Synthesis of the perdeuterated cellulose solvents 1-ethyl-3- methylimidazolium acetate (EMIM-OAc-d14) and 1-butyl-3- methylimidazolium acetate (BMIM-OAc-d18) and of 2- 13C-butyl-3-methylimidazolium acetate

Article abstract of DOI:10.1002/jlcr.1591

The syntheses of two perdeuterated ionic liquids (ILs), which have found use as solvents for cellulose derivatization and processing in addition, are described: 1-ethyl-3-methylimidazolium acetate (EMIM-OAc-d₁₄) and 1-butyl-3-methylimidazolium

Full text of DOI:10.1002/jlcr.1591

Research Article
Received 12 November 2008,
Revised 23 December 2008,
Accepted 20 January 2009
Published online 26 February 2009 in Wiley Interscience
(www.interscience.wiley.com) DOI: 10.1002/jlcr.1591
Synthesis of the perdeuterated cellulose
solvents 1-ethyl-3-methylimidazolium acetate
(EMIM-OAc-d14) and 1-butyl-3-
methylimidazolium acetate (BMIM-OAc-d18)
and of 2-13C-butyl-3-methylimidazolium
acetate
Yuko Yoneda,a,b Gerald Ebner,a Toshiyuki Takano,a,c Fumiaki Nakatsubo,c
Ã
Antje Potthast,a and Thomas Rosenaua
The syntheses of two perdeuterated ionic liquids (ILs), which have found use as solvents for cellulose derivatization and
processing in addition, are described: 1-ethyl-3-methylimidazolium acetate (EMIM-OAc-d14) and 1-butyl–3-methylimidazo-
lium acetate (BMIM-OAc-d18). The targets were obtained from imidazole in three-step sequences starting with butylation
and ethylation, respectively. The resulting 1-alkyl imidazoles were purified, and subsequently methylated according to
a novel protocol using dimethylcarbonate-d6. To obtain the 1-alkyl-3-methylimidazolium moiety, methylation of
1-alkylimidazoles proved to be superior to the conventional approach of alkylating 1-methylimidazole. Addition of acetic
acid-d4 caused traceless degradation of the methylcarbonate counter anions, which were neatly exchanged for acetate.
The IL 2-13C-butyl-3-methylimidazolium acetate, in which the isotopically enriched C-2 is a good NMR-indicator of
side reactions and solvent–solute interactions, was synthesized according to the same reaction sequence, starting from
2-13C-1-alkylimidazole which, in turn, was obtained by reaction of glyoxale, alkylamine, ammonia and paraformalde-
hyde-13C. Copyright r 2009 John Wiley & Sons, Ltd.
Keywords: cellulose solvents; ionic liquids; NMR solvents; BMIM acetate; EMIM acetate
communicated here is 2-13C-butyl-3-methylimidazolium acetate
to be used in such solution studies of cellulosics.
Introduction
Recently, ionic liquids (ILs) have attracted much interest in
cellulose chemistry as dissolution1,2 and derivatization media.3–5
Studies are going on to use ILs for large-scale production of
Results and discussions
cellulosic fibers.6,7 The swelling and dissolution of cellulose in ILs
(and in other cellulose solvents as well) are still far from being
Synthesis of perdeuterated ionic liquids 1-ethyl-3-methyl-
imidazolium acetate and 1-butyl-3-methylimidazolium
acetate
understood on a molecular level. Direct solution studies by
NMR are hampered by the unavailability of perdeuterated
The syntheses of the two ILs 1-ethyl–3-methylimidazolium
cellulose-dissolving ILs. In this study, the two most commonly
used IL-type cellulose solvents BMIM-OAc and EMIM-OAc were
acetate (EMIM-OAc-d14, 8) and 1-butyl-3-methylimidazolium
acetate (BMIM-OAc-d14, 9) proceeded in an analogous way. In
synthesized in perdeuterated form to allow for such experiments.
