PYRIDINE DERIVATIVES

Abstract: The invention relates to pyridine derivatives of formula (I), wherein Y is selected from F, Cl, -CF3, -OCF3, or -O CHF2; Z<1> and Z<2> are selected from -CH2-CH2-, -CO-O-, -O-CO-, -CH2-O-; O-CH2-, -C=C- or a single bond. A<1> and A<2> are rings; X=H, or in case of Y=F or Cl, also F; n=0,1 or 2; and R<1>=alkyl wherein one or two non-adjacent CH2-groups may be replaced by -O-, -O-CO-, -CO-O- and/or -CH=CH-which are used in liquid cristalline mixtures.

Description: Pyridine derivatives The invention relates to pyridine derivatives of the formula I wherein R denotes alkyl with up to 12 carbon atoms wherein one or two non-adjacent CH_-groups may also be replaced by -0-, -O-CO-, -CO-O- and/or -CH=CH-, Y is F, Cl, -CF 3 , -OCF 3 or -OCF 2 H, A 1 and A2 in each case independently of one another are trans-l,4-cyclohexylene, wherein one or two non-adjacent CH_,-groups may also be replaced by -O- and/or -S-, or 1,4-phenylene which is un- substituted or substituted by one or more halogen atoms and/or nitrile and/or CH_ groups, and wherein one or more CH groups may also be replaced by N, 1 2 . Z and Z m each case independently of one another are -CH 2 CH 2 -, -CO-O-, -O-C0-, -CH 2 0-, -OCH 2 ~, -C≡C- or a single bond, X is H, or in case of Y = F or Cl, also F and n is 0, 1 or 2, and also to liquid crystalline media being a mixture of at least 2 compounds, characterized in that at least one compound is a pyridine derivative according to formula I. The invention was based on the object of discovering new stable liquid crystal or mesogenic compounds which are suitable as components of liquid crystalline media and, in particular have advantageous values of optical and dielectric anisotropy, in particular for the value of Δ ε/ε_j_, combined with high ne atogenity. Similar pyridine compounds with cyano as the terminal group instead of fluoro or chloro atoms or -CF„ groups are, for example, described in EP 0194153. It has now been found that pyridine derivatives of the formula I are highly suitable as components of liquid crystalline media. In particular, they have advantageous values of optical and dielectric anisotropy and especially advantageous low values of Aε/ε \_. A small ratio of Δε/εJ_ has an important influence on the electrooptic charac- teristics of TN liquid crystal cells. It is also possible to obtain stable liquid crystal phases with a broad nematic mesophase range including a good deep temperature behaviour and a comparatively low viscosity with the aid of these compounds. Depending on the choice of the substituents, the com¬ pounds of the formula I can be used as the base materials from which liquid crystal media are predominantly com¬ posed; however, it is also possible for compounds of the formula I to be added to liquid crystal base materials of other classes of compounds, for example in order to influence the dielectric and/or optical anisotropy and/or the viscosity and/or the nematic mesophase range of such a dielectric. The compounds of the formula I are colourless in the pure state and are liquid crystalline in a temperature range which is favourable placed for electrooptical use. They are very stable towards chemicals, heat and light. The compounds of the formula I are further highly useful as starting material for the preparation of liquid crystalline compounds having the structural element - X The invention thus relates to the pyridine derivatives of the formula I, to liquid crystalline media with at least two liquid crystalline compounds, wherein at least one component is a compound of the formula I and to liquid crystal display devices containing such media. Above and below R 1, Y, A1, A2, Z1, Z2, n and X have the meaning indicated, unless something else is specific¬ ally stated. For the sake of simplicity in the following, Phe is a 1,4-phenylene group which may be substituted by one or more halogen atoms and/or CN and/or CH, groups, Cyc is a trans-l,4-cyclohexylene group, Dio is a 1,3-dioxane- 2,5-diyl group, Dit is a l,3-dithian-2,5-diyl group, Pyd is a pyridine-2,5-diyl group and Pyr is a pyrimidine- 2,5-diyl group. PydX denotes the The compounds of the formula I accordingly also include compounds of the partial formulae la to lb (having two rings), Ic to If (having three rings) and Ig to In (having four rings): R^A^PydX-Y la R 1 -A 2 -Z 2 -PydX-Y lb R 1 -A 1 -A 2 -PydX-Y Ic R 1 -A 1 -A 2 -Z 2 -PydX-Y Id R 1 -A 1 -Z 1 -A 2 -PydX-Y Ie R 1 -A 1 -Z 1 -A 2 -Z 2 -PydX-Y If R 1 -A 1 -A 1 -A 2 -PydX-Y Ig R 1 -A 1 -Z 1 -A 1 -A 2 -PydX-Y Ih R 1 -A 1 -A 1 -Z 1 -A 2 -PydX-Y Ii R 1-A1-A1-A2-Z2-PydX-Y Ij 1 1 1 1 1 2 R -A -Z -A -Z -A -PydX-Y Ik 1 1 1 1 2 2 R -A -Z -A -A -Z -PydX-Y II 1 1 1 1 2 2 R -A -A -Z -A -Z -PydX-Y . Im R 1-A1-Z1-A1-Z1-A2-Z2-PydX-Y In Among these, those of the formulae la, lb, Ic, Id, le, Ih, Ii, Ik and II are particularly preferred. The preferred compounds of the partial formulae la include those of the partial formulae laa to lad: R 1 -Phe-PydX-Y ^ laa R 1 -Cyc-PydX-Y lab R^Pyd-PydX-Y lac R^Pyr-PydX-Y lad Among these, those of the formulae laa and lab are particularly preferred. The preferred compounds of the partial formula lb include those of the partial formulae Iba to Ibj : R 1 -Phe-C≡C-PydX-Y Iba R 1 -Cyc-C≡C-PydX-Y Ibb R 1 -Phe-CO-0-PydX-Y Ibc R 1 -Cyc-CO-0-PydX-Y Ibd R 1 -Phe-CH 2 CH 2 -PydX-Y Ibe R 1 -Cyc-CH 2 CH 2 -PydX-Y Ibf R 1 -Phe-CH 2 0-PydX-Y Ibg R 1 -Cyc-CH 2 0-PydX-Y Ibh R 1 -Pyd-Z 2 -PydX-Y Ibi R 1 -Pyr-Z 2 -PydX-Y Ibj Among these, those of the formulae Iba, Ibb, Ibc, Ibd and Ibe are particularly preferred. The preferred compounds of the partial formula Ic include those of the partial formulae lea to Ich: R 1 -Cyc-Cyc-PydX-Y lea R 1 -Phe-Phe-PydX-Y Icb R 1 -Dio-Phe-PydX-Y Ice R 1 -Dit-Phe-PydX-Y led R 1 -Cyc-Phe-PydX-Y Ice R 1 -Phe-Pyd-PydX-Y Icf R 1 -Phe-Pyr-PydX-Y leg R 1 -Phe-Cyc-PydX-Y . Ich Among these, those of the partial formulae lea, Icb, Ice and Icf are particularly preferred. The preferred compounds of the partial formula Id include those of the partial formulae Ida to Idm: R 1 -Cyc-Cyc-C≡C-PydX-Y Ida R 1 -Phe-Phe-C≡C-PydX-Y Idb R 1 -Cyc-Phe-C≡C-PydX-Y Idc R 1 -Cyc-Phe-CH 2 CH 2 -PydX-Y Idd R 1 -Cyc-Cyc-CH 2 CH 2 -PydX-Y Ide R 1 -Phe-Phe-CH 2 CH 2 -PydX-Y Idf R 1 -Cyc-Cyc-COO-PydX-Y Idg R 1 -Phe-Cyc-COO-PydX-Y Idh R 1 -Phe-Phe-COO-PydX-Y Idi R 1 -Cyc-Phe-COO-PydX-Y Idj R 1 -Phe-Phe-CH_0-PydX-Y Idk R,1-Cyc-Phe-CH 2 0-PydX-Y Idl R 1 -Cyc-Cye-CH 2 0-PydX-Y Idm Among these, those of the formulae Ida, Idb, Idc, Ide, Idg and Idh are particularly preferred. The preferred compounds of the partial formula le include those of the partial formulae lea to Iem: R 1 -Cyc-CH 2 CH -Phe-PydX-Y lea R 1 -Phe-CH 2 CH 2 -Phe-PydX-Y leb R 1 -Cyc-C≡C-Phe-PydX-Y Iec R 1 -Phe-C≡C-Phe-PydX-Y led R 1 -Phe-CH 2 0-Phe-PydX-Y lee R 1 -Cyc-COO-Phe-PydX-Y Ief R 1 -Cyc-COO-Cyc-PydX-Y leg R 1 -A 1 -OCO-Phe-PydX-Y Ieh R 1 -A 1 -OCH 2 -Phe-PydX-Y lei R 1 -A 1 -Z 1 -Pyd-PydX-Y Iej R 1 -A 1 -Z 1 -Pyr-PyrdX-Y Iek R 1 -Cyc-C≡C-Cyc-PydX-Y Iel R 1 -Cyc-CH 2 CH 2 -Cyc-PydX-Y Iem Among these, those of partial formulae lea, leb, Iec, led, leg and Iel are particularly preferred. The preferred compounds of the partial formula If include those of the partial formulae Ifa to Ifh: R 1 -A 1 -Z 1 -Phe-C≡C-PydX-Y Ifa R 1 -A 1 -CH 2 CH 2 -Phe-CH 2 CH 2 -PydX-Y Ifb R 1 -A 1 -Z 1 -Phe-CH 2 CH 2 -PydX-Y Ifc R 1 -A 1 -Z 1 -Cyc-COO-PydX-Y Ifd R 1 -Cyc-Z 1 -Cyc-C≡C-PydX-Y Ife R 1 -Cyc-Z 1 -Cyc-CH 2 CH 2 -PydX-Y Iff R 1 -A 1 -COO-Phe-Z 2 -PydX-Y Ifg R 1 -A 1 -CH 2 0-Phe-Z 2 PydX-Y Ifh The preferred compounds of the formulae Ig to In include those of the partial formulae Iga to Igo: R 1 -A 1 -Cyc-Cyc-PydX-Y Iga R 1 -Cyc-Cyc-Phe-PydX-Y Igb R 1 -Phe-Phe-Cyc-PydX-Y Igc R 1 -A 1 -CH 2 CH 2 -A 1 -Cyc-PydX-Y Igd R 1 -Cyc-COO-A 1 -Phe-PydX-Y Ige R 1 -A 1 -A 1 -CH 2 CH 2 -Phe-PydX-Y Igf R 1 -Cyc-Cyc-Z 1 -A 2 -PydX-Y Igg R 1 -A 1 -Phe-Phe-C=C-PydX-Y Igh R 1 -A 1 -Cyc-Phe-C≡C-PydX-Y Igi R 1 -A 1 -A 1 -A 2 -CH 2 CH -PydX-Y Igj R 1 -A 1 -A 1 -A 2 -COO-PydX-Y Igk R 1 -Cyc-COO-A 1 -Z 1 -Phe-PydX-Y Igl R 1 -Phe-C≡C-A 1 -Z 1 -Phe-PydX-Y Igm In the compounds of the formulae above and below Y is F, Cl, -CF 3 , -OCF 3 or -OCF 2 H, preferably F or -CF 3 . X is H or F, preferably H. However, in case of Y is F or Cl, X preferably is F, too. In the compounds of the formulae above and below R is preferably alkyl, alkoxy, oxaalkyl, alkanoyloxy