An improved practical Pd/C-catalyzed Sonogashira cross-coupling reaction for the synthesis of liquid crystals of trans-cyclohexyltolans

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Abstract

An improved practical synthesis of liquid crystals of trans-cyclohexyltolans by Sonogashira cross-coupling reaction of 1-iodo-4-(trans-4-alkylcyclohexyl)benzene with aromatic terminal alkynes in the presence of Pd/C (palladium on activated carbon) as low as 0.03 mol% of Pd and CuI (2 mol%) in a mixture solvent of acetone–water (5:2 in volume) is described. The liquid crystals could be obtained in high yields as a solid with excellent purity by simple filtration, and the filtrate could be reused several times while still retaining high catalytic activity. Copyright © 2010 John Wiley & Sons, Ltd.

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