CN115806504B - Asymmetric chiral ligand and preparation method thereof, prepared catalyst, synthesis method and application thereof - Google Patents

Abstract

The invention discloses an asymmetric chiral ligand, a preparation method, a prepared catalyst, a synthesis method and application thereof, wherein the structural formula of the asymmetric chiral ligand is as followsThe catalyst is prepared by a secondary cooling crystallization method, is simple and time-saving and can be prepared in a large amount; the catalyst unit cell parameters prepared were: the space group is P3 ₂ ，α＝β＝90°，γ＝120°，Z=3; the catalyst structure has hydrophobic chiral pore canal with the size of 1.03nm and is inlaid with catalytic activity metallic copper sites with high density, so that 5-chloro-1-oxo-2, 3-indan-2-carboxylic acid methyl ester can be efficiently and cyclically catalyzed and oxidized to prepare S-configured 5-chloro-2, 3-dihydro-2-hydroxy-1-oxo-1H-indene-2-carboxylic acid methyl ester with the optical purity of 99.7 percent.

Description

An asymmetric chiral ligand and its preparation method, prepared catalyst, synthesis method and application

Technical Field

The present invention relates to the technical field of coordination chemistry and chiral chemistry, and in particular to an asymmetric chiral ligand and a preparation method thereof, a prepared catalyst, a synthesis method and application thereof.

Background technique

Indoxacarb is a carbamate insecticide with an oxadiazine structure. Because of its chiral carbon atom in its molecular structure, indoxacarb has two enantiomers, R and S, but only the S-configuration indoxacarb has insecticidal activity. In order to efficiently prepare insecticidal indoxacarb, most of the synthetic routes currently adopted are to asymmetrically catalytically convert 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester (abbreviated as β-indanone ester) into (2S)-5-chloro-2,3-dihydro-2-hydroxy-1-oxo-1H-indane-2-carboxylic acid methyl ester (a key intermediate of indoxacarb), and then synthesize a single S-configuration indoxacarb. The catalysts used in asymmetric catalytic transformation reactions are mainly cinchona alkaloid derivatives, chiral phosphine Schiff base-Cu(I), tartaric acid-derived chiral guanidines, chiral Salen-Zr complexes, chiral Zr-Salen polymers, S-timolol derivatives, etc., but these chiral catalysts have disadvantages such as unstable structure, few active sites and high preparation cost, which seriously restrict the synthesis of indoxacarb. Therefore, it is urgent to develop heterogeneous catalysts with stable framework structure, dense active sites and excellent catalytic effect for the synthesis of chiral key intermediates of indoxacarb.

Metal-organic framework materials (MOFs) are organic-inorganic hybrid crystalline materials with periodic network structures formed by coordination of functionalized organic ligands and metal ions. Their structures and functions can be achieved by rationally selecting and regulating the structures of organic ligands and the types of metal ions. Therefore, such materials become an ideal platform for constructing catalysts with different structures and functions. In particular, introducing chirality into porous metal-organic frameworks will help develop solid-phase chiral catalysts with asymmetric catalytic functions. For example, a Chinese patent application document with publication number CN101830920A discloses a chiral MOFs material with asymmetric catalytic effects induced by prolinol derivatives. The material can be used as a heterogeneous catalyst for asymmetric silylation reactions, so the catalyst can be recycled, with a yield of up to 100% and an ee value of 99%. A Chinese patent application document with publication number CN103301885A discloses a method for preparing chiral POM/MOFs with asymmetric catalytic effects. The synthesis is simple and easy to operate, the raw material price is low, the yield is high, and the obtained functional material has stable chemical properties and is easy to promote and apply on a large scale. MOFs catalytic materials have a large specific surface area, and only need to use 0.7% of the substrate to achieve good conversion rate and stereoselectivity, which is suitable for large-scale industrial production. Despite this, the design and synthesis of chiral polynuclear metal-organic framework solid-phase catalysts with stable framework structure, dense active sites and excellent catalytic effect still face great challenges at present, and efficient chiral polynuclear metal-organic framework catalysts that can be successfully used for the asymmetric conversion of β-indanone ester to (2S)-5-chloro-2,3-dihydro-2-hydroxy-1-oxo-1H-indene-2-carboxylic acid methyl ester are even rarer.

