Industrial synthesis method of DMAB

Abstract

The invention relates to the technical field of industrial synthesis of small organic molecules, in particular to an industrial synthesis method of DMAB. According to the method, dimethylamine hydrochloride and NaBH4 serve as raw materials, THF and water serve as solvents, DMAB is prepared through the steps of feeding, reacting, aftertreatment, purification and the like in the inert gas atmosphere, large-amount dehydration of an organic phase and deep dehydration of a high-concentration product are achieved through two times of drying, and the drying efficiency and the product stability are both considered; the process sequence of reduced pressure distillation and recrystallization is adopted, and after low-temperature concentration and preliminary impurity removal, deep purification is achieved through low-temperature recrystallization. According to the method, the temperature is strictly controlled in the whole process, the inert atmosphere is maintained, the safety risk and product degradation are reduced, the product yield is stabilized at 86-92%, the purity is consistent with that of commercially available analytically pure products, the process steps are simplified, parameters are controllable, the number of times of solution transfer is reduced, mother liquor can be recycled, and the method has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of industrial synthesis technology of small organic molecules, and in particular to an industrial synthesis method for DMAB. Background Technology

[0002] DMAB (dimethylaminoborane) is a key reducing agent in the pretreatment of chemical copper plating in PCB manufacturing processes. Its core function is to reduce the palladium ion layer adsorbed inside the holes and on the non-conductive substrate of the PCB material to a metallic palladium layer, providing an effective catalytic basis for the uniform deposition of chemical copper ions. It holds an irreplaceable position in the field of electronic chemical materials. However, existing DMAB preparation technologies still face many unresolved problems, seriously affecting its industrial production efficiency and application stability.

[0003] Chinese patent CN108586266A discloses a process for synthesizing dimethylamine borane. The process involves reacting borohydride with dimethylamine hydrochloride in a solvent under inert gas protection at 5-15°C. The product is then obtained after post-treatment processes such as filtration and vacuum distillation to remove organic solvents and salts. While inert gas protection reduces safety risks, the limited solubility of borohydride in organic solvents means that adding large amounts of solvent reduces economic efficiency, while adding water will cause the borohydride reaction to fail. Furthermore, the byproduct salts inhibit the dissolution of the raw materials, and prolonged reaction time easily leads to the generation of byproducts.

[0004] Although relevant patents have proposed different synthetic routes, none of them have effectively balanced reaction safety, raw material utilization and product purification efficiency, making it difficult to meet the industrial production requirements for low cost, high yield and high purity DMAB. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an industrial synthesis method for DMAB, comprising the following steps: S1. In an inert gas atmosphere, add 600~800mL of THF (tetrahydrofuran) to a reaction vessel equipped with a bottom valve, and then cool the system to -10~0℃; S2. Add 120-150g of dimethylamine hydrochloride and stir until homogeneous; S3. Divide 60-70g of NaBH4 into 20-30 portions, and add one portion of NaBH4 every 10-45 minutes; after the NaBH4 is added, react for 1-6 hours. S4. Mix 20-50 mL of water and 50-80 mL of THF to obtain a THF / H2O solution, divide it into 5-20 portions, and add one portion every 10-30 minutes; after the addition is complete, react for 0.5-2 hours. S5. Dissolve 10-20g of NaOH in 100-200g of water and add it to the reaction system all at once; S6. Let the reaction solution obtained in step S5 stand and separate into layers. Discharge the lower solid-liquid mixture from the bottom valve, retain the upper organic liquid, filter the lower solid-liquid mixture, wash the solid with THF, and extract the lower aqueous solution after separation and filtration with the washed solution. Combine the extracted solution with the upper organic liquid to obtain crude DMAB solution. S7, add desiccant to crude DMAB solution and perform first stirring and drying in an inert environment; drain the dried organic solvent from the bottom valve, filter, wash the filtered solid with THF, and collect the filtrate and the washing THF solution; S8, vacuum distillation treatment; S9. Add a desiccant to the reaction solution after vacuum distillation, perform a second stirring and drying treatment, filter, collect the organic phase, wash the solid with THF, combine the organic phase and the washing THF solution to obtain the THF solution of DMAB. S10. Recrystallize the THF solution of DMAB to obtain pure DMAB.

