Dibenzofuran and dibenzothiophene derivatives

Abstract

The invention relates to a compound of general formula (I), wherein the occurring radicals and parameters have the meanings indicated in claim 1, to its use in liquid-crystalline or mesogenic media and to liquid-crystalline or mesogenic media comprising these derivatives. They can be used in liquid-crystalline displays of the FFS type and other applications.

Description

[0001] The present application relates to dibenzofuran and dibenzothiophene derivatives, their use in liquid crystal media and liquid crystal media comprising the dibenzofuran and dibenzothiophene derivatives.

[0002] Liquid crystals have been used extensively since the first commercially available liquid crystal compounds were discovered about 40 years ago. Particular areas of known application are displays for watches and pocket calculators and large display panels, such as for railway stations, airports and sports arenas. Other areas of application are displays for portable computers and navigation systems and for video applications. In particular, for the last-mentioned applications, very high demands are made on the response times of the images and on the contrast.

[0003] The spatial arrangement of the molecules in a liquid crystal has the effect that many of its properties are direction-dependent. Of particular importance in the use in liquid crystal displays are the optical, dielectric and elastic-mechanical anisotropies. Depending on whether the longitudinal axis of the molecules is oriented perpendicular or parallel to the two plates of a capacitor, the latter have different capacitances; in other words, the dielectric constant ε of the liquid crystal medium has different values for the two orientations. The substance is called dielectrically positive when the dielectric constant is greater when the longitudinal axis of the molecules is oriented perpendicular to the plates of the capacitor than when it is oriented parallel. The majority of the liquid crystals used in the early displays belong to this group.

[0004] Both the polarizability and the permanent dipole moment of the molecules contribute to the dielectric anisotropy. On application of a voltage to the display, the longitudinal axes of the molecules themselves orientate in such a way that the greater of the parallel or perpendicular dielectric constants becomes effective. The strength of the interaction with the electric field depends on the difference between the two constants. In the case of a smaller difference, a higher switching voltage is required than in the case of a greater difference. The introduction of suitable polar groups, such as nitrile groups or fluorine, into the liquid crystal molecules makes it possible to achieve a wide range of operating voltages.

[0005] In the case of the liquid crystal molecules used in conventional liquid crystal displays, the dipole moment oriented along the longitudinal axis of the molecule is greater than the dipole moment oriented perpendicular to the longitudinal axis of the molecule. The orientation of the greater dipole moment along the longitudinal axis of the molecule also determines the orientation of the molecules in the field-free state in the liquid crystal display. In the most widespread TN ("twisted nematic") cell, a liquid crystal layer of thickness of only about 5 to 10 μm is arranged between two flat glass plates, each of which has a conductive transparent layer of tin oxide or indium tin oxide vapor-deposited thereon as an electrode. An alignment layer which is likewise transparent, usually composed of a polymer, such as polyimide, is positioned between these films and the liquid crystal layer. This alignment layer serves to bring the longitudinal axes of the adjacent liquid crystal molecules into a preferential direction by means of surface forces, so that in the voltage-free state they lie uniformly in a flat manner or with the same small tilt angle to the inside of the display surface in the same alignment. Two additional polarizing films which only let linearly polarized light in and out are adhesively bonded to the outside of the display in a specific arrangement.

[0006] With liquid crystals, in which the larger dipole moment is oriented parallel to the molecular longitudinal axis, high-performance displays have been developed. In most cases here, mixtures of 5 to 20 components are used in order to achieve a sufficiently wide temperature range of the mesophase and short response times and low threshold voltages. However, strong viewing-angle dependence still poses difficulties in liquid-crystal displays, for example, for notebook computers. The best imaging quality is achieved if the display surface is perpendicular to the viewing direction of the observer. If the display is tilted with respect to the viewing direction, the imaging quality in some cases drops sharply. In order to be more comfortable, it is sought to make the angle at which the display can be tilted with respect to the viewing direction of the observer as large as possible. Attempts have recently been made to improve the viewing-angle dependence using liquid-crystal compounds whose dipole moment perpendicular to the molecular longitudinal axis is greater than the dipole moment parallel to the molecular longitudinal axis. In the field-free state, these molecules are oriented perpendicular to the glass surface of the display. In this way, it is possible to achieve an improvement in the viewing-angle dependence. Displays of this type are called VA-TFT ("vertically aligned") displays.

[0007] So-called IPS ("in-plane switching") displays are also known, which contain an LC layer between two substrates with planar orientation, wherein two electrodes are arranged only on one of the two substrates and preferably have an interdigital comb structure. When a voltage is applied to the electrodes, an electric field is generated between the electrodes which has a significant component parallel to the LC layer. This causes the LC molecules to realign in the layer plane. Furthermore, so-called FFS ("fringe field switching") displays have been reported (see, inter alia, S. H. Jung et al., Jpn. J. Appl. Phys., Vol. 43, No. 3, 2004, 1028), which contain two electrodes on the same substrate, one of which is structured in comb form and the other is unstructured. A strong so-called "fringe field" is thereby generated, i.e. a strong electric field near the electrode edges, and an electric field is generated in the entire cell which has both a strong vertical component and a strong horizontal component. FFS displays have a viewing-angle dependence of the contrast which is low. FFS displays usually contain an LC medium with positive dielectric anisotropy and an alignment layer, usually made of polyimide, which provides the molecules of the LC medium with a planar alignment.

[0008] For FFS displays, it is suggested that not only the large absolute value of Δε is important, but also the components ε(parallel) and ε(perpendicular) are important in determining the switching behavior. It is desirable to achieve a large value of ε(perpendicular) because this improves the transmission of the display.

[0009] In DE 10 2005 012 585 A1, it is suggested to use dibenzofuran and dibenzothiophene derivatives in liquid-crystal media. However, due to their substitution pattern, the compounds described here exhibit a very strong negative dielectric anisotropy, which makes them unsuitable for use according to the application.

[0010] The development of the field of liquid-crystalline materials is far from complete. In order to improve the properties of liquid-crystalline display assemblies, there is a constant attempt to develop novel compounds which are able to optimize such displays.

[0011] It was an object of the present application to provide a more diverse group of compounds having advantageous properties for use in liquid-crystalline media.

[0012] This object is achieved according to the present application by the compounds of general formula I

[0013]

[0014] wherein

[0015] W denotes O or S,

[0016] R denotes H, an alkyl group having 1 to 15 C atoms, wherein one or more CH2groups in these radicals can each be replaced, independently of one another, by -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO-, in such a way that O atoms are not directly attached to one another, and in which one or more H atoms can be replaced by halogen,

[0017] A 1 denotes trans-1,4-cyclohexylene or 1,4-cyclohexenylene, wherein one or more non-adjacent CH2groups can be replaced by -O- and in which one or more H atoms can be replaced by F,

[0018] A 2 denotes trans-1,4-cyclohexylene or 1,4-cyclohexenylene, wherein one or more H atoms can be replaced by F,

[0019] Z denotes a single bond, -CF2O-, -OCF2-, -CH2CH2-, -CF2CF2-, -C(O)O-, -OC(O)-, -CH2O-, -OCH2-, -CF=CF-, -CH=CH- or -C≡C-, and

[0020] X denotes F, CI, CN, NCS, SF5, fluorinated alkyl, fluorinated alkoxy, fluorinated alkenyl or fluorinated alkenyloxy each having up to 5 C atoms, preferably F, CF3, CHF2, OCF3or OCHF2.

[0021] It was a further object of the present application to provide liquid-crystalline media, in particular for use in TN, IPS or FFS displays.

