Nitro Derivatives of 1,3-Dihydrobenzimidazol-2-one: I. synthesis of N-Nitrobenzimidazol-2-ones

Article abstract of DOI:10.1134/S1070428009060128

1,3,5,6-Tetranitro-2,3-dihydro-1H-benzimidazol-2-one, 1,5,6-trinitro-2,3- dihydro-1H-benzimidazol- 2-one, and 1,4,5,6-tetranitro-2,3-dihydro-1H- benzimidazol-2-one were synthesized for the first time by nitration of 5,6-di- and 4,5,6-trinitro-2,3-dihydro-

Full text of DOI:10.1134/S1070428009060128

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 6, pp. 872–878. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © E.V. Tatarnikova, V.V. Sizov, I.V. Tselinskii, 2009, published in Zhurnal Organicheskoi Khimii, 2009, Vol. 45, No. 6, pp. 885–861.
Dedicated to Full Member of the Russian Academy of Sciences
O.N. Chupakhin on his 75th anniversary
Nitro Derivatives of 1,3-Dihydrobenzimidazol-2-one:
I. Synthesis of N-Nitrobenzimidazol-2-ones
E. V. Tatarnikova, V. V. Sizov, and I. V. Tselinskii
St. Petersburg State Institute of Technology, Moskovskii pr. 26, St. Petersburg, 190013 Russia
e-mail: vvsizov@list.ru
Received January 27, 2009
Abstract—1,3,5,6-Tetranitro-2,3-dihydro-1H-benzimidazol-2-one, 1,5,6-trinitro-2,3-dihydro-1H-benzimidazol-
2
-one, and 1,4,5,6-tetranitro-2,3-dihydro-1H-benzimidazol-2-one were synthesized for the first time by nitra-
tion of 5,6-di- and 4,5,6-trinitro-2,3-dihydro-1H-benzimidazol-2-ones with concentrated nitric acid in acetic
anhydride.
DOI: 10.1134/S1070428009060128
Up to now, all C-nitro derivatives of 2,3-dihydro-
H-benzimidazol-2-one (I) that can be obtained by its
direct nitration have been reported, and facile introduc-
tion of nitro groups into the benzene ring of I has been
noted [1–5]. 5-Nitro derivative II is formed upon
treatment of benzimidazolone I with 30% nitric acid
It was proposed to synthesize 4,5,6,7-tetranitro-2,3-
dihydro-1H-benzimidazol-2-one (V) in two steps [1],
the first of which was nitration of benzimidazolone I in
sulfuric acid at 40–45°C until a mixture of compounds
II and III was formed. The product mixture thus
formed was nitrated in sulfuric acid at 100°C using
1
[3], as well as in the nitration of I with an equimolar
a large excess of 98% HNO . The nitration of I with
3
amount of 98% HNO in sulfuric acid at 0°C [1].
98% HNO in a mixture of acetic acid and acetic anhy-
3
3
5
,6-Dinitro derivative III was synthesized by heating
dride at 70°C also gave tetranitro derivative V [2].
compound I for a short time in 60–65% HNO taken in
3
Due to ready introduction of nitro groups into the
benzene ring of compound I the synthesis of nitro
derivatives IV and V requires no large excess of nitric
acid. In addition, 4,5,6,7-tetranitrobenzimidazolone V
is considerably better soluble in several solvents, as
compared to 5,6-di- and 4,5,6-trinitro derivatives III
and IV. Therefore, partial overnitration of the initial
compound is advisable to ensure complete conversion
of III (which is poorly soluble in organic solvents) and
higher purity of product IV.
large excess [2] or by reaction of I with an equimolar
amount of 98% nitric acid in concentrated sulfuric acid
at 5–10°C [1].
According to the data of [1, 2], 4,5,6-trinitro-2,3-
dihydro-1H-benzimidazol-2-one (IV) can be obtained
from compound I by heating in a large excess of
9
8% HNO for a short time [2] or by nitration of I in
3
sulfuric acid with an equimolar amount of 98% HNO3
at 40–45°C [1]. Compound IV was purified from
an impurity of III by recrystallization from ethanol [1]
or water [2]. However, this procedure is inconvenient
because of poor solubility of 4,5,6-trinitro derivative
IV in the above solvents.
We performed nitration of benzimidazolone I to
4,5,6-trinitro derivative IV in sulfuric acid with the use
of 50% excess of 63% HNO . The reaction at 55°C
3
(1.5 h) gave compound IV containing no more than
Scheme 1.
NO2
H
N
63% HNO –H SO
H
N
3
2
4
O N
2
5
5°C, 1.5 h
O
O
N
H
N
H
O N
2
I
IV, 81%
8
72

NITRO DERIVATIVES OF 1,3-DIHYDROBENZIMIDAZOL-2-ONE: I.
