JPH0212951B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel organic compound, and more particularly to a novel liquid crystal compound that can be used as a component of a liquid crystal material. As is well known, liquid crystal materials are display elements that use nematic liquid crystals with twisted liquid crystal alignment (so-called TN).
In addition to display devices that utilize the guest-host effect of liquid crystal substances or liquid crystal mixtures containing appropriate dyes, DS type display devices that utilize the dynamic scattering effect of liquid crystals, and cholesteric-nematic phase transition. It is widely used in display devices that utilize this technology, as well as DAP display devices that utilize the field-controlled birefringence effect of liquid crystals. These liquid crystal materials cannot be used as a single compound in terms of their properties, such as liquid crystal temperature range, operating voltage, response performance, etc., and for practical purposes, several types of liquid crystal compounds are mixed to achieve a certain level of performance. At present, we have obtained something that is usable. The present invention provides a compound useful as a component constituting such a stable liquid crystal composition with excellent practical performance. That is, the present invention is based on the general formula (In the above formula, R represents an alkyl group having 1 to 10 carbon atoms, and X represents F.) p-(trans-5-alkyl-
1,3-dioxan-2-yl)phenyl p-halogenobenzoate. The compound of formula () of the present invention is a novel liquid crystal compound with positive dielectric anisotropy, a wide liquid crystal temperature range, a high clearing point, and excellent stability. Since the compound of the present invention has a high melting point, it cannot be practically used alone, but it has excellent compatibility with other liquid crystal compounds, such as biphenyl, ester, azoxy, and cyclohexanecarboxylic acid compounds. It has the effect of raising the clearing point when mixed with one type or a mixture of several types of liquid crystals such as enyl ester type, phenylcyclohexane type, and phenylpyrimidine type. The compound of the present invention can be synthesized as follows. First, diethyl malonic acid ester is reacted with an alkyl bromide in an anhydrous ethyl alcohol solvent in the presence of sodium ethoxide to obtain a 2-alkyl diethyl malonic acid ester. This is reduced using lithium aluminum hydride in tetrahydrofuran (THF) solvent to obtain 2-alkyl-1,3-propanediol. Other known reducing agents and reduction methods can also be used to reduce the malonic acid ester. On the other hand, 4-fluorobenzoic acid is converted to the corresponding acid chloride using a chlorinating agent such as thionyl chloride or phosphorus pentachloride,
By reacting this with 4-hydroxybenzaldehyde in a basic solvent such as pyridine,
P-(4-fluorobenzoyloxy)benzaldehyde is obtained. The aldehyde thus obtained is reacted with the previously obtained 2-alkyl-1,3-propanediol in an inert organic solvent such as toluene using an acid catalyst such as p-toluenesulfonic acid. p-(5-alkyl-
1,3-dixan-2-yl)phenyl p-fluorobenzoate is obtained. This dioxane compound is a mixture of cis and trans forms, so if the cis form is removed by recrystallization, the desired trans form, p-(trans-5-alkyl-1,3-
Dioxane) phenyl p-fluorobenzoate is obtained. If the above is expressed as a chemical formula, Hereinafter, the compounds of the present invention will be explained in more detail by showing production examples and usage examples thereof as examples. Example 1 [p-(5-butyl-1,3-dioxane-2
-yl) phenyl p-fluorobenzoate (formula () where R is C ₄ H ₉ )] 41.3 g (0.61 mol) of sodium ethoxide was dissolved in 200 ml of absolute ethyl alcohol, and then 96 g (0.60 mol) of diethyl malonate was dissolved in 200 ml of absolute ethyl alcohol. mol) and heat and stir. 83.0 g (0.60 mol) of n-butyl bromide was gradually added dropwise thereto. After completion of the dropwise addition, the mixture was heated under reflux for 4 hours. Thereafter, ethyl alcohol was distilled off at normal pressure, and 200 ml of cold water was added to the reaction mixture to dissolve the sodium bromide precipitated by the reaction.
Next, the aqueous layer and organic layer were separated, the aqueous layer was extracted with 200 ml of normal hexane, the extract was combined with the upper organic layer, washed with water, the normal hexane was distilled off under reduced pressure, and the residue was distilled under reduced pressure to extract ethyl- 93.45 g (0.432 mol) of diethyl n-butylmalonate was obtained. Its boiling point was 86-90°C/3mmHg. Tetrahydrofuran was prepared by drying 65.7 g (0.3 mol) of diethyl n-butyl malonate obtained in this way using calcium hydride.