[0006] As an example of implementation, the molar ratio of NaBH4 to dimethylamine hydrochloride is 1:1.

[0007] This invention limits the molar ratio of NaBH4 to dimethylamine hydrochloride to 1:1. This is mainly because the commercial price of NaBH4 is approximately five times higher than that of dimethylamine hydrochloride. This molar ratio avoids excessive NaBH4 input, minimizing the consumption of expensive raw materials while meeting the stoichiometric ratio of the reaction, thus significantly reducing preparation costs. Simultaneously, NaBH4 has strong reducing properties; in excess, it easily undergoes excessive reduction or hydrolysis with water or products in the system, generating impurities and wasting raw materials. The 1:1 molar ratio allows NaBH4 to precisely participate in the main reaction to generate DMAB, effectively reducing side reactions and indirectly improving product purity. Furthermore, byproducts generated in the reaction, such as NaCl, dissolve in the solvent. If NaBH4 is in excess, unreacted NaBH4 and byproducts will share the solvent's dissolution space, further inhibiting the dissolution of raw materials and leading to incomplete reaction.

[0008] As an implementable example, the desiccant includes at least two of anhydrous MgSO4, Ca(OH)2, CaCl2, or CaO.

[0009] Furthermore, the mass ratio of the anhydrous MgSO4 to Ca(OH)2 is (3-5):1.

[0010] Anhydrous MgSO4 is a highly polar desiccant with a rapid water absorption rate. It can quickly adsorb free water in the organic phase and, at a ratio of (3-5):1, dominate the drying process, ensuring that the system moisture content is rapidly reduced to a low level to meet the requirements of subsequent vacuum distillation and recrystallization for low water content. Ca(OH)2 not only has a certain water absorption capacity but also neutralizes any trace acidic impurities that may remain in the system, such as residual acid from the raw material dimethylamine hydrochloride, preventing the acidic substances from reacting with the alkaline DMAB. Simultaneously, its alkalinity inhibits product hydrolysis, protecting product stability. The combination of the two in this ratio ensures drying efficiency through a high proportion of anhydrous MgSO4 while using a small amount of Ca(OH)2 to neutralize impurities and protect the product. Furthermore, both desiccants are low-cost and easy to filter and separate.

[0011] As an example of implementation, the desiccant in step S7 is 8-20% of the mass of the crude DMAB solution.

[0012] As an example of an feasible approach, the first stirring and drying process takes 1-4 hours.

[0013] As an example of implementation, the desiccant in step S9 is 10-35% of the mass of the reaction solution.

[0014] As an example of implementation, the second stirring and drying process takes 10-45 minutes.

[0015] In this invention, two drying processes work together to ensure product purity and the stability of subsequent processes. The first drying targets the combined organic phase after separation and extraction, with the core objective of removing a large amount of free water from the system. At this stage, the organic phase is prone to residual water introduced from the aqueous phase. If not dried in time, this water will not only azeotropically react with THF during subsequent vacuum distillation, increasing the difficulty of solvent separation, but may also lead to DMAB hydrolysis and the generation of impurities. At the same time, this drying also provides preliminary purification of the organic phase. The second drying targets the product solution with a concentration of 70-90 wt% after vacuum distillation, aiming to deeply remove residual trace amounts of water. Even a small amount of water in high-concentration products can significantly affect recrystallization and even cause product degradation. This drying further reduces the water content of the system, ensuring that a high-purity, high-yield DMAB product is obtained through recrystallization.

[0016] As an example of implementation, the vacuum distillation temperature is 20~40℃.

[0017] As an example of feasible implementation, the efficiency of the vacuum distillation is 0.2~3 L / min.