[0022] This object is achieved according to the present application by providing compounds of formula I having a neutral to positive dielectric anisotropy (Δε).

[0023] Compound I stands out due to its remarkably high positive dielectric anisotropy (Δε), making it particularly suitable for TN-TFT displays, as well as IPS and FFS displays. This compound has a relatively low melting point and an extremely high clarifying point, exhibiting excellent compatibility with conventional materials used in liquid crystal mixtures for displays and being completely soluble in such media. Furthermore, this compound exhibits extremely high ε... ┴ value.

[0024] The compounds according to the invention preferably have Δε in the positive region, preferably Δε > 0.5, more preferably Δε > 1.

[0025] Detailed description

[0026] If group R is an alkyl group and / or an alkoxy group, it can be straight-chain or branched. It is preferably straight-chain, having 2, 3, 4, 5, 6 or 7 carbon atoms, and is therefore preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, and also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonoxy, decoxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy.

[0027] R can be an alkenyl group having 2 to 15 carbon atoms, which can be straight-chain or branched. It is preferably straight-chain and has 2 to 7 carbon atoms. Therefore, it is preferably vinyl, propenyl or -2-enyl, butenyl, butenyl or -3-enyl, pentenyl, pentenyl, pentenyl, pentenyl or pentenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, hexenyl, or hexenyl, hexenyl.

[0028] R can be an oxaalkyl group, preferably a straight-chain 2-oxapropyl (=methoxymethyl), 2-oxabutyl (=ethoxymethyl) or 3-oxabutyl (=methoxyethyl), 2-oxapentyl, 3-oxapentyl or 4-oxapentyl, 2-oxahexyl, 3-oxahexyl, 4-oxahexyl or 5-oxahexyl or 2-oxaheptyl, 3-oxaheptyl, 4-oxaheptyl, 5-oxaheptyl or 6-oxaheptyl.

[0029] R can be an alkyl group having 1 to 15 carbon atoms, each independently of the others, wherein one CH2 group has been substituted with -O- and another with -CO-, wherein these are preferably adjacent. Thus, it contains an acyloxy group (-CO-O-) or an oxycarbonyl group (-O-CO-). It is preferably straight-chain and has 2 to 6 carbon atoms.

[0030] R can each, independently of one another, be an alkyl group having 1 to 15 carbon atoms, wherein one CH2group has been replaced by an unsubstituted or substituted -CH=CH- and adjacent CH2groups have been replaced by CO or CO-O or O-CO, wherein this can be linear or branched. It is preferably linear and has 4 to 13 carbon atoms.

[0031] R can each, independently of one another, be an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, each of which is monosubstituted by -CN or -CF3and is preferably linear. The substitution by -CN or -CF3may be at any desired position.

[0032] R can each, independently of one another, be an alkyl group in which two or more CH2groups have been replaced by -O- and / or -CO-O-, which can be linear or branched. It is preferably branched and has 3 to 12 carbon atoms.

[0033] R can each, independently of one another, be an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, each of which is monosubstituted by halogen, wherein the groups are preferably linear and the halogen is preferably -F or -Cl. In the case of multiple substitution, the halogen is preferably -F. The resulting groups also include perfluorinated groups, for example -CF3. In the case of monosubstitution, the fluorine or chlorine substituent can be at any desired position, but is preferably in the omega position.

[0034] The term “fluorinated alkyl” preferably encompasses monofluorinated or polyfluorinated groups. Perfluorinated groups are included. Particularly preferred are CF3, CH2CF3, CH2CHF2, CHF2, CH2F, CHFCF3and CF2CHFCF3.

[0035] The term “fluorinated alkoxy” preferably encompasses monofluorinated or polyfluorinated groups. Perfluorinated groups are included. Particularly preferred is OCF3.

[0036] In a preferred embodiment of the application, the compound of the formula I is selected from the group of compounds of the formulae I-1 to I-6:

[0037]

[0038]

[0039] wherein the radicals and parameters occurring have the meanings given above for formula I and independently:

[0040] R is preferably an alkyl or alkenyl group each having up to 7 C carbon atoms, wherein one or more CH2groups in these groups can each, independently of one another, be replaced by instead of

[0041] A1 preferably denotes trans-1,4-cyclohexylene, or

[0042] A 2 preferably denotes trans-1,4-cyclohexylene or cyclohexenylene.

[0043] Furthermore, the compounds of the formula I are preferably selected from the group of the compounds of the formulae I-A to I-F:

[0044]

[0045]

[0046] and more preferably from the group of the formulae I-A, I-B, I-D and I-E, wherein R and X are defined as above for formula I, and preferably X is F, CF3 or OCF3, and more preferably, for I-A to I-C, X is CF3 or OCF3.

[0047] In a preferred embodiment of the present application, in formula I and its subformulae, R denotes alkyl having 1 to 7 C atoms, in particular ethyl, propyl, butyl, pentyl, cyclopropylmethyl, cyclobutyl or cyclopentyl, with n-propyl and n-pentyl being most preferred.

[0048] In a preferred embodiment of the present application, in formula I, Z denotes a single bond.

[0049] The compounds of the general formula I are prepared by methods known per se, as described in the literature (for example in the standard works, such as Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), to be precise under reaction conditions which are known and suitable for these reactions. Use can here be made of variants which are known per se, but are not mentioned here in greater detail.

[0050] If desired, the starting materials can also be formed in situ, without their being isolated from the reaction mixture, but rather immediately converted further into compounds of the general formula I.

[0051] Preferred synthesis routes to the compounds of the application are shown in the schemes below and are further illustrated by way of working examples. By selecting appropriate starting materials, the synthesis can be adapted to the particular desired compound of the general formula I.

[0052] Dibenzofuran derivatives, i.e. compounds of the formula I wherein W denotes O (formula I'), are preferably synthesized as shown in Scheme 1 and can be obtained by intramolecular substitution of fluorine by nucleophilic attack of the phenoxide anion upon treatment of the phenol P with a base.

[0053] Scheme 1

[0054]

[0055] or, an analogous ring closure with the positions of the OH group and the fluorine atom interchanged can be performed as shown in Scheme 2.

[0056] Scheme 2

[0057]

[0058] Dibenzofuran derivatives (i.e. compounds of formula I wherein W represents S (formula I")) are preferably synthesized as shown in Scheme 3.

[0059] Scheme 3

[0060]

[0061] Intermediate S (Scheme 3) can be obtained from phenol P (Scheme 1) via the corresponding triflate according to Itoh, Takahiro and Mase, Toshiaki, Organic Letters, 6(24), 4587-4590; 2004. Treatment of compound S with a strong non-nucleophilic base, preferably potassium tert-butoxide, affords compound I" (cf. Jepsen, Tue Heesgaard et al., European Journal of Organic Chemistry, (1), 53-57, S53 / 1-S53 / 65; 2011).

[0062] Thus, another object of the present application is a compound of formula P or P'

[0063]

[0064] for use in a process for the synthesis of a compound of formula I,

[0065] wherein the radicals and parameters occurring have the meanings given above for formula I.

[0066] Another object of the present application is a process for the synthesis of a compound of formula I from a compound of formula P or P', preferably following the synthetic pathway depicted in Scheme 1, Scheme 2 or Scheme 3 above. The process for the preparation of a compound of formula I is characterized in that a compound of formula P or P' (preferably formula P) as defined above and below is subjected to a ring closing reaction, thereby producing a compound of formula I as defined above and below. The ring closing reaction is a nucleophilic aromatic substitution reaction. It is preferably performed in the presence of a base.

[0067] The reactions described should only be considered as illustrative. A person skilled in the art can carry out corresponding modifications to the described syntheses and follow other suitable synthetic routes to obtain the compounds of the formula I.

