5-Methoxy-2-amino-benzene-1-sulphonic acid prodn. for use as dyestuff intermediate - by conversion of a p-anisidine to mixt. of neutral and acid sulphate with sulphuric acid, then reaction with sulphamic acid

摘要

In the prodn. of 5-methoxy-2-aminobenzene-1-sulphonic acid (I) by reacting p-anisidine (II) with sulphamic acid (III) in the presence of a reaction promoter, (a) a mixt. (IV) of neutral and acid sulphate is formed by adding 0.6-0.9 mole H2SO4/mole (II); then (b) (IV) is reacted with 1-2 mole (III)/mole (II) at 160-200 deg.C. 95-100% H2SO4 is pref. used. USE/ADVANTAGE - (I) is a valuable intermediate for dyestuffs. Prior formation of (IV) eliminates the need for inert solvent, is very cheap, allows (I) to be worked up easily and leads to high yields (up to 90%) in short reaction times, whereas anisidine sulphate alone hardly reacts and anisidine hydrogen sulphate alone gives almost exclusively polysulphonated prods.