The formation of aryloxenium ion in the reaction of N-nitro-O-(4- nitrophenyl)hydroxylamine with strong acids

Article abstract of DOI:10.1007/s11172-011-0346-x

The reaction of N-nitro-O-(4-nitrophenyl)hydroxylamine (1) with conc. H₂SO₄ affords 4-nitropyrocatechol and that with conc. sulfonic acids (RSO₃H where R = Me, CF₃) affords 2-hydroxy-5-nitrophenyl-R-sulfonates in yields of 80-85%. These reactions are assumed to proceed through an intermediate (phenoxy)oxodiazonium ion [NO ₂C₆H₄O-N=N=O]⁺, which eliminates the N₂O molecule to form the aryloxenium ion [NO₂C ₆H₄O]⁺. The latter reacts with acid anions at the ortho-carbon atom of the phenyl ring. The thermodynamical parameters of the elementary reactions resulting in the formation of the (phenoxy)oxodiazonium ion [NO₂C₆H₄O-N=N=O]⁺ and aryloxenium ion [NO₂C₆H₄O]⁺ were calculated in the B3LYP/6-311+G(d) study of the combined molecular system (nitrohydroxylamine 1 + [H₃SO₄]⁺). The reaction of nitrohydroxylamine 1 with aqueous solutions of strong acids (～70% H ₂SO₄, CF₃SO₃H) affords mainly 4-nitrophenol. It appears that the mechanism of this reaction does not involve the formation of the aryloxenium ion.

Full text of DOI:10.1007/s11172-011-0346-x

Russian Chemical Bulletin, International Edition, Vol. 60, No. 11, pp. 2263—2274, November, 2011
2263
The formation of aryloxenium ion
in the reaction of NꢀnitroꢀOꢀ(4ꢀnitrophenyl)hydroxylamine
with strong acids*
M. S. Klenov, A. M. Churakov, V. N. Solkan, 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 (499) 135 5328. Eꢀmail: churakov@ioc.ac.ru
The reaction of NꢀnitroꢀОꢀ(4ꢀnitrophenyl)hydroxylamine (1) with conc. H2SO4 affords
4ꢀnitropyrocatechol and that with conc. sulfonic acids (RSO3H where R = Me, CF3) affords
2ꢀhydroxyꢀ5ꢀnitrophenylꢀRꢀsulfonates in yields of 80—85%. These reactions are assumed to
proceed through an intermediate (phenoxy)oxodiazonium ion [NO2C6H4O—N=N=O]+, which
eliminates the N2O molecule to form the aryloxenium ion [NO2C6H4O]+. The latter reacts
with acid anions at the orthoꢀcarbon atom of the phenyl ring. The thermodynamical parameters
of the elementary reactions resulting in the formation of the (phenoxy)oxodiazonium ion
[NO2C6H4O—N=N=O]+ and aryloxenium ion [NO2C6H4O]+ were calculated in the B3LYP/
6ꢀ311+G(d) study of the combined molecular system (nitrohydroxylamine 1 + [H3SO4]+). The
reaction of nitrohydroxylamine 1 with aqueous solutions of strong acids (~70% H2SO4,
CF3SO3H) affords mainly 4ꢀnitrophenol. It appears that the mechanism of this reaction does
not involve the formation of the aryloxenium ion.
Key words: hydroxylamines, nitramines, oxodiazonium ion, B3LYP/6ꢀ311+G(d) density
functional method, 15N NMR.
In the previous work,1 we have obtained NꢀnitroꢀOꢀ
(4ꢀnitrophenyl)hydroxylamine (1), which is the first nitroꢀ
hydroxylamine isolated in the H form, and its Oꢀmethyl
derivative 2. The 15Nꢀlabeled compounds 15Nꢀ1 and 15Nꢀ2
(degree of enrichment is 92%) have also been prepared.
While the nitrohydroxylamine derivative 2 is a relaꢀ
tively stable compound, the stability of the Hꢀform 1 deꢀ
pends significantly on its environment. Compound 1
decomposes rapidly in solid and nonꢀpolar solvents at
room temperature to form 4ꢀnitrophenol (3). 2,4ꢀdinitroꢀ
phenol (4) is produced in small amounts as a secondary
reaction product (Scheme 1). The stability of 1 increases
considerably in basic (Et2O, dioxane) and protic solvents
(H2O, MeOH). For example, in water the first signs of
decomposition emerged only after 6 days.
Scheme 1
It has been established1 that for the Hꢀform 1 there
exists a fast (NMRꢀtime scale) equilibrium between the
nitramine (1) and isonitramine (1´) forms, the contents of
both forms in the equilibrium mixture being comparable
* Dedicated the 80ꢀth anniversary of the academician of the
Russian Academy of Sciences O. M. Nefedov.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1221—1232, November, 2011.
1066ꢀ5285/11/6011ꢀ2263 © 2011 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011
Klenov et al.
Scheme 2
Ar = 4ꢀNO2C6H4
(Scheme 2). It was assumed1 that decomposition of 1 starts
from autoprotolysis, which can proceed either at the N
atom (intermediate А) followed by the formation of the
nitronium cation or at the O atom (intermediate B) folꢀ
lowed by the elimination of the Н2О molecule and formaꢀ
tion of the (phenoxy)oxodiazonium ion C. It seems imꢀ
possible to select one of these reaction pathways at the
present time, although we consider the second one as
a more probable.
during which the substance was in suspension, decreased
to 10 min and the complete decomposition time decreased
to 30 min. When performing the decomposition reaction
in 73% CF3SO3H at 40 °C, no induction period was obꢀ
served and the decomposition rate decreased to 10 min.
The decrease in the acid strength retarded decomposition.
For example, in 70% H2SO4 compound 1 decomposed
completely at 40 °C for 30 min. In a weaker 97% MeSO3H,
it dissolved immediately after mixing, but the complete
decomposition at 20 °C occured for 2 days. In MeSO3H,
there was no induction period, viz., virtually no decompoꢀ
sition products were observed for ~30 min (TLC control).
The influence of nitrating and nitrosating agents on
decomposition of 1 in 73% CF3SO3H is shown in Table 2.
Both particles almost eliminate the induction period even
at low concentrations.
In the present work, we studied the behavior of nitroꢀ
hydroxylamine 1 in strong acids (H2SO4, CF3SO3H,
MeSO3H, and HSO3F).
Results and Discussion
Decomposition of nitrohydroxylamine 1 in aqueous soꢀ
lutions of strong acids. The solubility of compound 1 in
aqueous solutions of strong acids is very low. For example,
when being in the form of suspension in conc. HCl (35%)
at 20 °C the substance undergoes no changes for two days.
In 70% H2SO4 and 73% CF3SO3H, nitrohydroxylamine 1
dissolves slowly and decomposes (Table 1). The main deꢀ
composition products of 1 in aqueous solutions of strong
acids are nitrophenol 3 and dinitrophenol 4 (see Scheme 1,
Table 1, the same products have been observed1 upon deꢀ
composition of 1 in CHCl3). As in CHCl3, a pronounced
induction period was observed. For example, in the case of
73% CF3SO3H the reaction at 0 °C proceeds as follows.
