Synthesis method of 1-methoxy-1-methyl-3-(3, 4-dichlorophenyl) urea
By using small molecule fatty amines and homogeneous reaction systems, combined with formaldehyde and formic acid, the environmental protection and safety problems in the synthesis of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea were solved, and a high-efficiency and low-cost synthesis process was achieved.
Patent Information
- Application Number
- CN202411985541.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-07-15
AI Technical Summary
In the prior art, the synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea has environmental protection and safety problems, and the production cost is relatively high.
Small-molecule fatty amines are used to replace macromolecule aromatic amines for actinization, methoxy isocyanate is prepared, and methoxyphenylurea is synthesized in a homogeneous system. Finally, it is synthesized by Eschweeiler-Clarke methylation reaction using formaldehyde and formic acid, which avoids the generation of salt-containing wastewater and the use of highly toxic substances.
It improves production efficiency and yield, reduces product production costs, and achieves a safer and more environmentally friendly synthesis process, which is in line with the concept of green chemistry.
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Abstract
Description
Technical Field
[0001] The present invention relates to the field of chemical synthesis, and in particular to a method for synthesizing 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea. Background Art
[0002] 1-Methoxy-1-methyl-3-(3,4-dichlorophenyl)urea, also known as linuron, is mainly used for controlling annual gramineous weeds in crops such as cotton, soybeans, tomatoes, tobacco, strawberries, grapes, orchards, and rubber plantations. In the laboratory, linuron may be used as a chemical reagent for specific chemical reactions or analytical tests. The preparation of linuron in the prior art is usually obtained by an acylation reaction, generating isocyanate, reacting with hydroxylamine to form hydroxyurea, and finally performing methylation reaction with dimethyl sulfate. However, this traditional synthesis method has many defects. For example: (1) 3,4-Dichloroaniline is reacted with phosgene to obtain 3,4-dichlorophenyl isocyanate. The reaction process requires low temperature to form a salt first and then high temperature to remove hydrogen chloride; the phosgenation salt-forming system generally has a low concentration, the aromatic amine has a large molecular weight, and for the same specification of phosgenation kettle, the feeding amount is small, resulting in limited production capacity. (2) 3,4-Dichlorophenyl isocyanate reacts with hydroxylamine sulfate to prepare 1-(3,4-dichlorophenyl)-3-hydroxyurea. Hydroxylamine sulfate needs to be dissociated with alkali first to generate mirabilite, producing a large amount of salty wastewater, which is difficult to treat environmentally; this reaction uses an oil-water heterogeneous system, the reaction is not sufficient, and 3,4-dichlorophenyl isocyanate is easily decomposed by water, resulting in a low yield. (3) Methylation of 1-(3,4-dichlorophenyl)-3-hydroxyurea usually uses dimethyl sulfate, haloalkane, etc. as methylation reagents, which are highly toxic substances, and there are certain safety risks in production; a large amount of alkali is also required to neutralize the by-product acid during the synthesis process, generating a large amount of wastewater containing inorganic salts such as mirabilite and sodium chloride, increasing the difficulty of separation and purification. (4) Based on 3,4-dichloroaniline, the yield is only about 85%.
[0003] In summary, the synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea in the prior art has significant environmental protection and safety problems, and the production cost of the product is relatively high. Summary of the Invention
[0004] The technical problem to be solved by the present invention is how to solve the environmental protection and safety problems in the synthesis process of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea and reduce the production cost of the product. In view of the above technical problems to be solved, a method for synthesizing 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea is proposed.
