Liquid crystal compounds

Abstract

Compounds of formula I containing a dioxane ring or a tetrahydropyran ring and a polyfluorinated biphenyl group: #imgabs0# wherein Y 1 represents ‑O‑ or ‑CH2‑, group R 1 ,Ar 1 ,Ar 2 and X 1 has the meaning indicated in claim 1. A process for the preparation thereof, as well as liquid-crystalline media comprising at least one compound of the formula I and electro-optical displays comprising liquid-crystalline media of this type.

Description

[0001] The present invention relates to compounds of the formula I as defined below, which contain, as structural elements, a 1,4-substituted cyclohexene ring other than a dioxane or tetrahydropyran ring and a substituted biphenyl group in combination. In addition, the present invention encompasses a preparation process, a liquid crystal medium comprising at least one compound of the formula I and its use as a component in a liquid crystal medium. In addition, the present invention relates to liquid crystals and electro-optical display components containing the liquid crystal medium according to the invention.

[0002] In the past few years, the application field of liquid crystal compounds has significantly expanded to various types of display devices, electro-optical devices, electronic components, sensors, etc. For this reason, many different structures have been proposed, especially in the field of nematic liquid crystals. So far, nematic liquid crystal mixtures have been found to be most widely used in flat panel display devices. They are especially used in passive TN or STN matrix displays or in systems with TFT active matrices.

[0003] The liquid-crystalline compounds according to the invention can be used as components of liquid-crystalline media, in particular for displays based on the twist cell principle, the guest-host effect, the orientation phase effect DAP or ECB (electrically controlled birefringence) effect, the IPS (in-plane switching) effect or the dynamic scattering effect.

[0004] The use of polar dioxane and tetrahydropyran compounds with four rings as liquid crystal substances is not unknown to the person skilled in the art. Various compounds containing O-heterocycles have been described as liquid crystal or mesogenic materials, as have their preparation methods, for example in the publication WO 2004 / 106460 A1. The compounds proposed therein do not contain a cyclohexene ring. The compounds contain, for example, -OCF3 or fluorine as polar end groups.

[0005] Cyclohexene compounds containing a dioxane ring are known from WO 2018 / 141759 A1, but contain only three ring groups in total.

[0006] The invention is based on the object of finding novel stable compounds which are suitable as components of liquid-crystal media. In particular, the compounds should simultaneously have a relatively low viscosity and a high dielectric anisotropy. For many current mixture concepts in the field of liquid crystals, the combined use of compounds with a positive dielectric anisotropy Δε and a moderate to high optical anisotropy is advantageous.

[0007] In view of the very wide range of fields of application of such compounds with high Δε, it would be desirable to have available further compounds, preferably with high bright spots and low viscosity, which have properties precisely adapted to the respective application.

[0008] It was therefore an object of the present invention to find novel stable compounds which are suitable as components of liquid-crystalline media, in particular for use, for example, in TN, STN, IPS, FFS and TN-TFT displays.

[0009] In addition, the compounds according to the invention should be thermally and photochemically stable under the prevailing conditions in the field of application. As mesogens, they should contribute to a broad nematic phase in a mixture with a liquid crystal co-component and be highly miscible with a nematic base mixture, especially at low temperatures. Substances with a low melting point and a low melting enthalpy are also preferred, since these parameters are in turn indicative of the desired properties mentioned above, such as high solubility in mixtures at low temperatures, a broad liquid crystal phase and a low tendency to spontaneous crystallization. In particular, solubility at low temperatures while avoiding any crystallization is important for safe operation and transportation of displays in vehicles and aircraft and outdoors.

[0010] Surprisingly, it has been found that the compounds according to the invention are extremely suitable as components of liquid-crystalline media. They can be used to obtain liquid-crystalline media for displays, in particular for IPS or FFS displays, which require high dielectric anisotropy and at the same time a high negative dielectric susceptibility (ε 20 ) orthogonal to the molecular axis. ┴ ) components. The compounds according to the invention are sufficiently stable and colorless. In particular, they are also characterized by a high dielectric anisotropy (Δε), because when used in optical switching components, lower layer thicknesses and thus lower threshold voltages are required. For compounds with similar properties, they have good solubility. In addition, the compounds according to the invention have a relatively high clearing point and at the same time low rotational viscosity values. The compounds have a relatively low melting point. With the aid of the compounds according to the invention, it is unexpectedly possible to prepare films with high values ​​of the elastic constant (K 11 / K 22 / K 33 ) without adversely affecting other parameters of use. This results in media with short response times and high contrast.

[0011] The provision of the compounds according to the invention very generally significantly broadens the range of liquid-crystalline substances which are suitable for the preparation of liquid-crystalline mixtures from the point of view of various applications.

[0012] The compounds according to the invention have a wide range of applications. Depending on the choice of substituents, these compounds can be used as base materials that primarily constitute liquid-crystalline media. However, liquid-crystalline base materials from other classes of compounds can also be added to the compounds according to the invention, for example to influence the dielectric and / or optical anisotropy of this type of dielectric, and / or to optimize its threshold voltage and / or viscosity.

[0013] Therefore, the present invention relates to compounds of formula I,

[0014]

[0015] in

[0016] Ar 1 -Ar 2 represents a group selected from the following sub-formulas

[0017]

[0018] Among them, Ar 1 represents the first benzene ring, and Ar 2 represents the second benzene ring,

[0019] X 1 represents F, CF3, OCF3, Cl, OCHF2, CHF2, SCN or CN, preferably F, CF3 or OCF3,

[0020] Y 1 represents O or CH2,

[0021] R 1 represents an alkyl radical having 1 to 15 C atoms, wherein in addition one or more CH2 groups in these radicals can in each case be independently of one another replaced by -C≡C-, -CH=CH-, -O-, -S-, -CO-O- or -O-CO- is replaced in such a way that the O / S atoms are not directly connected to each other, and wherein in addition one or more H atoms may be replaced by halogen, or represents H,

[0022] Preference is given to halogenated alkyl or unsubstituted alkyl having 1 to 15 C atoms, wherein in addition one or more CH2 groups in these radicals may in each case be replaced independently of one another by -C≡C- or -CH=CH-, and

[0023] L 1 represents H or CH3, preferably H.

