CN102603472B - Lateral-difluoro-containing liquid crystal compounds, and preparation method and application thereof - Google Patents

Abstract

The invention discloses a liquid crystal compound containing lateral difluorine and its preparation method and application. Such compounds are shown in formula I. The liquid crystal compound provided by the invention has correct nuclear magnetic resonance detection, has linear, Z-shaped, banana-shaped and other molecular structures, can be used as liquid crystal display materials and liquid crystal monomers, and has important application value.

Description

Liquid crystal compound containing lateral difluorine and its preparation method and application

technical field

The invention belongs to the technical field of organic synthesis, and relates to liquid crystal compounds containing lateral difluorines and their preparation methods and applications.

Background technique

With the continuous development of liquid crystal display technology, liquid crystal displays have been more and more widely used in people's production and life. Due to people's higher and higher requirements for the quantity and quality of text and image display, the requirements for the physical properties and photoelectric technical performance of the liquid crystal display liquid (mixed liquid crystal) are also higher and higher. Low viscosity, can be used for multi-channel driving, fast response, low driving voltage, high dielectric anisotropy, suitable refractive index anisotropy, good chemical and optical stability and good voltage retention. Liquid crystal is the direction of future development and improvement.

Liquid crystal display uses the dielectric anisotropy and optical anisotropy properties of liquid crystal materials to realize the display function. Both the traditional TN-TFT and IPS modes use liquid crystal materials with positive dielectric anisotropy. In order to meet the requirement of Δε>0, a strong polar group, such as a cyano group, is generally introduced in the long axis direction of the liquid crystal molecule. Fluorine atom, trifluoromethyl group, trifluoromethoxy group, etc.; while the VA-TFT mode requires the liquid crystal material used to have negative dielectric anisotropy, that is, Δε<0, which needs to be in the short axis direction of the molecule, that is, A strong polar group is introduced on the side of the molecule. Although the liquid crystal compound containing the lateral cyano group has a large negative dielectric anisotropy, its resistivity is low, while the liquid crystal compound replaced by the lateral fluorine atom has a high resistivity and a large dielectric anisotropy, which can satisfy VA-TFT mode requirements.

In recent years, fluorine-containing liquid crystal materials have been developed rapidly. Almost all nematic liquid crystal materials are developed with fluorine-containing compounds as the main components, which are used in TN-LCD, STN-LCD, PDLC, It is an indispensable component in LCOS rear projection, especially in TFT-LCD display mode.

Therefore, in order to obtain liquid crystal materials with better performance, it is an inevitable trend in the development of liquid crystals to develop new liquid crystal compounds containing aromatic rings and lateral fluorine. The introduction of fluorine atoms into the liquid crystal molecules can make the liquid crystal have significant advantages such as low viscosity, high charge retention rate, and high stability. Especially when the cyclohexyl group in the molecule is connected with difluorobenzene, the viscosity of this type of liquid crystal molecules is lower, the degree of charge retention is higher, and the performance is superior.

Therefore, the present invention provides liquid crystal compounds containing lateral difluorine to improve the properties of conventional liquid crystal molecules. Two rod-shaped molecules containing side difluorine are connected through carbon chains or carbon chains containing oxygen atoms to transform the molecular shape and form compounds with different shapes such as V shape, U shape, Z shape, banana shape, and linear shape.

Contents of the invention

The object of the present invention is to provide a liquid crystal compound containing lateral difluorine and its preparation method and application.

The liquid crystal compound containing lateral difluorine provided by the present invention has a general structural formula as shown in formula I,

Formula I

In the formula I, R _A is R ¹ -(Z ¹ -A ¹ -Z ² ) _x -; R _B is -(Z ³ -A ² -Z ⁴ ) _y -R ² ;

Wherein, R ¹ and R ² are all selected from hydrogen, fluorine, chlorine, cyano, alkyl with a total of 1-25 carbon atoms, alkoxy with a total of 1-25 carbon atoms, and alkoxy with a total of 2-25 carbon atoms Among straight-chain alkenyl groups, fluorinated alkyl groups with a total of 1-25 carbon atoms, fluorinated alkoxy groups with a total of 1-25 carbon atoms, and fluorinated straight-chain alkenyl groups with a total of 2-25 carbon atoms any of

Z ¹ , Z ² , Z ³ and Z ⁴ are all selected from single bonds, -O-, -OCO-, -COO-, -CO-, -CH ₂ O-, -OCH ₂ -, -CF ₂ O-, -OCF ₂ -, straight-chain alkyl with 1-25 carbon atoms, straight-chain alkenyl with 2-25 carbon atoms, straight-chain alkynyl with 2-25 carbon atoms, fluorinated carbon atoms It is at least one of a straight-chain alkyl group with 1-25 carbon atoms, a fluorinated alkenyl group with a total of 2-25 carbon atoms, and a fluorinated straight-chain alkynyl group with a total carbon number of 1-25;

^{Both A1} and ^A2 are selected from single bond, 1,4-cyclohexyl, 1,4-phenyl, 2,5-pyrimidinyl, 2,5-pyridyl, 2,5-tetrahydro-2H-pyran Base, 1,3-dioxan-2,5-yl, 1,2,4-oxadiazol-3,5-yl, fluorinated 1,4-cyclohexyl, fluorinated 1,4-benzene At least one of a group and a fluorinated pyrancyclodiyl group;

n is an integer of 1-4;

Both x and y are integers from 0 to 3;

When x or y is both 2 or 3, in the structural unit Z ¹ -A ¹ -Z ² , Z ¹ is the same or different, A ¹ is the same or different, and Z ² is the same or different; the structural unit Z ³ -A ² - Among Z ⁴ , Z ³ is the same or different, A ² is the same or different, and Z ⁴ is the same or different.

The above compounds are preferably:

In the formula I, R ¹ and R ² are both selected from any one of hydrogen, fluorine, chlorine, cyano and C ₁ -C ₂₅ alkyl;

Both Z ¹ and Z ² are selected from at least one of -CF ₂ O- and C ₁ -C ₂₅ linear alkyl;

^A is selected from 1,4-cyclohexyl, 1,4-phenyl, 2,5-pyrimidinyl, 2,5-pyridyl, 2,5-tetrahydro-2H-pyranyl, 1,3-di At least one of oxalan-2,5-yl and 1,2,4-oxadiazol-3,5-yl.

