A kind of aryloxy cyclic ether skeleton metal complex catalyst and its preparation method and application

Abstract

The present invention provides an aryloxycyclic ether skeleton metal complex catalyst and its preparation method and application. With formula I as the ligand, the catalyst structure is as follows: The catalyst can be used in a method for preparing high-purity lactide from L-lactic acid. The catalyst has high thermal stability, good acid resistance, is not easy to decompose under low pressure, significantly improves the stereoselectivity of lactide, and has certain industrial prospects.

Description

Technical Field

[0001] The invention relates to an aryloxy cyclic ether skeleton metal complex catalyst and a preparation method thereof, as well as application of the catalyst in preparing lactide from L-lactic acid. Background Art

[0002] Lactide is an important raw material for synthesizing polylactic acid. Polylactic acid material has good biodegradability, biocompatibility and good mechanical strength. It is an ideal biodegradable material and has broad application prospects in human tissue repair, wound suture, controlled release of medicine and pesticides. In some other application fields, polylactic acid can replace traditional polymer materials to reduce pollution and harm to the environment. The mainstream method for synthesizing polylactic acid in industry is the ring-opening polymerization of lactide, which has been described in many patent documents, such as: US5053522A, US5247058A, US5357035A, US6005067A, US6277951B1, US6326458B1, US5274127A, US20050222379A1, US20120302724A1, US20110155557A1, CN1951933A, CN1594313A, CN1488628A, WO2010105143A2, etc. At present, the main method used in industrial production is to produce polylactic acid by high-temperature heating and vacuum environment, using tin-based chemicals as catalysts (such as stannous 2-ethylhexanoate (1I) and tin chloride, etc.) through four steps of dehydration, prepolymerization, depolymerization, and ring-opening polymerization. In order to avoid oxidation of the reactants under high temperature conditions (≥180°C), the chemical reaction is usually carried out in an inert gas atmosphere (such as nitrogen).

[0003] During the prepolymerization and depolymerization process, the high temperature and low pressure reaction conditions (temperature 200-240°C, pressure 5-15hpa) will depolymerize some oligomers, while further polymerizing other oligomers into higher molecular weight polymers. In this process, a large amount of yellow-brown residual polymers will often be produced. Although the tin-based catalyst is a homogeneous catalyst with a more obvious catalytic effect on the depolymerization process, it still cannot avoid the production of a large amount of residual polymers, and the optical purity of crude lactide is low, which increases the cost of subsequent separation and purification procedures. The yield of lactide synthesized by conventional methods is usually only 50%-70%. For example, U.S. patent application US5053522A mentions a method for synthesizing lactide using a tin-based catalyst, which requires a high temperature of 200-260°C to separate the lactide product, with a yield of 69%. In the single batch production of U.S. patent application US5274127A, the yield of lactide is 56.8%. The low catalytic efficiency of other metal compounds for prepolymerization and depolymerization reactions leads to a decrease in the production yield of lactide (<70%). For example, zinc oxide particles are used in US Patent US201203027A1, and the lactide product is obtained by distillation separation at a high temperature of 230-240°C, and the yield is less than 72%. At the same time, according to experimental and literature experience, the use of low-purity lactide raw materials will produce a large number of by-products in the process of lactide ring-opening polymerization of polylactic acid, and it is impossible to produce polylactic acid products that can be used on a large scale. Therefore, the high-yield and high-purity lactide process produced by the prepolymerization and depolymerization synthesis steps is the decisive core step in the synthesis of large-scale industrial-grade polylactic acid products. In the current mainstream process of synthesizing lactide from lactic acid, the lactide synthesis method has a low yield, and the reaction conditions require high temperature and high vacuum, which are harsh conditions and need to be further optimized and improved to reduce energy consumption in the production process and reduce production costs. Summary of the invention

[0004] The purpose of the present invention is to provide an aryloxycyclic ether skeleton metal complex catalyst and a preparation method thereof. The ligand structure of the present invention has a large molecular space and obtains a large steric hindrance, which significantly enhances the stereoselectivity of the catalyst for crude lactide and the catalytic stability under the system; on the other hand, the active metal is used as the central atom, which enhances the reaction activity of the catalyst, significantly improves the optical purity of crude lactide in the lactide synthesis reaction process, and further significantly improves the regularity of the spatial structure of the polymerization product.

[0005] The present invention also provides the use of the catalyst in preparing lactide from L-lactic acid, so that the lactide yield and optical purity in the lactide synthesis and depolymerization process are relatively high (the lactide yield can reach 80.0-95.0%, and the optical purity is above 99.9%).

[0006] In order to achieve the above invention object, the technical solution provided by the present invention is as follows:

[0007] An aryloxy cyclic ether skeleton metal complex catalyst, the catalyst uses II-IVA, IIB and transition metal as active components M, preferably one or more of Sn, Zn, Ga, Ti, Zn, Al, Zr, and the ligand structural formula is as follows:

[0008]

[0009] Among them, R1~R 12 Selected from hydrogen, halogen or any one of the following groups: C 1-6 Alkyl, C 1-6 Alkoxy, C 3-10 Cycloalkyl, C 3-10 Cycloalkyloxy, C 6-14 Aryl, C 6-14 Aryloxy; T1 and T2 are each independently selected from a divalent hydrocarbon or silane group having 1 to 20 atoms other than hydrogen, or an inert substituted derivative of the above group; X is a monovalent substituent group having 1 to 20 atoms other than hydrogen, or two X groups together are a divalent substituent group having 1 to 40 atoms excluding hydrogen.

[0010] Preferably, R 1～ R 12 Any one selected from substituted methyl, substituted phenyl, dibenzocyclo, alkyl, fluorenyl, anthracenyl; more preferably, tert-butyl, 3,5-di-tert-butylphenyl, benzyl, fluorenyl, diphenylmethyl.

[0011] Preferably, T1 and T2 are each independently selected from a divalent hydrocarbon group having 3 to 10 atoms; preferably, T1 and T2 are both 1,3-propylene, 1,4-butanediyl, 2,4-pentanediyl, 1,5-pentanediyl, 1,3-di(propylene)phenyl, and methylene trans-1,2-cyclohexanediyl.

[0012] Preferably, X is independently selected from a monovalent substituent group having 1 to 10 atoms, or two X groups together are a divalent substituent group having 1 to 20 atoms excluding hydrogen; further preferably, X is halogen, methyl, benzyl or dimethylamino; more preferably, X is chlorine, methyl or benzyl.

