A monomolecular bifunctional organic catalyst, its preparation method and application

Abstract

The application discloses a single-molecule bifunctional organic catalyst, and a structural formula is shown in the following formula (I), wherein X is selected from a urea or thiourea containing group, a structural formula is shown in the following formula (II), Y is selected from a potassium alcoholate or sodium alcoholate group, a structural formula is shown in the following formula (III), and L is selected from an unsubstituted C2-C4 alkyl group; the single-molecule bifunctional organic catalyst disclosed by the application has a novel structure, has super-high activity and high controllability when catalyzing ring-opening polymerization of a lactone, and the highest turnover number (TON) can reach 900, and the highest turnover frequency (TOF) can reach 4860 min ‑1 , and the prepared polymer has high molecular weight and low molecular weight distribution.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic polymerization, in particular to a single-molecule bifunctional organic catalyst, its preparation method and its application in catalyzing cyclic lactone. BACKGROUND

[0002] Petroleum-based plastics have a relatively wide application in our daily life, and the global annual production of petrochemical-based plastics is close to 400 million tons. However, petroleum-based plastics cannot be automatically degraded after being released into the environment, leading to serious environmental problems. Therefore, it is increasingly necessary to develop sustainable polymers to reduce the dependence on petrochemical plastics. Ring-opening polymerization (ROP) of cyclic lactones is a method for synthesizing aliphatic polyesters, which are defined as sustainable polymers because they are derived from renewable resources and have the characteristics of biodegradability. In order to further expand the application of polyesters, developing new catalytic methods is a challenging research topic aimed at improving the synthesis efficiency of polymers and the precise control of polymer structure.

[0003] In the catalytic ring-opening polymerization of cyclic lactones, reactivity and controllability are often difficult to achieve. High-activity catalysts can accelerate the polymerization reaction. However, high activity may also lead to difficult-to-control reactions, easily causing side reactions such as ester exchange, making the molecular weight distribution of the polymer wide, and the properties of the final product difficult to predict. In order to achieve controllable polymerization, it is usually necessary to limit the reaction rate by fine-tuning the reaction conditions or using specially designed catalysts. This approach can ensure more controllable molecular weight, molecular weight distribution, and structure of the polymer, but may also reduce the reaction speed, resulting in a decrease in reaction efficiency.

[0004] Waymouth's group [Macromolecules 2006, 39, 8574-8583.] developed a thiourea / tertiary amine binary system catalyst that exhibits good control behavior in the ring-opening polymerization (ROP) of cyclic lactones. The synergistic mechanism of this catalyst system is that the tertiary amine activates the initiator / chain end, and the thiourea activates the monomer through hydrogen bonding. The ring-opening polymerization of cyclic lactones undergoes a three-molecule reaction, and the concentrations of thiourea and chain growth species are low, so the catalytic activity is low. And even if the tertiary amine and thiourea groups are combined in one molecule, the reactivity of this catalyst system is still relatively low.

[0005] In 2016, the Waymouth group developed an organic catalyst system combining alkoxide and thiourea [Nature Chemistry 2016, 8, 1047-1053.], which improved the catalytic efficiency of hydrogen-bonded organic catalysts to some extent compared with the thiourea / tertiary amine binary catalyst system, but the catalytic efficiency was still much lower than that of metal complex system. The turnover number (TON) was 90, and the turnover frequency (TOF) was 2. And this binary organic catalyst system usually needs to use 3-5 equivalents of (sulfur) urea catalyst (relative to alkoxide) to activate the initiator / chain end, so as to achieve good control of ROP. The excessive use of organic catalysts increases the production cost, and it is difficult to completely separate or remove after the reaction is completed, affecting the subsequent product purification step. SUMMARY

[0006] In view of the above problems existing in the prior art, the present application discloses a novel single-molecule bifunctional organic catalyst with a novel structure, which has ultra-high activity and high controllability in catalyzing ring lactone ring-opening polymerization reaction, the turnover number (TON) is as high as 900, the turnover frequency (TOF) can be as high as 4860 min-1, and the prepared polymer has high molecular weight and low molecular weight distribution.

[0007] The specific technical solutions are as follows:

[0008] A single-molecule bifunctional organic catalyst for ring lactone ring-opening polymerization, the structural formula is shown in the following formula (I):

[0009] X-L-Y (I);

[0010] In formula (I), X is selected from a urea or thiourea-containing group, and the structural formula is shown in the following formula (II):

[0011]

[0012] In formula (II):

[0013] N is a nitrogen atom;

[0014] R1 is selected from one or more of C6-C8 aromatic groups;

[0015] R2 is selected from O or S;

[0016] represents a connecting bond;

[0017] Y is selected from a potassium alkoxide or sodium alkoxide group, and the structural formula is shown in the following formula (III):

[0018]

[0019] In formula (III):

[0020] O is an oxygen atom;

[0021] R3 is selected from Na and / or K;

[0022] represents a connecting bond;

[0023] L is selected from unsubstituted C2-C4 alkyl.

