Application of temperature-controlled phase transfer Pd nanocatalyst in Heck reaction

Abstract

This invention discloses the application of a temperature-controlled phase-transfer Pd nanocatalyst in the Heck reaction, belonging to the field of nanocatalyst technology. This invention achieves reversible migration of the catalyst between the aqueous and organic phases with temperature changes by introducing functional groups with both polyether segments and hydrogen bonding on a traditional arylphosphine framework. Simultaneously, the large-volume groups on the ligands enhance the electron density and stability of the palladium center. The temperature-controlled phase-transfer Pd nanocatalyst prepared by this invention exhibits excellent catalytic activity in the Heck reaction at 85℃, with a conversion rate exceeding 75%; furthermore, this catalytic system shows good stability in the aqueous / organic two-phase system and can be reused at least four times.

Description

Technical Field

[0001] This invention belongs to the field of nanocatalyst technology, and more specifically, relates to the application of a temperature-controlled phase-transfer Pd nanocatalyst in the Heck reaction. Background Technology

[0002] The Heck reaction is a coupling reaction in which unsaturated haloalkanes react with alkenes under strong base and palladium catalysis to form substituted alkenes. It is an important class of carbon-carbon bond formation reactions in organic synthesis. In recent decades, the Heck reaction has achieved significant progress in the field of homogeneous catalysis. In homogeneous systems, palladium catalysts are dissolved in the reaction system, allowing for sufficient contact with the reactants and resulting in high reactivity and selectivity. Traditionally, homogeneous palladium catalysts are often used in combination with phosphine ligands to improve catalytic efficiency by adjusting the electronic properties and spatial configuration of the metal center.

[0003] However, existing homogeneous catalytic systems face a series of challenges in practical applications. First, conventional phosphine ligands are prone to oxidative deactivation under high temperature or aerobic conditions. Second, the separation of catalyst and product is difficult, leading to the residue and loss of the precious metal palladium, which not only increases production costs but also affects product purity and limits catalyst recycling. Therefore, how to achieve efficient separation and recovery of catalyst while ensuring catalytic activity has become a key problem that urgently needs to be solved in this field.

[0004] To address these challenges, researchers have recently developed thermoregulated phase transfer (TPT) catalysis. This technique introduces specific functional groups into ligands or promoters, enabling the catalyst to reversibly migrate between two phases (e.g., aqueous and organic phases) at different temperatures. As the temperature increases, weak interactions such as hydrogen bonds are disrupted, allowing the catalyst to migrate from the polar phase to the organic phase to participate in the reaction. After the reaction, cooling causes the catalyst to return to the polar phase, achieving separation and recovery. This strategy combines the advantages of high homogeneous catalytic activity and easy separation in heterogeneous catalysis, and has demonstrated excellent performance in reactions such as olefin hydrogenation, hydroformylation, and Suzuki coupling. However, existing TPT systems are mostly based on nano-metal catalysts containing polyether chains, and research on thermoregulated reversible design for small-molecule phosphine ligands is relatively limited. Especially in palladium-catalyzed CC coupling reactions, traditional phosphine ligands struggle to simultaneously achieve both efficient phase transfer functionality and precise electronic control capabilities.

[0005] Therefore, providing a novel temperature-controlled phase-transfer Pd nanocatalyst and its application in the Heck reaction is of great significance for constructing green and sustainable catalytic processes. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, the technical problem this invention aims to solve is to provide a temperature-controlled phase-transfer Pd nanocatalyst that maintains high catalytic activity while also exhibiting excellent phase-transfer performance and recyclability. Another technical problem this invention aims to solve is to provide a method for preparing the aforementioned temperature-controlled phase-transfer Pd nanocatalyst. By introducing functional groups with both polyether segments and hydrogen bonding interactions onto a traditional arylphosphine framework, reversible migration of the catalyst between the aqueous and organic phases with temperature changes is achieved. Simultaneously, the large-volume groups on the ligands enhance the electron density and stability of the palladium center. A further technical problem this invention aims to solve is to provide the application of the aforementioned temperature-controlled phase-transfer Pd nanocatalyst in the Heck reaction of iodobenzene and butyl acrylate.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A temperature-controlled phase-transfer Pd nanocatalyst, wherein the catalyst is prepared by hydrogen reduction of a raw material comprising Na₂PdCl₄ and a phosphine ligand, and the structural formula of the phosphine ligand is as follows: .

[0008] Preferably, the molar ratio of Na2PdCl4 to phosphine ligand is 2~3:1.

