Facile one-pot synthesis of 1-alkyl-3-polyfluoroalkyl imidazolium ionic liquids

Article abstract of DOI:10.1055/s-0029-1217530

Imidazolium-based ionic liquids bearing a polyfluorinated alkyl group on the cation were efficiently synthesized in excellent yields and selectivities from the one-pot reaction of a fluoroolefin with [1-alkyl-3H-imidazolium]X, where X = Cl, NO₃

Full text of DOI:10.1055/s-0029-1217530

LETTER
2101
Facile One-Pot Synthesis of 1-Alkyl-3-polyfluoroalkyl Imidazolium Ionic
Liquids
1
-Alkyl-3-polyfluo
o
roalkyl Imid
n
azoliumIoni
g
c
Liquids Sub Kim,a Debby Natalia,a Dihn Quan Nguyen,b Dong Jin Suh,a Honggon Kim,a Hoon Sik Kim,*b
Hyunjoo Lee*a
a
Division of Energy and Environment, Korea Institute of Science & Technology, Hawolgok-dong, Sungbuk-gu, Seoul 136-791, Korea
Fax +82(2)9585807; E-mail: hjlee@kist.re.kr
Department of Chemistry, Kyung Hee University, 1 Hoegi-dong, Dondaemoon-gu, Seoul 130-701, Korea
Fax +82(2)9654408; E-mail: khs2004@khu.ac.kr
b
Received 25 March 2009
Y–
1. CF3(CF2)nCH2CH2I
2. MY
Abstract: Imidazolium-based ionic liquids bearing a polyfluorinat-
ed alkyl group on the cation were efficiently synthesized in excel-
lent yields and selectivities from the one-pot reaction of a
fluoroolefin with [1-alkyl-3H-imidazolium]X, where X = Cl, NO3,
CF3CO2, BF4 or (CF3SO2)2N, formed in situ from the interaction of
an alkylimidazole with an acid, HX.
+
MI
N
N
N
N
R
R
CH2CH2(CF2)nCF3
1
5
Scheme 1 Conventional method for polyfluoroalkyl imidazolium
ILs
Key words: ionic liquids, imidazolium, fluorine, fluoroolefin, hy-
droamination
ward the formation of fluoroalkylated product 5 (imidazo-
lium iodide), and the involvement of tedious and
problematic anion exchange.
Ionic liquids (ILs) have received great interest in various
fields of chemistry, due to their unique properties such as
negligible vapor pressures, wide liquid temperature rang-
es, and highly polar yet non-coordinating character.1
More importantly, the physical and chemical properties of
ILs can be tailored to specific purposes by introducing a
functional group or groups on the cation and/or anion. ILs
bearing ether, ester, sulfonate, amino or hydroxy groups
have been employed as electrolytes for lithium batteries,2
capture agents for CO2 and SO2 separation,3 and media for
nanoparticle preparation.4
Herein, we report a straightforward and highly selective
one-pot synthesis of 1-alkyl-3-polyfluoroalkyl imidazoli-
um-based ionic liquids (Scheme 2).
X–
1. HX,THF, 0 °C
N
N
N
N
2. fluoroalkene, r.t.