[0024] The present application is based on long-term research on organic catalytic polymerization, and discloses a single-molecule bifunctional organic catalyst, which combines (thio) urea and alkoxide in a single-molecule catalyst / initiator, so as to realize effective intramolecular activation of the initiator / chain end. The catalyst can improve the catalytic efficiency and controllability, and reduce the amount of (thio) urea required for catalyzing ROP in the existing (thio) urea / alkoxide binary system.

[0025] Preferably, L is selected from unsubstituted C3 alkyl.

[0026] Specifically, the structural formula of the single-molecule bifunctional organic catalyst is selected from one or more of the following formula (I-1) to formula (I-9):

[0027]

[0028]

[0029] Preferably, the structural formula is selected from formula (I-1), (I-6), (I-7) or (I-8); further preferably, the structural formula is selected from formula (I-1), (I-6) or (I-8); more preferably, the structural formula is selected from formula (I-1) or (I-6).

[0030] It is found through experiments that, with the continuous optimization of the structural formula of the single-molecule bifunctional organic catalyst, the catalytic activity and controllability of the catalyst in the catalysis of ring lactone ring-opening polymerization reaction are continuously improved.

[0031] The present application also discloses a preparation method of the single-molecule bifunctional organic catalyst for ring lactone ring-opening polymerization, comprising the following steps:

[0032] Raw material 1 with the following formula W1 structure, raw material 2 with the following formula W2 structure and solvent A are mixed to obtain raw material liquid I, and after a Michael addition reaction, an intermediate product is obtained; the intermediate product, raw material 3 and solvent B are mixed to obtain raw material liquid II, and after a substitution reaction, the single-molecule bifunctional organic catalyst is obtained.

[0033]

[0034] In the formula, O, N and C respectively represent an oxygen atom, a nitrogen atom and a carbon atom.

[0035] R1 is selected from one or more of C6-C8 aromatic groups; R2 is selected from a sulfur atom or an oxygen atom; and R3 is selected from one or more of unsubstituted C2-C4 alkyl groups.

[0036] Preferably,

[0037] The raw material 1 is selected from one or more of 3,5-bis(trifluoromethyl)phenyl isothiocyanate, 3,4-dichlorophenyl isothiocyanate, 4-(trifluoromethyl)phenyl isothiocyanate, phenyl isothiocyanate, 3,5-bis(trifluoromethyl)phenyl isocyanate;

[0038] The raw material 2 is selected from one or more of 3-amino-1-propanol, 4-amino-1-butanol, 2-amino-1-ethanol;

[0039] The solvent A is selected from one or more of dichloromethane, tetrahydrofuran, acetone, methanol, ethanol, isopropanol;

[0040] The molar ratio of the raw material 1 to the raw material 2 is 1:(1.0-1.1); and the concentration of the raw material 2 in the raw material solution I is 0.8-1.2 mol / L;

[0041] The temperature of the Michael addition reaction is 0-80℃, and the Michael addition reaction is followed by a post-treatment process of removing impurities and organic solvents and drying treatment.

[0042] Preferably, the temperature of the Michael addition reaction is 25-60℃.

[0043] The raw material 3 is selected from sodium metal and / or potassium metal;

[0044] The solvent B is selected from one or more of tetrahydrofuran, dichloromethane, acetone, methanol, ethanol, toluene, chloroform;

[0045] The molar ratio of the intermediate product to the raw material 3 is 1:(0.9-1.0); and the concentration of the intermediate product in the raw material solution II is 1.0-2.0 mol / L;

[0046] The temperature of the substitution reaction is 0-30℃, and the substitution reaction is followed by a treatment of removing impurities and organic solvents, washing and drying.

[0047] Preferably, the substitution reaction is carried out at room temperature.

[0048] The application further discloses application of the monomolecular bifunctional organic catalyst in catalyzing ring lactone ring-opening polymerization reaction, and specifically refers to the following steps.

[0049] The ring lactone monomer and the monomolecular bifunctional organic catalyst are mixed to perform a polymerization reaction under autogenous pressure.

[0050] It is found through experiments that the monomolecular bifunctional organic catalyst disclosed in the application has the advantages of high catalytic efficiency and controllable reaction, which is reflected in that the molecular weight of the prepared polymer can be accurately controlled by regulating the molar ratio of the cyclic lactone monomer (if there are multiple monomers, it is the total number of moles of multiple monomers) to the initiator. It is found through tests that the actual number average molecular weight determined by gel permeation chromatography is basically consistent with the theoretical number average molecular weight. The catalytic efficiency is controlled by regulating the catalyst concentration, the reactant concentration, the reaction time and the reaction temperature.

[0051] Preferably, the cyclic lactone is selected from one or more of L-lactide, valerolactone, caprolactone; and further preferably, the cyclic lactone is L-lactide.