[0013] Furthermore, the bimetallic complex of the aryloxyether skeleton in the present invention can be prepared by the following method: The reaction process is shown in the following formula:

[0014]

[0015] The following steps are involved:

[0016] (1) reacting substituted brominated phenol, triphenylphosphine and aldehyde No. 1 in the presence of n-butyl lithium to prepare product No. 3, preferably, the molar ratio of substituted brominated phenol: aldehyde No. 1: triphenylphosphine: n-butyl lithium is 1: (1.1-1.5): (1.1-2): (1.1-1.5), the reaction temperature is 80-100° C., and the reaction time is 8-12 hours;

[0017]

[0018] (2) reacting compound 3 with dihydropyran in the presence of p-toluenesulfonic acid and pyridine to prepare compound 4; preferably, the molar ratio of compound 3: dihydropyran: p-toluenesulfonic acid: pyridine = 1: (1.1-1.7): (0.1-0.4): (0.2-0.4), the reaction temperature is -10-0°C, and the reaction time is 1-3h;

[0019]

[0020] (3) reacting compound 4 with trimethylborate in the presence of butyl lithium to obtain compound 5, preferably, the molar ratio of compound 4: trimethylborate: butyl lithium = 1: (0.4-1.5): (0.9-1.5), the reaction temperature is -20-0°C, and the reaction time for each step is 0.5-2h;

[0021]

[0022] (4) Compound 5 and Compound 6 are reacted under alkaline conditions and in a solvent to obtain Compound 7, wherein the catalyst is (bis(diphenylphosphinothiocene)palladium dichloride); preferably, Na2CO3 provides alkaline conditions, and the ratio is Compound 5: Compound 6: Na2CO3: Catalyst = 1: (1.1-1.9): (2-4.8): (0.0005-0.001), the reaction temperature is 60-80°C, the reaction time is 2-4h, and Compound 7 is reacted with pyridine p-toluenesulfonate in the presence of methanol to obtain Compound 8, the reaction is carried out at 60-70°C, the reaction time is 2-4h, and preferably, the molar ratio of Compound 7: pyridine p-toluenesulfonate: methanol is 1: (0.1-0.25): (2-4.3).

[0023]

[0024] (5) reacting compound 8 with a dibromo substituent in an alkaline solution to obtain compound 9, the reaction temperature being 40-80° C. and the reaction time being 5-8 h. Preferably, reactant 8: dibromo substituent: base is preferably Cs2CO3=1:(1.3-2):(3-6);

[0025]

[0026] (6) Compound 9 is subjected to a hydrogenation reaction under Pd / C catalysis to prepare Compound 10,

[0027] The reaction temperature is 50-70°C, the reaction time is 1-3h, the reaction H2 pressure is 0.5-0.9Mpa, preferably, the molar ratio of compound 9: pd / C = 1: (0.1-0.2);

[0028] (7) Compound 10 is reacted with an active metal source at 50-90° C. for 3-5 hours to obtain the target catalyst; preferably, the molar ratio of compound 10:active metal source=1:(1.2-2.5)

[0029]

[0030] As a preferred solution, the method for preparing the catalyst comprises the following steps:

[0031] (1) Add the substituted brominated phenol to a three-necked flask equipped with a reflux condenser and containing a solvent (the solvent can be toluene, tetrahydrofuran, ethylene glycol dimethyl ether, preferably toluene) (200 ml), add triphenylphosphine to the stirred solution and heat the reaction to 80-100°C for 1-2 hours, and cool the reaction mixture to room temperature. Collect the salt by vacuum filtration and rinse off the excess triphenylphosphine with hexane; dry the phosphine salt under vacuum for >24 hours to ensure complete removal of residual solvent and water; add the phosphine salt to a flame-dried 3-necked round-bottom flask equipped with a stirring bar and a reflux condenser, suspend the phosphine salt in toluene solvent, and add nBuLi. After 30 minutes, add aldehyde No. 1 under a nitrogen stream, and heat the reaction under reflux for 8-12 hours. Products No. 3 with different R structures are prepared.

[0032] (2) Add dihydropyran to a dichloromethane solution (80 ml) of compound 3 at -10 to 0°C, and simultaneously add p-toluenesulfonic acid and pyridine. After the reaction is completed, neutralize with 1M sodium hydroxide, extract with dichloromethane and water, wash the organic phase with saturated sodium chloride solution, concentrate, and pass through a column (petroleum ether: dichloromethane = 8:1). Obtain product No. 4 with different R structures.

[0033] (3) Under nitrogen atmosphere, product No. 4 was dissolved in dry THF, stirred at -20 to 0°C for 3 to 10 minutes, butyl lithium was slowly added dropwise, and after reacting for 0.5 to 2 hours, trimethylborate was slowly added dropwise. The reaction flask was taken out and stirred at room temperature for 0.5 to 2 hours, and then 1 M hydrochloric acid solution was added to adjust the pH of the solution to 6. The solution was extracted with ether, dried and the solvent was spin-dried, and recrystallized from n-hexane to obtain white solid compound 5.

[0034] (4) Product No. 5 and reactant No. 6 were reacted in ethylene glycol dimethyl ether (DME, 150 ml), and 2M Na2CO3 15-35 ml was added to the reaction solution, nitrogen atmosphere; reaction temperature 60-80°C, reaction time 2-4 h, conventional catalyst (bis(diphenylphosphinothiocene) palladium dichloride (Pd(dppf)2Cl2) was used for catalytic reaction, and ethyl acetate: water 2:1, 300 ml was used to quench the reaction after the reaction was completed. The yield was >90%, and product 7 was obtained by column (petroleum ether: ethyl acetate = 10:1). Pyridine p-toluenesulfonate (PPTS) and methanol were added, and the reaction was carried out at 60-70°C for 2-4 h. Water was added to the reaction solution, and the layers were separated after sufficient stirring. The aqueous phase was drained, extracted three times, and the organic phase was concentrated. The organic phase was concentrated, 0.4 L of methanol was added, and stirred for 1 h. After filtering, methanol was added again for crystallization and purification to obtain THP-free powder No. 8.

[0035] (5) Take reactant No. 8 and put it into 50 ml of acetone, take the dibromosubstituted product, add 200-350 ml of 0.17-0.34 mol / LC s2CO3 solution; reaction temperature 40-80°C, reaction time 5-8 h. Cool to room temperature, evaporate most of the acetone, add 200 ml of a mixed solution of CH2Cl2 and water (1:1), separate the organic layer, extract the aqueous phase with CH2Cl2 three times, remove the solvent under reduced pressure, and purify the crude product by column chromatography, using petroleum ether: dichloroethane = 10:1, to obtain product 9.

[0036] (6) Product No. 9, pd / C, and EtOH (100 ml, ligand mass fraction 5% to 9%) were placed in a hydrogenation reactor and replaced with nitrogen three times. The reaction H2 pressure was 0.5 to 0.9 MPa, the reaction temperature was 50 to 70°C, and the reaction time was 1 to 3 h. After filtering with a sintered filter head, the colorless solution was cooled to room temperature and filtered to obtain the debenzylated ligand 10.

