Catalyst Ag4 / TNT and its application in the cyclization reaction of CO2 with propargylamine

Abstract

The present invention discloses a catalyst Ag4 / TNT and its application in catalyzing the cyclization reaction of CO2 and propargylamine, wherein the catalyst Ag4 / TNT is a catalyst obtained by loading silver nanoclusters on a titanium nanotube carrier; the molecular formula of the silver nanoclusters is [(dppf)2Ag4[(C≡C t The Ag4 / TNT catalyst of the present invention can convert propargylamine substrates with high activity under mild reaction conditions, requires low catalyst dosage, and exhibits good substrate compatibility. Furthermore, the Ag4 / TNT catalyst can be recycled multiple times and produce gram-scale products, demonstrating excellent practicality.

Description

Technical Field

[0001] The present invention relates to a catalyst Ag4 / TNT and application thereof in catalyzing the cyclization reaction of CO2 and propargylamine. Background Art

[0002] In recent years, carbon dioxide (CO2) has garnered significant attention as a major contributor to global warming. With the rapid global economic growth and parallel industrial production, CO2 emissions are rising, and CO2 management remains a global challenge. Therefore, reducing CO2 emissions and lowering CO2 concentrations through CO2 conversion is an effective and sustainable approach. Chemical CO2 conversion is an effective approach to overcoming the energy crisis (Coordination Chemistry Reviews, 2022, 454:214340).

[0003] In recent years, a variety of products prepared from carbon dioxide have been developed, including starch (Science, 2021, 373(6562):1523-1527), carboxylic acid (Journal of the American Chemical Society, 2020, 142(9):4126-4130), propylene carbonate (Angewandte Chemie International Edition, 2021, 60(19):10573-10576), 2-oxazolidinone (Angewandte Chemie International Edition, 2020, 59(45):20031-20036), etc. Among them, 2-oxazolidinone can be synthesized by fixing carbon dioxide with propargylamine, which plays a vital role in organic intermediates, antibacterial agents and chiral auxiliary agents (ACS Catalysis, 2020, 10(5):3241-3248). However, for most catalysts with a single active site, it is difficult to achieve the conversion of both acetylene (-C≡C) and amino (-NH-) functional groups. For example, when N-2-propynylaniline is used to exchange the substrate for CO2 fixation, the reported catalysts have problems such as poor performance and low efficiency. For example, Ag@2,6-FPP-TAPT as a catalyst did not convert to the corresponding product at 50°C (Green Chemistry, 2022, 24(2):930-940); Ag@BT-COP did not successfully convert phenylpropyl-2-yn-1-amine under catalytic conditions of 60°C for 14h (Applied Surface Science, 2022, 604:154566); Cu2O@ZIF-8 only obtained a 2% yield under reaction conditions of 40°C and 12h (Angewandte Chemie International Edition, 2022, 61(19):e202114817). Currently, KCC-1 / IL / Ni@PdNPs (Applied Organometallic Chemistry 2018, 32, e3941) and Ag@TpTta (ACS Sustain. Chem. Eng. 2020, 8, 5495-5513) can be used to efficiently fix CO2 using phenylpropyl-2-yn-1-amine. However, these catalysts suffer from high reaction temperatures (80°C) and the high use of precious metals. Therefore, for the sake of green chemistry and economic chemistry, designing a catalyst with excellent substrate versatility under mild reaction conditions is an urgent issue.

[0004] Therefore, the purpose of this invention is to design and prepare more effective and targeted catalytic materials for the efficient cyclization of CO2 propargylamines. Based on this, the present invention successfully customized a novel catalyst, Ag4 / TNT, for the efficient cyclization of CO2 propargylamines. Ag4 / TNT achieves high activity for the conversion of propargylamine substrates at room temperature. Finally, the Ag4 / TNT catalyst was subjected to cycling tests and gram-scale experiments, demonstrating that it can be recycled multiple times and produce gram-scale products. Summary of the Invention

[0005] The present invention addresses the problems of the prior art by providing a catalyst, Ag4 / TNT, and its use in the cyclization reaction of CO2 with propargylamine. The novel Ag4 / TNT catalyst of the present invention can efficiently catalyze the cyclization reaction of CO2 with propargylamine under mild reaction conditions. It exhibits good catalytic activity, is broadly compatible with a wide range of substrates, and can be recycled multiple times, allowing for the production of gram-scale products.

