A chiral oxazoline pyridine-cobalt compound and its synthesis method and application

Abstract

The present invention discloses a chiral oxazoline pyridine-cobalt compound, its synthesis method and application. The synthesis method is as follows: Starting from 6-bromo-2-pyridinecarbaldehyde, it undergoes Suzuki coupling with arylboronic acid under the catalysis of tetrakis(triphenylphosphine)palladium to obtain 6-aryl-2-pyridinecarbaldehyde; then this compound, 6-bromo-2-pyridinecarbaldehyde or 2-pyridinecarbaldehyde undergoes ring closure with different chiral amino alcohols to form the corresponding 2-aryl-6-(oxazoline)pyridine ligands. These ligands react with anhydrous cobalt chloride to successfully prepare the corresponding chiral metal cobalt catalysts. The metal cobalt catalysts synthesized in the present invention have different chiral groups, electronic effects and steric hindrances, and can catalyze the polymerization reaction of isoprene. When the reaction time is 2 h, the reaction temperature is 25 °C, and Al / Co = 80, the molecular weight of the prepared polyisoprene can reach up to 1.44×10<supgt;5< / supgt> g·mol<supgt;‑1< / supgt>, and at this time PDI = 2.14.

Description

Technical Field

[0001] The invention belongs to the technical field of polyolefin catalysis, and specifically relates to a chiral oxazoline pyridine-cobalt compound and a synthesis method and application thereof. Background Art

[0002] Polyolefin elastomers are widely used and have greatly improved the convenience and quality of modern life. Among them, artificial polyisoprene (PIP), as one of the important synthetic materials to replace natural rubber, has been widely used in industrial fields such as tires and medical devices. The chemical and stereoselective polymerization of isoprene has given it a wide and diverse range of applications. Therefore, even if a single monomer isoprene is used, a variety of polymer materials can be obtained depending on the selectivity of the catalyst. With the increasing demand for high-performance synthetic rubbers, the development of high-quality elastomers through the polymerization of conjugated dienes has become increasingly important.

[0003] Nowadays, polyisoprene synthesis has been rapidly developed. According to the synthesis route, its catalytic system is mainly divided into three categories: lithium, titanium and rare earth catalysts. Subsequently, complexes represented by late transition metals (Fe, Co, Ni) have also received more and more attention as a new type of catalyst in polymerization. This type of catalyst is simple to obtain, low cost, high activity, relatively low Lewis acidity, and the electrical properties of the substituents have a great influence on the polymerization selectivity. It has received more and more attention in the field of catalysis, which has led to more research focusing on this type of low-cost and abundant late transition metal compounds. Among them, cobalt-based catalysts are the most widely used type of catalysts, with diverse coordination atoms, showing better reaction activity and stereoselectivity for polymerization, and polymers with different microstructures can be obtained by regulating the ligand structure (CN202210125064.9). Summary of the invention

[0004] The purpose of the present invention is to provide a synthesis method of a chiral oxazoline pyridine-cobalt compound and its application. By adjusting the substituents on the oxazoline and pyridine rings, the electronic effect and steric effect of the metal center can be adjusted to obtain a chiral oxazoline pyridine-cobalt catalyst with excellent performance, which is successfully used to catalyze the polymerization reaction of isoprene.

[0005] The present invention adopts the following technical solutions to achieve the above purpose:

[0006] A chiral oxazoline pyridine-cobalt compound, the structural formula of the compound is as follows:

[0007]

[0008] Among them, R 1 is benzyl, phenyl, isopropyl or hydrogen; R 2is phenyl, naphthyl, hydrogen, bromine, p-(trifluoromethyl)phenyl or p-methoxyphenyl.

[0009] As an example, the compound II of the present invention has the structure shown in the following formula II1-II9:

[0010]

[0011] The present invention also provides a chiral oxazoline pyridine ligand represented by the following formula I:

[0012]

[0013] R 1 is benzyl, phenyl, isopropyl or hydrogen; R 2 is phenyl, naphthyl, hydrogen, bromine, p-methoxyphenyl or p-(trifluoromethyl)phenyl.

[0014] As an example, the ligand shown in Formula I has a structure shown in the following Formula I1-9:

[0015]

[0016] The synthesis method of the chiral oxazoline pyridine-cobalt compound of the present invention is as follows: 6-bromo-2-pyridine carboxaldehyde is used as a starting material, and Suzuki coupling is performed with arylboronic acid under the catalysis of tetrakis(triphenylphosphine)palladium to obtain 6-aryl-2-pyridine carboxaldehyde; then the compound is cyclized with different chiral amino alcohols to form corresponding 2-aryl-6-(oxazoline)pyridine ligands. The ligand reacts with anhydrous cobalt chloride to successfully prepare a corresponding chiral metal cobalt catalyst.

