DIBENZOFURAN AND DIBENZOTHIOPHENE DERIVATIVES

Description

[0001] The present invention relates to dibenzofuran and dibenzothiophene derivatives, to the use thereof in liquid crystalline media and to liquid crystalline media comprising the dibenzofuran and dibenzothiophene derivatives.

[0002] Liquid crystals have found widespread use since the first commercially usable liquid-crystalline compounds were found about 40 years ago. Known areas of application are, in particular, displays for watches and pocket calculators, and large display panels as used in railway stations, airports and sports arenas. Further areas of application are displays of portable computers and navigation systems and video applications. For the lastmentioned applications in particular, high demands are made of the response times and contrast of the images.

[0003] The spatial arrangement of the molecules in a liquid crystal has the effect that many of its properties are direction-dependent. Of particular importance for use in liquid-crystal displays are the optical, dielectric and elastomechanical anisotropies. Depending on whether the molecules are oriented with their longitudinal axes perpendicular or parallel to the two plates of a capacitor, the latter has a different capacitance; in other words, the dielectric constant ε of the liquid-crystalline medium has different values for the two orientations. Substances whose dielectric constant is larger when the longitudinal axes of the molecules are oriented perpendicular to the capacitor plates than when they are oriented parallel are known as being dielectrically positive. Most liquid crystals used in earlier displays fall into this group.

[0004] Both the polarisability of the molecule and the permanent dipole moment play a role for the dielectric anisotropy. On application of a voltage to the display, the longitudinal axis of the molecules orients itself in such a way that the larger of the dielectric constants 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 small differences, higher switching voltages are necessary than in the case of large differences. The introduction of suitable polar groups, such as, for example, nitrile groups or fluorine, into the liquid-crystal molecules enables a broad range of working voltages to be achieved.

[0005] In the case of the liquid-crystalline molecules used in conventional liquid-crystal displays, the dipole moment oriented along the longitudinal axis of the molecules is larger than the dipole moment oriented perpendicular to the longitudinal axis of the molecules. The orientation of the larger dipole moment along the longitudinal axis of the molecule also determines the orientation of the molecule in a liquid-crystal display in the field-free state. In the most widespread TN ("twisted nematic") cells, a liquid-crystalline layer with a thickness of only from about 5 to 10 µm is arranged between two flat glass plates, onto each of which an electrically conductive, transparent layer of tin oxide or indium tin oxide has been vapour-deposited as electrode. A likewise transparent alignment layer, usually consisting of a polymer (for example polyimides), is located between these films and the liquid-crystalline layer. This alignment layer serves to bring the longitudinal axes of the adjacent crystalline molecules into a preferential direction through surface forces in such a way that, in the voltage-free state, they lie uniformly on the inside of the display surface with the same alignment in a flat manner or with the same small tilt angle. Two additional polarisation films which only enable linear-polarised light to enter and escape are adhesively bonded to the outside of the display in a certain arrangement.

[0006] By means of liquid crystals in which the larger dipole moment is oriented parallel to the longitudinal axis of the molecule, high-performance displays have already been developed. In most cases here, mixtures of from 5 to 20 components are used in order to achieve a sufficiently broad temperature range of the mesophase and short response times and low threshold voltages. However, difficulties are still caused by the strong viewing-angle dependence in liquid-crystal displays as are used, for example, for laptops. The best imaging quality can be achieved if the sur-face of the display is perpendicular to the viewing direction of the observer. If the display is tilted relative to the observation direction, the imaging quality drops drastically under certain circumstances. For greater comfort, attempts are being made to make the angle through which the display can be tilted from the viewing direction of an observer as large as possible. Attempts have recently been made to improve the viewing-angle dependence using liquid-crystalline compounds whose dipole moment perpendicular to the longitudinal axis of the molecules is larger than that 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 has been possible to achieve an improvement in the viewing-angle dependence. Displays of this type are known as VA-TFT ("vertically aligned") displays.

[0007] Also known are so-called IPS ("in-plane switching") displays, which contain an LC layer between two substrates with planar orientation, where the two electrodes are arranged on only one of the two substrates and preferably have interdigitated, comb-shaped structures. On application of a voltage to the electrodes an electric field with a significant component parallel to the LC layer is generated between them. This causes realignment of the LC molecules in the layer plane. Furthermore, so-called FFS ("fringe-field switching") displays have been reported (see, inter alia, S.H. Jung et al., Jpn. J. Appl. Phys., Volume 43, No. 3, 2004, 1028), which contain two electrodes on the same substrate, one of which is structured in a comb-shaped manner and the other is unstructured. A strong, so-called "fringe field" is thereby generated, i.e. a strong electric field close to the edge of the electrodes, and, throughout the cell, an electric field which has both a strong vertical component and also a strong horizontal component. FFS displays have a low viewing-angle dependence of the contrast. FFS displays usually contain an LC medium with positive dielectric anisotropy, and an alignment layer, usually of polyimide, which provides planar alignment to the molecules of the LC medium.

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

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

[0010] In EP 3 460 025 A1 fluorinated dibenzothiophenes and dibenzofurans as liquid-crystalline materials are disclosed. WO 2019 / 107394 A1 presents further fluorinated dibenzothiophenes for use in liquid crystals and display elements.

[0011] Development in the area of liquid-crystalline materials is far from complete. In order to improve the properties of liquid-crystalline display elements, attempts are constantly being made to develop novel compounds which enable such displays to be optimised.

[0012] An object of the present invention was to provide more diverse compounds having advantageous properties for use in liquid-crystalline media.

[0013] This object is achieved in accordance with the invention by compounds of the general formula I in which Wdenotes O or S, Rdenotes H, an alkyl radical having 1 to 15 C atoms, wherein one or more CH 2 groups in these radicals may each be replaced, independently of one another, by -C≡C- , -CF 2 O-, -OCF 2 -, -CH=CH-, -O-, -CO-O- or -O-CO- in such a way that O atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen, A 1< denotes a trans-1,4-cyclohexylene or 1,4-cyclohexenylene, in which one or more non-adjacent CH 2 groups may be replaced by -O- and in which one or more H atoms may be replaced by F, A 2< denotes trans-1,4-cyclohexylene or 1,4-cyclohexenylene, in which one or more H atoms may be replaced by F, Zdenotes a single bond, -CF 2 O-, -OCF 2 -, -CH 2 CH 2 -, -CF 2 CF 2 -, -C(O)O-, -OC(O)-, -CH 2 O-, -OCH 2 -, -CF=CF-, -CH=CH- or -C≡C-, and Xdenotes F, Cl, CN, NCS, SF 5 , fluorinated alkyl, fluorinated alkoxy, fluorinated alkenyl or fluorinated alkenyloxy each having up to 5 C atoms, preferably F, CF 3 , CHF 2 , OCF 3 or OCHF 2 .

[0014] A further object of the present invention is to provide liquid-crystalline media, in particular for use in TN, IPS or FFS displays.

[0015] This object is achieved in accordance with the invention by the provision of compounds of formula I with neutral to positive dielectric anisotropy (Δε).

[0016] The compounds of formula I are distinguished by a surprisingly large positive dielectric anisotropy (Δε) and are therefore suitable, in particular, for use in TN-TFT displays, and in IPS- and FFS displays. The compounds have a comparatively very low melting point, a very high clearing point, they exhibit very good compatibility with the conventional substances used in liquid-crystal mixtures for displays and are well soluble in such media. Even further the compounds show a very high value of ε⊥.

[0017] The compounds according to the invention preferably have a Δε in the positive region, preferably Δε > 0.5, more preferably Δε > 1.Detailed description

[0018] If the group R is an alkyl radical and / or an alkoxy radical, this can be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and accordingly is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy.

[0019] R may each, independently of one another, be an alkenyl radical having from 2 to 15 carbon atoms, which may be straight-chain or branched. It is preferably straight-chain and has from 2 to 7 carbon atoms. Accordingly, it is preferably vinyl, prop-1- or -2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, or hept-1-, -2-, -3-, -4-, -5- or -6-enyl.

[0020] R may each, independently of one another, be oxaalkyl, preferably straight-chain 2-oxapropyl (= methoxymethyl), 2-oxabutyl (= ethoxymethyl) or 3-oxabutyl (= methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, or 2-, 3-, 4-, 5- or 6-oxaheptyl.

[0021] R may each, independently of one another, be an alkyl radical having from 1 to 15 carbon atoms in which one CH 2 group has been replaced by -O- and one has been replaced by -CO-, where these are preferably adjacent. This thus contains an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-. This is preferably straight-chain and has from 2 to 6 carbon atoms.

[0022] R may each, independently of one another, be an alkyl radical having from 1 to 15 carbon atoms in which one CH 2 group has been replaced by unsubstituted or substituted -CH=CH- and an adjacent CH 2 group has been replaced by CO or CO-O or O-CO, where this may be straight-chain or branched. It is preferably straight-chain and has from 4 to 13 carbon atoms.

[0023] R may each, independently of one another, be an alkyl radical having from 1 to 15 carbon atoms or alkenyl radical having from 2 to 15 carbon atoms, each of which is monosubstituted by -CN or -CF 3 and is preferably straight-chain. The substitution by -CN or -CF 3 is possible in any desired position.

