DE4113053A1 - Fluoro benzene liq. crystal derivs. for low viscosity - useful as components of liq. crystal media for electro=optical displays, with wide mesophase range and low temp. anisotropy - Google Patents

Abstract

Fluoro benzene derivs. of formula (I) are new. R = H or 1-15C alk(en)yl opt. substd. by are CN or CF3 or by halogen(s) and opt. having -CH2- gp(s). replaced by -O-, -S-, 1,4-cyclobutylene, -CO-, -CO.O-, -O.CO- or -O.CO.O- so O atoms are not directly linked to each other; L = H or F; Y = F or Cl; m and n = 1 or 2; and Q = single bond, -CF2-, -O.CF2- or -O.CHF-, if L = F, when both Q = single bond and n = 1. USE/ADVANTAGE - Resin their optical and dielectric anisotropy at low temps.

Description

The invention relates to novel fluorobenzene derivatives of Formula I,

wherein
R H, an unsubstituted, simply substituted by CN or CF₃ or at least one halogen-substituted alkyl or alkenyl radical having 1 to 15 carbon atoms, wherein in these radicals also one or more CH₂ groups each independently

may be replaced so that O atoms are not directly linked to each other,
L H or F,
m and n are each independently 1 or 2,
Y F or Cl, and
Q is a single bond, -CF₂-, -OCF₂- or -OCHF-
with the proviso that L = F, if Q is a single bond and at the same time n = 1.

The invention further relates to the use of these Compounds as components of liquid-crystalline media and liquid crystal and electro-optical display elements, which ent ent the liquid-crystalline media according to the invention hold.

The compounds of the formula I can be used as components liquid crystalline media are used, in particular for displays based on the principle of the twisted cell, the Guest-host effect, the effect of deformation more upright Phases or the effect of dynamic dispersion.

The invention was based on the object new stable to find liquid-crystalline or mesogenic compounds which are suitable as components of liquid-crystalline media and especially at the same time a comparatively small Possess viscosity as well as a relatively high dielectric Anisotropy.  

It has now been found that compounds of the formula I as Components of liquid-crystalline media excellently suitable are. In particular, they have comparatively low high viscosities. With their help can be stable liquid-crystalline media with a broad mesophase range and advantageous values for the optical and dielectric Obtained anisotropy. These media also have a lot good low temperature behavior.

Liquid crystals of the formula

are already known from EP 04 10 233 A2. From the EP 02 05 988 A2 are compounds of the formulas

and from WO 91 03 445

known.  

Various compounds having liquid-crystalline properties in which a terminal CF ₃ group is bonded are already known (USP 4,330,426, USP 4,684,476, JC Liang and S. Kumar, Mol. Cryst. Liq. Cryst., 1987, Vol 142, pp. 77-84). However, these compounds often have a highly smectogenic character and are less suitable for many practical applications.

With regard to the most diverse fields of application suchi However, it was desirable for compounds with a high Δε have further connections available on the specific applications precisely tailor-made properties respectively.

With the provision of compounds of the formula I is also quite generally the range of liquid crystalline Substances that vary in their application aspects of the production of liquid crystalline Mixtures are suitable, considerably widened.

The compounds of the formula I have a broad application dung area. Depending on the selection of the Substi These compounds can be used as base materials serve, from which liquid-crystalline media predominate the part are composed; but it can also verbin compounds of the formula I liquid-crystalline base materials be added to other classes of compounds, for example example, the dielectric and / or optical anisotropy of a to influence such dielectric and / or its Threshold voltage and / or to optimize its viscosity.  

The compounds of the formula I are colorless in the pure state and form liquid crystalline mesophases in one for the Electro-optical use conveniently located Temperaturbe rich. Chemically, thermally and against light, they are stable.

The invention thus relates to the compounds of Formula I and the use of these compounds as Components of liquid-crystalline media. Subject of the Invention are also liquid-crystalline media with a Content of at least one compound of the formula I and Liquid crystal display elements, in particular electroopic Display elements containing such media.

