Three‐Component Synthesis of Ynediones by a Glyoxylation/Stephens–Castro Coupling Sequence

One step back, two steps forward! Starting from diverse heterocycles, the title reaction furnishes ynediones under very mild conditions in a direct and preparatively simple one-pot process. The key to avoiding decarbonylation is the CuI-catalyzed Stephens–Castro alkynylation rather than the usually more efficient Sonogashira coupling. In addition, novel highly atom-economical four-component syntheses of various heterocycles can be achieved.