StØphane Anguille et al.
COMMUNICATIONS
red during 12 h under vacuum at 608C. After the transfer of
argon to the reaction flask, the temperature was increased
to 1508C and the trichlorotoluene 1 was added via a syringe.
After the appropriate reaction time, the samples were re-
moved from the reaction mixture via a syringe and extracted
with diethyl ether. The contents of the organic phases were
analysed by GC (HP 5890 A, SE-30 capillary column) using
authentic samples of compounds 1 to 5 as references.
of KPF6 at a 3.6M concentration in sulfolane), the
monofluorinated derivative 2 is obtained in over 85%
yield after only 3 h at 1508C. Excellent results are
also obtained in 5 h with 0.2 equivalents of KPF6 at
5.5M in sulfolane.
This new method for nucleophilic fluorination ap-
pears very attractive from the synthetic point of view
but the reasons leading to this unusual activation by
KPF6 are not clear at this stage. Further studies and,
in particular, in depth physicochemical experiments
dealing with the structure and properties of the ionic
species in solution, will be necessary before suggesting
a rationale for this process. Finally, a very unusual ac-
tivation of the fluorination by KF has been demon-
strated both in ionic liquids and in sulfolane.
Acknowledgements
We thank CNRS and RHODIA for the support of this re-
search programme.
This study confirms that the nucleophilic fluorina-
tion can be successfully performed in ionic liquids. References
Furthermore, it has been shown that such fluorination
[1] P. Wasserscheid, T. Welton, Ionic Liquids in Organic
processes can be activated by bromide salts. Finally, a
very unusual activation by KPF6, both in ionic liquids
and in sulfolane, has been discovered.
Synthesis; Wiley-VCH, Weinheim, 2003.
[2] For review articles, see: a) T. Welton, Chem. Rev. 1999,
99, 2071–2084; b) M. J. Earle, K. R. Seddon, Pure
Appl. Chem. 2000, 72, 1391–1398; c) P. Wasserscheid,
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Jain, A. Kumar, S. Chauhan, S. M. S. Chauhan, Tetrahe-
dron 2005, 61, 1015–1060 and references cited therein.
[3] For a review article, see: a) J. H. Davis Jr, Chem. Lett.
2004, 33, 1072–1077; for some recent examples of sup-
ported reagents, see also: b) S. Anjaiah, S. Chandrase-
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c) M. Kort, A. W. Tuin, S. Kuiper, H. S. Overkleeft,
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WO 2004029004, 2004; for some recent examples of
supported catalysts see also: e) K. W. Kottsieper, O.
Stelzer, P. Wasserscheid, J. Mol. Cat. A, 2001, 175, 285–
288; f) N. Audic, H. Clavier, M. Mauduit, J. C. Guille-
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Experimental Section
The butylmethylimidazolium salts were prepared and dried
following literature procedures.[13] The ionic liquids were
dried under vacuum (ꢀ 3 mm Hg) at 708C during 24 h
before their use; the sulfolane was also kept under vacuum
(ꢀ 3 mm Hg) at 608C during 24 h before being used. Spray-
dried potassium fluoride (RHODIA), ammonium bromide,
phosphonium bromide and potassium hexafluorophosphate
were dried under vacuum (ꢀ 3 mm Hg) at 708C during 24 h
before being used in the reactions.
Representative Procedure for the Fluorination
Reactions Performed in Ionic Liquids
To potassium fluoride (58 mg, 1 mmol) in a 5 mL flask was
added the ionic liquid (4 mL). The reaction mixture was stir-
red during 12 h under vacuum at 708C and then the temper-
ature was increased to 1508C during 10 min to remove all
traces of water. After the transfer of argon to the reaction
flask, the trichlorotoluene 1 was added via a syringe to the
reaction mixture at 1508C. After the appropriate reaction
time, the samples were removed from the reaction mixture
via a syringe and extracted with diethyl ether. The contents
of the organic phases were analyzed by GC (HP 5890 A,
SE-30 capillary column) using authentic samples of com-
pounds 1 to 5 as references.
[6] a) H. Lee, K. W. Kim, H. Kim, S. D. Lee, H. S. Kim, J.
Fluorine Chem. 2004, 125, 95–97; b) D. W. Kim, D. J.
Kim, J. W. Seo, H. S. Kim, H. K. Kim, C. E. Song, D. Y.
Chi, J. Org. Chem. 2004, 69, 3186–3189.
Representative Procedure for the Fluorination
Reactions Performed in Sulfolane
To potassium fluoride (58 mg, 1 mmol) in a 5 mL flask was
added the sulfolane (4 mL). The reaction mixture was stir-
[7] S. K. Boovanahalli, D. W. Kim, D. Y. Chi, J. Org.
Chem. 2004, 69, 3340–3344.
1152
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2006, 348, 1149 – 1153