For the sake of simplicity, A ³ in the following mean a radical of the formula

Cyc is a 1,4-cyclohexylene radical.
L is preferably F. Y is preferably F.

The compounds of the formula I accordingly comprise Compounds of Partial Formulas Ia to Id:

R-Cyc-CH₂CH₂-Cyc-A³-Q-Y (Ia)

R-Cyc-Cyc-CH₂CH₂CH₂CH₂-A³-Q-Y (Ib)

R-Cyc-Cyc-CH₂CH₂-Cyc-A³-Q-Y (Ic)

R-Cyc-Cyc-Cyc-CH₂CH₂CH₂CH₂-A³-Q-Y

Of these, particularly those of partial formula Ib are preferred.
R is preferably alkyl, furthermore alkoxy.
m is preferably 1.

If R is an alkyl radical and / or an alkoxy radical, this may be straight-chain or branched. Preferably if it is straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and Accordingly, 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 tetradecoxy.

Oxaalkyl is preferably straight-chain 2-oxapropyl (= Methoxymethyl), 2- (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxo-octyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

If R is an alkyl radical in which a CH₂ group is replaced by -CH = CH-, so this can be straight or be branched. Preferably, it is straight-chain and has 2 up to 10 C atoms. He means especially vinyl, Prop-1, or prop-2-enyl, but-1, 2- or but-2-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.

If R is an alkyl radical in which a CH₂ group replaced by -O- and one by -CO-, these are preferably adjacent. Thus, these include an acryloxy group -CO-O- or an oxycarbonyl group -O-CO-. Preferably these are straight-chain and have 2 to 6 carbon atoms.

They therefore mean especially acetyloxy, propionyloxy, Butyryloxy, pentanoyloxy, hexanoyloxy, acetyloxymethyl, Propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 4-acetyloxybutyl, Methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxy carbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxy carbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2- (methylcarbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propylcarbonyl) ethyl, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl) propyl, 4- (methoxycarbonyl) -butyl.

If R is an alkyl radical in which a CH₂ group by unsubstituted or substituted -CH = CH- and a adjacent CH₂ group replaced by CO or CO-O or O-CO- is, it may be straight or branched. Preferably it is straight-chain and has 4 to 13 carbon atoms. He therefore means especially acryloyloxymethyl,  2-acryloyloxyethyl, 3-acryloyloxy-propyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxy heptyl, 8-acryloyloxyoctyl, 9-acryloyloxynonyl, 10-acryloyloxydecyl, methacryloxyloxymethyl, 2-metha cryloyloxyethyl, 3-methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxy pentane, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl, 9-Methacryloyloxynonyl.

If R monosubstituted by CN or CF ₃ means an alkyl or alkenyl radical, this radical is straight in front of and preferably the substitution by CN or CF ₃ in ω-position.

If R is at least simply substituted by halogen th means alkyl or alkenyl radical, then this radical is preferably straight-chain and halogen is preferably F or Cl. In the case of multiple substitution, halogen is preferably F. The resulting radicals also include perfluorinated radicals. For single substitution, the fluorine or chlorine substitution can be used ent in any position, but preferably in ω-position.

Compounds of the formula I which are above for polymerization Reactions suitable wing groups R are suitable for the preparation of liquid-crystalline polymers.

Compounds of the formulas I with branched wing groups R occasionally because of better solubility in the  Of conventional liquid-crystalline base materials of importance but especially as chiral dopants, if they are are optically active. Smectic compounds of this kind eig as components for ferroelectric materials.

Compounds of the formula I with S _A phases are suitable for example for thermally addressed displays.

Branched groups of this type usually do not contain more than one chain branch. Preferred branched radicals R is isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methyl butyl), 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.

