JPH04352768A - 2,5-disubstituted pyrimidine derivative - Google Patents

Abstract

PURPOSE:To provide the subject new compounds useful as an electron-optical display material and capable of, if mixed with a nematic liquid crystal material, reducing the threshold voltage and improving the responsibility. CONSTITUTION:Compounds of formula I (R<1> is 1-5C alkyl; R<2> is 1-7C alkyl; n is 2-7; Ring A is 1,4-phenylene, trans-1,4-cyclohexylene), e.g. 2-(trans-4- propylcyclohexyl)-5-(3-methoxypropyl)pyrimidine. The compounds of formula I can be obtained by catalytically reducing a compound of formula II in the presence of a catalyst such as palladium carbon in a solvent. The temperature dependence of threshold voltage can be reduced and driving over a wide temperature range is possible. The above-mentioned disubstituted pyrimidine derivatives are useful as a material for a liquid crystal display cell of a television, a word processor, etc., carried on a car.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel pyrimidine liquid crystal compound useful as an electro-optical display material.

0002

[Prior Art] Typical liquid crystal display cells include M. Schadt and others [APPLIED PH
SICS LETTERS 18, 127-128
(1971)] or the field effect mode cell proposed by G.H. Heilmeier.
etc. [PROCEEDING OF THE I. E. E
．． E. 56 1162-1171 (1968)] or the dynamic scattering mode cell proposed by G.H.
G.H. Heilmeier et al. [A
PPLIED PHYSICSLETTERS 13,
91 (1968)] or D.L. White etc. [JOURNAL OF
APPLIED PHYSICS 45,4718 (
There is a guest-host type cell proposed by [1974].

[0003] These liquid crystal display cells are required to have various characteristics, but the common characteristics are low threshold voltage and high-speed response, especially high-speed response in a low temperature range. This is an important required characteristic.

Compounds that lower the threshold voltage and simultaneously lower the viscosity of liquid crystal compositions are useful for liquid crystal display cells such as automotive liquid crystal display cells and liquid crystal televisions that require the above-mentioned properties. It is the material. In particular, the response time (τ
) is the viscosity (η) of the liquid crystal material and the formula

[0005]

[Math 1]

Since there is a proportional relationship as follows, if a liquid crystal material with low viscosity is used, a liquid crystal display cell with excellent high-speed response can be manufactured.

[0007]

[Problem to be Solved by the Invention] Conventionally, in order to reduce the viscosity of a liquid crystal material, formulas (a) and (b) are used.

0008
]

[Case 2]

A liquid crystal compound represented by the following was used. However, although the compounds of formulas (a) and (b) above can reduce the viscosity of a liquid crystal composition, they cannot reduce the threshold voltage. Additionally, there was a problem in that the responsiveness in a low temperature range was not sufficient.

[0010] The problem to be solved by the present invention is currently:
The object of the present invention is to provide a novel compound that, when added to a parent liquid crystal that is commonly used as a nematic liquid crystal material, has the effect of lowering the threshold voltage of the parent liquid crystal and improving responsiveness.

[0011]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides formula (I)

0012

[C3]

(In the formula, R1 represents a straight-chain alkyl group having 1 to 5 carbon atoms, particularly preferably a methyl group, and R2
represents a linear alkyl group having 1 to 7 carbon atoms, particularly preferably an ethyl group, a propyl group, or a butyl group; n represents an integer of 2 to 7, particularly preferably an integer of 2 to 4; A is 1,4-phenylene group or trans-1,4-
Represents a cyclohexylene group. ) is provided.

The compound represented by the general formula (I) according to the present invention can be produced, for example, according to the following production method.

