Palladium-nitrogen heterocyclic carbene skeleton organic porous polymer and its preparation method and application

Abstract

The present invention belongs to the field of catalysis technology, and in particular to a palladium nitrogen heterocyclic carbene skeleton organic porous polymer and its preparation method and application. The structural unit of the palladium nitrogen heterocyclic carbene skeleton organic porous polymer is as shown in Formula I or Formula II or Formula III, and the preparation method is as follows: using dimethanol formal as a cross-linking agent, 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt and polyphenyl compound are synthesized by FeCl3-catalyzed Friedel-Crafts alkylation reaction to obtain an organic porous polymer; the organic porous polymer is coordinated with PdCl2 under alkaline conditions to obtain a palladium nitrogen heterocyclic carbene skeleton organic porous polymer. The organic porous polymer has the characteristics of high stability, large specific surface area, wide pore size distribution, and can efficiently catalyze the Suzuki-Miyaura coupling reaction with chlorobenzene as a substrate; the preparation method is simple, convenient and feasible, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of catalysis technology, and in particular relates to a palladium-nitrogen heterocyclic carbene skeleton organic porous polymer and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] The palladium-catalyzed Suzuki-Miyaura (SM) cross-coupling reaction is one of the most commonly used reactions for constructing C-C bonds and is widely used in organic chemistry and materials science. Homogeneous palladium precatalysts exhibit excellent catalytic efficiency for the cross-coupling of aryl halides and arylboronic acids, but the high cost and difficulty of recycling palladium catalysts restrict their further industrial application. Furthermore, in the synthesis of pharmaceuticals and their intermediates, the amount of palladium leaching must be strictly controlled. Therefore, heterogeneous catalysis is considered a green chemical process that can avoid contamination of reaction products with heavy metal palladium.

[0004] Organic porous materials are widely used in gas adsorption, sensing, organic photoelectricity and heterogeneous catalysis due to their advantages such as large specific surface area, adjustable pore size, light weight, high stability and easy functionalization. In particular, in recent years, the use of organic porous materials as supports to support palladium catalysts for heterogeneous catalytic CC bond coupling has made great progress. Despite this, in these heterogeneous catalytic systems, aromatic iodides and bromides are still the best choices for reactant electrophiles, but there are few reports on cheaper and more readily available aromatic chlorides as reaction substrates. According to these studies based on palladium-supported organic porous polymers, palladium-supported organic porous polymers are limited by their small size or lack of electron-rich supporting ligands, resulting in much lower efficiency for aromatic chlorides.

[0005] Studies of homogeneous palladium-catalyzed SM cross-coupling reactions have shown that the structures of the ligand and precatalyst play a key role, with bulky, electron-rich ligands generally favoring the conversion, providing insights into the modification of palladium-supported organic porous polymers. Since Arduengo first reported the free, stable nitrogen-heterocyclic carbonyl (NHC) in 1991, NHC ligands have been identified as reliable alternatives to the traditional phosphine ligands used in palladium-catalyzed coupling reactions. The strong σ-electron donor and steric bulk of the NHC ligand yield Pd-NHC precatalysts with high catalytic activity. Among all the Pd-NHC complexes described in the literature, the Pd-PEPPSI precatalyst (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation) is considered a versatile, simple-to-prepare, highly active, and user-friendly catalyst, widely used in many cross-coupling reactions. However, the Pd-PEPPSI precatalyst still has the defects of having few coordination sites between palladium and ligands, easy loss of palladium ions, and weak adsorption ability of the catalyst for reactants when used in heterogeneous catalysis of SMSM cross-coupling reaction. Summary of the Invention

[0006] In order to address the deficiencies of the prior art, the present invention aims to provide a palladium-nitrogen heterocyclic carbene skeleton organic porous polymer, its preparation method, and application. In the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer provided by the present invention, the nitrogen heterocyclic carbene units are uniformly distributed in the organic polymer skeleton, providing coordination sites capable of coordinating with metal ions. The palladium ions bind to the nitrogen heterocyclic carbene skeleton through coordination and chemical bonds, reducing the loss of palladium ions, enhancing the heterogeneous catalytic recycling effect of the organic porous polymer catalyst, and efficiently catalyzing the SM cross-coupling reaction with low-activity chloroaryl hydrocarbons as substrates.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, the present invention provides a palladium-nitrogen heterocyclic carbene skeleton organic porous polymer, wherein the structural unit of the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer is as shown in Formula I, Formula II, or Formula III;

