Electron-rich tridentate ligand and synthesis method thereof
By using cyano compound and zinc triflate in reflux reaction and column chromatography purification methods, the existing trident ligand synthesis steps and low efficiency are solved, and the efficient synthesis of electron-rich trident ligands is achieved.
Patent Information
- Application Number
- CN202510177525.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-18
- Publication Date
- 2025-05-23
AI Technical Summary
The existing three-dentate ligand synthesis methods are complicated and require multiple steps of synthesis and purification. Carboxylic acids with multiple carboxylate are used as the reaction raw material, with many side reaction paths, which affect the synthesis efficiency.
The cyano compound is used as the reaction raw material, and the use of carboxylic acid is avoided. Reflux reaction and column chromatography are carried out under zinc triflate medium to simplify the synthesis steps and improve the reaction efficiency.
The efficient synthesis of electron-rich trident ligands is achieved, the synthesis steps are simplified, the reaction efficiency is improved, and the occurrence of side reactions is avoided.
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Figure CN120025291A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of organic synthesis, and in particular to an electron-rich tridentate ligand and a synthesis method thereof. Background Art
[0002] In the current tridentate ligand synthesis method, carboxylic acid is generally used as a reaction raw material when synthesizing an oxazoline ring. The carboxyl group in the carboxylic acid and the amino group in the chiral amino alcohol undergo condensation reaction to obtain a product intermediate, which is then ring-closed via an intramolecular nucleophilic reaction. However, this method requires more synthesis steps, which means that the overall yield will be affected, and the intermediate product needs to add a purification step, which is more cumbersome in obtaining the final product. In addition, when polycarboxylic acid is used as a reaction raw material, there are more side reaction pathways, which affects the synthesis efficiency.
[0003] Therefore, providing an electron-rich tridentate ligand with a simple reaction system and few synthesis steps and a synthesis method thereof is a technical problem that urgently needs to be solved in the art. Summary of the invention
[0004] In order to solve the above problems, the present invention proposes an electron-rich tridentate ligand and a synthesis method thereof. The present invention uses a cyano compound as a reaction raw material, avoids the use of carboxylic acid in the synthesis of the substrate, and makes the reaction raw material easier to obtain and purify; and does not involve the use of carboxylic acid in the synthesis step, shortens the synthesis step, and improves the efficiency of the synthesis reaction.
[0005] In order to achieve the above object, the present invention adopts the following technical solution:
[0006] A method for synthesizing an electron-rich tridentate ligand comprises the following specific steps:
[0007] The amino alcohol, cyano compound and chlorobenzene are added to zinc trifluoromethanesulfonate, and the electron-rich tridentate ligand is obtained by column chromatography after reflux reaction.
[0008] Preferably, the mass ratio of the amino alcohol, the cyano compound and the zinc trifluoromethanesulfonate is 3.0-3.4:1:3.5-3.8, and the final concentration of the chlorobenzene is 1 mmol / 20-30 mL.
[0009] Preferably, the zinc trifluoromethanesulfonate is pretreated as follows: heat-treated at 110-125° C. for 1-1.5 h under stirring in a vacuum environment.
[0010] Preferably, the structural formula of the amino alcohol is Where R is Cy, i Pr, Bn, t Bu, CH 2 t Bu, Ph and Any one of .
[0011] Preferably, the cyano compound is Any of the following:
[0012] Among them, R 1 and R 2 Each is independently selected from any one of H, Me and OMe.
[0013] Preferably, the relevant reaction scheme is as follows:
[0014]
[0015] Preferably, the relevant reaction scheme is as follows:
[0016]
[0017]
[0018] Preferably, the cyano compound The preparation method is as follows: adding potassium tert-butoxide to substrate S1 and substrate S2, reacting at room temperature for 20 to 24 hours, extracting and recrystallizing to obtain the cyano compound;
[0019] Wherein, the structural formula of the substrate S1 is The structural formula of the substrate S2 is R 1 and R 2 Same structure as R 1 or R 2 ;
[0020] The cyano compound The preparation method is as follows: add cuprous cyanide to substrate S5, reflux for 10 to 12 hours, filter, wash, extract the reaction solution after the reaction is completed, and then sequentially dry, concentrate, and purify by column chromatography to obtain the product;
[0021] Wherein, the structural formula of the substrate S5 is
[0022] Preferably, the mass ratio of the substrate S1, the substrate S2 and the potassium tert-butoxide is 1:1.1:1.1-1.3;
[0023] The mass ratio of the substrate S5 to the cuprous cyanide is 1:2.4-2.6.