[0005] To achieve the above object, the present invention provides the following technical solution: A method for synthesizing 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea, which includes, step S1, preparation of methoxy isocyanate: Methoxyamine hydrochloride is irradiated with light in an inert solvent, without salification, and the intermediate methoxy isocyanate is directly prepared by high-temperature dehydrochlorination. The reaction equation is as follows:
[0006]
[0007] Step S2, synthesis of methoxyphenylurea: Methoxy isocyanate reacts with 3,4-dichloroaniline in a homogeneous system to synthesize 1-methoxy-3-(3,4-dichlorophenyl)urea (abbreviation: methoxyphenylurea). The reaction equation is as follows:
[0008]
[0009] Step S3, preparation of linuron: Methoxyphenylurea undergoes an Eschweiler-Clarke methylation reaction with formaldehyde and formic acid to obtain 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea (trade name: linuron). The reaction equation is as follows:
[0010]
[0011] More preferably, the organic solvent in step S1 is a halogenated alkane solvent, an aromatic solvent or a heterocyclic solvent. Among them, halogenated alkanes such as dichloroethane, chlorobenzene, o-dichlorobenzene, etc.; aromatics such as benzene, toluene, xylene, etc.; heterocyclics such as tetrahydrofuran, dioxane, etc.; as a preferred option, toluene, chlorobenzene, dichloroethane can be selected.
[0012] Preferably, in step S1, the molar ratio of methoxyamine hydrochloride to phosgene is 1:1 to 3.
[0013] More preferably, in step S1, the molar ratio of methoxyamine hydrochloride to phosgene is 1:1.3 to 2.
[0014] Preferably, in step S1, the weight of methoxyamine hydrochloride accounts for 10-50% of the total weight of methoxyamine hydrochloride and toluene.
[0015] More preferably, the weight of methoxyamine hydrochloride accounts for 20-25% of the total weight of methoxyamine hydrochloride and toluene.
[0016] Preferably, in step S2, the molar ratio of 3,4-dichloroaniline to methoxy isocyanate is 1:1 to 1.5.
[0017] More preferably, in the step S2, the molar ratio of 3,4-dichloroaniline to methoxyisocyanate is 1:1 to 1.1.
[0018] Preferably, in the step S2, the dosage ratio of 3,4-dichloroaniline to toluene is 10 - 50 g of 3,4-dichloroaniline per 100 g of the mixture of toluene and 3,4-dichloroaniline.
[0019] More preferably, in the step S2, the dosage ratio of 3,4-dichloroaniline to toluene is 30 - 40 g of 3,4-dichloroaniline per 100 g of the mixture of toluene and 3,4-dichloroaniline.
[0020] Preferably, in the step S2, methoxyisocyanate M1 is added dropwise to the mixed system of 3,4-dichloroaniline and organic solvent, wherein the dropping temperature is 0 - 100 °C and the dropping time is 1 - 10 hours.
[0021] More preferably, the dropping temperature is 40 - 50 °C and the dropping time is 4 - 6 hours.
[0022] Preferably, in the step S3, the molar ratio of methoxyphenylurea to formaldehyde and formic acid is 1:1 - 5:1 - 5.
[0023] More preferably, in the step S3, the molar ratio of methoxyphenylurea to formaldehyde and formic acid is 1:1.1 - 2:1.15 - 2.5.
[0024] Preferably, the solvent in the step S3 is water.
[0025] Preferably, the formic acid in the step S3 is added dropwise to the mixed slurry of methoxyphenylurea, formaldehyde and solvent, and after the dropping is completed, a heat preservation reaction is carried out, wherein the dropping temperature is 20 - 100 °C, the heat preservation temperature is 20 - 100 °C, and the heat preservation time is 1 - 10 hours.
[0026] More preferably, the dropping temperature is 50 - 70 °C, the heat preservation temperature is 80 - 100 °C, and the heat preservation time is 2 - 4 hours.
[0027] Compared with the prior art, the beneficial effects of the present invention are:
[0028] By using small-molecule fatty amines instead of large-molecule aromatic amines for the photochemical reaction to prepare isocyanates, the production efficiency is improved; and in the preparation of methoxyphenylurea, an anhydrous homogeneous system is adopted to avoid the hydrolysis of isocyanates. Since the homogeneous reaction is more complete, the yield is increased and no salty wastewater is generated; in the last step of methylation, formaldehyde and formic acid are used for Eschweiler-Clarke methylation to generate pollution-free carbon dioxide and water, which is a low-toxic and pollution-free synthesis route, greatly improving the environmental protection in the synthesis process of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea. The method provided by the present invention improves the production capacity and yield, reduces the production cost of the product, and has the advantages of safer and more environmentally friendly process, meeting the concept of green chemistry. Detailed implementation manners
[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0030] According to the following feasible steps and reaction formulas, the synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea of the present invention will be described through multiple embodiments.
