Spiro Salen ligand, preparation method and application

Abstract

The invention belongs to the technical field of catalysts, relates to spiro Salen ligands as well as a preparation method and application thereof, and particularly relates to application of the spiro Salen ligands to preparation of degradable polyhydroxyalkanoate by catalyzing ring-opening polymerization of beta-butyrolactone. According to the invention, spiro-o-hydroxyaldehyde and dialdehyde are designed and synthesized and are applied to preparation of spiro-Salen ligands, so that the variety of the Salen ligands is enriched, and the derivation application range of spiro-compounds is widened. The invention also relates to ring opening polymerization participated by the ligand. By adopting a catalytic system formed by the Salen ligand and a yttrium metal precursor, the high-activity and high-selectivity poly-3-hydroxybutyrate with a regular stereostructure can be obtained. The method has the advantages that the catalyst is low in dosage and high in activity, the poly-3-hydroxybutyrate product has high syndiotactic degree, the defect that only isotactic products can be obtained by a biological method can be effectively overcome, and the method has industrial application value.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and specifically relates to a preparation method of a class of Salen ligands containing spirocyclic hydroxyaldehydes and their application in the stereoselective ring-opening polymerization of β-butyrolactone to prepare highly syndiotactic poly-3-hydroxybutyrate. Background Art

[0002] Salen-type ligands are a class of [O,N,N,O] tetradentate bis-Schiff base ligands and are widely used in asymmetric catalysis from small molecule reactions to polymerization reactions. In the past few decades, significant breakthroughs have been made in the field of stereoselective ring-opening polymerization of Salen complex catalytic systems. For example, the stereoselective ring-opening polymerization of epoxides to produce polyethers, polyesters, polycarbonates, polyurethanes, etc. Scientific researchers at home and abroad have designed and optimized the structures of a variety of chiral Salen ligands in order to maximize their stereoselective induction in asymmetric catalytic reactions.

[0003] Spirocyclic skeleton chiral ligands exhibit excellent catalytic activity and excellent enantioselectivity in a variety of asymmetric catalytic reactions, making many asymmetric catalytic reactions that were previously difficult to achieve high enantioselectivity possible. However, currently, the spirocyclic structure with chiral superiority is only developed in the form of a diamine skeleton in Salen ligands, and has not been applied to the construction of the hydroxyaldehyde part in Salen ligands, nor has there been any application report on Salen-type ligands characterized by a spirocyclic hydroxyaldehyde structure in organic asymmetric catalytic reactions or polymerization reactions.

[0004] Plastic waste pollution has become a global environmental problem. A large amount of plastic waste is discarded, landfilled or incinerated at will, posing a serious threat to the ecosystem. Traditional plastics are difficult to degrade, and harmful substances will be released during the process, polluting the soil and water sources. Even if they are degraded, microplastics in the food chain may eventually enter the human body and endanger health. Solving the problem of plastic pollution is extremely urgent. In recent years, scientific researchers at home and abroad have focused on the research and development of biodegradable plastics and developed a series of new plastic products that are environmentally friendly and have excellent material properties.

[0005] P3HB (poly-3-hydroxybutyrate), as a polymer produced by natural microbial fermentation, has biodegradability and excellent material properties, and is considered a powerful alternative to traditional petroleum-based PP (polypropylene) materials. The properties of poly-3-hydroxybutyrate are closely related to its stereoregularity. Poly-3-hydroxybutyrate produced by natural biological fermentation is an isotactic polymer, and the isotacticity (P m)Greater than 0.99. However, the production scale of the biological preparation method is small, and the production cost is high. In recent years, scientists have used inexpensive racemic quaternary cyclic monomer β-butyrolactone as a raw material and used metal complexes for selective polymerization to prepare polymers with high regularity, which is an effective solution for chemically synthesizing isotactic poly-3-hydroxybutyrate and is expected to replace the biological fermentation method. Although a large number of chemical methods have achieved the preparation of P3HB with high isotacticity, the development of chemical preparation methods for high syndiotacticity (P r >0.9) is still limited. Summary of the Invention

[0006] The present invention aims to design and synthesize a class of spiro-hydroxyaldehydes and Salen-type ligands constructed with spiro-hydroxyaldehydes as the feature, and develop an in-situ catalytic system containing this class of ligands. By applying this catalytic system, the selective ring-opening polymerization of racemic β-butyrolactone is realized to prepare poly-3-hydroxybutyrate with different syndiotactic regularities. This application case can achieve the preparation of syndiotactic poly-3-hydroxybutyrate with a syndiotacticity Pr of up to 0.95, indicating that this class of ligands has certain potential in the field of catalytic selective ring-opening polymerization.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A class of spiro-Salen ligands, the spiro-Salen ligands include symmetric mononuclear spiro-Salen ligands and asymmetric mononuclear spiro-Salen ligands, and contain one or two spiro-o-hydroxyaldehyde compounds connected by Schiff base bonds with diamines; the structural general formulas of the symmetric mononuclear spiro-Salen ligands and the asymmetric mononuclear spiro-Salen ligands are shown as follows:

[0009]

[0010] Among them, R 1 、R 2 、R 3 、R 4 and R 5 are independently hydrogen, alkyl, cycloalkyl, alkoxy, aryl, halogen, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, substituted heteroaryl, and R 1 is not hydrogen; R 6 is phenyl, racemic or chiral cyclohexyl group, binaphthyl group, tetrahydrobinaphthyl group or spiro group.

[0011] Further, the R 1 、R 2 、R 3 、R 4 and R 5 are independently hydrogen, C1-C 10 alkyl, C3-C5 cycloalkyl, C1-C 10Alkoxy, C6-C 14 Aryl, halogen, 5- to 6-membered heteroaryl, substituted C1-C 10 Alkyl, substituted C1-C 10 Alkoxy, substituted by one or more R 1a Substituted C6-C 14 Aryl, substituted by one or more R 1a Substituted 5- to 6-membered heteroaryl; R 1a Is C1-C 10 Alkyl, C1-C 10 Alkoxy or halogen; R 7 And R 8 Independently are hydrogen, C1-C 10 Alkyl, C3-C5 cycloalkyl, C1-C 10 Alkoxy, C6-C 14 Aryl or halogen; Indicates the connection position; each R 6 Independently is a racemate, a meso form, an enantiomerically pure S configuration or an enantiomerically pure R configuration.

[0012] Furthermore, the R 1 , R 2 , R 3 , R 4 And R 5 Independently are hydrogen, fluorine, chlorine, bromine, iodine, methyl, ethyl, tert-butyl, isopropyl, cyclopropyl, cyclobutyl, cyclohexyl, furyl, pyridyl, biphenyl, 2-phenylbiphenyl, trityl, cumyl, benzyl, adamantyl, C1-C3 perfluoroalkoxy, C1-C3 perfluoroalkyl, arylmethylene, heteroarylmethylene, arylmethylidene or heteroarylmethylidene.

[0013] Furthermore, the symmetric mononuclear spirocyclic Salen ligand is characterized in that it is condensed from two molecules of the same spirocyclic o-hydroxyaldehyde group substituted with axially chiral R 1 And one molecule of a diamine compound, has two Schiff base bonds with the same chemical environment, and has two phenolate oxygen and two imine nitrogen coordination sites, presenting a tetradentate coordination cavity; the asymmetric mononuclear spirocyclic Salen ligand is characterized in that it is condensed from one molecule of a spirocyclic o-hydroxyaldehyde group substituted with axially chiral R 1 And one molecule of a salicylaldehyde derivative group with one of the amino groups in one molecule of a diamine compound respectively; has two Schiff base bonds with different chemical environments, has two phenolate oxygen and two imine nitrogen coordination sites, presenting a tetradentate coordination cavity.

