Bayer Aktiengesellschaft

Werner Bussmann

Helmut Fiege

Hans-Joachim Santel

Markus Dollinger

Reinhard Lantzsch

Franz-Josef Mais

Stefan Antons

Josef Kasbauer

Hartmut Richter

The invention relates to the use of the known compound 2,6-dichloro-3-fluoro-benzonitrile as active compound in selectively-herbicidal compositions, and to new preparation processes and new intermediates for the preparation of this compound.

Herbicidal compositions based on 2,6-dichloro-3-fluoro-benzonitrile, and

3-Fluoro-4,6-dichlorotoluene can be prepared in a particularly favourable manner by first chlorinating 3-fluorotoluene at low temperature in the presence of a Friedel-Crafts catalyst and a heterocyclic cocatalyst to give a mixture containing 3-fluoro-4-chlorobenzene and 3-fluoro-6-chlorobenzene, and subsequently, without intermediate isolation, further chlorinating this mixture, at higher temperature, after addition of further Friedel-Crafts catalyst and further heterocyclic cocatalyst, to give 3-fluoro-4,6-dichlorotoluene.

Process for preparing 3-fluoro-4,6-dichlorotoluene

3-Fluoro-4,6-dichlorotoluene is prepared with reduced formation of 3-fluoro-2,6-dichlorotoluene by chlorinating 3-fluorotoluene in the presence of a catalyst system to give a mixture containing 3-fluoro-6-chlorotoluene and 3-fluoro-4-chlorotoluene and chlorinating this in the presence of another catalyst system to give 3-fluoro-4,6-dichlorotoluene.

Alkyl-(3-chlorophenyl)-sulphones are particularly advantageously obtained by chlorination of alkylphenylsulphones if alkylphenylsulphones are chlorinated in molten form with elemental chlorine in the presence of iron(III) chloride and optionally iodine and/or sulphur.

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Leverkusen, Germany

Werner Bussmann