[0009]

[0010]

[0011] In a second aspect, the present invention provides a method for preparing a palladium-nitrogen heterocyclic carbene skeleton organic porous polymer as described in the first aspect, comprising the following steps:

[0012] S1. Evenly mix 1,3-bis(4-benzhydryl-2,6-diisopropylphenyl)imidazolium salt, a polyphenyl compound, dimethylformal, and an organic solvent, add a Lewis acid catalyst, and place the reaction system in an oil bath under nitrogen atmosphere with stirring to react. The obtained solid product is filtered, washed, Soxhlet extracted, and dried to obtain an organic porous polymer;

[0013] S2, adding an organic porous polymer and a base to 3-chloropyridine, then adding palladium dichloride, placing the reaction system in an oil bath and stirring for reaction, filtering, washing, Soxhlet extraction, and drying the obtained solid product to obtain the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer;

[0014] The polyphenyl compound is one of 1,3,5-triphenylbenzene, tetraphenylmethane or biphenyl.

[0015] In the above preparation method, the preparation method of the 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt comprises the following steps:

[0016] 4-bromo-2,6-diisopropylaniline and glyoxal are mixed and dissolved in methanol, formic acid is added dropwise to react to obtain a diimine compound, and then the diimine compound is mixed with paraformaldehyde and dissolved in ethyl acetate, trimethylsilyl chloride is added, and the reaction system is placed in an oil bath and stirred for reaction. After the reaction is completed, the product is filtered, washed, and dried to obtain 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt;

[0017] Preferably, the molar ratio of 4-bromo-2,6-diisopropylaniline to glyoxal is 2 to 3:1, and the amount of formic acid added is 2 to 3 drops;

[0018] Preferably, the ratio of glyoxal to methanol is 1 mmol:4-6 mL;

[0019] Preferably, the reaction conditions for obtaining the diimine compound are room temperature for 6 to 8 hours;

[0020] Preferably, the molar ratio of the diimine compound, paraformaldehyde, and trimethylchlorosilane is 1:2-3:2-3;

[0021] Preferably, the ratio of the diimine compound to ethyl acetate is 1 mmol:4-6 mL;

[0022] Preferably, the stirring reaction condition in the oil bath is 75-85° C. for 11-13 hours.

[0023] In the above preparation method, in step S1, the molar ratio of the 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt, the polyphenyl compound, the dimethylformal and the Lewis acid catalyst is 1:1:10-25:10-25;

[0024] The ratio of 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt and organic solvent is 1mmol:16~17mL

[0025] Preferably, the Lewis acid catalyst is one or a combination of anhydrous ferric chloride, anhydrous aluminum chloride and anhydrous zinc chloride.

[0026] Preferably, the organic solvent is chloroform or 1,2-dichloroethane.

[0027] In the above preparation method, in step S1, the reaction system is placed in an oil bath at 60-80° C. and stirred for reaction for 11-13 hours.

[0028] In the above preparation method, in step S2, the molar ratio of the organic porous polymer to palladium chloride and base is 1:2-3:3-5;

[0029] The ratio of the organic porous polymer to 3-chloropyridine is 1 g:9-11 mL;

[0030] Preferably, the base is one or a combination of potassium carbonate, sodium carbonate or cesium carbonate.

[0031] In the above preparation method, in step S2, the reaction system is placed in an oil bath at 75-85° C. and stirred for reaction for 11-13 hours.

[0032] In the above preparation method, the washing is performed by washing with methanol, chloroform, water and acetone 3-5 times; the Soxhlet extraction is performed by Soxhlet extraction with methanol for 11-13 hours; and the drying is performed by vacuum drying at 75-85° C. for 11-13 hours.

[0033] In a third aspect, the present invention provides a use of the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer as described in the first aspect in catalyzing the Suzuki-Miyaura coupling reaction of aryl chloride and arylboronic acid.

