CN114835738B - Method for preparing allyl borate by using biomass-based catalytic material - Google Patents

Abstract

The invention discloses a method for preparing allyl borate using biomass-based catalytic materials, which includes the following steps: 1) combining MBH ester compound I, pinacol diborate and biomass-based catalytic material Schiff-CS@ Cu is added to the pure water solvent, and the reaction is mixed and stirred at room temperature for 12 to 24 hours; 2) After the reaction is completed, filter, separate and purify the filtrate to obtain allyl borate II, and wash and dry the precipitate to obtain the recovered catalytic material Schiff‑ CS@Cu. The catalytic material Schiff-CS@Cu of the present invention has high catalytic activity and can be used to catalyze the boron addition reaction of various MBH esters. It uses pure water as the solvent and reacts at room temperature. It is simple and easy to operate; it has the advantages of low catalyst consumption and high reaction efficiency. It has the advantages of mild conditions and high product yield. The yields of the target products are all above 81%, and the yields of some specific allyl borate can exceed 90%.

Description

A method for preparing allyl borate using biomass-based catalytic materials

Technical field

The invention relates to the field of organic synthesis, and specifically refers to a method for preparing allyl borate using biomass-based catalytic materials.

Background technique

Allyl metal reagents have received widespread attention in recent years due to their effective construction of CC bonds in allylation reactions and cross-coupling reactions. Among these allyl metal reagents, allyl borate has excellent stability. and have received widespread attention due to their low toxicity, easy availability and ease of reprocessing. MBH esters are widely used in organic synthesis because they have both α,β-unsaturated carbonyl and allyl moieties. In 2004, the literature (J.Org.Chem., 2004, 69, 5807.) reported the use of divalent palladium salt Pd(OAc) ₂ to catalyze the boron addition reaction of MBH ester to obtain allyl borate. This work used 3 mol % Pd(OAc) ₂ was added as a catalyst, toluene was used as a solvent, and the reaction was performed at 50°C to obtain allyl borate. Although the reaction achieved a high-efficiency conversion of MBH ester to allyl borate, the reaction process Precious metals are used as catalysts, and the catalyst dosage is large. At the same time, the organic solvent toluene is used, which is not friendly to the environment. In the same year, the literature (Org. Lett., 2004, 6, 481.) reported the use of monovalent copper salt CuCl to catalyze the boronization reaction of MBH ester to obtain allyl borate ester salt. This work used CuCl as the catalyst, and LiCl and KOAc were added as bases. , DMF (N,N-dimethylformamide) as solvent. Although this reaction avoids the use of precious metals, a strong base and organic solvent DMF are added during the reaction, which pollutes the environment. The catalyst monovalent copper salt used at the same time is unstable and the operation is cumbersome. Although the above method achieves the conversion from MBH ester to allyl borate, there are problems such as high cost, cumbersome operation, limited reaction conditions, environmental pollution, and the inability to recycle the catalyst, which greatly limit this type of process. Application of the method in actual production. Therefore, it is very urgent to develop a new green and environmentally friendly method that is low-cost, easy to operate, has mild conditions and can directly convert MBH ester into allyl borate with high yield.

Chitosan is obtained by the deacetylation of chitin, which is the second most abundant biopolymer in nature. It has wide sources and low cost. At the same time, chitosan is the only alkaline polysaccharide in nature, does not pollute the environment, and has It has good antibacterial properties, biocompatibility and degradability, but has shortcomings such as poor mechanical strength and easy swelling. The chitosan Schiff base material obtained by modifying chitosan with aldehyde compounds can not only retain the good antibacterial properties, biocompatibility and degradability of chitosan, but also improve the physical and chemical properties of chitosan and improve Chitosan stability. The chitosan Schiff base material structure contains a large number of imine groups and hydroxyl groups, which can easily coordinate with transition metals and is widely used in the field of catalysis. Among them, there are reports that the chitosan Schiff base transition metal catalytic material obtained by modifying chitosan with aldehyde compounds to adsorb transition metals has achieved the construction of C-C bonds and C-N bonds. However, so far, there is no research on the construction of C-B bonds in this type of material. There are fewer reports in .

Contents of the invention

The purpose of the present invention is to solve the deficiencies of the above background technology and provide a method for preparing allyl borate using biomass-based catalytic materials, aiming to overcome to a certain extent the catalysts in the prior art that use expensive metals and cannot Problems such as recycling, high cost, and difficulty in industrialization.

