DE10050880A1 - New pyridine derivatives useful as stabilizers for liquid crystals - Google Patents

Abstract

Pyridine derivatives (I) are new. Pyridine derivatives of formula (I) are new: Ra, Rb, Rc = H or optionally CN- or halo-substituted 1-12C alkyl or alkenyl in which one or more nonadjacent CH2 groups are optionally replaced by O, S, CO, OCO, COO or CC; and m, n = 0-2. Independent claims are also included for the following: (1) a liquid crystal composition comprising at least two liquid-crystalline compounds and containing at least one compound (I); (2) an electro-optic display comprising the composition of (1).

Description

The present invention relates to pyridine derivatives of formula I.

wherein
R ^a , R ^b and R ^c each independently of one another H, an unsubstituted or with CN or with at least one halogen substituted alkyl or alkenyl radical having up to 12 carbon atoms, wherein one or more non-adjacent CH ₂ groups are selected by a radical can be replaced from the group -O-, -S-, -CO-, -O-CO-, -CO-O- and -C könnenC-, and
m and n each independently of one another 0, 1 or 2,
mean.

The stabilization of acid labile liquid crystals or liquid crystalline Mixtures that contain acid-labile components is often a Problem.

The stabilizers for the purposes mentioned must not be toxic, should show high effectiveness at low concentrations, no changes in taste, smell and color call, not even with long storage or heating, they should in the Substrate can be easily soluble or easily distributed, no adverse influence exert a slight volatility on the substance to be protected and analytically as quantitative as possible.  

Furthermore, the stabilizers should be easy and inexpensive to manufacture as well as their handling and familiarization.

The object of the present invention was therefore to provide inexpensive stabilizers to find sensors that all meet the stated conditions.

Surprisingly, it has now been found that pyridine derivatives of Formula I is highly effective even at low concentrations Have stabilizer without adversely affecting the protective substance. Furthermore, the fiction according to partly sterically hindered pyridines by their temperature resistance, their low viscosity and volatility.

The invention thus relates to pyridine derivatives of the formula I.

Pyridine derivatives of the formula I are notable for their basic properties and their structure as a stabilizer of liquid crystals or liquid crystalline mixtures. Due to the substituent in the 4-position liquid-crystalline properties of the stabilizer itself to reach.

Due to their structure, these materials are particularly low vapor pressure and can therefore operate even at high temperatures be used. Like their reaction products, they are colorless and therefore do not lead to any discoloration of the stabilized Materials.

In the compounds of formula I, the sum of n + m is preferably 0, 1, 2 or 3. In the case n ≠ 0, m is preferably 1. R ^b and R ^c are preferably H, primary, secondary or tertiary alkyl or Alkenyl residues.

If R ^a , R ^b and / or R ^{c is} an alkyl radical and / or an alkoxy radical, this can be straight-chain or branched. Preferably R ^{a is} a straight chain alkyl group and R ^b and R ^c are preferably tertiary alkyl groups. The radicals have 1, 2, 3, 4, 5, 6 or 7 carbon atoms and accordingly preferably mean methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore Methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy.

Oxaalkyl preferably means straight-chain 2-oxapropyl (= methoxy methyl), 2 - (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxa heptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxa nonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

If R ^a , R ^b and / or R ^{c is} an alkyl radical in which a CH ₂ group has been replaced by -CH = CH-, this can be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. Accordingly, it means especially vinyl, prop-1-, or prop-2-enyl, but-1-, 2- or but-3-enyl, pent-1-, 2-, 3- or pent-4-enyl, hex -1-, 2-, 3-, 4- or hex-5-enyl, hept-1-, 2-, 3-, 4-, 5- or hept-6-enyl, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-, 3-, 4-, 5-, 6-, 7- or non-8-enyl, Dec-1 -, 2-, 3-, 4-, 5-, 6-, 7-, 8- or Dec-9-enyl.

If R ^a , R ^b and / or R ^{c is} an alkyl radical in which one CH ₂ group has been replaced by -O- and one has been replaced by -CO-, these are preferably adjacent. Thus, these include an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-. These are preferably straight-chain and have 2 to 6 carbon atoms.

Accordingly, they mean especially acetyloxy, propionyloxy, butyryloxy, Pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, Butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxy ethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, Butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxy carbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2- (methoxycarbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propoxy carbonyl) ethyl, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl) propyl, 4- (methoxycarbonyl) butyl.

