Molecular trilobal junction compound and synthesis method thereof
By conducting multiple steps in an inert atmosphere, a series of new molecular trilobe junction compounds with different alkyl chain lengths were successfully prepared, which solved the problem of difficulty in preparing molecular trilobe junctions of different sizes and tightness in the prior art, achieved efficient synthesis and provided important experimental data for the research.
Patent Information
- Application Number
- CN202510290697.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-12
- Publication Date
- 2025-06-13
AI Technical Summary
The existing synthetic strategies are difficult to prepare a series of molecular trilobite compounds with different alkyl chain lengths, and then study the relationship between molecular trilobite size and tightness.
By carrying out imine condensation reaction, imine reduction reaction, nucleophilic acylation reaction and acid-catalyzed cleavage reaction under the protection of an inert atmosphere, a series of new molecular trilobite compounds with different alkyl chain lengths were successfully prepared.
The efficient synthesis of molecular trilobite compounds of different sizes and tightness has been achieved, providing rich experimental data and theoretical basis for studying the structural and performance relationship of molecular trilobite junctions, and has potential application value.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of mechanically interlocked molecules, relates to molecular knot compounds, and particularly relates to a molecular trefoil knot compound and a synthesis method thereof. Background Art
[0002] Mechanically Interlocked Molecules (MIMs) are a class of molecules formed by different components intertwined with each other in space through mechanical bonds or topological bonds, such as rotaxanes, catenanes, and molecular knots. Their unique topological structure and controllable dynamic properties have made them a research hotspot in supramolecular chemistry.
[0003] So far, MIMs have been widely applied in fields such as artificial molecular machines (AMMs), catalysis, life science, and nanoscience, and play an important role in them. Among them, due to its unique topological entanglement spatial configuration, molecular knots have triggered breakthrough progress in frontier fields such as asymmetric catalysis, circularly polarized luminescent materials, and spintronic devices, and at the same time provided new solutions to scientific problems of traditional materials such as liquid crystal phase state regulation. The multidisciplinary cross - characteristic of molecular knot research makes it a bridge connecting mathematical topology, molecular nanotechnology, and functional material science, continuously promoting the deeper development of MIMs science.
[0004] Since the J.-P. Sauvage research group proposed the metal - template strategy and used it for the construction of molecular trefoil knots, various synthesis strategies based on different templates have been developed and used for the synthesis of molecular knots in the past few decades, thus laying a material foundation for studying their structures, properties, and applications. Among various structural characteristics such as crossing number, entanglement mode, and overall curvature radius, the tightness has always been a research hotspot in chemical topology. Exploring the size and tightness limits of molecular knots has always been an attractive research topic. The tightness of molecular knots can be quantified by the ratio of the number of atoms in the shortest molecular path (backbone atoms) to the crossing number (Backbone Crossing Ratio, BCR).
[0005] To achieve the synthesis of molecular knots with a smaller BCR, molecular trefoil knots will be suitable research objects because they have the smallest crossing number, and only the influence of the number of molecular backbone atoms on BCR needs to be considered. However, so far, the existing synthesis strategies are not applicable to the construction of a series of molecular trefoil knots with different alkyl chain lengths to achieve the construction of the smallest and tightest trefoil knots, and further study the relationship between the size and tightness of molecular trefoil knots. Summary of the Invention
[0006] In view of the above deficiencies in the prior art, the object of the present invention is to provide a molecular trefoil knot compound and a preparation method thereof. The present invention can prepare a series of molecular trefoil knot compounds with different alkyl chain lengths to study the relationship between the size and tightness of the molecular trefoil knot.
[0007] The technical solution of the present invention is realized as follows:
[0008] A molecular trefoil knot compound, the structural formula of the molecular trefoil knot compound is as follows:
[0009]
[0010] Among them, n in the structural formula is 1, 2, 3, 4.
