Synthesis and Energetic Properties of 4-Diazo-2,6-dinitrophenol and 6-Diazo-3-hydroxy-2,4-dinitrophenol

Article abstract of DOI:10.1002/ejoc.201500465

4-Amino-3,5-dinitroaniline (3) was synthesized by fluorine/amine exchange of 4-fluoro-3,5-dinitroaniline in ethanol. 4-Diazo-2,6-dinitrophenol (Iso-DDNP, 4) was obtained after nitration in HNO₃ (100%) and acetic anhydrid. 4-Amino-2,3,5-trinitrophenol (7) was obtained by nitration of N-(4-acetoxyphenyl)acetamide and deprotection of the amine. Further nitration resulted in 6-diazo-3-hydroxy-2,4-dinitrophenol (8). The thermal stability and sensitivity of 4 and 8 toward impact and friction was compared to commercially used DDNP (2-diazo-4,6-dinitrophenol). All target compounds were characterized by single-crystal X-ray diffraction, NMR and elemental analysis and DSC. The sensitivities were determined by BAM methods (drophammer and friction tester). The heats of formation were calculated by using CBS-4M electronic enthalpies and the atomization method. Various detonation parameters such as detonation velocity and pressure were computed by using the EXPLO5 computer code V6.01. The very sensitive diazophenol derivatives diazo-2,6-dinitrophenol and 6-diazo-3-hydroxy-2,4-dinitrophenol could be synthesized by nitration reactions. They are promising alternatives to the commercially used sensitizer DDNP (2-diazo-4,6-dinitrophenol).

Full text of DOI:10.1002/ejoc.201500465

SHORT COMMUNICATION
DOI: 10.1002/ejoc.201500465
Synthesis and Energetic Properties of 4-Diazo-2,6-dinitrophenol and
6-Diazo-3-hydroxy-2,4-dinitrophenol
Thomas M. Klapötke,*[a] Andreas Preimesser,[a] and Jörg Stierstorfer[a]
Keywords: Diazo compounds / Energetic materials / NMR spectroscopy / Structure elucidation
4-Amino-3,5-dinitroaniline (3) was synthesized by fluorine/
amine exchange of 4-fluoro-3,5-dinitroaniline in ethanol. 4-
Diazo-2,6-dinitrophenol (Iso-DDNP, 4) was obtained after
nitration in HNO3 (100%) and acetic anhydrid. 4-Amino-
2,3,5-trinitrophenol (7) was obtained by nitration of N-(4-
acetoxyphenyl)acetamide and deprotection of the amine.
Further nitration resulted in 6-diazo-3-hydroxy-2,4-dinitro-
phenol (8). The thermal stability and sensitivity of 4 and 8
toward impact and friction was compared to commercially
used DDNP (2-diazo-4,6-dinitrophenol). All target com-
pounds were characterized by single-crystal X-ray diffrac-
tion, NMR and elemental analysis and DSC. The sensitivities
were determined by BAM methods (drophammer and fric-
tion tester). The heats of formation were calculated by using
CBS-4M electronic enthalpies and the atomization method.
Various detonation parameters such as detonation velocity
and pressure were computed by using the EXPLO5 computer
code V6.01.
amide in concentrated sulfuric acid. However, for synthesis
in larger scales, this reaction is useless, and a proper synthe-
sis had to be developed. Alternatively, the substitution of
the chlorine atom or the methoxy group of 4-chloro-2,6-
dinitroaniline,[7] as well as its 4-methoxy derivative,[8] failed.
Even the use of ammonia in high-pressure vessels did not
result in any notable conversion. Finally, 3 could be synthe-
sized by fluorine/amine exchange of 4-fluoro-3,5-dinitro-
aniline in ethanol. A further approach was the nitration of
4-aminophenol; however, all nitration attempts finally re-
sulted in the formation of highly energetic diazophenols.
