Dimethyl biphenyl-naphthalene-salen ligand, salen catalyst and preparation method and application thereof

Abstract

The application provides a dimethyl biphenyl-naphthalene-Salen ligand, a Salen catalyst and a preparation method and application thereof, and relates to the field of catalysts. The dimethyl biphenyl-naphthalene-Salen ligand and the Salen catalyst are synthesized by using dimethyl biphenyl diamine and naphthalene salicylaldehyde derivatives for the first time, the types of the Salen ligand and the Salen catalyst are enriched, and a series of poly(3-hydroxybutyric acid) (P3HB) polymers with continuously adjustable stereoregularity can be conveniently prepared by adjusting the enantiomeric excess (ee) of the Salen catalyst. The application not only establishes an efficient and controllable way for the synthesis of customized P3HB, but also provides a scalable method for accurate stereoregulation in polymer synthesis.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically, to a dimethylbiphenyl-naphthyl-Salen ligand, a Salen catalyst, its preparation method, and its application. Background Technology

[0002] The properties of polymers are influenced by multi-level structural parameters, among which stereoregularity is particularly critical to crystallinity, thermal properties, and mechanical properties. For example, isotactic polypropylene exhibits semi-crystalline properties and a melt transition temperature (TNT). T m） The temperature range is 130–175 °C, while atactic polypropylene is amorphous and lacks a defined phase. T m This fully demonstrates that stereoregularity directly determines material properties. With the increasing prominence of environmental problems and the depletion of non-renewable resources, polyhydroxyalkanoates (PHAs), due to their inherent biodegradability and excellent biocompatibility, have become a greener and more sustainable polymer. They possess perfect stereoregularity (…). P m Natural poly-3-hydroxybutyric acid (P3HB) with a content greater than 0.99% exhibits excellent thermal properties and tensile strength. T m At 180 °C, the ultimate tensile strength (σ) B） With a strength of 30.3 MPa, its performance is comparable to that of commercially available isotactic polypropylene. However, it has not yet been achieved using inexpensive and readily available racemic four-membered ring lactone monomers. β -Butyrolactone ( rac -BBL) stereoselective ring-opening polymerization yields perfectly isotactic P3HB. Although those skilled in the art have devoted considerable effort to designing numerous catalyst systems for rac -BBL exhibits stereoselective ring-opening polymerization, but catalyst systems capable of inducing isoselectivity are still scarce. Therefore, designing novel catalyst structures for... rac -Identical selective ring-opening polymerization of BBL is particularly important.

[0003] Recent studies have also found that isotactically enriched P3HB exhibits superior ductility compared to natural P3HB, further demonstrating the influence of stereoregularity on material properties. In addition to thermal and mechanical properties, researchers have also revealed the effect of stereoregularity on the adhesion properties of P3HB. Therefore, precise control of stereoselectivity is crucial for fully realizing the molecular tunability of materials. Common methods for stereoselectivity regulation include adjusting the enantiomeric excess (ee) value of chiral monomers and designing stereoselective catalysts. However, the former method typically requires multi-step synthesis of enantiomeric enriched monomers, and the final polymer is limited to isotactic and isotactically enriched products. Furthermore, the design of stereoselective catalysts requires laborious synthesis of catalysts with different structures, and catalyst structures must be designed from scratch for different stereoselectivity targets. Although a large amount of research has been dedicated to developing stereoselective catalysts, constructing high-performance stereoselective catalysts is fraught with trial and error and remains a long and arduous task. Therefore, new stereoselectivity control strategies are urgently needed to circumvent the shortcomings of these traditional synthetic routes.

[0004] Although the inventors had previously studied Salen catalysts based on spirocyclic diamines, the synthesis of spirocyclic diamines was cumbersome and costly. Therefore, there was a need to explore new, inexpensive, readily available, and commercially viable catalyst structures. Summary of the Invention

[0005] The purpose of this invention is to provide a dimethylbiphenyl-binaphthyl-Salen ligand, a Salen catalyst, a method for preparing the same, and its applications. By synthesizing the dimethylbiphenyl-binaphthyl-Salen ligand and the corresponding Salen catalyst, and by adjusting the enantiomeric excess (ee) of the Salen catalyst, a series of P3HB polymers with continuously tunable stereoregularity can be conveniently prepared.

