A green and facile photochemical thiolate-catalyzed strategy for borylation of aryl fluorides with NHC–borane

Direct C–F bond borylation of polyfluoroarenes is a straightforward way to obtain poly-fluorinated organoboron compounds, valuable building blocks for bioactive and material molecules. However, the high BDE of C–F bonds makes the direct borylation of aromatic C–F bonds very challenging. Here, we demonstrated an efficient visible-light-induced protocol of radical-type borylation of polyfluoroarenes with a readily available aryl thiol as a catalyst and pyridine as a base. The reaction doesn't need an expensive photocatalyst and has a good substrate scope. Key mechanistic insights include: (1) boryl sulfide was formed during the reaction and affords boryl & thiyl radicals under visible light; (2) aryl thiolate worked as the single-electron reductant to generate the key delocalized anion intermediate, which then releases the fluorine anion and yields the final product.