[0024] R may each, independently of one another, be an alkyl radical in which two or more CH 2 groups have been replaced by -O- and / or -CO-O-, where this may be straight-chain or branched. It is preferably branched and has from 3 to 12 carbon atoms.

[0025] R may each, independently of one another, be an alkyl radical having from 1 to 15 carbon atoms or an alkenyl radical having from 2 to 15 carbon atoms, each of which is at least monosubstituted by halogen, where these radicals are preferably straight-chain and halogen is preferably -F or -Cl. In the case of polysubstitution, halogen is preferably -F. The resultant radicals also include perfluorinated radicals, such as -CF 3 . In the case of monosubstitution, the fluorine or chlorine substituent can be in any desired position, but is preferably in the ω-position.

[0026] The term "fluorinated alkyl radical" preferably encompasses mono- or polyfluorinated radicals. Perfluorinated radicals are included. Particular preference is given to CF 3 , CH 2 CF 3 , CH 2 CHF 2 , CHF 2 , CH 2 F, CHFCF 3 and CF 2 CHFCF 3 .

[0027] The term "fluorinated alkoxy radical" preferably encompasses mono- or polyfluorinated radicals. Perfluorinated radicals are included. Particular preference is given to OCF 3 .

[0028] In a preferred embodiment of the present invention the compounds of formula I are selected from the compounds of the formulae I-1 to I-6: in which the occurring groups and parameters have the meanings given above for formula I, and independently: Rpreferably is an alkyl or alkenyl radical each having up to 7 C atoms, wherein one or more CH 2 groups in these radicals may each be replaced, independently of one another, by or A 1< preferably denotes trans-1,4-cyclohexylene, or A 2< preferebly denotes trans-1,4-cyclohexylene or cyclohexenylene.

[0029] Further, the compounds of formula I are preferably selected from the compounds of the formulae I-A to I-F: and more preferably from the group of formulae I-A, I-B, I-D and I-E, wherein R and X are as defined as for formula I above, and preferably X is F, CF 3 or OCF 3 , while more preferably X is CF 3 or OCF 3 for I-A to I-C.

[0030] In a preferred embodiment of the present invention, in the formula I and its sub-formulae, R denotes alkyl having 1 to 7 C atoms, in particular ethyl, propyl, buty, pentyl, cyclopropylmethyl, cyclobutyl or cyclopentyl, where n-propyl and n-pentyl are most preferred.

[0031] In a preferred embodiment of the present invention, in the formula I Z denotes a single bond.

[0032] The compounds of the general formula I are prepared by methods known per se, as described in the literature (for example in the standard works, such as Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), to be precise under reaction conditions which are known and are suitable for the said reactions. Use can be made here of variants which are known per se, but are not mentioned here in greater detail.

[0033] If desired, the starting materials can also be formed in situ by not isolating them from the reaction mixture, but instead immediately converting them further into the compounds of the general formula I.

[0034] Preferred synthetic pathways towards compounds according to the invention are shown in the schemes below and are further illustrated by means of the working examples. The syntheses can be adapted to the particular desired compounds of the general formula I by choice of suitable starting materials.

[0035] The dibenzofuran derivatives, i.e. the compounds of formula I wherein W denotes O (formula I') are preferably synthesized as shown in scheme 1 and are obtainable by intramolecular substitution of fluorine by nucleophilic attack of a phenolate by treatment of the phenol P with a base.

[0036] Alternatively, the analogous ring closure where the position of the OH group and the fluorine atom are interchanged, is possible as shown in scheme 2.

[0037] The dibenzofuran derivatives, i.e. the compounds of formula I wherein W denotes S (formula I") are preferably synthesized as shown in scheme 3.

[0038] The intermediates S (scheme 3) are obtainable from the phenols P (scheme 1) via the corresponding triflate according to Itoh, Takahiro and Mase, Toshiaki, Organic Letters, 6(24), 4587-4590; 2004. Treatment of the compounds S with a strong, non-nucleophilic base, preferably potassium tert.-butanoate yields compounds I" (cf. Jepsen, Tue Heesgaard et al., European Journal of Organic Chemistry, (1), 53-57, S53 / 1-S53 / 65; 2011).

[0039] Another object of the present invention is thus a compound of formula P or P' for use in a process for the synthesis of compounds of formula I, in which the occurring groups and parameters have the meanings given above for formula I.

[0040] A further object of the present invention is a process for the synthesis of the compound of formula I from a compound of formula P or P', preferably following the synthetic pathway depicted in scheme 1, scheme 2 or scheme 3 above. A process for the preparation of a compound of formula I is characterised in that a compound of formula P or P', preferably of formula P, as defined above and below, is subjected to a ring closing reaction leading to a compound of formula I as defined above and below. The ring closing reaction is a nucleophilic aromatic substitution reaction. It is preferably carried out in the presence of a base.

[0041] The reactions described should only be regarded as illustrative. The person skilled in the art can carry out corresponding variations of the syntheses described and also follow other suitable synthetic routes in order to obtain compounds of the formula I.

[0042] The compounds of the general formula I can be used in liquid-crystalline media. The present invention therefore also relates to a liquid-crystalline medium comprising two or more liquid-crystalline compounds, comprising one or more compounds of the general formula I.

[0043] The media according to the invention preferably comprise 1 to 30%, particularly preferably 2 to 20%, of the compounds of the formula I according to the invention.

[0044] The media preferably comprise one, two, three, four or five compounds of the formula I according to the invention.

[0045] In a preferred embodiment of the present invention the liquid-crystalline medium comprises a) one or more compounds selected from the group of compounds of formulae II and III, preferably having a dielectric anisotropy of greater than 3: in which R 2< denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms and preferably alkyl or alkenyl, on each appearance, independently of one another, denote preferably or L 21< and L 22< denote H or F, preferably L 21< denotes F, X 2< denotes halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, preferably F, Cl, -OCF 3 , -O-CH 2 CF 3 , -O-CH=CF 2 or -CF 3 , very preferably F, Cl, -O-CH=CF 2 or - OCF 3 , mis 0, 1, 2 or 3, preferably 1 or 2 and particularly preferably 1, R 3< denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms and preferably alkyl or alkenyl, on each appearance, independently of one another, are preferably or L 31< and L 32< ,independently of one another, denote H or F, preferably L 31< denotes F, X 3< denotes halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, preferably F, Cl, -OCF 3 , -OCHF 2 , -O-CH 2 CF 3 , -O-CH=CF 2 , -O-CH=CH 2 or -CF 3 , very preferably F, Cl, -O-CH=CF 2 , -OCHF 2 or -OCF 3 , Z 3< denotes -CH 2 CH 2 -, -CF 2 CF 2 -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2 O- or a single bond, preferably -CH 2 CH 2 -, -COO-, trans-CH=CH- or a single bond and very preferably -COO-, trans-CH=CH- or a single bond, and nis 0, 1, 2 or 3, preferably 1,2 or 3 and particularly preferably 1, and b) optionally one or more, preferably dielectrically neutral, compounds selected from the group of formulae IV and V: in which R 41< and R 42< ,independently of one another, have the meaning indicated above for R 2< under formula II, preferably R 41< denotes alkyl and R 42< denotes alkyl or alkoxy or R 41< denotes alkenyl and R 42< denotes alkyl, independently of one another and, if occurs twice, also these independently of one another, denote preferably one or more of denotes or denote, Z 41< and Z 42< ,independently of one another and, if Z 41< occurs twice, also these independently of one another, denote -CH 2 CH 2 -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2 O-, -CF 2 O-, -C=C- or a single bond, preferably one or more thereof denotes / denote a single bond, and pdenotes 0, 1 or 2, preferably 0 or 1, and R 51< and R 52< ,independently of one another, have 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, alkenyl or alkenyloxy having 2 to 7 C atoms, preferably having 2 to 4 C atoms, preferably alkenyloxy, if present, each, independently of one another, denote preferably or preferably denotes and, if present, preferably denotes Z 51< to Z 53< each, independently of one another, denote -CH 2 -CH 2 -, -CH 2 -O-, -CH=CH-, -C=C-, -COO- or a single bond, preferably -CH 2 -CH 2 -, -CH 2 -O- or a single bond and particularly preferably a single bond, i and jeach, independently of one another, denote 0 or 1, (i + j)preferably denotes 0, 1 or 2, more preferably 0 or 1 and, most preferably, 1.

[0046] In a further preferred embodiment, the medium comprises one or more compounds of formula V selected from the group of the compounds of the formulae V-1 to V-5, preferably one or more of formula V-3, V-4 and V-5, in which the parameters have the meanings given above under formula V, and preferably R 51< denotes alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C atoms, and R 52< denotes alkyl having 1 to 7 C atoms, alkenyl having 2 to 7 C atoms or alkoxy having 1 to 6 C atoms, preferably alkyl or alkenyl.

[0047] In a further preferred embodiment the medium contains one or more compounds of the formula V-3 in which at least one of the R 51< and R 52< radicals is alkenyl having 2 to 6 carbon atoms, preferably those selected from the following formulae: in which "Alkyl" has the definition given above, and is preferably methyl or ethyl. Particular preference is given to compounds of the formula V-3d.

[0048] In a further preferred embodiment, the medium comprises one or more compounds of formula V-4 selected from the group of the compounds of the formulae V-4a to V-4c, in which alkyl and alkyl* are each independently straight-chain alkyl radical having 1 to 6 carbon atoms, especially methyl, ethyl, n-propyl and pentyl.