[0017] The specific steps are as follows:

[0018] (1) In an argon atmosphere, 6-bromo-2-pyridinecarboxaldehyde, tetrakis(triphenylphosphine)palladium, anhydrous toluene, 2M sodium carbonate solution and methanol solution of arylboronic acid were added to a reaction bottle in sequence, and the mixture was reacted at 40-160° C. for 4-48 hours. After the reaction was completed, the mixture was extracted with dichloromethane, the organic layer was collected, and purified by column chromatography (PE / CH 2 Cl 2 =1 / 1) to obtain the corresponding 6-aryl-2-pyridinecarboxaldehyde compound.

[0019] (2) Under an argon atmosphere, add the corresponding chiral amino alcohol to a tert-butyl alcohol solution of 6-aryl-2-pyridine carboxaldehyde, and stir at room temperature for 2 to 48 hours; then add potassium carbonate and elemental iodine to the above reaction system, and react at 40 to 160° C. for 5 to 48 hours. After the reaction is completed, add a saturated solution of sodium thiosulfate to quench the reaction, cool to room temperature, extract with dichloromethane, collect the organic phase, separate by column chromatography or purify by recrystallization to obtain the corresponding 2-aryl-6-(oxazoline)pyridine ligand.

[0020] (3) The obtained ligand is reacted with anhydrous cobalt chloride in tetrahydrofuran, and after the reaction is completed, the solvent is removed and the product is washed with anhydrous ether three times to obtain a chiral oxazoline pyridine-cobalt compound.

[0021] Furthermore, in the step (1), the molar ratio of 6-bromo-2-pyridinecarboxaldehyde, arylboronic acid, tetrakis(triphenylphosphine)palladium and sodium carbonate is 1:1.1:0.01:2.8.

[0022] Furthermore, in the step (2), the molar ratio of 6-aryl-2-pyridinecarboxaldehyde, chiral amino alcohol, potassium carbonate and elemental iodine is 1:1.1:3:2.

[0023] Furthermore, in the step (2), petroleum ether and ethyl acetate are used as eluents for column chromatography separation, and the volume ratio of petroleum ether to ethyl acetate is 5:1 to 10:1; and the mixed solvent used for recrystallization purification is dichloromethane / ethyl acetate and petroleum ether.

[0024] Furthermore, in step (3), the molar ratio of the ligand to anhydrous cobalt chloride is 1:1 to 1:3.

[0025] Furthermore, the solvent in step (3) is redistilled tetrahydrofuran, and the detergent used for separation is redistilled ether.

[0026] Furthermore, in step (3), the reaction temperature is room temperature and the reaction time is 12 to 72 hours.

[0027] Furthermore, 6-bromo-2-pyridinecarboxaldehyde or 2-pyridinecarboxaldehyde is used to replace the 6-aryl-2-pyridinecarboxaldehyde in step (2) to obtain the corresponding chiral oxazoline pyridine ligand.

[0028] The present invention also provides the use of the chiral oxazoline pyridine-cobalt compound as a catalyst in catalyzing the polymerization reaction of isoprene. The chiral oxazoline pyridine-cobalt compound and diethylaluminum chloride are used to catalyze the polymerization of isoprene. When the reaction time is 2 hours, the reaction temperature is 25° C., and the Al / Co molar ratio is 80, the molecular weight of the prepared polyisoprene can be as high as 1.44×10 5 g·mol -1 , at this time PDI = 2.14.

[0029] Beneficial effects of the invention: The invention relates to the synthesis and application of a chiral oxazoline pyridine-cobalt catalyst. The method has a simple synthesis route, low cost and is easy to purify. The prepared metal catalyst can successfully catalyze the polymerization reaction of isoprene. By adjusting the substituents on the oxazoline and pyridine rings, the electronic effect and steric effect of the metal center can be significantly changed, thereby adjusting the reaction activity of the catalyst, wherein the highest reaction activity of catalyzing the polymerization of isoprene can reach 13.6×10 5g·mol -1 ·h -1 The obtained polyisoprene has a high molecular weight (M n =1.7~14.4×10 4 g·mol -1 ·h -1 ), the molecular weight distribution is narrow (PDI = 2-3). When the reaction time is 2h, the reaction temperature is 25°C, and Al / Co is 80, the molecular weight of the prepared polyisoprene can reach up to 1.44×10 5 g·mol -1 , at this time PDI = 2.14. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the single crystal structure diagram of the chiral oxazoline pyridine cobalt compound II-1.

