Nitrosation of salts of 1-hydroxyimino-2,2-dinitro-1-R-ethanes, a novel method for the preparation of isomeric 3(4)-nitro-4(3)-R-furoxans

Article abstract of DOI:10.1007/s11172-009-0292-z

A novel general method for the synthesis of isomeric 3(4)-nitro-4(3)-R- furoxans is developed. 3-Nitro isomers were obtained by reaction of hydroximoyl chlorides with dinitromethane sodium salt followed by conversion of the resulting 1-substituted 1-hydroxyimino-2,2-dinitroethanes into dipotassium (or disodium salts) and their subsequent nitrosation with NaNO₂ in AcOH or with N₂O₄. Thermal isomerization of 3-nitro isomers afforded 4-nitro isomers were prepared in high yields.

Full text of DOI:10.1007/s11172-009-0292-z

Russian Chemical Bulletin, International Edition, Vol. 58, No. 10, pp. 2137—2146, October, 2009
2137
Nitrosation of salts of 1ꢀhydroxyiminoꢀ2,2ꢀdinitroꢀ1ꢀRꢀethanes,
a novel method for the preparation of isomeric 3(4)ꢀnitroꢀ4(3)ꢀRꢀfuroxans
I. V. Ovchinnikov, A. O. Finogenov, M. A. Epishina, A. S. Kulikov, Yu. A. Strelenko, and N. N. Makhova
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5328. Eꢀmail: mnn@ioc.ac.ru
A novel general method for the synthesis of isomeric 3(4)ꢀnitroꢀ4(3)ꢀRꢀfuroxans is develꢀ
oped. 3ꢀNitro isomers were obtained by reaction of hydroximoyl chlorides with dinitromethane
sodium salt followed by conversion of the resulting 1ꢀsubstituted 1ꢀhydroxyiminoꢀ2,2ꢀdinitroꢀ
ethanes into dipotassium (or disodium salts) and their subsequent nitrosation with NaNO2 in
AcOH or with N2O4. Thermal isomerization of 3ꢀnitro isomers afforded 4ꢀnitro isomers were
prepared in high yields.
Key words: isomeric 3(4)ꢀnitrofuroxans, bis[3(4)ꢀnitrofuroxanꢀ4(3)ꢀyl]arenes, αꢀnitro
oximes, hydroximoyl chlorides, aciꢀnitro compounds, dinitromethane sodium salt, nitrosation,
thermal isomerization, regiospecific synthesis.
The furoxan ring has a special place among various
azoles, as it contains two atoms of active oxygen, which
are not bonded to the carbon or hydrogen atoms being
involved in the "hidden" nitro group.1,2 The furoxan derivꢀ
atives possess high density together with positive enthalpy
of formation, which enables synthesis of highꢀenergetic
compounds on their basis. Nitrofuroxans are of particular
importance among functional furoxan derivatives that, on
the one hand, possess biological activity as nitrogen oxide
donors,3,4 and, on the other hand, are attractive as promꢀ
ising components for highꢀenergy compositions. Howevꢀ
er, general synthetic methods furnishing 3(4)ꢀnitrofurꢀ
oxans in satisfactory yields have not been described. Oxiꢀ
dation of aminofuroxans is one of the wellꢀknown apꢀ
proaches toward nitrofuroxans, but only 4ꢀaminofuroxans
could be involved in this reaction5. The aim of the present
work was the quest for novel general methods for the synꢀ
thesis of 3(4)ꢀnitrofuroxans bearing diverse substituents at
the C(4) (or C(3)) atom of the ring.*
the location of the nitro group in αꢀnitro oxime 4; it is
from this side that the oxygen atom of the Nꢀoxide apꢀ
pears in the resulting furoxan 1 (Scheme 1).
Scheme 1
To solve this problem, we used the wellꢀknown methꢀ
od for the furoxan ring construction based on dehydration
of αꢀnitro oximes. This method was developed7,8 more
than 100 years ago for the synthesis of alkylarylfuroxans 1
by the reaction of the corresponding 1ꢀalkylꢀ2ꢀarylethylꢀ
enes 2 with sodium nitrite in acetic acid. It has been asꢀ
sumed that in the initial step N2O3 adds to the double
bond of the starting ethylene 2 to give pseudonitrosite 3,
which successively isomerized in situ into αꢀnitro oxime 4
and its aciꢀform 5, dehydration of which furnished furꢀ
oxan 1. Regiospecifity of this reaction is determined by
Later9—11 this method has been extended to other oleꢀ
fins. Pseudonitrosites 3´ in the form of the nitroso dimers
were obtained by passing a mixture of gaseous NO and
oxygen or air through a solution of the starting 1,2ꢀdialkylꢀ
ethylene 6 in diethyl ether or benzene. Heating of pseudꢀ
onitrosites 3´ in dipolar aprotic solvents (DMF, DMSO,
HMPA) is a facile and convenient method for the isomerꢀ
ization of pseudonitrosites 3´ into αꢀnitro oximes 4´.
Transformation of αꢀnitro oximes 4´ into aciꢀnitro comꢀ
pounds 5´ as well as its dehydration into dialkylfuroxans 7
* Brief communication, see Ref. 6.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2072—2081, October, 2009.
1066ꢀ5285/09/5810ꢀ2137 © 2009 Springer Science+Business Media, Inc.

2138
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
Ovchinnikov et al.
was carried out by short heating in concentrated sulfuric
or polyphosphoric acid. (Scheme 2).
wise addition of a large excess of NaNO2 (10—15 mol) is
required, and the yields of the resulting furoxan are low
(21—26%). The lengthy reaction and low yield of furoxan
are probably due to the difficulty of converting the nitro
group in the aciꢀform under the reaction conditions.
