DE4004281A1 - MESOGENIC AND PROMESOUS NONTRACEMIC CHIRAL COMPOUNDS - Google Patents

Abstract

Mesogenic and pro-mesogenic non-racemic chiral compounds of the general formula I <IMAGE> wherein the symbols have the meanings shown in claim 1, are used in liquid crystalline mixtures. The addition of the compounds in even small quantities produces the induction of twisted liquid crystalline phases such as N* or smectic C*.

Description

The invention is defined in claims 1, 2, 3 and 4 and relates to mesogenic and promesogenic nonracemic chiral Compounds for crystalline-liquid mixtures, process for Production and use of the above compounds in of optoelectronics and thermography.

Liquid crystals are already available for a larger number of applications known. A special role is played by such Types of liquid crystals that have a twisted structure, in particular the twisted nematic phases (cholesteric liquid crystals) as well as twisted smectic C phases (C * phases), both in chiral compounds occurrence. Both twisted nematic and C * phases can be used in optoelectronic displays (E. Kaneko: Liquid Crystal TV Displays: Principles and Applications of Liquid Crystal Displays, KTK Scientific Publ. Tokyo 1987).

Furthermore, twisted nematic compounds (cholesterol Compounds) were used for thermography (H. Kelker, R. Hatz; Handbook of Liquid Crystals, Verlag Chemie Weinheim 1980).

Depending on the desired application, in turn, connections needed with very specific properties. There are no single substances, which are even close to the practical Requirements regarding the temperature range of the mesophases, optical, electro-optical, electrical and rheological Meet properties. Therefore, in practice, exclusively Mixtures used up to about 15 different components can exist. The properties of the mixtures depend from the properties of the components used. To the Mixtures specific requirements to be able to adapt optimally needed you have a large number of individual components with the most diverse Properties. To change connections with To be able to find properties, new substance classes are constantly being developed involved in liquid crystal chemistry. In particular There is still a great need in the field of chiral substances  different on mesogenic and promesogenic compounds Molecular structure.

It is already known (D.M. Walba, H.A. Razawi US 46 95 650), 4-Formylbenzoic acid (4-alkyloxyphenyl ester) with 2-alkyl to convert ethin-1-lithium into a prochiral ketone with Help of stoichiometric amounts of alpine-borane to the corresponding chiral hydroxy compounds is reduced, which then be hydrogenated in another synthesis step yet have to. This method is very limited. The enantioselective reduction of prochiral arylalkyl ketones II with BH₃ · THF in the presence of the catalyst IIIa was from Corey et al (J. Am. Chem. Soc., 109, 7925 (1987)). The prochiral However, ketones are after that described by Corey Method due to their low solubility in THF not effectively reducible.

The object of the invention is new mesogenic and promesogenic nonracemic chiral compounds for mixtures to Application in optoelectronic components as well as for thermography.

According to the invention, mesogenic and promesogenic are nonracemic chiral compounds of the general formula

in which
p, q, r, s, t, u = 0 or 1
p + q + r + s = 1 to 3 and t + u = 1 or 2
R¹ = R, RO, RCOO, ROOC, halogen, NC, SCN, F₃C, H
R = R '

-OOC- (with Z₁ subst.) 1,4-phenylene-Z²
R⁴ = alkyl chain having 1 to 18 carbon atoms
A¹, A², A³, A⁴ (same or different) = 1,4-phenylene; 1,4-cyclohexylene; wherein one of the rings A¹, A², A³ or A⁴ is also a benzene ring in which one or more CH groups are replaced by N; with Z3 subst. 1,4-phenylene; Thiadiazole-2,5-diyl; octylene 1,4-bicyclo (2,2,2); Piperidine-1,4-diyl can be as well
Q¹, Q², Q³, Q⁴ (same or different) = single bond, -CH₂O-, -OCH₂-, -COO-, -OOC-, -CH₂CH₂-, -C≡C-, subst. ethylene, -CH₂CH₂COO-, -OOCCH₂CH₂-
Z¹, Z³ (same or different) = halogen, -OCH₃, -CH₃, -CN, -OC₂H₅, H
Z 2 = halogen, H, -CN, -OC _n H _{2 n + 1} , -C _n H _{2 n + 1} with n = 3 to 18 and
R, R ', R "(same or different) = straight-chain or single-branched alkyl chain having 1 to 18 carbon atoms, in which any CH₂ group by -CH₂-phenyl-X- or cyclohexylene-Y-, in R or R "is also a CH₂ group, which is separated by at least 2 C-atoms of an O atom, by O, S, -COO-, -HC = CH- may be replaced
R '''= straight-chain or branched alkyl chain having 2-5 C atoms with
X, Y = -COO-, -OOC-, O, S and
C * = nonracemic asymmetric carbon atom
excluding the variant
p, q, t = O, Q³, Q⁴ = single bond, A³, A⁴ = phenylene, R¹ = alkyl or alkyloxy, R² = methyl, R³ = OH or ester group.

