Finding furoxan rings

Article abstract of DOI:10.1039/d0ta01538e

A furoxan ring is derived from a dinitromethyl group. A plausible mechanism is proposed based on ¹H, ¹³C and ¹⁵N NMR spectral analysis where a dinitromethyl group releases one molecule of nitric acid to form an unstable nitrile oxide and its dipole isomer which cyclize to a furoxan ring [3,4-bis(4-nitro-1,2,5-oxadizaol-3-yl)-1,2,5-oxadiazole-N-oxide (5)]. This new method of constructing a furoxan (1,2,5-oxadiazole 2-oxide) ring offers a potentially efficient way to obtain excellent energetic materials. In order to stabilize the dinitromethyl-containing precursor [3-(dinitromethyl)-4-nitro-1,2,5-oxadiazole (4)], a series of new energetic salts was synthesized and fully characterized. These materials exhibit high densities, excellent detonation properties and acceptable sensitivities. For example, the hydrazinium salt 9 has a high density of 1.92 g cm^-3, a detonation velocity of 9437 m s^-1 and a detonation pressure of 41.3 GPa, which approach those properties of CL-20 (ρ, 2.03 g cm^-3; v_D, 9406 m s^-1; P, 44.6 GPa) and which are superior to those of HMX (ρ, 1.90 g cm^-3; v_D, 9320 m s^-1; P, 39.2 GPa).

Full text of DOI:10.1039/d0ta01538e

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Materials for energy and sustainability
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Yu, A. K. Chinnam, P. Yin, G. H. Imler and D. A. Parrish, J. Mater. Chem. A, 2020, DOI:
10.1039/D0TA01538E.
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Pages 4883-5230
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DOI: 10.1039/D0TA01538E
ARTICLE
Finding Furoxan Rings
Qiong Yu,a Ajay Kumar Chinnam,a Ping Yin,b Gregory H. Imler,c Damon A. Parrish,c and Jean’ne M.
Shreeve*a
Received 00th January 20xx,
Accepted 00th January 20xx
Abstract: A furoxan ring is derived from a dinitromethyl group. A plausible mechanism is proposed based on 1H, 13C and 15
N
NMR spectral analysis where a dinitromethyl group releases one molecule of nitric acid to form an unstable nitrile oxide and
its dipole isomer which cyclize to a furoxan ring [3,4-bis(4-nitro-1,2,5-oxadizaol-3-yl)-1,2,5-oxadiazole-N-oxide (5)]. This new
method of constructing a furoxan (1,2,5-oxadiazole 2-oxide) ring offers a potentially efficient way to obtain excellent
energetic materials. In order to stabilize the dinitromethyl-containing precursor [3-(dinitromethyl)-4-nitro-1,2,5-oxadiazole
(4)], a series of new energetic salts was synthesized and fully characterized. These materials exhibit high densities, excellent
detonation properties and acceptable sensitivities. For example, the hydrazinium salt 9 has a high density of 1.92 g cm-3, a
detonation velocity of 9437 m s-1 and a detonation pressure of 41.3 GPa, which approach those properties of CL-20 (ρ, 2.03
g cm-3; vD, 9406 m s-1; P, 44.6 GPa) and which are superior to those of HMX (ρ, 1.90 g cm-3; vD, 9320 m s-1; P, 39.2 GPa).