During the first 50 min, the substance was in the form of
suspension without noticeable signs of decomposition.
Then, the substance dissolved completely for 1—2 min
and the most of compound 1 transformed into nitroꢀ
phenols 3 and 4, thanks to which the reaction mixture
became yellow. After 40 min, the reaction completed, i.e.,
there was no nitrohydroxylamine 1 in the reaction mixture
(TLC control).
The proposed decomposition scheme of compound 1
in aqueous solutions of strong acids consists of three main
steps. The first step is initiation. When protonation proꢀ
Table 1. The yields of nitrophenols 3 and 4 upon decomposition
of nitrohydroxylamines 1 and 15Nꢀ1 in aqueous solutions of acidsa
Acid
(С (%))
Acid : H2O
(mol/mol)
Т/°C
tb
Yield (%)
3
4
MeSO3H (97)
H2SO4 (70)
CF3SO3H (73)
CF3SO3H (73)
CF3SO3D (71)с
CF3SO3H (73)
1 : 0.16
1 : 2.3
1 : 3
1 : 3
1 : 3
20
40
40
20
20
0
2 day
30 min
10 min
30 min
30 min
1.5 h
57
63
62
64
69
72
29
21
24
26
16
12
1 : 3
a The product yields were determined by 1H NMR spectroscopy
(the conversion of compound 1 was 100%).
b The complete decomposition time of compound 1 (TLC control).
с Compound 15Nꢀ1 was used for the reaction in 71% CF3SO3D.
The reaction was performed in a sealed NMR tube with addition
of CD3OD (8 vol.%).
When the decomposition temperature of 1 in 73%
CF3SO3H was increased to 20 °C, the induction period,

Aryloxenium ion
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011 2265
Scheme 3
Note. Hereinafter, the labeled 15N atoms are bold.
ceeds at the nitrogen atom, nitric acid forms at the initiaꢀ
tion step (see Scheme 2, reaction 1), which reacts with 1
at the second step to form three nitrosating particles
(Scheme 3). At the third step, nitrosating particles react
with 1 to form N2O and HNO3 (Scheme 4) and, then, the
second step occurs again. It appears that a small amount
of ArONH2 that formed from 1 at the initiation step (see
Scheme 2, reaction 1) transforms into nitrophenol 3 and
N2O under the action of nitrosating particles.
The overall decomposition of nitrohydroxylamine 1 is
represented in Scheme 5.
Scheme 5
Scheme 4
Let us consider in more detail the reactions shown in
Scheme 3. Intermediate D can form in two ways: nitration
of 1 directly at the O atom or nitration of 1 at the N atom
to form the intermediate compound E followed by its
rearrangement. The key step of the process is rearrangeꢀ
ment of compound D into G, which can occur via the
ion pair F composed of (phenoxy)oxodiazonium and
nitrate ions.
Table 2. The yields of nitrophenols 3 and 4 in the reaction of
nitrohydroxylamine 1 with nitrating and nitrosating agents in
73% CF3SO3H at 0 °Ca
The reaction of the labeled compound 15Nꢀ1 with 71%
CF3SO3D (the molar ratio CF3SO3D : D2O is 1 : 3) conꢀ
firms the overall decomposition equation (see Scheme 5).
The reaction was performed in a sealed NMR tube and the
products were determined according to the 14N and
15N NMR spectra. The composition of products coincides
virtually with the composition of the products that formed
upon decomposition of 15Nꢀ1 in CHCl3 (see Ref. 1). The
15N NMR spectrum displays only the signals for H15NO3
and N15NO. The analysis of the 14N NMR spectrum (with
regard to details, see Ref. 1) shows that the ratio of the
nitrous oxide labeled at the central nitrogen atom (N15NO)
to the unlabeled nitrous oxide taking into account the
degree of enrichment is ~2 : 1. Note that the 14N NMR
spectrum displays also the signal for the unlabeled HNO3
that formed from compound 1 being present in the labeled
Reagent t1/minb
t2/hc
1 : Reagent
(mol/mol)
Yield (%)
3
4
d
—
50
5
1
5
0
1.5
1.15
1
1.15
1
1 : 0
1 : 0.1
1 : 1
1 : 0.1
1 : 1
72
72
64
72
37
12
12
20
13
55
HNO3
HNO3
NaNO2
NaNO2
a The product yields were determined by 1H NMR spectroscopy.
The conversion of compound 1 was 100%.
b The time from mixing of nitrohydroxylamine 1 with the acid to the
emergence of first traces of compounds 3 and 4 (TLC control).
c The complete decomposition time of nitrohydroxylamine 1
(TLC control).
d Decomposition of nitrohydroxylamine 1 without addition of
reagents.

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Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011
Klenov et al.
sample of 15Nꢀ1 (the degree of enrichment with 15N is
92%). After recording the spectrum, nitrophenol 3 and
dinitrophenol 4 were isolated from the reaction mixture in
yields of 69% and 16%, respectively (see Table 1). It
was defined by mass spectrometry that when taking into
account the degree of enrichment, the molar ratio of
compound 4 with the unlabeled nitro groups, one laꢀ
beled nitro group (15Nꢀ4), and two labeled nitro groups
(15N2ꢀ4) is 1 : 2.2 : 0.1. We have also observed1 the forꢀ
mation of a small amount of 15N2ꢀ4 labeled on two
nitro groups upon decomposition of 1 in CHCl3 (see Refs
2 and 3).
The reaction of 1 with strong concentrated acids. Upon
the reaction of compound 1 with strong concentrated acꢀ
ids, the composition of organic reaction products changes
dramatically. For example the reaction of 1 with concenꢀ
trated H2SO4, RSO3H (R = Me, CF3), and HSO3F afꢀ
fords 4ꢀnitropyrocatechol 5а and its sulfo derivatives 5b—d
in high yields (Scheme 6, Table 4). Nitrophenols 3 and 4,
which formed in slight amount, are side products.
Scheme 6
The special experiments showed that under the condiꢀ
tions analogous to the decomposition conditions of nitroꢀ
hydroxylamine 1 (73% CF3SO3H, 0 °C, 1.5 h), nitropheꢀ
nol 3 reacts with nitrating and nitrosating agents in 73%
CF3SO3H to form dinitrophenol 4 and some amount of
unidentified products, the nitrosating agents reacting fastꢀ
er than the nitrating ones (Table 3). Consequently, the
ratio of 4 to 15Nꢀ4 being equal to ~2 : 1 suggests that the
labeled and unlabeled nitrosating agents were also in the
ratio of 2 : 1.
Note that by comparison of the data from Tables 2 and
3, it is seen that compound 1 reacts with nitrating and
nitrosating agents considerably faster than compound 3.