[0014] A preparation method of a class of spirocyclic Salen ligands, a preparation method of a symmetric mononuclear spirocyclic Salen ligand: The one composed of R1 The substituted spiro ortho-hydroxy aldehyde and the diamine compound are subjected to an aldehyde-amine condensation reaction in a solvent under high temperature conditions, and after separation and purification, a symmetric mononuclear spiro Salen ligand is prepared; Preparation method of an asymmetric mononuclear spiro Salen ligand: First, the salicylaldehyde compound and the monohydrochloride of the diamine compound are reacted in a polar solvent at room temperature to carry out the first-step aldehyde-amine condensation reaction, and then R 1 substituted spiro ortho-hydroxy aldehyde and a basic auxiliary agent are added, and a non-polar solvent is added to assist dissolution, and the aldehyde-amine condensation reaction is further carried out at high temperature; The reaction product is separated and purified to obtain an asymmetric mononuclear spiro Salen ligand;

[0015] In the preparation process of the symmetric mononuclear spiro Salen ligand: The diamine compound is (NH2)2R 6 ; The temperature of the aldehyde-amine condensation reaction is 90-110 °C, and the time is 12-48 h; The molar ratio of the R 1 substituted spiro ortho-hydroxy aldehyde to the diamine compound is 2-2.5:1; The solvent is toluene, xylene or DMF;

[0016] In the preparation process of the asymmetric mononuclear spiro Salen ligand: The monohydrochloride of the diamine compound is (NH2)2R 6 ·HCl; The time for the first-step aldehyde-amine condensation reaction at room temperature is 0.5-1 h; The polar solvent is methanol, ethanol or isopropanol; The basic auxiliary agent is triethylamine, pyridine or diisopropylethylamine; The non-polar solvent is toluene, xylene or DMF; The temperature for further carrying out the aldehyde-amine condensation reaction at high temperature is 90-110 °C; The time is 12-48 h; The molar ratio of the salicylaldehyde compound to the monohydrochloride of the diamine (NH2)2R 6 ·HCl is 0.8-1.5:1; The molar ratio of the R 1 substituted spiro ortho-hydroxy aldehyde to the salicylaldehyde compound is 1-1.5:1; The molar ratio of the basic auxiliary agent to the salicylaldehyde compound is 1-2:1;

[0017] Among them, the structural general formulas of the R 1 substituted spiro ortho-hydroxy aldehyde and the salicylaldehyde compound are shown as follows:

[0018]

[0019] The R 1 substituted spiro ortho-hydroxy aldehyde has a 2,2’,3,3’-tetrahydro-1,1’-spirobi[1H-indene] as the basic skeleton, the 6th position is an aldehyde group, the 7th position is a phenolic hydroxyl group, and the 7’ position is R 1 substituent;

[0020] The diamine compound with a chiral structure, the monohydrochloride of the diamine compound and the R1 The substituted spiro ortho-hydroxy aldehyde is independently a racemate, a meso form, an enantiomerically pure S configuration, or an enantiomerically pure R configuration.

[0021] Furthermore, the 1 preparation method of the substituted spiro ortho-hydroxy aldehyde uses 2,2’,3,3’-tetrahydro-1,1’-spirobi[1H-indene]-7,7’-diol as the raw material, hereinafter simply referred to as spirobiphenol. After modification by the substituent R 1 , protection of the phenolic hydroxyl group, formylation to introduce an aldehyde group, and deprotection of the phenolic hydroxyl group, it is obtained; among them, the spirobiphenol is a racemate or an optically pure isomer, specifically (R)-spirobiphenol or (S)-spirobiphenol; the specific steps of the substituted spiro ortho-hydroxy aldehyde by R 1 are as follows:

[0022] Step (1), modification of the substituent R 1

[0023] (A) When R 1 is an alkoxy group or a substituted alkoxy group, R 1 is represented by OR

[0024] Using spirobiphenol as the raw material, KCO3 is added to create an alkaline environment, and in a polar aprotic solvent, an O-alkylation reaction is carried out on one phenolic hydroxyl group in spirobiphenol using an alkyl halide;

[0025] The reaction conditions are: stirring at room temperature for 8 - 24 h;

[0026] The alkyl halide is RX: where R is methyl, ethyl, tert-butyl or isopropyl; X is chlorine, bromine or iodine;

[0027] The polar aprotic solvent is acetonitrile, acetone, DMF or toluene;

[0028] The molar ratio of spirobiphenol to KCO3 to the alkyl halide is 1:1 - 2:1 - 1.5;

[0029] (B) When R 1 is a halogen, R 1 is chlorine or bromine

[0030] Using spirobiphenol as the raw material, KCO3 is added to create an alkaline environment, and in a polar aprotic solvent, a halogen displacement reaction is carried out on one phenolic hydroxyl group in spirobiphenol using a halogenating reagent;

[0031] The reaction conditions are: reacting at 20 - 120 °C for 0.5 - 3 h;

[0032] The halogenating reagent is phosphorus pentachloride, phosphorus oxychloride, phosphorus oxybromide or triphenylphosphonium dibromide;

[0033] The polar aprotic solvent is DMF, toluene or THF;

[0034] The molar ratio of the spirobiphenol to the halogenating reagent is 1:1 to 1.2;

[0035] (C)R 1 When it is an alkyl group, cycloalkyl group, aryl group, heteroaryl group, substituted alkyl group, substituted aryl group or substituted heteroaryl group

[0036]

[0037] Step (C-1): First, replace one phenolic hydroxyl group of the spirobiphenol with a leaving group LG using compound H, where LG is a halogen, alkoxy group, sulfonic acid group, p-toluenesulfonyloxy group or acyloxy group;

[0038] When LG is an alkoxy group or a halogen, the preparation method is the same as (A) or (B) respectively;

[0039] When LG is a sulfonic acid group, p-toluenesulfonyloxy group or acyloxy group, the preparation method is as follows: Using 1 molar equivalent of spirobiphenol as the starting material, dissolve it in a non-polar solvent, and at 0-5 °C in an ice bath, sequentially add 1-1.2 molar equivalents of an acid-binding agent and 1-1.2 molar equivalents of compound H, then remove the ice bath and stir at room temperature for 8-12 h; then separate and purify to obtain an intermediate product containing LG substitution; Compound H is chlorosulfonic acid, p-toluenesulfonyl chloride or trifluoromethanesulfonic anhydride; the acid-binding agent is triethylamine, pyridine, potassium carbonate or N,N-diisopropylethylamine; the non-polar solvent is dichloromethane, diethyl ether or tetrahydrofuran;

[0040] Step (C-2): Dissolve 1 molar equivalent of the intermediate product containing LG substitution and 0.1-0.2 molar equivalent of the catalyst 1,3-bis(diphenylphosphinopropane)nickel dichloride (represented by NiCl2(dppe)2 in the formula) in diethyl ether or tetrahydrofuran; slowly add 2-4 molar equivalents of R 1 magnesium bromide Grignard reagent dropwise at 0-5 °C; after the dropwise addition is complete, remove the ice bath and stir at room temperature for 12-24 h; then extract and separate, and purify by column chromatography to obtain;

[0041] Step (two) Protection of phenolic hydroxyl group, formylation reaction to introduce aldehyde and deprotection of phenolic hydroxyl group

[0042]

[0043] Step (2.1): The specific steps for the protection of the phenolic hydroxyl group are as follows: At 0-5 °C, add 1 molar equivalent of R prepared in step (one) 1The substituted spiro-monophenol after substitution is dissolved in an ether solvent, and then a solution of an ether solvent containing 1 to 1.5 molar equivalents of a deprotonating agent is added dropwise; after the addition, the ice bath is removed and stirred at room temperature for 5 to 8 h; then, under the ice bath, 1 to 1.2 equivalents of a protecting agent is added dropwise; after the addition is completed, the ice bath is removed and stirred at room temperature for 8 to 12 h; then quenched with water and purified by extraction and column chromatography;

[0044] The ether solvent is diethyl ether, tetrahydrofuran or 1,4-dioxane;

[0045] The deprotonating agent is NaH, CaH, NaOH or KOH;

[0046] The protecting agent is bromomethyl methyl ether or chloromethyl methyl ether;

[0047] In step (2.2), the specific steps of the formylation reaction are as follows: 1 molar equivalent of the product of step (2.1) is dissolved in an ether solvent, 1 to 1.5 molar equivalents of TMEDA is added dropwise and stirred; at -90 to -78 °C, 1 to 1.5 molar equivalents of an organolithium reagent is added dropwise, after stirring for 8 to 12 h, 1 to 3 molar equivalents of a formylating agent is added dropwise, and after the addition is completed, stirred at room temperature for 8 to 12 h; purified by extraction and column chromatography;

[0048] The ether solvent is diethyl ether, tetrahydrofuran, 1,4-dioxane;

[0049] The organolithium reagent is n-butyllithium or tert-butyllithium;

[0050] The formylating agent is formic acid, formyl cyanide methyl ester or N,N-dimethylformamide;

[0051] In step (2.3), the specific steps of the deprotection of the phenolic hydroxyl group are as follows: 1 molar equivalent of the product of step (2.2) is dissolved in a polar solution, and 1 to 2 molar equivalents of concentrated hydrochloric acid is added, and stirred for 8 to 12 h; then the pH is adjusted to 6 to 7, dissolved in water, the oil phase is extracted and recrystallized to obtain;

[0052] The polar solvent is methanol, ethanol or isopropanol.

