Pyridine-phenol compounds, polyesters prepared therefrom, and methods of making and using the same

Abstract

The present application discloses a pyridine-phenol compound, a polyester prepared from the pyridine-phenol compound, and a preparation method and application thereof. The pyridine-phenol compound has a structure shown in formula (I): in formula (I), R 1 is selected from amino, dimethylamino or pyrrolidinyl; R 2 is selected from nitro, fluoro or trifluoromethyl; R 3 is selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl or fluoro; R 4 is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl or fluoro. The pyridine-phenol compound of the present application is a highly efficient organic catalyst, which can catalyze ring-opening polymerization of a cyclic monomer to prepare an aliphatic polyester, the conversion rate of the cyclic monomer is high, and the synthesized polyester has a low dispersion index (PDI). The catalyst of the present application is not sensitive to the environment (stable to air and water), does not contain metal, has mild reaction conditions, high reaction selectivity and fast polymerization speed.

Description

Technical Field

[0001] This invention relates to the field of polyester preparation technology, specifically to pyridine-phenol compounds, polyesters prepared therefrom, their preparation methods, and applications. Background Technology

[0002] Aliphatic polyester polymers, such as polyvalve lactone (PVL) and polylactide (PLA), are increasingly being used in the field of environmentally friendly materials due to their excellent biocompatibility and biodegradability. These polyesters can be modified to obtain materials with specific functions, which can be used as drug carriers, tissue engineering materials, medical sutures, and alternatives to medical screws. Furthermore, the small molecule compounds obtained from the depolymerization of these polyester materials can be recycled and reused to alleviate the growing environmental and energy crises.

[0003] Currently, the main methods for preparing aliphatic polyesters include polycondensation and ring-opening polymerization. Compared to polycondensation of chain monomers, polyesters prepared by ring-opening polymerization of cyclic monomers have a narrow molecular weight distribution, mild reaction conditions, and no byproduct formation. Metal catalysts, such as stannous octoate, antimony trioxide, and aluminum alkoxy, are commonly used in ring-opening polymerization. However, the use of these metal catalysts easily leads to metal residues, thus limiting their application in biology, medicine, microelectronics, and other fields. Organic catalysts, due to their availability, ease of preparation, and safety (non-toxicity), are gradually becoming alternatives to metal catalysts. Since Hedrick first reported 4-dimethylaminopyridine (DMAP) as an organic catalyst for the ring-opening polymerization of lactide in 2001, the variety of organic catalysts catalyzing the ring-opening polymerization of lactones has increased significantly, with common examples including carbene, phosphazenes, bifunctional thioureaamines, guanidines, and Brønsted acids (Macromolecules, 2000, 33, 4316-4320; Polymer Chemistry, 2014, 5, 3098-3106). However, some of these catalysts use expensive raw materials, some are extremely sensitive to air and water, and some have poor activity. Considering industrial applications, the preparation of highly efficient organic catalysts using natural products or inexpensive industrial products (with mature industrial preparation technologies) as raw materials is of great significance in the catalytic preparation of aliphatic polyesters. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of expensive, unstable, and poorly active raw materials for polyester organic catalysts in existing technologies, and to provide pyridine-phenol compounds, polyesters prepared therefrom, their preparation methods, and applications. The pyridine-phenol compounds of this invention are inexpensive, readily available, and simple to prepare. They can be used as catalysts for ring-opening polymerization to prepare polyesters, exhibiting high catalytic activity, stability to air and water, metal-free composition, and mild reaction conditions. They also result in high conversion rates of cyclic monomers and polymers with high yields and narrow molecular weight distributions.

[0005] To achieve the above objectives, a first aspect of the present invention provides a pyridine-phenol compound having the structure shown in formula (I):

[0006]

[0007] In equation (I), R 1 Selected from amino, dimethylamino, or pyrrolidinyl; R 2 Selected from nitro, fluorine, or trifluoromethyl; R 3 Selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl, or halogen; R 4 It is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl, or halogen.