[0068] The compounds of the general formula I can be used in liquid-crystalline media. The present application therefore also relates to a liquid-crystalline medium comprising two or more liquid-crystalline compounds, comprising one or more compounds of the general formula I.

[0069] The medium according to the application preferably comprises 1 to 30 %, particularly preferably 2 to 20 %, of the compounds of the formula I according to the application.

[0070] The medium preferably comprises one, two, three, four or five compounds of the formula I according to the application.

[0071] In a preferred embodiment of the application, the liquid-crystalline medium comprises

[0072] a) one or more compounds selected from the group of compounds of the formulae II and III, which preferably have a dielectric anisotropy of greater than 3:

[0073]

[0074] wherein

[0075] R 2 represents an alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy group having 1 to 7 C atoms, an alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl group having 2 to 7 C atoms, and preferably is an alkyl or alkenyl group

[0076] and

[0077] independently of one another in each occurrence

[0078] Preferably

[0079]

[0080] L 21 and L 22 represents H or F, preferably L 21 represents F,

[0081] X 2 represents halogen, a halogenated alkyl or alkoxy group having 1 to 3 C atoms or a halogenated alkenyl or alkenyloxy group having 2 or 3 C atoms, preferably F, CI, -OCF3, -O-CH2CF3, -O-CH=CF2 or -CF3, very preferably F, CI, -O-CH=CF2 or -OCF3,

[0082] m is 0, 1, 2 or 3, preferably 1 or 2 and particularly preferably 1,

[0083] R 3 represents alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms and preferably is alkyl or alkenyl,

[0084] and

[0085] independently of one another in each occurrence are

[0086]

[0087] preferably

[0088]

[0089] L 31 and L 32 independently of one another represent H or F, preferably L 31 represents F,

[0090] X 3 represents halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, preferably F, CI, -OCF3, -OCHF2, -O-CH2CF3, -O-CH=CF2, -O-CH=CH2 or -CF3, very preferably F, CI, -O-CH=CF2, -OCHF2 or -OCF3,

[0091] Z 3 represents -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, preferably -CH2CH2-, -COO-, trans-CH=CH- or a single bond and very preferably -COO-, trans-CH=CH- or a single bond, and

[0092] n is 0, 1, 2 or 3, preferably 1, 2 or 3 and particularly preferably 1, and

[0093] b) optionally one or more preferably dielectrically neutral compounds selected from the group of formulae IV and V:

[0094]

[0095] wherein

[0096] R 41 and R 42independently of one another have one of the meanings given for R 2 independently of one another have one of the meanings given for R 41 denotes alkyl and R 42 denotes alkyl or alkoxy or R 41 denotes alkenyl and R 42 denotes alkyl,

[0097] and

[0098] independently of one another and if

[0099] occur twice,

[0100] these also independently of one another denote

[0101]

[0102] one or more of

[0103] and denote,

[0104]

[0105] Z 41 and Z 42 independently of one another and if Z 41 occur twice, these also independently of one another denote -CH2CH2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O-, -CF2O-, -C≡C- or a single bond, preferably one or more thereof denote a single bond, and

[0106] p denotes 0, 1 or 2, preferably 0 or 1, and

[0107] R 51 and R 52 independently of one another have one of the meanings given for R 41 and R 42 denote one of the meanings given for R and preferably denote alkyl having 1 to 7 C atoms, preferably n-alkyl, particularly preferably n-alkyl having 1 to 5 C atoms, alkoxy having 1 to 7 C atoms, preferably n-alkoxy, particularly preferably n-alkoxy having 2 to 5 C atoms, alkoxyalkyl having 2 to 7 C atoms, preferably having 2 to 4 C atoms, alkenyl or alkenyloxy, preferably alkenyloxy,

[0108] to

[0109] if present each independently of one another denote

[0110]

[0111] preferably

[0112]

[0113] preferably

[0114] denotes and, if present, at least one of

[0115] preferably denotes

[0116] Z 51 to Z 53 each, independently of one another, denotes -CH2-CH2-, -CH2-O-, -CH=CH-, -C≡C-, -COO- or a single bond, preferably -CH2-CH2-, -CH2-O- or a single bond and particularly preferably a single bond,

[0117] i and j each, independently of one another, denote 0 or 1,

[0118] (i + j) preferably denotes 0, 1 or 2, more preferably 0 or 1 and most preferably 1.

[0119] In a more preferred embodiment, the medium comprises one or more compounds of the formula V selected from the group of compounds of the formulae V-1 to V-5, preferably one or more compounds of the formulae V-3, V-4 and V-5,

[0120]

[0121]

[0122] wherein the parameters have the meanings given above under formula V, and preferably,

[0123] R 51 denotes alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C atoms, and

[0124] R 52 denotes alkyl having 1 to 7 C atoms, alkenyl having 2 to 7 C atoms or alkoxy having 1 to 6 C atoms, preferably alkyl or alkenyl.

[0125] In a more preferred embodiment, the medium comprises one or more compounds of the formula V-3, wherein at least one of the radicals R 51 and R 52 is alkenyl having 2 to 6 carbon atoms, preferably selected from the following formulae:

[0126]

[0127] wherein "Alkyl" has the definition given above, and is preferably methyl or ethyl. Particularly preferred are compounds of formula V-3d.

[0128] In a more preferred embodiment, the medium comprises one or more compounds of formula V-4 selected from the group of compounds of formulae V-4a to V-4c,

[0129]

[0130] wherein

[0131] alkyl and alkyl* are each independently a straight-chain alkyl group having 1 to 6 carbon atoms, in particular methyl, ethyl, n-propyl and pentyl.

[0132] The liquid-crystalline medium preferably comprises two, three or more compounds selected from the group of compounds of formulae V-4a, V-4b and V-4c.

[0133] In a more preferred embodiment, the medium comprises one or more compounds of formula V-5 selected from the group of compounds of formulae V-5a to V-5c, preferably V-5a:

[0134]

[0135] wherein

[0136] alkyl and alkyl* are each independently a straight-chain alkyl group having 1 to 6 carbon atoms, in particular methyl, ethyl or n-propyl, and

[0137] Alkenyl preferably denotes an alkenyl group having 2 to 5 C atoms, preferably having 2 to 4 C atoms, in particular preferably vinyl.

[0138] The application also relates to electro-optical liquid-crystalline display elements containing the liquid-crystalline medium according to the application.

[0139] The medium according to the application is prepared in a manner known per se. In general, the components are advantageously dissolved in one another at elevated temperature. By means of suitable additives, the liquid-crystalline phase according to the application can be modified in such a way that it can be used in all types of liquid-crystalline display elements which have been disclosed hitherto. This type of additive is known to the person skilled in the art and is described in detail in the literature (H. Kelker / R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, polychromatic dyes can be used for the production of colour guest-host systems or substances can be added in order to modify the dielectric anisotropy, the viscosity and / or the alignment of the nematic phase.

[0140] For the present application and the following examples, the structure of the liquid crystalline compounds is indicated in the form of an acronym, which is converted into a chemical formula according to the following Tables A to C. All groups C n H 2n+1 , C m H 2m+1 and C l H 2l+1 or C n H 2n , C m H 2m and C l H 2l are straight-chain alkyl or alkylene groups, having n, m and I C atoms, respectively, in each case. Preferably, n, m and I are independently of each other 1, 2, 3, 4, 5, 6 or 7. Table A shows the code of the ring elements of the core of the compounds, Table B lists the bridging units, and Table C lists the symbolic meaning of the left and right end groups of the molecules. The acronym consists of the code of the ring elements with optional linking groups, followed by a first hyphen and the code of the left end group, and a second hyphen and the code of the right end group. Table D shows illustrative structures of the compounds together with their respective acronyms.