[0018] As an example of implementation, the recrystallization temperature is -30 to -5°C.

[0019] The residual solution after recrystallization in this invention can be used as the solution for the next recrystallization, and therefore its yield is included in the yield of this recrystallization.

[0020] This invention employs a process sequence of "vacuum distillation followed by recrystallization," with the core objective of efficiently improving the purity and yield of DMAB while ensuring product stability. First, vacuum distillation rapidly removes a large amount of THF solvent from the organic phase at a low temperature of 20-40°C. This avoids product decomposition due to high temperatures and concentrates the DMAB concentration from low levels to 70-90 wt%, while also initially removing trace amounts of inorganic salts and low-boiling-point impurities dissolved in the solvent, reducing interference from impurities in subsequent purification stages. The subsequent recrystallization utilizes the product's rapid decrease in solubility at -30 to -5°C, causing crystals to precipitate from the high-concentration product solution. Residual trace impurities remain dissolved in the mother liquor, achieving deep purification through solid-liquid separation. Ultimately, a DMAB product with a purity matching commercially available analytical grade and a yield of 86-92% is obtained.

[0021] Beneficial effects (i) The present invention adopts a 1:1 molar ratio of NaBH4 to dimethylamine hydrochloride to avoid the waste of raw materials caused by excessive use of high-cost NaBH4, and at the same time reduces the side reactions caused by excessive raw materials. While meeting the reaction measurement requirements, it significantly reduces the preparation cost and solves the problems of high raw material consumption and poor economic efficiency in the existing process.

[0022] (ii) In this invention, anhydrous MgSO4 and Ca(OH)2 in a mass ratio of (3-5):1 are used as desiccants to carry out two drying processes. The former quickly adsorbs a large amount of water to ensure drying efficiency, while the latter neutralizes trace acidic impurities and inhibits product hydrolysis. The two drying processes respectively achieve large-scale dehydration of the organic phase and deep dehydration of high-concentration products, reducing the risk of product degradation.

[0023] (III) The present invention adopts the process of "reduced pressure distillation followed by recrystallization". Reduced pressure distillation concentrates the product at low temperature and initially removes inorganic salts and low-boiling-point impurities, avoiding high temperature damage to the product; subsequent recrystallization utilizes the characteristic of the product solubility dropping sharply at low temperature to achieve deep purification, and the final product has high purity, effectively solving the problems of the existing process of lengthy purification process and insufficient product purity.

[0024] (iv) In the preparation of DMAB, the present invention maintains an inert gas atmosphere throughout the process to avoid safety risks caused by the reaction of the product with oxygen and the accumulation of hydrogen; by adding raw materials in batches and controlling the dropping rate, the temperature is strictly controlled (the temperature rise does not exceed 3°C) to reduce the occurrence of side reactions. At the same time, the solvent system is optimized to solve the problem of raw material solubility, shorten the reaction time, and improve the overall reaction efficiency.

[0025] (v) By optimizing reaction conditions, reducing the number of solution transfers, and recycling recrystallization mother liquor, the product yield of this invention is maintained at a stable level of 86%-92%. Moreover, the process steps are simplified and the operating parameters such as temperature, time, and material ratio are clearly controllable, which facilitates large-scale industrial production. Attached Figure Description

[0026] Figure 1 The UV spectrum of commercially available analytical grade DMAB.

[0027] Figure 2 The image shows the UV spectrum of DMAB prepared in Example 1.

[0028] Figure 3 The image shows the UV spectrum of DMAB obtained in Example 2.

[0029] Figure 4 The image shows the UV spectrum of DMAB obtained in Example 3.

[0030] Figure 5 The image shows the UV spectrum of DMAB obtained in Example 4.

[0031] Figure 6 The image shows the UV spectrum of DMAB prepared in Comparative Example 1.

