GB2271563A - Liquid crystalline (2-(cyclylcarboxy)-5-pyrazyl)benzenes - Google Patents

Liquid crystalline (2-(cyclylcarboxy)-5-pyrazyl)benzenes Download PDF

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GB2271563A
GB2271563A GB9221512A GB9221512A GB2271563A GB 2271563 A GB2271563 A GB 2271563A GB 9221512 A GB9221512 A GB 9221512A GB 9221512 A GB9221512 A GB 9221512A GB 2271563 A GB2271563 A GB 2271563A
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groups
diyl
formula
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John William Brown
Derek Thomas Hurst
Jacqueline Patricia O'donovan
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Merck Patent GmbH
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Merck Patent GmbH
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D409/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having sulfur atoms as the only ring hetero atoms
    • C07D409/02—Heterocyclic compounds containing two or more hetero rings, at least one ring having sulfur atoms as the only ring hetero atoms containing two hetero rings
    • C07D409/12—Heterocyclic compounds containing two or more hetero rings, at least one ring having sulfur atoms as the only ring hetero atoms containing two hetero rings linked by a chain containing hetero atoms as chain links
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D241/00—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings
    • C07D241/02—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings not condensed with other rings
    • C07D241/10—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members
    • C07D241/14—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D241/18—Oxygen or sulfur atoms
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
    • C09K19/3441—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having nitrogen as hetero atom
    • C09K19/345—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having nitrogen as hetero atom the heterocyclic ring being a six-membered aromatic ring containing two nitrogen atoms
    • C09K19/3452—Pyrazine
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
    • C09K19/3491—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having sulfur as hetero atom
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
    • C09K19/3491—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having sulfur as hetero atom
    • C09K19/3497—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having sulfur as hetero atom the heterocyclic ring containing sulfur and nitrogen atoms

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  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Liquid Crystal Substances (AREA)

Abstract

Phenylpyrazine esters of the formula I <IMAGE> [wherein R1 and R2 are independently H, a C1-15 alkyl or alkenyl group, which is optionally substituted by CN or halogen and in which one or two non-adjacent CH2 groups may be replaced by O atoms and/or -CO-groups and/or -O-CO-groups and/or -CO-O-groups and/or -OCOO-groups and/or -CH-halogen groups; A is a) a 1,4-phenylene radical wherein one or two non-adjacent CH-groups can also be replaced by a N atom, b) a trans-1,4-cyclohexylene radical wherein one or two non-adjacent CH2 groups can also be replaced by -O- or -S-, c) a decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, 1,3,4-thiadiazole-2,5-diyl, 1,2,4-thiadiazole-3,5-diyl or a thiophene-2,5-diyl radical (where the radicals a) and b) may be monosubstituted or substituted by one or more halogen or cyano and/or methyl groups); and L<1>, L<2> and L<3> are independently H or F,] are suitable as components of liquid-crystalline phases.