Moreover, it has been demonstrated recently that ILs do not
behave as inert solvents to cellulose, but react with the reducing
end of the polymer under formation of a carbon–carbon bond
at C-2.8 To study such reaction by NMR was impossible because
of the signal intensities of the reacting centers being negligibly
aDepartment of Chemistry, University of Natural Resources and Applied Life
Sciences, Muthgasse 18, A-1190 Vienna, Austria
bFaculty of Agriculture, Kyoto Prefectural University, Kyoto 606–8522, Japan
cGraduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606–8502,
small as compared with the several hundred non-reacting Japan
glucopyranose units of the polymer and the large excess of non-
*Correspondence to: Thomas Rosenau, Department of Chemistry, University of
Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna,
Austria.
reacting IL. By introducing a 13C label at C-2 this situation is
improved in a way that the side reaction between solvent and
solute becomes directly observable. The second synthetic target E-mail: thomas.rosenau@boku.ac.at
J. Label Compd. Radiopharm 2009, 52 223–226
Copyright r 2009 John Wiley & Sons, Ltd.

Y. Yoneda et al.
principle, two pathways are viable for the synthesis of 1-alkyl-3- Addition of excess acetic acid-d4 (7) at 801C afforded directly the
methylimidazolium salts. Most commonly, 1-methylimidazole as desired products 1-ethyl–3-methylimidazolium acetate-d14 (8)
the starting material is N-alkylated. This protocol is simple and and 1-butyl–3-methylimidazolium acetate-d18 (9), respectively.
suitable for large-scale preparations. In addition, 1-methylimi- Carbon dioxide and methanol, resulting from the methylcarbo-
dazole is widely available. Alternatively, imidazole can be nate anions, as well as excess acetic acid-d4 were conveniently
alkylated first into 1-alkylimidazole and then be methylated in removed by once more applying vacuum at 801C, leaving
the following step. We chose this second approach, applying behind the colorless and pure products as confirmed by
dimethylcarbonate as a methylating agent that so far had not microanalysis and UV spectrometry. Applying ethereal DCl
been used in the preparation of imidazole-based ILs. It neatly instead of acetic acid-d4 introduced the chloride anion,
quaternizes 1-alkylimidazoles into the 1-alkyl-3-methylimidazo- producing the corresponding 1-alkyl-3-methylimidazolium
lium cations without side reactions and discoloration of the chlorides in neat form (data not shown). In addition, in this
reaction mixtures, but the reaction times are longer than in the case the decomposition products of the methylcarbonate
case of methyl halides or dimethyl sulfate as the alkylating anions, carbon dioxide and methanol, and excess DCl and
agents, and a pressurized vessel is required for the reaction. solvent are conveniently removed by applying vacuum.
However, dimethyl carbonate offers one big advantage, which
was decisive in our case: it leaves the methylcarbonate Synthesis of 2-13C-1-butyl-3-methylimidazolium acetate
counterion that can afterwards tracelessly be replaced by other
For a 13C-label to be introduced into 2-position of the BMIM
anions if needed. In the case of common alkylating agents, such
heterocycle, the imidazole core has to be constructed. From the
as alkyl halides, traceless exchange of the halide for the desired
several approaches available,9,10 the use of 13C-paraformalde-
anion is not trivial. In the case of dimethylcarbonate used for
hyde was the most appropriate one, allowing the 1-butylimida-
alkylation of the 1-alkylimidazole, the resulting methylcarbonate
zole to be built directly without the need to isolate imidazole
is simply decomposed into carbon dioxide and methanol by
itself. Although the yields of the corresponding four-component
addition of acetic acid, and the desired acetate remained as the
reaction11–13 (see Scheme 2) were only modest (56%), the good
counteranion.
