Hoechst Aktiengesellschaft

Werner Wykypiel

Heinrich Volk

Siegbert Rittner

Wolfgang Tronich

Helmold Von Plessen

Karl E Mack

Rudolf Neeb

Walter Reimann

Otto E Schweikert

Klaus Forstinger

The process for the preparation of 2(3H)-benzothiazolones which are optionally substituted on the benzene ring by reacting a 2-aminobenzothiazole which is optionally substituted on the benzene ring with a diazotization agent in the presence of aqueous hydrochloric acid, if appropriate with addition of a chloride, to give a diazonium chloride, reacting the diazonium chloride directly to give a 2-chlorobenzothiazole, which is optionally substituted on the benzene ring, and hydrolyzing the 2-chlorobenzothiazole, without intermediate isolation, at 120.degree.-200.degree. C. under reaction pressure.

Process for the preparation of 2(3H)-benzothiazolones

The invention relates to a process for purification of 2-hydroxynaphthalene-6-carboxylic acid by recrystallization. In this process, the crude acid is recrystallized from water-miscible linear or cyclic aliphatic ethers, aliphatic polyethers or aliphatic hydroxy ethers or from at least 10% strength by weight aqueous solutions of these ethers. Recrystallization from a 35-90% strength by weight aqueous solutions of 1,4-dioxane is particularly preferred.

Process for the purification of 2-hydroxynaphthalene-6-carboxylic acid

The invention relates to a process for the preparation of 2-hydroxy-(9H)-carbazole. In this process, 1,2,3,4-tetrahydro-7-hydroxy-(9H)-carbazole is dehydrogenated in an inert organic solvent.

Process for the preparation of 2-hydroxy-(9H)-carbazole

To prepare a 1-nitrobenzene-2-alkyloxycarbonyl-5-carboxylic acid, a dialkyl benzene-1,4-dicarboxylate is first nitrated in a customary manner and the dialkyl 1-nitrobenzene-2,5-dicarboxylate compound obtained is subjected to a partial acidic ester hydrolysis without isolating the nitro compound prepared as an intermediate. The acidic ester hydrolysis is carried out in the presence of a catalytic amount of an organic solvent which is completely or partially miscible with water and has a boiling point of above 90.degree. C. and/or of an emulsifier; it is preferably carried out at a temperature between 65.degree. and 110.degree. C.

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Werner Wykypiel