Preparation method of 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluoreneTechnical Field
The invention belongs to the field of organic synthesis, and particularly relates to a preparation method of 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene.
Background
6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene is an organic material. 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene can be prepared into 2, 8-dibromo-6, 6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene through bromination reaction, and two bromides of the 2, 8-dibromo-6, 6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene are replaced by diarylamine compounds to prepare the triarylamine compound shown in the formula (I), and the triarylamine compound can be applied to organic electroluminescent device materials.
In the formula (I), when Ar1Selected from phenyl, Ar2When the triarylamine compound is selected from 1-naphthyl, the structure is shown as a formula (II), CN101142170 of Mumura et al discloses the application of the triarylamine compound shown as the formula (II) as a hole transport material of an organic electroluminescent device, and a device using the compound shown as the formula (II) as the hole transport material of the organic electroluminescent device shows excellent performances in brightness and efficiency.
In the formula (I), when Ar1Selected from 4-methylphenyl, Ar2When selected from 4-methylphenyl, the structure is shown in formula (III), and the formula (III) is disclosed in CN101228250 by Host-Weister et alThe triarylamine compound is applied as the luminescent layer dopant of the organic electroluminescent device, and the device using the compound shown in the formula (III) as the luminescent layer dopant of the organic electroluminescent device shows excellent performance in the aspects of color coordinate, brightness and efficiency.
Therefore, the synthesis of 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene and the synthesis of the corresponding compound with the structure of formula (I) are important for the synthesis of organic electroluminescent materials.
At present, the preparation method of 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene mainly comprises the following two methods:
the first is the preparation method disclosed in CN101142170 by mummura et al, whose chemical reaction equation is as follows:
in the method, 2, 5-dibromo dimethyl terephthalate and phenylboronic acid are used for SUZUKI coupling reaction to prepare an intermediate 1 with the yield of 80%; the intermediate 1 is cyclized in 80 percent sulfuric acid at 180 ℃ to prepare an intermediate 2, and the yield is 70 percent; reducing the intermediate 2 with hydrazine hydrate in diethylene glycol at 200 ℃ to obtain an intermediate 3 with the yield of 50%; and (3) performing substitution reaction on the intermediate 3 and methyl iodide in dimethyl sulfoxide by taking potassium tert-butoxide as alkali, refining the prepared crude product by using a column chromatography, and preparing the target product 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene with the yield of 95%. The preparation method needs four-step reaction, the total reaction yield is 26.6%, the reaction temperature of the intermediate 2 and the intermediate 3 is high, the operation is not easy, and the final product 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene needs to be separated by column chromatography, so the operation is complicated.
The second is a preparation method disclosed by Van Chung Pham et al in Bull. Korean chem. Soc.2011, Vol.32, No. 51781-1783, the chemical reaction formula of the method is as follows:
in the method, 2, 5-dibromo-p-xylene and phenylboronic acid are subjected to coupling reaction to prepare an intermediate 4, and then oxidized by potassium permanganate to obtain an intermediate 5, wherein the two-step reaction yield is 92%; then the intermediate 5 reacts with thionyl chloride and methanol in sequence to prepare an intermediate 6 with the yield of 100 percent, the intermediate 6 and methyl magnesium bromide are subjected to addition reaction and then hydrolyzed to prepare an intermediate 7 with the yield of 96 percent; and adding concentrated hydrochloric acid into the intermediate 7 in dichloromethane for reflux to obtain a target product 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene with the yield of 80%. The preparation method requires 5 steps of reaction, and the total yield is 70.65%. This process provides a significant improvement in yield over the preparation process disclosed in CN101142170 to murmura et al, but still suffers from a number of disadvantages. Firstly, in the process of preparing the intermediate 5 from the intermediate 4, 12 equivalents of potassium permanganate are needed for oxidation, and more solid wastes are generated in the reaction, so that the treatment is difficult; secondly, in the process of preparing the intermediate 6 from the intermediate 5, thionyl chloride which is very easy to hydrolyze is needed, so that the operation difficulty is increased, and the mass production is inconvenient; thirdly, in the reaction of preparing the target product 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene from the intermediate 7, concentrated hydrochloric acid needs to be added into dichloromethane for reflux, and during batch production, the volatile hydrogen chloride gas in the hydrochloric acid is easy to pollute the production environment and possibly corrode production equipment.
Disclosure of Invention
The invention provides a preparation method of 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene, which solves the technical problems of harsh conditions, complex operation and low yield in the prior art.