[0037] (7) Ligand No. 10 is further dissolved in 50-100 ml of toluene, added to dichloromethane (100-200 ml) containing an active metal source at a reaction temperature of -15-0°C, stirred and dispersed, reacted at 50-90°C for 3-5 hours, filtered, washed once with 200 mL of anhydrous n-hexane, and filtered to obtain the target catalyst.

[0038] The present invention also provides the use of the metal organic catalyst to catalyze the polycondensation of lactic acid monomers and the synthesis of lactide. The lactide reaction step is two steps: the first is the polycondensation reaction, and the second is the lactide synthesis reaction. According to the use, the polycondensation reaction temperature is 140-170°C, preferably 150-160°C, the reaction pressure is 30-50hpa, and the reaction time is 0.5-3h; and / or, in the lactide synthesis stage, the reaction temperature is 160-280°C, preferably 160-240°C, the reaction pressure is 10-25hpa, and the reaction time is 0.5-1h. The amount of catalyst added in the polycondensation and lactide synthesis stages is 0.01% to 1%, based on the mass of lactic acid. Further, under the optimal conditions, the optical purity of the crude lactide obtained in the lactide reaction process is 97.8-99.9%.

[0039] The present invention improves the reaction activity and controllability by changing the steric hindrance and activity of the central metal by using an amine donor; in particular, for the reaction of synthesizing lactide from lactic acid oligomers, high-purity lactide can be obtained.

[0040] The present invention has the following positive effects: the catalyst used in the present invention is green and environmentally friendly and can realize the polycondensation of monomers and the synthesis of cyclic esters under normal conditions, and has high efficiency and high controllable active polymerization, which can significantly improve the optical purity index of lactide. The present invention also has the following advantages:

[0041] (1) The metal catalyst used in the present invention catalyzes polyester reactions, especially the synthesis and polymerization of polylactic acid. Metal zinc, calcium, magnesium, and tin are cheap and readily available, and zinc, calcium, and magnesium are preferred. As trace elements of the human body, they have good biocompatibility, making the polymerization process more environmentally friendly and reducing environmental pollution. At the same time, the synthesized polyester material also has less biological toxicity, making it have a wider application prospect in the fields of biomedicine and the like;

[0042] (2) The catalyst described in the present invention has strong stability in a high temperature acidic environment. The use of the catalyst can make the molecular weight of the lactic acid prepolymer controllable and can stably reach 1000-3500, and reduce the residual yield in the polymerization process, significantly improve the selectivity of L-lactide in crude lactide, and has strong industrial application prospects.

[0043] (3) The principle by which the catalyst system of the present invention can significantly improve the process conditions for lactide synthesis in the prepolymerization and depolymerization processes is as follows: the closed cyclic ether skeleton structure makes it stable in high-temperature polymerization and a certain acidic environment, and can efficiently open the π bond between the carbon-oxygen bonds in the esterification reaction, promote its efficient formation of tetrahedral intermediates, reduce the reaction activation energy and accelerate the reaction; at the same time, the catalyst can significantly improve the selectivity of L-lactide in crude lactide through its unique spatial structure.

[0044] (4) The metal catalyst reaction system used in the present invention has a weak dependence on the raw material L-lactic acid, a high selectivity for L-lactide, an L-lactide content (optical purity) >99%, and the catalyst has good thermal stability and acid resistance, which complies with the principle of green development and has certain prospects for industrial application. DETAILED DESCRIPTION

[0045] The following embodiments are not intended to limit the scope of implementation of the present invention. Any modification or equivalent substitution of the present invention without departing from the spirit and scope of the present invention shall be included in the protection scope of the claims of the present invention.

[0046] Analytical method, instruments and conditions:

[0047] 1. Nuclear Magnetic Resonance Spectroscopy The instrument model of nuclear magnetic resonance is: Bruker DMX-500 (H: 500MHz, 13C: 125MHz). The sample configuration for hydrogen spectrum is 5-10mg, and the sample configuration for carbon spectrum is about 20mg, and 0.5-0.6mL of deuterated reagent is added. The test temperature is room temperature.

[0048] 2. GPC test

[0049] GPC measurements were performed on a LC-20AD solvent delivery pump, a Wyatt OPTILAB rEX refractive index detector and a combination of Styragel P8512-10E3A10, P8512-10E4A10 and P8512-10E5A10, with effective molar mass ranges of 100 to 40,000, 400 to 500,000 and 10,000 to 2,000,000, respectively. THF was used as the eluent (flow rate 1 mL min1, T = 40°C).

[0050] 3.GC test

[0051] Agilent6820 gas chromatograph, chromatographic column: OV-1 capillary column (50m*0.25mm); column temperature: (programmed temperature rise) initial temperature 129℃, hold for 4min, heating rate 0.5℃ / min, end temperature 132℃, hold for 35min; vaporization temperature: 280℃; detector temperature: 250℃; split ratio: 80:1; carrier gas: high-purity hydrogen, pressure 0.1MPa; tail gas: 29ml / min; injection mode: split injection; injection volume: 0.2uL.

[0052] The experimental methods used in the following examples are all conventional methods unless otherwise specified. The concentrations in the following examples are all molar concentrations unless otherwise specified. The materials, reagents, etc. used in the following examples can all be obtained from commercial channels, and the main information is as follows:

[0053] 2-Bromomethyl-4,6-di-tert-butylphenol: (Sinnoco Catalyst Co., Ltd.)

[0054] 6-Benzyl-1-(benzyloxy)-7-bromo-8-(tert-butyl)-4-(9H-fluoren-9-yl)-2-naphthaldehyde: (Sinnoco Catalyst Co., Ltd.)

[0055] 4-Methylenediphenyl-2-(bromomethyl)-6-(tert-butyl)phenol: (Sinnoco Catalyst Co., Ltd.)

[0056] 1-(Benzyloxy)-7-bromo-3,5-bis(3,5-di-tert-butylphenyl)-2-naphthaldehyde (Sinok Catalyst Co., Ltd.)

