CN114031598B

CN114031598B - Preparation method of polysubstituted dibenzochromene compound

Info

Publication number: CN114031598B
Application number: CN202111067137.5A
Authority: CN
Inventors: 范为正; 王明华; 张鹤军; 宋化灿; 朱国勋; 宋森川; 司云凤; 刘洋
Original assignee: Jiangsu Shike New Material Co ltd
Current assignee: Jiangsu Shike New Material Co ltd
Priority date: 2021-09-10
Filing date: 2021-09-10
Publication date: 2023-07-28
Anticipated expiration: 2041-09-10
Also published as: CN114031598A

Abstract

A preparation method of polysubstituted dibenzochromene compounds is shown in reaction formula 1The method comprises the following steps: (1) Reacting the compound I-1 with a lithium ethyne ethylenediamine complex to obtain a compound I-2; (2) Cyclizing the compound I-2 and the compound I-3 in the presence of camphorsulfonic acid to obtain a compound I-4; (3) Reacting the compound I-5 with a lithium ethyne ethylenediamine complex to obtain a compound I-6; (4) Cyclizing the compound I-6 and the compound I-7 in the presence of camphorsulfonic acid to obtain a compound I-8; (5) Compounds I-4 and I-8 were reacted at room temperature by DEAD and triphenylphosphine to give compound I-9. The preparation method is simple and has high yield. The prepared compound of the general formula (I-9) has high color development sensitivity, excellent durability and extremely short fading half-life.

Description

Preparation method of polysubstituted dibenzochromene compound

Technical Field

The invention relates to the field of photochromic materials, in particular to a preparation method of a polysubstituted dibenzochromene compound.

Background

Photochromic is a phenomenon in which when light including ultraviolet rays is irradiated to some compounds, the color changes rapidly, and when the light is stopped from being irradiated and placed in a dark place, the original color is restored. The compound with the property is called a photochromic compound, and the photochromic material has wide application prospect in the fields of photochromic glasses, optical information storage, molecular switches, defending and identifying technologies and the like, and is one of research hot spots in the fields of chemistry and material science.

Naphthopyrans are known to be photochromic compounds that are capable of changing color under the influence of polychromatic or monochromatic light, such as UV light. When the irradiation is stopped, or under the influence of temperature and/or polychromatic or monochromatic light different from the initial light, the compound returns to its initial color. Naphthopyrans find application in various fields, for example in the manufacture of ophthalmic lenses, contact lenses, sunglasses, filters, optical cameras or other optical devices, as well as viewing devices, glazing and decorative objects. The 2H-chromene has in some cases a neutral gray or brown colour after UV irradiation, which is of particular interest when used in a dichroic mirror, since it does not require the use of dye mixtures of different colours to obtain the desired hue. In fact, dyes of different colors may have different UV aging resistance characteristics, different fade kinetics or different thermal dependencies, resulting in a change in the hue of the lens during use. For example, for ophthalmic lenses, for visual comfort and safety reasons (e.g., when driving), it is highly desirable that photochromic articles decolorize rapidly in the absence of UV light.

Disclosure of Invention

In studying naphthopyrans, the present inventors have found that compounds have a short discoloration half-life when an electron-withdrawing group is introduced on the benzene ring of 2H naphtho [1,2-b ] pyran (benzochromene). And when two benzo chromene compounds are connected through an electron donating group O, the fading half-life period can be obviously shortened, and the ageing resistance can be improved. Thus, various polysubstituted dibenzochromene compounds are synthesized, and a preparation method thereof is provided.

