WO1989009764A1

WO1989009764A1 - Chiral or achiral cyclic compounds

Info

Publication number: WO1989009764A1
Application number: PCT/EP1989/000354
Authority: WO
Inventors: Andreas WÄCHTLER; Klaus-Peter Stahl; Reinhard Hittich; Thomas Geelhaar; Volker Reiffenrath
Original assignee: MERCK Patent Gesellschaft mit beschränkter Haftung
Priority date: 1988-04-13
Filing date: 1989-04-01
Publication date: 1989-10-19
Also published as: JPH02503803A; JP2843629B2; DE3812191A1; EP0370081A1; KR900700429A; DD283832A5

Abstract

Chiral or achiral cyclic compounds of formula R1-(A1-Z1)m-A2-Q1-C*R°CF3-X, wherein R1 denotes alkyl or perfluoralkyl which can be interrupted by O- and/or -CO- and/or -CO-O- and/or -CH=CH- and/or -CH halogen- and/or -CHCN- and/or -O-CO-CH halogen- and/or -CO-O-CHCN-, F, Cl, Br, CN or -Q1-C*R°CF3-X; A1 and A2 denote unsubstituted 1,4-phenylene or 1,4-phenylene substituted with one or two F and/or CH3 and/or CN, wherein one or two CH groups can also be replaced by 1,4-cyclohexane, wherein one or two non-neighbouring CH2 groups can be replaced by O and/or S, 1-(4-) cyano-1,4-cyclohexylene, piperidin-1,4-diyl, 1,4-bicyclo(2,2,2)-octylen, 1,3,4-thiadiazol-2,5-diyl naphthalen-2,6-diyl, decahydronaphthalen-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl; Z1 denotes -CO-O-, -O-CO-, -CH2CH2-, -OCH2-, -CH2O, -C=C-, or a single bond; X denotes H or CH3; C* denotes a carbon atom bonded to four different substituents; or m = 1, 2 or 3; Q1 denotes -O-, -O-CO-, -CO-O- or a single bond, and in the case in which at least one of the rings A1 and A2 is replaced by 1,4-phenylene substituted by one or two F atoms or A1 is unsubstituted 1,4-phenylene, wherein one CH group is replaced by N, also denotes -O-(CH2)n-, -O-CO-(CH2)n- or -CO-O-(CH2)n, where n = 1, 2, 3 or 4; R° is alkyl different from X, or, if Q is a single bond, alkoxy or alkanoyloxy. Said compounds can be used as chirally oriented smectic liquid crystal phases.

Description

Chiral or achiral ring connections

The invention relates to chiral or achiral ring compounds of the formula I.

R ¹ - (A ¹ -Z ¹ ) _m -A ² -Q ¹ -C * R ° CF ₃ -XI

wherein

R ^{1 is} an alkyl or perfluoroalkyl group, each having 1-12 C atoms, in which one or two non-adjacent CH ₂ or CF ₂ groups are also represented by O atoms and / or -CO groups and / or -CO -O groups and / or -CH = CH groups and / or -CH-halogen and / or -CHCN groups and / or -O-CO-CH-halogen and / or -CO-O-CHCN groups can be replaced , F, Cl, Br, CN, or -Q ¹ -C * R ° CF ₃ -X, where Q ¹ , R ° and X have the meaning given,

A ¹ and A ² each independently of one another 1,4-phenylene which is unsubstituted or substituted by one or two F and / or CH ₃ groups and / or CN groups, in which one or two CH groups can also be replaced by N, 1,4-cyclohexylene, which is also a or two non-adjacent CH ₂ groups can be replaced by O atoms and / or S atoms, 1- (4-) cyano-1,4-cyclohexylene, a piperidine-1,4-diyl, 1,4- Bicyclo (2,2,2) octylene-, 1,3,4-thiadiazole-2,5-diyl-, naphthalene-2,6-diyl-, decahydronaphthalene-2,6-diyl- or 1,2,3, 4- tetrahydronaphthalene-2,6-diyl group,

Z ^{1 in} each case -CO-O-, -O-CO-, -CH ₂ CH ₂ -, -OCH ₂ -, -CH ₂ O-, -C≡C- or a single bond,

XH or CH ₃ ,

C * is a carbon atom linked to four different substituents,

m 1, 2 or 3

Q ¹ -O-, -O-CO-, -CO-O- or a single bond, in the event that at least one of the rings A ¹ and A ² is substituted by one or two F atoms or 1,4-phenylene or A 1 unsubstituted 1,4-phenylene, in which a CH group is replaced by N, also means -O- (CH ₂ ) _n -, -O-CO- (CH ₂ ) _n - or -CO-O- (CH ₂ ) _n , where n is 1, 2, 3 or 4, and

R ° is an alkyl group other than X with 1 to 10 C atoms, or, if Q denotes a single bond, also an alkoxy or alkanoyloxy group each with 1 to 10

C atoms

mean with the provisos that

a) X means CH ₃ when Q ^{1 is} -O-CO- and b) Q ¹ , -O-, -O-CO- or a single bond and / or R ¹ -Q ¹ -C * R ° CF ₃ -X means and / or X means CH ₃ if m is 1 or 2 , Z is -CO-O- or a single bond and the groups A ¹ and A ^{2 are} unsubstituted 1,4-phenylene.

The compounds of the formula I, like similar compounds described in DE-OS 35 15 373, can be used as components of chiral-tapped smectic liquid-crystalline phases.

By JW Goddby and TM Leslie (Liquid Crystals and ordered Fluids, Vol. 4, Proceedings of an American Chemical Society Symposium, Las Vegas, March 29 to April 1, 1982, New York, Plenum Press, 1984 page 1-32) chiral 4'-octyloxybiphenyl-4-ylcarboxylic acid (1-trifluoromethyl) heptyl ester, which is unsuitable as a dopant for chirally-phased phases (S _c *) due to its orthogonal smectic phases (S _A , S _E ).

Similar chiral dopants have been described in DE-OS 35 34 777 and 35 34 778, which, however, are derived from 2,2,2-trifluoro-1-phenylethanol and 2,2,2-trifluoro-1- ( Derive 9'-anthryl) ethanol and have relatively high viscosities due to the 1-phenyl or 1- (9'-anthryl) group.

K. Yoshino et al. (e.g., Jpn. J. Appl. Phys., Part 1, 26 (Suppl. 26-2) 97-103, 1987), optically active 3-ethoxy-3-oxo-1- (trifluoromethyl) propyl and 3-phenyl-1- (trifluoromethyl) propyl ester of 4'-alkoxybiphenyl-4-ylcarbonyloxybenzoic acid also have relatively high viscosity values. Similar compounds are known from European patent applications EP-A1-0300497 and EP-A1-0301511, but in which a chiral C * H-CF ₃ group is bonded to a mesogenic residue via an alkylene group. However, the mesogenic residues described there have no fluorinated 1,4-phenylene groups or pyridine-2,5-diyl groups.

Chiral-chopped smectic liquid-crystalline phases with ferroelectric properties can be produced by adding a suitable chiral dopant to basic mixtures with one or more chased smectic phases (LA Beresnev et al., Mol. Cryst. Liq. Cryst. 89, 327 (1982 HR Brand et al., J. Physique 44, (lett.), L-771 (1983), such phases can be used as dielectrics for fast switching displays based on the principle of SSFLC technology described by Clark and Lagerwall (NA Clark and ST Lagerwall, Appl. Phys. Lett. 36, 899 (1980); USP 4,367,924) on the basis of the ferroelectric properties of the chiral-tinted phase. The elongated phase is in this phase

Molecules arranged in layers, the molecules having a tilt angle to the layer normal. When moving from layer to layer, the tilt direction changes by a small angle with respect to an axis perpendicular to the layers, so that a helical structure is formed. In displays that are based on the principle of SSFLC technology, the smectic layers are arranged perpendicular to the plates of the cell. The helical arrangement of the tilt directions of the molecules is suppressed by a very small distance between the plates (approx. 1-2 μm). This forces the long axes of the molecules to line up in a plane parallel to the plates of the cell, creating two excellent tilt orientations. By The application of a suitable alternating electric field can be switched back and forth between these two states in the liquid-crystalline phase which has a spontaneous polarization. This switching process is much faster than with conventional twisted cells (TN-LCD's), which are based on nematic liquid crystals.

