Preparation method of 3, 5-dichloro-2-pentanone

Abstract

The invention belongs to the technical field of chemistry and chemical engineering, and particularly relates to a preparation method of 3, 5-dichloro-2-pentanone. Through the synergistic effect of the photosensitizer and the solid catalyst, the one-pot direct chlorination of 2-pentanone is realized, and the separation and purification steps of the traditional multi-step reaction are avoided. By strictly controlling the dosage and the dropping speed of H2O2, the chlorination reaction is ensured to be complete, and the product yield can reach 84% or above. NaCl is used as a chlorine source, air is used as an oxygen source, and visible light catalysis is combined, so that the use of chlorine or a strong oxidant in a traditional chlorination process is avoided, and corrosive byproducts and three-waste pollution are reduced from the source. The Mn-Schiff base complex is loaded on the magnetic carrier, magnetic separation and recovery of the catalyst can be achieved, the yield is kept to be larger than 80% after 5 times of circulation, the phosphate buffer solution can be recycled, and the production cost is effectively reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical industry, and particularly relates to a preparation method of 3,5-dichloro-2-pentanone. BACKGROUND

[0002] 3,5-dichloro-2-pentanone is an important intermediate for the synthesis of medicines and pesticides, and is particularly a key intermediate of the fungicide prothioconazole developed by Bayer Company in the aspect of pesticides. Prothioconazole (common name: Prothioconazole) is a new type of triazole sulfone fungicide developed by Bayer Company, which is mainly used for preventing and treating many diseases of cereal crops, wheat crops, legume crops and the like. Prothioconazole has low toxicity, no teratogenicity, no mutagenicity, no toxicity to embryos, and is safe to human and environment. In order to prevent the occurrence of resistance, adapt to the needs of special crops and prevention of different diseases, Bayer Company is currently developing prothioconazole single agent and mixed preparation composed of other drugs. In addition to being mixed with the fungicide fluazinam, prothioconazole can also be compounded with tebuconazole, triflumizole and spiroxamine, and has a wide market application prospect.

[0003] At present, the mainstream synthesis route reported in the literature is to take alpha-acetyl-gamma-butyrolactone as raw material, to perform chlorination by chlorine gas (or sulfuryl chloride), to perform chloro ring-opening and decarboxylation reaction (or in the presence of Lewis acid, phase transfer catalyst) with hydrochloric acid (or using glacial acetic acid as solvent) to obtain a mixture of 3,5-dichloro-2-pentanone and hydrochloric acid, and to obtain pure 3,5-dichloro-2-pentanone by distillation or steam distillation. The above-mentioned process disclosed has a series of problems such as complicated process, high energy consumption, high cost of raw materials, poor comprehensive utilization of by-products, large amount of tar and the like, which seriously affect the large-scale production of the intermediate.

[0004] Based on this, a preparation method of 3,5-dichloro-2-pentanone is provided, hoping to solve the problems in the prior art. SUMMARY

[0005] The application aims at the existing problems, and provides a preparation method of 3,5-dichloro-2-pentanone.

[0006] The application is implemented by the following technical scheme: A preparation method of 3,5-dichloro-2-pentanone, comprising the following steps: S1, dissolving 2-pentanone, NaCl and a photosensitizer in a phosphate buffer, adding a solid catalyst, introducing air, irradiating with a 450nm LED light source, and dropping a 5-10% mass fraction H2O2 aqueous solution; S2, after continuously reacting for 6-7h, recovering the catalyst by magnetic separation, extracting with ethyl acetate, and distilling to obtain 3,5-dichloro-2-pentanone.

[0007] Further, the concentration of 2-pentanone in step S1 is 0.5-1 M, and the concentration of NaCl is 0.2-0.5 M; The photosensitizer is rose bengal B with a purity of ≥98%, and the amount of rose bengal B is 0.5-2 mol% relative to 2-pentanone. The dropping speed of the H2O2 aqueous solution is 0.1-0.3 mL / min, and the molar ratio of H2O2 to 2-pentanone is 2-4:1.

[0008] Further, the phosphate buffer in step S1 is composed of 0.1 M Na2HPO4 / KH2PO4, and the pH value is 6.8.

[0009] Further, the air input rate in step S1 is 0.1-0.3 mL / min.