According to an aspect of the present invention, there is provided a method for preparing 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene, the method comprising:
coupling reaction: carrying out coupling reaction on 1 equivalent of o-dibromobenzene and 1-1.4 equivalent of 9, 9-dimethylfluorene-2-boric acid to generate a compound shown as a formula M-1;
addition reaction: the compound shown as the formula M-1 reacts with 1-1.5 equivalents of butyl lithium, then the compound reacts with 1-2 equivalents of acetone in an addition reaction mode, and then the compound is hydrolyzed to generate a compound shown as the formula M-2;
and (3) cyclization reaction: carrying out cyclization reaction on a compound shown as a formula M-2 in the presence of 3-16 equivalents of acid to convert the compound into 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene shown as the formula M;
alternatively, according to the preparation method of the present invention, in the cyclization reaction, the acid is selected from methane sulfonic acid, trifluoromethanesulfonic acid, trichloroacetic acid.
Alternatively, the preparation method according to the invention:
in the coupling reaction, the dosage of the 9, 9-dimethylfluorene-2-boric acid is 1.05-1.2 equivalent;
in the addition reaction, the consumption of butyl lithium is 1.1-1.3 equivalent, and the consumption of acetone is 1.2-1.7 equivalent;
in the cyclization reaction, the amount of the acid is 4-10 equivalents.
Further optimization, the preparation method according to the invention comprises the following steps:
in the coupling reaction, the amount of 9, 9-dimethylfluorene-2-boronic acid used is 1.1 equivalents;
in the addition reaction, the consumption of butyl lithium is 1.2 equivalents, and the consumption of acetone is 1.5 equivalents;
in the cyclization reaction, the amount of the acid is 6 equivalents.
Moreover, the preparation method according to the invention:
in the coupling reaction, after the reaction is finished, cooling, separating liquid, washing an organic layer with water, drying with anhydrous sodium sulfate, decoloring with a silica gel column, concentrating an eluent to dryness, adding tetrahydrofuran to obtain a tetrahydrofuran solution containing the compound shown in the formula M-1, and directly carrying out addition reaction on the tetrahydrofuran solution containing the compound shown in the formula M-1 without further separation and purification.
In the addition reaction, a tetrahydrofuran solution containing the compound shown as the formula M-1 is cooled to-78 ℃, and reacts with butyl lithium to prepare a corresponding lithium salt, then the lithium salt reacts with acetone, the addition reaction is carried out, hydrolysis is carried out, dichloromethane is extracted, anhydrous sodium sulfate is dried, a drying agent is filtered out, a dichloromethane solution containing the compound shown as the formula M-2 is obtained, and the dichloromethane solution containing the compound shown as the formula M-2 is directly subjected to cyclization reaction without further separation and purification.
Alternatively, according to the preparation method of the present invention, in the cyclization reaction, the acid is methanesulfonic acid or trifluoromethanesulfonic acid.
Alternatively, according to the preparation method of the present invention, in the cyclization reaction, the acid is trichloroacetic acid, since trichloroacetic acid is solid at room temperature, and in the reaction operation, a dichloromethane solution of trichloroacetic acid is used.
Optionally, according to the preparation method of the invention, a cyclization reaction is carried out in a dichloromethane solvent, methanesulfonic acid is dripped into a reaction system at-10-0 ℃, and after the dripping of the methanesulfonic acid is finished, the reaction system reacts for 60min at 20-30 ℃ to obtain 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene shown in formula M.
The invention has the following beneficial effects:
the preparation method has the advantages of simple process, mild reaction conditions and easy operation; the required raw materials are easy to obtain and the cost is low; and the yield is up to 77-90%; therefore, the method is suitable for large-scale production.
Detailed Description
The present invention will now be described in detail with reference to the following examples, which are intended to illustrate and not to limit the scope of the invention.
According to the present invention, a process for producing 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene, which comprises:
coupling reaction: carrying out coupling reaction on 1 equivalent of o-dibromobenzene and 1-1.4 equivalent of 9, 9-dimethylfluorene-2-boric acid to generate a compound shown as a formula M-1;
addition reaction: the compound shown as the formula M-1 reacts with 1-1.5 equivalents of butyl lithium, then the compound reacts with 1-2 equivalents of acetone in an addition reaction mode, and then the compound is hydrolyzed to generate a compound shown as the formula M-2;
and (3) cyclization reaction: performing cyclization reaction on a compound shown as a formula M-2 in the presence of 3-16 equivalents of acid to convert the compound into 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene shown as the formula M;
in the preparation method of 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene, the preparation method comprises three steps of coupling reaction, addition reaction and cyclization reaction.