[0024] The invention further relates to the use of compounds of the formula I in liquid-crystalline media.

[0025] The invention also relates to liquid-crystalline media having at least two liquid-crystalline components which comprise at least one compound of the formula (I).

[0026] The compound of formula I contains the structural element Ar 1 -Ar 2 , which contains a 2,3-difluorophenyl ring in addition to a 2-fluoro- or 2-6-difluorophenyl ring. The compounds of formula I have a wide range of applications. Depending on the choice of substituents, these compounds can be used as base materials that primarily constitute liquid crystal media; however, the compounds of formula I can also be added to liquid crystal base materials from other classes of compounds, for example to influence the dielectric and / or optical anisotropy of this type of dielectric, and / or to optimize its threshold voltage and / or viscosity.

[0027] In the pure state, the compounds of formula I are colorless and form liquid crystal mesophases in a temperature range advantageously set for electro-optical purposes, either by themselves or in a mixture. The compounds according to the invention enable a wide nematic phase range to be achieved. In liquid crystal mixtures, the materials according to the invention significantly increase the optical anisotropy compared to comparable mixtures with high dielectric anisotropy, and / or lead to an improvement in low temperature storage stability. At the same time, the compounds are characterized by good UV stability.

[0028] The group R in formula I and its subformulae 1 Preferably, R represents an alkyl or alkenyl group having up to 8 carbon atoms. 1 Particular preference is given to straight-chain alkyl having 1 to 7 C atoms or unbranched alkenyl having 2 to 8 C atoms, in particular unbranched alkyl having 2 to 7 C atoms.

[0029] The group X of formula I 1 Preferably it represents F, CF3, OCF3 or -SCN, particularly preferably F, CF3 or OCF3 and very particularly preferably F.

[0030] Containing branched or substituted wing group R 1 Compounds of the formula I may frequently be of interest due to their improved solubility in customary liquid-crystalline base materials. 1 A straight chain is preferred.

[0031] Group R 1 Particularly preferably, it is selected from the following parts:

[0032] -CH3

[0033] -C2H5

[0034] -C3H7

[0035] -C4H9

[0036] -C5H 11

[0037] -C6H 13

[0038] -CH=CH2

[0039] -CH=CH2-CH3

[0040] -CH2-CH2-CH=CH2

[0041] -CH2-CH2-CH=CH-CH3

[0042] The alkyl chain is preferably unbranched (normal alkyl).

[0043] Substituted group R 1 is selected from cyclopentyl, 2-fluoroethyl, cyclopropylmethyl, cyclopentylmethyl, cyclopentylmethoxy, cyclobutylmethyl, 2-methylcyclopropyl, 2-methylcyclobutyl and 2-alkoxyethoxy.

[0044] Particularly preferred compounds of formula I are compounds of formulae I-1 to I-4:

[0045]

[0046] Where R 1 R independently has the meaning indicated above. Among the compounds of formulae I-1 to I-4, compounds of formulae I-1 and I-2 are preferred. 1 Particularly preferably, L represents an n-alkyl radical having 2, 3, 4, 5, 6 or 7 C atoms. 1 Preferably it represents H.

[0047] Illustrative compounds are the following:

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] The compounds of formula I are prepared by methods known per se, such as those described in the literature (e.g. in standard works, such as Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), specifically under reaction conditions known and suitable for the reaction. Variants known per se and not mentioned in more detail herein may also be used in this context.

[0056] Compounds of formula I can advantageously be prepared as shown in the following illustrative syntheses and examples (Schemes 1 and 2):

[0057]

[0058] Scheme 1. For the preparation of formula I (Y 1 =O) of dioxane compounds. 1 , L 1 and X 1 As defined for Formula I, L 2 , L 3 , L 4 Indicates H or F.

[0059] Modification of the starting compounds of Scheme 1 may alternatively lead to Synthetic Scheme 2 for the preparation of the corresponding tetrahydropyran compounds.

[0060]

[0061] Scheme 2. For the preparation of 1 General synthetic scheme for compounds of formula I (2,5-tetrahydropyran derivatives) with R =CH2. 1 , L 1 and X 1 As defined for Formula I, L 2 , L 3 , L 4 Indicates H or F.

[0062] The corresponding starting materials can generally be prepared easily by a person skilled in the art by synthetic methods known from the literature or are commercially available.

[0063] Instead of the Grignard compounds according to Schemes 1 and 2, it is also possible to use aryl lithium compounds which are obtainable similarly by halogen-metal exchange with alkyl lithium compounds at low temperatures (see, for example, US Pat. No. 4,940,822).

[0064] Therefore, the present invention also relates to a process for preparing a compound of formula I, which comprises the process step of reacting an aryl-halogen compound of formula II with a compound of formula III to give a compound of formula IV, and in a further reaction step, converting it into a compound of formula I,

[0065] Hal-Ar 1 -Ar 2 -X 1 II

[0066] Where X 1 ,Ar 1 and Ar 2 As defined for Formula I, and

[0067] Hal represents Br, I or Cl, preferably Br,

[0068]

[0069] in

[0070] R 1 and Y 1 As defined for formula (I),

[0071]

[0072] wherein the groups are as defined above.

[0073] Furthermore, the invention relates to compounds of the formula IV as indicated above and below.

[0074] For the reaction of compound II with III, compound II is usually first metallated, for example by reaction with an alkylmagnesium halide, magnesium or alkyllithium compound. The alkylmetal compound is then reacted with cyclohexyl ketone III. The cyclohexanol product of formula IV is converted into cyclohexene of formula I by acid-catalyzed elimination of water.

