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Synlett 2002(10): 1697-1699
DOI: 10.1055/s-2002-34210
LETTER
© Georg Thieme Verlag Stuttgart · New York

Trifluoromethylation Reactions with Potassium Trifluoromethanesulfinate under Electrochemical Oxidation

Jean-Bernard Tommasino*, Anne Brondex, Maurice Médebielle, Marc Thomalla, Bernard R. Langlois, Thierry Billard
Université Claude Bernard-Lyon 1 (UCBL), Laboratoire Synthèse, Electrosynthèse et Réactivité des Composés Organiques Fluorés(SERCOF), UMR CNRS-UCBL 5622, Bâtiment E. Chevreul, 43 Bd du 11 Novembre 1918, F-69622 Villeurbanne Cedex, FRANCE
Fax: +33(4)72431323; e-Mail: jbtomasi@univ-lyon1.fr;
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Publication History

Received 30 July 2002
Publication Date:
23 September 2002 (online)

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Abstract

The electrochemical oxidation of potassium trifluoromethanesulfinate (CF3SO2K) in the presence of electron-rich aromatics and alkenes provides the corresponding trifluoromethylated products.

Key words

trifluoromethylation - potassium trifluoromethanesulfinate - electrolysis - fluorinated compounds - trifluoromethylated alkanes and alkenes - trifluoromethylated aromatics

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10

A representative preparative-scale electrolysis for the synthesis of 5/6 is described as follows: A solution of CF3SO2K 1 (0.38g, 2.2 mmol) and NEt4ClO4 (2.87g, 12.5 mmol) in anhyd DMF (50 mL) containing 2 (1.53g, 11 mmol) was oxidized at 1.15V vs SCE in a three compartments cell, under positive nitrogen atmosphere, until the starting material was almost consumed (as checked by cyclic voltammetry, 2 F/mol). A circular platinum gauze (5 cm × 5 cm) was used as the anode which was separated from the cathodic solution (DMF-0.25 M NEt4ClO4 with platinum as cathode) with a glass frit of porosity 4. The yellowish solution was hydrolyzed with brine (150 mL), and extracted with Et2O (3 × 100 mL). The combined organic solutions were washed with brine (3 × 100 mL), H2O (3 × 100 mL) and dried over MgSO4. Evaporation to dryness left a crude material which was directly analyzed by 19F NMR with a known concentration of PhOCF3 (δF -58.3 ppm/CFCl3) as internal standard. 19 F NMR (CDCl3-CFCl3): 1,3-dimethoxy-2-trifluoromethyl benzene 5, δF -54.26 (s, 3 F); 1,3-dimethoxy-4-trifluoromethyl benzene 6, δF -60.69 (s, 3 F).