A kind of diazabicyclic carbene-metal green catalyst and its synthesis method

Abstract

The present invention provides a bis(azacyclic carbene)-metal green catalyst and a synthesis method thereof. The structural formula of the catalyst is: #imgabs0# or #imgabs1#. R is one of ferric chloride, zinc chloride, magnesium chloride, manganese chloride, aluminum chloride, ferric bromide, zinc bromide, magnesium bromide, manganese bromide or aluminum bromide. #imgabs2# is an unsubstituted straight-chain alkyl group, and n is an integer from 2 to 10. The bis(azacyclic carbene)-metal green catalyst provided by the present invention contains two azacyclic carbene active catalytic centers, forming a bis(azacyclic carbene) structure, and the types and lengths of the functional groups connecting the bis(azacyclic carbene) imidazolyl groups are adjustable. Non-toxic or low-toxic metal salts are coordinated with the azacyclic carbene structure to meet the requirements of chemical reactions for catalytic activity. The green catalyst can be used to catalyze polymerization reactions dominated by nucleophilic reactions, reduce the harm to the environment and human body while ensuring catalytic activity, enhance the biocompatibility of polymer materials, and can also achieve precise regulation of the structure of polymer materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a bis(azolium) carbene-metal green catalyst and a synthesis method thereof. Background Art

[0002] Catalysts are an essential auxiliary in the synthesis of polymer materials, and play a key role in controlling the reaction kinetics of polymer material synthesis and the final properties of products. For example, organotin and organobismuth are widely used catalytic systems in the synthesis of polyurethanes, polyesters and the ring-opening of lactide, but the environmental harm of such heavy metal catalysts limits their development. In addition, the heavy metal catalysts remaining in the polymer are liable to cause material aging and affect the application of the material in the biomedical field. Although amine catalysts can also catalyze such reactions and have low toxicity, on the one hand, the catalytic efficiency of amines is not as good as that of organometals, and on the other hand, the use of amine catalysts will cause some odors in the product. Therefore, it is of great significance to find a more effective, widely applicable and environmentally friendly green catalyst.

[0003] At present, organic small molecule catalysts have great potential in polymer synthesis. In recent years, N-Heterocyclic Carbenes (NHC) have attracted extensive attention due to their unique electronic structure and inductive effect. Olivier et al. (Polymer Chemistry, 2012, 3(3): 605-608) demonstrated that NHC has a catalytic effect on aliphatic diisocyanates and diols to form soluble linear polyurethanes, and has higher catalytic activity than tertiary amines (DABCO), and can react at a lower loading (1%) and a lower temperature (30-50 °C). Bhasher et al. (Polyurethane Synthesis 2009, 15(13): 3103-3109) synthesized CO2-protected NHC and NHC-Sn delayed catalysts, and these catalysts exceed the existing industrial catalysts in terms of catalytic activity and induction period. Gregory W et al. (Journal of the American Chemical Society 2003 124(6): 914-5.) found that the structure of N-Heterocyclic Carbene was used to catalyze the ring-opening reaction of lactide and lactone, and it was found that imidazole carbene has higher catalytic efficiency than thiophene carbene structure. However, pure NHC still cannot meet the requirements of industrial catalysis, but the increasing environmental protection requirements limit the application of heavy metal ion-containing catalysts. Therefore, the present invention designs and proposes a green, environmentally friendly and highly efficient polymer synthesis catalyst for synthesizing non-toxic or low-toxic metal ion-coordinated NHC. Summary of the Invention

[0004] The present invention provides a green catalyst of diazabicyclic carbene-metal and its synthesis method. This catalyst is non-toxic or low-toxic and environmentally friendly, and can be applied to the synthesis and preparation of green polymer materials with high biocompatibility. While achieving efficient catalysis, it broadens the application fields of polymer materials, especially their applications in the biomedical field.

[0005] The synthesis of the green catalyst of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a green catalyst of diazabicyclic carbene-metal, and its chemical formula is

[0007]

[0008] wherein, R is one of ferric chloride, zinc chloride, magnesium chloride, manganese chloride, aluminum chloride, ferric bromide, zinc bromide, magnesium bromide, manganese bromide or aluminum bromide, is an unsubstituted straight-chain alkyl group, and n is an integer from 2 to 10.

