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 CO 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.

Highly substituted 2-cyclopentenones were stereospecifically and regioselectively constructed with high catalytic efficiency through Lewis-acid catalyzed decarboxylative Nazarov cyclization of the cyclic carbonate derivative, which is prepared by reacting the propargyl alcohol with carbon dioxide in the presence of a silver catalyst. The stereochemistry of the 2-cyclopentenone is strictly controlled by the geometry of the alkene in the starting material. This method is applicable for various substrates.

Asymmetric synthesis of 2-cyclopentenones was achieved by chirality transfer based on Lewis acid catalyzed decarboxylative Nazarov cyclization of optically active cyclic enol carbonates, which are prepared by silver-catalyzed carbon dioxide incorporation into optically pure propargyl alcohols. The stereochemistry at the 4,5-positions of the 2-cyclopentenones was cleanly constructed by reflecting the stereochemistry of the starting materials. This method could be applied to various substrates to obtain the corresponding products in high yields with highly efficient chirality transfer.

Highly substituted 2-cyclopentenones were stereospecifically and regioselectively constructed with high catalytic efficiency through Lewis-acid catalyzedd ecarboxylative Nazarovc yclization of the cyclic carbonate derivative,w hich is prepared by reacting the propargyl alcohol with carbon dioxide in the presence of asilver catalyst. The stereochemistry of the 2-cyclopentenone is strictly controlled by the geometry of the alkene in the starting material. This method is applicable for various substrates. Scheme 1. Backgrounda nd concept.

Decarboxylative homo-Nazarov cyclization catalyzed by a rhenium complex was achieved using a cyclic enol carbonate bearing a cyclopropane moiety as a substrate.