JPH0689331B2 - Liquid crystal mixture - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to novel liquid crystal mixtures and novel compounds used in these mixtures, as well as the preparation of the novel compounds and mixtures,
And its use for electro-optical purposes.

Recently, liquid crystals have gained considerable importance as dielectrics in display devices because the optoelectronic properties of such materials can be affected by the applied voltage. Liquid crystal-based electro-optical devices are well known to those skilled in the art, and they have various effects such as dynamic scattering, aligned phase deformation (DA).
P type), Schadt-Helfrich
effect) (rotating cell), guest / host effect (quest / h
ost effect) and also cholesteric-nematic (chol
esteric-nematic) phase transition (phase change effect).

Liquid crystals have to fulfill many needs in order to be suitable as dielectrics for electro-optical displays. For example, the liquid crystal should have good chemical stability, low viscosity and short response time, should show good contrast, and within the entire temperature range of operating the liquid crystal, nematic or cholesteric mesophase. Should have Other properties, such as dielectric anisotropy, optical anisotropy, electrical conductivity, etc., must satisfy different conditions depending on the cell used.

In general, it is not possible to achieve all the desired properties and, to some extent, conflicting properties with a single compound, so that by mixing with several ingredients the properties for a particular application can be improved. Most attempts are made to optimize. However, in this case, it is important that the components do not chemically react with each other and have good miscibility with each other. Furthermore,
The resulting mixture should not have a smectic mesophase, at least at the temperature at which the liquid crystal cell is operated.

Liquid crystal mixtures containing pyrimidine derivatives are already known. In particular, mixtures containing cyano-substituted pyrimidines are known, with which compounds nematic or cholesteric mixtures can easily be prepared. However, pyrimidine derivatives having non-polar end groups have heretofore been rarely used and these derivatives often induce smectic mesophases in mixtures with other liquid crystals.

This time, the general formula Where Y represents nitrogen and Z represents CH, or Z represents nitrogen and Y represents CH; n is the number 0
Or ring 2; rings A and B represent 1,4-phenylene or trans-1,4-cyclohexylene; R ¹ represents p-alkylphenyl, trans-4-alkylcyclohexyl, or n represents number 2. To the extent that also represents alkyl; and the alkyl residue in R ² and R ¹ represents straight-chain C ₁ -C ₁₀ -alkyl and at least one compound of the general formula In the formula, R ³ represents a straight-chain C ₁ -C ₁₀ -alkyl; R ⁴ represents alkyl, alkoxy, p-alkylphenyl, p-alkoxyphenyl, trans-4-alkylcyclohexyl,
4'-alkyl-4-biphenylyl, p- (trans-4-alkylcyclohexyl) phenyl, 2- (trans-4-alkylcyclohexyl) ethyl, p- [2- (trans-4-
Alkylcyclohexyl) ethyl] phenyl or 2-
Represents a [p- (trans-4-alkylcyclohexyl) phenyl] ethyl; the alkyl residue in R ⁴ represents a linear C ₁ -C ₁₀ -alkyl and the alkoxy residue in R ⁴ represents a linear A compound of the formula C ₁ -C ₁₀ -alkoxy or a general formula Wherein ring C represents 1,4-phenylene or trans-1,4-cyclohexylene; R ⁵ represents linear C ₁ -C ₁₀ -alkyl; and R ⁶ represents linear C ₁ To C ₁₀ -alkyl or linear C _{1 to} C ₁₀ -alkoxy, the liquid crystal mixtures containing at least one of the compounds of are relatively large nematic (or cholesteric by the addition of optically active compounds) mesophases. (Mesophases), good melting behavior, relatively low viscosity, good chemical and photochemical stability and especially the elastic constants K ₃₃ [bend] and K
It has been found to have a favorable ratio of ₁₁ [splay], a steep slope transmission curve and good multiplexibility.

The compounds of formula I in which n represents the number 2 have improved solubility, and R ¹ is p-alkylphenyl or trans-4-
The compounds of the formula I which represent alkylcyclohexyl have a particularly high clearing point and at the same time a relatively low value of K ₃₃ / K ₁₁ .

The term "linear C ₁ -C ₁₀ -alkyl" includes the group ethyl,
Includes ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl and decyl and includes "linear
C ₁ -C ₁₀ - Arukoshiru "term in the groups methoxy, ethoxy, propyloxy, butyloxy, pentyloxy,
Hexyloxy, heptyloxy, octyloxy, nonyloxy and decyloxy are included.

