Dibenzofuran and dibenzothiophene derivatives

Abstract

Compounds of general formula (I) wherein the radicals and parameters occurring have the meanings indicated in claim 1, their use in liquid-crystalline or mesogenic media, and liquid-crystalline media comprising these derivatives. It can be used in FFS-type liquid-crystalline displays and other applications. The compounds contribute to energy-saving displays.

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] Since the discovery of the first commercially viable liquid crystal compounds about 40 years ago, liquid crystals have been widely used. Known applications include displays for watches and pocket calculators, as well as large display panels, such as those used in train stations, airports, and sports arenas. Other areas of application include displays for portable computers, navigation systems, and video applications. The latter applications, in particular, place extremely high demands on image response time and contrast.

[0003] The spatial arrangement of molecules in liquid crystals has the effect of making many of their properties directionally dependent. Optical, dielectric, and elasto-mechanical anisotropies are particularly important for use in liquid crystal displays. Depending on whether the longitudinal axes of the molecules are oriented perpendicular or parallel to the two plates of a capacitor, the latter exhibits different capacitances; in other words, the dielectric constant ε of the liquid crystal medium has different values ​​for the two orientations. Materials whose dielectric constant is greater when the longitudinal axes of the molecules are oriented perpendicular to the capacitor plates than when they are parallel are said to be dielectrically positive. Most liquid crystals used in early displays belong to this group.

[0004] Both the polarizability and the permanent dipole moment of the molecules contribute to dielectric anisotropy. When a voltage is applied to the display, the longitudinal axes of the molecules orient themselves so that the larger of the dielectric constants, either parallel or perpendicular, 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 larger difference. Introducing suitable polar groups (such as nitrile groups or fluorine) into the liquid crystal molecules enables a wide range of operating voltages.

[0005] In the case of liquid crystal molecules used in conventional liquid crystal displays, the dipole moment oriented along the longitudinal axis of the molecules is greater than the dipole moment oriented perpendicular to the longitudinal axis. The orientation of the larger dipole moment along the longitudinal axis of the molecules also determines the orientation of the molecules in the liquid crystal display in the field-free state. In the most common TN (twisted nematic) cell, a liquid crystal layer, only about 5 to 10 μm thick, is placed between two flat glass plates, each of which has a conductive, transparent layer of tin oxide or indium tin oxide vapor-deposited 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 align 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 positioned on the inside of the display surface in the same alignment, either flat or at the same small tilt angle. Two additional polarizing films, which allow only linearly polarized light to enter and escape, are adhesively bonded to the outside of the display in a specific configuration.

[0006] Very high-performance displays have been developed using liquid crystals in which the larger dipole moment is oriented parallel to the longitudinal axis of the molecules. In most cases, mixtures of 5 to 20 components are used to achieve a sufficiently wide mesophase temperature range, short response times, and low threshold voltages. However, the strong viewing angle dependence still poses difficulties in liquid crystal displays, such as those used in laptop computers. The best image quality is achieved if the display surface is perpendicular to the viewer's direction of view. If the display is tilted relative to the viewing direction, the image quality can drop sharply in some cases. For greater comfort, efforts are underway to make the angle at which the display can be tilted relative to the viewer's direction of view 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 molecules is larger than the dipole moment parallel to the longitudinal axis. In the field-free state, these molecules are oriented perpendicular to the glass surface of the display. This approach makes it possible to achieve improved viewing angle dependence. This type of display is known as a VA-TFT ("vertically aligned") display.

[0007] So-called IPS ("in-plane switching") displays are also known, which contain an LC layer between two planarly oriented substrates, with two electrodes arranged on only one of the two substrates, preferably having 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. Furthermore, 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 unstructured. This generates strong so-called "fringe fields," i.e., strong electric fields near the edges of the electrodes, and an electric field with both a strong vertical component and a strong horizontal component throughout the cell. FFS displays have a low contrast dependence on viewing angle. FFS displays typically contain an LC medium with positive dielectric anisotropy and an alignment layer, typically made of polyimide, which provides a planar alignment for the molecules of the LC medium.

[0008] For FFS displays, it is suggested that not only a large absolute value of Δε is important, but also the components ε(parallel) (ε∥) and ε(perpendicular) (ε ⊥ ) is also important in determining the switching behavior. A large ε (perpendicular) value is desirable because it improves the transmittance of the display. Large transmittance improves contrast and brightness, but also helps save energy.

[0009] 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 there exhibit a very strong negative dielectric anisotropy, which makes them unsuitable for the use according to the present invention.

[0010] Document DE 10 2015 004 271 describes further compounds with strongly negative Δε, which consist of dibenzothiophene and fluorinated benzene rings linked by -CF 2 O- groups, as described below.

[0011]

[0012] These compounds are difficult to adapt for use in the present invention, primarily due to the different substitutions of the fluorine atoms.

[0013] Developments in the field of liquid crystal materials are far from complete. In order to improve the properties of liquid crystal display components, efforts are constantly underway to develop novel compounds that can optimize such displays.

[0014] It was an object of the present invention to provide a more diverse range of compounds having advantageous properties for use in liquid-crystalline media.

[0015] This object is achieved according to the invention by compounds of the general formula I

[0016]

[0017] in

[0018] W means O or S,

[0019] R represents H, an alkyl radical having 1 to 15 C atoms, wherein one or more CH2 radicals in these radicals can each independently of one another be replaced by -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO- is replaced in such a way that the O atoms are not directly connected to each other and one or more H atoms may be replaced by halogen,

[0020] A represents 1,4-phenylene, in which one or more H atoms may be replaced by F or CH3,

[0021] Preferably represents a group selected from the following

[0022] More preferred

[0023] Z represents -CF2O-, -OCF2-, -C(O)O-, -OC(O)-, -CH2O- or -OCH2-, preferably -CF2O-, -C(O)O- or -CH2O-,

[0024] X represents F, Cl, CN, NCS, fluoroalkyl, fluoroalkoxy, fluoroalkenyl or fluoroalkenyloxy, each having up to 5 C atoms, preferably F, OCF3 or OCHF2, and

[0025] L 1 , L 2 independently denotes H or -CH3, preferably H.

[0026] It is another object of the present application to provide liquid-crystalline media, in particular for use in TN, IPS or FFS displays.

[0027] This object is achieved according to the present application by providing compounds of formula I having a neutral to positive dielectric anisotropy (Δε).

[0028] The compounds of formula I are characterized by a high clearing point and a surprisingly large positive dielectric constant (ε ⊥ ) perpendicular to the electric field director and are therefore particularly suitable for use in TN-TFT displays, and in IPS- and FFS displays. The compounds have a relatively low melting point, which exhibits an excellent compatibility with the usual substances used in liquid-crystalline mixtures for displays.

[0029] The compounds according to the present application preferably have a Δε in the positive region, preferably Δε > 0.5, more preferably Δε > 1.

[0030] Detailed description

[0031] If the radical R is an alkyl radical and / or an alkoxy radical, it can 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, pentoxy, hexoxy or heptoxy, but also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy.