A major disadvantage for many applications of the currently available materials with chiral-chopped smectic phases (such as Sc *) is their relatively high optical anisotropy, the switching times which are not sufficiently short due to relatively high viscosity values, and that the dielectric anisotropy values are greater than zero or if negative, has little nonzero values. Negative values of the dielectric anisotropy are required if the required planar orientation is brought about by superimposing the control field with an AC holding field with a 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 blended smectic mixtures can substantially reduce the disadvantages mentioned. The compounds of the formula I are therefore particularly suitable as components of chiral-chopped smectic liquid-crystalline phases. In particular, chemically particularly stable chiral-chopped smectic liquid-crystalline phases with favorable ferroelectric phase ranges, in particular with wide Sc * phase ranges, negative or also positive dielectric anisotropy, low optical anisotropy, favorable pitch height, are lower Viscosity and for such phases high values for spontaneous polarization and very short switching times can be produced. P is the spontaneous polarization in nC / cm ² .

With the provision of the compounds of the formula I, the range of liquid-crystalline substances which are suitable for the production of ferroelectric 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 phases 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, for example to improve the dielectric and / or optical anisotropy and / or the 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 vary. The compounds of the formula I are also suitable as intermediates for the preparation of other substances which can be used as constituents of liquid-crystalline phases.

The compounds of the formula I are colorless in the pure state and have favorable values of optical anisotropy. Some of the compounds of the formula I show liquid-crystalline mesophases in a temperature range which is favorably located for electro-optical use, but it is also possible to use isotropic or monotropically liquid-crystalline compounds of the formula I as components of chiral chopped smectic phases. They are very stable chemically, thermally and against light. The invention thus relates to the compounds of the formula I and to the use of the compounds of the formula I as components of liquid-crystalline phases.

The invention also relates to chiral-chopped smectic liquid-crystalline phases containing at least one compound of the formula I having at least one carbon atom linked to four different substituents.

The invention further relates to such phases containing at least one compound of the formula I and to liquid-crystal display elements, in particular electro-optical display elements, which contain such phases.

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

The 1,4-phenylene group can be substituted by one or two F atoms and / or CH ₃ and / or CN groups.

Above and below, R ¹ , m, A ¹ , A ² , Q ¹ , X, R ° and Z ^{1 have} the meaning given, unless expressly stated otherwise. Accordingly, the compounds of the formula I include, in particular, compounds of the sub-formula la (with two rings)

R ¹ -A ¹ -Z ¹ -A ² -Q ¹ -C * R ° CF ₃ X la

and Ib (with three rings):

R ¹ - (A ¹ -Z ¹ ) ₂ -A ² -Q ¹ -C * R ° CF ₃ X Ib

and Ic (with four rings):

R ¹ - (A ¹ -Z ¹ ) ₃ -A ² -Q ¹ -C * R ° CF ₃ X Ic

Among them, those of the formulas la and ib are particularly preferred.

Of the compounds of the formula I in which the ring A ^{1 is} a pyridine-2,5-diyl group or at least one of the rings A ¹ and A ^{2 is} a 2-fluoro,

3-fluorine or 2,3-difluorophenylene group are preferred, those in which Q is a group -O- (CH ₂ ) _n -, -O-CO- (CH ₂ ) _n - or -CO-O- (CH ₂ ) _n - means.

The preferred compounds of the formula Ia include those of the sub-formulas Ia1 to Ia4:

R ¹ -Ph-Z ¹ -Ph-Q ¹ -C * R ° CF ₃ X la1

R ¹ -Ph-Z ¹ -Cy-Q ¹ -C * R ° X CF ₃ Ia2 R ¹ -Cy-Z ¹ -Ph-Q ¹ -C * RºCF ₃ X Ia3

R ¹ -Cy-Z ¹ -Cy-Q ¹ -C * R ° CF ₃ X Ia4

Among them, those of the sub-formulas III are particularly preferred. The preferred compounds of the formula Ib include those of the sub-formulas Ib1 to Ib9:

R ¹ -Ph-Z ¹ -Ph-Z ¹ -Ph-Q ¹ -C * R ° CF ₃ X Ib1

R ¹ -Ph-Z ¹ -Ph-Z ¹ -Cy-Q ¹ -C * R ° CF ₃ X Ib2 R ¹ -Cy-Z ¹ -Ph-Z ¹ -Cy-Q ¹ -C * R ° CF ₃ X Ib3

R ¹ -Ph-Z ¹ -Cy-Z ¹ -Ph-Q ¹ -C * R ° CF ₃ X Ib4

R ¹ -Ph-Z ¹ -Cy-Z ¹ -Cy-Q ¹ -C * R ° CF ₃ X Ib5

R ¹ -Cy-Z ¹ -Cy-Z ¹ -Ph-Q ¹ -C * R ° CF ₃ X Ib6

R ¹ -Cy-Z ¹ -Ph-Z ¹ -Cy-Q ¹ -C * R ° CF ₃ X Ib7 R ¹ -Cy-Z ¹ -Cy-Z ¹ -Cy-Q ¹ -C * R ° CF ₃ X Ib8

R ¹ -Cy-Z ¹ -Ph-Z ¹ -Ph-Q ¹ -C * R ° CF ₃ X Ib9

Compounds of the formula I in which R ° is an alkyl group different from X and preferably having 1 to 7 C atoms are particularly preferred. Hexyl, pentyl, butyl, i-butyl, propyl, i-propyl, methyl and ethyl, in particular methyl, are particularly preferred. Q preferably denotes -O-CO- (where the carbonyl carbon atom is linked to the asymmetric C atom C *), -O-, -CO-O- (where this group is linked via the oxygen atom to the asymmetric C atom C * ) or a single bond (-).

In the preferred compounds of the formulas above and below in which Q ¹ denotes a single bond, R ° is an alkyl group other than X with preferably 1 to 7 C atoms, an alkoxy or an alkanoyloxy group with preferably 1 to 7 C each Atoms.

Particularly preferred alkyl groups are hexyl, pentyl, butyl, i-butyl, propyl, i-propyl, methyl and ethyl, in particular methyl (X = H); particularly preferred alkoxy groups are hexoxy, pentoxy, i-butoxy, propoxy, i-propoxy, methoxy and ethoxy, in particular methoxy; particularly preferred Alkanoyloxy groups are hexanoyloxy, pentanoyloxy, butyryloxy, propionyloxy, acetyloxy and formyloxy, especially acetyloxy.

In the preferred compounds of the formulas above and below, the alkyl radicals, in which a CH ₂ group (alkoxy or oxaalkyl) can also be replaced by an O atom, can be straight-chain or branched. They preferably have 5, 6, 7, 8, 9 or 10 carbon atoms and accordingly preferably mean pentyl, hexyl, heptyl, octyl, nonyl, decyl, pentoxy, hexoxy, heptoxy, octoxy, nonoxy or decoxy, and 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-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl.

