Selective Single C(sp)-F Bond Cleavage in Trifluoromethylarenes: Merging Visible-Light Catalysis with Lewis Acid Activation.

The conversion of easily available trifluoromethylarenes into aryldifluoromethyl compounds, which are valuable motifs in the pharmaceutical chemistry, is highly atom- and step-economical. However, the single C(sp)-F bond cleavage of ArCF is a great challenge because of the chemical inertness of the C(sp)-F bond and the difficult selectivity control of monodefluorination. We report here the first example of single C(sp)-F functionalization of trifluoromethylarenes via visible-light catalysis merged with Lewis acid activation. The method allows good chemoselectivity control and shows good functional group tolerance. Mechanistic studies suggest an in situ-generated borenium cationic species as the key intermediate for C(sp)-F bond cleavage in this reaction.