Generation of oxodiazonium ions 2.* Synthesis of benzotetrazine-1,3- dioxides from 2-(tert-butyl-NNO-azoxy)-N-nitroanilines

Article abstract of DOI:10.1007/s11172-011-0310-9

A new method for the synthesis of benzotetrazine-1,3-dioxides was developed, which involves the reaction of 2-(tert-butyl-NNO-azoxy)-N- nitroanilines with the Ac₂O/H₂SO₄ system. This method was also used for the synthesis of [1,2,5]oxadiazolo[3,4-c]cinnoline-5- oxide from 3-nitramino-4-phenylfurazan. The suggested mechanism of these reactions involves the formation of the intermediate oxodiazonium ion, resulting from acetylation of the oxygen atom of the nitramine group, followed by protonation and ionic dissociation. Then the oxodiazonium ion enters the intramolecular reaction with the neighboring tert-butyl-NNO-azoxy or phenyl group to form the corresponding heterocyclic systems.

Full text of DOI:10.1007/s11172-011-0310-9

Russian Chemical Bulletin, International Edition, Vol. 60, No. 10, pp. 2040—2045, October, 2011
2040
Generation of oxodiazonium ions
2.* Synthesis of benzotetrazineꢀ1,3ꢀdioxides
from 2ꢀ(tertꢀbutylꢀNNOꢀazoxy)ꢀNꢀnitroanilines
M. S. Klenov, V. P. Zelenov, A. M. Churakov, Yu. A. Strelenko, and V. A. Tartakovsky
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (495) 135 5328. Eꢀmail: churakov@ioc.ac.ru
A new method for the synthesis of benzotetrazineꢀ1,3ꢀdioxides was developed, which inꢀ
volves the reaction of 2ꢀ(tertꢀbutylꢀNNOꢀazoxy)ꢀNꢀnitroanilines with the Ac2O/H2SO4 sysꢀ
tem. This method was also used for the synthesis of [1,2,5]oxadiazolo[3,4ꢀc]cinnolineꢀ5ꢀoxide
from 3ꢀnitraminoꢀ4ꢀphenylfurazan. The suggested mechanism of these reactions involves the
formation of the intermediate oxodiazonium ion, resulting from acetylation of the oxygen atom
of the nitramine group, followed by protonation and ionic dissociation. Then the oxodiazonium
ion enters the intramolecular reaction with the neighboring tertꢀbutylꢀNNOꢀazoxy or phenyl
group to form the corresponding heterocyclic systems.
Key words: 1,2,3,4ꢀtetrazineꢀ1,3ꢀdioxides, cinnolines, azoxy compounds, nitramines, oxoꢀ
diazonium cation, electrophilic aromatic substitution, 1H, 13C, and 14N NMR spectroscopy.
We have previously developed the methods for syntheꢀ
acid anhydrides and strong mineral acids have recently5
been used. The main purpose of this work is to study the
possibility of using the Ac2O/H2SO4 system for cyclizaꢀ
tion of 2ꢀ(tertꢀbutylꢀNNOꢀazoxy)ꢀNꢀnitroanilines in BTDO.
2ꢀ(tertꢀButylꢀNNOꢀazoxy)ꢀNꢀnitroaniline and its monoꢀ
and dibromosubstituted derivatives were chosen as model
compounds.
Synthesis of the initial compounds. Nitration of 2ꢀ(tertꢀ
butylꢀNNOꢀazoxy)anilines 1а—с with nitronium tetrafluꢀ
oroborate in MeCN as a solvent at –30 °C (Scheme 2)
resulted in Nꢀnitroamines 2а—с.
