A 3-bromofluorenone and its preparation method

Abstract

The application provides a kind of 3-bromofluorenone and preparation method thereof, it relates to the technical field of organic photoelectric material.The method is prepared by using 2-bromofluorenone and benzophenone imine under the condition of palladium catalyst to react 2-amino fluorenone, purification is convenient;Using 2-amino fluorenone and N-bromosuccinimide under ice water bath, the impurity can be controlled, purification is convenient, cost is controlled;Using with tert-butyl nitrite can obtain high purity 3-bromofluorenone compound target product;Using N-bromosuccinimide in ice water bath, accurately locate the 3 position of fluorenone, without the help of other catalysts, simplify the reaction;Using the way of dropping tert-butyl nitrite THF solution into the reaction system, can greatly improve the utilization rate of tert-butyl nitrite, finally improve the yield of the whole reaction.The preparation method provided by the application has the advantages of controllable impurity, easy purification and cost economy.

Description

Technical Field

[0001] This invention relates to the field of organic optoelectronic materials technology, and in particular to a 3-bromofluorenone and its preparation method. Background Technology

[0002] 3-Bromoxyfluorenone compound, molecular formula C 13 H7BrO, molecular weight: 257.97, structural formula as follows:

[0003]

[0004] 3-Bromofluorenone and its downstream product 3-bromospirobisfluorene are important organic functional intermediates for OLEDs in organic optoelectronic materials, but their high synthesis cost limits their further application prospects.

[0005] Currently, there are many existing methods for preparing 3-bromofluorenone compounds. The more common preparation methods are as follows:

[0006] (1) In 1935, Miller, Harry F. and Bachman, G. Bryant disclosed in the Journal of the American Chemical Society (Volume 57, 2443-2446) a technique for obtaining 3-bromofluorenone by diazotization of 2-amino-4-bromoacetophenone to produce a diazonium salt, followed by cyclization. However, the high price of 2-amino-4-bromoacetophenone and the low yield of this step remain problems that need to be solved.

[0007] (2) In 2010, Song, Yabin et al. published in Tetrahedron Letters [51(37), 4894-4897] using phenanthrenequinone as a raw material to obtain 3-bromofluorenone via bromination, hydrolysis rearrangement and oxidation. Although the materials used were cheaper and more readily available than 2-amino-4-bromoacetophenone, the overall yield of the route was low, the reaction time was long, and purification was difficult.

[0008] (3) CN105294415 discloses a method for preparing general formula 3-bromofluorenone using methyl 2-bromo-4-nitrobenzoate as the starting material via Suzuki reaction, reduction reaction, diazotization reaction, and cyclization reaction. The disadvantage of this route is that the reaction route is too long, which increases the preparation cost and makes it difficult to meet the requirements of organic optoelectronic materials.

[0009] Therefore, the present invention urgently needs to develop a 3-bromofluorenone compound that is cost-effective, has a simple process, and a high yield. Summary of the Invention

[0010] This invention provides a 3-bromofluorenone and its preparation method, the purpose of which is to solve the above-mentioned problems existing in the background art.

[0011] To achieve the above objectives, embodiments of the present invention provide a 3-bromofluorenone and its preparation method. The method involves reacting 2-bromofluorenone with benzophenone imine to obtain the intermediate 2-aminofluorenone, which is then reacted with N-bromosuccinimine to obtain the intermediate 2-amino-3-bromofluorenone compound. This intermediate is further prepared by reacting with tert-butyl nitrite to obtain the 3-bromofluorenone compound. The preparation method provided by the present invention has advantages such as controllable impurities, convenient purification, and economical cost. Furthermore, the preparation method provided by the present invention has advantages such as simple operation, readily available raw materials, high product purity, high yield, and suitability for industrial production.

