DE19607999A1 - Stable liquid crystalline or mesogenic substituted cyclopentenyl derivatives - Google Patents

Abstract

Substituted cyclopent-3-en-1-yl derivatives of formula (I) are new. In (I): R1 = hydrogen (H), 1-15C alk(en)yl, optionally mono-substituted by cyano (CN) or trifluoromethyl (CF3) or at least mono-substituted by halogen, in which 1 or more methylene groups (CH2) may be replaced by oxygen (-O-), sulphur (-S-), 1,3-cyclobutylene, carbonyl (-CO-), carboxyl (-CO-O- or -O-CO-) or carbonate (-O-CO-O-) without directly linked O atoms; A<1> and A<2> are: (a) trans-1,4-cyclohexylene, in which 1 or more non-adjacent CH2 groups may be replaced by -O- and/or -S-; (b) 1,4-phenylene, in which 1 or 2 CH groups may be replaced by nitrogen (N); (c) 1,4-cyclohexenylene; or (d) 1,4-cyclohexenylene, 1,4-bicyclo(2,2,2)-octylene, piperidin-1,4-diyl, naphth-2,6-diyl, decahydronaphth-2,6-diyl or 1,2,3,4-tetrahydronaphth-2,6-diyl, in which groups (a-c) may be mono- or di-substituted by fluorine (F); Z<1> and Z<2> = -CO-O-, -O-CO-, methyleneoxy (-CH2O- or -OCH2-), ethylene (-CH2CH2-), ethenylene (-CH=CH-), acetylene (-C?=C-), butylene (-(CH2)4-), butenylene (-CH=CH-CH2CH2-) or a single bond; m = 0, 1 or 2; and L<1>and L<2> = H, F, chlorine (Cl), CN, isocyanato (NCO), isothiocyanato (NCS) or optionally substituted 1-6 C alk(en)yl, in which 1 or more CH2 groups may be replaced by -O-, -CO- or -CO-O- without directly linked O atoms. Also claimed is a liquid crystalline (LC) medium containing >= 2 LC components, including compound(s) (I).

Description

The invention relates to substituted cyclopent-3-en-1-yl derivatives of Formula I.

wherein
R¹ H, an unsubstituted, a simply by CN or CF₃ or an at least monosubstituted by halogen or alkyl or alkenyl radical having 1 to 15 carbon atoms, in which radicals one or more CH₂ groups each independently

can be replaced in such a way that O atoms are not directly linked to one another,
A¹ and A² are each independently

• (a) trans-1,4-cyclohexylene radical, in which also one or more non-adjacent CH₂ groups by -O- and / or -S- can be replaced
• (b) 1,4-phenylene, which also contains one or two CH groups can be replaced by N,
• (c) 1,4-cyclohexenylene,
• (d) radical from the group 1,4-dyclohexenylene, 1,4-bicyclo (2,2,2) octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, Decahydronaphthalene-2,6-diyl and 1,2,3,4-tetra-hydronaphthalene-2,6-diyl,

where the radicals (a) to (c) can be substituted by one or two fluorine,
Z¹ and Z² each independently of one another -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CH₂CH₂-, -CH = CH-, -C≡C-, - (CH₂) ₄-, CH = CH-CH₂CHr, or a single bond,
m 0, 1 or 2, and
L¹ and L² each independently of one another H, F, Cl, CN, OCN, NCS, an unsubstituted or an at least monosubstituted alkyl or alkenyl radical having 1 to 6 carbon atoms, one or more CH₂ groups in each of these radicals being independent can be replaced by one another by -O-, -CO-, -CO-O- such that O atoms are not directly linked to one another,
mean.

The invention further relates to the use of these compounds as Components of liquid crystalline media as well as liquid crystal and electro optical display elements, the liquid-crystalline according to the invention Media included.

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

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

It has now been found that compounds of the formula I as components liquid crystalline media are particularly suitable. In particular, have they have comparatively low viscosities. With their help stable liquid-crystalline media with a wide mesophase range and above obtained partial values for the optical and dielectric anisotropy. These media also have very good low-temperature behavior.

