Iron-Catalyzed ortho-Selective C-H Borylation of 2-Phenylpyridines and Their Analogs

Treatment of 2-phenylpyridines (or their analogs) with a 9-bicycloboranonane dimer (9-BBN dimer) in the presence of a catalytic amount of a commercially available iron salt, FeBr3, gave ortho-borylated products in moderate to excellent yields with good functional group tolerance. The reaction proceeded in good yield, even in gram-scale, and also occurred at the C-H bond of heteroaromatic compounds. The cost of the C-H borylation is dramatically lower than that of a previously reported similar palladium-catalyzed reaction. The products exhibit an intramolecular B-N Lewis acid-base interaction and fluoresce in both solution and solid states due to their electron push-pull structures.