[0012] An embodiment of the present invention provides a method for preparing 3-bromofluorenone, comprising the following steps:

[0013] S1. Add 2-bromofluorenone, benzophenone imine, sodium tert-butoxide, tri-tert-butylphosphine tetrafluoroborate and tris(dibenzylideneacetone)dipalladium to toluene, purge with nitrogen, then heat to carry out the reaction, add hydrochloric acid, filter under vacuum to obtain 2-aminofluorenone;

[0014] S2. Add 2-aminofluorenone to N,N-dimethylformamide, add N-bromosuccinimide in batches under ice-water bath conditions, then heat to 20 to 25°C to carry out the reaction, add water, filter, and obtain 2-amino-3-bromofluorenone;

[0015] S3. The 2-amino-3-bromofluorenone was added to tetrahydrofuran, stirred, and tert-butyl nitrite was added dropwise while heating to carry out the reaction. The mixture was then concentrated and crystallized to obtain 3-bromofluorenone.

[0016] Preferably, the molar ratio of 2-bromofluorenone to benzophenone imine is 1:(1.0 to 2.5).

[0017] Preferably, the molar ratio of 2-aminofluorenone to N-bromosuccinimide is 1:(1.0 to 2.5).

[0018] More preferably, the molar ratio of 2-aminofluorenone to N-bromosuccinimide is 1:1.05.

[0019] Preferably, the amount of tert-butyl nitrite used is 1.0 to 2.0 of the molar amount of 2-amino-3-bromo-fluorenone.

[0020] Preferably, the reaction conditions in step S1 are: temperature 70-130℃, time 2-16h.

[0021] Preferably, in step S2, the ice-water bath temperature is 0–10°C and the reaction time is 1–10 h.

[0022] Preferably, the reaction conditions in step S3 are: temperature 60–130°C, time 2–16 h.

[0023] More preferably, the reaction conditions in step S3 are: temperature 70–110°C, time 2–10 h.

[0024] Based on a general inventive concept, embodiments of the present invention provide a 3-bromofluorenone obtained by the above-described preparation method, wherein the 3-bromofluorenone has a purity of 99.5%.

[0025] The above-described solution of the present invention has the following beneficial effects:

[0026] (1) In this invention, 2-aminofluorenone and N-bromosuccinimide are reacted in an ice-water bath. Impurities are controllable, purification is convenient, and costs are controlled. The target product of 3-bromofluorenone compound can be obtained by reacting with tert-butyl nitrite.

[0027] (2) The second step of the present invention uses only N-bromosuccinimide in an ice-water bath, which accurately locates the 3-position of fluorenone without the need for other catalysts, thus simplifying the reaction.

[0028] (3) Tert-butyl nitrite is prone to deterioration under high temperature conditions, which ultimately results in a low overall reaction yield. In the third step of this invention, a tert-butyl nitrite THF solution is added to the reaction system dropwise, which can greatly improve the utilization rate of tert-butyl nitrite and ultimately improve the overall reaction yield.

[0029] (4) The synthesis method of the present invention is simple to operate, the raw materials are readily available, the product has high purity and high yield, and it is suitable for industrial production. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is the 3-bromofluorenone prepared in Example 1 of the present invention. 1 H NMR spectrum;

[0032] Figure 2 This is an HPLC chromatogram of step three of the 3-bromofluorenone prepared in Example 1 of the present invention;

[0033] Figure 3 This is an HPLC chromatogram of the purified 3-bromofluorenone product prepared in Example 1 of the present invention. Detailed Implementation

[0034] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] In the following examples, DMF specifically refers to N,N-dimethylformamide; THF specifically refers to tetrahydrofuran.

[0038] This invention addresses existing problems by providing a 3-bromofluorenone and its preparation method, with the reaction formula shown below.

[0039]

[0040] Example 1

[0041] A method for preparing 3-bromofluorenone specifically includes the following steps:

[0042] Step 1: Weigh 50g of 2-bromofluorenone, 38.5g of benzophenone imine, 55g of sodium tert-butoxide, 1g of tri-tert-butylphosphine tetrafluoroborate and 0.88g of tris(dibenzylacetone)dipalladium and add them to toluene in a three-necked flask. Add 200mL of toluene and stir. After purging with nitrogen, heat to 100℃ and react for 10h. After the reaction is complete, cool down, add hydrochloric acid, and filter to obtain 2-aminofluorenone.

