Dibenzofuran and dibenzothiophene derivatives

Abstract

The present invention relates to compounds of the general formula (I) #imgabs0#, wherein the groups and parameters occurring therein have the meanings indicated in claim 1, to their use in liquid crystals or mesogenic media and to liquid crystals or mesogenic media comprising these derivatives.

Description

[0001] The present invention 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 widely used since the discovery of the first commercially usable liquid crystal compounds about 30 years ago. Known fields of application are, in particular, displays for watches and pocket calculators and large display panels, such as are used in railway stations, airports and sports arenas. Other fields of application are displays for portable computers and navigation systems and video applications. In particular, for the last-mentioned applications, very high requirements are made on the response time and contrast of the image.

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

[0004] Both the polarizability and the permanent dipole moment of the molecules contribute to the dielectric anisotropy. When a voltage is applied to the display, the molecular longitudinal axis orients itself in such a way that a larger dielectric constant 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 large difference. The introduction of suitable polar groups (e.g. nitrile groups or fluorine) into the liquid crystal molecules enables a wide range of operating voltages to be achieved.

[0005] In the case of 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 larger dipole moment along the longitudinal axis of the molecule also determines the orientation of the molecules in the liquid crystal display in the field-free state. In the most widespread TN ("twisted nematic") cell, a liquid crystal layer with a thickness of only about 5 μm to 10 μm is arranged between two flat glass plates, each of which has been vapor-deposited with a conductive transparent layer of tin oxide or indium tin oxide as an electrode. An equally transparent alignment layer, usually composed of a polymer (such as polyimide), is positioned between these films and the liquid crystal layer. This alignment layer serves to place the longitudinal axes of adjacent liquid crystal molecules in a preferred direction by means of surface forces, so that in the voltage-free state they are uniformly placed on the inside of the display surface in the same alignment in a flat manner or at the same small tilt angle. Two polarizing films that allow only linearly polarized light to enter and escape are adhesively bonded to the outside of the display in a specific configuration.

[0006] With the aid of liquid crystals in which the larger dipole moment is oriented parallel to the longitudinal axis of the molecule, extremely 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 intermediate phase temperature range and short response times and low threshold voltages. However, the strong viewing angle dependence still poses difficulties in liquid crystal displays such as are used, for example, in notebook computers. The best image quality can be achieved if the display surface is perpendicular to the viewing direction of the observer. If the display is tilted relative to the viewing direction, the image quality drops sharply in some cases. For greater comfort, attempts are being made to make the angle at which the display can be tilted from the viewing direction of the observer as large as possible. Recently, attempts have been made to improve the viewing angle dependence using liquid crystal compounds in which the dipole moment perpendicular to the longitudinal axis of the molecule is greater than the dipole moment parallel to the longitudinal axis of the molecule. 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. This type of display is called a VA-TFT ("vertically aligned") display.

[0007] So-called IPS (“in-plane switching”) displays are also known, which contain an LC layer between two substrates with a planar orientation, wherein two electrodes are arranged on only one of the two substrates and preferably have an interdigitated comb structure. When a voltage is applied to the electrodes, an electric field with a significant component parallel to the LC layer is generated between the electrodes. This causes the LC molecules to realign in the layer plane. In addition, so-called FFS (“fringe field switching”) displays have been reported (see, in particular, SH 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 a comb-like manner and the other is not structured. Strong so-called “fringe fields” are thereby generated, i.e. strong electric fields close to the edges of the electrodes, and an electric field with both a strong vertical component and a strong horizontal component is generated throughout the cell. FFS displays have a low contrast viewing angle dependence. FFS displays usually contain an LC medium with positive dielectric anisotropy and an alignment layer, usually made of polyimide, which provides a planar alignment for the molecules of the LC medium.

[0008] In DE 10 2005 012 585 A1, dibenzofuran and dibenzothiophene derivatives are proposed for use in liquid-crystalline media. However, due to their substitution pattern, the compounds described therein exhibit a negative dielectric anisotropy, which makes them unsuitable for use according to the present invention.

[0009] Research and development in the field of liquid crystal materials is still far from complete. In order to improve the properties of liquid crystal display elements, attempts are constantly being made to develop novel compounds that would enable these displays to be optimized.

[0010] It was an object of the present invention to provide compounds having advantageous properties for use in liquid-crystalline media.

[0011] This object is achieved according to the invention by compounds of the general formula I

[0012]

[0013] in

[0014] W means O or S,

[0015] R represents H, an alkyl radical having 1 to 15 C atoms, wherein one or more CH2 groups in these radicals may each independently of one another be replaced by -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO-, wherein one or more H atoms may be replaced by halogen,

[0016] A, at each occurrence, identically or differently, represents a group selected from the following group:

[0017] a) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclohexenylene and decahydronaphthalene-2,6-diyl, wherein one or more non-adjacent CH2 groups may be replaced by -O- and / or -S-, and wherein one or more H atoms may be replaced by F,

[0018] b) the group consisting of 1,4-phenylene and 2,6-naphthylene, in which one or two CH groups may be replaced by N and in which one or more other H atoms may be replaced by L,

[0019] c) the group consisting of 1,3-dioxane-2,5-diyl, tetrahydrofuran-2,5-diyl, cyclobutane-1,3-diyl, thiophene-2,5-diyl, selenophene-2,5-diyl and 1,2,3,4-tetrahydronaphthalene-2,6-diyl, each of which may be mono- or polysubstituted by L,

