Paired electrochemical synthesis method of anisaldehyde and phthalide

Abstract

The invention discloses a paired electrochemical synthesis method of anisaldehyde and phthalide, which comprises the following steps of: adopting p-methyl anisole and phthalate as raw materials, oxidizing p-methyl anisole at an anode to generate anisaldehyde through electrolytic reaction in the same electrolytic bath, and reducing phthalate at a cathode to generate phthalide, an electrolyte system adopted in the electrolytic reaction comprises an electrolyte, water, N, N-dimethylformamide and methanol. In the same electrochemical synthesis system, p-methyl anisole and phthalate are used as raw materials, the mixed solvent which is low in price and easy to obtain is used, anisaldehyde is generated on an anode and phthalide is generated on a cathode through an electrolytic reaction, high-added-value products exist in the anode and the cathode, an oxidizing agent and a noble metal catalyst are not needed, and the method is simple and convenient to operate. Basically no three wastes are generated, and no hydrogen and oxygen are generated in the reaction process, so that the method is safer.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical synthesis of compounds, and in particular to a paired electrochemical synthesis method of anisaldehyde and phthalide. Background Art

[0002] Anisaldehyde (p-anisaldehyde, 4-methoxybenzaldehyde), also known as p-anisaldehyde, p-methoxybenzaldehyde, 4-methoxybenzaldehyde, and anise aldehyde, has a boiling point of 246 °C, a melting point of 0 °C, a density of 1.123 g / mL (20 °C), a refractive index of 1.5720, and a flash point of 117.8 °C. It is a colorless oily liquid at room temperature, with a strong aroma of anise and hawthorn, and the fragrance is long-lasting. p-Methoxybenzaldehyde and its derivatives have a wide range of applications: 1. In the pharmaceutical industry, anisaldehyde can be used as an intermediate for antihistamine drugs, for the manufacture of antimicrobial drugs, and for the synthesis of porphyrin photosensitizers, amoxicillin, oseltamivir, etc.; 2. In the agricultural field, anisaldehyde is often used to synthesize 1,2-bis(4-methoxyphenyl)ethanone, etc. as pesticides; 3. In the fragrance and flavor industry, corresponding thioacetals, anisic nitrile, and p-methoxycinnamate esters are synthesized from anise aldehyde; 4. In the electroplating industry, as an excellent brightener for cyanide-free zinc plating additives, it can increase anodic polarization within a wide current range and obtain a bright coating; 5. It can also be used as a fluorescent probe for the determination of biological macromolecules such as nucleic acids. Currently, the methods for preparing anisaldehyde mainly include the following: 1. Traditional chemical oxidation method: A large amount of heavy metal salts such as chromium and manganese and a large amount of acids and bases are consumed during the reaction, and a large amount of manganese salt waste residue, chromium residue, and wastewater are generated, resulting in the problem of difficult treatment of "three wastes" pollution, causing great pollution to the environment. At the same time, the presence of acid will cause serious corrosion to the production equipment; 2. Ozone oxidation method: Ozone can oxidize double bonds and does not attack the benzene ring. However, a large amount of organic solvents are required during the preparation of anisaldehyde by the ozone oxidation method. On the one hand, the recovery of organic solvents is difficult, with large losses, and the product purification is also difficult. On the other hand, there are high safety hazards in the ozone oxidation reaction, such as explosion accidents, making it difficult to achieve industrial production; 3. Electrochemical oxidation method: The electrochemical oxidation method uses graphite or DSA as the anode, stainless steel as the cathode, an 80%-90% ethanol aqueous solution as the solvent, 0.25 mol / L H2SO4 as the electrolyte, and the concentration of natural anethole is not more than 0.15 mol / L. The yield of anisaldehyde obtained is about 60%.