Thus, one can state that the main decomposition steps
of nitrohydroxylamine 1 in CHCl3 (see Ref. 1) and aboveꢀ
mentioned acids (see Table 1) proceeds according to the
identical schemes. At the same time, there can be differꢀ
ences in the initiation steps: it is most likely that denitraꢀ
tion plays a key role upon decomposition in these acids
(see Scheme 2, reaction 1).
R = Me (b), CF3 (c)
The reaction of 1 with 100% H2SO4 at 10 °C results in
the fast formation of pyrocatechol 5a in 79% yield. Nitroꢀ
phenol 3 forms in a yield of 11% (see Scheme 6, Table 4).
Upon dilution of sulfuric acid to 85% (the molar ratio
H2SO4/H2O is 1 : 1), the yield of compound 5a does not
change virtually, but the reaction rate decreased and 100%
conversion of 1 at 20 °C took 2 h. At 40 °C, the same
reaction proceeds for 5 min and the yield of 4ꢀnitroꢀ
pyrocatechol 5a even increased slightly. Further dilution
of the acid decreases the yield of compound 5а and inꢀ
creases the yield of 3 and, if the water content is more than
2 moles per 1 mole of H2SO4, 4ꢀnitropyrocatechol 5а does
not form at all (see Table 1).
Table 3. The reaction of nitrophenol 3 with nitrating and nitroꢀ
sating agents in 73% CF3SO3H to form dinitrophenol 4a
Reagent
3 : Reagent Conversion of 3 Yield of 4
(mol/mol)
(%)b
HNO3
NaNO2
NaNO2 : HNO3
(1 : 1)
1 : 1
1 : 1
1 : (1 : 1)
3
8
13
65
96
67
The reaction of 1 with a weaker acid, viz., 100%
MeSO3H, proceeds much slower than that with H2SO4.
Nevertheless, sulfonate 5b forms in a high yield
(see Scheme 6, Table 4). However, the addition of
a The reaction temperature is 0 °C and the reaction time is 1.5 h.
b Determined by 1H NMR spectroscopy.

Aryloxenium ion
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011 2267
Table 4. The reaction of nitrohydroxylamines 1 and 15Nꢀ1 with strong concentrated acidsa
Run
Acid
(C (%))
Acid : H2O
(mol/mol)
Т/°C
tb
5
Yeild (%)
5
3
4
1
2
3
4
5
6
7
8
H2SO4 (100)
H2SO4 (96)
H2SO4 (93)
H2SO4 (85)
H2SO4 (85)
1 : 0
1 : 0.23
1 : 0.35
1 : 0.96
1 : 0.96
1 : 1.8
1 : 0
10
00
20
20
40
40
20
00
<5 min
<5 min
5 min
2 h
5 min
20 min
3 day
1 h
а
а
а
а
а
а
b
a
c
c
c
c
c
c
c
a
d
79
79
83
74
87
58c
82
13
73
85
88
87
46
12
12
3
11
8
6
12
6
37c
8
3
3
0
0
0
0
0
0
0
H2SO4 (75)
MeSO3H (100)
CF3SO3H (100),
1 : 0
6
d
CHCl3
9
CF3SO3H (97)
CF3SO3D (97)e
CF3SO3H (89)
CF3SO3H (88)
CF3SO3H (85)
CF3SO3H (81)
HSO3F (97)
1 : 0.25
1 : 0.23
1 : 1
1 : 1.2
1 : 1.5
1 : 1.9
1 : 0.17
00
00
40
40
40
40
00
5 min
5 min
5 min
5 min
10 min
10 min
5 min
5
3
9
25
53
66
6
0
5
10
11
12
13
14
15
<1
19
32
19
0
82
0
a The product yields were determined by 1H NMR spectroscopy. The conversion of compound 1 was 100%.
b The complete decomposition time of compound 1 (TLC control).
c The conversion of compound 1 was 70%.
d A solution of 100% CF3SO3H (20 equiv.) in CHCl3.
e Compound 15Nꢀ1 was used for the reaction in 97% CF3SO3D. The reaction was performed in a sealed NMR tube
with addition of CD3OD (8 vol.%).
Scheme 7
0.16 mol.% of water terminates this process completely
(see Table 1).
The reaction of 1 with CF3SO3H containing no more
than 11% of water (the molar ratio CF3SO3H/H2O is 1 : 1)
affords sulfonate 5c in a good yield (see Scheme 6, Table
4). The reaction of 1 with 20 equiv. of 100% CF3SO3H in
CHCl3 proceeds considerably slower than in the case where
pure CF3SO3H was used. This is likely due to the fact the
acid decomposition rate of 1 depends strongly on the acid
concentration. If the molar ratio of water to CF3SO3H is
more than 1 : 1, the yield of sulfonate 5с decreases, and, if
the water content is more than 2 moles per 1 mole of
CF3SO3H, the sulfonate does not form at all (see Table 1).
The reaction of 1 with 97% FSO3H affords the cyclic
sulfate 5d in a yield of 82% and a small amount of nitroꢀ
phenol 3 (6%) (see Scheme 6, Table 4).
Sulfonates 5b—c and sulfate 5d were obtained for the
first time and their structures were confirmed by 1H, 13C,
14N, and 19F spectroscopy. The position of the sulfo group
in products 5b—c was confirmed by the NOESY experiꢀ
ment for compound 6, which is the methylation product
of sulfonate 5с at the hydroxyl group using diazomethane
(Scheme 7). The NOESY spectrum displayed interaction
of the OMe protons with H(3).
At the first step, the protonation of the isonitramine form
1´ at the O atom followed by water elimination (see
Scheme 2, reaction 2) results in ion pair H composed of
the (phenoxy)oxodiazonium ion and weak nucleophilic
anion (RSO2O–, R = Me, OH, CF3, F), which is incapable
of reacting at the terminal nitrogen atom of the cation
–N=N=O+ (Scheme 8). This cation evolves the N2O molꢀ
ecule to form the pꢀnitrophenyloxenium ion I, which can
react as an ambident cation with the RSO2O– anion at the
orthoꢀcarbon atom of the phenyl ring to form finally comꢀ
pounds 5a—d. The aryloxenium ions of type I have been
discussed earlier.4,5
The Oꢀmethyl derivative 2 is a model of the isonitrꢀ
amine form 1´ and could also form the (phenoxy)oxoꢀ
diazonium ion C after protonation and elimination of
methanol (Scheme 9). Note that at least at the first reacꢀ
To explain the formation of 4ꢀnitropyrocatechol 5а
and its sulfoderivatives 5b—d in the strong concentrated
acid medium, we proposed the following reaction scheme.

2268
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011
Klenov et al.
Scheme 8
R = Me (b), CF3 (c)
tion steps, compound 2 cannot undergo denitration to
form HNO3.
trated acids (97% CF3SO3H and 97% HSO3F) occured
over the same period as the reaction of 1 with these acids.