DOI: 10.1039/x0xx00000x
N
O
R
NaNO2
H
N
O
R
NOH
Cl
R
Introduction
R
R
C N
O
R
NOH
NOH
Base
Furoxan is a heterocycle of the isoxazole family and an amine
oxide derivative of furazan which has been shown to exert a
variety of NO-related bioactivities, including mutagenicity,
immuno suppression, central muscle relaxant properties,
anticonvulsive effects, and monoamino oxidase inhibition
among others.1Since the discovery of the furoxan ring in 1896,
studies of its properties have been ongoing. The furoxan ring
can be synthesized using many different methodologies, for
example, cyclization of nitrile oxides,2 oxidation of o-nitro and
amino groups,3 denitrification of o-nitro and azide groups,4
condensation of chloroxime,5 dehydrogenation of two o-oxime
groups,6 oxidation of carboxylic acid,7 dehydration of o-nitro
and oxime groups,8 and oxidation of the C=C moiety when
bonded to the benzene ring7a,b,9 (Fig. 1). Furoxans have
attracted much interest in energetic materials chemistry since
they have high nitrogen and oxygen content and often have
high density.10 In recent years, many research efforts have been
focused on the properties and applications of compounds based
on a furoxan ring.11 No new routes to obtain the furoxan ring
have been reported recently.
Br 2
O
R
NO2
R
R
N
N
O
O
O
O
R
R
R
NH2
NO2
OH
O
-OH
-N2
R
NOH
R
N3
R
NO2
NO2
NO2
R
This work
Fig. 1 Methods of constructing the furoxan ring.
Fig.
2 Formation of a furoxan ring from a dinitromethyl-containing
compound.
In our continuing efforts to develop new high energy density
materials (HEDMs) which contain the furoxan ring, it was found
that dinitromethyl groups attached to nitro furazan cyclized to
a furoxan ring at room temperature (Fig. 2). Although
compound 4 is stable when maintained at -10 C, it cyclizes
slowly to the furoxan product 5 at 25 C. This was monitored by
thin-layer chromatography [ethyl:hexane (1:2)]. The structures
for 4 and 5 were confirmed by X-ray single crystal diffraction.
a. Department of Chemistry, University of Idaho, Moscow, ID 83844-2343 United
States.
b. School of Chemistry and Chemical Engineering, Beijing Institute of Technology, 5
South Zhongguancun Street, Beijing 100081 China.
c. Naval Research Laboratory, 4555 Overlook Avenue, Washington, D.C. 20375
United States.
† Footnotes relating to the title and/or authors should appear here.
Electronic Supplementary Information (ESI) available: crystal refinements,
calculation detail, X-ray crystallographic files in CIF format for 3, 4, 5, and 8 [CCDC
number: 1968919, 1968921, 1968922, and 1968920]. See DOI: 10.1039/x0xx00000x
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Page 2 of 7
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Journal Name
O
O
Compound 5 which was reported earlier attracted the
attention of the energetic materials community because it has
a crystal density of 1.93 g/cm3 with a heat of formation of 657
kJ mol-1, a decomposition temperature of 292 C, and an
N
N
N
N
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NH4Cl
AgNO3
DOI: 10.1039N/DO0TA01538E
3
NO2
Ag
2
O2N
O2N
or NH2OH
HCl
O2N
O2N
Cation
or N2H4 HCl
6
(89.0%)
7-9
Cation
NH3NH2
NH3OH
=
NH4
excellent detonation velocity of 9250
m
s-1.5b,12 The
7
8
9
(78.0%) (74.0%)
(75.0%)
dinitromethyl group is an important functional group in the
design of energetic compounds and can be synthesized by many
methods.13As a result the new method for synthesis of the
furoxan ring provides a potentially efficient way to synthesize
energetic compounds with that moiety. To stabilize compound
4, a series of its energetic salt derivatives were synthesized and
they were shown to exhibit good properties.
Scheme 2 Synthesis of energetic salts 6-9.
A series of energetic salts of 4 was designed and synthesized
(Scheme 2). The silver salt 6 was easily obtained by reacting 3
with silver nitrate in water. Salts 7-9 were obtained alternatively
by a metathesis reaction of 6 with ammonium chloride,
hydroxylamine hydrochloride or hydrazine hydrochloride,
respectively.