[0049] The liquid crystalline medium preferably comprises two, three or more compounds selected from the group of compounds of formulae V-4a, V-4b and V-4c.

[0050] In a further preferred embodiment, the medium comprises one or more compounds of formula V-5 selected from the group of the compounds of the formulae V-5a to V-5c, preferably V-5a: in which alkyl and alkyl* are each independently straight-chain alkyl radical having 1 to 6 carbon atoms, especially methyl, ethyl or n-propyl, and alkenyl preferably denotes alkenyl having 2 to 5 C atoms, preferably having 2 to 4 C atoms, particularly preferably vinyl.

[0051] The present invention also relates to electro-optical liquid-crystal display elements containing a liquid-crystalline medium according to the invention.

[0052] The media according to the invention are prepared in a manner conventional per se. In general, the components are dissolved in one another, advantageously at elevated temperature. By means of suitable additives, the liquid-crystalline phases of the present invention can be modified in such a way that they can be used in all types of liquid-crystal display elements that have been disclosed hitherto. 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, pleochroic dyes can be used for the preparation of coloured guesthost systems or substances can be added in order to modify the dielectric anisotropy, the viscosity and / or the alignment of the nematic phases.

[0053] For the present invention and in the following examples, the structures of the liquid-crystal compounds are indicated by means of acronyms, with the transformation into chemical formulae taking place in accordance with Tables A to C below. All radicals C n H 2n+1 , C m H 2m+1 and C l H 2l+1 or C n H 2n , C m H 2m and C l H 2l are straight-chain alkyl radicals or alkylene radicals, in each case having n, m and l C atoms respectively. Preferably n, m and l are independently of each other 1, 2, 3, 4, 5, 6, or 7. Table A shows the codes for the ring elements of the nuclei of the compound, Table B lists the bridging units, and Table C lists the meanings of the symbols for the left- and right-hand end groups of the molecules. The acronyms are composed of the codes for the ring elements with optional linking groups, followed by a first hyphen and the codes for the left-hand end group, and a second hyphen and the codes for the right-hand end group. Table D shows illustrative structures of compounds together with their respective abbreviations. Table A: Ring elements C D DI A AI P G GI U UI Y U(Me) P(F, CI)Y P(CI,F)Y np n3f nN3fl th thl tH2f tH2fl o2f o2fl dh B B(S) O S K KI L LI F FI Table B: Bridging units E-CH 2 -CH 2 -V -CH=CH-T -C≡C-W -CF 2 -CF 2 -B -CF=CF-Z -CO-O-ZI -O-CO-X -CF=CH-XI -CH=CF-O -CH 2 -O-OI -O-CH 2 -Q -CF 2 -O-QI -O-CF 2 - Table C: End groups On the left individually or in combination On the right individually or in combination -n- CnH2n+1--n -CnH2n+1-nO- C n H 2n+1 -O--On -O-C n H 2n+1 -V- CH 2 =CH--V -CH=CH 2 -nV- C n H2 n+1 -CH=CH--nV -C n H2 n -CH=CH 2 -Vn- CH 2 =CH- C n H 2n --Vn -CH=CH-C n H 2n+1 -nVm- C n H 2n+1 -CH=CH-C m H 2m --nVm - C n H 2n -CH=CH-C m H 2m+1 -N- N≡C--N -C≡N-S- S=C=N--S -N=C=S-F- F--F -F-CI- Cl--CI -Cl-M- CFH 2 --M -CFH 2 -D- CF 2 H--D -CF 2 H-T- CF 3 --T -CF 3 -MO- CFH 2 O --OM -OCFH 2 -DO- CF 2 HO --OD -OCF 2 H-TO- CF 3 O --OT -OCF 3 -A- H-C≡C--A -C≡C-H-nA- C n H 2n+1 -C≡C--An -C≡C-C n H 2n+1 -NA- N≡C-C≡C--AN -C≡C-C≡N On the left only in combination On the right only in combination -...n...- -C n H 2n --...n... -C n H 2n --...M...- -CFH--...M... -CFH--...D...- -CF 2 --...D... -CF 2 --...V...- -CH=CH--...V... -CH=CH-...Z... -CO-O--...Z... -CO-O-...ZI... -O-CO--...ZI... -O-CO--...K...- -CO--...K... -CO--...W ...--CF=CF--...W... -CF=CF- in which n and m are each integers, and the three dots "..." are placeholders for other abbreviations from this table.

[0054] In addition to the compounds of formula I, the mixtures according to the invention preferably comprise one or more compounds of the compounds shown in Table D below.

[0055] The following abbreviations are used: (n, m, k and l are, independently of one another, each an integer, preferably 1 to 9 preferably 1 to 7, k and l possibly may be also 0 and preferably are 0 to 4, more preferably 0 or 2 and most preferably 2, n preferably is 1, 2, 3, 4 or 5, in the combination "-nO-" it preferably is 1, 2, 3 or 4, preferably 2 or 4, m preferably is 1, 2, 3, 4 or 5, in the combination "-Om" it preferably is 1, 2, 3 or 4, more preferably 2 or 4. The combination "-IVm" preferably is "2V1".) Table D Examples of compounds of formula I

[0056] Exemplary, preferred dielectrically positive compounds that can be used in combination with compounds of formula I

[0057] Exemplary, preferred dielectrically neutral compounds that can be used in combination with compounds of formula I

[0058] Table E shows chiral dopants which are optionally employed in the mixtures according to the invention.

[0059] In a preferred embodiment of the present invention, the media according to the invention comprise one or more compounds selected from the group of the compounds from Table E.

[0060] Table F shows stabilisers which can preferably be employed in the mixtures according to the invention in addition to the compounds of formula B. The parameter n here denotes an integer in the range from 1 to 12. In particular, the phenol derivatives shown can be employed as additional stabilisers since they act as antioxidants.

[0061] In a preferred embodiment of the present invention, the media according to the invention comprise one or more compounds selected from the group of the compounds from Table F.

[0062] The invention is explained in greater detail below with reference to working examples, but without being restricted thereby.Examples

[0063] The following examples explain the present invention without restricting it. However, they show the person skilled in the art preferred mixture concepts with compounds preferably to be employed and the respective concentrations thereof and combinations thereof with one another. In addition, the examples illustrate which properties and property combinations are accessible.

[0064] Unless explicitly noted otherwise, all temperature values indicated in the present application, such as, for example, for the melting point T(C,N), the transition from the smectic (Sm) to the nematic (N) phase T(Sm,N) and the clearing point T(N,I), are quoted in degrees Celsius (°C). M.p. denotes melting point, cl.p. = clearing point. The data between these symbols represent the transition temperatures.

[0065] 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 for a temperature of 20°C, and Δn is determined at 589 nm and Δε at 1 kHz, unless explicitly indicated otherwise in each case.

[0066] Above and below, Δn denotes the optical anisotropy (589 nm, 20°C) and Δε denotes the dielectric anisotropy (1 kHz, 20°C).

[0067] The Δε and Δn values of the compounds according to the invention are obtained by extrapolation from liquid-crystalline mixtures consisting of 10% of the respective compound according to the invention and 90% of the commercially available liquid-crystal mixture ZLI-4792 (Merck KGaA, Darmstadt). In cases of limited solubility, the compound is measured in a mixture comprising only 5% of the compound.Abbreviations:

[0068] dist.distilled DMPU1,3-Dimethyltetrahydro-2(1H)-pyrimidinone THFTetrahydrofuran MTB etherMethyl tert.-butyl ether DIPEAN-Ethyldiisopropylamine DMAP4-(Dimethylamino)pyridine CataCXium ADi(1-adamantyl)-n-butylphosphine TEATriethylamine Crcrystalline Smsmectic (optionally with subtype, e.g. SmA, if known) Nnematic Iisotropic

[0069] In addition, the following symbols are used: n e extraordinary refractive index at 20°C and 589 nm,n 0 ordinary refractive index at 20°C and 589 nm,Δnoptical anisotropy at 20°C and 589 nm,ε⊥dielectric permittivity perpendicular to the director at 20°C and 1 kHz,ε∥dielectric permittivity parallel to the director at 20°C and 1 kHz,Δεdielectric anisotropy at 20°C and 1 kHz,cl.p., T(N,I)clearing point [°C],γ 1 rotational viscosity at 20°C [mPa·s],K 1 elastic constant, "splay" deformation at 20°C [pN],K 2 elastic constant, "twist" deformation at 20°C [pN],K 3 elastic constant, "bend" deformation at 20°C [pN]. Synthesis ExamplesSynthesis Example 1 (CCB-3-F)3,4,6-Trifluoro-7-[4-(4-propylcyclohexyl)cyclohexyl]dibenzofuran

[0070] Step 1.1: 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2,3-difluoro-phenol

[0071]

[0072] A mixture of 6-bromo-2,3-difluoro-phenol (CAS 186590-23-8) (7.0 g, 27 mmol), potassium carbonate (5.7 g, 41 mmol), tris(dibenzylideneacetone)-dipalladium(0) (55 mg, 0.06 mmol) and CataCXium A (35 mg, 0.09 mmol) in THF (30 mL) and dist. water (25 mL) is heated to reflux under nitrogen atmosphere, followed by dropwise addition of a solution of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]boronic acid (CAS 931415-69-9) (10.1 g, 27 mmol) in THF (45 mL). The reaction mixture is heated at reflux temperature overnight. Then it is cooled to room temperature and diluted with MTB ether and dist. water. The aqueous phase is separated and extracted with MTB ether. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent 1-chlorobutane). 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]-phenyl]-2,3-difluoro-phenol is isolated as a yellow solid.Step 1.2: 3,4,6-Trifluoro-7-[4-(4-propylcyclohexyl)cyclohexyl]dibenzofuran

[0073]

[0074] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2,3-difluoro-phenol (4.0 g, 8.9 mmol), potassium phosphate monohydrate (2.6 g, 10.8 mmol) and DMPU (40 mL) is stirred at 110°C overnight. Then the reaction mixture is filtered through silica gel (solvent n-heptane). The residue is purified by crystallization (heptane / ethanol) to give white crystals of 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohexyl]dibenzofuran (4 ).

