Preparation method of 9-fluorenone

Abstract

The invention discloses a preparation method of 9-fluorenone, and relates to the technical field of synthesis of organic compounds, and the preparation method is characterized in that benzophenone is used as a reaction raw material, and a 9-fluorenone product is prepared through a reaction in an acidic medium under the synergistic effect of a palladium catalyst and a silver cocatalyst and oxygen or air as an oxidizing agent; according to the method, the benzophenone which is low in price and wide in source is used as a raw material, the high-purity 9-fluorenone is synthesized through one-step oxidation reaction under the high-pressure or normal-pressure condition under the synergistic catalysis of the palladium catalyst and the silver cocatalyst by selecting air or oxygen as a green oxidizing agent, the reaction condition is mild, operation is easy and convenient, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of organic compound synthesis, and specifically provides a high-efficiency chemical synthesis method for preparing 9-fluorenone (9-Fluorenone) by using benzophenone as a reaction raw material through a one-step catalytic oxidation reaction. Background Art

[0002] 9-Fluorenone is an important fine organic chemical intermediate, which is widely used in the fields of medicine, pesticides, dyes, optoelectronics and functional polymer materials. Its chemical name was once dibenzophenone or dibenzopentacyclic ketone, and its chemical formula is C 13 H 8 O, with the appearance of yellow crystals, melting point of 84℃, and boiling point of 341.5℃. Thanks to its unique chemical structure and properties, 9-fluorenone has become an indispensable reaction intermediate in the field of fine chemicals, and plays an important role in the fields of medicine, pesticides, dyes, polymer materials and optical materials. For example, it is a key intermediate for the synthesis of anticonvulsant drugs such as 2-hydroxyaminoacetylfluorenone, anticancer drugs and sympathetic nerve inhibitors, and is also an intermediate for the preparation of pesticides, plant growth regulators and aromatic diamine dyes. In addition, compounds with bisphenol fluorene structures synthesized with 9-fluorenone as raw materials are important monomers and modifiers for the preparation of new engineering plastics. Its resin materials have excellent optical properties, high heat resistance, high transparency and high refractive index. They are widely used in optoelectronic materials such as smartphone lenses, digital camera lenses, liquid crystal display films and driving recorder probes, and have broad market prospects. With the continuous expansion of the application field of 9-fluorenone and the continuous deepening of research, the demand for 9-fluorenone in the domestic and foreign markets will continue to grow year by year.

[0003] At present, the main preparation method of 9-fluorenone is to achieve it through the oxidation reaction of fluorene, and the reaction raw material fluorene used is separated from a large amount of coal tar. Coal tar is a complex mixture containing hundreds of compounds with different chemical structures, among which the content of fluorene is not high, only 1-2%. Therefore, to separate fluorene from the complex coal tar mixture requires high-precision separation technology, such as distillation, extraction, recrystallization, etc., the process is complicated and the production cost is high. In addition, the waste and emissions generated in the process of coal tar refining cause serious pollution to the environment, because these wastes contain a large amount of heavy metals, polycyclic aromatic hydrocarbons and other harmful substances, which pose a serious threat to water bodies, soil and atmospheric environment. On the other hand, the traditional method of fluorene oxidation usually uses chromium trioxide (CrO 3 ) and potassium permanganate (KMnO 4) and other heavy metal oxidants, which are not only expensive, but also easily produce peroxidation products, which reduce product selectivity and increase the difficulty of product separation. Although air oxidation of fluorene can also be used to prepare 9-fluorenone, the selectivity of the corresponding oxidation reaction is not ideal, and a large amount of black tar byproducts that are difficult to remove will be produced, further increasing the difficulty of product separation.

[0004] Since it is difficult to obtain fluorene (or 9-fluorenone prepared from fluorene) from coal tar to meet the growing market demand, the development of efficient and environmentally friendly chemical synthesis methods to prepare 9-fluorenone has extremely high academic research value and industrial significance. At present, studies have explored the reaction routes for preparing 9-fluorenone from non-fluorene raw materials, mainly including the synthesis strategy of preparing 9-fluorenone using biphenyl derivatives and benzophenone or its derivatives as reaction raw materials. For example, 9-fluorenone can be prepared by Friedel-Crafts reaction using derivatives such as 2-carboxybiphenyl (Tetrahedron Lett., 2015, 56 (4), 612-618; J. Org. Chem., 1979, 44 (21), 3724-3725; Chemical Research and Applications, 2024, 36 (3), 663-667). However, the preparation cost of 2-carboxybiphenyl is relatively high, and it is usually prepared by hydrolysis of 9-fluorenone under alkaline conditions (CN1775726A), so this chemical synthesis route is difficult to achieve industrialization. Similarly, benzanilide can also be used as a raw material to prepare 9-fluorenone through the Comberg-Bachmann reaction (Synthetic Chemistry, 2015, 23 (5), 428-430; Green Chem., 2017, 19, 5390-5395). The preparation of 9-fluorenone through this chemical synthesis route also lacks cost advantages! Up to now, there is no process route for preparing 9-fluorenone by chemical synthesis methods without fluorene sources with industrialization prospects. Therefore, it is of great significance to develop an efficient, environmentally friendly and low-cost chemical synthesis method for 9-fluorenone, which can break through the industrial bottleneck of preparing 9-fluorenone by extracting fluorene from coal tar.

