Vinylogous thiol esters and a-oxo ketene dithioacetals can be converted into a-pyrones by a strategy involving 1, 2-nucleophilic addition of ester, ketone, or hydrazone enolate anions, followed by acid-promoted rearrangement to a &keto ester, thiol ester, or acid and subsequent enol lactonization. These multistep procedures can be carried out without isolation and purification of intermediates and afford a-pyrones in good overall yields. The ...
