Sn (II) catalyst as well as preparation method and application thereof
By preparing Sn(II) catalysts and utilizing its unique electronic structure and oxidation state transformation, the problem of catalytic activity of low-priced Group 14 element compounds in the field of organic synthesis has been solved, and the defluorination and hydrogenation of polyfluoroaromatics and nitroaromatics have been achieved. The reduction replaces the application of precious metal catalysts.
Patent Information
- Application Number
- CN202411434632.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-15
- Publication Date
- 2025-01-21
- Estimated Expiration
- 2044-10-15
AI Technical Summary
In the prior art, low-priced Group 14 elemental compounds have failed to find an effective method to modify, have catalytic activity, and are difficult to replace the application of precious metal catalysts in the field of organic synthesis.
通过使用骨架分子双(三苯基膦)卡本和正丁基锂与二氯化锡进行反应,制备出Sn(II)催化剂,利用其亲电性和亲核性,以及Sn(II)/Sn( IV) The transformation of oxidation state is used as a transition metal catalyst in the reaction of dewme hydride hydride hydride hydride and nitric gabita.
It achieves efficient defluorination and hydrogenation of polyfluorinated aromatics and efficient reduction of nitroaromatics. It has high catalytic activity and stability and can replace traditional transition metal catalysts. The raw materials are easily available and the synthesis is simple.
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Figure CN119331018A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of organic synthesis, in particular to a Sn(II) catalyst and a preparation method and application thereof. Background Art
[0002] Homogeneous catalysis is an important research field in chemistry and has a wide range of applications in industrial fields such as organic chemicals, fine chemicals, pharmaceuticals, and polymer production. Traditional homogeneous catalytic synthesis mainly uses precious metal complexes such as palladium, ruthenium, and rhodium as catalysts. However, precious metals have limited reserves in the earth's crust, are expensive, and difficult to recycle, which does not conform to the concept of green and sustainable development. From a long-term development perspective, the development of cheap, accessible, and environmentally friendly main-group element catalysts is one of the main development trends in the field of catalytic synthetic chemistry. In recent years, synthetic chemists have conducted a lot of research on low-valent main-group element compounds with transition metal-like valence electron structures. In addition to studying new structures, new properties, and new reaction activities of low-valent main-group compounds, chemists have been trying to develop more green, environmentally friendly, cheap, and accessible main-group element catalysts to replace low-abundance, expensive, and potentially toxic precious metal catalysts.
[0003] At present, main group element compounds can be used as coordination groups of transition metals in the field of organic catalysis. This is to utilize the electronic properties and steric properties of the main group compounds themselves to modify the valence electron structure of the central metal, thereby changing the catalytic activity of the transition metal catalyst. However, this strategy still cannot avoid the use of transition metal catalysts. The main group compounds only serve as ligands and do not participate in the reaction as catalytically active species. In addition, main group element compounds can be used as organic small molecule catalysts to participate in organic small molecule catalytic reactions by utilizing their electrophilicity or nucleophilicity. However, this type of catalytic system has problems such as slow reaction rate, narrow substrate range, and large amount of catalyst, and has limited development prospects in industrial applications. In the prior art, researchers have successively synthesized low-valent phosphorus compounds and low-valent bismuth compound catalysts, and used them in the field of organic synthesis as a substitute for transition metal catalysts. However, for low-valent group 14 element compounds whose raw materials are cheap and easy to obtain and can simulate the reactivity of transition metal reactions, people have not been able to find a corresponding method to modify them and make them catalytically active. How to establish a balance between the stability, reactivity and catalytic activity of Group XIV element compounds, develop main-group catalysts centered on Group XIV elements, and apply them to the field of organic synthesis has always been a key scientific issue that needs to be solved urgently. Summary of the invention
[0004] In view of the technical problems of the existing main group catalysts such as difficulty in synthesis, low efficiency and limited application, the present invention provides a Sn(II) catalyst and a preparation method thereof.
[0005] The preparation method of the Sn(II) catalyst provided by the present invention is as follows:
[0006] S1. Add the backbone molecule and solvent A into a reaction vessel, introduce an inert gas to exclude air, and place the reaction vessel in an ice bath to lower the solution temperature to 0°C. Then add n-butyl lithium, stir at 0°C for 30 minutes, and then stir at room temperature for 30 minutes to obtain solution A.
[0007] The solvent A is selected from at least one of diethyl ether, diisopropyl ether, tetrahydrofuran and tetrahydropyran.
