Urea-accelerated iridium-catalyzed 2-position-selective CH borylation of indole derivatives

We developed iridium-catalyzed 2-position-selective CH borylation of indole derivatives by modifying the structure of a bipyridine-type ligand. The yields ranged from good to excellent, even on a gram scale, and were dramatically improved by the addition of a urea derivative catalyst. The introduced boryl group was converted to chloro, bromo, and phenyl groups without isolation of the borylated intermediate. Preliminary results indicated the importance of hydrogen bonding between the substrate and the urea additive.