[0052] It is found through experiments that when the cyclic lactone monomer used is L-lactide, the prepared polylactic acid is a stereoregular crystalline polymer.

[0053] Preferably, the molar ratio of the cyclic lactone monomer to the monomolecular bifunctional organic catalyst is 100-2000:1. Within this range, the monomolecular bifunctional organic catalyst disclosed in the application has excellent catalytic activity.

[0054] Further preferably, the molar ratio of the cyclic lactone monomer to the monomolecular bifunctional organic catalyst is 500-1000:1.

[0055] When the polymerization reaction is solution polymerization, a solvent commonly used in the art for solution polymerization reaction can also be added.

[0056] Preferably, the temperature of the polymerization reaction is 25-60℃.

[0057] Compared with the prior art, the application has the following advantages:

[0058] (1) The application discloses a monomolecular bifunctional organic catalyst which can catalyze the homopolymerization of cyclic lactone, and the catalyst exhibits high activity and good reaction controllability in the ring-opening polymerization (ROP) of cyclic ester. The ultra-high activity of the organic catalyst is comparable to that of metal complexes, with a turnover number (TON) of up to 900 and a turnover frequency (TOF) of up to 4860 min-1; and the reaction controllability is high, and the polyester with a customized structure, a predictable molecular weight, a narrow molecular weight distribution, less racemization and minimal transesterification reaction can be prepared. The synthesis process of the catalyst is simple and scalable, and the ROP activity can be widely adjusted.

[0059] (2) The monomolecular bifunctional organic catalyst disclosed in the application will undergo a two-molecule reaction in the ring-opening polymerization of cyclic lactone, in which the concentration of the lactone is high, and the amount of (sulfo) urea required for catalyzing ROP in the prior thiourea / alkoxide binary system is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 This is a schematic diagram of the principle using the single-molecule bifunctional organic catalyst prepared in Example 1 as an example;

[0061] Figure 2 The single-molecule bifunctional organic catalyst prepared in Example 1 1 H NMR spectrum;

[0062] Figure 3 The single-molecule bifunctional organic catalyst prepared in Example 2 1 H NMR spectrum;

[0063] Figure 4 The single-molecule bifunctional organic catalyst prepared in Example 3 1 H NMR spectrum;

[0064] Figure 5 The single-molecule bifunctional organic catalyst prepared in Example 4 1 H NMR spectrum;

[0065] Figure 6 The single-molecule bifunctional organic catalyst prepared in Example 5 1 H NMR spectrum;

[0066] Figure 7 The single-molecule bifunctional organic catalyst prepared in Example 6 1 H NMR spectrum;

[0067] Figure 8 The single-molecule bifunctional organic catalyst prepared in Example 7 1 H NMR spectrum;

[0068] Figure 9 The single-molecule bifunctional organic catalyst prepared in Example 8 1 H NMR spectrum;

[0069] Figure 10 The single-molecule bifunctional organic catalyst prepared in Example 9 1 H NMR spectrum;

[0070] Figure 11 Homonuclear decoupling of the methylene peak of polylactic acid prepared in Example 1 1 H NMR spectrum. Detailed Implementation

[0071] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0072] Example 1 Synthesis of Catalyst 1

[0073] Step 1: Synthesis of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3- hydroxypropyl)thiourea.

[0074] To a solution of 3-amino-1-propanol (0.75 g, 0.01 mol) in anhydrous CH2Cl2(10 mL) under N2atmosphere, 3,5-bis(trifluoromethyl)phenyl isothiocyanate (2.71 g, 0.01 mol) was added. The resulting stock solution I was allowed to react at 45 °C with stirring for 24 h. The resulting reaction mixture was concentrated under vacuum. The product was collected and dried under vacuum at 40 °C until constant weight (3.38 g, 98% yield).

[0075] Step 2: Synthesis of Catalyst 1

[0076] To a Schlenk flask equipped with a stir bar was added a solution of 1-(3,5- bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)thiourea (3.46 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). The flask was placed under N2atmosphere and sodium (0.22 g, 0.0095 mol) was added. The resulting stock solution II was allowed to react at 25 °C for 4 h and then cooled to room temperature. The resulting reaction mixture was concentrated under vacuum to obtain a crude solid product which was further purified by washing with isopropyl ether three times. The product was then concentrated under vacuum for 2 h to obtain a yellowish solid product 3.58 g (97% yield).

[0077] The reaction scheme for the preparation of the catalyst in this example is shown below:

[0078]

[0079] Figure 1 A schematic diagram of the principle of the monomolecular bifunctional organic catalyst prepared in this example. As can be seen, this is a completely new structure of catalyst / initiator structure. Figure 1

[0080] The properties of Catalyst 1 prepared in this example are as follows: 1 The H NMR spectrum is shown in Figure 2

[0081] Synthesis of Catalyst 2 in Example 2

[0082] Step 1: 1-(3,5-bis(trifluoromethyl)phenyl)-3-(2-hydroxyethyl)thiourea.