[0075] The title compound has the following phase characteristics: Cr 169 N 285 I. Δε:-0.3ε⊥:8.9Δn:0.187 Synthesis Example 2 (CCB-3-OT)4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethoxy)dibenzofuran

[0076] Step 2.1: 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenol

[0077]

[0078] A mixture of 6-bromo-2-fluoro-3-(trifluoromethoxy)phenol (CAS 1805580-01-1) (12.0 g, 39 mmol), potassium carbonate (8.5 g, 62 mmol), tris(dibenzylideneacetone)-dipalladium(0) (80 mg, 0.08 mmol) and CataCXium A (50 mg, 0.13 mmol) in THF (50 mL) and dist. water (40 mL) is heated to reflux under nitrogen atmosphere, followed by dropwise addition of a solution of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]boronic acid (CAS 931415-69-9) (14.5 g, 39 mmol) in THF (70 mL). The reaction mixture is heated at reflux temperature overnight. Then it is cooled to room temperature and diluted with MTB ether and dist. water. The aqueous phase is separated and extracted with MTB ether. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent 1-chlorobutane), and 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenol is isolated as a yellow solid.Step 2.2: 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethoxy)dibenzofuran

[0079]

[0080] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenol (7.1 g, 14 mmol), potassium phosphate monohydrate (4.0 g, 17 mmol) and DMPU (70 mL) is stirred at 110°C overnight. Then the reaction mixture is filtered through silica gel (solvent n-heptane). The residue is purified by crystallization (heptane / ethanol) to give white crystals of 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethoxy)dibenzofuran (4 ).

[0081] The title compound has the following phase characteristics: Cr 123 SmA 223 N 272 I. Δε:0.9ε⊥.9.2Δn:0.177 Synthesis Example 3 (CCB-3-T) 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethyl)dibenzofuran

[0082] Step 3.1: 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenol

[0083]

[0084] A mixture of 6-bromo-2-fluoro-3-(trifluoromethyl)phenol (CAS 1804908-52-8) (10.0 g, 38 mmol), potassium carbonate (8.0 g, 58 mmol), tris(dibenzylideneacetone)-dipalladium(0) (80 mg, 0.08 mmol) and CataCXium A (50 mg, 0.13 mmol) in THF (30 mL) and dist. water (33 mL) is heated to reflux under nitrogen atmosphere, followed by dropwise addition of a solution of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]boronic acid (CAS 931415-69-9) (14.0 g, 38 mmol) in THF (70 mL). The reaction mixture is heated at reflux temperature overnight. Then it is cooled to room temperature and diluted with MTB-ether and dist. water. The aqueous phase is separated and extracted with MTB ether. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent 1-chlorobutane). 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenol is isolated as a yellow solid.Step 3.2: 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethyl)dibenzofuran

[0085]

[0086] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenol (6.9 g, 14 mmol), potassium phosphate monohydrate (4.0 g, 17 mmol) and DMPU (70 mL) is stirred at 110°C overnight. Then the reaction mixture is filtered through silica gel (solvent n-heptane). The residue is purified by crystallization (heptane / ethanol) to give white crystals of 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7(trifluoromethyl)dibenzofuran (4 ).

[0087] The title compound has the following phase characteristics: Cr 127 SmA 175 N 256 I. Δε:3.0ε⊥.10.1Δn:0.194

[0088] The compound has an surprisingly high value of ε⊥.Synthesis Example 4 (CCB(S)-3-F)3,4,6-Trifluoro-7-[4-(4-propylcyclohexyl)cyclohexyl]dibenzothiophene

[0089] Step 4.1: [6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2,3-difluoro-phenyl] trifluoromethanesulfonate

[0090]

[0091] Trifluoromethanesulfonic anhydride (3.1 mL, 19 mmol) is slowly added to a solution of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2,3-difluoro-phenol (6.9 g, 15 mmol), TEA (3.2 mL, 23 mmol) and DMAP (60 mg, 0.49 mmol) in dichloromethane (70 mL) at 5°C under nitrogen atmosphere. The solution is stirred at room temperature overnight. Then the reaction mixture is filtered through silica gel (solvent 1-chlorbutane) to give [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2,3-difluoro-phenyl] trifluoromethanesulfonate as a white solid.Step 4.2: 3,4,6-Trifluoro-7-[4-(4-propylcyclohexyl)cyclohexyl]dibenzothiophene

[0092]

[0093] This reaction is performed as a one-pot procedure. In the first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2,3-difluoro-phenyl] trifluoromethanesulfonate (8.9 g, 15 mmol), 3-mercapto-propionic acid 2-ethylhexyl ester (4.5 mL, 19 mmol) and DIPEA (4.0 mL, 24 mmol) in toluene (50 mL) is treated with tris(dibenzylideneacetone)-dipalladium(0) (150 mg, 0.16 mmol) and (oxydi-2,1-phenylene)bis-(diphenylphosphine) (170 mg, 0.31 mmol) under argon atmosphere, and the reaction mixture is heated at reflux temperature overnight. In the second step, a solution of potassium tert-butylate (2.0 g, 18 mmol) in THF (15 mL) is added to the reaction mixture at room temperature. Then the reaction mixture is heated at reflux temperature for 6 h, followed by addition of a second portion of a solution of potassium tert-butylate (1.0 g, 9 mmol) in THF (10 mL) and heating again at reflux temperature overnight. A third portion of a solution of potassium tert-butylate (1.0 g, 9 mmol) in THF (10 mL) is added, and the reaction mixture is heated at reflux temperature for additional 6 h. Then it is cooled to room temperature, quenched with dist. water and hydrochloric acid (25 %) at 0°C and diluted with MTB ether and THF. The aqueous phase is separated and extracted with MTB ether and THF. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent heptane) and crystallization (heptane / ethanol) to give 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohexyl]dibenzothiophene as white crystals.

[0094] The title compound has the following phase characteristics: Cr 178 N 344 I. Δε:2.0ε⊥.7.1Δn:0.182 Synthesis Example 5 (CCB(S)-3-OT)4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethoxy)dibenzothiophene

[0095] Step 5.1: [6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenyl] trifluoromethanesulfonate

[0096]

[0097] Trifluoromethanesulfonic anhydride (4.7 mL, 23 mmol) is slowly added to a solution of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenol (12.0 g, 23 mmol), TEA (5.0 mL, 36 mmol) and DMAP (90 mg, 0.74 mmol) in dichloromethane (100 mL) at 5°C under nitrogen atmosphere. The solution is stirred at room temperature overnight. Then the reaction mixture is filtered through silica gel (solvent 1-chlorbutane) to give [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenyl] trifluoromethanesulfonate as a yellow solid.Step 5.2: 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethoxy)dibenzothiophene

[0098]

[0099] This reaction is performed as a one-pot procedure. In the first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenyl] trifluoromethanesulfonate (15.0 g, 21 mmol), 3-mercapto-propionic acid 2-ethylhexyl ester (6.0 mL, 26 mmol) and DIPEA (5.6 mL, 33 mmol) in toluene (70 mL) is treated with tris(dibenzylideneacetone)dipalladium(0) (210 mg, 0.22 mmol) and (oxydi-2,1-phenylene)bis(diphenylphosphine) (240 mg, 0.44 mmol) under argon atmosphere, and the reaction mixture is heated at reflux temperature overnight. In the second step, a solution of potassium tert-butylate (3.0 g, 27 mmol) in THF (30 mL) is added to the reaction mixture at room temperature. The reaction mixture is heated at reflux temperature for 6 h, followed by addition of a second portion of a solution of potassium tert-butylate (1.5 g, 13 mmol) in THF (15 mL) and heating again at reflux temperature overnight. A third portion of a solution of potassium tert-butylate (1.5 g, 13 mmol) in THF (15 mL) is added, and the reaction mixture is heated at reflux temperature for additional 6 h. Then it is cooled to room temperature, quenched with dist. water and hydrochloric acid (25 %) at 0°C and diluted with MTB ether and THF. The aqueous phase is separated and extracted with MTB ether and THF. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent heptane) and crystallization (heptane / 2-propanol) to give yellow crystals of 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethoxy)dibenzothiophene (6). The title compound has the following phase characteristics: Cr 154 Sm 168 SmA 253 N 332. Δε:4.1ε⊥.7.1Δn:0.189 Synthesis Example 6 (CCB(S)-3-T)4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethyl)dibenzothiophene

