DE19900517B4 - 2,3-dihydro-6,7-difluorbenzofuran derivatives - Google Patents

Abstract

2,3-Dihydro-6,7-difluorobenzofuran derivatives of the formula I R1- (A1-Z1) n-A2-Z2-WIworin R1 H, an unsubstituted alkyl radical which is monosubstituted by CN or CF3 or by at least one halogen-substituted alkyl radical 1 to 12 C atoms or alkenyl radical having 2 to 12 C atoms, where in these radicals also one or more CH 2 groups are each independently denoted by -O-, -S-, -CO-, -CO-O-, - O-CO- or -O-CO-O- can be replaced so that heteroatoms are not directly linked to each other, R2H or an alkyl radical having 1 to 8 carbon atoms, A1 and A2 are each independently a) trans-1 , 4-cyclohexylene radical, in which also one or more non-adjacent CH 2 groups can be replaced by -O- and / or -5-, b) 1,4-cyclohexenylene radical, c) 1,4-phenylene radical, in which also one or two D) radical from the group consisting of 1,4-bicyclo (2,2,2) -octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2, 6-diyl and 1,2,3,4-tetrahydronaphthalene-2 , 6-diyl, wherein the radicals a), b) and c) may be substituted by CN, Cl or F, Z1 and Z2 are each independently -CO-O-, -O-CO-, -CH2O-, -O -CH2-, -CH2CH2-, -CH = CH-, -CC- or a single bond and n is 0, 1 or 2.

Description

R¹ H, einen unsubstituierten, einen einfach durch CN oder CF₃ oder einen mindestens einfach durch Halogen substituierten Alkylrest mit 1 bis 12 C-Atomen oder Alkenylrest mit 2 bis 12 C-Atomen, wobei in diesen Resten auch eine oder mehrere CH₂-Gruppen jeweils unabhängig voneinander durch -O-, -S-, -CO-, -CO-O-, -O-CO- oder -O-CO-O- so ersetzt sein können, daß Heteroatome nicht direkt miteinander verknüpft sind,
R² H oder einen Alkylrest mit 1 bis 8 C-Atomen,
A¹ und A² jeweils unabhängig voneinander einen
a) trans-1,4-Cyclohexylenrest, worin auch eine oder mehrere nicht benachbarte CH₂-Gruppen durch -O- und/oder -S- ersetzt sein können,
b) 1,4-Cyclohexenylenrest,
c) 1,4-Phenylenrest, worin auch eine oder zwei CH-Gruppen durch N ersetzt sein können,
d) Rest aus der Gruppe 1,4-Bicyclo(2,2,2)-octylen, Piperidin-1,4-diyl, Naphthalin-2,6-diyl, Decahydronaphthalin-2,6-diyl und 1,2,3,4-Tetrahydronaphthalin-2,6-diyl,
wobei die Reste a), b) und c) durch CN, Cl oder F substituiert sein können,
Z¹ und Z² jeweils unabhängig voneinander -CO-O-, -O-CO-, -CH₂O-, -O-CH₂-, -CH₂CH₂-, -CH=CH-, -C≡C- oder eine Einfachbindung
und
n 0, 1 oder 2
bedeuten.The invention relates to 2,3-dihydro-6,7-difluorobenzofuran derivatives of the formula I. R ¹ - (A ¹ -Z ¹ ) _n -A ² -Z ² -WI wherein

