WO2018141759A1

WO2018141759A1 - Liquid-crystalline compounds

Info

Publication number: WO2018141759A1
Application number: PCT/EP2018/052322
Authority: WO
Inventors: Constanze Brocke; Achim Goetz
Original assignee: Merck Patent Gmbh
Priority date: 2017-02-03
Filing date: 2018-01-31
Publication date: 2018-08-09
Also published as: CN110325522B; DE102018000075A1; CN110325522A; TWI761441B; TW201840828A

Abstract

The invention relates to compounds of formula (I), wherein R1, L1, L2 and X have the meanings defined in claim 1, to a method for the production thereof, to liquid-crystalline media containing at least one compound of formula (I), and to electro-optical displays containing such a liquid-crystalline medium.

Description

Liquid crystalline compounds

The invention relates to compounds of the formula I as defined below, a process for their preparation, liquid-crystalline media comprising at least one compound of the formula I and their use as component (s) in liquid-crystalline media. Moreover, the present invention relates to liquid crystal and electro-optical

Display elements which contain the liquid-crystalline media according to the invention. The compounds according to the invention have as structural element a characteristically substituted 2- (4-phenyl-cyclohex-3-enyl) - [1,3] -dioxane group.

In recent years, the areas of application for

Liquid crystalline compounds on various types of display devices, electro-optical devices, electronic components, sensors, etc. significantly expanded. For this reason, a number of different structures have been proposed, especially in the field of nematic liquid crystals. The nematic liquid-crystal mixtures have hitherto found the widest application in flat display devices. They were especially in passive TN or

STN matrix displays or systems with a TFT active matrix used.

The liquid-crystalline compounds according to the invention can be used as component (s) of liquid-crystalline media, in particular for displays based on the principle of the twisted cell, the guest-host effect, the effect of deformation of upright phases DAP or ECB (electrically controlled birefringence), based on the IPS effect (in-plane switching) or the effect of dynamic dispersion. The use of polar dioxane compounds having three rings as liquid-crystalline substances is not unknown to the person skilled in the art. Various compounds have been described with a dioxane ring as a liquid crystalline or mesogenic material and its preparation, such as. In document CN 105038816 A. The compounds proposed therein have no cyclohexene ring. As a polar end group, the compounds contain z. For example, -OCF ₃ or fluorine. It is an object of the present invention to find novel stable compounds which are suitable as component (s) of liquid-crystalline media. In particular, the compounds should simultaneously have a comparatively low viscosity, as well as a high dielectric

Possess anisotropy. For many current mixing concepts in the field of liquid crystals, it is advantageous to use compounds with a positive dielectric anisotropy Δε in conjunction with a medium to high optical anisotropy.

With regard to the most diverse applications of such compounds with high Δε, it was desirable to have available further compounds, preferably with a high clearing point and low viscosity, which have precisely tailor-made properties for the respective applications.

The invention was thus an object of new stable

Find compounds that as component (s) liquid-crystalline media, in particular for z. As TN, STN, IPS, FFS and TN TFT displays are suitable.

In addition, the compounds of the invention should be thermally and photochemically stable under the conditions prevailing in the fields of application. As mesogens they should have a broad

enable nematic phase in mixtures with liquid crystalline co-components as well as be miscible with nematic base mixtures, especially at low temperatures. Also preferred are substances with a low melting point and a low enthalpy of fusion, since these quantities are in turn indicative of the above-mentioned desirable properties, such as. B. a high

Solubility, a broad liquid crystalline phase and a low tendency for spontaneous crystallization in mixtures at low temperatures.

Especially the solubility at low temperature while avoiding any crystallization is important for the safe operation and transport of displays in vehicles and aircraft and outdoors. Surprisingly, it has been found that the compounds according to the invention are outstandingly suitable as components of liquid-crystalline media. With their help, liquid-crystalline media can be obtained for displays that require particularly high dielectric anisotropies, in particular for IPS or FFS displays, but also for TN or STN displays. The compounds of the invention are sufficiently stable and colorless. In particular, they are distinguished by high dielectric anisotropies Δε, as a result of which, in the application in optical switching elements, lower layer thicknesses and thus

lower threshold voltages are required. They are for

Compounds with comparable properties readily soluble. In addition, the compounds of the invention have a

comparatively very high clearing point and at the same time low values for the rotational viscosity. The compounds have relatively low melting points. Surprisingly, it is possible with the compounds according to the invention to prepare liquid-crystalline mixtures having high values for the elastic constants (K ¹¹ / K ²² / K ³³ ) without adversely affecting the other application parameters.

