Optically active aromatic compounds, preparation process thereof, and liquid crystal compositions and elements

Abstract: Disclosed in the present invention are the optically active aromatic compounds having a trifluoromethyl group useful as a component of ferroelectric liquid crystal compositions, a process for preparing the above compounds, liquid crystal compositions having the above compounds as an active ingredient, and liquid crystal elements using the above compositions. The optically active aromatic compounds of the present invention represented by the formula: have the very excellent properties as a liquid crystal material and are useful for the preparation of liquid crystal compositions and the liquid crystal elements using such compositions.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to the novel organic compounds, a process for preparing such compounds, liquid crystal compositions having said compounds as active ingredient, and liquid crystal elements using such compositions. More particularly, the invention relates to the optically active aromatic compounds having trifluoromethyl groups useful as a primary component of ferroelectric liquid crystal compositions, a process for preparing such compounds, liquid crystal compositions having said compounds as active ingredient, and liquid crystal elements using said compositions. Description of the Prior Art A TN (twisted nematic) type display system is most popular for use in the liquid crystal display elements at present. The TN liquid crystal display elements have many advantages such as low driving voltage and small power consumption. This type of display element, however, is inferior to the luminous type display elements such as cathode-ray tube displays, electroluminenscent displays and plasma displays in response speed. A new model of TN type display element having a twisted angle set in the range of 180-270° has been developed, but this still is inferior to the luminous type display elements in response speed. Thus, in spite of many efforts made for the improvement, there has yet been realized no TN type display element with high response speed. However a possibility of realizing marked improvement or response speed is noted in the new display system using ferroelectric liquid crystals which are being carefully studied by many researches (Clark et al: Applied Phys. Lett., 36 , 899, 1980). This system makes use of a chiral smectic C phase (hereinafter referred to as Sc * phase) which shows ferroelectricity. Sc * phase is not the only phase which shows ferroelectricity. It is known that chiral smectic F phase, G phase, H phase and I phase also exhibit ferroelectricity. The ferroelectric liquid crystal material used for the actually utilized ferroelectric liquid crystal display elements are required to meet may property requirements. At present, there is available no single compound which can meet these requirements; it is necessary for satisfying these requirements to use a ferroelectric liquid crystal composition obtained by mixing several different liquid crystal compounds or non-liquid crystal compounds. Beside the ferroelectric liquid crystal compositions composed of ferroelectric liquid crystal compounds alone, it is reported that a ferroelectric liquid crystal composition can be obtained by using as base material a compound or a composition assuming a non-chiral smectic phase, such as non-chiral smectic C, F, G, H or I phase (hereinafter referred to as Sc phase, etc.) and mixing therewith one or more compounds assuming a ferroelectric liquid crystal phase (Japanese Patent Application Kokai (Laid-Open) No. 195187/86). A report has also been made disclosing the obtaining of a ferroelectric liquid crystal composition by using as base material a compound or composition assuming Sc phase, etc., and mixing therewith one or more compounds which don't assume a ferroelectric liquid crystal phase (Mol. Cryst. Liq. Cryst., 89 , 327, 1982). In the light of these disclosures, it is noted that there can be composed a ferroelectric liquid crystal composition by mixing one or more optically active compounds with a base material no matter whether said compounds assume a ferroelectric liquid crystal phase or not. However, it is desirable that the optically active substance used for forming a ferroelectric liquid crystal composition is the one which assumes a liquid crystal phase, or if it does not assume a liquid crystal phase, its structure is analogous to that of the liquid crystal compounds, that is, it is a "quasi" liquid crystal substance. For all the efforts made so far in the art, there has not yet been found any liquid crystal material which shows spontaneous polarization required for high speed response which is low in viscosity and displays a liquid crystal phase at low temperature regions. SUMMARY OF THE INVENTION In view of the above, the present invention has for its object to provide a ferroelectric liquid crystal material which shows sufficient spontaneous polarization, is capable of high speed response and assumes a liquid crystal phase at lower temperature regions that with the conventional materials. DETAILED DESCRIPTION OF THE INVENTION The present invention provides optically active aromatic compounds having a trifluoromethyl group represented by the following formula: wherein R 1 is an alkyl group having 3-20 carbon atoms; R 2 is an alkyl or alkoxyalkyl group having 1-20 carbon atoms which may be substituted with a halogen atom; k is a number of 0 or 1; p is a number of 0 or 1; Ar is preferably Ar is Y is -0-, -COO- or -OCO-; X is -COO- and * mark denotes an asymmetric carbon atom, a process for preparing such compounds, the liquid crystal compositions containing said compounds as active ingredient, and the liquid crystal elements using such compositions. Among the aromatic compounds having a trifluoromethyl group of the formula (1) according to this invention, those of the formula (1) wherein X is -COO- can be produced by reacting a carboxylic acid compound represented by the formula (2): (wherein R 1 , k, Ar and Y have the same meaning as those defined above, and R' is a hydroxyl group or a halogen atom) with an optically active phenol derivative represented by the formula (3): (wherein R 2 , p and * mark have the same meaning as those defined above) in the presence of a catalyst or a condensation agent. Examples of the carboxylic acid compounds of the formula (2) usable in the above reaction include 4-alkoxybenzoic acid, 4-alkylbenzoic acid, 4-alkoxycarbonylbenzoic acid, 4-alkylcarbonyloxybenzoic acid, 4'-alkoxy-4-biphenylcarboxylic acid, 4'-alkyl-4-biphenylcarboxylic acid, 4'-alkoxycarbonyl-4-biphenylcarboxylic acid, 4'-alkylcarbonyloxy-4-biphenylcarboxylic acid, 2-(4-hydroxycarbonylphenyl)-5-alkoxypyrimidine, 2-(4-hydroxycarbonylphenyl)-5-alkylpyrimidine, 2-(4-hydroxycarbonylphenyl)-5-alkoxycarbonylpyrimidine, and 2-(4-hydroxycarbonylphenyl)-5-alkylcarbonyloxypyrimidine. These carboxylic acids can be used in the form of an acid halide such as acid chloride or acid bromide. The "alkyl" or "alkoxyl" in the above-mentioned compounds refers to an alkyl group R 1 of 3-20 carbon