Bicentral oxidation of nitrosolic acids: Synthesis of 1,1-dinitroalkanes

Article abstract of DOI:10.1016/j.mencom.2010.06.011

gem-Dinitrozo compounds are cleanly oxidized into the gem-dinitro analogues on treatment with formic acid/hydrogen peroxide system.

Full text of DOI:10.1016/j.mencom.2010.06.011

Mendeleev
Communications
Mendeleev Commun., 2010, 20, 215–217
Bicentral oxidation of nitrosolic acids:
synthesis of 1,1-dinitroalkanes
Aleksei B. Sheremetev,*a Natal’ya S. Aleksandrovaa and Kyrill Yu. Suponitskyb
a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow,
Russian Federation. Fax: +7 499 135 5328; e-mail: sab@ioc.ac.ru
b A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow,
Russian Federation. Fax: +7 499 135 5085; e-mail: kirshik@yahoo.com
DOI: 10.1016/j.mencom.2010.06.011
gem-Dinitrozo compounds are cleanly oxidized into the gem-dinitro analogues on treatment with formic acid/hydrogen peroxide
system.
The chemical oxidation of mono-C-nitroso to C-nitro alkanes1
was previously performed using CrO3/AcOH,2 NO,3 N2O4,4
N2O5,4(c),5 air,6 ozone,7 aq. H2O2/AcOH,8 aq. H2O2/HNO3,9
H2O2/(CF3CO)2O,10 MCPBA,11 aq. HNO3,12 aq. HNO3/AcOH,13
conc. HNO3,14 aq. NaOCl/Bu4N·HSO4/benzene,15 periodic acid16
and iodosylbenzene17 as the reagents.
gem-Dinitroso compounds have been known since 1905,
when Wieland18 first described the isolation of a blue crys-
talline salt 1a from a complex mixture of products obtained by
Our research in this area is focused on the hydrogen peroxide
oxidation. Present strategy was based on our previous observa-
tion27 that the oxidative activity of hydrogen peroxide mixtures
depended on its concentration, amount as well as manner of its
addition to the reactant.
Here, we describe the new oxidation of nitrosolates 1† with
in situ generated peroxy acids affording 1,1-dinitroalkanes 4
(Scheme 2).
the disproportionation of N-hydroxy amidoxime 2a under basic con-
NO2
N
O
O
[O], H+
ditions (Scheme 1). Since then analogous anionic α,α-dinitroso
compounds 1a–d, termed also as nitrosolates or dinitrosometh-
anides, were prepared from N-hydroxy amidoximes 2a–d by
disproportionation or, more recently, by periodate oxidation.19
R
R
H
N
NO2
1a–d
4a–d
a R = H
b R = Me
c R = Et
d R = Ph
NHOH
NOH
N
N
N
N
OH
O
O
O
B, [O]
KMnO4
R
R
Ph
Scheme 2
(for 1d)
O
Preliminary experiments (Table 1) showed that oxidation of
nitrosolate 1a with a mixture of H2O2 and strong inorganic
acids provided only low yields (up to 10%) of dinitromethane 4a.
The most of the starting nitrosolate was lost in the hydrolytic
2a–d
1a–d
3
a R = H
b R = Me
c R = Et
d R = Ph
Scheme 1
Table 1 Oxidation of compounds 1a–d with H2O2/strong acid mixtures.
The corresponding acids, termed as nitrosolic acids by Wieland,
were shown to exist for a short time in solutions on cooling.
However, their attempted isolation resulted in decomposition.
In contrast, salts 1 are sufficiently stable and can be isolated.
Both the acids and their anions are blue coloured. Their struc-
ture was determined by a series of chemical degradation,18(b),(c)
UV,19(b),(c) 1H and 13C NMR20 and X-ray crystallographic
studies.20,21 The polarography of some salts has been inves-
tigated19 and the pK values19(c) of a series of acids have been
determined. The single literature precedent22 demonstrates the
susceptibility of α,α-dinitroso compounds anions to oxidation,
viz., the oxidation of one NO group to NO2 group in compound
1d was performed with KMnO4 in the presence of a base to
give the corresponding nitrolic acid 3 (see Scheme 1). On the
Yields of dinitroalkanes (%)
Entry Reagents and conditions
4a
4b
4c
4d
1
2
3
4
5
6
7
8
30% H2O2 + 56% HNO3,
–5 °C ® room temperature
50% H2O2 + 56% HNO3,
–5 °C ® room temperature
50% H2O2 + 100% HNO3,
–5 °C ® room temperature
30% H2O2 + 50% H2SO4,
–10 °C ® room temperature
30% H2O2 + 96% H2SO4,
–10 °C ® room temperature
50% H2O2 + 96% H2SO4,
–10 °C ® room temperature
6
4
2
traces
4
3
3
5
6
0
0
6
traces
2
5
8
traces traces
traces traces traces
4
11
7
traces
2
14
5
50% H2O2 + KHSO5 + 10% H2SO4, 10
7
5
23
other hand, oxidation of nitrolic acids using N2O4 or nitric
acid24 afforded 1,1-dinitroalkanes.
–10 °C ® room temperature
50% H2O2 + KHSO5 + 50% H2SO4,
–10 °C ® room temperature
3
With this knowledge, we explored an intriguing possibility of
the one-step preparation of 1,1-dinitroalkanes from nitrosolates
1. 1,1-Dinitroalkanes are of great interest as intermediates in the
synthesis of highly nitrated compounds25 and nitrogen hetero-
cycles.26
†
Potassum nitrosolates 1a–c were used, whereas phenyl analogue 1d
was applied in the form of silver salt as the corresponding potassium salt
is unknown.
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© 2010 Mendeleev Communications. All rights reserved.

