One-Pot Alkynylation/Isomerization Cascade of β-Formylated Enoates to Functionalized Ynones.

The previously unknown γ-hydroxy esters bearing both propargylic and allylic alcohol moieties were obtained from β-formylated enoates and terminal alkynes. Their easy base-catalyzed allylic isomerization into γ-keto esters occurred chemoselectively under metal-free conditions. In contrast to the classical two-step synthesis of carbonyl compounds from allylic alcohols involving an oxidation-reduction sequence, this protocol provides functionalized ynones in a single step from readily available starting materials. Density functional theory calculations were performed to elucidate the plausible mechanism for the cascade transformations.