[0024] Preferably, the reflux reaction time is 72 to 75 hours;
[0025] The mobile phase of the column chromatography is petroleum ether and ethyl acetate in a volume ratio of 10-5:1.
[0026] Preferably, after the reflux reaction, the process further comprises: adding water to the reaction solution to quench the reaction, then diluting with ethyl acetate, washing, drying and concentrating in sequence, and then performing column chromatography.
[0027] The electron-rich tridentate ligand is obtained by the preparation method described above.
[0028] Preferably, the electron-rich tridentate ligand has the following structural formula:
[0029]
[0030] The chiral tridentate ligand synthesized by this method can be used for asymmetric transformation reactions catalyzed by transition metals such as copper, nickel, and zinc, such as copper-catalyzed enantioselective aryl alkynylation of olefins and photo-promoted copper-catalyzed asymmetric alkylation of azole compounds. This type of ligand can achieve good chirality control and obtain target products with high enantioselectivity.
[0031] Compared with the prior art, the present invention has the following beneficial effects:
[0032] (1) The method of the present invention uses a cyano compound as a reaction raw material, avoiding the use of carboxylic acid in the synthesis of the substrate, making the reaction raw material easier to obtain and purify; and the synthesis step does not involve the use of carboxylic acid, simplifying the synthesis step;
[0033] (2) In the synthesis of the oxazoline ring ligand, the method of the present invention uses zinc trifluoromethanesulfonate as a reaction aid, thereby avoiding the use of zinc chloride in the previous method. Zinc chloride has stronger water absorption and the reaction effect is more easily affected by the environmental humidity and storage environment of the zinc reagent;
[0034] (3) In the method of the present invention, the amount of the reaction auxiliary zinc reagent is increased to ensure that the condensation reaction is carried out thoroughly, and the zinc reagent is heated and vacuum dehydrated to maintain the repeatability of the condensation reaction. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. The drawings in this description are only embodiments of the present invention.
[0036] Figure 1 This is the H NMR spectrum of the electron-rich tridentate ligand L1 of Example 1 of the present invention;
[0037] Figure 2 This is the H NMR spectrum of the electron-rich tridentate ligand L5 of Example 1 of the present invention;
[0038] Figure 3 This is the H NMR spectrum of the electron-rich tridentate ligand L7 of Example 1 of the present invention;
[0039] Figure 4 This is the H NMR spectrum of the electron-rich tridentate ligand L8 of Example 1 of the present invention;
[0040] Figure 5 This is the H NMR spectrum of the electron-rich tridentate ligand L9 of Example 1 of the present invention;
[0041] Figure 6 This is the H NMR spectrum of the electron-rich tridentate ligand L10 in Example 1 of the present invention. DETAILED DESCRIPTION
[0042] Embodiments of the present invention are described below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but are not to be construed as limiting the present invention.