[0015]

[C4]

(In each of the above formulas (II) to (VII),
R1 represents a linear alkyl group having 1 to 5 carbon atoms,
R2 represents a linear alkyl group having 1 to 7 carbon atoms,
n represents an integer of 2 to 7, and ring A represents a 1,4-phenylene group or a trans-1,4-cyclohexylene group. ) First step: A compound represented by general formula (II) is reacted with ethanol and hydrogen chloride in ether to form general formula (II).
A compound represented by I) is produced. Second step: A compound represented by general formula (III) is reacted with ammonia in ethanol to produce a compound represented by general formula (IV). Third step: Treating the compound represented by general formula (IV) and the compound represented by general formula (V) with a strong base such as sodium ethoxide in ethanol to produce the compound represented by general formula (VI). . Fourth step: By treating the compound represented by the general formula (VI) with a chlorinating agent such as phosphorus oxychloride, the compound represented by the general formula (VI) is treated with a chlorinating agent such as phosphorus oxychloride.
A compound represented by VII) is prepared. Fifth step: Catalytic reduction of the compound represented by general formula (VII) in a solvent using a catalyst such as palladium carbon,
A compound represented by general formula (I) according to the present invention is produced.

Table 1 lists the phase transition temperatures of typical compounds represented by the general formula (I) thus produced.

[0018]

[Table 1]

(In Table 1, C represents a crystal phase and I represents an isotropic liquid phase.) The compound represented by the general formula (I) according to the present invention has, for example, a positive or negative dielectric constant difference. It can be used as a material for field-effect display cells in the form of a mixture with other nematic liquid crystal compounds having orientation.

As described above, representative examples of preferable compounds that can be used in combination with the compound represented by the general formula (I) include 4-substituted benzoic acid 4-substituted phenyl ester, 4-substituted cyclohexane carbon acid 4-
Substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4'-substituted biphenyl ester, 4-(4-substituted cyclohexanecarbonyloxy)benzoic acid 4-substituted phenyl ester, 4-(4-substituted cyclohexyl)benzoic acid 4-substituted phenyl ester , 4-(4-substituted cyclohexyl)benzoic acid 4-substituted cyclohexyl ester, 4
, 4'-substituted biphenyl, 1-(4-substituted phenyl)4
-substituted cyclohexane, 4,4''-substituted terphenyl,
Examples include 1-(4'-substituted biphenylyl)4-substituted cyclohexane, 2-(4-substituted phenyl)5-substituted pyrimidine, and the like.

Table 2 shows 90% by weight of the base liquid crystal (A), which is currently widely used as a nematic liquid crystal material, and No. 1 compound 10
A mixed liquid crystal consisting of 75% by weight of the base liquid crystal (A) and No.
A mixed liquid crystal containing 25% by weight of compound No. 2 was prepared, and the response time and threshold voltage of each mixed liquid crystal at -20°C, 0°C and 20°C were measured, and the results are posted.

For comparison, a mixed liquid crystal consisting of 90% by weight of the base liquid crystal (A) and 10% by weight of the compound of formula (a), 75% by weight of the base liquid crystal (A) and 25% of the compound of formula (b) was prepared.
The response times and threshold voltages measured in the same manner for the mixed liquid crystal consisting of % by weight and the base liquid crystal (A) itself are listed.

[0023] The parent liquid crystal (A) is

[0024]

[C5]

It consists of the following.

[0026]

[Table 2]

(In Table 2, Vth is the threshold voltage (V)
, τ represents the response time (ms represents milliseconds), respectively. ) From Table 2 above, it can be seen that the compound represented by general formula (I) has a higher parent liquid crystal (
It can be seen that the response in the low temperature range of A) is improved, the threshold voltage is lowered, and the temperature dependence of the threshold voltage is further reduced.

[0028]

[Example] The present invention will be explained in more detail by referring to Examples of the present invention. However, the present invention is not limited to these examples.