According to the invention, the compounds of general formula I prepared by enantioselective reduction of prochiral ketones of the general formula II with BH₃ · THF in the presence of 0.2 to 10 mole fraction in% of one of the chiral catalysts III in THF with the addition of 5 to 90% by weight in% of a solvent, such as As toluene, benzene, diglyme, at temperatures between -10 ° C and + 80 ° C, preferably at 20 ° C.

Here are the nonracemic chiral benzyl alcohols IV in practically quantitative chemical yield and in high optical Purity (66-98%). This allows them without further cleaning operation by means of known methods (Houben Weyl, Methods of Organic Chemistry) to obtain or reverse the relative configuration in the compounds of the general Formula I are transferred.

R⁴ = -CH (CH₃) ₂ (IIIb)
R⁴ = -CH₂-phenyl (IIIc)
R⁴ = -CH₂-CH (CH₃) ₂ (IIId)

The compounds of the invention are chemical and thermal stable and have favorable transformation temperatures. Lots The compounds themselves are crystalline-liquid, all are good miscible with other liquid crystals and their mixtures and can be added in high concentrations without the Clearing point of the liquid crystal is significantly reduced. The addition of even small amounts of compounds causes the Induction of twisted crystalline-liquid phases such as N * or smectic C *.

Tables 1, 2 and 3 show examples of substances according to the invention with their transformation temperatures. Where:
N = nematic, N * = cholesteric phase
cr = crystalline-solid, is = isotropic-liquid
S _A , S _C = smectic phases of type A, C, (index star means chiral variant)
. = liquid-crystalline phase exists
- = liquid-crystalline phase does not exist
Numbers between two points: Conversion temperature between these phases
Numbers in parentheses indicate monotrophic transformations

Table 1

Table 2

Table 3

Exemplary embodiments for the production of the invention links example 1 (R) -4- (4-h-Decylbenzoyloxy) -benzoic acid / 4- (1-hydroxy-n-docyl) - phenyl ester / 1/5

In an Erlenmeyer flask, 2.0 mmol (1.2 g) of 4- (4-n-decylbenzoyloxy) -benzoic acid 4-n-decanoylphenyl ester in a mixture of 10 ml absol. Toluen solved. While stirring and inert gas at about 0 ° C 0.1 mmol (27.6 g) of the catalyst IIIa in 2 ml absol. THF added. To the resulting solution at 0 ° C 2.0 mmol of BG₃ · THF, dissolved in 10 ml absol. THF, added dropwise during 10 min. After warming to room temperature, the mixture is stirred for a further 1 hour and then carefully hydrolyzed with 2 ml of cold 2N HCl. After dilution with 50 ml of ether, the organic phase is separated and washed three times with 10 ml of 2N HCl, with 10 ml of saturated NaHCO solution and with 10 ml of water. The ethereal solution is dried over Na₂SO₄ and the solvent is distilled off on a rotary evaporator. Recrystallization from ethanol gives the chiral alcohol 1/5 in 90% chemical yield.
/ α / = + 8.9 ° (c = 2.64, THF) 85% ee
Phase behavior: cr 105 S _C * 119 S _A 127 is

Example 2 (R) -4-n-octyloxybenzoic acid / 4- (1-methoxyethyl) phenyl ester / 2/1

1.0 mmol (0.37 g) of (R) -4-n-octyloxybenzoic acid / 4- (1-hydroxyethyl) - phenyl ester / is absol in 15 ml. Dioxane with 3.0 mmol (0.7 g) freshly precipitated, dried Ag₂O and 5.0 mmol (0.71 g) CH₃I added and with the exclusion of light and moisture Shaken for 24 hours at room temperature. Subsequently, the Mixture heated to 60 ° C for 8 hours. After dilution of the solution with 50 ml of ether, the residue is filtered off with suction and this twice washed with 10 ml of ether. The solutions are united and the solvent is distilled off on a rotary evaporator.  By recrystallization of the crude product from methanol is obtained the compound 2/1 in a yield of 80%. Melting point 40 ° C.