[0075] The reaction methods and reagents used are known in principle from the literature. Other reaction conditions are disclosed in the working examples.

[0076] Further preferred process variants not mentioned above are disclosed in the examples or in the claims.

[0077] The subsequent treatment of the method and the reaction mixture can be carried out in the form of a batch reaction or a continuous reaction procedure. The continuous reaction procedure encompasses, for example, reactions in a continuous stirred tank reactor, a stirred tank reactor cascade, a loop or cross-flow reactor, a flow tube or a microreactor. If necessary, the reaction mixture is optionally treated by solid phase filtration, chromatography, separation between immiscible phases (e.g., extraction), adsorption onto a solid support, by distillation, selective distillation, sublimation, crystallization, co-crystallization or by nanofiltration on a membrane to remove solvent and / or azeotropic mixture.

[0078] In the present disclosure, the 2,5-disubstituted dioxane ring of the formula

[0079]

[0080] Preferably, it refers to a dioxane ring in 2,5-trans configuration, that is, the substituents are preferably all in the equatorial position, in a preferred chair configuration. A 2,5-disubstituted tetrahydropyran ring of the formula

[0081]

[0082] Likewise preferred is a tetrahydropyran ring in the 2,5-trans configuration, ie the substituents are preferably all in the equatorial position, in the preferred chair configuration.

[0083] The present invention also relates to a liquid-crystalline medium comprising one or more compounds of the formula I according to the invention. The liquid-crystalline medium comprises at least two components. They are preferably obtained by mixing the components with one another. Thus, the process according to the invention for preparing a liquid-crystalline medium is characterized in that at least one compound of the formula I is mixed with at least one further mesogenic compound and optionally an additive is added.

[0084] The achievable combinations of clearing point, viscosity at low temperatures, thermal / UV stability, dielectric anisotropy, response time and contrast ratio are far superior to previous materials of the prior art.

[0085] The liquid-crystalline media according to the invention preferably contain 2 to 40, particularly preferably 4 to 30, components as further constituents in addition to one or more compounds according to the invention. In particular, these media 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 nematic (unidirectional or isotropic) substances, in particular substances from the following classes: azoxybenzene, benzylideneaniline, biphenyl, terphenyl, phenyl benzoate or cyclohexyl benzoate, phenyl ester of cyclohexanecarboxylic acid or cyclohexyl ester of cyclohexanecarboxylic acid, phenyl ester of cyclohexylbenzoic acid or cyclohexyl ester of cyclohexanecarboxylic acid, phenyl ester of cyclohexylbenzoic acid or cyclohexyl ester of cyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl benzoate, cyclohexylphenyl ester of cyclohexanecarboxylic acid or cyclohexylphenyl ester of cyclohexanecarboxylic acid, cyclohexylphenyl benzoate, cyclohexylphenyl ester of cyclohexanecarboxylic acid or cyclohexylphenyl ester of cyclohexanecarboxylic acid, phenylcyclohexane, cyclohexylbiphenyl, phenylcyclohexylcyclohexane, cyclohexyl Cyclohexane, cyclohexylcyclohexylcyclohexane, 1,4-dicyclohexylbenzene, 4,4'-dicyclohexylbiphenyl, phenylpyrimidine or cyclohexylpyrimidine, phenylpyridine or cyclohexylpyridine, phenyldioxane or cyclohexyldioxane, phenyl-1,3-dithiane or cyclohexyl-1,3-dithiane, 1,2-diphenylethane, 1,2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1-cyclohexyl-2-(4-phenylcyclohexyl)ethane, 1-cyclohexyl-2-diphenylethane, 1-phenyl-2-cyclohexylphenylethane, optionally halogenated stilbene, benzylphenyl ether, diphenylacetylene and substituted cinnamic acid. The 1,4-phenylene group in these compounds may also be fluorinated.

[0086] The most important compounds suitable as further constituents of the medium according to the invention can be characterized by formulae 1, 2, 3, 4 and 5:

[0087] R'-LER" 1

[0088] R'-L-COO-ER" 2

[0089] R'-L-CF2O-ER" 3

[0090] R'-L-CH2CH2-ER" 4

[0091] R'-LC≡CER" 5

[0092] In the formulae 1, 2, 3, 4 and 5, L and E, which may be identical or different, in each case independently of one another, represent a divalent radical from the group formed by the structural elements -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -Py-, -G-Phe-, -G-Cyc- and mirror images thereof, wherein Phe represents unsubstituted or fluorine-substituted 1,4-phenylene, Cyc represents trans-1,4-cyclohexylene, Pyr represents pyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio represents 1,3-dioxane-2,5-diyl, Py represents tetrahydropyran-2,5-diyl and G represents 2-(trans-1,4-cyclohexyl)ethyl.

[0093] Preferably, one of the groups L and E is Cyc, Phe or Pyr. E is preferably Cyc, Phe or Phe-Cyc. The medium according to the invention preferably comprises one or more components selected from the group consisting of compounds of formulae 1, 2, 3, 4 and 5, wherein L and E are selected from the group consisting of Cyc, Phe and Pyr; and simultaneously comprises one or more components selected from the group consisting of compounds of formulae 1, 2, 3, 4 and 5, wherein one of the groups L and E is selected from the group consisting of Cyc, Phe, Py and Pyr, and the other group is selected from the group consisting of -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-; and optionally comprises one or more components selected from the group consisting of compounds of formulae 1, 2, 3, 4 and 5, wherein the groups L and E are selected from the group consisting of -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.

[0094] R' and / or R" each independently represent alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkylacyloxy with up to 8 C atoms, -F, -Cl, -CN, -NCS or -(O) i CH 3-k F k , where i is 0 or 1 and k is 1, 2, or 3.