In the present work, with the aim at synthesizing an
isomeric αꢀnitro oxime with the oxime moiety located
near the aryl substituent and the nitro group at the neighꢀ
boring carbon atom, we carried out the reaction of arylꢀ
hydroximoyl chlorides 13 with 2 mol. equiv. of dinitroꢀ
methane sodium salt 14. The reaction was conducted in
DMF at –10—0 °C with subsequent keeping at 0 °C for
15—24 h and at room temperature for 3—4 h. The excess
of dinitromethane sodium salt 14 was used to achieve more
complete conversion of the starting chloride 13 into αꢀnitro
oxime 16, which in turn gave monosodium salt 15, since
the acidity of nitro oxime 16 is higher than that of diniꢀ
tromethane. After aqueous workꢀup of the reaction mixꢀ
ture, dinitromethane that formed was extracted with chloꢀ
roform, the aqueous layer was carefully acidified with
15—20% H2SO4, and αꢀnitro oxime 16 was extracted with
diethyl ether, then methanol was added to the etheral
extract. Removal of diethyl ether in vacuo and treatment
of the residue with a solution of anhydrous AcOK in methꢀ
anol furnished dipotassium salt 17 (Scheme 4). All operaꢀ
tions were performed quickly at temperature no higher
than 10 °C. In all cases, the yields of salts 17 were higher
than 80%.
Scheme 2
PPA is polyphosphoric acid
The use of this approach for an access to nitrofuroxans
required synthesis of αꢀnitro oximes bearing the nitro group
as one of the substituents. Previously,12 we have developed
a similar pathway toward 3ꢀarylꢀ4ꢀnitrofuroxans 8, which
was based on the reaction of βꢀnitrostyrenes 9 with NaNO2
in AcOH. In this case, the addition of the N2O3 fragments
to the double bond followed another pattern than that
shown in Scheme 1. The NO2 fragment adds to the carbon
atom adjacent to the Arꢀsubstituent, while the NO fragment
adds to the carbon atom of the CHNO2 group to give
isomeric pseudonitrosites 10, which, apparently, were conꢀ
verted in 4ꢀnitrofuroxans 8 via αꢀnitro oximes 11 and their
aciꢀnitro form 12 by the pattern similar to that shown in
Scheme 1 (Scheme 3). This method has significant disadꢀ
vantages: the reaction is very slow (several days), portionꢀ
Scheme 4
Scheme 3
Ar
= 4ꢀMeOꢀ3,5ꢀ(NO2)2C6H2 (a), Ph (b), 2ꢀNO2C6H4 (c),
3ꢀNO2C6H4 (d), 4ꢀNO2C6H4 (e), 4ꢀBrC6H4 (f)
Structures of dipotassium salts 17 were established
based on the data from IR spectroscopy and elemental
analysis (Table 1). It is of note that no absorption bands of
the OH groups in the range of 3200—3400 cm–1 were
found in IR spectra indicating the absence of the free oxime
units. Besides, the ionization constants of dinitromethyl
and oxime fragments were determined by UV spectroscoꢀ

Synthesis of 3(4)ꢀnitroꢀ4(3)ꢀRꢀfuroxans
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
2139
Table 1. Yields, IR spectroscopic data, and elemental analysis data of synthesized dipotassium salts of 1ꢀarylꢀ1ꢀhydroxyiminoꢀ2,2ꢀ
dinitroethane 17a—f and tetrapotassium salt of 1,4ꢀbis(2,2ꢀdinitroethylꢀ1ꢀhydroxyimino)benzene 25b
Comꢀ
pound
Ar
Yield
(%)
Found
Calculated
Molecular
formula
IR, ν/cm–1
(%)
C
H
N
17a
17b
4ꢀMeOꢀ3,5ꢀ(NO2)2C6H2
Ph
87
82
25.47
25.65
1.31
1.20
16.50
16.62
С9H5K2N5O10
С8H5K2N3O5
3170, 1550, 1540, 1500, 1470,
1440, 1410, 1350, 1300, 1210,
1200, 1115, 1090, 1020, 1005, 990
3160, 2850, 1500, 1480, 1440,
1440, 1410, 1370, 1300, 1270,
1215, 1180, 1150, 1120, 1090,
1010, 990, 930
31.78
31.89
1.72
1.67
13.81
13.94
17c
17d
17e
17f
2ꢀNO2C6H4
3ꢀNO2C6H4
4ꢀNO2C6H4
4ꢀBrC6H4
86
83
85
87
90
27.61
27.74
1.09
1.16
16.03
16.18
С8H4K2N4O7
С8H4K2N4O7
С8H4K2N4O7
С8H4BrK2N2O5
С10H4K4N6O10
3160, 1550, 1540, 1485, 1450,
1410, 1380, 1305, 1240, 1210,
1125, 1010, 940
3160, 1500, 1480, 1440, 1410,
1380, 1300, 1190, 1130, 1090,
1005
3170, 1500, 1480, 1410, 1350,
1340, 1300, 1280, 1220, 1180,
1120, 1090, 1000, 940
3150, 1490, 1420, 1340, 1300,
1285, 1205, 1140, 1030, 1005,
980, 920, 890
27.56
27.74
1.11
1.16
16.30
16.18
27.70
27.74
1.04
1.16
16.33
16.18
26.40
26.24
1.08
1.10
7.71
7.65
25b*
pꢀPhenylene
22.71
22.90
0.58
0.76
16.20
16.03
3140, 1552, 1492, 1384, 1368,
1236, 1188, 1132, 996, 936,
848, 828, 808, 752, 700
* 1Н NMR of compound 25b in DMSOꢀd6: δ 7.38 (s, 4 H, Ar).
Scheme 5
py by an example of compound 17a. It was found that pKa
of the dinitromethyl group is 2.23 and pKa of the oxime
group is 4.43 (pKa of AcOH is 4.76). The ionization conꢀ
stants were calculated by the standard equations.13
Thus, we synthesized αꢀnitro oximes 16 as stable dipoꢀ
tassium salts 17 that could be used for the development of
the synthetic method toward furoxans. If αꢀnitro oximes
16 are prone to ring closure, they should be isolated from
the salts, and conditions for the cyclization could be found.
Initially, we tried to acidify salt 17a with dry HCl in diethꢀ
yl ether in the hope that the resulting αꢀnitro oxime 16a
would not immediately transform from aciꢀform 16a´ into
nitro compound but will undergo ring closure to 4ꢀarylꢀ3ꢀ
nitrofuroxan 18a (Scheme 5). Nitrofuroxan 18a was isoꢀ
lated, but in the yield of only 4%. Apparently, under seꢀ
lected conditions, the isomerization of aciꢀform 16a´
into nitro compound 16 occurred much faster than the
ring closure to give furoxan 18a. The existence of the
gemꢀdinitromethyl group in the aciꢀform in the equilibriꢀ
um with the nitro form have previously been shown
by IR spectroscopy by the example of the solution of diꢀ
nitromethane salt in concentrated sulfuric acid.14 Howevꢀ
er, the replacement of HCl by H2SO4 resulted in the
increase in the yield of furoxan 18a up only to 14%
(see Scheme 5).
