A preparation method of N,N-dimethylpyrrole tetrafluoroborate

Abstract

The present invention relates to the technical field of preparation of N,N-dimethylpyrrole tetrafluoroborate, and specifically to a preparation method of N,N-dimethylpyrrole tetrafluoroborate. A preparation method of N,N-dimethylpyrrole tetrafluoroborate, the preparation method comprising the following steps: S1. Obtaining N,N-dimethylpyrrole methyl carbonate; S2. Obtaining a crude product of N,N-dimethylpyrrolidine tetrafluoroborate; S3. Obtaining N,N-dimethylpyrrolidine tetrafluoroborate. The preparation method of N,N-dimethylpyrrole tetrafluoroborate provided in the present application can obtain high-purity, low-water content N,N-dimethylpyrrole tetrafluoroborate.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of N,N-dimethylpyrrole tetrafluoroborate, and in particular to a method for preparing N,N-dimethylpyrrole tetrafluoroborate. Background Art

[0002] Ionic liquids are emerging green solvents and functional materials with advantages such as good solubility, wide liquid range, low vapor pressure, and designability. They are widely used in organic synthesis reactions, material surface modification, electrochemical deposition, and preparation of high energy density electrolytes. N,N-dimethylpyrrole tetrafluoroborate is an ionic liquid with good stability and high catalytic performance in organic synthesis reactions, and has received widespread attention. At present, the preparation method of N,N-dimethylpyrrole tetrafluoroborate is generally obtained by reacting N-methylpyrrolidine with tetrafluoroboric acid at high temperature and then recrystallizing it multiple times; or by reacting sodium tetrafluoroborate with N-methylpyrrolidine at high temperature and then recrystallizing it multiple times. The above preparation method can obtain N,N-dimethylpyrrole tetrafluoroborate, but the product purity is not high and contains a large amount of impurities, which affects its catalytic performance in organic synthesis reactions; the preparation process is complicated, and the processing steps of multiple recrystallizations not only increase the production cost but also reduce the production efficiency; the product has a high moisture content, which may not only cause corrosion to the equipment but also affect its performance in applications such as electrochemical deposition; and a large amount of solvents need to be used in the processing process, which not only pollutes the environment but also increases the production cost.

[0003] The Chinese invention patent with patent publication number CN113045512A discloses a one-step preparation method of N,N-dimethylpyrrolidinium salt, but does not disclose a technical solution to solve the technical problem of high purity and low moisture content.

[0004] Therefore, providing an N,N-dimethylpyrrole tetrafluoroborate with high purity and low water content is the main technical problem that needs to be solved at present. Summary of the invention

[0005] In order to improve the purity of N,N-dimethylpyrrole tetrafluoroborate and reduce its water content, the present invention provides a method for preparing N,N-dimethylpyrrole tetrafluoroborate, which comprises the following steps:

[0006] S1. N-methylpyrrolidine, methanol, and dimethyl carbonate are sequentially added to a reaction vessel, and the reaction vessel is heated to react to obtain N,N-dimethylpyrrole methyl carbonate;

[0007] S2. Decolorizing N,N-dimethylpyrrole carbonate methyl ester, and adding tetrafluoroboric acid aqueous solution dropwise to N,N-dimethylpyrrole carbonate methyl ester, and stirring to obtain a crude product of N,N-dimethylpyrrolidine tetrafluoroborate;

[0008] S3. Recrystallize the crude product of N,N-dimethylpyrrolidine tetrafluoroborate to obtain N,N-dimethylpyrrolidine tetrafluoroborate.

[0009] In one embodiment, in S1, the temperature of the reactor is raised to 135°C-150°C.

[0010] In one embodiment, the reaction time in S1 is 12-20 hours.

[0011] In one embodiment, the reaction time in S1 includes but is not limited to 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, and 20 h.

[0012] In one embodiment, the molar ratio of N-methylpyrrolidine and dimethyl carbonate in S1 is 1:(1-1.7), and the mass ratio of methanol to N,N-dimethylpyrrole methyl carbonate is (1-1.2):1.

[0013] In one embodiment, the purity of the N-methylpyrrolidine is ≥99%, and the water content is 100-1000 ppm.