[0083] ​​To a solution of 2-amino-1-ethanol (0.61 g, 0.01 mol) in dry CH2Cl2(10 mL) under N2atmosphere was added 3,5-bis(trifluoromethyl)phenyl isothiocyanate (2.71 g, 0.01 mol). The resulting stock solution I was allowed to react at 45 °C with stirring for 24 h. The resulting reaction mixture was concentrated under vacuum. The product was collected and dried under vacuum at 40 °C until constant weight (3.28 g, 99% yield).

[0084] Step 2: Synthesis of catalyst 2

[0085] To a Schlenk flask equipped with a stir bar was added a solution of 1-(3,5- bis(trifluoromethyl)phenyl)-3-(2-hydroxyethyl)thiourea (3.32 g, 0.01 mol) in dry tetrahydrofuran (10 mL). The flask was placed under N2atmosphere and sodium (0.22 g, 0.0095 mol) was added. The resulting stock solution II was allowed to react at 25 °C for 4 h and then cooled to room temperature. The resulting reaction mixture was concentrated under vacuum to obtain a crude solid product which was further purified by washing with isopropyl ether 3 times. The product was then concentrated under vacuum for 2 h to obtain a yellowish solid product 3.48 g (98% yield). The reaction scheme for the preparation of catalyst 2 in this example is shown below:

[0086]

[0087] The properties of catalyst 2 prepared in this example are summarized in Table 1. 1 The H NMR spectrum is shown in Figure 1. Figure 3

[0088] Example 3 Synthesis of catalyst 3

[0089] Step 1: 1-(3,5-bis(trifluoromethyl)phenyl)-3-(4-hydroxybutyl)thiourea

[0090] To a solution of 4-amino-1-butanol (0.89 g, 0.01 mol) in dry CH2Cl2(10 mL) under N2atmosphere was added 3,5-bis(trifluoromethyl)phenyl isothiocyanate (2.71 g, 0.01 mol). The resulting stock solution I was allowed to react at 45 °C with stirring for 24 h. The resulting reaction mixture was concentrated under vacuum. The product was collected and dried under vacuum at 40 °C until constant weight (3.52 g, 98% yield).

[0091] Step 2: Synthesis of catalyst 3

[0092] ​A Schlenk flask equipped with a stir bar was charged with a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(4-hydroxybutyl)thiourea (3.60 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). The flask was placed under a N2atmosphere and sodium (0.22 g, 0.0095 mol) was added. The resulting stock solution II was allowed to react for 4 h at 25 °C and then cooled to room temperature. The resulting reaction mixture was concentrated in vacuo to give a crude solid product which was further purified by washing with isopropyl ether three times. The product was then concentrated in vacuo for 2 h to give a yellow solid product 3.80 g (99% yield). The reaction scheme for the preparation of catalyst in this example is shown below:

[0093]

[0094] The properties of catalyst 3 prepared in this example are shown in Table 1. 1 The H NMR spectrum is shown in Figure 1. Figure 4

[0095] Example 4 Synthesis of catalyst 4

[0096] Step 1: 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)thiourea

[0097] A Schlenk flask equipped with a stir bar was charged with a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(4-hydroxybutyl)thiourea (3.60 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). The flask was placed under a N2atmosphere and sodium (0.22 g, 0.0095 mol) was added. The resulting stock solution II was allowed to react for 4 h at 25 °C and then cooled to room temperature. The resulting reaction mixture was concentrated in vacuo to give a crude solid product which was further purified by washing with isopropyl ether three times. The product was then concentrated in vacuo for 2 h to give a yellow solid product 3.80 g (99% yield). The reaction scheme for the preparation of catalyst in this example is shown below:

[0098] Step 2: Synthesis of catalyst 4

[0099] A Schlenk flask equipped with a stir bar was charged with a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(4-hydroxybutyl)thiourea (3.60 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). The flask was placed under a N2atmosphere and sodium (0.22 g, 0.0095 mol) was added. The resulting stock solution II was allowed to react for 4 h at 25 °C and then cooled to room temperature. The resulting reaction mixture was concentrated in vacuo to give a crude solid product which was further purified by washing with isopropyl ether three times. The product was then concentrated in vacuo for 2 h to give a yellow solid product 3.80 g (99% yield). The reaction scheme for the preparation of catalyst in this example is shown below:

[0100]

[0101] The properties of catalyst 4 prepared in this example are shown in Table 1. 1 ​H NMR spectrum is shown in Figure 5

[0102] Example 5 Synthesis of Catalyst 5

[0103] Step 1: 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)urea

[0104] To a solution of 3-amino-1-propanol (0.75 g, 0.01 mol) in dry CH2Cl2(10 mL) under N2atmosphere was added 3,5-bis(trifluoromethyl)phenyl isocyanate (2.55 g, 0.01 mol). The resulting stock solution I was allowed to react at 45 °C with stirring for 24 h. The resulting reaction mixture was concentrated under vacuum. The product was collected and dried under vacuum at 40 °C until constant weight (1.95 g, 59% yield).

