A mild method for halofluorination of alkenes with ionic liquid EMIMF(HF)2.3

Article abstract of DOI:10.1016/j.jfluchem.2004.10.023

Halofluorination of alkene in the presence of N-halosuccinimide and ionic liquid, 3-ethyl-1-methyl-imidazorium oligo hydrogen fluoride (EMIMF(HF) _2.3), as a HF source was demonstrated. Various alkenes were converted into β-halo organofluorides

Full text of DOI:10.1016/j.jfluchem.2004.10.023

Journal of Fluorine Chemistry 126 (2005) 121–123
www.elsevier.com/locate/fluor
A mild method for halofluorination of alkenes
with ionic liquid EMIMF(HF)2.3
a
a,
a
*
Hideaki Yoshino , Seijiro Matsubara , Koichiro Oshima ,
Kazuhiko Matsumotob, Rika Hagiwarab, Yasuhiko Itob
aDepartment of Material Chemistry, Graduate School of Engineering, Kyoto University,
Kyotodaigaku-Katsura, Nishikyo, Kyoto 615-8501, Japan
bDepartment of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University,
Yoshida hon-machi, Sakyo, Kyoto 606-8501, Japan
Received 25 August 2003; accepted 26 October 2004
Available online 19 December 2004
Abstract
Halofluorination of alkene in the presence of N-halosuccinimide and ionic liquid, 3-ethyl-1-methyl-imidazorium oligo hydrogen fluoride
(EMIMF(HF)2.3), as a HF source was demonstrated. Various alkenes were converted into b-halo organofluorides in good yields and with high
regioselectivity.
# 2004 Published by Elsevier B.V.
Keywords: Iodofluorination of alkene; Bromofluorination of alkene; Ionic liquid; Hydrogen fluoride
1. Introduction
2. Results and discussion
Halofluorination of unsaturated hydrocarbon has been a
useful method to incorporate fluorine atom, and the obtained
b-halo subunit acquires for further reaction to gain various
organofluoro compounds [1,2]. To prepare it, alkenes are
treated with halonium ion and fluoride ion. However,
fluoride ion source in these procedures, elemental fluorine
[3,4], hydrogen fluoride [5,6], HF-pyridine (Olah’s reagent)
[7,8] and Et3N-3HF [9] contain difficulty to handle in
some extent. In this situation, ionic liquid containing
fluoride ion may have a possibility to solve these difficulty.
3-Ethyl-1-methyl-imidazorium oligo hydrogen fluoride
(EMIMF(HF)2.3), ionic liquid, is available in air with easy
and safety handle due to its non-volatility and poor solubility
to organic solvent. Herein, we wish report halofluorination
of alkenes with combination of halosuccinimide and this
ionic liquid as a fluorinating reagent.
EMIMF(HF)2.3 was synthesized by a direct reaction of 1-
ethyl-3-methyl-imidazolium chloride and anhydrous hydro-
gen fluoride [10]. This ionic liquid is stable against moisture
in air. It consists of 3-ethyl-1-methyl-imidazorium cation
and F(HF)2.3 anion, which a rapid exchange of HF between
H2F3 and H3F4 occurs [10]. So, we expected that this HF
could be available as fluoride ion source (Fig. 1).
Reactions were carried out in polypropylene toll tube that
is easy for decantation in work-up process. To a mixture of
substrate in CH2Cl2 and ionic liquid, N-iodosuccinimide
(NIS) was added in several portions. The reaction mixture
gradually turned to be clear and yellow. Extraction of
product is only to add hexane to the reaction mixture. The
resulting mixture became biphase. Decantation of upper
phase gave a hexane solution of the produced b-halofluoride.
After the solution was passed through short silica-gel
column, it was concentrated under reduced pressure
(Scheme 1).
Results of iodofluorination of alkenes are summarized in
Table 1. NIS required two equivalent for substrate otherwise
* Corresponding author. Tel.: +81 75 383 2441; fax: +81 75 383 2438.
E-mail address: matsubar@mc.kyoto-u.ac.jp (S. Matsubara).
0022-1139/$ – see front matter # 2004 Published by Elsevier B.V.
doi:10.1016/j.jfluchem.2004.10.023

122
H. Yoshino et al. / Journal of Fluorine Chemistry 126 (2005) 121–123
Table 2
Bromofluorination of alkenes
Entry Alkene
1
Time (h) Product
Yield (%)
86
3
1
Fig. 1. EMIMF(HF)2.3
.
2
90
3
4
5
1
1
1
90
95
81
Scheme 1.
Table 1
lodofluorination of alkenes
Entry
1
Alkene
Time (h)
3
Product
Yield (%)
80
2
3
36
1
64a
91
6
7
1
1
87
93
4
5
6
1
1
1
95
98
70
occurred to give (Z)-1-fluoro-1-phenylpropene stereospeci-
fically (Scheme 2) as reported by Schlosser [11,12].
Bromofluorination of alkenes were also occurred under
the same conditions using N-bromosuccinimide (NBS)
instead of NIS. Results are summarized in Table 2. Bromo
fluoride compounds were gained in the same or higher yield
than iodo fluoride compounds due to their stability.
Chlorofluorination was also examined by N-chlorosuccini-
mide, but it resulted in low yields in spite of longer reaction
time (Scheme 3).
7
8
1
1
88
78
a
N1S of 1 mmol was used and 30% of starting material was remained.
In summary, we demonstrated halofluorination of alkenes
with mild and safe fluorinating reagent EMIMF(HF)2.3
under open air.
starting material was remained (Table 1, entries 1 and 2).
The iodofluorination products of various alkenes, aliphatic,
cyclic, and aryl alkenes, were gained in good yields and with
high regioselectivity. The stereochemistry of this addition is
anti-manner (entries 3 and 4). When 1-fluoro-2-iodo-1-
phenylpropane, prepared from (E)-1-phenylpropene, was
treated with DBU at room temperature, dehydroiodination
3. Experimental
Reagents were purchased from Wako Chemical Inc. or
Tokyo Kasei, and used without further purification. Reactions
Scheme 2.