[0053] Application of a kind of spiro-Salen ligand, constructing a polymerization reaction catalytic system, including a spiro-Salen ligand, a metal precursor MX n and an initiator.

[0054] Further, the metal precursor MX nIn this, M is Zn, Co, Cr, Cu, Fe, Pd, Ni, Mn, Y, La, Ln, Sc, Yb, AI, Ru or Ti; n is 1, 2 or 3; each independent X is a furyl group, -N(SiHMe2)2, -N(SiMe3)2, an alkyl group, an alkoxy group, an aryl group, a phenol group or a halogen; the initiator is an alkyl alcohol, an alkyl mercaptan, a benzyl alcohol or a benzyl mercaptan.

[0055] Furthermore, the polymerization reaction catalytic system is applied in the selective ring-opening polymerization of racemic β-butyrolactone to prepare poly-3-hydroxybutyrate with different regularities, including the following steps: adding racemic β-butyrolactone, a spirocyclic Salen ligand, a metal precursor MX n , an initiator and a solvent into a reaction device, reacting at 20 - 45 °C for 5 s - 2 h, and the molar ratio of racemic β-butyrolactone, the spirocyclic Salen ligand, the metal precursor MX n and the initiator is 100 - 10000:1 - 5:1 - 5:1 - 5; the reaction structural formula is as shown below

[0056]

[0057] Furthermore, the solvent is dichloromethane, dimethyl sulfoxide, tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylformamide or toluene; the highest syndiotactic polymer P of the obtained poly-3-hydroxybutyrate r = 0.95.

[0058] The beneficial effects of the present invention: The present invention innovatively develops the spirocyclic structure into a hydroxyaldehyde group and applies it to the construction of the Salen ligand, enriching the types of Salen ligands and their catalytic systems; combines yttrium metal as the catalytic metal center to construct a catalytic system, giving full play to the rich production advantage of rare earth metals in our country and enriching the types of rare earth organometallic catalysts; provides an application case of selectively ring-opening polymerizing racemic β-butyrolactone to prepare highly syndiotactic poly-3-hydroxybutyrate, providing a new scheme for the preparation of polyester materials by chemical catalysis and broadening the application scope of Salen ligands and their catalytic systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is the 1 1H NMR chart of Compound 1 in Example 1.

[0060] Figure 2 It is the 1 1H NMR chart of Compound 2 in Example 1.

[0061] Figure 3 It is the 1 1H NMR chart of Compound 3 in Example 1.

[0062] Figure 41H NMR spectrum of Compound 4 in Example 1 1 1H NMR spectrum

[0063] Figure 5 1H NMR spectrum of (S)-phenylspirobenzaldehyde in Example 1 1 1H NMR spectrum

[0064] Figure 6 1H NMR spectrum of (S,S,S,S)-L1 in Example 4 1 1H NMR spectrum

[0065] Figure 7 1H NMR spectrum of (S,S,S)-L2 in Example 4 1 1H NMR spectrum

[0066] Figure 8 1H NMR spectrum of (S,R,S)-L2 in Example 4 1 1H NMR spectrum

[0067] Figure 9 1H NMR spectrum of (S,S)-L3 in Example 7 1 1H NMR spectrum

[0068] Figure 10 1H NMR spectrum of (R,S)-L3 in Example 7 1 1H NMR spectrum

[0069] Figure 11 1H NMR spectrum of poly-3-hydroxybutyrate with high syndiotacticity (0.95) in Example 9 1 1H NMR spectrum

[0070] Figure 12 13C NMR spectrum of poly-3-hydroxybutyrate with high syndiotacticity (0.95) in Example 9 13 13C NMR spectrum Detailed Description of the Invention

[0071] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the embodiments. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following detailed description of the provided embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0072] Example 1

[0073] This example provides a preparation method of (S)-2,2’,3,3’-tetrahydro-7-hydroxy-7’-phenyl-1,1’-spirobi[1H-indene]-6-carbaldehyde (hereinafter abbreviated as “(S)-phenylspirophthalaldehyde”), and the specific synthesis route is shown as follows:

[0074]

[0075] Wherein: a represents: dichloromethane, trifluoromethanesulfonic anhydride, N,N-diisopropylethylamine; b represents: ether, phenylmagnesium bromide, 1,3-bis(diphenylphosphinopropane)nickel dichloride; c represents: purified tetrahydrofuran, sodium hydride, bromomethyl methyl ether, 0 °C; d represents: purified ether, N,N,N’,N’-tetramethylethylenediamine, n-butyllithium, N,N-dimethylformamide, -78 °C; e represents: methanol, concentrated hydrochloric acid, room temperature.

[0076] The specific steps in the above synthesis route are as follows:

[0077] Step a: Under nitrogen protection, using (S)-spirobiphenol (6.00 g, 23.8 mmol) as the starting material, dissolve it in 100 ml of purified dichloromethane. Under the condition of an ice bath at 0 °C, sequentially add N,N-diisopropylethylamine (3.38 g, 26.1 mmol) and trifluoromethanesulfonic anhydride (7.38 g, 26.1 mmol), then remove the ice bath and stir at room temperature for 8 h. Add 4M hydrochloric acid solution to quench the N,N-diisopropylethylamine auxiliary agent, adjust the pH value to slightly acidic with sodium bicarbonate, extract with dichloromethane, add anhydrous sodium sulfate to dry the obtained oil phase, and filter. The filtrate is purified by silica gel column chromatography, and the mobile phase is petroleum ether:dichloromethane = 3:2. Concentrate and spin-dry the product solution to obtain a transparent oily compound 1 (6.65 g, yield 73%).

[0078] Step b: Under nitrogen protection, dissolve compound 1 (6.65 g, 17.3 mmol) and the catalyst 1,3-bis(diphenylphosphinopropane)nickel dichloride (1.37 g, 2.6 mmol) in 100 ml of ether. Slowly add a solution of phenylmagnesium bromide in ether (3M in ether, 17.3 ml, 51.9 mmol) dropwise at zero degree. After the addition is completed, remove the ice bath and stir at room temperature for 24 h. Quench the reaction solution with sodium bicarbonate and extract with ethyl acetate. Add anhydrous sodium sulfate to dry the extracted oil phase and filter. The filtrate is purified by silica gel column chromatography, and the mobile phase is petroleum ether:ethyl acetate = 10:1. Spin-dry the product solution to obtain compound 2 (5.00 g, yield 92%).

[0079] Step c: Under nitrogen protection and at 0 °C in an ice bath, in a 500 ml three-necked flask, dissolve compound 2 (5.00 g, 16.0 mmol) in 25 ml of purified tetrahydrofuran. Then add sodium hydride (60% dispersion in mineral oil, 0.90 g, 22.4 mmol) to 100 ml of tetrahydrofuran, and gradually add it dropwise to the three-necked flask through a constant-pressure dropping funnel. During the dropping process, fine bubbles are generated in the reaction solution. After the dropping is complete, remove the ice bath and stir at room temperature for 5 h. Then, in an ice bath, add bromomethyl methyl ether (2.27 g, 17.6 mmol) dropwise. The reaction solution changes from a gray suspension to a milky white emulsion. After the dropping is complete, remove the ice bath and stir at room temperature for 12 h. Then quench with water to obtain a light yellow clear solution. After evaporating the THF, extract with ethyl acetate, and dry the organic phase with anhydrous sodium sulfate. Purify by silica gel column chromatography with the mobile phase of petroleum ether: ethyl acetate = 10:1. Concentrate the product solution and evaporate to dryness. Obtain a light yellow oily compound 3 (5.70 g, yield 99%).