or alkenyl and can exhibit a straight-chain or branched structure. Alkyl or alkoxy preferably are straight-chain and have 2, 3, 4, 5, 6 or 7 C atoms. Accordingly they are prefer¬ ably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, or heptoxy, also methyl, octyl, nonyl, decyl, undecyl, dodecyl, methoxy, octoxy, nonoxy, decoxy or undecoxy. Oxaalkyl is preferably straight-chain 2-oxapropyl (= methoxy methyl), 2-(= ethoxymethyl) or 3-oxybutyl (= 2-methoxyethyl) , 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4- 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-, 7-, 8-, or 9-oxadecyl. Alkenyl is preferably straight-chain and has 2 to 10 C atoms. It is accordingly, in particular, vinyl, prop-1- or prop-2- enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-l-, -2-, -3-, -4- or -5-enyl, hept-1-, -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. Compounds of the formula I containing a branched terminal group can occasionally be of importance because of an improved solubility in the customary liquid crystal base materials, but in particular as ehiral doping substances if they are optically active. Branched groups of this type as a rule contain not more than one chain branching. Preferred branched radicals are isopropyl, 2-butyl (= 1-methylpropyl) , isobutyl (= 2- methylpropyl, 2-methylbutyl, isopentyl, (= 3-methylbutyl), 2-methylpentyl, 2-ethylhexyl, 2-propylpentyl, 2-octyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbut- oxy, 2-methylpentoxy, 3-meth lpentoxy, 2-ethylhexoxy, 2-methylhexoxy, 1-methylhexoxy, 1-methylheptoxy (= 2-octyl- oxy), 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methyl- hexyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methyloctoxy, 6- methyloetanoyloxy, 4-methylheptyloxycarbonyl, 2-methylbuty- ryloxy, 3-methylvaleryloxy, 4-methylhexanoyloxy, 2-methyl-3- oxapentyl and 2-methyl-3-oxahexyl. In the case of compounds with a branched terminal group R , formula I includes both the optical antipodes and racemates as well as mixtures thereof. n is preferably 0 or 1. If n is 2, the two groups A and Z may be identical or different from one another. Z 1 and Z2 are preferably a single bond, a -CH 2 CH 2 ~, a -CO-O- or a -CH 2 CH 2 -group, also -0-CO-, -C__ 2 0- or -OCT_ 2 -. A 1 and A2 are preferably unsubstituted 1,4-phenylene or trans 1,4-cyclohexylene. Compounds wherein A 1 and/or A2 are substituted 1,4-phenylene are also preferred. They are then preferably mono- or disubstituted by fluorine and the 1,4-phenylene group has preferably the following structures: A and A 2 also preferably have the meaning of Pyd or Pyr. The following group of compounds of the formula I is particularly preferred: Alkyl-Phe-CH ZCH Δ Y = F, Cl, -CF 3 or - Alkoxy-Phe-CH CH^-Phe-^O^-Y, Y = F, Cl, -CF, or - Alkyl-Phe-{θ)-Y, Y = F, Cl, -CF, or - ^N Alkoxy-Phe- cT)-Y, Y = F, Cl, -CF 3 or - Y = F, Cl, -CF, or - • R 1 -Cyc-Cyc-CH CH -(cT)-Y, Y = F, Cl, -CF, or - Alkyl-Cyc-COO-(θ N >-Y, Y = F, Cl, -CF 3 or - ^N Alkyl-Cyc-Cyc-COO-(θ)-Y, Y = F, Cl, -CF, or - R 1 -Cyc-Phe -(θ)-Y, Y = F, Cl, -CF, or - R -Cyc-Cyc-(cT.-Y, F, Cl, CF, or -OCF. Y = F or Cl Y = F or Cl Y = F or Cl Y = F or Cl Y = F or Cl Y = F, Cl or -CF, R 1 -Cyc-Cyc- θ -Y, Y = F or Cl F r Y = F, Cl, -CF, or - X X R 1 -Phe-CH 2 CH 2 -Phe- θ -Y, Y = F or Cl Y = F, Cl- -CF, or - X Y = F, Cl -CF 3 or -O R -Cyc-Phe-CH 2 CH 2 -<0)-Y, Y = F, Cl, -CF 3 or - X Y = F or Cl X Of The compounds of the formula I and εubformula thereof, those in which at least one of the radicals contained therein has one of the preferred meanings given are pre- ferred. The compounds of the formula I are prepared by methods which are known per εe, such as are 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), and in particular under reaction conditions which are known and suitable for the reactions mentioned. Variants which are known per se and are not mentioned in more detail here can also be used in this connection. If desired, the starting materials can also be formed in situ, such that they are not isolated from the reaction mixture but are immediately reacted further to give the compounds of the ormula I. The most important starting materials for most of the synthesis routes are the following substances: X X These key intermediates are preparable by the following routes (LDA = lithiumdiisopropylamide) LDA • (θ)-Y > (J) Br-(θ)-Y Br, (J 2 ) ~ N LDA 0)-Y (OH), B-<0)-Y -N 2. B + (0CH 3 ) 3 -N H /H 2 0~ H H + /NaNO 0.,N-(0>-Y — > H N-(0^-Y -> Br-< O^-l 2 Λ -N Pd-C 2 N HBr Λ - N X X CBr^F-, Fe/HCl C1- OS-N0, ^—> * -F",C~-£ / θ' Λ )-N.,O„, > v 2 Cu/Cul 3 S 2 Charcoal X The compounds of the formula I thus can be prepared preferably by the following coupling reactions which are known per se: Scheme 1 X - Pd°-catalyst R 1 -(A 1 -Z 1 X Scheme 2 R 1 -(A 1 -Z 1 ) -Cyc-Br .Pd°-catalyst R 1 -(A 1 -Z 1 ) n -Cyc-(θ)-Y X Scheme 3 R 1 -(A 1 -Z 1 ) Pd(II)-catalyst CuJ R 1 -(A 1 -Z 1 ) -A 2 -C≡C-(0>-Y n X H, Pd-C Scheme 4 R 1 -(A 1 -Z 1 ) n -A 2 -COOH + HO-<0)-Y X φ dicyclohexylcarbodiimide (DCC) dimethylaminopyridine (DMAP) R 1 -(A 1 -Z 1 ) n -A 2 -COO-<O -Y N X Scheme 5 X -C 2) R ,1 1 - (,A.1 1 -Z~1 1 1) H 2 Scheme 6 The compounds of the formula I wherein X denotes -OCF, can be obtained for example from the compounds of the formula I wherein X denotes Cl or F by nucleophilic substitution with sodium trifluoromethanolate. The compounds of the formula I wherein X denotes -OCF_H can be prepared as described in WO 90/01056, for example, by reacting the hydroxypyridines of the formula I' R 1 -(A 1 -Z 1 ) ' -A 2 -Z 2 -{0 -OH I' n Λ"N X with chlorodifluoromethane. The reaction conditions are known to the skilled worker or described in the literature already mentioned. Other routes are apparent to the skilled worker. Compounds of the formula I wherein X = Y = F are highly useful as starting materials for liquid crystalline com¬ pounds with the structural element O Compounds having this structural element are obtained by a nucleophilic substitution of the terminal F atom by -OR, wherein R is an organic residue. In addition to one or more compounds of the formula I the liquid crystal media according to the invention prefer- ably contain 2-40 components and in particular 4-30 com¬ ponents. Liquid crystal media being composed of one or more compounds of formula I and 7-25 other components are especially preferred. These additional components are preferably chosen from the nematic or nematogenic (monotropic or isotropic) substances; in particular from the classes of azoxy- benzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl cyclohexanecarboxylateε, phenyl or cyclohexyl cyclohexyl- benzoates, phenyl or cyclohexyl cyclohexylcyclohexane- carboxylates, cyclohexylphenylbenzoates, cyclohexylphenyl cyclohexanecarboxylates, cyclohexylphenyl cyclohexylcyclo- hexanecarboxylateε, phenylcyclohexaneε, cyclohexylbiphenyls, phenylcyclohexylcyclohexaneε, cyclohexylcyclohexanes, cyclohexyleyelohexenes, cyclohexylcyclohexylcyclohexene, 1,4-bis-cyclohexylbenzenes, 4,4 l -bis-cyclohexylbiphenyls, phenyl- or cyclohexylpyrimidineε, phenyl- or cyclohexyl- pyridines, phenyl- or cyclohexyldioxanes, phenyl- or cyclo- hexyl-l,3-dithianes, 1,2-diphenylethanes, 1,2-dicyclohexyl- ethaneε, l-phenyl-2-cyclohexylethanes, l-cyclohexyl-2-(4- phenyl-cyclohexyl)-ethanes, l-cyclohexyl-2-biphenylethanes, l-phenyl-2-cyclohexyl-phenylethaneε, optionally halogenated εtilbeneε, benzyl phenyl etherε, tolεineε and εubstituted cinnamic acids. The 1,4-phenylene groups of these compounds may be fluorinate The most important compounds which are posεible constituentε of liquid crystal media according to the invention can be characterized by the formalae 1, 2, 3, 4 and 5: R'-L-U-R" 1 R « -L-COO-U-R" 2 R'-L-OOC-U-R" 3 R ! -L-d-^CHg-U-R" 4 R'-L-C≡C-U-R" 5 In the formulae 1, 2, 3, 4 and 5 L and ϋ may be equal or different from each other. L and U independently from each other denote a bivalent residue selected from the group consisting of -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe-, -G-Cyc- and their mirror images; in thiε compilation of reεidueε Phe denotes un- substituted or fluorinated 1, -phenylene, Cyc tranε- 1,4- cyclohexylene or 1,4-cyclohexenylene, Pyr pyrimidine-2,5- diyl or pyridine-2,5-diyl, Dio l,3-dioxane-2,5-diyl and G 2-(tranε-l,4-cyclohexyl)-ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or