Process for the preparation of contrast agents

摘要

The invention provides a process for the preparation of an N-alkyl-acylamino-phenyl-carboxylic acid or carboxylic acid derivative by liquid phase acylation and subsequent N-alkylation of a corresponding amino-phenyl-carboxylic acid (or carboxylic acid derivative), the improvement comprising the addition of an alkylating agent to a solution containing the reaction products of said acylation, to effect said N-alkylation.