Synthesis of camphorquinone

Abstract

The application discloses a camphorquinone synthesis method and belongs to the field of organic chemistry. The camphorquinone synthesis method adopts a 3-bromocamphor air oxidation process, and the catalyst used comprises 2,2,6,6-tetramethylpiperidine N-oxide. In the presence of oxygen, 2,2,6,6-tetramethylpiperidine N-oxide can catalyze oxygen to oxidize iodine camphor to generate camphorquinone and iodine, and has high catalytic efficiency; when the feeding amount of 3-bromocamphor increases (for example, greater than 20g), the camphorquinone can still maintain high yield and purity; it is non-toxic and non-polluting; it can be recycled, and even if recycled more than 10 times, the yield of camphorquinone will not be reduced; it is suitable for being detected by using a gas chromatography method or a mass spectrometry method, and thus the purity of camphorquinone can be conveniently and accurately detected.

Description

Technical Field

[0001] This invention relates to the field of organic chemistry, and in particular to a method for synthesizing camphorquinone. Background Technology

[0002] DL-camphorquinone (abbreviated as camphorquinone), also known as 1,7,7-trimethylbicyclo[2.2.1]heptane-2,3-dione, is not only a highly efficient and low-toxicity photoinitiator, but also an important chiral intermediate. The synthesis methods of DL-camphorquinone include the following: selenium dioxide synthesis, selenium oxidation synthesis, 3-diazocamphor method, and 3-bromocamphor air oxidation method.

[0003] The air oxidation method of 3-bromocamphor is based on the oxidation of 3-bromocamphor in the presence of sodium iodide to form camphorquinone. The catalysts used in the air oxidation method of 3-bromocamphor are usually cobalt acetate, manganese acetate, or metal porphyrin.

[0004] However, the currently disclosed air oxidation method for 3-bromocamphor exhibits high product yield and purity with small feed amounts. However, once the feed amount is increased (e.g., greater than 20g), even with increased oxygen flux and extended reaction time, the reaction yield remains low. Furthermore, cobalt acetate and manganese acetate are toxic and cause environmental pollution; and the different light absorption intensities of metalloporphyrins and camphorquinone make it difficult to accurately detect the impurity content in the reaction products (i.e., product purity is difficult to determine). Summary of the Invention

[0005] In view of this, the present invention provides a method for synthesizing camphorquinone, which can solve the above-mentioned technical problems.

[0006] Specifically, the following technical solutions are included:

[0007] A method for synthesizing camphor quinone, wherein the method employs an air oxidation process with 3-bromocamphor and the catalyst used comprises 2,2,6,6-tetramethylpiperidine nitride.

[0008] In some possible implementations, the catalyst further includes potassium iodide and / or sodium iodide.

[0009] In some possible implementations, the catalyst is a combination of 2,2,6,6-tetramethylpiperidine nitride and potassium iodide.

[0010] In some possible implementations, the molar amount of 2,2,6,6-tetramethylpiperidine N-oxide is 0.05 to 0.1 times the molar amount of the reactant 3-bromocamphor;

[0011] The molar amount of potassium iodide is 1 to 1.2 times the molar amount of the reactant 3-bromocamphor.

[0012] In some possible implementations, the method for synthesizing camphorquinone includes the following steps:

[0013] Dissolve at least one of 3-bromocamphor, potassium iodide, and sodium iodide in a solvent to obtain a first mixed solution;

[0014] The first mixed solution is mixed evenly with 2,2,6,6-tetramethylpiperidine nitride to obtain a second mixed solution;

[0015] Air is introduced into the second mixed solution while the reaction system is heated to the reaction temperature to carry out the reaction.

[0016] After the reaction was completed, the reaction product system was separated to obtain camphorquinone.

[0017] In some possible implementations, during the reaction process, the 3-bromocamphor in the reaction system is detected by gas chromatography or mass spectrometry to determine the reaction endpoint.

[0018] In some possible implementations, the air flow rate is 1L / h to 12L / h for every 20g-250g of 3-bromocamphor.

[0019] In some possible implementations, the reaction temperature is 140°C-160°C.

[0020] In some possible implementations, the separation of the reaction product system includes:

[0021] The reaction product system was extracted to obtain an organic phase;

[0022] The organic phase was sequentially washed with water, dried, subjected to rotary evaporation to remove the extractant, and recrystallized with anhydrous ethanol to obtain camphorquinone.

