Depolymerization method of 3-chloro-5-hydroxy-2-pentanone dimer and 3-chloro-5-hydroxy-2-pentanone solution

Abstract

The invention discloses a depolymerization method of a 3-chloro-5-hydroxy-2-pentanone dimer and a 3-chloro-5-hydroxy-2-pentanone solution, and relates to the field of organic synthesis. The depolymerization method comprises the following steps: mixing a 3-chloro-5-hydroxy-2-pentanone dimer with a polar solvent to obtain a first solution; mixing the first solution with a basic catalyst and an aromatic carboxylic acid compound containing hydroxyl to obtain a second solution; carrying out a depolymerization reaction on the second solution at a first temperature to obtain a third solution; and adjusting the pH value of the third solution to obtain the 3-chloro-5-hydroxy-2-pentanone solution. The depolymerization method of the 3-chloro-5-hydroxy-2-pentanone dimer, disclosed by the invention, has the characteristics of high depolymerization rate, high selectivity and high product purity, and is beneficial to full utilization of chemical resources.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and more specifically, to a method for depolymerizing 3-chloro-5-hydroxy-2-pentanone dimer and a 3-chloro-5-hydroxy-2-pentanone solution. Background Technology

[0002] 3-Chloro-5-hydroxy-2-pentanone (OHCH2-CH2-CH(Cl)-C(=O)-CH3) belongs to the β-hydroxy ketone class of compounds and is commonly used in the synthesis of vitamin B1 or lipid-lowering drugs such as atorvastatin and rosuvastatin, enjoying widespread market demand. Conventional preparation methods for 3-chloro-5-hydroxy-2-pentanone typically involve sequential hydrolysis ring-opening and decarboxylation reactions in acidic aqueous solutions. However, the molecule of 3-chloro-5-hydroxy-2-pentanone contains active hydroxyl and carbonyl groups, making it highly susceptible to intermolecular polymerization during concentration or under acidic conditions, forming a 3-chloro-5-hydroxy-2-pentanone dimer (CH3-C(OH)(O-CH2-CH2-CH(Cl)-C(=O)-CH3)-CH(Cl)-CH2-CH2OH), leading to a decrease in the yield of 3-chloro-5-hydroxy-2-pentanone. Furthermore, the 3-chloro-5-hydroxy-2-pentanone dimer in the reaction residue can usually only be disposed of as waste, which not only wastes raw materials but also pollutes the environment. Summary of the Invention

[0003] The main objective of this invention is to provide a method for depolymerizing 3-chloro-5-hydroxy-2-pentanone dimer and a 3-chloro-5-hydroxy-2-pentanone solution, in order to solve the problems in the prior art where the formation of 3-chloro-5-hydroxy-2-pentanone dimer leads to a decrease in the yield of 3-chloro-5-hydroxy-2-pentanone, and 3-chloro-5-hydroxy-2-pentanone dimer can usually only be treated as waste, which not only wastes raw materials but also pollutes the environment.

[0004] To achieve the above objectives, according to one aspect of the present invention, a method for depolymerizing 3-chloro-5-hydroxy-2-pentanone dimer is provided, comprising the following steps:

[0005] The 3-chloro-5-hydroxy-2-pentanone dimer was mixed with a polar solvent to obtain the first solution;

[0006] The first solution is mixed with an alkaline catalyst and an aromatic carboxylic acid compound containing a hydroxyl group to obtain a second solution;

[0007] The second solution is subjected to a depolymerization reaction at the first temperature to obtain the third solution;

[0008] The pH of the third solution was adjusted to obtain a 3-chloro-5-hydroxy-2-pentanone solution.

[0009] Furthermore, in the molecules of aromatic carboxylic acid compounds containing hydroxyl groups, the number of hydroxyl groups is greater than or equal to two.

[0010] Furthermore, aromatic carboxylic acid compounds containing hydroxyl groups have ortho-hydroxyl groups in their molecules.

[0011] Furthermore, the aromatic carboxylic acid compound containing a hydroxyl group is selected from at least one of 2,3-dihydroxybenzoic acid, gallic acid, and gentianic acid.

[0012] Furthermore, in the second solution, the mass ratio of the aromatic carboxylic acid compound containing hydroxyl groups to the 3-chloro-5-hydroxy-2-pentanone dimer is (0.1~0.5):100.

[0013] Furthermore, the alkaline catalyst is selected from at least one of sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium carbonate, potassium carbonate, sodium methoxide, sodium ethoxide, triethylamine, and 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU).

[0014] Furthermore, in the second solution, the mass ratio of the alkaline catalyst to the 3-chloro-5-hydroxy-2-pentanone dimer is (0.1~5):100.

[0015] Furthermore, the polar solvent is selected from at least one of water, methanol, ethanol, and tetrahydrofuran.

[0016] Furthermore, in the first solution, the mass-to-volume ratio of the 3-chloro-5-hydroxy-2-pentanone dimer to the polar solvent is 1:(3~5) g / mL.

