Liquid crystal compound and preparation method and application thereof

Abstract

The invention relates to the technical field of liquid crystal compounds, and particularly discloses a liquid crystal compound and a preparation method and application thereof. The liquid crystal compound as shown in the formula I is prepared by introducing a cyano group with strong negativity, a stable tetrahydropyran ring and a fluorine element with special properties into an aromatic hydrocarbon molecule, and R1 represents a straight-chain alkyl group with 2-5 carbon atoms; and R2 represents linear alkyl or alkoxy with 1-8 carbon atoms or aryl or cyclohexyl containing a substituent group. Compared with the traditional lateral difluoro aromatic hydrocarbon liquid crystal compound, the liquid crystal compound provided by the invention has the advantages that the negative dielectric anisotropy value is higher, and the liquid crystal compound has a better application prospect in VA type mixed liquid crystal materials. # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid crystal compounds, and in particular relates to a liquid crystal compound and a preparation method and application thereof. Background Art

[0002] With the rapid development of science and technology, liquid crystal display technology has made significant progress in the past decade or so and has quickly penetrated into people's daily lives, becoming an indispensable part. With its advantages of lightness, energy saving, and high definition, liquid crystal display products have occupied a dominant position in the display field. To continuously improve the performance of liquid crystal displays, researchers are constantly exploring new liquid crystal display methods. Among them, optically compensated bend mode (OCB), in-plane switching liquid crystal display (IPS), vertical alignment mode (VA), axisymmetric microstructure liquid crystal display (ASM), and multi-domain twisted liquid crystal display have emerged, greatly enriching the application scenarios of liquid crystal displays.

[0003] Among the many liquid crystal display modes, the vertical alignment mode (VA) has attracted much attention due to its unique molecular arrangement and excellent display performance. In VA mode, the liquid crystal molecules are perpendicular to the direction of the glass substrate and parallel to the vertically incident light in the zero electric field state. When the polarizers are arranged orthogonally, the VA mode can display a good dark state effect, thereby ensuring a high contrast ratio of the device. In addition, the response time of the VA mode is faster than that of the twisted mode device, about half of the latter. This advantage gives the VA mode a significant advantage in high-speed response display applications.

[0004] Liquid crystal materials themselves play a crucial role in improving the performance of liquid crystal displays (LCDs). In particular, reducing the rotational viscosity and increasing the dielectric anisotropy (Δε) of liquid crystal materials contribute to faster display response. However, reducing the rotational viscosity and elastic constant of liquid crystal materials is relatively difficult, so increasing the dielectric anisotropy has become a more feasible technical approach.

[0005] In recent years, negative liquid crystal monomers based on pendant fluorinated aromatic hydrocarbons, such as ethylcyclohexylphenyl-2,3-difluorophenylethyl ether (cas323178-01-4) and propyldicyclohexyl-2,3-difluorophenylpropyl ether (cas473257-14-6), have been widely used in liquid crystal mixtures. These monomers have improved the performance of liquid crystal materials to a certain extent, but there is still room for further improvement.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a liquid crystal compound and its preparation method and application. The present invention prepares a new type of liquid crystal compound by introducing a more negative cyano group into an aromatic hydrocarbon molecule, combined with the introduction of a tetrahydropyran ring and a fluorine element, further enhancing the negative dielectric anisotropy value of the liquid crystal monomer, so that the liquid crystal compound provided by the present invention has better application prospects in VA type hybrid liquid crystal materials.

[0008] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0009] The first object of the present invention is to provide a liquid crystal compound having the general formula shown in Formula I:

[0010]

[0011] in,

[0012] R1 is selected from a linear alkyl group with 2 to 5 carbon atoms;

[0013] R2 is selected from a linear alkyl group or alkoxy group having 1 to 8 carbon atoms, and a substituted aryl group.

[0014] The present invention prepares a novel liquid crystal compound by introducing a more negatively charged cyano group into an aromatic hydrocarbon molecule, combined with a tetrahydropyran ring and the element fluorine. The cyano group (-CN) is a highly polar group with significant electronegativity. Introducing a cyano group into a liquid crystal molecule increases the molecular dipole moment, thereby enhancing the polarity of the molecule. This enhanced polarity facilitates the orientation and alignment of the liquid crystal molecules in an electric field. In particular, in VA-type liquid crystal displays, the increased negative dielectric anisotropy contributes to the stable vertical alignment of the liquid crystal molecules. The tetrahydropyran ring (also known as the hexahydropyran ring) is a stable cyclic structure with a certain degree of rigidity. The introduction of the tetrahydropyran ring increases the rigidity of the liquid crystal molecules, making it easier for them to form an ordered arrangement. This ordered arrangement enhances the response speed and stability of the liquid crystal molecules in an electric field. Fluorine has a small atomic radius and a high electronegativity. Introducing fluorine into the liquid crystal molecule reduces the molecular volume while increasing its polarity. The introduction of fluorine also helps improve the chemical and thermal stability of the liquid crystal molecules.