Description

Phenylpyrazine esters The invention relates to phenylpyrazine esters of the formula I
wherein R1 and R2 are each independently of one another H, an alkyl or alkenyl group having up to 15 C at oms, which is unsubstituted or substituted by CN or halogen and in which one or two non adjacent CH2 groups may be replaced by O atoms and/or -CO-groups and/or -O-CO-groups and/or -CO-O-groups and/or -OCOO-groups and/or -CH-halogen groups, A is a) a 1,4-phenylene radical wherein one or two non-adjacent CH-groups can also be replaced by a N atom, b) a trans-1,4-cyclohexylene radical wherein one or two non-adjacent CH2 groups can also be replaced by -O- or -S-, c) a decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6- diyl, 1,3,4-thiadiazole-2,5-diyl, 1,2,4-thiadiazole-3,5-diyl or a thio phene-2,5-diyl radical were the radicals a) and b) may be monosub stituted or substituted by one mor more F atoms, and L1, L2 and L3 are each independently of one another H or F, with the proviso that in the case A is
at least one of L1, L2 or L3 being F the others are H or F or R2 is H, and also to liquid crystalline media being a mixture of at least 2 compounds, characterized in that at least one compound is a phenylpyrazine esters according to formula 1.
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 for optical and dielectric anisotropy combined with low viscosity and high nematogenity. Similar phenylpyrazine esters are known from the US 4,913, 837:
R, R2 = alkyl or alkoxy It has now been found that the compounds of formula I are highly suitable as polar components of liquid crystalline media. In particular, they have especially advantageous values of optical and dielectric anisotropy and are not strongly smectogenic.It is also possible to obtain stable liquid crystal phases with a broad nematic mesophase range including a good deep temperature behaviour, a high resistivity and a comparatively low viscosity with the aid of these compounds.
Depending on the choice of R, R2, A, L11 L2 and L3, the compounds of the formula I can be used as the base materials from which liquid crystal media are predominantly composed; 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 range of such a dielectric.
The compounds of the formula I are in particular suitable as components for liquid crystal media for displays which are based on the principle of polymer dispersed liquid crystals (pdlc) or polymer liquid crystals (pnlc) due to their favorable optical anisotropy and the dielectric anisotropy.
The compounds of the formula I are colourless in the pure state and are liquid crystalline in a temperature range which is favourably placed for electrooptical use. They are very stable towards chemicals, heat and light.
The invention thus relates to the phenylpyrazines of the formula I, to liquid crystalline media with at least two liquid crystalline components, wherein at least one component is a compound of the formula I and to liquid crystal display devices containing such media.
Above and below, RI, R2, A, L1, L2 and L3 have the meaning given unless expressly indicated otherwise.
The compounds of the formula I include phenylpyrazine esters of the formulae Ia to Ih:
Thereof those of the partial formula Ia, Ig, Id and Ie are particularly preferred.
The preferred compounds comprise those of the formula IA to IE
R1 and R2 is preferably alkyl, alkoxy, oxaalkyl 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 preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, tridecoxy or tetradecoxy.
Oxaalkyl is preferably straight-chain 2-oxypropyl (= methoxymethyl), 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 or 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-1-, -2-, -3-, -4- or 5-enyl, hept-1-, -2-, -3-, -4-, -5or -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 chiral 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-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 2-methylhexoxy, 1-methylhexoxy, 1-methylheptoxy (= 2-octyloxy), 2-oxa-3-methylbutyl, 3-oxy-4-methylpentyl, 4-methylhexyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methyloctoxy, oxy, 2-thyl-3-oxapentyl and 2-methyl-3-oxyhexyl.
In the case of compounds with a branched terminal group R1 or R2, formula I includes both the optical antipodes and racemates as well as mixtures thereof.
Of the compounds of the formula I and subformulae thereof, those in which at least one of the radicals contained therein has one of the preferred meanings given are preferred.
The compounds of the formula I are prepared by methods which are known per se, 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 formula I.
Preferred route for preparation of the phenylpyrazine esters are shown in the following schemes.
Scheme 1:
All starting materials are known or prepared in analogy to known starting materials.
