JPH0819074B2 - Optically active cyanobiphenyl compounds - Google Patents

Description

The present invention relates to a novel cyanobiphenyl compound having a positive dielectric anisotropy, and more particularly to a cyanobiphenyl compound having an alkoxy group having an asymmetric carbon.

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, 4-n-alkyl or alkoxy-4'-
It is known that a mixture of cyanobiphenyl compounds takes a liquid crystal phase in a relatively wide temperature range, but even in these mixtures, the crystal-liquid crystal phase transition temperature is -10 ° or higher, which is not satisfactory. It was

In addition, as a liquid crystal compound that gives a cholesteric phase,
4- (2-methylbutyl) -4'-cyanobiphenyl is known, but since the compound has a low liquid crystal-isotropic liquid phase transition temperature of about -30 ° C, it is necessary to obtain desired physical properties. However, there was a drawback that it was necessary to mix 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, R represents a hydrogen atom or an ethyl group, and * represents an asymmetric carbon atom.

Hereinafter, the present invention having the above gist will be described in more detail.

The compound represented by the general formula (I) is, for example, 4-
It can be easily prepared by a well-known etherification reaction in which a halide or tosylate of hydroxy-4′-cyanobiphenyl and an optically active alcohol is reacted in the presence of an alkali compound.

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

Example 1 4- (6 "-chloro-4" -methylhexyloxy)-
Preparation of 4'-cyanobiphenyl 4-hydroxy-4'-cyanobiphenyl (1.00 g), potassium hydroxide (0.43 g) and methyl ethyl ketone (20 ml) were taken and stirred under reflux for 1 hour.

To this, p-toluenesulfonic acid ester synthesized from 1.16 g of optically active 6-chloro-4-methylhexanol ([α] _D = -3.76 °, 27 ° C, C = 2, chloroform solution) was added, and the mixture was refluxed. It was stirred for 12 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 resulting residue is n-
Purify with a silica gel column using hexane / ether (85/15) as a developing solvent to obtain the desired product, 4- (6 ″ -chloro-).
1.3 g of 4 "-methylhexyloxy) -4'-hydroxybiphenyl was obtained.

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), 2860cm ^-1 (m), 2220cm ^-1 (s), 16
^{00cm -1 (vs), 1490cm -1} (s), 1465cm -1 (m), 1245cm -1 (vs), 10
^{35cm -1 (w), 820cm -1} (s), 655cm -1 addition (w), the following optical rotation of the resulting product.

[Α] _D = + 3.79 ° (27 ° 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 4- (6 "-chloro-4" -methyloctoxy) -4 '
Preparation of cyanobiphenyl Instead of p-toluenesulfonic acid ester synthesized from optically active 6-chloro-4-methylhexanol, optically active 6-chloro-4-methyloctanol ([α]
_The title compound was synthesized in the same manner as in Example 1 except that 2.56 g of p-toluenesulfonic acid ester synthesized from _D = + 0.75 °, 28 ° C., C = 1, chloroform solution) was used.

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), 2975cm ^-1 (s), 2890cm ^-1 (m), 2240cm ^-1 (s), 16
^{05cm -1 (vs), 1500cm -1} (vs), 1470cm -1 (m), 1255cm -1 (vs), 1
040 cm ^-1 (w), 825 cm ^-1 (s), 665 cm ^-1 (w) Moreover, the optical rotation of the obtained product is shown below.

[Α] _D = + 7.87 ° (27 ° 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.

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 less, which is extremely low, and thus is suitable for obtaining a liquid crystal mixture having a low phase transition temperature. is there.

Continuation of front page (56) References JP-A-56-95977 (JP, A) Mol. Cryst. Lig. Crys t. , 104 [3-4] (1984) P. 335-345 Mol. Cryst. Lig. Crys t. , 37 [1-4] (1976) p. 189 ~ 211

Claims (1)

[Claims] 1. An optically active cyanobiphenyl compound represented by the following general formula (I). (In the formula, R represents a hydrogen atom or an ethyl group, and * represents an asymmetric carbon.)