separability of the product, the low prices of the labeled
In the synthesis of perdeuterated material (Scheme 1), the
compound and the good upscaling potential were the decisive
pros. With the 2-13C-1-butylimidazole (10), the subsequent steps
starting compounds were imidazole-d4 (1) and a perdeuterated
alkyl halide (ethyl iodide, butyl iodide) for introduction of the 1-
were as described above in Scheme 1, providing the target
substituent. The perdeuterated intermediates, 1-(pentadeute-
molecule 11 in a 76% overall yield in analytically pure form.
roethyl)imidazole-d3 (2) and 1-(nonadeuterobutyl)imidazole-d3
(3), respectively, can be conveniently purified by microdistilla-
tion. The quaternization reaction with 1.2 equivalents of
Experimental
dimethylcarbonate-d6 (4) proceeded at 2101C in a teflon-coated
autoclave over 2 h, catalyzed by acidic aluminum oxide
Materials
All chemicals were commercially available. Thin layer chromato-
graphy was performed on silica gel 60 plates (5 Â 10 cm,
0.25 mm) with fluorescence detection under UV light at
254 nm. Column chromatography was performed on silica
gel G60 plates (40–63 mm). Melting points, determined on a
Kofler-type micro hot stage with Reichert-Biovar microscope,
(Brockmann grade I). The resulting reaction mixture was
colorless, which is not at all common for the syntheses of ILs
that are mostly accompanied by chromophore generation. From
the intermediates 1-ethyl-3-methylimidazolium methylcarbo-
nate-d14 (5) and 1-butyl-3-methylimidazolium methylcarbo-
nate-d18 (6), excess dimethylcarbonate-d6 was removed
under vacuum; non-reacted 1-alkylimidazole was not detected.
1
are uncorrected. H NMR spectra were recorded at 400.13 MHz,
O
D
D
D3C
CD3
O
O
D
D
N
N
ii
i
4
N
N
D
D
D
R
1
2 R = C2D5
3 R = C4D9
D
D
O
CD3
CD3
O
D
D
N
N
+
+
O
DO
CD3
O
iii
7
N
N
CD3
D
-CD3OD, -CO2
O
O
D
CD3
R
R
5 R = C2D5
6 R = C4D9
8 R = C2D5
9 R = C4D9
i: autoclave, C2D5-I / C4D9-I (1 eq.), Na2CO3 / NaOH, toluene, 150°C, 5h
(79% of 5, 84% of 6), ii: a) autoclave, Al2O3 (acidic), 1.2 eq. 4, r.t. to 210°C, 2h,
iii: 80°C, 1.5 eq. 7, 30 min, overall 76% of 8, overall 81% of 9.
Scheme 1. Synthesis of perdeuterated 1-ethyl-3-methylimidazolium acetate (8) and 1-butyl-3-methylimidazolium acetate (9), employing dimethylcarbonate-d6 as
alkylating agent and precursor of a conveniently exchangeable anion.
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J. Label Compd. Radiopharm 2009, 52 223–226

Y. Yoneda et al.
O
C4H9
H2N
H
H
C4H9
C4H9
_
N
N
i
ii, iii
AcO
+
O
H
13C
H
+
N
N
*
(NH4)2CO3
O
*
Me
* = 13C (>99%)
10
11
n
i: autoclave, components equimolar, 200°C, 4h (56%),
ii: Me2CO3 (1.2 eq.), autoclave, Al2O3 (acidic), r.t. to 210°C, 2h,
iii: AcOH (1.5 eq.), 80°C, 30 min, overall 76%
Scheme 2. Synthesis of 2-13C-1-butyl-3-methylimidazolium acetate (11), employing
a
four-component reaction to construct the imidazole ring with 13C-
paraformaldehyde as the source of the 13C-label.