[0015] In the above technical solution, R1 is a straight-chain alkyl group having 2 or 3 carbon atoms.

[0016] In the above technical solution, R2 is selected from a linear alkyl group or an alkoxy group having 2 to 8 carbon atoms.

[0017] In the above technical solution, the substituent on the aryl group is selected from one or more of F, a linear alkyl group having 1 to 8 carbon atoms, and an alkoxy group.

[0018] In the above technical solution, the aryl group containing a substituent is selected from:

[0019]

[0020] Among them, L 1 It is selected from a linear alkyl or alkoxy group having 1 to 8 carbon atoms.

[0021] In the above technical solution, the liquid crystal compound is selected from the following formula:

[0022]

[0023] wherein X1 is selected from a linear alkyl group with 2 or 3 carbon atoms, L 1 It is selected from a linear alkyl or alkoxy group having 1 to 8 carbon atoms.

[0024] A second object of the present invention is to provide a method for preparing a liquid crystal compound, comprising the following steps:

[0025] (1) Substrates A-1 and A-2 undergo a palladium-catalyzed Suzuki coupling reaction to generate intermediate B-1;

[0026] (2) The aldehyde group of intermediate B-1 is converted into a cyano group through oximation reaction and dehydration reaction to obtain intermediate C-1;

[0027] (3) After the intermediate C-1 is lithiated, an R2 group is introduced into the terminal of the intermediate C-1 through alkylation and / or etherification and / or aryl substitution reaction to obtain a liquid crystal compound;

[0028] in,

[0029] The structural formula of substrate A-1 is

[0030] The structural formula of substrate A-2 is

[0031] The structural formula of intermediate B-1 is

[0032] The structural formula of intermediate C-1 is

[0033] in,

[0034] R1 is selected from a linear alkyl group with 2 to 5 carbon atoms;

[0035] R2 is selected from a linear alkyl group or alkoxy group having 1 to 8 carbon atoms, and a substituted aryl group.

[0036] Optionally, the molar ratio of substrate A-2 to substrate A-1 is 1.0-1.1.

[0037] In the above technical solution, when R2 is a linear alkyl group having 1 to 8 carbon atoms, step (3) comprises the following operations:

[0038] The intermediate C-1 is lithiated at -70 to -80°C under the action of butyl lithium, and then coupled with a straight-chain halogenated alkane to obtain a liquid crystal compound.

[0039] Optionally, the molar ratio of butyl lithium to intermediate C-1 is 1.0-1.3, and the molar ratio of the linear halogenated alkane to intermediate C-1 is 1.0-2.0.

[0040] In the above technical solution, when R2 is an alkoxy group having 1 to 8 carbon atoms, step (3) comprises the following operations:

[0041] a) The intermediate C-1 is lithiated at -70 to -80°C under the action of butyl lithium, and then reacted with borate to obtain the intermediate D-2;

[0042] b) oxidizing the intermediate D-2 with hydrogen peroxide to obtain the intermediate E-1;

[0043] c) intermediate E-1 undergoes etherification reaction with a linear bromoalkane in a DMF + potassium carbonate system to obtain a liquid crystal compound;

[0044] in,

[0045] The structural formula of intermediate D-2 is

[0046] The structural formula of intermediate E-1 is

[0047] Optionally, the molar ratio of butyl lithium to intermediate C-1 is 1.0-1.3, the molar ratio of borate to intermediate C-1 is 1.0-1.5; the molar ratio of hydrogen peroxide to intermediate D-2 is 1.0-3.0; the molar ratio of linear bromoalkane to intermediate E-1 is 1.0-2.0; DMF + potassium carbonate system is used as the solvent, wherein the molar ratio of potassium carbonate to intermediate E-1 is 1.0-2.0, and the volume of DMF is 1-5 times that of intermediate E-1.

