CN117327027A - Ligand compound with oxazole structure, preparation method thereof and nickel catalyst - Google Patents

Abstract

The present disclosure proposes a ligand compound with an oxazole structure, whose structure is shown in formula (I), Among them, _R1 is selected from any one of methyl and benzyl; Ar is selected from one of naphthyl, benzothienyl, substituted or unsubstituted benzene, when the above-mentioned substituted or unsubstituted benzene has When a substituent is used, the substituent is selected from an electron-withdrawing substituent or an electron-donating substituent.

Description

Ligand compound with oxazole structure and preparation method, nickel catalyst

Technical Field

The present invention belongs to the technical field of organic synthesis, and in particular relates to a compound having an oxazole structure, a preparation method, and a nickel catalyst.

Background Art

In recent years, the discovery of late transition metal catalysts has promoted the rapid development of the field of olefin polymerization. The regulation of olefin polymerization process by catalyst structural design has always been a frontier scientific issue in this field. Due to the low cost and high abundance of metallic nickel, nickel catalysts show broad application prospects in the field of olefin polymerization. In 1978, the discovery of SHOP catalyst attracted widespread attention from researchers around the world. It has high activity in producing α-olefins with Flory distribution. Ethylene oligomers obtained by SHOP nickel catalyst can be used as basic components of lubricants and functional additives in surface modifiers, and have high application value. Since then, the synthesis of ethylene oligomers by ethylene coordination reaction catalyzed by nickel catalysts has been widely studied. There is still a need to explore effective catalytic synthesis of ethylene oligomers in related technologies.

Summary of the invention

In view of this, in order to solve at least one of the above and other technical problems in the related art, the present disclosure provides a ligand compound having an oxazole structure, the structure of which is shown in formula (I),

Wherein, R ₁ is selected from any one of methyl and diphenylmethyl;

Ar is selected from naphthyl, benzothiophenyl, substituted or unsubstituted benzene,

When the above-mentioned substituted or unsubstituted benzene has a substituent, the substituent is selected from an electron-withdrawing substituent or an electron-donating substituent.

According to an embodiment of the present disclosure, the electron-withdrawing substituent of the ligand compound having an oxazole structure is selected from any one of trifluoromethyl, hydroxyl, and nitro, and the electron-donating substituent is selected from methoxy.

According to the embodiments of the present disclosure, the structural formula of the ligand compound having an oxazole structure is shown in any one of the following formulas (I-a) to (I-c):

Wherein, _R2 is selected from any one of trifluoromethyl, hydroxyl, nitro, and methoxy.

In some specific embodiments, the structural formula of the ligand compound having an oxazole structure is as follows:

In another aspect of the present disclosure, a method for preparing the above-mentioned ligand compound is provided, comprising:

The compound represented by formula (A) is reacted with a keto acid methyl ester compound to obtain a compound represented by formula (B);

The compound represented by formula (B) is reacted with 2-amino-2-methyl-1-propanol to obtain a compound represented by formula (C);

The compound represented by formula (C) is subjected to autoisomerization and dehydration reaction to obtain the compound represented by formula (I).

According to an embodiment of the present disclosure, compound (A) and keto acid methyl ester compound are mixed in a molar ratio of 1:1, p-toluenesulfonic acid monohydrate is added, and the mixture is refluxed at 140° C. to 145° C. for 40 h, and compound (B) is obtained after recrystallization;

Compound (B) and 2-amino-2-methyl-1-propanol are mixed in a molar ratio of 1:2 to 1:2.5, reacted at 140° C. to 145° C. for 24 hours, and compound (C) is separated;

After the compound (C) is dissolved, triethylamine, 4-dimethylaminopyridine and 4-toluenesulfonyl chloride are added and reacted at 80° C. to 85° C. for 40 hours to obtain a ligand compound.

In another aspect of the present disclosure, a nickel catalyst having an oxazole structure is provided, and its structure is shown in formula (II),

Wherein, R ₁ is selected from any one of methyl and diphenylmethyl;

Ar is selected from naphthyl, benzothiophenyl, substituted or unsubstituted benzene,

When the substituted or unsubstituted benzene has a substituent, the substituent is selected from an electron-withdrawing substituent or an electron-donating substituent;

Among them, the electron-withdrawing substituent is preferably any one of trifluoromethyl, hydroxyl, and nitro;

The electron donating substituent is preferably a methoxy group.

According to an embodiment of the present disclosure, the structural formula of the nickel catalyst having an oxazole structure is shown in any one of the following formulas (II-a) to (II-c):

Wherein, R ₂ includes any one of trifluoromethyl, hydroxyl, nitro, and methoxy.

In some specific embodiments, the nickel catalyst having an oxazole structure has the following structural formula:

In another aspect of the present disclosure, a method for preparing the above-mentioned nickel catalyst having an oxazole structure is proposed, comprising:

The above ligand compound having an oxazole structure is dissolved, reacted with ethylene glycol dimethyl ether nickel bromide, n-hexane is added, stirred and filtered to obtain a nickel catalyst.

According to the embodiments of the present disclosure, a novel nickel catalyst having an oxazole structure is synthesized by using a ligand compound having an oxazole structure. Compared with aniline having a larger steric hindrance, the oxazole ring has a smaller steric hindrance, which is beneficial to the insertion of ethylene, thereby improving the ethylene polymerization activity. At the same time, the oxazole ring having a smaller steric hindrance forms an asymmetric structure with the aniline having a larger steric hindrance, which is beneficial to the chain walking process in ethylene polymerization, thereby producing highly branched polyethylene.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a method for synthesizing a ligand compound having an oxazole structure in the present disclosure;

FIG2 is a schematic diagram of the single crystal structure of the nickel catalyst (II-2) having an oxazole structure in Example 8 of the present disclosure;

FIG3A is a hydrogen nuclear magnetic resonance spectrum of the intermediate product (B-1) in Example 1 of the present disclosure;

FIG3B is a carbon NMR spectrum of the intermediate product (B-1) in Example 1 of the present disclosure;

FIG4A is a hydrogen nuclear magnetic resonance spectrum of compound (I-1) in Example 1 of the present disclosure;

FIG4B is a carbon NMR spectrum of compound (I-1) in Example 1 of the present disclosure;

FIG5A is a hydrogen nuclear magnetic resonance spectrum of the intermediate product (B-2) in Example 2 of the present disclosure;

FIG5B is a carbon NMR spectrum of the intermediate product (B-2) in Example 2 of the present disclosure;

FIG6A is a hydrogen nuclear magnetic resonance spectrum of the intermediate product (C-2) in Example 2 of the present disclosure;