The technical scheme of the invention is as follows:

a preparation method of a polysubstituted dibenzochromene compound has a structure shown in the following formula:

wherein:

r1, R2, R5, R6 are each selected from hydrogen, methyl, methoxy, methylthio, aryl, halogen, CN, NO ₂ 、CF ₃ Or CF (CF) ₂ H；

R3, R4, R7, R8 are each selected from hydrogen, methyl, methoxy, methylthio, halogen, CN, NO ₂ 、CF ₃ Or CF (CF) ₂ H, and at least one of R3, R4, R7 and R8 is an electron withdrawing group;

the reaction formula of the preparation method is as follows:

the preparation method comprises the following steps:

(1) Reacting the compound I-1 with lithium ethynyl to obtain a compound I-2;

(2) Cyclizing the compound I-2 and the compound I-3 in the presence of camphorsulfonic acid to obtain a compound I-4;

(3) Reacting the compound I-5 with a lithium ethyne ethylenediamine complex to obtain a compound I-6;

(4) Cyclizing the compound I-6 and the compound I-7 in the presence of camphorsulfonic acid to obtain a compound I-8;

(5) Compounds I-4 and I-8 were reacted at room temperature by DEAD and triphenylphosphine to give compound I-9.

The preparation method is preferably that R3 and R7 are each H, and R4 and R8 are each F.

The preparation method is preferably that R3 and R7 are each H, R4 and R8 are each CF ₃ 。

The preparation method is preferably that R3, R7, R4 and R8 in the compound are each F.

The preparation method as described above, preferably, the specific operation of the step (1) is as follows: dissolving a compound I-1 in ethylenediamine, and adding a lithium ethyne ethylenediamine complex, wherein the molar ratio of the compound I-1 to the lithium ethyne ethylenediamine complex is 1: (2-4); stirring for 2-4 hours at room temperature under nitrogen atmosphere; the reaction solution was extracted with ethyl acetate, and the organic layer was washed with water, saturated sodium chloride, dried, concentrated, and the crude product was purified by silica gel column chromatography to give compound I-2.

The preparation method as described above, preferably, the specific operation of the step (2) is as follows: dissolving a compound I-2 in toluene, and adding a compound I-3 and camphorsulfonic acid, wherein the molar ratio of the compound I-2 to the compound I-3 to the camphorsulfonic acid is 1: (1-1.5): (0.2 to 0.4); then stirring for 2-4 hours at 50-80 ℃, concentrating after the reaction is finished, and purifying the crude product by silica gel column chromatography to obtain the compound I-4.

The preparation method as described above, preferably, the specific operation of the step (3) is as follows: dissolving a compound I-5 in ethylenediamine, and adding a lithium ethyne ethylenediamine complex, wherein the molar ratio of the compound I-5 to the lithium ethyne ethylenediamine complex is 1: (2-4); stirring for 2-4 hours at room temperature under nitrogen atmosphere; the reaction solution was extracted with ethyl acetate, and the organic layer was washed with water, saturated sodium chloride, dried, concentrated, and the crude product was purified by silica gel column chromatography to give compound I-6.

The preparation method as described above, preferably, the specific operation of the step (4) is as follows: dissolving a compound I-6 in toluene, and adding a compound I-7 and camphorsulfonic acid, wherein the molar ratio of the compound I-6 to the compound I-7 to the camphorsulfonic acid is 1: (1-1.5): (0.2 to 0.4); then stirring for 2-4 hours at 50-80 ℃, concentrating after the reaction is finished, and purifying the crude product by silica gel column chromatography to obtain the compound I-8.

The preparation method as described above, preferably, the specific operation of the step (5) is as follows: dissolving a compound I-4 and a compound I-8 in tetrahydrofuran, and adding diethyl azodicarboxylate and triphenylphosphine, wherein the molar ratio of the compound I-4 to the compound I-8 to the diethyl azodicarboxylate to the triphenylphosphine is 1:1:0.6-1.2:0.6-1.2; after the reaction is completed for 12 to 24 hours, the mixture is concentrated and separated by a silica gel preparation plate to obtain the compound I-9.