Ar = 4ꢀMeOꢀ3,5ꢀ(NO2)2C6H2
For the development of the synthetic pathways toward
4ꢀarylꢀ3ꢀnitrofuroxans 18, nitrosation of salts 17 was studꢀ
ied. At first, N2O4 was used for nitrosation. The reaction
was carried out in chloroform at 20 °C using salts 17a,b as
model compounds. In comparison with the reaction of
salt 17a with acids, this approach is more efficient, howꢀ
ever, this reaction yielded a mixture of arylnitrofuroxan

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Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
Ovchinnikov et al.
Scheme 7
isomers (8a,b and 18a,b) in 30% total yield. Apparently,
under these conditions nitration of the oxime moiety to
give nitrosomethyl fragment as well as nitrosation of the
dinitromethyl group to give dinitronitrosomethyl fragment
take place. Intermediates 19 were converted into furoxans
by elimination of N2O4 via dinitroethylenes 20 in nonꢀ
regiospecific reaction, which furnished a mixture of isomeꢀ
ric furoxans 8a,b and 18a,b in the ratio 1 : 1 (Scheme 6).
Scheme 6
Ar
= 4ꢀMeOꢀ3,5ꢀ(NO2)2C6H2 (a), Ph (b), 2ꢀNO2C6H4 (c),
3ꢀNO2C6H4 (d), 4ꢀNO2C6H4 (e), 4ꢀBrC6H4 (f)
ic 3(4)ꢀnitroꢀ4(3)ꢀ(3,4,5ꢀtrinitrophenyl)furoxans 18h and
8h. The best yields (76—82%) were obtained using the
latter oxidizing reagent (Scheme 8, see Table 2).
Synthesis of 3ꢀnitorfuroxans 18 by nitrosation of dipoꢀ
tassium salts 17 is a hitherto unknown approach to the
construction of the furoxan ring. The 15Nꢀlabeled chloride
13f´ was synthesized using 15NH2OH•HCl; the correꢀ
sponding 3ꢀ and 4ꢀnitrofuroxans 18f´ and 8f´ were deꢀ
rived to confirm the involvement in the cyclization of the
oxime group that formed in the reaction of arylhydroxiꢀ
moyl chloride 13 with dinitromethane sodium salt 14. Data
from 15N and 13C NMR spectroscopy using the 13C—15N
coupling constant showed that the 15Nꢀlabel was incorpoꢀ
rated completely in the resulting furoxans. (This part of
the research will be presented as a separate publication.)
Synthetic approach toward arylnitrofuroxans 8 and 18
with one nitrofuroxan ring was extended to the synthesis
of compounds bearing two nitrofuroxanyl moieties in the
aromatic ring, 1,3ꢀ (22a,c) and 1,4ꢀbis(3ꢀnitrofuroxanꢀ
yl)arenes (22b), and isomeric 1,3ꢀ (23a,c) and 1,4ꢀbisꢀ
(4ꢀnitrofuroxanyl)arenes 23b*. 3ꢀNitro isomers 22a—c were
obtained under conditions similar to those employed for
the synthesis of 4ꢀarylꢀ3ꢀnitrofuroxans 18. Reaction of
bis(chlorides) of 1,3ꢀ and 1,4ꢀaryl(bishydroximic)acids
24a—c with dinitromethane sodium salt resulted in tetꢀ
rapotassium salts 25a—c. The structure of salt 25b was
confirmed by the data from IR and 1H NMR spectroscoꢀ
py. Due to sensitivity to the mechanical manipulations,
no spectroscopic study of tetrapotassium salts 25a and 25c
was carried out. Their formation was proved by the isolaꢀ
tion of their 3ꢀnitrofuroxan derivatives, which were obꢀ
tained by in situ nitrosation of salts 25a and 25c with
sodium nitrite in acetic acid. The yields of 1,3ꢀ and 1,4ꢀbisꢀ
(3ꢀnitrofuroxanyl)arenes 22a—c are 42—56%. 3ꢀNitro isoꢀ
mers 22a—c were thermally isomerized into 4ꢀnitro isoꢀ
mers 23a—c in high yields (Scheme 9, Tables 1—3).
Ar = 4ꢀMeOꢀ3,5ꢀ(NO2)2C6H2 (a), Ph (b)
The use of NaNO2 in glacial AcOH instead of N2O4
resulted in regiospecific nitrosation of salts 17. Under these
conditions, 4ꢀarylꢀ3ꢀnitrofuroxans 18 were exclusively obꢀ
tained in significantly increased yields of 50—55%. Probꢀ
ably, under these conditions, the oxime group exists as the
anion and the initial step of the reaction is nitrosation of
the dinitromethyl anion to give intermediate 21. Later,
the anion of the oxime group attacks the nitroso group of
the intermediate to result in furoxan ring closure with elimꢀ
ination of the NO2 anion. The mechanistic pattern was
refined by the use in the reaction of an additional amount
of AcOK, which maintained the anionic form of the oxime
fragment. Indeed, under these conditions the yield of
furoxan 18a increased to 80%; the yields of 3ꢀnitrofuroxans
18b—f also markedly increased. The resulting 3ꢀnitrofuroxꢀ
ans 18a—f underwent thermal isomerization into 4ꢀnitroꢀ
furoxans 8a—f in nearly quantitative yields (Scheme 7,
Table 2).
The methoxy group of isomeric nitrofuroxans 8a and
18a with 4ꢀMeOꢀ3,5ꢀ(NO2)2C6H2 substituent was conꢀ
verted into NO2 group. At first, the MeO group was reꢀ
placed by the amino group to give the corresponding amiꢀ
no derivatives 18g and 8g (in the case of 3ꢀnitro isomer
18a ammonium hydrogencarbonate in a DMF—MeOH
mixture was used, while 4ꢀnitro isomer 8a was treated
with dry ammonia in chloroform, because the aboveꢀmenꢀ
tioned conditions resulted in partial replacement of the
4ꢀnitro group with the MeOꢀgroup). The aromatic amino
groups in isomers 18g and 8g were oxidized with perfluoꢀ
roacetic acid or 85% H2O2 in conc. H2SO4 to give isomerꢀ
* Brief communication, see Ref. 15.