[0009] A method for preparing the temperature-controlled phase-transfer Pd nanocatalyst includes the following steps: 1) Add Na2PdCl4 aqueous solution, deionized water, phosphine ligand and n-pentanol to the polytetrafluoroethylene liner, replace the gas in the reactor with hydrogen and then introduce hydrogen. 2) Place the high-pressure vessel from step 1) in a constant-temperature oil bath for stirring reaction. After the reaction is complete, remove the high-pressure vessel and place it in an ice-water bath to cool for 2 hours. Release the pressure and open the vessel to obtain the temperature-controlled phase transfer Pd nanocatalyst.

[0010] Preferably, in step 1), hydrogen gas is introduced to a pressure of 4 MPa.

[0011] Preferably, in step 1), the mass ratio of Na2PdCl4 aqueous solution to phosphine ligand is 0.2~0.3:3~3.5, and the mg / mL / mL ratio of phosphine ligand, deionized water and n-pentanol is 3.2:3.5:2.

[0012] Preferably, in step 2), the mixture is placed in a constant temperature oil bath at 80°C and stirred at a speed of 350 r / min for 3 hours.

[0013] Preferably, the phosphine ligand is prepared by the following steps: 1) After a halogen-metal exchange reaction of 2-bromo-2',4',6'-triisopropyl-3,6-dimethoxy-1,1'-biphenyl with n-butyllithium in an inert solvent, a phosphine chloride reagent is added to carry out a phosphine chlorination reaction to obtain 2-lithium-2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]yl)lithium; the molar ratio of 2-bromo-2',4',6'-triisopropyl-3,6-dimethoxy-1,1'-biphenyl, n-butyllithium and phosphine chloride reagent is 1:1:1, the reaction temperature of the halogen-metal exchange reaction is -78℃, and the reaction time is 1.5h; 2) The 2-lithium-2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]yl)lithium obtained in step 1) is subjected to a monosubstituted reaction with phenyl dichlorophosphine to obtain chloro(phenyl)[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine; the molar ratio of 2-lithium-2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]yl)lithium to phenyl dichlorophosphine is 1:1~1.1, the reaction temperature of the monosubstituted reaction is -78℃, and the reaction time is 2h; 3) The chloro(phenyl)[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine obtained in step 2) was purified by rotary evaporation and then subjected to a halogen-metal exchange reaction with excess lithium metal in an inert solvent to obtain lithium phenyl[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine; the molar ratio of the chloro(phenyl)[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine to lithium metal was 1:5, the reaction temperature of the halogen-metal exchange reaction was 0℃, and the reaction time was 12h; 4) The phenyl[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine lithium obtained in step 3) is reacted with polyethylene glycol monomethyl ether ethyl sulfonate in an inert solvent, and the phosphine ligand is obtained by purification; the molar ratio of phenyl[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine lithium to polyethylene glycol monomethyl ether ethyl sulfonate is 1:0.4.

[0014] Preferably, in step 1), the phosphine chloride reagent is phenyl dichlorophosphine.

[0015] Preferably, in step 4), the preparation process of polyethylene glycol monomethyl ether ethyl sulfonate is as follows: polyethylene glycol monomethyl ether is dissolved in toluene, and under ice-water bath and stirring conditions, a toluene solution of ethyl sulfonyl chloride is added dropwise to the system, and triethylamine is added as an acid-binding agent. After the reaction is completed, the mixture is extracted, concentrated under reduced pressure, and dried to obtain polyethylene glycol monomethyl ether ethyl sulfonate.

[0016] Preferably, the mass ratio of polyethylene glycol monomethyl ether, ethyl sulfonyl chloride and triethylamine is 8~8.5:1~1.1:1.

[0017] The application of the temperature-controlled phase-transfer Pd nanocatalyst in the Heck reaction, wherein the Heck reaction is the Heck reaction of iodobenzene and butyl acrylate.

[0018] A method for catalyzing the Heck reaction using the temperature-controlled phase-transfer Pd nanocatalyst includes the following steps: S1. Under argon protection, temperature-controlled phase transfer Pd nanocatalyst, iodobenzene, butyl acrylate, cuprous iodide and triethylamine were added to the solvent to obtain the reaction system; S2. Under normal pressure and argon protection, the reaction system obtained in step S1 is placed in an oil bath at 85°C and reacted for 150 min. After naturally cooling to room temperature, the catalyst and product are separated.