[0003] Phthalide is an important class of heterocyclic compounds existing in nature, and many drugs or drug intermediates contain phthalide units. More and more studies have shown that phthalide derivatives have pharmacological activities such as antipyretic, analgesic, anti-tumor, antibacterial and antifungal. For example, pomalidomide (Pomalyst) has good anti-tumor activity. In 2020, the Yu Jinquan group reported the synthesis of phthalide compounds (Ligand-Enabled Pd(II)-Catalyzed C(sp 3 )–H Lactonization Using Molecular Oxygen as Oxidant. Org. Lett. 2020, 22, 3960-3963) with o-methylbenzoic acid as the raw material and Pd-catalyzed reaction. Although this reaction is efficient, the synthesis catalyst cost of the raw material is high, the reaction conditions are harsh, and the reaction time is long.

[0004] Electrochemical synthesis methods are regarded as green synthesis technologies because of their mild conditions, simple operation and no pollution to the environment. Especially the paired electrosynthesis technology not only has the general advantages of electrosynthesis, but also has the advantages of high current efficiency, high space-time efficiency, low production cost and energy saving, so it has attracted much attention. Paired electrosynthesis uses both the anodic oxidation reaction and the cathodic reduction reaction to generate high-value-added products. The electrolysis efficiency can theoretically reach 200%. The existing technologies only report the electrochemical synthesis methods of phthalide and its derivatives, or only disclose the methods for synthesizing o-, m-, p-methoxybenzaldehyde by electrolysis, and do not involve the process of simultaneously synthesizing anisaldehyde and phthalide in a single electrochemical reactor. Summary of the Invention

[0005] In view of this, the main object of the present invention is to provide a paired electrochemical synthesis method of anisaldehyde and phthalide, which can synthesize anisaldehyde and phthalide in an electrolytic cell, and has high current efficiency and high space-time efficiency, showing the economic advantages of paired electrosynthesis.

[0006] To achieve the above invention object, the first aspect of the present invention provides a paired electrochemical synthesis method of anisaldehyde and phthalide, comprising the following steps:

[0007] Using p-methylanisole and phthalate as raw materials, in the same electrolytic cell, p-methylanisole is oxidized to anisaldehyde at the anode through an electrolysis reaction, and at the same time, phthalate is reduced to phthalide at the cathode. The electrolyte system used in the electrolysis reaction comprises an electrolyte, water, an aprotic polar solvent and methanol.

[0008] Further, the electrolyte is one or more of ammonium tetrabutylborate, ammonium tetraethylammonium tetrafluoroborate, ammonium tetrabutyl perchlorate, lithium perchlorate, sodium trifluoromethanesulfonate, sodium benzenesulfonate, sodium p-toluenesulfonate, tetraethylammonium fluoride, potassium fluoride, sodium fluoride, ammonium tetrabutyl hexafluorophosphate, and boron trifluoride diethyl etherate.

[0009] Further, the aprotic polar solvent is selected from one or more of DMF (N,N-dimethylformamide), DMSO (dimethyl sulfoxide), DCM (dichloromethane), NMP (N-methylpyrrolidone), and THF (tetrahydrofuran).

[0010] In the present invention, the above-mentioned aprotic polar solvent has a relatively strong polarity and is a relatively excellent polar solvent, which helps to dissolve the supporting electrolyte. The relatively high solvent polarity is conducive to the dissolution and dissociation of the electrolyte, significantly affects the cathode reduction reaction process, and is more helpful for improving the reaction effect. The above-mentioned aprotic polar solvent helps the cathode reduction, while methanol (MeOH) is a protic polar solvent, which is more conducive to the anodic oxidation reaction.

[0011] Further, the phthalate is any one or two of dimethyl phthalate, diethyl phthalate, methyl ethyl phthalate, dipropyl phthalate, and dibutyl phthalate; preferably, the phthalate is dimethyl phthalate.