R ¹ H, an unsubstituted, a simply by CN or CF ₃ or at least one halogen-substituted alkyl radical having 1 to 12 carbon atoms or alkenyl radical having 2 to 12 carbon atoms, wherein in these radicals also one or more CH ₂ - Each group independently of one another may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO- or -O-CO-O- so that heteroatoms are not directly linked to one another,
R ² H or an alkyl radical having 1 to 8 C atoms,
A ¹ and A ² each independently
a) trans-1,4-cyclohexylene radical, in which also one or more non-adjacent CH ₂ groups can be replaced by -O- and / or -S-,
b) 1,4-cyclohexenylene radical,
c) 1,4-phenylene radical, in which also one or two CH groups can be replaced by N,
d) radical from the group consisting of 1,4-bicyclo (2,2,2) octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl and 1,2,3 , 4-tetrahydronaphthalene-2,6-diyl,
where the radicals a), b) and c) can be substituted by CN, Cl or F,
Each of Z ¹ and Z ² is independently -CO-O-, -O-CO-, -CH ₂ O-, -O-CH ₂ -, -CH ₂ CH ₂ -, -CH = CH-, -C≡C - or a single bond
and
n 0, 1 or 2
mean.

The invention further relates to the use of the compounds of general formula I as components of liquid-crystalline media and to the use of the compounds of general formula I in liquid-crystal and electro-optical display elements.

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 upright phases DAP or ECB (Electrically Controlled Birefringence) or the effect of based on dynamic dispersion. The substances used hitherto for this purpose always have certain disadvantages, for example too little stability against the action of heat, light or electric fields, unfavorable elastic and / or dielectric properties.

However, the compounds of the formula I according to the invention can also be used for the preparation of chiral tilted smectic liquid-crystalline phases having ferroelectric properties. In this case, achiral compounds of the formula I can serve as base materials, from which the liquid-crystalline smectic phases are predominantly composed. By contrast, chiral compounds of the formula I are suitable for inducing the ferroelectric properties in a smectic base mixture.

worin z. B.

einen Cyclohexan-, Cyclohexen- oder Phenylring bedeutet, die eine extrem große Anzahl von Verbindungen umfaßt, die jedoch eine andere Struktur aufweisen, als die Verbindungen der Formel I der vorliegenden Anmeldung. DE 43 00 066 A1 discloses a general formula (I) R ¹ - (A ¹ -Z ¹ ) _m -A ² -Z ² -W one end of which "-W" is a ring unit of a six-membered ring member having a five-membered ring member fused thereto, selected from the three sub-formulas

wherein z. B.

a cyclohexane, cyclohexene or phenyl ring comprising an extremely large number of compounds but having a different structure than the compounds of formula I of the present application.

The invention had the object of finding new stable liquid-crystalline or mesogenic compounds which are suitable as components of liquid-crystalline media, in particular for TFT and STN displays.

It has now been found that the compounds of the formula I are particularly suitable as components of liquid-crystalline media. With their help, it is possible to obtain stable liquid-crystalline media, in particular suitable for TFT or STN displays. The new compounds are characterized above all by a high thermal stability and have advantageous values for the "holding ratio". The compounds of the formula have, in particular, a strongly negative dielectric anisotropy Δε and are therefore particularly suitable for displays which are based on the effect of deformation of upright phases DAP or ECB. The compounds of the formula I according to the invention are furthermore distinguished by medium to very low optical anisotropies Δn and by a favorable phase behavior.

With the provision of compounds of the formula I, the range of liquid-crystalline substances, which are suitable for the production of liquid-crystalline mixtures from various application-technical points of view, is also generally widened considerably.

The compounds of the formula I have a wide range of applications. Depending on the choice of substituents, these compounds may serve as base materials from which liquid crystalline media are predominantly composed; However, it is also possible to add compounds of the formula I to liquid-crystalline base materials from other classes of compounds in order, for example, to influence the dielectric and / or optical anisotropy of such a dielectric and / or to optimize its threshold voltage and / or its viscosity.

The meaning of the formula I includes all isotopes of the chemical elements bound in the compounds of the formula 1.

The compounds of the formula I are colorless in the pure state and form liquid-crystalline mesophases in a temperature range which is favorably located for the electro-optical use. Chemically, thermally 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 furthermore relates to liquid-crystalline media having at least two liquid-crystalline components, the liquid-crystalline media containing at least one compound of the formula I and the use of the liquid-crystalline media in liquid-crystal display elements, in particular in electro-optical display elements.