[0105] Step 2: Synthesis of Catalyst 5

[0106] To a Schlenk flask equipped with a stir bar was added a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)urea (1.95 g, 0.006 mol) in dry tetrahydrofuran (10 mL). The flask was placed under N2atmosphere and sodium (0.13 g, 0.0057 mol) was added. The resulting stock solution II was allowed to react at 25 °C for 4 h and then cooled to room temperature. The resulting reaction mixture was concentrated under vacuum to give a crude solid product which was further purified by washing with isopropyl ether 3 times. The product was then concentrated under vacuum for 2 h to give a yellow solid product 2.03 g (98% yield). The reaction scheme for the preparation of the catalyst in this example is shown below:

[0107]

[0108] The H NMR spectrum of the catalyst 5 prepared in this example is shown in 1 Figure 6

[0109] Example 6 Synthesis of Catalyst 6

[0110] Step 1: 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)urea

[0111] The preparation process is exactly the same as Step 1 in Example 5.

[0112] Step 2: Synthesis of Catalyst 6

[0113] ​​​Into a Schlenk flask equipped with a stir bar was added a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)urea (1.95 g, 0.006 mol) in anhydrous tetrahydrofuran (10 mL). The flask was placed under a N2atmosphere and potassium (0.22 g, 0.0057 mol) was added. The resulting stock solution II was allowed to react for 4 h at 25 °C and then cooled to room temperature. The resulting reaction mixture was concentrated in vacuo to give a crude solid product which was further purified by washing with isopropyl ether three times. The product was then concentrated in vacuo for 2 h to give a yellow solid product 2.13 g (98% yield). The reaction scheme for the preparation of catalyst in this example is shown below:

[0114]

[0115] The H NMR spectrum of the catalyst 6 prepared in this example is shown in Figure 1. 1 H NMR spectrum of the catalyst 6 prepared in this example is shown in Figure 1. Figure 7

[0116] Example 7 Synthesis of catalyst 7

[0117] Step 1: 1-(3,4-dichlorophenyl)-3-(3-hydroxypropyl)thiourea

[0118] Into a Schlenk flask equipped with a stir bar was added a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)urea (1.95 g, 0.006 mol) in anhydrous tetrahydrofuran (10 mL). The flask was placed under a N2atmosphere and potassium (0.22 g, 0.0057 mol) was added. The resulting stock solution II was allowed to react for 4 h at 25 °C and then cooled to room temperature. The resulting reaction mixture was concentrated in vacuo to give a crude solid product which was further purified by washing with isopropyl ether three times. The product was then concentrated in vacuo for 2 h to give a yellow solid product 2.13 g (98% yield). The reaction scheme for the preparation of catalyst in this example is shown below:

[0119] Step 2: Synthesis of catalyst 7

[0120] Into a Schlenk flask equipped with a stir bar was added a solution of 1-(3,5-bis(trifluoromethyl)phenyl)-3-(3-hydroxypropyl)urea (1.95 g, 0.006 mol) in anhydrous tetrahydrofuran (10 mL). The flask was placed under a N2atmosphere and potassium (0.22 g, 0.0057 mol) was added. The resulting stock solution II was allowed to react for 4 h at 25 °C and then cooled to room temperature. The resulting reaction mixture was concentrated in vacuo to give a crude solid product which was further purified by washing with isopropyl ether three times. The product was then concentrated in vacuo for 2 h to give a yellow solid product 2.13 g (98% yield). The reaction scheme for the preparation of catalyst in this example is shown below:

[0121]

[0122] The H NMR spectrum of the catalyst 7 prepared in this example is shown in Figure 2.​1 H NMR spectrum is shown in Figure 8

[0123] Synthesis of Catalyst 8

[0124] Step 1 : 1 -(3-Hydroxypropyl)-3-(4-(trifluoromethyl)phenyl)thiourea

[0125] To a solution of 3-amino-1-propanol (0.75 g, 0.01 mol) in dry CH2CI2(10 mL) under N2atmosphere was added phenyl isothiocyanate (1.35 g, 0.01 mol). The resulting stock solution I was allowed to react at 45 °C with stirring for 24 h. The resulting reaction mixture was concentrated under vacuum. The product was collected and dried under vacuum at 40 °C until constant weight (2.05 g, 98% yield).