FIG6B is a carbon NMR spectrum of the intermediate product (C-2) in Example 2 of the present disclosure;

FIG7A is a hydrogen nuclear magnetic resonance spectrum of compound (I-2) in Example 2 of the present disclosure;

FIG7B is a carbon NMR spectrum of compound (I-2) in Example 2 of the present disclosure;

FIG8A is a hydrogen nuclear magnetic resonance spectrum of the intermediate product (B-3) in Example 3 of the present disclosure;

FIG8B is a carbon NMR spectrum of the intermediate product (B-3) in Example 3 of the present disclosure;

FIG9A is a hydrogen nuclear magnetic resonance spectrum of the intermediate product (C-3) in Example 3 of the present disclosure;

FIG9B is a carbon NMR spectrum of the intermediate product (C-3) in Example 3 of the present disclosure;

FIG10A is a hydrogen nuclear magnetic resonance spectrum of compound (I-3) in Example 3 of the present disclosure;

FIG10B is a carbon NMR spectrum of compound (I-3) in Example 3 of the present disclosure;

FIG11A is a hydrogen nuclear magnetic resonance spectrum of the intermediate product (B-4) in Example 4 of the present disclosure;

FIG11B is a carbon NMR spectrum of the intermediate product (B-4) in Example 4 of the present disclosure;

FIG12A is a hydrogen nuclear magnetic resonance spectrum of the intermediate product (C-4) in Example 4 of the present disclosure;

FIG12B is a carbon NMR spectrum of the intermediate product (C-4) in Example 4 of the present disclosure;

FIG13A is a hydrogen nuclear magnetic resonance spectrum of compound (I-4) in Example 4 of the present disclosure;

FIG13B is a carbon NMR spectrum of compound (I-4) in Example 4 of the present disclosure;

FIG14A is a hydrogen nuclear magnetic resonance spectrum of the intermediate product (B-5) in Example 5 of the present disclosure;

FIG14B is a carbon NMR spectrum of the intermediate product (B-5) in Example 5 of the present disclosure;

FIG15A is a hydrogen nuclear magnetic resonance spectrum of the intermediate product (C-5) in Example 5 of the present disclosure;

FIG15B is a carbon NMR spectrum of the intermediate product (C-5) in Example 5 of the present disclosure;

FIG16A is a hydrogen nuclear magnetic resonance spectrum of compound (I-5) in Example 5 of the present disclosure;

FIG16B is a carbon NMR spectrum of compound (I-5) in Example 5 of the present disclosure;

FIG17A is a hydrogen nuclear magnetic resonance spectrum of compound (I-6) in Example 6 of the present disclosure;

FIG17B is a carbon NMR spectrum of compound (I-6) in Example 6 of the present disclosure;

FIG18 is a perspective view of the optimized structure of the nickel catalyst (II-1) in one embodiment of the present disclosure; and

FIG. 19 is a three-dimensional diagram of the optimized structure of the nickel catalyst (II-2) in one embodiment of the present disclosure.

DETAILED DESCRIPTION

In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

The endpoints and any values of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this disclosure.

The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "include", "comprising", etc. used herein indicate the existence of the features, steps, operations and/or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have the usual meanings understood by persons with ordinary skills in the field to which the present disclosure belongs. If the full text involves descriptions such as "first", "second", etc., the descriptions such as "first", "second", etc. are only used to distinguish similar objects, and cannot be understood as indicating or implying their relative importance, order of precedence, or implicitly indicating the number of technical features indicated. It should be understood that the data described by "first", "second", etc. can be interchangeable under appropriate circumstances.

Similarly, in order to simplify the present disclosure and help understand one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this disclosure.

Nickel catalysts used to produce ethylene oligomers tend to have strong β-H elimination reactions, so sterically less hindered groups or electron-deficient substituents are usually installed on the ligands. Some imino nickel catalysts can produce highly branched ethylene oligomers through a chain walking process consisting of repeated β-H elimination reactions and olefin reinsertion.

On this basis, we synthesized a series of nickel catalysts with oxazole structures to produce hyperbranched ethylene oligomers. Compared with aniline and other groups with large steric hindrance, the oxazole ring has less steric hindrance, which is conducive to the insertion of ethylene, thereby improving the polymerization activity of ethylene. At the same time, the oxazole ring with less steric hindrance and the aniline with greater steric hindrance can form an asymmetric structure, which is conducive to the chain walking process during ethylene polymerization, thereby producing highly branched polyethylene.

The catalytic mechanism of the nickel catalyst with an oxazole structure proposed in the present disclosure in actual polymerization is as follows:

It is well known to those skilled in the art that the ethylene polymerization process mainly includes three steps: chain growth, chain transfer and chain walking. When the nickel catalyst with an oxazole structure proposed in the present disclosure is used, the chain growth process refers to the coordination of ethylene with the metal center of the nickel catalyst and the insertion of the metal-alkyl bond; the chain transfer process refers to the β-H elimination that occurs during the ethylene insertion process, and the metal center vacancy of the nickel catalyst coordinates with new ethylene; the chain walking process refers to the β-H elimination of ethylene, the flipping of 180°, and the re-coordination and insertion with the metal center of the nickel catalyst.

The present disclosure provides a ligand compound having an oxazole structure, the structure of which is shown in formula (I):

Wherein, R ₁ is selected from any one of methyl and diphenylmethyl;

Ar is selected from naphthyl, benzothiophenyl, substituted or unsubstituted benzene,

When the above-mentioned substituted or unsubstituted benzene has a substituent, the substituent is selected from an electron-withdrawing substituent or an electron-donating substituent.

According to an embodiment of the present disclosure, the electron-withdrawing substituent of the ligand compound having an oxazole structure is selected from any one of trifluoromethyl, hydroxyl, and nitro, and the electron-donating substituent is selected from methoxy.

According to the embodiments of the present disclosure, the structural formula of the ligand compound having an oxazole structure is shown in any one of the following formulas (I-a) to (I-c):

Wherein, _R2 is selected from any one of trifluoromethyl, hydroxyl, nitro, and methoxy.

In some specific embodiments, the structural formula of the ligand compound having an oxazole structure is as follows:

In another aspect of the present disclosure, a method for preparing the above-mentioned ligand compound is provided, comprising:

The compound represented by formula (A) is reacted with a keto acid methyl ester compound to obtain a compound represented by formula (B);

The compound represented by formula (B) is reacted with 2-amino-2-methyl-1-propanol to obtain a compound represented by formula (C);

The compound represented by formula (C) is subjected to autoisomerization and dehydration reaction to obtain the compound represented by formula (I).