The technical solution of the present invention is: a method for preparing allyl borate using biomass-based catalytic materials, which is characterized in that it includes the following steps:

1) Add MBH ester compound I, pinacol diborate and chitosan Schiff base solid-supported copper catalytic material Schiff-CS@Cu into pure water solvent, mix and stir for 12 to 24 hours at room temperature, according to the substance The amount ratio is MBH ester compound I: pinacol diborate: chitosan Schiff base solid-supported copper catalytic material Schiff-CS@Cu copper content = 1: (1.2～2): (0.005～0.03), Chemistry The reaction equation is as follows:

Among them, R ₁ is phenyl, p-methylphenyl, p-methoxyphenyl, m-methoxyphenyl, o-chlorophenyl, or p-chlorophenyl;

2) After the reaction is completed, filter, and the filtrate obtained is separated and purified to obtain allyl borate II. The precipitate is washed and dried to obtain the recovered chitosan Schiff base copper catalytic material Schiff-CS@Cu, which is recycled in the next step. use. OAc in MBH ester compound I is an acetoxy group, which is a CH ₃ COO- group.

Preferably, in step 1), the copper content in the chitosan Schiff base-immobilized copper catalytic material Schiff-CS@Cu is 0.5 to 1.4 mmol/g.

Preferably, in step 1), the mass ratio of copper in the MBH ester compound I: pinacol diborate: chitosan Schiff base solid-supported copper catalytic material Schiff-CS@Cu is 1:2:0.01.

Preferably, in step 1), the ratio of the amount of chitosan Schiff base-supported copper catalytic material Schiff-CS@Cu supported copper to pure water is 0.001 to 0.006 mmol: 2 ml.

Preferably, in step 1), the reaction is carried out with mixing and stirring at room temperature for 12 hours.

Preferably, the filtrate obtained in step 2) is separated and purified to obtain allyl borate II, which specifically includes: extracting the filtrate with ethyl acetate to obtain an organic phase containing the product, drying over anhydrous Na ₂ SO ₄ , filtering, and rotary evaporation Excess organic solvent was removed, and the remaining organic phase was purified by column chromatography in a mixed solvent of ethyl acetate and petroleum ether to obtain allyl borate II.

Preferably, the chitosan Schiff base-supported copper catalytic material Schiff-CS@Cu in step 1) is prepared by a method including the following steps:

a. Add chitosan and aldehyde compounds into a mixed solution of ethanol and acetic acid, and stir for 12 to 24 hours at 65 to 75°C. The aldehyde compounds are 5-methyl salicylaldehyde, salicylaldehyde, and 5-nitrate. One of the aldehyde-based salicylaldehydes. The molar ratio of the aldehyde group -CHO in the aldehyde compound to the amino group _-NH2 in chitosan is 2 to 6:1. After the reaction is completed, the chitosan Schiff base powder is obtained by separation and processing;

b. Place the chitosan Schiff base powder in the divalent copper ion solution and stir for 3 to 9 hours at 50-75°C to adsorb divalent copper ions. After the adsorption is completed, separate and process to obtain chitosan Schiff base solid-supported copper. Catalytic material Schiff-CS@Cu.

Further, in step a, the ethanol-acetic acid mixed solution is obtained by mixing glacial acetic acid and absolute ethanol in a volume ratio of 1:6 to 8. The molar ratio of the aldehyde group -CHO in the aldehyde compound and _the amino group -NH in chitosan is 4: 1. The acetic acid of the present invention uses commercially available glacial acetic acid, that is, anhydrous acetic acid, ethanol acetic acid mixed solution, as a solvent.

Further, in step b, the molar ratio of Cu ²⁺ contained in the divalent copper ion solution to the amino-NH ₂ in chitosan is at least 1:1, and the copper ion concentration in the divalent copper ion solution is 0.1 to 0.5 mol/L. In the present invention, the source of divalent copper ions is copper sulfate pentahydrate, the divalent copper ion solution is copper sulfate solution, and the chitosan Schiff base material loads the divalent copper ion solution through self-adsorption.

Further, the separation processing in steps a and b includes: filtration, repeated and alternate washing with absolute ethanol and distilled water, and drying in an oven at 50°C for 12 hours.

The invention uses chitosan Schiff base powder to immobilize copper catalytic material to prepare allyl borate. The chitosan Schiff base material itself contains a large number of imine groups and the unreacted amino groups present in the material provide an alkaline environment for the entire reaction system without adding any alkali; in addition, chitosan The Schiff base powder-supported copper catalytic material has unique spatial structure and biocompatibility, higher catalytic activity, and stronger complexation; it can be recycled, conforms to the concept of green chemistry, and has broad industrial application prospects.