R
RF
R
1
3 or 4
3 RF = CF2CHFCF3
4 RF = CF2CHF2
R = butyl, methyl or methyl propionate
X– = CF3COO–, BF4–, Cl–, NO3–, TFSI–
Scheme 2 New synthetic route to fluorinated ILs
ILs bearing fluorinated functional groups have attracted
particular attention because the properties of conventional
ILs can be significantly altered. For instance, the inertness
to organic solvents, resistance to corrosive acids and
bases, and resistance to extremes of temperature and pres-
sure can be greatly improved by the presence of highly
electron-withdrawing fluorine atoms.5
Imidazolium-based ILs bearing a fluorinated alkyl group
on the cation were obtained in high yields from a one-pot
reaction of alkylimidazole with the corresponding acids,
in the presence of a fluoroolefin. To our knowledge, this
is the first example of the synthesis of fluorinated ILs di-
rectly from the reaction between a quaternary imidazoli-
um salt and a fluoroolefin. A typical synthesis of a 1-
alkyl-3-polyfluoroalkyl imidazolium salt is as follows: In
a 100 mL high-pressure glass reactor, 1-butylimidazole
(7.6 mmol) was reacted with trifluoroacetic acid (TFA;
7.6 mmol) in tetrahydrofuran (35 mL) at 0 °C for one
hour. To this solution was added hexafluoropropylene
(HFP; 15.2 mmol) and reacted for five hours at ambient
temperature. Evaporation of all the volatiles under re-
duced pressure produced 1-butyl-3-(1,1,1,2,3,3-hexafluo-
ropropyl)imidazolium trifluoroacetate (3a) as a viscous
Accordingly, a number of methods have been reported for
the preparation of fluorinated ILs, but most of the reports
have been focused on the synthesis of ILs with a fluorinat-
–
–
ed anion such as BF4 , PF6 , TFSI–, TFES–, BETI– and
– 6
CF3CO2 . In contrast, very little is known for the synthe-
sis of ILs bearing a fluorinated functional group on the
cation. A representative example is the two-step reaction
of alkyl imidazole with fluoroalkyl iodide followed by an-
ion metathesis with an alkali metal salt (MY), as shown in
Scheme 1.7
However, this methodology has serious drawbacks such liquid in >99% yield.
as the use of costly fluoroalkyl iodide, low selectivity to-
As listed in Table 1, other imidazolium salts, were simi-
larly obtained in high yields of over 95%, except for 3h
with a trifluoromethanesulfonimide (TFSI) anion, which
was obtained in yield of 39%. Interestingly, the yield of
3h increased to >99% when the reaction was conducted at
SYNLETT 2009, No. 13, pp 2101–2104
Advanced online publication: 01.07.2009
DOI: 10.1055/s-0029-1217530; Art ID: U03409ST
© Georg Thieme Verlag Stuttgart · New York
x
x
.x
x
.2
0
0
9

2102
D. S. Kim et al.
LETTER
Table 1 Synthesis of ILs Starting from 1-Alkylimidazolea
tion between [BHIm]CF3CO2 and TFE. To investigate the
effect of solvent, [BHIm]CF3CO2 was reacted with HFP
in a range of solvents for five hours; the results are sum-
marized in Table 2. For clarity, [BHIm]CF3CO2 was sep-
arately prepared and used for the fluorination reaction.
F-IL
R
Fluoroalkene HA
Yield
(%)b
Selectivity
(%)b
3a
3b
3c
3d
3e
3f
Bu
Bu
Bu
Bu
Me
Me
MPc
Bu
Bu
Bu
Bu
Bu
HFP
HFP
HFP
HFP
HFP
HFP
HFP
HFP
HFP
TFE
TFE
CTFEf
TFA
99.5
95.8
99.8
99.8
99.5
99.7
95.1
38.5
99.7
60.6
99.4
50.4
100
100
100
100
100
100
99.4
99.8
100
100
100
100
HCl
Table 2 Synthesis of ILs Starting from Butylimidazolium Trifluo-
roacetatea
HNO3
HBF4
HNO3
TFA
Entry Solvent
Temp
(°C)
Conv.
(%)b
Product composition
(saturated:unsaturated) b
1
2
3
4
5
6
7
8
MeCN
DMF
Et2O
r.t.
r.t.
r.t.
80
r.t.
80
80
80
>99
>99
76
1:0.95
1:0.73
1:0.51
1:0.32
1:0.24
1:0.17
n.r.