Synthesis of 3(4)ꢀnitroꢀ4(3)ꢀRꢀfuroxans
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
2141
Scheme 8
Scheme 9
a: R = H, 1,3ꢀisomer; b: R = H, 1,4ꢀisomer; c: R = Me, 1,3ꢀisomer
Reagent and conditions: i. 1) NaCH(NO2)2/DMF, 2) H2SO4/H2O, 3) AcOK/MeOH; ii. NaNO2, AcOH (AcOK).
Scheme 10
The method developed for the synthesis of the isomerꢀ
ic 3(4)ꢀarylꢀ4(3)ꢀnitrofuroxans 8 and 18 is suitable for the
preparation of isomeric nitrofuroxans with nonꢀaromatic
substituents, namely, COMe and CO2Et. However, the
procedure for the conversion of the hydroximoyl chlorides
26a,b into 3ꢀnitrofuroxans 27a,b significantly differed from
that for 4ꢀarylꢀ3ꢀnitrofuroxans 18. It was found that dipoꢀ
tassium salts, similar to salts 17, cannot be isolated from
the reaction mixture of chlorides 26a,b with 2 mol. equiv.
of dinitromethane sodium salt 14. Therefore, an excess of
AcONa was added to the reaction mixture of compounds
26 and 14 yielding disodium salts 28a,b, which underwent
in situ nitrosation with N2O4. The yields of the resulting
3ꢀnitrofuroxans 27a,b (28—44%) were lower as compared
with 4ꢀarylꢀ3ꢀnitrofuroxans 18. However, the reaction proꢀ
ceeded regiospecifically furnishing exclusively 3ꢀnitro isoꢀ
mers 27a,b, which were thermally isomerized into 4ꢀnitro
isomers 29a,b in nearly quantitative yields (Scheme 10,
see Tables 2 and 3).
In summary, a convenient general method for the synꢀ
thesis of isomeric 3ꢀ and 4ꢀnitorfuroxans bearing aromatic
or functional substituents at the C(4) (C(3)) atom of the
R = COMe (a), CO2Et (b)

2142
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
Ovchinnikov et al.
Table 2. Yields and selected physicochemical parameters of synthesized 3ꢀ (18a—h, 22a—c, 27a,b) and 4ꢀnitrofuroxans
(8a—h, 23a—c, 29a,b)
Comꢀ
pound
Yield
(%)
M.p./°C
[(b.p./°C)/p/Torr]
Rf
(eluent)
Found
Calculated
Molecular
formula
(%)
C
H
N
18a
8a
68
80
74
85
78
78
79
82
80
80
83
87
76
88
76
82
56
91
45
90
42
70
28
94
44
92
149—150
126—127
0.43
(CHCl3)
0.43
(CHCl3)
33.10
33.04
33.15
33.04
—
1.51
1.54
1.46
1.54
—
21.47
21.41
21.27
21.41
—
С9H5N5O9
С9H5N5O9
—
18b
8b
109—110
(106—107)5
97—98
(97—97.5)5
127—128
0.66
(C6H14—CH2Cl2 (3 : 1))
0.63
(CHCl3)
0.48
(CHCl3)
0.48
(CHCl3)
0.45
(CHCl3)
0.45
(CHCl3)
0.50
(CHCl3)
0.50
(CHCl3)
0.46
(CHCl3)
0.46
(CHCl3)
0.27
(CHCl3)
0.27
(CHCl3)
0.25
(CHCl3)
0.25
(CHCl3)
0.27
(CCl4—EtOAc (1 : 1))
0.21
(ССl4—CHCl3 (1 : 1))
0.31
(CCl4—EtOAc (1 : 1))
0.20
(ССl4—CHCl3 (1 : 1))
0.20
(ССl4—CHCl3 (1 : 1))
0.20
(ССl4—CHCl3 (1 : 1))
0.44
(CHCl3)
0.71
(C6H14—EtOAc (3 : 1))
0.60
(CHCl3)
0.60
(CHCl3)
—
—
—
—
18c
8c
38.00
38.11
38.02
38.11
38.30
38.11
38.20
38.11
38.17
38.11
38.27
38.11
33.70
33.59
33.77
33.59
30.66
30.78
30.70
30.78
28.03
28.08
27.83
28.08
35.61
35.73
35.64
35.73
35.69
35.73
35.84
35.73
37.59
37.73
37.60
37.73
27.67
27.75
27.54
27.75
29.40
29.57
29.72
29.57
1.67
1.60
1.71
1.60
1.72
1.60
1.63
1.60
1.62
1.60
1.70
1.60
1.35
1.41
1.40
1.41
1.34
1.29
1.21
1.29
0.41
0.59
0.43
0.59
1.21
1.20
1.28
1.20
1.18
1.20
1.22
1.20
1.72
1.73
1.81
1.73
1.76
1.71
1.65
1.71
2.41
2.48
2.43
2.48
22.10
22.22
22.05
22.22
22.33
22.22
22.07
22.22
22.17
22.22
22.20
22.22
14.78
14.69
14.66
14.69
27.07
26.92
26.95
26.92
24.50
24.56
24.41
24.56
24.85
25.00
24.97
25.00
25.01
25.00
25.05
25.00
24.13
24.00
24.07
24.00
24.32
24.40
24.56
24.40
20.58
20.69
20.89
20.69
С8H4N4O6
С8H4N4O6
С8H4N4O6
С8H4N4O6
С8H4N4O6
С8H4N4O6
С8H4BrN3O4
С8H4BrN3O4
С8H4N6O8
С8H4N6O8
С8H2N6O10
С8H2N6O10
С10H4N6O8
С10H4N6O8
С10H4N6O8
С10H4N6O8
С11H6N6O8
С11H6N6O8
С4H3N3O5
С4H3N3O5
С5H5N3O6
С5H5N3O6
91—92
117—118
92—93
18d
8d
18e
8e
132—133
101—102
80—81
18f
8f
56—57
18g
8g
194—195
214—215
163—164
192
18h
8h
22a
23a
22b
23b
22c
23c
27a
29a
27b
29b
139—140
142—144
180—203*
212—214
122—124
138—141
Oil
[72—74/1]
Heavy oil
[58/0.3]
* Melting of 3ꢀnitro isomer 22b resulted in 4ꢀnitro isomer 23b with higher melting point.