In some specific embodiments, the keto acid methyl ester compound comprises the following structure:

In some specific embodiments, the structure of compound B is as follows:

In some specific embodiments, the structure of compound C is shown below:

FIG1 is a flow chart of a method for synthesizing a ligand compound having an oxazole structure in the present disclosure.

According to an embodiment of the present disclosure, as shown in FIG1 , the method for preparing the above-mentioned ligand compound specifically includes the following steps S1 to S3:

Step S1: Compound (A) and keto acid methyl ester compound are mixed in a molar ratio of 1:1, p-toluenesulfonic acid monohydrate is added, and the mixture is refluxed at 140° C. to 145° C. for 40 h, and compound (B) is obtained after recrystallization;

Step S2: Compound (B) and 2-amino-2-methyl-1-propanol are mixed at a molar ratio of 1:2 to 1:2.5, reacted at 140° C. to 145° C. for 24 hours, and compound (C) is separated;

Step S3: After compound (C) is dissolved, triethylamine, 4-dimethylaminopyridine and 4-toluenesulfonyl chloride are added and reacted at 80° C. to 85° C. for 40 hours to obtain a ligand compound.

According to the embodiments of the present disclosure, triethylamine and 4-dimethylaminopyridine are added as catalysts in the reaction, and 4-toluenesulfonyl chloride is an alcohol sulfonylating agent that can promote the epoxidation reaction of diols.

In another aspect of the present disclosure, a nickel catalyst having an oxazole structure is provided, and its structure is shown in formula (II),

Wherein, R ₁ is selected from any one of methyl and diphenylmethyl;

Ar is selected from naphthyl, benzothiophenyl, substituted or unsubstituted benzene,

When the substituted or unsubstituted benzene has a substituent, the substituent is selected from an electron-withdrawing substituent or an electron-donating substituent;

Among them, the electron-withdrawing substituent is preferably any one of trifluoromethyl, hydroxyl, and nitro;

The electron donating substituent is preferably a methoxy group.

According to the embodiments of the present disclosure, when the substituent Ar is an electron-donating substituent, the electron cloud density of the nickel metal center increases, that is, the nucleophilicity of the metal center is increased, and the ethylene coordination rate is reduced, so a polymer with lower activity is obtained. At the same time, the chain walking ability and chain transfer ability of the catalyst are reduced, so a polymer with higher molecular weight is obtained.

According to an embodiment of the present disclosure, when the substituent Ar is an electron-withdrawing substituent, the electron cloud density of the nickel metal center is reduced, that is, the electrophilicity of the metal center is increased, and the result obtained is opposite to that when the substituent is an electron-donating substituent, but its branching degree is higher than when the substituent Ar is an electron-donating substituent.

According to the embodiments of the present disclosure, when the substituent Ar is a large steric hindrance substituent, the spatial shielding effect of the metal center is increased, that is, the spatial hindrance of the metal center is increased, and the β-H elimination reaction is less likely to occur during the polymerization process, that is, the chain walking efficiency is reduced, so a polymer with a relatively low degree of branching is obtained; at the same time, it also increases the energy barrier for ethylene coordination insertion, and the activity and molecular weight of the resulting polymer are lower.

According to the embodiments of the present disclosure, a novel nickel catalyst having an oxazole structure is synthesized by using a ligand compound having an oxazole structure. Compared with aniline having a larger steric hindrance, the oxazole ring has a smaller steric hindrance, which is beneficial to the insertion of ethylene, thereby improving the ethylene polymerization activity. At the same time, the oxazole ring having a smaller steric hindrance forms an asymmetric structure with the aniline having a larger steric hindrance, which is beneficial to the chain walking process in ethylene polymerization, thereby producing highly branched polyethylene.

According to an embodiment of the present disclosure, the structural formula of the nickel catalyst having an oxazole structure is shown in any one of the following formulas (II-a) to (II-c):

Wherein, R ₂ includes any one of trifluoromethyl, hydroxyl, nitro, and methoxy.

In some specific embodiments, the nickel catalyst having an oxazole structure has the following structural formula:

FIG2 is a schematic diagram of the single crystal structure of the nickel catalyst (II-2) having an oxazole structure in Example 8 of the present disclosure.

In some specific embodiments, as shown in FIG. 2 , the correctness of the structure of the nickel catalyst (II-2) is intuitively reflected, and the spatial structure of the compound, ie, the relative position relationship of the atoms, is indicated.

In another aspect of the present disclosure, a method for preparing the above-mentioned nickel catalyst having an oxazole structure is proposed, comprising: dissolving the above-mentioned ligand compound having an oxazole structure, reacting with ethylene glycol dimethyl ether nickel bromide, adding n-hexane, stirring and filtering, and obtaining a nickel catalyst.

In other aspects of the present disclosure, a method for preparing polyolefin using the nickel catalyst having an oxazole structure is also proposed, which comprises preparing polyolefin by polymerization reaction using the nickel catalyst having an oxazole structure as a catalyst.

According to an embodiment of the present disclosure, the polymerization reaction includes any one of a homopolymerization reaction and a copolymerization reaction.

In some specific embodiments, the polymerization reaction includes homopolymerization of olefins and copolymerization of olefins with polar monomers. The polar monomers are mainly long-chain polar monomers. The long-chain polar monomers include but are not limited to 6-chloro-1-hexene and 10-undecenoic acid.

In some specific embodiments, a hyperbranched ethylene oligomer with a branching degree ranging from 60 to 130 can be obtained by using the nickel catalyst with an oxazole structure proposed in the present disclosure as a catalyst to prepare polyolefins through a polymerization reaction.

It should be noted that the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present disclosure, other embodiments obtained by ordinary technicians in the field without creative work are all within the scope of protection of the present disclosure.

Example 1

Step S1: 2,4-dimethyl-6-benzhydrylaniline (5.7 g, 20 mmol) (ie, compound A-1), methyl benzoylformate (3.28 g, 20 mmol), PTSA (50 mg) and toluene (40 mL) were placed in a 250 mL eggplant-shaped bottle. The resulting mixture was stirred and heated to 140 ° C, and then the reaction system was refluxed for 24 h with a water separator to remove water and cooled to room temperature. The solvent was spin-dried, recrystallized with 200 mL of methanol, and washed with methanol (3×100 mL) to obtain the intermediate product (B-1) (8.1 g, 93%) in the form of a yellow solid, and the reaction process is shown in the following formula:

The structure of the intermediate product (B-1) was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum. The specific characterization results are shown in FIG. 3A and FIG. 3B .

