Bayer Aktiengesellschaft

Bayer Aktiengsellschaft

Willi Streicher

Heinz U Blank

Horst Behre

Gerhard Marzolph

Friedrich-Wilhelm Ullrich

Karlheinrich Meisel

Volker Glock

Gunther Klag

Dieter Irmscher

Hans-Joachim Laakmann

Nikolaus Schulz

Method for preparing 2-nitro-5-(phenylthio)-anilines

In a process, improved in respect of yield, purity and simple procedure, for the preparation of aromatic methoxycarboxylic acid methyl esters by methylation of the corresponding aromatic hydroxycarboxylic acids with dimethyl sulfate in the presence of water and a base, a procedure is followed in which the water, base and aromatic hydroxycarboxylic acid are initially introduced into the reaction vessel, 1 to 2.5 times the molar amount of dimethyl sulfate (based on the methylatable hydroxyl and carboxyl groups) is metered in and, during this procedure, the pH of the reaction mixture is controlled by addition of an aqueous base in finely divided form.

Process for the preparation of aromatic methoxycarboxylic acid methyl

Indoles of the formula ##STR1## can be prepared by reaction of a phenylhydrazine of the formula ##STR2## which is unsubstituted in at least one ortho-position, with a ketone of the formula ##STR3## in an aqueous medium in the presence of an acid compound, less than 5 equivalents, based on 1 mol of phenylhydrazine, of an acid compound having a pK value of 1.3-4.5 being employed.

Process for the preparation of indoles

Crude nitrobenzaldehyde can be substantially purified from the undesired positional isomers if a treatment with 100-10,000% by weight of water and 1-30% by weight of an emulsifier, all with reference to the dry weight of the crude nitrobenzaldehyde, is undertaken at a temperature of 30.degree.-140.degree. C. and at a pH of 3-14.

Process for the purification of nitrobenzaldenhyde

New process for the preparation of 1-aminonaphthalene-2,4,7-trisulphonic acid and, if appropriate, 1,7-Cleve's acid, in which 1-nitronaphthalene is reacted by the Piria method with bisulphites in a manner which is known per se, the sulphamate mixture obtained in this Piria reaction is sulphonated with sulphur trioxide in sulphuric acid to give 1-aminonaphthalene-2,4,7-trisulphonic acid and, if appropriate, this is hydrolysed to 1,7-Cleve's acid by heating in aqueous sulphuric acid.

Process for the preparation of 1-aminonaphthalene-2,4,7-trisulphonic

The invention relates to a new process for the preparation of 1-aminonaphthalene-2,4,7-trisulphonic acid and 1-aminonaphthalene-7-sulphonic acid (1,7-Cleve's acid), in which 1-aminonaphthalene or naphthionic acid is sulphonated selectively in the presence of certain additives to give 1-aminonaphthalene-2,4,7-trisulphonic acid and this is hydrolyzed to 1,7-Cleve's acid by warming in aqueous sulphuric acid.

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Krefeld, Germany

Willi Streicher