Synthesis of 3(4)ꢀnitroꢀ4(3)ꢀRꢀfuroxans
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
2143
Table 3. 1H, 13С, 14N NMR, IR, and MS spectral data of synthesized 3ꢀ (18a—h, 22a—c, 27a,b) and 4ꢀnitrofuroxans (8a—h,
23a—c, 29a,b)
Comꢀ
pound
IR, ν/cm–1
1H NMR, δ (J/Hz)
[MS, m/z (Irel (%))]
3С NMR, δ
[
14N NMR, δ, Δν1/2/Hz]
18a
8a
3100, 1649, 1570, 1555, 1541,
1521, 1480, 1450, 1422, 1405,
1352, 1121, 1060, 1021, 978,
920, 860
4.08* (s, 3 H, MeO);
8.70 (s, 2 Н, Ar)
[327 [M]+ (16), 311 (3), 297 (10),
281 (31), 267 (3), 251 (100), 222 (21)]
64.8* (MeO), 120.8 (С(1), Ar),
131.0 (C(2), C(6), Ar), 140.4 (С(4), Ar),
144.5 (C(3), C(5), Ar),
127.8 (С(3) in the furoxan ring),
149.4 (C(4) in the furoxan ring)
3100, 1639, 1590, 1580, 1571,
1555, 1541, 1526, 1510, 1490,
1458, 1429, 1411, 1357, 1300,
1280, 1265, 1170, 1120, 1031,
980, 919, 890, 842
4.10* (s, 3 H, MeO);
8.73 (s, 2 Н, Ar)
[327 [M]+ (9), 311 (2), 297 (8),
281 (20), 267 (3), 251 (100), 223 (88)]
—
18c
8c
3120, 3080, 1655, 1640, 1622,
1539, 1527, 1510, 1458, 1428,
1355, 1150, 1018, 860, 853, 800
8.00* (m, 3 Н, Ar);
8.45 (d, 1 Н, Ar)
[252 [M]+ (13), 222 (68), 206 (100),
160 (15), 130 (17), 106 (34)]
119.6* (С(1), Ar), 146.9 (C(2), Ar),
125.2, 133.2, 133.4, 135.2 (C, Ar),
127.2 (С(3) in the furoxan ring),
150.1 (С(4) in the furoxan ring)
3100, 1649, 1638, 1624, 1589,
1580, 1572, 1540, 1510, 1490,
1460, 1371, 1352, 1320, 1292,
1175, 1140, 1082, 1050, 1010,
991, 970, 860
7.96* (m, 3 Н, Ar); 8.35 (d, 1 Н, Ar)
[176 (15), 148 (44), 134 (30),
102 (100)]
118.8* (С(1), Ar), 142.2 (C(2), Ar),
123.4, 135.3, 135.9, 136.2 (C, Ar),
109.2 (С(3) in the furoxan ring),
158.2 (С(4) in the furoxan ring)
18d
8d
3120, 1590, 1520, 1460, 1410,
1355, 1209, 1110, 1030, 1018,
1005, 920, 875, 860, 820, 800
8.35* (m, 3 Н, Ar); 8.50 (s, 1 Н, Ar)
[252 [M]+ (24), 222 (63), 176 (90),
148 (59), 130 (36), 102 (100)]
—
—
3110, 1630, 1572, 1490, 1378,
1360, 1315, 1278, 1150, 1100,
1018, 1020, 909, 880, 850, 812
8.35* (m, 3 Н, Ar); 8.63 (s, 1 Н, Ar)
[252 [M]+ (3), 222 (50), 176 (100),
148 (60), 130 (26), 118 (4), 102 (90)]
18e
3120, 1650, 1618, 1542, 1525,
1442, 1404, 1355, 1320, 1295,
1201, 1118, 1020, 990, 859
7.98*, 8.36 (both d, 4 Н, Ar, 3J = 9.6)
[252 [M]+ (39), 236 (5), 222 (100),
206 (14), 176 (100), 160 (12)]
130.9* (С(1), Ar), 123.9 (С(3), C(5), Ar),
131.3 (C(2), C(6), Ar), 149.6 (C(4), Ar),
128.2 (С(3) in the furoxan ring),
151.5 (С(4) in the furoxan ring)
8e
3130, 1630, 1580, 1540, 1520,
1498, 1410, 1305, 1280, 1079,
860,800
7.98*, 8.36 (both d, 4 Н, Ar, 3J = 9.6)
[194 (28), 176 (3), 148 (60),
118 (70), 102 (100)]
—
18f
3090, 1624, 1540, 1508, 1472,
1428, 1388, 1332, 1276, 1256,
1192, 1072, 1016, 1008, 980,
964, 852, 824, 792, 752, 724,
712, 672
7.58****, 7.71 (both d, 4 H, Ar,
3J = 8.2)
122.7**** (С(1), Ar), 127.2 (C(4), Ar),
130.5 (С(3), C(5), Ar), 131.7 (C(2), C(6),
Ar), 126.5 (С(3) in the furoxan ring),
150.5 (С(4) in the furoxan ring)
[–38.7 NO2****, Δν1/2 = 11]
8f
3088, 1612, 1572, 1504, 1480,
1396, 1360, 1304, 1284, 1124,
1072, 1012, 984, 828, 800, 756,
744, 708, 692
7.47****, 7.68 (both d, 4 Н, Ar,
3J = 8.4)
118.3**** (С(1), Ar), 126.7 (C(4), Ar),
130.4 (С(3), C(5), Ar), 132.4 (C(2), C(6),
Ar), 108.8 (С(3) in the furoxan ring),
157.7 (С(4) in the furoxan ring)
[–34.4 NO2****, Δν1/2 = 36]
18g
8g
3475, 3370, 3090, 1650, 1641,
1589, 1555, 1542, 1510, 1454,
1410, 1371, 1360, 1349, 1278,
1225, 1120, 1060, 1022, 939,
910, 860
3.15** (s, 2 H, NH2);
9.06 (s, 2 Н, Ar)
—
[312 [M]+ (15), 296 (3), 266 (21),
236 (100), 208 (28), 194 (15),
190 (9), 174 (6)]
3470, 3362, 3110, 1658, 1632,
1575, 1560, 1520, 1510, 1465,
1412, 1370, 1348, 1258, 1082,
1035, 921, 905, 850
3.15* (s, 2 H, NH2);
—
8.90 (s, 2 Н, Ar)
[312 [M]+ (6), 296 (2), 266 (7),
252 (9), 236 (42), 208 (100)]
(to be continued)

2144
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
Ovchinnikov et al.
