Catalysts, their preparation methods, and methods for preparing 6-methoxy-2-acetylnaphthalene

Abstract

This invention discloses a catalyst and its preparation method, as well as a method for preparing 6-methoxy-2-acetnaphthalene. The active component of the catalyst includes an inorganic metal salt, which comprises aluminum trichloride, ferrous chloride, and zinc chloride. The ratio of aluminum trichloride to ferrous chloride and zinc chloride is (7.5-17):(1.5-2):1. The catalyst of this invention can be used in the reaction for preparing 6-methoxy-2-acetnaphthalene, effectively increasing the yield of the 6-methoxy-2-acetnaphthalene product to over 85%, thus overcoming the problem of low product yield in existing methods for preparing 6-methoxy-2-acetnaphthalene.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical intermediate synthesis technology, specifically relating to catalysts and their preparation methods, and methods for preparing 6-methoxy-2-acetylnaphthalene. Background Technology

[0002] 6-Methoxy-2-acetylnaphthalene is a pharmaceutical intermediate used in the synthesis of the antipyretic and analgesic drugs naproxen (Xiaotongning) and nabumetone. Naproxen (Xiaotongning) and nabumetone have 10 times greater anti-inflammatory effects than phenylbutazone, and 8 to 20 times greater antipyretic and analgesic effects than aspirin, making them suitable for various inflammations and pains.

[0003] Document CN101270040A discloses a method for producing 6-methoxy-2-acetnaphthalene, but this method has the problem of low product yield, with the finished product yield being below 70%.

[0004] Therefore, it is necessary to improve the method for preparing 6-methoxy-2-acetylnaphthalene. Summary of the Invention

[0005] The purpose of this invention is to provide a catalyst and its preparation method, as well as a method for preparing 6-methoxy-2-acetylnaphthalene. Using the catalyst of this invention in the method for preparing 6-methoxy-2-acetylnaphthalene can solve the problem of low product yield in existing methods for preparing 6-methoxy-2-acetylnaphthalene.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] The catalyst, the active component of which comprises an inorganic metal salt, including aluminum trichloride, ferrous chloride, and zinc chloride, wherein the mass ratio of aluminum trichloride to ferrous chloride and zinc chloride is (7.5-17):(1.5-2):1. The catalyst of this invention can be used in the preparation of 6-methoxy-2-acetnaphthalene, effectively increasing the yield of the 6-methoxy-2-acetnaphthalene product. The catalyst of this invention can increase the yield of the 6-methoxy-2-acetnaphthalene product to over 85%, thus improving the problem of low product yield in existing methods for preparing 6-methoxy-2-acetnaphthalene.

[0008] According to an embodiment of the present invention, the mass ratio of aluminum trichloride to ferrous chloride and zinc chloride is (7.5-17):(1.5-2):1. Aluminum trichloride, as the main component of a Lewis acid, can enhance its ability to attract electron pairs. Ferrous chloride can weaken the reaction of aluminum trichloride as a Lewis acid with water in solution to produce hydrogen chloride. Zinc chloride can maintain an acidic environment in the solution and adjust the pH. When the ratio of the three components is within the above range, the mixed Lewis acid can better exhibit its electrophilic ability, and the catalytic reaction is milder. If the content of aluminum trichloride is too low, it will lead to a weakened electrophilic ability. If the content of aluminum trichloride is too high, it will lead to the formation of cross-linked aluminum hydroxide with water. If the content of ferrous chloride is too low, it cannot effectively weaken the adverse effects of aluminum trichloride hydrolysis. If the content of ferrous chloride is too high, it will weaken the electrophilic ability as a Lewis acid. If the content of zinc chloride is too low, it will lead to a high pH in the solution environment, which cannot effectively inhibit the hydrolysis of aluminum trichloride to produce hydrogen chloride. If the zinc chloride content is too high, it can lead to adverse effects such as weakened electrophilicity. In other words, when aluminum trichloride, ferrous chloride, and zinc chloride are used as inorganic metal salts, and their contents are within the above-mentioned range, their electrophilicity in Lewis acid electrophilic addition can be effectively improved.

[0009] According to an embodiment of the present invention, the catalyst further includes a binder located between the inorganic metal salts; the binder is formed by crosslinking polymerization of borax and polyvinyl alcohol. This allows different types of inorganic metal salts to be tightly bonded together.

[0010] This invention does not limit the degree of polymerization or degree of hydrolysis of polyvinyl alcohol (PVA). Those skilled in the art can select the degree of polymerization and degree of hydrolysis of PVA according to their needs. For example, PVA with a degree of polymerization of 1700 and a degree of hydrolysis of 88% (i.e., PVA1788) can be used.

