Preparation method of 2-alkyl-6-acyl naphthalene

Abstract

The invention belongs to the technical field of organic synthesis, and particularly relates to application of a mixed Lewis acid catalyst in catalyzing acylation of 2-alkyl naphthalene Friedel-Crafts to prepare 2-alkyl-6-acyl naphthalene. According to the method, 2-alkyl naphthalene is taken as a substrate, acyl halogen or acid anhydride is taken as an acylation reagent, two or more Lewis acid catalysts are dissolved in a nitro compound solvent, and Friedel-Crafts acylation can be effectively catalyzed to synthesize 2-alkyl-6-acyl naphthalene. However, the invention discovers that the mixed catalyst composed of two or more Lewis acids can quickly catalyze the Friedel-Crafts acylation reaction, does not need to increase the total dosage of the catalyst, and has innovativeness. The reaction process is simple, the cost is low, the yield is high, and industrial production is easy.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis and relates to a method for preparing 2-alkyl-6-acylnaphthalene by catalyzing 2-alkylnaphthalene with a mixed Lewis catalyst. Background Art

[0002] Polyethylene naphthalate (PEN) is a new type of specialty polyester. Due to its excellent physical and chemical properties, its performance in all aspects is superior to that of traditional polyethylene terephthalate (PET). It has a wide range of applications in the fields of fiber, film and electronics. At present, the production capacity of PEN is mainly restricted by the production of the key monomer 2,6-naphthalene dicarboxylic acid (2,6-NDA). However, for the catalytic oxidation of 2,6-dialkylnaphthalene such as 2,6-dimethylnaphthalene, 2,6-diethylnaphthalene, and 2,6-diisopropylnaphthalene, the production of 2,6-NDA is limited due to the long synthesis route, poor selectivity, and difficulty in product separation. With the efficient development of coal resources, the preparation of 2-alkyl-6-acylnaphthalene by Friedel-Crafts acylation reaction using 2-alkylnaphthalene as raw material has attracted widespread attention. Because it uses Friedel-Crafts acylation reaction, the selectivity of 2,6-disubstituted naphthalene will be improved compared with alkylation.

[0003] The synthetic route of 2-alkyl-6-acylnaphthalene has been partially studied. Patent CN1817843A discloses a method for preparing 2-alkyl-6-acylnaphthalene, in which halogenated hydrocarbons are used as solvents and nitro compounds are used as complexing agents, respectively, which improves the product selectivity, but makes the process complicated. Patent CN107879909A discloses a method for synthesizing acylnaphthalene using a microchannel reactor, but the microchannel reactor is expensive, which greatly increases the equipment and production costs, making it difficult to industrialize production. Patent CN1146213228A discloses a modified H β The method of synthesizing acyl naphthalene by zeolite molecular sieve is environmentally friendly and has a small amount of wastewater discharge, but the product selectivity of the obtained 2-alkyl-6-acyl naphthalene is relatively low. Patent 115554914A discloses a device for preparing 2-methyl-6-propionyl naphthalene by continuous acylation, with low reactor back mixing, relatively high reaction conversion rate and selectivity, but the process is relatively complicated.

[0004] At present, the catalysts used in the prior art for synthesizing 2-alkyl-6-acylanapthalenes are mostly single Lewis acid catalysts or solid acid catalysts. There are no reports on the effects of mixed Lewis acid catalysts on the Friedel-Crafts acylation reaction, and there is no in-depth study on the effects on the mechanism, which limits the further application of Friedel-Crafts acylation to prepare aromatic ketones.

[0005] Therefore, there is a need in the art for a mixed Lewis acid catalyst to catalyze the Friedel-Crafts acylation of the aromatic hydrocarbon substrate 2-alkylnaphthalene to prepare 2-alkyl-6-acylnaphthalene. Summary of the invention

[0006] The technical problem to be solved by the present invention is the problem of the catalytic performance of mixed Lewis acid in the existing Friedel-Crafts acylation technology. A mixed Lewis acid catalyst is provided to catalyze the Friedel-Crafts acylation of an aromatic hydrocarbon substrate 2-alkylnaphthalene to prepare 2-alkyl-6-acylnaphthalene. The method is applicable to a variety of 2-alkylnaphthalene substrates and can effectively improve the reaction rate, substrate conversion rate and 2,6-acylnaphthalene selectivity.