873
5
mol % of 4,5,6,7-tetranitrobenzimidazolone V
stals. After filtration, compounds III and IV were
isolated by dilution of the filtrate with water. Separa-
tion of III from IV involved no difficulties due to poor
solubility of 5,6-dinitro derivative III in organic sol-
vents (in contrast to IV). The product ratio changed,
depending on the composition of the acid mixture and
(
Scheme 1). The latter was removed from the crude
product by treatment at 35–40°C with 40% aqueous
ethanol where 4,5,6,7-tetranitro derivative V is sol-
uble much better than in water or pure ethanol. Com-
pound IV without additional purification can be
brought into further nitration to obtain 4,5,6,7-tetra-
nitrobenzimidazolone V.
amount of nitric acid. When the ratio of HNO to
3
acetic anhydride was reduced to equimolar, the yield of
trinitrobenzimidazolones IV and VI decreased, and
compound III became the major product. Our attempts
to synthesize 1,5-dinitro- and/or 1,6-dinitro derivatives
VII and VIII via further reducing the amount of nitric
acid and temperature (to –10°C) were unsuccessful.
Either compound VI was formed, or 5,6-dinitrobenz-
imidazolone III was isolated as the only product.
4
,5,6-Trinitro-2,3-dihydro-1H-benzimidazol-2-one
IV) was converted into 4,5,6,7-tetranitro derivative
V by treatment at 70–75°C with 100% excess of
5% HNO in sulfuric acid, the H SO –IV weight ratio
(
9
3
2
4
being 9:1 (Scheme 2). 4,5,6-Trinitro derivative IV was
consumed almost completely in 4.5 h, and 4,5,6,7-tet-
ranitrobenzimidazolone V separated from the reaction
solution. After cooling, filtration, and washing, the
crude product contained no more than 0.3 mol % of
compound IV (according to the HPLC data). The
waste acid mixture may be reused after strengthening
with oleum. 4,5,6,7-Tetranitrobenzimidazolone V may
be additionally purified by recrystallization from 93–
Our further experiments on nitration of 5-nitrobenz-
imidazolone II with excess concentrated nitric acid in
acetic anhydride (molar ratio 2:1) showed that the
composition of nitration products strongly depends on
the reaction temperature. When 5-nitrobenzimidazo-
lone II was added to the nitrating mixture at 15–20°C,
N-mononitro derivative VI (1,5,6-trinitro-2,3-dihydro-
9
6% sulfuric acid or acetic acid.
1
H-benzimidazol-2-one) separated. Raising the tem-
Scheme 2.
perature to 35°C resulted in the formation of N,N′-di-
nitro derivative, 1,3,5,6-tetranitro-2,3-dihydro-1H-
benzimidazol-2-one (IX) in 47% yield (Scheme 4).
After separation of compound IX by filtration, the fil-
trate was poured onto ice. We thus obtained a mixture
of nitration products, which contained (according to
NO2
9
7
5% HNO –H SO
H
N
3
2
4
O N
2
0–75°C, 4.5 h
IV
O
N
H
O N
2
NO2
1
the HPLC and H NMR data) 1,3,5,6-tetranitro-,
V, 80%
1
,5,6-trinitro-, and 1,4,5,6-tetranitro derivatives IX,
VI, and X at a molar ratio of 1:2.5:8.5.
Unlike C-nitro-substituted benzimidazol-2-ones,
N-nitro derivatives of compound I were not reported
previously. With a view to synthesize N,C-nitrobenz-
imidazolones we examined nitration of compounds
II–V with nitric acid in acetic anhydride at relatively
low temperature.
N-Nitro derivative VI can be synthesized in 56%
yield by nitration of benzimidazolone I with an equi-
molar mixture of nitric acid and acetic anhydride
(6 equiv of HNO3).
Nitration of 5,6-dinitrobenzimidazolone III also led
to different products. The reaction of III with an equi-
molar mixture of nitric acid and acetic anhydride at
room temperature gave mono-N-nitro derivative,
1,5,6-trinitro-2,3-dihydro-1H-benzimidazol-2-one
(VI), while the nitration with a 2:1 HNO –Ac O mix-
The nitration of II with excess nitric acid in acetic
anhydride (HNO –Ac O molar ratio 2:1) at room tem-
3
2
perature gave a mixture of 1,5,6-trinitro-, 5,6-dinitro-,
and 4,5,6-trinitrobenzimidazolones VI, III, and IV at
a weight ratio of 2:1:1 (Scheme 3). Compound VI
separated from the reaction mixture as colorless cry-
3
2
ture resulted in the formation of a mixture of com-
Scheme 3.