[0043] Example 1
[0044] The present invention provides a method for synthesizing an electron-rich tridentate ligand (L1), which specifically comprises the following steps:
[0045] (1) Substrate S1 (1 equivalent) and substrate S2 (1.1 equivalent) were placed in a reaction bottle, DMSO (1 mmol / 30 mL) was added as a reaction solvent, and 1.1 equivalent of potassium tert-butoxide was slowly added thereto under stirring conditions (600-700 rpm). After the addition was completed, the reaction was allowed to react at room temperature for 24 hours. After the reaction was completed, water was added thereto to quench the reaction, and the reaction was extracted with ethyl acetate, washed with saturated saline solution, concentrated, and recrystallized in methanol to obtain pure substrate S3;
[0046] (2) Zinc trifluoromethanesulfonate (3.5 equivalents) was placed in a reaction bottle and a stirring bar was added. A vacuum oil pump was connected and the mixture was heated to 110°C under vacuum. Stirring was started (100-150 rpm). The mixture was stirred under vacuum and heating conditions for 1.5 hours. After the heating was completed, the mixture was cooled to room temperature naturally. Amino alcohol (3.0 equivalents) and substrate S3 (1 equivalent) and anhydrous chlorobenzene (1 mmol / 20 mL) were added thereto. The reflux temperature (136-140°C) was maintained and heated and stirred (600-700 rpm) for 72 hours. After the reaction was completed, an appropriate amount of water was added thereto to quench the reaction. The mixture was diluted with ethyl acetate and washed three times with a saturated aqueous ammonium chloride solution and a saturated aqueous sodium chloride solution in sequence. The reaction system was dried over anhydrous sodium sulfate and concentrated. The product was purified on a silica gel chromatography column with petroleum ether / ethyl acetate 10:1 to 5:1 to obtain a pure electron-rich tridentate ligand L1. Figure 1 This is the L1 NMR hydrogen spectrum, the data are as follows:
[0047] L1: 1H NMR(500MHz,Chloroform-d)δ7.81(d,J=7.9Hz,2H),7.38(dd,
[0048] J=8.4,1.1Hz,2H),7.27(m,2H),6.92–6.87(m,2H),4.34–4.27(m,2H),4.09–3.96(m,4H),1.97(d,J=13 .1Hz,2H),1.73(d,J=12.7Hz,5H),1.69–1.40(m,7H),1.19(dt,J=24.3,12.7Hz,6H),1.11–0.89(m,2H).
[0049] The relevant synthetic routes are as follows:
[0050]
[0051] Example 2
[0052] The present invention provides a method for synthesizing an electron-rich tridentate ligand (L5), which specifically comprises the following steps:
[0053] (1) Substrate S1 (1 equivalent) and substrate S2 (1.1 equivalent) were placed in a reaction bottle, DMSO (1 mmol / 30 mL) was added as a reaction solvent, and 1.3 equivalents of potassium tert-butoxide was slowly added thereto under stirring conditions (600-700 rpm). After the addition was completed, the reaction was allowed to react at room temperature for 24 hours. After the reaction was completed, water was added thereto to quench the reaction, and the reaction was extracted with ethyl acetate, washed with a saturated saline solution, concentrated, and recrystallized in methanol to obtain a pure substrate S3;
[0054] (2) Zinc trifluoromethanesulfonate (3.8 equivalents) was placed in a reaction bottle and a stirring bar was added. A vacuum oil pump was connected and the mixture was heated to 120°C under vacuum. Stirring was started (100-150 rpm). The mixture was stirred under vacuum and heating conditions for 1.5 h. After the heating was completed, the mixture was cooled to room temperature naturally. Amino alcohol (3.4 equivalents) and substrate S3 (1 equivalent) and anhydrous chlorobenzene (1 mmol / 20 mL) were added thereto. The reflux temperature (136-140°C) was maintained and heated with stirring (600-700 rpm) for 72 h. After the reaction was completed, an appropriate amount of water was added thereto to quench the reaction. The mixture was diluted with ethyl acetate and washed three times with a saturated aqueous ammonium chloride solution and a saturated aqueous sodium chloride solution in sequence. The reaction system was dried over anhydrous sodium sulfate and concentrated. The product was purified on a silica gel chromatography column with petroleum ether / ethyl acetate 10:1 to 5:1 to obtain a pure electron-rich tridentate ligand L5. Figure 2 This is the L5 NMR hydrogen spectrum, the data are as follows:
[0055] L5: 1H NMR(500MHz,Chloroform-d)δ10.91(s,1H),7.82(d,J=7.9Hz,
[0056] 2H),7.47(dd,J=8.4,1.1Hz,2H),7.30(ddd,J=8.6,7.2,1.7Hz,2H),7.25–7.16(m,10H),6.94–6.89(m,2H),4.49(qd,J =8.2,5.5Hz,2H),4.28–4.20(m,2H),3.99(t,J=7.9Hz,2H),3.17(dd,J=13.7,5.5Hz,2H),2.72(dd,J=13.7,8.3Hz,2H).
