Abstract
We have developed iridium-catalyzed C–H borylation and silylation reactions using
pyrazolonaphthyridine (PzNPy) ligands. The readily tunable PzNPy system provides easy
control of the ligand characteristics, enabling selective functionalization at the
least hindered positions. With the new catalytic system, 1,4-disubstituted and multi-substituted
toluene derivatives preferentially underwent borylation at benzylic positions, whereas
1,3-disubstituted arenes favored the least hindered sp2 positions. The Ir/PzNPy system
also showed applicability in the C–H borylation of heteroarenes and metallocenes.
Furthermore, increasing steric bulk near nitrogen atoms of ligand enabled C–H silylation
of five-membered heteroarenes. These results expand the toolbox of bidentate nitrogen
ligands for the development of iridium-catalyzed C–H functionalization reactions,
suggesting the potential of tailorable PzNPy ligands to extend beyond their applications
in palladium catalysis.
Keywords
Borylation - Silylation - Ligand - Iridium - C–H Activation
