<i>Ortho</i>-Selective C–H Borylation of Aromatic Ethers with Pinacol-borane by Organo Rare-Earth Catalysts

The regioselective C–H borylation of aromatic ethers such as anisoles is of much interest and importance, but has remained a challenge to date. We report herein the catalytic ortho-selective C–H borylation of a wide range of aromatic ethers with pinacolborane (HBpin) by rare-earth metallocene complexes. This protocol offers an efficient and straightforward route for the synthesis of a variety of borylated aromatic ether derivatives. A proper metal/ligand combination for the rare-earth metal catalysts was found to be critically important to promote this transformation.