[0023] In some possible implementations, after recrystallization of the anhydrous ethanol, the mother liquor is collected, the solvent in the mother liquor is removed, and 2,2,6,6-tetramethylpiperidine nitride is obtained.

[0024] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0025] This invention employs an air oxidation process of 3-bromocamphor to prepare camphor quinone. In other words, some of the preparation procedures involved in conventional 3-bromocamphor air oxidation processes are suitable for this invention. Specifically, unlike related technologies, the 3-bromocamphor air oxidation process of this invention uses 2,2,6,6-tetramethylpiperidine nitride as a catalyst, which has at least the following advantages: In the presence of oxygen, 2,2,6,6-tetramethylpiperidine nitride can catalyze the oxidation of iodine camphor to camphor quinone and iodine, exhibiting high catalytic efficiency; when the amount of 3-bromocamphor added increases (e.g., greater than 20g), the yield and purity of camphor quinone can still be maintained at a high level; it is non-toxic and pollution-free; it can be repeatedly recycled, and even after being recycled more than 10 times, the yield of camphor quinone will not decrease; it is suitable for detection by gas chromatography or mass spectrometry, thus allowing the purity of camphor quinone to be conveniently and accurately detected. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] DL-camphorquinone (abbreviated as camphorquinone) has been prepared using the air oxidation method of 3-bromocamphor. The chemical structural formula of 3-bromocamphor is shown below:

[0028]

[0029] The chemical structural formula of DL-camphorquinone is shown below:

[0030]

[0031] The currently disclosed method for preparing DL-camphorquinone by air oxidation of 3-bromocamphor has at least the following technical problems:

[0032] When the feed amount is small, the product yield and purity are both high. However, once the feed amount is increased (e.g., greater than 20g), even with increased oxygen flux and extended reaction time, the reaction yield remains low. Furthermore, cobalt acetate and manganese acetate, used as catalysts, are toxic and cause environmental pollution. The different light absorption intensities of metalloporphyrin and camphorquinone, also used as catalysts, make it difficult to accurately detect the impurity content in the reaction products (i.e., product purity is difficult to determine).

[0033] To address the aforementioned technical problems, embodiments of the present invention provide a method for synthesizing camphor quinone. This method employs an air oxidation process with 3-bromocamphor, and the catalyst used includes 2,2,6,6-tetramethylpiperidinooxy (TEMPO).

[0034] This invention employs a 3-bromocamphor air oxidation process to prepare camphor quinone. In other words, some of the preparation procedures involved in conventional 3-bromocamphor air oxidation processes are suitable for this invention. Specifically, unlike related technologies, the 3-bromocamphor air oxidation process of this invention uses 2,2,6,6-tetramethylpiperidine nitride as a catalyst, which has at least the following advantages:

[0035] In the presence of oxygen, 2,2,6,6-tetramethylpiperidine N-oxide can catalyze the oxidation of iodine camphor to camphorquinone and iodine with high catalytic efficiency. When the amount of 3-bromocamphor added increases (e.g., more than 20g), camphorquinone can still maintain a high yield and purity. It is non-toxic and pollution-free. It can be repeatedly recycled, and even if it is reused more than 10 times, the yield of camphorquinone will not decrease. It is suitable for detection by gas chromatography or mass spectrometry, so that the purity of camphorquinone can be conveniently and accurately detected.

[0036] In the preparation of camphorquinone based on the air oxidation process of 3-bromocamphor, the catalyst may include not only 2,2,6,6-tetramethylpiperidine nitride, but also potassium iodide and / or sodium iodide. This allows the iodine in potassium or sodium iodide to first replace the bromine in 3-bromocamphor, resulting in more easily oxidized iodinated camphor. Then, in the presence of oxygen, 2,2,6,6-tetramethylpiperidine nitride catalyzes the oxidation of iodinated camphor to camphorquinone and iodine.

[0037] In some examples, the catalyst provided in the embodiments of the present invention is a combination of 2,2,6,6-tetramethylpiperidine nitride and potassium iodide.

[0038] Potassium iodide is cheaper than sodium iodide. In this embodiment of the invention, potassium iodide, which is inexpensive and readily available, is used instead of sodium iodide. This not only reduces production costs but also ensures that the yield of camphorquinone remains unchanged.

