A process for the preparation of 2-adamantanone

Abstract

The application discloses a preparation method of 2-adamantanone and belongs to the technical field of chemical synthesis. The steps are as follows: adamantane is mixed with sulfuric acid to generate a mixture of 2-adamantanone, 2-adamantanone and adamantane, ice water is added to cool the mixture, and dichloromethane is used for extraction; the organic phase is added to a solvent, and then an oxidant and a catalytic system are added to perform an oxidation reaction to obtain 2-adamantanone. The application uses a simple, inexpensive and green compound to replace sulfuric acid as an oxidant, reduces the sulfuric acid consumption, and reduces the generation of tar in the preparation process. The application has higher yield, better product quality and is more friendly to the environment. The overall preparation process of the application adopts a step-by-step reaction, which is compared with one-step synthesis, reduces the reaction harshness, has milder conditions and higher yield.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and more specifically to a method for preparing 2-adamantanone. Background Technology

[0002] Adamantane is a highly symmetrical, diamond-like cage-like compound that has seen rapid development and expanding applications in recent decades. Adamantane derivatives, due to their heat resistance and transparency, are widely used in semiconductors, optics, heat-resistant plastics, adhesives, cosmetics, and the medical field. 2-Adamantane ketone, as one of the important adamantane derivatives, has become an indispensable intermediate for many commodities and is increasingly important as a new generation of fine chemical raw materials.

[0003] Currently reported methods for synthesizing 2-adamantane mainly involve the oxidation of adamantane or 1-adamantaneol with sulfuric acid. This method consumes a large amount of sulfuric acid, generating a large volume of acidic waste liquid containing coke, which not only pollutes the environment but is also difficult to treat.

[0004] To address the issue of high sulfuric acid consumption, various optimization studies have been conducted on the original process:

[0005] The route provided by CN1980877 is to prepare 2-adamantanone by using adamantane or 1-adamantanol as raw materials and oxidizing them with oxidants that coexist with carboxylic acids or sulfonic acids and sulfuric acid.

[0006] The route provided in CN1980875 uses 1-adamantanol as a raw material, employs Lewis acid and solid acid catalysts as catalysts, and simultaneously uses carboxylic acid, sulfonic acid, or phosphoric acid compounds to oxidize and obtain 2-adamantanol and 2-adamantanone.

[0007] The route provided by CN102850199 uses alkane as raw material and replaces part of the concentrated sulfuric acid with sulfur trioxide gas or fuming sulfuric acid during the sulfuric acid oxidation process to maintain the sulfuric acid concentration at 90-95% by weight.

[0008] However, the above methods all use acid or acidic compounds to replace sulfuric acid, which still produces a large amount of waste acid during the reaction process and requires equipment with high corrosion resistance.

[0009] Therefore, providing a simple, safe, and environmentally friendly method for preparing 2-adamantanone is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0010] In view of this, the present invention provides a simple, safe and environmentally friendly method for preparing 2-adamantanone. The present invention uses adamantane as raw material, and oxidizes it with sulfuric acid at a low temperature to obtain a mixture of 2-adamantanol, 2-adamantanone and a small amount of adamantane, and then oxidizes it with an oxidant to obtain 2-adamantanone.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing 2-adamantanone includes the following steps: (1) Mix adamantane with sulfuric acid and heat the mixture in a water bath under the oxidation of sulfuric acid to produce a mixture of 2-adamantanol, 2-adamantanone and adamantane. After cooling the mixture with ice water, extract it with dichloromethane at least three times and combine the resulting organic phases. (2) The organic phase obtained in step (1) is added to the solvent, and then an oxidant and a catalytic system are added to carry out the oxidation reaction. After the reaction is completed, the organic phase is separated, and then the organic phase is washed and dried to remove the organic solvent, so as to obtain 2-adamantanone.

[0012] Furthermore, the mass fraction of sulfuric acid mentioned in step (1) is 95-98%; The mass ratio of adamantane to sulfuric acid is 1:(4-6).

