EP0400068A1

EP0400068A1 - Derivatives of 2,3-difluorophenol

Info

Publication number: EP0400068A1
Application number: EP89903139A
Authority: EP
Inventors: Volker Reiffenrath; Joachim Krause; Andreas WÄCHTLER; Georg Weber; Thomas Geelhaar
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 1988-03-10
Filing date: 1989-02-28
Publication date: 1990-12-05
Also published as: DE3807957A1; KR900700425A; JPH02503436A; WO1989008632A1

Abstract

Des dérivés de 2,3-difluorophénol ont la formule (I), dans laquelle R1 et R2 représentent indépendamment l'un de l'autre un groupe alkyle ayant entre 1 et 15 atomes C et dans lequel un ou deux groupes CH2 non adjacents peuvent être substitués par -O-, -CO-, -CH=CH- et/ou -C=C-, m est égal à 1 ou 2, et Q représente -CO- ou -CH2. Ces dérivés sont utiles comme composants de phases de cristaux liqides.2,3-Difluorophenol derivatives have the formula (I), in which R1 and R2 independently of one another represent an alkyl group having between 1 and 15 C atoms and in which one or two non-adjacent CH2 groups can be substituted by -O-, -CO-, -CH = CH- and / or -C = C-, m is 1 or 2, and Q represents -CO- or -CH2. These derivatives are useful as components of liquid crystal phases.

Description

Derivatives of 2,3-difluorophenol

The invention relates to derivatives of 2,3-difluorophenol of the formula I,

F

wherein

R 1 and R2 each independently of one another are an alkyl group having 1 to 15 carbon atoms, in which one or two non-adjacent CH ^ groups are also represented by -0-, -CO-,

-CH = CH- and / or -C≡C- can be replaced,

m 1 or 2, and

Q means -CO- or -CH -, -.

For the sake of simplicity, Cyc in the following means a 1,4-cyclohexylene group and PheF- means a group of the formula

The compounds of the formula I can be used as components of liquid-crystalline media, in particular for displays, which are based on the principle of the twisted cell, the guest-host effect, the effect of the deformation of aligned phases or the effect of dynamic scattering.

The compounds of the formula I are distinguished by a clearly negative anisotropy of the dielectric constant and are aligned with their longitudinal axes in an electric field perpendicular to the field direction. This effect is known and is used to control the optical transparency in various liquid crystal displays, e.g. in liquid crystal cells of light scattering t p (dynamic scattering), of the so-called DAP type (deformation of erected phases) or ECB type (electrically controlled birefringence) or of the guest / host type (guest host interaction).

There have so far been synthesized already pie a number of liquid crystalline compounds with ^~ weakly negative dielectric Anisotro¬. On the other hand, relatively few liquid crystal components with a large negative anisotropy of the dielectric constant are known. In addition, the latter generally have disadvantages, such as poor solubility in mixtures, high viscosity, high melting points and chemical instability. There is therefore a need for further compounds with negative dielectric anisotropy, which make it possible to further improve the properties of mixtures for a wide variety of electro-optical applications.

Liquid crystal compounds with negative dielectric anisotropy, which have two or three rings linked via carboxyl groups or covalent bond and one or more side groups, such as halogen, cyano or nitro groups, are known from DE 22 40 864, DE 26 13 293, DE 28 35 662, DE 28 36 086 and EP 023 728.

EP 084 194 encompasses the compounds claimed here in a broad formula. However, no individual compounds of the formula according to the invention are mentioned there. The person skilled in the art could therefore neither easily derive synthesis possibilities for the claimed compounds from the prior art nor recognize that the compounds according to the invention predominantly have conveniently located mesophase regions and are distinguished by a large negative anisotropy of the dielectric with a simultaneously low viscosity.

Furthermore, dibenzoic acid esters of 2,3-dichlorohydroquinone are known (e.g. Bristol et al., J. Org. Chem. 39_, 3138 (1974) or ^~ Clanderman et al., J. Am. Chem. Soc. 97, 1585 ( 1975)), which are monotropic or have very small mesophase ranges. The method described by Eidenschink et al. described esters of 4-hydroxy-2,3-dichlorobenzoic acid (Angew. Chem. 89_, 103 (1977)) likewise only have narrow mesophase ranges. The 4-alkyl-2,3-dichlorophenyl-4'-alkylbicyclohexyl-4-carboxylic acid esters known from DE OS 29 33 563 do not allow any technical application because of their high viscosity.

The object of the invention was to demonstrate stable, liquid-crystalline or mesogenic compounds with a large negative anisotropy of dielectric and at the same time low viscosity.

