JPH0791258B2 - Optically active cyanobiphenyl compound - Google Patents

Description

The present invention relates to a novel cyanobiphenyl compound having a positive dielectric anisotropy, and more specifically to a cyanobiphenyl ester of (R) -citronellyl acid or a cyanobiphenyl ether of (R) -citronellol. It is provided.

Optically active liquid crystals having a positive dielectric anisotropy are used for twisted nematic type display devices and cholesteric-nematic phase transition type display devices. The liquid crystals used for these are chemically and optically stable, and it is desired that they exhibit a liquid crystal state stably from low temperature to high temperature.

However, no single compound satisfying all such properties has been known so far, and therefore, several kinds of liquid crystal compounds have been used as a mixture.

For example, it is known that a mixture of 4-n-alkyl or alkoxy-4'-cyanobiphenyl compounds takes a liquid crystal phase in a relatively wide temperature range, and even in these mixtures, the crystal-liquid crystal phase transition temperature is -10 ℃ or above,
I was not satisfied.

Further, as a liquid crystal compound giving a cholesteric phase, 4
-(2-Methylbutyl) -4'-cyanobiphenyl is known. However, since the compound has a low liquid crystal-isotropic liquid phase transition temperature of about -30 ° C, in order to obtain desired physical properties,
There was a drawback that it was necessary to blend a large amount.

The inventors of the present invention should find a compound useful as a component of a liquid crystal mixture for a display device, which has a low crystal-liquid crystal phase transition temperature and a high liquid crystal-isotropic liquid phase transition temperature when giving a cholesteric phase. As a result of extensive studies, the novel optically active cyanobiphenyl compound represented by the following general formula (I) has a remarkably low crystal-liquid crystal phase transition temperature, and when the compound gives a cholesteric phase, a liquid crystal-etc. It has been found that the compound is a very suitable compound for use for the above purpose because of its high phase transition temperature of an isotropic liquid.

(In the formula, X represents —CH ₂ — or —CO—, and * represents an asymmetric carbon.) Hereinafter, the present invention having the above gist will be described in more detail.

The compound represented by the above general formula (I) can be produced, for example, by subjecting 4-hydroxy-4′-cyanobiphenyl and (R) -citronellic acid or (R) -citronellol to a well-known esterification or etherification method. It can be easily produced by carrying out a reaction.

Next, the present invention will be described with reference to examples. However, the present invention is not limited by the following examples.

Example 1 Preparation of (R) -4-citronelloyloxy-4'-cyanobiphenyl 0.94 g of (R) -citronellyl acid and 4-hydroxy-
0.96 g of 4'-cyanobiphenyl was dissolved in 10 ml of dichloromethane and then 1.13 g of dicyclohexylcarbodiimide.
And 4-pyrrolidinopyridine (0.1 g) were added, and the mixture was stirred at room temperature for 3 hours. After removing the solvent, ethyl acetate was added, the generated dicyclohexylurea was filtered off, and the solvent was removed.

The obtained residue was purified by a silica gel column using n-hexane / ether (8/2) as a developing solvent to obtain 1.2 g of the target (R) -4-citronelloyloxy-4'-cyanobiphenyl. .

As a result of infrared spectroscopic analysis, the obtained product had the following characteristic absorptions and was confirmed to be the target product.

^{2950cm -1 (s), 2230cm -1} (m), 1750cm -1 (s), 1600cm -1 (m), 1180cm -1 (s), 1120cm -1 (s), 830cm -1 addition (s), The optical rotation of the obtained product is shown below.

[Α] _D = + 6.26 ° (25 ° C., C = 1, CHCl ₃ solution) As a result of observing the phase morphology of this compound with a polarization microscope, the following phase transitions were confirmed.

Example 2 Preparation of (R) -4-citronellyloxy) -4′-cyanobiphenyl 1.00 g of 4-hydroxy-4′-cyanobiphenyl, 0.24 g of potassium hydroxide and 10 ml of dioxane were taken and stirred here, , (R) -citronellol p-toluenesulfonic acid ester (1.6 g) was added, and the mixture was stirred under reflux for 10 hours. After removing the solvent, diethyl ether was added, the mixture was neutralized with 5% hydrochloric acid, washed with water, dried and then desolvated.

The obtained residue was purified by a silica gel column using n-hexane / ether (9/1) as a developing solvent to obtain 1.4 g of the target (R) -4-citronellyloxy-4'-cyanobiphenyl.

As a result of infrared spectroscopic analysis, the obtained product had the following characteristic absorptions and was confirmed to be the target product.

^{3050cm -1 (w), 2950cm -1} (s), 2230cm -1 (s), 1600cm -1 (s), 1495cm -1 (s), 1290cm -1 (m), 1250cm -1 (s), 1180cm ^-1 (m), 820 cm ^-1 (s) Moreover, the optical rotation of the obtained product is shown below.

[Α] _D = + 3.86 ° (25 ° C., C = 1, CHCl ₃ solution) As a result of observing the phase morphology of this compound with a polarizing microscope, the following phase transitions were confirmed.

From the results of the above examples, it is clear that the cyanobiphenyl compound of the present invention has a crystal-liquid crystal phase transition temperature of -15 ° C. or lower, which is extremely low, and thus is suitable for obtaining a liquid crystal mixture having a low phase transition temperature. is there.

Claims (1)

[Claims] 1. An optically active cyanobiphenyl compound represented by the following general formula (I). (In the formula, X represents —CH ₂ — or —CO—, and * represents an asymmetric carbon.)