JP3160964B2 - Optically active cyanocyclopropyl benzoate derivative and intermediates thereof, liquid crystal composition containing the same, and liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optically active cyanocyclopropyl benzoate derivative and a liquid crystal material containing the same, and more particularly to a ferroelectric liquid crystal display material excellent in responsiveness, orientation, memory and the like. .

[0002]

2. Description of the Related Art Liquid crystal display devices are widely used at present because of their excellent features (low-voltage driving, low power consumption, thin display, use in bright places, and no eyestrain). However, the TN type, which is the most common display method, has a very slow response compared to other light-emitting display methods such as a CRT, and has a display memory (memory effect) when the applied electric field is cut off. Therefore, there are many restrictions on application to moving images such as an optical shutter and a printer head that require a high-speed response, and a television that requires a time-division drive, and the display method is not always suitable.

Recently, a display method using a ferroelectric liquid crystal has been reported.
Since a high-speed response of 1000 times and a memory effect can be obtained, it is expected as a next-generation liquid crystal display device, and research and development are being actively conducted at present.

The liquid crystal phase of the ferroelectric liquid crystal belongs to a tilt type chiral smectic phase. Among them, a chiral smectic C (hereinafter abbreviated as SC ^* ) phase has the lowest viscosity and is most desirable. Many liquid crystal compounds exhibiting the SC ^* phase (hereinafter abbreviated as SC ^* compounds) have already been synthesized and studied. However, in order to use them as ferroelectric liquid crystal display devices, the following conditions must be satisfied. is there.
(A) exhibiting the SC ^* phase in a wide temperature range including room temperature; (ii) having an appropriate phase series on the high temperature side of the SC ^* phase in order to obtain good orientation, and having a helical pitch of Large, (c) having an appropriate tilt angle, (d) low viscosity, (e) spontaneous polarization to some extent,
(F) It is necessary to satisfy conditions such as a high-speed response. However, a compound that satisfies these conditions alone is not known. Therefore, it is necessary to mix several or more kinds of compounds and use them as a liquid crystal composition exhibiting an SC ^* phase (hereinafter abbreviated as SC ^* liquid crystal composition).

[0005] As a method for preparing an SC ^* liquid crystal composition, a smectic C (hereinafter referred to as SC) comprising an achiral compound is used.
Is abbreviated. A) a method of adding a dopant composed of an optically active compound as a so-called chiral dopant to a matrix liquid crystal exhibiting a phase can obtain a composition having a lower viscosity;
This is the most common because a high-speed response is possible. Here, the compound used as the chiral dopant alone does not necessarily need to show the SC ^* phase, and does not need to show even the liquid crystal phase, but it can induce sufficient spontaneous polarization in the liquid crystal composition with a small amount of addition, It is necessary to exhibit properties such as a sufficiently large spiral pitch induced as a chiral dopant.

In order to induce large spontaneous polarization as a chiral dopant, it is necessary that a group having a strong dipole moment is fixed as close as possible to the central skeleton (core) and asymmetric carbon of the compound molecule. That is already known. Based on such an idea, the present inventors have made general formula (III)

[0007]

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(Wherein Mes represents a liquid crystal skeleton and R represents an n-alkyl group). An optically active cyanocyclopropane derivative represented by the following formula is synthesized. It has been found that a responsive SC ^* liquid crystal composition can be prepared. (36 pages of the proceedings of the 16th LCD Discussion Meeting, and Japanese Patent Application No. 1-331270)
issue. )

[0009]

As described above, when the compound represented by the general formula (III) can obtain a large spontaneous polarization and a high-speed response when added to a base liquid crystal as a chiral dopant, the SC ^* liquid crystal composition It tends to lower the upper limit temperature (Tc) of the SC * phase of the product, and in the high temperature range, narrows the temperature range of the chiral nematic (hereinafter abbreviated as N ^* ) phase or tends to be easily eliminated. Was.

[0010] From the practicality as a liquid crystal display element, SC *
Needless to say, it is desirable that the maximum temperature (Tc) of the phase is high, but the presence of the N ^* phase in the phase series is also important for the orientation. Generally, the SC ^* liquid crystal is not easy to align as compared with a nematic (hereinafter abbreviated as N) liquid crystal, and various methods have been tried. However, as a liquid crystal material, an isotropic liquid (hereinafter, referred to as I) is used. Omitted.) Upon cooling from the phase, take a phase series of transition to SC ^* phase via N ^* phase, smectic A (hereinafter abbreviated as SA) phase,
Further, it is necessary that the pitch of the spiral in the N ^* phase and the SC ^* phase (particularly, the N ^* phase) is sufficiently large.

Therefore, in order to obtain an SC ^* liquid crystal composition having a wide temperature range and good orientation by using the compound represented by the general formula (III) as a chiral dopant, the amount of the compound should be limited. As the parent liquid crystal, the maximum temperature of the SC phase is high, and the temperature range of the N phase is considerably wide.
It was necessary to use a liquid crystal composition showing a C phase. However, the limitation of the amount used as a dopant causes a decrease in the spontaneous polarization of the liquid crystal composition, and the use of a host liquid crystal having a high maximum temperature of the SC phase increases the viscosity of the liquid crystal composition.
All had an adverse effect on their responsiveness.

The problem to be solved by the present invention is that by adding a small amount as a chiral dopant to a base liquid crystal,
An optically active compound that induces a large spontaneous polarization and enables a high-speed response, and hardly lowers the maximum temperature of the SC ^* phase and does not narrow the temperature range of the N ^* phase, Another object of the present invention is to provide such a ferroelectric liquid crystal composition.

