Nitro derivatives of 1,3-dihydrobenzimidazol-2-one: II. Rearrangement of N-nitrobenzimidazol-2-ones

Article abstract of DOI:10.1134/S1070428009100170

N-Nitrobenzimidazol-2-ones readily undergo rearrangement to C-nitro derivatives on heating in various solvents (ethyl acetate, butyl acetate, acetonitrile, acetone, dioxane, o-dichlorobenzene, anisole, acetic acid). This rearrangement was used to develop

Full text of DOI:10.1134/S1070428009100170

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 10, pp. 1523–1527. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © E.V. Tatarnikova, V.V. Sizov, A.V. Aleksandrov, I.V. Tselinskii, 2009, published in Zhurnal Organicheskoi Khimii, 2009, Vol. 45,
No. 10, pp. 1539–1543.
Nitro Derivatives of 1,3-Dihydrobenzimidazol-2-one:
II.* Rearrangement of N-Nitrobenzimidazol-2-ones
E. V. Tatarnikova, V. V. Sizov, A. V. Aleksandrov, and I. V. Tselinskii
St. Petersburg State Institute of Technology, Moskovskii pr. 26, St. Petersburg, 190013 Russia
e-mail: vvsizov@list.ru
Received April 1, 2009
Abstract—N-Nitrobenzimidazol-2-ones readily undergo rearrangement to C-nitro derivatives on heating in
various solvents (ethyl acetate, butyl acetate, acetonitrile, acetone, dioxane, o-dichlorobenzene, anisole, acetic
acid). This rearrangement was used to develop a procedure for the synthesis of 4,5,6,7-tetranitro-1,3-
dihydrobenzimidazol-2-one in high yield (90–96%) by nitration of 1,3-dihydrobenzimidazol-2-one, as well as
of 5,6-dinitro- and 4,5,6-trinitro-1,3-dihydrobenzimidazol-2-ones, with a small excess of concentrated nitric
acid in a mixture with acetic anhydride and acetic acid at 50–60°C.
DOI: 10.1134/S1070428009100170
In the preceding communication [1] we reported on
the synthesis of hitherto unknown 1,4,5,6-tetranitro-
azole [6, 7], pyrazole [8–10], and indazole [11] were
described. This rearrangement is performed in practice
by prolonged heating of a solution of an N-nitro com-
pound in a high-boiling solvent, such as anisole, nitro-
benzene, toluene, or chlorobenzene, at a temperature
2
,3-dihydro-1H-benzimidazol-2-one (I), 1,3,5,6-tetra-
nitro-2,3-dihydro-1H-benzimidazol-2-one (II), and
,5,6-trinitro-2,3-dihydro-1H-benzimidazol-2-one
III). In continuation of our studies in this line, in the
1
(
o
above 110 C. As a result, the corresponding C-nitro
derivatives are formed in high yields. The thermal rear-
rangement is an irreversible intramolecular first-order
reaction [5, 6, 9–11]. Its mechanism is likely to involve
present work we examined some chemical transforma-
tions of N-nitro compounds I–III, namely their rear-
rangement into the corresponding C-nitro derivatives,
which occurred on heating in various organic solvents.
[1,5]-sigmatropic migration of nitro group, followed
by fast tautomerization.
Acid-catalyzed rearrangement of aromatic N-nitro
amines (Bamberger rearrangement) involving migra-
tion of nitro group from nitrogen atom to the aromatic
ring was the subject of numerous studies [2, 3].
Another version of such intramolecular rearrangement,
so-called thermal rearrangement in N-nitro compounds,
has been studied to a lesser extent. This reaction was
reported in a few publications where rearrangements of
some N-nitro derivatives of imidazole [4, 5], 1,2,4-tri-
We have found that analogous rearrangement of
N-nitrobenzimidazol-2-ones I–III occurs under con-
siderably milder conditions. In such solvents as ace-
tone and acetonitrile, slow rearrangement of I–III is
observed even at room temperature.
The rearrangement of 1,4,5,6-tetranitro-2,3-dihy-
dro-1H-benzimidazol-2-one (I) on heating in organic
solvents was most selective: the products were 4,5,6,7-
Scheme 1.
NO2
NO2
H
N
H
N
O N
O N
O N
2
2
N
2
Δ
O
O
+
O
N
H
N
H
N
H
O N
2
O N
2
O N
2
NO2
NO2
NO2
I
IV
V
*
For communication I, see [1].