[0014] In one embodiment, the dimethyl carbonate has a purity of ≥99% and contains 100-500 ppm of water.

[0015] In one embodiment, the purity of the methanol is ≥99%, and the water content is 0-100 ppm.

[0016] In order to improve the purity of N,N-dimethylpyrrole tetrafluoroborate and reduce its water content, the preparation method of N,N-dimethylpyrrole tetrafluoroborate provided by the present invention has low requirements for production equipment. Only in the high-pressure reactor, the high-pressure reactor is sealed, the high-pressure reactor is heated to 135-150° C., the reaction time in S1 is 12-20 hours, the molar ratio of N-methylpyrrolidine and dimethyl carbonate is 1:(1-1.7), and the mass ratio of methanol to N,N-dimethylpyrrole methyl carbonate is (1-1.2):1. The residual amount of N-methylpyrrole in N,N-dimethylpyrrole methyl carbonate can be reduced to less than 100 ppm, and no halogen elements are introduced in the preparation process. The by-product is carbon dioxide, and the effect of achieving high purity can be achieved.

[0017] In one embodiment, water and activated carbon are used to decolorize N,N-dimethylpyrrole carbonate methyl ester in S2, the mass ratio of water to N,N-dimethylpyrrole carbonate methyl ester is (1-2):1, and the amount of activated carbon added is 3-5wt% of N,N-dimethylpyrrole carbonate methyl ester.

[0018] In one embodiment, the molar ratio of the tetrafluoroboric acid aqueous solution to the N,N-dimethylpyrrole carbonate methyl salt in S2 is 1:(1-1.3).

[0019] The preparation process of the crude N,N-dimethylpyrrolidine tetrafluoroborate provided in the present application defines that water and activated carbon are used to decolorize N,N-dimethylpyrrole carbonate methyl ester salt at 65° C. for 6 hours in S2, the mass ratio of water to N,N-dimethylpyrrole carbonate methyl ester salt is (1-2):1, and the amount of activated carbon added is 3-5wt% of N,N-dimethylpyrrole carbonate methyl ester salt. The molar ratio of tetrafluoroboric acid aqueous solution to N,N-dimethylpyrrole carbonate methyl ester salt in S2 is defined as 1:(1-1.3); the reaction is carried out at room temperature, the energy consumption is relatively low, and the reaction is safe.

[0020] In one embodiment, the method of recrystallizing the crude N,N-dimethylpyrrolidine tetrafluoroborate product in S3 comprises:

[0021] The crude product of N,N-dimethylpyrrolidine tetrafluoroborate is dissolved in acetonitrile, and then ethanol is added for stirring, and frozen recrystallization is performed at low temperature. The recrystallization steps are repeated to obtain N,N-dimethylpyrrolidine tetrafluoroborate.

[0022] In one embodiment, the amount of acetonitrile added is 10-30wt% of the crude product of N,N-dimethylpyrrolidine tetrafluoroborate, and the mass ratio of ethanol to acetonitrile is (5-10):1.

[0023] In one embodiment, the amount of acetonitrile added is 19-21wt% of the crude product of N,N-dimethylpyrrolidine tetrafluoroborate, and the mass ratio of ethanol to acetonitrile is (5-10):1.

[0024] In one embodiment, the conditions for performing freeze-recrystallization at low temperature are freezing at -10°C to -30°C for 3-4 hours for recrystallization, and then filtering; repeating the recrystallization step 1-3 times to obtain N,N-dimethylpyrrolidine tetrafluoroborate.

[0025] In one embodiment, the conditions for performing freeze-recrystallization at low temperature are freezing at -20°C for 3-4 hours for recrystallization, and then filtering; repeating the recrystallization step twice to obtain N,N-dimethylpyrrolidine tetrafluoroborate.

[0026] The method for recrystallizing the crude N,N-dimethylpyrrolidine tetrafluoroborate product provided in the present application limits the amount of acetonitrile added to 10-30wt% of the crude N,N-dimethylpyrrolidine tetrafluoroborate product, and the mass ratio of ethanol to acetonitrile is (5-10):1, and in particular, when the amount of acetonitrile added is 19-21wt% of the crude N,N-dimethylpyrrolidine tetrafluoroborate product, a yield value of 87.2% is obtained. The amount of acetonitrile added in the present application is small, and compared with the existing recrystallization method, the present application greatly saves the amount of ethanol used and reduces the burden on the environment.

