DE19531135A1 - Bis:tri:fluoro-methyl-dioxane(s) combining low viscosity with high dielectric anisotropy - Google Patents

Abstract

Bis(trifluoromethyl)-dioxanes (I) contg. a unit (-Dio(CF3)2) of formula (A) are new. Also claimed is a liquid crystalline (LC) medium contg. >= 2 LC cpds., including cpd(s). (I).

Description

The invention relates to bis (trifluoromethyl) -dioxanes containing a structure element of general formula I.

The invention further relates to a process for the preparation of bis (tri fluoromethyl) -dioxanes, in this process by ongoing intermediate products and the use of bis (trifluoromethyl) -dioxanes as Components of liquid-crystalline media as well as liquid crystal and electro optical display elements comprising the liquid-crystalline Media included.

The compound of the formula I can be used as components of liquid-crystalline Media are used, especially for displays based on the principle the twisted cell, the guest-host effect, the effect of deformation upright phases or the effect of dynamic dispersion based.

The invention was based on the object new stable liquid crystalline or to find mesogenic compounds that are liquid as components crystalline media are suitable and in particular at the same time a have relatively low viscosity and a relatively high dielectric anisotropy.

It has now been found that compounds of the formula I as components liquid-crystalline media are eminently suitable. In particular They have comparatively low viscosities. With their help can be stable liquid-crystalline media with a broad mesophase range and before partial values for the optical and dielectric anisotropy. These media also have a very good low temperature behavior.  

Liquid crystalline dioxane derivatives have long been known.

From EP 0 447 565 z. B. 1,3-dioxanes of the formula

and their use in STN blends.

In U.S. Pat. 5,322,638 are z. B. 1,3-dioxanes of the formula

where R¹ is an alkenyl radical, A² is a 1,4-phenyl ring or trans-1,4-cyclo hexene ring, X¹ is F or Cl and X² is fluorine.

From EP 0 400 861 z. B. phenyldioxanes of the formula

known.

With regard to the various applications of 1,3-dioxanes with high Δε, however, it was desirable to have other high-level compounds Nematogeneity available to the respective appl have tailor-made properties.  

With the provision of compounds of bis (trifluoromethyl) -dioxanes is also quite generally the range of liquid crystalline Substances that differ in various application Aspects are suitable for the preparation of liquid-crystalline mixtures, considerably widened.

The compounds of the formula I have a broad application Area. Depending on the choice of substituents, these may Compounds serve as base materials from which liquid crystalline Media are composed for the most part; but it can also compounds of formula I liquid-crystalline base materials be added to other classes of compounds, for example, the dielectric and / or optical anisotropy of such a dielectric to influence and / or the threshold voltage and / or to optimize its viscosity. The compounds of the invention are especially characterized by their broad mesophase range good viscosity properties and Δε values.

The compounds of the formula I are colorless in the pure state and form liquid-crystalline mesophases in one for electro-optical use conveniently located temperature range. Chemical, thermal and against Light are they stable.

The invention thus provides the bis (trifluoromethyl) -dioxanes of Formula I, a process for preparing these compounds and the this process, new intermediates and the Use of these compounds as components of liquid-crystalline Media. The invention furthermore relates to liquid-crystalline media containing at least bis (trifluoromethyl) -dioxanes of the formula I and liquid crystal display elements, in particular electro-optical Display elements containing such media.  

Preferred bis (trifluoromethyl) -dioxanes are those of the formula II

wherein
R¹ is an unsubstituted or substituted by CN or at least one halogen alkyl or alkenyl radical having up to 18 carbon atoms, wherein one or more non-adjacent CH₂ groups by a radical selected from the group -O-, -S-, - CO, -O-CO-, -CO-O- and -C≡C- may be replaced,
Each A¹ independently

• a) a 1,4-phenylene radical, wherein one or two CH groups can be replaced by N,
• b) a cyclohexenylene or a 1,4-cyclohexylene radical, wherein one or two non-adjacent CH₂ groups -O- or -S- may be replaced,
• c) a piperidine-1,4-diyl, a 1,4-bicyclo [2,2,2] octylene or a naphthalene-2,6-diyl radical

where the radicals a) and b) may be substituted one or more times by halogen atoms, cyano and / or methyl groups,
Each Z¹ independently represents -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CH₂CH₂-, -CH = CH-, -C≡C- or a single bond
n 1, 2 or 3
in particular bis (trifluoromethyl) -dioxanes according to claim 1 or 2 containing a structural element of the formula Ia

In the compounds of formula II, R 1 is preferably straight chain alkyl or alkenyl with 1-5 C atoms. The alkenyl radical is preferably 1E-alkenyl, 3E-alkenyl or 4-alkenyl.