[0017] Furthermore, the pH value of the second solution is 8.0~9.0.

[0018] Furthermore, the pH value of the 3-chloro-5-hydroxy-2-pentanone solution is 6.5~7.5.

[0019] Furthermore, the pH value of the third solution is adjusted using a pH adjuster to obtain a 3-chloro-5-hydroxy-2-pentanone solution. The pH adjuster is selected from at least one of boric acid solution, hydrochloric acid solution, sulfuric acid solution, and nitric acid solution.

[0020] Furthermore, the first temperature is 60℃~80℃.

[0021] Furthermore, the depolymerization reaction takes 2 to 4 hours.

[0022] Furthermore, during the depolymerization reaction of the second solution at the first temperature, the depolymerization method of the 3-chloro-5-hydroxy-2-pentanone dimer also includes refluxing the second solution to obtain a third solution.

[0023] Furthermore, when the conversion rate of the 3-chloro-5-hydroxy-2-pentanone dimer is greater than or equal to 96%, a third solution is obtained.

[0024] According to another aspect of the present invention, a 3-chloro-5-hydroxy-2-pentanone solution is provided, which is prepared by any of the depolymerization methods of the 3-chloro-5-hydroxy-2-pentanone dimer described in the foregoing schemes.

[0025] Applying the technical solution of this invention, an alkaline catalyst helps promote the cleavage of ether bonds within the 3-chloro-5-hydroxy-2-pentanone dimer molecule, significantly improving the depolymerization rate and selectivity for obtaining 3-chloro-5-hydroxy-2-pentanone. Aromatic carboxylic acid compounds containing hydroxyl groups help reduce side reactions during depolymerization, improving the yield and purity of 3-chloro-5-hydroxy-2-pentanone. In the molecular structure of hydroxyl-containing aromatic carboxylic acid compounds, the hydroxyl group (-OH) can form hydrogen bonds with the hemiketal oxygen atom adjacent to the chlorine atom in the 3-chloro-5-hydroxy-2-pentanone dimer molecule, thereby altering the local electronic environment of the chlorination site; the carboxyl group (-COOH) has a local buffering effect on the pH value near the 3-chloro-5-hydroxy-2-pentanone dimer molecule; the aromatic ring can provide a hydrophobic microenvironment for the 3-chloro-5-hydroxy-2-pentanone dimer molecule, while simultaneously increasing the C-Cl bond cleavage barrier through dipole interactions. The structures of the above-mentioned aromatic carboxylic acid compounds containing hydroxyl groups all help protect the chlorination site and inhibit OH... - Alternatively, H₂O can nucleophilically attack chlorine atoms. By using a basic catalyst and an aromatic carboxylic acid compound containing a hydroxyl group to act on the 3-chloro-5-hydroxy-2-pentanone dimer, it is helpful to fully depolymerize the 3-chloro-5-hydroxy-2-pentanone dimer to obtain 3-chloro-5-hydroxy-2-pentanone, thereby increasing the yield of 3-chloro-5-hydroxy-2-pentanone, while making full use of chemical raw materials and protecting the environment. Attached Figure Description

[0026] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention.

[0027] Figure 1 This is a gas chromatogram obtained using 3-chloro-5-hydroxy-2-pentanone standard;

[0028] Figure 2 This is a gas chromatogram obtained using a 3-chloro-5-hydroxy-2-pentanone dimer standard;

[0029] Figure 3 Here is a gas chromatogram of the 3-chloro-5-hydroxy-2-pentanone dimer used in the examples and comparative examples;

[0030] Figure 4 The image shows a gas chromatogram obtained using the 3-chloro-5-hydroxy-2-pentanone solution from Example 1. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0032] As described in the background section of this invention, the formation of 3-chloro-5-hydroxy-2-pentanone dimers in the prior art leads to a decrease in the yield of 3-chloro-5-hydroxy-2-pentanone, and these dimers are typically treated as waste, resulting in both waste of raw materials and environmental pollution. To address these problems, in a typical embodiment of this invention, a method for depolymerizing 3-chloro-5-hydroxy-2-pentanone dimers is provided, comprising the following steps:

[0033] The 3-chloro-5-hydroxy-2-pentanone dimer was mixed with a polar solvent to obtain the first solution;

[0034] The first solution is mixed with an alkaline catalyst and an aromatic carboxylic acid compound containing a hydroxyl group to obtain a second solution;

[0035] The second solution is subjected to a depolymerization reaction at the first temperature to obtain the third solution;

[0036] The pH of the third solution was adjusted to obtain a 3-chloro-5-hydroxy-2-pentanone solution.

[0037] In this invention, an alkaline catalyst facilitates the breaking of ether bonds within the 3-chloro-5-hydroxy-2-pentanone dimer and its depolymerization to yield 3-chloro-5-hydroxy-2-pentanone, significantly improving the depolymerization rate and selectivity. The reaction formula for the depolymerization reaction of the 3-chloro-5-hydroxy-2-pentanone dimer is as follows:

[0038] .

