DE19955932B4 - Cyclobutane derivatives and liquid crystalline medium - Google Patents

Abstract

Cyclobutane derivatives of the formula Iworin pure unsubstituted, at least one substituted by halogen or CN substituted alkyl radical with 1-12 carbon atoms, in which one or more CH groups are each independently of one another by -O-, -S-, -CO- ,, -CO-O-, -O-CO-, -O-CO-O- or -CH = CH- can be replaced in such a way that heteroatoms are not directly connected, QC = O, CF or C = CXX, X, XH, Cl or F, Y CH-R, RH, A, A independently of one another, even if it occurs several times, a) trans-1,4-cyclohexylene radical, in which one or more non-adjacent CH groups are also replaced by -O- and / or - S- can be replaced, b) 1,4-phenylene radical, it being possible for radicals a), b) and d) to be substituted by CN, Cl or F, Z —CO — O—, —O — CO if they occur several times, independently of one another -, -CHO-, -O-, -O-CH-, -CHCH-, -CH = CH-, -C≡C-, or a single bond, and m is 1 or 2.

Description

worin

R¹

H, -CN, -F, -OCHF₂, -OCF₃, -OCHFCF₃, -OCH₂CF₃ oder -OCF₂CF₃, einen unsubstituierten, einen mindestens einfach durch Halogen oder CN substituierten Alkylrest mit 1-12 C-Atomen, worin auch eine oder mehrere CH₂-Gruppen jeweils unabhängig voneinander durch -O-, -S-, -CO-,

-CO-O-, -O-CO-, -O-CO-O- oder -CH=CH- so ersetzt sein können, daß Heteroatome nicht direkt verbunden sind,

Q

C=O, CCl₂, CF₂ oder C=CX¹X²,

X¹, X²

H, Cl oder F,

Y

CH-R2 oder sofern Q die Bedeutung CCl₂ oder CF₂ aufweist, auch C=CH₂,

R²

H oder einen Alkylrest mit 1-12 C-Atomen, worin auch eine oder mehrere CH₂-Gruppen jeweils unabhängig voneinander durch -O-, -S-, -CO-,

-CO-O-, -O-CO-, -O-CO-O- oder -CH=CH- so ersetzt sein können, daß Heteroatome nicht direkt verbunden sind,

A, A¹

unabhängig voneinander einen

• a) trans-1,4-Cyclohexylenrest, worin auch eine oder mehrere nicht benachbarte CH₂-Gruppen durch -O- und/oder -S- ersetzt sein können,
• b) 1,4-Phenylenrest, worin auch eine oder zwei CH-Gruppen durch N ersetzt sein können,
• c) Rest aus der Gruppe 1,4-Bicyclo(2,2,2)-oxtylen, Piperidin-1,4-diyl, Naphthalin-2,6-diyl, Decahydronaphthalin-2,6-diyl und 1,2,3,4-Tetrahydronaphthalin-2,6-diyl,
• d) 1,4-Cyclohexenylen,

wobei die Reste a), b) und d) durch CN, Cl oder F substituiert sein können,

Z¹

bei mehrfachem Auftreten unabhängig voneinander -CO-O-, -O-CO-, -CH₂O-, -O-, -O-CH₂-, -CH₂CH₂-, -CH=CH-, -C≡C-, -CH₂O-, -O-, -O-CH₂-, -CH₂CH₂-, -CH=CH-, -C≡C-, oder eine Einfachbindung,

und

m

1, 2 oder 3

bedeutet.The invention relates to new cyclobutane derivatives of the formula I.

wherein

R ¹

H, -CN, -F, -OCHF ₂ , -OCF ₃ , -OCHFCF ₃ , -OCH ₂ CF ₃ or -OCF ₂ CF ₃ , an unsubstituted, an at least monosubstituted by halogen or CN alkyl radical with 1-12 C- Atoms in which one or more CH ₂ groups are each independently of one another by -O-, -S-, -CO-,

-CO-O-, -O-CO-, -O-CO-O- or -CH = CH- can be replaced so that heteroatoms are not directly connected,

Q

C = O, CCl ₂ , CF ₂ or C = CX ¹ X ² ,

X ¹ , X ²

H, Cl or F,

Y

CH-R2 or, if Q is CCl ₂ or CF ₂ , also C = CH ₂ ,

R ²

H or an alkyl radical with 1-12 C atoms, in which one or more CH ₂ groups are each independently of one another by -O-, -S-, -CO-,

-CO-O-, -O-CO-, -O-CO-O- or -CH = CH- can be replaced so that heteroatoms are not directly connected,

A, A ¹

one independently

• a) trans-1,4-cyclohexylene radical, in which one or more non-adjacent CH ₂ groups can also be replaced by -O- and / or -S-,
• b) 1,4-phenylene radical, in which one or two CH groups can also be replaced by N,
• c) residue from the group 1,4-bicyclo (2,2,2) oxylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl and 1,2,3 , 4-tetrahydronaphthalene-2,6-diyl,
• d) 1,4-cyclohexenylene,

where the residues a), b) and d) can be substituted by CN, Cl or F,

Z ¹

with multiple occurrences independently of one another -CO-O-, -O-CO-, -CH ₂ O-, -O-, -O-CH ₂ -, -CH ₂ CH ₂ -, -CH = CH-, -C≡ C-, -CH ₂ O-, -O-, -O-CH ₂ -, -CH ₂ CH ₂ -, -CH = CH-, -C≡C-, or a single bond,

and

m

1, 2 or 3

means.

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

The compounds of formula 1 often have low positive to strongly negative values of the dielectric anisotropy with at the same time very low values of the optical anisotropy Δn and viscosity and can be used as components of liquid-crystalline media, in particular for displays based on the principle of the twisted cell, the Guest-host effect, the effect of the deformation of aligned phases DAP or ECB (Electrically controlled birefringence) or the effect of dynamic scattering.

The substances previously used for this purpose always have certain disadvantages, for example insufficient stability against the action of heat, light or electrical fields, unfavorable elastic and / or dielectric properties.

The object of the invention was to find new stable liquid-crystalline or mesogenic compounds with particularly small optical anisotropy Δn and negative or slightly positive dielectric anisotropy with low viscosity, which are suitable as components of liquid-crystalline media, in particular for TFT and STN displays.