If R¹ in the compounds of the formula II is an alkyl radical and / or a Alkoxy, it may be straight or branched. Preferably, it is straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and therefore preferably denotes 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.

Oxaalkyl is preferably straight-chain 2-oxapropyl (= methoxy methyl), 2- (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

If R¹ is an alkyl radical in which a CH₂ group by -CH = CH- is replaced, it may be straight-chain or branched. It is preferably straight-chain and has 2 to 10 C atoms. He means Accordingly, especially vinyl, prop-1, or prop-2-enyl, but-1, 2 or But-3-enyl, pent-1, 2-, 3- or pent-4-enyl, hex-1, 2-, 3-, 4- or Hex-5-enyl, hept-1, 2-, 3-, 4-, 5- or hept-6-enyl, oct-1, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-, 3-, 4-, 5-, 6-, 7- or non-8-enyl, Dec-1, 2-, 3-, 4-, 5-, 6-, 7-, 8- or dec-9-enyl.  

If R¹ is an alkyl radical in which a CH₂ group by -O- and one replaced by -CO-, these are preferably adjacent. Thus These include an acyloxy group -CO-O- or an oxycar bonyl group -O-CO-. Preferably, these are straight-chain and have 2 up to 6 C atoms.

They therefore mean especially acetyloxy, propionyloxy, butyryloxy, Pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, Butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyl oxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, Butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxy carbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2- (methoxycarbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propoxycarbonyl) ethyl, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl) propyl, 4- (methoxy carbonyl) -butyl.

If R¹ is an alkyl or C₁ to C durch alkyl substituted by C₁ to C CF alkyl Alkenyl means, this radical is preferably straight-chain and the Substitution by CN or CF₃ in the e-position.

If R 1 is an alkyl radical which is at least monosubstituted by halogen, or alkenyl radical, this radical is preferably straight-chain and halogen is preferably F or Cl. When multiple substitution is Halogen preferably F. The resulting radicals also include perfluorinated radicals. For simple substitution, the fluorine or Chlorine substituent in any position, but preferably in ω- Position.

Compounds of the formula I with branched wing groups R¹ can occasionally because of a better solubility in the usual liquid-crystalline base materials, in particular but as chiral dopants when 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 branching. Preferred branched radicals R 1 are isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methyl butoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methyl hexoxy, 1-methylheptoxy.

Formula II includes both the racemates of these compounds and the optical antipodes and their mixtures.

Among these compounds of formula II and the sub-formulas are those in which at least one of them contains Rests has one of the preferred meanings given.

The compounds of the formula I are prepared by methods known per se as described in the literature (eg in the standard works such as Houben-Weyl, Methods of Organic Chemistry, Georg-Thieme-Verlag, Stuttgart), under reaction conditions suitable for the said reactions are known and suitable.

One can also of known per se, not mentioned here Make use of variants.

However, the compounds are not directly accessible by the 1,3-Dioxane ring by dehydration in the reaction of corresponding diol is formed with hexafluoroacetone.

The compounds of the invention can be z. B. as follows produce:  

Scheme 1

Scheme 2

The invention further relates to a process for the preparation of compound according to the invention, starting from phenyl dioxanes of the formula III (Scheme 1) by bromination of benzoic acid esters of formula IV, saponified with base and the resulting 3-bromo converts alcohols of formula V with hexafluoroacetone and the resulting Hemiacetal of formula IV treated with a strong base.

Another object of the invention are those in the invention according to current procedures, new intermediates of the Formulas IV, V and VI.  

The bromination of the phenyldioxanes of the formula III is usually carried out in an inert solvent with conventional brominating agents. Preferably, the bromination agent used is N-bromosuccinimide.

The alkaline saponification of the benzoic acid esters is usually carried out in an aqueous or alcoholic / aqueous diluent with a inorganic base, preferably with an alkali hydroxide, in particular Others with lithium hydroxide. The reaction of the 3-bromo alcohol of Formula V with hexafluoroacetone is usually carried out by initiating the gaseous hexafluoroacetone into a solution or suspension of Compound of formula V in an inert solvent at room temperature. In the resulting reaction mixture is the strong base, preferably an alkali metal hydride, in particular sodium hydride or an organometallic compound, in particular butyllithium or Diisopropylamide and heated to temperatures between 30 and 100 ° C.

