CA2046590A1 - 1,4-disubstituted 2,6-difluorobenzene compounds, and a liquid crystalline medium - Google Patents

1,4-disubstituted 2,6-difluorobenzene compounds, and a liquid crystalline medium

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Publication number
CA2046590A1
CA2046590A1 CA002046590A CA2046590A CA2046590A1 CA 2046590 A1 CA2046590 A1 CA 2046590A1 CA 002046590 A CA002046590 A CA 002046590A CA 2046590 A CA2046590 A CA 2046590A CA 2046590 A1 CA2046590 A1 CA 2046590A1
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Prior art keywords
propyl
compounds
pentyl
ocf3
ethyl
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Abandoned
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CA002046590A
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French (fr)
Inventor
Eike Poetsch
Volker Meyer
Volker Reiffenrath
Andreas Wachtler
Ulrich Finkenzeller
Hans-Adolf Kurmeier
Reinhard Hittich
Bernhard Rieger
David Coates
Simon Greenfield
Robert W. Clemitson
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Merck Patent GmbH
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Individual
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Priority claimed from DE4000535A external-priority patent/DE4000535B4/en
Priority claimed from DE4000534A external-priority patent/DE4000534C2/en
Application filed by Individual filed Critical Individual
Publication of CA2046590A1 publication Critical patent/CA2046590A1/en
Abandoned legal-status Critical Current

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Abstract

Abstract 1,4-Disubstituted 2,6-difluorobenzene compounds of the formula I

I

where R is an alkyl or alkenyl radical having 1 to 15 carbon atoms which is unsubstituted or at least monosubstituted by halogen, it also being possible for one or more CH2 groups in these radicals to be replaced, in each case in-dependently of one another, by -O-, -S-,, , -CO-, -CO-O-, -O-CO- or -O-CO-O- in such a manner that oxygen atoms are not linked directly to one another, A1 and A2, in each case independently of one another, are (a) a trans-1,4-cyclohexylene radical in which, in addition, one or more non-adjacent CH2 groups may be replaced by -O- and/or -S-, (b) a 1,4-phenylene radical in which, in addition, one or two CH groups may be replaced by N, (c) a radical from the group comprising 1,4-cyclo-hexenylene,1,4-bicyclo(2,2,2)octylene,piperi-dine-1,4-diyl,naphthalene-2,6-diyl,decahydro-naphthalene-2,6-diyl and 1,2,3,4-tetrahydro-naphahalene-2,6-diyl, it being possible for the radicals (a) and (b) to be substituted by CN or monosubstituted or disubstituted by fluorine, Z1 and Z2 in each case independently of one another, are -CO-O-,-O-CO-,-CH2O-,-OCH2-, -CH2CH2-, -CH=CH-, -C?C- or a single bond, m and n in each case independently of one another, are 0, 1, 2 or 3, where (m+n) is 1, 2 or 3, and X has one of the meanings of R or is F, Cl, -CF3, -OCF3-, -OCF2H, -OC2F5, -CN or -NCS, with the proviso that at least one of the radicals Z1 and ZZ present in the molecule is -CO-O-, -O-CO-, -CH2-O-, -OCH2-, -CH2CH2-, -CH=CH- or -C?C and/or at least one of the radicals A1 and A2 present in the molecule is or and/or n is 1 or 2, where, in the case where -(Z2-A2)n =

Description

~4~
1,4-Disubstituted 2,6-difluorobenzene compounds, and a liquid-crystalline medium The invention relates to novel 1,4-disubstituted 2,6-difluorobenzene compounds of the formula I

' F

where R is an alkyl or alkenyl radical having 1 to 15 carbor. atoms which is unsubstituted or at least monosubstituted by halogen, it also being possible for one or more CH2 groups in these radicals to be replaced, in each case in-dependently of one another, by -O-, -S~
- ~ - , -CO-, -CO-O-, -O-CO- or -O-CO-O- in such a manner that oxygen atoms are not linked directly to one another, 15 A1 and A2, in each case independently of one another, are _ (a) a trans-1,4-cyclohexylene radical in which, in addition, one or more non-ad;acent CH2 groups may be replaced by -O and/or -S-, (b) a 1,4-phenylene radical in which, in addition, one or two CH groups may be replaced by N, (c) a radical from the group comprising 1,4-cyclo-hexenylene,l,4-bicyclo~2,2,2)octylene,piperi-dine-1,4-diyl,naphthalene-2,6-diyl,decahydro-naphthalene-2,6-diyl and 1,2,3,4-tetrahydro-naphthalene-2,6-diyl, it being possible for the radicals (a) and (b) to be - 2 - 2~4~3~
substituted by CN or monosubstitllted or disubstituted by fluorine, Zl and Z2 in each case independently of one another, are -CO-O-,-O-CO-, -CH2O-,-OCH2-, -CH2CH2-,-CH=CH-, -C3C- or a single bond, m and n in each case independently of one another, are 0, 1, 2 or 3, where (m+n) is 1, 2 or 3, and X has one of the meanings of R or is F, Cl, -CF3, -OCF3-, -OCF2H, -OC2F5, -CN or -NCS, with the proviso that at least one of the radicals Z1 and Z2 present in the molecule is -CO-O-, -O-CO-, -CH2-O-, -OC~2-, -CHzCH2-, -CH=CH- or -C3C and/or at least one of the radicals A1 and A2 present in the molecule is ~ F ,F
~ - or ~ - and/or n is 1 or 2, where, in the case where -(Z2-A2)n = ~ ~ ~ ~

X is F, Cl, -CF3, -OCF3, -OCF2H, -OC2F5, -CN or -NCS.

.~J The invention furthermore relates to the use of these compounds as components of liquid crystalline media, and to liq~id-crystal and electrooptical displays which contain the liquid-crystalline media according to the invention.
The compounds of the formula I 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 deformation of aligned phases or the effect of dynamic scattering.
The invention had the object of finding novel stable liquid-crystalline or mesogenic compounds which are suitable as components of liquid-crystalline media - 3 ~ 2~
and in particular have at the same time comparatively low viscosity and a relatively high dielectric anisotropy.
It has now been found that compounds of the formula I are eminently suitable as components of liquid-crystalline media. In particular, they have comparative-ly low viscosities. Using them, stable liquid-crystalline media which have a broad mesophase range, advantageous values for the optical and dielectric anisotropy and outstanding ultraviolet and temperature stability are obtained.
Liquid crystals of the formula ,F
alkyl-(- ~ ~)r ~ CN r = 1 or 2 F
have already been disclosed in DE 3209178. JP 62-103057 discloses compounds of the formulae F

alkyl~~CH2C~2~-CN

and alkyl ~ ~ -C~2CH2- ~ -CN
F

, . .
` Finally, JP 63-216858 describes compounds of the formula Y ~ 2CH2 ~ ~ CN

In view of the very wide range of areas of application of such compounds having very high ~, it was, however, desirable to have further compounds available which have properties precisely customized to the particular ap-plications.
Liquid crystals of the formula -- 4 ~ L/~
R~ 3~ R2 have already been disclosed in WO 89/02425 and are distinguished by high birefringence and relatively high viscosity.
In view of the very wide variety of areas of application of such compounds having positive ~, it was desirable to have further compounds available which have properties precisely customized to the particular ap-plications.
~~ In addition, the provision of the compounds of the formula I very generally considerably extends the range of liquid-crystalline substances which are suit-able, from various applicational points of view, for the preparation of liquid-crystalline mixtures.
~he compounds of the formula I have a broad field of application. Depending on the choice of substituents, these compounds can be used as base materials from which liquid-crystalline media are predominantly composed;
however, compounds of the formula I can also be added to liquid-crystalline base materials from other classes of compound, in order, for example, to influence the dielec-tric and/or optical anisotropy of a dielectric of this type and/or to optimize its threshold voltage and/or its viscosity.
In the pure state, the compounds of the formula I are colorless and form liquid-crystalline mesophases in a very favorable temperature range for electrooptical use. They are stable chemically, thermally and to light.
The invention thus relates to the compounds of the formula I and to the use of these compounds as com-ponents of liquid-crystalline media. The invention furthermore relates to liquid-crystalline media contain-ing at least one compound of the formula I, and to liquid-crystal display elements, in particular electro-optical display elements, which contain media of this _ type.
For reasons of simplicity below, A3 is a radical , F
of the formula - ~ -, , Cyc is a 1,4-cyclohexylene F , F _~ F
radical, A4 is a radical of the forrnula - ~ - or ~ -, Che is a 1,4-cyclohexenylene radical, Dio is a 1,3-diox-ane-2,5-diyl radical, ~it is a 1,3-dithiane-2,5-diyl radical, Phe is a 1,4-phenylene radical, Pyd is a pyri-dine-2,5-diyl radical, Pyr is a pyrLmidine-2,5-diyl radical and Bi is a bicyclo(2,2,2)octylene radical.
10The compounds of the formula I accordingly ` ,l include the preferred dinuclear compounds of the sub-formulae Ia and Ib:
R-A3_A2_X Ia R A3 z2 A2 X Ib Trinuclear compounds of the sub-formulae Ic to If:

R-A3_Z2_A2_z2 A2 X Ic R-Al_zl_A3_z2 A2 X Id R-A1_zl_A4_zI A3 X Ie R-A4_zl_Al_zl A3 X I f and tetranuclear compounds of the sub-formulae Ig to I;:

R-Al_zl-A3_z2_A2_z2 A2 X Ig R-Al_zl_Al_zl_A3_z2 A2 X Ih R-Al-zl_Al_zl_A4_zl A3 X Ii R-Al_zl_A4_zl_Al_zl A3 X Ij 15Of these, those of the sub-formulae Id, Ie, Ih and Ii are particularly preferred.
In the compounds of the formulae above and below, X is preferably -OCF3, -OCHF2, -CF3, F or Cl. Likewise preferred are compounds of the formulae above and below in which X has one of the meanings of ~.