3g
3h
3hd
4i
TFA
HTFSI
HTFSI
TFA
Et2O
>99
>99
>99
0
THF
THF
4ie
5j
TFA
toluene
CHCl3
TFA
0
n.r.
a Reaction conditions: imidazole (1 equiv), acid (1 equiv), fluoroalk-
ene (2 equiv), r.t., 5 h.
a Reaction conditions: imidazolium trifluoroacetate (1 equiv), HFP (2
equiv), 5 h.
b Yields and selectivities were calculated based on NMR results.
c Methyl propionate [MeOC(=O)CH2CH2-].
d Reaction carried out at 120 °C, 12 h.
e Solvent: MeCN.
b Conversion of imidazolium acetate and product molar ratio (saturat-
ed:unsaturated) were calculated based on NMR results.
f Chlorotrifluoroethylene.
Insertion of the N–H bond of butylimidazolium trifluoro-
acetate into the double bond of HFP proceeded almost
quantitatively in polar solvents such as N,N-dimethyl-
formamide and acetonitrile. In contrast, the reaction in a
solvent of medium polarity, such as diethyl ether or tet-
rahydrofuran, was much slower and required higher tem-
peratures of 80 °C in order to attain similar conversions.
No reaction was observed in a low-polarity solvents such
as toluene or chloroform, demonstrating the importance of
the polarity of the solvent.
120 °C for an extended reaction time of 24 hours. The for-
mation of the intermediate species, 1-butylimidazolium
trifluoromethanesulfonimide or the subsequent insertion
of HFP into the N–H bond of the imidazolium ring, seems
to proceed very slowly at room temperature. It is notewor-
thy that the fluorinated IL 3g, bearing an ester group on
the imidazolium ring, was also obtained in excellent yield.
The presence of an ester group was found to play a favor-
able role in CO2 capture and lithium ion transport in a
lithium ion battery.2b,8 Methyl 3-(1H-imidazol-1-yl)propi-
onate was prepared from the reaction between imidazole
and methyl acrylate under microwave-assisted conditions;
the reaction was complete in 20 minutes under these con-
ditions, otherwise 16 hours in refluxing methyl acrylate
was required.9 In general, the yields of fluorinated ILs
were not influenced by variation of the anion or the alkyl
group on the imidazolium cation.
It is worth mentioning here that, unlike the one-pot reac-
tion starting from 1-butylimidazole as shown in Table 1,
an unsaturated side product was always co-produced
when 1-butylimidazolium trifluoroacetate was used as the
starting material; the formation of the side product was
more pronounced in polar solvents (Scheme 3).
X
X
X
+
HFP
N
N
N
N
N
NH
Fluorinated ILs with 1,1,2,2-tetrafluoroethyl or chlorotri-
fluoroethyl groups on the imidazolium ring, 4i and 5j, re-
spectively, were also obtained from 1-butylimidazole,
TFA, and tetrafluoroethylene (TFE) or chlorotrifluoroeth-
ylene (CTFE) in THF, but the yields of these ILs were
much lower than those prepared from HFP.
R
CF2CHFCF3
CF=CFCF3
R
R
2
3
6
product
side product
Scheme 3 Reaction of alkyl imidazolium salt with HFP
The formation of unsaturated olefinic side-products was
also observed in the reactions of fluoroolefins with amine
or alcohol under a basic conditions.10 In the fluorination of
2,2,2-trifluoroethanol with HFP or TFE, it was suggested
that the base-assisted generation of a carbanionic species
and the subsequent defluorination are responsible for the
However, the yield of 4i was significantly increased to
over 99% when tetrahydrofuran was replaced by acetoni-
trile, implying that the solvent may play a pivotal role in
the formation of the intermediate, 1-butyl-3H-imidazoli-
um trifluoroacetate {[BHIm]CF3CO2} and/or in the reac-
Synlett 2009, No. 13, 2101–2104 © Thieme Stuttgart · New York

LETTER
1-Alkyl-3-polyfluoroalkyl Imidazolium Ionic Liquids
2103
formation of olefinic side products. In this regard, the
complete suppression of such olefinic side product forma-
tion is quite unusual in the one-pot synthesis of fluorinat-
ed ILs. The abstraction of fluorine from the carbanionic
intermediate species seems to be prohibited by the possi-
ble presence of free acid in the one-pot process.
