Preparation method and application of triphenylphosphine doped PEEK-Pd catalyst

Abstract

The invention relates to the technical field of chemical synthesis, in particular to a preparation method of a triphenylphosphine doped PEEK-Pd catalyst, which comprises the following steps: (1) sequentially adding tris (4-fluorophenyl) phosphine oxide, p-hydroxyphenol, potassium carbonate and a solvent into a dry reaction container for condensation polymerization to obtain PEEK-Ph3P = O; (2) reducing the PEEK-Ph3P = O by using phenyl silane, so as to obtain PEEK-Ph3P; and (3) carrying out coordination on the PEEK-Ph3P by using palladium acetate, so as to obtain the PEEK-Ph3P-Pd (OAc) 2 catalyst. The PEEK-Ph3P-Pd (OAc) 2 catalyst prepared by the method contains a large number of stable catalytic sites and can be applied to regioselective synthesis of alkenyl silane.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and in particular to a method for preparing a triphenylphosphine-doped PEEK-Pd catalyst and its application. Background Technology

[0002] The rapid development of nanomaterials has epoch-making significance in the field of organic catalysis. Currently, to maximize catalytic efficiency, researchers are attempting to solidify costly homogeneous catalytic systems to construct heterogeneous catalytic systems more suitable for industrial applications. However, this transformation faces the following challenge: in inorganic nanocatalysts that focus only on the metal center and its coordinating atoms, the role of organic ligands in modulating the electronic properties of the metal cannot be realized.

[0003] Single-atom-site (SAS) catalysts serve as a bridge between homogeneous and heterogeneous catalysis. However, they also have limitations: the optimization space for their active sites is limited by the support material. More importantly, the diversity of reaction substrates in organic synthesis requires catalytic systems with excellent universality, which typically necessitates synergistic modification and fine-tuning of the metal center and ligands. Currently, most single-atom catalysts struggle to achieve this precise and flexible control, thus limiting their ability to address substrate tolerance issues.

[0004] Alkenylsilanes, as important organosilicon compounds, are widely used in the polysilicon compound industry and the synthesis of complex organic molecules. The hydrosilylation of alkynes is the most direct method for constructing alkenylsilane structures, boasting 100% atom economy. However, the hydrosilylation reaction between aryl alkynes and secondary silanes still faces several challenges: firstly, the carbon-carbon triple bond is weakly polar, making effective activation difficult; secondly, secondary silanes themselves have low reactivity; furthermore, the reaction process easily generates unnecessary hydrogenation byproducts, further reducing the selectivity of the target product.

[0005] To address these challenges, researchers have developed various homogeneous metal / ligand catalytic systems. As early as 1994, Paserob's team attempted to use Pt / C and Pt / Al₂O₃ nanocatalysts to drive the reaction, but the product selectivity remained unsatisfactory (J. Mol. Catal. 1994, 91, 83–90). Subsequently, gold and rhodium nanocatalysts were also introduced into the system; however, controlling their regioselectivity remains challenging (Adv. Synth. Catal. 2015, 357, 89–99; Tetrahedron2012, 68, 8724–8731). Under conventional reaction conditions, controlling the size of nanoparticles or clusters is difficult, and their uneven distribution results in poor dispersion of metal active sites, with some sites being masked or deactivated during the reaction. This structural inhomogeneity weakens the ligand's electronic control over the metal nanoparticles, limiting further improvements in catalytic performance.

[0006] Therefore, developing novel nanocatalytic materials with controllable structures and well-defined active sites is of great significance for achieving efficient and highly selective hydrosilylation reactions between aryl alkynes and secondary silanes. Summary of the Invention

[0007] To address the problems mentioned above in the background art, the first objective of this invention is to provide a method for preparing a PEEK-Ph3P-Pd(OAc)2 catalyst. The PEEK-Ph3P-Pd(OAc)2 catalyst prepared by this method has a large number of stable catalytic sites and can catalyze hydrosilylation reactions with high selectivity.