Results and discussion
Mechanism study
Synthesis
In an attempt to understand the cyclization process which 4
undergoes to form 5, 1H, 13C and 15N NMR spectra were
monitored over a 24 hour period using CDCl3 as the locking
solvent (Fig. 3-5). Initially only signals of 4 were observed. After
24 hours, a proton signal at 9.7 ppm (Fig. 4) and a broad
nitrogen peak at -49.7 ppm (Fig. 6 – 24 hr) were observed which
can be assigned to nitric acid. From the 13C (Fig. 5) and 15N NMR
spectra, it was found that a portion of 4 cyclized to 5 after 24
hours.
As shown in Scheme 1, AAOF and ACOF were synthesized
according to previously reported methods.12b A procedure for
the preparation of 1 by oxidation of ACOF using70% aqueous
H2O2 and a tungsten-based catalyst, (Bmim)4W10O23, was
found.5b In this work, 1 was obtained by using aq. 50% H2O2 in
the presence of sodium tungstate and methane sulfonic acid
with ACOF. Initially the reaction mixture was stirred at 25 C,
and then heated at 50 ºC for 2 h followed by an extractive work-
up to obtain 1 as a pale yellow liquid. Compound 1 was nitrated
with 100% nitric acid in trifluoroacetic anhydride (TFAA) at 0 ºC
to give 2 as a pale yellow solid. When 2 was treated with
potassium iodide in methanol, the potassium salt 3 did not
precipitate but after the methanol was removed, the residue
was washed with chloroform and recrystallized from acetone to
yield 3. Compound 4 was obtained by acidification of 3 with 50%
sulfuric acid. Recrystallization of 4 from dichloromethane at
room temperature gave the unexpected crystalline compound
5. Solid 4 was characterized by 1H and 13C NMR. After 24 hours
at 25 C, 4 had been converted to a mixture of 4 and 5.
Compound 4 was stable when stored at -10 C for extended
periods.
O
O
N
N
N
N
Fig. 3 1H NMR spectra of 4 in CDCl3 at t = 0 and t = 24 h.
1.NaNO2 AcOH
2. NaOH
NaNO2
HCl
NC
CN
NOH
NOH
H2N
H2N
NH2OH
HCl
H2N
Cl
AAOF
ACOF
O
O
N
N
N
100% HNO3
TFAA
N
H2O2, NaWO4
CH3SO2H
NO2
Cl
NOH
O2N
O2N
Cl
O2N
1
2
(70.0%)
(60.0%)
O
O
N
N
N
N
50% H2SO4
KI
MeOH
NO2
NO2
O2N
O2N
K
O2N
O2N
3
(70.0%)
4
(68.8%)
O
N
O2N
N
N
O
NO2
N
O
N
N
O
5
(86.5%)
Scheme 1 Synthesis of 1-5.
Fig. 4 13C NMR spectra of 4 in CDCl3 t = 0 and t = 24h.
2 | J. Name., 2012, 00, 1-3
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Journal of Materials Chemistry A
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DOI: 10.1039/D0TA01538E
Fig. 6 Single crystal X-ray structures of (a) 3 and (b) 8.
Structure
Compounds 3-5 and 7-9 were fully characterized by infrared
(IR), 1H and 13C NMR spectroscopy, and elemental analysis.
Crystals of 3, 4, 5, and 8, suitable for single-crystal X-ray
diffraction structuring, were obtained at room temperature
(except 4 at -15 C) by slow evaporation of an acetone (3),
dichloromethane (4), chloroform (5), or acetonitrile (8) solution,
respectively. The crystal structures of 4 and 5, and 3 and 8 are
shown in Fig. 2 and 6, respectively.
Fig. 5 15N NMR spectra of 4 in CDCl3 t = 0 and t = 24h.
O
N
N
O
O
O
O
N
N
N
N
N
N
N
N
O
-HNO3
r.t.