[0007] In order to solve the above problems, the technical solution adopted by the present invention is as follows: The method of 2-alkyl-6-acylnaphthalene comprises the steps of: (1) fully dissolving two or more Lewis acid catalysts in a solvent nitro compound; (2) In a three-necked flask, dissolve the acylating agent and the aromatic hydrocarbon substrate 2-alkylnaphthalene in a solvent nitro compound, and add the mixed Lewis acid catalyst solution described in (1) into the three-necked flask at a certain flow rate and dropwise addition temperature; (3) After the feeding is completed, continue the reaction for 0.2~5h, pour the reaction mixture into ice water, and adjust the pH to neutral.

[0008] (4) Extract the mixed solution, remove the aqueous phase, and distill the organic phase under reduced pressure to obtain a crude product of 2-alkyl-6-acylnaphthalene.

[0009] (5) Recrystallizing the crude 2-alkyl-6-acylnaphthalene product using an alcohol-water solution to obtain a 2-alkyl-6-acylnaphthalene product.

[0010] The invention adopts a mixed Lewis acid catalyst and mixes Lewis acids to effectively improve the conversion rate of the substrate and the selectivity of 2-alkyl-6-acylnaphthalene.

[0011] In the above technical solution, the solvent in step (1) is a mixture of one or more of nitrobenzene, nitromethane and nitroethane.

[0012] In the above technical scheme, the catalyst in step (1) is a Lewis acid catalyst, such as aluminum chloride, ferric chloride, gallium chloride, aluminum bromide, ferric bromide, gallium bromide, etc.

[0013] In the above technical solution, the molar ratio of the catalyst to the substrate in step (1) is 0.8~2:1.

[0014] In the above technical solution, the molar ratio of the different Lewis acid catalysts in step (1) is (0.5~1):1.

[0015] In the above technical solution, the 2-alkylnaphthalene in step (2) is 2-methylnaphthalene or 2-ethylnaphthalene.

[0016] In the above technical solution, the mass ratio of the solvent to the substrate in step (2) is (3-10):1.

[0017] In the above technical scheme, the acylating agent described in step (2) is acetyl chloride, acetyl bromide, propionyl chloride, propionyl bromide, acetic anhydride, propionic anhydride, etc.

[0018] In the above technical solution, the reaction temperature is 0~50°C.

[0019] In the above technical solution, the dropping speed is 20~160ml / h.

[0020] In the above technical solution, the dropping temperature is -10~10℃.

[0021] In the above technical solution, the alcohol-water solution in step (5) refers to a lower alcohol having a monohydroxyl group, mainly including but not limited to one of methanol, ethanol, isopropanol or a mixture of two thereof, wherein the mass ratio of alcohol to water is (7-9.5):1.

[0022] The product of the invention is dissolved in anhydrous ethanol before vacuum distillation and then analyzed by gas chromatography.

[0023] The technical key of the present invention is to form a more electron-rich Lewis acid structure by mixing different Lewis acid catalysts. When the Lewis acid structure is coordinated with the acylating agent, a stronger electrophilic reagent is formed, thereby improving the reaction conversion rate and selectivity. DETAILED DESCRIPTION

[0024] [Example 1] This example uses 2-methylnaphthalene, acetyl chloride, aluminum chloride and aluminum bromide as raw materials.