This results in media with low switching time and high contrast.

With the provision of the compounds according to the invention is quite generally the range of liquid-crystalline substances, which vary from various application aspects

Production of liquid-crystalline mixtures are significantly widened.

The compounds of the invention have a broad

Scope of application. Depending on the choice of substituents, these compounds may serve as base materials from which liquid crystalline media are predominantly composed. But it can also be the compounds of the invention

liquid crystal base materials can be added from other classes of compounds, for example, to influence the dielectric and / or the optical anisotropy of such a dielectric and / or to optimize its threshold voltage and / or its viscosity. The invention thus relates to compounds of the formula I

CF ₃ , OCF ₃ , F, Cl, OCHF ₂ , CHF ₂ , SCN, CN, -C ^ C-CF ₃ or -CH = CH-CF ₃ , an alkyl radical having 1 to 15 C atoms, wherein in these radicals also one or more CH ₂ groups each independently of one another by -C = -O = CH-,

-CO-O-, or -O-CO- can be replaced so that O / S atoms are not directly linked to each other, and wherein also one or more H atoms may be replaced by halogen, or H, preferably a halogenated or unsubstituted alkyl radical having 1 to 15 C atoms, wherein in these radicals also one or more CH ₂ groups may each be independently replaced by -C ^ C- or -CH = CH-, and

L ¹ and L ² independently of one another are H or F, preferably H,

mean.

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

Likewise provided by the present invention are liquid-crystalline media having at least two liquid-crystalline components which contain at least one compound of the formula I. The compounds of the formula I have a wide range of applications. Depending on the choice of substituents, these compounds may 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 influence the dielectric and / or optical anisotropy of such a dielectric and / or to optimize its threshold voltage and / or its viscosity.

The compounds of the formula I are colorless in the pure state and form liquid-crystalline mesophases in their own or in mixtures in a temperature range which is favorably located for electrooptical use. With the compounds according to the invention, broad nematic phase ranges can be achieved. In liquid-crystalline mixtures, the substances according to the invention significantly increase the optical anisotropy and / or lead to an improvement in the low-temperature storage stability compared to comparable mixtures with a high dielectric content

Anisotropy. At the same time, the compounds are characterized by good UV stability.

The radical R ^{1 of} the formula I and its sub-formulas preferably denotes alkyl or alkenyl having up to 8 carbon atoms. R ¹ particularly preferably denotes a straight-chain alkyl radical having 1 to 7 C atoms or an unbranched alkenyl radical having 2 to 8 C atoms, in particular

unbranched alkyl having 2 to 7 carbon atoms.

The radical X of the formula I is preferably CF ₃ , OCF ₃ , F, -SCN, -C ^ C-CF ₃ or -CH = CH-CF ₃ , particularly preferably CF ₃ , OCF ₃ or F, and very particularly preferably CF ₃ or OCF ₃ . The radical -CH = CH-CF ₃ is preferably trans-configured.

Compounds of formula I with branched or substituted

Wing groups R ¹ may occasionally be of importance for better solubility in the usual liquid crystalline base materials. The group R ¹ is preferably straight-chain. Preference is given to compounds of the formulas I in which L ^{1 is} H, in particular in which L ¹ and L ^{2 are} H. The radical R ¹ is particularly preferably selected from the substructures: -CH ₃

-CeH

-CH = CH ₂

-CH = CH ₂ -CH ₃

-CH ₂ -CH ₂ -CH = CH ₂

-CH ₂ -CH ₂ -CH = CH-CH ₃

wherein the alkyl chains are preferably unbranched (n-alkyl).

Particularly preferred compounds of the formula I are the compounds of the formulas 1-1 to I-6:

wherein R ¹ independently has the meanings given above. Among the compounds of the formulas 1-1 to I-6, the formulas 1-1, I-2, I-4 and I-5 are preferred, in particular the compounds of the formula 1-1 and I-2.

Very particularly preferred compounds are mentioned below:



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) are described under reaction conditions, which are known and suitable for the above reactions. One can also make use of known per se, not mentioned here variants.