[0019] Preferably, in step S1, the molar ratio of the temperature-controlled phase transfer Pd nanocatalyst, iodobenzene, butyl acrylate, cuprous iodide, and triethylamine is 0.05:1:1:0.05:2.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following advantages: 1) This invention connects reversible hydrogen-bonded groups with polyether segments to a traditional arylphosphine skeleton, enabling the ligand to transfer from the aqueous phase to the organic phase upon heating. This allows the catalyst to automatically stratify with temperature changes and transfer between the aqueous and organic phases. Simultaneously, to enhance the ligand's ability to donate electrons to Pd(0) species, thereby improving its reactivity and stability, large-volume groups such as triisopropyl and methoxy groups are added to the ligand. This design approach, which adjusts both structure and function, aims to break through the limitations of traditional ligand design, endowing the system with excellent phase transfer performance and recyclability while maintaining high catalytic activity. 2) The phosphine ligands prepared by this invention break through the limitations of traditional ligand design and have good temperature-controlled phase transfer characteristics, exhibiting reversible migration under specific temperature conditions, which can provide a more efficient and environmentally friendly method for catalyst separation and recovery; in addition, its mechanism of regulating electrons at the molecular level also lays a theoretical foundation for the development of green and sustainable catalytic systems. 3) The temperature-controlled phase transfer Pd nanocatalyst prepared by this invention exhibits good catalytic activity for the Heck reaction at 85℃, with a conversion rate exceeding 75%; and the catalytic system has good stability in the water / organic two-phase system and can be reused at least 4 times. Attached Figure Description

[0021] Figure 1The infrared spectrum of the polyethylene glycol monomethyl ether ethyl sulfonate prepared in Example 1; Figure 2 The 1H NMR spectrum of the polyethylene glycol monomethyl ether ethyl sulfonate prepared in Example 1; Figure 3 The carbon NMR spectrum of the polyethylene glycol monomethyl ether ethyl sulfonate prepared in Example 1; Figure 4 The 1H NMR spectrum of chloro(phenyl)[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine prepared in Example 1; Figure 5 The infrared spectrum of the phosphine ligand prepared in Example 1; Figure 6 The 1H NMR spectrum of the phosphine ligand prepared in Example 1; Figure 7 The UV-Vis absorption spectra of the temperature-controlled phase-transfer Pd nanocatalyst before and after reduction in Example 2 are shown below. Figure 8 This is a graph showing the effect of the number of cycles on the yield of the temperature-controlled phase-transfer Pd nanocatalyst in Example 4; Figure 9 This is a graph showing the effect of different solvent systems on the Heck reaction efficiency in Example 5; Figure 10 This is a diagram showing the temperature-controlled phase transfer process of a divalent palladium catalyst in a water / 1-hexanol two-phase system. Figure 11 A temperature-controlled phase transfer process in a water / 1-hexanol two-phase system using a zero-valent palladium catalyst; Figure 12 The gas chromatography-mass spectra of the products after the catalytic reaction in Example 3 are shown below. Figure 13 The 1H NMR spectrum of the product after the catalytic reaction in Example 3; Figure 14 The image shows the carbon NMR spectrum of the product after the catalytic reaction in Example 3. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described below with reference to specific embodiments. Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0023] In the following examples, lithium was purchased from the Aladdin Reagent Bottle Platform; toluene from Sichuan Xilong Scientific Co., Ltd.; tetrahydrofuran from Tianjin Fuyu Fine Chemical Co., Ltd.; triethylamine from Anhui Zesheng Co., Ltd.; polyethylene glycol monomethyl ether (PEG 1000) from Shandong Keyuan Biochemical Co., Ltd.; sodium palladium tetrachloride from Shandong Keyuan Biochemical Co., Ltd.; phenyl dichlorophosphine and ethyl sulfonyl chloride from Shandong Keyuan Biochemical Co., Ltd.; mercury and butyl acrylate from Shanghai Aladdin Biochemical Technology Co., Ltd.; argon and hydrogen from Xinghui Gas Supply Station. All reagents and gases were of analytical grade.