The mixtures according to the invention preferably contain a total of about 3 to 70% by weight, in particular about 20 to 50% by weight, of compounds of the formulas I and II. This mixture preferably contains at least one compound of formula II and at least one compound of formula III.
The amount of the compound of formula I in the mixture according to the invention is preferably about 1-40% by weight, in particular about 3-20% by weight.

Preferred compounds of formula I are those in which n represents the number 0, rings A and B represent 1,4-phenylene, and R ¹ is trans-4-
It represents alkylcyclohexyl. Furthermore, n
Compounds of formula I in which R represents the number 2 and R ¹ is alkyl are preferred. The alkyl residue in R ² and / or R ¹ preferably represents straight-chain C ₃ -C ₇ -alkyl.

Preferred compounds of formula II used are those in which R ⁴ is alkyl, alkoxy, trans-4-alkylcyclohexyl, p- (trans-4-alkylcyclohexyl) phenyl or 2-
Compounds representing [p- (trans-4-alkylcyclohexyl) phenyl] ethyl, especially compounds in which R ⁴ represents alkoxy. R ³ preferably represents straight-chain C ₃ -C ₇ -alkyl. Furthermore, the alkyl residue in R ⁴ preferably represents linear C ₁ -C ₇ alkyl, and the alkoxy residue in R ⁴ preferably represents linear C ₁ -C ₆ -alkoxy.

In formula III, ring C preferably represents trans-1,4-cyclohexylene. R ⁵ preferably represents C ₂ -C ₇ -alkyl. Preferred residues R ⁶ are linear C ₁ -C ₇ -alkyl and especially linear C ₁ -C ₆ -alkoxy.

The mixtures according to the invention have additional compounds, such as Schiff bases, azobenzenes, azoxybenzenes, cyclohexanecarboxylic acid cyclohexyl esters, biphenyls, terphenyls, phenylcyclohexanes, phenylpyrimidines, cyclohexylphenylpyrimidines. , A phenyl dioxane, and the like. Such compounds are known to those skilled in the art, and many of these are commercially available.

The mixtures according to the invention preferably contain, in addition to the compounds of the formulas I to III, one or more compounds of the general formula: Wherein ring C represents 1,4-phenylene or trans-1,4-cyclohexylene; R ⁷ and R ⁸ represent linear C ₁ -C ₇ -alkyl; and R ⁹ represents linear Represents C ₁ -C ₇ -alkyl or straight-chain C ₁ -C ₆ -alkoxy.

In particular, the positive anisotropy of the permittivity (Δε = ε _|| −ε _⊥ > 0, ε _|| represents the permittivity along the vertical axis of the molecule, and ε _⊥ Represents a dielectric constant perpendicular thereto) according to the invention preferably contains, in addition to the compounds of the formulas I to III, at least one compound of the formulas IV to IX.

Furthermore, the mixtures according to the invention can contain suitable optically active compounds (for example optically active biphenyls) and / or dichroic colorants (for example azo, azoxy or anthraquinone colorants). The amount of such compound depends on the solubility and the desired pitch, color,
It is determined by absorption or the like. Preferably the amount of optically active compound is up to about 4% by weight and the amount of dichroic coloring material is up to about 10% by weight.

The preparation of the mixtures according to the invention can be carried out in a manner known per se, for example by heating the mixture of the components to a temperature slightly above the clearing point and then cooling the mixture.

The production of electro-optical devices can also be carried out in a manner known per se, for example by emptying a suitable cell and introducing the mixture into this empty cell.

The compounds of formulas II-XI are known or are homologues of known compounds.

Formula I, wherein Y represents nitrogen and Z represents CH, or Z
Represents nitrogen and Y represents CH; n represents the number 0 or 2; rings A and B represent 1,4-phenylene or trans 1,4-cyclohexylene; R ¹ is p-alkylphenyl , Trans-4-alkylcyclohexyl or n
Also represents alkyl, as long as represents the number 2; and the alkyl residue at R ² and R ¹ is linear C ₁
The compounds represented by ˜C ₁₀ -alkyl are new and also form an object of the invention.