O2
O2
N
4b
O2N
NO2
NO2
O2
N
N
O
O2
N
N
N
N
N
O
N
O2
4
N
4a
O
O
5
Physicochemical and energetic properties
N
N
O
4a
The physicochemical and energetic properties for 3–5 and 7–9
are summarized in Table 1. Thermal stabilities were determined
using differential scanning calorimetry (DSC) at a heating rate of
5 C min-1. Compound 4 decomposed at 58 C which increased
to 231 ºC after cyclizing to 5. The energetic salts 3, 7, 8, and 9
decomposed at 196, 131, 130, and 161 ºC, respectively, without
melting. The densities of compounds 3–5 and 7–9 were
measured with a gas pycnometer at room temperature. As
Scheme 3 A plausible mechanism for formation of 5.
A plausible mechanism for the formation of 5 is given in
Scheme 3. A molecule of nitric acid is readily released by 4 at
ambient temperature which leads to the extremely unstable
isomers of alkyne and alkene-based nitrile oxide derivatives 4a
and 4b. Later the two isomers undergo rapid cyclization to form
stable furoxan 5 at 25 C.
Table 1. Properties of energetic compounds (3–5 and 7–9).
Comp.
Tda (oC)
196
58
db (g cm-3)
ΔHfc (kJ g-1)
-0.23
0.62
1.93
0.27
0.47
0.85
-
vDd (m s-1)
8081
8900
9043
9158
9028
9437
-
Pe (GPa)
29.5
35.7
35.5
38.2
37.0
41.3
-
ISf (J)
2
FSg (N)
120
240
360
160
80
OBh (%)
24.9
25.5
9.9
Ispi (s)
222.5
259.7
273.4
269.5
271.1
277.3
202l
-
3
2.04
4
1.88
8
5
231j
131
130
161
159
210
1.81
14
5
7
1.88
13.6
19.0
9.6
8
1.83
4
9
1.92
5
40
ADNk
RDXm
1.81
3-5
7.4n
64-72
120
25.8
0
1.82
0.36
8748
34.9
HMXm
CL-20o
280
210
1.90
2.03
0.36
0.90
9320
9406
39.5
44.6
7.4
4
120
94
0
-
11.0
-
a
o
b
c
d
Decomposition temperature (onset) under nitrogen gas (DSC, 5 C/min). Density measured by gas pycnometer (25 °C). Heat of formation. Detonation pressure
(calculated with Explo5 v6.01). e Detonation velocity (calculated with Explo 6.01). f Impact sensitivity. g Friction sensitivity. h Oxygen balance (based on CO) for CaHbOcNd,
i
1600(c-a-b/2)/MW, MW = molecular weight. Specific impulse (values obtained from Explo5 v6.01 and calculated at an isobaric pressure of 70 bar and initial
temperature of 3300 K). j Compound 5 has a melting point of 109 °C. k Ref. 16. l Calculated with Explo5 v6.01.m Ref. 17. n Idaho expt’l value. o Ref. 18.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
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Journal Name
expected, the potassium salt (3) has the highest density at 2.04 Caution! All of the new compounds should be VtireewaAtrteicdle Ownilitnhe
g cm-3. Others are in the range from 1.81 to 1.92 g cm-3. The extreme care. Although we have encountered no difficulties in
DOI: 10.1039/D0TA01538E
heats of formation were computed by using the method of preparing these compounds in this work, manipulations must
isodesmic reactions with the Gaussian 03 suite of programs be carried out by using appropriate standard safety
(Scheme S1).14 All the compounds have positive heats of precautions. Eye protection must be worn. Mechanical actions
formation except 3 (-0.23 kJ g-1) ranging from 0.27 to 1.93 kJ g- of these energetic materials involving scratching or scraping
1. Among them, 5 has the highest heat of formation of 1.93 kJ must be avoided!
g-1 which arises from the high heats of formation of the furoxan
and furazan rings.