It has now been found that the compounds of the formula I are particularly suitable as components of liquid-crystalline media. With their help, stable liquid-crystalline media, particularly suitable for TFT or STN displays, can be obtained. The new compounds are characterized above all by their high thermal stability, which is advantageous for a high holding ratio, and they show favorable values for the clearing points. At a reduced temperature of 0.9 and a wavelength of 589 nm, the compounds of the formula 1 have a value for the optical anisotropy Δn of <0.03, preferably <0.02, which goes back to a particularly large value of n _⊥ .

The reduced temperature is defined as follows: $$\frac{\text{Measuring temperature in K}}{\text{Clear point temperature in K}}=\text{reduced temperature}$$

Liquid-crystalline media with very small values of optical anisotropy are particularly important for reflective and transflective applications, i.e. applications in which the respective LCD experiences no or only supportive backlighting.

Very low values of the Δn are obtained in particular in the case of preferred compounds of the formula I in which Q has the meaning C = CX ¹ X ² , since this group assumes an angle of approximately 90 ° to the longitudinal axis of the molecule. The increased polarizability transversely to the _{longitudinal axis of} the molecule results in an increased n _⊥ and thus a low optical anisotropy. If these compounds of the formula IX ¹ and / or X ² are Cl or F, a large negative value of the dielectric anisotropy is also found.

In general, compounds of the formula I without aromatic rings have particularly low Δn values and are therefore particularly suitable for lowering the Δn of liquid-crystalline mixtures.

Similar connections are for example in the DE 4206771 A1 described. The subject of this document is liquid-crystalline methylene cyclobutane derivatives which are distinguished by medium positive values of the dielectric anisotropy with a comparatively large optical anisotropy.

In contrast, the subject of the present application is directed to compounds which have low or negative values of dielectric anistotropy and very low values of Δn and are therefore suitable for reflective or transflective applications.

Similar compounds with a 2-substituted methylene cyclobutane group are also known, but they have no liquid-crystalline properties.

So describe e.g. B. WR Dolbier et al., Tetrahedron Letters 28 (14), 1491-1492, 1987 , the production of 3-phenyl-2,2-difluoro-1-methylenecyclobutane. The compounds of formula I or their methods of preparation are not mentioned therein.

The provision of compounds of the formula I broadly broadens the range of liquid-crystalline substances which are suitable for the production of liquid-crystalline mixtures from various application points of view.

The compounds of formula I have a wide range of applications. Depending on the selection of the substituents, these compounds can serve as base materials from which liquid-crystalline media are composed for the most part; However, it is also possible to add compounds of the formula I to liquid-crystalline base materials from other classes of compounds, for example the to influence the dielectric and / or optical anisotropy of such a dielectric and / or to optimize its threshold voltage and / or its viscosity. By adding the compounds of the formula I to liquid-crystalline dielectrics, Δn values and Δε values of such media can be significantly reduced.

The meaning of the formula I includes all isotopes of the chemical elements bound in the compounds of the formula I. In enantiomerically pure or enriched form, the compounds of the formula I are also suitable as chiral dopants and generally for achieving chiral mesophases.

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

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

Above and below, m, R ¹ , R ² , X ¹ , X ² , Z ¹ , A, A ¹ , Q and Y have the meaning given, unless expressly stated otherwise. If the radical X ¹ occurs more than once, it can have the same or different meanings. The same applies to all other groups that occur multiple times.

For the sake of simplicity, Phe in the following means a 1,4-phenylene radical, Cyc a cyclohexane-1,4-diyl radical or a 1- or 4-silacyclohexane-1,4-diyl radical, Dio a 1,3-dioxane-2,5- diyl radical, dit a 1,3-dithiane-2,5-diyl radical, a bicyclo- (2,2,2) -octylene radical, where Phe and Cyc can be unsubstituted or substituted one or more times by F or CN.

worin Q und Y die oben angegebene Bedeutung aufweisen. W means the following structural element:

wherein Q and Y have the meaning given above.

worin R² die oben angegebene Bedeutung aufweist und bevorzugt H oder Alkyl mit 1-7 C-Atomen bdeutet.Preferred meanings of group W represent the sub-formulas W1 to W4:

wherein R ^{2 has} the meaning given above and preferably denotes H or alkyl having 1-7 C atoms.

W particularly preferably denotes one of the groups W 5 to W9:

Formula comprises the preferred compounds of sub-formulas Ia1 to Ia42, which contain two six-membered rings in addition to group W: R ¹ -Cyc-Cyc-W Ia1 R ¹ -Dio-Cyc-W Ia2 R ¹ -Phe-Cyc-W Ia3 R ¹ -Cyc-CH ₂ CH ₂ -Cyc-W Ia4 R ¹ -dio-CH ₂ CH ₂ -Cyc-W Ia5 R ¹ -Phe-CH ₂ CH ₂ -Cyc-W Ia6 R ¹ -Cyc-COO-Cyc-W Ia7 R ¹ -dio-COO-Cyc-W Ia8 R ¹ -Cyc-OOC-Cyc-W Ia9 R ¹ -Dio-OOC-Cyc-W Ia10 R ¹ -Phe-OOC-Cyc-W Ia11 R ¹ -Cyc-CH = CH-Cyc-W Ia12 R ¹ -dio-CH = CH-Cyc-W Ia13 R ¹ -Phe-CH = CH-Cyc-W Ia14 R ¹ -Cyc-Dio-W Ia15 R ¹ -Dio-Dio-W Ia16 R ¹ -Phe-Dio-W Ia17 R ¹ -Cyc-CH ₂ CH ₂ -dio-W Ia18 R ¹ -dio-CH ₂ CH ₂ -dio-W Ia19 R ¹ -Phe-CH ₂ CH ₂ -dio-W Ia20 R ¹ -Cyc-COO-Dio-W Ia21 R ¹ -Dio-COO-Dio-W Ia22 R ¹ -Cyc-OOC-Dio-W Ia23 R ¹ -Dio-OOC-Dio-W Ia24 R ¹ -Phe-OOC-Dio-W Ia25 R ¹ -Cyc-CH = CH-Dio-W Ia26 R ¹ -dio-CH = CH-dio-W Ia27 R ¹ -Phe-CH = CH-Dio-W Ia28 R ¹ -Cyc-Phe-W Ia29 R ¹ -Dio-Phe-W Ia30 R ¹ -Phe-Phe-W Ia31 R ¹ -Cyc-CH ₂ CH ₂ -Phe-W Ia32 R ¹ -dio-CH ₂ CH ₂ -Ph _e -W Ia33 R ¹ -Phe-CH ₂ CH ₂ -Phe-W Ia34 R ¹ -Cyc-COO-Phe-W Ia35 R ¹ -Dio-COO-Phe-W Ia36 R ₁ -Cyc-OOC-Phe-W Ia37 R ¹ -Dio-OOC-Phe-W Ia38 R ¹ -Phe-OOC-Phe-W Ia39 R ¹ -Cyc-CH = CH-Phe-W Ia40 R ¹ -dio-CH = CH-Phe-W Ia41 R ¹ -Phe-CH = CH-Phe-W Ia42

