DE19909760A1 - New benzo(b)furan derivatives used as components of liquid crystal media for liquid crystal and electro-optical displays - Google Patents

Abstract

Benzo(b)furan derivatives (I), with a mesogenic substituent, are new. Benzo(b)furan derivatives of formula (I), with a mesogenic substituent, are new: W = a benzofuran-5-yl group of formula (IIA) or (IIB); L<1>, L<2> = hydrogen (H) or fluorine (F); Y = CF2, C=O, C=CF2 or CH-CHF2; X<1>, X<2> = H, F, cyano (CN) or a 1-12 carbon (C) alkyl, 1-12 C alkoxy, 2-12 C alkenyl or 2-12 C alkenyloxy group, optionally with 1 or more F substituents; R<1> = H or optionally substituted 1-12 C alkyl or 2-12 C alkenyl; A<1>, A<2> = optionally substituted cycloaliphatic or (hetero)aromatic rings; Z<1>, Z<2> = -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CH2CH2-, -CH=CH-, -CC- or a single bond; n = 0, 1 or 2; at least one of L<1-3> = F or X<2> not = H if X<1> = unsubstituted alkyl or alkoxy . Compounds in which L<1>, L<2> = F, L<3>, X<2> = H and X<1> = H or unsubstituted alkyl are excluded. The full definitions are given in the DEFINITIONS (Full Definitions) Field.

Description

The invention relates to benzofuran derivatives of the formula I.

R ¹ - (A ¹ -Z ¹ ) _n -A ² -Z ² -WI

where W

L ¹ , L ² and L ³ each independently of one another H or F,
Y CF ₂ , C = O, C = CF ₂ or CH-CHF ₂ ,
X ¹ and X ² each independently of one another are H, F, CN, an unsubstituted or a straight-chain or branched alkyl or alkoxy radical having 1 to 12 carbon atoms substituted by one or more fluorine atoms, or an unsubstituted or one by one or more Fluorine atoms substituted straight-chain or branched alkenyl or alkenyloxy radical having 2 to 12 carbon atoms,
R ¹ is H, an unsubstituted, monosubstituted by CN or CF ₃ or a straight-chain or branched alkyl radical at least monosubstituted by halogen having 1 to 12 C atoms or alkenyl having 2 to 12 C atoms, where in these radicals one or more CH ₂ groups each independently
-O-, -S-, -CO-, -CO-O-, -O-CO-
or -O-CO-O- can be replaced so that heteroatoms are not directly linked to one another,
A ¹ and A ² each 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-cyclohexenylene radical,
• c) 1,4-phenylene radical, which also includes one or two CH groups can be replaced by N,
• d) radical from the group 1,4-bicyclo (2,2,2) octylene, Piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydro naphthalene-2,6-diyl and 1,2,3,4-tetrahydronaphthalene 2,6-diyl,

where the residues a), b) and c) can be substituted by CN, Cl or F,
Z ¹

and Z ²

each independently of the other -CO-O-, -O-CO-, -CH ₂

O-, -OCH ₂

-, -CH ₂

CH ₂

-, -CH = CH-, -C∼C- or a single bond
and
n 0.1 or 2
mean,
in which

• (a) at least one of the radicals L ¹ to L ³ F, or
• (b) X ^{2 has} a meaning other than H,

if X ¹

is an unsubstituted alkyl or alkoxy radical
and compounds are excluded, wherein L ¹

and L ²

F, L ³

and X ²

H and X ¹

H or unsubstituted alkyl.

The invention further relates to the use of these compounds general formula I as components of liquid-crystalline media and Liquid crystal and electro-optical display elements that the Invention contain according to liquid crystalline media.

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 DAP or ECB (electrically controlled birefringence)  or based on the effect of dynamic scattering. So far for this Purpose-used substances always have certain disadvantages, for example show insufficient stability against the effects of heat, light or electrical fields, unfavorable elastic and / or dielectric Characteristics.

The invention was based on the object, new stable liquid-crystalline or to find mesogenic compounds that are liquid as components crystalline media, particularly suitable for TFT and STN displays are.

It has now been found that the compounds of the formula I are excellent as Components of liquid crystalline media are suitable. With your help can be stable liquid crystalline media, particularly suitable for TFT or STN displays. The new connections stand out through high thermal stability and have advantageous values for the "holding ratio". In particular, the connections stand out of the formula I by negative to strongly positive dielectric anisotropies Δε, medium to extremely high optical anisotropies Δn and a favorable one Phase behavior.

With the provision of compounds of formula I is also whole generally the range of liquid crystalline substances that can be found under various application-related aspects of 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 influence and / or around its threshold voltage and / or its Optimize viscosity.

The meaning of formula I excludes all isotopes in the compounds of formula I bound chemical elements.

JP 07179856 discloses similar benzofuran-2,5-diyl compounds known, but preferably for applications in smectic Mixtures are suitable.

DE 43 00 066 describes fluorine-containing benzofurans and 2,3-dihydro benzofurane known, but in the 6-position by a rest are substituted, which contains at least one ring.

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 components of liquid crystalline Media. The invention also relates to liquid-crystalline media at least two liquid-crystalline components, the liquid crystalline media contain at least one compound of formula I. and liquid crystal display elements, in particular electro-optical Display elements which contain such liquid-crystalline media.