[0048] In the above technical solution, when R2 is an aromatic group containing a substituent, step (3) includes the following operations:

[0049] a) The intermediate C-1 is lithiated at -70 to -80°C under the action of butyl lithium, and then reacted with borate to obtain the intermediate D-2;

[0050] b) intermediate D-2 and intermediate G-1 undergo Suzuki coupling reaction in the presence of palladium catalyst to obtain a liquid crystal compound;

[0051] in,

[0052] The structural formula of intermediate D-2 is

[0053] The intermediate G-1 is a polysubstituted bromoaryl hydrocarbon, and the substituent of the intermediate G-1 is selected from one or more of F, a linear alkyl having 1 to 8 carbon atoms, and an alkoxy group;

[0054] Alternatively, intermediate G-1 is selected from

[0055] Among them, L 1 It is selected from a linear alkyl or alkoxy group having 1 to 8 carbon atoms.

[0056] Optionally, the molar ratio of butyl lithium to intermediate C-1 is 1.0-1.3, and the molar ratio of borate to intermediate C-1 is 1.0-1.5;

[0057] Optionally, the molar ratio of intermediate D-2 to intermediate G-1 is 1.0-1.1.

[0058] The third object of the present invention is to provide an application of the liquid crystal compound in the above technical solution in the preparation of VA type mixed liquid crystal material.

[0059] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art.

[0060] The liquid crystal compounds prepared by introducing a strongly negative cyano group, a stable tetrahydropyran ring, and a fluorine element with unique properties into aromatic hydrocarbon molecules exhibit stronger negative dielectric anisotropy than traditional side-positioned difluoroaromatic liquid crystal compounds. Due to this enhanced negative dielectric anisotropy, the liquid crystal compounds provided by the present invention have promising applications in VA-type hybrid liquid crystal materials. These liquid crystal materials can exhibit higher contrast, faster response times, and more stable performance, thus meeting the demand for high-performance materials in modern liquid crystal displays. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an undue limitation of the present invention. Obviously, the drawings described below are only some embodiments. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without inventive effort. In the accompanying drawings:

[0062] Figure 1 is a mass spectrum of the liquid crystal compound prepared in Example 3;

[0063] Figure 2 is the H NMR spectrum of the liquid crystal compound prepared in Example 3;

[0064] Figure 3is the mass spectrum of the liquid crystal compound prepared in Example 5;

[0065] Figure 4 is the H NMR spectrum of the liquid crystal compound prepared in Example 5;

[0066] Figure 5 is the mass spectrum of the liquid crystal compound prepared in Example 7;

[0067] Figure 6 This is the H NMR spectrum of the liquid crystal compound prepared in Example 7.

[0068] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but rather to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0070] Experimental instruments and conditions

[0071] Gas chromatograph (Agilent 8860), experimental conditions: chromatographic column HP-5, column temperature first raised to 200 °C for 4 min, then raised to 290 min at a rate of 10 °C / min, carrier gas was N2, injection volume was 1.0 μL.

[0072] Dielectric constant tester (Agilent E4980A 20 Hz-2 MHz), experimental conditions: add the sample to the sample box, test at 1 kHz, 25 ° C, and calculate the △ε value.

[0073] The structure of the liquid crystal compound is shown in Formula I:

[0074]

[0075] in,

[0076] R1 is selected from a linear alkyl group with 2 to 5 carbon atoms;

[0077] R2 is selected from a linear alkyl group or alkoxy group having 1 to 8 carbon atoms, a substituted aryl group or a cyclohexyl group.

[0078] In order to more clearly illustrate the method for preparing the liquid crystal compound of the present invention, the reaction process is exemplified as follows:

[0079] (1) Preparation of intermediate C-1:

[0080]

[0081] Substrate A-1 and substrate A-2 are subjected to Suzuki coupling in the presence of a palladium catalyst to prepare intermediate B-1. Intermediate B-1 is heated to reflux by adding hydroxylamine hydrochloride and sodium acetate to toluene to prepare an oxime intermediate, which is further reacted and heated, and then thionyl chloride is added for dehydration to prepare intermediate C-1.

[0082] (2) Preparation of liquid crystal compounds:

[0083] 1) Liquid crystal compound D-1 wherein R2 is a linear alkyl group having 1 to 8 carbon atoms:

[0084]

[0085] The intermediate C-1 is lithiated at -70 to -80°C under the action of butyl lithium, and then coupled with a straight-chain halogenated alkane to obtain the liquid crystal compound D-1.

[0086] 2) Liquid crystal compound F-1 wherein R2 is an alkoxy group having 1 to 8 carbon atoms:

[0087]

[0088] Intermediate C-1 is lithiated at -70 to -80°C with butyl lithium, and a borate ester is added dropwise to prepare intermediate D-2. Intermediate D-2 is then oxidized with hydrogen peroxide to prepare intermediate E-1. Intermediate E-1 is etherified with a linear bromoalkane in a DMF + potassium carbonate system to yield liquid crystal compound F-1.

