Synthesis method of 2-nitro-4-methylsulfonyl toluene

Abstract

The invention relates to a synthesis method of 2-nitro-4-methylsulfonyl toluene, which comprises the following steps: reacting 2-nitro-4-chlorotoluene with sodium methyl mercaptide and other raw materials to synthesize 2-nitro-4-methylthio toluene, and oxidizing to obtain 2-nitro-4-methylsulfonyl toluene, the synthesis route is simple, the problem of large amount of waste acid and waste water is solved, and the synthesis method is green and environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of compound synthesis technology, and specifically to a method for synthesizing 2-nitro-4-methylsulfonyl toluene. Background Technology

[0002] 2-Nitro-4-methylsulfonyltoluene is a chemical intermediate in which the nitro group can be reduced to an amino group for the synthesis of amine-containing drugs; the sulfonyl group is commonly found in antibacterial and anti-inflammatory drugs, and is also used as a precursor for herbicides or insecticides in agrochemicals, stabilizing the active molecule structure through the sulfonyl group. The multifunctional nature of this compound makes it valuable in multiple industrial sectors, but its synthesis and application still require further optimization in terms of safety and sustainability.

[0003] Currently, the main methods for synthesizing 2-nitro-4-methylsulfonyl toluene are as follows:

[0004] The first method uses toluene as the starting material, introducing a methylthio group. Toluene reacts with methanethiol under Lewis acid catalysis via electrophilic substitution to produce 4-methylthiotoluene. Then, it is oxidized in acetic acid with 30% hydrogen peroxide or by ozone to produce 4-methylsulfonyltoluene. Finally, under a mixed acid environment of concentrated nitric acid and concentrated sulfuric acid, it is added dropwise at low temperature to control the temperature and avoid side reactions, producing 2-nitro-4-methylsulfonyltoluene.

[0005] The second method uses toluene as a starting material. After sulfonation with sulfuric acid, chlorosulfonic acid, sulfur trioxide, and other sulfonating agents, p-toluenesulfonic acid is obtained. This material is then chlorinated with thionyl chloride or chlorosulfonic acid to obtain p-toluenesulfonyl chloride. Under alkaline conditions, it is reduced with sulfur dioxide to produce sodium p-toluenesulfinate, which then reacts with a methylating agent to produce p-methylsulfonyltoluene. Finally, it is reacted with mixed acid to produce 2-nitro-4-methylsulfonyltoluene.

[0006] Other alternative synthesis methods include microwave-assisted synthesis, where microwave radiation accelerates the nitration or oxidation steps and shortens the reaction time; solid acid catalysis, which uses zeolite or ion exchange resin to replace traditional mixed acids, reducing waste acid pollution; and enzyme-catalyzed oxidation, where biological enzymes catalyze the oxidation of sulfides to sulfones, which is mild but has a low yield.

[0007] However, these synthetic routes are still not mature enough or have low yields, which has prevented them from being widely used. Summary of the Invention

[0008] The purpose of this invention is to provide a method for synthesizing 2-nitro-4-methylsulfonyl toluene. The method involves reacting 2-nitro-4-chlorotoluene with sodium methanethiol and other raw materials to synthesize 2-nitro-4-methylthiotoluene, which is then oxidized to obtain 2-nitro-4-methylsulfonyl toluene. The synthesis route is simple, solves the problem of large amounts of waste acid and wastewater, and is green and environmentally friendly.

[0009] The technical solution of this invention is:

[0010] A method for synthesizing 2-nitro-4-methylsulfonyl toluene, the key technical points of which include the following steps:

[0011] Step 1: Add dilute sulfuric acid to the reactor for nitrogen inertization replacement, turn on the stirrer, control the reaction temperature within the set range, add sodium methanethiol solution dropwise to the reactor, continue to keep the temperature high after the addition is complete, and slowly raise the temperature to the set temperature range to generate methanethiol gas.

[0012] Step 2: Add solvent and strong base to another reactor, cool down, and then pass the dry methanethiol gas produced in Step 1 through until the reaction is complete and there is still methanethiol gas dissolved in the solvent.