Other routes are apparent to the skilled worker. All these steps and the corresponding reaction conditions are known to the skilled worker.
In addition to one or more compounds for formula I the liquid crystal media according to the invention preferably contain 2-40 components and in particular 4-30 components. 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 preferred chosen from the nematic or nematogenic (monotropic or isotropic) substances; in particular from the classes of azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl cyclohexanecarboxylates, phenyl or cyclohexyl cyclohexylbenzoates, phenyl or cyclohexyl cyclohexylcyclohexanecarboxylates, cyclohexylphenylbenzoates, cyclohexylphenyl cyclohexanecarboxylates, cyclohexylphenyl cyclohexylcyclohexanecarboxylates, phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexenes, cyclohexylcyclohexylcyclohexene, 1,4-bis-cyclohexylbenzenes, 4,4'-bis-cyclohexylbiphenyl, phenyl- or cyclohexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclohexyldioxanes, phenyl -or cyclohexyl-1,3-dithianes, 1,2-diphenylethanes, 1,2-dicyclohexylethanes, 1-phenyl-2-cyclohexylethanes, 1-cyclohexyl-2-(4-phenyl-cyclohexyl)-ethanes, 1-cyclohexyl-2-biphenylethanes, 1-phenyl-2-cyclohexyl-phenylethanes, optionally halogenated stilbenes, benzyl phenyl ethers, tolanes and substituted cinnamic acids.
The 1,4-phenylene groups of these compounds may be fluorinated.
The most important compounds which are possible constituents of liquid crystal media according to the invention can be characterized by the formulae 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-CH2CH2-U-R" 4 R' -L-CeC-U-R" 5 In the formulae 1, 2, 3, 4 and 5 L and U may 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 this compilation of residues Phe denotes unsubstituted or fluorinated 1,4-phenylen, Cyc trans-1,4-cyclohexylene or 1,4-cyclohexenylen, Pyr pyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio 1,3-dioxane-2,4-diyl and G 2-(trans-1,4-cyclohexyl)-ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5diyl.
One of the residues L and U is 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, said liquid crystal media further containing at the same time one or more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with one of the residues L and U denoting Cyc, Phe and Pyr and the other residue being selected from the group consisting of -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Cyc-, said liquid crystal media containing in addition to this optionally one or more components selected from the compounds 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 independently from each other alkyl, alkenyl, alkoxy, alkenoxy with up to 8 carbon atoms. R' and R" differ from one another in most of these compounds, one of the residues usually being alkyl or alkenyl. In another preferred subgroup of the compounds of formulae 1, 2, 3, 4 and 5 (subgroup 2) R" denotes -CN, -CF3, -OCF3, -OCHF2, -F, -Cl or -NCS while R' has the meaning indicated in subgroup 1 and is preferably alkyl or alkenyl. Other variants of the envisaged substituents in the compounds of formulae 1, 2, 3, 4 and 5 are also customary. Many such substances are commercially available. All these substances are obtainable by methods which are known from the literature or by analogous methods.
The liquid crystal media according to the invention preferably 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 compounds according to the invention and the compounds of subgroup 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 according 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 is prepared in a manner which is customary per se. As a rule, the components are dissolved in one another, advantageously at elevated temperature. The liquid crystal media according to the invention can be modified by suitable 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 Crystals, Verlag Chemie, Weinheim, 1980). For example, it is possible to add pleochroic dyestuffs to prepare colored guest-host systems or substances for modifying the dielectric anisotropy, the viscosity and/or the orientation of the nematic phases.
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 following all parts and percentages are by weight and the temperatures are set forth in degrees Celsius. "Customary 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: crystalline-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 two of these symbols denotes the temperature of phase change.
Example 1
a) 4-n-ProDvlDhenvlqlooxal hvdrate 0.154 mol 4-n-propylacetophenone was added to a solution of selenium dioxide (0.154 mol) in 95 % aqueous ethanol which was then refluxed for four hours. After cooling the selenium was filtered off and the solvent was removed under reduced pressure. The resultant yellow/orange oil was purified by vacuum distillation. A stable hydrate was formed by stirring the oil in water for 24 hours. mp.
