Prepn. of 5-amino- 2,4,6-tri:iodo- 1,3-benzene di:carboxylic acid di:chloride - by reacting 5-amino- 2,4,6-tri:iodo- 1,3-benzene di:carboxylic acid and thionyl chloride in heterogeneous phase in solvent in presence of catalytic amt. of tert. amine

摘要

Prepn. of 5-amino-2,4,6-triiodo-1,3-benzenedicarboxylic acid dichloride (I) comprises (a) reacting 5-amino-2,4,6-triiodo-1,3-benzenedicarboxylic acid and thionyl chloride in heterogenous phase in a solvent selected from 7-16C hydrocarbons, 7-8C aromatic hydrocarbons, 1,1,1-trichloroethane, n-butylacetate or diglyme, in the presence of a catalytic amt. of a tert. amine. Also claimed is the intermediate 5-sulphinyl-amino-2,4,6-triiodo-1,3-benzenedicarboxylic acid dichloride (II). Further claimed is the prepn. of (I) comprising (i) catalytic hydrogenation of 5-nitro-1,3-benzene dicarboxylic acid in neutral or basic medium to give an aq. soln. of 5-amino-1,3-benzene dicarboxylic acid sodium sa (ii) direct iodination of this salt soln. without further purificn. with a soln. of ICl in HCl, being the 5-amino-1,3-benzene dicarboxylic acid sodium salt soln. previously added with HCl and H2SO4 to give 5-amino-2,4,6-triiodo-1,3-benzene dicarboxylic acid; followed by step (a) as above.