[0057] The relevant synthetic routes are as follows:
[0058]
[0059] Example 3
[0060] The present invention provides a method for synthesizing an electron-rich tridentate ligand (L7), which specifically comprises the following steps:
[0061] (1) Substrate S1 (1 equivalent) and substrate S2 (1.1 equivalent) were placed in a reaction bottle, DMSO (1 mmol / 30 mL) was added as a reaction solvent, 1.1 equivalent of potassium tert-butoxide was slowly added thereto under stirring conditions (600-700 rpm), and after the addition was completed, the reaction was allowed to react at room temperature for 20 hours. After the reaction was completed, water was added thereto to quench the reaction, and the reaction was extracted with ethyl acetate, washed with saturated saline solution, concentrated, and recrystallized in methanol to obtain pure substrate S3;
[0062] (2) Zinc trifluoromethanesulfonate (3.5 equivalents) was placed in a reaction bottle and a stirring bar was added. A vacuum oil pump was connected and the mixture was heated to 110°C under vacuum. Stirring was started (100-150 rpm). The mixture was stirred under vacuum and heating conditions for 1.5 h. After the heating was completed, the mixture was cooled to room temperature naturally. Amino alcohol (3 equivalents) and substrate S3 (1 equivalent) and anhydrous chlorobenzene (1 mmol / 20 mL) were added thereto. The reflux temperature (136-140°C) was maintained and heated and stirred (600-700 rpm) for 72 h. After the reaction was completed, an appropriate amount of water was added thereto to quench the reaction. The mixture was diluted with ethyl acetate and washed three times with a saturated aqueous ammonium chloride solution and a saturated aqueous sodium chloride solution in sequence. The reaction system was dried over anhydrous sodium sulfate and concentrated. The product was purified on a silica gel chromatography column with petroleum ether / ethyl acetate 10:1 to 5:1 to obtain a pure electron-rich tridentate ligand L7. Figure 3 This is the L7 NMR hydrogen spectrum, the data are as follows:
[0063] L7: 1 H NMR(500MHz,Chloroform-d)δ10.61(s,1H),7.82–7.75(m,2H),7.40(d,J=1.1Hz,2H),7.28(d,J=1.6Hz,2H),6.92–6.86(m,2H),4.46(d d,J=9.3,7.9Hz,2H),4.33(tt,J=8.9,4.4Hz,2H),3.86(t,J=8.3Hz,2H),1.91–1.85(m,2H),1.41(dd,J=13.9,8.1Hz,2H),0.97(s,18H).
[0064] The relevant synthetic routes are as follows:
[0065]
[0066] Example 4
[0067] The present invention provides a method for synthesizing an electron-rich tridentate ligand (L8), which specifically comprises the following steps:
[0068] (1) Substrate S1 (1 equivalent) and substrate S2 (1.1 equivalent) were placed in a reaction bottle, DMSO (1 mmol / 30 mL) was added as a reaction solvent, and 1.1 equivalent of potassium tert-butoxide was slowly added thereto under stirring conditions (600-700 rpm). After the addition was completed, the reaction was allowed to react at room temperature for 24 hours. After the reaction was completed, water was added thereto to quench the reaction, and the reaction was extracted with ethyl acetate, washed with saturated saline solution, concentrated, and recrystallized in methanol to obtain pure substrate S3;
[0069] (2) Zinc trifluoromethanesulfonate (3.5 equivalents) was placed in a reaction bottle and a stirring bar was added. A vacuum oil pump was connected and the mixture was heated to 110°C under vacuum. Stirring was started (100-150 rpm). The mixture was stirred under vacuum and heating conditions for 1.5 h. After the heating was completed, the mixture was cooled to room temperature naturally. Amino alcohol (3 equivalents) and substrate S3 (1 equivalent) and anhydrous chlorobenzene (1 mmol / 20 mL) were added thereto. The reflux temperature (136-140°C) was maintained and heated and stirred (600-700 rpm) for 72 h. After the reaction was completed, an appropriate amount of water was added thereto to quench the reaction. The mixture was diluted with ethyl acetate and washed three times with a saturated aqueous ammonium chloride solution and a saturated aqueous sodium chloride solution in sequence. The reaction system was dried over anhydrous sodium sulfate and concentrated. The product was purified on a silica gel chromatography column with petroleum ether / ethyl acetate 10:1 to 5:1 to obtain a pure electron-rich tridentate ligand L8. Figure 4 This is the L8 NMR hydrogen spectrum, the data are as follows:
[0070] L8:1 H NMR(500MHz,Chloroform-d)δ10.80(s,1H),7.82(dd,J=7.9,1.7Hz,2H),7.39(dd,J=8.3,1.2Hz,2H),7.29–7.26(m,2H),6 .89(td,J=7.5,1.2Hz,2H), 4.24(dd,J=9.8,8.2Hz,2H), 4.11(t,J=8.1Hz,2H), 4.05(dd,J=9.8,7.9Hz,2H), 0.91(s,18H).