[0020] d) the group consisting of bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl and spiro[3.3]heptane-2,6-diyl, in which one or more H atoms may be replaced by F,

[0021] L each, identically or differently, represents halogen, cyano, alkyl having 1 to 7 C atoms, alkoxy, alkylcarbonyl or alkoxycarbonyl, in which one or more H atoms may be substituted by F or Cl,

[0022] Z represents, identically or differently on each occurrence, a single bond, -CF2O-, -OCF2-, -CH2CH2-, -CF2CF2-, -C(O)O-, -OC(O)-, -CH2O-, -OCH2-, -CF=CH-, -CH=CF-, -CF=CF-, -CH=CH- or -C≡C-,

[0023] Y 1 , Y 2 and Y 3 Identically or differently represent H, F, Cl, CF3 or CHF2, wherein Y 1 and Y 2 One of them is not H,

[0024] X represents F, Cl, CN, NCS, SF5, fluorinated alkyl, alkoxy, alkenyl or alkenyloxy, each having up to 5 C atoms, preferably F, CF3, OCF3 or NCS, and

[0025] n is 0, 1 or 2, preferably 0 or 1.

[0026] It was a further object of the present invention to provide liquid-crystalline media which are used in particular in TN, IPS or FFS displays.

[0027] This object is achieved according to the invention by providing compounds of the formula I which have a positive dielectric anisotropy (Δε).

[0028] The compounds of the formula I are characterized by a surprisingly large positive dielectric anisotropy (Δε) and are therefore particularly suitable for TN-TFT displays and IPS- and FFS displays. The compounds have a relatively low melting point, high bright spots and they exhibit very good compatibility with the conventional substances used in liquid crystal mixtures for displays and dissolve well in these media.

[0029] The compounds according to the invention preferably have a Δε>9, preferably>15 and particularly preferably>20.

[0030] If R or L is an alkyl and / or alkoxy radical, it may be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and is therefore preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy or heptyloxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy.

[0031] R or L can be independently of each other an alkenyl group with 2 to 15 carbon atoms, which can be straight or branched. It is preferably straight and has 2 to 7 carbon atoms. Therefore, it is preferably vinyl, prop-1-enyl or -2-enyl, but-1-enyl, but-2-enyl or -3-enyl, penta-1-enyl, penta-2-enyl, penta-3-enyl or penta-4-enyl, hex-1-enyl, hex-2-enyl, hex-3-enyl, hex-4-enyl or hex-5-enyl or hept-1-enyl, hept-2-enyl, hept-3-enyl, hept-4-enyl, hept-5-enyl or hept-6-enyl.

[0032] R or L can each independently of one another be oxaalkyl, preferably a linear 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 a 2-oxaheptyl, 3-oxaheptyl, 4-oxaheptyl, 5-oxaheptyl or 6-oxaheptyl.

[0033] R or L can each independently of one another be an alkyl radical having 1 to 15 carbon atoms, in which one CH2 group has been replaced by -O- and one by -CO-, wherein these are preferably adjacent. It thus contains an acyloxy-CO-O- or oxycarbonyl-O-CO-. It is preferably straight-chain and has 2 to 6 carbon atoms.

[0034] R or L can each independently be an alkyl group having 1 to 15 carbon atoms, in which one CH2 group has been replaced by unsubstituted or substituted -CH=CH- and the adjacent CH2 group has been replaced by CO or CO-O or O-CO, where this can be straight-chain or branched. It is preferably straight-chain and has 4 to 13 carbon atoms.

[0035] R or L can be each independently an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, each of which is monosubstituted with -CN or -CF3 and is preferably straight chain. The substitution with -CN or -CF3 can be at any desired position.

[0036] R or L may each independently be an alkyl group in which two or more CH2 groups have been replaced by -O- and / or -CO-O-, which may be linear or branched. It is preferably branched and has 3 to 12 carbon atoms.

[0037] R or L can each independently of one another be an alkyl radical having 1 to 15 carbon atoms or an alkenyl radical having 2 to 15 carbon atoms, each of which is at least monosubstituted by halogen, wherein these radicals are preferably straight-chain and the halogen is preferably -F or -Cl. In the case of polysubstitution, the halogen is preferably -F. The resulting radicals also include perfluorinated radicals, such as -CF3. In the case of monosubstitution, the fluorine or chlorine substituents may be in any desired position, but are preferably in the ω position.

[0038] The term "fluorinated alkyl" preferably encompasses monofluorinated or polyfluorinated groups. Including perfluorinated groups. Particularly preferred are CF3, CH2CF3, CH2CHF2, CHF2, CH2F, CHFCF3 and CF2CHFCF3.

[0039] The term "fluorinated alkoxy" preferably encompasses monofluorinated or polyfluorinated groups. Including perfluorinated groups. Especially preferred is OCF3.

[0040] In a preferred embodiment of the present invention, the compound of formula I is selected from the compounds of formula I-1 to I-6:

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] The radicals and parameters occurring therein have the meanings given above for formula I and preferably R denotes H, alkyl or alkoxy, each having 1 to 7 C atoms, wherein one or more CH2 groups in these radicals may each independently of one another be replaced by:

[0048]

[0049] A denotes trans-1,4-cyclohexylene, 1,4-cyclohex-1-enylene or 1,4-phenylene, in which one or two CH groups may be replaced by N and in which one or more other H atoms may be replaced by L,

[0050] L represents F or Cl,

[0051] Z, at each occurrence, identically or differently, represents a single bond, -CH2CH2-, -CF2CF2-, -CH2O- or -C≡C-, preferably a single bond,

[0052] X represents F, CF3, OCF3 or NCS,

[0053] n is 0 or 1.