A ¹ and A ² are preferably Cy or Ph. In the compounds of the formulas above and below, Ph preferably denotes a 1,4-phenylene (Phe), a 1 substituted once or twice by F, CN and / or CH ₃ , 4-phenylene group (PheX) a pyrimidine-2,5-diyl- (Pyr), a pyridine-2,5-diyl- (Pyn), a pyrazine-3,6-diyl- or a pyridazine- 2,5- diyl group, particularly preferably Phe, PheX, Pyr or Pyn. The compounds according to the invention preferably contain no more than one 1,4-phenylene group in which one or two CH groups are replaced by N. Cy preferably represents a 1,4-cyclohexylene group. However, particular preference is given to compounds of the formula I in which one of the groups A ¹ and A ^{2 is} one in 1- or 4-position by CN sub means substituted 1,4-cyclohexylene group and the nitrile group is in the axial position, ie the group A ² or A ^{2 has} the following configuration:

Compounds of the formula I and the above partial formulas which contain a group -Ph-Ph- are particularly preferred. -Ph-Ph- is preferably -Phe-Phe-, Phe-Pyr or Phe-Pyn. The groups are particularly preferred

and as well

further unsubstituted or mono- or polysubstituted by fluorine 4,4'-biphenylyl. Compounds of the formula I and the partial formulas below which contain a 2,3-difluoro-1,4-phenylene group are particularly preferred.

The groups Z each independently of one another preferably denote a single bond, in the second place preferably -O-CO-, -CO-O-, -C≡C- or -CH ₂ CH ₂ - groups. Particular preference is given to compounds of the formulas I or of the partial formulas Ib1 to Ib9 in which one group is Z ¹ -CH ₂ CH ₂ - and the other is -O-CO- or -CO-O-. X in the compounds of the formulas above and below, preferably CH ₃ .

The preferred meaning of Q is -O-, -O-CO-, -CO-O- and a single bond. In the compounds of the formula I in which Q ¹ denotes a single bond and X is a hydrogen atom, the group adjacent to the asymmetric C atom C * means

A ² preferably Cy.

Compounds of the formulas above and below with branched wing groups R ¹ can be important.

Branched groups of this type usually contain no more than two chain branches. R ¹ is preferably a straight-chain group or a branched group with no more than one 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-methylhexyl, 2-propylpentyl, 6-methylheptyl, 7-methyloctyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1 -Methylhexoxy, 1-methylheptoxy, 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl.

The radical R ¹ can also be an optically active organic

Rest with an asymmetric carbon atom. The asymmetrical carbon atom is then preferably linked to two differently substituted carbon atoms, one hydrogen atom and one substituent selected from the group consisting of halogen (in particular F, Cl or Br), alkyl or alkoxy, each having 1 to 5 carbon atoms and CN. The optically active organic radical preferably has the formula

wherein X '-CO-O-, -O-CO-, -O-CO-O-, -CO-, -O-, -S-,

-CH = CH-, -CH = CH-COO- or a single bond,

Q 'alkylene with 1 to 5 C atoms, in which a CH ₂ group which is not linked to X' is also replaced by -O-, -CO-, -O-CO-, -CO-O- or -CH = CH- can be, or a single bond,

CN, halogen, methyl or methoxy, and

R ^{5 is} an alkyl group different from Y with 1 to 15 C atoms, in which also one or two non-adjacent CH ^ groups are represented by -O-, -CO-, -O-CO-, -CO-O- and / or - CH = CH- can be replaced,

means.

X 'is preferably -CO-O-, -O-CO-, -CH = CH-COO- (trans) or a single bond. -CO-O - / - O-CO- or a single bond are particularly preferred.

Q 'is preferably -CH ₂ -, -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ - or a single bond, particularly preferably a single bond.

is preferably CH ₃ , -CN, F or Cl, particularly preferably CN or F.

R ⁵ is preferably straight-chain or branched alkyl having 1 to 10, in particular having 1 to 7, carbon atoms. Preferred compounds of the formula I and Ia to Ic are those in which at least one of the radicals contained therein has one of the preferred meanings indicated.

In the compounds of the formula I and in the formulas _above and below, - (A ¹ -Z ¹ ) _m -A ² - is preferably a group of the following formulas 1 to 39 or its mirror image:

(P = 1, 2, 3, or 4; q = 0, 1, 2, 3 or 4)

-

- |

-

Groups of the formulas 1, 5, 7, 9, 10, 11, 12, 13, 14, 22 and 39, in particular those of the formulas 5 and 7, are particularly preferred. Some other preferred smaller group of compounds of formula I are those of sub-formulas B, C, D, E, F, G, H, J and K:

R ¹ - (A ¹ ) mA ² -OOC-C * (CH ₃ ) (CF ₃ ) -Rº B

R ¹ - (A ¹ ) _m -A ² -OC * (CH ₃ ) (CF ₃ ) -R ° C

R ¹ - (A ¹ ) mA ² -C * (CH ₃ ) (CF ₃ ) -OCO-Rº D

R ¹ - (A ¹ ) _m -A ² -C * (CH ₃ ) (CF ₃ ) -OR ° E

R ¹ - (A ¹ ) _m -A ² -C * (CH ₃ ) (CF ₃ ) -R ° F

R ¹ - (A ¹ ) _m -A ² -C * H- (CF ₃ ) -O-CO-R ° G

R ¹ - (A ¹ ) _m -A ² -C * H- (CF ₃ ) -OR ° H

R ¹ - (A ¹ ) _m -A ² -CO-OC * H- (CF ₃ ) -R ° J

R ¹ - (A ¹ ) K mA ² -OC * H- (CF ₃ ) -R °

wherein R ¹ R °, A ¹ and A ^{2 have} the meaning given for formula I. m is preferably 1 or 2. - (A ¹ ) _m -A ² - preferably means

-

or or a reflection of this shape

ln. In the case of the compounds of the formula J, according to the proviso b) - (A ¹ ) -A ² - is not

Further preferred small groups of compounds of the formula I are those of the subgroups L to Z,

R ¹ -Pyd-A ² -O- (CH ₂ ) _n -C * (CH ₃ ) (CF ₃ ) -R ° L

R ¹ -Pyd-A ² -OOC- (CH ₂ ) _n -C * (CH ₃ ) (CF ₃ ) -R ° M

R ¹ -Pyd-A ² -COO- (CH ₂ ) _n -C * (CH ₃ ) (CF ₃ ) -R ° N

R ¹ -Pyd-A ² -COO- (CH ₂ ) _n -C * H (CF ₃ ) -R ° O

R ¹ -Pyd-A ² -OOC- (CH ₂ ) _n -C * H (CF ₃ ) -R ° P

R ¹ -Pyd-A ² -O- (CH ₂ ) _n -C * H (CF ₃ ) -R ° Q

R ¹ -PheF-A ² -O- (CH ₂ ) _n -C * H (CF ₃ ) -R ° R

R ¹ -PheF-A ² -OOC- (CH ₂ ) _n -C * H (CF ₃ ) -R ° S

R ¹ -PheF-A ² -COO- (CH ₂ ) _n -C * H (CF ₃ ) -R ° T

R ¹ -PheF-A ² -COO- (CH ₂ ) _n -C * (CH ₃ ) (CF ₃ ) -R ° U

R ¹ -PheF-A ² -OOC- (CH ₂ ) _n -C * (CH ₃ ) (CF ₃ ) -R ° V

R ¹ -PheF-A ² -O- (CH ₂ ) _n -C * (CH ₃ ) (CF ₃ ) -R ° W R ¹ -A ¹ -PheF-O- (CH ₂ ) _n -C * (CH ₃ ) (CF ₃ ) -R ° X

R ¹ -A ¹ -PheF-OCO- (CH ₂ ) _n -C * (CH ₃ ) (CF ₃ ) -R ^o Y

R ¹ -A ¹ -PheF-COO- (CH ₂ ) _n -C * (CH ₃ ) (CF ₃ ) -R ° Z

wherein R ¹ , R °, A ¹ and n have the meaning given for formula I and Pyd a pyridine-2,5-diyl group and PheF a 2-fluoro-1,4-phenylene, a 3-fluoro-1,4 -phenylene or a 2,3-difluorophenylene group.