l,3-dioxane-2,5-diyl. One of the reεidueε L and U iε preferably Cyc, Phe or Pyr. U preferably denotes Cyc, Phe or Phe-Cyc. The liquid crystal media according to the invention preferably contain one or more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with L and U meaning Cyc, Phe and Pyr, εaid liquid cryεtal media further containing at the same time one ore more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with one of the residueε L and U denoting Cyc, Phe and Pyr and the other reεidue being se¬ lected from the group conεiεting of -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Cyc-, said liquid crystal media containing in addition to thiε optionally one or more components se¬ lected from the compoundε of formulae 1, 2, 3, 4 and 5 with L and U being selected from the group consisting of -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc. In a preferred subgroup of the compounds of formulae 1, 2, 3, 4 and 5 (subgroup 1) R' and R" are independent¬ ly from each other alkyl, alkenyl, alkoxy, alkenoxy with up to 8 carbon atoms. R f and R" differ from one another in most of theεe compoundε, one of the residueε uεually being alkyl or alkenyl. In another preferred εubgroup of the compoundε of formulae 1, 2, 3, 4 and 5 (subgroup 2) R" denotes -CN, -CF 3 , -F, -Cl or -NCS while R' has the meaning indicated in subgroup 1 and is preferably alkyl or alkenyl. Other variants of the envisaged subεtituentε in the compounds of formulae 1, 2, 3, 4 and 5 are alεo cuεtomary. Many such subεtances are commercially available. All these substances are obtainable by methods wh-ch are known from the literature or by analogous methods. The liquid crystal media according to the invention pre¬ ferably contain in addition to components selected from subgroup 1 also components of subgroup 2, the percentage of these components being as follows: subgroup 1: 20 to 90 %, in particular 30 to 90 % subgroup 2: 10 to 50 %, in particular 10 to 50 % In these liquid crystal media the percentages of the com¬ pounds according to the invention and the compoundε of sub¬ group 1 and 2 may add up to give 100 %. The media according to the invention preferably contain 1 to 40 %, in particular 5 to 30 % of the compounds ac¬ cording to the invention. Media containing more than 40 %, in particular 45 to 90 % of the compounds according to the invention are further preferred. The media contain preferably 3, 4 or 5 compounds according to the invention. The media according to the invention are prepared in a manner which is customary per se. As a rule, the com¬ ponents are dissolved in one another, advantageously at elevated temperature. The liquid cjrystal media according to the invention can be modified by εuitable additives so that they can be used in all the types of liquid crystal display devices. Such additives are known to the expert and are described in detail in the literature (H. Kelker/ R. Hatz, Handbook of Liquid Crystalε, Verlag Chemie, Weinheim, 1980). For example, it iε poεsible to add pleo- chroic dyestuffε to prepare colored guest-host systemε or εubεtanceε for modifying the dielectric aniεotropy, the viεcoεity and/or the orientation of the nematic phaεeε. The following examples are to be construed as merely illustrative and not limitative, m.p. = melting point, c.p. = clearing point. In the foregoing and in the fol¬ lowing all parts and percentages are by weight and the temperatures are set forth in degrees Celsius. "Custo¬ mary work-up" means that water is added, the mixture is extracted with methylene chloride, the organic phase is separated off, dried and evaporated, and the product is purified by crystallization and/or chromatography. Further are: C: cryεtalline-solid state, S: smectic phase (the index denoting the type of smectic phase), N: nematic phase, Ch: cholesteric phase, I: isotropic phase. The number being embraced by 2 of these symbolε denotes the tempera¬ ture of phase change. Example 1 a) 48.5 mM of magnesium in 8 ml of THF is slowly added under dry nitrogen to a mixture of 44.1 mM of 2- fluoro-5-bromopyridine (obtainable by reacting 2- chloro-5-nitropyridine with anhydrous KF in DMF at 120°, hydrogenation of the nitro-group and trans- ferring the NH 2 ~group with NaN0 2 via the diazonium salt al d with HBr into the bromo-derivative) in 50 ml of THF. The Grignard reagent is refluxed for a further hour, cooled in ice and 53.4 mM of trimethylborate iε added. After εtirring overnight the borate ester is hydrolyεed with dilute HCl, the product extracted into ether, dried and the solvent removed. b) 35 mM of 4-(trans-4-pentylcyclohexyl)-bromobenzene, 38.5 mM of 2-fluoro-pyridine-5-bromic acid and -4 Pd(PPh, ). (4 x 10 ) are refluxed overnight under nitrogen, in a mixture of toluene (45 ml), aqueous N 2 C0 3 (20 ml) and 15 ml of IMS. Customary work-up gives 2-fluoro-5-[4-(trans-4- pentylcyclohexyl)phenyl]-pyridine. The following compoundε are obtained analogouεly: 2-fluoro-5-[4-(trans-4-ethylcyclohexyl)phenyl]-pyridine 2-fluoro-5-[ -(trans-4-propylcyclohexyl)phenyl]-pyridine 2-fluoro-5-[4-(tranε-4-butylcyclohexyl)phenyl]-pyridine 2-fluoro-5-[4-(trans-4-hexylcyclohexyl)phenyl]-pyridine 2-fluoro-5-[4-(tranε-4-heptylcyclohexyl)phenyl]-pyridine 2-chloro-5-[4-(tranε-4-ethylcyclohexyl)phenyl]-pyridine 2-chloro-5-[4-( rans-4-propylcyclohexyl)phenyl]-pyridine, K 142 N 191.3 I vise 80 cSt 2-chloro-5-[4-( rans-4-butylcyclohexyl)phenyl]-pyridine 2-chloro-5-[ -(trans-4-pentylcyclohexyl)phenyl]-pyridine 2-chloro-5-[4-(tranε-4-hexylcyclohexyl)phenyl]-pyridine 2-chloro-5-[4-(tranε-4-heptylcyclohexyl)phenyl]-pyridine 2-trifluoromethyl-5-[4-(trans-4-ethylcyclohexyl)phenyl]- pyridine 2-trifluoromethyl-5-[4-(trans-4-propylcyclohexyl)phenyl]- pyridine 2-trifluoromethyl-5-[ -(trans-4-butylcyclohexyl)phenyl]- pyridine 2-trifluoromethyl-5-[4-(tranε-4-pentylcyclohexyl)phenyl]- pyridine 2-trifluoromethyl-5-[4-(trans-4-hexylcyclohexyl)phenyl]- pyridine 2-trif luoromethyl-5 -[ 4- ( tr anε-4-hep tylcyclohexyl )phenyl] - pyridine 2-fluoro-5-[4-(tranε-4-ethylcyclohexylethyl)phenyl]- pyridine 2-fluoro-5-[4-(tranε-4-propylcyclohexylethyl)phenyl]- pyridine 2-fluoro-5-[4-(tranε-4-butylcyclohexylethyl)phenyl]- pyridine 2-fluoro-5-[4-(tranε-4-pentylcyclohexylethyl)phenyl]- pyridine 2-fluoro-5-[4-(tranε-4-hexylcyclohexylethyl)phenyl]- pyridine 2-fluoro-5-[4-(tranε-4-heptylcyclohexylethyl)phenyl]- pyridine 2-chloro-5-[4- ' (tranε-4-ethylcyclohexylethyl)phenyl]- pyridine 2-chloro-5-[4-(tranε-4-propylcyclohexylethyl)phenyl]- pyridine, K 142 N 159 I viεc 83 cSt 2-chloro-5-[4-(trans-4-butylcyclohexylethyl)phenyl]- pyridine 2-chloro-5-[4-(tranε-4-pentylcyclohexylethyl)phenyl]- pyridine 2-chloro-5-[4-(trans-4-hexylcyclohexylethyl)phenyl]- pyridine 2-chloro-5-[4-(trans-4-heptylcyclohexylethyl)phenyl]- pyridine 2-trifluoromethyl-5-[4-(tranε-4-ethylcyclohexylethyl)- phenyl]-pyridine 2-trifluoromethyl-5-[4-(tranε-4-propylcyclohexylethyl)■ phenyl]-pyridine 2-trifluoromethyl-5-[4-(tranε-4-butylcyclohexylethyl)- phenyl]-pyridine 2-trifluoromethyl-5-[4-(tr-anε-4-pentylcyclohexylethyl)« phenyl]-pyridine 2-trifluoromethyl-5-[4-(tranε-4-hexylcyclohexylethyl)- phenyl]-pyridine 2-trifluoromethyl-5-[4-(tranε-4-heptylcyclohexylethyl)- phenyl]-pyridine 2-fluoro-5-[4-(trans-4-ethylcyclohexyl)-2-fluorophenyl]- pyridine 2-fluoro-5-[4-(trans-4-propylcyclohexyl)-2-fluorophenyl]- pyridine 2-fluoro-5-[4-(trans-4-butylcyclohexyl)-2-fluorophenyl]- pyridine 2-fluoro-5-[4-(trans-4-pentylcyclohexyl)-2-fluorophenyl]- pyridine 2-fluoro-5-[4-(tranε-4-hexylcyclohexyl)-2-fluorophenyl]- pyridine 2-fluoro-5-[4-(trans-4-heptylcyclohexyl)-2-fluorophenyl]- pyridine 2-fluoro-5-[4-(trans-4-octylcyclohexyl)-2-fluorophenyl]- pyridine 2-chloro-5-[4-(trans-4-ethylcyclohexyl)-3-fluorophenyl]- pyridine 2-chloro-5-[4-(tranε-4-propylcyclohexyl)-3-fluorophenyl]- pyridine 2-chloro-5-[4-(tranε-4-butylcyclohexyl)-3-fluorophenyl]- pyridine 2-chloro-5-[4-(trans-4-pentylcyclohexyl)-3-fluorophenyl]- pyridine 2-chloro-5-[4-(tranε-4-hexylcyclohexyl)-3-fluorophenyl]- pyridine 2-chloro-5-[4-(trans-4-heptylcyclohexyl)-3-fluorophenyl]- pyridine 2-trifluoromethyl-5-[4-(tranε-4-ethylcyclohexylethyl)-2- fluorophenyl]-pyridine 2-trifluoromethyl-5-[4-(trans-4-propylcyclohexylethyl)-2- fluorophenyl]-pyridine 2-trifluoromethyl-5-[4-(trans-4-butylcyclohexylethyl)-2- fluorophenyl]-pyridine 2-trifluoromethyl-5-[4-(trans-4-pentylcyclohexylethyl)-2- fluorophenyl]-pyridine 