[0011] According to an embodiment of the present invention, for every 100 parts by mass of inorganic metal salt, the corresponding amount of borax solution is 2.5 to 5 parts by mass, and the corresponding amount of polyvinyl alcohol solution is 2.5 to 5 parts by mass. The borax solution is formed by dissolving borax in water, and the mass fraction of the borax solution is 4 to 6%. The polyvinyl alcohol solution is formed by dissolving polyvinyl alcohol in water, and the mass fraction of the polyvinyl alcohol solution is 4 to 6%. That is, the mass ratio of the borax solution to the inorganic metal salt is 2.5:100 to 5:100, and the mass ratio of the polyvinyl alcohol solution to the inorganic metal salt is 2.5:100 to 5:100; thus, the technical effect of cross-linking polymerization can be achieved. If the mass ratio of the borax solution to the inorganic metal salt, or the mass ratio of the polyvinyl alcohol solution to the inorganic metal salt, is too small, incomplete cross-linking will result. If the mass ratio of the borax solution to the inorganic metal salt is too large, excessive viscosity and moisture will result in a reduction of the effective components in the polymer. If the mass ratio of polyvinyl alcohol solution to inorganic metal salt is too high, it will lead to problems such as raw material waste, excessive product moisture, and reduced effective components.

[0012] According to embodiments of the present invention, the particle size of the catalyst is 40-200 mesh. Therefore, the catalyst of the present invention has a large surface area, which is beneficial to improving the catalytic effect, making the reaction more complete, and thus increasing the product yield. If the particle size of the catalyst is too small, the components cannot be effectively formed into a cross-linked polymer, and the catalytic effect of the catalyst cannot be maximized. If the particle size of the catalyst is too large, during use, due to the reduced contact area, there will be adverse problems such as reduced catalytic efficiency.

[0013] This invention also provides a method for preparing the catalyst described above. The method includes: mixing an inorganic metal salt with a polyvinyl alcohol solution, then adding a borax solution, wherein the polyvinyl alcohol and the borax undergo a crosslinking polymerization reaction to form a binder, the binder being located between the inorganic metal salts, thereby obtaining the catalyst. Thus, the catalyst prepared by this method possesses all the characteristics and advantages of the catalyst described above, which will not be repeated here. In summary, when the catalyst prepared by this method is used in the reaction for preparing 6-methoxy-2-acetenaphthalene, it can effectively improve the yield of the 6-methoxy-2-acetenaphthalene product.

[0014] Specifically, the metal ions in inorganic metal salts can interact with the hydroxyl groups in polyvinyl alcohol (PVA). Adding borax causes PVA to gel, thereby achieving cross-linking of different types of inorganic metal salts. In other words, the method of this application can tightly bond different types of inorganic metal salts together. Borax and PVA can cross-link to form a network structure, tightly encapsulating the inorganic metal salt powder. This network structure forms a larger polymer, and the cross-linked structure acts as a microporous framework. Active inorganic metal salts are filled into this microporous structure in appropriate proportions. When added to the reaction system, the various active components in the inorganic metal salts can exert their optimal effects. Furthermore, the cross-linked microporous structure increases the reaction contact area, further enhancing the catalytic efficiency.

[0015] The process of mixing an inorganic metal salt with a polyvinyl alcohol solution includes: adding the inorganic metal salt to a reaction vessel, followed by adding the polyvinyl alcohol solution to the reaction vessel. The resulting catalyst exhibits good catalytic performance.

[0016] According to some embodiments of the present invention, the temperature of the crosslinking polymerization reaction is 50°C to 65°C, for example, 50°C, 55°C, 60°C, or 65°C. Thus, under these temperature conditions, polyvinyl alcohol and borax can undergo a crosslinking polymerization reaction to form a binder, and the binder is positioned between the inorganic metal salts to obtain a catalyst.

[0017] The cross-linking polymerization reaction takes 0.5 to 2 hours. Therefore, the cross-linking polymerization reaction can be completed in a relatively short time, yielding the catalyst.

[0018] According to an embodiment of the present invention, after the crosslinking polymerization reaction is completed, the method further includes the steps of drying, pulverizing, and sieving the obtained material, wherein the drying temperature is 80–105°C. The drying step effectively removes the solvent, resulting in a dry catalyst.