[0080] Step d: Under nitrogen protection, dissolve compound 3 (5.70 g, 16.0 mmol) in 100 ml of purified ether, add TMEDA (2.23 g, 19.2 mmol) dropwise and stir for 5 min. At -78 °C, add n-butyllithium (2.5 M in hexane, 7.67 ml, 19.2 mmol) dropwise. The reaction solution changes from light yellow to an orange-yellow clear solution. Keep stirring at low temperature for 12 h. Then, at -78 °C, add purified DMF (3.51 g, 48.0 mmol) dropwise. After the dropping is complete, stir at room temperature for 8 h. Quench the reaction solution with water and extract with ethyl acetate. Dry the extracted organic phase with anhydrous sodium sulfate. Purify by silica gel column chromatography with the mobile phase of petroleum ether: ethyl acetate = 10:1. Concentrate the product solution and evaporate to dryness to obtain white crystal compound 4 (4.12 g, yield 67%).

[0081] Step e: Dissolve the obtained compound 4 (4.12 g, 11.0 mmol) in 5 ml of methanol solution, add 1.5 ml of concentrated hydrochloric acid, and stir for 8 h. Then adjust the pH to 7; evaporate the methanol and dissolve in water, extract with dichloromethane. Add anhydrous sodium sulfate to dry the obtained organic phase, filter, and then evaporate the filtrate to dryness and recrystallize in methanol to obtain the light yellow powdery target product (3.63 g, yield 99%)

[0082] The NMR and mass spectrometry characterizations of the intermediate products and the target product involved in this example are as follows:

[0083] Compound 1: 11H NMR (400 MHz, CDCl3) δ 7.25 - 7.18 (m, 2H), 7.13 - 7.07 (m, 1H), 7.04 (t, J = 7.7 Hz, 1H), 6.82 (d, J = 7.4 Hz, 1H), 6.43 (d, J = 7.9 Hz, 1H), 4.44 (s, 1H), 3.12 - 2.92 (m, 4H), 2.35 - 2.17 (m, 4H). 13 13C NMR (101 MHz, CDCl3) δ 152.15, 148.13, 146.28, 145.71, 139.87, 132.24, 129.15, 128.96, 124.71, 118.62, 118.61, 117.34, 113.88, 59.07, 38.31, 38.30, 31.38, 31.17. HRMS (ESI, m / z): [M - H] - (C 18 H 14 F3O4S - ) was measured to be 383.0571 (theoretical value 383.0570). [2M - H] - (C 36 H 29 F6O8S2 - ) was measured to be 767.1212 (theoretical value 767.1213).

[0084] Compound 2: 1 1H NMR (500 MHz, CDCl3) δ 7.32 (dt, J = 14.8, 7.4 Hz, 2H), 7.09 - 6.96 (m, 6H), 6.88 (t, J = 7.7 Hz, 1H), 6.55 (d, J = 7.4 Hz, 1H), 6.37 (d, J = 8.0 Hz, 1H), 4.30 (s, 1H), 3.18 - 3.04 (m, 2H), 2.88 (dt, J = 15.8, 9.1 Hz, 1H), 2.61 (ddd, J = 16.1, 8.9, 2.9 Hz, 1H), 2.35 - 2.19 (m, 4H). 13 13C NMR (126 MHz, CDCl3) δ 151.98, 144.73, 144.72, 144.06, 140.50, 139.77, 134.05, 129.74, 128.87, 128.35, 127.73, 126.91, 126.49, 124.40, 116.65, 113.59, 59.91, 40.11, 39.25, 30.94, 30.78. HRMS (ESI, m / z): [M - H] - (C 23H 19 O - ) with a measured value of 311.1442 (theoretical value 311.1441). [2M-H] - (C 46 H 39 O - ) with a measured value of 623.2951 (theoretical value 623.2955).

[0085] Compound 3: 1 H NMR (500 MHz, CDCl3) δ 7.25 (d, J = 7.5 Hz, 1H), 7.17 (t, J = 7.4 Hz, 1H), 7.07 - 7.00 (m, 1H), 7.00 - 6.91 (m, 4H), 6.82 - 6.76 (m, 2H), 6.60 (dd, J = 17.9, 7.8 Hz, 2H), 4.90 (d, J = 6.5 Hz, 1H), 4.82 (d, J = 6.5 Hz, 1H), 3.20 - 3.02 (m, 5H), 2.82 - 2.68 (m, 1H), 2.57 (ddd, J = 12.6, 8.9, 7.5 Hz, 1H), 2.38 - 2.11 (m, 4H). 13 C NMR (126 MHz, CDCl3) δ 152.18, 146.04, 144.69, 143.32, 139.87, 138.45, 136.77, 127.90, 127.74, 126.90, 125.76, 125.05, 124.96, 122.19, 116.58, 109.55, 92.00, 59.74, 54.44, 40.18, 39.41, 30.43, 29.82. HRMS (ESI, m / z): [M+Na] + (C 25 H 24 NaO2 + ) with a measured value of 379.1655 (theoretical value 379.1669). [M+NH4] + ,(C 25 H 28 NO2 + ) with a measured value of 374.2114 (theoretical value 374.2115).

[0086] Compound 4: 11H NMR (400 MHz, CDCl3) δ 9.99 (s, 1H), 7.53 (d, J = 7.8 Hz, 1H), 7.28 - 7.16 (m, 2H), 7.04 - 6.93 (m, 4H), 6.83 - 6.73 (m, 3H), 4.43 - 4.29 (m, 2H), 3.25 - 3.03 (m, 5H), 2.80 - 2.68 (m, 1H), 2.60 - 2.48 (m, 1H), 2.41 - 2.28 (m, 1H), 2.25 - 2.12 (m, 3H). 3.18 - 3.04 (m, 2H) 13 13C NMR (101 MHz, CDCl3) δ 190.56, 157.17, 153.67, 146.38, 144.33, 143.58, 140.77, 139.81, 129.35, 129.16, 129.05, 128.37, 127.11, 126.90, 126.47, 123.75, 120.81, 100.66, 60.60, 56.98, 42.10, 40.74, 31.55, 31.33. HRMS (ESI, m / z): [M + Na] + (C 26 H 24 NaO3 + ), found 407.1622 (calcd 407.1617). [2M + Na] + ,(C 52 H 48 NaO6 + ), found 791.3346 (calcd 791.3342).

[0087] (S)-Phenylspirobenzofuran-2(3H)-one: 1 1H NMR (400 MHz, CDCl3) δ 10.98 (s, 1H), 9.65 (s, 1H), 7.33 - 7.20 (m, 2H), 7.11 (d, J = 7.8 Hz, 1H), 7.00 - 6.88 (m, 6H), 6.61 - 6.54 (m, 1H), 3.15 - 3.07 (m, 2H), 2.91 - 2.79 (m, 1H), 2.60 - 2.49 (m, 2H), 2.38 - 2.31 (m, 2H), 2.13 - 2.05 (m, 1H). 1313C NMR (101 MHz, CDCl3) δ 194.71, 157.06, 153.79, 144.82, 142.71, 139.72, 138.21, 134.53, 132.16, 127.75, 127.64, 125.67, 125.63, 125.12, 122.69, 118.37, 115.01, 58.86, 38.63, 38.40, 30.60, 29.92. HRMS (ESI, m / z): [M-H] - (C 24 H 19 O2 - ), found 339.1390 (calcd 339.1390).

[0088] Example 2

[0089] This example provides a preparation method of (R)-2,2',3,3'-tetrahydro-7-hydroxy-7'-methoxy-1,1'-spirobi[1H-indene]-6-carbaldehyde (hereinafter referred to as "(R)-benzyloxy-substituted spiro ortho-hydroxy aldehyde" for short). The specific synthesis method is as follows: Potassium carbonate (5.60 g, 40 mmol) and methyl iodide (4.26 g, 30 mmol) were added to a DMF (100 ml) solution of (R)-spirobiphenol (5.05 g, 20 mmol). After stirring at room temperature for 20 hours, about 200 ml of 0.5 mol / L aqueous sodium hydroxide solution was added to the reaction solution to adjust the pH to 7. Then the reaction mixture was extracted with diethyl ether and washed with brine and dried. The solvent was removed under reduced pressure, and purification was carried out by silica gel column chromatography using petroleum ether / ethyl acetate (10 / 1) as the mobile phase to obtain the methoxy-substituted intermediate. Then the aldehyde addition operation was carried out. The experimental steps and conditions were the same as those in steps b, c, d, and e of Example 1.

