DE3915698A1 - Novel fluorine-contg. phenylene cyclohexylene optically active cpds. - useful as components of chiral smectic liq. crystals - Google Patents

Abstract

Novel optically-active cpds. of formula (I) are claimed as are also multi-component chiral smectic liq. crystal compsns. contg. (I) and L.C. displays using the compsn. as the dielectric. In (I), R = up to 15C alk(en)yl opt. substd. by one CN or by at least one F or Cl; the alk(en)yl gp. opt. also being interrupted by one -O-, -CO-, -O.CO-, -CO.O-, or -O.CO.O-gp.; A1 and A2 = the following gps. opt. substd. by one or two F atoms: 1,4-phenylene, pyridin-2,5-diyl, pyrimidin-2,5 diyl, pyrazin-2,5-diyl, pyridazin-3,6-diyl, 1,3,4-thiadiazol -2,5-diyl, 1,2,4-thiadiazol-3,5-diyl, trans-1,4-cyclohexylene (opt. with 1 or 2 neighbouring CH2 gps. replaced by -O- and/or -S-, and/or with one CH gp. replaced by -C(CN)-), 1,4-cyclohexylene, 1,4-bi-cyclo(2,2,2)-octylene or piperidin-1,4-diyl; Z1-Z3 = a bond, -CO.O-, -O.CO-. -CH2O-, -OCH2-, -CH2CH2-, -CH=CH- or -CC-; X = H or F; Q = -OCH2-, -COOCH2 or -CH2OCH2-; p = 1-12; and one or both m and n = 0 and the other is 0 or 1; with the proviso that when Q = -OCH2- or -COOCH2-; ,

Description

The invention relates to optically active compounds Formula I.

wherein
R is an unsubstituted, an alkyl or alkenyl radical with up to 15 C atoms which is simply substituted by -CN or an at least monosubstituted by fluorine or chlorine, with a CH₂ group in these radicals also being -O-, -CO-, O-CO-, -CO-O- or -O-CO-O- can be replaced,
A¹ and A² each independently represent an unsubstituted or substituted by one or two fluorine atoms 1,4-phenylene radical, pyridine-2,5-diyl radical, pyrimidine-2,5-diyl radical, pyrazine-2,5- diyl radical, pyridazine-3,6-diyl radical, 1,3,4-thiadiazole-2,5-diyl radical, 1,2,4-thiadiazole-3,5-diyl radical, trans-1, 4-cyclohexylene radical, in which one or two non-adjacent CH₂ groups can be replaced by -O- and / or -S- and / or a CH group can be replaced by -C (CN) -, 1.4 Cyclohexenylene radical, 1,4-bicyclo (2,2,2) octylene radical or a piperidine-1,4-diyl radical,
Z¹, Z² and Z³ each independently of one another -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CH₂CH₂-, -CH = CH-, -C≡C- or a single bond,
XH or F,
Q -OCH₂-, -COOCH₂- or -CH₂OCH₂-,
o 1 to 12,
and one of the two values
m and n are 0 and the other is 0 or 1,
with the provisos that if Q = -OCH₂- or -COOCH₂-

• (a) n = 1 and m = 0,
• (b) one of the rings A¹ and A² 1,3,4-thiadiazole-2,5- diyl, 1,2,4-thiadiazole-3,5-diyl, trans-1,4-cyclo hexylene, where one or two non-contiguous CH₂ groups are replaced by -O- and / or -S- and / or a CH group is replaced by -C (CN) - is 1,4-cyclohexenylene, 1,4-bicyclo (2,2,2) octylene, Piperidine-1,4-diyl or 2,3-difluoro-1,4- phenylene means
• (c) n = 0 and Z¹ and / or Z² means -O-CO-, -CH₂O, -CH₂O-, -CH₂CH₂-, -CH = CH- or -C≡C-, or
• (d) R is an alkyl or alkenyl radical with up to 15 C atoms which is simply substituted by -CN or an at least monosubstituted by fluorine or chlorine, a CH₂ group in these radicals also being -O-, -CO-, -O -CO-, -CO-O- or -O-CO-O- can be replaced, or
  an unsubstituted alkenyl radical with up to 15 carbon atoms, in which radical a CH₂ group can also be replaced by -O-, -CO-, -O-CO-, -CO-O- or -O-CO-O- can.

