Decarboxylative Borylation and Cross-Coupling of (Hetero)aryl Acids Enabled by Copper Charge Transfer Catalysis

We report a copper-catalyzed strategy for arylboronic ester synthesis that exploits photoinduced ligand-to-metalcharge transfer (LMCT) to convert (hetero)aryl acids into aryl radicals amenable to ambient-temperature borylation. This near-UVprocess occurs under mild conditions, requires no prefunctionalization of the native acid, and operates broadly across diverse aryl,heteroaryl, and pharmaceutical substrates. We also report a one-pot procedure for decarboxylative cross-coupling that mergescatalytic LMCT borylation and palladium-catalyzed Suzuki-Miyaura arylation, vinylation, or alkylation with organobromides toaccess a range of value-added products. The utility of these protocols is highlighted through the development of a heteroselectivedouble-decarboxylative C(sp2)-C(sp2) coupling sequence, pairing copper-catalyzed LMCT borylation and halogenation processesof two distinct acids (including pharmaceutical substrates) with subsequent Suzuki-Miyaura cross-coupling.