Use of biomass-based CS-pnipaam-MBAA@cu 2+ catalyst in synthesis of chiral boron compound

Abstract

The use of a biomass-based CS-PNIPAAm-MBAA@Cu2+ catalyst in the synthesis of a chiral boron compound. In a synthesis reaction, chalcone and bis(pinacolato)diboron are used as raw materials, a chiral ligand is also added thereto, and the prepared catalyst is applied to a boron addition reaction in a water-containing medium to synthesize a chiral boron-based compound. The catalyst used in the synthesis reaction has the characteristic of being recoverable by means of filtration, and the operation is simple and convenient; the catalytic reaction is a catalytic reaction in a water medium, and is high in terms of catalytic efficiency, and green and environmentally friendly; and the whole synthesis reaction has a high yield, and the enantio-selectivity is also high.

Description

A biomass-based CS-PNIPAAm-MBAA@Cu 2+ Application of catalysts in the synthesis of chiral boron compounds

[0001] This application is filed with the China Patent Office on September 7, 2023, with application number 202311162781.X, and the invention name is "A Biomass-Based CS-PNIPAAm-MBAA@Cu 2+ The entire contents of the Chinese patent application entitled "Application of catalyst in the synthesis of chiral boron compounds" are incorporated herein by reference. Technical Field

[0002] The present invention relates to the field of chiral catalysis, and in particular to a biomass-based CS-PNIPAAm-MBAA@Cu 2+ Application of catalysts in the synthesis of chiral organoboron compounds. Background Art

[0003] Chiral organoboron compounds are important synthetic intermediates for the efficient construction of optically active molecules and have significant applications in pharmaceutical synthesis. Therefore, the synthesis of chiral organoboron compounds is crucial. In recent years, synthetic chemists have developed a series of highly efficient synthetic reactions, including asymmetric hydroboration, asymmetric addition of unsaturated bonds, and C-H borylation, to construct chiral organoboron compounds.

[0004] Transition-metal-catalyzed conjugate addition of boron to α,β-unsaturated carbonyl groups and related compounds provides the most efficient and direct route to functionalized organoboron reagents. The products generated by this reaction serve as important intermediates in synthesis and can be converted into a variety of important functional groups such as hydroxyl, aryl, and alkenyl groups via Suzuki coupling reactions. These products hold significant value in the fields of fine chemicals, pharmaceuticals, and materials science.

[0005] Chitosan is a rare alkaline polysaccharide among natural polymers. It is insoluble in water and organic solvents, but soluble in dilute acid with a pH of <6.5. In dilute acid, its glucosamine is converted into R-NH 3+, forming a polycationic gel solution containing both hydroxyl and amino groups. These can be synthesized through reactions such as acylation, carboxylation, hydroxylation, cyanation, etherification, alkylation, esterification, aldimination, azidation, salt formation, chelation, hydrolysis, oxidation, halogenation, grafting, and cross-linking to produce derivatives with diverse structures and properties. In 1811, French scientist H. Braconnot extracted chitin from animal shells. In 1859, Frenchman Rouget boiled chitin in a concentrated KOH solution, washed it, and dissolved it in organic acids to produce chitosan. The first patent for the preparation of chitosan and related substances appeared in the United States in 1934, and chitosan artificial skin and surgical sutures were successfully produced in 1941. In the 1990s, the application and production of chitosan reached a peak, with global annual chitosan production reaching tens of thousands of tons.

[0006] Chitosan with a deacetylation purity of over 95% is of high purity and has extremely strong activity. This product uses finished products with a deacetylation degree of over 95%.

[0007] Due to its excellent properties such as biodegradability, low toxicity, and good biocompatibility, chitosan is widely used in related fields such as medicine and health, cleaning products, cosmetics, food, agriculture, chemistry and chemical engineering, and runs through people's clothing, food, housing, and transportation. In addition, chitosan-loaded metal catalytic materials have good application prospects due to their low cost and low toxicity.

