Ionic liquid-assisted synthesis of trinitroethyl esters

Article abstract of DOI:10.1070/MC2006v016n05ABEH002350

The first, highly efficient esterification of 2,2,2-trinitroethanol with alkanoyl, cycloalkanoyl, aroyl and hetaroyl chloride promoted by simple ionic liquids is described; trinitroethyl esters were characterised by X-ray crystallography.

Full text of DOI:10.1070/MC2006v016n05ABEH002350

Mendeleev
Communications
Mendeleev Commun., 2006, 16(5), 264–266
Ionic liquid-assisted synthesis of trinitroethyl esters
a
a
b
Aleksei B. Sheremetev,* Igor L. Yudin and Kirill Yu. Suponitsky
a
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation.
Fax: +7 495 135 5328; e-mail: sab@ioc.ac.ru
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow, Russian Federation.
b
Fax: +7 495 135 5085; e-mail: kira@xrlab.ineos.ac.ru
DOI: 10.1070/MC2006v016n05ABEH002350
The first, highly efficient esterification of 2,2,2-trinitroethanol with alkanoyl, cycloalkanoyl, aroyl and hetaroyl chloride promoted
by simple ionic liquids is described; trinitroethyl esters were characterised by X-ray crystallography.
Polynitro compounds are of significant interest as oxygen-rich
energetic materials for propulsion and explosive applications.1–3
dependent and the sequence with which the reactions were
carried out played a significant role in their successful execution.
Because reported methods were not amenable to reproducible
yields and potential explosion hazard, an alternate route was
required.
2
,2,2-Trinitroethanol has long been recognised as a useful
building block for such materials. Progress in the synthesis
and chemistry of the electronegatively substituted alcohol and
4,5
its analogues has been the subject matter of monographs
Room-temperature ionic liquids (RTILs) (Figure 1), may be
advantageous reaction media. The general utility and advantages
of RTILs are well documented.1
and reviews.6
–8
1–14
Trinitroethyl esters of carboxylic acids are of particular interest
9,10
as the ingredients of gas-generating compositions. Some syn-
thetic strategies used to form these esters have been reported.4
The low reactivity of the alcohol requires the use of a strong
condensing agent or a reactive carboxylic acid derivative to
effect reaction. The esterification via the Lewis acid catalysed
reaction of the acid chloride at reflux temperature is the most
preferable procedure. The yields of trinitroethyl esters obtained
in a number of the cited transformations were curiously substrate
–8
Me
Et
N
N
[emim] = ethylmethylimidazolium
X = AlCl , BF , PF
X
4
4
6
Figure 1 Structure of [emim][X].
Recently, we described the straightforward use of RTILs as
inert reaction media for poor nucleophiles,1
5,16
in particular,
2,2,2-trinitroethanol. Our attention, therefore, was focused upon
2
64 Mendeleev Commun. 2006

Mendeleev Commun., 2006, 16(5), 264–266
Table 1 Yields and characteristics of compounds 2a–d from ionic liquid esterifications.
1H NMR (CDCl3)
Yield Mp/°C
13C NMR (CDCl3)
Product
R
14N NMR
–34.6
(%) (Lit.)
CH2
R
C(NO2)3 CH2 CO2
R
7
(
6–76.5
2a
2b
2c
Ph
93
95
92
5.63 7.49, 7.64, 7.97
5.61 7.46, 7.90
123.3
125.4
122.6
61.1 163.7 126.9, 128.6, 130.2, 134.5
61.1 163.1 125.4, 129.2, 131.3, 141.3
61.3 167.3 28.0, 29.3, 128.1
76–77)17
84–85
p-ClC H
–34.8
–35.5
–31.2 (from R)
6
4
9
2–93
(O N) CCH CH
5.47 2.91, 3.45
18
2
3
2
2
(92–93)
2
d
e
85
79
3–5
5.29 0.94, 1.59
123.3
123.2
60.5 172.2 9.7, 12.3
–34.5
–34.8
2
48–49
5.58 6.58, 7.26, 7.67
60.6 155.3 112.5, 121.1, 141.7, 148.4
O
–
35.9
2
f
92
95
123–124 5.64 7.37
122.6
122.4
61.3 153.9 111.1, 121.3, 141.6, 153.4
61.4 152.0 8.6, 145.3, 155.9
NO2
–33.5 (from R)
O
Me
2g
59–60
70–72
5.73 2.54
–35.7
N
N
O
N
2h
74
5.72 8.72, 8.83, 9.19
5.46 3.63
19
122.8
122.2
61.5 161.3 141.0, 145.0, 146.3, 148.7
61.2 162.5 39.5
–35.3
–35.4
N
5
6–57
4
CH [CO CH C(NO ) ] 95
2
2
2
2 3 2
(56–57)
the synthesis of 2,2,2-trinitroethanol derivatives in RTILs, and
we describe here the result of the application of the media to the
esterification of the unusual alcohol.
