Method for efficiently synthesizing isopentenoic acid

Abstract

The invention discloses a method for efficiently synthesizing isopentenoic acid. The method comprises the following steps: dropwise adding acetone and methyl pyruvate into alkali liquor under heating and stirring to obtain sodium 4-hydroxy-4-methyl-2-ketovalerate, sequentially adding sulfuric acid and hydrogen peroxide, and carrying out sectional heating to obtain the isopentenoic acid. According to the invention, acetone and methyl pyruvate are used as raw materials, and isopentenoic acid is synthesized through a two-step one-pot method; the efficient conversion from the cheap and easily available raw materials acetone and methyl pyruvate to the isopentenoic acid is realized. The method disclosed by the invention has the advantages of high yield, high safety, clean reaction, few three wastes and the like. The reaction is carried out in a water phase, so that the use of a large amount of organic solvent is avoided; the used sodium bicarbonate, sulfuric acid and hydrogen peroxide are conventional chemicals, the post-treatment is simple, the three wastes are few, and the principle of green chemistry is met. The total yield of the isopentenoic acid (based on methyl pyruvate) can reach 87% or above, and the method has very high industrial application value.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method for the efficient synthesis of isopentenyl acid. Background Technology

[0002] Isoprenic acid, also known as 3,3-dimethylacrylic acid, is an important fine chemical raw material widely used in pharmaceuticals, pesticides, fragrances, and many other fields. In pharmaceutical synthesis, isoprenic acid serves as a key precursor in the synthesis of antibiotics and other drugs. In food processing, it can be used as an additive to flavor food and improve its taste. In the daily chemical industry, isoprenic acid is a key ingredient in perfumes and cosmetic fragrances. It can also be used in pesticides to enhance their effectiveness.

[0003] Currently, there are several main methods for synthesizing isoprenic acid: Patent CN120590257 reports the use of isopropylidene acetone as a raw material, reacting it with hypohalite to generate the corresponding isoprenic acid, which is then acidified to obtain isoprenic acid. This is the main industrial synthesis method for isoprenic acid. Isopropylidene acetone is derived from the condensation of acetone, and the reaction generates polymers, resulting in a low yield, with the highest yield being only 80%. The second step uses sodium hypochlorite as an oxidant, generating a large amount of saline wastewater. Based on isopropylidene acetone, the yield of isoprenic acid is around 85%. This method still has room for improvement in yield and results in significant pollution from wastewater. ; US Patent 2450117A reports a [2+2] cycloaddition reaction of ketene and acetone under the catalysis of zinc thiocyanate to produce dimethyl-substituted proprolactone, which is then hydrolyzed and eliminated to obtain isopentenyl acid. However, the reaction yield is only 40-50% based on ketene, resulting in low yield and high production cost of isopentenyl acid. Furthermore, the raw material ketene is produced by the cracking of acetic acid or the high-temperature pyrolysis of acetone, limiting its availability and posing certain safety risks. ; CN1069629C discloses a process for directly dehydrating α,β-unsaturated acids using concentrated sulfuric acid or concentrated polyphosphoric acid as a dehydrating agent. However, this method still has the following technical problems: 1) Limited applicable substrate range: Both the claims and examples limit the substrate to systems containing aryl groups at the α-position, making it difficult to extrapolate to a wider range of substrates. 2) The dehydration process requires an excess of concentrated sulfuric acid or phosphoric acid. The strong acid system leads to a violently exothermic reaction and may cause excessive oxidation of the substrate / product, which is detrimental to process safety and selectivity control.

[0004] Therefore, there is an urgent need to develop a novel method for the synthesis of isoprenic acid to address the problems of low yield, high cost, and significant environmental pollution associated with existing technologies. This method would utilize readily available and inexpensive raw materials to achieve efficient conversion of isoprenic acid, resulting in high yield, low production cost, and compliance with environmentally friendly and green chemistry requirements. Summary of the Invention

[0005] In view of the above-mentioned prior art, the purpose of this invention is to provide a highly efficient method for synthesizing isopentenyl acid. This invention uses acetone and methyl pyruvate as raw materials and synthesizes isopentenyl acid through a "two-step, one-pot" method; achieving efficient conversion from inexpensive and readily available raw materials acetone and methyl pyruvate to isopentenyl acid. The method of this invention has advantages such as high yield, high safety, clean reaction, and low waste.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for the efficient synthesis of isopentenyl acid, the method comprising: Acetone and methyl pyruvate were added dropwise to an alkaline solution under heating and stirring to obtain sodium 4-hydroxy-4-methyl-2-ketovalerate. Sulfuric acid and hydrogen peroxide were then added sequentially, followed by staged heating to obtain isopentenic acid.