[0009] The present invention also provides a synthesis method of the green catalyst of diazabicyclic carbene-metal, which at least includes the following steps:

[0010] Under anhydrous and anaerobic conditions, add 2,4,6-trimethylaniline, glyoxal and methanol into the reactor and stir;

[0011] Add ammonium chloride, formaldehyde solution and methanol into the reactor and conduct heat treatment;

[0012] Add phosphoric acid solution into the reactor for treatment, and monitor the reaction process by thin layer chromatography; after the reaction is completed, remove the solvent, pour the reaction product into crushed ice, and add potassium hydroxide solution drop by drop to adjust the pH value of the mixture;

[0013] Extract the mixture with reagent A, dry the obtained organic layer with reagent B, evaporate and concentrate to obtain a crude product, and further purify to obtain product a;

[0014] Add reagent C, the product a and reagent D into the reactor. After the reaction is completed, remove the solvent to obtain a crude product, and put the crude product into a mixture of reagent E and reagent F for crystallization, and purify to obtain product b; and

[0015] Add product b, reagent G and tetrahydrofuran into a dry reactor for reaction. After the reaction is completed, remove the solvent, filter, and dry to obtain the final product c.

[0016] In an embodiment of the present invention, the stirring time is 24 - 48 h.

[0017] In one embodiment of the present invention, the molar ratio of ammonium chloride to formaldehyde is (1 - 2):1.

[0018] In one embodiment of the present invention, the temperature of the heat treatment is 70 °C and the time of the heat treatment is 1 h.

[0019] In one embodiment of the present invention, the time for treating with the phosphoric acid solution is 12 - 24 h, and the pH value of the mixture is adjusted to 8 - 10.

[0020] In one embodiment of the present invention, the reagent A is one or a mixture of several of ethyl acetate, dichloromethane or ether, and the reagent B is one or a mixture of several of anhydrous magnesium sulfate, anhydrous sodium sulfate or anhydrous sodium carbonate.

[0021] In one embodiment of the present invention, the reagent C is one or a mixture of several of p - dibromoxylene, 1,2 - dibromoethane, 1,3 - dibromopropane, 1,4 - dibromobutane, 1,5 - dibromopentane, 1,6 - dibromohexane, 1,7 - dibromoheptane, 1,8 - dibromooctane, 1,9 - dibromononane, 1,10 - dibromodecane, 1,2 - dichloroethane, 1,3 - dichloropropane, 1,4 - dichlorobutane, 1,5 - dichloropentane, 1,6 - dichlorohexane, 1,7 - dichloroheptane, 1,8 - dichlorooctane, 1,9 - dichlorononane or 1,10 - dichlorodecane; the reagent D is dichloromethane and / or toluene; the reagent E is one or a mixture of several of methanol, dichloromethane or ethyl acetate; the reagent F is petroleum ether and / or ether.

[0022] In one embodiment of the present invention, the reaction temperature of the reagent C, the product a and the reagent D is 60 - 110 °C, and the reaction time is 24 - 48 h.

[0023] In one embodiment of the present invention, the reagent G is selected from any one of anhydrous ferric chloride, anhydrous magnesium chloride, anhydrous zinc chloride, anhydrous manganese chloride, anhydrous aluminum chloride, anhydrous ferric bromide, anhydrous magnesium bromide, anhydrous zinc bromide, anhydrous manganese bromide or anhydrous aluminum bromide.

[0024] The present invention provides a bis - N - heterocyclic carbene - metal green catalyst and its synthesis method, which can achieve efficient catalysis and precise synthesis in the process of polymer synthesis, can be used to prepare green polymer materials that are non - toxic or low - toxic and have high biocompatibility, are environmentally friendly, and have potential application value. Moreover, the synthesized bis - N - heterocyclic carbene - metal green catalyst can not only achieve efficient catalysis, but also avoid the damage to personnel and the environment caused by the use of harmful metal ion catalysts. In addition, since the bis - N - heterocyclic carbene - metal green catalyst that is harmless to the biological environment is used for the synthesis and preparation of polymer materials, the application scope of many polymer materials can be expanded, especially in the biomedical field. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a flowchart of a synthesis method of a bis(azol-2-ylidene)carbene-metal green catalyst in the present invention.

[0027] Figure 2 It is the 1H NMR spectrum of 2,4,6-phenylimidazole in Example 1 of the present invention.