[0008] Summary of the Invention

[0009] The present application aims to provide a biomass-based copper-loaded catalyst material for use in the synthesis of chiral organoboron compounds. This catalyst material, by introducing a hydrophilic material and utilizing the widespread availability and inexpensive availability of chitosan, achieves temperature-controlled recovery. The catalyst material is catalytically active by loading a divalent copper salt, and can be applied to chiral organoboron addition reactions in aqueous media. This catalyst material enhances both catalytic activity and chiral catalytic effects, resulting in high-yield, high-enantiomeric excess compounds. The biomass material of the present invention allows for the catalyst to be filtered and recovered after the reaction, allowing for effective reuse.

[0010] To achieve the above objectives, this application provides the following technical solutions:

[0011] A bio-based CS-PNIPAAm-MBAA@Cu 2+ Catalyst comprising a CS-PNIPAAm-MBAA material and Cu supported in the pore structure of the CS-PNIPAAm-MBAA material 2+ .

[0012] Preferably, the preparation method of the CS-PNIPAAm-MBAA material comprises the following steps:

[0013] Step 1.1, dissolving chitosan: adding chitosan powder to a solvent and stirring thoroughly to obtain a chitosan mixed solution;

[0014] Step 1.2, polymerization with a hydrophilic material: the chitosan mixed solution, N-isopropylacrylamide and N-N'-methylenebispropylacrylamide are mixed, an initiator is added, and a polymerization reaction is initiated in a closed environment at room temperature. The product obtained by the initiated polymerization reaction is dried in a vacuum to obtain a CS-PNIPAAm-MBAA material.

[0015] Preferably, in step 1.1, the solvent is 1% to 3% acetic acid in water, and the stirring is continued at room temperature for 6 to 12 hours.

[0016] Preferably, the chitosan is a natural polycationic linear polysaccharide derived from chitin, and the degree of deacetylation is greater than 95%.

[0017] Preferably, in step 1.2, the mass ratio of N-N'methylenebispropyl acrylamide to chitosan is 1:5-15, and the mass ratio of N-isopropyl acrylamide to chitosan is 1:0.1-1.

[0018] Preferably, after the reaction in step 1.2 is completed, the step further comprises repeatedly evacuating and passing nitrogen 15 times, and finally the reaction is carried out in a nitrogen environment.

[0019] Preferably, in step 1.2, the initiators are N,N,N',N'-tetramethylethylenediamine and ammonium persulfate; the usage ratio of N,N,N',N'-tetramethylethylenediamine and ammonium persulfate is 20 μL:1.2741 g;

[0020] The mass ratio of the ammonium persulfate to chitosan is 1 to 3:1.

[0021] Preferably, the time for initiating the polymerization reaction is 12 hours.

[0022] Preferably, in step 1.2, the drying temperature is 50° C. and the drying time is 12 hours.

[0023] The present invention also provides the bio-based CS-PNIPAAm-MBAA@Cu 2+ The preparation method of the catalyst comprises the following steps:

[0024] The CS-PNIPAAm-MBAA material was mixed with a divalent copper salt solution and stirred at room temperature for reaction, and then filtered and dried in a vacuum drying oven to obtain the bio-based CS-PNIPAAm-MBAA@Cu 2+ catalyst.

[0025] Preferably, the divalent copper salt in the divalent copper salt solution is copper sulfate and / or copper chloride.

[0026] Preferably, the stirring reaction time is 12 hours.

[0027] Preferably, the drying temperature is 50° C. and the drying time is 6 to 9 hours.

[0028] Preferably, the method further comprises the following steps before filtering: placing the reaction system in a water bath for heating, and then filtering while hot;

[0029] The temperature of the water bath is 70° C., and the water bath heating time is 10 to 30 minutes.

