1-Fluoro-3,5-dimethyl-benzene → 2,4-Dichloro-1-fluoro-3,5-dimethylbenzene

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Reaction Steps

An alternative process for the preparation of the intermediate compound 2,4-dichloro-3-cyano-5-fluoro-benzoyl chloride, which serves as a starting material for the preparation of 7-chloro-8-cyano-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid (EP-A-0 276 700) and which can converted into 3-cyano-2,4,5-trifluoro-benzoyl fluoride, starts from 5-fluoro-1,3-xylene: 5-fluoro-1,3-xylene is dichlorinated in the nucleus under ionic conditions in the presence of a catalyst to give 2,4-dichloro-5-fluoro-1,3-dimethylbenzene and this is then chlorinated under free-radical conditions in the side chains to give 2,4-dichloro-5-fluoro-3-dichloromethyl-1-trichloromethylbenzene. This is hydrolysed via 2,4-dichloro-5-fluoro-3-dichloromethylbenzoic acid to give 2,4-dichloro-5-fluoro-3-formyl-benzoic acid and then reacted to give 2,4-dichloro-5-fluoro-3-N-hydroxyiminomethyl-benzoic acid. By treatment with thionyl chloride, 2,4-dichloro-3-cyano-5-fluoro-benzoyl chloride is obtained, which can additionally be reacted by means of a chlorine/fluorine exchange to give 3-cyano-2,4,5-trifluoro-benzoyl fluoride. ##STR4##

Provenance & Evidence