Example 3 (R) -4- (4-n-Decylbenzoyloxy) -benzoic acid / 4- (1-octanoyloxy-n- decyl) phenyl ester / 2/14

5.0 mmol (3.07 g) of (R) -4- (4-n-decylbenzoyloxy) benzoic acid / 4- (1-hydroxy-n-decyl) -phenyl ester / are dissolved in 20 ml of absol. Submitted CH₂Cl₂. After addition of 15 mmol (1.52 g) of triethylamine and about 20 mg of DMAP, 5.0 mmol (0.81 g) of octanoyl chloride are added dropwise with stirring at room temperature within 5 minutes. After 6 hours, diluted with 100 ml of ether and washed three times with 20 ml of 2N HCl, with 20 ml of NaHCO solution and 10 ml of water. The organic phase is dried over Na₂SO₄, the solvent is removed on a rotary evaporator and the crude product obtained from methanol recrystallized, the pure ester 2/14 is obtained in a yield of 85%.
Melting point: 63 ° C.

Example 4 (S) -4-n-Octyloxybenzoic acid / 4- (1-chloropentyl) phenyl ester / 2/7

2.0 mmol (0.74 g) of (R) -4-n-octyloxybenzoic acid / 4- (1-hydroxypentyl) phenyl ester / are dissolved in 10 ml of absol. CCl₄ dissolved and stirred and cooled at 0 ° C to a suspension of 2.0 mmol (0.42 g) PCl₅ in 5 ml absol. CCl₄ added dropwise within 10 minutes. After stirring for 12 hours at 0 to 5 ° C with exclusion of atmospheric moisture, the solution is diluted with 10 ml of CCl₄ and filtered to remove small PCl₅ residues. On a rotary evaporator, the solvent and the resulting POCl₃ is distilled off at about 30 ° C. Recrystallization of the crude product from hexane gives the compound 2/7 in a yield of 82%.
Melting point: 44 ° C.

Example 5 (R) -1-hydroxyethylhydroquinone-bis (4-n-octyloxybenzoate) 3/1

In an Erlenmeyer flask, 2.0 mmol (1.23 g) of acetylhydroquinone-bis-4-n-octyloxybenzoate are dissolved in 15 ml of absolute THF. While stirring at 0 ° C., 0.1 mmol (27.6 mg) of (S) -tetrahydro-3,3-diphenyl-1-methyl-1H, 3H-pyrrolo (1,2 c) (1, 3,2) oxazaborole in 2 ml absol. THF added. To the resulting solution with stirring at 0 ° C 2.0 mmol BH₃ · THF dissolved in 10 ml absol. THF, dropped for 10 minutes. After warming to room temperature, the mixture is stirred for a further hour and then carefully hydrolyzed with 2 ml of cold 2N HCl. After dilution with 50 ml of ether, the organic phase is separated and washed three times with 10 ml of 2N HCl, with 10 ml of saturated NaHCO solution and with 10 ml of water. The ethereal solution is dried over Na₂SO₄ and the solvent is distilled off on a rotary evaporator. Recrystallization from petrol (bp 60-85 ° C) gives compound 3/1 in a yield of 95% of theory.
/ α / = + 2.53 ° (c = 3.16, acetone), enantiomeric purity: 71% ee, conversion behavior: cr 58 N * 84 is

Example 6 (S) -1-Chloroethyl hydroquinone bis (4-n-hexyloxybenzoate) 3/5

2.0 mmol (1.12 g) of compound 1/2 are dissolved in 10 ml of absolute. CCl₄ dissolved and stirred and cooled at 0 ° C to a suspension of 2.0 mmol (0.42 g) PCl₅ in 5 ml absol. CCl₄ added dropwise within 10 minutes. After stirring for 12 hours at 0 to 5 ° C with exclusion of atmospheric moisture, the solution is diluted with 10 ml of CCl₄ and filtered to remove small PCl₅ residues. On a rotary evaporator, the solvent and the resulting POCl₃ is distilled off at 30 ° C. Recrystallization of the crude product from gasoline (bp 60-85 ° C) provides the compound
3/5 in a yield of 80% of theory. Transformation behavior: cr 57 N * 88 is

Example 7 (R) -1-methoxyethylhydroquinone-bis (4-n-octyloxybenzoate) 3/6

1.0 mmol (0.61 g) of compound 1/1 are dissolved in 15 ml of absolute. Dioxane with 3.0 mmol (0.7 g) freshly precipitated, dried Ag₂O and 5.0 mmol (0.71 g) CH₃I and shaken under exclusion of light and moisture for 24 hours at room temperature. Subsequently, the mixture is heated to 50 ° C for 8 hours. After dilution of the solution with 50 ml of ether, the residue is filtered off with suction and washed twice with 10 ml of ether. The solutions are combined and the solvent is distilled off on a rotary evaporator. By recrystallization of the crude product from n-hexane gives the ether 3/6 in a yield of 75%.
Transformation behavior: cr 70 N * 86 is

Exemplary embodiments for a more detailed explanation of the application example 1

Using a DSC calorimeter, the following melting enthalpies became (kJ / mol) determines:

Verb no. melting enthalpy 2.13 34.6 2/16 30.6 2.17 24.2

Example 2

For displays based on ferroelectric smectic C * phases (N.A. Clark, S.T. Lagerwall: Appl. Phys. Lett., 36, 899 (1980)) For example, mixtures with smectic C * phases are required chiral induction with the aid of substances according to the invention Substances with non-chiral C-phases can be obtained. This is demonstrated by the following mixtures.