In the case where X is F, Cl, -CF3, -OCF3, -OCHF2, -OC2F5, -CN or ~NCS, at least one of the radicals A1 and A2 present in the molecule of the formula I is preferably F I F
_ or ~ ' and/or n is 1 or 2.
F

R is preferably alkyl, furthermore alkoxy. A1 and/or A2 are preferably Phe, Cyc, Che, Pyr or Dio. The compounds of the formula I preferably contain not more than one of the radicals Bi, Pyd, Pyr, Dio or Dit.
Preferred compounds of the formula I and of all the sub-formulae are those in which Al and/or A2 are 1,4-phenylene which is monosubstituted or disubstituted by F
-~ or monosubstituted by CN. These are, in particular, 2-~~ fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene and 2,3-difluoro-1,4-phenylene, and 2-cyano-1,4-phenylene and 3-cyano-1,4-phenylene.
Z1 and Z2 are preferably a single bond, -CO-O-, -O-CO- and -CH2CH2-, and secondarily preferably -CH20- and -OCH2-. Preferably, only one of the groups Z1 and Z2 present in the molecule is other than a single bond.
If R is an alkyl radical and/or an alkoxy radi-cal, it may be straight-chain or branched. It is prefer-ably straight-chain, has 2, 3, 4, 5, 6 or 7 C atoms and is accordingly preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy 2S or heptoxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxyl octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy.
Oxaalkyl is preferably straight-chain 2-oxapropyl (= methoxymethyl), 2- (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-l 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, or 2-, 3-, 4-, 5-, 5-, 7-, 8- or 9-oxadecyl.
If R is an alkyl radical in which one CH2 group has been replaced by -CH=CH~ may be straight-chain or branched. It is preerably straight-chain and has 2 to 10 _ 7 _ 2~
C atoms. I~ i9 accordingly particularly ~inyl, prop-1- or -2-enyl, but~ 2- or -3 enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept~ 2-, -3-, -4-, -5- or -6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6-or -7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7- or -8-enyl, or dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl.
If R is an alkyl radical in which one CH2 group has been replaced by -O- and one has been replaced by -CO-, these are preferably adjacent. These thus contain an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-.
These are preferably straight-chain and have 2 to 6 C atoms.
~~ They are accordingly particularly acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxy-ethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyl-oxypropyl, 4-acetyloxybutyl, methoxycarbonyl, ethoxy-carbonyl, propoxycarbonyl, butoxycarbonyl, pentoxy-carbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2-(methoxy-carbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(propoxy-carbonyl)ethyl, 3-(methoxycarbonyl)propyl, 3-(ethoxy-carbonyl)propyl and 4-(methoxycarbonyl)butyl.
If R is an alkyl radical in which one CH2 group has been replaced by unsubstituted or subs~ituted -CH=CH-and an àdjacent CH2 group has been replaced by CO or CO-O
or O-CO-, it may- be straight-chain or branched. It is preferably straight-chain and has 4 to 13 C atom~. It is accordingly particularly acryloyloxymethyl, 2-acryloyl-oxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyhep-tyl, 8-acryloyloxyoctyl, 9-acryloyloxynonyl, 10-acryloyl-oxydecyl, methacryloyloxymethyl, 2-meth~cryloyloxyethyl, 3-methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl, 7-meth-acryloyloxyheptyl, 8-methacryloyloxyoctyl or 9-methacryl-oyloxynonyl.

~ 8 - 2 Compounds of the formula I which contain wing groups R which are suitable for polymerization reactions are suitable for the preparation of liquid-crystalline polymers.
5Compounds of the formula I containing branched wing qroups may occasionally be of importance due to better solubility in the customary liquid-crystalline base materials, but in particular as chiral dopes if they are optically active. Smectic compounds of this type are 1~suitable as components of ferroelectric materials.
Compounds of the formula I having SA phases are suitable, for example, for thermally addressed displays.
Branched groups of this type generally contain not more than one chain branch. Preferred branche~
15radicals R are isopropyl, 2-butyl (= l-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, 3-20methylpentoxy, 2-ethylhexoxy, l-methylhexoxy or l-methyl-heptoxy.
If R is an alkyl radical in which two or more CH2 groups have been replaced by -O- and/or -CO-O-, it may be straight-chain or branched. It is preferably branched and 25has 3 to 12 C atoms. It is accordingly particularly biscarboxymethyl, 2,2-biscarboxyethyl, 3,3-biscarbo~y-propyl, 4,4-biscarboxybutyl, 5,5-biscarboxypentyl, 6,6-biscarboxyhexyl, 7,7-biscarboxyheptyl, 8,8-biscarboxy-octyl, 9,9-biscarboxynonyl, 10,10-biscarboxydecyl, bis-30(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(methoxy-carbonyl)h~xyl, 7,7-bis(methoxycarbonyl)heptyl, 8,8-bis(methoxycarbonyl)octyl, bis(ethoxycarbonyl)methyl, 352,2-bis(ethoxycarbonyl)ethyl, 3,3-bis(ethoxycarbonyl)-propyl, 4,4-bis(ethoxycarbonyl)butyl or 5,5-bis(ethoxy-carbonyl)hexyl.
Compounds of the formula I which contain ~ing groups R which are suitable for pslycondensations are - 9 ~ J~
suitable for the preparation of liquid-crystalline polycondensates.
The formula I covers the racemates of these compounds and the optical antipodes, and mixtures there-of.
Of these compounds of the formula I and the sub-formulae, those are preferred in which at least one of the radicals present therein has one of the preferred meanings indicated.
10In the compounds of the formula I, those stereo-isomers in which the rings Cyc and piperidine are trans-1,4-disubstituted are preferred. Those of the above-mentioned formulae which contain one or more groups Pyd, -~ Pyr and/or Dio in each case include the two 2,5-position-al isomers~
~ he 1,4-cyclohexenylene group preferably has the following structures:

{~~~ ~~
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, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart, Vol. IX, pp. 867 ff.), to be precise under reaction conditions ~which are known and suitable for the reactions mentioned.
Use can also be made here of variants which are known per se, but are not *escribed in greater detail here.
The compounds according to the invention can be prepared, for example, by reacting a compound of the formula II

R-(Al_z1) - ~ II
' F

in which R, Al, z1 and m are as defined, in accordance with the following reaction schemes:

2 ~ B

F LDA or Bu-Li R- ( Hl-Z~ >
F B(OMe)3 F Br-A2 _ ( z2 _A2 ) n l-X
R-(Al-Zl)m-<~-B(OH)2 >
F Na2C03/Pd-cat.

F BuLi ,~ R-(Al-Zl ) - ~ F
, __ 2 F B(OH)2-A2(Z2-A2)n l-X
R_(Al-z~ >
F Na2C03/Pd cat.

Further synthesis methods are apparent to a person skilled in the art. For example, appropriately S-substituted 1,3-difluorobenzene compounds can be con-verted in accordance with the above scheme into 2-sub-stituted 1,3-difluoro compounds, and the radical R-(A1-Z1)m- can subsequently be introduced by customary reactions of liquid-crystal chemistry (for example esterification, etherification or coupling, for example in accordance with the article E. Poetsch, Rontakte (Darmstadt) 1988 (2), p. 15), or vice versa.
The compounds of the formula II can be prepared, for example, in accordance with the following synthetic schemes:

~ 3 ~J~3 Scheme 1 (A = ~(Al-Zl)m l-A -) R-A-CH2p Ph3I~ + OHC

R-A-CH=CH- ~ F Br2 R-A-C-C ~
F -2HBr F

H2/Pd-C

7 2 H2 ~

Scheme 2 (A = (Al-Zl) l-Al-) F 1. n-BuLi Br- ~ 2. B(OCH3)3 / F
` F 3. H ~ (OH2)~ ~

¦ R-A-Br ¦ Pd- cat.

