A convenient and highly regio and stereoselective method for the synthesis of (E)-3-alkylidene isobenzofuran-1(3H)-ones (phthalides)

2-Iodobenzyl alcohol on treatment with acetylenic carbinols in the presence of a palladium catalyst and copper(I) iodide as a co-catalyst afforded disubstituted alkynes. Jones oxidation of the disubstituted alkynes led to (E)-3-alkylidene isobenzofuran-1(3H)-ones in good yields in a highly regio and stereoselective manner. The E-isomers were obtained exclusively instead of the more stable Z-isomers.