[0006] The technical problem solved by this invention is achieved by the following technical solution.

[0007] In a first aspect, embodiments of this application provide a dimethylbiphenyl-binaphthyl-Salen ligand, the general structural formula of which is shown in Formula I: Formula I; Among them, R 1 It is any one of hydrogen, alkyl, cycloalkyl, alkoxy, aryl, biphenyl, benzyl, adamantyl, halogen, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, and substituted heteroaryl; R 2 It is any one of hydrogen, trifluoromethyl, tert-butyl, methoxy, phenyl, and adamantyl.

[0008] Furthermore, the dimethylbiphenyl-binaphthyl-Salen ligand is a racemic mixture or an optically pure isomer, and its specific structural formula is any one of the following:

[0009] In the above structural formula, rac Represents racemization. R, S It represents optical purity.

[0010] Secondly, embodiments of this application provide a method for preparing the above-mentioned dimethylbiphenyl-binaphthyl-Salen ligand, the general reaction formula of which is shown in Formula II: Formula II; The specific reaction steps are as follows: Dimethylbenzidine and naphthalene salicylaldehyde derivative are mixed in a molar ratio of 1:2, dissolved in sufficient ethanol, and then refluxed at 90 °C for 24 hours. After the reaction is completed, the reaction product is separated and purified to obtain the dimethylbenzidine-naphthalene-Salen ligand. It should be noted that dimethylbenzidine is an optically pure isomer, which is (…). R） -Dimethylbenzidine or ( S） -Dimethylbenzyldiamine; the binaphthyl salicylaldehyde derivative is also an optically pure isomer.

[0011] Furthermore, the structural formula of the binatyl salicylaldehyde derivative is shown in Formula III: Formula III; Among them, R 1 It is any one of hydrogen, alkyl, cycloalkyl, alkoxy, aryl, biphenyl, benzyl, adamantyl, halogen, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, and substituted heteroaryl; R 2 It is any one of hydrogen, trifluoromethyl, tert-butyl, methoxy, phenyl, and adamantyl.

[0012] Thirdly, embodiments of this application provide a dimethylbiphenyl-naphthyl-Salen catalyst, which uses the aforementioned dimethylbiphenyl-naphthyl-Salen ligand as a ligand.

[0013] Furthermore, the general structural formula of the dimethylbiphenyl-naphthyl-Salen catalyst is shown in Formula IV: Formula IV; Among them, R 1 It is any one of hydrogen, alkyl, cycloalkyl, alkoxy, aryl, biphenyl, benzyl, adamantyl, halogen, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, and substituted heteroaryl; R 2It is any one of hydrogen, trifluoromethyl, tert-butyl, methoxy, phenyl, and adamantyl; M is any one of Zn, Mg, Co, Cr, Cu, Fe, Pd, Ni, Mn, Y, La, Ln, Sc, Yb, Al, Ru, and Ti; m is 1 or 2; X is any one of furanyl, -N(SiHMe2)2, -N(SiMe3)2, alkyl, alkoxy, aryl, phenolic, and halogen.

[0014] Fourthly, this application provides a method for preparing the above-mentioned dimethylbiphenyl-naphthyl-Salen catalyst, the general reaction formula of which is shown in Formula V: Formula V; Specifically, the preparation method includes the following steps: mixing dimethylbiphenyl-binaphthyl-Salen ligand and the metal reagent MX m After mixing in a molar ratio of 1:1-1.1, add sufficient reaction solvent, then set the reaction temperature to 25-110 ℃ and react for 1-3 days under anhydrous and oxygen-free conditions. After the reaction is completed, remove the remaining reaction solvent and purify the reaction product to obtain the dimethylbiphenyl-binaphthyl-Salen catalyst.

[0015] Furthermore, the reaction solvent can be any one of toluene, benzene, dichloromethane, or tetrahydrofuran.

[0016] Fifthly, embodiments of this application provide the application of the above-mentioned dimethylbiphenyl-naphthyl-Salen catalyst in regulating the stereoselectivity of polymers.