[0057] Dichloromethane: AR, Aladdin

[0058] Dihydropyran: AR, Aladdin

[0059] Pyridine: AR, Aladdin

[0060] Trimethyl borate: AR, Aladdin

[0061] Sodium chloride: AR, Aladdin Ether: AR, Aladdin

[0062] p-Toluenesulfonic acid: AR, Aladdin

[0063] Hydrochloric acid: AR, Aladdin

[0064] Dichloro[1,1'-bis(diphenylphosphino)ferrocene]palladium(Pd(dppf)2Cl2):AR,Aladdin1,3-Dibromopropane:AR,Innochem1,3-Bis(3-bromopropyl)benzene:AR,Innochem

[0065] Sncl4(thf)2:AR,Innochem

[0066] Methyl calcium bromide: AR, Innochem

[0067] Toluene: AR, Innochem

[0068] Triphenylphosphine: AR, Innochem

[0069] nBuLi:AR,Innochem

[0070] Palladium on carbon: AR, Innochem

[0071] Silica gel: AR, 200-300 mesh Alfa Ethylene glycol dimethyl ether: AR, Innochem Ethyl acetate: AR, Innochem

[0072] Petroleum ether: AR, Innochem

[0073] Methanol: AR, Innochem

[0074] n-Hexane: AR, Innochem

[0075] Synthesis route 1 is shown below:

[0076] [Example 2]

[0077] Preparation of compound 3

[0078] 2-Bromomethyl-4,6-di-tert-butylphenol (0.024 mol) was added to a three-necked flask equipped with a reflux condenser and toluene (200 ml). Triphenylphosphine (0.026 mol) was added to the stirred solution and the reaction was heated to 80°C for 8 hours. The reaction mixture was cooled to room temperature. The salt was collected by vacuum filtration and the excess triphenylphosphine was rinsed off with hexane; the phosphonium salt was dried under vacuum for >24 hours to ensure complete removal of residual solvent and water; the phosphonium salt was added to a flame-dried 3-necked round-bottom flask equipped with a stirring bar and a reflux condenser. The salt was suspended in the solvent and nBuLi (0.026 mol) was added. After 30 minutes, the reactant 6-benzyl-1-(benzyloxy)-7-bromo-8-(tert-butyl)-4-(9H-fluoren-9-yl)-2-naphthaldehyde (Compound No. 1, 0.022 mol) was added under a nitrogen stream and the reaction was heated to reflux for 8 hours. Product No. 3 was prepared with a yield of 75%.

[0079] δ H (400MHz,Chloroform-d)7.90(2H,d,J 8.5),7.73(1H,s),7.55(2H,d,J8.5),7.48(2H,d,J 7.5),7.40(2H,t,J 7.5),7.38(3H,d,J 8.5),7.32(1H,m)7.28(4H,m),7.23(2H,d,J 7.5),7.20(1H,t,J 7.5),7.16(1H,s),7.06(1H,s),7.05(2H,d,J 15.1),5.84(1H,s),5.16(3H,s),4.10(2H,s),1.48(9H,s),1.40(9H,s),1.35(9H,s).

[0080] Preparation of compound 5

[0081] At -10°C, dihydropyran (0.0194 mol) was added to a dichloromethane solution (80 ml) of product 3 (0.018 mol), and p-toluenesulfonic acid (0.0034 mol) and pyridine (0.0034 mol) were added simultaneously. After the reaction was completed for 1 h, the mixture was neutralized with 1M sodium hydroxide, extracted with dichloromethane and water, and the organic phase was washed with saturated sodium chloride solution, concentrated, and passed through a column (petroleum ether: dichloromethane = 8:1). Product No. 4 (0.017 mol) was obtained with a yield of 97%.

[0082] Under nitrogen atmosphere, product No. 4 (0.017 mol) was dissolved in 60 ml of dry THF, stirred at -20 ° C for 3 minutes, 2.2 M butyl lithium (7.7 ml) was slowly added dropwise, and after reacting for 2 h, trimethylborate (0.87 ml) was slowly added dropwise. The reaction bottle was taken out and stirred at room temperature for 0.5 h, and then 1 M hydrochloric acid solution was added to adjust the pH of the solution to 6, extracted with ether, dried and the solvent was spin-dried, and recrystallized from n-hexane to obtain a white solid 5 with a yield of 85% (0.0145 mol).

[0083] δ H (400MHz,Chloroform-d)7.90(2H,d,J 8.5),7.68(1H,s),7.55(2H,d,J8.5),7.48(2H,d,J 7.5),7.40(2H,t,J 7.5),7.38(2H,d,J 8.5),7.32(2H,m)7.28(4H,m),7.23(3H,d,J 7.5),7.20(1H,t,J 7.5),7.05(2H,d,J 15.1),5.80(1H,m),5.16(3H,s),4.10(2H,s),4.02(2H,s),3.74(1H,dd,J 12.4,7.1),3.64(1H,m),1.91(2H,m),1.78(2H,m),1.57(2H,m),1.48(9H,s),1.40(9H,s),1.35(9H,s).

[0084] Preparation of compound 8

[0085] To the solution of product No. 5 (0.015 mol) and reactant No. 6' (0.016 mol) in ethylene glycol dimethyl ether (DME, 150 ml) were added catalyst Pd(dppf)2Cl2 (0.0000075 mol), 2M Na2CO3 15 ml, nitrogen atmosphere; reaction temperature 60 ° C, reaction time 2h, catalytic reaction using conventional, after the reaction is completed, ethyl acetate: water 2:1, 300 ml quenching reaction. Yield> 90%, column (petroleum ether: ethyl acetate = 10:1) to obtain product 7 (0.0123 mol). Then add pyridine p-toluenesulfonate (PPTS) (0.00123 mol) and methanol (0.0246 mol), 60 ° C reaction for 2h. 300 ml of water was added to the reaction solution, and the mixture was stirred thoroughly to separate the layers. The aqueous phase was drained and extracted three times with 200 ml of ethyl acetate. The organic phase was concentrated and 0.4 L of methanol was added to stir for 2 h. After filtration, methanol was added to crystallize and purify again to obtain product No. 8 (0.011 mol) with a yield of 73.3%.

[0086] δ H (400MHz,Chloroform-d)9.58(1H,s),7.93(1H,s),7.90(2H,d,J 8.5),7.55(2H,d,J 8.5),7.50(1H,s),7.48(2H,d,J 7.5),7.43(1H,s),7.40(2H,t,J 7.5),7.38(2H,d,J 8.5),7.32(1H,m),7.28(6H,m),7.23(4H,d,J 7.5),7.20(2H,t,J7.5),7.17(1H,s),7.16(1H,s),7.06(1H,s),7.05(2H,d,J 15.1),5.84(1H,s),5.16(3H,s),4.10(2H,s),4.07(2H,s),1.48(9H,s),1.40(18H,s),1.35(9H,s).

[0087] Preparation of compound 9

[0088] Take reactant No. 8 (0.011 mol) into 50 ml acetone, take dibromo substitution (T1 = 1,3-dibromopropane, 0.015 mol, T2 = 1,3-bis(3-bromopropyl)benzene, 0.015 mol), add 200 ml of 0.17 mol / L Cs2CO3 solution; reaction temperature 40°C for 5 h. Cool to room temperature, evaporate most of the acetone, add 200 ml of a mixed solution of CH2Cl2 and water (1:1), separate the organic layer, extract the aqueous phase with CH2Cl2 3 times, remove the solvent under reduced pressure, and purify the crude product by column chromatography, using petroleum ether: dichloromethane = 10:1, to obtain product 9 (0.0085 mol), with a yield of 78%.

