CN115703720A

CN115703720A - Spiro Salen ligand, salen catalyst, preparation method and application of spirocyclic Salen ligand and Salen catalyst in ring-opening polymerization

Info

Publication number: CN115703720A
Application number: CN202110887204.1A
Authority: CN
Inventors: 朱剑波; 黄皓毅; 蔡中正
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2021-08-03
Filing date: 2021-08-03
Publication date: 2023-02-17
Anticipated expiration: 2041-08-03
Also published as: CN115703720B

Abstract

The invention discloses a spiro Salen ligand, a Salen catalyst, a preparation method and application thereof in ring-opening polymerization, belongs to the technical field of catalysts, firstly provides a spiro Salen ligand and a Salen catalyst based on a spiro skeleton, enriches the types of the Salen ligand and the Salen catalyst, widens the application field of the Salen ligand and the Salen catalyst, and also relates to a polymerization reaction system containing the Salen catalyst.

Description

Spiro Salen ligand, salen catalyst, preparation method and application of spirocyclic Salen ligand and Salen catalyst in ring-opening polymerization

Technical Field

The invention relates to the technical field of catalysts, in particular to a spiro Salen ligand, a preparation method of a Salen catalyst and application of the spiro Salen ligand in preparation of poly-3-hydroxybutyrate prepared by stereoselective ring-opening polymerization of beta-butyrolactone.

Background

Spiro backbone chiral ligands have received a great deal of attention since the 21 st century and have evolved into a distinct class of chiral ligands. The spiro backbone chiral ligand shows excellent catalytic activity and enantioselectivity in various asymmetric catalytic reactions such as asymmetric catalytic hydrogenation, asymmetric carbon-carbon bond formation, asymmetric carbon-heteroatom bond formation and the like, and makes possible many asymmetric catalytic reactions in which enantioselectivity is difficult to control before. Nowadays, the spiro structure has become an 'advantageous structure', and corresponding spiro ligands and catalysts thereof have been widely adopted by researchers at home and abroad. However, the spiro backbone compound with the chiral dominant structure is not applied to the construction of the Salen ligand backbone at present, and is not applied to organic asymmetric catalytic reaction or polymerization reaction.

Since the invention of high polymer materials, plastic products have become the most widely used artificial materials with the largest output. The production of plastic products increased from two million tons in 1950 to 3.11 million tons in 2015. But with the concomitant large amount of plastic waste, people now have produced about 26.3 million tons of plastic wastes. Most of the plastic wastes adopt the treatment modes of landfill and incineration, and the landfill and incineration treatment generate harm to the environment and cause atmospheric pollution. Even if degraded, these chemically stable plastics continue to exist in the human living environment in a form invisible to the naked eye, such as in the form of micro-plastics and the like, and finally enter the human body through the food chain, thus endangering the health of the human body.

At present, aliphatic polyester based on biomass sources is considered as a potential green substitute of petroleum-based high polymer materials due to unique degradability, and has certain application in the fields of biological medicine, tissue engineering, packaging and the like. For example, P3HB (poly-3-hydroxybutyrate) is taken as a polymer produced by fermentation of a natural microorganism, has excellent performance and is considered as a powerful substitute of PP (polypropylene) material. The performance of the poly-3-hydroxybutyrate is closely related to the stereoregularity, the naturally biologically fermented poly-3-hydroxybutyrate is an isotactic polymer, and the isotacticity P _m Greater than 0.99. The method directly starts from cheap racemic four-membered ring monomer beta-butyrolactone, and the preparation of the high-regularity polymer by selective polymerization of the metal complex is a powerful way for chemically synthesizing the poly-3-hydroxybutyrate, and the cost is obviously lower than that of a biological fermentation method. However, the device is not suitable for use in a kitchenTo date, those skilled in the art have not obtained a polymer product (P) having the same degree of regularity as the natural poly-3-hydroxybutyrate by a number of methods and attempts _m ＝0.06-0.80)。

Disclosure of Invention

Aiming at the defects, the invention aims to provide a spiro Salen ligand, a Salen catalyst, a preparation method and application thereof in ring-opening polymerization, and also relates to a polymerization reaction system containing the Salen catalyst, and a method for preparing poly-3-hydroxybutyrate with different tacticity by selectively ring-opening polymerizing racemic beta-butyrolactone by using the polymerization reaction system containing the Salen catalyst can effectively solve the problem of low tacticity of poly-3-hydroxybutyrate prepared by the selective ring-opening polymerization of beta-butyrolactone in the prior art, and the stereoselectivity is maximally greater than 0.99; the invention firstly provides a spiro-ring Salen ligand and a spiro-ring Salen catalyst based on a spiro-ring skeleton, enriches the types of the Salen ligand and the Salen catalyst, and widens the application fields of the Salen ligand and the Salen catalyst.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a spiro Salen ligand, which has the following structural general formula:

wherein each R is ¹ 、R ² 、R ³ And R ⁴ Independently hydrogen, alkyl, cycloalkyl, alkoxy, aryl, halo, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, substituted heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atoms to which they are attached, and/or, adjacent carbon atoms, each independently form a cycloalkyl, heteroaryl, or aryl group.

The spiro Salen ligands of the invention have C ₂ And (4) symmetry.

Further, each R ¹ 、R ² 、R ³ And R ⁴ Independently of one another is hydrogen, C ₁ ～C ₁₀ Alkyl radical、C ₃ ～C ₆ Cycloalkyl radical, C ₁ ～C ₁₀ Alkoxy radical, C ₆ ～C ₁₄ Aryl, halogen, 5-6 membered heteroaryl, substituted C ₁ ～C ₁₀ Alkyl, substituted C ₁ ～C ₁₀ Alkoxy, by one or more R ^1a Substituted C ₆ ～C ₁₄ Aryl radicals, substituted by one or more R ^1a Substituted 5-6 membered heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atoms to which they are attached and/or, independently of one another, the adjacent carbon atoms form C ₃ ～C ₇ Cycloalkyl, 5-6 membered heteroaryl or phenyl; r ^1a Is C ₁ ～C ₁₀ Alkyl radical, C ₁ ～C ₁₀ Alkoxy or halogen.

Further, each R ¹ 、R ² 、R ³ And R ⁴ Independently hydrogen, fluorine, chlorine, bromine, iodine, methyl, ethyl, tert-butyl, isopropyl, cyclopropyl, cyclobutyl, cyclohexyl, furyl, pyridyl, biphenyl, 2-phenylbiphenyl, trityl, cumyl, benzyl, adamantyl, C ₁ ～C ₃ Perfluoroalkoxy, C ₁ ～C ₃ Perfluoroalkyl, arylmethylene, heteroarylmethylene, arylmethine, or heteroarylmethine.

Further, the spiro Salen ligand is racemic or optically pure isomer.

Further, the structural formula of the spiro Salen ligand is shown below:

the R group can be modified, with the general formula written:

or alternatively

R can be of the structure, for example:

wherein rac represents racemic, R, S represent optically pure, and Cumyl represents Cumyl.

The invention also provides a preparation method of the spiro Salen ligand, which comprises the following steps: performing ketoamine condensation reaction on salicylaldehyde compounds and spiro diamine under an acidic condition, and separating and purifying reaction products after the reaction is finished to obtain the salicylic aldehyde compound;

wherein, the structural general formula of the salicylaldehyde compound is shown as follows:

R ¹ 、R ² 、R ³ and R ⁴ Independently hydrogen, alkyl, cycloalkyl, alkoxy, aryl, halo, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, substituted heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atoms to which they are attached, and/or, adjacent carbon atoms, each independently form a cycloalkyl, heteroaryl, or aryl group.