The liquid-crystalline media according to the invention preferably contain in addition to one or more compounds of the invention as further constituents 2 to 40, in particular 4 to 30 components. Most preferably, these media contain one or more several compounds of the invention 7 to 25 components. These other ingredients are preferably selected from nematic or nematogenic (monotropic or isotropic) subunit especially substances from the classes of azoxybenzenes, Benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoate, cyclohexane-carboxylic acid phenyl or cyclohexyl ester, Phenyl or cyclohexyl esters of cyclohexylbenzoic acid, phenyl or Cyclohexyl ester of cyclohexylcyclohexanecarboxylic acid, cyclohexyl phenylester of benzoic acid, the cyclohexanecarboxylic acid, or the Cyclohexylcyclohexanecarboxylic acid, phenylcyclohexanes, cyclohexyl biphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, Cyclohexylcyclohexylcyclohexanes, 1,4-bis-cyclohexylbenzenes, 4,4'-bis- cyclohexylbiphenyls, phenyl or cyclohexylpyrimidines, phenyl or Cyclohexylpyridines, phenyl or cyclohexyldioxanes, phenyl or  Cyclohexyl-1,3-dithiane, 1,2-diphenylethane, 1,2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1-cyclohexyl-2- (4-phenylcyclohexyl) ethane, 1-cyclohexyl-2-biphenylylethane, 1-phenyl-2-cyclohexyl phenylethanes, optionally halogenated stilbenes, benzylphenyl ethers, tolans and substituted cinnamic acids. The 1,4-phenylene groups in these compounds may also be fluorinated.

The most important compounds which may be used as further constituents of media according to the invention can be characterized by the formulas 1, 2, 3, 4 and 5:
R'-AER '' (1)
R'-A-COO-ER '' (2)
R'-A-OOC-ER '' (3)
R'-A-CH₂CH₂E-R '' (4)
R'-AC≡CER '' (5)

In the formulas 1, 2, 3, 4 and 5, A and E denote the same or ver can be separate, each independently a bivalent The residue of -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio, -G-Phe and -G-Cyc and their mirror images formed group, where Phe is unsubstituted or fluorine-substituted 1,4-phenylene, Cyc trans-1,4-cyclohexylene or 1,4-cyclohexylene, Pyr pyrimidine-2,5-diyl or pyridine-2,5-diyl, bio-1,3-dioxane-2,5-diyl and G 2- (trans-1,4-cyclo hexyl) -ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl mean.

Preferably, one of A and E is Cyc, Phe or Pyr. E is present preferably Cyc, Phe or Phe-Cyc. Preferably, the inventions contain According to the media one or more components selected from the compounds of formulas 1, 2, 3, 4 and 5, wherein A and E are selected are from the group Cyc, Phe and Pyr and at the same time one or more Components selected from the compounds of the formulas 1, 2, 3, 4 and 5, in which one of the radicals A and E is selected from the group Cyc, Phe and Pyr and the other rest is selected from the group  -Phe-Phe, -Phe-Cyc, -Cyc-Cyc, -G-Phe and -G-Cyc-, and optionally one or more components selected from the Compounds of the formulas 1, 2, 3, 4 and 5, wherein the radicals A and E are selected from the group -Phe-Cyc, -Cyc-Cyc, -G-Phe- and G-Cyc.

R 'and R "in a smaller subgroup of the compounds mean Formulas 1, 2, 3, 4 and 5 are each independently alkyl, alkenyl, Alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy of up to 8 carbon atoms. In the following, this smaller subgroup is called group A. and the compounds are described with sub-formulas 1a, 2a, 3a, 4a and 5a designated. For most of these compounds R 'and R "are of different from each other, wherein one of these radicals is usually alkyl, alkenyl, Alkoxy or alkoxyalkyl is.

In a smaller subgroup of compounds of formulas 1, 2, 3, 4 and 5, other than group B, R '' is -F, -Cl, -NCS or - (O) _i CH ₃ - _{(k + 1)} F _k Cl₁, where i is 0 or 1 and k + 1 is 1, 2 or 3; the compounds in which R "has this meaning are designated by sub-formulas 1 b, 2 b, 3 b, 4 b and 5 b. Particularly preferred are those connec tions of the sub-formulas 1b, 2b, 3b, 4b and 5b, in which R '' is -F, -Cl, -NCS, -CF₃, -OCHF₂ or -OCF₃.