[0017] Furthermore, in the above applications, regulating the stereoselectivity of the polymer refers to the ability to prepare P3HB polymers with continuously tunable stereoregularity by adjusting the enantiomeric excess value of the dimethylbiphenyl-binaphthyl-Salen catalyst; the general reaction formula is shown in Formula VI: Formula VI; in, P m Isoselectivity; monomer rac The molar ratio of -BBL to dimethylbiphenyl-naphthyl-Salen catalyst is 50-1000:1; the reaction temperature is room temperature; the reaction solvent is any one of benzene, toluene, or dichloromethane; and the reaction time is 1 min-24 h.

[0018] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: This invention presents for the first time a dimethylbiphenyl-binaphthyl-Salen ligand and a Salen catalyst, and its preparation method is simple and easy to operate, enriching the variety of Salen ligands and Salen catalysts; at the same time, this Salen ligand and Salen catalyst are used in four-membered ring monomers. β The selective ring-opening polymerization of β-butyrolactone utilizes a strategy of stereoregular control based on enantiomeric catalysts, enantiomeric site control (ESC), and polymeric exchange between enantiomer pairs. By simply adjusting the enantiomeric excess (ee) value of the catalyst, a series of P3HB polymers with continuously tunable stereoregularity can be readily prepared. This invention not only establishes an efficient and controllable route for the customized synthesis of P3HB but also provides a scalable method for precise stereoregular control in polymerization synthesis. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The Salen ligand obtained in Example 1 of this invention 1 H NMR spectrum; Figure 2 The Salen ligand obtained in Example 1 of this invention 13 C NMR spectrum; Figure 3 The Salen ligand obtained in Example 2 of this invention 1 H NMR spectrum; Figure 4 The Salen ligand obtained in Example 2 of this invention 13 C NMR spectrum; Figure 5 The Salen catalyst prepared in Example 3 of this invention 1 H NMR spectrum; Figure 6 The Salen catalyst prepared in Example 3 of this invention 13 C NMR spectrum; Figure 7 This is a schematic diagram of the single-crystal structure of the Salen catalyst prepared in Example 3 of the present invention; Figure 8 The Salen catalyst prepared in Example 4 of this invention 1H NMR spectrum; Figure 9 The Salen catalyst prepared in Example 5 of this invention 1 H NMR spectrum; Figure 10 The Salen catalyst prepared in Example 6 of this invention 1 H NMR spectrum; Figure 11 The P3HB polymers prepared under Salen catalysts with different ee values ​​in Example 7 of this invention 1 HNMR comparison chart; Figure 12 The P3HB polymers prepared under Salen catalysts with different ee values ​​in Example 7 of this invention 13 CNMR comparison chart; Figure 13 This is a DSC curve analysis diagram of the P3HB polymers prepared under Salen catalysts with different ee values ​​in Example 7 of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.

[0023] Example 1 This embodiment provides a detailed method for preparing the dimethylbiphenyl-binaphthyl-Salen ligand, the reaction route of which is shown in Formula VII: Formula VII; The specific reaction steps are as follows: Referring to existing literature, optically pure dimethylbenzidine was synthesized in the laboratory. R )-1 or ( S） -1] (compound 1 in formula VII) and optically pure binaphthalene salicylaldehyde derivatives [( R )-2 or ( S）-2] (compound 2 in formula VII), then take 1 mmol of compound 1 and 2 mmol of compound 2 into a reaction vessel, add 8 mL of ethanol to dissolve, reflux at 90 °C for 24 hours, after the reaction is completed, remove the excess ethanol solvent, and then separate and purify the reaction product by recrystallization with methanol to obtain dimethylbiphenyl-binaphthyl-Salen ligand.