[0030] The present invention also provides a biomass-based CS-PNIPAAm-MBAA@Cu 2+ The use of the catalyst in synthesizing a chiral boron-based compound comprises the following steps:

[0031] Step (1): Using α,β-unsaturated aldehyde and ketone compounds and bipyraclostrobin as raw materials, biomass-based CS-PNIPAAm-MBAA@Cu 2+ As a catalyst, a chiral ligand is added at the same time, and the mixture is stirred uniformly in an aqueous organic mixed solvent at room temperature to obtain a mixed system containing a β-boronic acid ester substituted carbonyl compound;

[0032] Step (2): pre-treating the mixed system containing the β-boronic acid ester-substituted carbonyl compound obtained in step (1) to obtain a chiral boron-based compound;

[0033] The structural formula of the α,β-unsaturated aldehyde and ketone compound is

[0034] The structural formula of the β-boronic acid ester substituted carbonyl compound is

[0035] The structural formula of the chiral boron-based compound is

[0036] Wherein, R1 is one of phenyl, p-methylphenyl, p-methoxyphenyl, and m-methylphenyl;

[0037] R2 is one of phenyl, p-methylphenyl, p-methoxyphenyl, p-fluorophenyl, p-chlorophenyl, p-bromophenyl, o-chlorophenyl, m-bromophenyl, and m-chlorophenyl;

[0038] The chiral ligand is (R)-1-1[(S)-2-(diphenylphosphino)ferrocene]ethyldicyclohexylphosphine.

[0039] Preferably, after step (2) is completed, step 3 is further included;

[0040] The step 3 comprises: mixing the obtained chiral boron-based compound with sodium perborate tetrahydrate, tetrahydrofuran, and deionized water, reacting at room temperature, and performing a secondary treatment to obtain a chiral hydroxyl compound;

[0041] The structural formula of the chiral hydroxyl compound is:

[0042] Preferably, in step (1), the aqueous organic mixed solvent is a mixed reagent of toluene and distilled water in a volume ratio of 10:1 to 7:1.

[0043] Preferably, in step (1), the ratio of the amount of the catalyst to the amount of the aqueous organic mixed solvent is 1-10 mg:2 mL.

[0044] Preferably, the molar ratio of the α,β-unsaturated aldehyde and ketone compound, the diboric acid pinacol ester, the catalyst and the chiral ligand is 1:(1.0-3.0):(1%-10%):(1%-10%).

[0045] Preferably, the mixing and stirring time in step (1) is 10 to 20 hours.

[0046] Preferably, in step (3), the reaction time at room temperature is 4 to 8 hours.

[0047] Preferably, in step (3),

[0048] The usage ratio of the sodium borate tetrahydrate, tetrahydrofuran and deionized water is 244 mg:3 mL:2 mL.

[0049] Preferably, the secondary treatment comprises: extraction, rotary drying and thin layer chromatography.

[0050] Compared with the prior art, the catalyst prepared by the present invention has the following advantages in the application of synthesizing chiral boron compounds:

[0051] 1. The catalyst material uses inexpensive and readily available chitosan as its raw material. This raw material is widely available, inexpensive, and exhibits excellent biocompatibility, safety, and microbial degradability. Furthermore, the introduction of the thermosensitive material N-isopropylacrylamide imparts a degree of hydrophilicity to the product, enhancing contact with hydrophobic substrates and accelerating the reaction. This catalytic application in boron addition reactions allows for the synthesis of chiral organoboron compounds, broadening its application areas.

[0052] 2. The catalyst can catalyze at room temperature without light, broadening the conditions for the catalyst's use and increasing its scope of application, with broad application prospects. Furthermore, the catalytic reaction is an organic catalysis in an aqueous medium, achieving green catalysis with high catalytic efficiency, good stability, and environmental friendliness.

[0053] 3. After the reaction is complete, the catalyst can be recovered and reused simply by filtration. Because the catalyst contains chitosan, which is hydrophobic and insoluble in water, it can be directly recovered by filtration. In the reaction of synthesizing chiral boron compounds, the temperature is too high, and heating is not energy-efficient. Therefore, considering cooling to room temperature, the catalyst can be directly filtered and recovered.

[0054] 4. The reaction conditions for the preparation of the catalyst are mild, with an aqueous solution of acetic acid as the solvent, and most of the reaction is carried out at room temperature, which is simple and easy to operate; there are fewer by-products and a higher yield.

