JPH0761973B2 - Optically active 2-fluoroalkanoic acid and liquid crystal composition containing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel optically active substance and a liquid crystal composition containing the same.

[Background technology]

As the various optical elements characterized by having optical activity, many are known as exemplified below.

1) Utilizing the cholesteric / nematic phase transition effect in the liquid crystal state (JJWysoki, A. Adams and WH
aas; Phys.Rev.Lett., 20,1024 (1968)), 2) White Taylor type guest in the liquid crystal state. Using host effect (DLWhite and GNTaylor;
J.Appl.Phys., 45 , 4718 (1974)), 3) Chiral smectic C phase, H in liquid crystal state
(NAClark and STLagerwall; Appl.Phys.) That utilizes the ferroelectric effect of the phase, F phase, I phase, G phase, K phase, and J phase.
Lett., 36 , 899 (1980)), 4) What is used as a notch filter or band bass filter by fixing the one having a cholesteric phase in the liquid crystal state in the matrix and utilizing its selective scattering property (FJKahn). , Appl.Phys.Lett., 18,231
(1971)), which is used as a circularly polarized beam splitter using circularly polarized light characteristics (SDJacobs, SPIE, 37,98 (1
981)); etc.

A detailed description of each method is omitted, but it is important as any display element or modulation element.

An optically active compound is used as a main component of a functional material constituting these optical elements or as an important functional component although it is a relatively small amount component. For example H. Arnol
d, Z.Phys.Chem., 226,1446 (1964) is expressed in a liquid crystal state by adding another optically active substance or a liquid crystalline compound to the above-mentioned optical element material, particularly a liquid crystal material. It is disclosed to control the type of liquid crystal phase and the temperature range. In addition, liquid crystal materials driven by electric field response,
It is expected that a liquid crystal material having a better electric field response will be obtained by introducing a compound having a large dipole.

However, conventionally known optically active substances are not easy to change the length of a group to be introduced, and thus many of them are not suitable for controlling the liquid crystal state.

Many of such optically active functional materials are themselves synthesized via optically active intermediates.

Conventionally, as an optically active intermediate for synthesizing a functional material required for an optical element characterized by having optical activity, 2-methylbutanol, secondary octyl alcohol,
Secondary butyl alcohol, p- (2-methylbutyl) chloride
Benzoic acid, secondary phenethyl alcohol, amino acid derivatives, camphor derivatives, cholesterol derivatives and the like are known.

However, these have the following drawbacks. The structure of the optically active chain hydrocarbon derivative is difficult to change, and, except for some, it is very expensive. Amino acid derivatives are relatively inexpensive and their structures can be easily modified, but the hydrogen groups of amines are chemically strongly active, and hydrogen bonding and chemical reactions are likely to occur, which tends to limit the properties of functional materials. . It is difficult to change the structure of the camphor derivative and the cholesterol derivative, and the characteristics of the functional material are likely to be adversely affected by steric hindrance.

Further, among the optical elements characterized by having optical activity, in the method of using the electric field response optical effect in the liquid crystal state, a polar group has been introduced in order to enhance the responsiveness. Most of the optically active intermediates of (1) had a small polarity or could not effectively utilize the polar group.

In particular, in a ferroelectric liquid crystal, it is known that the response speed is proportional to the spontaneous polarization, and it is desired to increase the spontaneous polarization for speeding up. From such a point P.
Keller et al. Have shown that the introduction of a chlorine group into the asymmetric carbon can increase spontaneous polarization and increase the response speed (CRAcad.Sc.Paris, 282 C, 639 (1976)). However, the chlorine group introduced into the asymmetric carbon is chemically unstable and has a drawback that the stability of the liquid crystal phase is deteriorated due to its large atomic radius, and therefore its improvement is desired. ing.

Furthermore, optically active 2-fluoroalkanoic acid is known as a fluorocarbon group introduced into an asymmetric carbon. This is a method of diazotizing an α-amino acid in hydrogen fluoride / pyridine by GAOLAH et al. [J. Org. Chem., Vo
l.44 (2) 3872-3881 (1979)] has been reported.
The alkane moiety of 2-fluoroalkanoic acid is a methyl group, an ethyl group, an isopropyl group, an isobutyl group, or a se group because an optically active α-amino acid is used as a starting material.
A c-butyl group or the like is used. However, since these alkane moieties are all short and lack linearity,
When used as an optically active functional material or an optically active intermediate, it has been a major limitation.

[Object of the Invention]

In view of the above-mentioned circumstances, the main purpose of the present invention is not only useful as a suitable optically active intermediate, but also useful for obtaining high stability and large spontaneous polarization when induced into a liquid crystal compound. Another object of the present invention is to provide an optically active substance and a liquid crystal composition containing the same.

Further, according to the present invention, it is easy to change the length of the alkyl group, which results in H. Arnold, Z. Phys. Chem., 226, 146 (1
964), it is an object of the present invention to provide a liquid crystal compound capable of controlling the type and temperature range of a liquid crystal phase that develops in a liquid crystal state, and a liquid crystal composition containing at least one compound component thereof. To do.

[Outline of Invention]

The present invention firstly comprises the general formula (I) (Wherein R is a linear alkyl group having 7 to 12 carbon atoms, and C * is an asymmetric carbon atom), and an optically active 2-fluoroalanoic acid is provided.

The compound represented by the general formula (I) has the effects of controlling the liquid crystal state and improving the electric field response as described above, and further binds to another functional intermediate without losing its optical activity. It is also expected that various derivatives will be synthesized.

However, to date, no optically active compound as represented by the formula (I) has been known.

The inventors of the present invention have conducted extensive studies based on the above findings, and as a result, partially oxidize the optically active 2-fluoro-1-alkanol represented by the following general formula (II) using an appropriate oxidizing agent. Thus, the optically active compound represented by the above formula (I) was successfully synthesized, and the present invention was completed.

(In the general formula (II), R represents a straight-chain alkyl group having 7 to 12 carbon atoms, and C * represents an asymmetric carbon atom.) A novel one represented by the general formula (I) of the present invention. The optically active substance itself is a useful liquid crystal component as described above. For example, by adding a very small amount to a nematic liquid crystal composition for a twisted nematic (TN) type display element, it is possible to prevent the occurrence of a stripe pattern (reverse domain) on the display surface and increase the uniformity of the display. It can be used effectively.

That is, the present invention also provides a liquid crystal composition containing at least one optically active compound represented by the above general formula (I).

[Specific Description of the Invention]

According to the present invention, in order to produce the optically active compound of the above formula (I), the optically active 2-fluoro-1-alkanol represented by the above formula (II) is used as a starting material. Such an optically active 2-fluoro-1-alkanol can be obtained by, for example, a method of loading hydrogen fluoride on an optically active 1,2-epoxyalkane as shown in the specification of Japanese Patent Application No. 60-232886. Easily obtained by.

Next, by reacting the above optically active 2-fluoro-1-alkanol with acetic anhydride or acetyl chloride,
After forming the acetic acid ester, the target optically active 2-fluoroalkanoic acid can be obtained by acting concentrated nitric acid in an acetic acid solvent.

In the optically active compound represented by the formula (I) of the present invention, the above R can be widely changed by changing the carbon number of the alkane moiety of 2-fluoro-1-alkanol as a starting material. The present invention provides that R is an alkyl group having 7 to 12 carbon atoms.

The optically active compound represented by the formula (I) thus obtained has a carboxylic acid group in place of the optically active chain hydrocarbon derivative, amino acid derivative, camphor derivative and cholesterol derivative as described above. It can be used to bond with other intermediates by ester bond or the like.
Therefore, it is useful as an intermediate for producing a functional material for forming an optical element, and also as an intermediate for the synthesis of various natural optically active substances.

Further, the optically active substance of the formula (I) is effective in preventing the generation of the reverse domain in the TN type cell by adding to the liquid crystal of the mastic. In this case, it is preferable to use the optically active substance of the formula (I) in an amount of 0.01 to 50% by weight of the obtained liquid crystal composition.

Also, by adding to nematic liquid crystal or chiral nematic liquid crystal, as chiral nematic liquid crystal,
It can be used as a liquid crystal composition in a phase transition type liquid crystal element or a white Taylor type guest-host type liquid crystal element. In this case, 0.01 to 80% by weight of the obtained liquid crystal composition
It is preferable to use the optically active substance of the formula (I) so that

Further, the optically active substance of the above formula (I) is contained in the liquid crystal composition exhibiting the ferroelectric chiral smectic liquid crystal state by itself in an amount of 0.01 to 80% by weight of the obtained liquid crystal composition. Properties such as durability can be improved by adding the optically active substance of the formula (I) to. Further, a liquid crystal composition exhibiting a ferroelectric chiral smectic phase can be provided by adding it to a smectic liquid crystal having structural formulas and phase transition temperatures shown below as 1) to 5). In this case, 0.01 to 80% by weight of the obtained liquid crystal composition
It is preferable to add the optically active substance of the formula (I) in such a proportion that When an optically active substance of the formula (I) is added and used to provide a chiral smectic liquid crystal composition as described above, a large spontaneous polarization can be obtained, and the response time can be shortened. The threshold voltage can be lowered.

Here, the symbols indicate the following phases, respectively.

Cryst .: Crystal phase, SmA: Smectic phase A, SmB: Smectic phase B, SmC: Smectic phase C N: Nematic phase, Iso .: Isotropic phase.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 An optically active 2-fluorooctanoic acid was produced according to the following reaction process formula.

(1) Synthesis of optically active 2-fluorooctyl acetate 2.22 g (15.5 mmol) of 2-fluorooctyl alcohol, 1.61 g (15.8 mmol) of acetic anhydride, 0.56 g of sodium acetate (6.
(8 mmol) was added to 5 ml of dry benzene and refluxed at 90 ° C. for 4 hours. After the reaction was completed, 5 ml of water was added and the mixture was extracted twice with 10 ml of benzene. The extract was washed twice with 10 ml of water, dried, evaporated to remove the solvent, and distilled under reduced pressure to obtain 2.19 g (11.5 mmol) of 2-fluorooctyl acetate.

bp 114 ℃ -117 ℃ / 27mmHg Yield 77% ▲ [α] ^22.8 _D ▼ ＋ 3.91 ° (C = 1.124 Et ₂ O) ▲ [α] ^22.0 ₄₃₅ ▼ + 9.61 ° (C = 1.124 Et ₂ O) (2) Synthesis of optically active 2-fluorooctanoic acid 2.14 g (11.3 mmol) of 2-fluorooctyl acetate was added with 5.6 ml of acetic acid and 6.8 ml of 16N nitric acid, and then at 55 ° C-60 ° C for 24 hours,
It was stirred. After the reaction was completed, 40 ml of ice water was added, and the mixture was extracted once with 30 ml of ether and four times with 10 ml. 50 ml of 2N-sodium carbonate aqueous solution was added to the extract to make it alkaline, the organic layer was removed, and 6N-hydrochloric acid was added to the aqueous layer to make it acidic (PH = 4), once with 30 ml of ether and three times with 10 ml of ether. Extracted. The extract was washed twice with 10 ml of water, dried, distilled off the solvent and distilled under reduced pressure to obtain 1.26 g (7.78 mmol) of 2-fluorooctanoic acid.

bp 101 ℃ -102 ℃ / 3mmHg Yield 69% ▲ [α] ^22.8 _D ▼ -13.6 ° (C = 1.060 Et ₂ O) ▲ [α] ^22.4 ₄₃₅ ▼ -21.7 ° (C = 1.060 Et ₂ O) IR (Liquid) Membrane) cm ^-1 2940,2880,1720,1460,1385,1340,1250,1140,1120,1090,
1040, 930, 720, [Example 2] Synthesis of optically active 2-fluoro-1-heptanoic acid Acetate of optically active 2-fluoro-1-heptanol [synthesized from optically active 2-fluoro-1-heptanol in the same manner as in Example 1] . ▲ [α] ¹⁵ _D ▼ + 2.6 ° (C = 2.0, acetone)] 0.70 g (4 mM), glacial acetic acid 2 ml and concentrated nitric acid (d =
1.42) 2.4 ml of the mixture was heated and stirred at 60 ° C. for 25 hours. To this reaction solution, 25 ml of cold water was added and extracted with 10 ml of ether three times. This ether solution was added with 5.04 g of sodium hydrogen carbonate and water 2
Add 0 ml little by little to the suspension, stir well, separate the ether layer, acidify the aqueous layer with 2N hydrochloric acid,
It was extracted 3 times with 10 ml of ether, and the ether layer was dried over anhydrous magnesium sulfate. The ether was distilled off under reduced pressure and then distilled using a Kugelrohr distillation apparatus to obtain 0.33 g (2.3 mM) of 2-fluoro-1-heptanoic acid. 55% yield, boiling point 130-140
℃ / 15mmHg, (however, the temperature of the tube of Kugelrohr distillation unit) ▲ [α] ²⁰ _D ▼ -10.6 ° (C = 2.0 CH ₂ Cl ₂ ) IR (liquid film) cm ^-1 ; 2940,2860,1720,1450, 1385,1340,1250,1140,1085,1030,
930,730 [Examples 3 to 4] According to Example 1 or 2, 2-fluoro-1-alkanol acetates having different R in the general formula (I) and 2-fluoro-1-alkanoic acid were obtained. The results are summarized in Table 1 and Table 2.

Example 5 A liquid crystal composition was obtained by adding 5 parts by weight of the optically active substance of Example 1 to 95 parts by weight of MORA8 having the structure shown below. This liquid crystal composition exhibits an SmC * phase, has spontaneous polarization 1.8 times that of MORA8 alone, and has a response time of ± 15 V under conditions of 25 V.
It was about 60% with msec.

[Example 6] A polyimide resin precursor [SP manufactured by Toray Industries, Inc.] was formed on a glass substrate on which an ITO (Indium Tin Oxide) film was formed as a transparent electrode.
-510] to form a film by spinner coating, then 300 ℃
And baked for 60 minutes to form a polyimide film. Next, this coating was subjected to orientation treatment by rubbing, and cells were prepared so that the rubbing treatment axes were orthogonal to each other. (Cell spacing 8 μm) A nematic liquid crystal composition [Rixon GR-63: biphenyl liquid crystal mixture manufactured by Chitso Corp.] was injected into the above cell to form a TN (twisted nematic) cell, which was observed with a polarizing microscope. However, it turned out that a reverse domain (striped pattern) had occurred.

When a liquid crystal mixture obtained by adding the optically active substance (1 part by weight) of Example 1 of the present invention to Rixon GR-63 (99 parts by weight) was observed as a TN cell in the same manner as above,
The reverse domain was not seen, and the nematic phase had good homogeneity. From this, it was found that the optically active substance of the present invention is effective in preventing the reverse domain.

〔The invention's effect〕

As described above, the present invention provides the optically active substance represented by the formula (I) in which a fluorine group having a large dipole moment is directly introduced into an asymmetric carbon atom.

Further, this optically active substance becomes a useful liquid crystal component by itself, and by mixing at least one kind of this optically active substance, the generation of reverse domain of the TN type liquid crystal composition is prevented, or the chiral nematic liquid crystal or the chiral smear is formed. It is also possible to improve the characteristics such as the electric field response of the click liquid crystal and to control the liquid crystal state.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichiharu Katagiri 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Mariko Kai Nihonbashi Muromachi, Chuo-ku, Tokyo 3-1-10 Yamakawa Within Pharmaceutical Industry Co., Ltd.

Claims (2)

[Claims] 1. The following general formula (I): (Here, R is a linear alkyl group having 7 to 12 carbon atoms, and C ^* is an asymmetric carbon atom.) An optically active 2-fluoroalkanoic acid. 2. The following general formula (I) (Here, R is a linear alkyl group having 7 to 12 carbon atoms, and C ^* is an asymmetric carbon atom.) At least one kind of optically active 2-fluoroalkanoic acid represented by A characteristic liquid crystal composition.