Late-Stage Functionalization of 1,2-Dihydro-1,2-azaborines via Regioselective Iridium-Catalyzed C–H Borylation: The Development of a New N,N-Bidentate Ligand Scaffold

The
first general late-stage functionalization of monocyclic 1,2-azaborines
at the C(6) position is described. Ir-catalyzed C–H borylation
occurs regioselectively at the C(6) position of B-substituted 1,2-azaborines and is compatible with a range of substitution
patterns at boron (e.g., hydride, alkoxide, alkyl, and aryl substituents).
Subsequent Suzuki cross coupling with aryl- and heteroaryl bromides
furnishes 1,2-azaborine-based biaryl compounds including 6-[pyrid-2-yl]-1,2-azaborines
that represent novel κ2-N,N-bidentate ligands. The
6-[pyrid-2-yl]-B-Me-1,2-azaborine ligand has been
demonstrated to form an emissive coordination complex with dimesitylboron
that exhibits bathochromically shifted absorption and emission maxima
and a higher photoluminescence quantum yield compared to its carbonaceous
analogue.