NO2
H
N
H
N
9
2
8–99% HNO –Ac O
3 2
0–25°C, 3 h
O N
O N
O N
2
2
2
N
O
O
+
O
+
IV
N
H
N
N
H
O N
2
O N
2
H
II
VI
III
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 6 2009

8
74
TATARNIKOVA et al.
Scheme 4.
NO2
NO2
H
N
9
2
8–99% HNO –Ac O
3 2
5°C, 3 h
O N
2
O N
2
N
II
O
+
VI
+
O
N
N
O N
2
O N
2
NO2
NO2
IX
X
pounds IX, X, and V (Scheme 5). Compound IX sepa-
rated from the reaction mixture as colorless crystals,
and was isolated by filtration, and the filtrate was
evaporated under reduced pressure and analyzed. As
might be expected, a mixture of N-nitro compounds VI
and IX was obtained when the amount of nitric acid
was reduced to an HNO –Ac O molar ratio of 1.5:1,
other conditions being equal. Compound IX was also
synthesized by nitration of 2-chloro-5,6-dinitro-1H-
benzimidazole (XI) under analogous conditions
was obtained as the major product (yield 62%,
Scheme 7) with an impurity of ~10 mol % of 4,5,6,7-
tetranitrobenzimidazolone V (according to the HPLC
data).
Taking into account that the formation of acetyl
nitrate and nitrogen(V) oxide necessary for nitration at
the nitrogen atom requires some time [6], the above
findings suggest that compound III is partially proto-
nated at the benzene ring with subsequent N-nitration.
On the other hand, increased acidity of the reaction
mixture in the initial step (due to the presence of free
3
2
(
Scheme 6).
HNO ) is likely to promote sharp acceleration of the
acid-catalyzed N→C transfer of the nitro group to the
benzene ring (like Bamberger rearrangement [7, 8]).
3
Scheme 5.
1
:1
VI
VI
IX
7
8%
Unlike 5,6-dinitrobenzimidazolone III, 1-acetyl-
5,6-dinitro-2,3-dihydro-1H-benzimidazol-2-one (XII)
undergoes nitration with excess nitric acid in acetic
anhydride at room temperature at both nitrogen and
aromatic carbon atoms. From the reaction mixture we
isolated a mixture of 1-acetyl-3,5,6-trinitro-2,3-dihy-
dro-1H-benzimidazol-2-one (XIII) and 1-acetyl-4,5,6-
trinitro-2,3-dihydro-1H-benzimidazol-2-one (XIV) at
9
2
8–99% HNO –Ac O
3 2
0–25°C, 2 h
1.5:1
III
+
+
IX
2
:1
X
+
V
7
5%
Scheme 6.
H
N
9
2
8–99% HNO –Ac O
3 2
0–25°C, 2 h
O N
Scheme 8.
2
Cl
IX
Ac
6
3%
Ac O, H+
1
N
2
O N
2
O N
2
N
00–110°C, 5 min
XI
III
O
N
H
O N
2
As expected, the product composition in the nitra-
XII
tion of 5,6-dinitrobenzimidazolone III with excess
concentrated nitric acid in acetic anhydride (molar
ratio 2:1) strongly depended on the order of mixing of
the reactants. Addition of compound III to a prelimi-
narily prepared mixture of nitric acid and acetic anhy-
dride at room temperature resulted in the formation of
Ac
9
8–99% HNO –Ac O
3 2
O N
2
N
20–25°C, 5 h
XII
O
N
O N
2
NO2
XIII
N,N′-dinitro derivative IX. When HNO was added
3
under analogous conditions to a suspension of III in
acetic anhydride, 1,4,5,6-tetranitrobenzimidazolone X
Ac
O N
2
N
+
O
Scheme 7.
N
H
O N
2
9
2
8–99% HNO3
0–25°C, 24 h
NO
XIV
2
III
+
Ac O
2
X
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 6 2009

NITRO DERIVATIVES OF 1,3-DIHYDROBENZIMIDAZOL-2-ONE: I.
875
a molar ratio of 1:2 (Scheme 8). Trinitro derivative
XIV was also synthesized independently, by acylation
of 4,5,6-trinitrobenzimidazolone IV with acetic anhy-
dride on heating in the presence of sulfuric acid.
4,5,6,7-tetranitrobenzimidazolone V. Compound XV is
unstable to the action of water and organic solvents, as
well as of anhydrous carboxylic acids and their anhy-
drides, except for trifluoroacetic anhydride; therefore,
1
15
we failed to obtain its satisfactory H and N NMR
spectra. Taking into account the above stated, we pre-
sumed that the colorless crystalline product is N-nitro
derivative, most probably 1,4,5,6,7-pentanitro-2,3-di-
hydro-1H-benzimidazol-2-one (XV).