[0011] The present invention also provides a synthesis method of the above-mentioned molecular trefoil knot compound, which specifically includes the following steps:
[0012] S1: Under the protection of an inert atmosphere, compound An, compound B and iron(II) bis(trifluoromethanesulfonylimide) undergo an imine condensation reaction in an acetonitrile solvent to obtain compound Cn; the structural formulas of compound An, compound B and compound Cn are as follows:
[0013]
[0014] S2: Add a mixed solvent of methanol and acetonitrile to compound Cn and mix, then add sodium borohydride for an imine reduction reaction, and then add the reduced compound and di-tert-butyl dicarbonate to a mixed solvent of triethylamine and dichloromethane for a nucleophilic acylation reaction to obtain compound Dn; the structural formula of compound Dn is as follows:
[0015]
[0016] S3: Mix compound Dn and dichloromethane, and then add trifluoroacetic acid for an acid-catalyzed cleavage reaction to obtain the molecular trefoil knot compound.
[0017] Furthermore, the synthesis method of An in step S1 is as follows:
[0018] (1) React compound S1-n and 1,1-bis(4-aminophenyl)cyclohexane with a molar ratio of 1:2 in an acetonitrile solvent to synthesize S2-n; the structural formulas of S1-n and S2-n are as follows:
[0019]
[0020] (2) Under the protection of an inert atmosphere, compound S3, compound S2-n are reacted with a mixed solvent of dichloromethane and tributylphosphine to obtain compound S4-n; the molar ratio of compound S3 to compound S2-n is 1:2.5; the structural formulas of S3 and S4-n are as follows:
[0021]
[0022] (3) Under the protection of an inert atmosphere, after mixing compound S4-n, tetrahydrofuran and methanol, hydrazine hydrate is added and reacted at 60 °C for 12 h, thereby synthesizing the said compound An.
[0023] Further, in step S1, B is synthesized by reacting pentaethylene glycol ditosylate and 5-hydroxy-2-pyridinecarboxaldehyde with a molar ratio of 1:2.5 in an acetonitrile solvent.
[0024] Further, in step S1, the molar ratio of compound An, compound B and iron(II) bis(trifluoromethanesulfonyl)imide is 1:1:0.5 - 2, preferably 1:1:1.
[0025] Further, in step S1, the temperature of the imine condensation reaction is 65 - 85 °C, preferably 75 °C; the reaction time is 4 - 18 h, preferably 12 h.
[0026] Further, in step S2, the volume ratio of methanol to acetonitrile in the mixed solvent of methanol and acetonitrile is 1:1; the volume ratio of triethylamine to dichloromethane in the mixed solvent of triethylamine and dichloromethane is 1:10; the molar ratio of compound Cn to di-tert-butyl dicarbonate is 1:2 - 20, preferably 1:10.
[0027] Further, in step S2, the temperature of the nucleophilic acylation reaction is 0 - 35 °C, preferably 25 °C; the reaction time is 4 - 18 h, preferably 12 h.
[0028] Further, in step S3, the molar ratio of compound Dn to trifluoroacetic acid is 1:2 - 100, preferably 1:50.
[0029] Further, in step S3, the temperature of the cleavage reaction is 0 - 35 °C, preferably 25 °C; the reaction time is 1 - 4 h, preferably 2 h.
[0030] Compared with the prior art, the present invention has the following beneficial effects:
[0031] 1. The synthesis process of the present invention is simple and efficient. By changing the alkyl chain length of compound An, novel molecular trefoil knot compounds with different sizes and tightness can be successfully prepared, solving the problem of serial synthesis of molecular trefoil knot compounds and providing the possibility for industrial production. Under the protection of an inert atmosphere, the novel molecular trefoil knot compound TKn is successfully prepared through steps such as imine condensation reaction, imine reduction reaction, nucleophilic acylation reaction, and acid-catalyzed cleavage reaction. This preparation process has mild conditions, is easy to operate and control, and the raw materials are easily available, making it suitable for large-scale industrial production.
[0032] 2. The series of novel molecular trefoil knot compounds prepared by the present invention are the molecular knots with the fewest backbone atoms reported so far, being a group of the smallest molecular trefoil knots. These molecular trefoil knot compounds have similar crossing numbers but different sizes and tightness, and can be further applied to study the relationship between the size and tightness of molecular trefoil knots. By changing the alkyl chain length of compound An, the size and tightness of the molecular trefoil knot compounds can be regulated, thus providing rich experimental data and theoretical basis for studying the relationship between the structure and properties of molecular trefoil knots. In addition, these novel molecular trefoil knot compounds have potential application values in frontier fields such as asymmetric catalysis, circularly polarized luminescent materials, and spintronic devices, and are expected to bring new breakthroughs to the development of these fields. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 - The structural formula of the molecular trefoil knot compound of the present invention.