[0032] Figure 7 The image shows the UV spectrum of DMAB prepared in Comparative Example 2. Detailed Implementation

[0033] Example 1 This example provides a method for preparing DMAB, specifically the following steps: In a 1.2L straight four-necked flask with a bottom valve, the air in the flask is first replaced with N2. Then, N2 is introduced at a flow rate of 1L / 15min throughout the process. Then, 650mL of THF is added, and the system is cooled to -5℃. S2. Add 140g (1.7mol) of dimethylamine hydrochloride and stir at 150rpm until homogeneous; S3. Divide 65.5g (1.7mol) NaBH4 into 20 portions, and add one portion of NaBH4 every 15min. Keep the temperature stable during the feeding process (temperature change does not exceed ±3℃); after the NaBH4 is added, react for 4h. S4. Mix 30 mL of water and 70 mL of THF to obtain a THF / H2O solution, divide it into 10 portions, and add one portion every 15 minutes, keeping the temperature stable during the addition process; after the addition is complete, react for 2 hours. S5. Dissolve 15.2g NaOH in 122g water and add it to the reaction system all at once, then stir for 2 minutes. S6. Let the reaction solution obtained in step S5 stand and separate into layers. Discharge the lower solid-liquid mixture from the bottom valve, retain the upper organic liquid, filter the lower solid-liquid mixture, wash the solid with 150 mL THF, and extract the lower aqueous solution after separation and filtration with the washed solution. Combine the extracted solution with the upper organic liquid to obtain the crude DMAB solution. S7. Add 75g of anhydrous MgSO4 and 25g of Ca(OH)2 to the crude DMAB solution and perform the first stirring and drying treatment in a N2 environment for 1h; keep one flask mouth continuously blowing nitrogen gas in, one flask mouth venting gas, one other flask mouth as a stirring port, and the other flask mouth sealed; drain the dried organic solvent from the bottom valve, filter, wash the filtered solid with 100mL of THF, and collect the filtrate and the washing THF solution, totaling 930mL; S8. Place the filtrate collected in step S7 into a flask, connect the vacuum distillation device, and attach the heating device to perform vacuum distillation, and collect the distilled THF solvent; control the vacuum distillation temperature at 35℃ and the vacuum distillation efficiency at 0.4L / min. S9. When the theoretical DMAB mass concentration is 80wt% by vacuum distillation (total solution mass is 130g, non-product salt and a small amount of water account for 5g), add 5g of anhydrous MgSO4 and 1.67g of Ca(OH)2, perform a second stirring and drying treatment for 15min, filter, collect the organic phase, wash the solid with 15mL of THF, combine the organic phase and the washing THF solution to obtain a DMAB THF solution with a mass concentration of 72wt%, totaling 910mL. S10. Recrystallize the THF solution of DMAB at -15℃ to obtain 87.2g of pure DMAB, with a yield of 87.2%. The mother liquor can be retained and incorporated into the next recrystallization preparation.

