WO1990014404A1

WO1990014404A1 - Trifluorotoluol compounds and liquid crystalline medium

Info

Publication number: WO1990014404A1
Application number: PCT/EP1990/000799
Authority: WO
Inventors: Hans-Adolf Kurmeier; Reinhard Hittich; Eike Poetsch; Volker Meyer; Herbert Plach; David Coates
Original assignee: MERCK Patent Gesellschaft mit beschränkter Haftung
Priority date: 1989-05-26
Filing date: 1990-05-18
Publication date: 1990-11-29
Also published as: JPH04500682A; EP0427829A1

Abstract

Trifluorotoluol compounds of formula (I), where n is a number between 1 and 12 and Q is (a), (b), (c), (d) or (e), are suitable as components of liquid crystalline media.

Description

Trifluorotoluene compounds

and liquid crystalline medium

The invention relates to trifluorotoluene compounds

Formula I C

wherein n is 1 to 12 and Q r

ö

means. The invention further relates to the use of these compounds as components of liquid-crystalline media and liquid-crystal and electro-optical display elements which contain the liquid-crystalline media according to the invention.

The compounds of the formula I can be used as components of liquid-crystalline media, in particular for displays which are based on the principle of the twisted cell, including more highly twisted cells, the guest-host effect, the effect of the deformation of aligned phases or the effect of dynamic scattering . The invention was based on the object of finding new stable liquid-crystalline or mesogenic compounds which are suitable as components of liquid-crystalline media and in particular at the same time have a comparatively low viscosity and a relatively high dielectric anisotropy.

It has now been found that compounds of the formula I are particularly suitable as components of liquid-crystalline media. In particular, they have comparatively low viscosities. With their help, stable liquid-crystalline media with a wide mesophase range, very good low-temperature behavior, very high electrical resistance and advantageous values for the optical and dielectric anisotropy can be obtained. Derivatives of 4'-hydroxy-4-trifluoromethylbiphenyl with liquid crystalline properties are already known (P. Le Barny et al., Mol. Cryst. Liq. Cryst., 1985,

Vol. 127, pp. 413-429). However, these compounds have a strongly smectogenic character and are less suitable for many practical applications.

Recently 4- (2- (4-trans-alkylcyclohexyl) phenyl) ethyl) p-benzotrifluoride (JC Liong et al., Mol. Cryst. Liq. Cryst. 1989, Vol. 167, pp. 253-258 ) described.

These compounds are either isotropic or have higher-order smectic (S ₊ ) phases, which makes them appear unsuitable for practical applications.

With the provision of compounds of the formula I, the range of liquid-crystalline substances which are suitable for the production of liquid-crystalline mixtures from various application points of view is also very broadly widened. The compounds of formula I have a wide range of uses. Depending on the choice of the substituents, these compounds can serve as base materials from which liquid-crystalline media are predominantly composed; However, it is also possible to add compounds of the formula I to liquid-crystalline base materials from other classes of compounds in order, for example, to influence the dielectric and / or optical anisotropy of such a dielectric and / or to optimize its threshold voltage and / or its viscosity.

The compounds of the formula I are colorless in the pure state and form liquid-crystalline mesophases in a temperature range which is favorable for electro-optical use. They are stable chemically, thermally and against light.

The invention thus relates to the compounds of the formula I and the use of these compounds as components of liquid-crystalline media. The invention further relates to liquid-crystalline media containing at least one compound of the formula I and liquid-crystal display elements, in particular electro-optical display elements, which contain such media. The compounds of the formula I accordingly comprise compounds of the sub-formulas Ia-Ie:

<

>>

Ia, Ib and Ic, but especially Ic, are particularly preferred.

The radical C _n H _{2n + 1} can be straight-chain or branched.

It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and accordingly preferably means ethyl, propyl,

Butyl, pentyl, hexyl, heptyl, furthermore methyl, octyl, nonyl, decyl, uhdecyl, dodecyl.

Compounds of the formula I with branched radicals C _n H _{2n + 1} can occasionally be of importance because of their better solubility in the customary liquid-crystalline base materials, but in particular as chiral dopants if they are optically active. Smectic compounds of this type are suitable as components for ferroelectric materials. Compounds of the formula I with S _A phases are suitable, for example, for thermally addressed displays.

Branched groups of this type usually contain no more than one chain branch. Preferred branched radicals are isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2- Propylpentyl. Formula I includes both the racemates of these compounds and the optical antipodes and mixtures thereof.

Among these compounds of the formula I and the sub-formulas, preference is given to those in which at least one of the radicals contained therein has one of the preferred meanings indicated.