The above compound is more preferably: the compound shown in the formula I is the following compound (wherein, the definition of each substituent is the same as above):

The method for the compound in which n is 1 in the preparation formula I provided by the present invention comprises the following steps:

1) Perform lithiation reaction of 4- _RA -1,2-difluorobenzene and n-butyllithium in a solvent, keep the temperature for 1-2 hours after the reaction is completed, then add DMF for substitution reaction, and heat up to room temperature after 1-2 hours After continuing to react for 1-2 hours, 5- _RA -2,3-difluorobenzaldehyde was obtained;

2) After reducing the 5- _RA -2,3-difluorobenzaldehyde obtained in step 1) and sodium borohydride in a solvent, the resulting reduction reaction product is chlorinated with thionyl chloride or reacted with Phosphorus oxybromide is carried out bromination reaction, and reaction is completed to obtain 5- _RA- 2,3-difluorophenyl bromethane or 5- _RA -2,3-difluorophenyl bromethane;

3) Perform lithiation reaction of 4-R _B -1,2-difluorobenzene and n-butyllithium in a solvent, keep the temperature after the reaction and then add the 5-R _A -2,3-difluorophenyl obtained in step 2) Chloromethane or 5- _RA -2,3-difluorophenylbromomethane undergoes a substitution reaction, and after 1-2 hours, the temperature is raised to room temperature and the reaction is continued for 1-2 hours to obtain the compound in which n is 1 in the formula I;

In the above method, in the step 1), the molar ratio of the 4- _RA -1,2-difluorobenzene, n-butyllithium, and DMF is 1:1.2-1.5:1.2-1.5, preferably 1 : 1.2: 1.5; said 4- _RA -1,2-difluorobenzene and n-butyllithium are carried out in the step of lithiation reaction in a solvent, the temperature is -90°C～-80°C, preferably -80°C, and the time is 1-2 hours, preferably 1 hour;

In the step 2), the molar ratio of the 5- _RA -2,3-difluorobenzaldehyde to sodium borohydride is 1:1-3, preferably 1:2; in the reduction reaction step, The temperature is 20-60°C, and the time is 1-2 hours, preferably 1 hour; the molar ratio of the reduction product to the thionyl chloride or phosphorus oxybromide is 1:1-2, preferably 1:1.25 ; In the chlorination reaction or bromination reaction step, the temperature is 25-65°C, preferably 60°C, and the time is 1-5 hours, preferably 3 hours;

In the step 3), the 4-R _B -1,2-difluorobenzene, n-butyllithium, and the 5-R _A -2,3-difluorophenylchloromethane or 5-R obtained in the step 2) The molar ratio of _A -2,3-difluorophenyl bromide is 1:1.2-1.5:1-1.5, preferably 1:1.2:1.2; the 4-R _B -1,2-difluorobenzene and n-butyl In the step of lithium-based lithiation reaction in a solvent, the temperature is -90°C to -80°C, preferably -80°C, and the time is 0.5-2 hours, preferably 1 hour;

In the step 1) to step 3), the solvent is at least one selected from tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran.

The method for preparing the compound in which n is 2 in the formula I provided by the present invention comprises the following steps:

1) Mix 4- _RA -1,2-difluorobenzene and n-butyllithium in a solvent for lithiation reaction. After the reaction, keep the temperature and then add iodine for iodination reaction. After 1-2 hours, heat up to room temperature and continue After reacting for 1-2 hours, 5- _RA -2,3-difluoroiodobenzene was obtained;

2) Under the condition that the pH value in the reaction system is maintained at 8-14 and Pd(PPh ₃ ) ₄ exists as a catalyst, the 5-RA _- 2,3-difluoroiodobenzene obtained in step 1) is mixed with 2-methyl Base 3-butyn-2-ol is mixed and reacted, and the reaction is completed to obtain 4-(2,3-difluoro-5- _RA phenyl)-2-methyl-3-butyn-2-ol;

3) 4-(2,3-difluoro-5- _RA phenyl)-2-methyl-3-butyn-2-ol obtained in step 2) is mixed with a strong base for reaction, and the reaction is completed to obtain 5 -R _A -2,3-difluorophenylacetylene;

4) Perform lithiation reaction of 4- _RB -1,2-difluorobenzene and n-butyllithium in a solvent, keep the temperature for 1-2 hours after the reaction is completed, then add iodine for iodination reaction, and heat up to After continuing to react at room temperature for 1-2 hours, 5- _RB -2,3-difluoroiodobenzene was obtained;

5) Under the condition that the pH value in the reaction system is maintained at 8-14 and Pd(PPh ₃ ) ₄ exists as a catalyst, the 5-RA _- 2,3-difluorophenylacetylene obtained in step 3) is combined with step 4 ) Gained 5- _RB -2,3-difluoroiodobenzene is mixed and reacted, and the reaction is completed to obtain a diphenylacetylene compound;

6) In the presence of a Pd/C catalyst, the diphenylacetylene compound obtained in step 5) is subjected to a hydrogenation reduction reaction with hydrogen to obtain a compound in which n is 2 in the formula I.

In step 1) of the above method, the molar ratio of 4- _RA- 1,2-difluorobenzene, n-butyllithium and iodine is 1:1.2-1.5:1.2-1.5, preferably 1:1.5: 1.5: In the lithiation reaction step of the 4- _RA -1,2-difluorobenzene and n-butyllithium in a solvent, the temperature is -90°C to -80°C, preferably -80°C, and the time is 1-2 hour, preferably 1 hour; the solvent is selected from at least one of tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran;

In the step 2), the molar ratio of 5- _RA- 2,3-difluoroiodobenzene and 2-methyl 3-butyn-2-ol obtained in the step 1) is 1:1-3, Preferably 1:2; the molar dosage of the Pd(PPh ₃ ) ₄ is 0.1-0.5%, preferably 0.5%, of the 5-RA _- 2,3-difluoroiodobenzene obtained in the step 1); the reaction In the step, the temperature is 40-70°C, preferably 60°C, and the time is 1-4 hours, preferably 2 hours;

In the step 3), the strong base is selected from at least one of sodium hydroxide and potassium hydroxide; the step 2) obtained 4-(2,3-difluoro-5- _RA phenyl)- The molar ratio of 2-methyl-3-butyn-2-ol to strong base is 1:1.2-1.5, preferably 1:1.2; in the reaction step, the temperature is 80-110°C, preferably 100°C, and the time For 2-6 hours, preferably 4 hours;

In the step 4), the molar ratio of the 4- _RB -1,2-difluorobenzene, n-butyllithium and iodine is 1:1.2-1.5:1.2-1.5, preferably 1:1.5:1.5 ; In the lithiation reaction step of the 4- _RB -1,2-difluorobenzene and n-butyllithium in a solvent, the temperature is -90°C to -80°C, preferably -80°C, and the time is 1-2 hours , preferably 1 hour; the solvent is selected from at least one of tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran;

In the step 5), the moles of the 5-R _A -2,3-difluorophenylacetylene obtained in the step 3) and the 5-R _B -2,3-difluoroiodobenzene obtained in the step 4) The ratio is 1:1-1.2, preferably 1:1; the molar dosage of Pd(PPh ₃ ) ₄ is 0.1-0.5 of the 5- _RA- 2,3-difluorophenylacetylene obtained in step 3). %, preferably 0.5%; in the reaction step, the temperature is 60-110°C, preferably 85°C, and the time is 2-6 hours, preferably 4 hours;

In the step 6), the amount of the Pd/C catalyst is 1%-5% of the mass amount of the diphenylacetylene compound obtained in the step 5), preferably 2%; in the reaction step, the temperature is 20- 40°C, preferably 30°C, the time is 12-24 hours, preferably 12 hours; the pressure is 0.2-1MPa, preferably 1MPa.