[0005] Benzophenone is a low-cost, widely available organic chemical raw material, often used in the preparation of fragrance fixatives, ultraviolet light absorbers and photocuring reaction initiators. As early as 1975, et al. first reported a method for synthesizing 9-fluorenone from benzophenone using palladium acetate as a catalyst, but this method requires the consumption of 2 equivalents of palladium acetate and the yield is only 65% ​​(J. Org. Chem., 1975, 40, 1365-1367). Subsequently, researchers continued to improve the experimental method by introducing 2-3 equivalents of silver oxide as an oxidant and reducing the amount of palladium acetate catalyst to catalytic equivalents (5-10 mol%), successfully increasing the yield to about 85% (Org. Lett., 2012, 14, 4850-4853; Chem. Comm., 2012, 48, 9379-9381; Catal. Sci. Technol., 2015, 5, 3363-3367). Although these improvements provide new ideas for the development of methods for synthesizing 9-fluorenone, further optimization is still needed to reduce costs and improve reaction efficiency. Therefore, developing an efficient, environmentally friendly, and low-cost chemical synthesis method for 9-fluorenone has important scientific significance and practical application value. Summary of the invention

[0006] In view of the problems of high cost, serious environmental pollution, complex process and the like in the prior art chemical synthesis method of 9-fluorenone, the present invention provides an efficient, environmentally friendly and economical chemical synthesis method of 9-fluorenone.

[0007] A method for preparing 9-fluorenone is characterized in that benzophenone is used as a reaction raw material, and the 9-fluorenone product is prepared by reaction in an acidic medium through the synergistic effect of a palladium catalyst and a silver co-catalyst and with oxygen or air as an oxidant.

[0008] The present invention uses benzophenone, which is cheap and widely available, as a raw material, through the synergistic catalytic action of a palladium catalyst and a silver co-catalyst, and uses air or oxygen as a green oxidant to synthesize high-purity 9-fluorenone through a one-step oxidation reaction under high pressure or normal pressure. The chemical reaction equation involved is as follows:

[0009]

[0010] Further settings are as follows:

[0011] The palladium catalyst is selected from any one or more of palladium acetate, palladium chloride and palladium nitrate, preferably palladium acetate, and the amount of the palladium catalyst is 0.05-15 mol.%, preferably 1-5 mol.% of benzophenone.

[0012] The silver promoter is selected from any one or more of silver oxide, silver nitrate, silver chloride, silver carbonate and silver oxalate, preferably silver oxide. The amount of the silver promoter is 0.05-15 mol, preferably 1-5 mol.% of benzophenone.

[0013] The acidic medium is selected from any one or more of acetic acid, propionic acid, trifluoroacetic acid, methanesulfonic acid and trifluoromethanesulfonic acid, preferably trifluoroacetic acid.

[0014] The oxidant is air or oxygen, preferably oxygen, and the oxygen pressure is 0.5 to 1.0 atmosphere.

[0015] The reaction temperature is 50-200° C., preferably 100-160° C.; the reaction time is 2-24 hours, preferably 6-12 hours.

[0016] Preferably, benzophenone, palladium catalyst, silver co-catalyst and acidic medium are added to a reactor together, and stirred sufficiently to dissolve the substances; then, the reaction system is sealed, and air or oxygen is introduced therein, the reactor is heated, and the reaction is continued for a certain period of time. After the reaction is completed, the material is cooled, and then water is added, separated, and recrystallized to obtain a pure 9-fluorenone product.

[0017] The beneficial effects of the present invention are as follows:

[0018] (1) Low raw material cost: Using cheap and readily available benzophenone as the starting reaction raw material significantly reduces production costs.

[0019] (2) Green and environmentally friendly: Using air or oxygen as the oxidant avoids the environmental pollution and other problems caused by the use of toxic or expensive oxidants (such as chromium trioxide and potassium permanganate) in traditional methods.

[0020] (3) High efficiency and high selectivity: Through the synergistic effect of palladium catalyst and silver co-catalyst, the reaction selectivity is high, the by-products are few, and the products are easy to separate and purify.

[0021] (4) Simple process: mild reaction conditions, easy operation, and suitable for large-scale industrial production.

[0022] (5) High yield: The optimized process can achieve high-yield synthesis and meet the needs of industrial production. The present invention not only solves the problems of high raw material cost, serious environmental pollution and complex process in the prior art, but also provides an efficient, environmentally friendly and economical chemical synthesis route for the industrial production of 9-fluorenone, which has broad market application prospects.