[0025] (1) 3.34g aluminum chloride, 6.67g aluminum bromide, and 55g nitrobenzene were placed in a single-necked flask and stirred thoroughly to dissolve. 3.93g acetyl chloride, 7.1g 2-methylnaphthalene, and 35g nitrobenzene were placed in a three-necked flask and placed in a low-temperature tank. The mixed Lewis acid catalyst solution was slowly added to the three-necked flask through a feed pump, and the drop rate was controlled at 60mL / min. The temperature of the low-temperature tank was kept constant at 0°C. After the addition of the materials, the reaction was carried out at 20°C for 0.5 hours. The reaction product was poured into ice water containing crushed ice. After stirring for half an hour, 4.5g sodium bicarbonate was added to adjust the pH. The reaction product was poured into a separatory funnel for phase separation. The organic layer was taken and the fraction at about 160°C / 2mmHg was collected by vacuum distillation to obtain 6.3g of crude product. The mixture was analyzed by gas chromatography. The yield of 2-methyl-6-acetylnaphthalene was 68.8%.

[0026] (2) 6.3 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55 °C for 1 hour. The mixture was then cooled to 5 °C and filtered and dried to obtain 3.0 g of 2-methyl-6-acetylnaphthalene with a purity of 97.7%.

[0027] [Example 2] This example uses 2-methylnaphthalene, propionyl chloride, aluminum chloride and aluminum bromide as raw materials.

[0028] (1) 3.34g aluminum chloride, 6.67g aluminum bromide, and 55g nitrobenzene were placed in a single-necked flask and stirred thoroughly to dissolve. 4.63g propionyl chloride, 7.1g 2-methylnaphthalene, and 35g nitrobenzene were placed in a three-necked flask and placed in a low-temperature tank. The mixed Lewis acid catalyst solution was slowly added to the three-necked flask through a feed pump, and the drop rate was controlled at 60mL / min. The temperature of the low-temperature tank was kept constant at 0°C. After the addition of the materials, the reaction was carried out at 20°C for 0.5 hours. The reaction product was poured into ice water containing crushed ice. After stirring for half an hour, 4.5g sodium bicarbonate was added to adjust the pH. The reaction product was poured into a separatory funnel for phase separation. The organic layer was taken and the fraction at about 160°C / 2mmHg was collected by vacuum distillation to obtain 7.0g of crude product. The mixture was analyzed by gas chromatography. The yield of 2-methyl-6-propionylnaphthalene was 70.7%.

[0029] (2) 7.0 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55°C for 1 hour. The mixture was then cooled to 5°C and filtered and dried to obtain 3.7 g of 2-methyl-6-propionylnaphthalene with a purity of 96.5%.

[0030] [Example 3] This example uses 2-methylnaphthalene, acetyl chloride, ferric chloride and ferric bromide as raw materials.

[0031] (1) Put 4.1g of ferric chloride, 7.4g of ferric bromide, and 55g of nitrobenzene into a single-necked flask and stir thoroughly to dissolve. Put 3.93g of acetyl chloride and 35g of nitrobenzene into a three-necked flask and place it in a low-temperature tank. Slowly add the mixed Lewis acid catalyst solution into the three-necked flask through a feed pump, control the drop rate at 60mL / min, and keep the temperature of the low-temperature tank constant at 0℃. After the addition of the materials, react at 20℃ for 2 hours, pour the reaction product into ice water containing crushed ice, stir for half an hour, add 4.5g of sodium bicarbonate to adjust the pH, pour into a separatory funnel for phase separation, take the organic layer and collect the fraction of about 160℃ / 2 mmHg by vacuum distillation to obtain 6.2g of crude product. The mixture was analyzed by gas chromatography, and the yield of 2-methyl-6-acetylnaphthalene was 67.1%.

[0032] (2) 6.2 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55 °C for 1 hour. The mixture was then cooled to 5 °C and filtered and dried to obtain 3.0 g of 2-methyl-6-acetylnaphthalene with a purity of 97.3%.

[0033] [Example 4] This example uses 2-methylnaphthalene, propionyl chloride, ferric chloride and ferric bromide as raw materials.

