Copper-containing titanium oxygen cluster catalyst and application thereof in synthesis of cyclic carbamate

Abstract

The invention is applicable to the technical field of organic chemistry, and provides a copper-titanium-containing oxygen cluster catalyst and application thereof in synthesis of cyclic carbamate, a preparation method of the copper-titanium-containing oxygen cluster catalyst comprises the following steps: adding ligands into an alcohol solvent, stirring and mixing, the ligands being phenylphosphoric acid, nicotinic acid and triphenylphosphine; adding a copper source, and stirring to uniformly mix; adding a titanium source, and stirring to uniformly mix to obtain a reaction precursor mixture; and placing the sealed reaction precursor mixture in a drying oven for heating reaction to obtain a reaction mixture, cooling the reaction mixture to obtain a yellow crystal, washing, drying, and grinding to obtain yellow powder. The copper-containing titanium oxygen cluster with accurate atoms is prepared in a solvothermal mode and is applied to catalysis of carbon dioxide and propargylamine at normal temperature and normal pressure to directly synthesize the cyclic carbamate compound, copper sites are fully exposed through the copper-containing titanium oxygen cluster with the accurate atoms, meanwhile, adsorption of reactants can be enhanced through coordination of triphenylphosphine, and therefore the cyclic carbamate compound is obtained. The activation energy of the reaction is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic chemistry, and particularly relates to a copper-containing titanium-oxygen cluster catalyst and its application in the synthesis of cyclic carbamates. Background Art

[0002] As a safe, inexpensive, and abundant carbon source, carbon dioxide can produce various value-added chemical substances through specific catalytic reactions. However, due to the kinetic inertness and thermodynamic stability of carbon dioxide, the chemical conversion directly involving carbon dioxide faces many challenges, such as low solubility in water and organic solvents, weak intermolecular interactions with transition metals, etc.; in addition, traditional carbon dioxide conversion and fixation usually require harsh reaction conditions. Therefore, the application of carbon dioxide in chemical synthesis has always been one of the most challenging research issues in the chemical industry.

[0003] Carbon dioxide, as a sustainable and low-cost carbon source, can reduce the dependence on fossil fuels and promote the sustainable utilization of resources, thus promoting the industrial production and application of carbamates. Cyclic carbamates are an important class of nitrogen-containing heterocyclic compounds with important biological properties and pharmacophore effects. The development of cyclic carbamate compounds is of great significance in the fields of drug synthesis, organic chemical synthesis, daily chemical industry, etc. Currently, there are many methods for synthesizing cyclic carbamates. However, with the marketization of cyclic carbamates, more environmentally friendly and inexpensive methods are needed to solve the complexity and toxicity in the preparation of cyclic carbamates. Compared with traditional organic synthesis methods, the carbon dioxide-based synthesis method will improve many defects existing in the synthesis process of cyclic carbamates, such as environmental pollution, high cost, and complex process. The carbon dioxide cycloaddition reaction shows the greatest potential in the field of organic chemistry. Among them, the carboxylation cyclization reaction of carbon dioxide using propargylamine substrates is widely regarded as an efficient and green synthesis strategy, but it also faces challenges such as low catalyst selectivity and limited reaction rate. High-activity and low-cost catalysts can promote the further large-scale application of the carbon dioxide cycloaddition method in the synthesis of cyclic carbamates. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a copper-containing titanium-oxygen cluster catalyst, aiming to solve the problems proposed in the above background art.

[0005] The embodiments of the present invention are implemented as follows. The copper-containing titanium-oxygen cluster catalyst has a preparation method including the following steps:

[0006] Add the ligand into an alcohol solvent, stir and mix. The ligand is phenylphosphonic acid, nicotinic acid, and triphenylphosphine;

[0007] Add a copper source and stir to mix it evenly;

[0008] Add a titanium source and stir to mix evenly to obtain a reaction precursor mixture;

[0009] Seal the reaction precursor mixture;

[0010] Place the sealed reaction precursor mixture in an oven, heat it up for reaction to obtain a reaction mixture. After the reaction mixture cools, obtain yellow crystals, wash and dry them, and then grind to obtain yellow powder.