[0100] Step 6.1: [6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenyl] trifluoromethanesulfonate

[0101]

[0102] Trifluoromethanesulfonic anhydride (4.5 mL, 27 mmol) is slowly added to a solution of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenol (11.1 g, 22 mmol), TEA (4.6 mL, 33 mmol) and DMAP (90 mg, 0.74 mmol) in dichloromethane (100 mL) at 5°C under nitrogen atmosphere. The solution is stirred at room temperature overnight. Then the reaction mixture is filtered through silica gel (solvent 1-chlorbutane) to give [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenyl] trifluoromethanesulfonate as a yellow solid.Step 6.2: 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethyl)dibenzothiophene

[0103]

[0104] This reaction is performed as a one-pot procedure. In the first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohexyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenyl] trifluoromethanesulfonate (13.9 g, 21 mmol), 3-mercapto-propionic acid 2-ethylhexyl ester (5.8 mL, 25 mmol) and DIPEA (5.3 mL, 31 mmol) in toluene (65 mL) is treated with tris(dibenzylideneacetone)dipalladium(0) (190 mg, 0.20 mmol) and (oxydi-2,1-phenylene)bis(diphenylphosphine) (230 mg, 0.42 mmol) under argon atmosphere, and the reaction mixture is heated at reflux temperature overnight. In the second step, a solution of potassium tert-butylate (2.8 g, 25 mmol) in THF (25 mL) is added to the reaction mixture at room temperature. The reaction mixture is heated at reflux temperature for 6 h, followed by addition of a second portion of a solution of potassium tert-butylate (1.4 g, 12 mmol) in THF (15 mL) and heating again at reflux temperature overnight. A third portion of a solution of potassium tert-butylate (1.4 g, 12 mmol) in THF (15 mL) is added, and the reaction mixture is heated at reflux temperature for additional 6 h. Then it is cooled to room temperature, quenched with dist. water and hydrochloric acid (25 %) at 0°C and diluted with MTB ether and THF. The aqueous phase is separated and extracted with MTB ether and THF. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent heptane) and crystallization (heptane / 2-propanol) to give light yellow crystals of 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohexyl]-7-(trifluoromethyl)dibenzothiophene (6 ).

[0105] The title compound has the following phase characteristics: Cr 179 Sm (172) N 317. Δε:6.9ε⊥.7.7Δn:0.189 Synthesis Example 7 (CLB-3-F)3,4,6-Trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl]dibenzofuran

[0106] Step 7.1: [2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]boronic acid

[0107]

[0108] N-Butyllithium (122 mL, 1.6 M in hexanes) is slowly added to a solution of 1,2-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]benzene (CAS 1184184-30-2) (56.0 g, 0.17 mol) in THF (1.0 L) at -70°C under argon atmosphere, and the reaction mixture is stirred for 1 h at this temperature. Then trimethyl borate (22.0 mL, 0.19 mol) is added, and the reaction mixture is stirred for an additional hour at -70°C. Then it is allowed to warm up to room temperature and is stirred overnight. The reaction is quenched with dist. water, and the suspension is diluted with MTB ether and treated with hydrochloric acid (25%). The aqueous phase is separated and extracted with MTB ether. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by crystallization (n-heptane) to give white crystals of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]boronic acid (2 ).Step 7.2: 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3-difluoro-phenol

[0109] mixture of 6-bromo-2,3-difluoro-phenol (CAS 186590-23-8) (7.0 g, 27 mmol), potassium carbonate (5.7 g, 41 mmol), tris(dibenzylideneacetone)-dipalladium(0) (55 mg, 0.06 mmol) and CataCXium A (35 mg, 0.09 mmol) in THF (30 mL) and dist. water (25 mL) is heated to reflux under nitrogen atmosphere, followed by dropwise addition of a solution of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]boronic acid (10.0 g, 27 mmol) in THF (45 mL). The reaction mixture is heated at reflux temperature overnight. Then it is cooled to room temperature and diluted with MTB ether and dist. water. The aqueous phase is separated and extracted with MTB ether. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent 1-chlorobutane). 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3-difluoro-phenol is isolated as a yellow solid.Step 7.3: 3,4,6-Trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl]dibenzofuran

[0110]

[0111] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3-difluoro-phenol (4.0 g, 9 mmol), potassium phosphate monohydrate (2.6 g, 11 mmol) and DMPU (40 mL) is stirred at 110°C overnight. Then the reaction mixture is filtered through silica gel (solvent n-heptane). The residue is purified by crystallization (heptane / ethanol) to give white crystals of 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl]dibenzofuran (5 ).

[0112] The title compound has the following phase characteristics: Cr 146 SmA 183 N 263 I. Δε:-0.5ε⊥.9.1Δn:0,219 Synthesis Example 8 (CLB-3-OT)4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethoxy)dibenzofuran

[0113] Step 8.1: 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenol

[0114]

[0115] A mixture of 6-bromo-2-fluoro-3-(trifluoromethoxy)phenol (CAS 1805580-01-1) (12.0 g, 39 mmol), potassium carbonate (8.5 g, 62 mmol), tris(dibenzylideneacetone)-dipalladium(0) (80 mg, 0.08 mmol) and CataCXium A (50 mg, 0.13 mmol) in THF (50 mL) and dist. water (40 mL) is heated to reflux under nitrogen atmosphere, followed by dropwise addition of a solution of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-boronic acid (14.5 g, 40 mmol) in THF (70 mL). The reaction mixture is heated at reflux temperature overnight. Then it is cooled to room temperature and diluted with MTB ether and dist. water. The aqueous phase is separated and extracted with MTB ether. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent 1-chlorobutane). 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenol is isolated as a yellow solid.Step 8.2: 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethoxy)dibenzofuran

[0116]

[0117] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenol (6.9 g, 13 mmol), potassium phosphate monohydrate (4.0 g, 17 mmol) and DMPU (70 mL) is stirred at 110°C overnight. The residue is purified by crystallization (heptane / ethanol) to give white crystals of 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethoxy)dibenzofuran (5 ).

[0118] The title compound has the following phase characteristics: Cr 101 SmA 251 N 258 I. Δε:1.1ε⊥.9.5Δn:0.204

[0119] The compound combines a low melting point, high N-I transition and a very high value for ε⊥.Synthesis Example 9 (CLB-3-T)4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethyl)dibenzofuran

[0120] Step 9.1: 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenol

[0121]

[0122] A mixture of 6-bromo-2-fluoro-3-(trifluoromethyl)phenol (CAS 1804908-52-8) (10 g, 38 mmol), potassium carbonate (8.0 g, 58 mmol), tris(dibenzylideneacetone)-dipalladium(0) (80 mg, 0.08 mmol) and CataCXium A (50 mg, 0.13 mmol) in THF (60 mL) and dist. water (33 mL) is heated to reflux under nitrogen atmosphere, followed by dropwise addition of a solution of [2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]boronic acid (14.0 g, 38 mmol) in THF (40 mL). The reaction mixture is heated at reflux temperature overnight. Then it is cooled to room temperature and diluted with MTB ether and dist. water. The aqueous phase is separated and extracted with MTB ether. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent 1-chlorobutane). 6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenol is isolated as a yellow solid.Step 9.2: 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethyl)dibenzofuran

[0123]

[0124] A mixture of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenol (6.5 g, 13 mmol), potassium phosphate monohydrate (4.0 g, 17 mmol) and DMPU (60 mL) is stirred at 110°C overnight. Then the reaction mixture is filtered through silica gel (solvent n-heptane). The residue is purified by crystallization (heptane) to give white crystals of 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethyl)dibenzofuran (5 ). The title compound has the following phase characteristics: Cr 118 SmA 227 N 247 I. Δε:3.3ε⊥.10.3Δn:0.205

[0125] The compound has an surprisingly high value of ε⊥.Synthesis Example 10 (CLB(S)-3-F)3,4,6-Trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl]dibenzothiophene

[0126] Step 10.1: [6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3-difluorophenyl] trifluoromethanesulfonate

[0127]

[0128] Trifluoromethanesulfonic anhydride (3.5 mL, 18 mmol) is slowly added to a solution of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3-difluorophenol (7.4 g, 17 mmol), TEA (3.5 mL, 25 mmol) and DMAP (65 mg, 0.53 mmol) in dichloromethane (75 mL) at 5°C under nitrogen atmosphere. The solution is stirred at room temperature overnight. Then the reaction mixture is filtered through silica gel (solvent 1-chlorbutane) to give [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3-difluorophenyl] trifluoromethanesulfonate as a yellow solid.Step 10.2: 3,4,6-Trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl]dibenzothiophene

[0129]

[0130] This reaction is performed as a one-pot procedure. In the first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2,3-difluorophenyl] trifluoromethanesulfonate (8.9 g, 14 mmol), 3-mercapto-propionic acid 2-ethylhexyl ester (4.5 mL, 19 mmol) and DIPEA (4.0 mL, 24 mmol) in toluene (50 mL) is treated with tris(dibenzylideneacetone)dipalladium(0) (150 mg, 0.16 mmol) and (oxydi-2,1-phenylene)-bis(diphenylphosphine) (170 mg, 0.31 mmol) under argon atmosphere, and the reaction mixture is heated at reflux temperature overnight. In the second step, a solution of potassium tert-butylate (2.0 g, 18 mmol) in THF (15 mL) is added to the reaction mixture at room temperature. Then the reaction mixture is heated at reflux temperature for 6 h, followed by addition of a second portion of a solution of potassium tert-butylate (1.0 g, 9 mmol) in THF (10 mL) and heating again at reflux temperature overnight. A third portion of a solution of potassium tert-butylate (1.0 g, 9 mmol) in THF (10 mL) is added, and the reaction mixture is heated at reflux temperature for additional 6 h. Then it is cooled to room temperature, quenched with dist. water and hydrochloric acid (25 %) at 0°C and diluted with MTB ether and THF. The aqueous phase is separated and extracted with MTB ether and THF. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent heptane) and crystallization (heptane / ethanol) to give white crystals of 3,4,6-trifluoro-7-[4-(4-propylcyclohexyl)cyclohex-1-enyl]dibenzothiophene (7 ).