Above and below, R ¹ , A ¹ , Z ¹ , n, A ² , Z ² , L ¹ , L ² , L ³ , Y, X ¹ , X ² and W have the meaning given, unless expressly stated otherwise is.

For the sake of simplicity, Cyc in the following means a 1,4-cyclo hexylene radical, Che a 1,4-cyclohexenylene radical, dio a 1,3-dioxane-2,5- diyl residue, Dit a 1,3-dithiane-2,5-diyl residue, Phe a 1,4-phenylene residue, Pyd a pyridine-2,5-diyl radical, Pyr a pyrimidine-2,5-diyl radical and Bco one Bicyclo (2,2,2) octylene radical, where Cyc and / or Phe is unsubstituted or can be substituted one or more times by Cl, F or CN.

The compounds of formula I include compounds with three rings of sub-formulas Ia and Ib:

R ¹ -A ² -W Ia

R ¹ -A ² -Z ² -W Ib

Connections with four rings of the sub-formulas Ic to If:

R ¹ -A ¹ -A ² -W Ic

R ¹ -A ¹ -A ² -Z ² -W Id

R ¹ -A ¹ -Z ¹ -A ² -W Ie

R ¹ -A ¹ -Z ¹ -A ² -Z ² -W If

as well as compounds with five rings of the sub-formulas Ig to In:

R ¹ -A ¹ -A ¹ -A ² -W Ig

R ¹ -A ¹ -Z ¹ -A ¹ -A ² -W Ih

R ¹ -A ¹ -A ¹ -Z ¹ -A ² -W i

R ¹ -A ¹ -A ¹ -A ² -Z ² -W Ij

R ¹ -A ¹ -Z ¹ -A ¹ -Z ¹ -A ² -W Ik

R ¹ -A ¹ -Z ¹ -A ¹ -A ² -Z ² -W Il

R ¹ -A ¹ -A ¹ -Z ¹ -A ² -Z ² -W Im

R ¹ -A ¹ -Z ¹ -A ¹ -Z ¹ -A ² -Z ² -W In.

These include in particular those of the sub-formulas Ia, Ib, Ic, Id, Ie, Ig, Ih and Ii preferred.

The preferred compounds of sub-formula Ia include those of sub-formulas Iaa and Iab:

R ¹ -Phe-W Iaa

R ¹ -Cyc-W Iab.

The preferred compounds of sub-formula Ib include those of sub-formulas Iba and Ibb:

R ¹ -Phe-Z ² -W Iba

R ¹ -Cyc-Z ² -W Ibb.

The preferred compounds of sub-formula Ic include those of sub-formulas Ica to Ici:

R ¹ -Cyc-Cyc-W Ica

R ¹ -Cyc-Phe-W Icb

R ¹ -Phe-Phe-W Icc

R ¹ -Pyd-Phe-W Icd

R ¹ -Phe-Cyc-W Ice

R ¹ -Dio-Phe-W Icf

R ¹ -Pyr-Phe-W Icg

R ¹ -Cyc-Dio-W i

R ¹ -Dio-Cyc-W Ici.

These include those of the formulas Ica, Icb, Icc, Ice, Ich and Ici particularly preferred.

The preferred compounds of sub-formula Id include those of sub-formulas Ida to Idg:

R ¹ -Cyc-Cyc-Z ² -W Ida

R ¹ -Cyc-Phe-Z ² -W Idb

R ¹ -Phe-Phe-Z ² -W Idc

R ¹ -Pyr-Phe-Z ² -W Idd

R ¹ -Pyd-Phe-Z ² -W Ide

R ¹ -Cyc-Phe-CH ₂ CH ₂ -W Idf

R ¹ -A ¹ -Phe-CH ₂ CH ₂ -W Idg.

The preferred compounds of sub-formula Ie include those of sub-formulas Iea to Ieh:

R ¹ -Cyc-Z ¹ -Cyc-W Iea

R ¹ -A ¹ -CH ₂ CH ₂ -A ² -W Ieb

R ¹ -Cyc-Z ¹ -Phe-W Iec

R ¹ -A ¹ -OCO-Phe-W Ied

R ¹ -Phe-Z ¹ -Phe-W Iee

R ¹ -Pyr-Z ¹ -A ² -W Ief

R ¹ -Pyd-Z ¹ -A ² -W Ieg

R ¹ -Dio-Z ¹ -A ² -W Ieh.

Among them, those of the sub-formulas Iea, Ieb, Iec and Iee are special prefers.

The preferred compounds of the sub-formula If include those of the sub-formulas Ifa to Ife:

R ¹ -Phe-CH ₂ CH ₂ -A ² -Z ² -W Ifa

R ¹ -A ¹ -COO-Phe-Z ² -W Ifb

R ¹ -Cyc-Z ¹ -Cyc-Z ² -W Ifc

R ¹ -Phe-Z ¹ -Phe-Z ² -W Ifd

R ¹ -Cyc-CH ₂ CH ₂ -Phe-Z ² -W Ife.