[0034] In a fourth aspect, the present invention provides a Suzuki-Miyaura coupling reaction method of aryl chloride and arylboronic acid, characterized in that it comprises the following steps:

[0035] After adding the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer, chloroaryl hydrocarbon, arylboronic acid, base and reaction solvent as described in the first aspect into a pressure-resistant reaction tube, the reaction system is placed in an oil bath under nitrogen atmosphere and stirred to react to obtain a product biphenyl compound;

[0036] Preferably, the molar ratio of the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer, chloroaryl hydrocarbon, arylboronic acid, and base is 1:20-40:40-60:40-60;

[0037] Preferably, the structural formula of the chlorinated aromatic compound is Wherein R is one of H, Me, OMe, F, CF3, CN, CHO, COCH3 and NO2;

[0038] Preferably, the structural formula of the arylboronic acid is wherein R1 is one of H, Me, OMe, F, CF3, CN, COOMe, COCH3 and NO2;

[0039] Preferably, the base is one or more of potassium carbonate, potassium phosphate, sodium carbonate, potassium tert-butoxide, cesium carbonate, and sodium hydroxide;

[0040] Preferably, the reaction solvent is one of methanol, ethanol, a mixed solvent of methanol and water, and a mixed solvent of ethanol and water.

[0041] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0042] The present invention obtains a functionalized nitrogen heterocyclic carbene precursor molecule with large steric hindrance and a connection site through molecular design, and then utilizes an efficient and concise synthesis strategy to synthesize an organic porous polymer carrier rich in nitrogen heterocyclic carbene precursors on a large scale. The nitrogen heterocyclic carbene units are evenly distributed in the organic polymer skeleton, providing coordination sites that can coordinate with metal ions. The organic porous polymer skeleton has a large number of micropores and mesopores, a large specific surface area, and an enhanced adsorption effect on the catalytic substrate. The coordination of the nitrogen heterocyclic carbene with large steric hindrance and the metal palladium ion can inhibit the agglomeration of palladium, thereby improving the catalytic activity of palladium. At the same time, palladium is combined with the nitrogen heterocyclic carbene skeleton through chemical bonds, which can reduce the loss of palladium ions and enhance the heterogeneous catalytic recycling effect of the organic porous polymer catalyst.

[0043] The palladium-nitrogen heterocyclic carbene framework organic porous polymer (Pd-PEPPSI-HCP) prepared by this invention can efficiently catalyze the SM coupling reaction using low-reactivity aryl chlorides as substrates, achieving a chlorobenzene conversion rate exceeding 99%. Compared with previously reported palladium-supported heterogeneous catalysts of this type, Pd-PEPPSI-HCP offers advantages such as good stability, high catalytic efficiency, and wide substrate applicability.

[0044] The preparation method of the present invention is efficient and simple, suitable for large-scale preparation, and has prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0046] Figure 1 is the hydrogen nuclear magnetic resonance spectrum of 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt in Example 1;

[0047] Figure 2 is the C NMR spectrum of 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt in Example 1;

[0048] Figure 3 The solid-state nuclear magnetic resonance spectroscopy of the organic porous polymer NHC-HCP-1 in Example 1 is 13 C spectrum;

[0049] Figure 4 The Pd 3d X-ray photoelectron spectrum of the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer Pd-PEPPSI-HCP-1 in Example 1;

[0050] Figure 5 This is a scanning electron microscope image of the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer Pd-PEPPSI-HCP-1 in Example 1;

[0051] Figure 6 This is a nitrogen adsorption curve of the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer Pd-PEPPSI-HCP-1 in Example 1;

[0052] Figure 7 This is the pore size distribution diagram of the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer Pd-PEPPSI-HCP-1 in Example 1. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0054] Example 1

[0055] In this embodiment, a palladium-nitrogen heterocyclic carbene skeleton organic porous polymer with a structural unit shown in the following formula is provided, and is named Pd-PEPPSI-HCP-1:

[0056]

[0057] The preparation method is as follows:

[0058]

[0059] A 100 mL round-bottom flask was charged with 1.37 g (4.0 mmol, 2.0 eq) of 4-benzhydryl-2,6-diisopropylaniline, 290 mg (2.0 mmol, 40% water) of glyoxal, and 10 mL of methanol. A few drops of formic acid were added as a catalyst. The reaction mixture immediately changed color from colorless to yellow, and a yellow precipitate formed after several hours. The reaction system was stirred for 24 hours. The yellow solid was collected by filtration and washed with cold methanol to obtain the intermediate diimine compound. Yield: 1.06 g (75%). A magnetic stirrer was placed in a 100 mL two-necked flask. The corresponding diimine compound (780 mg, 1.1 mmol) and paraformaldehyde (60 mg, 2.0 mmol) were added to the mixture, followed by 5.0 mL of ethyl acetate. TMSCl (216 mg, 2.0 mmol) was added to the round-bottom flask via syringe at room temperature. The reaction mixture was stirred at 70°C for 12 h. After completion, the white precipitate was filtered, washed with ethyl acetate, and dried under vacuum to obtain 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt as a white powdery solid. Yield: 599 mg (72%).