[0008] A second aspect of the present invention provides a method for preparing a pyridine-phenol compound, the method comprising: reacting a pyridine derivative with a phenol derivative to obtain a pyridine-phenol compound; wherein the pyridine-phenol compound has the structure shown in formula (I); the pyridine derivative has the structure shown in formula (II); and the phenol derivative has the structure shown in formula (III).

[0009]

[0010] Among them, R 1 Selected from amino, dimethylamino, or pyrrolidinyl; R 2 Selected from nitro, fluorine, or trifluoromethyl; R 3 Selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl, or halogen; R 4 It is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl, or halogen.

[0011] A third aspect of the present invention provides a pyridine-phenol compound prepared by the aforementioned preparation method.

[0012] The fourth aspect of the present invention provides the use of the aforementioned pyridine-phenol compounds in the preparation of polyesters.

[0013] The fifth aspect of the present invention provides a method for preparing a polyester, the method comprising: performing a ring-opening polymerization reaction on a cyclic monomer in the presence of a catalyst to obtain a polyester; wherein the catalyst is the aforementioned pyridine-phenol compound.

[0014] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0015] (1) The pyridine-phenol compound of the present invention uses industrially available organic bases and weak acid phenol as raw materials to prepare the catalyst in one step through a simple acid-base reaction. The preparation method is simple, easy to operate, and the raw materials are inexpensive and readily available, and there are no by-products.

[0016] (2) The pyridine-phenol compound of the present invention is a highly efficient organic catalyst that can catalyze the ring-opening polymerization of cyclic monomers to prepare aliphatic polyesters. The conversion rate of cyclic monomers is high, and the synthesized polyester has a low dispersion index (PDI). The catalyst is not sensitive to the environment (stable to air and water), does not contain metals, has mild reaction conditions, high reaction selectivity, and fast polymerization rate, which greatly enhances the process feasibility of the reaction and reduces industrial production costs. Attached Figure Description

[0017] Figure 1 The 4-dimethylaminopyridine-p-nitrophenol salt (catalyst 1a) obtained in Example 1 of this invention was prepared. 1 HNMR spectrum;

[0018] Figure 2 The polyvalerol obtained in Example 1 of this invention 1 HNMR spectrum;

[0019] Figure 3 The polylactide obtained in Example 2 of this invention 1 HNMR spectrum;

[0020] Figure 4 The spectrum of polyvalerol obtained in Example 1 of this invention is obtained in size exclusion chromatography. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] A first aspect of the present invention provides a pyridine-phenol compound having the structure shown in formula (I):

[0023]

[0024] In equation (I), R 1 Selected from amino, dimethylamino, or pyrrolidinyl; R 2 Selected from nitro, fluorine, or trifluoromethyl; R 3 Selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl, or halogen; R 4 It is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl, or halogen.

[0025] In this invention, the halogen is selected from fluorine, chlorine, bromine or iodine.

[0026] In some embodiments of the present invention, R 1 Selected from amino, dimethylamino, or pyrrolidinyl; R 2 Selected from nitro, fluorine, or trifluoromethyl; R 3 Selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl, or fluorine; R 4 It is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl, or fluorine.

[0027] In some embodiments of the present invention, the pyridine-phenol compound has at least one of the structures shown in Formula I-1 to Formula I-3:

[0028]

[0029] A second aspect of the present invention provides a method for preparing a pyridine-phenol compound, the method comprising: reacting a pyridine derivative with a phenol derivative to obtain a pyridine-phenol compound; wherein the pyridine-phenol compound has the structure shown in formula (I); the pyridine derivative has the structure shown in formula (II); and the phenol derivative has the structure shown in formula (III).

[0030]

[0031] Among them, R 1 Selected from amino, dimethylamino, or pyrrolidinyl; R 2 Selected from nitro, fluorine, or trifluoromethyl; R 3 Selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl, or halogen; R 4 It is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl, or halogen.

[0032] In this invention, the halogen is selected from fluorine, chlorine, bromine or iodine.

