JPH06765B2 - Fluorine-containing pyrazine derivative and liquid crystal composition containing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a novel fluorine-containing pyrazine derivative, and the fluorine-containing pyrazine derivative of the present invention can be used as a blending component of a liquid crystal composition.

[Conventional technology]

In recent years, a liquid crystal display (LCD) has been actively used as a display system.

This liquid crystal for liquid crystal display is stable to heat, light, moisture, etc., exhibits a liquid crystal phase in a wide temperature range around room temperature, has an appropriate threshold voltage and saturation voltage, and has a fast response speed. The liquid crystal composition obtained by appropriately mixing various liquid crystal compounds and non-liquid crystal compounds has been used in order to satisfy such demands.

[Problems to be solved by the invention]

The conventional liquid crystal composition cannot sufficiently satisfy the performances required as a liquid crystal such as the threshold voltage and the steepness of the voltage-transmittance characteristic.

Therefore, an object of the present invention is to provide a liquid crystal composition satisfying the performance required as a liquid crystal.

[Means for solving problems]

The present invention provides compounds represented by the general formula (I) as compounds used in a liquid crystal composition. (In the formula, R represents an aliphatic alkyl group having 1 to 12 carbon atoms or an aliphatic alkoxy group having 1 to 12 carbon atoms, X represents F or H, and Y is an aliphatic alkoxy group having 1 to 10 carbon atoms. ,
Indicates F or CF ₃ . However, X is H and Y has 1 to 1 carbon atoms.
Excluding the case of 10 aliphatic alkoxy groups. The object is achieved by providing a fluorine-containing pyrazine derivative represented by:

Many of the fluorine-containing pyrazine derivatives of the present invention show liquid crystal properties even when used alone, are colorless and stable to heat and light, and are chemically stable, and are also compatible with other liquid crystalline substances. Since it has good compatibility, it can be used as a liquid crystal composition by appropriately mixing it with other liquid crystal compounds or non-liquid crystal compounds depending on the purpose and application. In particular, when the fluorine-containing pyrazine derivative of the present invention is used as a liquid crystal composition (liquid crystal composition of the present invention) by mixing with other liquid crystal compounds, it is compared with a liquid crystal composition containing no fluorine-containing pyrazine derivative of the present invention. As a result, the threshold voltage can be lowered or the voltage-transmittance characteristic can be made steep.

First, the fluorine-containing pyrazine derivative of the present invention will be described in detail below.

In the fluorine-containing pyrazine derivative of the present invention represented by the general formula (I), the aliphatic alkyl group having 1 to 12 carbon atoms represented by R is methyl, ethyl, n-propyl, n-butyl, n- Pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-
Undecyl, n-dodecyl, and various isomers thereof are mentioned, and examples of the aliphatic alkoxy group having 1 to 12 carbon atoms represented by R include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyl. Examples thereof include oxy, n-hexyloxy, n-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-undecyloxy, n-dodecyloxy, and various isomers thereof.

In addition, examples of the aliphatic alkoxy group having 1 to 10 carbon atoms represented by Y include methoxy, ethoxy, n-propoxy, and n.
Examples include -butoxy, n-pentyloxy, n-hexyloxy, n-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, and various isomers thereof.

Therefore, examples of the fluorine-containing pyrazine derivative of the present invention represented by the general formula (I) include the following compounds.