~ F
R-A ~

Scheme 3 F HCl, EtOH NH \ F
NC~ > /C~
F OEt \F

CH(oEt)2 NE~3 ¦ R- [ _Al_zl_ ] -CH-CHO

- R-[-A _zl_]m_co )~ F

Scheme 4 F 1. n-BuLi Br{~ 2 . B(OCH3 )3 ~F
F > (HO)2B~
3. H~ F

F~-L-A ~Z ~)m-l~¢~~Br ~ P~ - ~at R- [ -Al-Z~

- 2 ~ 3 Scheme 5 Br ~ -Br + (Ho)2B- ~ _ > Br ~ - ~
\F cat. \F

_ _> R- ~ ~
pdI _ cat. F
.T

The starting materials are either known or can be prepared analogously to known compounds.
Esters of the formula I can also be obtained by esterification of appropriate carboxylic acids (or reactive derivatives thereof) using alcohols or phenols tor reactive derivatives thereof) 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 or alternatively by reacting metallated II with suitable electrophiles (B(OH)3/H202 or CO2).
The synthesis of some particularly preferred compounds is given in greater detail below (Y = H or F, Z = H or F):

` - 14 - ~ ~$~33 - Scheme 6 R-(A -Z )m_1-A -CH2P~ph)3 1. OHC ~ /Wittig ¦ 2- H2/Pd ~-(A1-Zl)m 1-Al-C2H4- ~ -B(OH)2 ~ Br- ~ -X
,~
.

R~(A1~Zl)m 1-A -C2H4- ~ ~ ~ X

In a further process for the preparation of the compounds of the formula I, an aryl halide is reacted with an olefin in the presence of a tertiary amine and a palladium catalyst (cf. R.~. 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 which are necessary for the success of the coupling reaction, such as, for example, triethylamine, are also suitable as solvents.
Suitable palladium catalysts are, for example, salts thereof, in particular Pd(II) acetate, with organic phosphorus(III) compounds, such as, for example, tri-arylphosphines. The reaction can be carried out in the presence or absence of an inert solvent at temperatures between 0 and 159, preferably be~ween 20 and 100;
suitable solvents are, for example, nitriles, such as acetonitrile, or hydrocarbons, such as benzene or toluene. The aryl halides and olefins employed as -- 15 -- ~ ~ L~ .r ~J ~
starting materials are in many cases commercially avail-able or can be prepared by processes known from the literature, for example by halogenation of appropriate parent compounds or by elimination reactions on appro-priate alcohols or halides.
In this way, stilbene derivatives, for example, can be prepared. Stilbenes may also be prepared by reacting a 4-substituted benzaldehyde with an appropriate phosphorus ylide by the Wittig method. However, it is also possible to prepare tolans of the formula I by replacing the olefin by monosubstituted acetylene (Synthesis 627 (1980) or Tetrahedron Lett. 27, 1171 (1986)).
`- Furthermore, aryl halides can be reacted with aryl zinc compounds for the couplinq of aromatics. These reactions are preferably carried out with addition of a catalyst, such as, for example, a palladium(0) complex, in inert solvents, such as hydrocarbons, at elevated temperatures, for example in boiling xylene, under a protective gas.
Coupling reactions of alkynyl compounds with aryl halides may be carried out analogously to the process described by A.O. King, E. Negishi, F.~. Villani and A. Silveira in J. Org. Chem. 43, 35~ (1978).
Tolans of the formula I can also be prepared by the Fritsch-Buttenberg-Wiechell rearrangement (Ann. 279, 31q, 332, 1984), in which 1,1-diaryl-2-haloethylenes are rearranged in the presence of strong bases to give diarylacetylenes.
Tolans of the formula I can also be prepared by brominating the corresponding stilbenes and subsequently subjecting the bromination products to dehydrohalogena-tion. Use may be made here of variants of this reaction which are known per se but not described here in greater detail.
Ethers of the formula I are obtained by etherifi-cation of corresponding hydroxyl compounds, preferably corresponding phenols, the hydroxyl compound is sxpediently first converted into an appropriate metal derivative, for example into the corresponding metal alkali alcoholate or alkali metal phenolate by treatment with NaH, NaNH2, NaOH, KOH, NazCO3 or K2CO3. Thi can then be reacted with the appropriate alkyl halide, alkyl sulfonate or dialkyl sulfate, expediently in an inert solvent, such as, for example, acetone, 1,2-dimethoxy-ethane, DMF or dimethyl sulfoxide, or alternatively with an excess of aqueous or aqueous-alcoholic NaOH or KOH at temperatures between about 20 and 100.
Particular preference is given to the compounds of the formula Ia F F /Ll ~ F ~ F \L2 Ia in which R, z~, Z2 and X are as defined above, m is 1 or 2, and L1 and L2, in each case independently of one ano~her, are H or F. In the case where m = 2, the wo radicals Z~ are iden~ical or different. Preferably, at least one of the radicals Z~ and Z2 present in the mole-cule of formula Ia i5 other than a single bond and is preferably -CH2C~2-, -C=C- or -CO-O-.
The compounds can be prepared by methods known F

per se starting from commercial Br ~ - . Apart F
from the linking possibilities shown in the above scheme, analogous synthesis processes by Friedel-Crafts acylation or the Wittig reaction with subsequent reduction or hydrogenation are possible for synthesizing the CH2-CH2 linked substances.
The CH2-C-containing compounds can be converted ll into CH~C\ derivatives by chlorination using PCl5 and Cl Cl subsequently into the acetylenas by HCl elimination using a base. The transformation of the -CH=CH- bridged sub stances, which can be prepared by Heck coupling or the - 17 - 2 O'x6~3-3i) Wittig reaction, is carried out in a conventional manner, for example by bromination and double elimination of HBr.
The carboxylate group is introduced analogously to the introduction of the CH2CH2 group (cf. compound 7, formula scheme below) by means of CO2. The acids formed as intermediates can be esterified using the appropriate phenols, which can be prepared from 1 by synthesis step ba.

a l b 1 ~ ld F HO~ F ~OH

F F
) R~met91 ~ 1 ~ Pd- or1--> m~ ~ R~U~a --> R-C ~ ~ hydrogenation b~) 3 ~ H202 --> HO ~F y ~ alkyl-O ~ ~ F

b) 1 __> Ll ~ B(CH3)3~[ 9 c) O~ rnat~ Pd- --> ~, ~c~ 3 ~8r ~ Pd- --> ~
F OCH3 ,, F OH
d) 1 ~ BuLI/KOt ~ Trneda ~ B(OCH~)3 --> Br~ H~ B ~E~ OH

- 18 - 2~A $ ~

~ ~ { ~ ~ 0~

R ~ ~ R ~ l~ a~

,' R ~ . ~F

e) 2 + BuLi/KOT + Tmeda + Hal2 (Br2 or I2) f) 2 + BuLi/KOT + Tmeda + vinyl bromide + Pd g) 2 + BuLiJKoT + Tmeda + 1 bromine, 3,5-difluoroben-zene + Pd h) 6 + 3 + Pd i) 4 + BuLi/KOT + Tmeda + Hal2 (Brz or Iz) j) Dimethylphenylvinylsilane + 5 + Pd + NBu4Fe + MeOH
(Heck reaction) ~~ k) 7 + 5 + Pd (Heck reaction) - 19 - h ~ ~'3~
Compound 8 can be converted into 12 in accordance with d) and into 13 analogously to e). 12 is converted into 14 by means of vinyl bromide in accordance with bc) and 13 is converted into 14 by means of divinyl zinc in accordance with c). 15 is obtained from 12 and 1 by cross-coupling in accordance with h) or from 13 and 3 by cross-coupling.
By a suitable combination of components 1-15, all the precursors of Ia in which Z is C~C or a single bond can be synthesized. The CH=CH group can be converted into the CH2-CHz or -C-C- group.
Ll The end group ~ -X is introduced either using ~ ) \L2 a coupling step with D ~ -X(D = hal, m, B-,~` , ~ ) or by intro-\L2 HO ~ L1 ducing X into compounds containing the end group ~ L2 The preparation of likewise the compounds containing the COz and/or C~C bridging members can be carried out analogously in accordance with analogous formula schemes.
Further synthesis variants are known to those skilled in the art and proceed from appropriately sub-stituted bromobiphenyls. Preferred variants are given in the following schemes. All the starting materials are either known or can be prepared analogously to known compounds.
These bromobiphenyls can be prepared in a manner known per se by cross-coupling reactions which are catalyzed by noble metals (E. Poetsch, Kontakte (Darmstadt) 1988 (2) p. 15~.
One variant is given below as an example:

Br{~ C 1 Zn~> -OCF3 Br-~ OCF3 Scheme 3 / F , y Br-~-~ -X
''~
1 Heck reaction with Ct,H2~ 3CH=CHz CnH2D~-CH=CH-C~- ~~ X

H2/Pd-C

CnH2n~CH2-CH2- <~ <~X

( Y and Z each H or F ) - 21 - 2~
- Scheme 4 8r~ X

Mg / DMF

OHC- <~-X

C~Hzn. ~ -CHzPPh3 I
~ 1 CnHzn~ 3CH=CH-~ X

Hz / Pd-C

C HZo~ 3~~CHzCHz~C~~X

( Y and Z each H or F ) - 22 - 2~
Scheme 5 CnH2n~ 1~ ~0= ~ MgBr- ~-Br F
CnH~n~ -Br Hz /Pd-C

CnH2n~ 3{~)-Br F
,i ~ Resolution of the isomers CnH2n- 1-~ S -Br coupled to (HO)2B- ~ -X

'` C H2 ~ _X

(Y and ~ each H or F) - 23 - ~ J
- Scheme 6 F 1) BuLi -70 R- ( Al_Z1 ~ >
F 2) I2 X

F Z
R_(Al-zl) ~ -I >
F Pd/Ni F ,Y
R-(Al-zl)m ~ _( ~ ~)n~X
\F Z

(Y and Z each H or F) Some particularly preferred, smaller ~roups of compounds of the formula I are given below:

R ~ - ~ ~ -X - Il ; F

R- ~ - ~ -X I2 F

F Y
R- ~ -(C2H~)r~ ~ ~)-X I3 -24- 2Q~

R{~t- ( C2H4 ) ~ X I4 R~ ( C2H4 ) r~<~~~~X I 5 F

~F , F
R{~ - ( C2H4 ) r~(~~X I 6 ..~
,' , F ,F
R{~ -@-~-X I 7 R~ c2H4-(~-x I 8 R-<~ -C-C-<~}X I9 R~-~-~-X I 10 ,F ,F ,F
4~ 2 4 <~ (~? X I 11 R C`~ C2H4~ <~:? X 112 -- 25 - ~ n ~? ~ r ,F F
~) 2 H4 -@! ~i X I 13 F F

R~ C2H ~ X I14 ~F ~ F ~F
R-C)-~-C2H -<~-X I15 F F

R{~\? {~? -C2H4 -(~)-X I 16 R_(~C2H4-@~ X I17 F F
R_~_~?_C2E14{~_X I18 F F

F F
R~ (C2H4)r~ Il9 F F

F F Y
R ~ -(C2H4)r ~ i ~ -X I20 F F Z

(r = O or 1, Y and Z each H or F) In formula 18, X is prefera~ly R.
Particular preference is also given to compounds according to the invention in which one of the radicals Z1 and Z2 is -CH=CH-. These can be prepared, for example, in accordance with the following scheme:

F 1) BuLi (-70) R-(A _Zl)m~ ~ - >
F 2) 1/2 ZnC12 -70 to 20 ~FNiC12(2PPh3) -(Al_zl) ~ =)2-Zn ~, \F/~ Br/20 /F Z
R-(Al-Z1) ~ ~/ >
FHeck-coupling (acetonitrile/reflow NEt3/Pd(OAc)2/Tri-(O-toly)-phosphine) _(Al-zl) ~ ~ ( ~ )n X

(Y and Z each H or F) Corresponding compounds containing -CH2CH2- in place of -CH=CH- can also be obtained by hydrogenation on Pd/C or PtO2 at 1-4 bar.
Particular preference is given to compounds of the formula I, in which one of the radicals Z1 and Z2 is -CO-O-, -O-CO-, -CH2CH2-, -CH=CH- or -C~C- and the other radicals Zl and Z2 are a single bond. 2 ~ ;q~ 3 Particularly preferred tolan derivatives can he prepared in accordance with the following schemes analo-gously to the known Heck coupling reactions:

HC_C-( ~ ~)n~X

R-(Al-Z1)m- ~ -I >
F Pd/CuI/N~t3 R-(A1-Z~ C--C-(- ~ -) -X
F Z
., Br~ ) -X

R-(Al_zl) ~ -C--CH >
Pd/CuI/N~t3 R-(Al_Zl)m- ~ >-C-C-( ~ )n F

(Y and Z each H or F) ~-~ Further details on the synthesis or on correspon-ding precursors are given in the International Patent Applications PCT/EP 90/01471, PCT/EP 90/01437 and WO
90/08757.
The liquid-crystalline media according to the invention preferably contain 2 to 40, in particular 4 to 30, components as further constituents besides one or more compounds according to the invention. These media very particularly preferably contain 7 to 25 components besides one or more compounds according to the invention.
These further constituents are preferably selected from nematic or nematogenic (monotropic or isotropic) - 28 - ~ ,.vi substances, in particular substances from the classes of the a~oxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl esters of cyclohexanecarboxylic acid, phenyl or cyclohexyl esters of cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl esters of benzoic acid, of cyclo-hexanecarboxylic acid and of cyclohexylcyclohexanecar-boxylic acid, phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexenes, cyclohexylcyclohexylcyclohexenes, 1,4-bis-cyclohexylbenzenes, 4,4'-bis-cyclohexylbiphenyls, phenyl- or cyclohexylpyrimidines, phenyl- or cyclohexyl-pyridines, phenyl- or cyclohexyldioxanes, phenyl- or cyclohexyl-1,3-dithianes, 1,2-diphenylethanes, 1,2-dicyclohexylethanes, l-phenyl-2-cyclohexylethanes, 1-cyclohexyl-2-(4-phenylcyclohexyl)ethanes, l-cyclohexyl-2-biphenylylethanes, 1-phenyl-2-cyclohexylphenylethanes, optionally halogenated stilbenes, benzyl phenyl ethers, tolans and substituted cinnamic acids. The 1,4-phenylene groups in these compounds may also be fluorinated.
The most important compounds suitable as further constituents of media according to the invention can be characterized by the formulae 1, 2, 3, 4 and 5:

R'-L-E-R"
R'-L-COO-E-R" 2 R'-L-OOC-E-R" 3 R'-L-CH2CHz-E-R'' 4 R'-L-C~C-E-R" 5 In the formulae 1, 2, 3, 4 and 5, L and E, which may be identical or different, are, in each case indepen-dently of one another, a bivalent radical from the group formed by -Phe-, -Cyc-, -Phe-Phe, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe- and -G-Cyc- and their mirror images, where Phe is unsubstituted or fluorine-substituted 1,4-phenylene, Cyc is trans-1,4-cyclohexylene or 1,4-cyclohexenylene, Pyr is pyrimidine-2,5-diyl or - 29 - h4~
~ pyridine-2,5-diyl, Dio is 1,3-dioxane-2,5-diyl and G is 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. ~he media according to the invention preferably contain one or more components selected from the compounds of the formulae 1, 2, 3, 4 and 5 in which L and E are selected from the group comprising Cyc, Phe and Pyr and simul-taneously one or more components selected from thecompounds of the formulae 1, 2, 3, 4 and 5 in which one of the radicals L and E is selected from the group comprising Cyc, Phe and Pyr and the other radical is selected from the group comprising -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-, and optionally one or more components selected from the compounds of the formulae 1, 2, 3, 4 and 5 in which the radicals L and E
are selected from the group comprising -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.
In the compounds of the sub-formulae la, 2a, 3a, 4a and 5a, R' and R" are, in each case independently of one another, alkyl, alkenyl, alkoxy, alkenyloxy or alkanoyloxy having up to 8 carbon atoms. In most of these compounds, R' and R~ are different from one another, one of these radicals usually being alkyl or alkenyl. In the compounds of the sub-formulae lb, 2b, 3b, 4b and 5b, R"
_~ is -CN, -CF3, F, Cl or -NCS; in this case, R has the meaning given for the compounds of the sub-formulae la to Sa and is preferably alkyl or alkenyl. However, other variants of the proposed substituents in the compounds of the formulae 1, 2, 3, 4 and 5 are common. Many such substances or alternatively mixtures thereof are commer-cially available. All these substances can be obtained by methods which are known from the literature or analogous-ly thereto.
Besides components from the group comprising the compounds la, 2a, 3a, 4a and 5a (Group 1), thP media according to the invention also preferably contain components ~rom the group comprising the compounds lb, 2b, 3b, 4b and Sb (Group 2), whose proportions are preferabl.y as follows:
Group 1: 20 to 90~, in particular 30 to 90~, Group 2: 10 to 80%, in particular 10 to 50%, the sum of the proportions of the compounds according to the invention and of the compounds from Groups 1 and 2 adding up to 100%.
The media according to the invention preferably contain 1 to 40%, in particular preferably 5 to 30%, of compounds according to the invention. Further preferred media are those which contain more than 40%, in parti-cular 45 to 90%, of compounds according to the invention.
The media preferably contain three, four or five com-pounds according to the invention.
The media according to the invention are prepared in a manner which is customary per se. In general, the components are dissolved in one another, expediently at elevated temperature. By means of suitable additives, the liquid-crystalline phases can be modified in accordance with the invention in a manner such that they can be used in all types of liquid-crystal display elements which have hitherto been disclosed. Additives of this type are known to those skilled in the art and are described in detail in the literature (H. Kelker/R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980)~ For example, pleochroic dyes can be added for the production of colored guest-host systems, or substances can be added to modify the dielectric anisotropy, the viscosity and/or the orientation of the nematic phases.
The examples below are intended to illustrate the invention without representing a limitation. Above and below, percentages are percent by weight. Temperatures are given in degrees Celsius. Mp. denotes melting point, Bp. = clear point. Furthermore, C = crystalline stage, N = nematic phase, S = smectic phase and I = isotropic phase. The data between these symbols represent the transition temperatures. ~n denotes optical anisotropy (589 nm, 20C), and the viscosity (mm2/sec) was determined t 20C.