N-Nitration of 4,5,6-trinitrobenzimidazolone IV
with a mixture of nitric acid and acetic anhydride
occurs at a considerably lower rate as compared to the
nitration of III. As in the reactions with 5-mono- and
5
,6-dinitro derivatives II and III, the product gradually
separated as colorless crystals from the reaction
mixture; however, much longer time is necessary to
achieve an acceptable yield. The nitration with HNO3–
The newly synthesized N-nitro-substituted benz-
imidazolones VI, IX, and X are crystalline substances
with low decomposition points, and they are unstable
in solution. After removal of traces of strong acids by
vacuum drying over alkali, crystalline compounds VI,
IX, and X can be stored in a closed vessel for at least
several months without appreciable decomposition.
The structure of compounds VI, IX, and X was con-
Ac O (molar ratio 2:1) gave 43% of compound X in
2
7
h (Scheme 9).
Scheme 9.
9
2
8–99% HNO –Ac O
0–25°C, 7 h
3
2
1
IV
X
firmed by the H NMR and IR spectra and elemental
analyses (see Experimental).
With the use of an equimolar mixture of nitric acid
and acetic anhydride, other conditions being equal,
N-nitro derivative X was obtained only in 34% yield.
N-Nitration of 4,5,6-trinitrobenzimidazolone IV with
a mixture of nitric acid and trifluoroacetic anhydride
occurred at a considerably higher rate and with higher
conversion. The reaction at room temperature gave
EXPERIMENTAL
The IR spectra were recorded from samples pre-
pared as KBr pellets on a Shimadzu FTIR 8400 spec-
trometer. The H NMR spectra were measured on
1
a Bruker WM-400 instrument at 400 MHz using hexa-
methyldisiloxane as internal reference. The elemental
compositions were determined on a Hewlett–Packard
185B CHN analyzer. The products were analyzed by
HPLC on a Milikhrom liquid chromatograph equipped
with a UV detector (λ 250 nm) and data acquisition
and processing system. Product mixtures were separat-
ed in a Silasorb C18 column, 63×2 mm (grain size
6
8% of compound X in 1 h. The process looks similar
to the nitration in acetic anhydride. The reaction mix-
ture gradually becomes homogeneous, and colorless
crystals of 1,4,5,6-tetranitro derivative X begin to sep-
arate from the solution after a short time.
Our attempts to effect nitration of 4,5,6,7-tetra-
nitrobenzimidazolone V in Ac O were unsuccessful,
2
5
μm, Lachema, Czechia); eluent water–acetonitrile–
acetic acid (100:22:1, by weight), flow rate 100 μl ×
but the reaction in trifluoroacetic anhydride was simi-
lar to the nitration of 4,5,6-trinitro derivative IV. Initial
yellow 4,5,6,7-tetranitrobenzimidazolone V dissolved
to give a colorless solution, and colorless crystalline
product separated in a short time (Scheme 10). After
filtration and washing with trifluoroacetic acid on
a filter on exposure to air, we observed vigorous de-
composition of the product with liberation of nitrogen
oxide and formation of yellow crystals of initial
–
1
min ; sample volume 2–4 μl. The retention times were
as follows (in order of elution): III, 243 s; IV, 380 s;
X, 485 s; IX, 569 s; V, 957 s. The components were
quantitated by the internal normalization technique
using calibration coefficients.
Initial compounds II, III, and XI were synthesized
according to the procedures described in [2, 9].
4
,5,6-Trinitro-2,3-dihydro-1H-benzimidazol-2-
one (IV). Compound I, 41 g (0.306 mol), was dis-
solved in 360 ml of 93% H SO , and 140 g (1.400 mol)
of 63% nitric acid was added at such a rate that the
temperature of the mixture did not exceed 55°C. The
mixture was kept for 1.5 h at 55°C, cooled to room
temperature, poured into 1.5 l of cold water, and stirred
for 30 min. The precipitate was filtered off and washed
Scheme 10.
NO2
H
2
4
9
2
8–99% HNO –TFA
0–25°C, 5 h
3
O N
2
N
V
O
N
O N
2
NO2
NO2
XV
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 6 2009

8
76
TATARNIKOVA et al.
with water. According to the HPLC data, the product
contained 3–4 mol % of compound V. To remove the
latter, the crude product was dispersed in 250 ml of
743 (CH), 719 (N–NO ), 654, 619, 560 (N–NO ).
2
2
1
H NMR spectrum (acetone-d
), δ, ppm: 7.90 s (1H,
6
Harom), 8.55 s (1H, Harom), 12.05 s (1H, NH). Found, %:
4
3
0% aqueous ethanol, thoroughly stirred for 15 min at
5°C, and the precipitate was filtered off and washed
C 31.34; H 1.56; N 25.94. C
C 31.24; H 1.12; N 26.02.