Further, R ¹ 、R ² 、R ³ And R ⁴ Independently of one another is hydrogen, C ₁ ～C ₁₀ Alkyl radical, C ₃ ～C ₆ Cycloalkyl, C ₁ ～C ₁₀ Alkoxy radical, C ₆ ～C ₁₄ Aryl, halogen, 5-6 membered heteroaryl, substituted C ₁ ～C ₁₀ Alkyl, substituted C ₁ ～C ₁₀ Alkoxy, by one or more R ^1a Substituted C ₆ ～C ₁₄ Aryl radicals, substituted by one or more R ^1a Substituted 5-6 membered heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atoms to which they are attached and/or, independently of one another, the adjacent carbon atoms form C ₃ ～C ₇ Cycloalkyl, 5-6 membered heteroaryl or phenyl; r ^1a Is C ₁ ～C ₁₀ Alkyl radical, C ₁ ～C ₁₀ Alkoxy or halogen.

Further, R ¹ 、R ² 、R ³ And R ⁴ Independently hydrogen, fluorine, chlorine, bromine, iodine, methyl, ethyl, tert-butyl, isopropyl, cyclopropyl, cyclobutyl, cyclohexyl, furyl, pyridyl, biphenyl, 2-phenylbiphenyl, trityl, cumyl, benzyl, adamantyl, C ₁ ～C ₃ Perfluoroalkoxy, C ₁ ～C ₃ Perfluoroalkyl, arylmethylene, heteroarylmethylene, arylmethine, or heteroarylmethine.

Further, the spirodiamine is raceme or optical pure isomer; the optically pure isomer is (R) -spirocyclic diamine or (S) -spirocyclic diamine.

Further, the preparation method of the spiro Salen ligand comprises the following specific processes: adding salicylaldehyde compounds, spiro diamine and a solvent into a reaction device, carrying out reflux reaction for 1-24 hours under an acidic condition, and separating and purifying a reaction product after the reaction is finished to obtain the salicylic aldehyde compound; wherein the molar ratio of the spirocyclic diamine to the salicylaldehyde compound is 1-2.

Further, the time of the reflux reaction is 12 hours, and the molar ratio of the spiro diamine to the salicylaldehyde compound is 1.

Further, the solvent is methanol, ethanol, isopropanol, toluene, acetonitrile or N, N-dimethylformamide, preferably methanol.

The spirocyclic diamines of the invention are prepared according to the prior art.

The reaction structural formula of the preparation method of the spiro Salen ligand is as follows:

the invention also provides a Salen catalyst, and the Salen catalyst adopts the spiro Salen ligand as a ligand.

Further, the structural formula of the Salen catalyst is as follows:

wherein each R is ¹ 、R ² 、R ³ And R ⁴ Independently hydrogen, alkyl, cycloalkyl, alkoxy, aryl, halo, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, substituted heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atoms to which they are attached, and/or, the adjacent carbon atoms, independently form a cycloalkyl, heteroaryl or aryl group, respectively; m is a metal element of group IIB, IIIA, IVA, VA or VIA; m is 1 or 2; each X is independently C ₁ ～C ₂₀ Alkyl, substituted amino, C ₃ ～C ₆ Cycloalkyl radical, C ₃ ～C ₆ Heterocycloalkyl, C ₆ ～C ₁₄ Aryl or 5-6 membered heteroaryl.

Further, each R ¹ 、R ² 、R ³ And R ⁴ Independently of one another is hydrogen, C ₁ ～C ₁₀ Alkyl radical, C ₃ ～C ₆ Cycloalkyl, C ₁ ～C ₁₀ Alkoxy radical, C ₆ ～C ₁₄ Aryl, halogen, 5-6 membered heteroaryl, substituted C ₁ ～C ₁₀ Alkyl, substituted C ₁ ～C ₁₀ Alkoxy, by one or more R ^1a Substituted C ₆ ～C ₁₄ Aryl radical, by one or more R ^1a Substituted 5-6 membered heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atoms to which they are attached and/or, independently of one another, the adjacent carbon atoms form C ₃ ～C ₇ Cycloalkyl, 5-6 membered heteroaryl or phenyl; r ^1a Is C ₁ ～C ₁₀ Alkyl radical, C ₁ ～C ₁₀ Alkoxy or halogen.

Further, each timeA R ¹ 、R ² 、R ³ And R ⁴ Independently hydrogen, fluorine, chlorine, bromine, iodine, methyl, ethyl, tert-butyl, isopropyl, cyclopropyl, cyclobutyl, cyclohexyl, furyl, pyridyl, biphenyl, 2-phenylbiphenyl, trityl, cumyl, benzyl, adamantyl, C ₁ ～C ₃ Perfluoroalkoxy, C ₁ ～C ₃ Perfluoroalkyl, arylmethylene, heteroarylmethylene, arylmethine, or heteroarylmethine.

Further, M is Zn, co, cr, cu, fe, pd, ni, mn, Y, la, ln, sc, yb, al, ru, ti or the like, preferably Zn, Y, la or Yb.

Further, X is furyl, -N (SiHMe) ₂ ) ₂ 、-N(SiMe ₃ ) ₂ Alkyl, alkoxy, aryl, phenolic, halogen, and the like, preferably furyl, -N (SiHMe) ₂ ) ₂ or-N (SiMe) ₃ ) ₂ 。

The invention also provides a preparation method of the Salen catalyst, which comprises the following steps: carrying out coordination on the spiro Salen ligand and a metal reagent MXn to obtain the spiro Salen ligand;

wherein each R is ¹ 、R ² 、R ³ And R ⁴ Independently hydrogen, alkyl, cycloalkyl, alkoxy, aryl, halo, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, substituted heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atoms to which they are attached, and/or, the adjacent carbon atoms, independently form a cycloalkyl, heteroaryl or aryl group, respectively; m is a metal element of group IIB, IIIA, IVA, VA or VIA; n is 1, 2,3, 4, 5 or 6; m is 1 or 2; each X is independently C ₁ ～C ₂₀ Alkyl, substituted amino, C ₃ ～C ₆ Cycloalkyl radical, C ₃ ～C ₆ Heterocycloalkyl, C ₆ ～C ₁₄ Aryl or 5-6 membered heteroaryl.

Furthermore, the molar ratio of spiro Salen ligand to metal reagent MXn is 1 to 3, preferably 1.2.

Further, each R ¹ 、R ² 、R ³ And R ⁴ Independently of one another is hydrogen, C ₁ ～C ₁₀ Alkyl radical, C ₃ ～C ₆ Cycloalkyl radical, C ₁ ～C ₁₀ Alkoxy radical, C ₆ ～C ₁₄ Aryl, halogen, 5-6 membered heteroaryl, substituted C ₁ ～C ₁₀ Alkyl, substituted C ₁ ～C ₁₀ Alkoxy, by one or more R ^1a Substituted C ₆ ～C ₁₄ Aryl radicals, substituted by one or more R ^1a Substituted 5-6 membered heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atom to which it is attached, and/or the adjacent carbon atoms each independently form C ₃ ～C ₇ Cycloalkyl, 5-6 membered heteroaryl or phenyl; r ^1a Is C ₁ ～C ₁₀ Alkyl radical, C ₁ ～C ₁₀ Alkoxy or halogen.

