Cobalt-Catalyzed Site Selective C-H Borylation of Polyarenes via π-Activation Strategy

Site-selective C-H functionalization of electron-rich (poly)arenes remains a significant challenge in base-metal catalysis. We report a cobalt catalyst supported by a pyridyl-substituted terpyridine ligand that, in combination with a π-activation strategy, enables exquisite site selectivity in the borylation of polyarenes and electron-rich substrates. This system establishes a cobalt-based, earth-abundant alternative to the prior site-selective C-H borylation of polyarenes, which relies on iridium catalysis. The synthetic utility of this approach is demonstrated through a sequence of Suzuki-Miyaura cross-coupling, triple C-H borylation of a trimetallic chromium complex, and decomplexation, providing streamlined access to complex polyaromatic boronates from simple precursors. This work provides a general conceptual framework for advancing non-directed C-H functionalization with base-metal catalytic systems, in which metal-arene π-interactions play a central role in governing reactivity and selectivity.