At the same time, the reaction of 2 with 20 equiv. of 100%
CF3SO3H in CHCl3 occured under much more severe
conditions than those for 1. This is likely due to the fact
that the acid decomposition rate of 2 depends on the acid
concentration stronger than that of 1. In a weaker 100%
H2SO4, complete decomposition of 2 occurs slower than
that of 1 and completed in 10 min. In a yet weaker 100%
MeSO3H, the decomposition rate of 2 is severalfold less
than that of 1. Successive dilution of H2SO4 to the conꢀ
centrations of 96, 93, and 85% results in a dramatic delay
of decomposition of 2 compared to 1. When the molar
ratio of acid : H2O is equal to 1 : 1, the solubility of comꢀ
pound 2 decreases considerably and the portion of 2 is in
the heterogeneous phase, which leads to a great increase
in the reaction time. The increase in the temperature to
70 °C increases the solubility of 2 and accelerates considꢀ
erably the reaction, the yield and ratio of the products
changing slightly.
In a yet more diluted solutions of acids (50—70%
H2SO4 and CF3SO3H), the reaction of 2 proceeds quite
slow even at 70 °C. This is due the fact decomposition
occurs in the heterogeneous medium and compound 2
dissolves slowly as the reaction proceeds. It is interesting
that in contrast to nitrohydroxylamine 1, decomposition of
compound 2 in such diluted acid solutions even so results
in small amounts of 4ꢀnitropyrocatechol 5а (see Table 5).
In general, the reaction rate of the Oꢀmethyl comꢀ
pound 2 with strong acids is lower than that of compound 1,
although the direct comparison of the reaction rates of
these compounds with acids can be performed only up to
Scheme 9
R = Me (b), CF3 (c)
OꢀMethyl derivative 2 was introduced into the reacꢀ
tions with the same acids, with which nitrohydroxylamine 1
reacted (Scheme 10, Table 5), to result in 4ꢀnitropyrocatꢀ
echol 5a and its sulfo derivatives 5b—d in high yields, as
well as a small amount of nitrophenol 3 as a side product.
Scheme 10
The reaction rate of the Oꢀmethyl compound 2 with
concentrated acids is defined by their strength and water
content. For example, the reaction of 2 with very concenꢀ

Aryloxenium ion
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011 2269
Table 5. The reaction of compounds 2 and 15Nꢀ2 with strong acidsa
Run
Acid
(C (%))
Acid : H2O
(mol/mol)
Т/°C
tb Conversion of 2
5
a
Yield (%)
(%)
5
3
1
H2SO4 (100)
1 : 0
10
10 min
100
91
(57)е
87
4
—
4
2
3
4
5
6
7
8
H2SO4 (96)
H2SO4 (93)
H2SO4 (85)
H2SO4 (85)
H2SO4 (70)
H2SO4 (50)
MeSO3H (100)
1 : 0.23
1 : 0.35
1 : 0.96
1 : 0.96
1 : 2.3
1 : 5.4
1 : 0
0
3 h
4 h
100
100
79
89
66
a
a
a
a
a
a
b
20
20
70
70
70
70
86
84
83
35
10
88
4
8
5 day
30 min
14 h
14 h
8 h
10
56
72
5
—
4
50
97
(50)е
84
9
10
11
MeSO3H (100)
CF3SO3H (100)
CF3SO3H (100),
CHCl3
CF3SO3H (97)
1 : 0
1 : 0
1 : 0
20
0
61
11 day
5 min
1.3 h
56
100
95
b
c
a
c
c
86
10
73
86
3
7
c
12
1 : 0.25
0
5 min
100
3
—
2
(56)е
92
13
14
15
16
17
18
CF3SO3D (97)d
CF3SO3H (89)
CF3SO3H (89)
CF3SO3H (70)
CF3SO3H (50)
HSO3F (97)
1 : 0.23
1 : 1
1 : 1
1 : 3.6
1 : 8.3
1 : 0.17
0
5 min
5 day
30 min
9 h
100
66
100
72
c
c
c
c
c
d
30
70
70
70
0
86
82
28
7
70е
6
5
58
85
—
9 h
54
5 min
100
a The conversion of compound 2 and product yields were determined by 1H spectroscopy.
b The decomposition time of compound 2.
c A solution of 100% CF3SO3H (20 equiv.) in CHCl3.
d Compound 15Nꢀ2 was used for the reaction in 97% CF3SO3D. The reaction was performed in a sealed NMR
tube with addition of CD3OD (8 vol.%).
e The yields are given for the isolated product (nitrophenol 3 was not isolated).
the molar ratio acid/H2O of 1 : 1, at which the decompoꢀ
sition reactions of both compounds can be performed in
a homogeneous solution. For the preparation of products
5a—d, the reactions of the Oꢀmethyl compound 2 are more
convenient than the corresponding reaction of 1 due to
a low thermal stability of the latter and its tendency to
selfꢀdecomposition.
one can suggest the scheme including the protonation of 1
at the nitrogen atom followed by elimination of the nitrꢀ
amide molecule (Scheme 11). The similar mechanism has
been proposed earlier to explain the formation of the
phenyloxenium ion from NꢀsulfonylꢀOꢀphenylhydroxylꢀ
amines in the acid medium.5
The reaction of the labeled samples 15Nꢀ1 and 15Nꢀ2
with 97% CF3SO3D (the molar ratio CF3SO3D : D2O is
1 : 0.2) confirms the proposed mechanism of the formaꢀ
tion of products 5a—d through the intermediate (phenꢀ
oxy)oxodiazonium ion (see Schemes 8 and 9, Tables 4 and 5,
the reaction with 97% CF3SO3D). The reactions were perꢀ
formed in a sealed NMR tube and the products were deꢀ
termined according to the 14N and 15N NMR spectra. The
15N NMR spectrum displays only the signal for N15NO
and contains no signals for the labeled nitrogen molecules
and H15NO3. The 14N NMR spectrum displays the signal
for the terminal nitrogen atom of N15NO and low signals for
the unlabeled N2O corresponding to the degree of enrichꢀ
ment of the samples 15Nꢀ1 and 15Nꢀ2 with the 15N label.
By analyzing the alternative formation mechanisms of the
pꢀnitrophenyloxenium ion I from nitrohydroxylamine 1,
Scheme 11
To decide between the proposed generation mechaꢀ
nisms of cation I from compound 1, we performed theoꢀ
retical studies.
Theoretical study of the generation of the oxenium ion I
from nitrohydroxylamine 1 in H2SO4. The main purpose of

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Klenov et al.
the theoretical studies was to confirm the formation of the
(phenoxy)oxodiazonium ion [ArO—N=N=O]+ (C) as
a kinetically independent particle upon the reaction of
compound 1 with conc. H2SO4.
N
By the B3LYP/6ꢀ311+G(d) density functional methꢀ
od,6,7 we studied the potential energy surface (PES) of
the combined molecular system {isonitramine form 1´ +
+ [H3SO4]+} (Scheme 12).