Formula furthermore comprises the preferred compounds of sub-formulas Ib1 to Ib105 which, in addition to group W, contain three six-membered rings: R ¹ -Phe-CH = CH-Phe-W Ib1 R ¹ -Dio-Cyc-Cyc-W Ib2 R ¹ -Phe-Cyc-Cyc-W Ib3 R1-Cyc-CH ₂ CH ₂ -Cyc-Cyc-W Ib4 R ¹ -Phe-CH ₂ CH ₂ -Cyc-Cyc-W Ib5 R ¹ -Dio-COO-Cyc-Cyc-W Ib6 R ¹ -Phe-OOC-Cyc-Cyc-W Ib7 R1-Cyc-CH = CH-Cyc-Cyc-W Ib8 R ¹ -Phe-CH = CH-Cyc-Cyc-W Ib9 R ¹ -Cyc-Dio-Cyc-W Ib10 R ¹ -dio-dio-Cyc-W Ib11 R ¹ -Phe-Dio-Cyc-W Ib12 R ¹ -Cyc-CH ₂ CH ₂ -dio-Cyc-W Ib13 R ¹ -Cyc-COO-Dio-Cyc-W Ib14 R ¹ -dio-COO-dio-Cyc-W Ib15 R ¹ -Phe-OOC-Dio-Cyc-W Ib16 R ¹ -Cyc-CH = CH-Dio-Cyc-W Ib17 R ¹ -Phe-CH = CH-Dio-Cyc-W Ib18 R ¹ -Cyc-Phe-Cyc-W Ib19 R ¹ -Dio-Phe-Cyc-W Ib20 R ¹ -Phe-Phe-Cyc-W Ib21 R ¹ -Cyc-CH ₂ CH ₂ -Phe-Cyc-W Ib22 R ¹ -Phe-CH ₂ CH ₂ -Phe-Cyc-W Ib23 R ¹ -Cyc-COO-Phe-Cyc-W Ib24 R ¹ -Phe-OOC-Phe-Cyc-W Ib25 R ¹ -Cyc-CH = CH-Phe-Cyc-W Ib26 R ¹ -Cyc-Cyc-CH ₂ CH ₂ -Cyc-W Ib27 R ¹ -Cyc-Dio-CH ₂ CH ₂ -Cyc-W Ib28 R ¹ -dio-Phe-CH ₂ CH ₂ -Cyc-W Ib29 R ¹ -Phe-Phe-CH ₂ CH ₂ -Cyc-W Ib30 R ¹ -Cyc-Cyc-OOC-Cyc-W Ib31 R ¹ -Phe-Cyc-OOC-Cyc-W Ib32 R ¹ -Phe-Phe-OOC-Cyc-W Ib33 R ¹ -Cyc-Cyc-CH = CH-Cyc-W Ib34 R ¹ -Phe-Dio-CH = CH-Cyc-W Ib35 R ¹ -Phe-Phe-CH = CH-Cyc-W Ib36 R ¹ -Dio-Cyc-Dio-W Ib37 R ¹ -Phe-Cyc-Dio-W Ib38 R ¹ -Cyc-CH ₂ CH ₂ -Cyc-DiO-W Ib39 R ¹ -DiO-C _H2 CH ₂ -Cyc-Dio-W Ib40 R ¹ -Cyc-COO-Cyc-Dio-W Ib41 R ¹ -dio-COO-Cyc-Dio-W Ib42 R ¹ -Dio-OOC-Cyc-Dio-W Ib43 R ¹ -Phe-OOC-Cyc-Dio-W Ib44 R ¹ -Dio-CH = CH-Cyc-Dio-W Ib45 R ¹ -Phe-CH = CH-Cyc-Dio-W Ib46 R ¹ -Cyc-Dio-Dio-W Ib47 R ¹ -Phe-Dio-Dio-W Ib48 R ¹ -Cyc-CH ₂ CH ₂ -dio-dio-W Ib49 R ¹ -dio-CH ₂ CH ₂ -dio-dio-W Ib50 R ¹ -Dio-OOC-Dio-Dio-W Ib51 R ¹ -Phe-OOC-Dio-Dio-W Ib52 R ¹ -Cyc-CH = CH-Dio-Dio-W Ib53 R ¹ -Phe-CH = CH-Dio-Dio-W Ib54 R ¹ -Cyc-Phe-Dio-W Ib55 R ¹ -Phe-Phe-Dio-W Ib56 R ¹ -Cyc-CH ₂ CH ₂ -Phe-Dio-W Ib57 R ¹ -Dio-CH ₂ CH ₂ -Phe-Dio-W Ib58 R ¹ -Phe-CH ₂ CH ₂ -Phe-Dio-W Ib59 R ¹ -Dio-COO-Phe-Dio-W Ib60 R ¹ -Cyc-OOC-Phe-Dio-W Ib61 R ¹ -Dio-OOC-Phe-Dio-W Ib62 R ¹ -Cyc-CH = CH-Phe-Dio-W Ib63 R ¹ -Dio-CH = CH-Phe-Dio-W Ib64 R ¹ -Phe-CH = CH-Phe-Dio-W Ib65 R ¹ -Dio-Cyc-CH ₂ CH ₂ -Dio-W Ib66 R ¹ -Cyc-Dio-CH ₂ CH ₂ -Dio-W Ib67 R ₁ -dio-dio-CH ₂ CH ₂ -dio-W Ib63 R ¹ -Cyc-Phe-CH ₂ CH ₂ -Dio-W Ib69 R ₁ -dio-Phe-CH ₂ CH ₂ -dio-W Ib70 R ¹ -Cyc-Cyc-COO-Dio-W Ib71 R ¹ -Cyc-Cyc-OOC-Dio-W Ib72 R ¹ -Phe-Phe-OOC-Dio-W Ib73 R ¹ -Cyc-Cyc-CH = CH-Dio-W Ib74 R ¹ -Dio-Phe-CH = CH-Dio-W Ib75 R ¹ -Phe-Phe-CH = CH-Dio-W Ib76 R ¹ -Cyc-Cyc-Phe-W Ib77 R ¹ -Phe-Cyc-Phe-W Ib78 R ¹ -Cyc-CH ₂ CH ₂ -Cyc-Phe-W Ib79 R ¹ -Cyc-COO-Cyc-Phe-W Ib80 R ¹ -dio-COO-Cyc-Phe-W Ib81 R ¹ -Phe-OOC-Cyc-Phe-W Ib82 R ¹ -Cyc-CH = CH-Cyc-Phe-W Ib83 R ¹ -Cyc-Dio-Phe-W Ib84 R ¹ -Phe-Dio-Phe-W Ib85 R ¹ -dio-CH ₂ CH ₂ -dio-Phe-W Ib86 R ¹ -Dio-OOC-Dio-Phe-W Ib87 R ¹ -Cyc-CH = CH-Dio-Phe-W Ib88 R ¹ -Phe-CH = C _H -dio-Phe-W Ib89 R ¹ -Cyc-Phe-Phe-W Ib90 R ¹ -Phe-Phe-Phe-W Ib91 R ¹ -dio-CH ₂ CH ₂ -Ph _e -Ph _e -W Ib92 R ¹ -Cyc-COO-Phe-Phe-W Ib93 R ¹ -Dio-OOC-Phe-Phe-W Ib94 R ¹ -Dio-CH = CH-Phe-Phe-W Ib95 R ¹ -Cyc-Cyc-CH ₂ CH ₂ -Phe-W Ib96 R ¹ -Dio-Cyc-CH ₂ CH ₂ -Phe-W Ib97 R ¹ -Phe-Dio-CH ₂ CH ₂ -Phe-W Ib98 R ¹ -Cyc-Phe-CH ₂ CH ₂ -Phe-W Ib99 R ¹ -Phe-Phe-CH ₂ CH ₂ -Phe-W Ib100 R ¹ -Cyc-Cyc-COO-Phe-W Ib101 R1-Dio-Dio-OOC-Phe-W Ib102 R ¹ -Dio-Phe-OOC-Phe-W Ib103 R ¹ -Cyc-Cyc-CH = CH-Phe-W Ib104 R ¹ -Dio-Phe-CH = CH-Phe-W Ib105