[0011] Preferably, the amount of substance of phenylphosphonic acid is 0.6 - 1.2 mmol, the amount of substance of nicotinic acid is 1.0 - 2.0 mmol, and the amount of substance of triphenylphosphine is 1.0 - 2.0 mmol; the alcohol solvent is isopropyl alcohol.

[0012] Preferably, the copper source is copper bromide, and its amount of substance is 0.7 - 1.4 mmol.

[0013] Preferably, the titanium source is isopropyl titanate.

[0014] Preferably, in the step of placing the sealed reaction precursor mixture in an oven and heating it up for reaction, the heating rate is 4 - 8 °C / min, the reaction temperature is 80 °C, and the time is 72 h.

[0015] Another object of the embodiments of the present invention is to provide an application of a copper-titanium oxygen cluster catalyst in the synthesis of cyclic carbamates, including the following steps:

[0016] Add the copper-titanium oxygen cluster catalyst to a container containing acetonitrile and a magnetic stir bar, and perform ultrasonic treatment to obtain a uniformly dispersed solution;

[0017] Add an organic base to the solution to obtain a solution to be reacted;

[0018] Seal the solution to be reacted;

[0019] Introduce pure carbon dioxide gas into the solution to be reacted;

[0020] Add a propargylamine substrate to the solution to be reacted;

[0021] Magnetically stir the solution to be reacted for reaction, and ensure that carbon dioxide is sufficient during the reaction process;

[0022] After the reaction is completed, add 1,3,5-trimethoxybenzene, perform centrifugation, and take the supernatant to obtain cyclic carbamate.

[0023] Preferably, the organic base is 1,8-diazabicyclo(5,4,0)-7-undecene, and its amount of substance is 0.5 mmol.

[0024] Preferably, the pressure when carbon dioxide is introduced is 0.1 MPa.

[0025] Preferably, the amount of substance of the propargylamine substrate is 0.5 mmol.

[0026] Preferably, the magnetic stirring speed is 600 - 1400 r / min, and the reaction time is 3 - 5 h.

[0027] In the embodiment of the present invention, atomically precise copper-containing titanium oxo clusters were prepared by a solvothermal method and applied to the direct synthesis of cyclic carbamates from carbon dioxide and propargylamine under normal temperature and pressure. The atomically precise copper-containing titanium oxo clusters fully expose the copper sites, strengthening the adsorption and activation of carbon dioxide molecules. At the same time, the coordination of triphenylphosphine can enhance the adsorption of reactants and reduce the activation energy of the reaction, enabling the propargylamine substrate to be converted into cyclic carbamate compounds with a reaction rate close to 100%, which is beneficial to the practical application of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Comparison of the catalyst prepared in Example 1 of the present invention with the theoretical X-ray diffraction pattern;

[0029] Figure 2 Schematic diagram of the atomic structure of the catalyst prepared in Example 2 of the present invention;

[0030] Figure 3 1H NMR analysis diagram of the product prepared in Example 3 of the present invention;

[0031] Figure 4 1H NMR analysis diagram of the product prepared in Example 4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] A copper-containing titanium oxo cluster catalyst, and its preparation method includes the following steps:

[0034] S1. Add the ligands to the isopropanol solvent and stir to mix them evenly. The ligands are phenylphosphonic acid, nicotinic acid, and triphenylphosphine, and their amounts of substance are 0.6 - 1.2 mmol, 1.0 - 2.0 mmol, and 1.0 - 2.0 mmol respectively, and the volume of the alcohol solvent is 5 - 10 mL;

[0035] S2. Add copper bromide to the solution in step S1, stir to mix evenly, and the amount of copper bromide added is 0.7 - 1.4 mmol;

[0036] S3. Add isopropyl titanate to the solution in step S2, stir to mix evenly, and the volume of isopropyl titanate added is 0.9 - 1.8 mL;

[0037] S4. Transfer the reaction solution in step S3 to a 20 mL glass bottle, cover it with a rubber stopper, and seal it with an aluminum cap (the volume ratio of the reaction solution to the container is 1:4 - 6);