Acetylation with acetyl chloride of the silver salt obꢀ
tained from nitramine 2b made it possible to synthesize
NꢀnitroꢀNꢀacetyl compound 3b in a moderate yield
(Scheme 3). No product of Оꢀacetylation of nitramine
was observed.
sis of benzotetrazineꢀ1,3ꢀdioxides (BTDO) by the reacꢀ
tion of 2ꢀ(tertꢀbutylꢀNNOꢀazoxy)ꢀNꢀnitroanilines with
nitrating2,3 (N2O5, NO2BF4) or phosphorylating4 (P4O10,
PCl5) agents. In these reactions, the assumed mechanism
of formation of 1,2,3,4ꢀtetrazineꢀ1,3ꢀdioxide ring includes
the formation of the oxodiazonium ion reacting with the
adjacent azoxy group (Scheme 1). The oxodiazonium ion
is formed by the reaction of the nitramine group with
nitrating or phosphorylating agents.
A drawback of the synthesis of BTDO using nitrating
agents is poor availability or high cost of the latter. When
phosphorylating agents are used for the synthesis of BTDO,
the yield of the desired product depends considerably on
the substituents in the benzene ring.
For cyclization of some 3ꢀnitraminoꢀ4ꢀ(RꢀNNOꢀ
azoxy)furazans in [1,2,5]oxadiazolo[3,4ꢀe][1,2,3,4]tetrꢀ
azineꢀ4,6ꢀdioxide, the systems consisting of carboxylic
The product obtained from compound 1a was identiꢀ
cal to the earlier described4 nitramine 2a. The structures
Scheme 1
* For Part 1, see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2003—2008, October, 2011.
1066ꢀ5285/11/6010ꢀ2040 © 2011 Springer Science+Business Media, Inc.

Oxodiazonium ions
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 10, October, 2011
2041
Scheme 2
Scheme 4
i. Ac2O, H2SO4.
i. NO2BF4, –30 °C.
R1 = R2 = H (a), R1 = H, R2 = Br (b), R1 = R2 =Br (c)
R1 = R2 = H (a), R1 = H, R2 = Br (b), R1 = R2 = Br (c)
When catalytic amounts of 93% H2SO4 (10 mol.%
with respect to nitramine) are used at 0 °C, the reaction
rate is very low: the total conversion of the starting nitrꢀ
amine is attained within 2—10 days depending on the subꢀ
strate. The temperature increase to 25 °C slightly accelerates
the reaction (the reaction time was from 12 h to 2 days).
An increase in the amount of H2SO4 to 1 equiv. allows
nitramines 2a,b to be transformed into the corresponding
BTDO 4a,b within 5 min at 0 °C in almost quantitative
yields. At the same time, ring closure of nitramine 2с
requires 1 day under the same conditions and the yield of
BTDO 4с does not exceed 84%. An increase in the amount
of sulfuric acid to 10 equiv. shortens the cyclization of
nitramine 2с to 5 min. A fairly low reaction rate of nitroꢀ
aniline 2с and the low yield of BTDO 4с can be explained
by the steric effect of the Br atom at the orthoꢀposition to
the tertꢀbutylꢀNNOꢀazoxy group.
The reactions using 1 equiv. of sulfuric acid are most
suitable for preparative synthesis of BTDO 4a,b (see Table 1,
entries 3 and 6). After hydrolysis of excess Ac2O, the deꢀ
sired tetrazineꢀ1,3ꢀdioxides 4a,b were isolated in quantiꢀ
tative yields by extraction with CH2Cl2. The conditions of
entry 11 presented in Table 1 are optimum for synthesis of
BTDO 4с. Tetrazineꢀ1,3ꢀdioxide 4с precipitates in an alꢀ
Scheme 3
i. 1) AgNO3, NH3•H2O, 2) AcCl, Et2O, –30→0 °C.
of nitramines 2b,c and NꢀnitroꢀNꢀacetyl compound 3b
were confirmed by the 1H, 13C, and 14N NMR spectra. In
the 13C NMR spectra of these compounds, the signals
were completely assigned using the 2D 1H—13C NMR
spectra (HMBC and HSQC).
Synthesis of BTDO 4а—с by the reaction of nitramines
2а—с with the Ac2O/H2SO4 system. The reaction of
2ꢀ(tertꢀbutylꢀNNOꢀazoxy)ꢀNꢀnitroanilines 2а—с with
Ac2O starts only after the addition of H2SO4. As a result,
BTDO 4а—с are formed in good yields (Scheme 4, Table 1).