Formula includes the likewise preferred compounds of sub-formulas Ic1 to Ic7, which contain four six-membered rings in addition to group W: R ¹ -Cyc-Cyc-Cyc-Cyc-W Ib1 R ¹ -Phe-Cyc-Cyc-Cyc-W Ib2 R ¹ -Cyc-CH ₂ CH ₂ -Cyc-Cyc-Cyc-W Ib3 R ¹ -Phe-CH ₂ CH ₂ -Cyc-Cyc-W Ib4 R ¹ -Phe-Phe-CH ₂ CH ₂ -Cyc-Cyc-W Ib5 R ¹ -Cyc-OOC-Phe-Dio-Cyc-W Ib6 R ¹ -Cyc-Cyc-Cyc-CH = CH-Phe-W Ib7 wherein Cyc, Dio, Phe, R ¹ and W have the meaning given above.

R ¹ preferably denotes -CN, F, OCF ₃ , CF ₃ , straight-chain alkyl or alkoxy with 1 to 10 C atoms or alkenyl or alkenyloxy with 2 to 10 C atoms, in particular F, OCF ₃ , alkyl or alkoxy with 1 to 7 carbon atoms.

R2 preferably means H.

X ¹ and X ^{2 are} preferably F or H.

In preferred compounds of the formula I, X ¹ and X ² simultaneously assume the meaning F, Cl or H.

A and A ¹ independently of one another mean Cyc, Dio or Phe.

Preference is also given to compounds of the formula I and all sub-formulas in which A and / or A ^{1 is} cyclohexane which is substituted once or twice by F or CN.

oder

m ist vorzugsweise 1 oder 2, insbesondere bevorzugt 1 .A and / or A preferably denotes ¹

or

m is preferably 1 or 2, particularly preferably 1.

Z ¹ in the case of multiple occurrences independently of one another preferably denotes -CH ₂ CH ₂ -, -COO-, -OOC- or a single bond, particularly preferably a single bond or -CH ₂ -CH ₂ -.

Compounds of formula I which do not contain more than one dioxane ring also represent a preferred embodiment of the invention.

In particular, those compounds of the formula I which are characterized in that R ^{1 is} straight-chain alkyl or alkoxy having 1 to 10 C atoms and R ^{2 is} H are particularly preferred.

worin R¹, A¹, Z¹ und W die oben angegebene Bedeutung aufweisen und L¹, L² unabhängig voneinander F oder H bedeuten.The following group of compounds of partial formulas I1 to I38 represents further preferred embodiments of the invention:

wherein R ¹ , A ¹ , Z ¹ and W have the meaning given above and L ¹ , L ² independently of one another are F or H.

If R ¹ and / or R ² in the formulas above and below denotes an alkyl radical, this can be straight-chain or branched.

It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and accordingly preferably means ethyl, propyl, butyl, pentyl, hexyl or heptyl, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl , Tetradecyl or pentadecyl.

If R ¹ and / or R ^{2 is} an alkyl radical in which a CH ₂ group has been replaced by -O-, this can be straight-chain or branched. It is preferably straight-chain and has 1 to 10 carbon atoms. The first CH ₂ group of this alkyl radical is preferably replaced by -O-, so that the radical R ¹ and / or R2 is alkoxy and preferably methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy .

Furthermore, a CH ₂ group can also be replaced elsewhere by -O-, so that the radical R ¹ and / or R2 is preferably straight-chain 2-oxapropyl (= methoxymethyl), 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 means.

If R ¹ and / or R ^{2 is} an alkenyl radical, this can be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. Accordingly, it means 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.