[0055] 5. The catalyst is applicable to the commercially available chiral ligand (R)-1-1[(S)-2-(diphenylphosphino)ferrocene]ethyldicyclohexylphosphine, and can obtain a higher yield of chiral organoboron compound when using less ligand (2% of the substrate). BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is a SEM image of CS-PNIPAAm-MBAA;

[0057] Figure 2 shows CS-PNIPAAm-MBAA@Cu 2+ SEM images of

[0058] Figure 3 shows the distribution of CS (chitosan), NIPAAm, CS-PNIPAAm-MBAA and CS-PNIPAAm-MBAA@Cu 2+ Infrared spectrum of . DETAILED DESCRIPTION

[0059] In order to better understand the present invention, the present invention will be described in detail with reference to the accompanying drawings and specific examples. The embodiments described are partial embodiments of the present invention, not all embodiments. The present invention will be described in detail with reference to the accompanying drawings and specific examples. The present invention uses chitosan with a deacetylation degree greater than 95%, hydrophilic materials N-isopropylacrylamide, and N,N'-methylenebisacrylamide as raw materials, N-isopropylacrylamide as a hydrophilic monomer, TEMED and APS as initiators, and the system is prepared in deionized water and then adsorbs copper ions to form biomass-based CS-PNIPAAm-MBAA@Cu 2+ Catalytic materials, and the prepared materials are characterized by SEM, infrared and other means to study their structure, morphology and composition.

[0060] Example 1

[0061] 1. Weigh 0.5 g of chitosan powder at room temperature and place it in a 50 mL single-neck flask. Use a graduated cylinder to measure 30 mL of deionized water and 1 mL of glacial acetic acid and add them to the single-neck flask in that order. Select a magnetic rod of appropriate size and place it in the single-neck flask. Seal the system and start a magnetic stirrer. Stir until the chitosan is completely dissolved to obtain a CS-HAc solution, which is set aside.

[0062] 2. Weigh 46.4 mg of MBAA, 1 g of NIPAAm, and 1.2741 g of APS into a 50 mL Schlenk tube at room temperature. Transfer the CS-HAc solution prepared in step 1 above and 20 μL of TEMED to the tube. Select a magnetic rod of appropriate size and place it into the tube. Repeat vacuuming and nitrogen purging at room temperature 15 times. Seal the system and stir at room temperature for 12 h.

[0063] 3. After the reaction in step 2 is completed, the solution in the Schlenk tube is transferred to a petri dish of appropriate size and dried in a vacuum drying oven at 50°C for 12 hours to obtain the dried CS-PNIPAAm-MBAA material. The product is removed, ground, and set aside.

[0064] The CS-PNIPAAm-MBAA material was characterized by SEM. The results are shown in Figure 1. The product has an irregular shape and an overall porous structure, which is conducive to the loading of metal ions.

[0065] 4. Weigh 4.9936 g of copper sulfate pentahydrate into a beaker. Use a graduated cylinder to measure 50 mL of deionized water and add it to the beaker. Add a magnetic rod of appropriate size and stir evenly to obtain a 0.4 mol / L copper solution. Set aside.

[0066] 5. Take the CS-PNIPAAm-MBAA material synthesized in step 3 above and the copper solution prepared in step 4, transfer them to a 100 mL single-necked flask for copper loading, and the copper loading time is 12 h.

[0067] 6. The reaction system in step 5 was placed in a 70°C water bath and heated for 10 min to 30 min. The mixture was filtered while hot using a triangular suction funnel, washed with hot water, and the product was transferred to a petri dish and dried in a vacuum drying oven at 50°C for 12 h to obtain dry biomass-based CS-PNIPAAm-MBAA@Cu 2+ Catalyst, take out the product, grind it and set aside.

[0068] Biomass-based CS-PNIPAAm-MBAA@Cu 2+SEM characterization was performed, and the results are shown in Figure 2. The surface of the material becomes smooth after copper loading. Infrared characterization of the prepared catalytic material is performed, and the results are shown in Figure 3. -1 It is the characteristic peak of hydrophilic materials in catalytic materials, 681cm -1 It is the characteristic peak of copper ion coordination.