[0039] During the depolymerization process, the 3-chloro-5-hydroxy-2-pentanone obtained from the depolymerization of the 3-chloro-5-hydroxy-2-pentanone dimer readily reacts with OH groups. - Alternatively, H2O may undergo a side reaction, generating 1,3-diol byproducts, leading to a decrease in yield and purity. The reaction equation is as follows:

[0040] (1) with OH - reaction

[0041] ;

[0042] (2) Reaction with H2O

[0043] .

[0044] This invention, by adding an aromatic carboxylic acid compound containing a hydroxyl group, can effectively reduce the occurrence of side reactions during depolymerization and improve the yield and purity of 3-chloro-5-hydroxy-2-pentanone. Firstly, the hydroxyl group (-OH) in the aromatic carboxylic acid compound forms a hydrogen bond with the hemiketal oxygen atom adjacent to the chlorine atom in the 3-chloro-5-hydroxy-2-pentanone dimer, which helps to change the local electronic environment of the chlorination site in the 3-chloro-5-hydroxy-2-pentanone dimer. Secondly, the carboxyl group (-COOH) in the aromatic carboxylic acid compound has a local buffering effect on the pH value near the 3-chloro-5-hydroxy-2-pentanone dimer, promoting the OH group to react with the hydroxyl group. - The concentration increases slowly; thirdly, the aromatic ring in the hydroxyl-containing aromatic carboxylic acid molecule is hydrophobic, providing a hydrophobic microenvironment for the 3-chloro-5-hydroxy-2-pentanone dimer, inhibiting the nucleophilic attack of water molecules on the chlorine atom; fourthly, the aromatic ring in the hydroxyl-containing aromatic carboxylic acid molecule can also increase the breaking energy barrier of the C-Cl bond through dipole interaction. All of these effects protect the chlorination sites, helping to reduce side reactions and improve the yield and purity of 3-chloro-5-hydroxy-2-pentanone.

[0045] It should be noted that when a compound contains all three structures—hydroxyl, carboxyl, and aromatic ring—it significantly promotes the depolymerization of the 3-chloro-5-hydroxy-2-pentanone dimer to 3-chloro-5-hydroxy-2-pentanone. However, the absence of one or two of these three structures may actually hinder depolymerization. For example, the hydrogen bond formed between the hydroxyl group and the 3-chloro-5-hydroxy-2-pentanone dimer provides conditions for the local protection of the reaction site by the carboxyl and aromatic rings. Without the hydroxyl group, the carboxyl and aromatic rings not only fail to provide local protection but may also trigger side reactions, inhibiting the effective depolymerization of the 3-chloro-5-hydroxy-2-pentanone dimer.

[0046] In this invention, the 3-chloro-5-hydroxy-2-pentanone dimer can be, but is not limited to, obtained by polymerizing two molecules of 3-chloro-5-hydroxy-2-pentanone.

[0047] Furthermore, depolymerization in polar solvents helps promote the full dissolution of reactants, such as 3-chloro-5-hydroxy-2-pentanone dimers, basic catalysts, and aromatic carboxylic acid molecules containing hydroxyl groups, thereby improving depolymerization efficiency and depolymerization rate.

[0048] Adjusting the pH of the third solution helps control the reaction process, preventing the depolymerization product 3-chloro-5-hydroxy-2-pentanone from continuing to react in an alkaline environment to generate 1,3-diol byproducts, thus improving the stability of 3-chloro-5-hydroxy-2-pentanone.

[0049] In some embodiments, the number of hydroxyl groups in the molecule of the aromatic carboxylic acid compound is greater than or equal to two. Preferably, the number of hydroxyl groups in the molecule of the aromatic carboxylic acid compound is two to three.

[0050] In the above embodiments of this application, by limiting the number of hydroxyl groups within the aforementioned range, the hydroxyl groups in the aromatic carboxylic acid compound molecule containing hydroxyl groups form hydrogen bonds with the hemiketal oxygen and carbonyl oxygen adjacent to the chlorine atom in the 3-chloro-5-hydroxy-2-pentanone dimer molecule, respectively, ultimately forming an intermolecular hydrogen bond network. This helps to suppress OH groups by utilizing the steric shielding effect. - Attack on chlorinated carbon increases the yield of 3-chloro-5-hydroxy-2-pentanone.

[0051] In some embodiments, the aromatic carboxylic acid compound containing a hydroxyl group has an ortho-hydroxyl group in its molecule.

[0052] In the above embodiments of this application, limiting the relative position of hydroxyl groups helps to adjust the hydrogen bond network structure formed between the aromatic carboxylic acid compound molecule containing hydroxyl groups and the 3-chloro-5-hydroxy-2-pentanone dimer molecule, thereby improving the spatial shielding effect on chlorinated carbon and thus improving the depolymerization rate and depolymerization selectivity.