[0013]

According to the present invention, there is provided a compound represented by the general formula (I):

[0014]

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(In the formula, R ¹ represents an alkyl group having 1 to 18 carbon atoms or an alkylcyclopropyl group having 4 to 18 carbon atoms, and these are a fluorine atom, a chlorine atom, a cyano group or a C 1 -C 1 It may be substituted by 10 alkoxyl groups, but preferably has 3 to 1 carbon atoms.
4 represents an alkyl group, an optically active alkoxyalkyl group having 3 to 18 carbon atoms, or an optically active 1-cyano-2-alkylcyclopropyl group. X is a single bond, -O-,
-S-, -CO-, -COO-, -OCO- or -OC
OO-, preferably a single bond, -O- or -C
Represents OO-, more preferably R ¹ is 3 carbon atoms
In the case of a 14 alkyl group, X represents a single bond or —O—, and when R ¹ is an optically active alkoxyalkyl group having 3 to 18 carbon atoms, X represents —COO—, or R ¹ represents an optically active alkoxyalkyl group. In the case of an active 1-cyano-2-alkylcyclopropyl group, X represents a single bond. Ring A and Ring B
Each independently represents a 1,4-phenylene group, a 1,4-phenylene group substituted by one or two fluorine atoms,
Trans-1,4-cyclohexylene group, pyridine-
Represents a 2,5-diyl group, a pyrimidine-2,5-diyl group, a pyrazine-2,5-diyl group, a pyridazine-3,6-diyl group or a 1,3-dioxane-2,5-diyl group, Preferably, a 1,4-phenylene group, one or two
Represents a 1,4-phenylene group, a trans-1,4-cyclohexylene group or a pyrimidine-2,5-diyl group substituted by two fluorine atoms. m represents 0 or 1, and when m is 1, ring B is preferably a 1,4-phenylene group. R ² represents an alkyl group having 1 to 18 carbon atoms, and the asymmetric carbon atoms at the 1- and 2-positions of the cyclopropane ring are each independently in the (R) or (S) configuration. The present invention provides an optically active cyanocyclopropylbenzoate derivative represented by the following formula:

The present invention also relates to an intermediate for the synthesis of the compound represented by the general formula (I)

[0017]

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(Wherein R ² and the asymmetric carbon atom of the cyclopropane ring have the same meanings as in formula (I))
And an optically active cyanocyclopropylbenzoic acid derivative represented by the formula:

The present invention further provides a liquid crystal composition containing the optically active cyanocyclopropyl benzoate derivative represented by the general formula (I).

The liquid crystal composition of the present invention contains at least one of the compounds represented by the above general formula (I) as a component. Particularly, as a material for a ferroelectric liquid crystal display, the main component is An SC ^* containing at least one compound represented by the above general formula (I) as a part or all of a chiral dopant in a base liquid crystal exhibiting a certain SC phase (hereinafter abbreviated as SC base liquid crystal). Liquid crystal compositions are suitable. Further, by adding a small amount of the compound represented by the general formula (I) of the present invention to a nematic liquid crystal, the compound can be used as a TN type liquid crystal for preventing a so-called reverse domain or for use as an STN type liquid crystal.

The compound represented by the general formula (I) according to the present invention can be produced, for example, according to the following production method. That is, the optically active cyanocyclopropylbenzoic acid derivative represented by the general formula (II) and the general formula (IV)

[0022]

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(Wherein R ¹ , X, ring A, ring B and m have the same meaning as in the general formula (I)) and a condensing agent such as dicyclohexylcarbodiimide (DCC). Can be easily produced by reacting in the presence of Alternatively, it can be produced by converting the carboxylic acid represented by the general formula (II) into an acid chloride and then reacting the acid chloride with a compound represented by the general formula (IV) in the presence of a base such as pyridine.

The optically active cyanocyclopropylbenzoic acid derivative represented by the general formula (II), which is an intermediate,
For example, it can be manufactured as follows. That is, the general formula (V)

[0025]

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(Wherein, R ² and the asymmetric carbon atom of the cyclopropane ring have the same meaning as in formula (I))
An optically active cyanocyclopropylphenol derivative represented by the following formula (this compound can be synthesized by the method described in the above-mentioned Japanese Patent Application No. 1-331270) is reacted with trifluoromethanesulfonic anhydride to give a triflate. -Reaction with triethylamine, methanol and carbon monoxide in a polar solvent such as -dimethylformamide (DMF) in the presence of a catalyst such as palladium acetate and 1,1'-bisdiphenylphosphinoferrocene to obtain a compound represented by the general formula (V)
I)

[0027]

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(Wherein R ² and the asymmetric carbon atom of the cyclopropane ring have the same meanings as in formula (I))
The optically active cyanocyclopropyl benzoic acid methyl ester represented by the following formula can be obtained. This can be hydrolyzed by a conventional method to obtain a compound represented by the general formula (II).

Many of the compounds represented by the general formula (IV) are already known as intermediates of liquid crystal compounds, and can be obtained by ordinary synthesis means.

As described above, the general formula (I) of the present invention
And compounds represented by the general formula (II) can be obtained. Specific compounds belonging to these compounds include phase transition temperature such as melting point, elemental analysis, infrared absorption spectrum (I
R), nuclear magnetic resonance spectrum (NMR), mass spectrum (MS) and the like.

Table 1 shows typical examples of the compounds represented by the general formula (I) thus obtained.

[0032]

[Table 1]

(In Table 1, Cr represents a crystal phase, SA represents a smectic A phase, and I represents an isotropic liquid phase.
Inside indicates a monotropic phase. As a structural feature of the compound represented by the general formula (I) of the present invention, a great difference from the compound represented by the general formula (III) shown in Japanese Patent Application No. 1-331270 is that The point is that the direction of the ester bond of the connecting group in the central skeleton (core) is reversed. That is, the general formula (II)
The compound represented by the formula (I) is cyanocyclopropylphenol, while the compound represented by the formula (I) is a cyanocyclopropylbenzoate. The effect of this reversal of the ester bond direction is apparent from the following examples.

As will be described in the examples described later, No. 1 in Table 1. SC liquid crystal (B-1) composed of 5% by weight of compound (1) and a phenylpyrimidine derivative (this liquid crystal exhibits an SC phase at 55.5 ° C. or less and an SA phase at 64.5 ° C. or less).
The phase shows N phase below 70 ° C. A) SC ^* liquid crystal composition (M-1) consisting of 95% by weight. This SC ^* liquid crystal composition (M-1) exhibited an SC ^* phase at 54.5 ° C or lower, an SA phase at 61 ° C or lower, and an N ^* phase at 67 ° C or lower. Further, 90% by weight of SC parent liquid crystal (B-1) and No. An SC ^* liquid crystal composition (M-2) consisting of 10% by weight of the compound (1) was prepared. This SC ^* liquid crystal composition (M
-2) shows an SC ^* phase at 53.5 ° C. or lower, and 57.5 ° C.
The following shows the SA phase, the N ^* phase at 63.5 ° C. or lower,
^* The maximum temperature of the phase (Tc) and the temperature range of the N ^* phase are both SC ^*
It was not much different from the liquid crystal composition (M-1). On the other hand, 95% by weight of the same SC parent liquid crystal (B-1) and a compound represented by the general formula (III),
A compound of the formula (P-1), which is different from the compound (1) only in the direction of the ester bond of the central linking group.