[0131] The title compound has the following phase characteristics: Cr 136 SmA 208 N 303 Δε:3.5ε⊥.6.7Δn:0.217 Synthesis Example 11 (CLB(S)-3-OT)4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethoxy)dibenzothiophene

[0132] Step 11.1: [6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenyl] trifluoromethanesulfonate

[0133]

[0134] Trifluoromethanesulfonic anhydride (4.0 mL, 24 mmol) is slowly added to a solution of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenol (10.0 g, 20 mmol), TEA (4.1 mL, 30 mmol) and DMAP (80 mg, 0.66 mmol) in dichloromethane (100 mL) at 5°C under nitrogen atmosphere. The solution is stirred at room temperature overnight. The reaction mixture is purified by silica gel chromatography (solvent 1-chlorbutane) to give [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenyl] trifluoromethanesulfonate as a yellow solid.Step 11.2: 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethoxy)dibenzothiophene

[0135]

[0136] This reaction is performed as a one-pot procedure. In the first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethoxy)phenyl] trifluoromethanesulfonate (12.3 g, 17 mmol), 3-mercapto-propionic acid 2-ethylhexyl ester (5.0 mL, 21 mmol) and DIPEA (4.5 mL, 26 mmol) in toluene (60 mL) is treated with tris(dibenzylideneacetone)dipalladium(0) (170 mg, 0.18 mmol) and (oxydi-2,1-phenylene)bis(diphenylphosphine) (190 mg, 0.35 mmol) under argon atmosphere, and the reaction mixture is heated at reflux temperature overnight. In the second step, a solution of potassium tert-butylate (2.3 g, 21 mmol) in THF (20 mL) is added to the reaction mixture at room temperature. Then the reaction mixture is heated at reflux temperature for 6 h, followed by addition of a second portion of a solution of potassium tert-butylate (1.2 g, 11 mmol) in THF (15 mL) and heating again at reflux temperature overnight. A third portion of a solution of potassium tert-butylate (1.2 g, 11 mmol) in THF (15 mL) is added, and the reaction mixture is heated at reflux temperature for additional 6 h. Then it is cooled to room temperature, quenched with dist. water and hydrochloric acid (25 %) at 0°C and diluted with MTB ether and THF. The aqueous phase is separated and extracted with MTB ether and THF. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent heptane) and crystallization (heptane / isopropanol) to give pale yellow crystals of 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethoxy)dibenzothiophene (7). The title compound has the following phase characteristics: Cr 131 SmA 295 N 318. Δε:4.7ε⊥.7.1Δn:0.221 Synthesis Example 12 (CLB(S)-3-T)4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethyl)dibenzothiophene

[0137] Step 12.1: [6-[2,3-Difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenyl] trifluoromethanesulfonate

[0138]

[0139] Trifluoromethanesulfonic anhydride (4.5 mL, 27 mmol) is slowly added to a solution of 6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenol (11.0 g, 21.69 mmol), TEA (4.7 mL, 34 mmol) and DMAP (90 mg, 0.74 mmol) in dichloromethane (100 mL) at 5°C under nitrogen atmosphere. The solution is stirred at room temperature overnight. The reaction mixture is purified by silica gel chromatography (solvent 1-chlorbutane) to give [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenyl] trifluoromethanesulfonate as a yellow solid.Step 12.2: 4,6-Difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethyl)dibenzothiophene

[0140]

[0141] This reaction is performed as a one-pot procedure. In the first step, a solution of [6-[2,3-difluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-enyl]phenyl]-2-fluoro-3-(trifluoromethyl)phenyl] trifluoromethanesulfonate (13.3 g, 20 mmol), 3-mercapto-propionic acid 2-ethylhexyl ester (5.5 mL, 23 mmol) and DIPEA (5.0 mL, 29 mmol) in toluene (60 mL) is treated with tris(dibenzylideneacetone)dipalladium(0) (180 mg, 0.19 mmol) and (oxydi-2,1-phenylene)bis(diphenylphosphine) (210 mg, 0.38 mmol) under argon atmosphere, and the reaction mixture is heated at reflux temperature overnight. In the second step, a solution of potassium tert-butylate (2.6 g, 23 mmol) in THF (20 mL) is added to the reaction mixture at room temperature. Then the reaction mixture is heated at reflux temperature for 6 h, followed by addition of a second portion of a solution of potassium tert-butylate (1.3 g, 12 mmol) in THF (15 mL) and heating again at reflux temperature overnight. A third portion of a solution of potassium tert-butylate (1.3 g, 12 mmol) in THF (15 mL) is added, and the reaction mixture is heated at reflux temperature for additional 6 h. Then it is cooled to room temperature, quenched with dist. water and hydrochloric acid (25 %) at 0°C and diluted with MTB ether and THF. The aqueous phase is separated and extracted with MTB ether and THF. The combined organic phases are washed with dist. water and brine, dried (sodium sulphate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent heptane) and crystallization (heptane / ethanol) to give white crystals of 4,6-difluoro-3-[4-(4-propylcyclohexyl)cyclohex-1-enyl]-7-(trifluoromethyl)dibenzothiophene (7). The title compound has the following phase characteristics: Cr 138 SmA 256 N 302. Δε:7.2ε⊥.8.1Δn:0.204 Further Synthesis Examples:

[0142] In analogy to the above described examples the following exemplary compounds are obtained: In the following table the following abbreviations for the end groups are used c-C 3 H 5 c-C 3 H 5 CH 2 c-C 4 H 7 c-C 5 H 7 c-C 5 H 9