atoms. Examples of said alkyl groups are propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and eicosyl. Exemplary of the optically active phenol derivatives usable as a reactant in the above reaction are 4-(1-alkoxy-2,2,2-trifluoroethyl)phenol, 4-(2-alkoxy-3,3,3-trifluoropropyl)phenol, 4-(3-alkoxy-4,4,4-trifluorobutyl)phenyl, 4-(4-alkoxy-5,5,5-trifluoropentyl)phenol, 4-(5-alkoxy6,6,6-trifluorohexyl)phenol, and 4-(6-alkoxy-7,7,7-trifluoroheptyl)phenol. It is also possible to use the compounds in which "alkoxy" in the above-cited derivatives was replaced by alkoxyalkoxy, alkylcarbonyloxy or alkoxyalkylcarbonyloxy. The alkoxy, alkoxyalkoxy, alkylcarbonyloxy and alkoxyalkylcarbonyloxy mentioned above correspond to in the above-shown formula (3), and the substituent R 2 therein is an alkyl or alkoxyalkyl group of 1-20 carbon atoms which may be substituted with a halogen atom. Such an alkyl or alkoxyalkyl group may be of straight chain or branched. In the latter case, said group may be an optical active group. Examples of said alkyl or alkoxyalkyl group are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, methoxymethyl, methoxyethyl, methoxypropyl, methoxybutyl, methoxypentyl, methoxyhexyl, methoxyheptyl, methoxyoctyl, methoxynonyl, methoxydecyl, ethoxymethyl, ethoxyethyl, ethoxypropyl, ethoxybutyl ethoxypentyl, ethoxyhexyl, ethoxyheptyl, ethoxyoctyl, ethoxynonyl, ethoxydecyl, propoxymethyl, propoxyethyl, propoxypropyl, propoxybutyl, propoxypentyl, propoxyhexyl, propoxyheptyl, propoxyoctyl, propoxynonyl, propoxydecyl, butoxymethyl, butoxyethyl, butoxypropyl, butoxybutyl, butoxypentyl, butoxyhexyl, butoxyheptyl, butoxyoctyl, butoxynonyl, butoxydecyl, pentyloxymethyl, pentyloxyethyl, pentyloxypropyl, pentyloxybutyl, pentyloxypentyl, pentyloxyhexyl, pentyloxyoctyl, pentyloxydecyl, hexyloxymethyl, hexyloxyethyl, hexyloxypropyl, hexyloxybutyl, hexyloxypentyl, hexyloxyhexyl, hexyloxyoctyl, hexyloxynonyl, hexyloxydecyl, heptyloxymethyl, heptyloxyethyl, heptyloxypropyl, heptyloxybutyl, heptyloxypentyl, octyloxymethyl, octyloxyethyl, octyloxypropyl, decyloxymethyl, decyloxyethyl, decyloxypropyl, 1-methylethyl, 1-methylpropyl, 1-methylbutyl, 1-methylpropyl, 1-methylbutyl, 1-methylpentyl, 1-methylhexyl, 1-methylheptyl, 1-methyloctyl, 2-methylethyl, 2-methylbutyl, 2,3-dimethylbutyl, 2,3,3-trimethylbutyl, 2-methylpentyl, 3-methylpentyl, 2,3-dimethylpentyl, 2,4-dimethylpentyl, 2,3,3,4-tetramethylpentyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 2,5-dimethylhexyl, 2-methylheptyl, 2-methyloctyl, 2-trihalomethylpentyl, 2-trihalomethylhexyl, 2-trihalomethylbutyl, 2-haloethyl, 2-halopropyl, 3-halopropyl, 3-halo-2-methylpropyl, 2,3-dihalopropyl, 2-halobutyl, 3-halobutyl, 4-halobutyl, 2,3-dihalobutyl, 2,4-dihalobutyl, 3,4-dihalobutyl, 2-halo-3-methylbutyl, 2-halo-3,3-dimethylbutyl, 2-halopentyl, 3-halopentyl, 4-halopentyl, 5-halopentyl, 2,4-dihalopentyl, 2,5-dihalopentyl, 2-halo-3-methylpentyl, 2-halo-4-methylpentyl, 2-halo-3-monohalomethyl-4-methylpentyl, 2-halohexyl, 3-halohexyl, 4-halohexyl, 5-halohexyl, 6-halohexyl, 2-haloheptyl, and 2-halooctyl, ("Halo" in the above alkyl groups denotes fluorine, chlorine, bromine or iodine.) When p in the above formula is 1, the substituent R 2 may be, beside those mentioned above, halomethyl, 1-haloethyl, 1-halopropyl, 1-halobutyl, 1-halopentyl, 1-halohexyl, 1-haloheptyl, 1-haloocytl and the like. An ordinary esterification method may be applied for performing the reaction between said carboxylic acid compound (2) and optically active phenol derivative (3). This reaction can be carried out either in the presence or in the absence of a solvent. In case of using a solvent in this reaction, such a solvent is selected from those which are inert to the reaction, for example, aliphatic or aromatic hydrocarbons, ethers, halogenated hydrocarbons, organic amines and the like. More specifically, they include tetrahydrofuran, ethylether, acetone, methyl ethyl ketone, toluene, benzene, chlorobenzene, dichloromethane, dichloroethane, chloroform, carbon tetrachloride, dimethylformamide, hexane, pyridine and the like. These solvents may be used either singly or in combination. The amount of the solvent(s) used in the reaction is not subject to particular restrictions. In this reaction, since the optically active phenol derivatives (3) are relatively expensive, it is recommended to use the other reactant, viz. carboxylic acid compound (2), in an excess amount. Usually the compound (2) is used in an amount of 1-4 equivalents, preferably 1-2 equivalents to the derivative (3). As catalyst, there can be used, for example, organic or inorganic basic substances such as dimethylaminopyridine, triethylamine, tri-n-butylamine, pyridine, picoline, collidine, imidazole, sodium carbonate, sodium methylate, or potassium hydrogencarbonate. It is also possible to use such organic or inorganic acids as toluenesulfonic acid, methanesulfonic acid, sulfuric acid or the like. The amount of the catalyst used in the reaction is variable depending on the kind of the reaction starting materials, combination thereof with the catalyst used and other factors, but in case of using, for instance, an acid halide as the reactant (2), a basic substance is used (as catalyst) in an amount of more than one equivalent to said acid halide. In case the carboxylic acid compound of the formula (2) is a carboxylic acid, it is preferred to use a carbodiimide such as N,N'-dicyclohexylcarbodiimide, N-cyclohexyl-4'-(4-diethylamino)cyclohexylcarbodiimide or the like as condensation agent, and if necessary an organic base such as 4-pyrrolidinopyridine, pyridine, triethylamine or the like may be used jointly with said condensation agent. The condensation agent is used in an amount of usually 1-1.2 equivalents to the optically active phenol derivative (3), and in case of jointly using an organic base, its amount used is usually 0.01-0.2 equivalent to the condensation agent. The reaction temperature used in the reaction between the carboxylic acid compound (2) and optically active phenol derivative (3) is usually in the range from -30°C to 100°C, preferably from -25°C to 80°C. The reaction time is not specifically defined. After the reaction, the objective optically active aromatic compound having a trifluoromethyl group represented by the formula (1) (where X is -COO-) can be isolated from the reaction mixture by a usual separating means such as extraction, liquid separation, concentration, etc. If necessary the resulting product may be purified by suitable means such as column chromatography, recrystallization, etc. An optically active phenol derivative (3) used as a starting material can be produced according to any of the processes described below. (In the above formulae, R 2 , p and * mark denote the same as defined above, A is chlorine, bromine or iodine atom, and R 3 is lower alkyl group). The process will be described in detail stepwise below. The first step of the process comprises a Grignard reaction where a Grignard reagent represented by the formula (4) and a trifluoroacetic acid or a derivative thereof are reacted to give a trifluoroacetophenone derivative represented by the formula (5). The