A CONTINUOUS DEACETYLATION AND PURIFICATION PROCESS IN SYNTHESIS OF NON-IONIC X-RAY CONTRAST AGENTS

PURPOSE: A continuous deacetylation and purification method for the synthesis of non-ionic x-ray contrast agents is provided to prepare 5-acetamido-N,N'-bis(2,3-dihydroxypropyl)-2,4,6-triiodoisophthalamide with constant quality and high yield. CONSTITUTION: A process for the industrial preparation of 5-acetamido-N,N'-bis(2,3-dihydroxypropyl)-2,4,6-triiodoisophthalamide ("Compound A") comprises the following steps: (i) deacetylating the acetylated hydroxyl group of 5-amino-N,N'-bis(2,3-dihydroxypropyl)-2,4,6-triiodoisophthalamide ("Compound B") in a first reactor at a pH between approximately 11 and 12 by adding a base; (ii) crystallising Compound A in a second reactor at a pH between approximately 11 and 12 at a temperature between approximately 10 deg.C and about 70deg.C; (iii) crystallizing Compound A in a third reactor at a pH between approximately 6 and 8 and at a temperature higher than or equal to about 10deg.C and lower than or equal to the temperature in step (ii); and (iv) filtering and washing the crystals of Compound A.