[0141] Table A: Ring elements

[0142]

[0143]

[0144]

[0145] Table B: Bridging units

[0146]

[0147] Table C: End groups

[0148]

[0149]

[0150] wherein n and m are each an integer, and the three dots "..." are placeholders for further abbreviations of this table.

[0151] In addition to the compounds of formula I, the mixtures of the present application preferably comprise one or more of the compounds shown in the following Table D.

[0152] The following abbreviations are used:

[0153] (n, m, k and I are each independently of the other an integer, preferably 1 to 9, preferably 1 to 7, k and I can also be 0 and are preferably 0 to 4, more preferably 0 or 2 and most preferably 2, n is preferably 1, 2, 3, 4 or 5, in the combination "-nO-", it is preferably 1, 2, 3 or 4, preferably 2 or 4, m is preferably 1, 2, 3, 4 or 5, in the combination "-Om", it is preferably 1, 2, 3 or 4, more preferably 2 or 4. The combination "-IVm" is preferably "2V1 ".)

[0154] Table D

[0155] Examples of compounds of formula I

[0156]

[0157] Exemplary preferred dielectric positive compounds which can be used in combination with compounds of formula I

[0158]

[0159]

[0160]

[0161]

[0162]

[0163]

[0164]

[0165]

[0166]

[0167] Exemplary preferred dielectric neutral compounds which can be used in combination with compounds of formula I

[0168]

[0169]

[0170]

[0171]

[0172]

[0173]

[0174] Table E shows chiral dopants which are optionally used in mixtures according to the application.

[0175] Table E

[0176]

[0177]

[0178]

[0179] In a preferred embodiment of the present application, the medium of the present application comprises one or more compounds selected from the group of compounds of Table E.

[0180] Table F shows preferred stabilizers which can be employed in the mixtures of the present application in addition to the compounds of formula B. The parameter n here denotes an integer in the range from 1 to 12. In particular, phenol derivatives show to be useful as additional stabilizers because they act as antioxidants.

[0181] Table F

[0182]

[0183]

[0184]

[0185]

[0186]

[0187] In a preferred embodiment of the present application, the medium of the present application comprises one or more compounds selected from the group of compounds of Table F.

[0188] The present application is explained in more detail hereinafter with reference to working examples, but is not intended to be restricted thereby. Examples

[0189] The following examples explain the present application without restricting it. However, they show the person skilled in the art the preferred mixture concepts of the compounds to be employed preferably and their respective concentrations and combinations with each other. Furthermore, the examples illustrate which properties and property combinations are achievable.

[0190] All temperature values indicated in the present application, such as, for example, for melting points T (°C, N), transition from smectic (Sm) to nematic (N) phase T(Sm, N) and clearing points T(N, I) are indicated in degrees Celsius (°C). M.p. means melting point, cl.p. = clearing point. The data between these symbols represent the transition temperatures.

[0191] All physical properties are and have been determined in accordance with "Merck Liquid Crystals, Physical Properties of Liquid Crystals", Status Nov. 1997, Merck KGaA, Germany, and are applicable to a temperature of 20 °C, and Δn is determined at 589 nm and Δε is determined at 1 kHz, unless explicitly indicated otherwise in each case.

[0192] In the foregoing and hereinafter, Δn denotes the optical anisotropy (589 nm, 20 °C) and Δε denotes the dielectric anisotropy (1 kHz, 20 °C).

[0193] The Δε and Δn values of the compounds according to the application were obtained by extrapolation from liquid crystal mixtures consisting of 10% of the respective compound according to the application and 90% of the commercially available liquid crystal mixture ZLI-4792 (Merck KGaA, Darmstadt). In the case of limited solubility, the compounds were determined in mixtures containing only 5% of the compound.

[0194] Abbreviations:

[0195] dist. distillation

[0196] DMPU 1,3-dimethyltetrahydro-2(1 H)-pyrimidinone

[0197] THF tetrahydrofuran

[0198] MTB ether methyl tert-butyl ether

[0199] DIPEA N-ethyldiisopropylamine

[0200] DMAP 4-(dimethylamino)pyridine CataCXium A bis(1 -adamantyl)-n- butylphosphine

[0201] TEA triethylamine

[0202] Cr crystalline

[0203] Sm smectic (if known, optionally with a subtype, e.g. SmA)

[0204] N nematic

[0205] I isotropic

[0206] Furthermore, the following symbols are used:

[0207] n e extraordinary refractive index at 20 °C and 589 nm,

[0208] n oordinary refractive index at 20 °C and 589 nm,

[0209] Δn optical anisotropy at 20 °C and 589 nm,

[0210] ε ⊥ dielectric constant perpendicular to the director at 20 °C and 1 kHz,

[0211] ε || dielectric constant parallel to the director at 20 °C and 1 kHz,

[0212] Δε dielectric anisotropy at 20 °C and 1 kHz,

[0213] cl.p., T(N, I) clear point [°C],

[0214] γ1 rotational viscosity at 20 °C [mPa-s],

[0215] K1 elastic constant, "splay" deformation at 20 °C [pN],

[0216] K2 elastic constant, "twist" deformation at 20 °C [pN],

[0217] K3 elastic constant, "bend" deformation at 20 °C [pN].

[0218] Synthesis Example

[0219] Synthesis Example 1 (CCB-3-F)

[0220] 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohexyl]dibenzofuran

[0221]

[0222] Step 1.1: 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2,3- difluorophenol

[0223]

[0224] A mixture of 6-bromo-2,3-difluorophenol (CAS 186590-23-8) (7.0 g, 27 mmol), potassium carbonate (5.7 g, 41 mmol), tris(dibenzylideneacetone)-dipalladium(0) (55 mg, 0.06 mmol) and CataCXium A (35 mg, 0.09 mmol) in THF (30 mL) and distilled water (25 mL) was heated to reflux under nitrogen, then a solution of [2,3-difluoro-4-[4-(4- propylcyclohexyl)cyclohexyl]phenyl]boronic acid (CAS 931415-69-9) (10.1 g, 27 mmol) in THF (45 mL) was added dropwise. The reaction mixture was heated at reflux temperature overnight. It was then cooled to room temperature and diluted with MTB ether and distilled water. The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent 1-chlorobutane). 6-[2,3-Difluoro-4-[4-(4- propylcyclohexyl)cyclohexyl]phenyl]-2,3-difluorophenol was isolated as a yellow solid.

[0225] Step 1.2: 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohexyl]dibenzofuran

[0226]

[0227] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2,3- difluorophenol (4.0 g, 8.9 mmol), potassium phosphate monohydrate (2.6 g, 10.8 mmol) and DMPU (40 mL) was stirred at 110°C overnight. The reaction mixture was then filtered over silica gel (solvent n-heptane). The residue was purified by crystallization (heptane / ethanol) to give 3,4,6-trifluoro-7-[4-(4- propylcyclohexyl)cyclohexyl]dibenzofuran as white crystals (4).

[0228] The title compound has the following spectral characteristics:

[0229] Cr 169 N 285 I.