These species represent a very interesting group of energetic
zwitterionic molecules. A paper discussing the increased-
valence bond structure of DDNP, as opposed to the zwit-
terionic approach, was published in 2003.[10] The mecha-
nism of formation of ortho-diazophenols was described in
detail by Atkins and Wilson in 1986.[9] Most compounds
containing a nitro group in ortho position to a nitramine
functionality eliminate nitric acid during the nitration reac-
tion or boiling process in organic solvents. Including a
cyclic transition state, this rearrangement results in the for-
mation of ortho-diazophenols. DDNP (2-diazo-4,6-dinitro-
phenol) was synthesized for the first time by Griess in
1858.[11] It is an extremely sensitive primary explosive,
which is commercially used in stab detonators.[12] Sensitiza-
tion of lead azide using DDNP as an energetic additive was
intensively studied by Spear and Elischer in 1982.[13] This
study provides a comparison (e.g. sensitivities, thermal be-
havior) of the two title diazophenols to DDNP. While the
synthesis of DDNP by oxidation of the primary aromatic
amine of picramic acid (2-amino-4,6-dinitrophenol) has
been published,[14] the formation of para-diazophenols is
only rarely described.[9]
Introduction
Synthesis of energetic materials based on a benzene
backbone has had a long tradition since the discovery of
trinitrotoluene (TNT) in 1863.[1] Because of its important
property as a melt-castable explosive it is still in use nowa-
days, even though it is highly toxic for the environment.[2]
1,3,5-Triamino-2,4,6-trinitrobenzene (TATB) was synthe-
sized in 1888. It is a well-known insensitive explosive with
a high melting point (Tmelt Ͼ 350 °C) due to its strong in-
tramolecular hydrogen bonds between alternation of amino
and nitro groups.[3,4] This leads to a high density of ρ =
1.937 gcm–3 at 298 K, which was confirmed by its crystal
structure[5] in 1965. For many applications, TATB shows
a meager performance and is too insensitive to detonate,
therefore alternatives with a better performance, less toxic
properties and lower sensitivities towards external stimuli
like impact, friction and electrostatic discharge, are desired.
Originally, our research goals had been the synthesis of 4-
amino-2,3,5,6-tetranitrophenol and 1,4-diamino-2,3,5,6-
tetranitrobenzene. In order to obtain the latter, 4-amino-
3,5-dinitroaniline (3) seemed to be a promising starting ma-
terial. Its synthesis was already mentioned by Chu and
Griffiths.[6] They reported on the nitration of N,NЈ-bis-
(phenylsulfonyl)-p-phenylenediamine and received three dif-
ferent C-nitrated dinitro isomers, which were separated by
column chromatography after the cleavage of the sulfon-
[a] Department of Chemistry, Ludwig-Maximilian University of
Munich
81377 Munich, Germany
E-mail: tmk@cup.uni-muenchen.de
http://www.hedm.cup.uni-muenchen.de/index.html
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201500465.
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T. M. Klapötke, A. Preimesser, J. Stierstorfer
SHORT COMMUNICATION
Results and Discussion
resulted in decomposition or the formation of compound
8, which is 6-diazo-3-hydroxy-2,4-dinitrophenol.
An overall synthetic protocol is displayed in Scheme 1. 4-
All target compounds and intermediates were charac-
Fluoro-3,5-dinitroaniline (2) was synthesized as described terized extensively. Single crystals of 3, 4, 7 and 8 could be
by Nielsen et al.[15] Compound 3 was obtained by reaction grown from organic solvents (3 and 8 from acetone; 4 from
of 2 with ammonia in ethanol. Any further attempts to syn- ethanol; 7 from benzene) and their structures determined
thesize a tri- or tetranitro derivative of 1,4-diaminobenzene by low-temperature X-ray diffraction (details are given in
by various nitration conditions resulted in the formation the Supporting Information). Figures 1 and 2 show the mo-
of 4-diazo-2,6-dinitrophenol (4). Even if the amine in C1 lecular structures of 3, 4, 7 and 8. They crystallize in the
position was protected with an acetyl or methylsulfonyl monoclinic or orthorhombic crystal system in common
group, no other product but 4 was obtained, indicating that space groups (3: P21/c; 4: P212121; 7 and 8: Pbca).
the protection group was cleaved quickly in nitrating media.