[0031] Figure 2 This is the single crystal structure diagram of the chiral oxazoline pyridine cobalt compound II-6. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with specific examples. It should be understood that the following examples are only used to illustrate the present invention and are not used to limit the scope of the present invention, and those skilled in the art in this field can make some non-essential improvements and adjustments based on the content of the above invention.

[0033] Example 1

[0034] The structural formula of the chiral oxazoline pyridine-cobalt compound Co1 in this embodiment is as follows

[0035]

[0036] The synthesis method is as follows:

[0037] (1) 6-Bromo-2-pyridinecarboxaldehyde (1.85 g, 10 mmol) and tetrakis(triphenylphosphine)palladium (0.12 g, 0.1 mmol) were added to a 100 mL Shrek bottle in sequence, and the gas was replaced three times by vacuum line. Then anhydrous toluene (14 mL) and 2 M sodium carbonate solution (14 mL) were added, and finally a methanol solution (15 mL) of phenylboronic acid (1.34 g, 11 mmol) was added. The mixture was refluxed at 110° C. for 24 hours. After the reaction was completed, the mixture was cooled to room temperature, extracted with dichloromethane, the organic layer was collected, the solvent was dried, and column chromatography (PE / CH 2 Cl 2 =1 / 1) to obtain the target compound 6-phenyl-2-pyridinecarboxaldehyde as a colorless oil with a yield of 92%. 1 H NMR (600 MHz, CDCl 3)δ10.17(s,1H),8.11–8.06(m,2H),7.98–7.87(m,3H),7.49(m,3H). 13 C NMR (151 MHz, CDCl 3 )δ193.91,157.88,152.75,138.11,137.78,129.69,128.93,127.02,124.43,119.77.

[0038] (2) Under argon atmosphere, L-phenylglycinol (0.83 g, 5.5 mmol) was added to a tert-butyl alcohol solution (75 mL) of 6-phenyl-2-pyridinecarboxaldehyde (0.92 g, 5 mmol), and the mixture was stirred at room temperature for 2 hours; potassium carbonate (2.07 g, 15 mmol) and elemental iodine (2.54 g, 10 mmol) were then added to the above reaction system, and the mixture was reacted at 110° C. for 8 hours. After the reaction was completed, a saturated solution of sodium thiosulfate was added to quench the reaction, the mixture was cooled to room temperature, extracted with dichloromethane, the organic phase was collected, the solvent was dried, and column chromatography (PE / EA=10:1) was used to separate the mixture, and a white solid L1 was obtained with a yield of 61%. 1 H NMR (600 MHz, CDCl 3 )δ8.07–8.00(m,3H),7.87–7.80(m,2H),7.45(m,3H),7.32(t,J=7.6Hz,2H),7.29–7.21(m,3H),4.72–4.64 (m,1H),4.51–4.44(m,1H),4.30–4.25(m,1H),3.33(dd,J=13.8,5.1Hz,1H),2.78(dd,J=13.8,9.2Hz,1H). 13 C NMR (151 MHz, CDCl 3 )δ163.58,157.68,146.93,138.80,137.99,137.40,129.35,128.85,128.71,127.30,126.67,122.55,122.50,72.58,68.25,41.85.

[0039] (3) Under argon atmosphere, the above ligand compound L1 (0.31 g, 1 mmol), anhydrous cobalt chloride (0.13 g, 1 mmol) and 10 mL of tetrahydrofuran were added to a 25 mL Shrek bottle in sequence and stirred at room temperature for 24 hours. After the reaction was completed, the solvent was concentrated, anhydrous ether was added, filtered, and the obtained solid was washed three times with anhydrous ether and dried to obtain the metal compound Co1. The yield was 83% for a blue solid. [α] D 30= +69.62 (c 0.260, CH 2 Cl 2 ).

[0040] The structure of the metal compound Co1 was further confirmed by X-ray single crystal diffraction. Figure 1 shown.