The compounds of the formula I are prepared by methods known per se, as described in the literature (e.g. in the standard works such as Houben-Weyl, Methods of Organic Chemistry, Georg-Thieme-Verlag, Stuttgart Bd IX,

P. 867 ff.) Are described, namely under reaction conditions which are known and suitable for the reactions mentioned. Use can also be made of variants which are known per se and are not mentioned here in detail.

The compounds of the formula I according to the invention are preferably prepared by coupling corresponding zinc organyls with p-bromotrifluorotoluene with transition metal catalysis. The process conditions known per se can be found in WO 88/02357 or the article

E. Poetsch, contacts (Darmstadt) 1988 (2), pp. 15-28.

The compounds of the formula I according to the invention are further preferably prepared by treating the benzoic acids corresponding to the formula I with dialkylamino sulfur trifluorides, for example DAST (diethylamino sulfur trifluoride) [W.J. Middleton, J. Org. Chem. 40 (1975), 547] or sulfur tetrafluoride [A. Haus, M. Spitzer, M. Lieb, Chem. Ber. 121 (1988) 1329] according to the scheme

implements. The benzoic acids corresponding to formula I are corresponding to formula I, for example by hydrolysis

Carbonitrile producible.

If desired, starting materials can also be formed in situ in such a way that they are not isolated from the reaction mixture, but instead are immediately reacted further to give the compounds of the formula I.

In addition to one or more compounds according to the invention, the liquid-crystalline media according to the invention preferably contain 2 to 40, in particular 4 to 30, components as further constituents. These media very particularly preferably contain 7 to 25 components in addition to one or more compounds according to the invention. These further constituents are preferably selected from nematic or nematogenic (monotropic or isotropic) substances, in particular substances from the classes of

Azoxybenzenes, benzylidene anilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl cyclohexane-carboxylic acid esters, phenyl or cyclohexyl esters of cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, cyclohexyl phenyl ester of benzoic acid, of cyclohexanecarboxylic acid, or cyclohexylcyclohexane carboxylic acid, phenylcyclohexane, cyclohexylbiphenyls, phenylcyclohexylcyclohexane, cyclohexylcyclohexane, cyclohexylcyclohexene, cyclohexylcyclohexylcyclohexene, 1,4-biscyclohexylbenzenes, 4,4'-bis-cyclohexylcyclophenyl, phenyl or cyclylhexylpyrenyl, phenyl or cyclylhexylpyphenyl, phenyl or cyclylhexylpyridyl, phenyl or cyclohexyl cyclophenyl Cyclohexyl-dioxanes, phenyl- or cyclohexyl-1,3-dithiane, 1,2-diphenylethanes, 1,2-dicyclohexylethanes, 1-phenyl-2-cyclohexylethanes, 1-cyclohexyl-2- (4-phenyl-cyclohexyl) ethanes , 1-cyclohexyl-2-biphenylylethane, 1-phenyl-2-cyclohexylphenylethane, optionally halogenated stilbene,

Benzylphenyl ether, tolanes and substituted cinnamic acids. The 1,4-phenylene groups in these compounds can also be fluorinated.

The most important compounds which are suitable as further constituents of media according to the invention can be characterized by the formulas 1, 2, 3, 4 and 5:

R'-L-E-R "1

R'-L-COO-E-R "2

R'-L-OOC-E-R "3

R'-L-CH ₂ CH ₂ -ER "4

R'-L-C≡C-E-R "5

In formulas 1, 2, 3, 4 and 5, L and E, which may be the same or different, each independently represent a bivalent radical from the group consisting of -Phe-,

-Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe- and -G-Cyc- as well as their mirror images formed group, whereby Phe unsubstituted or by

Fluorine-substituted 1,4-phenylene, Cyc trans-l, 4-cyclohexylene or 1,4-cyclohexenylene, pyr pyrimidine-2, 5-diyl or pyridine-2, 5-diyl, diol, 3-dioxane-2 , 5-diyl and G

2- (trans-1,4-cyclohexyl) ethyl, pyrimidine-2,5-diyl,

Pyridine-2, 5-diyl or -1,3-dioxane-2, 5-diyl mean.