[0033] In some embodiments of the present invention, R 1 Selected from amino, dimethylamino, or pyrrolidinyl; R 2 Selected from nitro, fluorine, or trifluoromethyl; R 3 Selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl, or fluorine; R 4 It is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl, or fluorine.

[0034] The method of the present invention uses industrially readily prepared organic bases (such as 4-pyrrolidinylpyridine or 4-dimethylaminopyridine) and weak acid phenol as raw materials to prepare pyridine-phenol compounds in one step through a simple acid-base reaction.

[0035] The pyridine base and the various substituted phenols selected in this invention are all raw materials with relatively mature industrial synthesis technology. The organic base pyridine and the weak acid phenol can be reacted in one step to produce pyridine-phenol compounds. The preparation method of this invention is simple, easy to operate, and the raw materials are inexpensive and readily available, with no by-products.

[0036] In some embodiments of the present invention, the molar ratio of the pyridine derivative to the phenol derivative is 0.5-2:1.

[0037] In some embodiments of the present invention, the reaction temperature is 25-80°C and the time is 6-24 hours.

[0038] In some embodiments of the present invention, the reaction is carried out in a solvent selected from one or more of tetrahydrofuran, dichloromethane, trichloromethane, and toluene.

[0039] A third aspect of the present invention provides a pyridine-phenol compound prepared by the aforementioned preparation method.

[0040] In some embodiments of the present invention, the pyridine-phenol compound has one of the structures shown in Formula I-1 to Formula I-3:

[0041]

[0042] The pyridine-phenol compound of the present invention is a highly efficient organic catalyst that is stable to air and water, contains no metals, and operates under mild reaction conditions. It can catalyze the ring-opening polymerization of cyclic monomers to prepare aliphatic polyesters.

[0043] The fourth aspect of the present invention provides the use of the aforementioned pyridine-phenol compounds in the preparation of polyesters.

[0044] The fifth aspect of the present invention provides a method for preparing a polyester, the method comprising: performing a ring-opening polymerization reaction on a cyclic monomer in the presence of a catalyst to obtain a polyester; wherein the catalyst is the aforementioned pyridine-phenol compound.

[0045] The pyridine-phenol compound of this invention is a highly efficient organic catalyst that can catalyze the ring-opening polymerization of cyclic monomers to prepare aliphatic polyesters. In the pyridine-phenol compound, the protonated pyridine can act as a hydrogen bond donor to activate the carbonyl group of the cyclic monomer, and the phenoxy anion acts as a hydrogen bond acceptor to activate the initiator alcohol, promoting its nucleophilic attack on the carbonyl group of the cyclic monomer. The protonated pyridine base and the phenoxy anion constitute a bifunctional catalyst.

[0046] This invention utilizes an inexpensive, readily available, and easily prepared catalyst to catalyze the ring-opening polymerization of cyclic monomers to synthesize polyesters. Using pyridine-phenol as the catalyst for the ring-opening polymerization reaction results in mild reaction conditions, high selectivity, and a fast polymerization rate, yielding polymers with precise molecular weights and low dispersibility. Furthermore, the pyridine-phenol produced in this process is not environmentally sensitive, significantly enhancing the feasibility of the reaction. As an inexpensive and easily prepared catalyst, it can reduce costs in industrial production.

[0047] In some embodiments of the present invention, the cyclic monomer is selected from cyclic lactones, cyclic lactides, or cyclic carbonates.

[0048] Furthermore, the cyclic lactone has the structure shown in formula (IV), the cyclic lactone has the structure shown in formula (V), and the cyclic carbonate has the structure shown in formula (VI);

[0049]

[0050] In equation (IV), A represents the general formula [-(CR 7 R 8 )-] n The structure shown is given, where n is an integer from 2 to 10; R 7 and R 8 Each is independently selected from hydrogen, C1-C5 substituted or unsubstituted straight-chain or branched alkyl groups;

[0051] In equation (V), A and B are each independently general formula [-(CR 7 R 8 ))-] m The structure shown is given, where m is an integer from 1 to 10, and A and B may be the same or different; R 7 and R 8 Selected from hydrogen, and C1-C5 substituted or unsubstituted straight-chain or branched alkyl groups;

[0052] In equation (VI), R 5 and R 6 Each is independently selected from hydrogen, substituted or unsubstituted straight-chain or branched alkyl groups of C1-C5, hydroxyl groups or halogens.