[0069] Application Example 1

[0070] This application example uses the biomass-based CS-PNIPAAm-MBAA@Cu 2+ Catalyst, the specific steps are as follows:

[0071] The chemical reaction equation of step 1 is as follows:

[0072] The chemical reaction equation of step 3 is as follows:

[0073] 1. At room temperature, 0.2 mmol (41.7 mg) of benzylidene acetophenone (chalcone), 0.24 mmol (60.9 mg) of biboronic acid pinacol ester, 0.002 mmol of chiral ligand (R)-1-1[(S)-2-(diphenylphosphino)ferrocene]ethyldicyclohexylphosphine (1.0% of the molar amount of substrate benzylidene acetophenone), 0.002 mmol of biomass-based CS-PNIPAAm-MBAA@Cu 2+ Catalyst (Cu 2+ The molar mass of the substrate benzylideneacetophenone is 1.0% of the molar mass of the substrate benzylideneacetophenone) is placed in a sample bottle, and then 1.8 mL of toluene and 0.2 mL of deionized water are added to the sample bottle. A magnetic rod of appropriate size is selected and placed in the sample bottle, and the mixture is sealed and stirred with a magnetic stirrer at room temperature for 12 hours to generate a mixed system containing a β-boronic acid ester-substituted carbonyl compound;

[0074] 2. After the reaction is completed, the mixed system containing the β-boronic acid ester-substituted carbonyl compound obtained in step 1 is extracted with ethyl acetate as an extractant to separate the liquids, separate the organic phase, dry it over anhydrous Na2SO4, filter it, and remove the ethyl acetate using a rotary evaporator to obtain a chiral boron-based compound;

[0075] 3. Add 244 mg of sodium perborate tetrahydrate, 3 mL of tetrahydrofuran, and 2 mL of deionized water to the reaction bottle in step 2. Select a magnetic bar of appropriate size and place it in the above reaction bottle. Stir with a magnetic stirrer at room temperature for 4 hours;

[0076] 4. After the reaction in step 3 is completed, ethyl acetate is used as the extractant to extract and separate the liquid, separate the organic phase, dry it over anhydrous Na2SO4, filter it, remove the ethyl acetate by rotary evaporator, and finally separate it by column chromatography to obtain the product chiral hydroxyl compound. The volume ratio of ethyl acetate and petroleum ether used for column chromatography is 1:4.

[0077] An appropriate amount of isopropanol was added to the reaction flask in step 4 to dissolve the product, and a nylon filter membrane was used for pretreatment. The enantiomeric selectivity of the chiral hydroxy compound was measured by high performance liquid chromatography to be 60%, and the product yield was 58%.

[0078] Application Example 2

[0079] The chemical reaction equation of step 1 is as follows:

[0080] The chemical reaction equation of step 3 is as follows:

[0081] This application example uses the biomass-based CS-PNIPAAm-MBAA@Cu 2+ Catalyst, chiral boron compound was prepared by the same method as in Application Example 1, except that the chiral ligand used in this application example was (R)-1-1[(S)-2-(diphenylphosphino)ferrocene]ethyldicyclohexylphosphine, and the amount of the substance was 1.5% of the substrate. The specific steps were as follows:

[0082] 1. At room temperature, weigh 0.2 mmol (41.7 mg) of benzylidene acetophenone, 0.24 mmol (60.9 mg) of biboronic acid pinacol ester, 0.003 mmol of chiral ligand (R)-1-1[(S)-2-(diphenylphosphino)ferrocene]ethyldicyclohexylphosphine, 0.002 mmol of biomass-based CS-PNIPAAm-MBAA@Cu 2+ Catalyst (Cu 2+ The molar mass of the substrate benzylideneacetophenone is 1.0% of the molar mass of the substrate benzylideneacetophenone) is placed in a sample bottle, and then 1.8 mL of toluene and 0.2 mL of deionized water are added to the sample bottle. A magnetic rod of appropriate size is selected and placed in the sample bottle, and the mixture is sealed and stirred with a magnetic stirrer at room temperature for 12 hours to generate a mixed system containing a β-boronic acid ester-substituted carbonyl compound;