[0034] Figure 2 - The structural formulas of TK1, TK2, TK3, and TK4.
[0035] Figure 3 - The 1H NMR spectra of compound D1, compound D2, compound D3, and compound D4.
[0036] Figure 4 - The 13C NMR spectra of compound D1, compound D2, compound D3, and compound D4.
[0037] Figure 5 - The 1H NMR spectra of compound TK1, compound TK2, compound TK3, and compound TK4.
[0038] Figure 6 - The 13C NMR spectra of compound TK1, compound TK2, compound TK3, and compound TK4.
[0039] Figure 7 - The ratio diagrams of fragment ion peaks to molecular ion peaks in the gradient tandem mass spectra of compound TK1, compound TK2, compound TK3, and compound TK4. DETAILED DESCRIPTION OF THE INVENTION
[0040] The structural formula of the molecular trefoil knot compound of the present invention is as follows Figure 1 shown, where n in the structural formula is 1, 2, 3, or 4, representing the number of C atoms.
[0041] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.
[0042] S1-n was synthesized with reference to the literature ((Org. Lett. 2022, 13, 764 - 767.), and S3 was synthesized with reference to the literature (Eur. J. Inorg. Chem. 2000, 5, 959 - 969.).
[0043] Example 1
[0044] (1) Synthesis of compound An
[0045] 1.1 Weigh compound S1-n (16.88 mmol) and 1,1-bis(4-aminophenyl)cyclohexane (2.0 equiv.) in a round-bottom flask, and then add 200 mL of acetonitrile solvent pre-dried with anhydrous sodium sulfate. After stirring evenly, add potassium carbonate (1.5 equiv.) to the reaction flask. Heat the resulting suspension to 88 °C and reflux overnight. After the reaction is completed, cool the reaction solution to room temperature, then filter the reaction mixture and concentrate the filtrate under vacuum. The obtained residue was purified by column chromatography to obtain a white solid S2-n, and the yields were: S2-1: 35.1%; S2-2: 37.0%; S2-3: 36.3%; S2-4: 33.9%.
[0046]
[0047] 1.2 Weigh S3 (1.84 mmol) and compound S2-n (2.5 equiv) in a Schlenk reaction flask, then evacuate and replace with nitrogen three times. Under a nitrogen atmosphere, add anhydrous and oxygen-free dichloromethane solvent (10 mL) and tributylphosphine (TBP, 3.0 equiv) through a syringe. After the reaction solution is stirred evenly, slowly add 1,1′-(azodicarbonyl)dipiperidine (ADDP, 3.0 equiv). Slowly raise the temperature to room temperature and react at room temperature for 12 hours. After the reaction is completed, filter the reaction mixture and concentrate the filtrate under vacuum. The obtained mixture was purified by column chromatography to obtain a white solid S4-n, and the yields were: S4-1: 43.4%; S4-2: 64.8%; S4-3: 47.8%; S4-4: 69.4%.
[0048]
[0049] 1.3 Weigh compound S4-n (0.83 mmol) into a Schlenk reaction flask, then evacuate and replace with nitrogen three times. Add a mixed solvent of anhydrous and anaerobic tetrahydrofuran (40 mL) and methanol (10 mL) through a syringe, and then add hydrazine hydrate (0.5 mL) under a nitrogen atmosphere. Subsequently, heat the reaction solution to 60 °C and react for 12 h. After the reaction is completed, cool the reaction solution to room temperature. Filter the reaction mixture and concentrate the filtrate under vacuum. The obtained residue is extracted with aqueous sodium hydroxide solution (20 mL) and dichloromethane (3 × 20 mL), then dried over anhydrous sodium sulfate and concentrated to obtain white solid An, and the yields are as follows: A1: 85.8%; A2: 95.3%; A3: 80.6%; A4: 90.5%.
