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. A compound of formula I1, I2 or I4 ##STR00017## in which X denotes CF.sub.3, —C≡C—CF.sub.3 or —CH═CH—CF.sub.3, and R denotes an unsubstituted alkyl radical having 1 to 15 C atoms, in which one or more CH.sub.2 groups are optionally each replaced, independently of one another, by —C≡C— or —CH═CH—.

2. The compound according to claim 1, wherein R denotes alkyl or alkenyl having up to 8 carbon atoms.

3. The compound according to claim 1, wherein X denotes CF.sub.3.

4. A liquid-crystalline medium comprising at least two mesogenic compounds, one of which is at least one compound of formula I1, I2 or I4 according to claim 1.

5. An electro-optical liquid-crystal display containing a liquid-crystalline medium according to claim 4.

6. The compound according to claim 1, which is a compound of formula I1.

7. The compound according to claim 1, which is a compound of formula I2.

8. The compound according to claim 1, which is a compound of formula I4.

9. A liquid-crystalline medium comprising at least two mesogenic compounds, one of which is at least one compound of formula I1 according to claim 1.

10. A liquid-crystalline medium comprising at least two mesogenic compounds, one of which is at least one compound of formula I2 according to claim 1.

11. A liquid-crystalline medium comprising at least two mesogenic compounds, one of which is at least one compound of formula I3 or I4 ##STR00018## in which X denotes CF.sub.3, —C≡C—CF.sub.3 or —CH═CH—CF.sub.3, and R denotes a halogenated or unsubstituted alkyl radical having 1 to 15 C atoms, in which one or more CH.sub.2 groups are optionally each replaced, independently of one another, by —C≡C— or —CH═CH—.

12. A liquid-crystalline medium comprising at least two mesogenic compounds, one of which is at least one compound of formula I3 according to claim 11.

13. A liquid-crystalline medium comprising at least two mesogenic compounds, one of which is at least one compound of formula I4 according to claim 11.

14. A liquid-crystalline medium comprising at least two mesogenic compounds, one of which is at least one compound of formula I1 according to claim 1, in which the at least one compound of formula I1 is present at 5 to 30%.

15. A liquid-crystalline medium comprising at least two mesogenic compounds, one of which is at least one compound of formula I2 according to claim 1, in which the at least one compound of formula I2 is present at 5 to 30%.

16. A liquid-crystalline medium comprising at least two mesogenic compounds, one of which is at least one compound of formula I3 according to claim 11, in which the at least one compound of formula I3 is present at 5 to 30%.

17. A liquid-crystalline medium comprising at least two mesogenic compounds, one of which is at least one compound of formula I4 according to claim 11, in which the at least one compound of formula I4 is present at 5 to 30%.

18. A process for preparing a compound of formula I1, I2 or I4 according to claim 1, comprising reacting a boronic acid of formula IIA or an open-chain or cyclic boron acid ester of formula IIB ##STR00019## in which X denotes CF.sub.3, —C≡C—CF.sub.3 or —CH═CH—CF.sub.3, L.sup.1, L.sup.2 independently of one another, denote H or F, and R.sup.3, R.sup.4 denote an alkyl having 1-12 C atoms or R.sup.3+R.sup.4 together denote an alkylene, or denote 1,2-phenylene, where phenylene, R.sup.3, R.sup.4 and R.sup.3+R.sup.4 are optionally substituted, with a compound of formula III ##STR00020## in which R denotes an unsubstituted alkyl radical having 1 to 15 C atoms, in which one or more CH.sub.2 groups are optionally each 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 are optionally replaced by N and in which one or more H atoms are optionally replaced by Cl, F, CN, methyl, methoxy or a mono- or polyfluorinated methyl or methoxy group, or 2,6-naphthyl, in which one or more H atoms are optionally replaced by Cl, F, CN, methyl, methoxy or a mono- or polyfluorinated methyl or methoxy group, n is 0, L.sup.3 denotes H or F, and Hal denotes O(SO.sub.2)CF.sub.3, Cl, Br or I, in the presence of a transition-metal catalyst.

Description

EXAMPLE 1

Step 1

(1) ##STR00011##

(2) 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

(3) ##STR00012##

(4) 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%.

(5) C 45 l

(6) Δε=28

(7) Δn=0.096

(8) γ.sub.1=33 mPa.Math.s

(9) The following are prepared analogously or comparably:

(10) ##STR00013## ##STR00014##

FURTHER EXAMPLES

(11) ##STR00015##

(12) 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

(13) ##STR00016##

(14) C 100 SmA (94) l

(15) Δε=28

(16) Δn=0.234

(17) γ.sub.1=401 mPa.Math.s

(18) 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.