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Renewable Reagent for Nucleophilic Fluorination

Blaž Alič*, Jan Petrovčič, Jan Jelen, Gašper Tavčar* and Jernej Iskra*

*Jožef Stefan Institute, Jamova 39, 1000 Ljubljana; University of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia, Email: blaz.alicijs.si, gasper.tavcarijs.si, jernej.iskrafkkt.uni-lj.si

B. Alič, J. Petrovčič, J. Jelen, G. Tavčar, J. Iskra, J. Org. Chem., 2022, 87, 5987-5993.

DOI: 10.1021/acs.joc.2c00247


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Abstract

[IPrH][F(HF)2] is a highly selective and soluble reagent for a microwave-assisted fluorination of various organic substrates. The scope of substrates includes benzyl bromides, iodides, chlorides, aliphatic halides, tosylates, mesylates, α-haloketones, a silyl chloride, acyl and sulfuryl chlorides, and a nitroarene. The reagent can be regenerated using hydrofluoric acid without organic solvents.

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Fluorination of benzyl bromides on preparative scale

0.5 mmol of benzylic substrate was dissolved in 1 ml of acetonitrile. 0.6 equivalents of [IPrH][F(HF)2] and 1.8 equiv. of DIPEA were added. Reaction mixture was transferred into a microwave reactor vial using an additional 1 ml of acetonitrile. Reactions were carried out under microwave irradiation at 120 °C for 1 h. After the reaction, 5 drops of diethylamine were added and reaction mixture was reheated to 80 °C for 5 minutes. Acetonitrile was removed under reduced pressure. A few milliliters of mobile phase was poured over the obtained residue causing imidazolium salts to precipitate. Resulting solution of crude fluorinated product was purified using flash column chromatography to yield corresponding benzyl fluoride.


Key Words

benzyl fluorides, microwave synthesis


ID: J42-Y2022