[0024] The obtained product was tested, and the experimental results are as follows: Figure 1 and Figure 2 As shown, the ligand obtained in this example was detected by nuclear magnetic resonance (NMR) using deuterated chloroform (CDCl3) as solvent. The detection results are as follows: 1 H NMR (400 MHz, CDCl3) δ 11.54(s, 2H, OH), 8.01 (d, J = 8.5 Hz, 2H, Ar H), 7.93 (d, J = 8.2 Hz, 2H, Ar H),7.63 (d, J = 8.4 Hz, 2H, Ar H), 7.57 (s, 2H, Ar H), 7.43 (m, 2H, Ar H), 7.36(d, J = 8.4 Hz, 4H, Ar H), 7.32 – 7.26 (m, 8H, Ar H), 7.24 (m, 6H, Ar H), 7.19 (m, 6H, Ar) H), 7.15 – 7.09 (m, 8H, Ar H), 7.00 (d, J = 8.6 Hz, 2H, Ar H), 6.71 (d, J = 7.8 Hz, 2H, Ar H), 6.53 (s, 2H, N=CH), 1.95 (s, 6H, Me). 13CNMR (100 MHz, CDCl3) δ 164.81, 153.80, 149.43, 141.85, 140.41, 140.01,139.13, 136.80, 136.09, 135.05, 132.98, 132.79, 131.32, 131.13, 129.33,129.18, 128.73, 128.66, 128.58, 128.49, 128.32, 128.10, 128.06, 127.12,126.63, 126.54, 126.32, 126.22, 125.77, 124.93, 123.10, 120.22, 119.56,116.27 (Ar), 19.64 (Me).

[0025] The corresponding dimethylbiphenyl-binaphthyl-Salen ligand structure obtained is as follows: .

[0026] Example 2 The steps in this embodiment are basically the same as those in Example 1, the only difference being that the substituents of the binaphthyl salicylaldehyde derivative are different, and its reaction route is shown in Formula VIII: Formula VIII.

[0027] The reaction steps and parameters were consistent with those in Example 1, and the yield of the dimethylbiphenyl-naphthyl-Salen ligand was 80-90%. The obtained product was then analyzed, and the experimental results are as follows: Figure 3 and Figure 4 As shown, the ligand obtained in this example was detected by nuclear magnetic resonance using deuterated chloroform (CDCl3) as solvent. The detection results are as follows: 1 H NMR (400 MHz, CDCl3) δ 11.45(s, 2H, OH), 7.99 (d, J = 8.1 Hz, 2H, Ar-H), 7.92 (d, J = 8.3 Hz, 2H, Ar-H), 7.59 (d, J = 8.5 Hz, 2H, Ar-H), 7.41 (d, J = 8.2 Hz, 2H, Ar-H), 7.37 (s, 2H), 7.36 – 7.24 (m, 12H, Ar-H), 7.24 – 7.09 (m, 12H, Ar-H), 6.88 (d, J= 8.1 Hz, 2H, Ar-H), 6.79 (d, J = 6.7 Hz, 2H, Ar-H), 6.28 (s, 2H, N=CH), 1.98 (s, 6H,Me). 13 C NMR (100 MHz, CDCl3) δ 165.40, 153.65, 149.99, 143.09, 140.45, 136.81,136.14, 135.33, 132.96, 132.68, 130.99, 130.93, 129.14, 129.04, 128.61,128.53, 128.46, 128.37, 128.14, 128.03, 127.74, 126.51, 126.47, 126.18,125.77, 124.97, 122.99, 120.12, 119.41, 116.59 (Ar), 19.65 (Me).

[0028] Example 3 This embodiment further provides a method for preparing a dimethylbiphenyl-naphthyl-Salen catalyst, the reaction route of which is shown in Formula IX: Formula IX.

[0029] The specific reaction steps are as follows: Referring to existing literature, the metal reagent Y(N(SiH(CH3)2)2)3•2THF was synthesized in the laboratory. Then, in a glove box, 2 mL of toluene solution containing 0.1 mmol of metal reagent Y(N(SiH(CH3)2)2)3•2THF was slowly added dropwise to 2 mL of toluene solution containing 0.1 mmol of dimethylbiphenyl-binaphthyl-Salen ligand (as shown in compound 3 of formula IX). The reaction was then carried out for 2 days under anhydrous and oxygen-free conditions at room temperature. After the reaction time was completed, excess solvent was removed under vacuum. The obtained solid was washed with ice-cold hexane and ice-cold pentane, respectively, to obtain the catalyst shown in compound 4 of formula IX, with a yield of 68%.