H N O . Calculated, %:
7 3 5 7
with ethanol. After purification, the concentration of V
in the product was 0.4 mol %. Yield 66.7 g (81%),
light yellow crystals, mp 313–315°C (decomp.); pub-
b. Nitric acid (98–99%), 3.5 ml, was added at 20–
5°C to 8 ml of acetic anhydride, and 2 g (8.9 mmol)
2
of compound III was added in small portions at such
a rate that the temperature did not exceed 20°C. The
mixture was stirred for 2 h at 20°C, and the precipitate
was filtered off, thoroughly washed with 1,2-dichloro-
ethane, and dried under reduced pressure over NaOH.
Yield 1.9 g (78%), colorless crystals, mp 141–143°C
(decomp.).
–
1
lished data [2]: mp 313–314°C. IR spectrum, ν, cm :
145 (C–N, CH), 1752 (CH), 1644 (C=O), 1615 (C=O,
C=C), 1550 (ArNO ), 1492 (C=C), 1452, 1424, 1360
3
2
(
C=C), 1330 (ArNO ), 1267 (N–NO ), 1196 (C–N),
2 2
9
76 (N–N), 919, 886, 835 (CH), 778 (CH), 751
1
(
N–NO ), 745 (N–NO ), 676, 654, 623. H NMR spec-
2 2
trum (DMSO-d ), δ, ppm: 12.65 s (1H, NH), 12.25 s
6
1
,3,5,6-Tetranitrobenzimidazol-2-one (IX). Nitric
(
1H, NH), 7.95 s (1H, CHarom). Found, %: C 31.30;
acid (98–99%), 7 ml, was added at 20–25°C to 8 ml of
acetic anhydride, and 1 g (4.1 mmol) of 2-chloro-5,6-
dinitro-1H-benzimidazole (XI) was added in portions
at such a rate that the temperature did not exceed 25°C.
The mixture was stirred for 2 h at 25°C, and the
precipitate was filtered off, thoroughly washed with
H 1.24; N 25.93. C H N O . Calculated, %: C 31.24;
7
3
5
7
H 1.12; N 26.02.
,5,6,7-Tetranitro-2,3-dihydro-1H-benzimidazol-
-one (V). Compound IV, 10 g (37.2 mmol), was
mixed at room temperature with 50 ml of 93% H SO ,
4
2
2
4
6
g (90.5 mmol) of 95% HNO was added, and the
3
1
,2-dichloroethane, and dried under reduced pressure
mixture was stirred for 4.5 h at 70–75°C. The mixture
was cooled to 20°C, and the precipitate was filtered off
and dispersed in 150 ml of water, the suspension was
thoroughly stirred, and the precipitate was filtered off,
washed with water, and dried at 80°C. Yield 9.5 g
over NaOH. Yield 0.82 g (63%), colorless crystals,
–1
mp 120–122°C (decomp.). IR spectrum, ν, cm : 3390,
3
(
1
(
(
(
135 (CH), 2887 (CH), 1818 (CH), 1633 (C=O), 1606
C=O, C=C), 1543 (NO ), 1470 (C=C), 1385 (C=C),
2
361 (NO ), 1267 (N–NO ), 1232, 1140 (NH), 1060
2 2
(
80%), bright yellow crystals, mp 317–319°C (de-
N–N), 910, 890, 853, 820 (CH), 770 (CH), 757
comp.); published data [2]: mp 317°C. IR spectrum, ν,
1
N–NO ), 733, 703 (N–NO ), 657. H NMR spectrum
–
1
2
2
cm : 3401 (NH), 3138, 1752 (Carom), 1618 (C=O,
acetone-d ): δ 8.80 ppm, s (Harom). Found, %: C 26.77;
6
C=C), 1550 (NO ), 1501 (C=C), 1400 (C=C), 1339
2
H 0.64; N 26.75. C H N O . Calculated, %: C 26.50;
7
2
6
9
(
(
NO ), 1206 (N–NO ), 1054, 987, 931, 911, 864
2 2
H 0.61; N 26.54.
,4,5,6-Tetranitro-2,3-dihydro-1H-benzimidazol-
-one (X). a. Acetic anhydride, 8 ml, was mixed at 20–
5°C with 7 ml of 98–99% HNO , and 1 g (3.7 mmol)
1
Carom), 760, 690, 443. H NMR spectrum (DMSO-d ):
6
1
δ 13.0 ppm, br.s (2H, NH). Found, %: C 26.76; H 0.69;
2
2
N 26.63. C H N O . Calculated, %: C 26.77; H 0.64;
7
2
6
9
N 26.75.
3
of compound IV was added in small portions. The
mixture was stirred for 7 h at 20°C, and the precipitate
was filtered off, thoroughly washed with 1,2-dichloro-
ethane, and dried under reduced pressure over NaOH.