¹ H: NMR (400MHz, CDCl ₃ ) δ7.70 (m, 2H), 7.52-7.46 (m, 1H), 7.41 (m, 2H), 7.28 (m, 3H), 7.23 (d, J = 11.6Hz ,3H),7.20-7.05(m,6H),6.89(d,J＝1.9Hz,1H),6.57(d,J＝1.9Hz,1H),5.49(s,1H,CH),3.58(s, 3H,CH ₃ ), 2.20 (s, 3H, CH ₃ ), 2.07 (s, 3H, CH ₃ ).

¹³ C: NMR (101MHz, CDCl ₃ ) δ165.11(s), 160.21(s), 145.27(s), 133.61(s), 132.62(s), 132.40(s), 131.80(s), 129.88(s) ),129.58(s),129.27(s),128.70(s),128.16(s),128.08(s),127.66(s),126.13(s),125.86(s),51.95(s),51.88(s) ),21.17(s),18.25(s).

Step S2: Add the intermediate product (B-1) (8.6 g, 19.8 mmol), 2-amino-2-methyl-1-propanol (3.52 g, 39.6 mmol) and methanol (60 mL) prepared in step S1 into a 350 mL sealed bottle. Stir and heat the resulting mixture to 140° C., reflux for 40 h, and cool to room temperature. The solvent is spin-dried and separated by column chromatography to obtain a yellow solid intermediate product (C-1) (4.9 g, 50%).

Step S3: The intermediate product (C-1) (2.5 g, 5 mmol), 4-dimethylaminopyridine (DMAP) (0.73 g, 6 mmol), triethylamine (5 mL) and dichloromethane (20 mL) were placed in a 350 mL sealed bottle and placed at 0°C. 4-toluenesulfonyl chloride (TsCl) (1.14 g, 6 mmol) was added to the mixture and stirred for 2 h. The mixture was stirred at 80°C for 40 h. The solution was extracted with saturated NaCl aqueous solution and DCM, the organic phase was collected, the solvent was dried, and column chromatography was used to separate the yellow solid as the compound represented by formula (I-1) (2.2 g, 95%).

The structure of compound (I-1) was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum. The specific characterization results are shown in Figures 4A and 4B.

¹ H NMR (400MHz, C ₆ D ₆ ) δ8.27-8.18(m,2H),7.24-7.15(m,5H),7.11(m,2H),3.35(s,2H,CH ₂ ),3.22( d,J＝6.8Hz,2H,CH),1.36(d,J＝7.0Hz,6H, ^iPr ),1.22(d,J＝7.0Hz,6H, ^iPr ),0.87(s,6H,CH ₃ ).

¹³ C NMR (101MHz, C ₆ D ₆ ) δ158.39(s), 156.19(s), 147.18(s), 136.83(s), 135.92(s), 131.71(s), 128.91(s), 128.45( s),124.41(s),122.68(s),78.54(s),68.20(s),28.77(s),27.97(s),23.86(s),22.19(s).

Example 2

The synthesis route of compound (I-2) is shown below:

Step S1: 2,6-dibenzhydryl-4-methylaniline (20 mmol) (ie, compound A-2), methyl benzoylformate (3.28 g, 20 mmol), PTSA (50 mg) and toluene (40 mL) were placed in a 250 mL eggplant-shaped bottle. The resulting mixture was stirred and heated to 140 ° C, and then the reaction system was refluxed for 24 h with a water separator to remove water and cooled to room temperature. The solvent was spin-dried, recrystallized with 200 mL of methanol, and washed with methanol (3×100 mL) to obtain the intermediate product (B-2) (10.8 g, 92%) in the form of a yellow solid.

The structure of the intermediate product (B-2) was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum. The specific characterization results are shown in FIG. 5A and FIG. 5B .

¹ H NMR (400MHz, C ₆ D ₆ ) δ7.59-7.55(m,2H),7.39(d,J＝7.6Hz,4H),7.10-7.08(m,2H),7.05(d,J＝4.2 Hz,12H),7.02-6.96(m,5H),6.95(s,2H),5.85(s,2H,CH),3.11(s,3H,CH ₃ ),1.88(s,3H,CH ₃ ).

¹³ C NMR (101 MHz, C ₆ D ₆ )δ164.91(s),159.30(s),145.50(s),143.95(s),143.11(s),142.95(s),133.56(s),132.59(s),132.55(s),131.51(s),130.16(s),129.66(s), 129.49(s),129.28(s),129.24(s),128.70(s),128.42(s),128.35(s),128.21(s),128.16(s),126.49(s),126.15(s),126.01(s),52.06(s),51 .31(s),20.85(s).

Step S2 is the same as step S2 in Example 1, wherein the output of the intermediate product (C-2) is 5.7 g, and the yield is 45%.

The structure of the intermediate product (C-2) was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum. The specific characterization results are shown in FIG6A and FIG6B .

¹ H NMR (400MHz, C ₆ D ₆ ) δ7.49-7.45 (m, 2H), 7.17 (d, J = 7.3Hz, 6H), 7.14 (s, 3H), 7.12 (d, J = 1.7Hz, 3H),7.10-7.03(m,7H),6.98(d,J＝7.5Hz,3H),6.83(s,2H),6.72(s,1H),5.37(s,2H,CH ₂ ),4.70- 4.60 (m, 1H, NH), 3.71 (d, J = 5.2Hz, 2H, CH), 1.87 (s, 3H, CH ₃ ), 1.09 (s, 6H, CH ₃ ).

¹³ C NMR (101MHz, C ₆ D ₆ ) δ163.73(s), 159.82(s), 142.96(s), 142.94(s), 133.64(s), 132.68(s), 132.13(s), 130.50( s),130.22(s),129.77(s),129.56(s),129.38(s),128.73(s),128.51(s),126.80(s),126.54(s),70.63(s),55.87( s),53.08(s),24.26(s),21.11(s).

Step S3 is the same as step S3 in Example 1, wherein the yield of compound (I-2) is 2.8 g, and the yield rate is 90%.

The structure of compound (I-2) was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum. The specific characterization results are shown in Figures 7A and 7B.

¹ H NMR (400MHz, C ₆ D ₆ ) δ7.82-7.77(m,2H),7.59(d,J＝7.6Hz,4H),7.33(m,4H),7.28(s,3H),7.24- 7.17(m,10H),7.14-7.12(m,2H),7.04(s,2H),6.01(s,2H,CH ₂ ),3.56(s,2H,CH),2.04(s,3H,CH ₃ ),1.13(s,6H,CH ₃ ).