[0050]
[0051] (2) Synthesis of compound B
[0052] Weigh pentaethylene glycol ditosylate (0.40 mmol) and 5-hydroxy-2-pyridinecarboxaldehyde (1.00 mmol) into a round-bottom flask, and then add 10 mL of acetonitrile solvent pre-dried with anhydrous sodium sulfate. After the reaction solution is stirred evenly, add potassium carbonate (1.60 mmol) to the reaction flask. Heat the obtained suspension to 88 °C and reflux overnight. After the reaction is completed, cool the reaction solution to room temperature, then filter the reaction mixture and concentrate the filtrate under vacuum. The obtained residue is purified by column chromatography to obtain white solid B, and the yield is 91.3%.
[0053]
[0054] (3) Synthesis of compound Cn
[0055] Weigh compound An (0.20 mmol), compound B (0.20 mmol) and iron(II) bis(trifluoromethanesulfonyl)imide (0.20 mmol) into a Schlenk reaction flask, then evacuate and replace with nitrogen three times. Subsequently, add anhydrous and anaerobic acetonitrile solvent. The obtained reaction solution is refluxed overnight at 75 °C. After the reaction is completed, cool the reaction solution to room temperature, then filter the reaction mixture and concentrate the filtrate under vacuum. The obtained residue is washed with ether to obtain purple solid Cn (yields: C1, 95.5%; C2, 94.7%; C3, 97.8%; C4, 96.4%).
[0056] The reaction route is as follows:
[0057]
[0058] (4) Synthesis of compound Dn
[0059] Compound Cn (0.20 mmol) was weighed into a round-bottom flask, and then a mixed solvent of acetonitrile (20 mL) and methanol (40 mL) was added. Sodium borohydride (20.0 equiv.) was added in batches at room temperature. The reaction mixture was stirred at room temperature for 1 hour and then refluxed overnight at 75 °C. After the reaction was completed, the reaction mixture was cooled to room temperature, and then the reaction mixture was filtered and the filtrate was concentrated under vacuum. It was extracted with water (50 mL) and dichloromethane (3 × 30 mL). The combined organic layers were dried over anhydrous sodium sulfate and concentrated to obtain a pink solid, which was used without further purification. The above-obtained solid was placed in a round-bottom flask, and then a mixed solvent of triethylamine (1 mL) and dichloromethane (10 mL) was added. Di-tert-butyl dicarbonate (2.00 mmol) was added under ice bath conditions. The reaction was carried out at room temperature for 12 h. After the reaction was completed, the solution was concentrated, and the obtained residue was purified by column chromatography and preparative gel permeation chromatography (GPC) to obtain a pink solid Dn (yield: D1, 25.5%; D2, 27.6%; D3, 26.3%; D4, 23.9%).
[0060] The reaction route is as follows:
[0061]
[0062] (5) Synthesis of novel molecular trefoil knot compound TKn
[0063] Dn (0.20 mmol) was weighed into a round-bottom flask, and then dichloromethane (10.0 mL) solvent was added. Subsequently, trifluoroacetic acid (10.00 mmol) was slowly added at room temperature. The reaction mixture was reacted at room temperature for 2 h. After the reaction was completed, the pH value of the reaction mixture was adjusted to 8 with 20% aqueous sodium carbonate solution. The aqueous phase was continuously extracted with dichloromethane (3 × 20 mL), and the organic phase was dried over anhydrous sodium sulfate and concentrated under vacuum to obtain the novel molecular trefoil knot compound TKn (yield: TK1, 94.4%; TK 2, 94.8%; TK3, 95.9%; TK4, 98.5%). The structural formulas of TK1, TK2, TK3, and TK4 are as Figure 2 shown.
[0064] The reaction route is as follows:
[0065]
[0066] 1. The 1H NMR spectra and 13C NMR spectra of the compounds D1, D2, D3, and D4 prepared in this example are respectively as Figure 3 and Figure 4 shown. The 1H NMR spectra and 13C NMR spectra of the compounds TK1, TK2, TK3, and TK4 prepared in this example are respectively as Figure 5 and Figure 6As shown, it can be seen from the figure that compounds D1, D2, D3, and D4, as well as compounds TK1, TK2, TK3, and TK4, were successfully prepared.