The compounds of formula I can be like similar in DE-OS 35 15 373 compounds as components chiral tilted smectic liquid crystalline Phases are used.

Chiral tilted smectic liquid crystalline phases with ferroelectric properties can be manufactured by using base mixtures with an or several tilted smectic phases with a suitable one chiral dopant added (L.A. Beresnev et al., Mol. Cryst. Liq. Cryst. 89: 327 (1982); MR. Brand et al., J. Physique 44, (lett.), L-771 (1983). Such phases can be used as dielectrics for fast switching displays used on the Clark and Lagerwall described principle of SSFLC technology (N.A. Clark and S.T. Lagerwall, Appl. Phys. Lett. 36: 899 (1980); USP 43 67 924) based on the ferroelectric Eigen chiral tilted phase. In this Phase are the elongated molecules in layers arranged, the molecules tilting to the layers normal. As layer progresses Layer, the tilt direction changes by a small angle with respect to a perpendicular to the layers Axis so that a helical structure is formed. In Displays based on the principle of SSFLC technology based, the smectic layers are perpendicular to the Arranged plates of the cell. The helical arrangement  the tril directions of the molecules is marked by a very suppressed small distance between the plates (approx. 1-2 µm). This forces the long axes of the molecules itself in a plane parallel to the plates of the cell to arrange, creating two excellent tilt orientations arise. By applying a suitable electrical Alternating field can result in spontaneous polarization pointing liquid crystalline phase between these be switched back and forth in both states. This Shifting is much faster than with conventional Lichen twisted cells (TN-LCD's) based on nematic Liquid crystals are based.

A major disadvantage for many of the applications currently available materials with chiral tilted smek phases (such as Sc *) is their relatively high optical anisotropy due to relatively high viscosity values do not result in a sufficiently short switching times, as well as that dielectric anisotropy values greater than zero or, if negative, little of zero has different values. Negative values of dielek tric anisotropy are required if the requ planar orientation by superimposing the Control field with an AC holding field with small amplitude (J.M. Geary, SID Conference, Orlando / Florida, April / May 1985, lecture 8.3).

It has now been found that the use of compounds of the formula I as components of chiral tilted smectic mixtures the disadvantages mentioned essential Lich diminish. The compounds of formula I are thus as components of chiral tilted smectic Liquid-crystalline phases are particularly suitable. In particular special are chemically particularly stable with their help chiral tilted smectic liquid crystalline phases with favorable ferroelectric phase ranges, esp  especially with wide Sc * phase ranges, negative or also positive dielectric anisotropy, lower optical anisotropy, favorable pitch height, lower Viscosity and for such phases high values for the spontaneous polarization and very short switching times adjustable. P is the spontaneous polarization in nC / cm².

With the provision of the compounds of formula I the range of liquid is also very general crystalline substances that can be found among different application aspects for manufacturing ferroelectric mixtures are suitable, considerably broadened.

The compounds of formula I have a wide range Scope of application. Depending on the selection of the Substituents can use these compounds as base mates rialien serve from which liquid crystalline phases to the majority are composed; but it can also compounds of formula I liquid crystalline base materials from other classes of compounds added be, for example, the dielectric and / or optical Anisotropy and / or spontaneous polarization and / or the phase range and / or the tilt angle and / or the Pitch and / or the switching times of such a phase too vary. The compounds of formula I are suitable also as intermediates for the manufacture of others Substances that are components of liquid crystalline Let phases be used.

The compounds of formula I are in a pure state colorless and show favorable values of the optical Aniso tropie on. Some of the compounds of formula I liquid crystalline mesophases in one for the electro-optic use conveniently located temperature range, but it can also be isotropic or monotropic liquid crystalline compounds of formula I as a compo  chiral tilted smectic phases advantage be used in custody. Chemical, thermal and against Light they are very stable.