R ¹ is preferably straight-chain alkyl or alkoxy having 5 to 12 carbon atoms. R ° is preferably straight-chain or branched alkyl having 1 to 5 carbon atoms.

Those of the formulas mentioned above which contain one or more groups dio, dit, pip and / or pyr each encompass the two possible 2,5- (dio, dit, pyr) and 1,4-position isomers (pip).

The compounds of the formula I are prepared by methods known per se, as described in the literature (for example in the standard works such as Houben-Weyl, Methods of Organic Chemistry, Georg-Thieme-Verlag, Stuttgart), and under reaction conditions that are known and suitable for the implementations mentioned. Use can also be made of variants which are known per se and are not mentioned here in detail. If desired, the 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 converted further into the compounds of the formula I.

For example, the compounds of the formula I or suitable precursors for their preparation can be prepared by reducing a compound which otherwise corresponds to the formula I but contains one or more reducible groups and / or C-C bonds instead of H atoms.

Possible reducible groups are preferably -CH = CH groups, furthermore, for example, free or esterified hydroxyl groups, aromatically bound halogen atoms or carbonyl groups. Preferred starting materials for the reduction correspond to the formula I, but can instead of a -CH ₂ CH ₂ group a -CH = CH group and / or instead of a -CH ₂ group a -CO group and / or instead of an H atom, contain a free or a functional OH group (for example in the form of its p-toluenesulfonate).

The reduction can be carried out, for example, by catalytic hydrogenation at temperatures between about 0 ° and about 200 ° and pressures between about 1 and 200 bar in an inert solvent, for example an alcohol such as methanol, ethanol or isopropanol, an ether such as tetrahydrofuran (THF) or dioxane , an ester such as ethyl acetate, a carboxylic acid such as acetic acid or a hydrocarbon such as cyclohexane. Suitable catalysts are suitably noble metals such as Pt or Pd, which can be used in the form of oxides (for example PtO ₂ , PdO), on a support (for example Pd on carbon, calcium carbonate or strontium carbonate) or in finely divided form. Ketones can also be prepared using the Clemmensen methods (with zinc, amalgamated zinc or tin and hydrochloric acid, expediently in an aqueous-alcoholic solution or in a heterogeneous phase with water / toluene at temperatures between about 80 and 120 °) or Wolff-Kishner (with hydrazine, expediently reduced in the presence of alkali such as KOH or NaOH in a high-boiling solvent such as diethylene glycol or triethylene glycol at temperatures between about 100 and 200 °) to the corresponding compounds of formula I which contain alkyl groups and / or -CH ₂ CH ₂ bridges .

Reductions with complex hydrides are also possible. For example, arylsulfonyloxy groups can be removed reductively with LiAlH ₄ , in particular p-toluenesulfonyloxymethyl groups can be reduced to methyl groups, expediently in an inert solvent such as diethyl ether or THF at temperatures between about 0 and 100 °. Double bonds can be hydrogenated (even in the presence of CN groups!) With NaBH ₄ or tributyltin hydride in methanol; for example, the corresponding cyclohexane derivatives are formed from 1-cyanocyclohexene derivatives.

Esters of the formula I can also be obtained by esterifying corresponding carboxylic acids (or their reactive derivatives) with alcohols or phenols (or their reactive derivatives).

Suitable reactive derivatives of the carboxylic acids mentioned are, in particular, the acid halides, especially the chlorides and bromides, and also the anhydrides, for example also mixed anhydrides, azides or esters, in particular alkyl esters with 1 to 4 carbon atoms in the alkyl group. Suitable reactive derivatives of the alcohols or phenols mentioned are in particular the corresponding metal alcoholates or phenolates, preferably an alkali metal such as Na or K.

The esterification is advantageously carried out in the presence of an inert solvent. In particular, ethers such as diethyl ether, di-n-butyl ether, THF, dioxane or anisole, ketones such as acetone, butanone or cyclohexanone, amides such as DMF or phosphoric acid hexamethyltriamide, hydrocarbons such as benzene, toluene or xylene, halogenated hydrocarbons such as carbon tetrachloride or tetrachlorethylene and sulfoxides are particularly suitable Dimethyl sulfoxide or sulfolane. Water-immiscible solvents can at the same time advantageously be used for azeotropically distilling off the water formed during the esterification. Occasionally an excess of an organic base, e.g. Pyridine, quinoline or triethylamine can be used as a solvent for the esterification. The esterification can also be carried out in the absence of a solvent, e.g. by simply heating the components in the presence of sodium acetate. The reaction temperature is usually between -50 ° and + 250 °, preferably between -20 ° and + 80 °. At these temperatures, the esterification reactions are usually complete after 15 minutes to 48 hours.

In particular, the reaction conditions for the esterification largely depend on the nature of the starting materials used. A free carboxylic acid with a free alcohol or phenol is usually in the presence of a strong acid, for example a mineral acid such as hydrochloric acid or sulfuric acid. A preferred reaction mode is the reaction of an acid anhydride or in particular an acid chloride with an alcohol, preferably in a basic medium, the bases being in particular alkali metal hydroxides such as sodium or potassium hydroxide, alkali metal carbonates or hydrogen carbonates such as sodium carbonate, potassium carbonate or potassium hydrogen carbonate, alkali metal acetates such as sodium or potassium acetate, Alkaline earth metal hydroxides such as calcium hydroxide or organic bases such as triethylamine, pyridine, lutidine, collidine or quinoline are important. A further preferred embodiment of the esterification consists in first converting the alcohol or the phenol into the sodium or potassium alcoholate or phenolate, for example by treatment with ethanolic sodium or potassium hydroxide solution, isolating it and together with sodium bicarbonate or potassium carbonate with stirring suspended in acetone or diethyl ether and this suspension mixed with a solution of the acid chloride or anhydride in diethyl ether, acetone or DMF, advantageously at temperatures between about -25 ° and + 20 °.

Dioxane derivatives or dithiane derivatives of the formula I are expediently prepared by reacting an appropriate aldehyde (or one of its reactive derivatives) with a corresponding 1,3-diol or a corresponding 1,3-dithiol (or one of its reactive derivatives), preferably in the presence an inert solvent such as benzene or toluene and / or a catalyst, for example a strong acid such as sulfuric acid, benzene or p-toluenesulfonic acid, at temperatures between 20 ° and about 150 °, preferably between 80 ° and 120 °. Acetals are primarily suitable as reactive derivatives of the starting materials. Some of the aldehydes and 1,3-diols or 1,3-dithiols mentioned and their reactive derivatives are known, and all of them can be prepared without difficulty from standard compounds of organic chemistry from compounds known from the literature. For example, the aldehydes can be obtained by oxidation of corresponding alcohols or by reduction of corresponding carboxylic acids or their derivatives, the diols by reduction of corresponding diesters and the dithiols by reaction of corresponding dihalides with NaSH.

Ethers of the formula I can be obtained by etherification of corresponding hydroxyl compounds, preferably corresponding phenols, the hydroxyl compound advantageously first being converted into a corresponding metal derivative, for example by treatment with NaH, NaNH ₂ , NaOH, KOH, Na ₂ CO ₃ or K ₂ CO ₃ corresponding alkali metal alcoholate or alkali metal phenolate is converted. This can then be reacted with the corresponding alkyl halide, sulfonate or dialkyl sulfate, advantageously in an inert solvent such as acetone, 1,2-dimethoxyethane, DMF or dirnethyl sulfoxide or even an excess of aqueous or aqueous-alcoholic NaOH or KOH at temperatures between about 20 ° and 100 °.

Compounds of the formula I which contain a 2,3-difluoro-1,4-phenylene group can be prepared starting from 1,2-difluorobenzene analogously to the process described in DE 3807910.