Grignard reagent (4) can be prepared from a corresponding halogenobenzene derivative and magnesium. As trifluoroacetic acid or a derivative thereof used in the above reaction, there can be employed, beside trifluoroacetic acid, trifluoroacetyl halides such as trifluoroacetyl chloride and trifluoroacetyl bromide, esters such as methyl trifluoroacetate and ethyl trifluoroacetate, acid amides such as N-trifluoroacetylimidazole, trifluoroacetic acid anhydride, or the like. The amount of trifluoroacetic acid or a derivative thereof used in the above reaction needs to be not less than one equivalent, usually 1-3 equivalents to the Grignard reagent (4) excepting the case where trifluoroacetic acid is used. In the latter case, the reaction is carried out by using the Grignard reagent (4) in an amount of 2 or greater equivalents, usually 2-4 equivalents, to one equivalent of trifluoroacetic acid. As solvent, one can use ethers such as ethyl ether and tetrahydrofuran, aromatic hydrocarbons such as benzene, toluene and xylene, and the like, either singly or in combination. No particular restrictions are imposed on the amount of the solvent used in the reaction. The reaction temperature is usually in the range from -120°C to 0°C, preferably from -100°C to 20°C. Reaction time is not specifically defined. Isolation of the trifluoroacetophenone derivative of the formula (5) from the reaction mixture can be effected by subjecting the reaction mixture to the ordinary after-treatment operations such as extraction, liquid separation, concentration and recrystallization or column chromatography. The second step of the process comprises reducing the trifluoroacetophenone derivative of the formula (5) to obtain a β-phenethyl alcohol derivative represented by the formula (6). In this reducing reaction, there is used a reducing agent that can reduce ketone into alcohol. Typical examples of such reducing agent are lithium aluminum hydride, sodium borohydride and boron hydride. Such a reducing agent is used in an amount of one or greater equivalents, usually 1-10 equivalents, to the trifluoroacetophenone derivative (5) used as starting material. This reducing reaction is carried out in a 25 solvent. As such a solvent, there can be used ethers such as tetrahydrofuran, dioxane or ethyl ether, alcohols such as methanol, ethanol, n-propyl alcohol or isopropyl alcohol, aromatic hydrocarbons such as toluene and benzene, or halogenated hydrocarbons such as chloroform and dichloromethane. These solvents may be used either singly or in combination. The reaction is carried out at a temperature usually in the range from -30°C to 100°C, preferably from -20°C to 90°C. The end point of the reaction is usually supposed to be the moment when the trifluoroacetophenone derivative (5) has disappeared from the reaction system. Isolation of the β-phenetyl alcohol derivative of the formula (6) can be achieved by conducting the ordinary after-treatment operations such as extraction, liquid separation, concentration, etc. The third step comprises acylating the β-phenyl alcohol derivative (6) with a carboxylic acid represented by the formula (10): R 3 COOH (wherein R 3 is as defined above) or a derivative thereof in a solvent in the presence of a catalyst to form an ester represented by the formula (7). As said carboxylic acid (10) or a derivative thereof, there can be used, for example, acetic acid, propionic acid, acetic anhydride, propionic anhydride, acetic acid chloride or bromide, propionic acid chloride or bromide, butyryl chloride or bromide, valeroyl chloride or bromide, and the like. The amount of such a carboxylic acid or a derivative thereof used in the acylation should be not less than one equivalent to the β-phenetyl alcohol derivative (6). The upper limit of said amount is not specifically restricted but recommended to be 4 equivalents to the β-phenetyl alcohol derivative (6). The acylation is conducted in the presence of a catalyst. As catalyst, there can be used, for example, organic or inorganic basic substances such as dimethylaminopyridine, triethylamine, tri-n-butylamine, pyridine, picoline, imidazole, sodium carbonate, sodium methylate and potassium hydrogencarbonate. It is also possible to use acids such as toluenesulfonic acid, methanesulfonic acid and sulfuric acid. The amount of such a catalyst used in the acylation is not specified, but usually it is used in an amount of 1-5 equivalents to the β-phenetyl alcohol derivative (6). The solvent used in said acylation reaction is the one which is inert to the reaction, for example, aliphatic or aromatic hydrocarbons, ethers, halogenated hydrocarbons, aprotic polar solvents and organic amines, more specifically, tetrahydrofuran, ethyl ether, acetone, methyl ethyl ketone, hexane, toluene, benzene, chlorobenzene, dichloromethane, dichloroethane, chloroform, carbon tetrachloride, dimethylformamide, pyridine and the like. These solvents may be used either singly or in combination. No particular limitations are given to the amount of the solvent used in the reaction. In case of using an organic amine as solvent, it may also act as a catalyst. Reaction temperature is usually in the range from -30°C to 100°C, preferably from -20°C to 90°C. Reaction time is not specifically defined. The moment when the starting material β-phenetyl alcohol derivative (6) has disappeared from the reaction system may be regarded as the end point of the reaction. Isolation of an ester of the formula (7) may be accomplished by subjecting the reaction mixture to the ordinary after-treatment operations such as extraction, liquid separation, concentration, recrystallization, etc. The fourth step comprises asymmetric hydrolysis of the ester (7) with an esterase having the ability to preferentially hydrolyze one of the optical isomers of said ester to produce an optically active alcohol compound. The esterase used in the above asymmetric hydrolysis reaction is obtainable from animals, vegetables or microorganisms. It can be used in various forms such as purified enzyme, crude enzyme, enzyme-containing substance, liquid culture of microorganism, culture, cell, culture filtrate and treated substance thereof. A combination of an enzyme and a microorganism is also usable. It is further possible to use the fixed enzyme or fixed cell formed by fixing the enzyme or cell to a resin or other substance. The term "esterase" used in this specification of the invention means esterase in its broad sense, which includes lipase. As the microorganism producing an esterase used in the above asymmetric hydrolysis reaction, there can be employed any of those microorganisms which can produce an esterase having the ability to asymmetrically hydrolyze an ester of the formula (7). Examples of these microorganisms are those belonging to the general Enterobacter, Arthrobacter, Previbacterium, Pseudomonas, Alcaligenes, Micrococcus, Chromobacterium, Microbacterium, Corynebacterium, Bacillus, Lactobacillus, Trichoderma, Candida, Saccharomyces, Rhodotorula, Cryptococcus, Torulopsis, Befia, Penicillium, Aspergillus, Rhizopus, Mucor, Aureobacidium, Actinomucor, Nocardia, Streptomyces, Hansenula and