If R ^a , R ^b and / or R ^{c is} an alkyl radical in which one CH ₂ group is replaced by unsubstituted or substituted -CH = CH- and an adjacent CH ₂ group is replaced by CO or CO-O or O-CO , it can be straight or branched. It is preferably straight-chain and has 4 to 13 carbon atoms. Accordingly, it means in particular acryloyloxymethyl, 2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl, 8-acryloyloxyoctyl, 9-acryloyloxynonyl, 10-acryloyloxoyloxydoxymyl Methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl, 9-methacryloyloxynonyl.

If R ^a , R ^b and / or R ^{c is} an alkyl or alkenyl radical which is at least monosubstituted by halogen, this radical is preferably straight-chain and halogen is preferably F or Cl. In the case of multiple substitution, halogen is preferably F. The resulting residues also include perfluorinated residues. In the case of single substitution, the fluorine or chlorine substituent can be in any position, but preferably in the ω position.

Branched radicals R ^a , R ^b and / or R ^c usually contain no more than two chain branches. Preferred branched radicals R ^a , R ^b and / or R ^c are isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methyl butoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 1-methylheptoxy, t-butyl or t-pentyl.

If R ^a , R ^b and / or R ^{c represents} an alkyl radical in which two or more CH ₂ groups have been replaced by -O- and / or -CO-O-, this can be straight-chain or branched. It is preferably branched and has 3 to 12 carbon atoms. Accordingly, it means especially bis-carboxy-methyl, 2,2-bis-carboxy-ethyl, 3,3-bis-carboxy-propyl, 4,4-bis-carboxy-butyl, 5,5-bis-carboxy-pentyl, 6,6-bis-carboxy-hexyl, 7,7-bis-carboxy-heptyl, 8,8-bis-carboxy-octyl, 9,9-bis-carboxy-nonyl, 10,10-bis-carboxy-decyl, Bis (methoxycarbonyl) methyl, 2,2-bis (methoxycarbonyl) ethyl, 3,3-bis (methoxycarbonyl) propyl, 4,4-bis (methoxycarbonyl) butyl, 5,5-bis (methoxycarbonyl) pentyl, 6,6-bis (methoxycarbonyl) hexyl, 7,7-bis (methoxycarbonyl) heptyl, 8,8-bis (methoxycarbonyl) octyl, bis (ethoxycarbonyl) methyl, 2,2-bis (ethoxycarbonyl) ethyl, 3,3-bis (ethoxycarbonyl) propyl, 4,4-bis (ethoxycarbonyl) butyl, 5,5-bis (ethoxycarbonyl) hexyl.

In the formula I and in the preferred sub-formulas, R ^a preferably denotes straight-chain alkyl, alkoxy, alkenyl having up to 6 carbon atoms. The radicals R ^b and / or R ^{c are} in particular H, tert-butyl or tert-pentyl. Compounds in which R ^b = R ^c are particularly preferred.

Smaller groups of compounds of the formula I are preferably those of the sub-formulas I1 to I3:

The compounds of the formulas I1, I2 and I3 are particularly preferred, in which R ^a and R ^{b are} secondary or tertiary alkyl radicals.

The compounds of formula I are according to methods known per se presented as they are in the literature (e.g. in the standard works such as Houben-Weyl, Methods of Organic Chemistry, Georg Thieme Verlag, Stuttgart) are described, namely under reaction conditions that for the implementations mentioned are known and suitable. You can also of variants Ge known per se, not mentioned here in more detail make use of.

The compounds of the invention can e.g. B. according to scheme 1 getting produced:

Scheme 1

The compounds of formula I have a wide range of uses Area. They can easily be used as stabilizers in the food sector and used in technical products.

The invention also relates to the use of the invention ß compounds as an additive to liquid crystal mixtures, liquid crystal individual linen components, lubricants, heat transfer media, fuels, Pharmaceutical products, vitamin preparations, cosmetics, food, paint substances, paints, polymers, elastomers, detergents, solutions agents, paper and pesticides.

The compounds of formula I are used in concentrations of 0.01 to 5% by weight, preferably 0.01 to 2% by weight, and in particular 0.01 to 1 wt .-% added to the substance to be stabilized.

Due to the rod-like structure, the connections of the Formula I in particular as stabilizers of liquid-crystalline single components and liquid crystal mixtures as they are the liquid crystalline Properties interfere far less than the stabilizers from the stand of the technique.