The compound I-4 and the compound I-8 in the reaction formula 1 of the invention can be the same compound, and the preparation reaction is shown in the reaction formula 2, and the preparation method comprises the following steps:

(1) Reacting the compound I-1 with a lithium ethyne ethylenediamine complex to obtain a compound I-2;

(2) Cyclizing the compound I-2 with the compound I-3 in the presence of camphorsulfonic acid to obtain a compound I-4;

(3) Dissolving the compound I-4 in a polar solvent, adding DEAD and triphenylphosphine, and reacting for 10-14 hours to obtain the compound I-10.

The term "alkyl" as used herein refers to a straight or branched chain monovalent saturated hydrocarbon group having 1 to 8 carbon atoms, examples of which include, but are not limited to, methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-methyl-1-propyl, 2-butyl, 2-methyl-2-propyl, t-butyl, 1-hexyl, 2-ethylbutyl, and the like.

The term "cyclic alkyl" as used herein refers to cycloalkyl groups of 3 to 8 carbon atoms, but is not limited to cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, alkyl substituted cycloalkyl.

The term "aryl" as used herein by itself or as part of another substituent refers to a monovalent aromatic hydrocarbon radical derived from the removal of one hydrogen atom from a single carbon atom of the parent aromatic ring system. Aryl encompasses 5-and 6-membered carbocyclic aromatic rings, for example, benzene; bicyclic ring systems wherein at least one ring is carbocyclic and aromatic, e.g., naphthalene, indane, and tetrahydronaphthalene; and tricyclic ring systems, wherein at least one ring is carbocyclic and aromatic, e.g., fluorene. Aryl encompasses polycyclic ring systems having at least one carbocyclic aromatic ring fused to at least one carbocyclic aromatic ring, cycloalkyl ring, or heterocycloalkyl ring.

The term "halogen" as used in the present invention refers to fluorine, chlorine or bromine.

Indicating the attachment of substituents therefrom.

The invention has the beneficial effects that: the preparation method is simple and has high yield. The prepared compound of the general formula (I-9) has high color development sensitivity, excellent durability and extremely short fading half-life. There are various uses of color-changing materials, for example, a memory material, a dimming material, a photochromic lens material, an optical filter material, a display material, an optical information device, an optical switching element, a photoresist material, a light meter, a decorative material, or the like.

Detailed Description

The following examples illustrate, but do not limit, the synthesis of compounds of the general formula (I-9). The temperatures are in degrees celsius. All the evaporation was carried out under reduced pressure, if not otherwise stated. Reagents were purchased from commercial suppliers and used without further purification, if not otherwise indicated. The structure of the end products, intermediates and starting materials is confirmed by standard analytical methods, such as elemental analysis, spectroscopic characterization, such as MS, NMR. Abbreviations used are conventional in the art.

Preparation of the intermediate:

1. preparation of intermediate A-5: 10-fluoro-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ] chromen-5-ol

(1) A-3: preparation of 1, 1-bis (4-methoxyphenyl) prop-2-yn-1-ol

4,4' -Dimethoxybenzophenone A-1 (500 mg,2.06 mmol) was dissolved in 10mL ethylenediamine, and lithium ethyne ethylenediamine complex A-2 (578 mg,6.20 mmol) was added. Stirring was carried out at room temperature for 2 hours under nitrogen atmosphere. After the completion of the reaction, the reaction mixture was quenched with ice water, and the reaction mixture was extracted with ethyl acetate. The organic layer was washed with water, saturated sodium chloride and dried over anhydrous sodium sulfate. Concentration and purification of the crude product by silica gel column chromatography gave 1, 1-bis (4-methoxyphenyl) prop-2-yn-1-ol a-3 (450 mg, white solid), yield: 81%. ESI-MS m/z:269[ M+H ]] ⁺ 。

(2) A-5: preparation of 10-fluoro-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ] chromen-5-ol

