Ni-Catalyzed Chelation-Assisted Direct Functionalization of Inert C-H Bonds

During the last two decades, impressive advancements have been achieved in transition metal-catalyzed chelation-assisted C-H functionalization reaction. While reactions in this field are still dominated by precious 4d or 5d metals (e.g., Pd, Rh, Ir), the 3d base metals (e.g., Ni, Co, Cu, Fe) have made significant headway partially due to their relatively large abundance, low cost, low toxicity as well as their occasionally occurred novel reactivity when compared to their noble cousins. This review will give a comprehensive summary on Ni-catalyzed functionalization of inert C-H bonds assisted by chelation groups. For clarity, the content is classified by the newly formed chemical bonds, namely C-C, C-N, C-chalcogen and C-halogen bond formation.