Achromobacter. Cultivation of said microorganisms can be usually accomplished according to a conventional method, and a liquid culture can be obtained by performing liquid cultivation. For instance, a sterilized liquid medium [a malt extract/yeast extract medium (prepared by dissolving 5 g of peptone, 10 g of glucose, 3 g of malt extract and 3 g of yeast extract in 1 litre of water, with pH adjusted to 6.5) for mold and yeast and a sweetened bouillon medium (prepared by dissolving 10 g of glucose, 5 g of peptone, 5 g of meat extract and 3 g of NaCl in 1 litre of water, with pH adjusted to 7.2) for bacterial] is inoculated with a microorganism and the latter is subjected to reciprocal shaking culture usually at 20 to 40°C for 1 to 3 days. Solid culture may be employed if necessary. Among the esterases derived from the microorganisms such as mentioned above, there are those which are commercially prepared and easily available. Listed below are the examples of the commercially available esterases: Lipase P (lipase of the genus Pseudomonas, available from Amano Pharmaceutical Co., Ltd.), Lipase AP (lipase of the genus Aspergillus, available from Amano Pharmaceutical Co., Ltd.), Lipase M-AP (lipase of the genus Mucor, available from Amano Pharmaceutical Co., Ltd.), Lipase MY (lipase of Candida , available from Meito Sangyo Co., Ltd.), Lipase PL (lipase of the genus Alcaligenes, available from Meito Sangyo Co., Ltd.), Lipase Al (lipase of the genus Acromobacter, available from Meito Sangyo Co., Ltd.), Lipase Godo BSL (lipase of the genus Arthrobacter, available from Godo Shusei Co., Ltd.), lipase of the genus Chromobacterium, available from Toyo Brewage Co., Ltd., Talipase (lipase of Rhizopus·delemer, available from Tanabe Pharmaceutical Co., Ltd.), and Lipase Saiken (lipase of the genus Rhizopus, available from Osaka Bacteria Research Institute. It is also possible to use esterases of animal or vegetable sources. Examples of such esterases are steapsin, pancreatin, swine liver esterase, and wheat germ esterase. The asymmetric hydrolysis reaction is carried out by vigorously stirring a mixture of a starting ester of the formula (7) and one of said enzymes or microorganisms usually in a buffer solution. The buffer solution used in the above reaction can be a commonly employed buffer solution of a salt of an inorganic acid such as sodium phosphate and potassium phosphate or a salt of an organic acid such as sodium acetate and sodium citrate. The pH of such a buffer solution is preferably 8 to 11 in the case of liquid cultures of alkaliphilic bacteria or alkaline esterases and 5 to 8 in the case of liquid cultures of non-alkaliphilic microorganisms or esterases having no alkali resistance. Concentration of the buffer solution is usually in the range of 0.05 to 2 M, preferably 0.05 to 0.5 M. Reaction temperature is usually 10 to 60°C, and reaction time is generally 10 to 70 hours, but both are not always defined within said ranges. It is to be noted that in case of using lipase belonging to the genus Pseudomonas or genus Arthrobacter in said asymmetric hydrolysis reaction, there can be obtained an optically active alcohol compound (8) with a relatively high optical purity. In carrying out said asymmetric hydrolysis, it is possible to use an organic solvent inert to the reaction, such as toluene, chloroform, methyl isobutyl ketone, dichloromethane and the like in addition to a buffer solution. Use of such a solvent enables advantageous execution of said asymmetric hydrolysis reaction. In said asymmetric hydrolysis reaction, only one of the optical isomers of the starting ester (7) is preferentially hydrolyzed to produce an optically active alcohol compound represented by the formula (8). The other optical isomer remains in the form of ester compound as a residue of asymmetric hydrolysis. Isolation of the optically active alcohol compound (8) from the reaction mixture can be accomplished, for example, in the following way: the reaction mixture, which has undergone the ordinary after-treatments, is extracted with a solvent such as ethyl acetate, then the solvent is evaporated away from the obtained organic layer, and the residue is concentrated and column chromatographed. In this way, there are obtained an optically active alcohol compound (8) as the asymmetric hydrolysis product and an optically active ester (7) as the residue of the asymmetric hydrolysis. If desired, this residual optically active ester may be further hydrolyzed and made into an optically active alcohol compound (8) which is an enantiomer of the compound obtained from said asymmetric hydrolysis reaction. The fifth step comprises acylation or alkylation of the optically active alcohol compound (8) to obtain an optically active benzyloxybenzene derivative represented by the formula (9). The optically active benzyloxybenzene derivative represented by the formula (9) in which p is 1 can be produced by reacting an optically active alcohol compound (8) with a carboxylic acid represented by the formula (11): R 2 COOH (wherein R 2 has the same meaning as defined above) or a derivative thereof in the presence of a catalyst or a condensation agent. The substituent R 2 in the above formula (11) may be the same alkyl or alkoxyl group as the substituent R 2 in the optically active phenol derivatives represented by the above-shown formula (3). In said acylation reaction, there is used a carboxylic acid having said substituent R 2 , an acid anhydride or an acid halide such as acid chloride or acid bromide. Said carboxylic acids or derivatives thereof may be either a racemate or an optically active form. In the latter case, some of such carboxylic acids can be obtained through oxidation of corresponding alcohols or reductive deamination of amino-acids. Also, there are those which occur naturally or can be derived from the optically active amino-acids or optically active oxyacids which are obtainable through resolution. Examples of such optically active amino-acids or oxyacids include aniline, valine, leucine, isoleucine, phenylalanine, serine, threonine, allothreonine, homoserine, alloisoleucine, tert-leucine, 2-aminobutyric acid, norvaline, norleucine, ornithine, lysine, hydroxylysine, phenylglycine, trifluoroalanine, aspartic acid, glutamic acid, lactic acid, mandelic acid, tropic acid, 3-hydroxybutyric acid, malic acid, tartaric acid, and isopropylmalic acid. The reaction of such a carboxylic acid or a derivative thereof with an optically active alcohol compound of the formula (8) is carried out either in the presence of or without a solvent. As solvent, there can be used, for example, aliphatic or aromatic hydrocarbons such as tetrahydrofuran, ethyl ether, acetone, methyl ethyl ketone, toluene, benzene, chloroform, chlorobenzene, dichloromethane, dichloroethane, carbon tetrachloride, dimethylformamide or hexane, and the solvents which are inert to the reaction, such as ethers, ketones, amides or halogenated hydrocarbons. These solvents may be used either singly or in combination. No particular restrictions are imposed on the amount of such a solvent used in the reaction. In the case of using an acid anhydride or an acid halide in