[0126] Step 2: Synthesis of Catalyst 8

[0127] To a Schlenk flask equipped with a stir bar was added a solution of 1 -(3- hydroxypropyl)-3-(4-(trifluoromethyl)phenyl)thiourea (2.78 g, 0.01 mol) in dry tetrahydrofuran (10 mL). The flask was placed under N2atmosphere and sodium (0.22 g, 0.0095 mol) was added. The resulting stock solution II was allowed to react at 25 °C for 4 h and then cooled to room temperature. The resulting reaction mixture was concentrated under vacuum to give a crude solid product which was further purified by washing with isopropyl ether 3 times. The product was then concentrated under vacuum for 2 h to give a yellow solid product 2.98 g (99% yield). The preparation reaction of catalyst in this example is shown in the following scheme:

[0128]

[0129] The properties of the catalyst 8 prepared in this example are as follows: 1 H NMR spectrum is shown in Figure 9

[0130] Synthesis of Catalyst 9

[0131] Step 1 : 1 -(3-Hydroxypropyl)-3-phenylthiourea

[0132] To a solution of 3-amino-1-propanol (0.75 g, 0.01 mol) in dry CH2CI2(10 mL) under N2atmosphere was added phenyl isothiocyanate (1.35 g, 0.01 mol). The resulting stock solution I was allowed to react at 45 °C with stirring for 24 h. The resulting reaction mixture was concentrated under vacuum. The product was collected and dried under vacuum at 40 °C until constant weight (2.05 g, 98% yield).

[0133] ​​Step 2: Synthesis of catalyst 9

[0134] To a Schlenk flask equipped with a stir bar was added a solution of 1-(3- hydroxypropyl)-3-phenylthiourea (2.10 g, 0.01 mol) in anhydrous tetrahydrofuran (10 mL). The flask was placed under a N2atmosphere and sodium (0.22 g, 0.0095 mol) was added. The resulting reaction mixture was allowed to react for 4 h at 25 °C and then cooled to room temperature. The resulting reaction mixture was concentrated under vacuum to give a crude solid product which was further purified by washing with isopropyl ether three times. The product was then concentrated under vacuum for 2 h to give a yellow solid product 2.30 g (99% yield). The reaction scheme for the preparation of catalyst in this example is shown below:

[0135]

[0136] The properties of catalyst 9 prepared in this example are as follows: 1 The H NMR spectrum is shown in Figure 1. Figure 10

[0137] Comparative Example 1 Binary system TU-1 / KOCH3

[0138] In the article "Fast and selective ring-opening polymerizations by alkoxides and thioureas", Waymouth et al. used a binary catalytic system TU-1 / KOCH3, the structure of which is shown below:

[0139]

[0140] Comparative Example 2 Binary system TU-1 / NaOCH3

[0141] In the article "Fast and selective ring-opening polymerizations by alkoxides and thioureas", Waymouth et al. used a binary catalytic system TU-1 / NaOCH3, the structure of which is shown below:

[0142]

[0143] Application Example 1: Use of catalyst 1 to catalyze the ring opening of L-lactide to produce polylactic acid (PLLA)

[0144] ​In a glove box under N2atmosphere, 10 mL pressure tube with a magnet was dried in an oven at 110 °C overnight, then immediately put into the glove box. After keeping under vacuum for 2-3 hours, the pressure tube was moved into the N2atmosphere glove box. In a 10 mL pressure tube with a magnet, catalyst 1 (1.0 mg, 2.76 μmol), L-lactide (L-LA, 200 mg, 1.38 mmol), dichloromethane (DCM, 1.0 mL) were added. The reaction mixture was stirred at 25 °C for 5 seconds. Then a portion of the sample was taken from the crude product and quenched with benzoic acid to determine the conversion of L-lactide by1H NMR. 1 The composition of the crude product was determined by1H NMR spectrum. The crude product was dissolved in CH2Cl2, and the polymer was precipitated from cooled ethanol. The product was collected by centrifugation, and finally the obtained polymer was dried to constant weight in a vacuum drying oven at 40 °C. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography, and the test results are shown in Table 1.

[0145] Figure 11 Homonuclear decoupling of methylene peaks prepared for this application example 1 The1H NMR spectrum confirmed that the application example prepared was a crystalline polylactic acid.

[0146] Application Examples 2-9: Use of catalysts 2-9 to catalyze the ring opening of L-lactide to generate PLLA

[0147] The preparation process is basically the same as that of application example 1, except that the catalysts for the polymerization reaction are replaced in turn by catalysts 2-9 (the molar ratio of L-LA to each catalyst is 500:1). The molecular weight and molecular weight distribution of the polymer prepared in each application example were determined by gel chromatography, and the test results are shown in Table 1.

[0148] Application Examples 10-12: Use of catalyst 1, catalyst 6, and catalyst 8 to catalyze the ring opening of L-lactide to generate PLLA

[0149] The preparation process is basically the same as that of application examples 1, 6, and 8, except that the molar ratio of monomer to catalyst for the polymerization reaction is replaced by 1000:1, and the specific reaction time is shown in Table 1. The molecular weight and molecular weight distribution of the polymer prepared in each application example were determined by gel chromatography, and the test results are shown in Table 1.

