Iridium-Catalyzed C(sp3)-H Borylation Using Silyl-Bipyridine Pincer Ligands

New ligands for the iridium-catalyzed C(sp(3))-H borylation of aliphatic compounds were established. In sharp contrast to 6-methyl-2,2 '-bipyridine and 6-isobutyl-2,2 '-bipyridine, 2,2 '-bipyridine and 1,10-phenanthroline derivatives bearing a hydrosilylmethyl group (which would give a thermally stable NNSi pincer complex) served as suitable ligands for the reaction. Among them, a phenanthroline-based NNSi pincer ligand was shown to be an excellent ligand, and various aliphatic compounds were efficiently converted to the corresponding borylated products using the Ir/NNSi pincer catalyst system. The NNSi pincer ligand showed unique selectivity and enabled the iridium-catalyzed C(sp(3))-H borylation using pinacolborane [H-B(pin)] instead of B-2(pin)(2). The formation of an iridium complex bearing a quinoline-based NNSi pincer ligand from [IrCl(cod)](2) was observed, and the catalytic activity of the complex was demonstrated.

Automated summary

New ligands have been discovered for iridium-catalyzed C(sp(3))-H borylation of aliphatic compounds. A phenanthroline-based NNSi pincer ligand has shown excellent performance and enables efficient conversion of aliphatic compounds to borylated products using an Ir/NNSi pincer catalyst system.