[0024] Example 1: Preparation of Phosphine Ligands Synthesis of 1,2-lithium-2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]yl)lithium 12.55 mmol of 2-bromo-2',4',6'-triisopropyl-3,6-dimethoxy-1,1'-biphenyl was dissolved in 50 mL of anhydrous THF. 7.84 mL of 1.6 M n-butyllithium solution was slowly added dropwise at -78 °C under a nitrogen atmosphere. After the addition was complete, the mixture was stirred at -78 °C for 1.5 h to complete the metal-halogen exchange reaction. Subsequently, a solution containing 12.55 mmol of phenylphosphine dichloride in 10 mL of anhydrous THF was slowly added dropwise to the reaction system. After the addition was complete, the mixture was heated to room temperature and stirred for 3 h to obtain the target intermediate 2-lithium-2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]yl)lithium, whose chemical reaction formula is shown below: ; 2. Synthesis of Chloro(phenyl)[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine Take a dry 100 mL three-necked flask, with a magnetic stir bar inside. After fully purging the flask with argon gas, add 11.95 mmol of phenylphosphine dichloride and 30 mL of anhydrous THF, stirring until the phenylphosphine dichloride is completely dissolved. Place the reaction system under an argon protective atmosphere, cool to -78 °C, and maintain the temperature for 15 min using an ethanol bath to allow the system to cool completely. Then, at -78 °C, slowly add the solution of 11.95 mmol of phenylphosphine dichloride to the system dropwise using a double-ended needle. The 2-lithium-2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]yl)lithium solution obtained in step 1 was added in mmol. The dropping rate was controlled to avoid temperature fluctuations. After the addition was complete, the reaction was maintained at -78°C for 2 hours to ensure complete reaction and suppress the disubstitution side reaction. Then, the temperature was slowly raised to room temperature and stirred overnight to obtain chloro(phenyl)[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine, the chemical reaction formula of which is shown below: ; 3. Synthesis of phenyl(2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl)phosphine lithium Under argon protection, 11.92 mmol of chloro(phenyl)[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine obtained in step 2 was dissolved in tetrahydrofuran after removing n-butyl bromide by rotary evaporation. The solution was then cooled to 0°C in an ice-water bath, followed by the addition of 59.6 mmol of chopped excess lithium metal. The reaction was continued with stirring in an ice bath for 12 h to ensure complete lithium substitution. After the reaction was complete, the remaining lithium metal was removed from the mixture under argon protection using stainless steel tweezers. The reaction solution was the THF solution of the target product, lithium phenyl[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine, and its chemical reaction formula is shown below: ; Synthesis of polyethylene glycol monomethyl ether ethyl sulfonate 1) Under argon protection, repeatedly replace the stop reaction tube 3-5 times. Dissolve 12.5g of polyethylene glycol monomethyl ether in 20mL of dehydrated and deoxygenated toluene in a flask. Then add 5mL of dehydrated and deoxygenated toluene to a constant pressure dropping funnel. Add 1.52g of triethylamine to the stop reaction tube. Then add 1.61g of ethylsulfonyl chloride to the constant pressure dropping funnel. 2) Open the constant pressure dropping funnel and add the liquid dropwise into the flask under ice-water bath and magnetic stirring, controlling the dropping time to 10 min; after the dropping is completed, keep the reaction in the ice-water bath for 3 h, and then stir overnight at room temperature. 3) The solution obtained in step 2) was diluted with 250 mL of water and extracted with dichloromethane (5 × 50 mL). The organic phase was washed successively with 1 M HCl solution (4 × 50 mL) and saturated brine (4 × 50 mL), dried over anhydrous Na2SO4, concentrated under reduced pressure, and the crude product was dissolved in diethyl ether to precipitate. The precipitate was collected by filtration, washed with diethyl ether, and dried under vacuum at room temperature for 6 h to finally obtain 13.38 g of white solid polyethylene glycol monomethyl ether ethyl sulfonate (PEG-SE), with a yield of 98%. The chemical reaction formula is shown below: ; 5. Phosphine ligand synthesis reaction A magnetic stirrer was placed in a 250 mL three-necked flask equipped with a constant-pressure dropping funnel and a double exhaust valve. After leak testing, the flask was evacuated and the system was purged with argon 3-5 times to establish an inert atmosphere. 5.21 g (0.4 eq) of polyethylene glycol monomethyl ether ethyl sulfonate was dissolved in 30 mL of anhydrous tetrahydrofuran and transferred to the dropping funnel. Subsequently, a THF solution of phenyl(2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl)phosphine lithium (1 eq) obtained in step 3 was connected to the constant-pressure dropping funnel. The THF solution of polyethylene glycol monomethyl ether ethyl sulfonate prepared in step 4 was slowly added dropwise under stirring while cooling in an ice-water bath. The system temperature was kept at around 0°C during the addition. After the addition was completed, the mixture was stirred overnight in an ice-water bath to obtain the phosphine ligand. The chemical reaction formula is shown below: ; 6. Post-processing and purification of phosphine ligands After the reaction in step 5 is complete, add 1 mL of anhydrous oxyacetic acid and 15 mL of deionized water to a three-necked flask, stir to mix, and let stand. Then, under a nitrogen atmosphere, transfer the mixture to a separatory funnel, collect the upper organic phase, and extract the lower aqueous phase three times with tetrahydrofuran. Combine all organic layers in a Schlenk round-bottom flask, remove THF under reduced pressure, add 40 mL of toluene, stir well, and let cool in an ice-water bath. Transfer the solution to a separatory funnel under nitrogen protection, add 15 mL of deoxygenated deionized water, and let stand overnight. The next day, collect the lower aqueous phase in a Schlenk flask, and back-extract the organic phase three times with deionized water. Combine all aqueous layers, remove water under reduced pressure at 80°C to obtain the phosphine ligand (denoted as P). TPT22 It is a white or yellowish-white waxy solid.