The invention thus relates to the compounds of Formula I and the use of the compounds of Formula I as components of liquid-crystalline phases.

The invention also relates to chiral tilted smek tables liquid crystalline phases containing at least one compound of formula I with at least one carbons linked with four different substituents substance atom.

The invention further relates to such phases a content of at least one compound of the formula I. and liquid crystal display elements, in particular elec trooptic display elements, such phases contain.

For the sake of simplicity, Ph means a in the following 1,4-phenylene group, which also contains one or two CH groups can be replaced by N, Cy is a 1,4-cyclohexylene group, in which one or two non-adjacent CH₂- Group can be replaced by O atoms and Bi one Bicyclo (2,2,2) octylene group.

Above and below, R, A¹, Z¹, A², Z², m , X, Z³, n , Q and o have the meaning given, unless expressly stated otherwise.

In the preferred compounds of the above and below Formulas can be the alkyl radicals, in which also a CH₂ group (alkoxy or oxaalkyl) by an O atom can be replaced, straight-chain or branched. Before preferably they have 5, 6, 7, 8, 9 or 10 carbon atoms and  are preferably phenyl, hexyl, heptyl, octyl, Nonyl, decyl, pentoxy, hexoxy, heptoxy, octoxy, nonoxy or decoxy, also also ethyl, propyl, butyl, undecyl, Dodecyl, propoxy, ethoxy, butoxy, undecoxy, dodecoxy, 2-oxapropyl (= 2-methoxymethyl), 2- (= ethoxymethyl) or 3-oxabutyl (= 2-methoxypentyl), 2-, 3- or 4-oxa pentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl.

A¹ and A² are preferably Cy or Ph. In the compounds of the formulas above and below means Ph preferred a 1,4-phenylene (Phe), a pyrimidine-2,5-diyl (Pyr), a pyridine-2,5-diyl- (pyn), a pyrazine-3,6- diyl or a pyridazine-2,5-diyl group, in particular preferably Phe, Pyr or Pyn. Preferably contain the compounds according to the invention not more than a 1,4- Phenylene group, in which one or two CH groups by N are replaced. Cy is preferably a 1,4-cyclo hexylene group. However, ver Compounds of formula I, wherein one of the groups A² is a 1,4-cyclo substituted in the 1- or 4-position by CN means hexylene group and the nitrile group in axial Position, d. H. a group A², the following Configuration has:

Compounds of the formula I and are particularly preferred of the preceding sub-formulas, which are a grouping -Ph-Ph- included. -Ph-Ph- is preferably -Phe-Phe-, Phe-Pyr or Phe-Pyn. Those are particularly preferred groups  

such as

further unsubstituted or one or more times Fluorine-substituted 4,4'-biphenylyl.

Z¹ is preferably a single bond, secondarily preferably -O-CO-, -CO-O-, -C≡C- or -CH₂CH₂ groups.

Particularly preferred for Z¹ is -CO-O-, -O-CO-, -C≡C- or -CH₂CH₂-, especially the -CH₂CH₂- and the -C≡C group.

Connections of the formulas above and below with ver branched wing groups R can be of importance. Ver Branched groups of this type usually do not contain more than two chain branches. R is preferred a straight-chain group or a branched group with no more than a chain branch.

Preferred branched radicals are isopropyl, 2-butyl (= 1- Methylpropyl), isobutyl (= 2-methylpropyl), tert.-butyl, 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 2-ethylhexyl, 5-methyl hexyl, 2-propylpentyl, 6-methylheptyl, 7-methyloctyl, iso propoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methyl hexoxy, 1-methylheptoxy, 2-oxa-3-methylbutyl, 3-oxa-4- methylpentyl.

Among the compounds of formula I are those preferred, in which at least one of the contained therein Radicals has one of the preferred meanings indicated.  

Those of the above formulas, the one or contain several groups dio, dit, pip and / or pyr, enclose the two possible 2.5- (Dio, Dit, Pyr) or 1,4-position isomers (Pip).