[0041] Example 2

[0042] The structural formula of the chiral oxazoline pyridine-cobalt compound Co2 in this embodiment is as follows:

[0043]

[0044] The synthesis method is as follows:

[0045] (1) Same as step (1) of Example 1, except that phenylboric acid was replaced by naphthaleneboric acid. Yellow solid. Yield: 75%. 1 H NMR (600 MHz, CDCl 3 )δ10.18(s,1H),8.07–7.91(m,5H),7.79(dd,J=7.4,1.4Hz,1H),7.64(dd,J=7.0,1.3Hz,1H),7.61–7.55(m,1H),7.55–7.46(m,2H). 13 C NMR (151 MHz, CDCl 3 )δ193.82,160.00,152.74,137.50,137.28,134.02,131.00,129.56,129.29,128.56,127.76,126.80,126.16,125.35,125.20,119.85.

[0046] (2) Same as step (2) of Example 1. 6-phenyl-2-pyridinecarboxaldehyde was replaced with 6-naphthyl-2-pyridinecarboxaldehyde. Yellow solid L2 was obtained. The yield was 54%. [α] D 25 =-20.30(c 0.537,CH 2 Cl 2 ). 1 H NMR (600 MHz, CDCl 3)δ8.16(dd,J=7.8,1.1Hz,1H),8.01(d,J=8.4Hz,1H),7.94–7.88(m,2H),7.68(dd,J= 7.8,1.1Hz,1H),7.64(dd,J=7.0,1.3Hz,1H),7.54(dd,J=8.2,7.0Hz,1H),7.51–7.44 (m,2H),7.32(t,J=7.5Hz,2H),7.30–7.22(m,2H),4.72–4.63(m,1H),4.45(t,J=9.0H z,1H),4.28–4.22(m,1H),3.32(dd,J=13.8,5.1Hz,1H),2.79(dd,J=13.8,9.1Hz,1H). 13 C NMR (151 MHz, CDCl 3 )δ163.54,159.33,146.95,138.00,137.94,136.86,133.94,131.35,129.32,129.12,128.66,1 28.40,127.85,127.09,126.63,126.59,125.90,125.47,125.34,122.52,72.62,68.16,41.81.

[0047] (3) Same as step (3) of Example 1. Replace L1 with L2. Blue solid. Yield: 85%. [α] D 30 =-25.65(c0.503,CH 2 Cl 2 ).

[0048] Example 3

[0049] The structural formula of the chiral oxazoline pyridine-cobalt compound Co3 in this embodiment is as follows:

[0050]

[0051] The synthesis method is as follows:

[0052] (1) Same as step (2) of Example 1. 6-phenyl-2-pyridinecarboxaldehyde was replaced by 2-pyridinecarboxaldehyde. A white solid L3 was obtained. The yield was 56%. 1 H NMR (600 MHz, CDCl 3)δ8.69(d,J=4.8Hz,1H),8.04(d,J=7.9Hz,1H),7.76(m,1H),7.44–7.35(m,1H),7.34–7.13(m,5H),4.68–4.60 (m,1H),4.45–4.39(m,1H),4.21(t,J=8.1Hz,1H),3.28(dd,J=13.8,5.1Hz,1H),2.74(dd,J=13.8,9.1Hz,1H). 13 C NMR (151 MHz, CDCl 3 )δ162.84,149.47,146.52,137.54,136.36,128.98,128.34,126.32,125.32,123.69,72.21,67.84,41.42.

[0053] (2) Same as step (3) of Example 1. Replace L1 with L3. Blue solid. Yield: 81%. [α] D 30 = +42.11 (c 0.257, EtOH).

[0054] Example 4

[0055] The structural formula of the chiral oxazoline pyridine-cobalt compound Co4 in this embodiment is as follows:

[0056]

[0057] The synthesis method is as follows:

[0058] (1) The same as step (2) of Example 1, except that 6-phenyl-2-pyridinecarboxaldehyde was replaced by 6-bromo-2-pyridinecarboxaldehyde to obtain white solid L4 with a yield of 61%. 1 H NMR (600 MHz, CDCl 3 )δ8.03(dd,J=7.4,1.1Hz,1H),7.67–7.58(m,2H),7.34–7.28(m,2H),7.26–7.21(m,3H),4.69–4.61(m, 1H),4.48–4.42(m,1H),4.26–4.21(m,1H),3.28(dd,J=13.8,5.2Hz,1H),2.75(dd,J=13.8,9.0Hz,1H). 13 C NMR (151 MHz, CDCl 3)δ161.97,147.65,142.03,138.78,137.63,130.35,129.22,128.64,126.66,122.86,72.72,68.17,41.60.