2-Methyl-5- (3-fluoro-4-butoxyphenyl) pyrazine, 2-methyl-5- (3-fluoro-4-)
Pentyloxyphenyl) pyrazine, 2-methyl-5-
(3-fluoro-4-hexyloxyphenyl) pyrazine, 2-methyl-5- (3-fluoro-4-heptyloxyphenyl) pyrazine, 2-ethyl-5- (3-fluoro-4-propoxyphenyl) pyrazine, 2-ethyl-5- (3-fluoro-4-butoxyphenyl) pyrazine, 2-ethyl-5- (3-fluoro-4-pentyloxyphenyl) pyrazine, 2-ethyl-5- (3-fluoro-4-) Hexyloxyphenyl) pyrazine, 2-ethyl-5- (3-fluoro-4-heptyloxyphenyl) pyrazine, 2-ethyl-5- (3-fluoro-4-)
Octyloxyphenyl) pyrazine, 2-ethyl-5
(3-Fluoro-4-decyloxyphenyl) pyrazine, 2-propyl-5- (3-fluoro-4-ethoxyphenyl) pyrazine, 2-propyl-5- (3-fluoro-4-propoxyphenyl) pyrazine, 2 -Propyl-5- (3-fluoro-4-butoxyphenyl) pyrazine, 2-propyl-5- (3-fluoro-4-pentyloxyphenyl) pyrazine, 2-propyl-5- (3-
Fluoro-4-hexyloxyphenyl) pyrazine, 2
-Propyl-5- (3-fluoro-4-heptyloxyphenyl) pyrazine, 2-propyl-5- (3-fluoro-4-octyloxyphenyl) pyrazine, 2-butyl-5- (3-fluoro-4-) Propoxyphenyl) pyrazine, 2-butyl-5- (3-fluoro-4-butoxyphenyl) pyrazine, 2-butyl-5- (3-fluoro-4-pentyloxyphenyl) pyrazine, 2-butyl-5- (3 -Fluoro-4-hexyloxyphenyl) pyrazine, 2-butyl-5- (3-fluoro-4-)
Heptyloxyphenyl) pyrazine, 2-butyl-5-
(3-Fluoro-4-octyloxyphenyl) pyrazine, 2-pentyl-5- (3-fluoro-4-methoxyphenyl) pyrazine, 2-pentyl-5- (3-fluoro-4-ethoxyphenyl) pyrazine, 2 -Pentyl-
5- (3-fluoro-4-propoxyphenyl) pyrazine, 2-pentyl-5- (3-fluoro-4-butoxyphenyl) pyrazine, 2-pentyl-5- (3-fluoro-4-pentyloxyphenyl) pyrazine , 2-pentyl-5- (3-fluoro-4-hexyloxyphenyl) pyrazine, 2-pentyl-5- (3-fluoro-4)
-Heptyloxyphenyl) pyrazine, 2-pentyl-
5- (3-fluoro-4-octyloxyphenyl) pyrazine, 2-pentyl-5- (3-fluoro-4-nonyloxyphenyl) pyrazine, 2-hexyl-5- (3
-Fluoro-4-methoxyphenyl) pyrazine, 2-hexyl-5- (3-fluoro-4-ethoxyphenyl)
Pyrazine, 2-hexyl-5- (3-fluoro-4-propoxyphenyl) pyrazine, 2-hexyl-5- (3
-Fluoro-4-butoxyphenyl) pyrazine, 2-hexyl-5- (3-fluoro-4-pentyloxyphenyl) pyrazine, 2-hexyl-5- (3-fluoro-
4-hexyloxyphenyl) pyrazine, 2-hexyl-5- (3-fluoro-4-heptyloxyphenyl)
Pyrazine, 2-hexyl-5- (3-fluoro-4-octyloxyphenyl) pyrazine, 2-hexyl-5-
(3-Fluoro-4-decyloxyphenyl) pyrazine, 2-heptyl-5- (3-fluoro-4-methoxyphenyl) pyrazine, 2-heptyl-5- (3-fluoro-4-ethoxyphenyl) pyrazine, 2 -Heptyl-
5- (3-fluoro-4-propoxyphenyl) pyrazine, 2-heptyl-5- (3-fluoro-4-butoxyphenyl) pyrazine, 2-heptyl-5- (3-fluoro-4-pentyloxyphenyl) pyrazine , 2-heptyl-5- (3-fluoro-4-hexyloxyphenyl) pyrazine, 2-heptyl-5- (3-fluoro-4)
-Heptyloxyphenyl) pyrazine, 2-heptyl-
5- (3-fluoro-4-octyloxyphenyl) pyrazine, 2-octyl-5- (3-fluoro-4-methoxyphenyl) pyrazine, 2-octyl-5- (3-fluoro-4-methoxyphenyl) pyrazine , 2-octyl-5- (3-fluoro-4-ethoxyphenyl) pyrazine, 2-octyl-5- (3-fluoro-4-propoxyphenyl) pyrazine, 2-octyl-5- (3-fluoro-4-). Butoxyphenyl) pyrazine, 2-octyl-5- (3-fluoro-4-pentyloxyphenyl) pyrazine, 2-octyl-5- (3-fluoro-4)
-Hexyloxyphenyl) pyrazine, 2-octyl-
