Synthesis of linear and cyclic compounds containing the 3,4-bis(furazan-3-yl)furoxan fragment

Article abstract of DOI:10.1007/s11172-012-0132-4

Some chemical transformations of 3,4-bis(4-aminofurazan-3-yl)furoxan (1) and 3,4-bis-(4-nitrofurazan-3-yl)furoxan (2) were considered. Compounds 1 and 2 are valuable synthons for the preparation of linear and cyclic compounds containing the 3,4-bis(furaza

Full text of DOI:10.1007/s11172-012-0132-4

Russian Chemical Bulletin, International Edition, Vol. 61, No. 5, pp. 1024—1040, May, 2012
1024
Synthesis of linear and cyclic compounds
containing the 3,4ꢀbis(furazanꢀ3ꢀyl)furoxan fragment
A. I. Stepanov,a A. A. Astrat´ev,a D. V. Dashko,a N. P. Spiridonova,b S. F. Mel´nikova,b and I. V. Tselinskiib
aSpecial DesignꢀEngineering Bureau "Technolog",
33ꢀA Sovetskii prosp, 192076 Saint Petersburg, Russian Federation.
Eꢀmail: stepanoff@pisem.net
bSaint Petersburg State Institute of Technology (Technical University),
26 Moskovskii prosp., 190013 Saint Petersburg, Russian Federation.
Eꢀmail: sve2437@yandex.ru
Some chemical transformations of 3,4ꢀbis(4ꢀaminofurazanꢀ3ꢀyl)furoxan (1) and 3,4ꢀbisꢀ
(4ꢀnitrofurazanꢀ3ꢀyl)furoxan (2) were considered. Compounds 1 and 2 are valuable synthons
for the preparation of linear and cyclic compounds containing the 3,4ꢀbis(furazanꢀ3ꢀyl)furoxan
fragment. The reaction of compound 2 with a series of Nꢀ and Оꢀnucleophiles afforded novel
heterocyclic systems: 7ꢀRꢀ7Нꢀdifurazano[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]azepine and difurꢀ
azano[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]oxepin.
Key words: 3,4ꢀbis(4ꢀaminofurazanꢀ3ꢀyl)furoxan, 3,4ꢀbis(4ꢀnitrofurazanꢀ3ꢀyl)furoxan,
1,2,5ꢀoxadiazole, electrophilic and nucleophilic substitution.
Heterocyclic systems containing the 1,2,5ꢀoxadiazole
Although a number of linear chemical compounds21
and macrocyclic systems22,23 containing several 1,2,5ꢀoxaꢀ
diazole rings, which are linked through bridging groups,
have been obtained, the synthesis of compounds consisting
of two or more 1,2,5ꢀoxadiazole rings linked directly to
each other presents certain difficulties and relatively few
examples of such compounds are known. Among the 3,3´ꢀbiꢀ
furazan derivatives, the best known is 4,4´ꢀdinitroꢀ3,3´ꢀ
bifurazan (DNBF),19 which was obtained in 1968 and is a
powerful high explosive (HE) substance. Despite the sucꢀ
cesses achieved in the synthesis of its precursor, viz., 4,4´ꢀdiꢀ
aminoꢀ3,3´ꢀdifurazan,24 the application of DNBF is limꢀ
ited due to its high sensitivity to a mechanical impact.25
The compounds containing three conjugated 1,2,5ꢀoxaꢀ
diazole rings in their structures are mainly exemplified by
the 3,4ꢀbis(furazanꢀ3ꢀyl)furoxan derivatives. In particuꢀ
lar, 3,4ꢀbis(4ꢀaminofurazanꢀ3ꢀyl)furoxan26 (1) is considꢀ
ered as a heatꢀresistant high explosive27 and the prepaꢀ
ration of its substituted analogs has been described.28
3,4ꢀBis(4ꢀaminofurazanꢀ3ꢀyl)furazan was obtained by the
reduction of the furoxan ring of compound 1 with SnCl2.29
The oxidation of diamine 1 with hydrogen peroxide in the
acidic medium afforded the powerful meltꢀcasting highꢀ
explosive substance, viz., 3,4ꢀbis(4ꢀnitrofurazanꢀ3ꢀyl)ꢀ
furoxan (2).30—32 Also, 3,4ꢀbis(4ꢀazidofurazanꢀ3ꢀyl)ꢀ
furoxan26,33 (3) was proposed for application as energetic
compound. It has been shown that a number of 3,4ꢀbis(4ꢀ
Rꢀfurazanꢀ3ꢀyl)furoxans,34 as well as the furoxan trimꢀ
ers35 4а—g possess a pronounced biological activity being
efficient NO donors.
ring in their structures are well known in the organic chemꢀ
istry.1 By analogy with furan, this system was called as
"furazan".2 The synthesis of 1,2,5ꢀoxadiazole Nꢀoxide origꢀ
inated from the work dedicated to the preparation of diꢀ
bromofuroxan by the reaction of bromine with mercuric
fulminate.3 The beginning of the furoxan chemistry should
be referred to 1880, when the first general procedures for
the synthesis of furoxans were elaborated.4 In 1908,
the term "furoxan" was used for the modern formula of
1,2,5ꢀoxadiazoleꢀ2ꢀoxide.5
A rapid development of the heterocyclic chemistry beꢀ
ing observed in recent decades also concerned this class of
compounds, which attract attention due to a variety of
chemical transformations and pronounced biological acꢀ
tivity. There is a number of articles and reviews dedicated
to the synthesis, chemical properties, and potential appliꢀ
cation of the 1,2,5ꢀoxadiazole derivatives.6—18 It should
be noted that a positive experience in the use of the
3ꢀnitrofurazan fragment for design of novel powerful enꢀ
ergetic materials19 gave rise to the chemistry of the heteroꢀ
cyclic systems under consideration. The aromatic system
of the furazan (furoxan) ring not only provides a high
energy compound with a certain thermal stability, but also
increases its density due to planarity of the structure. In
addition, in contrast to the most of other oxygenꢀcontainꢀ
ing heterocyclic systems furoxans and furazans contain
"active oxygen", which does not bound to carbon or hyꢀ
drogen atoms and, consequently, can oxidize these atoms
to release energy.20
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1019—1034, May, 2012.
1066ꢀ5285/12/6105ꢀ1024 © 2012 Springer Science+Business Media, Inc.

Properties of bis(nitrofurazanyl)furoxan
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
1025
tions is accompanied by not only saponification of both
nitro groups, but also complete destruction of the moleꢀ
cule; a considerable heat effect and intense gas evolution
were observed upon the hydrolysis. A solid product 2 can
inflame upon the action of alkali solutions. In nonꢀaqueous
solvents, the reaction pathway of the dinitro derivative 2
with bases depends on a solvent. In particular, if the reacꢀ
tion is performed in methanol or ethanol with sodium
hydroxide or, taking into account a low stability of comꢀ
pound 2 towards strong bases, with potassium carbonate
as a base, the corresponding dialkoxy derivatives 7a—с are
produced in high yields (Scheme 2). Similarly to the reacꢀ
tion of 3ꢀaminoꢀ4ꢀnitrofurazan with 2ꢀazidoethanol in
aqueous acetonitrile in the presence of NaOH,42 substituꢀ
tion of the 2ꢀazidoethoxy groups for the nitro groups of
compound 2 can occur to form 3,4ꢀbis[4ꢀ(2ꢀazidoethꢀ
oxy)furazanꢀ3ꢀyl]furoxan (7c) in a moderate yield. Perꢀ
forming the reaction with potassium carbonate (as a base)
in dichloromethane allowed us to increase the yield of
compound 7c to 70%.
The reaction of dinitro derivative 2 with potassium
carbonate in anhydrous acetonitrile at 60—70 C affords
the cyclic difurazanyl ether, viz., difurazano[3,4ꢀb:3´,4´ꢀf]ꢀ
furoxano[3,4ꢀd]oxepine (8), in 70% yield (see Scheme 2).
In the latter case, the reaction is accompanied by evoluꢀ
tion of nitrogen oxides whose formation can be explained
by the fact that the reaction proceeds through the acetoꢀ
nitrile carbanionꢀinitiated intramolecular rearrangeꢀ
ment of the nitro group to nitrite.41 The nitrite or its
decomposition product, viz, the hydroxyfurazan anion,
undergoes nucleophilic substitution of another nitro group
of the substrate molecule to form the cyclic ether (see
Scheme 2).
R = NH2 (1), NO2 (2), N3 (3)
4: R´ = Ph (a), Me (b), Pr (c), CH2Cl (d), CH2OH (e), EtO (f), PhO (g)
An efficient synthetic procedure for 3,4ꢀbis(4ꢀRꢀfurꢀ
azanꢀ3ꢀyl)furoxan derivatives 1 (R = NH2) and 2
(R = NO2) has been described,36 which involves transforꢀ
mation of hydroxymoyl chloride 5 to nitrile oxide 6 folꢀ
lowed by dimerization of the latter (Scheme 1). However,
the chemical properties of compounds 1 and 2 obtained
were studied scarcely. Meanwhile, the synthetic availabilꢀ
ity of diamine 1 and its dinitro derivative 2 allows one to
consider them not only as high energy compounds, but
also as intermediates in the synthesis of some novel 3,4ꢀbisꢀ
(4ꢀRꢀfurazanꢀ3ꢀyl)furoxan derivatives.
It is known that 3ꢀnitroꢀ4ꢀRꢀfurazans (furoxans) are
highly reactive in nucleophilic substitution of the nitro
group due to a strong electronꢀwithdrawing effect of the
1,2,5ꢀoxadiazole ring.13,15,16 This reaction is an efficient
tool for the preparation of 1,2,5ꢀoxadiazole derivatives that
are lowꢀavailable or nonꢀavailable by other methods.
The reactions of nitro furazans with Oꢀ and Nꢀ nucleoꢀ
philes are the most studied. For example, the nitro group
at the furazan ring is replaced with the alkoxy or phenoxy
group under the action of excess alkoxide or phenoxide to
afford the nucleophilic substitution products in high
yields.37—39 In the waterꢀcontaining systems, the reacꢀ
tions of 3ꢀnitroꢀ4ꢀRꢀfurazans with weak bases40,41 result
in the replacement of the nitro group with the hydroxy
group, while under anhydrous conditions symmetric diꢀ
furazanyl ethers are produced. In the case where the moꢀ
lecular structure includes two terminal 4ꢀnitrofurazan fragꢀ
ments, this reaction can proceed via intramolecular conꢀ
densation to form macrocyclic ethers.40 Various furazanyl
ethers were also obtained in the reaction of sodium salts of
hydroxyfurazans with nitrofurazans.21
Oxepine 8 has a negative oxygen balance (–54.2%),
but, according to the total explosive characteristics (Table 1),
can be of a certain practical interest as a component in the
formulations of meltcastable explosives and compositions
processed by pressing.43
The cyclic ether 8 is insoluble in a cold aqueous soluꢀ
tion of NaOH and reacts with base solutions at elevated temꢀ
peratures to result in the oxepine ring opening followed by
destruction of the starting compound. Alcoholysis of comꢀ
pound 8 in methanol in the presence of K2CO3 is accomꢀ
panied by the oxepin ring opening and the formation of
Our studies showed that 3,4ꢀbis(4ꢀnitrofurazanꢀ3ꢀ
yl)furoxan (2) is extremely sensitive to nucleophilic agents.
The reaction of compound 2 with aqueous alkaline soluꢀ
Scheme 1
i. H2O2, H2SO4, MeCN.

