Acetylation using reduced concentration of acetic acid anhydride for synthesizing non-ionic X-ray contrast agents

摘要

This invention relates to an improved method for the synthesis of 5-acetamido-N,N'-bis(2,3-dihydroxypropyl)-2,4,6-triiodoisophthalamide ("Compound A"), an intermediate in the industrial preparation of non-ionic X-ray contrast agents. In particular, it relates to acetylation of 5-amino-N, N'-bis(2,3-dihydroxypropyl)-2,4,6-triiodo-1,3-bcnzcncdicarboxamide ("Compound B") using a reagent mixture containing about 50 v/v % to about 85 v/v % acetic anhydride and about 15 v/v % to about 50 v/v % acetic acid as a reagent mixture for acetylation of 5-amino-N, N'-bis(2,3-dihydroxypropyl)-2,4,6-triiodo-1,3-benzenedicarboxamide ("Compound B"). Preferably, following the acetylation reaction, the reagent and solvent mixture is distilled for re-use.