It has been found that the compounds of the formula I are particularly suitable as components of liquid-crystalline media. In particular, they can be used to produce stable liquid-crystalline media with a wide mesophase range and comparatively low viscosity.

With the provision of the compounds of the formula I, the range of liquid-crystalline substances which are suitable for the production of liquid-crystalline mixtures from various technical points of view is also very broadly broadened.

The compounds of formula I have a wide range of applications. Depending on the selection of the substituents, these compounds can serve as base materials from which liquid-crystalline media are predominantly composed; However, it is also possible to add compounds of the formula I to liquid-crystalline base materials from other classes of compounds in order, for example, to vary the dielectric and / or optical anisotropy and / or the viscosity and / or the phase ranges and / or the tilt angle of such a dielectric. The compounds of the formula I are also suitable as intermediates for the preparation of other substances which can be used as constituents of liquid-crystalline dielectrics.

The compounds of the formula I are colorless in the pure state and form liquid-crystalline mesophases in a temperature range which is conveniently located for electro-optical use. They are very stable chemically, thermally and against light.

The invention thus relates to the compounds of the formula I and to a process for their preparation, characterized in that a corresponding carboxylic acid or one of its reactive derivatives is reacted with a corresponding hydroxy compound or one of its reactive derivatives.

The invention furthermore relates to the use of the compounds of the formula I as components of liquid-crystalline media. The invention further relates to liquid-crystalline media containing at least one compound of the formula I, and to liquid-crystal display elements containing such media. Such media have particularly advantageous elastic constants and are suitable because of their low Δε / ε. , Values especially for TFT mixtures.

R 1, R2 and m have the given before and after

Meaning, unless expressly stated otherwise. The compounds of the formula I accordingly comprise compounds with two rings of the sub-formulas Ia and Ib:

R ¹ -Cyc-COO-PheF ₂ -R ² Ia

R ¹ -Cyc-CH ₂ 0-PheF ₂ -R ² Ib

and compounds with three rings of the sub-formulas Ic and Id

R ¹ -Cyc-Cyc-COO-PheF ₂ -R ² Ic R ¹ -Cyc-Cyc-CH ₂ 0-PheF ₂ -R ² Id

Among them, those of the sub-formulas Ia and Ic are particularly preferred.

In the compounds of the formulas above and below, R 1 and R2 are preferably alkyl or alkoxy.

Also preferred are compounds of the formulas above and below, in which one of the radicals R 1 and R2,

Alkenyl or oxaalkyl (e.g. Al oxymethyl).

In the formulas above and below, R 1 and R2 preferably have 2-12 C atoms, in particular 3-10 C atoms. One or two CH ₂ groups can also be replaced in R 1 and R2. Preferably only one CH ₂ group is replaced by -O-, or -CH = CH-.

In the formulas above and below, R and

R preferably alkyl, alkoxy or another oxaalkyl group, furthermore also alkyl groups in which one or two CH -, - groups can be replaced by -CH = CH-. If R1 and R2 are alkyl radicals in which one (“alkoxy” or “oxaalkyl”) or two (“alkoxylakoxy” or “dioxaalkyl”) non-adjacent CH ₂ groups can be replaced by O atoms, mean, they can be straight-chain or branched. They are preferably straight-chain, have 2, 3, 4, 5, 6 or 7 carbon atoms and accordingly preferably mean ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl , Octyl, Nonyl, Decyl, Undecyl, Dodecyl, Tridecyl, Tetradecyl, Pentadecyl, Methoxy, Octoxy, Nonoxy, Decoxy, Undecoxy, Dodecoxy, Tridecoxy or Tetra-decoxy.

Oxaalkyl preferably means straight-chain 2-oxypropyl (= methoxymethyl), 2- (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-0xapentyl, 2-, 3-, 4- or 5- Oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6 -, 7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl, 1,3-dioxabutyl (= methoxymethoxy), 1,3-, 1 , 4-, 2,4-dioxapentyl, 1,3-, 1,4-, 1,5-, 2,4-, 2,5- or 3,5-dioxahexyl, 1,3-, 1, 4-, 1,5-, 1,6-, 2,4-, 2,5-, 2,6-, 3,5-, 3,6- or 4,6-dioxahepty1.