2-trifluoromethyl-5-[4-(trans-4-hexylcyclohexyl)-2-fluoro¬ phenyl]-pyridine 2-trifluoromethyl-5-[4-(trans-4-heptylcyclohexyl)-2-fluoro¬ phenyl] -pyridine 2-trifluoromethyl-5-[4-(trans-4-octylcyclohexyl)-2-fluoro¬ phenyl]-pyridine 2-fluoro-5- 4-ethylbiphenyl-4 » -yl)-pyridine 2-fluoro-5- 4-propylbiphenyl-4'-yl)-pyridine 2-fluoro-5- 4-butylbiphenyl-4'-yl)-pyridine 2-fluoro-5- 4-pentylbiphenyl-4'-yl)-pyridine 2-fluoro-5- 4-hexylbiphenyl-4'-yl)-pyridine 2-fluoro-5- 4-heptylbiphenyl-4*-yl)-pyridine 2-fluoro-5- 2-fluoro-4-ethylbiphenyl-4'-yl)-pyridine 2-fluoro-5- 2-fluoro-4-propylbiphenyl-4'-yl)-pyridine 2-fluoro-5- 2-fluoro-4-butylbiphenyl-4'-yl)-pyridine 2-fluoro-5- 2-fluoro-4-pentylbiphenyl-4'-yl)-pyridine 2-fluoro-5- 2-fluoro-4-hexylbiphenyl-4 • -yl)-pyridine 2-fluoro-5- 2-fluoro-4-heptylbiphenyl-4'-yl)-pyridine 2-chloro-5- -fluoro-4-ethylbiphenyl-4'-yl)-pyridine 2-chloro-5- -fluoro-4-propylbiphenyl-4'-yl)-pyridine 2-chloro-5- -fluoro-4-butylbiphenyl-4'-yl)-pyridine 2-chloro-5- -fluoro-4-pentylbiphenyl-4'-yl)-pyridine 2-chloro-5- -fluoro-4-hexylbiphenyl-4'-yl)-pyridine 2-chloro-5- -fluoro-4-heptylbiphenyl-4'-yl)-pyridine 2-trifluoromethyl-5-(3-fluoro-4-ethylbiphenyl-4'-yl)- pyridine 2-trifluoromethyl-5-(3-fl oro-4-propylbiphenyl-4'-yl)- pyridine 2-trifluoromethyl-5-(3-fluoro-4-butylbiphenyl-4'-yl)- pyridine 2-trifluoromethyl-5-(3-fluoro-4-pentylbiphenyl-4'-yl)- pyridine 2-trifluoromethyl-5-(3-fluoro-4-hexylbiphenyl-4 '-yl)- pyridine 2-trifluoromethyl-5-(3-fluoro-4-heptylbiphenyl-4'-yl)- pyridine 2-trifluoromethyl-5-(3-fluoro-4-methylbiphenyl-4'-yl)- pyridine 2-trifluoromethyl-5-(4-ethoxybiphenyl-4'-yl)-pyridine 2-trifluoromethyl-5-(4-propoxybiphenyl-4'-yl)-pyridine 2-trifluoromethyl-5-(4-methoxybiphenyl-4'-yl)-pyridine 2-trifluoromethyl-5-(4-butoxybiphenyl-4'-yl)-pyridine 2-trifluoromethyl-5-(4-pentyloxybiphenyl-4'-yl)-pyridine 2-trifluoromethyl-5-(4-hexyloxybiphenyl-4'-yl)-pyridine 2-trifluoromethyl-5-(4-heptyloxybiphenyl-4'-yl)-pyridine 2-trifluoromethyl-5-(4-octyloxybiphenyl-4'-yl)-pyridine 2-fluoro-5-(4-ethoxybiphenyl-4'-yl)-pyridine 2-fluoro-5-(4-propoxybiphenyl-4'-yl)-pyridine 2- luoro-5-(4-butoxybiphenyl-4'-yl)-pyridine 2- luoro-5-(4-pentyloxybiphenyl-4*-yl)-pyridine 2-fluoro-5-(4-heptyloxybiphenyl-4'-yl)-pyridine 2-fluoro-5-(4-ethylphenyl)-pyridine 2-fluoro-5-(4-propylphenyl)-pyridine 2-fluoro-5-(4-butylphenyl)-pyridine 2-fluoro-5-(4-pentylphenyl)-pyridine 2-fluoro-5-(4-hexylphenyl)-pyridine 2-fluoro-5-(4-heptylphenyl)-pyridine 2-fluoro-5-(4-ethoxyphenyl)-pyridine 2-fluoro-5-(4-butoxyphenyl)-pyridine 2-fluoro-5-(4-propoxyphenyl)-pyridine 2-fluoro-5-(4-pentyloxyphenyl)-pyridine 2-chloro-5-(4-ethylphenyl)-pyridine 2-chloro-5-(4-propylphenyl)-pyridine 2-chloro-5-(4-butylphenyl)-pyridine 2-chloro-5-(4-pentylphenyl)-pyridine 2-chloro-5-(4-hexylphenyl)-pyridine 2-chloro-5-( -heptylphenyl)-pyridine 2-chloro-5-(4-ethoxyphenyl)-pyridine 2-chloro-5-(4-propoxyphenyl)-pyridine 2-chloro-5-(4-pentyloxyphenyl)-pyridine 2-chloro-5-(4-octyloxyphenyl)-pyridine 2-fluoro-5-(2-fluoro-4-ethylphenyl)-pyridine 2-fluoro-5-(2-fluoro-4-propylphenyl)-pyridine 2-fluoro-5-(2-fluoro-4-butylphenyl)-pyridine 2-fluoro-5-(2-fluoro-4-pentylphenyl)-pyridine 2-fluoro-5-(2-fluoro-4-hexylphenyl)-pyridine 2-fluoro-5-(2-fluoro-4-heptylphenyl)-pyridine 2-trifluoromethyl-5-(4-ethoxyphenyl)-pyridine 2-trifluoromethyl-5-(4-propoxyphenyl)-pyridine 2-trifluoromethyl-5-(4-butoxyphenyl)-pyridine 2-trifluoromet_byl-5-(4-pentyloxyphenyl)-pyridine 2-trifluoromethyl-5-(4-ethylphenyl)-pyridine • 2-trifluoromethyl-5-(4-propylphenyl)-pyridine 2-trifluoromethyl-5-(4-butylphenyl)-pyridine 2-trifluoromethyl-5-(4-pentylphenyl)-pyridine 2-trifluoromethyl-5-(4-hexylphenyl)-pyridine 2-trifluoromethyl-5-(4-heptylphenyl)-pyridine 2-trifluoromethoxy-5-(4-ethylphenyl)-pyridine 2-trifluoromethoxy-5-(4-propylphenyl)-pyridine 2-trifluoromethoxy-5-(4-butylphenyl)-pyridine 2-trifluoromethoxy-5-(4-pentylphenyl)-pyridine 2-difluoromethoxy-5-(4-ethylphenyl)-pyridine 2-difluoromethoxy-5-(4-propylphenyl)-pyridine 2-difluoromethoxy-5-(4-butylphenyl)-pyridine 2-difluoromethoxy-5-(4-pentylphenyl)-pyridine 2-difluoromethoxy-5-(4-hexylphenyl)-pyridine 2-difluoromethoxy-5-(4-ethoxyphenyl)-pyridine Example 2 To a mixture of 0.1 M of 2,6-difluoro-3-hydroxypyridine (obtainable by reaction of 2,6-difluoro-pyridine-3-boronic acid with H 2 0 2 in ether), 0.1 M of trans-4-pentylcyclo- hexane earboxylic acid, 0.1 M dimethylaminopyridine (DMAP) and 200 ml of CH 2 C1 2 a solution of 0.11 M of dicyclohexyl¬ carbodiimide (DCC) in CH 2 C1 2 is added at 15-20 °C. After εtirring for 5 hourε at room temperature and cuεtomary work-up, 2,6-difluoropyridine-3-yl trans- 4-pentylcyclohexanecarboxylate is obtained. The following components are obtained analogously: 2,6-difluoropyridine-3-yl trans-4-ethylcyclohexanecarb- oxylate 2,6-difluoropyridine-3-yl trans-4-propylcyclohexanecarb- oxylate 2,6-difluoropyridine-3-yl trans-4-butylcyclohexanecarb- ox late 2,6-difluoropyridine-3-yl trans-4-(tranε-4-ethylcyclo- hexyl)-cyclohexanecarboxylate 2,6-difluoropyridine-3-yl trans-4-(tranε-4-propylcyclo- hexyl)-cyclohexanecarboxylate 2,6-difluoropyridine-3-yl tranε-4-(trans-4-butylcyclo- hexyl)-cyclohexanecarboxylate 2,6-difluoropyridine-3-yl trans-4-(tranε-4-pentylcyclo- hexyl)-cyclohexanecarboxylate 2-fluoropyridine-5-yl trans-4-(tranε-4-ethylcyclohexyl)- cyclohexanecarboxylate 2-fluoropyridine-5-yl trans-4-(tranε-4-propylcyclohexyl)- cyclohexanecarboxylate 2-fluoropyridine-5-yl trans-4-(trans-4-butylcyclohexyl)- cyclohexanecarboxylate 2-fluoropyridine-5-yl tranε-4-(tranε-4-pentylcyclohexyl)- cyclohexanecarboxylate 2-fluoropyridine-5-yl trans-4-(trans-4-heptylcyclohexyl)- cyclohexanecarboxylate 2-chloropyridine-5-yl trans-4-(trans-4-ethylcyclohexyl)- cyclohexanecarboxylate 2-chloropyridine-5-yl trans-4-(tranε-4-propylcyclohexyl)- cyclohexanecarboxylate 2-chloropyridihe-5-yl tranε-4-(tranε-4-butylcyclohexyl)- cyclohexanecarboxylate 2-chloropyridine-5-yl trans-4-(trans-4-pentylcyclohexyl)- cyclohexanecarboxylate 2-chloropyridine-5-yl trans-4-(trans-4-octylcyclohexyl)- cyc1ohexanecarboxy1a e 2-trifluoromethylpyridine-5-yl tranε-4-ethylcyclohexane¬ carboxylate 2-trifluoromethylpyridine-5-yl tranε-4-propylcyclohexane¬ carboxylate 2-trifluoromethylpyridine-5-yl trans-4-butylcyclohexane- carboxylate 2-trifluoromethylpyridine-5-yl trans-4-pentylcyclohexane¬ carboxylate 2-trifluoromethylpyridine-5-yl trans-4-hexylcyclohexane¬ carboxylate 2-trifluoromethoxypyridine-5-yl trans-4-propylcyclohexane- carboxylate 2-trifluoromethoxypyridine-5-yl tranε-4-butylcyclohexane- carboxylate 2-trifluoromethoxypyridine-5-yl tranε-4-pentylcyclohexane- carboxylate 2-trifluoromethoxypyridine-5-yl tranε-4-hexylcyclohexane- carboxylate 2-difluoromethoxypyridine-5-yl trans-4-propylcyclohexane- carboxylate 2-difluoromethoxypyridine-5-yl tranε-4-butylcyclohexane¬ carboxylate 2-difluoromethoxypyridine-5-yl tranε-4-pentylcyclohexane¬ carboxylate 2-difluoromethoxypyridine-5-yl tranε-4-hexylcyclohexane- carboxylate 2-difluoromethoxypyridine-5-yl trans-4-heptylcyclohexane- carboxylate 2-fluoro-6-chloropyridine-3-yl trans-4-ethylcyclohexane¬ carboxylate 2-fluoro-6-chloropyridine-3-yl trans-4-propylcyclohexane- carboxylate 2-fluoro-6-chloropyridine-3-yl trans-4-butylcyclohexane¬ carboxylate 2-fluoro-6-chloropyridine-3-yl trans-4-pentylcyclohexane- carboxylate 2,6-difluoropyridine-3-yl 4-ethylbenzoate 2, 6-difluoropyridine-3-yl 4-propylbenzoate 2,6-difluoropyridine-3-yl 4-butylbenzoate 2,6-difluoropyridine-3-yl 4-pentylbenzoate 2,6-difluoropyridine-3-yl 4-ethoxybenzoate 2,6-difluoropyridine-3-yl 4-propoxybenzoate 2,6-difluoropyridine-3-yl 4-butoxybenzoate 2,6-difluoropyridine-3-yl 4-pentyloxybenzoate 2,6-difluoropyridine-3-yl 4-hexyloxybenzoate 2,6-difluoropyridine-3-yl 4-heptyloxybenzoate 2,6-difluoropyridine-3-yl 4-octyloxybenzoate 2-fluoropyridine-5-yl 4-ethylbenzoate 2-fluoropyridine-5-yl 4-propylbenzoate 2-fluoropyridine-5-yl 4-butylbenzoate 2-fluoropyridine-5-yl 4-pentylbenzoate 2-fluoropyridine-5-yl 4-ethoxybenzoate 2-fluoropyridine-5-yl 4-propoxybenzoate 2-fluoropyridine-5-yl 4-butoxybenzoate 2-fluoropyridine-5-yl 4-pentyloxybenzoate 2-fluoropyridine-5-yl 4-hexyloxybenzoate 2-fluoropyridine-5-yl 4-heptyloxybenzoate 2-fluoropyridine-5-yl 4-octyloxybenzoate 2-trifluoromethylpyridine-5-yl 4-ethylbenzoate 2-trifluoromethylpyridine-5-yl 4-propylbenzoate 