[0027] In one embodiment, the N,N-dimethylpyrrolidine tetrafluoroborate obtained in S3 is placed in a vacuum oven, and the temperature of the vacuum oven is controlled to be 50-70° C. to obtain a product with relatively low moisture content. The N,N-dimethylpyrrolidine tetrafluoroborate is then placed in a glove box and irradiated with infrared light until the moisture content of the N,N-dimethylpyrrolidine tetrafluoroborate is less than 20 ppm.

[0028] In order to control the moisture content in N,N-dimethylpyrrolidine tetrafluoroborate in the present invention, the inventors found during the experiment that by using a vacuum oven to control the moisture content in N,N-dimethylpyrrolidine tetrafluoroborate, by using a glove box and performing infrared light irradiation, compared with operations such as heating and vacuuming, using a solvent to carry moisture, and using an organic solvent for azeotropy, the drying method provided by the present invention is easier to operate, has lower moisture content, and is more environmentally friendly.

[0029] Beneficial Effects

[0030] 1. The preparation method of N,N-dimethylpyrrole tetrafluoroborate provided in the present application can obtain high-purity, low-water content N,N-dimethylpyrrole tetrafluoroborate.

[0031] 2. In the present application, by limiting the temperature of the high-pressure reactor to 135-150° C., the reaction time to 12-20 h, the molar ratio of N-methylpyrrolidine and dimethyl carbonate to 1:(1-1.7), and the mass ratio of methanol to N,N-dimethylpyrrole methyl carbonate to (1-1.2):1, the residual amount of N-methylpyrrole in N,N-dimethylpyrrole methyl carbonate can be reduced to less than 100 ppm, and no halogen elements are introduced during the preparation process, and the by-product is carbon dioxide, so that the effect of achieving high purity can be achieved.

[0032] 3. In the present application, water and activated carbon are used to decolorize N,N-dimethylpyrrole carbonate for 6 hours at 65°C, the mass ratio of water to N,N-dimethylpyrrole carbonate is (1-2):1, and the amount of activated carbon added is 3-5wt% of N,N-dimethylpyrrole carbonate. The molar ratio of tetrafluoroboric acid aqueous solution to N,N-dimethylpyrrole carbonate is 1:(1-1.3); the reaction is carried out at room temperature, the energy consumption is relatively low, and the reaction is safe.

[0033] 4. In the present application, the amount of acetonitrile added is limited to 10-30wt% of the crude product of N,N-dimethylpyrrolidine tetrafluoroborate, and the mass ratio of ethanol to acetonitrile is (5-10):1. In particular, when the amount of acetonitrile added is 19-21wt% of the crude product of N,N-dimethylpyrrolidine tetrafluoroborate, a yield value of 87.2% is obtained. In the present application, a small amount of acetonitrile is added. Compared with the existing recrystallization method, the present application greatly saves the amount of ethanol used and reduces the burden on the environment.

[0034] 5. In the present application, the moisture content in N,N-dimethylpyrrolidine tetrafluoroborate is controlled by limiting the use of a vacuum oven, and a glove box is used and infrared light is irradiated. Compared with operations such as heating and vacuuming, using solvents to carry moisture, and using organic solvents for azeotropy, the drying method provided by the present invention is easier to operate, has lower moisture content, and is more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of N,N-dimethylpyrrolidine tetrafluoroborate provided in Example 13.

[0036] Figure 2 State diagram for N,N-dimethylpyrrolidine tetrafluoroborate provided for Example 13. DETAILED DESCRIPTION

[0037] The first set of experiments provides a method for preparing N,N-dimethylpyrrole carbonate methyl ester.

[0038] The second set of experiments provided a method for preparing the crude product of N,N-dimethylpyrrolidine tetrafluoroborate.

[0039] The third group of experiments provides a method for preparing N,N-dimethylpyrrolidine tetrafluoroborate.

