An Improved Catalytic System for Solid-state Iridium(I)-catalyzed C-H Borylation Using Mechanochemistry

An improved catalytic system for solid-state iridium(I)-catalyzed C-H borylation under mechanochemical conditions using ball milling is described. The use of bipyridine bearing ester groups at the 4-and 4-positions as the ligand was vital for achieving highly efficient solid-state C-H borylation of various heteroaromatic compounds that are barely reactive under previously developed mechanochemical conditions employing the conventional 4,4-di-tert-butylbipyridine ligand. Notably, this unprecedented ligand-induced acceleration effect was not observed in solution but was only pronounced under solid-state mechanochemical conditions.