The compounds of formula I are per se known methods, as used in the literature (e.g. in the standard works such as Houben-Weyl, methods of organic chemistry, Georg-Thieme-Verlag, Stuttgart) are described, namely under reaction conditions, known and suitable for the above-mentioned implementations are. You can also from well-known, here make use of variants not mentioned in more detail.

If desired, the starting materials can also be in situ are formed such that they can be removed from the reaction mix not isolated, but immediately to the Reacts compounds of formula I.

The optically active compounds of formula I are obtained through the use of appropriate optically active output materials and / or by separating the optical anti Pod by means of chromatography using known methods.

The phases according to the invention contain at least one, preferably at least two compounds of the formula I. Chirals according to the invention are particularly preferred tilted smectic liquid crystalline phases, their achiral Base mixture in addition to compounds of formula I at least another component with negative or amount contains small positive dielectric anisotropy. The chirality is preferably partially or fully based constantly chiral compounds of formula I. These Phases preferably contain one or two chiral ver Binding of formula I. However, it can also be achiral Compounds of formula I (for example in the form of a  Racemates) are used, with the chirality the phase through other optically active connections is called. If chiral compounds of the formula I are used in addition to the purely optical ones Antipodes also mixtures with an enantiomeric excess. The above-mentioned other component (s) of the achiral Base mixture can be 1 to 50%, preferably 10 to 25%, make up the base mix. As additional components with small positive or negative dielectric Anisotropy are suitable compounds of the sub-formulas Va to Vp:

R⁴ and R⁵ are each preferably straight-chain or branched alkyl, alkoxy, alkanoyloxy or alkoxycarbonyl, each having 3 to 12 carbon atoms. X '' is O or S, preferably O. n is 0 or 1.

The compounds of the part are particularly preferred formulas Va, Vb, Vd and Vf, where R⁴ and R⁵ are each even chain alkyl or alkoxy, each with 5 to 10 carbon atoms means.

The compounds of the sub-formulas Vc, Vh and Vi are suitable themselves as additives for lowering the melting point and normally the base mixes with no more than 5%, preferably 1 to 3% added. R⁴ and R⁵ mean in the connections of the sub-formulas Vc, Vh and Vi preferred as straight-chain alkyl with 2 to 7, preferably 3 to 5, carbon atoms. Another for lowering the melting point suitable connection in the phases according to the invention class is that of the formula

where R⁴ and R⁵ before the given for Vc, Vh and Vi have significant meaning.

As further components with negative dielectric Anisotropy are also suitable containing compounds the structural element M, N or O.

Preferred compounds of this type correspond to the Formulas VIb and VIc:

R 'and R' 'each preferably represent straight-chain Alkyl or alkoxy groups, each with 2 to 10 carbon atoms. Q¹ and Q² each represent 1,4-phenylene, trans-1,4-cyclo hexylene, 4,4'-biphenylyl, 4- (trans-4-cyclohexyl) phenyl, trans, trans-4,4'-bicyclohexyl or one of the groups Q¹ and Q² also a single bond.

Q³ and Q⁴ each represent 1,4-phenylene, 4,4'-biphenylyl or trans-1,4-cyclohexylene. One of the groups Q³ and Q⁴ can also mean 1,4-phenylene, in which at least one CH group is replaced by N. R '' 'is an optical active residue with an asymmetric carbon atom  the structure

R '' 'preferably has the formula

with the preferred meanings mentioned above.

Particularly preferred components with negative dielek trical anisotropy are those described in WO 86-00 529 Connections with the structural element M or N. Those of the formula VId are particularly preferred

wherein alkyl is a straight chain or branched alkyl group is preferably 3 to 10 carbon atoms and R 'is the above has the meaning given. Connections are also preferred according to formula VId, wherein one or both of them Rings linking single bonds through a group selected from -CH₂CH₂-, -O-CO- or -CO-O- are replaced. Particularly preferred compounds of the formula VIc are those of formula VIc ′:

wherein A is 1,4-phenylene or trans-1,4-cyclohexylene, Z ° CH or N and n is 0 or 1.