[0143] The physical properties are given at a temperature of 20°C and γ 1 is given in mPa·s. Phase transition temperatures are given in °C. No: A-RXPhase Range; properties1CH 3 F2C 2 H 5 F3n-C 3 H 7 Fsee Synthesis Example 14n-C 4 H 9 F5n-C 5 H 11 F6n-C 6 H 13 F7n-C 7 H 15 F8n-C 8 H 17 F9c-C 3 H 5 F10c-C 3 H 5 CH 2 F11c-C 4 H 7 F12c-C 5 H 7 F13c-C 5 H 9 F14CH 2 =CHF15CH 3 CH=CHF16CH 2 =CH(CH 2 ) 2 F17CH 3 OF18C 2 H 5 OF19n-C 3 H 7 OF20n-C 4 H 9 OF21n-C 5 H 11 OF22CH 3 CF 3 23C 2 H 5 CF 3 24n-C 3 H 7 CF 3 see Synthesis Example 325n-C 4 H 9 CF 3 26n-C 5 H 11 CF 3 27n-C 6 H 13 CF 3 28n-C 7 H 15 CF 3 29n-C 8 H 17 CF 3 30c-C 3 H 5 CF 3 31c-C 3 H 5 CH 2 CF 3 32c-C 4 H 7 CF 3 33c-C 5 H 7 CF 3 34c-C 5 H 9 CF 3 35CH 2 =CHCF 3 36CH 3 CH=CHCF 3 37CH 2 =CH(CH 2 ) 2 CF 3 38CH 3 OCF 3 39C 2 H 5 OCF 3 40n-C 3 H 7 OCF 3 41n-C 4 H 9 OCF 3 42n-C 5 H 11 OCF 3 43CH 3 OCF 3 44C 2 H 5 OCF 3 45n-C 3 H 7 OCF 3 see Synthesis Example 246n-C 4 H 9 OCF 3 47n-C 5 H 11 OCF 3 48n-C 6 H 13 OCF 3 49n-C 7 H 15 OCF 3 50n-C 8 H 17 OCF 3 51c-C 3 H 5 OCF 3 52c-C 3 H 5 CH 2 OCF 3 53c-C 4 H 7 OCF 3 54c-C 5 H 7 OCF 3 55c-C 5 H 9 OCF 3 56CH 2 =CHOCF 3 57CH 3 CH=CHOCF 3 58CH 2 =CH(CH 2 ) 2 OCF 3 59CH 3 OOCF 3 60C 2 H 5 OOCF 3 61n-C 3 H 7 OOCF 3 62n-C 4 H 9 OOCF 3 63n-C 5 H 11 OOCF 3 No: D-RXPhase Range; properties1CH 3 F2C 2 H 5 F3n-C 3 H 7 Fsee Synthesis Example 44n-C 4 H 9 F5n-C 5 H 11 F6n-C 6 H 13 F7n-C 7 H 15 F8n-C 8 H 17 F9c-C 3 H 5 F10c-C 3 H 5 CH 2 F11c-C 4 H 7 F12c-C 5 H 7 F13c-C 5 H 9 F14CH 2 =CHF15CH 3 CH=CHF16CH 2 =CH(CH 2 ) 2 F17CH 3 OF18C 2 H 5 OF19n-C 3 H 7 OF20n-C 4 H 9 OF21n-C 5 H 11 OF22CH 3 CF 3 23C 2 H 5 CF 3 24n-C 3 H 7 CF 3 see Synthesis Example 625n-C 4 H 9 CF 3 26n-C 5 H 11 CF 3 27n-C 6 H 13 CF 3 28n-C 7 H 15 CF 3 29n-C 8 H 17 CF 3 30c-C 3 H 5 CF 3 31c-C 3 H 5 CH 2 CF 3 32c-C 4 H 7 CF 3 33c-C 5 H 7 CF 3 34c-C 5 H 9 CF 3 35CH 2 =CHCF 3 36CH 3 CH=CHCF 3 37CH 2 =CH(CH 2 ) 2 CF 3 38CH 3 OCF 3 39C 2 H 5 OCF 3 40n-C 3 H 7 OCF 3 41n-C 4 H 9 OCF 3 42n-C 5 H 11 OCF 3 43CH 3 OCF 3 44C 2 H 5 OCF 3 45n-C 3 H 7 OCF 3 see Synthesis Example 546n-C 4 H 9 OCF 3 47n-C 5 H 11 OCF 3 48n-C 6 H 13 OCF 3 49n-C 7 H 15 OCF 3 50n-C 8 H 17 OCF 3 51c-C 3 H 5 OCF 3 52c-C 3 H 5 CH 2 OCF 3 53c-C 4 H 7 OCF 3 54c-C 5 H 7 OCF 3 55c-C 5 H 9 OCF 3 56CH 2 =CHOCF 3 57CH 3 CH=CHOCF 3 58CH 2 =CH(CH 2 ) 2 OCF 3 59CH 3 OOCF 3 60C 2 H 5 OOCF 3 61n-C 3 H 7 OOCF 3 62n-C 4 H 9 OOCF 3 63n-C 5 H 11 OOCF 3 No: B-RXPhase Range; properties1CH 3 F2C 2 H 5 F3n-C 3 H 7 Fsee Synthesis Example 74n-C 4 H 9 F5n-C 5 H 11 F6n-C 6 H 13 F7n-C 7 H 15 F8n-C 8 H 17 F9c-C 3 H 5 F10c-C 3 H 5 CH 2 F11c-C 4 H 7 F12c-C 5 H 7 F13c-C 5 H 9 F14CH 2 =CHF15CH 3 CH=CHF16CH 2 =CH(CH 2 ) 2 F17CH 3 OF18C 2 H 5 OF19n-C 3 H 7 OF20n-C 4 H 9 OF21n-C 5 H 11 OF22CH 3 CF 3 23C 2 H 5 CF 3 24n-C 3 H 7 CF 3 see Synthesis Example 925n-C 4 H 9 CF 3 26n-C 5 H 11 CF 3 27n-C 6 H 13 CF 3 28n-C 7 H 15 CF 3 29n-C 8 H 17 CF 3 30c-C 3 H 5 CF 3 31c-C 3 H 5 CH 2 CF 3 32c-C 4 H 7 CF 3 33c-C 5 H 7 CF 3 34c-C 5 H 9 CF 3 35CH 2 =CHCF 3 36CH 3 CH=CHCF 3 37CH 2 =CH(CH 2 ) 2 CF 3 38CH 3 OCF 3 39C 2 H 5 OCF 3 40n-C 3 H 7 OCF 3 41n-C 4 H 9 OCF 3 42n-C 5 H 11 OCF 3 43CH 3 OCF 3 44C 2 H 5 OCF 3 45n-C 3 H 7 OCF 3 see Synthesis Example 846n-C 4 H 9 OCF 3 47n-C 5 H 11 OCF 3 48n-C 6 H 13 OCF 3 49n-C 7 H 15 OCF 3 50n-C 8 H 17 OCF 3 51c-C 3 H 5 OCF 3 52c-C 3 H 5 CH 2 OCF 3 53c-C 4 H 7 OCF 3 54c-C 5 H 7 OCF 3 55c-C 5 H 9 OCF 3 56CH 2 =CHOCF 3 57CH 3 CH=CHOCF 3 58CH 2 =CH(CH 2 ) 2 OCF 3 59CH 3 OOCF 3 60C 2 H 5 OOCF 3 61n-C 3 H 7 OOCF 3 62n-C 4 H 9 OOCF 3 63n-C 5 H 11 OOCF 3 No: E-RXPhase Range; properties1CH 3 F2C 2 H 5 F3n-C 3 H 7 Fsee Synthesis Example 104n-C 4 H 9 F5n-C 5 H 11 F6n-C 6 H 13 F7n-C 7 H 15 F8n-C 8 H 17 F9c-C 3 H 5 F10c-C 3 H 5 CH 2 F11c-C 4 H 7 F12c-C 5 H 7 F13c-C 5 H 9 F14CH 2 =CHF15CH 3 CH=CHF16CH 2 =CH(CH 2 ) 2 F17CH 3 OF18C 2 H 5 OF19n-C 3 H 7 OF20n-C 4 H 9 OF21n-C 5 H 11 OF22CH 3 CF 3 23C 2 H 5 CF 3 24n-C 3 H 7 CF 3 see Synthesis Example 1225n-C 4 H 9 CF 3 26n-C 5 H 11 CF 3 27n-C 6 H 13 CF 3 28n-C 7 H 15 CF 3 29n-C 8 H 17 CF 3 30c-C 3 H 5 CF 3 31c-C 3 H 5 CH 2 CF 3 32c-C 4 H 7 CF 3 33c-C 5 H 7 CF 3 34c-C 5 H 9 CF 3 35CH 2 =CHCF 3 36CH 3 CH=CHCF 3 37CH 2 =CH(CH 2 ) 2 CF 3 38CH 3 OCF 3 39C 2 H 5 OCF 3 40n-C 3 H 7 OCF 3 41n-C 4 H 9 OCF 3 42n-C 5 H 11 OCF 3 43CH 3 OCF 3 44C 2 H 5 OCF 3 45n-C 3 H 7 OCF 3 see Synthesis Example 1146n-C 4 H 9 OCF 3 47n-C 5 H 11 OCF 3 48n-C 6 H 13 OCF 3 49n-C 7 H 15 OCF 3 50n-C 8 H 17 OCF 3 51c-C 3 H 5 OCF 3 52c-C 3 H 5 CH 2 OCF 3 53c-C 4 H 7 OCF 3 54c-C 5 H 7 OCF 3 55c-C 5 H 9 OCF 3 56CH 2 =CHOCF 3 57CH 3 CH=CHOCF 3 58CH 2 =CH(CH 2 ) 2 OCF 3 59CH 3 OOCF 3 60C 2 H 5 OOCF 3 61n-C 3 H 7 OOCF 3 62n-C 4 H 9 OOCF 3 63n-C 5 H 11 OOCF 3 Use Examples

[0144] Liquid crystalline media using the compounds according to the invention as a component are prepared in the following. Unless indicated otherwise, percentages are % by weight. Stabilizers according to table F are optionally added to the mixtures presented below.

[0145] A nematic liquid-crystal mixture N-1 having the composition and properties as indicated in the following table is used as the basis (host mixture) for preparation of several of the exemplary mixtures.Mixture N-1:

[0146] APUQU-2-F5.0%Clearing point [°C]:78.5CC-3-V31.5%Δn [589 nm, 20°C]:0.1001CC-3-V16.5%n e [589 nm, 20°C]:1.5877CCP-3-36.0%n o [589 nm, 20°C]:1.4876CCP-V-112.0%Δε [1 kHz, 20°C]:6.0CCP-V2-112.0%ε ∥ [1 kHz, 20°C]:9.0CPGP-5-22.0%ε ⊥ [1 kHz, 20°C]:3.0PP-1-2V15.0%γ 1 [mPa s, 20°C]:64PUQU-3-F20.0%K 1 [pN, 20°C]:13.3Σ100.0%K 3 [pN, 20°C]:15.5 Mixture Example 1

[0147] A nematic liquid-crystal medium M-1 consisting of 95% of the medium N-1 and 5% of the compound CCB-3-T of Synthesis Example 3 has the following properties: Host mixture N-195.0%Clearing point [°C]:85.5CCB-3-T5.0%Δn [589 nm, 20°C]:0.1044Σ100.0%n e [589 nm, 20°C]:1.5915n o [589 nm, 20°C]:1.4871Δε [1 kHz, 20°C]:5.8ε ∥ [1 kHz, 20°C]:9.2ε ⊥ [1 kHz, 20°C]:3.3γ 1 [mPa s, 20°C]:77K 1 [pN, 20°C]:14.4K 3 [pN, 20°C]:16.3