[0053] R 7 and R 8 Selected from the same or different groups. R 5 and R 6 Selected from the same or different groups.

[0054] In some embodiments of the present invention, the cyclic monomer is valproic acid lactone, caprolactone, octyl lactone, decyl lactone, nonanolactone, dodecyl lactone, 3-methyl-5-valproic acid lactone, lactide, glycolide, or a six-membered cyclic carbonate.

[0055] Preferably, the cyclic monomer is δ-valerolactone, ε-caprolactone, or L-lactide.

[0056] In this invention, the conversion rate of the cyclic monomer is 80-99%, preferably 90-98%.

[0057] In some embodiments of the present invention, the molar ratio of the cyclic monomer to the catalyst is 100-1000:1.

[0058] In some embodiments of the present invention, the ring-opening polymerization reaction is carried out at a temperature of 80-300°C for a time of 0.5-24 hours.

[0059] In this invention, polyesters include, but are not limited to: polyvalerol, polycaprolactone, polyoctyl lactone, polydecyl lactone, polynonolactone, polydodecyl lactone, poly3-methyl-5-valerolactone, polylactide, polyglycolic acid, or polyhexacyclic carbonate.

[0060] In this invention, the ring-opening polymerization reaction is carried out in the presence of a solvent or in the absence of a solvent; when polymerization is carried out in the presence of a solvent, the solvent includes, but is not limited to, one or more of the following: acetone, cyclohexanone, dioxane, tetrahydrofuran, benzene, toluene, xylene, dichloromethane, chloroform, tetrachloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and acetonitrile; preferably tetrahydrofuran, toluene, dichloromethane, chloroform, or N,N-dimethylformamide.

[0061] In this invention, the ring-opening polymerization reaction can be carried out with or without an initiator; when the ring-opening polymerization reaction is carried out in the presence of an initiator, the initiator includes, but is not limited to, one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, benzyl alcohol, phenethyl alcohol, ethylene glycol, 5-hexen-1-ol, and water. Preferably, the molar ratio of the initiator to the catalyst is 0.01-10:1.

[0062] In this invention, the ring-opening polymerization reaction is carried out under vacuum with a vacuum degree of 1-500 Pa; or it is carried out under a protective gas (inert gas, such as Ar) with a pressure of 100-101325 Pa.

[0063] In the solution prior to the ring-opening polymerization reaction, the initial reaction concentration of the cyclic monomer is 0.1 mol / L-100 mol / L. After the ring-opening polymerization reaction is completed, a terminator, namely triethylamine, is added. A precipitation solvent, such as methanol, ethanol, diethyl ether, or n-hexane, is added after the terminator.

[0064] The sixth aspect of the present invention provides a polyester prepared by the aforementioned preparation method, wherein the number-average molecular weight of the polyester is 1,000-100,000 g / mol, the molecular weight distribution coefficient is 1-2, and the metal content is 0.

[0065] Using the pyridine-phenol compound of the present invention as a catalyst, the conversion rate of cyclic monomers is high (80-99%), and the corresponding polyester dispersion index (PDI) is low.

[0066] This invention enables the efficient synthesis of polyesters by using the aforementioned pyridine-phenol compound as a catalyst. Compared with polyesters synthesized using metal-containing catalysts, the polyesters obtained by the method of this invention have no metal residues, a narrow molecular weight distribution, and no chain transesterification reaction, and have broad application prospects. They also have great commercial application potential in the fields of biomedicine and microelectronics.