The method for preparing any one of the compounds in which n is 3 in the formula I provided by the present invention comprises the following steps:

1) Mix 4- _RA -1,2-difluorobenzene and n-butyllithium in a solvent for lithiation reaction, keep the temperature after the reaction, then add 1,3-dibromopropane for substitution reaction, 1-2 hours Afterwards, the temperature was raised to room temperature and the reaction was continued for 1-2 hours to obtain 5- _RA- 2,3-difluorophenylbromopropane;

2) Mix 4-R _B -1,2-difluorobenzene and n-butyllithium in a solvent to carry out lithiation reaction, keep the temperature after the reaction and then add the 5-R _A -2,3 obtained in the step 1) -difluorophenylbromopropane for reaction, after 0.5-1 hour, the temperature is raised to room temperature and the reaction is continued for 1-2 hours, and the compound in which n is 3 in the formula I is obtained after the reaction is completed.

In step 1) of the method, the molar ratio of 4- _RA -1,2-difluorobenzene, n-butyllithium and 1,3-dibromopropane is 1:1.2-1.5:1.2- 1.5, preferably 1:1.2:1.2; the 4- _RA -1,2-difluorobenzene and n-butyllithium are carried out in the step of lithiation reaction in a solvent, the temperature is -90°C～-80°C, preferably -80°C ° C, the time is 1-2 hours, preferably 1 hour; the solvent is selected from at least one of tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran;

In the step 2), the feeding of the 4-R _B -1,2-difluorobenzene, n-butyllithium and the 5-R _A -2,3-difluorophenylbromopropane obtained in the step 1) The molar ratio is 1: 1.2-1.5: 1.2-1.5, preferably 1: 1.5: 1.2; the 4- _RB -1,2-difluorobenzene and n-butyllithium are carried out in a solvent in the lithiation reaction step, the temperature is -90°C to -80°C, preferably -80°C, the time is 1-2 hours, preferably 1 hour; the solvent is selected from tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran at least one of;

The method for preparing the compound in which n is 4 in the formula I provided by the present invention comprises the following steps:

1) Mix 4- _RA -1,2-difluorobenzene and n-butyllithium in a solvent for lithiation reaction, keep the temperature after the reaction and then add 1,4-dibromobutane for substitution reaction, 1-2 After one hour, the temperature was raised to room temperature and the reaction was continued for 1-2 hours to obtain 5- _RA -2,3-difluorophenylbromobutane;

2) Mix 4-R _B -1,2-difluorobenzene and n-butyllithium in a solvent to carry out lithiation reaction, keep the temperature after the reaction and then add the 5-R _A -2,3 obtained in the step 1) -Difluorophenylbromobutane is reacted, and after 0.5-1 hour, the temperature is raised to room temperature and the reaction is continued for 1-2 hours. After the reaction is completed, any compound in which n is 4 in the formula I is obtained.

In step 1) of the method, the molar ratio of 4- _RA- 1,2-difluorobenzene, n-butyllithium and 1,4-dibromobutane is 1:1.2-1.5:1.2 -1.5, preferably 1:1.2:1.2; the 4- _RA -1,2-difluorobenzene and n-butyllithium are carried out in a solvent for the lithiation reaction step, the temperature is -90 ° C ~ -80 ° C, preferably - 80°C for 1-2 hours, preferably 1 hour; the solvent is at least one selected from tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran;

In the step 2), the 4-R _B -1,2-difluorobenzene, n-butyllithium and the 5-R _A -2,3-difluorophenylbromobutane obtained in the step 1) The feeding molar ratio is 1: 1.2-1.5: 1.2-1.5, preferably 1: 1.5: 1.2; the 4- _RB -1,2-difluorobenzene and n-butyllithium are carried out in the lithiation reaction step in a solvent, the temperature It is -90°C to -80°C, preferably -80°C, and the time is 1-2 hours, preferably 1 hour; the solvent is selected from tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyl At least one of tetrahydrofuran;

In addition, in the above four preparation methods, in the 4- _RA- 1,2-difluorobenzene and 4- _RB -1,2-difluorobenzene, the _RA and _RB are the same as defined above.

The synthesis route of the liquid crystal compound shown in the general structural formula of formula 1 provided by the present invention is as follows:

Synthetic route 1 (n=1)

Synthetic Route 2 (n=2)

The application of the compound represented by formula I provided by the present invention in the preparation of liquid crystal display materials, organic light-emitting diode materials or semiconductor materials also belongs to the protection scope of the present invention.

The liquid crystal compound provided by the invention has correct nuclear magnetic resonance detection, has linear, Z-shaped, banana-shaped and other molecular structures, can be used as liquid crystal display materials and liquid crystal monomers, and has important application value.

Detailed ways

The present invention will be further described below in conjunction with specific examples, but the present invention is not limited to the following examples. The methods are conventional methods unless otherwise specified. The materials can be obtained from public commercial sources unless otherwise specified.

The liquid crystal compounds shown in formula II prepared in the following examples were all tested for optical anisotropy and dielectric anisotropy and measured for fitting parameters according to the following methods:

The commercial liquid crystal compound No. SLC090105 produced by Shijiazhuang Chengzhi Yonghua Display Material Co., Ltd. (China) was selected as the matrix, and the liquid crystal compound represented by formula II was dissolved in the matrix at a ratio of 5%, and conventional parameters were tested. Its conventional parameters (optical anisotropy Δn (20°C, 589nm), dielectric anisotropy Δε (20°C, 1000Hz)) were linearly fitted according to the proportion added in the matrix.

Example 1 4-(3-(2,3-difluoro-5-(4'-pentylbis(cyclohexyl)-4-yl)benzyl)-4,5-difluorophenyl)-4' - Preparation of ethyl bis(cyclohexane)

Step 1: Preparation of 5-(4'-ethylbis(cyclohexyl)-4-yl)-2,3-difluorobenzaldehyde

In the 250mL reaction flask, drop into 30mmol of 4-(4-(4'-ethylcyclohexyl)cyclohexyl)-1,2-difluorobenzene, then drop into 100mL of THF and 30mL of methyl tert-butyl ether, The temperature of the system was lowered to below -80 °C with a liquid nitrogen/ethanol bath under the protection of _N2 . Add 36 mmol of n-BuLi hexane solution dropwise, and keep the reaction temperature below -80° C. for 1 hour after the drop is completed. Keep the temperature and add 45mmol of DMF dissolved in THF dropwise. After the dropwise addition, keep the temperature and react for 1 hour, then gradually rise to room temperature and react for 2 hours, add 30mL of ethyl acetate and 30mL of saturated saline solution, separate the liquid, and use it for the water phase 30 mL of ethyl acetate was extracted twice, the organic phases were combined, and spin-dried under reduced pressure to obtain a yellow oil, which was separated and purified by a silica gel column to obtain 5-(4'-ethylbis(cyclohexyl)-4-yl)-2, 3-Difluorobenzaldehyde, white solid, GC: 98%, yield: 80%.