Summary of the invention

The technical problem to be solved by the present invention is to provide a new asymmetric chiral ligand, and to provide a new chiral multinuclear copper metal-organic framework catalyst with a stable structure, dense active sites and excellent catalytic effect in the process of highly enantioselectively catalyzing the conversion of β-indanone ester into S-configuration 5-chloro-2,3-dihydro-2-hydroxy-1-oxo-1H-indene-2-carboxylic acid methyl ester.

The present invention solves the above technical problems through the following technical means:

An asymmetric chiral ligand, the structural formula of which is as follows:

The present invention also provides a method for preparing the asymmetric chiral ligand, comprising the following steps: dissolving 3-tert-butyl-5-aldehyde-4-hydroxybenzoic acid and L-phenylalaninol in methanol, refluxing the mixture, and filtering the mixture while hot after the reaction is completed to obtain the asymmetric chiral ligand.

Preferably, the chemical structural formula of the 3-tert-butyl-5-formyl-4-hydroxybenzoic acid is: The preparation method can be based on the method described in J.Am.Chem.Soc., 2010.132(43):15390-15398, which specifically includes the following steps:

4-Hydroxy-3-tert-butylbenzoic acid (1.55 g, 7.95 mmol) and hexamethylenetetramine (2.23 g, 15.9 mmol) were placed in a 250 mL round bottom flask, and trifluoroacetic acid (63 mL) was added and the solution was heated to reflux for 18 hours. Then 50 mL of 33% H ₂ SO ₄ was added to the reaction, and the solution was refluxed for another 3 hours. After the reaction was completed, the mixed solution was diluted with ether and washed with water and brine, and then the organic phase was dried over magnesium sulfate and concentrated in vacuo to obtain 1.2 g of 3-tert-butyl-5-formyl-4-hydroxybenzoic acid.

Preferably, the molar ratio of 3-tert-butyl-5-formyl-4-hydroxybenzoic acid to L-phenylalaninol is 1:1.2-1.5.

Preferably, the reflux reaction time is 5 to 10 hours.

The present invention also provides a chiral multinuclear copper metal-organic framework catalyst, which is prepared using the asymmetric chiral ligand as a ligand, and has a chemical formula of Cu ₃ L ₂ , wherein the structural formula of L is as follows:

The unit cell parameters of the chiral multi-nuclear copper metal-organic framework catalyst are as follows: the space group is P3 ₂ , α＝β＝90°，γ＝120°， Z=3.

The present invention adopts an asymmetric Schiff base chiral ligand H ₃ L (i.e. (S, E)-3-(tert-butyl)-4-hydroxy-5-((1-hydroxy-3-phenylpropane-2-yl)imino)methyl)benzoic acid) with a tridentate chelating site as a bridging unit to construct a chiral metal-organic framework catalyst with a trinuclear copper structure; the ligand H ₃ L is obtained by reflux reaction of 3-tert-butyl-5-aldehyde-4-hydroxybenzoic acid and L-phenylalaninol in methanol; the connection mode between the chiral ligand and the metal copper ion in the single crystal structure of the chiral multinuclear copper metal-organic framework catalyst is as follows;

Wherein, n is any integer;

Beneficial effects: The chiral multinuclear copper metal-organic framework catalyst of the present invention has a framework composed of a trinuclear Cu ₃ O ₈ N ₂ cluster with a 4-connection effect and four surrounding chiral asymmetric Schiff bases connected to each other. The catalyst structure has a 1.03nm hydrophobic chiral pore in which unsaturated metal copper sites are periodically embedded, and can be used as a potential recyclable solid-phase chiral catalyst.

The present invention also proposes a method for synthesizing the chiral multi-nuclear copper metal-organic framework catalyst, which uses copper salt as the metal salt, the asymmetric chiral ligand as the organic bridging ligand, and N,N'-dimethylformamide and methanol as solvents for coordination reaction. After the reaction is completed, the reaction is cooled to room temperature, and the reaction product is placed in an ice water bath for cooling to obtain the chiral multi-nuclear copper metal-organic framework catalyst.