The optically active ethers of the formula I (in which Q ¹ = 0) are obtained from the optically active carboxylic acids of the formula R ¹ - (A ¹ -Z ¹ ) _m -A ² -OC * R ° (CO ₂ H) -X Reaction with sulfur tetrafluoride according to US Pat. No. 4,187,381. These optically active carboxylic acids can be prepared from the corresponding benzyl esters by hydrogenolytic cleavage. These benzyl esters are obtained by reacting the alcohols or phenols of the formula

R ¹ - (A ¹ - Z ¹ ) _m - A ² -OH with the optically active 2-hydroxycarboxylic acid benzyl esters according to the method of O. Mitsunobu,

Synthesis 1981, 1st

To prepare nitriles of the formula I or to prepare suitable precursors, corresponding chlorine or bromine compounds of the formula I or suitable precursors can also be reacted with a cyanide, advantageously with a metal cyanide such as NaCN, KCN or Cu ₂ (CN) ₂ , for example in Presence of pyridine in an inert solvent such as DMF or N-methylpyrrolidone at temperatures between 20 ° and 200 °.

The optically active compounds of the formula I are obtained by using appropriate optically active starting materials and / or by separating the optical antipodes by means of chromatography using known methods.

Esters of the formula I in which Q is -O-CO- and the carbonyl carbon atom is linked directly to the asymmetric C atom C * can easily be obtained from the corresponding optically active 2-trifluoromethyl-2-methylcarboxylic acids (X = CH ₃ ) by esterification with mesogenic alcohols or phenols, for example of the formula R ¹ - (A ¹ -Z ¹ ) _m -A ² -OH or with alcohols of the formula R ° -OH. The esterification can be carried out by one of the methods mentioned above. However, the DCC method given in the examples is preferably used. The optically active 2-trifluoromethylcarboxylic acids are obtained from the optically active dialkylated malonic half-esters according to US Pat. No. 4,187,381 by reaction with sulfur tetrafluoride and subsequent saponification of the ester.

Also by reacting the optically active dialkylated 2-cyanocarboxylic acids (produced according to DE-OS 36 38 026) with sulfur tetrafluoride, reducing the cyano group with e.g. Diisobutylaluminum hydride and subsequent oxidation give optically active 2-trifluoromethyl carboxylic acids.

The optically active or dialkylated malonic half-esters can e.g. according to F. Bjorkling et al., Tetrahedron Letters by enzymatic cleavage of the corresponding malonic diesters, e.g. with pork liver esterase.

It is also possible to separate the racemic malon half esters by resolving racemates using optically active bases. Ephedrine, quinine, threobase and dehydroabietylamine may be mentioned as preferred bases here. A preferred embodiment of this racemate resolution is, after the desired diastereomer has been separated off, to convert the remaining one into the racemate by means of an intramolecular transesterification and to subject it to racemate resolution again. (see DE-OS 35 41 450).

Esters of the formula I in which Q ¹ -CO-O- or R ° denotes an alkanoyloxy group can easily be obtained from the corresponding optically active 1-trifluoromethylalkan-1-ols by esterification with mesogenic carboxylic acids, for example of the formula R -

(A ¹ -Z ¹ ) _m -A ² -CO ₂ H or with carboxylic acids of the formula R ° -CO ₂ H. The esterification can be carried out by one of the methods mentioned above. However, the DCC method given in the examples is preferred. The optically active 1-trifluoromethylalkan-1-ols can be obtained by reducing the corresponding trifluoromethylalkyl ketones with optically active reducing agents or enzymatically with dehydrogenases.

They can also be obtained by racemate resolution from the racemic 1-trifluoroalkan-1-ol, as described in Optical Resolution Procedures for Chemical Compounds, Vol. 3, Manhattan College, Riverdale, New York 10471.

Optically active 1-trifluoroalkan-1-ols can also be obtained by enzymatic cleavage of the racemic 2-acetyloxy-1,1,1-trifuoralkanes with lipases according to J.T. Lin, T. Yamazaki, T. Kitazume J. Org. Chem., 52 3211-3217 (1987).

The trifluoromethyl ketones required as starting materials can e.g. according to E.T. McBee, O.R. Pierce, D.O. Meyer, J. Am. Chem. Soc, 77, 917 (1955) can be obtained by reacting lithium organylene or Grignard reagents with trifluoroacetic acid or its derivatives.

The racemic 1-trifluoromethylalkan-1-ols can e.g. according to T. Kitazume et al., J. of Fluorine Chemistry, 24, 419 (1984) can also be obtained by reacting lithium organylene with trifluoroacetaldehyde.

Examples of suitable mesogenic acids are listed below:

The phases according to the invention contain at least one, preferably at least two compounds of the formula I. Particular preference is given to chiral tutated smectic liquid-crystalline phases whose achiral base mixture contains, in addition to compounds of the formula I, at least one other component with a negative or small positive dielectric anisotropy. The chirality is preferably partly or completely based on chiral compounds of the formula I. These phases preferably contain one or two chiral compounds of the formula I. However, achiral compounds of the formula I (for example in the form of a racemate) can also be used, in which case the Chirality of the phase is caused by other optically active compounds. If chiral

Compounds of the formula I are used, in addition to the pure optical antipodes, mixtures with an enantiomeric excess are also suitable. The above-mentioned further component (s) of the achiral base mixture can make up 1 to 50%, preferably 10 to 25%, of the base mixture. Compounds of the sub-formulas Va to Vq are suitable as further components with small positive or negative dielectric anisotropy:

Compounds containing the structural element M, N or O are also suitable as further components with negative dielectric anisotropy.

Preferred compounds of this type correspond to formulas VIb and VIc:

R'-Q ³ -Q ⁴ -R '''VIc

R 'and R''each preferably represent straight-chain alkyl or alkoxy groups each having 2 to 10 carbon atoms. Q ¹ and Q ² each represent 1,4-phenylene, trans-1,4-cyclohexylene, 4,4'-biphenylyl, 4- (trans-4-cyclohexyl) phenyl, trans, trans-4,4'-bicyclohexyl or one of the groups Q ¹ and Q ² also a single bond.

Q ³ and Q ⁴ each represent 1,4-phenylene, 4,4'-biphenylyl or trans-1,4-cyclohexylene. One of the groups Q ³ and Q ⁴ can also mean 1,4-phenylene, in which at least one

CH group is replaced by N. R '' 'is an optically active residue with an asymmetric carbon atom

the structure has preferably

the formula

R ⁴ and R ⁵ 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.

Particularly preferred are the compounds of the partial forms Va, Vb, Vd and Vf, in which R ⁴ and R ⁵ each represent straight-chain alkyl or alkoxy each having 5 to 10 carbon atoms.

The compounds of the partial form in Vc, Vh and Vi are suitable as additives for lowering the melting point and are normally added to the base mixtures in an amount of not more than 5%, preferably 1 to 3%. R ⁴ and R ⁵ in the compounds of the partial form in Vc, Vh and Vi are preferably straight-chain alkyl having 2 to 7, preferably 3 to 5, carbon atoms. Another class of compounds suitable for lowering the melting point in the phases according to the invention is that of the formula

wherein R ⁴ and R ^{5 have} the preferred meaning given for Vc, Vh and Vi. with the preferred meanings mentioned above.

Particularly preferred components with negative dielectric anisotropy are the compounds with the structural element M or N described in WO 86-00529. Those of the formula VId are particularly preferred

wherein alkyl is a straight-chain or branched alkyl group with preferably 3 to 10 carbon atoms and R 'has the meaning given above. Also preferred are compounds according to formula VId, in which one or both single bonds linking the rings are replaced by a group selected from -CH ₂ CH ₂ -, -O-CO- or -CO-O-. Particularly preferred compounds of the formula VIc are those of the 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 components of nematic liquid crystalline phases, e.g. to avoid reverse twist.