[0150] Application Example 13: Use of catalyst 6 to catalyze the ring opening of valerolactone to generate polyvalerolactone (PVL)

[0151] A 10 mL pressure tube with a magnetic bar was dried in an oven at 110 °C overnight under N2atmosphere and immediately placed in the glovebox. After 2-3 hours under vacuum, the pressure tube was moved into the N2atmosphere glovebox. In a 10 mL pressure tube equipped with a magnetic bar, catalyst 6 (6.1 mg, 0.0167 mmol), valerolactone (VL, 500 mg, 5 mmol), DCM (1.0 mL) were added. The reaction mixture was stirred at 25 °C for 300 s. Then a portion of the sample was taken from the crude product and quenched with benzoic acid to determine the conversion of VL by1H NMR. 1 The composition of the crude product was determined by1H NMR spectroscopy. The crude product was dissolved in CH2Cl2and the polymer was precipitated from cooled ethanol. The product was collected by centrifugation and the resulting polymer was finally oven-dried to constant weight in a vacuum drying oven at 40 °C. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography. The results are shown in Table 1.

[0152] Application Example 14: PVL production by ring-opening of valerolactone catalyzed by catalyst 6

[0153] The preparation process was essentially the same as in Application Example 13, except that the molar ratio of monomer to catalyst was replaced by 500:1 and the reaction mixture was stirred at 60 °C for 360 s. The molecular weight and molecular weight distribution of the polymer produced in this application example were determined by gel chromatography. The results are shown in Table 1.

[0154] Application Example 15: PCL production by ring-opening of caprolactone catalyzed by catalyst 6

[0155] A 10 mL pressure tube with a magnetic bar was dried in an oven at 110 °C overnight under N2atmosphere and immediately placed in the glovebox. After 2-3 hours under vacuum, the pressure tube was moved into the N2atmosphere glovebox. In a 10 mL pressure tube equipped with a magnetic bar, catalyst 6 (5.4 mg, 0.015 mmol), caprolactone (CL, 500 mg, 4.38 mmol), DCM (1.0 mL) were added. The reaction mixture was stirred at 25 °C for 1200 s. Then a portion of the sample was taken from the crude product and quenched with benzoic acid to determine the conversion of CL by1H NMR. 1 The composition of the crude product was determined by1H NMR spectroscopy. The crude product was dissolved in CH2Cl2and the polymer was precipitated from cooled ethanol. The product was collected by centrifugation and the resulting polymer was finally oven-dried to constant weight in a vacuum drying oven at 40 °C. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography. The results are shown in Table 1.

[0156] Application Example 16: PCL production by ring-opening of caprolactone catalyzed by catalyst 6

[0157] The preparation process is basically the same as that in application example 15, except that the molar ratio of monomer and catalyst is replaced by 500:1, and the reaction mixture is stirred at 60℃ for 1800s. The molecular weight and molecular weight distribution of the polymer prepared in this application example are determined by gel chromatography, and the test results are shown in Table 1.

[0158] Application Comparative Example 1: PLLA is generated by ring-opening of L-lactide using TU-1 / potassium methoxide binary catalytic system

[0159] The preparation process is basically the same as that in application example 1, except that the catalyst for polymerization is replaced by TU-1 / potassium methoxide (molar ratio of L-LA, TU-1 and potassium methoxide is 500:5:1) provided in application comparative example 1, and the reaction mixture is stirred at 25℃ for 45min. The molecular weight and molecular weight distribution of the polymer are determined by gel chromatography, and the test results are shown in Table 2.

[0160] Application Comparative Example 2: PLLA is generated by ring-opening of L-lactide using TU-1 / sodium methoxide binary catalytic system

[0161] The preparation process is basically the same as that in application example 1, except that the catalyst for polymerization is replaced by TU-1 / sodium methoxide (molar ratio of L-LA, TU-1 and sodium methoxide is 200:10:1) provided in application comparative example 2, and the reaction mixture is stirred at 25℃ for 360s. The molecular weight and molecular weight distribution of the polymer are determined by gel chromatography, and the test results are shown in Table 2.

[0162] Table 1

[0163]

[0164]

[0165] Note: 1 Conv.(%): Monomer conversion is calculated by the formula 1 H NMR determination. 2 Turnover number (TON) = (mole number of consumed monomer) / (mole number of catalyst). 3 Turnover frequency (TOF) = (mole number of consumed monomer) / (mole number of catalyst·min). 4 Mn Theo : Theoretical number average molecular weight is calculated by the formula MW mon × [M]0 / [I]0 × conv. 5 M n GPC : Number average molecular weight is determined by gel permeation chromatography. 6 PDI: Molecular weight distribution is determined by gel permeation chromatography.

[0166] Table 2

[0167]

[0168] The above description is merely that of several specific embodiments of the present application. It is to be understood that numerous variants and modifications can be made by those skilled in the art, all of which are intended to be included within the scope of the present application, without departing from the scope of the present application as defined in the claims.