(Example 1) Synthesis of 2-(trans-4-propylcyclohexyl)-5-(3-methoxypropyl)pyrimidine (compound No. 1 in Table 1)
1-a) Synthesis of trans-4-propylcyclohexanecarboximidate ethyl hydrochloride Trans-4-propylcyclohexanecarbonitrile 39.1g (259 mmol) and ethanol 15.3
g was dissolved in 120 ml of ether and saturated with hydrogen chloride gas under ice cooling. After stirring this mixture at room temperature for 2 days, the solvent was distilled off under reduced pressure, and the resulting residue was mixed with 30% ether.
0 ml was added, and the precipitated crystals were collected by filtration and dried under vacuum to obtain 29.1 g (126 mmol) of the title compound.

(1-b) Synthesis Example (1) of trans-4-propylcyclohexanecarboxamidine hydrochloride
29.0 g (125 mmol) of trans-4-propylcyclohexanecarboximidate ethyl hydrochloride obtained in -a) was dissolved in 200 ml of ethanol, and the solution was saturated with ammonia gas under ice cooling. After stirring this mixture at room temperature for 2 days, the solvent was distilled off under reduced pressure, 300 ml of ether was added to the resulting residue, the precipitated crystals were collected by filtration, and the crystals were vacuum-dried to yield 23.6 g of the title compound ( 116 mmol) was obtained.

(1-c) 2-(trans-4-propylcyclohexyl)-5-(3-methoxypropyl)
Synthesis of -4,6-dihydroxypyrimidine Ethanol 2
18.0 g (77 mmol) of diethyl 2-(3-methoxypropyl)malonate and trans-4-propyl obtained in Example (1-b) were added to a sodium ethoxide solution prepared from 50 ml and 5.9 g of sodium. 15.4 g (76 mmol) of cyclohexanecarboxamidine hydrochloride was added, and the mixture was heated under reflux for 14 hours. After the reaction was completed, the reaction mixture was allowed to cool to room temperature, concentrated hydrochloric acid was added until the pH of the reaction mixture became 1, 200 ml of water was further added, the precipitated crystals were collected by filtration, and the crystals were dried under vacuum to obtain 22.3 g of the title compound ( 73
mmol) was obtained.

(1-d) 2-(trans-4-propylcyclohexyl)-5-(3-methoxypropyl)
Synthesis of -4,6-dichloropyrimidine After dropping 12.0 g of N,N-dimethylaniline into 100 ml of phosphorus oxychloride, 2-(trans-4-propylcyclohexyl)- obtained in Example (1-c) was added dropwise to 100 ml of phosphorus oxychloride. 5-
22.3 g (73 mmol) of (3-methoxypropyl)-4,6-dihydroxypyrimidine was added and reacted at 100°C for 15 hours. After the reaction, phosphorus oxychloride was distilled off under reduced pressure, the resulting residue was added to 300 ml of water, the precipitated crystals were collected by filtration, and after vacuum drying, silica gel column chromatography (developing solvent: hexane/ Purification using ethyl acetate = 5/1) gave the title compound 6.8
g (21 mmol) was obtained.

(1-e) 2-(trans-4-propylcyclohexyl)-5-(3-methoxypropyl)
Synthesis of pyrimidine

[0034]

[C6]

6.8 g of 2-(trans-4-propylcyclohexyl)-5-(3-methoxypropyl)-4,6-dichloropyrimidine obtained in Example (1-d) (
21 mmol) was dissolved in 70 ml of ethyl acetate, 0.7 g of 5% palladium carbon, 3.5 g of magnesium oxide and 7 ml of water were added to this solution, hydrogen gas was introduced into this mixture, and the mixture was allowed to react for 2 days at room temperature and normal pressure. Ta. After the reaction was completed, the reaction mixture was filtered and the solvent was distilled off from the filtrate, and the resulting residue was purified using silica gel column chromatography (developing solvent: hexane/ethyl acetate = 4/1), and further purified from pentane. Recrystallize to give 1.4g of the listed compound.
(5 mmol) was obtained.