[0007] Preferably, the heating and stirring temperature is 40~60 ℃; after the acetone and methyl pyruvate are added dropwise, the reaction continues for 1~2 hours.

[0008] Preferably, the molar ratio of acetone to methyl pyruvate is 1.05 to 1.6:1.

[0009] Preferably, the alkaline solution is a sodium bicarbonate solution with a concentration of 1.5~2.0 mol / L; the molar ratio of sodium bicarbonate to methyl pyruvate is 1.2~1.6:1.

[0010] Preferably, the dropping time for both acetone and methyl pyruvate is 2-4 hours.

[0011] Preferably, the sulfuric acid has a mass concentration of 40%; the molar ratio of sulfuric acid to sodium bicarbonate is 0.6~0.8:1.

[0012] Preferably, the hydrogen peroxide has a mass concentration of 25-30%; the amount of hydrogen peroxide added is 0.95-1.2 eq of methyl pyruvate.

[0013] Preferably, the segmented heating involves first heating to 40-50°C for 2 hours, and then, after no more bubbles emerge from the system, raising the temperature to 70-80°C and heating for another 1-3 hours.

[0014] A second aspect of the invention provides the application of the above-described method in improving the yield of isoprenic acid and reducing post-processing.

[0015] The products of this invention are isopentenic acid and carbon dioxide. The carbon dioxide can be collected and reused, and the post-treatment method is simple and produces little waste.

[0016] The structural formula of isoprenic acid is: The structural formula of its isomer is .

[0017] This invention improves the yield of isoprenic acid by inhibiting the isomerization products of isoprenic acid and reducing acetone polymerization.

[0018] The beneficial effects of this invention are: (1) The present invention adopts a “two-step one-pot” process route and uses mild reaction conditions to continuously complete key transformations such as condensation, acidification, decarboxylation and dehydration in the same reaction system, while inhibiting olefin isomerization and polymerization, so as to achieve efficient preparation of isopentenyl acid.

[0019] (2) During the condensation stage, sodium bicarbonate provides mild alkaline conditions, which preferentially deprotonates methyl pyruvate and serves as a C-providing agent. - The reactive building blocks participate in the condensation, thereby reducing the risk of self-condensation and polymerization side reactions that acetone is prone to under strong alkaline conditions, improving the selectivity of the condensation stage and reducing the generation of by-products in acetone polymerization.

[0020] (3) After the condensation is completed, 40% sulfuric acid and hydrogen peroxide are added to the same system in sequence. The synergistic effect of "sulfuric acid + hydrogen peroxide" and segmented temperature control avoids the accumulation of side reactions caused by decarboxylation and dehydration, improves the overall conversion efficiency and selectivity, and helps to suppress side reactions such as polymerization of unsaturated products and isomerization of products.

[0021] (4) The present invention can achieve efficient preparation of isoprenic acid, with a total yield of isoprenic acid (based on methyl pyruvate) up to 95%, which has high industrial application value. Attached Figure Description

[0022] Figure 1 Liquid phase spectrum of the intermediate reaction solution in Example 1; Figure 2 : The hydrogen nuclear magnetic resonance spectrum of the isoprenic acid product in Example 1. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0024] As introduced in the background section, existing methods for preparing isoprenic acid cannot simultaneously achieve high yield and low pollution, as well as minimal post-treatment of waste. Therefore, the production cost of isoprenic acid is high and the environmental pollution is significant.

[0025] Therefore, the purpose of this invention is to provide an efficient method for synthesizing isopentenyl acid. This invention uses acetone and methyl pyruvate as raw materials to synthesize isopentenyl acid via a two-step, one-pot method. The specific synthetic route is as follows: .