[0013] Step 3: Add 2-nitro-4-chlorotoluene to the reactor from Step 2, purge with nitrogen, and carry out the reaction at a set time and pressure. After the reaction is complete, take a sample to check the system. Then, replace the system with nitrogen, distill off the solvent under negative pressure, and cool down.

[0014] Step 4: Add water to the oily material after distillation in Step 3 for hydrolysis, then add a certain amount of sulfuric acid, control the temperature within the set range, add oxidant dropwise, keep the temperature for a certain period of time after the addition is complete, and take a sample to test the raw material to see if the reaction is complete.

[0015] Step 5: Add sodium sulfite and liquid alkali to the product of step 4 to adjust the pH value and oxidizing power. After adjustment, cool down and control the temperature within the set range. Filter and separate the product to obtain the target product 2-nitro-4-methylsulfonyl toluene.

[0016] In the above-described method for synthesizing 2-nitro-4-methylsulfonyl toluene, in step 1, the molar ratio of sodium methanethiol to 2-nitro-4-chlorotoluene is 1.5:1 to 2.0:1.

[0017] In the above-described method for synthesizing 2-nitro-4-methylsulfonyl toluene, in step 1, the molar ratio of dilute sulfuric acid to 2-nitro-4-chlorotoluene is 3.0:1 to 4.0:1.

[0018] In the above-mentioned method for synthesizing 2-nitro-4-methylsulfonyl toluene, step 1 involves finally heating the temperature to 60℃-100℃.

[0019] In the above-described method for synthesizing 2-nitro-4-methylsulfonyl toluene, in step 2, the solvent is an aprotic solvent, namely one of DMF, DMSO, DMAC, or NMP.

[0020] In the above-described method for synthesizing 2-nitro-4-methylsulfonyl toluene, step 2, the strong base is either sodium hydroxide or potassium hydroxide.

[0021] In the above-described method for synthesizing 2-nitro-4-methylsulfonyl toluene, step 3 involves a reaction temperature of 90℃-140℃ and a reaction pressure of 0.40MPa-0.60MPa.

[0022] In the above-described method for synthesizing 2-nitro-4-methylsulfonyl toluene, in step 4, the oxidant is one of hydrogen peroxide and sodium hypochlorite, and the molar ratio of the oxidant to 2-nitro-4-chlorotoluene is 0.8:1-1.2:1.

[0023] In the above-described method for synthesizing 2-nitro-4-methylsulfonyl toluene, step 4 involves controlling the temperature to be between 50°C and 80°C.

[0024] In the above-described method for synthesizing 2-nitro-4-methylsulfonyl toluene, step 5 involves adjusting the pH value to 5-8 and controlling the temperature to 30℃-50℃.

[0025] The beneficial effects of this invention are:

[0026] This process involves relatively small amounts of solvents, acids, and water, thus reducing the discharge of a large amount of waste acid and wastewater. Detailed Implementation

[0027] The present invention will now be described in detail with reference to specific embodiments.

[0028] The synthetic method for 2-nitro-4-methylsulfonyl toluene is as follows:

[0029]

[0030] The reaction mechanism of this invention is as follows:

[0031] The first step involves activation of the site and nucleophilic attack. In the structure of 2-nitro-4-chlorotoluene, the nitro group (-NO2) is a strong electron-withdrawing group. Through conjugation and inductive effects, the ortho and para positions on the benzene ring, especially the chlorine atom at position 4, become significantly electron-deficient, thus activating the site and making it more susceptible to nucleophilic substitution. The chlorine atom (C1), as a leaving group, is more easily attacked by nucleophiles under the synergistic effect of the strong electron-withdrawing group (nitro). The methylthio group (CH3S) in sodium methanethiol (CH3SNa) is further activated by the methylthio group (CH3S). - As a strong nucleophile, it attacks the electron-deficient carbon atom containing the chlorine atom, forming a Meissenheimer complex intermediate. Subsequently, the chloride ion (Cl...) - It detaches as a leaving group, generating an intermediate.