[0012] Further, the concentration of the p-methylanisole or phthalate in the electrolyte system is between 5% and 40%. For example, 5%, 8%, 9%, 10%, 12%, 15%, 16%, 19%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, or 40%. The raw material concentration can affect the conversion rate and selectivity of the reaction. If the raw material concentrations of the anode and cathode are high, the raw material conversion rate and product selectivity will increase, but the impurities will also increase, which is not conducive to the reaction; if the raw material concentration is low, the raw material conversion rate and product selectivity are low, and the yield is too low. Preferably, the concentration range of p-methylanisole is 10% - 25%, and the concentration range of phthalate is 16% - 40%.

[0013] Further, the mass ratio of the electrolyte: water: aprotic polar solvent: methanol is (1 - 10):(1 - 5):(10 - 30):(60 - 70). Among them, methanol not only provides methoxy as a raw material but also acts as a solvent to cooperate with the aprotic polar solvent. The mixing ratio of methanol and the aprotic polar solvent, such as the ratio of the two being 1:1, 1:3, 1:4, 1:5, etc., will affect the conversion rate of the raw material and the selectivity of the product.

[0014] In the present invention, a novel electrolyte system is designed. Adding the above-mentioned mixed solvent containing water, methanol and aprotic polar solvent helps to improve the reaction activity of the reduction of phthalate at the cathode, and finally achieves a very high selectivity for the cathode and anode reactions. Adjusting the ratio of water, MeOH and aprotic polar solvent helps the anodic oxidation and cathodic reduction, greatly improves the solubility of the electrolyte, and then affects the mass transfer between the electrodes, resulting in a high overall reaction activity.

[0015] Further, the electrolytic reaction is carried out at a temperature of 20 - 60 °C and a current density of 2.0 - 10.0 A / dm 2 ², and the end point of the electrolytic reaction is determined according to 100 - 150% of the theoretical reaction charge.

[0016] In the present invention, the end point of the electrolytic reaction can be optimized and adjusted according to the ratio of the theoretical reaction charge, which will affect its conversion rate and selectivity. The longer the end point of the electrolytic reaction, the higher the raw material conversion rate, but the product selectivity will decrease, and the generation of impurities will also increase, affecting the reaction effect. Preferably, the end point of the electrolytic reaction is determined according to 120% of the theoretical reaction charge.

[0017] Further, the cathode and anode are graphite electrodes.

[0018] Further, most or all of the cathode and anode are placed in the electrolyte system. The cathode and anode are arranged oppositely, with a distance of 0.1 - 3 mm, preferably 0.5 - 1 mm.

[0019] Further, in the prepared raw material reaction solution, the molar ratio of the raw material p-methylanisole of the feeding anode to the raw material dimethyl phthalate of the cathode is 1:1.

[0020] Further, the electrolytic cell is a diaphragmless electrolytic cell.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The present invention provides a paired electrochemical synthesis method of anisaldehyde and phthalide. Using p-methylanisole and phthalate as raw materials, and adopting an electrolyte system containing electrolyte, water, aprotic polar solvent and methanol, in the same electrolytic cell, p-methylanisole is oxidized to anisaldehyde at the anode through electrolytic reaction, and at the same time, phthalate is reduced to phthalide at the cathode, that is, high-value-added anisaldehyde and phthalide products are obtained simultaneously.

[0023] The present invention does not require the use of redox reagents and noble metal catalysts, and has the significant advantage of low reaction costs; it directly uses inexpensive and readily available phthalic acid esters and p-methylanisole as starting materials, eliminating the pre-activation step of the substrate. Compared with previous synthesis methods, it has significant atom economy and step economy; it uses clean electrons as a "trace-free" oxidant to replace highly flammable, explosive, toxic, and harmful chemical strong oxidizing reagents, greatly enhancing the safety of the process, reducing the "three wastes" emissions of the process, and conforming to the background of the times of green synthesis and safe production. And it ensures that the anodic current efficiency is between 70-90%, the cathodic current efficiency is between 60-98%, and the total current efficiency of the electrolysis reaction can reach more than 160% at most, reducing the reaction energy consumption, improving the space-time efficiency, and having good economic benefits and industrial value.