In the compounds of sub-formulas 1 b, 2b, 3b, 4b and 5b R 'has the at the meaning of the compounds of sub-formulas 1a-5a and is preferably alkyl, alkenyl, alkoxy or alkoxyalkyl.

In a further smaller subgroup of the compounds of the formulas 1, 2, 3, 4 and 5 are R "-CN; this subgroup is hereafter referred to as Group C and become the compounds of this subgroup according to sub-formulas 1c, 2c, 3c, 4c and 5c described. In the Compounds of sub-formulas 1c, 2c, 3c, 4c and 5c have R 'in the Compounds of the sub-formulas 1a-5a given meaning and is preferably alkyl, alkoxy or alkenyl.  

In addition to the preferred compounds of groups A, B and C are also other compounds of formulas 1, 2, 3, 4 and 5 with other variants the proposed substituents in use. All these substances are by literature methods or in analogy available.

In addition to compounds of the formula I according to the invention, the media according to the invention preferably contain one or more compounds which are selected from group A and / or group B and / or group C. The mass fractions of the compounds from these groups on the media according to the invention are preferably
Group A: 0 to 90%, preferably 10 to 90%, in particular 30 to 90%
Group B: 0 to 80%, preferably 10 to 80%, in particular 10 to 65%
Group C: 0 to 80%, preferably 5 to 80%, in particular 5 to 50%
wherein the sum of the mass fractions of the compounds of the groups A and / or B and / or C contained in the respective inventive media is preferably 5 to 90% and in particular 10 to 90%.

The media according to the invention preferably contain 1 to 40%, in particular preferably 5 to 30% of inventive Ver bonds. Further 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 inventive Links.

The preparation of the media according to the invention takes place in per se Wise. In general, the components are dissolved in each other, purpose moderately at elevated temperature. By suitable additives, the liquid crystalline phases according to the invention are modified so that  they are in all hitherto known types of liquid crystal display elements can be used. Such additives are the subject known and described in detail in the literature (H. Kelker / R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, pleochroic dyes for producing colored Guest host systems or substances for changing the dielectric Anisotropy, viscosity and / or orientation of the nematic Phases are added.

In the present application and in the following examples, the structures of the liquid crystal compounds are indicated by acronyms, wherein the transformation into chemical formulas according to the following Tabel len A and B takes place. All radicals C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl radicals with n or m C atoms. The coding according to Table B is self-evident. In Table A, only the acronym for the basic body is given. In the individual case, a code for the substituents R 1, R 2, L 1 and L 2 follows separately from the acronym for the main body with a dash:

Table A

Table B

The following examples are intended to illustrate the invention without being limits. Above and below mean percentages by weight center. All temperatures are in degrees Celsius. Mp means Melting point, bp. = Clearing point. Furthermore, K = crystalline state, N = nematic phase, S = smectic phase and I = isotropic phase. The Information between these symbols represents the transition temperatures Δn means optical anisotropy (589 nm, 20 ° C) and viscosity (mm² / sec) was determined at 20 ° C.

"Conventional work-up" means: optionally water is extracted with dichloromethane, diethyl ether or toluene, separated, the organic phase is dried, evaporated and the product is purified by distillation under reduced pressure or crystallization and / or Chromato graphy. The following abbreviations are used:
DAST: diethylaminosulfur trifluoride
DMEU: 1,3-dimethyl-2-imidazolidinone KOT: potassium tertiary butoxide
THF: tetrahydrofuran
pTsOH: p-toluenesulfonic acid

example 1

To a sodium ethoxide solution prepared from 46 g (2.0 mol) of sodium and 1 liter of ethanol at 320 ° C 320.4 g (2.0 mol) of diethyl malonate dripped. After 112 hours of stirring, 287 g (1 mol) of 4-propyl-4'- added bromobicyclohexyl:

After usual work-up, 130 g (35.5% of theory) of the product are obtained as colorless crystals.

A mixture of 130 g of 1A and 300 ml of THF slowly becomes an under Refluxed suspension of 17.1 g (0.45 mol) of lithium alumi niumhydride, 100 ml of toluene and 400 ml of THF.

