Liquid Crystal Control of Bimolecular Thermal Reactions. Highly Regioselective Pericycloaddition of Fumarates to 2,6-Dialkoxyanthracenes in Liquid−Crystalline Media

Abstract

The ability of liquid crystalline solvent phases to control the stereochemical course of bimolecular thermal reactions of 2,6-dialkoxyanthracenes with a series of fumarates conducted at 130−180 °C has been examined, primarily with respect to the structural compatibility of the solutes with the solvent mesogens. For the case of the model thermal [4 + 2] cycloadditions of 2,6-bis(decyloxy)anthracene to bis (trans-4-cyclohexylcyclohexyl) and cholesteryl trans-4-cyclohexylcyclohexyl fumarates at 130−150 °C, cholesteryl 2,4-dichlorobenzoate(CDCB) and bis(4-pentyloxyphenyl) trans-1,4-cyclohexanedicarboxylate(BPCD) serve well as cholesteric and smectic liquid crystalline solvents and result in the preferential formation of syn -isomers with an extremely high level of regioselection ( syn / anti ≥ 20/1). In contrast, the isotropic solvents with closely related structures give isomer ratios of only ≥3/1. Structural similarities between the solutes and the solvent mesogens appear to play a key and influential role in controlling the stereochemical course of the reaction. The temperature dependence for the isomer distribution affords an estimate of the differences of solvation enthalpy and entropy between syn and anti transition states in the anisotropic media.

Synthesis and Mesophase Behaviour of Morpholinium Ionic Liquid Crystals

“…The layer spacing of Mor 1, 16 BF 4 in the crystal and mesophase was determined by virable temperature small angle XRD and the correlation between the layer spacing and temperature was discussed. The introduction of the morpholinium headgroup should be the reason for the formation of palm-like texture, the effect of 4 …”

“…Crystal structure and mesomorphism structure analysis of Mor 1, 16 BF 4 Results here reported the mesomorphism structure analysis of Mor 1,16 BF 4 . According to the DSC data and POM textures, the formation of morpholinium ionic liquid crystals depends both on the alkyl length and the anion.…”

“…Just as ionic liquids, the properties of ionic liquid crystals can be tuned by an appropriate choice of anions and cations. These salts have been used in various applications such as ordered solvents, [2][3][4] templates for the synthesis of mesoporous and zeolitic materials, [5][6][7] optoelectronics, 8,9 and dye-sensitized solar cells. 10 Molecular liquid crystals have been extensively designed and studied, [11][12][13] however, the type of ionic liquid crystals is still limited.…”

“…The effect of different cations on the ionic liquid crystals was investigated. Extensive hydrogen bonding interactions between the 4 …”

“…Cations could undergo rearrangement with the asymmetric effect of hydrogen bonds in Figure 4. Three morpholinium cations approached the 4 …”