[0043] Step 2: Weigh 50g of 2-aminofluorenone into a three-necked flask, add 200mL of DMF and stir to dissolve; cool to 5-10℃ in an ice-water bath, weigh 47.8g of NBS into a beaker, protect from light, add 150mL of DMF to dissolve and transfer to a constant pressure dropping funnel; add NBS solution dropwise, controlling the temperature not to exceed 15℃; after the addition is complete, heat to 20-25℃ and react for 6 hours, then transfer the reaction system into 500mL of water and filter to obtain a yellow solid;

[0044] Step 3: Weigh 66.5g of 2-amino-3-bromofluorenone into a three-necked flask, add 400ml of THF and stir to dissolve; take 29.7g of tert-butyl nitrite and add it dropwise to the reaction flask at room temperature through a constant pressure dropping funnel; after the addition is complete, raise the temperature to 80℃, and there is obvious reflux. Maintain reflux and continue the reaction for 6 hours. Concentrate the mother liquor, add 2.5V ethanol and heat to form a slurry, then gradually cool to 20℃ to induce crystallization, with a yield of 75%.

[0045] Example 2

[0046] A method for preparing 3-bromofluorenone specifically includes the following steps:

[0047] Step 1: Weigh 50g of 2-bromofluorenone, 38.5g of benzophenone imine, 55g of sodium tert-butoxide, 1g of tri-tert-butylphosphine tetrafluoroborate and 0.88g of tris(dibenzylacetone)dipalladium and add them to toluene in a three-necked flask. Add 200mL of toluene and stir. After purging with nitrogen, heat to 100℃ and react for 10h. After the reaction is complete, cool down, add hydrochloric acid, and filter to obtain 2-aminofluorenone.

[0048] Step 2: Weigh 50g of raw material into a three-necked flask, add 200mL of DMF and stir to dissolve; cool to 5-10℃ in an ice-water bath, weigh 47.8g of NBS into a beaker, protect from light, add 150mL of DMF to dissolve and transfer to a constant pressure dropping funnel; add NBS solution dropwise, controlling the temperature not to exceed 15℃; after the addition is complete, heat to 20-25℃ and react for 6 hours, then transfer the reaction system into 500mL of water and filter to obtain a yellow solid;

[0049] Step 3: Weigh 66.5g of 2-amino-3-bromofluorenone into a three-necked flask, add 400ml of THF and stir to dissolve; take 29.7g of tert-butyl nitrite and add it dropwise to the reaction flask at room temperature through a constant pressure dropping funnel; after the addition is complete, raise the temperature to 60℃, and there is obvious reflux. Maintain reflux and continue the reaction for 6 hours. Concentrate the mother liquor, add 2.5V ethanol and heat to form a slurry, then gradually cool to 20℃ to induce crystallization, with a yield of 65%.

[0050] Example 3

[0051] A method for preparing 3-bromofluorenone specifically includes the following steps:

[0052] Step 1: Weigh 50g of 2-bromofluorenone, 38.5g of benzophenone imine, 55g of sodium tert-butoxide, 1g of tri-tert-butylphosphine tetrafluoroborate and 0.88g of tris(dibenzylacetone)dipalladium and add them to toluene in a three-necked flask. Add 200mL of toluene and stir. After purging with nitrogen, heat to 100℃ and react for 10h. After the reaction is complete, cool down, add hydrochloric acid, and filter to obtain 2-aminofluorenone.

[0053] Step 2: Weigh 50g of raw material into a three-necked flask, add 200mL of DMF and stir to dissolve; cool to 5-10℃ in an ice-water bath, weigh 47.8g of NBS into a beaker, protect from light, add 150mL of DMF to dissolve and transfer to a constant pressure dropping funnel; add NBS solution dropwise, controlling the temperature not to exceed 15℃; after the addition is complete, heat to 20-25℃ and react for 6 hours, then transfer the reaction system into 500mL of water and filter to obtain a yellow solid;

[0054] Step 3: Weigh 66.5g of 2-amino-3-bromofluorenone into a three-necked flask, add 400ml of THF and stir to dissolve; take 24g of tert-butyl nitrite and add it dropwise into the reaction flask at room temperature through a constant pressure dropping funnel; after the addition is complete, raise the temperature to 80℃, and there is obvious reflux phenomenon. Maintain reflux and continue the reaction for 6h. Concentrate the mother liquor, add 2.5V ethanol and heat to slurry, then gradually cool to 20℃ to induce crystallization, with a yield of 67%.

