Method for synthesizing carvacol by using isopinocamphone as raw material

Abstract

The application belongs to the technical field of organic synthesis, and specifically discloses a method for synthesizing carvacol from isopinocamphene, which comprises the following steps: isopinocamphene is reduced by hydrogen under the action of a hydrogen catalyst in a polar solvent to obtain an intermediate A; the intermediate A is epoxidized under the action of sodium acetate and peracetic acid to obtain an intermediate B; the intermediate B is isomerized at a high temperature under catalysis to obtain an intermediate C; the intermediate C is oxidized by Oppenauer to obtain an intermediate D; the intermediate D is subjected to an epoxidation reaction to obtain an intermediate E; and the intermediate E is subjected to catalytic rearrangement to obtain carvacol. The method uses inexpensive isopinocamphene as a raw material, and high-purity carvacol can be obtained through six steps of hydrogenation, epoxidation, isomerization, oxidation, epoxidation and rearrangement, and the yield of each step is higher than 90%. The method provides a novel and efficient process path for the preparation of carvacol, is easy to realize industrial scale production, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology and relates to the synthesis of the fragrance compound carvacrol, specifically to a method for synthesizing carvacrol using isoterpinene as a raw material. Background Technology

[0002] Carvacrol is a colorless to pale yellow viscous liquid. It possesses strong antibacterial properties and effectively inhibits the growth of harmful organisms such as mites and insects. As a green, low-toxicity food additive, broad-spectrum bactericide and antioxidant, it has been listed as a safe food flavoring in the United States and the European Union, and is commonly used in toothpaste, mouthwash, cosmetics, and food preservation. Natural carvacrol is mainly found in various Lamiaceae plants, such as thyme and oregano. However, natural extraction methods suffer from high costs and limited yields, failing to meet the demands of large-scale industrial production. Therefore, developing efficient chemical synthesis processes is of significant practical importance.

[0003] Currently, carvacrol is mainly synthesized through the following methods: The first method uses o-methylphenol as a raw material and employs strong Lewis acids such as aluminum chloride or ferric chloride as catalysts to carry out a Friedel-Crafts alkylation reaction with isopropanol or 2-chloropropane to prepare carvacrol. This method has been proposed in patent CN1488615. However, this method generates a large amount of metal salts, polluting the environment and making large-scale production and application difficult.

[0004] The second method uses carvone as a raw material to synthesize carvacrol via aromatization under the action of strong acid or metal catalyst. For example, in patent CN101475448A, PEG is used as an auxiliary agent to promote the intramolecular rearrangement of carvone to synthesize carvacrol through acid catalysis. However, the market price of carvone is usually higher than that of carvacrol, making it difficult to control the production cost of this method and resulting in poor economic efficiency.

[0005] The third method involves sulfonating p-isopropyltoluene with sulfuric acid to produce p-isopropyltoluene-2-sulfonic acid, followed by alkali fusion treatment to obtain carvacrol. This method uses large amounts of acids and alkalis, requiring highly corrosion-resistant production equipment and generating a large amount of wastewater, thus placing significant pressure on environmental protection. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for synthesizing carvacrol from isotretinoin. This invention utilizes inexpensive isotretinoin as a raw material and, through six steps—hydrogenation, epoxidation, isomerization, oxidation, epoxidation again, and rearrangement—obtains carvacrol with a purity >99%, and the yield of each step is higher than 90%. The equipment used in this invention is simple, does not generate large amounts of metal salts, and the metal catalyst can be reused multiple times. This invention provides a novel and efficient process route for the preparation of carvacrol, and is easily scalable for industrial production, showing promising application prospects.

[0007] This invention is achieved through the following technical solution: A method for synthesizing carvacrol from isoprene includes the following steps: (1) Hydrogenation reaction: Isorhodotorylene, polar solvent and metal hydrogenation catalyst are added into hydrogenation reactor and reduced with hydrogen to obtain intermediate A; (2) Epoxidation reaction: After mixing intermediate A with sodium acetate as a base, peracetic acid is added dropwise to carry out the epoxidation reaction to obtain intermediate B; (3) Isomerization reaction: After mixing intermediate B with an acidic homogeneous transition metal salt catalyst as a base, intermediate C is obtained by high-temperature isomerization reaction; (4) Oxidation reaction: After mixing intermediate C with organoaluminum Lewis acid catalyst as a base, intermediate D is obtained by Oppenauer oxidation; (5) Epoxidation reaction: After mixing intermediate D with sodium acetate as a base, peracetic acid is added dropwise to carry out the epoxidation reaction to obtain intermediate E; (6) Rearrangement reaction: After mixing intermediate E, solvent and homogeneous acid catalyst as a base, carvacrol is obtained by reflux to remove water; The homogeneous acid catalyst is a Brønsted acid catalyst or a Lewis acid catalyst. The reaction route is shown below: .

