1) The reaction of 3-bromophthalide with 2-hydroxybenzoic acid (I), previously salified with triethylamine in refluxing acetone gives 1,3-dihydro-3-oxo-1-isobenzofuranyl 2-hydroxybenzoate (II). Compound (II) is acetylated with acetic anhydride, using sulfuric acid as catalizer.
2) By condensation of an organic salt of 2-acetyloxybenzoic acid (III) with 3-bromophthalide.