1
523

1
524
TATARNIKOVA et al.
Table 1. Rearrangement of 1,4,5,6-tetranitro-2,3-dihydro-1H-benzimidazol-2-one (I) in different solvents
a
Product composition, mol %
Temperature,
Reaction
time, h
Solvent
°C
V
13.0
86.0
97.5
09.0
07.0
25.0
98.0
77.0
23.0
95.0
25.0
07.0
100.00
IV
Acetic acid
Methanol
055
050
050
065
065
080
075
100
055
100
126
065
110
5.0
3.0
3.0
2.0
2.0
0.5
1.0
0.5
0.5
0.5
0.1
3.0
0.2
87.0
14.0
02.5
91.0
93.0
75.0
02.0
23.0
77.0
05.0
75.0
93.0
0.
Isopropyl alcohol
Ethyl acetate
Ethyl acetate–dichloroethane (1:1)
Acetonitrile
b
Anisole
b
Dioxane
Acetone
b
o-Dichlorobenzene
Butyl acetate
Butyl acetate
b
Toluene
a
According to the HPLC data.
Compound I is poorly soluble in these solvents.
b
tetranitro and 4,5,6-trinitro derivatives IV and V
whose ratio depended on the conditions (Scheme 1,
Table 1).
C-nitro compounds IV and V increases in parallel with
the number of nitro groups in the initial N-nitro deriv-
ative. Presumably, the process follows a radical pattern
where the rate-determining step is homolytic dissocia-
tion of the N–N bond in initial N-nitro compound. The
data in Tables 1 and 2 show that the denitration prod-
uct is formed with the largest yield by rearrangement
of the least strained 1,5,6-trinitro derivative III; under
analogous conditions, tetranitro derivatives I and II
As might be expected, 1,3,5,6-tetranitro-2,3-dihy-
dro-1H-benzimidazol-2-one (II) under analogous con-
ditions gave rise to a mixture of denitration product,
5
,6-dinitro-2,3-dihydro-1H-benzimidazol-2-one (VI),
with compounds V and IV, the latter prevailing
Scheme 2, Table 2). A mixture of compounds IV–VI
was also formed in the rearrangement of 1,5,6-trinitro-
,3-dihydro-1H-benzimidazol-2-one (III), e.g., in
(
Scheme 2.
2
NO2
butyl acetate (Scheme 3, Table 2). This unexpected
result indicates that the rearrangement of N-nitrobenz-
imidazolones cannot be regarded as strictly intra-
molecular.
O N
2
N
Δ
O
IV
+
V
N
O N
2
NO2
Some general relations were revealed while study-
ing the rearrangement should be noted. The yield of
II
H
N
O N
2
Table 2. Rearrangements of 1,3,5,6-tetranitro-2,3-dihydro-
+
O
1
1
H-benzimidazol-2-one (II) and 1,5,6-trinitro-2,3-dihydro-
H-benzimidazol-2-one (III) in butyl acetate at 70°C
N
H
O N
2
VI
(reaction time 3 h)
a
Scheme 3.
Product composition, mol %
Initial compound
no.
NO2
IV
V
VI
O N
2
N
Δ
II
63.4
05.0
28.4
50.0
08.2
45.0
IV
+
V
+
VI
O
III
N
O N
2
H
a
According to the HPLC data.
III
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 10 2009

NITRO DERIVATIVES OF 1,3-DIHYDROBENZIMIDAZOL-2-ONE: II.
1525
give rise to higher yield of C-nitro derivatives. The
N-nitro group in 1,3,5,6-tetranitrobenzimidazolone II
is the most reactive. Unlike compounds I and III, dis-
solution of 1,3,5,6-tetranitro derivative II in ethanol is
accompanied by elimination of one N-nitro group with
quantitative formation of compound III (the reaction is
complete in 1 min). For comparison, complete N-de-
nitration of 1,4,5,6-tetranitrobenzimidazolone I in
ethanol at room temperature requires 36 h.
AcOH) afforded 87% of 1,3-dimethyl-4,5,6-trinitro-
2,3-dihydro-1H-benzimidazol-2-one (IX) (Scheme 5).
Scheme 5.
NO2
Me
Me
98–99% HNO –Ac O
AcOH, 55–60°C, 4 h
3
2
O N
2
N
N
O
O
87%
N
N
O N
2
Me
Me
It is not advisable to carry out the rearrangement in
a boiling solvent even if its boiling point is not high.