[0089] δ H (400MHz,Chloroform-d)7.93(2H,s),7.90(4H,d,J 8.5),7.55(4H,d,J8.5),7.50(2H,s),7.48(4H,d,J 7.5),7.43(2H,s),7.40(4H,t,J 7.5),7.38(4H,d,J8.5),7.32(2H,m),7.28(12H,m),7.23(8H,d,J 7.5),7.20(5H,t,J 7.5),7.17(2H,s),7.16(2H,s),7.06(2H,s),7.05(4H,d,J 15.1),7.02(2H,d,J 7.5),6.96(1H,s),5.16(6H,s),4.12(4H,d,J 7.1),4.10(4H,s),4.09(4H,m),4.07(4H,s),2.70(4H,d,J 7.1),2.20(2H,m),1.98(4H,m),1.48(18H,s),1.40(36H,s),1.35(18H,s).

[0090] 9: 13C NMR(100MHz,chloroform-d)δ154.72,154.49,152.68,144.73,143.92,143.30,142.70,141.73,140.36,139.28,139.08,137.75, 136.91,136.10,136.03,135.14,134.90,134.85,131.53,130.93,130.71,129.71,129.59,129.20,128.99,128.91,128.89,128. 82,128.60,128.37,128.35,128.34,128.24,128.01,127.93,127.89,127.75,127.48,127.20,127.12,126.91,126.33,125.02,124.77,121.99,119.75,74.95,72.25,69.62,51.26,42.49,41.05,36.57,35.25,34.91,32.75,31.84,31.36,30.41,30.29,29.42.

[0091] Preparation of Catalyst 10

[0092] Take ligand No. 9 (0.0085 mol), Pd / C (0.0009 mol), EtOH (100 ml) in a hydrogenation reactor, replace with nitrogen 3 times, reaction H2 pressure 0.5 MPa, reaction temperature 50 ° C, reaction time 3 h, after filtering with a sintered filter head, cool the colorless solution to room temperature and filter to obtain debenzylated ligand (0.0076 mol), which is further dissolved in 50 ml of toluene, added to dichloromethane (100 ml) containing active metal source Sncl4 (thf) 2 (0.0091 mol) at a reaction temperature of -15 ° C, stirred and dispersed, reacted at 50 ° C for 3 h, filtered, washed once with 200 mL of anhydrous n-hexane, and filtered to obtain the target catalyst 10 (0.006 mol).

[0093] δ H(400MHz,Chloroform-d)7.93(2H,s),7.90(4H,d,J 8.5),7.55(4H,d,J8.5),7.50(2H,s),7.43(2H,s),7.38(4H,d,J 8.5),7.28(12H,m),7.23(8H,d,J7.5),7.20(5H,t,J 7.5),7.17(2H,s),7.16(2H,s),7.06(2H,s),7.05(4H,d,J 15.1),7.02(2H,d,J 7.5),6.96(1H,s),5.16(2H,s),4.12(4H,d,J 7.1),4.10(4H,s),4.09(4H,m),4.07(4H,s),2.70(4H,d,J 7.1),2.20(2H,m),1.98(4H,m),1.48(18H,s),1.40(36H,s),1.35(18H,s).

[0094] 10: 13 C NMR(100MHz,chloroform-d)δ154.72,154.49,151.51,144.73,143.83,143.30,142.70,141.73,140.36,139.32,139.0 8,137.75,136.91,135.26,135.24,135.14,134.93,132.04,131.65,130.71,129.72,129.20,129.18,128.99,128.89,1 28.82,128.34,128.24,128.01,127.89,127.82,127.75,127.48,127.20,127.12,126.91,126.48,126.33,125.02,123.74,123.62,119.75,72.25,69.62,51.30,42.49,41.05,36.54,35.25,34.91,32.75,31.87,31.36,30.41,30.29,29.42.

[0095] Synthesis route 2 is shown below:

[0096]

[0097] [Example 2]

[0098] Preparation of compound 3'

[0099] 4-Methylenediphenyl-2-(bromomethyl)-6-(tert-butyl)phenol (0.044 mol) was added to a three-necked flask equipped with a reflux condenser and toluene (200 ml). Triphenylphosphine (0.088 mol) was added to the stirred solution and the reaction was heated to 100°C for 2 hours. The reaction mixture was cooled to room temperature. The salt was collected by vacuum filtration and the excess triphenylphosphine was rinsed off with hexane; the phosphonium salt was dried under vacuum for >24 hours to ensure complete removal of residual solvent and water; the phosphonium salt was added to a round-bottom flask equipped with a stirring bar and a reflux condenser. The salt was suspended in the solvent and nBuLi (0.066 mol) was added. After 2 hours, the reactant 1-(benzyloxy)-7-bromo-3,5-bis(3,5-di-tert-butylphenyl)-2-naphthaldehyde (substance No. 1, 0.066 mol) was added under a nitrogen stream and the reaction was heated to reflux for 2 hours. The product No. 3' (0.033) was prepared with a yield of 75%.

[0100] δ H (400MHz,Chloroform-d)8.54(1H,s),7.73(4H,s),7.55(2H,s),7.48(3H,d,J7.5),7.45(1H,s),7.40(2H,t,J 7.5),7.31(5H,m),7.21(2H,m),7.14(4H,d,J 7.5),7.05(2H,d,J 15.1),6.93(2H,s),5.84(1H,s),5.41(1H,s),5.16(2H,s),1.40(9H,s),1.32(36H,s).

[0101] Preparation of compound 5'

[0102] At 0°C, dihydropyran (0.0561 mol) was added to a dichloromethane solution (80 ml) of the product 3' (0.033 mol), and p-toluenesulfonic acid (0.0132 mol) and pyridine (0.0132 mol) were added simultaneously. After the reaction was completed, the mixture was neutralized with 1M sodium hydroxide, extracted with dichloromethane and water, and the organic phase was washed with a saturated sodium chloride solution, concentrated, and passed through a column (petroleum ether: dichloromethane = 8:1). Product 4' (0.032 mol) was obtained with a yield of 97%.

[0103] Under nitrogen atmosphere, product 4' (0.032 mol) was dissolved in 60 ml dry THF, stirred at 0°C for 10 minutes, 2.2 M butyl lithium (21.81 ml) was slowly added dropwise, and after reacting for 2 hours, trimethylborate (18.3 mol / L, 2.63 ml) was slowly added dropwise. The reaction bottle was taken out and stirred at room temperature for 2 hours, and then 1 M hydrochloric acid solution was added to adjust the solution pH to 6, extracted with ether, dried and the solvent was spin-dried, and recrystallized from n-hexane to obtain a white solid 5' with a yield of 85% (0.027 mol).