[0038] S5. Place the glass bottle containing the reaction precursor mixture in step S4 in an oven at 80 °C (with a heating rate of 4 - 8 °C / min) and react for 3 days;

[0039] S6. Wait for the reaction mixture in step S5 to cool, filter to obtain yellow crystals (the filtration is carried out by suction filtration using a water pump), wash the sample three times with isopropanol, and then dry it in an oven at 60 °C;

[0040] S7. Take out the sample dried in step S6, grind it (a ceramic crucible can be used), and collect the yellow powder;

[0041] In steps S1 to S4, the stirring can be magnetic stirring or mechanical stirring, and the stirring rate is 800 - 1400 r / min.

[0042] The copper-titanium-oxygen cluster catalyst is used to thermally catalyze the direct synthesis of cyclic carbamates from carbon dioxide and propargylamine, which specifically includes the following steps:

[0043] S1. Add an atomically precise copper-titanium-oxygen cluster catalyst (5 g) to a glass bottle containing acetonitrile (2 mL) and a magnetic stir bar, and ultrasonicate (the power of ultrasonication is 40 - 100 kHz, and the ultrasonication time is 5 - 60 min) to obtain a uniformly dispersed solution;

[0044] S2. Use a microsyringe to add the organic base 1,8-diazabicyclo(5,4,0)-7-undecene (DBU) (the amount of substance is 0.05 mmol) to the solution in step S1, and seal the glass tube with a rubber stopper and an aluminum cap;

[0045] S3. Introduce carbon dioxide (pressure is 0.1 MPa) into the solution to be reacted in step S2 to remove the air dissolved in acetonitrile;

[0046] S4. Use a microsyringe to add a propargylamine substrate (the amount of substance is 0.5 mmol) to the solution to be reacted in step S3;

[0047] S5. Insert a syringe filled with carbon dioxide gas at the bottle cap in step S4 to ensure an adequate amount of carbon dioxide during the reaction process;

[0048] S6. Place the reaction mixture in step S5 on a magnetic stirrer and stir at a magnetic stirrer speed of 800 - 1400 r / min;

[0049] S7. After the reaction is completed, add 1,3,5-trimethoxybenzene (with a molar amount of 0.2 mmol) as an internal standard, and then centrifuge the reaction solution obtained in step (6) to take the supernatant to obtain the product. The centrifugation speed is 10000 - 14000 r / min, and the centrifugation time is 1 - 20 min.

[0050] The following describes the specific implementation of the present invention in detail in combination with specific embodiments.

[0051] Example 1. A copper-containing titanium-oxygen cluster catalyst, and its preparation method includes the following steps:

[0052] S1. Add 0.6 mmol of phenylphosphonic acid, 1.0 mmol of nicotinic acid, and 1.0 mmol of triphenylphosphine to 5 mL of isopropanol, and the stirring rate is 800 r / min;

[0053] S2. Add 0.7 mmol of copper bromide to the solution in step S1, and stir magnetically to completely mix it, with a stirring rate of 800 r / min;

[0054] S3. Drop 0.9 mL of titanium isopropoxide into the solution in step S2, and stir magnetically with a stirring rate of 8000 r / min to obtain a reaction solution;

[0055] S4. Transfer the reaction solution in step S3 to a 20 mL glass bottle and seal it with a rubber stopper and an aluminum cap;

[0056] S5. Transfer the glass bottle containing the mixture in step S4 to an oven and react at 80 °C for 72 h;

[0057] S6. After the reaction is completed, filter the yellow crystals in step S5 and wash them with isopropanol;

[0058] S7. Place the washed sample in an oven at 60 °C and dry it for 24 h, and then grind and collect it.

[0059] Characterize the prepared atomically precise copper-containing titanium-oxygen cluster by an X-ray diffractometer, and the results are as Figure 1 shown. It can be seen that the experimental results of the XRD pattern of the obtained atomically precise copper-containing titanium-oxygen cluster catalyst are consistent with the theory.