Beneficial effects: The invention prepares the chiral multi-nuclear copper metal-organic framework catalyst by a secondary cooling crystallization method, which is simple, time-saving and can be prepared in large quantities.

Preferably, the method for synthesizing the chiral multi-nuclear copper metal-organic framework catalyst comprises the following steps:

S1. Mix copper salt, N,N'-dimethylformamide and methanol, and then add dropwise to the methanol solution of the asymmetric chiral ligand, remove the blue turbidity after heating and stirring, and take a blue clear liquid;

S2. The blue clear liquid in S1 is sealed in a high-pressure reactor with a polytetrafluoroethylene liner to carry out a solvothermal reaction. After the reaction is completed, the reaction product is cooled to room temperature and then placed in an ice water bath to cool to obtain the chiral multi-nuclear copper metal-organic framework catalyst.

Preferably, the molar ratio of the asymmetric chiral ligand to the copper salt is 1:1.5-3; the volume ratio of N,N'-dimethylformamide, methanol for dissolving the copper salt, and methanol for dissolving the asymmetric chiral ligand is 1:1-3:1-3; the temperature of the solvent thermal reaction is 90-110°C, and the time is 1-2.5h.

Preferably, the molar ratio of the asymmetric chiral ligand to the copper salt is 1:2; the temperature of the solvent thermal reaction is 100° C. and the time is 1 hour.

Preferably, the volume ratio of N,N'-dimethylformamide, methanol for dissolving the copper salt, and methanol for dissolving the asymmetric chiral ligand is 1:2:1.

Preferably, the copper salt is a mixture of one or more of Cu(OAc) ₂ ·H ₂ O, Cu(ClO ₄ ) ₂ ·6H ₂ O, Cu(NO ₃ ) ₂ ·3H ₂ O, and CuCl ₂ ·2H ₂ O.

Preferably, the copper salt is Cu(OAc) ₂ ·H ₂ O.

Preferably, in S1, the blue turbidity is removed after heating to 35-45°C and stirring for 25-35 minutes.

Preferably, in S1, the blue turbidity is removed after heating to 40°C and stirring for 30 minutes.

The present invention also proposes an application of the chiral multi-nuclear copper metal-organic framework catalyst in the asymmetric catalytic oxidation of 5-chloro-1-oxo-2,3-dihydroindene-2-carboxylic acid methyl ester to prepare S-configuration 5-chloro-2,3-dihydro-2-hydroxy-1-oxo-1H-indene-2-carboxylic acid methyl ester.

Preferably, the oxidant used is cumene hydroperoxide; the solvent used is toluene; and the reaction temperature is room temperature.

Preferably, the molar ratio of the oxidant used and the reaction substrate 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester is 1.3-1.7:1; the mass ratio of the chiral multi-nuclear copper metal-organic framework catalyst to the reaction substrate 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester is 1:25.

Preferably, the molar ratio of the oxidant to the reaction substrate 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester is 1.5:1.

Beneficial effect: The amount of the oxidant is 1.5 times that of the reaction substrate 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester, which is more appropriate. The yield is reduced when the oxidant is reduced, and there is no obvious change in the yield when it exceeds 1.5 times.

Beneficial effects: The chiral multinuclear copper metal-organic framework catalyst of the present invention can catalyze the oxidation of 5-chloro-1-oxo-2,3-dihydroindene-2-carboxylic acid methyl ester with 99.7% enantioselectivity and 93% yield to prepare S-configuration 5-chloro-2,3-dihydro-2-hydroxy-1-oxo-1H-indene-2-carboxylic acid methyl ester, and the catalyst can be recycled for multiple times without losing activity.