Elevated temperature is likely to favor denitration of
N-nitrobenzimidazolones. Poor solubility of N-nitro
compound I in high-boiling aromatic solvents (anisole,
o-dichlorobenzene, toluene) is a factor favoring deni-
tration, and the major product is 4,5,6-trinitrobenzim-
idazolone V.
VIII
IX
It is known that [12–17] aromatic N-nitro amines,
such as N-nitroaniline and N-nitropyridin-2-amine, in
aqueous solutions of strong acids undergo rearrange-
ment involving migration of the nitro group into the
aromatic ring. The major products of this rearrange-
ment are the corresponding ortho-nitro derivatives,
though some amounts of para-nitro derivatives were
also detected. The yield of the rearrangement products
exceeds 95% at high acidity of the medium. Low acid
concentration favors tarring. The authors presumed
The yield of compound IV in the rearrangement of
1
,4,5,6-tetranitrobenzimidazolone I in acetic acid was
unexpectedly high. This prompted us to develop a pro-
cedure for the synthesis of 4,5,6,7-tetranitro derivative
IV by nitration of 5,6-dinitro-2,3-dihydro-1H-benzim-
idazol-2-one (VI) or 4,5,6-trinitro-2,3-dihydro-1H-
benzimidazol-2-one (V) under mild conditions appro-
priate for both nitration at the nitrogen atom and N→C
migration of the nitro group in N-nitrobenzimidazolone
derivatives. We examined nitration of compounds V
and VI with nitric acid in acetic anhydride (HNO3–
[
12–17] that the rearrangement is intramolecular.
According to the HPLC data, dissolution of 1,3,5,6-
tetranitrobenzimidazolone II in 93% H SO at room
2
4
temperature is accompanied by its fast (within ~1 min)
disappearance, and the concentration of the corre-
sponding C-nitro derivatives, 4,5,6-trinitrobenzimid-
azolone V and 4,5,6,7-tetranitrobenzimidazolone IV
gradually increases (Table 3). These findings suggest
that the rearrangement is not intramolecular. Presum-
ably, the initial step is fast denitration of 1,3,5,6-tetra-
nitrobenzimidazolone II, and next follows nitration of
Ac O molar ratio 1:1) with addition of acetic acid at
2
5
0–60°C. The nitration of 5,6-dinitrobenzimidazolone
VI with nitric acid (4.5 mol of HNO per mole of VI;
3
reaction time 5 h) at 55°C gave 4,5,6,7-tetranitro
derivative IV in 96% yield, while the fraction of
the denitrated product with 2 equiv of HNO3.
4
0
,5,6-trinitrobenzimidazolone V was less than
.3 mol %. Analogous results were obtained in the
To conclude, we showed that N-nitrobenzimidazo-
lones I–III readily undergo rearrangement into the cor-
responding C-nitro derivatives on heating in various
organic solvents (ethyl acetate, butyl acetate, aceto-
nitrile, acetone, dioxane, o-dichlorobenzene, anisole).
The ease of this rearrangement allowed us to develop
a procedure for the synthesis of 4,5,6,7-tetranitro-2,3-
nitration of compound V. Larger amount of nitric acid
was necessary for the nitration of 2,3-dihydro-1H-ben-
zimidazol-2-one (VII) to 4,5,6,7-tetranitro derivative
IV; in this case, compound IV was formed in 92%
yield (Scheme 4).
Scheme 4.
Table 3. Transformation of 1,3,5,6-tetranitro-2,3-dihydro-
1H-benzimidazol-2-one (II) in 93% sulfuric acid at 20–25°C
H
N
98–99% HNO –Ac O
3 2
AcOH, 55–60°C, 8 h
O
IV
a
Product composition, mol %
Reaction
9
2%
N
H
time, h
IV
V
VI
VII
0
2
7
1
4
2
–
–
13.00
63.00
98.54
87.00
37.00
00.16
1
,3-Dimethyl-2,3-dihydro-1H-benzimidazol-2-one
(
VIII) is a compound for which the rearrangement
under study is impossible. The nitration of VIII under
analogous conditions (HNO –Ac O molar ratio 1:1,
1.30
a
According to the HPLC data.
3
2
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 10 2009

1
526
TATARNIKOVA et al.
dihydro-1H-benzimidazol-2-one (IV) in high yield
mixture was kept for 2 h at 20°C. The precipitate was
filtered off, thoroughly washed with 1,2-dichloro-
ethane, and dried under reduced pressure over NaOH.
