Visible-Light Photoredox Trifluoromethylation via Perfluoroarene Iodine(III) Reagent Decarboxylaytion
Experimental procedure: A Schlenk flask is charged with
tris(2,2'-bipyridine)ruthenium(II) bis(hexafluorophosphate) (9.0 mg, 0.01 mmol, 2 mol%), [bis(trifluoroacetoxy)iodo]pentafluorobenzene (650.0 mg, 1.25 mmol, 2.5 equiv.), 2,6-dibromopyridine (0.5 mmol, 1.0 equiv.). Then, acetonitrile (7.5 mL) is added to the reaction mixture. The mixture is degassed twice by the freeze-pump-thaw procedure, then irradiated under blue LED strips (4.8 W). The reaction mixture is subsequently stirred at 35 °C for 12 h. After the reaction is completed, it is diluted with water (8.0 mL). The aqueous phase is extracted with ether (8.0 mL) three times. The combined organic layers are washed with brine and dried over anhydrous sodium sulfate, and are concentrated
in vacuo. The residue is purified by silica gel column chromatography (hexane) to afford 2,6-dibromo-3-(trifluoromethyl)pyridine in 32% yield (48.8 mg).