[0054] In a preferred embodiment of the invention, in formula I and its subformulae I-1, I-2, I-3, I-4, I-5 and I-6, R represents an alkoxy group having 1 to 7 C atoms, in particular methoxy, ethoxy, n-propoxy, n-butoxy or n-pentoxy, and n is 0, wherein the other radicals have the meanings given above.

[0055] In a preferred embodiment of the invention, in formula I and its subformulae I-1, I-2, I-3, I-4, I-5 and I-6, n is 1, Z represents a single bond, and A represents 4-alkylcyclohexen-1-yl, where alkyl represents a straight-chain alkyl radical having 1 to 7 C atoms, and where the other radicals have the meanings given above.

[0056] The compounds of the general formula I are prepared by methods known per se, as described in the literature (for example in standard works, such as Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), precisely under reaction conditions known and suitable for these reactions. It is also possible here to use variants known per se, but not mentioned in greater detail here.

[0057] If desired, the starting materials can also be formed in situ, without isolating them from the reaction mixture, but rather converting them further immediately into compounds of the formula I.

[0058] Preferred synthetic routes to the compounds of the invention are shown in the schemes below and are further illustrated by means of working examples. The synthesis can be tailored to the particular desired compound of formula I by selection of appropriate starting materials.

[0059] Dibenzofuran derivatives, ie compounds of formula I wherein W represents O (Formula I'), are preferably synthesized as shown in Scheme 1 and can be obtained by treating phenol P with a base to intramolecularly replace the fluorine via nucleophilic attack of the phenolate.

[0060] Solution 1

[0061]

[0062] Alternatively, a similar ring closure in which the positions of the OH group and the fluorine atom are interchanged can be as shown in Scheme 2.

[0063] Solution 2

[0064]

[0065] Dibenzofuran derivatives (ie compounds of formula I (Formula I") wherein W represents S) are preferably synthesized as shown in Scheme 3.

[0066] Solution 3

[0067]

[0068] 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).

[0069] Therefore, another object of the present invention is a compound of formula P or P'

[0070]

[0071] They are used in the processes for the synthesis of compounds of the formula I, in which the radicals and parameters occurring have the meanings given above for formula I.

[0072] A further object of the present invention is a process for synthesizing compounds of formula I from compounds of formula P or P', preferably following the synthetic routes depicted in Scheme 1, Scheme 2 or Scheme 3 above.

[0073] The reactions described should be considered as illustrative only. A person skilled in the art may make corresponding changes to the synthesis described and follow other suitable synthetic routes to obtain compounds of formula I.

[0074] The compounds of the general formula I can be used in liquid-crystalline media. The present invention therefore also relates to liquid-crystalline media comprising two or more liquid-crystalline compounds, comprising one or more compounds of the general formula I.

[0075] The invention also relates to liquid-crystalline media which, in addition to one or more compounds of the formula I according to the invention, comprise as further constituents 2 to 40, preferably 4 to 30, components. These media particularly preferably comprise, in addition to one or more compounds according to the invention, 7 to 25 components. These further constituents are preferably selected from nematic or nematic (monotropic or isotropic) substances, in particular substances from the following classes: azobenzene oxide, benzylideneaniline, biphenyl, terphenyl, 1,3-dioxane, 2,5-tetrahydropyran, phenyl or cyclohexyl benzoate, phenyl or cyclohexyl ester of cyclohexanecarboxylic acid, phenyl or cyclohexyl ester of cyclohexylbenzoic acid, phenyl or cyclohexyl ester of cyclohexylcyclohexanecarboxylic acid; phenylcyclohexane, cyclohexylbiphenyl, phenylcyclohexylcyclohexane; hexane, cyclohexylcyclohexane, cyclohexylcyclohexylcyclohexene, 1,4-dicyclohexylbenzene, 4',4'-dicyclohexylbiphenyl, phenylpyrimidine or cyclohexylpyrimidine, phenylpyridine or cyclohexylpyridine, phenyldioxane or cyclohexyldioxane, phenyl-1,3-dithiane or cyclohexyl-1,3-dithiane, 1,2-diphenylethane, 1,2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1-cyclohexyl-2-(4-phenylcyclohexyl)ethane, 1-cyclohexyl-2-biphenylethane, 1-phenyl-2-cyclohexylphenylethane, optionally halogenated , benzylphenyl ether, tolan and substituted cinnamic acid. The 1,4-phenylene in these compounds can also be monofluorinated or polyfluorinated.

[0076] The most important compounds suitable as further components of the medium according to the invention can be characterized by the formulae (II), (III), (IV), (V) and (VI):

[0077] R'-LER" (II)

[0078] R'-L-(CO)OER” (III)

[0079] R'-LO(CO)-ER” (IV)

[0080] R'-L-CH2CH2-ER” (V)

[0081] R'-L-CF2O-ER" (VI)

[0082] In formulae (II), (III), (IV), (V) and (VI), L and E may be identical or different and each independently represent a divalent group from the group formed by: -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -Thp-, -G-Phe- and -G-Cyc- and mirror images thereof, wherein Phe represents unsubstituted or fluorine-substituted 1, 4-phenylene, Cyc represents trans-1,4-cyclohexylene or 1,4-cyclohexenylene, Pyr represents pyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio represents 1,3-dioxane-2,5-diyl, Thp represents tetrahydropyran-2,5-diyl and G represents 2-(trans-1,4-cyclohexyl)ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl, 1,3-dioxane-2,5-diyl or tetrahydropyran-2,5-diyl.