References and Notes
(1) (a) Wasserscheid, P.; Welton, T. Ionic Liquids in Synthesis,
2nd ed.; Wiley-VCH: Weinheim, 2008. (b) Sheldon, R. A.;
Arends, I.; Hanefeld, U. In Green Chemistry and Catalysis;
Wiley-VCH: Weinheim, 2007. (c) Welton, T. Chem. Rev.
1999, 2071. (d) Bonhote, P.; Dias, A.-P.; Papageorgiou, N.;
Kalyanasundaram, K.; Gratzel, M. Inorg. Chem. 1996, 35,
1168.
(2) (a) Tiyapiboonchaiya, C.; Pringle, J. M.; Sun, J.; Byrne, N.;
Howlett, P. C.; MacFarlane, D. R.; Forsyth, M. Nat. Mater.
2004, 3, 29. (b) Lee, J. S.; Quan, N. D.; Hwang, J. M.; Bae,
J. Y.; Kim, H.; Cho, B. W.; Kim, H. S.; Lee, H. Electrochem.
Commun. 2006, 8, 460. (c) Hayamizu, K.; Tsuzuki, S.; Seki,
S.; Ohno, Y.; Miyashiro, H.; Kobayashi, Y. J. Phys. Chem.
B. 2008, 112, 1189.
(3) (a) Bates, E. D.; Mayton, R. D.; Ntai, I.; Davis, J. H. Jr.
J. Am. Chem. Soc. 2002, 124, 926. (b) Gutowski, K. E.;
Maginn, E. J. J. Am. Chem. Soc. 2008, 130, 14690.
(c) Huang, J.; Riisager, A.; Wasserscheid, P.; Fehrmann, R.
Chem. Commun. 2006, 4027.
(4) (a) Ueno, K.; Imaizumi, S.; Hata, K.; Watanabe, M.
Langmuir 2009, 25, 825. (b) Leger, B.; Roucoux, A.;
Olivier-Bourbigou, H. WO 2008/145836, 2008. (c) Zhang,
Y. J.; Shen, Y. F.; Yuan, J. H.; Han, D. X.; Wang, Z. J.;
Zhang, Q. X.; Niu, L. Angew. Chem. Int. Ed. 2006, 45,
5867. (d) Dorjnamjin, D.; Ariunaa, M.; Shim, Y. K. Int. J.
Mol. Sci. 2008, 9, 807.
Physical properties of these fluorinated ILs, including
melting points, thermal decomposition temperatures, and
viscosities, were measured and the results are listed in
Table 3. All the fluoroalkyl-substituted imidazolium salts
exhibit relatively high thermal stability and exist as liq-
uids at room temperature, except for 3b and 3e. Especial-
–
ly, the thermal stability of fluorinated ILs with BF4 or
TFSI– anions were extremely high in comparison to those
of others; these ILs had decomposition temperatures of
292 °C and 368 °C, respectively. Unfortunately, all the
ILs tested exhibited rather high viscosities. The presence
of highly electron-withdrawing fluorinated alkyl groups
will obviously increase the cationic character of the imi-
dazolium ring and thus the ionic interaction between cat-
ion and anion will be strengthened.
Table 3 Physical Properties of Imidazolium-Based Fluorinated ILs
([1-R-3-RF-Imidazolium]X)
(5) (a) Xue, H.; Shreeve, J. M. Eur. J. Inorg. Chem. 2005, 2573.
(b) Merrigan, T. L.; Bates, E. D.; Dorman, S. C.; Davis, J. H.
Jr. Chem. Commun. 2000, 2051. (c) Pringle, J. M.; Golding,
J.; Baranyai, K.; Forsyth, C. M.; Beacon, G. B.; Scott, J. L.;
MacFarlane, D. R. New J. Chem. 2003, 27, 1504. (d)Li,X.;
Zeng, Z.; Garg, S.; Twamley, B.; Shreeve, J. M. Eur. J.