If R 1 and R2 are an alkyl radical, i • n is a CH -, -

Group is replaced by -CH = CH-, the trans form is preferred. This ^" alkenyl radical can be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. Accordingly, it means especially vinyl, prop-1, or prop-2-enyl, but-1-, 2- or But-3-enyl, pent-1-, 2-, 3- or pent-4-enyl, hex-1-, 2-, 3-, 4- or hex-5-enyl, hept-1-, 2- , 3-, 4-, 5- or hept-6-enyl, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-, 3-, 4-, 5-, 6-, 7- or non-8-enyl, Dec-1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- or Dec-9 -enyl. Compounds of formula I with branched wing groups

R 1 and / or R2 may occasionally be due to a better one

Solubility in the usual liquid-crystalline base materials may be important, but in particular as chiral dopants if they are optically active. Smectic compounds of this type are suitable as components for ferroelectric materials. _

Branched groups of this type usually contain no more than one chain branch. Preferred branched radicals R1 and / or R2 are isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3 -Methylpentyl,

2-ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy,

2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 1-methylheptoxy,

2-oxa-3-ethylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl,

2-nonyl, 2-decyl, 2-dodecyl, 6-methyloctoxy.

Formula I includes both the racemates of these compounds and the optical antipodes and mixtures thereof.

Preferred compounds of the formulas I and Ia to Id are those in which at least one of the radicals contained therein has one of the preferred meanings indicated.

The compounds of the formula I are prepared by methods known per se, as described in the literature (for example in the standard works such as Houben-Weyl, Methods of Organic Chemistry, Georg-Thieme-Verlag, Stuttgart) ben are, under reaction conditions that are known and suitable for the reactions mentioned. Use can also be made here of variants which are known per se and are not mentioned here in detail. If desired, the starting materials can also be formed in situ in such a way that they are not isolated from the reaction mixture, but instead are immediately reacted further to give the compounds of the formula I.

Compounds of the formula I can be obtained starting from 1,2-difluorobenzene. This is done according to a known procedure

(e.g. A.M. Roe et al., J. Chem. Soc. Chem. Comm., 22,

582 (1965)) metalized and with the corresponding electrical

₂ phil implemented. With the 1-R-2,3-diflurobenzene obtained in this way, this reaction sequence can be carried out a second time, for example using tert-butyl hydroperoxide as an electrophile, and the 2,3-difluoro-4-R 2- is thus obtained. phenols.

2nd . . .

1,2-Difluorobenzene or 1-R -2,3-Difluorobenzene is in an inert solvent such as diethyl ether, tetrahydrofuran, dirthhoxyethane, tert-butyl methyl ether or dioxane, hydrocarbons such as hexane, heptane, cyclohexane, benzene or toluene or mixtures thereof Solvent optionally with the addition of a complexing agent such as tetramethylethylenediamine (TMEDA) or hexamethylphosphoric triamide with phenyllithium, lithium tetramethylpiperidine, n-, sec- or tert-butyllithium at temperatures from -100 ° C to +50 ° C, preferably -78 ° C to 0 ° C implemented.

The lithium-2,3-difluorophenyl compounds are reacted at -100 ° C. to 0 ° C., preferably at -50 ° C., with the corresponding electrophiles. Suitable electrophiles are aldehydes, ketones, nitriles, epoxides, carboxylic acid derivatives such as esters, anhydrides or halides, halogen formic acid esters or carbon dioxide. For reaction with aliphatic or aromatic halogen compounds, the lithium 2,3-difluorophenyl compounds are transmetallated and coupled under transition metal catalysis. The zinc (cf. DE OS 36 32 410) or the titanium 2,3-difluorophenyl compounds (cf. DE OS 37 36489) are particularly suitable for this.

The compounds of the formula I can be prepared by esterifying corresponding carboxylic acids (or their reactive derivatives) with alcohols or phenols (or their reactive derivatives).

Suitable reactive derivatives of the carboxylic acids mentioned are especially the acid halides, especially the chlorides and bromides, and also the anhydrides, e.g. B. also mixed anhydrides, azides or esters, especially alkyl esters with 1-4 C atoms in the alkyl group.

Suitable reactive derivatives of the alcohols or phenols mentioned are, in particular, the corresponding metal alcoholates or phenolates, preferably an alkali metal such as Na or K.

The esterification is advantageously carried out in the presence of an inert solvent. In particular, ethers such as diethyl ether, di-n-butyl ether, THF, dioxane or anisole, ketones such as acetone, butanone or cyclohexanone, amides such as DMF or phosphoric acid hexamethyltriamide, hydrocarbons such as benzene, toluene or xylene are particularly suitable. Halogenated hydrocarbons such as carbon tetrachloride or Tetrachlorethylene and sulfoxides such as dimethyl sulfoxide or sulfolane. Solvents immiscible with water can at the same time advantageously be used for azeotropically distilling off the water formed during the esterification. Occasionally, an excess of an organic base, for example pyridine, chinese or triethylamine, can also be used as a solvent for the esterification. The esterification can also be carried out in the absence of a solvent, for example by simply heating the components in the presence of sodium acetate. The reaction temperature is usually between -50 ° and +250 °, preferably between -20 ° and +80 °. At these temperatures, the esterification reactions are generally complete after 15 minutes to 48 hours.

