Abstract: A process for the preparation of iodixanol by dimerization of 5-acetamido-N,N?-bis(2,3-dihydroxypropyl)-2,4,6-triiodo-isophthalamide (“Compound A”) in which, after the dimerization step, unreacted Compound A is precipitated from the reaction mixture and recovered for re-use. The process substantially increases the net yield of iodixanol and simplifies its purification.

Abstract: A process for the preparation of iodixanol by dimerisation of 5-acetamido-N,N′-bis(2,3-dihydroxypropyl)-2,4,6-triiodo-isophthalamide (“Compound A”) in which, after the dimerisation step, unreacted Compound A is precipitated from the reaction mixture and recovered for re-use. The process substantially increases the net yield of iodixanol and simplifies its purification.

Abstract: The invention provides an improved 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 derivative there of with an iodine halide iodinating agent in an aqueous reaction medium, characterised in that the iodinating agent is added to an aqueous medium containing the 5-amino-benzoic acid or derivative at two different temperature ranges: (A) one or more primary portions of the agent are added at a temperature in the range 40 to 70° C. and then one or more secondary portions of the agent are added at a temperature in the range 75 to 95° C. or (B) one or more primary portions of the agent are added at a temperature in the range 75 to 95° C. and then one or more secondary portions of the agent are added at a temperature of 60 to 70° C.