1026
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
Stepanov et al.
Scheme 2
7: R = Me (a), Et (b), CH2CH2N3 (c)
3ꢀ(4ꢀhydroxyfurazanꢀ3ꢀyl)ꢀ4ꢀ(4ꢀmethoxyfurazanꢀ3ꢀyl)ꢀ
furoxan (9).
lack of hydrogen atoms in the starting compound 2 comꢀ
plicates the signal assignment to particular carbon atoms
in the 13C NMR spectra (Table 4). Only the signals of the
terminal groups can be interpreted unambiguously: the
most upfield chemical shift at ~104 (С(3)) was assigned to
the carbon atoms at the Nꢀoxide group of the furoxan
ring11 and two broadened signals with the most downfield
chemical shift were assigned to the carbon atoms linked
with the nitro group (С(1) and С(6)). A low signal intenꢀ
sity in the latter case is caused by quadrupolar broadening
on the 14N nuclei (see Refs 44–48). The analogous phenoꢀ
menon has been observed in the spectra of 4,4´ꢀdinitroꢀ
3,3ꢀbifurazan45 and other nitrofurazan derivatives46 and is
generally typical of the compounds containing the C—NO2
fragment (see Ref. 47). Using twoꢀdimensional 13C NMR
spectroscopy (see Ref. 36) to establish the bond order of
the carbon atoms with different chemical shifts and using
computational methods48, the signals for dinitro derivaꢀ
tive 2 were assigned as follows: 160.4 (С(1)); 137.3 (С(2));
103.8 (С(3)); 143.2 (С(4)); 139.8 (С(5)); 160.4 (С(6))
To confirm the structure of the compounds obtained,
1
we used the H and 13C NMR and electron impact mass
spectral data (Tables 2 and 3). It should be noted that the
Table 1. Comparison of the energy characteristics of some
3,4ꢀbis(furazanꢀ3ꢀyl)furoxan derivatives
Comꢀ
pound
d
V
Q
/J g–1

/g cm–3
/m s–1
(10 kg, 25 cm)
131
1.795
1.937
1.743
1.866
1.903
1.816
8100
9250
8525
8256
9100
8800
—
24
94
86—100
12
100
80
232
6054
6162
6162
5799
5315
333
843
Octogene
Hexogene
Note: d is a density; V is a detonation velocity; Q is a heat of
explosion;  is an impact sensitivity.
Table 2. 1H and 13C NMR spectra of the products obtained upon the reaction of compound 2 with Оꢀnucleophiles
Compound
13C NMR, 
Oxadiazole atoms
1H NMR, 
Atoms of the side
substituents R
С(1) С(2) С(3) С(4) С(5) С(6)
164.6 134.2 104.2 144.2 136.8 164.4
7a
7c
60.91; 60.79
4.14 (s, 3 H, OCH3);
4.04 (s, 3 H, OCH3)
4.40 (m, 4 H, OCH2);
3.55 (m, 4 H, CH2N3)
—
4.14 (s, 3 H, OCH3)
4.10 (s, 3 H, OCH3)
4.18 (s, 6 H, 2 OCH3)
164.34 134.0 103.7 143.7 136.5 163.18
72.27 (CH2N3);
49.21 (OCH2)
8
9
160.5 135.5 105.0 144.3 137.7 159.9
164.5 134.7 104.7 144.4 137.0 163.0
164.9 137.1 107.2 144.6 138.2 168.2
164.4 137.2 142.9 142.9 137.2 164.4
—
60.78
60.31
60.8
9 (K salt)
10

Properties of bis(nitrofurazanyl)furoxan
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
1027
Table 3. Mass and IR spectra of the compounds obtained upon the reaction of compound 2 with O nucleophiles
Comꢀ
pound
Yield
(%)
M.p./C
MS, m/z
IR spectrum, /cm–1
1
—
169—171
252 [M]+ (85); 222 [M – NO]+ (75);
192 [M – 2 NO]+ (100);
58 [NH2 – C=N – O]+ (25);
30 [NO]+ (30)
3464; 3421; 3335; 3259 (H—N—H); 1639
(NO); 1609 (H2N—C); 1578 (H—N—H,
scissor.); 1561 (N=C—N, stretch.); 1540;
1463 (O—NO); 1417; 1408; 1361 (C—N);
1147; 1010; 991 (N—O—N, symm.); 964,
883, 829 (NO, stretch.); 696
2
—
70
75
109—110
51—52
312 [M]+ (17); 282 [M – NO]+ (20);
130 (10); 100 (21); 88 (9); 78 (20);
60 (100); 46 (87); 38 (11)
304 [M+] (7); 274 [M – NO]+ (16);
102 (34); 88 (12); 76 (74); 62 (58);
50 (42); 38 [C2N]+ (100)
1640, 1584, 1564, 1516, 1448, 1356, 1316,
1284, 1176, 1000, 964, 912, 880
3
2178, 2150 (N3), 1645; 1600, 1555, 1425,
1385 (furazan ring), 1630, 1532,
1463, 1230 (furazan ring)
7a
52—53
282 [M]+ (6); 252 [M – NO]+ (30);
222 [M – 2 NO]+ (12); 192 [M – 3 NO]+ 1390; 1340; 1220; 1150; 990; 870; 810; 700;
3005; 2950; 1635; 1600; 1570; 1450; 1420;
(2); 135 (4); 107 (14); 91 (10); 76 (17);
62 (15); 54 (60); 43 (100)
690
7c
70
55—56
—
2540; 2300; 2160; 2120; 2100; 1630; 1610;
1590; 1580; 1550; 1480; 1440; 1435; 1410;
1380; 1350; 1330; 1300; 1260; 1220; 1160;
1060; 1045; 1035; 1030; 1010; 990
8
9
75
60
91—92
(Ref. 43: 92—93)
236 [M]+ (15); 62 (7); 38 (6);
32 (26); 30 [NO]+ (100)
1650; 1620; 1560; 1545; 1520; 1475; 1390;
1350; 1220; 1150; 1000; 975; 930; 830; 790;
600; 450
67
238 [M – 30]+ (11); 211 [M – NO]+
(12); 210 [M – CO – NO]+ (100);
180 (11); 163 (20); 150 (32); 93 (11);
78 (14); 77 (29); 76 (15); 69 (13); 64
(11); 62 (20); 58 (14); 54 (58); 43 (72);
38 (29); 31 [CH3O]+ (99); 29 (64)
3610; 3590; 3010; 2950; 2920; 2850; 1630;
1610; 1590; 1575; 1560; 1450; 1315; 1215;
1150; 995; 960; 820; 700
10
45
19—21
266 [M]+ (5); 236 [M – NO] (5); 191
(7); 163 (6); 151 (5); 135 (6); 111 (44);
83 (100); 72 (13); 67 (13); 59 (10); 54
(74); 43 [HCNO]+ (91)
3000 (as CH3); 2930 ( CH3); 1600; 1560;
s
1450 (as CH3); 1380 ( CH3); 1350; 1310;
s
1170 (as C—O—C); 1050 ( C—O—C);
s
1020; 990; 970; 900; 860
(see Table 4), which allowed interpretation of the 13C NMR
spectra of the 3,4ꢀbis(3ꢀRꢀfurazanꢀ3ꢀyl)furoxans derivaꢀ
tives obtained (see Table 2).
Since in compound 9, there remains the 13C NMRmethoxy
group with the chemical shift in the more downfield reꢀ
The oxepine ring opening in compound 8 with the
methoxide anion can result in the formation of two strucꢀ
tures of type 9 differing in the position of the methoxy
group relative to the furoxan ring. The conclusion in favor
of the isomer proposed can be made on the basis of comꢀ
parison of the 13C NMR spectra of compound 9, its potasꢀ
sium salt, and 3,4ꢀbis(4ꢀmethoxyfurazanꢀ3ꢀyl)furazan
(10), the latter being obtained by reduction of the furoxan
ring of the dimethoxy derivative 7a with stannous chloride
under the conditions analogous to those used for the reꢀ
duction of furoxan 1 (see Ref. 29). In addition, according
to the rule of Mallory and Cammarata,49 due to the shieldꢀ
ing effect of the Nꢀoxide group, the signals of the substituꢀ
ents adjacent to this group are in the more upfield region.
Table 4. Signal assignment in the 13C NMR spectrum of 3,4ꢀbisꢀ
(4ꢀnitrofurazanꢀ3ꢀyl)furoxan (2)
Atom

Calculation48
Experiment
48
31
С(1)
С(2)
С(3)
С(4)
С(5)
С(6)
156.2
137.9
103.6
146.1
140.9
156.1
—
—
—
160.436
160.4*
137.6*
103.9*
143.2*
139.9*
160.0*
140.448
104.448
138.148
137.336
103.836
143.236
139.836
160.436
31
104.431
138.131
48
31
—
—
143.748
143.731
* Our data.