[0025] Depend on Figure 1 It can be seen that the infrared spectrum is at 2861 cm⁻¹ -1 A distinct -CH2- / -CH3 stretching vibration peak appears at 1464 cm⁻¹, which is a characteristic absorption of the polyether backbone; -1 and 1342cm-1 These correspond to CH2 scissor and rocking vibrations, respectively. At 1240cm... -1 An asymmetric stretching vibration band with S=O can be observed, 1110cm. -1 and 1103cm -1 The strong absorption peak at 595 cm⁻¹ is characteristic of the stretching and contraction of polyether COC. -1 The weak absorption is attributed to the CS / SO bending vibration. The 3400 cm⁻¹ peak is not observed in the spectrum. -1 The broad peak indicates that the end groups are fully methylated and there are very few hydroxyl residues, indicating that the target sulfonate polyether compound was successfully obtained.

[0026] Depend on Figure 2 The 1H NMR spectrum of polyethylene glycol monomethyl ether ethyl sulfonate is as follows: 1H NMR (600 MHz, CDCl3) δ 4.4-4.2 (q, CH2), 3.75-3.5 (m, 86H, CH2), 3.31 (t, 3H, CH3), 3.17-3.08 (m, 2H, CH2), 1.36 (s, 3H, CH3).

[0027] Depend on Figure 3 The NMR spectrum of polyethylene glycol monomethyl ether ethyl sulfonate is as follows: 13C NMR (151 MHz, CDCl3) δ 71.90, 70.57, 69.07, 68.92, 58.98, 45.00, 8.15.

[0028] Depend on Figure 4 The 1H NMR spectrum of chloro(phenyl)[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine is as follows: 1H NMR (600 MHz, DMSO-d6) δ 7.71 (dt,2H,CH), 7.51-7.27 (m, 3H,CH), 7.03-6.84 (m, 3H,CH), 6.58-6.50 (m, 1H,CH), 3.75-3.59 (m, 6H,CH3), 3.56 (s,2H,CH), 2.88 (q,1H,CH), 1.13 (d,12H,CH3), 1.00 (s, 6H,CH3).

[0029] Depend on Figure 5 It can be seen that 2869 cm⁻¹ in the infrared spectrum -1 These correspond to the asymmetric and symmetric stretching vibrations of the isopropyl group, respectively. 1635 cm⁻¹ -1 This is a stretching vibration of the aromatic C=C skeleton, 1348 cm⁻¹ -1 The vibration is a deformational vibration of -CH3, 1248 cm. -1This is due to CO stretching absorption of the -OCH3 group on the aromatic ring. (At 1092 cm⁻¹) -1 A distinct PC(Ar) stretching vibration peak appears at 710 cm⁻¹. -1 This is a P-Ph vibrational band. The 1180-1200 cm⁻¹ region was not detected in the spectrum. -1 The characteristic absorption peak at P=O indicates that the phosphine group has not undergone oxidation. Comprehensive analysis confirms that this compound has a triarylphosphine structure containing aryl and isopropyl substitutions.

[0030] Depend on Figure 6 The 1H NMR spectrum of the prepared phosphine ligand is as follows: 1H NMR (600 MHz, D2O) δ 7.88 - 7.72 (m, 5H,,CH), 7.69 - 7.58 (m, 3H,CH), 7.56 (s, 1H), 3.89 (d, 8H,CH3,CH2), 3.74 (t, 84H,CH2), 3.42 (dd, 6H,CH3,CH), 2.94 (q,2H,CH2), 1.42 (d, 18H,CH3).