[0060] Example 2. A copper-containing titanium oxo cluster catalyst, and its preparation method includes the following steps:

[0061] S1. Add 1.2 mmol of phenylphosphonic acid, 2.0 mmol of nicotinic acid, and 2.0 mmol of triphenylphosphine into 10 mL of isopropanol, and the stirring rate is 800 r / min;

[0062] S2. Add 1.4 mmol of copper bromide into the solution in step S1, and magnetically stir to make it completely mixed, and the stirring rate is 800 r / min;

[0063] S3. Drop 1.8 mL of titanium isopropoxide into the solution in step S2, and magnetically stir, and the stirring rate is 8000 r / min to obtain a reaction solution;

[0064] S4. Transfer the reaction solution in step S3 to a 20 mL glass bottle, and seal it with a rubber stopper and an aluminum cap;

[0065] S5. Transfer the glass bottle containing the mixture in step S4 to an oven and react at 80 °C for 72 h;

[0066] S6. After the reaction is completed, filter the yellow crystals in step S5 and wash them with isopropanol;

[0067] S7. Place the washed sample in an oven at 60 °C to dry for 24 h, and then grind and collect it.

[0068] The schematic diagram of the atomic structure of the atomically precise copper-containing titanium oxo cluster prepared is as Figure 2 shown.

[0069] Example 3. Using the atomically precise copper-containing titanium oxo cluster as a catalyst to directly synthesize cyclic carbamate from carbon dioxide and propargylamine under normal temperature and pressure, this method includes the following steps:

[0070] (1) Take 5 mg of the atomically precise copper-containing titanium oxo cluster prepared in Example 1, add it to a glass bottle containing 2 mL of acetonitrile and a magnetic stir bar, and ultrasonicate for 5 min at a frequency of 100 kHz to obtain a uniformly dispersed solution;

[0071] (2) Add 0.05 mmol of an organic base, 1,8-diazabicyclo(5,4,0)-7-undecene (DBU), to the solution in step (1) to obtain a solution to be reacted, and then seal the glass bottle with a rubber stopper and an aluminum cap;

[0072] (3) Introduce carbon dioxide into the solution to be reacted in step (2) for 5 minutes;

[0073] (4) Use a microsyringe to add 0.5 mmol of N-benzylprop-2-yn-1-amine to the solution to be reacted in step (3);

[0074] (5) Insert a 30 mL syringe filled with carbon dioxide gas at the bottle cap of step (4);

[0075] (6) Place the glass bottle on a magnetic stirrer and allow the system to react for 3 hours under magnetic stirring conditions at 800 r / min;

[0076] (7) Add 0.2 mmol of 1,3,5-trimethoxybenzene to the reaction solution obtained in step (6), then centrifuge at 10000 r / min for 2 min and take the supernatant to obtain the product 3-benzyl-5-methylene-2-oxazolidinone.

[0077] The yield of the prepared product was analyzed by proton nuclear magnetic resonance spectroscopy, and the results are as Figure 3 shown. It can be seen that the copper-containing titanium oxo cluster catalyst prepared in the examples of the present invention has a selectivity of 100% for the direct synthesis of cyclic carbamates from carbon dioxide and propargylamine under normal temperature and pressure. No peaks of other by-products were detected, and the conversion rate of cyclic carbamate relative to propargylamine was 98%.

[0078] Example 4: Using an atomically precise copper-containing titanium oxo cluster as a catalyst, carbon dioxide and propargylamine are directly synthesized into cyclic carbamates under normal temperature and pressure. The method includes the following steps:

[0079] (1) Take 5 mg of the atomically precise copper-containing titanium oxo cluster prepared in Example 1 and add it to a glass bottle containing 2 mL of acetonitrile and a magnetic stir bar, and ultrasonicate at a frequency of 100 kHz for 5 min to obtain a uniformly dispersed solution;

[0080] (2) Add 0.05 mmol of the organic base 1,8-diazabicyclo(5,4,0)-7-undecene (DBU) to the solution in step (1) to obtain a solution to be reacted, and then seal the glass bottle with a rubber stopper and an aluminum cap;