5- (3-fluoro-4-heptyloxyphenyl) pyrazine, 2-octyl-5- (3-fluoro-4-octyloxyphenyl) pyrazine, 2-nonyl-5- (3
-Fluoro-4-methoxyphenyl) pyrazine, 2-nonyl-5- (3-fluoro-4-ethoxyphenyl) pyrazine, 2-nonyl-5- (3-fluoro-4-propoxyphenyl) pyrazine, 2-nonyl- 5- (3-fluoro-4-butoxyphenyl) pyrazine, 2-nonyl-
5- (3-fluoro-4-pentyloxyphenyl) pyrazine, 2-nonyl-5- (3-fluoro-4-hexyloxyphenyl) pyrazine, 2-nonyl-5- (3-
Fluoro-4-heptyloxyphenyl) pyrazine, 2
-Nonyl-5- (3-fluoro-4-octyloxyphenyl) pyrazine, 2-decyl-5- (3-fluoro-
4-methoxyphenyl) pyrazine, 2-decyl-5-
(3-Fluoro-4-ethoxyphenyl) pyrazine, 2
-Decyl-5- (3-fluoro-4-propoxyphenyl) pyrazine, 2-decyl-5- (3-fluoro-4-)
Butoxyphenyl) pyrazine, 2-decyl-5- (3-
Fluoro-4-pentyloxyphenyl) pyrazine, 2
-Decyl-5- (3-fluoro-4-hexyloxyphenyl) pyrazine, 2-decyl-5- (3-fluoro-
4-heptyloxyphenyl) pyrazine, 2-undecyl-5- (3-fluoro-4-methoxyphenyl) pyrazine, 2-undecyl-5- (3-fluoro-4-ethoxyphenyl) pyrazine, 2-undecyl-5- (3-
Fluoro-4-propoxyphenyl) pyrazine, 2-undecyl-5- (3-fluoro-4-butoxyphenyl) pyrazine, 2-undecyl-5- (3-fluoro-
4-pentyloxyphenyl) pyrazine, 2-undecyl-5- (3-fluoro-4-hexyloxyphenyl) pyrazine, 2-undecyl-5- (3-fluoro-
4-heptyloxyphenyl) pyrazine, 2-dodecyl-5- (3-fluoro-4-methoxyphenyl) pyrazine, 2-dodecyl-5- (3-fluoro-4-ethoxyphenyl) pyrazine, 2-dodecyl-5- (3-Fluoro-4-propoxyphenyl) pyrazine, 2-dodecyl-5- (3-fluoro-4-butoxyphenyl) pyrazine, 2-dodecyl-5- (3-fluoro-4-pentyloxyphenyl) pyrazine, 2 -Dodecyl-5- (3-
Fluoro-4-hexyloxyphenyl) pyrazine, 2
-Dodecyl-5- (3-fluoro-4-heptyloxyphenyl) pyrazine, 2-ethyl-5- (4-fluorophenyl) pyrazine, 2-propyl-5- (4-fluorophenyl) pyrazine, 2-butyl- 5- (4-fluorophenyl) pyrazine, 2-pentyl-5- (4-fluorophenyl) pyrazine, 2-hexyl-5- (4-fluorophenyl) pyrazine, 2-heptyl-5- (4-
Fluorophenyl) pyrazine, 2-octyl-5- (4
-Fluorophenyl) pyrazine, 2-nonyl-5- (4
-Fluorophenyl) pyrazine, 2-decyl-5- (4
-Fluorophenyl) pyrazine, 2-undecyl-5-
(4-Fluorophenyl) pyrazine, 2-dodecyl-5
-(4-Fluorophenyl) pyrazine, 2-ethoxy-
5- (4-fluorophenyl) pyrazine, 2-propoxy-5- (4-fluorophenyl) pyrazine, 2-butoxy-5- (4-fluorophenyl) pyrazine, 2-pentyloxy-5- (4-fluorophenyl) ) Pyrazine, 2-hexyloxy-5- (4-fluorophenyl) pyrazine, 2-heptyloxy-5- (4-fluorophenyl) pyrazine, 2-octyloxy-5- (4
-Fluorophenyl) pyrazine, 2-nonyloxy-5
-(4-fluorophenyl) pyrazine, 2-decyloxy-5- (4-fluorophenyl) pyrazine, 2-methoxy-5- (4-trifluoromethylphenyl) pyrazine, 2-ethoxy-5- (4-trifluoro Methylphenyl) pyrazine, 2-propoxy-5- (4-trifluoromethylphenyl) pyrazine, 2-butoxy-5-
(4-Trifluoromethylphenyl) pyrazine, 2-pentyloxy-5- (4-trifluoromethylphenyl) pyrazine, 2-hexyloxy-5- (4-trifluoromethylphenyl) pyrazine, 2-heptyloxy-5 -(4-trifluoromethylphenyl) pyrazine,
2-octyloxy-5- (4-trifluoromethylphenyl) pyrazine, 2-nonyloxy-5- (4-trifluoromethylphenyl) pyrazine, 2-decyloxy-5- (4-trifluoromethylphenyl) pyrazine.