R ¹ and / or R ² particularly preferably denotes an alkenyl radical from the following group:

If R ¹ and / or R ^{2 represents} an alkenyloxy radical, this can be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. It particularly preferably means a radical from the following group:

If R ¹ and / or R ^{2 is} an alkyl radical in which one CH ₂ group has been replaced by -O- and one has been replaced by -CO-, these are preferably adjacent. Thus, they contain an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-. These are preferably straight-chain and have 2 to 6 carbon atoms.

Accordingly, they mean, in particular, acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetyloxylyloxylyloxy, methoxycarbonyl, methoxycarbonyl, methyloxycarbonyl Propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2- (methoxycarbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propoxycarbonyl) ethyl, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl) propyl, 4 - (Methoxycarbonyl) butyl.

If R ¹ and / or R ^{2 is} an alkyl radical which is at least monosubstituted by halogen, this radical is preferably straight-chain. Halogen is preferably F or Cl. In the case of multiple substitution, halogen is preferably F. The resulting residues also include perfluorinated residues. In the case of single substitution, the fluorine or chlorine substituent can be in any position, but preferably in the ω position.

Compounds of the formula 1 with branched wing groups R ¹ and / or R ² may occasionally be important because of their better solubility in the customary liquid-crystalline base materials, but in particular as chiral dopants if they are optically active. Smectic compounds of this type are suitable as components for ferroelectric materials.

Branched groups of this type usually contain no more than one chain branch. Preferred branched radicals R ¹ and / or R ² 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-methylbutoxy, 2-methylpentyloxy, 3-methylpentyloxy, 2-ethylhexyloxy, 1-methylhexyloxy, 1-methylheptyloxy.

Formula I includes both the racemates of these compounds and the optical antipodes and mixtures thereof.

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

In the compounds of the formula I, those stereoisomers in which the rings Cyc and piperidine are trans-1,4-disubstituted are preferred. Those of the above formulas which contain one or more groups Dio each enclose the two 2,5-position isomers.

worin R¹, R², L¹ und L² die angegebene Bedeutung aufweisen. L¹ und L² nehmen bevorzugt gleichzeitig die Bedeutung F oder H an.Some very particularly preferred smaller groups of compounds of the formula I are those of the sub-formulas I39 to I97:

wherein R ¹ , R ² , L ¹ and L ^{2 have} the meaning given. L ¹ and L ² preferably assume the meaning F or H at the same time.

Very particularly preferred compounds of this group are those of the formulas I39, I43, I45, I46, I52, I57, I59, I73, I81, I87 and 92.

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 which are suitable for the implementations mentioned are known and suitable.

Use can 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.

The synthesis of the compounds of the formula I in which A and / or A ¹ denotes axially fluorinated cyclohexane can be effected by using hydrogen fluoride under pressure or by amine-hydrogen fluoride adducts (for example AV Grosse, CB Linn, J. Org. Chem. 3 , (1938) 26; GA Olah, M. Nojima, I. Kerekes, Synthesis, (1973) 779); GA Olah, XY. Li, Q. Wang, GKS Prakash, Synthesis (1993) 693).

The compounds according to the invention can be prepared, for example, according to the following reaction schemes:

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) or by the DCC method (DCC = dicyclohexylcarbodiimide).

The corresponding carboxylic acids and alcohols or phenols are known or can be prepared analogously to known processes.

Suitable reactive derivatives of the carboxylic acids mentioned are, in particular, the acid halides, especially the chlorides and bromides, furthermore the anhydrides, azides or esters, in particular alkyl esters with 1-4 C 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. Particularly suitable are 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 Dimethyl sulfoxide or sulfolane. Solvents immiscible with water can at the same time be used advantageously for azeotropically distilling off the water formed during the esterification. Occasionally, an excess of an organic base, for example pyridine, quinoline or triethylamine, can also be used as a solvent for the esterification. The esterification can also be carried out in the absence of a solvent, for example 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 is usually reacted with a free alcohol or phenol 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, sodium hydrogen 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. Another preferred embodiment of the esterification is that the alcohol or the phenol is first converted into the sodium or potassium alcoholate or phenolate, e.g. by treatment with ethanolic sodium or potassium hydroxide solution, this is isolated and reacted with an acid anhydride or in particular acid chloride.

Nitriles can be obtained by exchanging halogens with copper cyanide or alkali cyanide.

In a further process for the preparation of the compounds of the formula I, in which Z ¹ denotes -CH = CH-, an aryl halide is reacted with an olefin in the presence of a tertiary amine and a palladium catalyst (cf. RF Heck, Acc. Chem. Res. 12 (1979) 146). Suitable aryl halides are, for example, chlorides, bromides and iodides, in particular bromides and iodides. The tertiary amines required for the coupling reaction to succeed, such as triethylamine, are also suitable as solvents. Suitable palladium catalysts are, for example, its salts, in particular (Pd (II) acetate, with organic phosphorus (III) compounds such as, for example, triarylphosphanes. In the presence or absence of an inert solvent, temperatures between about 0 ° C. and 150 ° C. , preferably between 20 ° C. and 100 ° C. Suitable solvents are, for example, nitriles such as acetonitrile or hydrocarbons such as benzene or toluene. The aryl halides and olefins used as starting materials are commercially available in many cases or can be prepared by processes known from the literature, for example by halogenation of corresponding parent compounds or by elimination reactions on corresponding alcohols or halides.

In this way, stilbene derivatives can be produced, for example. The stilbenes can also be produced by reacting a 4-substituted benzaldehyde with a corresponding phosphorylide according to Wittig.

Aryl halides can also be reacted with aryltin compounds to couple aromatics. These reactions are preferred with the addition of a catalyst such as e.g. a palladium (0) complex in inert solvents such as hydrocarbons at high temperatures, e.g. in boiling xylene, carried out under protective gas.

Ethers of the formula I can be obtained by etherification of corresponding hydroxyl compounds, preferably corresponding phenols, the hydroxyl compound expediently 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, for example, acetone, 1,2-dimethoxythane, DMF or dimethyl sulfoxide or with an excess of aqueous or aqueous-alcoholic NaOH or KOH at temperatures between about 20 ° C and 100 ° C.

Corresponding aniline derivatives with sodium nitrite and either with tetrafluoroboric acid (for introducing an F atom) or with copper (I) chloride (for introducing a Cl atom) can be used to produce the laterally substituted fluorine or chlorine compounds of the formula I Diazonium salts are implemented, which are then thermally decomposed at temperatures of 100 ° -140 °.