[0032] The second step is nucleophilic attack. The sulfur atom (lone pair electron) in the methylthio group nucleophilically attacks an oxygen atom in hydrogen peroxide (H2O2), forming a cyclic ternary transition state; OO bond breaking: the peroxy bond (OO) breaks, sulfur combines with oxygen to form an SO bond, and a water molecule (H2O) is released simultaneously; sulfoxide formation: the oxidation state of sulfur rises from -2 to +4, forming sulfoxide (methylsulfinyl); secondary nucleophilic attack: the sulfur atom in the sulfoxide (still containing a lone pair electron) attacks another oxygen atom in another molecule of H2O2, forming a similar transition state; second S=O bond formation: the peroxy bond breaks, sulfur combines with a second oxygen atom to form a second S=O bond; sulfone formation: the oxidation state of sulfur rises to +6, forming sulfone (methylsulfinyl).

[0033] The specific synthesis steps are as follows:

[0034] Step 1: Add a certain amount of dilute sulfuric acid to a reactor for nitrogen inertization; turn on the stirrer, control the reaction temperature, and add a certain amount of sodium methanethiol solution dropwise to the reactor. After the addition is complete, continue to keep the reaction at a constant temperature, slowly raising the temperature to 60℃-100℃ to generate methanethiol gas.

[0035] Step 2: Add a solvent and a strong base to another reactor. After cooling, the methanethiol gas produced in Step 1 is dried and then introduced into this reactor until the reaction is complete and a large amount of methanethiol gas dissolves into the solvent. The solvent is an aprotic solvent such as DMF, DMSO, DMAC, or NMP, preferably NMP. The strong base is either sodium hydroxide or potassium hydroxide, preferably potassium hydroxide.

[0036] Step 3: Add 2-nitro-4-chlorotoluene to the reactor from Step 2, purge with nitrogen, and carry out the reaction at a set time and pressure. The reaction temperature is 90℃-140℃, preferably 130-140℃, and the reaction pressure is 0.40MPa-0.60MPa, preferably 0.55MPa-0.60MPa. After sampling to confirm the completeness of the reaction, purge the system with nitrogen, distill off the solvent under negative pressure, and cool down. In the above reaction system, the molar ratio of sodium methanethiol to 2-nitro-4-chlorotoluene is 1.5:1-2.0:1, preferably 2.0:1. The molar ratio of dilute sulfuric acid to 2-nitro-4-chlorotoluene is 3.0:1-4.0:1, 4.0:1.

[0037] Step 4: Add an appropriate amount of water to the oily material after distillation in Step 3 for hydrolysis, then add a measured amount of sulfuric acid. Control the temperature at 50℃-80℃, preferably 50℃-60℃, and add the oxidant dropwise. After the addition is complete, maintain the temperature for a certain period of time, and take a sample to test if the reaction is complete. The oxidant can be one of hydrogen peroxide, sodium hypochlorite, etc., preferably hydrogen peroxide. The molar ratio of the oxidant to 2-nitro-4-chlorotoluene is 0.8:1-1.2:1.

[0038] Step 5: Add sodium sulfite and liquid alkali to the oxidation liquid produced in step 4 to adjust the pH and oxidizing properties. Adjust the pH value to 5-8. After adjustment, cool down and control the temperature at 30℃-50℃, preferably 40℃. Filter and separate the material to obtain the target product 2-nitro-4-methylsulfonyl toluene.

[0039] Example 1.

[0040] Step 1: Add 224g of 35% dilute sulfuric acid to a reactor for nitrogen inertization; start stirring, control the temperature at 60℃, and add 141.6g of 20% sodium methanethiol solution dropwise to the reactor. After the addition is complete, continue the reaction at the specified temperature, slowly raising the temperature to 90℃ to distill off the gaseous methanethiol, which is then dried using a drying device. The molar ratio of dilute sulfuric acid to sodium methanethiol is 2:1.

[0041] Step 2: Add 171.5g of NMP and 11.8g of potassium hydroxide to another reactor. After cooling to 20°C, pass the dry methanethiol gas generated in Step 1 into this reactor until the reaction is complete and a large amount of methanethiol gas dissolves into the solvent.

