Walking Metals for Remote Functionalization.

The distant and selective activation of unreactive C-H and C-C bonds remains one of the biggest challenges in organic chemistry. In recent years, the development of remote functionalization has received growing interest as it allows for the activation of rather challenging C-H and C-C bonds distant from the initiation point by means of a "metal-walk". A "metal-walk" or "chain-walk" is defined by an iterative series of consecutive 1,2- or 1,3-hydride shifts of a metal complex along a single hydrocarbon chain. With this approach, simple building blocks or mixtures thereof can be transformed into complex scaffolds in a convergent and unified strategy. A variety of catalytic systems have been developed and refined over the past decade ranging from late-transition-metal complexes to more sustainable iron- and cobalt-based systems. As the possibilities of this field are slowly unfolding, this area of research will contribute considerably to provide solutions to yet unmet synthetic challenges.