General Methods
Reagents were purchased from Aldrich and Acros Organics and
were used as received. 1H, and 13C spectra were recorded on a
300/500 MHz (Bruker AVANCE 300/500) nuclear magnetic
resonance spectrometers operating at 300.13/500.17, and
75.48/36.14 MHz, respectively. CDCl3, CD3CN, d6-acetone,or d6-
DMSO were used as solvent and locking solvent. 15N spectra
were obtained on a 500 MHz (Bruker AVANCE 500) nuclear
magnetic resonance spectrometer operating at 50.69 MHz.
To evaluate the detonation performance of compounds 3–5
and 7–9, the detonation velocity and pressure were calculated
using the EXPLO5 (version 6.01) program package15 by using the
calculated heats of formation and measured densities.
Compound 9 exhibits the highest detonation velocity (9437 m s-
1) and pressure (41.3 GPa) values cellent detonation velocities
(8900 m s-1, 9043 m s-1, 9158 m s-1, and 9028 m s-1, respectively)
which are higher than that of RDX (vD, 8748 m s-1). The specific
impulse values (Isp), a measure of the efficiency of a propellant
(in seconds), were also calculated (Explo 5 v6.01) for all
compounds. These values range from 222.5 to 277.3 s, which
are higher than that of ADN (202 s). All the compounds exhibit
positive oxygen balances ranging from 9.6% to 25.5% (Table 1).
For initial safety testing, the impact and friction sensitivities of
3-5 and 7-9, were measured by employing BAM standard
methods.19 Neutral compounds 4 (IS, 8 J; FS, 240 N) and 5 (IS,
14 J; FS, 360 N) were less sensitive towards impact and friction
than the energetic salts 3, 7-9.
1
Chemical shifts in the H and 13C spectra are reported relative
to Me4Si and 15N relative to nitromethane. The melting and
decomposition (onset temperature) points were obtained on a
differential scanning calorimeter (TA Instruments Co., model
Q2000) at a heating rate of 5 °C min-1. IR spectra were recorded
using KBr pellets with a FTIR spectrometer (Thermo Nicolet
AVATAR 370). Density was determined at room temperature by
employing a Micromeritics AccuPyc II 1340 gas pycnometer.
Elemental analyses (C, H, N) were performed on a Vario Micro
cube Elementar Analyser. Impact and friction sensitivity
measurements were made using a standard BAM Fallhammer
and a BAM friction tester
3-Chlorocarbohydroxymoyl-4-nitro-1,2,5-oxadiazole (1)
Conclusions
Sodium tungstate (1.65 g, 5.0 mmol) was added slowly to 30%
hydrogen peroxide solution (12 mL) at 0 °C. 3-Amino-4-
chlorocarbohydroxymoyl-1,2,5-oxadiazole (0.49 g, 3.0 mmol) in
methanesulfonic acid (3 mL) was added to the solution with
In
summary,
3,4-bis(4-nitro-1,2,5-oxadizaol-3-yl)-1,2,5-
oxadiazole-N-oxide (5) was obtained by an unexpected
cyclization of 3-(dinitromethyl)-4-nitro-1,2,5-oxadiazole (4) at
25 C in absence of a catalyst. To understand the mechanism of
the cyclization of 4 to 5, the 1H, 13C and 15N NMR spectra were
monitored at the beginning and after 24 hours. Nitric acid was
stirring at 0 C. The reaction mixture was warmed to room
temperature slowly and then held at 50 ºC for 2 h. It was diluted
with water (30 mL) and extracted with ethylacetate (3 × 15 mL).
The combined organic layer was dried over anhydrous sodium
sulfate and filtered. The filtrate was evaporated on a rotary
evaporator under vacuum to dryness to obtain product 1 (0.41
g, 70.0% yield) as a pale yellow liquid. 1H NMR (d6-acetone): δ
12.9 (br, 1H); 13C NMR (d6-acetone): δ 158.2, 145.3, 124.0.
