Palladium-Catalyzed Tandem Reactions via Allene Intermediates for the Rapid Synthesis of a Fused Indenone–Indole Scaffold

A palladium-catalyzed tandem reaction of 1-(2-iodophenyl)-3-arylprop-2-yn-1-ones and 1-(2-azidophenyl)propargyl ethers is developed to provide the rapid construction of a fused polycyclic indenone-indole scaffold under mild conditions. The reaction proceeds via a highly ordered process involving Sonogashira coupling, propargyl-allenyl isomerization, allene-azide cycloaddition, denitrogenation, and diradical coupling. The proposed reaction mechanism is supported by experimental and computational studies.