The preferred compounds of the sub-formulas Ig to In include those of the sub-formulas Io to Iv:

R ¹ -A ¹ -Cyc-Cyc-W Io

R ¹ -A ¹ -Cyc-Phe-W Ip

R ¹ -A ¹ -CH ₂ CH ₂ -A ¹ -Phe-W Iq

R ¹ -Cyc-Z ¹ -A ¹ -Z ¹ -Phe-W Ir

R ¹ -Phe-Phe-Phe-W Is

R ¹ -Phe-Z ¹ -A ¹ -Phe-W It

R ¹ -A ¹ -Phe-Z ¹ -Phe-W Iu

R ¹ -A ¹ -Z ¹ -Cyc-Phe-Z ² -W Iv.

In the compounds of the formulas above and below, R ^{1 is} preferably alkyl or alkenyl, more preferably alkoxy. R ¹ is particularly preferably a straight-chain unsubstituted alkyl radical or a straight-chain unsubstituted alkenyl radical. Among the alkenyl residues, vinyl and the 1E and 3E alkenyl residues are preferred.

A ¹ and A ² independently of one another are preferably Phe, Cyc, Che, Pyd, Pyr or Dio. The compounds of the formula I preferably contain no more than one of the radicals Bco, Pyd, Pyr, Dio or Dit.

If the ring A ^{1 is} present twice, the two rings can have the same or different meanings. The same applies to bridge Z ¹ .

A ¹ and / or A ² each preferably independently of one another are trans-1,4-cyclohexylene or 1,4-phenylene which is mono- or disubstituted by F or CN. A ¹ and / or A ^{2 are} particularly preferably

A ¹ and / or A ² are very particularly preferably each independently of the other

n is preferably 0 or 1.

Z ¹ and Z ² independently of one another are preferably -CH ₂ CH ₂ -, -CO-O-, -O-CO- or a single bond, particularly preferably -CO-O-, -O-CO- or a single bond and very extraordinarily preferably a single bond.

In a particularly preferred embodiment, n 0 and Z ^{2 are} -CO-O-, -O-CO- or a single bond or n 1 and Z ¹ and Z ^{2 are} a single bond.

In the structural element W, Y is preferably CO, CF ₂ or C = CF ₂ , particularly preferably Y is CO.

X ¹ preferably denotes H, F, CN, an unsubstituted alkyl radical or an alkyl radical substituted by one or more fluorine atoms.

X ² preferably denotes H, F or CN, in particular H or F.

The formulas (1) to (9) represent preferred meanings of the structural element W:

In a preferred embodiment, X ^{1 is} F or CN and at least one of the radicals L ¹ to L ³ is F or X ² has a meaning other than H.

In another preferred embodiment, X ^{1 is} an unsubstituted alkenyl or alkenyloxy radical or an alkyl, alkoxy, alkenyl or alkenyloxy radical substituted by one or more fluorine atoms and at least one of the radicals L ¹ to L ³ is F or X ² has another Meaning as H.

The formulas (2a) and (4a) represent particularly preferred meanings of the structural element W:

If R ¹ in the formulas above and below denotes an alkyl radical or an alkoxy 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, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl , Octyl, nonyl, decyl, undecyl, dodecyl, methoxy, octoxy, nonoxy, decoxy or undecoxy.

If X ¹ and / or X ² each independently of one another in the formulas above and below represent an alkyl radical or an alkoxy radical, these can be straight-chain or branched. They are preferably straight-chain, have 1, 2, 3, 4, 5, 6 or 7 carbon atoms and are therefore preferably methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, Hexoxy or heptoxy, also octyl, nonyl, decyl, undecyl, dodecyl, octoxy, nonoxy, decoxy, undoxy or dodecoxy.

If R ^{1 is} oxaalkyl, this radical 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.

If R ¹ , X ¹ and / or X ² each independently represent an alkenyl radical, these can be straight-chain or branched. They are preferably straight-chain and have 2 to 10 carbon atoms. Accordingly, they mean in particular 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 R ¹ , X ¹ and / or X ² each independently represent an alkenyloxy radical, these can be straight-chain or branched. They are preferably straight-chain and have 2 to 10 carbon atoms. Accordingly, they mean in particular vinyloxy, prop-1 or prop-2-enyloxy, but-1-, 2- or but-3-enyloxy, pent-1-, 2-, 3- or pent4-enyloxy, hex-1- , 2-, 3-, 4- or hex-5-enyloxy, hept-1-, 2-, 3-, 4-, 5- or hept-6-enyloxy, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyloxy, non-1-, 2-, 3-, 4-, 5-, 6-, 7- or non-8-enyloxy, dec-1-, 2 -, 3-, 4-, 5-, 6-, 7-, 8- or Dec-9-enyloxy.

If R ^{1 is} an alkyl radical in which one CH ₂ group has been replaced by -O- and one has been replaced by -CO-, these groups are preferably adjacent. This radical thus contains an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-. It is preferably straight-chain and has 2 to 6 carbon atoms. Accordingly, it means especially acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxy methyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, methoxybutyloxypyloxy, propyloxyoxy, Ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxy carbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2- (methoxycarbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propoxy carbonyl) ethyl, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl ) propyl or 4- (methoxycarbonyl) butyl.

If R ^{1 is} an alkenyl radical in which a CH ₂ group adjacent to the double bond is replaced by -CO- or -CO-O- or -O-CO-, this can be straight-chain or branched. It is preferably straight-chain and has 4 to 12 carbon atoms. Accordingly, it means in particular acryloyloxymethyl, 2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxy butyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl, 8-acryloyloxyoctyl, 9-acryloyloxynonyl, methacryloyloxymoyloxyloxyethyl, 2-acryloyloxymyloxy, 4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl or 8-methacryloyloxyoctyl.