[0053] In some embodiments, the aromatic carboxylic acid compound containing a hydroxyl group is selected from at least one of 2,3-dihydroxybenzoic acid, gallic acid, and gentianic acid.

[0054] In the above embodiments of this application, by limiting the specific types of aromatic carboxylic acid compounds containing hydroxyl groups, it is helpful for the aromatic carboxylic acid compounds containing hydroxyl groups to be uniformly dispersed in polar solvents, to fully contact with 3-chloro-5-hydroxy-2-pentanone dimer molecules and form a hydrogen bond network structure, thereby improving the reaction selectivity.

[0055] In some embodiments, the mass ratio of the hydroxyl-containing aromatic carboxylic acid compound to the 3-chloro-5-hydroxy-2-pentanone dimer in the second solution is (0.1 to 0.5):100. Typical, but not limiting, mass ratios of the hydroxyl-containing aromatic carboxylic acid compound to the 3-chloro-5-hydroxy-2-pentanone dimer are 0.1:100, 0.2:100, 0.3:100, 0.4:100, 0.5:100, or any combination of two such values.

[0056] In the embodiments described above in this application, by limiting the amount of aromatic carboxylic acid compounds containing hydroxyl groups within the above range, it is helpful to further improve the selectivity of the reaction while balancing the depolymerization efficiency.

[0057] In some embodiments, the alkaline catalyst is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium methoxide, sodium ethoxide, triethylamine, and DBU. Preferably, the alkaline catalyst is selected from at least one of sodium hydroxide, potassium hydroxide, and triethylamine.

[0058] In the embodiments described above in this application, by limiting the type of alkaline catalyst, it is helpful to provide OH groups for the ether bond cleavage in the 3-chloro-5-hydroxy-2-pentanone dimer molecule. - A suitable pH environment is also important. Among them, sodium hydroxide, potassium hydroxide, and triethylamine are moderately alkaline and easily electrolyzed, which helps to improve depolymerization efficiency and selectivity.

[0059] In some embodiments, the mass ratio of the basic catalyst to the 3-chloro-5-hydroxy-2-pentanone dimer in the second solution is (0.1 to 5):100. Typical, but not limiting, mass ratios of the basic catalyst to the 3-chloro-5-hydroxy-2-pentanone dimer are 0.1:100, 0.5:100, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100, 5:100, or any combination of two of these values.

[0060] In the above embodiments of this application, by limiting the amount of alkaline catalyst within the above range, it is helpful to control the pH environment of the reaction system while improving the depolymerization efficiency, thereby improving the selectivity of the depolymerization reaction.

[0061] In some embodiments, the polar solvent is selected from at least one of water, methanol, ethanol, and tetrahydrofuran. Preferably, when the polar solvent is water, it is selected from at least one of distilled water and deionized water.

[0062] In the embodiments described above, limiting the type of polar solvent helps to promote the complete dissolution of reactants, such as 3-chloro-5-hydroxy-2-pentanone dimer, basic catalysts, and aromatic carboxylic acid compounds containing hydroxyl groups. In specific embodiments, the polar solvent can be adapted to the selected basic catalyst. For example, when the basic catalyst is sodium hydroxide, water is preferred as the polar solvent; when the basic catalyst is DBU, tetrahydrofuran is preferred as the polar solvent; and when the basic catalyst is sodium methoxide, methanol is preferred as the polar solvent.

[0063] In some embodiments, the mass-to-volume ratio of the 3-chloro-5-hydroxy-2-pentanone dimer to the polar solvent in the first solution is 1:(3~5) g / mL. Typical, but not limiting, mass-to-volume ratios of the 3-chloro-5-hydroxy-2-pentanone dimer to the polar solvent are 1:3 g / mL, 1:3.5 g / mL, 1:4 g / mL, 1:4.5 g / mL, 1:5 g / mL, or any combination of two such values.

[0064] In the above embodiments of this application, by limiting the mass ratio, it is helpful to control the concentration of 3-chloro-5-hydroxy-2-pentanone dimer in the system within a moderate range, so as to promote the rapid dissolution and uniform dispersion of 3-chloro-5-hydroxy-2-pentanone dimer, alkaline catalyst and aromatic carboxylic acid compound containing hydroxyl group, thereby increasing the mass transfer efficiency during the depolymerization process.

[0065] In some embodiments, the pH of the second solution is 8.0 to 9.0. Typically, but not limitingly, the pH of the second solution is 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, or a range of any two of these values.

[0066] In the above embodiments of this application, the depolymerization reaction is preferably carried out within a pH range of 8.0 to 9.0, resulting in optimal reaction efficiency and selectivity. When the pH of the second solution is controlled within the range of 8.0 to 9.0, the pH of the reaction system can be maintained within this range without the need for alkali replenishment before the reaction ends, thereby promoting the catalytic efficiency of the alkaline catalyst and improving depolymerization efficiency and selectivity.