2-trifluoromethylpyridine-5-yl 4-butylbenzoate 2-trifluoromethylpyridine-5-yl 4-pentylbenzoate 2-trifluoromethoxypyridine-5-yl 4-ethoxybenzoate 2-trifluoromethoxypyridine-5-yl 4-propoxybenzoate 2-trifluoromethoxypyridine-5-yl 4-butoxybenzoate 2-trifluoromethoxypyridine-5-yl 4-penthyloxybenzoate 2-trifluoromethoxypyridine-5-yl 4-hexyloxybenzoate 2-trifluoromethoxypyridine-5-yl 4-heptyloxybenzoate 2-trifluoromethoxypyridine-5-yl 4-octyloxybenzoate 2-difluoromethoxypyridine-5-yl 4-ethoxybenzoate 2-difluoromethoxypyridine-5-yl 4-propoxybenzoate 2-difluoromethoxypyridine-5-yl 4-butoxybenzoate 2-difluoromethoxypyridine-5-yl 4-pentoxybenzo ' ate 2-difluoromethoxypyridine-5-yl 4-hexoxybenzoate 2-difluoromethoxypyridine-5-yl 4-heptoxybenzoate 2-fluoropyridine-5-yl tranε-4-ethylcyclohexanecarboxylate 2-fluoropyridine-5-yl tranε-4-propylcyclohexanecarboxylate 2-fluoropyridine-5-yl tranε-4-butylcyclohexanecarboxylate 2-fluoropyridine-5-yl trans-4-pentylcyclohexanecarboxylate 2-trifluoromethylpyridine-5-yl trans-4-(trans-4-ethyl- cyclohexyl)-cyclohexanecarboxylate 2-trifluoromethylpyridine-5-yl tranε-4-(trans-4-propyl- cyclohexyl)-cyclohexanecarboxylate 2-trifluoromethylpyridine-5-yl trans-4-(trans-4-butyl- cyclohexyl)-cyclohexanecarboxylate 2-trifluoromethylpyridine-5-yl trans-4-(trans-4-pentyl- cyclohexyl)-cyclohexanecarboxylate 2-chloropyridine-5-yl 4-(4-ethylphenyl)benzoate 2-chloropyridine-5-yl 4-(4-propylphenyl)benzoate 2-chloropyridine-5-yl 4-(4-butylphenyl)benzoate 2-chloropyridine-5-yl 4-(4-pentylphenyl)benzoate 2-chloropyridine-5-yl 4-(4-octylphenyl)benzoate 6-chloro-2-fluoropyridine-3-yl 4-(4-ethylphenyl)benzoate 6-chloro-2-fluoropyridine-3-yl 4-(4-propylphenyl)benzoate 6-chloro-2-fluoropyridine-3-yl 4-(4-butylphenyl)benzoate 6-chloro-2-fluoropyridine-3-yl 4-(4-pentylphenyl)benzoate 6-chloro-2-fluoropyridine-3-yl 4-(4-heptylphenyl)benzoate 2,6-di luoropyridine-3-yl 4-(trans-4-ethylcyclohexyl)- benzoate 2,6-difluoropyridine-3-yl 4-(trans-4-propylcyclohexyl)- benzoate 2,6-difluoropyridine-3-yl 4-(tranε-4-butylcyclohexyl)- benzoate 2,6-difluoropyridine-3-yl 4-(trans-4-pentylcyclohexyl)- benzoate 2,6-difluoropyridine-3-yl trans-4-(4-ethylphenyl)cyclo¬ hexanecarboxylate 2,6-difluoropyridine-3-yl trans-4-(4-propylphenyl)cyclo- hexanecarboxylate 2,6-difluoropyridine-3-yl trans-4-(4-butylphenyl)cyclo¬ hexanecarboxylate 2, 6-difluoropyridine-3-yl trans-4-(4-pentylphenyl)cyclo¬ hexanecarboxyl te Example 3 a) .0,6 M of n-butyllithium are added at -10° to 0,6 M of diisopropylamin in 600 ml THF. The mixture is cooled to -70°, 0,6 M of 2, 6-difluoropyridin are added and after stirring for 15 minutes 0,6 M of trimethylborate are added at the same temperature. The mixture is allowed to warm up to -30°. Then the borate ester is hydrolyεed with dilute HCl, the product extracted with ether, washed, dried and the solvent removed. Thus, 2, 6-difluoro-pyridine-3- boronic acid is obtained. b) A mixture of 0,05 M of 4-(trans-4-pentylcyclohexyl)- bromobenzene, 0,06 M of 2,6-di luoropyridine-3- boronic acid, 1,25 g of Pd(PPh 3 ) 4 , 100 ml of toluene, 40 ml of ethanol and 50 ml of 2 M Na 2 CO,-solution is heated at 60 °C under stirring for 2 hour^ . Customary work-up and recrystalliεation from ethanol gives 2,6-difluoro-3-[4-(trans-4-pentylcyclohexyl)- phenyl] -pyridine with C 58° N 107° I. The following compounds are obtained analogously: 2,6-difluoro-3-[4-(tranε-4-ethylcyclohexyl)phenyl]- pyridine 2,6-difluoro-3-[4-(trans-4-propylcyclohexyl)phenyl] - pyridine 2,6-difluoro-3-[4-(tranε-4-butylcyclohexyl)phenyl]- pyridine 6-chloro-2- luoro-3-[4-(trans-4-ethylcyclohexylJphenyl]- pyridine 6-chloro-2-fluoro-3-[4-(trans-4-propylcyclohexyl)phenyl]- pyridine 6-chloro-2-fluoro-3-[4-( ranε-4-butylcyclohexyl)phenyl]- pyridine 6-chloro-2-fluoro-3-[4-(tranε-4-pentylcyclohexyl)phenyl]- pyridine 6-chloro-2-fluoro-3-[4-(trans-4-hexylcyclohexyl)phenyl]- pyridine 2,6-difluroro-3-[4-(trans-4-ethylcyclohexylethyl)phenyl]- pyridine 2,6-difluroro-3-[4-(trans-4-propylcyclohexylethyl)phenyl]- pyridine 2,6-difluroro-3-[4-(trans-4-butylcyclohexylethyl)phenyl]- pyridine 2,6-difluroro-3-[4-(trans-4-pentylcyclohexylethyl)phenyl]- pyridine 2,6-difluroro-3-[4-(trans-4-octylcyclohexylethyl)phenyl]- pyridine 6-chloro-2-fluoro-3-[4-(trans-4-ethylcyclohexylethyl)- phenyl]-pyridine 6-chloro-2-fluoro-3-[4-(trans-4-propylcyclohexylethyl)- phenyl]-pyridine 6-chloro-2-fluoro-3-[4-(trans-4-butylcyclohexylethyl)- phenyl]-pyridine 6-chloro-2-fluoro-3-[4-(tranε-4-pentylcyclohexylethyl)- phenyl]-pyridine 2,6-difluoro-3-[4-(trans-4-ethylcyclohexyl)-2-fluoro¬ phenyl]-pyridine 2, 6-difluoro-3-[4-(trans-4-propylcyclohexyl)-2-fluoro¬ phenyl]-pyridine 2,6-difluoro-3-[4-(trans-4-butylcyclohexyl)-2-fluoro¬ phenyl] -pyridine 2,6-difluoro-3-[4-(trans-4-pentylcyclohexyl)-2-fluoro¬ phenyl]-pyridine 2, 6-difluoro-3-[4-(trans-4-heptylcyclohexyl)-2-fluoro- phenyl]-pyridine 2,6-difluoro-3-(4-ethylbiphenyl-4'-yl)-pyridine 2, 6-difluoro-3-(4-propylbiphenyl-4*-yl)-pyridine 2, 6-difluoro-3-(4-butylbiphenyl-4'-yl)-pyridine 2, 6-difluoro-3-(4-pentylbiphenyl-4*-yl)-pyridine 2,6-difluoro-3-(4-ethoxybiphenyl-4'-yl)-pyridine 2, 6-difluoro-3-(4-propoxybiphenyl-4 f -yl)-pyridine 2, 6-difluoro-3-(4-butoxybiphenyl-4'-yl)-pyridine 2, 6-difluoro-3-(4-pentyloxybiphenyl-4 1 -yl)-pyridine 2,6-difluoro-3-(4-hexyloxybiphenyl-4*-yl)-pyridine 2, 6-difluoro-3-(4-heptyloxybiphenyl-4'-yl)-pyridine 2,6-difluoro-3-(4-octyloxybiphenyl-4 » -yl)-pyridine 2,6-difluoro-3-(4-ethylphenyl)-pyridine 2,6-difluoro-3-(4-propylphenyl)-pyridine 2,6-difluoro-3-(4-butylphenyl)-pyridine 2, 6-difluoro-3-(4-pentylphenyl)-pyridine 6-chloro-2-fluoro-3-(4-ethylphenyl)-pyridine 6-chloro-2-fluoro-3-(4-propylphenyl)-pyridine 6-chloro-2-fluoro-3-( -butylphenyl)-pyridine 6-chloro-2-fluoro-3-(4-pentylphenyl)-pyridine 6-chloro-2-fluoro-3-(4-hexylphenyl)-pyridine 2,6-difluoro-3-(4-ethoxyphenyl)-pyridine 2,6-difluoro-3-(4-propoxyphenyl)-pyridine 2,6-difluoro-3-(4-butoxyphenyl)-pyridine 2,6-difluoro-3-(4-pentyloxyphenyl)-pyridine 2,6-difluoro-3-(4-octyloxyphenyl)-pyridine Example 4 0,2 mM of Pd(Ph 3 P) 2 Cl 2 and 0,1 mM of CuJ are added to a mixture of 0,01 M of 3-bromo-2,6-difluoropyridine (pre¬ paration: 2,6-difluoropyridine is reacted with lithium- diisopropylamide (LDA) as described in example 3a, then Br 2 is added at -60° to -70°. The mixture is allowed to warm up to room temperature and worked up, the product is purified by distillation), 0,01 M of 4-pentylphenyl- acetylene and 200 ml of triethylamine. The mixture is stirred for 8 hours at room temperature; after customary work-up and purification by crystallization and chroma- tography 1-(4-pentylphenyl)-2-(2,6-difluoropyridine-3- yl)acetylene is obtained. The following compounds are obtained analogously: 1-(4-ethylphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene 1-(4-propylphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene 1-(4-butylphenyl)-2-(2,6-di luoropyridine-3-yl)acetylene 1-(4-hexylphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene l-(4-ethoxyphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene 1-(4-butoxyphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene 1-(4-methoxyphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene 1-(4-propoxyphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene 1-(4-pentyloxyphenyl)-2-(2,6-difluoropyridine-3-yl)-acetylen l-(4-ethylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetylen l-(4-propylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetyle 1-(4-butylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetylen l-(4-pentylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetyle 1-(4-ethylbiphenyl-4'-yl)-2-(2, 6-difluoropyridine-3-yl)- acetylene l-(4-propylbiphenyl-4'-yl)-2-(2, 6-difluoropyridine-3-yl)- acetylene 1-(4-butylbiphenyl-4'-yl)-2-(2, 6-difluoropyridine-3-yl)- acetylene l-(4-pentylbiphenyl-4'-yl)-2-(2, 6-difluoropyridine-3-yl)- acetylene l-(4-ethoxybiphenyl-4'-yl)-2-(2, 6-difluoropyridine-3-yl)- acetylene 1-(4-propoxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)- acetylene l-(4-butoxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)- acetylene 1-(4-pentyloxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)- acetylene l-[4-(trans-4-ethylcyclohexyl)phenyl]-2-(2,6-difluoro- pyridine-3-yl)acetylene l-[4-(trans-4-propylcyclohexyl)phenyl] -2-(2,6-difluoro¬ pyridine-3-yl)acetylene