In particular, the reaction conditions for the esterification largely depend on the nature of the starting materials used. For example, a free carboxylic acid is generally reacted with a free alcohol or phenol in the presence of a strong acid, for example a mineral acid such as hydrochloric acid or sulfuric acid. A preferred reaction is the reaction of an acid anhydride or, in particular, an acid chloride with an alcohol, preferably in a basic medium, the bases being in particular alkali metal hydroxides such as sodium or potassium hydroxide, alkali metal carbonates or hydrogen carbonates such as sodium carbonate, sodium hydrogen carbonate, potassium carbonate or potassium hydrogen carbonate, alkali metal acetates such as sodium or potassium acetate, alkaline earth metal hydroxides such as calcium hydroxide or organic bases such as triethylamine, pyridine, lutidine, collidine or quinoline are important. A a further preferred embodiment of the esterification consists in first converting the alcohol or the phenol into the sodium or potassium alcoholate or phenolate, for example by treatment with ethanolic sodium hydroxide solution or potassium hydroxide solution, isolating it and together with sodium hydrogen carbonate or Potassium carbonate suspended in acetone or diethyl ether with stirring and a solution of the acid chloride or anhydride in diethyl ether, acetone or DMF was added to this suspension, advantageously at temperatures between about -25 ° and +20 °.

The methyl ethers of formula I can be represented by known etherifications, e.g. by a compound of formula

wherein Z is OH, OMe, SH or SMe, where Me is an equivalent of a metal cation and shark is a halogen atom, preferably chlorine or bromine, with a compound of the formula

wherein Z _ß -CH ₂ -Hal, in the presence of a base. The radicals R ₂ and R ₂ have the meanings given in the formula (I). The reaction conditions for these ether syntheses are the usual ones for such reactions; polar, aprotic solvents are used as solvents, for example, methyl sulfoxide, N, N-dimethylformamide or N-methylpyrrolidone; alkali salts are preferably used as bases weak acids, for example sodium acetate, potassium carbonate or sodium carbonate. The reactions can be carried out at temperatures between 0 ° C. and the boiling point of the lowest-boiling component of the reaction mixture; it has proven to be particularly advantageous to use temperatures between 60 and 120 ° C. Some of the starting materials are known, and some of them can be prepared analogously to known compounds using standard synthetic organic chemistry processes.

In addition to one or more compounds according to the invention, the liquid-crystalline media according to the invention preferably contain 2 to 40, in particular 4 to 30, components as further constituents. These media very particularly preferably contain 7 to 25 components in addition to one or more compounds according to the invention. These further constituents are preferably selected from nematic or nematogenic (monotropic or isotropic) substances, in particular substances from the classes of azoxybenzenes, benzylidene anilines, biphenyls, terphenyls, phenyl- or cyclohexylbenzoates, cyclohexane-carboxylic acid phenyl or cyclohexyl esters , phenyl or cyclohexyl esters of cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, cyclohexyl phenyl ester of benzoic acid, of cyclohexanecarboxylic acid, or cyclohexylcyclohexanecarboxylic, phenylcyclohexane hexane, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexenes, cyclohexyl cyclohexylcyclohexenes, 1 , 4-bis-cyclohexylbenzenes, 4,4'-bis-cyclohexylbiphenyls, phenyl- or cyclohexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclohexyl-dioxanes, phenyl- or cyclohexyl-1,3-dithiane, 1,2-di- phenylethane, 1,2-dicyclohexylethane, l-phenyl-2-cyclohexylethane, l-cycl ohexyl-2- (4-phenyl-cyclohexyl) ethanes, l-Cyclohexyl-2-biphenylylethane, l-phenyl-2-cyclohexylphenylethane, optionally halogenated stilbenes, benzylphenyl ether, tolanes and substituted cinnamic acids. The 1,4-phenylene groups in these compounds can also be fluorinated.