[0071] The relevant synthetic routes are as follows:
[0072]
[0073] Example 5
[0074] The present invention provides a method for synthesizing an electron-rich tridentate ligand (L9), which specifically comprises the following steps:
[0075] (1) The substrate S5 (1 equivalent) was dissolved in NMP, and then cuprous cyanide (2.5 equivalents) was added thereto, and the reaction was heated to 180°C to reflux, and the reaction was stirred (600-700 rpm) for 12 hours. After the reaction was completed, it was cooled to room temperature, filtered through diatomaceous earth, and the filtrate was collected and washed with aqueous ammonium hydroxide solution, extracted with ethyl acetate, and the organic phase was collected, dried with anhydrous sodium sulfate, concentrated, and the product was purified on a silica gel chromatography column with petroleum ether / ethyl acetate 10:1 to 5:1 to obtain pure substrate S6;
[0076] (2) Zinc trifluoromethanesulfonate (3.5 equivalents) was placed in a reaction bottle and a stirring bar was added. A vacuum oil pump was connected and the mixture was heated to 110°C under vacuum. Stirring was started (100-150 rpm). The mixture was stirred under vacuum and heating conditions for 1.5 h. After the heating was completed, the mixture was cooled to room temperature naturally. Amino alcohol (3 equivalents) and substrate S6 (1 equivalent) and anhydrous chlorobenzene (1 mmol / 20 mL) were added thereto. The reflux temperature (136-140°C) was maintained and heated and stirred (600-700 rpm) for 72 h. After the reaction was completed, an appropriate amount of water was added thereto to quench the reaction. The mixture was diluted with ethyl acetate and washed three times with a saturated aqueous ammonium chloride solution and a saturated aqueous sodium chloride solution in sequence. The reaction system was dried over anhydrous sodium sulfate and concentrated. The product was purified on a silica gel chromatography column with petroleum ether / ethyl acetate 10:1 to 5:1 to obtain a pure electron-rich tridentate ligand L9. Figure 4 This is the L9 NMR hydrogen spectrum, the data are as follows:
[0077] L9: 1H NMR(500MHz,Chloroform-d)d 11.80(s,1H),8.30(d,J1 / 41.5Hz,2H),8.03(d,J1 / 41.8Hz,2H),4.47-4.56(m,2H),4.19-4.3 0(m,4H),1.90-1.97(m,2H),1.54(s,18H),1.20(d,J1 / 46.6Hz,6H),1.07(d,J1 / 46.6Hz,6H).
[0078] The relevant synthetic routes are as follows:
[0079]
[0080] Example 6
[0081] The present invention provides a method for synthesizing an electron-rich tridentate ligand (L10), which specifically comprises the following steps:
[0082] (1) The substrate S5 (1 equivalent) was dissolved in NMP, and then cuprous cyanide (2.5 equivalents) was added thereto, and the reaction was heated to 180°C to reflux, and the reaction was stirred (600-700 rpm) for 12 hours. After the reaction was completed, it was cooled to room temperature, filtered through diatomaceous earth, and the filtrate was collected and washed with aqueous ammonium hydroxide solution, extracted with ethyl acetate, and the organic phase was collected, dried over anhydrous sodium sulfate, concentrated, and the product was purified on a silica gel chromatography column with petroleum ether / ethyl acetate 10:1 to 5:1 to obtain pure substrate S6;
[0083] (2) Zinc trifluoromethanesulfonate (3.5 equivalents) was placed in a reaction bottle and a stirring bar was added. A vacuum oil pump was connected and the mixture was heated to 110°C under vacuum. Stirring was started (100-150 rpm). The vacuum and heating conditions were maintained for 1.5 hours. After the heating was completed, the mixture was cooled to room temperature naturally. Amino alcohol (3 equivalents) and substrate S6 (1 equivalent) and anhydrous chlorobenzene (1 mmol / 20 mL) were added thereto. The reflux temperature (136-140°C) was maintained and heated with stirring (600-700 rpm) for 72 hours. After the reaction was completed, an appropriate amount of water was added thereto to quench the reaction. The mixture was diluted with ethyl acetate and washed three times with a saturated aqueous ammonium chloride solution and a saturated aqueous sodium chloride solution in sequence. The reaction system was dried over anhydrous sodium sulfate and concentrated. The product was purified on a silica gel chromatography column with petroleum ether / ethyl acetate 10:1 to 5:1 to obtain a pure electron-rich tridentate ligand L10. Figure 4 This is the L10 NMR hydrogen spectrum, the data are as follows:
[0084] 1H NMR(500MHz,Chloroform-d)δ8.25(d,J=2.1Hz,2H),7.71(d,J=2.0Hz,2H),6.65(t,J=7.4Hz,2H),6. 50(t,J=7.6Hz,4H),5.80–5.74(m,4H),4.36–4.23(m,4H),3.85(dd,J=7.8,6.1Hz,2H),1.57(s,18H).