[0083] One of the groups L and E is preferably Cyc or Phe. E is preferably Cyc, Phe or Phe-Cyc. The medium according to the invention preferably comprises one or more components selected from the group consisting of compounds of the formulae (II), (III), (IV), (V) and (VI), wherein L and E are selected from the group Cyc and Phe; and at the same time one or more components selected from the group consisting of compounds of the formulae (II), (III), (IV), (V) and (VI), wherein one of the groups L and E is selected from the group Cyc and Phe and the other 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 group consisting of compounds of the formulae (II), (III), (IV), (V) and (VI), wherein the groups L and E are selected from the group -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.

[0084] In a smaller subgroup of compounds of the formulae (II), (III), (IV), (V) and (VI), R' and R" each independently of one another represent an alkyl, alkenyl, alkoxy, alkoxyalkyl(oxaalkyl), alkenyloxy or alkanoyloxy group having up to 8 C atoms. This smaller subgroup is referred to hereinafter as group A and the compounds are referred to by the sub-formulae (IIa), (IIIa), (IVa), (Va) and (VIa). In most of these compounds, R' and R" are different from one another, one of these groups being generally alkyl, alkenyl, alkoxy or alkoxyalkyl(oxaalkyl).

[0085] In another smaller subgroup of compounds of formula (II), (III), (IV), (V) and (VI), referred to as Group B, E represents a fluorinated phenylene group of the formula

[0086]

[0087] In the compounds of group B referred to by sub-formulae (IIb), (IIIb), (IVb), (Vb) and (VIb), R′ and R″ have the meanings indicated for the compounds of sub-formulae (IIa) to (VIa) and are preferably alkyl, alkenyl, alkoxy or alkoxyalkyl (oxaalkyl).

[0088] In another subgroup of compounds of formula (II), (III), (IV), (V) and (VI), R" represents -F, -Cl, -CN, -NCS or -(O) i CH 3-k F k , wherein i is 0 or 1 and k is 1, 2 or 3. This subgroup is referred to hereinafter as group C and the compounds of this subgroup are described by the sub-formulae (IIc), (IIIc), (IVc), (Vc) and (VIc), respectively. In the compounds of sub-formulae (IIc), (IIIc), (IVc), (Vc) and (VIc), R' has the meaning indicated for the compounds of sub-formulae (IIa) to (VIa) and is preferably alkyl, alkenyl, alkoxy or alkoxyalkyl (oxaalkyl).

[0089] In addition to the preferred compounds of groups A, B and C, further compounds of the formulae (II), (III), (IV), (V) and (VI) with other variants of the substituents mentioned are also common. All these substances can be obtained by methods known from the literature or analogous thereto.

[0090] In addition to the compounds of the general formula I according to the invention, the medium according to the invention preferably comprises one or more compounds from groups A, B and / or C. The medium preferably comprises one or more compounds from group A and one or more compounds from group B for dielectrically negative mixtures or additionally one or more compounds from group C for dielectrically positive mixtures. The weight proportions of the compounds from these groups in the medium according to the invention are:

[0091] Group A:

[0092] 0 to 90%, preferably 15 to 90%, especially 20 to 85%.

[0093] Group B:

[0094] 0 to 80%, preferably 10 to 85%, especially 15 to 80%.

[0095] Group C:

[0096] 0 to 80%, preferably 15 to 90%, especially 20 to 85%.

[0097] The media according to the invention preferably comprise 1% to 30%, particularly preferably 2% to 20%, of a compound of the formula I according to the invention.

[0098] The medium preferably comprises one, two, three, four or five compounds of the formula I according to the invention.

[0099] In a preferred embodiment of the present invention, the liquid-crystalline medium comprises

[0100] a) one or more compounds selected from the group of compounds of formula II and III, which preferably have a dielectric anisotropy greater than 3:

[0101]

[0102]

[0103] in

[0104] 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 an alkyl or alkenyl group,

[0105]

[0106] In each occurrence, they are expressed independently of each other

[0107]

[0108]

[0109] Best

[0110]

[0111] L 21 and L 22 Indicates H or F, preferably L 21 Indicates F,

[0112] X 2 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, Cl, -OCF3, -O-CH2CF3, -O-CH=CF2 or -CF3, very preferably F, Cl, -O-CH=CF2 or -OCF3,

[0113] m is 0, 1, 2 or 3, preferably 1 or 2, and particularly preferably 1,

[0114] R 3represents an alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy radical having 1 to 7 C atoms, an alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl radical having 2 to 7 C atoms, and preferably an alkyl or alkenyl radical,

[0115]

[0116] In each occurrence, independently of each other,

[0117]

[0118]

[0119] Best

[0120]

[0121] L 31 and L 32 independently represent H or F, preferably L 31 Indicates F,

[0122] 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, Cl, -OCF3, -OCHF2, -O-CH2CF3, -O-CH═CF2, -O-CH═CH2 or -CF3, very preferably F, Cl, -O-CH═CF2, -OCHF2 or -OCF3,