13C NMR spectra at 100.42 MHz in CDCl3 as the solvent and TMS 30 min, vacuum (10-3 Torr) was applied for another 30 min. After
as the internal standard, if not stated otherwise. NMR data are cooling to r.t. mixture, 1-ethyl-3-methylimidazolium acetate-d14
given for the deuterated compounds, and also for non- (8) was obtained as colorless liquid (866 mg, 96%). 1H NMR
deuterated title products and key intermediates for comparison. (DMSO-d6, 0.1 M): d 3.56 (s, br, H2O/HDO). 13C NMR (DMSO-d6):
It should be noted that in standard attached proton test (APT) d 14.3 (sept., JC,D = 22 Hz, CD3 in ethyl), 24.9 (sept, JC,D = 21 Hz,
spectra of BMIM-type ILs the resonance of C-2 can be inverted or CD3 in acetate), 35.8 (sept., JC,D = 20 Hz, CD3–N), 45.4 (pent,
even ‘missing’. The large C–H coupling constant at this position
JC,D = 20 Hz, CD2–N), 121.5 (t, JC,D = 18 Hz, CD), 122.8
(4220 Hz) – in combination with the standard APT pulse (t, JC,D = 18 Hz, CD), 137.5 (t, JC,D = 20 Hz, CD), 174.0 (s, COO in
sequence – is responsible for this effect, so that for spectral acetate). Comparison to the non-deuterated product (1-ethyl–3-
assignment the APT technique is less suitable than conventional methylimidazolium acetate): 1H NMR (CDCl3, 0.1 M): d 1.42 (t, 3H,
13C spectra.14
CH3 in ethyl), 1.58 (s, 3H, CH3 in acetate), 3.85 (s, 3H, N–CH3), 4.19
(q, 2H, N–CH2), 7.92 (t, 1H, CH), 8.00 (t, 1H, CH), 10.32 (s, 1H, CH).
13C NMR (DMSO-d6): d 15.2, 26.1, 36.5, 45.5, 122.1, 123.9, 137.5,
1-Ethylimidazole-d8 (2)
Into a stainless steel autoclave with teflon coating, imidazole-d4 173.6. Microanalysis: calcd. for C8D14N2O2 (184.30): C 52.14, H
(0.72 g, 10 mmol), ethyl iodide-d5 (1.61 g, 10 mmol), freshly 7.60, N 15.20; found: C 52.36, H 7.88; N 14.98.
powdered, anhydrous sodium carbonate (1 g), freshly powdered
sodium hydroxide (ground from dry NaOH pellets), and dry 1-Butylimidazole-d12 (3)
toluene (100 mL) were added. The vessel was flushed with The same procedure was used as described above for the
argon, sealed and heated under efficient stirring at 1501C for 5 h. preparation of 2, with the following alterations: imidazole-d4
After cooling to r.t., solids were removed by filtration, and the (0.72 g, 10 mmol) and butyl iodide-d9 (1.94 g, 10 mmol) were
residue was microdistilled twice to provide 1-ethylimidazole-d8 employed to provide 1-butylimidazole-d12 (1.09 g, 84%) as
(823 mg, 79%) as colorless liquid.
colorless liquid. 1H NMR (CDCl3, 0.1 M): d 4.5 (s, br, HDO). 13C
1H NMR (CDCl3, 0.1 M): d 2.5 (s, br, H2O). 13C NMR (DMSO-d6): d NMR (DMSO-d6): d 12.9 (sept., JC,D = 22 Hz, CD3 in butyl), 19.3
15.3 (sept., JC,D = 22 Hz, CD3 in ethyl), 41.0 (pent, JC,D = 20 Hz, (pent, JC,D = 20 Hz, CD2 in butyl), 33.8 (pent, JC,D = 20 Hz, CD2 in
CD2–N), 118.1 (t, JC,D = 18 Hz, CD), 129.1 (t, JC,D = 18 Hz, CD), 136.1 butyl), 46.0 (pent, JC,D = 19 Hz, CD2–N), 118.0 (t, JC,D = 18 Hz, CD),
(t, JC,D = 20 Hz, CD). Comparison to the non-deuterated product 127.3 (t, JC,D = 18 Hz, CD), 137.0 (t, JC,D = 20 Hz, CD). Comparison
1
(1-ethylimidazole): H NMR (CDCl3, 0.1 M): d 1.40 (s, 3H, CH3 in to the non-deuterated product (1-butylimidazole): 1H NMR
ethyl), 3.92 (q, 2H, CH2 in ethyl), 6.92 (s, 1H, CH), 7.04 (s, 1H, CH), (CDCl3, 0.1 M): d 0.92 (t, 3H, CH3), 1.39 (sext, 2H, CH3–CH2), 1.76
7.48 (s, 1H, CH). 13C NMR (DMSO-d6): d 16.3, 41.5, 118.5, 128.9, (pent, 2H, N–CH2–CH2), 3.90 (t, 2H, N–CH2), 6.85 (s, 1H), 7.04 (s,
136.5. Microanalysis: calcd. for C5D8N2 (104.18): C 57.65, H 7.74, 1H), 7.49 (s, 1H). 13C NMR (DMSO-d6): d 13.6, 19.4, 34.2, 46.8,
N 26.89; found: C 57.85, H 7.37; N 27.01.