These are according to the invention a) to prepare compounds of the formula I in which Y represents nitrogen and Z represents CH. Compound of the general formula in the presence of a base Wherein R ¹ , R ² , n and rings A and B have the meanings given above,
And R ¹⁰ represents alkyl, or b) is reacted with an acid addition salt of a compound of formula b) to prepare a compound of formula I in which Z represents nitrogen and Y represents CH. Compound of the general formula in the presence of a base Wherein R ¹ , R ² , n and rings A and B have the meanings given above,
And R ¹⁰ represents alkyl, or by reacting with an acid addition salt of a compound of c) or c) to prepare a compound of formula I in which n is 2 Wherein R ² , Y, Z and rings A and B have the meanings given above, and R ¹ represents p-alkylphenyl, trans-4-alkylcyclohexyl or alkyl. Therefore, it can be manufactured.

The reaction of a compound of formula XIII or XV with an acid addition salt of a compound of formula XIV or XVI is advantageously carried out in water or an organic solvent such as an alcohol, eg methanol, ethanol, ethylene glycol etc. in the presence of a base. Methanol and ethanol are the preferred solvents. Acid addition salts of compounds of formulas XIV and XVI include hydrochloric acid, hydrobromic acid,
It may be a salt formed by sulfuric acid, p-toluenesulfonic acid or the like. Preferably the hydrochloride salt of a compound of formula XIV and XVI is used. Alkali metal alcoholates, especially sodium methylate and sodium ethylate, are preferred bases. R ¹⁰ advantageously includes alkyl radicals having 1 to 5 carbon atoms, such as methyl, ethyl, propyl, isopropyl, etc., preferably methyl and ethyl. The temperature and pressure at which this reaction is carried out are not critical. The reaction is advantageously carried out at atmospheric pressure and a temperature between room temperature and the reflux temperature of the reaction mixture, preferably room temperature.

Catalytic hydrogenation of a compound of formula XVII can be carried out in a manner known per se using conventional hydrogenation catalysts such as palladium, platinum, Raney nickel etc. (optionally supported on an inert carrier material, eg carbon). . Palladium and platinum are the preferred catalysts. As the solvent, inert organic solvents such as saturated alcohols, ethers, esters, carboxylic acids, aromatic hydrocarbons and the like such as ethanol, dioxane, ethyl acetate, glacial acetic acid and toluene can be used. The temperature and pressure at which catalytic hydrogenation is carried out are not critical. This catalytic hydrogenation is advantageously carried out at temperatures between room temperature and the boiling point of the reaction mixture and pressures of about 1 to 5 atmospheres.

The compounds of the formulas XIII and XVI in which n represents the number 0 and the compounds of the formulas XIV and XV are either known or homologues of the known compounds.

Compounds of formulas XIII and XVI in which n represents the number 2 and formula XVI
The compounds of I are new. These can be produced according to a method known per se, for example, according to the following reaction schemes 1 and 2; in the reaction scheme, R ¹ , R ² , R ¹⁰ and rings A and B are as described above. Has meaning.

The compound of formula XII is also novel. These can be prepared in a similar manner to the compound of formula I.

The compounds of formula XXVII are also novel. These can be obtained in a manner known per se from the corresponding anilines, for example by reaction with triethylamine and carbon disulfide, followed by reaction of the ammonium salt with triethylamine and ethyl chloroformate.

The mixtures according to the invention are explained in more detail by means of the following mixture examples. V ₁₀ and V ₅₀ represent the voltage for 10% or 50% transmission (in a rotating cell with a tilt angle of 0 °), p ₀ = V ₅₀ -V ₁₀ ) / V ₁₀ is a measure for the steep slope of the transmission curve. , K ₁₁ (spray) and K ₃₃ (bend) are elastic constants, η represents the viscosity (bulk viscosity), and Δ
n represents optical anisotropy. Unless otherwise specified, measurement is 22 ℃
I went there.

Basic mixture A p- (trans-4-pentylcyclohexyl) benzonitrile 16.9% by weight, 1-ethoxy-4- (trans-4-propylcyclohexyl) benzene 3.0% by weight, p- (5-butyl-2-pyrimidinyl) benzo Nitrile 8.6% by weight, p- (5-heptyl-2-pyrimidinyl) benzonitrile 5.0
% By weight, trans-4-butylcyclohexanecarboxylic acid p-ethoxyphenyl ester 10.1% by weight, trans-4-pentylcyclohexanecarboxylic acid p-methoxyphenyl ester 9.2% by weight, trans-4-pentylcyclohexanecarboxylic acid p-propoxy Phenyl ester 15.0% by weight, 1-ethyl-4- [2- (trans-4-propylcyclohexyl) ethyl] benzene 7.0% by weight, 4 '-(trans-4-pentylcyclohexyl) -4-cyanobiphenyl 6.0% by weight, 6.1% by weight of p- [5-trans-4-ethylcyclohexyl) -2-pyrimidinyl] benzonitrile, 1- [2- (trans-4-butylcyclohexyl) ethyl]
-4- (trans-4-pentylcyclohexyl) benzene
13.1% by weight; melting point -20 ° C or lower, clearing point 72 ° C, nematic: V ₁₀ = 1.71
V, p ₀ = 0.128; η = 27 cp, Δn = 0.119, k ₃₃ = k ₁₁ = 1.1
9.