1028
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
Stepanov et al.
gion, one can assume that this group is placed on the side
opposite to the Nꢀoxide atom.
under the action of sodium azide in acetonitrile.51 To perꢀ
form successfully the analogous reaction with the dinitro
derivative 2, the selection of solvent is important: in the
anionꢀsolvating aprotic solvent (DMF), NaN3 behaves like
a base and singleꢀelectron reducing agent and the reaction
proceeds to evolve nitrogen oxides and affords mainly the
cyclic ether 8; in less basic acetonitrile and acetone, the
reaction proceeds in favor of nucleophilic substitution of
the nitro group for azide to result in the highꢀyield formaꢀ
tion of 3,4ꢀbis(4ꢀazidofurazanꢀ3ꢀyl)furoxan (3). The alꢀ
ternative procedures proposed earlier26,33 for the synthesis
of diazide 3 based on dimerization of 4ꢀazidofurazanꢀ3ꢀ
carbonitrile oxide (11) generated in situ from oxime chlorꢀ
ide 12 are less productive and practically less convenient,
since the intermediate preparation of the corresponding
diazonium salt 13 is required for introduction of the azido
group to the molecule (Scheme 3).
Diazide 3 can also be synthesized by diazotization of
diamine 1. It should be taken into account that diazotizaꢀ
tion of the weakly basic amine groups of amino furazans
proceeds generally in the strong acid medium52 (sulfuric
acid or its mixtures with orthophosphoric or acetic acid)
using nitrososulfuric acid. Concentrated sulfuric acid was
found to be the most suitable solvent for diazotization of
3,4ꢀbis(4ꢀaminofurazanꢀ3ꢀyl)furoxan (1). The treatment
of the obtained solution of bisꢀdiazonium salt 14 with an
aqueous solution of sodium azide or anisole affords the
diazido derivative 3 (Scheme 3) or the azocoupling prodꢀ
uct 15 (Scheme 4), respectively.
The mass spectrum of the dimethoxy derivative 7a conꢀ
tains a lowꢀintensity peak of the molecular ion C8H6N6O6,
282 [M]+ (6). The mode of fragmentation is typical
of 1,2,5ꢀoxadiazoles50, i.e., successive elimination of
NO molecules is observed: 252 [M – NO]+ (30); 222
[M – 2 NO]+ (12); 192 [M – 3 NO]+ (2). The magnetic
nonequivalence of the hydrogen and carbon nuclei of two
methoxy groups in the 1H and 13C NMR spectra of comꢀ
pound 7a is explained by asymmetry of the furoxan
ring and can be indirect evidence of the substitution of
both nitro groups for the methoxy groups in the starting
compound 2 (in the case of the monosubsituted product,
1
only one signal in the H NMR spectrum would correꢀ
spond to the methoxy group). The data from thinꢀlayꢀ
er chromatorgraphy support the individuality of comꢀ
pound 7a obtained.
The mass spectrum of the cyclic ether 8 contains a lowꢀ
intensity peak of the molecular ion C6N6O5, 236 [M]+
(15) and the peak of NO has the maximum intensity. The
mass spectrum of compound 9 contains no peak of the
molecular ion; the peak at m/z 238 (11) corresponds to
elimination of NO from the molecule of the starting comꢀ
pound and the maximum intensities were observed for the
peaks of the ions at m/z 211 [M – CO – NO]+ and
31 [CH3O]+.
It is known that the nitro group of 3ꢀnitroꢀ4Rꢀfurꢀ
azans can be replaced by the azido one in a high yield
Scheme 3

Properties of bis(nitrofurazanyl)furoxan
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
1029
Scheme 4
withdrawing effect of three conjugated 1,2,5ꢀoxadiazole
rings (for example, if only one nitro group in the 3,4ꢀdiꢀ
nitrofurazan molecule is readily replaced by an amine, the
reaction of 4,4´ꢀdinitroꢀ3,3´ꢀbifurazan is difficult to stop
at the step of monosubstitution28). It is convenient to perꢀ
form the reaction of the dinitro derivative 2 with highly
basic amines in acetonitrile; however, other organic solꢀ
vents nonreacting with the starting amines can be used. It
is known that many primary amines are available as salts.
In this case, the pure base can be isolated from the reacꢀ
tion mixture by addition of the corresponding amount of
sodium bicarbonate, which neutralizes the acid part of the
ammonium salt. The yields of the reaction products are
usually 70—85%.
Scheme 5
3,4ꢀBis(4ꢀazidofurazanꢀ3ꢀyl)furoxan (3) possesses
a high sensitivity to mechanical impact, which is typical
of azides (see Table 1). Introduction of the azido groups
results in a dramatic decrease in the packing densities of
the molecules and, consequently, a decrease in the density
of the single crystal and the detonation velocity. Neverꢀ
theless, due to a low melting point (51—52 С) and high
thermal stability, the compound can be of certain interest
for formulation of fusible explosives.
Nitrofurazans react with aqueous ammonia to afford
both the hydrolysis and ammonolysis products of the nitro
group.37 To avoid hydrolysis, this reaction is performed in
anhydrous solutions of ammonia in organic solvents at
low temperature. In the same manner, the nitro group can
be replaced by other highly basic amines under mild conꢀ
ditions.28 The reaction with arylamines is complicated by
side formation of azo dyes due to diazotization of the startꢀ
ing amine with the produced nitrous acid followed by azo
coupling with the excess of the amine.
The reaction of compound 2 with ammonia and highly
basic amines proceeds fast even at low temperatures
(0—10 C) and is accompanied by a considerable exotherꢀ
mic effect. Depending on the structure of the amine used,
we isolated two different types of products of substitution
of the nitro group for other nucleophiles.53 When perꢀ
forming the reaction with the excess of an amine (the
stoichiometry requires using at least 4 moles of the amine
per 1 mole of the starting compound), the products of
substitution of nitro groups for both amino groups are
produced (Scheme 5). In the lack of the amine, disubstiꢀ
tuted amino derivatives are also produced, but the reacꢀ
tion is accompanied by side processes and we failed to
isolate the monosubstitution products from the resulted
mixture. Given that substitution of strong electron withꢀ
drawing nitro groups for mesomeric electron releasing
group occurs in the course of the reaction, substitution of
two nitro group for amine implies a considerable electron
NR2 = morpholino (16); NEt2 (17); piperidino (18); 4ꢀmethylꢀ
piperidino (19); 4ꢀmethylpiperazinꢀ1ꢀyl (20); N(Me)CH2CH2OH (21);
R = NHBut (22)
The NMR spectra of 3,4ꢀbis(3ꢀRꢀfurazanꢀ4ꢀyl)furꢀ
oxans 16—21 and compound 22 are given in Table 5.
The nonequivalence of the carbon atoms of the furaꢀ
zan rings, as well as of the substituents in the NMR specꢀ
tra of compounds 16—22 is caused by the molecular asymꢀ
metry due to the exocyclic NO group of the furoxan fragꢀ
ment. The chemical shifts of the signals in the 13C NMR
spectra of compounds 3 and 16—22 are close to those in
3,4ꢀbis(4ꢀaminofurazanꢀ3ꢀyl)furoxan (1). The mass specꢀ
tra of the synthesized compounds (Table 6) contain lowꢀ
intensity peaks of the ions whose mode of fragmentation is
similar to those of the close analogs.28
The reaction of compound 2 with highly basic primary
amines or ammonia proceeds readily even at low temperaꢀ
tures. But, contrary to the formation of disubstituted amino
derivatives of 3,4ꢀbis(furazanꢀ3ꢀyl)furoxan as in the case
of the reaction with secondary amines, the reaction with
ammonia and primary amines proceeds unusually, i.e., the
replacement of both nitro groups in one molecule takes place
with one molecule of the starting primary amine resulting
in the formation of a novel sevenꢀmembered heterocyclic
structure, viz., 7ꢀRꢀ7Нꢀdifurazano[3,4ꢀb:3´,4´ꢀf]furoxanoꢀ
[3,4ꢀd]azepine (23—27) (Scheme 6).

1030
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
Stepanov et al.
Table 5. 1H and 13C NMR spectra of 3,4ꢀbis(4ꢀRR´Nꢀfurazanꢀ3ꢀyl)furoxans
Compound
13C NMR, 
Oxadiazole atoms
С(1) С(2) С(3) С(4) С(5)
1H NMR, 
Atoms of the side
substituents R
С(6)
1 (R = NH2)
156.3 133.5 104.6 147.0 136.3 155.3
—
—
6.37 (s, 2 H, NH2);
6.47 (s, 2 H, NH2)
3 (R = N3)
154.6 136.0 103.4 144.5 138.8 153.9
—
15 (R = N=NC6H4OMe)
165.98 135.8 105.9 145.4 139.1 165.87 162.53; 162.24; 7.82; 7.80; 7.75; 7.73;
146.4; 146.3; 7.16; 7.14; 7.01; 6.98
127.03; 127.02; (8 s, 1 Н each, 2 C6H4);
115.8; 115.6;
56.65, 58.58
(2 ОСН3)
3.95, 3.89 (2 s, 3 Н each,
2 OСН3)
16 (R2N = morpholino)
17 (R2N = NEt2)
159.6 134.3 105.5 145.1 138.0 159.5
157.7 136.5 107.4 146.7 137.4 157.6
65.61, 65.59;
49.41, 48.81
3.61, 3.53 (m, 8 Н, 2 О(CH2)2);
3.23(m, 4 H, C1N(CH2)2);
3.11 (m, 4 H, C6N(CH2)2)
44.76; 41.70;
12.48; 11.36
3.28 (q, 4 H, C(1)N(CH2)2,
J = 6.5 Hz); 2.85 (q, 4 H,
C(6)N(CH2)2, J = 6.5 Hz);
1.17—1.06 (q, 12 H, 2 CH3)
18 (R2N = pyperidino)
159.9 134.5 105.4 145.2 138.1 159.8
159.8 134.5 105.4 145.1 138.1 159.7
50.40; 49.90;
24.80; 24.74;
23.31
3.17 (m, 4 H, C(1)N(CH2)2);
3.04 (m, 4 H, C(6)N(CH2)2);
1.52 (m, 8 H); 1.45 (m, 4 H)
19 (R2N = 4ꢀmethylꢀ
pyperidino)
50.35; 49.26;
33.01; 29.92;
21.70
3.2, 3.05 (m, 8 H, 4 CH2CH2);
2.5 (m, 2 H, 2 CH);
2.3 (m,6 H, 2 CH3)
20 (R2N = ꢀmethylꢀ
pyperazinꢀ1ꢀyl)
159.58 134.5 105.4 145.0 138.0 159.54 53.82; 53.75;
3.16 (m, 8 H, 4 CH2); 3.10
(m, 3 H) and 2.35 (m, 3 H)
(3 CH2); 2.28, 2.25, 2.21
49.19; 48.76;
46.06
(m, overlap., 8 H, CH2, 2 CH3)
21 (R2N = NMeCH2CH2OH) 164.8 136.3 106.3 144.5 138.0 159.8
77.21; 53.00;
38.17
4.58 (t, 4 H, CH2, J = 5.5 Hz);
3.63 (t, 4 H, CH2, J = 5.5 Hz);
3.10 (s, 6 H, 2 CH3)
22 (R = NHBut)
159.9 135.4 105.0 144.3 137.7 159.8
51.18, 50.31;
27.82, 27.54
7.50 (s, 1 H, NH); 1.30 (s, 9 Н,
С(СH3)3); 1.29 (s, 9 Н, С(СH3)3)
Scheme 6
It should be noted that, in a series of 1,2,5ꢀoxadiazole
derivatives annulated with the sevenꢀmembered nitrogenꢀ
containing heterocycles, diazepine structures obtained by
the reaciton of 3,4ꢀdiaminofurazan with ꢀdicarbonyl
compounds are mainly studied.54,55 Among possible four
modes of 1,2,5ꢀoxadiazole and azepine rings annulation,
only few furazano[3,4ꢀc]azepine derivatives have been obꢀ
tained to date.14,56
The high yield of compounds 23—27, as well as the
absence of linear diamino derivatives among the reaction
products can be explained by the certain preorganized naꢀ
ture of dinitro compound 2, which favors the formation of
cyclic products. For example, it was established by Xꢀray
diffraction study that, in the crystalline state, the planes of
two furazan rings in the molecule of compound 2 are turned
to each other.30,57 It seems that such spatial arrangement
R = H (23), Me (24), CH2Ph (25), CH2CH2OH (26), cycloꢀC7H13 (27)