Step 2: Preparation of 4-(3-(bromomethyl)-4,5-difluorophenyl)-4'-ethylbis(cyclohexane)

Into a 250mL reaction flask, put 12mmol of 5-(4'-ethylbis(cyclohexyl)-4-yl)-2,3-difluorobenzaldehyde and 100mL of THF, and add 24mmol of hydroboration in batches at room temperature Sodium solid, stirred and reacted for 1 hour after adding, added 20mL saturated saline solution, separated the organic phase, extracted the water phase twice with 30mL ethyl acetate, combined the organic phases, and spin-dried under reduced pressure to obtain (5-(4'-B Bis(cyclohexyl)-4-yl)-2,3-difluorophenyl)methanol, white solid, GC: 98%, yield: 98%

Into the 250mL reaction flask, drop 12mmol of (5-(4'-ethylbis(cyclohexyl)-4-yl)-2,3-difluorophenyl)methanol and 100mL of chloroform, then add 15mmol of tribromo Oxyphosphorus, heated to reflux and stirred for 3 hours, spin-dried under reduced pressure to obtain a yellow oil, decolorized through a silica gel column to obtain 4-(3-(bromomethyl)-4,5-difluorophenyl)-4'-ethane Bis(cyclohexane), colorless oil product, GC: 92%, yield: 80%.

Step 3: 4-(3-(2,3-Difluoro-5-(4'-pentylbis(cyclohexyl)-4-yl)benzyl)-4,5-difluorophenyl)-4' - Preparation of ethyl bis(cyclohexane)

In the 100mL reaction flask, drop into 10mmol of 4-(3,4-difluorophenyl)-4'-pentyl bis(cyclohexane), then drop into 40mL of THF and 10mL of methyl tert-butyl ether, in Under the protection of _N2 , the temperature of the system was lowered to below -80 °C with a liquid nitrogen/ethanol bath. Add 12 mmol of n-BuLi hexane solution dropwise, keep it below -80°C and stir for 1 hour after the drop is complete, then add 12 mmol of 4-(3-(bromomethyl)-4,5-difluorophenyl) dropwise -THF solution of 4'-ethylbis(cyclohexane), keep the temperature for 1 hour after the dropwise addition, and then gradually rise to room temperature for 2 hours. Add 30mL saturated saline solution, separate the organic phase for use, extract the aqueous phase twice with 30mL ethyl acetate, combine the organic phases, and spin dry to obtain a yellow oil, add 40mL of diethyl ether to raise the temperature to boiling, cool to room temperature, and filter to obtain the target Compound, white solid, HPLC: >99%, yield: 50%.

The experimental results are as follows:

(1) ¹ HNMR (δ, CDCl ₃ ): 0.84～1.94(50H, m); 2.43(2H, m); 3.71(2H, m); 6.88～6.95(2H, m); 7.16(1H, m) ; 7.27 (1H, m). It is confirmed _{that the} product obtained through the ^above multi-step reaction _is indeed the compound 4-( ^3- ( _2,3 -Difluoro-5-(4'-pentylbis(cyclohexyl)-4-yl)benzyl)-4,5-difluorophenyl)-4'-ethylbis(cyclohexane).

(2) Compound melting point mp: 108.22°C

(3) Compound clearing point cp: 257.98°C

₍ ⁴ ) Test the synthesized ^liquid crystal monomer _{4- (} 3-( _2,3 -difluoro-5 Optical Anisotropy and Dielectric Properties of -(4'-Pentylbis(cyclohexyl)-4-yl)benzyl)-4,5-difluorophenyl)-4'-ethylbis(cyclohexane) Anisotropy, the obtained fitting parameters are Δn=0.0656, Δε=-0.8.

Example 2 4-(3-(2,3-difluoro-5-(4-pentanecyclohexyl)phenethyl)-4,5-difluorophenyl)-4'-propylbis(cyclohexane ) preparation

Step 1: Preparation of 4-(3,4-difluoro-5-iodophenyl)-4'-propylbis(cyclohexane)

In the 1000mL reaction flask, drop into 0.10mol of 4-(3,4-difluorophenyl)-4'-propylbis(cyclohexane), then drop into 300mL of THF and 100mL of methyl tert-butyl ether, Under the protection of _N2 , use a liquid nitrogen/ethanol bath to lower the system temperature below -80°C, add 0.15 mol of n-BuLi hexane solution dropwise, keep it below -80°C and stir for 1 hour after dropping. 0.15 mol of iodine dissolved in THF was added dropwise while maintaining the temperature. After the dropwise addition was completed, the temperature was maintained for 1 hour, and then gradually raised to room temperature for 2 hours. Then add 100mL saturated aqueous sodium thiosulfate solution, separate the organic phase, wash 3 times with 30mL saturated brine, dry the organic phase with anhydrous sodium sulfate, and spin dry under reduced pressure to obtain a yellow oil, which crystallizes at room temperature to obtain 4- (3,4-difluoro-5-iodophenyl)-4'-propylbis(cyclohexane), GC: 95%, yield: 80%

Step 2: Preparation of 4-(2,3-difluoro-5-(4'-propylbis(cyclohexyl)-4-yl)phenyl)-2-methyl-3-butyn-2-ol

Into a 250mL reaction flask, put 10mmol of 5-(4-(4'-propylcyclohexyl)cyclohexyl)-2,3-difluoroiodobenzene and 0.5mol% of Pd(PPh ₃ ) ₄ into 10mL of Triethylamine made the pH of the reaction system to be 9, and then 20 mL of anhydrous THF was added, and the temperature was raised to 60 ° C under the protection of N ₂ , and 20 mmol of methyl butynol THF solution was added dropwise, and the reaction was stirred for 2 hours, and the reaction was carried out under reduced pressure. Dry to obtain a yellow oil, separate and purify with a silica gel column to obtain the product 4-(2,3-difluoro-5-(4'-propylbis(cyclohexyl)-4-yl)phenyl)-2-methyl -3-butyn-2-ol, yellow solid, yield: 95%

Step 3: Preparation of 4-(3-ethynyl-4,5-difluorophenyl)-4'-propylbis(cyclohexane)

Into a 250mL reaction flask, put 10mmol of 4-(2,3-difluoro-5-(4'-propylbis(cyclohexyl)-4-yl)phenyl)-2-methyl-3-butyne -2-alcohol and 12mmol of potassium hydroxide were put into 40mL of toluene, heated to 100°C, stirred and reacted for 4 hours, cooled to room temperature, spin-dried under reduced pressure, and the residue was separated and purified by silica gel column to obtain 4-(3-acetylene 4,5-difluorophenyl)-4'-propylbis(cyclohexane), yellow solid, yield: 85%

Step 4: Preparation of 1,2-difluoro-3-iodo-5-(4-pentylcyclohexyl)benzene

Into a 1000mL reaction flask, put 0.10mol of 1,2-difluoro-4-(4-pentylcyclohexyl)benzene, then _put in 250mL of THF and 80mL of methyl tert-butyl ether, and use Liquid nitrogen/ethanol bath lowers the system temperature to below -80°C, adds dropwise 0.15 mol of n-BuLi in hexane, and keeps below -80°C to react for 1 hour after dropping. 0.15 mol of iodine dissolved in THF was added dropwise while maintaining the temperature. After the dropwise addition was completed, the temperature was maintained for 1 hour, and then gradually raised to room temperature for 2 hours. Then add 100mL saturated aqueous sodium thiosulfate solution, separate the organic phase, wash 3 times with 30mL saturated brine, dry the organic phase with anhydrous sodium sulfate, and spin dry under reduced pressure to obtain a yellow oil, which crystallizes at room temperature to obtain 1, 2-Difluoro-3-iodo-5-(4-pentylcyclohexyl)benzene, GC: 95%, yield: 82%.