If R ¹ is a monosubstituted by CN or CF ₃ alkyl or alkenyl radical, this radical is preferably straight-chain and the substitution by CN or CF ₃ in the u position.

If R ^{1 is} an alkyl or alkenyl radical which is at least monosubstituted by halogen, this radical is preferably straight-chain and 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.

If X ¹ and / or X ² each independently represent an alkyl, alkoxy, alkenyl or alkenyloxy radical substituted by one or more F atoms, these can be straight-chain or branched. They are preferably straight-chain and have 1 to 8 and particularly preferably 1 to 4 carbon atoms. In this case, X ¹ and / or X ² each independently mean, in particular preferably CHF ₂ , CF ₃ , OCHF ₂ , OCF ₃ , CHFCF ₃ , CF ₂ CHF ₂ , OCH ₂ CHF ₂ , OCH ₂ CF ₃ , OCHFCF ₃ , OCF ₂ CHF ₂ , OC ₂ F ₅ , CH = CHF, CH = CF ₂ , CF = CF ₂ , OCH = CF ₂ , OCF = CF ₂ , C ₂ H ₄ CHF ₂ , CF ₂ CH ₂ CF ₃ , OCH ₂ CF ₂ CHF ₂ , OCH ₂ C ₂ F ₅ , OCF ₂ CHFCF ₃ , OCF = CFCF ₃ , O (CH ₂ ) ₃ CF ₃ , OCH ₂ C ₃ F ₇ or OCF = CF-C ₂ F ₅ and extremely preferably CHF ₂ , CF ₃ , OCHF ₂ , OCF ₃ , OCHFCF ₃ , OC ₂ F ₅ or OCH = CF ₂ .

Compounds of the formula I with a branched wing group R ¹ , X ¹ and / or X ² may occasionally be of importance 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. However, the optically inactive compounds of the formula I are preferred.

Branched groups of this type usually contain no more than one chain branch. Preferred branched radicals R ¹ , X ¹ and / or X 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-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 1-methylheptoxy.

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.

Some very particularly preferred smaller groups of compounds of the formula I are those of the sub-formulas I1 to I11:

L ^a , L ^b , L ^c , L ^d = each independently H or F.

Particularly preferred formulas from the group of sub-formulas I1 to I11 are the formulas I1, I4, I5 and I10. Among formulas I4 and I5, sub-formulas I4a and I5a are particularly preferred

L ^b , L ^c = each independently H or F.

Further preferred sub-formulas of the formulas I1, I4a, I5a and I10 are the formulas I1a, I4a1, I5a1 and I10a:

o = 2, 3, 4 or 5,
L ^b = H or F.

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 do this from known, not mentioned here Make use of variants.

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

The compounds of the invention can e.g. B. according to the following Reaction schemes 1 to 8 are made:  

Scheme 1

Representation of Br-W

Scheme 2

Representation of Br-W

Scheme 3

Representation of Br-W

Scheme 4

The coupling of the connections Br-W produced analogously to schemes 1 to 4 to the mesogenic base body R ¹ - (A ¹ -Z ¹ ) _n -A ² -Z ² - can be carried out according to methods known from the literature.

Linking a non-aromatic ring with an aromatic one Nucleus or the connection of two aromatic nuclei can for example as shown in Scheme 4.

The preparation of compounds of formula I in which Z ^{2 is} a single bond and the radical A ^{2 is} a 1,3-dioxane-2,5-diyl radical can, for example, by acetalization of a diol with an aldehyde, for. B. in the presence of an acid such as p-toluenesulfonic acid in an inert solvent such as. B. n-pentane, cyclohexane or toluene. The representation of the aldehydes OHC-W from the aryl bromides Br-W can, for. B. can be achieved by converting the aryl bromides with magnesium into the corresponding Grignard compounds, reacting them with triethyl orthoformate and hydrolyzing the reaction product (CA Dornfeld, GH Coleman, Org. Synth. III, 701 (1955)).

The aromatic aldehydes OHC-W can, for. B. also from the ent Talking nitriles obtained, for example, with chlorine implemented hydrogen in the presence of anhydrous stannous chloride and are then hydrolyzed (Stephen reduction).

The nitriles NC-W can e.g. B. can be obtained by corresponding Chenden aryl bromides for example with cyanides such. B. copper cyanide implemented (L. Friedman, H. Shechter, J. Org. Chem. 26, 2522 (1961); M.S. Newman, H. Boden, J. Org. Chem. 26, 2525 (1961); Mowry, Chem. Rev. 42,189 (1948)).  

The compounds of the formula I in which Z ^{2 is} -O-CO- or -CO-O- can be prepared, for example, by esterification reactions from the carboxylic acids HOOC-W or from the phenols HO-W (or from their reactive derivatives) . To build esters in which Z ^{2 means} -O-CO-, the nitriles NC-W z. B. be converted into the corresponding carboxylic acids, for. B. by heating in the presence of mineral acids. To build esters in which Z ^{2 is} -CO-O-, the aryl bromides Br-W z. B. convert into phenols HO-W. For this purpose, the aryl bromides can, for example, first be reacted with diborane and lithium in THF and then oxidized with alkaline H ₂ O ₂ (GM Pickles, FG Thorpe, J. Organomet. Chem 76, C23 (1974)).

