Preparation of tri-iodo benzene compounds

A process for the preparation of a compound containing a 2,4,6-triiodinated benzene ring, said process comprising reacting a 2,4,6-unsubstituted 5-amino-benzoic acid or a derivative thereof which is a 5-amino-benzamide which is alkylated at the amide nitrogen by one or more straight or branched alkyl groups optionally substituted by one or more hydroxyl groups or said 5-amino-benzamide derivative is a 5-amino-N-alkyl isophthalamide acid or a salt or ester thereof, and wherein the alkyl group at the amide nitrogen is a straight or branched alkyl group optionally substituted by one or more hydroxyl groups;

• with an iodine halide iodinating agent in an aqueous reaction medium, wherein the iodinating agent is added to an aqueous medium containing the 5-amino-benzoic acid or derivative at two different temperature ranges such that either (A) one or more first portions of the iodinating agent are added at a temperature in the range of 40-70° C. and then one or more second portions of the iodinating agent are added at a temperature in the range of 75-95° C. or (B) one or more first portions of the iodinating agent are added at a temperature in the range of 75-95° C. and then one or more second portions of the iodinating agent are added at a temperature of 60-70° C.