Yield 0.44 g (43%), colorless crystals, mp 144–145°C
1
,5,6-Trinitro-2,3-dihydro-1H-benzimidazol-2-
one (VI). a. Nitric acid (98–99%), 6 g (93.3 mmol),
was added at 20–25°C to 10 g (98 mmol) of acetic
anhydride, and 2 g (14.9 mmol) of compound I was
added in portions at such a rate that the temperature of
the mixture did not exceed 25°C. The mixture was
stirred for 3 h at 25°C, and the precipitate was filtered
off, thoroughly washed with 1,2-dichloroethane, and
dried under reduced pressure over NaOH. Yield 2 g
50%), colorless crystals, mp 140–142°C (decomp.).
IR spectrum, ν, cm : 3362 (NH), 3164 (C–H), 3133
C–H), 3078 (C–H), 1773 (CH), 1629 (C=O), 1593
C=O, C=C), 1546 (NO ), 1487 (C=C), 1460 (C=C),
–
1
(
(
(
decomp.). IR spectrum, ν, cm : 3435 (NH), 3126
C–N, CH), 1825, 1796 (CH), 1622 (C=O, C=C), 1558
NO ), 1484 (C=C), 1446, 1398 (C=C), 1345 (NO ),
2
2
1
259 (N–NO ), 1152 (C–N), 1082, 931 (N–N), 822
2
(
CH), 760 (CH), 740 (N-NO ), 664, 649, 564.
2
(
1
–
1
H NMR spectrum (acetone-d ): δ 8.95 ppm, s (1H,
6
Harom). Found, %: C 26.89; H 0.79; N 26.83.
C H N O . Calculated, %: C 26.77; H 0.64; N 26.75.
(
(
7
2
6
9
2
1
404, 1365, 1339 (NO ), 1253 (N–NO ), 1229, 1170
b. Trifluoroacetic anhydride, 24 ml, was mixed at
5–10°C with 7 ml of 98–99% HNO , 1 g (3.7 mmol) of
2
2
(
NH), 1129, 1079 (N–N), 981, 892, 856, 826 (CH),
3
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 6 2009

NITRO DERIVATIVES OF 1,3-DIHYDROBENZIMIDAZOL-2-ONE: I.
877
compound IV was added, and the mixture was stirred
for 1 h at 20°C. The precipitate was filtered off,
washed with a small amount of trifluoroacetic acid,
and dried in air at room temperature. Yield 0.8 g
The precipitate was filtered off, thoroughly washed
with 1,2-dichloroethane, and dried under reduced pres-
sure over NaOH. Yield of 1,3,5,6-tetranitrobenzimid-
azolone IX 6.6 g (67%), colorless crystals, mp 120–
121°C (decomp.).
(
69%), colorless crystals, mp 144–145°C (decomp.).
Nitration of 5-nitro-2,3-dihydro-1H-benzimid-
The filtrate was poured onto ice, the mixture was
kept for 30 min, and the precipitate was filtered off,
washed with water, and dried in air. The product was
1.75 g of a mixture consisting of 1,4,5,6- and 4,5,6,7-
tetranitro derivatives X and V at a weight ratio of
azol-2-one (II) with nitric acid in acetic anhydride.
a. Nitric acid (98–99%), 7 ml, was added at 20–25°C
to 8 ml of acetic anhydride, and 2 g (11.1 mmol) of
compound II was added in small portions at such a rate
that the temperature did not exceed 20°C. The mixture
was stirred for 3 h at 20°C, and the precipitate was
filtered off, thoroughly washed with 1,2-dichloro-
ethane, and dried under reduced pressure over sodium
hydroxide. The product was 1,5,6-trinitro-2,3-dihydro-
1
2.3:1 (according to the H NMR and HPLC data).
b. Compound III, 7 g (31.2 mmol), was dispersed
at room temperature in 50 ml of acetic anhydride, and
5
0 ml of 98–99% HNO was slowly added to the sus-
3
pension, maintaining the temperature at 15–20°C. The
mixture was stirred for 24 h at 20°C and poured onto
ice (~500 ml of water); after 30 min, the precipitate
was filtered off, washed with water, and dried in air.
The product was 7.0 g (62%) of 1,4,5,6-tetranitrobenz-
imidazolone X colored yellow due to the presence of
1
H-benzimidazol-2-one (VI), yield 1 g (33%), color-
less crystals, mp 141–142°C (decomp.).
The filtrate was poured onto ice, the mixture was
left overnight, and the precipitate was filtered off,
washed with water, and dried in air. The product, 1 g,
was a mixture consisting of 5,6-di- and 4,5,6-trinitro
derivatives III and IV at a molar ratio of 1:1. It was
thoroughly stirred with acetone at room temperature,
and the precipitate was filtered off and washed with
acetone to obtain 0.45 g (18%) of 5,6-dinitro-2,3-di-
hydro-1H-benzimidazol-2-one (III). The acetone
filtrate was evaporated to isolate 0.47 g (16%) of
4
,5,6,7-tetranitrobenzimidazolone V as an impurity
~10 mol %, according to the HPLC data).