[0030] The obtained product was then tested, and the experimental results are as follows: Figure 5 and Figure 6 As shown, the ligand obtained in this example was detected by nuclear magnetic resonance using deuterated benzene (C6D6) as a solvent. The detection results are as follows: 1H NMR (400 MHz, C6D6) δ 8.09 – 7.82(m, 4H, Ar-H), 7.73 – 7.54 (m, 10H, Ar-H), 7.49 – 7.21 (m, 18H, Ar-H), 7.00(m, 10H, ArH), 6.81 (t, J = 7.2 Hz, 4H, Ar-H), 6.67 (s, 2H, N=CH), 4.99 –4.89 (m, 2H, N(Si H Me2)2)), 3.21 – 2.96 (m, 4H, THF), 2.09 – 1.91 (m, 6H, Me),1.03 (s, 4H, THF), 0.18 (d, J = 3.1 Hz, 6H, N(SiH Me 2)2), -0.06 (d, J = 3.1 Hz,6H, N(SiH Me 2)2). 13 C NMR (100 MHz, C6D6) δ 171.50, 170.92, 161.88, 161.09,153.54, 148.88, 141.69, 141.20, 139.97, 139.60, 139.07, 138.80, 137.43,137.18, 135.61, 134.05, 133.56, 131.24, 130.66, 130.29, 129.19, 128.73,127.11, 126.58, 126.38, 125.70, 125.01, 124.99, 122.77, 121.86, 121.63 (Ar), 69.75 (THF), 25.30 (THF), 20.02 (Me), 3.33 (-SiHMe), 2.31 (-SiHMe).

[0031] For further details, please refer to... Figure 7 , Figure 7 The image shows the single crystal structure of the Salen catalyst, grown from compound 4 of formula IX in a system using benzene and hexane as solvents, as determined by single-crystal X-ray diffraction. It can be seen that this complex employs... cis The -α configuration, in which a tetrahydrofuran molecule and a –N(SiHMe2)2 group occupy the equatorial coordination site, and the larger optically pure binaphthalene group occupies the axial position of the metal and restricts the channel on the equatorial metal site, thereby achieving efficient kinetic resolution during polymerization. Example 4 The steps in this embodiment are basically the same as those in Example 3, the only difference being the different substituents of the Salen ligand. The reaction route is shown in Formula X: Formula X.

[0032] The reaction steps and parameters were consistent with those in Example 3, and the yield of the Salen catalyst was 75%. The obtained catalyst was then tested, and the experimental results are as follows: Figure 8 As shown, the ligand obtained in this example was detected by nuclear magnetic resonance using deuterated benzene (C6D6) as a solvent. The detection results are as follows: 1 H NMR (400 MHz, C6D6) δ 7.99 (m, 2H, Ar-H), 7.84 (m, 2H,Ar-H), 7.74 – 7.45 (m, 10H, Ar-H), 7.36 (m, 2H, Ar-H), 7.30 – 7.23 (m, 4H,Ar-H), 7.09 – 6.97 (m, 4H, Ar-H), 6.93 (m, 6H, Ar-H), 6.82 – 6.65 (m, 8H, Ar-H), 6.55 (s, 2H, N=CH), 4.94 (p, J = 3.1 Hz, 2H, N(Si H Me2)2)), 3.08 (m, 4H,THF), 2.09 – 1.93 (m, 6H, Me), 1.01 (s, 4H, THF), 0.20 (d, J = 3.1 Hz, 6H, N(SiH Me 2)2), -0.07 (d, J = 3.1 Hz, 6H, N(SiH Me 2) 2） .

[0033] Based on this, other enantiomers can also be obtained by following the same reaction steps.

[0034] Example 5 The steps in this embodiment are basically the same as those in Example 3, the only difference being the different metal reagents. In this example, La(N(SiH(CH3)2)2)3•2THF) is used as the metal reagent, and the reaction route is shown in Formula XI: Formula XI.

