Ruthenium-Catalyzed Dimerization of Propiolates: A Simple Route to α‑Pyrones

A ruthenium-catalyzed regioselective intermolecular multistep homo- and hetero­dimerization of substituted propiolates providing α-pyrone-5-carboxylates and α-pyrone-6-carboxylates is described. The synthetic utilities of α-pyrone derivatives are shown. The proposed mechanism is strongly supported by experimental evidence.