[0035]

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The SC ^* liquid crystal composition (H-1) composed of 5% by weight of the compound of Example 3 exhibits an SC ^* phase at a temperature of 47 ° C. or lower.
It showed SA below 5 ° C and N ^* phase below 67 ° C.

From this, Tc drops greatly and N ^*
It can be seen that the temperature range of the phase is considerably narrow.

Further, 90% by weight of SC parent liquid crystal (B-1)
And a SC ^* liquid crystal composition (H-2) comprising 10% by weight of the compound of the formula (P-1), the Tc of the SC ^* liquid crystal composition (H-2) further dropped to 38 ° C. Also, the N ^* phase in the high temperature range disappeared.

A liquid crystal cell was prepared using the SC ^* liquid crystal composition (M-1), and its spontaneous polarization and response speed were measured. The spontaneous polarization was as large as 6.7 nC / cm ² and the response was 51 μm. Seconds and fast. On the other hand, the spontaneous polarization of the SC ^* liquid crystal composition (H-1) was slightly small at 4.5 nC / cm ^2, and the response was slightly slow at 76 μs.

As described above, No. 1 in Table 1 was used. The liquid crystal composition using 1 compound, compared to the liquid crystal composition of the compound was used in the represented expression by the formula (III) (P-1) , Tc is high, a large amount added be N ^* phase It can be understood that spontaneous polarization is large without disappearance, and a high-speed response of the same level or higher can be obtained.

Further, 98% by weight of SC parent liquid crystal (B-1) and No. 1 in Table 1 were used. SC ^* consisting of 2% by weight of compound 1
When the liquid crystal composition (M-3) was prepared, the spontaneous polarization was 1.7 nC / cm ² and the response speed was 150 μsec. This is because SC derived from (S) -2-methylbutanol has been most commonly used as an asymmetric source in liquid crystals.
^* Compound, for example 4-decyloxybenzoic acid 4-
It can be seen that the spontaneous polarization of [(S) -2-methylbutoxy] phenyl is very large as compared with the fact that the spontaneous polarization is the same when measured alone without being added to the base liquid crystal. Therefore, if the compound represented by the general formula (I) of the present invention is added to the non-chiral host liquid crystal in an amount of about 1 to 2% by weight or more, spontaneous polarization sufficient for high-speed response can be induced. .

In the compound represented by the general formula (I) of the present invention, by selecting an optically active group as R ¹ -X-, the spontaneous polarization or the helical pitch can be further increased. can do. In addition, asymmetric carbon atoms are present at the 1- and 2-positions of the cyanocyclopropane ring, respectively. When R ¹ is an achiral group, the absolute configuration at the 1-position determines the polarity of spontaneous polarization, The arrangement mainly affects the direction of the helical pitch, for example, the most easily obtained (1
In the (R, 2S) body, the polarity of spontaneous polarization is +, and the direction of the helical pitch in the N ^* phase is to the left. So in this case,
The polarity of the spontaneous polarization is + as R ¹ -X-, and the direction of the helical pitch in the N ^* phase is right. If an (S) -2-alkoxyalkanoyloxy group or the like is selected, the spontaneous polarization is added and becomes larger. The spiral pitch is offset,
It can be larger. Such examples include:
For example, No. 1 in Table 1. Compound 2 can be mentioned. This No. When a SC ^* liquid crystal composition (M-4) composed of 5% by weight of the compound No. 2 and 95% by weight of the above-mentioned SC mother liquid crystal (B-1) was prepared, the spontaneous polarization was 8.9 nC /
cm ² , and exhibited a greater spontaneous polarization than the SC ^* liquid crystal composition (M-1). Further, the SC ^* liquid crystal composition (M-
The helical pitch in the N ^* phase of 4) was much larger than that of the SC ^* liquid crystal composition (M-1), and the orientation was even better.

From Table 1, it can be seen that many of the compounds represented by the general formula (I) do not show an SC ^* phase or even a liquid crystal phase by themselves, but as described above, the addition amount is small. In many cases, the amount of SC
The temperature range of the ^* phase and the N ^* phase does not become too narrow.

The SC compound used in the base liquid crystal to which the compound represented by the general formula (I) of the present invention is added as a dopant includes, for example, the following general formula (A)

[0045]

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Wherein R ^a and R ^b represent an alkyl group, an alkoxyl group, an alkoxycarbonyl group, an alkanoyloxy group or an alkoxycarbonyloxy group;
They may be the same or different. ), A phenylbenzoate compound represented by the general formula (B):

[0047]

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(Wherein, R ^a and R ^b have the same meanings as in formula (A)). The general formula (C) including the general formulas (A) and (B)

[0049]

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(Wherein ^Ra and ^Rb have the same meanings as in formula (A), and ring L and ring M are each a 1,4-phenylene group, a 1,4-cyclohexylene group, a pyridine-
2,5-diyl group, pyrimidine-2,5-diyl group, pyrazine-2,5-diyl group, pyridazine-3,6-diyl group, 1,3-dioxane-2,5-diyl group or halogens thereof represent substituents or different may be the same, Z ^a is -COO -, - OCO -, - C
_{H 2 O -, - OCH 2} -, - CH 2 CH 2 -, -C≡C-
Or a single bond. The compound represented by the formula (1) can be used for the same purpose.

In order to extend the temperature range of the SC phase to a high temperature range, the general formula (D)

[0052]

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(Wherein, R ^a and R ^b have the same meanings as in formula (A), and ring L, ring M and ring N have the same meanings as ring L and ring M in formula (C). have, may be the same or different and represented by Z ^a and Z ^b have the same meaning as Z ^a of each said the general formula (C), and may be the same or different.) Tricyclic compounds can be used.

It is effective that these compounds are mixed and used as an SC liquid crystal composition.
It is sufficient to show the C phase, and it is not necessary to show the SC phase for each compound.

By adding the compound represented by the general formula (I) of the present invention and, if necessary, other optically active compounds as chiral dopants to the thus obtained SC liquid crystal composition, a wide temperature range including room temperature can be easily obtained. A liquid crystal composition exhibiting an SC ^* phase within the range can be obtained.