[0090] (R)-Benzyloxy-substituted spiro ortho-hydroxy aldehyde: 1 1H NMR (500 MHz, CDCl3) δ 10.94 (s, 1H), 9.78 (s, 1H), 7.70 (d, J = 7.8 Hz, 1H), 7.18 - 7.10 (m, 2H), 6.92 (t, J = 7.4 Hz, 1H), 6.81 (d, J = 8.1 Hz, 1H), 3.20 - 3.02 (m, 7H), 2.60 - 2.49 (m, 2H), 2.31 - 2.21 (m, 2H). 1313C NMR (101 MHz, CDCl3) δ 193.21, 160.49, 156.95, 149.43, 144.79, 135.78, 134.80, 131.06, 127.99, 122.02, 120.12, 117.70, 110.73, 55.95, 55.52, 36.81, 36.74, 30.88, 30.64. HRMS (ESI, m / z): [M-H] - (C 19 H 17 O3 - ), found 293.1170 (calcd 293.1183).

[0091] Example 3

[0092] This example provides a preparation method of (R)-2,2’,3,3’-tetrahydro-7-hydroxy-7’-chloro-1,1’-spirobi[1H-indene]-6-carbaldehyde (hereinafter referred to as “(R)-chlorospirophthalide” for short), and the specific synthesis method is as follows:

[0093] Phosphorus pentachloride (4.16 g, 20 mmol) was added to a solution of (R)-spirobiphenol (5.00 g, 20 mmol) in dichloromethane (100 ml). The reaction was carried out at 45 °C for 3 h; then about 200 ml of 0.5 mol / L aqueous sodium hydroxide solution was added to the reaction solution to adjust the pH to 7, and then the reaction mixture was extracted with dichloromethane, washed with brine and dried. The solvent was removed under reduced pressure, and purification was carried out by silica gel column chromatography with petroleum ether / ethyl acetate (20 / 1) as the mobile phase to obtain the intermediate product. Then the aldehyde addition operation was carried out, and the experimental steps were the same as those in steps b, c, d and e of Example 1.

[0094] (R)-Chlorospirophthalide: 1 1H NMR (500 MHz, CDCl3) δ 10.94 (s, 1H), 9.60 (s, 1H), 7.27 (d, J = 7.5 Hz, 1H), 6.94 (dd, J = 6.4, 2.0 Hz, 1H), 6.87–6.79 (m, 2H), 6.74 (dt, J = 7.6, 1.0 Hz, 1H), 3.01 - 2.80 (m, 1H), 2.60 - 2.49 (m, 2H), 2.35 - 2.05 (m, 5H). 1313C NMR (101 MHz, CDCl3) δ 193.21, 160.58, 149.30, 145.72, 143.04, 134.50, 131.63, 131.06, 129.55, 127.97, 122.75, 122.02, 119.97, 55.23, 36.86, 36.80, 30.65, 30.49 . . HRMS (ESI, m / z): [M + H] + (C 18 H 16 ClO2 + ), found 299.1050 (calcd 299.0833).

[0095] Example 4

[0096] In this example, (S,S)-cyclohexanediamine and the (S)-phenylspirocyclic salicylaldehyde obtained in Example 1 were used as starting materials. The reaction formula of the corresponding symmetric Salen ligand is as follows:

[0097]

[0098] The specific synthesis steps were as follows: Activated molecular sieve (50 mg / mmol) was added to a 50 ml toluene solution containing (S,S)-cyclohexanediamine (0.084 g, 0.7 mmol) and the (S)-phenylspirocyclic salicylaldehyde (0.50 g, 1.5 mmol) obtained in Example 1. Then the mixture was heated to 110 °C and reacted for 48 h. After the reaction was completed, the temperature was cooled to room temperature, and the reaction solution was filtered to remove the molecular sieve. The filtrate was concentrated by rotary evaporation and separated by column chromatography (silica gel column, mobile phase: petroleum ether / ethyl acetate = 20 / 1), and recrystallized from methanol. After drying, the target product was obtained as a yellow solid (4.01 g, 72%).

[0099] (S,S,S,S)-L1 yield 72%: 11H NMR (400 MHz, CDCl3) δ 13.37 (s, 2H), 8.14 (s, 2H), 7.35 - 7.27 (d, J = 7.4 Hz, 4H), 6.99 (d, J = 7.3 Hz, 2H), 6.93 - 6.82 (m, 6H), 6.78 (t, J = 7.6 Hz, 6H), 6.32 (d, J = 7.7 Hz, 2H), 3.28 - 3.13 (m, 4H), 3.11 - 3.00 (m, 2H), 2.73 - 2.53 (m, 4H), 2.29 - 2.15 (m, 6H), 2.10 - 2.03 (m, 2H), 1.89 - 1.75 (m, 4H), 1.60 (d, J = 12.6 Hz, 2H), 1.34 (t, J = 10.7 Hz, 2H). 13 13C NMR (126 MHz, CDCl3) δ 163.55, 156.72, 148.11, 145.52, 143.10, 139.80, 138.77, 135.00, 129.92, 127.75, 127.58, 125.87, 125.31, 125.09, 122.60, 115.82, 113.59, 70.81, 59.23, 39.05, 38.73, 32.28, 30.16, 30.14, 23.18. HRMS (ESI, m / z): for ligand (S,S,S,S)-L1 [M + H] + (C 54 H 51 N2O2 + ), found 759.3214 (calcd 759.3872).

[0100] Example 5

[0101] To prepare (S,S,S)-L2, simply replace (S,S)-cyclohexanediamine in Example 4 with (S)-spirodiamine. The remaining preparation methods and conditions are the same as those for (S,S,S,S)-L1, with a yield of 60%: 11H NMR (500 MHz, CDCl3) δ 11.43 (s, 2H), 8.14 (s, 2H), 7.36 (d, J = 7.4 Hz, 2H), 7.30 (t, J = 7.4 Hz, 2H), 6.97 (d, J = 7.3 Hz, 2H), 6.93 (t, J = 7.3 Hz, 2H), 6.84 (t, J = 7.4 Hz, 4H), 6.81 - 6.69 (m, 10H), 6.60 (d, J = 7.5 Hz, 2H), 6.31 (d, J = 7.7 Hz, 2H), 3.18 - 3.02 (m, 4H), 3.00 - 2.81 (m, 4H), 2.71 - 2.62 (m, 2H), 2.50 - 2.41 (m, 2H), 2.30 - 2.10 (m, 10H), 1.98 - 1.91 (m, 2H). 13 13C NMR (126 MHz, CDCl3) δ 161.76, 157.64, 149.84, 147.17, 145.28, 144.34, 144.12, 141.61, 141.05, 139.56, 135.58, 131.40, 128.92, 128.67, 128.35, 126.62, 126.12, 126.04, 123.57, 123.47, 117.52, 115.92, 114.54, 60.31, 60.21, 40.11, 39.72, 38.05, 31.41, 31.27, 31.04. HRMS (ESI, m / z): For ligand (S,S,S)-L2, [M + H] + + (C 65 H 55 N2O2 + ), found 895.2182 (calcd 895.4264). [M + Na] + + (C 65 H 54 N2O2Na + ), found 917.2210 (calcd 917.4083).

