A method for synthesizing isobutylene hydrazine

Abstract

The application discloses a synthesis method of isobutylene hydantoin, and belongs to the technical field of drug production process innovation, and is characterized by comprising the following steps: taking hydantoin and isobutyl aldehyde as raw materials, taking polyionic liquid SP-PIL-OH as a catalyst, taking deionized water as a solvent, and reacting under a reflux state for 8-12 hours; after the reaction is completed, isobutylene hydantoin is prepared through extraction, concentration and drying; the application prepares polyionic liquid SP-PIL-OH containing a spiropyran, which is used as a catalyst to catalyze the hydrolysis of benzaldehyde hydantoin to generate isobutylene hydantoin; through experiments, it is found that the aforementioned alkaline polyionic liquid can be well recycled when used as a catalyst to prepare isobutylene hydantoin, the yield of isobutylene hydantoin is improved, and the technical difficulties of large alkali consumption, low yield and large three-waste emission in the prior art are effectively solved.

Description

TECHNICAL FIELD

[0001] The application provides a synthesis method of isobutylene hydantoin, and belongs to the technical field of pharmaceutical production process innovation (organic compounds). BACKGROUND

[0002] Isobutylene hydantoin, also known as 5-isopropylidene hydantoin or 5-(2-propylidene) imidazolidine-2,4-dione, is applied to drug synthesis, is a synthesis precursor of alpha-ketoisocaproic acid and its salt (one of the intermediates of compound alpha-keto acid tablets), and usually plays an important role in analgesics for pain and fever. Compound alpha-keto acid tablets are one of the drugs for treating uremia, provide essential amino acids for patients with kidney disease and minimize the intake of amino nitrogen, and have played a good role in slowing down the deterioration of kidney function. In the treatment of uremic diseases, it has a significant medical effect. The preparation method of isobutylene hydantoin mainly includes the hydantoin method. The reaction uses hydantoin and isobutyl aldehyde as raw materials. Since isobutyl aldehyde is an aliphatic aldehyde, the reactivity of aliphatic aldehyde ketone compounds is stronger than that of aromatic aldehyde ketone compounds, so the selection of catalyst in the reaction using isobutyl aldehyde as the raw material requires higher than that of aromatic aldehyde ketone. For example, when a strong base is used as a catalyst, isobutyl aldehyde is prone to side reactions, so only a weak base can be selected as a catalyst, but this also brings certain disadvantages. In the reaction, the amount of catalyst needs to be greatly increased to make the reaction proceed. At present, it is disclosed that in the master's thesis of Dingwei, "Synthesis of several alpha-keto acids and alpha-keto acid salts by hydantoin method", and in the article of Huajinxiu et al. in Chemical Industry Journal, "Synthesis of several alpha-keto acid salts by hydantoin method", 0.8 times the molar amount of potassium bicarbonate is used to prepare isobutylene hydantoin, and the yield is 81.0%. Patent CN104058954 A discloses a co-catalysis of sodium hydroxide and ethanolamine. Patent CN113735776A discloses a method for preparing isobutylene hydantoin using ammonia water (with a molar ratio of 1:1 to hydantoin) as a catalyst. Regardless of which alkaline substance is used as a catalyst, the amount of base used is too large, the reaction generates a large amount of waste, too much acid is used in neutralization, the yield is low, and the cost is high. Therefore, it is urgent to find a catalyst to replace the high-dose alkali, simplify the reaction steps, and improve the yield of isobutylene hydantoin. SUMMARY

[0003] In view of the problems in the prior art, the purpose of the present application is to provide a catalyst that can replace traditional organic bases and inorganic bases, thereby reducing the amount of alkali used in post-processing and improving the yield of isobutylene hydantoin, and applying it to the synthesis of isobutylene hydantoin.

[0004] The technical scheme adopted by the present application is as follows:

[0005] The application relates to a synthesis method of isobutylene hydantoin, characterized by comprising the following steps: taking hydantoin and isobutyl aldehyde as raw materials, taking a polyionic liquid (SP-PIL-OH) catalyst, taking deionized water as a solvent, and reacting under a reflux state for 8-12 hours to obtain isobutylene hydantoin.

[0006] The reaction flow of the application is as follows:

[0007]

[0008] Further preferred settings are:

[0009] The reaction raw materials are hydantoin and isobutyl aldehyde; the amount of hydantoin and isobutyl aldehyde is hydantoin:isobutyl aldehyde=1:1-1.5 (molar ratio).