¹³ C NMR (101 MHz, C ₆ D ₆ )δ157.22(s),156.60(s),146.49(s),144.66(s),143.46(s),143.36(s),135.49(s),132.62(s),132.20(s),131.60(s),130.68(s),130.01(s), 129.86(s),129.63(s),129.59(s),128.77(s),128.45(s),128.39(s),128.16(s),126.84(s),126.42(s),126.21(s),78.64(s),68.46(s),52.5 1(s),28.19(s),21.29(s).

Example 3

The synthesis route of compound (I-3) is shown below:

The preparation method of Example 3 is the same as that of Example 1, and the reactant is replaced by methyl benzoylformate with methyl 2-(4-methoxyphenyl)-2-oxoacetate.

The yield of the intermediate product (B-3) was 11.4 g, with a yield of 93%. The structure of the intermediate product (B-3) was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum, and the specific characterization results are shown in FIG8A and FIG8B .

¹ H NMR (400MHz, CDCl ₃ ) δ7.44 (d, J＝8.4Hz, 2H), 7.36-7.27 (m, 6H), 7.21 (d, J＝7.0Hz, 10H), 7.00 (d, J＝ 6.9Hz,4H),6.90(d,J＝8.5Hz,2H),6.67(s,2H),5.53(s,2H,CH),3.86(s,3H,CH ₃ ),3.57(s,3H, CH ₃ ),2.20(s,3H,CH ₃ ).

¹³ C NMR (101MHz, CDCl ₃ ) δ164.89(s), 162.41(s), 157.96(s), 145.23(s), 143.66(s), 143.18(s), 132.18(s), 131.98(s) ,130.07(s),129.99(s),129.41(s),128.38(s),128.16(s),127.89(s),126.09(s),125.89(s),113.80(s),51.93(s) ,21.48(s).

The yield of the intermediate product (C-3) was 6.5 g, with a yield of 49%. Its structure was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum, and the specific characterization results are shown in Figures 9A and 9B.

¹ H NMR (400MHz, C ₆ D ₆ ) δ7.45-7.42(m,2H),7.06(m,11H),7.00-6.92(m,8H),6.80(s,2H),6.70(s,1H ),6.59-6.53(m,2H,CH ₂ ),5.34(s,2H,CH),3.65(s,1H,NH),3.15(s,3H,CH ₃ ),1.82(s,3H,CH ₃ ),1.01(s,6H,CH ₃ ).

¹³ C NMR (101MHz, C ₆ D ₆ ) δ164.23(s), 161.82(s), 159.21(s), 143.89(s), 143.09(s), 133.38(s), 132.17(s), 131.94( s),130.27(s),129.57(s),129.47(s),128.71(s),128.52(s),126.76(s),126.52(s),124.98(s),113.71(s),70.78( s),55.88(s),54.86(s),53.09(s),24.30(s),21.15(s).

The yield of compound (I-3) was 3.0 g, with a yield of 92%. Its structure was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum, and the specific characterization results are shown in Figures 10A and 10B.

¹ H NMR (400MHz, C ₆ D ₆ ) δ7.70 (d, J = 8.4 Hz, 2H), 7.57 (d, J = 7.6 Hz, 4H), 7.30 (m, 4H), 7.24 (s, 1H) ,7.17(d,J＝7.5Hz,5H),7.13(d,J＝17.1Hz,6H),6.99(s,2H),6.69(d,J＝8.4Hz,2H),6.00(s,2H, CH ₂ ),4.39(s,1H,CH),3.58(s,1H,CH),3.25(s,3H,CH ₃ ),2.01(s,3H,CH ₃ ),1.13(s,6H,CH ₃ ).

¹³ C NMR (101MHz, C ₆ D ₆ ) δ162.83(s), 156.87(s), 156.28(s), 146.63(s), 144.79(s), 143.47(s), 132.88(s), 131.94( s),130.69(s),130.52(s),129.87(s),128.45(s),126.41(s),126.15(s),113.94(s),78.63(s),68.46(s),54.84( s),53.41(s),52.53(s),28.26(s),21.34(s).

Example 4

The synthesis route of compound (I-4) is shown below:

The preparation method of Example 4 is the same as that of Example 1, and the reactant is replaced by methyl benzoylformate with methyl 2-(4-trifluoromethylphenyl)-2-oxoacetate.

The yield of the intermediate product (B-4) was 11.9 g, with a yield of 91%. Its structure was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum, and the specific characterization results are shown in Figures 11A and 11B.

¹ H NMR (400MHz, CDCl ₃ ) δ7.68 (d, J = 8.0 Hz, 2H), 7.56 (d, J = 8.2 Hz, 2H), 7.37 (m, 5H), 7.31 (m, 6H), 7.20 (d,J＝7.6Hz,5H),7.05-6.96(m,4H),6.69(s,2H),5.47(s,2H,CH),3.62(s,3H,CH ₃ ),2.23(s, 3H,CH ₃ ).

¹³ C NMR (101MHz, CDCl ₃ ) δ163.63(s), 157.64(s), 144.76(s), 143.27(s), 142.95(s), 136.89(s), 132.67(s), 131.55(s) ,129.99(s),129.41(s),128.68(s),128.57(s),128.30(s),128.05(s),126.82(s),126.31(s),126.12(s),125.39(s) ,51.97(s),21.51(s).

The yield of the intermediate product (C-4) was 7.5 g, with a yield of 53%. Its structure was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum, and the specific characterization results are shown in Figures 12A and 12B.

¹ H NMR (400MHz, C ₆ D ₆ ) δ7.26 (s, 5H), 7.18 (s, 4H), 7.14 (s, 4H), 7.13-7.04 (m, 6H), 6.91 (d, J = 7.2 Hz,5H),6.87(s,2H),5.29(s,2H,CH ₂ ),4.23(d,J＝5.9Hz,1H,NH),3.69(d,J＝4.5Hz,2H,CH), 1.89(s,3H,CH ₃ ), 1.13(s,6H,CH ₃ ).

¹³ C NMR (101MHz, C ₆ D ₆ ) δ162.69(s),158.78(s),142.55(s),142.39(s),141.97(s),135.34(s),133.96(s),131.87( s),130.10(s),129.78(s),129.65(s),129.23(s),129.18(s),128.85(s),128.45(s),128.25(s),126.67(s),126.34( s),124.74(s),124.70(s),69.90(s),55.56(s),52.66(s),23.82(s),20.70(s).

The yield of compound (I-4) was 3.2 g, with a yield of 92%. Its structure was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum, and the specific characterization results are shown in Figures 13A and 13B.