Step 5: 4-(3-((2,3-Difluoro-5-(4-pentylcyclohexyl)phenyl)ethynyl)-4,5-difluorophenyl)-4'-propylbis (Cyclohexane) Preparation

Into a 250mL reaction flask, put 10mmol of 4-(3-ethynyl-4,5-difluorophenyl)-4'-propylbis(cyclohexane) and 10mmol of 1,2-difluoro-3- Iodo-5-(4-pentylcyclohexyl)benzene, put into 0.5mol% Pd(PPh ₃ ) ₄ and 10mL triethylamine to _make the pH value of the reaction system 9, then add 20mL of toluene, protect The temperature was raised to 85° C., stirred for 4 hours, spin-dried under reduced pressure, 30 mL of anhydrous diethyl ether was added to the residue, stirred and dispersed, and filtered to obtain the target compound 4-(3-((2,3-difluoro-5 -(4-pentylcyclohexyl)phenyl)ethynyl)-4,5-difluorophenyl)-4'-propylbis(cyclohexyl), white solid, HPLC: >99%, yield: 40%

Step 6: 4-(3-(2,3-Difluoro-5-(4-pentancyclohexyl)phenethyl)-4,5-difluorophenyl)-4'-propylbis(cyclohexane ) preparation

Into a 500mL autoclave, put 0.01mol of 4-(3-((2,3-difluoro-5-(4-pentylcyclohexyl)phenyl)ethynyl)-4,5-difluorophenyl )-4'-propylbis(cyclohexane) and 250mL of THF and 50mL of methanol, then drop into 0.12g of 10%Pd/C catalyst, seal the reactor, and replace it with hydrogen for three times, finally make the pressure reach 1MPa, room temperature The reaction was stirred for 12 hours, during which hydrogen was added to maintain the pressure in the kettle at about 1 MPa, the reaction solution was removed, filtered, the filtrate was spin-dried under reduced pressure, and the silica gel column was separated and purified to obtain the target product, a white solid product, yield: 95%

The experimental results are as follows:

(1) ¹ HNMR (δ, CDCl ₃ ): 0.84～1.91 (46H, m); 2.38 (2H, m); 2.52 (4H, m); 7.02 (2H, m); 7.12 (2H, m). It is confirmed _that the product obtained through _{the above} multi-step reaction is indeed 4-( ^3- ( _2,3 ^- di Fluoro-5-(4-pentancyclohexyl)phenethyl)-4,5-difluorophenyl)-4'-propylbis(cyclohexane).

_{( 2} ) _Test the synthesized liquid ^crystal monomer 4-(3-( _2,3 - ^difluoro -5 Optical and dielectric anisotropy of -(4-pentancyclohexyl)phenethyl)-4,5-difluorophenyl)-4'-propylbis(cyclohexane), obtained from the fitted The parameters are Δn=0.0856, Δε=0.6.

Example 3 4-(3,4-difluoro-5-(3-(2',4,5,6'-tetrafluoro-4'-(4-propylcyclohexyl)biphenyl-3-yl) Preparation of propyl)phenyl)-4'-ethylbis(cyclohexane)

Step 1: Preparation of 4-(3-(3-bromopropyl)-4,5-difluorophenyl)-4'-ethylbis(cyclohexane)

Into a 100mL reaction flask, put 10mmol of 4-(3,4-difluorophenyl)-4'-ethylbis(cyclohexane), then add 40mL of anhydrous THF and 20mL of methyl tert-butyl ether , under the protection of _N2 , use a liquid nitrogen/ethanol bath to lower the system temperature to below -80°C, add 12 mmol of n-BuLi hexane solution dropwise, keep it below -80°C and stir the reaction for 1 hour after the drop, and add to the reaction 12 mmol of 1,3-dibromopropane was quickly injected into the liquid, and after the dropwise addition, the temperature was maintained for 1 hour, and then gradually raised to room temperature for 2 hours. Then add 30mL saturated saline solution, separate the organic phase, wash 3 times with 30mL saturated brine, and extract the aqueous phase twice with 30mL ethyl acetate, combine the organic phases, dry over anhydrous sodium sulfate, filter, and spin the filtrate under reduced pressure After drying, a yellow oil was obtained, which was purified by a silica gel column to obtain the intermediate 4-(3-(3-bromopropyl)-4,5-difluorophenyl)-4'-ethylbis(cyclohexane), Colorless oil, yield: 80%

Step 2: 4-(3,4-Difluoro-5-(3-(2',4,5,6'-tetrafluoro-4'-(4-propylcyclohexyl)biphenyl-3-yl) Preparation of propyl)phenyl)-4'-ethylbis(cyclohexane)

Into a 100mL reaction bottle, put 6mmol of 2,3',4',6-tetrafluoro-4-(4-propylcyclohexyl)biphenyl, then add 50mL of anhydrous THF and 15mL of methyl tert-butyl Ether, under the protection of _N2 , use a liquid nitrogen/ethanol bath to lower the system temperature below -80 °C, add 7.5 mmol of n-BuLi hexane solution dropwise, keep it below -80 °C and stir for 1 hour after the drop, Slowly add 7.2 mmol of 4-(3-(3-bromopropyl)-4,5-difluorophenyl)-4′-ethylbis(cyclohexane) in anhydrous THF dropwise to the reaction liquid The solution was kept at the temperature for half an hour after the dropwise addition, and then gradually raised to room temperature for 1 hour. Then add 30mL saturated saline solution, separate the organic phase, wash 3 times with 30mL saturated brine, and extract the aqueous phase twice with 30mL ethyl acetate, combine the organic phases, dry over anhydrous sodium sulfate, filter, and spin the filtrate under reduced pressure After drying, a yellow oil was obtained, which was heated to boiling by adding 40 mL of anhydrous ether, cooled to room temperature, and filtered to obtain the target compound as a white solid, yield: 50%

The experimental results are as follows:

(1) ¹ HNMR (δ, CDCl ₃ ): 0.84～1.95 (42H, m); 2.35 (2H, m); 2.66 (4H, m); 6.72～6.85 (4H, m); 7.42～7.46 (2H, m). It is confirmed that the product obtained through the above multi-step reaction is indeed 4-(3,4-difluoro-5-(3-(2',4,5,6'-tetrafluoro-4'-(4 -Propylcyclohexyl)biphenyl-3-yl)propyl)phenyl)-4'-ethylbis(cyclohexane).

(2) Compound melting point mp: 105.76°C

(3) Compound clearing point cp: 131.80°C

(4) 4-(3,4-difluoro-5-(3-(2',4,5,6'-tetrafluoro-4'-(4) shown in the synthetic liquid crystal monomer formula I compound I Optical and dielectric anisotropy of -propylcyclohexyl)biphenyl-3-yl)propyl)phenyl)-4'-ethylbis(cyclohexane), the resulting fitting parameters are Δn =0.0642, Δε=-0.3.

