E-Olefins through intramolecular radical relocation

Olefin shuffle for just a nickel Controlling the geometry of carbon-carbon double bonds is a central component of chemical manufacturing. One useful trick is to shift hydrogen atoms around to interconvert C=C isomers selectively. However, this approach typically requires precious metals. Kapat et al. now report that more-abundant nickel can catalyze rapid conversion of terminal olefins into internal olefins with high selectivity for trans geometry. The odd-electron nickel complex relies on a radical mechanism to shuttle hydrogen to the terminal carbon from the saturated carbon adjacent to the double bond. Science, this issue p. 391 A nickel catalyst selectively converts terminal olefins into internal olefins with trans geometry via a radical mechanism. Full control over the selectivity of carbon–carbon double-bond migrations would enable access to stereochemically defined olefins that are central to the pharmaceutical, food, fragrance, materials, and petrochemical arenas. The vast majority of double-bond migrations investigated over the past 60 years capitalize on precious-metal hydrides that are frequently associated with reversible equilibria, hydrogen scrambling, incomplete E/Z stereoselection, and/or high cost. Here, we report a fundamentally different, radical-based approach. We showcase a nonprecious, reductant-free, and atom-economical nickel (Ni)(I)-catalyzed intramolecular 1,3-hydrogen atom relocation to yield E-olefins within 3 hours at room temperature. Remote installations of E-olefins over extended distances are also demonstrated.