[0104] δ H (400MHz,Chloroform-d)8.54(1H,s),7.73(4H,s),7.55(2H,s),7.48(3H,d,J7.5),7.45(1H,s),7.40(2H,t,J 7.5),7.31(5H,m),7.21(2H,m),7.14(4H,d,J7.5),7.05(2H,d,J 15.1),6.93(2H,s),5.80(1H,m),5.41(1H,s),5.16(2H,s),4.02(2H,s),3.74(1H,dd,J 12.4,7.1),3.64(1H,m),1.91(2H,m),1.78(2H,m),1.69(2H,m),1.57(2H,m),1.40(9H,s),1.32(36H,s).

[0105] Preparation of Compound 8'

[0106] To the solution of product 5' (0.027 mol) and reactant 6' (2-(4-(anthracen-9-yl)-2-bromophenoxy)tetrahydro-2H-pyran, 0.0275 mol) in ethylene glycol dimethyl ether (DME, 150 ml) were added catalyst Pd(dppf)2Cl2 (0.0000027 mol), 2M Na2CO3 15 ml, nitrogen atmosphere; reaction temperature 80°C, reaction time 4h, catalytic reaction using conventional, after the reaction was completed, ethyl acetate: water 2:1, 300 ml quenching reaction. Yield> 90%, column (petroleum ether: ethyl acetate = 10:1) to obtain product 7' (0.0243 mol). Then add pyridine p-toluenesulfonate (PPTS) (0.00625 mol) and methanol (0.1044 mol), react at 70°C for 4h. 300 ml of water was added to the reaction solution, and the mixture was stirred thoroughly to separate the layers. The aqueous phase was drained and extracted three times with 200 ml of ethyl acetate. The organic phase was concentrated and 0.4 L of methanol was added and stirred for 1 h. After filtration, methanol was added again for crystallization and purification to obtain product No. 8' (0.0198 mol) with a yield of 73.3%.

[0107] δH (400MHz,Chloroform-d)8.39(1H,s),8.33(1H,s),8.18(2H,d,J 8.7),8.03(2H,d,J 8.7),7.94(1H,s),7.73(4H,s),7.67(1H,s),7.58(1H,s),7.55(2H,d,J 7.5),7.48(3H,m),7.43(4H,m),7.40(2H,t,J 7.5),7.31(5H,m),7.21(3H,m),7.14(4H,d,J7.5),7.05(2H,d,J 15.1),6.93(2H,s),5.84(1H,s),5.41(1H,s),5.16(2H,s),4.58(1H,s),3.63(2H,t,J 7.1),2.87(2H,t,J 7.1),1.40(9H,s),1.32(36H,s).

[0108] Preparation of Compound 9'

[0109] Take reactant 8' (0.0198 mol) into 50 ml acetone, take dibromo (T1 = (1,11-dibromododecan-4,7-diyl) diphenyl, 0.026 mol, T2 = 1,3-bis(4-bromobutyl) cyclohexane, 0.027 mol), add 350 ml of 0.34 mol / L Cs2CO3 solution; reaction temperature 80℃ 8h. Cool to room temperature, evaporate most of the acetone, add 200 ml of a mixed solution of CH2Cl2 and water (1:1), separate the organic layer, extract the aqueous phase with CH2Cl2 3 times, remove the solvent under reduced pressure, purify the crude product by column chromatography, use petroleum ether: dichloromethane = 10:1, and obtain product 9' (0.015 mol), with a yield of 78%.

[0110] δ H(400MHz,Chloroform-d)8.39(2H,s),8.33(2H,s),8.18(4H,d,J 8.7),8.03(4H,d,J 8.7),7.94(2H,s),7.73(8H,s),7.67(2H,s),7.58(2H,s),7.55(4H,d,J 7.5),7.48(6H,m),7.43(8H,m),7.40(4H,t,J 7.5),7.31(10H,m),7.28(4H,m),7.25(4H,m),7.21(8H,m),7.14(8H,d,J 7.5),7.05(4H,d,J 15.1),6.93(4H,s),5.41(2H,s),5.16(4H,s),4.02(4H,m),3.63(4H,t,J 7.1),3.53(4H,m),2.87(4H,t,J 7.1),2.57(2H,m),1.92(4H,m),1.85(2H,m),1.82(4H,m),1.71(6H,m),1.56(4H,m),1.45(4H,m),1.42(6H,m),1.40(18H,s),1.36(6H,m),1.32(72H,s).

[0111] 13C NMR(100MHz,chloroform-d)δ155.11,152.79,152.03,151.86,146.87,146.79,1 43.52,139.00,138.73,137.60,137.34,137.05,136.69,136.62,136.49,136.03 ,135.99,135.91,135.52,133.42,132.92,131.87,130.93,130.30,129.79,129.62,128.90,128.85,128.82,128.81,128.60,128.40,128.37,127.87,127.53,12 7.34,127.31,127.18,127.16,127.14,127.07,126.88,126.79,126.26,125.73,125.58,125.44,124.47,123.56,123.21,121.71,121.34,74.95,72.53,72.46,7 1.02,68.08,56.68,46.36,46.04,38.31,35.32,34.93,34.90,34.67,33.77,33.60,33.53,32.83,32.66,31.27,30.41,29.46,29.21,27.24,25.17,24.64,22.65.

[0112] Preparation of Catalyst 10'

[0113] Take ligand 9' (0.015 mol), pd / C (0.0003 mol), EtOH (100 ml) in a hydrogenation reactor, replace with nitrogen 3 times, reaction H2 pressure 0.9 MPa, reaction temperature 70 ° C, reaction time 3 h, after filtering with a sintered filter head, cool the colorless solution to room temperature and filter to obtain debenzylated ligand (0.0133 mol), which is further dissolved in 50 ml of toluene, added to dichloromethane (200 ml) containing active metal source methyl calcium bromide (0.0333 mol) at a reaction temperature of 0 ° C, stirred and dispersed, reacted at 90 ° C under nitrogen protection for 5 h, filtered, washed once with 200 mL of anhydrous n-hexane, and filtered to obtain the target catalyst 10' (0.013 mol)

[0114] δ H(400MHz,Chloroform-d)8.39(1H,s),8.33(1H,s),8.18(2H,d,J 8.7),8.03(2H,d,J 8.7),7.94(1H,s),7.73(4H,s),7.67(1H,s),7.58(1H,s),7.55(2H,d,J 7.5),7.48(1H,s),7.43(4H,m),7.31(4H,m),7.28(2H,m),7.25(2H,m),7.21(4H,m),7.14(4H,d,J7.5),7.05(2H,d,J 15.1),6.93(2H,s),5.41(1H,s),4.02(2H,m),3.63(2H,t,J 7.1),3.53(2H,m),2.87(2H,t,J 7.1),2.57(1H,m),2.12(3H,s),1.92(2H,m),1.85(1H,m),1.82(2H,m),1.71(2H,m),1.56(2H,m),1.45(2H,m),1.42(3H,m),1.40(9H,s),1.36(3H,m),1.32(36H,s).