[0039] To achieve better catalytic performance while controlling the amount of catalyst used, the molar amount of 2,2,6,6-tetramethylpiperidine N-oxide is 0.05 to 0.1 times the molar amount of the reactant 3-bromocamphor, for example, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1 times. The molar amount of potassium iodide is 1 to 1.2 times the molar amount of the reactant 3-bromocamphor, for example, 1, 1.05, 1.08, 1.1, 1.12, 1.15, 1.17, or 1.8 times.

[0040] The specific operational steps involved in the synthesis of camphorquinone are described below by way of example:

[0041] Step 1: Dissolve at least one of 3-bromocamphor, potassium iodide, and sodium iodide in a solvent to obtain a first mixed solution.

[0042] For example, 3-bromocamphor and potassium iodide are dissolved in a solvent to obtain a first mixed solution.

[0043] 3-Bromocamphor reacts with potassium iodide or sodium iodide in a solvent to produce iodocamphor. In other words, the first mixed solution includes not only the solvent but also iodocamphor.

[0044] The solvents applicable to the embodiments of the present invention include, but are not limited to, solvents without hydroxyl groups and halogen leakage such as dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAC), which enable the raw materials in the reaction solution to be uniformly dispersed.

[0045] Step 2: Mix the first mixed solution with 2,2,6,6-tetramethylpiperidine nitride to obtain the second mixed solution.

[0046] The first mixed solution can be obtained in a reaction flask, such as a three-necked flask, and correspondingly, the second mixed solution can be obtained in the same reaction flask.

[0047] Place 2,2,6,6-Tetramethylpiperidine N-oxide in a reaction flask containing the first mixed solution and stir until homogeneous to obtain the second mixed solution.

[0048] In some examples, the catalyst provided in the embodiments of the present invention is a composition of 2,2,6,6-tetramethylpiperidine nitride and potassium iodide. The molar amount of 2,2,6,6-tetramethylpiperidine nitride is 0.05 to 0.1 times the molar amount of the reactant 3-bromocamphor, and the molar amount of potassium iodide is 1 to 1.2 times the molar amount of the reactant 3-bromocamphor.

[0049] Step 3: Introduce air into the second mixed solution while heating the reaction system to the reaction temperature to carry out the reaction.

[0050] In step 3, oxygen is provided by bubbling air into the second mixed solution. In the presence of oxygen, 2,2,6,6-tetramethylpiperidine nitride can catalyze the oxidation of iodine camphor to camphorquinone and iodine.

[0051] As mentioned above, the second mixed solution is obtained in a reaction flask, so air can be introduced into the reaction flask to dissolve it in the second mixed solution.

[0052] The air flow rate is appropriately increased according to the amount of 3-bromocamphor fed. For example, for every 20g-250g of 3-bromocamphor, the air flow rate is 1L / h-12L / h.

[0053] To give a further example, when the amount of 3-bromocamphor added is in the range of 20g-150g, the flow rate of the air introduced is 1L / h-5L / h; and,

[0054] When the amount of 3-bromocamphor fed is in the range of 150g-250g, the air flow rate is 5L / h-12L / h.

[0055] The above relationship between the amount of 3-bromocamphor fed and the air flow rate shows that a higher air flow rate is beneficial to increasing the reaction yield of camphorquinone.

[0056] For example, when the air flow rate is 1L / h-12L / h, this includes, but is not limited to, the following: 1L / h, 2L / h, 3L / h, 4L / h, 5L / h, 6L / h, 7L / h, 8L / h, 9L / h, 10L / h, 11L / h, 12L / h, etc.

[0057] The applicable reaction temperature for the above catalytic reaction is 140℃-160℃, including but not limited to: 140℃, 145℃, 150℃, 155℃, 160℃, etc. The reaction time is 3h-8h, including but not limited to: 3h, 4h, 5h, 6h, 7h, 8h, etc.

[0058] During the reaction, gas chromatography or mass spectrometry is used to detect 3-bromocamphor in the reaction system to determine the reaction endpoint.

[0059] In other words, the reaction can be stopped when the detection amount of 3-bromocamphor reaches a set threshold. Ideally, this set threshold should be 0, meaning the reaction should stop when GC (gas chromatography) does not detect the presence of 3-bromocamphor in the reaction system. However, a detection amount of 0 does not mean that no 3-bromocamphor is present in the reaction product system; trace amounts may still be present, just below the detectable threshold. These trace amounts of residual 3-bromocamphor can be easily removed by separation methods.

