Access to Tetronic Acids via Silver-Catalyzed CO₂ Incorporation into Conjugated Ynones

Facile and versatile access to highly functionalized tetronic acids has been successfully achieved through the reaction of conjugated ynones with carbon dioxide. In the presence of a base, the enolates generated from the ynones capture CO₂ via a carbon-carbon bond-forming reaction, accompanied by a 5-exo-dig cyclization reaction of the resulting carboxylate to the alkyne, activated by a silver catalyst. The present method should be applicable to the synthesis of a wide variety of tetronic acids.