Remote steric control for undirected -selective C-H activation of arenes.

Regioselective functionalization of arenes remains a challenging problem in organic synthesis. Steric interactions are often used to block sites adjacent to a given substituent, but they do not distinguish the remaining remote sites. We report a strategy based on remote steric control, whereby a roof-like ligand protects the distant site in addition to the sites, and thereby enables selective activation of carbon-hydrogen (C-H) bonds in the absence of or substituents. We demonstrate this concept for iridium-catalyzed -selective borylation of various monosubstituted arenes, including complex drug molecules. This strategy has the potential to expand the toolbox of C-H bond functionalization to previously nondifferentiable reaction sites.