[0019] This invention also provides a method for preparing 6-methoxy-2-acetylnaphthalene, see reference. Figure 1The method comprises: mixing the catalyst described above, or the catalyst prepared by the method described above, with β-naphthyl methyl ether, acetyl chloride, an isomer transposition promoter, and a solvent, and reacting to obtain 6-methoxy-2-acetnaphthalene. Using the catalyst of the present invention, the yield of 6-methoxy-2-acetnaphthalene can be effectively increased, reaching over 85%. Furthermore, this method has the advantages of high product quality and few reaction byproducts. Specifically, the purity of the 6-methoxy-2-acetnaphthalene product obtained using the method of the present invention can reach over 99%, and the content of isomer impurities is as low as below 2%. Moreover, the method for preparing 6-methoxy-2-acetnaphthalene using the catalyst of the present invention also has the advantages of simple operation and simple post-processing; the catalyst has a significant catalytic effect and can recover most of the effective components. In addition, this method has the advantages of good safety and environmental friendliness, and is suitable for industrial production of various scales.

[0020] Specifically, in the synthesis of 6-methoxy-2-acetnaphthalene, isomers and other byproducts are easily generated. The catalyst of this invention can improve the conversion efficiency of isomer transformation promoters, converting isomer byproducts back into the desired product. Appropriate catalyst selection can minimize the equilibrium byproducts generated during the reversible formation of carbocations. When forming reversible carbocations, the catalyst of this invention can reduce the generation of equilibrium byproducts, decrease substrate consumption, and thus allow for greater conversion during the isomer transformation promoter reaction. Simultaneously, it can degrade and re-involve the byproducts, thereby increasing the product yield.

[0021] According to embodiments of the present invention, the isomer transformation promoter comprises a nitroalkane, which includes at least one of nitromethane, nitrobenzene, and nitrobanane; the molar ratio of β-naphthyl methyl ether to the isomer transformation promoter is 1:1 to 1:3, for example, 1:1, 1:2, or 1:3. Thus, the nitroalkane can convert the byproduct into the desired product, exhibiting a better transformation effect and effectively avoiding the generation of isomer byproducts. Furthermore, nitroalkane also has the advantages of low toxicity and low price, which is beneficial to improving reaction safety and reducing production costs. Moreover, when the molar ratio of β-naphthyl methyl ether to the isomer transformation promoter is within the above-mentioned content range, the generation of isomers can be effectively avoided, and the product yield can be improved. If the content of the isomer transformation promoter is too low, the conversion rate of the product will decrease, thereby reducing the product yield. If the content of the isomer transformation promoter is too high, the effect of improving the product yield is not significant, and it will also increase production costs.

[0022] According to an embodiment of the present invention, the solvent includes a haloalkane, the haloalkane including 1,2-dichloroethane, and the reactants have high solubility in the solvent, which is beneficial to the reaction.

[0023] According to an embodiment of the present invention, the molar ratio of β-naphthyl methyl ether to acetyl chloride is 1:1 to 1:3, for example, 1:1, 1:2, or 1:3, which is conducive to the full reaction of β-naphthyl methyl ether and acetyl chloride.

[0024] According to embodiments of the present invention, the weight ratio of β-naphthyl methyl ether to the catalyst is 1:0.9 to 1:2, for example, 1:0.9, 1:1, 1:1.2, 1:1.3, 1:1.5, or 1:2. Thus, the catalyst and the isomer transformation promoter work together to effectively convert the isomer byproducts into the product of the present invention, thereby effectively improving the product yield. If the amount of catalyst is too small, the conversion rate of the isomer byproducts will decrease, leading to a decrease in product yield. If the amount of catalyst is too large, the excess catalyst will not further accelerate the reaction, nor will it further promote the conversion rate of side reactions.

[0025] According to embodiments of the present invention, the solvent volume corresponding to each gram of β-naphthyl methyl ether is 4 to 8 ml, for example, 4 ml, 5 ml, 6 ml, 7 ml, or 8 ml. If too much solvent is used, the reaction time will be prolonged and the reaction rate will be reduced; if too little solvent is used, the final product yield and product purity will be too low.

[0026] According to an embodiment of the present invention, the mixing of the catalyst with β-naphthyl methyl ether, acetyl chloride, an isomer transformation promoter, and a solvent comprises: adding the solvent, β-naphthyl methyl ether, and the isomer transformation promoter to a reaction vessel; after dissolving, adding the catalyst; after the catalyst dissolves, adding acetyl chloride dropwise to the reaction system; and after the acetyl chloride has been added, heating the reaction system until the reaction temperature is reached to carry out the reaction, thereby obtaining 6-methoxy-2-acetylnaphthalene. The reaction of the present invention is an exothermic reaction. By using the method of adding acetyl chloride dropwise to the reaction system, the present invention can effectively control the reaction rate and avoid adverse problems such as excessively high temperature and excessive side reactions caused by an excessively fast reaction rate.