[0028] Figure 3 It is the 1H NMR spectrum of bis(azol-2-ylidene)carbene imidazolium salt in Example 1 of the present invention.

[0029] Figure 4 It is the infrared spectrum of 2-NHC-FeCl3 in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] The following illustrates the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0031] The following further elaborates on the technical solutions of the present invention in conjunction with several embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0032] The present invention provides a bis(azol-2-ylidene)carbene-metal green catalyst, and the structural formula of this catalyst is:

[0033]

[0034] Among them, R is one of ferric chloride, zinc chloride, magnesium chloride, manganese chloride, aluminum chloride, ferric bromide, zinc bromide, magnesium bromide, manganese bromide or aluminum bromide, is an unsubstituted straight-chain alkyl group, and n is an integer from 2 to 10. The obtained diazabicyclic carbene-metal green catalyst contains two diazabicyclic carbene active catalytic centers, forming a diazabicyclic carbene structure, which has high catalytic activity and can be widely used in polymerization reactions dominated by nucleophilic reactions, such as polyester, lactide ring-opening, and polyurethane synthesis. The types and lengths of the functional groups connecting the diazabicyclic carbene imidazole groups are adjustable, with high molecular designability, and can achieve the greening of the catalyst, reduce the harm to the environment and the human body, enhance the biocompatibility of polymer materials, and are expected to broaden its application in the biomedical field.

[0035] Please refer to Figure 1 As shown, the present invention also provides a synthesis method of a diazabicyclic carbene-metal green catalyst, including but not limited to steps S10-S40.

[0036] Step S10: Under anhydrous and anaerobic conditions, add 2,4,6-trimethylaniline, glyoxal, and methanol to the reactor and stir.

[0037] Step S20: Add ammonium chloride, formaldehyde solution, and methanol to the reactor and perform heat treatment.

[0038] Step S30: Add phosphoric acid solution to the reactor for treatment, and monitor the reaction process by thin-layer chromatography; after the reaction is completed, remove the solvent, pour the reaction product into crushed ice, and gradually add potassium hydroxide (KOH) solution to adjust the pH value of the mixture.

[0039] Step S40: Extract the mixture with reagent A, dry the obtained organic layer with reagent B, evaporate and concentrate to obtain a crude product, and further purify to obtain product a.

[0040] Step S50: Add reagent C, product a, and reagent D to the reactor. After the reaction is completed, remove the solvent to obtain a crude product, and crystallize the crude product in a mixture of reagent E and reagent F, and purify to obtain product b.

[0041] Step S60: Add product b, reagent G, and tetrahydrofuran to a dry reactor for reaction. After the reaction is completed, remove the solvent, filter, and dry to obtain the final product c.

[0042] Please refer to Figure 1 As shown, in step S10, in an embodiment of the present invention, for example, introduce a protective gas into the reactor to remove oxygen in the reactor, and the protective gas is, for example, nitrogen or argon. After adding 2,4,6-trimethylaniline, glyoxal, and methanol to the reactor, stir at room temperature to form a homogeneous mixed solution, where methanol is used as a solvent, and the stirring time is, for example, 24-48 h.

[0043] Please refer to Figure 1 As shown, in step S20, in an embodiment of the present invention, the molar ratio of ammonium chloride to formaldehyde added is, for example, (1 - 2):1. After adding ammonium chloride, formaldehyde solution and methanol to the reactor, heat treatment is carried out, and the temperature of the heat treatment is, for example, 70 °C, and the time of the heat treatment is, for example, 1 h. In an embodiment of the present invention, the reactor is heated under the condition of condensation reflux, which can prevent the volatilization of glyoxal, formaldehyde, methanol and other substances during the heat treatment, thereby reducing the loss of raw materials.

[0044] Please refer to Figure 1 As shown, in step S30, in an embodiment of the present invention, the reaction conditions in step S20 are kept unchanged, that is, under the condition of condensation reflux and at a temperature of 70 °C, phosphoric acid is added to the reactor to provide an acidic environment for the reaction of 2,4,6-trimethylaniline and glyoxal. In an embodiment of the present invention, for example, thin layer chromatography (TLC) is used to monitor the reaction process, and the reaction time in this process is, for example, 12 - 24 h. After the reaction is completed, the solvent in the mixed solution is removed, the reaction product is poured into crushed ice, and KOH solution is added dropwise to adjust the pH value of the mixture, for example, the pH value of the mixture is adjusted to 8 - 10.