[0040] The first set of experiments

[0041] The first group of experiments provides a method for preparing N,N-dimethylpyrrole methyl carbonate, comprising the following steps: adding N-methylpyrrolidine, methanol, and dimethyl carbonate to a reactor in sequence, heating the reactor, and reacting to obtain N,N-dimethylpyrrole methyl carbonate.

[0042] The purity of the N-methylpyrrolidine was 99%, and the water content was 156 ppm.

[0043] The purity of the dimethyl carbonate is 99%, and the water content is 322 ppm.

[0044] The purity of the methanol was 99.8%, and the water content thereof was 116 ppm.

[0045] The first group of experiments includes Example 1, Example 2, Example 3, Example 4, and Example 5.

[0046] Example 1

[0047] Example 1 provides a method for preparing N,N-dimethylpyrrole carbonate methyl ester, comprising the following steps:

[0048] 50 g of N-methylpyrrolidine was placed in a high-pressure reactor, and then 150 g of methanol and 79.34 g of dimethyl carbonate were added into the high-pressure reactor. The high-pressure reactor was sealed, and the temperature of the high-pressure reactor was increased to 120° C., and then the temperature was kept and stirred for 10 hours. The stirring speed was 300 RPM. After the reaction, N,N-dimethylpyrrole methyl carbonate was obtained.

[0049] Example 2

[0050] Example 2 provides a method for preparing N,N-dimethylpyrrole carbonate methyl ester, comprising the following steps: placing 50 g of N-methylpyrrolidine in a high-pressure reactor, adding 150 g of methanol and 79.34 g of dimethyl carbonate to the high-pressure reactor, sealing the high-pressure reactor, and heating the high-pressure reactor to 120° C. and then keeping it warm and stirring for 15 hours, the stirring speed is 300 RPM, and N,N-dimethylpyrrole carbonate methyl ester is obtained after the reaction is completed.

[0051] Example 3

[0052] Example 3 provides a method for preparing N,N-dimethylpyrrole carbonate methyl ester, comprising the following steps: placing 50 g of N-methylpyrrolidine in a high-pressure reactor, adding 150 g of methanol and 79.34 g of dimethyl carbonate into the high-pressure reactor, sealing the high-pressure reactor, and heating the high-pressure reactor to 120° C. and then keeping it warm and stirring for 20 hours, the stirring speed is 300 RPM, and N,N-dimethylpyrrole carbonate methyl ester is obtained after the reaction is completed.

[0053] Example 4

[0054] Example 4 provides a method for preparing N,N-dimethylpyrrole carbonate methyl ester, comprising the following steps: placing 50 g of N-methylpyrrolidine in a high-pressure reactor, adding 150 g of methanol and 79.34 g of dimethyl carbonate to the high-pressure reactor, sealing the high-pressure reactor, and heating the high-pressure reactor to 135° C. and then keeping it warm and stirring for 15 hours, the stirring speed is 300 RPM, and N,N-dimethylpyrrole carbonate methyl ester is obtained after the reaction is completed.

[0055] Example 5

[0056] Example 5 provides a method for preparing N,N-dimethylpyrrole carbonate methyl ester, comprising the following steps: placing 50 g of N-methylpyrrolidine in a high-pressure reactor, adding 150 g of methanol and 79.34 g of dimethyl carbonate into the high-pressure reactor, sealing the high-pressure reactor, and heating the high-pressure reactor to 150° C. and then keeping it warm and stirring for 15 hours, the stirring speed is 300 RPM, and N,N-dimethylpyrrole carbonate methyl ester is obtained after the reaction is completed.

[0057] The N,N-dimethylpyrrole methyl carbonate provided in the first group of experiments was tested for N-methylpyrrole residue using a gas chromatograph. The test results are shown in Table 1.

[0058] Table 1

[0059] Example N-methylpyrrolidine residue / ppm Example 1 ＞500 Example 2 ＜500 Example 3 ＜500 Example 4 ＜100 Example 5 ＜100

[0060] It can be seen from the experimental test data in Table 1 that in the first group of experiments, when the reaction time used in Example 1 is less than 12 hours and the reaction temperature used in Examples 1 to 3 is less than 130°C, the reaction will be incomplete and the residual N-methylpyrrolidine will be high. In the preparation methods of N,N-dimethylpyrrole carbonate methyl ester provided in Examples 4 and 5, the residual N-methylpyrrolidine can be obtained to be less than 100 ppm. In order to save energy, the preparation method of N,N-dimethylpyrrole carbonate methyl ester provided in Example 4 can be selected to obtain N,N-dimethylpyrrole carbonate methyl ester.

