Superseding Substrate Control with Catalyst Control to Improve Regioselectivity in Aryne Annulations

Abstract

The utility of reactions using unsymmetrically substituted aryne intermediates is negatively impacted by issues with regiose-lectivity. There have been numerous reports about how to enhance or reverse this regioselectivity in free aryne reactions by altering the electronics of the substrate. To the best of our knowledge, no such studies exist for systems with metal-bound aryne intermediates, which often suffer from worse regioselectivities. Herein we report a means of achieving regioselectivity in a metal catalyzed aryne difunctionalization via catalyst control. Through the use of an unsymmetrical ligand environment, selectivity can be induced (up to 91:9 r.r.). We also report the reversal of regioselectivity between ligand environments. These investigations demonstrate that catalyst control can supersede substrate control in metal-catalyzed aryne reactions.