1, 1-bis (4-methoxyphenyl) prop-2-yn-1-ol A-3 (450 mg,1.68mmo 1) was dissolved in toluene (10 mL), 8-fluoronaphthalene-1, 3-diol A-4 (356 mg,2.01 mmol) and camphorsulfonic acid (89 mg,0.5 mmol) were added, followed by stirring at 60℃for 2 hours, after completion of the reaction, concentration and purification of the crude product by silica gel column chromatography to give 10-fluoro-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ]]Chromen-5-ol A-5 (200 mg, white solid), yield：28％。ESI-MS m/z：429[M+H] ⁺ 。

2. Preparation of intermediate A-7: 10-trifluoromethyl-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ] chromen-5-ol

1, 1-bis (4-methoxyphenyl) prop-2-yn-1-ol A-3 (450 mg,1.68 mmol) was dissolved in toluene (10 mL), 8-trifluoromethylnaphthalene-1, 3-diol A-6 (458 mg,2.01 mmol) and camphorsulfonic acid (89 mg,0.5 mmol) were added, followed by stirring at 60℃for 2 hours, after completion of the reaction, concentration and purification of the crude product by silica gel column chromatography to give 10-trifluoromethyl-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ]]Chromen-5-ol a-7 (180 mg, white solid), yield: 22%. ESI-MS m/z:479[ M+H ]] ⁺ 。

3. Preparation of intermediate A-9:8, 10-difluoro-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ] chromen-5-ol

1, 1-bis (4-methoxyphenyl) prop-2-yn-1-ol A-3 (450 mg,1.68 mmol) was dissolved in toluene (10 mL), 8, 10-difluoronaphthalene-1, 3-diol A-8 (349 mg,2.01 mmol) and camphorsulfonic acid (89 mg,0.5 mmol) were added, then stirred at 60℃for 2 hours, after the reaction was completed, concentrated, and the crude product was purified by silica gel column chromatography to give 8, 10-difluoro-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ]]Chromen-5-ol a-9 (220 mg, white solid), yield: 29%. ESI-MS m/z:447[ M+H ]] ⁺ 。

4. Preparation of intermediate A-12: 10-fluoro-2, 2-bis (4-thiomethylphenyl) -2H-benzo [ H ] chromen-5-ol

4,4' -Dimethylthiobenzophenone A-10 (500 mg,1.82 mmol) was dissolved in 10mL of ethylenediamine, and acetylene was addedLithium ethylenediamine complex A-2 (491 mg,5.46 mmol). Stirring was carried out at room temperature for 2 hours under nitrogen atmosphere. After the completion of the reaction, the reaction mixture was quenched with ice water, and the reaction mixture was extracted with ethyl acetate. The organic layer was washed with water, saturated sodium chloride and dried over anhydrous sodium sulfate. Concentration and purification of the crude product by silica gel column chromatography gave 1, 1-bis (4-methylthiophenyl) prop-2-yn-1-ol a-11 (400 mg, white solid), yield: 73%. ESI-MS m/z:301[ M+H ]] ⁺ 。

1, 1-bis (4-methylthiophenyl) prop-2-yn-1-ol A-11 (400 mg,1.33mmo 1) was dissolved in toluene (10 mL), 8-fluoronaphthalene-1, 3-diol A-4 (284 mg,1.6 mmol) and camphorsulfonic acid (92 mg,0.4 mmol) were added, followed by stirring at 60℃for 2 hours, after the completion of the reaction, the crude product was concentrated and purified by silica gel column chromatography to give 10-fluoro-2, 2-bis (4-methylthiophenyl) -2H-benzo [ H ]]Chromen-5-ol a-12 (174 mg, white solid), yield: 28%. ESI-MS m/z:461[ M+H ]] ⁺ 。

Example 1: preparation of 5,5' -oxybis (10-fluoro-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ] chromene)

10-fluoro-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ]]Chromene-5-ol A-5 (200 mg,0.47 mmol) was dissolved in tetrahydrofuran (5 mL), diethyl azodicarboxylate (DEAD, 35mg,0.2 mmol) and triphenylphosphine (52 mg,0.2 mmol) were added, reacted for 16 hours, after the reaction was completed, concentrated, and isolated by silica gel preparation plate to give 5,5' -oxybis (10-fluoro-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ]]Chromene) (75 mg, white solid), yield: 38%. ESI-MS m/z:839[ M+H ]] ⁺ 。