[0102] Example 6

[0103] To prepare (S,R,S)-L2, simply replace (S,S)-cyclohexanediamine in Example 4 with (R)-spirodiamine, and the remaining preparation methods and conditions are the same as those of (S,S,S,S)-L1, with a yield of 84%: 11H NMR (500 MHz, CDCl3) δ 11.73 (s, 2H), 8.12 (s, 2H), 7.42 - 7.32 (m, 4H), 7.04 - 6.95 (m, 4H), 6.89 - 6.83 (m, 6H), 6.71 - 6.61 (m, 8H), 6.41 (d, J = 7.5 Hz, 2H), 6.33 (d, J = 7.7 Hz, 2H), 3.32 - 3.23 (m, 2H), 3.11 - 3.03 (m, 2H), 2.96 - 2.86 (m, 2H), 2.83 - 2.75 (m, 2H), 2.67 - 2.58 (m, 2H), 2.52 - 2.44 (m, 2H), 2.27 - 2.07 (m, 8H), 2.05 - 1.9 (m, 4H). 13 13C NMR (101 MHz, CDCl3) δ 161.12, 157.82, 150.09, 146.95, 144.91, 144.78, 144.41, 141.78, 141.19, 139.94, 136.52, 131.25, 129.30, 128.70, 128.58, 126.76, 126.20, 126.10, 123.33, 123.18, 117.44, 115.93, 114.64, 60.28, 60.18, 40.94, 40.79, 38.11, 31.78, 31.49, 30.85. HRMS (ESI, m / z): for ligand (S,S,S)-L2 [M + H] + + (C 65 H 55 N2O2 + ), found 895.2182 (calcd 895.4264). [M + Na] + + (C 65 H 54 N2O2Na + ), found 917.2210 (calcd 917.4083).

[0104] Example 7

[0105] In this example, (S)-spirodiamine, 3,5-di-tert-butylsalicylaldehyde and (S)-phenylspirobenzaldehyde obtained in Example 1 were used as starting materials, and the synthesis reaction formula of the corresponding asymmetric Salen ligand is as shown in the formula:

[0106]

[0107] The specific synthesis steps were as follows: Under nitrogen protection, (S)-spirodiamine monohydrochloride (0.28 g, 1.0 mmol), 3,5-di-tert-butylsalicylaldehyde (0.23 g, 1.0 mmol) and several The molecular sieve was added to a three-necked flask, and 50 mL of anhydrous methanol was added. It was stirred at room temperature for 1 h, and the solution showed a bright yellow color. Salicylaldehyde (S)-phenylspirocyclic ortho-hydroxyaldehyde (0.3 g, 0.9 mmol), toluene (40 mL), and refined triethylamine (00.18 g, 1.7 mmol) were added to the reaction system, and it was refluxed and stirred at 110 °C for 24 h. The reaction solution was filtered to remove the molecular sieve, concentrated by rotary evaporation and separated by column chromatography (silica gel column, mobile phase: petroleum ether / ethyl acetate = 20 / 1), recrystallized with methanol, and dried to obtain the target product as a yellow solid (0.25 g, yield 36%).

[0108] (S,S)-L3 yield 36%: 1 H NMR (500 MHz, CDCl3) δ 12.13 (s, 1H), 11.50 (s, 1H), 8.22 (d, J = 17.1 Hz, 2H), 7.40 - 7.28 (m, 3H), 7.19 - 7.09 (m, 2H), 7.02 - 6.91 (m, 3H), 6.89 - 6.73 (m, 8H), 6.62 (d, J = 7.1 Hz, 1H), 6.32 (d, J = 7.7 Hz, 1H), 3.22 - 3.13 (m, 1H), 3.11 - 2.94 (m, 4H), 2.93 - 2.84 (m, 1H), 2.73 - 2.63 (m, 1H), 2.52 - 2.44 (m, 1H), 2.32 - 2.16 (m, 7H), 2.00 - 1.92 (m, 1H), 1.31 (s, 9H), 1.27 (s, 9H). 13 C NMR (126 MHz, CDCl3) δ 162.67, 161.91, 158.08, 157.70, 149.94, 147.13, 145.59, 144.98, 144.83, 144.40, 144.19, 141.84, 141.81, 141.06, 139.86, 139.59, 136.63, 135.71, 131.46, 128.95, 128.69, 128.56, 128.35, 127.39, 126.65, 126.53, 126.15, 126.07, 123.68, 123.48, 123.33, 118.22, 117.50, 116.26, 116.13, 114.59, 60.38, 60.22, 40.21, 39.83, 38.21, 38.05, 35.06, 34.22, 31.62, 31.43, 31.32, 31.04, 29.45. HRMS (ESI, m / z): [M + H] of ligand (R, rac, R)-L6 + (C 56H 57 N2O2 + ),measured value 789.4467 (theoretical value 789.4415), [M+Na] + (C 56 H 56 N2O2Na + ),measured value 811.4274 (theoretical value 811.4234).

[0109] Example 8

[0110] To prepare (R,S)-L3, just replace the (S)-spirodiamine monohydrochloride in Example 7 with (R)-spirodiamine monohydrochloride, and the remaining preparation methods and conditions are the same as those of (S,S)-L3, with a yield of 40%: 1 H NMR (500 MHz, CDCl3) δ 12.16 (s, 1H), 11.74 (s, 1H), 8.24 (d, J = 10.3 Hz, 2H), 7.43 - 7.28 (m, 3H), 7.18 (t, J = 7.6 Hz, 1H), 7.12 (d, J = 7.4 Hz, 1H), 7.04 - 6.96 (m, 3H), 6.94 - 6.85 (m, 3H), 6.78 (d, J = 7.7 Hz, 1H), 6.68 - 6.60 (m, 4H), 6.45 - 6.39 (m, 1H), 6.36 (d, J = 7.7 Hz, 1H), 3.34 - 3.24 (m, 1H), 3.09 - 2.92 (m, 4H), 2.87 - 3.78 (m, 1H), 2.68 - 6.57 (m, 1H), 2.49 - 2.40 (m, 1H), 2.27 - 2.12 (m, 6H), 2.07 - 1.92 (m, 2H), 1.33 (s, 9H), 1.25 (s, 9H). 1313C NMR (126 MHz, CDCl3) δ 162.67, 161.19, 158.11, 157.83, 150.12, 146.86, 145.06, 145.03, 144.91, 144.79, 144.46, 142.17, 141.60, 141.22, 140.01, 139.91, 136.69, 136.60, 131.34, 129.37, 128.72, 128.67, 128.55, 127.44, 126.82, 126.54, 126.23, 126.05, 123.36, 123.32, 118.26, 117.44, 116.33, 116.18, 114.63, 60.39, 60.20, 41.00, 40.92, 38.30, 38.03, 35.09, 34.21, 31.82, 31.60, 31.47, 31.01, 30.86, 29.47. HRMS (ESI, m / z): for ligand (R, rac, R)-L6 [M + H] + (C 56 H 57 N2O2 + ), found 789.4467 (calcd 789.4415), [M + Na] + (C 56 H 56 N2O2Na + ), found 811.4274 (calcd 811.4234).

[0111] Example 9

[0112] This example provides a method for synthesizing the metal reagent Y[N(SiHMe)2]3(THF)2, which specifically includes the following steps:

[0113] Inside the glove box, dissolve anhydrous yttrium trichloride (1.00 g, 5.1 mmol) in tetrahydrofuran (100 mL), inject it into a 250 mL two-necked flask, and heat it to reflux at 110 °C for 1.5 hours. Then cool it to room temperature and evaporate the solvent to obtain a white powder (2.10 g). By comparing the weight difference between YCl3 and the obtained white THF adduct, it is judged that the product is [YCl3·3(THF)].

[0114] Under nitrogen protection, NH(SiHMe2)2 (4.00 g, 30 mmol) was dissolved in 30 ml of refined hexane and placed in a 100 ml three-necked flask. At -78 °C, n-BuLi (1.6 M in hexane, 18.0 ml, 28.8 mmol) was added dropwise to the reaction solution from a constant pressure dropping funnel. After the addition was complete, the mixture was stirred at room temperature for another 2 hours. The resulting white suspension was filtered in a glove box, and the filter cake was dried to obtain white powder LiN(SiHMe2)2 (2.97 g, yield 73%).

[0115] In a glove box, LiN(SiHMe2)2 (1.00 g, 7.2 mmol) and YCl3(THF)3 (1.00 g, 2.4 mmol) were successively added to 20 ml of n-hexane. The reaction was carried out at room temperature for 12 hours, filtered, and the resulting filtrate was evacuated to dry the solvent to obtain white crystals. Then, the crystals were recrystallized twice in cold n-pentane to prepare the yttrium metal precursor Y[N(SiHMe2)2]3(THF)2 (1.02 g, yield: 72%).