[0067] The seventh aspect of the present invention provides the application of the aforementioned polyester in biomedical materials or plastic packaging materials.

[0068] The polyester obtained by the method of the present invention can be used as a biomedical material or a plastic packaging material, especially a biodegradable food packaging material. For example, polycaprolactone (PCL) and polylactide (PLA) can be used as biodegradable surgical sutures. Polycaprolactone can also be used as a medical surgical splint, and polylactide can also be used as a food packaging bag, straw, lunch box, etc.

[0069] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the following description.

[0070] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0071] The 1H NMR spectra involved in the following examples were measured using a Bruker Ascend™-400 1H NMR spectrometer, and the deuterated reagents used were deuterated chloroform (CDCl3) and deuterated dimethyl sulfoxide (DMSO-d6).

[0072] Preparation Example 1

[0073] 4-Dimethylaminopyridine (1.22 g, 10 mmol, 1.0 equiv) and 4-nitrophenol (1.39 g, 10 mmol, 1.0 equiv) were added to a 50 mL reaction flask. Tetrahydrofuran (20 mL) was used as the solvent, and the mixture was stirred at room temperature for 2 hours to obtain a white precipitate. The precipitate was filtered, washed three times with tetrahydrofuran (20 mL), and dried under vacuum for 6 hours to obtain catalyst 1a (2.4 g, 91% yield) with the structure shown in Formula I-1.1 H NMR spectrum as follows Figure 1 As shown, 1 H NMR(400MHz,Chloroform-d)δ8.14(s,4H),6.89(s,4H),6.60(s,1H),3.14(s,6H). By Figure 1 As can be seen, the presence of hydrogen signals in the aromatic region of the pyridine salt, as well as methyl hydrogen signals and aryl hydrogen signal groups of the phenoxy anion, indicates that catalyst 1a with the structure shown in Formula I-1 is obtained.

[0074] Preparation Example 2

[0075] 4-Dimethylaminopyridine (1.22 g, 10 mmol, 1.0 equiv) and 4-nitrophenol (1.39 g, 10 mmol, 1.0 equiv) were added to a 50 mL reaction flask. Tetrahydrofuran (20 mL) was used as the solvent, and the mixture was stirred at room temperature for 2 hours to obtain a white precipitate. The precipitate was filtered, washed three times with tetrahydrofuran (20 mL), and dried under vacuum for 6 hours to obtain catalyst 1b (2.4 g, 91% yield) with the structure shown in Formula I-2.

[0076] Preparation Example 3

[0077] 4-Dimethylaminopyridine (1.22 g, 10 mmol, 1.0 equiv) and 4-nitrophenol (1.39 g, 10 mmol, 1.0 equiv) were added to a 50 mL reaction flask. Tetrahydrofuran (20 mL) was used as the solvent, and the mixture was stirred at room temperature for 2 hours to obtain a white precipitate. The precipitate was filtered, washed three times with tetrahydrofuran (20 mL), and dried under vacuum for 6 hours to obtain catalyst 1c (2.4 g, 91% yield) with the structure shown in Formula I-3.

[0078] Preparation of Comparative Example 1

[0079] Following the method of Preparation Example 1, except that 4-dimethylaminopyridine was replaced with chloropyridine to obtain catalyst D1.

[0080] Example 1

[0081] Catalyst 1a (0.0261 g, 0.1 mmol, 1.0 equiv), δ-valerolactone (0.91 mL, 10.0 mmol, 100 equiv), and benzyl alcohol (1.03 μL, 0.1 mmol, 1.0 equiv) were added to a reaction flask without solvent. The mixture was stirred at 100 °C for 6 hours under argon protection. The reactants were concentrated and poured into methanol. The precipitate was filtered and dried to constant weight to obtain a white polyvalerolactone product. The conversion rate of δ-valerolactone was 91%. The number-average molecular weight (Mn) of polyvalerolactone was 6600 g / mol, and the PDI of dispersity was 1.04 (size exclusion chromatography, Waterscolumn: 5 mm, 300 × 7.8 mm, tetrahydrofuran as mobile phase, 0.7 mL·min). -1 (Polystyrene was used as a standard). The obtained polyvalerol... 1 H NMR such as Figure 2 As shown, the obtained size exclusion chromatogram is as follows: Figure 4 As shown, by Figure 2 It is evident that this polymer has high purity and low monomer residue. (From...) Figure 4 It can be seen that the number-average molecular weight is 6.6 kg / mol and the molecular weight distribution coefficient is 1.04.