Table 1. Synthesis of BTDO 4a—c from nitramines 2a—c
Entry
Nitramine 2
Mole ratio
2 : H2SO4
T/°Ca
Reaction
time
BTDO
Yield of BTDO 4
(%)b
1
2
3
4
5
6
7
8
2a
2a
2a
2b
2b
2b
2b
2c
2c
2c
2c
1 : 0.1
1 : 0.1
1 : 1
1 : 0.1
1 : 0.1
1 : 1
1 : 10
1 : 0.1
1 : 0.1
1 : 1
25
0
0
25
0
0
25
0
25
0
12 h
4a
4a
4a
4b
4b
4b
4b
4c
4c
4c
4c
99
98
99
98
96
97
98
60
71
84
86c
02 days
05 min
02 days
07 days
05 min
02 min
10 days
02 days
01 day
05 min
9
10
11
1 : 10
0
а Reaction temperature.
b The yields of BTDO 4a—c were determined from the 1Н NMR spectra. The conversion of compounds 2a—c is complete.
c The yield of BTDO 4c based on the isolated product. The conversion of compound 2c is complete.

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Klenov et al.
Scheme 5
i. conc. HNO3 (3—5 equiv.), Ac2O, 0 °С, 5 min; ii. 93% H2SO4 (10 equiv.), 0 °С, 15 min.
Scheme 6
most pure form partially from the reaction mixture and
partially after dilution of the reaction mixture with water.
Synthesis of BTDO 4b,c was also carried out directly
from 2ꢀ(tertꢀbutylꢀNNOꢀazoxy)anilines 1b,c (Scheme 5,
Table 2). For this purpose, an excess of concentrated
HNO3 was first added to a solution of aniline 1b,c in
acetic anhydride until the starting compound disappeared
completely. This resulted in the formation of nitramines
2b,c (TLC monitoring). Then an excess of H2SO4 was
added to the reaction mixture. However, the yield of BTDO
4b,c obtained by this procedure is substantially lower,
which is due to the formation of a number of byꢀproducts
impeding the isolation of BTDO.
Assumed scheme for the generation of the oxodiazonium
ion from Nꢀnitroamines under the action of the Ас2О/H2SO4
system. It is assumed that the mechanism of formation of
the 1,2,3,4ꢀtetrazineꢀ1,3ꢀdioxide cycle in the above preꢀ
sented reactions, as well as in the reactions considered in
the previous publications,1—4 includes the step of formaꢀ
tion of oxodiazonium ion A. The mechanism proposed for
the formation of cation А from nitramines under the acꢀ
tion of the Ac2O/H2SO4 system is shown in Scheme 6.
The reaction of Ac2O with H2SO4 affords acetyl sulfate,6
which acetylates nitramine at the oxygen atom with the
formation of compound В. This compound is protonated
by sulfuric acid and eliminates a molecule of AcOH yieldꢀ
ing cation А, which further participates in the formation
of the tetrazineꢀ1,3ꢀdioxide cycle (see Scheme 1).
ternative reaction scheme could include the formation
of compound С and its transformation into compound В
due to migration of the acetyl group from the nitrogen
atom to the oxygen atom via the intraꢀ or intermolecuꢀ
lar mechanism. Additional studies were carried out to
exclude the possibility of occurrence of the reaction via
this scheme.