The fluorine-containing pyrazine derivative of the present invention represented by the general formula (I) can be produced in the same manner as a conventionally known method for producing a pyrazine derivative. That is, for example, it can be manufactured by the following method.

As shown in the following formula, first, the acetophenone derivative (a)
The phenylglyoxal derivative (b) is obtained by oxidizing the compound with selenium dioxide or the like. Then, the derivative (b) is reacted with aminoacetamide hydrochloride to give 5-phenyl-2
-Pyrazinol derivative (c) is obtained, and the derivative (c) further contains P
By reacting with a chlorinating agent such as Cl ₅ or POCl ₃ , 5
-Phenyl-2-chloropyrazine derivative (d) is obtained. Then, the pyrazine derivative (I) is obtained by reacting the derivative (d) with an alkylmagnesium bromide (Grineer's reagent) or sodium alkoxide.

(In the formula, R represents an aliphatic alkyl group having 1 to 12 carbon atoms or an aliphatic alkoxy group having 1 to 12 carbon atoms, X represents F or H, and Y is an aliphatic alkoxy group having 1 to 10 carbon atoms. ,
Indicates F or CF ₃ . However, X is H and Y has 1 to 1 carbon atoms.
Excluding the case of 10 aliphatic alkoxy groups. ) Next, the liquid crystal composition of the present invention will be described.

The liquid crystal composition of the present invention is obtained by appropriately mixing the above-mentioned fluorine-containing pyrazine derivative of the present invention with another liquid crystal compound or a non-liquid crystal compound, and the fluorine-containing pyrazine derivative of the present invention is contained in an amount of 1 to 50% by weight. It is particularly preferable that the content is 5 to 20% by weight.

Examples of the above liquid crystal compound that can be used by mixing with the fluorine-containing pyrazine derivative of the present invention include the following.