69-72 OC.
b) 5-(4-n-Propylphenyl)-2-pyrazinol 0.07 mol 4-n-propylphenylglyoxal hydrate was dissolved in methanol, cooled to below -40 C and then dry powdered glycinamide hydrochloride (0.07 mol) was added to the stirred solution. The temperature was allowed to rise slowly to 30 C and maintained at this temperature while NaOH (0.186 mol in 25 cm3 H2O) was added dropwise. The reaction mixture was then maintained and stirred for 3 hours at -20-0 C and 2 hours at 0-20 OC. After cooling to 0 C the pH was adjusted to 5,0 with concentrated hydrochloric acid when an orange/brown precipitate of 5-(4-n-propylphenyl)-2-pyrazinol was formed which was collected and washed with water. Purification of the crude product was carried out by dissolving it in dichlo romethane and extracting with 1 N NaOH.The aqueous layer was washed with dichloromethane. The pH of the aqueous layer was adjusted to 5.0 with conc. HCl and the solid which precipitated was filtered off and washed with water. A final purification was carried out by suspending the production in boiling water and adding 12 N NaOH dropwise until all of the solid has just dissolved. After cooling to 10 OC the solution was again acidified to pH 5.0 and the solid was filtered off and washed again with water. mp. 150-151 OC.
c) 2- (trans-4-n-Ethvlcvclohexvl) carbonvloxv-5- (4-n-rovl- Dhenyl)-pvrazine 0.0047 mol 5-(4-n-propylphenyl)pyrazinol was added to a stirred solution of 0.0047 mol trans-4-ethylcyclohexane 1-carboxylic acid and 0.0056 mol trifluoroacetic anhy dride in dry dichloromethane. After 4 hours the reaction mixture was washed with 1 N NaOH solution and dried (MgSO4). The solvent was removed under reduced pressure to give a white crystalline solid which was purified by column chromatography on silica gel eluting with toluene.
The ester was recrystallized from n-hexane.
C 91 S (89) N 164 I.
The following compounds of the formula
are prepared analogously.
R1 Mesophases n-C3H7 C 88 S (81) N 189 I n-C4H9 C 72 S (64) N 169 I n-C5Hll C 82 S (64) N 186 I n-C6H13 C 81 S (70) S (67) N 171 I n-C7H15 C 82 Sg (81) S (62) N 174 I Example 2
a) The pentylthiophene (0.013 mol) was dissolved in dry ether at -10 C under nitrogen. To this well stirred solution was added 1.5 M ethereal n-butyllithium (8.5 cm3, 0.013 mol) in dry ether over 20 min. The reaction mixture was stirred for a further 30 min after which a large excess of powdered dry ice was added. Stirring was main tained for a further 30 min during which period the reaction mixture was allowed to warm to room temperature.
Water was then added to the yellow solution and stirring continued for 10 min after which the ether was removed under reduced pressure. Water was added to the oily residue, and the resulting solution was cooled in ice and acidified with 4M-aqueous hydrochloric acid. The beige precipitate was filtered off, dried, and recrystallised from hexane to yield the 5-n-pentylthiophene-2-carboxylic acid as a white crystalline solid. m.p. 68-69 00.
b) 0.05 mol 5-(4-n-propylphenyl)pyrazinol was added to a stirred solution of 0.05 mol 4-n-pentyl-thiophene-2-car boxylic acid and 0.06 mol trifluoroacetic anhydride in dry dichloromethane. After 4 hours the reaction mixture was washed with 1 N NaOH solution and dried (MgSO4). The solvent was removed under reduced pressure to give a white crystalline solid. C 53 N 109 I.
The follwoing compounds of the formula
are prepared analogously.
R1 R2 H13C6-n n-C3H7 H15C7-n n-C3H7 H1 7C8-n n-C3H7 H19C9-n n-C3H7 H21C10-n n-C3H7 H25C12-n n-C3H7 H11C5-n n-C4H9 H13C6-n n-C4H9 H15C7-n n-C4H9 H17C8-n n-C4H9 H19C9-n n-C4H9 H21C10-n n-C4H9 H25C12-n n-C4H9 Example 3
a) 3-Fluoro-4-methoxvacetohenone 0.119 mol 2-methoxyfluorobenzene was added to a mixture of dried dichloromethane (100 cm3) and anhydrous alumunium chloride (0.131 mol). The mixture was cooled to 0 OC and 0.119 mol acetylchloride was added dropwise over 40 minutes. The red/orange solution was stirred overnight.
After stirring the solution was poured into ice and stirred for 1 hour. The two layers were separated and the organic layer was washed with water and dried (MgSO4). The solvent was removed under reduced pressure to give a white solid. m.p. 92 OC.
b) 3-Fluoro-4-methoxyphenylglvoxal hvdrate 3-fluoro-4-methoxy acetophenone (0.059 mol) was added to a solution of selenium dioxide (0.059 mol) in 95 % etha nol which was then refluxed for 4 hours. After cooling the selenium was filtered off and the solvent was removed under reduced pressure to yield a pale yellow solid which was recrystallized from aqueous acetone to give a white solid. m.p. 96-101 OC.