Starting from the phenols HO-W, compounds of the formula I in which Z ² denotes -CH ₂ O- can also be obtained, for example, by etherification. Ethers of the formula I in which Z ² denotes -OCH ₂ - can be obtained, for example, by etherification of the compounds HOCH ₂ -W (or their reactive derivatives). The corresponding alcohols can e.g. B. obtained by reduction of the aldehydes OHC-W.

Scheme 5

Scheme 6

Scheme 7

Scheme 8

The ring closure shown in Schemes 1 and 6 to the 5-position substituted 3H-benzofuran-2-ones can e.g. B. analogous to that in A. Closse, W. Haeflinger, D. Hauser, J. Med. Chem. 24 (1981) 1465-1471 described methods are carried out.

These compounds can be converted into the corresponding 2,2-difluoro-2,3-dihydrobenzofurans by reaction with suitable fluorinating agents, for example SF ₄ in methylene chloride. By dehydrofluorination with suitable bases, such as. B. lithium diisopropylamide in THF, the 5-substituted 2-fluorobenzofurans are obtained.

However, the 3H-benzofuran-2-ones can also be used in the 2-difluoromethylene 2,3-dihydrobenzofurans can be converted. This is suitable for for example the reaction with dibromodifluoromethane in the presence of Zinc and hexamethyltriaminophosphine in THF (J.S. Houlton, W.B. Mother well, B.C. Ross, M.J. Tozer, D.J. Williams, A.M.Z. Slavin, Tetrahedron 49 (1993) 8087-8106). The reduction of these compounds, for example the catalytic hydrogenation with precious metals such as Pd provides the corresponding 2-difluoromethyl-2,3-dihydrobenzofurans.

The ring closure shown in Schemes 2 and 7 to the 5-position substituted benzofuran-3-ones can e.g. B. analogous to that in D.M.X. Donnelly, J.-P. Finet, J.M. Kielty, Tetrahedron Lett. 32 (1991) 2835-2836 described method can be performed.

By suitable reduction of these compounds, e.g. B. with NaBH ₄ in methanol, and subsequent dehydration, for example acid catalyzed with p-toluenesulfonic acid in toluene, the corresponding benzofurans can be synthesized.

These benzofurans substituted in the 5-position can be analogous to Schemes 3 and 8 are electrophilically substituted, the corresponding corresponding 2,5-disubstituted benzofurans can be obtained. The electrophilic substitution takes place in such a way that the substitute in the 5-position Benzofurans first with a suitable base, for example Butyllithium in n-hexane or lithium diisopropylamide in solvents such as Tetrahydrofuran or dimethylformamide, deprotonated and then be implemented with a suitable electrophile. This way you can the benzofurans halogenated, alkylated or in the 2-position, for example be cyanized. Suitable electrophilic reagents are e.g. B. Selectfluor for fluorination, p-toluenesulfonyl cyanide for cyanation or  5-trifluoromethyldibenzoselenophenium trifluoromethanesulfonate for Introduction of a trifluoromethyl group.

The benzofuran-3-ones substituted in the 5-position can be analogous to Schemes 2 and 7 also in the corresponding 2,3-difluorobenzofurans being transformed. To do this, the Benzofuran-3-one is first by electrophilic substitution, e.g. B. by deprotonation with LDA in THF and fluorination with N-fluorobenzenesulfonimide, in the corresponding 2-Fluorobenzofuran-3-one transferred.

After reaction with suitable fluorinating agents such as for example diethylaminosulfur trifluoride and dehydrofluorination of Fluorination products can be implemented to the desired products. Suitable bases can be used for dehydrofluorination, such as e.g. B. Lithium diisopropylamide in THF. The ones in schemes 2 and 7 additionally The syntheses of the 2- and 3-fluorobenzofurans shown are carried out by previously described reactions.

Preferred compounds of formula I are prepared as follows:

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Esters of the formula I can also be correspondingly esterified Carboxylic acids (or their reactive derivatives) with alcohols or Phenols (or their reactive derivatives) or according to the DCC Method (DCC = dicyclohexylcarbodiimide) can be obtained.

The corresponding carboxylic acids and alcohols or phenols are known or can be prepared in analogy to known methods become.  

Suitable reactive derivatives of the carboxylic acids mentioned are especially 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.

As reactive derivatives of the alcohols or phenols mentioned come in particular the corresponding metal alcoholates or Phenolates, preferably an alkali metal such as Na or K, into consideration.

The esterification is advantageous in the presence of an inert solvent carried out. 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 hexamethyl triamid, hydrocarbons such as benzene, toluene or xylene, halogen carbons Hydrogen such as carbon tetrachloride or tetrachlorethylene and Sulfoxides such as dimethyl sulfoxide or sulfolane. Immiscible with water Solvents can simultaneously be advantageous for azeotropic Distilling off the water formed during the esterification become. Occasionally, an excess of an organic base, e.g. As pyridine, quinoline or triethylamine, as a solvent for the Esterification can be applied. The esterification can also take place in Absence of a solvent, e.g. B. by simply heating the Components are carried out in the presence of sodium acetate. The Reaction temperature is usually between -50 ° and + 250 °, preferred between -20 ° and + 80 °. At these temperatures they are Esterification reactions usually take 15 minutes to 48 hours completed.  