[0031] Step S1: Preparation of methoxy isocyanate: Methoxyamine hydrochloride is irradiated with light in an inert solvent. Without salt formation, hydrogen chloride is removed at high temperature to directly prepare the intermediate methoxy isocyanate. The reaction formula is as follows:
[0032]
[0033] Step S2, Synthesis of methoxyphenylurea: Methoxy isocyanate reacts with 3,4-dichloroaniline in a homogeneous system to synthesize 1-methoxy-3-(3,4-dichlorophenyl)urea (abbreviation: methoxyphenylurea). The reaction formula is as follows:
[0034]
[0035] Step S3, Preparation of linuron: Methoxyphenylurea reacts with formaldehyde and formic acid in an Eschweiler-Clarke methylation reaction to obtain 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea (trade name: linuron). The reaction formula is as follows:
[0036]
[0037] Example 1
[0038] This specific embodiment was prepared under laboratory conditions according to the above steps and reaction process to obtain 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea.
[0039] (1) Preparation of Methoxy Isocyanate
[0040] Charge 258 g of anhydrous toluene and 86 g (99%, 1.02 mol) of methoxyamine hydrochloride into a 500 ml flask. The weight of methoxyamine hydrochloride accounts for 25% of the total weight of the toluene and methoxyamine hydrochloride mixture. Stir and cool down to -5 to 0 °C, and react with phosgene at low temperature for 5 to 6 hours. Then slowly raise the temperature while passing light, and when the temperature rises to 80 to 90 °C, continue to keep warm for 1 hour. Take a sample for in-process control. The residue of methoxyamine is less than 0.5%. Stop passing light. Switch to nitrogen to drive off phosgene, and control the temperature for driving off phosgene at 80 to 90 °C for 1 to 2 hours. After driving off phosgene, cool down to room temperature for standby. The content of methoxy isocyanate is greater than 99% (GC), and the yield can reach 98%.
[0041] (2) Synthesis of Methoxyphenylurea
[0042] Charge 350 ml of anhydrous toluene and 164 g (99%, 1 mol) of 3,4-dichloroaniline into a 1000 ml flask. Stir and heat up to 45 to 50 °C, and continue to stir for 0.5 hour until 3,4-dichloroaniline is completely dissolved and clear. Then, dropwise add the toluene solution of the above methoxy isocyanate to the flask through a feeding pump. Control the dropping temperature at 45 to 50 °C and the dropping time at 4 to 5 hours. After the dropping is completed, continue to keep warm and react for 1 hour. Take a sample for in-process control. The content of 3,4-dichloroaniline is less than 0.5% (HPLC). After the reaction is completed, cool the material to 35 °C, filter by suction, and dry to obtain 232.6 g of 1-methoxy-3-(3,4-dichlorophenyl)urea (abbreviated as methoxyphenylurea), with a content of 98% (HPLC) and a yield of 97% (calculated based on 3,4-dichloroaniline).
[0043] (3) Preparation of Linuron
[0044] In a 1000 ml flask, add 400 ml of water, 157.3 g (1.94 mol) of 37% formaldehyde, and 232.6 g (98%, 0.97 mol) of the above-mentioned methoxyphenylurea, stir into a slurry, heat up to 60 - 65 °C, and slowly add dropwise 111.6 g (88%, 2.135 mol) of formic acid through a dropping funnel. Adjust the dropping rate of formic acid according to the release rate of tail gas carbon dioxide. After dropping, gradually heat up to 90 - 94 °C and continue to hold the temperature for reaction at 90 - 94 °C for 2 hours. Take a sample for in-process control. When the content of methoxyphenylurea is less than 0.5% (HPLC), the reaction ends. Cool the material to 35 °C, filter by suction, and dry to obtain 235 g of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea (trade name: linuron), with a content of 98% (external standard) and a yield of 92.5% (calculated based on 3,4-dichloroaniline).
