JPH0764785B2 - Optically active compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a specific optically active compound, and more particularly to a biscitronellic acid ester of hydroquinone or a biscitronellol ester compound of terephthalic acid.

Liquid crystals have been applied as various electro-optical elements and have been put to practical use for displays such as watches and calculators. Most of the currently practically used liquid crystal display devices utilize the dielectric alignment effect of twisted nematic liquid crystals and cholesteric liquid crystals. However, recently, other types of liquid crystal display methods have been actively developed, and STN methods and cholesteric / nematic phase transition type display methods are used.

The liquid crystal compositions used in these liquid crystal display devices are adjusted to have respective helical pitches by introducing an optically active substituent into nematic liquid crystal or by adding an optically active substance.

For example, p-alkoxybenzaldehyde and (+)-p
Schiff base type liquid crystals made from -amino-2-methylbutylbenzene are known. The optically active substance added is 4- (2-methylbutyloxy)-
Although 4'-cyanobiphenyl is known, this compound has a drawback that a large amount of compound is required to obtain desired physical properties because the twist pitch of the cholesteric liquid crystal is long.

The present inventors have found that the crystal-liquid crystal phase transition temperature useful as a component of the liquid crystal mixture for a display element is low, and the liquid crystal-isotropic liquid phase transition temperature is high when giving a cholesteric phase, and the helical pitch is short. As a result of extensive studies to find a compound, the optically active compound represented by the following general formula (I) or (II) has a significantly low crystal-liquid crystal phase transition temperature,
Further, it has been found that when the compound gives a cholesteric phase, it has a high liquid crystal-isotropic liquid phase transition temperature, so that it is an extremely suitable compound for use for the above purpose.

(In the formula, * represents an asymmetric carbon atom.) The compound represented by the above general formula is, for example, a usual esterification reaction of (R) -citronellic acid and hydroquinone or (R) -citronellol and terephthalic acid. It can be easily manufactured.

Next, the present invention will be described with reference to examples.

Example 1 Preparation of (R) -1,4-bis- (3,7-dimethyl-6-octenyloxycarbonyl) -benzene (R) -Citronellic acid 0.94 g (5.5 × 10 ⁻³ mol), and hydroquinone 0.28 g (2.5 × 10 ^-3 mol) was dissolved in 5 ml of dichloromethane, 1.1 g (5.5 × 10 ^-3 mol) of DCC (dicyclohexylcarbadiimide) was added, and the mixture was stirred at room temperature for 5 hours.

After removing the solvent, the mixture was extracted with n-hexane, and the produced dicyclohexylurea was filtered off. The obtained filtrate was desolvated, and the residue was treated with a silica gel column (developing solvent ether / n-hexane = 7/93) to obtain the desired product.

An infrared spectroscopic analysis, the resulting product has the following characteristic absorption, 2875cm ^-1 was confirmed to be the desired product ^{(s), 1760cm -1 (s} ), 1500cm -1 (s ^{), 1180cm -1 (s),} 1120cm -1 (s), 920cm -1 (m), it is a 840 ^-1 (m) this compound is manufactured by Merck nematic liquid crystal ZLI-1565
The pitch was measured with a Kano's wedge-shaped cell, and the results are shown in the table below.

As a comparative example, C-15 manufactured by BDH was used.

It is clear that the above compound has a shorter helical pitch and less temperature heterogeneity than C-15 of Comparative Example.

Example 2 Production of (R) -1,4-bis- (citronellyloxycarbonyl) -benzene (R) -Citronellol 0.86 g (2.5 × 10 ⁻³ mol) and 0.42 g of terephthalic acid were dissolved in 5 ml of dichloromethane to prepare dicyclohexyl. Carbodiimide (1.10 g, 5.5 × 10 ^-3 mol) was added, and the mixture was stirred at room temperature for 6 hours. The same treatment as in Example 1 was carried out, and the obtained residue was treated with a silica gel column (developing solvent ether / n-hexane = 1/9). The obtained transparent liquid was subjected to Krogel roll distillation to obtain the desired product.

Boiling point 222 ° C / 0.8mmHg) As a result of infrared spectroscopic analysis, the obtained product had the following characteristic absorption and was confirmed to be the target product.

^{2900cm -1 (s), 1720cm -1} (s), 1263cm -1 (s), 1110cm -1 (s), 730cm -1 (s)

Claims (1)

[Claims] 1. An optically active compound represented by the following general formula (I) or (II). (In the formula, * represents an asymmetric carbon atom.)