Issue Date: July 1, 2013
Copper Enables Direct Aromatic Fluorinations
Using a copper catalyst and directing groups, chemists have devised a versatile reaction that adds one or two fluorine atoms to selected positions on aromatic rings (J. Am. Chem. Soc. 2013, DOI: 10.1021/ja4047125). The development adds to recent advances in organofluorine chemistry that are making it easier for chemists to synthesize pharmaceuticals, agrochemicals, and radiolabeled agents for medical imaging applications. Thanh Truong, Kristine Klimovica, and Olafs Daugulis of the University of Houston developed the procedure by building on earlier work by the Daugulis group for palladium- and copper-catalyzed ortho C–H activation and functionalization of aromatic rings. Key to those selective reactions was using bidentate aminoquinoline or picolinamide directing groups on the aromatic substrate. Daugulis and coworkers reasoned that similar chemistry should work for directed fluorinations. They show that selective fluorination of benzamides (shown) and benzylamides can be accomplished by using copper iodide as the catalyst and silver fluoride as the fluorine source under oxidizing conditions. The ability to add one or two fluorine atoms to the aromatic ring can be controlled by altering the amount of catalyst and the reagent ratios.
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