Properties of bis(nitrofurazanyl)furoxan
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
1031
Table 6. Mass and IR spectra of 3,4ꢀbis(4ꢀRR´Nꢀfurazanꢀ3ꢀyl)furoxans
Comꢀ
pound
Yield
(%)
M.p./C
MS, m/z
IR, /cm–1
15
16
17
18
40
70
63
70
137
490 [M]+ (0.3); 147 (11); 135
3100 (Ar—H); 2975 (as, CH3); 2940 (s, CH3);
1660; 1510; 1420; 1370; 1330; 1270; 1230;
1150; 1000; 990; 860; 560
[CH3OC6H4N=N]+ (26); 107 [CH3OC6H4]+
(100); 92 [C6H4O]+ (42); 78 (16); 77 (70);
64 (19); 30 [NO]+ (22)
119
122
94
392 [M]+ (5); 375 [M – OH]+ (22); 362
[M – NO]+ (2); 328 (6); 86 [O(CH2CH2)2N]+ 1470; 1450; 1370; 1260; 1210; 1160; 1120;
(39); 69 [86—OH] (33); 56 C2H2NO (92);
45 (100)
2980; 2960; 2860; 1625; 1590; 1545; 1530;
1070; 1020; 990; 965; 913; 890; 807; 720; 550
364 [M]+ (0.1); 234 (6); 167 (84); 83 (7);
73 (8); 72 (5); 69 (7); 58 (39); 56 (31);
55 (16); 44 (7); 43 (8); 42 (17); 41 (7);
30 [NO] (100); 29 [C2H5]+ (81)
2985; 2940; 2880; 2860; 2470; 2405; 1625;
1570; 1540; 1470; 1460; 1385; 1360; 1290;
1225; 1200; 1045; 990; 960; 860; 810
388 [M]+ (0.2); 372 [M – O]+ (2); 371
[M – OH]+ (12); 177 (13); 125 (10); 109
(26); 84 [(CH2)5N]+ (12); 83 (9); 82 (12);
69(34); 68 (12); 67 (12); 6 (12); 55 (85);
54 (15); 53 (10); 43 [CH2NH=CH2]+ (11);
42 [CH2NH=CH2]+ (60); 41 (100); 39 (17);
30 (27); 29 (33)
2940 (as, CH2); 2860 (s, CH2); 1630; 1590;
1445; 1385; 1280; 1260; 1220; 1160; 1140;
1110; 1010; 990; 965; 900; 810; 715; 600
20
63
117
418 [M]+ (3); 124 (6); 123 (51); 99 (8);
98 (6); 97 (17); 86 (11); 83 (6); 72 (5);
71 (24); 70 (29); 58 (14); 57 (27); 56 (34);
55 (6); 54 (8); 44 (25); 43 [CH2NH=CH2]+
(100); 42 [CH2NH=CH2]+ (78); 41 (7);
40 (5); 32 (59); 30 [NO]+ (16); 29 (8)
2970; 2940; 2852; 2800; 2770; 1620; 1540;
1530; 1450; 1375; 1300; 1290; 1280; 1210;
1145; 1080; 1005; 995; 970;910; 815; 785
21
22
60
64
120
*
293 [M – 75] (24); [M – CH3NCH2CH2OH – 2980; 2940; 2920; 1630; 1590; 1575; 1550;
– H]; 205 (24); 137 (7); 130 (6); 69 (20);
68 (14); 67 (6); 57 (13); 55 (7); 44 (11); 43
(26); 42 (74); 30 (100)
1535; 1475; 1450; 1440; 1410; 1325; 1285;
1190; 1155; 1140; 1030; 995; 980; 965; 880;
805; 600; 535
364 [M]+ (0.5); 349 [M – CH3]+ (1.5);
334 [M – NO]+ (2.5); 309 [M – C4H7]+ (1);
293 [M – NO – CH2=CH – CH2]+ (18);
167 (23); 83 (28); 58 (99); 56 [C4H8]+ (99);
41 (100); 40 (100)
3410; 3280; 2980; 2940; 2880; 1650; 1620;
1560; 1540; 1470; 1300; 1150; 1090; 1050;
1030; 990; 820; 780; 715
* Liquid.
of furazan rings in compound 2 is also preferred in soluꢀ
tion. Consequently, the sterically favorable arragnement
of substituents in the furazan rings favors the fact that,
after the replacement of the first amino group with the
amine, despite a dramatic decrease in its basicity, this
substituent is still capable of nucleophilic substitution of
the second nitro group to form the cyclic product. The
importance of the steric factor is confirmed by the formaꢀ
tion of the only linear diamino derivative 22 analogous to
compounds 16—21 in the reaction of compound 2 with
the sterically hindered tertꢀbutylamine.
tial explosion risk of dinitro derivative 2 and a considerable
exothermal effect of the reaction, the addition of a soluꢀ
tion of 2 to a solution of the corresponding amine taken in
excess seems to be preferable from the viewpoint of safe
conducting the reaction. Variation of the reaction condiꢀ
tions and the use of other solvents instead of acetonitrile,
such as dichloromethane or dioxane, influence weakly the
yield of cyclic products and do not result in the formation
of linear diaminosubstituted 3,4ꢀbis(4ꢀRꢀfurazanꢀ3ꢀyl)ꢀ
furoxan derivatives. In any case, the replacement of nitro
groups proceeds fast and the rate of addition of reactants is
limited by the possibilities of cooling the reaction mass.
In contrast to the examples considered above, the reꢀ
action of compound 2 with ethylenediamine, depending
The order of reagent mixing upon the preparation of
azepines 23—27 has no noticeable effect on the results of
the reaction. Nevertheless, taking into account the potenꢀ

1032
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
Stepanov et al.
Scheme 7
on the reaction conditions, can afford two different prodꢀ
ucts (Scheme 7). If ethylenediamine is added slowly to
a solution of compound 2 in acetonitrile, both amino
groups are involved in the reaction which results in 1,2ꢀbisꢀ
[7Нꢀdifurazano[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]azepinꢀ7ꢀ
yl]ethane (28). Upon the reverse order of reagents mixꢀ
ing and addition of excess ethylenediamine, only one amino
group of the substrate is involved in the reaction to furnish
7ꢀ(2ꢀethylamino)ꢀ7Нꢀdifurazano[3,4ꢀb:3´,4´ꢀf]furoxanoꢀ
[3,4ꢀd]azepine (29). Note that while product 28 is
a thermally stable compound melting at 318 C without
decomposition upon heating in a capillary tube, amine 29
decomposes violently at 160 C without melting. Such
behavior of the latter is likely caused by the highꢀtemperaꢀ
ture reaction of the highly basic free amino group with the
furoxan rings.
The formation of cyclic products was proved by inꢀ
strumental analysis methods (Tables 7 and 8) and conꢀ
firmed by the chemical properties of the compounds
obtained.
1
The H NMR spectra of compounds 24—28 contain
no signals, which correspond to the NH group in the case
of linear nucleophilic substitution product. In the 1H NMR
spectrum of compound 23 (R = H) obtained by the reacꢀ
tion of compound 2 with ammonia, the downfield shift of
the proton signal for the N—H group ( = 12.4) compared
to the signals for the NH2 groups of the linear diamino
derivative 1 ( = 6.37 and 6.4758) suggests the presence of
strong electronꢀwithdrawing substituents at the amino
i. Lack of EDA; ii. Excess of EDA.
group under consideration. The IR spectrum of comꢀ
pound 23 slightly differ from that of compound 1, the
greatest differences are observed in the highꢀfrequency reꢀ
gion (the region of characteristic stretching frequencies of
1
Table 7. H and 13C NMR spectra of the 7ꢀRꢀ7Нꢀdifurazano[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]azepine derivatives 23—29
Comꢀ
pound
R
13C NMR, 
Oxadiazole atoms
1H NMR, 
Atoms of the side
substituents R
С(1) С(2) С(3) С(4) С(5) С(6)
23
24
25
H
152.4 135.8 106.4 145.6 138.1 152.0
154.4 135.4 106.6 145.3 137.5 154.1
154.0 135.6 106.2 145.6 137.7 153.7
—
12.4 (s, 1 H, NH)
3.72 (s, 3 H, CH3)
CH3
38.47
CH2Ph
Ar: 134.4 (C(1´)); 128.9
(C(3´)); 128.2 (C(4´));
127.6 (C(2´)); 55.16 (CH2)
5.41 (s, CH2);
7.53—7.51, 7.38—7.27
(m, 2 Н, m, 3 H, Ar)
26
27
CH2CH2OH
154.0 135.4 106.0 145.3 137.6 153.6
153.46 136.05 105.91 145.3 138.2 153.03
56.0; 53.8
4.29 (t, 2 H, J = 6 Hz);
3.79 (t, 2 H, J = 6 Hz);
5.0—4.7 (s, 1 H, OH)
cycloꢀC7H13
66.82; 30.17;
27.74; 25.79
4.62 (m, 1 H, C—H);
2.38 (m, 2 H, CH2);
1.87 (m, 2 H, CH2); 1.70
(m, 2 H, CH2); 1.69—1.59
(m, 6 H, CH2CH2CH2)
28 —CH2—CH2— 153.95 135.4 105.7 145.0 137.6 153.55
29 CH2CH2NH2 154.1 135.4 106.0 145.4 137.6 153.7
47.20
4.65 (s, 4 H, CH2CH2)
54.79; 37.60
4.22 (t, 2 H, CH2ꢀHet,
J = 7 Hz); 3.00 (t, 2 H,
CH2—NH2, J = 7 Hz);
2.5—1.0 (NH2 + D2O)