[0083] 2. After the reaction is completed, the mixed system containing the β-boronic acid ester-substituted carbonyl compound obtained in step 1 is extracted with ethyl acetate as an extractant to separate the liquids, separate the organic phase, dry it over anhydrous Na2SO4, filter it, and remove the ethyl acetate using a rotary evaporator to obtain a chiral boron-based compound;

[0084] 3. Add 244 mg of sodium perborate tetrahydrate, 3 mL of tetrahydrofuran, and 2 mL of deionized water to the reaction bottle in step 2. Select a magnetic bar of appropriate size and place it in the above reaction bottle. Stir with a magnetic stirrer at room temperature for 4 hours;

[0085] 4. After the reaction in step 3 is completed, ethyl acetate is used as the extractant to extract and separate the liquid, separate the organic phase, dry it over anhydrous Na2SO4, filter it, remove the ethyl acetate by rotary evaporator, and finally separate it by column chromatography to obtain the product chiral hydroxyl compound. The volume ratio of ethyl acetate and petroleum ether used for column chromatography is 1:4.

[0086] An appropriate amount of isopropanol was added to the reaction flask in step 4 to dissolve the product, and pre-treated with a nylon filter membrane. The enantiomeric selectivity of the chiral hydroxy compound was measured by high performance liquid chromatography to be 85%, and the product yield was 78%.

[0087] Application Example 3

[0088] The chemical reaction equation of step 1 is as follows:

[0089] The chemical reaction equation of step 3 is as follows:

[0090] This application example uses the biomass-based CS-PNIPAAm-MBAA@Cu 2+ Catalyst, the chiral boron compound catalytic material was prepared by the same method as in Application Example 2, except that the amount of the chiral ligand (R)-1-1[(S)-2-(diphenylphosphino)ferrocene]ethyldicyclohexylphosphine used in this application example was 2.0% (0.004 mmol) of the substrate benzylideneacetophenone, and the biomass-based CS-PNIPAAm-MBAA@Cu 2+ Cu in catalyst 2+ The amount of the substance was 1.5% (0.003 mmol) of the substrate benzylidene acetophenone. The enantiomeric selectivity of the chiral hydroxy compound was determined by high performance liquid chromatography to be 93%, and the product yield was 97%.

[0091] Application Example 4

[0092] This example provides a biomass-based CS-PNIPAAm-MBAA@Cu 2+ The application method of the catalytic material in the synthesis of chiral boron-based compounds using (E)-3-(4-p-chlorophenyl)-1-2-en-1-one as a substrate, the specific experimental steps refer to Application Example 3, the chemical reaction equation of step (1) is as follows:

[0093] The chemical reaction equation of step (3) is as follows:

[0094] Biomass-based CS-PNIPAAm-MBAA@Cu 2+ The catalytic material is applied to the chiral boron addition reaction of (E)-3-(4-p-chlorophenyl)-1-2-ene-1-one, and the yield and enantiomeric selectivity of the target product (chiral hydroxy compound) in step (3) are 92% and 90%, respectively.

[0095] Application Example 5

[0096] This example provides a biomass-based CS-PNIPAAm-MBAA@Cu 2+ The application method of the catalytic material in the synthesis of chiral boron-based compounds using (E)-3-(4-p-bromophenyl)-1-2-en-1-one as a substrate, the specific experimental steps refer to Application Example 3, the chemical reaction equation of step (1) is as follows:

[0097] The chemical reaction equation of step (3) is as follows:

[0098] Biomass-based CS-PNIPAAm-MBAA@Cu 2+ The catalytic material is applied to the chiral boron addition reaction of (E)-3-(4-p-bromophenyl)-1-2-ene-1-one. The yield and enantiomeric selectivity of the target product (chiral hydroxy compound) in step (3) are 86% and 89%, respectively.

[0099] Application Example 6

[0100] This example provides a biomass-based CS-PNIPAAm-MBAA@Cu 2+ The application method of the catalytic material in the synthesis of chiral boron-based compounds using (E)-3-(4-p-methoxyphenyl)-1-2-en-1-one as a substrate, the specific experimental steps refer to Application Example 3, the chemical reaction equation of step (1) is as follows:

[0101] The chemical reaction equation of step (3) is as follows:

[0102] Biomass-based CS-PNIPAAm-MBAA@Cu 2+ The catalytic material is applied to the chiral boron addition reaction of (E)-3-(4-p-methoxyphenyl)-1-2-ene-1-one. The yield and enantiomeric selectivity of the target product (chiral hydroxy compound) in step (3) are 94% and 92%, respectively.