[0035] In this embodiment, the metal reagent La(N(SiH(CH3)2)2)3•2THF) was synthesized according to the literature route, and the remaining reaction steps and parameters were consistent with those in Example 3. The yield of the Salen catalyst was 70%. The obtained catalyst was then tested, and the experimental results are as follows: Figure 9 As shown, the ligand obtained in this example was detected by nuclear magnetic resonance using deuterated benzene (C6D6) as a solvent. The detection results are as follows: 1 H NMR (400 MHz, C6D6) δ 8.12 (s, 1H, Ar-H), 7.99 (s, 1H, Ar-H), 7.85 – 7.64 (m, 8H, Ar-H), 7.53 (m, 6H, Ar-H), 7.38 (m, 4H, Ar-H), 7.31 (m,8H, Ar-H), 7.21 (m, 2H, Ar-H), 7.00 (m, 12H, Ar-H), 6.80 (m, 4H, Ar-H), 6.70(d, J = 7.4 Hz, 2H, N=CH), 4.97 (p, J = 3.0 Hz, 2H, N(Si H Me2)2)), 2.94 (m, 4H,THF), 1.96 (d, J = 41.3 Hz, 6H, Me), 1.01 (s, 4H, THF), 0.15 (d, J = 3.0 Hz, 6H, N(SiH) Me 2)2), -0.02 (d, J = 3.0 Hz, 6H, N(SiH Me 2) 2） .

[0036] Example 6 The steps in this embodiment are basically the same as those in Example 3. The main difference is that the metal reagent is different. In this example, Zn(N(Si(CH3)3)2 is used as the metal reagent, and the reaction route is shown in Formula XIII: Formula XIII.

[0037] The specific reaction steps are as follows: Referring to existing literature, the metallic reagent Zn(N(Si(CH3)3)2 was synthesized in the laboratory. Then, in a glove box, 2 mL of a tetrahydrofuran solution containing 0.1 mmol of the metallic reagent Zn(N(Si(CH3)3)2 was slowly added dropwise to 2 mL of a tetrahydrofuran solution containing 0.1 mmol of dimethylbiphenyl-binaphthyl-Salen ligand (as shown in compound 3 of formula XIII). The reaction was then carried out for 6 h under anhydrous and oxygen-free conditions at room temperature. 1 After H NMR monitoring showed that the ligands had completely reacted, excess solvent was removed under vacuum. The resulting solid was washed with ice hexane and ice pentane, respectively, to obtain the catalyst shown as compound 8 in formula XIII, with a yield of 82%.

[0038] The obtained catalyst was then tested, and the experimental results are as follows: Figure 10 As shown, the ligand obtained in this example was detected by nuclear magnetic resonance using deuterated benzene (C6D6) as a solvent. The detection results are as follows: 1 H NMR (400 MHz, C6D6) δ 7.72 (m, 4H,Ar-H), 7.66 – 7.58 (m, 8H, Ar-H), 7.49 – 7.43 (m, 4H, Ar-H), 7.34 (m, 2H, Ar-H), 7.15 – 7.03 (m, 16H, Ar-H), 6.98 – 6.94 (m, 4H, Ar-H), 6.88 (m, 4H, Ar-H), 6.78 (m, 2H, Ar-H), 6.66 – 6.63 (m, 2H, Ar-H), 5.53 – 5.49 (m, 2H, N=CH), 1.65 (s, 6H, Me).

[0039] Example 7 This embodiment provides a Salen catalyst prepared in Example 3, which, by adjusting the enantiomeric excess value of the Salen catalyst, is applied to racemic reactions. β In the stereoselective ring-opening polymerization of butyrolactone, polymers with different degrees of regularity are prepared. 3 The reaction route for the hydroxybutyrate method is shown in Formula XIV: Formula XIV.

[0040] Among them, (d) R , a R , a R） -3, (d S , a S , a S)-3 are all catalysts obtained in Example 3, with Ph2CHCH2OH as the initiator and toluene as the solvent. The specific preparation steps of the above reaction route are as follows: racemic... β -Butyrolactone ( rac -BBL) (86 mg, 1 mmol), initiator Ph2CHCH2OH (0.99 mg, 0.005 mmol), dissolved in toluene (0.4 mL), then 0.1 mL of a toluene solution with Salen catalyst concentration of 0.05 mol / L was added. After mixing, the mixture was reacted at room temperature for 8-30 min. Then, a chloroform solution with a mass concentration of 10 mg / mL benzoic acid was added to dissolve the product. A small amount of the solution was taken for further processing. 1 H NMR analysis was used to determine the conversion rate. The remaining reaction solution was added dropwise into methanol to cause the polymer to precipitate. The precipitated solid was filtered, washed three times with methanol, and then dried in a vacuum drying oven at 60 °C for 12 h to obtain white poly(3-hydroxybutyrate).