[0230] Δε: -0.3

[0231] ε ┴ : 8.9

[0232] Δn: 0.187

[0233] Synthesis Example 2 (CCB-3-OT)

[0234] 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7- (trifluoromethoxy)dibenzo[b,d]furan

[0235]

[0236] Step 2.1 : 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2- fluoro-3-(trifluoromethoxy)phenol

[0237]

[0238] A mixture of 6-bromo-2-fluoro-3-(trifluoromethoxy)phenol (CAS 1805580-01-1) (12.0 g, 39 mmol), potassium carbonate (8.5 g, 62 mmol), tris(dibenzylideneacetone)-dipalladium(0) (80 mg, 0.08 mmol) and CataCXium A (50 mg, 0.13 mmol) in THF (50 mL) and distilled water (40 mL) was heated to reflux under nitrogen atmosphere, followed by dropwise addition of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]boronic acid (CAS 931415-69-9) (14.5 g, 39 mmol) in THF (70 mL). The reaction mixture was heated at reflux temperature overnight. It was then cooled to room temperature and diluted with MTB ether and distilled water. The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent 1-chlorobutane) and 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3- (trifluoromethoxy)phenol was isolated as a yellow solid.

[0239] Step 2.2: 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7- (trifluoromethoxy)dibenzo[b,d]furan

[0240]

[0241] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3- (trifluoromethoxy)phenol (7.1 g, 14 mmol), potassium phosphate monohydrate (4.0 g, 17 mmol) and DMPU (70 mL) was stirred at 110 °C overnight. The reaction mixture was then filtered over silica gel (solvent n-heptane). The residue was purified by crystallization (heptane / ethanol) to give 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7- (trifluoromethoxy)dibenzo[b,d]furan (4) as white crystals.

[0242] The title compound has the following phase characteristics:

[0243] Cr 123 SmA 223 N 272 I.

[0244] De: 0.9

[0245] e ┴ : 9.2

[0246] An: 0.177

[0247] Synthesis Example 3 (CCB-3-T)

[0248] 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethyl)dibenzofuran

[0249]

[0250] Step 3.1: 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3- (trifluoromethyl)phenol

[0251]

[0252] A mixture of 6-bromo-2-fluoro-3-(trifluoromethyl)phenol (CAS 1804908-52-8) (10.0 g, 38 mmol), potassium carbonate (8.0 g, 58 mmol), tris(dibenzylideneacetone)-dipalladium(0) (80 mg, 0.08 mmol) and CataCXium A (50 mg, 0.13 mmol) in THF (30 mL) and distilled water (33 mL) was heated to reflux under a nitrogen atmosphere, followed by dropwise addition of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]boronic acid (CAS 931415-69-9) (14.0 g, 38 mmol) in THF (70 mL). The reaction mixture was heated at reflux temperature overnight. It was then cooled to room temperature and diluted with MTB ether and distilled water. The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent 1-chlorobutane). 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3- (trifluoromethyl)phenol was isolated as a yellow solid.

[0253] Step 3.2: 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethyl)dibenzofuran

[0254]

[0255] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2- fluoro-3-(trifluoromethyl)phenol (6.9 g, 14 mmol), potassium phosphate monohydrate (4.0 g, 17 mmol) and DMPU (70 mL) was stirred at 110 °C overnight. The reaction mixture was then filtered over silica gel (solvent n-heptane). The residue was purified by crystallization (heptane / ethanol) to give 4,6-difluoro-3-[4-(4- propylcyclohexyl)cyclohexyl]-7-(trifluoromethyl)dibenzofuran as white crystals (4).

[0256] The title compound has the following phase characteristics:

[0257] Cr 127 SmA 175 N 256 I.

[0258] Δε: 3.0

[0259] ε ┴ : 10.1

[0260] Δn: 0.194

[0261] The compound has a surprisingly high ε ┴ value.

[0262] Synthesis Example 4 (CCB (S)-3-F)

[0263] 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohexyl]dibenzothiophene

[0264]

[0265] Step 4.1: [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2,3- difluorophenyl] trifluoromethanesulfonate

[0266]

[0267] To a solution of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2,3- difluorophenol (6.9 g, 15 mmol), TEA (3.2 mL, 23 mmol) and DMAP (60 mg, 0.49 mmol) in dichloromethane (70 mL) was slowly added trifluoromethanesulfonic anhydride (3.1 mL, 19 mmol) at 5 °C under a nitrogen atmosphere. The solution was stirred at room temperature overnight. The reaction mixture was then filtered over silica gel (solvent 1-chlorobutane) to give [6-[2,3-difluoro-4-[4-(4- propylcyclohexyl)cyclohexyl]phenyl]-2,3-difluorophenyl] trifluoromethanesulfonate as a white solid.

[0268] Step 4.2: 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohexyl]dibenzothiophene

[0269]

[0270] The reaction was performed in a one-pot procedure. In a first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2,3-difluorophenyl] trifluoromethanesulfonate (8.9 g, 15 mmol), 3-mercapto propionic acid 2-ethylhexyl ester (4.5 mL, 19 mmol) and DIPEA (4.0 mL, 24 mmol) in toluene (50 mL) was treated with tris(dibenzylideneacetone)dipalladium(0) (150 mg, 0.16 mmol) and (oxybis-2,1-phenylene)bis(diphenylphosphane) (170 mg, 0.31 mmol) under an argon atmosphere and the reaction mixture was heated at reflux temperature overnight. In a second step, a solution of potassium tert-butoxide (2.0 g, 18 mmol) in THF (15 mL) was added to the reaction mixture at room temperature. The reaction mixture was then heated at reflux temperature for 6 hours, followed by the addition of a second portion of potassium tert-butoxide (1.0 g, 9 mmol) in THF (10 mL) and heating again at reflux temperature overnight. A third portion of potassium tert-butoxide (1.0 g, 9 mmol) in THF (10 mL) was added and the reaction mixture was heated at reflux temperature for another 6 hours. It was then cooled to room temperature, quenched with distilled water and hydrochloric acid (25%) at 0°C and diluted with MTB ether and THF. The aqueous phase was separated and extracted with MTB ether and THF. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane) and crystallization (heptane / ethanol) to give 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohexyl]dibenzothiophene as white crystals.

[0271] The title compound has the following spectral characteristics:

[0272] Cr 178N 344I.

[0273] Δε: 2.0 ε ┴ :

[0274] 7.1 Δn: 0.182

[0275] Synthesis Example 5 (CCB(S)-3-OT)

[0276] 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethoxy)dibenzothiophene

[0277]

[0278] Step 5.1: [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3- (trifluoromethoxy)phenyl] trifluoromethanesulfonate

[0279]

[0280] To a solution of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2- fluoro-3-(trifluoromethoxy)phenol (12.0 g, 23 mmol), TEA (5.0 mL, 36 mmol) and DMAP (90 mg, 0.74 mmol) in dichloromethane (100 mL) was slowly added trifluoromethanesulfonic anhydride (4.7 mL, 23 mmol) at 5 °C under nitrogen atmosphere. The solution was stirred at room temperature overnight. The reaction mixture was then filtered over silica gel (solvent 1-chlorobutane) to give [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3- (trifluoromethoxy)phenyl] trifluoromethanesulfonate as a yellow solid.