Further, M is Zn, co, cr, cu, fe, pd, ni, mn, Y, la, ln, sc, yb, al, ru, ti or the like.

Further, X is furyl, -N (SiHMe) ₂ ) ₂ 、-N(SiMe ₃ ) ₂ Alkyl, alkoxy, aryl, phenolic, halogen, and the like.

The metal reagent MXn of the present invention can be prepared according to the prior art.

The invention also provides a polymerization reaction system, which comprises the Salen catalyst and an initiator.

Further, the initiator includes alkyl alcohol, alkyl mercaptan, benzyl alcohol, benzyl mercaptan or the like.

The invention also provides application of the polymerization reaction system in selective ring-opening polymerization of racemic beta-butyrolactone to prepare poly-3-hydroxybutyrate with different tacticity, which specifically comprises the following steps: adding racemic beta-butyrolactone, a Salen catalyst, an initiator and a solvent into a reaction device, reacting for 5 s-2 h at 20-45 ℃, and separating and purifying a reaction product to obtain the compound; wherein the mol ratio of the racemic beta-butyrolactone to the Salen catalyst to the initiator is 100-10000.

Further, the solvent is a conventional organic solvent such as methylene chloride, dimethyl sulfoxide, tetrahydrofuran, N-methylpyrrolidone, N-dimethylformamide, toluene and the like, and is preferably toluene.

The reaction structural formula for preparing the poly-3-hydroxybutyrate with different tacticity by using the polymerization reaction system to realize the selective ring-opening polymerization of the racemic beta-butyrolactone is shown as follows:

the poly-3-hydroxybutyrate prepared by the preparation method has high regularity and good thermal property; the syndiotactic polymer P obtained _r =0.99, isotactic polymer P obtained _m =0.98; wherein P is in the art _r Represents isoselectivity, P _m Represents isotactic selectivity; regardless of the regularity of the polymer, there is a definition: p is _r +P _m Is constantly equal to 1; p _r =1 being perfectly syndiotactic, P _m =1 is perfectly isotactic.

It is to be noted that the term "substituted" in the present invention means that hydrogen atoms and/or carbon atoms in the basic structure have been replaced by radicals and/or functional groups, and/or heteroatoms or heteroatom-containing groups. Thus, the term "alkyl" includes heteroatom-containing groups. For purposes herein, a heteroatom is defined as any atom other than carbon and hydrogen. For example, methylcyclopentadiene (Cp) is a Cp group substituted with a methyl group (which is the basic structure), which may also be referred to as the methyl functionality, ethanol is an ethyl group (which is the basic structure) substituted with an — OH functionality, and pyridine is a phenyl group substituted with a nitrogen atom at a carbon within the basic structure of the phenyl ring.

It is understood that for purposes herein, when a group is listed, it represents the basic structure of the group (the group type) and all other groups formed upon substitution of the group as described above. The alkyl group and the like as exemplified include all isomers including, if necessary, cyclic isomers, for example, butyl including n-butyl, 2-methylpropyl, 1-methylpropyl, t-butyl and cyclobutyl (and the like substituted cyclopropyl); pentyl includes n-pentyl, cyclopentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl and neopentyl (and analogous substituted cyclobutyl and cyclopropyl). Cyclic compounds having substituents include all isomeric forms, for example, methylphenyl would include o-methylphenyl, m-methylphenyl and p-methylphenyl; dimethylphenyl will include 2, 3-dimethylphenyl, 2, 4-dimethylphenyl, 2, 5-dimethylphenyl, 2, 6-diphenylmethyl, 3, 4-dimethylphenyl and 3, 5-dimethylphenyl.

In summary, the invention has the following advantages:

1. the invention provides a spiro Salen ligand and a Salen catalyst based on a spiro framework for the first time, and the preparation method is simple and easy to operate, and enriches the types of the Salen ligand and the Salen catalyst; meanwhile, a spiro Salen ligand and a Salen catalyst are used for selective ring-opening polymerization of the four-membered ring monomer beta-butyrolactone, and the poly-3-hydroxybutyrate prepared by the preparation method has high regularity and good thermal property. The syndiotactic polymer P obtained _r =0.99, isotactic polymer P obtained _m =0.98, effectively solves the problem of low regularity of the poly-3-hydroxybutyrate prepared by the selective ring-opening polymerization of the beta-butyrolactone.

Drawings

FIG. 1 shows salen ligand rac-3h prepared in the present invention

Single crystal diffraction spectrum of (a);

FIG. 2 shows a salen catalyst prepared in the present invention

Single crystal diffraction spectrum of (a);

FIG. 3 is a nuclear magnetic carbon spectrum of syndiotactic poly (3-hydroxybutyrate) prepared in example 9 of the present invention;

FIG. 4 is a nuclear magnetic carbon spectrum of isotactic poly (3-hydroxybutyrate) prepared in example 14 of the present invention;

FIG. 5 is a nuclear magnetic carbon spectrum of syndiotactic poly (3-hydroxybutyrate) obtained in example 9 compared with that of isotactic poly (3-hydroxybutyrate) obtained in example 14 according to the present invention;

FIG. 6 is a DSC of isotactic poly (3-hydroxybutyrate) obtained in example 14 of the present invention;

FIG. 7 is a magnified comparison of the nuclear magnetic carbon spectrum of syndiotactic poly (3-hydroxybutyrate) obtained in example 9 and the nuclear magnetic carbon spectrum of isotactic poly (3-hydroxybutyrate) obtained in example 14 in accordance with the present invention;

FIG. 8 is a DSC of syndiotactic poly (3-hydroxybutyrate) obtained in example 9 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

Thus, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

This example provides a process for the preparation of spiro indane spiro diamines having a key backbone, the reaction scheme is shown below:

the specific reaction steps in the preparation route are as follows:

1. synthesis of Compound 1b

Pyridine and trifluoromethanesulfonic anhydride were added dropwise to a solution of compound 1a (5 g,19.8 mmol) in dichloromethane (100 mL) at 0 deg.C, reacted overnight at room temperature, the solvent was removed under vacuum, diluted with 80mL ethyl acetate, and diluted with 5% hydrochloric acid solution, saturated NaHCO ₃ The organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, concentrated in vacuo, and subjected to silica gel column chromatography to give product 1b (10 g, yield > 99%).

2. Synthesis of Compound 1c

Under the anhydrous and oxygen-free conditions, pd (OAc) is added ₂ (1g,4.45mmol)，Cs ₂ CO ₃ Benzylamine (20mL, 183mmol) and (+/-) -BINAP (3.36g, 5.40mmol) are sequentially added into a toluene solution (100 mL) of (16.4g, 50.3mmol) and (+/-) -BINAP (3.36g, 5.40mmol), the system reacts at 100 ℃ for 2 hours, the temperature is reduced to room temperature, a funnel paved with kieselguhr is used for filtration, filtrate is collected, the solvent is removed in vacuum, and the product 1c is obtained through column chromatography separation (the yield is 83 percent and 4.5 g).

