Ligand coordination- and dissociation-induced divergent allylic alkylations using alkynes

Summary In transition metal catalysis, the nature of ligand coordination plays a vital role in defining the reactivity of the catalytic system. Achieving multi-substrate coordination and coupling by leveraging dynamic ligand dissociation is rare. Here, we report the discovery of such a phenomenon in nickel/copper-co-catalyzed divergent allylic alkylation of vinyl epoxides and aziridines using alkynes. Under otherwise identical conditions, the use of either strong bisphosphine ligands or hemilabile P,N-ligands leads to bimolecular allylic alkynylation or trimolecular dienyne formation, respectively. DFT calculations provide key insights for these ligand-induced divergent reactivities, particularly ligand-dissociation-enabled coordination of three substrates on nickel for trimolecular coupling. This catalytic system couples a remarkably broad range of readily available terminal alkynes with vinyl epoxides, carbonates, and aziridines in high regio- and stereo-selectivity. The utility of the versatile enyne and dienyne products, coupled with the use of abundant nickel/copper catalysts, makes this a practical method in synthetic and medicinal chemistry.