The X-ray densities at 173 K increase with the number
Compound 5 was easily synthesized by using acetic an- of nitro groups [1.742 (3) Ͻ 1.824 (4) Ͻ 1.837 (8)
hydride both as acetylating reagent and solvent. Nitration Ͻ 1.839 gcm–3 (7)]. In the case of 3 a nearly planar system
of 5 by using 65% nitric acid yielded compound 6 in moder- is formed. Both nitro groups lie within the ring plane fixed
ate quantities. To obtain compound 7 in high purity, 6 must by the intermolecular hydrogen bonds N1–H···O1 and N1–
be stirred in concentrated sulfuric acid for at least 3 d, H···O4.
which indicates that the amide cleavage of 6 works only very
Proton-coupled 15N NMR spectra of compounds 4, 7
slowly. Compound 7 could easily purified by recrystalli- and 8 were recorded and are displayed in Figure 3. All four
zation from benzene. Further nitration attempts of 7 always nitrogen atoms of 4 could be assigned. Nα is the only nitro-
Scheme 1. Synthesis protocol of compounds 1–8.
Figure 1. Molecular structure of 3 (left) and 4-diazo-2,6-dinitrophenol (4, right). Ellipsoids of non-hydrogen atoms in all structures are
drawn at the 50% probability level.
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Eur. J. Org. Chem. 2015, 4311–4315

4-Diazo-2,6-dinitrophenol and 6-Diazo-3-hydroxy-2,4-dinitrophenol
Figure 2. Molecular structure of 4-amino-2,3,6-trinitrophenol (7, left) and 6-diazo-3-hydroxy-2,4-dinitrophenol (8, right).
gen atom, which shows a singlet at δ = –21.7 ppm. The Nδ and thus the value of N observed corresponds roughly to
and Nβ signals appear as doublets at δ = –17.2 (3JN,H
=
3JN,H. In the 15N NMR spectrum of compound 8 four sig-
2.9 Hz) and –19.9 ppm (4JN,H = 1.2 Hz). Even the nitrogen- nals could be observed. Nβ of the diazo group shows a sing-
proton coupling (3JN,H = 2.4 Hz) of the amine could be let at δ = –33.2 ppm. Nα shows a doublet at δ = –134.9 ppm
observed. In the 15N NMR spectrum of compound 7 three (3JN,H = 1.8 Hz). Nγ appears as singlet and Nδ and as doub-
signals could be detected. Nβ of the diazo group shows a let (3JN,H = 2.8 Hz).
singlet at δ = –45.0 ppm. Nα shows a first-order triplet at
Energetic properties of compounds 4 and 8 in compari-
3
δ = –139.3 ppm (t, JN,H = 2.4 Hz). In contrast, for Nγ a son to DDNP are displayed in Table 1. The impact sensiti-
deceptively simple triplet is observed. In fact the 15N NMR vity of all three compounds is 1 J, typically for primary ex-
signal of Nγ represents the X part of an AAЈX spectrum, plosives. Therefore handling of these compounds should be
5
from which N = |3JN,H + JN,H| = 3.0 Hz is determined. carried out only with proper safety measures! Interestingly,
5
The coupling constant JN,H is expected to be very small, compounds 4 and 8 are also very sensitive toward friction
Figure 3. 15N NMR spectra of 4 (top), 7 (center) and 8 (bottom).
Eur. J. Org. Chem. 2015, 4311–4315
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T. M. Klapötke, A. Preimesser, J. Stierstorfer
SHORT COMMUNICATION
but slightly less than DDNP, what makes them safer for the thermal stability and calculated performance are
handling. In addition they are slightly better (ca. 10–12 °C) slightly better from a statistical point of view.