In addition to one or more compounds according to the invention, these 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, in addition to one or more of the invention Components 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 cyclohexylbenzoates, cyclohexane-carboxylic acid phenyl- or cyclohexyl-esters, phenyl- or cyclohexyl-esters of cyclohexylbenzoic acid, cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl of benzoic acid, of cyclohexanecarboxylic acid, or of cyclohexylcyclohexanecarboxylic acid, phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexenes, cyclohexylcyclohexylcyclohexenes, 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-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'-LC = CER "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 fluorine substituted 1,4-phenylene, Cyc trans- 1,4-cyclohexylene or 1,4-cyclohexenylene, pyr pyrimidine-2, 5-diyl or pyridine-2, 5-diyl, dio 1,3-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.

One of the radicals L and E is preferably 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 optionally one or more components selected from the compounds of the formulas 1, 2, 3, 4 and 5, in which the radicals L and E are selected from the group -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.

In the compounds of the sub-formulas Ia, 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 each other different, one of these radicals is usually alkyl or alkenyl. In the Compounds of the sub-formulas Ib, 2b, 3b, 4b and 5b mean R "-CN, -CF ₃ , F, Cl or -NCS; R has the meaning given for the compounds of the sub-formulas 1a to 5a and is preferably alkyl or alkenyl. However, other variants of the proposed substituents in the compounds of the formulas 1, 2, 3, 4 and 5 are also common .. Many such substances or mixtures thereof are commercially available, all of which can be obtained by methods known from the literature or by analogy.

In addition to components from the group of compounds Ia, 2a, 3a, 4a and 5a (group 1), the media according to the invention preferably also contain components from the group of compounds Ib, 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, expediently 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, mp. = Melting point, cp. = Clearing point. Percentages above and below mean percentages by weight; all temperatures are given in degrees Celsius. "Conventional work-up" means: water is added, water is added, the mixture is extracted with methylene chloride, the mixture is separated off, the organic phase is dried, evaporated and the product is purified 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

To a mixture of 0.1 mol of optically active 2-methyl-2-trifluoromethyloctanoic acid (prepared from the optically active 2-methoxy-2-hexylmalonic acid monomethyl ester with sulfur tetrafluoride and subsequent saponification with

Potassium hydroxide in ethanol), 0.1 mol of 4-hexyloxy-4'-hydroxybiphenyl, 150 ml of dichloromethane and 1 mmol of 4-N, N-dimethylaminopyridine are added to a mixture of 0.1 mol of dicyclohexylcarbodiimide and 50 ml of dichloromethane. After stirring for 24 hours at room temperature, filtering off the solid constituents and customary working up, optically active 4- (2-methyl-2-trifluoromethyloctanoyloxy) -4'-hexyloxybiphenyl is obtained.

The following optically active connections are produced analogously

4- (2-methyl-2-trifluoromethylpropionyloxy) -4'-hexyloxybiphenyl

4- (2-methyl-2-trifluoromethylbutyryloxy) -4'-hexyloxybiphenyl 4- (2-methyl-2-trifluoromethylpentanoyloxy) -4'-hexyloxybiphenyl

4- (2-methyl-2-trifluoromethylhexanoyloxy) -4'-hexyloxybiphenyl

4- (2-methyl-2-trifluoromethylheptanoyloxy) -4'-hexyloxybiphenyl

4- (2-methyl-2-trifluoromethylnonanoyloxy) -4'-hexyloxybiphenyl 4- (2-methyl-2-trifluoromethylpropionyloxy) -4'-octyloxybiphenyl

4- (2-methyl-2-trifluoromethylbutyryloxy) -4'-octyloxybiphenyl 4- (2-methyl-2-trifluoromethylpentanoyloxy) -4'-octyloxybiphenyl

4- (2-methyl-2-trifluoromethylhexanoyloxy) -4'-octyloxybiphenyl

4- (2-methyl-2-trifluoromethylheptanoyloxy) -4'-octyloxybiphenyl

4- (2-methyl-2-trifluoromethyloctanoyloxy) -4'-octyloxybiphenyl

4- (2-methyl-2-trifluoromethylnonanoyloxy) -4'-octyloxybiphenyl

Analogously, 4- (trans-alkylcyclohexyl) phenols give optically active 4- (2-methyl-2-trifluoromethylalkanoyloxy) -1- (trans-4-alkylcyclohexyl) benzenes:

4- (2-methyl-2-trifluoromethylnonanoyloxy) -1- (trans-4-pentylcyclohexyl) benzene 4- (2-methyl-2-trifluoromethylpropionyloxy) -1- (trans-4-pentylcyclohexyl) benzene

4- (2-methyl-2-trifluoromethylbutyryloxy) -1- (trans-4-pentylcyclohexyl) benzene 4- (2-methyl-2-trifluoromethylpentanoyloxy) -1- (trans-4-pentylcyc1ohexyl) benzene

4- (2-methyl-2-trifluoromethylheptanoyloxy) -1- (trans-4-pentylcyclohexyl) benzene 4- (2-methyl-2-trifluoromethyloctanoyloxy) -1- (trans-4-pentylcyclohexyl) benzene With 4-alkyl-2 ', 3'-difluoro-4'-hydroxybiphenyl (prepared from 4'-alkyl-2,3-difluorobiphenyl by ortho-lithiation with n-butyllithium, reaction with trimethyl borate and subsequent cleavage with H ₂ O ₂ in acetic acid) gives analogously optically active 4- (2-methyl-2-trifluoromethylalkanoyloxy) -2,3-difluoro-4'-alkylbiphenyls:

4- (methyl-2-trifluoromethylpropionyloxy) -2,3-difluoro-4'-propylbiphenyl

4- (methyl-2-trifluoromethylbutyryloxy) -2,3-difluoro-4'-propylbiphenyl

4- (methyl-2-trifluoromethylpentanoyloxy) -2,3-difluoro-4'-propylbiphenyl

4- (methyl-2-trifluoromethylhexanoyloxy) -2,3-difluoro-4'-propylbiphenyl 4- (methyl-2-trifluoromethylheptanoyloxy) -2,3-difluoro-4'-propylbiphenyl

4- (methyl-2-trifluoromethyloctanoyloxy) -2,3-difluoro-4'-propylbiphenyl

4- (methyl-2-trifluoromethylnonanoyloxy) -2,3-difluoro-4'-propylbiphenyl

With 4- (5-alkylpyrimidin-2-yl) phenols, optically active 4- (2-methyl-2-trifluoromethylalkanoyloxy) -1- (5-alkylpryrimidin-2-yl) benzenes are obtained analogously:

4- (2-methyl-2-trifluoromethylpropionyloxy) -1- (5-pentylpyrimidin-2-yl) benzene

4- (2-methyl-2-trifluoromethylbutyryloxy) -1- (5-pentylpyrimidin-2-yl) benzene

4- (2-methyl-2-trifluoromethylpentanoyloxy) -1- (5-pentylpyrimidin-2-yl) benzene 4- (2-methyl-2-trifluoromethylhexanoyloxy) -1- (5-pentylpyrimidin-2-yl) benzene

4- (2-methyl-2-trifluoromethylheptanoyloxy) -1- (5-pentylpyrimidin-2-yl) benzene

4- (2-methyl-2-trifluoromethyloctanoyloxy) -1- (5-pentylpyrimidin-2-yl) benzene

4- (2-methyl-2-trifluoromethylnonanoyloxy) -1- (5-pentylpyrimidin-2-yl) benzene

Example 2

To a mixture of 0.1 mol of 4-octyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (made from 4-octyloxy-2', 3'-difluorobiphenyl by ortho-lithiation and n-butyllitium and subsequent carboxylation with Dry ice), 0.1 mol optically active 1-trifluoromethylethanol (manufactured according to JW Crawford J. Chem. Soc. 1965, 4280),

1 mmol of 4-N, N-dimethylaminopyridine and 150 ml of dichloromethane are added to a mixture of 0.1 mol of dicyclohexylcarbodiimide and 50 ml of dichloromethane. After stirring for 10 hours at room temperature, filtering off the solid constituents and customary working up, optically active 4-octyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylethyl) ester is obtained.

