Preparation method of DNDMH nitration reagent

Abstract

The invention discloses a preparation method of a DNDMH nitration reagent, which specifically comprises the following steps: dissolving lithium nitrate in nitromethane, sequentially adding trifluoroacetic anhydride and 5, 5-dimethylhydantoin in an ice-water bath at 0 DEG C, and stirring overnight; removing the solvent under reduced pressure, slowly dropwise adding a saturated sodium bicarbonate solution into residues under stirring for quenching treatment, then adding dichloromethane for extraction, combining organic phases, drying with anhydrous sodium sulfate, and removing the solvent under reduced pressure to obtain the DNDMH nitration reagent. The DNDMH nitration reagent prepared by the method provided by the invention not only solves the problems that the use of ammonium nitrate is easy to explode and has high risks of operation and storage, but also realizes the purpose that DNDMH can be more safely put into the nitration process of a compound; in addition, the DNDMH nitration reagent synthesized by the method is simple to separate and purify and relatively high in purity, the yield can reach 83% or above, and commercialization can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of nitrating reagents, and particularly relates to a preparation method of a DNDMH nitrating reagent. Background Art

[0002] Dinitro-5,5dimethylhydantoin, hereinafter referred to as DNDMH (N,N-dinitrodimethylhydantoin) nitrating reagent, is a new type of nitrating reagent and has application prospects in the nitration reaction of organic compounds. However, its original preparation method uses ammonium nitrate and has an explosion risk, making it unable to meet commercial applications. Therefore, developing a DNDMH nitrating reagent with good process safety is still one of the main topics for current researchers to overcome. Summary of the Invention

[0003] In view of this, the main object of the present invention is to provide a preparation method of a DNDMH nitrating reagent, and the technical problem to be solved is to replace ammonium nitrate originally required for synthesizing DNDMH with safer and more easily available nitrate types, such as lithium nitrate, etc., for synthesizing a more convenient, safer and batch-preparable DNDMH nitrating reagent for commercial use, so as to solve the problems of safety hazards and difficulty in obtaining when using ammonium nitrate.

[0004] To achieve the above object, the technical solution of the present invention is realized as follows: A preparation method of a DNDMH nitrating reagent, characterized in that the method uses 5,5-dimethylhydantoin, lithium nitrate, and trifluoroacetic anhydride as raw materials and nitromethane as a solvent for reaction; the chemical structural formula of the DNDMH nitrating reagent is as follows:

[0005]

[0006] Preferably, the method is specifically as follows: Dissolve lithium nitrate in nitromethane, and successively add trifluoroacetic anhydride and 5,5-dimethylhydantoin under an ice-water bath at 0°C, and stir overnight; remove the solvent under reduced pressure, slowly add a saturated sodium bicarbonate solution dropwise to the residue under stirring for quenching treatment, then add dichloromethane for extraction, combine the organic phases, dry with anhydrous sodium sulfate, and remove the solvent under reduced pressure to obtain the DNDMH nitrating reagent.

[0007] Preferably, the molar ratio of 5,5-dimethylhydantoin, trifluoroacetic anhydride, and lithium nitrate is 1:(4 - 5):(3.5 - 5.5).

[0008] Preferably, the ratio of 5,5-dimethylhydantoin to nitromethane is 1 g / (8 - 12) mL.

[0009] Preferably, the temperature of the ice-water bath is 0°C.

[0010] Compared with the prior art, the method of the present invention synthesizes the DNDMH nitrating reagent by using 5,5-dimethylhydantoin, lithium nitrate, and trifluoroacetic anhydride as raw materials and nitromethane as a solvent. This not only solves the problem of the easy explosion of ammonium nitrate, which poses high risks in operation and storage, but also achieves the purpose of safely introducing DNDMH into the nitration process of compounds. In addition, the DNDMH nitrating reagent synthesized by the method of the present invention is simple to separate and purify, has a high purity, and the yield can reach more than 83%, making it commercially available. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 1H NMR spectrum of the DNDMH nitrating reagent obtained in Example 1 of the present invention 1 ;

[0012] Figure 2 13C NMR spectrum of the DNDMH nitrating reagent obtained in Example 1 of the present invention 13 ; DETAILED DESCRIPTION OF THE INVENTION

[0013] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0014] A method for preparing a DNDMH nitrating reagent provided by an embodiment of the present invention is prepared by reacting 5,5-dimethylhydantoin, lithium nitrate, and trifluoroacetic anhydride as raw materials and nitromethane as a solvent; the chemical structural formula of the DNDMH nitrating reagent is as follows:

[0015]

[0016] In a specific implementation process, the method is specifically as follows: Lithium nitrate is added to the nitromethane solvent, and then trifluoroacetic anhydride and 5,5-dimethylhydantoin are added successively under an ice-water bath at 0 °C, and stirred overnight; the solvent is removed under reduced pressure, the residue is quenched by slowly dropping a saturated sodium bicarbonate solution with stirring, and then extracted with dichloromethane. The organic phases are combined, dried with anhydrous sodium sulfate, and the solvent is removed under reduced pressure to obtain the DNDMH nitrating reagent.