[0085] The relevant synthetic routes are as follows:
[0086]
[0087] The synthesis method in the existing literature has a long synthesis step and requires the use of highly toxic carbon monoxide gas. The condensation process requires two steps to complete the construction of the oxazoline ring, and the synthesis efficiency is low. The specific synthesis route is as follows:
[0088]
[0089] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for synthesizing an electron-rich tridentate ligand, characterized in that: The specific steps include: The amino alcohol, cyano compound and chlorobenzene are added to zinc trifluoromethanesulfonate, and the electron-rich tridentate ligand is obtained by column chromatography after reflux reaction.
2. The method for synthesizing an electron-rich tridentate ligand according to claim 1, characterized in that: The mass ratio of the amino alcohol, the cyano compound and the zinc trifluoromethanesulfonate is 3.0-3.4:1:3.5-3.8, and the final concentration of the chlorobenzene is 1 mmol / 20-30 mL.
3. The method for synthesizing an electron-rich tridentate ligand according to claim 1, characterized in that: The zinc trifluoromethanesulfonate is pretreated as follows: heat-treated at 110-125° C. for 1-1.5 h under stirring in a vacuum environment.
4. The method for synthesizing an electron-rich tridentate ligand according to claim 1, characterized in that: The structural formula of the amino alcohol is Where R is Cy, i Pr, Bn, t Bu, CH2 t Bu, Ph and Any one of .
5. The method for synthesizing an electron-rich tridentate ligand according to claim 1, characterized in that: The cyano compound is Any of the following: Wherein, R1 and R2 are independently selected from any one of H, Me and OMe.
6. The method for synthesizing an electron-rich tridentate ligand according to claim 1, characterized in that: The cyano compound The preparation method is as follows: adding potassium tert-butoxide to substrate S1 and substrate S2, reacting at room temperature for 20 to 24 hours, extracting and recrystallizing to obtain the cyano compound; Wherein, the structural formula of the substrate S1 is The structural formula of the substrate S2 is R 1 and R 2 The structure is the same as R1 or R2; The cyano compound The preparation method is as follows: add cuprous cyanide to substrate S5, reflux for 10 to 12 hours, filter, wash, extract the reaction solution after the reaction is completed, and then sequentially dry, concentrate, and purify by column chromatography to obtain the product; Wherein, the structural formula of the substrate S5 is 7. The method for synthesizing an electron-rich tridentate ligand according to claim 6, characterized in that: The mass ratio of the substrate S1, the substrate S2 and the potassium tert-butoxide is 1:1.1:1.1-1.3; The mass ratio of the substrate S5 to the cuprous cyanide is 1:2.4-2.
6.
8. The method for synthesizing an electron-rich tridentate ligand according to claim 1, characterized in that: The reflux reaction time is 72 to 75 hours; The mobile phase of the column chromatography is petroleum ether and ethyl acetate in a volume ratio of 10-5:
1.
9. The method for synthesizing an electron-rich tridentate ligand according to claim 1, characterized in that: After the reflux reaction, the method further comprises: adding water to the reaction solution to quench the reaction, then diluting with ethyl acetate, washing, drying and concentrating in sequence, and then performing column chromatography.
10. The electron-rich tridentate ligand obtained by the preparation method according to any one of claims 1 to 9.