[0061] The second set of experiments

[0062] The second group of experiments provides a method for preparing a crude product of N,N-dimethylpyrrolidine tetrafluoroborate, comprising the following steps: decolorizing N,N-dimethylpyrrole methyl carbonate, adding a tetrafluoroboric acid aqueous solution dropwise to N,N-dimethylpyrrole methyl carbonate, and stirring to obtain a crude product of N,N-dimethylpyrrolidine tetrafluoroborate.

[0063] In the second group of experiments, N,N-dimethylpyrrole carbonate methyl salt was decolorized to obtain decolorized N,N-dimethylpyrrole carbonate methyl salt, and the method steps adopted were:

[0064] The N,N-dimethylpyrrole carbonate methyl ester provided in Example 4 was decolorized at 65° C. for 6 hours using 205.9 g of water and 5.1 g of activated carbon.

[0065] The second group of experiments includes Example 6, Example 7, Example 8, Example 9, and Example 10, which respectively use the N,N-dimethylpyrrole carbonate methyl ester provided in Example 4 as an intermediate to prepare the crude product of N,N-dimethylpyrrolidine tetrafluoroborate.

[0066] Example 6

[0067] Example 6 provides a method for preparing N,N-dimethylpyrrolidine tetrafluoroborate, comprising the following steps:

[0068] 103.13 g of 50% tetrafluoroboric acid aqueous solution was added dropwise to 105.12 g of decolorized N,N-dimethylpyrrole methyl carbonate at 25° C., with a dropping speed of 2 drops per second. The mixture was stirred at 25° C. with a magnetic stirrer at gear 3 for 4 hours. The reaction was completed to obtain a crude product of N,N-dimethylpyrrolidine tetrafluoroborate.

[0069] The N,N-dimethylpyrrole carbonate methyl ester salt is prepared by the preparation method provided in Example 4.

[0070] Example 7

[0071] Example 7 provides a method for preparing N,N-dimethylpyrrolidine tetrafluoroborate, comprising the following steps:

[0072] 154.7 g of 50% tetrafluoroboric acid aqueous solution was added dropwise to 105.12 g of decolorized N,N-dimethylpyrrole methyl carbonate at 25° C., with a dropping speed of 2 drops per second. The mixture was stirred at 25° C. with a magnetic stirrer at gear 3 for 4 hours. The reaction was completed to obtain a crude product of N,N-dimethylpyrrolidine tetrafluoroborate.

[0073] The N,N-dimethylpyrrole carbonate methyl ester salt is prepared by the preparation method provided in Example 4.

[0074] Example 8

[0075] Example 8 provides a method for preparing N,N-dimethylpyrrolidine tetrafluoroborate, comprising the following steps:

[0076] 206.26 g of 50% tetrafluoroboric acid aqueous solution was added dropwise to 105.12 g of decolorized N,N-dimethylpyrrole methyl carbonate at 25° C., with a dropping speed of 2 drops per second. The mixture was stirred at 25° C. with a magnetic stirrer at gear 3 for 4 hours. The reaction was completed to obtain a crude product of N,N-dimethylpyrrolidine tetrafluoroborate.

[0077] The N,N-dimethylpyrrole carbonate methyl ester salt is prepared by the preparation method provided in Example 4.

[0078] Example 9

[0079] Example 9 provides a method for preparing N,N-dimethylpyrrolidine tetrafluoroborate, comprising the following steps:

[0080] 103.13 g of 50% tetrafluoroboric acid aqueous solution was added dropwise to 105.12 g of decolorized N,N-dimethylpyrrole methyl carbonate at 25° C., with a dropping speed of 2 drops per second. The mixture was stirred at 25° C. with a magnetic stirrer at gear 3 for 8 hours. The reaction was completed to obtain a crude product of N,N-dimethylpyrrolidine tetrafluoroborate.