[0042] Step 3: Add 34.3 g of 2-nitro-4-chlorotoluene (0.2 mol) to the reactor from Step 2. The molar ratio of methanethiol to 2-nitro-4-chlorotoluene is 2:1. Then, purge with nitrogen, raise the reaction temperature to 130°C, and the reaction pressure to 0.55-0.60 MPa. After the reaction is complete, 3.4% of the raw material remains, and the content of the target product, 1-methyl-2-nitro-4-methylthiobenzene, is 74.2%. Replace the nitrogen in the system. Distill off the solvent under negative pressure and cool down.

[0043] Step 4: Add 102.9g of water to the oily material after distillation in Step 3 for hydrolysis, then add 84g of 35% sulfuric acid. Control the temperature at 50℃-80℃, and add 19.5g of 35% hydrogen peroxide dropwise. After the addition is complete, maintain the temperature for 2 hours. Sampling and testing revealed 0.9% intermediate residue and 69.3% of the target product, 2-nitro-4-methylsulfonyl toluene. In the above reaction system, the molar ratio of the oxidant hydrogen peroxide to 2-nitro-4-chlorotoluene was 1:1.

[0044] Step 5: Add sodium sulfite and liquid alkali to the oxidizing liquid produced in Step 4 to adjust the pH and oxidizing properties. Adjust the pH to 7-8, then cool down to 40°C. Filter, wash, and separate the product to obtain the target product 2-nitro-4-methylsulfonyl toluene with a purity of 97.8%, a weight of 22.4g, and a total yield of 50.9%.

[0045] Example 2.

[0046] Step 1: Add 224g of 35% dilute sulfuric acid to the reactor for nitrogen inertization; start stirring, control the temperature at 60℃, and add 141.6g of 20% sodium methanethiol solution dropwise to the reactor. After the addition is complete, continue the reaction at the specified temperature, slowly raising the temperature to 90℃ to distill off the methanethiol, and then dry it using a drying device. The molar ratio of dilute sulfuric acid to sodium methanethiol is 2:1.

[0047] Step 2: Add 1.5g of DMF17 and 11.8g of potassium hydroxide to another reactor. After cooling to 20°C, pass the methanethiol gas generated in Step 1 into this reactor until the reaction is complete and a large amount of methanethiol gas dissolves into the solvent.

[0048] Step 3: Add 34.3 g of 2-nitro-4-chlorotoluene (0.2 mol) to the reactor from Step 2. The molar ratio of methanethiol to 2-nitro-4-chlorotoluene is 2:1. Then, purge with nitrogen, raise the reaction temperature to 130°C, and the reaction pressure to 0.55-0.60 MPa. After the reaction is complete, 6.6% of the raw material remains, and the target product, 1-methyl-2-nitro-4-methylthiobenzene, is found to be 69.4%. Replace the nitrogen in the system. Distill off the solvent under negative pressure and cool down.

[0049] Step 4: Add 102.9g of water to the oily material after distillation in Step 3 for hydrolysis, then add 84g of 35% sulfuric acid. Control the temperature at 50℃-80℃, and add 19.5g of 35% hydrogen peroxide dropwise. After the addition is complete, maintain the temperature for 2 hours. Sampling and testing revealed 0.7% intermediate residue and 61.4% of the target product, 2-nitro-4-methylsulfonyl toluene. In the above reaction system, the molar ratio of the oxidant hydrogen peroxide to 2-nitro-4-chlorotoluene was 1:1.

[0050] Step 5: Add sodium sulfite and liquid alkali to the oxidation solution from Step 4 to adjust the pH and oxidizing properties, adjusting the pH to 7-8. After adjustment, maintain the temperature at 40℃, filter, wash, and separate the product to obtain the target product 2-nitro-4-methylsulfonyltoluene. Purity: 96.9%, Weight: 19.7g, Overall yield: 45.81%.

[0051] Example 3.