With regard to the various areas of application of such a connection However, it was desirable to use additional connections to have high nematogenicity available on the precisely tailored properties for each application exhibit. 3,4-Substituted cyclopent-3-ene is a polar end group for Liquid-crystalline compounds are particularly suitable since the dipole moments of both cyclopentene C heteroatom bonds predominantly are aligned along the longitudinal axis of the molecule. Let her through relatively high Δε values are achieved.

With the provision of compounds of formula I is also whole generally the range of liquid crystalline substances, which can be found under ver various application-related aspects for the production liquid-crystalline mixtures are suitable, considerably broadened.

The compounds of formula I have a wide range of uses Area. Depending on the selection of the substituents, these can Compounds serve as base materials from which liquid crystalline The majority of the media are composed; but it can also compounds of the formula I from liquid-crystalline base materials other classes of compounds, for example the dielectric and / or optical anisotropy of such a dielectric to influence and / or its threshold voltage and / or optimize its viscosity.  

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

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

For the sake of simplicity, A³ in the following means a remainder of formula

Cyc one
1,4-cyclohexyl, Che a 1,4-cyclohexenylene, dio a 1,3-dioxane-2,5-diyl, dit a 1,3-dithiane-2,5-diyl, Phe a 1,4-phenylene, Pyd is a pyridine-2,5-diyl radical, Pyr is a pyrimidine-2,5-diyl radical and Bi is a bicyclo (2,2,2) octylene radical, it being possible for Cyc and / or Phe to be unsubstituted or mono- or disubstituted by F. .

A¹ and A² are preferably selected from the group Cyc, Che, Phe, Pyr, Pyd and Dio.

The compounds of the formula I accordingly comprise compounds with two rings of sub-formulas Ia and Ib:

R¹-A²-A³ Ia

R¹-A²-Z²-A³ Ib

Compounds with three rings of the sub-formulas Ic to Ie

R¹-A¹-A²-A³ Ic

R¹-A¹-Z¹-A²-A³ Id

R¹-A¹-A²-Z²-A³ Ie

as well as connections with four rings of the sub-formulas If to Ii:

R¹-A¹-A¹-A²-A³ If

R¹-A¹-Z¹-A¹-A²-A³ Ig

R¹-A¹-A¹-A²-Z²-A³ Ih

R¹-A¹-Z¹-A¹-A²-Z²-A³ Ii

Compounds of the formula I and all sub-formulas are also preferred, in those A¹ and / or A² substituted by F once or twice 1,4-phenylene means. In particular, these are 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene and 3,5-difluoro-1,4-phenylene.

A₁ and A² are preferred

Z¹ and Z² are preferably a single bond, -CO-O-, -O-CO- and -CH₂CH₂-, preferably second -CH₂O- and -OCH₂-. If one of the Radicals Z¹ and Z² - (CH₂) ₄- or -CH = CH-CH₂CH₂- means, that is other radicals Z¹ or Z² (if present) preferably a single bin dung.

L¹ and L² are preferably H, F, CN, OCF₃, OCHF₂, OCH = CF₂, OCF = CF₂, CF₃, CH₃, C₂H₅, OCH₃, especially F. Preferred combinations ions of L¹ and L²

L¹ H, L² = H
L¹ = H, L² = CN
L¹ = CN, L² = CN
L¹ = H, L² = CH₃
L¹ = CH₃, L² = CH₃
L¹ = H, L² = F
L¹ = H, L² = OCH₃
L¹ = OCH₃, L² = OCH₃.

Compounds in which L 1 = L 2 = F are particularly preferred.

m is preferably 0 or 1.

If R¹ is an alkyl radical and / or an alkoxy radical, then this can be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and therefore preferably means ethyl, Propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, Hexoxy or heptoxy, furthermore methyl, octyl, nonyl, decyl, undecyl, Dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, Decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy.