[0008] The solution adopted by this invention to solve its technical problem is: a method for preparing a PEEK-Ph3P-Pd(OAc)2 catalyst, specifically as follows: (1) Tris(4-fluorophenyl)phosphine oxide, p-hydroxyphenol, potassium carbonate and solvent were added sequentially to a dry reaction vessel to carry out a polycondensation reaction to obtain PEEK-Ph3P=O; (2) PEEK-Ph3P=O, phenylsilane and toluene were placed in a reaction vessel and stirred and reduced under reflux. After the reaction was completed, solid product B was obtained by filtration. After washing and drying, PEEK-Ph3P was obtained. (3) PEEK-Ph3P, palladium acetate and 1,1,2,2-tetrachloroethane were added to the reaction vessel and stirred under an inert atmosphere. After the reaction was completed, the mixture was filtered to obtain solid product C. Solid product C was washed and dried to obtain PEEK-Ph3P-Pd(OAc)2 catalyst.

[0009] Preferably, in step (1), the ratio of tris(4-fluorophenyl)phosphine oxide, p-hydroxyphenol, potassium carbonate and solvent is 664 mg: 330 mg: 828 mg: 16 ml.

[0010] Preferably, the solvent is a mixture of sulfolane and toluene, wherein the volume ratio of sulfolane to toluene is 5:3.

[0011] Preferably, in step (3), the ratio of PEEK-Ph3P, palladium acetate and 1,1,2,2-tetrachloroethane is 500 mg: 12 mg: 5 mL.

[0012] The second objective of this application is to provide an application of the PEEK-Ph3P-Pd(OAc)2 catalyst in the regioselective synthesis of alkenylsilanes, characterized in that the synthesis method specifically comprises: Diarylaceyne, diphenylsilane, triethylamine, PEEK-Ph3P-Pd(OAc)2 catalyst and THF were mixed and stirred at room temperature or under heating for 12 hours. After the reaction was completed, a mixture was obtained. The mixture was cooled to room temperature, and then the solvent in the mixture was removed under reduced pressure. The mixture was then separated by column chromatography to obtain cis-addition alkenylsilane.

[0013] Preferably, the ratio of diarylaceyne, diphenylsilane, triethylamine, PEEK-Ph3P-Pd(OAc)2 catalyst, and THF is 35.6 mg: 55.2 mg: 10.1 mg: 20 mg: 1 mL. In summary, the beneficial effects of the present invention are as follows: (1) In this application, tris(4-fluorophenyl)phosphine oxide units are introduced during the polymerization of polyether ether ketone (PEEK-Ph3P-Pd(OAc)2) and then completely reduced to tris(4-fluorophenyl)phosphine in subsequent steps, resulting in a large number of stable triphenylphosphine ligand sites in the obtained PEEK-Ph3P-Pd(OAc)2 skeleton. These phosphine groups can form strong and stable coordination with metal ions, significantly increasing the electron density of the metal active center and enhancing the catalytic activity.

[0014] (2) The PEEK-Ph3P-Pd(OAc)2 skeleton is highly aromatic and has a certain porous structure. In the reaction, it can not only undergo π–π interactions with aromatics, increasing the enrichment of the substrate around the metal center and the regioselectivity of the reaction, but also the spatial confinement effect brought about by the abundant pores inside PEEK-Ph3P-Pd(OAc)2, which makes the substrate stereoconfined when it is close to the metal active site, thereby further optimizing the regioselectivity and stereoselectivity of the reaction.

[0015] (3) The high rigidity and high thermal stability of PEEK-Ph3P-Pd(OAc)2 material can effectively inhibit the migration and aggregation of metal particles and ensure the high dispersion of metal sites on the support. This structural feature, combined with the strong electron supply effect of phosphine ligands, not only improves the reaction conversion rate, but also enables the catalyst to exhibit excellent heat resistance and solvent resistance under high temperature and strong polar solvent conditions.

[0016] (4) In terms of recyclability, the strong coordination of phosphine-metal significantly reduces the loss of metal during the reaction process, while the chemical inertness and mechanical strength of the PEEK-Ph3P-Pd(OAc)2 framework ensure that the catalyst can still maintain high activity and high selectivity after multiple filtrations and recycling, with excellent recycling performance, which significantly improves the green level of the process.