[0024] Other features and advantages of the present invention will be described in detail in the following specific embodiments. Specific Embodiments

[0025] The following details the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention.

[0026] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0027] The sources of the instruments and reagents are shown in Table 1 below:

[0028] Table 1

[0029] Instruments and Reagents Source Specification / Purity Electrolytic Cell Suzhou Fenggang Titanium Equipment Co., Ltd. Customized Electrolytic Cell Gas Chromatograph Shimadzu GC-2010 p-Methylanisole Commercially available >99％ Methanol Aladdin >99％ N,N-Dimethylformamide Aladdin 99％ Electrolyte InnoChem 99％

[0030] The analysis and calculation methods are as follows:

[0031] After diluting the electrolysis reaction solution 20 times with a methanol solution, external standard method in gas chromatography is used for quantification.

[0032] Gas Chromatography: Shimadzu gas chromatography is used, nitrogen is used as the carrier gas, Shimadzu DB-5 chromatographic column is used, the carrier gas is nitrogen, the carrier gas flow rate is 1.0 ml / min, the initial column temperature is 100 °C, rising to 300 °C at a rate of 10 °C / min, the vaporization chamber temperature is 300 °C, and the detector temperature is 300 °C.

[0033] The test or calculation method for the conversion rate (σ) is:

[0034]

[0035] In the formula,

[0036] n0 is the amount of substance of the anode p - anisole or the cathode dimethyl phthalate input in the reaction, in mol;

[0037] m is the total mass of the reaction solution, in g;

[0038] ω is the mass fraction of the anode p - anisole or the cathode dimethyl phthalate in the reaction solution;

[0039] M is the relative molecular mass of the anode product anisaldehyde or the cathode product phthalide in the reaction solution.

[0040] The method for testing or calculating the selectivity (δ) is as follows:

[0041]

[0042] In the formula,

[0043] n0 is the amount of substance of the anode p - anisole or the cathode dimethyl phthalate input in the reaction, in mol;

[0044] n1 is the amount of substance of the remaining anode p - anisole or the cathode dimethyl phthalate in the reaction solution, in mol;

[0045] m is the total mass of the reaction solution, in g;

[0046] ω1 is the mass fraction of the anode product anisaldehyde or the cathode product phthalide in the reaction solution;

[0047] M is the relative molecular mass of the anode product anisaldehyde or the cathode product phthalide in the reaction solution.

[0048] The following examples are helpful for further understanding of the present invention, but the content of the present invention is not limited thereto.

[0049] Example 1

[0050] A diaphragm - free electrolytic cell is selected, and the anode and the cathode are made of graphite. The electrolyte solution contains an electrolyte, water, DMF and MeOH, the temperature is 50 °C, and the current density is 2.0 A / dm 2 , the electrolyte is sodium benzenesulfonate. Calculated based on the total mass of the electrolyte solution system and the raw materials (p - anisole and dimethyl phthalate) being 100%, the mass ratio of the electrolyte, water, DMF and MeOH is 5:2:20:60, and the remainder is p - anisole and dimethyl phthalate. The cathode and the anode are arranged opposite to each other, and the distance is 0.2 mm; the concentration of p - anisole in the electrolyte solution is 12%, and the concentration of phthalate in the electrolyte solution is 19%.

[0051] During the electrolysis process, the anodic reaction is the electrooxidation of p - anisole to anisaldehyde, and the cathodic reaction is the reduction of dimethyl phthalate to phthalide. The electrolysis end - point is determined according to 120% of the theoretical reaction electric quantity. After the reaction, the conversion rate of anisaldehyde is 82% and the selectivity is 85%; the conversion rate of phthalide is 93% and the selectivity is 90%.