[0281] Step 5.2: 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7- (trifluoromethoxy)dibenzothiophene

[0282]

[0283] The reaction was performed in a one-pot procedure. In the first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3- (trifluoromethoxy)phenyl] trifluoromethanesulfonate (15.0 g, 21 mmol), 3- mercaptopropionic acid 2-ethylhexyl ester (6.0 mL, 26 mmol) and DIPEA (5.6 mL, 33 mmol) in toluene (70 mL) was treated with tris(dibenzylideneacetone)dipalladium(0) (210 mg, 0.22 mmol) and (oxydi-2,1-phenylene)bis(diphenylphosphine) (240 mg, 0.44 mmol) under an argon atmosphere and the reaction mixture was heated at reflux overnight. In the second step, a solution of potassium tert-butoxide (3.0 g, 27 mmol) in THF (30 mL) was added to the reaction mixture at room temperature. The reaction mixture was heated at reflux for 6 hours, then a second portion of potassium tert-butoxide (1.5 g, 13 mmol) in THF (15 mL) was added and heated at reflux overnight again. A third portion of potassium tert-butoxide (1.5 g, 13 mmol) in THF (15 mL) was added and the reaction mixture was heated at reflux for a further 6 hours. It was then cooled to room temperature, quenched with distilled water and hydrochloric acid (25%) at 0°C and diluted with MTB ether and THF. The aqueous phase was separated and extracted with MTB ether and THF. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane) and crystallization (heptane / 2-propanol) to give 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7- (trifluoromethoxy)dibenzothiophene as yellow crystals (6).

[0284] The title compound has the following phase characteristics:

[0285] Cr 154 Sm 168 SmA 253 N 332.

[0286] Δε: 4.1

[0287] ε ┴ : 7.1

[0288] Δn: 0.189

[0289] Synthesis Example 6 (CCB(S)-3-T)

[0290] 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethyl)dibenzothiophene

[0291]

[0292] Step 6.1 : [6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3- (trifluoromethyl)phenyl] trifluoromethanesulfonate

[0293]

[0294] Step 6.1 : [6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3- (trifluoromethyl)phenyl] trifluoromethanesulfonate

[0295] Step 6.2: 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethyl)dibenzothiophene

[0296]

[0297] The reaction was performed in a one-pot procedure. In the first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3- (trifluoromethyl)phenyl] trifluoromethanesulfonate (13.9 g, 21 mmol), 3- mercaptopropionic acid 2-ethylhexyl ester (5.8 mL, 25 mmol) and DIPEA (5.3 mL, 31 mmol) in toluene (65 mL) was treated with tris(dibenzylideneacetone)dipalladium(0) (190 mg, 0.20 mmol) and (oxybis-2,1-phenylene)bis(diphenylphosphine) (230 mg, 0.42 mmol) under an argon atmosphere and the reaction mixture was heated at reflux overnight. In the second step, a solution of potassium tert-butoxide (2.8 g, 25 mmol) in THF (25 mL) was added to the reaction mixture at room temperature. The reaction mixture was heated at reflux for 6 h, then a second portion of potassium tert-butoxide (1.4 g, 12 mmol) in THF (15 mL) was added and heated at reflux overnight again. A third portion of potassium tert-butoxide (1.4 g, 12 mmol) in THF (15 mL) was added and the reaction mixture was heated at reflux for another 6 h. It was then cooled to room temperature, quenched with distilled water and hydrochloric acid (25%) at 0°C and diluted with MTB ether and THF. The aqueous phase was separated and extracted with MTB ether and THF. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane) and crystallization (heptane / 2-propanol) to give 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethyl)dibenzo[b,d]thiophene as light yellow crystals (6).

[0298] The title compound has the following properties:

[0299] Cr 179 Sm (172) N 317.

[0300] Δε: 6.9 ε ┴ : 7.7

[0301] Δn: 0.189

[0302] Synthesis Example 7 (CLB-3-F)

[0303] 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl]dibenzo[b,d]furan

[0304] Step 7.1 : [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]boronic acid

[0305]

[0306] At -70 °C, under an argon atmosphere, n-butyllithium (122 mL, 1.6 M contained in hexane) was slowly added to a solution of 1,2-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]benzene (CAS 1184184-30-2) (56.0 g, 0.17 mol) in THF (1.0 L) and the reaction mixture was stirred at this temperature for 1 hour. Then trimethylborate (22.0 mL, 0.19 mol) was added and the reaction mixture was stirred for another hour at -70 °C. Then it was allowed to warm up to room temperature and stirred overnight. The reaction was quenched with distilled water and the suspension was diluted with MTB ether then treated with hydrochloric acid (25%). The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by crystallization (n-heptane) to give [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]boronic acid as white crystals (2).

[0307] Step 7.2: 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3- difluorophenol

[0308]

[0309] A mixture of 6-bromo-2,3-difluorophenol (CAS 186590-23-8) (7.0 g, 27 mmol), potassium carbonate (5.7 g, 41 mmol), tris(dibenzylideneacetone)-dipalladium(0) (55 mg, 0.06 mmol) and CataCXium A (35 mg, 0.09 mmol) in THF (30 mL) and distilled water (25 mL) was heated to reflux under an argon atmosphere, then a solution of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]boronic acid (10.0 g, 27 mmol) in THF (45 mL) was added dropwise. The reaction mixture was heated at reflux temperature overnight. Then it was cooled to room temperature and diluted with MTB ether and distilled water. The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent 1-chlorobutane). 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3-difluorophenol was isolated as a yellow solid.

[0310] Step 7.3: 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl]dibenzofuran

[0311]

[0312] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]- 2,3-difluorophenol (4.0 g, 9 mmol), potassium phosphate monohydrate (2.6 g, 11 mmol) and DMPU (40 mL) was stirred at 110 °C overnight. The reaction mixture was then filtered over silica gel (solvent n-heptane). The residue was purified by crystallization (heptane / ethanol) to yield white crystals of 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl] dibenzofuran (5).

[0313] The title compound has the following phase characteristics:

[0314] Cr 146 SmA 183 N 263 I.

[0315] Δε: -0.5

[0316] ε ┴ : 9.1

[0317] Δn: 0.219

[0318] Synthesis Example 8 (CLB-3-OT)

[0319] 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethoxy)dibenzofuran

[0320] Step 8.1: 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2- fluoro-3-(trifluoromethoxy)phenol

[0321]

[0322] A mixture of 6-bromo-2-fluoro-3-(trifluoromethoxy)phenol (CAS 1805580-01-1) (12.0 g, 39 mmol), potassium carbonate (8.5 g, 62 mmol), tris(dibenzylideneacetone)-dipalladium(0) (80 mg, 0.08 mmol) and CataCXium A (50 mg, 0.13 mmol) in THF (50 mL) and distilled water (40 mL) was heated to reflux under nitrogen, then a solution of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]boronic acid (14.5 g, 40 mmol) in THF (70 mL) was added dropwise. The reaction mixture was heated at reflux temperature overnight. It was then cooled to room temperature and diluted with MTB ether and distilled water. The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent 1-chlorobutane). 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3- (trifluoromethoxy)phenol was isolated as a yellow solid.

[0323] Step 8.2: 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethoxy)dibenzo[b,d]furan

[0324]

[0325] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2- fluoro-3-(trifluoromethoxy)phenol (6.9 g, 13 mmol), potassium phosphate monohydrate (4.0 g, 17 mmol) and DMPU (70 mL) was stirred at 110 °C overnight. The residue was purified by crystallization (heptane / ethanol) to give 4,6-difluoro-3-[4-(4- propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethoxy)dibenzo[b,d]furan as white crystals (5).

[0326] The title compound has the following phase characteristics:

[0327] Cr 101 SmA 251 N 258 I.

[0328] Δε: 1.1

[0329] ε ┴ : 9.5

[0330] Δn: 0.204

[0331] This compound combines a low melting point, a high N-I transition and an extremely high ε ┴ value.

[0332] Synthesis of Example 9 (CLB-3-T)

[0333] 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethyl)dibenzothiophene

[0334] Step 9.1 : 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2- fluoro-3-(trifluoromethyl)phenol.