[0034] (1) Put 4.1g of ferric chloride, 7.4g of ferric bromide, and 55g of nitrobenzene into a single-necked flask and stir thoroughly to dissolve. Put 3.93g of acetyl chloride, 7.1g of 2-methylnaphthalene, and 35g of nitrobenzene into a three-necked flask and place it in a low-temperature tank. Slowly add the mixed Lewis acid catalyst solution into the three-necked flask through a feed pump, control the drop rate at 60mL / min, and keep the temperature of the low-temperature tank constant at 0℃. After the addition of the materials, react at 20℃ for 0.5 hours, pour the reaction product into ice water containing crushed ice, stir for half an hour, add 4.5g of sodium bicarbonate to adjust the pH, pour into a separatory funnel for phase separation, take the organic layer and collect the fraction of about 160℃ / 2mmHg by vacuum distillation to obtain 6.8g of crude product. The mixture was analyzed by gas chromatography, and the yield of 2-methyl-6-propionylnaphthalene was 68.9%.

[0035] (2) 6.8 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55 °C for 1 hour. The mixture was then cooled to 5 °C and filtered and dried to obtain 3.2 g of 2-methyl-6-propionylnaphthalene with a purity of 96.7%.

[0036] [Example 5] This example uses 2-methylnaphthalene, acetyl chloride, gallium chloride and gallium bromide as raw materials.

[0037] (1) Put 4.4g of gallium chloride, 7.4g of gallium bromide, and 55g of nitrobenzene into a single-necked flask and stir thoroughly to dissolve. Put 3.93g of acetyl chloride, 7.1g of 2-methylnaphthalene, and 35g of nitrobenzene into a three-necked flask and place it in a low-temperature tank. Slowly add the mixed Lewis acid catalyst solution into the three-necked flask through a feed pump, control the drop rate at 60mL / min, and keep the temperature of the low-temperature tank constant at 0℃. After the addition of the materials, react at 20℃ for 0.5 hours, pour the reaction product into ice water containing crushed ice, stir for half an hour, add 4.5g of sodium bicarbonate to adjust the pH, pour into a separatory funnel for phase separation, take the organic layer and collect the fraction of about 160℃ / 2mmHg by vacuum distillation to obtain 6.5g of crude product. The mixture was analyzed by gas chromatography, and the yield of 2-methyl-6-propionylnaphthalene was 70.5%.

[0038] (2) 6.5 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55°C for 1 hour. The mixture was then cooled to 5°C, filtered and dried to obtain 3.8 g of 2-methyl-6-acetylnaphthalene with a purity of 95.3%. [Example 6] This example uses 2-methylnaphthalene, acetyl chloride, aluminum chloride and ferric chloride as raw materials.

[0039] (1) 3.34g aluminum chloride, 4.1g ferric chloride, and 55g nitrobenzene were placed in a single-necked flask and stirred thoroughly to dissolve. 3.93g acetyl chloride, 7.1g 2-methylnaphthalene, and 35g nitrobenzene were placed in a three-necked flask and placed in a low-temperature tank. The mixed Lewis acid catalyst solution was slowly added to the three-necked flask through a feed pump, and the drop rate was controlled at 60mL / min. The temperature of the low-temperature tank was kept constant at 0°C. After the addition of the materials, the reaction was carried out at 0°C for 0.5 hours. The reaction product was poured into ice water containing crushed ice. After stirring for half an hour, 5.0g sodium bicarbonate was added to adjust the pH. The reaction product was poured into a separatory funnel for phase separation. The organic layer was taken and the fraction at about 160°C / 2mmHg was collected by vacuum distillation to obtain 6.4g of crude product. The mixture was analyzed by gas chromatography. The yield of 2-methyl-6-acetylnaphthalene was 69.8%.

[0040] (2) 6.4 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55 °C for 1 hour. The mixture was then cooled to 5 °C and filtered and dried to obtain 3.5 g of 2-methyl-6-acetylnaphthalene with a purity of 97.2%.

[0041] [Example 7] This example uses 2-ethylnaphthalene, acetyl chloride, ferric chloride and gallium chloride as raw materials.