Mendeleev Commun., 2010, 20, 215–217
process, and if too great excess of the oxidizing mixture was
Table 2 Oxidation of 1a with in situ organic peroxy acids.
used, the only product was a gas. Similar results were observed
for the oxidation of compounds 1b–d.
Yield
of 5a (%)
Entry
Reagents and conditions
We attributed the low yields of the oxidation with H2O2/HNO3
and H2O2/H2SO4 to the Nef reaction28 that proceeded when
salts of the forming nitro compounds were exposed to strong
acid. We supposed that application of a mixture of H2O2 with
weaker organic acids could be more successful. We reasoned
that during the use of an acid weaker than dinitroalkanes (the
pKa values29 are: dinitromethane, 3.60; dinitroethane, 5.21; dinitro-
propane, 5.53), both oxidized precursor and forming product
would exist as anions that should prevent the Nef reaction.
Organic peroxy acids are the weak acids having pKa values
ca. 3.5–4 units greater than those of the parent acids.30 The
published30 pKa values for HCO3H and MeCO3H are 7.10 and
8.2, respectively. Therefore, they could be anticipated to be the
competent oxidants.
In fact, exposure of potassium nitrosolate 1a to the mixture
of 95% H2O2 (pKa 11.6)30 with Ac2O gave dinitromethane salt
5a in moderate yield (Table 2, entry 1; Scheme 3). The use of
more diluted H2O2 (Table 2, entries 2, 3), as well as the mixtures
of hydrogen peroxide with acetic acid (Table 2, entries 4–6) led
to lower yields.
1
2
3
4
5
6
7
8
9
95% H2O2 + Ac2O, –5 °C ® 35 °C
80% H2O2 + Ac2O, –5 °C ® 35 °C
50% H2O2 + Ac2O, –5 °C ® 35 °C
95% H2O2 + AcOH, 0 °C ® 35 °C
80% H2O2 + AcOH, 0 °C ® 35 °C
50% H2O2 + AcOH, 15 °C ® 55 °C
80% H2O2 + HCOOH, 15 °C ® 45 °C
50% H2O2 + HCOOH, 15 °C ® 60 °C
35% H2O2 + HCOOH, 15 °C ® 65 °C
53
48
32
29
25
26
86
71
58
The structure of 5c was ultimately confirmed by single crystal
X-ray crystallography33 using a sample recrystallized from
water.§
General view of molecule of 5c is presented in Figure 1. An
asymmetric unit cell consists of half of dinitropropane-potas-
sium salt which occupies special position (on the mirror plane).
Each potassium cation is coordinated with eight oxygen atoms.
Both nitro groups of the anion are equally involved in coor-
dination, and negative charge is delocalized over NO2–C–NO2
moiety that is nearly planar (mean deviation is 0.034 Å).
The C(1)–N(1)[N(1A)] bonds [1.3807(11) Å] are shorter than
Csp2–NO2 single bonds for neutral molecules (1.40–1.46 Å).34
The lenghts of eight K···O contacts vary in the range of
2.72–2.93 Å which corresponds to normally observed distances.34
Cation–anion interactions link molecules to the layers parallel
to ab crystallogrphic plane while the layers are connected to
each other by ordinary van der Waals interactions between
ethyl groups.
O
N
N
N
N
O
O
O
O
H2O2/HCO2H
K+
R
R
O
1a–d
5a–d
In conclusion, we have developed a simple and efficient
method for the oxidative synthesis of α,α-dinitroalkanes, com-
pounds of significant synthetic interest. To the best of our
knowledge, this is the first example of oxidative formation of
a R = H
b R = Me
c R = Et
d R = Ph
Scheme 3
We supposed that moving to a stronger carboxylic acid could
provide more active peroxy species. In fact, the oxidation of