[0010] Further, the amount of the solid catalyst added in step S1 is 5-8% of the mass of 2-pentanone. The preparation of the solid catalyst includes the following steps: (1) Salicylaldehyde and ethylenediamine are added to ethylene glycol dimethyl ether at a molar ratio of 2:1, and after stirring at 50-55°C for 1-1.5 h, Mn(OAc)2·4H2O is added to the system, and the temperature is raised to 60-65°C, and stirring is continued for 2-2.5 h to form a Mn(II)-Schiff base complex. A 30% H2O2 aqueous solution is added dropwise, and the oxidation is completed within 30 min. After cooling, crystals are precipitated, filtered, washed with deionized water for 3-4 times, and then dried at 55-65°C under vacuum for 2-3 h to obtain a Mn(III)-Schiff base complex. (2) The magnetic carrier is ultrasonically dispersed in an ethanol / water solution at a volume ratio of 3:1. After uniform dispersion, 0.1-0.2 times the mass of the magnetic carrier of the Mn(III)-Schiff base complex is added, and the mixture is stirred at 100-200 rpm. After the addition of triethylamine is completed, the temperature is raised to 70-75°C, and the reaction is refluxed for 4-4.5 h. After the reaction is completed, the heating is stopped, and the stirring is continued to cool to room temperature. The product is adsorbed by a magnet, and then washed with an ethanol / water solution at a volume ratio of 3:1 for 3-4 times. After washing, the product is dried at 70-80°C under vacuum for 3-4 h.

[0011] Further, the molar ratio of Mn(OAc)2·4H2O to salicylaldehyde in step (1) is 1:2. The molar ratio of H2O2 to Mn(OAc)2·4H2O is 1.1-1.3:1.

[0012] Further, the preparation of the magnetic carrier in step (2) includes the following steps: 1) FeCl3·6H2O and FeSO4·7H2O were added into a three-necked flask in a molar ratio of 2:1, and 0.1M NaOH aqueous solution was added dropwise under N2 protection to adjust the pH to 10-11 at a dropwise adding speed of 2mL / min. After the dropwise adding was completed, the reaction was continued under N2 protection in a 60-65℃ water bath with stirring at 200-300rpm for 1-2h. After the reaction was completed, the generated Fe3O4 nanoparticles were adsorbed by a magnet, and washed with deionized water until the pH of the supernatant was neutral to obtain Fe3O4 nanoparticles; 2) The Fe3O4 nanoparticles were dispersed into an ethanol / water mixture with a volume ratio of 1:1 in a mass volume ratio of 1g:20-30mL, and a uniform suspension was formed by ultrasonic treatment at 200W for 15-20min. The suspension was transferred into a three-necked flask, and TEOS (tetraethyl orthosilicate) was added dropwise under stirring at 200-300rpm, with Fe3O4:TEOS=1g:0.5-1mL at a dropwise adding speed of 0.5-0.7mL / min. After the dropwise adding was completed, the reaction was continued in a 30-35℃ water bath with stirring for 4-5h. After the reaction was completed, the product was adsorbed by a magnet, and washed with ethanol for 3-4 times, and then vacuum dried at 55-65℃ for 1.5-2.5h to obtain Fe3O4@SiO2 nanoparticles; 3) The Fe3O4@SiO2 nanoparticles were ultrasonically dispersed (at a power of 200W) into ethanol in a mass volume ratio of 1g:50-60mL, and γ-aminopropylmethyldimethoxysilane was added, with the mass volume ratio of Fe3O4@SiO2 nanoparticles to γ-aminopropylmethyldimethoxysilane being 1g:0.05-0.06mL. The reaction was carried out in a 50-55℃ water bath with stirring at 100-200rpm for 2-2.5h. After the reaction was completed, the product was adsorbed by a magnet, and washed with ethanol for 3-4 times, and then vacuum dried at 55-65℃ for 1.5-2.5h to obtain amino-modified Fe3O4@SiO2 nanoparticles; 4) The amino-modified Fe3O4@SiO2 nanoparticles and SBA-15 were added into deionized water in a mass ratio of 1:4-5, and the mass volume ratio of the amino-modified Fe3O4@SiO2 nanoparticles to deionized water was 1g:200-250mL. The mixture was ultrasonically treated at 300W for 30-40min, and then vacuum dried at 55-65℃ for 4-5h after filtration to obtain a magnetic carrier.

[0013] Further, the mass volume ratio of the magnetic carrier to the ethanol / water solution in step (2) was 1g:25-30mL. The molar ratio of triethylamine to the Mn(Ⅲ)-Schiff base complex was 1.2-1.5:1.