O
O
O
O
Cl
Cl
OCH2C(NO2)3
OCH C(NO )
2 3
i
The addition of 2,2,2-trinitroethanol to a solution of benzoyl
chloride 1a in [emim][AlCl ] at room temperature leads to rapid
4
2
gas evolution with concurrent formation of a light yellow colour.
1
13
As found by H and C NMR spectroscopy and TLC, the major
aromatic product was 2,2,2-trinitroethyl benzoate 2a (Scheme 1)
even after 0.5 h. With [emim][PF ] or [emim][BF ], the reaction
3
4
Scheme 2 Reagents and conditions: i, [emim][PF ], ambient temperature.
6
6
4
was slower but led to a vary similar result. Ester 2a was generally
formed in a nearly quantitative yield. The recycling/reuse of the
solvent in several syntheses of compound 2a were performed
without regeneration of the ionic liquid with no drop in yields.
Other aromatic acid chlorides reacted similarly. Moreover, alkanoyl,
of the structures are shown in Figure 1. In all the compounds,
the Ar–C(O)OC fragment is slightly nonplanar. The nonplanarity
is more pronounced for 2g with the exocyclic torsion angle
C(5)–C(4)–C(3)–O(2) being 19.3(2)°. For the comparison of
the orientations of C–C(NO ) groups, we choose the torsion
2
3
cycloalkanoyl and hetaroyl chlorides reacted immediately with
angles listed in Table 2. It can be seen that the orientation of the
C(NO ) group relative to the C(2)–O(2) bond is nearly the same
†
2
,2,2-trinitroethanol under the same conditions to give corre-
2
3
sponding products in good yields (Table 1). In all of the reactions,
the solvent and reactants were thoroughly dried before use.
We found that it is possible to effect a similar esterification
of a diacid dichloride to a diester. Thus, when a solution of
for all the compounds, which is in an agreement with NMR data.
‡
Reflections for compounds 2a, 2b and 2g were collected on a SMART
1
000 CCD diffractometer [l(MoKα) = 0.71073 Å, graphite monochromator,
w-scans] at 120 K. The structures were solved by the direct methods and
refined by the full-matrix least-squares procedure against F in an
malonyl dichloride 3 in [emim][PF ] was treated with 2,2,2-tri-
6
2
nitroethanol (Scheme 2), desired ester 4 was obtained in 95% yield.
anisotropic approximation. All the hydrogen atoms were placed in
geometrically calculated positions and refined within a riding model.
1
13
14
The ester structures were established by H, C and N NMR
spectroscopy (Table 1). The location region of chemical shifts
For 2a (C H N O ): triclinic, space group P1, a = 7.703(3), b =
1
13
14
9
7
3
8
in the H, C and N NMR spectra, corresponding to the trinitro-
ethyl moiety, are consistent between products. By this expedient
these chemical shift values can be used as the diagnostics of
=
7.972(4), c = 9.910(3) Å, a = 85.08(3)°, b = 84.90(4)°, g = 72.88(4)°,
3
–3
–1
V = 578.2(4) Å , Z = 2, M = 285.18, d = 1.638 g cm , m = 0.148 mm ,
calc
F(000) = 292, wR = 0.1163, GOF = 0.995 for 2691 independent reflec-
2
2
,2,2-trinitroethanol esters.
tions with 2q < 56°, R = 0.0504 for 2116 reflections with I > 2s(I).
1
Compounds 2a, 2b and 2g were also characterised by single
For 2b (C H ClN O ): triclinic, space group P1, a = 7.3983(11),
9
6
3
8
‡
crystal X-ray crystallography for the first time. ORTEP views
b = 9.3861(13), c = 10.2912(15) Å, a = 109.731(3)°, b = 105.536(3)°,
3
–3
g = 102.726(3)°, V = 608.87(15) Å , Z = 2, M = 319.62, d = 1.743 g cm ,
calc
Cl
OCH C(NO )
m = 0.363 mm–1, F(000) = 324, wR = 0.1113, GOF = 1.047 for 2891
2
2 3
2
i
R
+
HOCH2C(NO2)3
R
independent reflections with 2q < 56°, R = 0.0472 for 2248 reflections
1
O
O
with I > 2s(I).