[0034] Example 2 This example provides a method for preparing DMAB, specifically the following steps: In a 1.2L straight four-necked flask with a bottom valve, the air in the flask is first replaced with N2. Then, N2 is introduced at a flow rate of 1L / 15min throughout the process. Then, 650mL of THF is added, and the system is cooled to -5℃. S2. Add 140g (1.7mol) of dimethylamine hydrochloride and stir at 150rpm until homogeneous; S3. Divide 65.5g (1.7mol) NaBH4 into 20 portions, and add one portion of NaBH4 every 15min. Keep the temperature stable during the feeding process (temperature change does not exceed ±3℃); after the NaBH4 is added, react for 4h. S4. Mix 30 mL of water and 70 mL of THF to obtain a THF / H2O solution, divide it into 10 portions, and add one portion every 20 minutes, keeping the temperature stable during the addition process; after the addition is complete, react for 2 hours. S5. Dissolve 15.2g NaOH in 122g water and add it to the reaction system all at once, then stir for 2 minutes. S6. Let the reaction solution obtained in step S5 stand and separate into layers. Discharge the lower solid-liquid mixture from the bottom valve, retain the upper organic liquid, filter the lower solid-liquid mixture, wash the solid with 150 mL THF, and extract the lower aqueous solution after separation and filtration with the washed solution. Combine the extracted solution with the upper organic liquid to obtain the crude DMAB solution. S7. Add 80g of anhydrous MgSO4 and 20g of Ca(OH)2 to the crude DMAB solution and perform the first stirring and drying treatment in a N2 environment for 1h; keep one flask continuously blowing nitrogen into it, one flask venting nitrogen, one other flask venting nitrogen, and the remaining flask venting nitrogen, while sealing the other flask vent; drain the dried organic solvent from the bottom valve, filter the solution, wash the filtered solid with 100mL of THF, and collect the filtrate and the washing THF solution, totaling 930mL; S8. Place the filtrate collected in step S7 into a flask, connect the vacuum distillation device, and attach the heating device to perform vacuum distillation, and collect the distilled THF solvent; control the vacuum distillation temperature at 35℃ and the vacuum distillation efficiency at 0.3L / min. S9. When the theoretical DMAB mass concentration is 90wt% by vacuum distillation (total solution mass is 115g, non-product salt and a small amount of water account for 5g), add 4g of anhydrous MgSO4 and 1g of Ca(OH)2, perform a second stirring and drying treatment for 30min, filter, collect the organic phase, wash the solid with 20mL of THF, combine the organic phase and the washed THF solution to obtain a DMAB THF solution with a mass concentration of 78wt%, 920mL. S10. Recrystallize the THF solution of DMAB at -10℃ to obtain 90.1g of pure DMAB, with a yield of 90.1%. The mother liquor can be retained and incorporated into the next recrystallization preparation.

[0035] Example 3 This example provides a method for preparing DMAB, specifically the following steps: In a 200L reactor with a bottom valve, the air in the bottle is first replaced with N2. Then, N2 is input at a flow rate of 100L / 15min throughout the process. Then, 65L of THF is added, and the system is cooled to -5℃. S2. Add 14 kg (170 mol) of dimethylamine hydrochloride and stir at 150 rpm until homogeneous; S3. Divide 6.55 kg (170 mol) of NaBH4 into 20 portions, and add one portion of NaBH4 every 20 minutes. Keep the temperature stable during the feeding process (temperature change does not exceed ±3℃); after the NaBH4 is added, react for 2 hours. S4. Mix 3L of water and 7L of THF to obtain a THF / H2O solution, divide it into 10 portions, and add one portion every 30 minutes, keeping the temperature stable during the addition process; after the addition is complete, react for 1 hour. S5. Dissolve 1.52 kg of NaOH in 12.2 kg of water and add it to the reaction system all at once, then stir for 5 min. S6. Let the reaction solution obtained in step S5 stand and separate into layers. Discharge the lower solid-liquid mixture from the bottom valve, retain the upper organic liquid, filter the lower solid-liquid mixture, wash the solid with 10L THF, and extract the lower aqueous solution after separation and filtration with the washed solution. Combine the extracted solution with the upper organic liquid to obtain the crude DMAB solution. S7. Add 8 kg of anhydrous MgSO4 and 2 kg of Ca(OH)2 to the crude DMAB solution and perform the first stirring and drying treatment in a N2 environment for 1 hour. Keep one flask continuously blowing nitrogen into it, one flask venting nitrogen, one other flask venting nitrogen, and the other flask venting nitrogen. The other flask vent is closed. Discharge the dried organic solvent from the bottom valve and filter the solution. Wash the filtered solid with 10 L of THF and collect the filtrate and the washing THF solution, totaling 93 L. S8. Place the filtrate collected in step S7 into a flask, connect the vacuum distillation device, and attach the heating device to perform vacuum distillation, and collect the distilled THF solvent; control the vacuum distillation temperature at 35℃ and the vacuum distillation efficiency at 1.5L / min. S9. When the theoretical DMAB concentration is 72wt% by vacuum distillation (total solution mass is 12.3kg, non-product salt and a small amount of water account for 0.5kg), 400g of anhydrous MgSO4 and 100g of Ca(OH)2 are added, and the mixture is stirred and dried for a second time for 45min. After filtration, the organic phase is collected, and the solid is washed with 2L of THF. The organic phase and the washed THF solution are combined to obtain a 66wt% DMAB THF solution, 89.3L. S10. Recrystallize the THF solution of DMAB at -20℃ to obtain 8.66 kg of pure DMAB, with a yield of 86.6%. The mother liquor can be retained and incorporated into the next recrystallization preparation.

