New (1R,4R)-2-arylidene-p-menthan-3-ones with a bridging ester group in the arylidene fragment. Synthesis and behavior in liquid-crystalline systems |
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Authors: | Vashchenko V V Kutulya L A Pivnenko M N Shkolnikova N I |
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Institution: | (1) Institute for Single Crystals, National Academy of Sciences of Ukraine, 60 prosp. Lenina, 61001 Kharkov, Ukraine;(2) Department of Engineering, University of Cambridge, Trumpington str., CB2 1PZ Cambridge, UK |
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Abstract: | (1R,4R)-2-(4-Hydroxybenzylidene)- and (1R,4R)-2-(4"-hydroxybiphenyl-4-yl)methylene-p-menthan-3-ones were synthesized by condensation of (–)-menthone with O-tetrahydropyran-2-yl derivatives of 4-hydroxybenzaldehyde and 4"-hydroxy-4-formylbiphenyl, respectively, in a DMSO—base medium followed by the removal of the protective group. The reactions of these hydroxy derivatives with 4-alkylbenzoic, 4-alkyloxybenzoic, trans-4-alkylcyclohexane-4-carboxylic, and 4"-alkylbiphenyl-4-carboxylic acids afforded three series of new chiral esters. Compounds containing the arylidene moiety with three benzene rings were found to exhibit liquid-crystalline properties. The characteristic features of these compounds are discussed based on the results of studies by polarizing microscopy, differential scanning calorimetry, and small-angle X-ray scattering. It was found that the mesomorphic compounds under study can form a smectic A mesophase, twist grain boundary mesophases (TGBA), and blue phases in a wide temperature range. Upon dissolution of certain of chiral compounds in 4"-cyano-4-pentylbiphenyl, a rather high twisting power and the thermal stabilizing effect on mesophases were observed. |
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Keywords: | (1R 4R)-2-(4-hydroxybenzylidene)- and (1R p-menthan-3-ones" target="_blank">4R)-2-(4"-hydroxybiphenyl-4-yl)methylene-p-menthan-3-ones chiral esters synthesis mesomorphic properties smectic A mesophase twist grain boundary mesophase (TGBA) blue phases helical twisting power |
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