[0006] The catalyst Ag4 / TNT of the present invention is a catalyst obtained by loading silver nanoclusters on titanium nanotube (TNT) carriers. The molecular formula of the silver nanoclusters is [(dppf)2Ag4[(C≡C t Bu)]2(CH3OH)2](BF4)2·2CH3OH, abbreviated as Ag4. The maximum absorption peak of metal nanocluster Ag4 in methanol solution is at 448nm ( Figure 4 A), the structure of the Ag4 nanocluster is mainly composed of four Ag atoms, two bis(diphenylphosphinoferrocene) ligands, two 3,3-dimethyl-butyne ligands and two methanol ligands ( Figure 4 B).

[0007] The catalyst Ag4 / TNT of the present invention is prepared by a method comprising the following steps:

[0008] Step 1: Synthesis of [AgC≡C t Bu] n

[0009] Ag2O (12.9 mmol, 3 g) was slowly added to a reaction flask containing 60 mL of ammonia water (24 mmol, 840 mg), and a new silver ammonia solution was obtained under stirring in an ice bath. The clarified silver ammonia solution was then carefully filtered, and 5 mL of ethanol solution containing 3,3-dimethyl-1-butyne (25.8 mmol, 2.12 g) was added under stirring to obtain a white precipitate. After reacting for about 5-8 minutes, the mixture was filtered under reduced pressure, and then appropriate amounts of deionized water, ethanol and ether were added in sequence for washing and drying to obtain [AgC≡C t Bu] n ;

[0010] Step 2: Synthesis of Ag4 nanoclusters

[0011] 0.3mmol[AgC≡C t Bu] n (0.057g) was ultrasonically dissolved in 6mL of methanol solution containing AgBF4 (0.058g, 0.3mmol) at ambient temperature for 15min. The ultrasonic frequency and power (intensity) were 40kHz and 150W, respectively. With the help of ultrasound, a fast, high-quality and uniform solution was achieved. To the obtained colorless solution, 0.2mmol of dppf (0.11g) was added, and the color of the solution changed from yellow to yellow-brown, and then the mixture was kept at a constant temperature of 70°C for 20h; after cooling to ambient temperature, the solution was filtered and the resulting solution was slowly evaporated to obtain yellow crystals, which were Ag4 nanoclusters. Yield: 47.6% (9mg, based on [AgC≡C t Bu] n ).

[0012] Step 3: Preparation of TNT carrier by hydrothermal method

[0013] TNTs (titanium nanotubes) were synthesized via a hydrothermal method. First, 1g of TiO2 powder was added to 100mL of a 10mol NaOH solution and stirred for 30 minutes. The mixture was then transferred to a 250mL autoclave and heated at 150°C for 24 hours. The suspension was then cooled and washed with deionized water until the pH dropped to 7. After acid washing for 3 hours under continuous magnetic stirring, the precipitate was washed again with distilled water until the washing solution was neutral and dried overnight at 70°C to obtain the TNT support.

[0014] Step 4: The TNT carrier is uniformly dispersed in the dichloromethane solution by ultrasonic treatment to obtain a suspension A;

[0015] Step 5: Add a dichloromethane solution containing Ag4 nanoclusters to the suspension A obtained in step 4, stir for 0.5 h, separate, wash and dry to obtain an Ag4 / TNT nanocomposite material.

[0016] We characterized Ag4 / TNT by transmission electron microscopy (TEM) and elemental distribution. TEM showed ( Figure 1 ABC), the TNT prepared by the present invention presents an elongated tubular shape, and no aggregated Ag nanoparticles are found on the composite Ag4 / TNT catalyst, proving that Ag4NC does not aggregate and migrate. Element distribution diagram ( Figure 1 D) shows that the Ag, Fe, and P elements in Ag4NC are uniformly dispersed on the TNT nanotubes, indicating that a small amount of Ag4NC is monodispersed on the TNT material.