The beneficial effects of the present invention are:

1. Chitosan Schiff base has good immobilization effect on metallic copper, has good biocompatibility, has wide sources, low cost, and is green and environmentally friendly. After the catalytic reaction is completed, the chitosan Schiff base-supported copper catalytic material can be separated from other components in the reaction system by means of solid-liquid phase separation. It can be reused after simple regeneration, reducing production costs and being environmentally friendly. Higher conversions can be achieved by using less expensive catalytic materials and using smaller quantities of catalytic materials.

2. In the process of catalytically preparing allyl borate, there is no need to add a base and the reaction is carried out at room temperature. The reaction conditions are mild and simple and easy to operate. It only needs to use a lower-cost catalyst and a lower catalyst dosage to achieve it. The reaction product has a high conversion rate; the substrate has wide applicability and can realize the boron addition of different types of MBH esters to prepare the corresponding allyl borate.

3. The adsorption of Cu ²⁺ by chitosan Schiff base materials is mainly based on imine group coordination (2). The main reactions include:

Schiff reaction: R′-NH ₂ +RCHO→R′-N＝CHR (1)

In this application, after modifying the biomass-based material chitosan with aldehyde compounds, the coordination ability of chitosan is changed and the catalytic activity of the catalyst is improved. The aldehyde group (RHC=O) of the aldehyde compound reacts with the amino group (R'-NH ₂ ) on chitosan to form an imine containing a carbon-nitrogen double bond (R ₂ C=NR'-). The surface of chitosan is rich in hydroxyl groups. The N atoms in the C=N double bond formed by the Schiff base reaction and the O atoms in the adjacent OH can easily coordinate with Cu ²⁺ to form a stable conjugated plane. The complexing effect is stronger.

4. When modifying chitosan with aldehyde compounds, since the aldehyde group of the aldehyde compound and the hydroxyl group of chitosan will undergo an acetalization reaction, the -C=O of the aldehyde compound is relative to the -NH of the chitosan unit. When there is a large excess of ₂ , sufficient imine groups can be generated to form a stable complex with copper ions. However, when it is too excessive, the O atoms in the OH adjacent to the N atoms in the C=N double bond are reduced due to the acetal reaction, reducing the complexing effect on copper ions. Therefore, Schiff-CS@Cu is prepared, that is, chitosan Schiff When using alkali powder, the molar ratio of C=O in aldehyde and _-NH2 in chitosan is 4:1.

Description of the drawings

Figure 1 is the hydrogen nuclear magnetic spectrum of the target product in Example 4;

Figure 2 is the NMR carbon spectrum of the target product in Example 4.

Detailed ways

The following specific examples further illustrate the present invention in detail. The drugs used in the examples are all commercially available products unless otherwise specified, and the methods used are conventional methods in this field unless otherwise specified.

Example 1

This embodiment provides a method for modifying chitosan with 5-methyl salicylaldehyde to obtain Schiff-CS@Cu catalytic material L1. The specific preparation process is as follows:

a. Preparation of chitosan Schiff base powder: Add chitosan powder (1.0g) and 5-methylsalicylicaldehyde (3.4g) to 85 ml ethanol acetic acid mixed solution (the ethanol acetic acid mixed solution is prepared from 75 mL anhydrous (obtained by mixing ethanol and 10 ml of glacial acetic acid) and stirred at 65°C for 12 hours. The precipitate was recovered by filtration, washed repeatedly and alternately with absolute ethanol and distilled water to remove unreacted 5-methylsalicylicaldehyde, and dried in an oven at 50°C for 12 hours to obtain chitosan Schiff base powder. The molecular formula of chitosan is (C ₆ H ₁₁ NO ₄ )N. 1.0g chitosan contains approximately 6.2mmol-NH ₂ . In this example, the amount of aldehyde used is based on the aldehyde group -CHO and the amino group -NH in chitosan. ₂ The molar ratio is determined as 4:1. 5-Methyl salicylaldehyde undergoes Schiff reaction with -NH ₂ in chitosan, consuming -NH ₂ in chitosan to generate imine groups, changing the coordination ability to metals and improving catalytic performance.

b. Add the chitosan Schiff base powder obtained in step a to 30 mL of copper sulfate solution (prepared from 1.6 g of copper sulfate pentahydrate, containing 6.4 mmol Cu ²⁺ ) and stir at 50°C for 6 hours, and separate the Cu ²⁺ loaded solution by filtration. The powder was washed repeatedly and alternately with absolute ethanol and distilled water to remove free copper ions and sulfate ions, and finally dried in an oven at 50°C for 12 hours to obtain the Schiff-CS@Cu catalytic material designated as L1.