Compounds of the formula I can advantageously be prepared as shown in the following exemplary synthesis and examples (Schemes 1 to 3):

Grignard

Scheme 1. General synthetic scheme for the representation of

Compounds of the formula I. Bn is benzyl radical. X is a radical X as defined in formula I. R ¹ is a radical R ¹ is as in formula I.

The two polar end groups -CH = CH-CF ₃ and -C = C-CF ₃ can be represented as follows:

Scheme 2. Synthesis of end groups X = -CH = CH-CF ₃ and -C ^ C-CF ₃ ; Ar represents the substituted phenyl radical of the compounds of the formula I. In the first step, a molecular sieve is preferably added to absorb water.

By reversing the reaction sequence from Scheme 1, the synthetic scheme 3 results alternatively.

Scheme 3. Alternative general scheme of synthesis for the preparation of compounds of formula I. R ¹ and X are defined according to formula I.

Corresponding starting materials can usually be obtained from

One skilled in the art readily produce by literature methods of synthesis or are commercially available.

Instead of the outlined Grignard compounds according to Schemes 1 and 3, it is also possible to use aryllithium compounds which can be obtained analogously by halogen-metal exchange with alkyllithium compounds at low temperatures (cf., for example, US 4,940,822).

The invention therefore also has a process for the preparation of

The invention relates to compounds of the formula I which comprise a process step in which an arylmetal compound of the formula II

wherein X, L ¹ and L ^{2 are} as defined for formula I, and

M means Li, MgBr or MgCl,

with a compound of formula III

wherein

PG is a protecting group, preferably benzyl,

is reacted, and in further reaction steps comprising

Cleavage of the protective group PG (replacement by H) and oxidation of the resulting CH ₂ OH group to the aldehyde CH = O,

with a 2-substituted 1,3-diol of the formula IV

to a compound of formula I

wherein the groups are as defined above,

is implemented.

The reaction methods and reagents used are prin

known from the literature. Further reaction conditions may be the

Embodiments are taken.

Further, not mentioned above, preferred process variants can be taken from the examples or the claims.

The process and the subsequent work-up of the

Reaction mixture can in principle be carried out as a batch reaction or in a continuous reaction mode. The continuous reaction includes z. As the reaction in a continuous stirred tank reactor, a stirred tank cascade, a loop or cross-flow reactor, a flow tube or in a microreactor. The work-up of the reaction mixtures is optionally carried out, as required, by filtration over solid phases, chromatography, separation between immiscible phases (eg extraction), adsorption on solid supports, distilling off solvents and / or azeotropic mixtures, selective distillation, sublimation, crystallization, cocrystallization or by nanofiltration on membranes.

In the present disclosure, the 2,5-disubstituted

Dioxane ring of the formula

preferably prefers a 2,5-trans-configured dioxane ring, i. the

Substituents in the preferred chair conformation are both preferably in the equatorial position.

The invention also relates to liquid-crystalline media containing one or more of the compounds of the formula I. The liquid-crystalline media contain at least two components. They are preferably obtained by mixing the components together. A process according to the invention for the preparation of a liquid-crystalline medium is therefore characterized in that at least one compound of the formula I is mixed with at least one further mesogenic compound and, if appropriate, additives are added.

The achievable combinations of clearing point, low temperature viscosity, thermal / UV stability, dielectric anisotropy, switching time and contrast far exceed previous prior art materials.

The liquid-crystalline media according to the invention contain

preferably in addition to one or more inventive

Compounds as further constituents 2 to 40, more preferably 4 to 30 components. In particular, these media include next to one or more compounds of the invention 7 to 25 components. These further constituents are preferably selected from nematic or nematogenic (monotropic or isotropic) substances, in particular substances from the classes of azoxybenzenes,

Benzylideneanilines, biphenyls, terphenyls, phenyl or

Cyclohexyl benzoates, cyclohexane-carboxylic acid-phenyl or

cyclohexyl ester, phenyl or cyclohexyl ester of

Cyclohexylbenzoesäure, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic, Cyclohexylphenylester of benzoic acid, cyclohexanecarboxylic or Cyclohexylcyclohexancarbonsäure, Phenylcyclohexane, Cyclohexylbiphenyls, Phenylcyclohexylcyclohexane, Cyclohexylcyclohexane, Cyclohexylcyclohexylcyclohexane, 1, 4-bis-cyclo-hexylbenzenes, 4,4'-bis-cyclohexylbiphenyls , 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-cyclohexyl-2- (4-phenyl-cyclohexyl) -ethanes, 1-cyclohexyl-2-biphenylethanes, 1-phenyl-2-cyclohexyl-phenylethanes, optionally halogenated silibens, benzyl phenyl ethers, tolans and substituted cinnamic acids. The 1,4-phenylene groups in these compounds may also be fluorinated.

