New Synthesis of the Liquid Crystalline Bicyclohexylbenzene Derivatives

Abstract

A new improved approach to prepare the liquid crystalline bicyclohexylbenzene derivatives is proposed. The key stage is the synthesis of 3-(trans-4-arylcyclohexyl)-6-alkyl (or aryl) cyclohex-2-en-1-ones via the condensation of the corresponding Mannich salts with 2-substituted acetoacetic esters (or methyl benzyl ketones) in the presence of a base. The catalytic hydrogenation of these cyclohexenones in base media gives mainly saturated trans-ketones which are promising semiproducts for the preparation of different kinds of the LC compounds containing a bicyclohexyl fragment. The chemical transformations of the prepared cyclohexanones were carried out and as a result a range of LC compounds both known and new ones were synthesized.