The conversion of NꢀnitroꢀNꢀacetyl compound 3b to
BTDO 4b (Scheme 7) was studied under the same condiꢀ
tions (reactant ratio and concentrations) used for the transꢀ
formation of nitramine 2b into BTDO 4b (see Scheme 4,
Table 1, entry 7). Compound 3b completely disappears
from the reaction mixture within 3 h at 25 °С (TLC data
Note that for topological reasons oxodiazonium catꢀ
ion A, leading to the tetrazineꢀ1,3ꢀdioxide cycle, can be
formed directly only from Оꢀacetylated compound В, but
not from Nꢀacetylated derivative С. Nevertheless, the alꢀ
1
and the yield of BTDO 4b is only 22% (data of H NMR
Table 2. Synthesis of BTDO 4b,c from anilines 1b,ca
spectroscopy). Only trace amounts of BTDO 4b and byꢀ
products are observed 5 min after the beginning of the
reaction (TLC data). At the same time, the transformaꢀ
tion of nitramine 2b into BTDO 4b was already completed
in 2 min under the same conditions (see Scheme 4, Table 1,
Aniline
HNO3
(экв.)
BTDO
Yield
(%)b
1b
1c
5
3
4b
4c
73
60
1
entry 7), the yield of BTDO 4b is 98% (data of H NMR
а Reaction time was 5 min.
b The yields of BTDO 4b,c based on the isolated product. The
conversion of compounds 1b,c is complete.
spectroscopy), and no even trace amounts of NꢀnitroꢀNꢀ
acetyl compound 3b are observed in the reaction mixture
(TLC data).

Oxodiazonium ions
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 10, October, 2011
2043
Схема 7
Unidentified products
i. Ac2O, 93% H2SO4 (10 equiv.), 25 °С, 3 h.
Scheme 8
Thus, it can be asserted that almost no NꢀnitroꢀNꢀ
acetyl compound 3b is formed in the reaction of nitramine
2b with the Ас2О/H2SO4 system (see Scheme 4), i.e., the
reaction of the nitramine group with the Ас2О/H2SO4
system includes mainly Оꢀ rather than Nꢀacetylation,
although Nꢀacetylated nitramine is more stable than the
Оꢀacetylated analog according to the quantum chemical
calculations. For example, the difference in enthalpies of
formation between compounds 3а and 5 is 6.8 kcal mol–1
(calculation using the Gaussianꢀ98 program in the
B3LYP/6ꢀ31G(d,p) basis set).
Experimental
1
Н NMR spectra were recorded on Bruker AMꢀ300 and
Bruker DRX 500 instruments with frequencies of 300.13 and
500.13 MHz, respectively. 13С and 14N NMR spectra were meaꢀ
sured on a Bruker DRX 500 instruments with frequencies of
125.76 and 36.14 MHz, respectively. Chemical shifts are preꢀ
sented relative to Me4Si (1H, 13C) or MeNO2 14N, external
(
standard, the upfield chemical shifts are negative). IR spectra
were recorded on a Specord Mꢀ80 spectrometer. Mass spectra
were obtained on a Kratos MSꢀ300 instrument (EI, 70 eV). Only
peaks with isotopes 79Br are given for the fragments containing
bromine atoms. The reaction course and purity of the comꢀ
pounds were monitored by thin layer chromatography (Silufol
UVꢀ254 and Merck 60 F254). Silica gel was used for preparative
thin layer chromatography. 2ꢀ(tertꢀButylꢀNNOꢀazoxy)aniline,7
5ꢀbromoꢀ2ꢀ(tertꢀbutylꢀNNOꢀazoxy)aniline,7 3,5ꢀdibromoꢀ2ꢀ
(tertꢀbutylꢀNNOꢀazoxy)aniline,7 and 3ꢀnitraminoꢀ4ꢀphenylꢀ
1,2,5ꢀoxadiazole1 were synthesized by known procedures. Disꢀ
tilled colorless HNO3 (d = 1.5 g cm–1) was used in the reactions.
3,5ꢀDibromoꢀ2ꢀ(tertꢀbutylꢀNNOꢀazoxy)ꢀNꢀnitroaniline (2c).