The most important compounds which are suitable as further constituents of media according to the invention can be characterized by the formulas 1, 2, 3, 4 and 5:

R'- -E-R "1 R'-L-COO-E-R" 2

R'-L-OOC-E-R "3

R'-L-CH ₂ CH ₂ -ER "4

R'-L-C≡C-E-R "5

In formulas 1, 2, 3, 4 and 5, L and E, which may be the same or different, each independently represent a bivalent radical from the group consisting of -Phe-, -Cyc-, -Phe-Phe-, -Phe- Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe- and -G-Cyc- and their mirror images formed group, where Phe unsubstituted or substituted by fluorine-substituted 1,4-phenylene, Cyc trans-l, 4-cyclohexylene or 1,4-cyclohexenylene, pyr pyrimidine-2,5-diyl or pyridine-2,5-diyl, diol, 3-dioxane-2,5-diyl and G 2- ( mean trans-1,4-cyclohexyl) ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl.

Preferably one of the residues L and E is Cyc, Phe or

Pyr. E is preferably Cyc, Phe or Phe-Cyc. The media according to the invention preferably contain one or more components selected from the compounds of the formulas 1, 2, 3, 4 and 5, in which L and E are selected from the group Cyc, Phe and Pyr and at the same time one or more components selected from the links of the formulas 1, 2, 3, 4 and 5, in which one of the radicals L and E is selected from the group Cyc, Phe and Pyr and the other radical is selected from the group -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-, and optionally one or more components selected from the compounds of the formulas 1, 2, 3, 4 and 5, in which the radicals L and E are selected from the group -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.

In a preferred subgroup of the compounds of the formulas 1, 2, 3, 4 and 5, R ¹ and R "in each case independently of one another denote alkyl, alkenyl, alkoxy, alkenyloxy or alkanoyloxy with up to 8 carbon atoms (group 1). Most of these compounds, R * and R "are different from one another, one of these radicals usually being alkyl or alkenyl. In another preferred

Subgroup of the compounds of the formulas 1, 2, 3, 4 and 5 is R "-CN, -CF ₃ , F, Cl or -NCS; R has the meaning given for the compounds of group 1 and is preferably alkyl or Alkenyl (group 2), but other variants of the envisaged substituents in the compounds of the formulas 1, 2, 3, 4 and 5 are also common, and many such substances or mixtures thereof are commercially available, all of which are known from the literature Methods or available in analogy.

In addition to components from group 1, the media according to the invention preferably also contain components from group 2, the proportions of which are preferably as follows:

Group 1: 20 to 90%, in particular 30 to 90%, group 2: 10 to 80%, in particular 10 to 50%, the sum of the proportions of the compounds according to the invention and of the compounds from groups 1 and 2 giving up to 100%.

The media according to the invention preferably contain 1 to 40%, particularly preferably 5 to 30%, of compounds according to the invention. Also preferred are media containing more than 40%, in particular 45 to 90%, of compounds according to the invention. The media preferably contain three, four or five compounds according to the invention.

The media according to the invention are produced in a conventional manner. As a rule, the components are dissolved in one another, expediently at elevated temperature. By means of suitable additives, the liquid-crystalline phases can be modified according to the invention in such a way that they can be used in all types of liquid-crystal display elements which have hitherto become known. Such additives are known to the person skilled in the art and are described in detail in the literature (H. Kelker / R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim,

1980). For example, pleochroic dyes can be added to produce colored guest-host systems or substances to change the dielectric anisotropy, the viscosity and / or the orientation of the nematic phases.

The following examples are intended to illustrate the invention without limiting it, mp. = Melting point, cp. = Clearing point. Percentages above and below mean percentages by weight; all temperatures are given in degrees Celsius. "Conventional work-up" means: water is added, the mixture is extracted with methylene chloride, the mixture is separated off, the organic phase is dried, evaporated and the product is purified by crystallization and / or chromatography. It also means:

K: crystalline solid state, S: smectic phase (the index characterizes the phase type), N: nematic state, Ch: cholesteric phase, I: isotropic phase. The number between two symbols indicates the transition temperature in degrees Celsius.

The melting point is denoted by T _M , the clearing point by T-; the temperatures are given in degrees Celsius.

Example 1:

0.1 mol 2,3-difluoro-4-ethylphenol (producible from o-difluorobenzene by reaction with butyllithium in the presence of potassium tert-butoxide at -90 to 100 ° in tetrahydrofuran (THF), alkylation of the potassium compound with ethyl bromide / l , 3-dimethyltetrahydro-2- (1H) -pyrimidinone (DMPU), isolation of 2,3-difluoroethylbenzene, renewed metalation and reaction with N-formylpiperidine to form the aldehyde, the oxidation of which, according to Baeyer-Villiger, to formate and subsequent Hydrolysis), 0.1 mol of potassium carbonate and 0.1 mol of trans-4-pentyl-1-bromomethylcyclohexane are heated in 120 ml of diethylformamide at 120 ° for 15 hours. The inorganic salts are filtered off, concentrated to almost dryness, the residue is taken up in dichloromethane, washed with water and dried. After the solvent has been distilled off, trans- (4-pentylcyclohexyl) methoxy-2,3-difluoro-4-ethylbenzene is obtained.