In the coupling reaction, 1 equivalent of o-dibromobenzene and 1-1.4 equivalents of 9, 9-dimethylfluorene-2-boric acid are adopted to carry out coupling reaction to generate a compound shown as a formula M-1, wherein the reaction equation is shown as follows:
in the reaction, 9, 9-dimethylfluorene-2-boric acid is excessive, so that the reaction of o-dibromobenzene is sufficient, the residual o-dibromobenzene is avoided, and although a small amount of by-products shown in the formula M-3 can be generated, the by-products shown in the formula M-3 can not participate in the reaction in the subsequent addition reaction and cyclization reaction and can be conveniently removed from the product, therefore, after the coupling reaction is completed, the tetrahydrofuran solution containing the compound shown in the formula M-1 can be directly subjected to the addition reaction without further separation and purification, and has no adverse effect on the subsequent reaction.
In the addition reaction, the compound shown as the formula M-1 is firstly reacted with 1-1.5 equivalents of butyl lithium, then is subjected to addition reaction with 1-2 equivalents of acetone, and is hydrolyzed to generate the compound shown as the formula M-2, wherein the reaction equation is shown as follows:
in the reaction, the tetrahydrofuran solution containing the compound shown in the formula M-1 is cooled to-78 ℃, firstly reacts with butyl lithium to prepare corresponding lithium salt, then carries out addition reaction with acetone, then carries out hydrolysis, dichloromethane extraction, anhydrous sodium sulfate drying, and filtration of a drying agent to obtain a dichloromethane solution containing the compound shown in the formula M-2, and the dichloromethane solution containing the compound shown in the formula M-2 is directly subjected to cyclization reaction without further separation and purification.
In the cyclization reaction, a compound shown as a formula M-2 is subjected to cyclization reaction in the presence of 3-16 equivalents of acid and converted into 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene shown as a formula M, and the reaction equation is shown as follows:
in this step of the reaction, the acid is methanesulfonic acid, trifluoromethanesulfonic acid, or trichloroacetic acid.
According to the preparation method of the 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene, methane sulfonic acid and trifluoromethanesulfonic acid are strong acids, and methane sulfonic acid or trifluoromethanesulfonic acid is directly added into the reaction in a large amount, which can release a large amount of heat to intensify the reaction, so that the methane sulfonic acid or trifluoromethanesulfonic acid needs to be dropped at low temperature when added into the reaction system, which can reduce the amount of byproducts generated in the reaction to the minimum, increase the purity of the product and improve the yield of the product. Meanwhile, the reaction temperature is controlled to be-10-0 ℃ when the methanesulfonic acid or the trifluoromethanesulfonic acid is dripped, the temperature is slowly increased to 20-30 ℃ after the addition, the reaction is sufficient, the reaction condition is mild, and the operation is simple.
Since trichloroacetic acid is solid at room temperature, when trichloroacetic acid is selected as the acid in the reaction operation, a dichloromethane solution of trichloroacetic acid, i.e., a dichloromethane solution of trichloroacetic acid is added dropwise to the reaction.
The preparation method of 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene according to the present invention provides a lot of optional factors, and different embodiments can be combined according to the claims of the present invention, and the embodiments are only used for further description of the present invention and do not limit the present invention. The present invention will be further described with reference to the following examples.
Example 1
The synthetic route is as follows:
according to the preparation method of the 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene, the reaction is carried out in three steps:
(1) coupling reaction
A1000 ml three-neck flask is added with 23.59 g (0.1mol, 1eq) of o-dibromobenzene, 26.18 g (0.11mol, 1.1eq) of 9, 9-dimethylfluorene-2-boric acid, 27.6 g (0.2mol, 2eq) of potassium carbonate, 200 ml of toluene, 150 ml of ethanol, 80 ml of water, 0.58 g (0.0005mol, 0.005eq) of tetratriphenylphosphine palladium is added under the protection of nitrogen, the mixture is slowly heated to 70-80 ℃ for reaction for 8 hours, cooled, added with water for liquid separation, an organic layer is washed with water, dried by anhydrous sodium sulfate, decolored by a silica gel column, an eluent is concentrated to dryness, and 300 ml of tetrahydrofuran is added to obtain a tetrahydrofuran solution containing the compound shown in the formula M-1.