Mixture Example 1 90% by weight of basic mixture A, 5- (trans-4-pentylcyclohexyl) -2- [2-
(Trans-4-propylcyclohexyl) ethyl] pyrimidine 10% by weight; melting point -20 ° C or lower, clearing point 78 ° C, nematic; V ₁₀ = 1.76
V, p ₀ = 0.127; = 30 cp, Δn = 0.114, k ₃₃ / k ₁₁ = 1.15.

Mixture Example 2 90% by weight of basic mixture A, 10% by weight of 5- (p-butylphenyl) -2- [2- (trans-4-propylcyclohexyl) ethyl] pyrimidine; melting point -20 ° C, clearing point 76 ° C, nematic; V ₁₀ = 1.72V, p ₀
= 0.123, η = ₃₃ cp, Δn = 0.119, k ₃₃ / k ₁₁ = 1.17.

Mixture Example 3 90% by weight of basic mixture A, 5- (p-butylphenyl) -2- (p-propylphenethyl)
Pyrimidine 10% by weight; melting point -20 ° C, clearing point 76 ° C, nematic: V ₁₀ = 1.78V, p ₀
= 0.124; η = 31 cp, Δn = 0.123, k ₃₃ / k ₁₁ = 1.15.

Mixture Example 4 90% by weight of basic mixture A, 10% by weight of 5- (p-butylphenyl) -2- (p-pentylphenyl) pyrimidine; melting point about 0 ° C, clearing point 82 ° C, nematic; V ₁₀ = 1.81V, p ₀
= 0.118; η = 34 cp, Δn = 0.130, k ₃₃ / k ₁₁ = 0.97.

The preparation of compounds of formula I and XII is described in more detail by the examples below. C represents a crystalline phase, S represents a smectic phase, S _A represents a smectic A phase, S _B represents a smectic B phase, N represents a nematic phase,
And I represents the isotropic phase.

Example 1 4.3 g of 5- (p-butylphenyl) -2- [2E- (trans-4-propylcyclohexyl) vinyl] pyrimidine was dissolved in 125 ml of toluene, and this solution was added to palladium / carbon (10
%) 0.6 g and hydrogenated at room temperature and atmospheric pressure until the uptake of hydrogen ceased. After separating the crystals and concentrating the liquid, the resulting 5- (p-butylphenyl) -2- [2- (trans-4-propylcyclohexyl) ethyl] pyrimidine was recrystallized from hexane. Yield 3.5 g; mp (CS _A) 101.
0 ° C, S _A -N 104.8 ° C, clearing point (NI) 117.8 ° C.

5- (p-Butylphenyl) -2- [2E used as starting material
-(Trans-4-propylcyclohexyl) vinyl] pyrimidine was prepared as follows: a) A sodium methylate solution prepared from 6.2 g of sodium and 150 ml of methanol under nitrogen atmosphere under 2- (p-butylphenyl) -3. -Ethoxyacrolein (Z.Nata
rforsch.) 33b , 433 (1978)] 34.
The mixture was added dropwise to a mixture of 9 g, 2-hydroxyacetamidine hydrochloride (18.2 g) and methanol (200 ml). The suspension obtained is 1
It was left for days, then treated with 7 ml of concentrated hydrochloric acid and suctioned off. The liquid was concentrated and the residue was dissolved in diethyl ether. The solution was washed neutral with water, dried over sodium sulfate, passed and concentrated. The residue was chromatographed on 400 g of silica gel with toluene / acetone (4: 1 by volume) to give 5- (p-butylphenyl).
24.0 g of 2-pyridinecarbinol were obtained; melting point 67.2-69.
3 ℃, purity 98.9%.