The chiral multi-nuclear copper metal-organic framework catalyst of the present invention is a three-dimensional structure crystal with nano hydrophobic chiral channels formed by secondary cooling crystallization with Cu as the metal center and chiral ligand H ₃ L, and its molecular formula is Cu ₃ L ₂ , wherein the chiral ligand H ₃ L is (S, E)-3-(tert-butyl)-4-hydroxy-5-((1-hydroxy-3-phenylpropane-2-yl)imino)methyl)benzoic acid; the structural formula of H ₃ L is

The invention has the advantages that the chiral multi-nuclear copper metal-organic framework catalyst is prepared by a secondary cooling crystallization method, which is simple, time-saving and can be prepared in large quantities; the catalyst structure has a hydrophobic chiral pore with a size of 1.03 nm, and is densely inlaid with catalytically active metal copper sites, so that β-indanone esters can be simply and efficiently catalytically oxidized to prepare the key intermediate S-configuration-5-chloro-2,3-dihydro-2-hydroxy-1-oxo-1H-indene-2-carboxylic acid methyl ester of a single configuration of indoxacarb, and the catalyst can be recycled for multiple times.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a nuclear magnetic resonance spectrum of the asymmetric chiral ligand H ₃ L prepared in Example 1 of the present invention;

FIG2 is a diagram showing the coordination and connection mode of copper ions in the chiral multi-nuclear copper metal-organic framework catalyst prepared in Example 1 of the present invention;

FIG3 is a three-dimensional porous structure diagram of the chiral multi-nuclear copper metal-organic framework catalyst prepared in Example 1 of the present invention;

FIG4 is an infrared spectrum of the chiral multinuclear copper metal-organic framework catalyst and the chiral ligand H ₃ L in Example 1 of the present invention;

FIG5 is a hydrogen nuclear magnetic resonance spectrum of the catalytic reaction product in Example 4 of the present invention;

FIG6 is a high performance liquid chromatography spectrum of the catalytic reaction product in Example 4 of the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

Example 1

The synthesis of the asymmetric chiral ligand H ₃ L is as follows: 3-tert-butyl-5-formyl-4-hydroxybenzoic acid (2.2 g, 10 mmol) and L-phenylalaninol (1.8 g, 12 mmol) are dissolved in 30 mL of methanol, refluxed for 5 hours, and filtered while hot to obtain a yellow solid, namely the asymmetric chiral ligand H ₃ L, with a yield of 80%. The prepared asymmetric chiral ligand H ₃ L is tested by nuclear magnetic resonance, and its nuclear magnetic spectrum is shown in Figure 1. ¹ H NMR (600 MHz, DMSO-d ₆ )δ12.43(s,1H,COOH),8.40(s,1H,NCH ),7.87–7.73(m,2H,2×ArH ),7.29–7.07(m,5H,5×ArH ),5.03(s,1H,ArOH),3.90(d,J＝5.7Hz,1H,CH ₂ OH), 3.67–3.60 (m, 2H, CH ₂ OH), 3.52–3.48 (m, 1H, NCH), 3.01–2.84 (m, 2H, ArCH ₂ ), 1.35 (s, 9H, C(CH ₃ ) ₃ ).

A method for synthesizing a chiral multi-nuclear copper metal-organic framework catalyst specifically comprises the following steps:

(1) Cu(OAc) ₂ · _H2O (399 mg, 2.0 mmol) was dissolved in a mixture of 10 mL DMF and 20 mL methanol (MeOH), and added dropwise to a solution of asymmetric chiral ligand _H3L (355 mg, 1.0 mmol) in MeOH (10 mL). After heating and stirring at 40°C for 30 min, the blue turbidity was removed by filtration, and the blue clear liquid was sealed in a 100 mL polytetrafluoroethylene-lined autoclave.

(2) The reactor was heated in a high temperature constant temperature oven at 100° C. for 1 hour to ensure that the metal salt and the chiral ligand were fully reacted.

(3) stopping heating and cooling to room temperature, then placing the blue solution in the autoclave in an ice-water bath to obtain blue rice-like crystals, filtering, washing, and air-drying to obtain the chiral multi-nuclear copper metal-organic framework catalyst with a yield of 60%.