[0027] According to an embodiment of the present invention, the temperature of the reaction system during the dropwise addition of the acetyl chloride is 5–20°C, for example, 5°C, 10°C, 15°C, or 20°C, and the dropwise addition time of the acetyl chloride is 3–6 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours. This effectively controls the reaction rate, avoids the formation of byproducts, and thus improves the yield and purity of the product.

[0028] According to embodiments of the present invention, the heating time is 3 to 5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours, and 5 hours. According to some embodiments of the present invention, a gradient heating method can be used for heating.

[0029] According to an embodiment of the present invention, the reaction temperature is 20 to 50°C, for example 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, and 50°C. At a relatively mild reaction temperature, the target product can be obtained efficiently.

[0030] According to embodiments of the present invention, the reaction time is 15–40 hours, for example, 15 hours, 16 hours, 20 hours, 25 hours, 30 hours, 35 hours, or 40 hours. Therefore, the target product can be obtained in a shorter time.

[0031] Under the above conditions, the reaction can achieve a high product yield, high product purity, and fewer byproducts.

[0032] According to an embodiment of the present invention, reference Figure 1 After the reaction is complete, the method further includes: adding ice water to the reaction system after the reaction is complete, extracting to obtain an aqueous phase and an organic phase, washing the aqueous phase with an organic solvent, mixing the resulting organic layer with the organic phase, distilling under reduced pressure, and recrystallizing to obtain 6-methoxy-2-acetylnaphthalene. Thus, high-quality 6-methoxy-2-acetylnaphthalene can be obtained.

[0033] According to an embodiment of the present invention, the organic solvent includes 1,2-dichloroethane; the vacuum degree of the vacuum distillation is not less than 0.07 MPa, for example, the vacuum degree can be 0.07 MPa or 0.085 MPa.

[0034] According to an embodiment of the present invention, the solvent used for recrystallization includes an alcohol compound, which includes at least one of methanol, ethanol, and isopropanol. Recrystallization can improve the purity of 6-methoxy-2-acetylnaphthalene. Attached Figure Description

[0035] Figure 1 This is a flowchart of the method for preparing 6-methoxy-2-acetylnaphthalene in Sample Example 1 of the present invention. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0037] Example 1: Preparation of Catalyst

[0038] Example 1 provides a catalyst and its preparation method.

[0039] The catalyst in this embodiment comprises aluminum trichloride, ferrous chloride, and zinc chloride in a mass ratio of 8.5:1:0.5.

[0040] The catalyst preparation method in this embodiment includes the following steps:

[0041] Aluminum trichloride, ferrous chloride, and zinc chloride were ground into powder using a ball mill, maintaining a well-ventilated and dry environment. Aluminum trichloride, ferrous chloride, and zinc chloride were added to a horizontal twin-shaft mixer at a mass ratio of 8.5:1:0.5, totaling 100 kg, and the mixture was heated to 50°C while stirring. First, 5 kg of a 5% PVA1788 solution was sprayed evenly until the raw material became a moist dry powder. Then, 5 kg of a 5% borax solution was added for cross-linking polymerization, ensuring no large particles were formed during the addition process. After the material in the mixer granulated, the mixture was stirred at 55°C for another half hour, and then the material was removed. It was dried at 105°C, pulverized, and then sieved to obtain 40–200 mesh particles, which became the catalyst.

[0042] Example 2: Preparation of Catalyst

[0043] Example 2 provides a catalyst and its preparation method.

[0044] The catalyst in this embodiment comprises aluminum trichloride, ferrous chloride, and zinc chloride in a ratio of 7.5:1.5:1.

[0045] The catalyst preparation method in this embodiment includes the following steps:

[0046] Aluminum trichloride, ferrous chloride, and zinc chloride were ground into powder using a ball mill, maintaining a well-ventilated and dry environment. Aluminum trichloride, ferrous chloride, and zinc chloride were added to a horizontal twin-shaft mixer at a mass ratio of 7.5:1.5:1, totaling 100 kg, and the mixture was heated to 50°C while stirring. First, 5 kg of a 5% PVA1788 solution was sprayed evenly until the raw material became a moist dry powder. Then, 5 kg of a 5% borax solution was added for cross-linking polymerization, ensuring no large particles were formed during the addition process. After the material in the mixer granulated, the mixture was stirred at 55°C for another half hour, and then the material was removed. It was dried at 105°C, pulverized, and then sieved to obtain 40–200 mesh particles, which became the catalyst.