Next, the SC ^* liquid crystal composition obtained by adding the compound represented by the general formula (I) of the present invention to the above-mentioned SC matrix liquid crystal was used to form a liquid crystal between two transparent glass electrodes.
When enclosed as a thin film of about 20 μm, it can be used as a display cell. To get good contrast,
It must be a monodomain that is uniformly oriented. For this reason, many methods have been tried. However, in order to exhibit good orientation, as described above, the liquid crystal material has a phase sequence of I phase-N ^* phase-SA phase-SC ^* phase from the high temperature side. And N ^*
It is said that it is necessary to increase the helical pitch in the phase and the SC ^* phase. In order to increase the helical pitch, a method is generally used in which an appropriate amount of chiral compounds having opposite twisting directions are mixed with each other. Is very easy to adjust because the amount of addition required is small.

[0057]

【Example】

Hereinafter, the present invention will be described in detail with reference to examples. However, of course, the gist and scope of the present invention are not limited by these examples.

The structure of the compound is as follows: NMR, IR, MS
And elemental analysis. The phase transition temperature was measured using a polarizing microscope equipped with a temperature control stage and a differential scanning calorimeter (DSC). (KBr) in IR
Indicates measurement by tablet molding, and (neat) indicates measurement by liquid film. CDCl _{3 in} NMR represents a solvent, s is a singlet, d is a doublet, t is a triplet,
q represents a quadruple, m represents a multiplet, and, for example, dt represents a double triplet. J represents a coupling constant. M ^{+ in} MS represents the parent peak, and the number in parentheses represents the relative intensity of that peak. All “%” in the composition represent “% by weight”.

Example 1 Synthesis of 4-[(1R, 2S) -1-cyano-2-hexylcyclopropyl] benzoic acid (compound represented by the general formula (II)) (1-a) Synthesis of 2S) -1-cyano-2-hexyl-1- (4-trifluoromethanesulfonyloxyphenyl) cyclopropane

[0061]

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(1R, 2S) -1-cyano-2-hexyl-1- (4-hydroxyphenyl) cyclopropane (this compound is disclosed in Japanese Patent Application No. 1-331270 and Tetrahed.
Synthesized according to ron Letters, Vol 32, P939, (1991). 510 mg (1.1 mmol) of trifluoromethanesulfonic anhydride was added to a solution of 220 mg (0.90 mmol) in 2 ml of pyridine under ice-cooling, followed by stirring for 1 hour. After completion of the reaction, a saturated aqueous solution of sodium chloride 5
The reaction product was extracted three times with 50 ml of ether. After concentrating the organic layer of the extract, the obtained residue was separated and purified using silica gel column chromatography (hexane / ethyl acetate = 10/1) to give (1R, 2S)
-1-cyano-2-hexyl-1-1 (4-trifluoromethanesulfonyloxyphenyl) cyclopropane 3
18 mg (94% yield) were obtained.

Colorless viscous liquid [α] _D + 27.0 ° (c = 1.22, CHCl ₃ , 2
0 ° C) IR (neat) 2940, 2860, 2240, 15
05, 1425, 1250, 1215, 1140, 89
_{^{0cm -1 1 H NMR (CDCl 3}} ) δ 0.89 (t, J =
6.9 Hz, 3H), 1.27 to 1.42 (m, 6
H), 1.47 to 1.63 (m, 5H), 1.66 to
1.80 (m, 2H), 7.25 (d, J = 8.9H)
z, 2H), 7.35 (d, J = 8.9 Hz. 2H) MS (m / z) 375 (M ⁺ , 11), 293 (2
5), 278 (21), 277 (82), 243 (1
5), 242 (81), 213 (36), 144 (10
0) Elemental _{analysis: C 17 H 20 NF 3 O} 3 S Calculated: C, 54.39%; H, 5.37%; N, 3.73%; S, 8.54% Found: C, 54.37%; H, 5.33%; N, 3.69%; S, 8.57%

(1-b) 4-[(1R, 2S) -1-
Synthesis of Methyl Cyano-2-hexylcyclopropyl] benzoate

[0065]

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(1R, 2) obtained in Example (1-a)
S) -1-cyano-2-hexyl-1- (4-trifluoromethanesulfonyloxyphenyl) cyclopropane (474 mg, 1.26 mmol) in 1 ml of methanol,
In a 4 ml solution of N, N-dimethylformamide, 22 mg (0.037 mmol) of palladium acetate and 42 mg (0.07 mmol) of 1,1'-bisdiphenylphosphinoferrocene.
6 mmol) and 0.35 ml of triethylamine.
The mixture was stirred at 60 ° C. for 2 hours under a carbon monoxide atmosphere (1 atm). After completion of the reaction, 2 ml of 3M hydrochloric acid was added, followed by filtration through celite, and the reaction product was extracted three times with 50 ml of ethyl acetate. After concentrating the organic layer of the extract, the obtained residue was separated and purified using silica gel column chromatography (hexane / ethyl acetate = 10/1) to obtain 4-[(1
267 mg (74% yield) of methyl (R, 2S) -1-cyano-2-hexylcyclopropyl] benzoate was obtained.

Colorless viscous liquid [α] _D + 55.6 ° (c = 0.95, CHCl ₃ , 2
0 ° C) IR (neat) 2950, 2870, 2240, 17
25, 1610, 1430, 1280, 1190, 11
_{^{15,1015,860cm -1 1 H NMR (CDCl 3}} ) δ 0.89 (t, J =
7.0 Hz, 3H), 1.27 to 1.42 (m, 6
H), 1.45-1.61 (m, 4H), 1.65-
1.81 (m, 3H), 3.91 (s, 3H), 7.3
2 (d, J = 8.7 Hz, 2H), 8.00 (d, J =
8.7 Hz, 2H) MS (m / z) 285 (M ⁺ , 21), 203 (2
9), 187 (40), 156 (100), 128 (2
0) Elemental analysis: C ₁₈ H ₂₃ NO ₂ Calculated: C, 75.76%; H, 8.12%; N, 4.91% Found: C, 75.55%; H, 8.19 %; N, 4.89%

(1-c) 4-[(1R, 2S) -1-
Synthesis of Cyano-2-hexylcyclopropyl] benzoic acid

[0069]

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The 4-[(1) obtained in Example (1-b)
To a solution of 236 mg (0.83 mmol) of methyl (R, 2S) -1-cyano-2-hexylcyclopropyl] benzoate in 3 ml of methanol was added 5 ml of a 30% aqueous sodium hydroxide solution, and the mixture was stirred for 3 hours. After completion of the reaction, 3M hydrochloric acid was added until the pH of the reaction solution became 1, and the reaction product was extracted twice with 50 ml of dichloromethane. The organic layer of the extract was concentrated to obtain 4-[(1R, 2S) -1-cyano-2-hexylcyclopropyl] benzoic acid.

