Dual Photoredox/Cu-Catalysis Enables Diastereoselective Synthesis of 3-β-Ethynyltropanes via Decarboxylative Alkynylation

An efficient decarboxylative alkynylation of a tropane redox-active ester with terminal alkynes is described, yielding ethynyltropanes with exclusive β-configuration. This cost-effective process utilizes mild, nontoxic copper-catalyzed, photoinduced reaction conditions. Beyond introducing a novel pathway for the catalytic alkynylation of nortropanes, this method offers a versatile and convergent approach for synthesizing complex nortropane derivatives through further functionalization of the triple bond, including reductions, and inverse demand Diels–Alder reactions.