4-alkyl-4'-cyanobiphenyl, 4-alkoxy-4'-cyanobiphenyl, p- (trans-4-alkylcyclohexyl) benzonitrile, trans-4
-Alkyl-1- (p-alkoxyphenyl) cyclohexyl, trans-5-alkyl-2- (p-cyanophenyl) -1,3-dioxane, trans-5-alkyl-2- (p-alkoxyphenyl) -1 , 3-dioxane, 5-alkyl-2- (p-alkoxyphenyl)
Pyrimidine, 2-alkyl-5- (p-cyanophenyl) pyrazine, 2-cyano-5- (p-alkylphenyl) pyrazine, 4- (trans-4-alkylcyclohexyl) -4'-cyanobiphenyl, 4- ( Transformer
4-alkylcyclohexyl) -4'-alkylbiphenyl, 4- (trans-4-alkylcyclohexyl)
-4 '-(trans-4-alkylcyclohexyl) biphenyl, 2-alkyl-5- (p-alkoxyphenyl) pyrazine, p-alkoxyphenyl-4-alkylcyclohexanecarboxylate, trans-4-alkylcyclohexanecarboxylate, p -Alkylphenyl benzoate, p-alkyl benzoate, p-
Cyanophenyl benzoate and p-alkyl benzoate.

The liquid crystal composition of the present invention can be prepared according to conventionally used techniques.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to examples and use examples.

Example 1 Preparation of 2-n-pentyl-5- (3-fluoro-4-ethoxyphenyl) pyrazine To a solution prepared by dissolving 5.0 g of metallic Na in 60 ml of methanol was added 24.4 g of o-fluorophenol, and then ethyl iodide was added. Three
5 g was added and the mixture was heated under reflux for 3.5 hours. After the reaction, water was added and the mixture was extracted with ether. The ether extract was washed with an aqueous Na ₂ CO ₃ solution and water and then fractionally distilled to obtain 27.0 g of 2-fluoro-ethoxybenzene (boiling point 75-80 ° C, 25 mmHg).

27.0 g of this 2-fluoro-ethoxybenzene was added to a mixed solution of 22 ml of acetic anhydride, 55 g of AlCl ₃ and 300 ml of dichloromethane at 0 to 5 ° C, and the mixture was stirred at 5 to 10 ° C for 4 hours.
After the reaction, it was poured into 100 ml of water and extracted with dichloromethane. After washing the dichloromethane extract well with water, the solvent was distilled off to give 3-fluoro-4-ethoxyacetophenone.
9.6 g (melting point 42-44 ° C) were obtained.

Add 2.1 ml of water and 6.0 g of SeO _{2 to} 50 ml of dioxane and add about 8
The mixture was heated to 0 ° C. and stirred to dissolve SeO ₂ . The above 3
9.27 g of -fluoro-4-ethoxyacetophenone was added, and the mixture was heated under reflux for 10 hours. After the reaction, Se was filtered off, and dioxane was distilled off from the filtrate under reduced pressure. After adding 150 ml of water to the obtained liquid and boiling it for 1 hour, it was cooled with ice water and the solid was collected by filtration. The obtained solid was recrystallized from acetone-water to obtain 9.8 g of crystals of 3-fluoro-4-ethoxyphenylglyoxal hydrate.

The crystals of phenylglyoxal hydrate (9.8 g) were added to 100 ml of methanol and cooled to -40 ° C. To this, 5.1 g of aminoacetamide hydrochloride was added, and a caustic soda aqueous solution (NaOH 4.2 g, water 11 ml) was added dropwise with stirring so that the temperature of the reaction solution was kept at -30 to -40 ° C. After that, about -20 ° C for 1 hour, about -10 ° C for 1 hour, and about 0 ° C for 12 hours.
After stirring for each hour, the mixture was made acidic (pH 3) with hydrochloric acid. The precipitate was collected by filtration, washed well with water and dried to give 5- (3-fluoro-
Crude crystal of 4-ethoxyphenyl) -2-pyrazinol 7.
7 g was obtained.