Example 4 4-(3-(4-(5-(4'-butylbis(cyclohexyl)-4-yl)-2,3-difluorophenyl)butyl)-4,5-difluoro Preparation of phenyl)-4'-ethylbis(cyclohexane)

Step 1: Preparation of 4-(3-(4-bromobutyl)-4,5-difluorophenyl)-4'-ethylbis(cyclohexane)

Into a 100mL reaction flask, put 10mmol of 4-(3,4-difluorophenyl)-4'-ethylbis(cyclohexane), then add 40mL of anhydrous THF and 20mL of methyl tert-butyl ether , under the protection of _N2 , use a liquid nitrogen/ethanol bath to lower the system temperature to below -80°C, add 12 mmol of n-BuLi hexane solution dropwise, keep it below -80°C and stir the reaction for 1 hour after the drop, and add to the reaction 12 mmol of 1,4-dibromobutane was quickly injected into the liquid, and after the dropwise addition, the temperature was maintained for 1 hour, and then gradually raised to room temperature for 2 hours. Then add 30mL saturated saline solution, separate the organic phase, wash 3 times with 30mL saturated brine, and extract the aqueous phase twice with 50mL ethyl acetate, combine the organic phases, dry over anhydrous sodium sulfate, filter, and spin the filtrate under reduced pressure After drying, a yellow oil was obtained, which was purified by a silica gel column to obtain the intermediate 4-(3-(4-bromobutyl)-4,5-difluorophenyl)-4'-ethylbis(cyclohexane), White solid, yield: 68%

Step 2: 4-(3-(4-(5-(4'-Butylbis(cyclohexyl)-4-yl)-2,3-difluorophenyl)butyl)-4,5-difluoro Preparation of phenyl)-4'-ethylbis(cyclohexane)

In the 100mL reaction flask, drop into 6mmol of 4-butyl-4'-(3,4-difluorophenyl)bicyclohexane, then add 50mL of anhydrous THF and 15mL of methyl tert-butyl ether, in N ₂ Under protection, use a liquid nitrogen/ethanol bath to lower the temperature of the system below -80°C, add 7.5mmol of n-BuLi hexane solution dropwise, keep it below -80°C and stir for 1 hour after the drop, and pour into the reaction solution Slowly add 7.2 mmol of 4-(3-(4-bromobutyl)-4,5-difluorophenyl)-4'-ethylbis(cyclohexane) dissolved in anhydrous THF solution dropwise After completion, keep the temperature for reaction for half an hour, then gradually rise to room temperature and react for 1 hour. Then add 30mL saturated saline solution, separate the organic phase, wash 3 times with 30mL saturated brine, and extract the aqueous phase twice with 50mL ethyl acetate, combine the organic phases, dry over anhydrous sodium sulfate, filter, and spin the filtrate under reduced pressure After drying, a yellow oil was obtained, which was heated to boiling by adding 50 mL of anhydrous ether, cooled to room temperature, and filtered to obtain the target compound as a white solid, yield: 45%

The experimental results are as follows:

(1) ¹ HNMR (δ, CDCl ₃ ): 0.84～1.88 (56H, m); 2.35 (2H, m); 2.64 (4H, m); 6.70～6.72 (2H, d); 6.77～6.84 (2H, m). It is confirmed that the product obtained through the above multi-step reaction is indeed compound I-1 (n=4, R ¹ =C ₂ H ₅ , R ² =C ₄ H ₉ ) 4-(3-(4-(5-(4'-Butylbis(cyclohexyl)-4-yl)-2,3-difluorophenyl)butyl)-4,5-difluorophenyl)-4'-ethylbis(cyclohexane).

(2) Compound melting point mp: 121.41°C

(3) Compound clearing point cp: 162.41°C

( ₄ ) Test _{the 4-} ( ^3- ( ^4- ( _5- (4 '-Butylbis(cyclohexyl)-4-yl)-2,3-difluorophenyl)butyl)-4,5-difluorophenyl)-4'-ethylbis(cyclohexane) optics Anisotropy and dielectric anisotropy, the obtained fitting parameters are Δn=0.0629, Δε=0.2.

Example 5

Following exactly the same steps as in Example 1, only the reactants were replaced with different substituent groups in the following products to obtain the target products with different structures as shown in the following formula I. NMR structure confirmation data indicated that it was the target product. The properties of optical anisotropy and dielectric anisotropy are not substantially different from those of Example 1, and will not be repeated here.

Example 6

Following exactly the same steps as in Example 2, only the reactants were replaced with different substituent groups in the following products to obtain the target products with different structures as shown in the following formula I. NMR structure confirmation data indicated that it was the target product. The properties of optical anisotropy and dielectric anisotropy are not substantially different from those of Example 2, and will not be repeated here.

Example 7

Following exactly the same steps as in Example 3, only the reactants were replaced with different substituent groups in the following products to obtain the target products with different structures as shown in the following formula I. NMR structure confirmation data indicated that it was the target product. Its optical anisotropy and dielectric anisotropy properties are not substantially different from those of Example 3, and will not be repeated here.

Example 8

Following exactly the same steps as in Example 4, only the reactants were replaced with different substituent groups in the following products to obtain the target products with different structures as shown in the following formula I. NMR structure confirmation data indicated that it was the target product. The properties of optical anisotropy and dielectric anisotropy are not substantially different from those of Example 4, and will not be repeated here.

Claims (5)

