Iodination procedure for the preparation of compounds of aromatic amines 2,4,6-triiodo-3,5-disubstituted

A process for preparing compounds of formula (II): Formula ** ** wherein R1 is independently selected from the group consisting of carboxyl group (-COOH), carboxylic ester group (-COOR 3) and carboxamide group (-CONH2, -CONHR 3 or -CONR4R5), R2 is independently selected from the group consisting of: carboxylic ester group (-COOR 3) and carboxamido group (-CONH2, -CONHR 3 or -CONR4R5) wherein R3, R4 and R5 are identical or different, independently, C1-C4 linear one or branched group optionally substituted with one or more, preferably one or two hydroxyl groups, comprising: a) reacting an oxyacid iodine, or salt thereof, with elemental iodine in a solvent under acidic conditions in the presence of an acid or a salt of a strong acid to generate the reagent in situ iodination, and in turn reacting the iodination reagent with compounds of formula (I) added to produce compounds of f FORMULA (II), ** ** Formula wherein R1 and R2 are as defined in formula (II), (b) during the iodination reaction, an excess of iodine introduced as steam in the reaction system, and then adding an additional quantity of oxyacid of iodine or salt thereof to the reaction system iodination after a period of reaction time, (c) sublimating and collecting excess free iodine after completion of the iodination reaction, ( d) filtering and purifying the crude product of the iodination reaction to obtain the compounds of formula (II), and (e) optionally, recycling the excess free iodine collected after sublimation, the mother liquor from the iodination reaction and / or the mother of the purification step to the iodination reaction of step (a) liquor.