l-[4-(tranε-4-butylcyclohexyl)phenyl] -2-(2,6-difluoro¬ pyridine-3-yl)acetylene l-[4-(trans-4-pentylcyclohexyl)phenyl]-2-(2,6-difluoro- pyridine-3-yl)acetylene l-[trans-4-(4-ethylphenyl)cyclohexyl]-2-(2,6-difluoro¬ pyridine-3-yl)acetylene ' 1-[trans-4-(4-propylphenyl)cyclohexyl]-2-(2,6-difluoro- pyridine-3-yl)acetylene 1-[trans-4-(4-butylphenyl)cyclohexyl]-2-(2,6-difluoro¬ pyridine-3-yl)acetylene 1-[tranε-4-(4-pentylphenyl)cyclohexyl]-2-(2,6-difluoro¬ pyridine-3-yl)acetylene l-[tranε-4-(4-hexylphenyl)cyclohexyl]-2-(2,6-difluoro- pyridine-3-yl)acetylene 1-[tranε-4-(tranε-4-ethylcyclohexyl)cyclohexyl]-2- (2,6-difluoropyridine-3-yl)acetylene l-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-2- (2, 6-difluoropyridine-3-yl)acetylene 1-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]-2- (2,6-difluoropyridine-3-yl)acetylene 1-[trans-4-(tranε-4-pentylcyclohexyl)cyclohexyl]-2- (2,6-difluoropyridine-3-yl)acetylene 1-[trans-4-( rans-4-heptylcyclohexyl)cyclohexyl]-2- (2, 6-difluoropyridine-3-yl)acetylene 1-(trans-4-ethylcyclohexyl)-2-(2,6-difluoropyridine- 3-yl)acetylene 1-(trans-4-propylcyclohexyl)-2-(2,6-difluoropyridine- 3-yl)acetylene l-(trans-4-butylcyclohexyl)-2-(2,6-difluoropyridine- 3-yl)acetylene 1-(tranε-4-pentylcyclohexyl)-2-(2,6-difluoropyridine- 3-y1)acetylene l-[trans-4-(4-ethoxyphenyl)cyclohexyl]-2-(2,6-difluoro- pyridine-3-yl)acetylene 1-[trans-4-(4-propoxyphenyl)cyclohexyl] -2-(2, 6-difluoro¬ pyridine-3-yl)acetylene l-[trans-4-(4-butoxyphenyl)cyclohexyl] -2-(2, 6-difluoro- pyridine-3-yl)acetylene 1-[trans-4-(4-pentyloxyphenyl)cyclohexyl] -2-(2,6-difluoro- pyridine-3-yl)acetylene l-[trans-4-(4-octyloxyphenyl)cyclohexyl] -2-(2, 6-difluoro- pyridine-3-yl)acetylene 1-[4-(trans-4-ethylcyclohexyl)phenyl)-2-(6-chloro-2- fluoropyridine-3-yl)acetylene l-[4-(tranε-4-propylcyclohexyl)phenyl)-2-(6-chloro-2- fluoropyridine-3-yl)acetylene 1-[4-(trans-4-butylcyclohexyl)phenyl)-2-(6-chloro-2- fluoropyridine-3-yl)acetylene 1-[4-(trans-4-pentylcyclohexyl)phenyl)-2-(6-chloro-2- fluoropyridine-3-yl)acetylene Example 5 Hydrogenation of 1-(4-pentylphenyl)-2-(2,6-difluoro¬ pyridine-3-yl)acetylene yields after cuεtomary work-up 1-(4-pentyϊphenyl)-2-(2,6-difluoropyridine-3-yl)ethane. The following compounds are obtained analogouεly: 1-(4-ethylphenyl)-2-(2, 6-difluoropyridine-3-yl)ethane 1-(4-propylphenyl)-2-(2,6-difluoropyridine-3-yl)ethane 1-(4-butylphenyl)-2-(2,6-difluoropyridine-3-yl)ethane 1-(4-hexylphenyl)-2-(2,6-difluoropyridine-3-yl)ethane 1-(4-ethoxyphenyl)-2-(2, 6-difluoropyridine-3-yl)ethane 1-(4-butoxyphenyl)-2-(2,6-difluoropyridine-3-yl)ethane 1-(4-methoxyphenyl)-2-(2,6-difluoropyridine-3-yl)ethane 1-(4-propoxyphenyl)-2-(2,6-difluoropyridine-3-yl)ethane 1-(4-pentyloxyphenyl)-2-(2,6-difluoropyridine-3-yl)ethane 1-(4-ethylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)ethane 1-(4-propylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)ethane 1-(4-butylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)ethane 1-(4-pentylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)ethane l-(4-ethylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)- ethane 1-(4-propylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)- ethane 1-(4-butylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)- ethane l-(4-pentylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)- ethane 1-(4-ethoxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)- ethane 1-(4-propoxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)- ethane 1-(4-butoxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)- ethane 1-(4-pentyloxybiphenyl-4•-yl)-2-(2,6-difluoropyridine-3-yl)- ethane 1-[4-(tranε-4-ethylcyclohexyl)phenyl] -2-(2,6-difluoro¬ pyridine-3-yl)ethane l-[4-(tranε-4-propylcyclohexyl)phenyl]-2-(2,6-difluoro¬ pyridine-3-yl)ethane l-[4-(tranε-4-butylcyclohexyl)phenyl]-2-(2,6-difluoro¬ pyridine-3-yl)ethane 1-[ -(trans-4-pentylcyclohexyl)phenyl] -2-(2, 6-difluoro¬ pyridine-3-yl)ethane 1-[tranε-4-(4-ethylphenyl)cyclohexyl]-2-(2, 6-difluoro¬ pyridine-3-yl)ethane 1-[tranε-4-(4-propylphenyl)cyclohexyl]-2-(2, 6-difluoro¬ pyridine-3-yl)ethane 1-[tranε-4-(4-butylphenyl)cyclohexyl]-2-(2,6-difluoro¬ pyridine-3-yl)ethane 1-[tranε-4-(4-pentylphenyl)cyclohexyl]-2-(2,6-difluoro- pyridine-3-yl)ethane l-[tranε-4-(4-hexylphenyl)cyclohexyl]-2-(2,6-difluoro- pyridine-3-yl) ' ethane l-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]-2- (2,6-difluoropyridine-3-yl)ethane l-[tranε-4-(trans-4-propylcyclohexyl)cyclohexyl]-2- (2, 6-difluoropyridine-3-yl)ethane l-[trans-4-(tranε-4-butylcyclohexyl)cyclohexyl] -2- (2,6-difluoropyridine-3-yl)ethane 1-[trans-4-(tranε-4-pentylcyclohexyl)cyclohexyl]-2- (2,6-difluoropyridine-3-yl)ethane 1-[tranε-4-(trans-4-heptylcyclohexyl)cyclohexyl]-2- (2, 6-difluoropyridine-3-yl)ethane 1-(trans-4-ethylcyclohexyl)-2-(2,6-difluoropyridine- 3-yl)ethane 1-(trans-4-propylcyclohexyl)-2-(2, 6-difluoropyridine- 3-yl)ethane 1-(tranε-4-butylcyclohexyl)-2-(2,6-difluoropyridine- 3-yl)ethane 1-(trans-4-pentylcyclohexyl)-2-(2,6-difluoropyridine- 3-yl)ethane 1-[trans-4-(4-ethoxyphenyl)cyclohexyl]-2-(2,6-difluoro¬ pyridine-3-yl)ethane 1-[trans-4-(4-propoxyphenyl)cyclohexyl]-2-(2, 6-difluoro¬ pyridine-3-yl)ethane 1-[tranε-4-(4-butoxyphenyl)cyclohexyl]-2-(2,6-difluoro¬ pyridine-3-yl)ethane 1-[tranε-4-(4-pentyloxyphenyl)cyclohexyl]-2-(2, 6-difluoro¬ pyridine-3-yl)ethane l-[tranε-4-(4-octyloxyphenyl)cyclohexyl]-2-(2,6-difluoro- pyridine-3-yl)ethane 1-[4-(tranε-4-ethylcyclohexyl)phenyl)-2-(6-chloro-2- fluoropyridine-3-yl)ethane 1-[4-(trans-4-propylcyclohexyl)phenyl)-2-(6-chloro-2- fluoropyridine-3-yl)ethane 1-[4-(tranε-4-butylcyclohexyl)phenyl)-2-(6-chloro-2- fluoropyridine-3-yl)ethane 1~[4-(tranε-4-pentylcyclohexyl)phenyl)-2-(6-chloro-2- fluoropyridine-3-yl)ethane Example 6 Analogously to Example 4 1-(4-pentylphenyl)-2-(2-fluoro- pyridine-5-yl)acetylene is obtained by reacting 2-fluoro- 5-bromopyridine (preparation deεcribed in example la) with 4-pentylphenylacetylene. The following compoundε are obtained analogously: 1-(4-ethylphenyl)-2-(2-fluoropyridine-5-yl)acetylene 1-(4-propylphenyl)-2-(2-fluoropyridine-5-yl)acetylene 1-(4-butylphenyl)-2-(2-fluoropyridine-5-yl)acetylene 1-(4-heptylphenyl)-2-(2-fluoropyridine-5-yl)acetylene 1-(4-ethoxyphenyl)-2-(2-fluoropyridine-5-yl)acetylene 1-(4-propoxyphenyl)-2-(2-fluoropyridine-5-yl)acetylene 1_(4-butoxyphenyl)-2-(2-fluoropyridine-5-yl)acetylene 1-(4-pentyloxyphenyl)-2-(2-fluoropyridine-5-yl)acetylene l-(4-ethylphenyl)-2-(2-chloropyridin-5-yl)acetylene 1-(4-propylphenyl)-2-(2-chloropyridin-5-yl)acetylene l-(4-butylphenyl)-2-(2-chloropyridin-5-yl)acetylene 1-(4-pentylphenyl)-2-(2-chloropyridin-5-yl)acetylene l-(4-ethoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)- acetylene 1-(4-propoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)- acetylene 1-(4-butoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)- acetylene l -(4-pentyloxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)- acetylene l-(4-ethoxyphenyl)-2-(2-trifluormethoxypyridine-5-yl)- acetylene 1 -( 4 -propoxyphenyl)-2-(2-trifluormethoxypyridine-5-yl)- acetylene 1-(4-butoxyphenyl)-2-(2-trifluormethoxypyridine-5-yl)- acetylene 1_(4-pentyloxyphenyl)-2-(2-trifluormethoxypyridine-5-yl)- acetylene i-(4-propyloxyphenyl)-2-(2-trifluormethoxypyridine-5-yl)- acetylene 1_(4-ethoxyphenyl)-2-(2-chloropyridine-5-yl)acetylene 1- ( 4-propoxyphenyl)-2-(2-chloropyridine-5-yl)acetylene 1-(4-butoxyphenyl)-2-(2-chloropyridine-5-yl)acetylene l - (4 -pentyloxyphenyl)-2-(2-chloropyridine-5-yl)acetylene l-(4-ethylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)- acetylene ■ l-(4-propylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)- acetylene l-(4-butylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)- acetylene 1-(4-pentylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)- acetylene l-(4-ethylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine- 5-yl)acetylene l-(4-propylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine- 5-yl)acetylene l-(4-butylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine- 5-yl)acetylene 1-(4-pentylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine- 5-yl) cetylene l-(4-ethylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine- 5-yl)acetylene 1-(4-propylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine- 5-yl)acetylene 1-(4-butylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine- 