[0060] Testing revealed that, using the synthesis method provided in this invention, the reaction conversion rate of 3-bromocamphor was above 95%, even reaching 100%. The purity of camphorquinone was above 98%, even reaching 99.56%, and the yield of camphorquinone was above 95%, even reaching 99.5%.

[0061] Step 4: After the reaction is complete, the reaction product system is separated to obtain camphorquinone.

[0062] In addition to camphorquinone, the reaction product system also includes iodine, catalyst, residual solvent and trace reactants. High-purity camphorquinone is obtained by separating and processing the reaction product system.

[0063] In some examples, the reaction product system is separated, including the following steps:

[0064] Step 41: Extract the reaction product system to obtain the organic phase.

[0065] The extractant used during extraction can be a solvent with a density less than water, immiscible with water, and capable of dissolving camphorquinone, such as ethyl acetate or toluene.

[0066] For example, the extractant is ethyl acetate. Furthermore, ethyl acetate is mixed with a saturated sodium thiosulfate solution to obtain even better extraction results. This is because saturated sodium thiosulfate can reduce iodine in the reaction product system to iodide ions, which are then dissolved in water for removal.

[0067] The extraction operation can be performed once or multiple times.

[0068] Step 42: The organic phase is washed with water, dried with anhydrous sodium sulfate, removed by rotary evaporation to remove the extractant, and recrystallized with anhydrous ethanol to obtain camphorquinone.

[0069] When washing the organic phase with water, pure water can be used, and the washing can be performed multiple times, such as 2, 3, 4, 5 or more times.

[0070] After washing the organic phase with water, a small amount of water inevitably remains in the solvent and cannot be completely removed. Therefore, anhydrous sodium sulfate or anhydrous magnesium sulfate is added to the washed product for drying, followed by rotary evaporation to remove the solvent. Then, recrystallization is performed once or multiple times (e.g., twice, three times, four times, etc.) with anhydrous ethanol. This process precipitates camphorquinone, yielding high-purity camphorquinone. Meanwhile, 2,2,6,6-tetramethylpiperidine N-oxide and other impurities dissolve in ethanol, forming the mother liquor.

[0071] Understandably, the mother liquor contains 2,2,6,6-tetramethylpiperidine nitride, ethanol solvent, and some other impurities as provided in the feed. In particular, in this embodiment of the invention, after recrystallization with anhydrous ethanol, the mother liquor is collected, the solvent in the mother liquor is removed, and 2,2,6,6-tetramethylpiperidine nitride is obtained.

[0072] After solvent removal from the mother liquor, trace amounts of camphorquinone and 3-iodine camphor may remain. These camphorquinone and 3-iodine camphor are mixed into 2,2,6,6-tetramethylpiperidine nitride, but this does not affect the reuse of 2,2,6,6-tetramethylpiperidine nitride as a catalyst. Tests have shown that, compared to using 98% purity (analytical grade) 2,2,6,6-tetramethylpiperidine nitride, the yield and purity of camphorquinone do not decrease after 8, 9, 10, or more times of recycling and reuse.

[0073] In summary, the method for synthesizing DL-camphorquinone provided in the embodiments of the present invention has at least the following advantages:

[0074] The catalyst used is non-toxic and environmentally friendly, with high catalytic efficiency. Even when the feed amount is increased to more than 20g, camphorquinone can still achieve high yield and high production rate. Other reaction raw materials are safe, readily available, and inexpensive, which helps to reduce synthesis costs. It is also convenient for large-scale promotion and application.

[0075] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the examples, they are performed according to techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products. In the following examples, unless otherwise explicitly stated, "%" refers to mass percentage. 2,2,6,6-Tetramethylpiperidine nitride in the following examples is abbreviated as TEMPO.

[0076] Example 1

[0077] Take a three-necked flask and add 3-bromocamphor (200 mmol, 46.23 g) and potassium iodide (240 mmol, 39.84 g) to it. Then add 200 mL of dimethyl sulfoxide to the flask to dissolve the 3-bromocamphor and potassium iodide, obtaining the first mixed solution. After the first mixed solution becomes clear and transparent, add TEMPO (20 mmol, 3.13 g) to the three-necked flask.

[0078] Air was introduced into the three-necked flask using a glass tube at a flow rate of 1.5 L / h. The mixture was stirred and heated to 160 °C. After 3 hours, heating was stopped when 3-bromocamphor was no longer detected by gas chromatography. The conversion rate was found to be 98%.