- 31 ~ ,r3 "Customary work-up" means that water is added if necessary, the mixture i~ extracted with methylene chloride, diethyl ether or toluene, the organic phase is separated off, dried and ev~porated, the product is purified by distillation under reduced pressure or crystallization and/or chromatography. The following abbreviations are used:

DAST Diethylaminosulfur trifluoride DCC Dicyclohexylcarbodiimide DDQ Dichlorodicyanobenzoquinone DIBALH Diisobutylaluminum hydride KOT Potassium tertiary-butoxide THF Tetrahydrofuran pTSOH p-Toluenesulfonic acid TMEDA Tetramethylethylenediamine In the present application and in the examples below, the structures of the liquid-crystal compounds are indicated by acronyms, the trans~ormation into chemical formulae taking place in accordance with Tables A and B
below. All the radical [sic] CnH2n+l and C~H~+1 are straight-chain alkyl radicals containing n or m carbon atoms respectively. The coding in Table B needs no explanation. In ~able A, only the acronym for the parent structure is given. In individual cases, the acronym for the parent structure is followed, separated by a dash, by a code for the substituents R1, R2, Ll and L2:

Code f or Rl, R l R2 ~ L' R2, Ll, L2 nmCnH2 ~CI C,R~........................ N ~1 ~

nmF C~HHzn~ I C,Hz,. I F H

nOCF2 CnH22n I Nc~2 H H
rVsN CrH2r~l-CH=CH-C~H2!.- CN H H
nrEFN CnHz~ I CN H H
nAm CnHzD~ I COOCoH2~ I H H

- Table A: 2 ~ r~ ~3 ~

Rl-Co >-~z ~N

PYP PYRP

Ll LZ

R'~ -RZ Rl C~ <~>{\>-<~-RZ
,~ OE
i ....

R' -C~\9~-RZ Rl -~_~ RZ
CCH CCP

R~ 3-CO(~ _R2 R~ > -C. C-~_R2 CP cPrP

L~ L2 - Ll L2 ~`~ Rl{~)~-CzH~~~~COC~_R2 Rl~-COO~_R2 CEPI'P - D

Rl ~ _C2H_~>-R2 R~ L~L2 ECCP CECP

- 34 - 2~

R~ C2H4~>-R2 <~
EPCH ~P

R'-~3-coo~ R2 Rl-~_~_R2 ME PCH

R'{ ~LR2 R'-C~>-C'C-~LR2 PDX PTP

Rl-C~{~>-C2H4- ~R2 BECH EBCH

R~ ~R2 2 ~

Table B-CsH~ CN CnHzn~ ~ -CN

Tl 5 K3n CnH2n~l-o- ~-CN CnH2n~l- ~ ~ ~ ~ CmH2m !

M3n ~ H-n. Fm CnHzn~l~ ~ CzH4-~\ 0 ~> ~ /~CmH2m~1 CnH2n~ SOOc~cmH2m~

Inm C-nm C~3 CH3 C2Hs-CH-CH2-O-(~ C~-CN C2Hs-cH-cH2{~{~-cN

"H2D.,~ -~-~

CBC-nmF

,CN

CnHZn~ 1 ~ ~0 ~CmH2m.

CCN-nm - 36 ~ 2 ~ ;d ~

CDH2n~l~ ~ ~ ~COO ~ ~ ~ -CmHzm~

CCPC-~

CnH2n~ '9-coo- ~mHZm~ I CnH2n~ 1 -C~- ~ -OOC~ ~-CmH2m CH-nm HD-nm CN
CnHzn~l ~ _ ~ COO~ ~ CmHZm~l CnH2n~l~ ~ ~ C ~ CmH2m-~ -nm N~-~

C H2 ~~3-coo-~-cmH2m~l C2Hs~C~~COO~C~ -CN

C1~3 CnHZn~ }c2H4~ cmH2m 1 EQC-nm CnH2D- ~ -C2H~- 3CmH2m. I CnHZn~ }CHZ~cmH2m~ 1 EXX~H-nm CX~H-nlEm CnH2n. 1{~3 ~ ~ -CN

T-nFn CnH2n~ 1 -~-CZH4- ~CmHZm~ 1 ECCH-nm CnH2n~ ~CH2~Cm CCH-nlEm CnH2n~ ~-CN

, ~ F
T-nFn CnH2n~ -CHZCH2CF3 CCH-n2CF3 CnH2n~ ~ F

:`
CCP-nF . F . F .

CnH2n~ -F

BCH-nF . F . F

? r~
ExamDle 1 A mixture of 9.2 g of 2,6-difluoro-4-[2-(p-ethoxyphenyl)ethyl]phenylboric acid (prepared by reacting 3,5-difluorobenzaldehyde with p-ethoxybenzyltriphenyl-phosphonium iodide by the Wittig method and subsequentlyhydrogenating the resultant styrene derivative on Pd/C~, 5.9 g of 1-bromo-3,4-difluorobenzene, 38 ml of 2 molar aqueous Na2CO3 solution, 0.6 g of tetrakis(triphenyl-phosphine)palladium(0) and 75 ml of toluene is refluxed for two hours. The aqueous phase is extracted twice with toluene and combined with the organic phase. Customary aqueous work-up and chromatographic purification of the residue give 4-[2-(p-ethoxyphenyl)ethyl]-2,6,3',4'-; tetrafluorobiphenyl, C 92 I, ~ + 24.
Examples 2 to 58 The following compounds according to the inven-tion are obtained from the appropriate precursors of the formula Il analogously to one of the two schemes on page 12:
R (Al_zl) ~z2_A2) X
F
(2) n-Propyl ~ 2H4 ~ F

(3) n-Pentyl ~ 2H4 ~ F
-(4) n-Propyl ~ C2H4 ~ ~ OCF3 . - 39 -2 ~
(5) n-Pentyl~ C2H4 ~ ~ OCF3 (6) n-Propyl- ~ ~-C2H~ F
(7) n-Propyl- ~ j-C2H4 ~ _ Cl (8) n-Propyl~ C2H4 ~ ~ ~ Cl (9) n-Propyl~ -C2H4 ~C~r CN
(10) n-Propyl~> C2H4 _ ~ _ CN
(11) n-Propyl~ 2H4 ~ ~ CF3 (12) n-Propyl~ ~ -C2H4- ~ ~ ~ OCF3 (13) n-Propyl~ ~ 2H4 ~ CF3 (14) n-Propyl~ ~ C2H4- ~ ~ ~ CN
(15) n-Propyl~ ~ -C2H4- ~ ~ ~ F
(16) n-Propyl~ ~ C2H4 ~ OCF3 (17) n-Propyl~ ~ C2H4- ~ ~ CF3 (18) n-Propyl~ ~ C2H4- ~ ~ CN

~ ~ ~ 6 ~ e.
(19) n-Propyl ~ ~ ~-C2H4~ F
(20) n-Propyl ~ C ~~C2H4- ~ ~ ~ OCF3 (21) n-Propyl ~ C~C2H4_ ~~`~ F3 (22) n-Propyl ~ ~-C2H4- ~ ~ ~_ CN
(23) n-Propyl ~ ~ t-C2H4- ~ @ '~ F