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

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

If R¹ is an alkyl radical in which a CH₂ group by -O- and one is replaced by -CO-, these are preferably adjacent. Consequently 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 especially acetyloxy, propionyloxy, butyryloxy, Pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, buty ryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 4-acetyl oxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxy carbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonyl methyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2- (methoxy-carbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propoxycarbonyl) ethyl, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl) propyl, 4- (methoxycarbonyl) butyl.

If R¹ is an alkyl radical in which a CH₂ group by unsub substituted or substituted -CH = CH- and an adjacent CH₂ group is replaced by CO or CO-O or O-CO, this can be straight-chain or be branched. It is preferably straight-chain and has 4 to 13 carbon atoms. Accordingly, it means especially acryloyloxymethyl, 2-acrylic oyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl, 8-acryloyloxyoctyl, 9-acryloyl oxynonyl, 10-acryloyloxydecyl, methacryloyloxymethyl, 2-methacryloyloxy ethyl, 3-methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyl oxypentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl, 8-methacrylic oyloxyoctyl, 9-methacryloyloxynonyl.

If R¹ is a simply substituted by CN or CF₃ alkyl or Alkenyl radical means, this radical is preferably straight-chain and Substitution by CN or CF₃ in the ω position.  

If R¹ is an at least mono-substituted alkyl or alkenyl radical, this radical is preferably straight-chain and halogen is preferably F or Cl. With multiple substitution Halogen preferably F. The resulting residues also close perfluorinated residues. With single substitution, the fluorine or Chlorine substituent in any position, but preferably in ω position.

Compounds of the formula I which are suitable for polymerization reactions nete wing groups R are suitable for liquid crystal display liner polymer.

Compounds of formula I with branched wing groups R can occasionally due to better solubility in the usual liquid crystalline base materials are of importance, but especially as chiral dopants if they are optically active. Smectic connections this type are suitable as components for ferroelectric materials.

Compounds of the formula I with S _A phases are suitable, for example, for thermally addressed displays.

Branched groups of this type usually do not contain more than one Chain branch. Preferred branched radicals R are isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, Isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2 ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methyl butoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methyl hexoxy, 1-methylheptoxy.

If R¹ is an alkyl radical in which two or more CH₂ groups are replaced by -O- and / or -CO-O-, this can be straight-chain or be branched. It is preferably branched and has 3 to 12 carbon atoms. Accordingly, it means especially bis-carboxy-methyl, 2,2-bis-carboxyethyl, 3,3-bis-carboxy-propyl, 4,4-bis-carboxy-butyl, 5,5-bis-carboxy-pentyl, 6,6-bis-carboxy-hexyl, 7,7-bis-carboxy-heptyl, 8,8-bis-carboxy  octyl, 9,9-bis-carboxy-nonyl, 10,10-bis-carboxy-decyl, Bis (methoxycarbonyl) methyl, 2,2-bis (methoxycarbonyl) ethyl, 3,3-bis (methoxycarbonyl) propyl, 4,4-bis (methoxycarbonyl) butyl, 5,5-bis (methoxycarbonyl) pentyl, 6,6-bis (methoxycarbonyl) hexyl, 7,7-bis (methoxy-carbonyl) heptyl, 8,8-bis-methoxycarbonyl) octyl, Bis (ethoxycarbonyl) methyl, 2,2-bis (ethoxycarbonyl) ethyl, 3,3-bis-ethoxycarbonyl) propyl, 4,4-bis (ethoxycarbonyl) butyl, 5,5-bis (ethoxycarbonyl) hexyl.

Compounds of the formula I which are suitable for polycondensation Wing groups R have, are suitable for the representation of liquid crystalline Polycondensates.

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

Among these are compounds of formula I and the sub-formulas preferred those in which at least one of those contained therein Radicals has one of the preferred meanings indicated.

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

Preferred smaller groups of compounds are those of the Sub-formulas I1 to I17:

The 1,4-cyclohexenylene group preferably has the following structures:

The compounds of formula I are according to methods known per se presented as they are in the literature (e.g. in the standard works such as Houben-Weyl, Methods of Organic Chemistry, Georg-Thieme-Verlag, Stuttgart) are described, namely under reaction conditions that for the implementations mentioned are known and suitable.