1. the compound shown in formula I, Specifically selected from any of the following: Wherein, R ¹ and R ² are selected from any one of C1-C5 alkyl, C1 alkoxy and C2-C3 linear alkenyl; n is an integer of 1-4. 2. A method for preparing the compound of claim 1, which is any one of the following method one to method four, Wherein, said method one is the method for preparing any one of said compounds in which n is 1 described in claim 1, comprising the steps of: 1) Perform lithiation reaction of 4- _RA -1,2-difluorobenzene and n-butyllithium in a solvent, keep the temperature for 1-2 hours after the reaction is completed, then add DMF for substitution reaction, and heat up to room temperature after 1-2 hours After continuing to react for 1-2 hours, 5- _RA -2,3-difluorobenzaldehyde was obtained; 2) After reducing the 5- _RA -2,3-difluorobenzaldehyde obtained in the step 1) with sodium borohydride in a solvent, the resulting reduction reaction product is chlorinated with thionyl chloride or Phosphorus oxybromide is carried out bromination reaction, and the reaction is completed to obtain 5- _RA- 2,3-difluorophenyl bromide or 5- _RA -2,3-difluorophenyl bromide; 3) Perform lithiation reaction of 4-R _B -1,2-difluorobenzene and n-butyllithium in a solvent, keep the temperature after the reaction and then add the obtained 5-R _A -2,3-difluorophenyl in step 2) Chloromethane or 5-R _A -2,3-difluorophenyl bromide undergoes a substitution reaction, and after 1-2 hours, it is warmed up to room temperature and continues to react for 1-2 hours to obtain any of the formulas in which n is 1. compound; The second method is a method for preparing any of the compounds in which n is 2 according to claim 1, comprising the steps of: 1) Mix 4- _RA -1,2-difluorobenzene and n-butyllithium in a solvent for lithiation reaction. After the reaction, keep the temperature and then add iodine for iodination reaction. After 1-2 hours, heat up to room temperature and continue After reacting for 1-2 hours, 5- _RA -2,3-difluoroiodobenzene was obtained; 2) Under the conditions of keeping the pH value in the reaction system at 8-14 and Pd(PPh ₃ ) ₄ as a catalyst, the 5-R _A -2,3-difluoroiodobenzene obtained in step 1) was combined with 2-methyl Base 3-butyn-2-ol is mixed and reacted, and the reaction is completed to obtain 4-(2,3-difluoro-5- _RA phenyl)-2-methyl-3-butyn-2-ol; 3) Mix 4-(2,3-difluoro-5- _RA phenyl)-2-methyl-3-butyn-2-ol obtained in step 2) with a strong base to react, and the reaction is completed to obtain 5 -R _A -2,3-difluorophenylacetylene; 4) Perform lithiation reaction of 4- _RB -1,2-difluorobenzene and n-butyllithium in a solvent, keep the temperature for 1-2 hours after the reaction is completed, then add iodine for iodination reaction, and heat up to After continuing to react at room temperature for 1-2 hours, 5- _RB -2,3-difluoroiodobenzene was obtained; 5) Under the condition that the pH value in the reaction system is kept at 8-14 and Pd(PPh ₃ ) ₄ exists as a catalyst, the 5-RA _- 2,3-difluorophenylacetylene obtained in step 3) is combined with step 4 ) The obtained 5- _RB -2,3-difluoroiodobenzene is mixed and reacted, and the diphenylacetylene compound is obtained after the reaction is completed; 6) In the presence of a Pd/C catalyst, the diphenylacetylene compound obtained in step 5) is subjected to a hydrogenation reduction reaction with hydrogen to obtain any one of the compounds in which n is 2 in the formula I; The third method is a method for preparing any of the compounds in which n is 3 according to claim 1, comprising the steps of: 1) Mix 4-R _A -1,2-difluorobenzene and n-butyllithium in a solvent for lithiation reaction, keep the temperature after the reaction, then add 1,3-dibromopropane for substitution reaction, 1-2 hours Then warm up to room temperature and continue the reaction for 1-2 hours to obtain 5- _RA -2,3-difluorophenylbromopropane; 2) Mix 4-R _B -1,2-difluorobenzene and n-butyllithium in a solvent for lithiation reaction, keep the temperature after the reaction and then add the 5-R _A -2,3 obtained in step 1) -Difluorophenylbromopropane is reacted, and after 0.5-1 hour, the temperature is raised to room temperature and the reaction is continued for 1-2 hours, and the reaction is completed to obtain any compound in which n is 3 in the formula I; The fourth method is a method for preparing any of the compounds in which n is 4 according to claim 1, comprising the steps of: 1) Mix 4-R _A -1,2-difluorobenzene and n-butyllithium in a solvent for lithiation reaction, keep the temperature after the reaction and then add 1,3-dibromobutane for substitution reaction, 1-2 After one hour, the temperature was raised to room temperature and the reaction was continued for 1-2 hours to obtain 5- _RA -2,3-difluorophenylbromobutane; 2) Mix 4-R _B -1,2-difluorobenzene and n-butyllithium in a solvent for lithiation reaction, keep the temperature after the reaction and then add the 5-R _A -2,3 obtained in step 1) -Difluorophenylbromobutane is reacted, and after 0.5-1 hour, the temperature is raised to room temperature and the reaction is continued for 1-2 hours, and the reaction is completed to obtain any compound in which n is 4 in the formula I; In the 4- _RA -1,2-difluorobenzene and 4- _RB -1,2-difluorobenzene, the _RA and _RB are the same as defined in claim 1. 3. The method according to claim 2, characterized in that: in the method one, in the step 1), the 4-RA _- 1,2-difluorobenzene, n-butyllithium, DMF The molar ratio of feeding is 1:1.2-1.5:1.2-1.5; the 4-RA _- 1,2-difluorobenzene and n-butyllithium are carried out in the solvent for lithiation reaction step, the temperature is -90°C～- 80℃, the time is 1-2 hours; In the step 2), the molar ratio of 5- _RA- 2,3-difluorobenzaldehyde to sodium borohydride is 1:1-3; in the reduction reaction step, the temperature is 20-60 °C, the time is 1-2 hours; the molar ratio of the reduction product to the thionyl chloride or phosphorus oxybromide is 1:1-2; in the chlorination reaction or bromination reaction step, the temperature 25-65°C, the time is 1-5 hours; In the step 3), the 4-R _B -1,2-difluorobenzene, n-butyllithium, and the 5-R _A -2,3-difluorophenylchloromethane or 5-R obtained in the step 2) The molar ratio of _A -2,3-difluorophenyl bromide is 1:1.2-1.5:1-1.5; the 4-R _B -1,2-difluorobenzene and n-butyllithium are carried out in a solvent for lithium In the chemical reaction step, the temperature is -90°C to -80°C, and the time is 0.5-2 hours; In the step 1) to step 3), the solvent is selected from at least one of tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran; In the method two, in step 1), the molar ratio of 4- _RA- 1,2-difluorobenzene, n-butyl lithium and iodine is 1:1.2-1.5:1.2-1.5; 4-R _A -1,2-difluorobenzene and n-butyl lithium are carried out in the step of lithiation reaction in a solvent, the temperature is -90°C to -80°C, and the time is 1-2 hours; the solvent is selected from tetrahydrofuran, At least one of hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran; In the step 2), the molar ratio of 5- _RA- 2,3-difluoroiodobenzene and 2-methyl 3-butyn-2-ol obtained in the step 1) is 1:1-3; The molar dosage of Pd(PPh ₃ ) ₄ is 0.1-0.5% of the 5- _RA- 2,3-difluoroiodobenzene obtained in the step 1); in the reaction step, the temperature is 40-70°C , the time is 1-4 hours; In the step 