[0067] In some embodiments, the pH of the 3-chloro-5-hydroxy-2-pentanone solution is 6.5 to 7.5. Typical, but not limiting, pH values ​​of the 3-chloro-5-hydroxy-2-pentanone solution are 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, or a range of any two of these values.

[0068] In the above embodiments of this application, by controlling the pH value of the 3-chloro-5-hydroxy-2-pentanone solution within the above range, it is helpful to remove excess alkaline catalyst in the system, terminate the depolymerization reaction and other side reactions in a timely manner, and ensure that the product 3-chloro-5-hydroxy-2-pentanone solution remains stable in subsequent processing.

[0069] In some embodiments, a pH adjuster is used to adjust the pH of the third solution to obtain a 3-chloro-5-hydroxy-2-pentanone solution. The pH adjuster is selected from at least one of boric acid solution, hydrochloric acid solution, sulfuric acid solution, and nitric acid solution. The concentration of the pH adjuster is sufficient to adjust the pH of the solution to 6.5-7.5. Specifically, the concentration of the boric acid solution is 0.05 mol / L to 1 mol / L, and / or the concentration of the hydrochloric acid solution is 0.05 mol / L to 1 mol / L, and / or the concentration of the sulfuric acid solution is 0.05 mol / L to 1 mol / L, and / or the concentration of the nitric acid solution is 0.05 mol / L to 1 mol / L.

[0070] In the embodiments described above, limiting the type of pH adjuster helps to effectively control the pH value of the third solution while ensuring the stability of the components in the solution. Furthermore, limiting the concentration of the pH adjuster also helps to control the hydrogen ions (H+) near the product 3-chloro-5-hydroxy-2-pentanone. + The concentration was increased slowly, which improved the stability of the product 3-chloro-5-hydroxy-2-pentanone.

[0071] In some implementations, the first temperature is 60°C to 80°C. Typically, but not limitingly, the first temperature is a range of 60°C, 65°C, 70°C, 75°C, 80°C, or any two of these values.

[0072] In the above embodiments of this application, by limiting the first temperature within the above range, it is helpful to carry out the depolymerization reaction in a milder environment, providing energy for the reaction while improving the selectivity of the reaction, and improving the reaction efficiency and product purity.

[0073] In some implementations, the depolymerization reaction takes 2 to 4 hours. Typically, but not limitingly, the depolymerization reaction takes 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or any combination of two of these values.

[0074] In the above embodiments of this application, by limiting the depolymerization reaction time within the above range, sufficient reaction time can be provided for depolymerization, and the reaction can be terminated in time, ensuring the stability of the product 3-chloro-5-hydroxy-2-pentanone in the system.

[0075] In some embodiments, the depolymerization method of 3-chloro-5-hydroxy-2-pentanone dimer during the depolymerization reaction of the second solution at the first temperature further includes refluxing the second solution to obtain a third solution.

[0076] In the above embodiments of this application, condensing and refluxing the second solution helps to improve reaction stability, while also improving mass transfer efficiency and conversion rate.

[0077] In some embodiments, a third solution is obtained when the conversion rate of the 3-chloro-5-hydroxy-2-pentanone dimer is greater than or equal to 96%.

[0078] In the embodiments described above, the reaction process can be monitored in real time using methods such as gas chromatography, liquid chromatography, or thin-layer chromatography to determine the reaction endpoint. The reaction can be terminated when the conversion rate of the 3-chloro-5-hydroxy-2-pentanone dimer reaches a certain value, yielding a third solution. This setup helps improve the efficiency and selectivity of depolymerization, thereby increasing the reaction yield.

[0079] In another typical embodiment of the present invention, a 3-chloro-5-hydroxy-2-pentanone solution is provided, which is prepared by any of the depolymerization methods of 3-chloro-5-hydroxy-2-pentanone dimers described in the foregoing schemes.

[0080] In the embodiments described above in this application, the 3-chloro-5-hydroxy-2-pentanone solution can be purified to obtain high-purity 3-chloro-5-hydroxy-2-pentanone, which helps to improve the purity and conversion rate of its downstream products. The purification methods include, but are not limited to, extraction, distillation, and drying, and can be adapted according to laboratory or factory conditions.

[0081] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0082] Some of the materials used in the examples and comparative examples are as follows:

[0083] 3-Chloro-5-hydroxy-2-pentanone standard: purity ≥97.0%, purchased from Guangdong Yuanfeng Chemical Reagent Co., Ltd., its gas chromatogram is shown below. Figure 1 As shown;

[0084] 3-Chloro-5-hydroxy-2-pentanone dimer standard: purity ≥95.0%, purchased from Guangdong Yuanfeng Chemical Reagent Co., Ltd., its gas chromatogram is shown below. Figure 2 As shown;

[0085] 3-Chloro-5-hydroxy-2-pentanone dimer: Obtained from the reaction residue of the synthesis of 3-chloro-5-hydroxy-2-pentanone, with a purity of 100%. Its gas chromatogram is shown below. Figure 3 As shown;

[0086] 2,3-Dihydroxybenzoic acid: purity 99.5%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0087] Gallic acid: chemical name 3,4,5-trihydroxybenzoic acid, purity 99.5%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0088] Gentian acid: chemical name 2,5-dihydroxybenzoic acid, purity 99.5%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0089] The pH values ​​of the solutions in the examples and comparative examples were obtained using a Mettler FE28-standard F2 FE28-CN pH meter.