[0008] A further improvement to the present invention is as follows: The operation process of step (1) is as follows: put isoterpinene, polar solvent and metal hydrogenation catalyst into high pressure vessel, start stirring and make the reaction system in nitrogen atmosphere, heat up and pass hydrogen to carry out hydrogenation reaction. When the isoterpinene content is less than 1%, cool down to end the reaction. After simple filtration and vacuum distillation, intermediate A is obtained from the reaction residue. The pressure is controlled at 5-30 bar throughout the reaction and the reaction temperature is controlled at 30-100℃.

[0009] Furthermore, the polar solvent is one or a mixture of two or more of methanol, ethanol, isopropanol, dioxane, dichloromethane or dichloroethane; Furthermore, the metal hydrogenation catalyst is one or a mixture of two or more of Raney nickel, palladium / carbon, palladium / alumina, ruthenium / carbon, and ruthenium / alumina; Furthermore, the mass ratio of isoterpinene to the polar solvent is 1:0.5-3, and the mass ratio of isoterpinene to the metal hydrogenation catalyst is 1:0.001-0.01.

[0010] Further, the operation process of step (2) is as follows: intermediate A is mixed with sodium acetate as a base. When the system is stirred evenly and the system temperature reaches the required level, peracetic acid is slowly added dropwise to carry out the epoxidation reaction. When the content of intermediate A is less than 30%, the temperature is lowered to end the reaction. The reaction residue is washed with 10% sodium sulfite and 10% sodium hydroxide respectively, and then intermediate B is obtained by vacuum distillation. The reaction is an atmospheric pressure reaction and the reaction temperature is controlled at 10-40℃. Furthermore, the mass ratio of intermediate A to sodium acetate is 1:0.01-0.2, and the mass ratio of intermediate A to peracetic acid is 1:1-2.

[0011] Further, the operation process of step (3) is as follows: intermediate B is mixed with acidic homogeneous transition metal salt catalyst as a base. After the system is stirred evenly, the temperature is raised to the specified temperature and stirred to carry out the isomerization reaction. When the content of intermediate B is less than 1%, the temperature is lowered to end the reaction. The reaction residue is washed with 1% sodium hydroxide and then intermediate C is obtained by vacuum distillation. The reaction is an atmospheric pressure reaction and the reaction temperature is controlled at 80-170℃. Furthermore, the acidic homogeneous transition metal salt catalyst is one or more of the sulfates, acetates or halides of iron, nickel, zinc, palladium, copper or platinum; Furthermore, the mass ratio of intermediate B to the acidic homogeneous transition metal salt catalyst is 1:0.005-0.15.

[0012] Further, the operation process of step (4) is as follows: mix intermediate C with organoaluminum Lewis acid catalyst as a base, start stirring, wait for the temperature to rise to the specified temperature, add oxidant dropwise to carry out oxidation reaction, when the content of intermediate C is less than 1%, cool down to end the reaction, the reaction residue is distilled under reduced pressure to obtain intermediate D, the reaction is an atmospheric pressure reaction, and the reaction temperature is controlled at 30-100℃. Furthermore, the organoaluminum Lewis acid catalyst is aluminum isopropoxide; Furthermore, the oxidant is one or a mixture of two or more of acetone, butanone, or cyclohexanone; Furthermore, the mass ratio of intermediate C to organoaluminum leucic acid catalyst is 1:0.01-0.1, and the mass ratio of intermediate C to oxidant is 1:0.1-1.

[0013] Further, the operation process of step (5) is as follows: mix intermediate D with sodium acetate as a base, and when the system is stirred evenly and the system temperature reaches the required level, start slowly adding peracetic acid to carry out the epoxidation reaction. When the content of intermediate D is less than 30%, cool down to end the reaction. Wash the reaction residue with 10% sodium sulfite and 10% sodium hydroxide respectively, and then obtain intermediate E by vacuum distillation. The reaction is an atmospheric pressure reaction, and the reaction temperature is controlled at 10-40℃. Furthermore, the mass ratio of intermediate D to sodium acetate is 1:0.01-0.2, and the mass ratio of intermediate D to peracetic acid is 1:1-2.