b) 5- (p-butylphenyl) in dry dichloromethane
A solution of 24.0 g of 2-pyrimidinecarbinol and 28.8 g of triphenylphosphine was treated portionwise with 41.5 g of tetrabromomethane at -30 ° C under a nitrogen atmosphere. The reaction mixture was stirred at −30 ° C. for a further 30 minutes then allowed to warm to room temperature overnight. The mixture is concentrated and the residue is treated with 300 g of silica gel.
Chromatography above with hexane / ethyl acetate (4: 1 by volume). 25.0 g of yellowish 2- (bromoethyl) -5- (p-butylphenyl) pyrimidine having a melting point of 85.0-85.2 ° C. was obtained, which was immediately used in the next step.

c) 2- (Bromomethyl) -5- (p- in 350 ml of toluene
Butylphenyl) pyrimidine 25.0 g solution in toluene 250
drop-wise to a solution of 25.8 g of triphenylphosphine in ml,
The reaction mixture was stirred at room temperature for 3 days. Precipitated pale yellowish [5- (p-butylphenyl) -2-pyrimidinyl]
Methyl-triphenylphosphonium bromide was absorbed, washed with toluene and dried. Yield 41.0
g, melting point 176-178 ° C.

d) A solution of 13.6 g of [5-p-butylphenyl) -2-pyrimidinyl] methyl-triphenylphosphonium bromide in 125 ml of dichloromethane at 0 ° C. under a nitrogen atmosphere.
The solution was treated dropwise with sodium methylate solution prepared from 0.55 g of sodium and 10 ml of methanol and the mixture was stirred for a further 15 minutes. Then the mixture is 25 ml of dichloromethane
A solution of 3.1 g trans-4-propylcyclohexanecarboxaldehyde in was treated dropwise at 0 ° C. and the resulting mixture was stirred at 0 ° C. for another hour and at room temperature overnight. Then the reaction mixture was passed, the solution was washed with sodium hydrogencarbonate solution and water, dried over sodium sulphate and concentrated. The residue was chromatographed on 150 g of silica gel with hexane / ethyl acetate (9: 1 by volume) and recrystallized once from hexane to give 5- (p-butylphenyl) -2- [2E- (trans- 4-Propylcyclohexyl) vinyl] pyrimidine (4.4 g) was obtained. Melting point (CN) 124
℃, clearing point (NI) 203.5 ℃.

In a similar manner, the following compound was prepared: 5- (p-butylphenyl) -2- [2- (trans-4-pentylcyclohexyl) ethyl] pyrimidine; melting point (C-
S _A ) 85 ° C, S _A -N112.2 ° C, Clearing point (NI) 121 ° C, 5- (p-butylphenyl) -2- (p-propylphenethyl)
Pyrimidine; melting point (CS _A ) 89 ° C, S _A -N109.5 ° C, clearing point (NI) 109.5 ° C, 5- (trans-4-pentylcyclohexyl) -2- (p-butylphenethyl) pyrimidine; melting point (CS _B ) 51 ° C, clearing point (S _B -I) 140.5 ° C, 5- (trans-4-pentylcyclohexyl) -2- [2-
(Trans-4-propylcyclohexyl) ethyl] pyrimidine; melting point (CS _B ) 82.5 ° C, clearing point (S _B -I) 15
0.5 ° C, 5-butyl-2- [2- (trans-4-propylcyclohexyl) ethyl] pyrimidine; melting point (CI) 22.5 ° C, 5-butyl-2- (p-butoxyphenethyl) pyrimidine; melting point (CI ) 43 ° C.

Example 2 Crude 3-methoxy-2- [2- (trans-4-pentylcyclohexyl) ethyl] acrolein in 60 ml of methanol
A solution of 2.5 g and p-propylbenzamidine hydrochloride 2.0 g was treated dropwise with sodium methylate prepared from 0.5 g sodium and 10 ml methanol and the resulting suspension was stirred overnight at room temperature. The mixture was then adjusted to a pH value of 5 by adding concentrated hydrochloric acid. The precipitate was separated and dissolved in dichloromethane. The solution was washed with water to neutrality, dried over sodium sulfate and concentrated. The resulting 5- [2- (trans-4-pentylcyclohexyl) ethyl] -2- (p-propylphenyl) pyrimidine (2.3 g) was purified over 40 g silica gel with hexane / ethyl acetate (19: Chromatography (1 volume ratio) and then recrystallized from hexane. Yield 2.1g; melting point (CS) 64
SS dislocation and clearing point (S _A -I) 164 at ℃, 76 ℃ and 103 ℃
° C.