3-(Chlorodinitromethyl)-4-nitro-1,2,5-oxadiazole (2)
Compound 1 (0.96 g, 5 mmol) dissolved in chloroform (5 mL)
was added dropwise to mixture of trifluoroacetic acid anhydride
(3.5 mL) and 100% nitric acid (2 mL) with stirring at a reaction
temperature below 0 ºC. After the addition was complete, the
ice bath was removed, and the reaction mixture was allowed to
warm slowly to room temperature. It was stirred for another 3
h, and then poured into ice water (30 mL) and extracted with
chloroform (3 x 10 mL). The organic phases were combined,
washed with water and brine, dried over sodium sulfate, and
then evaporated under vacuum to provide 2 (0.76 g, 60.0%
yield) as a pale yellow solid. 13C NMR: δ 157.5, 143.6, 113.9;
elemental analysis (%) calcd. for C3ClN5O7 (253.51): C, 14.21; H,
0; N, 27.23; found: C, 14.17; H, 0.19; N, 26.48.
1
detected by H and 15N NMR spectral measurements after 24
hours which shows the formation of a molecule of nitric acid by
the dinitromethyl group on standing at 25 C. Compounds 4 and
5 were fully characterized by infrared (IR), H and 13C NMR
1
spectroscopy, elemental analysis and single-crystal X-ray
diffraction structuring. Compound 5 has a measured density of
1.81 g cm-3 with a heat of formation of 1.93 kJ g-1, a melting
point of 109 C, an onset decomposition temperature of 231 C,
a detonation velocity of 9043 m s-1, and impact sensitivity of 14
J, which makes it a highly desirable energetic ingredient for
melt-pour formulations. A series of energetic salts of 4 were
also synthesized and characterized. They exhibit high densities
(1.83-2.04 g cm-3), acceptable decomposition temperatures
(130-196 C), good detonation properties (vD, 8081-9437 m s-1;
P, 21.5–41.3 GPa), and moderate sensitivities (IS, 2-5 J; FS, 40-
160 N), which suggest potential applications as primary
explosives.
Potassium dinitro(4-nitro-1,2,5-oxadiazol-3-yl)methanide (3)
Experimental section
4 | J. Name., 2012, 00, 1-3
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Potassium iodide (0.17 g, 1 mmol) in methanol (5 mL) was for C3H4N6O7 (236.1): C, 15.26; H, 1.71; N, 35.6; found: C, 15.41;
View Article Online
added to 2 (0.25 g, 1 mmol), the reaction mixture was stirred H, 1.71; N, 35.24.
overnight at room temperature. Methanol was evaporated on Hydroxylammonium
DOI: 10.1039/D0TA01538E
dinitro(4-nitro-1,2,5-oxadiazol-3-
a rotary evaporator under vacuum, the brown residue was
washed with chloroform until colorless and recrystallized from
acetone to give 3 (0.18 g, 70.0% yield) as a light yellow crystal.
Td (onset): 196 oC. 13C NMR (d3-acetone): δ = 160.2, 145.4,
120.9; IR (KBr pellet): ῦ 3449, 157, 1555, 1509, 1470, 1401,
1378, 1353, 1303, 1265, 1241, 1159, 1053, 1003, 902, 877, 833,
810, 784, 748, 568 cm-1; elemental analysis (%) calcd. for
C3KN5O7 (257.16): C, 14.01; H, 0.00; N, 27.23; found: C, 14.08;
H, 0.21; N, 26.5.
yl)methanide (8)
Yellow solid, 74.0% yield. Td (onset): 130 oC. 1H NMR (d3-
acetonitrile): δ 8.7 (br, 4H); 13C NMR (d3-acetonitrile): δ 160.2,
145.1, 121.7; IR (KBr pellet): ῦ 3445, 2962, 2721, 1578, 1555,
1509, 1471, 1401, 1385, 1354, 1303, 1265, 1159, 1053, 1003,
902, 877, 833, 810, 784, 62, 624, 568 cm-1; elemental analysis
(%) calcd. for C3H4N6O8 (252.10): C, 14.29; H, 1.60; N, 33.34;
found: C, 13.82; H, 1.40; N, 31.72.
