JPS63264573A - Optically active 6-substituted pyridine-3-carboxylic ester and liquid crystal - Google Patents

Abstract

NEW MATERIAL:An optically active 6-substituted-pyridine-3-carboxylic acid ester of formula I (R1 is 6-13C alkyl; R2 is optically active alkyl). EXAMPLE:(S)-2-Methylbutyl 6-(4'-n-dodecyloxybenzoyloxy)pyridine-3-carboxylate. USE:It is used as a component of liquid crystal composition. It is stable to moisture and light, resists to weathering, becomes chiral smectic C liquid crystals in the range of room temperature. It effectively expands the temperature range of chiral smectic C phase in a liquid phase composition. PREPARATION:As shown in the reaction equations, a compound of formula II is heated together with thionyl chloride under reflux and the unreacting thionyl chloride is distilled off to give the corresponding acid chloride. The acid chloride of formula III is dissolved in benzene or the like and allowed to react with a compound of formula IV in the presence of a pyridine to give the compound of formula I.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to novel 6-substituted-pyridine-3-carboxylic acid ester compounds.

Such 6-substituted-pyridine-3-carboxylic acid ester compounds are useful as liquid crystal compounds.

Liquid crystals include nematic liquid crystals, smectic liquid crystals, and cholesteric liquid crystals, among which the compound of the present invention is a smectic liquid crystal, particularly a chiral smectic C liquid crystal, which has strong electrostatic properties and is useful as a display element material.

[Conventional technology]

Chiral smectic cFpi crystals have a helical structure with a fairly long pitch length, but in cells with a cell gap shorter than the pitch length of the helical structure, they exhibit residual spontaneous polarization and exhibit extremely high velocity ( 1-10
0 microseconds) and also exhibits memory properties (N,
A, C1ark et al. App 1. Phys, let t,
, 36.899 (1980)).

By utilizing the high-speed optical switching phenomenon of chiral smectic C liquid crystal, it becomes possible to produce liquid crystal display elements with significantly faster response times than conventional twisted nematic type liquid crystal display elements, making it possible to manufacture large-screen liquid crystal display devices. It can be put into practical use.

As such chiral smectic C liquid crystal, p-
Decyloxybenzylidene-p”-amino-2-methylbutylcinnamate (hereinafter abbreviated as DOBAMBC)
is known (R, B.

(See MeyBr et al. J, de Physique 3rd edition, L-69 (1975)).

Several liquid crystals having pyridine rings have been reported as nematic liquid crystal materials (Japanese Patent Laid-Open No. 58-12127
Publication No. 2, JP-A-60-163864, JP-A-6
0-163865, etc.), but there are few examples of smectic liquid crystals, and almost no compounds identified as smectic C are known.

[Problem that the invention seeks to solve]

However, since DOBAMBC has a Schiff base structure, it is unstable to moisture, and the ethylene structure of cinnamic acid is unstable to light, which are serious drawbacks, so it cannot be widely used as a liquid crystal. I can't.
Furthermore, the temperature range of the chiral smectic C phase that enables high-speed switching phenomena is higher than room temperature, which is not practical.

[Means and effects for solving the problem] The present inventors have discovered that chiral smectic C has excellent weather resistance and can be used at room temperature.
As a result of intensive studies aimed at providing a novel compound exhibiting liquid crystallinity, we found that the general formula (I) (wherein R1 represents an alkyl group having 6 to 18 carbon atoms, R
We have discovered an optically active 6-substituted-pyridine-3-carboxylic acid ester compound represented by (2 represents an optically active alkyl group), and the compound exhibits the ability to form the desired chiral smectic C liquid crystal in a temperature range around room temperature. We have discovered that this is the case, and have arrived at the present invention. Further, since such a compound has good compatibility with other liquid crystal compounds, when used as a component of a liquid crystal composition, it is effective in expanding the temperature range of the chiral smectic C phase of the liquid crystal composition. R1 in general formula (I) is an alkyl group having 6 to 18 carbon atoms. Further, R2 in the general formula (I) is an optically active alkyl group, and examples of optically active groups that can be preferably used include an optically active 2-methylbutyl group, 2-methylpentyl group, 2-methylhexyl group, 2-methylhebutyl group, 2-methylhexyl group, and 2-methylhexyl group. Methyloctyl group, 1-methylpropyl group, 1-methylbutyl group, 1-methylpentyl group, 1-methylhexyl group, 1-
Examples include methylhebutyl group, 3-methylpentyl group, 3-methylhexyl group, 3-methylheptyl group, 5-methylhebutyl group, and use of optically active 2-methylbutyl group is particularly preferred.

