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. 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.