¹ H NMR (400MHz, C ₆ D ₆ ) δ7.66 (d, J = 8.1 Hz, 2H), 7.56 (d, J = 7.6 Hz, 4H), 7.36 (m, 6H), 7.30 (s, 1H) ,7.27-7.17(m,6H),7.14(d,J＝4.7Hz,5H),7.04(s,2H),5.91(s,2H,CH ₂ ),3.58(s,2H,CH),2.04( s,3H,CH ₃ ),1.16(s,6H,CH ₃ ).

¹³ C NMR (101MHz, C ₆ D ₆ ) δ156.08(s),146.11(s),144.29(s),143.16(s),138.61(s),132.64(s),132.11(s),130.58( s),129.77(s),129.19(s),128.54(s),128.49(s),126.59(s),126.37(s),125.33(s),125.29(s),125.26(s),78.75( s),68.51(s),52.55(s),28.14(s),21.27(s).

Example 5

The synthesis route of compound (I-5) is shown below:

The preparation method of Example 5 is the same as that of Example 1, and the reactant is replaced by methyl benzoylformate with methyl 2-(naphthalene-2-yl)-2-oxoacetate.

The yield of the intermediate product (B-5) was 11.5 g, with a yield of 90%. The structure of the intermediate product (B-5) was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum, and the specific characterization results are shown in Figures 14A and 14B.

¹ H NMR (400MHz, CDCl ₃ ) δ7.87 (m, 3H), 7.76 (d, J = 8.7Hz, 1H), 7.54 (m, 3H), 7.32-7.28 (m, 4H), 7.25-7.13 ( m,12H),7.00-6.92(m,4H),6.65(d,J＝3.1Hz,2H),5.51(d,J＝3.4Hz,2H,CH),3.71-3.53(m,3H,CH ₃ ), 2.18 (d, J = 2.3Hz, 3H, CH ₃ ).

¹³ C NMR (101MHz, CDCl ₃ ) δ164.74(s), 158.86(s), 145.21(s), 143.55(s), 143.16(s), 135.02(s), 132.69(s), 132.27(s) ,131.98(s),131.12(s),130.04(s),129.73(s),129.49(s),129.23(s),128.48(s),128.23(s),127.99(s),127.90(s) ,126.62(s),126.17(s),125.97(s),124.25(s),52.20(s),51.93(s),21.54(s).

The yield of the intermediate product (C-5) was 6.6 g, with a yield of 48%. Its structure was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum, and the specific characterization results are shown in Figures 15A and 15B.

¹ H NMR (400MHz, C ₆ D ₆ ) δ7.95 (s, 1H), 7.48 (d, J = 7.6Hz, 4H), 7.40 (d, J = 9.5Hz, 2H), 7.20 (m, 2H) ,7.09(d,J＝4.5Hz,9H),6.94(d,J＝7.4Hz,3H),6.89(d,J＝7.1Hz,2H),6.83(d,J＝7.4Hz,5H),6.76 (s,2H),5.39(s,2H,CH ₂ ),4.54(s,1H,NH),3.67(s,2H,CH),1.78(s,3H,CH ₃ ),1.05(s,6H, CH ₃ ).

¹³ C NMR (101 MHz, C ₆ D ₆ )δ163.88(s),160.14(s),143.64(s),143.10(s),142.84(s),134.27(s),133.68(s),132.84(s),132.27(s),130.78(s),130.56(s),130.12(s), 129.63(s),129.40(s),129.34(s),129.17(s),128.69(s),128.56(s),126.74(s),126.62(s),126.57(s),126.15(s),70.66(s),55.97(s),53.1 0(s),24.34(s),21.11(s).

The yield of compound (I-5) was 3.1 g, with a yield of 92%. Its structure was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum, and the specific characterization results are shown in Figures 16A and 16B.

¹ H NMR (400MHz, C ₆ D ₆ ) δ8.20(s,1H),7.72-7.66(m,1H),7.65-7.58(m,1H),7.48(m,6H),7.22(m,6H ),7.08(m,12H),6.95(s,2H),5.95(s,2H,CH ₂ ),3.51(s,2H,CH),1.94(s,3H,CH ₃ ),1.08(s,6H , CH ₃ ).

¹³ C NMR (101MHz, C ₆ D ₆ ) δ157.14(s), 156.74(s), 146.56(s), 144.63(s), 143.36(s), 135.43(s), 133.19(s), 133.13( s),132.63(s),132.22(s),130.68(s),130.22(s),129.91(s),129.43(s),128.49(s),126.46(s),126.21(s),124.92( s),78.71(s),68.57(s),52.62(s),28.26(s),21.33(s).

Example 6

The synthesis route of compound (I-6) is shown below:

Under nitrogen atmosphere, compound (I-3) (0.49 g, 0.74 mmol) and dichloromethane (10 mL) were added to a 200 mL Schlenk bottle, and BBr ₃ (7.5 mL, 1 mmol/mL) was added dropwise to the mixture at 0°C. After stirring for 2 h, the mixture was heated to 20°C and stirred for 12 h. BBr ₃ was quenched with saturated aqueous NaCl solution at 0°C, and extracted with DCM. The organic phase was collected, the solvent was dried, and the yellow solid was separated by column chromatography to obtain compound (I-6) (0.28 g, 59%).

The structure of compound (I-6) was characterized by ¹ H NMR spectrum and ¹³ C NMR spectrum. The specific characterization results are shown in Figures 17A and 17B.

¹ H NMR (400MHz, C ₆ D ₆ ) δ7.10 (m, 1.8Hz, 10H), 7.00 (m, 11H), 6.83 (s, 2H), 6.65 (s, 1H), 6.39–6.36 (m, 2H),5.49(s,2H),3.60(s,2H),1.82(s,3H),1.06(s,7H).

¹³ C NMR(101MHz,DMSO)δ173.71(s),161.36(s),156.63(s),156.26(s),145.97(s),144.05(s),142.81(s),132.24(s), 130.28(s),129.96(s),129.69(s),129.25(s),128 .70(s),128.56(s),128.25(s),127.58(s),126.74(s),126.56(s),126.35(s),125.86(s),115.67(s),78.64(s) ,68.44(s),51.57(s),28.24(s),22.99(s),21.56(s).

Example 7

The synthesis route of nickel catalyst (II-1) is shown below:

In a glove box, compound (I-1) (0.47 g, 1.0 mmol) was added to a mixed solution of 20 mL DCM and (DME)NiBr ₂ (0.31 g, 1.0 mmol), stirred at room temperature for 12 h, the solution was drained on a vacuum line, 30 mL of n-hexane was added, stirred for 15 min, and filtered to obtain a dark red solid as nickel catalyst (II-1) (0.62 g, 90%).

Results of mass spectrometry analysis: MALDI-TOF (m/z): calculated value: C ₃₃ H ₃₂ Br ₂ N ₂ NiO: 691.13, found value: 610.870 [M-Br] ⁺ .