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

R'-L-E-R '

R'-L-COO-E-R '2

R'-L-CF ₂ O "3

R'-L-CH ₂ CH ₂ -EG '4

R'-LC = CE "5 In the formulas 1, 2, 3, 4 and 5, L and E, which may be the same or different, each independently represent a bivalent radical of the structural elements -Phe-, -Cyc-, -Phe- Phe-, - Phe-Cyc, -Cyc-Cyc, -Pyr, -Dio, -Py, -G-Phe, -G-Cyc and their mirror images formed group, wherein Phe is unsubstituted or substituted by fluorine 1, 4 Phenylene, Cyc trans-1, 4-cyclohexylene, Pyr pyrimidine-2,5-diyl or pyridine-2,5-diyl, diol 1, 3-dioxane-2,5-diyl, Py

Tetrahydropyran-2,5-diyl and G 2- (trans-1,4-cyclohexyl) -ethyl. Preferably, one of L and E is Cyc, Phe or Pyr. E is preferably Cyc, Phe or Phe-Cyc. The media according to the invention preferably comprise 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 simultaneously 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, Py 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 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 / or R "each independently represent alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy having up to 8 C atoms, -F, -Cl, -CN, -NCS or - (O) iCH ₃ -kF _k , where i is 0 or 1 and k is 1, 2 or 3.

R 'and R "each independently represent alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy having up to 8 C atoms in a smaller subgroup of the compounds of the formulas 1, 2, 3, 4 and 5 Subgroup group A called and the compounds are with the subformulae 1 a, 2 a, 3 a, 4 a and 5 a

designated. In most of these compounds R 'and R "are different from each other, one of these radicals is usually alkyl, alkenyl, alkoxy or alkoxyalkyl. In another known as group B smaller subgroup of the compounds of formulas 1, 2, 3, 4 and 5, R "is -F, -Cl, -NCS or - (O) I _3-k F _k, where i is 0 or 1 and k is 1, 2 or 3. The compounds in which R "has this meaning are designated by the subformulae 1 b, 2b, 3b, 4b and 5b. Particular preference is given to those compounds of the subformulae 1 b, 2b, 3b, 4b and 5b in which R "has the meaning -F, -Cl, -NCS, -CF ₃ , -OCHF ₂ or -OCF ₃ .

In the compounds of the subformulae 1 b, 2b, 3b, 4b and 5b, R 'has the meanings given for the compounds of the subformulae 1a to 5a and is preferably alkyl, alkenyl, alkoxy or alkoxyalkyl.

In a further smaller subgroup of the compounds of the formulas 1, 2, 3, 4 and 5, R "denotes -CN. This subgroup is referred to below as group C and the compounds of this subgroup are correspondingly reacted with partial formulas 1 c, 2c, 3c, 4c and 5c In the compounds of the subformulae 1c, 2c, 3c, 4c and 5c, R 'has the meanings given for the compounds of the subformulae 1a to 5a and is preferably alkyl, alkoxy or alkenyl.

In addition to the preferred compounds of groups A, B and C, other compounds of formulas 1, 2, 3, 4 and 5 with other variants of the proposed substituents are also used. All of these substances are available by methods known from the literature or in analogy thereto.

In addition to compounds of the formula I according to the invention, the media according to the invention preferably comprise one or more compounds which are selected from the groups A, B and / or C. The mass fractions of the compounds from these groups in the media according to the invention are preferably:

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

Group B: 0 to 80%, preferably 10 to 80%, particularly preferably 10 to 65%; Group C: 0 to 80%, preferably 0 to 80%, particularly preferably 0 to 50%; wherein the sum of the mass fractions of the compounds of the groups A, B and / or C contained in the respective inventive media is preferably 5 to 90% and particularly preferably 10 to 90%.