Lithium aluminum hydride was dissolved in 500 ml of dry tetrahydrofuran.
15 g (0.4 mol) was suspended and added dropwise to the vigorously stirred solution at 20°C. After the addition was complete, the mixture was heated under reflux for 2 hours. After heating, cool the reaction mixture in an ice bath and add ethyl acetate to decompose excess lithium aluminum hydride.
Added 10ml. Then add 200ml of 20% sulfuric acid,
The mixture was stirred vigorously until the inorganic substances such as lithium hydroxide were dissolved. The product was extracted with 100 ml of ether, and the extract was washed twice with a 5% aqueous sodium bicarbonate solution, further washed with water, and then dried over anhydrous sodium sulfate. Next, ether was distilled off from the extract, and the residue was distilled under reduced pressure to obtain 27.7 g (0.21 mol) of 2-n-n-butyl-1,3-propanediol. Boiling point is 105
The temperature was ~107°C/3mmHg. Meanwhile, 4-fluorobenzoyl chloride was added to a mixed solution of 35 g (0.29 mol) of 4-oxybenzaldehyde, 400 ml of anhydrous benzene, and 40 ml of dry pyridine.
52.4g (0.3mol) is added dropwise while maintaining the reaction temperature at 30-40%. After the dropwise addition was completed, heating and stirring was continued for 3 hours at a reaction temperature of 60°C, and then the reaction mixture was poured into 200ml of water. The organic phase was separated, washed with dilute hydrochloric acid solution and dilute sodium hydroxide solution and water, then dried over anhydrous sodium sulfate. After distilling off the solvent, the residue was recrystallized using ethanol to obtain 40.6 g (0.16 mol) of p-(4-fluorobenzoyloxy)benzaldehyde with a melting point of 99.6°C (yield 52%). Take 2.6g (0.01 mol) of this and add it to the previously obtained 2-butylpropane-1,3-
A mixture of 1.32 g (0.01 mol) of diol and 50 ml of toluene and 50 mg of 4-toluenesulfonic acid as a catalyst was placed in a flask equipped with a water separator and heated to reflux. Water stopped coming out in about 1 hour and the reaction stopped. finish. The reaction mass is poured into 100 ml of water and the organic phase is separated, washed with 5% sodium bicarbonate solution and then with water before drying over anhydrous sodium sulfate. Next, the solvent (toluene) was distilled off under reduced pressure, and the residue was recrystallized twice with 10 ml of a mixed solvent of 7 ethyl alcohol and 3 parts benzene to obtain the desired p-(trans-5-butyl-1,3-dioxane- 1.8 g (yield: 48%) of 2-yl)phenyl p-fluorobenzoate was obtained. C of this thing
-N point (nematic point) is 91.0 to 91.5℃, N-I
The clearing point is 165°C, and the elemental analysis values are in good agreement with the theoretical values as shown below. Analytical value (%) Calculated value (as C ₂₁ H ₂₄ O ₄ F) (%) C 70.6 70.2 H 6.4 6.7 Examples 2 to 9 Using another alkyl bromide in place of butyl bromide in Example 1, Also, X in formula () is Br or Cl
In the case of 4-bromobenzoyl chloride or 4-bromobenzoyl chloride respectively in place of 4-fluorobenzoyl chloride
-A compound of formula () shown in Table 1 was obtained in the same manner as in Example 1 except that chlorobenzoyl chloride was used. Its physical properties are shown in Table 1, including the results of Example 1.

[Table] Example 10 (Application example) The nematic liquid crystal temperature range of the liquid crystal composition consisting of is -3 to 52℃, the viscosity at 20℃ is 23cp, and △ε is
10.5, the threshold voltage was 1.53V and the saturation voltage was 2.12V when sealed in a TN cell with a cell thickness of 10μ.
In addition to 85 parts of the above liquid crystal composition, a compound of formula () of the present invention is added. Nematic liquid crystal temperature range of liquid crystal compositions containing
It spreads from 10 to 65℃, and the viscosity at 20℃ is 28cp.
Δε was 10.0, and when sealed in a TN cell of the same thickness, the threshold voltage was 1.54V and the saturation voltage was 2.13V, almost unchanged.

Claims (1)

[Claims] 1. General formula (In the above formula, R represents an alkyl group having 1 to 10 carbon atoms, and X represents F.) p-(trans-5-alkyl 1,
3-Dioxan-2-yl)phenyl p-halogenobenzoate. 2 General formula (In the above formula, R represents an alkyl group having 1 to 10 carbon atoms, and X represents F.) p-(trans-5-alkyl 1,
A liquid crystal composition containing at least one component of 3-dioxan-2-yl) phenyl p-halogenobenzoate.