The crystal structure of the chiral multi-nuclear copper metal-organic framework catalyst obtained in Example 1 was determined.

Determination method: Shanghai Light Source synchrotron radiation technology is used to collect data on single crystal samples of the present invention of suitable size, APEX3 software is used to restore the obtained diffraction data, and the crystal structure is analyzed and refined using the SHELXS-2014 program. During this process, all non-hydrogen atoms are determined by the full-matrix least-squares refinement based on F2 and the anisotropic refinement of atoms is completed, while the hydrogen atoms on the asymmetric chiral ligand skeleton are completed by theoretical hydrogenation.

Measurement results: The unit cell parameters of the chiral multi-nuclear copper metal-organic framework catalyst single crystal of the present invention are as follows: the space group is P3 ₂ , α＝β＝90°，γ＝120°， Z=3.

By analyzing the single crystal data of the chiral multi-nuclear copper metal-organic framework catalyst of the present invention, it can be known that it crystallizes in the chiral P3 ₂ space group of the trigonal system, and its asymmetric unit contains two crystal-phase independent metal ligand CuL units and a Cu(II) ion. As shown in Figure 2, the two crystal-phase independent metal ligand CuL units and the Cu(II) ion form a Cu ₃ O ₈ N ₂ trinuclear copper metal cluster under the bridging effect of the terminal carboxyl groups of the other two CuL ligands. The Cu(II) ions in the two metal ligands CuL in the trinuclear copper cluster adopt a four-coordinated distorted planar structure, while the other one Cu(II) ion adopts a four-coordinated distorted tetrahedral structure. The trinuclear copper cluster can be connected to the surrounding four ligands as a 4-connected node to form a three-dimensional chiral metal-organic framework with a chiral channel of 1.03nm along the c-axis. The chiral channel is not only filled with hydrophobic groups such as tert-butyl and benzene rings, but also densely inlaid with unsaturated metal copper ions, as shown in Figure 3. This type of structure is similar to the chiral pocket of metal enzymes, and can be used as a potential asymmetric catalyst. In addition, by comparing the infrared spectra of chiral ligands and chiral multinuclear copper metal-organic framework catalysts (as shown in Figure 4), it can be found that the characteristic vibration peak of the chiral ligand carboxyl group of the chiral multinuclear copper metal-organic framework catalyst at 1675cm ^-1 disappears, which can prove that the metal copper ions are coordinated with the ligands, which is consistent with the results of single crystal structure analysis.

Example 2

A method for synthesizing a chiral multi-nuclear copper metal-organic framework catalyst specifically comprises the following steps:

(1) Cu(OAc) ₂ ·H ₂ O (1.5 mmol) was dissolved in a mixed solution of 10 mL DMF and 10 mL MeOH, and added dropwise to a solution of asymmetric chiral ligand H ₃ L (355 mg, 1.0 mmol) in MeOH (10 mL). After heating and stirring at 35° C. for 25 min, the blue turbidity was removed by filtration, and the blue clear liquid was sealed in a 100 mL polytetrafluoroethylene-lined autoclave.

(2) The reactor was heated in a high temperature constant temperature oven at 110° C. for 1.5 hours to ensure that the metal salt and the chiral ligand were fully reacted.

(3) stopping heating and cooling to room temperature, then placing the blue solution in the autoclave in an ice water bath to obtain blue rice-like crystals, filtering, washing, and air-drying to obtain the chiral multi-nuclear copper metal-organic framework catalyst.

Example 3

A method for synthesizing a chiral multi-nuclear copper metal-organic framework catalyst specifically comprises the following steps:

(1) Cu(OAc) ₂ ·H ₂ O (3.0 mmol) was dissolved in a mixed solution of 10 mL DMF and 30 mL MeOH, and added dropwise to a solution of asymmetric chiral ligand H ₃ L (355 mg, 1.0 mmol) in MeOH (30 mL). After heating and stirring at 45° C. for 25 min, the blue turbidity was removed by filtration, and the blue clear liquid was sealed in a 100 mL polytetrafluoroethylene-lined autoclave.

