Fully Substituted Pyranones via Quasi-Heterogeneous Genuinely Ligand-Free Migita–Stille Coupling of Iodoacrylates

Migita–Stille coupling of (<i>Z</i>)-β-iodoacrylates with (<i>E</i>)-α-stannyl allylic alcohols to furnish 5-alkylidene-4-substituted-5,6-dihydro-2<i>H</i>-pyran-2-ones is efficiently catalyzed by 2% Pd black in DMF, while Pd­(PPh₃)₄ is inactive. Heterogeneous Pd released in solution is most likely responsible for the catalysis. The reaction is applicable to other substrates, without having to resort to ligands, additives, and/or solid support for Pd. The resulting pyranones can be rearranged to fully functionalized pyranones in another single step.