[0089] 3) R2 is (L 1 Liquid crystal compound H-1 selected from a linear alkyl or alkoxy group having 1 to 8 carbon atoms:

[0090]

[0091] Intermediate C-1 is lithiated at -70 to -80°C under the action of butyl lithium, and borate is added dropwise to prepare intermediate D-2. Then, intermediate D-2 and intermediate G-1 undergo Suzuki coupling under the catalysis of a palladium catalyst to obtain liquid crystal compound H-1.

[0092] Example 1

[0093] (1) Preparation of intermediate 3-1, the preparation process is as follows:

[0094]

[0095] 1) Into a 2L four-necked flask, 134.5g of intermediate 1-1 (commercially available), 92.4g of intermediate 1-2 (commercially available), 104g of potassium carbonate, 300mL of toluene, 300mL of ethanol, and 300mL of water were stirred evenly. Then, 0.2g of dichlorodi-tert-butyl-(4-dimethylaminophenyl)phosphine palladium (II) was added under nitrogen protection and heated to reflux for 5 hours under stirring. After completion of the reaction, the liquid was separated at room temperature. After the toluene layer was washed with 150mL of water, anhydrous sodium sulfate drying and filtration were used to obtain a yellow crude toluene solution of intermediate 2-1. The purity of intermediate 2-1 was 98.5% by GC (gas chromatography).

[0096] 2) 82g of anhydrous sodium acetate and 52g of hydroxylamine hydrochloride were added to the crude toluene solution of intermediate 2-1, heated to reflux for 3 hours, and after the aldehyde reaction was completed by GC (gas chromatography), the temperature was lowered to 50°C, 90g of thionyl chloride was added dropwise, and the addition was completed and heated to 50-60°C for 4 hours. After the oxime reaction was completed, the temperature was lowered to 0-10°C and 100g of water (acid gas was absorbed by alkali) was added dropwise and stirred for 1 hour. After separation, 150mL of saturated sodium bicarbonate solution was used to wash 2 times, and then 150mL of water was washed once. After separation, the mixture was dried over anhydrous sodium sulfate and filtered, and the solvent was evaporated to obtain the crude intermediate 3-1. The crude intermediate 3-1 was recrystallized from ethanol to obtain 130g of white crystals of intermediate 3-1, which was detected by GC (gas chromatography) to have a purity of 99.6%.

[0097] (2) Liquid crystal compound 4-1 was prepared using intermediate 3-1. The preparation process is as follows:

[0098]

[0099] To a 1L four-necked flask, add 30.9g of intermediate 3-1, 200mL of tetrahydrofuran, and 13g of diisopropylamine. Under nitrogen protection, cool to -78°C and add 50mL of 2.5mol / L butyl lithium dropwise. After the addition is complete, incubate for 2 hours. Then, add 25.5g of iodopropane dropwise at -78°C and incubate for 2 hours. Then, slowly warm to room temperature and add dilute hydrochloric acid to quench the reaction. Add 100mL of toluene and 100mL of water to extract the product, then wash it with 100mL of water several times until neutral. After drying over anhydrous sodium sulfate, pass it through a silica gel column, and evaporate the toluene to obtain a crude liquid crystal compound 4-1. Then, further crystallization and purification using ethanol yields 24.9g of white crystals of liquid crystal compound 4-1, which has a purity of 99.85% as determined by GC (gas chromatography).

[0100] Example 2

[0101] (1) Intermediate 3-1 was prepared by the same method as in Example 1;

[0102] (2) Liquid crystal compound 7-1 was prepared using intermediate 3-1. The preparation process is as follows:

[0103]

[0104] 1) To a 1L four-necked flask, add 30.9g of intermediate 3-1, 200mL of tetrahydrofuran, and 13g of diisopropylamine. Under nitrogen, cool to -78°C, and dropwise add 50mL of 2.5mol / L butyl lithium. Incubate for 2 hours after addition. Then, dropwise add 15.6g of trimethyl borate at -78°C and incubate for 2 hours. Then, slowly warm to room temperature, add dilute hydrochloric acid to quench the reaction, and adjust the pH to 5-6 to obtain a solution of intermediate 5-1. Control the temperature at 0-10°C, and dropwise add 23g of 30% hydrogen peroxide to the solution of intermediate 5-1. Then, incubate at 30-40°C for 2 hours. The reaction progress of intermediate 5-1 was monitored by GC (gas chromatography). After the reaction of intermediate 5-1 was complete, the temperature was lowered by 0-10°C and sodium sulfite solution was added dropwise to adjust the mixture to a non-oxidizing state (this can be confirmed by testing with starch potassium iodide paper; if the paper does not turn blue, it indicates that the mixture is non-oxidizing). Then, 200 mL of dichloromethane was added to extract the product by separation. After separation, the product was washed twice with 100 mL of water. The solvent was evaporated to dryness to obtain 27.6 g of a light red solid, which was the product intermediate 6-1. The purity of intermediate 6-1 was 95.7% as determined by GC (gas chromatography).