You can also use known ones that are not mentioned here Make use of variants.  

Scheme 1

Scheme 2

Scheme 3

The liquid-crystalline media according to the invention preferably contain in addition to one or more compounds according to the invention as further Components 2 to 40, especially 4 to 30 components. Very special more preferably, these media contain one or more inventions compounds according to the invention 7 to 25 components. These others 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 cyclohexyl benzoates, cyclohexane carboxylic acid phenyl or cyclohexyl ester, phenyl or cyclohexyl ester of cyclohexylbenzoic acid, phenyl or cyclohexyl ester of cyclo hexylcyclohexane carboxylic acid, cyclohexyl phenyl ester of benzoic acid cyclohexane carboxylic acid or cyclohexylcyclohexane carboxylic acid, Phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, Cyclohexylcyclohexanes, cyclohexylcyclohexylcyclohexenes, 1,4-biscyclo hexylbenzenes, 4,4'-biscyclohexylbiphenyls, phenyl- or cyclohexyl pyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclohexyl  dioxanes, phenyl- or cyclohexyl-1,3-dithiane, 1,2-diphenylethanes, 1,2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1-cyclohexyl 2- (4-phenylcyclohexyl) ethane, 1-cyclohexyl-2-biphenylylethane, 1-phenyl-2-cyclohexyl-phenylethane, optionally halogenated Stilbenes, benzylphenyl ethers, tolanes and substituted cinnamic acids. The 1,4-phenylene groups in these compounds can also be fluorinated.

The most important as further components of media according to the invention in Compounds in question can be represented by formulas 1, 2, 3, 4 and 5 characterize:

R′-L-E-R ′ ′ 1

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

R′-L-OOC-E-R ′ ′ 3

R'L-CH₂CH₂-E-R '' 4

R′-L-C≡C-E-R ′ ′ 5

In formulas 1, 2, 3, 4 and 5, L and E mean the same or ver can be different, each independently a bivalent Balance from the from -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr- -Dio-, -G-Phe- and -G-Cyc- as well as their mirror images formed group, where Phe is unsubstituted or fluorine-substituted 1,4-phenylene, Cyc trans-1,4-cyclohexylene or 1,4-cyclohexylene, pyr pyrimidine-2,5-diyl or pyridine-2,5-diyl, bio 1,3-dioxane-2,5-diyl and G 2- (trans-1,4-cyclo hexyl) ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl mean.

One of the radicals L and E is preferably Cyc, Phe or Pyr. E is in front preferably Cyc, Phe or Phe-Cyc. Preferably contain the inventions media according to the invention selected one or more components the compounds of formulas 1, 2, 3, 4 and 5, wherein L and E are selected are from the group Cyc, Phe and Pyr and simultaneously one or more Components selected from the compounds of the 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 rest of the rest is selected from the group -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-, and optionally one or more components selected from the Compounds of the formulas 1, 2, 3, 4 and 5, in which the radicals L and E are selected from the group -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.

R 'and R' 'mean in a smaller subset of the compounds of Formulas 1, 2, 3, 4 and 5 each independently of the other alkyl, alkenyl, Alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy with up to 8 carbon atoms. This smaller subgroup is called Group A below and the compounds are represented by sub-formulas 1a, 2a, 3a, 4a and 5a designated. For most of these compounds, R 'and R' 'are the same others different, one of these radicals mostly alkyl, alkenyl, alkoxy or alkoxyalkyl.

In another smaller subgroup of the compounds of the formulas 1, 2, 3, 4 and 5 referred to as group B, R ′ ′ -F, -Cl, -NCS or - (O) _i CH _{3- (k + 1)} ) F _k Cl₁ where i is 0 or 1 and k + 1 1, 2 or 3; the compounds in which R '' has this meaning are designated by the sub-formulas 1b, 2b, 3b, 4b and 5b. Such compounds of the sub-formulas 1b, 2b, 3b, 4b and 5b are particularly preferred in which R '' has the meaning -F, -Cl, -NCS, -CF₃, -OCHF₂ or -OCF₃.

