Direct Functionalization of C−H Bonds by Iron, Nickel, and Cobalt Catalysis

Abstract Non‐precious‐metal‐catalyzed reactions are of increasing importance in chemistry due to the outstanding ecological and economic properties of these metals. In the subfield of metal‐catalyzed direct C−H functionalization reactions, recent years have shown an increasing number of publications dedicated to this topic. Nickel, cobalt, and last but not least iron, have started to enter a field which was long dominated by precious metals such as palladium, rhodium, ruthenium, and iridium. The present review article summarizes the development of iron‐, nickel‐, and cobalt‐catalyzed C−H functionalization reactions until the end of 2016, and discusses the scope and limitations of these transformations.