[0105] 2) Add 27.6g of intermediate 6-1, 15.6g of bromopropane, 150mL of DMF, and 17.9g of potassium carbonate to a 500mL four-necked flask and heat to 90°C for 12 hours. After the reaction is complete, add 150mL of water + 150mL of toluene and extract the product by liquid separation. After separation, the toluene layer is washed 3 times with 150mL of water. After separation, pass through a silica gel column and evaporate the toluene to obtain a crude liquid crystal compound 7-1. Use ethanol crystallization and multiple purification to obtain 25.8g of white crystals of liquid crystal compound 7-1, which is detected by GC (gas chromatography) with a purity of 99.91%.

[0106] Example 3

[0107] (1) Intermediate 6-1 was prepared by the same method as in Example 2;

[0108] (2) Liquid crystal compound 8-1 was prepared using intermediate 6-1. The preparation process is as follows:

[0109]

[0110] To a 500mL four-necked flask, 27.6g of intermediate 6-1, 19.2g of bromopentane, 150mL of DMF, and 17.9g of potassium carbonate were added and heated to 90°C for 12 hours. After the reaction is complete, 150mL of water + 150mL of toluene are added to extract the product by liquid separation. After separation, the toluene layer is washed 3 times with 150mL of water. After separation, the mixture is passed through a silica gel column and the toluene is evaporated to obtain a crude liquid crystal compound 8-1. 25.8g of white crystals of liquid crystal compound 8-1 are obtained by repeated purification using ethanol crystallization, and the purity is 99.83% by GC detection.

[0111] The obtained liquid crystal compound 8-1 was subjected to mass spectrometry analysis, and the mass spectrum is shown in FIG. Figure 1 , it can be seen that the molecular ion peaks M / Z are 395.3 and 396.2 respectively; the obtained liquid crystal compound 8-1 was subjected to nuclear magnetic hydrogen spectrum analysis, that is, the liquid crystal compound 8-1 was dissolved in DMSO to prepare a sample suitable for NMR analysis, and the measurement was carried out under a 600MHz radio frequency electromagnetic field. The NMR spectrum is shown in Figure 2 ; Mass spectrometry and nuclear magnetic hydrogen spectrum analysis showed that the compound was consistent with the structure and molecular weight of the target liquid crystal compound 8-1.

[0112] Example 4

[0113] (1) Intermediate 6-1 was prepared by the same method as in Example 2;

[0114] (2) Liquid crystal compound 9-1 was prepared using intermediate 6-1. The preparation process is as follows:

[0115]

[0116] To a 500mL four-necked flask, add 27.6g of intermediate 6-1, 24.5g of bromooctane, 150mL of DMF, and 17.9g of potassium carbonate, and heat to 90°C for 12 hours. After the reaction is complete, add 150mL of water + 150mL of toluene and extract the product by liquid separation. After separation, the toluene layer is washed 3 times with 150ml of water. After separation, pass through a silica gel column, and evaporate the toluene to obtain a crude liquid crystal compound 9-1. Use ethanol crystallization and multiple purification to obtain 28.9g of white crystals of liquid crystal compound 8-1, which is detected by GC and has a purity of 99.89%.

