Process for preparing 3,5-dichloro-.alpha.-methylstyrene

US4760209A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Heinz U. Blank · Odenthal, DE
• Erich Wolters · Neunburg vorm Wald, DE
• Bernhard Beitzke · Bensberg, DE
• Karlfried Wedemeyer · Cologne, DE
• Michael Herzhoff · Much, DE
• Karl-Wilhelm Henneke · Leverkusen, DE
• Guido Steffan · Odenthal, DE
• Otto Neuner

Key dates

• Filing date: Dec 11, 1986
• Grant date: Jul 26, 1988
• Expiry date: Dec 11, 2006

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C17/358
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

In the preparation of 3,5-dichloro-.alpha.-methylstyrene by isopropylation of an m/p-dichlorobenzene mixture, isomerization of the resulting alkylation mixture, subsequent side chain bromination of the alkylation mixture and dehydrobromination of the resulting bromination mixture, the improvement which comprises reacting an excess of an m/p-dichlorobenzene mixture which contains at least 50% by weight of m-dichlorobenzene with isopropyl halide, isomerizing the resulting alkylation mixture under pressure in the presence of aluminum chloride until thermodynamic equilibrium has been attained, separating off the isomerized alkylation mixture from the unreacted m/p-dichlorobenzene mixture, and recycling the unreacted mixture for further reaction.