[0067] 2. Using dichloromethane as the medium, the relationship between the size and tightness of molecular trefoils was studied by gradient tandem mass spectrometry. First, compounds TK1 (1 mg), TK2 (1 mg), TK3 (1 mg), and TK4 (1 mg) were separately dissolved in 1 mL of dichloromethane. Subsequently, the above solutions were separately subjected to gradient tandem mass spectrometry experiments, and the dissociation voltage was adjusted (0 V, 10 V, 20 V, 30 V, 40 V, 41 V, 42 V, 43 V, 44 V, 45 V, 46 V, 47 V, 48 V, 49 V, 50 V, 51 V, 52 V, 53 V, 54 V, 55 V, 56 V, 57 V, 58 V, 59 V, 60 V, 61 V, 62 V, 63 V, 64 V, 65 V, 66 V, 67 V, 68 V, 69 V, 70 V, 72 V, 74 V, 76 V, 78 V, 80 V, 82 V, 84 V, 86 V, 88 V, 90 V). The ratios of the fragment ion peaks to the molecular ion peaks of compounds TK1, TK2, TK3, and TK4 are as Figure 7 shown. It can be seen from the figure that the ratios from largest to smallest are compound TK2, compound TK1, compound TK4, and compound TK3. Therefore, the smallest molecular trefoil TK1 with a backbone atom number of 70 and a BCR of 23.33 is not the tightest molecular knot, while the molecular trefoil TK-2 with a BCR of 24 is a tight molecular knot.
[0068] Example 2
[0069] This example is the same as Example 1, except that in the synthesis of compound Cn, ferrous bis(trifluoromethanesulfonylimide) in this example is (0.14 mmol); in the synthesis of compound Dn, di-tert-butyl dicarbonate in this example is (1.00 mmol); in the synthesis of compound TKn, trifluoroacetic acid in this example is (6.00 mmol).
[0070] In this example, the yields of compounds C1, C2, C3, and C4 are 66.8%, 68.9%, 65.3%, and 64.7% respectively; the yields of compounds D1, D2, D3, and D4 are 16.9%, 19.3%, 17.4%, and 18.0% respectively; the yields of compounds TK1, TK2, TK3, and TK4 are 66.7%, 68.2%, 65.3%, and 68.0% respectively.
[0071] Example 3
[0072] This example is the same as Example 1, except that when synthesizing compound Cn, bis( trifluoromethylsulfonyl) imide iron(II) in this example is (0.30 mmol); when synthesizing compound Dn, di-tert-butyl dicarbonate in this example is (3.00 mmol); when synthesizing compound TK n, trifluoroacetic acid in this example is (14.00 mmol).
[0073] In this example, the yields of compounds C1, C2, C3 and C4 are 47.1%, 43.2%, 49.6% and 45.5% respectively; the yields of compounds D1, D2, D3 and D4 are 13.4%, 12.7%, 14.6% and 13.3% respectively; the yields of compounds TK1, TK2, TK3 and TK4 are 50.9%, 55.3%, 54.8% and 52.5% respectively.
[0074] Comparative Example 1
[0075] This example is the same as Example 1, except that when synthesizing compound Cn, bis( trifluoromethylsulfonyl) imide iron(II) in this example is (0.10 mmol); when synthesizing compound Dn, di-tert-butyl dicarbonate in this example is (0.40 mmol); when synthesizing compound TK n, trifluoroacetic acid in this example is (0.40 mmol).
[0076] In this example, the yields of compounds C1, C2, C3 and C4 are 27.6%, 25.7%, 29.4% and 26.8% respectively; the yields of compounds D1, D2, D3 and D4 are 9.4%, 8.8%, 7.6% and 8.0% respectively; the yields of compounds TK1, TK2, TK3 and TK4 are 30.6%, 31.5%, 34.8% and 33.2% respectively.
[0077] Comparative Example 2
[0078] This example is the same as Example 1, except that when synthesizing compound Cn, bis( trifluoromethylsulfonyl) imide iron(II) in this example is (0.40 mmol); when synthesizing compound Dn, di-tert-butyl dicarbonate in this example is (4.00 mmol); when synthesizing compound TK n, trifluoroacetic acid in this example is (20.00 mmol).
[0079] In this example, the yields of compounds C1, C2, C3 and C4 are 17.7%, 16.2%, 14.8% and 19.6% respectively; the yields of compounds D1, D2, D3 and D4 are 4.8%, 3.9%, 4.0% and 4.4% respectively; the yields of compounds TK1, TK2, TK3 and TK4 are 15.3%, 17.2%, 16.8% and 18.0% respectively.