[0014] Further, the distance between the LED light source and the reactor in step S1 was 15-20cm.

[0015] Further, the ethyl acetate extraction in step S2 is extracted 3-4 times with equal volume, each time with 1 / 3-1 / 2 of the volume of the reaction solution, and the ethyl acetate can be recovered by distillation. The distillation is reduced pressure distillation, and the fraction collected at 85-90℃ / 15mmHg.

[0016] Compared with the prior art, the present application has the following advantages: In the present application, 2-pentanone, NaCl and a photosensitizer are dissolved in a phosphate buffer, a solid catalyst is added, air is introduced, and a 450nm LED light source is used for irradiation, while a 5-10% mass fraction H2O2 aqueous solution is added dropwise, the reaction is continued for 6-7h, the catalyst is recovered by magnetic separation, ethyl acetate extraction and distillation to obtain 3,5-dichloro-2-pentanone. Through the synergistic effect of the photosensitizer and the solid catalyst, one-pot direct chlorination of 2-pentanone is realized, avoiding the separation and purification steps of traditional multi-step reactions. By strictly controlling the amount and dropwise addition rate of H2O2, the chlorination reaction is ensured to be complete, and the product yield can reach more than 84%. NaCl is used as a chlorine source, air is used as an oxygen source, and visible light catalysis is combined to avoid the use of chlorine gas or strong oxidizing agents in traditional chlorination processes, thereby reducing corrosive by-products and three-waste pollution from the source. Moreover, the magnetic carrier loaded with Mn-Schiff base complex in the present application can realize magnetic separation and recovery of the catalyst, and the yield remains >80% after 5 cycles, and the phosphate buffer can be recycled, effectively reducing the production cost. DETAILED DESCRIPTION

[0017] In order to further explain the present application, the following specific examples are used for illustration. Example 1