[0013] The beneficial effects of adopting the above-mentioned further scheme are as follows: the amount of sulfuric acid used in this invention can promote the reaction to proceed in the forward direction and reduce the formation of by-products. Using high-concentration sulfuric acid can also suppress the decrease in reaction rate caused by the by-product water and reduce tar production.

[0014] Furthermore, the reaction temperature in step (1) is 30-100℃, preferably 30-80℃; the reaction time is 0.5-20h, preferably 2-10h.

[0015] The beneficial effect of adopting the above-mentioned further solution is that the above-mentioned solution defined by the present invention can not only meet the heat required for the reaction, but also avoid concentrated sulfuric acid from accelerating the corrosion rate due to high temperature, thereby corroding the equipment.

[0016] Furthermore, the oxidant in step (2) is a gas containing oxygen or hypochlorite.

[0017] Furthermore, the oxygen-containing gas is oxygen or air; The hypochlorite is any one or a mixture of sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, and lithium hypochlorite.

[0018] Furthermore, when the oxidant is an oxygen-containing gas, the catalytic system includes catalyst A, catalyst B, and catalyst C; Wherein, catalyst A has any one of the following structures:

[0019]

[0020]

[0021]

[0022] ; The catalyst B is any one or a mixture of more than one of nitric oxide, nitrogen dioxide, sodium nitrite, potassium nitrite and nitrite esters; The catalyst C is any one or a mixture of multiple of the following: bromide, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, hydrobromic acid, hydrofluoric acid, hydroiodic acid, methanesulfonic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, sodium bisulfate, potassium bisulfate, and sodium dihydrogen phosphate.

[0023] Furthermore, the amount of catalyst A used is 0.1-10% of the molar amount of adamantane, preferably 1-5%; The amount of catalyst B is 0.1-10% of the molar amount of adamantane, preferably 0.5-2%; The amount of catalyst C used is 0.1-10% of the molar amount of adamantane, preferably 1-5%.

[0024] The beneficial effects of adopting the above-mentioned further solution are as follows: the solution of the present invention uses oxygen and hypochlorite as oxidants, which are inexpensive, have good selectivity, high yield, and simple post-processing. The product can be obtained by simple water washing and concentration, thus realizing green and clean production.

[0025] Using 2,2,6,6-tetramethylpiperidine oxide and its derivatives as catalysts, a highly efficient oxidation process from alcohol to ketone can be achieved, with advantages of high yield and good selectivity.

[0026] Using the above dosage range satisfies the requirements of the oxidation reaction while avoiding excessive cost increases. If the dosage is too low, the oxidation effect will be insufficient, the reaction rate will be slow, the reaction time will be long, and the reaction may be incomplete; if the dosage is too high, the reaction cost will increase, making it uneconomical.

[0027] In this invention, catalyst A contains TEMPO-type nitrogen oxide radicals—the main catalytic selective oxidation core: it specifically targets the 2-adamantane alcohol hydroxyl group in the substrate, preferentially abstracting the α-H of the alcohol hydroxyl group to generate an alkoxy radical intermediate; it has extremely high selectivity for the oxidation of secondary alcohols to ketones, and hardly oxidizes the cage-like hydrocarbon skeleton (adamantane parent nucleus is stable and does not have side reactions), avoiding tar polymerization byproducts and ensuring the purity of the target product.

[0028] In catalyst B, NO / NO2 / nitrites act as an oxygen source for activation and a free radical mediator: they can undergo electron transfer with oxygen to activate molecular oxygen (solving the problem of oxygen's inertness at room temperature and difficulty in participating in reactions), generating active oxygen species; at the same time, they act as a "free radical relay station": receiving the deactivated intermediates after reaction A, completing the valence state cycle regeneration, and avoiding the rapid deactivation of the main catalyst A and the precipitous drop in catalytic efficiency.