[0026] This invention utilizes sodium bicarbonate to provide mild alkaline conditions during the condensation stage. Compared to conventional strong alkaline conditions, sodium bicarbonate preferentially deprotonates pyruvate and acts as a C⁻-donating reactive unit in the condensation, thereby reducing the risk of self-condensation and polymerization side reactions that easily occur in acetone under strong alkaline conditions, improving the selectivity of the condensation stage, and reducing the formation of polymer byproducts. After condensation, 40% sulfuric acid and hydrogen peroxide are added sequentially to the same system, and a controlled temperature gradient is used to promote decarboxylation and dehydration reactions under mild conditions, effectively suppressing the formation of isomerization products and thus improving the reaction yield. Furthermore, gradient heating effectively suppresses common side reactions of isopentenyl acid, improving product selectivity and quality stability. The synthesis principle is as follows: .

[0027] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0028] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0029] Example 1 S1: In a 1000mL three-necked round-bottom flask equipped with a reflux condenser, a constant-pressure dropping funnel, and a mechanical stirrer, add 42.0g (0.50mol) of sodium bicarbonate and 300mL of deionized water. Start stirring and heat, controlling the system temperature at 50℃. Add 31.9g (40.4mL, 0.55mol) of acetone and 43.0g (98% methyl pyruvate, 0.37mol) dropwise to the reaction system at a uniform rate through two dropping funnels. The dropping time should be controlled to be completed synchronously within 3 hours. After the dropping is completed, continue stirring at 50℃ for 1 hour to obtain a reaction solution containing the intermediate sodium 4-hydroxy-4-methyl-2-ketovalerate. Use 4-hydroxy-4-methyl-2-ketovalerate (CAS: 5799-83-7) as a standard for liquid chromatography analysis of this reaction solution under the following conditions: Chromatographic column: Atlantis@HILIC Silica column, 250 mm × 4.6 mm × 3 μm; Mobile phase: Acetonitrile + 10 mmol sodium dihydrogen phosphate solution (1.2 g anhydrous sodium dihydrogen phosphate was dissolved in 900 mL of water, 0.5 mL of ammonia was added, the pH was adjusted to 6.0 with phosphoric acid, and then diluted to 1000 mL with water) = 80 + 20 (v / v); Flow rate: 0.8 mL / min; Column temperature: 30℃; Injection volume: 10 μL; UV-Vis detector: 210 nm; Results obtained are as follows Figure 1 As shown.

[0030] according to Figure 1 It can be seen that the peak at 4.172 min is consistent with that of the standard, indicating that the intermediate is sodium 4-hydroxy-4-methyl-2-ketovalerate.

[0031] S2: Cool the reaction solution obtained in S1 to room temperature. While stirring, add 73.6 g (0.3 mol) of a 40% sulfuric acid solution to the reaction solution; then add 46.6 g (0.37 mol) of hydrogen peroxide (27% by mass). First, heat to 50℃ and continue the reaction for about 2 hours. A large amount of gas (carbon dioxide) is released during the reaction; collect the carbon dioxide for reuse. After no more bubbles emerge from the system, heat to 80℃ and continue the reaction for 3 hours. After the reaction is complete, cool the reaction mixture to room temperature to obtain a mixture containing isoprenic acid. Extract the aqueous phase three times with ethyl acetate (80 mL each time), combine the extracts, concentrate and recover 200 mL of solvent, cool the concentrated mother liquor to -10℃, stir and crystallize for 2 hours, filter and dry to obtain 35.5 g of isoprenic acid product with a purity of 99.0%. The results of proton NMR analysis of the obtained isoprenic acid are shown below. Figure 2 , 1 H NMR (400 MHz, CDCl3) δ 11.85 (s, 1H), 5.60 (s, 1H), 2.07 (s, 3H), 1.84 (s, 3H). The yield of isopentenyl acid was 95% based on methyl pyruvate.

[0032] Example 2 Step S1: In a 1000 mL three-necked round-bottom flask equipped with a reflux condenser, a constant-pressure dropping funnel, and a mechanical stirrer, add 42.0 g (0.50 mol) of sodium bicarbonate and 300 mL of deionized water. Start stirring and heat, controlling the system temperature at 55 °C. Add 31.9 g (40.4 mL, 0.55 mol) of acetone and 43.0 g (0.37 mol) of methyl pyruvate dropwise to the reaction system at a uniform rate using two dropping funnels. The addition should be completed within 2 hours. After the addition is complete, continue stirring the reaction at 55 °C for 1 hour to obtain a reaction solution containing the intermediate sodium 4-hydroxy-4-methyl-2-ketovalerate.