3. Synthesis of Compound rac-1d

Compound 1c obtained above was added to a mixed solvent [ ethyl acetate/methanol =500mL/200ml]In, 10% of Pd (OH) was further added thereto ₂ And C (1 g), then replacing the reaction system with hydrogen, reacting for 16h under the conditions of normal pressure, 40 ℃ and hydrogen atmosphere, filtering the obtained mixture after the reaction is finished, collecting the filtrate, concentrating, and carrying out column chromatography separation to obtain the product, namely white powder rac-1d (3.6 g, the yield is more than 99%).

Example 2

This example provides a method for the preparation of spiro Salen ligands, the reaction scheme of which is shown below:

wherein, the compound rac-1d is prepared by the method of example 1, and the compound (R) -1d and the compound (S) -1d are synthesized by a literature route;

in salicylaldehyde compounds 2 a-i:

2a:R ¹ ＝R ² ＝H； 2b:R ¹ ＝R ² ＝Me；

2c：R ¹ ＝R ² ＝ ^t Bu； 2d：R ¹ ＝R ² ＝Cl；

2e：R ¹ ＝R ² ＝Cumyl； 2f：R ¹ ＝ ⁱ Pr，R ² ＝H；

2g：R ¹ ＝ ^t Bu，R ² ＝F； 2h：R ¹ ＝CMePh ₂ ，R ² ＝Me；

2i：R ¹ ＝CPh ₃ ,R ² ＝Me；

the specific reaction steps in the preparation route are as follows: spirocyclic diamine (2 mmol) and the corresponding salicylaldehyde (2 a-i) (4 mmol) were added to 20mL methanol, followed by two drops of formic acid, and the reaction was refluxed overnight. Recrystallization from methanol gives the corresponding product.

The spiro Salen ligands 3a-i obtained in this example were arranged in the following order from left to right and then from top to bottom:

wherein, the first and the second end of the pipe are connected with each other,

the single crystal diffractogram of rac-3h is shown in FIG. 1;

example 3

This example provides a method for the preparation of spiro Salen ligands, differing from example 2 only in that: salicylaldehyde compounds are

The corresponding spiro Salen ligand is obtained as

(ii) a The rest steps and parameters are the same.

Example 4

This example provides the metal reagent Y [ N (SiHMe) ₂ ) ₂ ] ₃ (THF) ₂ The synthesis method specifically comprises the following steps: in a glove box, liN (SiHMe) ₂ ) ₂ (859.3mg, 6.2mmol) was slowly added to the YCl ₃ (THF) ₃ (970.7mg, 2.4mmol) in N-hexane suspension (17 mL) at room temperature for 12 hours, filtering to give a white solid, washing with chilled N-hexane, vacuum drying the solvent, and recrystallizing the resulting white solid twice in N-pentane to obtain the metal reagent Y [ N (SiHMe) ₂ ) ₂ ] ₃ (THF) ₂ (yield: 82%,2.07 g), the nuclear magnetic hydrogen spectrum of which is shown in FIG. 2.

Other metal reagents of the present invention, such as ytterbium (Yb) metal reagent synthesis, zinc (Zn) metal reagent synthesis, or lanthanum (La) metal reagent synthesis, can be prepared by reference to the above procedures.

The specific process is as follows:

the metal ytterbium (Yb) reagent was synthesized as follows:

in a glove box, 1mol/L LiNSIME ₃ Was added to YbCl (30 mL) ₃ (1.95g, 10mmol) in tetrahydrofuran (12 mL), refluxing overnight, removing the solvent in vacuo, adding 30mL of toluene and heating to dissolve the resulting solid, collecting the supernatant by filtration, and recrystallizing at room temperature to give the product Yb [ N (SiMe 3) 2](μ-Cl)Li(THF) ₃ (yield: 63%,5.21 g).

The metallic zinc (Zn) reagent was synthesized as follows:

in a glove box, 2mol/L NaNSiMe ₃ To the hexane solution (20 mL) was added ZnCl ₂ (1.34g, 10 mmol) of tetrahydrofuran (12 mL) at 50 ℃Flowing for 5 hours, filtering and collecting filtrate, removing the solvent in vacuum, and distilling under reduced pressure to obtain a product Zn [ N (TMS) ₂ ] ₂ (yield: 38%,4.4 g).

The lanthanum (La) metal reagent is synthesized as follows:

in the glove box, la [ N (TMS) ₂ ] ₃ (3.1g, 5mmol) and tetrahydrofuran (3.6g, 50mmol) are sequentially added into 35mL of toluene, reflux is carried out for 30 minutes at 90 ℃, and the solvent is vacuumized to obtain the product La [ N (SiHMe) ₂ ) ₂ ] ₃ (THF) ₂ (yield: 99%,2.65 g).

Example 5

This example provides a method for preparing a Salen catalyst by reacting the spiro Salen ligand (3 a-k) L obtained in examples 2 to 3 with the metal reagent MXn (SiHMe) obtained in example 4, (Y [ N (SiHMe) ₂ ) ₂ ] ₃ (THF) ₂ 、Yb[N(SiMe3)2](μ-Cl)Li(THF) ₃ 、Zn[N(TMS) ₂ ] ₂ 、La[N(SiHMe ₂ ) ₂ ] ₃ (THF) ₂ ) And the directly purchased Metal reagent AlEt ₃ Coordination is carried out, and the reaction route is shown as follows:

the preparation method of the Salen catalyst comprises the following specific steps:

taking yttrium (Y) metal reagent as an example:

a solution of salen ligand L (3 a) (0.2 mmol) in toluene (5 mL) was slowly added dropwise to Y [ N (SiHMe) in a glove box ₂ ) ₂ ] ₃ (THF) ₂ (0.2 mmol) in hexane (5 mL). Reacting at room temperature for 24h, removing the solvent in vacuum, washing the obtained solid with pentane stored at-35 ℃ for three times to obtain the corresponding Salen catalyst 4a with the yield of 92 percent, and the nuclear magnetic hydrogen spectrum of the catalyst is shown in FIG. 3; the remaining Salen ligands L (3 b-k) were subjected to the above procedure to give the corresponding Salen catalyst 4b-k,the yield is 70-95%.

Example 6

This example provides a process for the selective ring-opening polymerization of racemic β -butyrolactone to produce poly-3-hydroxybutyrate of varying tacticity using the Salen catalyst from example 5, the reaction scheme of which is shown below:

wherein the Salen catalyst is

The initiator is Ph ₂ CHCH ₂ OH, and the solvent is toluene.

The preparation method of the reaction route comprises the following specific steps:

racemic beta-butyrolactone (86mg, 1mmol), initiator Ph ₂ CHCH ₂ OH (0.99mg, 0.005mmol) in toluene (0.4 mL), and 0.1mL of a toluene solution of 0.05mol/L Salen catalyst rac-A (shown in the above structure); the total volume of the polymerization was 0.5mL, the initial concentration of racemic β -butyrolactone monomer was 2mol/L, the concentration of Salen catalyst was 0.01mol/L, the concentration of initiator was 0.01mol/L, the molar ratio of racemic β -butyrolactone monomer/catalyst/initiator was 200; reacting at room temperature for 10 seconds, adding a chloroform solution with the mass concentration of 10mg/mL of benzoic acid to dissolve the product, and taking a small amount of solution to perform reaction ¹ H NMR analysis was performed to determine the conversion, the remaining reaction solution was poured into methanol to precipitate the polymer, and the precipitated solid was filtered, washed three times with methanol, and dried in a vacuum oven at 60 ℃ for 12 hours to obtain white poly (3-hydroxybutyrate).

