anti-Hydroarylation of Activated Internal Alkynes: Merging Pd and Energy Transfer Catalysis

A general catalytic anti-hydroarylation of electron-deficient internal alkynes compatible with both electron-poor and electron-rich aryl reagents is reported. This selectivity is achieved through a sequential syn-carbopalladation of the alkyne by an Ar–Pd species, followed by a tandem, Ir-photocatalyzed, counter-thermodynamic EZ isomerization. The use of ortho-substituted boronic acids enables direct access to pharmaceutically relevant heterocyclic cores via a cascade process. Mechanistic insight into the involvement of Ar–Pd versus Pd–H as an active species is provided.