Above and below, R ¹ , A ¹ , Z ¹ , n, A ² , Z ² , W and R ^{2 have} the meaning indicated, unless expressly stated otherwise.

For the sake of simplicity, in the following Cyc is a 1,4-cyclohexylene radical, Che is a 1,4-cyclohexenylene radical, Dio is a 1,3-dioxane-2,5-diyl radical, Dit is a 1,3-dithiane-2,5-diyl radical, Phe a 1,4- Phenylene radical, Pyd is a pyridine-2,5-diyl radical, Pyr is a pyrimidine-2,5-diyl radical and Bco is a bicyclo (2,2,2) -octylene radical, where Cyc and / or Phe are unsubstituted or mono- or polysubstituted by Cl, F or CN can be substituted.

The compounds of the formula I include compounds having three rings of the subformulae Ia and Ib: R ¹ -A ² -W Ia R ¹ -A ² -Z ² -W Ib

Compounds with four rings of the subformulae 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 subformulae 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 -WIi 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 -2 ¹ -A ² -Z ² -W Im R ¹ -A ¹ -Z ¹ -A ¹ -Z ¹ -A ² -Z ² -W In

Of these, especially those of sub-formulas Ia, Ib, Ic, Id, Ie, Ig, Ih and Ii are 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 Icg: 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

Of these, those of the forms Ica, Icb, Icc and Ice are particularly preferred.

The preferred compounds of partial formula Id include those of partial 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 -Wegeg R ¹ -Dio-Z ¹ -A ² -W Ieh

Of these, those of the partial formulas Iea, Ieb, Iec and Iee are particularly preferred.

The preferred compounds of sub-formula If include those of 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 sub-formulas Ig to In include those of 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 R1-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, furthermore preferably alkoxy. R ¹ is particularly preferably a straight-chain unsubstituted alkyl radical having 1 to 12 C atoms or a straight-chain unsubstituted alkenyl radical having 2 to 12 C atoms. Among the alkenyl radicals, vinyl and the 1E and 3E alkenyl radicals 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 exists twice, the two rings can have the same or different meanings. The same applies to the bridge Z ¹ .

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

n ist vorzugsweise O oder 1.Most preferably, A ¹ and / or A ^{2 are} each independently

n is preferably O or 1.

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

More preferably n 0 and Z ^{2 are} a single bond, or n 1 and Z ¹ and Z ^{2 are} a single bond.

In the structural element W, R ^{2 is} preferably H, CH ₃ , C ₂ H ₅ , nC ₃ H ₇ , nC ₄ H ₉ , nC ₅ H ₁₁ , nC ₆ H ₁₃ , nC ₇ H ₁₅ or nC ₈ H ₁₇ . In a particularly preferred embodiment, R ^{2 is} H. In another particularly preferred embodiment, R ^{2 is} CH ₃ , C ₂ H ₅ , nC ₃ H ₇ , nC ₄ H ₉ or nC ₅ H ₁₁ . Most preferably R ^{2 is} H, CH ₃ , C ₂ H ₅ or nC ₃ H ₇ .

p = 0, 1, 2, 3, 4
q = 0, 1, 2, 3, 4 The formulas (1) - (4) represent particularly preferred meanings of the structural element W:

p = 0, 1, 2, 3, 4
q = 0, 1, 2, 3, 4

Very exceptionally preferred meanings of the structural element W are the formulas (1) and (3), and the formula (2) wherein p is 0, 1 or 2 and the formula (4) wherein q is 0, 1 or 2.

If R ¹ in the formulas above and below denotes an alkyl radical and / or an alkoxy radical, this may be straight-chain or branched. Preferably, it is straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and thus preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl , Octyl, nonyl, decyl, undecyl, dodecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy or dodecoxy.