Yield 6.6 g (67%), colorless crystals, mp 120–121°C
(decomp.). IR spectrum, ν, cm : 3390, 3135 (CH),
2887 (CH), 1818 (CH), 1633 (C=O), 1606 (C=O,
(
5
90–96%) by nitration of benzimidazol-2-one (VII),
,6-dinitrobenzimidazolone VI, and 4,5,6-trinitroben-
zimidazolone V using a small excess of concentrated
nitric acid in a mixture with acetic anhydride and
acetic acid at 50–60°C.
–
1
C=C), 1543 (C–NO ), 1470 (C=C), 1385 (C=C), 1361
2
EXPERIMENTAL
(C–NO ), 1267 (N–NO ), 1232, 1143 (NH), 1060
2
2
(
(
(
N–N), 910, 890, 853, 820 (CH), 770 (CH), 757
1
The IR spectra were recorded on a Shimadzu FTIR
N–NO ), 733, 703 (N–NO ), 657. H NMR spectrum
2
2
8
400 spectrometer from samples prepared as KBr
acetone-d ): δ 8.80 ppm, s (2H). Found, %: C 26.77;
6
1
pellets. The H NMR spectra were measured on
a Bruker WM-400 instrument at 400 MHz using hexa-
methyldisiloxane as internal reference. The elemental
compositions were determined on a Hewlett–Packard
H 0.64; N 26.75. C H N O . Calculated, %: C 26.50;
7
2
6
9
H 0.61; N 26.54.
,5,6-Trinitro-2,3-dihydro-1H-benzimidazol-2-
one (III). Nitric acid (98–99%), 3.5 ml, was added at
0–25°C to 8 ml of acetic anhydride, and 2 g
8.9 mmol) of compound VI was added in small
1
1
85B CHN analyzer. The reaction mixtures were ana-
2
(
lyzed by HPLC on a Milikhrom liquid chromatograph
equipped with a spectrophotometric detector (working
wavelength λ 250 nm); Silasorb C18 column
portions at such a rate that the temperature did not
exceed 20°C. The mixture was kept for 2 h at 20°C,
and the precipitate was filtered off, thoroughly washed
with 1,2-dichloroethane, and dried under reduced pres-
sure over NaOH. Yield 1.9 g (78%), colorless crystals,
(
LaChema, Czechia), 63 mm×2 mm, grain size 5 μm;
eluent water–acetonitrile–acetic acid, 100:22:1 (by
weight), flow rate 100 μl/min; sample volume 2–4 μl.
Listed below are compound no. and retention time, s:
VI, 243; V, 380, I, 485; III, 569; IV, 957. The com-
ponents were quantitated by the internal normalization
technique using calibration factors.
–
1
mp 141–143°C (decomp.) IR spectrum, ν, cm : 3362
NH), 3164 (CH), 3133 (CH), 3078 (CH), 1773 (CH),
629 (C=O), 1593 (C=O, C=C), 1546 (C–NO ), 1487
(
1
(
2
C=C), 1460 (C=C), 1339 (C–NO ), 1253 (N–NO ),
2 2
5
,6-Dinitro-2,3-dihydro-1H-benzimidazol-2-one
VI) and 4,5,6-trinitro-2,3-dihydro-1H-benzimidazol-
-one (V) were synthesized according to the proce-
dures described in [1, 18].
,4,5,6-Tetranitro-2,3-dihydro-1H-benzimidazol-
1170 (NH), 1079 (N–N), 856, 826 (CH), 743 (CH),
1
(
2
719 (N–NO
2
), 654, 619, 560 (N–NO
2
). H NMR spec-
trum (acetone-d
), δ, ppm: 7.90 s (1H, Harom), 8.55 s
6
(1H, Harom), 12.05 s (1H, NH). Found, %: C 31.34;
H 1.56; N 25.94. C H N O . Calculated, %: C 31.24;
7
3
5
7
1
H 1.12; N 26.02.
2
-one (I). Acetic anhydride, 8 ml, was added at 20–
2
5°C to 7 ml of 98–99% nitric acid, and 1 g (3.7 mmol)
Rearrangement of N-nitrobenzimidazolones I–
III into C-nitro compounds (general procedure).