Preferably one of the radicals L and E is Cyc, Phe or Pyr. E is preferably Cyc, Phe or Phe-Cyc. The media according to the invention preferably contain one or more components selected from the compounds of the formulas 1, 2, 3, 4 and 5, in which L and E are selected from the group Cyc, Phe and Pyr and at the same time one or more components selected from the compounds of Formulas 1, 2, 3, 4 and 5, in which one of the radicals L and E is selected from the group Cyc, Phe and Pyr and the other radical is selected from the group -Phe-Phe-, -Phe-Cyc-, - Cyc-Cyc-, -G-Phe- and -G-Cyc-, and given- if one or more components selected from the compounds of formulas 1, 2, 3, 4 and 5, wherein the radicals L and E are selected from the group -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-. In the compounds of partial formulas 1a, 2a, 3a, 4a and 5a, R 'and R "each independently represent alkyl, alkenyl, alkoxy, alkenyloxy or alkanoyloxy having up to 8 carbon atoms. In most of these compounds, R' and R" are different from one another different, one of these radicals is usually alkyl or alkenyl. In the compounds of partial formulas 1b, 2b, 3b, 4b and 5b, R "means -CN, -CF ₃ , F, Cl or -NCS; R has the meaning given for the compounds of partial formulas 1a to 5a and is preferably alkyl or Alkenyl, but also other variants of the proposed substituents in the compounds of the formulas 1, 2, 3, 4 and 5 are common. Many such substances or mixtures thereof are commercially available. All of these substances are obtainable by methods known from the literature or in analogy thereto .

In addition to components from the group of compounds 1a, 2a, 3a, 4a and 5a (group 1), the media according to the invention preferably also contain components from the group of compounds 1b, 2b, 3b, 4b and 5b (group 2), the proportions of which are preferably as follows are:

Group 1: 20 to 90%, in particular 30 to 90%,

Group 2: 10 to 80%, in particular 10 to 50%, the sum of the proportions of the compounds according to the invention and of the compounds from groups 1 and 2 giving up to 100%. The media according to the invention preferably contain

1 to 40%, particularly preferably 5 to 30%, of compounds according to the invention. Also preferred are media containing more than 40%, in particular 45 to 90%, of compounds according to the invention. The media preferably contain three, four or five compounds according to the invention.

The media according to the invention are produced in a conventional manner. As a rule, the components are dissolved in one another, advantageously at elevated temperature. By means of suitable additives, the liquid-crystalline phases according to the invention can be modified so that they can be used in all types of liquid-crystal display elements which have hitherto become known. Such additives 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 added to produce colored guest-host systems or substances to change the dielectric anisotropy, the viscosity and / or the orientation of the nematic phases.

The following examples are intended to illustrate the invention without limiting it. Above and below mean

Potency data percent by weight. All temperatures are given in degrees Celsius. Mp. Means melting point Kp = clearing point. Furthermore, K = crystalline state, N = nematic phase, S = smectic phase and I = isotropic phase. The data between these symbols represent the transition temperatures. Δn means optical anisotropy (589 nm, 20 ° C) and the viscosity (mm ² / sec) was determined at 20 ° C. "Customary work-up" means: water is optionally added, extracted with methylene chloride, diethyl ether or toluene, the mixture is separated off, the organic phase is dried, evaporated and the product is purified by distillation under reduced pressure or crystallization and / or chromatography. The following abbreviations are used:

DAST Diethylaminosulfur trifluoride

DCC dicyclohexylcarbodiimide

DDQ dichlorodicyanobenzoquinone

DIBALH diisobutyl aluminum hydride

KOT potassium tertiary butanolate

THF tetrahydrofuran

pTSOH p-toluenesulfonic acid

Example 1 11.2 g of anhydrous zinc bromide are added at about 0 ° to a Grignard solution prepared from 20 g of 4-n-propylbromobenzene and 2.4 g of magnesium shavings in 100 ml of THF

25 ml of THF added dropwise. After stirring for 2 hours, a mixture of 22.5 g of 4-bromotrifluorotoluene, 1.5 g of [(diphenylphosphine) ferrocenyl] palladium (II) chloride and 25 ml of THF is added dropwise, the mixture is stirred for 24 hours at room temperature and in 100 ml of saturated ammonium chloride solution poured. After the usual work-up, one obtains

4- (4-n-propylphenyl) trifluorotoluene, mp. 97 ° C, Δε = 14.2, viscosity η (20 ° C) = 6 mm ² / s.

Example 2

An anhydrous, vigorously stirred mixture of 40.3 g of 4 '- (4-trans-pentylcyclohexyl) -2' -fluoro-4-bromobiphenyl, 38.0 g of copper (I) iodide and 300 ml of 1-methyl 2-pyrrolidone, which also contains 0, 33 mol of ice, trans, trans-1, 5, 9-cyclododecatriene (as a carbene scavenger), is under Nitrogen at 160 ° C. over the course of 4 hours with an anhydrous solution of 60.0 g of sodium trifluoroacetate in 350 ml of 1-methyl-2-pyrrolidone. The reaction mixture is then stirred at 160 ° C. for a further 3.5 hours. After cooling, the NMP is distilled off in vacuo. The evaporation residue, which is still approx. 80 ° C, is stirred with 500 ml of toluene and 400 ml of saturated saline. The copper salts are filtered off with suction, washed with toluene, the organic phase of the filtrate is separated off, washed with brine, dried over sodium sulfate and evaporated in vacuo. The evaporation residue is dissolved in dichloromethane, applied to silica gel and purified by column chromatography (silica gel / petroleum spirit 40-80 °). After recrystallization from isopropyl alcohol, 4- (2-fluoro-4- (trans-4-pentylcyclohexyl) phenyl) trifluorotoluene is obtained; K 78.7 N (74.2), Δε = 14.9, η (20 ° C) = 37 mm ² / s