To 7.7 g of this crude pyrazinol crystal was added POCl ₃ 35 ml and PCl ₅
8g was added and heated at 140 ° C for 7 hours. After the reaction, it was poured into ice water and neutralized with aqueous ammonia. The pH was adjusted to 12 or higher by adding a 10% aqueous sodium hydroxide solution, and the mixture was extracted with chloroform.
The residue obtained by distilling off chloroform was subjected to silica gel column chromatography (developing solution benzene) to obtain brown crystals. Recrystallized from chloroform, melting point 103-1
2.68 g of 2-chloro-5- (3-fluoro-4-ethoxyphenyl) pyrazine at 06 ° C were obtained.

1.34 g of this chloropyrazine and 0.86 g of tetrabutylammonium bromide were dissolved in 30 ml of THF, and Grignard reagent (prepared from 2.25 g of n-pentyl bromide, 0.36 g of Mg and 10 ml of THF) was added dropwise thereto at -30 ° C. Further FeCl
_{After 3} 0.02 g was added, the mixture was stirred for 30 minutes. After washing with a saturated saline solution, THF was distilled off under reduced pressure, and the obtained solid was subjected to silica gel column chromatography (developing solution: ether-hexane) and recrystallized with methanol to give 2-n-
1.16 g of white crystals of pentyl-5- (3-fluoro-4-ethoxyphenyl) pyrazine were obtained. The measurement results of the melting point, elemental analysis value, IR spectrum and NMR spectrum of this white crystal are as follows, and it was confirmed that this white crystal was the target product.

Melting point 63 to 64 ° C Elemental analysis value Measured value (%) C; 70.60 H; 7.58 N; 9.88 Calculated value (%) C; 70.81 H; 7.34 N; 9.72 IR spectrum (KBr) 2940, 2920, 1610, 1520, 1485, 1470, 1285, 1210, 1125, 1030, 925, 870, 800 cm ^-1 NMR spectrum (CDCl ₃ ) 0.91 (3H, t, J = 3.3Hz), 1.38 (4H, m), 1.49 (3H, t, J = 3.4Hz), 1.68 to 1.84 (2H, m), 2.83 (2H, t, J = 3.8Hz), 4.16 (2H, q, J = 3.4Hz), 8.45 (1H, d, J = 1.4Hz) , 8.85 (1H, d, J = 1.4Hz) ppm Example 2 The compound of Example 2 wherein R is nC ₇ H ₁₅ , X is F and Y is C ₂ H ₅ O in the general formula (I). Were synthesized in the same manner as in Example 1.

The melting point of this compound is shown in Table 1 below. In addition, it was confirmed by IR spectrum and NM that the obtained compound was the desired product.
It was also confirmed by the R spectrum.

Example 3 Preparation of 2-n-pentyl-5- (4-fluorophenyl) pyrazine.

20.1 g of SeO ₂ was added to a mixed solution of 180 ml of dioxane and 7.4 ml of water, and heated at 60 ° C. to dissolve. To this, 25.0 g of 4-fluoroacetophenone was added, and the mixture was heated under reflux for 7 hours.
After the reaction, Se was filtered off, and the filtrate was concentrated under reduced pressure. The resulting oily substance was distilled under reduced pressure to give 16.6 g of 4-fluorophenylglyoxal (boiling point 100 to 105 ° C, 25 mmHg).
Got Then, this glyoxal was stirred with 300 ml of water to give a solid 4-fluorophenylglyoxal hydrate [IR spectrum (KBr); 3360,3210,1690,15].
95,1240,1090,1065,970 cm ^-1 ] 17.5 g was collected by filtration.

9.0 g of this 4-fluorophenylglyoxal hydrate
And 5.85 g of glycinamide hydrochloride were added to 150 ml of methanol, and the mixture was stirred at -40 ° C with caustic soda solution (NaOH).
5.1 g, water 15 ml) was added dropwise over 7 minutes. Then -3
After stirring at 0 to -40 ° C for 3 hours and at -5 to -10 ° C for 2 hours, the mixture was left standing at 0 ° C for 12 hours. Add 10 ml of hydrochloric acid to this
The pH was adjusted to 1 and the pH was adjusted to 4 by adding 4.9 g of sodium bicarbonate. Precipitated 5- (4-fluorophenyl) -1,2-dihydropyrazin-2-one solid [melting point 207-210 ° C, I
R spectrum (KBr); 360-2500,1660,1615,1510,122
5,830 cm ⁻¹ ] 6.6 g was collected by filtration and washed well with water.