[0033] Step S2: Cool the reaction solution obtained in S1 to room temperature. While stirring, add 98.1 g (0.4 mol) of a 40% sulfuric acid solution to the reaction solution. Then add 46.6 g (0.37 mol) of hydrogen peroxide (27% by mass). Heat to 40 °C and continue the reaction for approximately 2 hours. Collect the carbon dioxide produced in the reaction. After no more bubbles emerge from the system, heat to 80 °C and continue the reaction for 2 hours. After the reaction is complete, cool to room temperature to obtain a mixture containing isopentenyl acid. Extract the aqueous phase three times with ethyl acetate (80 mL each time). Combine the extracts and concentrate to recover 200 mL of solvent. Cool the concentrated mother liquor to -10 °C. o C, stirred and crystallized for 2 h, filtered and dried to obtain 34.4 g of isoprenic acid product with a purity of 99.2%. The reaction yield was 92% based on methyl pyruvate.

[0034] Example 3 Step S1: In a 1000 mL three-necked round-bottom flask equipped with a reflux condenser, a constant-pressure dropping funnel, and a mechanical stirrer, add 50.0 g (0.60 mol) of sodium bicarbonate and 300 mL of deionized water. Start stirring and heat, controlling the system temperature at 60 °C. Add 33.0 g (0.55 mol) of acetone and 45.0 g (0.38 mol) of methyl pyruvate dropwise to the reaction system at a uniform rate using two dropping funnels. The addition should be completed within 3 hours. After the addition is complete, continue stirring at 60 °C for 1 hour to obtain a reaction solution containing the intermediate sodium 4-hydroxy-4-methyl-2-ketovalerate.

[0035] Step S2: Cool the reaction solution obtained in S1 to room temperature. While stirring, add 88.3 g (0.36 mol) of a 40% sulfuric acid solution to the reaction solution. Then add 47.9 g (0.38 mol) of hydrogen peroxide (27% by mass). Heat to 40 °C and continue the reaction for approximately 2 h. Collect the carbon dioxide produced in the reaction. After no more bubbles emerge from the system, heat to 80 °C and continue the reaction for 3 h. After the reaction is complete, cool to room temperature to obtain a mixture containing isopentenyl acid. Extract the aqueous phase three times with ethyl acetate (80 mL each time). Combine the extracts and concentrate to recover 200 mL of solvent. Cool the concentrated mother liquor to -10 °C. o C. Stir and crystallize for 2 hours, filter and dry to obtain 34.2 g of isoprenic acid product with a purity of 99.0%. The reaction yield is 89% based on methyl pyruvate.

[0036] Example 4 Step S1: In a 500 mL three-necked round-bottom flask equipped with a reflux condenser, a constant-pressure dropping funnel, and a mechanical stirrer, add 35.0 g (0.42 mol) of sodium bicarbonate and 250 mL of deionized water. Start stirring and heat, controlling the system temperature at 45 °C. Add 28.5 g (0.48 mol) of acetone and 38.0 g (0.32 mol) of methyl pyruvate dropwise to the reaction system at a uniform rate using two dropping funnels. The addition should be completed within 2.5 hours. After the addition is complete, continue stirring the reaction at 45 °C for 1 hour to obtain a reaction solution containing the intermediate sodium 4-hydroxy-4-methyl-2-ketovalerate.

[0037] Step S2: Cool the reaction solution obtained in S1 to room temperature. While stirring, add 82.4 g (0.33 mol) of a 40% sulfuric acid solution to the reaction solution. Then add 42.8 g (0.34 mol) of hydrogen peroxide (27% by mass). Raise the temperature to 45 °C and continue the reaction for approximately 2 h. Collect the carbon dioxide produced in the reaction. After no more bubbles emerge from the system, raise the temperature to 80 °C and continue the reaction for 3 h. After the reaction is complete, cool to room temperature to obtain a mixture containing isopentenyl acid. Extract the aqueous phase three times with ethyl acetate (80 mL each time). Combine the extracts and concentrate to recover 200 mL of solvent. Cool the concentrated mother liquor to -10 °C. o C, stirred and crystallized for 2 hours, filtered and dried to obtain 28.3 g of isoprenic acid product with a purity of 98.6%. The reaction yield was 87% based on methyl pyruvate.