[0123] Z 3 represents -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond,

[0124] Preferred is -CH2CH2-, -COO-, trans-CH=CH- or a single bond, and very preferably -COO-, trans-CH=CH- or a single bond, and

[0125] n is 0, 1, 2 or 3, preferably 1, 2 or 3, and particularly preferably 1, and

[0126] b) optionally one or more preferably dielectrically neutral compounds selected from the group consisting of formulae IV and V:

[0127]

[0128]

[0129] in

[0130] R 41 and R42 Independently of each other, the above formula II for R 2 The indicated meaning, preferably R 41 represents an alkyl group and R 42 represents an alkyl group or an alkoxy group, or R 41 represents an alkenyl group and R 42 represents an alkyl group,

[0131]

[0132] Independently and in

[0133] In the case of two occurrences, these also represent independently of each other

[0134]

[0135]

[0136] Best

[0137]

[0138] One or more of the following means,

[0139]

[0140] Z 41 and Z 42 Independently of each other and in Z 41 In the case of two occurrences, these also independently represent -CH2CH2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O-, -CF2O-, -C≡C- or a single bond, preferably one or more of which represent a single bond, and

[0141] p represents 0, 1 or 2, preferably 0 or 1, and

[0142] R 51 and R 52 Independently of each other, they have 41 and R 42 one of the meanings given and preferably represents 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, alkenyl or alkenyloxy, preferably alkenyloxy, having 2 to 7 C atoms, preferably 2 to 4 C atoms,

[0143]

[0144] In the presence of each, they are expressed independently of each other

[0145]

[0146]

[0147] Best

[0148]

[0149] Best

[0150] express

[0151] And if it exists,

[0152] Preferred representation

[0153] Z 51 To Z 53 each independently represents -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,

[0154] i and j each independently represent 0 or 1,

[0155] (i+j) preferably represents 0, 1 or 2, more preferably 0 or 1, and most preferably 1.

[0156] The invention furthermore relates to electro-optical liquid-crystal display elements comprising the liquid-crystal media according to the invention.

[0157] The medium according to the invention is prepared in a conventional manner per se. Generally, the components are advantageously dissolved in one another at elevated temperatures. With the aid of suitable additives, the liquid-crystalline phases according to the invention can be modified in such a way that they can be used for all types of liquid-crystal display elements disclosed to date. Additives of this type are known to the person skilled in the art and are described in detail in the literature (H. Kelker / R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, polychromatic dyes can be used for the preparation of colored guest-host systems or substances can be added to modify the dielectric anisotropy, the viscosity and / or the alignment of the nematic phase.

[0158] In the present invention and the following examples, the structures of the liquid crystal compounds are indicated by means of acronyms, which are converted into chemical formulae according to Tables A to C below. n H 2n+1 , C m H 2m+1 and Cl H 2l+1 or C n H 2n , C m H 2m and C l H 2l is a straight-chain alkyl or alkylene group, having n, m and 1 C atoms, respectively, in each case. Preferably, n, m and 1 are independently 1, 2, 3, 4, 5, 6 or 7. Table A shows the ring element codes of the compound core, Table B lists the bridging units, and Table C lists the symbolic meanings of the left and right end groups of the molecule. The acronyms consist of the code of the ring element with the optional linking group, followed by the first hyphen and the code of the left end group and the second hyphen and the code of the right end group. Table D shows the illustrative structures of the compounds and their respective acronyms.

[0159] Table A: Ring elements

[0160]

[0161]

[0162]

[0163] Table B: Bridge Unit

[0164]

[0165]

[0166] Table C: Terminal Groups

[0167]

[0168]

[0169]

[0170] Where n and m are each integers, and the three dots "..." are placeholders for other abbreviations in this table.

[0171] In addition to the compounds of the formula I, the mixtures according to the invention preferably comprise one or more of the compounds shown in Table D below.

[0172] The following abbreviations are used:

[0173] (n, m, k and l are each independently an integer, preferably 1 to 9, preferably 1 to 7, k and l may also be 0 and 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 "-lVm" is preferably "2V1".)

[0174] Table D

[0175] Examples of compounds of formula I

[0176]

[0177]

[0178] Exemplary, preferred dielectrically positive compounds that can be used in combination with the compounds of Formula I

[0179]

[0180]

[0181]

[0182]

[0183]

[0184]

[0185]

[0186]

[0187]

[0188] Exemplary, preferred dielectrically neutral compounds that can be used in combination with compounds of Formula I

[0189]

[0190]

[0191]

[0192]

[0193]

[0194]

[0195] Table E shows chiral dopants that are preferably employed in the mixtures of the present invention.

[0196] Table E

[0197]

[0198]

[0199]

[0200] In a preferred embodiment of the invention, the medium according to the invention comprises one or more compounds selected from the group of compounds of Table E.

[0201] Table F shows preferably employable stabilizers in the mixtures according to the invention in addition to the compounds of the formula B. The parameter n here denotes an integer in the range from 1 to 12. In particular, phenol derivatives have been shown to be useful as additional stabilizers, since they act as antioxidants.

[0202] Table F

[0203]

[0204]

[0205]

[0206]

[0207]

[0208] In a preferred embodiment of the invention, the medium according to the invention comprises one or more compounds selected from the group of compounds of Table F.

[0209] The invention is explained in more detail hereinafter with reference to working examples, without intending to be restricted thereby.