The connection of an aromatic nucleus with a non-aromatic nucleus or two non-aromatic nuclei is preferably obtained by condensation of an organolithium or organomagnesium compound with a ketone if there is to be an aliphatic group Z ¹ between the nuclei.

The organometallic compounds are prepared, for example, by metal-halogen exchange (for example according to Org. React. 6, 339-366 (1951)) between the corresponding halogen compound and a lithium organic compound such as preferably tert-butyllithium or lithium naphthalenide or by conversion with magnesium shavings forth.

The linking of two aromatic rings or aliphatic group Z ¹ with an aromatic ring is preferably carried out by Friedel-Crafts alkylation or acylation by reacting the corresponding aromatic compounds with Lewis acid catalysis. Suitable Lewis acids are, for example, SnCl ₄ , ZnCl ₂ or especially AlCl ₃ and TiCl ₄ .

Furthermore, the linking of two aromatic rings by the Ullmann reaction (eg Synthesis 1974, 9) between aryl iodides with copper iodide, but preferably between an aryl-copper compound and an aryl iodide, or by the Gomberg-Bachmann reaction between an aryl Carry out the diazonium salt and the corresponding aromatic compound (for example Org. React. 2, 224 (1944)).

In addition, the compounds of the formula I 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 carbonyl groups, in particular keto groups, furthermore, for example, free or esterified hydroxyl groups or aromatically bonded halogen atoms. Preferred starting materials for the reduction are compounds corresponding to the formula I, but instead of a cyclohexane ring a cyclohexene ring or cyclohexanone ring and / or instead of a -CH ₂ CH ₂ group, a -CH = CH group and / or instead of a -CH ₂ group contain a -CO group and / or instead of an H atom a free or a functionally modified (for example in the form of its p-toluenesulfonate) OH group.

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 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 methods of Clemmensen (with zinc, amalgamated zinc or tin and hydrochloric acid, suitably in aqueous-alcoholic solution or in a heterogeneous phase with water / toluene at temperatures between about 80 and 120 °) or Wolff-Kishner (with hydrazine, expediently 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 with NaBH ₄ or tributyltin hydride in methanol.

The starting materials are either known or can be prepared analogously to known compounds.

In addition to one or more compounds according to the invention, the liquid-crystalline media according to the invention preferably contain 2 to 40, in particular 4 to 30, components as further constituents. These media very particularly preferably contain 7 to 25 components in addition to one or more compounds according to the invention. These further constituents are preferably selected from nematic or nematogenic (monotropic or isotropic) substances, in particular substances from the classes of azoxybenzenes, benzylidene anilines, biphenyls, terphenyls, phenyl- or cyclohexylbenzoates, cyclohexanecarboxylic acid phenyl- or cyclohexyl esters, phenyl- or cyclohexyl esters of cyclohexyl benzoic acid, Phenyl or cyclohexyl ester of cyclohexylcyclohexane carboxylic acid, cyclohexyl phenyl ester of benzoic acid, cyclohexane carboxylic acid, or cyclohexylcyclohexane carboxylic acid, phenylcyclohexane, cyclohexylbiphenyle, phenylcyclohexylcyclohexane, cyclohexylcyclohexylhexyl, cyclohexylhexyl, cyclohexylbenzyl, cyclohexylhexyl, cyclohexylhexyl, cyclohexylhexyl, cyclohexylhexyl, cyclohexylhexyl, cyclohexylhexyl, cyclohexyl, hexyl 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) ethane, 1-cyclohexyl 2-biphenylylethane, 1-phenyl-2-cyclohexyl-phenylethane, optionally halogenated stilbenes, 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'-LER " 1 R'-L-COO-ER " 2nd R'-L-OOC-ER " 3rd R'-L-CH ₂ CH ₂ -ER " 4th 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 substituted by fluorine-substituted 1,4-phenylene, Cyc- 1,4-cyclohexylene or 1,4-cyclohexylene, 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 a smaller subgroup of the compounds of the formulas 1, 2, 3, 4 and 5, R 'and R "each independently represent alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy having up to 8 carbon atoms. In the following, this smaller subgroup becomes a group Called A and the compounds are designated with the partial formulas 1a, 2a, 3a, 4a and 5a. In most of these compounds, R 'and R "are different from one another, one of these radicals usually being alkyl, alkenyl, alkoxy or alkoxyalkyl.

In another smaller subgroup, referred to as group B, of the compounds of the formulas 1, 2, 3, 4 and 5, R "means -F, -Cl, -NCS or - (O) _i CH _{3- (k + l} ) F _k Cl _l , where i is 0 or 1 and k and I are 1, 2 or 3; the compounds in which R "has this meaning are denoted by the sub-formulas 1b, 2b, 3b, 4b and 5b. Those compounds of the sub-formulas 1b, 2b, 3b, 4b and 5b in which R "has the meaning -F, -Cl, -NCS, -CF ₃ , -OCHF ₂ or -OCF ₃ are particularly preferred.

In the compounds of partial formulas 1b, 2b, 3b, 4b and 5b, R 'has the meaning given for the compounds of partial 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, R "-CN; this subgroup is referred to below as group C and the compounds of this subgroup are correspondingly represented by subformulas 1c, 2c, 3c, 4c and 5c In the compounds of sub-formulas 1c, 2c, 3c, 4c and 5c, R 'has the meaning given for the compounds of sub-formulas 1a-5a and is preferably alkyl, alkoxy or alkenyl.

In addition to the preferred compounds of groups A, B and C, other compounds of the formulas 1, 2, 3, 4 and 5 with other variants of the proposed substituents are also common. All of these substances can be obtained by methods known from the literature or by analogy.

In addition to the 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 in the media according to the invention are preferably: Group A: 0 to 90%, preferably 20 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 from groups A and / or B and / or C contained in the respective media according to the invention is preferably 5% -90% and in particular 10% to 90%.

The media according to the invention preferably contain 1 to 40%, particularly preferably 5 to 30% of the 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 for producing colored guest-host systems or substances for changing the dielectric anisotropy, the viscosity and / or orientation of the nematic phases can be added.