Inorg. Chem. 2008, 3353.
(6) (a) Matsumoto, K.; Hagiwara, R. J. Fluorine Chem. 2007,
128, 317. (b) Xue, H.; Verma, R.; Shreeve, J. M. J. Fluorine
Chem. 2006, 127, 159. (c) Harmer, M. A.; Junk, C. P.;
Vickery, J. WO 2007/050492, 2007.
(7) Singh, R. P.; Manandhar, S.; Shreeve, J. M. Tetrahedron
Lett. 2002, 43, 9497.
(8) (a) Beckman, E. J. Chem. Commun. 2004, 1885.
(b) Raveendran, P.; Wallen, S. L. J. Am. Chem. Soc. 2002,
124, 7274.
(9) Wasserscheid, P.; Drießen-Hölscher, B.; van Hal, R.;
Steffens, H. C.; Zimmermann, J. Chem. Commun. 2003,
2038.
(10) (a) Rudyuk, V. V.; Fedyuk, D. V.; Yagupolskii, L. M.
J. Fluorine Chem. 2004, 125, 1465. (b) Chambers, R. D.;
Mobbs, R. H. Adv. Fluorine Chem. 1965, 50. (c) Kang,
J. E.; Lee, J. S.; Kim, D. S.; Lee, S. D.; Lee, H.; Kim, H. S.;
Cheong, M. J. Catal. 2009, 262, 177.
F-IL
R
RF
X–
Tg
(°C)
Td
Viscosity
(°C) (mPas)a
–
3a
3b
3c
3d
3e
3f
Bu
Bu
Bu
Bu
CF3CHFCF2 CF3CO2
CF3CHFCF2 Cl–
–58.3
111.2b
–55.4
–48.3
83.5b
–73.0
–40.4
–66.8
–63.3
189
217
162
292
170
190
200
368
194
374
–
–
CF3CHFCF2 NO3
2960
2162
–
–
CF3CHFCF2 BF4
–
Me CF3CHFCF2 NO3
Me CF3CHFCF2 CF3CO2
MPc CF3CHFCF2 CF3CO2
–
–
778
1264
525
575
3g
3h
4i
Bu
Bu
CF3CHFCF2 TFSI–
CHF2CF2 CF3CO2
–
a Measured at 30 °C.
b Melting point.
c Methyl propionate [MeOC(=O)CH2CH2].
In conclusion, we were able to synthesize various 1-alkyl-
3-polyfluoroalkyl imidazolium salts in high yields with-
out producing any olefinic side-products through a simple
one-pot, two-step reaction.11
(11) Representative example of the synthesis of 1-butyl-3-
(1,1,1,2,3,3-hexafluoropropyl)imidazolium
trifluoroacetate (3a). In a 100 mL high-pressure glass
reactor, 1-butylimidazole (7.6 mmol) was reacted with TFA
(7.6 mmol) in THF (35 mL) at 0 °C for 1 h. To this solution
was added hexafluoropropylene (HFP; 15.2 mmol) and the
reaction was continued for 5 h at an ambient temperature.
Evaporation of all the volatiles under a reduced pressure
produced 1-butyl-3-(1,1,1,2,3,3-hexafluoropropyl)imid-
azolium trifluoroacetate, as a viscous liquid in >99% yield.
1H NMR (300 MHz, CD3CN): d = 9.87 (s, 1 H), 7.94 (s,
1 H), 7.71 (s, 1 H), 6.6–6.38 (m, 1 H), 4.33–4.28 (t, J = 7.5
Hz, 2 H), 1.87–1.81 (m, 2 H), 1.46–1.30 (m, 2 H), 1.00–0.96
(t, J = 7.2 Hz, 3 H). 19F NMR (300 MHz, D2O): d = 1.38–
1.27 (m, 3 F), 0.53–0.34 (m, 3 F), –11.44 to –12.31 (m, 1 F),
–18.40 to –19.29 (m, 1 F), –134.70 to –134.94 (m, 1 F).