Oxaalkyl 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-oxo-octyl, 2-, 3-, 4-, 5-, 6 -, 7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

If R ^{1 is} an alkenyl radical, this may be straight-chain or branched. It is preferably straight-chain and has 2 to 10 C atoms. It therefore particularly denotes vinyl, prop-1-one or prop-2-enyl, but-1, 2- or but-3-enyl, pent-1, 2-, 3- or pent-4-enyl, hexane 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 is} an alkyl radical in which one CH ₂ group is replaced by -O- and one by -CO-, these are preferably adjacent. Thus, they include an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-. Preferably, these are straight-chain and have 2 to 6 carbon atoms. They therefore mean especially acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl, 2-6utyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl, Propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2- (methoxycarbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propoxycarbonyl) ethyl, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl) propyl, 4 - (methoxycarbonyl) butyl.

If R ^{1 is} an alkenyl radical in which one of the double bond adjacent CH ₂ group is replaced by -CO- or -CO-O- or -O-CO-, this may be straight-chain or branched. It is preferably straight-chain and has 4 to 12 C atoms. It therefore particularly means acryloyloxymethyl, 2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl, 8-acryloyloxyoctyl, 9-acryloyloxynonyl, methacryloyloxymethyl, 2-methacryloyloxyethyl, 3-methacryloyloxypropyl, 4- Methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl or 8-methacryloyloxyoctyl.

If R ^{1 is} a monosubstituted by CN or CF ₃ is substituted alkyl or alkenyl radical, this radical is preferably straight-chain and the substitution by CN or CF ₃ in ω-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 radicals also include perfluorinated radicals. For single substitution, the fluoro or chloro substituent may be in any position, but preferably in the ω position.

Occasionally, compounds of the formula I having branched wing group R ¹ may be of importance for better solubility in the usual liquid-crystalline base materials, but especially as chiral dopants, if they are optically active. Smectic compounds of this type are useful as components of ferroelectric materials.

Branched groups of this type usually contain no more than one chain branch. Preferred branched radicals R ¹ 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.

Preferred among these compounds of the formula I and the sub-formulas are those in which at least one of the radicals contained therein has one of the preferred meanings given.

In the compounds of formula I those stereoisomers are preferred in which the rings Cyc and piperidine are trans-1,4-disubstituted.

Those of the above formulas containing one or more groups Pyd, Pyr and / or Dio each include the two 2,5-position isomers.

L¹, L², L³, L⁴ = jeweils unabhängig voneinander H oder F.Some very particularly preferred smaller groups of compounds of the formula I are those of the partial formulas I1 to I10:

L ¹ , L ² , L ³ , L ⁴ = each independently H or F.

Particularly preferred formulas from the group of the sub-formulas I1 to I10 are, in addition to the formulas I1 and I6, the sub-formulas I4a and I5a:

The compounds of the formula I are prepared by methods known per se, as described in the literature (for example in the standard works such as Houben-Weyl, Methods of Organic Chemistry, Georg-Thieme-Verlag, Stuttgart), namely under Reaction conditions which are known and suitable for the said reactions.

One can make use of known per se, not mentioned here variants.

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

Schema 2

Schema 3

The compounds of the invention may, for. For example, according to the following Reaction Schemes 1 to 3: Scheme 1

Scheme 2

Scheme 3

Schema 5

Schema 6

Preferred compounds of formula I are prepared as follows: Scheme 4

Scheme 5

Scheme 6

Esters of the formula I can also be obtained by esterification of corresponding carboxylic acids (or their reactive derivatives) with alcohols or phenols (or their reactive derivatives) or by the DCC method (DCC = dicyclohexylcarbodiimide).

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

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 (see RF Heck, Acc Res. 12 (1979) 146). Suitable aryl halides are, for example, chlorides, bromides and iodides, in particular bromides and iodides. The required for the success of the coupling reaction tertiary amines such. As triethylamine, are also suitable as a solvent. As palladium catalysts are, for example, its salts, in particular Pd (II) acetate, with organic phosphorus (III) compounds such. B. triarylphosphines suitable. It is possible to 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 a solvent come z. As nitriles such as acetonitriles or hydrocarbons such as benzene or toluene into consideration. The aryl halides and olefins used as starting materials are widely available commercially or can be prepared by literature methods, for example by halogenation of corresponding parent compounds or by elimination reactions of corresponding alcohols or halides.