[0060]

[0061] Under nitrogen atmosphere, a dry, clean 50 mL round-bottom flask was equipped with a magnetic stirrer. 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt (227.2 mg, 0.3 mmol), 1,3,5-triphenylbenzene (91.8 mg, 0.3 mmol), and dimethylformal (304 mg, 4.0 mmol) were dispersed in 5 mL of 1,2-dichloroethane. Anhydrous ferric chloride (649 mg, 4.0 mmol) was added as a catalyst at room temperature. The reaction system was stirred at 60°C for 12 h. Heating and stirring were then stopped, and the reaction mixture was cooled. The resulting solid was filtered and washed several times with methanol, chloroform, water, and acetone. Finally, the solid was Soxhlet extracted with methanol and dried in vacuo at 80°C to obtain a yellow powder. This organic porous polymer was named NHC-HCP-1.

[0062]

[0063] Under nitrogen atmosphere, a magnetic stirrer was added to a dry and clean 50 mL round-bottom flask, and NHC-HCP-1 (100 mg), palladium chloride (25 mg) and potassium carbonate (69 mg) were dispersed in 1.0 mL 3-chloropyridine. The mixture was magnetically stirred at 80°C for 12 h, and then heating and stirring were stopped and cooled to room temperature. The obtained mixture was filtered, and the obtained solid was washed back and forth with dichloromethane, methanol, water, and acetone several times to wash away the unreacted palladium chloride. The solid was then extracted with methanol by Soxhlet, and then dried in vacuo at 80°C to obtain a brown-yellow powder, thereby obtaining a palladium-nitrogen heterocyclic carbene skeleton organic porous polymer, named Pd-PEPPSI-HCP-1.

[0064] The content of metallic palladium in the synthesized product was measured by an ICP testing instrument to be 4.31 wt%, indicating that palladium chloride was successfully loaded into NHC-HCP-1 to generate a Pd-PEPPSI-HCP-1 organic porous catalyst.

[0065] like Figure 1 As shown, 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt 1 The attribution of each signal in the H NMR spectrum is consistent with the theoretical attribution signal peak of hydrogen. Figure 2 As shown, the nuclear magnetic carbon spectrum characterization further proves that the monomer structure is the target monomer of the present invention, 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt.

[0066] like Figure 3 As shown, the solid-state NMR of NHC-HCP-1 13 The C spectrum shows broad signals in the 120-150 ppm range associated with carbon atoms in the benzene ring, while signals in the 15-30 ppm range are attributed to the aliphatic carbon atoms of the functionalized monomer imidazole salt. The peak at 56 ppm is attributed to the tertiary carbon atom of the functionalized monomer imidazole. The peak at 37 ppm is attributed to the methylene carbon in the linker, indicating the successful synthesis of the organic polymer NHC-HCP-1 via Friedel-Crafts alkylation.

[0067] like Figure 4 As shown, the Pd 3d XPS spectrum of Pd-PEPPSI-HCP-1 shows that the binding energy (BE) of the Pd3d5 / 2 orbital is 337.70 eV, indicating that the Pd species in Pd-PEPPSI-HCP-1 exists in the +2 valence state.

[0068] like Figure 5 As shown, Pd-PEPPSI-HCP-1 is composed of abundant nanorods and a small amount of nanosheets, and the size of the nanorods is between 20 and 50 μm.

[0069] like Figure 6 As shown, the specific surface area of ​​Pd-PEPPSI-HCP-1 is 568 m 2 / g. Figure 7 As shown in Figure 3, the pore size distribution curve shows that there are a large number of micropores and mesopores in the HCP material.

