Process for the preparation of 2,4,6-triiodoisophthalic bisamides

A process for the preparation of a 2,4,6-triiodoisophthalic bisamide of formula (I)

• wherein
• R is selected from hydrogen, a linear or branched C1-C6 alkyl-carbonyl, optionally substituted by —OCOCH3, and a group 2-(propan-2-yl)-1,3-dioxane-5-carbonyl;
• R1 is each independently hydrogen or methyl;
• and
• R2 is each independently a group —CH(CH2OH)2 or —CH2CH(OH)CH2OH,
• said process comprising the step of
• a) reacting a substituted 2,4,6-triiodo-1,3-benzenedicarboxylic acid dichloride of formula (II)
• wherein R is as defined above,
• with an amine of formula (III)
• R1—NH—R2 (III)
• wherein R1 and R2 are as defined above,
• characterized in that the reaction of step a) is carried out in a mixture comprising a solvent selected from hydrotropic ethers and glycols in the presence of an amount of water ranging from 0.1% and 15% v/v and in that the molar ratio between the amine of formula (III) and the acyl chloride of formula (II) is comprised between 3:1 and 7:1.