[0045] Example 2
[0046] (1) Preparation of methoxy isocyanate
[0047] In a 500 ml flask, add 90 g of anhydrous chlorobenzene and 91.1 g (99%, 1.08 mol) of methoxyamine hydrochloride. The weight of methoxyamine hydrochloride accounts for about 50% of the total weight of chlorobenzene and methoxyamine hydrochloride. Stir and cool down to -5 - 0 °C, and react with phosgene at low temperature for 5 - 6 hours. Then slowly heat up while passing phosgene, and when the temperature rises to 80 - 90 °C, continue to hold the temperature for 1 hour. Take a sample for in-process control. When the residue of methoxyamine is less than 0.5%, stop passing phosgene. Switch to nitrogen to drive away phosgene, control the temperature for driving away phosgene at 80 - 90 °C, and drive away phosgene for 1 - 2 hours. After driving away phosgene, cool down to room temperature for use. The content of methoxy isocyanate is greater than 99% (GC), and the yield is 97.2%.
[0048] (2) Synthesis of methoxyphenylurea
[0049] In a 1000 ml flask, add 350 ml of anhydrous chlorobenzene and 164 g (99%, 1 mol) of 3,4-dichloroaniline, stir and heat up to 40 - 45 °C, and continue to stir for 0.5 hour until 3,4-dichloroaniline is completely dissolved and clear. Then, through a feeding pump, slowly add dropwise the toluene solution of the above-mentioned methoxy isocyanate to the flask, control the dropping temperature at 40 - 45 °C, and control the dropping time at 4 - 5 hours. After dropping, continue to hold the temperature for reaction for 1 hour. Take a sample for in-process control. When the content of 3,4-dichloroaniline is less than 0.5% (HPLC), the reaction ends. Cool the material to 35 °C, filter by suction, and dry to obtain 231.4 g of 1-methoxy-3-(3,4-dichlorophenyl)urea (abbreviation: methoxyphenylurea), with a content of 98% (HPLC) and a yield of 96.5% (calculated based on 3,4-dichloroaniline).
[0050] (3) Preparation of linuron
[0051] Into a 1000 ml flask, add 400 ml of water, 117.6 g (1.45 mol) of 37% formaldehyde, and 231.4 g (98%, 0.965 mol) of the above-mentioned methoxyphenylurea. Stir to form a slurry, heat up to 60 - 65 °C, and uniformly add 83.5 g (88%, 1.6 mol) of formic acid dropwise through a dropping funnel. Adjust the dropping rate of formic acid according to the release rate of tail gas carbon dioxide. After dropping, gradually heat up to 90 - 94 °C and continue to hold the reaction at 90 - 94 °C for 2 hours. Take a sample for in-process control. The content of methoxyphenylurea is less than 0.5% (HPLC). After the reaction is completed, cool the material to 35 °C, filter by suction, and dry to obtain 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea (trade name: linuron 234 g, content 97.6% (external standard), yield 91.7% (calculated based on 3,4-dichloroaniline).
[0052] Example 3:
[0053] (1) Preparation of methoxy isocyanate
[0054] Into a 500 ml flask, add 390 g of anhydrous toluene and 130 g (99%, 1.54 mol) of methoxyamine hydrochloride. The weight of methoxyamine hydrochloride accounts for 25% of the total weight of chlorobenzene and methoxyamine hydrochloride. Stir and cool down to -5 - 0 °C, and react with phosgene at low temperature for 5 - 6 hours. Then slowly heat up while passing phosgene, and when the temperature rises to 80 - 90 °C, continue to hold for 1 hour. Take a sample for in-process control. The residue of methoxyamine is less than 0.5%. Stop passing phosgene. Switch to nitrogen to drive away phosgene, and control the temperature for driving away phosgene at 80 - 90 °C for 1 - 2 hours. After driving away phosgene, cool down to room temperature for standby. The content of methoxy isocyanate is greater than 99% (GC), and the yield is 97.5%.