[0090] Example 1

[0091] An embodiment of the depolymerization method for the 3-chloro-5-hydroxy-2-pentanone dimer in this invention includes the following steps:

[0092] S1, 200g of 3-chloro-5-hydroxy-2-pentanone dimer is mixed with 700mL of polar solvent deionized water to obtain the first solution; wherein, the mass-to-volume ratio of 3-chloro-5-hydroxy-2-pentanone dimer to polar solvent is 1:3.5g / mL;

[0093] S2, the first solution is mixed with 4g of alkaline catalyst sodium hydroxide and 0.6g of hydroxyl-containing aromatic carboxylic acid compound 2,3-dihydroxybenzoic acid to obtain the second solution; wherein the mass ratio of alkaline catalyst to 3-chloro-5-hydroxy-2-pentanone dimer is 2:100, and the mass ratio of hydroxyl-containing aromatic carboxylic acid compound to 3-chloro-5-hydroxy-2-pentanone dimer is 0.3:100; the pH value of the second solution is 8.5;

[0094] S3 involves depolymerizing the second solution at 70°C, followed by reflux condensation to obtain the third solution; the depolymerization reaction takes 3.5 hours.

[0095] S4, the pH of the third solution was adjusted to 7 using a pH adjuster to obtain a 3-chloro-5-hydroxy-2-pentanone solution; the pH adjuster was a 0.5 mol / L hydrochloric acid solution.

[0096] Examples 2-8

[0097] The difference from Example 1 is that the type of alkaline catalyst is different, and the type of polar solvent is adapted to the type of alkaline catalyst, as detailed in Table 1.

[0098] Examples 9-10

[0099] The difference from Example 1 is that the alkaline catalyst is obtained by combining two alkaline agents. Specifically, the alkaline catalyst used in Example 9 is obtained by combining 2g NaOH and 2g potassium carbonate, and the alkaline catalyst used in Example 10 is obtained by combining 2g NaOH and 2g DBU. In addition, the type of polar solvent is adapted according to the type of alkaline catalyst, as detailed in Table 1.

[0100] Examples 11-13 and Comparative Example 1

[0101] The difference from Example 1 is that the mass ratio of the alkaline catalyst to the 3-chloro-5-hydroxy-2-pentanone dimer is different, or the alkaline catalyst is not added, as detailed in Table 1.

[0102] Examples 14-16

[0103] The difference from Example 1 is that the types of aromatic carboxylic acid compounds containing hydroxyl groups are different, as detailed in Table 1.

[0104] Comparative Examples 2-4

[0105] The difference from Example 1 is that the aromatic carboxylic acid compound containing hydroxyl groups is replaced with other compounds, as detailed in Table 1.

[0106] Examples 17-19 and Comparative Example 5

[0107] The difference from Example 1 is that the mass ratio of the hydroxyl-containing aromatic carboxylic acid compound to the 3-chloro-5-hydroxy-2-pentanone dimer is different, or the hydroxyl-containing aromatic carboxylic acid compound is not added, as detailed in Table 1.

[0108] Comparative Example 6

[0109] The difference from Example 1 is that no alkaline catalyst and aromatic carboxylic acid compounds containing hydroxyl groups are added, as detailed in Table 1.

[0110] Comparative Example 7

[0111] The difference from Example 1 is that the alkaline catalyst is replaced with an acidic catalyst. Specifically, 4.0g of NaOH is replaced with 10.8g of hydrochloric acid solution with a mass concentration of 37% (containing 4.0g of hydrogen chloride), as detailed in Table 1.

[0112] Examples 20-22

[0113] The differences from Example 1 are as follows: the mass-to-volume ratio of the 3-chloro-5-hydroxy-2-pentanone dimer to the polar solvent is different, the temperature of the depolymerization reaction is different, the time of the depolymerization reaction is different, and the pH value of the 3-chloro-5-hydroxy-2-pentanone solution is different, as detailed in Table 1. Among them, the pH values ​​of the 3-chloro-5-hydroxy-2-pentanone solution are 7.5 (Example 20), 6.5 (Example 21), and 6 (Example 22), respectively.

[0114] In Table 1, "dimer" refers to "3-chloro-5-hydroxy-2-pentanone dimer" and "compound" includes "aromatic carboxylic acid compounds containing hydroxyl groups".