[0010] The reaction condition is refluxing under a reflux state and magnetic stirring for 8-12 hours.

[0011] After the reaction is completed, the reaction mother liquor is extracted, separated, dried and concentrated to obtain white solid, which is isobutylene hydantoin product.

[0012] After the reaction is completed, the reaction mother liquor after extraction and separation can be reused.

[0013] In the reaction, the catalyst is a polyionic liquid (SP-PIL-OH), and the amount of the catalyst is 1%-10% of the mass of the hydantoin.

[0014] The polyionic liquid (SP-PIL-OH) has the following structural formula:

[0015]

[0016] The polyionic liquid SP-PIL-OH is prepared by the following method:

[0017] (1) Preparation of bromohexyl-6-nitrospiropyran SPEt:

[0018] 2,3,3-trimethyl-3-hydro-indole and 1,6-dibromohexane are dissolved in acetonitrile, and reflux reaction is carried out under inert gas protection; the obtained product and 5-nitrosalicylaldehyde are dissolved in methanol, triethylamine is added, and reaction is carried out under inert gas protection to obtain bromohexyl-6-nitrospiropyran SPEt;

[0019] (2) Preparation of polyvinylimidazole PVIm:

[0020] 1-vinylimidazole and azobisisobutyronitrile are dissolved in methanol, and stirring is carried out at 60-80 DEG C for 50-70 hours to obtain polyvinylimidazole PVIm;

[0021] (3) Preparation of SP-PIL-Br containing spiropyran group polyionic liquid:

[0022] The PVIm compound and SPEt were dissolved in methanol, and reacted at 60-80°C for 80-90h under the protection of inert gas atmosphere. Then bromoethane was added, and the reaction was continued for 12-36h to obtain SP-PIL-Br containing spiropyran group polyionic liquid.

[0023] (4) Preparation of SP-PIL-OH containing spiropyran group polyionic liquid:

[0024] The SP-PIL-Br was dissolved in ethanol, and NaOH solid was added to obtain SP-PIL-OH containing spiropyran group polyionic liquid.

[0025] Further provided are:

[0026] The SP-PIL-OH polyionic liquid is prepared by the following method:

[0027] (1) Preparation of bromohexyl-6-nitrospiropyran SPEt:

[0028] 2,3,3-trimethyl-3H-indole and 1,6-dibromohexane were dissolved in acetonitrile, and refluxed overnight under the protection of inert gas atmosphere to form a deep purple solution. Filtration, concentration, and then washing with a mixture of petroleum ether and ethyl acetate, and oven drying overnight to obtain a deep purple oil. The above product and 5-nitrosalicylaldehyde were dissolved in methanol, and triethylamine was added. The mixture was reacted at 70°C for 4h under the protection of inert gas atmosphere, concentrated, and then purified by silica gel column chromatography, and oven dried to obtain bromohexyl-6-nitrospiropyran SPEt.

[0029] (2) Preparation of polyvinylimidazole PVIm:

[0030] The purified 1-vinylimidazole and azobisisobutyronitrile were dissolved in methanol, and the mixture was stirred at 70°C for 60h. The mixture was precipitated by diethyl ether, suction filtered, and vacuum dried, and then ground to obtain polyvinylimidazole PVIm.

[0031] (3) Preparation of SP-PIL-Br containing spiropyran group polyionic liquid:

[0032] The PVIm compound and SPEt were dissolved in methanol, and reacted at 70°C for 84h under the protection of inert gas atmosphere. Then bromoethane was added, and the reaction was continued for 24h. The mixture was precipitated by diethyl ether, suction filtered, and dried to obtain SP-PIL-Br containing spiropyran group polyionic liquid.

[0033] (4) Preparation of SP-PIL-OH containing spiropyran group polyionic liquid:

[0034] The SP-PIL-Br is dissolved in a proper amount of ethanol, an equivalent amount of NaOH solid is added, stirred overnight, separated after centrifugation, and precipitated with diethyl ether to obtain the liquid containing the spiropyran-based polyionic liquid SP-PIL-OH.

[0035] The beneficial effects of the present application are as follows:

[0036] 1. The present application prepares a new basic polyionic liquid (SP-PIL-OH), which is used as a catalyst to prepare isobutylene hydantoin, and has very good catalytic effect.