-Acetyl-5,6-dinitro-2,3-dihydro-1H-benzimid-
azol-2-one (XII). Compound III, 5 g (22.3 mmol), and
3% H SO , 1–2 drops, were added at room tempera-
(
1
9
2
4
ture to 10 ml of acetic anhydride. The mixture was
heated for 5 min at 100–110°C and cooled to room
temperature, and the precipitate was filtered off,
thoroughly squeezed, washed with acetic anhydride
and diethyl ether, and dried in air. Yield 4.2 g (71%),
light brown crystals, mp 234–236°C (decomp.; from
4
,5,6-trinitrobenzimidazolone IV.
b. Nitric acid (98–99%), 14 ml, was added at
0–25°C to 16 ml of acetic anhydride, and 4 g
22.2 mmol) of compound II was added in small
portions at such a rate that the temperature did not
exceed 35°C. The mixture was kept for 3 h at 25°C,
and the precipitate was filtered off, thoroughly washed
with 1,2-dichloroethane, and dried under reduced pres-
sure over NaOH. We thus isolated 3.3 g (47%) of
2
(
–
1
ethanol). IR spectrum, ν, cm : 3462, 3130 (C–N),
026 (CH), 1741 (CH), 1628 (C=O), 1609 (C=O,
C=C), 1545 (NO ), 1486 (C=C), 1410, 1358 (C=C),
3
2
1
1
340 (NO ), 1297 (N–NO ), 1238 (C–N), 1158, 1105,
2 2
053 (N–N), 1038, 997, 896, 880, 847 (CH), 834
1
1
,3,5,6-tetranitrobenzimidazolone IX as colorless crys-
tals with mp 120–122°C (decomp.).
(
CH), 750 (N–NO ), 707 (N–NO ), 686, 626. H NMR
2 2
spectrum (DMSO-d ), δ, ppm: 12.48 s (1H, NH),
6
The filtrate was poured onto ice. After 30 min, the
precipitate was filtered off, washed with water, and
dried in air. The product was 1.71 g of a mixture con-
sisting of 1,3,5,6-tetra-, 1,5,6-tri-, and 1,4,5,6-tetranitro
8.60 s (1H, Harom), 7.70 s (1H, Harom), 2.70 s (3H, CH
3
).
H N O . Cal-
6 4 6
Found, %: C 40.76; H 2.58; N 21.44. C
culated, %: C 40.61; H 2.27; N 21.05.
9
1
-Acetyl-4,5,6-trinitro-2,3-dihydro-1H-benzimid-
azol-2-one (XIV). Compound IV, 2 g (7.4 mmol), and
3% H SO , 1–2 drops, were added at room tempera-
derivatives IX, VI, and X at a molar ratio of 1:2.5:8.5
1
(
according to the H NMR and HPLC data).
9
2
4
Nitration of 5,6-dinitro-2,3-dihydro-1H-benz-
ture to 5 ml of acetic anhydride, the mixture was
heated for 5 min at 100–110°C and cooled to room
temperature, and the precipitate was filtered off, thor-
oughly squeezed, washed with acetic anhydride and
diethyl ether and dried in air. Yield 1.80 g (78%), light
yellow crystals, mp 252–254°C (decomp.; from etha-
imidazol-2-one (III) with nitric acid in acetic anhy-
dride (molar ratio 2:1). a. Acetic anhydride, 50 ml,
was mixed at 20–25°C with 50 ml of 98–99% HNO3,
g (31.2 mmol) of compound III was added in small
portions, and the mixture was stirred for 2 h at 20°C.
7
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 6 2009

8
78
TATARNIKOVA et al.
–
1
nol). IR spectrum, ν, cm : 3436 (NH), 3138 (C–N,
was stirred for 5 h at 20°C, and the colorless precip-
itate was filtered off and washed with a small amount
of trifluoroacetic anhydride. The product, 1,4,5,6,7-
pentanitro-2,3-dihydro-1H-benzimidazol-2-one (XV),
decomposed in 1 min on exposure to air at room tem-
perature to 4,5,6,7-tetranitro derivative V (according to
the HPLC data) with liberation of nitrogen oxides. The
complete transformation of compound XV into V upon
drying under reduced pressure over NaOH required
approximately 5–6 days. Yield of V 0.68 g. Compound
XV is unstable to the action of water, polar nonaque-
ous solvents, and anhydrous carboxylic acids and their
anhydrides; therefore, we failed to obtain its satis-
CH), 1761 (CH), 1731 (C=O), 1623 (C=O), 1610
C=O, C=C), 1570, 1558 (NO ), 1550 (C–N, NH),
488 (C=C), 1353 (C=C), 1334 (NO ), 1315, 1279
2
N–NO ), 1185 (C–N), 1151, 1103, 1070 (N–N), 964,
17, 769 (CH, N–NO ), 676 (N–NO ), 654, 622.