After stirring for 1ündiger the mixture is cooled to 10 ° C and with Hydrolyzed 40 ml of water. After customary workup, 19.6 g (19.8% of theory) as a white powder.

0.1 mol of 1B, 0.1 mol of benzaldehyde, in 100 ml of toluene are mixed with 1.7 g of p- Toluene sulfonic acid added and boiled for 1 h on a water. you allowed to cool to room temperature, mixed with water and working as usual, receives 27.2 g (80% of theory) of the product as white crystals.

A mixture of 24.0 g 1C, 15 g N-bromosuccinimide, 9.0 g barium carbonate and 150 ml of dichloromethane is heated to boiling for 4 hours.

After customary workup, 28.4 g (97.6% of theory) are obtained as yellow Crystalline, which is further processed without further purification.

A mixture of 15.6 g of 1D, 0.86 g of lithium hydroxide, 15 ml of water, 100 ml THF and 100 ml of ethanol are stirred for 3 hours at room temperature. After stirring for 1 hour at 25 ° C is worked up as usual and off Hexane crystallized around. The product (7.6 g 63 3% of theory) is obtained as White dust.

In a mixture of 7.5 g of 1E and 70 ml of THF are within 1.5 Hours between 20 ° C and 28 ° C 5.0 g of gaseous hexafluoroacetone initiated.

After purging with nitrogen, a suspension of 1.2 g NaH with THF added to the reaction mixture. After heating for 20 hours 45 ° C is worked up as usual. After recrystallization from hexane you get the pure product, K 133 l.

Analog are produced:

Example A

A nematic mixture is prepared consisting of:

PCH-5F | 9.0% PCH-6F 7.2% PCH-7F 5.4% CCP 20CF₃ 7.2% CCP 30CF₃ 10.8% CCP 40CF₃ 8.1% CCP 50CF₃ 8.1% BCH 3F.F 10.8% BCH 5F.F 9.0% ECCP 30CF₃ 4.5% ECCP 50CF₃ 4.5% CBC-33F 1.8% CBC-53F 1.8% CBC-55F 1.8% CCD 3-CF₃ 10.0% clearing point: 85.6 ° C .DELTA.n: .0919 Viscosity: 17.0 mm² / s Δε: 6.62

Example B

A nematic mixture is prepared consisting of:

PCH-5F | 9.0% PCH-6F 7.2% PCH-7F 5.4% CCP 20CF₃ 7.2% CCP 30CF₃ 10.8% CCP 40CF₃ 8.1% CCP 50CF₃ 8.1% BCH 3F.F 10.8% BCH 5F.F 9.0%   ECCP 30CF₃ 4.5% ECCP 50CF₃ 4.5% CBC-33F 1.8% CBC-53F 1.8% CBC-55F 1.8% CCD-5-CF₃ 10.0% clearing point: 86.8 ° C .DELTA.n: 0.92 Viscosity: 19.0 mm² / s Δε: 6.54

Claims (6)

1. bis (trifluoromethyl) -dioxanes containing a structural element of the general formula 2. bis (trifluoromethyl) -dioxanes according to claim 1 of the formula II wherein
R¹ is an unsubstituted or substituted by CN or at least one halogen substituted alkyl or alkenyl radical having up to 18 carbon atoms, wherein one or more non-adjacent CH₂ groups by a radical selected from the group -O-, -S-, -CO-, -O-CO-, -CO-O- and -C≡C- may be replaced,
Al each independently

• a) a 1,4-phenylene radical in which one or two CH groups may be replaced by N,
• b) a 1,4-cyclohexylene radical in which one or two non-adjacent CH₂ groups may be replaced by -O- or -S-,
• c) a 1,4-cyclohexenylene, a piperidine-1,4-diyl, a 1,4-bicyclo [2,2,2] octylene or a naphthalene-2,6-diyl radical

where the radicals a) and b) may be substituted one or more times by halogen atoms, cyano and / or methyl groups,
Each Z¹ independently represents -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CH₂CH₂-, -CH = CH-, -C≡C- or a single bond
n 1, 2 or 3
mean. 3. bis (trifluoromethyl) -dioxanes according to claim 1 or 2 comprising a structural element of the formula Ia 4. Liquid-crystalline medium containing at least two liquid crystalline compounds, characterized in that it contains at least bis (trifluoromethyl) -dioxane according to claim 1 contains. 5. Electro-optical display containing a liquid-crystalline medium according to claim 4.