[0037] The polyionic liquid is a functional polyelectrolyte material containing anion and cation groups, and one of the ion groups is "fixed" on the rigid main chain, so that it has the characteristics of both ionic liquid and polymer. The structure-stable polyionic liquid can overcome the water absorption and flowability of small molecule ionic liquid, so that it can be applied in most environments. The present application prepares a spiropyran-containing polyionic liquid (SP-PIL-OH) which is used as a catalyst to catalyze the hydrolysis of benzaldehyde hydantoin to produce isobutylene hydantoin.

[0038] 2. It is found through experiments that the aforementioned basic polyionic liquid as a catalyst to prepare isobutylene hydantoin can be recycled well, improve the yield of isobutylene hydantoin, and effectively solve the technical difficulties of large amount of alkali, low yield, and large amount of three wastes in the existing process.

[0039] 3. The present application carries out the reaction at a lower temperature, avoids the safety hidden trouble caused by high-temperature reaction, is easy to control the reaction, and at the same time, the reaction operation process and post-treatment are simple.

[0040] 4. The process provided by the present application is simple, the conditions are mild, the catalyst can be recycled, the preparation cost is reduced, and at the same time, high yield and high purity products are obtained, which shows better reaction advantages and economic advantages, and is more suitable for industrialized production.

[0041] The present application is further described below through the description of the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0042] Figure 1 It is the nuclear magnetic resonance hydrogen spectrum of bromohexyloxymethyl spiropyran (SPEt) in Example 1.

[0043] Figure 2 It is the nuclear magnetic resonance hydrogen spectrum of polyvinylimidazole (PVIm) in Example 1.

[0044] Figure 3 It is the nuclear magnetic resonance hydrogen spectrum of the spiropyran-containing polyionic liquid (SP-PIL-Br) in Example 1.

[0045] Figure 4 The 1H NMR spectrum of the spiropyran-containing basic polyionic liquid (SP-PIL-OH) in Example 1 is shown.

[0046] Figure 5 The 1H NMR spectrum of isobutylenehydantoin in Example 2. Detailed Implementation

[0047] The materials and reagents used in this invention are as follows:

[0048] 2,3,3-Trimethyl-3-hydro-indole (AR) was purchased from Damas-beta; 5-nitrosalicylic acid (AR) was purchased from Damas-beta; 1,6-dibromohexane (AR) was purchased from Meryer; acetonitrile (AR) was purchased from Hangzhou Shuanglin Chemical Reagent Co., Ltd.; triethylamine (TEA, AR) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; vinylimidazole (VIm, AR) was purchased from Damas-beta; bromoethane (AR) was purchased from Huzhou Shuanglin Chemical Technology Co., Ltd.; azobisisobutyronitrile (AIBN, 99%) was purchased from Tianjin Guangfu Fine Chemical Research Institute; petroleum ether (PE, AR) was purchased from Shanghai Husheng Laboratory Equipment Co., Ltd.; ethyl acetate (EA, AR) was purchased from Shanghai Husheng Laboratory Equipment Co., Ltd.; dichloromethane (DCM, AR) was purchased from Shanghai Husheng Laboratory Equipment Co., Ltd.; methanol (MeOH, AR) was purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd.; and diethyl ether (AR) was purchased from Damas-beta.

[0049] Example 1: Preparation of spiropyran-containing polyionic liquid SP-PIL-OH

[0050] (1) Preparation of bromhexyl-6-nitrospiropyran (SPEt)

[0051] 2,3,3-Trimethyl-3-hydro-indole (5.00 g, 31.4 mmol) and 1,6-dibromohexane (15 g, 62.8 mmol) were dissolved in 25 mL of acetonitrile at room temperature and refluxed overnight at 85 °C under an inert atmosphere to produce a deep purple solution. The solution was filtered, concentrated, and then washed with a mixture of petroleum ether and ethyl acetate (PE:EA 1:2 v / v) as the washing solution. The product was dried overnight in an oven at 70 °C to obtain a deep purple oil in 89% yield.

[0052] The above product (2.45 g, 7.58 mmol) and 5-nitrosalicylaldehyde (1.26 g, 9.10 mmol) were dissolved in 25 ml of methanol, triethylamine (1.53 g, 15.16 mmol) was added, and the mixture was stirred at 70 °C for 4 h under an inert atmosphere. The mixture was concentrated and then purified by column chromatography on silica gel using PE:EA (40:1 v / v) as eluent. The product was dried in an oven at 70 °C overnight to give a green solid with a yield of 37.5%.