[0014] Further, the operation process of step (6) is as follows: mix intermediate E, solvent and homogeneous acid catalyst as a base, start stirring, raise the temperature to the point where the solvent is refluxed to carry out the rearrangement reaction, when the content of intermediate E is less than 1%, cool down to end the reaction, wash the reaction residue with 1% sodium hydroxide, and then obtain carvacrol product by vacuum distillation. The reaction is an atmospheric pressure reaction and the reaction temperature is controlled at 80-170℃.

[0015] Furthermore, the homogeneous acid catalyst is one or a mixture of two or more of sulfuric acid, hydrochloric acid, phosphoric acid, p-toluenesulfonic acid, or halides of metallic iron, nickel, zinc, palladium, copper, and platinum. Furthermore, the solvent is one or a mixture of two or more of cyclohexane, toluene, xylene, trimethylbenzene or anisole; Furthermore, the mass ratio of intermediate E to solvent is 1:0.1-2, and the mass ratio of intermediate E to homogeneous acid catalyst is 1:0.001-0.1.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses inexpensive isoprene as a raw material and, through a six-step reaction involving hydrogenation, epoxidation, isomerization, oxidation, and rearrangement, yields carvacrol with a purity >99%, with each step achieving a yield exceeding 90%. The equipment used in this process is simple, does not generate large amounts of metal salts, and the metal catalyst can be reused multiple times. This method provides a novel and efficient process route for the preparation of carvacrol, and is easily scalable for industrial production, demonstrating promising application prospects. Detailed Implementation

[0017] This invention provides a method for synthesizing carvacrol using isoprene as a raw material. In specific embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available. The invention will now be described in detail with reference to specific embodiments.

[0018] Example 1 (1) First step hydrogenation reaction: 500g of isoterpinene, 250g of methanol and 2.5g of 5% palladium on carbon were put into a high pressure reactor, the stirring was turned on and the system was replaced with nitrogen three times, the temperature was raised and hydrogen was introduced. When the isoterpinene content was less than 1%, the temperature was lowered to end the reaction. The reaction residue was simply filtered and vacuum distilled to obtain 481g of intermediate A. The reaction yield was 95%. The pressure was controlled at 10 bar throughout the reaction and the reaction temperature was controlled at 80℃.

[0019] (2) Second step epoxidation reaction: 481g of intermediate A was mixed with 20g of sodium acetate as a base. When the system was stirred evenly and the system temperature reached 20℃, 1000g of 20% peracetic acid was slowly added dropwise. When the content of intermediate A was less than 30%, the temperature was lowered to end the reaction. The reaction residue was washed once with 10% sodium sulfite and 10% sodium hydroxide, and then 356g of intermediate B was obtained by vacuum distillation. The reaction was carried out under normal pressure and the reaction yield was 95%.

[0020] (3) Third step of isomerization reaction: 356g of intermediate B and 1.5g of ferric sulfate were mixed as a base. After the system was stirred evenly, the temperature was raised to 140℃. When the content of intermediate B was less than 1%, the temperature was lowered to end the reaction. The reaction residue was washed once with 1% sodium hydroxide and then 331g of intermediate C was obtained by vacuum distillation. The reaction was carried out under normal pressure and the reaction yield was 93%.

[0021] (4) Fourth step oxidation reaction: Mix 331g of intermediate C with 20g of aluminum isopropoxide as a base, start stirring, and when the temperature rises to 90℃, slowly add 210g of cyclohexanone. When the content of intermediate C is less than 1%, cool down to end the reaction. The reaction residue is distilled under reduced pressure to obtain 297g of intermediate D. The reaction is an atmospheric pressure reaction with a yield of 91%.

[0022] (5) Fifth step epoxidation reaction: 297g of intermediate D and 12g of sodium acetate were mixed as a base. When the system was stirred evenly and the system temperature reached 20℃, 530g of 20% peracetic acid was slowly added dropwise. When the content of intermediate A was less than 30%, the temperature was lowered to end the reaction. The reaction residue was washed once with 10% sodium sulfite and 10% sodium hydroxide, and then 218g of intermediate E was obtained by vacuum distillation. The reaction was carried out under normal pressure and the reaction yield was 95%.