[0031] Example 2: Preparation of temperature-controlled phase transfer Pd nanocatalysts 0.5 mL of 0.5 mg / mL Na₂PdCl₄ aqueous solution, 3.5 mL of deionized water, 3.2 mg of the phosphine ligand prepared in Example 1 (2 eq relative to palladium each time), and 2 mL of n-pentanol were added sequentially to a polytetrafluoroethylene liner. The autoclave was then tightened and purged five times with 1 MPa of hydrogen gas, followed by 4 MPa of hydrogen gas. The autoclave was placed in a constant-temperature oil bath at 80 °C, and the rotor speed was set to 350 r / min. After reacting for 3 h, the autoclave was removed and cooled in an ice-water bath for 2 h. After cooling, the pressure was released and the autoclave was opened. The aqueous phase in the liner was observed to be brownish-black, while the upper organic phase was colorless and transparent, indicating that the reaction was complete. After separation, the temperature-controlled phase-transfer Pd nanocatalyst was obtained, denoted as P. TPT22 -Pd.

[0032] The PTPT prepared in Example 2 was verified by ultraviolet-visible spectroscopy. 22 - Valence state of palladium in Pd nanocatalyst: Under argon protection, 0.5 mL of temperature-controlled phase-transfer Pd nanocatalyst was placed in a cuvette, diluted with deionized water, and then subjected to UV-Vis spectroscopy. A mixed aqueous solution of Na₂PdCl₄·xH₂O and phosphine ligands before reduction was used as a control, and the same method was applied. The results are as follows: Figure 7 As shown.

[0033] Depend on Figure 7It can be seen that before reduction, the mixture exhibits an absorption peak near 385 nm, which corresponds to charge transfer between the temperature-regulated ligand and Pd; after reduction, the peak completely disappears, confirming the presence of Pd. 0 The formation of.

[0034] Example 3: Application of temperature-controlled phase-transfer Pd nanocatalysts in the Heck reaction In this embodiment, the temperature-controlled phase transfer Pd nanocatalyst prepared in Example 2 is used for the Heck reaction of iodobenzene and butyl acrylate.

[0035] 1) Under argon protection, add 4 mL of water, 2 mL of toluene, and 0.106 mg of P to a pre-filled container. TPT22 0.1 mL of iodobenzene, 0.104 mmol of butyl acrylate, 7.95 mg of cuprous iodide, and 168.94 mg of triethylamine were added to the pressure-resistant reaction tube of -Pd. 2) Under normal pressure argon protection, the pressure-resistant reaction tube of step 1) was placed in an oil bath at 85°C for 150 min. During the reaction, the catalyst was uniformly dispersed in the organic phase, and the system was a black uniform suspension. 3) After the reaction in step 2) is completed, the pressure-resistant reaction tube is naturally cooled to room temperature. At this time, the catalyst precipitates from the organic phase and transfers to the lower water layer. The upper organic phase gradually changes from black to colorless and clear. After standing and separating, the interface between the two phases is clear. The upper organic phase is taken out and analyzed by GC-MS.

[0036] Example 4: Recycling performance of temperature-controlled phase transfer Pd nanocatalysts After the reaction in Example 3 was completed, all the upper toluene layer was removed, and the catalyst was washed with toluene (2 mL × 3). After washing, 2 mL of toluene solvent was added again, followed by an additional 16 mg of phosphine ligand P. TPT22 Argon gas was introduced for protection; the pressure-resistant reaction tube was placed in a constant temperature oil bath at 85℃ and stirred for 150 minutes to allow the phosphine ligand P to react. TPT22 Completely dissolved in the lower aqueous phase, then following the steps of Example 3, iodobenzene, butyl acrylate, triethylamine, and cuprous iodide were added, and the next round of reaction was carried out under the same reaction conditions as in Example 3. The results are as follows. Figure 8 As shown.

[0037] Depend on Figure 8It is evident that the reaction yield gradually decreases with increasing catalytic cycles. Even though the catalyst maintains a certain level of catalytic activity after multiple uses, its effectiveness gradually weakens with time and the number of cycles. Possible reasons for this phenomenon include: partial loss of palladium species during each reaction and separation process; accumulation of reaction intermediates or ligands, leading to the covering of active sites and reduced catalytic efficiency; and changes in the phase transfer environment within the reaction system, potentially causing a decrease in the contact efficiency between the catalyst and the substrate, thus affecting the overall reaction rate. Although the catalyst still exhibits high activity in the first three cycles, and the temperature-controlled phase transfer palladium catalytic system demonstrates good reusability under specific conditions, it still shows a tendency for gradual deactivation, indicating the need to improve catalyst stability and activity protection measures.

