The hydrolysis of the ortho ester 1, 1-diethoxy-1, 3-dihydroisobenzofuran (1) is described. This hydrolysis proceeds with initial expulsion of an exocyclic ethoxy group, producing upon hydration of the oxocarbonium ion 1-hydroxy-1-ethoxy-1, 3-dihydroisobenzofuran (7), the tetrahedral intermediate of the lactonization of ethyl (2-hydroxymethyl) benzoate (6) to phthalide (8). Based on the kinetic behavior of the ortho ester hydrolysis, the pH variation ...