[0210] In this context, Δn denotes the optical anisotropy (589 nm, 20° C.) and Δε denotes the dielectric anisotropy (1 kHz, 20° C.).

[0211] The Δε and Δn values ​​of the compounds according to the invention were obtained by extrapolation from a liquid crystal mixture consisting of 10% of the respective compound according to the invention and 90% of the commercial liquid crystal mixture ZLI-2857 (for Δε) or ZLI-4792 (for Δn) (Merck KGaA, Darms tadt). In the case of limited solubility, the compound was measured in a mixture containing only 5% of the compound, which can be annotated by adding (5%) after the value in question.

[0212] abbreviation

[0213] THF Tetrahydrofuran

[0214] MTB ether methyl tert-butyl ether

[0215] CataCXium A Di(1-adamantyl)-n-butylphosphine

[0216] Cr crystal

[0217] S Smectite

[0218] N Nematic

[0219] I Isotropic

[0220] S X Serves as a general label for unidentified higher-order smectic phases.

[0221] Synthesis Example

[0222] Example 1: 2,4-difluoro-7-(4-propylcyclohexen-1-yl)-3-(trifluoro-methyl)dibenzofuran (1)

[0223]

[0224] Step 1.1: 1-(4-Bromo-3-fluoro-phenyl)-4-propyl-cyclohexanol

[0225]

[0226] A solution of 1-bromo-2-fluoro-4-iodo-benzene (CAS No. 136434-77-0, 40.2 g, 134 mmol) in THF (250 mL) was cooled to -5 °C, followed by dropwise addition of a solution of isopropylmagnesium chloride (2 mol / L in THF, 68 mL, 136 mmol) and THF (100 mL). The reaction mixture was stirred at 0 °C for 90 min. A solution of 4-propylcyclohexanone (CAS No. 40649-36-3, 19.1 g, 136 mmol) in THF (50 mL) was then added dropwise at 0 °C, and the reaction mixture was slowly warmed to room temperature and stirred for 3 h. The reaction mixture was hydrolyzed with ice water, diluted with MTB ether and acidified with hydrochloric acid (2 N). The aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with brine, dried (sodium sulfate) and concentrated in vacuo. 1-(4-Bromo-3-fluoro-phenyl)-4-propyl-cyclohexanol was isolated as a yellow oil.

[0227] Step 1.2: 1-Bromo-2-fluoro-4-(4-propylcyclohexen-1-yl)benzene

[0228]

[0229] A mixture of 1-(4-bromo-3-fluoro-phenyl)-4-propyl-cyclohexanol (44 g, 97 mmol) and toluene-4-sulfonic acid monohydrate (1.5 g, 8 mmol) in toluene (400 mL) was heated at reflux temperature for 2 h. It was then cooled to room temperature, neutralized with sodium hydroxide solution (2 N) and diluted with water. The aqueous phase was separated and extracted with toluene. The combined organic phases were dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent n-heptane) to obtain 1-bromo-2-fluoro-4-(4-propylcyclohexene-1-yl)benzene as a colorless oil.

[0230] Step 1.3: [2-Fluoro-4-(4-propylcyclohexen-1-yl)phenyl]boronic acid

[0231]

[0232] A solution of 1-bromo-2-fluoro-4-(4-propylcyclohexene-1-yl)benzene (80g, 245mmol) in THF (650mL) was cooled to -65°C, followed by dropwise addition of butyl lithium solution (175mL, 279mmol) at -60°C and stirring for 1h. A solution of trimethyl borate (31mL, 273mmol) in THF (100mL) was added dropwise at -65°C and stirred for another 60 minutes. The reaction mixture was then slowly heated and hydrolyzed with water at 5°C, diluted with MTB ether and acidified with a hydrochloride solution (2N). The aqueous phase was separated and extracted with MTB ether, the combined organic phases were washed with brine, dried (sodium sulfate) and concentrated in vacuo. The residue was extracted with n-heptane to obtain [2-fluoro-4-(4-propylcyclohexene-1-yl)phenyl]boronic acid as a light yellow solid.

[0233] Step 1.4: 6-Bromo-2,4-difluoro-3-(trifluoromethyl)phenol

[0234]

[0235] A solution of 5-bromo-1,3-difluoro-2-(trifluoromethyl)benzene (CAS No. 156243-64-0, 86 g, 321 mmol) in THF (400 mL) was cooled to -75°C, followed by the addition of lithium diisopropylamide solution (200 mL, 400 mmol) dropwise and stirred at -75°C for 1 h. Trimethyl borate (75 mL, 660 mmol) was then added dropwise at -75°C, and the reaction mixture was stirred for a further 60 minutes. It was then warmed to 0°C and a mixture of hydrochloric acid (10%, 500 mL) and THF (100 mL) was added. After phase separation, the organic phase was cooled to 0°C. Hydrogen peroxide (210 mL, 2.68 mol) was added to the reaction mixture at 0°C, which was stirred for 1 h and then heated to 40°C and stirred overnight. It was cooled to room temperature, diluted with MTB ether, and the phases were separated. The organic phase is washed with distilled water, brine and sodium sulfite solution until free of peroxide. The organic layer is dried (sodium sulfate) and concentrated in vacuo. The residue is washed with sodium hydroxide solution and hydrochloric acid and purified by silica gel chromatography (solvent dichloromethane) to obtain 6-bromo-2,4-difluoro-3-(trifluoromethyl)phenol as a brown oil.