in thermal stability. Due to the higher densities of 4 and 8 in
comparison to DDNP higher detonation parameters were
calculated by using the EXPLO5 V6.01 computer code. Sta-
tistically, detonation pressure and velocity of 4 and 8 are
ca. 5% higher than those of DDNP. An empirical confirm-
Experimental Section
4-Fluoro-3,5-dinitrobenzoic Acid (1): To oleum (25% SO3 by weight,
175 mL) was added nitric acid (100%, 50 mL) under cooling. 4-
ation of these values has to be further researched in order
Fluorobenzoic acid (25.0 g, 178 mmol) was dissolved in this solu-
to determine the relevance, as well as the benefits of those
tion portionwise. After complete dissolution, the mixture was
heated slowly to 95 °C. This temperature was kept for 5 h. Com-
pound 1 slowly started to precipitate. After cooling, the suspension
was poured onto crushed ice (600 g). The product was filtered and
washed three times with of ice-cold water (3ϫ 100 mL) to remove
the acid. Compound 1 was obtained as a bright-shining colorless
powder (32 g, 78%). C7H3FN2O6 (230.11): calcd. C 36.54, H 1.31,
compounds. For selected applications like initiation of sec-
ondary explosives, these advantages could surpass the detri-
ment of an increased number of synthetic steps to produce
4 and 8.
Table 1. Energetic properties of compounds 4 and 8 in comparison
to DDNP.
1
N 12.17; found C 36.58, H 1.24, N 12.44. H NMR (400.1 MHz,
4
[D6]acetone): δ = 8.94 [d, J(H,F) = 6.3 Hz, 2 H, CH], 11.59 (br. s,
4
8
DDNP[a]
1 H, COOH) ppm. 13C NMR (100.6 MHz, [D6]acetone): δ = 127.4
Empirical formula
Formula mass
IS [J][b]
C6H2N4O5
210.10
1 (Ͻ 100 μm)
C6H2N4O6
226.10
1 (Ͻ 100 μm) 1 (Ͻ 100–500 μm)
C6H2N4O5
210.10
4
(d, JC,F = 5.8 Hz, 1 C, C-COOH), 131.6 (s, 2 C, C-H), 139.2 (d,
2JC,F = 6.7 Hz, 2 C, C-NO2), 152.0 (d, 1JC,F = 283.7 Hz, 1 C, C-F),
162.8 (s, 1 C, COOH) ppm. 19F NMR (376.5 MHz, [D6]acetone): δ
FS [N][c]
40 (Ͻ 100 μm) 16 (Ͻ 100 μm) 5 (Ͻ 100–500 μm)
4
N [%][d]
26.67
168
24.78
170
26.67
= –121.0 (t, JH,F = 6.5 Hz, 1 F) ppm.
Tdec. [°C][e]
158[16]
1.727[16]
142.4[16]
742.6[16]
–60.9
4-Fluoro-3,5-dinitroaniline (2): Compound 1 (10 g, 43.5 mmol) was
dissolved in oleum (25% SO3 by weight, 25 mL). Afterwards,
chloroform (40 mL) was added. Then the suspension was heated to
45 °C, and sodium azide (4.80 g, 73.8 mmol) was added portion-
wise so that the temperature did not exceed 55 °C. After that, the
suspension was stirred for 1 h and then heated to reflux (75 °C) for
16 h. After cooling, the mixture was poured onto crushed ice
(500 g), and 2 precipitated as a yellow-brownish powder (7.7 g,
88%). C6H4FN3O4 (201.11): calcd. C 35.83, H , N 20.89; found C
35.68, H 2.20, N 20.96. 1H NMR (400.2 MHz, [D6]acetone): δ =
ρ [gcm–3][f]
1.790[g]
184.1
941.0
–60.9
1.803[g]
–42.0
–120.0
–49.5
ΔfHm° [kJmol–1][h]
ΔfU° [kJkg–1][i]
Ω [%][j]
EXPLO 6.01 values:[k]
–ΔExU° [kJkg–1][l]
Tdet [K][m]
5241
3816
269
7978
620
4755
3579
263
7900
627
5009
3737
241
7685
632
PCJ [kbar][n]
Vdet [ms–1][o]
V [Lkg–1][p]
o
4
[a] A DDNP sample of high purity was provided by another group
member.[16] [b] Impact sensitivity (BAM drophammer, 1 of 6). [c]
Friction sensitivity (BAM friction tester 1 of 6). [d] Nitrogen con-
tent. [e] Decomposition temperature from DSC (β = 5 °C). [f] From
X-ray diffraction. [g] Density at 298 K was calculated by using the
formula ρ298 K = ρT/1 + αV(298 – T0) with αV = 1.50ϫ10–4 K–1 (αV
is the volume coefficient of thermal expansion; V = volume) and
T0 = 173 K.[8,17] [h] Calculated (CBS-4M) heat of formation. [i]
Energy of formation. [j] Oxygen balance. [k] Values have been cal-
culated by using room-temperature densities. [l] Energy of ex-
plosion. [m] Explosion temperature. [n] Detonation pressure. [o]
Detonation velocity. [p] Assuming only gaseous products.