[0103] Application Example 7

[0104] After the reaction is completed, the reaction mixture is cooled to room temperature, the catalyst is recovered by filtration, washed with n-hexane, dried and reused. 2+ The catalytic material was applied to the chiral boron addition reaction of chalcone for the fifth time. The specific experimental steps were referred to Application Example 3. The yield and enantiomeric selectivity of the target product (chiral hydroxyl compound) were 91% and 89%, respectively.

[0105] The results of this embodiment show that the biomass-based CS-PNIPAAm-MBAA@Cu 2+ The catalytic material achieved the highest conversion and enantioselectivity for chalcone in the boron addition reaction, with the yield and enantioselectivity of the target product (chiral hydroxyl compound) reaching 97% and 93%, respectively. The catalytic material is also recyclable, with four catalytic cycles followed by a fifth application in the chiral boron addition reaction of chalcone, achieving a yield and enantioselectivity of 91% and 89%, respectively.

[0106] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A bio-based CS-PNIPAAm-MBAA@Cu 2+ A catalyst, characterized in that The invention comprises a CS-PNIPAAm-MBAA material and a Cu loaded in the pore structure of the CS-PNIPAAm-MBAA material. 2+ .

2. The bio-based CS-PNIPAAm-MBAA@Cu as claimed in claim 1 2+ A catalyst, characterized in that The preparation method of the CS-PNIPAAm-MBAA material comprises the following steps: Step 1.1, dissolving chitosan: adding chitosan powder into a solvent and stirring sufficiently to obtain a chitosan mixed solution; Step 1.2, polymerization with hydrophilic material: the chitosan mixed solution, N-isopropyl acrylamide and N-N'methylenebispropyl acrylamide are mixed, and then an initiator is added to initiate a polymerization reaction in a closed environment at room temperature, and the product obtained by the initiated polymerization reaction is placed in a vacuum and dried to obtain a CS-PNIPAAm-MBAA material.

3. The bio-based CS-PNIPAAm-MBAA@Cu as claimed in claim 2 2+ A catalyst, characterized in that In the step 1.1, the solvent is 1% to 3% acetic acid in water, and the stirring is continued at room temperature for 6 to 12 hours.

4. The bio-based CS-PNIPAAm-MBAA@Cu as claimed in claim 2 2+ A catalyst, characterized in that The chitosan is a natural polycationic linear polysaccharide derived from chitin, and the deacetylation degree is greater than 95%.

5. The bio-based CS-PNIPAAm-MBAA@Cu as claimed in claim 2 2+ A catalyst, characterized in that In the step 1.2, the mass ratio of the N-N'methylenebispropyl acrylamide to chitosan is 1:5-15, and the mass ratio of the N-isopropyl acrylamide to chitosan is 1:0.1-1.

6. The bio-based CS-PNIPAAm-MBAA@Cu as claimed in claim 2 2+ A catalyst, characterized in that After the reaction in step 1.2 is completed, the step further includes repeatedly evacuating the air and passing nitrogen for 15 times, and finally the reaction is carried out in a nitrogen environment.

7. The bio-based CS-PNIPAAm-MBAA@Cu as claimed in claim 2 2+ A catalyst, characterized in that In the step 1.2, the initiator is N,N,N',N'-tetramethylethylenediamine and ammonium persulfate; the dosage ratio of N,N,N',N'-tetramethylethylenediamine and ammonium persulfate is 20 μL:1.2741 g; The mass ratio of the ammonium persulfate to chitosan is 1 to 3:

1.

8. The bio-based CS-PNIPAAm-MBAA@Cu as claimed in claim 2 2+ A catalyst, characterized in that The time for initiating the polymerization reaction is 12 hours.