[0117] Example 5

[0118] (1) Intermediate 3-1 was prepared by the same method as in Example 1;

[0119] (2) Liquid crystal compound 11-1 was prepared using intermediate 3-1. The preparation process is as follows:

[0120] 1) To a 1L four-necked flask, add 30.9g of intermediate 3-1, 200mL of tetrahydrofuran, and 13g of diisopropylamine. Under nitrogen, cool to -78°C and add 50mL of 2.5mol / L butyllithium dropwise. Incubate for 2 hours after addition. Then, add 15.6g of trimethyl borate dropwise at -78°C and incubate for 2 hours. Then, slowly warm to room temperature and quench the reaction with dilute hydrochloric acid. Add 100mL of toluene, separate the layers, and wash the toluene layer once with 50mL of water to obtain a solution of intermediate 5-1. 2)

[0122]

[0123] To a 1L four-necked flask was added a solution of intermediate 5-1, 20.7g potassium carbonate, 21.2g intermediate 10-1 (commercially available), and 60mL water. After stirring evenly, 0.2g of dichlorodi-tert-butyl-(4-dimethylaminophenyl)phosphine palladium (II) was added under nitrogen protection, and the mixture was stirred and heated under reflux for 5 hours. After the reaction was complete, the liquid was separated at room temperature, and the toluene layer was washed twice with 150mL of water, passed through a silica gel column, and the toluene was evaporated to obtain a yellow crude product of liquid crystal compound 11-1. After repeated crystallization and purification with ethanol, 35.6g of white crystals of liquid crystal compound 11-1 were obtained, which was detected by GC (gas chromatography) to have a purity of 99.92%.

[0124] The obtained liquid crystal compound 11-1 was subjected to mass spectrometry analysis, and the mass spectrum is shown in FIG. Figure 3 , it can be seen that the molecular ion peaks M / Z are 465.5 and 466.5 respectively; the obtained liquid crystal compound 11-1 was subjected to nuclear magnetic hydrogen spectrum analysis, that is, the liquid crystal compound 11-1 was dissolved in DMSO to prepare a sample suitable for NMR analysis, and the measurement was carried out under a 600MHz radio frequency electromagnetic field. The NMR spectrum is shown in Figure 4 ; Mass spectrometry and nuclear magnetic hydrogen spectrum analysis showed that the compound was consistent with the structure and molecular weight of the target liquid crystal compound 11-1.

[0125] Example 6

[0126] (1) Intermediate 3-1 was prepared by the same method as in Example 1;

[0127] (2) Liquid crystal compound 13-1 was prepared using intermediate 3-1. The preparation process is as follows:

[0128] 1) To a 1L four-necked flask, add 30.9g of intermediate 3-1, 200mL of tetrahydrofuran, and 13g of diisopropylamine. Under nitrogen, cool to -78°C and add 50mL of 2.5mol / L butyllithium dropwise. Incubate for 2 hours after addition. Then, add 15.6g of trimethyl borate dropwise at -78°C and incubate for 2 hours. Then, slowly warm to room temperature and quench the reaction with dilute hydrochloric acid. Add 100mL of toluene, separate the layers, and wash the toluene layer once with 50mL of water to obtain a solution of intermediate 5-1. 2)

[0130]

[0131] To a 1L four-necked flask was added a solution of intermediate 5-1, 20.7g potassium carbonate, 24g intermediate 12-1 (commercially available), and 60mL water. After stirring evenly, 0.2g dichlorodi-tert-butyl-(4-dimethylaminophenyl)phosphine palladium (II) was added under nitrogen protection, and the mixture was stirred and heated under reflux for 5 hours. After the reaction was completed, the liquid was separated at room temperature, and the toluene layer was washed twice with 150mL water, passed through a silica gel column, and the toluene was evaporated to obtain a yellow crude product of liquid crystal compound 13-1. After repeated crystallization and purification with ethanol, 38.2g of white crystals of liquid crystal compound 13-1 were obtained, which was detected by GC (gas chromatography) with a purity of 99.91%.

[0132] Example 7

[0133] (1) Intermediate 3-1 was prepared by the same method as in Example 1;

[0134] (2) Liquid crystal compound 15-1 was prepared using intermediate 3-1. The preparation process is as follows:

[0135] 1) To a 1L four-necked flask, add 30.9g of intermediate 3-1, 200mL of tetrahydrofuran, and 13g of diisopropylamine. Under nitrogen, cool to -78°C and add 50mL of 2.5mol / L butyllithium dropwise. Incubate for 2 hours after addition. Then, add 15.6g of trimethyl borate dropwise at -78°C and incubate for 2 hours. Then, slowly warm to room temperature and quench the reaction with dilute hydrochloric acid. Add 100mL of toluene, separate the layers, and wash the toluene layer once with 50mL of water to obtain a solution of intermediate 5-1. 2)

[0137]

[0138] To a 1-liter four-necked flask, a solution of intermediate 5-1 (about 0.1 mol), 20.7 g potassium carbonate, 16.7 g intermediate 14-1 (commercially available), and 60 mL of water were added. After stirring evenly, 0.2 g of dichlorodi-tert-butyl-(4-dimethylaminophenyl)phosphine palladium (II) was added under nitrogen protection, and the mixture was stirred, heated, and refluxed for 5 hours. After the reaction was complete, the liquid was separated at room temperature, and the toluene layer was washed twice with 150 mL of water, passed through a silica gel column, and the toluene was evaporated to obtain a yellow crude product of liquid crystal compound 15-1. After repeated crystallization and purification using toluene, 31.8 g of white crystals of liquid crystal compound 15-1 were obtained, which was detected by GC (gas chromatography) to have a purity of 99.78%.