[0008] The structural formula of the backbone molecule is as follows:
[0009]
[0010] The Chinese name of the backbone molecule is bis(triphenylphosphine) carbene, which is the Chinese translation of carbodiphosphorane.
[0011] S2. Dissolve tin dichloride in solvent B to obtain solution B, add solution B to solution A, stir at room temperature for 6-18 hours, then remove solvent B by distillation under reduced pressure, add solvent C for extraction, extract the target product with solvent C, and then remove solvent C under reduced pressure to obtain Sn(II) catalyst, also known as tin carbene catalyst.
[0012] The solvent B is selected from at least one of tetrahydrofuran, ether, toluene, benzene, xylene or trimethylbenzene.
[0013] The solvent C is selected from at least one of benzene, toluene, chlorobenzene, xylene and trimethylbenzene.
[0014] Preferably, the molar ratio of the backbone molecule, n-butyl lithium and tin dichloride is 1:(2.0-2.2):1.
[0015] Preferably, in step S1, the prepared solution A is subjected to reduced pressure distillation to remove solvent A in solution A, and then the subsequent step S2 is performed. Because when solution A contains solvent A, the effective storage time of solution A is very short, and removing solvent A from solution A can extend the storage time.
[0016] Preferably, in step S2, solvent B is removed by distillation under reduced pressure, and solvent C is added after solvent B is completely removed, and the amount of solvent C is controlled so that the target product is completely dissolved without dissolving the by-product lithium chloride. After adding solvent C, ultrasonic dispersion is performed to completely dissolve the target product while lithium chloride is not dissolved, and then the mixture is allowed to stand for several minutes, and solid lithium chloride is removed by suction filtration, and the obtained liquid phase is subjected to reduced pressure to remove solvent C, thereby obtaining the target product.
[0017] The preparation reaction formula of Sn(II) catalyst is as follows:
[0018]
[0019] The Sn(II) catalyst can be used as a catalyst in the defluorination hydrogenation reaction of polyfluoroaromatic hydrocarbons and the reduction reaction of nitroaromatic hydrocarbons.
[0020] The solvent used in the defluorination hydrogenation reaction of polyfluoroaromatics and the reduction reaction of nitroaromatics is one of tetrahydrofuran, toluene, benzene, xylene and trimethylbenzene. The reaction temperature is 20-120° C. and the reaction time is 0.5-48 hours.
[0021] The molar ratio of the Sn(II) catalyst to the polyfluoroaromatic hydrocarbon is (1-10):100.
[0022] The molar ratio of the Sn(II) catalyst to the nitroaromatic hydrocarbon is (1-100):1000.
[0023] Compared with the prior art, the present invention is beneficial in that:
[0024] (1) The present invention utilizes the spatial geometric constraint strategy of the ligand to change the valence electron structure of the central atom Sn(II), so that the compound has both electrophilicity and nucleophilicity, can undergo Sn(II) / Sn(IV) oxidation state conversion, and can be used in the field of organic synthesis as a transition metal-like catalyst.
[0025] (2) The low-valent tin compound can be used as a catalyst to realize the defluorination hydrogenation of polyfluoroaromatic systems to generate corresponding hydrogenation products; it can realize the efficient reduction of nitroaromatic systems to generate reduction products such as azobenzene and aniline according to demand. Existing Sn(II) compounds cannot undergo the Sn(II) / Sn(IV) valence-changing catalytic cycle, and therefore cannot be used as catalysts for the defluorination hydrogenation of polyfluoroaromatics and the reduction of nitroaromatics. The catalyst prepared by the present invention realizes the defluorination hydrogenation of polyfluoroaromatics and the reduction of nitroaromatics for the first time using heavy group XIV compounds.
[0026] (3) Compared with traditional transition metal catalysts, the catalyst raw materials are easily available and the synthesis is simple, so it can replace transition metal catalysts in organic synthesis reactions. In addition, this compound is the first organic tin compound that can realize Sn(II) / Sn(IV) catalytic cycle, and it is also the first Group 14 organic compound that can realize redox cycle.
[0027] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 The catalyst prepared in Example 1 119Sn NMR test results.
[0029] Figure 2 The catalyst prepared in Example 1 was used before, during and after the hydrogenation reaction of perfluoropyridine. 31 P NMR test results.
[0030] Figure 3 The catalyst prepared in Example 1 was used for hydrogenation of perfluoropyridine 19 F NMR test results.
[0031] Figure 4 The catalyst prepared in Example 1 was used before, during and after the reduction reaction of nitrobenzene. 31 P NMR test results. DETAILED DESCRIPTION
[0032] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.