[0095] In a smaller subgroup of compounds of the formulae 1, 2, 3, 4 and 5, R' and R" each independently of one another represent an alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkylacyloxy group having up to 8 C atoms. This smaller subgroup is referred to hereinafter as group A and the compounds are represented by the sub-formulae 1a, 2a, 3a, 4a and 5a. In most of these compounds, R' and R" are different from one another, one of these groups being typically alkyl, alkenyl, alkoxy or alkoxyalkyl.

[0096] In another smaller subgroup of compounds of Formulae 1, 2, 3, 4 and 5 (referred to as Group B), R" represents -F, -Cl, -NCS or -(O) i CH 3-k F k , wherein i is 0 or 1 and k is 1, 2 or 3. Compounds in which R" has this meaning are represented by the sub-formulae 1b, 2b, 3b, 4b and 5b. Particular preference is given to those compounds of the sub-formulae 1b, 2b, 3b, 4b and 5b in which R" has the meaning -F, -Cl, -NCS, -CF3, -OCHF2 or -OCF3.

[0097] In the compounds of the sub-formulae 1b, 2b, 3b, 4b and 5b, R′ has the meaning indicated in the case of the compounds of the sub-formulae 1a to 5a and is preferably alkyl, alkenyl, alkoxy or alkoxyalkyl.

[0098] In another smaller subgroup of compounds of formulae 1, 2, 3, 4 and 5, R" represents -CN. This subgroup is referred to hereinafter as group C and the compounds of this subgroup are described by subformulae 1c, 2c, 3c, 4c and 5c, respectively. In the compounds of subformulae 1c, 2c, 3c, 4c and 5c, R' has the meaning indicated in the case of the compounds of subformulae 1a to 5a and is preferably alkyl, alkoxy or alkenyl.

[0099] Besides the preferred compounds of groups A, B and C, further compounds of the formulae 1, 2, 3, 4 and 5 with further variants of the substituents mentioned are also customary. All these substances are obtainable by processes known from the literature or analogous thereto.

[0100] In addition to the compound of formula I according to the invention, the medium according to the invention preferably comprises one or more compounds selected from groups A, B and / or C. The weight proportions of the compounds from these groups in the medium according to the invention are preferably:

[0101] Group A: 0 to 90%, preferably 20 to 90%, particularly preferably 30 to 90%;

[0102] Group B: 0 to 80%, preferably 10 to 80%, particularly preferably 10 to 65%;

[0103] Group C: 0 to 80%, preferably 0 to 80%, particularly preferably 0 to 50%;

[0104] The sum of the proportions by weight of the compounds from groups A, B and / or C present in the respective medium according to the invention is preferably 5 to 90% and particularly preferably 10 to 90%.

[0105] The media according to the invention preferably comprise 1 to 40%, particularly preferably 3 to 30%, of the compounds according to the invention.

[0106] The liquid crystal mixture according to the invention is prepared in a conventional manner per se. Typically, the desired amount of the component used in smaller amounts is dissolved in the component constituting the main component, preferably at elevated temperatures. It is also possible to mix solutions of the components in organic solvents (e.g. acetone, chloroform or methanol) and remove the solvent again after sufficient mixing, e.g. by distillation. In addition, the mixture can be prepared in other conventional ways, e.g. by using a premix of, e.g., a homologue mixture, or using a so-called "multi-bottle" system.

[0107] The dielectric may also contain other additives known to the person skilled in the art and described in the literature. For example, 0 to 15%, preferably 0 to 10%, of pleochroic dyes, chiral dopants, stabilizers or nanoparticles may be added. The added individual compounds are used in concentrations of 0.01 to 6%, preferably 0.1 to 3%. However, the concentrations indicated for the other components of the liquid crystal mixture (i.e. the liquid crystal or mesogenic compound) are indicated in this document without taking into account the concentrations of these additives.

[0108] The liquid-crystal mixtures according to the invention make it possible to significantly broaden the usable parameter latitude.

[0109] The invention also relates to electro-optical displays containing media of this type (in particular TFT displays having two parallel planar outer plates which together with a frame form a cell, an integrated non-linear component for switching the individual pixels on the outer plates, and a nematic liquid crystal mixture with positive dielectric anisotropy and high specific resistance located in the cell), and to the use of these media for electro-optical purposes.

[0110] The expression "alkyl" encompasses unbranched and branched alkyl radicals having 1 to 15 carbon atoms, especially the unbranched radicals methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl and n-heptyl. Radicals having 2 to 5 carbon atoms are generally preferred.

[0111] The expression "alkenyl" encompasses non-branched and branched alkenyls, especially non-branched groups, with up to 15 carbon atoms. Particularly preferred alkenyls are C2-C7-1E-alkenyls, C4-C7-3E-alkenyls, C5-C7-4-alkenyls, C6-C7-5-alkenyls and C7-6-alkenyls, especially C2-C7-1E-alkenyls, C4-C7-3E-alkenyls and C5-C7-4-alkenyls. The example of preferred alkenyls is vinyl, 1E-propenyls, 1E-butenyls, 1E-pentenyls, 1E-hexenyls, 1E-heptenyls, 3-butenyls, 3E-pentenyls, 3E-hexenyls, 3E-heptenyls, 4-pentenyls, 4Z-hexenyls, 4E-hexenyls, 4Z-heptenyls, 5-hexenyls, 6-heptenyls etc. Groups having up to 5 carbon atoms are generally preferred.

[0112] The expression "halogenated alkyl" preferably encompasses monofluorinated or polyfluorinated and / or chlorinated groups. This includes perhalogenated groups. Particularly preferred are fluorinated alkyl groups, in particular CF3, CH2CF3, CH2CHF2, CHF2, CH2F, CHFCF3 and CF2CHFCF3. The expression "halogenated alkenyl" and related expressions are interpreted accordingly.