[0036] Example 4 This example provides a method for preparing DMAB, specifically the following steps: In a 200L reactor with a bottom valve, the air in the bottle is first replaced with N2. Then, N2 is input at a flow rate of 100L / 15min throughout the process. Then, 65L of THF is added, and the system is cooled to -8℃. S2. Add 14 kg (170 mol) of dimethylamine hydrochloride and stir at 150 rpm until homogeneous; S3. Divide 6.55 kg (170 mol) of NaBH4 into 20 portions, and add one portion of NaBH4 every 15 min. Keep the temperature stable during the feeding process (temperature change does not exceed ±3℃); after the NaBH4 is added, react for 4 h. S4. Mix 3L of water and 7L of THF to obtain a THF / H2O solution, divide it into 10 portions, and add one portion every 30 minutes, keeping the temperature stable during the addition process; after the addition is complete, react for 1 hour. S5. Dissolve 1.52 kg of NaOH in 12.2 kg of water and add it to the reaction system all at once, then stir for 5 min. S6. Let the reaction solution obtained in step S5 stand and separate into layers. Discharge the lower solid-liquid mixture from the bottom valve, retain the upper organic liquid, filter the lower solid-liquid mixture, wash the solid with THF, and extract the lower aqueous solution after separation and filtration with the washed solution. Combine the extracted solution with the upper organic liquid to obtain crude DMAB solution. S7. Add 9 kg of anhydrous MgSO4 and 2 kg of Ca(OH)2 to the crude DMAB solution and perform the first stirring and drying treatment in a N2 environment for 1.5 h. Keep one flask continuously blowing nitrogen into it, one flask venting nitrogen, one other flask venting nitrogen, and the other flask venting nitrogen. The other flask vent is closed. The dried organic solvent is discharged from the bottom valve and filtered. The filtered solid is washed with 10 L of THF. Collect the filtrate and the washing THF solution, totaling 93 L. S8. Place the filtrate collected in step S7 into a flask, connect the vacuum distillation device, and attach the heating device to perform vacuum distillation, and collect the distilled THF solvent; control the vacuum distillation temperature at 40℃ and the vacuum distillation efficiency at 2L / min. S9. When the theoretical DMAB concentration is 75wt% by vacuum distillation (total solution mass is 13.8kg, non-product salt and a small amount of water account for 0.5kg), 450g of anhydrous MgSO4 and 100g of Ca(OH)2 are added, and the mixture is stirred and dried for a second time for 45min. After filtration, the organic phase is collected, and the solid is washed with 2.5L of THF. The organic phase and the washed THF solution are combined to obtain a DMAB THF solution with a mass concentration of 64.5wt%, 89.7L. S10. Recrystallize the THF solution of DMAB at -20℃ to obtain 8.86 kg of pure DMAB, with a yield of 88.6%. The mother liquor can be retained and incorporated into the next recrystallization preparation.