[0082] Example 2

[0083] Catalyst 1b (0.0287 g, 0.1 mmol, 1.0 equiv), lactide (4.32 mL, 30.0 mmol, 300 equiv), and n-butanol (9.1 mg, 0.1 mmol, 1.0 equiv) were added to a reaction flask and dissolved in 2.0 mL of tetrahydrofuran. The mixture was stirred at 25 °C for 48 hours under argon protection. The reactants were then concentrated and poured into diethyl ether. The precipitate was filtered and dried to constant weight to obtain a white polylactide product. The conversion rate of lactide was 97%, the number-average molecular weight (Mn) of the polylactide was 43200 g / mol, and the PDI of the polylactide was 1.34. The obtained polylactide... 1 H NMR such as Figure 3 As shown, by Figure 3 It is evident that the polymer has high purity and low monomer residue.

[0084] Example 3

[0085] Catalyst 1c (0.0291 g, 0.1 mmol, 1.0 equiv), ε-caprolactone (0.33 mL, 3.0 mmol, 30 equiv), and propynyl alcohol (5.8 μL, 0.1 mmol, 1.0 equiv) were added to a reaction flask and dissolved in 1.0 mL of toluene. The mixture was stirred at 25 °C for 24 hours under argon protection. The reactants were then concentrated and poured into ethanol. The precipitate was filtered and dried to constant weight to obtain a white polycaprolactone product. The conversion rate of ε-caprolactone was 95%, the number-average molecular weight (Mn) of polycaprolactone was 4720 g / mol, and the dispersion (PDI) was 1.17.

[0086] Example 4

[0087] Catalyst 1c (0.0145 g, 0.05 mmol, 1.0 equiv), lactide (720 mg, 5 mmol, 100 equiv), and methanol (2.05 μL, 0.05 mmol, 1.0 equiv) were added to a reaction flask. Bulk polymerization was carried out at 150 °C without solvent, and the reaction was stirred at 25 °C for 1 hour under argon protection. The reaction was terminated by adding triethylamine. The reactants were concentrated and poured into diethyl ether. The precipitate was filtered and dried to constant weight to obtain a white polylactide product. The conversion rate of lactide was 99%, the number average molecular weight (Mn) of polylactic acid was 14500 g / mol, and the dispersion (PDI) was 1.04.

[0088] Example 5

[0089] Catalyst 1c (0.0145 g, 0.05 mmol, 1.0 equiv), valerolactone (150 mg, 1.5 mmol, 30 equiv), and benzyl alcohol (5.2 μL, 0.05 mmol, 1.0 equiv) were added to a reaction flask and dissolved in 1.5 mL of dichloromethane. The mixture was stirred at 200 °C for 2 hours under argon protection. The reaction was terminated by adding triethylamine. The reactants were concentrated and poured into methanol. The precipitate was filtered and dried to constant weight to give 0.102 g of white polyvalerolactone product. The conversion rate of valerolactone was 95%. The number-average molecular weight (Mn) of polyvalerolactone was 4300 g / mol, and the dispersion (PDI) was 1.16.