[0079] Extraction was performed in a three-necked flask using 200 mL of ethyl acetate and 200 mL of saturated sodium thiosulfate (Na₂S₂O₃), and the organic phase was collected. The organic phase was then washed five times with water, dried over anhydrous sodium sulfate, the solvent was removed by rotary evaporation, and it was recrystallized twice with anhydrous ethanol. After final drying, 31.7 g of a yellow powdery solid camphorquinone was obtained. The yield was 95.36%, and the purity of the camphorquinone sample was 98.41% as determined by HPLC.

[0080] Example 2

[0081] Take a three-necked flask and add 3-bromocamphor (1 mol, 231.13 g) and potassium iodide (1.2 mol, 199.2 g) to it. Then add 1000 mL of dimethyl sulfoxide to the flask to dissolve the 3-bromocamphor and potassium iodide, obtaining the first mixed solution. After the first mixed solution becomes clear and transparent, add TEMPO (100 mmol, 15.65 g) to the three-necked flask.

[0082] The liquid in the three-necked flask was bubbled with air through a glass tube at a flow rate of 10 L / h. The mixture was stirred and heated to 160 °C for 6 h. Heating was stopped when 3-bromocamphor was no longer detected by gas chromatography. The reaction conversion rate was found to be 99%.

[0083] Extraction was performed in a three-necked flask using 1 L of ethyl acetate and 1 L of saturated sodium thiosulfate, and the organic phase was collected. The organic phase was then washed five times with water, dried over anhydrous sodium sulfate, the solvent was removed by rotary evaporation, and it was recrystallized three times with anhydrous ethanol. After final drying, 159.74 g of a yellow powdery solid camphorquinone was obtained, with a yield of 96.1%. HPLC analysis showed the purity of the camphorquinone sample to be 99.29%.

[0084] In addition, after recrystallization from anhydrous ethanol, the mother liquor was collected, the solvent in the mother liquor was removed, and 2,2,6,6-tetramethylpiperidine nitride was obtained as a catalyst for later use.

[0085] Example 3

[0086] Take a three-necked flask and add 1 mol of 3-bromocamphor (231.13 g) and 1.0 mol of potassium iodide (166.02 g). Then, add 1000 mL of dimethyl sulfoxide to the flask to dissolve the 3-bromocamphor and potassium iodide, obtaining a first mixed solution. After the first mixed solution becomes clear and transparent, continue adding TEMPO recovered in Example 2 to the three-necked flask. The amount of TEMPO added is the same as in Example 2.

[0087] The liquid in the three-necked flask was bubbled with air through a glass tube at a flow rate of 10 L / h. The mixture was stirred and heated to 160 °C for 6 h. Heating was stopped when 3-bromocamphor was no longer detected by gas chromatography. The reaction conversion rate was found to be 99.5%.

[0088] Using the same separation method as shown in Example 2, 160.92 g of yellow powdery solid camphorquinone was obtained, with a yield of 96.8%. HPLC analysis showed the purity of the camphorquinone sample to be 99.36%.

[0089] After recrystallization from anhydrous ethanol, the mother liquor was collected, and the solvent in the mother liquor was removed to obtain 2,2,6,6-tetramethylpiperidine nitride, which was used as a catalyst.

[0090] Example 4

[0091] Take a three-necked flask, add 3-bromocamphor (1 mol, 231.13 g) and potassium iodide (1.05 mol, 174.33 g) to the three-necked flask, and then dissolve it with 1050 mL of dimethyl sulfoxide. After the first mixed solution is clear and transparent, continue to add TEMPO recovered in Example 3 to the three-necked flask.

[0092] The liquid in the three-necked flask was bubbled with air through a glass tube at a flow rate of 10 L / h. The mixture was stirred and heated to 160 °C for 6 h. Heating was stopped when no unreacted 3-bromocamphor was detected by gas chromatography. The reaction conversion rate was found to be 98.5%.

[0093] Using the same separation method as shown in Example 2, 161.58 g of yellow powdery solid camphorquinone was obtained, with a yield of 97.2%. HPLC analysis showed the purity of the camphorquinone sample to be 98.91%.

[0094] After recrystallization from anhydrous ethanol, the mother liquor was collected, and the solvent in the mother liquor was removed to obtain 2,2,6,6-tetramethylpiperidine nitride, which was used as a catalyst.