[0113] The total amount of compounds of the formula I in the mixtures according to the invention is not critical. The mixtures may therefore comprise one or more further components for the purpose of optimizing various properties.

[0114] The structure of the matrix display according to the invention consisting of polarizers, electrode substrates and surface-treated electrodes corresponds to the common design of this type of display. The term common design is used broadly in this article and also covers all derivatives and variants of matrix displays (especially matrix display components based on polysilicon TFTs).

[0115] However, an essential difference between the display according to the invention and hitherto conventional displays based on twisted nematic liquid crystal cells lies in the choice of the liquid crystal parameters of the liquid crystal layer.

[0116] The following examples illustrate the invention without limiting it. A person skilled in the art will be able to gather from the examples working details which are not given in detail in the general description, generalize them according to general expertise and apply them to specific problems.

[0117] In the above and below, percentage data represent weight percentages. All temperatures are indicated in degrees Celsius. Furthermore, C=crystalline state, N=nematic phase, Sm=smectic phase (more specifically, SmA, SmB, etc.), Tg=glass transition temperature and I=isotropic phase. The data between these symbols represent transition temperatures. Δn represents optical anisotropy (589 nm, 20° C.), Δε represents dielectric anisotropy (1 kHz, 20° C.), and γ1 represents rotational viscosity (20° C.; in mPa·s).

[0118] The physical, physicochemical and electro-optical parameters are determined by generally known methods, in particular as described in the handbook "Merck Liquid Crystals - -Physical Properties of Liquid Crystals -Description of the Measurement Methods", 1998, Merck KGaA, Darmstad.

[0119] The dielectric anisotropy Δε of the individual substances was determined at 20° C. and 1 kHz. For this purpose, 5 to 10% by weight of the substance to be investigated dissolved in the dielectrically positive mixture ZLI-4792 (Merck KGaA) was measured and the measured values ​​were extrapolated to 100% concentration. The optical anisotropy Δn was determined at 20° C. and a wavelength of 589.3 nm, and the rotational viscosity γ1 was determined at 20° C., both also determined by linear extrapolation.

[0120] In this application, unless expressly stated otherwise, plural forms of terms refer to both the singular and the plural, and vice versa. Other combinations of embodiments and variations of the invention according to the description also come from the appended claims or combinations of a plurality of these claims.

[0121] In the above and below, the abbreviations have the following meanings:

[0122] RT Room temperature

[0123] DCM Dichloromethane

[0124] EA Ethyl acetate

[0125] THF Tetrahydrofuran

[0126] MTB ether methyl tert-butyl ether

[0127] sat. saturated

[0128] dist. Distillation Example

[0129] The present invention is described in detail by the following non-limiting examples.

[0130] Example 1 :2-[4-[3-fluoro-4-(2,3,4-trifluorophenyl)phenyl]cyclohex-3-en-1-yl]-5-propyl-1,3-dioxane

[0131]

[0132] Step 1.1 :4-(5-propyl-1,3-dioxane-2-yl)cyclohexanone

[0133]

[0134] Toluene-4-sulfonic acid monohydrate (6.4 g, 32 mmol) was added to a solution of 2-propylpropane-1,3-diol 1 (CAS 2612-28-4, 23.9 g, 193 mmol) and 4-oxacyclohexanecarboxaldehyde 2 (CAS 96184-81-5, 30.0 g, 170 mmol) in DCM (270 ml), and the mixture was refluxed on a water separator. After 90 min, the reaction mixture was cooled to RT and chromatographed on silica gel (DCM / EA 9:1). 4-(5-propyl-1,3-dioxane-2-yl)cyclohexanone 3 was isolated as a yellow transparent oil, which formed crystals after solidification.

[0135] Step 1.2 :1-(4-bromo-2-fluorophenyl)-2,3,4-trifluorobenzene

[0136]

[0137] A solution of 4-bromo-2-fluoro-1-iodobenzene 4 (CAS 105931-73-5, 30.0 g, 98 mmol), sodium carbonate (20.7 g, 106 mmol), distilled water (70 ml) and toluene (165 ml) was warmed to 70 °C and tetrakis(triphenylphosphine)palladium(0) (3.4 g, 3 mmol) was added. A solution of (2,3,4-trifluorophenyl)boric acid 5 (17.2 g, 98 mmol) in ethanol (28 ml) was added dropwise to the boiling reaction mixture and the mixture was refluxed overnight. Distilled water was added to the reaction mixture, which was then diluted with toluene. The aqueous phase was separated and extracted with toluene. The combined organic phases were washed with saturated sodium chloride solution, dried over sodium sulfate, filtered and evaporated in vacuo. The crude product was chromatographed on silica gel (heptane) to give 1-(4-bromo-2-fluorophenyl)-2,3,4-trifluorobenzene 6 as a colorless oil.

[0138] Step 1.3 :1-[3-Fluoro-4-(2,3,4-trifluorophenyl)phenyl]-4-(5-propyl-1,3-dioxane-2-yl)cyclohexanol

[0139]

[0140] A solution of 1-(4-bromo-2-fluorophenyl)-2,3,4-trifluorobenzene 6 (10.0 g, 28 mmol) in THF (50 ml) was added dropwise to a solution of isopropylmagnesium chloride / lithium chloride (43 ml, 56 mmol, 1.3 mol / l in THF) at 30°C. After 60 min, a solution of 4-(5-propyl-1,3-dioxane-2-yl)cyclohexanone 3 (9.7 g, 29 mmol) in THF (100 ml) was added dropwise at a maximum of 30°C. After a further 60 min, distilled water was added to the reaction mixture, which was then adjusted to pH=5 using hydrochloric acid (1 M). The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with saturated sodium bicarbonate solution, dried over sodium sulfate, filtered and evaporated in vacuo. The residue gave 1-[3-fluoro-4-(2,3,4-trifluorophenyl)phenyl]-4-(5-propyl-1,3-dioxan-2-yl)cyclohexanol 7 in the form of pale yellow crystals.