[0037] Comparative Example 1 This example provides a method for preparing DMAB, specifically the following steps: In a straight four-necked flask with a volume of S1 and 2L, the air in the flask is first replaced with N2. Then, N2 is introduced at a flow rate of 1L / 15min throughout the process. Then, 650mL of THF is added, and the system is cooled to -5℃. S2. Add 140g (1.7mol) of dimethylamine hydrochloride and stir at 150rpm until homogeneous; S3. Divide 65.5g (1.7mol) NaBH4 into 20 portions, and add one portion of NaBH4 every 15min. Keep the temperature stable during the feeding process (temperature change does not exceed ±3℃); after the NaBH4 is added, react for 4h. S4. Mix 30 mL of water and 70 mL of THF to obtain a THF / H2O solution, divide it into 10 portions, and add one portion every 15 minutes, keeping the temperature stable during the addition process; after the addition is complete, react for 2 hours. S5. Dissolve 15.2g NaOH in 122g water and add it to the reaction system all at once, then stir for 2 minutes. S6. Filter the solution and solid in the flask, collect the filtrate, separate the liquid and collect the upper organic liquid, wash the solid with 150 mL THF, and extract the lower aqueous solution after separation with the washing tetrahydrofuran solution. Combine the extracted THF solution with the upper organic liquid, for a total of 850 mL. S7. Place the organic phase collected in step S6 into a 2L straight four-necked flask, then add 90g of anhydrous MgSO4 and stir and dry for 1h. Filter the dried organic solvent and collect the filtrate. S8. Place the filtrate into a three-necked flask, connect the vacuum distillation apparatus, and attach the heating device. Perform vacuum distillation at 35°C and collect the solvent. After vacuum distillation, filter and collect the liquid phase to obtain crude DMAB containing a small amount of solvent, and collect approximately 800 mL of solvent. Then, place the product in a vacuum drying oven at 35°C for vacuum drying. After drying, 97.2 g of crude DMAB is obtained, with a yield of 97.2%. Dissolve the crude DMAB in THF to form a 70 wt% concentration, and recrystallize at 5°C to obtain 88.1 g of pure product, with a yield of 88.1%. The mother liquor is retained and can be included in the next recrystallization preparation.

[0038] Comparative Example 2 This example provides a method for preparing DMAB, specifically the following steps: In a straight four-necked flask with a volume of S1 and 2L, the air in the flask is first replaced with N2. Then, N2 is introduced at a flow rate of 1L / 15min throughout the process. Then, 650mL of THF is added, and the system is cooled to -5℃. S2. Add 140g (1.7mol) of dimethylamine hydrochloride and stir at 150rpm until homogeneous; S3. Divide 65.5g (1.7mol) NaBH4 into 20 portions, and add one portion of NaBH4 every 30min, keeping the temperature stable during the feeding process (temperature change not exceeding ±3℃); after the NaBH4 is completely added, react for 2h. S4. Mix 30 mL of water and 70 mL of THF to obtain a THF / H2O solution, divide it into 10 portions, and add one portion every 30 minutes, keeping the temperature stable during the addition process; after the addition is complete, react for 0.5 hours. S5. Dissolve 15.2g NaOH in 122g water and add it to the reaction system all at once, then stir for 5 minutes. S6. Filter the solution and solid in the flask, collect the filtrate, separate the liquid and collect the upper organic liquid, wash the solid with 150 mL THF, and extract the lower aqueous solution after separation with the washing tetrahydrofuran solution. Combine the extracted THF solution with the upper organic liquid, for a total of 850 mL. S7. Place the organic phase collected in step S6 into a 2L straight four-necked flask, then add 90g of anhydrous MgSO4 and stir and dry for 2h. Filter the dried organic solvent and collect the filtrate. S8. Place the filtrate into a three-necked flask, connect the vacuum distillation apparatus, and attach the heating device. Perform vacuum distillation at 35°C and collect the solvent. After vacuum distillation, filter and collect the liquid phase to obtain crude DMAB containing a small amount of solvent, and collect approximately 800 mL of solvent. Then, place the product in a vacuum drying oven at 35°C for vacuum drying. After drying, 94.6 g of crude DMAB is obtained, with a yield of 94.6%. Dissolve the crude DMAB in THF to form a 70 wt% concentration, and recrystallize at 5°C to obtain 86.8 g of pure product, with a yield of 86.8%. The mother liquor is retained and can be included in the next recrystallization preparation.