[0148] The compound CCB-3-T is well soluble in the medium N-1.Mixture Example 2

[0149] A nematic liquid-crystal medium M-2 consisting of 90% of the medium N-1 and 10% of the compound CCB-3-OT of Synthesis Example 2 has the following properties: Host mixture N-190.0%Clearing point [°C]:92CCB-3-OT10.0%Δn [589 nm, 20°C]:0.1081Σ100.0%n e [589 nm, 20°C]:1.5944n o [589 nm, 20°C]:1.4863Δε [1 kHz, 20°C]:5.5ε ∥ [1 kHz, 20°C]:9.1ε ⊥ [1 kHz, 20°C]:3.6γ 1 [mPa s, 20°C]:90K 1 [pN, 20°C]:14.9K 3 [pN, 20°C]:17.0

[0150] The compound CCB-3-OT is well soluble in the medium N-1. The mixture has an advantageously high clearing point.Mixture Example 3

[0151] A nematic liquid-crystal medium M-3 consisting of 95% of the medium N-1 and 5% of the compound CCB(S)-3-OT of Synthesis Example 5 has the following properties: Host mixture N-195.0%Clearing point [°C]:87.5CCB(S)-3-OT5.0%Δn [589 nm, 20°C]:0.1054Σ100.0%n e [589 nm, 20°C]:1.5926n o [589 nm, 20°C]:1.4872Δε [1 kHz, 20°C]:5.9ε ∥ [1 kHz, 20°C]:9.1ε ⊥ [1 kHz, 20°C]:3.2γ 1 [mPa s, 20°C]:77 Mixture Example 4

[0152] A nematic liquid-crystal medium M-4 consisting of 95% of the medium N-1 and 5% of the compound CLB-3-OT of Synthesis Example 8 has the following properties: Host mixture N195.0 %Clearing point [°C]:85.5CLB-3-OT5.0 %Δn [589 nm, 20°C]:0.1064Σ100.0 %n e [589 nm, 20°C]:1.5937n o [589 nm, 20°C]:1.4873Δε [1 kHz, 20°C]:5.8ε ∥ [1 kHz, 20°C]:9.1ε ⊥ [1 kHz, 20°C]:3.3γ 1 [mPa s, 20°C]:75K 1 [pN, 20°C]:14.3K 3 [pN, 20°C]:16.3 Mixture Example 5

[0153] A nematic liquid-crystal medium M-5 consisting of 95% of the medium N-1 and 5% of the compound CLB-3-T of Synthesis Example 9 has the following properties: Host mixture N-195.0 %Clearing point [°C]:85.5CLB-3-T5.0 %Δn [589 nm, 20°C]:0.1059Σ100.0 %n e [589 nm, 20°C]:1.5935n o [589 nm, 20°C]:1.4876Δε [1 kHz, 20°C]:5.6ε ∥ [1 kHz, 20°C]:9.0ε ⊥ [1 kHz, 20°C]:3.3γ 1 [mPa s, 20°C]:70K 1 [pN, 20°C]:14.5K 3 [pN, 20°C]:16.3 Mixture Example 6

[0154] A nematic liquid-crystal medium M-6 consisting of the compounds indicated in the following table is prepared APUQU-2-F4.5 %Cclearing point [°C]:85.5APUQU-3-F4.0 %Δn [589 nm, 20°C]:0.1243PGUQU-3-F4.0 %n e [589 nm, 20°C]:1.6114PGUQU-4-F4.5 %n o [589 nm, 20°C]:1.4871PGUQU-5-F3.0 %Δε [1 kHz, 20°C]:5.7PPGU-3-F0.5 %ε ∥ [1 kHz, 20°C]:9.4CCP-V-12.0 %ε ⊥ [1 kHz, 20°C]:3.7PGP-1-2V4.0 %γ 1 [mPa s, 20°C]:69PGP-2-2V6.0 %K 1 [pN, 20°C]:14.8PGP-3-2V3.0 %K 3 [pN, 20°C]:14.7CC-3-V45.0 %LTS bulk [h, -20°C]:1000CC-3-V16.5 %PP-1-2V12.0 %LB(S)-3-OT5.5 %LB-3-T2.0 %CCB-3-OT3.5 %Σ100.0 %

[0155] The mixture is suitable for use in an FFS display.Mixture Example 7

[0156] A nematic liquid-crystal medium M-7 consisting of the compounds indicated in the following table is prepared APUQU-2-F4.5 %Clearing point [°C]:85APUQU-3-F4.5 %Δn [589 nm, 20°C]:0.1250PGUQU-3-F4.5 %n e [589 nm, 20°C]:1.6150PGUQU-4-F4.5 %n o [589 nm, 20°C]:1.4900PGUQU-5-F3.0 %Δε [1 kHz, 20°C]:5.9PPGU-3-F0.5 %ε ∥ [1 kHz, 20°C]:9.0CCP-V-17.0 %ε ⊥ [1 kHz, 20°C]:3.2PGP-1-2V6.0 %γ 1 [mPa s, 20°C]:66PGP-2-2V8.0 %K 1 [pN, 20°C]:14.5PGP-3-2V2.0 %K 3 [pN, 20°C]:15.3CC-3-V43.5 %LTS bulk [h, -20°C]:1000CC-3-V16.5 %PP-1-2V13.5 %CLB-3-T2.0 %Σ100.0 % Mixture Example 8

[0157] A nematic liquid-crystal medium M-8 consisting of the compounds indicated in the following table is prepared APUQU-2-F4.5 %Clearing point [°C]:85.5APUQU-3-F4.0 %Δn [589 nm, 20°C]:0.1251PGUQU-3-F4.0 %n e [589 nm, 20°C]:1.6131PGUQU-4-F4.5 %n o [589 nm, 20°C]:1.4880PGUQU-5-F3.0 %Δε [1 kHz, 20°C]:5.8PPGU-3-F0.5 %ε ∥ [1 kHz, 20°C]:9.5CCP-V-14.0 %ε ⊥ [1 kHz, 20°C]:3.6PGP-1-2V4.5 %γ 1 [mPa s, 20°C]:69PGP-2-2V6.0 %K 1 [pN, 20°C]:15.1PGP-3-2V2.5 %K 3 [pN, 20°C]:14.9CC-3-V44.0 %LTS bulk [h, -20°C]:1000CC-3-V16.5 %PP-1-2V12.0 %LB(S)-3-OT6.0 %LB-3-T2.0 %CLB-3-T2.0 %Σ100.0 %

[0158] The mixture is suitable for use in an FFS display.

Claims

1. A compound of formula I in which W denotes O or S R denotes H, an alkyl radical having 1 to 15 C atoms, wherein one or more CH2 groups in these radicals may each be replaced, independently of one another, by -C≡C- , -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO- in such a way that O atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen, A1 independently is trans-1,4-cyclohexylene or 1,4-cyclo-hexenylene, in which one or more non-adjacent CH2 groups may be replaced by -O- and in which one or more H atoms may be replaced by F, A2 independently is trans-1,4-cyclohexylene or 1,4-cyclo-hexenylene, and in which one or more H atoms may be replaced by F, Z independently denotes a single bond, -CF2O- , -OCF2-, - CH2CH2-, -CF2CF2-, -C(O)O-, -OC(O)-, -CH2O- , -OCH2-, -CF=CF-, -CH=CH- or -C≡C-, and X denotes F, Cl, CN, NCS, fluorinated alkyl, fluorinated alkoxy, fluorinated alkenyl or fluorinated alkenyloxy each having up to 5 C atoms.

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

3. The compound according to claim 1 or 2, wherein Z denotes a single bond.

4. The compound according to one or more of claims 1 to 3, wherein W denotes O.

5. The compound according to one or more of claims 1 to 3, wherein W denotes S.

6. The compound according to one or more of claims 1 to 5 selected from the following sub-formulae: in which R, A1 and A2 have the meanings given in claim 1.

7. The compound according to one or more of claims 1 to 6, wherein ring A1 denotes a trans-1,4-cyclohexylene ring.

8. The compound according to one or more of claims 1 to 7, wherein ring A2 denotes a trans-1,4-cyclohexenylen ring.

9. The compound according to one or more of claims 1 to 7, wherein ring A2 denotes a trans-1,4-cyclohexylene ring.

10. The compound according to one or more of claims 1 to 6 selected from the following formulae in which R and X are defined as in claim 1.

11. The compound according to one or more of claims 1 to 10, wherein W is O and X is CF3 or OCF3, or W is S and X is F, CF3 or OCF3.

12. A process for the preparation of a compound of formula I of claim 1, characterised in that a compound of formula P or P' wherein the groups are defined as in claim 1, is subjected to a ring closing reaction leading to a compound of formula I as of claim 1.

13. A liquid-crystalline medium comprising one or more compounds of formula I according to one or more of claims 1 to 11.

14. A liquid-crystalline medium according to claim 13, comprising one or more compounds selected from the group of compounds of formulae II and III: in which R2 denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms and preferably alkyl or alkenyl, on each appearance, independently of one another, denote L21 and L22 denote H or F, X2 denotes 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, R3 denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, L31 and L32 independently of one another, denote H or F, X3 denotes halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, Z3 denotes -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, and n is 0, 1, 2 or 3.

15. Use of a compound according to one or more of claims 1 to 11 in liquid-crystalline media.

16. Electro-optical display element containing a liquid-crystalline medium according to claim 13 or 14.