Improved method for the synthesis of (E)-cyclic-β-alkoxyacrylates under mild conditions

The oxidative cyclization–methoxycarbonylation of cyclic- and acyclic-4-yn-1-ols 1 in the presence of Pd(II)/p-benzoquinone in methanol at 0°C under a carbon monoxide atmosphere (balloon) afforded (E)-cyclic-β-alkoxyacrylates 2 in good to excellent yields. The present reaction is applicable to the above-mentioned substrates bearing the additional functional groups such as acetate, hydroxyl, ketone, ester, terminal acetylene and the acid-sensitive protecting groups (TBDPS, TBDMS, MOM and THP). A new synthesis of the left part of the cystothiazoles is presented.