3,5-Di:fluoro-4-chloro-benzene derivs. - by Grignard reaction of 3,5-di:fluoro-benzene with cyclohexanone, dehydration, oxidn.or redn., and treatment with base and chlorinating agent

摘要

3,5-Difluoro -4-chlorobenzenes of formula (I) are produced by reaction of 3,5-difluorobromobenzene (II) with Mg metal, followed by reaction of the resulting Grignard reagent with a cyclohexanone deriv. of formula (III), dehydration of the carbinol obtd., oxidn. (if A= 1,4-phenylene) or hydrogenation (if A= 1,4-cyclohexylene), and reaction of the intermediate (IV) with a strong base and a chlorinating agent. R1= 1-10C alkyl or alkoxy; A= 1,4-phenylene or 1,4-cyclohexylene. USE/ADVANTAGE - Cpds. (IV) are useful as components of liq. crystal (LC) media (claimed); also claimed are LC media with at least 2 LC components, at least one of which is a cpd. (IV), and LC displasy contg. such LC media. The invention provides a simple process for the prodn. of (I) (which are also useful as LC components) from readily available starting materials, without the formation of a mixt. of regio-isomers.