[0018] A method for preparing 3,5-dichloro-2-pentanone, comprising the following steps: S1, 0.5M 2-pentanone, 0.2M NaCl, rose Bengal (purity ≥98%) are dissolved in a phosphate buffer (0.1M Na2HPO4 / KH2PO4, pH value is 6.8), the amount of rose Bengal is 0.5mol% relative to 2-pentanone, 5% of the solid catalyst of the mass of 2-pentanone is added, air is introduced, the introduction rate is 0.1mL / min, a 450nm LED light source is used for irradiation, the distance between the LED light source and the reactor is 15cm, and a 5% mass fraction H2O2 aqueous solution is added dropwise, the dropwise addition rate is 0.1mL / min, and the molar ratio of H2O2 to 2-pentanone is 2:1; S2, after the reaction is continued for 6h, the catalyst is recovered by magnetic separation, 3 times of ethyl acetate extraction with equal volume, each time with 1 / 3 of the volume of the reaction solution, and the ethyl acetate can be recovered by distillation, and 3,5-dichloro-2-pentanone is obtained by reduced pressure distillation. The preparation of the solid catalyst comprises the following steps: (1) Salicylaldehyde and ethylenediamine are added to ethylene glycol dimethyl ether in a molar ratio of 2:1, after stirring at 50°C for 1 h, Mn(OAc)2·4H2O is added to the system, the molar ratio of Mn(OAc)2·4H2O to salicylaldehyde is 1:2, the temperature is raised to 60°C, and stirring is continued for 2 h to form a Mn(II)-Schiff base complex, a 30% mass fraction H2O2 aqueous solution is added dropwise, the molar ratio of H2O2 to Mn(OAc)2·4H2O is 1.1:1, the oxidation is completed within 30 min, crystals are precipitated after standing and cooling, and after filtration, the crystals are washed with deionized water for 3 times, and then vacuum dried at 55°C for 2 h to obtain a Mn(III)-Schiff base complex; (2) FeCl3·6H2O and FeSO4·7H2O are added to a three-necked flask in a molar ratio of 2:1, under N2 protection, a 0.1M NaOH aqueous solution is added dropwise to adjust the pH to 10, the dropwise addition speed is 2 mL / min, after the dropwise addition is completed, the reaction is continued under N2 protection in a 60°C water bath with stirring at 200 rpm for 1 h, after the reaction is completed, the generated Fe3O4 nanoparticles are adsorbed by a magnet, and washed with deionized water until the pH of the supernatant is neutral to obtain Fe3O4 nanoparticles; (3) The Fe3O4 nanoparticles are dispersed in a 1:1 volume ratio ethanol / water mixture in a mass volume ratio of 1 g:20 mL, and ultrasonic treatment is performed at 200 W for 15 min to form a uniform suspension, which is transferred to a three-necked flask, TEOS (tetraethyl orthosilicate) is added dropwise under stirring at 200 rpm, the Fe3O4:TEOS ratio is 1 g:0.5 mL, the dropwise addition speed is 0.5 mL / min, after the dropwise addition is completed, the reaction is continued with stirring at a 30°C water bath for 4 h, after the reaction is completed, the product is adsorbed by a magnet, washed with ethanol for 3 times, and then vacuum dried at 55°C for 1.5 h to obtain Fe3O4@SiO2 nanoparticles; (4) The Fe3O4@SiO2 nanoparticles are ultrasonically dispersed (the power is 200 W) in ethanol in a mass volume ratio of 1 g:50 mL, γ-aminopropylmethyldimethoxysilane is added, the mass volume ratio of Fe3O4@SiO2 nanoparticles to γ-aminopropylmethyldimethoxysilane is 1 g:0.05 mL, the reaction is carried out with stirring at 100 rpm in a 50°C water bath for 2 h, after the reaction is completed, the product is adsorbed by a magnet, washed with ethanol for 3 times, and then vacuum dried at 55°C for 1.5 h to obtain amino-modified Fe3O4@SiO2 nanoparticles; (5) The amino-modified Fe3O4@SiO2 nanoparticles and SBA-15 are added into deionized water in a mass ratio of 1:4, the mass / volume ratio of the amino-modified Fe3O4@SiO2 nanoparticles and deionized water is 1 g:200 mL, and 300 W ultrasonic treatment is performed for 30 min, followed by suction filtration and vacuum drying at 55°C for 4 h to obtain the magnetic carrier; (6) The magnetic carrier is ultrasonically dispersed into an ethanol / water solution in a volume ratio of 3:1 in a mass / volume ratio of 1 g:25 mL, 0.1 times the mass of the magnetic carrier of the Mn(III)-Schiff base complex is added after uniform dispersion, and the mixture is uniformly stirred at 100 rpm, followed by dropwise addition of triethylamine, the molar ratio of triethylamine to the Mn(III)-Schiff base complex is 1.2:1, after the dropwise addition is completed, the temperature is increased to 70°C, and reflux reaction is performed for 4 h, after the reaction is completed, the heating is stopped, and the stirring is continued to cool to room temperature, the product is adsorbed by a magnet, washed with an ethanol / water solution in a volume ratio of 3:1 for 3 times, and vacuum dried at 70°C for 3 h after washing. Example 2