In this example, nuclear Magnetic Resonance (NMR) detection of the poly (3-hydroxybutyrate) product showed 99% conversion of the monomer; determination of polymers ¹³ C NMR analysis showed the degree of syndiotacticity P of the polymer _r And was 0.93. The melting temperature and glass transition of poly (3-hydroxybutyrate) were measured by Differential Scanning Calorimetry (DSC), and the results showed that poly (3-hydroxybutyrate) prepared in this example had a melting pointThe temperature was 175 ℃.

Example 7

This example provides a method of using the Salen catalyst of example 5 in the selective ring-opening polymerization of racemic β -butyrolactone to produce poly-3-hydroxybutyrate with different tacticity, as described in example 6

The initiator is Ph ₂ CHCH ₂ OH, and the solvent is toluene.

racemic beta-butyrolactone (86mg, 1mmol), initiator Ph ₂ CHCH ₂ OH (0.99mg, 0.005mmol), dissolved in toluene (0.4 mL), was added to 0.1mL of a toluene solution of 0.05mol/L of the catalyst (R) -A (shown in the above structure); the total volume of polymerization was 0.5mL, the initial concentration of monomer was 2mol/L, the concentration of catalyst was 0.01mol/L, and the concentration of initiator was 0.01mol/L. The molar ratio monomer/catalyst/initiator is 200; reacting at room temperature for 1h, adding chloroform solution with mass concentration of 10mg/mL benzoic acid to dissolve the product, and taking a small amount of solution to perform reaction ¹ H NMR analysis was performed to determine the conversion, the remaining reaction solution was poured into methanol to precipitate the polymer, and the precipitated solid was filtered, washed three times with methanol, and dried in a vacuum oven at 60 ℃ for 12 hours to obtain white poly (3-hydroxybutyrate).

In this example, the poly (3-hydroxybutyrate) obtained was examined by Nuclear Magnetic Resonance (NMR), and the conversion of the monomer was 79%. Determination of polymers ¹³ C NMR, analysis showed the degree of syndiotacticity P of the polymer _r Is 0.71.

Example 8

This example provides a method of using the Salen catalyst prepared in example 5 in the selective ring-opening polymerization of racemic β -butyrolactone to produce poly-3-hydroxybutyrate with various tacticities, as described in example 6,

wherein the Salen catalyst is

The initiator is Ph ₂ CHCH ₂ OH, and the solvent is toluene.

racemic beta-butyrolactone (86mg, 1mmol), initiator Ph ₂ CHCH ₂ OH (0.99mg, 0.005mmol), dissolved in toluene (0.4 mL), was added to 0.1mL of a toluene solution of 0.05mol/L of the catalyst (S) -A (shown in the above structure); the total volume of polymerization was 0.5mL, the initial concentration of monomer was 2mol/L, the concentration of catalyst was 0.01mol/L, and the concentration of initiator was 0.01mol/L. Monomer/catalyst/initiator molar ratio 200; reacting at room temperature for 1h, adding chloroform solution with mass concentration of 10mg/mL benzoic acid to dissolve the product, and taking a small amount of solution to perform reaction ¹ H NMR analysis was performed to determine the conversion, the remaining reaction solution was poured into methanol to precipitate the polymer, and the precipitated solid was filtered, washed three times with methanol, and dried in a vacuum oven at 60 ℃ for 12 hours to obtain white poly (3-hydroxybutyrate).

In this example, the poly (3-hydroxybutyrate) obtained was examined by Nuclear Magnetic Resonance (NMR) and showed 78% conversion of the monomer. Determination of polymers ¹³ C NMR, analysis showed the degree of syndiotacticity P of the polymer _r Is 0.70.

Example 9

This example provides a method of using the Salen catalyst of example 5 in the selective ring-opening polymerization of racemic β -butyrolactone to produce poly-3-hydroxybutyrate with different tacticity, as described in example 6,

wherein the Salen catalyst is

(its single crystal diffraction pattern is shown in FIG. 2), initiator Ph ₂ CHCH ₂ OH, and toluene as a solvent.

The preparation steps of the reaction route are as follows:

racemic beta-butyrolactone (86mg, 1mmol), initiator Ph ₂ CHCH ₂ OH (0.99mg, 0.005mmol) was dissolved in toluene (0.4 mL), and the resulting solution was added at a concentration (above knot)Shown in structure) 0.05mol/L of toluene solution of catalyst (rac) -B is 0.1mL; the total volume of polymerization was 0.5mL, the initial concentration of monomer was 2mol/L, the concentration of catalyst was 0.01mol/L, and the concentration of initiator was 0.01mol/L. The molar ratio monomer/catalyst/initiator is 200; reacting at room temperature for 20s, adding chloroform solution with 10mg/mL benzoic acid to dissolve the product, and taking a small amount of solution to perform reaction ¹ H NMR analysis to determine the conversion, the remaining reaction solution was poured into methanol to precipitate the polymer, and the precipitated solid was filtered, washed three times with methanol, and dried in a vacuum oven at 60 ℃ for 12 hours to give white poly (3-hydroxybutyrate).

In this example, the poly (3-hydroxybutyrate) obtained was examined by Nuclear Magnetic Resonance (NMR), and the conversion of the monomer was 99%. Determination of polymers ¹³ C NMR analysis showed the degree of syndiotacticity P of the polymer _r Is 0.99. The resulting poly (3-hydroxybutyrate) ¹³ C NMR, as shown in FIG. 4, split at 169.4ppm,40.85ppm,19.96ppm as shown below, all of which were found to be single peaks, demonstrating that the polymer syndiotactic degree could reach 0.99. Wherein, the nuclear magnetic carbon spectrogram of the syndiotactic poly (3-hydroxybutyrate) prepared by the method is shown in figure 3; the DSC spectrum is shown in figure 8.

In this example, the melting temperature and glass transition of poly (3-hydroxybutyrate) were measured by Differential Scanning Calorimetry (DSC), and as shown in FIG. 5, it was found that poly (3-hydroxybutyrate) prepared in this example had a melting temperature of 184 ℃ C., 191 ℃ C., a glass transition temperature of 11.56 ℃ C., and a change in enthalpy of fusion of 80.01J/g.

Example 10

wherein the Salen catalyst is

The initiator is Ph ₂ CHCH ₂ OH, and toluene as a solvent.

The preparation steps of the reaction route are as follows:

racemic beta-butyrolactone (86mg, 1mmol), initiator Ph ₂ CHCH ₂ OH (0.99mg, 0.005mmol), dissolved in toluene (0.4 mL), was added 0.1mL of a toluene solution of 0.05mol/L catalyst (rac) -B (shown in the above structure); the total volume of polymerization was 0.5mL, the initial concentration of monomer was 2mol/L, the concentration of catalyst was 0.001mol/L, and the concentration of initiator was 0.01mol/L. The monomer/catalyst/initiator molar ratio is 2000; reacting at room temperature for 17min, adding chloroform solution with mass concentration of 10mg/mL benzoic acid to dissolve the product, and taking a small amount of solution to perform reaction ¹ H NMR analysis to determine the conversion, the remaining reaction solution was poured into methanol to precipitate the polymer, and the precipitated solid was filtered, washed three times with methanol, and dried in a vacuum oven at 60 ℃ for 12 hours to give white poly (3-hydroxybutyrate).