The reaction conditions for the esterification depend in particular largely depends on the nature of the raw materials used. So will a free carboxylic acid with a free alcohol or phenol usually in the presence of a strong acid, for example a mineral acid such as Hydrochloric acid or sulfuric acid. A preferred response is the implementation of an acid anhydride or in particular one Acid chloride with an alcohol, preferably in a basic environment, where as bases in particular alkali metal hydroxides such as sodium or Potassium hydroxide, alkali metal carbonates or bicarbonates 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 from Meaning. Another preferred embodiment of Ver esterification is that the alcohol or the phenol is first in transfers the sodium or potassium alcoholate or phenolate, e.g. B. by Treatment with ethanolic sodium or potassium hydroxide solution, this isolated and reacted with an acid anhydride or in particular acid chloride.

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

In a further process for the preparation of the compounds of the formula I in which Z ¹ or Z ^{2 is} -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 success of the coupling reaction, such as. B. triethylamine, are also suitable as solvents. Examples of palladium catalysts are its salts, in particular Pd (II) acetate, with organic phosphorus (III) compounds, such as, for. B. triarylphosphanes, suitable. You can work in the presence or absence of an inert solvent at temperatures between about 0 ° C and 150 ° C, preferably between 20 ° C and 100 ° C. As solvents such. B. nitriles such as acetonitriles or hydrocarbons such as benzene or toluene. The aryl halides and olefins used as starting materials are widely available commercially or can be prepared by processes known from the literature, for example by halogenating corresponding parent compounds or by elimination reactions on corresponding alcohols or halides.

In this way, stilbene derivatives can be produced, for example. The style bene can still be made by reacting a 4-sub substituted benzaldehyde with an appropriate phosphorylide Wittig. However, tolanes of the formula I can also be prepared by: uses monosubstituted acetylene instead of the olefin (Synthesis 627 (1980) or Tetrahedron Lett. 27, 1171 (1986)).

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

Couplings of alkynyl compounds with aryl halides can be carried out analogously that of A.O. King, E. Negishi, F.J. Villani and A. Silveira in J. Org. Chem. 43, 358 (1978).  

Tolanes of the formula I in which Z ¹ or Z ^{2 are} —C∼C- can also be prepared via the Fritsch-Buttenberg-Wiechell rearrangement (Ann. 279, 319, 1984) in which 1,1-diaryl 2-Halogenethylenes are rearranged to diarylacetylenes in the presence of strong bases.

Tolanes of formula I can also be prepared by the the corresponding stilbene is brominated and then a dehydro subject to halogenation. You can do it here, but not here Apply the variants of this implementation mentioned in more detail.

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, e.g. B. by treatment with NaH, NaNH ₂ , NaOH, KOH, Na ₂ CO ₃ or K ₂ CO ₃ , is converted into the corresponding alkali metal alcoholate or alkali metal phenolate. This can then be reacted with the corresponding alkyl halide, sulfonate or dialkyl sulfate, advantageously in an inert solvent such as. B. acetone, 1,2-dimethoxyethane, 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.

For the production of laterally substituted fluorine or chlorine compounds of the formula I corresponding aniline derivatives with sodium nitrite and either with tetrafluoroboric acid (to introduce an F atom) or with Copper (I) chloride (to introduce a Cl atom) to the diazonium salts are implemented, which then thermally at temperatures of 100 ° -140 ° be decomposed.  

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 magnesium compound with a ketone if there is to be an aliphatic group Z ¹ and / or Z ² between the nuclei.

The organometallic compounds are put through, for example Metal-halogen exchange (e.g. according to Org. React. 6, 339-366 (1951)) between the corresponding halogen compound and one organolithium compound such as preferably n-butyllithium, tert.- Butyllithium or lithium naphthalenide or by sales with Magnesium shavings.

The linking of two aromatic rings or an aliphatic group Z ¹ and / or Z ² 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 e.g. B. SnCl ₄ , ZnCl ₂ or especially AlCl ₃ and TiCl ₄ .

Furthermore, the connection of two aromatic rings by the Ullmann reaction (e.g. 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 diazonium salt and the corresponding aromatic compound (e.g. Org. React. 2, 224 (1944)). The representation of the tolanes of formula I (Z ¹ and / or Z ² = -C∼C-) z. B. by reacting the corresponding aryl halides with an acetylide in a basic solvent with transition metal catalysis; Palladium catalysts can preferably be used here, in particular a mixture of bis (triphenylphosphine) palladium (II) chloride and copper iodide in piperidine as solvent.

In addition, the compounds of the formula I can be prepared by adding a compound which otherwise corresponds to the formula I Instead of H atoms, one or more reducible groups and / or Contains C-C multiple bonds, reduced.

As reducible groups are preferably carbonyl groups, in particular keto groups, further z. B. free or esterified hydroxyl groups or aromatic 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 functional (e.g. in the form of its p-toluenesulfonate) modified OH group.