[0139] The obtained liquid crystal compound 15-1 was subjected to mass spectrometry analysis, and the mass spectrum is shown in FIG. Figure 5 , it can be seen that the molecular ion peaks M / Z are 413.4 and 412.6 respectively; the obtained liquid crystal compound 15-1 was subjected to nuclear magnetic hydrogen spectrum analysis, that is, the liquid crystal compound 15-1 was dissolved in DMSO to prepare a sample suitable for NMR analysis, and the measurement was carried out under a 600MHz radio frequency electromagnetic field. The NMR spectrum is shown in Figure 6 ; Mass spectrometry and nuclear magnetic hydrogen spectrum analysis showed that the compound was consistent with the structure and molecular weight of the target liquid crystal compound 15-1.

[0140] Example 8

[0141] The difference from Example 1 is that propylpyranylbromobenzene (Formula II) is used instead of intermediate 1-1 to prepare intermediate 3-2, and then intermediate 3-2 is used to prepare liquid crystal compound 16-1.

[0142] The reaction example for preparing intermediate 3-2 is as follows:

[0143]

[0144] The structure of the prepared liquid crystal compound 16-1 is as follows:

[0145]

[0146] Example 9

[0147] The difference from Example 2 is that the liquid crystal compound 17-1 is prepared using the intermediate 3-2.

[0148] The structure of the prepared liquid crystal compound 17-1 is as follows:

[0149]

[0150] Example 10

[0151] The difference from Example 5 is that the liquid crystal compound 18-1 is prepared using the intermediate 3-2.

[0152] The structure of the prepared liquid crystal compound 18-1 is as follows:

[0153]

[0154] Example 11

[0155] The difference from Example 7 is that the liquid crystal compound 19-1 is prepared using the intermediate 3-2.

[0156] The structure of the prepared liquid crystal compound 19-1 is as follows:

[0157]

[0158] The following liquid crystal compounds can be prepared by changing the raw materials using the methods of Examples 8-11. The specific preparation process will not be described in detail here:

[0159]

[0160]

[0161] Among them, L 1 It represents a straight-chain alkyl group or alkoxy group having 1 to 8 carbon atoms.

[0162] experiment:

[0163] The liquid crystal compound was introduced into the mother liquor mixed liquid crystal MEST-01 for performance testing.

[0164] The matrix mixed liquid crystal MEST-01 includes 13 monomers, and the details of each monomer and their mass ratios are shown in Table 1.

[0165] Table 1

[0166]

[0167]

[0168] Experimental Example 1

[0169] Without adding any new components to the matrix mixed liquid crystal MEST-01, the negative dielectric anisotropy performance test of MEST-01 was directly performed. The test results are shown in Table 2.

[0170] Experimental Example 2-5

[0171] The liquid crystal compounds prepared in Examples 2-5 were respectively added to the mother mixed liquid crystal MEST-01 and mixed evenly to obtain five liquid crystal compositions containing the newly added components (referred to as Experimental Examples 2-5). These compositions were then tested for negative dielectric anisotropy, as shown in Table 2. The weight proportion of the newly added liquid crystal compound in the liquid crystal compositions of Experimental Examples 2-5 was 10%.

[0172] Experimental Examples 6-9

[0173] Four existing liquid crystal compounds (commercially available) were added to the mother mixed liquid crystal MEST-01 and mixed evenly to obtain four liquid crystal compositions with newly added components (as Experimental Examples 6-9). These compositions were then tested for negative dielectric anisotropy. The four existing liquid crystal compounds added and the test results are shown in Table 2. The weight proportion of the newly added liquid crystal compound (commercially available) in the liquid crystal compositions of Experimental Examples 6-9 was 10%.

