Palladium-Catalyzed Ligand-Directed C-H Functionalization Reactions

Ligand-directed C-H functionalization reactions catalyzed by palladium were studied. Ligand-directed C-H functionalization at Pd centers can be used to install many different types of bonds, including carbon-oxygen, carbon-halogen, carbon-nitrogen, carbon-sulfur, and carbon-carbon linkages. The first examples of Pd-catalyzed ligand-directed sp2 C-H bond oxygenation used PhI(OAc)2 as a stoichiometric oxidant in conjunction with catalytic Pd(OAc)2. Polymer-immobilized ArI(OAc)2 has also been used for the Pd catalyzed acetoxylation of many of the substrates. The first report of Pd-catalyzed ligand-directed sp3 C-H bond oxygenation also used PhI(OAc)2 as the terminal oxidant. The iodine (I) reagent IOAc has been successfully utilized for the Pd(OAc)2-catalyzed acetoxylation of methyl groups in Boc-protected N-methylamine derivatives. Mechanistic studies are expected to continue to inform the design and discovery of new highly active and selective catalysts for Pd-catalyzed ligand-directed C-H functionalization processes.