Keary Engle

Because internal alkenes are more challenging synthetic targets than terminal alkenes, metal‐catalyzed olefin mono‐transposition (i.e., positional isomerization) approaches have emerged to afford valuable E ‐ or Z‐ internal alkenes from their complementary terminal alkene feedstocks. However, the applicability of these methods has been hampered by lack of generality, commercial availability of precatalysts, and scalability. Here, we report a nickel‐catalyzed platform for the stereodivergent E / Z ‐selective synthesis of internal alkenes at room temperature. Commercial reagents enable this one‐carbon transposition of terminal alkenes to valuable E ‐ or Z ‐internal alkenes via a Ni−H‐mediated insertion/elimination mechanism. Though the mechanistic regime is the same in both systems, the underlying pathways that lead to each of the active catalysts are distinct, with the Z ‐selective catalyst forming from comproportionation of an oxidative addition complex followed by oxidative addition with substrate and the E ‐selective catalyst forming from protonation of the metal by the trialkylphosphonium salt additive. In each case, ligand sterics and denticity control stereochemistry and prevent over‐isomerization.