[0081] The N,N-dimethylpyrrole carbonate methyl ester salt is prepared by the preparation method provided in Example 4.

[0082] Example 10

[0083] Example 10 provides a method for preparing N,N-dimethylpyrrolidine tetrafluoroborate, comprising the following steps:

[0084] 103.13 g of 50% tetrafluoroboric acid aqueous solution was added dropwise to 105.12 g of decolorized N,N-dimethylpyrrole methyl carbonate at 25° C., with a dropping speed of 2 drops per second. The mixture was stirred at 25° C. with a magnetic stirrer at gear 3 for 12 hours. The reaction was completed to obtain a crude product of N,N-dimethylpyrrolidine tetrafluoroborate.

[0085] The N,N-dimethylpyrrole carbonate methyl ester salt is prepared by the preparation method provided in Example 4.

[0086] For the crude product of N,N-dimethylpyrrolidine tetrafluoroborate provided in the second group of experiments, its properties were recorded and its yield was calculated. The recorded results are shown in Table 2.

[0087] Yield % = actual mass / theoretical mass * 100%

[0088] Table 2

[0089] Example Characteristics Yield / % Example 6 White solid 95.05 4h Example 7 Light red solid 91.6 4h Example 8 Red solid 91.0 4h Example 9 White solid 94.5 8h Example 10 White solid 96.48 12h

[0090] It can be seen from the results recorded in Table 2 that the reaction time has little effect on the yield of N,N-dimethylpyrrolidine tetrafluoroborate, and the reaction ratio of tetrafluoroboric acid aqueous solution and N,N-dimethylpyrrole methyl carbonate will affect the color of the crude product of N,N-dimethylpyrrolidine tetrafluoroborate. It can be seen from the results recorded in Table 2 that the reaction time used in Examples 6-8 is 4 hours, and the yield can exceed 90%, especially the yield of the crude product of N,N-dimethylpyrrolidine tetrafluoroborate in Example 6 reaches 95.05%; the reaction time used in Example 10 is 12 hours, and the yield of the crude product of N,N-dimethylpyrrolidine tetrafluoroborate obtained reaches 96.48%.

[0091] The third group of experiments

[0092] The third group of experiments provides a method for preparing N,N-dimethylpyrrolidine tetrafluoroborate. The third group of experiments includes Example 11, Example 12, and Example 13. The crude N,N-dimethylpyrrolidine tetrafluoroborate product provided in Example 6 is used for recrystallization; the N,N-dimethylpyrrolidine tetrafluoroborate obtained by Example 11, Example 12, and Example 13 is placed in a vacuum oven, and the temperature of the vacuum oven is controlled to be 55°C to obtain a product with a moisture content of 147 ppm. The N,N-dimethylpyrrolidine tetrafluoroborate is then placed in a glove box and irradiated with infrared light with a wavelength of 4 μm until the moisture content of the N,N-dimethylpyrrolidine tetrafluoroborate is less than 20 ppm.

[0093] Embodiment 11

[0094] Example 11 provides a method for preparing N,N-dimethylpyrrolidine tetrafluoroborate, comprising the following steps:

[0095] 175.3 g of crude N,N-dimethylpyrrolidine tetrafluoroborate was dissolved in 87.65 g of acetonitrile, stirred at 65° C. for 15 minutes under the stirring condition of a magnetic stirrer at gear 4 and dissolved by stirring, then 876.5 g of ethanol was added, cooled to 25° C., stirred at the stirring condition of a magnetic stirrer at gear 3 for 30 minutes, and then frozen at -20° C. for 4 hours for recrystallization, and then filtered; the recrystallization step was repeated twice to obtain N,N-dimethylpyrrolidine tetrafluoroborate.

[0096] The crude N,N-dimethylpyrrolidine tetrafluoroborate product is prepared by the preparation method provided in Example 6.