[0023] The following will further clearly and completely describe the technical solutions in the embodiments of the present invention in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention. DETAILED DESCRIPTION

[0024] Example 1

[0025] In a high pressure reactor, add 36g of benzophenone, 0.5g of palladium acetate, and Ag 2 O: 0.48g, trifluoroacetic acid: 100mL, oxygen pressure: 1.0MPa, reaction temperature 160°C, time 12 hours. After the reaction is completed, add 500mL of water, filter to separate the precipitate, and then recrystallize to obtain 9-fluorenone, with a yield of 93% and a purity greater than 99%.

[0026] Example 2

[0027] The preparation method is the same as that of Example 1, except that the type and amount of the palladium catalyst are adjusted, and the effect thereof on the reaction yield is tested.

[0028] Table 1

[0029] Serial number Palladium catalyst Dosage(g) Yield (%) Example 2-1 Pd / C (palladium content: 5%) 10.7 88 Example 2-2 Pd / C (palladium content: 5%) 4.28 82 Example 2-3 Palladium nitrate 0.5 90 Embodiment 2-4 Palladium acetate 0.1 75 Embodiment 2-5 Palladium acetate 1.0 94 .

[0030] Analysis: From the experimental results in Table 1, it can be seen that different types of palladium catalysts have a great influence on the reaction yield. When palladium acetate is selected as the catalyst and the dosage is 1 mol.% of benzophenone, the best cost and yield are achieved.

[0031] Example 3

[0032] The preparation method is the same as that of Example 1, except that the type and amount of the silver promoter are adjusted, and the effect thereof on the reaction yield is tested.

[0033] Table 2

[0034]

[0035]

[0036] Analysis: From the experimental results in Table 2, it can be seen that the addition of silver catalyst has a great influence on the reaction. Silver catalyst can promote the oxidation of zero-valent palladium to divalent palladium. 2 When O is used as a co-catalyst, the amount of catalyst used is 1 mol.% of benzophenone, which is optimal in terms of cost and yield.

[0037] Example 4

[0038] The preparation method is the same as that of Example 1, except that the type and amount of the acidic medium are adjusted, and the effect thereof on the reaction yield is tested.

[0039] Table 3

[0040] Serial number Acidic medium Dosage(mL) Yield (%) Example 4-1 Trifluoroacetic acid 100 93 Example 4-2 Acetic acid 100 82 Example 4-3 Propionic acid 100 70 Example 4-4 Methanesulfonic acid / acetic acid 20 / 80 91 Embodiment 4-5 Methanesulfonic acid / dichlorobenzene 50 / 50 86 .

[0041] Analysis: From the experimental results in Table 3, it can be seen that different acidic media have a great influence on the reaction, among which: when trifluoroacetic acid is used as the acidic medium, the reaction effect is the best.

[0042] Example 5

[0043] The preparation method is the same as that of Example 1, except that the reaction temperature and reaction time are adjusted, and the effects on the reaction yield are tested.

[0044] Table 4

[0045]

[0046]

[0047] Analysis: From the experimental results in Table 4, it can be seen that the optimal reaction temperature is about 160°C and the reaction time is 12h. Too long a reaction time causes a decrease in the reaction yield. The reason may be that 9-fluorenone will undergo a destructive side reaction during a long reaction process.

Claims

1. A method for preparing 9-fluorenone, characterized in that: Benzophenone is used as a reaction raw material, and a 9-fluorenone product is prepared by reaction in an acidic medium through the synergistic effect of a palladium catalyst and a silver co-catalyst and with oxygen or air as an oxidant.

2. The method for preparing 9-fluorenone according to claim 1, characterized in that: The palladium catalyst is selected from any one or more of palladium acetate, palladium chloride and palladium nitrate, and the dosage of the palladium catalyst is 0.05-15 mol.% of benzophenone.

3. The method for preparing 9-fluorenone according to claim 2, characterized in that: The palladium catalyst is palladium acetate, and the dosage of the palladium catalyst is 1-5 mol.% of benzophenone.

4. The method for preparing 9-fluorenone according to claim 1, characterized in that: The silver promoter is selected from any one or more of silver oxide, silver nitrate, silver chloride, silver carbonate and silver oxalate, and the amount of the silver promoter is 0.05-15 mol of benzophenone.

5. The method for preparing 9-fluorenone according to claim 4, characterized in that: The silver co-catalyst is silver oxide, and the amount of the silver co-catalyst is 1-5 mol.% of benzophenone.

6. The method for preparing 9-fluorenone according to claim 1, characterized in that: The acidic medium is selected from any one or more of acetic acid, propionic acid, trifluoroacetic acid, methanesulfonic acid and trifluoromethanesulfonic acid.

7. The method for preparing 9-fluorenone according to claim 6, characterized in that: The acidic medium is trifluoroacetic acid.

8. The method for preparing 9-fluorenone according to claim 1, characterized in that: The oxidant is air or oxygen. When the oxidant is oxygen, the oxygen pressure is 0.5 to 1.0 atmosphere.

9. The method for preparing 9-fluorenone according to claim 1, characterized in that: The reaction temperature is 50-200° C., and the reaction time is 2-24 hours.

10. The method for preparing 9-fluorenone according to claim 9, characterized in that: The reaction temperature is 100-160° C. and the reaction time is 6-12 hours.

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