Table 3 (continued)
Comꢀ
pound
IR, ν/cm–1
1H NMR, δ (J/Hz)
[MS, m/z (Irel (%))]
3С NMR, δ
14N NMR, δ, Δν1/2/Hz]
[
18h
8h
3110, 1649, 1629, 1590, 1571,
1555, 1510, 1465, 1430, 1408,
1364, 1350, 1290, 1270, 1160,
1094, 1060, 1020, 933, 914,
859, 849
8.92** (s, 2 Н, Ar)
—
—
[342 [M]+ (12), 326 (2), 312 (61),
296 (26), 266 (100), 174 (5)]
3110, 1648, 1590, 1580, 1570,
1560, 1530, 1485, 1445, 1410,
1365, 1350, 1311, 1295, 1185,
1152, 1090, 1080, 1030, 935,
912, 848
9.42* (s, 2 Н, Ar)
[342 [M]+ (31), 326 (3), 312 (61),
296 (36), 266 (100), 174 (5)]
22a
23a
3096, 1632, 1544, 1468, 1448,
1392, 1264, 1220, 1172, 1040,
1000, 984, 856, 808, 756, 720
7.92*** (t, 1 Н, С(5), Ar, 3J = 7.9);
8.15 (d, 2 Н, С(4),(6), Ar, 3J = 7.9);
8.28 (s, 1 Н, С(2), Ar)
125.4*** (С(1), C(3), Ar), 129.0, 129.8
(С(2), C(5), Ar), 132.2 (С(4), C(6), Ar),
127.3 (С(3) in the furoxan ring),
151.4 (С(4) in the furoxan ring)
[–38.4 NO2****, Δν1/2 = 18]
1632, 1568, 1512, 1484, 1372,
1296, 1268, 1144, 1116, 1072,
1028, 1000, 988, 896, 828, 796,
792, 704
7.92*** (t, 1 Н, С(5), Ar, 3J = 7.9);
8.09 (d, 2 Н, С(4),(6), Ar), 3J = 7.9;
8.22 (s, 1 Н, С(2), Ar)
121.9*** (С(1), C(3), Ar),
129.5, 131.04 (С(2), C(5), Ar), 132.8 (С(4),
C(6), Ar), 110.0 (С(3) in the furoxan ring),
158.9 (С(4) in the furoxan ring)
[–34.9 NO2****, Δν1/2 = 37]
22b
23b
22c
3112, 2800, 2332, 1632, 1548,
1436, 1340, 1200, 1012, 984,
844, 792, 712
8.13*** (s, 4 Н, Ar)
8.09*** (s, 4 Н, Ar)
129.8*** (С(1), C(4), Ar), 129.8 (С(2),
C(3), C(5), C(6), Ar), 128.2 (С(3) in the
furoxan ring), 151.8 (С(4) in the furoxan
ring) [–38.3 NO2***, Δν1/2 = 15]
1624, 1612, 1536, 1488, 1408,
1364, 1292, 1268, 1132, 1076,
992, 840, 792
123.9*** (С(1), C(4), Ar), 130.2 (С(2),
C(3),C(5), C(6), Ar), 110.1 (С(3) in the
furoxan ring), 158.9 (С(4) in the furoxan
ring) [–34.9 NO2***, Δν1/2 = 38]
2932, 2876, 1648, 1628, 1536,
1468, 1412, 1348, 1260, 1172,
1076, 880, 844, 776
2.60*** (s, 3 Н, Me);
7.97 (s, 2 Н, Ar);
8.08 (s, 1 Н, Ar)
20.3*** (Me), 127.4 (С(5), Ar),
132.9 (С(4), C(6), Ar), 139.7 (С(2), Ar),
125.7 (С(3) in the furoxan ring),
151.8 (С(4) in the furoxan ring)
[–38.4 NO2***, Δν1/2 = 18]
23c
27a
2920, 1624, 1560, 1504, 1356,
1304, 1272, 1136, 1076, 1048,
1016, 1000, 872, 832, 776,
744, 704
2.56*** (s, 3 Н, Me);
7.88 (s, 2 Н, Ar);
7.99 (s, 1 Н, Ar)
20.3*** (Me), 121.8 (С(1), C(3), Ar),
128.2 (С(2), Ar), 133.1 (С(4), C(6), Ar),
110.0 (С(3) in the furoxan ring),
158.9 (С(4) in the furoxan ring)
[–35.1 NO2***, Δν1/2 = 40]
2930, 2820, 1725, 1640,
1540, 1360
2.77**** (s, 3 Н, Me)
2.63**** (s, 3 Н, Me)
26.6**** (Me), 167.2 (СО),
126.3 (С(3) in the furoxan ring),
149.9 (С(4) in the furoxan ring)
[–40.6 NO2****, Δν1/2 = 17]
29a
27b
2940, 1730, 1640, 1520,1350
27.0**** (Me),
108.8 (С(3) in the furoxan ring),
158.1 (С(4) in the furoxan ring), 186.8 (СО)
2990, 2940, 2915, 2845, 1755,
1650, 1575, 1550, 1350
1.42**** (t, 3 Н, Me);
4.48 (q, 2 Н, СН2)
14.3**** (Me), 65.20 (СН2), 156.2 (СО),
127.0 (С(3) in the furoxan ring),
145.8 (С(4) in the furoxan ring)
[–40.3 NO2****, Δν1/2 = 18]
29b
3000, 2955, 2925, 1765, 1665,
1580, 1325
1.36**** (t, 3 Н, Me);
4.51 (q, 2 Н, СН2)
14.0**** (Me), 64.9 (СН2), 154.4 (СО),
103.8 (С(3) in the furoxan ring),
157.9 (С(4) in the furoxan ring)
[–35.3 NO2****, Δν1/2 = 35]
The NMR spectra were recorded in: * (CD3)2SO, ** CD3CN, *** (CD3)2CO, **** CDCl3.

Synthesis of 3(4)ꢀnitroꢀ4(3)ꢀRꢀfuroxans
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
2145
B. To a stirred 98% H2SO4 (40 mL), salt 17a (1.00 g,
2.4 mmol) was carefully added portionwise at 0—5 °C (flashing
could be observed). The resulting solution was heated to 60—70 °C
and stirred for 30 min. After cooling to room temperature, the
mixture was poured onto ice (100 g) and extracted with chloroꢀ
form (3×20 mL); the combined organics was washed with 5%
aqueous NaHCO3 (3×50 mL), dried with MgSO4, and the solꢀ
vent was removed in vacuo. Compound 18a was obtained in the
yield of 0.11 g (14%).