The following are produced analogously:

trans- (4-pentylcyclohexyl) methoxy-2,3-difluoro-4-propyl-benzene trans- (4-pentylcyclohexyl) methoxy-2,3-difluoro-4-butyl-benzene trans- (4-pentylcyclohexyl) methoxy-2,3-difluoro-4-pentylbenzene trans- (4-pentylcyclohexyl) methoxy-2,3-difluoro-4-heptylbenzene

trans- (4-butylcyclohexyl) methoxy-2,3-difluoro-4-ethylbenzene ___ trans- (4-butylcyclohexyl) methoxy-2,3-difluoro-4-propylbenzene trans- (4-butylcyclohexyl) -methoxy-2,3-difluoro-4-butyl-benzene trans- (4-butylcyclohexyl) -methoxy-2,3-difluoro-4-pentyl-benzene trans- (4-butylcyclohexyl) -methoxy-2,3-difluoro -4-heptylbenzene trans- (4-butylcyclohexyl) methoxy-2,3-difluoro-4-methoxymethylbenzene trans- (4-butylcyclohexyl) methoxy-2,3-difluoro-4-but-3-enylbenzene

trans- (4-propylcyclohexyl) methoxy-2,3-difluoro-4-ethylbenzene trans- (4-propylcyclohexyl) methoxy-2,3-difluoro-4-propylbenzene trans- (4-propylcyclohexyl) - methoxy-2,3-difluoro-4-butylbenzene trans- (4-propylcyclohexyl) methoxy-2,3-difluoro-4-pentylbenzene trans- (4-propylcyclohexyl) methoxy-2,3-difluoro- 4-heptylbenzene trans- (-propylcyclohexyl) methoxy-2,3-difluoro-4-methoxymethylbenzene trans- (4-propylcyclohexyl) methoxy-2,3-difluoro-4-but-3-enylbenzene trans-4- (trans-4-propylcyclohexyl) cyclohexyl-methoxy-2,3-difluoro-4-ethyl-benzene trans-4- (trans-4-propylcyclohexyl) cyclohexyl-methoxy-2,3-difluoro-4 -propyl-benzene trans-4- (trans-4-propylcyclohexyl) -cyclohexyl-methoxy-2,3-difluoro-4-butyl-benzene trans-4- (trans-4-propylcyclohexyl) -cyclohexyl-methoxy-2,3 -difluoro-4-pentyl-benzene trans-4- (trans-4-propylcyclohexyl) -cyclohexyl-methoxy-2,3-difluoro-4-heptyl-benzene trans-4- (trans-4-propylcyclohexyl) -cyclohexyl-methoxy - 2,3-difluoro-4-methoxymethyl-benzene trans-4- (trans-4-propylcyclohexyl) cyclohexyl-methoxy-2,3-difluoro-4-but-3-enyl-benzene

Example 2:

By lithiation of o-difluorobenzene and reaction with octanal, dehydration and hydrogenation, 2,3-difluorooctylbenzene is obtained and from it, as in the previous example, the 4-octyl-2,3-difluorophenol via the formyl compound.

0.1 mol of this phenol, 0.1 mol of trans-4-butylcyclohexanecarboxylic acid and 0.01 mol of 4-dimethylaminopyridine are placed in 150 ml of dichloromethane, the solution of 0.1 mol of dicyclohexylcarbodiimide in 30 ml of dichloromethane is added dropwise at 10 ° while stirring and then added for 15 hours

Stirred room temperature. It is suction filtered through silica gel, the solvent is evaporated off and the residue obtained is (2,3-difluoro-4-octylphenyl) trans-4-butylcyclohexanoate.

The following are produced analogously:

(2,3-difluoro-4-pentylphenyl) trans-4-pentylcyclohexanoate T-. = 13, _c = 28.5 (2,3-difluoro-4-propylphenyl) trans-4-pentylcyclohexanoate (2,3-difluoro-4-heptylphenyl) trans-4-pentylcyclohexanoate (2,3-difluoro-4-butoxymethyl) trans-4- pentylcyclohexanoate (2,3-difluoro-4-propoxymethyl) trans-4-pentylcyclohexanoate (2,3-difluoro-4- (but-3-enyl) phenyl) trans-4-pentylcyclohexanoate

Example 3:

Analogously to Example 2, 2,3-difluoro-4-pentylphenol is obtained and esterified with trans-4- (trans-4-pentylcyclohexyl) cyclohexane carboxylic acid. Conventional work-up gives (2,3-difluoro-4-pentylphenyl) trans-4- (trans-4-pentylcyclohexyl) cyclohexanoate.