[0032] R can each, independently of the others, be an alkenyl radical 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. It is therefore preferably vinyl, prop-1 -enyl or -2-enyl, but-1 -enyl, but-2-enyl or -3-enyl, pent-1 -enyl, pent-2-enyl, pent-3-enyl or pent-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.

[0033] R can each independently of one another be oxaalkyl, 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 a 2-oxaheptyl, 3-oxaheptyl, 4-oxaheptyl, 5-oxaheptyl or 6-oxaheptyl group.

[0034] R may each independently be an alkyl group 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. 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.

[0035] R may each independently be an alkyl radical having 1 to 15 carbon atoms, wherein one CH2 group is replaced by unsubstituted or substituted -CH=CH- and the adjacent CH2 group is replaced by CO or CO-O or O-CO, wherein this may be straight-chain or branched. It is preferably straight-chain and has 4 to 13 carbon atoms.

[0036] R 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 by -CN or -CF3 and is preferably straight-chain. The substitution by -CN or -CF3 can be at any desired position.

[0037] R may each independently be an alkyl radical 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.

[0038] R can each independently be an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, each of which is at least monosubstituted by halogen, wherein these groups 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 groups, such as -CF3. In the case of monosubstitution, the fluorine or chlorine substituents can be in any desired position, but are preferably in the ω position.

[0039] The term "fluoroalkyl" preferably encompasses mono- or poly-fluorinated groups, including perfluorinated groups. Particularly preferred are CF3, CH2CF3, CH2CHF2, CHF2, CH2F, CHFCF3 and CF2CHFCF3.

[0040] The term "fluoroalkoxy" preferably encompasses mono- or poly-fluorinated groups, including perfluorinated groups. Particularly preferred is OCF3.

[0041] In a preferred embodiment of the present invention, the compound of formula I is selected from the group consisting of compounds of formulae I-1 to I-6:

[0042]

[0043]

[0044] The radicals occurring therein have the meanings given above for formula I and are independently:

[0045] R is preferably an alkyl or alkenyl group each having up to 7 C atoms, wherein one or more CH2 groups in these groups may each be independently replaced by Alternative,

[0046] Z is preferably -CF2O- or -OCH2-, and

[0047] X is preferably F.

[0048] Furthermore, the compound of formula I is preferably selected from the compounds of formulae IA to IJ:

[0049]

[0050]

[0051] and more preferably selected from the formulae IA, IB, IF and IG, wherein R and Z are as defined above in formula I or have any of the preferred definitions given above.

[0052] In a preferred embodiment of the invention, in formula I and its subformulas, R represents alkyl having 1 to 7 C atoms, in particular ethyl, propyl, butyl, pentyl, cyclopropyl, cyclopropylmethyl, cyclobutyl, cyclobutylmethyl, cyclopentyl, cyclopentylmethyl or 3-methylcyclopentylmethyl, with n-propyl, n-butyl and n-pentyl being most preferred.

[0053] In a more preferred embodiment of the present invention, in formula I and subsidiary structures, Z represents a group -CF2O-.

[0054] Substituent L 1 and L 2 Preferably both are H or L 1 and L 2 One of the is H and the other is methyl.

[0055] Structure I is preferably any one of the following structures:

[0056]

[0057] The most preferred 1 and L2 Both are H.

[0058] The compounds of the general formula I are prepared by methods known per se, as described in the literature (e.g. in standard works such as Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), specifically under reaction conditions known and suitable for these reactions. Variants known per se but not mentioned in greater detail here can also be used.

[0059] If desired, the starting materials can also be formed in situ and not isolated from the reaction mixture, but converted further immediately into compounds of the general formula I.

[0060] Preferred synthetic routes to the compounds of the invention are shown in the schemes below and are further illustrated with the aid of the working examples.The syntheses can be adapted to the specific desired compounds of formula I by selecting suitable starting materials.

[0061] 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 by the phenolate.

[0062] Scheme 1. Synthesis of compounds of formula I, wherein W is O. x represents -ZAX, a precursor group thereof or H.

[0063]

[0064] 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.

[0065] Scheme 2. Alternative synthesis of compounds of formula I(I') wherein W is O. R x As defined above.

[0066]

[0067] Dibenzothiophene derivatives (ie compounds of formula I (Formula I'") wherein W represents S) are preferably synthesized as shown in Scheme 3.

[0068] Scheme 3. Synthesis of subgroups of compounds of formula I (I") wherein W is S. R x Represents -ZAX as described above.

[0069]

[0070] The starting material of Scheme 3 can be obtained from the phenol in Scheme 1 via the corresponding triflate according to Itoh, Takahiro and Mase, Toshiaki, Organic Letters, 6(24), 4587-4590; 2004. Treatment of the compound with a strong non-nucleophilic base, preferably potassium tert-butoxide, affords the compound of formula I" (cf. Jepsen, Tue Heesgaard et al., European Journal of Organic Chemistry, (1), 53-57, S53 / 1-S53 / 65; 2011).

[0071] the group R x The construction into the final substituent -Z-A-X is preferably carried out after the formation of the dibenzofuran or dibenzothiophene ring. This is achieved by known reactions established for the chemistry of each group involved. In the case of R x In the case of R being halogen, this position can be functionalized by deprotonation and addition of an electrophile. Details are provided in the examples.

[0072] The reactions outlined should be considered only as illustrative. A person skilled in the art can make corresponding changes to the syntheses described and follow other suitable synthetic routes to obtain compounds of formula I.

[0073] The compounds of 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 general formula I.

[0074] The present application also relates to a liquid-crystalline medium comprising 2 to 40, preferably 4 to 30 components as further components in addition to one or more compounds of formula I according to the application. In addition to one or more compounds according to the application, these media particularly preferably comprise 7 to 25 components.

[0075] The medium according to the application preferably comprises 1 to 20 %, particularly preferably 2 to 10 %, of the compounds of formula I according to the application.

[0076] The medium preferably comprises one, two, three, four or five compounds of formula I according to the application.

[0077] In a preferred embodiment of the application, the liquid-crystalline medium comprises

[0078] a) one or more compounds selected from the group of compounds of formulae II and III, which preferably have a dielectric anisotropy of greater than 3:

[0079]

[0080]

[0081] in

[0082] R 2 represents an alkyl, alkoxy, fluoroalkyl or fluoroalkoxy radical having 1 to 7 C atoms; an alkenyl, alkenyloxy, alkoxyalkyl or fluoroalkenyl radical having 2 to 7 C atoms, and is preferably an alkyl or alkenyl radical, wherein one or more CH2 radicals in these radicals may each independently of one another be replaced by Alternative,

[0083] and

[0084] Indicated independently of each other at each occurrence

[0085] Preferred

[0086]

[0087] L 21 and L 22 represents H or F, preferably, L 21 Indicates F,

[0088] 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,

[0089] m is 0, 1, 2 or 3, preferably 1 or 2 and particularly preferably 1,

[0090] R 3 represents an alkyl, alkoxy, fluoroalkyl or fluoroalkoxy radical having 1 to 7 C atoms; an alkenyl, alkenyloxy, alkoxyalkyl or fluoroalkenyl radical having 2 to 7 C atoms, and is preferably an alkyl or alkenyl radical, wherein one or more CH2 radicals in these radicals may each independently of one another be replaced by Alternative,