The relative content of active ingredient copper in L1 was detected by ICP to be 1.36mmol/g.

Example 2

This embodiment provides a method for modifying chitosan with salicylaldehyde to obtain Schiff-CS@Cu catalytic material L2. The specific preparation process is as follows:

a. Preparation of chitosan Schiff base powder: Add chitosan powder (1.0g) and salicylaldehyde (3.0g) to 85 ml ethanol acetic acid mixed solution (the ethanol acetic acid mixed solution is composed of 75 ml absolute ethanol, 10 ml ice Mix acetic acid to obtain), stir and react at 75°C for 18 hours. The precipitate was recovered by filtration, washed repeatedly with absolute ethanol and distilled water to remove unreacted salicylaldehyde, and dried in an oven at 50°C for 12 hours to obtain chitosan Schiff base powder. The molecular formula of chitosan is (C ₆ H ₁₁ NO ₄ )N. 1.0g chitosan contains approximately 6.2mmol-NH ₂ . In this example, the amount of aldehyde used is based on the aldehyde group -CHO and the amino group -NH in chitosan. ₂ The molar ratio is determined as 4:1.

b. Add the chitosan Schiff base powder obtained in step a to 30 mL of copper sulfate solution (prepared from 1.6 g copper sulfate pentahydrate, containing 6.4 mmol Cu ²⁺ ), stir at 50°C for 6 hours, and separate the Cu ²⁺ -loaded powder by filtration. , repeatedly and alternately washed with absolute ethanol and distilled water to remove free copper ions and sulfate ions, and finally dried in an oven at 50°C for 12 hours to obtain the Schiff-CS@Cu catalytic material recorded as L2.

The relative content of active ingredient copper in L2 was detected by ICP to be 0.877mmol/g.

Example 3

This embodiment provides a method for modifying chitosan with 5-nitrosalicylicaldehyde to obtain Schiff-CS@Cu catalytic material L3. The specific preparation process is as follows:

a. Preparation of chitosan Schiff base powder: Add chitosan powder (1.0g) and 5-nitrosalicylicaldehyde (4.1g) to 85 ml of ethanol-acetic acid mixed solution (the ethanol-acetic acid mixed solution is prepared from 75 mL of anhydrous (obtained by mixing ethanol and 10 ml of glacial acetic acid), stir and react at 75°C for 24 hours. The precipitate was recovered by filtration, washed repeatedly and alternately with absolute ethanol and distilled water to remove unreacted 5-nitrosalicylicaldehyde, and dried in an oven at 50°C for 12 hours to obtain chitosan Schiff base powder. The molecular formula of chitosan is (C ₆ H ₁₁ NO ₄ )N. 1.0g chitosan contains approximately 6.2mmol-NH ₂ . In this example, the amount of aldehyde used is based on the aldehyde group -CHO and the amino group -NH in chitosan. ₂ The molar ratio is determined as 4:1.

b. Add the chitosan Schiff base powder obtained in step a to 30 mL of copper sulfate solution (prepared from 1.6 g of copper sulfate pentahydrate, containing 6.4 mmol Cu ²⁺ ), stir at 50°C for 6 hours, and separate the loaded Cu ²⁺ by filtration. The powder was washed repeatedly and alternately with absolute ethanol and distilled water to remove free copper ions and sulfate ions, and finally dried in an oven at 50°C for 12 hours to obtain the Schiff-CS@Cu catalytic material designated as L3.

The relative content of active ingredient copper in L3 was detected by ICP to be 0.528mmol/g.

Comparative ratio

This embodiment provides a method in which the carrier is chitosan-immobilized copper CS@Cu catalytic material L4. The specific preparation process is as follows:

Chitosan powder (1.0g) was added to 30mL copper sulfate solution (prepared from 1.6g copper sulfate pentahydrate, containing 6.4mmol Cu ²⁺ ) and stirred at 50°C for 6 hours. The powder loaded with Cu ²⁺ was separated by filtration and washed with absolute ethanol. Repeatedly wash with distilled water to remove free copper ions and sulfate ions, and finally dry in an oven at 50°C for 12 hours to obtain the CS@Cu catalytic material designated as L4.

The relative content of active ingredient copper in L4 was detected by ICP to be 1.75mmol/g.