[0174] Table 2

[0175]

[0176] As shown in Table 2, the anisotropy performance values ​​(negativity values) of Experimental Examples 2-5 are significantly better than those of Experimental Examples 1 and Experimental Examples 6-9, indicating that the negative values ​​of the liquid crystal compounds prepared by the present invention are significantly better than those of existing side-difluoro liquid crystal compounds. When the liquid crystal compounds are used in VA-type liquid crystal displays, the increase in negative dielectric anisotropy values ​​helps achieve higher contrast and faster response times. Therefore, the liquid crystal compounds provided by the present invention have promising application prospects in VA-type hybrid liquid crystal materials.

[0177] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present invention can make slight changes or modifications to equivalent embodiments using the above-mentioned technical contents without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the solution of the present invention.

Claims

1. A liquid crystal compound, characterized in that The structure of the liquid crystal compound is shown in Formula I: in, R1 is selected from a linear alkyl group with 2 to 5 carbon atoms; R2 is selected from a linear alkyl group or alkoxy group having 1 to 8 carbon atoms, and a substituted aryl group.

2. A liquid crystal compound according to claim 1, characterized in that: R1 is a linear alkyl group having 2 or 3 carbon atoms.

3. A liquid crystal compound according to claim 1, characterized in that: R2 is selected from a linear alkyl group or alkoxy group having 2 to 8 carbon atoms.

4. A liquid crystal compound according to claim 1, characterized in that: The substituents on the aryl group are selected from one or more of F, a linear alkyl group having 1 to 8 carbon atoms, and an alkoxy group.

5. The liquid crystal compound according to claim 1, characterized in that: The aryl group containing a substituent is selected from: Among them, L 1 It is selected from a linear alkyl or alkoxy group having 1 to 8 carbon atoms.

6. The liquid crystal compound according to any one of claims 1 to 5, which is selected from the following formula: in, X1 is selected from a linear alkyl group with 2 or 3 carbon atoms, L 1 It is selected from a linear alkyl or alkoxy group having 1 to 8 carbon atoms.

7. A method for preparing the liquid crystal compound according to any one of claims 1 to 6, comprising the following steps: (1) Substrates A-1 and A-2 undergo a palladium-catalyzed Suzuki coupling reaction to generate intermediate B-1; (2) The aldehyde group of intermediate B-1 is converted into a cyano group through oximation reaction and dehydration reaction to obtain intermediate C-1; (3) After the intermediate C-1 is lithiated, an R2 group is introduced into the terminal of the intermediate C-1 through alkylation and / or etherification and / or aryl substitution reaction to obtain a liquid crystal compound; in, The structural formula of substrate A-1 is The structural formula of substrate A-2 is The structural formula of intermediate B-1 is The structural formula of intermediate C-1 is in, R1 is selected from a linear alkyl group with 2 to 5 carbon atoms; R2 is selected from a linear alkyl group or alkoxy group having 1 to 8 carbon atoms, and a substituted aryl group.

8. The preparation method according to claim 7, characterized in that When R2 is a linear alkyl group having 1 to 8 carbon atoms, step (3) comprises the following operations: The intermediate C-1 is lithiated at -70 to -80°C under the action of butyl lithium, and then coupled with a straight-chain halogenated alkane to obtain a liquid crystal compound.

9. The preparation method according to claim 7, characterized in that When R2 is an alkoxy group having 1 to 8 carbon atoms, step (3) comprises the following operations: a) The intermediate C-1 is lithiated at -70 to -80°C under the action of butyl lithium, and then reacted with borate to obtain the intermediate D-2; b) oxidizing the intermediate D-2 with hydrogen peroxide to obtain the intermediate E-1; c) intermediate E-1 undergoes etherification reaction with a linear bromoalkane in a DMF + potassium carbonate system to obtain a liquid crystal compound; in, The structural formula of intermediate D-2 is The structural formula of intermediate E-1 is 10. The preparation method according to claim 7, characterized in that When R2 is an aryl group containing a substituent, step (3) comprises the following operations: a) The intermediate C-1 is lithiated at -70 to -80°C under the action of butyl lithium, and then reacted with borate to obtain the intermediate D-2; b) intermediate D-2 and intermediate G-1 undergo Suzuki coupling reaction in the presence of palladium catalyst to obtain a liquid crystal compound; in, The structural formula of intermediate D-2 is The intermediate G-1 is a polysubstituted bromoaryl hydrocarbon, and the substituent of the intermediate G-1 is selected from one or more of F, a linear alkyl having 1 to 8 carbon atoms, and an alkoxy group; Preferably, intermediate G-1 is selected from Among them, L 1 It is selected from a linear alkyl or alkoxy group having 1 to 8 carbon atoms.

11. Use of the liquid crystal compound according to any one of claims 1 to 6 in preparing a VA type mixed liquid crystal material.

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