[0045] Please refer to Figure 1 As shown, in step S40, in an embodiment of the present invention, the mixture is extracted with reagent A, and the organic layer collected after extraction is dried with reagent B and evaporated to concentrate, and the obtained crude product is further purified to obtain product a, and product a is 2,4,6-phenylimidazole, and the synthesis route of product a is, for example

[0046] In an embodiment of the present invention, reagent A is, for example, selected from one or several mixtures of ethyl acetate, dichloromethane or ether, etc., and reagent B is, for example, selected from one or several mixtures of anhydrous magnesium sulfate, anhydrous sodium sulfate or anhydrous sodium carbonate, etc.

[0047] Please refer to Figure 1As shown, in step S50, in an embodiment of the present invention, the prepared product a, reagent C, and reagent D are added to a reactor for reaction, and the reaction temperature is, for example, 60 - 110°C, and the reaction time is, for example, 24 - 48 h. Among them, reagent C is, for example, selected from one or several mixtures of p - xylylene dibromide, 1,2 - dibromoethane, 1,3 - dibromopropane, 1,4 - dibromobutane, 1,5 - dibromopentane, 1,6 - dibromohexane, 1,7 - dibromoheptane, 1,8 - dibromooctane, 1,9 - dibromononane, 1,10 - dibromodecane, 1,2 - dichloroethane, 1,3 - dichloropropane, 1,4 - dichlorobutane, 1,5 - dichloropentane, 1,6 - dichlorohexane, 1,7 - dichloroheptane, 1,8 - dichlorooctane, 1,9 - dichlorononane, or 1,10 - dichlorodecane, etc., and reagent D is, for example, selected from dichloromethane and / or toluene, etc. After the reaction is completed, the solvent is evaporated to remove to obtain a crude product, and the crude product is put into a mixture of reagent E and reagent F for recrystallization to obtain product b, and product b is a diazabicyclic carbene imidazolium salt. In an embodiment of the present invention, reagent E is, for example, one or several mixtures of methanol, dichloromethane, or ethyl acetate, etc., and reagent F is, for example, petroleum ether and / or diethyl ether, etc. In Example 1, reagent C is, for example, selected as p - xylylene dibromide, reagent D is, for example, selected from dichloromethane, and the synthesis route of product b is, for example:

[0048]

[0049] Please refer to Figure 1As shown, in step S50, in an embodiment of the present invention, the prepared product b, reagent G, and tetrahydrofuran (THF) are added together to a dry reactor for reaction. The reaction temperature is, for example, 60°C, and the reaction time is, for example, 8 - 12 h. After the reaction is completed, the solvent is removed. After filtration, it is dried in a dryer to obtain the final product c, where product c is a diazabicycloalkene-metal green catalyst. In an embodiment of the present invention, reagent G is, for example, selected from any one of anhydrous ferric chloride, anhydrous magnesium chloride, anhydrous zinc chloride, anhydrous manganese chloride, anhydrous aluminum chloride, anhydrous ferric bromide, anhydrous magnesium bromide, anhydrous zinc bromide, anhydrous manganese bromide, or anhydrous aluminum bromide, etc. Non-toxic or low-toxic metal salts such as (ferric chloride, zinc chloride, manganese chloride, magnesium chloride, etc.) are used to coordinate with the azabicycloalkene structure to meet the requirements of catalytic activity for chemical reactions. Moreover, the synthesized diazabicycloalkene-metal green catalyst contains two azabicycloalkene active catalytic centers in its molecular structure, forming a diazabicycloalkene structure. The types and lengths of the functional groups connecting the diazabicycloalkene imidazole groups are adjustable, enabling precise regulation of the polymer material structure and achieving precise synthesis. This green catalyst can be widely used in catalyzing polymerization reactions dominated by nucleophilic reactions, such as polyester, lactide ring-opening, and polyurethane synthesis, etc. While ensuring catalytic activity, it realizes the greening of the catalyst, reduces the harm to the environment and the human body, enhances the biocompatibility of polymer materials, and is expected to broaden its application in the biomedical field.