[0017] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0018] Figure 1 The solid-state phosphorus NMR spectrum of PEEK-Ph3P=O; Figure 2 The solid-state NMR phosphorus spectrum of PEEK-Ph3P; Figure 3 The 1H NMR spectrum of an alkenylsilane; Figure 4 The image shows the carbon NMR spectrum of an alkenylsilane. Figure 5 The reaction flow diagram of PEEK-Ph3P-Pd(OAc)2; Figure 6 This is a reaction flow diagram for alkenylsilanes. Detailed Implementation

[0019] To make the content of this invention easier to understand, the invention will be further described below with reference to specific embodiments and accompanying drawings.

[0020] I. Preparation of PEEK-Ph3P-Pd(OAc)2 catalyst The preparation steps are as follows: S1. At 0 °C, tris(4-fluorophenyl)phosphine (1.58 g, 5 mmol) was dissolved in dichloromethane (10 mL), followed by the addition of 30% hydrogen peroxide solution (0.6 mL, 7.5 mmol). The mixture was stirred at room temperature for 6 hours to obtain reaction system A.

[0021] S2. Add water (10 mL) to reaction system A for quenching, then separate the layers. After separating the organic layer, wash it three times with saturated sodium chloride solution, dry it (anhydrous sodium sulfate), filter it, and concentrate it under reduced pressure to finally obtain 1.66 g of white solid tris(4-fluorophenyl)phosphine oxide, with a yield of 100%.

[0022] S3. Under nitrogen protection, tris(4-fluorophenyl)phosphine oxide (2 mmol, 664 mg), p-hydroxyphenol (3 mmol, 330 mg), and potassium carbonate (6 mmol, 828 mg) were sequentially added to a dry three-necked flask, and a condenser was connected. Sulfolane (10 mL) and toluene (6 mL) were added to the three-necked flask as solvents. The mixture was then stirred at 160 °C for 2 hours, and then the temperature was raised to 210 °C and stirred for another 2 hours to complete the polycondensation reaction and obtain reaction system B.

[0023] S4. Pour out reaction system B and collect solid product A by filtration through a Buchner funnel. Then wash solid product A with deionized water and anhydrous ethanol in sequence to remove residual salts and solvents on its surface. After drying, 950 mg of PEEK-Ph3P=O is obtained as a grayish-white powder.

[0024] S5. Under nitrogen protection, 500 mg of pre-dried PEEK-Ph3P=O was placed in a clean, dry three-necked flask and a condenser was connected. Then, phenylsilane and toluene were added sequentially to the reaction vessel, and the mixture was stirred at 118 °C for three days. After the reaction was completed, reaction system C was obtained. S6. After the reaction system C is cooled to room temperature, dichloroethane (40 mL × 3) is added to the reaction system C and extracted three times. The organic phases are combined and the solvent is removed by rotary evaporation to obtain solid product B. The obtained solid product B is washed three times with petroleum ether and then dried under vacuum to obtain 480 mg of PEEK-Ph3P, which is a white powder solid. S7. 500 mg of PEEK-Ph3P and 12 mg of palladium acetate were added sequentially to a round-bottom flask, followed by 5 mL of 1,1,2,2-tetrachloroethane as a solvent. The mixture was stirred for two days under an inert atmosphere. After the reaction was complete, the solid product C was recovered by filtration through a Buchner funnel. Solid product C was washed with deionized water (50 mL × 3) and anhydrous ethanol (30 mL × 3) to remove unreacted substances and impurities from its surface. Solid product C was then dried under vacuum to obtain 410 mg of PEEK-Ph3P-Pd(OAc)2 catalyst, which appeared as a gray powder.

[0025] The specific reaction process of PEEK-Ph3P-Pd(OAc)2 is as follows: Figure 5 As shown. Solid-state nuclear magnetic resonance (NMR) was used to characterize samples PEEK-Ph3P=O and PEEK-Ph3P. The solid-state NMR phosphorus spectrum of PEEK-Ph3P=O is shown below. Figure 1 As shown, the solid-state NMR phosphorus spectrum of PEEK-Ph3P is as follows: Figure 2 As shown.