Hydrazinium dinitro(4-nitro-1,2,5-oxadiazol-3-yl)methanide (9)
3-(Dinitromethyl)-4-nitro-1,2,5-oxadiazole (4)
Yellow solid, 75.0% yield. Td (onset): 161 oC. 1H NMR (d6-
acetone): δ = 3.7 (br, 5H); 13C NMR (d6-DMSO): δ = 159.6, 140.5,
120.5; IR (KBr pellet): ῦ 3448, 3051, 1580, 1508, 1464, 1401,
139, 1378, 1354, 1302, 1268, 1241, 1159, 1083, 1053, 1003,
962, 902, 877, 810, 833, 784, 747, 568 cm-1; elemental analysis
(%) calcd. for C3H5N7O7 (251.12): C, 14.35; H, 2.01; N, 39.05;
found: C, 13.87; H, 1.87; N, 36.96.
Concentrated sulfuric acid (1 mL) was added dropwise into a
stirred mixture of 3 (0.26 g, 1 mmol) and water (0.5 mL) at 5 ºC.
After the addition was complete, the mixture was stirred for
another 30 minutes, and then extracted with dichloromethane
(6 × 5 mL). The combined extracts were concentrated under
vacuum to provide white solid 4 (0.33 g, 68.8% yield).
Compound 4 should be stored in the refrigerator. Td (onset): 58
oC. 1H NMR (d6-acetone): δ 7.7 (s, 1H); 13C NMR (d6-acetone): δ
158.7, 139.9, 100.7; IR (KBr pellet): ῦ 3423, 2984, 2897, 1612,
1578, 1551, 1506, 1463, 1403, 1353, 1323, 1297, 1260, 115,
1158, 1053, 1036, 1005, 957, 909, 890, 849, 834, 803, 782, 745,
631, 619, 575, 530, 403 cm-1; elemental analysis (%) calcd. for
C3HN5O7 (219.07): C, 16.45; H, 0.46; N, 31.97; found: C, 16.49;
H, 0.67; N, 30.45.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was supported by the Office of Naval Research
(N00014-16-1-2089) and the Defense Threat Reduction Agency
(HDTRA 1-15-1-0028).
3,4-Bis(4-nitro-1,2,5-oxadizaol-3-yl)-1,2,5-oxadiazole-N-oxide (5)
Compound 4 (0.22 g, 1 mmol) was dissolved in chloroform at
room temperature. Compound 5 (0.27 g, 86.5% yield) was
recrystallized from chloroform as a colorless crystal. Td (onset):
o
231 C. 13C NMR (d3-chloroform): δ 158.7, 158.5, 141.2, 138.3,
136.4, 102.2; IR (KBr pellet): ῦ 3448, 1638, 1586, 1564, 1516,
1448, 1412, 1384, 1355, 1318, 1285, 1176, 1119, 1038, 1001,
961, 907, 881, 832, 806, 732, 619, 510 cm-1; elemental analysis
(%) calcd. for C6N8O8 (312.11): C, 23.09; H, 0; N, 35.90; found: C,
23.45; H, 0.20; N, 36.36.
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Silver dinitro(4-nitro-1,2,5-oxadiazol-3-yl)methanide (6)
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General procedure for salts 7-9
Compound 6 (0.33 g, 1 mmol) was added to an ethyl acetate
solution (15 mL) of ammonium chloride (0.053 g, 1 mmol),
hydroxylammonium chloride (0.069 g, 1 mmol), or hydrazinium
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Ammonium dinitro(4-nitro-1,2,5-oxadiazol-3-yl)methanide (7)
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6
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J. Name., 2013, 00, 1-3 | 5
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Journal of Materials Chemistry A
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6 | J. Name., 2012, 00, 1-3
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Dinitromethyl groups form an unstable nitrile oxide and its dipole isomer which cyclize to a furoxan ring.
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