The media according to the invention preferably contain 1 to 40%, particularly preferably 3 to 30%, of the compounds according to the invention.

The preparation of the liquid-crystal mixtures according to the invention is carried out in a conventional manner. In general, the desired amount of the components used in lesser amount in the main constituent components is dissolved, preferably at elevated

Temperature. It is also possible to use solutions of the components in an organic solvent, e.g. in acetone, chloroform or methanol, and to remove the solvent again after thorough mixing, for example by distillation. Furthermore, it is possible to

Mixtures in other conventional ways, eg. By using premixes, e.g. Homologous mixtures or using so-called "multi-bottle" systems produce.

The dielectrics may also contain further additives known to the person skilled in the art and described in the literature. For example, 0 to 15%, preferably 0 to 10%, pleochroic dyes, chiral

Dopants, stabilizers or nanoparticles can be added. The individual added compounds are used in concentrations of 0.01 to 6%, preferably from 0.1 to 3%. However, the concentration data of the other constituents of the liquid-crystal mixtures ie the liquid-crystalline or mesogenic compounds are given, without taking into account the concentration of these additives. The liquid-crystal mixtures according to the invention enable a significant expansion of the available parameter space. The invention also provides electro-optical displays (in particular TFT displays with two plane-parallel carrier plates which form a cell with a border, integrated non-linear elements for switching individual pixels on the carrier plates and a nematic liquid crystal mixture having positive dielectric anisotropy and in the cell high resistivity) containing such media and the use of these media for electro-optical purposes. The term "alkyl" embraces unbranched and branched alkyl groups having 1-15 carbon atoms, in particular the unbranched groups methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl and n-heptyl. Groups of 2-5 carbon atoms are generally preferred. The term "alkenyl" includes unbranched and branched alkenyl groups having up to 15 carbon atoms, especially the unbranched groups. Particularly preferred alkenyl groups are C ₂ -C ₇ -1 E-alkenyl, C ₄ -C ₇ -3E-alkenyl, C ₅ -C ₇ -4-alkenyl, C ₆ -C ₇ -5-alkenyl and C ₇ -6 Alkenyl, in particular C ₂ -C ₇ -1 E-alkenyl, C ₄ -C ₇ 3E-alkenyl and C ₅ -C ₇ -4-alkenyl. Examples of preferred alkenyl groups are vinyl, 1 E-propenyl,

1 E-butenyl, 1 E-pentenyl, 1 E-hexenyl, 1 E-heptenyl, 3-butenyl,

3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl,

4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like.

Groups of up to 5 carbon atoms are generally preferred.

The term "halogenated alkyl" preferably includes mono- or polyfluorinated and / or chlorinated radicals. Perhalogenated radicals are included. Particularly preferred are fluorinated alkyl radicals,

in particular CF ₃ , CH ₂ CF ₃ , CH ₂ CHF ₂ , CHF ₂ , CH ₂ F, CHFCF ₃ and

CF ₂ CHFCF ₃ . The term "halogenated alkenyl" and related expressions are explained accordingly.

The total amount of compounds of the formula I in the mixtures according to the invention is not critical. The mixtures may therefore contain one or more other components to optimize various properties. The structure of the matrix display of polarizers, electrode base plates and electrodes with surface treatment according to the invention corresponds to the usual construction for such displays. Here, the term of the usual construction is broad and includes all

Modifications and modifications of the matrix display, in particular matrix display elements based on poly-Si TFT.

However, a significant difference of the displays of the invention on the basis of the usual twisted nematic cell is the choice of the liquid crystal parameters of the liquid crystal layer.

The following examples illustrate the invention without limiting it. Those skilled in the art will be able to derive details of the embodiments from the examples, which are not detailed in the general description, to generalize them to general skill, and to apply them to a particular problem.

Above and below, percentages are by weight. All temperatures are in degrees Celsius. Further, K = crystalline state, N = nematic phase, Sm = smectic phase (more specifically SmA, SmB, etc.), Tg = glass point and I = isotropic phase. The data between these symbols represents the transition temperatures Δη means optical anisotropy (589 nm, 20 ° C), Δε the dielectric anisotropy (1 kHz, 20 ° C) and γ ^ the rotational viscosity (20 ° C, in the unit mPa- s).