N
N
Scheme 12
O
C
H
S
ΔH = –4.4 kcal mol–1
Since the reacition under consideration proceeds in
concentrated H2SO4, we studied also PES for the comꢀ
bined molecular system {[ArO—N=N=O]+•3 H2SO4} (8)
(Scheme 13). The simulation of solvation was performed
within the supramolecular approach taking clear account
of three H2SO4 molecules without consideration of the
H2O molecule, which in a strongꢀacid medium transforms
readily into the [H3O]+ ion and leaves the internal solvaꢀ
tion sphere of the (phenoxy)oxodiazonium ion C.
Fig. 1. DFT/B3LYP optimized geometry of complex 7 obtained
in the study of the PES of the combined molecular system
{isonitramine form 1´ + [H3SO4]+}.
oxodiazonium ion [ArO—N=N=O]+ (C) (see Fig. 1) is
characterized by the positive net charge (0.35 e).
Let us consider the reaction in Scheme 13. The study
of the combined molecular system {[ArO—N=N=O]+•3
H2SO4} (8) (see Scheme 13, Fig. 2, Table 6) allowed loꢀ
calization of a minimum on the PES, which confirms that
the [ArO—N=N=O]+ ion (C) can exists as a kinetically
independent particle. In addition, we revealed the miniꢀ
mum corresponding to the complex {[ArO]+•N2O•
•3 H2SO4} (9) (see Scheme 13, Fig. 3). The performed
calculations of the thermodynamic parameters of these
complexes show that the reaction is extremely exothermic.
However, the complexity of the combined molecular system
{[ArO—N=N=O]+•3 H2SO4} (8) did not allow us to locaꢀ
lize the transition state related to the decomposition coorꢀ
dinate and to estimate the activation barrier of this process.
Scheme 13
ΔH = –42.1 kcal mol–1, ΔG = –45.4 kcal mol–1
To confirm the local minima on the PES, the vibraꢀ
tional spectra of the particles under study were calculated.
Let us consider the reacion in Scheme 12. Taking into
account a high acidity of the medium under considerꢀ
ation, the protonated molecule of sulfuric acid [H3SO4]+
was regarded as a protonating agent. It has been shown
earlier8,9 that the [H3SO4]+ ions can exist in 100% sulꢀ
furic acid as complexes containing one or two H2SO4
molecules.
Table 6. Selected geometry parameters (bond lengths (d)
and angles (ω)) of the О—N=N=O fragment in the complex
{[ArO—N=N=O]+•H2O•H2SO4} (7) (see Fig. 1) and comꢀ
plex {[ArO—N=N=O]+•3 H2SO4} (8) (see Fig. 2) (B3LYP/6ꢀ
311+G(d))
...
The study of the PES of the combined molecular sysꢀ
tem (isonitramine form 1´ + [H3SO4]+) (see Scheme 12)
Comꢀ d (О—N) d (N—N) d (N—O) ω (N—N—O) d (N O)
plex
/deg
/Å
Å
showed that upon approximation of molecule 1´ and the
+
...
[H3SO4] cation, elongation of the N OH2 bond occurs,
7
8
1.35
1.40
1.21
1.18
1.16
1.16
145.6
159.6
2.03a
2.37b
which is accompanied by the activationless formation of
complex 7 consisting of the (phenoxy)oxodiazonium ion
[ArO—N=N=O]+ (C), the H2O molecule, and the H2SO4
a
The distance between the central nitrogen atom of the
—N=N=O fragment and the oxygen atom of the H2O molecule
in the complex.
...
molecule (Fig. 1, Table 6), where the distance N OH2 is
b The distance between the central nitrogen atom of the —N=N=O
fragment and the oxygen atom of the H2SO4 molecule in the
complex.
2.03 Å. The formation of this complex is a low exothermic
reaction. As it follows from the computed effective Mulꢀ
liken charges, the –N=N=O fragment in the (phenoxy)ꢀ

Aryloxenium ion
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011 2271
By the study of the PES of the molecular system (Fig. 4),
it was found that upon protonation of 1 with [H3SO4]+ at
the nitrogen atom of hydroxylamine, there occur elongaꢀ
tion of the N NO2 bond and activationless formation
of complex 10 consisting of the ArONH2 molecule,
O
C
H
S
...
nitronium ion, and H2SO4 molecule (see Fig. 4), where
N
...
S
the distance N NO2 is 1.78 Å. Note that the hypoꢀ
thetic formation reaction of the oxenium ion [ArO]+ (I)
and the NH2NO2 molecule from the complex
{ArONH2•[NO2]+•H2SO4} (10) is endothermal (ΔH =
= +18.6 kcal mol–1). At the same time, the formation
of the oxenium ion [ArO]+ (I) upon protonation of
the isonitramine form 1´ is exothermal (ΔH is about
–40 kcal mol–1). Thus, the second pathway of the formaꢀ
tion of [ArO]+ (I) upon protonation of the nitramine
form 1 at the nitrogen atom of hydroxylamine cannot ocꢀ
cur due to a more thermodynamically favorable denitraꢀ
tion process.
N
N
When 75—96% H2SO4 (but not 100% H2SO4) was
used, the [H3O]+ hydroxonium ion can act as a protonatꢀ
ing particle. However, when considering the comparable
proton affinities of the water and sulfuric acid molecules,10
the thermodynamics of the formation of [ArO]+ (I) from 1´
Fig. 2. DFT/B3LYP optimized geometry of complex 8 obtained
in the study of the PES of the combined molecular system
{isonitramine form 1´ + [H3SO4]+ + 2 H2SO4}.
changes within the range of 3 kcal mol–1
.
Thus, by the B3LYP density functional study of the
combined molecular systems {isonitramine form 1´ +
+ [H3SO4]+} and {nitramine form 1 + [H3SO4]+} and
localizatioin of some stationary points on the PES, we
showed that the formation pathway of the oxenium ion I
from the isonitramine form 1´ is the most thermodynamꢀ
ically favorable and confirmed the existence possibility of
the (phenoxy)oxodiazonium ion [ArO—N=N=O]+ (C)
as a kinetically independent particle. The thermodynamiꢀ
cal parameters of elementary reactions resulting in the
formation of intermediate [ArO]+ (I) were calculated.
It was interesting to compare the stability of the nonꢀ
solvated oxodiazonium ion studied earlier11, wherein the
–N=N=O fragment is linked with the C atom, with the nonꢀ
solvated (phenoxy)oxodiazonium ion [ArO—N=N=O]+
S
O
S
C
S
H
N
N
N
Fig. 3. DFT/B3LYP optimized geometry of the oxenium ion I in
complex 9. The distance between the O atom of the oxenium
ion I and the terminal N atom of the N2O molecule in complex 9
is 2.9 Å.
N
We performed also the study of the complex {nitraꢀ
mine form 1 + [H3SO4]+} as an alternative intermediate
in the reaction with H2SO4 (see Scheme 11).
S
N
N
As noted above for the Hꢀform 1, there exists a fast
(NMRꢀtime scale) equilibrium between nitramine 1 and
isonitramine 1´ forms, the contents of both forms in the
equilibrium mixture being comparable (see Scheme 2).
