JPS5810381B2 - Method for producing liquid crystal compounds - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing a liquid crystalline ester compound.

The liquid crystalline ester provided by the present invention is a compound of the general formula (wherein R represents a linear alkyl group containing 4 to 10 carbon atoms).

Nematic liquid crystal molecules have dielectric anisotropy as well as optical anisotropy.

Nematic liquid crystal molecules arranged in a twisted manner at a 90° angle between two transparent electrodes rotate the light deflection plane along the twist due to their optical anisotropy.

Therefore, if polarizing plates orthogonal to each other are placed on both sides of a cell made in this way, light will pass through.

Next, when an electric field is applied between the electrodes of this cell, the nematic liquid crystal molecules are aligned with their longitudinal axes facing the direction of the electric field due to their dielectric anisotropy, so no rotation of the plane of polarization of the light occurs. Light no longer passes between the orthogonal polarizing plates.

Such a field-effect photorotation cell has low voltage and low power consumption, so it has great advantages as a display element for desktop computers, wristwatches, and other portable consumer devices.

In such a liquid crystal display element, it is desirable to use a compound that exhibits a nematic liquid crystal state over a wide range of convergence centered around room temperature.

Surprisingly, it has been found that the compounds of formula (1) above according to the invention have liquid crystal properties that meet this requirement.

It has been found that mixtures of the compounds with each other or with other nematic or non-nematic materials exhibit a wide liquid crystal temperature range.

Conventional nematic liquid crystals with large positive dielectric anisotropy for low-voltage driving have had the disadvantage that their clearing point is relatively low in terms of temperature range.

This is an advantage of the liquid crystal compound according to the present invention, which expands the usage conditions of the display cell and increases the utility value of the display cell.

Yet another advantage of the invention is that the compounds of formula (1) yield colorless opalescent nematic phases.

The compounds of formula (1) are preferably used in the form of mixtures with each other and with other nematic or non-nematic substances.

Especially when aiming at low voltage drive, a two-component system with a nematic material with large positive dielectric anisotropy, or a three-component system,
Or a mixture in which the composition of a multi-component system corresponding to a eutectic composition is particularly preferred.

The compounds of the above formula (1) can be prepared by the methods provided by the present invention, such as the general formula (wherein R represents a straight-chain alkyl group containing 4 to 10 carbon atoms, and can be prepared by reacting the compound (representing) with 3-chloro-4-hydroxybenznitrile.

In formula (2), the leaving atom or group represented by X is a halogen atom, lower alkoxy, lower alkanoyloxy, lower aryl-alkoxy, lower aryl-
It can be an alkanoyloxy, lower alkylsulfonyloxy or arylsulfonyloxy group.

In an embodiment of the process according to the invention, a compound of formula (2) is reacted with 3-chloro-4-hydroxybenznitrile.

The reaction is carried out in an inert organic solvent, such as ebuluene, benzene, cyclohexane, or carbon tetrachloride.

In the compound of formula (2), X preferably represents a halogen atom, especially a chlorine atom.

In order to combine the hydrogen halides liberated during the reaction,
It is advantageous to have an acid binder present in the reaction mixture.

Suitable acid binders are tertiary amines, pyridine, etc.
Preferably, it is present in large excess so that it can simultaneously serve as a solvent and an acid binder.

The reaction is generally carried out at atmospheric pressure and at a temperature between room temperature or the boiling temperature of the reaction mixture.

A compound of formula (2) in which X represents a chlorine atom can be produced by reacting the corresponding benzoic acid with thionyl chloride.

Furthermore, this benzoic acid can be produced in good yield by, for example, reacting P-alkylbenzoic acid chloride and P-hydroxybenzoic acid in pyridine at room temperature.

The physical properties of the nematic compound of formula (1) provided by the present invention are shown in Table 1.

The compounds of formula (1) are preferably used in mixtures with each other or with other nematic or non-nematic substances, mixtures corresponding to eutectics being particularly preferred.

Examples of mixtures are shown in the table below.

The following examples relate to specific examples provided by the present invention.

Example 1 0.5 g of 4-(4-n-hexylbenzoyloxy)benzoic acid chloride (0,001
5 mol), 0.2 g (0,0015 mol) of 3-chloro-4-hydroxybenznitrile, and 5 ml of pyridine were added, and the mixture was heated under reflux for 3 hours.

This reaction mixture was washed with water, diluted hydrochloric acid, further washed with water,
After washing with a dilute aqueous sodium hydroxide solution and finally washing again with water, the toluene solution was dried to remove toluene.

The product of the composition was recrystallized from ethanol and n-hexane to obtain 0.4 g of purified product.