In this way, for example stilbene derivatives can be produced. The stilbenes can be further prepared by reacting a 4-substituted benzaldehyde with a corresponding Wittig phoshorylide. However, it is also possible to prepare tolans of the formula I by using monosubstituted acetylene instead of the olefin (Synthesis 627 (1980) or Tetrahedron Lett. 27, 1171 (1986)).

Furthermore, aryl halides can be reacted with aryl tin compounds for the coupling of aromatics. These reactions are preferred with the addition of a catalyst such as. B. a palladium (0) complex in inert solvents such as hydrocarbons at high temperatures, eg. B. in boiling xylene, carried out under inert gas.

Couplings of alkynyl compounds with aryl halides can be carried out analogously to the method described by 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 is} -C≡C- can also be prepared via the Fritsch-Buttenberg-Wiechell rearrangement (Ann., 279, 319, 1984), in which 1,1-diaryl-2 -halogenoethylenes are rearranged to diarylacetylenes in the presence of strong bases.

Tolans of formula I can also be prepared by brominating the appropriate stilbene and then subjecting to dehydrohalogenation. In this case, one can use known per se, not mentioned here variants of this implementation.

Ethers of the formula I are obtainable by etherification of corresponding hydroxy compounds, preferably corresponding phenols, wherein the hydroxy compound is first expediently converted into a corresponding metal derivative, eg. 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 or alkali metal phenolate. This can then be reacted with the corresponding alkyl halide, sulfonate or dialkyl sulfate, suitably in an inert solvent such. As 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.

The starting materials are either known or can be prepared in analogy 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 constituents 2 to 40, in particular 4 to 30 components. With very particular preference these media contain, in addition to one or more compounds according to the invention, 7 to 25 components. These further constituents are preferably selected from nematic or nematogenic (monotropic or isotropic) substances, in particular substances from the classes of the azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, cyclohexanecarboxylic acid phenyl or cyclohexyl esters, phenyl or cyclohexyl esters of Cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, cyclohexyl phenyl esters of benzoic acid, of cyclohexanecarboxylic acid or of cyclohexylcyclohexanecarboxylic acid, phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexylcyclohexenes, 1,4-biscyclohexylbenzenes, 4,4'-bis- cyclohexylbiphenyls, phenyl- or cyclohexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclohexyl-dioxanes, phenyl- or cyclohexyl-1,3-dithiane, 1,2-diphenylethane, 1,2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1 Cyclohexyl-2- (4-phenyl-cyclohexyl) -ethanes, 1- Cyclohexyl-2-biphenylylethanes, 1-phenyl-2-cyclohexyl-phenylethanes, optionally halogenated stilbenes, benzylphenyl ethers, tolans and substituted cinnamic acids. The 1,4-phenylene groups in these compounds can also be fluorinated.

The most important compounds which may be used 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'-LC≡CE-R "5

In formulas 1, 2, 3, 4 and 5, L and E, which may be the same or different, each independently represents a bivalent radical selected from the group consisting of -Phe-, -Cyc-, -Phe-Phe-, -Phe- Cyc, -Cyc-Cyc, -Pyr-, -Dio, -G-Phe- and -G-Cyc- and their mirror images formed group, wherein Phe is unsubstituted or substituted by fluorine 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-2,5-diyl.

