Iridium-Catalyzed Silylation of Five-Membered Heteroarenes: High Sterically Derived Selectivity from a Pyridyl-Imidazoline Ligand

We report that the silylation of five-membered ring heteroarenes occurs with high sterically derived regioselectivity when catalyzed by the combination of[Ir(cod)(OMe)]2 and a phenanthroline ligand or a new pyridylimidazoline ligand that further increases the regioselectivity. The silylation reactions with these catalysts produce high yields of heteroarylsilanes from functionalization at the most sterically accessible C–H bonds of these rings under conditions that the borylation of C–H bonds with previously reported catalysts formed mixtures of products or products that are unstable.