5.40 (br. s, 2 H, NH2), 7.63 (d, JH,F = 5.5 Hz, 2 H, C-H) ppm.
13C NMR (100.6 MHz, [D6]acetone): δ = 121.3 (d, 3JC,F = 27.8 Hz,
4
2 C, C-H), 134.9 (d, JC,F = 7.7 Hz, 1 C, C-NH2), 139.1 (s, 2 C,
1
C-NO2), 149.5 (d, JC,F = 237.7 Hz, 1 C, C-F) ppm. 19F NMR
(376.5 MHz, [D6]acetone): δ = –147.5 (t, 4JH,F = 4.3 Hz, 1 F) ppm.
14N NMR (29.0 MHz, [D6]acetone): δ = –14 (s, 2 N, NO2), –308
(br. s, 1 N, NH2) ppm.
4-Amino-3,5-dinitroaniline (3): Ethanol (300 mL) was placed into a
three-neck flask and cooled to –75 °C by using a CO2/ethanol cool-
ing bath. Then gaseous ammonia was bubbled through the mixture
for ca. 30 min. Then 2 (20.0 g, 99.5 mmol) was suspended in this
solution. The color of the suspension turned deep red relatively
quickly. The temperature was kept at –45 °C for at least 6 h, and
then the suspension was further stirred at ambient temperature for
ca. 2 d. After removal of the ethanol, the dark brown precipitate
was washed several times with ice-cold water to remove the ammo-
nium fluoride. Compound 3 was obtained as a “dark red-black”
powder (17.4 g, 88%). C6H6N4O4 (198.14): calcd. C 36.37, H 3.05,
Conclusions
From this experimental study the following conclusions
can be drawn: 4-Amino-3,5-dinitroaniline (3) can be synthe-
sized in three steps in high purity and on large scales
(Ͼ 20 g). 4-Amino-2,3,6-trinitrophenol (7) can also be syn-
thesized by a three-step protocol in good yields. Unfortu-
nately, 7 is only stable up to 119 °C and therefore not of
interest for any explosive-based applications. Further
nitration of compounds 3 and 7 resulted in the formation
of the very sensitive diazophenol derivatives 4 (diazo-2,6-
1
N 28.28; found C 36.48, H 2.98, N 27.96. H NMR (400.2 MHz,
[D6]DMSO): δ = 5.40 (br. s, 2 H, NH2), 7.85 (br. s, 2 H, NH2),
7.89 (s, 2 H, C-H) ppm. 13C NMR (100.6 MHz, [D6]DMSO): δ =
119.5 (s, 2 C, C-H), 134.3 (s, 1 C, C-NH2), 135.3 (s, 2 C, C-NH2),
137.6 (s, 2 C, C-NO ) ppm. IR (ATR): ν = 3443, 3361, 3298, 3099,
˜
2
1614, 1578, 1521, 1506, 1420, 1251, 1231, 1114, 1022, 988, 896,
878, 803, 766 (m) cm–1.
dinitrophenol) and
phenol). The molecular structures of 3, 4, 7 and 8 were
determined by single-crystal X-ray diffraction. The sensiti-
8
(6-diazo-3-hydroxy-2,4-dinitro-
4-Diazo-2,6-dinitrophenol (4): Acetic anhydride (10 mL) was cooled
to –10 °C, and nitric acid (100%, 1 mL) was added slowly. After
stirring for 1 h, 3 (500 mg, 2.52 mmol) was added. The solution
vities of 4 and 8 are in the range of DDNP’s values, while was stirred at 0 °C for 3 h and further at ambient temperature for
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4-Diazo-2,6-dinitrophenol and 6-Diazo-3-hydroxy-2,4-dinitrophenol
16 h. As soon as 24 °C was reached, 4 started to precipitate slowly
from the solution. Afterwards, the suspension was poured onto
crushed ice (50 g). A beige precipitate of 4 (344 mg, 65%) was ob-
tained. It was filtered and washed with cold water and twice with
ice-cold ethanol (20 mL). DSC (5 °Cmin–1): Tdec. = 168 °C.
onto crushed ice (100 g). After a few minutes, 8 precipitated as a
bright yellow powder (695 mg, 75%). DSC (5 °C min–1): Tdec.
