An efficient and general synthesis of furan-2-acetic esters by palladium-catalyzed oxidative carbonylation of (Z)-2-en-4-yn-1-ols

A variety of (Z)-2-en-4-yn-1-ols have been carbonylated under oxidative conditions to give substituted furan-a-acetic esters in good yields. The cyclization-alkoxycarbonylation process occurs in alcoholic media at 50-70 degrees C and under 100 atm pressure of a 9:1 mixture of carbon monoxide and air in the presence of catalytic amounts of PdI2 in conjunction with KI. The proposed reaction pathway involves the in situ isomerization of the initially formed (E)-2-[(alkoxycarbonyl)methylene]-2,5-dihydrofuran species, which in some cases have been isolated and shown to be the intermediates.