Azo coupling of 2-nitroanilines with 2,4-disubstituted phenols

摘要

A process is described for the preparation of compounds of the formula I <IMAGE> wherein R<1> and R<2>, independently of one another, are C1-C7-alkyl; and R<3> is hydrogen or halogen, by reaction of a diazonium salt of a 2-nitroaniline in acidic aqueous solution with a phenol dispersed in water. The process is characterised in that the dispersant employed is a C8-C20-alkanesulphonic acid or a corresponding alkanesulphonate or a mixture of sulphonic acid and sulphonate together with a polyvinyl alcohol. The compounds of the formula I obtained can advantageously be reacted further to give benzotriazoles of the formula V <IMAGE> which are used as light screens.o