118.4, 129.5, 137.2, 173.6. Microanalysis: calcd. for C7D12N2
(136.26): C 61.70, H 8.88, N 20.56; found: C 61.86, H 9.02; N 20.22.
1-Ethyl-3-methylimidazolium acetate (EMIM-OAc-d14, 8)
1-Butyl-3-methylimidazolium acetate (BMIM-OAc-d18, 9)
1-Ethylimidazole-d8 (2, 520 mg, 5 mmol), dimethylcarbonate-d6
(4, 580 mg, 6.03 mmol) and acidic aluminum oxide (Brockmann The same procedure was used as described above for the
grade I, 0.2 g) was charged into a stainless steel autoclave with preparation of 8, with the following alterations: 1-butylimida-
teflon coating, and the mixture was heated at a rate of 51C/min zole-d12 (3, 680 mg, 5 mmol), dimethylcarbonate-d6 (4, 580 mg,
to 2101C, kept at this temperature for 2 h, and cooled to r.t. The 6.03 mmol), and acidic aluminum oxide (Brockmann grade I,
vessel was opened, the colorless white remainder triturated with 0.2 g) were used for the heterogeneous gas–solid phase
diethyl ether (ca. 50 mL), and the solids removed by filtration. reaction. The amount of recovered dimethylcarbonate-d6 was
The ether was evaporated and the viscous remaining solid was 82 mg (0.85 mmol). Acetic acid-d4 (7, 0.5 g, 7.8 mmol) was used
heated to 801C under vacuum, which provided a small amount to introduce the anion, and 1-butyl-3-methylimidazolium
of recovered dimethylcarbonate-d6 (not quantified). Under acetate-d18 (9) was obtained as colorless liquid (1.04 g) in 96%
1
ambient pressure and efficient stirring at 801C, acetic acid-d4 yield. H NMR (CDCl3, 0.1 M): d 2.5 (s, br, H2O). 13C NMR (DMSO-
(7, 0.5 g, 7.8 mmol) was added, upon which the clear liquid d6): d 12.0 (sept., JC,D = 22 Hz, CD3 in butyl), 18.1 (pent,
turned cloudy due to evolved gases. After stirring for additional
JC,D = 20 Hz, CD2 in butyl), 24.9 (sept, JC,D = 21 Hz, CD3 in acetate),
J. Label Compd. Radiopharm 2009, 52 223–226
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Y. Yoneda et al.