Example 4

This embodiment provides a method for catalytically preparing allyl borate using chitosan Schiff base-immobilized copper catalytic material Schiff-CS@Cu. The specific steps are as follows:

1) Add MBH ester compound I, pinacol diborate and Schiff-CS@Cu catalytic material L3 (prepared in Example 3) into 2 ml of pure water, in which MBH ester compound I 0.20 mmol, pinacol diborate 0.40mmol, catalytic material L3 contains 0.002mmol of copper, mix and stir for 12 hours at room temperature. In this example, MBH ester compound I is 2-(acetoxy(phenyl)methyl)methyl acrylate, where R ₁ is phenyl , the reaction formula is as follows;

2) After the reaction, filter, and the precipitate is repeatedly washed and dried with water and ethanol. The chitosan Schiff base-supported copper catalytic material Schiff-CS@Cu is recovered for recycling. The filtrate is extracted with ethyl acetate (3×10mL) , the organic phase containing the product was obtained, which was dried over anhydrous Na ₂ SO ₄ , filtered, and rotary evaporated to remove excess organic solvent. The remaining organic phase was purified by column chromatography using a mixed solvent of ethyl acetate/petroleum ether = 1:20 to obtain allyl borate II (R ₁ is phenyl). Product yield was 91% (55.0 mg).

The hydrogen and carbon NMR spectra of the target product are shown below, and the spectra are shown in Figures 1 and 2.

¹ H NMR (400MHz, Chloroform-d); δ = 7.67 (s, 1H), 7.38–7.36 (m, 5H), 3.80 (s, 3H), 2.14 (s, 2H), 1.23 (s, 12H).

¹³ C NMR (100MHz, Chloroform-d); δ=169.2,137.7,136.3,130.2,129.5,128.4,128.1,83.6,52.2,24.8.

Example 4 shows that under the catalytic conditions of the Schiff-CS@Cu catalytic material L3 provided in this example, the conversion rate of methyl 2-(acetoxy(phenyl)meth)acrylate is very high, and its boron addition The product yield reached 91%.

The catalytic material L1 prepared in Example 1 was applied to the boron addition reaction of methyl 2-(acetoxy(phenyl)methyl)acrylate and pinacol diborate according to the above reaction steps, and the yield was 57%. .

The catalytic material L2 prepared in Example 2 was applied to the boron addition reaction of 2-(acetoxy(phenyl)methyl)methyl acrylate and pinacol diborate according to the above reaction steps, and the yield was 72%. .

The catalytic material L4 prepared in the comparative example was applied to the boron addition reaction of methyl 2-(acetoxy(phenyl)methyl)acrylate and pinacol diborate according to the above reaction steps, and the yield was 61%.

The catalytic activity of the catalytic material L3 is improved compared to the control group catalytic material L4. The stronger the electron-attracting ability of the substituent at position 5 of the benzene ring of the salicylaldehyde compound, the better the catalytic effect. The aldehyde group of salicylaldehyde compounds is located at position 2 of the benzene ring, which is the meta group of the substituent at position 5. The stronger the electron-withdrawing ability of the group, the more obvious the activation of the meta substituent, and the easier it is to react. The more imine groups obtained by the reaction, the better the catalytic effect.

Example 5

This embodiment provides a method for catalytically preparing allyl borate using chitosan Schiff base-immobilized copper catalytic material Schiff-CS@Cu. The specific steps are as follows:

1) Add MBH ester compound I, pinacol diborate and Schiff-CS@Cu catalytic material L3 (prepared in Example 3) into 2 ml of pure water, in which MBH ester compound I 0.20 mmol, pinacol diborate 0.40mmol, the catalytic material L3 contains 0.002mmol of copper, and the mixture is stirred and reacted at room temperature for 12 hours. In this example, MBH ester compound I is 2-(acetoxy(p-tolyl)methyl)methyl acrylate, where R ₁ is p Tolyl, the reaction formula is as follows;

2) After the reaction is completed, filter, and the precipitate is repeatedly washed and dried with water and ethanol. The chitosan Schiff base copper catalytic material is recovered and recycled. The filtrate is extracted with ethyl acetate (3 × 10 mL) to obtain an organic phase containing the product. , dried over anhydrous Na ₂ SO ₄ , filtered, and rotary evaporated to remove excess organic solvent. The remaining organic phase was purified by column chromatography using a mixed solvent of ethyl acetate/petroleum ether = 1:20 to obtain allyl borate II (R ₁ is p-tolyl). Product yield was 86% (54.4 mg).