This procedure is a modification of the earlier developed proceꢀ
dure.4 To a suspension of aniline 1с (0.3 g, 0.85 mmol) in anhyꢀ
drous acetonitrile (8 mL), NO2BF4 (0.15 g, 1.12 mmol) was
added by three portions for 15 min with vigorous stirring at –35 °C
under argon. The reaction mixture was kept for 15 min at –35 °C,
and then, without rising temperature, the reaction mixture was
poured into a solution of NaHCO3 (0.8 g) in water (20 mL). The
aqueous layer was separated, washed with CH2Cl2 (3×7 mL),
and acidified with a 10% aqueous solution of HCl to pH 2. The
precipitate formed was filtered off, washed with H2O (3×5 mL),
and dried in a vacuum desiccator with P2O5. Nitramine 2с was
obtained as light yellow crystals in a yield of 211 mg (62%), m.p.
129—131 °C (decomp.). An additional amount of nitramine 2с
Reaction of 3ꢀnitraminoꢀ4ꢀphenylfurazan 6 with the
Ас2О/H2SO4 system. To confirm that the oxodiazonium
ion is formed from nitramines under the action of acetyl
sulfate, this cation was "captured" on the benzene ring in
the intramolecular reaction of electrophilic aromatic subꢀ
stitution. These reactions of oxodiazonium cations generꢀ
ated from nitramines or their Oꢀmethyl derivatives were
considered previously.1
The interaction of nitramine 6 with 2 equiv. of H2SO4 in
Ac2O results in furazano[3,4ꢀc]cinnolineꢀ5ꢀoxide 7 (see
Ref. 1) in 70% yield (Scheme 8). The reaction completes
within several minutes as the reaction mixture is heated from
0 to 20 °С. The probable mechanism of generation of the oxoꢀ
diazonium cation from nitramine 6 is described by Scheme 6.
Thus, we developed the new method for synthesis of
benzotetrazineꢀ1,3ꢀdioxides (BTDO) from 2ꢀ(tertꢀbutylꢀ
NNOꢀazoxy)ꢀNꢀnitroanilines under the action of the
Ас2О/H2SO4 system. The assumption about the transꢀ
formation of the primary Nꢀnitroamine group into the
oxodiazonium fragment [N=N=O]+ under the action of
this system was confirmed by the conversion of 3ꢀnitrꢀ
aminoꢀ4ꢀphenylfurazan 6 to furazanocinnolineꢀ5ꢀoxide 7
using as an example.

2044
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 10, October, 2011
Klenov et al.
was obtained by extraction of the combined aqueous filtrate with
CH2Cl2 (5×5 mL). The organic extracts were combined, washed
with brine (3 mL), dried (MgSO4), and evaporated in vacuo.
Additionally 56 mg (17%) of nitramine 2с were obtained as light
orange crystals. The overall yield was 79%. Found (%): С, 30.29;
H, 3.08; N, 14.09. C10H12Br2N4O3. Calculated (%): С, 30.44;
H, 3.05; N, 13.82. IR (КBr), ν/cm–1: 1244 w, 1308 s, 1360 w,
1460 w, 1488 s, 1560 w, 1596 s, 3260 s. 1H NMR (CDCl3), δ:
1.50 (s, 9 H, 3 Me); 7.79, 7.88 (both d, 1 Н each, Н(4), Н(6),
J = 2.0 Hz); 10.29 (br.s, 1 H, NH). 13C NMR (CDCl3), δ: 25.4
(Me); 61.8 (CMe3); 116.5 (C(3)); 123.5 (C(5) or C(1)); 129.3
(C(6)); 129.7 (C(1) or C(5)); 135.5 (С(4)); 140.7 (br.s, С(2)).
–43 (N—NO2, Δν1/2 = 35 Hz); –55 (N→O, Δν1/2 = 70 Hz). MS,
m/z: 313 [M + H – NO2]+.
