PROCESS FOR THE PREPARATION OF 1-OXO-1,3-DIHYDRO-5-ISOBENZOFURANCARBOXYLIC ACID AND ITS USE FOR THE PRODUCTION OF CITALOPRAM

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% by weight of SO3, then adding formaldehyde to the mixture, heating the mixture at a temperature of 120-145 DEG C and isolating 5-carboxyphthalide from the reaction mixture.