Preferably, one of L and E is Cyc, Phe or Pyr. E is preferably Cyc, Phe or Phe-Cyc. The media according to the invention preferably comprise one or more components selected from the compounds of the formulas 1, 2, 3, 4 and 5, in which L and E are selected from the group Cyc, Phe and Pyr and simultaneously one or more components selected from the compounds of the Formulas 1, 2, 3, 4 and 5, wherein one of the radicals L and E is selected from the group Cyc, Phe and Pyr and the other radical is selected from the group -Phe-Phe-, -Phe-Cyc-, - Cyc-Cyc, -G-Phe and -G-Cyc-, and optionally one or more components selected from the compounds of formulas 1, 2, 3, 4 and 5, wherein 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 subgroup of the compounds of formulas 1, 2, 3, 4 and 5 are each independently alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy of up to 8 carbon atoms. Hereinafter, this smaller subgroup will be called group A and the compounds will be denoted by the subformulae 1a, 2a, 3a, 4a and 5a. In most of these compounds R 'and R "are different from each other, one of these radicals is usually alkyl, alkenyl, alkoxy or alkoxyalkyl.

In a smaller subgroup of compounds of formulas 1, 2, 3, 4 and 5, other than group B, R '' is -F, -Cl, -NCS or - (O) _i CH ₃ - _{(k + 1)} F _k Cl _l , where i is 0 or 1 and k + l is 1, 2 or 3; the compounds in which R "has this meaning are designated by the subformulae 1b, 2b, 3b, 4b and 5b. Particular preference is given to those compounds of the subformulae 1b, 2b, 3b, 4b and 5b in which R "has the meaning -F, -Cl, -NCS, -CF ₃ , -OCHF ₂ or -OCF ₃ .

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

In another smaller subgroup of the compounds of formulas 1, 2, 3, 4 and 5, R "is -CN; this subgroup is referred to below as group C and the compounds of this subgroup are described respectively with sub-formulas 1c, 2c, 3c, 4c and 5c. In the compounds of sub-formulas 1c, 2c, 3c, 4c and 5c, R 'has the meaning given for the compounds of sub-formulas 1a-5a and is preferably alkyl, alkoxy or alkenyl.

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

In addition to 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 on the media according to the invention are preferably Group A: 0 to 90%, preferably 20 to 90%, in particular 30 to 90% Group B: 0 to 80%, preferably 10 to 80%, especially 10 to 65% Group C: 0 to 80%, preferably 5 to 80%, especially 5 to 50% wherein the sum of the mass fractions of the compounds of the groups A and / or B and / or C contained in the respective inventive media is preferably 5% to 90% and in particular 10% to 90%.

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

The preparation of the media according to the invention is carried out in a conventional manner. In general, the components are dissolved in each other, useful at elevated temperature. By means of suitable additives, the liquid-crystalline phases according to the invention can be modified so that they can be used in all hitherto known types of liquid-crystal display elements. Such additives are known to the person skilled in the art and are described in detail in the literature (H. Kelker / R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, pleochroic dyes can be added to produce colored guest-host systems or to modify the dielectric anisotropy, viscosity and / or orientation of the nematic phases.

The following examples are intended to illustrate the invention without limiting it. Above and below, percentages are by weight. All temperatures are in degrees Celsius. Mp means melting point, Kp = clearing point. Furthermore, K = crystalline state, N = nematic phase, S = smectic phase, I = isotropic phase and T _g = glass transition temperature. The data between these symbols represent the transition temperatures. Δn means optical anisotropy (589 nm, 20 ° C) and the viscosity (mm ² / sec) was determined at 20 ° C.

"Conventional workup" means: water is optionally added, if necessary, depending on the constitution of the final product to pH values between 2 and 10, extracted with dichloromethane, diethyl ether, methyl tert-butyl ether or toluene, separated, dried organic phase, evaporated and the product purified by distillation under reduced pressure or crystallization and / or chromatography.