Synthesis of BTDO 4а—c by the reaction of nitramines 2а—c
with the Ac2O/H2SO4 system (general procedure). A solution of
93% H2SO4 (the amount is given in Table 1) in Ac2O (0.1 mL)
was added in one portion to a solution of nitramine 2 (0.05 mmol)
in Ac2O (0.4 mL) with vigorous stirring under argon (the
temperature is indicated in Table 1). Then the reaction mixture
was kept at the same temperature for some time (see Table 1)
and worked up. Method A was used for the spectral determinaꢀ
tion of the yield of BTDO 4а—c. Water (2 mL) was added dropꢀ
wise to the reaction mixture at 0 °C. The mixture was stirred for
1 h at 20 °C until hydrolysis of Ac2O was completed and then
extracted with СH2Cl2 (2×3 mL). The organic extracts were
combined, washed with H2O (2 mL) and brine (1 mL), dried
(MgSO4), and evaporated in vacuo. The yields of BTDO 4a—c
were determined by 1H NMR spectroscopy after removal of the
solvent. Method B was used for the isolation of BTDO 4c. The
yellow precipitate of BTDO 4c was filtered off, washed with
H2O (0.5 mL), and dried in air. To obtain an additional amount
of product 4c, the filtrate was cooled to 0 °C, H2O (2 mL) was
added dropwise, and the mixture was stirred for 1 h at 20 °C. The
precipitate was filtered off, washed with H2O (1 mL), and dried
in air. The yield of BTDO 4c was determined from the overall
yield of the precipitates. Purity of synthesized BTDO 4c was
monitored by 1H NMR. The 1H NMR spectra of compounds
4a—c are identical to the spectra described.3
Synthesis of BTDO 4b,c from anilines 1b,c (general proceꢀ
dure). A solution of concentrated HNO3 (for the amount of
HNO3, see Table 2) in Ac2O (0.2 mL) was added on one portion
at 0 °C with vigorous stirring under argon to a solution of
aniline 1 (0.14 mmol) in Ac2O (0.5 mL). The reaction mixture
was stirred for 5 min at 0 °C, then a solution of 93% H2SO4
(0.076 mL, 1.4 mmol) in Ac2O (0.2 mL) was added in one portion,
and the mixture was stirred at 0 °C for 15 min more. To isolate
BTDO 4b, H2O (8 mL) was added dropwise at 0 °C to the reacꢀ
tion mixture, and the mixture was stirred for 1 h at 20 °C. The
mixture was cooled to 0 °C, and the yellow precipitate of BTDO
4b was filtered off, washed with H2O (2×1 mL), and dried in air.
BTDO 4b was obtained in a yield of 26 mg (73%). To isolate
BTDO 4c, the yellow precipitate was filtered off, washed with H2O
(2 mL), and dried in air. BTDO 4c was obtained in a yield of 14 mg
(30%). To obtain an additional amount of product 4c, the filtrate
was cooled to 0 °C, H2O (2 mL) was added dropwise, the mixture
was stirred for 1 h at 20 °C, and extracted with СH2Cl2 (2×4 mL).
The organic extracts were combined, washed with H2O (2 mL)
and brine (1 mL), dried (MgSO4), and evaporated in vacuo.
Product 4c was isolated by preparative TLC (petroleum ether—
CHCl3 (4 : 1, then 1 : 1) as eluent). Additional 14 mg (30%) of
BTDO 4c were obtained. The overall yield was 28 mg (60%).
Reaction of NꢀacetylꢀNꢀnitroaniline 3b with the Ac2O/H2SO4
system. A solution of 93% H2SO4 (0.015 mL, 0.28 mmol) in
Ac2O (0.1 mL) was added to a solution of NꢀacetylꢀNꢀnitroꢀ
aniline 3b (10 mg, 0.028 mmol) in Ac2O (0.4 mL) at 20 °C with
vigorous stirring under argon. The reaction mixture was kept for
3 h at 20 °C and then cooled to 0 °C, H2O (2 mL) was added
dropwise, and the mixture was stirred for 1 h at 20 °C, and
extracted with СH2Cl2 (3×2 mL). The organic extracts were comꢀ
bined, washed with brine (1 mL), dried (MgSO4), and evaporatꢀ
ed in vacuo. The yield of BTDO 4b was determined by the
1H NMR spectroscopy.
14N NMR (CDCl3), δ: –38 (N—NO2, Δν
(N→O, Δν1/2 = 130 Hz).