[0017] The loading amount of Ag4 in the Ag4 / TNT catalyst of the present invention is 0.5wt%-4wt%, such as 0.5wt%, 1wt%, 2wt%, 4wt%, preferably 2wt%-4wt%.

[0018] The application of the catalyst Ag4 / TNT of the present invention in the catalytic cyclization reaction of CO2 and propargylamine specifically comprises the following steps:

[0019] Catalyst Ag4 / TNT, propargylamine, DBU, and acetonitrile were combined in a 10 mL reaction tube and reacted at 25°C in a carbon dioxide atmosphere using a balloon for 2 hours. After the reaction ceased, the reaction solution and catalyst (solid) were separated by centrifugation. The reaction solution was diluted and the conversion and selectivity were determined by gas chromatography and column chromatography (EtOAc / PE = 1:5, v / v). The catalyst was washed with acetonitrile, dried under vacuum, and then recycled.

[0020] Gram-scale reaction: Combine the catalyst Ag4 / TNT, propargylamine, DBU, and acetonitrile in a 25 mL reaction tube and react at 25°C under a CO atmosphere using a balloon for 12 h. After the reaction is complete, centrifuge the reaction mixture and catalyst (solid) to separate the mixture. Dilute the mixture, and determine conversion and selectivity by gas chromatography and column chromatography (EtOAc / PE = 1:5, v / v).

[0021] The loading amount of Ag4 nanoclusters in the catalyst Ag4 / TNT is 0.5wt%-4wt%.

[0022] The substrate propargylamine is selected from N-benzyl-2-propargylamine, N-2-propynylaniline, N-butyl-2-propargylamine, and N-2-propynyl-1-cyclohexylamine.

[0023] The molar ratio of propargylamine to DBU is 1:0.1.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. The Ag4 / TNT catalyst of the present invention can efficiently catalyze the cyclization of CO2 propargylamine to the corresponding dioxazolidinone at room temperature (25°C) and normal pressure (one CO2 ball) without any by-products, meeting the requirements of green chemistry;

[0026] 2. The Ag4 / TNT catalyst of the present invention has a wide range of applicability to substrates;

[0027] 3. The Ag4 / TNT catalyst of the present invention can be recycled;

[0028] 4. The Ag4 / TNT catalyst of the present invention can be used for gram-level experiments and yield gram-level products. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1These are the TEM images and element distribution images of Ag4 / TNT.

[0030] Figure 2 This is a schematic diagram of the gram-scale experiment of Ag4 / TNT.

[0031] Figure 3 This is the cycle experiment diagram of Ag4 / TNT.

[0032] Figure 4 This is the structure and UV image of Ag4 nanoclusters. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0034] Example 1: Ag4 / TNT catalyzes the cyclization of N-benzyl-2-propynylamine in tetrahydrofuran solution

[0035] 0.5 mmol N-benzyl-2-propargylamine, 25 mg Ag4 / TNT (2 wt%), 0.05 mmol DBU and 1 mL tetrahydrofuran were added in sequence to a 10 mL Schlenk reaction flask, and the reaction flask was sealed, evacuated and connected to a CO2 balloon, and the reaction was carried out at room temperature for 2 h. After the reaction, the reaction liquid was detected by gas chromatography to obtain the target product 3-benzyl-5-methylene-2-oxazolidinone with a conversion rate of 53.00%.

[0036] Example 2: Ag4 / TNT catalyzes the cyclization of N-benzyl-2-propargylamine in acetonitrile solution

[0037] 0.5 mmol N-benzyl-2-propargylamine, 25 mg Ag4 / TNT (2 wt%), 0.05 mmol DBU and 1 mL acetonitrile were added in sequence to a 10 mL Schlenk reaction flask, and the reaction flask was sealed, evacuated and connected to a CO2 balloon, and the reaction was carried out at room temperature for 2 h. After the reaction, the reaction liquid was detected by gas chromatography to obtain the target product 3-benzyl-5-methylene-2-oxazolidinone with a conversion rate of 99.00%.