Example 8

The synthesis route of nickel catalyst (II-2) is shown below:

The synthesis method of nickel catalyst (II-2) is as shown in Example 7, wherein the output of nickel catalyst (II-2) is 0.62 g, and the yield is 74%.

Results of mass spectrometry analysis: MALDI-TOF (m/z): calculated for C ₄₅ H ₄₀ Br ₂ N ₂ NiO: 843.33, found: 763.169 [M-Br] ⁺ .

Example 9

The synthesis route of nickel catalyst (II-3) is shown below:

The synthesis method of nickel catalyst (II-3) is as shown in Example 7, wherein the output of nickel catalyst (II-3) is 0.75 g, and the yield is 86%.

Results of mass spectrometry analysis: MALDI-TOF (m/z): calculated for C ₄₆ H ₄₂ Br ₂ N ₂ NiO ₂ : 873.36, found: 793.083 [M-Br] ⁺ .

Example 10

The synthesis route of nickel catalyst (II-4) is shown below:

The synthesis method of nickel catalyst (II-4) is as shown in Example 7, wherein the output of nickel catalyst (II-4) is 0.76 g, and the yield is 83%.

Results of mass spectrometry analysis: MALDI-TOF (m/z): calculated for C ₄₆ H ₃₉ Br ₂ F ₃ N ₂ NiO: 911.33, found: 831.179 [M-Br] ⁺ .

Embodiment 11

The synthesis route of nickel catalyst (II-5) is shown below:

The synthesis method of nickel catalyst (II-5) is as shown in Example 7, wherein the output of nickel catalyst (II-5) is 0.68 g, and the yield is 83%.

Results of mass spectrometry analysis: MALDI-TOF (m/z): calculated for C ₄₉ H ₄₂ Br ₂ N ₂ NiO: 893.39, found: 813.217 [M-Br] ⁺ .

Example 12

The synthesis route of nickel catalyst (II-6) is shown below:

The synthesis method of nickel catalyst (II-6) is as shown in Example 7, wherein the output of nickel catalyst (II-6) is 0.72 g, and the yield is 84%.

Results of mass spectrometry analysis: MALDI-TOF (m/z): calculated for C ₄₅ H ₄₀ Br ₂ N ₂ NiO ₂ : 859.33, found: 779.132 [M-Br] ⁺ .

Test Example 1

The nickel catalyst (II-1) and the nickel catalyst (II-2) in the present disclosure were calculated by density functional theory (DFT) to obtain two model molecules Ni1 ⁺ and Ni2 ⁺ . In addition, the optimized structural stereograms of Ni1 ⁺ and Ni2 ⁺ were obtained by using the SambVca 2.1A tool, and their structures are shown in Figures 18 and 19, and the relevant parameters are recorded in Table 1 below.

Table 1

Ni1 ⁺ Ni2 ⁺ ΔG(KJ/mol) 19.8 27.1

The results show that the buried volume of the nickel center is: Ni2 ⁺ (54.7%)>Ni1 ⁺ (52.9%), which indicates that the steric effect of the oxazole structure proposed in the present disclosure effectively inhibits the chain walking process, thereby leading to different branching degrees of ethylene polymers. The DFT calculation results of the ethylene coordination barrier show: Ni2 ⁺ (27.2kJ/mol)>Ni1 ⁺ (19.8kJ/mol), indicating that larger steric hindrance can inhibit the coordination of ethylene, thereby reducing the activity of Ni2 and the molecular weight of the polymer.

Test Example 2

The method for using the nickel catalyst with oxazole structure prepared by the present disclosure in olefin homopolymerization reaction includes: in a glove box, under a nitrogen atmosphere, 18mL of n-heptane and 200eq of _Et2AlCl are added to a pressure-resistant bottle of a 350mL autoclave (with a magnetic stirring device, an oil bath heating device and a thermometer). The container is connected to a high-pressure pipeline and the pipeline is evacuated. The container is controlled at an appropriate temperature using an oil bath, and the nickel catalyst prepared in a certain amount of the embodiment dissolved in 2mL of dichloromethane is injected into the polymerization system by a syringe. The valve is closed, and after adjusting the ethylene pressure to 8 atmospheres, the reaction is carried out for 30min. The reaction is stopped, the reactor is opened, and the obtained polymer is vacuum-drained to obtain a yellow oily substance. Among them, the effects of different nickel catalysts with oxazole structure on catalytic ethylene homopolymerization under different reaction conditions are recorded in Table 2 as follows:

Table 2

^a The polymerization conditions in Table 2 are: nickel catalyst = 2 μmol, reaction time = 30 min, n-heptane (Hep) = 18 mL, ethylene pressure = 8 atm. The polymerization was repeated at least 2 times. ^b Activity = 10 ⁶ g·mol ^-1 ·h ^-1 . ^c Molecular weight determination was calculated by ¹ H NMR, deuterated chloroform was used as solvent. ^d The degree of branching (B) of polyethylene was determined by ¹ H NMR analysis.

In Table 2, Ni1 corresponds to the nickel catalyst (II-1) prepared in Example 7; Ni2 corresponds to the nickel catalyst (II-2) prepared in Example 8; Ni3 corresponds to the nickel catalyst (II-3) prepared in Example 9; Ni4 corresponds to the nickel catalyst (II-4) prepared in Example 10; and Ni5 corresponds to the nickel catalyst (II-5) prepared in Example 11.

At 20°C and 8 atm ethylene pressure, complex Ni1 has excellent catalytic activity (2.6×10 ⁶ g·mol ^-1 ·h ^-1 ) and catalytically produces polymers with a suitable molecular weight (1750 g·mol ^-1 ). Under the same conditions, the polymer produced by the sterically larger complex Ni2 has lower activity and molecular weight than Ni1 (Table 2, rows 1 and 2).

At 20°C and 8 atm ethylene pressure, the branching degree of oligomers produced by Ni1 and Ni2 is: Ni1 (102/1000C) > Ni2 (68/1000C). The activity and molecular weight further increase with the increase of ethylene pressure, while the branching degree of the oligomer decreases (Table 2, rows 5 and 6). In addition, internal double bonds can be observed in the ¹ H NMR spectra of all oligomers in this system, which may be generated by the chain walking process of the polymer.