[0042] (1) Put 4.1g of ferric chloride, 4.4g of gallium chloride, and 55g of nitrobenzene into a single-necked flask and stir thoroughly to dissolve. Put 3.93g of acetyl chloride, 7.6g of 2-ethylnaphthalene, and 35g of nitrobenzene into a three-necked flask and place it in a low-temperature tank. Slowly add the mixed Lewis acid catalyst solution to the three-necked flask through a feed pump, control the drop rate at 60mL / min, and keep the temperature of the low-temperature tank constant at 0℃. After the addition of the materials, react at 20℃ for 2 hours, pour the reaction product into ice water containing crushed ice, stir for half an hour, add 5.0g of sodium bicarbonate to adjust the pH, pour into a separatory funnel for phase separation, take the organic layer and collect the fraction of about 164℃ / 2mmHg by vacuum distillation to obtain 6.5g of crude product. The mixture was analyzed by gas chromatography, and the yield of 2-ethyl-6-acetylnaphthalene was 65.2%.

[0043] (2) 6.5 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55 °C for 1 hour. The mixture was then cooled to 5 °C and filtered and dried to obtain 3.3 g of 2-ethyl-6-acetylnaphthalene with a purity of 98.2%.

[0044] [Example 8] This example uses 2-ethylnaphthalene, acetyl chloride, aluminum chloride and gallium chloride as raw materials.

[0045] (1) 3.34g aluminum chloride, 4.4g gallium chloride, and 55g nitrobenzene were placed in a single-necked flask and stirred thoroughly to dissolve. 3.93g acetyl chloride, 7.6g 2-ethylnaphthalene, and 35g nitrobenzene were placed in a three-necked flask and placed in a low-temperature tank. The mixed Lewis acid catalyst was slowly added to the three-necked flask through a feed pump, and the drop rate was controlled at 60mL / min. The temperature of the low-temperature tank was kept constant at 0°C. After the addition of the materials, the reaction was carried out at 20°C for 2 hours. The reaction product was poured into ice water containing crushed ice. After stirring for half an hour, 4.5g sodium bicarbonate was added to adjust the pH. The reaction product was poured into a separatory funnel for phase separation. The organic layer was taken and the fraction at about 160°C / 2mmHg was collected by vacuum distillation to obtain 7.1g of crude product. The mixture was analyzed by gas chromatography. The yield of 2-ethyl-6-acetylnaphthalene was 71.5%.

[0046] (2) 7.1 g of the crude product and 30 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55 °C for 1 hour. The mixture was then cooled to 5 °C and filtered and dried to obtain 3.8 g of 2-ethyl-6-acetylnaphthalene with a purity of 97.5%.

[0047] [Comparative Example 1] This comparative example uses 2-methylnaphthalene, acetyl chloride and aluminum chloride as raw materials.

[0048] (1) Put 6.67g aluminum chloride and 55g nitrobenzene into a single-necked flask, stir and dissolve them thoroughly to obtain a catalyst solution. Put 3.93g acetyl chloride, 7.1g 2-methylnaphthalene and 35g nitrobenzene into a three-necked flask, place it in a low-temperature tank, stir and dissolve them thoroughly, and then slowly add the catalyst solution (catalyst aluminum chloride and solvent) into the three-necked flask through a feed pump, control the drop rate at 60mL / min, and keep the temperature of the low-temperature tank constant at 0℃. After the addition of the materials, react at 20℃ for 0.5 hours, pour the reaction product into ice water containing crushed ice, stir for half an hour, add 4.5g sodium bicarbonate to adjust the pH, pour into a separatory funnel for phase separation, take the organic layer and collect the fraction of about 160℃ / 2 mmHg by vacuum distillation to obtain 4.8g of crude product. The mixture was analyzed by gas chromatography, and the yield of 2-methyl-6-acetylnaphthalene was 52.1%.

[0049] (2) 4.8 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55 °C for 1 hour. The mixture was then cooled to 5 °C and filtered and dried to obtain 2.1 g of 2-methyl-6-acetylnaphthalene with a purity of 99.0%.

[0050] [Comparative Example 2] This comparative example uses 2-methylnaphthalene, propionyl chloride and aluminum chloride as raw materials.