c) 5-(3-Fluoro-4 methoxyphenvl)-2-pvrazinol 0.05 mol 3-fluoro-4-methoxy phenylglyoxal hydrate was dissolved in methanol cooled to below -40 OC and then 0.05 mol dry powdered glycinamide hydrochloride was added to the stirred solution. The temperature was allowed to rise slowly to 30 C and maintained at this temperature while NaOH (0.12 mol in 25 cm3 H2O) was added dropwise.
The reaction mixture was then maintained and stirred for 3 hours at -20-0 C and 2 hours at 0-20 00. After cooling to 0 C the pH was adjusted to 5.0 with conc. HCl when an orange/brown precipitate of 5- (3-fluoro-4-methoxyphenyl) - 2-pyrazinol was formed which was collected and washed with water purified by dissolving in aqeous NaOH and washing with dichloromethane and reprecipitating with HCl. m.p. 242-244 C (decomposes).
d) 2-(trans-4-Pronvlcvclohexvl) carbonvloxv-5- (3-fluoro-4- methoxvthenvl) vrazine 5-(3-fluoro-4-methoxyphenyl)-2-pyrazinol (0.0045 mol) was added to a stirred solution of trans-4-propylcyclohexane 1-carboxylic acid (0.0045 mol) and trifluoroacetic anhy dride (0.0054 mol) in dry dichloromethane. After 4 hours the reaction mixture was washed with 1 N NaOH solution and dried (MgSO4). The solvent was removed under reduced pressure to give a white crystalline solid which was purified by column chromatography (silica gel). C 97.9 N 186.6 I.
ExamPle 4
5- (3-fluoro-4-methoxyphenyl) -2-pyrazinol (0.005 mol) was added to a stirred solution propoxybenzoic acid (0.005 mol) and trifluoroacetic anhydride (0.006 mol) in dry dichloromethane. After 4 hours the reaction mixture was washed with 1 N NaOH solution and dried (MgSO4). The solvent was removed under reduced pressure to give a solid which was purified by column chromatography. C 143 N 210 I.
The following compounds of the formula
are prepared analogously.
R1 L2 H5C2O H C 162 N 230 I H2C2O F H7C30 F H9C40 H C 113 N 207 I H9C4O F H11C5O H C 120 N 196 I H13C6O H C 99 N 194 I R1 L2 H13C6O F H15C7O H C 120 N 186 I H15C7O F H17C8O H C 94 N 184 I Hl7C8O F H1gCgO H C 94 N 177 I H19C9O F Example 5
a) 2-Ethoxvfluorobenzene 1-Bromethane (1.084 mol) was added to a mixture of THF, potassium carbonate (34.5 mol) and 2-fluorophenol (0.115 mol). The mixture was refluxed for 6 hours after which it was allowed to cool and the salts were filtered off and washed. The washings were combined with the filtrate and the solvent removed under reduced pressure.
b) 3-Fluoro-4-ethoxyacetophenone 0.119 mol 2-ethoxyfluorobenzene was added to a mixture of dried dichloromethane (100 cm3) and anhydrous alumunium chloride (0.131 mol). The mixture was cooled to 0 C and 0.119 mol acetylchloride was added dropwise over 40 minutes. The red/orange solution was stirred overnight.
After stirring the solution was poured into ice and stirred for 1 hour. The two layers were separated and the organic layer was washed with water and dried (MgSO4). The solvent was removed under reduced pressure to give a white solid.
c) 3-Fluoro-4-ethoxvohenvlalvoxal hvdrate 3-fluoro-4-ethoxy acetophenone (0.059 mol) was added to a solution of selenium dioxide (0.059 mol) in 95 % ethanol which was then refluxed for 4 hours. After cooling the selenium was filtered off and the solvent was removed under reduced pressure to yield a solid which was recrys tallized from aqueous acetone.
d) 5- (3-Fluoro-4-ethoxvohenvl-2-vrazinol 0.05 mol 3-fluoro-4-ethoxy phenylglyoxal hydrate was dissolved in methanol cooled to below -40 OC and then 0.05 mol dry powdered glycinamide hydrochloride was added to the stirred solution. The temperature was allowed to rise slowly to 30 OC and maintained at this temperature while NaOH (0.12 mol in 25 cm3 H2O) was added dropwise.
The reaction mixture was then maintained and stirred for 3 hours at -20-0 OC and 2 hours at 0-20 OC. After cooling to 0 OC the pH was adjusted to 5.0 with conc. HCl when an orange/brown precipitate of 5- (3-fluoro-4-ethoxyphenyl) - 2-pyrazinol was formed which was collected and washed with water purified by dissolving in aqeous NaOH and washing with dichloromethane and reprecipitating with HCl.
e) 2-(4-n-ProPvlPhenvl)carbonvloxv-5-(3-fluoro-4-ethOxv- phenyl)pyrazine 5-(3-fluoro-4-ethoxyphenyl)-2-pyrazinol (0.005 mol) was added to a stirred solution propoxybenzoic acid (0.005 mol) and trifluoroacetic anhydride (0.006 mol) in dry dichloromethane. After 4 hours the reaction mixture was washed with 1 N NaOH solution and dried (MgSO4). The solvent was removed under reduced pressure to give a solid which was purified by column chromatography. C 128 N 217 I.
The following compounds of the formula
are prepared analogously.
R1 L2 H3CO H C 128 N 232 I H5C2O H C 133 N 234 I H5C2O F H7C30 F H9C4O H C 106 N 213 I HllC5O H C 105 N 205 I H11C50O F R1 L2 H13C6O H C 114 N 206 I H13C6O F H15C7O H H17C8O H C 91 Sc 97 N 198 I H19C9O H C 83 Se 102 N 184 I H21CloO H C 99 Sc 122 N 180 I H21C10O F H25C12O H C 87 Sc 125 N 174 I