The hydrogen and carbon NMR spectra of the target product are as follows:

¹ H NMR (400MHz, Chloroform-d); δ = 7.65 (s, 1H), 7.30–7.28 (m, 2H), 7.19–7.16 (m, 2H), 3.79 (s, 3H), 2.76 (s, 3H) ),2.14(s,2H),1.23(s,12H).

¹³ C NMR (100MHz, Chloroform-d); δ = 169.5, 138.3, 137.9, 133.5, 129.6, 129.4, 129.2, 83.6, 52.2, 24.9, 21.5.

Example 5 shows that under the catalytic conditions of Schiff-CS@Cu catalytic material L3 provided in the embodiment of the present invention, the conversion rate of methyl 2-(acetoxy(p-tolyl)methyl)acrylate is very high, and its boron The yield of the addition product reached 86%.

Example 6

This embodiment provides a method for catalytically preparing allyl borate using chitosan Schiff base-immobilized copper catalytic material Schiff-CS@Cu. The specific steps are as follows:

1) Add MBH ester compound I, pinacol diborate and Schiff-CS@Cu catalytic material L3 (prepared in Example 3) into 2 ml of pure water, wherein MBH ester compound I 0.20 mmol, pinacol diborate 0.40mmol of ester and 0.002mmol of catalytic material L3 containing copper were mixed and stirred at room temperature for 12 hours. In this example, MBH ester compound I is methyl 2-(acetoxy(p-methoxyphenyl)methyl)acrylate, where R ₁ is p-methoxyphenyl, and the reaction formula is as follows;

2) After the reaction is completed, filter, and the precipitate is repeatedly washed and dried with water and ethanol. The chitosan Schiff base copper catalytic material is recovered and recycled. The filtrate is extracted with ethyl acetate (3×10 mL) to obtain an organic phase containing the product. , dried over anhydrous Na ₂ SO ₄ , filtered again, and rotary evaporated to remove excess organic solvent. The remaining organic phase was purified by column chromatography using a mixed solvent of ethyl acetate/petroleum ether = 1:20 to obtain allyl borate II (R ₁ is p-methoxyphenyl). Product yield was 81% (53.8 mg).

The hydrogen and carbon NMR spectra of the target product allyl borate II are as follows:

¹ H NMR (400MHz, Chloroform-d); δ = 7.62 (s, 1H), 7.37–7.35 (m, 2H), 6.91–6.88 (m, 2H), 3.82 (s, 3H), 3.78 (s, 3H) ),2.15(s,2H),1.23(s,12H).

¹³ C NMR (100MHz, Chloroform-d); δ = 169.5, 159.5, 137.5, 131.2, 128.8, 128.2, 113.9, 83.5, 55.4, 52.1, 24.8.

Example 6 shows that under the catalytic conditions of Schiff-CS@Cu catalytic material L3 provided in the embodiment of the present invention, the conversion rate of methyl 2-(acetoxy(p-methoxyphenyl)methyl)acrylate is very high , the yield of boron addition product reached 81%.

Example 7

This embodiment provides a method for catalytically preparing allyl borate using chitosan Schiff base-immobilized copper catalytic material Schiff-CS@Cu. The specific steps are as follows:

1) Add MBH ester compound I, pinacol diborate and Schiff-CS@Cu catalytic material L3 (prepared in Example 3) into 2 ml of pure water, in which MBH ester compound I 0.20 mmol, pinacol diborate 0.40mmol, the catalytic material L3 contains 0.002mmol of copper, and the mixture is stirred and reacted at room temperature for 12 hours. In this example, MBH ester compound I is 2-(acetoxy(m-methoxyphenyl)methyl)methyl acrylate, where R ₁ is m-methoxyphenyl, the reaction formula is as follows;

2) After the reaction is completed, filter, and the precipitate is repeatedly washed and dried with water and ethanol. The chitosan Schiff base copper catalytic material is recovered and recycled. The filtrate is extracted with ethyl acetate (3×10 mL) to obtain an organic phase containing the product. , dried over anhydrous Na ₂ SO ₄ , filtered, and rotary evaporated to remove excess organic solvent. The remaining organic phase was purified by column chromatography using a mixed solvent of ethyl acetate/petroleum ether = 1:20 to obtain allyl borate II (R ₁ is m-methoxyphenyl). Product yield was 82% (54.5 mg).

The hydrogen and carbon NMR spectra of the target product allyl borate II are as follows:

¹ H NMR (400MHz, Chloroform-d); δ = 7.65 (s, 1H), 7.29–6.83 (m, 4H), 3.81 (s, 3H), 3.80 (s, 3H), 2.14 (s, 2H), 1.23(s,12H).