[0017] In a specific implementation process, the molar ratio of 5,5-dimethylhydantoin, trifluoroacetic anhydride, and lithium nitrate is 1:(4-5):(3.5-5.5).

[0018] In a specific implementation process, the ratio of 5,5-dimethylhydantoin to nitromethane is 1 g / (8-12) mL.

[0019] In a specific implementation process, the temperature of the ice-water bath is 0 °C.

[0020] The following are specific examples

[0021] Example 1

[0022] The DNDMH nitrating reagent provided in this Example 1 was obtained by the following method:

[0023] 1.08 g of lithium nitrate was added to a flask containing 5 mL of nitromethane. After adding 2.5 mL of trifluoroacetic anhydride under an ice bath at 0 °C, 0.5 g of 5,5-dimethylhydantoin was added thereto, and the mixture was stirred overnight. The solvent was removed under reduced pressure. The residue was quenched by slowly dropping a saturated sodium bicarbonate solution with stirring, extracted with dichloromethane, the organic phases were combined and dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure to obtain 710 mg of a white product. The 1H NMR spectrum was detected as the target product spectrum, and then further verified by 13C NMR spectrum, confirming that the obtained product was the DNDMH nitrating reagent, and the yield could reach 83.5%.

[0024] The DNDMH nitrating reagent obtained in this example was subjected to nuclear magnetic resonance detection, combined with Figure 1 and Figure 2 , and the detection data are as follows:

[0025] 1 1H NMR: (400 MHz, CDCl3) δ 1.90 (s, 6H) ppm.

[0026] 13 13C NMR: (101 MHz, CDCl3) δ 161.33, 139.06, 66.35, 21.99 ppm.

[0027] Example 2

[0028] The DNDMH nitrating reagent provided in this Example 2 was obtained by the following method:

[0029] 2.65 g of sodium nitrate was added to a flask containing 5 mL of nitromethane. After adding 2.5 mL of trifluoroacetic anhydride under an ice bath at 0 °C, 0.5 g of 5,5-dimethylhydantoin was added thereto, and the mixture was stirred overnight. The solvent was removed under reduced pressure. The residue was quenched by slowly dropping a saturated sodium bicarbonate solution with stirring, extracted with dichloromethane, the organic phases were combined and dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure to obtain 556 mg of a white product. The 1H NMR spectrum was detected as the target product spectrum, and then further verified by 13C NMR spectrum, confirming that the obtained product was the DNDMH nitrating reagent, and the yield could reach 65%.

[0030] The DNDMH nitrating reagent obtained in this example was subjected to nuclear magnetic resonance detection, and the detection data are as follows:

[0031] 11H NMR: (400 MHz, CDCl3) δ 1.91 (s, 6H) ppm.

[0032] 13 13C NMR: (101 MHz, CDCl3) δ 161.35, 139.08, 66.38, 22.02 ppm.

[0033] Example 3

[0034] The DNDMH nitrating reagent provided in this Example 3 was obtained by the following method:

[0035] 2.65 g of sodium nitrate was added to a flask containing 5 mL of nitromethane. After adding 2.5 mL of trifluoroacetic anhydride at 20 °C, 0.5 g of 5,5-dimethylhydantoin was added thereto and stirred overnight. The solvent was removed under reduced pressure. The residue was quenched by slowly dropping a saturated sodium bicarbonate solution with stirring, extracted with dichloromethane, the organic phases were combined and dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure to obtain 376 mg of a white product. The 1H NMR detected the hydrogen spectrum of the target product, and then further verified by 13C NMR, confirming that the obtained product was the DNDMH nitrating reagent, and the yield could reach 44%.

[0036] The DNDMH nitrating reagent obtained in this example was subjected to nuclear magnetic resonance detection, and the detection data was as follows:

[0037] 1 1H NMR: (400 MHz, CDCl3) δ 1.88 (s, 6H) ppm.

[0038] 13 13C NMR: (101 MHz, CDCl3) δ 161.31, 139.04, 66.32, 21.96 ppm.