[0023] (6) Sixth rearrangement reaction: Mix 218g of intermediate E, 218g of toluene and 1.6g of phosphoric acid as a base, start stirring and raise the temperature to reflux. When the content of intermediate E is less than 1%, cool down to end the reaction. Wash the reaction residue once with 1% sodium hydroxide, and then obtain 184g of carvacrol product by vacuum distillation. The reaction is an atmospheric pressure reaction with a reaction yield of 95%.

[0024] Example 2 (1) First step hydrogenation reaction: 500g of isoterpinene, 250g of dioxane and 2.5g of Raney nickel were put into a high pressure vessel, the stirring was turned on and the system was replaced with nitrogen three times. The temperature was raised and hydrogen was introduced. When the content of isoterpinene was less than 1%, the temperature was lowered to end the reaction. The reaction residue was simply filtered and vacuum distilled to obtain 476g of intermediate A. The reaction yield was 94%. The pressure was controlled at 30 bar and the reaction temperature was controlled at 50℃ throughout the reaction.

[0025] (2) Second step epoxidation reaction: 476g of intermediate A was mixed with 20g of sodium acetate as a base. When the system was stirred evenly and the system temperature reached 20℃, 1000g of 20% peracetic acid was slowly added dropwise. When the content of intermediate A was less than 30%, the reaction was stopped by cooling. The reaction residue was washed once with 10% sodium sulfite and 10% sodium hydroxide, and then 353g of intermediate B was obtained by vacuum distillation. The reaction yield was 95%.

[0026] (3) Third step of isomerization reaction: 353g of intermediate B and 1.3g of zinc chloride were mixed as a base. After the system was stirred evenly, the temperature was raised to 160℃. When the content of intermediate B was less than 1%, the temperature was lowered to end the reaction. The reaction residue was washed once with 1% sodium hydroxide and then 321g of intermediate C was obtained by vacuum distillation. The reaction was carried out under normal pressure and the reaction yield was 91%.

[0027] (4) Fourth step oxidation reaction: Mix 321g of intermediate C with 12g of aluminum isopropoxide as a base, start stirring, and when the temperature rises to 60℃, slowly add 130g of acetone. When the content of intermediate C is less than 1%, cool down to end the reaction. The reaction residue is distilled under reduced pressure to obtain 284g of intermediate D. The reaction is an atmospheric pressure reaction with a yield of 90%.

[0028] (5) Fifth step epoxidation reaction: 284g of intermediate D and 10.5g of sodium acetate were mixed as a base. When the system was stirred evenly and the system temperature reached 20℃, 500g of 20% peracetic acid was slowly added dropwise. When the content of intermediate A was less than 30%, the temperature was lowered to end the reaction. The reaction residue was washed once with 10% sodium sulfite and 10% sodium hydroxide, and then 208g of intermediate E was obtained by vacuum distillation. The reaction was carried out under normal pressure and the reaction yield was 95%.

[0029] (6) Sixth rearrangement reaction: Mix 208g of intermediate E, 208g of cyclohexane and 0.8g of sulfuric acid as a base, start stirring and raise the temperature to reflux. When the content of intermediate E is less than 1%, cool down to end the reaction. Wash the reaction residue once with 1% sodium hydroxide, and then obtain 176g of carvacrol product by vacuum distillation. The reaction is an atmospheric pressure reaction with a reaction yield of 95%.

[0030] Example 3 (1) First step hydrogenation reaction: 500g of isoterpinene, 250g of dichloroethane and 2.5g of 5% palladium on carbon were put into a high pressure reactor, the stirring was turned on and the system was replaced with nitrogen three times, the temperature was raised and hydrogen was introduced. When the isoterpinene content was less than 1%, the temperature was lowered to end the reaction. The reaction residue was simply filtered and vacuum distilled to obtain 466g of intermediate A. The reaction yield was 92%. The pressure was controlled at 10 bar throughout the reaction and the reaction temperature was controlled at 80℃.

[0031] (2) Second step epoxidation reaction: 466g of intermediate A was mixed with 20g of sodium acetate as a base. When the system was stirred evenly and the system temperature reached 20℃, 1000g of 20% peracetic acid was slowly added dropwise. When the content of intermediate A was less than 30%, the reaction was stopped by cooling. The reaction residue was washed once with 10% sodium sulfite and 10% sodium hydroxide, and then 346g of intermediate B was obtained by vacuum distillation. The reaction yield was 95%.