IR (KBr) 3100, 2980, 29
40, 2240, 1690, 1615, 1425, 13
_{^{25,1295,1190,940,860cm -1 1 H NMR (CDCl 3}} ) δ 0.89 (t, J =
7.0 Hz, 3H), 1.26 to 1.44 (m, 6
H), 1.46-1.64 (m, 4H), 1.68-
1.84 (m, 3H), 7.36 (d, J = 8.7H)
z, 2H), 8.09 (d, J = 8.7 Hz, 2H) MS (m / z) 271 (M ⁺ , 24), 242 (1
9), 189 (56), 174 (60), 173 (9
5), 171 (13), 156 (47), 147 (3
1), 41 (100)

Example 2 4-[(1R, 2S) -1
-Cyano-2-hexylcyclopropyl] benzoic acid 4-
Synthesis of octyloxyphenyl (No. 1 compound in Table 1)

[0073]

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The 4-[(1) obtained in Example (1-c)
(R, 2S) -1-cyano-2-hexylcyclopropyl] benzoic acid (50 mg, 0.18 mmol) in dichloromethane (3 ml), dicyclohexylcarbodiimide (DCC), 46 mg (0.22 mmol), 4-N, N
-Dimethylaminopyridine (5 mg) was added and the mixture was stirred for 10 minutes. Then, 61 mg of 4-octyloxyphenol
(0.27 mmol) and stirred at room temperature for 2 hours.
After completion of the reaction, 3 ml of a saturated aqueous sodium chloride solution was added,
The reaction product was extracted three times with 50 ml of ethyl acetate. After concentrating the organic layer of the extract, the resulting residue was subjected to silica gel thin-layer chromatography (hexane / ethyl acetate = 5/5).
Separated and purified using 1), 4-[(1R, 2S) -1
-Cyano-2-hexylcyclopropyl] benzoic acid 4-
54 mg (yield 69%) of octyloxyphenyl was obtained.

Colorless powder Melting point 59 ° C. [α] _D + 28.5 ° (c = 0.94, CHCl ₃ , 2
0 ° C) IR (KBr) 2980, 2940, 2470, 175
0,1635,1530,1495,1285,121
_{^{0,1100,1040,895cm -1 1 H NMR (CDCl 3}} ) δ 0.89 (t, J =
6.8 Hz, 6H), 1.25 to 1.65 (m, 22
H), 1.68-1.83 (m, 5H), 3.96.
(T, J = 6.6 Hz, 2H), 6.93 (d, J =
6.8 Hz, 2H), 7.10 (d, J = 6.8 Hz,
7.2H), 7.38 (d, J = 8.7 Hz, 2H), 8.
15 (d, J = 8.7 Hz, 2H) MS (m / z) 475 (M ⁺ , 10), 255 (1
9), 254 (100), 156 (56)

Hereinafter, Embodiments 3 to 9 will be described. The procedure of Example 2 was repeated, except that 4-[(1R, 2S) -1-cyano-2-hexylcyclopropyl] benzoic acid was reacted with the corresponding substituted phenol or cyclohexanol. 2-No. Nine compounds were synthesized.

Example 3 4-[(1R, 2S) -1-
Cyano-2-hexylcyclopropyl] benzoic acid 4-
[4-{(2S) -2-propyloxypropanoyloxy} phenyl] phenyl (compound No. 2 in Table 1)

White powder (fine needles) Transition temperature 66 ° C. (Cr-I) 42 ° C. (SA-I) [α] _D + 6.4 ° (c = 1.18, CHCl ₃ , 20)
° C) IR (KBr) 2950, 2870, 2240, 176
5,1735,1615,1495,1275,120
_{^{5,1165,1135,1005,810cm -1 1 H NMR (CDCl 3}} ) δ 0.90 (t, J =
7.0 Hz, 3H), 0.98 (t, J = 7.4 Hz,
3H), 1.28 to 1.44 (m, 6H), 1.51 to
1.83 (m, 9H), 1.59 (d, J = 6.9H)
z, 3H), 3.47 (dt, J = 8.9 and 6.7)
Hz, 1H), 3.67 (dt, J = 8.9 and 6.
7 Hz, 1 H), 4.22 (q, J = 6.9 Hz, 1
H), 7.19 (d, J = 8.7 Hz, 2H), 7.2
9 (d, J = 8.7 Hz, 2H) MS (m / z) 553 (M ⁺ , 2), 440 (17),
439 (54), 254 (67), 156 (52), 8
7 (51), 45 (100) Elemental analysis: C ₃₅ H ₃₉ NO ₅ Calculated: C, 75.92%; H, 7.10%; N, 2.53% Found: C, 76.01 %; H, 7.23%; N, 2.44%

Example 4 4-[(1R, 2S) -1-
Cyano-2-hexylcyclopropyl] 4-decyloxy-3-fluorophenyl benzoate (No.
Compound 3)

Colorless plate crystals Melting point 43.5 ° C. [α] _D + 29.3 ° (c = 0.56, CHCl ₃ , 2
0 ° C) IR (KBr) 2930, 2850, 2230, 174
0, 1740, 1610, 1510, 1470, 125
0, 1210, 1145, 1120, 1070, 101
_{^{5,955cm -1 1 H NMR (CDCl 3}} ) δ 0.88 (t, J =
7.0 Hz, 3H), 0.89 (t, J = 6.9 Hz,
3H), 1.24 to 1.65 (m, 24H), 1.69.
８６1.86 (m, 5H), 4.03 (t, J = 6.6H)
z, 3H), 6.92 (ddd, J = 8.9, 2.7,
and 1.3 Hz, 1H), 6.96 to 7.02 (m,
7.2H), 7.39 (d, J = 8.7 Hz, 2H), 8.
14 (d, J = 8.7 Hz, 2H) MS (m / z) 521 (M ⁺ , 3), 254 (10
0), 156 (66), 128 (11) Elementary analysis: Calculated _{C 33 H 44 NO 3: C} , 75.97%; H, 8.50%; N, 2.69% Found: C, 75.81%; H, 8.61%; N, 2.65%

Example 5 4-[(1R, 2S) -1-
Cyano-2-hexylcyclopropyl] benzoic acid
-Difluoro-4-octylphenyl (N in Table 1
o. 4 compound)