[0047] Sample Example 1: Preparation of 6-methoxy-2-acetylnaphthalene

[0048] Sample Example 1 provides a method for preparing 6-methoxy-2-acetylnaphthalene.

[0049] The preparation method of 6-methoxy-2-acetylnaphthalene in Sample Example 1 includes the following steps: In a 500ml four-necked flask equipped with a stirrer, thermometer, and reflux condenser, add 200ml of 1,2-dichloroethane (5ml of 1,2-dichloroethane per gram of β-naphthyl methyl ether), 40g of β-naphthyl methyl ether, and 22.5g of nitromethane (the molar ratio of β-naphthyl methyl ether to nitromethane is 1:1.5), stir to dissolve, and then reflux... The temperature was raised to 5°C, and 40.6 g of the catalyst prepared in Example 1 (the weight ratio of β-naphthyl ether to catalyst was 1:1) was added. After dissolution, 23.2 g of acetyl chloride (the molar ratio of β-naphthyl ether to acetyl chloride was 1:1.2) was added dropwise at 15°C. After the addition was completed, the temperature was slowly raised for 4 h until it reached 35°C. The temperature was then maintained at 38°C for 20 h. The product was sampled and tested and found to be 94.35%, with 0.8% isomers. The reaction solution was dissolved in ice water. Since the unreacted acetyl chloride reacted exothermically with water, the temperature was controlled at 38°C using ice water. The mixture was allowed to stand and separate into layers. The aqueous layer was washed with 1,2-dichloroethane. After washing, the organic layer was incorporated into the original organic phase. The solvent was removed by vacuum distillation. After solvent removal, the crude product was recrystallized from ethanol to obtain a white to pale yellow finished product. Liquid chromatography conditions: C18 column, wavelength 248 nm, column temperature 25°C, mobile phase: methanol:water 80:20 mixture, flow rate 1 mL / min. Liquid chromatography analysis showed a product purity of 99.2% and a yield of 85.80%.

[0050] Sample Example 2: Preparation of 6-methoxy-2-acetylnaphthalene

[0051] Sample Example 2 provides a method for preparing 6-methoxy-2-acetylnaphthalene.

[0052] The preparation method of 6-methoxy-2-acetylnaphthalene in Sample Example 2 includes the following steps: 200 ml of 1,2-dichloroethane (5 ml of 1,2-dichloroethane per gram of β-naphthyl methyl ether), 40 g of β-naphthyl methyl ether, and 23 g of nitromethane (molar ratio of β-naphthyl methyl ether to nitromethane is 1:1.5) are added to a 500 ml four-necked flask equipped with a stirrer, thermometer, and reflux condenser. After stirring and dissolving, the mixture is cooled to 10°C, and 41.5 g of the catalyst prepared in Example 1 (weight ratio of β-naphthyl methyl ether to catalyst is 1:1) is added. After dissolving, 23 g of acetyl chloride (molar ratio of β-naphthyl methyl ether to acetyl chloride is 1:1.2) is added dropwise at 12°C. After the addition is complete, the temperature is slowly increased for 4 hours until it reaches 40°C. The temperature is maintained at 40°C for 20 hours. A sample is taken for analysis, and the product content is 95.03%, with 0.96% isomers. The reaction solution was dissolved in ice water at 38°C. The mixture was allowed to stand and separate into layers. The aqueous layer was washed with 1,2-dichloroethane. After washing, the organic layer was incorporated into the original organic phase. The solvent was removed by vacuum distillation. After solvent removal, the crude product was recrystallized from ethanol to obtain a white to pale yellow product with a purity of 99.35% and a yield of 85.72%.

[0053] Sample Example 3: Preparation of 6-methoxy-2-acetylnaphthalene

[0054] Sample Example 3 provides a method for preparing 6-methoxy-2-acetylnaphthalene.

[0055] The preparation method of 6-methoxy-2-acetylnaphthalene in Sample Example 3 includes the following steps: 200 ml of 1,2-dichloroethane (5 ml of 1,2-dichloroethane per gram of β-naphthyl methyl ether), 40 g of β-naphthyl methyl ether, and 23.5 g of nitromethane (the molar ratio of β-naphthyl methyl ether to nitromethane is 1:1.5) are added to a 500 ml four-necked flask equipped with a stirrer, thermometer, and reflux condenser. After stirring and dissolving, the mixture is cooled to 8°C, and 43.7 g of the catalyst prepared in Example 1 is added. After dissolving, 23.5 g of acetyl chloride (the molar ratio of β-naphthyl methyl ether to acetyl chloride is 1:1.2) is added dropwise at 10°C. After the addition is complete, the temperature is slowly increased for 4 hours until it reaches 38°C. The temperature is then maintained at 36°C for 20 hours. A sample is taken for analysis, and the product content is 94.65%, with 0.93% isomers. The reaction solution was dissolved in ice water at 38°C. The mixture was allowed to stand and separate into layers. The aqueous layer was washed with 1,2-dichloroethane. After washing, the organic layer was incorporated into the original organic phase. The solvent was removed by vacuum distillation. After solvent removal, the crude product was recrystallized from ethanol to obtain a white to pale yellow product with a purity of 99.29% and a yield of 88.11%.