[0032] (3) Third step of isomerization reaction: 346g of intermediate B and 1.5g of copper sulfate were mixed as a base. After the system was stirred evenly, the temperature was raised to 160℃. When the content of intermediate B was less than 1%, the temperature was lowered to end the reaction. The reaction residue was washed once with 1% sodium hydroxide and then 328g of intermediate C was obtained by vacuum distillation. The reaction was carried out under normal pressure and the reaction yield was 95%.

[0033] (4) Fourth step oxidation reaction: Mix 328g of intermediate C with 20g of aluminum isopropoxide as a base, start stirring, and when the temperature rises to 80℃, slowly add 155g of butanone. When the content of intermediate C is less than 1%, cool down to end the reaction. The reaction residue is distilled under reduced pressure to obtain 297g of intermediate D. The reaction is an atmospheric pressure reaction with a yield of 92%.

[0034] (5) Fifth step epoxidation reaction: 297g of intermediate D and 12g of sodium acetate were mixed as a base. When the system was stirred evenly and the system temperature reached 20℃, 530g of 20% peracetic acid was slowly added dropwise. When the content of intermediate A was less than 30%, the temperature was lowered to end the reaction. The reaction residue was washed once with 10% sodium sulfite and 10% sodium hydroxide, and then 218g of intermediate E was obtained by vacuum distillation. The reaction was carried out under normal pressure and the reaction yield was 95%.

[0035] (6) Sixth rearrangement reaction: Mix 218g of intermediate E, 218g of anisole and 1g of zinc chloride as a base, start stirring and raise the temperature to reflux. When the content of intermediate E is less than 1%, cool down to end the reaction. Wash the reaction residue once with 1% sodium hydroxide, and then obtain 189g of carvacrol product by vacuum distillation. The reaction is an atmospheric pressure reaction with a reaction yield of 97%.

[0036] The above description of the embodiments is only for illustrating the technical concept and features of the present invention. Its purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. Those skilled in the art can obviously easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative effort. Therefore, the above embodiments should not be used to limit the scope of protection of the present invention. All improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for synthesizing carvacrol from isoprene, characterized in that, Includes the following steps: (1) Hydrogenation reaction: Isorhodotorylene, polar solvent and metal hydrogenation catalyst are added into hydrogenation reactor and reduced with hydrogen to obtain intermediate A; (2) Epoxidation reaction: After mixing intermediate A with sodium acetate as a base, peracetic acid is added dropwise to carry out the epoxidation reaction to obtain intermediate B; (3) Isomerization reaction: After mixing intermediate B with an acidic homogeneous transition metal salt catalyst as a base, intermediate C is obtained by high-temperature isomerization reaction; (4) Oxidation reaction: After mixing intermediate C with organoaluminum Lewis acid catalyst as a base, intermediate D is obtained by Oppenauer oxidation; (5) Epoxidation reaction: After mixing intermediate D with sodium acetate as a base, peracetic acid is added dropwise to carry out the epoxidation reaction to obtain intermediate E; (6) Rearrangement reaction: After mixing intermediate E, solvent and homogeneous acid catalyst as a base, carvacrol is obtained by reflux to remove water; The homogeneous acid catalyst is a Brønsted acid catalyst or a Lewis acid catalyst. The reaction route is shown below: 。 2. The method for synthesizing carvacrol from isoprene according to claim 1, characterized in that: The operation process of step (1) is as follows: put isoterpinene, polar solvent and metal hydrogenation catalyst into high pressure vessel, start stirring and make the reaction system in nitrogen atmosphere, heat up and pass hydrogen to carry out hydrogenation reaction. When the isoterpinene content is less than 1%, cool down to end the reaction. After simple filtration and vacuum distillation, intermediate A is obtained from the reaction residue. The pressure is controlled at 5-30 bar throughout the reaction and the reaction temperature is controlled at 30-100℃.

3. A method for synthesizing carvacrol from isoprene according to claim 1 or 2, characterized in that: The polar solvent is one or a mixture of two or more of methanol, ethanol, isopropanol, dioxane, dichloromethane or dichloroethane; And / or, the metal hydrogenation catalyst is one or a mixture of two or more of Raney nickel, palladium / carbon, palladium / alumina, ruthenium / carbon, and ruthenium / alumina; And / or, the mass ratio of isoterpinene to polar solvent is 1:0.5-3, and the mass ratio of isoterpinene to metal hydrogenation catalyst is 1:0.001-0.