Claims

1. A monomolecular bifunctional organic catalyst for the ring-opening polymerization of cyclic lactones, characterized in that, The structural formula is shown in the following formula (I): （Ⅰ）； In formula (I), X is selected from a urea or thiourea-containing group, and the structural formula is shown in the following formula (II): （Ⅱ）； In formula (II), N is a nitrogen atom; R1 is selected from one or more of 3,5-bis(trifluoromethyl)phenyl, 3,4-dichlorophenyl, and 4-(trifluoromethyl)phenyl; R2 is selected from O or S; Y is selected from a potassium alcoholate or sodium alcoholate group, and the structural formula is shown in the following formula (III): represents a bond; In formula (III), O is an oxygen atom; （Ⅲ）； R3 is selected from Na and / or K; L is selected from an unsubstituted C2-C4 alkyl group. L is selected from an unsubstituted C3 alkyl group. represents a bond; The structural formula is selected from one or more of the following formulas (I-1) to (I-9):

2. The monomolecular bifunctional organic catalyst for ring-opening polymerization of a cyclic lactone according to claim 1, characterized by The structural formula is selected from the following formulas (I-1), (I-6), (I-7), or (I-8).

3. The monomolecular bifunctional organic catalyst for ring-opening polymerization of a cyclic lactone according to claim 1, wherein The structural formula is selected from the following formulas (I-1), (I-6), or (I-8). （Ⅰ-1）； （Ⅰ-2）； （Ⅰ-3）； （Ⅰ-4）； （Ⅰ-5）； （Ⅰ-6）； （Ⅰ-7）； （Ⅰ-8）； （Ⅰ-9）。 4. The monomolecular bifunctional organic catalyst for ring-opening polymerization of a cyclic lactone according to claim 3, characterized by The structural formula is selected from the following formulas (I-1) or (I-6).

5. The monomolecular bifunctional organic catalyst for ring-opening polymerization of a cyclic lactone according to claim 3, wherein The method comprises the following steps:

6. The monomolecular bifunctional organic catalyst for ring-opening polymerization of a cyclic lactone according to claim 3, wherein Raw material 1 having the following formula W1 structure, raw material 2 having the following formula W2 structure, and solvent A are mixed to obtain raw material solution I, and after a Michael addition reaction, an intermediate product is obtained; 7. A method for preparing a monomolecular bifunctional organic catalyst for ring-opening polymerization of a cyclic lactone according to claim 1, characterized by, The intermediate product, raw material 3, and solvent B are mixed to obtain raw material solution II, and after a substitution reaction, the monomolecular bifunctional organic catalyst is obtained; In the formula, O, N, and C respectively represent an oxygen atom, a nitrogen atom, and a carbon atom; R1 is selected from one or more of 3,5-bis(trifluoromethyl)phenyl, 3,4-dichlorophenyl, and 4-(trifluoromethyl)phenyl; R2 is selected from a sulfur atom or an oxygen atom; and R3 is selected from one or more of unsubstituted C2-C4 alkyl groups; ； Solvent A is selected from one or more of dichloromethane, tetrahydrofuran, acetone, methanol, ethanol, and isopropanol; Solvent B is selected from one or more of tetrahydrofuran, dichloromethane, acetone, methanol, ethanol, toluene, and chloroform; Raw material 3 is selected from sodium metal and / or potassium metal.

8. The method for preparing a monomolecular bifunctional organic catalyst for ring lactone ring-opening polymerization according to claim 7, characterized in that: Raw material 1 is selected from one or more of 3,5-bis(trifluoromethyl)phenyl isothiocyanate, 3,4-dichlorophenyl isothiocyanate, 4-(trifluoromethyl)phenyl isothiocyanate, phenyl isothiocyanate, and 3,5-bis(trifluoromethyl)phenyl isocyanate; Raw material 2 is selected from one or more of 3-amino-1-propanol, 4-amino-1-butanol, and 2-amino-1-ethanol; The molar ratio of raw material 1 to raw material 2 is 1: (1.0-1.1); and the concentration of raw material 2 in raw material solution I is 0.8-1.2 mol / L; The temperature of the Michael addition reaction is 0-80°C; The molar ratio of the intermediate product to raw material 3 is 1: (0.9-1.0); and the concentration of the intermediate product in raw material solution II is 1.0-2.0 mol / L; The temperature of the substitution reaction is 0-30°C. The ring lactone is selected from one or more of L-lactide, valerolactone, and caprolactone. The ring lactone is L-lactide.

9. Use of a single-molecule bifunctional organocatalyst according to any one of claims 1 to 6 for catalyzing the ring-opening polymerization of a cyclic lactone, characterized in that, ​ 10. Use of the monomolecular bifunctional organocatalyst according to claim 9 for catalysing the ring-opening polymerization of lactones, characterized in that, ​

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