3), the strong base is selected from at least one of sodium hydroxide and potassium hydroxide; the obtained 4-(2,3-difluoro-5- _RA phenyl)- The molar ratio of 2-methyl-3-butyn-2-ol to strong base is 1:1.2-1.5; in the reaction step, the temperature is 80-110°C and the time is 2-6 hours; In the step 4), the molar ratio of the 4- _RB -1,2-difluorobenzene, n-butyllithium and iodine is 1:1.2-1.5:1.2-1.5; the 4- _RB -1,2-Difluorobenzene and n-butyllithium are carried out in the step of lithiation reaction in a solvent, the temperature is -90°C to -80°C, and the time is 1-2 hours; the solvent is selected from tetrahydrofuran, hexane, methane At least one of tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran; In the step 5), the moles of the 5-R _A -2,3-difluorophenylacetylene obtained in the step 3) and the 5-R _B -2,3-difluoroiodobenzene obtained in the step 4) The ratio is 1:1-1.2; the molar dosage of the Pd(PPh ₃ ) ₄ is 0.1-0.5% of the 5- _RA- 2,3-difluorophenylacetylene obtained in the step 3); the reaction In the step, the temperature is 60-110°C, and the time is 2-6 hours; In the step 6), the dosage of the Pd/C catalyst is 1%-5% of the mass dosage of the diphenylacetylene compound obtained in the step 5); in the reaction step, the temperature is 20-40°C, and the time 12-24 hours; pressure 0.2-1MPa; In the method three, in the step 1), the molar ratio of the 4-RA _- 1,2-difluorobenzene, n-butyllithium and 1,3-dibromopropane is 1:1.2- 1.5: 1.2-1.5; the 4- _RA -1,2-difluorobenzene and n-butyllithium are lithiated in a solvent, the temperature is -90°C ~ -80°C, and the time is 1-2 hours ; The solvent is selected from at least one of tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran; In the step 2), the feeding of the 4-R _B -1,2-difluorobenzene, n-butyllithium and the 5-R _A -2,3-difluorophenylbromopropane obtained in the step 1) The molar ratio is 1:1.2-1.5:1.2-1.5; the 4-R _B -1,2-difluorobenzene and n-butyllithium are carried out in a solvent in the lithiation reaction step, and the temperature is -90 ° C ~ -80 ° C , the time is 1-2 hours; the solvent is selected from at least one of tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran; In the method four, in the step 1), in the step 1) of the method, the 4- _RA- 1,2-difluorobenzene, n-butyllithium and 1,3-dibromobutane The molar ratio of the molar feed is 1:1.2-1.5:1.2-1.5; the 4- _RA -1,2-difluorobenzene and n-butyllithium are carried out in the step of lithiation reaction in a solvent, and the temperature is -90°C～ -80°C, the time is 1-2 hours; the solvent is at least one selected from tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran; In the step 2), the 4-R _B -1,2-difluorobenzene, n-butyllithium and the 5-R _A -2,3-difluorophenylbromobutane obtained in the step 1) The feeding molar ratio is 1:1.2-1.5:1.2-1.5; the 4-R _B -1,2-difluorobenzene and n-butyllithium are carried out in the solvent for the lithiation reaction step, and the temperature is -90°C～-80°C °C for 1-2 hours; the solvent is at least one selected from tetrahydrofuran, hexane, methyl tert-butyl ether, anhydrous ether and 2-methyltetrahydrofuran. 4. The method according to claim 3, characterized in that: in the method one, in the step 1), the 4-RA _- 1,2-difluorobenzene, n-butyllithium, DMF The molar ratio of feeding is 1:1.2:1.5; in the lithiation reaction step of the 4-RA _- 1,2-difluorobenzene and n-butyllithium in a solvent, the temperature is -80°C and the time is 1 hour; In the step 2), the molar ratio of 5- _RA- 2,3-difluorobenzaldehyde to sodium borohydride is 1:2; in the reduction reaction step, the time is 1 hour; the The molar ratio of the reduction product to the thionyl chloride or phosphorus oxybromide is 1:1.25; in the chlorination or bromination step, the temperature is 60°C and the time is 3 hours; In the step 3), the 4-R _B -1,2-difluorobenzene, n-butyllithium, and the 5-R _A -2,3-difluorophenylchloromethane or 5-R obtained in the step 2) The molar ratio of _A -2,3-difluorophenyl bromide is 1:1.2:1.2; the 4-R _B -1,2-difluorobenzene and n-butyllithium are carried out in the step of lithiation reaction in a solvent , the temperature is -80°C, and the time is 1 hour; In the method two, in step 1), the molar ratio of the 4-RA _- 1,2-difluorobenzene, n-butyllithium and iodine is 1:1.5:1.5; the 4- _RA -1,2-difluorobenzene and n-butyllithium are carried out in the step of lithiation reaction in a solvent, the temperature is -80 ° C, and the time is 1 hour; In the step 2), the molar ratio of 5- _RA- 2,3-difluoroiodobenzene and 2-methyl 3-butyn-2-ol obtained in the step 1) is 1:2; The molar dosage of Pd(PPh ₃ ) ₄ is 0.5% of the 5- _RA -2,3-difluoroiodobenzene obtained in the step 1); in the reaction step, the temperature is 60°C and the time is 2 hours; In the step 3), the strong base is selected from at least one of sodium hydroxide and potassium hydroxide; the obtained 4-(2,3-difluoro-5- _RA phenyl)- The molar ratio of 2-methyl-3-butyn-2-ol to strong base is 1:1.2; in the reaction step, the temperature is 100°C and the time is 4 hours; In the step 4), the molar ratio of the 4- _RB -1,2-difluorobenzene, n-butyllithium and iodine is 1:1.5:1.5; the 4- _RB -1,2 - In the lithiation reaction step of difluorobenzene and n-butyllithium in a solvent, the temperature is -80°C and the time is 1 hour; In the step 5), the moles of the 5-R _A -2,3-difluorophenylacetylene obtained in the step 3) and the 5-R _B -2,3-difluoroiodobenzene obtained in the step 4) The ratio is 1:1; the molar dosage of the Pd(PPh ₃ ) ₄ is 0.5% of the 5- _RA- 2,3-difluorophenylacetylene obtained in the step 3); in the reaction step, the temperature at 85°C for 4 hours; In the step 6), the amount of the Pd/C catalyst is 2% of the mass of the diphenylacetylene compound obtained in the step 5); in the reaction step, the temperature is 30°C and the time is 12 hours; the pressure is _1MPa ; In the third method, in the step 1), the molar ratio of the 4- _RA- 1,2-difluorobenzene, n-butyllithium and 1,3-dibromopropane is 1:1.2: 1.2: In the lithiation reaction step of the 4- _RA- 1,2-difluorobenzene and n-butyllithium in a solvent, the temperature is -80°C and the time is 1 hour; In the step 2), the feeding of the 4-R _B -1,2-difluorobenzene, n-butyllithium and the 5-R _A -2,3-difluorophenylbromopropane obtained in the step 1) The molar ratio is 1:1.5:1.2; the lithiation reaction step of the 4- _RB -1,2-difluorobenzene and n-butyllithium in a solvent is carried out at a temperature of -80°C for 1 hour; In the method four, in the step 1), in the step 1) of the method, the 4- _RA- 1,2-difluorobenzene, n-butyllithium and 1,3-dibromobutane The molar molar ratio of the feed is 1:1.2:1.2; the 4- _RA -1,2-difluorobenzene and n-butyllithium are carried out in a solvent for the lithiation reaction step, the temperature is -80°C, and the time is 1 hour ; In the step 2), the 4-R _B -1,2-difluorobenzene, n-butyllithium and the 5-R _A -2,3-difluorophenylbromobutane obtained in the step 1) The feeding molar ratio is 1:1.5:1.2; the lithiation reaction step of the 4- _RB -1,2-difluorobenzene and n-butyllithium in a solvent is performed at a temperature of -80° C. for 1 hour. 5. The application of the compound described in claim 1 in the preparation of liquid crystal display materials, organic light emitting diode materials or semiconductor materials.