[0090] Example 6

[0091] Catalyst 1a (0.0261 g, 0.1 mmol, 1.0 equiv), valerate (0.45 mL, 5 mmol, 50 equiv), and 1-propanol (7.5 μL, 0.1 mmol, 1.0 equiv) were added to a 10 mL polymerization tube. The mixture was heated to 80 °C under an argon atmosphere and reacted for 40 minutes. The reaction was then terminated by adding triethylamine. 1The conversion rate of polyvalerate was 98% as determined by ¹H NMR spectroscopy. The polymer was dissolved in dichloromethane of a sufficient quantity, and the solution was poured into cold methanol. The precipitate was filtered and dried in a vacuum oven to constant weight, yielding 0.38 g of polyvalerate with a number-average molecular weight (Mn) of 5120 g / mol and a dispersion of 1.08.

[0092] Example 7

[0093] Catalyst 1a (2.61 g, 10.0 mmol, 100.0 equiv), butylated dodecyl lactone (5.949 g, 30.0 mmol, 300 equiv), and 5-hexen-1-ol (12.0 μL, 0.1 mmol, 1.0 equiv) were added to a reaction flask and dissolved in 3.0 mL of chloroform. The mixture was stirred at 25 °C for 16 hours under argon protection, and the reaction was terminated by adding triethylamine. The reactants were concentrated and poured into n-hexane. The precipitate was filtered and dried to constant weight to obtain a white polypentanolide product. The conversion rate of butylated dodecyl lactone was 80%, the number-average molecular weight (Mn) of polybutylated dodecyl lactone was 46700 g / mol, and the dispersion (PDI) was 1.12.

[0094] Example 8

[0095] Catalyst 1b (2.87 g, 10 mmol, 1.0 equiv), six-membered ring carbonate (3.06 g, 30.0 mmol, 300 equiv), and phenylethanol (11.9 μL, 0.1 mmol, 1.0 equiv) were added to a reaction flask and dissolved in 5.0 mL of dichloromethane. The mixture was stirred at room temperature for 12 hours under argon protection, and the reaction was terminated by adding triethylamine. The reactants were concentrated and poured into n-hexane. The precipitate was filtered and dried to constant weight to obtain a white polypentanolide product. The conversion rate of the six-membered ring carbonate was 91%, the number-average molecular weight (Mn) of poly(butylene dodecyl lactone) was 92900 g / mol, and the dispersion (PDI) was 1.21.

[0096] Example 9

[0097] Catalyst 1c (0.0145 g, 0.05 mmol, 1.0 equiv) and valerolactone (150 mg, 1.5 mmol, 30 equiv) were added to a reaction flask without an initiator. The mixture was dissolved in 5 mL of dichloromethane and stirred at 0 °C for 24 hours under argon protection. The reaction was terminated by adding triethylamine. The reactants were concentrated and poured into methanol. The precipitate was filtered and dried to constant weight to obtain a white polyvalerolactone product. The conversion rate of valerolactone was 87%, the number-average molecular weight (Mn) of polyvalerolactone was 3800 g / mol, and the dispersion (PDI) was 1.09.

[0098] Comparative Example 1

[0099] The preparation method was the same as in Example 1, except that catalyst 1a was replaced with catalyst D1 obtained in Comparative Example 1. The conversion rate of δ-valerolactone was 46%, the number-average molecular weight was 1560 g / mol, and the PDI of dispersion was 1.34.

[0100] The results of the above embodiments and comparative examples are listed in Table 1.

[0101] Table 1

[0102]

[0103] As can be seen from the results in Table 1, the catalyst of the present invention achieves a monomer conversion rate of over 80%, which is higher than that of Comparative Example 1. Compared with Comparative Example 1, the present application has significantly better performance.

[0104] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. The application of pyridine-phenol compounds in the preparation of polyesters, characterized in that, The pyridine-phenol compound has the structure shown in formula (I): In equation (I), R 1 Selected from amino, dimethylamino, or pyrrolidinyl; R 2 Selected from nitro, fluorine, or trifluoromethyl; R 3 Selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl, or halogen; R 4 It is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl, or halogen.

2. The application according to claim 1, wherein, R 3 Selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl, or fluorine; R 4 It is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl, or fluorine.