[0097] Example 12

[0098] Example 12 provides a method for preparing N,N-dimethylpyrrolidine tetrafluoroborate, comprising the following steps:

[0099] S1. Dissolve 175.3 g of crude N,N-dimethylpyrrolidine tetrafluoroborate in 58.4 g of acetonitrile, stir at 65°C for 15 minutes under the stirring condition of a magnetic stirrer at gear 4 and stir to dissolve, then add 584 g of ethanol and cool to 25°C and stir at the stirring condition of a magnetic stirrer at gear 3 for 30 minutes, then freeze at -20°C for 4 hours for recrystallization, and then filter; repeat the recrystallization step twice to obtain N,N-dimethylpyrrolidine tetrafluoroborate.

[0100] The crude N,N-dimethylpyrrolidine tetrafluoroborate product is prepared by the preparation method provided in Example 6.

[0101] Embodiment 13

[0102] Example 13 provides a method for preparing N,N-dimethylpyrrolidine tetrafluoroborate, comprising the following steps:

[0103] S1. Dissolve 175.3 g of crude N,N-dimethylpyrrolidine tetrafluoroborate in 35 g of acetonitrile, stir at 65°C for 15 minutes under the stirring condition of a magnetic stirrer at gear 4 and stir to dissolve, then add 350 g of ethanol and cool to 25°C and stir at the stirring condition of a magnetic stirrer at gear 3 for 30 minutes, then freeze at -20°C for 4 hours for recrystallization, and then filter; repeat the recrystallization step twice to obtain N,N-dimethylpyrrolidine tetrafluoroborate.

[0104] The crude N,N-dimethylpyrrolidine tetrafluoroborate product is prepared by the preparation method provided in Example 6.

[0105] The N,N-dimethylpyrrolidine tetrafluoroborate provided in the third group of experiments was dried, its properties were recorded, and its yield was calculated. The recorded results are shown in Table 3.

[0106] Yield % = actual mass / theoretical mass * 100%

[0107] Table 3

[0108] Example Yield / % Characteristics Embodiment 11 57.1 White solid Example 12 64.4 White solid Example 13 87.2 White solid

[0109] It can be seen from the results recorded in Table 3 that the amount of acetonitrile used in the recrystallization process in Examples 11-13 has a great influence on the yield of the final N,N-dimethylpyrrolidine tetrafluoroborate. When the amount of acetonitrile is 19-21wt% of the crude N,N-dimethylpyrrolidine tetrafluoroborate product, a yield value of 87.2% is obtained.

[0110] Performance Testing

[0111] 1. Magnetic resonance imaging test:

[0112] The N,N-dimethylpyrrolidine tetrafluoroborate provided in Example 13 was subjected to a nuclear magnetic resonance test to obtain a hydrogen nuclear magnetic resonance spectrum. Figure 1 .

[0113] pass Figure 1 The 1HNMR spectrum showed that the obtained product was N,N-dimethylpyrrole tetrafluoroborate.

[0114] From the nuclear magnetic resonance hydrogen spectrum, based on the different hydrogen peak times and peak heights, it can be clearly seen that the detected substance is N,N-dimethylpyrrole tetrafluoroborate.

[0115] 2. Moisture content test:

[0116] The moisture content of N,N-dimethylpyrrolidine tetrafluoroborate provided in Example 13 was tested, and the test results are shown in Table 4.

[0117] 3. Purity test:

[0118] The N,N-dimethylpyrrolidine tetrafluoroborate provided in Example 13 was subjected to ion chromatography test. In the ion chromatography test, a 1% ratio was used and the mobile phase was water phase for testing. The test results of the ion content (chloride ion, bromide ion, fluoride ion, sulfate ion) were shown in Table 4.

[0119] The ion chromatography test uses a 1% ratio and a mobile phase of water for testing:

[0120] 4. Trace ion content test:

[0121] The N,N-dimethylpyrrolidine tetrafluoroborate provided in Example 13 was subjected to ICP test to obtain trace ion content (potassium ion, sodium ion, calcium ion, magnesium ion). The test results are shown in Table 4.

[0122] 5. Appearance test:

[0123] The appearance of the N,N-dimethylpyrrolidine tetrafluoroborate provided in Example 13 after drying is recorded. The test results are shown in Table 4. The appearance is shown in Figure 2 .