Therefore, we studied the PES of the combined molecular
system {nitramine form 1 + [H3SO4]+} in order to estabꢀ
lish the existence possibility of the [ArO—NH2—NO2]+
ion (A) and the possibility of its decomposition to elimiꢀ
nate the NH2NO2 molecule and to form the oxenium ion
[ArO]+ (I) (see Scheme 11).
O
C
H
Fig. 4. DFT/B3LYP optimized geometry of complex 10 obtained
in the study of the PES of the combined molecular system {nitraꢀ
mine form 1 + [H3SO4]+}. The distance N…NO2 in complex 10
is 1.78 Å.

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Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011
Klenov et al.
given in Tables 1 and 4. After completion of the reaction, the
mixture was poured into ice water (3 mL) and extracted with
CH2Cl2 (5×2 mL) and AcOEt (2×3 mL). The AcOEt extract was
washed with water (1 mL). The organic extracts were combined,
washed with a saturated aqueous solution of NaCl (2 mL), dried
with MgSO4, and evaporated in vacuo. The product yields were
determined by 1H NMR spectroscopy (see Tables 1 and 4).
Decomposition of 15Nꢀ1 in 71% CF3SO3D. Nitrohydroxylꢀ
amine 15Nꢀ1 (20 mg, 0.10 mmol) crushed at 0 °C was placed
under argon into an NMR tube cooled to –30 °C. A mixture of
CF3SO3D (a 71% solution in D2O, 0.55 mL) and CD3OD
(0.05 mL) precooled to –20 °C was added. The cooled tube was
sealed, heated to 20 °C, and kept for 30 min by shaking at times.
The 14N and 15N NMR spectra were recorded. 14N NMR
(CF3SO3D/D2O/CD3OD), δ: –11 (the NO2 groups of 3 and 4,
Δν = 900 Hz), –40 (HNO3, Δν = 40 Hz; the signal coinꢀ
O
C
N
H
N
N
Fig. 5. DFT/B3LYP optimized geometry of the oxenium ion I
in the complex {[ArO]+ + N2O}. The distance {[ArO]+...NNO}
is 3.6 Å.
1/2
1/2
cides with the signal for the knowing sample of HNO3 in the same
solvent mixture), –149 (the central N atom in NNO, Δν1/2 = 30 Hz),
–232 (the terminal N atom in NNO and N15NO, Δν1/2 = 30 Hz).
The molar ratio NNO : N15NO equal to 0.3 : 0.7 was determined
by the integral intensity ratio of the signals for the central and
terminal N atoms taking into account the integral intensities of
the corresponding signals for the knowing sample of N2O in the
same solvent mixture. 15N NMR (CF3SO3D/D2O/CD3OD), δ:
–17.7, –19.3, –21.1 (C—15NO2 groups), –43.4 (H15NO3),
–152.9 (t, the central N atom in N15NO, 1J(14N—15N) = 6 Hz,
cf. Ref. 13).
(C) where the –N=N=O fragment is linked with the
O atom. When studying the PES of the free (phenoxy)ꢀ
oxodiazonium ion [ArO—N=N=O]+ (C) (Fig. 5), we
found the activationless pathway of its decomposition to
eliminate the N2O molecule and to form the oxenium ion
[ArO]+ (I). Thus, the calculations show that the cation
with the O—N=N=O fragment is less stable than that
with the C—N=N=O fragment, which has been localized
by us on the PES as a minimum.
After recording the NMR spectra, the tube was unsealed and
the reaction mixture was poured into ice water (3 mL) and exꢀ
tracted with CH2Cl2 (4×3 mL). The extracts were combined,
washed with a saturated aqueous solution of NaCl (1 mL), dried
with MgSO4, and evaporated in vacuo. The product yields were
Experimental
1
H, 13C, and 14N NMR spectra were recorded on Bruker
1
determined by H NMR spectroscopy (see Table 1). The reacꢀ
AMꢀ300 (300.13, 75.5, and 21.5 MHz) and Bruker DRXꢀ500
(500.13, 125.76, and 36.14 MHz) instruments, respectively.
15N NMR spectra were recorded on a Bruker DRXꢀ500
(50.70 MHz) instrument. Chemical shifts are given relative to
SiMe4 (1H, 13C) or MeNO2 (14N, external standard, upfield
chemical shifts are negative). IR spectra were recorded on
a Specord Mꢀ80 spectrometer. Mass spectra were recorded on
a Kratos MSꢀ300 (EI, 70 eV) instrument. The course of reacꢀ
tions was monitored by thinꢀlayer chromatography (Silufol UVꢀ254
and Merck 60 F254). CF3SO3D and its solutions in D2O were
prepared by heating the corresponding amounts of (CF3SO3)2O
and D2O at 60 °C for 2 h. A solution of nitrohydroxylamine 1 in
diethyl ether (see Ref. 1), the Oꢀmethyl derivative 2 (see Ref. 1),
labeled samples 15Nꢀ1 and 15Nꢀ2 (see Ref. 1), a solution of
diazomethane in diethyl ether (see Ref. 12) were prepared acꢀ
cording to known procedures. The yields of reaction products
were determined by 1H NMR spectroscopy.
The reaction of nitrohydroxylamine 1 with acids (general proꢀ
cedure). To prepare a solid sample of nitrohydroxylamine 1, the
standard procedure was used, which consists in evaporation to
dryness of a solution of 1 (10 mg, 0.05 mmol) in Et2O (1 mL) in
a oneꢀneck flask under reduced pressure (1 Torr) at 0 °C for 5 min.
Subsequent manipulations were performed in the same flask.
The acid* (see Tables 1 and 4) was added with vigorous stirring
in single portion at 0 °C. The reaction temperature and time are
tion products were separated by preparative TLC on silica gel
(the eluent was CHCl3) to yield 4ꢀnitrophenol (3) (8 mg) and
2,4ꢀdinitrophenol (4) (3 mg). The resulted dinitrophenol 4 was
analyzed by mass spectrometry. MS, m/z (the ratio of integral
intensities): 287, 288, 289 [M]+ (1 : 2.0 : 0.1). Taking into acꢀ
count the degree of enrichment, the molar ratio of compound 4
with the unlabeled nitro groups, one labeled nitro group (15Nꢀ4),
and two labeled nitro groups (15N2ꢀ4) is 1 : 2.2 : 0.1.
The reaction of 1 with HNO3 in 73% CF3SO3H. To the sample
of nitrohydroxylamine 1 prepared according to the standard proꢀ
cedure, a precooled to 0 °C solution of HNO3 (the amount is
given in Table 2) in 73% CF3SO3H (0.5 mL) was added with
stirring at 0 °C. The reaction mixture gained an intense yellow
color as compound 1 dissolved for 1—5 min. The reaction mixꢀ
ture was stirred at 0 °C for the time given in Table 2, poured into
ice water (2 mL), and extracted with CH2Cl2 (5×3 mL). The
organic extracts were combined, washed with a saturated aqueous
solution of NaCl (1 mL), dried with (MgSO4), and evaporated
in vacuo. The product yields were determined by 1H NMR specꢀ
troscopy (see Table 2).