potassium nitrosolate 1a using a mixture of hydrogen peroxide
and formic acid gave product 5a‡ in yields as high as 71–86%
(Table 2, entries 6, 7).
K(1)
Investigating scope and limitations of our procedure we found
that salts 1b or 1c when treated with HCOOH/80% H2O2
transformed into the desired dinitromethyl derivatives 5b and 5c
in 85% and 76% yields, respectively. However, attempted oxida-
tion of Ag-salt 1d† under these conditions failed to give any
of dinitro compounds. On the other hand, similar oxidation
in the presence of K2HPO4 provided the desired K-salt 5d in
47% yield.
O(2)
O(2')
N(1)
N(1')
C(1)
C(2)
O(1)
O(1')
Compounds 4 and 5 were identified by elemental analyses,
1H, 13C and 14N NMR spectral data31 and infrared absorption
spectra,32 which were consistent with the data described recently.
C(3)
Figure 1 ORTEP view of molecule of 5c. The displacement ellipsoids are
‡
General procedure for the synthesis of gem-dinitroalkane K-salts 5.
drawn at 50% probability level.
Potassium salt of dinitrosomethanide 1a (1.12 g, 10 mmol) was added
very slowly to a stirred solution of formic acid (5 ml) in 80% H2O2
(10 ml) at 15 °C, maintaining the temperature of the solution below 18 °C
(Caution! The reaction is exothermic and potentially explosive). Stirring
was continued at this temperature for 30 min and then the mixture was
heated to 45 °C. The reaction mixture was diluted with water and left on
stirring at 0 °C for 2 h. The precipitated solid was collected by filtration.
The filtrate was concentrated, and the precipitation was repeated. The
two crops were combined and crystallized from H2O. After filtration and
washing with water, the yellow solid was dried under vacuum to give the
product 5a (1.24 g, 86%); mp 207 °C (explosion!) [lit., 207–208 °C
(decomp.)]. All compounds described in this paper gave satisfactory
physico-chemical data. Caution! Compounds 1a–d and 5a–d are sensitive
to heat, sparks, friction, and impact, hence, fluoroplastic spatulas should
be used. Grounding straps, thick gloves, and a face shield should be
worn during all manipulations.
§
Crystal data for 5c. Crystals of (C3H5N2O4)–K+ are monoclinic, space
group P21/m: a = 4.1938(3), b = 7.7949(6) and c = 9.7764(8) Å, b =
= 99.161(2)°, V = 315.52(4) Å3, Z = 2, M = 172.2, dcalc = 1.812 g cm–3,
m = 0.797 mm–1. 3401 reflections were collected on a SMART 1000 CCD
diffractometer [l(MoKα) = 0.71073 Å, graphite monochromator, w-scans,
2q < 58°] at 120 K. The structure was solved by the direct methods and
refined by the full-matrix least-squares procedure in anisotropic approxi-
mation. 889 independent reflections (Rint = 0.0203) were used in the
refinement procedure that was converged to wR2 = 0.0533 calculated on
F2hkl [GOF = 1.018, R1 = 0.0229 calculated on Fhkl using 832 reflections
with I > 2s(I)].
CCDC 779124 contains 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.
For details, see ‘Notice to Authors’, Mendeleev Commun., Issue 1, 2010.
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Mendeleev Commun., 2010, 20, 215–217
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Received: 2nd February 2010; Com. 10/3457
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