(2) The reaction vessel was heated in a high temperature constant temperature oven at 90° C. for 2 hours to ensure that the metal salt and the chiral ligand were fully reacted.

(3) stopping heating and cooling to room temperature, then placing the blue solution in the autoclave in an ice water bath to obtain blue rice-like crystals, filtering, washing, and air-drying to obtain the chiral multi-nuclear copper metal-organic framework catalyst.

Example 4

A method for synthesizing a chiral multi-nuclear copper metal-organic framework catalyst specifically comprises the following steps:

(1) Cu(OAc) ₂ ·H ₂ O (3.0 mmol) was dissolved in a mixed solution of 10 mL DMF and 15 mL MeOH, and added dropwise to a solution of asymmetric chiral ligand H ₃ L (355 mg, 1.0 mmol) in MeOH (20 mL). After heating and stirring at 40° C. for 35 min, the blue turbidity was removed by filtration, and the blue clear liquid was sealed in a 100 mL polytetrafluoroethylene-lined autoclave.

(2) The reactor was heated in a high temperature constant temperature oven at 105° C. for 2.5 hours to ensure that the metal salt and the chiral ligand were fully reacted.

(3) stopping heating and cooling to room temperature, then placing the blue solution in the autoclave in an ice water bath to obtain blue rice-like crystals, filtering, washing, and air-drying to obtain the chiral multi-nuclear copper metal-organic framework catalyst.

Example 5

A method for synthesizing a chiral multi-nuclear copper metal-organic framework catalyst specifically comprises the following steps:

Cu(ClO ₄ ) ₂ ·6H ₂ O (2.0 mmol) was dissolved in a mixed solution of 10 mL DMF and 30 mL MeOH, and then added dropwise to a solution of asymmetric chiral ligand H ₃ L (355 mg, 1.0 mmol) in MeOH (30 mL). After heating and stirring at 45° C. for 25 minutes, the blue turbidity was removed by filtration, and the blue clear liquid was sealed in a 100 mL autoclave with a polytetrafluoroethylene liner, and the autoclave was heated in a high temperature constant temperature oven at 90° C. for 2 hours. The heating was stopped, cooled to room temperature, and then the blue solution in the autoclave was placed in an ice water bath to obtain blue rice-like crystals, which were filtered, washed, and air-dried to obtain the chiral multi-nuclear copper metal-organic framework catalyst.

Example 6

A method for synthesizing a chiral multi-nuclear copper metal-organic framework catalyst specifically comprises the following steps:

Cu(NO ₃ ) ₂ ·3H ₂ O (2.0 mmol) was dissolved in a mixed solution of 10 mL DMF and 30 mL MeOH, and then added dropwise to a MeOH (30 mL) solution of asymmetric chiral ligand H ₃ L (355 mg, 1.0 mmol), heated and stirred at 45° C. for 25 minutes, filtered to remove blue turbidity, and sealed the blue clear liquid in a 100 mL polytetrafluoroethylene-lined autoclave, heated the autoclave in a high-temperature constant temperature oven at 90° C., and continued to react for 2 hours. Heating was stopped, cooled to room temperature, and then the blue solution in the autoclave was placed in an ice-water bath to obtain blue rice-like crystals, which were filtered, washed, and air-dried to obtain the chiral multi-nuclear copper metal-organic framework catalyst.

Example 7

A method for synthesizing a chiral multi-nuclear copper metal-organic framework catalyst specifically comprises the following steps:

CuCl ₂ ·2H ₂ O (2.0 mmol) was dissolved in a mixed solution of 10 mL DMF and 30 mL MeOH, and then added dropwise to a solution of asymmetric chiral ligand H ₃ L (355 mg, 1.0 mmol) in MeOH (30 mL). After heating and stirring at 45° C. for 25 minutes, the blue turbidity was removed by filtration, and the blue clear solution was sealed in a 100 mL autoclave with a polytetrafluoroethylene liner, and the autoclave was heated in a high-temperature constant temperature oven at 90° C. for 2 hours. The heating was stopped, the autoclave was cooled to room temperature, and then the blue solution in the autoclave was placed in an ice water bath to obtain blue rice-like crystals, which were filtered, washed, and air-dried to obtain the chiral multi-nuclear copper metal-organic framework catalyst.