[0019] A method for preparing 3,5-dichloro-2-pentanone, comprising the following steps: S1, 0.75M 2-pentanone, 0.35M NaCl, rose Bengal (purity≥98%) are dissolved in phosphate buffer solution (0.1M Na2HPO4 / KH2PO4 composition, pH value is 6.8), the amount of rose Bengal is 1mol% relative to 2-pentanone, 6.5% of solid catalyst by mass of 2-pentanone is added, air is introduced at a rate of 0.2mL / min, a 450nm LED light source is irradiated, the distance between the LED light source and the reactor is 18cm, and an 8% H2O2 aqueous solution by mass fraction is added dropwise at a rate of 0.2mL / min, the molar ratio of H2O2 to 2-pentanone is 3:1; S2, after 6.5h of continuous reaction, the catalyst is recovered by magnetic separation, extracted with equal volume of ethyl acetate for 3 times, each time using 1 / 3 of the volume of the reaction solution, and the ethyl acetate can be recovered by distillation, and 3,5-dichloro-2-pentanone is obtained by reduced pressure distillation; The preparation of the solid catalyst comprises the following steps: (1) Salicylaldehyde and ethylenediamine were added to ethylene glycol dimethyl ether in a molar ratio of 2:1, and stirred at 52°C for 1.2h. Then Mn(OAc)2·4H2O was added to the system, and the molar ratio of Mn(OAc)2·4H2O to salicylaldehyde was 1:2. The temperature was raised to 62°C, and the stirring was continued for 2.2h to form a Mn(II)-Schiff base complex. Then 30% H2O2 aqueous solution was added dropwise, and the molar ratio of H2O2 to Mn(OAc)2·4H2O was 1.2:1. The oxidation was completed within 30min. After cooling, crystals were precipitated, and were filtered and washed with deionized water for 3 times. Then the crystals were vacuum dried at 60°C for 2.5h to obtain a Mn(III)-Schiff base complex; (2) FeCl3·6H2O and FeSO4·7H2O were added to a three-necked flask in a molar ratio of 2:1. Under N2 protection, 0.1M NaOH aqueous solution was added dropwise to adjust the pH to 10.5, and the dropwise addition rate was 2mL / min. After the dropwise addition was completed, the reaction was continued under N2 protection at 62°C water bath and 250rpm stirring for 1.5h. After the reaction was completed, the generated Fe3O4 nanoparticles were adsorbed by a magnet, and were washed with deionized water until the pH of the supernatant was neutral to obtain Fe3O4 nanoparticles; (3) Fe3O4 nanoparticles were dispersed in a mixture of ethanol / water (volume ratio 1:1) in a mass / volume ratio of 1g:25mL, and were treated with ultrasonic waves at 200W for 18min to form a uniform suspension. The suspension was transferred to a three-necked flask, and TEOS (tetraethyl orthosilicate) was added dropwise under the condition of 250rpm stirring, and the mass / volume ratio of Fe3O4 to TEOS was 1g:0.75mL, and the dropwise addition rate was 0.6mL / min. After the dropwise addition was completed, the reaction was continued under stirring at 32°C water bath for 4.5h. After the reaction was completed, the product was adsorbed by a magnet, and was washed with ethanol for 3 times, and was vacuum dried at 60°C for 2h to obtain Fe3O4@SiO2 nanoparticles; (4) Fe3O4@SiO2 nanoparticles were dispersed in ethanol in a mass / volume ratio of 1g:55mL by ultrasonic treatment (the power was 200W). Then γ-aminopropylmethyldimethoxysilane was added, and the mass / volume ratio of Fe3O4@SiO2 nanoparticles to γ-aminopropylmethyldimethoxysilane was 1g:0.055mL. The reaction was carried out at 52°C water bath and 150rpm stirring for 2.2h. After the reaction was completed, the product was adsorbed by a magnet, and was washed with ethanol for 3 times, and was vacuum dried at 60°C for 2h to obtain amino-modified Fe3O4@SiO2 nanoparticles; (5) The amino-modified Fe3O4@SiO2 nanoparticles and SBA-15 are added into deionized water in a mass ratio of 1:4.5, the mass-volume ratio of the amino-modified Fe3O4@SiO2 nanoparticles to deionized water is 1g:220mL, 300W ultrasonic treatment for 35min, vacuum drying at 60℃ for 4.5h after suction filtration to obtain a magnetic carrier; (6) The magnetic carrier is ultrasonically dispersed into an ethanol / water solution in a volume ratio of 3:1 in a mass-volume ratio of 1g:28mL, 0.15 times the mass of the magnetic carrier of the Mn(III)-Schiff base complex is added after uniform dispersion, stirred at 150rpm, then triethylamine is added dropwise, the molar ratio of triethylamine to Mn(III)-Schiff base complex is 1.3:1, after the addition is completed, the temperature is raised to 72℃, refluxed for 4.3h, after the reaction is completed, the heating is stopped, continue to stir and cool to room temperature, the product is adsorbed by a magnet, washed with an ethanol / water solution in a volume ratio of 3:1 for 3 times, and vacuum dried at 75℃ for 3.5h after washing. Example 3