[0059] (2) Same as step (3) of Example 1. Replace L1 with L4. Blue solid. Yield: 72%. [α] D 30 = +43.86 (c0.299, CH 2 Cl 2 ).

[0060] Example 5

[0061] The structural formula of the chiral oxazoline pyridine-cobalt compound Co5 in this embodiment is as follows:

[0062]

[0063] The synthesis method is as follows:

[0064] (1) The same as step (1) of Example 1, except that phenylboronic acid was replaced by p-(trifluoromethyl)phenylboronic acid. A white solid was obtained. The yield was 89%. 1 H NMR (600 MHz, CDCl 3 )δ10.17(s,1H),8.22(d,J=8.2Hz,2H),8.03–7.93(m,3H),7.78(d,J=7.9Hz,2H). 13 C NMR (151 MHz, CDCl 3 )δ194.23,161.16,157.73,152.80,137.77,130.87,128.47,123.79,119.20,114.47,55.54.

[0065] (2) Same as step (2) of Example 1. 6-phenyl-2-pyridinecarboxaldehyde was replaced with 6-(4-trifluoromethyl)phenyl-2-pyridinecarboxaldehyde. Recrystallization from dichloromethane / petroleum ether gave a white solid L5. The yield was 62%. [α] D 25 =-46.26(c0.508,CH 2 Cl 2 ). 1 H NMR (600 MHz, CDCl 3)δ8.16(d,J=8.1Hz,2H),8.08(dd,J=7.5,1.2Hz,1H),7.92–7.84(m,2H),7.73(d,J=8.2Hz,2H),7.32(t,J=7.5Hz,2H),7.26( m,3H),4.73–4.65(m,1H),4.51–4.46(m,1H),4.31–4.25(m,1H),3.32(dd,J=13.8,5.1Hz,1H),2.79(dd,J=13.8,9.1Hz,1H). 13 C NMR (151 MHz, CDCl 3 )δ163.34,156.15,147.27,142.12,137.92,137.74,131.25,129.38,128. 76,127.66,126.75,125.83,125.17,123.41,122.81,72.69,68.32,41.84. 19 FNMR (565MHz, CDCl 3 )δ-62.60.

[0066] (3) Same as step (3) of Example 1. Replace L1 with L5. Blue solid. Yield: 87%. [α] D 30 = +64.41(c0.252,CH 2 Cl 2 ).

[0067] Example 6

[0068] The structural formula of the chiral oxazoline pyridine-cobalt compound Co6 in this embodiment is as follows:

[0069]

[0070] The synthesis method is as follows:

[0071] (1) The same as step (1) of Example 1, except that phenylboronic acid was replaced by p-methoxyphenylboronic acid. A white solid was obtained. The yield was 91%. 1 H NMR (600 MHz, CDCl 3 )δ10.15(s,1H),8.06(d,J=8.8Hz,2H),7.92–7.87(m,2H),7.84(dd,J=5.7,3.0Hz,1H),7.04(d,J=8.9Hz,2H),3.89(s,3H). 13 C NMR (151 MHz, CDCl 3)δ194.23,161.16,157.73,152.80,137.77,130.87,128.47,123.79,119.20,114.47,55.54.

[0072] (2) Same as step (2) of Example 1. 6-phenyl-2-pyridinecarboxaldehyde was replaced with 6-(4-methoxy)phenyl-2-pyridinecarboxaldehyde. Recrystallization from dichloromethane / petroleum ether gave a white solid L6. The yield was 65%. [α] D 25 =-32.50(c 0.520,CH 2 Cl 2 ). 1 H NMR (600 MHz, CDCl 3 )δ8.04–7.99(m,2H),7.96(dd,J=7.4,1.3Hz,1H),7.84–7.75(m,2H),7.32(t,J=7.6Hz,2H),7.29–7.20(m,3H),7.02–6.96(m,2H), 4.71–4.63(m,1H),4.49–4.44(m,1H),4.30–4.24(m,1H),3.86(s,3H),3.33(dd,J=13.8,5.0Hz,1H),2.77(dd,J=13.8,9.2Hz,1H). 13 CNMR (151MHz, CDCl 3 )δ163.74,160.89,157.36,146.81,138.08,137.34,131.49,129.40,128. 76,128.66,126.72,121.92,121.78,114.28,72.61,68.30,55.50,41.91.

[0073] (3) Same as step (3) of Example 1. Replace L1 with L6. Green solid. Yield: 81%. [α] D 30 =+101.56(c0.257,CH 2 Cl 2 ).

