GB859818A - Tetra-iodo-phthalamic acids and their salts - Google Patents

Abstract

The invention comprises compounds of the formula: <FORM:0859818/IV(b)/1> where R1 and R2, which may be the same or different, each represent an alkyl group which may be substituted by one or more hydroxyl groups, or R1 represents a hydrogen atom and R2 has the above meaning, or R1 and R2 together with the adjacent nitrogen atom, form a heterocyclic ring; and salts thereof; and the preparation thereof by reacting 3, 4, 5, 6-tetraiodophthalic anhydride with an amine, other than methylamine, of the formula R1-NH-R2, or when (R1 represents hydrogen) by hydrolysing an appropriate N- substituted 3, 4, 5, 6-tetraiodophthalimide under alkaline conditions; and, if desired, converting the products into their salts. N-substituted 3, 4, 5, 6-tetraiodophthalimides are prepared by reacting 3, 4, 5, 6-tetraiodophthalic anhydride with N-substituted formamides or by reacting an alkali metal salt of 3, 4, 5, 6-tetraiodophthalimide with an alkyl halide. N-methyl-3, 4, 5, 6-tetraiodophthalimide is prepared by reacting 3, 4, 5, 6-tetraiodophthalic anhydride with methylamine. In the Provisional Specification, R1 and R2 can represent aryl or aralkyl groups in addition to alkyl groups, any of which groups may be substituted by one or more hydroxyl groups, halogen atoms, alkyl or alkoxy groups; or together with the adjacent nitrogen atom, a heterocyclic ring which may be substituted and which may, if desired, contain further hetero atoms.