( 24 ) n-Propyl ~ o-C2H4~ ~ OCF3 ( 2 5) n-Propyl - ~ ~C2H4- _ @~~ CF3 (26) n-Propyl ~ ~ C2H4- - ~ _ CN

(27) n-Propyl ~ C2H4- ~ ~ ~ F

(28) n-Pentyl - ~ - ~ - CN, . ~ C 124 N 151 I

(29) n-Pentyl ~ - - ~ - F

(30) n-Pentyl - ~ - - ~ - CF3 (31) n-Pentyl ~ - ~ - OCF3 (32) n-Pentyl ~ - ~ ?N

(33) n-Pentyl {O,- ~ F

(34) n-Pentyl -CO~- - ~ - CF3 (35) n-Pentyl -~O~- - ~ - OCF3 ~. ,.
(36) n-Pentyl N ~ CN

(37) n-Pentyl - ~ - @ F

(38) n-Pentyl - ~ - - ~ - CF3 (39) n-Pentyl - ~,- - ~ - OCF3 (40) n-Propyl - 2 4 ~ ~

(41) n-Propyl - 2 4 ~ - ~ - CF3 (42) n-Propyl - 2H4 ~ _ ~ _ F

- ~2 -~ ~ ~ 6 ~

t43) n-Propyl - -C2H4- ~ ~ )- OCF3 F
(44) n-Propyl- ~ - ~ - OCF3 F

(45) n-Propyl ~ - - ~ - F

(46) n-Propyl - ~ ~ - CN

(47) n-Propyl @ ~ CF3 (48) n-Propyl - ~ - @, OCF3 (49) n-Propyl - ~ F

(50) Ethoxy - ~ -C2H4- ~ ~ OCF~, C 112 I

(51) Ethoxy - ~ -C2H4- ~ - F, C 102 I

(52) n-Propyl - - ~ ~ - CN

(53) n-Propyl - - ~ ~ - F

(54) n-Propyl - ~~ r ~ - F

~ 3 (55) n-Propyl - -~O>- ~ - C~
N
N

(56~ n-Propyl ~ ~ >- OCF3 (57) n-Pentyl - - ~ - OCF3, C-4 I
f ~ f 3 c (58) n-Pentyl - ~ - CF3, C 35 1 (S~.~l Fl~y _ ~ Ct~ C ~
Example 59 A solution of 0.1 mol of p-bromotrifluoromethoxy-benzene in 100 ml of THF is added dropwise to a suspen-sion of 0.1 mol of Mg turnings in 50 ml of THF at such a rate that the reaction mixture boils gently. After the mixture has been stirred for one hourr 0.1 mol of tri-methyl borate is added dropwise at room temperature, and the mixture is stirred for a further hour and hydrolyzed using dilute hydrochloric acid. After extractive work-up, the re~Aultant boric acid (0.05 mol) i~ refluxed for two hours together with 0.05 mol of 4-(trans-4-n-pentyl-cyclohexyl)-2,6-difluoroiodobenzene [obtainable by :_~ reacting 4-pentylcyclohexanone with 3,5-difluorophenyl-magnesium bromide, eliminating water, and hydrogenating the cyclohexenebenzene on Pd/C. The resultant 3,5-difluoropenyl [sic] compound is metallated at -70 in THF/TMEDA using n-BuLi and subsequently reacted wi~h iodine in THF at -70], 38 ml of 2 molar aqueous Na2CO3 solution, 0.6 g of tetrakis(triphenylphosphine)palladium-(0) and 75 ml of toluene. Customary aqueous work-up and chromatographic purification give 4-(trans-4-n-pentyl-cyclohexyl)-2,6-difluoro-4'-trifluoromethoxybiphenyl.
The preferred compounds of the formula s*~ ~
F L
R-( ~ )m ( 2 4 r ~ F ~ L2 in which R, m, and X are as defined for the formula I, and r is 0 or 1 and L1 and L2 are, in each case indepen-dently of one another, H or F, are obtained analogously from the corresponding difluoroiodo derivatives and boric acid.

Example R m r X L~ L2 _ _ (60) Ethyl 1 0 OC.F H H
(61~ Propyl 1 o OC F33 H H
(62) Butyl 1 0 OC F3 H H
(63) Ethyl 1 1 OCF3 H H
(64) Propyl 1 1 OCF3 H H
(65) Butyl 1 1 OCF3 H H
(66) Pentyl 1 1 OCF3 H H, C 49 N 68,5 I
(67) Ethyl 2 0 OCF3 H H
(68) Propyl 2 0 OCF3 H H, C 112 N 270 I
~69) Butyl 2 0 OCF3 H H
(70) Pentyl 2 0 OCF3 H H
(71) Ethyl 2 1 OCF3 H H
(72) Propyl 2 1 OCF3 H H, C 91 N 213 I
(73) Butyl 2 1 OCF3 H H
(74) Pentyl 2 1 OCF3 H H
(75) Ethyl 1 0 CF3 H H
(76) Propyl 1 0 CF3 H H
(77) Butyl 1 0 CF3 H H
(78) Pentyl 1 0 CF3 H H

Example R m r X L L
.. .. _ _ _ ... _ _ (79) Ethyl 1 1 CF3 H H
(80) Propyl 1 1 CF3 H H
(81) Butyl 1 1 CF3 H H
(82) Pentyl 1 1 CF3 H H, C 93 I
(83) Ethyl 2 CF3 H H
(84) Propyl 2 0 CF3 H H
(85) Butyl 2 CF3 H H
(86) Pentyl 2 0 CF3 H H
(87) Ethyl 2 1 CF3 H H
(88) Propyl 2 l CF3 H H
~~ (89) Butyl 2 1 CF3 H H
(90) Pentyl 2 1 CF3 H H
(91) Ethyl l 0 F H H
~92) Propyl l 0 F H H
(93) Butyl l 0 F H H
(94~ Pentyl l 0 F H H, C lO0 N (64) I
(95) Ethyl l l F H H
(96) Propyl 1 l F H H
(97) Butyl 1 1 F H H
(98) Pentyl l l F H H, C 91 I
viscosity 18 . 8 cSt (99) Ethyl 2 0 F H H
`~ (100) Propyl 2 0 F H H
(101) Butyl 2 0 F H H
(102) Pentyl 2 0 F H H
(103) Ethyl 2 l F H H
(104) Propyl 2 l F ~ H, C 140 N 212 I
(105) Butyl 2 l F H H
(106) Pentyl 2 1 F H H
(107) Ethyl l 0 F F H
(108) Propyl 1 0 F F H, C 81 I, ~ 11 . O
(109) Butyl 1 0 F F H
(110) Pentyl l 0 F F H

2 ~ U
Example R m r X L~ L2 (111) Ethyl 1 1 F F H
(112) Propyl 1 1 F F H
(113) Butyl 1 1 F F H
(114) Pentyl 1 1 F F H, C 40 N 46.6 I
(115) Ethyl ~L O F F H
(116) Propyl 2 0 F F H, C 133 N 242 I
~ 12.3 (117) Butyl Z 0 F F H
(118) Pentyl 2 0 F F H
(119) Ethyl 2 1 F F H
( 120 ) Propyl 2 1 F F H
(121) Butyl 2 1 F F H
(122) Pentyl 2 1 F F H
(123) Ethyl 1 0 F F F
(124) Propyl 1 0 F F F
(125) Butyl 1 0 F F F
(126) Pentyl 1 0 F F F
(127) Ethyl 1 1 F F F
(128) Propyl 1 1 F F F
(129) Butyl 1 1 F F F
(130) Pentyl 1 1 F F F~ C ~S
(131) Ethyl 2 0 F F F
(132) Propyl 2 0 F F F
(133) Butyl 2 0 F F F
(134) Pentyl 2 0 F F F C ~56 ~ '~? L
(135) Ethyl 2 1 F F F
(136) Propyl 2 1 F F F
(137) Butyl 2 1 F F F
(138) Pentyl 2 1 F F F
(139) Ethyl 1 0 Cl H H
(140) Propyl 1 0 Cl H H
(141) Butyl 1 0 Cl H H
(142) Pentyl 1 0 Cl H H

