PROCESS FOR THE PREPARATION OF IOPAMIDOL

The present invention discloses a process for the preparation of lopamidol of formula (II) and comprising the following steps: a) reacting the Compound (I) wherein X is OR 2 or R 3 , and wherein R 2 and R 3 are a C 1 -C 6 linear or branched alkyl, C 3 -C 6 cycloalkyl, C 6 aryl, optionally substituted with a group selected from the group consisting of methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, t-butyl and phenyl, with the acylating agent (S)-2-(acetyloxy)propanoyl chloride in a reaction medium to provide the acetyloxy derivative of Compound (I); b) hydrolyzing the intermediate from step a) with an aqueous solution at a pH comprised from 0 to 7, by adding water or a diluted alkaline solution such as sodium hydroxide or potassium hydroxide, freeing the hydroxyls from the boron-containing protective groups, obtaining the N-(S)-2-(acetyloxy)propanoyl derivative of Compound (II); c) alkaline hydrolysis to restore the (S)-2-(hydroxy)propanoyl group and to obtain lopamidol (II) and optional recovery of the boron derivative from the solution obtained in step b). The boron-containing protective group is versatile, efficient and recyclable. A one-pot synthesis, without intermediate isolation is provided, leading to a decreasing of recovered and recycled solvents and a significant increasing in the yield, representing a significant advantage in terms of cost-effectiveness of the entire process and environmental awareness.