Phosphorus pentachloride (8.57 g) was added to phosphorus oxychloride (23.2 ml), and the above 5- (4-fluorophenyl) -1,2 was added thereto.
-6.6 g of dihydropyrazin-2-one were added. This was heated at 90 ° C for 1 hour and then at 140 ° C for 8 hours. After cooling, it was poured into 300 ml of chloroform-ice, neutralized by adding 30 ml of ammonia water, and then 10% aqueous sodium hydroxide solution 2
00 ml was added. The insoluble material was filtered through Celite, and the filtrate was extracted with chloroform (150 ml × 3 times). The extract is dried and then concentrated to dryness, and the benzene-soluble portion is subjected to silica gel column chromatography (developing solution: benzene 30% -hexane 70%) to give 2-chloro-5-
(4-fluorophenyl) pyrazine [melting point: 101-10
3 ° C (after recrystallization from hexane), IR spectrum (KB
r); 1600,1455,1240,1155,1135,830 cm ⁻¹ ] 4.46 g was obtained.

This 2-chloro-5- (4-fluorophenyl) pyrazine (1.59 g) and tetrabrylammonium bromide (0.72 g) were added to TH.
It was dissolved in 40 ml of F, and Grineer's reagent (prepared from 3.16 g of n-pentyl bromide, 0.51 g of Mg and 25 ml of THF) was added dropwise thereto at -20 ° C. Ferric chloride at -20 ° C
0.01 g was added and stirred for 15 minutes. 50 ml of water was added, the organic layer was separated, and the aqueous layer was extracted with ether (80 ml). The organic layers were combined, washed with water (50 ml × 3 times), dried and the solvent was distilled off under reduced pressure to obtain 2.0 g of a black solid. This solid was subjected to silica gel column chromatography (developing solution: ether 1-2% -hexane), and the obtained crystals were recrystallized twice from methanol to give 2-n-pentyl-5-.
0.41 g of white crystals of (4-fluorophenyl) pyrazine were obtained. The melting point of the white crystal was measured by elemental analysis and IR spectrum as follows, and it was confirmed that the white crystal was a target.

Melting point 54-56 ° C Elemental analysis value Measured value (%) C; 73.58 H; 7.13 N; 11.68 Calculated value (%) C; 73.74 H; 7.01 N; 11.47 IR spectrum (KBr) 2950, 2920, 2850, 1600, 1480, 1240, 1155, 1045, 1015, 840 cm ^-1 Example 4 Preparation of 2-pentyloxy-5- (4-fluorophenyl) pyrazine 2-chloro-5- (4-fluorophenyl) pyrazine (of Example 3) An intermediate substance (obtained in the same manner as in Example 3) 0.80 g was dissolved in 20 ml of THF, and 7.7 ml of Na pentyl oxide solution (prepared from 10 ml of n-pentyl alcohol and 0.23 g of Na) was added to the solution. Stir at room temperature for 4 hours. 50 ml of water was added to the reaction solution and extracted with chloroform. After the chloroform extract was dried, the solvent was distilled off under reduced pressure and the obtained solid was subjected to silica gel column chromatography (after development: ether-hexane). The obtained crystals were recrystallized from hexane to obtain 0.54 g of white crystals of 2-pentyloxy-5- (4-fluorophenyl) pyrazine. The measurement results of the melting point, elemental analysis value and IR spectrum of this white crystal are as follows, and it was confirmed that this white crystal was the target product.

