Arylthianthrenium Salts Enabled Palladium-Catalyzed Regioselective Arylation: Access to Value-Added 7-Azaindoles

A step-economic and efficient palladium-catalyzed protocol for regioselective C-2 arylation of 7-azaindoles with arylthianthrenium salts has been developed under base- and ligand-free conditions. The reaction proceeds smoothly with broad substrate scope, requires low catalyst loading, exhibits excellent functional group tolerance, and provides C-2 arylated products in moderate to excellent yields. Moreover, given the ready availability of arylthianthrenium salts from simple arenes, this strategy offers a valuable platform for the late-stage functionalization of structurally complex and bioactive molecules. The origin of the observed regioselectivity has been elucidated through density functional theory (DFT) calculations.