3-methoxy-2- [2- (trans-
4-Pentylcyclohexyl) ethyl] acrolein was prepared as follows: a) (trans-4-
A solution of 76.1 g of pentylcyclohexyl) acetyl chloride was added dropwise with stirring to the suspension of 12.5 g of lithium aluminum hydride in 750 ml of anhydrous diethyl ether, while preventing the reaction mixture from boiling too strongly. The mixture is stirred for a further 2 hours, then first 30 ml of acetone and then 75 ml of water are added dropwise. Then the reaction mixture was acidified with 3N hydrochloric acid, the organic phase was separated and the aqueous phase was back-extracted with 200 ml of diethyl ether. The combined organic phase is washed with water to neutral,
Dry over sodium sulphate, concentrate and use as a luteal fluid
2- (trans-4-pentylcyclohexyl) ethanol
62.6 g was obtained.

b) N-bromosuccinimide (50.1 g) was stirred and cooled in an ice bath within 30 minutes to ensure that the temperature did not rise above 30 ° C. and 2- (trans-4-pentylcyclohexyl) in 160 ml dichloromethane. ) Ethanol 49.6 g and triphenylphosphine 71.9 g were added in portions to a solution. The mixture is then stirred for a further 3 hours, then the suspension is suctioned off and the liquid is concentrated on a rotary evaporator. The still warm residue (2 phases) was slowly treated with 200 ml of hexane with shaking. The fine, granular orange precipitate was aspirated off and rinsed several times with hexane. The liquid was concentrated and the resulting crude trans-1- (2-bromoethyl) -4-pentylcyclohexane was distilled under vacuum. Yield: Main distillate 53.3g; Boiling point 93-99 ℃
/ About 0.1 Torr; Purity 98.2%.

c) Sodium cyanide 9.77 g, sodium iodide 0.2
A mixture of 1 g and 175 ml of dimethylsulfoxide was heated to 98 ° C. The heating was then stopped and the mixture was treated dropwise with 45.3 g of trans-1- (2-bromoethyl) -4-pentylcyclohexane within 20 minutes, whereby the temperature rose to 115 ° C. The reaction mixture was kept at 100 ° C. for a further hour, then allowed to cool, poured into 600 ml of ice water and extracted 3 times with 200 ml of diethyl ether each time. The extract was washed 3 times with 150 ml of water each time, dried over sodium sulfate and concentrated to give 3- (trans-4-pentylcyclohexyl) propionitrile 36.2 g as a brown oil.
was gotten.

d) A solution of 36.1 g of 3- (trans-4-pentylcyclohexyl) propionitrile in 750 ml of dry toluene,
Within 60 minutes at 0 ° C. under nitrogen, it was treated dropwise with 225 ml of a 20% (vol.%) Solution of diisobutylaluminium hydride in toluene. The mixture was further stirred at 0 ° C. for 1 hour and then for 3 hours while warming to room temperature. The reaction mixture is then charged to 0.
It was poured into 5N sulfuric acid 2.5 and extracted 3 times with 1 each of diethyl ether. The extract was washed with saturated sodium hydrogen carbonate solution and water, dried over sodium sulfate, concentrated and crude
35.8 g of 3- (trans-4-pentylcyclohexyl) propanal was obtained.

e) In the same manner as the reaction with trans-4-pentylcyclohexanecarboxaldehyde described in Z. Naturforschung 34b , 1535 (1979), 3- (trans- 4-pentylcyclohexyl) propanal tert-
Reaction with methoxymethyl-triphenylphosphonium chloride and potassium tert-butyrate in butyl methyl ether yields 1-methoxy-4- (trans-4-pentylcyclohexyl) -1-butene, which is prepared in methyl orthoformate. Was converted to [2- (trans-4-pentylcyclohexyl) ethyl] malondialdehyde tetramethylacetal with boron trifluoride etherate and heated with 1 equivalent of water and a catalytic amount of toluenesulfonic acid. So finally, the crude
3-Methoxy-2- [2-trans-4-pentylcyclohexyl) ethyl] acrolein was obtained.