[0039] Example 4

[0040] The DNDMH nitrating reagent provided in this Example 4 was obtained by the following method:

[0041] 1.08 g of lithium nitrate was added to a flask containing 5 mL of nitromethane. After adding 2.5 mL of trifluoroacetic anhydride in an ice-water bath at 20 °C, 0.5 g of 5,5-dimethylhydantoin was added thereto and stirred overnight. The solvent was removed under reduced pressure. The residue was quenched by slowly dropping a saturated sodium bicarbonate solution with stirring, extracted with dichloromethane, the organic phases were combined and dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure to obtain 564.6 mg of a white product. The 1H NMR detected the hydrogen spectrum of the target product, and then further verified by 13C NMR, confirming that the obtained product was the DNDMH nitrating reagent, and the yield could reach 66%.

[0042] Example 5

[0043] The DNDMH nitrating reagent provided in Example 5 is obtained by the following method:

[0044] 1.08 g of lithium nitrate was added to a flask containing 5 mL of dichloromethane. After adding 2.5 mL of trifluoroacetic anhydride in an ice bath at 0 °C, 0.5 g of 5,5-dimethylhydantoin was added thereto, and the mixture was stirred overnight. The solvent was removed under reduced pressure. The residue was quenched by slowly dropping saturated sodium bicarbonate solution with stirring, extracted with dichloromethane, the organic phases were combined, dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure to obtain 684 mg of a white product. The 1H NMR spectrum detected the target product's 1H NMR spectrum, and then it was further verified by 13C NMR, confirming that the obtained product was the DNDMH nitrating reagent, and the yield could reach 80%.

[0045] Example 6

[0046] The DNDMH nitrating reagent provided in Example 6 is obtained by the following method:

[0047] 1.08 g of lithium nitrate was added to a flask containing 5 mL of nitromethane. After adding 2.5 mL of trifluoroacetic anhydride in an ice bath at 0 °C, 0.5 g of 5,5-dimethylhydantoin was added thereto, and the mixture was stirred for 6 hours. The solvent was removed under reduced pressure. The residue was quenched by slowly dropping saturated sodium bicarbonate solution with stirring, extracted with dichloromethane, the organic phases were combined, dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure to obtain 682 mg of a white product. The 1H NMR spectrum detected the target product's 1H NMR spectrum, and then it was further verified by 13C NMR, confirming that the obtained product was the DNDMH nitrating reagent, and the yield could reach 79.8%.

[0048] By analyzing the Figure 1 and Figure 2 and the NMR detection data of the products obtained in Comparative Example 1 - Example 6, it can be seen that the DNDMH nitrating reagent prepared by the method of the present invention has high purity and a yield as high as 83.5%.

[0049] In summary, in the method of the present invention, by replacing the nitrate in the original step of synthesizing DNDMH and reacting under the same conditions, the structure of the product was determined and the final yield was calculated. By comparison, the best nitrate replacing ammonium nitrate was lithium nitrate. This not only solves the problem that ammonium nitrate is prone to explosion and has high risks in operation and storage, but also achieves the purpose of safely introducing DNDMH into the nitration process of compounds. In addition, the DNDMH nitrating reagent synthesized by the method of the present invention is simple to separate and purify, has high purity, and the yield can reach more than 83%, and can be applied commercially.

[0050] As described above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A preparation method of a DNDMH nitrating reagent, characterized in that, This method is prepared by using 5,5-dimethylhydantoin, lithium nitrate, and trifluoroacetic anhydride as raw materials and nitromethane as a solvent; the chemical structural formula of this DNDMH nitrating reagent is as follows:

2. The preparation method of the DNDMH nitrating reagent according to claim 1, wherein, Specifically, this method involves dissolving lithium nitrate in nitromethane, and sequentially adding trifluoroacetic anhydride and 5,5-dimethylhydantoin under an ice-water bath at 0 °C, followed by stirring overnight; the solvent is removed under reduced pressure, and the residue is quenched by slowly dropping a saturated sodium bicarbonate solution with stirring, then dichloromethane is added for extraction, the organic phases are combined, dried over anhydrous sodium sulfate, and the solvent is removed under reduced pressure to obtain the DNDMH nitrating reagent.

3. The preparation method of the DNDMH nitrating reagent according to claim 2, wherein The molar ratio of the 5,5-dimethylhydantoin, trifluoroacetic anhydride, and lithium nitrate is 1:(4 - 5):(3.5 - 5.5).

4. The preparation method of the DNDMH nitrating reagent according to claim 2, wherein, The ratio of the 5,5-dimethylhydantoin to the nitromethane is 1 g / (8 - 12) mL.

5. The preparation method of the DNDMH nitrating reagent according to claim 2, characterized in that, The temperature of the ice-water bath is 0 °C.

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