The compounds of formula I are also suitable as a com components of nematic liquid-crystalline phases, e.g. B. for Avoiding reverse twist.

These liquid crystalline phases according to the invention consist of 2 to 25, preferably 3 to 15 components, including at least one compound of formula I. Die other ingredients are preferably selected from the nematic or nematogenic substances, in particular the known substances from the classes of azoxybenes zoles, benzylidene anilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, cyclohexane carboxylic acid phenyl or cyclohexxyl ester, phenylcyclohexane, cyclohexylbi phenyls, cyclohexylcyclohexanes, cyclohexylnaphthalenes, 1,4-bis-cyclohexylbenzenes, 4,4'-bis-cyclohexylbiphenyls, Phenyl- or cyclohexylpyrimidines, phenyl- or cyclo hexylpyridazines and their N-oxides, phenyl or cyclo hexyldioxane, phenyl- or cyclohexyl-1,3-dithiane, 1,2-diphenylethane, 1,2-dicyclohexylethane, 1-phenyl-2- cyclohexylethanes, optionally halogenated stilbenes, Benzylphenyl ether, tolanes and substituted cinnamic acids.

The main as components of such liquid leave crystalline phases in question are characterized by the formula I ′,

R′-L-G-E-R ′ ′ (I ′ ′)

where L and E each have a carbocyclic or heterocyclic ring system from that of 1,4-disubstituted benzene and cyclo hexane rings, 4,4'-disubstituted biphenyl, phenylcyclo hexane and cyclohexylcyclohexane systems, 2,5-disubstituted ized pyrimidine and 1,3-dioxane rings, 2,6-disubstituted Naphthalene, di- and tetrahydronaphthalene, quinazoline and tetrahydroquinazoline formed group,

or a single CC bond,
Y halogen, preferably chlorine, or -CN, and
R 'and R''alkyl, alkoxy, alkanoyloxy, alkoxycarbonyl or alkoxycarbonyloxy having up to 18, preferably up to 8 carbon atoms, or one of these radicals is also CN, NC, NO₂, CF₃, F, Cl or Br.

For most of these compounds, R 'and R' 'are of different from one another, one of these residues usually being one Is alkyl or alkoxy group. But also other variants the proposed substituents are common. Lots such substances or mixtures thereof are commercially available available. All of these substances are according to literature known methods available.

The phases according to the invention contain about 0.1 to 99, preferably 10 to 95%, one or more verbin extensions of formula I. Also preferred are fiction appropriate liquid crystalline phases containing 0.1-40 preferably 0.5-30% of one or more compounds of the Formula I.

The phases according to the invention are produced in in a usual way. As a rule, the components dissolved in one another, expediently at elevated temperature.  

By means of suitable additives, the liquid crystalline Phases according to the invention are modified so that they in all types of liquid known so far crystal display elements can be used.

Such additives are known to the expert and in the Literature described in detail. For example, you can Conductive salts, preferably ethyl-dimethyl-dodecyl-ammonium 4-hexyloxybenzoate, tetrabutylammonium tetraphenylboranate or complex salts of crown ethers (cf. e.g. I. Haller et al., Mol. Cryst. Liq. Cryst. Volume 24, pages 249-258 (1973)) to improve conductivity, pleochroi dyes for the production of colored guest-host Systems or substances for changing the dielectric Anisotropy, viscosity and / or orien tation of the nematic phases can be added.

Such substances are e.g. B. in DE-OS 22 09 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430, 28 53 728 and 29 02 177.

The following examples are intended to illustrate the invention, without limiting it. Mp. = Melting point, Kp. = Clarifying Point. Above and below mean percentages Weight percent; all temperatures are in degrees Celsius specified. "Normal work-up" means: water is given added, extracted with methylene chloride, separated, dried the organic phase, evaporates and purifies the product by crystallization and / or chromatography.