Properties of bis(nitrofurazanyl)furoxan
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
1033
Table 8. Mass and IR spectra of the 7ꢀRꢀ7Нꢀdifurazano[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]azepine derivatives (23—29, 32)
Comꢀ
pound
Yield
(%)
M.p./C
MS, m/z
IR spectrum, /cm–1
23
24
68
72
226
235 [M]+ (100); 205 [M – NO]+ (26);
175 [M – 2 NO]+ (30); 145 [M – NO]+
(11); 53 [C2HN2]+ (63)
3570 (as, NH); 3500 (s, NH); 3000, 2850,
2760 (assoc. NH); 1620 (skeletal vibrations
of furazan + planar C=NO of furoxan);
1600, 1570, 1530 (furoxan); 1500; 1470;
1360; 1150; 1000; 970; 830
198
249 [M]+ (92); 233 [M – O]+ (1); 219
[M – NO]+ (15); 189 [M – 2 NO]+
(100); 159 [M – 3 NO]+ (16); 105 (18);
83 (33); 67 (44)
3400, 1650 (furoxan), 1610, 1600, 1560,
1540, 1350, 1130, 1050, 990, 970, 850
25
26
78
60
174
193
325 [M]+ (2.7); 309 [M – O]+ (1);
91 [PhCH2]+ (100), 65 (16); 39 (56);
30 [NO]+ (23)
279 [M]+ (19); 249 [M – NO]+ (6.5);
248 [M – CH2 – OH]+ (13);
236 [M – CH2=CH – O]+ (65) or
[M – HNCO]+; 205 [236 – NO – H]+
(8); 189 [M – 3 NO]+ (24); 176
[236 – 2 NO]+ (15); 45 [CH2CH2OH]+
(100)
3065; 3032; 2920; 1650; 1310; 1590; 1560;
1530; 1480; 1455; 1432; 1390; 1360;1230;
1160; 1020; 990; 900; 830
3550 (OH); 2980 ( CH2); 2920 ( CH2);
as
s
1640; 1610; 1590; 1570; 1520; 1480; 1350;
1640; 1610; 1590; 1570; 1520; 1480; 1350;
1200; 1160; 1070 (as C—C—O); 1020; 980;
970; 900; 840
27
60
219
331 [M]+ (1.4); 98 [C7H14]+ (82); 97
[C7H13]+ (88); 96 (24); 81 (7); 69 (14);
67 (13); 56 (8); 55 (100); 54 (8); 53 (13);
43 (16); 42 (8); 41 (69); 40 (5); 39 (27);
30 (91); 29 (30)
2930; 2855; 1650; 1620; 1585; 1555; 1525;
1475; 1390; 1350; 1330; 1230; 1160; 1010;
990; 970; 890; 850; 825; 790; 720; 680; 590;
545
28
29
70
70
318
496 [M]+ (4); 436 [M – 2 NO]+ (1); 262
(58); 248 [M/2]+ (100); 232 [M/2 – O]+
(20); 201 (88); 188 [M/2 – 2 NO]+ (90)
278 [M]+ (7); 248 [M – NO]+ (2.5); 232
[M – NO – O]+ (6); 188 [M – 3 NO]+
(11); 42 [C2H4N]+ (100)
2980 ( CH2); 2920 ( CH2); 1640; 1610;
1600; 1560; 1520; 1480;1360; 1210; 1160;
1020; 990; 970; 900; 840
as
s
160 (dec.)
3370 ( NH2); 3200 ( NH2); 1650; 1610;
as
as
1600; 1550; 1520; 1480; 1440; 1360; 1200;
1140;1010; 980; 960; 900; 880; 830; 800;
720; 590
the N—H groups). In general, the comparision of the IR
spectra of the annulated systems 23—29 with those of the
linear products 16—21 shows a certain complication of
the spectrum in the wavelength range of 1650—1500 cm–1
due to the emergence of a new ring.
slightly shifted downfield ( 3—6) compared to the acyclic
analogs, which is likely due to involvement of lone pair
electrons at the nitrogen atom of the azepine ring in the
ꢀsystem of the molecule to result in the electron density
redistribution.
The absence of signal splitting of the hydrogen atoms
of the methyl group in the NMR spectra of compound 24
agrees with the cyclic form of the product; in the case of
the formation of the linear substitution product of two
nitro groups for methylamino groups, the chemical shifts
of the signals for two methyl substituents must differ slightꢀ
ly in view of nonsymmetry of the furoxan ring being part of
the molecule. The analogous pattern is observed in the
NMR spectra of the other cyclic products.
It is interesting to note that despite the closeness beꢀ
tween the chemical shifts of the corresponding carbon
atoms of the heterocyclic system and its acyclic analogs
(see Table 6), the signals for the C(1) and C(6) carbon
atoms in the 13C NMR spectra of products 23—29 are
The intensity of molecular ion peaks in the mass specꢀ
tra of products 23—29 is usually higher than in the case of
the linear diamino derivatives 17—22. The mass numbers
of molecular ion peaks correspond to the cyclic structure
proposed. The relative intensities of the ion peaks with
m/z [M + 1]/[M] and [M + 2]/[M] do not contradict the
intensities calculated according to the natural content of
the N and O isotopes in the structures proposed. The mode
of molecular fragmentation of the compounds synthesized
under the electron impact is typical of that for furazan and
furoxan derivatives.59
Compared to the linear diamino derivatives, which are
very soluble in the most of organic solvents (except CCl4
and petroleum ether) and characterized by relatively low

1034
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
Stepanov et al.
Scheme 8
melting points, compounds 23—29 having annulated
structure melt at a higher temperature and much less soluꢀ
ble in organic solvents.
Chemical properties of the synthesized annulated hetꢀ
erocyclic systems confirm their structures. In contrast to
3,4ꢀbis(4ꢀaminofurazanꢀ3ꢀyl)furoxan (1), which is readiꢀ
ly acylated at the terminal amino groups to form monoꢀ34,
diꢀ (30), and even triacetyl (31) derivatives (see Experiꢀ
mental), compoudns 23—25, 27, and 28 were found to be
indifferent toward acetic anhydride. In the case of comꢀ
pound 23 (R = H), the result can be explained by a deꢀ
crease in the nucleophilicity of the amino group of the
sevenꢀmembered ring due to a strong electronꢀwithdrawꢀ
ing effect of two adjacent furazan substituents and, in other
cases, suggests the absence of free N—H groups in the
molecule and confirms indirectly the cyclic structure proꢀ
posed, since in the case of the preparation of the linear
diamino substituted product, the N—H groups must be
acylated easily by analogy to the properties of compound 1.
In addition, compound 23 undergoes alkylation of the
imino group with methyl iodide, dimethyl sulfate, and
benzyl chloride to form the corresponding 7ꢀalkyl substiꢀ
tuted derivatives, which, according to IR spectra, are idenꢀ
tical to compounds 24 and 25 obtained by the reaction of 1
with methylamine and benzylamine, respectively. Alkylaꢀ
tion proceeds slowly, which is likely due to a steric effect
of the adjacent furazan rings.
In contrast to the starting azepine 23, the resulting
dimer 32 is insoluble in aqueous alkali; hardly soluble in
nitric, trifluoroacetic, acetic acids, ethanol, and chloroꢀ
benzene even when heated; and readily soluble in diethyl
carbonate and diethylformamide. Heating of solutions of
the dimer in DMF above 100 C is accompanied by N—N
bond cleavage and the formation of the starting comꢀ
pound 23. To a large extent, such unusual behavior of 23
in different nitrating systems is similar to the features
of nitration of 4,8ꢀdihydrofurazano[3,4ꢀb,e]pyrazine
(BFP)17, as well as to those of oxidation of its 4,8ꢀdiamino
derivative.60 The failed attempts to prepare the Nꢀnitro
BFP derivative61 are associated with the formation of
a stable biradical stabilized due to the negative mesomeric
effect of two furazan rings and the formation of the
14ꢀelectron aromatic system.62 Apparently, dimerization
of azepine 23 proceeds also through the intermediate
formation of a radical stabilized by the system of three
1,2,5ꢀoxadiazole rings.
The sideꢀchain substituents containing functional
groups undergo reactions typical of the functional groups
under consideration (Scheme 9). The presence of free hydrꢀ
oxyl group in compound 26 is confirmed by the formation
of the corresponding acetate 33 and nitrate 34. Under the
action of sodium azide, the nitrate group is replaced by the
azido group to form compound 35 (Table 9).
The presence of the primary amino group in comꢀ
pound 29 is confirmed by the salt formation, acylaꢀ
tion, nitration, and diazotization of this group (see
Table 9). The alcohol formed in the latter case had the
Inertness of compounds 24, 27, and 28 toward difꢀ
ferent nitrating mixtures (HNO3, HNO3/H2SO4, and
HNO3/Ac2O) also evidences the absence of the free N—H
group in the compound obtained.
The study of the behavior of azepine 23 in different
nitrating systems showed an unusual result. The compound
was inert toward concentrated nitric acid and a mixture of
acetyc anhydride and ammonium nitrate (a); however, in
such systems as HNO3/Ac2O, HNO3/H2SO4, HNO3/oleꢀ
um, and HNO3/(CF3CO)2O (b), oxidative "dimerization"
of the starting compound to form a new N(7)—N(7´) bond
between two substrate molecules and precipitation of diꢀ
azepinyl 32 was observed instead of the expected Nꢀnitraꢀ
tion (Scheme 8).
Table 9. Chemical shifts of the protons in the substituted 7ꢀ(2ꢀXꢀethyl) derivatives of 7Нꢀdifurazano[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]ꢀ
azepine (33—38)
Comꢀ
pound
R