If R represents an alkyl radical in which two or more CH₂ groups are replaced by -O- and / or -CO-O-, so can this be straight-chain or branched. Preferably, he is branched and has 3 to 12 carbon atoms. He means accordingly especially bis-carboxy-methyl, 2,2-bis-carboxy-ethyl, 3,3-bis-carboxy-propyl, 4,4-bis-carboxy-butyl, 5,5-bis-carboxy-pentyl, 6,6-bis-carboxy-hexyl, 7,7-bis-carboxy-heptyl, 8,8-bis-carboxy-octyl, 9,9-bis-carboxy-nonyl, 10,10-bis-carboxy-decyl, Bis (methoxycarbonyl) methyl, 2,2-bis (methoxycarbonyl) ethyl, 3,3-bis- (methoxycarbonyl) -propyl, 4,4-bis (methoxycarbonyl) -butyl, 5,5-bis- (methoxy-carbonyl) -pentyl,  6,6-bis (methoxycarbonyl) hexyl, 7,7-bis (methoxycarbonyl) heptyl, 8,8-bis (methoxycarbonyl) octyl, bis (ethoxycarbonyl) methyl, 2,2-bis- (ethoxycarbonyl) -ethyl, 3,3-bis (ethoxycarbonyl) propyl, 4,4-bis (ethoxycarbonyl) butyl, 5,5-bis- (ethoxycarbonyl) -hexyl.

Compounds of the formula I which are more than suitable for polycondensations suitable wing groups R are suitable for presentation development of liquid crystalline polycondensates.

Formula I includes both the racemates of these compounds as also the optical antipodes and their mixtures.

Among these compounds of the formula I and the sub Formulas are those in which at least one the radicals contained therein one of the specified Favor has meanings.

In the compounds of formula I those are stereo isomers are preferred in which the rings Cyc and piperidine trans-1,4-disubstituted.

The compounds of the formula I are known per se Methods presented in the literature (eg in the Standard works such as Houben-Weyl, Methods of the Organic Chemistry, Georg Thieme Verlag, Stuttgart Bd IX, p 867 ff). are described, under reaction conditions, the known and suitable for the reactions mentioned.  

It is also known by itself, not closer make use of the variants mentioned.

The compounds of the invention may, for. B. manufactured, by dissolving a compound of formula II,

metalated according to the following reaction scheme and then reacted with a suitable electrophile:

Scheme 1

From the resulting phenol are the target products with Q = OCF ₂ or OCHF by known methods, for. B. by reaction with chlorodifluoromethane or carbon tetrachloride / HF available.

Other synthetic methods are apparent to those skilled in the art. For example, in the 5-position, appropriately substituted 1,3-difluorobenzene compounds or mono fluorinated analogs (L = H) according to the above scheme can be converted into the 2-OCF ₂ Y-1,3-difluoro compounds or monofluorinated analogs (L = H). and the radical R- (Cyc) _m - (CH ₂ CH ₂ ) _n -Cyc is subsequently reacted by reactions customary in liquid-crystal chemistry (for example esterification, etherification or couplings, for example, in accordance with Article E. Poetsch , Contacts (Darmstadt) 1988 (2), p. 15).

Scheme 2

Other synthetic methods are apparent to those skilled in the art. For example, in the 5-position, appropriately substituted 1,3-difluorobenzene compounds according to the above scheme can be converted into the 2-Y-1,3-difluoro compounds and the radical R- (Cyc) _m - (CH ₂ CH ₂ ) _n -Cyc can then be cited by reactions customary in liquid-crystal chemistry (for example, esterification, etherification or couplings, for example, in accordance with the article E. Poetsch, Contacts (Darmstadt) 1988 (2), page 15).

