahydro-4H-benzimidazol-
4-one (4g). Yield 59%, white powder, mp 225–228°C
(from EtOH). IR spectrum: ν 1658 cm–1 (C=O). UV
4. Bansal, Y. and Silakari, O., Bioorg. Med. Chem., 2012,
vol. 20, p. 6208.
5. Zhang, L., Peng, X.-M., Damu, G.L.V., Geng, R.-X.,
1
spectrum: λmax 268 nm (logε 3.80). H NMR spectrum
and Zhou, Ch.-H., Med. Res. Rev., 2014, vol. 34, p. 340.
(DMSO-d6), δ, ppm: 1.90–2.00 m (2H, CH2), 2.22 s
6. Gaba, M. and Mohan, Ch., Med. Chem. Res., 2016,
(3H, CH3), 2.27–2.34 m (2H, CH2), 2.59–2.66 m (2H,
vol. 25, p. 173.
13
CH2). C NMR spectrum (DMSO-d6), δC, ppm: 14.23
7. Spasov, A.A., Yozhitsa, I.N., Bugaeva, L.I., and Anisi-
(CH3); 23.63, 23.99, 37.80 (CH2); 128.25, 149.16,
153.24, 188.25 (C=O). Mass spectrum, m/z (Irel, %):
150 (100) [M]+, 122 (46), 94 (35). Found, %: C 64.08;
H 6.76; N 18.70. [M]+ 150.0791. C8H10N2O. Calculat-
ed, %: C 63.98; H 6.71; N 18.65. M 150.0788.
mova, V.A. Pharm. Chem. J., 1999, vol. 33, p. 232.
8. Alekshun, M.N., Amoo, V.K., Oak, K., and
Verma, A.K., WO Patent no. 2006076009.
9. Levy, S.B., Alekshun, M.N., Podlogar, B.L.,
Ohemeng, K., Verma, A.K., Warchol, T., Bhatia, B.,
Bowser, T., and Grier, M., US Patent no. 20050124678.
1,5,6,7-Tetrahydro-4H-benzimidazol-4-one (4h).
Yield 68%, white powder, mp 190–192°C (from
EtOH). IR spectrum, ν, cm–1: 1656, 1678 (C=O). UV
spectrum: λmax 263 nm (logε 3.78). 1H NMR spectrum
(DMSO-d6), δ, ppm: 1.99–2.06 m (2H, CH2), 2.35–
2.43 m (2H, CH2), 2.73–2.80 m (2H, CH2), 7.80 s (1H,
2-H), 10.56 br.s and 12.91 br.s (1H, NH). 13C NMR
spectrum (H2SO4), δC, ppm: 18.42, 21.28, 34.98 (CH2);
136.92 (C2), 121.24, 143.32, 197.61 (C=O). Mass
spectrum, m/z (Irel, %): 136 (6) [M]+, 69 (10), 58 (34),
43 (100). Found, %: C 61.90; H 5.85; N 20.50. [M]+
136.0630. C7H8N2O. Calculated, %: C 61.75; H 5.92;
N 20.58. M 136.0631.
10. Levy, S.B., Alekshun, M.N., Podlogar, B.L.,
Ohemeng, K., Verma, A.K., Warchol, T., Bhatia, B.,
Bowser, T., and Grier, M., WO Patent no. 2004041209.
11. Levy, S.B., Alekshun, M.N, Podlogar, B.L.,
Ohemeng, K., Verma, A.K., Warchol, T., and Bhatia, B.,
US Patent no. 20030229065.
12. Tarun, E.I., Zheldakova, T.A., and Metelitsa, D.I.,
Biomed. Khim., 2008, vol. 54, p. 588.
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Vecchiati, G., J. Heterocycl. Chem., 1980, vol. 17,
p. 1723.
2-(Propan-2-yl)-1,5,6,7-tetrahydro-4H-benzimid-
azol-4-one (4i). Yield 69%, white powder, mp 222–
223°C (from EtOH). IR spectrum: ν 1661 cm–1 (C=O).
15. Kempter, G., Spindler, J., Fiebig, H.-J., and Sarod-
nick, G., J. Prakt. Chem., 1971, vol. 313, p. 977.
1
UV spectrum: λmax 269 nm (logε 3.80). H NMR spec-
16. Aren, A.K. and Bite, Dz.V., Zh. Vses. Khim. O–va.,
trum (CDCl3), δ, ppm: 1.30 d (6H, CH3, J = 7.4 Hz),
1.98–2.17 m (2H, CH2), 2.40–2.50 m (2H, CH2),
2.72–2.82 m (2H, CH2), 3.04–3.18 m (1H, CH),
1967, vol. 12, p. 708.
17. Krichevskii, E.S., Alekseeva, L.M., Anisimova, O.S.,
and Granik, V.G., Pharm. Chem. J., 1995, vol. 29,
p. 644.
13
11.95 br.s (1H, NH). C NMR spectrum (CDCl3), δC,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 53 No. 1 2017

SYNTHESIS OF 1,5,6,7-TETRAHYDRO-4H-BENZIMIDAZOL-4-ONE DERIVATIVES
73
18. Nikitina, P.A., Kuz’mina, L.G., Perevalov, V.P., and
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