[0020] A preparation method of 3,5-dichloro-2-pentanone, comprising the following steps: S1, 1M 2-pentanone, 0.5M NaCl, rose Bengal (purity≥98%) are dissolved in phosphate buffer solution (0.1M Na2HPO4 / KH2PO4 composition, pH value is 6.8), the amount of rose Bengal is 2mol% relative to 2-pentanone, 8% of solid catalyst by mass of 2-pentanone is added, air is introduced at a rate of 0.3mL / min, a 450nm LED light source is irradiated, the distance between the LED light source and the reactor is 20cm, and a 10% H2O2 aqueous solution by mass fraction is added dropwise at a rate of 0.3mL / min, the molar ratio of H2O2 to 2-pentanone is 4:1; S2, after 7h of continuous reaction, the catalyst is recovered by magnetic separation, extracted with equal volume of ethyl acetate for 4 times, each time using 1 / 2 of the volume of the reaction solution, and the ethyl acetate can be recovered by distillation, 3,5-dichloro-2-pentanone is obtained by reduced pressure distillation; The preparation of the solid catalyst comprises the following steps: (1) Salicylaldehyde and ethylenediamine were added to ethylene glycol dimethyl ether in a molar ratio of 2:1, and stirred at 55°C for 1.5h. Then Mn(OAc)2·4H2O was added to the system, and the molar ratio of Mn(OAc)2·4H2O to salicylaldehyde was 1:2. The temperature was raised to 65°C, and the stirring was continued for 2.5h to form a Mn(II)-Schiff base complex. Then 30% H2O2 aqueous solution was added dropwise, and the molar ratio of H2O2 to Mn(OAc)2·4H2O was 1.3:1. The oxidation was completed within 30min. After cooling, crystals were precipitated, and were filtered and washed with deionized water for 4 times. Then the Mn(III)-Schiff base complex was obtained by vacuum drying at 65°C for 3h; (2) FeCl3·6H2O and FeSO4·7H2O were added to a three-necked flask in a molar ratio of 2:1. Under N2 protection, 0.1M NaOH aqueous solution was added dropwise to adjust the pH to 11, and the dropwise speed was 2mL / min. After the dropwise addition was completed, the reaction was continued at 65°C water bath under N2 protection and 300rpm stirring for 2h. After the reaction was completed, the generated Fe3O4 nanoparticles were adsorbed by a magnet, and were washed with deionized water until the pH of the supernatant was neutral to obtain Fe3O4 nanoparticles; (3) Fe3O4 nanoparticles were dispersed in a mixture of ethanol / water (volume ratio 1:1) in a mass / volume ratio of 1g:30mL, and were treated with ultrasonic waves at 200W for 20min to form a uniform suspension. Then the suspension was transferred to a three-necked flask, and TEOS (tetraethyl orthosilicate) was added dropwise under stirring at 300rpm. The mass ratio of Fe3O4 to TEOS was 1g:1mL, and the dropwise speed was 0.7mL / min. After the dropwise addition was completed, the reaction was continued at 35°C water bath under stirring for 5h. After the reaction was completed, the product was adsorbed by a magnet, and was washed with ethanol for 4 times. Then Fe3O4@SiO2 nanoparticles were obtained by vacuum drying at 65°C for 2.5h; (4) Fe3O4@SiO2 nanoparticles were dispersed in ethanol in a mass / volume ratio of 1g:60mL by ultrasonic treatment (power 200W). Then γ-aminopropylmethyldimethoxysilane was added, and the mass / volume ratio of Fe3O4@SiO2 nanoparticles to γ-aminopropylmethyldimethoxysilane was 1g:0.06mL. The reaction was carried out at 55°C water bath under stirring at 200rpm for 2.5h. After the reaction was completed, the product was adsorbed by a magnet, and was washed with ethanol for 4 times. Then amin-modified Fe3O4@SiO2 nanoparticles were obtained by vacuum drying at 65°C for 2.5h; (5) Amin-modified Fe3O4@SiO2 nanoparticles and SBA-15 were added to deionized water in a mass ratio of 1:5, and the mass / volume ratio of amin-modified Fe3O4@SiO2 nanoparticles to deionized water was 1g:250mL. Then the mixture was treated with ultrasonic waves at 300W for 40min. After suction filtration, the magnetic carrier was obtained by vacuum drying at 65°C for 5h. (6) The magnetic carrier was dispersed in a 3:1 volume ratio of ethanol / water solution at a mass volume ratio of 1 g:30 mL, and after uniform dispersion, 0.2 times the mass of the magnetic carrier of the Mn(III)-Schiff base complex was added, and after stirring at 200 rpm, triethylamine was added dropwise, and the molar ratio of triethylamine to the Mn(III)-Schiff base complex was 1.5:1. After the addition was completed, the temperature was raised to 75°C, and refluxed for 4.5 h. After the reaction was completed, the heating was stopped, and the product was continuously stirred and cooled to room temperature, and then the product was adsorbed by a magnet, and washed 4 times with a 3:1 volume ratio of ethanol / water solution, and then dried at 80°C under vacuum for 4 h.

[0021] Comparative Example 1 This comparative example is compared with Example 2, and the solid catalyst in step S1 is replaced with the Mn(III)-Schiff base complex prepared in step (1), and steps (2)-(6) are omitted, and the other steps are the same as Example 2.