[0141] Step 1.4 :2-[4-[3-fluoro-4-(2,3,4-trifluorophenyl)phenyl]cyclohex-3-en-1-yl]-5-propyl-1,3-dioxane

[0142]

[0143] Toluene-4-sulfonic acid monohydrate (1.0 g, 6 mmol) was added to a solution of 1-[3-fluoro-4-(2,3,4-trifluorophenyl)phenyl]-4-(5-propyl-1,3-dioxane-2-yl)cyclohexanol 7 (20.3 g, 23 mmol) in toluene (150 ml), and the mixture was refluxed on a water separator for 90 min. The reaction mixture was cooled to RT, evaporated in vacuo and chromatographed over silica gel (heptane / MTB ether 9:1). After crystallization from 2-propanol and heptane, 2-[4-[3-fluoro-4-(2,3,4-trifluorophenyl)phenyl]cyclohex-3-en-1-yl]-5-propyl-1,3-dioxane 8 was isolated as a colorless solid.

[0144] Compound 8 exhibits the following phase behavior:

[0145] C 78SmA 158N 199.7I.

[0146] Δε:10.5

[0147] ε ┴ :8.8

[0148] Δn:0.176

[0149] Example 2:2-[4-[4-[2,3-difluoro-4-(trifluoromethyl)phenyl]-3-fluorophenyl]cyclohex-3-en-1-yl]-5-propyl-1,3-dioxane

[0150]

[0151] Step 2.1 :1-(4-bromo-2-fluorophenyl)-2,3-difluoro-4-(trifluoromethyl)benzene

[0152]

[0153] A solution of 4-bromo-2-fluoro-1-iodobenzene 4 (34.5 g, 112 mmol), sodium carbonate (23.8 g, 225 mmol), distilled water (80 ml) and toluene (190 ml) was warmed to 70 °C and tetrakis(triphenylphosphine)palladium(0) (3.4 g, 3 mmol) was added. A solution of [2,3-difluoro-4-(trifluoromethyl)phenyl]boronic acid 9 (25.5 g, 112 mmol) in ethanol (33 ml) was added dropwise to the boiling reaction mixture, which was then refluxed overnight. Distilled water was added to the reaction mixture, which was then diluted with toluene. The aqueous phase was separated and extracted with toluene. The combined organic phases were washed with saturated sodium chloride solution, dried over sodium sulfate, filtered and evaporated in vacuo. The crude product was chromatographed on silica gel (heptane) to give 1-(4-bromo-2-fluorophenyl)-2,3-difluoro-4-(trifluoromethyl)benzene 10 as a colorless oil.

[0154] Step 2.2 :1-[4-[2,3-difluoro-4-(trifluoromethyl)phenyl]-3-fluorophenyl]-4-(5-propyl-1,3-dioxane-2-yl)cyclohexanol

[0155]

[0156] A solution of 1-(4-bromo-2-fluorophenyl)-2,3-difluoro-4-(trifluoromethyl)benzene 10 (6.1 g, 11 mmol) in THF (20 ml) was added dropwise to a solution of isopropylmagnesium chloride / lithium chloride (17.2 ml, 22 mmol, 1.3 mol / l in THF) at 30°C. After 60 min, a solution of 4-(5-propyl-1,3-dioxane-2-yl)cyclohexanone 3 (3.8 g, 11 mmol) in THF (30 ml) was added dropwise at a maximum of 30°C. After a further 60 min, distilled water was added to the reaction mixture, which was then adjusted to pH=5 using hydrochloric acid (1 M). The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with saturated sodium bicarbonate solution, dried over sodium sulfate, filtered and evaporated in vacuo. The residue gave 1-[4-[2,3-difluoro-4-(trifluoromethyl)phenyl]-3-fluorophenyl]-4-(5-propyl-1,3-dioxan-2-yl)cyclohexanol 11 in the form of pale yellow crystals.

[0157] Step 2.3 :2-[4-[4-[2,3-difluoro-4-(trifluoromethyl)phenyl]-3-fluorophenyl]cyclohex-3-en-1-yl]-5-propyl-1,3-dioxane

[0158]

[0159] Toluene-4-sulfonic acid monohydrate (0.3 g, 2 mmol) was added to a solution of 1-[4-[2,3-difluoro-4-(trifluoromethyl)phenyl]-3-fluorophenyl]-4-(5-propyl-1,3-dioxane-2-yl)cyclohexanol 11 (8.3 g, 8 mmol) in toluene (50 ml), and the mixture was refluxed on a water separator for 90 min. The reaction mixture was cooled to RT, evaporated in vacuo and chromatographed over silica gel (heptane / MTB ether 95:5). After crystallization from 2-propanol and heptane, 2-[4-[4-[2,3-difluoro-4-(trifluoromethyl)phenyl]-3-fluoro-phenyl]cyclohex-3-ene-1-yl]-5-propyl-1,3-dioxane 12 was isolated as a colorless solid.

[0160] Compound 12 exhibits the following phase behavior:

[0161] C 91SmA 206I.