= 60 Hz); –60
1/2
2ꢀ(tertꢀButylꢀNNOꢀazoxy)ꢀNꢀnitroaniline (2а) was syntheꢀ
sized similarly in 50% yield, m.p. 91—92 °С (cf. Ref. 4: m.p.
91—92 °С) and is identical to the earlier obtained product4
(1Н NMR spectrum).
5ꢀBromoꢀ2ꢀ(tertꢀbutylꢀNNOꢀazoxy)ꢀNꢀnitroaniline (2b) was
synthesized similarly in 75% yield, m.p. 106—107 °C. Found (%):
С, 37.82; H, 4.16; N, 17.61. C10H13BrN4O3. Calculated (%):
С, 37.95; H, 4.12; N, 17.79. IR (КBr), ν/cm–1: 1260 s, 1312 s,
1384 w, 1472 w, 1484 s, 1580 w, 1596 s, 3236 s. 1H NMR
(CDCl3), δ: 1.50 (s, 9 H, 3 Me); 7.47 (dd, 1 Н, Н(4), J = 8.9 Hz,
J = 1.8 Hz); 8.02 (d, 1 Н, Н(3), J = 8.9 Hz); 8.25 (d, 1 Н, Н(6),
J = 1.8 Hz); 13.27 (br.s, 1 H, NH). 13C NMR (CDCl3), δ: 25.6
(Me); 60.6 (CMe3); 125.7 (C(3)); 126.2 (C(5)); 126.9 (C(6));
129.4 (C(4)); 130.7 (С(1)); 135.6 (br.s, С(2)). The signals were
assigned by means of HMBC and HSQC experiments. 14N NMR
(CDCl3), δ: –37 (N—NO2, Δν1/2 = 30 Hz); –53 (N→O, Δν
=
1/2
= 90 Hz).
NꢀAcetylꢀ5ꢀbromoꢀ2ꢀ(tertꢀbutylꢀNNOꢀazoxy)ꢀNꢀnitroaniline
(3b). A saturated aqueous solution of NH3 (0.1 mL) was added to
a suspension of nitramine 2b (0.26 g, 0.82 mmol) in distilled
water (3 mL), during this addition nitramine 2b was dissolved
completely. Then a solution of AgNO3 (0.14 g, 0.82 mmol) in
distilled water (0.5 mL) was added dropwise to the obtained
solution. A white precipitate that formed was filtered off, washed
with distilled water (3 mL) and EtOH (2 mL), and dried for 12 h
in a vacuum desiccator over P2O5. The silver salt was obtained in
a yield of 260 mg (75%) in the form of white crystals. The obꢀ
tained salt was thoroughly milled in an agate mortar and used on
the next step without additional purification. AcCl (0.02 mL,
0.28 mmol) was added as one portion to a suspension of the silver
salt (0.12 g, 0.28 mmol) in anhydrous Et2O (6 mL) at –30 °C
under argon. The reaction mixture was stirred for 3 h at 0 °C and
then kept for three days at the same temperature. The precipiꢀ
tate was filtered off and washed with Et2O (2×4 mL). The filꢀ
trates were combined, and the solvent was evaporated in vacuo.
The oily product was purified by preparative TLC (petroleum
ether—AcOEt (20 : 1) mixture as eluent). NꢀAcetylꢀNꢀnitroꢀ
aniline 3b was obtained in a yield of 40 mg (39%) as a yelꢀ
lowꢀorange oil. Found (%): С, 40.18; H, 4.19; N, 15.55.
C12H15BrN4O4. Calculated (%): С, 40.03; H, 4.21; N, 15.80.