The following are produced analogously:

(2,3-difluoro-4-pentylphenyl) trans-4- (trans-4-propylcyclohexyl) cyclohexanoate; T- = 180

(2,3-difluoro-4-ethylphenyl) trans-4- (trans-4-propylcyclohexyl) cyclohexanoate

(2,3-difluoro-4-propylphenyl) trans-4- (trans-4-propylcyclo-hexyl) cyclohexanoate (2,3-difluoro-4-butylphenyl) trans-4- (trans-4-propylcyclo- hexyl) cyclohexanoate

(2,3-difluoro-4-heptylphenyl) trans-4- (trans-4-propylcyclohexyl) cyclohexanoate

(2,3-difluoro-4-ethylphenyl) trans-4- (trans-4-propylcyclohexyl) cyclohexanoate

(2,3-difluoro-4-propylphenyl) trans-4- (trans-4-propylcyclohexyl) cyclohexanoate

(2,3-difluoro-4-butylphenyl) trans-4- (trans-4-propylcyclohexyl) cyclohexanoate Example 4:

Analogously to Example 1, metalation of o-difluorobenzene with butyllithium / potassium tert-butylate and reaction with ethoxyethyl bromide gives 2,3-difluoroethoxyethylbenzene and the 2,3-difluoro-4-ethoxyethylphenol is obtained therefrom via the aldehyde. Alkylation with trans-4- (trans-4-pentylcyclohexyl) -1-bromomethylcyclohexane in the presence of potassium carbonate and dimethylformamide (DMF) as the solvent gives l- [trans- 4- (trans-4-pentylcyclohexyl) cyclohexyl] methoxy-2 , 3-di-fluoro-4-ethoxyethylbenzene.

The following are produced analogously:

1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] methoxy-2,3-difluoro-4-pentylbenzene; T-, = 35, T _c = 118

1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] methoxy-2,3-difluoro-4-ethoxymethylbenzene

1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] methoxy-2,3-difluoro-4-propoxymethylbenzene

1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] methoxy-2,3-difluoro-4-butoxymethylbenzene

1- [trans-4- (trans-4-pentylcyclohexyl) cyclohexyl] methoxy

2,3-difluoro-4-ethylbenzene

1- [trans-4- (trans-4-pentylcyclohexyl) cyclohexyl] methoxy-

2,3-difluoro-4-propylbenzene

1- [trans-4- (trans-4-pentylcyclohexyl) cyclohexyl] methoxy-2,3-difluoro-4-butylbenzene

1- [trans-4- (trans-4-pentylcyclohexyl) cyclohexyl] methoxy-

2,3-difluoro-4-pentylbenzene Example 5:

By lithiation of o-difluorobenzene with butyllithium / tetramethylethylenedia in (TMEDA) in THF at -70 to -80 ° and reaction with solid carbonic acid, reduction of the acid with lithium alanate, conversion of the alcohol to tosylate and reaction with sodium pentanolate, 2.3 is obtained -Difluoropentyloxymethylbenzene. As described in Example 1, the phenol is obtained therefrom and by esterification with trans-4-propylcyclohexane carboxylic acid (2,3-difluoro-4-pentyloxymethylphenyl) trans-4-propylcyclohexanoate.

The following are produced analogously:

(2,3-difluoro-4- (hex-2-enyl) phenyl) tr ns-4-propylcyclohexanoate

(2,3-difluoro-4-pentylphenyl) trans-4-ethylcyclohexanoate (2,3-difluoro-4-pentylphenyl) trans-4-butylcyclohexanoate (2,3-difluoro-4-pentylphenyl) ) -trans-4-heptylcyclohexanoate (2,3-difluoro-4- (pent-2-enyl) phenyl) -trans-4-butylcyclohexanoate (2,3-difluoro-4- (hex-2-enyl) -phenyl) trans-4-butylcyclohexanoate

(2,3-difluoro-4-pentylphenyl) trans-4-pentylcyclohexanoate (2,3-difluoro-4-hexylphenyl) trans-4-pentylcyclohexanoate (2,3-difluoro-4-heptylphenyl ) trans-4-pentylcyclohexanoate (2,3-difluoro-4-octyl-phenyl) trans-4-pentylcyclohexanoate

