Ruthenium-Catalyzed <i>meta</i>-Selective C_ArH Bond Formylation of Arenes

The meta-CArH bond formylation of arenes has been achieved using CHBr3 as a formyl source in the presence of [Ru­(p-cym)­(OAc)2] as a catalyst. This method provides efficient access to the preparation of various meta-substituted aromatic compounds, such as alcohols, ethers, amines, nitriles, alkenes, halogens, carboxylic acids, and their derivatives, through transformation of the versatile formyl group. Furthermore, mechanistic studies show that the key active species is a pentagonal ruthenacycle complex.