Regiodivergent Cross-Dehydrogenative Coupling of Pyridines and Benzoxazoles: Discovery of Organic Halides as Regio-Switching Oxidants.

Cross-dehydrogenative coupling (CDC) of two unfunctionalized heteroarenes has been recognized as an ideal transformation to synthesize privileged heterobiaryl scaffolds. However, regioselective activation and transformation of a specific set of two heterocyclic C-H bonds among other bonds have been extremely challenging. Thus, discovering a new controlling element to achieve regio-controlled and regio-divergent heterocyclic CDCs is considered crucial. In this Letter, the unprecedented use of organic halides as an oxidant to achieve the CDC reaction of pyridines and benzoxazoles with palladium catalyst is described. Moreover, the regioselectivity of the pyridine functionalization site can be controlled by the choice of organic halides.