For 2g (C H N O ): orthorhombic, space group Pbca, a = 8.2018(13),
6
5
5
9
1
a–d
2a–d
3
b = 11.506(2), c = 23.245(4) Å, V = 2193.6(6) Å , Z = 8, M = 291.15,
–
3
–1
Scheme 1 Reagents and conditions: i, [emim][X], ambient temperature.
dcalc = 1.763 g cm , m = 0.169 mm , F(000) = 1184, wR2 = 0.0748,
GOF = 1.047 for 2376 independent reflections with 2q < 54°, R =
1
†
General procedure for the preparation of 2,2,2-trinitroethyl benzoate
= 0.0361 for 1658 reflections with I > 2s(I).
2
a. To a mixture of [emim][PF ] (20 ml) and benzoyl chloride 1a (1.4 g,
0 mmol), trinitroethanol (1.81 g, 10 mmol) was added under argon and
Atomic coordinates, bond lengths, bond angles and thermal param-
eters have been deposited at the Cambridge Crystallographic Data Centre
(CCDC). These data can be obtained free of charge via www.ccdc.cam.uk/
conts/retrieving.html (or from the CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: +44 1223 336 033; or deposit@ccdc.cam.ac.uk).
Any request to the CCDC for data should quote the full literature citation
and CCDC reference numbers 613201, 613202 and 613203 for 2a, 2b and
2g, respectively. For details, see ‘Notice to Authors’, Mendeleev Commun.,
Issue 1, 2006.
6
1
anhydrous conditions. The reaction mixture was stirred at room tempe-
rature until the complete consumption of the starting reactants (0.5–3 h,
according to TLC and NMR). The product was separated from the residue
by extraction with a mixture of CH Cl and diethyl ether (1:1). The
2
2
combined extracts were washed with cold water and dried with MgSO4.
The solution was passed through a short SiO pad and evaporated to give
product 2a (see Table 1).
2
Mendeleev Commun. 2006 265

Mendeleev Commun., 2006, 16(5), 264–266
Table 2 Selected torsion angles for esters 2a, 2b and 2g.
Cl(1)
C(7)
Torsion angle
2a
2b
2g
163.26(12)
–77.51(15)
43.46(17)
–174.72(13)
–179.87(12)
C(6)
N(1)–C(1)–C(2)–O(2)
N(3)–C(1)–C(2)–O(2)
N(2)–C(1)–C(2)–O(2)
C(1)–C(2)–O(2)–C(3)
C(2)–O(2)–C(3)–C(4)
162.98(14)
42.78(19)
–78.57(18)
–135.83(15)
–178.49(14)
159.32(16)
41.0(2)
–81.6(2)
119.82(18)
173.43(16)
C(8)
C(7)
C(8)
C(9)
C(6)
C(5)
C(5)
C(9)
C(4)
C(3)
C(4)
O(2)
References
O(6)
O(6)
C(3)
1
Yu. N. Orlova, Khimiya
Chemistry and Technology of High Explosives), 2 edn., Khimiya,
Leningrad, 1973 (in Russian).
i tekhnologiya vzryvchatykh veshchestv
O(2)
C(2)
O(1)
N(2)
nd
(
O(1)
O(5)
O(8)
N(2)
C(2)
C(1)
N(1)
O(5)
O(7)
2
3
4
5
Organic Energetic Compounds, ed. P. L. Marinkas, Nova Science
Publishers, Inc., New York, 1996, p. 108.
C(1)
N(1)
O(3)
N(3)
Energeticheskie kondensirovannye sistemy (Energetic Condensed Systems),
N(3)
nd
O(7)
2
edn., ed. B. P. Zhukov, Yanus-K, Moscow, 2000 (in Russian).
O(4)
O(4)
L. M. Kozlov and V. I. Burmistrov, Nitrospirty i ikh proizvodnye
(Nitroalcohols and their Derivatives), Kazan, 1960 (in Russian).
S. S. Novikov, M.-G. A. Shvekhgeimer, V. V. Sevostyanova and V. A.
O(8)
O(3)
2
a
2b
Shlyapochnikov, Khimiya alifaticheskikh
i alitsiklicheskikh nitro-
soedinenii (Chemistry of Aliphatic and Alicyclic Nitrocompounds),
Khimiya, Moscow, 1974, pp. 56–114 (in Russian).