[0038] Example 5 Step S1: In a 1000 mL three-necked round-bottom flask equipped with a reflux condenser, a constant-pressure dropping funnel, and a mechanical stirrer, add 45.0 g (0.54 mol) of sodium bicarbonate and 300 mL of deionized water. Start stirring and heat, controlling the system temperature at 50 °C. Add 30.5 g (0.51 mol) of acetone and 40.5 g (0.34 mol) of methyl pyruvate dropwise to the reaction system at a uniform rate using two dropping funnels. The addition should be completed within 2.5 hours. After the addition is complete, continue stirring the reaction at 50 °C for 1 hour to obtain a reaction solution containing the intermediate sodium 4-hydroxy-4-methyl-2-ketovalerate.

[0039] Step S2: Cool the reaction solution obtained in S1 to room temperature. While stirring, add 98.1 g (0.4 mol) of a 40% sulfuric acid solution to the reaction solution. Then add 47.9 g (0.38 mol) of hydrogen peroxide (27% by mass). Raise the temperature to 45 °C and continue the reaction for approximately 2 h. Collect the carbon dioxide produced in the reaction. After no more bubbles emerge from the system, raise the temperature to 80 °C and continue the reaction for 3 h. After the reaction is complete, cool to room temperature to obtain a mixture containing isopentenyl acid. Extract the aqueous phase three times with ethyl acetate (80 mL each time). Combine the extracts and concentrate to recover 200 mL of solvent. Cool the concentrated mother liquor to -10 °C. o C. Stir and crystallize for 2 hours, filter and dry to obtain 31.9 g of isoprenic acid product with a purity of 99.2%. The reaction yield is 93% based on methyl pyruvate.

[0040] Example 6 Step S1: In a 1000 mL three-necked round-bottom flask equipped with a reflux condenser, a constant-pressure dropping funnel, and a mechanical stirrer, add 40.0 g (0.48 mol) of sodium bicarbonate and 280 mL of deionized water. Start stirring and heat, controlling the system temperature at 52 °C. Add 32.0 g (0.54 mol) of acetone and 42.5 g (0.35 mol) of methyl pyruvate dropwise to the reaction system at a uniform rate using two dropping funnels. The addition should be completed within 3 hours. After the addition is complete, continue stirring at 52 °C for 1 hour to obtain a reaction solution containing the intermediate sodium 4-hydroxy-4-methyl-2-ketovalerate.

[0041] Step S2: Cool the reaction solution obtained in S1 to room temperature. While stirring, add 88.3 g (0.36 mol) of a 40% sulfuric acid solution to the reaction solution. Then add 45.3 g (0.36 mol) of hydrogen peroxide (27% by mass). Heat to 50 °C and continue the reaction for approximately 2 h. Collect the carbon dioxide produced in the reaction. After no more bubbles emerge from the system, heat to 80 °C and continue the reaction for 3 h. After the reaction is complete, cool to room temperature to obtain a mixture containing isoprenic acid. Extract the aqueous phase three times with ethyl acetate (80 mL each time). Combine the extracts and concentrate to recover 200 mL of solvent. Cool the concentrated mother liquor to -10 °C. o C. Stir and crystallize for 2 hours, filter and dry to obtain 31.1 g of isoprenic acid product with a purity of 99.1%. The reaction yield is 88% based on methyl pyruvate.

[0042] Example 7 Step S1: In a 500 mL three-necked round-bottom flask equipped with a reflux condenser, a constant-pressure dropping funnel, and a mechanical stirrer, add 38.0 g (0.45 mol) of sodium bicarbonate and 250 mL of deionized water. Start stirring and heat, controlling the system temperature at 48 °C. Add 30.0 g (0.51 mol) of acetone and 41.0 g (0.34 mol) of methyl pyruvate dropwise to the reaction system at a uniform rate using two dropping funnels. The dropping process should be completed within 3 hours. After the addition is complete, continue stirring the reaction at 48 °C for 1 hour to obtain a reaction solution containing the intermediate sodium 4-hydroxy-4-methyl-2-ketovalerate.

[0043] Step S2: Cool the reaction solution obtained in S1 to room temperature. While stirring, add 85.8 g (0.35 mol) of a 40% sulfuric acid solution to the reaction solution. Then add 47.9 g (0.38 mol) of hydrogen peroxide (27% by mass). Heat to 40 °C and continue the reaction for approximately 2 h. Collect the carbon dioxide produced in the reaction. After no more bubbles emerge from the system, heat to 80 °C and continue the reaction for 3 h. After the reaction is complete, cool to room temperature to obtain a mixture containing isopentenyl acid. Extract the aqueous phase three times with ethyl acetate (80 mL each time). Combine the extracts and concentrate to recover 200 mL of solvent. Cool the concentrated mother liquor to -10 °C. o C. Stir and crystallize for 2 hours, filter and dry to obtain 30.8 g of isoprenic acid product with a purity of 99.4%. The reaction yield is 90% based on methyl pyruvate.