[0091] and

[0092] In each occurrence, independently of each other

[0093]

[0094] Preferred

[0095]

[0096] L 31 and L 32 independently represent H or F, preferably, L 31 Indicates F,

[0097] 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,

[0098] 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

[0099] n is 0, 1, 2 or 3, preferably 1, 2 or 3 and particularly preferably 1, and

[0100] b) optionally, one or more preferably dielectrically neutral compounds selected from the group of formulae IV and V:

[0101]

[0102] in

[0103] R 41 and R 42 Independently of each other, they have the above R under formula II 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

[0104] represents an alkyl group,

[0105] and

[0106] Independently of each other and if

[0107] Appears twice,

[0108] These also represent independently of each other

[0109]

[0110] one or more of

[0111] and

[0112] denotes

[0113]

[0114] Z 41 and Z 42 independently of one another and if Z 41 occur twice, these also denote, independently of one another, -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,

[0115] p denotes 0, 1 or 2, preferably 0 or 1,

[0116] R 51 and R 52 have independently of one another one of the meanings given for R 41 and R 42 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 2 to 4 C atoms, alkenyl or alkenyloxy, preferably alkenyloxy,

[0117] to

[0118] each, if present, independently of one another denotes

[0119]

[0120] one or more of

[0121]

[0122] one or more of

[0123] denotes and, if present,

[0124] preferably denotes

[0125] Z 51 to Z​53 each independently of one another 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,

[0126] i and j each independently represent 0 or 1, and

[0127] (i+j) is preferably 0, 1 or 2, more preferably 0 or 1 and most preferably 1.

[0128] In a preferred embodiment of the present invention, the liquid-crystalline medium additionally comprises

[0129] c) one or more compounds selected from compounds of formula Y

[0130]

[0131] where each radical has the following meanings, identically or differently on each occurrence:

[0132] and Independently of each other,

[0133]

[0134] R 11 、R 12 Identically or differently unsubstituted or halogenated straight-chain or branched alkyl or alkoxy radicals having 1 to 15 C atoms, wherein one or more CH2 radicals in these radicals may each independently of one another be Preferably or is replaced by -C≡C-, -CF2O-, -CH=CH-, -O-, -CO-O-, or -O-CO- in such a way that the O atoms are not directly connected to each other, and R 12 Alternatively, F

[0135] Z x , Z y is -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C2F4-, -CF=CF-, -CH=CH-CH2O-, or a single bond, preferably a single bond,

[0136] L 1 , L 2 is F or Cl, preferably F,

[0137] L 3 , L 4is H, F, Cl or CH3, preferably H or F,

[0138] Y represents H, F, Cl, CF3, CHF2 or CH3, preferably H or CH3, particularly preferably H, and

[0139] x and y are 0, 1 or 2, where x+y≤3.

[0140] The combination of a compound of formula I with a compound of formula II and / or III, and further with a compound selected from formula Y or its subformulae, results in a liquid-crystalline medium exhibiting a moderately positive dielectric anisotropy, with a dielectric constant ε perpendicular to the longitudinal axis of the liquid-crystalline molecules of ⊥ Increase while maintaining low rotational viscosity and low γ1 / K 11 This enables the realization of LCDs with high brightness and high transmittance as well as low response time, especially HB-FFS, FFS and IPS mode LCDs.

[0141] The present invention further relates to a process for preparing the liquid-crystalline media according to the invention by mixing one or more compounds of the formula I or its preferred subformulae with one or more low molecular weight liquid-crystalline compounds or liquid-crystalline mixtures and optionally further liquid-crystalline compounds and / or additives.

[0142] The invention furthermore relates to an electro-optical liquid-crystal display element comprising the liquid-crystal medium according to the invention.

[0143] The medium of the present invention is prepared in a conventional manner. Generally, the components are advantageously dissolved in one another at elevated temperatures. With the aid of suitable additives, the liquid crystal phases of the present invention can be modified in a manner such that they can be used in all types of liquid crystal display elements disclosed to date. Additives of this type are known to those 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 to prepare colored guest-host systems, or substances can be added to modify the dielectric anisotropy, viscosity, and / or alignment of the nematic phase.

[0144] For the present invention and the following examples, the structures of the liquid crystal compounds are indicated by acronyms, which are converted into chemical formulae according to Tables A to C below. 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 lH 2l is a straight-chain alkyl or alkylene radical, each having n, m, and 1 carbon atoms, respectively. Preferably, n, m, and 1 are independently 1, 2, 3, 4, 5, 6, or 7. Table A shows the ring element codes for 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 for the ring element with the optional linking group, followed by the first hyphen and the code for the left end group, and the second hyphen and the code for the right end group. Table D shows illustrative structures of the compounds and their respective acronyms.

[0145] Table A: Ring elements

[0146]

[0147]

[0148]

[0149] Table B: Bridge Unit

[0150]

[0151] Table C: End Groups

[0152]

[0153]

[0154] Where n and m are each integers, and the three dots "..." are placeholders for other abbreviations in this table.

[0155] 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.

[0156] In the acronyms above and below, n, m, k and l are each independently of one another an integer, preferably 1 to 9, preferably 1 to 7, k and l may possibly 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".

[0157] Table D

[0158] Exemplary preferred dielectrically positive compounds that can be used in combination with compounds of Formula I

[0159]

[0160]

[0161]

[0162]

[0163]

[0164]

[0165]

[0166]

[0167]

[0168] Exemplary preferred dielectrically neutral compounds that can be used in combination with compounds of Formula I

[0169]

[0170]

[0171]

[0172]

[0173]

[0174]

[0175]

[0176] Exemplary dielectrically negative compounds that can be used in combination with compounds of Formula I

[0177]

[0178]

[0179]

[0180]

[0181]

[0182]

[0183]

[0184]

[0185]

[0186]

[0187] Table E shows chiral dopants that are optionally used in the mixtures according to the invention.

[0188] Table E

[0189]

[0190]

[0191]

[0192] 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.

[0193] 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.

[0194] Table F

[0195]

[0196]

[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 F.

[0201] The invention is explained in more detail hereinafter with reference to working examples, without intending to be restricted thereby. Example

[0202] The following examples illustrate the present invention without limiting it. However, they show to those skilled in the art the preferred mixture concept of the compounds to be preferably employed and their respective concentrations and their combinations thereof. In addition, this example illustrates which properties and property combinations are accessible.

[0203] All temperature values indicated in this application, such as for example for melting point T(C,N), transition from smectic (Sm) to nematic (N) phase T(Sm,N) and clearing point T(N,I) are expressed in degrees Celsius (°C) unless explicitly indicated otherwise. M.p. means melting point, cl.p. = clearing point. The data between these symbols represent the transition temperature.

[0204] 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 apply 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.

[0205] In the above and below, Δn means optical anisotropy (589 nm, 20 °C) and Δε means dielectric anisotropy (1 kHz, 20 °C).