[0162] Δε:16.9

[0163] ε ┴ :9.0

[0164] Δn:0.169

[0165] Example 3:2-[4-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]cyclohex-3-en-1-yl]-5-propyl-1,3-dioxane

[0166]

[0167] Step 3.1 :1-Bromo-2,3-difluoro-4-(3,4,5-trifluorophenyl)benzene

[0168]

[0169] THF (5 ml), bis(triphenylphosphine)palladium(II) chloride (15% of Pd) (2.2 g, 3 mmol) and hydrazine hydroxide (0.2 ml, 3 mmol) were added to a solution of sodium metaborate tetrahydrate (13.0 g, 94 mmol) in distilled water (42 ml), and the mixture was stirred for 5 min. 1-Bromo-2,3-difluoro-4-iodobenzene 13 (CAS 207989-04-6, 25.0 g, 78 mmol), (3,4,5-trifluorophenyl)boric acid 14 (CAS 143418-49-9, 17.2 g, 98 mmol) and THF (40 ml) were then added, and the reaction mixture was refluxed overnight. (3,4,5-Trifluorophenyl)boric acid 14 (2.5 g, 14 mmol) and sodium metaborate tetrahydrate (2.5 g, 18 mmol) were then added again to the reaction mixture, followed by reflux overnight. Distilled water was added to the reaction mixture, followed by dilution with MTB ether. The aqueous phase was separated and extracted with MTB ether. The combined organic phase was washed with saturated sodium chloride solution, dried over sodium sulfate, filtered and evaporated in vacuo. The crude product was chromatographed on silica gel (heptane) to give 1-bromo-2,3-difluoro-4-(3,4,5-trifluorophenyl)benzene 15 as a clear, colorless oil.

[0170] Step 3.2 :1-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]-4-(5-propyl-1,3-dioxane-2-yl)cyclohexanol

[0171]

[0172] A solution of 1-bromo-2,3-difluoro-4-(3,4,5-trifluorophenyl)benzene 15 (8.0 g, 20 mmol) in THF (50 ml) was added dropwise to a solution of isopropylmagnesium chloride / lithium chloride (31 ml, 41 mmol, 1.3 mol / l in THF) at 30°C. After 60 min, a solution of 4-(5-propyl-1,3-dioxane-2-yl)cyclohexanone 3 (6.8 g, 21 mmol) in THF (30 ml) was added dropwise at a maximum of 30°C. After a further 60 min, distilled water was added to the reaction mixture, which was then adjusted to pH=5 using hydrochloric acid (2 M). The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with saturated sodium bicarbonate solution, dried over sodium sulfate, filtered and evaporated in vacuo. The residue gave 1-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]-4-(5-propyl-1,3-dioxan-2-yl)cyclohexanol 16 in the form of light red crystals.

[0173] Step 3.3 :2-[4-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]cyclohex-3-en-1-yl]-5-propyl-1,3-dioxane

[0174]

[0175] Sulfuric acid (0.1 ml, 8 mmol) was added to a solution of 1-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]-4-(5-propyl-1,3-dioxane-2-yl)cyclohexanol 16 (12.7 g, 9 mmol) in xylene (50 ml) and the mixture was refluxed on a water separator for 5 h. The reaction mixture was cooled to RT, evaporated in vacuo and chromatographed on silica gel (heptane / MTB ether 95:5). After crystallization from 2-propanol and heptane, 2-[4-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]cyclohex-3-ene-1-yl]-5-propyl-1,3-dioxane 17 was isolated as a colorless solid.

[0176] Compound 17 exhibits the following phase behavior:

[0177] C 80SmA 138N 173I.

[0178] Δε:10.5

[0179] ε ┴ :8.4

[0180] Δn:0.176

[0181] Example 4:2-[4-[3-fluoro-4-(2,3,4-trifluorophenyl)phenyl]cyclohex-3-en-1-yl]-5-propyl-tetrahydropyran

[0182]

[0183] Step 4.1 :4-(5-propyltetrahydropyran-2-yl)cyclohexanone

[0184]

[0185] 4-(5-Propyltetrahydropyran-2-yl)phenol 18 (CAS 879544-24-8, 50.0 g, 227 mmol) was dissolved in xylene (330 ml), Pd / C (5%, 4.4 g) and sodium carbonate (0.2 g, 2.3 mmol) were added, and the mixture was hydrogenated with hydrogen (10.2 l) under pressure. After 8 h, the solution was filtered and evaporated in vacuo. The crude product was dissolved in heptane (200 ml), and a mixture of sulfur trioxide / pyridine complex (37.0 g, 233 mmol) and diatomaceous earth (50 g) was added, and the mixture was stirred overnight at RT. Then diatomaceous earth (20 g) and silica gel (20 g) were added again, and the mixture was stirred. After 90 min, the reaction mixture was filtered under suction. The filtrate was washed with distilled water and saturated sodium bicarbonate solution, dried over sodium sulfate, filtered and evaporated in vacuo. The residue gave 4-(5-propyltetrahydropyran-2-yl)cyclohexanone 19 as a clear light yellow oil.

[0186] Step 4.2 :1-[3-Fluoro-4-(2,3,4-trifluorophenyl)phenyl]-4-(5-propyltetrahydropyran-2-yl)cyclohexanol

[0187]

[0188] A solution of 1-(4-bromo-2-fluorophenyl)-2,3,4-trifluorobenzene 6 (8.5 g, 24 mmol) in THF (50 ml) was added dropwise to a solution of isopropylmagnesium chloride / lithium chloride (37 ml, 48 mmol, 1.3 mol / l in THF) at 30°C. After 60 min, a solution of 4-(5-propyltetrahydropyran-2-yl)cyclohexanone 19 (5.7 g, 25 mmol) in THF (50 ml) was added dropwise at a maximum of 30°C. After a further 60 min, distilled water was added to the reaction mixture, which was then adjusted to pH=5 using hydrochloric acid (2 M). The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with saturated sodium bicarbonate solution, dried over sodium sulfate, filtered and evaporated in vacuo. The residue gave 1-[3-fluoro-4-(2,3,4-trifluorophenyl)phenyl]-4-(5-propyltetrahydropyran-2-yl)cyclohexanol 20 as a reddish brown oil which crystallized upon standing.