B(OMe)₃

Borsäuretrimethylester

BrCH(COOEt)₂

Monobrommalonsäurediethylester

BuLi

Butyllithium

DMF

N,N-Dimethylformamid

EtOH

Ethanol

KO¹Bu

Kalium-tert.-butylat

NMP

N-Methyl-2-pyrrolidinon

Pd-C-5%

5 Gew.-% Palladium auf Kohle

Pd(C)

Palladium auf Aktivkohle

PhNEt₂

N,N-Diethylanilin

Propargyibromid

3-Bromprop-1-in

RT

Raumtemperatur

THF

Tetrahydrofuran

Urotropin

Hexamethylentetramin

The following abbreviations are used:

B (OMe) ₃

borate

BrCH (COOEt) ₂

Monobrommalonsäurediethylester

BuLi

butyllithium

DMF

N, N-dimethylformamide

EtOH

ethanol

KO ¹ Bu

Potassium tert-butoxide

NMP

N-methyl-2-pyrrolidinone

Pd-C 5%

5% by weight of palladium on carbon

Pd (C)

Palladium on activated carbon

PhNEt ₂

Diethylaniline

Propargyibromid

3-bromoprop-1-yne

RT

room temperature

THF

tetrahydrofuran

urotropin

hexamethylenetetramine

Example 1: Synthesis analogous to Scheme 4

• Step 1
  
• To a mixture of 51.0 mmol of 1 60.0 mmol of potassium carbonate and 150 ml of N, N-dimethylformamide was added dropwise 60.0 mmol of 3-bromoprop-1-yn and stirred at room temperature for 24 h. Subsequently, as usual worked up. 2 is obtained as white crystals.

step 2

A mixture of 42.0 mmol of 2, 55 mmol cesium fluoride and 90 ml of N, N-diethylaniline was stirred at 170 ° C for 48 h. Subsequently, as usual worked up. 3 is obtained as white crystals; K 89 N 173.6 I; Δε = -5.4; Δn = +0.117.

step 3

16 mmol of 3 were dissolved in 150 ml of THF and hydrogenated at room temperature on palladium-carbon (5%). After usual workup, 4 are obtained as white crystals; K 112 N (105,1) I; Δε = -6.7; Δn = +0.073.

Example 2: Synthesis analogous to Scheme 5

• Step 1
  

To a mixture of 65 mmol 5 and 130 mmol K ₂ CO ₃ in 100 ml THF and 200 ml water was added 75 mmol solid I _{2 in} portions at 19 ° C. After stirring for 24 hours was worked up as usual. Excess I ₂ was removed by washing the organic phase with aqueous sodium bisulfite solution. 6 are obtained as crystals.

step 2

To a mixture of 27 mmol 6, 0.8 mmol of bis (triphenylphosphine) palladium (II) chloride, 0.8 mmol of copper (I) iodide, 53 mmol of triethylamine and 70 ml of N, N-dimethylformamide were 27 mmol 1 Added dropwise and the mixture for 24 h at RT and 4 h at 60 ° C stirred. After usual workup, 7 are obtained as white crystals; K 76 S _A 97 N 140 I; Δε = -4.4; Δn = + 0.101.

step 3

20 mmol of 7 were dissolved in 200 ml of THF and hydrogenated at room temperature on palladium-carbon (5%). After usual workup, 8 are obtained as white crystals; K 88 S _B 95 S _A 104 N 135.2 I; Δε = -6.5; Δn = + 0.083.

Example 3: Synthesis analogous to Scheme 6

• Step 1
  

300 mmol of hexamethylenetetramine were added dropwise to a mixture of 150 mmol of 9 and 225 ml of trifluoroacetic acid so that the temperature did not rise above 40 ° C. The mixture was then heated to reflux with stirring for 28 h and stirred at room temperature for a further 12 h. Thereafter, first 170 ml of H ₂ O and then 85 ml of 50% sulfuric acid were added and stirred for a further 2 h at room temperature. After usual workup, 10 are obtained as white crystals.

step 2

A mixture of 141 mmol 0 160 mmol monobromomalonic acid diethylester, 350 mmol K ₂ CO ₃ and 580 ml 2-butanone was heated to reflux for 7 h with stirring and then stirred for a further 12 h at room temperature. After usual workup, 11 are obtained as white crystals.

step 3

A mixture of 48 mmol 11, 53 mmol KOH and 275 ml of ethanol was heated with stirring for 2 h to reflux and then stirred for a further 12 h at room temperature. After usual workup, 12 are obtained as yellow crystals.