[0206] 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.

[0207] Abbreviations:

[0208] dist. distillation

[0209] DMAP 4-(dimethylamino)pyridine

[0210] DMF N,N-dimethylformamide

[0211] DCM dichloromethane

[0212] MTBE methyl tert-butyl ether

[0213] TEA triethylamine

[0214] THF tetrahydrofuran

[0215] TPP triphenylphosphine

[0216] Cr crystalline

[0217] Sm smectic (if known, optionally with a subtype, e.g. SmA)

[0218] N nematic

[0219] I isotropic

[0220] Additionally, the following symbols are used:

[0221] n e The extraordinary refractive index at 20°C and 589nm is

[0222] n o Ordinary refractive index at 20℃ and 589nm,

[0223] Δn optical anisotropy at 20°C and 589nm,

[0224] ε ⊥ The dielectric constant perpendicular to the director at 20°C and 1kHz,

[0225] ε || The dielectric constant parallel to the director at 20°C and 1kHz,

[0226] Dielectric anisotropy of Δε at 20°C and 1kHz,

[0227] cl.p., T(N,I) clearing point [℃],

[0228] γ1 rotational viscosity at 20°C [mPa·s],

[0229] K1 elastic constant, "diffusion" deformation at 20°C [pN],

[0230] K2 elastic constant, "twist" deformation at 20°C [pN],

[0231] K3 elastic constant, "bending" deformation at 20°C [pN].

[0232] Synthesis Example

[0233] Synthesis Example 1 (BQU-3-F)

[0234] 3-[Difluoro-(3,4,5-trifluorophenoxy)methyl]-4,6-difluoro-7-propyl-dibenzofuran

[0235]

[0236] Step 1.1 :4,6-difluoro-7-propyl-dibenzofuran-3-carboxylic acid

[0237]

[0238] At -70 ° C under argon atmosphere, n-butyllithium solution (178 mL, 1.6 M in hexane, 0.28 mol) was added to a solution of 4,6-difluoro-3-propyl-dibenzofuran (1, CAS 1809083-80-4) (58.2 g, 0.24 mol) in THF (1 L), and the mixture was stirred for 1 hour. Dry ice (12.5 g, 0.28 mol) was added very carefully in small amounts, and the reaction mixture was stirred again at -70 ° C for 1 hour. It was then heated to -10 ° C and quenched with distilled water and hydrochloric acid (25%). The suspension was vacuum filtered and the remaining solid was washed with n-heptane. The residue was purified by recrystallization (n-heptane) to give white crystals of 4,6-difluoro-7-propyl-dibenzofuran-3-carboxylic acid (2).

[0239] Step 1.2 :4,6-difluoro-7-propyl-dibenzofuran-3-carbonyl chloride

[0240]

[0241] A suspension of 4,6-difluoro-7-propyl-dibenzofuran-3-carboxylic acid (2) (39.3 g, 0.13 mol), thionyl chloride (20 mL, 0.28 mol) and DMF (0.5 mL, 6 mmol) was heated at reflux overnight. The reaction mixture was then cooled to room temperature and concentrated in vacuo to afford 4,6-difluoro-7-propyl-dibenzofuran-3-carbonyl chloride (3) as a yellow solid.

[0242] Step 1.3 :3-(5,6-dihydro-4H-1,3-dithio-1-ium-2-yl)-4,6-difluoro-7-propyl-dibenzofuran trifluoromethanesulfonate

[0243]

[0244] 1,3-Propanedithiol (15.0 mL, 0.15 mol) was slowly added to a solution of 4,6-difluoro-7-propyl-dibenzofuran-3-carbonyl chloride (3) (41.0 g, 0.13 mol) in dichloromethane (300 mL) at 0°C under a nitrogen atmosphere, and the mixture was stirred at 10°C for 10 minutes. Trifluoromethanesulfonic acid (19.0 mL, 0.22 mol) was slowly added at -5°C, and the reaction mixture was stirred at -5°C for 30 minutes. Acetic anhydride (50.0 mL, 0.53 mol) was then slowly added at 0°C, followed by diethyl ether (200 mL), and the reaction mixture was stirred at 10°C for 1 hour. Finally, it was cooled to -30°C and stirred for 10 minutes. The precipitate was quickly vacuum filtered under nitrogen atmosphere, washed with cold ether and dried in vacuo to give 3-(5,6-dihydro-4H-1,3-dithio-1-ium-2-yl)-4,6-difluoro-7-propyl-dibenzofuran-trifluoromethanesulfonate (4) as yellow crystals.

[0245] Step 1.4 :3-[difluoro-(3,4,5-trifluorophenoxy)methyl]-4,6-difluoro-7-propyl-dibenzofuran

[0246]

[0247] A mixture of 3,4,5-trifluorophenol (5, CAS 99627-05-1) (3.3 g, 22 mmol) and TEA (3.5 mL, 25 mmol) in dichloromethane (10 mL) was added to a solution of 3-(5,6-dihydro-4H-1,3-dithio-1-ium-2-yl)-4,6-difluoro-7-propyl-dibenzofuran trifluoromethanesulfonate (4) (10.5 g, 20 mmol) in dichloromethane (70 mL) at -70°C, and the reaction mixture was stirred at -70°C for 1 h. The mixture was treated with triethylamine trihydrofluoride (6.8 mL, 41 mmol) at -70°C, and after 1 h, a solution of bromine (2.6 mL, 51 mmol) in dichloromethane (10 mL) was added. The reaction mixture was stirred at -70°C for 30 min. Morpholine (3.5 mL, 40 mmol) was then added at -20 ° C, and the mixture was stirred for another 30 min at 0 ° C. The reaction mixture was poured into a mixture of ice / water and aqueous potassium hydroxide solution. The aqueous phase was separated and extracted with dichloromethane. The combined organic phase was washed with sodium bicarbonate, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane / 1-chlorobutane) and crystallization (heptane / ethanol) to give white crystals of 3-[difluoro-(3,4,5-trifluorophenoxy)methyl]-4,6-difluoro-7-propyl-dibenzofuran (6).

[0248] Compound (6) has the following phase characteristics:

[0249] K 109℃I.

[0250] Synthesis Example 2 (B(S)QU-2O-F)

[0251] 3-[Difluoro-(3,4,5-trifluorophenoxy)methyl]-7-ethoxy-4,6-difluoro-dibenzothiophene

[0252]

[0253] Step 2.1 :7-ethoxy-4,6-difluoro-dibenzothiophene-3-carboxylic acid

[0254]

[0255] At -70 ° C under argon atmosphere, n-butyllithium solution (145 mL, 1.6 M in hexane, 0.23 mol) was added to a solution of 3-ethoxy-4,6-difluoro-dibenzothiophene (1, CAS 1820028-78-1) (50.0 g, 0.19 mol) in THF (1.0 L). After stirring for 1 hour, dry ice powder (10.0 g, 0.23 mol) was added very carefully in small amounts. The reaction mixture was stirred at -70 ° C for 1 hour. It was then allowed to warm to -10 ° C, the reaction was quenched with distilled water (200 mL), and acidified with hydrochloric acid. The suspension was vacuum filtered and the remaining solid was washed with n-heptane. The residue was purified by recrystallization from n-heptane to give white crystals of 7-ethoxy-4,6-difluoro-dibenzothiophene-3-carboxylic acid (2).