[0236] Step 1.5: 2,4-Difluoro-6-[2-fluoro-4-(4-propylcyclohexen-1-yl)phenyl]-3-(trifluoromethyl)phenol

[0237]

[0238] A mixture of 6-bromo-2,4-difluoro-3-(trifluoromethyl)phenol (9.5 g, 30 mmol), potassium carbonate (6.1 g, 44 mol), tris(dibenzylideneacetone)-dipalladium(0) (57 mg, 0.1 mmol) and CataCXium A (33 mg, 0.1 mmol) in THF (50 mL) and distilled water (25 mL) was heated to reflux under a nitrogen atmosphere, followed by dropwise addition of a solution of [2-fluoro-4-(4-propylcyclohexen-1-yl)phenyl]boronic acid 5 (7.8 g, 30 mmol) in THF (25 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 brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent 1-chlorobutane). 2,4-Difluoro-6-[2-fluoro-4-(4-propylcyclohexen-1-yl)phenyl]-3-(trifluoromethyl)phenol 8 was isolated as a light brown solid.

[0239] Step 1.6: 2,4-Difluoro-7-(4-propylcyclohexen-1-yl)-3-(trifluoromethyl)dibenzofuran

[0240]

[0241] A mixture of 2,4-difluoro-6-[2-fluoro-4-(4-propylcyclohexen-1-yl)phenyl]-3-(trifluoromethyl)phenol 8 (3.2 g, 8 mmol), potassium phosphate monohydrate (2.4 g, 10 mmol) and 1,3-dimethyltetrahydro-2(1H)-pyrimidinone (30 mL, 248 mmol) was stirred overnight at 110° C. The reaction mixture was purified by silica gel chromatography (solvent n-heptane) and crystallization (ethanol) to obtain 2,4-difluoro-7-(4-propylcyclohexen-1-yl)-3-(trifluoromethyl)dibenzofuran as a colorless solid.

[0242] Phase sequence: Tg-35Cr 67S X (33)SmA(40)I.

[0243] Δε=18.5

[0244] Δn=0.2036

[0245] Example 2: 2,4-difluoro-7-(4-propylcyclohexen-1-yl)-3-(trifluoromethyl)dibenzothiophene

[0246]

[0247] Step 2.1: Trifluoromethanesulfonic acid [2,4-difluoro-6-[2-fluoro-4-(4-propylcyclohexen-1-yl)phenyl]-3-(trifluoromethyl)phenyl] ester

[0248]

[0249] Trifluoromethanesulfonic anhydride (3 mL, 18 mmol) was slowly added to a solution of 2,4-difluoro-6-[2-fluoro-4-(4-propylcyclohexen-1-yl)phenyl]-3-(trifluoromethyl)phenol (6 g, 14 mmol), triethylamine (3 mL, 21 mmol) and 4-(dimethylamino)-pyridine (52 mg, 0.4 mmol) in dichloromethane (65 mL) at 5 ° C. under a nitrogen atmosphere. The solution was stirred at room temperature overnight. The reaction mixture was purified by silica gel chromatography (solvent 1-chlorobutane) to obtain trifluoromethanesulfonic acid [2,4-difluoro-6-[2-fluoro-4-(4-propylcyclohexen-1-yl)phenyl]-3-(trifluoromethyl)phenyl] ester as a yellow oil.

[0250] Step 2.2: 2,4-Difluoro-7-(4-propylcyclohexen-1-yl)-3-(trifluoromethyl)dibenzothiophene

[0251]

[0252] A solution of [2,4-difluoro-6-[2-fluoro-4-(4-propylcyclohexen-1-yl)phenyl]-3-(trifluoromethyl)phenyl]trifluoromethanesulfonate (8.2 g, 15 mmol), 2-ethylhexyl 3-mercapto-propionic acid ester (4.3 mL, 18 mmol) and N-ethyldiisopropylamine (3.7 mL, 22 mmol) in toluene (40 mL) was degassed with argon. Tris(dibenzylideneacetone)dipalladium(0) (140 mg, 0.2 mmol) and (oxydi-2,1-phenylene)bis(diphenylphosphine) (160 mg, 0.3 mmol) were quickly added to the solution, and the reaction mixture was heated to reflux overnight. It was then cooled to room temperature, and a solution of potassium tert-butoxide (2.0 g, 18 mmol) in THF (12 mL) was added in situ to the reaction mixture containing the intermediate. The reaction mixture was heated to reflux overnight, followed by addition of a second portion of potassium tert-butoxide (1.0 g, 9 mmol) in THF (6 mL). The reaction mixture was heated to reflux overnight again. It was then cooled to room temperature, quenched with water, acidified with hydrochloric acid (25%) at 0 ° C and diluted with MTB ether. The aqueous phase was separated and extracted with MTB ether. The combined organic phase was washed with distilled water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent n-heptane) and crystallized (ethanol) to obtain 2,4-difluoro-7-(4-propylcyclohexene-1-yl)-3-(trifluoromethyl)dibenzothiophene 12 as colorless crystals.

[0253] Phase sequence: Cr 150S X 116 I.

[0254] Δε=22.9

[0255] Δn=0.2101

[0256] Embodiment 3:

[0257] Similar to Example 1, obtain:

[0258]

[0259] Phase sequence: Cr 85 I

[0260] Δε=12.3

[0261] Δn=0.1742

[0262] Analogously to the above examples, the following exemplary compounds of formula I and its various subformulae were obtained: In the following table, the following abbreviations for the end groups are used:

[0263]

[0264] Physical properties are given at a temperature of 20°C and γ1 is given in mPa·s. Phase transition temperatures are given in °C.