[0055] (2) Synthesis of methoxyphenylurea
[0056] Into a 1000 ml flask, add 350 ml of anhydrous toluene and 164 g (99%, 1 mol) of 3,4-dichloroaniline. Stir and heat up to 90 - 100 °C, and continue to stir for 0.5 hour until 3,4-dichloroaniline is completely dissolved and clear. Then, through a feeding pump, dropwise add the toluene solution of the above-mentioned methoxy isocyanate into the flask. Control the dropping temperature at 90 - 100 °C and the dropping time at 1 - 2 hours. After dropping, continue to hold the reaction for 1 hour. Take a sample for in-process control. The content of 3,4-dichloroaniline is less than 0.5% (HPLC). After the reaction is completed, cool the material to 35 °C, filter by suction, and dry to obtain 1-methoxy-3-(3,4-dichlorophenyl)urea (abbreviation: methoxyphenylurea) 223.8 g, content 96.2% (HPLC), yield 91.6% (calculated based on 3,4-dichloroaniline).
[0057] (3) Preparation of linuron
[0058] Into a 1000 ml flask, add 400 ml of water, 74.3 g (0.916 mol) of 37% formaldehyde, and 223.8 g (96.2%, 0.916 mol) of the above methoxyphenylurea, stir to form a slurry, heat up to 20 - 30 °C, and uniformly add 50.3 g (88%, 0.962 mol) of formic acid dropwise through a dropping funnel. Adjust the dropping rate of formic acid according to the release rate of tail gas carbon dioxide. After dropping, continue to keep the temperature at 20 - 30 °C for reaction for 8 - 10 hours, take a sample for in - process control, the content of methoxyphenylurea is less than 10% (HPLC), the reaction ends, directly filter the material by suction, and dry it to obtain 1 - methoxy - 1 - methyl - 3 - (3,4 - dichlorophenyl)urea (trade name: linuron) 238.9 g, with a content of 86.5% (external standard) and a yield of 83% (calculated based on 3,4 - dichloroaniline).
[0059] Example 4:
[0060] (1) Preparation of methoxy isocyanate
[0061] Into a 500 ml flask, add 300 ml of anhydrous toluene and 86 g (99%, 1.02 mol) of methoxyamine hydrochloride. The weight of methoxyamine hydrochloride accounts for about 25% of the total weight of chlorobenzene and methoxyamine hydrochloride. Stir and cool down to - 5 - 0 °C, conduct a low - temperature reaction with phosgene for 5 - 6 hours, then slowly heat up while passing phosgene, when the temperature rises to 80 - 90 °C, continue to keep the temperature for 1 hour, take a sample for in - process control, the residue of methoxyamine is less than 0.5%, stop passing phosgene. Switch to nitrogen to drive away phosgene, control the temperature for driving away phosgene at 80 - 90 °C, drive away phosgene for 1 - 2 hours, after driving away phosgene, cool down to room temperature for use. The content of methoxy isocyanate is greater than 99% (GC), and the yield can reach 98%.
[0062] (2) Synthesis of methoxyphenylurea
[0063] Into a 1000 ml flask, add 350 ml of anhydrous toluene and 164 g (99%, 1 mol) of 3,4 - dichloroaniline, stir and heat up to 0 - 10 °C, continue to stir for 0.5 hour until 3,4 - dichloroaniline is completely dissolved and clear. Then, add the toluene solution of the above methoxy isocyanate dropwise to the flask through a feeding pump, control the dropping temperature at 0 - 10 °C, control the dropping time at 8 - 10 hours. After dropping, continue to keep the temperature for reaction for 1 hour, take a sample for in - process control, the content of 3,4 - dichloroaniline is less than 3% (HPLC). After the reaction ends, cool the material to 35 °C, filter by suction, and dry it to obtain 1 - methoxy - 3 - (3,4 - dichlorophenyl)urea (abbreviation: methoxyphenylurea) 229.4 g, with a content of 97% (HPLC) and a yield of 94.7% (calculated based on 3,4 - dichloroaniline).