[0029] Acid / bromine-based promoters in catalyst C—microenvironment regulation + interface activation: On the one hand, they provide an acidic microenvironment, improve the interfacial solubility of adamantanol substrates in the organic phase, and bring the substrates closer to the active catalytic sites; on the other hand, protons / bromine ions can assist in breaking hydroxyl OH bonds, reduce the activation energy of dehydrogenation reactions, and at the same time inhibit excessive free radical polymerization and reduce the generation of coking impurities.

[0030] The reaction logic of the three-way catalyst of the present invention includes: Oxygen source activation start-up: Catalyst B (nitrite / nitrogen oxides) preferentially reacts with the introduced oxygen / air, converting ground-state inert O2 into singlet-state active oxygen, establishing an "energy start-up threshold" for the oxidation reaction, allowing oxidation to occur under mild conditions without the need for high-temperature and highly corrosive operating conditions; Main catalytic selective dehydrogenation: The reaction microenvironment created by active oxygen and acidic promoter C allows catalyst A to accurately identify the secondary hydroxyl group of 2-adamantane alcohol, efficiently dehydrogenating it to generate 2-adamantane oxygen radicals, which are then directionally converted to ketone intermediates without any skeletal destruction side reactions.

[0031] Valence state regeneration: The reduced intermediate generated after the A catalytic reaction reacts again with reactive oxygen species under the mediation of catalyst B, realizing the in-situ regeneration cycle of TEMPO radicals; catalyst C continuously stabilizes the pH and ion concentration of the system, locks in the steady state of the free radical chain reaction, prevents catalyst poisoning and system deactivation, and extends the catalytic cycle life.

[0032] Oxygen / air is green and inexpensive, but its activity at room temperature is low, and TEMPO (A) alone cannot initiate the reaction. Without an acidic catalyst (C), the substrate solubility is poor and the reaction interface is blocked. The coupling of these three elements perfectly solves the three major industry pain points: oxygen source inertness, catalytic deactivation, and high byproduct levels. After being paired with a three-way catalytic converter, oxidation can be completed under low pressure, medium and low temperature conditions. It is matched with the low sulfuric acid pre-processing stage in the early stage, reducing dependence on strong acids and tar generation throughout the process. This not only improves the yield (above 89%), but also achieves green industrialization adaptability, which is a significant improvement over traditional single-acid oxidation and single-catalyst oxidation.

[0033] Furthermore, when the oxidant is hypochlorite, the catalytic system is at least one of the following structural formulas:

[0034]

[0035]

[0036]

[0037] .

[0038] Furthermore, the amount of catalyst used is 0.1-10% of the molar amount of adamantane, preferably 5-10%; The molar ratio of hypochlorite to adamantane is 1-5:1. Furthermore, the solvent mentioned in step (2) is any one or a mixture of dichloromethane, dichloroethane, toluene, xylene, chlorobenzene, chloroform, fluorobenzene, and trifluorotoluene; The oxidation reaction temperature is 0-100℃, preferably 0-50℃; the oxidation time is 0.5-24h, preferably 1-6h.

[0039] The beneficial effects of adopting the above-mentioned further solutions are as follows: the solvent used in this invention can uniformly disperse the reactants, promote the contact and mixing between the reactants, accelerate the reaction rate, and shorten the reaction time.

[0040] Selecting the above temperature range to complete the oxidation reaction can promote the forward reaction and reduce the occurrence of side reactions.

[0041] As can be seen from the above technical solution, compared with the prior art, this invention discloses a simple, safe, and environmentally friendly method for preparing 2-adamantanone. This invention uses a simple, inexpensive, and environmentally friendly compound to replace sulfuric acid as the oxidant, reducing the amount of sulfuric acid used and decreasing the generation of tar during the preparation process. This not only results in higher yield and better product quality but is also more environmentally friendly. The overall preparation process of this invention adopts a stepwise reaction, which, compared with the one-step synthesis method, reduces the harshness of the reaction, provides milder conditions, and achieves a higher yield.