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

In a further smaller subgroup of the compounds of the formulas 1, 2, 3, 4 and 5 means R ′ ′ - CN; this subgroup is hereinafter referred to as Group C designated and the compounds of this subgroup described accordingly with sub-formulas 1c, 2c, 3c, 4c and 5c. In the Compounds of sub-formulas 1c, 2c, 3c, 4c and 5c has R 'in the Compounds of the sub-formulas 1a-5a given meaning and is before preferably alkyl, alkoxy or alkenyl.  

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

The media according to the invention contain, in addition to ver compounds of the formula I preferably one or more compounds, which are selected from group A and / or group B and / or group C. The mass fractions of the compounds from these Groups on the media according to the invention are preferred

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%

where the sum of the mass fractions of the invention in each according to media contained compounds from groups A and / or B and / or C preferably 5 to 90% and in particular 10 to 90% is.

The media according to the invention preferably contain 1 to 40%, ins particularly preferably 5 to 30% of compounds according to the invention In addition, media containing more than 40% are preferred special 45 to 90% of compounds according to the invention. The media preferably contain three, four or five verb according to the invention fertilize.

The media according to the invention are produced in a manner which is customary per se Wise. As a rule, the components are dissolved into one another, for this purpose moderate at elevated temperature. With suitable additives, the liquid crystalline phases are modified according to the invention so that  it in all types of liquid crystal display that have become known elements can be used. Such additives are the subject known and extensively described in the literature (H. Kelker / R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, pleochroic dyes can be used to produce colored ones Guest host systems or substances for changing the dielectric Anisotropy, the viscosity and / or the orientation of the nematic Phases are added.

In the present application and in the following examples, the structures of the liquid crystal compounds are indicated by acronyms, the transformation into chemical formulas taking place according to Tables A and B below. All radicals C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl radicals with n or m C atoms. The coding according to Table B goes without saying. In Table A only the acronym for the basic body is given. In individual cases, there is a line for the substituents R¹, R², L¹ and L² separated from the acronym for the basic body:

Liquid-crystalline mixtures according to the invention contain in addition to or several compounds of formula I, especially components selected from Tables A and B.

Table A

Table B

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

"Normal work-up" means: if necessary, water is added, extracted with dichloromethane, diethyl ether, methyl tert. Butyl ether or Toluene, separates, dries the organic phase, evaporates and cleanses the product by distillation under reduced pressure or crystallization and / or chromatography. The following abbreviations are used:

DAST Diethylaminosulfur trifluoride
DMEU 1,3-dimethyl-2-imidazolidinone
KOT potassium tertiary butanolate
THF tetrahydrofuran
pTsOH p-toluenesulfonic acid

example 1 7,8-difluoro-1,4-dioxaspiro [4,4] non-7-ene (3)

A solution of 100 mmol 1 (prepared according to A.E. Graham, W. A. Loughlin, R.J.K. Taylor, Tetrahedron Lett. 1994, 35, 7281-7284 and S. M. Jeffrey, A.G. Sutherland, S.M. Pyke, A.K. Powell, R.J. K Taylor, J. Chem. Soc. Perkin Trans. 1, 1993, 2317-2327) and 500 mmol NFSi (N-fluorben benzenesulfonimide) in 200 ml THF is added dropwise at -78 ° C over 2 h mixed with 220 ml of a 1 M KOtBu solution in THF. After stirring for 6 h  300 ml of 1 M KOtBu solution are again at the same temperature added dropwise, and the mixture is allowed to slowly enter the room over a period of 6 hours temperature come. 500 mmol of tri are slowly added at 0.degree ethylamine and stirred for 30 min at room temperature. After adding 1 l of saturated saline is extracted with toluene. The United organic phases are with saturated NaHCO₃ solution and water washed, dried over MgSO₄ and chromatographed.