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synlett.
Synlett 2009, No. 13, 2101–2104 © Thieme Stuttgart · New York

2104
D. S. Kim et al.
LETTER
Anal. Calcd for C12H13F9N2O2: C, 37.12; H, 3.38; N, 7.22.
Found: C, 37.32; H, 3.56; N, 7.41.
14.24. Found: C, 28.77; H, 2.46; N, 14.04.
1-(1,1,2,3,3,3-Hexafluoropropyl)-3-methylimidazolium
trifluoroacetate (3f). 1H NMR (300 MHz, D2O): d = 9.63
(s, 1 H), 7.99 (s, 1 H), 7.76 (s, 1 H), 6.28–6.04 (m, 1 H), 4.02
(s, 3 H). 19F NMR (300 MHz, D2O): d = 1.43–1.38 (m, 3 F),
0.43 (s, 3 F), –11.38 to –12.26 (m, 1 F), –18.43 to –19.36 (m,
1 F), –134.69 to –134.96 (m, 1 F). Anal. Calcd for
C9H7F9N2O2: C, 31.23; H, 2.04; N, 8.09. Found: C, 30.96; H,
2.07; N, 8.00.
1-(1,1,2,3,3,3-Hexafluoropropyl)-3-(methoxyl-carbonyl-
ethyl)imidazolium trifluoroacetate (3g). 1H NMR (400
MHz, D2O): d = 9.72 (s, 1 H), 7.93 (s, 1 H), 7.80 (s, 1 H),
6.16–6.02 (m, 1 H), 4.57–4.54 (t, J = 6.1 Hz, 2 H), 3.65 (s,
3 H), 3.03–3.00 (t, J = 6.2 Hz, 2 H). 19F NMR (300 MHz,
D2O): d = 1.39–1.26 (m, 3 F), 0.52 (s, 3 F), –11.40 to –12.26
(m, 1 F), –18.41 to –19.30 (m, 1 F), –134.73 to –135.00 (m,
1 F). Anal. Calcd for C12H11F9N2O4: C, 34.46; H, 2.65; N,
6.70. Found: C, 34.64; H, 2.71; N, 6.88.
3-Butyl-1-(1,1,2,3,3,3-hexafluoropropyl)imidazolium
bis(trifluoromethanesulfonyl)imide (3h). 1H NMR (300
MHz, CD3CN): d = 9.08 (s, 1 H), 7.79 (s, 1 H), 7.69 (s, 1 H),
5.96–5.75 (m, 1 H), 4.27–4.22 (t, J = 7.5 Hz, 2 H), 1.91–1.80
(m, 2 H), 1.44–1.32 (m, 2 H), 0.99–0.94 (t, J = 7.2 Hz, 3 H).
19F NMR (300 MHz, D2O): d = 3.85–3.72 (m, 3 F), –1.34 (s,
6 F), –10.10 to –10.96 (m, 1 F), –15.87 to –16.75 (m, 1 F),
–132.11 to –132.31 (m, 1 F). Anal. Calcd for
3-Butyl-1-(1,1,2,3,3,3-hexafluoropropyl)imidazolium
chloride (3b). 1H NMR (300 MHz, D2O): d = 8.01 (s, 1 H),
7.84 (s, 1 H), 6.30–6.02 (m, 1 H), 4.33–4.37 (t, J = 7.2 Hz,
2 H), 1.87–1.97 (m, 2 H), 1.29–1.41 (m, 2 H), 0.91–0.96 (t,
J = 7.5 Hz, 3 H). 19F NMR (300 MHz, D2O): d = 1.41–1.29
(m, 3 F), –11.45 to –12.33 (m, 1 F), –18.34 to –19.27 (m,
1 F), –134.69 to –134.91 (m, 1 F). Anal. Calcd for
C10H13ClF6N2: C, 38.66; H, 4.22; N, 9.02. Found: C, 39.12;
H, 4.43; N, 8.89.