Synthesis of 4ꢀsubstituted 3ꢀnitrofuroxans 18a,b and 3ꢀsubꢀ
stituted 4ꢀnitrofuroxans 8a,b by reaction of 1ꢀarylꢀ1ꢀhydroxyimiꢀ
noꢀ2,2ꢀdinitroethane dipotassium salts 17a,b with N2O4 (general
procedure). A suspension of dipotassium salts 17a,b (4.75 mmol)
in chloroform (80 mL) was cooled to 5—10 °C and N2O4 (0.46 g,
5 mmol) was added dropwise with stirring. After being stirred
for 20 min, the reaction mixture was washed with 5% aqueous
NaHCO3 (3×50 mL), dried with MgSO4, and concentrated
in vacuo to 10—20 mL. The residue was passed through a silica
gel pad (40/100 mesh, 2 cm), the sorbent was washed with chloroꢀ
form. Removal of the solvent afforded mixture of compounds
18a,b and 8a,b.
Synthesis of 4ꢀsubstituted 3ꢀnitrofuroxans 18a—f and 1,3ꢀ
and 1,4ꢀbis(3ꢀnitrofuroxanyl)arenes 22a—c by reaction of 1ꢀarylꢀ
1ꢀhydroxyiminoꢀ2,2ꢀdinitroethane dipotassium salts 17a—f and
1,3ꢀ and 1,4ꢀbis(1ꢀhydroxyiminoꢀ2,2ꢀdinitro)arene tetrapotassiꢀ
um salts 25a—c with NaNO2 in AcOH (general procedure). To
a stirred mixture of glacial AcOH (60 mL) and AcOK (6.8 g,
70 mmol) at 15—20 °C (ice bath cooling), compound 17a—e
(23 mmol) (or compound 25a—c (11.5 mmol) and NaNO2 (4.0 g,
58 mmol) were added alternately in small portions. The reaction
mixture was stirred for 15 min, heated to 50 °C, and stirred for
20—30 min with portionwise addition of water (150 mL). The
white precipitate that formed was filtered off, washed with dilute
AcOH, water, and hexane, and dried in air.
Isomerization of 4ꢀsubstituted 3ꢀnitrofuroxans 18a—f into
3ꢀsubstituted 4ꢀnitrofuroxans 8a—f, and of 1,3ꢀ and 1,4ꢀbisꢀ
(3ꢀnitrofuroxanyl)arenes 22a—c into bis(4ꢀnitrofuroxanyl)arenes
23a—c (general procedure). A suspension of compounds 18a—f
(20 mmol) (or compounds 22a—c (10 mmol)) in toluene (30 mL)
was refluxed for 2.5—3 h. Toluene was removed in vacuo, the
product was recrystallized from AcOH and dried in air.
4ꢀ(4ꢀAminoꢀ3,5ꢀdinitrophenyl)ꢀ3ꢀnitrofuroxan (18g). A stirꢀ
red solution of 4ꢀ(4ꢀmethoxyꢀ3,5ꢀdinitrophenyl)ꢀ3ꢀnitrofuroxꢀ
an 18a (10 g, 30.6 mmol) in a mixture of DMF (30 mL) and
MeOH (10 mL) was heated to 35—40 °C, and NH4HCO3 (3.16 g,
40 mmol) was added portionwise (by portions of 300—500 mg)
over a period of 30 min. The mixture was stirred until full conꢀ
version of the starting compound was achieved (TLC monitorꢀ
ing), then a mixture of water (30 mL), MeOH (30 mL) and
AcOH (5 mL) was added over a period of 30 min. The yellow
precipitate that formed was filtered off, washed with MeOH
(2×5 mL), water (2×5 mL), and hexane (3×10 mL), and dried in air.
3ꢀ(4ꢀAminoꢀ3,5ꢀdinitrophenyl)ꢀ4ꢀnitrofuroxan (8g). Dry amꢀ
monia was slowly passed through a solution of 3ꢀ(4ꢀmethoxyꢀ
3,5ꢀdinitrophenyl)ꢀ4ꢀnitrofuroxan (8a) (2.6 g, 8 mmol) in anhyꢀ
drous MeOH (180 mL) at 25—30 °C. In the course of reaction,
the mixture acquired yellow color and the precipitate formed.
The reaction mixture was stirred until complete consumption of
the starting compound (TLC monitoring), cooled to –5—0 °C,
the precipitate that formed was filtered off, washed with chloroꢀ
form (2×3 mL), and dried in air.
furoxan ring, including the compounds with two furoxaꢀ
nyl rings in one aromatic core was developed. This methꢀ
od could be extended to the synthesis of other isomeric
nitrofuroxans. The yields and physicochemical and specꢀ
tral characteristics of the compounds synthesized are givꢀ
en in Tables 1—3. The chemical shifts of the signals for
the C(3)NO2 or C(4)NO2 groups in the 13C or 15N NMR
spectra are the characteristic parameters for the assignꢀ
ment of the compound to the C(3)NO2 or C(4)NO2 isoꢀ
mer. All signals for the C(3)NO2 groups appeared in highꢀ
er fields as compared with the corresponding signals for
the C(4)NO2 groups (see Table 2), while Δν1/2 value of
3ꢀnitro isomers is nearly twofold smaller than that of
4ꢀnitro isomers. We have previously established similar
patterns for phenylnitrofuroxans.5
Experimental
The IR spectra were measured on a URꢀ20 spectrometer in
KBr pellets. The NMR spectra were obtained on Bruker WMꢀ250
(1H, 250 MHz) and Bruker AMꢀ300 (13C, 75.5 MHz; 14N,
21.5 MHz) instruments. Chemical shifts in the 1H and 13C NMR
spectra are given relative to Me4Si (internal standard), relative
to MeNO2 (external standard) in the 14N NMR spectra. Mass
spectra were recorded on a Varian MAT CH 6 (70 eV) spectromꢀ
eter. TLC was carried out on Silufol UVꢀ254 plates, visualizaꢀ
tion with UV light.