this reaction, the reaction is conducted by using a catalyst. An acid anhydride or an acid halide is used in an amount not less than one equivalent to the optically active alcohol compound (8). The upper limit of the amount of such acid anhydride or acid halide usable in the reaction is not specifically defined, but preferably it is not greater than 4 equivalents to said compound (8). As catalyst, there can be used organic or inorganic basic substances such as dimethylaminopyridine, triethylamine, tri-n-butylamine, pycoline, imidazole, sodium carbonate and potassium hydrogen carbonate. It is also possible to use organic or inorganic acids such as toluenesulfonic acid, methanesulfonic acid and sulfuric acid. The amount of the catalyst used in the reaction is not specified, but in the case of using, for instance, an acid halide, the catalyst is used in an amount not less than one equivalent to the acid halide. In case of using a carboxylic acid represented by the formula (11) in the reaction, the reaction is carried out in the presence of a condensation agent. The amount of the carboxylic acid used in the reaction is usually 1 to 2 equivalents to the optically active alcohol compound (8). As condensation agent, carbodiimides such as N,N'-dicyclohexylcarbodiimide and N-cyclohexyl-N'-(4-diethylamino)cyclohexylcarbodiimide are preferably used. If necessary, an organic base such as 4-pyrrolidinopyridine, pyridine and triethylamine may be used in combination with the condensation agent. The amount of the condensation agent used in the reaction is 1 to 1.2 equivalents to the carboxylic acid (11), and in case of using an organic base, it is used in an amount of 0.01 to 0.2 equivalent to the condensation agent. The reaction is carried out at a temperature usually in the range of -80°C to 120°C, preferably -20°C to 90°C. Reaction time is not specifically defined. The moment when the optically active alcohol compound (8) has disappeared from the reaction system may be considered as the end point of the reaction. Isolation of the optically active benzyloxybenzene derivative of the formula (9) where p is 1 from the reaction mixture can be accomplished by conducting the ordinary after-treatment operations such as extraction liquid separation, concentration, recrystallization or column chromatography. The optically active benzoxybenzene derivative of the formula (9) where p is 0 can be obtained by alkylating the optically active alcohol compound (8) with an alkylating agent represented by the formula (12): R 2 -Z (wherein R 2 designates the same as defined above, and Z represents a halogen atom or -OSO 2 R" where R" is a lower alkyl group or a phenyl group which may be substituted) in a solvent in the presence of a basic substance. As the basic substance, there can be used alkali metal hydrides such as sodium hydride and potassium hydride; alkali metal or alkaline earth metal hydroxides such as sodium hydroxide, potassium hydroxide and calcium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; butyl lithium; or alkali metals such as lithium, sodium and potassium. Such a basic substance is used in an amount not less than one equivalent to the optically active alcohol compound (8). The upper limit of the usable amount of this substance is not restricted but preferably not greater than 5 equivalents to said compound (8). The alkylating agent (12) used in this reaction is selected from the halides such as chlorides, bromides and iodides having an alkyl or alkoxyalkyl group of 1 to 20 carbon atoms which may be substituted with a halogen atom or the sulfonic acid esters (methanesulfonic acid ester, ethanesulfonic acid ester, benzenesulfonic acid ester, toluenesulfonic acid ester, benzenesulfonic acid ester, toluenesulfonic acid ester, etc.). The substituent R 2 in the alkylating agents represented by the formula (12) is identical with the substituent R 2 in the optically active phenol derivatives represented by the formula (3). These alkylating agents (12) can be easily prepared from the corresponding alcohols as desired. The substituent R 2 in the alkylating agent (12) may be an optically active group, and the alkylating agents (halides or sulfonic acid esters) having such an optically active group can be synthesized from the corresponding optical active alcohols as desired. Some of said optically active alcohols can be easily obtained from asymmetric reduction of the corresponding ketones with an asymmetric metallic catalyst, microorganism or enzyme. There are also those of said optically active alcohols which occur naturally or can be derived from the optically active amino acids or optically active oxyacids such as mentioned below which can be obtained by resolution: valine, leucine, isoleucine, phenylalanine, threonine, allothreonine, homoserine, alloisoleucine, tert-leucine, 2-aminobutyric acid, norvaline, norleucine, ornithine, lysine, hydroxylysine, phenylglycine, aspartic acid, glutamic acid, mandelic acid, tropic acid, 3-hydroxybutyric acid, malic acid, tartaric acid, isopropylmalic acid or the like. The amount of the alkylating agent (12) used in the reaction can be optionally selected provided that it is not less than one equivalent to the optically active alcohol compound (8), but usually said alkylating agent is used in an amount of 1 to 5 equivalents to said compound (8). As the reaction solvent, there can be used ethers such as tetrahydrofuran and ethyl ether, ketones such as acetone and methyl ethyl ketone, aromatic hydrocarbons such as toluene and benzene, halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane and chlorobenzene, aliphatic hydrocarbons such as pentane and hexane, and polar solvents such as dimethylformamide, dimethyl sulfoxide, hexamethylphosphoramide or N-methylpyrrolidone. The reaction is usually carried out at a temperature of usually -50°C to 120°C, preferably-80°C to 100°C. Reaction time is not specifically defined, but usually the moment when the optically active alcohol compound of the formula (8) has disappeared from the reaction system may be supposed to be the end point of the reaction. Isolation of the optically active benzyloxybenzene derivative of the formula (9) wherein p is 0 from the reaction mixture can be effectuated by performing the ordinary after-treatments such as extraction, liquid separation, concentration, recrystallization or column chromatography. The sixth step comprises debenzylation of the optically active benzyloxybenzene derivative (9) in the presence of a hydrogenerated catalyst and hydrogen to obtain the objective optically active phenol derivative of the formula (3) wherein n is 0. The hydrogenated catalysts usable in the above debenzylation reaction include platinum catalysts such as PtO 2 and Pt-C, palladium catalysts such as Pd-C, Pd-BaSO 4 and palladium black, rhodium catalysts such as Rh-C and Rh-Al 2 O 3 , ruthenium catalysts such as RuO 2 and Ru-C, and nickel catalysts such as Raney nickel. Among them, palladium catalysts are the most preferred. The hydrogenated catalyst is used in an amount of usually 0.01 to 100% by weight, preferably 0.1 to 50% by weight, based on the optically active benzyloxybenzene