In this example, nuclear Magnetic Resonance (NMR) analysis of the poly (3-hydroxybutyrate) produced showed 40% conversion of the monomer. Determination of polymers ¹³ C NMR analysis showed the degree of syndiotacticity P of the polymer _r Is 0.99. The melting temperature and glass transition of poly (3-hydroxybutyrate) were measured by Differential Scanning Calorimetry (DSC), and the results showed that poly (3-hydroxybutyrate) prepared in this example had a maximum melting temperature of 186 ℃ and a glass transition temperature of 11.55 ℃.

Example 11

wherein the Salen catalyst is

The initiator is Ph ₂ CHCH ₂ OH, and the solvent is toluene.

The preparation steps of the reaction route are as follows:

racemic beta-butyrolactone (86mg, 1mmol), initiator Ph ₂ CHCH ₂ OH (0.99mg, 0.005mmol) was dissolved in methylene chloride (0.4 mL) and added at a concentration of(shown in the above structure) 0.05mol/L of a solution of catalyst (rac) -B in methylene chloride 0.1mL; the total volume of polymerization was 0.5mL, the initial concentration of monomer was 2mol/L, the concentration of catalyst was 0.001mol/L, and the concentration of initiator was 0.01mol/L. Monomer/catalyst/initiator molar ratio 200; reacting at room temperature for 20s, adding chloroform solution with mass concentration of 10mg/mL benzoic acid to dissolve the product, and taking a small amount of solution to perform reaction ¹ H NMR analysis to determine the conversion, the remaining reaction solution was poured into methanol to precipitate the polymer, and the precipitated solid was filtered, washed three times with methanol, and dried in a vacuum oven at 60 ℃ for 12 hours to give white poly (3-hydroxybutyrate).

In this example, the poly (3-hydroxybutyrate) obtained was examined by Nuclear Magnetic Resonance (NMR), and the conversion of the monomer was 90%. Determination of polymers ¹³ C NMR analysis showed the degree of syndiotacticity P of the polymer _r And was 0.99.

Example 12

This example provides a process for the selective ring-opening polymerization of racemic β -butyrolactone to produce poly-3-hydroxybutyrate of varying tacticity using the Salen catalyst from example 5, differing from example 11 only in that: the reaction solvent is tetrahydrofuran, and the rest steps and parameters are the same.

In this example, the poly (3-hydroxybutyrate) obtained was examined by Nuclear Magnetic Resonance (NMR), and the conversion of the monomer was 99%. Determination of polymers ¹³ C NMR analysis showed the degree of syndiotacticity P of the polymer _r And was 0.99.

Example 13

This example provides a process for the selective ring-opening polymerization of racemic β -butyrolactone to produce poly-3-hydroxybutyrate of varying tacticity, wherein the Salen ligand has the formula:

the specific process is as follows: racemic beta-butyrolactone (86mg, 1mmol), initiator Ph ₂ CHCH ₂ OH (0.99mg, 0.005mmol), dissolved in toluene (0.4 mL)Adding 0.05mol/L ligand C- (sR, aS, aS) and 0.1mol/L metal reagent Y [ N (SiHMe) into the solution ₂ ) ₂ ] ₃ (THF) ₂ 0.1mL of the mixed solution; the total volume of polymerization was 0.5mL, the initial concentration of racemic β -butyrolactone monomer was 2mol/L, the catalyst concentration was 0.01mol/L, and the initiator concentration was 0.01mol/L. The molar ratio of the monomer/ligand/metal reagent/initiator is 200 ¹ H NMR analysis was performed to determine the conversion, the remaining reaction solution was poured into methanol to precipitate the polymer, and the precipitated solid was filtered, washed three times with methanol, and dried in a vacuum oven at 60 ℃ for 12 hours to obtain white poly (3-hydroxybutyrate).

In this example, nuclear Magnetic Resonance (NMR) analysis of the obtained poly (3-hydroxybutyrate) showed that the conversion of the monomer was 67%. Determination of polymers ¹³ C NMR analysis showed the degree of syndiotacticity P of the polymer _r Is 0.94.

Example 14

This example provides a process for the selective ring-opening polymerization of racemic β -butyrolactone to produce poly-3-hydroxybutyrate of varying tacticity, wherein the Salen ligand has the formula shown below:

the specific process is as follows: racemic beta-butyrolactone (86mg, 1mmol), initiator Ph ₂ CHCH ₂ OH (0.99mg, 0.005mmol) was dissolved in toluene (0.4 mL), and a solution containing (the formula shown above) 0.05mol/L of ligand E- (sR, aS, aS) and 0.1mol/L of metal reagent Y [ N (SiHMe) ₂ ) ₂ ] ₃ (THF) ₂ 0.1mL of the mixed solution; the total volume of polymerization was 0.5mL, the initial concentration of racemic β -butyrolactone monomer was 2mol/L, the catalyst concentration was 0.01mol/L, and the initiator concentration was 0.01mol/L. The molar ratio of the monomer/ligand/metal reagent/initiator is 200Dissolving the product, and taking a small amount of solution for ¹ H NMR analysis was performed to determine the conversion, the remaining reaction solution was poured into methanol to precipitate the polymer, and the precipitated solid was filtered, washed three times with methanol, and dried in a vacuum oven at 60 ℃ for 12 hours to obtain white poly (3-hydroxybutyrate).

In this example, nuclear Magnetic Resonance (NMR) analysis of the poly (3-hydroxybutyrate) obtained showed that the conversion of the monomer was 99%. Determination of polymers ¹³ C NMR analysis showed isotacticity P of the polymer _m Is 0.99. Wherein, the nuclear magnetic carbon spectrogram of the isotactic poly (3-hydroxybutyrate) prepared by the embodiment is shown in figure 4; its DSC spectrum is shown in figure 6; the nuclear magnetic carbon spectrum of syndiotactic poly (3-hydroxybutyrate) obtained in this example compared with that of isotactic poly (3-hydroxybutyrate) obtained in example 14 is shown in FIGS. 5 and 7, which indicates that: syndiotactic poly-3-hydroxybutyrate nuclear magnetic resonance carbon spectrum: ¹³ C NMR(101MHz,CDCl ₃ ) δ 169.38,67.80,40.88,19.97; isotactic poly-3-hydroxybutyrate nuclear magnetic resonance carbon spectrum: ¹³ C NMR(101MHz,CDCl ₃ )δ169.28,67.78,40.98,19.92。

from the above examples 6-14, it can be seen that the present invention is directed to the selective polymerization of racemic β -butyrolactone, in different types of solutions, the catalyst Rac-B can achieve iso-selectivity of 0.97-0.99, and exhibit extremely high activity, with a monomer/catalyst ratio of 2000/1 still having high activity. In addition, the catalysts E- (sS, aR and aR) can realize the isotactic selectivity polymerization of racemic beta-butyrolactone, and the isotacticity is 0.97-0.99.

Comparative example 1

This example provides a process for the preparation of poly-3-hydroxybutyrate with varying degrees of tacticity from racemic β -butyrolactone, differing from example 14 only in that: the following catalysts were used:

in this example, the poly (3-hydroxybutyrate) obtained was examined by Nuclear Magnetic Resonance (NMR), and the conversion of the monomer was 99%. Determination of polymers ¹³ C NMR, analysis showed the isotacticity P of the polymer _m And was 0.70.