The reduction can e.g. B. done by catalytic hydrogenation at temperatures between about 0 ° and about 200 ° and pressures between about 1 and 200 bar in an inert solvent, for. B. 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 (e.g. PtO ₂ , PdO), on a support (e.g. Pd on carbon, calcium carbonate or strontium carbonate) or in finely divided form .

Ketones can also by the methods of Clemmensen (with zinc, amalgamated zinc or tin and hydrochloric acid, expediently in aqueous alcoholic solution or in a heterogeneous phase with water / toluene at temperatures between about 80 and 120 °) or Wolff-Kishner (with hydrazine, expedient 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, the alkyl groups and / or -CH ₂ CH ₂ - bridges, reduced will.

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 made in analogy be made to known compounds.

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-bis-cyclo hexylbenzenes, 4,4'-bis-cyclohexylbiphenyls, 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-phenyl-cyclohexyl) 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 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'-LE-R '' 1

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

R'-L-OOC-E-R '' 3

R'-L-CH ₂ CH ₂ -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-cyclohexenylene, pyr pyrimidine 2,5-diyl or pyridine-2,5-diyl, dio 1,3-dioxane-2,5-diyl and G2- (trans 1,4-cyclohexyl) ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane Mean 2,5-diyl.

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 other remainder 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 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' 'in a smaller subset of the compounds of the 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, referred to as group B, of the compounds of the formulas 1, 2, 3, 4 and 5, R '' is -F, -Cl, -NCS or - (O) _i CH _{3- (k + l)} F _k Cl _l , where i are 0 or 1 and k + l are 1, 2 or 3. The connections in which R ″ has this meaning are denoted by sub-formulas 1b, 2b, 3b, 4b and 5b. Those compounds of partial 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 sub-formulas 1b, 2b, 3b, 4b and 5b, R 'has the at 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 the sub-formulas 1c, 2c, 3c, 4c and 5c have R 'those in the Compounds of sub-formulas 1a-5a given meaning and is preferably alkyl, alkoxy or alkenyl.

In addition to the preferred compounds of groups A, B and C are also other compounds of formulas 1, 2, 3, 4 and 5 with other variants of the proposed substituents in use. All of these substances are obtainable according to methods known from the literature or in 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 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 Is 90%.

The media according to the invention preferably contain 1 to 40%, particularly preferably 5 to 30% of the verbin according to the invention fertilize. Media containing more than 40% are also preferred. in particular 45 to 90% of compounds according to the invention. The Media preferably contain three, four or five according to the invention Links.  

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.

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. Mp. Means melting point, Kp = clearing point. Furthermore, K = crystalline state, N = nematic phase, S = smectic phase and I = isotropic phase. The data between these symbols represent the transition temperatures. An means optical anisotropy (589 nm, 20 ° C.) and the viscosity (mm ² / sec) was determined at 20 ° C.

"Normal work-up" means: if necessary, water is added, if necessary, adjusts to pH values depending on the constitution of the end product between 2 and 10, extracted with dichloromethane, diethyl ether, methyl tert-butyl ether or toluene, separates, dries the organic phase, evaporates and purifies the product by distillation under reduced Pressure or crystallization and / or chromatography.  

The following abbreviations are used:
AcOH: glacial acetic acid
Ac ₂ O: acetic anhydride
BuLi: n-butyllithium
DAST: Diethylamino sulfur trifluoride
DCC: dicyclohexylcarbodiimide
DMF: dimethylformamide
LDA: lithium diisopropylamide
MeOH: methanol
NaOAc: sodium acetate
NFSi: N-fluorobenzenesulfonimide
PdCl ₂ (dppf): (Diphenylphosphinoferrocene) palladium dichloride
Pd-C: palladium on activated carbon
PPh ₃ : triphenylphosphine
P (NMe ₂ ) ₃ : hexamethyltriaminophosphine
Selectfluor: N-fluoro-N-chloromethyltriethylenediamine bis (tetrafluoroborate)
THF: tetrahydrofuran
TsCN: p-toluenesulfonyl cyanide
TsOH: p-toluenesulfonic acid.

example 1

A mixture of 13.3 mmol trans-4-pentylcyclohexane-carboxylic acid, 13.3 mmol 1 , 16 mmol DCC and 150 ml THF is stirred for 12 h at room temperature. A further 11 mmol of DCC are then added and, after stirring for four hours at 45 ° C., worked up as usual. You get 2 ; K 139 l.

Example 2

Step 1

A solution of 1.5 mol NaOH in 150 ml H ₂ O is added to a mixture of 760 mmol 3 , 860 mmol bromoacetic acid and 600 ml H ₂ O. The mixture is then heated to gentle boiling for 12 hours with gentle stirring, then 148 ml of aqueous hydrochloric acid (37% by weight) are added and the resulting suspension is subjected to steam distillation. After the usual work-up, 4 is obtained .

step 2

A mixture of 530 mmol 4 , 2.32 mol sodium acetate, 490 ml acetic anhydride and 490 ml glacial acetic acid is heated to reflux with stirring for 48 h. The hot solution is then poured into 2.5 l of ice water and worked up as usual. You get 5 .

step 3

At 2 ° C., 48 mmol of lithium granules are added to 24 mmol of 6 , 12 mmol of ZnBr ₂ and 36 ml of a toluene / THF mixture (toluene: THF 4: 1). The mixture is treated with ultrasound at 5 ° C. for 4 h, then 24 mmol of 5 and 0.2 g of PdCl ₂ (dppf) are added and the mixture is stirred at room temperature for 48 h. After adding 25 ml of a saturated NH ₄ Cl solution and stirring for one hour at room temperature, the mixture is worked up as usual. You get 7 ; K 80 S _B 110 N 158 l; Δε = +0.83; Δn = +0.108.