Further, in the optically active alkyl group represented by R2 in general formula (I), some of the carbon atoms in the carbon chain may be substituted with oxygen atoms. Examples of such optically active groups that can be preferably used include 2-methoxypropyl group, 2-ethoxypropyl group, 2-propoxypropyl group, 2-butoxypropyl group, 2-bentroxypropyl group, and 2-hexyloxypropyl group. Examples include propyl group.

Optically active 6-substituted pyridine of general formula (I) of the present invention
3-Carboxylic acid ester compounds do not have functional groups that are unstable to moisture or light, such as azomethine, azo, azoxy, or ethynyl groups as structural components, and are composed only of stable ester and ether groups. Therefore, it has excellent weather resistance and becomes a chiral smectic C liquid crystal in the temperature range around room temperature, so it is highly practical.

The optically active 6-substituted-pyridine-3-carboxylic acid ester compound of general formula (I) can be synthesized according to the reaction formula described below.

R engineering 0 (J) (■) 〇111---→ (I) Formula (After heating and refluxing the old compound with an excess amount of thionyl chloride for several hours, unreacted thionyl chloride was distilled off under reduced pressure. The acid chloride (III) is then dissolved in an aromatic hydrocarbon solvent such as benzene or toluene in the presence of an organic base compound such as pyridine or triethylamine. The compound of general formula (I) is synthesized by reacting with 6-hydroxynicotinic acid optically active alkyl ester (IV) at room temperature or under heating conditions for several hours.The obtained crude compound (I) is subjected to a column. Purify using conventional methods such as chromatography and recrystallization.

Further, the compound of formula (II) can be prepared by reacting an alkyl halide having 6 to 18 carbon atoms, preferably an alkyl bromide, with 4-hydroxybenzoic acid in ethanol and an aqueous potassium hydroxide solution to prepare potassium 4-alkoxybenzoate. It can be easily synthesized by converting it into a salt and making it acidic with hydrochloric acid.

The compound of formula (IV) can be obtained by esterifying 6-hydroxynicotinic acid with a predetermined optically active alcohol in the presence of a sulfuric acid catalyst or by protecting the hydroxyl group as a benzyl ether and then converting it into an acid chloride. It can be easily synthesized by reacting with an optically active alcohol and hydrogenolyzing benzyl ether as a protecting group.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 6-(4'-n-dobutyloxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-methylbutyl ester (R1=CrzHas, R2 in general formula (I)
= (S)-2-methylbutyl)6-hydroxynicotinic acid 20.0g (0,144 mol), (S)-2
-Methylbutyl alcohol 37.95g (0,431
A mixture of 8.9 ml of concentrated sulfuric acid and 70 ml of toluene was heated under reflux for 10 hours while azeotropically removing by-product water.

After cooling, 200 ml of chloroform was added to extract the produced ester, and the chloroform layer was washed twice with a 5% aqueous sodium carbonate solution, washed with water, and dried over anhydrous magnesium sulfate. The crude product obtained by distilling off the solvent under reduced pressure was subjected to silica gel column chromatography and n-hexane/
Purified by recrystallization from ethyl acetate mixed solvent, 6-
14.14 g (yield: 47%) of hydroxynicotinic acid (S)-2-methylbutyl ester was obtained. The melting point of this compound was 103-4°C.

0.92 g (3.0 mmol) of 4-n-dobusyloxybenzoic acid was added to 4 ml of thionyl chloride, and the mixture was heated under reflux for 2 hours, and then unreacted thionyl chloride was distilled off under reduced pressure.

After adding and dissolving the obtained crude acid chloride in 10 ml of benzene, 6-hydroxynicotinic acid (S)-2-
Methyl butyl ester 0.84-g (4.0 mmol), triethyl, amine 2.02-g (20 mmol)
and 5 ml of benzene at room temperature, and the mixture was heated under reflux for 4 hours. After cooling, the reaction mixture was filtered, and the filtrate was washed successively with 1N HCl, 1N NaOH, and saturated brine, and dried over anhydrous magnesium sulfate.

The crude product obtained by distilling off the solvent under reduced pressure was purified by silica gel column chromatography and recrystallization from an ethanol/water mixed solvent. The yield of 6-(4'-n-dobutyloxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-methylbutyl ester is 0.60
The yield was 40%. The infrared absorption spectrum of this compound is shown in FIG. Further, the δ (ppm) of the HNMR spectrum (CD Cl g, TMS internal standard) was as follows.

6.89-9.07 (m, 7H, pyridine ring and benzene ring) 4.21 (d, J=6Hz, 2H,0-CH--C
H) 4.03 (t, J=6Hz, 2H10-CH-CHx
) 0.7 to 2.1 (m, 32H) The results of elemental analysis of this compound are as follows, and were in good agreement with the theoretical values. Theoretical value (CioHatNO5 and r) C72, 40% H8, 71% N2.81
% Analysis value C72.3% H8.8% N 2.7%.

Based on the above analytical data, this compound is 6-(4=-n
-dobutyloxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-methylbutyl ester.

Further, this compound exhibited the following liquid crystal phase transition and had a monotropic chiral smectic C phase near room temperature.

Examples 2 to 5 The following 6-(4- -n-
Alkoxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-methylbutyl ester was synthesized.

Indeed Example 2 6-(4'-n-hexyloxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-methylbutyl ester (Rs'' in general formula (I))
C6Hs 3, R1L= (S)-2-methylbutyl) Example 36-(4''-n-octyloxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-methylbutyl ester (in general formula (I) R1=CeH
s, Rt= (S) 2-methylbutyl) Example 46-(4--n-decyloxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-methylbutyl ester (R in general formula (I) ,=Ct.Ht
l, R5L= (S)-2-methylbutyl) Example 56-(4--n-hexadecyloxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-methylbutyl ester (in general formula (I) R1=Cl1;
R13, Rt=(S)2-methylbutyl) The identification of these compounds was determined by infrared absorption spectra, 'HN
Performed by MR spectroscopy (CDC1x, TMS internal standard) and elemental analysis.

The measurement results of liquid crystal phase transition of the compounds of Examples 2 to 5 are shown in Table 1 together with the results of Example 1.

(Margin below) Table 1 Example 6 6-(4--n-decyloxybenzoyloxy)pyridine-3-carboxylic acid (S) -2-butoxypropyl ester (R1=Ct o H in general formula (I)
t t, Rz = (S) 2-butoxypropyl) Instead of (S)-2-methylbutyl alcohol, (S)
The title compound was synthesized in exactly the same manner as in Example 4, except that (S)-2-butoxy-1-propatool synthesized from )-lactic acid ethyl ester was used. Identification of this compound was performed by infrared absorption spectrum, 'HNMR spectrum (CDC13, TMS internal standard) and elemental analysis.

This compound showed the following liquid crystal phase transition.

Incidentally, (S)-2-butoxy-1-propanol was synthesized by the following method.

Adding 92.8 g (0.4 mol) of silver oxide to a mixture of 35.4 g (0° 3 mol) of (S)-lactic acid ethyl ester and 147.2 g (0° 8 mol) of n-butyl iodide, Stirred at room temperature for 3 days. By filtering off silver oxide, concentrating the filtrate, and then distilling it, (S)-2-butoxypropionic acid ethyl ester (b, p, 93°C/24m
mHg) 30.6 g (0.18 mol) were obtained. Add 3.8 liters of lithium aluminum hydride to a nitrogen-substituted flask.
Weigh out g (0゜1 mole) and add 100m of dry ether.
1 was added thereto, and 22.7 g (0.13 moles) of (S)-2-butoxypropionic acid ethyl ester was added dropwise over 20 minutes while stirring at room temperature. After continuing stirring at room temperature for 1 hour, 3.6 ml of water and 3.6 ml of 15% aqueous sodium hydroxide solution were added.
．． 6 ml of water and 10.8 ml of water were sequentially added dropwise and stirred for 30 minutes. After filtering out the aluminum oxide produced, the filtrate is concentrated and distilled to produce (S)-2-butoxy-
1-Proper tool (92℃/39mmHg) 13.5g
I got it.

Example 7 6-(4′-n-decyloxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-ethoxypropyl ester (R1=C1゜I(zt
, R4=(S) 2-ethoxypropyl) The title compound was synthesized in the same manner as in Example 4 using (S)-2-nitoxy-1-propatool. Identification of this compound was performed by infrared absorption spectrum, 'HNMR spectrum (CDC1a, TMS internal standard) and elemental analysis.

The melting point of this compound was 45°C.

Example 8 (Liquid crystal composition) 6-(4'-n-dobutyloxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-methylbutyl ester of Example 1 (R+=CxtH in general formula (I))
ts, Rt= (S) 2-methylbutyl) and 6-(4--n-decylbiphenyl-4- of the following structural formula (V))
carbonyloxy) and lysine-3-carboxylic acid (S)
A liquid crystal composition was prepared by mixing equimolar amounts of -2-methylbutyl ester.

The phase transition temperature of this liquid crystal composition upon cooling is as follows, and chiral smectic C is observed in a wide temperature range around room temperature.
It had a phase.

84° 54° 11' I (i-form)→SA-+Sc8→C (crystal) The phase transition temperature of compound (■) alone upon cooling is as follows.

Example 9 (Liquid crystal composition) 6-(4''-n-hexadecyloxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-methylbutyl ester of Example 5 (R1= in general formula (I) C.I.
6813, R2 = (S) 2-methylbutyl) and 6-n-hexyloxy-3-pyridinecarbonyl a-4--(S)-2-methylbutyroxycarbonyl-4-piphenyl of the following structural formula (VI) A liquid crystal composition was prepared by mixing equimolar amounts of esters.

The phase transition temperature of this liquid crystal composition upon cooling is as follows, and chiral smectic C is observed in a wide temperature range around room temperature.
It had a phase.

The phase transition temperature of compound (Vl) alone upon cooling is as follows.

Example 10 (Liquid crystal composition) 6-(4'-n-ocderoxybenzoyloxy)pyridine-3-carboxylic acid (S)-2-methylbutyl ester of Example 3 (RI= Ca
H17, Rz=(S) 2-methylbutyl) and Compound (V) of Example 8 were mixed in equimolar amounts to prepare a liquid crystal composition.

The phase transition temperature of this liquid crystal composition upon cooling was as follows, and it had a chiral smectic C phase in the temperature range below room temperature.

The compound of Example 3 does not become a liquid crystal when used alone, but when used as a composition, it exhibits a chiral smectic C liquid crystal phase in a low temperature range.

〔Effect of the invention〕

According to the present invention, a novel pyridine compound can be provided.

In addition, the compound of the present invention is stable against moisture and light,
It has excellent weather resistance and becomes a chiral smectic C liquid crystal in the temperature range around room temperature.

[Brief explanation of the drawing]

FIG. 1 shows the compound 6-(4=-n-dobutyloxybenzoyloxy)pyridine-3-carboxylic acid (S
2 is a chart of an infrared absorption spectrum of )-2-methylbutyl ester. Patent application Daitoshi Co., Ltd.

Claims (3)

[Claims] (1) General formula (I) ▲Mathematical formula, chemical formula, table, etc.▼(I) (In the formula, R_1 represents an alkyl group having 6 to 18 carbon atoms,
R_2 represents an optically active alkyl group), an optically active 6-substituted pyridine-3-carboxylic acid ester compound. (2) Optically active 6 according to claim 1, wherein R_2 in general formula (I) is an optically active 2-methylbutyl group.
-Substituted-pyridine-3-carboxylic acid ester compound. (3) General formula (I) ▲Mathematical formula, chemical formula, table, etc.▼(I) (In the formula, R_1 represents an alkyl group having 6 to 18 carbon atoms,
A liquid crystal comprising an optically active 6-substituted pyridine-3-carboxylic acid ester compound represented by R_2 represents an optically active alkyl group.