[0033] Example 1
[0034] A method for preparing a Sn(II) catalyst, comprising the following specific steps:
[0035] (1) 0.1 mmol of bis(triphenylphosphine) carbene and 20 mL of ether were added to a reaction container; the reaction container was then replaced with gas three times under argon protection, and the reaction container was placed in an ice bath to reduce the solution temperature to 0°C, and then 0.22 mmol of n-butyl lithium (a commercially available n-butyl lithium solution with a concentration of 1.6 or 2.5 M in n-hexane) was added, and the mixture was stirred at 0°C for 30 min, and then stirred at room temperature for 30 min to obtain a solution A; the solution A was subjected to reduced pressure distillation to remove the solvent ether.
[0036] (2) 0.1 mmol of tin dichloride was dissolved in 20 mL of tetrahydrofuran to obtain solution B; solution B was added to the material after the solvent was removed by vacuum distillation in step S1, and the mixture was stirred at room temperature for 12 h. The solvent tetrahydrofuran was removed by vacuum distillation to obtain a solid; then 30 mL of toluene was added, and ultrasonic dispersion was performed for 10 min to dissolve the target catalyst in toluene, while the by-product lithium chloride did not dissolve. After standing for 10 min, the lithium chloride was filtered out by suction, and the filter cake was washed three times with toluene. The liquid phases were combined and vacuum distilled to dryness to obtain the target Sn(II) catalyst with a yield of 85%.
[0037] The chemical reaction formula is as follows:
[0038]
[0039] In another embodiment, the solution A obtained in step (1) may be directly used in the subsequent steps without being evaporated under reduced pressure to remove the solvent ether.
[0040] The catalyst prepared in Example 1 was characterized and the results are as follows: 31 P NMR (162MHz, benzene-d6): δ = 24.1 (s). like Figure 1 As shown, 119 Sn NMR (149MHz, benzene-d6): δ = 135.9 (s). HRMS(ESI):m / zcalculated for C 37 H 28 P2Sn[M+MeO] + :685.0876, found:685.0875.UV-vis(THF solution)[nm]:λ=320.
[0041] Application Example 1
[0042] The catalyst prepared in Example 1 was used for the defluorination hydrogenation reaction of polyfluoroaromatics, and the reaction equation was as follows:
[0043]
[0044] The specific method is as follows: 30 μL of pentafluoropyridine, 30 mg of catalyst, 30 μL of phenylsilane and 1.5 mL of tetrahydrofuran are mixed and added to a reaction tube, replaced with argon three times, and reacted at 60°C for 2 hours. After the reaction, the mixture is cooled to room temperature, and the conversion rate of pentafluoropyridine, the yield of the product and the state of the catalyst are detected by nuclear magnetic resonance. The results are shown in Figure 2 and Figure 3 , the substrate conversion rate and the target product yield were both 99%, and there was no catalyst loss.
[0045] Application Example 2
[0046] The catalyst prepared in Example 1 was used for the reduction reaction of nitroaromatic hydrocarbons, and the reaction equation was as follows:
[0047]
[0048] Specific method: 50 μL nitrobenzene, 30 mg catalyst, 60 μL phenylsilane and 1.5 mL tetrahydrofuran were mixed and added to the reaction tube, replaced with argon three times, and stirred at room temperature for 30 minutes. After the reaction, it was cooled to room temperature, and the conversion rate of nitrobenzene, the yield of aniline and the state of the catalyst were detected by gas chromatography-mass spectrometry. The results are shown in Figure 4 , the substrate conversion rate and the target product yield were both 99%, and there was no catalyst loss.
[0049] Comparative Example 1
[0050] In order to illustrate the advantages of the catalyst prepared by the present invention, this comparative example provides an application of an existing reported tin catalyst 1 in defluorination hydrogenation, and the molecular structure of the catalyst 1 is as follows:
[0051]
[0052] The catalytic reaction equation is as follows:
[0053]
[0054] The specific reaction conditions are the same as those of the Sn(II) catalyst in Application Example 1: 30 μL of pentafluoropyridine, 30 mg of catalyst 1, 30 μL of phenylsilane and 1.5 mL of tetrahydrofuran were mixed and added to a reaction tube, replaced with argon three times, and reacted at 60° C. for 2 h. After the reaction, the mixture was cooled to room temperature, and the conversion rate of pentafluoropyridine and the yield of the product were detected by nuclear magnetic resonance. The substrate conversion rate and the yield of the target product were both less than 1%.