[0038] Example 5: Effect of different solvent systems on Heck reaction efficiency P prepared in Example 2 was selected TPT22 The Heck reaction was carried out using a Pd catalyst with only the solvent system changed, while keeping other conditions constant. The process is as follows: Under argon protection, 0.106 mg P was added to a pre-filled organic / water two-phase solvent. TPT22 0.1 mL of iodobenzene, 0.104 mmol of butyl acrylate, 7.95 mg of cuprous iodide, and 168.94 mg of triethylamine were added to a pressure-resistant tube containing -Pd. Under atmospheric pressure and argon protection, the pressure-resistant reaction tube was placed in an oil bath at 85 °C and reacted for 150 min. After natural cooling to room temperature, the upper organic phase was collected for GC-MS analysis. The results are shown in Table 1 and... Figure 9 As shown.

[0039] Table 1. Heck reaction results under different solvent systems From Table 1 and Figure 9 It was found that the reaction yield was highest in the pure toluene system, reaching 80%. Adding a small amount of water reduced the yield to 78%, indicating that the presence of water inhibited the catalyst activity. When the solvent was changed to n-pentanol, the yield significantly decreased to 40%; while in the n-pentanol / water mixed solvent or pure water system, the reaction hardly occurred, with a yield of 0%. Therefore, this catalytic system is significantly dependent on the hydrophobicity of the solvent. Aromatic solvents are more conducive to the formation of stable active palladium species, while highly polar alcohols or water exhibit significant inhibitory effects.

[0040] like Figure 10 As shown, P obtained in Example 2 TPT22A Pd catalyst (0.0904 mg Pd) was dissolved in a two-phase system consisting of water (4 mL) and 1-hexanol (2 mL). After standing at room temperature, the catalyst was mainly distributed in the lower aqueous phase; when heated to 47 °C, the catalyst completely migrated to the upper organic phase. Upon cooling to room temperature, the catalyst returned to the aqueous phase, exhibiting reversible phase transfer behavior. The phase transfer temperature P was measured. TPT22 ≈47℃.

[0041] like Figure 11 As shown, P obtained in Example 1 TPT22 (0.09 mg) dissolved in a two-phase system consisting of water (2 mL) and 1-hexanol (4 mL). After standing at room temperature for 5 min, the catalyst was mainly distributed in the lower aqueous phase; when heated to 47 °C, the phosphine ligands completely migrated to the upper organic phase, and when cooled to room temperature, the phosphine ligands returned to the aqueous phase, exhibiting reversible phase transfer behavior.

[0042] like Figure 12 As shown, after the catalytic reaction in Example 3 was completed, 2 mL of toluene solvent was extracted, evaporated to dryness, and then redissolved in 2 mL of methanol. Gas chromatography analysis revealed good product separation. The toluene solvent contained relatively pure butyl cinnamate, the target product.

[0043] like Figure 13 and Figure 14 As shown, 2 ml of toluene phase after the reaction in Example 3 was rotary evaporated. The product was purified by column chromatography and analyzed by 1H and 1C NMR spectra. The results were as follows: 1H NMR (600 MHz, Methanol-d4) δ 7.67-7.53 (m, 3H, Ar), 7.41-7.29 (m, 3H, Ar), 6.50 (dt, 1H, CH2), 4.24-4.11 (m, 2H, CH2), 1.67 (dp, 2H, CH2), 1.44-1.28 (m, 2H, CH2), 0.97 - 0.83 (m, 3H, CH3). 13C NMR (151 MHz, Methanol-d4) δ 167.29, 144.71, 134.36, 130.10, 130.02, 128.65, 127.85. 127.24, 117.64, 64.11, 30.56, 18.87, 12.74.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A temperature-controlled phase-transfer Pd nanocatalyst, characterized in that, The catalyst was prepared by hydrogen reduction of a raw material containing Na₂PdCl₄ and a phosphine ligand, and the structural formula of the phosphine ligand is as follows: 。 2. The temperature-controlled phase-transfer Pd nanocatalyst according to claim 1, characterized in that, The molar ratio of Na2PdCl4 to phosphine ligand is 2~3:

1.