[0095] Example 5

[0096] Take a three-necked flask, add 3-bromocamphor (1 mol, 231.13 g) and potassium iodide (1.1 mol, 182.63 g) to the flask, and then dissolve it with 1000 mL of dimethyl sulfoxide. After the first mixed solution is clear and transparent, continue to add TEMPO recovered in Example 4 to the three-necked flask.

[0097] The liquid in the three-necked flask was bubbled with air through a glass tube at a flow rate of 10 L / h. The mixture was stirred and heated to 160 °C for 8 hours. Heating was stopped when 3-bromocamphor was no longer detected by gas chromatography. The reaction conversion rate was found to be 100%.

[0098] Using the same separation method as shown in Example 2, 165.34 g of yellow powdery solid camphorquinone was obtained, with a yield of 99.5%. HPLC analysis showed the purity of the camphorquinone sample to be 99.17%.

[0099] After recrystallization from anhydrous ethanol, the mother liquor was collected, and the solvent in the mother liquor was removed to obtain 2,2,6,6-tetramethylpiperidine nitride, which was used as a catalyst.

[0100] Example 6

[0101] Take a three-necked flask, add 3-bromocamphor (1 mol, 231.13 g) and potassium iodide (1.15 mol, 190.93 g) to the flask, and then dissolve it with 900 mL of dimethyl sulfoxide. After the first mixed solution is clear and transparent, continue to add TEMPO recovered in Example 5 to the three-necked flask.

[0102] The liquid in the three-necked flask was bubbled with air through a glass tube at a flow rate of 10 L / h. The mixture was stirred and heated to 140 °C for 5 h. Heating was stopped when 3-bromocamphor was no longer detected by gas chromatography. The reaction conversion rate was found to be 98%.

[0103] Using the same separation method as shown in Example 2, 158.11 g of yellow powdery solid camphorquinone was obtained, with a yield of 95.1%. HPLC analysis showed the purity of the camphorquinone sample to be 99.44%.

[0104] After recrystallization from anhydrous ethanol, the mother liquor was collected, and the solvent in the mother liquor was removed to obtain 2,2,6,6-tetramethylpiperidine nitride, which was used as a catalyst.

[0105] Example 7

[0106] Take a three-necked flask, add 3-bromocamphor (1 mol, 231.13 g) and potassium iodide (1.2 mol, 199.23 g) to the flask, and then dissolve it with 800 mL of dimethyl sulfoxide. After the first mixed solution is clear and transparent, continue to add TEMPO recovered in Example 6 to the three-necked flask.

[0107] The liquid in the three-necked flask was bubbled with air through a glass tube at a flow rate of 10 L / h. The mixture was stirred and heated to 160 °C for 3 h. Heating was stopped when 3-bromocamphor was no longer detected by gas chromatography. The reaction conversion rate was found to be 96.8%.

[0108] Using the same separation method as shown in Example 2, 160.04 g of yellow powdery solid camphorquinone was obtained, with a yield of 96.3%. HPLC analysis showed the purity of the camphorquinone sample to be 99.29%.

[0109] After recrystallization from anhydrous ethanol, the mother liquor was collected, and the solvent in the mother liquor was removed to obtain 2,2,6,6-tetramethylpiperidine nitride, which was used as a catalyst.

[0110] Example 8

[0111] Take a three-necked flask, add 3-bromocamphor (1 mol, 231.13 g) and potassium iodide (1.1 mol, 182.63 g) to the flask, and then dissolve it with 1200 mL of dimethyl sulfoxide. After the first mixed solution is clear and transparent, continue to add TEMPO recovered in Example 7 to the three-necked flask.

[0112] The liquid in the three-necked flask was bubbled with air through a glass tube at a flow rate of 10 L / h. The mixture was stirred and heated to 160 °C for 4 h. Heating was stopped when 3-bromocamphor was no longer detected by gas chromatography. The reaction conversion rate was found to be 96.5%.

[0113] Using the same separation method as shown in Example 2, 159.19 g of yellow powdery solid camphorquinone was obtained, with a yield of 95.8%. HPLC analysis showed the purity of the camphorquinone sample to be 99.03%.

[0114] After recrystallization from anhydrous ethanol, the mother liquor was collected, and the solvent in the mother liquor was removed to obtain 2,2,6,6-tetramethylpiperidine nitride, which was used as a catalyst.