Comparative example 2

This example provides a process for the preparation of poly-3-hydroxybutyrate with varying degrees of tacticity from racemic β -butyrolactone, differing from example 9 only in that: the following catalysts were used:

in this example, the obtained poly (3-hydroxybutyrate) was measured for the polymer ¹³ C NMR analysis showed that the polymer had a degree of syndiotacticity P _r ＝0.74。

Part of the characterization data of the Salen ligand and Salen catalyst prepared in the present invention are as follows:

¹ H NMR(400MHZ,CDCl ₃ ，25℃)

¹ H NMR(400MHz,cdcl ₃ )δ11.58(s,2H),8.19(s,2H),7.29–7.14(m,8H),6.85–6.79(m,2H),6.76(d,J＝8.3Hz,2H),6.68(dd,J＝7.2,1.4Hz,2H),3.06(dd,J＝9.2,3.6Hz,4H),2.40–2.18(m,4H).

¹ H NMR(400MHZ,CDCl ₃ ,25℃)

¹ H NMR(400MHz,CDCl ₃ )δ12.19(s,2H),8.31(s,2H),7.30(d,J＝2.4Hz,2H),7.20–7.11(m,4H),7.02(d,J＝2.4Hz,2H),6.78(dd,J＝7.0,1.8Hz,2H),3.13–2.95(m,4H),2.37–2.17(m,4H),1.32(s,18H),1.27(s,18H).

¹³ C NMR(101MHz,CDCl ₃ )δ162.75,158.14,145.22,144.87,142.00,139.89,136.66,128.57,127.48,126.55,123.51,118.22,116.43,60.44,38.21,35.09,34.24,31.62,31.05,29.47.

¹ H NMR(400MHZ，CDCl ₃ ，25℃)

¹ H NMR(400MHz,CDCl ₃ )δ11.78(s,2H),7.90(s,2H),7.35–7.14(m,16H),7.08(dd,J＝12.2,7.3Hz,6H),7.00(t,J＝7.6Hz,2H),6.92–6.82(m,4H),6.46(d,J＝7.8Hz,2H),3.48(s,4H),3.00–2.83(m,2H),2.76(dd,J＝15.9,8.7Hz,2H),2.14(dd,J＝12.6,7.6Hz,2H),2.03(q,J＝11.4,10.8Hz,2H),1.79-1.56(m,16H),1.52(s,12H). ¹³ C NMR(101MHz,CDCl ₃ )δ162.20,157.59,150.90,150.64,144.62,144.48,141.60,139.20,136.06,129.33,128.37,128.17,128.13,127.64,126.81,126.02,125.75,124.97,123.32,118.26,116.57,60.19,51.02,42.48,42.03,38.14,31.03,31.01,30.76,29.43,29.01.

¹ H NMR(400MHZ,CDCl ₃ ,25℃)

¹ H NMR(400MHz,CDCl ₃ )δ12.33(s,2H),8.13(s,2H),7.32(d,J＝2.5Hz,2H),7.28–7.13(m,4H),7.09(d,J＝2.5Hz,2H),6.69(d,J＝7.6Hz,2H),3.13–3.05(m,4H),2.37(dq,J＝12.8,4.4,3.9Hz,2H),2.22(dt,J＝12.7,10.1Hz,2H). ¹³ C NMR(101MHz,CDCl ₃ )δ160.06,155.51,145.24,143.98,141.66,132.45,129.55,128.76,124.73,122.99,122.47,120.17,116.49,60.15,38.36,30.94.

¹ H NMR(400MHZ,CDCl ₃ ,25℃)

¹ H NMR(400MHz,CDCl ₃ )δ12.19(s,2H),8.19(s,2H),7.21–7.10(m,4H),6.99(dd,J＝10.7,3.1Hz,2H),6.74(dd,J＝7.3,2.9Hz,4H),3.17–2.97(m,4H),2.41–2.18(m,4H),1.30(s,18H). ¹³ C NMR(101MHz,CDCl ₃ )δ161.30(d,J＝3.1Hz),156.56(d,J＝1.4Hz),145.05,144.63,141.98,139.64(d,J＝5.6Hz),128.68,124.02,118.33(d,J＝7.6Hz),117.78,117.54,116.29,114.51,114.28,60.37,38.27,35.08,31.01,29.16.

¹ H NMR(400MHZ,CDCl ₃ ,25℃)

¹ H NMR(400MHz,CDCl ₃ )δ11.33(s,2H),7.96(s,2H),7.30–7.10(m,30H),7.07(d,J＝2.1Hz,2H),6.84(d,J＝2.2Hz,2H),6.67(t,J＝7.6Hz,2H),6.56(d,J＝7.4Hz,2H),6.37(d,J＝7.7Hz,2H),2.75(ddd,J＝44.5,16.3,8.2Hz,4H),2.17(s,6H),2.13–1.93(m,4H).

¹ HNMR(400MHZ,CDCl ₃ ,25℃)

¹ H NMR(400MHz,CDCl ₃ )δ11.82(s,2H),8.09(s,2H),7.32–7.20(m,12H),7.10–7.00(m,8H),6.88(t,J＝7.6Hz,2H),6.84(d,J＝2.2Hz,2H),6.77–6.71(m,2H),6.49(d,J＝7.8Hz,2H),6.37(d,J＝2.2Hz,2H),2.95–2.82(m,2H),2.76(dd,J＝15.8,8.6Hz,2H),2.18–2.12(m,8H),2.08(s,8H). ¹³ C NMR(125MHz,cdcl ₃ )δ161.97,157.46,148.70,148.38,144.69,144.38,141.48,135.77,134.50,130.88,128.64–128.09(m),127.62(d,J＝3.8Hz),125.82,125.53,123.39,118.83,116.14,60.07,51.59,38.14,30.68,27.39,20.58.

¹ H NMR(400MHZ,CDCl ₃ ,25℃)

¹ H NMR(400MHz,CDCl ₃ CDCl ₃ )δ11.83(s,2H),8.09(s,2H),7.31–7.19(m,12H),7.09–7.03(m,8H),6.89(t,J＝7.6Hz,2H),6.84(d,J＝2.2Hz,2H),6.74(dd,J＝7.5,1.0Hz,2H),6.50(d,J＝7.8Hz,2H),6.38(d,J＝2.2Hz,2H),2.88(dt,J＝10.7,7.9Hz,2H),2.76(dd,J＝15.9,8.6Hz,2H),2.20–2.13(m,8H),2.08(s,8H).

¹ H NMR(400MHz,CDCl ₃ )δ11.83(s,2H),8.09(s,2H),7.31–7.17(m,12H),7.11–7.03(m,8H),6.89(t,J＝7.6Hz,2H),6.85(d,J＝2.2Hz,2H),6.74(d,J＝7.4Hz,2H),6.50(d,J＝7.7Hz,2H),6.38(d,J＝2.2Hz,2H),2.98–2.83(m,2H),2.76(dd,J＝15.8,8.6Hz,2H),2.17(s,8H),2.09(s,8H). ¹³ C NMR(125MHz,cdcl ₃ )δ161.97,157.46,148.70,148.38,144.69,144.38,141.48,135.77,134.50,130.88,128.64–128.09(m),127.62(d,J＝3.8Hz),125.82,125.53,123.39,118.83,116.14,60.07,51.59,38.14,30.68,27.39,20.58.