Comparative Example 1

When dimethyl sulfoxide (DMSO) was used instead of DMF in Example 1, and tetrahydrofuran was used instead of methanol in Example 1, while other conditions and operation procedures were kept consistent with Example 1, blue rice-shaped target chiral multi-nuclear copper metal-organic framework catalyst crystals could not be obtained.

Example 8

The asymmetric catalytic oxidation of 5-chloro-1-oxo-2,3-dihydroindene-2-carboxylic acid methyl ester into S-configuration 5-chloro-2,3-dihydro-2-hydroxy-1-oxo-1H-indene-2-carboxylic acid methyl ester was carried out. The route is as follows:

In view of the presence of open hydrophobic chiral nanopores and abundant catalytic active sites in the chiral multi-nuclear copper metal-organic framework catalyst, we examined its ability to asymmetric catalytic oxidation of β-indanone ester 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester. The specific experimental process is as follows: 2.24 grams (10 mmol) of 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester, 25 mL of toluene, and 90 mg of the chiral multi-nuclear copper metal-organic framework catalyst prepared in Example 1 of the present invention were stirred and mixed for 30 minutes, and then 2.28 grams (15 mmol) of isopropylbenzene hydroperoxide (CHP) was added to the above mixed reaction solution, reacted at room temperature for 3 hours, filtered to recover the catalyst, and the filtrate was concentrated and separated by silica gel chromatography to obtain 2.23 grams of white solid, i.e., the target product S-configuration 5-chloro-2,3-dihydro-2-hydroxy-1-oxo-1H-indane-2-carboxylic acid methyl ester (yield 93%, NMR as shown in Figure 5). After high performance liquid chromatography analysis, the high performance liquid chromatography spectrum is shown in Figure 6, and its optical purity is 99.7%. After the chiral multi-nuclear copper metal-organic framework catalyst is filtered and recovered, it is washed with anhydrous acetone and naturally air-dried, and then the reaction can be continued to be catalyzed. The results show that the yield after the fifth catalytic reaction is still as high as 90%, and the optical purity of the product can still be maintained.

Example 9

The difference from Example 8 is that in the specific experimental process, the amount of cumene hydroperoxide is 13 mmol; when the amount of the chiral multi-nuclear copper metal-organic framework catalyst of the present invention is 90 mg, the yield of the target product is reduced to about 85%.

Example 10

The difference from Example 8 is that in the specific experimental process, the amount of isopropylbenzene hydroperoxide is 17 mmol; when the amount of the chiral multi-nuclear copper metal-organic framework catalyst of the present invention is 90 mg, the yield of the target product is maintained at about 93%, without a significant increase.

Comparative Example 2

The difference from Example 8 is that during the specific experiment, when the oxidant is replaced with hydrogen peroxide of the same amount, while other reaction conditions remain unchanged, the catalytic oxidation reaction can hardly obtain the target product with high optical purity.

Comparative Example 3

When the amount of the oxidant CHP and the reaction substrate 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester is adjusted to 1:1, the catalytic reaction yield is significantly reduced. The specific implementation scheme is as follows: 2.24 grams (10 mmol) of 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester, 25 mL of toluene, and 90 mg of the chiral multi-nuclear copper metal-organic framework catalyst of Example 1 of the present invention are stirred and mixed for 30 minutes, and then 1.52 grams (10 mmol) of CHP is added dropwise to the above mixed reaction liquid, reacted at room temperature for 3 hours, filtered to recover the catalyst, and the filtrate is concentrated and separated by silica gel chromatography to obtain 1.80 grams of the target product, with a yield of about 75%.