Claims (8)

  1. Claims 1. Phenylpyrazine esters of the formula I
    wherein R1 and R2 are each independently of one another H, an alkyl or alkenyl group having up to 15 C at oms, which is unsubstituted or substituted by CN or halogen and in which one or two non adjacent CH2 groups may be replaced by O atoms and/or -CO-groups and/or -O-CO-groups and/or -CO-O-groups and/or -OCOO-groups and/or -CH-halogen groups, A is a) a 1,4-phenylene radical wherein one or two non-adjacent CH-groups can also be replaced by a N atom, b) a trans-1,4-cyclohexylene radical wherein one or two non-adjacent CH2 groups can also be replaced by -O- or -S-,
    c) a decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6- diyl, 1,3,4-thiadiazole-2,5-diyl, 1,2,4-thiadiazole-3,5-diyl or a thio phene-2,5-diyl radical were the radicals a) and b) may be monosub stituted or substituted by one mor more halo gen or cyano and/or methyl groups, and L1, L2 and L3 are each independently of one another H or F, with the proviso that in the case A is
    at least one of L1, L2 or L3 being F the others are H or F or R2 is H.
  2. 2. Compounds of the formula Ia,
    wherein R1 and R2 have the meaning given in claim 1.
  3. 3. Compounds of the formula Ic,
    wherein R1 and R2 have the meaning given in claim 1.
  4. 4. Compounds of the formula Ih,
    wherein R1 and R2 have the meaning given in claim 1.
  5. 5. Use of the compounds of the formula I according to Claim 1 as components of liquid-crystalline media.
  6. 6. Liquid-crystalline medium containing at least two liquid crystalline components, characterized in that at least one component is a compound of the formula I.
  7. 7. Liquid crystal display element, characterized in that it contains a medium according to Claim 5.
  8. 8. Electro-optical display element according to Claim 7, characterized in that it contains as dielectric a medium according to Claim 5.
GB9221512A 1992-10-13 1992-10-13 Liquid crystalline (2-(cyclylcarboxy)-5-pyrazyl)benzenes Withdrawn GB2271563A (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59144771A (en) * 1983-02-08 1984-08-18 Ube Ind Ltd Liquid crystal pyrazine derivative and its preparation
JPS60199882A (en) * 1984-03-26 1985-10-09 Nippon Kayaku Co Ltd Pyrazine derivative
EP0293910A2 (en) * 1987-06-04 1988-12-07 Canon Kabushiki Kaisha Liquid crystal composition and liquid crystal device containing same
EP0294852A2 (en) * 1987-06-12 1988-12-14 Canon Kabushiki Kaisha Ferroelectric liquid crystal device
JPH0269467A (en) * 1988-09-05 1990-03-08 Canon Inc Liquid crystal compound, liquid crystal composition and element containing the same compound

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59144771A (en) * 1983-02-08 1984-08-18 Ube Ind Ltd Liquid crystal pyrazine derivative and its preparation
JPS60199882A (en) * 1984-03-26 1985-10-09 Nippon Kayaku Co Ltd Pyrazine derivative
EP0293910A2 (en) * 1987-06-04 1988-12-07 Canon Kabushiki Kaisha Liquid crystal composition and liquid crystal device containing same
EP0294852A2 (en) * 1987-06-12 1988-12-14 Canon Kabushiki Kaisha Ferroelectric liquid crystal device
JPH0269467A (en) * 1988-09-05 1990-03-08 Canon Inc Liquid crystal compound, liquid crystal composition and element containing the same compound

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Chemical Abstracts, Vol. 102(9), abstract number 78913u & JP59144771 A 18.08.84 *
Chemical Abstracts, Vol. 104(24), abstract number 216673k & JP60199882 A 09.10.85 *
Chemical Abstracts, Vol. 114(10), abstract number 92394e & JP02069467 A 08.03.90 *

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