[0056] Sample Example 4: Preparation of 6-methoxy-2-acetylnaphthalene

[0057] Sample Example 4 provides a method for preparing 6-methoxy-2-acetylnaphthalene.

[0058] The preparation method of 6-methoxy-2-acetylnaphthalene in Sample Example 4 includes the following steps: 200 ml of 1,2-dichloroethane (5 ml of 1,2-dichloroethane per gram of β-naphthyl methyl ether), 40 g of β-naphthyl methyl ether, and 23 g of nitromethane (molar ratio of β-naphthyl methyl ether to nitromethane is 1:1.5) are added to a 500 ml four-necked flask equipped with a stirrer, thermometer, and reflux condenser. After stirring and dissolving, the mixture is cooled to 10°C, and 41.5 g of the catalyst prepared in Example 2 (weight ratio of β-naphthyl methyl ether to catalyst is 1:1) is added. After dissolving, 23 g of acetyl chloride (molar ratio of β-naphthyl methyl ether to acetyl chloride is 1:1.2) is added dropwise at 15°C. After the addition is complete, the temperature is slowly increased for 4 hours until it reaches 40°C. The temperature is then maintained at 38°C for 20 hours. A sample is taken and the product content is 94.12%, with 1.03% isomers. The reaction solution was dissolved in ice water at 38°C. After standing and separating the layers, the aqueous layer was washed with 1,2-dichloroethane. The organic layer was then incorporated into the original organic phase. The solvent was removed by vacuum distillation. After solvent removal, the crude product was recrystallized from ethanol to obtain a white to pale yellow product with a purity of 99.06% and a yield of 86.33%.

[0059] Comparative Sample Example 1: Preparation of 6-methoxy-2-acetylnaphthalene

[0060] Compared with the catalyst of Sample Example 1, the active components of the catalyst include aluminum trichloride, ferrous chloride and zinc chloride in a ratio of 7:2:1.

[0061] The preparation method of the catalyst in Comparative Sample 1 includes the following steps:

[0062] Aluminum trichloride, ferrous chloride, and zinc chloride were ground into powder using a ball mill, maintaining a well-ventilated and dry environment. Aluminum trichloride and ferrous chloride were added to a horizontal twin-shaft mixer at a mass ratio of 7:2:1, totaling 100 kg, and the mixture was heated to 50°C while stirring. First, 5 kg of a 5% PVA1788 solution was sprayed evenly until the raw material became a moist dry powder. Then, 5 kg of a 5% borax solution was added for cross-linking polymerization, ensuring no large particles were formed during the addition process. After the material in the mixer granulated, it was stirred for another half hour at 55°C. The material was then removed and dried at 105°C, pulverized, and then sieved to obtain 40–200 mesh particles, which became the catalyst.

[0063] The preparation method of 6-methoxy-2-acetylnaphthalene in Comparative Sample Example 1 includes the following steps: 200 ml of 1,2-dichloroethane (5 ml of 1,2-dichloroethane per gram of β-naphthyl methyl ether), 40 g of β-naphthyl methyl ether, and 23 g of nitromethane (molar ratio of β-naphthyl methyl ether to nitromethane 1:1.5) are added to a 500 ml four-necked flask equipped with a stirrer, thermometer, and reflux condenser. After stirring and dissolving, the mixture is cooled to 10 °C, and 41.5 g of catalyst (weight ratio of β-naphthyl methyl ether to catalyst 1:1) is added. After dissolving, 23 g of acetyl chloride (molar ratio of β-naphthyl methyl ether to acetyl chloride 1:1.2) is added dropwise at 15 °C. After the addition is complete, the temperature is slowly increased for 4 h until it reaches 40 °C. The temperature is then maintained at 38 °C for 20 h. A sample is taken and the product content is 91.11%, with 1.39% being isomers. The reaction solution was dissolved in ice water at 38°C. After standing and separating the layers, the aqueous layer was washed with 1,2-dichloroethane. The organic layer was then incorporated into the original organic phase. The solvent was removed by vacuum distillation. After solvent removal, the crude product was recrystallized from ethanol to obtain a white to pale yellow product with a purity of 99.52% and a yield of 83.46%.