[0074] The structure of the chiral oxazoline pyridine-cobalt compound Co6 was further confirmed by X-ray single crystal diffraction. Figure 2 shown.

[0075] Example 7

[0076] The structural formula of the chiral oxazoline pyridine-cobalt compound Co7 in this embodiment is as follows:

[0077]

[0078] The synthesis method is as follows:

[0079] (1) Same as step (1) of Example 1.

[0080] (2) Same as step (2) of Example 1. L-phenylglycinol was replaced by L-phenylalaninol. White solid L7 was obtained. The yield was 59%. 1 H NMR (600 MHz, CDCl 3 )δ8.15–8.10(m,1H),8.08–8.03(m,2H),7.87–7.81(m,2H),7.47(m,2H),7.42(t,J=7.3Hz,1H),7.39–7.33( m,4H),7.32–7.26(m,1H),5.47(dd,J=10.3,8.5Hz,2H),4.92(dd,J=10.3,8.5Hz,2H),4.41(t,J=8.5Hz,2H). 13 C NMR (151 MHz, CDCl 3 )δ164.35,157.71,146.82,142.08,138.80,137.45,129.38,128.88,127.82,127.31,126.96,122.84,122.67,75.50,70.45.

[0081] (3) Same as step (3) of Example 1. Replace L1 with L7. Blue solid. Yield: 73%. [α] D 30 = +263.10(c0.252,CH 2 Cl 2 ).

[0082] Example 8

[0083] The structural formula of the chiral oxazoline pyridine-cobalt compound Co8 in this embodiment is as follows:

[0084]

[0085] The synthesis method is as follows:

[0086] (1) Same as step (1) of Example 1.

[0087] (2) Same as step (2) of Example 1. L-phenylglycinol was replaced by L-valinol. Recrystallization from ethyl acetate / petroleum ether gave a white solid L8. The yield was 65%. 1 H NMR (600 MHz, CDCl 3)δ8.04(m,3H),7.85–7.79(m,2H),7.47(m,2H),7.44–7.39(m,1H),4.54(dd,J=9.7,8.3Hz,1H) ,4.25(t,J=8.3Hz,1H),4.18(m,1H),1.92(m,1H),1.08(d,J=6.8Hz,3H),0.96(d,J=6.8Hz,3H). 13 C NMR (151 MHz, CDCl 3 )δ162.92,157.50,146.23,139.26,137.22,129.20,128.73,127.22,122.48,122.26,72.92,70.80,32.85,19.11,18.23.

[0088] (3) Same as step (3) of Example 1. Replace L1 with L8. Blue solid. Yield: 70%. [α] D 30 =+78.50(c0.254,CH 2 Cl 2 ).

[0089] Example 9

[0090] The structural formula of the oxazoline pyridine-cobalt compound Co9 in this embodiment is as follows:

[0091]

[0092] The synthesis method is as follows:

[0093] (1) Same as step (1) of Example 1.

[0094] (2) Same as step (2) of Example 1. L-phenylglycinol was replaced by ethanolamine. A white solid L9 was obtained. The yield was 63%. 1 HNMR (600MHz, CDCl 3 )δ8.07–8.03(m,2H),7.97(dd,J=6.1,2.6Hz,1H),7.86–7.80(m,2H),7.44(m,3H),4.54(t,J=9.7Hz,2H),4.15(t,J=9.7Hz,2H). 13 C NMR (151 MHz, CDCl 3 )δ164.18,157.58,146.79,138.71,137.38,129.30,128.78,127.23,122.33,122.28,68.25,55.24.

[0095] (3) Same as step (3) of Example 1. Replace L1 with L9. Blue solid. Yield: 67%.

[0096] Example 10

[0097] The polymerization of isoprene was catalyzed by compound Co1 and diethylaluminum chloride, and the specific steps are as follows:

[0098] (1) In a glove box, Co1 (3.79 mg, 5 μmol), 5 mL toluene, and 0.4 mmol AlEt were added to a 25 mL Shrek bottle. 2 Cl and 2mL of isoprene, at this time Al / Co=80 / 1, react at room temperature for 2 hours; methanol solution acidified by hydrochloric acid is added dropwise to the reaction system to quench the reaction to obtain a polymer precipitate, which is washed several times with ethanol, dried to constant weight, and weighed.

[0099] Polymerization activity: 1.36×10 5 g·mol -1 ·h -1 ,Polymer molecular weight: 1.39×10 5 g·mol -1 , PDI=2.03.