[0256] Step 2.2 :7-ethoxy-4,6-difluoro-dibenzothiophene-3-carbonyl chloride

[0257]

[0258] Thionyl chloride (25.0 mL, 0.35 mol) was added to 7-ethoxy-4,6-difluoro-dibenzothiophene-3-carboxylic acid (2) (51.5 g, 0.16 mol). A second portion of thionyl chloride (75 mL, 1.04 mol) was then added and the suspension was heated at reflux overnight. The reaction mixture was cooled to room temperature and excess thionyl chloride was removed using a Dean Stark trap. The residue was concentrated in vacuo to afford 7-ethoxy-4,6-difluoro-dibenzothiophene-3-carbonyl chloride (3) as a yellow solid.

[0259] Step 2.3 :3-(5,6-dihydro-4H-1,3-dithio-1-ium-2-yl)-7-ethoxy-4,6-difluoro-dibenzothiophene-trifluoromethanesulfonate

[0260]

[0261] 1,3-Propanedithiol (17.0 mL, 0.17 mol) was slowly added to a solution of 7-ethoxy-4,6-difluoro-dibenzothiophene-3-carbonyl chloride (3) (53.6 g, 0.16 mol) in DCM (650 mL) at 0°C under a nitrogen atmosphere. The solution was stirred at 10°C for 10 min. Trifluoromethanesulfonic acid (22.0 mL, 0.25 mol) was slowly added at -5°C, and the mixture was stirred at this temperature for 30 min. It was then carefully treated with acetic anhydride (55.0 mL, 0.58 mol) at 0°C. Diethyl ether (220 mL) was added, and the mixture was stirred at 10°C for 1 h. Finally, the reaction mixture was cooled to -30 °C and stirred for 10 min. The precipitate was vacuum filtered under nitrogen atmosphere, washed with cold ether and dried (dessicator) to obtain red crystals of 3-(5,6-dihydro-4H-1,3-dithio-1-ium-2-yl)-7-ethoxy-4,6-difluoro-dibenzothiophene-trifluoromethanesulfonate (4).

[0262] Step 2.4 :3-[difluoro-(3,4,5-trifluorophenoxy)methyl]-7-ethoxy-4,6-difluoro-dibenzothiophene

[0263]

[0264] A solution of 3-(5,6-dihydro-4H-1,3-dithioxo-1-ium-2-yl)-7-ethoxy-4,6-difluoro-dibenzothiophene-trifluoromethanesulfonate (4) (7.0 g, 13 mmol) in dichloromethane (100 mL) was treated with a mixture of 3,4,5-trifluorophenol (5, CAS 99627-05-1) (2.0 g, 13 mmol) and TEA (2.2 mL, 16 mmol) in DCM (10 mL) at -70°C. The suspension was stirred at -70°C for 1 h. Triethylamine trihydrofluoride (4.5 mL, 27 mmol) was then added at -70°C. After 1 h, a solution of bromine (1.7 mL, 33 mmol) in DCM (10 mL) was added, and the reaction mixture was stirred at -70°C for 30 min. Finally, morpholine (2.3 mL, 26 mmol) was added at -20 ° C, and the reaction mixture was stirred for another 30 min at 0 ° C. The reaction mixture was poured into a mixture of ice / water and potassium hydroxide. The aqueous phase was separated and extracted with dichloromethane. The combined organic phase was washed with sodium bicarbonate, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane / 1-chlorobutane) and crystallization (heptane / ethanol) to obtain white crystals of 3-[difluoro-(3,4,5-trifluorophenoxy)methyl]-7-ethoxy-4,6-difluoro-dibenzothiophene (6).

[0265] Compound (6) has the following phase characteristics:

[0266] K 126℃SmA 130℃I.

[0267] Synthesis Example 3 (B(S)QU-4O-F)

[0268] 3-Butoxy-7-[difluoro-(3,4,5-trifluorophenoxy)methyl]-4,6-difluoro-dibenzothiophene

[0269] Step 3.1 :4,6-difluorodibenzothiophene-3-ol

[0270]

[0271] Boron tribromide (8.5 mL, 90 mmol) was added to a solution of 3-ethoxy-4,6-difluoro-dibenzothiophene (1, CAS 1820028-78-1) (21.8 g, 79 mmol) in DCM (150 mL) at 15°C, and the suspension was stirred at room temperature overnight. The reaction mixture was poured into ice / water, the aqueous phase was separated and extracted with MTB ether. The combined organic phases were washed with sodium bicarbonate, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent DCM) to give yellow crystals of 4,6-difluorodibenzothiophene-3-ol (2).

[0272] Step 3.2 :3-Butoxy-4,6-difluoro-dibenzothiophene

[0273]

[0274] Under nitrogen atmosphere at room temperature, diisopropyl azodicarboxylate (25 mL, 0.13 mol) was slowly added to a solution of 4,6-difluorodibenzothiophene-3-ol (2) (22.3 g, 94 mmol), TPP (31.0 g, 0.12 mol) and 1-butanol (12 mL, 0.13 mol) in THF (250 mL). The reaction mixture was stirred at room temperature for 3 days and then concentrated in vacuo. The residue was purified by silica gel chromatography (solvent 1-chlorobutane) to obtain 3-butoxy-4,6-difluoro-dibenzothiophene (3) in the form of a white solid.

[0275] Step 3.3 :7-Butoxy-4,6-difluoro-dibenzothiophene-3-carboxylic acid

[0276]

[0277] At -70 ° C under nitrogen atmosphere, n-butyllithium solution (70 mL, 1.6 M in hexane, 0.11 mol) was added to a solution of 3-butoxy-4,6-difluoro-dibenzothiophene (3) (26.6 g, 88 mmol) in THF (500 mL). After 1 h, dry ice powder (5.0 g, 0.11 mol) was carefully added. The reaction mixture was stirred at -70 ° C for 1 h. It was then warmed to -10 ° C and quenched with distilled water and hydrochloric acid (25%). The suspension was vacuum filtered and the remaining solid was washed with n-heptane. The residue was purified by crystallization (n-heptane) to obtain white crystals of 7-butoxy-4,6-difluoro-dibenzothiophene-3-carboxylic acid (4).

[0278] Step 3.4 :7-Butoxy-4,6-difluoro-dibenzothiophene-3-carbonyl chloride

[0279]

[0280] Thionyl chloride (11.0 mL, 0.15 mol) was added to 7-butoxy-4,6-difluoro- dibenzothiophene-3-carboxylic acid (4) (24.9 g, 74 mmol). A second portion of thionyl chloride (100 mL) was then added and the suspension was heated at reflux temperature overnight. It was then allowed to cool to room temperature. Thionyl chloride (50 mL) was added again and the mixture was stirred at reflux temperature overnight. The reaction mixture was concentrated in vacuo to give 7-butoxy-4,6-difluoro-dibenzothiophene-3- carbonyl chloride (5) as a yellow solid.