[0022] Comparative Example 2 This comparative example 2 is compared with Example 2, and in the preparation of the solid catalyst, steps (2)-(5) are omitted, and the magnetic carrier in step (6) is replaced with SBA-15, and the other steps are the same as Example 2.

[0023] Comparative Example 3 This comparative example 3 is compared with Example 2, and the solid catalyst is omitted, and the other steps are the same as Example 2.

[0024] Comparative Example 4 This comparative example 4 is compared with Example 2, and rose Bengal B is omitted, and the other steps are the same as Example 2.

[0025] Comparative Example 5 This comparative example 5 is compared with Example 2, and the 450 nm LED light source is turned off, and the other steps are the same as Example 2.

[0026] The above-mentioned Examples 1-3 and Comparative Examples 1-5 were used to prepare 3,5-dichloro-2-pentanone, respectively. The reaction liquid was extracted with ethyl acetate, and then subjected to quantitative analysis by GC-MS to calculate the conversion rate of 2-pentanone. The reaction liquid was extracted with ethyl acetate, purified by vacuum distillation, and the actual mass of the product was weighed, and the yield was calculated based on the theoretical yield. The test results are shown in Table 1 below.

[0027] Table 1 Comparison of performance of Examples and Comparative Examples

[0028] From the above Table 1, it can be seen that the reaction almost stops in the dark or without rose Bengal B, the conversion rate is <10% without catalyst, and the catalyst is difficult to recover without magnetic carrier, indicating that the solid catalyst of the present application has high catalytic activity and recyclability, and the use of rose Bengal B and LED of the present application is a necessary condition for the reaction.

[0029] The catalyst of Example 2 was recovered, washed with ethanol, dried at 55°C under vacuum, weighed, and the recovery rate was calculated. The recovered catalyst was used for the next round of reaction (conditions same as Example 2), and the yield of 3,5-dichloro-2-pentanone and the recovery rate of the catalyst were calculated for 5 times, and 3,5-dichloro-2-pentanone was calculated for 3 times. The statistical results are shown in Table 2.

[0030] Table 2 Stability of catalyst recycling (catalyst of Example 2)

[0031] From the above Table 2, it can be seen that the solid catalyst prepared by the method of the present application has a yield of >80% and a catalyst recovery rate of >88% after 5 cycles, and can be reused.

[0032] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing 3,5-dichloro-2-pentanone, characterized in that, Includes the following steps: S1. Dissolve 2-pentanone, NaCl, and photosensitizer in phosphate buffer solution, add solid catalyst, pass air through, irradiate with a 450nm LED light source, and simultaneously add 5-10% (w / w) H2O2 aqueous solution. S2. After continuous reaction for 6-7 hours, the catalyst was recovered by magnetic separation, and 3,5-dichloro-2-pentanone was obtained by ethyl acetate extraction and distillation.

2. The method for preparing 3,5-dichloro-2-pentanone according to claim 1, characterized in that, The concentration of 2-pentanone in step S1 is 0.5~1M, and the concentration of NaCl is 0.2~0.5M; The photosensitizer is Rose Red B, with a purity ≥98%, and its dosage relative to 2-pentanone is 0.5~2 mol%; The H2O2 aqueous solution is added at a rate of 0.1~0.3 mL / min, and the molar ratio of H2O2 to 2-pentanone is 2~4:

1.

3. The method for preparing 3,5-dichloro-2-pentanone according to claim 1, characterized in that, The phosphate buffer solution described in step S1 consists of 0.1M Na2HPO4 / KH2PO4 with a pH of 6.

8.

4. The method for preparing 3,5-dichloro-2-pentanone according to claim 1, characterized in that, The air introduction rate in step S1 is 0.1~0.3 mL / min.

5. The method for preparing 3,5-dichloro-2-pentanone according to claim 1, characterized in that, The amount of solid catalyst added in step S1 is 5-8% of the mass of 2-pentanone; The preparation of the solid catalyst includes the following steps: (1) Salicylaldehyde and ethylenediamine were added to ethylene glycol dimethyl ether at a molar ratio of 2:

1. After stirring at 50-55℃ for 1-1.5h, Mn(OAc)2·4H2O was added to the system. The temperature was raised to 60-65℃ and stirring was continued for 2-2.5h to form Mn(II)-Schiff base complex. A 30% H2O2 aqueous solution was added dropwise. Oxidation was completed within 30min. After standing and cooling, crystals were precipitated. After filtration, the crystals were washed with deionized water 3-4 times and then vacuum dried at 55-65℃ for 2-3h to obtain Mn(III)-Schiff base complex. (2) Disperse the magnetic carrier ultrasonically into an ethanol / water solution with a volume ratio of 3:

1. After the dispersion is uniform, add 0.1 to 0.2 times the mass of the magnetic carrier of Mn(Ⅲ)-Schiff base complex. Stir and mix at 100 to 200 rpm. Then add triethylamine dropwise. After the addition is complete, heat to 70 to 75°C and reflux for 4 to 4.5 h. After the reaction is complete, stop heating, continue stirring and cool to room temperature. Adsorb the product with a magnet and wash it 3 to 4 times with an ethanol / water solution with a volume ratio of 3:

1. After washing, vacuum dry at 70 to 80°C for 3 to 4 h.

6. The method for preparing 3,5-dichloro-2-pentanone according to claim 5, characterized in that, The molar ratio of Mn(OAc)2·4H2O to salicylaldehyde in step (1) is 1:2; The molar ratio of H2O2 to Mn(OAc)2·4H2O is 1.1~1.3:

1.

7. The method for preparing 3,5-dichloro-2-pentanone according to claim 5, characterized in that, The preparation of the magnetic carrier described in step (2) includes the following steps: 1) Add FeCl3·6H2O and FeSO4·7H2O to a three-necked flask in a molar ratio of 2:

1. Under N2 protection, add 0.1M NaOH aqueous solution dropwise to adjust the pH to 10-11 at a dropping rate of 2mL / min. After the addition is complete, continue to stir the reaction under N2 protection in a water bath at 60-65℃ for 200-300rpm for 1-2h. After the reaction is complete, use a magnet to adsorb the generated Fe3O4 nanoparticles and wash with deionized water until the pH of the supernatant is neutral to obtain Fe3O4 nanoparticles. 2) Disperse Fe3O4 nanoparticles into a 1:1 ethanol / water mixture at a mass-to-volume ratio of 1g:20~30mL. Sonicate the mixture at 200W for 15~20min to form a uniform suspension. Transfer the suspension to a three-necked flask and add TEOS dropwise at a stirring rate of 0.5~0.7mL / min, with Fe3O4:TEOS = 1g:0.5~1mL. After the addition is complete, continue stirring in a water bath at 30~35℃ for 4~5h. After the reaction is complete, adsorb the product with a magnet, wash with ethanol 3~4 times, and then vacuum dry at 55~65℃ for 1.5~2.5h to obtain Fe3O4@SiO2 nanoparticles. 3) Fe3O4@SiO2 nanoparticles were ultrasonically dispersed in ethanol at a mass-to-volume ratio of 1g:50~60mL. γ-aminopropylmethyldimethoxysilane was added, with a mass-to-volume ratio of 1g:0.05~0.06mL. The mixture was stirred at 100~200rpm in a water bath at 50~55℃ for 2~2.5h. After the reaction was completed, the product was adsorbed with a magnet, washed with ethanol 3~4 times, and then vacuum dried at 55~65℃ for 1.5~2.5h to obtain amino-modified Fe3O4@SiO2 nanoparticles. 4) The aminated Fe3O4@SiO2 nanoparticles and SBA-15 were added to deionized water at a mass ratio of 1:4~5. The mass-volume ratio of the aminated Fe3O4@SiO2 nanoparticles to deionized water was 1g:200~250mL. The mixture was ultrasonically treated at 300W for 30~40min, filtered, and then vacuum dried at 55~65℃ for 4~5h to obtain the magnetic carrier.

8. The method for preparing 3,5-dichloro-2-pentanone according to claim 5, characterized in that, The mass-to-volume ratio of the magnetic carrier to the ethanol / water solution in step (2) is 1g:25~30mL; The molar ratio of triethylamine to the Mn(III)-Schiff base complex is 1.2~1.5:

1.

9. The method for preparing 3,5-dichloro-2-pentanone according to claim 1, characterized in that, The distance between the LED light source and the reactor in step S1 is 15~20cm.

10. The method for preparing 3,5-dichloro-2-pentanone according to claim 1, characterized in that, In step S2, the ethyl acetate extraction is performed 3 to 4 times with equal volumes, each time using 1 / 3 to 1 / 2 of the reaction liquid volume, and the ethyl acetate can be recovered by distillation; the distillation is vacuum distillation.

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