3. A method for preparing the temperature-controlled phase-transfer Pd nanocatalyst according to any one of claims 1-2, characterized in that, Includes the following steps: 1) Add Na2PdCl4 aqueous solution, deionized water, phosphine ligand and n-pentanol to the polytetrafluoroethylene liner, replace the gas in the reactor with hydrogen and then introduce hydrogen. 2) Place the high-pressure vessel from step 1) in a constant-temperature oil bath for stirring reaction. After the reaction is complete, remove the high-pressure vessel and place it in an ice-water bath to cool for 2 hours. Release the pressure and open the vessel to obtain the temperature-controlled phase transfer Pd nanocatalyst.

4. The method for preparing temperature-controlled phase-transfer Pd nanocatalyst according to claim 3, characterized in that, In step 1), hydrogen gas is introduced until the pressure reaches 4 MPa.

5. The method for preparing temperature-controlled phase-transfer Pd nanocatalyst according to claim 3, characterized in that, In step 1), the mass ratio of Na2PdCl4 aqueous solution to phosphine ligand is 0.2~0.3:3~3.5, and the mg / mL / mL ratio of phosphine ligand, deionized water and n-pentanol is 3.2:3.5:

2.

6. The method for preparing temperature-controlled phase-transfer Pd nanocatalyst according to claim 3, characterized in that, In step 2), the mixture is placed in a constant temperature oil bath at 80°C and stirred at 350 r / min for 3 hours.

7. The method for preparing temperature-controlled phase-transfer Pd nanocatalyst according to claim 3, characterized in that, The phosphine ligand is prepared by the following steps: 1) After a halogen-metal exchange reaction of 2-bromo-2',4',6'-triisopropyl-3,6-dimethoxy-1,1'-biphenyl with n-butyllithium in an inert solvent, a phosphine chloride reagent is added to carry out a phosphine chlorination reaction to obtain 2-lithium-2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]yl)lithium; the molar ratio of 2-bromo-2',4',6'-triisopropyl-3,6-dimethoxy-1,1'-biphenyl, n-butyllithium and phosphine chloride reagent is 1:1:1, the reaction temperature of the halogen-metal exchange reaction is -78℃, and the reaction time is 1.5h; 2) The 2-lithium-2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]yl)lithium obtained in step 1) is subjected to a monosubstituted reaction with phenyl dichlorophosphine to obtain chloro(phenyl)[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine; the molar ratio of 2-lithium-2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]yl)lithium to phenyl dichlorophosphine is 1:1~1.1, the reaction temperature of the monosubstituted reaction is -78℃, and the reaction time is 2h; 3) The chloro(phenyl)[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine obtained in step 2) was purified by rotary evaporation and then subjected to a halogen-metal exchange reaction with excess lithium metal in an inert solvent to obtain lithium phenyl[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine; the molar ratio of the chloro(phenyl)[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine to lithium metal was 1:5, the reaction temperature of the halogen-metal exchange reaction was 0℃, and the reaction time was 12h; 4) The phenyl[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine lithium obtained in step 3) is reacted with polyethylene glycol monomethyl ether ethyl sulfonate in an inert solvent, and the phosphine ligand is obtained by purification; the molar ratio of phenyl[2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl]phosphine lithium to polyethylene glycol monomethyl ether ethyl sulfonate is 1:0.

4.

8. The application of the temperature-controlled phase-transfer Pd nanocatalyst according to any one of claims 1-2 in the Heck reaction, characterized in that, The Heck reaction is the Heck reaction between iodobenzene and butyl acrylate.

9. A method for catalyzing the Heck reaction using the temperature-controlled phase-transfer Pd nanocatalyst according to any one of claims 1-2, characterized in that, Includes the following steps: S1. Under argon protection, temperature-controlled phase transfer Pd nanocatalyst, iodobenzene, butyl acrylate, cuprous iodide and triethylamine are added to the solvent to obtain the reaction system; S2. Under normal pressure and argon protection, the reaction system obtained in step S1 is placed in an oil bath at 85°C and reacted for 150 min. After naturally cooling to room temperature, the catalyst is separated from the product.

10. The method for catalyzing the Heck reaction using a temperature-controlled phase-transfer Pd nanocatalyst according to claim 9, characterized in that, In step S1, the molar ratio of temperature-controlled phase transfer Pd nanocatalyst, iodobenzene, butyl acrylate, cuprous iodide and triethylamine is 0.05:1:1:0.05:2.

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