[0064] (3) Preparation of linuron
[0065] Into a 1000 ml flask, add 400 ml of water, 383.5 g (4.73 mol) of 37% formaldehyde, and 229.4 g (97%, 0.947 mol) of the above-mentioned methoxyphenylurea. Stir to form a slurry, heat up to 90 - 100 °C, and slowly add 247 g (88%, 4.73 mol) of formic acid dropwise through a dropping funnel. Adjust the dropping rate of formic acid according to the release rate of tail gas carbon dioxide. After dropping, continue to keep the temperature at 90 - 100 °C for reaction for 2 hours. Take a sample for in-process control. The content of methoxyphenylurea is less than 0.5% (HPLC). After the reaction is completed, cool the material to 35 °C, filter by suction, and dry to obtain 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea (trade name: linuron) 238.6 g, with a content of 89% (external standard) and a yield of 85.3% (calculated based on 3,4-dichloroaniline).
[0066] In addition, the effects of the changes in each component and condition in the above-mentioned examples on the product are summarized as follows:
[0067] Table 1: Effects of methoxyhydrochloric acid concentration on the content and yield of methoxyisocyanate
[0068]
[0069] As the concentration of methoxyhydrochloric acid increases, the light-passing solution becomes more and more viscous. When the concentration is higher than 50%, the flow rate of the light-passing solution significantly decreases, which is not conducive to stirring. When the concentration of methoxyhydrochloride decreases, the photochemical reaction rate becomes slower, and the light-passing time needs to be extended to ensure sufficient reaction.
[0070] Table 2: Effects of molar ratio, dropping temperature and time on the content and yield of methoxyphenylurea
[0071]
[0072] As the molar ratio of 3,4-dichloroaniline to methoxyisocyanate increases, the excessive methoxyisocyanate will precipitate from the solvent and be wrapped in methoxyphenylurea, reducing its main content. When the dropping temperature increases, the reaction rate significantly accelerates, but impurities are easily generated, affecting the content and yield of the product. When the dropping temperature decreases, the reaction rate becomes slower, and the dropping time needs to be extended to reduce the residue of 3,4-dichloroaniline.
[0073] Table 3: Effects of molar ratio, dropping temperature and time on the content and yield of linuron
[0074]
[0075] With the increase in the molar ratio of methoxyphenylurea to formaldehyde and formic acid, the residue of methoxyphenylurea decreases, and the quality and yield of linuron increase. When the dropping temperature rises, the amounts of formaldehyde and formic acid used increase, and the reaction rate significantly accelerates. However, impurities are easily generated, reducing the content and yield of the product. When the dropping temperature decreases, the reaction rate slows down, and the dropping time needs to be extended. However, if the temperature is too low, the residue of methoxyphenylurea increases, reducing the content and yield of the product.
[0076] In addition, in step S2, the dosage ratio of 3,4-dichloroaniline to toluene is 10 - 50 g of 3,4-dichloroaniline per 100 g of the mixture of toluene and 3,4-dichloroaniline. It is further preferably 30 - 40 g of 3,4-dichloroaniline per 100 g of the mixture of toluene and 3,4-dichloroaniline, thereby saving costs.
[0077] In addition, in each of the above embodiments, the organic solvent in step S1 can be a halogenated alkane solvent, an aromatic solvent, or a heterocyclic solvent. More preferably, among them, halogenated alkanes such as dichloroethane, chlorobenzene, o-dichlorobenzene, etc.; aromatics such as benzene, toluene, xylene, etc.; heterocyclics such as tetrahydrofuran, dioxane, etc. As a preferred solution, toluene, chlorobenzene, or dichloroethane can be selected. The above listing is not for limiting this solution, but for better implementation by those skilled in the art. The solvent in this step does not limit the progress of the reaction. As long as it is an organic solvent that can realize the reaction, it belongs to the protection scope of the present invention.
[0078] In addition, more preferably, in other embodiments, in step S1, the molar ratio of methoxyamine hydrochloride to phosgene can be 1:1 - 3. More preferably, to save costs, the molar ratio of methoxyamine hydrochloride to phosgene is 1:1.3 - 2.