[0041] Furthermore, in this embodiment, the Salen catalyst is prepared with different enantiomeric excess values ​​(ee), calculated as follows:

[0042] Additionally, the total volume of the polymer system is 0.5 mL, and it is racemic. β The initial concentration of β-butyrolactone monomer was 2 mol / L, the concentration of Salen catalyst was 0.01 mol / L, the concentration of initiator was 0.01 mol / L, and the racemic mixture was used. β The molar ratio of butyrolactone monomer / catalyst / initiator was 200:1:1. Then, the polymer properties were determined separately. 13 C NMR analysis showed that the polymer was isotactic. P m The values ​​ranged from 0.07 to 0.90, and the melting temperature and glass transition temperature of poly(3-hydroxybutyrate) were determined using differential scanning calorimetry (DSC). The measurement results are as follows: Figure 11 - Figure 13 And as shown in Table 1: Table 1. Effect of Salen catalysts with different ee values ​​on polymer polymerization results.

[0043] It can be seen that the enantiomeric excess value of Salen catalyst significantly regulates the stereoselectivity of the polymerization process and the properties of the resulting polymer: Salen catalyst with an ee value of 100% can achieve... P mThe P3HB value was 0.90, and the monomer conversion rate reached 46%; when the Salen catalyst ee value decreased to 99%, the monomer conversion rate of the polymerization reaction increased to 62%, and the P3HB value... P m The value decreased to 0.75; the ee value continued to decrease to 90%, and the stereoselectivity of the P3HB product gradually changed from isomeric enrichment ( P m = 0.67) transforms into interregular enrichment ( P m = 0.22), while the monomer conversion rate increased; further reducing the ee value improved both the catalytic activity and syndiotactic selectivity of P3HB. When the ee value was 0, the desired catalytic activity was obtained. P m = 0.07 for P3HB. This demonstrates that the stereoregularity of P3HB can be controlled by adjusting the ee value of a single catalyst. Product melting temperature. T m Overall, the trend shows a decrease followed by an increase as the catalyst ee value decreases. For identically enriched samples, the DSC curve typically exhibits two... T m ,along with P m It decreased from 0.90 to 0.54. T m When the temperature is decreased from 124 / 140 °C to 118 °C, and the polymer is enriched in a syndiotactic manner, T m Value with P m The value gradually increases as it decreases. This highlights the effect of the enantiomeric excess value of the Salen catalyst on the stereoregularity and thermal properties of P3HB.

[0044] Therefore, it can be seen that Salen catalysts with different ee values ​​can prepare P3HB polymers with continuously tunable stereoregularity; that is, those skilled in the art can precisely control the enantiomeric excess value of the Salen catalyst. β Stereoregularity of -butyrolactone during stereoselective ring-opening polymerization.

[0045] In summary, the embodiments of the present invention provide a dimethylbiphenyl-binaphthyl-Salen ligand, a Salen catalyst, its preparation method, and its application. This invention is the first to propose a dimethylbiphenyl-binaphthyl-Salen ligand and a Salen catalyst, and its preparation method is simple and easy to operate, enriching the types of Salen ligands and Salen catalysts. Furthermore, this Salen ligand and Salen catalyst are used in four-membered ring monomers. βThe stereoselective ring-opening polymerization of β-butyrolactone utilizes a strategy of stereoregularity control based on enantiomeric pure catalysts, enantiomeric site control mechanisms, and polymer chain exchange between enantiomeric pairs. By simply adjusting the enantiomeric excess (ee) value of the catalyst, a series of P3HB polymers with continuously tunable stereoregularity can be conveniently prepared. This invention not only establishes an efficient and controllable route for the customized synthesis of P3HB but also provides a scalable method for precise stereoregularity control in polymerization synthesis.