[0064] Comparative Sample Example 2: Preparation of 6-methoxy-2-acetylnaphthalene

[0065] Compared with the catalyst of sample example 2, the active components of the catalyst include aluminum trichloride and ferrous chloride in a ratio of 8.5:1.5.

[0066] The preparation method of the catalyst in Comparative Sample Example 2 includes the following steps:

[0067] Aluminum trichloride and ferrous chloride were ground into powder using a ball mill, maintaining a well-ventilated and dry environment. Aluminum trichloride and ferrous chloride were added to a horizontal twin-shaft mixer at a mass ratio of 8.5:1.5, totaling 100 kg, and the mixture was heated to 50°C while stirring. First, 5 kg of a 5% PVA1788 solution was sprayed evenly until the raw material became a moist dry powder. Then, 5 kg of a 5% borax solution was added to initiate cross-linking polymerization, ensuring no large particles were formed during the addition process. After the material in the mixer granulated, it was stirred for another half hour at 55°C. The material was then removed and dried at 105°C, pulverized, and then sieved to obtain 40–200 mesh particles, which became the catalyst.

[0068] The preparation method of 6-methoxy-2-acetylnaphthalene in Comparative Sample Example 2 includes the following steps: 200 ml of 1,2-dichloroethane (5 ml of 1,2-dichloroethane per gram of β-naphthyl methyl ether), 40 g of β-naphthyl methyl ether, and 23 g of nitromethane (molar ratio of β-naphthyl methyl ether to nitromethane 1:1.5) are added to a 500 ml four-necked flask equipped with a stirrer, thermometer, and reflux condenser. After stirring and dissolving, the mixture is cooled to 10°C, and 41.5 g of catalyst (weight ratio of β-naphthyl methyl ether to catalyst 1:1) is added. After dissolving, 23 g of acetyl chloride (molar ratio of β-naphthyl methyl ether to acetyl chloride 1:1.2) is added dropwise at 15°C. After the addition is complete, the temperature is slowly increased for 4 hours until it reaches 40°C. The temperature is then maintained at 38°C for 20 hours. A sample is taken and the product is found to be 87.03%, with 1.52% isomers. The reaction solution was dissolved in ice water at 38°C. The mixture was allowed to stand and separate into layers. The aqueous layer was washed with 1,2-dichloroethane. After washing, the organic layer was incorporated into the original organic phase. The solvent was removed by vacuum distillation. After solvent removal, the crude product was recrystallized from ethanol to obtain a white to pale yellow product with a purity of 99.35% and a yield of 80.12%.

[0069] Comparative Sample Example 3: Preparation of 6-methoxy-2-acetylnaphthalene

[0070] Compared to the catalyst in Sample Example 3, the active component of the catalyst is aluminum trichloride.

[0071] The preparation method of the catalyst in Comparative Sample 3 includes the following steps:

[0072] Aluminum trichloride was ground into powder using a ball mill, maintaining a well-ventilated and dry environment. 100 kg of aluminum trichloride was added to a horizontal twin-shaft mixer, and the temperature was raised to 50°C while stirring. First, 5 kg of a 5% PVA1788 solution was sprayed evenly. Once the raw material was in a moist, dry powder state, 5 kg of a 5% borax solution was added for cross-linking polymerization, ensuring no large particles were formed during the addition process. After the material in the mixer granulated, the temperature was maintained at 55°C and stirring continued for half an hour. The material was then removed and dried at 105°C, pulverized, and then sieved to obtain 40–200 mesh particles, which constituted the catalyst.

[0073] To a 500ml four-necked flask equipped with a stirrer, thermometer, and reflux condenser, add 200ml of 1,2-dichloroethane (5ml of 1,2-dichloroethane per gram of β-naphthyl methyl ether), 40g of β-naphthyl methyl ether, and 23.5g of nitromethane (molar ratio of β-naphthyl methyl ether to nitromethane 1:1.5). After stirring and dissolving, cool to 8℃, add 43.7g of catalyst, and after dissolving, add 23.5g of acetyl chloride (molar ratio of β-naphthyl methyl ether to acetyl chloride 1:1.2) dropwise at 15℃. After the addition is complete, slowly raise the temperature for 4 hours until it reaches 38℃. Maintain this temperature at 38℃ for 20 hours. Samples were taken and the product was found to be 82.87%, with 2.93% isomers. The reaction solution was dissolved in ice water at 38°C. The mixture was allowed to stand and separate into layers. The aqueous layer was washed with 1,2-dichloroethane. After washing, the organic layer was incorporated into the original organic phase. The solvent was removed by vacuum distillation. After solvent removal, the crude product was recrystallized from ethanol to obtain a white to pale yellow product with a purity of 99.09% and a yield of 73.51%.