[0052] Example 2

[0053] A diaphragm - free electrolytic cell is selected, and the anode and cathode are made of graphite. The electrolyte solution contains electrolyte, water, DMF, MeOH, at a temperature of 20 °C, and the current density is 4.0 A / dm 2 , the electrolyte is sodium fluoride, and the mass ratio of the four is 5:1:10:50. The cathode and anode are arranged opposite to each other with a distance of 0.2 mm; the concentration of p - anisole in the electrolyte solution is 12%, and the concentration of phthalate in the electrolyte solution is 19%.

[0054] During the electrolysis process, the anodic reaction is the electrooxidation of p - anisole to anisaldehyde, and the cathodic reaction is the reduction of diethyl phthalate to phthalide. The electrolysis end - point is determined according to 120% of the theoretical reaction electric quantity. After the reaction, the conversion rate of anisaldehyde is 85% and the selectivity is 80%; the conversion rate of phthalide is 90% and the selectivity is 88%.

[0055] Example 3

[0056] A diaphragm - free electrolytic cell is selected, and the anode and cathode are made of graphite. The electrolyte solution contains electrolyte, water, DMF, MeOH, at a temperature of 35 °C, and the current density is 7.0 A / dm 2 , the electrolyte is tetrabutylammonium hexafluorophosphate, and the mass ratio of the four is 3:1:10:57. The cathode and anode are arranged opposite to each other with a distance of 0.2 mm; the concentration of p - anisole in the electrolyte solution is 12%, and the concentration of phthalate in the electrolyte solution is 19%.

[0057] During the electrolysis process, the anodic reaction is the electrooxidation of p - anisole to anisaldehyde, and the cathodic reaction is the reduction of dibutyl phthalate to phthalide. The electrolysis end - point is determined according to 120% of the theoretical reaction electric quantity. After the reaction, the conversion rate of anisaldehyde is 90% and the selectivity is 80%; the conversion rate of phthalide is 85% and the selectivity is 90%.

[0058] Example 4

[0059] A diaphragm - free electrolytic cell is selected, and the anode and cathode are made of graphite. The electrolyte solution contains electrolyte, water, NMP, MeOH, at a temperature of 50 °C, and the current density is 10.0 A / dm 2, the electrolyte is sodium benzenesulfonate, and the ratio of the four is 10:1:15:60. The cathode and the anode are arranged oppositely with a distance of 0.2 mm; the concentration of p-methylanisole in the electrolyte is 5%, and the concentration of phthalate in the electrolyte is 8%.

[0060] During the electrolysis process, the anodic reaction is the electrooxidation of p-methylanisole to anisaldehyde, and the cathodic reaction is the reduction of ethyl methyl phthalate to phthalide. The electrolysis end point is determined according to 120% of the theoretical reaction electric quantity. After the reaction is completed, the conversion rate of anisaldehyde is measured to be 88% and the selectivity is 90%; the conversion rate of phthalide is 93% and the selectivity is 90%.

[0061] Example 5

[0062] A diaphragm-free electrolytic cell is selected, and the anode and the anode are made of graphite. The electrolyte solution contains an electrolyte, water, DMF, and MeOH, with a temperature of 50 °C and a current density of 5.0 A / dm 2 , the electrolyte is boron trifluoride diethyl ether, and the mass ratio of the four is 5:1:15:60. The cathode and the anode are arranged oppositely with a distance of 0.2 mm; the concentration of p-methylanisole in the electrolyte is 25%, and the concentration of phthalate in the electrolyte is 40%.

[0063] During the electrolysis process, the anodic reaction is the electrooxidation of p-methylanisole to anisaldehyde, and the cathodic reaction is the reduction of ethyl methyl phthalate to phthalide. The electrolysis end point is determined according to 120% of the theoretical reaction electric quantity. After the reaction is completed, the conversion rate of anisaldehyde is measured to be 90% and the selectivity is 80%; the conversion rate of phthalide is 88% and the selectivity is 80%.