[0115] 13C NMR(100MHz,chloroform-d)δ155.11,152.23,152.03,151.86,146.87,146.7 9,143.52,139.28,138.73,137.75,137.34,136.99,136.80,136.70,136.69,1 35.91,135.52,134.39,132.92,131.87,131.36,130.02,129.79,129.62,129.52,128.94,128.85,128.82,128.81,128.60,128.40,127.83,127.53,127.29 ,127.18,127.16,127.14,127.07,126.88,126.79,126.42,126.26,125.73,124.47,123.56,123.37,123.21,121.60,120.29,72.53,72.46,71.02,68.08,5 6.68,46.36,46.04,38.31,35.32,34.93,34.90,34.67,33.77,33.60,33.53,32.83,32.66,31.27,30.41,29.46,29.21,27.24,25.17,24.64,22.65,20.72.

[0116] [Example 3]

[0117] The synthesis steps of Ti series metal catalysts are similar to those of Example 1. Ligand No. 9 (0.0085 mol), pd / C (0.0009 mol), and EtOH (100 ml) are placed in a hydrogenation reactor, replaced with nitrogen three times, and the reaction H2 pressure is 0.9 MPa, the reaction temperature is 50°C, and the reaction time is 3 h. After filtering with a sintered filter head, the colorless solution is cooled to room temperature and filtered to obtain the debenzylated ligand (0.0076 mol). The debenzylated ligand is further dissolved in 50 ml of toluene, and added to dichloromethane (100 ml) containing an active metal source TiCl4(THF)2 (0.0094 mol) at a reaction temperature of -15°C, stirred and dispersed, reacted at 60°C for 1 h, and then filtered, washed once with 200 mL of anhydrous n-hexane, and filtered to obtain the target catalyst 10 (0.006 mol).

[0118] [Example 4]

[0119] The synthesis method of zirconium metal catalyst is similar to that of Example 2. Finally, the active metal complex is to take ligand No. 9' (0.015 mol), Pd / C (0.00018 mol), EtOH (100 ml) in a hydrogenation reactor, replace with nitrogen 3 times, react with H2 pressure of 0.5 MPa, reaction temperature of 90°C, reaction time of 3 h, and filter with a sintered filter head. Then, the colorless solution is cooled to room temperature and filtered to obtain the debenzylated ligand (0.0133 mol), which is further dissolved in 50 ml of toluene. At a reaction temperature of 0°C, dichloromethane (200 ml) containing methyl calcium bromide (0.0019 mol) as an active metal source is added, stirred and dispersed, reacted for 5 h under nitrogen protection at 40°C, and then filtered, washed once with 200 mL of anhydrous n-hexane, and filtered to obtain the target catalyst 10' (0.013 mol).

[0120] [Example 5] The condensation reaction and lactide synthesis reaction are as follows: 300g of D,L-lactic acid aqueous solution (87wt%) are added to a 1L prepolymerization reactor, the system temperature is raised to 160°C and dehydrated at 50hpa to a water content of <0.1%. Under nitrogen protection, 0.286g of the prepared catalyst SnL2 (Example 1) is added, the system pressure is 30hpa, the reaction is carried out for 60min, and the molecular weight distribution of the lactic acid oligomer obtained by the prepolymerization reaction is about 1500, and the distribution coefficient is 1.21-1.27; finally, the prepolymerization reaction liquid is taken out and placed in a depolymerization reactor, the temperature is raised to 240°C, the system pressure is 25hpa, and the reaction is carried out for 30min to obtain crude lactide with an optical purity of 99.7%.

[0121] [Example 6] The condensation reaction and lactide synthesis reaction are as follows: 300g of D,L-lactic acid aqueous solution (87wt%) are added to a 1L prepolymerization reactor, the system temperature is raised to 150°C and dehydrated at 50hpa to a water content of <0.1%. Under nitrogen protection, 0.292g of the prepared catalyst CaL2 (Example 2) is added, the system pressure is 25hpa, the reaction is carried out for 60min, and the molecular weight distribution of the lactic acid oligomers obtained by the prepolymerization reaction is about 1500, and the distribution coefficient is 1.23-1.29; finally, the prepolymerization reaction liquid is taken out and placed in a depolymerization reactor, the temperature is raised to 200°C, the system pressure is 25hpa, and the reaction is carried out for 1h to obtain crude lactide with an optical purity of 99.6%.

[0122] [Example 7] The condensation reaction and lactide synthesis reaction are as follows: 300g of D,L-lactic acid aqueous solution (87wt%) are added to a 1L prepolymerization reactor, the system temperature is raised to 150°C and dehydrated at 100hpa to a water content of <0.1%. Under nitrogen protection, 0.295g of the prepared catalyst TiL2 (Example 3) is added, the system pressure is 25hpa, and the reaction is carried out for 3h. The molecular weight distribution of the lactic acid oligomer obtained by the prepolymerization reaction is about 1500, and the distribution coefficient is 1.29; finally, the prepolymerization reaction liquid is taken out and placed in a depolymerization reactor, the temperature is raised to 280°C, the system pressure is 25hpa, and the reaction is carried out for 2h to obtain crude lactide with an optical purity of 99.3%.

[0123] [Example 8] The condensation reaction and lactide synthesis reaction are as follows: 300g D,L-lactic acid aqueous solution (87wt%) is added to a 1L prepolymerization reactor, the system temperature is raised to 150°C and dehydrated at 50hpa to a water content of <0.1%. Under nitrogen protection, 0.304g of the prepared catalyst ZrL2 (Example 4) is added, the system pressure is 25hpa, the reaction is carried out for 60min, and the molecular weight distribution of the lactic acid oligomer obtained by the prepolymerization reaction is about 1500, and the distribution coefficient is 1.24; finally, the prepolymerization reaction liquid is taken out and placed in a depolymerization reactor, the temperature is raised to 260°C, the system pressure is 25hpa, and the reaction is carried out for 1h to obtain crude lactide with an optical purity of 99.4%.

[0124] [Comparative Example 1] The condensation reaction and lactide synthesis reaction are as follows: 300g of D,L-lactic acid aqueous solution (87wt%) are added to a 1L prepolymerization reactor, the system temperature is raised to 150°C and dehydrated at 50hpa to a water content of <0.1%. Under nitrogen protection, 0.294g of the prepared catalyst stannous octoate is added. The molecular weight distribution of the lactic acid oligomer obtained by the prepolymerization reaction is about 1500, and the distribution coefficient is 1.39-1.51; finally, the prepolymerization reaction liquid is taken out and placed in a depolymerization reactor, the temperature is raised to 260°C, the system pressure is 25hpa, and the reaction is carried out for 30min to obtain crude lactide with an optical purity of 49.6%.