[0079] In addition, since the influence of the reaction intermediate on the overall reaction and preparation process is only limited to the sufficiency of the reaction or cost savings, the effective progress of the reaction can be ensured in the case of excessive materials. Therefore, the dosages of formic acid, phosgene, etc. in the above embodiments are only some realizable embodiments and do not represent a limitation to the present invention. The extension of the above-mentioned ranges also belongs to the protection scope of the present invention. In addition, conditions such as temperature, heat preservation time, reaction time, etc. are similar. Those that exceed the preferred range or specified range shown in the above embodiments but still do not exceed the synthesis path of the present invention still belong to the protection scope of the present invention.
[0080] The present invention prepares isocyanate by using small-molecule fatty amine instead of large-molecule aromatic amine for photochemical reaction, which improves the production efficiency; and an anhydrous homogeneous system is adopted in the preparation of methoxyphenylurea to avoid the hydrolysis of isocyanate. Since the homogeneous reaction is more complete, the yield is improved and no salt-containing wastewater is generated; in the last step of methylation, formaldehyde and formic acid are used for Eschweiler-Clarke methylation to generate pollution-free carbon dioxide and water, which is a low-toxic and pollution-free synthesis route, greatly improving the environmental friendliness in the synthesis process of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea. The method provided by the present invention improves the production capacity and yield, reduces the production cost of the product, and has the advantages of safer and more environmentally friendly process, meeting the concept of green chemistry.
[0081] The above embodiments are only examples for better expressing the content of the present invention by elaborating on the solution of the present invention through a laboratory synthesis route, and do not limit the content of the present invention. The industrial improvement and process implementation carried out without departing from the synthesis idea of the present invention do not exceed the protection scope of the present invention. The present invention is not limited to the above-described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions, and variations made to these embodiments still fall within the protection scope of the present invention.
Claims
1. A method for synthesizing 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea, characterized in that, 1-Methoxy-1-methyl-3-(3,4-dichlorophenyl)urea is prepared through the following steps: Step S1: Methoxyamine hydrochloride reacts with phosgene in an organic solvent to obtain intermediate methoxy isocyanate M1; Step S2: M1 reacts with 3,4-dichloroaniline in a homogeneous system to synthesize 1-methoxy-3-(3,4-dichlorophenyl)urea M2; Step S3: M2 undergoes Eschweiler-Clarke methylation reaction with formaldehyde and formic acid in a solvent to obtain 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea.
2. The synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea according to claim 1, characterized in that, In the said Step S1, the weight of methoxyamine hydrochloride accounts for 10-50% of the total weight of methoxyamine hydrochloride and toluene.
3. The synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea according to claim 2, characterized in that, In the said Step S1, the weight of methoxyamine hydrochloride accounts for 20-25% of the total weight of methoxyamine hydrochloride and toluene.
4. The synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea according to claim 1, characterized in that, In the said Step S2, the molar ratio of 3,4-dichloroaniline to methoxy isocyanate is 1:1 to 1.
5.
5. The synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea according to claim 1, characterized in that, In the said Step S2, methoxy isocyanate M1 is added dropwise to the mixed system of 3,4-dichloroaniline and an organic solvent, wherein the dropping temperature is 0-100°C and the dropping time is 1-10 hours.
6. The synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea according to claim 5, characterized in that, The said dropping temperature is 40-50°C and the said dropping time is 4-6 hours.
7. The synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea according to claim 1, characterized in that, In the said Step S3, the molar ratio of methoxyphenylurea to formaldehyde and formic acid is 1:1 to 5:1 to 5.
8. The synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea according to claim 1, characterized in that, The solvent in the said Step S3 is water.
9. The synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea according to claim 1, characterized in that, In the said Step S3, formic acid is added dropwise to the mixed slurry of methoxyphenylurea, formaldehyde and the solvent. After the dropping is completed, heat preservation reaction is carried out, wherein the dropping temperature is 20-100°C, the heat preservation temperature is 20-100°C, and the heat preservation time is 1-10 hours.
10. The synthesis method of 1-methoxy-1-methyl-3-(3,4-dichlorophenyl)urea according to claim 9, characterized in that, The said dropping temperature is 50-70°C, the said heat preservation temperature is 80-100°C, and the said heat preservation time is 2-4 hours.