Oily substance [α] _D + 26.4 ° (c = 1.19, CHCl ₃ , 2
0 ° C) IR (neat) 2930, 2860, 2230, 17
50, 1610, 1500, 1480, 1270, 12
_{^{40,1190,1070,1015,880cm -1 1 H NMR (CDCl 3}} ) δ 0.886 (t, J =
7.0 Hz, 3H), 0.894 (t, J = 6.9H)
z, 3H), 1.24 to 1.43 (m, 16H), 1.
50 to 1.66 (m, 6H), 1.69 to 1.83
(M, 3H), 2.67 (t, 2H), 7.40 (d,
J = 8.6 Hz, 2H), 8.16 (d, J = 8.6H)
z, 2H) MS (m / z) 495 (M ⁺ , 1), 254 (10
0), 156 (52), 143 (12) Elemental analysis: C ₃₁ H ₃₉ NF ₂ O ₂ Calculated: C, 75.12%; H, 7.93%; N, 2.83% Found: C, 74.90%; H, 8.04%; N, 3.01%

Example 6 4-[(1R, 2S) -1-
Cyano-2-hexylcyclopropyl] trans-4-octylcyclohexyl benzoate (No. 5 in Table 1)
Compound)

Oily substance [α] _D + 25.7 ° (c = 1.13, CHCl ₃ , 2
0 ° C) IR (neat) 2930, 2850, 2230, 17
50, 1610, 1500, 1480, 1380, 12
_{^{70,1240,1070,1015,880cm -1 1 H NMR (CDCl 3}} ) δ 0.89 (t, J =
6.8 Hz, 3H), 1.01-1.12 (m, 2
H), 1.17 to 1.61 (m, 27H), 1.64 to
1.77 (m, 3H), 1.79 to 1.88 (m, 2
H), 2.05-2.12 (m, 2H), 4.90 (t
t, J = 11.1 and 4.3 Hz, 1H), 7.30
(D, J = 8.7 Hz, 2H), 7.99 (d, J =
8.7 Hz, 2H) MS (m / z) 465 (M ⁺ , 25), 272 (3
1), 271 (11), 254 (20), 194 (2
2), 189 (28), 174 (21), 171 (1
0), 156 (61), 149 (15), 128 (1
5), 115 (10), 96 (100)

Example 7 4-[(1R, 2S) -1-
Cyano-2-hexylcyclopropyl] benzoic acid 4-
[(2S) -2-propyloxypropanoyloxy]
Phenyl (No. 6 compound in Table 1)

Oily substance [α] _D + 3.1 ° (c = 1.23, CHCl ₃ , 20
° C) IR (neat) 2960, 2930, 2860, 22
30, 1770, 1610, 1500, 1270, 11
_{^{80,1120,1075,1015,885cm -1 1 H NMR (CDCl 3}} ) δ 0.89 (t, J =
7.0 Hz, 3H), 0.97 (t, J = 7.4 Hz,
3H), 1.29 to 1.43 (m, 6H), 1.51 to
1.82 (m, 10H), 1.58 (d, J = 6.8H)
z, 3H), 3.46 (dt, J = 8.9 and 6.7)
Hz, 1H), 3.65 (dt, J = 8.9 and 6.
7Hz, 1H), 4.20 (q, 6.9Hz, 1H),
7.18 (d, J = 9.2 Hz, 2H), 7.24
(D, J = 9.2 Hz, 2H), 7.40 (d, J =
8.7 Hz, 2H), 8.16 (d, J = 8.7 Hz,
2H) MS (m / z) 478 (M + + 1, trace), 36
3 (10), 254 (36), 87 (67), 45 (1
00)

Example 8 4-[(1R, 2S) -1-
Cyano-2-hexylcyclopropyl] 4-heptylphenyl benzoate (No. 7 compound in Table 1)

Oily substance [α] _D + 30.4 ° (c = 0.85, CHCl ₃ , 2
0 ° C) IR (neat) 2930, 2860, 2240, 17
40, 1610, 1505, 1465, 1410, 12
70, 1200, 1165, 1075, 1015, 86
_{^{0cm -1 1 H NMR (CDCl 3}} ) δ 0.886 (t, J =
7.1 Hz, 3H), 0.894 (t, J = 6.9H)
z, 3H), 1.25 to 1.43 (m, 14H), 1.
46 to 1.49 (m, 6H), 1.68 to 1.84
(M, 3H), 2.62 (t, J = 7.7 Hz, 2
H), 7.10 (d, J = 8.6 Hz, 2H), 7.2
2 (d, J = 8.6 Hz, 2H), 7.38 (d, J =
8.7 Hz, 2H), 8.16 (d, J = 8.7 Hz,
2H)

Example 9 4-[(1R, 2S) -1-
Cyano-2-hexylcyclopropyl] benzoic acid 4-
[(1R, 2S) -1-cyano-2-hexylcyclopropyl] phenyl (compound No. 8 in Table 1)

Oily substance [α] _D + 46.9 ° (c = 1.36, CHCl ₃ , 2
0 ° C) IR (neat) 2960, 2930, 2860, 22
35, 1740, 1610, 1510, 1460, 12
70, 1210, 1190, 1170, 1075, 10
_{^{15,860cm -1 1 H NMR (CDCl 3}} ) δ 0.89 (t, J =
5.3 Hz, 3H), 0.90 (t, J = 6.9 Hz,
3H), 1.28-1.46 (m, 13H), 1.41
To 1.64 (m, 8H), 1.68 to 1.82 (m, 5
H), 7.19 (d, J = 8.8 Hz, 2H), 7.3
4 (d, J = 8.8 Hz, 2H), 7.39 (d, J =
8.7 Hz, 2H), 8.15 (d, J = 8.7 Hz,
2H)

(Example 11) 4-[(1R, 2S) -1
-Cyano-2-hexylcyclopropylbenzoic acid 4-
(5-hexylpyrimidiso-2-yl) phenyl] (compound No. 9 in Table 1) Colorless needles Melting point 60.5 ° C [α] _D + 27.5 ° C (C = 0.65) CHCl ₃ ,
IR (KBr) 2925, 2860, 2320, 173
5,1610,1590,1430,1265,119
5,1075,790 cm-1 1H NMR (CDCl ₃ ) δ 0.90 (t, J =
6.9 Hz, 3H), 1.28 to 1.42 (m, 12
H), 1.51-1.84 (m, 11H), 2.64
(T, J = 7.6 Hz, 2H), 7.34 (d, J =
8.9 Hz, 2H), 7.41 (d, J = 8.6 Hz,
7.2H), 8.51 (d, J = 8.9 Hz, 2H),
63 (S, 2H) MS (m / z) 510 (M +, 3), 255 (21),
254 (100), 156, (75) Raw material analysis: C ₃₂ H ₃₉ N ₃ O ₂ Calculated: C, 77.77%; H, 7.71%; N, 8.24% Found: C, 77.65%; H, 7.78%; N, 8.25%

Example 11 Preparation of SC ^* Liquid Crystal Composition (1) An SC parent liquid crystal (B-1) having the following composition was prepared.