[0100] (2) The operation steps are the same as (1), except that Al / Co = 50 / 1, polymerization activity: 1.33×10 5 g·mol -1 ·h -1 ,Polymer molecular weight: 1.76×10 5 g·mol -1 , PDI=2.35.

[0101] (3) The operation steps are the same as (1), except that Al / Co = 20 / 1, polymerization activity: 1.15×10 5 g·mol -1 ·h -1 ,Polymer molecular weight: 1.05×10 5 g·mol -1 , PDI=2.82.

[0102] By screening the Al / Co molar ratio, it was determined that when Co1 was used as the main catalyst, AlEt 2 When Cl is used as a co-catalyst, the optimal molar ratio of Al / Co is 80 / 1, and the polymerization activity is 1.36×10 5 g·mol -1 ·h -1 ,Polymer molecular weight: 1.39×10 5 g·mol -1 , PDI=2.03.

[0103] Embodiment 11

[0104] The polymerization of isoprene was catalyzed by compound Co1 and diethylaluminum chloride, and the specific steps are as follows:

[0105] (1) In a glove box, Co1 (3.79 mg, 5 μmol), 5 mL toluene, 0.4 mmol AlEt 2 Cl and 2 mL of isoprene, at this time Al / Co=80 / 1, react at room temperature for 1 hour; methanol solution acidified by hydrochloric acid is added dropwise to the reaction system to quench the reaction to obtain a polymer precipitate, which is washed several times with ethanol, dried to constant weight, and weighed.

[0106] Polymerization activity: 2.64×10 5 g·mol -1 ·h -1 ,Polymer molecular weight: 8.79×10 4 g·mol -1 , PDI=1.95.

[0107] (2) The operation steps are the same as (1), except that the reaction time is 30 minutes. The polymerization activity is 5.12×10 5 g·mol -1 ·h -1 ,Polymer molecular weight: 4.46×10 4 g·mol -1 , PDI=1.79.

[0108] (3) The operation steps are the same as (1), except that the reaction time is 10 minutes. The polymerization activity is 13.6×10 5 g·mol -1 ·h -1 ,Polymer molecular weight: 1.15×10 4 g·mol -1 , PDI=2.82.

[0109] By screening the polymerization time, it is determined that when Co1 is used as the main catalyst, AlEt 2 When Cl is used as a co-catalyst, the polymerization activity is the highest when the reaction time is 10 minutes, which is 13.6×10 5 g·mol -1 ·h -1 When the reaction time is 2 hours, the polymer molecular weight is the highest, which is 1.39×10 5 g·mol -1 .

[0110] Example 12

[0111] The polymerization of isoprene was catalyzed by compound Co1 and diethylaluminum chloride, and the specific steps are as follows:

[0112] (1) In a glove box, Co1 (3.79 mg, 5 μmol), 5 mL toluene, 0.4 mmol AlEt 2 Cl and 2mL of isoprene, at this time Al / Co=80 / 1, the reaction time is 2 hours, and the reaction temperature is 50°C; methanol solution acidified by hydrochloric acid is dropped into the reaction system to quench the reaction to obtain a polymer precipitate, which is washed several times with ethanol, dried to constant weight, and weighed.

[0113] Polymerization activity: 1.32×10 5 g·mol -1 ·h -1 , polymer molecular weight: 1.09×10 5 g·mol -1 , PDI=2.21.

[0114] (2) The operation steps are the same as (1), except that the reaction temperature is 70°C, and the polymerization activity is 1.19×10 5 g·mol -1 ·h -1 ,Polymer molecular weight: 1.07×10 5 g·mol -1 , PDI=1.79.

[0115] (3) The operation steps are the same as (1), except that the reaction temperature is 90°C and the polymerization activity is 2.3×10 4 g·mol -1 ·h -1 ,Polymer molecular weight: 8.21×10 4 g·mol -1 , PDI=2.82.

[0116] By screening the polymerization temperature, it is determined that when Co1 is used as the main catalyst, AlEt 2 When Cl is used as a co-catalyst, the polymerization activity is the highest at 25°C, which is 1.36×10 5 g·mol -1 ·h -1 ; The maximum polymer molecular weight is 1.39×10 5 g·mol -1 , PDI=2.03.

[0117] Embodiment 13

[0118] When Al / Co=80 / 1, reaction time 2 hours, reaction temperature 25°C, different catalysts were used to replace Co1 to catalyze the polymerization of isoprene. The polymerization results were as follows:

[0119]

[0120] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A chiral oxazoline pyridine-cobalt compound, characterized in that The structural formula of the chiral oxazoline pyridine-cobalt compound is shown in Formula II: Wherein, R1 is benzyl, phenyl, isopropyl or hydrogen; R2 is phenyl, naphthyl, bromine, p-(trifluoromethyl)phenyl or p-methoxyphenyl.