[0070] Pd-PEPPSI-HCP-1 was used to catalyze the SM coupling reaction. The specific steps are as follows:

[0071] Using p-chlorotoluene (0.5 mmol) and phenylboronic acid (0.75 mmol) as the substrates, 8 mg of the polymer Pd-PEPPSI-HCP-1 was added as the catalyst under nitrogen protection. The reaction was incubated in an 80°C oil bath with magnetic stirring for 12 hours. The reaction conditions, base and solvent, were screened, and the catalyst dosage was the same as the substrate dosage. The yield was 100% isolated. As shown in Table 1, the experimental results show that the catalytic effect of EtOH / H2O (1 / 1, v / v) as the reaction solvent and K2CO3 as the base was the best, with a yield of approximately 95%.

[0072] Table 1 Screening of experimental conditions for SM coupling reaction catalyzed by Pd-PEPPSI-HCP-1

[0073]

[0074] Under the same experimental conditions, catalytic experiments were conducted with other commonly used homogeneous catalysts and reported heterogeneous catalysts, and their catalytic performance was compared with that of Pd-PEPPSI-HCP-1. As shown in Table 2, the results demonstrate that Pd-PEPPSI-HCP-1 exhibits superior catalytic activity for the low-reactivity substrate chlorobenzene compared to other catalysts, demonstrating the important role of the nitrogen heterocyclic carbene monomer in stabilizing the palladium ion. Furthermore, the catalyst can be recycled more than five times while maintaining excellent catalytic activity for chlorobenzene.

[0075] Table 2 Comparison of the effects of different catalysts on the Suzuki coupling reaction of chlorobenzene as substrate

[0076]

[0077] Example 2

[0078] In this embodiment, a palladium-nitrogen heterocyclic carbene skeleton organic porous polymer with a structural unit shown in the following formula is provided, and is named Pd-PEPPSI-HCP-2:

[0079]

[0080] The preparation method is as follows:

[0081] The synthesis of 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt was the same as in Example 1.

[0082] Under nitrogen atmosphere, a dry, clean 50 mL round-bottom flask was added with a magnetic stirrer. 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt (227.2 mg, 0.3 mmol), tetraphenylmethane (96.0 mg, 0.3 mmol), and dimethylformal (304 mg, 4.0 mmol) were dispersed in 5 mL of 1,2-dichloroethane. Anhydrous ferric chloride (649 mg, 4.0 mmol) was added as a catalyst at room temperature. The reaction system was stirred at 60°C for 12 h. Heating and stirring were stopped, and the reaction was cooled. The resulting solid was filtered and washed several times with methanol, chloroform, water, and acetone. Finally, the solid was Soxhlet extracted with a methanol solution and dried in vacuo at 80°C to obtain a yellow powder, thereby obtaining the organic porous polymer NHC-HCP-2.

[0083] Under nitrogen atmosphere, a magnetic stirrer was added to a dry and clean 50 mL round-bottom flask, and NHC-HCP-2 (100 mg), palladium chloride (25 mg) and potassium carbonate (69 mg) were dispersed in 1.0 mL 3-chloropyridine. The mixture was magnetically stirred at 80°C for 12 h, and then heating and stirring were stopped and cooled to room temperature. The obtained mixture was filtered, and the obtained solid was washed back and forth with dichloromethane, methanol, water, and acetone several times to wash away the unreacted palladium chloride. The solid was then extracted with methanol by Soxhlet, and then dried in vacuo at 80°C to obtain a brown-yellow powder, thereby obtaining a palladium-nitrogen heterocyclic carbene skeleton organic porous polymer Pd-PEPPSI-HCP-2.

[0084] Pd-PEPPSI-HCP-2 was used to catalyze the Suzuki coupling reaction, specifically:

[0085] Using p-nitrochlorobenzene (0.5 mmol) and phenylboronic acid (0.75 mmol) as the reaction substrates, 10 mg of the polymer Pd-PEPPSI-HCP-2 was added as the catalyst under nitrogen protection. The reaction was incubated in an 80°C oil bath with magnetic stirring for 12 hours. Screening of the reaction conditions, including base and solvent, revealed that EtOH / H2O (1 / 1, v / v) as the reaction solvent and K2CO3 as the base provided the best catalytic effect, achieving a yield of approximately 95%. The catalyst could be recycled more than five times and maintained excellent catalytic performance for the reaction of p-nitrochlorobenzene.

