Transition Metal-Catalyzed Regiodivergent C-H Arylations of Aryl-Substituted Azoles

The metal-catalyzed direct functionalization of two different C-H bonds of the same organic molecule - also called regiodivergent C-H bond functionalization - is an important research topic in organic chemistry. Over the last decades, the number of tools to control such regiodivergent C-H bond functionalizations has increased significantly. One of the most effective tools consists of employing different metal sources as the catalysts. Palladium and copper catalysts are very effective to promote the direct arylation of 5-membered ring heteroarenes, whereas the direct arylation using ruthenium and rhodium catalysts generally relies on the coordination of heteroelements to the metal. Therefore, in the presence of several aryl-substituted azoles, the arylation of both the aryl unit using Ru- or Rh-catalysis and of the azole unit using Pd- or Cu-catalysts is possible. In this review, we will describe the scope and current limits of the use of this tool for the regiodivergent direct arylation of aryl-substituted azoles.