- 47 ~ $ i ~ $

Example R m r X L~ L2 (143) Ethyl 1 1 Cl H H
(144) Propyl 1 1 Cl H H
(145) Butyl 1 1 Cl H H
(146) Pentyl 1 1 Cl H H, C 54 N 91 I
(147) Ethyl 2 0 Cl H H
(148) Propyl 2 0 C1 H H
(149) Butyl 2 0 Cl H H
(150) Pentyl 2 0 C1 H H
(151) Ethyl 2 1 C1 H H
(152) Propyl 2 1 C1 H H
(153) Butyl 2 1 Cl H H
(154) Peintyl 2 1 Cl H H
(155) Ethyl 1 0 Cl F H
(156) Propyl l 0 Cl F H
(157) Butyl 1 0 Cl F H
(158) Pentyl 1 0 Cl F H
(159) Ethyl 1 1 Cl F H
( 160 ) Propyl 1 l Cl F H
(161) Butyl 1 1 Cl F H
(162) Pentyl 1 1 Cl F H, C 47 N 74 I
~ 8.8 (163) Ethyl 2 0 Cl F H
~164) Propyl 2 0 Cl F H
(165) Butyl 2 0 Cl F H
(166) Pentyl 2 0 Cl F H
(167) Ethyl 2 1 C1 F H
( 168 ) Propyl 2 1 Cl F H
(169) Butyl 2 1 C1 F H
(170) Pentyl 2 1 Cl F H
(171) Ethyl 1 0 Cl F F
(172) Propyl 1 0 Cl F F
(173) Butyl 1 0 Cl F F
(174) Pentyl 1 0 C1 F F

~ ~$~
Example R m r X L~ L2 -(175) Ethyl 1 1 C1 F F
(176) Propyl 1 1 Cl F F
(177) Butyl l 1 Cl F F
(178) Pentyl 1 l Cl F F C ~ ~ ~
(179) Ethyl 2 0 Cl F F , ~C.~L ) (180) Propyl 2 0 C1 F F
(181) Butyl 2 0 Cl F F
(182) Pentyl 2 0 Cl F F
(183) Ethyl 2 1 Cl F F
(184) Propyl 2 1 Cl F F
~185) Butyl 2 1 Cl F F
(186) Pentyl 2 1 Cl F F
(187) Ethyl 1 0 CN H H
(188) Propyl 1 0 CN H H
(189) Butyl 1 0 CN H H
(190) Pentyl 1 0 CN H H
(191) Ethyl 1 1 CN H H
(192) Propyl 1 1 CN H H
(193) Butyl 1 1 CN H H
(194) Pentyl 1 1 CN H H, C 123 N 131 I
(195) Ethyl 2 0 CN H H
(196) Propyl 2 0 CN H H
(197) Butyl 2 0 CN H H
(198) Pentyl 2 0 CN H H
(199) Ethyl 2 1 CN H H
(200) Propyl 2 1 CN H
(201) Butyl Z 1 CN H H
(202) Pentyl 2 1 CN H H
(203) Ethyl 1 0 OCF3 F H
(204) Propyl 1 0 OCF3 F H
(205) Butyl 1 0 OCF3 F H
(206) Pentyl l 0 OCF3 F H
(207) Ethyl 1 l OCF3 F H
(208) Propyl l l OCF3 F H
(209) Butyl l 1 OCF3 F H
(210) Pentyl 1 1 OCF3 F H

2 ~ 3 ~

Example R m r X L? L2 (211) Ethyl 2 0 OCF3 F H
(212) Propyl 2 0 OCF3 F H
(213) Butyl 2 0 OCF3 F
(214) Pentyl 2 0 OCF3 F H
(215) Ethyl 2 l OCF3 F H
(216) Propyl 2 l OCF3 F H
(217) Butyl 2 1 OCF3 F H
(218) Pentyl 2 1 OCF3 F H
(219) Ethyl 1 0 OCF3 F F
(220) Propyl l 0 OCF3 F F
` (221) Butyl 1 OCF3 F F
(222) Pentyl 1 0 OCF3 F F
(223) Ethyl 1 1 OCF3 F F
(224) Propyl 1 1 OCF3 F F
(225) Butyl 1 1 OC~3 F F
(226~ Pentyl l 1 OCF3 F F
(227) Ethyl 2 0 OCF3 F F
(228) Propyl 2 0 OCF3 F F
(2~9) Butyl 2 0 OCF3 F F
(230) Pentyl 2 0 OCF3 F F
(231) Ethyl 2 1 C~F3 F F
(232) Propyl 2 1 OCF3 F F
(233) Butyl 2 1 OCF3 F F
- (234) Pentyl 2 1 OCF3 F F

Example 235 A mixture of 9.2 g of 2,6-difluoro-4-[2-(p-ethoxyphenyl)e~hyl]phenylboric acid tprepared by reacting3,5-dif luorobenzaldehyde with p-ethoxybenzyltriphenyl-phosphonium iodide by the Wittig method and subsequently hydrogenating the resulting styrene derivative on Pd/C), 6.0 g of 1-bromo-4-n-propylbenzene, 38 ml of 2 ml [sic]
aqueous Na2CO3 solution, O. 6 g of tetrakis(triphenyl-phosphine)palladium(O~ and 75 ml of toluene is refluxed for two hours. The aqueous phase i5 extracted twice with - 50 ~
toluene and combined with the organic phase. Conventional aqueous work-up and chromatographic purification of the residuegive4-[2-(p-ethoxyphenyl)ethyl]-2,6-difluoro-4'-n-propylbiphenyl.
Examples 236 to 242 The following compounds according to the inven-tion axe obtained analogously from the appropriate precursors of the foxmula II:

R (Al_zl) (z -A )m X
F
(236) n-Propyl - ~ -iC2H4 ~ Ethyl (237) n-PentYl - ~ -C2H4 ~ Ethyl (238) n-Propyl - ~ -C2H4 ~ Ethyl ~239) n-Pentyl - ~ -C2H4 ~ Ethyl (240) n-Propyl - ~ -C2H4 ~ n-Propyl (241) n_propyl - ~ -C2H4 ~ ; n-Pentyl (242) n-Propyl ~ -C2H4 ~ - n-Propyl - 51 ~ g~3~

(243) n-Propyl ~ -C2H4 - ~ - n-Pentyl (244) n-PrPYl - ~ -C2H4 @ Ethyl (245) n-Propyl ~ ~-C2H4 ~ n-Propyl (246) n-Propyl - ~ ~ -C2H4 ~ Methyl C`? (247) n-Propyl ~ ~ ' C2H4 ~ Ethyl (248) n-Propyl ~ ~ ~ -C2H4 ~ n-Propyl (249) n-Propyl - ~ - ~ C2H4 ~ n-Pentyl (250) n-Propyl ~ ~ C2H4 ~ Methyl (251) n-Propyl ~ ~ C2H4 ~ Ethyl `--3 (252) n-Propyl ~ - ~ C2H4 ~ n-Propyl (253) n-Propyl ~ - ~ C2H4 ~ Methoxy (254) n-Propyl ~ ~ C2H4 ~ Methyl (255) n-Propyl - ~ -C2H4- ~ - Ethyl ~ 52 - 2~

(256) n-Propyl ~ ~ -C2H4- ~ _ n-Propyl (257) n-Propyl - ~ ~ C2H4- - ~j_ n-Pentyl (258) n-Propyl - ~ 2 4 ~ Methyl (259) n-Propyl - ~ C2H4 ~ Ethyl (260) n-Propyl ~ -C2H4- ~ - n-Propyl (261) n-Propyl ~ -C2H4- ~ - n-Pentyl (262) n-Pentyl - ~ - ~ - n-Propyl (263) n-Pentyl - ~ - ~ - n-Pentyl (264~ n-Butoxy - ~ - - ~ n-Propyl (265) n-Butoxy - ~ - ~ - n-Pentyl (266) n-Pentyl {O)- ~ - Methyl (267) n-Pentyl ~O>- - ~ - Ethyl (268) n-Pentyl -~O)- - ~ - n-Propyl (269) n-Butoxy ~O)~ n-Heptyl (270) n-Pentyl ~ ~- @, Methyl (271) n-Pentyl ~ ~ Ethyl (272) n-Pentyl - ~ ~- - ~ - n-Propyl c~ , (273) n-Pentyl @, ~ n-Pentyl (274) n-Propyl - 2H4 ~ _ ~ _ Ethyl (275) n-Propyl - -C2H4- ~ - ~ - n-Propy (276) n-Propyl - -C2H4 ~ ~ - n-Butyl (277) n-Propyl - -C2H4 ~ - ~ n-Pentyl F
(278) n-Propyl ~ - ~ - Ethyl (279) n-Propyl ~ - ~ - n-Propyl 9 ~

(280) n-Propyl ~ - - ~ - Methyl (281) n-Propyl - ~ ~ )- Ethyl (282) n-Propyl - ~ ~- - C ,- n-Propyl, (283) n-Propyl ~ - ~ - n-Pentyl (2~4) Ethoxy ~ -C2H4- - ~ n-Propyl (285) Ethoxy ~ 2H4 ~ n~Pentyl F
(286) n-Propyl - - ~ - n-Propyl (287) n-Propyl - ~ - n-Propyl (288) n-Propyl - -CO~- ~ - n-Propyl (289) n-Propyl- - { ~ ~ n-Pentyl (290) n-Propyl - ~O~ ~ - n-Heptyl (291) n-Pentyl - ~ - - ~ ~ - n-P opyl, Example 292 ~ r~ s CsH~ tc2H4-Br I Br~F ~ CsHll{\rc}c2H~FF
F F F F
II III