The following examples are intended to illustrate the invention without limiting it. Percentages above and below mean percentages by weight. All temperatures are given in degrees Celsius. Fp. Means melting point, Klp. = Clearing point, Tg = glass temperature. Furthermore, K = crystalline state, N = nematic phase, Sm = smectic phase and I = isotropic phase. The information between these symbols represents the transition temperatures. Δn means optical anisotropy (589 nm 20 ° C) and Δε the dielectric anisotropy (1 kHz, 20 ° C). Δn and Δε values of the compounds according to the invention were obtained by extrapolation from liquid-crystalline mixtures which consisted of 10% of the respective compound of the invention and 90% of the commercially available liquid crystal ZLI 4792 (Merck, Darmstadt).

The viscosity (mm ² / sec) was determined at 20 ° C.

"Customary work-up" means: if necessary, water is added, extracted with methylene chloride, diethyl ether or toluene, the mixture is separated off, the organic phase is dried, evaporated and the product is purified by distillation under reduced pressure or crystallization and / or chromatography.

The following abbreviations are used: THF Tetrahydrofuran KOtBu Potassium tert-butoxide RT Room temperature MTB ether Methyl tert-butyl ether

Example 1:

2- (4'-Propylbicyclohexyl-4-yl) cyclobutanone

a) 4-Cyclopropylidenemethyl-4'-propylbicyclohexyl

61.40 g of (2-iodoethyl) triphenylphosphonium iodide are placed in 270 ml of ethylene glycol dimethyl ether and 9.12 g of sodium hydride are added. Then 27.90 g of 4'-propylbicyclohexyl-4-carbaldehyde (obtainable by Wittig reaction of 4'-propylbicyclohexyl-4-one with methoxymethyltriphenylphosphonium bromide and subsequent acidic hydrolysis) are added in portions at 5 ° C. with stirring and the cooling is removed, the Temperature rises to 38 ° C. After 15 min, the mixture was warmed to 70 ° C. and stirred at this temperature for 6 h. After the reaction mixture has been filtered, it is worked up in the customary manner, giving 4-cyclopropylidenemethyl-4'-propylbicyclohexyl.

b) 2- (4'-Propylbicyclohexyl-4-yl) cyclobutanone

16.71 g of 3-chloroperbenzoic acid are added at 5 ° C. to a solution of 10.10 g of 4-cyclopropylidenemethyl-4'-propylbicyclohexyl and 250 ml of dichloromethane. The suspension is stirred for 2 h at this temperature and then worked up as usual, whereby 2- (4'-propylbicyclohexyl-4-yl) cyclobutanone is obtained (K 63 SmB 137 I, Δε - 5.95, Δn 0.03).

The following compounds according to the invention are obtained analogously from the corresponding precursors:

Examples 2-17:

Examples 18-30:

Example 31:

5 ml of diethylaminosulfur trifluoride are added dropwise at 0 ° C. to a solution of 2.40 g of 2- (4'-propylbicyclohexyl-4-yl) cyclobutanone and 0.5 ml of dichloromethane. The mixture is stirred at this temperature for 0.5 h, then allowed to come to RT and stirred at this temperature overnight. After cooling to -25 ° C. and hydrolysis with water, the mixture is worked up in the customary manner, giving 4- (2,2-difluorocyclobutyl) -4'-propylbicyclohexyl (K 35 SmB 143 I, Δε -2.45, Δn 0.042).

Examples 32-47

Example 48-60

R ¹ - (A ¹ -Z) _n - (48) n-propyl

(49) n-pentyloxy

(50) CH ₂ = CHCH ₂ O

(51) n-butyl

(52) CH ₂ = CHCH ₂

(53) n-propyloxy

(54) F ₃ CO

(55) n-pentyloxy

(56) n-propyloxy

(57) n-pentyl

(58) CH ₂ = CHCH ₂ O

(59) n-propyloxy

(60) CH ₂ = CHCH ₂

Example 61:

8.00 g of 2- (4'-propylbicyclohexyl-4-yl) cyclobutanone in a mixture of 75 ml of 1,4-dioxane and 17 ml of THF are mixed with 5.46 ml of dibromodifluoromethane and 20.85 are added dropwise at 0 ° C. to 10 ° C. ml of hexamethyltriaminophosphine. The reaction mixture is stirred for 2 h and worked up as usual, whereby 4 '- (2-difluoromethylenecyclobutyl) -4-propylbicyclohexyl is obtained (K 44 SmB 64 I, Δε -1.01, Δn -0.003).

The following compounds according to the invention are obtained analogously from the corresponding precursors:

Examples 62-77:

R ¹ - (A ¹ -Z) _n - L ¹ L ² (62) n-propyl

F F (63) n-pentyl

H H (64) CH ₂ = CHCH ₂ O

F F (65) n-propyl

F F (66) n-pentyloxy

F F (67) CH ₂ = CHCH ₂ O

F F (68) CN

F F (69) n-butyl

H H (70) CH ₂ = CHCH ₂

F H (71) n-propyl

F F (72) n-pentyloxy

F F (73) CH ₂ = CH

F F (74) CH ₂ = CHCH ₂ O

F F (75) n-butyl

F F (76) CH ₂ = CHCH ₂

H H (77) n-propyloxy

H H

Examples 78-90:

R ¹ - (A ¹ -Z) _n - (78) n-propyl

(79) n-pentyloxy

(80) CH ₂ = CHCH ₂ O

(81) n-butyl

(82) CH ₂ = CHCH ₂

(83) n-propyloxy

(84) F ₃ CO

(85) n-pentyloxy

(86) n-propyloxy

(87) n-pentyl

(88) CH ₂ = CHCH ₂ O

(89) n-propyloxy

(90) CH ₂ = CHCH ₂

Example 91

A solution of 2.29 g of KOtBu in 100 ml of THF is added dropwise to a solution of 7.15 g of methyltriphenylphosphonium bromide in 50 ml of anhydrous THF at 0 ° C. to 5 ° C. with stirring. After 1 h, 4.50 g of 2- (4'-propylbicyclohexyl-4-yl) cyclobutanone are dissolved in 100 ml of THF and the reaction mixture is stirred overnight. After the usual work-up, 4 '- (2-methylenecyclobutyl) -4-propylbicyclohexyl (Tg - 66 SmB 92 I, Δε -2.16, Δn 0.00, viscosity 26 mm ² / s) is obtained.