[0055] Comparative Example 2
[0056] This comparative example provides a reported use of tin catalyst 2 and catalyst 3 in the reduction of nitroaromatics.
[0057] The molecular structures of catalyst 2 and catalyst 3 are as follows:
[0058]
[0059] The reaction equation is as follows:
[0060]
[0061] The specific reaction conditions are the same as those of the Sn(II) catalyst in Application Example 2: 50 μL of nitrobenzene, 12 mg of catalyst 2 or 30 mg of catalyst 3, 60 μL of phenylsilane and 1.5 mL of tetrahydrofuran are mixed and added to a reaction tube, replaced with argon three times, and stirred at room temperature for 30 min. After the reaction, the reaction is cooled to room temperature, and the conversion rate of nitrobenzene and the yield of aniline are detected by gas chromatography-mass spectrometry. The substrate conversion rate and the target product yield are both less than 1%.
[0062] Through the experimental comparison of the above two application examples and the comparative example, it can be concluded that the Sn(II) catalyst prepared by the present invention can simultaneously produce catalytic effects in the defluorination hydrogenation reaction of polyfluoroaromatic hydrocarbons and the reduction reaction of nitroaromatic hydrocarbons. However, the existing Sn(II) catalyst cannot undergo the valence state change of Sn(II) / Sn(IV), so it has no catalytic effect on the defluorination hydrogenation reaction of polyfluoroaromatic hydrocarbons and the reduction reaction of nitroaromatic hydrocarbons. Compared with traditional transition metal catalysts, the catalyst raw materials are easy to obtain, the synthesis is simple, and it can replace transition metal catalysts to participate in organic synthesis reactions.
[0063] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.
Claims
1. A Sn(II) catalyst, characterized in that The molecular structure is as follows:
2. A method for preparing the Sn(II) catalyst as claimed in claim 1, characterized in that: Here are the steps: S1, adding the skeleton molecule and solvent A into a reaction container, introducing an inert gas to exclude air, placing the reaction container in an ice bath to reduce the solution temperature to 0°C, then adding n-butyl lithium, stirring at 0°C for 30 minutes, and then stirring at room temperature for 30 minutes to obtain solution A; the solvent A is selected from at least one of diethyl ether, diisopropyl ether, tetrahydrofuran, and tetrahydropyran; The structural formula of the backbone molecule is as follows: S2, dissolving tin dichloride in solvent B to obtain solution B, adding solution B to solution A, stirring at room temperature for 6-18h, then removing solvent B by distillation under reduced pressure, adding solvent C, extracting the target product with solvent C, and then removing solvent C by distillation under reduced pressure to obtain Sn(II) catalyst; The solvent B is selected from at least one of tetrahydrofuran, ether, toluene, benzene, xylene or trimethylbenzene; The solvent C is selected from at least one of benzene, toluene, chlorobenzene, xylene and trimethylbenzene.
3. The method for preparing the Sn(II) catalyst according to claim 2, characterized in that: The molar ratio of the skeleton molecule, n-butyl lithium and tin dichloride is 1:(2.0-2.2):
1.
4. The method for preparing the Sn(II) catalyst according to claim 2, characterized in that: In step S1, the prepared solution A is then distilled under reduced pressure to remove the solvent A in the solution A, and then the subsequent step S2 is performed.
5. The method for preparing the Sn(II) catalyst according to claim 2, characterized in that: In step S2, solvent B is removed by distillation under reduced pressure. After solvent B is completely removed, solvent C is added, and the amount of solvent C is controlled so that the target product is completely dissolved without dissolving by-products.
6. The method for preparing the Sn(II) catalyst according to claim 5, characterized in that: In step S2, after adding solvent C, ultrasonic dispersion is performed to completely dissolve the target product, and then the mixture is allowed to stand for several minutes and then filtered. The obtained liquid phase is subjected to reduced pressure distillation to remove solvent C, thereby obtaining the target product.
7. A use of the Sn(II) catalyst as claimed in claim 1, characterized in that: Catalyst for the defluorination of polyfluoroaromatics or the reduction of nitroaromatics.
8. The use of Sn(II) catalyst as claimed in claim 7, characterized in that: The molar ratio of the Sn(II) catalyst to the polyfluoroaromatic hydrocarbon is (1-10):
100.
9. The use of Sn(II) catalyst as claimed in claim 7, characterized in that: The molar ratio of the Sn(II) catalyst to the nitroaromatic hydrocarbon is (1-100):1000.