[0116] This example provides a method for the selective ring-opening polymerization of racemic β-butyrolactone to prepare poly-3-hydroxybutyrate with different tacticity. The specific steps of the in-situ catalytic system are as follows:

[0117] The specific process is as follows: Racemic β-butyrolactone (86 mg, 1 mmol) and initiator Ph2CHCH2OH (0.99 mg, 0.005 mmol) were dissolved in 0.4 mL of toluene, and 0.1 mL of a mixed solution containing 0.05 mol / L of spirocyclic Salen ligand and 0.05 mol / L of yttrium metal precursor reagent Y[N(SiHMe2)2]3(THF)2 was added. The total volume of the polymerization was 0.5 mL, the initial concentration of the racemic butyrolactone monomer was 2 mo1 / L, the concentration of the catalyst was 0.0l mol / L, and the concentration of the initiator was 0.01 mol / L. The molar ratio of monomer / ligand / yttrium metal precursor / initiator was 200:1:1:1:1. The reaction was carried out at room temperature for 2 min, and a chloroform solution of benzoic acid with a mass concentration of l0 mg / mL was added to dissolve the product. A small amount of the solution was taken for 1 1H NMR analysis to determine the conversion rate. The remaining reaction solution was poured into methanol to precipitate the polymer. The precipitated solid was filtered, washed three times with methanol, and then dried in a vacuum drying oven at 60 °C for 12 h to obtain white poly-3-hydroxybutyrate.

[0118] In this example, the obtained poly-3-hydroxybutyrate was detected by nuclear magnetic resonance (NMR) to measure the 13 13C NMR of the polymer and analyze the tacticity P of the polymer rAnother small amount is dissolved in analytical pure DMF, filtered, and the filtrate is subjected to GPC testing to determine its polymer mass and mass distribution.

[0119] The corresponding catalytic systems of each spirocyclic Salen ligand and their polymerization results are shown in the following table:

[0120]

[0121] From the above examples, it can be seen that for the selective polymerization reaction of racemic β-butyrolactone, the present invention shows different activities and different syndiotactic selectivities in the solutions of catalytic systems with different Salen ligands. Among them, the ligand (S,S,S)-L2 exhibits a relatively high syndiotactic selectivity, and its P r value reaches 0.95.

[0122] The above content is only an example and explanation of the structure and application of the present invention. Modifications, supplements, or substitutions made by those skilled in the art to the specific embodiments described without creative efforts in a similar manner still fall within the protection scope of this patent.

Claims

1. A class of spiro Salen ligands, characterized in that, The spirocyclic Salen ligands described above include symmetric mononuclear spirocyclic Salen ligands and asymmetric mononuclear spirocyclic Salen ligands, which contain one or two spirocyclic o-hydroxyaldehyde compounds linked by Schiff base bonds formed with diamines; the general structural formulas of the symmetric mononuclear spirocyclic Salen ligands and the asymmetric mononuclear spirocyclic Salen ligands are shown as follows: Among them, R 1 , R 2 , R 3 , R 4 and R 5 are independently hydrogen, alkyl, cycloalkyl, alkoxy, aryl, halogen, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, substituted heteroaryl, and R 1 is not hydrogen; R 6 is a phenyl group, a racemic or chiral cyclohexyl group, a binaphthyl group, a tetrahydrobinaphthyl group or a spiro group.

2. The spiro Salen ligand according to claim 1, characterized in that, Said R 1 , R 2 , R 3 , R 4 and R 5 are independently hydrogen, C1-C 10 alkyl, C3-C5 cycloalkyl, C1-C 10 alkoxy, C6-C 14 aryl, halogen, 5-6 membered heteroaryl, substituted C1-C 10 alkyl, substituted C1-C 10 alkoxy, C6-C 1a aryl substituted with one or more R 14 groups, 5-6 membered heteroaryl substituted with one or more R 1a groups; R 1a is C1-C 10 alkyl, C1-C 10 alkoxy or halogen; R 7 and R 8 are independently hydrogen, C1-C 10 alkyl, C3-C5 cycloalkyl, C1-C 10 alkoxy, C6-C 14 aryl or halogen; represents the point of attachment; each R 6 is independently a racemate, a meso form, an enantiomerically pure S configuration or an enantiomerically pure R configuration.

3. The spiro Salen ligand according to claim 1 or 2, characterized in that, Said R 1 , R 2 , R 3 , R 4 , and R 5 are independently hydrogen, fluorine, chlorine, bromine, iodine, methyl, ethyl, tert-butyl, isopropyl, cyclopropyl, cyclobutyl, cyclohexyl, furyl, pyridyl, biphenyl, 2-phenylbiphenyl, trityl, cumenyl, benzyl, adamantyl, C1-C3 perfluoroalkoxy, C1-C3 perfluoroalkyl, arylmethylene, heteroarylmethylene, arylmethylidene or heteroarylmethylidene.

4. The spiro Salen ligand according to claim 1 or 2, characterized in that, The symmetric mononuclear spirocyclic Salen ligand is characterized in that it is condensed from two molecules of the same axially chiral R 1 -substituted spirocyclic salicylaldehyde groups and one molecule of a diamine compound, has two Schiff base bonds with the same chemical environment, and has two phenolate oxygen and two imine nitrogen coordination sites, presenting a four-tooth coordination cavity; the asymmetric mononuclear spirocyclic Salen ligand is characterized in that it is condensed from one molecule of an axially chiral R 1 -substituted spirocyclic salicylaldehyde group and one molecule of a salicylaldehyde derivative group with one of the amino groups in one molecule of a diamine compound respectively; it has two Schiff base bonds with different chemical environments, has two phenolate oxygen and two imine nitrogen coordination sites, presenting a four-tooth coordination cavity.

5. A method for preparing a class of spiro Salen ligands according to any one of claims 1-4, characterized in that, Preparation method of symmetric mononuclear spirocyclic Salen ligand: A spirocyclic o-hydroxy aldehyde substituted by R 1 and a diamine compound are subjected to an aldehyde-amine condensation reaction in a solvent under high-temperature conditions, and after separation and purification, a symmetric mononuclear spirocyclic Salen ligand is obtained; Preparation method of asymmetric mononuclear spirocyclic Salen ligand: A salicylaldehyde compound is first reacted with the monohydrochloride of a diamine compound in a polar solvent at room temperature to carry out the first aldehyde-amine condensation reaction, and then a spirocyclic o-hydroxy aldehyde substituted by R 1 and a basic auxiliary agent are added, and a non-polar solvent is added to assist dissolution, and the aldehyde-amine condensation reaction is further carried out at high temperature; The reaction product is separated and purified to obtain an asymmetric mononuclear spirocyclic Salen ligand; In the preparation process of the symmetric mononuclear spirocyclic Salen ligand: the diamine compound is (NH2)2R 6 ; the temperature of the aldehyde-amine condensation reaction is 90-110 °C, and the time is 12-48 h; from R 1 The molar ratio of the substituted spirocyclic o-hydroxyaldehyde to the diamine compound is 2-2.5:1; the solvent is toluene, xylene or DMF; In the preparation process of the asymmetric mononuclear spirocyclic Salen ligand: the monohydrochloride of the diamine compound is (NH2)2R 6 ·HCl; the time for the first-step aldehyde-amine condensation reaction at room temperature is 0.5 - 1 h; the polar solvent is methanol, ethanol or isopropanol; the basic auxiliary agent is triethylamine, pyridine or diisopropylethylamine; the non-polar solvent is toluene, xylene or DMF; the temperature for further aldehyde-amine condensation reaction at high temperature is 90 - 110 °C; the time is 12 - 48 h; the molar ratio of the salicylaldehyde compound to the monohydrochloride of the diamine (NH2)2R 6 ·HCl is 1 - 1.5:1; the molar ratio of the spirocyclic o-hydroxyaldehyde substituted by R 1 to the salicylaldehyde compound is 0.8 - 1.5:1; the molar ratio of the basic auxiliary agent to the salicylaldehyde compound is 1 - 2:1; Among them, the spiro ortho-hydroxy aldehyde and salicylaldehyde compounds substituted by R 1 have the following general structural formulas respectively: Based on R 1 The spirocyclic o-hydroxyaldehyde substituted by R has 2,2’,3,3’-tetrahydro-1,1’-spirobi[1H-indene] as the basic skeleton, with an aldehyde group at the 6th position, a phenolic hydroxyl group at the 7th position, and R at the 7’ position 1 Substituent; Diamine compounds with chiral structures, monohydrochlorides of diamine compounds, and spirocyclic o-hydroxyaldehydes substituted by R 1 are independently racemates, meso forms, enantiomerically pure S configurations, or enantiomerically pure R configurations.