¹ H-NMR(400MHz，DMSO-d ₆ )：δ7.83-7.62(m，2H)，7.47-7.32(m，10H)，7.30-7.15(m，2H)，6.88-6.70(m，10H)，6.58(d，.J＝7.2Hz，2H)，6.39(d，.J＝7.2Hz，2H)，3.52(s，12H)。

Example 2: preparation of 5,5' -oxybis (10-trifluoromethyl-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ] chromene)

10-trifluoromethyl-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ]]Chromen-5-ol A-7 (200 mg,0.42 mmol) was dissolved in tetrahydrofuran (5 mL), diethyl azodicarboxylate (DEAD, 31mg,0.18 mmol) and triphenylphosphine (47 mg,0.18 mmol) were added, reacted for 16 hours, after the reaction was completed, concentrated, and isolated by silica gel preparation plate to give 5,5' -oxybis (10-trifluoromethyl-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ]]Chromene) (50 mg, white solid), yield: 23%. ESI-MS m/z:939[ M+H ]] ⁺ 。

¹ H-NMR(400MHz，DMSO-d ₆ )：δ8.12-7.65(m，2H)，7.55-7.37(m，10H)，7.32-7.12(m，2H)，6.89-6.72(m，10H)，6.57(d，J＝7.2Hz，2H)，6.41(d，J＝7.2Hz，2H)，3.55(s，12H)。

Example 3: preparation of 5,5' -oxybis (8, 10-difluoro-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ] chromene)

8, 10-difluoro-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ]]Chromen-5-ol A-9 (200 mg,0.45 mmol) was dissolved in tetrahydrofuran (5 mL), diethyl azodicarboxylate (DEAD, 39mg,0.22 mmol) and triphenylphosphine (58 mg,0.22 mmol) were added, the reaction mixture was allowed to stand at room temperature for 16 hours, after the completion of the reaction, concentrated, and isolated as 5,5' -oxybis (8, 10-difluoro-2, 2-bis (4-methoxyphenyl) -2H-benzo [ H ] by a silica gel preparation plate]Chromene) (42 mg, white solid), yield: 21%. ESI-MS m/z:875[ M+H ]] ⁺ 。

¹ H-NMR(400MHz，DMSO-d ₆ )：δ7.92-7.72(m，2H)，7.45-7.31(m，8H)，7.33-7.12(m，2H)，6.91-6.73(m，10H)，6.57(d，J＝7.2Hz，2H)，6.38(d，J＝7.2Hz，2H)，3.52(s，12H)。

Example 4: preparation of 5,5' -oxybis (10-fluoro-2, 2-bis (4-thiomethylphenyl) -2H-benzo [ H ] chromene)

10-fluoro-2, 2-bis (4-methylthiophenyl) -2H-benzo [ H ]]Chromen-5-ol A-12 (200 mg,0.43 mmol) was dissolved in tetrahydrofuran (5 mL), diethyl azodicarboxylate (DEAD, 38mg,0.22 mmol) and triphenylphosphine (57 mg,0.22 mmol) were added, the reaction mixture was allowed to stand at room temperature for 16 hours, after the completion of the reaction, concentrated, and separated by a silica gel preparation plate to give 5,5' -oxybis (10-fluoro-2, 2-bis (4-methylthiophenyl) -2H-benzo [ H ]]Chromene) (35 mg, white solid), yield: 18%. ESI-MS m/z:903[ M+H ]] ⁺ 。

¹ H-NMR(400MHz，DMSO-d ₆ )：67.82-7.62(m，2H)，7.47-7.32(m，10H)，7.30-7.15(m，2H)，6.88-6.70(m，10H)，6.58(d，J＝7.2Hz，2H)，6.38(d，J＝7.2Hz，2H)，2.42(s，12H)。