[0042] In the present invention, a ternary system of catalyst A (TEMPO-type nitrogen oxide free radicals) + catalyst B (nitrite / nitrogen oxides) + catalyst C (acidic / bromine auxiliaries) is selected, which is precisely coupled with oxygen / oxygen-containing air sources to construct a free radical chain-like cyclic oxidation pathway. Each catalyst performs its own function and works synergistically at different levels, solving the problems of insufficient activity of single catalysts, difficulty in activating oxygen sources, and poor selectivity in alcohol-ketone conversion.

[0043] This invention features an innovative process architecture: a step-by-step reaction replaces a single-step oxidation, reducing reaction severity and increasing tolerance for errors. Simultaneously, the oxidation system is upgraded for environmental friendliness: using inexpensive oxygen sources and hypochlorite as the main oxidants, it reduces waste acid and tar byproducts at the source, meeting environmental compliance requirements for chemical production. The catalytic system is precisely tailored: a dedicated TEMPO-based catalytic system achieves highly selective oxidation of alcohols to ketones, improving product yield and quality. The solution boasts strong industrial adaptability: readily available raw materials and simple post-processing (washing + concentration and purification), balancing laboratory research and development with mass production. Attached Figure Description

[0044] Figure 1 The image shows the 1H NMR spectrum of 2-adamantanone prepared in Example 1 of this invention. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0046] Example 1 (1) Place 300g of 95% sulfuric acid in a 500mL three-necked flask, then add 50g of adamantane powder, heat in a water bath to 100℃, and keep stirring for 2h. Then pour the mixture obtained from the reaction into 400g of ice water, cool it, extract it three times with 50mL of dichloromethane, and then combine the organic phases.

[0047] (2) The obtained organic phase was placed in a three-necked flask, and 300 ml of dichloroethane and 3.2 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine nitric oxide radical (Formula 1) were added. The temperature was lowered to 0 °C, and 272.0 g of 20% sodium hypochlorite solution (0.72 mol) was added dropwise. After the addition was completed, the reaction was carried out at 0 °C for 6 h. After the reaction was stopped, the liquid was separated. The organic phase was washed three times with 10% sodium bisulfite aqueous solution, and then washed with water until neutral. After drying with anhydrous magnesium sulfate, the concentrate was concentrated to obtain 51.2 g of 2-adamantanone, with a yield of 91%.

[0048] Example 2 (1) Place 250g of 98% sulfuric acid in a 500mL three-necked flask, then add 50g of adamantane powder, heat in a water bath to 80℃, and keep stirring for 5h. Then pour the mixture into 400g of ice water, cool it, extract it three times with 50mL of dichloromethane, and combine the organic phases.

[0049] (2) The obtained organic phase was placed in a three-necked flask, and 300 ml of chlorobenzene and 6.2 g of 4-carbonyl-2,2,6,6-tetramethylpiperidine nitric oxide radical (Formula 2) were added. The temperature was raised to 50 °C, and 331.8 g of 20% potassium hypochlorite solution (0.367 mol) was added dropwise. After the addition was completed, the reaction was carried out at room temperature for 1 h. After the reaction was stopped, the liquid was separated. The organic phase was washed three times with 10% sodium thiosulfate aqueous solution, and then washed with water until neutral. After drying with anhydrous magnesium sulfate, the concentrate was concentrated to obtain 49.6 g of 2-adamantanone, with a yield of 90%.

[0050] Example 3 (1) Place 200g of 98% sulfuric acid in a 500mL three-necked flask, then add 50g of adamantane powder, heat in a water bath to 30℃, and keep stirring for 10h. Then pour the mixture into 400g of ice water, cool it, extract it three times with 50mL of dichloromethane, and combine the organic phases.