This product had a touch point of 90°C and a clearing point of 229°C, and its infrared absorption spectrum matched the predicted structural formula of 4-(4-n-hexylbenzoyloxy)benzoic acid-2'-chloro-41-cyanophenyl ester. .

The starting material could be prepared as follows.

That is, p-n-hexylbenzoic acid chloride 4.5
g (0.02 mol) of p-hydroxybenzoic acid 2.82 (0.02 mol) dissolved in pyridine 30d
was added dropwise to the solution and stirred.

This was stirred at room temperature for 30 minutes and then poured into a large amount of water.

Dilute hydrochloric acid was added to the mixture, and when the suspended matter began to aggregate, it was passed through the mouth and washed with water.

This was reconstituted from glacial acetic acid to obtain 5.5 g of L,4-(4-n-hexylbenzoyloxy)benzoic acid.

This product had a melting point of 138°C.

Furthermore, 5.5 g (0,01
7 mol), carbon tetrachloride 20rul, thionyl chloride 20r
After adding the mixture to rLl and heating under reflux for 5 hours, excess thionyl chloride and the solvent were removed.

The obtained crude product was recrystallized from toluene to obtain purified 4-(
5.02 of 4-n-hexylbenzoyloxy)benzoic acid chloride was obtained.

Example 2 Toluene 30IrLl, 4-(4-n-pentylbenzoyloxy)benzoic acid chloride 1.62(0,0
05 mol), 3-chloro-4-hydroxybenznitrile 0.75' (0,005 mol) and pyridine 5rf
Attach a reflux tube to the Ll in a 200r/Ll flask,
Heating and refluxing was performed for 3 hours using a mantle heater.

The reaction mixture was washed in the order of water washing, pickling, water washing, alkaline washing, and water washing, and the water in the toluene solution was removed with anhydrous calcium chloride, and the solution was concentrated.

A product of composition 1.1y was obtained from this solution by cooling.

The composition was recrystallized twice using a mixed solvent of n-hexane/toluene to obtain purified 4-(4-n-pentylbenzoyloxy)benzoic acid-2'-chloro-4'-cyanophenyl ester (melting point 153°C, clearing point 240°C or higher) o, sft was obtained.

The starting material was synthesized in a manner similar to Example 1. Example 3 Benzene 30rnf 4-(4-n-butylbenzoyloxy)benzoic acid chloride 1.2 F (0,004
mole), 3-chloro-4-hydroxybenznitrile 0
．． 6r (0,004 mol), 20 pyridine 5IILl
The mixture was heated under reflux for 3 hours in a 0ml flask.

Crystals precipitated as the solution cooled, and were passed through the mouth. Wash the mouth waste in the order of water washing, pickling, water washing, alkaline washing, and water washing.
Dry and composition 0.6? was gotten.

It was purified by recrystallization from a mixed solvent of n-hexane/benzene.

Melting point: 155°C, clearing point: 240°C or higher. The starting material was synthesized in a manner similar to Example 1.

Example 4 Toluene 30mf 4-(4-n-heptylbenzoyloxy)benzoic acid chloride 0.7f? (0,00
2 mol), 0.3 r (0,002 mol) of 3-chloro-4-hydroxybenznitrile, and 5 rfLl of pyridine were heated under reflux for 3 hours.

In the same manner as in Example 1, 0.41 of purified 4-(4-n-hebutylbenzoyloxy)benzoic acid-2'-chloro-4'-cyanophenyl ester was obtained.

The melting point was 118°C and the clearing point was 240°C or higher.

The starting material could be synthesized by a method similar to Example 1.

Example 5 Benzene 30 mf 4-(4-n-octylbenzoyloxy)benzoic acid chloride 0.92 (0,0024 mol), 3-chloro-4-hydroxybenznitrile 0.
A mixture of 4g (0,0024 mol) of pyridine and 5rILl was heated under reflux for 2 hours.

The reaction product was washed and the solvent was removed to obtain 0.8 g of a composition.

Purified 4-(4-n) was obtained by recrystallizing twice from toluene.
0.5 g of -octylbenzoyloxy)benzoic acid-2'-chloro-4'-cyanophenyl ester was obtained.

The starting material could be synthesized by a method similar to Example 1.

Claims (1)

[Scope of Claims] 1. A compound represented by the general formula R represents a linear alkyl group containing 4 to 10 carbon atoms, and X represents a leaving atom or group), 1. A method for producing a liquid crystal compound, which comprises producing a liquid crystal compound represented by the general formula (wherein R has the above meaning) by reacting with benzonitrile.