The determination of physical, physicochemical or electro-optical parameters is carried out according to generally known methods, as described, inter alia, in the brochure "Merck Liquid Crystals - Licristal® - Physical Properties of Liquid Crystals - Description of the Measurements Methods", 1998, Merck KGaA, Darmstadt ,

The dielectric anisotropy Δε of the individual substances is determined at 20 ° C and 1 kHz. For this purpose, 5-10% by weight of the substance to be investigated is dissolved in the dielectrically positive mixture ZLI-4792 (Merck KGaA) and the measured value is brought to a concentration of 100%. extrapolated. The optical anisotropy Δη is at 20 ° C and a

Wavelength of 589.3 nm determines the rotational viscosity

at 20 ° C, both also by linear extrapolation. In the present application, unless expressly stated otherwise, the plural form of a term means both the singular form and the plural form, and vice versa. Other combinations of

Embodiments and variants of the invention according to the description will become apparent from the appended claims or from

Combinations of several of these claims.

The following abbreviations are used:

DCM dichloromethane

DMSO dimethyl sulfoxide

EE ethyl acetate

MTB ether methyl tert-butyl ether

THF tetrahydrofuran

Example 1: 5-Propyl-2- [4- (4-trifluoromethyl-phenyl) -cyclohex-3-enyl] - [1,3-dioxane

Step 1

1 2 3

2.2 g (16 mmol) of magnesium turnings are initially charged in a little THF, then 20.3 g (90 mmol) of 4-bromobenzotrifluoride 1 are dissolved in 50 ml of THF and added dropwise so that the reaction mixture boils. The mixture is then heated at reflux for 1 h. The heat source is briefly removed and the batch is mixed with 20.0 g (90 mmol) of 4-benzyloxymethyl-cyclohexanone 2 and heated to reflux for a further 2 h and then at room temperature for 18 h touched. The mixture is poured onto ice water and adjusted to pH 2 with 2 M hydrochloric acid. The aqueous phase is separated and extracted with MTB ether. The combined organic phases are with

Washed sodium chloride solution, dried over sodium sulfate, filtered and concentrated. 4-Benzyloxymethyl-1- (4-bromo-phenyl) -cyclohexanol 3 is obtained as a red-brown oil, which is used without further purification in the next reaction step.

Step 2:

A solution of 34.1 g (78 mmol) of the crude product 3 in 340 ml of THF is treated with 12 g of Pd IC catalyst (1 12 mmol, 5% on activated charcoal). Using 2.34 liters of hydrogen, the protecting group is split off. The catalyst is then filtered off. The hydrogenation solution is evaporated to dryness to give the 4-hydroxymethyl-1 - (4-trifluoromethyl-phenyl) -cyclohexanol as a brown oil.

Step 3:

4 5

First, 7.27 ml (85 mmol) of oxalyl chloride are placed in 100 ml of DCM and at a temperature of -60 ° C 12 ml (170 mmol) of DMSO (dried) are added dropwise in 80 ml of DCM. Now, a solution of 10.2 g (13 mmol) of 4-hydroxymethyl-1 - (4-trifluoromethyl-phenyl) - cyclohexanol 4 in 310 ml DCM is added dropwise. After a stirring time of 15 minutes, 53 ml of triethylamine are added. After stirring for 5 minutes, the cooling bath is removed. Now, it is hydrolyzed at room temperature with water and diluted with DCM. The aqueous phase is separated and extracted with DCM. The combined organic phases are mixed with water and Washed sodium chloride solution, dried over sodium sulfate, filtered and evaporated to dryness to the residue. The crude product is then chromatographed on silica gel (DCM / EA 8: 2). 4-Hydroxy-4- (4-trifluoromethyl-phenyl) -cyclohexanecarbaldehyde 5 is obtained as a yellow oil.