The reaction of 1 with NaNO2 in 73% CF3SO3H. To the
sample of 1 prepared according to the standard procedure, a preꢀ
cooled to 0 °C solution of NaNO2 (the amount is given in Table 2)
in 73% CF3SO3H (0.5 mL) was added with stirring at 0 °C. The
reaction mixture gained an intense yellow color as compound 1
dissolved for 0—5 min. The reaction mixture was stirred at 0 °C
for the time given in Table 2 and treated as desribed in the
previous procedure.
* The acid was cooled to 0 °C prior to addition in the reactions
performed at 0 °C.

Aryloxenium ion
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011 2273
The reaction of nitrophenol (3) with HNO3 in 73% CF3SO3H.
A precooled to 0 °C solution of HNO3 (0.003 mL, 0.07 mmol) in
73% CF3SO3H (0.5 mL) was added with vigorous stirring to
nitrophenol 3 (10 mg, 0.07 mmol) in single portion. The reacꢀ
tion mixture was stirred for 1.5 h at 0 °C, poured into ice water
(2 mL), and extracted with CH2Cl2 (5×3 mL). The extracts were
combined, dried with MgSO4, and evaporated in vacuo. The
conversion of nitrophenol 3 and the yield of dinitrophenol 4
were determined by 1H NMR spectroscopy (see Table 3).
The reaction of nitrophenol (3) with NaNO2 73% CF3SO3H.
A precooled to 0 °C solution of NaNO2 (5 mg, 0.07 mmol) in
73% CF3SO3H (0.5 mL) was added with vigorous stirring to
nitrophenol 3 (10 mg, 0.07 mmol) in single portion. The reacꢀ
tion mixture was stirred for 1.5 h at 0 °C and then treated as
descibed in the previous procedure.
was washed with water (2 mL). The organic extracts were
combined, washed with a saturated aqueous solution of NaCl
(3 mL), dried with MgSO4, and evaporated in vacuo. Product 5a
was purified by column chromatography on silica gel (the eluent
was petroleum ether—acetone (1 : 1)). Products 5b—d were puꢀ
rified by the preparative TLC on silica gel: the eluent was
CHCl3—AcOEt (8 : 1) for 5b, CHCl3 and then CHCl3—AcOEt
(8 : 1) for 5c, and CHCl3 for 5d.
4ꢀNitropyrocatechol (5a). The yield was 25 mg (57%), m.p.
174—176 °C (from CHCl3) (cf. Ref. 14: m.p. 176 °C); identical
to the earlier obtained product15,16 (1H NMR and IR spectra).
2ꢀHydroxyꢀ5ꢀnitrophenyl methylsulfonate (5b). The yield was
33 mg (50%), m.p. 136—138 °C (from hexane). Found (%):
C, 36.16; H, 3.07; N, 5.93. C7H7NO6S. Calculated (%): C, 36.05;
H, 3.03; N, 6.01. IR (КBr), ν/cm–1: 1160 s, 1184 s, 1224 m, 1300 s,
1344 s, 1440 w, 1508 s, 1528 s, 1600 m, 3340 s. 1H NMR (acetꢀ
oneꢀd6), δ: 3.42 (s, 3 H, CH3); 7.28 (d, 1 H, H(3), J = 8.8 Hz);
8.16 (d.d, 1 H, H(4), J = 8.8 Hz, J = 3.0 Hz); 8.20 (d, 1 H,
H(6), J = 3.0 Hz). 13C NMR (acetoneꢀd6), δ: 38.7 (CH3);
118.2 (C(3) or C(6)); 121.2 (C(6) or C(3)); 124.9 (C(4)); 137.5
(C(1)); 141.0 (C(5)); 156.9 (C(2)). The spectral signals were
assigned by calculations according to the additive scheme.17
The reaction of nitrophenol (3) with the system NaNO2/HNO3 =
= 1 : 1 in 73% CF3SO3H. A precooled to 0 °C solution of HNO3
(0.003 mL, 0.07 mmol) in 73% CF3SO3H (0.25 mL) was added
with vigorous stirring to nitrophenol 3 (10 mg, 0.07 mmol) in
single portion. A cooled to 0 °C solution of NaNO2 (5 mg,
0.07 mmol) in 73% CF3SO3H (0.25 mL) was then added. The
reaction mixture was stirred for 1.5 h at 0 °C, poured into ice
water (2 mL), and extracted with CH2Cl2 (5×3 mL). The exꢀ
tracts were combined, dried with MgSO4, and evaporated
in vacuo. The conversion of nitrophenol 3 and the yield of dinitroꢀ
phenol 4 were determined by 1H NMR spectroscopy (see Table 3).
The reaction of 1 with 100% CF3SO3H in CHCl3. To the
sample of 1 prepared according to the standard procedure, preꢀ
cooled to 0 °C CHCl3 (2 mL) was added with stirring at 0 °C and
the reaction mixture was stirred at 0 °C until compound 1 was
dissolved completely. The resulted solution of 1 was added with
vigorous stirring in single portion to a solution of 100% CF3SO3H
(0.085 mL, 0.94 mmol) in CHCl3 (10 mL) at 0 °C under an argon
atmosphere. The reaction mixture was stirred at 0 °C for 1 h and
washed with water (3×3 mL). The combined aqueous layer was
extracted with AcOEt (2×3 mL). The combined organic layer
was washed with a saturated aqueous solution of NaCl (3 mL),
dried with MgSO4, and evaporated in vacuo. The product yields
were determined by 1H NMR spectroscopy (see Table 4).
The reaction of the Oꢀmethyl compound 2 with strong acids
(general procedure). Method A (was used upon spectral determiꢀ
nation of the yields of 5a—d). Compound 2 (10 mg, 0.047 mmol)
was added with vigourous stirring in small portions to the acid
(1 mL) (see Table 5). The reaction temperature and time are given
in Table 5. After completion of the reaction, the mixture was
poured into ice water (3 mL) and extracted with CH2Cl2
(5×2 mL) and AcOEt (2×3 mL). The AcOEt extract was washed
with water (1 mL). The organic extracts were combined, washed
with a saturated aqueous solution of NaCl (2 mL), dried with
MgSO4, and evaporated in vacuo. The conversion of 2 and product
yields were determined by 1H NMR spectroscopy (see Table 5).
Method B (was used upon isolation of compounds 5a—d).
Compound 2 (60 mg, 0.28 mmol) was added with vigorous stirꢀ
ring in small portions to the corresponding 97% or 100% acid
(1.5 mL) (see Table 5) at 0 °C. The reaction temperature and
time are given in Table 5. After completion of the reaction, the
mixture was poured into ice water (5 mL) and extracted with
CH2Cl2 (5×5 mL) and AcOEt (2×5 mL)*. The AcOEt extract
14N NMR (acetoneꢀd6), δ: –14 (NO2, Δν = 150 Hz). MS,
1/2
m/z: 233 [M]+.