Example 5: preparation of photochromic materials

A photochromic curable composition was prepared by thoroughly mixing 0.04 part by mass of the chromene compound obtained in examples 1 to 4, 13 parts by mass of tetraethyleneglycol dimethacrylate, 48 parts by mass of 2, 2-bis [4- (methacryloyloxyethoxy) phenyl ] propane, 2 parts by mass of polyethylene glycol monoallyl ether, 20 parts by mass of trimethylolpropane trimethacrylate, 9 parts by mass of glycidyl methacrylate, 6 parts by mass of α -methylstyrene, 2 parts by mass of a-methylstyrene dimer, and 1 part by mass of t-butyl peroxy 2-ethylhexanoate as a polymerization initiator. Then, the obtained photochromic curable composition was poured into a mold composed of a glass plate and a gasket (gasset) made of an ethylene-vinyl acetate copolymer, and cast polymerization was performed. The polymerization process is as follows: an air oven was used, which was slowly warmed from 30 ℃ to 90 ℃ over 18 hours and held at 90 ℃ for 2 hours. After the polymerization was completed, the polymer was removed from the glass mold of the mold to obtain a photochromic material sample prepared from the compounds of examples 1 to 4.

Experimental example 1: evaluation of photochromic Properties in solution

The photochromic cured product (photochromic optical article) was evaluated by the In mass method. The photochromic properties and half-life were evaluated except that each group of polymers (thickness 2mm, photochromic cured product (optical article)) obtained in example 5 was used as a sample, and the light irradiation time was set to 1 second. The results are shown in Table 1.

Maximum absorption wavelength (Amax): the maximum absorption wavelength after color development, which is obtained by a spectrophotometer (instantaneous multichannel photodetector MCPD 2000M) manufactured by the electronic industry of Otsuka, inc., is an index of the color tone at the time of color development.

Color development concentration (ABS): the absorbance after irradiation with light at the maximum absorption wavelength for 0.5 seconds is an indicator of the color development concentration. It can be said that the higher the value, the greater the change in coloration due to light irradiation, and the better the photochromic property.

Fading half-life (T1/2): the time required for the absorbance at the maximum absorption wavelength of the sample to decrease to a half value when the irradiation of light is stopped is an index of the fading speed. The shorter this time, the faster the fade rate.

Degree of Yellowing (YI): for evaluation of yellowing after polymerization curing, the color difference of the sample after polymerization curing was measured by using a color difference meter (SM-4) manufactured by test machine Co., ltd. The smaller the YI value, the higher the transparency of the polymer cured body (including the cured film), or the smaller the degree of deterioration of the evaluation compound.

Survival rate (A) ₅₀ /A ₀ X100): in order to evaluate the durability of the color development caused by light irradiation, the following degradation acceleration test was performed. The obtained polymer (sample) was accelerated to deteriorate for 50 hours by a xenon arc weather resistant machine X25 manufactured by test machine Co., ltd. Thereafter, the color development concentration was evaluated before and after the test, and the color development concentration (a ₀ ) Color development concentration after test (A) ₅₀ ) Comparing the ratio (A) ₅₀ /A ₀ ) The residual rate was set as an index of the durability of the color development. The higher the residual ratio, the higher the durability of the color development.

Table 1:

comparative example 1

For further comparison, photochromic cured films were prepared using the same method as in example 5, using the following compounds of formulas a to F, and the characteristics of the photochromic plastic lenses obtained were evaluated by the method of experimental example 1, and the results are shown in table 2:

TABLE 2

Experimental results show that the compound of the invention introduces electron withdrawing groups and simultaneously connects different substituted benzochromenes through electron donating groups O, and the compound has practical fading half-life and good ageing resistance, and has photochromic property which disappears instantly when the light irradiation is stopped.

Therefore, when a photochromic material such as a photochromic lens is manufactured using the polysubstituted dibenzochromene compound of the present invention, a photochromic lens having such a property can be manufactured that rapidly develops color when coming outdoors, rapidly fades and returns to the original color tone when returning outdoors to indoors, and can be used for a long period of time.