[0052] Step 1: Add 224g of 35% dilute sulfuric acid to the reactor for nitrogen inertization; start stirring, control the temperature at 60℃, and add 141.6g of 20% sodium methanethiol solution dropwise to the reactor. After the addition is complete, continue the reaction at the specified temperature, slowly raising the temperature to 90℃ to evaporate the methanethiol gas, which is then dried using a drying device. The molar ratio of dilute sulfuric acid to sodium methanethiol is 2:1.

[0053] Step 2: Add 1.5g of NMP17 and 8.4g of sodium hydroxide to another reactor. After cooling to 20°C, pass the methanethiol gas generated in Step 1 into this reactor until the reaction is complete and a large amount of methanethiol gas dissolves into the solvent.

[0054] Step 3: Add 34.3 g of 2-nitro-4-chlorotoluene (0.2 mol) to the reactor from Step 2. The molar ratio of methanethiol to 2-nitro-4-chlorotoluene is 2:1. Then, purge with nitrogen, raise the reaction temperature to 130°C, and the reaction pressure to 0.55-0.60 MPa. After the reaction is complete, 7.6% of the raw material remains, and the content of the target product, 1-methyl-2-nitro-4-methylthiobenzene, is 67.8%. Replace the nitrogen in the system. Distill off the solvent under negative pressure and cool down.

[0055] Step 4: Add 102.9g of water to the oily material after distillation in Step 3 for hydrolysis, then add 84g of 35% sulfuric acid. Control the temperature at 50℃-80℃, and add 19.5g of 35% hydrogen peroxide dropwise. After the addition is complete, maintain the temperature for 2 hours. Sampling and testing revealed 0.9% intermediate residue and 62.6% of the target product, 2-nitro-4-methylsulfonyl toluene. In the above reaction system, the molar ratio of the oxidant hydrogen peroxide to 2-nitro-4-chlorotoluene was 1:1.

[0056] Step 5: Add sodium sulfite and liquid alkali to the oxidation solution from Step 4 to adjust the pH and oxidizing power, adjusting the pH to 7-8. After adjustment, maintain the temperature at 40℃, filter, wash, and separate the product to obtain the target product 2-nitro-4-methylsulfonyltoluene. Purity: 97.6%, Weight: 20.4g, Overall yield: 46.3%.

[0057] Example 4.

[0058] Step 1: Add 224g of 35% dilute sulfuric acid to the reactor for nitrogen inertization; start stirring, control the temperature at 60℃, and add 141.6g of 20% sodium methanethiol solution dropwise to the reactor. After the addition is complete, continue the reaction at the specified temperature, slowly raising the temperature to 90℃ to evaporate the methanethiol gas, which is then dried using a drying device. The molar ratio of dilute sulfuric acid to sodium methanethiol is 2:1.

[0059] Step 2: Add 171.5g of NMP and 11.8g of potassium hydroxide to another reactor. After cooling to 20°C, pass the methanethiol gas generated in Step 1 into this reactor until the reaction is complete and a large amount of methanethiol gas dissolves into the solvent.

[0060] Step 3: Add 34.3 g of 2-nitro-4-chlorotoluene (0.2 mol) to the reactor from Step 2. The molar ratio of methanethiol to 2-nitro-4-chlorotoluene is 2:1. Then, purge with nitrogen, heat to 130°C, and maintain a reaction pressure of 0.55-0.60 MPa. After the reaction is complete, a sample is taken to determine the remaining raw material content (3.9%) and the target product (1-methyl-2-nitro-4-methylthiobenzene) content (73.9%). Replace the nitrogen in the system. Distill off the solvent under negative pressure and cool.

[0061] Step 4: Add 102.9g of water to the oily material after distillation in Step 3 for hydrolysis, then add 84g of 35% sulfuric acid. Controlling the temperature at 50-60 degrees Celsius, add 137.5g of 13% sodium hypochlorite dropwise. After the addition is complete, maintain the temperature for 2 hours. Sampling and testing revealed 1.4% intermediate residue and 62.3% of the target product, 2-nitro-4-methylsulfonyl toluene. In the above reaction system, the molar ratio of the oxidant sodium hypochlorite to 2-nitro-4-chlorotoluene was 1.2:1.