¹ H NMR(400MHz,CDCl ₃ )δ11.34(s,2H),8.37(d,J＝1.3Hz,2H),8.00(dd,J＝26.1,8.3Hz,4H),7.76–7.57(m,6H),7.54–7.41(m,2H),7.31–6.94(m,20H),6.77(t,J＝7.6Hz,2H),6.63(dd,J＝12.0,7.6Hz,4H),2.87(pd,J＝14.7,13.1,7.7Hz,4H),2.32–2.10(m,4H). ¹³ C NMR(101MHz,CDCl ₃ )δ162.01,154.81,145.03,144.67,142.29,141.71,140.42,135.64,134.11,133.17,133.09,131.54,128.86,128.61,128.43,128.28,128.02,127.32,127.25,126.99,126.38,126.17,125.70,125.01,123.97,123.15,120.58,120.01,116.67,60.10,38.24,30.88.

¹ H NMR(400MHZ,CDCl ₃ ,25℃)

¹ H NMR(400MHz,)δ7.57(s,2H),7.45(d,J＝2.7Hz,2H),7.05(d,J＝2.0Hz,2H),6.73(t,J＝7.3Hz,2H),6.56–6.51(m,2H),6.47(d,J＝7.4Hz,2H),5.01(p,J＝3.0Hz,2H),3.81(s,5H),2.69(s,2H),2.43(s,2H),2.03(s,2H),1.85-1.12(br,38H),0.80(dt,J＝13.1,6.4Hz,4H),0.31(dd,J＝28.3,3.0Hz,12H).

¹ H NMR(400MHz,C ₆ D ₆ )δ7.66(d,J＝45.8Hz,2H),7.54(s,1H),7.37–6.93(m,22H),6.85–6.64(m,3H),6.64–6.28(m,4H),4.68(p,J＝3.1Hz,2H),3.21(s,2H),2.99(s,2H),2.81(d,J＝58.8Hz,8H),2.60(t,J＝10.2Hz,1H),2.45(d,J＝10.0Hz,1H),2.16(d,J＝37.9Hz,2H),1.83(d,J＝4.7Hz,8H),1.14(d,J＝6.3Hz,4H),0.43(dd,J＝15.6,3.0Hz,12H).

the foregoing is illustrative and explanatory of the present invention, and it is not intended that the invention be limited to the specific embodiments described, but that modifications, additions, or substitutions in a similar manner will occur to those skilled in the art without inventive faculty.

Claims

1. A spiro Salen ligand is characterized in that the structural general formula of the spiro Salen ligand is as follows:

wherein each R is ¹ 、R ² 、R ³ And R ⁴ Independently hydrogen, alkyl, cycloalkyl, alkoxy, aryl, halo, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, substituted heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atoms connected with the compound and/or the adjacent carbon atoms independently form cycloalkyl and heteroarylOr an aryl group.

2. The spirocyclic Salen ligand of claim 1, wherein each R is ¹ 、R ² 、R ³ And R ⁴ Independently of one another is hydrogen, C ₁ ～C ₁₀ Alkyl radical, C ₃ ～C ₆ Cycloalkyl radical, C ₁ ～C ₁₀ Alkoxy radical, C ₆ ～C ₁₄ Aryl, halogen, 5-6 membered heteroaryl, substituted C ₁ ～C ₁₀ Alkyl, substituted C ₁ ～C ₁₀ Alkoxy, by one or more R ^1a Substituted C ₆ ～C ₁₄ Aryl radicals, substituted by one or more R ^1a Substituted 5-6 membered heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atom to which it is attached, and/or the adjacent carbon atoms each independently form C ₃ ～C ₇ Cycloalkyl, 5-6 membered heteroaryl or phenyl; r ^1a Is C ₁ ～C ₁₀ Alkyl radical, C ₁ ～C ₁₀ Alkoxy or halogen.

3. The spirocyclic Salen ligand of claim 2, wherein each R is ¹ 、R ² 、R ³ And R ⁴ Independently hydrogen, fluorine, chlorine, bromine, iodine, methyl, ethyl, tert-butyl, isopropyl, cyclopropyl, cyclobutyl, cyclohexyl, furyl, pyridyl, biphenyl, 2-phenylbiphenyl, trityl, cumyl, benzyl, adamantyl, C ₁ ～C ₃ Perfluoroalkoxy, C ₁ ～C ₃ Perfluoroalkyl, arylmethylene, heteroarylmethylene, arylmethine, or heteroarylmethine.

4. A process for the preparation of a spiro Salen ligand according to any one of claims 1 to 3, comprising the steps of: performing ketoamine condensation reaction on salicylaldehyde compounds and spirodiamine under an acidic condition, and separating and purifying reaction products after the reaction is finished to obtain the salicylaldehyde compound and the spirodiamine;

5. A Salen catalyst, wherein said Salen catalyst employs a spiro Salen ligand as defined in any one of claims 1 to 3 as a ligand.

6. The Salen catalyst according to claim 5, having the general structural formula:

wherein each R is ¹ 、R ² 、R ³ And R ⁴ Independently hydrogen, alkyl, cycloalkyl, alkoxy, aryl, halo, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, substituted heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atoms to which they are attached, and/or, adjacent carbon atoms, independently form a cycloalkyl, heteroaryl or aryl group, respectively; m is a metal element of group IIB, IIIA, IVA, VA or VIA; m is 1 or 2; each X is independently C ₁ ～C ₂₀ Alkyl, substituted amino, C ₃ ～C ₆ Cycloalkyl radical, C ₃ ～C ₆ Heterocycloalkyl, C ₆ ～C ₁₄ Aryl or 5-6 membered heteroaryl.

7. The process for the preparation of a spiro Salen catalyst according to claim 5 or 6, comprising the steps of: carrying out coordination on the spiro Salen ligand and a metal reagent MXn to obtain the spiro Salen ligand;

wherein each R is ¹ 、R ² 、R ³ And R ⁴ Independently hydrogen, alkyl, cycloalkyl, alkoxy, aryl, halo, heteroaryl, substituted alkyl, substituted alkoxy, substituted aryl, substituted heteroaryl or R ¹ 、R ² 、R ³ And R ⁴ The carbon atoms to which they are attached, and/or, the adjacent carbon atoms, independently form a cycloalkyl, heteroaryl or aryl group, respectively; m is a metal element of group IIB, IIIA, IVA, VA or VIA; n is 1, 2,3, 4, 5 or 6; m is 1 or 2; each X is independently C ₁ ～C ₂₀ Alkyl, substituted amino, C ₃ ～C ₆ Cycloalkyl radical, C ₃ ～C ₆ Heterocycloalkyl radical, C ₆ ～C ₁₄ Aryl or 5-6 membered heteroaryl.

8. A polymerization system comprising the Salen catalyst of claim 5 or 6 and an initiator.

9. The polymerization system of claim 8, wherein the initiator comprises an alkyl alcohol, an alkyl mercaptan, a benzyl alcohol, or a benzyl mercaptan.

10. Use of a polymerization system according to claim 8 or 9 for the selective ring-opening polymerization of racemic β -butyrolactone to produce poly-3-hydroxybutyrate of varying tacticity, comprising the steps of: adding racemic beta-butyrolactone, a Salen catalyst, an initiator and a solvent into a reaction device, reacting for 5 s-2 h at 20-45 ℃, and separating and purifying a reaction product to obtain the compound; wherein the mol ratio of the racemic beta-butyrolactone to the Salen catalyst to the initiator is 100-10000.