[0038] 1 HNMR (400MHz, CHLOROFORM-D) δ7.50-7.11(m,5H),4.71(d,J=2.9Hz,1H),4.45(s,2H),4.22(d,J=2.7Hz,1H),4.00(t,J=2.4Hz,2H). 13 CNMR(101MHz,CHLOROFORM-D)δ155.75,149.06,135.08,129.07,128.35,128.27,86.84,47.94,47.32.

[0039] Example 3: Cyclization of N-benzyl-2-propynylamine catalyzed by Ag4 / TNT

[0040] 0.5 mmol N-benzyl-2-propargylamine, 25 mg Ag4 / TNT (0.5 wt%), 0.05 mmol DBU and 1 mL acetonitrile were added in sequence to a 10 mL Schlenk reaction flask, and the flask was sealed, evacuated and connected to a CO2 balloon, and the reaction was carried out at room temperature for 2 h. After the reaction, the reaction liquid was detected by gas chromatography, and the conversion rate of the target product 3-benzyl-5-methylene-2-oxazolidinone was 23.8%.

[0041] Example 4: Cyclization of N-benzyl-2-propynylamine in Ag4 / TNT

[0042] 0.5 mmol N-benzyl-2-propargylamine, 25 mg Ag4 / TNT (1 wt%), 0.05 mmol DBU and 1 mL acetonitrile were added in sequence to a 10 mL Schlenk reaction flask, and the reaction flask was sealed, evacuated and connected to a CO2 balloon, and the reaction was carried out at room temperature for 2 h. After the reaction, the reaction liquid was detected by gas chromatography to obtain the target product 3-benzyl-5-methylene-2-oxazolidinone with a conversion rate of 47.30%.

[0043] Example 5: Cyclization of N-benzyl-2-propargylamine catalyzed by Ag4 / TNT

[0044] 0.5 mmol N-benzyl-2-propargylamine, 25 mg Ag4 / TNT (4 wt%), 0.05 mmol DBU and 1 mL acetonitrile were added in sequence to a 10 mL Schlenk reaction flask, and the reaction flask was sealed, evacuated and connected to a CO2 balloon, and the reaction was carried out at room temperature for 2 h. After the reaction, the reaction liquid was detected by gas chromatography to obtain the target product 3-benzyl-5-methylene-2-oxazolidinone with a conversion rate of 99.00%.

[0045] Example 6: Cyclization of N-benzyl-2-propargylamine catalyzed by Ag4 / TNT

[0046] 0.5 mmol N-benzyl-2-propargylamine, 25 mg Ag4 / TNT (2 wt%), 0.05 mmol K2CO3 and 1 mL acetonitrile were added in sequence to a 10 mL Schlenk reaction flask, and the flask was sealed, evacuated and connected to a CO2 balloon, and the reaction was carried out at room temperature for 2 h. After the reaction, the reaction liquid was detected by gas chromatography, and the conversion rate of the target product 3-benzyl-5-methylene-2-oxazolidinone was 15.70%.

[0047] Example 7: Cyclization of N-benzyl-2-propynylamine catalyzed by Ag4 / TNT

[0048] 0.5 mmol N-benzyl-2-propargylamine, 25 mg Ag4 / TNT (2 wt%), 0.05 mmol DBU and 1 mL acetonitrile were added in sequence to a 10 mL Schlenk reaction flask, and the flask was sealed, evacuated and connected to a CO2 balloon, and the reaction was carried out at room temperature for 1.5 h. After the reaction, the reaction liquid was detected by gas chromatography to obtain the target product 3-benzyl-5-methylene-2-oxazolidinone with a conversion rate of 71.50%.