01.

4. The method for synthesizing carvacrol from isoprene according to claim 1, characterized in that: The operation process of step (2) is as follows: Mix intermediate A with sodium acetate as a base. When the system is stirred evenly and the system temperature reaches the required level, start slowly adding peracetic acid to carry out the epoxidation reaction. When the content of intermediate A is less than 30%, cool down to end the reaction. Wash the reaction residue with 10% sodium sulfite and 10% sodium hydroxide respectively, and then obtain intermediate B by vacuum distillation. The reaction is an atmospheric pressure reaction and the reaction temperature is controlled at 10-40℃. And / or, the mass ratio of intermediate A to sodium acetate is 1:0.01-0.2, and the mass ratio of intermediate A to peracetic acid is 1:1-2.

5. The method for synthesizing carvacrol from isoprene according to claim 1, characterized in that: The operation process of step (3) is as follows: mix intermediate B with acidic homogeneous transition metal salt catalyst as a base, and after the system is stirred evenly, raise the temperature to the specified temperature and stir to carry out the isomerization reaction. When the content of intermediate B is less than 1%, cool down to end the reaction. Wash the reaction residue with 1% sodium hydroxide and then obtain intermediate C by vacuum distillation. The reaction is an atmospheric pressure reaction and the reaction temperature is controlled at 80-170℃. And / or, the acidic homogeneous transition metal salt catalyst is one or more of the sulfates, acetates or halides of iron, nickel, zinc, palladium, copper or platinum; And / or, the mass ratio of intermediate B to the acidic homogeneous transition metal salt catalyst is 1:0.005-0.

15.

6. The method for synthesizing carvacrol from isoprene according to claim 1, characterized in that: The operation process of step (4) is as follows: mix intermediate C with organoaluminum Lewis acid catalyst as a base, start stirring, wait for the temperature to rise to the specified temperature, add oxidant dropwise to carry out oxidation reaction, when the content of intermediate C is less than 1%, cool down to end the reaction, the reaction residue is obtained by vacuum distillation to get intermediate D, the reaction is an atmospheric pressure reaction, and the reaction temperature is controlled at 30-100℃. And / or, the organoaluminum Lewis acid catalyst is aluminum isopropoxide; And / or, the oxidant is one or a mixture of two or more of acetone, butanone or cyclohexanone; And / or, the mass ratio of intermediate C to organoaluminum Lewis acid catalyst is 1:0.01-0.1, and the mass ratio of intermediate C to oxidant is 1:0.1-1.

7. The method for synthesizing carvacrol from isoprene according to claim 1, characterized in that: The operation process of step (5) is as follows: mix intermediate D with sodium acetate as a base, and when the system is stirred evenly and the system temperature reaches the required level, start slowly adding peracetic acid to carry out the epoxidation reaction. When the content of intermediate D is less than 30%, cool down to end the reaction. Wash the reaction residue with 10% sodium sulfite and 10% sodium hydroxide respectively, and then obtain intermediate E by vacuum distillation. The reaction is an atmospheric pressure reaction, and the reaction temperature is controlled at 10-40℃. And / or, the mass ratio of intermediate D to sodium acetate is 1:0.01-0.2, and the mass ratio of intermediate D to peracetic acid is 1:1-2.

8. The method for synthesizing carvacrol from isoprene according to claim 1, characterized in that: The operation process of step (6) is as follows: mix intermediate E, solvent and homogeneous acid catalyst as a base, start stirring, raise the temperature to the point where the solvent is refluxed to carry out the rearrangement reaction, when the content of intermediate E is less than 1%, cool down to end the reaction, wash the reaction residue with 1% sodium hydroxide, and then obtain carvacrol product by vacuum distillation. The reaction is an atmospheric pressure reaction and the reaction temperature is controlled at 80-170℃.

9. A method for synthesizing carvacrol from isoprene according to claim 1 or 8, characterized in that: The homogeneous acid catalyst is one or a mixture of two or more of sulfuric acid, hydrochloric acid, phosphoric acid, p-toluenesulfonic acid, or halides of metallic iron, nickel, zinc, palladium, copper, and platinum. And / or, the solvent is one or a mixture of two or more of cyclohexane, toluene, xylene, trimethylbenzene or anisole; And / or, the mass ratio of intermediate E to solvent is 1:0.1-2, and the mass ratio of intermediate E to homogeneous acid catalyst is 1:0.001-0.1.

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