Step 4:

16.8 g (54 mmol) of 4-hydroxy-4- (4-trifluoromethyl-phenyl) -cyclohexane-carbaldehyde 5 are initially charged in 284 ml of toluene. There are 7.61 g (64 mmol) of 2-n-propylpropane-1, 3-diol and 1, 39 g (8 mmol) of toluene-4-sulfonic acid monohydrate added and heated for 1.5 h on a water to reflux. After completion of the reaction, the reaction mixture is chromatographed directly on silica gel. After two crystallizations from isopropyl alcohol / acetone and methylcyclohexane / heptane, the 5-propyl-2- [4- (4-trifluoromethyl-phenyl) -cyclohex-3-enyl] - [1,3] -dioxane 6 is obtained as a white, shiny crystals.

K 120 SmB 164 I

Δε = 22

Δη = 0.107

γι = 395 mPa-s

Analog or comparable are produced:

K 89 SmA 94 N 1 17 I

Δε = 13.4 Δη = 0.104

γι = 299 mPa-s

Κ72 SmB 160 SmA 166 I Δε = 17

Δη = 0.106

γι = 211 mPa-s

K 111 I

Δε = 26

Δη = 0.101

γι = 380 mPa-s

K 55 SmA 132 I

Δε = 20

Δη = 0.101

γι = 248 mPa-s

K 70 SmA 86 N 89 I Δε = 18

Δη = 0.090

γι = 247 mPas

Κ55 SmA (43) Ν (51) I Δ∈ = 22.5

Δη = 0.073

γι = 168 mPa-s

Sm 67 SmA 88 I

Δ∈ = 24.5

Δη = 0.099

γι = 258 mPa-s

I95 I

Δε = 32

Δη = 0.095

γι = 275 mPas

Claims

P 17020 ST.doc

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claims

1 . Compounds of the formula I,

10

wherein

X CF ₃ , OCF ₃ , F, Cl, OCHF ₂ , CHF ₂ , SCN, CN, -C ^ C-CF ₃ or -CH = CH-CF ₃ ,

15

R ^{1 is} an alkyl radical having 1 to 15 C atoms, where in this radical also one or more CH ₂ groups are each independently of one another by -C 1 -C-, -CH =CH-, -

20 "^ X ^", ^ ^~ · -S-. -CO-O- or -O-CO- can be replaced so that O and S atoms are not directly linked to one another, and in which also one or more H atoms can be replaced by halogen,

L ¹ and L ²

independently of one another H or F, mean.

Compounds according to claim 1, characterized in that

L ¹ H

means. Indications according to claim 1 or 2, characterized

R ¹ is alkyl or alkenyl having up to 8 carbon atoms P 17020 ST.doc

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means.

Compounds according to one or more of claims 1 to 3, characterized in that

X OCF _3, CF ₃ or F

means.

Compounds according to one or more of claims 1 to 4, characterized in that L ¹ and L ² signify H.

Compounds according to one or more of claims 1 to 5, characterized in that X is CF ₃ .

Compounds according to one or more of claims 1 to 5, characterized in that X is OCF ₃ .

Compounds according to one or more of claims 1 to 5 selected from the following formulas:

35 P 17020 ST.doc

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10

wherein R ^{1 has} the meanings given in claim 1 or 3.

9. Compounds according to one or more of claims 1 to 8, characterized in that R ^{1 is} a straight-chain alkyl radical having 1 to 7 carbon atoms or an unbranched alkenyl radical having 2 to 8 C

15

Atoms means.

10. A process for the preparation of compounds of the formula I according to

one or more of claims 1 to 9 comprising a process step in which an aryl metal compound of formula II

20

wherein X, L ¹ and L ^{2 are} as defined for formula I according to claim 1, and

M means Li, MgBr or MgCl,

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with a compound of formula III

35 in which

PG means a protecting group, P 17020 ST.doc

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is reacted, and in further reaction steps comprising removal of the protective group PG and oxidation of the resulting CH ₂ OH group to the aldehyde CH = O,

with a 2-substituted 1,3-diol of the formula IV

a compound of formula I

wherein the groups R ¹ , L ¹ , L ² and X are as defined in claim 1 is reacted.

20 1 1 Use of one or more compounds of the formula I according to one or more of claims 1 to 9 as a component in a liquid-crystalline medium.

12. Liquid-crystalline medium containing at least two mesogenic compounds, characterized in that it contains at least one compound of the formula I according to one or more of claims 1 to 9.

13. Use of the liquid-crystalline medium according to claim 12 for electro-optical purposes.

14. Electro-optical liquid crystal display containing a

Liquid-crystalline medium according to Claim 12.

35