Direct C-H Arylation of Heteroarenes Catalyzed by Palladium/Nitrogen-Based Ligand Complexes

Significant progress has been made in transition-metal-catalyzed direct functionalization of heteroarenes since the beginning of the 21st century. Particularly, palladium-catalyzed direct C-H arylations of heteroarenes have been extensively studied. Although a variety of catalytic systems have been applied in these reactions, phosphine-based ligands have mainly been used, and low reactivity at some positions, such as at the C4 position of azoles and the C3 position of heteroles, has remained a problem. Recently, the application of nitrogen-based ligands in palladium-catalyzed direct C-H arylations has attracted significant attention because the resulting catalytic systems are uniquely reactive. This Focus Review discusses recent advances in the use of palladium/nitrogen-based ligand systems for direct C-H arylation of heteroarenes.