[0064] Example 6

[0065] A diaphragm-free electrolytic cell is selected, and the anode and the anode are made of graphite. The electrolyte solution contains an electrolyte, water, DMF, and MeOH, with a temperature of 60 °C and a current density of 5.0 A / dm 2 , the electrolyte is boron trifluoride diethyl ether, and the mass ratio of the four is 5:1:15:60. The cathode and the anode are arranged oppositely with a distance of 0.2 mm; the concentration of p-methylanisole in the electrolyte is 10%, and the concentration of phthalate in the electrolyte is 16%.

[0066] During the electrolysis process, the anodic reaction is the electrooxidation of p-methylanisole to anisaldehyde, and the cathodic reaction is the reduction of ethyl methyl phthalate to phthalide. The electrolysis end point is determined according to 120% of the theoretical reaction electric quantity. After the reaction is completed, the conversion rate of anisaldehyde is measured to be 95% and the selectivity is 90%; the conversion rate of phthalide is 95% and the selectivity is 92%.

[0067] Different raw material concentrations can lead to different conversion rates and selectivities of the reaction, and the reaction effect of this example is the best.

[0068] Example 7

[0069] A diaphragmless electrolytic cell is selected, and graphite is used for both the anode and the cathode. The electrolyte solution contains an electrolyte, water, DMF, and MeOH, with a temperature of 50 °C and a current density of 5.0 A / dm 2 . The electrolyte is boron trifluoride ethyl ether, and the mass ratio of the four is 5:1:15:60. The cathode and the anode are arranged opposite to each other with a distance of 0.2 mm; the concentration of p-methylanisole in the electrolyte solution is 25%, and the concentration of phthalic acid ester in the electrolyte solution is 40%.

[0070] During the electrolysis process, the anodic reaction is the electrooxidation of p-methylanisole to anisaldehyde, and the cathodic reaction is the reduction of methyl ethyl phthalate to phthalide. The electrolysis end point is determined according to 100% of the reaction theoretical electricity quantity. After the reaction ends, the conversion rate of anisaldehyde is measured to be 88% and the selectivity is 78%; the conversion rate of phthalide is 85% and the selectivity is 80%.

[0071] Compared with Example 5, in this example, the electrolysis reaction end point is determined according to 100% of the reaction theoretical electricity quantity, and its conversion rate will decrease, and the selectivity will also decrease accordingly.

[0072] Comparative Example 1

[0073] A diaphragmless electrolytic cell is selected, and graphite is used for both the anode and the cathode. The electrolyte solution contains an electrolyte, water, and MeOH, with a temperature of 45 °C and a current density of 5.0 A / dm 2 . The electrolyte is boron trifluoride ethyl ether, and the mass ratio of the three is 2:1:65. During the electrolysis process, the anodic reaction is the electrooxidation of p-methylanisole to anisaldehyde, and the cathodic reaction is the reduction of methyl ethyl phthalate to phthalide. The electrolysis end point is determined according to 120% of the reaction theoretical electricity quantity. After the reaction ends, the conversion rate of anisaldehyde is measured to be 80% and the selectivity is 70%; the conversion rate of phthalide is 80% and the selectivity is 75%.

[0074] Comparative Example 2

[0075] A diaphragmless electrolytic cell is selected, and graphite is used for both the anode and the cathode. The electrolyte solution contains an electrolyte, water, DMF, and MeOH, with a temperature of 50 °C and a current density of 5.0 A / dm 2 . The electrolyte is boron trifluoride ethyl ether, and the mass ratio of the four is 0.5:0.5:5:50. During the electrolysis process, the anodic reaction is the electrooxidation of p-methylanisole to anisaldehyde, and the cathodic reaction is the reduction of methyl ethyl phthalate to phthalide. The electrolysis end point is determined according to 120% of the reaction theoretical electricity quantity. After the reaction ends, the conversion rate of anisaldehyde is measured to be 85% and the selectivity is 75%; the conversion rate of phthalide is 83% and the selectivity is 78%.