[0051] (2) The organic phase obtained in the previous step was added to a 500 mL high-pressure reactor and dissolved in 300 mL of dichloromethane. Then, 0.6 g of catalyst (Formula 15), 0.5 mL of hydrochloric acid (25 wt% solution), and 0.25 g of sodium nitrite were added. Oxygen was continuously introduced at 1 MPa and the reaction was stirred at 30 °C for 3 h. After the reaction was completed, the mixture was washed with water to separate the organic phase. After drying with anhydrous sodium sulfate, the organic solvent was removed by distillation to obtain 49.2 g of 2-adamantanone, with a yield of 89%.

[0052] Comparative Example 1100 g of 98% sulfuric acid was placed in a 1 L three-necked flask, and then 100 g of adamantane powder was added. The mixture was heated in a water bath to 80 °C with stirring. After reacting for 2 h, the mixture was poured into 800 g of ice water, cooled, and extracted three times with 100 mL of dichloromethane. The organic phases were combined, washed with 100 mL of saturated sodium chloride aqueous solution, dried over anhydrous sodium sulfate, and the organic solvent was removed by vacuum distillation to obtain 53.2 g of 2-adamantanone, with a yield of 48%.

[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing 2-adamantanone, characterized in that, Includes the following steps: (1) Mix adamantane with sulfuric acid, and under the oxidation of sulfuric acid, heat the mixture in a water bath to produce a mixture of 2-adamantanol, 2-adamantanone and adamantane. After cooling the mixture with ice water, extract it with dichloromethane at least three times and combine the resulting organic phases. (2) The organic phase obtained in step (1) is added to the solvent, and then an oxidant and a catalytic system are added to carry out the oxidation reaction. After the reaction is completed, the organic phase is separated, and then the organic phase is washed and dried to remove the organic solvent, so as to obtain 2-adamantanone.

2. The method for preparing 2-adamantanone according to claim 1, characterized in that, The sulfuric acid in step (1) has a mass fraction of 95-98%; The mass ratio of adamantane to sulfuric acid is 1:(4-6).

3. The method for preparing 2-adamantanone according to claim 2, characterized in that, The reaction temperature in step (1) is 30-100℃; the reaction time is 0.5-20h.

4. The method for preparing 2-adamantanone according to claim 1, characterized in that, The oxidant in step (2) is a gas containing oxygen or hypochlorite.

5. The method for preparing 2-adamantanone according to claim 4, characterized in that, The oxygen-containing gas is oxygen or air; The hypochlorite is any one or a mixture of sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, and lithium hypochlorite.

6. The method for preparing 2-adamantanone according to claim 4, characterized in that, When the oxidant is an oxygen-containing gas, the catalytic system includes catalyst A, catalyst B, and catalyst C; Wherein, catalyst A has any one of the following structures: ； The catalyst B is any one or a mixture of more than one of nitric oxide, nitrogen dioxide, sodium nitrite, potassium nitrite and nitrite esters; The catalyst C is any one or a mixture of multiple of the following: bromide, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, hydrobromic acid, hydrofluoric acid, hydroiodic acid, methanesulfonic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, sodium bisulfate, potassium bisulfate, and sodium dihydrogen phosphate.

7. The method for preparing 2-adamantanone according to claim 6, characterized in that, The amount of catalyst A used is 0.1-10% of the molar amount of adamantane; The amount of catalyst B used is 0.1-10% of the molar amount of adamantane; The amount of catalyst C used is 0.1-10% of the molar amount of adamantane.

8. The method for preparing 2-adamantanone according to claim 4, characterized in that, When the oxidant is hypochlorite, the catalytic system is at least one of the following structural formulas: 。 9. The method for preparing 2-adamantanone according to claim 8, characterized in that, The amount of catalyst used is 0.1-10% of the molar amount of adamantane; The molar ratio of hypochlorite to adamantane is 1-5:

1.

10. The method for preparing 2-adamantanone according to claim 1, characterized in that, The solvent mentioned in step (2) is any one or a mixture of dichloromethane, dichloroethane, toluene, xylene, chlorobenzene, chloroform, fluorobenzene, and trifluorotoluene; The oxidation reaction is carried out at a temperature of 0-100℃ and for a time of 0.5-24h.

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