Examples 3 to 40 The following are analogous to Example 1 or Example 2

Connections established:

(3) 4- (4-methylphenyl) trifluorotoluene

(4) 4- (4-ethylphenyl) trifluorotoluene

(5) 4- (4-n-Butylphenyl) trifluorotoluene

(6) 4- (4-n-pentylphenyl) trifluorotoluene

(7) 4- (4-n-Hexylphenyl) trifluorotoluene

(8) 4- (4-n-heptylphenyl) trifluorotoluene

(9) 4- (4-n-octylphenyl) trifluorotoluene

(10) 4- (4-n-Nonylphenyl) trifluorotoluene

(11) 4- (4-n-Decylphenyl) trifluorotoluene

(12) 4- (4-n-Undecylphenyl) trifluorotoluene

(13 4- (4-n-dodecylphenyl) trifluorotoluene (14) 4- (2-fluoro-4-methylphenyl) trifluorotoluene

(15) 4- (2-fluoro-4-ethylphenyl) trifluorotoluene

(16) 4- (2-Fluoro-4-n-propylphenyl) trifluorotoluene

(17) 4- (2-Fluoro-4-n-butylphenyl) trifluorotoluene

(18) 4- (2-Fluoro-4-n-pentylphenyl) trifluorotoluene

Mp 59 ° C, Δε = 16.1, η (20 ° C) = 7 mm ² / s

(19) 4- (2-Fluoro-4-n-hexylphenyl) trifluorotoluene

(20) 4- (2-Fluoro-4-n-heptylphenyl) trifluorotoluene

(21) 4- (2-Fluoro-4-n-octylphenyl) trifluorotoluene

(22) 4- (2-Fluoro-4-n-nonylphenyl) trifluorotoluene

(23) 4- (2-Fluoro-4-n-decylphenyl) trifluorotoluene

(24) 4- (2-Fluoro-4-n-undecylphenyl) trifluorotoluene

(25) 4- (2-Fluoro-4-n-dodecylphenyl) trifluorotoluene

(26) 4- (2-Fluoro-4- (trans-4-methylcyclohexyl) phenyl) trifluorotoluene

(27) 4- (2-Fluoro-4- (trans-4-ethylcyclohexyl) phenyl) trifluorotoluene

(28) 4- (2-Fluoro-4- (trans-4-n-propylcyclohexyl) phenyl) trifluorotoluene

(29) 4- (2-Fluoro-4- (trans-4-n-butylcyclohexyl) phenyl) trifluorotoluene

(30) 4- (2-Fluoro-4- (trans-4-n-hexylcyclohexyl) phenyl) trifluorotoluene

(31) 4- (2-Fluoro-4- (trans-4-n-heptylcyclohexyl) phenyl) trifluorotoluene

(32) 4- (2-Fluoro-4- (trans-4-n-octylcyclohexyl) phenyl) trifluorotoluene

(33) 4- (2-Fluoro-4- (trans-4-n-nonylcyclohexyl) phenyl) trifluorotoluene

(34) 4- (2-Fluoro-4- (trans-4-n-decylylcyclohexyl) phenyl) trifluorotoluene

(35) 4- (2-Fluoro-4- (trans-4-n-undecylcyclohexyl) phenyl) trifluorotoluene

(36) 4- (2-Fluoro-4- (trans-4-n-dodecylcyclohexyl) phenyl) trifluorotoluene (37) 4- (4'-Propylbiphenyl-3-fluoro-4-yl) trifluorotoluene

(38) 4- (4'-pentylbiphenyl-3-fluoro-4-yl) trifluorotoluene,

(39) 4- [p- (trans-4-Propylcyclohexyl) ethyl phenyl] trifluorotoluene

(40) 4- [p- (trans-4-Pentylcyclohexyl) ethyl phenyl] trifluorotoluene

Claims

1. Trifluorotoluene compounds of the formula I.

wherein n is 1 to 12 and Q

means.

2. Use of compounds of the formula I as components of liquid-crystalline media.

3. Liquid-crystalline medium with at least two liquid-crystalline components, characterized in that it contains at least one compound of the formula I.

4. Liquid crystal display element, characterized in that it contains a liquid crystalline medium according to claim 3.

5. Electro-optical display element, characterized in that it contains a liquid-crystalline medium as claimed in claim 3 as a dielectric.