The following optically active connections are made analogously:

4-octyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylpropyl) ester

4-octyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylbutyl) ester 4-octyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylpentyl) ester

4-octyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylhexyl) ester 4-octyloxy-2', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylheptyl) ester

4-octyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethyloctyl) ester

4-Hexyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylpropyl) ester

4-Hexyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylbutyl) ester

4-hexyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylpentyl) ester 4-hexyloxy-2', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylhexyl) -ester

4-Hexyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylheptyl) ester

4-Hexyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethyloctyl) ester

4-Ethyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylpropyl) ester

4-ethyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylbutyl) ester 4-ethyloxy-2', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylpentyl) ester

4-Ethyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylhexyl) ester

4-Ethyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylheptyl) ester

4-Ethyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethyloctyl) ester Analogously, 4-alkyl-2 ', 3'-difluorobiphenyl4'-ylcarboxylic acids (prepared from 4-alkyl-2', 3'-difluorobiphenylene by ortho-lithiation with n-butyllithium and

Carboxylation with carbon dioxide) optically active 4-alkyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylalkyl) ester:

4-Pentyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid 1-trifluoromethylethyl) ester

4-pentyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid 1-trifluoromethylpropyl) ester

4-pentyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid 1-trifluoromethylbutyl) ester

4-pentyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid 1-trifluoromethylpentyl) ester 4-pentyl-2', 3'-difluorobiphenyl-4'-ylcarboxylic acid 1-trifluoromethylhexyl) ester

4-Pentyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid 1-trifluoromethylheptyl) ester

4-Pentyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid 1-trifluoromethyloctyl) ester

4-octyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylethyl) ester

4-octyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylpropyl) ester 4-octyl-2', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylbutyl) ester

4-octyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylpentyl) ester

4-octyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylhexyl) ester 4-octyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethylheptyl) ester

4-octyl-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (1-trifluoromethyloctyl) ester

With 4- (trans-4-alkylcyclohexyl) benzoic acids, optically active 4- (trans-4-alkylcyclohexyl) benzoic acid (1-trifluoromethylalkyl) ester is obtained analogously:

4- (trans-4-pentylcyclohexyl) benzoic acid (1-trifluoromethylethyl) ester 4- (trans-4-pentylcyclohexyl) benzoic acid (1-trifluoromethylpropyl) ester

4- (trans-4-pentylcyclohexyl) benzoic acid (1-trifluoromethylbutyl) ester 4- (trans-4-pentylcyclohexyl) benzoic acid (1-trifluoromethylpentyl) ester

4- (trans-4-pentylcyclohexyl) benzoic acid (1-trifluoromethylhexyl) ester

4- (trans-4-pentylcyclohexyl) benzoic acid (1-trifluoromethylheptyl) ester 4- (trans-4-pentylcyclohexyl) benzoic acid (1-trifluoromethyl octyl) ester

Example 3

0.1 mol of 4- (2- (trans-4-heptylcyclohexyl) ethyl) phenyl-4-hydroxybenzoic acid ester (prepared by hydrogenolytic cleavage of the corresponding benzyl ether, which is obtained by esterifying 4-benzyloxybenzoic acid with 4- (2- (trans- Heptylcyclohexyl) ethyl) phenol with dicylcocarbodiimide is obtained) is analogous to Example 1 with 0.1 ml optically active 2-methyl-2-trifluoromethyloctanoic acid esterified. After customary working up, optically active 1- (2- (trans-4-nonylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethyloctanoyloxy) benzoyloxy) benzene is obtained.

The following optically active connections are made analogously:

1- (2-trans-4-ethylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethyloctanoyloxy) benzoyloxy) benzene.

1- (2-trans-4-propylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethyloctanoyloxy) benzoyloxy) benzene.

1- (2-trans-4-butylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethyloctanoyloxy) benzoyloxy) benzene. 1- (2-trans-4-pentylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethyloctanoyloxy) benzoyloxy) benzene. 1- (2-trans-4-hexylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethyloctanoyloxy) benzoyloxy) benzene. 1- (2-trans-4-heptylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethyloctanoyloxy) benzoyloxy) benzene. 1- (2-trans-4-octylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethyloctanoyloxy) benzoyloxy) benzene.

1- (2-trans-4-ethylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylbutyryloxy) benzoyloxy) benzene. 1- (2-trans-4-propylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylbutyryloxy) benzoyloxy) benzene. 1- (2-trans-4-butylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylbutyryloxy) benzoyloxy) benzene. 1- (2-trans-4-pentylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylbutyryloxy) benzoyloxy) benzene. 1- (2-trans-4-hexylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylbutyryloxy) benzoyloxy) benzene. 1- (2-trans-4-heptylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylbutyryloxy) benzoyloxy) benzene. 1- (2-trans-4-octylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylbutyryloxy) benzoyloxy) benzene.

1- (2-trans-4-ethylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylhexanoyloxy) benzoyloxy) benzene. 1- (2-trans-4-propylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylhexanoyloxy) benzoyloxy) benzene. 1- (2-trans-4-butylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylhexyanoyloxy) benzoyloxy) benzene.

1- (2-trans-4-pentylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylhexanoyloxy) benzoyloxy) benzene. 1- (2-trans-4-hexylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylhexanoyloxy) benzoyloxy) benzene. 1- (2-trans-4-heptylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylhexanoyloxy) benzoyloxy) benzene. 1- (2-trans-4-octylcyclohexyl) ethyl) -4- (4- (2-methyl-2-trifluoromethylhexanoyloxy) benzoyloxy) benzene.

Example 4

To a mixture of 4-octyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (manufactured according to Example 2), 0.1 mol (+) - 3-trifluoromethyl-1-nonanol (manufactured from (+) - 3 Trifluoromethylnonane carboxylic acid by reduction with lithium aluminum hydride), 1 mmol of 4-N, N-dimethylaminopyridine and 150 ml of dichloromethane are added to a mixture of 0.1 mol of dicyclohexylcarbodiimide and 50 ml of dichloroethane. After stirring for 10 hours at room temperature and customary work-up, the optically active 4-octyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester is obtained. The following optically active connections are made analogously:

4-Ethyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester 4-propyloxy-2', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-butyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-Pentyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-Hexyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-heptyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester 4-nonyloxy-2', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-Decyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-Ethyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylheptyl) ester

4-Propyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylheptyl) ester

4-butyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylheptyl) ester 4-pentyloxy-2', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylheptyl) ester

4-Hexyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylheptyl) ester

4-heptyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylheptyl) ester 4-Nonyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylheptyl) ester

4-Decyloxy-2 ', 3'-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylheptyl) ester

4-Ethoxy-2,3-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-Propyloxy-2,3-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-butyloxy-2,3-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-Pentyloxy-2,3-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-Hexyloxy-2,3-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester 4-heptyloxy-2,3-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-Nonyloxy-2,3-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

4-decyloxy-2,3-difluorobiphenyl-4'-ylcarboxylic acid (3-trifluoromethylnonyl) ester

Example 5

4- (5-Pentylpyridin-2-yl) benzoic acid (prepared by saponification of the corresponding benzonitrile, which is described in FR-A-2558831) is esterified analogously to Example 4 with (+) - 3-trifluoromethyl-1-nonanol. You get