[0039] The UV spectrum of commercially available analytical grade DMAB is as follows: Figure 1 As shown; the UV spectra of DMAB prepared in Examples 1-4 and Comparative Examples 1-2 are respectively shown in the figures. Figures 2-7 As shown.

[0040] The spectra of Examples 1-4 are almost identical to those of commercially available comparison samples, indicating high purity.

[0041] Compared to Examples 1 and 2, Comparative Examples 1 and 2 involved three solvent transfers: the first was after the reaction was complete, the second was after drying, and the third was before vacuum drying. In contrast, Examples 1 and 2 only required one solvent transfer, after drying, thus reducing the number of solvent transfers by two and simplifying the operation. The yield was comparable to that of the Comparative Examples, and the chromatogram purity was high, consistent with commercially available analytical grade solvents.

Claims

1. An industrial synthesis method for DMAB, characterized in that, Includes the following steps: S1. In an inert gas atmosphere, add 600~800mL of THF to a reaction vessel with a bottom valve, and then cool the system to -10~0℃; S2. Add 120-150g of dimethylamine hydrochloride and stir until homogeneous; S3. Divide 60-70g of NaBH4 into 20-30 portions, and add one portion of NaBH4 every 10-45 minutes; after the NaBH4 is added, react for 1-6 hours. S4. Mix 20-50 mL of water and 50-80 mL of THF to obtain a THF / H2O solution, divide it into 5-20 portions, and add one portion every 10-30 minutes; after the addition is complete, react for 0.5-2 hours. S5. Dissolve 10-20g of NaOH in 100-200g of water and add it to the reaction system all at once; S6. Let the reaction solution obtained in step S5 stand and separate into layers. Discharge the lower solid-liquid mixture from the bottom valve, retain the upper organic liquid, filter the lower solid-liquid mixture, wash the solid with THF, and extract the lower aqueous solution after separation and filtration with the washed solution. Combine the extracted solution with the upper organic liquid to obtain crude DMAB solution. S7 and crude DMAB solution were added to a desiccant and subjected to a first stirring and drying process in an inert environment. The dried organic solvent is discharged from the bottom valve, filtered, and the filtered solids are washed with THF. The filtrate and the washing THF solution are collected. S8. Perform vacuum distillation on the filtrate and the washed THF solution. S9. Add a desiccant to the reaction solution after vacuum distillation, perform a second stirring and drying treatment, filter, collect the organic phase, wash the solid with THF, combine the organic phase and the washing THF solution to obtain the THF solution of DMAB. S10. Recrystallize the THF solution of DMAB to obtain pure DMAB.

2. The industrial synthesis method of DMAB according to claim 1, characterized in that, The molar ratio of NaBH4 to dimethylamine hydrochloride is 1:

1.

3. The industrial synthesis method of DMAB according to claim 1, characterized in that, The desiccant includes at least two of anhydrous MgSO4, Ca(OH)2, CaCl2, or CaO.

4. The industrial synthesis method of DMAB according to claim 3, characterized in that, The mass ratio of the anhydrous MgSO4 to Ca(OH)2 is (3-5):

1.

5. The industrial synthesis method of DMAB according to claim 1, characterized in that, In step S7, the desiccant is 8-20% of the mass of the crude DMAB solution.

6. The industrial synthesis method of DMAB according to claim 1, characterized in that, The first stirring and drying process takes 1-4 hours.

7. The industrial synthesis method of DMAB according to claim 1, characterized in that, In step S9, the amount of desiccant is 10-35% of the mass of the reaction solution.

8. The industrial synthesis method of DMAB according to claim 1, characterized in that, The second stirring and drying process takes 10-45 minutes.

9. The industrial synthesis method of DMAB according to claim 1, characterized in that, The temperature for vacuum distillation is 20~40℃.

10. The industrial synthesis method of DMAB according to claim 1, characterized in that, The recrystallization temperature is -30 to -5℃.

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