170 °C. C6H2N4O6 (226.10): calcd. C 31.87, H 0.89, N 24.28; found
C 31.96, H 1.05, N 24.51. 1H NMR (400.1 MHz, [D6]acetone): δ
= 9.28 (s, 1 H, C-H), 11.37 (br. s, 1 H, O-H) ppm. 13C NMR
=
C6H2N4O5 (210.10): calcd. C 34.30, H 0.96, N 26.67; found C (100.6 MHz, [D6]acetone): δ = 90.9 (s, 1 C, C-N2) 123.8 (s, 1 C, C-
34.40, H 0.89, N 26.52. 1H NMR (400.2 MHz, [D6]acetone/[D6]- NO2), 132.3 (s, 1 C, C-NO2), 133.7 (s, 1 C, C-H), 154.1 (s, 1 C, C-
DMSO, 5:1): δ = 9.01 (s, 2 H, C-H) ppm. 13C NMR (100.6 MHz, OH), 164.6 (s, 1 C, C-O) ppm. 15N NMR (40.6 MHz, [D6]DMSO):
[D6]acetone/[D6]DMSO, 5:1): δ = 80.9 (s, 1 C, C-N2) 132.6 (s, 2 C,
δ = –13.7 (s, 1 N, NO2), –15.6 (d, 3JN,H = 2.8 Hz, 1 N, NO2), –33.2
3
C-H), 143.9 (s, 2 C, C-NO2), 161.8 (s, 1 C, C-O) ppm. 15N NMR (s, 1 N, N2), –134.9 (d, JN,H = 1.8 Hz, 1 N, N2) ppm. IR (ATR):
(40.6 MHz, [D6]DMSO): δ = –15.6 (t, N = |3JN,H + 5JN,H| = 3.0 Hz,
ν = 3075, 2192, 1638, 1606, 1516, 1492, 1449, 1368, 1304, 1215,
˜
3
2 N, NO2), –45.0 (s, 1 N, N2), –139.3 (t, JN,H = 2.4 Hz, 1 N, N2) 1172, 1084, 932, 915, 798, 770, 743, 706 cm–1.
ppm. IR (ATR): ν = 3033, 2204, 2186, 1639, 1616, 1522, 1504,
˜
CCDC-1057558 (for 3), -1057560 (for 4), -1057559 (for 7), and
-1057561 (for 8) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
1355, 1339, 1291, 1168, 1086, 938, 908, 900, 783, 706 cm–1.
N-(4-Acetoxyphenyl)acetamide
(5):
4-Aminophenol
(35 g,
320.7 mmol) was dissolved in acetic anhydride (250 mL). After-
wards the solution was stirred until a precipitate formed (typically
after 20–25 min). The suspension was heated to 95 °C for 16 h.
Then the suspension was poured on crushed ice (1 kg) and stirred
until all acetic anhydride was hydrolyzed. Compound 5 was ob-
tained as a white crystalline powder (50 g, 81%). C10H11NO3
(193.20): calcd. C 62.17, H 5.74, N 7.25; found C 62.01, H 5.80, N
6.96.
Supporting Information (see footnote on the first page of this arti-
cle): X-ray diffraction data; general methods; calculation of heat of
1
formation; H and 13C NMR spectra.