Example 3

A suspension of 0.2 g PdCl ₂ , 0.6 g PPh ₃ and 0.05 g NaBH _{4 is added} to a mixture of 50 mmol 5 and 50 mmol 8 in 50 ml THF and 75 mmol NaHCO ₃ in 25 ml H ₂ O. in 25 ml of THF, which had previously been stirred under nitrogen for 0.5 h. The mixture is then refluxed for 12 hours and worked up as usual. You get 9 ; K 187 N 189.2 l.

Example 4

A solution of 20 mmol BuLi in n-hexane (1.8 molar solution) is first added dropwise to a solution of 20 mmol 10 in 25 ml THF with inert gas and stirring at -78 ° C and then a suspension of 22 mmol Selectfluor in 35 ml of acetonitrile added. The mixture is stirred at -78 ° C for 2 h, then allowed to warm slowly to room temperature and stirred for a further 12 h. After the usual work-up, 11 is obtained .

The following are prepared analogously to Examples 1 to 4:

R ¹ - (A ¹ -Z ¹ ) _n -A ² -Z ² -W

Claims (13)

1. Benzofuran derivatives of the formula I.
R ¹ - (A ¹ -Z ¹ ) _n -A ² -Z ² -WI
where W
L ¹ , L ² and L ³ each independently of one another H or F,
Y CF ₂ , C = O, C = CF ₂ or CH-CHF ₂ ,
X ¹ and X ² each independently of one another are H, F, CN, an unsubstituted or a straight-chain or branched alkyl or alkoxy radical having 1 to 12 C atoms or substituted by one or more fluorine atoms or an unsubstituted or a straight-chain or one substituted by one or more fluorine atoms or branched alkenyl or alkenyloxy radical having 2 to 12 carbon atoms,
R ¹ is H, an unsubstituted, monosubstituted by CN or CF ₃ or at least monosubstituted sub-substituted by halogen, linear or branched alkyl radical having 1 to 12 C atoms or alkenyl having 2 to 12 C atoms, where in these radicals one or several CH ₂ groups can each be replaced independently of one another by -O-, -S-, -CO-, -CO-O-, -O-CO- or -O-CO-O- so that heteroatoms are not directly linked to one another are linked,
A ¹ and A ² each 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-cyclohexenylene radical,
• c) 1,4-phenylene radical, in which one or two CH groups can also be replaced by N,
• d) radical from the group 1,4-bicyclo (2,2,2) octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydro naphthalene-2,6-diyl and 1,2, 3,4-tetrahydro naphthalene-2,6-diyl,

where the residues a), b) and c) can be substituted by CN, Cl or F,
Z ¹ and Z ² each independently of one another -CO-O-, -O-CO-, -CH ₂ O-, -OCH ₂ -, -CH ₂ CH ₂ -, -CH = CH-, -C∼C- or a single bond
and
n 0.1 or 2
mean,
in which

• (a) at least one of the radicals L ¹ to L ³ F, or
• (b) X ^{2 has} a meaning other than H,

when X ^{1 is} an unsubstituted alkyl or alkoxy radical
and compounds are excluded, wherein L ¹ and L ^{2 are} F, L ³ and X ² H and X ¹ H or unsubstituted alkyl. 2. tetrahydrofuranocyclohexane derivatives according to claim 1, characterized in that R ^{1 is} a straight-chain unsubstituted alkyl radical or a straight-chain unsubstituted alkenyl radical. 3. Benzofuran derivatives according to one of claims 1 or 2, characterized in that n 0 and Z ^{2 are} -CO-O-, -O-CO- or a single bond, or that n 1 and Z ¹ and Z ^{2 are} one Single bond means. 4. Benzofuran derivatives according to any one of claims 1 to 3 of the formula I1
wherein R ¹ and W have the meanings given. 5. Benzofuran derivatives according to one of claims 1 to 3 of the formula I4
wherein L ^a , L ^b , L ^c and L ^d each independently represent H or F and R ¹ and W have the meanings given. 6. Benzofuran derivatives according to one of claims 1 to 3 of the formula I5
wherein L ^a , L ^b , L ^c and L ^d each independently represent H or F and R ¹ and W have the meanings given. 7. Benzofuran derivatives according to one of claims 1 to 3 of the formula I10
wherein R ¹ and W have the meanings given. 8. Benzofuran derivatives according to any one of claims 1 to 7 wherein W
means. 9. Benzofuran derivatives according to any one of claims 1 to 7 wherein W
means. 10. Use of compounds according to one of claims 1 to 9 as components of liquid crystalline media. 11. Liquid-crystalline medium with at least two liquid-crystalline ones Components, characterized in that there is at least one Compound of claims 1 to 9 contains. 12. Liquid crystal display element, characterized in that it is a contains liquid-crystalline medium according to claim 11. 13. Electro-optical display element, characterized in that it as a dielectric, a liquid-crystalline medium according to claim 11 contains.