A mixture of 0.1 g of N-nitrobenzimidazolone I–III
and 10 ml of appropriate solvent was heated as long as
necessary at a required temperature. The mixture was
then cooled to 20–25°C and evaporated, and the solid
residue was analyzed by HPLC. For reaction condi-
tions and product yields, see Tables 1 and 2.
of compound V was added in small portions under
stirring. The mixture was stirred for 7 h at 20°C, and
the precipitate was filtered off, thoroughly washed
with 1,2-dichloroethane, and dried under reduced pres-
sure over NaOH. Yield 0.44 g (43%), colorless crys-
–
1
tals, mp 144–145°C (decomp.). IR spectrum, ν, cm :
435 (NH), 3126 (C–N, CH), 1825, 1796 (CH), 1622
3
(
(
1
6
C=O, C=C), 1558 (C–NO ), 1484 (C=C), 1446, 1398
Transformation of 1,4,5,6-tetranitro-2,3-dihy-
dro-1H-benzimidazol-2-one (I) in 93% sulfuric
acid. A solution of 1 g (3.2 mmol) of compound I in
10 ml of 93% sulfuric acid was stirred for a required
time at room temperature. The mixture was poured
into 100 ml of cold water, and the precipitate was
filtered off, washed with water, and dried in air. The
product composition and ratio were determined by
HPLC (Table 3).
2
C=C), 1345 (C–NO ), 1259 (N–NO ), 1152 (C–N),
2
2
082, 931 (N–N), 822 (CH), 760 (CH), 740 (N–NO ),
2
1
64, 649, 564. H NMR spectrum (acetone-d ):
6
δ 8.95 ppm, s (1H). 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
1
,3,5,6-Tetranitro-2,3-dihydro-1H-benzimidazol-
2
-one (II). Acetic anhydride, 50 ml, was added at 20–
2
5°C to 50 ml of 98–99% nitric acid, 7 g (31.2 mmol)
4,5,6,7-Tetranitro-2,3-dihydro-1H-benzimidazol-
2-one (IV). a. Acetic anhydride, 5 g (49.0 mmol), and
of compound VI was added in small portions, and the
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 10 2009

NITRO DERIVATIVES OF 1,3-DIHYDROBENZIMIDAZOL-2-ONE: II.
1527
acetic acid, 5 g (83.3 mmol), were mixed at 20–25°C
with 3 g (46.6 mmol) of 98–99% nitric acid, 2 g
(C=C), 1462, 1428 (C=C), 1357 (NO ), 1334, 1265,
2
1238 (NO ), 1170, 1115, 993, 923, 858 (δC–Harom),
2
1
(
8.9 mmol) of 5,6-dinitrobenzimidazolone VI was
817, 779, 769, 755, 743, 668, 574. H NMR spectrum
added, and the mixture was stirred for 5 h at 55°C,
cooled to room temperature, and poured into 150 ml of
water. The precipitate was filtered off, thoroughly
washed with water, and dried at 80°C. According to the
HPLC data, the crude product contained 0.3 mol % of
(DMSO-d ), δ, ppm: 3.32 s (3H, CH ), 3.52 s (3H,
6
3
CH ), 8.41 s (1H, 7-H). Found, %: C 36.26; H 2.58;
3
N 23.74. C H N O . Calculated, %: C 36.37; H 2.37;
9
7
5
7
N 23.57.
4
2
,5,6-trinitrobenzimidazolone V as impurity. Yield
REFERENCES
.7 g (96%), bright yellow crystals, mp 317–319°C
–
1
(
(
(
(
decomp.). IR spectrum, ν, cm : 3401 (NH), 3138
C–N, Carom), 1752 (Carom), 1618 (C=O, C=C), 1550
NO ), 1501 (C=C), 1400 (C=C), 1339 (NO ), 1206
1. Tatarnikova, E.V., Sizov, V.V., and Tselinskii, I.V., Russ.
J. Org. Chem., 2009, vol. 45, p. 872.
2. Agrawal, J.P. and Hodgson, R.D., Organic Chemistry of
Explosives, New York: Wiley, 2007, p. 145.
2
2
NO ), 1054, 987, 931, 911, 864 (C–Harom), 760, 690,
2
1
4
43. H NMR spectrum (DMSO-d ): δ 13.0 ppm, br.s
3. 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.
6
(
2H, NH). Found, %: C 26.76; H 0.69; N 26.63.
C H N O . Calculated, %: C 26.77; H 0.64; N 26.75.