[0049] Example 8: Ag4 / TNT-catalyzed cyclization of N-2-propynylaniline

[0050] 0.5 mmol N-2-propynylaniline, 25 mg Ag4 / TNT, 0.05 mmol DBU and 1 mL acetonitrile were added in sequence to a 10 mL Schlenk reaction flask, and the reaction flask was sealed, evacuated and connected to a CO2 balloon, and the reaction was carried out at room temperature for 12 h. The reaction solution was analyzed by GC and the crude product was purified by column chromatography (EtOAc / PE=1:5) to obtain the target product 5-methylene-3-phenyl-2-oxazolidinone with a conversion rate of 87.00%.

[0051] 1 HNMR(400MHz,CHLOROFORM-D)δ7.53(dd,J=8.8,1.2Hz,2H),7.43-7.33(m,2H),7. 20-7.10(m,1H),4.84(q,J=2.8Hz,1H),4.61(t,J=2.4Hz,2H),4.46-4.37(m,1H). 13 CNMR(101MHz,CHLOROFORM-D)δ152.43,147.81,137.26,129.31,124.63,118.18,87.16,48.47.

[0052] Example 9: Cyclization of N-butyl-2-propynylamine catalyzed by Ag4 / TNT

[0053] 0.5 mmol N-butyl-2-propargylamine, 25 mg Ag4 / TNT, 0.05 mmol DBU and 1 mL acetonitrile were added in sequence to a 10 mL Schlenk reaction flask, and the reaction flask was sealed, evacuated and connected to a CO2 balloon, and the reaction was carried out at room temperature for 2 h. The reaction solution was analyzed by GC and the crude product was purified by column chromatography (EtOAc / PE=1:5) to obtain the target product 3-butyl-5-methylene-2-oxazolidinone with a conversion rate of 98.20%.

[0054] 1HNMR(400MHz,CHLOROFORM-D)δ4.71(d,J=2.9Hz,1H),4.31-4.23(m,1H),4.13(t,J=2.4Hz,2H ), 3.28 (t, J = 7.3Hz, 2H), 1.51 (d, J = 7.6Hz, 2H), 1.33 (d, J = 8.0Hz, 2H), 0.92 (t, J = 7.3Hz, 3H). 13 CNMR(101MHz,CHLOROFORM-D)δ155.67,149.25,86.46,47.85,43.54,29.35,19.83,13.69.

[0055] Example 10: Cyclization of N-2-propynyl-1-cyclohexylamine catalyzed by Ag4 / TNT

[0056] 0.5 mmol N-2-propynyl-1-cyclohexylamine, 25 mg Ag4 / TNT, 0.05 mmol DBU and 1 mL acetonitrile were added in sequence to a 10 mL Schlenk reaction flask, and the reaction flask was sealed, evacuated and connected to a CO2 balloon, and the reaction was carried out at room temperature for 2 h. The reaction solution was analyzed by GC and the crude product was purified by column chromatography (EtOAc / PE=1:5) to obtain the target product 3-cyclohexyl-5-methylene-2-oxazolidinone with a conversion rate of 98.20%.

[0057] 1 HNMR(400MHz,CHLOROFORM-D)δ4.70(q,J=2.7Hz,1H),4.25(q,J=2.4Hz,1H),4.11(t,J=2.4Hz,2H),3. 79-3.61(m,1H),1.80(dt,J=9.5,2.6Hz,4H),1.69-1.61(m,1H),1.41-1.26(m,4H),1.14-0.99(m,1H). 13 CNMR(101MHz,CHLOROFORM-D)δ155.01,149.74,86.32,52.45,44.20,30.36,25.35,25.32.

[0058] Example 11: Ag4 / TNT-catalyzed cyclization reaction of N-benzyl-2-propargylamine

[0059] In a 10 mL Schlenk reaction flask, 0.5 mmol N-benzyl-2-propargylamine, 50 mg Ag4 / TNT (2 wt%), 0.05 mmol DBU and 1 mL acetonitrile were added in sequence. The reaction flask was sealed, evacuated and connected to a CO2 balloon. The reaction was allowed to proceed at room temperature for 12 h to obtain the target product 3-benzyl-5-methylene-2-oxazolidinone with a conversion rate of 99.00%. After the reaction was stopped, the reaction solution and the catalyst (solid) were separated by centrifugation. The catalyst was washed with acetonitrile and dried in vacuo. The cycle was repeated several times without any significant decrease ( Figure 3 ).