The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. An asymmetric chiral ligand, characterized in that: its structural formula is as follows: 2. A method for preparing an asymmetric chiral ligand as claimed in claim 1, characterized in that it comprises the following steps: dissolving 3-tert-butyl-5-formyl-4-hydroxybenzoic acid and L-phenylalaninol in methanol, refluxing the mixture, and filtering the mixture while hot after the reaction is completed to obtain the asymmetric chiral ligand. 3. A chiral multinuclear copper metal-organic framework catalyst, characterized in that it is prepared using the asymmetric chiral ligand as claimed in claim 1 as a ligand, and its chemical formula is Cu ₃ L ₂ , wherein the structural formula of L is as follows: The unit cell parameters of the chiral multi-nuclear copper metal-organic framework catalyst are as follows: the space group is P3 ₂ , α＝β＝90°，γ＝120°， Z=3. 4. A method for synthesizing a chiral multi-nuclear copper metal-organic framework catalyst as claimed in claim 3, characterized in that: copper salt is used as the metal salt, the asymmetric chiral ligand is used as the organic bridging ligand, N,N'-dimethylformamide and methanol are used as solvents for coordination reaction, and after the reaction is completed, the reaction product is cooled to room temperature, and then placed in an ice water bath to cool to obtain the chiral multi-nuclear copper metal-organic framework catalyst. 5. The method for synthesizing the chiral multi-nuclear copper metal-organic framework catalyst according to claim 4, characterized in that it comprises the following steps: S1. Mix copper salt, N,N'-dimethylformamide and methanol, and then add dropwise to the methanol solution of the asymmetric chiral ligand, remove the blue turbidity after heating and stirring, and take a blue clear liquid; S2. The blue clear liquid in S1 is sealed in a high-pressure reactor with a polytetrafluoroethylene liner to carry out a solvothermal reaction. After the reaction is completed, the reaction product is cooled to room temperature and then placed in an ice water bath to cool to obtain the chiral multi-nuclear copper metal-organic framework catalyst. 6. The method for synthesizing a chiral multi-nuclear copper metal-organic framework catalyst according to claim 5 is characterized in that: the molar ratio of the asymmetric chiral ligand to the copper salt is 1:1.5-3; the volume ratio of N,N'-dimethylformamide, methanol for dissolving the copper salt, and methanol for dissolving the asymmetric chiral ligand is 1:1-3:1-3; the temperature of the solvent thermal reaction is 90-110°C, and the time is 1-2.5h. 7. The method for synthesizing a chiral multi-nuclear copper metal-organic framework catalyst according to any one of claims 4 _to 6, characterized in that the copper salt is a mixture of one or more of Cu( _OAc ) _2.H2O , Cu( _ClO4 ) _2.6H2O , Cu( _{NO3 ) 2.3H2O} , _{and CuCl2.2H2O} . 8. Use of the chiral multinuclear copper metal-organic framework catalyst as claimed in claim 3 in the asymmetric catalytic oxidation of 5-chloro-1-oxo-2,3-dihydroindene-2-carboxylic acid methyl ester to prepare S-configuration 5-chloro-2,3-dihydro-2-hydroxy-1-oxo-1H-indene-2-carboxylic acid methyl ester. 9. Use of the chiral multinuclear copper metal-organic framework catalyst according to claim 8 in the asymmetric catalytic oxidation of 5-chloro-1-oxo-2,3-dihydroindene-2-carboxylic acid methyl ester to prepare S-configuration 5-chloro-2,3-dihydro-2-hydroxy-1-oxo-1H-indene-2-carboxylic acid methyl ester, characterized in that: the oxidant used is cumene hydroperoxide; the solvent used is toluene; and the reaction temperature is room temperature. 10. Use of the chiral multinuclear copper metal-organic framework catalyst according to claim 8 or 9 in the asymmetric catalytic oxidation of 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester to prepare S-configuration 5-chloro-2,3-dihydro-2-hydroxy-1-oxo-1H-indane-2-carboxylic acid methyl ester, characterized in that the molar ratio of the oxidant used to the reaction substrate 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester is 1.3-1.7:1; and the mass ratio of the chiral multinuclear copper metal-organic framework catalyst to the reaction substrate 5-chloro-1-oxo-2,3-dihydroindane-2-carboxylic acid methyl ester is 1:25.