derivative of the formula (9). As solvent, there can be used alcohols such as methanol and ethanol, ethers such as dioxane and tetrahydrofuran, aromatic hydrocarbons such as benzene and toluene, aliphatic hydrocarbons such as n-hexane and cyclohexane, esters such as ethyl acetate, amides such as dimethylformamide, fatty acids such as acetic acid, and water. These solvents can be used either singly or in combination. Hydrogen pressure in the reaction is usually 0,987 to 197,4 bar (1 to 200 atm). Reaction temperature is usually 0 to 200°C, preferably 20 to 180°C. Reaction time is variable depending on he kind of the hydrogenated catalyst used, reaction temperature and hydrogen pressure, but the end point of the reaction is usually decided by the moment of disappearance of the optically active benzyloxybenzene derivative of the formula (9) or cessation of hydrogen absorption. Isolation of the optically active phenol derivative of the formula (3) where n is 0 from the reaction mixture can be accomplished by subjecting the reaction mixture to the ordinary after-treatments such as filtration, concentration, recrystallization, distillation or column chromatography. Listed below are the examples of the optically active aromatic compounds (1) having a trifluoromethyl group obtained according to the above-described process of this invention. Compounds wherein X is -COO-. 4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl]-phenyl 4-alkyl(C 3-20 )oxybenzoate, 4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl]-phenyl 4-alkyl(C 3-20 )benzoate, 4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl]-phenyl 4-alkyl(C 3-20 )oxycarbonylbenzoate, 4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl]-phenyl 4-alkyl(C 3-20 )carbonyloxybenzoate, 4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl]-phenyl 4'-alkyl(C 3-20 )oxy-4-biphenylcarboxylate 4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl]-phenyl 4'-alkyl(C 3-20 )-4-biphenylcarboxylate, 4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl]-phenyl 4'-alkyl(C 3-20 )oxycarbonyl-4-biphenylcarboxylate, 4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl]-phenyl 4'-alkyl(C 3-20 )carbonyloxy-4-biphenylcarboxylate, 2-[4-[4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl] phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )oxypyrimidine, 2-[4-[4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )-pyrimidine, 2-[4-[4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )-oxycarbonylpyrimidine, 2-[4-[4-[1-alkyl(C 1-20 )oxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )carbonyloxypyrimidine, 4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )oxybenzoate, 4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )benzoate, 4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )oxycarbonylbenzoate, 4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )carbonyloxybenzoate, 4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifluoroethyl]phenyl 4'-alkyl(C 3-20 )oxy-4-biphenyicarboxylate, 4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifluoroethyl]phenyl 4'-alkyl(C 3-20 )-4-biphenylcarboxylate, 4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifluoroethyl]phenyl 4'-alkyl(C 3-20 )oxycarbonyl-4-biphenylcarboxylate, 4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifuloroethyl]phenyl 4'-alkyl(C 3-20 )carbonyloxy-4-biphenylcarboxylate, 2-[4-[4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )-oxypyrimidine, 2-[4-[4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )-pyrimidine, 2-[4-[4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )-oxycarbonylpyrimidine, 2-[4-[4-[1-alkoxyalkyl(C 2-20 )oxy-2,2,2-trifluoroethyl)phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )-carbonyloxypyrimidine, 4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )oxybenzoate, 4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )benzoate, 4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )oxycarbonylbenzoate, 4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )carbonyloxybenzoate, 4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4'-alkyl(C 3-20 )oxy-4-biphenylcarboxylate, 4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4'-alkyl(C 3-20 )-4-biphenylcarboxylate, 4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4'-alkyl(C 3-20 )oxycarbonyl-4-biphenylcarboxylate, 4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4'-alkyl(C 3-20 )carbonyloxy-4-biphenylcarboxylate, 2-[4-[4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )-oxypyrimidine, 2-[4-[4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )-pyrimidine, 2-[4-[4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )-oxycarbonylpyrimidine, 2-[4-[4-[1-alkyl(C 1-20 )carbonyloxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl(C 3-20 )-carbonyloxypyrimidine, 4-[1-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )oxybenzoate, 4-[1-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )benzoate, 4-[1-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )oxycarbonylbenzoate, 4-[1-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4-alkyl(C 3-20 )carbonyloxybenzoate, 4-[-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4'-alkyl(C 3-20 )oxy-4-biphenylcarboxylate, 4-[1-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4'-alkyl(C 3-20 )-4-biphenylcarboxylate, 4-[1-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4'-alkyl(C 3-20 )oxycarbonyl-4-biphenylcarboxylate, 4-[1-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenyl 4'-alkyl(C 3-20 )carbonyloxy-4-biphenylcarboxylate, 2-[4-[4-[1-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl-(C 3-20 )oxypyrimidine, 2-[4-[4-[1-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl-(C 3-20 )pyrimidine, 2-[4-[4-[1-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl-(C 3-20 )oxycarbonylpyrimidine, 2-[4-[4-[1-alkoxyalkyl(C 2-20 )carbonyloxy-2,2,2-trifluoroethyl]phenoxycarbonyl]phenyl]-5-alkyl-(C 3-20 )carbonyloxypyrimidine, The optically active aromatic compound having a trifluoromethyl group represented by the general formula (1) can be obtained by the process described above. In case of utilizing said compounds as a liquid crystal material, especially as a ferroelectric liquid crystal material, it is preferred, in view of practical optical stability, etc., that R 2 in the formula (1) is an alkyl or alkoxyalkyl group which is not substituted with a halogen atom. In practical use of the compounds, it is also desirable that R 2 is an alkyl or alkoxyalkyl group having 1 to 10 carbon atoms as these compounds show the more favorable properties. As for the substituent R 1 , it is practically preferred that R 1 is an alkyl group with a carbon number of 8 to 16, but this does not apply in case of using the compounds as a component of a liquid crystal material. In ferroelectric liquid crystals in general, it is desirable that the liquid crystal compounds have a large value of spontaneous polarization for exhibiting their meritorious characteristic of high-speed responsiveness. In the optically active aromatic compounds having a trifluoromethyl group represented by the formula (1) according to the present invention, a trifluoromethyl group with a large dipole moment