[0281] Step 3.5 : 3-Butoxy-7-(5,6-dihydro-4H-l,3-dithia-l-ium-2-yl)-4,6-difluoro-dibenzothiophene trifluoromethanesulfonate

[0282]

[0283] At 0°C under nitrogen atmosphere, 1,3-propanedithiol (7.5 mL, 75 mmol) was slowly added to a solution of 7-butoxy-4,6-difluoro-dibenzothiophene-3-carbonyl chloride (5) (26.2 g, 74 mmol) in DCM (300 mL). The solution was stirred at 10°C for 10 min. It was treated with trifluoromethanesulfonic acid (9.8 mL, 0.11 mol) at -10°C and the reaction mixture was stirred at -5°C for 30 min. Acetic anhydride (24.5 mL, 0.26 mol) was then slowly added at 0°C. Ethyl ether (100 mL) was added and the reaction mixture was stirred at 10°C for 1 h. It was finally cooled to -30°C and stirred for 10 min. The precipitate was rapidly filtered under nitrogen atmosphere, washed with cold ethyl ether and dried (desiccator) to give 3-butoxy-7-(5,6-dihydro-4H-l,3-dithia-l-ium-2-yl)-4,6-difluoro-dibenzothiophene trifluoromethanesulfonate (6) as red crystals.

[0284] Step 3.6 : 3-Butoxy-7-[difluoro-(3,4,5-trifluorophenoxy)methyl]-4,6-difluoro-dibenzothiophene

[0285]

[0286] A solution of 3-butoxy-7-(5,6-dihydro-4H-1,3-dithioxo-1-ium-2-yl)-4,6-difluoro-dibenzothiophene-trifluoromethanesulfonate (6) (5.0 g, 9 mmol) in DCM (100 mL) was treated with a mixture of 3,4,5-trifluorophenol (7, CAS 99627-05-1) (1.4 g, 9 mmol) and TEA (1.5 mL, 11 mmol) in DCM (10 mL) at -70°C. The suspension was stirred at -70°C for 1 h. Triethylamine trihydrofluoride (3.0 mL, 18 mmol) was added at -70°C, and after 1 h, a solution of bromine (1.3 mL, 25 mmol) in DCM (10 mL) was added to the reaction mixture. The mixture was stirred at -70°C for 30 min. Finally, morpholine (1.6 mL, 18 mmol) was added at -20 ° C, and the mixture was stirred for another 30 min at 0 ° C. The reaction mixture was poured into a mixture of ice / water and potassium hydroxide. The aqueous phase was separated and extracted with DCM. The combined organic phase was washed with sodium bicarbonate, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane / 1-chlorobutane) and crystallization (ethanol) to give white crystals of 3-butoxy-7-[difluoro-(3,4,5-trifluorophenoxy)methyl]-4,6-difluoro-dibenzothiophene (8).

[0287] Compound (8) has the following phase characteristics:

[0288] K 112℃SmA 124℃I.

[0289] Synthesis Example 4 (B(S)QU-3-F)

[0290] 3-[Difluoro-(3,4,5-trifluorophenoxy)-methyl]-4,6-difluoro-7-propyl-dibenzothiophene

[0291]

[0292] Step 4.1 :(4,6-difluorodibenzothiophen-3-yl) trifluoromethanesulfonate

[0293]

[0294] Trifluoromethanesulfonic anhydride (35 mL, 0.21 mol) was added to a solution of 4,6-difluorodibenzothiophen-3-ol (2, see Step 3.1) (44.8 g, 0.19 mol), TEA (40.0 mL, 0.29 mol) and DMAP (1.0 g, 8 mmol) in DCM (400 mL) at 5°C. The reaction mixture was stirred at room temperature overnight. Purification by silica gel filtration (solvent 1-chlorobutane) gave white crystals of (4,6-difluorodibenzothiophen-3-yl) trifluoromethanesulfonate (3).

[0295] Step 4.2 :4,6-difluoro-3-propyl-dibenzothiophene

[0296]

[0297] [1,1'-Bis(diphenylphosphino)ferrocene]palladium(II)dichloride (4.0 g, 5.5 mmol) was added to a solution of (4,6-difluorodibenzothiophen-3-yl)trifluoromethanesulfonate (3) (69.7 g, 0.19 mol) in THF (700 mL) at room temperature. Propylzinc bromide solution (400 mL, 0.5 M in THF, 0.20 mol) was then added at 50°C. The reaction mixture was stirred 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 heptane) to give yellow crystals of 4,6-difluoro-3-propyl-dibenzothiophene (4).

[0298] Step 4.3 :4,6-difluoro-7-propyl-dibenzothiophene-3-carboxylic acid

[0299]

[0300] At -70 ° C under argon atmosphere, n-butyllithium solution (135 mL, 1.6 M in hexane, 0.22 mol) was added to a solution of 4,6-difluoro-3-propyl-dibenzothiophene (4) (46.9 g, 0.17 mol) in THF (500 mL). After 1 h, dry ice powder (9.5 g, 0.22 mol) was carefully added and the reaction mixture was stirred at -70 ° C for 1 h. It was then warmed to -10 ° C and quenched with distilled water and hydrochloric acid (25%). The suspension was vacuum filtered and the remaining solid was washed with n-heptane. The residue was purified by crystallization (n-heptane) to obtain white crystals of 4,6-difluoro-7-propyl-dibenzothiophene-3-carboxylic acid (5).

[0301] Step 4.4:4,6-difluoro-7-propyl-dibenzothiophene-3-carbonyl chloride

[0302]

[0303] 4,6-difluoro-7-propyl-dibenzothiophene-3-carboxylic acid (5) (48.2 g, 0.15 mol) was treated with thionyl chloride (25 mL, 0.35 mol) and DMF (1.0 mL, 13 mmol), followed by the addition of a second portion of thionyl chloride (50 mL). The suspension was heated at reflux overnight. Thionyl chloride (50 mL) was then added again and the reaction mixture was heated at reflux overnight. It was allowed to cool to room temperature and concentrated in vacuo to afford 4,6-difluoro-7-propyl-dibenzothiophene-3-carbonyl chloride (6) as a yellow solid.

[0304] Step 4.5 :3-(5,6-dihydro-4H-1,3-dithio-1-ium-2-yl)-4,6-difluoro-7-propyl-dibenzothiophene trifluoromethanesulfonate

[0305]

[0306] 1,3-Propanedithiol (17 mL, 0.17 mol) was slowly added to a solution of 4,6-difluoro-7-propyl-dibenzothiophene-3-carbonyl chloride (6) (52.6 g, 0.16 mol) in DCM (500 mL) at 0°C under a nitrogen atmosphere. The solution was stirred at 10°C for 10 min. Trifluoromethanesulfonic acid (22 mL, 0.25 mol) was slowly added at -10°C, and the reaction mixture was stirred at -5°C for 30 min. Acetic anhydride (54 mL, 0.57 mol) was then slowly added at 0°C. The reaction mixture was diluted with diethyl ether (250 mL) and stirred at 10°C for 1 h. Finally, it was cooled to -40°C and stirred for 30 min. The precipitate was quickly vacuum filtered under nitrogen, washed with cold ether and dried (dessicator) to give red crystals of 3-(5,6-dihydro-4H-1,3-dithio-1-ium-2-yl)-4,6-difluoro-7-propyl-dibenzothiophene trifluoromethanesulfonate (7).