[0055] Comparative Example

[0056] A method for preparing 3-bromofluorenone, the reaction formula of which is shown below, specifically includes the following steps:

[0057]

[0058] Step 1: 720g of 56% H2SO4 solution was added to a 2L beaker, followed by 82g of 2-amino-4'-bromobenzophenone. The mixture was heated to 60℃ and stirred for 2 hours, then cooled to 5℃. Sodium nitrite aqueous solution was added dropwise over half an hour, and the mixture was kept at this temperature for 90 minutes. 700mL of water was then added, and the temperature was raised to 60℃. The reaction was carried out for 6 hours. The aqueous phase was removed by filtration. The filter cake was refluxed with 400g of ethanol and slurried. After cooling and filtration, the mixture was dried. Subsequently, 160g of toluene was heated to 100℃ and completely dissolved. 320g of ethanol was added, and the mixture was cooled to 25℃ and filtered. The yield was 46%.

[0059] The cost of tribromofluorenone obtained from the raw material 2-bromofluorenone (750 yuan / kg) in the embodiment of the present invention is only 2,500 yuan / kg, while the cost of tribromofluorenone obtained from the raw material 2-amino-4'-bromobenzobenzophenone (6,900 yuan / kg) in the comparative example is 15,000 yuan / kg.

[0060] Meanwhile, the synthesis of the embodiments is simple, all three steps are continuous addition reactions, and there is no purification in the intermediate steps, which improves the overall smoothness of the route and greatly helps to reduce costs.

[0061] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for the preparation of 3-bromofluorenone, characterized in that, The method comprises the following steps: S1. Take 2-bromofluorenone, benzophenone imine, sodium tert-butyl alcohol, tri-tert-butyl phosphonium tetrafluoroborate and tris(dibenzylideneacetone)dipalladium, add them into toluene, pass nitrogen, then heat to react, add hydrochloric acid, extract and filter to obtain 2-aminofluorenone; S2. Take 2-aminofluorenone, add it into N,N-dimethylformamide, add N-bromosuccinimide in batches under ice water bath, then heat to 20-25℃ to react, add water, extract and filter to obtain 2-amino-3-bromofluorenone; S3. Take the 2-amino-3-bromofluorenone, add it into tetrahydrofuran, stir, add tert-butyl nitrite dropwise while heating to react, concentrate, crystallize to obtain 3-bromofluorenone.

2. The method of claim 1, wherein the 3-bromo fluorenone is prepared by the process comprising: reacting 9-bromo fluorene with a bromine source in the presence of a Lewis acid to form 3-bromo fluorenone. The molar ratio of the 2-bromofluorenone and the benzophenone imine is 1: (1.0-2.5).

3. The method for preparing 3-bromofluorenone according to claim 1, characterized in that, The molar ratio of the 2-aminofluorenone and the N-bromosuccinimide is 1: (1.0-2.5).

4. The method for preparing 3-bromofluorenone according to claim 3, characterized in that, The molar ratio of the 2-aminofluorenone and the N-bromosuccinimide is 1:1.

05.

5. The method for preparing 3-bromofluorenone according to claim 1, characterized in that, The amount of the tert-butyl nitrite used is 1.0-2.0 times the molar amount of the 2-amino-3-bromofluorenone.

6. The method for preparing 3-bromofluorenone according to claim 1, characterized in that, The reaction condition in step S1 is: temperature 70-130℃, time 2-16h.

7. The method for preparing 3-bromofluorenone according to claim 1, characterized in that, In step S2, the ice water bath temperature is 0-10℃, and the reaction time is 1-10h.

8. The method of claim 1, wherein the 3-bromo fluorenone is prepared by the process comprising: reacting 9-bromo fluorene with a bromine source in the presence of a Lewis acid to form 3-bromo fluorenone. The reaction condition in step S3 is: temperature 60-130℃, time 2-16h.

9. The method for preparing 3-bromofluorenone according to claim 8, characterized in that, The reaction condition in step S3 is: temperature 70-110℃, time 2-10h.

10. The method of any one of claims 1 to 9, wherein the 3-bromo fluorenone is prepared by the process comprising: reacting a 3-bromo fluorene with a base in a solvent to form a 3-bromo fluorenone. The purity of the 3-bromofluorenone reaches 99.5%.

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