6. The preparation method of a class of spiro Salen ligands according to claim 5, characterized in that, The preparation method of the spiro ortho-hydroxy aldehyde substituted by R 1 uses 2,2’,3,3’-tetrahydro-1,1’-spirobi[1H-indene]-7,7’-diol as the raw material, hereinafter simply referred to as spirodiol. After the modification of the substituent R 1 , the protection of the phenolic hydroxyl group, the formylation reaction to introduce an aldehyde group, and the deprotection of the phenolic hydroxyl group are carried out; among them, the spirodiol is a racemate or an optically pure isomer, specifically (R)-spirodiol or (S)-spirodiol; the specific steps of the spiro ortho-hydroxy aldehyde substituted by R 1 are as follows: Step (i), modification of substituent R 1 thereof (A)R 1 When it is an alkoxy group or a substituted alkoxy group, R 1 is represented by OR Prepared by using spirodiphenol as a raw material, adding KCO3 to create an alkaline environment, and performing an O-alkylation reaction on one phenolic hydroxyl group in the spirodiphenol with an alkyl halide in a polar aprotic solvent; The reaction conditions are: stirring at room temperature for 8 - 24 h; The alkyl halide is RX: where R is methyl, ethyl, tert-butyl or isopropyl; X is chlorine, bromine or iodine; The polar aprotic solvent is acetonitrile, acetone, DMF or toluene; The molar ratio of spirodiphenol to KCO3 to alkyl halide is 1:1 - 2:1 - 1.5; (B)R 1 When R is a halogen 1 R is chlorine or bromine Using spirodiphenol as a raw material, adding KCO3 to create an alkaline environment, and performing a halogen displacement reaction on one phenolic hydroxyl group in the spirodiphenol with a halogenating reagent in a polar aprotic solvent; The reaction conditions are: reacting at 20 - 120 °C for 0.5 - 3 h; The halogenating reagent is phosphorus pentachloride, phosphorus oxychloride, phosphorus oxybromide or triphenylphosphonium dibromide; The polar aprotic solvent is DMF, toluene or THF; The molar ratio of spirodiphenol to the halogenating reagent is: 1:1 - 1.2; (C)R 1 when it is alkyl, cycloalkyl, aryl, heteroaryl, substituted alkyl, substituted aryl or substituted heteroaryl Step (C-1), first use compound H to replace one phenolic hydroxyl group of spirodiphenol with a leaving group LG, where LG is halogen, alkoxy, sulfonic acid group, p-toluenesulfonyloxy or acyloxy; When LG is alkoxy or halogen, the preparation methods are the same as (A) or (B) respectively; When LG is sulfonic acid group, p-toluenesulfonyloxy or acyloxy, the preparation method is: using 1 molar equivalent of spirodiphenol as the starting material, dissolving it in a non-polar solvent, and sequentially adding 1 - 1.2 molar equivalents of a base scavenger and 1 - 1.2 molar equivalents of compound H under the condition of an ice bath at 0 - 5 °C, then removing the ice bath and stirring at room temperature for 8 - 12 h; then separating and purifying to obtain an intermediate product containing LG substitution; compound H is chlorosulfonic acid, p-toluenesulfonyl chloride or trifluoromethanesulfonic anhydride; the base scavenger is triethylamine, pyridine, potassium carbonate or N,N-diisopropylethylamine; the non-polar solvent is dichloromethane, ether or tetrahydrofuran; Step (C-2): Dissolve 1 molar equivalent of the LG-substituted intermediate product and 0.1 - 0.2 molar equivalent of the catalyst 1,3-bis(diphenylphosphinopropane)nickel dichloride in ether or tetrahydrofuran; slowly dropwise add 2 - 4 molar equivalents of R 1 magnesium bromide Grignard reagent at 0 - 5 °C; after the addition is complete, remove the ice bath and stir at room temperature for 12 - 24 h; then perform extraction and separation, and purify by column chromatography to obtain; Step (two) Protection of phenolic hydroxyl group, formylation reaction to introduce aldehyde and deprotection of phenolic hydroxyl group Step (2.1), the specific steps for the protection of phenolic hydroxyl groups are as follows: Under the condition of 0-5°C, 1 molar equivalent of R prepared in step (1) 1 The substituted spirocyclic monophenol after substitution is dissolved in an ether solvent, and then a solution of an ether solvent containing 1-1.5 molar equivalents of a deprotonating agent is added dropwise; after the addition is complete, the ice bath is removed, and the mixture is stirred at room temperature for 5-8 h; then, under the ice bath, 1-1.2 equivalents of a protecting agent are added dropwise; after the addition is complete, the ice bath is removed, and the mixture is stirred at room temperature for 8-12 h; then, water is added for quenching, and the product is obtained by extraction, separation, and column chromatography purification. The ether solvent is ether, tetrahydrofuran or 1,4-dioxane; The deprotonating reagent is NaH, CaH, NaOH or KOH; The protecting agent is bromomethyl methyl ether or chloromethyl methyl ether; Step (2.2), the specific steps of the formylation reaction are: dissolving 1 molar equivalent of the product of step (2.1) in an ether solvent, adding 1 - 1.5 molar equivalents of TMEDA and stirring; at -90 - -78 °C, dropwise adding 1 - 1.5 molar equivalents of an organolithium reagent, stirring for 8 - 12 h, then dropwise adding 1 - 1.5 molar equivalents of a formylating reagent, and stirring at room temperature for 8 - 12 h after the addition; performing extraction and separation and column chromatography purification to obtain; The ether solvent is ether, tetrahydrofuran, 1,4-dioxane; The organolithium reagent is n-butyllithium or tert-butyllithium; The formylation reagent is formic acid, methyl cyanoformate or N,N-dimethylformamide; For the specific steps of deprotecting the phenolic hydroxyl group in step (2.3): Dissolve 1 molar equivalent of the product from step (2.2) in a polar solution, add 1-2 molar equivalents of concentrated hydrochloric acid, and stir for 8-12 h; then adjust the pH to 6-7, extract the oil phase with water and recrystallize to obtain the product; The polar solvent is methanol, ethanol or isopropanol.

7. Use of the spiro-Salen ligand according to any one of claims 1-4, or the spiro-Salen ligand prepared by the preparation method according to any one of claims 5-6, characterized in that Construct a polymerization reaction catalytic system, including a spirocyclic Salen ligand, a metal precursor MX n and an initiator.

8. The application according to claim 7, wherein Metal precursor MX n wherein M in n is Zn, Co, Cr, Cu, Fe, Pd, Ni, Mn, Y, La, Ln, Sc, Yb, Al, Ru or Ti; n is 1, 2 or 3; each independent X is furyl, -N(SiHMe2)2, -N(SiMe3)2, alkyl, alkoxy, aryl, phenol or halogen; the initiator is alkyl alcohol, alkyl mercaptan, benzyl alcohol or benzyl mercaptan.

9. The application according to claim 7, wherein The polymerization reaction catalytic system is applied to the selective ring-opening polymerization of racemic β-butyrolactone to prepare poly-3-hydroxybutyrate with different regularities, including the following steps: adding racemic β-butyrolactone, spirocyclic Salen ligand, metal precursor MX n , initiator and solvent into a reaction device, reacting at 20-45 °C for 5 s-2 h, and the molar ratio of racemic β-butyrolactone, spirocyclic Salen ligand, metal precursor MX n to the initiator is 100-10000:1-5:1-5:1-5; the reaction structural formula is as follows 10. The application according to claim 9, wherein The solvent is dichloromethane, dimethyl sulfoxide, tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylformamide or toluene; the highest syndiotactic polymer P of the obtained poly-3-hydroxybutyrate r = 0.95.

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