Step 4

A mixture of 48 mmol 12, 16 mmol Cu powder and 20 ml of 1,3-dimethyl-2-imidazolidinone was stirred at 160 ° C for 3 h. After usual work-up, 13 are obtained as white crystals; K 37 I; Δε = -3.4; Δn = +0.044.

Step 5

20 mmol of 13 were dissolved in 200 ml of THF and hydrogenated at room temperature on palladium-carbon (5%). After usual work-up, 14 are obtained as white crystals; K 36 I; Δε = -4.9; Δπ = +0.015. Analogously to Examples 1 to 3 are prepared (Examples 4 to 111):

Claims (10)

2,3-Dihydro-6,7-difluorobenzofuran derivatives of the formula I R ¹ - (A ¹ -Z ¹ ) _n -A ² -Z ² -WI wherein

R ¹ H, an unsubstituted, a simply by CN or CF ₃ or at least one halogen-substituted alkyl radical having 1 to 12 carbon atoms or alkenyl radical having 2 to 12 carbon atoms, wherein in these radicals also one or more CH ₂ - Each group independently may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO- or -O-CO-O- so that heteroatoms are not directly linked to each other, R ² H or an alkyl group having 1 to 8 C atoms, A ¹ and A ^{2 are} each independently a) trans-1,4-cyclohexylene, wherein also one or more non-adjacent CH ₂ groups by -O- and / or B) 1,4-cyclohexenylene radical, c) 1,4-phenylene radical, in which also one or two CH groups may be replaced by N, d) radical from the group consisting of 1,4-bicyclo (2 , 2,2) -octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl and 1,2,3,4-tetrahydronaphthalene-2,6-diyl, wherein the Radicals a), b) and c) are substituted by CN, Cl or F. Z ¹ and Z ^{2 are} each independently -CO-O-, -O-CO-, -CH ₂ O-, -O-CH ₂ -, -CH ₂ CH ₂ -, -CH = CH-, - CC or a single bond and n is 0, 1 or 2. 2,3-Dihydro-6,7-difluorobenzofuran derivatives according to Claim 1, characterized in that R ^{1 is} a straight-chain unsubstituted alkyl radical having 1 to 12 C atoms or a straight-chain unsubstituted alkenyl radical having 2 to 12 C atoms. 2,3-Dihydro-6,7-difluorobenzofuran derivatives according to one of claims 1 or 2, characterized in that n 0 and Z ² denote a single bond, or that n 1 and Z ¹ and Z ² denote a single bond. 2,3-Dihydro-6,7-difluorobenzofuran derivatives according to one of claims 1 to 3, characterized in that R ^{2 is} H. 2,3-Dihydro-6,7-difluorobenzofuran derivatives according to one of Claims 1 to 3, characterized in that R ^{2 is} CH ₃ , C ₂ H ₅ , nC ₃ H ₇ , nC ₄ H ₉ or nC ₅ H ₁₁ , 2,3-Dihydro-6,7-difluorobenzofuran derivatives according to one of claims 1 to 5 of the formula I1

wherein R ¹ and W have the meanings indicated. 2,3-Dihydro-6,7-difluorobenzofuran derivatives according to one of claims 1 to 5 of the formula I6

wherein R ¹ and W have the meanings indicated. 2,3-Dihydro-6,7-difluorobenzofuran derivatives according to any one of claims 1 to 5 of the formula I4a

wherein R ¹ and W have the meanings indicated. Use of compounds according to one of claims 1 to 8 as components of liquid-crystalline media. Liquid-crystalline medium having at least two liquid-crystalline components, characterized in that it contains at least one compound of claims 1 to 8.