[0051] (1) 6.67g aluminum chloride and 55g nitrobenzene were placed in a single-necked flask, stirred and dissolved to obtain a catalyst solution. 3.93g acetyl chloride, 7.6g 2-ethylnaphthalene and 30g nitrobenzene were placed in a three-necked flask, placed in a low-temperature tank, stirred and dissolved, and then the catalyst solution ( was slowly added to the three-necked flask through a feed pump, and the drop rate was controlled at 60mL / min, and the temperature of the low-temperature tank was kept constant at 0°C. After the addition of the materials, the reaction was carried out at 20°C for 0.5 hours. The reaction product was poured into ice water containing crushed ice, stirred for half an hour, and 4.5g sodium bicarbonate was added to adjust the pH. The reaction product was poured into a separating funnel for phase separation. The organic layer was taken and the fraction at about 160°C / 2 mmHg was collected by vacuum distillation to obtain 5.4g of crude product. The mixture was analyzed by gas chromatography, and the yield of 2-methyl-6-acetylnaphthalene was 54.8%.

[0052] (2) 5.4 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55 °C for 1 hour. The mixture was then cooled to 5 °C and filtered and dried to obtain 2.5 g of 2-methyl-6-acetylnaphthalene with a purity of 98.7%.

[0053] [Comparative Example 3] This comparative example uses 2-methylnaphthalene, acetyl chloride and ferric chloride as raw materials.

[0054] (1) 8.1g of ferric chloride and 55g of nitrobenzene were placed in a single-necked flask, stirred and dissolved to obtain a catalyst solution. 3.93g of acetyl chloride, 7.1g of 2-methylnaphthalene and 35g of nitrobenzene were placed in a three-necked flask, placed in a low-temperature tank, stirred and dissolved, and then the catalyst solution was slowly added to the three-necked flask through a feed pump, and the drop rate was controlled at 60mL / min. The temperature of the low-temperature tank was kept constant at 0°C. After the addition of the materials, the reaction was carried out at 20°C for 0.5 hours. The reaction product was poured into ice water containing crushed ice, stirred for half an hour, and 4.5g of sodium bicarbonate was added to adjust the pH. The reaction product was poured into a separatory funnel for phase separation. The organic layer was taken and the fraction at about 160°C / 2 mmHg was collected by vacuum distillation to obtain 4.6g of crude product. The mixture was analyzed by gas chromatography. The yield of 2-methyl-6-acetylnaphthalene was 49.8%.

[0055] (2) 4.6 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55 °C for 1 hour. The mixture was then cooled to 5 °C and filtered and dried to obtain 2.1 g of 2-methyl-6-acetylnaphthalene with a purity of 99.4%.

[0056] [Comparative Example 4] This comparative example uses 2-methylnaphthalene, acetyl chloride and gallium chloride as raw materials.

[0057] (1) Put 8.8g of gallium chloride and 55g of nitrobenzene into a single-necked flask, stir and dissolve them thoroughly to obtain a catalytic solution. Put 3.93g of acetyl chloride, 7.1g of 2-methylnaphthalene and 35g of nitrobenzene into a three-necked flask, place it in a low-temperature tank, stir and dissolve them thoroughly, and then slowly add the catalytic solution into the three-necked flask through a feed pump, control the drop rate at 60mL / min, and keep the temperature of the low-temperature tank constant at 0℃. After the addition of the materials, react at 20℃ for 0.5 hours, pour the reaction product into ice water containing crushed ice, stir for half an hour, add 4.5g of sodium bicarbonate to adjust the pH, pour into a separatory funnel for phase separation, take the organic layer and collect the fraction of about 160℃ / 2 mmHg by vacuum distillation to obtain 4.9g of crude product. The mixture was analyzed by gas chromatography, and the yield of 2-methyl-6-acetylnaphthalene was 53.5%.

[0058] (2) 4.9 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55 °C for 1 hour. The mixture was then cooled to 5 °C and filtered and dried to obtain 2.4 g of 2-methyl-6-acetylnaphthalene with a purity of 98.2%.

[0059] [Comparative Example 5] This comparative example uses 2-methylnaphthalene, acetyl chloride and zinc chloride as raw materials.