3-Butyl-1-(1,1,2,3,3,3-hexafluoropropyl)imidazolium
nitrate (3c). 1H NMR (300 MHz, D2O): d = 9.73 (s, 1 H),
8.02 (s, 1 H), 7.85 (s, 1 H), 7.32–6.05 (m, 1 H), 4.38–4.33 (t,
J = 7.2 Hz, 2 H), 1.92–1.87 (m, 2 H), 1.39–1.29 (m, 2 H),
0.97–0.92 (t, J = 7.4 Hz, 3 H). 19F NMR (300 MHz, D2O):
d = 1.40–1.28 (m, 3 F), –7.19 to –12.35 (m, 1 F), –18.32 to
–19.28 (m, 1 F), –134.69 to –134.96 (m, 1 F). Anal. Calcd
for C10H13F6N3O3: C, 35.62; H, 3.89; N, 12.46. Found: C,
35.43; H, 4.05; N, 12.72.
3-Butyl-1-(1,1,2,3,3,3-hexafluoropropyl)imidazolium
tetrafluoroborate (3d). 1H NMR (300 MHz, CD3CN): d =
9.17 (s, 1 H), 7.84 (s, 1 H), 7.72 (s, 1 H), 6.05–5.83 (m, 1 H),
4.31–4.26 (t, J = 7.4 Hz, 3 H), 1.97–1.88 (m, 2 H), 1.43–1.35
(m, 2 H), 0.99–0.95 (t, J = 7.3 Hz, 3 H). 19F NMR (300 MHz,
D2O): d = 3.82–3.71 (m, 3 F), –10.38 to –11.24 (m, 1 F),
–15.98 to –16.90 (m, 1 F), –72.48 to –72.54 (d, J = 16.2 Hz,
1 F), –132.36 to –132.59 (m, 1 F). Anal. Calcd for
C10H13BF10N2: C, 33.18; H, 3.62; N, 7.74. Found: C, 33.48;
H, 3.88; N, 7.90.
1-(1,1,2,3,3,3-Hexafluoropropyl)-3-methylimidazolium
nitrate (3e). 1H NMR (300 MHz, D2O): d = 7.99 (s, 1 H),
7.96 (s, 1 H), 6.27–6.06 (m, 1 H), 4.04 (s, 3 H). 19F NMR
(300 MHz, D2O): d = 1.43–1.35 (m, 3 F), –11.42 to –12.33
(m, 1 F), –18.43 to –19.36 (m, 1 F), –134.69 to –134.96 (m,
1 F). Anal. Calcd for C7H7F6N3O3: C, 28.49; H, 2.39; N,
C12H13F12N3O4S2: C, 25.95; H, 2.36; N, 7.57. Found: C,
25.81; H, 2.26; N, 7.69.
3-Butyl-1-(1,1,2,2-tetrafluoroethyl)imidazolium
trifluoroacetate (4i). 1H NMR (400 MHz, D2O): d = 9.56 (s,
1 H), 7.87 (s, 1 H), 7.72 (s, 1 H), 6.77–6.51 (t, J = 51.9 Hz,
1 H), 4.28–4.22 (m, 2 H), 1.85–1.78 (m, 2 H), 1.30–1.20 (m,
2 H), 0.88–0.81 (t, J = 7.4 Hz, 3 H). 19F NMR (300 MHz,
D2O): d = 0.49 (s, 3 F), –22.91 (s, 2 F), –60.50 to –60.68 (d,
J = 55.2 Hz, 1 F). Anal. Calcd for C11H13F7N2O2: C, 39.06;
H, 3.87; N, 8.28. Found: C, 38.80; H, 3.61; N, 8.47.
Synlett 2009, No. 13, 2101–2104 © Thieme Stuttgart · New York

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