[0115] Table 1

[0116]

[0117]

[0118]

[0119] The depolymerization rate (hereinafter referred to as depolymerization rate), the content of 3-chloro-5-hydroxy-2-pentanone, the selectivity of 3-chloro-5-hydroxy-2-pentanone obtained by depolymerization (hereinafter referred to as selectivity), the content of 1,3-diol byproducts, and the content of impurities other than 1,3-diol byproducts of the 3-chloro-5-hydroxy-2-pentanone dimer in Examples 1-22 and Comparative Examples 1-7 were tested and calculated.

[0120] Test methods

[0121] Gas chromatography was used to detect 3-chloro-5-hydroxy-2-pentanone standard, 3-chloro-5-hydroxy-2-pentanone dimer standard, 3-chloro-5-hydroxy-2-pentanone dimer used in the examples and comparative examples, and 3-chloro-5-hydroxy-2-pentanone solutions prepared in the examples and comparative examples. The pretreatment method for the 3-chloro-5-hydroxy-2-pentanone solution was as follows: 50 mL of ethyl acetate was mixed with 10 mL of 3-chloro-5-hydroxy-2-pentanone solution, and extraction was performed to obtain the extracted solution. The ethyl acetate layer of the extracted solution was taken as the analyte for gas chromatography detection.

[0122] The gas chromatography detection conditions were as follows: DB-5 gas chromatographic column, column temperature 250~300℃, heating rate 20~30℃ / min, carrier gas flow rate 20~30mL / min, and Agilent 7890A gas chromatograph.

[0123] After detection, the peak area ratio of each component in the gas chromatogram was calculated using the normalization method to obtain the content of each component.

[0124] The components in the 3-chloro-5-hydroxy-2-pentanone solution include 3-chloro-5-hydroxy-2-pentanone dimer, 3-chloro-5-hydroxy-2-pentanone, 1,3-diol byproducts, and impurities other than 1,3-diol byproducts. The content of the aforementioned components can be calculated using a normalization method, and the depolymerization rate and selectivity can be further calculated based on the content of the aforementioned components. The formulas for calculating the depolymerization rate and selectivity are as follows:

[0125] Depolymerization rate = [1 - (content of 3-chloro-5-hydroxy-2-pentanone dimer)] / 1 × 100%;

[0126] Selectivity = (content of 3-chloro-5-hydroxy-2-pentanone / depolymerization rate) × 100%.

[0127] The contents of each component in the 3-chloro-5-hydroxy-2-pentanone solution and the depolymerization rate and selectivity calculated based on the contents of each component are shown in Table 2.

[0128] Table 2

[0129]

[0130] like Figures 1-4 As shown, the depolymerization method provided by this invention has successfully depolymerized the 3-chloro-5-hydroxy-2-pentanone dimer in Example 1 into 3-chloro-5-hydroxy-2-pentanone. Referring to Table 2, the depolymerization rate of the 3-chloro-5-hydroxy-2-pentanone dimer in Example 1 reached 99.1%, and 98.39% of the depolymerized 3-chloro-5-hydroxy-2-pentanone dimer selectively depolymerized into 3-chloro-5-hydroxy-2-pentanone. Furthermore, Examples 1-22 all exhibited higher depolymerization rates and / or selectivity compared to Comparative Examples 1-7, or generated fewer 1,3-diol byproducts and impurities other than 1,3-diol byproducts during the reaction. This indicates that the depolymerization method provided by this invention achieves effective reuse of the 3-chloro-5-hydroxy-2-pentanone dimer.

[0131] Furthermore, comparing the data from Examples 1-13 and Comparative Example 1, it can be seen that by limiting the type of alkaline catalyst and the mass ratio of alkaline catalyst to dimer, it is helpful to improve the depolymerization rate and selectivity, and reduce the generation of 1,3-diol byproducts and impurities other than 1,3-diol byproducts.

[0132] Comparing the data from Examples 14-19 and Comparative Examples 2-5, it can be seen that the simultaneous presence of hydroxyl, carboxylic acid, and aromatic ring structures in the compound helps to improve the depolymerization rate and selectivity. However, when the compound contains only one or two of the aforementioned structures, it may actually be detrimental to depolymerization. In Comparative Example 2, the chelating system formed by ethylenediaminetetraacetic acid has a certain protective effect on the 3-chloro-5-hydroxy-2-pentanone monomer obtained from depolymerization, but it cannot protect the chlorinated sites by forming a hydrogen bond network with the 3-chloro-5-hydroxy-2-pentanone dimer, resulting in more side reactions. In Comparative Example 3, benzoic acid contains a carboxyl group and an aromatic ring structure, but no hydroxyl group. In the depolymerization reaction, benzoic acid cannot form a hydrogen bond network with the 3-chloro-5-hydroxy-2-pentanone dimer, and its carboxyl group instead consumes the OH groups in the system. -This leads to a decrease in reaction efficiency. In Comparative Example 4, resorcinol contains an aromatic ring and two non-ortho-hydroxyl groups, but no carboxyl group. In the depolymerization reaction, resorcinol cannot form an effective hydrogen bond network with the 3-chloro-5-hydroxy-2-pentanone dimer, nor can it buffer the pH value near the reaction site. Instead, it may undergo self-oxidation or self-condensation under alkaline conditions, consuming not only OH groups but also... - It also produces new impurities.