By comparing the catalytic polymerization process of Ni2 to Ni5, the electronic effect of the ligand skeleton structure was further studied (Table 1, rows 6 to 9). Compared with the complex Ni2, the complex Ni3 with an electron-donating group (OMe) has a lower activity, while the complex Ni4 with an electron-deficient group (CF ₃ ) has a higher ethylene oligomerization activity. This is mainly due to the increase in electrophilicity, which increases the rate of ethylene coordination. The molecular weight of the polyethylene products is: Ni3>Ni2>Ni4, which is mainly due to the increase in electrophilicity, which increases the chain transfer rate. The branching degree of the oligomers obtained from Ni2 to Ni4 is: Ni4>Ni2>Ni3, which is largely due to the increase in electrophilicity, which increases the rate of repeated β-H elimination and olefin reinsertion of the chain. Compared with the complex Ni2, the complex Ni5 with naphthalene as the skeleton shows higher activity and branching degree, as well as lower molecular weight (Table 2, row 9). This is consistent with the trend of Ni4, and the main factor producing this result is the electronic effect of the naphthyl group. These results show that the electronic effect of the catalyst affects the activity of the catalyst to a certain extent.

Test Example 3

The method of using the nickel catalyst having an oxazole structure prepared by the present disclosure in the copolymerization reaction of olefins and polar monomers includes:

In a glove box, under a nitrogen atmosphere, a certain amount of n-heptane, polar monomer and _Et2AlCl were added to a pressure bottle of a 350 mL autoclave (with a magnetic stirring device, an oil bath heating device and a thermometer). The container was connected to a high-pressure pipeline and the pipeline was evacuated. The container was controlled at an appropriate temperature using a water bath, and a certain amount of the nickel catalyst prepared in the embodiment dissolved in 2 mL of dichloromethane was injected into the polymerization system through a syringe. The valve was closed, and the ethylene pressure was adjusted to 8 atmospheres, and the reaction was carried out for 1 hour. The reaction was stopped, the reactor was opened, and the solvent was vacuum-drained from the obtained polymer. The results of the copolymerization of olefins and polar monomers catalyzed by different nickel catalysts having an oxazole structure are recorded in the following Table 3:

Table 3

^a The polymerization conditions in Table 3 are: Ni catalyst = 10 μmol, reaction time = 1 h, ethylene pressure = 8 atm, Et ₂ AlCl = 200 eq, total volume of n-heptane, dichloromethane, Et ₂ AlCl and polar monomer = 20 mL, time = 1 h. The polymerization was repeated at least 2 times. ^b Activity = 10 ⁵ g·mol ^-1 ·h ^-1 , ^c Molecular weight was determined by ¹ H NMR, deuterated chloroform was used as solvent. ^d Insertion ratio of polar monomer was determined by ¹ H NMR. ^e Et ₂ AlCl = 2000 eq.

In the copolymerization of ethylene and 6-chloro-1-hexene (Table 3, rows 1 and 2), catalyst Ni1 showed a higher polar monomer insertion ratio than Ni2. This may be because the sterically more hindered complex Ni2 hinders the coordination of polar monomers. Biorenewable undecylenic acid was selected for copolymerization because it is slightly toxic to nickel metal centers. The copolymerization of ethylene and undecylenic acid has high activity (10 ⁵ g·mol ^-1 ·h ^-1 ) and appropriate polar monomer insertion ratio (0.4-0.8%), and Ni1 produces copolymers with lower polar monomer insertion ratio (0.8%) and lower molecular weight (Table 3, row 3). Ni2 produces copolymers with higher activity and lower molecular weight and lower insertion ratio (0.4%) (Table 3, row 4). The decrease in activity and polymer molecular weight, as well as the decrease in polar monomer insertion ratio (Table 3, row 4) shown by Ni2 are similar to the above-mentioned copolymerization process of ethylene and 6-chloro-1-hexene and are attributed to steric/electronic effects.

The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims (10)

1. A ligand compound with an oxazole structure is shown in a formula (I),

wherein R is ₁ Selected from any one of methyl, benzhydrylMeaning one;

ar is selected from one of naphthyl, benzothienyl and substituted or unsubstituted benzene,

when the above-mentioned substituted or unsubstituted benzene has a substituent, the substituent is selected from an electron withdrawing substituent or an electron donating substituent.

2. The ligand compound according to claim 1, wherein the electron withdrawing substituent is selected from any one of trifluoromethyl, hydroxyl, and nitro, and the electron donating substituent is selected from methoxy.

3. The ligand compound according to claim 1, wherein any one of the following formulas (i-a) to (i-c):

wherein R is ₂ Is selected from any one of trifluoromethyl, hydroxyl, nitro and methoxy.

4. The ligand compound of claim 1, wherein the structural formula is as follows:

5. a method of preparing the ligand compound of any one of claims 1 to 4, comprising:

reacting a compound shown as a formula (A) with a methyl ketonate compound to obtain a compound shown as a formula (B);

reacting a compound shown as a formula (B) with 2-amino-2-methyl-1-propanol to obtain a compound shown as a formula (C);

the compound shown in the formula (C) is subjected to self-isomerization and dehydration reaction to obtain the compound shown in the formula (I).

6. The method of claim 5, wherein,

the compound (A) and the methyl ketoacid ester compound are mixed in a molar ratio of 1:1, p-toluenesulfonic acid monohydrate is added, water is separated and reflux reacted for 40 hours at 140-145 ℃, and the compound (B) is obtained after recrystallization;

the compound (B) and 2-amino-2-methyl-1-propanol are mixed in a molar ratio of 1:2-1:2.5, react for 24 hours at 140-145 ℃, and are separated to obtain the compound (C);

and (3) after the compound (C) is dissolved, adding triethylamine, 4-dimethylaminopyridine and 4-toluenesulfonyl chloride, and reacting for 40 hours at 80-85 ℃ to obtain the ligand compound.

7. A nickel catalyst with an oxazole structure is shown in a formula (II),

wherein R is ₁ Any one selected from methyl and benzhydryl;

ar is selected from one of naphthyl, benzothienyl and substituted or unsubstituted benzene,

when the above-mentioned substituted or unsubstituted benzene has a substituent, the substituent is selected from an electron withdrawing substituent or an electron donating substituent;

wherein the electron withdrawing substituent is preferably any one of trifluoromethyl, hydroxyl and nitro;

the electron donating substituent is preferably methoxy.

8. The nickel catalyst according to claim 7, wherein the structural formula is represented by any one of the following formulas (II-a) to (II-c):

wherein R is ₂ Including any one of trifluoromethyl, hydroxy, nitro and methoxy.

9. The nickel catalyst according to claim 7 or 8, wherein the structural formula is as follows:

10. use of the nickel catalyst according to any of claims 7 to 9 for the preparation of polyolefins, comprising the preparation of polyolefins by polymerization using the nickel catalyst having an oxazole structure as catalyst.