[0050] Please refer to Figures 1 to 4 As shown, in Example 1, reagent G is, for example, selected from anhydrous ferric chloride, and product c and the synthesis route are, for example:

[0051] Figure 2 1H NMR spectrum of 2,4,6-phenylimidazole Figure 1 H NMR (600 MHz, DMSO), where 1H NMR δ = 7.56 (1.0H, m), 7.21 (1.0H, m), 7.14 (1.0H, m), 7.07 (2.0H, m), 2.53 (3.0H, m), 1.95 (6.0H, m). Figure 2 All the signal peaks in the 1H NMR and the spectrum in it are consistent with the structure of 2,4,6-phenylimidazole. Figure 3 1H NMR spectrum of diazabicycloalkene imidazole salt (2-NHC), where 1H NMR δ = 9.70 (2.0H, m), 8.14 (2.0H, m), 8.13 (2.0H, m), 8.01 (2.0H, m), 7.60 (4.0H, m), 7.20 (4.0H, m), 5.62 (4.0H, m), 2.37 (6.0H, m), 2.05 (12.0H, m). Figure 3All the signal peaks in the 1H NMR spectrum are consistent with the structure of the diazabicyclic carbene imidazolium salt (2-NHC). As Figure 4 shown, the peak shapes of 2-NHC and 2-NHC-FeCl3 are basically the same, and most of the peaks appear between 700-1750 cm -1 . The peaks at 2953 cm -1 and 2856 cm -1 correspond to the stretching vibrations of the C-H bonds of the symmetric phenyl group. The peaks at 1600 cm -1 , 1540 cm -1 and 1206 cm -1 correspond to the C=N bond, C=C bond, and C-N bond of NHC respectively. And 2-NHC-FeCl3 shows a new peak at 1587 cm -1 , which confirms the coordination bond between NHC and FeCl3. Therefore, the infrared spectroscopy (FT-IR) data clearly prove the successful synthesis of NHC and NHC-FeCl3 catalysts.

[0052] Hereinafter, the present invention will be more specifically explained by reference to examples, which should not be construed as restrictive. Appropriate modifications can be made within the scope consistent with the gist of the present invention, and all of them fall within the technical scope of the present invention.

[0053] Example 1

[0054] Under anhydrous and anaerobic conditions, 2,4,6-trimethylaniline, glyoxal, and methanol were added to the reactor and stirred at room temperature for 24 h.

[0055] Ammonium chloride and formaldehyde were added to the reactor in a molar ratio of 1:2, and a methanol solution was added, and the reaction was carried out at 70 °C for 1 h.

[0056] H3PO4 solution was added to the mixed solution, and the reaction was continued at 70 °C for 24 h. The reaction process was monitored by TLC. After the reaction was completed, the solvent was removed, and the reaction mixture was poured into crushed ice and KOH solution was added dropwise to adjust the pH to 9.

[0057] The mixture was extracted with ethyl acetate, and the collected organic layer was dried with anhydrous magnesium sulfate. After evaporation and concentration, the crude product was purified to obtain 2,4,6-phenylimidazole.

[0058] 1,4-Bis(bromomethyl)benzene, 2,4,6-phenylimidazole, and dichloromethane were added to the reactor. After the reaction was completed, the solvent was removed, and the crude product was recrystallized with methanol / ether to obtain the product diazabicyclic carbene imidazolium salt.

[0059] Under anhydrous and anaerobic conditions, a diazabicyclic carbene imidazolium salt, anhydrous iron(III) chloride, and THF were added to a reactor for reaction. After the reaction was completed, the solvent was removed. After filtration and drying, the final product 2-NHC-FeCl3 was obtained.

[0060] Example 2

[0061] Under anhydrous and anaerobic conditions, 2,4,6-trimethylaniline, glyoxal, and methanol were added to a reactor and stirred at room temperature for 24 h.

[0062] Ammonium chloride and formaldehyde were added to the reactor in a molar ratio of 1:2, and a methanol solution was added. The reaction was carried out at 70 °C for 1 h.

[0063] An H3PO4 solution was added to the mixed solution, and the reaction was continued at 70 °C for 24 h while monitoring the reaction progress by TLC. After the reaction was completed, the solvent was removed. The reaction mixture was poured into crushed ice and KOH solution was added dropwise to adjust the pH to 9.

[0064] The mixture was extracted with ethyl acetate. The collected organic layer was dried with anhydrous magnesium sulfate. After evaporation and concentration, the crude product was purified to obtain 2,4,6-phenylimidazole.