The following compounds according to the invention are obtained analogously from the corresponding precursors:

Examples 92-107

R ¹ - (A ¹ -Z) _n - L ¹ L ² (92) n-propyl

F F (93) n-pentyl

H H (94) CH ₂ = CHCH ₂ O

F F (95) n-propyl

F F (96) n-pentyloxy

F F (97) CH ₂ = CHCH ₂ O

F F (98) CN

F F (99) n-butyl

H H (100) CH ₂ = CHCH ₂

F H (101) n-propyl

F F (102) n-pentyloxy

F F (103) CH ₂ = CH

F F (104) CH ₂ = CHCH ₂ O

F F (105) n-butyl

F F (106) CH ₂ = CHCH ₂

H H (107) n-propyl

H H

Example 108-120:

R ¹ - (A ¹ -Z) _n - (108) n-propyl

(109) n-pentyloxy

(110) CH ₂ = CHCH ₂ O

(111) n-butyl

(112) CH ₂ = CHCH ₂

(113) n-propyloxy

(114) F ₃ CO

(115) F

(K 59 N (27) I, Δε 1.61, Δn 0.05) (116) n-propyl

(117) n-pentyl

(118) CH ₂ = CHCH ₂ O

(119) n-propyl

(120) CH ₂ = CHCH ₂

Example 121:

5.50 g of 2- (4'-propylbicyclohexyl-4-yl) cyclobutanone and 20.98 triphenylphosphine are suspended in 50 ml of acetonitrile and 3.87 ml of carbon tetrachloride are added to the suspension at 0 ° C. The reaction mixture is stirred overnight and worked up as usual, whereby 4 '- (2-dichloromethylenecyclobutyl) -4-propylbicyclohexyl is obtained (K 52 I, Δε -4.03, Δn -0.020).

The following compounds according to the invention are obtained analogously from the corresponding precursors:

Examples 122-134:

R ¹ - (A ^1- Z) _n - (122) n-propyl

(123) n-pentyloxy

(124) CH ₂ = CHCH ₂ O

(125) n-butyl

(126) CH ₂ = CHCH ₂

(127) n-propyloxy

(128) F ₃ CO

(129) n-pentyloxy

(130) n-propyloxy

(131) n-pentyl

(132) CH ₂ = CHCH ₂ O

(133) n-propyl

(134) CH ₂ = CHCH ₂

The following compounds according to the invention are obtained in an analogous manner to the preceding examples:

Example 135-150:

R ¹ - (A ¹ -Z) _n - L ¹ L ² (135) n-propyl

F F (136) n-pentyl

H H (137) CH ₂ = CHCH ₂ O

F F (138) n-propyl

F F (139) n-pentyloxy

F F (140) CH ₂ = CHCH ₂ O

F F (141) CN

F F (142) n-butyl

H H (143) CH ₂ = CHCH ₂

F H (144) n-propyl

F F (145) n-pentyloxy

F F (146) CH ₂ = CH

F F (147) CH ₂ = CHCH ₂ O

F F (148) n-butyl

F F (149) CH ₂ = CHCH ₂

H H (150) n-propyloxy

H H

Example 151-163:

R ¹ - (A ¹ -Z) _n - (151) n-propyl

(152) n-pentyloxy

(153) CH ₂ = CHCH ₂ O

(154) n-butyl

(155) CH ₂ = CHCH ₂

(156) n-propyloxy

(157) F ₃ CO

(158) n-pentyloxy

(159) n-propyl

(160) n-pentyl

(161) CH ₂ = CHCH ₂ O

(162) n-propyloxy

(163) CH ₂ = CHCH ₂

Claims (12)

Cyclobutane derivatives of the formula I.

in which R ^{1 is} an unsubstituted, at least monosubstituted or halogen-substituted alkyl radical having 1-12 C atoms, in which one or more CH ₂ groups are each independently of one another by -O-, -S-, -CO-,

, -CO-O-, -O-CO-, -O-CO-O- or -CH = CH- can be replaced so that heteroatoms are not directly connected, QC = O, CF ₂ or C = CX ¹ X ² , X ¹ , X ² H, Cl or F, Y CH-R ² , R ² H, A, A ¹ independently of one another, even if they occur repeatedly, a) trans-1,4-cyclohexylene radical, in which also one or several non-adjacent CH ₂ groups can be replaced by -O- and / or -S-, b) 1,4-phenylene radical, where the radicals a), b) and d) can be substituted by CN, Cl or F, Z ¹ in the event of multiple occurrences independently of one another -CO-O-, -O-CO-, -CH ₂ O-, -O-, -O-CH ₂ -, -CH ₂ CH ₂ -, -CH = CH-, - C≡C-, or a single bond, and m is 1 or 2. Cyclobutane derivatives after Claim 1 of the formula I, characterized in that they have a value for the optical anisotropy Δn of <0.03 at a reduced temperature of 0.9 and a wavelength of 589 nm. Cyclobutane derivatives after Claim 1 or 2nd of formula I, characterized in that R2 means H. Cyclobutane derivatives after Claim 1 , 2nd or 3rd of formula I, characterized in that m is 1 or 2. Cyclobutane derivatives after Claim 1 , 2nd , 3rd or 4th of the formula I that Z ^{1 is} independently -CH ₂ CH ₂ -, -COO-, -OOC- or a single bond in the event of multiple occurrences. Cyclobutane derivatives after Claim 1 to 5 of the formula I, characterized in that R ^{1 is} -CN, F, OCF ₃ , CF ₃ , straight-chain alkyl or alkoxy having 1 to 10 C atoms or alkenyl or alkenyloxy having 2 to 10 C atoms. Cyclobutane derivatives after Claim 1 to 6 of formula I, characterized in that X ¹ and X ^{2 have} the meaning H or F. Use of compounds of the formula I according to Claim 1 to 7 as components of liquid crystalline media. Liquid-crystalline medium with at least two liquid-crystalline components, characterized in that it contains at least one compound of the formula I according to one or more of the Claims 1 to 7 contains. Liquid crystal display element, characterized in that it is a liquid crystalline medium Claim 9 contains. Reflective or transflective liquid crystal display element, characterized in that it is a dielectric as a liquid crystalline medium Claim 9 contains. Electro-optical display element, characterized in that it is a dielectric as a liquid-crystalline medium Claim 9 contains.