[0060] (1) Put 6.8g zinc chloride and 55g nitrobenzene into a single-necked flask, stir and dissolve them thoroughly to obtain a catalyst solution. Put 3.93g acetyl chloride, 7.1g 2-methylnaphthalene and 35g nitrobenzene into a three-necked flask, place it in a low-temperature tank, stir and dissolve them thoroughly, and then slowly add the catalyst solution into the three-necked flask through a feed pump, control the drop rate at 60mL / min, and keep the temperature of the low-temperature tank constant at 0℃. After the addition of the materials, react at 20℃ for 0.5 hours, pour the reaction product into ice water containing crushed ice, stir for half an hour, add 4.5g sodium bicarbonate to adjust the pH, pour into a separatory funnel for phase separation, take the organic layer and collect the fraction of about 160℃ / 2 mmHg by vacuum distillation to obtain 4.2g of crude product. The mixture was analyzed by gas chromatography, and the yield of 2-methyl-6-acetylnaphthalene was 41.7%.

[0061] (2) 4.2 g of the crude product and 25 g of a 95 wt% methanol-water solution were placed in a 150 ml single-necked flask and fully dissolved at 55 °C for 1 hour. The mixture was then cooled to 5 °C and filtered and dried to obtain 1.9 g of 2-methyl-6-acetylnaphthalene with a purity of 99.5%.

Claims

1. A method for preparing 2-alkyl-6-acylnaphthalene (1), comprising the following steps: Two or more Lewis acid catalysts are dissolved in a solvent (2), a substrate 2-alkylnaphthalene (3) and an acylating agent (4) or (5) are dissolved in the solvent (2) in a three-necked flask, the mixed Lewis catalyst solution is added to the three-necked flask at a certain flow rate and dropwise addition temperature, the reaction is continued for 0.2-5 hours after the addition is completed, the resulting mixture is poured into ice water, the pH is adjusted to neutral, the mixture is extracted, the water phase is separated, the organic phase is subjected to reduced pressure distillation to obtain a crude 2-alkyl-6-acylnaphthalene product, and the crude 2-alkyl-6-acylnaphthalene product is recrystallized using an alcohol-water solution to obtain a 2-alkyl-6-acylnaphthalene product.

2. The preparation method according to claim 1, characterized in that: The 2-alkylnaphthalene R is a C1~C4 alkyl group, wherein the weight ratio of the organic solvent to the 2-alkylnaphthalene is (3~10):

1.

3. The preparation method according to claim 1, characterized in that: The catalyst Lewis acid catalyst refers to aluminum chloride, ferric chloride, gallium chloride, aluminum bromide, ferric bromide, gallium bromide, etc., wherein the molar ratio of the catalyst amount to the substrate 2-alkylnaphthalene is (0.8~2):

1.

4. The preparation method according to claim 1, characterized in that: The molar ratio of each Lewis acid in the mixed Lewis acid catalyst is (0.5-1):

1.

5. The preparation method according to claim 1, characterized in that: The solvent used is a nitro compound, etc. Mainly including but not limited to nitromethane, nitroethane, nitrobenzene, etc.

6. The preparation method according to claim 1, characterized in that: The acylating agent used is an acyl chloride or anhydride, mainly including but not limited to acetyl chloride, acetyl bromide, propionyl chloride, propionyl bromide, acetic anhydride, propionic anhydride, etc.

7. The preparation method according to claim 1, characterized in that: During the addition process, the drop rate of the mixed Lewis catalyst solution is 20~160mL / h.

8. The preparation method according to claim 1, characterized in that: During the addition process, the temperature of the dropwise addition (addition) is -10~10℃.

9. The preparation method according to claim 1, characterized in that: The reaction temperature is 0~50℃.

10. The preparation method according to claim 1, characterized in that: The alcohol-water solution used, the alcohol mainly includes but is not limited to one of methanol, ethanol, isopropanol or a mixture of two of them, wherein the mass ratio of alcohol to water is (7~9.5):1.

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