[0133] Comparing the data from Example 1 and Comparative Example 6, it can be seen that even under heating conditions, the 3-chloro-5-hydroxy-2-pentanone dimer remains stable and is difficult to depolymerize without the addition of an alkaline catalyst and an aromatic carboxylic acid compound containing a hydroxyl group. However, comparing the data from Example 1 and Comparative Example 7, it can be seen that an acidic catalyst cannot effectively promote the depolymerization of the 3-chloro-5-hydroxy-2-pentanone dimer.

[0134] As can be seen from the above, the present invention selectively depolymerizes 3-chloro-5-hydroxy-2-pentanone dimer into 3-chloro-5-hydroxy-2-pentanone by adding an alkaline catalyst and an aromatic carboxylic acid compound containing hydroxyl groups, thereby achieving the effective recycling of 3-chloro-5-hydroxy-2-pentanone dimer.

[0135] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for depolymerizing 3-chloro-5-hydroxy-2-pentanone dimer, characterized in that, The depolymerization method includes the following steps: The 3-chloro-5-hydroxy-2-pentanone dimer was mixed with a polar solvent to obtain a first solution; The first solution is mixed with an alkaline catalyst and an aromatic carboxylic acid compound containing a hydroxyl group to obtain a second solution; The second solution is subjected to a depolymerization reaction at a first temperature to obtain a third solution; The pH of the third solution was adjusted to obtain a 3-chloro-5-hydroxy-2-pentanone solution.

2. The method for depolymerizing the 3-chloro-5-hydroxy-2-pentanone dimer according to claim 1, characterized in that, In the molecule of the aromatic carboxylic acid compound containing hydroxyl groups, the number of hydroxyl groups is greater than or equal to two; and / or, The aromatic carboxylic acid compound containing a hydroxyl group has an ortho-hydroxyl group in its molecule.

3. The method for depolymerizing the 3-chloro-5-hydroxy-2-pentanone dimer according to claim 2, characterized in that, The aromatic carboxylic acid compound containing a hydroxyl group is selected from at least one of 2,3-dihydroxybenzoic acid, gallic acid, and gentianic acid; and / or, In the second solution, the mass ratio of the aromatic carboxylic acid compound containing hydroxyl groups to the 3-chloro-5-hydroxy-2-pentanone dimer is (0.1~0.5):

100.

4. The method for depolymerizing the 3-chloro-5-hydroxy-2-pentanone dimer according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The alkaline catalyst is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium methoxide, sodium ethoxide, triethylamine and 1,8-diazabicyclo[5,4,0]undec-7-ene; (2) In the second solution, the mass ratio of the alkaline catalyst to the 3-chloro-5-hydroxy-2-pentanone dimer is (0.1~5):

100.

5. The method for depolymerizing the 3-chloro-5-hydroxy-2-pentanone dimer according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The polar solvent is selected from at least one of water, methanol, ethanol and tetrahydrofuran; (2) In the first solution, the mass-to-volume ratio of the 3-chloro-5-hydroxy-2-pentanone dimer to the polar solvent is 1:(3~5)g / mL.

6. The method for depolymerizing the 3-chloro-5-hydroxy-2-pentanone dimer according to any one of claims 1 to 5, characterized in that, The pH value of the second solution is 8.0~9.

0.

7. The method for depolymerizing the 3-chloro-5-hydroxy-2-pentanone dimer according to claim 1, characterized in that, The pH value of the 3-chloro-5-hydroxy-2-pentanone solution is 6.5~7.

5.

8. The method for depolymerizing the 3-chloro-5-hydroxy-2-pentanone dimer according to claim 1 or 7, characterized in that, The pH value of the third solution is adjusted using a pH adjuster to obtain the 3-chloro-5-hydroxy-2-pentanone solution, wherein the pH adjuster is selected from at least one of boric acid solution, hydrochloric acid solution, sulfuric acid solution, and nitric acid solution.

9. The method for depolymerizing the 3-chloro-5-hydroxy-2-pentanone dimer according to any one of claims 1 to 5, characterized in that, At least one of the following conditions must be met: (1) The first temperature is 60℃~80℃; (2) The depolymerization reaction takes 2 to 4 hours; (3) During the depolymerization reaction of the second solution at the first temperature, the depolymerization method of the 3-chloro-5-hydroxy-2-pentanone dimer further includes refluxing the second solution to obtain the third solution; (4) When the conversion rate of the 3-chloro-5-hydroxy-2-pentanone dimer is greater than or equal to 96%, the third solution is obtained.

10. A 3-chloro-5-hydroxy-2-pentanone solution, characterized in that, The 3-chloro-5-hydroxy-2-pentanone solution was prepared by the depolymerization method of the 3-chloro-5-hydroxy-2-pentanone dimer according to any one of claims 1 to 9.

Images