Het—CH2
Terminal CH2 group
Substituent X
33
34
35
36
37
CH2CH2OAc
4.25 (t, 2 H, J = 7.0 Hz)
4.96 (br.s, 2 H)
4.40 (br.s, 2 H)
4.62 (t, J = 6.5 Hz)
4.25 (t, 2 H, J = 7.0 Hz)
3.47 (t, 2 H, J = 7.0 Hz)
4.61 (br.s, 2 H)
3.81 (br.s, 2 H)
4.25 (t, J = 6.5 Гц)
3.46 (t, 2 H, J = 7.0 Hz)
1.73 (s, 3 H, COCH3)
—
—
—
7.9—7.8 (br.s, 1 H, NH);
1.73 (s, 3 H, COCH3)
9.50 (br.s, 1 H, NH)
CH2CH2ONO2
CH2CH2N3
CH2CH2NH3+Cl–
CH2CH2NHAc
38
CH2CH2NHNO2
4.62 (t, 2 H, J = 3.5 Hz)
4.98 (t, 2 H, J = 3.5 Hz)

Properties of bis(nitrofurazanyl)furoxan
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
1035
Scheme 9
The spectral characteristics of the compounds obtained,
which are not given in Experimental, are listed in Tables 2, 3,
and 5—8.
IR spectrum identical to that of compound 26 considꢀ
ered above.
Thus, a high synthetic potential shown for 3,4ꢀbisꢀ
(4ꢀnitrofurazanꢀ3ꢀyl)furoxan (2) allows one to consider this
compound as a valuable building block for the design of
a wide spectrum of novel 1,2,5ꢀoxadiazole derivatives, inꢀ
cluding also complex polyheterocyclic annulated systems.
3,4ꢀBis(4ꢀmethoxyfurazanꢀ3ꢀyl)furoxan (7a). To a solution
of compound 1 (3 g, 0.0096 mmol) in anhydrous methanol
(40 mL), anhydrous K2CO3 (4.14 g, 0.03 mmol) was added. The
mixture was stirred for 8 h at 40 С and diluted with water
(150 mL). The separated oil slowly crystallized upon stirring.
The precipitate was filtered off, washed with water, and recrysꢀ
tallized from CH2Cl2—CCl4, 1 : 1 (v/v). The yield was 2.1 g
(75%), m.p. 52 С. Found (%): C, 33.87; H, 2.48; N, 25.75.
C8H6N6O6. Calculated (%): C, 34.04; H, 2.13; N, 25.53.
3,4ꢀBis[3ꢀ(2ꢀazidoethoxy)furazanꢀ4ꢀyl]furoxan (7c). A.
A solution of compound 2 (1.2 g, 4 mmol) in acetonitrile (30 mL)
was mixed with 2ꢀazidoethanol (0.7 g) as a 27% solution in
dichloromethane and a solution of NaOH (0.16 g, 10 mmol) in
the minimum amount of water was added at ~20 C. The reacꢀ
tion mass was left for 16 h, the precipitate was filtered off, the
solvent was removed in vacuo, and the residue was recrystallized
from CCl4. The yield was 0.4 g (27%), m.p. 55—56 C.
Experimental
Melting points were measured on a Kofler stage. IR spectra
were recorded on a FSMꢀ1201 IR spectrometer (KBr pellets).
1H and 13С NMR spectra (300.13 and 75.47 MHz) at the natural
isotope content were recorded on a Bruker DRXꢀ500 spectromꢀ
eter in DMSOꢀd6. The NMR spectral data are given in Tables
1—3, 5, 7, and 9. Mass spectra were recorded on Varian MAT
CHꢀ6 and Varian MAT CHꢀ111 (electron impact, 70 eV) specꢀ
trometers. TLC were performed on Silufol 254UV plates in the
benzene—dioxane—acetic acid—ethanol (90 : 24 : 4 : 4) solvent
system (UV irradiation was used for visualization). Compoudns
1 and 2 were prepared according to the published proceꢀ
dures.26,30—32,58
B. To a solution of compound 2 (6 g, 0.02 mol) in anhydrous
dichloromethane (50 mL), anhydrous K2CO3 (10 g, 0.02 mol),
2ꢀazidoethanol (2.5 g, 0.029 mol) as a 30% solution in CH2Cl2,
and triethylbenzylammonium chloride (50—100 mg) were addꢀ
ed. The mixture was stirred for 8 h at 35—40 С and diluted with
water (150 mL). The organic layer was separated and washed
Attention! The starting dinitro derivative 2, diazide 3, as well as
some compounds prepared are potentially explosive and require
delicate handling.

1036
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
Stepanov et al.
with aqueous alkali. The solvent was removed in vacuo and the
residue was recrystallized from CCl4. The yield was 6.0 g (70%),
m.p. 55—56 С. Found (%): C, 30.20; H, 2.50; N, 42.40.
C10H8N12O6. Calculated (%): C, 30.62; H, 2.06; N, 42.86.
Difurazano[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]oxepine (8). To
a solution of compound 2 (15.6 g, 0.05 mol) in anhydrous acetoꢀ
nitrile (100 mL), anhydrous K2CO3 (5 g, 0.036 mol) was added
with stirring. The reaction mass was stirred at 60 C until the
evolution of nitrogen oxides was terminated (3—5 h) and then
was filtered from inorganic salts. The filtrate was poured into
cold water (500 mL), stirred at room temperature until crystalliꢀ
zation of the intially formed oil was complete. The precipitate
was filtered off and washed with water until pH of the washing
waters became neutral. The residue was crystallized from methꢀ
anol. The yield was 8.8 g (75%), m.p. 91—92 C (cf. Ref. 43:
92—94 C). Found (%): C, 30.67; H, 0.03; N, 35.46. C6N6O5.
Calculated (%): C, 30.51; H, 0.00; N, 35.59.
3ꢀ(4ꢀHydroxyfurazanꢀ3ꢀyl)ꢀ4ꢀ(4ꢀmethoxyfurazanꢀ3ꢀyl)furꢀ
oxan (9). The cyclic ester 8 (2.3 g, 0.01 mol) was dissolved in
methanol (10 mL) and K2CO3 (2 g, 0.014 mol) was added. The
resulted mixture was stirred for 3 h at 65 C, cooled to room
temperature, and filtered off from inorganic salts. The filtrate
was evaporated to dryness in vacuo, the residue was dissolved in
the minimum amount of water and acidified with conc. HCl to
pH 2. The precipitate that formed was filtered off and recrystalꢀ
lized from methanol. The yield was 1.6 g (60%), m.p. 67 C.
Found (%): C, 26.71; H, 1.61; N, 31.17. C7H4N6O6. Calculatꢀ
ed (%): C, 26.86; H, 1.49; N, 31.34.
3,4ꢀBis(4ꢀmethoxyfurazanꢀ3ꢀyl)furazan (10). To a solution
of compound 7a (2.8 g, 0.01 mol) in methanol (50 ml), conc.
hydrochloric acid (20 mL) and stannous chloride dihydrate (9 g,
0.04 mol) were added. The reaction mass was heated with stirꢀ
ring for 4 h at 60 С. The mixture was cooled to room temperaꢀ
ture, diluted with water (150 mL), and extracted with dichloroꢀ
methane (2×25 mL). The organic layer was separated and stirred
for 20 min with a 1% aqueous solution of NaOH (50 mL) at
room temperature. The organic layer was separated, washed with
water, and dried over K2CO3. The solvent was removed in vacuo
and the resulted oil was dissolved in CCl4 (40 mL) and cooled
fast to –20 C (dry ice—dichloromethane bath). The oily precipꢀ
itate that formed was separated by decantation and recrystallizaꢀ
tion was repeated once more. The yield was 1.2 g (45%), m.p.
19—21 C. Found (%): C, 36.34; H, 2.44; N, 31.32. C8H6N6O5.
Calculated (%): C, 36.09; H, 2.25; N, 31.58.
Diazotization of 3,4ꢀbisꢀ(4ꢀaminofurazanꢀ3ꢀyl)furoxan (1),
preparation of a solution of diazonium salt (14). Compound 1 (10 g,
0.040 mol) was added portionwise with stirring to conc. H2SO4
(50 mL). If necessary, the mixture was heated to 40—50 C until
the complete dissolution of compound 1. A solution of nitrososꢀ
ulfuric acid prepared preliminary according to a known proceꢀ
dure63 from NaNO2 (6.9 g, 0.1 mol) and conc. H2SO4 (80 mL)
was added to the resulted solution at the temperature below 5 C.
After the dosage was complete, the mixture was stirred for 3 h at
0—5 C and the resulted solution of diazonium salt was used for
subsequent reactions (~140 mL, 0.3 mmol mL–1).
(2×20 mL). The organic layer was separated, washed with water,
and stirred vigorously with a 1% aqueous solution of NaOH
(100 mL) at 50 C. After the complete evaporation of CH2Cl2,
the resulted emulsion was stirred for 2 h at 50 C and cooled with
stirring to 5—10 C. The precipitate that formed was filtered off
and recrystallized from methanol. The yield was 2.1 g (70%),
m.p. 51—52 C (cf. Refs 26 and 33: 51—52 C). Found (%):
C, 23.45; H, 0.08; N, 55.61. C6N12O4. Calculated (%): C, 23.68;
H, 0.00; N, 55.26.
B. Synthesis of 3 from bisꢀdiazonium salt 14. To a cooled to
–10 C (dry ice—dichloromethane bath) solution of diazonium
salt 14 (50 mL, 0.015 mol) in sulfuric acid, a solution of NaN3
(4 g, 0.058 mol) in the minimum amount of water was added
dropwise with vigorous stirring using external cooling to maintain
the reaction temperature within –10–5 C. After the dosage
was complete, the reaction mass was stirred for 2 h at room
temperature and poured to iceꢀwater mixture (200 g). The prodꢀ
uct separated as an oil, which slowly crystallized. The precipiꢀ
tate was separated by filtration, washed several times with water,
and recrystallized from CH2Cl2—CCl4, 1 : 2 (v/v). The yield
was 2.5 g (55%), m.p. 51—52 С.
3,4ꢀBis[3ꢀ(pꢀmethoxyphenyl)azofurazanꢀ4ꢀyl]furoxan (15).
To a solution (50 mL) of diazonium salt 14 in sulfuric aicd,
CH2Cl2 (50 mL) was added with vigorous stirring. A solution of
anisole (3.24 g, 0.03 mol) in dichloromethane (10 mL) was addꢀ
ed to the resulted emulsion at the temperature below 5 С (dry
ice—dichloromethane bath). The reaction mass was stirred for 2 h
at this temperature and diluted slowly with water (200 mL) while
maintaining the reaction temperature in the range of 5—10 C.
The yellow precipitate was filtered off, washed with ethanol
and water from residual CH2Cl2, and recrystallized from
AcOH—EtOH, 1 : 5 (v/v). The yield was 5.7 g (40%), yellow
crystalls, m.p. 137 C. Found (%): C, 49.06; H, 2.99; N, 28.46.
C20H14N10O6. Calculated (%): C, 48.98; H, 2.86; N, 28.57.
Reactions of 3,4ꢀbis(4ꢀnitrofurazanꢀ3ꢀyl)furoxan (2) with secꢀ
ondary amines and tertꢀbutylamine: preparation of compounds
16—22 (general procedure). Compound 2 (0.01 mol, 3.12 g) was
dissolved in acetonitrile (20 mL). The resulted solution was
cooled to 5—10 C and a solution of the corresponding secondꢀ
ary amine (0.04 mol) in acetonitrile (10 mL) was added dropwise
with stirring at this temperature. After dosage of amine was comꢀ
pleted, the mixture was heated to 30—40 C and stirred for 2—3 h.
The resulted solution was poured to cold water (150 mL) and
extracted with dichloromethane (2×25 mL). The organic layer
was separated, washed several times with water, and dried over
Na2SO4. The solvent was removed in vacuo and the residue was
recrystallized from CCl4.
3,4ꢀBis(4ꢀmorpholinofurazanꢀ3ꢀyl)furoxan (16). The yield
was 2.7 g (70%), m.p. 118—119 С (cf. Ref 28: 118—120 C).
Found (%): C, 42.73; H, 4.23; N, 28.35. C14H16N8O6. Calculatꢀ
ed (%): C, 42.86; H, 4.08; N, 28.5.
3,4ꢀBis(4ꢀdiethylaminofurazanꢀ3ꢀyl)furoxan (17). The yield was
2.3 g (63%), m.p. 122 С. Found (%): C, 45.91; H, 5.62; N, 30.42.
C14H20N8O4. Calculated (%): C, 46.15; H, 5.49; N, 30.77.
3,4ꢀBis(4ꢀpiperidinofurazanꢀ3ꢀyl)furoxan (18). The yield was
2.7 g (70%), m.p. 94 С (cf. Ref. 28: 82—84 C). Found (%):
C, 49.67; H, 5.50; N, 28.24. C16H22N10O4. Calculated (%):
C, 49.48; H, 5.15; N, 28.86.
3,4ꢀBis(3ꢀazidofurazanꢀ4ꢀyl)furoxan (3). A. Synthesis of 3
from compound 2. To a suspension of NaN3 (2 g, 0.029 mol) in
acetonitrile (30 mL), compound 2 (3 g, 9.6 mmol) was added
portionwise with vigorous stirring at 20 C. The mixture was
stirred for additional 4 h at 40 C and poured into cold water
(150 mL). The separated oil was extracted with dichloromethane
3,4ꢀBis[4ꢀ(4ꢀmethylpiperidinofurazanꢀ3ꢀyl)]furoxan (19).
The yield was 1.9 g (45%), m.p. 58—60 C. Found (%): C, 49.89;
H, 5.49; N, 29.29. C16H22N10O4. Calculated (%): C, 49.48;