The melting point of this compound was 37°C. (Example 2) 2-(4-propylphenyl)-5-
(3-methoxypropyl)pyrimidine (No. in Table 1)
．． Synthesis of compound 2)

[0037]

[C7]

In Example 1, 2-(4-propylphenyl) -5-(3-methoxypropyl)pyrimidine 3.5
g (13 mmol) was obtained.

The melting point of this compound was 51°C. (Example 3) Preparation of liquid crystal composition (1)

[0040]

[Chemical formula 8]

A matrix liquid crystal (A) consisting of -20
The response time and threshold voltage were measured at 0.degree. C., 0.degree. C. and 20.degree. C., and the results were as follows. Temperature (℃)
Response time (ms) Threshold voltage (V)
20
38
1.50 0
125
1.72
-20 749
1.90 Weight of this base liquid crystal (A) and 2-(trans-4-propylcyclohexyl)-5-(3-methoxypropyl)pyrimidine obtained in Example 1

[0042]

[Chemical formula 9]

A mixed liquid crystal containing 10% by weight was prepared and the response time and threshold voltage were measured in the same manner, and the results were as follows. Temperature (℃)
Response time (ms) Threshold voltage (V)
20
44
1.27 0
118
1.41
-20 538
1.50 Also, for comparison, 90% by weight of base liquid crystal (A) and formula (a)

[0044]

[Chemical formula 10]

A mixed liquid crystal containing 10% by weight of the compound ##STR16## was prepared and the response time and threshold voltage were measured in the same manner, and the results were as follows. Temperature (℃)
Response time (ms) Threshold voltage (V)
20
35
1.42 0
115
1.56
-20 550
From the results of 1.75 or higher, the compound represented by the general formula (I) of the present invention is
Compared to the comparative compound of formula (a), the response time of the parent liquid crystal in the low temperature range is improved, the threshold voltage is lowered, and the temperature dependence of the threshold voltage is reduced. It can be understood. (Example 4) Preparation of liquid crystal composition (2) 75% by weight of the base liquid crystal (A) prepared in Example 3 and 2-(4-propylphenyl)-5-(3-methoxy obtained in Example 2) propyl)pyrimidine

[0046]

[Chemical formula 11]

A mixed liquid crystal containing 25% by weight was prepared, and the response time and threshold voltage were measured in the same manner as in Example 3, and the results were as follows. Temperature (℃)
Response time (ms) Threshold voltage (V)
20
45
1.21 0
124
1.35
-20 605
1.42 Also, for comparison, 75% by weight of base liquid crystal (A) and formula (b)

[0048]

[Chemical formula 12]

A mixed liquid crystal containing 25% by weight of the compound ##STR16## was prepared and the response time and threshold voltage were measured in the same manner, and the results were as follows. Temperature (℃)
Response time (ms) Threshold voltage (V)
20
38
1.34 0
124
1.53
-20 698
1.66 From the above results, the compound represented by the general formula (I) of the present invention is
It can be seen that, compared to the compound of formula (b), the response time of the parent liquid crystal in the low temperature range is improved, the threshold voltage is lowered, and the temperature dependence of the threshold voltage is reduced.

[0050]

Effects of the Invention The compound represented by the general formula (I) according to the present invention has excellent compatibility with the parent liquid crystal that is currently widely used as a nematic liquid crystal, and improves the responsiveness of the parent liquid crystal in the low temperature range. In addition, the threshold voltage can be lowered, and the temperature dependence of the threshold voltage can be further reduced.

[0051] Therefore, it can be driven in a wide temperature range,
It is useful as a material for liquid crystal display cells for vehicles, televisions, word processors, etc. that require high-speed response.

Claims (2)

[Claims] Claim 1: General formula (I) [Formula 1] (wherein, R1 represents a linear alkyl group having 1 to 5 carbon atoms, and R2 represents a linear alkyl group having 1 to 7 carbon atoms. where n represents an integer of 2 to 7, and ring A represents a 1,4-phenylene group or a trans-1,4-cyclohexylene group. 2. A liquid crystal composition containing the compound according to claim 1.