[0086] Example 3

[0087] In this embodiment, a palladium-nitrogen heterocyclic carbene skeleton organic porous polymer with a structural unit shown in the following formula is provided, and is named Pd-PEPPSI-HCP-3:

[0088]

[0089] The preparation method is as follows:

[0090] The synthesis of 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt was the same as in Example 1.

[0091] Under nitrogen atmosphere, a dry, clean 50 mL round-bottom flask was added with a magnetic stirrer. 1,3-bis(4-benzhydryl-2,6-diisopropylphenyl)imidazolium salt (227.2 mg, 0.3 mmol), biphenyl (46.2 mg, 0.3 mmol), and dimethylformal (304 mg, 4.0 mmol) were dispersed in 5 mL of 1,2-dichloroethane. Anhydrous ferric chloride (649 mg, 4.0 mmol) was added as a catalyst at room temperature. The reaction system was stirred at 60°C for 12 h. After heating and stirring were stopped, the reaction mixture was cooled, and the resulting solid was filtered. The solid was washed several times with methanol, chloroform, water, and acetone. Finally, the solid was Soxhlet extracted with a methanol solution and dried in vacuo at 80°C to obtain a yellow powder, thereby obtaining the organic porous polymer NHC-HCP-3.

[0092] Under nitrogen atmosphere, a magnetic stirrer was added to a dry and clean 50 mL round-bottom flask, and NHC-HCP-3 (100 mg), palladium chloride (25 mg) and potassium carbonate (69 mg) were dispersed in 1.0 mL 3-chloropyridine. The mixture was magnetically stirred at 80°C for 12 h, and then heating and stirring were stopped and cooled to room temperature. The obtained mixture was filtered, and the obtained solid was washed back and forth with dichloromethane, methanol, water, and acetone several times to wash away the unreacted palladium chloride. The solid was then extracted with methanol by Soxhlet, and then dried in vacuo at 80°C to obtain a brown-yellow powder, thereby obtaining a palladium-nitrogen heterocyclic carbene skeleton organic porous polymer Pd-PEPPSI-HCP-3.

[0093] Pd-PEPPSI-HCP-3 was used to catalyze the Suzuki coupling reaction, specifically:

[0094] Using p-nitrochlorobenzene (0.5 mmol) and phenylboronic acid (0.75 mmol) as the reaction substrates, 10 mg of the polymer Pd-PEPPSI-HCP-3 was added as the catalyst under nitrogen protection. The reaction was incubated in an 80°C oil bath with magnetic stirring for 12 hours. Screening of the reaction conditions, including base and solvent, revealed that EtOH / H2O (1 / 1, v / v) as the reaction solvent and K2CO3 as the base provided the best catalytic effect, achieving a yield of approximately 94%. The catalyst could be recycled more than five times while maintaining excellent catalytic performance for the reaction of p-nitrochlorobenzene.

[0095] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A palladium-nitrogen heterocyclic carbene skeleton organic porous polymer, characterized in that: The structural unit of the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer is as shown in Formula I, Formula II or Formula III; Formula I; Formula II; Formula III.

2. A method for preparing a palladium-nitrogen heterocyclic carbene skeleton organic porous polymer according to claim 1, characterized in that: The following steps are involved: S1. Evenly mix 1,3-bis(4-benzhydryl-2,6-diisopropylphenyl)imidazolium salt, a polyphenyl compound, dimethylformal, and an organic solvent, add a Lewis acid catalyst, and place the reaction system in an oil bath under nitrogen atmosphere with stirring to react. The obtained solid product is filtered, washed, Soxhlet extracted, and dried to obtain an organic porous polymer; S2, adding an organic porous polymer and a base to 3-chloropyridine, then adding palladium dichloride, placing the reaction system in an oil bath and stirring for reaction, filtering, washing, Soxhlet extraction, and drying the obtained solid product to obtain the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer; The polyphenyl compound is one of 1,3,5-triphenylbenzene, tetraphenylmethane or biphenyl.

3. The preparation method according to claim 2, wherein The preparation method of the 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt comprises the following steps: 4-Benzhydryl-2,6-diisopropylaniline and glyoxal are mixed and dissolved in methanol, and formic acid is added dropwise to react to obtain a diimine compound. The diimine compound is then mixed with paraformaldehyde and dissolved in ethyl acetate. Trimethylsilyl chloride is added, and the reaction system is placed in an oil bath and stirred for reaction. After the reaction is completed, the product is filtered, washed, and dried to obtain 1,3-bis(4-benzhydryl-2,6-diisopropylphenyl)imidazolium salt.

