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.