Melting point 61-63 ° C Elemental analysis value Actual value (%) C; 69.50 H; 6.72 N; 10.70 Calculated value (%) C; 69.21 H; 6.58 N; 10.76 IR spectrum (KBr) 2950,1460,1345,1295, 1230, 1170, 840 cm ⁻¹ Examples 5 to 13 The compounds of Examples 5 to 13 in which R, X and Y in the general formula (I) are groups shown in Table 1 below are prepared in the same manner as in Example 3. Each was synthesized.

The melting points and clearing points of these compounds are shown in Table 1 below. Further, it was confirmed by IR spectrum and NMR spectrum that the obtained compound was the desired product.

Use Example 1 Formulation Trans-4-propyl-1- (4-cyanophenyl) cyclohexane 24 wt% trans-4-pentyl-1- (4-cyanophenyl) cyclohexane 36 wt% trans-4-heptyl-1- (4-Cyanophenyl) cyclohexane 25% by weight 4-Cyano-4 '-(trans-4-pentylcyclohexyl) biphenyl 15% by weight The mixture (mother liquid crystal) having the above composition has a clearing point of 71.5 ° C. When it was sealed in a TN cell with a cell thickness of 9 μm (3
0 ° C) threshold voltage V ₉₀ = 1.73V and saturation voltage V ₁₀ = 2.48
It was V (30 ° C). That is, the steepness γ (V ₁₀ / V ₉₀ ) of the voltage-transmittance characteristic was 1.434.

90 parts by weight of this mother liquid crystal was treated with 2-heptyloxy-5- (4-trifluoromethylphenyl) obtained in Example 12.
10 parts by weight of pyrazine was mixed to obtain a liquid crystal composition of the present invention. This composition had a clearing point of 68 ° C, and the threshold voltage V ₉₀ and the saturation voltage V ₁₀ were measured in the same manner as in the case of the above mother liquid crystals. The threshold voltage V ₉₀ = 1.61 V and the saturation voltage V ₁₀ = 2.
It was 29V. That is, the steepness γ = V ₁₀ / V ₉₀ = 1.422.

In addition, 80 parts by weight of the mother liquid crystal obtained in Example 3
Pentyl-5- (4-fluorophenyl) pyrazine 20
By mixing parts by weight, a liquid crystal composition of the present invention was obtained. This composition has a clearing point of 49 ° C., and when the threshold voltage V ₉₀ and the saturation voltage V ₁₀ were measured in the same manner as in the case of the above mother liquid crystals,
The threshold voltage V _{90 was} 1.42V and the saturation voltage V ₁₀ was 2.02V. That is, the steepness γ = V ₁₀ / V ₉₀ = 1.423.

〔The invention's effect〕

The fluorine-containing pyrazine derivative of the present invention is mainly used as a blending component of a liquid crystal composition. When used as a liquid crystal composition, it improves the stability of the liquid crystal composition against heat, light, moisture, etc. The voltage can be lowered and the voltage-transmittance characteristic can be sharpened.

Claims (2)

[Claims] 1. A general formula (I) (In the formula, R represents an aliphatic alkyl group having 1 to 12 carbon atoms or an aliphatic alkoxy group having 1 to 12 carbon atoms, X represents F or H, and Y is an aliphatic alkoxy group having 1 to 10 carbon atoms. ,
Indicates F or CF ₃ . However, X is H and Y has 1 to 1 carbon atoms.
Excluding the case of 10 aliphatic alkoxy groups. ) A fluorine-containing pyrazine derivative represented by: 2. General formula (I) (In the formula, R represents an aliphatic alkyl group having 1 to 12 carbon atoms or an aliphatic alkoxy group having 1 to 12 carbon atoms, X represents F or H, and Y is an aliphatic alkoxy group having 1 to 10 carbon atoms. ,
Indicates F or CF ₃ . However, X is H and Y has 1 to 1 carbon atoms.
Excluding the case of 10 aliphatic alkoxy groups. ) A liquid crystal composition comprising at least one fluorine-containing pyrazine derivative represented by: