JPH0424336B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a novel optically active substance, 2-fluoro-1-alkanol, a method for producing the same, and a liquid crystal composition containing the same. BACKGROUND ART There are many known optical elements, as exemplified below, as various optical elements characterized by having optical activity. (1) Those that utilize the cholesteric-nematic phase transition effect in the liquid crystal state (JJWysoki,
A.Adams and W.Haas; Phys.Rev.Lett., 20,
1024 (1968)), (2) one that utilizes the White-Taylor type guest-host effect in the liquid crystal state (DLWhite
and GNTaylor; J.Appl.Phys., 45 , 4718
(1974)), (3) Chiral smectic C in the liquid crystal state
Phase, H phase, F phase, I phase, G phase, K phase, J phase (NAClark and
STLagerwall; Appl.Phys.Lett., 36 , 899
(1980)), (4) By fixing a substance with a cholesteric phase in the liquid crystal state into a matrix, its selective scattering properties can be utilized to utilize it as a notch filter or bandpass filter (F.
J. Kahn, Appl. Phys. Lett., 18, 231 (1971)),
Products used as circularly polarized beam splitters that utilize circularly polarized light characteristics (SDJacobs, SPIE,
37, 98 (1981)); etc. Although a detailed explanation of each method will be omitted, all of them are important as display elements and modulation elements. As a main component of the functional materials that make up these optical elements, or as a relatively small component,
Optically active compounds are used as important functional components. Many of such optically active functional materials are themselves synthesized via optically active intermediates. Conventionally, optically active intermediates for synthesizing functional materials required for optical elements characterized by having optical activity include 2-methylbutanol, secondary octyl alcohol, secondary butyl alcohol, and p-(chloride). Known examples include 2-methylbutylbenzoic acid, secondary phenethyl alcohol, amino acid derivatives, synthetic derivatives, and cholesterol derivatives. However, these have the following drawbacks. It is difficult to change the structure of optically active chain hydrocarbon derivatives and, with the exception of some, they are very expensive. Amino acid derivatives are relatively inexpensive and their structures can be easily changed, but the hydrogen groups of amines are chemically active and easily cause hydrogen bonds and chemical reactions, which tends to limit the properties of functional materials. . It is difficult to change the structure of chemical derivatives and cholesterol derivatives, and they tend to adversely affect the properties of functional materials due to steric hindrance. Furthermore, among optical elements characterized by having optical activity, polar groups have been introduced in order to improve responsiveness in methods using electro-responsive optical effects in a liquid crystal state. Most of the optically active intermediates had low polarity or were unable to utilize polar groups effectively. Particularly in ferroelectric liquid crystals, it is known that the response speed is proportional to the spontaneous polarization, and it is desired to increase the spontaneous polarization in order to increase the speed. From this point of view, P. Keller et al. showed that by introducing a chlorine group into an asymmetric carbon, it is possible to increase spontaneous polarization and speed up the response speed (CR
Acad. Sc. Paris, 282 C, 639 (1976)). but,
Chlorine groups introduced into asymmetric carbons are not only chemically unstable but also have the disadvantage of decreasing the stability of the liquid crystal phase due to their large atomic radius, so improvements are desired. . The above-mentioned drawbacks have been a major constraint on the development of various materials. Purpose of the Invention In view of the above-mentioned circumstances, the main object of the present invention is to provide a compound which is not only useful as a suitable optically active intermediate but also provides high stability and large spontaneous polarization when induced into liquid crystalline compounds. An object of the present invention is to provide a useful optically active substance, a method for producing the same, and a liquid crystal composition containing the same. In addition, in the present invention, it is easy to change the length of the alkyl group, and this allows H.Arnold, Z.Phys.
Chem., 226, 146 (1964), a liquid crystal compound capable of controlling the type and temperature range of a liquid crystal phase developed in a liquid crystal state, and a liquid crystal composition containing at least one compounded compound thereof. The purpose is to provide Furthermore, the present invention aims to provide a compound whose hydrophobic groups can be easily controlled and which can be stably formed when a monomolecular cumulative film is produced by the LB (Langmuir-Blodgett) film method. . Summary of the Invention The present invention first describes the general formula () (Here, R is an alkyl group having 1 to 16 carbon atoms, and C ^* represents an asymmetric carbon atom.) The present invention provides an optically active 2-fluoro-1-alkanol represented by: Because the compound represented by the above formula () has an asymmetric carbon atom and a hydroxyl group via a methylene group, it can be formed by an ester bond, an ether bond, a urethane bond, a carbonate bond, etc. without losing its optical activity. Since various derivatives can be easily synthesized, it is a compound that is expected to be used in a very wide range. However, to date, no optically active compound as represented by formula () is known. Based on the above knowledge, the present inventors conducted extensive research, and as a result, succeeded in synthesizing the compound represented by the above formula (), and completed the present invention. Therefore, the present invention also provides a method for producing the compound of the above (), which method comprises the following general formula (). By adding hydrogen fluoride to the optically active 1,2-epoxy-alkane represented by the following formula () It is characterized by obtaining an optically active 2-fluoroalkanol represented by: The novel optically active substance represented by the general formula () of the present invention is not only a useful optically active intermediate as described above, but also a useful liquid crystal component by itself. For example, by adding a very small amount to a nematic liquid crystal composition for twisted nematic (TN) type display elements, it can prevent the formation of striped patterns (reverse domains) on the display surface and increase the uniformity of the display. It can be used effectively. DETAILED DESCRIPTION OF THE INVENTION According to the present invention, optical activity 2 of the formula ()
- To produce fluoro-1-alkanol,
First, an optically active 1,2-epoxy-alkane represented by the above formula () is used as a starting material.
Such optically active 1,2-epoxy-alkanes can be easily obtained by asymmetric epoxidation of olefins using microorganisms (for example, H. Ohta,
H. Tetsukawa, Agric. Biol. Chem., 43 , 1979,
2099). Next, the optically active 1,2-epoxy-alkane is subjected to an addition reaction of hydrogen fluoride to obtain an optically active 2-fluoro-1-alkanol. An example of the synthesis method is shown below. Table 1 shows the compounds of the present invention synthesized in this way.
An example of -fluoro-1-alkanol is shown below (see Examples below for details of the synthesis method).

【table】

[Table] The 2-fluoro-1-alkanol of the present invention is
By changing the number of carbon atoms in the alkane moiety in 1,2-epoxyalkane as a starting material,
In the present invention, the above R can be varied widely, and in particular, an alkyl group having 6 to 16 carbon atoms is provided as R. Optical activity 2 of the formula () obtained in this way
As mentioned above, fluoro-1-alkanol can be used to create ester bonds, ether bonds, urethane bonds, etc. by using its hydroxyl group instead of optically active chain hydrocarbon derivatives, amino acid derivatives, synthetic derivatives, cholesterol derivatives, etc. It can be combined with other intermediates by bonding, carbonate bonding, etc., and is therefore useful as an intermediate for producing functional materials forming optical elements.
It is also used as an intermediate in the synthesis of various natural optically active substances. Furthermore, the optically active substance of the formula () is effective in preventing reverse domains in a TN cell by adding it to a nematic liquid crystal. In this case, it is preferable to use it in a proportion of 0.1 to 50% by weight of the liquid crystal composition. Furthermore, by adding it to a nematic liquid crystal, it can be used as a crystal composition in a phase change type liquid crystal element or a White-Taylor type guest-host type liquid crystal element as a chiral nematic liquid crystal. In this case, it is preferable to use it in a proportion of 0.1 to 80% by weight of the liquid crystal composition. Furthermore, the optically active substance of the formula () can be added, for example, from 0.1 to 80% by weight to a liquid crystal composition that exhibits a ferroelectric chiral smectic liquid crystal state by itself to improve properties such as durability. can. Furthermore, they can be added to smectic liquid crystals whose structural formulas and phase transition temperatures are shown below as (1) to (5) to provide a liquid crystal composition exhibiting a ferroelectric chiral smectic phase. In this case, the liquid crystal composition
It is preferably added in a proportion of 0.1 to 80% by weight.

【table】

[Table] Effects of the Invention As described above, according to the present invention, optically active 2- A fluoro-1-alkanol is provided. Moreover, by blending at least one kind of this optically active 2-fluoro-1-alkanol,
It is possible to prevent the occurrence of reverse domains in TN type liquid crystal compositions or to improve the characteristics of chiral nematic liquid crystals, chiral smectic liquid crystals, etc. Hereinafter, the method for producing the compound of the present invention will be explained in more detail with reference to Examples. Example 1 Synthesis of (-)-2-fluoroheptanol To 5 ml of dry ether (+)-1,2-epoxyheptane ([α]D+15.1° (neat), 1.14 g (10.0
(mM) was immediately added dropwise to 2 ml of ice-cooled hydrogen fluoride pyridine. After dropping, stir in an ice bath for 30 minutes, then add 10 ml of cold water.
Extracted three times with 10 ml of ether. The extract was washed three times with 10 ml of 1N sodium carbonate and dried over anhydrous magnesium sulfate. After distilling off the ether under reduced pressure, it was distilled using a Kugelrohr distillation apparatus to obtain (-)-2-
0.492 g of crude fluoroheptanol was obtained.
Crude product obtained by further repeating the above operation
1.35g was rectified using a Claisen flask,
Target (-)-2-fluoroheptanol
0.80g (600mM) was obtained. The yield was 20.0%, and the following physical properties were obtained. Boiling point: 126℃~129℃/104mmHg, [α) ^28.0 _D −11.5° (C=1.112, ether) IR (liquid film): 3330, 2950, 2850, 1450, 1380,
1050, 830cm ^-1 . Example 2 Synthesis of (-)-2-fluorooctanol In a plastic container, hydrogen fluoride pyridine 3
1.28g (10mM) of R-(+) under ice-cooling.
−1,2 epoxy octane ([α] ²⁵ _D +14.4°
(neat)) dissolved in 5 ml of dry ether was slowly added dropwise and stirred for 30 minutes. Add ice water to this solution 15
ml and extracted with 10 ml of ether. The aqueous layer was further extracted twice with 5 ml of ether. The ether layer was washed with 50 ml of 1N Na ₂ CO ₃ aqueous solution and then dried over anhydrous sodium sulfate. After drying, ether is distilled off under reduced pressure, and 0.64g of the purified target product is obtained by distillation under reduced pressure.
(4.3mM, yield 43%) was obtained. Its physical property values are as follows. Boiling point: 124℃/85mmHg, [α] ^26.0 _D −10.4° (C=2, Et ₂ O) IR (liquid film): 3330, 2950, 2850, 1450, 1380,
1050, 830cm ^-1 . ^1H -NMR ( _CDCl3 ): δ (ppm) 2.1-0.7 (m;
13H, -CH ₂ -, -CH ₃ -), 2.4 (broad, 1H, -OH), 3.2, 3.6 (t x 2, 2H,

【formula】), 4.9, 4.1 (m x 2, 1H,

【formula】). Example 4 (-)- by substantially the same method as Example 2
2-Fluorononanol was obtained. The yield was 22.2%, and the following physical properties were obtained. Boiling point: 135°C - 136°C / 45mmHg, [α] ^26.8 _D -10.3° (Cl, 101 ether) IR (solid film): 3330, 2900, 1630, 1450, 1380,
1050, 830. Examples 3, 5, 6 Optically active 2-fluoro-
Obtained alkanol. The physical properties are shown in Table 1 above. Example 7 98 parts by weight of p,p'-pentylazokibenzene,
2 parts by weight of the optically active substance of Example 4 was added to obtain a liquid crystal mixture. TN using this liquid crystal mixture
Cells (twisted nematic cells) were observed to have significantly reduced reverse domains compared to TN cells prepared without the addition of this compound. Example 8 Smectic liquid crystal MORA8 whose structure is shown below
A liquid crystal mixture was obtained by adding 5 parts by weight of the optically active substance of Example 1 to 95 parts by weight. This liquid crystal mixture exhibits SmC ^* phase and the spontaneous polarization is
The response time was 1.2 times that of MORA alone, and the response time under ±15V application conditions was 35msec, about 80%.

Claims (1)

[Claims] 1. The following general formula () (Here, R is an alkyl group having 1 to 16 carbon atoms, and C ^* represents an asymmetric carbon atom.) An optically active 2-fluoro-1-alkanol represented by: 2 General formula below () A general formula () characterized by an addition reaction between an optically active 1,2-epoxy-alkane represented by hydrogen fluoride and (R in the above general formula is an alkyl group of 1 to 16
A method for producing an optically active 2-fluoro-1-alkanol represented by (C ^* represents an asymmetric carbon atom). 3 General formula below () (Here, R is an alkyl group having 1 to 16 carbon atoms.
1. A liquid crystal composition comprising at least one optically active 2-fluoro-1-alkanol represented by (C ^* represents an asymmetric carbon).