[0189] Step 4.3 :2-[4-[3-fluoro-4-(2,3,4-trifluorophenyl)phenyl]cyclohex-3-en-1-yl]-5-propyltetrahydropyran

[0190]

[0191] Toluene-4-sulfonic acid monohydrate (0.6 g, 3 mmol) was added to a solution of 1-[3-fluoro-4-(2,3,4-trifluorophenyl)phenyl]-4-(5-propyltetrahydropyran-2-yl)cyclohexanol 20 (12.3 g, 14 mmol) in toluene (90 ml), and the mixture was refluxed on a water separator for 90 min. The reaction mixture was cooled to RT, evaporated in vacuo and chromatographed on silica gel (heptane / MTB ether 9:1). After crystallization from 2-propanol and heptane, 2-[4-[3-fluoro-4-(2,3,4-trifluorophenyl)phenyl]cyclohex-3-ene-1-yl]-5-propyltetrahydropyran 21 was isolated as a colorless solid.

[0192] Compound 21 exhibits the following phase behavior:

[0193] Tg-46C 87Sm?132I.

[0194] Δε:5.9

[0195] ε ┴ :8.3

[0196] Δn:0.176

[0197] Example 5 :2-[4-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]cyclohex-3-en-1-yl]-5-propyltetrahydropyran

[0198]

[0199] Step 5.1 :1-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]-4-(5-propyltetrahydropyran-2-yl)cyclohexanol

[0200]

[0201] A solution of 1-bromo-2,3-difluoro-4-(3,4,5-trifluorophenyl)benzene 15 (8.0 g, 20 mmol) in THF (50 ml) was added dropwise to a solution of isopropylmagnesium chloride / lithium chloride (31 ml, 41 mmol, 1.3 mol / l in THF) at 30°C. After 60 min, a solution of 4-(5-propyltetrahydropyran-2-yl)cyclohexanone 19 (4.9 g, 21 mmol) in THF (30 ml) was added dropwise at a maximum of 30°C. After a further 60 min, distilled water was added to the reaction mixture, which was then adjusted to pH=5 using hydrochloric acid (2 M). The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with saturated sodium bicarbonate solution, dried over sodium sulfate, filtered and evaporated in vacuo. The residue gave 1-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]-4-(5-propyltetrahydropyran-2-yl)cyclohexanol 22 in the form of light grey crystals.

[0202] Step 5.2 :2-[4-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]cyclohex-3-en-1-yl]-5-propyl-tetrahydropyran

[0203]

[0204] Sulfuric acid (0.1 ml, 1 mmol) was added to a solution of 1-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]-4-(5-propyltetrahydropyran-2-yl)cyclohexanol 22 (12.1 g, 12 mmol) in xylene (65 ml) and the mixture was refluxed on a water separator for 30 min. The reaction mixture was cooled to RT, evaporated in vacuo and chromatographed on silica gel (heptane / MTB ether 90:10). After crystallization from 2-propanol and heptane, 2-[4-[2,3-difluoro-4-(3,4,5-trifluorophenyl)phenyl]cyclohex-3-ene-1-yl]-5-propyl-tetrahydropyran 23 was isolated as a colorless solid.

[0205] Compound 23 exhibits the following phase behavior:

[0206] C 69SmA 91N 178I.

[0207] Δε:9.9

[0208] ε ┴ :7.5

[0209] Δn:0.153

[0210] Comparative Example:

[0211]

[0212] Mp: 55℃

[0213] ε ┴ :6.2

[0214] Δn:0.123

[0215] The comparative compounds have lower ε than the compounds according to the invention. ┴ And it does not have a nematic phase.

[0216] The following compounds were prepared similarly:

[0217]

Claims

1. A compound of formula I, in Ar 1 -Ar 2 represents a group selected from the following sub-formulas X 1 Indicates F, CF 3 、OCF 3 , Y 1 Indicates O or CH 2 , R 1 represents an alkyl radical having 1 to 15 C atoms, wherein in addition one or more of these radicals CH 2 The radicals may in each case be independently of one another represented by -C≡C-, -CH=CH-, -O-, -CO-O- or -O-CO- is replaced in such a way that the O atom and the S atom are not directly connected to each other, and wherein in addition one or more H atoms may be replaced by halogen, and L 1 Indicates H.

2. The compound according to claim 1, Features R 1 denotes an alkyl or alkenyl group having up to 8 C atoms.

3. The compound according to claim 1, Features Ar 1 -Ar 2 A group representing the following subformula 4. The compound according to claim 1, Features Ar 1 -Ar 2 A group representing the following subformula 5. The compound according to claim 1, Features Y 1 Indicates O.

6. The compound according to claim 1, Features Y 1 Indicates CH 2 .

7. The compound according to claim 1, which is selected from the following formula: Where R 1 and L 1 has the meaning indicated in claim 1 or 2.

8. The compound according to claim 1, Features R 1 represents straight-chain alkyl having 1 to 7 C atoms or unbranched alkenyl having 2 to 8 C atoms.

9. A process for the preparation of a compound of formula I according to any one of claims 1 to 8, comprising the step of reacting an aryl-halogen compound of formula II with a compound of formula III to obtain a compound of formula IV, and in a further reaction step, converting it into a compound of formula I, Weather-Ar 1 -And 2 -X 1 II Where X 1 ,Ar 1 and Ar 2 As defined in claim 1, and Hal represents Br, I or Cl, in R 1 and Y 1 As defined in claim 1, The group R 1 , Y 1 ,Ar 1 ,Ar 2 and X 1 As defined in claim 1.

10. Compounds of formula IV The group R 1 , Y 1 ,Ar 1 ,Ar 2 and X 1 As defined in claim 1.

11. Use of one or more compounds of the formula I according to any one of claims 1 to 8 as a component in a liquid-crystalline medium.

12. A liquid-crystalline medium comprising at least two mesogenic compounds, Features It comprises at least one compound of formula I according to any one of claims 1 to 8.

13. Use of a liquid-crystalline medium according to claim 11 for electro-optical purposes.

14. An electro-optical liquid crystal display comprising a liquid crystal medium according to claim 12.

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