Communications
obenzene (1 mmol) as an internal stan-
dard. The product was isolated by prep-
arative liquid chromatography with
MeCN as eluent.
Table 3: Anodic fluorination of some organic compounds based on the cation-exchange reaction
between KF and Amberlyst15Dry in the presence of 2,6-lutidine.
Received: January 4, 2007
Published online: March 30, 2007
Entry
1
Substrate
Current passed
Product
Yield[a,b]
[%]
[faradaymolÀ1
]
Keywords: alkali metals ·
.
cation exchange · electrochemistry ·
fluorides · ion pairs
4
71 (60)
68[c] (55)
93
2
2
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3
4.5
[a] Yield determined by 19F NMR spectroscopy with monofluorobenzene as internal standard. [b] Yield of
isolated product in parentheses. [c] A small amount of the difluorinated product was also formed.
In conclusion, we have developed a novel electrolytic
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chap. 25.
system for anodic fluorination based on the cation-exchange
reaction between alkali-metal fluorides and solid-supported
acids. This exchange reaction promotes the dissociation of
alkali-metal fluorides in MeCN in the presence of 2,6-lutidine
to generate 2,6-lutidine·HF, which acts as both a fluorinating
reagent and a supporting electrolyte. It is notable that this
system enables us to generate 2,6-lutidine·HF in situ without
the need to handle HF itself. We expect that this new
methodology will make a significant contribution to both
organofluorine chemistry and electrochemistry and open up a
new field of electro-organic synthesis. The limitations of this
new methodology and its further application in electro-
organic synthesis are currently under investigation.
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and Practice, Wiley, New York, 1998.
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Experimental Section
The anodic fluorination of the substrate (1 mmol) was carried out
under reflux in an undivided cell equipped with a reflux condenser
and platinum electrodes (2 2 cm2; distance between electrodes:
3 mm) in 0.8m KF/0.6m Amberlyst15Dry/0.4m 2,6-lutidine/MeCN
(50 mL) under constant-current conditions (10 mAcmÀ2; cell voltage:
3–5 V). Charge was passed through the reaction mixture until
complete consumption of the substrate, then the electrolytic solution
was passed through a chromatographic silica gel column with CHCl3
as eluent. The eluent was evaporated under vacuum. The yield of the
product was calculated by 19F NMR spectroscopy with monofluor-
[12] D. A. Wynn, M. M. Roth, B. D. Pollard, Talanta 1984, 31, 1036 –
1040.
3552
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2007, 46, 3550 –3552