LIQUID CRYSTAL COMPOUNDS

Abstract

The invention relates to compounds of the formula I,

##STR00001##

in which
R, A, n, L.sup.1, L.sup.2, L.sup.3 and X have the meanings given in Claim 1, to a process for their preparation, and to liquid-crystalline media comprising at least one compound of the formula I and electro-optical displays containing a liquid-crystalline medium of this type.

Claims

1. Compounds of the formula I, ##STR00017## in which X denotes CN, CF.sub.3, SCN, —C≡C—CF.sub.3 or —CH═CH—CF.sub.3, R denotes a halogenated or unsubstituted alkyl radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by —C≡C— or —CH═CH—, A in each case independently denotes 1,4-phenylene, in which one or two CH groups may be replaced by N and in which, in addition, one or more H atoms may be replaced by Cl, F, CN, methyl, methoxy or a mono- or polyfluorinated methyl or methoxy group, or 2,6-naphthyl, in which, in addition, one or more H atoms may be replaced by Cl, F, CN, methyl, methoxy or a mono- or polyfluorinated methyl or methoxy group, L.sup.1, L.sup.2 and L.sup.3, independently of one another, denote H or F, and n denotes 0, 1, 2 or 3.

2. Compounds according to claim 1, characterised in that L.sup.3 denotes F.

3. Compounds according to claim 1, characterised in that R denotes alkyl or alkenyl having up to 8 carbon atoms.

4. Compounds according to claim 1, characterised in that X denotes CF.sub.3.

5. Compounds according to claim 1, characterised in that L.sup.1 denotes fluorine.

6. Compounds according to claim 1, characterised in that L.sup.1 denotes fluorine and L.sup.2 denotes H.

7. Compounds according to claim 1, characterized in that L.sup.1 and L.sup.2 denote F.

8. Compounds according to claim 1, selected from the following formulae, ##STR00018## in which R has the meanings given for formula I.

9. Compounds according to claim 1, characterised in that n=0.

10. Process for the preparation of compounds of the formula I according to claim 1, including a process step in which a boronic acid of the formula IIA or an open-chain or cyclic boron acid ester of the formula IIB ##STR00019## in which X, L.sup.1 and L.sup.2 are defined as for formula I, and R.sup.3, R.sup.4 denote an alkyl having 1-12 C atoms or R.sup.3+R.sup.4 together also denote an alkylene, or denote 1,2-phenylene, where phenylene, R.sup.3, R.sup.4 and R.sup.3+R.sup.4 may also be substituted, is reacted with a compound of the formula III ##STR00020## in which R, A, L.sup.3 and n independently are defined as for formula I and Hal denotes O(SO.sub.2)CF.sub.3, Cl, Br or I, in the presence of a transition-metal catalyst.

11. (canceled)

12. Liquid-crystalline medium comprising at least two mesogenic compounds, characterised in that it comprises at least one compound of the formula I according to claim 1.

13. (canceled)

14. Electro-optical liquid-crystal display containing a liquid-crystalline medium according to claim 12.

Description

EXAMPLE 1

Step 1

[0084] ##STR00011##

[0085] The phenol 1, ethanol and triphenylphosphine (1 eq. each) are dissolved in THF, and the diazo compound 2 is added at a temperature below 30° C. The reaction mixture is subsequently stirred at room temperature for 12 h. The solvent is removed, and the residue is stirred with a mixture of toluene and n-heptane (9/1). The solid which forms is separated off, and the filtrate is passed through silica gel (toluene/n-heptane (9/1)). Yield 85%.

Step 2: 4′-Ethoxy-3,5,2′-4-trifluoromethylbiphenyl

[0086] ##STR00012##

[0087] THF, the catalyst (0.01 eq.) and a solution of 2 eq. of sodium metaborate tetrahydrate in water are added to the ether 3 and the boronic acid 4 (1 eq. each). After addition of hydrazine hydroxide (0.03 eq.), the mixture is heated under reflux for 4 h. MTB ether is subsequently added to the cooled reaction mixture. The separated-off organic phase is washed with water, dried over sodium sulfate and evaporated. The residue is passed though silica gel (chlorobutane). Yield: 70%.

[0088] C 45 l

[0089] Δε=28

[0090] Δn=0.096

[0091] γ.sub.1=33 mPa.Math.s

[0092] The following are prepared analogously or comparably:

##STR00013## ##STR00014##

FURTHER EXAMPLES

[0093] ##STR00015##

TABLE-US-00001 TABLE 1 Illustrative compounds and measurement values γ.sub.1 No. R L.sup.3 X Δε Δn [mPas] Phase 2 CH.sub.3 F CF.sub.3 25 0.086 27 C 49 I 3 C.sub.2H.sub.5 H CF.sub.3 25 0.137 38 C 54 I 4 C.sub.2H.sub.5 F CF.sub.3 28 0.096 33 C 45 I 5 C.sub.3H.sub.7 H CF.sub.3 24 0.116 37 C46 I 6 C.sub.3H.sub.7 F CF.sub.3 26 0.087 35 Tg −66 C 27 I 7 C.sub.4H.sub.9 H CF.sub.3 22 0.119 45 C 48 I 8 C.sub.4H.sub.9 F CF.sub.3 24 0.079 42 C 21 I 9 CH.sub.2CH═CH.sub.2 H CF.sub.3 20 0.120 35 C 27 I 10 CH.sub.2CH═CH.sub.2 F CF.sub.3 23 0.104 31 C 22 I 11 CH.sub.2CH═CHCH.sub.3 H CF.sub.3 24 0.147 58 C 76 I 12 CH.sub.2CH═CHCH.sub.3 F CF.sub.3 28 0.1221 52 C 35 I

EXAMPLE 13

[0094] ##STR00016##

[0095] C 100 SmA (94) l

[0096] Δε=28

[0097] Δn=0.234

[0098] γ.sub.1=401 mPa.Math.s

[0099] Further embodiments and variants of the invention in accordance with the description also arise from the following claims or from combinations of more than one of these claims.