Example 6:

10 ml of a 20% solution of diisobutylaluminum hydride in hexane are added to a solution of 0.01 mol of 1-hexyne and 5 ml of hexane and the mixture is heated at 50 ° for 3 hours. The mixture is then cooled to 25 °, 6.3 ml of a 15% solution of butyllithium in hexane are added dropwise, and after 30 minutes 0.01 mol of 2,3-difluoro 4 (trans-4-pentylcyclohexyl) methoxybenzyl bromide, dissolved in 15 ml of tetrahydrofuran, and heated under reflux for 12 hours. After working up, 2,3-difluoro-4 (trans-4-pentylcyclohexyl) methoxy-trans-hept-2-enylbenzene is obtained.

The required benzyl bromide is prepared from 2,3-difluoro (trans-4-pentylcyclohexyl) methoxybenzene by lithiation, reaction with N-formylpiperidine, reduction of the aldehyde with sodium borohydride and reaction of the benzyl alcohol with dibromotriphenylphosphorane.

The following are produced analogously:

2,3-difluoro-4- (trans-pentylcyclohexyl) methoxy-pentoxymethylbenzene

2,3-difluoro-4- (trans-pentylcyclohexyl) methoxy-hexoxy-methylbenzene 2,3-difluoro-4- (trans-pentylcyclohexyl) -methoxy-heptoxy-methylbenzene

2,3-difluoro-4- (trans-pentylcyclohexyl) methoxy-pentyl-benzene

2,3-difluoro-4- (trans-pentylcyclohexyl) methoxy hexyl benzene

2,3-difluoro-4- (trans-pentylcyclohexyl) methoxy-heptyl-benzene

The following examples relate to liquid-crystalline media according to the invention:

Example A

A liquid crystalline nematic medium consisting of

10% p-trans-4-ethylcyclohexyl-benzonitrile, 10% p-trans-4-butylcyclohexyl-benzonitrile, 5% p-ethylbenzoic acid (4-cyan-4-fluorophenyl ester), 5% p-propylbenzoic acid (4-cyan-4-fluorophenyl ester), 5% p-pentylbenzoic acid (4-cyan-3-fluorophenyl ester), 15% trans, trans-4-ethoxy-4'-pentylcyclohexylcyclohexane, 5% trans -4-propylcyclohexane carboxylic acid (p-methoxyphenyl ester),

5% trans-4-butylcyclohexane carboxylic acid (p-methoxyphenyl ester), _

5% trans-4-butylcyclohexanecarboxylic acid (p-ethox_ ^~ phenyl ester), 5% trans-4-pentylcyclohexanecarboxylic acid (p-ethoxyphenyl ester), 5% trans-4-pentylcyclohexanecarboxylic acid (p-methoxyphenyl ester), 5% (2,3-difluoro-4-pentyloxymethylphenyl) trans-4-propyl cyclohexanoate,

5% trans-4- (trans-4-propylcyclohexyl) cyclohexane carboxylic acid (p-propylphenyl ester), 5% trans-4- (trans-4-propylcyclohexyl) cyclohexane carboxylic acid (p-pentylphenyl ester), 5% trans-4- (trans-4-butylcyclohexyl) cyclohexane carboxylic acid (p-propylphenyl ester) and 5% (2,3-difluoro-4-pentylphenyl) trans-4- (trans-4-pentyl cyclohexyl) - cyclohexanoate

shows good multiplexing properties.

Claims

1. derivatives of 2,3-difluorophenol of the formula I,

wherein

R 1 and R2 j.ewei.ls independently of one another are an alkyl group having 1 to 15 C atoms, in which one or two non-adjacent CH ₂ groups are also represented by -0-, -CO-, -CH = CH- and or

-C≡C- can be replaced,

m 1 or 2, and

Q means -CO- or -CH -, -.

2. A process for the preparation of the derivatives of 2,3-difluorophenol according to claim 1, characterized in that a difluorophenol of the formula

or one of its reactive derivatives with a cyclohexane carboxylic acid of the formula

or esterified one of its reactive derivatives, or with a hydroxy compound of the formula

or one of their reactive derivatives.

3. Use of the derivatives according to claim 1 as components of liquid-crystalline media.

4. Liquid-crystalline medium with at least two liquid-crystalline components, characterized in that at least one component is a derivative according to claim 1.

5. Electro-optical display element, characterized gekenn¬ characterized in that it contains a medium according to claim 4 as a dielectric.