9. The bio-based CS-PNIPAAm-MBAA@Cu as claimed in claim 2 2+ A catalyst, characterized in that In the step 1.2, the drying temperature is 50° C. and the drying time is 12 h.

10. The bio-based CS-PNIPAAm-MBAA@Cu according to any one of claims 1 to 9 2+ The method for preparing a catalyst is characterized in that: The following steps are involved: The CS-PNIPAAm-MBAA material is mixed with a divalent copper salt solution, and stirred to react at room temperature, and then filtered and placed in a vacuum drying oven to obtain the bio-based CS-PNIPAAm-MBAA@Cu 2+ catalyst.

11. The preparation method according to claim 10, characterized in that: The divalent copper salt in the divalent copper salt solution is copper sulfate and / or copper chloride.

12. The preparation method according to claim 10, characterized in that: The stirring reaction time is 12 hours.

13. The preparation method according to claim 10, characterized in that: The drying temperature is 50° C. and the drying time is 6 to 9 hours.

14. The preparation method according to claim 10, characterized in that: Before filtering The method comprises the following steps: placing the reaction system in a water bath pot for water bath heating, and then filtering while hot; The temperature of the water bath is 70° C., and the water bath heating time is 10 to 30 minutes.

15. A biomass-based CS-PNIPAAm-MBAA@Cu 2+ The use of a catalyst in synthesizing a chiral boron-based compound is characterized in that: The following steps are involved: Step (1): Using α,β-unsaturated aldehyde and ketone compounds and bipyraclostrobin as raw materials, biomass-based CS-PNIPAAm-MBAA@Cu 2+ As a catalyst, a chiral ligand is added at the same time, and the mixture is stirred evenly in a water-containing organic mixed solvent at room temperature to obtain a mixed system containing a carbonyl compound substituted with β-boric acid ester; Step (2): subjecting the mixed system containing the carbonyl compound substituted with β-boric acid ester obtained in step (1) to initial treatment to obtain a chiral boron-based compound; The structural formula of the α,β-unsaturated aldehyde and ketone compound is The structural formula of the β-boronic acid ester substituted carbonyl compound is The structural formula of the chiral boron-based compound is Wherein, R1 is one of phenyl, p-methylphenyl, p-methoxyphenyl, and m-methylphenyl; R2 is one of phenyl, p-methylphenyl, p-methoxyphenyl, p-fluorophenyl, p-chlorophenyl, p-bromophenyl, o-chlorophenyl, m-bromophenyl, and m-chlorophenyl; The chiral ligand is (R)-1-1[(S)-2-(diphenylphosphino)ferrocene]ethyldicyclohexylphosphine.

16. The use according to claim 1, characterized in that After the step (2) is completed, the process further includes step 3; The step 3 is: mixing the obtained chiral boron compound with sodium perborate tetrahydrate, tetrahydrofuran and deionized water, reacting at room temperature, and obtaining a chiral hydroxy compound after secondary treatment; The structural formula of the chiral hydroxyl compound is:

17. The use according to claim 15, characterized in that: In the step (1), the aqueous organic mixed solvent is a mixed reagent of toluene and distilled water in a volume ratio of 10:1 to 7:

1.

18. The use according to claim 15, characterized in that In the step (1), the ratio of the amount of the catalyst to the amount of the aqueous organic mixed solvent is 1-10 mg:2 mL.

19. The use according to any one of claims 15 to 18, characterized in that: The molar ratio of the α,β-unsaturated aldehyde and ketone compound, the biphenyl borate pinacol ester, the catalyst and the chiral ligand is 1:(1.0-3.0):(1%-10%):(1%-10%).

20. The use according to claim 15, characterized in that The mixing and stirring time in step (1) is 10 to 20 hours.

21. The use according to claim 16, characterized in that In the step (3), the reaction time at room temperature is 4 to 8 hours.

22. The use according to claim 16, characterized in that In the step (3), The usage ratio of the sodium borate tetrahydrate, tetrahydrofuran and deionized water is 244 mg: 3 mL: 2 mL.

23. The use according to claim 16, characterized in that The secondary treatment includes extraction, rotary drying and thin layer chromatography.

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