5-yl)acetylene l-(4-pentylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine- 5-yl)acetylene 1-(4-hexylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine- 5-yl)acetylene 1-[4-(trans-4-ethylcyclohexyl)phenyl]-2-[2-fluoro- pyridine-5-yl]acetylene 1_[4_(tranε-4-propylcyclohexyl)phenyl] -2-[2-fluoro- pyridine-5-yl] acetylene 1-[4-(tranε-4-butylcyclohexyl)phenyl] -2-[2-fluoro¬ pyridine-5-yl] acetylene 1-[4-(trans-4-pentylcyclohexyl)phenyl]-2-[2-fluoro- pyridine-5-yl]acetylene 1-[4-(trans-4-octylcyclohexyl)phenyl]-2-[2-fluoro- pyridine-5-yl]acetylene 1-[trans-4-(4-ethylphenyl)cyclohexyl]-2-(2-chloro- pyridine-5-yl)acetylene 1-[trans-4-(4-propylphenyl)cyclohexyl]-2-(2-chloro- pyridine-5-yl)acetylene l-[trans-4-(4-butylphenyl)cyclohexyl]-2-(2-chloro- pyridine-5-yl)acetylene 1-[trans-4-(4-pentylphenyl)cyclohexyl]-2-(2-chloro- pyridine-5-yl)acetylene 1-[trans-4-(4-ethoxyphenyl)cyclohexyl]-2-(2-fluoro- pyridine-5-yl)acetylene l-[trans-4-(4-propoxyphenyl)cyclohexyl]-2-(2-fluoro¬ pyridine-5-yl)acetylene 1-[tranε-4-(4-butoxyphenyl)cyclohexyl] -2-(2-fluoro- pyridine-5-yl)acetylene l-[trans-4-(4-pentyloxyphenyl)cyclohexyl] -2-(2- luoro- pyridine-5-yl)acetylene l-(trans-4-ethylcyclohexyl)-2-(2-fluoropyridine-5-yl)- acetylene * * l-(tranε-4-propylcyclohexyl)-2-(2-fluoropyridine-5-yl)- acetylene 1-(tranε-4-butylcyclohexyl)-2-(2-fluoropyridine-5-yl)- acetylene 1-(trans-4-pentylcyclohexyl)-2-(2-fluoropyridine-5-yl)- acetylene 1-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]-2- (2-trifluoromethylpyridine-5-yl)acetylene l-[tranε-4-(tranε-4-propylcyclohexyl)cyclohexyl]-2- (2-trifluoromethylpyridine-5-yl)acetylene 1-[trans-4-(trans-4-butylcycIohexyl)cyclohexyl]-2- (2-trifluoromethylpyridine-5-yl)acetylene 1-[trans-4-(tranε-4-pentylcyclohexyl)cyclohexyl]-2- (2-tri luoromethylpyridine-5-yl)acetylene l-[trans-4-(trans-4-heptylcyclohexyl)cyclohexyl]-2- (2-trifluoromethylpyridine-5-yl)acetylene 1-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl] -2- (2-fluoropyridine-5-yl)acetylene 1-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-2- (2-fluoropyridine-5-yl)acetylene l-[trans-4-(tranε-4-butylcyclohexyl)cyclohexyl] -2- (2-fluoropyridine-5-yl)acetylene 1-[tranε-4-(tranε-4-pentylcyclohexyl)cyclohexyl]-2- (2-fluoropyridine-5-yl)acetylene Example 7 Hydrogenation of l-(4-pentylphenyl)-2-(2-fluoropyridine- 5-yl)acetylene yields after customary work-up l-(4- pentylphenyl)-2-(2-fluoropyridine-5-yl)ethane. The following compounds are prepared analogously: 1-(4-ethylphenyl)-2-(2-fluoropyridine-5-yl)ethane 1-(4-propylphenyl)-2-(2-fluoropyridine-5-yl)ethane 1-(4-butylphenyl)-2-(2-fluoropyridine-5-yl)ethane l-(4-heptylphenyl)-2-(2-fluoropyridine-5-yl)ethane 1-(4-ethoxyphenyl)-2-(2-fluoropyridine-5-yl)ethane 1-(4-propoxyphenyl)-2-(2-fluoropyridine-5-yl)ethane 1-(4-butoxyphenyl)-2-(2-fluoropyridine-5-yl)ethane 1-(4-pentyloxyphenyl)-2-(2-fluoropyridine-5-yl)ethane l-(4-ethylphenyl)-2-(2-chloropyridin-5-yl)ethane l-(4-propylphenyl)-2-(2-chloropyridin-5-yl)ethane 1-(4-butylphenyl)-2-(2-chloropyridin-5-yl)ethane l-(4-pentylphenyl)-2-(2-chloropyridin-5-yl)ethane 1-(4-ethoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)- ethane 1-(4-propoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)- ethane 1-(4-butoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)- ethane 1-(4-pentyloxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)- ethane 1-(4-ethoxyphenyl)-2-(2-chloropyridine-5-yl)ethane 1-(4-propoxyphenyl)-2-(2-chloropyridine-5-yl)ethane 1-(4-butoxyphenyl)-2-(2-chloropyridine-5-yl)ethane 1-(4-pentyloxyphenyl)-2-(2-chloropyridine-5-yl)ethane 1-(4-ethylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)- ethane 1-(4-propylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)- ethane l-(4-butylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)- ethane 1-(4-pentylbiphenyl-4'-yl)-2-(2- luoropyridine-5-yl)- ethane 1-(4-ethylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine- 5-yl)ethane 1_(4-propylbiphenyl-4*-yl)-2-(2-trifluoromethylpyridine- 5-yl)ethane 1-(4-butylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine- 5-yl)ethane 1-(4-pentylbiphenyl-4*-yl)-2-(2-trifluoromethylpyridine- 5-yl )ethane 1-(4-ethylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine- 5-yl)ethane l-(4-propylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine- 5-yl)ethane 1-(4-butylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine- 5-yl)ethane 1-(4-pentylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine- 5-yl)ethane l-(4-hexylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine- 5-yl)ethane l-[4-(tranε-4-ethylcyclohexyl)phenyl]-2-[2- luoro- pyridine-5-yl]ethane 1-[4-(tranε-4-propylcyclohexyl)phenyl]-2-[2-fluoro¬ pyridine-5-yl]ethane l-[4-(tranε-4-butylcyclohexyl)phenyl]-2-[2-fluoro- pyridine-5-yl]ethane 1-[4-(trans-4-pentylcyclohexyl)phenyl]-2-[2-fluoro- pyridine-5-yl]ethane 1-[4-(trans-4-octylcyclohexyl)phenyl]-2-[2-fluoro- pyridine-5-yl]ethane 1-[tranε-4-(4-ethylphenyl)cyclohexyl]-2-(2-chloro- pyridine-5-yl)ethane 1-[tranε-4-(4-propylphenyl)cyclohexyl]-2-(2-chloro- pyridine-5-yl)ethane 1-[tranε-4-(4-butylphenyl)cyclohexyl]-2-(2-chloro- pyridine-5-yl)ethane 1-[tranε-4-(4-pentylphenyl)cyclohexyl]-2-(2-chloro- pyridine-5-yl)ethane 1-[tranε-4-(4-ethoxyphenyl)cyclohexyl]-2-(2-fluoro- pyridine-5-yl)ethane 1-[trans-4-(4-propoxyphenyl)cyclohexyl]-2-(2-fluoro- pyridine-5-yl)ethane 1-[trans-4-(4-butoxyphenyl)cyclohexyl]-2-(2-fluoro- pyridine-5-yl)ethane l-[trans-4-(4-pentyloxyphenyl)cyclohexyl]-2-(2-fluoro- pyridine-5-yl)ethane l-(trans-4-ethylcyclohexyl)-2-(2-fluoropyridine-5-yl)- ethane 1-(trans-4-propylcyclohexyl)-2-(2-fluoropyridine-5-yl)- ethane l-(trans-4-butylcyclohexyl)-2-(2-fluoropyridine-5-yl)- ethane l-(trans-4-pentylcyclohexyl)-2-(2-fluoropyridine-5-yl)- ethane 1-[trans-4-(tranε-4-ethylcyclohexyl)cyclohexyl]-2- (2-trifluoromethylpyridine-5-yl)ethane 1-[trans-4-(tranε-4-propylcyclohexyl)cyclohexyl]-2- (2-trifluoromethylpyridine-5-yl)ethane 1-[tranε-4-(tranε-4-butylcyclohexyl)cyclohexyl]-2- (2-trifluoromethylpyridine-5-yl)ethane l-[trans-4-(tranε-4-pentylcyclohexyl)cyclohexyl]-2- (2-trifluoromethylpyridine-5-yl)ethane 1-[trans-4-(trans-4-heptylcyclohexyl)cyclohexyl]-2- (2-trifluoromethylpyridine-5-yl)ethane 1-[tranε-4-(tranε-4-ethylcyclohexyl)cyclohexyl]-2- (2-fluoropyridine-5-yl)ethane 1-[tranε-4-(tranε-4-propylcyclohexyl)cyclohexyl]-2- (2-fluoropyridine-5-y1)ethane l-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]-2- (2-fluoropyridine-5-yl)ethane. 1-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]-2- (2-fluoropyridine-5-yl)ethane l-(tranε-4-ethylcyclohexyl)-2-[4-(2-chloropyridin-5-yl)- phenyl]-ethane 1-( rans-4-propylcyclohexyl)-2-[4-(2-chloropyridin-5-yl)- phenyl]-ethane C 124 N 159 I 1-(trans-4-butylcyclohexyl)-2-[4-(2-chloropyridin-5-yl)- phenyl]-ethane 1-(tranε-4-pentylcyclohexyl)-2-[4-(2-chloropyridin-5-yl)- phenyl]-ethane 1-(tranε-4-hexylcyclohexyl)-2-[4-(2-chloropyridin-5-yl)- phenyl]-ethane 1-(tranε-4-heptylcyclohexyl)-2-[4-(2-chloropyridin-5-yl)- phenyl]-ethane Example 8 A εuεpenεion of 0,02 M of tranε-4-(tranε-4-ethylcyclo- hexyl)cyclohexylbromide, 0,04 M of lithium and 0,01 M of ZnBr_ iε εtirred for 2 hourε at about 10° with ultrasonic. 