[0053] Product confirmation: The proton nuclear magnetic resonance spectrum of bromohexyl-6-nitrospiropyran (SPEt) is shown in Figure 2. The presence of peaks at 5.5-8.5 ppm and 1-3.5 ppm for spiropyran and bromoethane, respectively, confirmed the successful preparation of the monomer. Figure 1

[0054] (2) Preparation of polyvinylimidazole (PVIm)

[0055] The purified 1-vinylimidazole (30.8068 g, 327.3 mmol) and azobisisobutyronitrile (AIBN) (0.5522 g, 3.36 mmol) were dissolved in 60 ml of methanol (MeOH). The mixture was stirred at 70 °C for 60 h. It was precipitated by diethyl ether, suction filtered, and dried in a vacuum oven at 30 °C. Grinding gave a white powdery solid with a yield of 90%.

[0056] Product confirmation: The proton nuclear magnetic resonance spectrum of polyvinylimidazole (PVIm) is shown in Figure 3. The presence of broad peaks at 2.5-3.5 ppm and 1.5-2.5 ppm for the vinyl group on 1-vinylimidazole confirmed the successful polymerization of 1-vinylimidazole. Figure 2

[0057] (3) Preparation of spiropyran-based polyionic liquid (SP-PIL-Br)

[0058] In a 100 mL flask, PVIm (2.0 g, 21.25 mmol) and SPEt (1.0 g, 2.12 mmol) were dissolved in 30 ml of methanol, and the mixture was stirred at 70 °C for 84 h under an inert atmosphere. Bromoethane was then added, and the reaction was continued for 24 h. It was precipitated by diethyl ether, suction filtered, and dried at 70 °C. This gave 2.78 g of dark red solid

[0059] Product confirmation: The proton nuclear magnetic resonance spectrum of the spiropyran-based polyionic liquid (SP-PIL-Br) is shown in Figure 4. The presence of peaks at 5.5-8.5 ppm and 1-3.5 ppm for spiropyran and bromoethane, respectively, and the presence of broad peaks at 6-8 ppm and 8-9 ppm for polyvinylimidazole confirmed the successful preparation of the polyionic liquid. Figure 3 ​​​

[0060] (4) Preparation of spiropyran-containing polyionic liquid (SP-PIL-OH)

[0061] Dissolve 2g of SP-PIL-Br in 10mL of ethanol, add 0.35g of NaOH solid, and stir overnight. After centrifugation, separate the liquid and precipitate with diethyl ether. 0.7856g of red powder solid is obtained.

[0062] Product confirmation: by proton nuclear magnetic resonance (NMR) spectroscopy (H1N). 1 H NMR confirmed the structure of the polyionic liquid as follows: Figure 4 As shown, peaks of spiropyran and bromoethane appear at 5.5–8.5 ppm and 1–3.5 ppm, and broad peaks of polyvinylimidazolium at 6.5–8.5 ppm and 9–10 ppm are still present, proving that the overall structure of the polyionic liquid remains intact.

[0063] Example 2: Application of alkaline polyionic liquid (SP-PIL-OH) in the preparation of isobutylenehydantoin

[0064] In a 50 ml three-necked flask, 100 mg of the polyionic liquid SP-PIL-OH prepared in Example 1 was added, followed by 20 ml of deionized water. The alkaline polyionic liquid was dissolved by sonication, and 1.0 g (0.01 mol) of hydantoin was added under magnetic stirring. The mixture was heated to 60 °C in an oil bath, and 0.93 g of isobutyraldehyde (0.013 mol) was slowly added dropwise. After all the isobutyraldehyde was added, the mixture was heated to reflux and reacted for 12 h. After the reaction was completed, the mixture was cooled to room temperature, acidified with dilute sulfuric acid to pH 3, extracted with water / ethyl acetate, and the organic phases were combined, concentrated, and dried to obtain a white solid product, i.e., isobutylenehydantoin, with a yield of 91.2%.

[0065] The product's 1H NMR spectrum is as follows Figure 5 As shown: 1 H NMR (400MHz, DMSO-d6) δ10.95(s,1H),10.14(s,1H),5.36(d,J=10.1Hz,1H),2.67–2.60(m,1H),2.51(p,J=1.9Hz,1H),1.00(d,J=6.7Hz,6H).

[0066] Replacement example

[0067] The preparation methods of Examples 1-12 are the same as those of Example 2, except that the molar ratio of hydantoin to isobutyraldehyde, the catalyst and its amount are adjusted, and their effects on the reaction are tested respectively, as shown in Table 1.

