Process for the preparation of benzothioxanthene dyestuffs

摘要

The present invention relates to a method for producing benzothioxanthene dyestuffs of the general formula I <IMAGE> in which R<1> and R<2> independently of one another denote hydrogen, (C1-C2)-alkyl, (C1-C2)-alkoxy or chlorine and R<3> and R<4> independently of one another denote hydrogen or bromine, by diazotisation and cyclisation of 3-(2'-aminophenylthio)- benzanthrones of the general formula II <IMAGE> in which R<1> to R<4> are as defined above, characterised in that diazotisation and cyclisation are simultaneously carried out in polar, aprotic solvents in the presence of water.