[0044] Comparative Example 1 The difference from Example 1 is that in step S2, an equimolar amount of concentrated sulfuric acid (98% by mass) replaces the 40% sulfuric acid solution, and hydrogen peroxide is not added; the remaining conditions are the same as in Example 1. The yield of isopentenyl acid is 32% based on methyl pyruvate.

[0045] Comparative Example 2 The difference from Example 1 is that, instead of staged heating, the reaction was carried out directly at 80°C until completion; all other conditions were the same as in Example 1. The yield of isopentenic acid was 44% based on methyl pyruvate.

[0046] Comparative Example 3 The difference from Example 1 is that in step S2, p-toluenesulfonic acid, in a molar amount twice that of sulfuric acid, is used instead of the sulfuric acid solution, and the amount of p-toluenesulfonic acid added is 0.6 mol; the other conditions are the same as in Example 1. The yield of isopentenyl acid, based on methyl pyruvate, is 79%.

[0047] Compared to Example 1, Comparative Example 1, which uses concentrated sulfuric acid, also had a lower yield. This is because although concentrated sulfuric acid in Comparative Example 1 is a strong dehydrating acid and can function, it is not suitable for this system. A sulfuric acid-hydrogen peroxide complex system is required to achieve efficient dehydration and decarboxylation at a lower reaction temperature, avoiding side reactions such as excessive oxidation and isomerization of the product / substrate, and product self-polymerization.

[0048] Comparative Example 2 eliminated the segmented heating and reacted directly at 100°C, resulting in a lower yield than Example 1. The high temperature caused side reactions such as isomerization, and the hydrogen peroxide decomposed violently, rendering it ineffective for decarboxylation. This demonstrates that the dehydration and decarboxylation process of this invention requires segmented heating: first, decarboxylation at a low temperature, followed by dehydration at a higher temperature, to reduce isomerization products and increase reaction yield.

[0049] Comparative document 3 uses p-toluenesulfonic acid as an acid catalyst and reacts under gradient temperature. Its yield is lower than that of Example 1. This is because the p-toluenesulfonic acid system requires a higher reaction temperature, and better results cannot be achieved within the temperature range of this invention.

[0050] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for efficiently synthesizing isopentenic acid, characterized in that, The method is as follows: Acetone and methyl pyruvate were added dropwise to an alkaline solution under heating and stirring to obtain sodium 4-hydroxy-4-methyl-2-ketovalerate. Sulfuric acid and hydrogen peroxide were then added sequentially, followed by staged heating to obtain isopentenic acid.

2. The method according to claim 1, characterized in that, The heating and stirring temperature is 40~60℃; after the addition of acetone and methyl pyruvate is completed, the reaction continues for 1~2 hours.

3. The method according to claim 1, characterized in that, The molar ratio of acetone to methyl pyruvate is 1.05 to 1.6:

1.

4. The method according to claim 1, characterized in that, The alkaline solution is a sodium bicarbonate solution with a concentration of 1.5~2.0 mol / L; the molar ratio of sodium bicarbonate to methyl pyruvate is 1.2~1.6:

1.

5. The method according to claim 1, characterized in that, The addition time for both acetone and methyl pyruvate is 2-4 hours.

6. The method according to claim 1, characterized in that, The sulfuric acid has a mass concentration of 40%; the molar ratio of sulfuric acid to sodium bicarbonate is 0.6~0.8:

1.

7. The method according to claim 1, characterized in that, The hydrogen peroxide has a mass concentration of 25-30%; the amount of hydrogen peroxide added is 0.95-1.2 eq of methyl pyruvate.

8. The method according to claim 1, characterized in that, The segmented heating process involves first heating to 40-50 ℃ for 2 hours, and then, after no more bubbles emerge from the system, raising the temperature to 70-80 ℃ and heating for another 1-3 hours.

9. The application of the method according to any one of claims 1 to 8 in improving the yield of isoprenic acid and reducing post-processing.

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