[0115] Example 9

[0116] Take a three-necked flask, add 3-bromocamphor (500 mmol, 115.57 g) and potassium iodide (600 mmol, 99.62 g) to the three-necked flask, and then dissolve it with 500 mL of dimethyl sulfoxide. After the first mixed solution is clear and transparent, continue to add 50% of the molar amount of TEMPO recovered in Example 8 to the three-necked flask.

[0117] The liquid in the three-necked flask was bubbled with air through a glass tube at a flow rate of 5 L / h. The mixture was stirred and heated to 160°C for 6 hours. Heating was stopped when 3-bromocamphor was no longer detected by gas chromatography. The reaction conversion rate was found to be 100%.

[0118] Extraction was performed in a three-necked flask using 500 mL of ethyl acetate and 500 mL of saturated sodium thiosulfate, and the organic phase was collected. The organic phase was then washed five times with water, dried over anhydrous sodium sulfate, the solvent was removed by rotary evaporation, and it was recrystallized three times with anhydrous ethanol, finally yielding 81.64 g of a yellow powdery solid camphorquinone. The yield was 98.2%. HPLC analysis showed the purity of the camphorquinone sample to be 99.20%.

[0119] After recrystallization from anhydrous ethanol, the mother liquor was collected, and the solvent in the mother liquor was removed to obtain 2,2,6,6-tetramethylpiperidine nitride, which was used as a catalyst.

[0120] Example 10

[0121] Take a three-necked flask, add 3-bromocamphor (500 mmol, 115.57 g) and potassium iodide (600 mol, 99.62 g) to the flask, and then dissolve it with 500 mL of dimethyl sulfoxide. After the first mixed solution is clear and transparent, continue to add TEMPO recovered in Example 9 to the three-necked flask.

[0122] The liquid in the three-necked flask was bubbled with air through a glass tube at a flow rate of 5 L / h. The mixture was stirred and heated to 140°C for 3.5 h. Heating was stopped when 3-bromocamphor was no longer detected by gas chromatography. The reaction conversion rate was found to be 97%.

[0123] Using the same separation method as shown in Example 9, 79.52 g of yellow powdery solid camphorquinone was obtained, with a yield of 95.7%; HPLC analysis showed that the purity of the camphorquinone sample was 98.69%.

[0124] The above description is merely for the purpose of enabling those skilled in the art to understand the technical solutions of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for synthesizing camphorquinone, characterized in that, The method for synthesizing camphor quinone employs the air oxidation process of 3-bromocamphor, and the catalysts used are potassium iodide and 2,2,6,6-tetramethylpiperidine nitrogen oxides. The molar amount of 2,2,6,6-tetramethylpiperidine N-oxide is 0.05 to 0.1 times the molar amount of the reactant 3-bromocamphor; The molar amount of potassium iodide is 1 to 1.2 times the molar amount of the reactant 3-bromocamphor.

2. The method for synthesizing camphorquinone according to claim 1, characterized in that, The method for synthesizing camphorquinone includes the following steps: Dissolve at least one of potassium iodide and sodium iodide, along with 3-bromocamphor, in a solvent to obtain a first mixed solution; The first mixed solution is mixed evenly with 2,2,6,6-tetramethylpiperidine nitride to obtain a second mixed solution; Air is introduced into the second mixed solution while the reaction system is heated to the reaction temperature to carry out the reaction. After the reaction was completed, the reaction product system was separated to obtain camphorquinone.

3. The method for synthesizing camphorquinone according to claim 2, characterized in that, During the reaction, the 3-bromocamphor in the reaction system is detected by gas chromatography or mass spectrometry to determine the reaction endpoint.

4. The method for synthesizing camphorquinone according to claim 2, characterized in that, For every 20g-250g of 3-bromocamphor, the air flow rate is 1L / h-12L / h.

5. The method for synthesizing camphorquinone according to claim 2, characterized in that, The reaction temperature is 140℃-160℃.

6. The method for synthesizing camphorquinone according to claim 2, characterized in that, The separation process of the reaction product system includes: The reaction product system was extracted to obtain an organic phase; The organic phase was sequentially washed with water, dried, subjected to rotary evaporation to remove the extractant, and recrystallized with anhydrous ethanol to obtain camphorquinone.

7. The method for synthesizing camphorquinone according to claim 6, characterized in that, After recrystallization of the anhydrous ethanol, the mother liquor is collected, and the solvent in the mother liquor is removed to obtain 2,2,6,6-tetramethylpiperidine nitride.

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