2ꢀHydroxyꢀ5ꢀnitrophenyl trifluoromethylsulfonate (5c). The
yield was 45 mg (56%), m.p. 106—108 °C. Found (%): C, 29.39;
H, 1.35; N, 4.94. C7H4F3NO6S. Calculated (%): C, 29.28;
H, 1.40; N, 4.88. IR (КBr), ν/cm–1: 1136 m, 1164 m, 1216 s,
1284 m, 1312 m, 1344 s, 1428 s, 1508 m, 1528 m, 1608 m, 3340 s.
1H NMR (CDCl3), δ: 7.20 (d, 1 H, H(3), J = 9.5 Hz); 8.18—8.22
(m, 2 H, H(4), H(6)). 13C NMR (CDCl3), δ: 117.8 (C(3) or
1
C(6)); 118.6 (q, CF3, J (13C—19F) = 320 Hz); 119.3 (C(6) or
C(3)); 125.4 (C(4)); 136.6 (C(1)); 140.8 (C(5)); 154.2 (C(2)).
The spectral signals were assigned by calculations according to
the additive scheme.17 14N NMR (CDCl3), δ: –16 (NO2,
Δν1/2 = 300 Hz). 19F NMR (CDCl3), δ: –74.0. MS, m/z: 287 [M]+.
6
5ꢀNitroꢀ1,3,2λ ꢀbenzodioxathiolꢀ2,2ꢀdione (5d). The yield
was 43 mg (70%), m.p. 50—52 °C (cf. Ref. 18: m.p. 68 °C (from
EtOH). Found (%): C, 33.11; H, 1.34; N, 6.52. C6H3NO6S.
Calculated (%): C, 33.19; H, 1.39; N, 6.45. IR (КBr), ν/cm–1
:
1060 w, 1120 w, 1216 s, 1348 s, 1432 s, 1480 m, 1540 s. 1H NMR
(CDCl3), δ: 7.43 (d, 1 H, H(6), J = 8.8 Hz); 8.17 (d, 1 H, H(3),
J = 1.5 Hz); 8.25 (d, 1 H, H(5), J = 8.8 Hz). 13C NMR (CDCl3),
δ: 108.2; 112.1; 121.7; 130.3; 142.1; 146.3. 14N NMR (CDCl3),
δ: –19 (NO2, Δν1/2 = 110 Hz). MS, m/z: 217 [M]+.
2ꢀMethoxyꢀ5ꢀnitrophenyl trifluoromethylsulfonate (6). A soꢀ
lution of diazomethane in Et2O (3 mL) prepared from Nꢀmethylꢀ
Nꢀnitrosourea (0.1 g) was added dropwise at 20 °C to a stirred
solution of trifluoromethylsulfonate 5c (30 mg, 0.1 mmol) in
Et2O (3 mL) until gas evolution was terminated and the solution
became paleꢀyellow. The solvent was removed in vacuo. The
residue was brought on a silica gel column (d = 10 mm, h = 20 mm)
and eluted with a CHCl3/AcOEt (8 : 1) mixture. The eluate was
evaporated in vacuo to yield compound 6 (31 mg, 99%) as a lightꢀ
yellow oil. Found (%): C, 32.01; H, 1.96; N, 4.75; C8H6F3NO6S.
Calculated (%): C, 31.90; H, 2.01; N, 4.65; 1H NMR (CDCl3),
δ: 4.06 (s, 3 H, CH3); 7.17 (d, 1 H, H(3), J = 8.8 Hz); 8.16 (d, 1 H,
H(6), J = 2.2 Hz); 8.30 (d.d, 1 H, H(4), J = 8.8 Hz, J = 2.2 Hz).
The positions of the substituents in the aromatic ring were conꢀ
firmed by the NOESY (1H—1H) experiment. 13C NMR (CDCl3),
1
* Only upon the preparation of products 5a and 5c.
δ: 57.1 (CH3); 118.7 (q, CF3, J (13C—19F) = 320 Hz); 112.5

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Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011
Klenov et al.
(C(3)); 119.0 (C(6)); 125.4 (C(4)); 137.8 (C(1)); 140.9 (C(5));
156.8 (C(2)). The spectral signals were assigned by the HSQC
and HMBC experiments. 14N NMR (CDCl3), δ: –17 (NO2,
References
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Δν
= 160 Hz). 19F NMR (CDCl3), δ: –74.3. MS, m/z:
1/2
301 [M]+.
The reaction of 2 with 100% CF3SO3H in CHCl3. A solution
of compound 2 (10 mg, 0.047 mmol) in CHCl3 (0.5 mL) was
added with vigorous stirring at once to a solution of 100%
CF3SO3H (0.085 mL, 0.94 mmol) in CHCl3 (7 mL) at 20 °C.
The reaction mixture was refluxed (61 °C) for 1.3 h and then
AcOEt (10 mL) was added. The resulted mixture was washed
with water (3×3 mL). The combined aqueous layer was extractꢀ
ed with AcOEt (2×3 mL). The combined organic extracts were
washed with a saturated aqueous solution of NaCl (2 mL), dried
with MgSO4, and evaporated in vacuo. The conversion of 2 and
product yields were determined by 1H NMR spectroscopy
(see Table 5).
Decomposition of 15Nꢀ1 or 15Nꢀ2 in 97% CF3SO3D (general
procedure). The crushed at 0 °C compound 15Nꢀ1 (20 mg,
0.10 mmol) or 15Nꢀ2 (20 mg, 0.09 mmol) was placed into an
NMR tube cooled to –30 °C under argon. A mixture of CF3SO3D
(a 97% solution in D2O) (0.55 mL) and CD3OD (0.05 mL)
precooled to –30 °C was added to the tube in single portion. The
cooled tube was sealed, heated to 0 °C, and kept for 5 min with
periodic shaking. The tube was then heated to 20 °C and the 14
and 15N NMR spectra were recorded. 14N NMR (CF3SO3D/
N
/D2O/CD3OD), δ: –148 (the central N atom in NNO, Δν
=
1/2
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= 20 Hz), –232 (the terminal N atom in NNO and N15NO,
Δν1/2 = 20 Hz). 15N NMR (CF3SO3D/D2O/CD3OD), δ: –148.5
(the central N atom in N15NO).
After recording the NMR spectra, the tube was unsealed and
the reaction mixture was poured into ice water (3 mL) and exꢀ
tracted with CH2Cl2 (4×3 mL). The extracts were combined,
washed with an aqueous solution of NaCl (1 mL), dried with
MgSO4, and evaporated in vacuo. The product yields were deꢀ
1
termined by H NMR spectroscopy (see Table 4, Run 10 and
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Table 5, Run 13).
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 10ꢀ03ꢀ00752)
and Ministry of Education and Science of the Russian
Federation (state contract No. 02.740.11.0258).
Received June 1, 2011;
in revised form September 13, 2011