[0335]

[0336] A mixture of 6-bromo-2-fluoro-3-(trifluoromethyl)phenol (CAS 1804908-52-8) (10 g, 38 mmol), potassium carbonate (8.0 g, 58 mmol), tris(dibenzylideneacetone)-dipalladium(0) (80 mg, 0.08 mmol) and CataCXium A (50 mg, 0.13 mmol) in THF (60 mL) and distilled water (33 mL) was heated to reflux under a nitrogen atmosphere, followed by dropwise addition of a solution of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]boronic acid (14.0 g, 38 mmol) in THF (40 mL). The reaction mixture was heated at reflux temperature overnight. It was then cooled to room temperature and diluted with MTB ether and distilled water. The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent 1-chlorobutane). 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3- (trifluoromethyl)phenol was isolated as a yellow solid.

[0337] Step 9.2: 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethyl)dibenzothiophene

[0338]

[0339] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2- fluoro-3-(trifluoromethyl)phenol (6.5 g, 13 mmol), potassium phosphate monohydrate (4.0 g, 17 mmol) and DMPU (60 mL) was stirred at 110 °C overnight. The reaction mixture was then filtered over silica gel (solvent n-heptane). The residue was purified by crystallization (heptane) to yield 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethyl)dibenzo[b,d]furan as white crystals (5). The title compound has the following phase characteristics:

[0340] Cr 118 SmA 227 N 247 I.

[0341] Δε: 3.3

[0342] ε ┴ : 10.3

[0343] Δn: 0.205

[0344] The compound has a surprisingly high ε ┴ value.

[0345] Synthesis Example 10 (CLB(S)-3-F)

[0346] 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl]dibenzo[b,d]thiophene

[0347]

[0348] Step 10.1: [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3- difluorophenyl] trifluoromethanesulfonate

[0349]

[0350] To a solution of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3- difluorophenol (7.4 g, 17 mmol), TEA (3.5 mL, 25 mmol) and DMAP (65 mg, 0.53 mmol) in dichloromethane (75 mL) was slowly added trifluoromethanesulfonic anhydride (3.5 mL, 18 mmol) at 5 °C under a nitrogen atmosphere. The solution was stirred at room temperature overnight. The reaction mixture was then filtered over silica gel (solvent 1-chlorobutane) to yield [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3- difluorophenyl] trifluoromethanesulfonate as a yellow solid.

[0351] Step 10.2: 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl] dibenzothiophene

[0352]

[0353] The reaction was performed in a one-pot procedure. In the first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3- difluorophenyl] trifluoromethanesulfonate (8.9 g, 14 mmol), 3-mercaptopropionic acid 2- ethylhexyl ester (4.5 mL, 19 mmol) and DIPEA (4.0 mL, 24 mmol) in toluene (50 mL) was treated with tris(dibenzylideneacetone)dipalladium(0) (150 mg, 0.16 mmol) and (oxybis-2,1-phenylene)bis(diphenylphosphine) (170 mg, 0.31 mmol) under an argon atmosphere and the reaction mixture was heated at reflux overnight. In the second step, a solution of potassium tert-butoxide (2.0 g, 18 mmol) in THF (15 mL) was added to the reaction mixture at room temperature. The reaction mixture was then heated at reflux for 6 h, followed by the addition of a second portion of potassium tert-butoxide (1.0 g, 9 mmol) in THF (10 mL) and heating at reflux overnight again. A third portion of potassium tert-butoxide (1.0 g, 9 mmol) in THF (10 mL) was added and the reaction mixture was heated at reflux for a further 6 h. It was then cooled to room temperature, quenched with distilled water and hydrochloric acid (25%) at 0 °C and diluted with MTB ether and THF. The aqueous phase was separated and extracted with MTB ether and THF. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane) and crystallisation (heptane / ethanol) to give 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl]dibenzothiophene as white crystals (7).

[0354] The title compound has the following phase characteristics:

[0355] Cr 136 SmA 208 N 303

[0356] Δε: 3.5

[0357] ε ┴ : 6.7

[0358] Δn: 0.217

[0359] Synthesis Example 11 (CLB(S)-3-OT)

[0360] 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethoxy)dibenzothiophene

[0361]

[0362] Step 11.1: [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2- fluoro-3-(trifluoromethoxy)phenyl] trifluoromethanesulfonate

[0363]

[0364] To a solution of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]- 2-fluoro-3-(trifluoromethoxy)phenol (10.0 g, 20 mmol), TEA (4.1 mL, 30 mmol) and DMAP (80 mg, 0.66 mmol) in dichloromethane (100 mL) was slowly added trifluoromethanesulfonic anhydride (4.0 mL, 24 mmol) at 5 °C under nitrogen atmosphere. The solution was stirred at room temperature overnight. The reaction mixture was purified by silica gel chromatography (solvent 1-chlorobutane) to give [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2- fluoro-3-(trifluoromethoxy)phenyl] trifluoromethanesulfonate as a yellow solid.

[0365] Step 11.2: 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethoxy)dibenzothiophene

[0366]

[0367] The reaction was performed in a one-pot procedure. In the first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3- (trifluoromethoxy)phenyl] trifluoromethanesulfonate (12.3 g, 17 mmol), 3- mercaptopropionic acid 2-ethylhexyl ester (5.0 mL, 21 mmol) and DIPEA (4.5 mL, 26 mmol) in toluene (60 mL) was treated with tris(dibenzylideneacetone)dipalladium(0) (170 mg, 0.18 mmol) and (oxydi-2,1-phenylene)bis(diphenylphosphine) (190 mg, 0.35 mmol) under an argon atmosphere and the reaction mixture was heated at reflux overnight. In the second step, a solution of potassium tert-butoxide (2.3 g, 21 mmol) in THF (20 mL) was added to the reaction mixture at room temperature. The reaction mixture was then heated at reflux for 6 hours, followed by the addition of a second portion of potassium tert-butoxide (1.2 g, 11 mmol) in THF (15 mL) and heating at reflux overnight again. A third portion of potassium tert-butoxide (1.2 g, 11 mmol) in THF (15 mL) was added and the reaction mixture was heated at reflux for a further 6 hours. It was then cooled to room temperature, quenched with distilled water and hydrochloric acid (25%) at 0°C and diluted with MTB ether and THF. The aqueous phase was separated and extracted with MTB ether and THF. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane) and crystallisation (heptane / isopropanol) to give 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethoxy)dibenzothiophene as light yellow crystals (7).

[0368] The title compound has the following phase characteristics:

[0369] Cr 131

[0370] SmA 295N 318.

[0371] Δε: 4.7 ε ┴ : 7.1

[0372] Δn: 0.221

[0373] Synthesis Example 12 (CLB(S)-3-T)

[0374] 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethyl)dibenzothiophene

[0375]

[0376] Step 12.1: [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2- fluoro-3-(trifluoromethyl)phenyl] trifluoromethanesulfonate

[0377]

[0378] Step 12.1: [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2- fluoro-3-(trifluoromethyl)phenyl] trifluoromethanesulfonate

[0379] Step 12.2: 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethyl)dibenzothiophene

[0380]

[0381] The reaction was performed in a one-pot procedure. In the first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3- (trifluoromethyl)phenyl] trifluoromethanesulfonate (13.3 g, 20 mmol), 3- mercaptopropionic acid 2-ethylhexyl ester (5.5 mL, 23 mmol) and DIPEA (5.0 mL, 29 mmol) in toluene (60 mL) was treated with tris(dibenzylideneacetone)dipalladium(0) (180 mg, 0.19 mmol) and (oxydi-2,1-phenylene)bis(diphenylphosphine) (210 mg, 0.38 mmol) under an argon atmosphere and the reaction mixture was heated at reflux overnight. In the second step, a solution of potassium tert-butoxide (2.6 g, 23 mmol) in THF (20 mL) was added to the reaction mixture at room temperature. The reaction mixture was then heated at reflux for 6 h, followed by the addition of a second portion of potassium tert-butoxide (1.3 g, 12 mmol) in THF (15 mL) and heating at reflux overnight again. A third portion of potassium tert-butoxide (1.3 g, 12 mmol) in THF (15 mL) was added and the reaction mixture was heated at reflux for a further 6 h. It was then cooled to room temperature, quenched with distilled water and hydrochloric acid (25%) at 0°C and diluted with MTB ether and THF. The aqueous phase was separated and extracted with MTB ether and THF. The combined organic phases were washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane) and crystallization (heptane / ethanol) to give 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7- (trifluoromethyl)dibenzothiophene as white crystals (7).