30.8 (pent, JC,D = 20 Hz, CD2 in butyl), 34.8 (sept., JC,D = 21 Hz, the 3-methyl substituent used dimethylcarbonate-d6 according
CD3–N), 47.4 (pent, JC,D = 19 Hz, CD2–N), 121.5 (t, JC,D = 18 Hz, to a novel protocol, utilizing a clean and quantitative gas–solid
CD), 122.8 (t, JC,D = 18 Hz, CD), 138.0 (t, JC,D = 20 Hz, CD), 174.0 reaction under elevated pressure, catalyzed by acidic aluminum
(s, COO in acetate). Comparison to the non-deuterated product oxide. The intermediate perdeuterated 1-alkyl-4-methylimidazo-
(BMIM-OAc): 1H NMR (DMSO-d6, 0.1 M): d 0.84 (t, 3H, CH3 in lium methylcarbonates were neatly converted into the target
butyl), 1.19 (sext, 2H, CH3–CH2 in butyl), 1.58 (s, 3H, CH3 in acetates by addition of acetic acid-d4, establishing methylcar-
acetate), 1.72 (pent, 2H, N–CH2–CH2 in butyl), 3.88 (s, 3H, bonate as a traceless replaceable counteranion. Construction of
N–CH3), 4.19 (q, 2H, N–CH2), 7.92 (t, 1H, CH), 8.01 (t, 1H, CH), the 1-butylimidazole moiety with a 13C-label at position 2
10.33 (s, 1H, CH). 13C NMR (DMSO-d6): d 13.2, 18.8, 26.1, 31.5, employed a four-component reaction with 13C-paraformalde-
35.4, 48.2, 122.3, 123.7, 138.2, 173.6. Microanalysis: calcd. for hyde as the source of the isotopic label. Conversion into the final
C10D18N2O2 (216.38): C 55.51, H 8.31, N 12.95; found: C 55.21, H target, 2-13C-1-butyl-3-methylimidazolium acetate (11), pro-
8.22; N 13.32.
ceeded in a way analogous to the perdeuterated ILs 8 and 9.
Besides having the advantages of high reproducibility and
good yields, the syntheses presented in Schemes 1 and 2 have
2-13C-1-butylimidazole (10)
Glyoxal (580 mg, 10 mmol), 1-butylamine (731 mg, 10 mmol), two general benefits: they are cheap – which is a factor that
ammonium carbonate (961 mg, 10 mmol) and 13C-paraformal- should not be underestimated – and they are able to provide
dehyde (310 mg, 10 mmol) were charged into a teflon-coated gram amounts of the perdeuterated products. The issue of
stainless steel autoclave, and heated to 2001C for 4 h. The availability in larger amounts is crucial in the case of NMR
mixture was cooled to r.t. and distilled under reduced pressure. solvents: in standard NMR experiments about 0.5 mL of solvent
After a small amount of butylamine distilling off, the main are employed, which cannot be fully purified and recycled in all
fraction consisted of the target product (706 mg, 56%). The cases.
remainder mainly contained imidazole and non-identified
condensation products of glyoxal. 1H NMR (CDCl3, 0.1 M): Acknowledgement
d 0.94 (t, 3H, CH3), 1.39 (sext, 2H, CH3–CH2), 1.75 (pent, 2H,
N–CH2–CH2), 3.92 (t, 2H, N–CH2), 6.86 (s, 1H, CH), 7.04 (s, 1H, CH),
7.49 (s, 1H, CH, JC,H = 144 Hz). 13C NMR (DMSO-d6, 4 scans):
d 138.1. 13C NMR (DMSO-d6, 512 scans): d 13.7, 19.4, 34.3, 46.6,
118.6, 129.4, 138.1, 173.1. Microanalysis: calcd. for C163CH12N2
(125.19): C 67.70, H 9.74, N 22.56; found: C 67.88, H 9.53; N 22.14.
¨
The financial support by the Austrian Fonds zur Forderung der
wissenschaftlichen Forschung, project P-17426 and by the
Christian Doppler Research Society (CD lab ‘Advanced Cellulose
Chemistry and Analytics’) is gratefully acknowledged. The
authors would like to thank Dr Andreas Hofinger, Department
of Chemistry at the University of Agricultural Sciences, Vienna,
for recording the NMR spectra.