The mixtures were determined using the following reference substance manufactured:

Example 3

For displays with twisted nematic layers and for the Thermography with liquid crystals is needed twisted nematic phases, which are obtained by chiral induction inventive substances from non-chiral nematic Phases can be won. This is to the following Be shown mixtures.

The nematic base mixture Mi 5 has the following composition:

30.2% 4-n-pentyloxybenzoic acid 4-n-octyloxyphenyl ester
13.3% 4-n-hexyloxybenzoic acid 4-n-heptyloxyphenyl ester
34.5% hexyl benzoic acid 4-n-butyloxyphenyl ester
22.0% methoxybenzoic acid 4-n-hexyloxyphenylester

The mixture is nematic at room temperature and has one Clarification point of 71 ° C.

To this Mi 5 substances according to the invention were added. The nematic base mixture became cholesterol and it resulted the depressions listed in the table below the clearing temperature.

Example 4

By admixing the substances according to the invention to others Crystalline-liquid substances produce chiral liquid crystal phases with twisted structure. This will be on the basis of the following Compilation shown in which a non-chiral Substance A with additives of various inventive Substances is provided.

Claims (4)

1. Mesogenic and promesogenic nonracemic chiral compounds of the general formula in which
p, q, r, s, t, u = 0 or 1
p + q + r + s = 1 to 3 and t + u = 1 or 2
R¹ = R, RO, RCOO, ROOC, halogen, NC, SCN, F₃C, H
R = R ' -OOC- (with Z₁ subst.) 1,4-phenylene-Z²
R⁴ = alkyl chain having 1 to 18 carbon atoms
A¹, A², A³, A⁴ (same or different) = 1,4-phenylene; 1,4-cyclohexylene; wherein one of the rings A¹, A², A³ or A⁴ is also a benzene ring in which one or more CH groups are replaced by N; with Z3 subst. 1,4-phenylene; Thiadiazole-2,5-diyl; octylene 1,4-bicyclo (2,2,2); Piperidine-1,4-diyl can be as well
Q¹, Q², Q³, Q⁴ (same or different) = single bond, -CH₂O-, -OCH₂-, -COO-, -OOC-, -CH₂CH₂-, -C≡C-, subst. ethylene, -CH₂CH₂COO-, -OOCCH₂CH₂-
Z¹, Z³ (same or different) = halogen, -OCH₃, -CH₃, -CN, -OC₂H₅, H
Z 2 = halogen, H, -CN, -OC _n H _{2 n + 1} , -C _n H _{2 n + 1} with n = 3 to 18 and
R, R ', R "(same or different) = straight-chain or single-branched alkyl chain having 1 to 18 carbon atoms, in which any CH₂ group by -CH₂-phenyl-X- or cyclohexylene-Y-, in R or R "is also a CH₂ group, which is separated by at least 2 C-atoms of an O atom, by O, S, -COO-, -HC = CH- may be replaced
R '''= straight-chain or branched alkyl chain having 2-5 C atoms with
X, Y = -COO-, -OOC-, O, S and
C * = nonracemic asymmetric carbon atom,
excluding the variant
p, q, t = O, Q³, Q⁴ = single bond, A³, A⁴ = phenylene, R¹ = alkyl or alkyloxy, R² = methyl, R³ = OH or ester group. 2. Crystalline-liquid mixtures containing compounds of the formula I. according to claim 1. 3. A process for the preparation of the compounds of the general formula I according to claim 1, characterized in that prochiral ketones of the general formula II with BH₃ · THF in suitable solvent mixtures in the presence of 0.2 to 10 mole fractions in% of one of the chiral catalysts III R⁴ = -CH (CH₃) ₂ (IIIb)
R⁴ = -CH₂-phenyl (IIIc)
R⁴ = -CH₂-CH (CH₃) ₂ (IIId) and a solubilizer, such as. As toluene, benzene, diglyme, at temperatures between -10 ° C and + 80 ° C, preferably at 20 ° C, to the chiral nonracemic benzyl alcohols IV and these are then converted into the chiral nonracemic compounds. 4. Application of the compounds of general formula I according to claim 1 in crystalline-liquid mixtures in optoelectronic components, in particular displays based on liquid crystals, as well as the thermography.