3,4-difluorocyclopent-3-en-1-ol (4)

50 mmol 3 are in a mixture of 100 ml dichloromethane and 200 ml of 1 N hydrochloric acid stirred vigorously. The organic phase is removed separates, washed with saturated NaHCO₃ solution and water, over MgSO₄ dried and evaporated to dryness. You solve the back was in 50 ml of ethanol and a solution of 70 mmol drips at 0 ° C NaBH₄ in 100 ml ethanol. After a reaction time of 3 h Add 600 ml of water and extract with dichloromethane. The organic Phase is worked up as usual. The product 4 becomes chromato graphically cleaned.

1-bromo-3,4-difluorocyclopent-3-ene (5)

A solution of 20 mmol 4 and 24 mmol triphenylphosphine in 100 ml Dichloromethane is added dropwise at 0 ° C with a solution of 30 mmol Tetrabromomethane in 50 ml dichloromethane. The mixture is stirred at 0 ° C. for 2 hours, then 18 h at room temperature and work up as usual. The Product 5 is purified by chromatography.

1 (4-pentylcyclohexyl) -3,4-difluorocyclopent-3-ene (7)

A suspension of 10 mmol 6, 5 mmol ZnBr₂ and 20 mmol Lithium granules in 50 ml of THF are mixed with vigorous stirring at 0-10 ° C for 10 h Treated with ultrasound. After adding 5 mmol 5, 150 mg NiCl₂ (PPh₃) ₂ and 10 mg CuBr is stirred for 48 h at room temperature. The mixture will mixed with 100 ml of saturated NH₄Cl solution and stirred for 15 min. The  organic phase is separated off, filtered through silica gel, with water washed and dried over MgSO₄. That after evaporating the Solvent remaining product 7 is purified by HPLC.

The following compounds of the formula become analogous

produced:

Claims (10)

1. Substituted cyclopent-3-en-1-yl derivatives of the formula I, wherein
R¹ H, an unsubstituted, a simply by CN or CF₃ or an at least monosubstituted by halogen or alkyl or alkenyl radical having 1 to 15 carbon atoms, in which radicals one or more CH₂ groups each independently can be replaced in such a way that O atoms are not directly linked to one another,
A₁ and A² each independently

• (a) trans-1,4-cyclohexylene radical, in which one or more non-adjacent CH₂ 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) 1,4-cyclohexenylene,
• (d) residue from the group 1,4-dyclohexenylene, 1,4-bicyclo (2,2,2) -octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6- diyl and 1,2,3,4-tetra-hydronaphthalene-2,6-diyl,

where the radicals (a) to (c) can be substituted by one or two fluorine,
Z¹ and Z² each independently of one another -CO-O-, -O-CO-, -CH₂O-, OCH₂-, -CH₂CH₂-, -CH = CH-, -C≡C-, - (CH₂) ₄-, -CH = CH-CH₂CH₂-, or a single bond,
m 0, 1 or 2, and
L¹ and L² each independently of one another H, F, Cl, CN, OCN, NCS an unsubstituted or an at least monosubstituted alkyl or alkenyl radical having 1 to 6 C atoms, one or more CH₂ groups in each of these radicals being independent of one another can be replaced by -O-, -CO-, -CO-O- in such a way that O atoms are not directly linked to one another,
mean. 2. Compounds of the formula I1, wherein R¹, L¹ and L² have the meaning given in claim 1. 3. Compounds of the formula I2, wherein R¹, L¹ and L² have the meaning given in claim 1. 4. Compounds of formula I3 wherein R¹, L¹ and L² have the meaning given in claim 1. 5. Compounds according to one of claims 1 to 4, characterized characterized in that L¹ = L² = F. 6. Use of compounds of formula I as components liquid crystalline media. 7. Liquid-crystalline medium with at least two liquid-crystalline ones Components, characterized in that there is at least one Contains compound of formula I. 8. Liquid crystal display element, characterized in that it is a contains liquid-crystalline medium according to claim 7. 9. Electro-optical display element, characterized in that it as a dielectric, a liquid-crystalline medium according to claim 7 contains.