Process for the preparation of iopamidol

A process for preparing iopamidol comprising the steps of:

• mixing 5-amino-2,4,6-triiodoisophthalyl dichloride and dimethylacetamide in a first reaction vessel,
• adding a solution comprising 2-amino-1,3-propanediol, triethylamine and dimethylacetamide to said first reaction vessel,
• heating said first reaction vessel,
• cooling said first reaction vessel,
• adding 4-dimethylaminopyridine to said first reaction vessel,
• adding acetic anhydride to said first reaction vessel to obtain N,N′-bis[2-(acetyloxy)-1-[(acetyloxy)methyl]ethyl]-5-amino-2,4,6-triiodo-1,3-benzenedicarboxamide,
• recovering said N,N′-bis[2-(acetyloxy)-1-[(acetyloxy)methyl]ethyl]-5-amino-2,4,6-triiodo-1,3-benzenedicarboxamide from said first reaction vessel,
• dissolving in a second reaction vessel said N,N′-bis[2-(acetyloxy)-1-[(acetyloxy)methyl]ethyl]-5-amino-2,4,6-triiodo-1,3-benzenedicarboxamide with dimethylacetamide,
• adding 2(S)-Acetoxypropionyl chloride to said second reaction vessel to obtain pentaacetyliopamidol,
• recovering said pentaacetyliopamidol from said second reaction vessel,
• mixing said pentaacetyliopamidol, methanol and aqueous hydrochloric acid in a third reaction vessel,
• heating said third reaction vessel,
• removing said methanol from said third reaction vessel,
• stirring an acid scavenging resin into said third reaction vessel,
• removing said acid scavenging resin from said third reaction vessel to leave a resulting solution,
• passing said resulting solution through a column of amberlite resin to recover an eluant,
• concentrating said eluant to provide an oil, and
• heating said oil in mixture comprising acetonitrile and ethanol to yield iopamidol.