[0265]

[0266]

[0267]

[0268]

[0269]

[0270]

[0271]

[0272]

[0273]

[0274]

[0275]

[0276]

[0277]

[0278]

[0279]

[0280]

[0281]

[0282]

[0283]

[0284]

[0285]

[0286]

[0287]

[0288]

[0289]

[0290]

[0291]

[0292]

[0293]

[0294]

[0295]

[0296]

[0297]

[0298]

[0299]

[0300]

[0301]

[0302]

[0303]

[0304]

[0305]

[0306]

[0307]

[0308]

[0309]

[0310]

[0311]

[0312]

[0313]

[0314]

[0315]

[0316]

[0317]

[0318]

[0319]

[0320]

[0321]

[0322]

[0323]

[0324]

[0325]

[0326]

[0327]

[0328]

[0329]

[0330]

[0331]

[0332]

[0333]

[0334]

[0335]

[0336]

[0337]

[0338]

[0339]

[0340] Use Example

[0341] A nematic liquid crystal mixture N-1 was prepared having the composition and properties indicated in the following table.

[0342] Mixture N-1

[0343]

[0344] The nematic liquid crystal medium M-1 composed of 90% medium N-1 and 10% of the compound of Synthesis Example 1 (compound (1)) has the following properties:

[0345]

[0346]

[0347] Compound (1) is sufficiently soluble in Medium N-1. Adding Compound (1) of the present invention to Medium N-1 has the effect of favorably increasing dielectric anisotropy.

[0348] The nematic liquid crystal medium M-2 composed of 95% of medium N-1 and 5% of the compound of Synthesis Example (2) (Compound (2)) has the following properties:

[0349]

[0350] Compound (2) is sufficiently soluble in medium N-1. Adding compound (2) of the present invention to medium N-1 has the effect of favorably increasing dielectric anisotropy.

Claims

1. A compound of formula I, in W means O or S, R represents H, an alkyl radical having 1 to 15 C atoms, wherein one or more CH2 groups in these radicals may each independently of one another be replaced by -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO-, wherein one or more H atoms may be replaced by halogen, A, at each occurrence, identically or differently, represents a group selected from the following group: a) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclohexenylene and decahydronaphthalene-2,6-diyl, wherein one or more non-adjacent CH2 groups may be replaced by -O- and / or -S-, and wherein one or more H atoms may be replaced by F, b) the group consisting of 1,4-phenylene and 2,6-naphthylene, in which one or two CH groups may be replaced by N and in which one or more other H atoms may be replaced by L, c) the group consisting of 1,3-dioxane-2,5-diyl, tetrahydrofuran-2,5-diyl, cyclobutane-1,3-diyl, thiophene-2,5-diyl, selenophene-2,5-diyl and 1,2,3,4-tetrahydronaphthalene-2,6-diyl, each of which may be mono- or polysubstituted by L, d) the group consisting of bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl and spiro[3.3]heptane-2,6-diyl, in which one or more H atoms may be replaced by F, L, identically or differently on each occurrence, represents halogen, cyano, alkyl having 1 to 7 C atoms, alkoxy, alkylcarbonyl or alkoxycarbonyl, in which one or more H atoms may be replaced by F or Cl, Z represents, identically or differently on each occurrence, a single bond, -CF2O-, -OCF2-, -CH2CH2-, -CF2CF2-, -C(O)O-, -OC(O)-, -CH2O-, -OCH2-, -CF=CH-, -CH=CF-, -CF=CF-, -CH=CH- or -C≡C-, Y 1 and Y 2 Indicates F and Y 3 Indicates H, X represents OCF3 or CF3, and n is 0, 1, or 2, The compound has positive dielectric anisotropy.

2. A compound according to claim 1, selected from the following subformulae: wherein R, A, Z, X and n have the meanings given in claim 1.

3. Compounds according to any one of claims 1 to 2, wherein Z represents a single bond.

4. The compound according to any one of claims 1 to 2, wherein n is 1 and A represents trans-1,4-cyclohexylene or 1,4-cyclohexenylene.

5. A compound of formula P or P', It is used in a process for synthesizing a compound of formula I according to claim 1, The radicals and parameters occurring therein have the meanings given for formula I in claim 1.

6. A method for preparing a compound of formula I according to claim 1, characterized in that The compound of formula P or P' according to claim 5 is treated with a base.

7. A liquid-crystalline medium comprising one or more compounds of the formula I according to any one of claims 1 to 4.

8. A liquid-crystalline medium according to claim 7, wherein the medium comprises one or more compounds selected from the group of compounds of the formulae II and III in 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 In each occurrence, they are expressed independently of each other L 21 and L 22 Indicates H or F, X 2 represents halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, m represents 0, 1, 2 or 3; R 3 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 In each occurrence, independently of each other, L 31 and L 32 independently of each other represent H or F, 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, Z 3 represents -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, and n is 0, 1, 2 or 3.

9. Use of a compound according to any one of claims 1 to 4 in a liquid-crystalline medium.

10. An electro-optical display element comprising a liquid-crystalline medium according to claim 7 or 8.

11. The display element according to claim 10, wherein the display element is a TN-TFT, IPS or FFS display.

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