1H NMR (CDCl3), δ: 1.37 (s, 9 H, 3 Me); 2.68 (s, 3 H, Ac); 7.51
(d, 1 Н, Н(6), J = 2.1 Hz); 7.74 (dd, 1 Н, Н(4), J = 8.7 Hz,
J = 2.1 Hz); 7.93 (d, 1 Н, Н(3), J = 8.7 Hz). 13C NMR (CDCl3)
δ: 25.3 (CMe3); 26.2 (C(O)Me); 60.1 (CMe3); 124.7 (C(5));
126.6 (C(3)); 128.9 (C(1)); 134.2 (C(6)); 134.6 (С(4)); 144.3
(br.s, С(2)); 168.6 (C(O)Me). The signals were assigned by means
of HMBC and HSQC experiments. 14N NMR (CDCl3), δ:

Oxodiazonium ions
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 10, October, 2011
2045
[1,2,5]ꢀOxadiazolo[3,4ꢀc]cinnolineꢀ5ꢀoxide (7). A solution
of 93% H2SO4 (0.017 mL, 0.3 mmol) in Ac2O (0.1 mL) was
added to a solution of 3ꢀnitraminoꢀ4ꢀphenylꢀ1,2,5ꢀoxadiazole (6)
(30 mg, 0.15 mmol) in Ac2O (1.4 mL) at 0 °C with vigorous
stirring. Cooling was removed, the reaction mixture was allowed
to warm to 20 °C and poured into water (10 mL), and the mixꢀ
ture was stirred for 1 h to complete the hydrolysis of Ac2O. The
reaction mixture was extracted with СH2Cl2 (5×5 mL), the comꢀ
bined organic extracts were washed with a saturated aqueous
solution of NaHCO3 (2×10 mL) and brine (3 mL), dried (MgSO4),
and evaporated in vacuo. Cinnolineꢀ5ꢀoxide 7 was isolated by
preparative TLC (petroleum ether—AcOEt (2 : 1) as eluent).
Cinnolineꢀ5ꢀNꢀoxide 7 was obtained in a yield of 19 mg (70%),
m.p. 167—169 °C (from CH2Cl2), and its physicochemical and
spectral characteristics are identical to the earlier syntheꢀ
sized product.1
2. A. M. Churakov, S. L. Ioffe, V. A. Tartakovsky, Mendeleev
Commun., 1991, 101.
3. A. M. Churakov, O. Yu. Smirnov, S. L. Ioffe, Yu. A. Streꢀ
lenko, V. A. Tartakovsky, Eur. J. Org. Chem., 2002, 2342.
4. A. E. Frumkin, A. M. Churakov, Yu. A. Strelenko, V. A.
Tartakovsky, Izv. Akad. Nauk, Ser. Khim., 2000, 480 [Russ.
Chem. Bull., Int. Ed., 2000, 49, 482].
5. V. P. Zelenov, A. A. Lobanova, S. V. Sysolyatin, Mater. dokl.
Mezhdunar. nauchnoꢀtekhn. i metodich. konf. "Sovremennye
problemy tekhnicheskoi khimii" [Proceedings of the International
Scientific Technical and Methodical Conference "Modern Probꢀ
lems of Technical Chemistry"] (Kazan, December 22—24, 2004),
Kazan, 2004, 337 (in Russian).
6. O. Stillich, Chem. Ber., 1905, 38, 1245.
7. A. M. Churakov, O. Yu. Smirnov, S. L. Ioffe, Yu. A. Streꢀ
lenko, V. A. Tartakovsky, Izv. Akad. Nauk, Ser. Khim., 1994,
1620 [Russ. Chem. Bull. (Engl. Transl.), 1994, 43, 1532].
The authors are grateful to V. N. Solkan (N. D. Zelinꢀ
sky Institute of Organic Chemistry, Russian Academy of
Sciences) for help in quantum chemical calculations.
This work was financially supported by the Russian
Foundation for Basic research (Project No. 10ꢀ03ꢀ00752).
References
1. M. S. Klenov, M. O. Ratnikov, A. M. Churakov, Yu. A. Streꢀ
lenko, V. A. Tartakovsky, Izv. Akad. Nauk, Ser. Khim., 2011,
523 [Russ. Chem. Bull., Int. Ed., 2011, 60, 536].
Received February 8, 2011;
in revised form March 25, 2011