Bimetal polymer catalyst as well as preparation method and application thereof

Abstract

The invention discloses a bimetallic polymer catalyst and a preparation method and application thereof.Two chiral ligands are complexed with metal, a random copolymer is synthesized through a free radical copolymerization method, and the catalyst has a chiral amplification effect and can cooperate with the advantages of two chiral catalysts; according to the present invention, the catalyst can be used for catalyzing the cascade reaction of the asymmetric hydrogenation reaction (ATH) and the decarboxylated Mannich reaction, the high catalytic activity and the high stereoselectivity are represented, the catalyst can be recycled, and the catalytic activity and the selectivity of the catalyst have the high cycle stability.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation and application of solid-supported catalysts, and specifically relates to a bimetallic polymer catalyst and a preparation method and application thereof. Background Art

[0002] In most cases, the use of bimetallic species shows better activity than monometallic species. Typically, unique reactivity, selectivity and modified catalytic activity of the corresponding monometallic species can be seen from the reactions catalyzed by bimetallic nanoparticles. The combined properties of the two different metals present in the catalyst are often referred to as the "synergistic effect", which is caused by the changes in the catalyst surface caused by heterogeneous metal-metal interactions. Although there are some reports on dual catalytic strategies, the multi-catalyst systems involved are not fully cooperative. It is of great significance to develop bimetallic catalysts to synergistically catalyze multi-step sequential reactions. However, the interaction of the inherent complex microenvironment and chirality of the dual catalysts leads to efficient catalysis in a single operation, which is a huge challenge.

[0003] On the one hand, polymer-supported chiral metal catalysts can promote the reaction under certain conditions, and on the other hand, they are conducive to the recycling of catalysts. Ding Yunjie et al. reported a phosphine-containing polymer chiral catalyst and applied it to asymmetric synthesis reactions. Because the chiral ligands were evenly embedded in the polymer skeleton, a high catalytic activity was achieved. They also reported a chiral hypercross-linked material with a pore structure for asymmetric hydrogenation reactions. However, there are no related cases of polymer-supported bimetallic chiral catalysts and their efficient and highly selective applications in asymmetric reactions. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a method for preparing a heterogeneous bimetallic chiral catalyst, which introduces noble metals and non-noble metals into a chiral polymer catalyst at the same time and avoids the exchange between ligands. The coordination induction and assembly of metals play a vital role in obtaining good yields and selectivity in catalytic reactions. The synergistic effect of the bimetallic catalyst is well exerted in random copolymers, and at the same time has a chiral amplification effect, achieving a catalytic effect that cannot be achieved by small molecule blending. The success of this research will make the application of chiral metal catalysts more economical, cheap and environmentally friendly.

[0005] The present invention adopts the following technical scheme to solve the above technical problems: a method for preparing a bimetallic chiral polymer catalyst, wherein two chiral ligands are complexed with metals, and then a random copolymer is synthesized by a free radical copolymerization method; the obtained catalyst has a chiral amplification effect, can synergize the advantages of the two chiral catalysts, catalyze asymmetric hydrogenation reactions and decarboxylation Mannich reaction cascade reactions, and exhibit high catalytic activity and stereoselectivity.

[0006] Further, the specific steps are: add the chiral ligands A-Ru and B-Cu into a Shrek bottle, add them into a dry solvent, dissolve them by ultrasonication, add AIBN, and react at 60-90°C for 8-24 hours. After the reaction, wash the reaction solution in a large amount of a mixed solvent of n-hexane / ether 1:1 to remove the unpolymerized monomers, and vacuum dry for 24 hours to obtain a chiral copolymer. The specific synthetic route in the preparation process is:

[0007] m=1000-60000, n=1000-80000.

[0008] The invention provides a bimetallic chiral polymer catalyst prepared by the method.

[0009] The present invention also provides a catalyst prepared by the above method for asymmetric hydrogenation reaction and decarboxylation Mannich reaction cascade reaction, the specific process is: β -keto acid 0.06 mmol, cyclic aldimine 0.04 mmol and polymer catalyst 5-50 mg were added to a round-bottom flask, 1-20 mL of solvent was added to dissolve them, and then 0.2 mmol of ammonium formate was added. After uniform dispersion, the mixture was reacted at -20 ° C for 5-10 h, and then at 60 ° C for 10-24 h. After the reaction, ether was added to separate the catalyst, and the catalyst was recovered by centrifugation, extracted with ethyl acetate and saturated brine respectively, dried over anhydrous MgSO4, and then the organic phase was concentrated by suction filtration and rotary evaporation, and then the product was purified by column chromatography PE:EA = 4:1.

[0010] Compared with the prior art, the present invention has the following advantages: the method introduces precious metals and non-precious metals into chiral polymer catalysts at the same time, and avoids the exchange between ligands. The coordination induction and assembly of metals play a vital role in obtaining good yield and selectivity in the catalytic reaction. The synergistic effect of the two-handed chiral metal catalyst is well exerted in the random copolymer, and at the same time has a chiral amplification effect, achieving a catalytic effect that cannot be achieved by small molecule blending. The success of this research will make the application of chiral metal catalysts more economical, cheap and environmentally friendly. In addition, the catalyst recovery method is simple and effective, and repeated recycling will not significantly reduce the catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is the CD test chart of the bimetallic catalyst prepared in Example 1. DETAILED DESCRIPTION