¹³ C NMR (100MHz, Chloroform-d); δ = 169.2, 159.5, 137.7, 137.6, 130.5, 129.4, 122.0, 114.5, 114.2, 83.6, 55.4, 52.2, 24.8.

Example 7 shows that under the catalytic conditions of Schiff-CS@Cu catalytic material L3 provided in the embodiment of the present invention, the conversion rate of methyl 2-(acetoxy(m-methoxyphenyl)methyl)acrylate is very high , the yield of boron addition product reached 82%.

Example 8

This embodiment provides a method for catalytically preparing allyl borate using chitosan Schiff base-immobilized copper catalytic material Schiff-CS@Cu. The specific steps are as follows:

1) Add MBH ester compound I, pinacol diborate and Schiff-CS@Cu catalytic material L3 (prepared in Example 3) into 2 ml of pure water, in which MBH ester compound I 0.20 mmol, pinacol diborate 0.40mmol, the catalytic material L3 contains 0.002mmol of copper, and the mixture is stirred and reacted at room temperature for 12 hours. In this example, MBH ester compound I is 2-(acetoxy(o-chlorophenyl)methyl)methyl acrylate, where R ₁ is O-chlorophenyl, the reaction formula is as follows;

2) After the reaction is completed, filter, and the precipitate is repeatedly washed and dried with water and ethanol. The chitosan Schiff base copper catalytic material is recovered and recycled. The filtrate is extracted with ethyl acetate (3×10 mL) to obtain an organic phase containing the product. , dried over anhydrous Na ₂ SO ₄ , filtered, and rotary evaporated to remove excess organic solvent. The remaining organic phase was purified by column chromatography using a mixed solvent of ethyl acetate/petroleum ether = 1:20 to obtain allyl borate II (R ₁ is o-chlorophenyl). Product yield was 82% (55.2 mg).

The hydrogen and carbon NMR spectra of the target product allyl borate II are as follows:

¹ H NMR (400MHz, Chloroform-d); δ = 7.72 (s, 1H), 7.42–7.38 (m, 2H), 7.25–7.23 (m, 2H), 3.81 (s, 3H), 2.00 (s, 2H) ),1.24(s,12H).

¹³ C NMR (100MHz, Chloroform-d); δ=168.7,134.8,134.2,132.1,130.6,129.6,126.5,83.6,52.2,24.8.

Example 8 shows that under the catalytic conditions of Schiff-CS@Cu catalytic material L3 provided in the embodiment of the present invention, the conversion rate of methyl 2-(acetoxy(o-chlorophenyl)methyl)acrylate is very high, and its conversion rate is very high. The yield of boron addition product reached 82%.

Example 9

This embodiment provides a method for catalytically preparing allyl borate using chitosan Schiff base-immobilized copper catalytic material Schiff-CS@Cu. The specific steps are as follows:

1) Add MBH ester compound I, pinacol diborate and Schiff-CS@Cu catalytic material L3 (prepared in Example 3) into 2 ml of pure water, in which MBH ester compound I 0.20 mmol, pinacol diborate 0.40mmol, the catalytic material L3 contains 0.002mmol of copper, and the mixture is stirred and reacted at room temperature for 12 hours. In this example, MBH ester compound I is 2-(acetoxy(p-chlorophenyl)methyl)methyl acrylate, where R ₁ is For p-chlorophenyl, the reaction formula is as follows;

2) After the reaction is completed, filter, and the precipitate is repeatedly washed and dried with water and ethanol. The chitosan Schiff base copper catalytic material is recovered and recycled. The filtrate is extracted with ethyl acetate (3×10 mL) to obtain an organic phase containing the product. , dried over anhydrous Na ₂ SO ₄ , filtered, and rotary evaporated to remove excess organic solvent. The remaining organic phase was purified by column chromatography using a mixed solvent of ethyl acetate/petroleum ether = 1:20 to obtain allyl borate II (R ₁ is p-chlorophenyl). Product yield was 88% (59.2 mg).

The hydrogen and carbon NMR spectra of the target product are shown below.

¹ H NMR (400MHz, Chloroform-d); δ = 7.60 (s, 1H), 7.33–7.32 (m, 4H), 3.80 (s, 3H), 2.10 (s, 2H), 1.24 (s, 12H).

¹³ C NMR (100MHz, Chloroform-d); δ = 169.1, 136.5, 134.8, 134.1, 131.0, 130.8, 128.8, 83.8, 52.3, 24.9.