2. The method for synthesizing a chiral oxazoline pyridine-cobalt compound according to claim 1, characterized in that The following steps are involved: (1) 6-aryl-2-pyridinecarboxaldehyde is cyclized with chiral amino alcohol to form a chiral oxazoline pyridine ligand; the structural formula of 6-aryl-2-pyridinecarboxaldehyde is as follows: ； The structural formula of chiral amino alcohol is as follows: ； The structural formula of the chiral oxazoline pyridine ligand is as follows: ； wherein R1 is benzyl, phenyl, isopropyl or hydrogen; R2 is phenyl, naphthyl, p-(trifluoromethyl)phenyl and p-methoxyphenyl; (2) Under an argon atmosphere, the chiral oxazoline pyridine ligand obtained in step (1) reacts with anhydrous cobalt chloride in tetrahydrofuran to obtain a chiral oxazoline pyridine-cobalt compound.

3. The method for synthesizing a chiral oxazoline pyridine-cobalt compound according to claim 2, characterized in that: The synthesis method of 6-aryl-2-pyridinecarboxaldehyde in step (1) is as follows: under an argon atmosphere, 6-bromo-2-pyridinecarboxaldehyde, tetrakis(triphenylphosphine)palladium, 2 M sodium carbonate solution and methanol solution of aryl boronic acid are added in a certain proportion in anhydrous toluene to react; after the reaction is completed, the mixture is cooled to room temperature, extracted with dichloromethane, the organic layer is collected, the solvent is removed after drying, and 6-aryl-2-pyridinecarboxaldehyde is obtained by purification by column chromatography.

4. The method for synthesizing a chiral oxazoline pyridine-cobalt compound according to claim 3, characterized in that: The molar ratio of the 6-bromo-2-pyridinecarboxaldehyde, arylboronic acid, tetrakis(triphenylphosphine)palladium and sodium carbonate is 1:1.1:0.01:2.

8.

5. The method for synthesizing a chiral oxazoline pyridine-cobalt compound according to claim 3, characterized in that: The reaction temperature is 40-160° C., and the reaction time is 4-48 hours.

6. The method for synthesizing a chiral oxazoline pyridine-cobalt compound according to claim 2, characterized in that: The synthesis method of the chiral oxazoline pyridine ligand in step (1) is as follows: under an argon atmosphere, a chiral amino alcohol is added to a tert-butyl alcohol solution of 6-aryl-2-pyridine carboxaldehyde, and stirred at room temperature for 2 to 48 hours; then potassium carbonate and elemental iodine are added, and the reaction is carried out at 40 to 160° C. for 5 to 48 hours; after the reaction is completed, the reaction is quenched with a saturated sodium thiosulfate solution, extracted with dichloromethane, and the organic layer is collected and purified by column chromatography or recrystallization to obtain a 2-aryl-6-(oxazoline)pyridine ligand.

7. The method for synthesizing a chiral oxazoline pyridine-cobalt compound according to claim 6, characterized in that: The molar ratio of the 6-aryl-2-pyridinecarboxaldehyde, the chiral amino alcohol, potassium carbonate and elemental iodine is 1:1.1:3:

2.

8. A method for synthesizing a chiral oxazoline pyridine-cobalt compound according to any one of claims 2 to 7, characterized in that: 6-Bromo-2-pyridinecarboxaldehyde or 2-pyridinecarboxaldehyde was used in place of 6-aryl-2-pyridinecarboxaldehyde.

9. The method for synthesizing a chiral oxazoline pyridine-cobalt compound according to claim 2, characterized in that: In the step (2), the molar ratio of the chiral oxazoline pyridine ligand to anhydrous cobalt chloride is 1:1-1:3, and the reaction is carried out at room temperature for 12-72 hours. After the reaction is completed, the solvent is removed and the mixture is washed three times with anhydrous ether to obtain a chiral oxazoline pyridine-cobalt compound.

10. Use of the chiral oxazoline pyridine-cobalt compound according to claim 1 as a catalyst in catalyzing the polymerization reaction of isoprene, characterized in that: Isoprene polymerization was catalyzed by chiral oxazoline pyridine-cobalt compounds and diethylaluminum chloride.

Images