[0012] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention. Example 1

[0013] Preparation of Polymeric Bimetallic Chiral Catalysts 2 mmol of chiral ligand A-Ru and 1 mmol of B-Cu were added to a Shrek bottle, and then added to 1 mL of DMF. After ultrasonic dissolution, 1% of AIBN based on the total amount of monomers was added and reacted at 70 °C for 24 h. After the reaction, the reaction solution was washed in a large amount of a mixed solvent of n-hexane / ether (1:1) to remove the unpolymerized monomers, and then vacuum dried for 24 h to obtain a chiral copolymer. Example 2

[0014] Will β -Keto acid (0.06 mmol), cyclic aldimine (0.04 mmol) and 5 mg of the chiral copolymer catalyst prepared in Example 1 were added to a 10 mL round-bottom flask, dissolved in 1.2 mL of THF / H2O 1:1 solvent, and then ammonium formate (0.2 mmol) was added. After uniform dispersion, the mixture was reacted at -20°C for 5 h, and then at 60°C for 18 h. After the reaction, 3 mL of ether was added to separate the catalyst, and then the catalyst was recovered by centrifugation, extracted with ethyl acetate and saturated brine, dried over anhydrous MgSO4, and then the organic phase was concentrated by suction evaporation, and then the product was purified by column chromatography (PE:EA = 4:1). Yield: 60%, ee value 99%, Dr: 96:1. Example 3

[0015] Will β -Keto acid (0.06 mmol), cyclic aldimine (0.04 mmol) and 5 mg of the chiral copolymer catalyst prepared in Example 1 were added to a 10 mL round-bottom flask, dissolved in 1.2 mL of THF / H2O 4:1 solvent, and then ammonium formate (0.2 mmol) was added. After uniform dispersion, the mixture was reacted at -20°C for 5 h, and then at 60°C for 18 h. After the reaction, 3 mL of ether was added to separate the catalyst, and then the catalyst was recovered by centrifugation, extracted with ethyl acetate and saturated brine, dried over anhydrous MgSO4, and then the organic phase was concentrated by suction evaporation, and then the product was purified by column chromatography (PE:EA = 4:1). Yield: 80%, ee value 98%, Dr: 99:1. Example 4

[0016] Will β-keto acid (0.06 mmol), cyclic aldimine (0.04 mmol) and 5 mg of the copolymer catalyzed in Example 3 were added to a 10 mL round-bottom flask, dissolved in 1.2 mL of THF / H2O 4:1 solvent, and then ammonium formate (0.2 mmol) was added. After uniform dispersion, the mixture was reacted at -20°C for 5 h, and then at 60°C for 18 h. After the reaction, 3 mL of ether was added to separate the catalyst, and then the catalyst was recovered by centrifugation, extracted with ethyl acetate and saturated brine, dried over anhydrous MgSO4, and then the organic phase was concentrated by suction filtration and rotary evaporation, and then the product was purified by column chromatography (PE:EA = 4:1). Yield: 79%, ee value 98%, Dr: 98:1. Example 5

[0017] Will β -keto acid (0.06 mmol), cyclic aldimine (0.04 mmol) and 5 mg of the copolymer catalyzed in Example 4 were added to a 10 mL round-bottom flask, dissolved in 1.2 mL of THF / H2O 4:1 solvent, and then ammonium formate (0.2 mmol) was added. After uniform dispersion, the mixture was reacted at -20°C for 5 h, and then at 60°C for 18 h. After the reaction, 3 mL of ether was added to separate the catalyst, and then the catalyst was recovered by centrifugation, extracted with ethyl acetate and saturated brine, dried over anhydrous MgSO4, and then the organic phase was concentrated by suction filtration and rotary evaporation, and then the product was purified by column chromatography (PE:EA = 4:1). Yield: 77%, ee value 98%, Dr: 99:1.

[0018] like Figure 1 As shown, the CD test results show that the bimetallic catalyst copolymerization has a chiral amplification effect.

Claims

1. A method for preparing a bimetallic polymer catalyst, characterized in that: After the two chiral ligands are complexed with metals, a random copolymer is synthesized by a free radical copolymerization method. The obtained catalyst has a chiral amplification effect, can synergize the advantages of the two chiral catalysts, catalyze asymmetric hydrogenation reactions and decarboxylation Mannich reaction cascade reactions, and exhibit high catalytic activity and stereoselectivity.

2. The method for preparing a bimetallic polymer catalyst according to claim 1, characterized in that: The specific steps are as follows: add the chiral ligands A-Ru and B-Cu into a Shrek bottle, add them into a dry solvent, dissolve them by ultrasonication, add AIBN, react at 60-90°C for 8-24 h, wash the reaction solution in a large amount of a mixed solvent of n-hexane / ether in a ratio of 1:1 after the reaction, remove the unpolymerized monomers, and vacuum dry for 24 h to obtain a chiral copolymer. The specific synthetic route in the preparation process is as follows: ； m=1000-60000, n=1000-80000.

3. A bimetallic polymer catalyst, characterized in that: Prepared according to any one of claims 1-2.

4. A bimetallic polymer catalyst according to claim 3 is used for asymmetric hydrogenation and decarboxylation Mannich reaction cascade reaction, characterized in that: The specific process is: β -Keto acid 0.06 mmol, cyclic aldimine 0.04 mmol and polymer catalyst 5-50 mg were added into a round-bottom flask, 1-20 mL of solvent was added to dissolve them, and then 0.2 mmol of ammonium formate was added. After uniform dispersion, the mixture was reacted at -20 °C for 5-10 h, and then at 60 °C for 10-24 h. After the reaction, ether was added to separate the catalyst, and the catalyst was recovered by centrifugation. The mixture was extracted with ethyl acetate and saturated brine respectively, dried over anhydrous MgSO4, and the organic phase was concentrated by suction filtration and rotary evaporation. The product was then purified by column chromatography with PE:EA = 4:1.

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