[0093]

Embedded image

The phase transition temperature of the base liquid crystal was as follows. 12.5 ° C (Cr → SC), 55.5 ° C (SC
-SA), 64.5 ° C (SA-N), 70 ° C (N-
I). 95% by weight of this SC mother liquid crystal (B-1) and No. 1 in Table 1 obtained in Example 2. An SC ^* liquid crystal composition (M-1) comprising 5% of the compound No. 1 was prepared. The phase transition temperature was as follows. 54.5 ° C (SC ^* -SA), 61 ° C (SA-N ^* ),
67 ° C (N ^* -I). The melting point was not clear.

Similarly, SC matrix liquid crystal (B-1) 90%
And No. 1 in Table 1. SC ^* consisting of 10% of one compound
A liquid crystal composition (M-2) was prepared. The phase transition temperature was as follows. 53 ° C (SC ^* -SA), 57.5 ° C (SA-N ^* ),
63.5 ° C (N ^* -I).

Similarly, SC mother liquid crystal (B-1) 98
% And No. in Table 1. SC ^* consisting of 2% of compound 1
A liquid crystal composition (M-3) was prepared. The phase transition temperature was as follows. 56 ° C (SC ^* -SA), 65.5 ° C (SA-N ^* ),
70.5 ° C (N ^* -I).

From the above, No. 1 in Table 1 was obtained. Compound 1 was added to the SC matrix liquid crystal to give the SC ^*
It can be seen that the upper limit temperature (Tc) of the phase does not decrease so much and the temperature width of the N ^* phase hardly changes.

Next, 95% of the SC base liquid crystal (B-1) and No. 1 in Table 1 were prepared. An SC ^* liquid crystal composition (M-4) consisting of 5% of compound 2 was prepared. The phase transition temperature was as follows. 57.5 ° C (SC ^* -SA), 65 ° C (SA-N ^* ),
68.5 ° C (N ^* -I).

Similarly, SC mother liquid crystal (B-1) 90
% And No. in Table 1 obtained in Example 3. An SC ^* liquid crystal composition (M-5) consisting of 10% of compound 2 was prepared. The phase transition temperature was as follows. 57.5 ° C (SC ^* -SA), 63.5 ° C (SA-N
^* ), 65 ° C (N ^* -I).

As described above, No. 1 in Table 1 was used. Compound 2 does not lower the Tc of the prepared liquid crystal composition by adding it to the SC base liquid crystal. Further, although the temperature range of the N ^* phase is slightly narrowed, 10% is added. Still, the temperature range of 1.5 ° C. is maintained. Further, the SC ^* liquid crystal composition (M-4) and the SC ^* liquid crystal composition (M-5)
^When the helical pitch in the ^* phase is compared with the SC ^* liquid crystal composition (M-1) and the SC ^* liquid crystal composition (M-2), respectively, it is clear that the helical pitch is much larger.

Next, an SC matrix liquid crystal (B-2) having the following composition was prepared.

[0102]

Embedded image

The phase transition temperature of the base liquid crystal (B-2) was as follows. -3 ℃ (Cr → SC) 、 43 ℃ (S
C-SA), 65 ° C (SA-N), 76.5 ° C (N-
I). 90% of this SC mother liquid crystal (B-2) and No. 1 in Table 1 above. SC ^* liquid crystal composition (M
-6) was prepared. The phase transition temperature was as follows. 50.5 ° C (SC ^* -SA), 65 ° C (SA-N ^* ),
71 ° C (N ^* -I). The melting point was not clear.

When this is compared with the SC * liquid crystal composition (M-4), Tc is rather increased, and in this case also, a sufficient N ^{* is obtained.}
It can be seen that the phase temperature range is maintained. Thereafter, similarly, the SC mother liquid crystal (B-1) and No. 1 in Table 1 were used. 3 to N
o. SC ^* liquid crystal compositions (M-7) to (M-15) comprising Compound No. 9 were prepared. Table 2 shows the amounts added and their phase transition temperatures.

[0105]

[Table 2]

(In Table 2, the transition temperature indicates the transition temperature from the left phase to the right phase. In each case, the melting point was not clear. In addition,-indicates that the pitch was so large that the direction could not be measured. Shown.)

Example 12 Preparation of SC ^* Liquid Crystal Composition (2) No. 1 in Table 1 represented by the general formula (I) Compound (2) (the direction of the helical pitch induced by this compound in the N ^* phase is right, and the polarity of spontaneous polarization is +) 9.7%, which belongs to the compound represented by the general formula (III) , The aforementioned equation (P-1)

[0108]

Embedded image

2.3% of the compound (the orientation of the helical pitch induced by this compound in the N * phase is on the left and the polarity of spontaneous polarization is +) and 88% of the above-mentioned base liquid crystal (B-1) An SC ^* liquid crystal composition (M-16) was prepared. The phase transition temperature was as follows. 55.5 ° C (SC ^* -SA), 62.5 ° C (SA-N
^* ), 64.0 ° C (N ^* -I). The melting point was not clear. The helical pitch of the N ^* phase of this composition was too large to be measured.

(Example 13) Preparation of a liquid crystal display device The SC ^* liquid crystal composition (M-1) obtained in Example 10 was heated to an isotropic liquid (I) phase, and this was heated to a thickness of 2 μm. A liquid crystal display element was prepared by filling a glass cell composed of a plurality of transparent electrode plates (polyimide coating-aligned by rubbing). This was gradually cooled to room temperature to obtain a uniformly oriented SC ^* phase cell.

An electric field strength of 10 V _PP / μm, 5
When an electro-optical response speed was measured by applying a rectangular wave of 0 Hz, a high-speed response of 51 μsec at 25 ° C. was confirmed. At this time, the tilt angle was 23.5 °, and the contrast was good. Spontaneous polarization is + 6.7n
C / cm ² .

Similarly, SC ^* liquid crystal composition (M-2)
To (M-16), a liquid crystal display device was prepared, and its characteristics were measured. The results are shown in Table 3.

[0113]

[Table 3]

From Table 3, it can be understood that the SC ^* liquid crystal composition containing the compound represented by the general formula (I) of the present invention has both good alignment properties and high-speed response.