The compounds of the formula I according to the invention in which LF and QY are CF ₃ can be prepared by metallation of the unsubstituted 3,5-difluorophenyl compounds with n-BuLi, subsequent reaction with iodine and reaction of the iodine compound with trifluoroacetic acid sodium salt according to the following scheme:

The compounds of the invention with L = H and QY = CF ₃ can be prepared by converting 3-fluoro-4-iodobromobenzene with CF ₃ COONa in the Benzotrifluoridverbindung and then the radical R (Cyc) _m (CH ₂ CH ₂ ) _n Cyc z. B. introduces conventional coupling reactions:

The compounds of the formula II can be, for example, according to following synthesis schemes are prepared:

Scheme 3

Scheme 4

The starting materials are either known or can be used in Be prepared analogously to known compounds.

The synthesis of some particularly preferred compounds is specified in the following:  

Scheme 5

Scheme 6

Scheme 7

In a further process for the preparation of the compounds of formula I is reacted with an aryl halide with an olefin in the presence of a tertiary amine and a palladium kata lysators (see R. F. Heck, Acc Chem. Res. 12 (1979) 146). Suitable aryl halides are, for example, chlorides, Bromides and iodides, especially bromides and iodides. The for the success of the coupling reaction required tertiary Amines, such as As triethylamine, are also suitable as Solvent. As palladium catalysts are, for example the salts thereof, in particular (Pd (II) acetate, with organi phosphorus (III) compounds such. B. triarylphosphines suitable. One can do this in the presence or absence of one inert solvent at temperatures between about 0 ° and 150 °, preferably between 20 ° and 100 °, work; when Solvents come z. As nitriles such as acetonitriles or Hydrocarbons such as benzene or toluene into consideration. The aryl halides and olefins used as starting materials are often commercially available or can be litera turbekannte methods are prepared, for example by halogenation of corresponding parent compounds or by elimination reactions with corresponding alcohols or halides.

The liquid-crystalline media according to the invention contain preferably in addition to one or more inventive Compounds as further constituents 2 to 40, in particular 4 to 30 components. Very particularly preferably included these media in addition to one or more inventive Compounds 7 to 25 components. This further inventory Parts are preferably selected from nematic or  nematogenic (monotropic or isotropic) substances, in particular Substances from the classes of the azoxybenzenes, Benzylidenaniline, Biphenyls, terphenyls, phenyl or cyclohexyl benzoates, Cyclohexane-carboxylic acid phenyl or cyclohexyl esters, Phenyl or cyclohexyl esters of cyclohexyl benzoic acid, phenyl or cyclohexyl esters of cyclohexylcy clohexancarbonsäure, Cyclohexyl-phenylester of benzoic acid, cyclohexanecarboxylic acid or cyclohexylcyclohexanecarboxylic acid, Phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, Cyclohexylcyclohexanes, cyclohexylcyclohexylcyclohexenes, 1,4-bis-cyclohexylbenzenes, 4,4'-biscyclohexylbiphenyls, Phenyl- or cyclohexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclohexyl-dioxanes, Phenyl or cyclohexyl-1,3-dithiane, 1,2-diphenylethane, 1,2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1-Cy clohexyl 2- (4-phenylcyclohexyl) ethanes, 1-cyclohexyl-2-biphenylylethanes, 1-phenyl-2-cyclohexyl-phenylethanes, optionally halogenated stilbenes, benzylphenyl ethers, Tolans and substituted cinnamic acids. The 1,4-phenylene groups in these compounds may also be fluorinated.

The most important as further constituents according to the invention Media eligible connections can be through the Formulas 1, 2, 3, 4 and 5 characterize:

R'-LER '' (1)
R'-L-COO-ER '' (2)
R'-L-OOC-ER "(3)
R'-L-CH₂CH₂-ER "(4)
R'-LC≡CER '' (5)

In formulas 1, 2, 3, 4 and 5, L and E are the same or may be different, each independently 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, wherein Phe unsubstituted or fluorine-substituted 1,4-phenylene, Cyc trans-1,4-cyclohexylene or 1,4-cyclohexylene, Pyr Pyrimidine-2,5-diyl or pyridine-2,5-diyl, Bio 1,3-dioxane-2,5-diyl and G 2- (trans-1,4-cyclohexyl) -ethyl, pyrimidine-2,5-diyl, Pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl mean.