It also means:
K: crystalline solid state, S: smectic phase (the index indicates the phase type), N: nematic state, Ch: cholesteric phase, I: isotropic phase. The number between two symbols indicates the transition temperature in degrees Celsius.

Example 1

0.05 mol of trans-4- (4'-octyloxybiphenyl-4-yl) cyclohexane carboxylic acid chloride (made from 4-octyloxy-4'-bromo biphenyl by lithiation, conversion into a titanium organic compound and reaction with 4-cyclohexanone ethyl carboxylate, dehydration and hydrogenation the double bond, saponification of the ester and implementation the acid with thionyl chloride), 0.05 mol (S) -2-fluorine octanol and 0.05 mol pyridine are in 100 mol toluene Heated to reflux for 5 hours. Sucks after cooling the pyridine hydrochloride and the filtrate is concentrated to Arrears.

The pure (S) -2-fluoroctyl- [trans-4- (4'-octyloxybiphenyl- 4-yl) cyclohexane] carboxylate is obtained by crystallization obtained from ethanol.

Example 2

0.1 mol of 4-hydroxybenzoic acid methyl ester, 0.1 mol (S) -2- Fluoroctanol-1 and 0.12 mol triphenylphosphine are in 250 ml of tetrahydrofuran dissolved and with stirring and ice cooling 0.12 mol of diethyl azodicarboxylate added dropwise. Man Allows to come to room temperature and stir for a further 8 hours to. Then the solvent is distilled and the Methyl 4- (2-fluoro-octyloxy) benzoate by column chromatography topography cleaned. By saponification with aqueous / alcohol Holic potash lye gives (S) -4- (2-fluorine) octyloxy) benzoic acid.  

0.01 mol of this acid, 0.001 mol of 4-dimethylaminopyrimidine and 0.01 mol of 4-n-octylphenol in 15 ml Dichloromethane submitted, a solution at 10 ° with stirring of 0.01 mol of dicyclohexylcarbodiimide was added dropwise and then stirred for 15 hours at room temperature. The mixture is filtered through silica gel and the solution is evaporated medium and obtained as residue (S) - (4-n-octylphenyl) - 4- (2-fluoroctyloxy) benzoate.

Example 3

Analogously, (S) -4- (2-fluoroctyloxy) benzoate is obtained acid and 2- (4-hydroxyphenyl) -5-n-nonylpyrimidine (S) - [4- (5-n-Nonylpyrimidin-2-yl) phenyl] -4- (2-fluor octyloxy) benzoate.

Example 4

4- {5- [2- (4-pentylphenyl) ethynyl] pyrimidin-2-yl} - benzoic acid is according to the following reaction scheme receive:

0.01 mol of this acid, 0.001 mol of dimethylaminopyridine and 0.01 mol (S) -2-fluoroctanol are in 15 ml Dichloromethane submitted, a solution at 10 ° with stirring of 0.01 mol of dicyclohexylcarbodiimide was added dropwise and then stirred for 15 hours at room temperature. The mixture is filtered through silica gel and the solution is evaporated medium and receives as residue [(S) -2-fluoroctyl] -4- {5- [2- (4-pentylphenyl) ethynyl] pyrimidin-2-yl} benzoate.

Example 5

By hydrogenating the compound obtained in Example 4 with hydrogen under normal pressure at room temperature and palladium-carbon as a catalyst gives [(S) -2- Fluoroctyl] -4- {5- [2- (4-pentylphenyl) ethyl] pyrimidine - 2-yl} benzoate.

Example 6

0.05 mol (S) -4- (2-fluoroctyloxy) -4'-hydroxy-biphenyl (Prepared by alkylation of 4-hydroxy-4'-benzyl oxybiphenyl by alkylation with (S) -2-fluoroctanol-1 after Mitsunobu and subsequent hydrogenolytic Elimination of the benzyl residue), 0.05 mol trans-4- (3E-pentenyl) - cyclohexane carboxylic acid (preparation described in EP 01 68 683) and 0.005 mol of 4-dimethylaminopyridine submitted in 75 ml of dichloromethane, at 10 ° with stirring a solution of 0.05 mol dicyclohexylcarbodiimide added drips and then 15 hours at room temperature stirred. After the usual work-up you get (S) - [4- (2-Fluoroctyloxy) biphenyl-4'-yl] trans-4- (3E- pentenyl) cyclohexane carboxylate.  