Properties of bis(nitrofurazanyl)furoxan
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 5, May, 2012
1037
H, 5.19; N, 28.85. IR, /cm–1: 2950; 2930; 2870; 2850; 1630;
1580; 1540; 1465; 1460; 1440; 1385; 1315; 1260; 1155; 990.
3,4ꢀBis(4ꢀmethylpiperazinofurazanꢀ3ꢀyl)furoxan (20). The
yield was 2.3 g (63%), m.p. 117 C. Found (%): C, 45.56; H, 5.60;
N, 33.24. C16H22N10O4. Calculated (%): C, 45.93; H, 5.26;
N, 33.49.
3,4ꢀBis{4ꢀ[NꢀmethylꢀNꢀ(2ꢀhydroxyethyl)amino]furazanꢀ4ꢀ
yl}furoxan (21). The yield was 2.3 g (63%), m.p. 117 C. Found (%):
C, 39.65; H, 4.68; N, 30.04. C16H22N10O4. Calculated (%):
C, 39.13; H, 4.35; N, 30.43.
3,4ꢀBis(3ꢀtertꢀbutylfurazanꢀ4ꢀyl)furoxan (22) was obtained
analogously to compounds 16—21. The second component was
tertꢀbutylamine (0.04 mol). The reaction product was purified by
passing through SiO2 column using CH2Cl2—hexane (1 : 5 v/v)
as the eluent. The yield was 2.35 g (64%), viscous oil.
Reactions of 3,4ꢀbis(4ꢀnitrofurazanꢀ3ꢀyl)furoxan (2) with
ammonia and primary amines: preparation of compounds 24—27
and 32 (general procedure). Compound 2 (3.12 g, 0.01 mol) (first
component) was dissolved in acetonitrile (20 mL). The resulted
solution was cooled to 5—10 C and a solution of the correꢀ
sponding primary amine (second component) (0.03 mol) in acꢀ
etonitrile (10 mL) was added with stirring at this temperature (in
the case of ammonia and methylamine, their aqueous solutions
were used). During the addition of the amine, the red color of
the solution was observed, which disappeared in several minꢀ
utes. At the end of addition, pH of the resulted solution should
be at least 8. After the dosage was complete, the mixture was
heated to 30—40 С and stirred for 2—3 h. The resulted solution
was diluted with 2ꢀ3 volumes of water and the most of acetoꢀ
nitrile was removed under reduced pressure. The precipitate was
filtered off and recrystallized from a suitable solvent.
this temperature, the excess of solvent was removed in vacuo, and
the residue was diluted with water. The precipitate that formed
was filtered off, washed with 10% HCl and water, and recrystalꢀ
lized from a DMF—АсОН (1 : 1 v/v) mixture. The yield was 1.7 g
(70%), m.p. 318 C. Found (%): C, 34.01; H, 1.01; N, 39.74.
C14H4N14O8. Calculated (%): С, 33.88; H, 0.81; N, 39.52.
7ꢀ(2ꢀAminoethyl)ꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxanoꢀ
[3,4ꢀd]azepine (29). To a solution of ethylenediamine (15 g,
0.25 mol) in acetonitrile (100 mL), compound 2 (15.6 g, 0.05 mol)
was added portionwise (per 1 g) with stirring while maintaining
temperature in the range of 15—20 C. When the dosage was
complete, the mixture was stirred for 2 h at this temperature, the
excess of solvent was removed in vacuo, and the residue was
diluted with water. The precipitate that formed was filtered off,
washed with water, and dissolved in 10% HCl (100 mL). The
resulted solution was filtered through a paper filter to separate
a slight amount of the the disubstituted product 28. To the filtrate
10% aqueous NaOH was added carefully to adjust pH to 10, the
mixture was cooled to room temperature, and the precipitate
was filtered off on a glass filter. The product was recrystallized from
an ethanol—DMF (10 : 1 v/v) mixture. The yield was 9.7 g (70%),
m.p. 160 C (dec.). Found (%): C, 34.65; H, 2.30; N, 39.98.
C8H6N8O4. Calculated (%): С, 34.53; H, 2.16; N, 40.29.
Alkylation of 7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]ꢀ
azepine (23) (general procedure). Compound 23 (0.01 mol) was
dissolved in DMF (25 mL), anhydrous K2CO3 (2 g, 0.015 mol)
and the corresponding alkylating agent (0.01 mol) were added,
and the mixture was stirred for 24 h at 50 С. The reaction mass
was poured with stirring into cold water (100 mL). The precipiꢀ
tate was filtered off, washed with water, and recrystallized from
an ethanol—acetic acid (2 : 1 v/v) mixture.
7НꢀDifurazanо[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]azepine (23).
The second component was 25% aqueous ammonia. The yield
was 1.6 g (68%), m.p. 226 С (H2O). Found (%): C, 41.54;
H, 0.60; N, 41.36. C6H1N7O4. Calculated (%): C, 41.70; H, 0.43;
N, 41.70.
7ꢀMethylꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]ꢀ
azepine (24). The alkylating agent was dimethyl sulfate or methꢀ
yl iodide (in the case of methyl iodide, the reaction was perꢀ
formed in a flask equipped with a reflux condenser). The yield
was 2.0 g (80%), m.p. 198 C.
7ꢀMethylꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]ꢀ
azepine (24). The second reactant was 25% aqueous methylꢀ
amine. The yield was 1.8 g (72%), m.p. 198 C (EtOH—DMF,
5 : 1 v/v). Found (%): C, 33.55; H, 1.54; N, 39.18. C7H3N7O4.
Calculated (%): C, 33.73; H, 1.20; N, 39.36.
7ꢀBenzylꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]ꢀ
azepine (25). The second reactant was benzylamine. The yield
was 2.5 g (78%), m.p. 174 C (EtOH—DMF, 5 : 1 v/v). Found (%):
C, 47.85; H, 2.42; N, 29.87. C13H7N7O4. Calculated (%):
C, 48.00; H, 2.15; N, 30.15.
7ꢀ(2ꢀHydroxyethyl)ꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxanoꢀ
[3,4ꢀd]azepine (26). The yield was 1.65 g (60%), m.p. 193 C
(EtOH—АсОН, 10 : 1 v/v). Found (%): C, 34.09; H, 1.97; N, 34.86.
C8H5N7O5. Calculated (%): С, 34.41; H, 1.79; N, 34.86.
7ꢀCycloheptylꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]ꢀ
azepine (27). The second reactant was cycloheptylamine. The
yield was 2.0 g (60%), m.p. 219 C (EtOH—AcOH, 5 : 1 v/v).
Found (%): C, 47.03; H, 4.05; N, 29.46. C13H13N7O4. Calculatꢀ
ed (%): C, 47.13; H, 3.93; N, 29.61.
7ꢀBenzylꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]ꢀ
azepine (25). The alkylating agent was benzyl chloride. The yield
was 2.6 g (80%), m.p. 174 C.
Acylation of 3,4ꢀbis(4ꢀaminofurazanꢀ3ꢀyl)furoxan (1). A.
Preparation of 3,4ꢀbis(4ꢀNꢀacetylaminofurazanꢀ3ꢀyl)furoxan
(30). To a solution of diamine 1 (5 g, 0.02 mmol) in Ас2О
(30 mL), conc. H2SO4 (two droplets) was added with stirring.
Precipitation began after 5 min. The reaction mass was kept for
15 min at room temperature and filtered. The precipitate was
washed with water, dried, and recrystallized from dichloroethane.
The yield was 4.4 g (66%), m.p. 173—174 C. Found (%):
C, 36.19; H, 2.79; N, 33.46. C10H8N8O6. Calculated (%):
1
C, 35.70; H, 2.38; N, 33.30. H NMR, : 11.6, 11.3 (s, 2 H,
2 NH); 2.06, 2.05 (s, 6 Н, 2 CH3CO). 13C NMR, : 1,2,5ꢀoxaꢀ
diazole atoms — 150.56 (C(1)); 133.8 (C(2)); 107.1 (C(3)); 145.8
(C(4)); 136.6 (C(5)); 150.36 (C(6)); substituents — 169.86, 169.81
(2 COCH3); 23.00, 22.66 (2 COCH3). IR, /cm–1: 3620 (N—H, as);
3430 (N—H, s); 3300—3100 (m, N—H assoc.); 2990 (Me); 1680
(C=O, amide 1); 1630; 1590 (stretch. heterocycle); 1560, 1530
1,2ꢀBis[7Hꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]ꢀ
azepineꢀ7ꢀyl]ethane (28). To a solution of compound 2 (3 g,
0.01 mol) in acetonitrile (40 mL), a solution of ethylenediamine
(2 g, 0.033 mol) in acetonitrile (25 mL) was added dropwise with
stirring while maintaining temperature in the range of 5—10 С.
When the dosage was complete, the mixture was stirred for 2 h at
(N—Hdef + C—Nstretch, amide 2); 1500; 1390; 1260 (C—Nstretch
+ N—Hdef, amide 3); 1000; 970; 950; 820; 800; 795; 600.
B. Preparation of 3ꢀ(4ꢀNꢀacetylaminofurazanꢀ3ꢀyl)ꢀ4ꢀ(4ꢀ
N,Nꢀdiacetylaminofurazanꢀ3ꢀyl)furoxan (31). Acylation was perꢀ
formed analogously to the previous procedure, but the reaction
temperature was maintained within 100—110 C and the reacꢀ
+