3. The application according to claim 1, wherein, The pyridine-phenol compound has one or more of the structures shown in Formula I-1 to Formula I-3: 。 4. The application according to claim 1, wherein, The method for preparing the pyridine-phenol compound includes: A pyridine derivative is reacted with a phenol derivative to obtain a pyridine-phenol compound; wherein the pyridine-phenol compound has the structure shown in formula (I); the pyridine derivative has the structure shown in formula (II); and the phenol derivative has the structure shown in formula (III). Among them, R 1 Selected from amino, dimethylamino, or pyrrolidinyl; R 2 Selected from nitro, fluorine, or trifluoromethyl; R 3 Selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl, or halogen; R 4 It is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl, or halogen.

5. The application according to claim 4, wherein, The molar ratio of the pyridine derivative to the phenol derivative is 0.5-2:

1.

6. The application according to claim 4 or 5, wherein, The reaction is carried out at a temperature of 25-80℃ for 6-24 hours. And / or, the reaction is carried out in a solvent selected from one or more of tetrahydrofuran, dichloromethane, trichloromethane, and toluene.

7. A method for preparing polyester, characterized in that, The preparation method includes: performing a ring-opening polymerization reaction on a cyclic monomer in the presence of a catalyst to obtain a polyester; wherein the catalyst is a pyridine-phenol compound, and the pyridine-phenol compound has the structure shown in formula (I): （I） In equation (I), R 1 Selected from amino, dimethylamino, or pyrrolidinyl; R 2 Selected from nitro, fluorine, or trifluoromethyl; R 3 Selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl, or halogen; R 4 It is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl, or halogen.

8. The preparation method according to claim 7, wherein, R 3 Selected from hydrogen, methoxy, methyl, isopropyl, tert-butyl, or fluorine; R 4 It is selected from hydrogen, methoxy, methyl, ethyl, isopropyl, tert-butyl, or fluorine.

9. The preparation method according to claim 7, wherein, The pyridine-phenol compound has one or more of the structures shown in Formula I-1 to Formula I-3: 。 10. The preparation method according to claim 7, wherein, The cyclic monomer is selected from cyclic lactones, cyclic lactides, or cyclic carbonates.

11. The preparation method according to claim 10, wherein, The cyclic lactone has the structure shown in formula (IV), the cyclic lactone has the structure shown in formula (V), and the cyclic carbonate has the structure shown in formula (VI). In formula (IV), A is the general formula [ (CR 7 R 8 ) ] n The structure shown is given, where n is an integer from 2 to 10; R 7 and R 8 Each is independently selected from hydrogen, substituted or unsubstituted straight-chain or branched alkyl groups of C1-C5; In formula (V), A and B are each independently general formulas. (CR 7 R 8 ) ] m The structure shown is given, where m is an integer from 1 to 10, and A and B may be the same or different; R 7 and R 8 Selected from hydrogen, and C1-C5 substituted or unsubstituted straight-chain or branched alkyl groups; In equation (VI), R 5 and R 6 Each is independently selected from hydrogen, substituted or unsubstituted straight-chain or branched alkyl groups of C1-C5, hydroxyl groups or halogens.

12. The preparation method according to claim 7, wherein, The cyclic monomers are valproic acid lactone, caprolactone, octyl lactone, decyl lactone, nonanolactone, dodecalactone, 3-methyl-5-valproic acid lactone, lactide, glycolide, or six-membered cyclic carbonates.

13. The preparation method according to claim 12, wherein, The cyclic monomer is δ-valerolactone, ε-caprolactone, or L-lactide.

14. The preparation method according to claim 7, wherein, The molar ratio of the cyclic monomer to the catalyst is 100-1000:1; And / or, the ring-opening polymerization reaction is carried out at a temperature of 80-300℃ for a time of 0.5-24h; And / or, the ring-opening polymerization reaction is carried out in the presence of an initiator selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, benzyl alcohol, phenethyl alcohol, ethylene glycol, 5-hexen-1-ol, and water.

15. The preparation method according to claim 14, wherein, The molar ratio of the initiator to the catalyst is 0.01-10:1.

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