CARBO-CHAIN

While originally designed to control the topology of polymers, catalytic chain-walking reactions have recently offered new vistas for forging carbon-carbon bonds at previously unfunctionalized C(sp3)–H sites by formally translocating the metal catalyst throughout the alkyl side-chain of a substrate. In particular, nickel catalysis has positioned at the forefront of this emerging field due to its modular reactivity through one- or two-electron pathways. Nevertheless, the chain-walking process is poorly understood in mechanistic terms, being the nature of the active intermediates still subject of considerable speculation, and with Ni(I) or Ni(II) species arbitrarily proposed with no supporting experimental evidence.