[0081] (3) Pass carbon dioxide into the solution to be reacted in step (2) for 5 minutes;

[0082] (4) Use a microsyringe to add 0.5 mmol of N-methylprop-2-yn-1-amine to the solution to be reacted in step (3);

[0083] (5) Insert a 30 mL syringe filled with carbon dioxide gas at the bottle cap of step (4);

[0084] (6) Place the glass bottle on a magnetic stirrer and let the system react for 3 hours under magnetic stirring at 800 r / min;

[0085] (7) Add 0.2 mmol of 1,3,5-trimethoxybenzene to the reaction solution obtained in step (6), then centrifuge at 10000 r / min for 2 min and take the supernatant to obtain the product 3-methyl-5-methylene-2-oxazolidinone.

[0086] The yield of the prepared product was analyzed by 1H NMR spectroscopy, and the results are as Figure 4 shown. It can be seen that the copper titanium oxo cluster catalyst prepared in the examples of the present invention has a selectivity of 100% for the direct synthesis of cyclic carbamates from carbon dioxide and propargylamine under normal temperature and pressure, and no peaks of other by-products were detected. The conversion rate of cyclic carbamates relative to propargylamine was 97%.

[0087] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A copper-containing titanium-oxygen cluster catalyst, characterized in that, The preparation method comprises the following steps: Add the ligand into an alcohol solvent and stir to mix. The ligand is phenylphosphonic acid, nicotinic acid, and triphenylphosphine. Add a copper source and stir to mix evenly. Add a titanium source and stir to mix evenly to obtain a reaction precursor mixture. Seal the reaction precursor mixture. Place the sealed reaction precursor mixture in an oven, raise the temperature for reaction to obtain a reaction mixture. After the reaction mixture cools, obtain yellow crystals, wash and dry them, and then grind to obtain yellow powder.

2. The copper-containing titanium-oxygen cluster catalyst according to claim 1, wherein The amount of substance of phenylphosphonic acid is 0.6 - 1.2 mmol, the amount of substance of nicotinic acid is 1.0 - 2.0 mmol, and the amount of substance of triphenylphosphine is 1.0 - 2.0 mmol; the alcohol solvent is isopropyl alcohol.

3. The copper-containing titanium-oxygen cluster catalyst according to claim 1, wherein The copper source is copper bromide, and its amount of substance is 0.7 - 1.4 mmol.

4. The copper-containing titanium-oxygen cluster catalyst according to claim 1, wherein The titanium source is isopropyl titanate.

5. The copper-containing titanium-oxygen cluster catalyst according to claim 1, wherein In the step of placing the sealed reaction precursor mixture in an oven and raising the temperature for reaction, the heating rate is 4 - 8 °C / min, the reaction temperature is 80 °C, and the time is 72 h.

6. Use of a copper titanium oxo cluster catalyst as described in any one of claims 1-5 in the synthesis of cyclic carbamates, characterized in that, Comprises the following steps: Add the copper-titanium-oxygen cluster catalyst into a container containing acetonitrile and a magnetic stirrer, and perform ultrasonic treatment to obtain a uniformly dispersed solution. Add an organic base to the solution to obtain a solution to be reacted. Seal the solution to be reacted. Introduce pure carbon dioxide gas into the solution to be reacted. Add a propargylamine substrate to the solution to be reacted. Magnetically stir the solution to be reacted for reaction, and ensure an adequate amount of carbon dioxide during the reaction process. After the reaction is completed, add 1,3,5-trimethoxybenzene, perform centrifugation, and take the supernatant to obtain cyclic carbamate.

7. The application according to claim 6, wherein The organic base is 1,8-diazabicyclo(5,4,0)-7-undecene, and its amount of substance is 0.5 mmol.

8. The application according to claim 6, characterized in that, The pressure during the introduction of carbon dioxide is 0.1 MPa.

9. The application according to claim 6, wherein The amount of substance of the propargylamine substrate is 0.5 mmol.

10. The application according to claim 6, wherein The magnetic stirring speed is 600 - 1400 r / min, and the reaction time is 3 - 5 h.

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