[0125] It should be understood that the specific embodiments described above are only used to explain the present invention, and are not used to limit the present invention. Obvious changes or modifications derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims

1. An aryloxy cyclic ether skeleton metal complex catalyst, characterized in that: The catalyst structural formula is as follows: The catalyst active component M is selected from one or more of Sn, Zn, Ca, Ti, and Zr; R1 to R 12 Selected from hydrogen, halogen or any one of the following groups: C 1-6 Alkyl, C 3-10 Cycloalkyl, C 6-14 Aryl; T1 and T2 are each independently selected from divalent hydrocarbon groups having 1 to 20 atoms except hydrogen; X is halogen, methyl, benzyl.

2. The catalyst according to claim 1, characterized in that The active component M is one or more of Sn, Ca, Ti and Zr.

3. An aryloxy cyclic ether skeleton metal complex catalyst, characterized in that: The catalyst structural formula is as follows: The catalyst active component M is selected from one or more of Sn, Zn, Ca, Ti, and Zr; R1 to R 12 Any one selected from methyl, phenyl, fluorenyl, anthracenyl; T1 and T2 are each independently selected from divalent hydrocarbon groups having 1 to 20 atoms except hydrogen; X is halogen, methyl, benzyl.

4. An aryloxy cyclic ether skeleton metal complex catalyst, characterized in that: The catalyst structural formula is as follows: The catalyst active component M is selected from one or more of Sn, Zn, Ca, Ti, and Zr; R1 to R 12 Any one selected from tert-butyl, 3,5-di-tert-butylphenyl, benzyl, diphenylmethyl; T1 and T2 are each independently selected from divalent hydrocarbon groups having 1 to 20 atoms except hydrogen; X is halogen, methyl, benzyl.

5. The catalyst according to claim 1, characterized in that T1 and T2 are each independently selected from divalent hydrocarbon groups having 3 to 10 atoms excluding hydrogen.

6. The catalyst according to claim 1, characterized in that T1 and T2 are both 1,3-propylene, 1,4-butanediyl, 2,4-pentanediyl, 1,5-pentanediyl, 1,3-di(propylene)phenyl, and methylene trans-1,2-cyclohexanediyl.

7. The catalyst according to claim 1, characterized in that X is chlorine, methyl or benzyl.

8. The method for preparing a catalyst according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) reacting substituted brominated phenol, triphenylphosphine and aldehyde No. 1 in the presence of n-butyl lithium to prepare product No. 3; (2) reacting compound 3 with dihydropyran in the presence of p-toluenesulfonic acid and pyridine to prepare compound 4; (3) reacting compound 4 with trimethylborate in the presence of butyl lithium to obtain compound 5; (4) Compound 5 is reacted with Compound 6 under alkaline conditions in a solvent to obtain Compound 7, wherein the catalyst is (bis(diphenylphosphinothiocene)palladium dichloride); Compound 7 is reacted with pyridine p-toluenesulfonate in the presence of methanol to obtain Compound 8; (5) reacting compound 8 with a dibromo substituent in an alkaline solution to obtain compound 9; (6) Compound 9 is subjected to a hydrogenation reaction under Pd / C catalysis to prepare Compound 10; (7) Compound 10 is reacted with an active metal source at 50 to 90° C. for 3 to 5 hours to obtain the target catalyst; 9. The preparation method according to claim 8, characterized in that: In step (1), the molar ratio of substituted brominated phenol: aldehyde No. 1: triphenylphosphine: n-butyl lithium is 1: (1.1-1.5): (1.1-2): (1.1-1.5), the reaction temperature is 80-100° C., and the reaction time is 8-12 hours.

10. The preparation method according to claim 8, characterized in that: In step (2), the molar ratio of compound 3: dihydropyran: p-toluenesulfonic acid: pyridine is 1: (1.1-1.7): (0.1-0.4): (0.2-0.4), the reaction temperature is -10-0°C, and the reaction time is 1-3h.

11. The preparation method according to claim 8, characterized in that: In step (3), the molar ratio of compound 4: trimethylborate: butyl lithium is 1: (0.4-1.5): (0.9-1.5), the reaction temperature is -20-0°C, and the reaction time for each step is 0.5-2h.

12. The preparation method according to claim 8, characterized in that: In step (4), Na2CO3 provides alkaline conditions, the ratio is compound 5: compound 6: Na2CO3: catalyst = 1: (1.1-1.9): (2-4.8): (0.0005-0.001), the reaction temperature is 60-80°C, and the reaction time is 2-4h.

13. The preparation method according to claim 8, characterized in that: In step (4), the reaction is carried out at 60-70°C for 2-4 hours, and the molar ratio of compound 7: pyridine p-toluenesulfonate: methanol is 1: (0.1-0.25): (2-4.3).

14. The preparation method according to claim 8, characterized in that: In step (5), the reaction temperature is 40-80°C, the reaction time is 5-8h, and the ratio of reactant No. 8: dibromo substituent: base is 1: (1.3-2): (3-6).

15. The preparation method according to claim 14, characterized in that: The base is Cs2CO3.

16. The preparation method according to claim 8, characterized in that: In step (6), the reaction temperature is 50-70°C, the reaction time is 1-3h, the reaction H2 pressure is 0.5-0.9Mpa, and the molar ratio of compound 9:pd / C is 1:(0.1-0.2).

17. The preparation method according to claim 8, characterized in that: In step (7), the molar ratio of compound 10:active metal source=1:(1.2-2.5).

18. Use of the catalyst according to any one of claims 1 to 7 or the catalyst prepared by the preparation method according to any one of claims 8 to 17 in catalyzing the polycondensation of lactic acid monomers and the synthesis of lactide.

19. The use according to claim 18, characterized in that The polycondensation reaction temperature is 140-170°C, the reaction pressure is 30-50hPa, and the reaction time is 0.5-3h; and / or, in the lactide synthesis stage, the reaction temperature is 160-280°C, the reaction pressure is 10-25hPa, and the reaction time is 0.5-1h.

20. The use according to claim 19, characterized in that The polycondensation reaction temperature is 150°C to 160°C.

21. The use according to claim 19, characterized in that During the lactide synthesis stage, the reaction temperature is 160°C to 240°C.

22. The use according to any one of claims 18 to 21, characterized in that The amount of catalyst added in the polycondensation and lactide synthesis stages is 0.01% to 1%, calculated on the basis of the mass of lactic acid.

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