Carbonylation of Alkynyl Epoxides:  Synthesis of 5-Hydroxy-2,3-dienoate Esters and 2,3-Dihydrofuran-3-ol Derivatives

The carbonylation of alkynyl oxiranes catalyzed by (MePh₂)₄Pd in the presence of 20 atm of carbon monoxide in methanol gives methyl 5-hydroxy-2,3-pentadienoates in good yields. When the reaction is performed on alkynyl oxiranemethanol derivatives, 4,5-dihydrofuran-3-ol derivatives are obtained stereoselectively. These products arise from the spontaneous cyclization of a dihydroxyallenyl ester intermediate.