[0065] 1,4-Bis(bromomethyl)benzene, 2,4,6-phenylimidazole, and dichloromethane were added to a reactor. After the reaction was completed, the solvent was removed. The crude product was recrystallized from methanol / ether to obtain the product diazabicyclic carbene imidazolium salt.

[0066] Under anhydrous and anaerobic conditions, a diazabicyclic carbene imidazolium salt, anhydrous zinc chloride, and THF were added to a reactor for reaction. After the reaction was completed, the solvent was removed. After filtration and drying, the final product 2-NHC-ZnCl2 was obtained.

[0067] Example 3

[0068] Under anhydrous and anaerobic conditions, 2,4,6-trimethylaniline, glyoxal, and methanol were added to a reactor and stirred at room temperature for 24 h.

[0069] Ammonium chloride and formaldehyde were added to the reactor under the condition of a molar ratio of 1:2, and a methanol solution was added. The reaction was carried out at 70 °C for 1 h. An H3PO4 solution was added to the mixed solution, and the reaction was continued at 70 °C for 24 h while monitoring the reaction progress by TLC. After the reaction was completed, the solvent was removed. The reaction mixture was poured into crushed ice and KOH solution was added dropwise to adjust the pH to 9.

[0070] The mixture was extracted with ethyl acetate. The collected organic layer was dried with anhydrous magnesium sulfate. After evaporation and concentration, the crude product was purified to obtain 2,4,6-phenylimidazole.

[0071] 1,4-dibromobutane, 2,4,6-phenylimidazole and toluene were added to the reactor. After the reaction was completed, the solvent was removed, and the crude product was recrystallized with methanol / ether to obtain the product diazacyclic carbene imidazolium salt.

[0072] Under anhydrous and anaerobic conditions, diazacyclic carbene imidazolium salt, anhydrous ferric chloride and THF were added to the reactor for reaction. After the reaction was completed, the solvent was removed. After filtration and drying, the final product C4-2NHC-FeCl3 was obtained.

[0073] Example 4

[0074] Under anhydrous and anaerobic conditions, 2,4,6-trimethylaniline, glyoxal and methanol were added to the reactor and stirred at room temperature for 24 h.

[0075] Ammonium chloride and formaldehyde were added to the reactor under the condition of a molar ratio of 1:2, and a methanol solution was added, and the reaction was carried out at 70 °C for 1 h.

[0076] H3PO4 solution was added to the mixed solution, and the reaction was continued at 70 °C for 24 h, and the reaction process was monitored by TLC. After the reaction was completed, the solvent was removed, and the reaction mixture was poured into crushed ice and KOH solution was added dropwise to adjust the pH to 9.

[0077] The mixture was extracted with ethyl acetate, the collected organic layer was dried with anhydrous magnesium sulfate, and after evaporation and concentration, the crude product was purified to obtain 2,4,6-phenylimidazole.

[0078] 1,4-dibromobutane, 2,4,6-phenylimidazole and toluene were added to the reactor. After the reaction was completed, the solvent was removed, and the crude product was recrystallized with methanol / ether to obtain the product diazacyclic carbene imidazolium salt.

[0079] Under anhydrous and anaerobic conditions, diazacyclic carbene imidazolium salt, anhydrous zinc chloride and THF were added to the reactor for reaction. After the reaction was completed, the solvent was removed. After filtration and drying, the final product C4-2NHC-ZnCl2 was obtained.

[0080] In summary, the present invention provides a bis(azolium) carbene-metal green catalyst and a synthesis method thereof. By changing the structure of the azolium carbene or coordinating the azolium carbene with different non-toxic or low-toxic metals, controlled living polymerization can be achieved, enabling precise synthesis of polymers. By regulating the synthesis rate of the polymer materials, the process time can be saved, and the invention has potential application value. Moreover, the bis(azolium) carbene-metal green catalyst synthesized by the present invention can not only achieve efficient catalysis but also replace traditional harmful metal ion catalysts, avoiding the damage to personnel and the environment caused by harmful metal ion catalysts. In addition, since the bis(azolium) carbene-metal green catalyst harmless to the biological environment is used for synthesizing and preparing polymer materials, the technical barrier that polymer materials cannot be widely applied in the biomedical field is broken, making it possible for polymer material design to be applied in a wider range of biomedical applications.

