,
2005, 15(5), 204–205
Synthesis of 2-R-2,2-dinitroethanol orthoesters in ionic liquids
Aleksei B. Sheremetev* and Igor L. Yudin
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation.
DOI: 10.1070/MC2005v015n05ABEH002157
The syntheses of tris(2-R-2,2-dinitroethyl)ortoformates and tetrakis(2-R-2,2-dinitroethyl)orthocarbonates in ionic liquids are described.
2
,2,2-Trinitroethyl and 2-fluoro-2,2-dinitroethyl compounds are
ii
OCH C(NO ) F
2 2 2
important energetic materials, which are used as the ingredients
of explosive compositions, propellant formulations and gas-
generating compositions. 2,2,2-Trinitroethanol 1a and 2-fluoro-
2
these compounds. The reactivity of electronegatively substituted
alcohols is much lower than that of usual alcohols. Moreover,
under basic conditions, alcohols 1a and 1b decompose.
CHCl3
i
1
2
F(O N) CCH O
OCH C(NO ) F
2 2 2
3
2
2
2
2
b
,2-dinitroethanol 1b are strategic precursors in the synthesis of
OCH C(NO )
2 3
4
2
(
O N) CCH O
OCH C(NO )
2 2 3
2
3
2
2
a
5
Hill reported the synthesis of trinitroethanol orthoesters by
refluxing a solution of dry alcohol 1a with trichloromethyl com-
F(O N) CCH O OCH C(NO ) F
2
2
2
2
2 2
5
ii
pounds in the presence of anhydrous ferric chloride. A similar
CCl4
i
approach was used for the synthesis of 2-fluoro-2,2-dinitro-
F(O N) CCH O OCH C(NO ) F
2 2 2 2 2 2
6
ethanol orthoesters. Because this method was long and potential
3
b
explosion hazard, an alternate route was required.
(
O N) CCH O OCH C(NO )
2 3 2 2 2 3
Room temperature ionic liquids are promising reaction media
for a variety of chemical processes.7 Ethylmethylimidazolium
salts (Figure 1) can be advantageous reaction media because
they are most widely available, fire-resistant, recyclable and
have a limited vapour pressure, allowing efficient recovery of
organic products.
,8
(
O N) CCH O OCH C(NO )
2 3 2 2 2 3
3
a
Scheme 1 Reagents and conditions: i, HOCH C(NO ) 1a, [emim][X],
2
2 3
70–100 °C; ii, HOCH C(NO ) F 1b, [emim][X], 70–100 °C.
2
2 2
[
emim] = ethylmethylimidazolium
formed without regeneration of the ionic liquid with no drop in
yields.
Me
Et
N
N
X
X = Cl, BF , PF , AlCl
4
6
4
Encouraged by these results, we studied other trichloromethyl
compounds and alcohols under optimised conditions, and Table 2
summarises the results. In all cases, electronegatively substituted
alcohols reacted with trichloromethyl compounds in [emim][AlCl4]
in high yields when catalysed by FeCl3.
In conclusion, we found that the displacement of a chlorine
atom in trichloromethyl compounds with electronegatively substi-
Figure 1 Structures of room temperature ionic liquids.
9
Previously, we described the reaction of CCl with poor
4
nucleophiles such as aminofurazans10 using [emim][AlCl ] as
4
the solvent and the catalyst. Two chlorine atoms of CCl were
displaced under these conditions and corresponding (3-R-furazan-
-yl)dichloroimines were prepared in good yields.
4
4
Here, we report the synthesis of trinitroethanol and 2-fluoro-
,2-dinitroethanol orthoformates 2 and orthocarbonates 3
†
General procedure for the preparation of tetrakis(2,2,2-trinitroethyl)-
2
orthocarbonate 3a. Trinitroethanol (1.81 g, 10 mmol) was added to a
mixture of [emim][AlCl4] (5 ml), CCl (0.5 ml) and FeCl (0.5 mmol)
under an atmosphere of argon and anhydrous conditions. The reaction
mixture was heated at 80 °C with stirring until the complete consumption
of the starting alcohol (2–3 h, according to TLC). CCl4 was removed
under a reduced pressure. The product was separated from the residue by
extraction with diethyl ether (7×10 ml). The combined extracts were
washed with cold water to neutral reaction and dried with MgSO . The
solution was passed through a short SiO2 pad and evaporated to give
the product 3a as a solid, mp 161–162 °C (lit., mp 163 °C). H NMR
(
Scheme 1) using the ionic liquids as both solvents and Lewis
1
1
4
3
acid catalysts.
We studied [emim][X] as a solvent for chlorine displacement
in CCl4 by trinitroethanol 1a as a model electronegatively
substituted alcohol. Table 1 summarises the results of these
experiments. In all of the reactions, both alcohol 1a and CCl4
were thoroughly dried before use. These reactants were converted
into desired orthocarbonates 3a in ionic liquids on heating with
4
5
1
†
stirring for ~3 h. Gaseous HCl evolved during the reaction.
2
13
2
(
[ H ]DMSO) d: 5.39 (CH ). C NMR ([ H ]DMSO) d: 62.3 (CH ),
Table 1 indicates that the anion played an important role in this
6 2 6 2
1
4
2
1
17.8 (C–O), 123.5 [C(NO ) ]. N NMR ([ H ]DMSO) d: –34.1 (NO ).
2 3 6 2
transformation. Thus, we found that [emim][AlCl ] was a more
4
–1
IR (n/cm ): 3012, 2964, 2892, 1604, 1452, 1396, 1304, 1296, 1192,
148, 1120, 1092, 1072. Found (%): C, 14.71; H 1.06; N, 23.00. Calc.
for C H N O (732.23) (%): C, 14.76; H, 1.10; N, 22.95.
effective medium than other ionic liquids in terms of yield
1
(
Table 1, entry 7). The reaction was unsuccessful when [emim][Cl]
was used (Table 1, entry 1). The treatment of trinitroethanol 1a
with CCl in the presence of FeCl in ionic liquids afforded
9
8
12 28
‡
In contrast, the FeCl -promoted reaction of trinitroethanol 1a with
3
4
3
CCl , which is a reagent and a solvent, afforded orthocarbonate 3a in
4
‡
desired orthocarbonates 3a in high yields. The recycling/re-use
of the solvent in several syntheses of compound 3a were per-
5
8
0% yield at refluxing for 24 h. A prolonged reaction time and violated
solvent make the process dangerous.
2
04 Mendeleev Commun. 2005
Sheremetev, Aleksei B.