[0307] Step 4.6 :3-[difluoro-(3,4,5-trifluorophenoxy)methyl]-4,6-difluoro-7-propyl-dibenzothiophene

[0308]

[0309] A mixture of 3,4,5-trifluorophenol (8, CAS 99627-05-1) (3.7 g, 24 mmol) and TEA (3.8 mL, 27 mmol) in DCM (15 mL) was added to a solution of 3-(5,6-dihydro-4H-1,3-dithio-1-ium-2-yl)-4,6-difluoro-7-propyl-dibenzothiophene trifluoromethanesulfonate (7) (12.0 g, 23 mmol) in DCM (70 mL) at -70°C. The reaction mixture was stirred at -70°C for 1 h and then treated with triethylamine trihydrofluoride (7.6 mL, 46 mmol). After 1 h, a solution of bromine (3.0 mL, 59 mmol) in DCM (15 mL) was added and the reaction mixture was stirred at -70°C for 30 minutes. Finally, morpholine (4.0 mL, 46 mmol) was added at -20 ° C and the mixture was stirred at 0 ° C for 30 min. It was poured into a mixture of ice water and potassium hydroxide. The aqueous phase was separated and extracted with DCM. The combined organic phase was washed with sodium bicarbonate, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane / 1-chlorobutane) and crystallization (heptane / ethanol) to obtain white crystals of 3-[difluoro-(3,4,5-trifluorophenoxy)methyl]-4,6-difluoro-7-propyl-dibenzothiophene (9).

[0310] Compound (9) has the following phase characteristics:

[0311] K 95℃I.

[0312] Δε=13.3

[0313] ε ∥ =22.8

[0314] ε ⊥ =9.5

[0315] Synthesis Example 5 (B(S)QU-3-OT)

[0316] 3-[[3,5-difluoro-4-(trifluoromethoxy)phenoxy]-difluoromethyl]-4,6-difluoro-7-propyl-dibenzothiophene

[0317]

[0318] Step 5.1 :3-[[3,5-difluoro-4-(trifluoromethoxy)phenoxy]-difluoromethyl]-4,6-difluoro-7-propyl-dibenzothiophene

[0319]

[0320] A mixture of 3,5-difluoro-4-(trifluoromethoxy)phenol (8, CAS 195206-85-0) (6.0 g, 24 mmol) and TEA (3.9 mL, 28 mmol) in DCM (15 mL) was added at -70 °C to a solution of 3-(5,6-dihydro-4H-l,3-dithia-l-ium-2-yl)-4,6-difluoro-7-propyl- dibenzothiophene trifluoromethanesulfonate (7, see step 4.5) (12.0 g, 23 mmol) in DCM (70 mL) and the reaction mixture was stirred for 1 h. Then it was treated with triethylamine trihydrofluoride (7.5 mL, 45 mmol) at -70 °C. After 1 h, a solution of bromine (2.9 mL, 57 mmol) in DCM (15 mL) was added and the mixture was stirred at -70 °C for 30 min. Finally, morpholine (4.0 mL, 46 mmol) was added at -20 °C and the reaction mixture was stirred at 0 °C for 30 min. It was poured into a mixture of ice water and potassium hydroxide. The aqueous phase was separated and extracted with DCM. The combined organic phases were washed with sodium bicarbonate, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane / 1-chlorobutane) and crystallization (heptane / ethanol) to give 3-[[3,5-difluoro-4-(trifluoromethoxy)phenoxy]- difluoromethyl]-4,6-difluoro-7-propyl-dibenzothiophene (9) as white crystals.

[0321] Compound (9) has the following phase characteristics:

[0322] K 103 °C SmA (92 °C) I.

[0323] Δε = 14.9

[0324] ε ∥ = 23.8

[0325] ε ⊥ = 8.9

[0326] Synthesis Example 6 (B(S)QU-3-T)

[0327] 3-[[3,5-difluoro-4-(trifluoromethyl)phenoxy]-difluoromethyl]-4,6-difluoro-7- propyl-dibenzothiophene

[0328]

[0329] Step 6.1 : 3-[[3,5-difluoro-4-(trifluoromethyl)phenoxy]-difluoromethyl]-4,6-difluoro-7- propyl-dibenzothiophene

[0330]

[0331] A mixture of 3,5-difluoro-4-(trifluoromethyl)phenol (8, CAS 116640-11-0) (7.5 g, 24 mmol) and TEA (3.8 mL, 27 mmol) in DCM (15 mL) was added to a solution of 3-(5,6-dihydro-4H-1,3-dithiox-1-ium-2-yl)-4,6-difluoro-7-propyl-dibenzothiophene trifluoromethanesulfonate (7, see step 4.5) (12.0 g, 23 mmol) in DCM (70 mL) at -70°C, and the reaction mixture was stirred for 1 h. It was then treated with triethylamine trihydrofluoride (7.6 mL, 46 mmol) at -70°C. After 1 h, a solution of bromine (3.0 mL, 59 mmol) in DCM (15 mL) was added, and the mixture was stirred at -70°C for 30 min. Finally, morpholine (4.0 mL, 46 mmol) was added at -20 ° C, and the reaction mixture was stirred at 0 ° C for 30 min. It was poured into a mixture of ice water and potassium hydroxide. The aqueous phase was separated and extracted with DCM. The combined organic phase was washed with sodium bicarbonate, dried (sodium sulfate) and concentrated in vacuo. The residue was purified by silica gel chromatography (solvent heptane / 1-chlorobutane) and crystallization (heptane / ethanol) to obtain white crystals of 3-[[3,5-difluoro-4-(trifluoromethyl)phenoxy]-difluoro-methyl]-4,6-difluoro-7-propyl-dibenzothiophene (9).

[0332] Compound (9) has the following phase characteristics:

[0333] K 128℃I.

[0334] Synthesis Example 7 (BOIU-2O-F)

[0335] 3-Ethoxy-4,6-difluoro-7-[(3,4,5-trifluorophenyl)methoxy]dibenzofuran

[0336]

[0337] Step 7.1 :3-ethoxy-4,6-difluoro-7-[(3,4,5-trifluorophenyl)methoxy]dibenzofuran

[0338]

[0339] Under argon atmosphere at room temperature, diisopropyl azodicarboxylate (3.4 mL, 17 mmol) was added dropwise to a mixture of 7-ethoxy-4,6-difluoro-dibenzofuran-3-ol (1, CAS 2254195-97-4) (4.0 g, 14 mmol), (3,4,5-trifluorophenyl)methanol (2) (2.8 g, 17 mmol) and TPP (4.5 g, 17 mmol) in THF (50 mL). The reaction mixture was stirred at room temperature overnight. It was then concentrated in vacuo. The residue was purified by silica gel chromatography (solvent DCM) and crystallization (1-chlorobutane) to give white crystals of 3-ethoxy-4,6-difluoro-7-[(3,4,5-trifluorophenyl)methoxy]dibenzofuran (3).