[0026] II. Application of PEEK-Ph3P-Pd(OAc)2 catalyst in stereoselective synthesis of alkenylsilanes The synthesis steps are as follows: Diarylacetylene (0.2 mmol, 35.6 mg), diphenylsilane (0.24 mmol, 55.2 mg), triethylamine (0.1 mmol, 10.1 mg), catalyst PEEK-Ph3P-Pd(OAc)2 (20 mg), and THF (1 mL) were mixed and stirred at room temperature for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, and then the solvent in the mixture was removed under reduced pressure. The mixture was then separated by silica gel column chromatography with ethyl acetate / petroleum ether to obtain alkenylsilane. The alkenylsilane separation yield was 27%, and the product was a colorless and transparent liquid with an E / Z isomer ratio of 50:1.

[0027] The specific reaction process of alkenylsilane is as follows: Figure 6 As shown. The alkenylsilane sample was characterized using nuclear magnetic resonance (NMR) technology. The proton NMR spectrum of the alkenylsilane is shown below. Figure 3 As shown, the carbon NMR spectrum of alkenylsilane is as follows: Figure 4 As shown.

[0028] The above experiments show that, under the catalysis of PEEK-Ph3P-Pd(OAc)2, this hydrosilylation reaction mainly produces the E-isomer, with an E / Z ratio as high as 50:1. This result demonstrates that the catalyst possesses excellent stereocontrol ability in the reaction and can achieve superior stereoselectivity.

[0029] The embodiments described above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and modifications made by those skilled in the art based on the invention shall fall within the scope of protection of the present invention.

Claims

1. A process for the preparation of a PEEK-Ph3P-Pd(OAc)2 catalyst, characterized in that, Specifically comprising the following steps: (1) tris (4-fluorophenyl) phosphine oxide, p-hydroxyphenol, potassium carbonate and solvent are sequentially added into a dry reaction container for polycondensation reaction to obtain PEEK-Ph3P=O; (2) PEEK-Ph3P=O, phenylsilane and toluene are placed in a reaction container and stirred under reflux conditions for reduction, after the reaction is completed, the solid product B is obtained by filtration, and after washing and drying, PEEK-Ph3P is obtained; (3) PEEK-Ph3P, palladium acetate and 1,1,2,2-tetrachloroethane are added into a reaction container and stirred under inert atmosphere, after the reaction is completed, the solid product C is obtained by filtration, and after washing and drying, PEEK-Ph3P-Pd(OAc)2 catalyst is obtained.

2. The method for preparing PEEK-Ph3P-Pd(OAc)2 catalyst according to claim 1, characterized in that, In step (1), the use ratio of tris (4-fluorophenyl) phosphine oxide, p-hydroxyphenol, potassium carbonate and solvent is 664 mg:330 mg:828 mg:16 ml.

3. The method for preparing PEEK-Ph3P-Pd(OAc)2 catalyst according to claim 2, characterized in that, The solvent is a mixture of sulfolane and toluene, and the volume ratio of sulfolane and toluene is 5:

3.

4. The method for preparing PEEK-Ph3P-Pd(OAc)2 catalyst according to claim 1, characterized in that, In step (3), the use ratio of PEEK-Ph3P, palladium acetate and 1,1,2,2-tetrachloroethane is 500 mg:12 mg:5 mL.

5. Use of PEEK-Ph3P-Pd(OAc)2 catalyst in the regioselective synthesis of alkenylsilanes, characterized in that, The synthesis method is specifically: Diarylacetylene, diphenylsilane, triethylamine, PEEK-Ph3P-Pd(OAc)2 catalyst and THF are mixed, stirred at room temperature or heated for 12 hours, after the reaction is completed, a mixture is obtained, the mixture is cooled to room temperature, then the solvent in the mixture is removed under reduced pressure, and then the cis addition of alkenylsilane is obtained by column chromatography.

6. Use according to claim 5, characterized in that, The use ratio of diarylacetylene, diphenylsilane, triethylamine, PEEK-Ph3P-Pd(OAc)2 catalyst and THF is 35.6 mg:55.2 mg:10.1 mg:20 mg:1 mL.

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