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Stepanov et al.
tion time was 2 h. After the separation of the precipitate of the
diacetyl derivative 30, the mother solution was poured into water
(100 mL). The precipitate formed was filtered off and extracted
with hot chloroform. Diacetyl derivative 30 (3.2 g) was isolated
from the precipitate. The chloroform extract was evaporated to
dryness and the residue was recrystallized from a CCl4—CHCl3
(1 : 1 v/v) mixture to yield triacetyl derivative 31 (1.25 g, 17%),
m.p. 150—151 С. Found (%): C, 38.25; H, 3.05; N, 29.93.
C12H10N8O7. Calculated (%): C, 38.10; H, 2.64; N, 29.93.
1H NMR, : 2.35 (s, 6 H, 2 CH3); 2.10 (s, 3 H, CH3); 11.7
(s, 1 H, NH).
Nitration of 7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxano[3,4ꢀd]ꢀ
azepine (23), preparation of 7,7´ꢀbis(7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]ꢀ
furoxano[3,4ꢀd]azepine) (32). To a vigorously stirred nitrating
mixture (HNO3—Ac2O 1 : 1; HNO3—H2SO4 1 : 2; HNO3—
20%ꢀoleum 1 : 2, or HNO3—(CF3CO)2O) 1 : 1 v/v) (30—40 mL),
amine 23 (4.7 g, 0.02 mol) was added portionwize at the temperꢀ
ature no higher than 5—10 C. (In the case of nitration in sulfuꢀ
ric acidꢀnitric acid or oleumꢀnitric acid mixtures, to avoid the
formation of clots, the starting amine was dissolved first in nitric
acid and then the resulted solution was added to sulfuric acid).
After the addition of the amine was completed, the mixture was
stirred for additional 3 h at 5—10 C and poured into iceꢀwater
mixture (150 g). The precipitate was filtered off on a Buchner
funnel and washed successively with HNO3 (d 1.5, 10 mL) and
water until neutral pH of the washing waters, and finally ethanol
(20 mL). The precipitate was dried and placed to boiling ethanol
(50 mL). The mixture was boiled with stirring for several minꢀ
utes and filtered while it was hot. The precipitate was washed
with boiling ethanol (3×20 mL) and dried at 50—60 C. The
yield was 3.7—4.2 g (80—90%), m.p. 280 C (dec.). Found (%):
C, 30.59; H, 0.08; N, 41.61. C12H0N14O8. Calculated (%):
С, 30.77; H, 0.00; N, 41.88. 13C NMR, : 150.8 (C(1)); 135.3 (C(2));
106.0 (C(3)); 144.6 (C(4)); 137.2 (C(5)); 150.7 (C(6)). IR,
/cm–1: 1650; 1610; 1600; 1560; 1510; 1460; 1380; 1210; 1000;
980; 860; 800. MS, m/z (Irel (%)): 468 [M] (2.5); 436 [M – 2 O]
(0.4); 234 [M/2] (100); 88 (32); 62 (70); 53 (60); 38 (57).
1560; 1520; 1480; 1360; 1290 ( NO2); 1220; 1000; 980; 970;
s
900; 840 (N—O); 760 ( NO2). 13C NMR, : 154.1; 153.7; 145.2;
137.7; 135.5; 105.9; 69.4 (CH2ONO2); 49.3 (CH2ꢀHet).
7ꢀ(2ꢀAzidoethyl)ꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxanoꢀ
[3,4ꢀd]azepine (35). To a solution of nitrate 34 (1 g, 3 mmol)
in DMF (15 mL), NaN3 (0.5 g, 7.7 mmol) was added. The
reaction mixture was stirred for 5 h at 50 C and poured into
water (100 mL). The precipitate that formed was filtered off and
recrystallized from methanol. The yield was 0.6 g (65%), m.p.
115 C. Found (%): C, 31.46; H, 1.41; N, 45.92. C8H4N10O4.
Calculated (%): C, 31.58; H, 1.32; N, 46.05. IR, /cm–1: 2950;
2920; 2110 (N3); 1650; 1610; 1590; 1545; 1500; 1460; 1420;
1370; 1300; 1270; 1230; 1190; 1030; 1000; 985; 930; 900; 870;
840; 640; 590. 13C NMR (DMSOꢀd6), : 154.1; 153.7; 145.2;
137.7; 135.5; 105.9; 50.8 (CH2N3); 46.9 (CH2ꢀHet).
7ꢀ[2ꢀ(NꢀAcetylamino)ethyl]ꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]ꢀ
furoxano[3,4ꢀd]azepine (37). Amine 26 (0.5 g, 2 mmol) was
mixed with acetic anhydride (4 ml) and sodium acetate (100 mg)
was added. The resulted suspension was refluxed for 2 h and then
poured into water (50 mL). After 1 day, the precipitate was
filtered off, washed with water, and recrystallized from proꢀ
panꢀ2ꢀol. The yield was 0.4 g (70%), m.p. 144 C. Found (%):
C, 37.64; H, 2.31; N, 35.16. C10H8N8O5. Calculated (%):
С, 37.50; H, 2.50; N, 35.00. IR, /cm–1: 3600 ( NH); 3530
as
( NH); 3230, 3080 (NH assoc.); 1650; 1600; 1590; 1550;
as
1520; 1460; 1370; 1300; 1270; 1220; 1000; 960; 890; 840;
790; 600; 590. MS, m/z: 320 [M]+ (4); 291 (0.5); 261
[291 — NO] (2.5); 248 (2.5); 201 (3); 188 (4); 84 (13); 72 (50);
43 [COCH3]+ (100).
7ꢀ[2ꢀ(NꢀNitramino)ethyl]ꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furꢀ
oxano[3,4ꢀd]azepine (38). Amine 26 (0.5 g, 2 mmol) was addꢀ
ed with stirring and cooling to a 1 : 1 (v/v) mixture (10 mL) of
acetic anhydride and HNO3 (d 1.5) at 0—5 С. Precipitation
began after 0.5 h. The reaction mixture was stirred for additional
0.5 h at 10 C and poured into iceꢀwater mixture (50 g). After
1 day, the precipitate that formed was filtered off, washed with
water, and recrystallized from methanol. The yield was 0.48 g
(75%), m.p. 129 С. Found (%): C, 29.25; H, 1.65; N, 38.13.
C8H5N9O6. Calculated (%): С, 29.18; H, 1.52; N, 38.30. IR,
/cm–1: 2950; 2921 ( ,  CH2); 1707; 1655; 1645; 1610; 1590
7ꢀ(2ꢀAcetoxyethyl)ꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxanoꢀ
[3,4ꢀd]azepine (33). Alcohol 26 (0.5 g, 1.8 mmol) was mixed
with acetic anhydride (3 mL) and conc. H2SO4 (one droplet)
was added. The mixture was kept for 30 min at 40 C and poured
into water (20 mL). After 1 day, the precipitate was filtered off
and recrystallized from methanol The yield was 0.4 g (80%), m.p.
107 C. Found (%): C, 37.49; H, 2.25; N, 30.19. C10H7N7O6.
Calculated (%): С, 37.38; H, 2.18; N, 30.53. IR, /cm–1: 2905;
1730; 1650; 1610; 1600; 1550; 1520; 1480; 1440; 1350; 1250;
1210; 1140; 1010; 980; 960; 900; 880; 830; 800; 720; 590.
as
s
(as NO2); 1570; 1540; 1480; 1430; 1390; 1370; 1330; 1310; 1290;
1220 (s NO2); 1180; 1140; 1070; 1040; 990; 970; 850. MS,
m/z: 43 (100); 42 (6); 30 [NO]+ (28).
References
7ꢀ(2ꢀNitroxyethyl)ꢀ7Нꢀdifurazanо[3,4ꢀb:3´,4´ꢀf]furoxanoꢀ
[3,4ꢀd]azepine (34). CH2Cl2 (20 mL) was added to a nitrating
mixture composed of HNO3 (d 1.5, 10 mL) and conc. sulfuric
acid (20 mL); after that alcohol 26 (3 g, 0.011 mol) was added in
small portions with stirring at the reaction temperature below
20 C. After the dosage was complete, the mixture was stirred for
2 h at 20 C and poured to iceꢀwater mixture (100 g). The organic
layer was separated and the aqueous layer was extracted with
CH2Cl2 (30 mL). The combined organic layers were washed
with water, 1% NaHCO3, and dried over Na2SO4. The solvent
was removed in vacuo and the residue was recrystallized from
ethanol. The yield was 2.6 g (75%), m.p. 135 C. Found (%):
C, 29.44; H, 1.43; N, 34.61. C8H4N8O7. Calculated (%):
С, 29.63; H, 1.23; N, 34.57. IR, /cm–1: 2910; 1650; 1600; 1590;
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Received December 12, 2011;
in revised form April 16, 2012