H. Yoshino et al. / Journal of Fluorine Chemistry 126 (2005) 121–123
123
3.7. (E)-1-Fluoro-1-phenyl-1-propene
To solution of (1-fluoro-2-iodo-propyl)-benzene
a
(0.5 mmol) in CH2Cl2 (5 ml) was added DBU (0.15 g,
1 mmol) at room temperature. The reaction mixture was
stirred for 12 h at ambient temperature, and then quenched
with sat. NH4Cl aq. and extracted with hexane three times.
The combined organic layer was dried over Na2SO4, and
evaporated. The crude was purified with silica-gel column
chromatography. 1H NMR (300 MHz, CDCl3): d 7.50–7.35
(m, 5H), 5.47 (dq, J = 22.5, 7.5 Hz, 1H), and 1.80 (dd,
J = 7.5, 2.7 Hz, 3H). 19F NMR (282 MHz, CDCl3): d 102.6
(dq, J = 22.5, 2.7 Hz).
Scheme 3.
were monitored by thin-layer chromatography using 25 mm
E. Merck silica-gel plates (silica-gel F254). Silica-gel was
purchased from Kanto Chemical Co. The polypropylene tube
used was a centrifuge tube (15 ml) with a screw cap, and was
purchased from Corning. NMR spectra were recorded on a
Varian Gemini 300 or Mercury 2000 in CDCl3.
EMIMF(HF)2.3 was prepared followed by the literature [10].
3.1. General procedure for halofluorination
3.8. 1-Bromo-2-fluoro-dodecane
Ina15-ml polypropylene tube, CH2Cl2 (500 ml)solutionof
alkene(1 mmol)andEMIMF(HF)2.3 (600 ml)wereplacedand
stirred with magnetic stirrer vigorously. To this reaction
mixture, N-halosuccinimide (2 mmol) was added in several
portions at room temperature. When the reaction finished,
1 ml of hexane or ether was added and the upper layer was
collected by decantation three times. The organic layer was
passed through short silica-gel column, and evaporated.
1H NMR (300 MHz, CDCl3): d 4.62 (dddt, J = 48.6, 7.5,
5.4, 5.4 Hz, 1H), 3.51 (ddd, J = 19.8, 10.8, 5.4 Hz, 2H),
1.77–1.64 (m, 2H), 1.49–1.26 (m, 16H), and 0.88 (t,
J = 6.8 Hz, 3H). 19F NMR (282 MHz, CDCl3): d 178.0
(dddt, J = 48.6, 27.0, 19.8, 19.8 MHz).
3.9. 2-Bromo-1-fluoro-1-phenyl-benzene
3.2. 2-Fluoro-1-iodo-dodecane
1H NMR (300 MHz, CDCl3): d 7.51–7.35 (m, 5H), 5.50
1H NMR (300 MHz, CDCl3): d 4.41 (ddt, J = 48.0, 10.8,
1.5 Hz, 1H), 3.31 (ddd, J = 20.1, 5.7, 2.1 Hz, 2H), 1.80–1.65
(m, 2H), 1.45–1.20 (m, 16H), and 0.88 (t, J = 6.9 Hz, 3H).
19F NMR (282 MHz, CDCl3): d 170.6 (m).
(ddd, J = 46.8, 7.2, 4.2 Hz, 1H), and 3.64–3.43 (m, 2H). 19
NMR (282 MHz, CDCl3): d 174.1 (ddd, J = 46.8, 23.7,
16.5 MHz).
F
3.3. 1-Fluoro-2-iodo-cyclohexane
Acknowledgements
1H NMR (300 MHz, CDCl3): d 4.52 (ddt, J = 47.7, 8.7,
4.5 Hz, 1H), 4.16–4.06 (m, 1H), 2.44–2.30 (m, 1H), 2.28–2.13
(m, 1H), 2.02–1.78 (m, 2H), 1.66–1.54 (m, 2H), and 1.50–
1.24(m, 2H). 19F NMR (282 MHz, CDCl3): d 159.5 (m).
Financial Support by a Grant-in-Aid from the Ministry
of Education, Science, Sports, and Culture is acknowl-
edged.
3.4. (1-Fluoro-2-iodo-ethyl)-benzene
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