(Comparative Example 1) No. 1 in Table 1 which belongs to the liquid crystal compound represented by the general formula (III) and is the liquid crystal compound represented by the general formula (I) of the present invention.
SC ^* consisting of 5% of the compound of formula (P-1), which is a compound in which the direction of the ester bond of the central linking group is different from that of the liquid crystal compound of No. 1, and 95% of the above-mentioned SC parent liquid crystal (B-1) A liquid crystal composition (H-1) was prepared. The phase transition temperature of this liquid crystal composition was as follows. 47 ° C (SC ^* -SA), 64.5 ° C (SA-N ^* ),
67 ° C (N ^* -I).

From these results, it can be seen that the SC ^* liquid crystal composition (M-
Compared with 1), Tc drops significantly (54.5 ° C. → 4
7 ° C.), and the temperature width of the N ^* phase is considerably narrowed (6 degrees → 2.5 degrees). This SC ^* liquid crystal composition (H
Using -1), a liquid crystal display device was prepared in exactly the same manner as in Example 13, and its characteristics were measured.
The response was reduced to 4.5 nC / cm ^2, and the response was slightly delayed to 76 μs. The tilt angle was 19.5 °.
The helical pitch in the N ^* phase is SC ^* liquid crystal composition (M
-1), the contrast was slightly reduced.

Next, 10% of the compound of the formula (P-1) and S
An SC ^* liquid crystal composition (H-2) consisting of 90% of the C base liquid crystal (B-1) was prepared. Tc of this liquid crystal composition is 38 ° C.
And dropped significantly as compared with the SC ^* liquid crystal composition (M-2). Also, the N ^* phase in the high temperature region disappeared, the orientation deteriorated, and the contrast decreased.

Comparative Example 2 A compound belonging to the compound represented by the general formula (III) and represented by the general formula (I) of the present invention
No. in Table 1 which is a compound represented by Formula (P-2), which is a compound that differs only in the direction of the ester bond of the central linking group as compared with the compound of Formula (2)

[0119]

Embedded image

10% of the compound and parent liquid crystal (B-1) 9
A SC ^* liquid crystal composition (H-3) consisting of 0% was prepared.
This liquid crystal composition shows an SC ^* phase at 57 ° C. or lower,
The SA phase is shown below, but not the N ^* phase.

The response measured in the same manner as in Example 13 was 2
Although it was as fast as 4 μsec, SC ^* liquid crystal composition (M-5)
As compared with, the orientation was poor and the contrast was low.

[0122]

The optically active compound represented by the general formula (I) of the present invention can induce a large spontaneous polarization in a liquid crystal composition by adding a small amount as a chiral dopant to another base liquid crystal. In addition, the liquid crystal composition has a large helical pitch, has excellent alignment properties, and is capable of high-speed response in a wide temperature range without lowering the maximum temperature of the SC ^* phase or losing the N ^* phase by being added. can do. Further, the compound represented by the general formula (I) of the present invention can be easily produced industrially, is colorless, has excellent chemical stability against water, light and the like, and is practical. Furthermore, in the chiral smectic liquid crystal composition of the present invention, 30 μm
It is possible to realize a high-speed response on the order of seconds, and it is extremely useful as a material for an optical switching element for display.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI // C07C 323/18 C07C 323/18 (72) Inventor Tetsuo Kusumoto 1-9-2-102 Minamidai, Sagamihara City, Kanagawa Prefecture (72) Inventor Kenichi Sato 35-11 Kamimizo, Sagamihara City, Kanagawa Prefecture (72) Inventor Akiko Nakayama 1380-K-702, Yamazaki-cho, Machida-shi, Tokyo (56) References JP-A-3-236365 (JP, A) JP-A-63 -190843 (JP, A) JP-A-3-115241 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 255/46 C09K 19/30 C09K 19/34 C09K 19/46 CA (STN) REGISTRY (STN)

Claims (9)

(57) [Claims] 1. A compound of the general formula (I) (Wherein, R ¹ represents an alkyl group having 1 to 18 carbon atoms or an alkylcyclopropyl group having 4 to 18 carbon atoms, such as a fluorine atom, a chlorine atom, a cyano group, or an alkoxyl group having 1 to 10 carbon atoms. X may be a single bond, -O-, -S-, -CO-,-
COO-, -OCO- or -OCOO-;
And ring B are each independently a 1,4-phenylene group, a 1,4-phenylene group substituted by one or two fluorine atoms, a trans-1,4-cyclohexylene group, a pyridine-2,5 -Diyl group, pyrimidine-2,5-diyl group, pyrazine-2,5-diyl group, pyridazine-3,6
-Diyl group or 1,3-dioxane-2,5-diyl group, m represents 0 or 1, and R ² represents 1 carbon atom.
-18 represents an alkyl group, and the asymmetric carbon atoms at the 1- and 2-positions of the cyclopropane ring are each independently in the (R) or (S) configuration. ) An optically active cyanocyclopropylbenzoic acid ester derivative represented by the formula: 2. Ring B represents a 1,4-phenylene group,
Ring A is 1,4-phenylene group, 1,4-phenylene group substituted by one or two fluorine atoms, trans-
1,4-cyclohexylene group or pyrimidine-2,5-
The optically active cyanocyclopropyl benzoate derivative according to claim 1, which is a diyl group. 3. The optically active cyanocyclopropyl benzoate derivative according to claim 2, wherein R ¹ represents an alkyl group having 3 to 14 carbon atoms, and X represents a single bond or —O—. 4. The optically active cyanocyclopropyl benzoate derivative according to claim 2, wherein R ¹ represents an optically active alkoxyalkyl group having 3 to 18 carbon atoms, and X represents —COO—. 5. The optically active cyanocyclopropyl benzoate derivative according to claim 2, wherein R ¹ represents an optically active 1-cyano-2-alkylcyclopropyl group and X represents a single bond. 6. A compound of the general formula (II) (In the formula, R ² represents an alkyl group having 1 to 18 carbon atoms, and the asymmetric carbon atoms at the 1- and 2-positions of the cyclopropane ring each independently have the (R) or (S) configuration.) An optically active cyanocyclopropylbenzoic acid derivative represented by the formula: 7. A liquid crystal composition comprising the optically active cyanocyclopropyl benzoate derivative according to claim 1. 8. The liquid crystal composition according to claim 7, which exhibits a ferroelectric chiral smectic phase. 9. A liquid crystal display device using the liquid crystal composition according to claim 7.