2 2
H NMR spectrum (DMSO-d ), δ, ppm: 8.97 s (1H,
Harom), 2.70 s (3H, CH ). Found, %: C 34.83; H 1.88;
N 22.41. C H N O . Calculated, %: C 34.74; H 1.62;
(
2
1
(
2
9
1
6
3
9
5
5
8
N 22.51.
1
-Acetyl-3,5,6-trinitro-2,3-dihydro-1H-benz-
imidazol-2-one (XIII). Acetic anhydride, 8 ml, was
mixed at 20–25°C with 7 ml of 98-99% HNO , and 1 g
3.7 mmol) of compound XII was added in small
3
1
15
(
factory H and N NMR spectra.
portions. The mixture was stirred for 5 h at 20°C, and
the precipitate was filtered off, washed with 1,2-di-
chloroethane, and dried under reduced pressure over
NaOH. The product, 0.2 g, was a mixture of 1-acetyl-
REFERENCES
1. Efros, L.S. and El’tsov, A.V., Zh. Obshch. Khim., 1957,
3
(
,5,6-trinitro-2,3-dihydro-1H-benzimidazol-2-one
XIII) and 1-acetyl-4,5,6-trinitro-2,3-dihydro-1H-
benzimidazol-2-one (XIV) at a molar ratio of 1:2
vol. 27, p. 127.
2. Schindlbauer, H. and Kwiecinski, W., Monatsh. Chem.,
1976, vol. 107, p. 1307.
1
(
according to the H NMR and HPLC data).
3. Mees, B. and Ribka, J., EU Patent no. 0014449, 1980;
Chem. Abstr., 1981, vol. 95, no. 114945d.
The filtrate was poured into 75 ml of cold water;
4
5
6
. Kraska, J. and Boruszczak, Z., Pol. Patent no. 154621,
991; Chem. Abstr., 1993, vol. 119, no. 162384f.
after 15 min, the precipitate was filtered off, washed
with water, and dried in air. Yield 0.42 g (36%),
1
–
1
. Boruszczak, Z. and Kraska, J., Dyes Pigm., 1999, vol. 40,
p. 261.
mp 219–223°C (decomp.). IR spectrum, ν, cm : 3421,
133 (C–N, CH), 1806 (CH), 1630 (C=O), 1604 (C=O,
C=C), 1545 (NO ), 1476 (C=C), 1385 (C=C), 1319
3
. Hoggett, J.G., Moodie, R.B., and Schofield, K., Nitration
and Aromatic Reactivity, London: Cambridge Univ.,
2
(
(
7
(
NO ), 1263 (N–NO ), 1229 (C–N), 1163, 1110, 1062
2 2
1
971, p. 80.
N–N), 961, 892, 843 (CH), 785 (CH), 756 (N–NO ),
2
1
7
8
. Agrawal, J.P. and Hodgson, R.D., Organic Chemistry of
Explosives, Chichester, Wiley, 2007, p. 145.
32, 708 (N–NO ), 623, 609. H NMR spectrum
2
acetone-d ), δ, ppm: 8.95 s (1H, Harom), 8.68 s (1H,
6
. Weaver, W.M., The Chemistry of the Nitro and Nitroso
Groups, Feuer, H., Ed., New York: Interscience, 1970,
vol. 2. Translated under the title Khimiya nitro- i
nitrozogrupp, Moscow: Mir, 1973, vol. 2, p. 34.
Harom), 2.80 s (3H, CH ). Found, %: C 34.46; H 1.72;
3
N 22.83. C H N O . Calculated, %: C 34.74; H 1.62;
9
5
5
8
N 22.51.
Nitration of 4,5,6,7-tetranitro-2,3-dihydro-1H-
benzimidazol-2-one (V) with nitric acid in trifluoro-
acetic anhydride. Trifluoroacetic anhydride, 25 ml,
9
. Chermova, E.Yu., Mokrushina, G.A., Chupakhin, O.N.,
Kotovskaya, S.K., Il’enko, V.I., Andreeva, O.T., Bore-
ko, E.I., Vladyko, G.V., Korobchenko, L.V., Garagu-
liya, A.D., and Dukhovnaya, V.M., Khim.-Farm. Zh.,
1991, vol. 25, no. 1, p. 50.
was mixed at 5–10°C with 7 ml of 98–99% HNO , 1 g
3
(
3.2 mmol) of compound V was added, the mixture
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 6 2009