[0074] In Samples 1-4, the conversion yield of the product reached over 94%, with isomers below 2%, indicating high product quality. The yield of the target product, 6-methoxy-2-acetnaphthalene, was high, consistently exceeding 85%, and the purity reached over 99%. This demonstrates that using the catalyst of this invention can effectively improve the product yield in the preparation of 6-methoxy-2-acetnaphthalene.

Claims

1. Catalyst for the preparation of 6-methoxy-2-acetonaphthalene, characterized in that, The active component of the catalyst is an inorganic metal salt, which is composed of aluminum trichloride, ferrous chloride, and zinc chloride. The mass ratio of aluminum trichloride to ferrous chloride and zinc chloride is (7.5-17):(1.5-2):

1. The catalyst also includes a binder located between the inorganic metal salts. The binder is formed by cross-linking polymerization of borax and polyvinyl alcohol. For every 100 parts by mass of inorganic metal salt, the corresponding amount of borax solution is 2.5-5 parts by mass, and the corresponding amount of polyvinyl alcohol solution is 2.5-5 parts by mass.

2. The catalyst for preparing 6-methoxy-2-acetylnaphthalene according to claim 1, characterized in that, The borax solution is formed by dissolving borax in water, and the mass fraction of the borax solution is 4-6%; the polyvinyl alcohol solution is formed by dissolving polyvinyl alcohol in water, and the mass fraction of the polyvinyl alcohol solution is 4-6%.

3. The catalyst for preparing 6-methoxy-2-acetylnaphthalene according to claim 1, characterized in that, The particle size of the catalyst is 40~200 mesh.

4. The method for preparing the catalyst according to any one of claims 1-3, characterized in that, The preparation method includes: An inorganic metal salt is mixed with a polyvinyl alcohol solution, followed by the addition of a borax solution. The polyvinyl alcohol and the borax undergo a crosslinking polymerization reaction to form a binder, which is located between the inorganic metal salts, thus obtaining a catalyst.

5. The method for preparing the catalyst according to claim 4, characterized in that, The cross-linking polymerization reaction is carried out at a temperature of 50~65℃.

6. The method for preparing the catalyst according to claim 5, characterized in that, The cross-linking polymerization reaction takes 0.5 to 2 hours.

7. The method for preparing the catalyst according to claim 4, characterized in that, After the crosslinking polymerization reaction is completed, the method further includes the steps of drying, pulverizing and sieving the obtained material, wherein the drying temperature is 80~105℃.

8. A method for preparing 6-methoxy-2-acetylnaphthalene, characterized in that, The method includes: The catalyst according to any one of claims 1-3 is mixed with β-naphthyl methyl ether, acetyl chloride, isomer transposition promoter and solvent, and reacted to obtain 6-methoxy-2-acetylnaphthalene.

9. The method for preparing 6-methoxy-2-acetylnaphthalene according to claim 8, characterized in that, The isomer transposition promoter includes nitroalkanes, and the nitroalkanes include at least one of nitromethane, nitromethane, and nitromethane; the molar ratio of β-naphthyl methyl ether to the isomer transposition promoter is 1:1 to 1:

3.

10. The method for preparing 6-methoxy-2-acetylnaphthalene according to claim 8, characterized in that, The weight ratio of β-naphthyl methyl ether to the catalyst is 1:0.9 to 1:

2.

11. A method for preparing 6-methoxy-2-acetylnaphthalene, characterized in that, The method includes: The catalyst prepared by the method according to any one of claims 4-7 is mixed with β-naphthyl methyl ether, acetyl chloride, isomer transposition promoter and solvent, and reacted to obtain 6-methoxy-2-acetylnaphthalene.

12. The method for preparing 6-methoxy-2-acetylnaphthalene according to claim 11, characterized in that, The isomer transposition promoter includes nitroalkanes, and the nitroalkanes include at least one of nitromethane, nitromethane, and nitromethane; the molar ratio of β-naphthyl methyl ether to the isomer transposition promoter is 1:1 to 1:

3.

13. The method for preparing 6-methoxy-2-acetylnaphthalene according to claim 11, characterized in that, The weight ratio of β-naphthyl methyl ether to the catalyst is 1:0.9 to 1:2.

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