Example 7

0.02 mol (S) -4- (2-fluoroctanoyloxy) -4'-hydroxybiphenyl (Made by reacting 4-benzoyloxy-4'-hydroxy biphenyl with (S) -2-fluoroctanoic acid chloride in the presence of pyridine and subsequent hydrolytic cleavage of the Benzyl group), 0.02 mol (S) -4- (2-fluoroctyloxy) benzo acid and 0.002 mol of 4-dimethylaminopyridine are in 30 ml dichloromethane submitted, at 10 ° with stirring one Dropwise solution of 0.02 ml of dicyclohexylcarbodiimide followed by 15 hours at room temperature stirs. After working up, (S, S) - [4- (2- Fluoroctanoyloxy) biphenyl-4'-yl] -4- (2-fluoroctyloxy) - benzoate.

Claims (4)

1. Optically active compounds of the formula I. wherein
R is an unsubstituted, an alkyl or alkenyl radical with up to 15 C atoms which is simply substituted by -CN or an at least monosubstituted by fluorine or chlorine -CO-, -CO-O- or -O-CO-O- can be replaced,
A¹ and A² each independently represent an unsubstituted or substituted by one or two fluorine atoms 1,4-phenylene radical, pyridine-2,5-diyl radical, pyrimidine-2,5-diyl radical, pyrazine-2,5-diyl Radical, pyridazine-3,6-diyl radical, 1,3,4-thiadiazole-2,5-diyl radical, 1,2,4-thiadiazole-3,5-diyl radical, trans-1,4 -Cyclohexylene radical, in which one or two non-adjacent CH₂ groups can also be replaced by -O- and / or -S- and / or a CH group can be replaced by -C (CN) -, 1,4- Cyclohexenylene radical, 1,4-bicyclo (2,2,2) octylene radical or a piperidine-1,4-diyl radical,
Z¹, Z² and Z³ each independently of one another -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CH₂CH₂-, -CH = CH-, -C≡C- or a single bond,
XH or F,
Q -OCH₂-, -COOCH₂- or -CH₂OCH₂-,
o 1 to 12,
and one of the two values
m and n are 0 and the other is 0 or 1,
with the provisos that if Q = -OCH₂- or -COOCH₂-

• (a) n = 1 and m = 0,
• (b) one of the rings A¹ and A² 1,3,4-thiadiazole-2,5-diyl, 1,2,4-thiadiazole-3,5-diyl, trans-1,4-cyclohexylene, wherein one or two not adjacent CH₂ groups are replaced by -O- and / or -S- and / or a CH group is replaced by -C (CN) -, 1,4-cyclohexenylene, 1,4-bicyclo (2,2, 2) octylene, piperidine-1,4-diyl or 2,3-difluoro-1,4-phenylene.
• (c) n = 0 and Z¹ and / or Z² means -O-CO-, -CH₂O-, -CH₂O-, -CH₂CH₂-, -CH = CH- or -C≡C-, or
• (d) R is an alkyl or alkenyl radical with up to 15 C atoms which is simply substituted by -CN or an at least monosubstituted by fluorine or chlorine, a CH₂ group in these radicals also being -O-, -CO-, -O -CO-, -CO-O- or -O-CO-O- can be replaced, or
  an unsubstituted alkenyl radical with up to 15 carbon atoms, in which radical a CH₂ group can also be replaced by -O-, -CO-, -O-CO-, -CO-O- or -O-CO-O- can.

2. Chiral tilted smectic liquid crystalline phase with at least two liquid crystalline components, characterized in that it has at least one ver contains bond of formula I according to claim 1. 3. Use of the compounds of formula I after Claim 1 as components of liquid crystalline phases. 4. Electro-optical display element, characterized in that that there is a phase after as a dielectric Claim 2 contains.