is bonded directly to each asymmetric carbon as a structural feature, so that it is possible to develop a large value of spontaneous polarization in said compounds. The optically active aromatic compounds (1) having a trifluoromethyl group according to the present invention can be used effectively as a component of ferroelectric liquid crystal compositions not only when said compounds assume a liquid crystal phase in themselves but also even when no such liquid crystal phase is generated. The liquid crystal compositions in accordance with the present invention contain as an essential component thereof at least one of said optically active aromatic compounds having a trifluoromethyl group represented by the formula (1). In said liquid crystal compositions, an optically active aromatic compound (1) having a trifluoromethyl group is contained in an amount of 0.1 to 99.9% by weight, preferably 1 to 99% by weight, based on the obtained composition. The liquid crystal compositions according to this invention find useful application to various types of liquid crystal elements, for example, optical switching elements. In such applications, said liquid crystal compositions can be used in the ways known in the art. As described above, the optically active aromatic compounds having a trifluoromethyl group represented by the general formula (1) according to the present invention have very excellent properties as a liquid crystal material and can be used advantageously for the liquid crystal compositions and for the liquid crystal elements using such compositions. Further, the above-said compounds can be obtained easily in a high yield according to the process of this invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will hereinafter be described more particulaly with reference to the preparation examples for the starting materials and the working examples of the invention. Preparation Example 1 2.4 g (0.1 mol) of magnesium chips and 50 ml of anhydrous tetrahydrofuran were placed into a four-necked flask equipped with a thermometer, a dropping funnel and a stirrer. Then a mixture of 2.6 g (10 mmol) of 4-benzyloxybromobenzene and 5 ml of anhydrous tetrahydrofuran and a small quality of iodine were further added to the flask, followed by heating of the flask contents to 60°C and dropwise addition thereto of a mixture of 23.7 g of 4-benzyloxybromobenzene and 45 ml of anhydrous tetrahydrofuran. Thereafter, the flask contents were stirred under reflux for 2 hours and then cooled to room temperature. The resulting mixture was added dropwise to a mixture of 31.5 g (0.15 mol) of trifluoroacetic anhydride and 150 ml of anhydrous tetrahydrofuran at -78°C. The mixture was stirred at -78°C for one hour and then heated gradually to -50°C. The mixture was then added with 100 ml of a saturated ammonium chloride solution at -50°C and then heated to room temperature. The resulting mixture was extracted with 300 ml of ether, and the obtained organic layer was washed successively with a 5% sodium bicarbonate solution, water and brine in that order, then dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue was subjected to silica gel column chromatography using a 1/2 mixture of toluene and hexane as eluent to obtain 18.2 g of 4-benzyloxy-α,α,α-trifluoroacetophenone (5) as a pale yellow solid having a melting point of 58-60°C in a yield of 65%. 16.8 g (60 mmol) of this product (5) was dissolved in 150 ml of ethanol, and the solution was added with 1.1 g (30 mmol) of sodium borohydride and stirred at room temperature for 4 hours. The reaction mixture was poured into water and extracted with ethyl acetate. The resultantly formed organic layer was washed with water and brine successively in that order, dried over anhydrous magnesium sulfate and concentrated under reduced pressure to give 16.7 g of 4-benzyloxy-α,α,α-trifluoro-β-phenethyl alcohol (6) as a pale yellow solid. Yield: 99%; m.p. 115-117°C. 15.5 g (55 mmol) of the product (6) was dissolved in 100 ml of pyridine, and the solution was added with 5.2 g (66 mmol) of acetyl chloride at 0-5°C and stirred at the same temperature for 2 hours. The reaction mixture was poured into water and extracted with ethyl acetate, and the resultantly formed organic layer was washed with 10% hydrochloric acid, water, a 5% sodium bicarbonate solution and brine successively in that order, then dried over anhydrous magnesium sulfate and concentrated under reduced pressure to obtain 17.8 g of 4-benzyloxy-1-(1-acetoxy-2,2,2-trifluoroethyl)benzene (7-1) as a pale yellow solid. Yield: 100%; m.p. 85-87°C. 17.8 g (55 mmol) of the product (7-1) was dissolved in 10 ml of chloroform, and the solution was added with 100 ml of 0.3 M phosphate buffer and 1.8 g of lipase (Amano P) and stirred vigorously at 36-38°C for 48 hours. The reaction mixture was filtered and the filtrate was extracted with ethyl acetate. The obtained organic layer was washed with brine, then dried over anhydrous magnesium sulfate and concentrated under reduced 5 pressure. The residue was subjected to silica gel column chromatography (eluent: toluene) to give 9.3 g of (-)-4-benzyloxy-1-(1-acetoxy-2,2,2-trifluoroethyl)benzene (yield: 52%; [α] 20 / D = -33.6° (c = 1, CHCl 3 )) and 7.3 g of (+)-4-benzyoxy-α,α,α-trifluoro-β-phenethyl alcohol (8-1) (yield: 47%; [α] 20 / D = +16.2° (c = 1, CHCl 3 ). 8.1 g (25 mmol) of thus obtained (-)-4-benzyoxy-1-(1-acetoxy-2,2,2-trifluoroethyl)benzene was dissolved in 50 ml of methanol, and the solution was added with 20 ml of a 20% sodium hydroxide solution and stirred at room temperature for one hour. The resulting reaction mixture was poured into water and extracted with ethyl acetate, and the formed organic layer was washed with water and a brine dried over anhydrous magnesium sulfate and concentrated under reduced pressure to obtain 6.9 g of (-)-4-benzyloxy-α,α,α-trifluoro-β-phenethyl alcohol (8-2). Yield: 98% [α] 20 / D = -14.1° (c = 1, CHCl 3 ). Preparation Example 2 1.4 g (5 mmol) of the product (8-1) obtained in Preparation Example 1 was dissolved in 20 ml of dimethylformamide, and the solution was added with 0.24 g (6 mmol) of sodium hydride (content: 60%) and stirred at room temperature for one hour. This was followed by addition of 1.5 g (6 mmol) of n-hexyl p-toluenesulfonate and stirring at room temperature for 3 hours. The reaction mixture was poured into water and extracted with ethyl acetate, and the obtained organic layer was washed with water and brine dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue was subjected to silica gel column chromatography (eluent: toluene/hexane (1/1)) to obtain 1.6 g of (+)-4-benzyloxy-1-(1-hexyloxy-2,2,2-trifluoroethyl)benzene (9-1). Yield: 88%; [α] = +36.6° (c = 1, CHCl 3 ). Preparation Examples 3 - 6 The procedure of Preparation Example 2 was followed except that the alkylating agents (12) shown in Table 1 were used in place of n-hexyl p-toluenesulfonate to obtain the optically active benzyloxybenzene derivatives (9) shown in Table 1. Preparation Examples 7 - 9 The procedure of Preparation Example 2 was followed except that the product (8-2) obtained in Preparation Example 1 was used in place of the product (8-1) as starting material, and that the alkylating agents shown in Table 2 were used in place of n-hexyl p-toluenesulfonate. The results are shown in Table 2. Preparation Example 10 0.85 g (3 mmol) of the product (8-2) obtained in Preparation Example 1 was dissolved in 10 ml of pyridine. The solution was cooled to 0-5°C, added with 0.48 g (3.6 mmol) of hexanoyl chloride and stirred at the same temperature for 2 hours. The reaction mixture was poured into water and extracted with ethyl acetate. The resultantly formed organic layer was washed with a 10% hydrochloric acid solution, water, a 5% sodium bicarbonate solution and brine successively in that order, then dried over anhydrous magnesium sulfate and concentrated under reduced pressure to yield 1.14 g of (-)-4-benzyloxy-1-(1-hexanoyloxy-2,2,2-trifluoroethyl)benzene (9-9). Yield: 100%; [α] 20 / D = -57.0° (c = 1, CHCl) 3 Preparation Examples 11 and 12 The procedure of Preparation Example 10 was followed except for use of the acylating agents (11) shown in Table 3 in place of hexanoyl chloride used in Preparation Example 1. The results are shown in Table 3. Preparation Example 13 1.1 g (3 mmol) of the product (9-1) of preparation Example 2 was dissolved in a mixture of 80 ml of tetrahydrofuran and 20 ml of methanol, and the solution was added with 0.2 g of 10% Pd/C and stirred vigorously under hydrogen pressure of 1-1.2 atm. for 8 hours. After the reaction, Pd/C was filtered out and the filtrate was concentrated to obtain 0.82 g of (+)-4-(1-hexyloxy-2,2,2-trifluoroethyl)phenol (3-1). Yield: 99%; [α] 20 / D= +44.0° (c = 1, CHCl 3 ). Preparation Examples 4 - 23 The procedure of Preparation Example 13 was followed except the optically active benzyloxybenzene derivatives (9) obtained in Preparation Examples 3 - 12 were used in place of the compound (9-1) used as starting material in Preparation Example 13. The results are shown in Table 4. Example 1 0.28 g (1 mmol) of the product (3-1) of Preparation Example 13, 0.36 g (1.3 mmol) of 4-decyloxybenzoic acid and 10 ml of anhydrous dichloromethane were placed into a four-necked flask equipped with a thermometer and a stirrer. The mixture was further added with 0.25 g (1.2 mmol) of N,N'-dicyclohexylcarbodiimide and 20 mg of 4-pyrrolidinopyridine and stirred at room temperature for 24 hours. After the reaction, the produced precipitate was filtered out and the filtrate was diluted with 50 ml of toluene, washed with water, 5% acetic acid, water, a 5% sodium bicarbonate solution and brine successively in that order, then dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue was subjected to silica gel column chromatography using a 1/1 mixture of toluene and hexane as eluent to obtain 0.49 g of (+)-4-(1-hexyloxy-2,2,2-trifluoroethyl)phenyl 4-decyloxybenzoate in a yield of 92%. Examples 2-18 The procedure of Example 1 was followed except for use of the starting materials shown in Table 5. The results are shown in Table 5. Examples 19-22 The liquid crystal compositions shown in Table 13 were prepared by using the specified liquid crystal compounds. For the preparation of each composition, weighed quantities of two specified compounds were put into a sample bottle and mixed while melting them by heating. The liquid crystal elements were produced by using the thus prepared liquid crystal compositions according to the method described below. Liquid crystal element producing method Polyimide type polymer films were formed on a pair of glass substrates provided with transparent electrodes of indium oxide, and said film-coated substrates were rubbed in a given direction with glass fiber (5 µm in diameter) used as spacer to constitute a liquid crystal cell, and said liquid crystal compositions were vacuum encapsulated in the thus formed respective cells to obtain liquid crystal elements. When these liquid crystal elements were combined with a deflector and an electric field of 20 V was applied thereto, there was observed a change in strength of transmitted light. The values of spontaneous polarization determined at this time (according to Soya-Toya method) are shown in Table 6. The phase series of the respective liquid crystal compositions are also shown in the Table. As seen from the above results, the optically active aromatic compounds having a trifluoromethyl group (1) according to the present invention, even if not assuming Sc* phase in themselves, can become a ferroelectric liquid crystal material operable in the room temperature region when they are made into a liquid crystal composition, and such a ferroelectric liquid crystal material can induce spontaneous polarization necessary for high-speed response. Known compound A Examples 23-29 Among the optically active aromatic compounds having a trifluoromethyl group (1) according to the present invention, those which exhibited Sc* phase in themselves and are shown in Table 14 were used singly for producing the liquid crystal elements according to the method described above, and the values of spontaneous polarization of the produced elements were measured. The results are shown in Table 7. Example No. Liquid crystal Preparation Example No. Value of spontaneous polarization (nC/cm 2 ) [Measuring temp.] 23 9 -105 [40°C] 24 10 -27 [20°C] 25 14 -93 [42°C] 26 15 -28 [21°C] 27 16 -119 [57°C] 28 17 -68 [47°C] 29 18 -8 [65°C]

Claims: Optically active aromatic compounds having a trifluoromethyl group represented by the following formula : wherein R 1 is an alkyl group having 3-20 carbon atoms; R 2 is an alkyl or alkoxyalkyl group having 1-20 carbon atoms which may be substituted with a halogen atom; k is a number of 0 or 1; p is a number of 0 or 1; Ar is y is -0-, -COO- or -OCO-; X is -COO- and * mark denotes an asymmetric carbon atom. The optically active aromatic compounds having a trifluoromethyl group according to claim 1, wherein Ar is Optically active phenol derivatives represented by the following formula: wherein R 2 , p and * mark represent the same as defined in claim 1. A process for producing an optically active aromatic compound having a trifluoromethyl group according to claim 1 wherein X in the formula is -COO-, which comprises reacting a carboxylic acid compound represented by the formula: (wherein R 1 , k, Ar and Y represent the same as defined in claim 1, and R' is a hydroxyl group or a halogen atom) with an optically active phenol derivative set forth in claim 5. Liquid crystal compositions containing at least one of the optically active aromatic compounds having a trifluoromethyl group according to claim 1 as an essential component. Liquid crystal elements using the liquid crystal compositions containing at least one of the optically active aromatic compounds having a trifluoromethyl group according to claim 1 as an essential component.

Inventors: FUJISAWA KOICHI, HIGASHII TAKAYUKI, KURIMOTO ISAO, MINAI MASAYOSHI, SEKINE CHIZU, TANI TAKESHI, TODA SHOJI, FUJISAWA, KOICHI, HIGASHII, TAKAYUKI, KURIMOTO, ISAO, MINAI, MASAYOSHI, SEKINE, CHIZU, TANI, TAKESHI, TODA, SHOJI
Applicants: SUMITOMO CHEMICAL CO, SUMITOMO CHEMICAL COMPANY LIMITED
Application year: 1990
Main classification: C07D239
IPC codes: C09K19, C07C43, C07C69