Acknowledgments
N-(4-Hydroxy-3,5,6-trinitrophenyl)acetamide (6): Compound
5
Financial support of this work by the Ludwig Maximilian Univer-
sity of Munich (LMU) and the Office of Naval Research (ONR)
under grant no. ONR.N00014-12-1-0538 is gratefully acknowl-
edged. The authors acknowledge collaborations with Dr. Mila
Krupka (OZM Research, Czech Republic) in the development of
new testing and evaluation methods for energetic materials and
with Dr. Muhamed Sucesca (Brodarski Institute, Croatia) in the
development of new computational codes to predict the detonation
and propulsion parameters of novel explosives. In addition we want
to thank Martin Härtel for providing a DDNP sample to us, Stefan
Huber for measuring the sensitivities of compounds 4 and 8 and
Prof. K. Karaghiosoff for measuring the 15N NMR spectra.
(12 g, 62.1 mmol) was dissolved in nitric acid (100 mL, 65%) at
0 °C. This temperature was kept for 5 h, and then the solution’s
temperature was slowly risen to ambient temperature (6–8 h) and
stirring continued for further 12 h. A yellow precipitate was
formed. The suspension was poured on crushed ice (500 g). After
the ice was molten, the suspension was filtered and washed with
only small amounts of ice-cold water to remove the nitric acid.
Compound 6 was obtained as a bright-shining yellow powder (10 g,
56%). C8H6N4O8 (286.16): calcd. C 33.58, H 2.11, N 19.58; found
C 33.41, H 2.30, N 19.76. 1H NMR (400.1 MHz, [D6]acetone): δ
= 2.19 (s, 3 H, CH3), 8.84 (s, 1 H, C-H), 9.58 (br. s, 1 H, N-H),
11.08 (br. s, 1 H, OH) ppm. 13C NMR (100.6 MHz, [D6]acetone):
δ = 22.6 (s, 1 C, CH3) 123.3 (s, 1 C, C-NH), 124.7 (s, 1 C, C-H),
135.8 (s, 1 C, C-NO2), 137.5 (s, 1 C, C-NO2), 139.7 (s, 1 C, C-NO2),
143.4 (s, 1 C, C-OH), 169.2 (s, 1 C, C=O) ppm.
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Received: April 16, 2015
4-Amino-2,3,6-trinitrophenol (7): Compound 6 (11.0 g, 38.4 mmol)
was dissolved in concentrated sulfuric acid (100 mL) at 0 °C. The
yellow solution was stirred at ambient temperature in an open flask
for at least 3 d. Afterwards it was poured onto crushed ice (400 g),
and a deep dark-reddish powder precipitated. After filtration and
subsequent washing with ice-cold water, 7 was obtained as a dark
powder (7.14 g, 76%). DSC (5 °Cmin–1): Tdec. = 119 °C. C6H4N4O7
(244.12): calcd. C 29.52, H 1.65, N 22.95; found C 29.40, H 1.39,
1
N 23.10. H NMR (400.1 MHz, [D6]acetone): δ = 6.60 (br. s, 2 H,
NH2), 8.13 (s, 1 H, C-H), 9.82 (br. s, 1 H, O-H) ppm. 13C NMR
(100.6 MHz, [D6]acetone): δ = 117.7 (s, 1 C, C-H) 127.1 (s, 1 C, C-
NH2), 135.1 (s, 1 C, C-NO2), 136.7 (s, 1 C, C-NO2), 138.6 (s, 1 C,
C-NO2), 140.9 (s, 1 C, C-OH) ppm. 15N NMR (40.6 MHz, [D6]-
3
4
acetone): δ = –17.2 (d, JN,H = 2.9 Hz, 1 N, NO2), –19.9 (d, JN,H
= 1.2 Hz, 1 N, NO2), –21.7 (s, 1 N, NO2), –313.8 (d, 3JN,H = 2.4 Hz,
1 N, NH ) ppm. IR (ATR): ν = 3500, 3385, 3286, 3095, 1602, 1577,
˜
2
1544, 1508, 1479, 1430, 1372, 1340, 1320, 1262, 1240, 1154, 1043,
903, 893, 806, 758, 736 cm–1.
6-Diazo-3-hydroxy-2,4-dinitrophenol (8): Compound
7 (1.00 g,
4.10 mmol) was dissolved in nitric acid (15 mL, 65%) at 65 °C. The
solution was stirred at 65–70 °C for 2 h. Afterwards it was poured
Published Online: June 5, 2015
Eur. J. Org. Chem. 2015, 4311–4315
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4315