M.-G. A. Shvekhgeimer, N. F. Pyatakov and S. S. Novikov, Usp. Khim.,
N(4)
C(5)
O(9)
6
7
8
9
1
959, 28, 484 (in Russian).
V. D. Nikolaev and M. A. Ishenko, Ross. Khim. Zh. (Zh. Ross. Khim.
Ob-va im. D. I. Mendeleeva), 1997, 41 (2), 14 (in Russian).
M.-G. A. Shvekhgeimer, Usp. Khim., 1998, 67, 39 (Russ. Chem. Rev.,
C(6)
N(5)
C(4)
1
998, 67, 35).
N. N. Makhova, A. B. Sheremetev, I. V. Ovchinnikov, I. L. Yudin, A. S.
Ermakov, P. V. Bulatov, D. B. Vinogradov, D. B. Lempert and G. B.
C(3)
O(6)
th
Manelis, Proc. 35 International Annual Conference of ICT – Energetic
N(2)
O(2)
C(2)
Materials: Reactions of Propellants, Explosives and Pyrotechnics,
2004, Karlsruhe, Germany, 140/1–12 and reference therein.
0 N. N. Makhova, A. S. Ermakov, I. V. Ovchinnikov, A. B. Sheremetev,
O(1)
O(8)
N(3)
O(5)
C(1)
1
I. L. Yudin, P. V. Bulatov, D. B. Vinogradov, V. A. Tartakovsky, D. B.
Lempert, I. N. Zyuzin and G. B. Manelis, Proc. 36 International Annual
th
Conference of ICT & Internatinal Pyrotechnics Seminar – Energetic
Materials: Performance and Safety, 2005, Karlsruhe, Germany, 185/1–10.
1 T. Welton, Chem. Rev., 1999, 99, 2071.
O(7)
N(1)
O(4)
1
1
O(3)
2 P. Wasserscheid and W. Keim, Angew. Chem., Int. Ed. Engl., 2000, 39,
3
772.
2
g
1
1
3 R. Sheldon, Chem. Commun., 2001, 2399.
4 N. Jain, A. Kumar, S. Chauhan and S. M. S. Chauhan, Tetrahedron,
Figure 1 ORTEP views of esters 2a, 2b and 2g.
2
005, 61, 1015.
For 2a and 2g, it can be attributed to the shortened O(2)···O(8)
contact [2.870(3) Å for 2a and 2.826(2) Å for 2g] that might
stabilise such an orientation while the corresponding distance in
1
5 A. B. Sheremetev, N. S. Aleksandrova and I. L. Yudin, Mendeleev
Commun., 2003, 30.
6 A. B. Sheremetev and I. L. Yudin, Mendeleev Commun., 2005, 204.
17 L. T. Eremenko and V. G. Oreshko, USSR Patent, 650993, 1979.
18 V. G. Matveev, L. D. Nazina, G. M. Nazin, D. A. Nesterenko and L. T.
Eremenko, Izv. Akad. Nauk, Ser. Khim., 1998, 2455 (Russ. Chem. Bull.,
1
2
b is equal to 2.945(2) Å. The structural differences arise mostly
from the rotation about the single C(3)–O(2) bond. Because of
a relatively small barier to rotation, different conformations can
1
998, 47, 2375).
be related to different intermolecular interactions.
The compounds are characterised by relatively high density.‡
19 R. E. Cochoy and R. R. McGuire, J. Org. Chem., 1972, 37, 3041.
In all the structures, there are many slightly shortened O···O and
O···N contacts with distances at the boundary between normal
and shortened ones. Several contacts of medium strength are
found in the structures of 2a and 2b, which allow us to describe
their crystal packing as the built up of columns (for 2a) and
layers (for 2b). In contrast, such contacts for the most dense
structure 2g are rather weak (O···O distances in the range
2
.9–3.1 Å). Probably, more close binding inside columns and
layers in 2a,b is overcompensated by a larger number of weak
contacts in 2g.
In conclusion, we have first demonstrated that the esterifica-
tion of 2,2,2-trinitroethanol with alkanoyl, cycloalkanoyl, aroyl
and hetaroyl chloride promoted by simple ionic liquids opens a
novel entry to the synthesis of trinitroethyl esters. The method
is facile and, more importantly, safe.
Caution. All trinitroethyl compounds should be considered
explosive and proper precautions should be taken in handling
and storage of them.
This work was supported by the International Science and
Technology Center (project no. 1882) and the Russian Academy
of Sciences.
Received: 13th March 2006; Com. 06/2695
2
66 Mendeleev Commun. 2006