1ꢀArylꢀ1ꢀhydroxyiminoꢀ2,2ꢀdinitroethane dipotassium salts
17a—f and 1,3ꢀ and 1,4ꢀbis(1ꢀhydroxyiminoꢀ2,2ꢀdinitroethyl)ꢀ
arene tetrapotassium salts 25a—c (general procedure). A stirred
solution of dinitromethane sodium salt 14 (10.5 g, 82 mmol) was
cooled to 10 °C, and hydroximoyl chloride 13 (41 mmol) (or
1,3ꢀ or 1,4ꢀdihydroximoyl chlorides 24a—c (20.5 mmol)) was
added. The reaction mixture was stirred for 2 h, kept at 0—5 °C
for 15—24 h, and then stirred at 15—20 °C for 3—4 h. The
mixture was poured into cold water (400 mL) and extracted with
CHCl3 (3×100 mL). The aqueous layer was cooled to 8—10 °C,
carefully acidified to pH 1—2 with H2SO4, and extracted with
diethyl ether (3×150 mL). The organic layer was dried with
MgSO4 and the solution was concentrated in vacuo at ≤20 °C to
60—80 mL, then MeOH (40 mL) was added and diethyl ether
completely removed in vacuo (~10 min). The residue was cooled
to 10 °C and a solution of anhydrous AcOK (20 g) in MeOH (50 mL)
was added gradually with stirring. The resulting thick suspension was
stirred for 1 h and cooled to 8—10 °C. The product was filtered
off, washed on the filter with MeOH (3×5 mL) and diethyl ether
(3×20 mL). The resulting potassium salts were dried in air.
4ꢀ(4ꢀMethoxyꢀ3,5ꢀdinitrophenyl)ꢀ3ꢀnitrofuroxan (18a). A.
To a suspension of 1ꢀhydroxyiminoꢀ1ꢀ(4ꢀmethoxyꢀ3,5ꢀdinitroꢀ
phenyl)ꢀ2,2ꢀdinitroethane dipotassium salt (17a) (3.99 g,
9.5 mmol, dried over P2O5 in a vacuum desiccator prior to use)
in anhydrous diethyl ether (60 mL), a saturated solution of hyꢀ
drogen chloride in diethyl ether (50 mL) was added. The reacꢀ
tion mixture was stirred for 10 min, then the solvent was decantꢀ
ed, and diethyl ether (50 mL) was added to the precipitate. This
procedure was repeated three more times. The combined etheꢀ
real solution was washed with 5% aqueous NaHCO3 (3×100 mL),
dried with MgSO4, and the solvent was removed in vacuo. Comꢀ
pound 18a was obtained in the yield of 0.124 g (4%).

2146
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
Ovchinnikov et al.
4ꢀ(3,4,5ꢀTrinitrophenyl)ꢀ3ꢀnitrofuroxan (18h) and 3ꢀ(3,4,5ꢀ
trinitrophenyl)ꢀ4ꢀnitrofuroxan (8h). A solution of 85% H2O2
(2 mL) in conc. H2SO4 (28 mL) was cooled to –5 °C, and 4ꢀ(4ꢀ
aminoꢀ3,5ꢀdinitrophenyl)ꢀ3ꢀnitrofuroxan 18g or 3ꢀ(4ꢀaminoꢀ
3,5ꢀdinitrophenyl)ꢀ4ꢀnitrofuroxan 8g (1.25 g, 4 mmol) was addꢀ
ed with stirring. The reaction mixture was stirred at 30—35 °C
for 1 h (until gas evolution ceased and yellow color of the reacꢀ
tion mixture disappeared). The greenish precipitate that formed
was filtered off, washed with 92%, 50%, and 20% aqueous H2SO4
(2×5 mL), water (2×3 mL), hexane (3×5 mL), and dried over
P2O5 in a vacuum disiccator. The dry product was recrystallized
from 100% HNO3.
4ꢀAcetylꢀ3ꢀnitrofuroxan (27a) and ethyl 3ꢀnitrofuroxanꢀ4ꢀ
carboxylate (27b). To a solution of dinitromethane sodium salt
14 (6.74 g, 52 mmol) in anhydrous DMF (50 mL) acethydroxiꢀ
moyl chloride 26a (3.2 g, 26 mmol) or ethoxyhydroximoyl chloꢀ
ride 26b (4.0 g, 26 mmol) was added at –5—0 °C. The reaction
mixture was stirred for 30 min, kept at 2—5 °C for 48 h, anhyꢀ
drous AcONa (8.6 g, 105 mmol) was added, and stirring was
continued for 30 min; then a solution of N2O4 (12 g, 130 mmol)
in CCl4 (15 mL) was added dropwise at 0—5 °C. The reaction
mixture was stirred at 10—15 °C for 1 h and poured into cold
water (300 mL). The resulting mixture was extracted with CCl4
(5×100 mL), the combined organics was washed with 0.5% aqueꢀ
ous NaHCO3 15 (mL), water (3×100 mL), dried with MgSO4,
and the solvent was removed in vacuo at ≤30 °C.
2. N. N. Makhova, I. V. Ovchinnikov, A. S. Kulikov, S. I.
Molotov, E. L. Baryshnikova, Pure Appl. Chem., 2004,
76, 1691.
3. A. Ya. Kots, M. A. Grafov, Yu. V. Khropov, V. L. Betin, N.
N. Belushkina, O. G. Busygina, M. Yu. Yazykova, I. V.
Ovchinnikov, A. S. Kulikov, N. N. Makhova, N. A. Medveꢀ
deva, T. V. Bulargina, I. S. Severina, Brit. J. Pharm., 2000,
129, 1163.
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Isomerization of 4ꢀacetylꢀ3ꢀnitrofuroxan (27a) and ethyl
3ꢀnitrofuroxanꢀ4ꢀcarboxylate (27b) into 3ꢀacetylꢀ4ꢀnitrofuroxan
(29a) and ethyl 4ꢀnitrofuroxanꢀ3ꢀcarboxylate (29b) was achieved
by heating compound 27a (1 g, 5.8 mmol) or compound 27b
(1 g, 5 mmol) on a water bath for 30 min.
This work was financially supported by the Division of
Chemistry and Materials Science of the Russian Academy
of Sciences (Program for basic research "Development of
Scientific Bases for Producing New Generation of Highꢀ
Energy Compounds").
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References
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(in Russian).
Received April 7, 2009;
in revised form June 23, 2009