Process for the preparation of 5-carboxyphthalide

摘要

There is described a process for the preparation of 5-carboxy phthalide, which comprises adding terephthalic acid to fuming sulfuric acid containing at least 20% of SO3, then adding formaldehyde to the mixture, heating the mixture at a temperature of 120-145° C. and isolating 5-carboxyphthalide from the reaction mixture.