[0382] The title compound has the following phase characteristics:

[0383] Cr 138 SmA 256 N 302.

[0384] Δε: 7.2

[0385] ε ┴ : 8.1

[0386] Δn: 0.204

[0387] Further synthesis examples:

[0388] In analogy to the examples described above, the following exemplary compounds were obtained:

[0389] In the following table, the following abbreviations for end groups are used

[0390]

[0391] The physical properties are given at a temperature of 20°C and γ1 is given in mPa s. The phase transition temperatures are given in °C.

[0392]

[0393]

[0394]

[0395]

[0396]

[0397]

[0398]

[0399]

[0400]

[0401]

[0402]

[0403]

[0404]

[0405]

[0406]

[0407]

[0408] Use Examples

[0409] Liquid crystal media using the compounds according to the application as components were prepared as follows. Percentages are % by weight, unless indicated otherwise. The stabilizers according to Table F were added to the mixtures presented below as required.

[0410] The nematic liquid crystal mixture N-1 having the composition and properties as indicated in the following table was used as a basis (host mixture) for the preparation of several exemplary mixtures.

[0411] Mixture N-1:

[0412]

[0413] Mixture Example 1

[0414] The nematic liquid crystal medium M-1 consisting of 95% of the medium N-1 and 5% of the compound CCB-3-T of Synthesis Example 3 has the following properties:

[0415]

[0416] The compound CCB-3-T is well dissolved in the medium N-1.

[0417] Mixture Example 2

[0418] The nematic liquid crystal medium M-2 consisting of 90% of the medium N-1 and 10% of the compound CCB-3-OT of Synthesis Example 2 has the following properties:

[0419]

[0420] The compound CCB-3-OT is well dissolved in the medium N-1. The mixture has an advantageously high clearing point.

[0421] Mixture Example 3

[0422] The nematic liquid crystal medium M-3 consisting of 95% of the medium N-1 and 5% of the compound CCB(S)-3-OT of Synthesis Example 5 has the following properties:

[0423]

[0424] Mixture Example 4

[0425] The nematic liquid crystal medium M-4 consisting of 95% of the medium N-1 and 5% of the compound CLB-3-OT of Synthesis Example 8 has the following properties:

[0426]

[0427] Mixture Example 5

[0428] The nematic liquid crystal medium M-5 consisting of 95% of the medium N-1 and 5% of the compound CLB-3-T of Synthesis Example 9 has the following properties:

[0429]

[0430] Mixture Example 6

[0431] The nematic liquid crystal medium M-6 consisting of the compounds indicated in the following table is prepared

[0432]

[0433] The mixture is suitable for FFS displays.

[0434] Mixture example 7

[0435] A nematic liquid crystal medium M-7 consisting of the compounds indicated in the following table was prepared

[0436]

[0437]

[0438] Mixture example 8

[0439] A nematic liquid crystal medium M-8 consisting of the compounds indicated in the following table was prepared

[0440]

[0441] This mixture is suitable for FFS displays.

Claims

1. A compound of formula I, ###0001### wherein W represents O or S wherein X represents F, CF3, CHF2, OCF3 or OCHF2, and wherein Z represents a single bond. R represents H, an alkyl group having 1 to 15 carbon atoms, wherein one or more CH2 groups of these groups can be independently converted via -C≡C-, -CF2O-, -OCF2-, -CH=CH-, ... The substitutions are -O-, -CO-O-, or -O-CO-, where the O atoms are not directly connected to each other, and one or more H atoms can be substituted with halogens. A 1 independently trans-1,4-cyclohexylene or 1,4-cyclohexenylene, wherein one or more non- adjacent CH2groups can be replaced by -O- and wherein one or more H atoms can be replaced by F, A 2 independently trans-1,4-cyclohexylene or 1,4-cyclohexenylene, and wherein one or more H atoms can be replaced by F, 2. The compound according to claim 1, wherein W represents O.

3. The compound according to claim 1 or 2, wherein W represents S.

4. The compound according to claim 1 or 2, which is selected from the following subformulae: ###0002### ###0003### ###0004### ###0005### ###0006### ###0007### ###0008### ###0009### ###0010### ###0011### ###0012### ###0013### ###0014### ###0015### ###0016### ###0017### ###0018### ###0019### ###0020### ###0021### ###0022### ###0023### ###0024### ###0025### ###0026### ###0027### ###0028### ###0029### ###0030### ###0031### ###0032### ###0033### ###0034### ###0035### ###0036### ###0037### ###0038### ###0039### ###0040### ###0041### ###0042### ###0043### ###0044### ###0045### ###0046### ###0047### ###0048### ###0049### ###0050### ###0051### ###0052### ###0053### ###0054### ###0055### ###0056### ###0057### ###0058### ###0059### ###0060### ###0061### ###0062### ###0063### ###0064### ###0065### ###0066### ###0067### ###0068### ###0069### ###0070### ###0071### ###0072### ###0073### ###0074### ###0075### ###0076### ###0077### ###0078### ###0079### ###0080### ###0081### ###0082### ###0083### ###0084### ###0085### ###0086### ###0087### ###0088### ###0089### ###0090### ###0091### ###0092### ###0093### ###0094### ###0095### ###0096### ###0097### ###0098### ###0099### ###0100### ###0101### ###0102### ###0103### ###0104### ###0105### ###0106### ###0107### ###0108### ###0109### ###0110### ###0111### ###0112### ###0113### ###0114### ###0115### ###0116### ###0117### ###0118### ###0119### ###0120### ###0121### ###0122### ###0123### ###0124### ###0125### ###0126### ###0127### ###0128### ###0129### ###0130### ###0131### ###0132### ###0133### ###0134### ###0135### ###0136### ###0137### ###0138### ###0139### ###0140### ###0141### ###0142### ###0143### ###0144### ###0145### ###0146### ###0147### ###0148### ###0149### ###0150### ###0151### ###0152### ###0153### ### ​ ​ wherein R, A 1 and A 2 have the meanings given in claim 1.

5. The compound according to claim 1 or 2, wherein ring A 1 represents a trans-1,4-cyclohexylene ring.

6. The compound according to claim 1 or 2, wherein ring A 2 represents a trans-1,4-cyclohexenylene ring.

7. The compound according to claim 1 or 2, wherein ring A 2 represents a trans-1,4-cyclohexylene ring. ​ ​ ​ 10. A process for the preparation of a compound of formula I according to claim 1, characterized in that ​ ​ ​ ​ ​ R 2 represents alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, independently of each other in each occurrence represent L 21 and L 22 denotes H or F, X 2 denotes halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, ​ R 3 represents alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, L 31 and L 32 independently of one another H or F, X 3 denotes halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, Z 3 represents -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, and ​ 13. Liquid-crystalline medium according to claim 12, wherein R 2 denotes alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C atoms. ​ ​

Images