Ni-catalysed remote C(sp3)–H functionalization using chain-walking strategies

The dynamic translocation of a metal catalyst along an alkyl side chain — often coined as ‘chain-walking’ — has opened new retrosynthetic possibilities that enable functionalization at unactivated C(sp3)–H sites. The use of nickel complexes in chain-walking strategies has recently gained considerable momentum owing to their versatility for forging sp3 architectures and their redox promiscuity that facilitates both one-electron or two-electron reaction manifolds. This Review discusses the relevance and impact that these processes might have in synthetic endeavours, including mechanistic considerations when appropriate. Particular emphasis is given to the latest discoveries that leverage the potential of Ni-catalysed chain-walking scenarios for tackling transformations that would otherwise be difficult to accomplish, including the merger of chain-walking with other new approaches such as photoredox catalysis or electrochemical activation. Ni-catalysed chain-walking blossomed as an effective synthetic tool to functionalize C(sp3)–H bonds in hydrocarbon chains. This Review provides a detailed overview of the most recent advances in this field, focusing on site-selective and regioselective manipulations at previously out-of-reach C(sp3)–H sites.