Process for the preparation of substituted 3,5-dichloro-2,4-difluoro-benzenes

US5081288A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Heinz U. Blank · Odenthal, DE
• Edwin Ritzer · Leverkusen, DE

Key dates

• Filing date: Oct 10, 1990
• Grant date: Jan 14, 1992
• Expiry date: Oct 10, 2010

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C209/365
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

Substituted 3,5-dichloro-2,4-difluoro-benzenes of the formula ##STR1## in which R represents nitro, amino (including the corresponding ammonium salts) or isocyanato, which can be prepared from 2,3,4,5-tetrachloro-nitrobenzene by means of the reaction, carried out initially, with alkali metal fluorides at elevated temperature in a polar, aprotic solvent, starting from a crude 2,3,4,5-tetrachloro-nitrobenzene containing 2,3,5,6-tetrachloro-nitrobenzene and/or 2,3,4,6-tetrachloro-nitrobenzene, and substituted 3,5-dichloro-2,4-difluoro-benzene being isolated from the reaction mixture at the nitro stage or, after reduction of the nitro group, at the amino stage or, after reduction and phosgenation of the amino group, at the isocyanate stage.