4- (5-pentylpyridin-2-yl) benzoic acid (3-trifluoromethylnonyl) estr The following are produced analogously

4- (5-Ethylpyridin-2-yl) benzoic acid (3-trifluoromethylnonyl) ester

4- (5-Propylpyridin-2-yl) benzoic acid (3-trifluoromethylnonyl) ester

4- (5-butylpyridin-2-yl) benzoic acid (3-trifluoromethylnonyl) ester

4- (5-Hexylpyridin-2-yl) benzoic acid (3-trifluoromethylnonyl) ester 4- (5-heptylpyridin-2-yl) benzoic acid (3-trifluoromethylnonyl) ester

4- (5-Octylpyridin-2-yl) benzoic acid (3-trifluoromethylnonyl) ester 4- (5-nonylpyridin-2-yl) benzoic acid (3-trifluoromethylnonyl) ester

4- (5-decylpyridin-2-yl) benzoic acid (3-trifluoromethylnonyl) ester

4- (5-Ethylpyridin-2-yl) benzoic acid (3-trifluoromethylheptyl) ester 4- (5-propylpyridin-2-yl) benzoic acid (3-trifluoromethylheptyl) ester

4- (5-Butylpyridin-2-yl) benzoic acid (3-trifluoromethylheptyl) ester 4- (5-hexylpyridin-2-yl) benzoic acid (3-trifluoromethylheptyl) ester

4- (5-heptylpyridin-2-yl) benzoic acid (3-trifluoromethylheptyl) ester

4- (5-Octylpyridin-2-yl) benzoic acid (3-trifluoromethylheptyl) ester 4- (5-nonylpyridin-2-yl) benzoic acid (3-trifluoromethylheptyl) ester

4- (5-decylpyridin-2-yl) benzoic acid (3-trifluoromethylheptyl) ester Example 6

A mixture of 0.1 mol of 2- (p-hydroxyphenyl) -5-heptylpyridine (produced according to EP-A2-0247804), 0.1 mol (+) - 3-trifluoromethyl-nonancarboxylic acid, 1 mmol of 4-N, N-diethylaminopyridine, 0.1 mol of dicyclohexylcarbodiimide and 200 ml of dichloromethane is stirred at room temperature for 10 hours. After the usual work-up, 2- (p- (3-trifluoromethylnonanoyloxy) -penyl) -5-heptylpyridine is obtained.

The following are produced analogously:

2- (p- 3-trifluoromethylnonanoyloxy) phenyl) -5-ethylpyridine 2- (p- 3-trifluoromethylnonanoyloxy) phenyl) -5-propylpyridine 2- (p- 3-trifluoromethylnonanoyloxy) phenyl) -5-butylpyridine 2- (p- 3-Trifluoromethylnonanoyloxy) phenyl) -5-pentylpyridine 2- (p- 3-Trifluoromethylnonanoyloxy) phenyl) -5-hexylpyridine 2- (p- 3-Trifluoromethylnonanoyloxy) phenyl) -5-octylpyridine 2- (p - 3-trifluoromethylnonanoyloxy) phenyl) -5-nonylpyridine 2- (p- 3-trifluoromethylnonanoyloxy) phenyl) -5-decylpyridine

2- (p- 3-trifluoromethylheptanoyloxy) phenyl) -5-ethylpyridine 2- (p- 3-trifluoromethylheptanoyloxy) phenyl) -5-propylpyridine 2- (p- 3-trifluoromethylheptanoyloxy) phenyl) -5-butylpyridine 2- (p- 3-Trifluoromethylheptanoyloxy) phenyl) -5-pentylpyridine 2- (p- 3-Trifluoromethylheptanoyloxy) phenyl) -5-hexylpyridine 2- (p- 3-Trifluoromethylheptanoyloxy) phenyl) -5-octylpyridine 2- (p - 3-trifluoromethylheptanoyloxy) phenyl) -5-nonylpyridine 2- (p- 3-trifluoromethylheptanoyloxy) phenyl) -5-decylpyridine Mixture example A

A liquid crystalline mixture consisting of the following components:

4% 2-p-hexyloxyphenyl-5-heptylpyrimidine 5% 2-p-heptyloxyphenyl-5-heptylpyrimidine

5% 2-p-octyloxyphenyl-5-heptylpyrimidine 5% 2-p-nonyloxyphenyl-5-heptylpyrimidine

7% 2-p-hexyloxyphenyl-5-nonylpyrimidine 5% 2-p-heptyloxyphenyl-5-nonylpyrimidine 4% 2-p-octyloxyphenyl-5-nonylpyrimidine 25% 2-p-nonyloxyphenyl-5-nonylpyrimidine 10% 4-octylthio- 4 '- (4-heptylbenzoyloxy) biphenyl

8% 4-octylthio-4 '- (4-nonylbenzoyloxy) biphenyl

10% 4-octylthio-4 '- (4-octyloxybenzoyloxy) biphenyl and

12% 4- (2-methyl-2-trifluoromethylnonanoyloxy) -4'-hexyloxybiphenyl

has a broad S _c range and high spontaneous polarization.

Claims

1. Chiral or achiral ring compounds of the formula I.

R ¹ - (A ¹ -Z ¹ ) mA ² -Q ¹ -C * R ° CF ₃ -XI

wherein

R ^{1 is} an alkyl or perfluoroalkyl group, each having 1-12 C atoms, in which one or two non-adjacent CH ₂ or CF ₂ groups are also represented by O atoms and / or -CO groups and / or -CO -O groups and / or -CH = CH groups and / or -CH halogen and / or

-CHCN groups and / or -O-CO-CHHalogen- and / or -CO-O-CHCN groups can be replaced, F, Cl, Br, CN, or -Q ¹ -C * R ° CF ₃ -X , where Q ¹ , R ° and X have the meaning given,

A ¹ and A ² each independently of one another 1,4-phenylene which is unsubstituted or substituted by one or two F and / or CH ₃ groups and / or CN groups, in which one or two CH groups can also be replaced by N, 1,4-cyclohexylene, which is also a or two non-adjacent CH ₂ groups can be replaced by O atoms and / or S atoms, 1- (4-) cyano-1,4-cyclohexlyene, a piperidine-1,4-diyl, 1,4- Bicyclo- (2,2,2) -octylene-, 1,3,4-thiadiazole-2,5-diyl, naphthalene-2,6-diyl-decahydronaphthalene-2, 6-diyl- or 1,2,3, 4-tetrahydronaphthalene-2, 6-diyl group,

XH or CH ₃ ,

C * is a carbon atom linked to four different substituents,

m ¹ , 2 or 3 Q ¹ -O-, -O-CO-, -CO-O- or a single bond, in the event that at least one of the rings A and A ² is substituted by one or two F atoms; Phenylene or A unsubstituted 1,4-phenylene, in which a CH group is replaced by N, also means -O- (CH ₂ ) _n -, -O-CO-

(CH ₂ ) _n - or -CO-O- (CH ₂ ) _n , where n is _{1, 2, 3} or 4, and

R ° is an alkyl group other than X with 1 to 10 C atoms, or, if Q ^{1 is} a single bond, also an alkoxy or alkanoyloxy group with 1 to 10 C atoms each

mean, b) Q ^{1 is} -O-, -O = CO- or a single bond, and / or R ^{1 is} -Q ¹ -C * R ° -CF ₃ -X and / or X is CH ₃ if m is 1 or 2 is, Z ¹

-COO- or a single bond and the groups A ¹ and A ² mean unsubstituted 1,4-phenylene.

2. Ring compounds according to claim 1, characterized in that Q ^{1 is} -CO-O- or -O-.

3. Liquid crystalline phase with at least two liquid crystalline components, characterized in that at least one component is a compound of formula I.

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

5. Electro-optical display element according to claim 2, characterized in that it contains a liquid-crystalline phase as claimed in claim 3 as a dielectric.