[0080] Finally, it should be noted that the above embodiments of the present invention are only examples for illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes and modifications can be made on the basis of the above description. It is impossible to list all the implementation manners here. Any obvious changes or modifications derived from the technical solutions of the present invention still fall within the protection scope of the present invention.
Claims
1. A molecular trefoil knot compound, characterized in that: The structural formula of the molecular trefoil compound is as follows: Among them, n in the structural formula is 1, 2, 3, or 4.
2. The method for synthesizing a molecular trefoil knot compound according to claim 1, characterized in that: The specific steps include: S1: Under the protection of an inert atmosphere, compound An, compound B and bis(trifluoromethylsulfonyl imide) ferrous acid are subjected to an imide condensation reaction in an acetonitrile solvent to obtain compound Cn; wherein the structural formulas of compound An, compound B and compound Cn are as follows: S2: A mixed solvent of methanol and acetonitrile is added to compound Cn and mixed, and then sodium borohydride is added to carry out an imine reduction reaction, and then the reduced compound and di-tert-butyl dicarbonate are added to a mixed solvent of triethylamine and dichloromethane to carry out a nucleophilic acylation reaction to obtain compound Dn; wherein the structural formula of compound Dn is as follows: S3: Compound Dn and dichloromethane are mixed, and then trifluoroacetic acid is added to carry out an acid-catalyzed cleavage reaction to obtain the molecular trefoil knot compound.
3. The method for synthesizing a molecular trefoil knot compound according to claim 2, characterized in that: The synthesis method of An in step S1 is as follows: (1) Compound S1-n and 1,1-bis(4-aminophenyl)cyclohexane in a molar ratio of 1:2 are reacted in an acetonitrile solvent to synthesize S2-n; wherein the structural formulas of S1-n and S2-n are as follows: (2) Under the protection of an inert atmosphere, compound S3 and compound S2-n react with a mixed solvent of dichloromethane and tributylphosphine to obtain compound S4-n; the molar ratio of compound S3 to compound S2-n is 1:2.5; the structural formulas of S3 and S4-n are as follows: (3) Under the protection of an inert atmosphere, compound S4-n, tetrahydrofuran and methanol were mixed, and hydrazine hydrate was added to react at 60° C. for 12 hours, thereby synthesizing the compound An.
4. The method for synthesizing a molecular trefoil knot compound according to claim 2, characterized in that: In step S1, B is synthesized by reacting pentanediol di-p-toluenesulfonate and 5-hydroxy-2-pyridinecarboxaldehyde in an acetonitrile solvent at a molar ratio of 1:2.
5.
5. The method for synthesizing a molecular trefoil knot compound according to claim 2 or 3, characterized in that: In step S1, the molar ratio of compound An, compound B and bis(trifluoromethylsulfonyl imide)ferrous iron is 1:1:0.5-2, preferably 1:1:
1.
6. The method for synthesizing a molecular trefoil knot compound according to claim 2, characterized in that: In step S1, the imine condensation reaction temperature is 65-85°C, preferably 75°C; the reaction time is 4-18h, preferably 12h.
7. The method for synthesizing a molecular trefoil knot compound according to claim 2, characterized in that: In step S2, the volume ratio of methanol to acetonitrile in the mixed solvent of methanol and acetonitrile is 1:1; the volume ratio of triethylamine to dichloromethane in the mixed solvent of triethylamine and dichloromethane is 1:10; the molar ratio of compound Cn to di-tert-butyl dicarbonate is 1:2-20, preferably 1:
10.
8. The method for synthesizing a molecular trefoil knot compound according to claim 2, characterized in that: In step S2, the nucleophilic acylation reaction temperature is 0 to 35°C, preferably 25°C; the reaction time is 4 to 18 hours, preferably 12 hours.
9. The method for synthesizing a molecular trefoil knot compound according to claim 2, characterized in that: In step S3, the molar ratio of compound Dn to trifluoroacetic acid is 1:2-100, preferably 1:
50.
10. The method for synthesizing a molecular trefoil knot compound according to claim 2, characterized in that: In step S3, the cracking reaction temperature is 0 to 35°C, preferably 25°C; the reaction time is 1 to 4 hours, preferably 2 hours.