[0068] Table 1

[0069] Serial number Molar ratio of hydantoin to isobutyraldehyde Catalyst and its amount Yield / % Example 1 1：1.3 Sodium bicarbonate 0.84 g 81.0 Example 2 1：1.3 Ethanolamine 0.48 g 79.3 Example 3 1：1 Polyionic liquid (SP-PIL-OH) 10 mg 30.1 Example 4 1：1.3 Polyionic liquid (SP-PIL-OH) 10 mg 33.4 Example 5 1：1.5 Polyionic liquid (SP-PIL-OH) 10 mg 33.2 Example 6 1：1 Polyionic liquid (SP-PIL-OH) 50 mg 62.4 Example 7 1：1.3 Polyionic liquid (SP-PIL-OH) 50 mg 67.4 Example 8 1：1.5 Polyionic liquid (SP-PIL-OH) 50 mg 67.6 Example 9 1：1 Polyionic liquid (SP-PIL-OH) 100 mg 88.7 Example 10 1：1.3 Polyionic liquid (SP-PIL-OH) 100 mg 91.2 Example 11 1：1.5 Polyionic liquid (SP-PIL-OH) 100 mg 90.1 Example 12 1：1.3 - - .

[0070] As can be seen from Table 1:

[0071] 1. Compared with the existing inorganic bases or organic bases such as sodium bicarbonate and ethanolamine, the polyionic liquid (SP-PIL-OH) is used as a catalyst in the catalytic synthesis of isobutylene hydantoin, which can greatly reduce the amount of base (the amount of polyionic liquid (SP-PIL-OH) is 1% of the mass of hydantoin, and a certain yield can be obtained), and can effectively improve the yield of isobutylene hydantoin.

[0072] 2. Under the same conditions, when the molar ratio of hydantoin to isobutyl aldehyde is 1:1.3, the polyionic liquid (SP-PIL-OH) The amount of polyionic liquid (SP-PIL-OH) is 50% of the mass of hydantoin (g), and the highest yield is 10% The number of times of repeated use of polyionic liquid catalyst / each time 100m Yield / % 91.2% 。

[0073] Example 3: Recycling of the catalyst

[0074] After the reaction of Example 2, the reaction liquid was extracted with ethyl acetate, and the aqueous phase reaction mother liquor obtained after separation was directly added into a 50ml three-necked flask without any treatment, 1.0g of hydantoin and 0.93g of isobutyl aldehyde were added, and the reaction conditions were consistent with those of Example 2. After the reaction, the mother liquor was continuously recovered for the next reaction, the solid product was purified in accordance with Example 2, and the yield was calculated. This cycle was repeated for 5 times, and the effect of different cycle times on the yield of the product was recorded, as shown in Table 2.

[0075] Table 2, effect of cycle times on the yield of the product

[0076] ​ ​ 1 90.2 2 90.1 3 89.3 4 89.9 5 89.6 .

[0077] As shown in Table 2:

[0078] The polyionic liquid (SP-PIL-OH) of the present application still has very good catalytic effect after being used for many times. After being recycled for 5 times, the yield can be maintained above 89%, and thus the catalyst of the present application can be recycled for more than 5 times, and has good industrial application prospect.

[0079] Summary:

[0080] 1. A new basic polyionic liquid (SP-PIL-OH) is prepared in the present application, which can be used as a catalyst to prepare isobutylene hydantoin, and has very good catalytic effect.

[0081] 2. It is found through experiments that the basic polyionic liquid (SP-PIL-OH) can be used as a catalyst to prepare isobutylene hydrazine, and can be recycled well, improve the yield, and reduce the emission of three wastes and production cost.

[0082] It can be understood that the above specific description of the application is only used to illustrate the application and is not limited to the technical solutions described in the embodiments of the application. Those skilled in the art should understand that the application can still be modified or replaced equivalently to achieve the same technical effect; as long as the use needs are met, it is within the protection scope of the application.

