Chelation-Assisted Nickel-Catalyzed C−H Functionalizations

Use of a directing group in C–H functionalizations, often referred to as chelation assistance, is one of the most reliable methods for achieving highly efficient and highly site-selective reactions. Although a variety of transition metals can be used in directed C–H functionalization reactions, Ni-catalyzed directed C–H functionalization reactions have remained a relatively underdeveloped area of research. Recently, interest in these reactions has been renewed due to the development of a combination of a Ni catalyst and an N,N′-bidentate group; the method is now emerging as a powerful tool for Ni-catalyzed C–H functionalization reactions. However, Ni-catalyzed C–H functionalizations that do not require the use of a specific directing group (e.g., N,N′-bidentate groups) have recently been reported. Thus, Ni-catalyzed C–H functionalizations have now reached a new and interesting stage.