[0340] Compound (3) has the following phase characteristics:

[0341] K 177℃I.

[0342] Synthesis Example 8 (B(S)OIU-2O-F)

[0343] 3-Ethoxy-4,6-difluoro-7-[(3,4,5-trifluorophenyl)methoxy]dibenzothiophene

[0344]

[0345] Step 8.1 :3-ethoxy-4,6-difluoro-7-[(3,4,5-trifluorophenyl)methoxy]dibenzothiophene

[0346]

[0347] Under argon atmosphere at room temperature, diisopropyl azodicarboxylate (3.4 mL, 17 mmol) was added dropwise to a mixture of 7-ethoxy-4,6-difluoro-dibenzothiophene-3-ol (1, CAS 1820028-80-5) (4.0 g, 14 mmol), (3,4,5-trifluorophenyl)methanol (2) (2.8 g, 17 mmol) and TPP (4.5 g, 17 mmol) in THF (50 mL). The reaction mixture was stirred at room temperature overnight. It was then concentrated in vacuo. The residue was purified by silica gel chromatography (solvent 1-chlorobutane) and crystallization (1-chlorobutane) to give yellow crystals of 3-ethoxy-4,6-difluoro-7-[(3,4,5-trifluorophenyl)methoxy]dibenzothiophene (3).

[0348] Compound (3) has the following phase characteristics:

[0349] K 169℃I.

[0350] Other synthesis examples:

[0351] Similar to the above examples, the following exemplary compounds were obtained:

[0352] In the following tables, the following abbreviations for terminal groups are used.

[0353] c-C3H5

[0354]

[0355] C3H5CH2

[0356] c-C4H7

[0357] c-C5H7

[0358] c-C5H9

[0359] Physical properties are given at a temperature of 20°C, γ1 is given in mPa·s. Phase transition temperatures are given in °C.

[0360]

[0361]

[0362]

[0363]

[0364]

[0365]

[0366]

[0367]

[0368]

[0369]

[0370]

[0371]

[0372]

[0373]

[0374]

[0375]

[0376] Application Examples

[0377] Liquid-crystalline media using the compounds according to the invention as components were prepared below. Unless otherwise stated, the percentages are in % by weight. Stabilizers according to Table F were optionally added to the mixtures given below.

[0378] Nematic liquid crystal mixture N-1 having the composition and properties shown in the table below was used as a basis (host mixture) for preparing several exemplary mixtures.

[0379] Mixture N-1:

[0380]

[0381] Host mixture N-1 is optionally stabilized with 0.05% of one of the compounds of Table F above.

[0382] Mixture Example 1

[0383] The nematic liquid crystal medium M-1 composed of 97.5% of medium N-1 and 2.5% of compound B(S)QU-2O-F of Synthesis Example 2 has the following properties:

[0384]

[0385] Compound B(S)QU-2O-F dissolved well in medium N-1 and increased ε ⊥ and the resulting transmittance.

[0386] Mixture Example 2

[0387] The nematic liquid crystal medium M-2, composed of 97.5% of medium N-1 and 2.5% of compound B(S)QU-4O-F of Synthesis Example 3, has the following properties:

[0388]

[0389] The compound is well soluble in medium N-1. The mixture has an increased Δε ⊥ Value, advantageously high clearing point.

[0390] Mixture Example 3

[0391] The nematic liquid crystal medium M-3, composed of 95% of medium N-1 and 5% of compound B(S)QU-3-F of Synthesis Example 4, has the following properties:

[0392]

[0393] Compound B(S)QU-3-F dissolved well in medium N-1 and increased ε ⊥ and the resulting transmittance.

[0394] Mixture Example 4

[0395] The nematic liquid crystal medium M-4, composed of 97.5% of medium N-1 and 2.5% of compound B(S)QU-3-OT of Synthesis Example 5, has the following properties:

[0396]

[0397] Compound B(S)QU-3-OT dissolved well in medium N-1 and increased ε ⊥ and the resulting transmittance.

Claims

1. Compounds of Formula I in W represents S, R represents H, an alkyl group having 1 to 15 C atoms, wherein one or more CH2 groups in these groups can each independently of one another be replaced by -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO- is replaced in such a way that the O atoms are not directly connected to each other and one or more H atoms may be replaced by halogen, A represents 1,4-phenylene, in which one or more H atoms may be replaced by F or CH3, Z represents -CF2O-, -C(O)O-, -OC(O)- or -CH2O-, and X represents F, Cl, CN, NCS, fluoroalkyl, fluoroalkoxy, fluoroalkenyl or fluoroalkenyloxy, each having up to 5 C atoms, and L 1 、L 2 independently represents H or -CH3.

2. The compound according to claim 1, wherein X represents F, CF3, OCF3, CHF2 or OCHF2.

3. The compound according to claim 1 or 2, wherein ring A represents 4. The compound according to claim 1, which is selected from the following sub-formulas wherein R, Z and X have the meanings given in claim 1.

5. The compound according to claim 1 or 2, which is selected from the following formulas IA to IK wherein R and Z are as defined in claim 1. The compound according to claim 1 , wherein Z represents —CF 2 O—, —C(O)O—, or —CH 2 O—.

7. The compound according to claim 1 or 2, wherein ring A represents 8. Use of a compound according to any one of claims 1 to 7 in a liquid-crystalline medium or for energy-saving displays.

9. Liquid-crystalline medium comprising one or more compounds of the formula I according to any one of claims 1 to 7.

10. The liquid-crystalline medium according to claim 9, comprising one or more compounds selected from the group consisting of compounds of the formulae II and III in R 2 represents an alkyl, alkoxy, fluoroalkyl or fluoroalkoxy radical having 1 to 7 C atoms; an alkenyl, alkenyloxy, alkoxyalkyl or fluoroalkenyl radical having 2 to 7 C atoms, wherein one or more CH2 groups in these radicals may each independently of one another be Alternative, Indicated independently of each other at each occurrence 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 is 0, 1, 2, or 3, R 3 represents an alkyl, alkoxy, fluoroalkyl or fluoroalkoxy radical having 1 to 7 C atoms; an alkenyl, alkenyloxy, alkoxyalkyl or fluoroalkenyl radical having 2 to 7 C atoms, wherein one or more CH2 groups in these radicals may each independently of one another be Alternative, L 31 and L 32 represent H or F independently of each other, 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.

11. Process for preparing a liquid-crystalline medium by mixing one or more compounds of the formula I according to any one of claims 1 to 7 with one or more low molecular weight liquid-crystalline compounds or liquid-crystalline mixtures, and optionally with further liquid-crystalline compounds and / or additives.

12. Electro-optical display element comprising a liquid-crystalline medium according to claim 9 or 10.

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