[0062] Step 5: Add sodium sulfite and liquid alkali to the oxidation solution from Step 4 to adjust the pH and oxidizing properties, adjusting the pH to 7-8. After adjustment, maintain the temperature at 40℃, filter, wash, and separate the product to obtain the target product 2-nitro-4-methylsulfonyltoluene. Purity: 96.8%, Weight: 19.4g, Overall yield: 43.67%.

[0063] Example 5.

[0064] Step 1: Add 168.7g of 35% dilute sulfuric acid to the reactor for nitrogen inertization; start stirring, control the temperature at 60℃, and add 106.2g of 20% sodium methanethiol solution dropwise to the reactor. After the addition is complete, continue the reaction at the specified temperature, slowly raising the temperature to 90℃ to distill off the methanethiol gas, which is then dried using a drying device. The molar ratio of dilute sulfuric acid to sodium methanethiol is 2:1.

[0065] Step 2: Add 171.5g of NMP and 11.8g of potassium hydroxide to another reactor. After cooling to 20°C, pass the methanethiol gas generated in Step 1 into this reactor until the reaction is complete and a large amount of methanethiol gas dissolves into the solvent.

[0066] Step 3: Add 34.3 g of 2-nitro-4-chlorotoluene (0.2 mol) to the reactor from Step 2. The molar ratio of methanethiol to 2-nitro-4-chlorotoluene is 1.5:1. Purge with nitrogen, heat to 130°C, and maintain a pressure of 0.55-0.60 MPa. After the reaction, sample and test to ensure 10.2% of the raw material remains and the target product (1-methyl-2-nitro-4-methylthiobenzene) content is 50.6%. Replace the nitrogen in the system. Distill off the solvent under negative pressure and cool.

[0067] Step 4: Add 102.9g of water to the oily material after distillation in Step 3 for hydrolysis, then add 84g of 35% sulfuric acid. Control the temperature at 50℃-80℃, and add 19.5g of 35% hydrogen peroxide dropwise. After the addition is complete, maintain the temperature for 2 hours. Sampling and testing revealed 0.4% intermediate residue and 45.4% target product content. In the above reaction system, the molar ratio of the oxidant hydrogen peroxide to 2-nitro-4-chlorotoluene was 1:1.

[0068] Step 5: Add sodium sulfite and liquid alkali to the oxidation solution from Step 4 to adjust the pH and oxidizing properties, adjusting the pH to 7-8. After adjustment, maintain the temperature at 40℃, filter, wash, and separate the product to obtain the target product 2-nitro-4-methylsulfonyltoluene. Purity: 94.8%, Weight: 16.5g, Overall yield: 36.37%.

[0069] Example 6.

[0070] Step 1: Add 224g of 35% dilute sulfuric acid to the reactor for nitrogen inertization; start stirring, control the temperature at 60℃, and add 141.6g of 20% sodium methanethiol solution dropwise to the reactor. After the addition is complete, continue the reaction at the specified temperature, slowly raising the temperature to 90℃ to distill off the methanethiol gas, which is then dried using a drying device. The molar ratio of dilute sulfuric acid to sodium methanethiol is 2:1.

[0071] Step 2: Add 171.5g of NMP and 11.8g of potassium hydroxide to another reactor. After cooling to 20°C, pass the methanethiol gas generated in Step 1 into this reactor until the reaction is complete and a large amount of methanethiol gas dissolves into the solvent.

[0072] Step 3: Add 34.3 g of 2-nitro-4-chlorotoluene (0.2 mol) to the reactor from Step 2. The molar ratio of methanethiol to 2-nitro-4-chlorotoluene is 2:1. Then, purge with nitrogen, heat to 100°C, and apply a pressure of 0.55-0.60 MPa. After the reaction is complete, 9.4% of the raw material remains, and the content of the target product, 1-methyl-2-nitro-4-methylthiobenzene, is 67.2%. Replace the nitrogen in the system. Distill off the solvent under negative pressure and cool.