(2) Addition reaction
Under the protection of nitrogen, the tetrahydrofuran solution containing the compound shown in the formula M-1 obtained in the previous step is cooled to-78 ℃, the temperature is controlled to be-70 to-78 ℃, 75 ml (0.12mol, 1.2eq) of 1.6M n-hexane solution of butyl lithium is slowly dripped, the temperature is kept for 40 minutes at-70 to-78 ℃ after the addition is finished, then controlling the temperature to be 70 ℃ below zero to 78 ℃ below zero, slowly adding 8.7 g (0.15mol, 1.5eq) of acetone, slowly heating the reaction solution to 25 ℃ after the addition is finished, reacting for 1 hour, slowly adding ammonium chloride solution for hydrolysis, then 100 ml dichloromethane and 200 ml water are added for separating liquid, the water layer is extracted by 50 ml dichloromethane, the dichloromethane layers are combined, the dichloromethane layer is washed by water, the saturated salt solution is washed by water, after being dried by anhydrous sodium sulfate, the anhydrous sodium sulfate was removed by filtration to obtain a dichloromethane solution containing the compound represented by the formula M-2.
(3) Cyclization reaction
And (3) cooling the dichloromethane solution containing the compound shown in the formula M-2 obtained in the previous step to-10 ℃, slowly dropwise adding 58g (0.6mol, 6eq) of methanesulfonic acid into the dichloromethane solution, keeping the reaction system at 0-10 ℃ until the dropwise addition of the methanesulfonic acid is finished, slowly heating the reaction system to 20-30 ℃ to react for 60min, filtering, washing with water and methanol to obtain 27.82g of 6,6,12, 12-tetramethyl-6, 12-dihydroindeno [1,2-b ] fluorene, wherein the product yield is 89.74%.
Feeding the obtained product intoGo on to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 2
The synthesis method is the same as example 1, except that the amount of 9, 9-dimethylfluorene-2-boronic acid used in the first coupling reaction is changed to 0.12mol, 27.60g of product is obtained, and the product yield is 89.03%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 3
The synthesis method is the same as example 1, except that the amount of 9, 9-dimethylfluorene-2-boronic acid used in the first coupling reaction is changed to 0.13mol, 25.60g of product is obtained, and the product yield is 82.58%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 4
The synthesis method is the same as example 1, except that the amount of 9, 9-dimethylfluorene-2-boronic acid used in the first coupling reaction is changed to 0.14mol, 23.94g of product is obtained, and the product yield is 77.22%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 5
The synthesis method was the same as example 1 except that the amount of butyllithium used in the second addition reaction was changed to 0.13mol, to obtain 27.77g of a product with a yield of 89.58%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 6
The synthesis method was the same as example 1 except that the amount of butyllithium used in the second addition reaction was changed to 0.14mol, to obtain 27.80g of a product with a yield of 89.67%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR (500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 7
The synthesis method was the same as example 1 except that the amount of acetone used in the second addition reaction was changed to 0.13mol, to obtain 27.83g of a product with a yield of 89.77%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 8
The synthesis method was the same as example 1 except that the amount of acetone used in the second addition reaction was changed to 0.17mol, to obtain 27.81g of a product with a yield of 89.70%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 9
The synthesis method was the same as example 1 except that the amount of acetone used in the second addition reaction was changed to 0.2mol, to obtain 27.70g of a product with a yield of 89.35%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 10
The synthesis method is the same as example 1, except that the amount of the methanesulfonic acid is changed from 0.6mol to 0.4mol, 25.18g of the product is obtained, and the product yield is 81.22%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 11
The synthesis method is the same as example 1, except that the amount of the methanesulfonic acid is changed from 0.6mol to 0.95mol, 26.71g of the product is obtained, and the product yield is 86.16%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 12
The synthesis method is the same as example 1, except that the amount of the methanesulfonic acid is changed from 0.6mol to 1.2mol, 26.02g of the product is obtained, and the product yield is 83.93%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 13
The synthesis method is the same as example 1, except that the amount of the methanesulfonic acid is changed from 0.6mol to 1.5mol, 23.88g of the product is obtained, and the product yield is 77.03%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 14
The synthesis method is the same as example 1, except that 0.6mol of methanesulfonic acid is changed to 0.6mol of trifluoromethanesulfonic acid, 26.97g of product is obtained, and the product yield is 87.00%.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m， 2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Example 15
The synthesis was performed as in example 1 except that 0.6mol of methanesulfonic acid was changed to 0.6mol of trichloroacetic acid in 50 ml of dichloromethane to obtain 25.91g of 83.58% product yield.
The obtained product is subjected to1The detection of the HNMR is carried out,1HNMR mapping data were as follows:1HNMR(500MHz，CDCl3)：8.07(m，2H)，7.98(s，2H)，7.55(m，2H)，7.44(m，2H)，7.28(m，2H)，1.70(2，12H)。
the obtained product was subjected to mass spectrometric detection to obtain an m/e value of 310.
Therefore, the preparation method has the advantages of simple process, mild reaction conditions and easy operation; the required raw materials are easy to obtain, the cost is low, the yield is 77-90%, and the method is suitable for large-scale production.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.