7
2
6
9
b. 4,5,6-Trinitrobenzimidazolone V, 2 g (7.7 mmol),
4
. Damavarapu, R., Jayasuriya, K., Vladimiroff, T., and
Iyer, S., US Patent no. 5387297, 1994; Chem. Abstr.,
was added to acid mixture prepared as described above
in a. The mixture was stirred for 6 h at 60°C, cooled to
room temperature, and poured into 150 ml of water,
and the precipitate was filtered off, thoroughly washed
with water, and dried at 80°C. Yield 2.1 g (90%),
bright yellow crystals, mp 318–319°C (decomp.).
1
995, vol. 123, no. 256634x.
5
6
7
. Grimmett, M.R., Hua, S.-T., Chang, K.-C., Foley, S.A.,
and Simpson, J., Aust. J. Chem., 1989, vol. 42, p. 1281.
. Habraken, C.L. and Cohen-Fernandes, P., J. Chem. Soc.,
Chem. Commun., 1972, no. 2, p. 37.
c. Acetic anhydride, 13 g (127.3 mmol), and acetic
. Pevzner, M.S., Kulibabina, T.N., Ioffe, S.L., Masli-
na, I.A., Gidaspov, B.V., and Tartakovskii, V.A., Khim.
Geterotsikl. Soedin., 1979, p. 550.
acid, 8 g (133.3 mmol), were mixed at 20–25°C with
7
.6 g (118.2 mmol) of 98–99% nitric acid, 2.7 g
(
(
5
2
20.1 mmol) of 2,3-dihydro-1H-benzimidazol-2-one
VII) was added, and the mixture was stirred for 8 h at
5–60°C, cooled to room temperature, and poured into
50 ml of water. The precipitate was filtered off,
8
9
. Kanishchev, M.I., Korneeva, N.V., Shevelev, S.A., and
Fainzil’berg, A.A., Khim. Geterotsikl. Soedin., 1988,
p. 435.
. Janssen, J.W.A.M. and Habraken, C.L., J. Org. Chem.,
thoroughly washed with water, and dried at 80°C.
According to the HPLC data, the crude product con-
tained 3 mol % of 4,5,6-trinitrobenzimidazolone V as
impurity. Yield 5.8 g (92%), bright yellow crystals,
mp 316–317°C (decomp.).
1971, vol. 36, p. 3081.
1
0. Janssen, J.W.A.M., Koeners, H.J., Kruse, C.G., and
Habraken, C.L., J. Org. Chem., 1973, vol. 38, p. 1777.
1
1. Cohen-Fernandes, P. and Habraken, C.L., J. Org.
Chem., 1971, vol. 36, p. 3084.
1
,3-Dimethyl-4,5,6-trinitro-2,3-dihydro-1H-ben-
zimidazol-2-one (IX). Acetic anhydride, 13 g
127.3 mmol), and acetic acid, 8 g (133.3 mmol), were
12. Banthorpe, D.V., Thomas, J.A., and Williams, D.L.H.,
J. Chem. Soc., 1965, p. 6135.
(
13. Banthorpe, D.V., Hughes, E.D., and Williams, D.L.H.,
J. Chem. Soc., 1964, p. 5349.
14. Brownstein, S., Bunton, C.A., and Hughes, E.D.,
mixed at 20–25°C with 7.6 g (118.2 mmol) of 98–99%
nitric acid, 2.5 g (15.4 mmol) of 1,3-dimethyl-2,3-di-
hydro-1H-benzimidazol-2-one (VIII) was added, and
the mixture was stirred for 4 h at 55–60°C, cooled to
room temperature, and poured into 250 ml of water.
The precipitate was filtered off, thoroughly washed
with water, and dried at 80°C. Yield 4.0 g (87%), yel-
low crystals, mp 202–204°C (decomp.; from EtOH).
J. Chem. Soc., 1958, p. 4354.
15. White, W.N., Lazdins, D., and White, H.S., J. Am.
Chem. Soc., 1964, vol. 86, p. 1517.
16. White, W.N., Hathaway, C., and Huston, D., J. Org.
Chem., 1970, vol. 35, p. 737.
17. Bradfield, A.E. and Orton, K.J.P., J. Chem. Soc., 1929,
–
1
IR spectrum, ν, cm : 3473, 3099 (C–Harom), 3070
p. 915.
(
(
C–Harom), 2960, 2893 (CH ), 1741 (Carom), 1621
18. Schindlbauer, H. and Kwiecinski, W., Monatsh. Chem.,
3
C=O, C=C), 1611 (C=O, C=C), 1547 (NO ), 1511
1976, vol. 107, p. 1307.
2
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 10 2009