[0046] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A dimethylbiphenyl-binaphthyl-Salen ligand, characterized in that, The general structural formula of the dimethylbiphenyl-binaphthyl-Salen ligand is shown in Formula I: Formula I; Among them, R 1 It is any one of hydrogen, alkyl, cycloalkyl, alkoxy, aryl, biphenyl, benzyl, adamantyl, halogen, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, and substituted heteroaryl; R 2 It is any one of hydrogen, trifluoromethyl, tert-butyl, methoxy, phenyl, and adamantyl.

2. The dimethylbiphenyl-binaphthyl-Salen ligand according to claim 1, characterized in that, The dimethylbiphenyl-binaphthyl-Salen ligand is a racemic mixture or an optically pure isomer, and its structural formula is any one of the following: in, rac Represents racemization. R, S It represents optical purity.

3. A method for preparing the dimethylbiphenyl-binaphthyl-Salen ligand as described in claim 1, characterized in that, Includes the following steps: Dimethylbenzidine and a naphthalene salicylaldehyde derivative were mixed in a molar ratio of 1:2, dissolved in ethanol, and then refluxed at 90 °C for 24 hours. After the reaction was completed, the reaction product was separated and purified to obtain the product. Both the dimethylbenzidine and the naphthalene salicylaldehyde derivative were optically pure isomers.

4. The preparation method according to claim 3, characterized in that, The structural formula of the binaphthyl salicylaldehyde derivative is shown in Formula III: Formula III; Among them, R 1 It is any one of hydrogen, alkyl, cycloalkyl, alkoxy, aryl, biphenyl, benzyl, adamantyl, halogen, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, and substituted heteroaryl; R 2 It is any one of hydrogen, trifluoromethyl, tert-butyl, methoxy, phenyl, and adamantyl.

5. A dimethylbiphenyl-naphthyl-Salen catalyst, characterized in that, The dimethylbiphenyl-binaphthyl-Salen catalyst uses the dimethylbiphenyl-binaphthyl-Salen ligand as described in claim 1 as the ligand.

6. The dimethylbiphenyl-naphthyl-Salen catalyst according to claim 5, characterized in that, The general structural formula of the dimethylbiphenyl-binaphthyl-Salen catalyst is shown in Formula IV: Formula IV; Among them, R 1 It is any one of hydrogen, alkyl, cycloalkyl, alkoxy, aryl, biphenyl, benzyl, adamantyl, halogen, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, and substituted heteroaryl; R 2 It is any one of hydrogen, trifluoromethyl, tert-butyl, methoxy, phenyl, and adamantyl; M is any one of Zn, Mg, Co, Cr, Cu, Fe, Pd, Ni, Mn, Y, La, Ln, Sc, Yb, Al, Ru, and Ti; m is 1 or 2; X is any one of furanyl, -N(SiHMe2)2, -N(SiMe3)2, alkyl, alkoxy, aryl, phenolic, and halogen.

7. A method for preparing the dimethylbiphenyl-naphthyl-Salen catalyst as described in claim 5, characterized in that, Includes the following steps: The dimethylbiphenyl-binaphthyl-Salen ligand and the metal reagent MX m After mixing in a molar ratio of 1:1-1.1, add sufficient reaction solvent, then set the reaction temperature to 25-110 ℃ and react for 1-3 days under anhydrous and oxygen-free conditions. After the reaction is completed, remove the remaining reaction solvent and purify the reaction product; thus, the product is obtained.

8. The preparation method according to claim 7, characterized in that, The reaction solvent is any one of toluene, benzene, dichloromethane, and tetrahydrofuran.

9. The application of the dimethylbiphenyl-naphthyl-Salen catalyst as described in claim 5 in regulating the stereoselectivity of polymers.

10. The application according to claim 9, characterized in that, The aforementioned regulation of polymer stereoselectivity refers to the preparation of P3HB polymers with continuously tunable stereoregularity by adjusting the enantiomeric excess value of the dimethylbiphenyl-naphthyl-Salen catalyst.

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