[0076] In Examples 1-7 of the present invention, by adjusting different variable parameters, a new type of electrolyte was designed, which is helpful for anodic oxidation and cathodic reduction. It greatly improves the solubility of the supporting electrolyte, thereby affecting the mass transfer between electrodes and making the overall reaction activity high; adding a mixed solvent helps to improve the reaction activity of the reduction of phthalate at the cathode, and finally achieves a very high selectivity for the cathode and anode reactions. In Comparative Example 1, since a mixed solvent was not used, and in Comparative Example 2, the proportions of the electrolyte, water, DMF, and MeOH are not within the preferred range of the present invention, it can be seen that the selectivity of the anode and cathode will be affected, resulting in a non-optimal result, which will affect the final energy consumption and device yield of the electrolytic cell.

[0077] Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to enumerate all the implementation manners here. Any obvious changes or modifications derived from the technical solutions of the present invention are within the spirit scope covered by the present invention.

Claims

1. A paired electrochemical synthesis method of anisaldehyde and phthalide, characterized in that, It includes the following steps: Using p-methylanisole and phthalate as raw materials, in the same electrolytic cell, through an electrolysis reaction, p-methylanisole is oxidized to anisaldehyde at the anode, and at the same time, phthalate is reduced to phthalide at the cathode. The electrolyte system used in the electrolysis reaction includes an electrolyte, water, an aprotic polar solvent, and methanol.

2. The paired electrochemical synthesis method according to claim 1, wherein The electrolyte is one or more of tetrabutylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, tetrabutylammonium perchlorate, lithium perchlorate, sodium trifluoromethanesulfonate, sodium benzenesulfonate, sodium p-toluenesulfonate, tetramethylammonium fluoride, potassium fluoride, sodium fluoride, tetrabutylammonium hexafluorophosphate, boron trifluoride diethyl etherate; The aprotic polar solvent is selected from one or more of DMF, DMSO, DCM, NMP, and THF.

3. The paired electrochemical synthesis method according to claim 1, wherein The phthalate is any one or two of dimethyl phthalate, diethyl phthalate, methyl ethyl phthalate, dipropyl phthalate, dibutyl phthalate; preferably, the phthalate is dimethyl phthalate.

4. The paired electrochemical synthesis method according to claim 1, wherein The concentration of the raw material p-methylanisole at the anode in the electrolyte system is between 5% and 40%, and the concentration of the raw material phthalate at the cathode in the electrolyte system is between 5% and 40%; preferably, the concentration range of p-methylanisole is 10% - 25%, and the concentration range of phthalate is 16% - 40%.

5. The paired electrochemical synthesis method according to claim 1, wherein The mass ratio of the electrolyte: water: aprotic polar solvent: methanol is (1 - 10):(1 - 5):(10 - 30):(60 - 70).

6. The paired electrochemical synthesis method according to claim 1, wherein The electrolysis reaction is carried out at a temperature of 20-60 °C and a current density of 2.0-10.0 A / dm 2 and the end point of the electrolysis reaction is determined according to 100-150% of the theoretical reaction charge.

7. The paired electrochemical synthesis method according to any one of claims 1-6, characterized in that, The cathode and anode are graphite electrodes.

8. The paired electrochemical synthesis method according to claim 7, characterized in that, Most or all of the cathode and anode are placed in the electrolyte system. The cathode and anode are arranged opposite to each other, and the distance is 0.1 - 3 mm, preferably 0.5 - 1 mm.

9. The paired electrochemical synthesis method according to claim 1, characterized in that, In the prepared raw material reaction solution, the molar ratio of the raw material p-methylanisole at the anode to the raw material dimethyl phthalate at the cathode is 1:

1.

10. The paired electrochemical synthesis method according to any one of claims 1-9, characterized in that, The electrolytic cell is a diaphragmless electrolytic cell.

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