Since the compounds of the invention are particularly low They can have vapor pressure, even at high temperatures be used. They have properties similar to liquid crystals and lead to no discoloration in the liquid crystal mixtures. in the In contrast to known stabilizers, they do not have a negative effect the clearing point of the liquid-crystalline individual components.

The stabilization of the liquid crystals or liquid crystal mixtures takes place in a conventional manner. As a rule, all components solved together, preferably at elevated temperature.

The stabilizers according to the invention are preferred in liquid crystal mixtures used for active matrix displays, since they do not belong to any significant impairment of the voltage holding ratio.

In particular, the stabilizers according to the invention are suitable for increasing the thermal load capacity of compounds which have the following structural units:

The invention therefore also relates to a liquid-crystalline medium, that contains at least two liquid crystalline compounds and additionally a pyridine of formula I.

The liquid-crystalline medium according to the invention generally exists from 2 to 25, preferably 3 to 15 liquid crystal components and a stabilizer of formula I. However, in individual cases it can also more than 25 components are components of a phase according to the invention be, e.g. B. up to 50 components and more. The other ingredients are preferably selected from the nematic or nemato gene substances, especially the known substances from the Classes of azoxybenzenes, benzylidene anilines, biphenyls, terphenyls, Phenyl or cyclohexyl benzoates, cyclohexane carboxylic acid phenyl or -cyclohexyl esters, phenylcyclohexanes, cyclohexylbiphenyls, cyclohexyl cyclohexanes, cyclohexylnaphthalenes, decahydronaphthalenes, 1,4-biscyclo hexylbenzenes, 4,4'-biscyclohexylbiphenyls, phenyl- or cyclohexylpyri midine, phenyl- or cyclohexyldioxane, phenyl- or cyclohexyldithiane, 1,2-bisphenylethane, 1,2-biscyclohexylethane, 1-phenyl-2-cyclohexyl ethanes, optionally halogenated stilbenes, benzylphenyl ether, tolanes and substituted cinnamic acids.

The most important compounds which are suitable as constituents of liquid-crystalline phases according to the invention can be characterized by the formula II

R ^{1 *} -LGER ^{2 *} II

where L and E each have a carbo- or heterocyclic ring system consisting of the 1,4-disubstituted benzene and cyclohexane rings, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,6-difluoro 1,4-phenylene, 4,4'-disubstituted biphenyl, phenylcyclohexane and cyclohexylcyclohexane systems, 2,5-disubstituted pyrimidine and 1,3-dioxane rings, 2,6-disubstituted naphthalene, di- and tetrahydronaphthalene, quinazoline and tetrahydro quinazoline educated group,

G

-CH = CH- -N (O) = N- -CH = CY- -CH = N (O) - -C∼C- -CH ₂ -CH ₂ - -CO-O- -CH ₂ -O- -CO-S- -CH ₂ -S- -CH = N- -COO-Phe-COO-

or a CC single bond, Y halogen, preferably fluorine or chlorine, or -CN, and R ¹

and R ²

unsubstituted or substituted by one or more fluorine atoms alkyl, alkoxy, alkanoyloxy or alkoxycarbonyloxy having up to 18, preferably up to 8 carbon atoms, or one of these radicals also CN, NO ₂

, CF ₃

, F, Cl or Br mean.

In most of these compounds, R ^{1 *} and R ^{2 *} are different from one another, one of these radicals usually being an alkyl or alkoxy group and the other alkyl, alkenyl, alkoxy, CN, F, Cl, OCF ₃ , OCHF ₂ , OCH ₂ CF ₃ , OCHFCF ₃ , OCF ₂ CHFCF ₃ , OCH = CF ₂ , OCF = CF ₂ or CH = CF ₂ . However, other variants of the proposed substituents are also commonly used. Many such substances or mixtures thereof are commercially available. All of these substances can be prepared by methods known from the literature or by analogy.

In the present application and in the following examples, the structures of the liquid crystal compounds are indicated by acronyms, the transformation into chemical formulas taking place according to Tables A and B below. All residues C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl residues with n or m C atoms. The coding according to Table B goes without saying. In Table A only the acronym for the basic body is given. In individual cases, there is a code for the substituents R ¹ , R ² , L ¹ and L ² separated from the acronym for the base body:

Preferred mixture components can be found in Tables A and B:

Table A

Table B

The following examples are intended to illustrate the invention without limiting it. "Conventional work-up" means: water is added, the mixture is extracted with dichloromethane, the mixture is separated off, the organic phase is dried, evaporated and the product is purified by crystallization and / or chromatography. Above and below, percentages mean percent by weight. All temperatures are given in degrees Celsius. Mp. Means melting point and Kp. = Clearing point. Furthermore, K = crystalline state, N = nematic phase, S = smectic phase and I = isotropic phase. The information between these symbols represents the transition temperatures. Δn means optical anisotropy (589 nm, 20 ° C). The viscosity (mm ² / sec) was determined at 20 ° C.

