4-(4-Hydroxy- or acetoxy-3-carbomethoxyphenylazo)-benzenesulphonyl chloride

Abstract

A method for the preparation of 2-[4-(4-hydroxy-3-carboxyphenylazo)-benzenesulfonamido]-pyridine by reacting 4-diazobenzenesulfonic acid with an ester of salicyclic acid having the formula ##STR1## in the presence of an alkali metal hydroxide to form a first reaction product having the formula ##STR2## reacting said first reaction product with an acylating agent to form a second reaction product having the formula ##STR3## treating said second reaction product with thionyl chloride in the presence of a tertiary formamide to form a chlorinated compound having the formula ##STR4## reacting said chlorinated compound with 2-amino-pyridine under water-free conditions in the presence of an acid binding agent, to form a third reaction product having the formula ##STR5## treating said third reaction product with alkali metal hydroxide in the presence of water to hydrolyze off the R and R.sub.1 groups, and recovering 2-[4-(4-hydroxy-3-carboxyphenylazo)-benzenesulfonamido]-pyridin e.

Dependencies are inferred from the claim text.