Preferably one of the radicals L and E is Cyc, Phe or Pyr. e is preferably Cyc, Phe or Phe-Cyc. Preferably ent the media of the invention one or more components selected from the compounds of the formulas 1, 2, 3, 4 and 5, wherein L and E are selected from the group Cyc, Phe and Pyr and at the same time one or more components selected from the compounds of the formulas 1, 2, 3, 4 and 5, wherein 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, wherein the radicals L and E are selected from the group -Phe-Cyc, -Cyc-Cyc, -G-Phe and -G-Cyc-.

R 'and R' 'in a smaller subgroup mean the Compounds of formulas 1, 2, 3, 4 and 5 are each independently  alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy of up to 8 carbon atoms. In the following this is called this smaller subgroup group A and the Compounds are described with the sub-formulas 1a, 2a, 3a, 4a and Designated 5a. For most of these compounds, R ' and R "are different from each other, wherein one of these radicals is usually alkyl, alkenyl, alkoxy or alkoxyalkyl.

In a smaller subgroup of compounds of formulas 1, 2, 3, 4 and 5 other than group B, R '' is -F, -Cl, -NCS or - (O) _i CH₃ _{- (k + 1)} F _k Cl₁ where i is 0 or 1 and k + 1 is 1, 2 or 3; the compounds in which R "has this meaning are designated by the subformulae 1b, 2b, 3b, 4b and 5b. Particular preference is given to those compounds of the subformulae 1b, 2b, 3b, 4b and 5b in which R "has the meaning -F, -Cl, -NCS, -CF₃, -OCHF₂ or -OCF₃.

In the compounds of sub-formulas 1b, 2b, 3b, 4b and 5b R 'has the compounds of the sub-formulas 1a-5a given meaning and is preferably alkyl, alkenyl, Alkoxy or alkoxyalkyl.  

In another smaller subgroup of compounds of Formulas 1, 2, 3, 4 and 5 are R "-CN; this subgroup is hereinafter referred to as group C and the Verbindun of this subgroup are correspondingly subformulated 1c, 2c, 3c, 4c and 5c. In the compounds of Partial formulas 1c, 2c, 3c, 4c and 5c has R 'in the verbin of the sub-formulas 1a-5a given meaning and is preferably alkyl, alkoxy or alkenyl.

In addition to the preferred compounds of groups A, B and C. are also other compounds of formulas 1, 2, 3, 4 and 5 with other variants of the proposed substituents common. All these substances are literaturbe knew methods or by analogy available.

The media of the invention contain in addition fiction compounds of the formula I preferably one or several compounds which are selected from the Group A and / or Group B and / or Group C. The Massenan parts of the compounds from these groups to the invention According to media are preferred

Group A:
0 to 90%, preferably 20 to 90%, in particular 30 to 90%
Group B:
0 to 80%, preferably 10 to 80%, especially 10 to 65%
Group C:
0 to 80%, preferably 5 to 80%, especially 5 to 50%

where the sum of the mass fractions in the respective Compounds of the invention contained in the Groups A and / or B and / or C preferably 5% -90% and especially 10% to 90%.

The media according to the invention preferably contain 1 to 40%, in particular preferably 5 to 30% of erfindungs proper connections. Further preferred are media, containing more than 40%, in particular 45 to 90% Compounds of the invention. The media included preferably three, four or five Verbindun invention gene.

The preparation of the media according to the invention takes place in usual way. In general, the components are dissolved in each other, useful at elevated temperature. By Suitable additives can after the liquid crystalline phases of the invention are modified so that they are in all hitherto have become known types of liquid crystal display elements can be used. Such additives are those skilled in the art known and described in detail in the literature (H. Kelker / R. Katz, Handbook of Liguid Crystals, publisher Chemistry, Weinheim, 1980). For example, pleochroiti dyestuffs for producing colored guest-host systems or substances for changing the dielectric Arlisotro pie, the viscosity and / or the orientation of the nemati phases are added.  