Claims

1. A method for synthesizing isobutylene hydrazine, characterized by, The method comprises the following steps: isobutylidene hydantoin is prepared by using hydantoin and isobutyraldehyde as raw materials, polyionic liquid SP-PIL-OH as a catalyst, deionized water as a solvent, and refluxing for 8-12 hours; the polyionic liquid SP-PIL-OH is prepared by the following method: (1) Preparation of bromohexyl-6-nitrospiropyran SPEt: 2,3,3-trimethyl-3H-indole and 1,6-dibromohexane are dissolved in acetonitrile, and refluxed under the protection of inert gas to obtain a product; the product and 5-nitrosalicylaldehyde are dissolved in methanol, triethylamine is added, and reaction is carried out under the protection of inert gas to obtain bromohexyl-6-nitrospiropyran SPEt; (2) Preparation of polyvinylimidazole PVIm: 1-vinylimidazole and azobisisobutyronitrile are dissolved in methanol, and stirred at 60-80 DEG C for 50-70 hours to obtain polyvinylimidazole PVIm; (3) Preparation of polyionic liquid SP-PIL-Br containing a spiropyran group: PVIm compound and SPEt are dissolved in methanol, and reacted at 60-80 DEG C under the protection of inert gas for 80-90 hours; then bromoethane is added, and the reaction is continued for 12-36 hours to obtain polyionic liquid SP-PIL-Br containing a spiropyran group; (4) Preparation of polyionic liquid SP-PIL-OH containing a spiropyran group: SP-PIL-Br is dissolved in ethanol, and NaOH solid is added, and reaction is carried out to obtain polyionic liquid SP-PIL-OH containing a spiropyran group.

2. The method of claim 1, wherein: In the reaction, the amount of hydantoin and isobutyraldehyde is as follows: the molar ratio of hydantoin to isobutyraldehyde is 1:1-1.

5.

3. The method of claim 1, wherein: The reaction is carried out under refluxing for 8-12 hours under magnetic stirring.

4. The method of claim 1, wherein: After the reaction is completed, cooling is carried out to room temperature, acidification, extraction, concentration and drying are carried out, and white solid isobutylidene hydantoin is obtained.

5. The method of claim 1, wherein: The reaction mother liquor obtained after extraction and liquid separation can be reused.

6. The method of claim 1, wherein: After the reaction is completed, extraction and liquid separation are carried out, and the reaction mother liquor obtained is directly added with hydantoin and isobutyraldehyde, and reaction is carried out under refluxing for 8-12 hours to obtain isobutylidene hydantoin.

7. The method for synthesizing isobutylene according to claim 1, characterized in that: In the reaction, the catalyst is polyionic liquid SP-PIL-OH, and the amount of the catalyst is 1%-10% of the mass of hydantoin.

8. The method of claim 1, wherein the isobutylene hydrazine is synthesized by the reaction of isobutylene with hydrazine hydrate in the presence of a catalyst. The polyionic liquid SP-PIL-OH is prepared by the following method: (1) Preparation of bromohexyl-6-nitrospiropyran SPEt: 2,3,3-trimethyl-3H-indole and 1,6-dibromohexane are dissolved in acetonitrile, and refluxed overnight under the protection of inert gas to form a deep purple solution; filtration, concentration, and then washing with a mixture of petroleum ether and ethyl acetate, and oven drying overnight to obtain a deep purple oil; the above product and 5-nitrosalicylaldehyde are dissolved in methanol, triethylamine is added, and reaction is carried out under the protection of inert gas for 4 hours; concentration, and then purification of the mixture by silica gel column chromatography, and oven drying to obtain bromohexyl-6-nitrospiropyran SPEt; (2) Preparation of polyvinylimidazole PVIm: 1-vinylimidazole and azobisisobutyronitrile are dissolved in methanol, and stirred at 60-80 DEG C for 50-70 hours to obtain polyvinylimidazole PVIm; The purified 1-vinylimidazole and azobisisobutyronitrile were dissolved in methanol, the mixture was stirred at 70℃ for 60h, settled by diethyl ether, suction filtered, vacuum dried, and grinded to obtain polyvinylimidazole PVIm; (3) Preparation of polyionic liquid containing spirobenzopyran group SP-PIL-Br: The PVIm compound and SPEt were dissolved in methanol, and reacted at 70℃ for 84h under the protection of inert gas atmosphere, then bromoethane was added and the reaction was continued for 24h, settled by diethyl ether, suction filtered, and dried to obtain polyionic liquid containing spirobenzopyran group SP-PIL-Br; (4) Preparation of polyionic liquid containing spirobenzopyran group SP-PIL-OH: The SP-PIL-Br was dissolved in appropriate amount of ethanol, and equal amount of NaOH solid was added, stirred overnight, separated by centrifugation, settled by diethyl ether, and polyionic liquid containing spirobenzopyran group SP-PIL-OH was obtained.

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