The following abbreviations are used:
BuLi butyllithium
DAST Diethylaminosulfur trifluoride
DCC dicyclohexylcarbodiimide
DIBALH diisobutyl aluminum hydride
DMAP 2-dimethylaminopyridine
DDQ dichlorodicyanobenzoquinone
KOT potassium tertiary butanolate
NH ₄ Cl ammonium chloride
THF tetrahydrofuran
TMEDA tetramethylethylenediamine
pTsOH p-toluenesulfonic acid

I. Examples

example 1

900 ml of THF are cooled to 0 ° C. and 0.388 mol of lithium diisopropylamide, 0.800 mol of 1,3-dimethyl-2-imidazolidinone dissolved in 100 ml of THF and 0.399 mol of 4-methylpyridine dissolved in 100 ml of THF are added with stirring. After 2 hours of stirring at 0 ° C., 0.400 mol of A dissolved in 400 ml of THF are slowly added dropwise to the reaction mixture. The mixture is allowed to warm up slowly to 20 ° C., diluted with water, neutralized with dilute HCl, and worked up as usual.
K 79 N (77.6) I, Δε = +4.5, Δn = +0.060

The following pyridines of the formula become analogous

produced:

II. Stability studies / influence of various stabilizers

The addition of 0.1-1% pyridine derivatives increases the thermal Resilience of z. B. axially fluorinated cyclohexane derivatives (1) and 2.2 difluoro-1,3-dioxanane (2). The temperature from which the decomposition occurs also depends on the host used. For stability tests was a solution of 10% w / w XIX-3-3 or XICU-3-F in Presence of various stabilizers in the course of 30 min Air access heated. Decomposition begins in the absence of air axial fluorine derivatives only at about 50 ° C higher temperature.

The 2,6-bis (t-butyl) pyridines A and C have the same stabilizing effect as the 4-unsubstituted body. The effectiveness of the 2,6-bis (t-butyl) pyridines and the unsubstituted pyridines is roughly comparable. However, especially for TFT applications, the unsubstituted pyridines from a concentration of approx. 0.1% lead to a significant reduction in the holding ratio. This effect only occurs for the sterically shielded 2,6-bis (t-butyl) pyridines at concentrations <0.5-1%. This is a decisive advantage over the previous state of the art.

III. Liquid crystal mixtures

D 0.90% PCH-302 8.93% CCH-301 29.48% CBC-53F 4.47% CBC-33 4.47% CBC-53 5.36% PCH-301 8.93% CBC-55F 4.47% CBC-33F 4.47% CCN-55 8.93% CCN-47 9.83% XEX-V-2V 9.75% Clarification point: 79 ° C Δε [1 kHz, 20 ° C]: -1.6

Claims (9)

1. pyridine derivatives of the formula I,
wherein
R ^a , R ^b and R ^c each independently of one another H, an unsubstituted or with CN or with at least one halogen substituted alkyl or alkenyl radical having up to 12 C atoms, wherein one or more non-adjacent CH ₂ groups are selected by a radical from the group -O-, -S-, -CO-, -O-CO-, -CO-O- and -C∼C- can be replaced, and
m and n each independently of one another 0, 1 or 2,
mean. 2. pyridines of the formulas I1 to I3,
wherein
R ^a , R ^b and R ^c each independently have the meanings given in Claim 1. 3. Pyridines according to claim 1 or 2, characterized in that R ^b and R ^c each independently represent H, t-butyl or t-pentyl. 4. Pyridines according to one of claims 1 to 3, characterized in that R ^b = R ^c . 5. Use of the pyridines according to one of claims 1 to 4 as Stabilizers. 6. Use of the pyridines according to claim 5 for the stabilization of acid-labile liquid crystals and liquid crystal mixtures. 7. Liquid crystalline medium containing at least two liquid crystals line connections, characterized in that there is at least one Contains pyridine according to claim 1.   8. Liquid-crystalline medium according to claim 7, characterized in net that it is 0.01 to 5 wt .-% of at least one pyridine of formula I. contains. 9. Electro-optical display containing a liquid-crystalline medium according to claim 7.