The following examples are intended to illustrate the invention without limiting it. Above and below mean Potenzanga ben weight percent. All temperatures are in degrees Celsius. Mp means melting point Kp = clearing point. Furthermore, K = crystalline state, N = nematic phase, S = smectic phase and I = isotropic phase. The data between these symbols represent the transition temperatures. An means optical anisotropy (589 nm, 20 ° C) and the viscosity (mm ² / sec) was determined at 20 ° C.

In the present application and in the following examples, the structures of the liquid crystal compounds are indicated by acronyms, wherein the transformation into chemical formulas according to following Tables A and B takes place. All radicals C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl radicals with n or m C atoms. The coding according to Table B is self-evident. In Table A, only the acronym for the main body is given. In the individual case, a code for the substituents R ¹ , R ² , L ¹ and L ² follows separately from the acronym for the main body with a dash:

Table A

Table B

"Usual work-up" means: one gives if necessary Add water, extracted with methylene chloride, diethyl ether or toluene, separates, the organic phase dries, evaporated and the product is purified by distillation reduced pressure or crystallization and / or Chromatogra phy. The following abbreviations are used:

DAST diethylaminosulfur DCC dicyclohexylcarbodiimide DDQ dichlorodicyanobenzoquinone DIBALH diisobutylaluminum KOT Potassium tert-butoxide THF tetrahydrofuran pTSOH p-toluenesulfonic acid TMEDA tetramethylethylenediamine

example 1

0.1 mol of 1- (3,4,5-trifluorophenyl) -4- [4- (trans-4-pentylcyclo hexyl) -butyl] -cyclohex-1-ene (prepared by a malonic ester synthesis with trans-4-pentylcyclohexyliodomethane, saponification and decarboxylation of the malonic ester, reduction of the trans-4-pentylcyclohexylpropionic acid with lithium alanate, Transfer of the alcohol into the iodide and then into  the triphenylphosphonium salt, reaction of the phosphonium salt with 4-benzyloxybenzaldehyde in a Wittig reaction, hydrogenolytic cleavage of the benzyl ether with simultaneous ger hydrogenation of the olefinic and aromatic Doppelbin tions and oxidation of the cyclohexanol derivative according to Iones to the ketone, reaction of the same with 3,4,5-trifluorophenyl magnesium bromide and dehydration of the resulting Carbinols) are in 500 ml of a 1: 1 mixture of Dissolved ethanol / ethyl acetate and with 12 g of Raney nickel at 5 bar Hydrogen pressure and room temperature hydrogenated. It arises predominantly trans-1- (3,4,5-trifluorophenyl) -4- (4- (trans-4-) pentylcyclohexyl) -butyl) -cyclohexane obtained by crystallization tion from the cis Shares.

Claims (5)

1. fluorobenzene derivatives of the formula I, wherein
RH, an unsubstituted, a simple by CN or CF₃ or at least one halogen-substituted alkyl or alkenyl radical having 1 to 15 carbon atoms, wherein in these radicals also one or more CH₂ groups each independently may be replaced so that O atoms are not directly linked to each other,
LH or F,
m and n are each independently 1 or 2,
YF or Cl and
Q is a single bond, -CF₂-, -OCF₂- or -OCHF-
with the proviso that L = F if Q is a single bond and n = 1 at the same time. 2. Use of compounds of the formula I as a component th liquid-crystalline media. 3. Liquid-crystalline medium with at least two liquids crystalline components, characterized in that it contains at least one compound of the formula I. 4. Liquid crystal display element, characterized in that it is a liquid-crystalline medium according to claim 3 contains. 5. Electro-optical display element, characterized gekennzeich net, that it is a liquid crystalline as a dielectric Medium according to claim 3 contains.