0,02 M of 3-bromo-2,6-difluoropyridine and 0,1 g of Pd(Ph,P). are added and the mixture is stirred for 4 hourε. After cuεtomary work-up 2,6-difluoro-3-[tranε-4-(tranε- 4-ethylcyclohexyl)cyclohexyl]pyridine iε obtained. The following compounds are obtained analogously: 2,6-difluoro-3-[tranε-4-(trans-4-methylcyclohexyl)- cyclohexyl]pyridine 2,6-difluoro-3-[trans-4-(trans-4-propylcyclohexyl)- cyclohexyl]pyridine 2,6-difluoro-3-[trans-4-(trans-4-butylcyclohexyl)- cyclohexyl]pyridine 2,6-difluoro-3-[trans-4-(tranε-4-pentylcyclohexyl)- cyclohexyl]pyridine 6-chloro-2-fluoro-3-[trans-4-(trans-4-ethylcyclohexyl)- cyclohexyl]pyridine 6-chloro-2-fluoro-3-[trans-4-(trans-4-propylcyclohexyl)- cyclohexyl]pyridine 6-chloro-2-fluoro-3-[trans-4-(trans-4-butylcyclohexyl)- cyclohexyl]pyridine 6-chloro-2-fluoro-3-[trans-4-(trans-4-pentylcyclohexyl)- cyclohexyl]pyridine 6-chloro-3-[trans-4-(trans-4-ethylcyclohexyl)-cyclohexyl] pyridine 6-chloro-3-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl] pyridine 6-chloro-3-[trans-4-(trans-4-butylcyclohexyl)-cyclohexyl] pyridine 6-chloro-3-[trajιs-4-(tranε-4-pentylcyclohexyl)-cyclohexyl] pyridine 6-chloro-3-[trans-4-(trans-4-heptylcyclohexyl)-cyclohexyl] pyridine 6-trifluoromethyl-3-[trans-4-(trans-4-ethylcyclohexyl)- cyclohexyl]pyridine 6-trifluoromethyl-3-[trans-4-(trans-4-propylcyclohexyl)- cyclohexyl]pyridine 6-trifluoromethyl-3-[trans-4-(trans-4-butylcyclohexyl)- cyclohexyl]pyridine 6-trifluoromethyl-3-[trans-4-(trans-4-pentylcyclohexyl)- cyclohexyl]pyridine 6-trifluoromethyl-3-[trans-4-(trans-4-hexylcyclohexyl)- cyclohexyl]pyridine 6-trifluoromethyl-3-[tranε-4-(trans-4-heptylcyclohexyl)- cyclohexyl]pyridine 6-trifluoromethoxy-3-[trans-4-(trans-4-ethylcyclohexyl)- cyclohexyl]pyridine 6-trifluoromethoxy-3-[tranε-4-(tranε-4-propylcyclohexyl)- cyclohexyl]pyridine 6-trifluoromethoxy-3-[tranε-4-(tranε-4-butylcyclohexyl)- cyclohexyl]pyridine 6-trifluoromethoxy-3-[tranε-4-(tranε-4-pentylcyclohexyl)- cyclohexyl]pyridine 6-difluoromethoxy-3-[tranε-4-(tranε-4-ethylcyclohexyl)- cyc1ohexy1]pyridine 6-difluoromethoxy-3-[trans-4-(trans-4-propylcyclohexyl)- cyclohexyl]pyridine 6-difluoromethoxy-3-[tranε-4-(tranε-4-butylcyclohexyl)- cyclohexyl]pyridine 6-difluoromethoxy-3-[tranε-4-(tranε-4-pentylcyclohexyl)- cyclohexyl]pyridine 2,6-difluoro-3-(trans-4-ethylcyclohexyl)pyridine 2,6-difluoro-3-(tranε-4-propylcyclohexyl)pyridine 2,6-difluoro-3-(trans-4-butylcyclohexyl)pyridine 2,6-difluoro-3-(tranε-4-pentylcyclohexyl)pyridine 2,6-difluoro-3-[tranε-4-(4-ethylphenyl)cyclohexyl]pyridine 2,6-difluoro-3-[tranε-4-(4-propylphenyl)cyclohexyl]pyridine 2,6-difluoro-3-[tranε-4-(4-butylphenyl)cyclohexyl]pyridine 2,6-difluoro-3-[tranε-4-(4-pentylphenyl)cyclohexyl]pyridine 2,6-difluoro-3-[tranε-4-(4-ethoxyphenyl)cyclohexyl]pyridine 2,6-difluoro-3-[tranε-4-(4-propoxyphenyl)cyclohexyl]pyridine 2,6-difluoro-3-[trans-4-(4-butoxyphenyl)cyclohexyl]pyridine 2,6-difluoro-3-[tranε-4-(4-pentyloxyphenyl)cyclohexyl]- pyridine 2,6-difluoro-3-[trans-4-(4-octyloxyphenyl)cyclohexyl]pyridin 6-chloro-2-fluoro-3-[trans-4-(4-ethylphenyl)cyclohexyl]- pyridine 6-chloro-2-fluoro-3-[trans-4-(4-propylphenyl)cyclohexyl]- pyridine 6-chloro-2-fluoro-3-[tranε-4-(4-butylphenyl)cyclohexyl]- pyridine 6-chloro-2-fluoro-3-[tranε-4-(4-pentylphenyl)cyclohexyl]- pyridine 2,6-difluoro-3-[tranε-4-(2-fluoro-4-ethylphenyl)cyclo- hexyl]pyridine 2,6-difluoro-3-[trans-4-(2-fluoro-4-propylphenyl)cyclo¬ hexyl]pyridine 2,6-difluoro-3-[trans-4-(2-fluoro-4-butylphenyl)cyclo¬ hexyl]pyridine 2,6-difluoro-3-[trans-4-(2-fluoro-4-pentylphenyl)cyclo- hexyl]pyridine Example 9 Analogously to example 8 2-fluoro-5-[trans-4-(trans-4- ethy1cyclohexyl)cyclohexyl]pyridine is obtained by reac- ting trans-4-(tranε-4-ethylcyclohexyl)cyclohexylbromide with 2-fluoro-5-bromopyridine. The following compounds are obtained analogouεly: 2-fluoro-5-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]- pyridine 2-fluoro-5-[tranε-4-(tran≤-4-butylcyclohexyl)cyclohexyl]- pyridine 2-fluoro-5-[tranε-4-(trans-4-pentylcyclohexyl)cyclohexyl]- pyridine 2-fluoro-5-[trans-4-(tranε-4-octylcyclohexyl)cyclohexyl]- pyridine 2-chloro-5-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]- pyridine 2-chloro-5-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]- pyridine 2-chloro-5-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]- pyridine 2-chloro-5-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]- pyridine 2-trifluoromethyl-5-(trans-4-ethylcyclohexyl)-pyridine 2-trifluoromethyl-5-(trans-4-propylcyclohexyl)-pyridine 2-trifluoromethyl-5-(trans-4-butylcyclohexyl)-pyridine 2-trifluoromethyl-5-(trans-4-pentylcyclohexyl)-pyridine 2-trifluoromethoxy-5-(trans-4-ethylcyclohexyl)-pyridine 2-trifluoromethoxy-5-(trans-4-propylcyclohexyl)-pyridine 2-trifluoromethoxy-5-(tranε-4-butylcyclohexyl)-pyridine 2-trifluoromethoxy-5-(trans-4-pentylcyclohexyl)-pyridine 2-difluoromethoxy-5-(trans-4-ethylcyclohexyl)-pyridine 2-difluoromethoxy-5-(trans-4-propylcyclohexyl)-pyridine 2-difluoromethoxy-5-(trans-4-butylcyclohexyl)-pyridine 2-difluoromethoxy-5-(trans-4-pentylcyclohexyl)-pyridine 2-fluoro-5-(tranε-4-ethylcyclohexyl)-pyridine 2-fluoro-5-(tranε-4-propylcyclohexyl)-pyridine 2-fluoro-5-(tranε-4-butylcyclohexyl)-pyridine 2-fluoro-5-(tranε-4-pentylcyclohexyl)-pyridine 2-fluoro-5-(tranε-4-hexylcyclohexyl)-pyridine 2-fluoro-5-[trans-4-(4-ethylphenyl)cyclohexyl]pyridine 2-fluoro-5-[trans-4-(4-propylphenyl)cyclohexyl]pyridine 2-fluoro-5-[trans-4-(4-butylphenyl)cyclohexyl]pyridine 2-fluoro-5-[tranε-4-(4-pentylphenyl)cyclohexyl]pyridine 2-fluoro-5-[trans-4-(4-ethoxyphenyl)cyclohexyl]pyridine 2-fluoro-5-[tranε-4-(4-propoxyphenyl)cyclohexyl]pyridine 2-fluoro-5-[tranε-4-(4-butoxyphenyl)cyclohexyl]pyridine 2-fluoro-5-[tranε-4-(4-pentyloxyphenyl)cyclohexyl]pyridine 2-chloro-5-[tranε-4-(4-ethylphenyl)cyclohexyl] yridine 2-chloro-5-[tranε-4-(4-propylphenyl)cyclohexyl]pyridine 2-chloro-5-[trans-4-(4-butylphenyl)cyclohexyl]pyridine 2-chloro-5-[trans-4-(4-pentylphenyl)cyclohexyl]pyridine 2-trifluoromethyl-5-[trans-4-(4-ethylphenyl)cyclohexyl]- pyridine 2-trifluoromethyl-5-[tranε-4-(4-propylphenyl)cyclohexyl]- pyridine 2-trifluoromethyl-5-[trans-4-(4-butylphenyl)cyclohexyl]- pyridine 2-trifluoromethyl-5-[trans-4-(4-pentylphenyl)cyclohexyl]- pyridine Example 10 A liquid crystalline medium consisting of a) 90 % of a mixture A consisting of 24 % p-(trans-4-propylcyclohexyl)benzonitrile, 36 % p-(trans-4-pentylcyclohexyl)benzonitrile, 25 % p-(tranε-4-heptylcyclohexyl)benzonitrile and 15 % 4 -cyano-4 ' - (tranε-4-pentylcyclohexyl )-biphenyl and b) 1 0 % 2, 6 -difluoro-3-[4-(trans-4-pentylcyclohexyl)- phenyl]pyridine has a clearing point of 71.2°. Example 11 A liquid cryεtalline medium conεiεting of a) 90 % of a mixture A conεiεting of 22 % p-(tranε-propylcyclohexyl)-ethylbenzene, 20 % p-(trans-propylcyclohexyl)-methoxybenzene, 15 % p-(tranε-propy1cyclohexyl)-ethoxybenzene, 19 % 4'-(tranε-propylcyclohexyl)-4-ethylbiphenyl 14 % 4'-(tranε-pentylcyclohexyl)-4-ethylbiphenyl 5 % bis-4,4'-(trans-propylcyclohexyl)biphenyl 5 % 4'-(trans-4-propylcyclohexyl)-4-(trans-4-pentyl- cyclohexyl)-biphenyl and b) 10 % of l-(trans-4-propylcyclohexyl)-2-[4-(2-chloro- pyridin-5-yl)-phenyl]-ethane has a clearing point of 77.1 °C.

Claims: Claims Pyridine derivatives of the formula I wherein • R denotes alkyl with up to 12 carbon atoms wherein one or two non-adjacent CH -groups may also be replaced by -0-, -0-CO-, -CO-O- and/or -CH=CH-, Y is F, Cl, -CF,, -OCF, or OCHF ^ ,, A 1 and A2 in each case independently of one another are trans-l,4-cyclohexylene, wherein one or two non-adjacent CH 2 -groupε may also be replaced by -O- and/or -S-, or 1,4- phenylene which is unsubstituted or substi¬ tuted by one or more halogen atoms and/or nitrile and/or CH_ groups, and wherein one or more CH groups may also be replaced by N, Z1 and Z2 in each caεe independently of one another are -CH 2 CH 2 ~, -CO-O-, -O-CO-, -CH 2 0-, -0CH 2 -, -C≡C- or a εingle bond, X iε H, or in caεe of Y = F or Cl, alεo F and n iε 0, 1 or 2. 2. Pyridine derivativeε of claim 1, wherein X iε H. 3. Pyridine derivativeε of claim 1, wherein X is F. 4. Pyridine derivatives of claim 1 or 2 wherein Y is F or Cl. 5. Pyridine derivatives of claim 1 or 3 wherein Y is F or Cl. 6. Pyridine derivatives of claim 1 wherein Y is -OCF 3 7. Pyridine derivatives of claim 1 wherein Y is -CF,. 8. Pyridine derivatives of claim 1 wherein Y is -OCHF^. 9. Pyridine derivatives of claims 1 to 8, wherein R R ddeennootteess aann uu_nbranched alkyl radical of 2 to 7 carbon atoms. 10. Pyridine derivatives of claims 1 to 9, wherein n is 0 or 1. 11. Pyridine derivatives of claimε 1 to 10, wherein Z 1 and Z2 are each a single bond. - 6t - 12. Pyridine derivativeε of claims 1 to 11, wherein Z 2 is -CO-O-, -CH,CH„- or -C≡C-. 13. Liquid crystalline medium being a mixture of at least two compounds, characterized in that at least one compound is a pyridine derivative according to claim 1. 14. Liquid crystal display device, characterized in that it contains a liquid crystalline medium according to claim 13. 15. Electrooptical diεplay device, characterized in that it contains a liquid cryεtalline medium according to claim 13.

Inventors: CLEMITSON ROBERT, COATES DAVID, GREENFIELD SIMON, PLACH HERBERT, REIFFENRATH VOLKER, SAGE IAN CHARLES, CLEMITSON, ROBERT, COATES, DAVID, GREENFIELD, SIMON, PLACH, HERBERT, REIFFENRATH, VOLKER, SAGE, IAN, CHARLES
Applicants: MERCK PATENT GMBH, MERCK PATENT GESELLSCHAFT MIT BESCHRAENKTER HAFTUNG
Application year: 1990
Main classification: C07D213
IPC codes: C07D213, C09K19