[0060] Example 12: Ag4 / TNT-catalyzed cyclization of N-benzyl-2-propargylamine at a gram-scale

[0061] In a 25 mL Schlenk reaction bottle, 1 g of N-benzyl-2-propargylamine, 300 mg of Ag4 / TNT (4 wt%), 0.69 mmol of DBU, and 10 mL of acetonitrile were added in sequence. The reaction bottle was sealed, evacuated, and connected to a CO2 balloon. The reaction was carried out at room temperature for 12 h to obtain the target product 1.2 g of 3-benzyl-5-methylene-2-oxazolidinone ( Figure 2 ).

Claims

1. A catalyst Ag4 / TNT for catalyzing the cyclization reaction of CO2 and propargylamine, characterized in that: The catalyst Ag4 / TNT is a catalyst obtained by loading silver nanoclusters on a titanium nanotube carrier; The molecular formula of the silver nanocluster is [(dppf)2Ag4[(C≡C t Bu)]2(CH3OH)2] (BF4)2∙2CH3OH, abbreviated as Ag4; the loading amount of Ag4 in the Ag4 / TNT catalyst is 0.5wt%-4wt%.

2. The use according to claim 1, characterized in that The catalyst Ag4 / TNT is prepared by a method comprising the following steps: Step 1: Synthesis of [AgC≡C t Bu] n Ag2O was added to a reaction bottle containing ammonia water, and a silver ammonia solution was obtained under stirring in an ice bath. The silver ammonia solution was filtered, and an ethanol solution containing 3,3-dimethyl-1-butyne was added under stirring to obtain a white precipitate. After reacting for 5-8 minutes, the solution was filtered under reduced pressure, and then washed with deionized water, ethanol and ether in sequence, and dried to obtain [AgC≡C t Bu] n ; Step 2: Synthesis of Ag4 nanoclusters [AgC≡C t Bu] n The AgBF4 was ultrasonically dissolved in a methanol solution at ambient temperature and ultrasonically dispersed to obtain a colorless solution. Dppf was added to the system, and the color of the solution changed from yellow to yellow-brown. The mixture was then kept at 70°C for 20 h. After cooling to ambient temperature, the solution was filtered and slowly evaporated to obtain yellow crystals, which were Ag4 nanoclusters. Step 3: Preparation of TNT carrier by hydrothermal method TiO2 powder was added to the NaOH solution and stirred to disperse evenly. The mixture was then transferred to an autoclave and heated at 150 °C for 24 h. Afterwards, the suspension was cooled and washed with deionized water until the pH value was 7. The suspension was acid-washed for 3 h under continuous magnetic stirring. The precipitate was washed again with distilled water until the precipitate washing solution was neutral and dried to obtain the TNT carrier. Step 4: The TNT carrier is uniformly dispersed in the dichloromethane solution by ultrasonic treatment to obtain a suspension A; Step 5: Add a dichloromethane solution containing Ag4 nanoclusters to the suspension A obtained in step 4, stir for 0.5 h, separate, wash and dry to obtain an Ag4 / TNT nanocomposite material.

3. The use according to claim 1, characterized in that: The catalyst Ag4 / TNT, propargylamine, DBU and solvent were mixed and added into a reaction tube, and a cyclization reaction of CO2 and propargylamine was carried out at 25°C in a carbon dioxide atmosphere.

4. The use according to claim 3, characterized in that: The solvent is acetonitrile.

5. The use according to claim 3, characterized in that: The substrate propargylamine is selected from N-benzyl-2-propargylamine, N-2-propynylaniline, N-butyl-2-propargylamine, and N-2-propynyl-1-cyclohexylamine.

6. The use according to claim 3, characterized in that: The loading amount of Ag4 nanoclusters in the catalyst Ag4 / TNT is 2wt%-4wt%.

7. The use according to claim 3, characterized in that: The molar ratio of propargylamine to DBU is 1:0.1.

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