4. The preparation method according to claim 3, wherein The molar ratio of 4-benzhydryl-2,6-diisopropylaniline to glyoxal is 2-3:1, and the amount of formic acid added is 2-3 drops.

5. The preparation method according to claim 3, wherein The ratio of glyoxal to methanol is 1 mmol:4~6 mL.

6. The preparation method according to claim 3, wherein The reaction conditions for obtaining the diimine compound are room temperature for 6 to 8 hours.

7. The preparation method according to claim 3, wherein The molar ratio of the diimine compound, paraformaldehyde and trimethylchlorosilane is 1:2-3:2-3.

8. The preparation method according to claim 3, wherein The ratio of diimine compound to ethyl acetate is 1 mmol:4~6 mL.

9. The preparation method according to claim 3, wherein The stirring reaction conditions in the oil bath are 75~85℃ and the reaction time is 11~13 h.

10. The preparation method according to claim 2, wherein In step S1, the molar ratio of the 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt, the polyphenyl compound, the dimethanol formal and the Lewis acid catalyst is 1:1:10-25:10-25; The ratio of 1,3-bis(4-diphenylmethyl-2,6-diisopropylphenyl)imidazolium salt to organic solvent is 1 mmol:16~17 mL.

11. The preparation method according to claim 10, characterized in that The Lewis acid catalyst is one of anhydrous ferric chloride, anhydrous aluminum chloride and anhydrous zinc chloride, or a combination of several of them.

12. The preparation method according to claim 10, wherein The organic solvent is chloroform or 1,2-dichloroethane.

13. The preparation method according to claim 2, wherein In step S1, the reaction system is placed in an oil bath at 60-80° C. and stirred for reaction for 11-13 hours.

14. The preparation method according to claim 2, wherein In step S2, the molar ratio of the organic porous polymer to palladium dichloride and the base is 1:2-3:3-5; The ratio of the organic porous polymer to 3-chloropyridine is 1 g:9-11 mL.

15. The preparation method according to claim 14, wherein The base is one or a combination of potassium carbonate, sodium carbonate or cesium carbonate.

16. The preparation method according to claim 2, wherein In step S2, the reaction system is placed in an oil bath at 75-85° C. and stirred for reaction for 11-13 hours.

17. The preparation method according to claim 2 or 3, characterized in that: The washing is performed by washing with methanol, chloroform, water, and acetone 3-5 times; the Soxhlet extraction is performed by Soxhlet extraction with methanol for 11-13 hours; and the drying is performed by vacuum drying at 75-85° C. for 11-13 hours.

18. Use of the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer as claimed in claim 1 in catalyzing the Suzuki-Miyaura coupling reaction of aryl chloride and arylboronic acid.

19. A Suzuki-Miyaura coupling reaction method of aryl chloride and arylboronic acid, characterized in that: The following steps are involved: After adding the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer as claimed in claim 1, chloroaryl hydrocarbon, arylboronic acid, base and reaction solvent into a pressure-resistant reaction tube, the reaction system is placed in an oil bath under nitrogen atmosphere and stirred for reaction to obtain a product biphenyl compound.

20. The method according to claim 19, wherein The molar ratio of the palladium-nitrogen heterocyclic carbene skeleton organic porous polymer, chloroaryl hydrocarbon, arylboronic acid and base is 1:20-40:40-60:40-60.

21. The method according to claim 20, wherein The structural formula of the chlorinated aromatic compound is , where R is one of H, Me, OMe, F, CF3, CN, CHO, COCH3 and NO2.

22. The method according to claim 20, wherein The structural formula of the arylboronic acid is , wherein R1 is one of H, Me, OMe, F, CF3, CN, COOMe, COCH3 and NO2.

23. The method of claim 20, wherein: The base is one or more of potassium carbonate, potassium phosphate, sodium carbonate, potassium tert-butoxide, cesium carbonate, and sodium hydroxide.

24. The method of claim 19, wherein: The reaction solvent is one of methanol, ethanol, a mixed solvent of methanol and water, and a mixed solvent of ethanol and water.

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