[0081] The above description is only a preferred embodiment of the present application and an explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by the specific combination of the above technical features. It should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, a technical solution formed by mutually replacing the above features with the (but not limited to) technical features having similar functions disclosed in the present application.

[0082] Except for the technical features described in the specification, the remaining technical features are well-known to those skilled in the art. To highlight the innovative features of the present invention, the remaining technical features are not described herein again.

Claims

1. A method for synthesizing a diazabicyclic carbene-metal green catalyst, characterized in that, Comprising at least the following steps: Under anhydrous and anaerobic conditions, add 2,4,6-trimethylaniline, glyoxal and methanol into a reactor and stir; Add ammonium chloride, formaldehyde solution and methanol into the reactor and conduct heat treatment; Add phosphoric acid solution into the reactor for treatment, and monitor the reaction process by thin layer chromatography; after the reaction is completed, remove the solvent, pour the reaction product into crushed ice, and add potassium hydroxide solution drop by drop to adjust the pH value of the mixture; Extract the mixture with reagent A, dry the obtained organic layer with reagent B, evaporate and concentrate to obtain a crude product, and further purify to obtain product a; Add reagent C, the product a and reagent D into a reactor, after the reaction is completed, remove the solvent to obtain a crude product, and crystallize the crude product in a mixture of reagent E and reagent F, and purify to obtain product b; and Add product b, reagent G and tetrahydrofuran into a dry reactor for reaction, after the reaction is completed, remove the solvent, filter, and dry to obtain the final product c; Wherein, the reagent G is any one of anhydrous ferric chloride, anhydrous magnesium chloride, anhydrous zinc chloride, anhydrous manganese chloride, anhydrous aluminum chloride, anhydrous ferric bromide, anhydrous magnesium bromide, anhydrous zinc bromide, anhydrous manganese bromide or anhydrous aluminum bromide; The time for adding the phosphoric acid solution for treatment is 12-24 h, and the pH value of the mixture is adjusted to 8-10; The reagent C is one or a mixture of several of p-xylene dibromide, 1,2-dibromoethane, 1,3-dibromopropane, 1,4-dibromobutane, 1,5-dibromopentane, 1,6-dibromohexane, 1,7-dibromoheptane, 1,8-dibromooctane, 1,9-dibromononane, 1,10-dibromodecane, 1,2-dichloroethane, 1,3-dichloropropane, 1,4-dichlorobutane, 1,5-dichloropentane, 1,6-dichlorohexane, 1,7-dichloroheptane, 1,8-dichlorooctane, 1,9-dichlorononane or 1,10-dichlorodecane; The reagent D is dichloromethane and / or toluene.

2. The synthesis method of the diazabicyclic carbene-metal green catalyst according to claim 1, characterized in that, The stirring time is 24-48 h.

3. The synthesis method of the diazabicyclic carbene-metal green catalyst according to claim 1, wherein The molar ratio of the ammonium chloride to the formaldehyde is (1-2):

1.

4. The synthesis method of the diazabicyclic carbene-metal green catalyst according to claim 1, characterized in that, The temperature of the heat treatment is 70 °C, and the time of the heat treatment is 1 h.

5. The synthesis method of the diazabicyclic carbene-metal green catalyst according to claim 1, characterized in that, The reagent A is one or a mixture of several of ethyl acetate, dichloromethane or ether, and the reagent B is one or a mixture of several of anhydrous magnesium sulfate, anhydrous sodium sulfate or anhydrous sodium carbonate.

6. The synthesis method of the diazabicyclic carbene-metal green catalyst according to claim 1, characterized in that, The reagent E is one or a mixture of several of methanol, dichloromethane or ethyl acetate; the reagent F is petroleum ether and / or ether.

7. The synthesis method of the diazabicyclic carbene-metal green catalyst according to claim 1, characterized in that, The reaction temperature of the reagent C, the product a and the reagent D is 60-110 °C, and the reaction time is 24-48 h.

8. A bis(azolium) carbene-metal green catalyst obtained by the synthesis method according to claim 1, characterized in that, The structural formula is as follows: Formula I; or Formula II; Among them, R is one of ferric chloride, zinc chloride, magnesium chloride, manganese chloride, aluminum chloride, ferric bromide, zinc bromide, magnesium bromide, manganese bromide or aluminum bromide, is an unsubstituted straight-chain alkyl group, and n is an integer from 2 to 10.

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