The polysubstituted dibenzochromene compound of the present invention exhibits the above excellent effects and is suitable for various applications, for example, light control materials, hologram materials, ink materials, optical information devices, optical switching elements, photoresist materials, and the like.

Claims

1. A preparation method of a polysubstituted dibenzochromene compound is characterized in that the compound has a structure as shown in the following formula:

wherein:

r1, R2, R5 and R6 are respectively selected from methoxy or methylthio;

r3, R4, R7, R8 are each selected from hydrogen, halogen or CF ₃ And at least one of R3, R4, R7, R8 is halogen or CF ₃ ；

The reaction formula of the preparation method is as follows:

reaction 1

The preparation method comprises the following steps:

(5) And (3) reacting the compounds I-4 and I-8 at room temperature under the condition of diethyl azodicarboxylate and triphenylphosphine to obtain a compound I-9.

2. The method of claim 1, wherein each of R3 and R7 is H and each of R4 and R8 is F.

3. The process according to claim 1, wherein R3 and R7 are each H, and R4 and R8 are each CF ₃ 。

4. The method of claim 1, wherein R3, R7, R4, R8 in the compound are each F.

5. The method of any one of claims 1-4, wherein the specific operation of step (1) is as follows: dissolving a compound I-1 in ethylenediamine, and adding a lithium ethyne ethylenediamine complex, wherein the molar ratio of the compound I-1 to the lithium ethyne ethylenediamine complex is 1:2-4; stirring for 2-4 hours at room temperature under nitrogen atmosphere; the reaction solution was extracted with ethyl acetate, and the organic layer was washed with water, saturated sodium chloride, dried, concentrated, and the crude product was purified by silica gel column chromatography to give compound I-2.

6. The method according to any one of claims 1 to 4, wherein the specific operation of step (2) is as follows: dissolving a compound I-2 in toluene, and adding a compound I-3 and camphorsulfonic acid, wherein the mol ratio of the compound I-2 to the compound I-3 to the camphorsulfonic acid is 1:1-1.5:0.2-0.4; then stirring for 2-4 hours at 50-80 ℃, concentrating after the reaction is finished, and purifying the crude product by silica gel column chromatography to obtain the compound I-4.

7. The preparation method according to any one of claims 1 to 4, wherein the specific operation of step (3) is as follows: dissolving a compound I-5 in ethylenediamine, and adding a lithium ethyne ethylenediamine complex, wherein the molar ratio of the compound I-5 to the lithium ethyne ethylenediamine complex is 1:2-4; stirring for 2-4 hours at room temperature under nitrogen atmosphere; the reaction solution was extracted with ethyl acetate, and the organic layer was washed with water, saturated sodium chloride, dried, concentrated, and the crude product was purified by silica gel column chromatography to give compound I-6.

8. The method of any one of claims 1-4, wherein the specific operation of step (4) is as follows: dissolving a compound I-6 in toluene, and adding a compound I-7 and camphorsulfonic acid, wherein the mol ratio of the compound I-6 to the compound I-7 to the camphorsulfonic acid is 1:1-1.5:0.2-0.4; then stirring for 2-4 hours at 50-80 ℃, concentrating after the reaction is finished, and purifying the crude product by silica gel column chromatography to obtain the compound I-8.

9. The method of any one of claims 1 to 4, wherein the specific operation of step (5) is as follows: dissolving a compound I-4 and a compound I-8 in tetrahydrofuran, and adding diethyl azodicarboxylate and triphenylphosphine, wherein the molar ratio of the compound I-4 to the compound I-8 to the diethyl azodicarboxylate to the triphenylphosphine is 1:1:0.6-1.2:0.6-1.2; after the reaction is completed for 12 to 24 hours, the mixture is concentrated and separated by a silica gel preparation plate to obtain the compound I-9.