0.1 mol of I are introduced into 150 ml of a solvent mixture of THF/toluene (1:4 ratio by volume), and 11.5 g of anhydrous zinc bromide and then 1.4 g of lithium granules are then added. The mixture is treated with ultrasound for 4 hours at between 0C and 10C under argon and with stirring in order to convert I into the corresponding dialkyl zinc compound. The organozinc compound is treated with 0.1 mol of II and 1.5 g t2 mol%) f 1,1'-bis(diphenylphosphino)ferrocene/palladium(II) dichloride (PdCl2 dppf), and the mixture is stirred at room temperature for 24 hours after the ultrasound bath and the cooling have been removed. The mixture is decom-posed using 100 ml of saturated NH4Cl solution with stirring, the organic phase is separated off, and the aqùeous phase is extracted 2 x with toluene. The combined organic extracts are dried, evaporated and chromatographed on silica gel using hexane to give III.

!

Example 293 F F 2 ~ t H~ICs~ 2)z-Br ~ Br~

HI~Cs~(a~2)2~
F F

1 . B~L i / THF
TME~A F F
H"Cs{)a ( CH2 ) 2~I
2 I2, THF 4 F F

CF3CO2Na. CuI
NMP ` F F
Hl I Cs 0~ ~ CH2 ) 2~CJ?3 F

100 mmol of I are converted into 3 by reaction with 2 analogously to the above example.
31 ml of n-BuLi (15% in hexane) are added dropwise at -65 to -70C to a mix~ure of 47 mmol of 3, ~i 7.5 ml of TMEDA (50 mmol) and 150 ml of THF, and the mixture is stirred for a further 1 hour at -70C. A
solution of 12.0 g (47 mmol) of iodine in 25 ml of THF is then added dropwise at -65 to -70C, and the mixture is stirred for a further 0.5 hour a~ -70C. The mixture is warmed to -30C and hydrolyzed during 15 ml of water, and excess iodine is reduced by adding 15 ml of sodium bisulfite solution. Customary work-up and recrys~alliza-tion from hexane give 4. 400 ml of NMP are removed by distillation from a mixture of 38 mmol of 4, 4.4 g (76 mmol) of KF, 22.8 g (168 mmol) of ~odium trifluoroacetate and 800 ml of NMP at 70C and 4 mbar. 1.4 g (76 mmol) of dried CuI are then added to the reaction mixture, which J
is stirred at 160C for 5 hours. About 300 ml of NMP are subsequently removed by distillation. The mixture is allowed to cool to RT, and 400 ml of MTB ether are added.
The mixture is washe~ with water, dried using Na2SO4, S filtered and evaporated to give a residue. Chromatography on silica gel using hexane gives 5.
Example 294 A solution of 0.1 m of 1-(trans-4-n-propylcyclo-hexyl)-2-(3,3',5'-trifluorobiphenylyl)ethane and 0.1 m of TMEDA in 300 ml of THF is treated dropwise at about -65 with 0.1 m of n-BuLi (1.5 M in hexane). The mixture is stirred at this temperature for a further 30 minutes, and 0.2 m of N-chlorosuccinimide in 70 ml of THF is then ; slowly added. When the addition is complete, the mixture is allowed to warm to -20 and is hydrolyzed using H2O.
The product is dissolved completely by adding diethyl ether. Extractive work-up and purification by chromatography and crystallization give l-(trans-4-n-propylcyclohexyl)-2-(4'-chloro-3,3',5'-trifluoro-biphenylyl)ethane.
Exam~e 301 A mixture of 10.5 g of 1-bromo-3,4-difluoro-benzene, 17.4 g of 4-(trans-4-4-propylcyclohexyl)-2,6-difluorostyrene (obtainable in accordance with the abovementioned schemes), 0.25 g of Pd acetater 0.6 g of tri-o-tolylphosphine, 7 g of triethylamine and 125 ml of acetonitrile is refluxed until the reaction is complete.
Customary work-up gives trans-1-(3,4-difluorophenyl)-2-[4-(trans-4-propyicyclohexyl)-2,6-difluorophenyl]ethene, C 101 N 156.5 I.
The following are [sic] prepared analogously:
trans-1-(3,4-difluorophenyl)-2-(2,6-difluoro-4-ethoxy-phenyl)ethene, C 92 I
Example A
A liquid-crystalline medium I comprises 2 ~

PCH-5F10,0 %
PCH-6F 8,0 %
PCH-7F 6,0 %
CCP-20CF38,0 %
CCP-30CF312,0 %
CCP-40CF39,0 %
CCP-50CF39,0 %
BCH-3F.F12,0 %
BCH-5F.F10,0 %
ECCP-3OCF35,0 %
ECCP-50CF35,0 %
CBC-33F2,0 %
CBC-53F2,0 %
CBC-55F2,0 %

A medium II according to the invention comprises 90% of medium I and 10% of ~F F
3 7 ~ ~ ~ ~ F
F

Medium I Medium II

Clear point 91C 102.4C
~n 0.094 0.102 ~ 5.2 6.0 Viscosity at 20 (cSt) 15.0 16.7

Claims (5)

Patent claims
1. 1,4-Disubstituted 2,6-difluorobenzene compounds of the formula I

I

where R is an alkyl or alkenyl radical having 1 to 15 carbon atoms which is unsubstituted or at least monosubstituted by halogen, it also being possible for one or more CH2 groups in these radicals to be replaced, in each case in-deoendently of one another, by -O-, -S-, , , - CO-, - CO-O - , -O - CO- or -O-CO-O- in such a manner that oxygen atoms are not linked directly to one another, A1 and A2, in each case independently of one another, are (a) a trans-1,4-cyclohexylene radical in which, in addition, one or more non-adjacent CH2 groups may be replaced by -O- and/or -S-, (b) a 1,4-phenylene radical in which, in addition, one or two CH groups may be replaced by N, (c) a radical from the group comprising 1,4-cyclo-hexenylene,1,4-bicyclo(2,2,2)octylene,piperi-dine-1,4-diyl,naphthalene-2,6-diyl,decahydro-naphthalene-2,6-diyl and 1,2,3,4-tetrahydro-naphthalene-2,6-diyl, it being possible for the radicals (a) and (b) to be substituted by CN or monosubstituted or disubstituted by fluorine, Z1 and Z2 in each case independently of one another, are -CO-O-,-O-CO-,-CH2O-,-OCH2-,-CH2CH2-,-CH=CH-, -C?C- or a single bond, m and n in each case independently of one another, are 0, 1, 2 or 3, where (m+n) is 1, 2 or 3, and X has one of the meanings of R or is F, Cl, -CF3, -OCF3-, -OCF2H, -OC2F5, -CN or -NCS, with the proviso that at least one of the radicals Z1 and Z2 present in the molecule is -CO-O-, -O-CO-, -CH2-O-, -OCH2-, -CH2CH2-, -CH=CH- or -C?C and/or at least one of the radicals A1 and A2 present in the molecule is or and/or n is 1 or 2, where, in the case where -(Z2-A2)n = , X is F, Cl, -CF3, -OCF3, -OCF2H, -OC2F5, -CN or -NCS.
2. Use of compounds of the formula I as components of liquid-crystalline media.
3. Liquid-crystalline medium containing at least two liquid-crystalline components, characterized in that it contains at least one compound of the formula I.
4. Liquid-crystal display element, characterized in that it contains a liquid-crystalline medium according to Claim 3.
5. Electrooptical display, characterized in that it contains, as dielectric, a liquid-crystalline medium according to Claim 3.
CA002046590A 1989-12-06 1990-12-06 1,4-disubstituted 2,6-difluorobenzene compounds, and a liquid crystalline medium Abandoned CA2046590A1 (en)

Applications Claiming Priority (8)

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DE3940343 1989-12-06
DEP3940343.2 1989-12-06
DE3941881 1989-12-19
DEP3941881.2 1989-12-19
DEP4000534.8 1990-01-10
DE4000535A DE4000535B4 (en) 1989-12-06 1990-01-10 1,4-disubstituted 2,6-difluorobenzene compounds and liquid-crystalline medium
DE4000534A DE4000534C2 (en) 1989-12-19 1990-01-10 1,4-disubstituted 2,6-difluorobenzene compounds and liquid-crystalline medium
DEP4000535.6 1990-01-10

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