[0124] Table 4

[0125]

[0126] It can be seen from the test results in Table 4 that the crude N,N-dimethylpyrrolidine tetrafluoroborate product obtained by using N-methylpyrrolidine, dimethyl carbonate, and tetrafluoroboric acid aqueous solution in the present application can increase the yield of N,N-dimethylpyrrolidine tetrafluoroborate to 87.2% after recrystallization. And compared with the current preparation method, the preparation method of N,N-dimethylpyrrolidine tetrafluoroborate provided by the present application uses less solvent, does not introduce halogen elements, is simple and easy to operate, and obtains N,N-dimethylpyrrolidine tetrafluoroborate with a purity greater than 99%, which can be better applied in various fields.

Claims

1. A method for preparing N,N-dimethylpyrrole tetrafluoroborate, characterized in that: The preparation method comprises the following steps: S1. N-methylpyrrolidine, methanol, and dimethyl carbonate are sequentially added to a high-pressure reactor, and the high-pressure reactor is heated to react to obtain N,N-dimethylpyrrole methyl carbonate; S2. Decolorizing N,N-dimethylpyrrole carbonate methyl ester, and adding tetrafluoroboric acid aqueous solution dropwise to the decolorized N,N-dimethylpyrrole carbonate methyl ester, and stirring to obtain a crude product of N,N-dimethylpyrrolidine tetrafluoroborate; S3. Recrystallize the crude product of N,N-dimethylpyrrolidine tetrafluoroborate to obtain N,N-dimethylpyrrolidine tetrafluoroborate.

2. The method for preparing N,N-dimethylpyrrole tetrafluoroborate according to claim 1, characterized in that: In S1, the high-pressure reactor is heated to 135-150°C.

3. The method for preparing N,N-dimethylpyrrole tetrafluoroborate according to claim 1, characterized in that: The reaction time in S1 is 12-20 hours.

4. The method for preparing N,N-dimethylpyrrole tetrafluoroborate according to any one of claims 1 to 3, characterized in that: The molar ratio of N-methylpyrrolidine and dimethyl carbonate in S1 is 1:(1-1.7), and the mass ratio of methanol to N,N-dimethylpyrrole methyl carbonate is (1-1.2):

1.

5. The method for preparing N,N-dimethylpyrrole tetrafluoroborate according to claim 1, characterized in that: In S2, water and activated carbon are used to decolorize N,N-dimethylpyrrole carbonate methyl ester, the mass ratio of water to N,N-dimethylpyrrole carbonate methyl ester is (1-2):1, and the amount of activated carbon added is 3-5wt% of N,N-dimethylpyrrole carbonate methyl ester.

6. The method for preparing N,N-dimethylpyrrole tetrafluoroborate according to claim 1, characterized in that: The molar ratio of the tetrafluoroboric acid aqueous solution to the N,N-dimethylpyrrole carbonate methyl ester in S2 is 1:(1-1.3).

7. The method for preparing N,N-dimethylpyrrole tetrafluoroborate according to claim 1, characterized in that: The method for recrystallizing the crude N,N-dimethylpyrrolidine tetrafluoroborate product in S3 comprises: The crude product of N,N-dimethylpyrrolidine tetrafluoroborate is dissolved in acetonitrile, and then ethanol is added for stirring, and frozen recrystallization is performed at low temperature. The recrystallization steps are repeated to obtain N,N-dimethylpyrrolidine tetrafluoroborate.

8. The method for preparing N,N-dimethylpyrrole tetrafluoroborate according to claim 7, characterized in that: The amount of acetonitrile added is 10-30wt% of the crude product of N,N-dimethylpyrrolidine tetrafluoroborate, and the mass ratio of ethanol to acetonitrile is (5-10):

1.

9. The method for preparing N,N-dimethylpyrrole tetrafluoroborate according to claim 7, characterized in that: The amount of acetonitrile added is 19-21 wt % of the crude N,N-dimethylpyrrolidine tetrafluoroborate product.

10. The method for preparing N,N-dimethylpyrrole tetrafluoroborate according to claim 7, characterized in that: The conditions for the freeze-recrystallization at low temperature are freezing at -10 to -30°C for 3-4 hours for recrystallization, and then filtering; repeating the recrystallization step 1-3 times to obtain N,N-dimethylpyrrolidine tetrafluoroborate.

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