Example 9 shows that under the catalytic conditions of Schiff-CS@Cu catalytic material L3 provided in the embodiment of the present invention, the conversion rate of methyl 2-(acetoxy(p-chlorophenyl)methyl)acrylate is very high, and its conversion rate is very high. The yield of boron addition product reached 88%.

Claims (9)

1. A method for preparing allyl borate by using biomass-based catalytic material, which is characterized by comprising the following steps:

1) Adding MBH ester compound I, bisboronic acid pinacol ester and chitosan Schiff base immobilized copper catalytic material Schiff-CS@Cu into pure water, mixing and stirring at room temperature for reacting for 12-24 h, wherein the mass ratio of the MBH ester compound I is as follows: di-boric acid pinacol ester: copper content=1 (1.2-2): (0.005-0.03) in the catalytic material Schiff-CS@Cu, and the chemical reaction equation is as follows:

wherein R is ₁ Phenyl, p-methylphenyl, p-methoxyphenyl, m-methoxyphenyl, o-chlorophenyl and p-chlorophenyl;

the chitosan Schiff base immobilized copper catalytic material Schiff-CS@Cu is prepared by a method comprising the following steps of:

a. adding chitosan and aldehyde compound into ethanol acetic acid mixed solution, stirring at 65-75 ℃ for reacting for 12-24 hours, wherein the aldehyde compound is one of 5-methyl salicylaldehyde, salicylaldehyde and 5-nitro salicylaldehyde, and aldehyde group-CHO in the aldehyde compound and amino-NH in the chitosan ₂ The molar ratio is 2-6:1, and after the reaction is finished, the chitosan Schiff base powder is obtained through separation treatment;

b. placing chitosan Schiff base powder into a cupric ion solution, stirring for 3-9 hours at 50-75 ℃ to adsorb cupric ions, and separating to obtain a chitosan Schiff base immobilized copper catalytic material Schiff-CS@Cu after adsorption is finished;

2) After the reaction is finished, filtering, separating and purifying the obtained filtrate to obtain allyl borate II, washing and drying the precipitate to obtain a recovered chitosan Schiff base copper catalytic material Schiff-CS@Cu, and carrying out the next recycling.

2. The method for preparing allyl borate by using biomass-based catalytic material as claimed in claim 1, wherein the copper content in the chitosan Schiff-cs@cu of step 1) is 0.5-1.4 mmol/g.

3. The method for preparing allyl borates using biomass-based catalytic materials according to claim 1, characterized in that in step 1) MBH ester compound I: di-boric acid pinacol ester: the catalytic material Schiff-CS@Cu contains copper in a mass ratio of 1:2:0.01.

4. The method for preparing allyl borate by using biomass-based catalytic material as claimed in claim 1, wherein the ratio of copper to pure water in the chitosan Schiff-CS@Cu supported copper catalytic material Schiff-CS@Cu in step 1) is 0.001-0.006mmol:2 ml.

5. The method for preparing allyl borate using biomass based catalytic material as claimed in claim 1, wherein the reaction is performed for 12 hours at room temperature with mixing and stirring in step 1).

6. The method for preparing allyl borate by using biomass-based catalytic material according to claim 1, wherein the filtrate obtained in the step 2) is separated and purified to obtain allyl borate II, specifically comprising: extracting the filtrate with ethyl acetate to obtain organic phase containing the product, and passing through anhydrous Na ₂ SO ₄ Drying, filtering, rotary evaporating to remove redundant organic solvent, and purifying the obtained residual organic phase by using ethyl acetate and petroleum ether mixed solvent column chromatography to obtain allyl borate II.

7. The method for preparing allyl borate by using biomass-based catalytic material as claimed in claim 1, wherein the ethanol acetic acid mixed solution in the step a is obtained by mixing glacial acetic acid and absolute ethyl alcohol according to a volume ratio of 1:7-8, wherein aldehyde-CHO in aldehyde compounds and amino-NH in chitosan ₂ The molar ratio was 4:1.

8. The method for preparing allyl borate using biomass based catalytic material as claimed in claim 1, wherein the cupric ion solution in step b contains Cu ²⁺ With amino-NH in chitosan ₂ The molar ratio is at least 1:1, and the concentration of copper ions in the cupric ion solution is 0.1-0.5 mol/L.

9. The method for preparing allyl borate using biomass-based catalytic material as claimed in claim 1, wherein the separation treatments in steps a and b each include: filtering, repeatedly and alternately washing with absolute ethyl alcohol and distilled water, and drying in an oven at 50 ℃ for 12 hours.