[0073] Step 4: Add 102.9g of water to the oily material after distillation in Step 3 for hydrolysis, then add 84g of 35% sulfuric acid. Control the temperature at 50℃-80℃, and add 19.5g of 35% hydrogen peroxide dropwise. After the addition is complete, maintain the temperature for 2 hours. Sampling and testing revealed 0.4% intermediate residue and 59.3% target product content. In the above reaction system, the molar ratio of the oxidant hydrogen peroxide to 2-nitro-4-chlorotoluene was 1:1.

[0074] Step 5: Add sodium sulfite and liquid alkali to the oxidation solution from Step 4 to adjust the pH and oxidizing power, adjusting the pH to 7-8. After adjustment, maintain the temperature at 40℃, filter, wash, and separate the product to obtain the target product 2-nitro-4-methylsulfonyltoluene. Purity: 97.0%, Weight: 19.4g, Overall yield: 43.7%.

[0075] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for synthesizing 2-nitro-4-methylsulfonyl toluene, characterized in that, Includes the following steps: Step 1: Add dilute sulfuric acid to the reactor for nitrogen inertization replacement, turn on the stirrer, control the reaction temperature within the set range, add sodium methanethiol solution dropwise to the reactor, continue to keep the temperature high after the addition is complete, and slowly raise the temperature to the set temperature range to generate methanethiol gas. Step 2: Add solvent and strong base to another reactor, cool down, and then pass the dry methanethiol gas produced in Step 1 through until the reaction is complete and there is still methanethiol gas dissolved in the solvent. Step 3: Add 2-nitro-4-chlorotoluene to the reactor from Step 2, purge with nitrogen, and carry out the reaction at a set time and pressure. After the reaction is complete, take a sample to check the system. Then, replace the system with nitrogen, distill off the solvent under negative pressure, and cool down. Step 4: Add water to the oily material after distillation in Step 3 for hydrolysis, then add a certain amount of sulfuric acid, control the temperature within the set range, add oxidant dropwise, keep the temperature for a certain period of time after the addition is complete, and take a sample to test the raw material to see if the reaction is complete. Step 5: Add sodium sulfite and liquid alkali to the product of step 4 to adjust the pH value and oxidizing power. After adjustment, cool down and control the temperature within the set range. Filter and separate the product to obtain the target product 2-nitro-4-methylsulfonyl toluene.

2. The method for synthesizing 2-nitro-4-methylsulfonyl toluene according to claim 1, characterized in that: In step 1, the molar ratio of sodium methanethiol to 2-nitro-4-chlorotoluene is 1.5:1 to 2.0:

1.

3. The method for synthesizing 2-nitro-4-methylsulfonyl toluene according to claim 1, characterized in that: In step 1, the molar ratio of the dilute sulfuric acid to 2-nitro-4-chlorotoluene is 3.0:1 to 4.0:

1.

4. The method for synthesizing 2-nitro-4-methylsulfonyl toluene according to claim 1, characterized in that: In step 1, the temperature is finally raised to 60℃-100℃.

5. The method for synthesizing 2-nitro-4-methylsulfonyl toluene according to claim 1, characterized in that: In step 2, the solvent is an aprotic solvent, namely one of DMF, DMSO, DMAC or NMP.

6. The method for synthesizing 2-nitro-4-methylsulfonyl toluene according to claim 1, characterized in that: In step 2, the strong base is either sodium hydroxide or potassium hydroxide.

7. The method for synthesizing 2-nitro-4-methylsulfonyl toluene according to claim 1, characterized in that: In step 3, the reaction temperature is 90℃-140℃ and the reaction pressure is 0.40MPa-0.60MPa.

8. The method for synthesizing 2-nitro-4-methylsulfonyl toluene according to claim 1, characterized in that: In step 4, the oxidant is one of hydrogen peroxide and sodium hypochlorite, and the molar ratio of the oxidant to 2-nitro-4-chlorotoluene is 0.8:1-1.2:

1.

9. The method for synthesizing 2-nitro-4-methylsulfonyl toluene according to claim 1, characterized in that: In step 4, the temperature is controlled between 50℃ and 80℃.

10. The method for synthesizing 2-nitro-4-methylsulfonyl toluene according to claim 1, characterized in that: In step 5, adjust the pH value to 5-8 and control the temperature to 30℃-50℃.

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