Example 3 A solution of 3.0 g of 2- (p-butylphenyl) -3-ethoxyacrolein and 3.8 g of p- (trans-4-propylcyclohexyl) benzamidine hydrochloride in 60 ml of methanol is prepared from 0.6 g of sodium and 10 ml of methanol. The resulting suspension was stirred dropwise at room temperature overnight. Then the mixture is brought to pH by adding concentrated hydrochloric acid.
The value was adjusted to 5. The precipitate was separated and dissolved in dichloromethane. The solution was washed with water to neutrality, dried over sodium sulfate and concentrated. For purification, the resulting 5- (p-butylphenyl) -2- [p- (trans-4-propylcyclohexyl) phenyl] pyrimidine is chromatographed on 30 g of silica gel with toluene and then with acetic acid. Recrystallized from ethyl. Yield: 3.3g; melting point (CS) 150 ℃, S-N174 ℃, clearing point (NI) 3
32 ° C.

In a similar manner the following compounds were prepared: 5- (p-butylphenyl) -2- (p-hexylphenyl) pyrimidine; melting point (CS _A ) 97.8 ° C., clearing point (S _A I) 1
83 ° C, 5- (p-butylphenyl) -2- (p-heptylphenyl) pyrimidine; melting point (CS _A ) 98.8 ° C, clearing point (S _A -I) 1
82 ° C, 5- (p-butylphenyl) -2- (p-pentylphenyl) pyrimidine; melting point (CS _A ) 106.0 ° C, clearing point (S _A -I)
184.7 ° C.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G09F 9/00 F 7610-5G

Claims (8)

[Claims] 1. A general formula Wherein Y represents nitrogen and Z represents CH, or Z represents nitrogen and Y represents CH; n represents the number 0 or 2; rings A and B are 1,4-phenylene or trans -1,4-cyclohexylene; R ¹ represents p-alkylphenyl, trans-4-alkylcyclohexyl or, as long as n represents the number 2, also alkyl; and alkyl in R ² and R ¹ . The residue represents a straight-chain C ₁ -C ₁₀ -alkyl, at least one of the compounds and the general formula In the formula, R ³ represents linear C ₁ -C ₁₀ -alkyl; R ⁴ is alkyl, alkoxy, p-alkylphenyl, p-alkoxyphenyl, trans-4-alkylcyclohexyl, 4′-alkyl. -4-biphenylyl, p- (trans-4-alkylcyclohexyl) phenyl, 2- (trans-4-alkylcyclohexyl) ethyl, p-
Represents [2- (trans-4-alkylcyclohexyl) ethyl] phenyl or 2- [p- (trans-4-alkylcyclohexyl) phenyl] ethyl; the alkyl residue in R ⁴ is linear C ₁ -C ₁₀ Represents an alkyl and the alkoxy residue in R ⁴ is a straight chain C ₁ -C
A compound or a general formula of ₁₀ -alkoxy Wherein ring C represents 1,4-phenylene or trans-1,4-cyclohexylene; R ⁵ represents linear C ₁ -C ₁₀ -alkyl; and R ⁶ represents linear C ₁ -C ₁₀ - alkyl or linear C ₁ -C ₁₀ - represents an alkoxy, a liquid crystal mixture containing at least one compound of the. 2. 1-40% by weight of a compound of formula I and formula II and
A liquid crystal mixture according to claim 1 which contains 3-70% by weight of the compound III. 3. A compound of formula I 3-20% by weight and a compound of formula II and
A liquid crystal mixture according to claim 1 containing 20 to 50% by weight of the compound of III. 4. Any of claims 1 to 3 in which n represents the number 0, rings A and B represent 1,4-phenylene, and R ¹ represents alkyl or trans-4-alkylcyclohexyl. The liquid crystal mixture according to claim 1. 5. An alkyl residue in R ² and R ¹ is linear.
C ₃ -C ₇ - liquid crystal mixture as claimed in any one of claims first through fourth term represents an alkyl. 6. R ⁴ is alkyl, alkoxy, trans-4
A liquid crystal according to any one of claims 1 to 5, which represents -alkylcyclohexyl, p- (trans-4-alkylcyclohexyl) phenyl or 2- [p- (trans-4-alkylcyclohexyl) phenyl] ethyl. blend. 7. A liquid crystal mixture according to any one of claims 1 to 5 in which R ⁴ represents alkoxy. 8. A method according to claim 1, wherein ring C represents trans-1,4-cyclohexylene and R ⁶ represents straight-chain C ₁ -C ₆ -alkoxy. Liquid crystal mixture.