2-13C-1-butyl-3-methylimidazolium acetate (BMIM-OAc, 11)
The same procedure was used as described above for the
preparation of 9, with the following alterations: 2-13C-1-
butylimidazole (10, 272 mg, 2 mmol), dimethylcarbonate (4,
290 mg, 3.02 mmol), and acidic aluminum oxide (Brockmann
grade I, 0.2 g) were used for the heterogeneous gas–solid phase
reaction. Excess dimethylcarbonate was not recovered. Glacial
acetic acid (0.3 g) was used to introduce the anion, and 2-13C-1-
butyl-3-methylimidazolium acetate (11) was obtained as color-
less liquid (303 mg) in 76% yield. 1H NMR (DMSO-d6, 0.1 M):
d 0.86 (t, 3H, CH3 in butyl), 1.20 (sext, 2H, CH3–CH2 in butyl), 1.59
(s, 3H, CH3 in acetate), 1.74 (pent, 2H, N–CH2-CH2 in butyl), 3.86
(s, 3H, N–CH3), 4.20 (q, 2H, N–CH2), 7.90 (t, 1H, CH), 8.00 (t, 1H,
CH), 10.28 (d, 1H, CH, JC,H = 225 Hz14). 13C NMR (DMSO-d6, 4
scans): d 138.3. 13C NMR (DMSO-d6, 512 scans): d 13.2, 18.9, 26.0,
31.8, 35.2, 48.4, 122.5, 123.7, 138.3, 174.6. Microanalysis: calcd.
for C193CH18N2O2 (199.27): C 60.58, H 9.15, N 14.13; found:
C 60.89, H 8.99; N 13.97.
REFERENCES
[1] S. Zhu, Y. Wu, Q. Chen, Z. Yu, C. Wang, S. Jin, Y. Dinga, G. Wuc,
Green Chem. 2006, 8, 325–327.
[2] R. P. Swatloski, S. K. Spear, D. John, J. D. Holbrey, R. D. Rogers,
J. Am. Chem. Soc. 2002, 124, 4974–4975.
[3] J. Wu, J. Zhang, H. Zhang, J. He, Q. Ren, M. Guo, Biomacromolecules
2004, 5, 266.
[4] S. Barthel, T. Heinze, Green Chem. 2006, 8, 301.
[5] T. Heinze, K. Schwikal, S. Barthel, Macromol. Biosci. 2005, 5, 520.
[6] N. Sun, R. P. Swatloski, M. L. Maxim, M. Rahman, A. G. Harland,
A. Haque, S. K. Spear, D. T. Daly, R. D. Rogers, J. Mater. Chem. 2008,
18, 283–290.
[7] F. Hermanutz, F. Meister, E. Uerdingen, Chem. Fiber Int. 2006, 6,
342–343.
[8] G. Ebner, S. Schiehser, A. Potthast, T. Rosenau, Tetrahedron Lett.
2008, 49, 7322–7324.
[9] A. R. Katritzky, Compr. Heterocycl. Chem. 1984, 5, 469–498.
[10] M. R. Grimmett, Imidazole and Benzimidazole Synthesis, Academic
Press, London, New York, San Diego 1997.
[11] H. Debus, Annalen der Chemie und Pharmacie 1858, 107, 199–208.
[12] R. D. Crouch, J. L. Howard, J. L. Zile, K. H. Barker, J. Chem. Educ.
2006, 83, 1658.
[13] A. J. Arduengo III, Process for manufacture of imidazoles. US
patent 6,177,575, 2001.
[14] G. Ebner, A. Hofinger, L. Brecker, T. Rosenau, Cellulose 2008, 15,
263–267.
Conclusion
Syntheses of the perdeuterated ionic liquids (ILs) 1-ethyl-3-
methylimidazolium acetate-d14 (8) and 1-butyl–3-methylimida-
zolium acetate-d18 (9) started from imidazole-d4, which
was ethylated-d5 (butylated-d9, respectively) to give the
corresponding perdeuterated 1-alkylimidazoles. Introduction of
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J. Label Compd. Radiopharm 2009, 52 223–226