Tetra-thia-diindole compounds and derivatives, synthetic methods and uses thereof

Abstract

This invention relates to a polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole and its derivatives, their synthesis method, and their applications. The synthesis method is as follows: under the catalysis of a monovalent copper salt, indole compounds and elemental sulfur are converted into a polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole and its derivatives. This invention has the following advantages: (1) The required reagents are stable, require no pretreatment, and are inexpensive and readily available; (2) It is a one-pot synthesis, with elemental sulfur, a byproduct of the petrochemical industry, providing "S4" synthesis building blocks, resulting in significant economic efficiency and saving time and effort; (3) The reaction does not require the addition of ligands, strong bases, or strong acids, and the requirements for the reaction equipment are low; (4) It uses a catalytic amount of inexpensive metallic copper salt to catalyze the reaction, saving costs; (5) The entire reaction system is simple, post-processing is convenient, the reaction equipment is small, and it is easy to scale up.

Description

Technical Field

[0001] This invention relates to a polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole and its derivatives, their synthesis methods and applications, belonging to the field of organic compound synthesis technology. Background Technology

[0002] [1,2,3,4]tetrathio[5,6-b:7,8-b']diindole and its derivatives are an important class of polysulfide heterocyclic compounds containing tetrasulfide atoms linked by "−S4−" bonds. Their eight-membered ring structure is composed of "S4C4," and this unique tetrasulfide-carbon eight-membered ring structure gives these compounds distinctive properties. Currently, the preparation of tetrathiodiindole compounds mainly involves synthesizing the symmetrical 5,10-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole (a). J. Am. Chem. Soc. 1960, 82, 2739c. Symmetrical type currently, regarding 10.1021 / ja01496a022; b) Tetrahedron 2001,57, 7185-7189. DOI: 10.1016 / S0040-4020(01)00660-3; c) J. Chem. Soc., Perkin Trans. 1 , 2002, (3): 330-334. DOI: 10.1039 / B109840C), these synthetic methods require the use of high-boiling-point polar solutions at high temperatures, or at low temperatures (-76°C). o C) Stepwise preparation using stoichiometric lithium metal reagents results in low reaction yield and cumbersome operation.

[0003] The structure and synthetic method of asymmetric 9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole compounds have not yet been reported. These compounds have poor spatial planarity, and the eight-membered ring constructed from tetrasulfide and tetracarbon has a chair conformation, which can effectively reduce spatial packing and improve the electrochemical performance of lithium-sulfur batteries. Therefore, it is essential to develop a simple one-pot method for preparing asymmetric tetrathiodiindole compounds using inexpensive and readily available starting materials. Summary of the Invention

[0004] One of the objectives of this invention is to provide a novel polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole and its derivatives.

[0005] A second objective of this invention is to provide a method for synthesizing polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole and its derivatives.

[0006] A third objective of this invention is to provide the application of the polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole and its derivatives in lithium-sulfur batteries.

[0007] The technical solution adopted by this invention to solve its technical problem is as follows: This invention provides a polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole and its derivatives, the general formula of which is Formula I:

[0008]

[0009] I

[0010] in

[0011] R 1 Selected from: hydrogen atoms; C1-C10 straight-chain alkyl, branched-chain alkyl; substituted or unsubstituted C6-C20 aryl; halogens, methoxy, benzyloxy.

[0012] R 2 Selected from: hydrogen atoms; C1-C10 straight-chain alkyl, branched alkyl, cyclic alkyl; substituted or unsubstituted C6-C20 aryl groups.

[0013] This invention also provides a method for synthesizing polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole and its derivatives, using a monovalent copper salt as a catalyst and elemental sulfur as the “S4” building block, comprising the following synthetic steps:

[0014] (1) Add indole compounds, elemental sulfur, monovalent copper salts and organic solvents;

[0015] (2) Mix the reactants thoroughly and heat them in air.

[0016] It also includes a purification step (3): purifying to obtain the product.

[0017] Preferably, in the synthesis method of the present invention, the indole compound is selected from C8-C30 aromatic indoles, and its general formula is Formula II:

[0018]

[0019] II

[0020] in

[0021] R 1 Selected from: hydrogen atoms; C1-C10 straight-chain alkyl, branched-chain alkyl; substituted or unsubstituted C6-C20 aryl; halogens, methoxy, benzyloxy.

[0022] R 2 Selected from: hydrogen atoms; C1-C10 straight-chain alkyl, branched alkyl, cyclic alkyl; substituted or unsubstituted C6-C20 aryl groups.

[0023] Preferably, in the synthesis method of the present invention, the indole compound is selected from: 1-methylindole, 1,4-dimethylindole, 1-methyl-4-chloroindole, 1,5-dimethylindole, 1-methyl-5-methoxyindole, 1-methyl-5-benzyloxyindole, 1-methyl-5-chloroindole, 1-methyl-5-bromoindole, 1,6-dimethylindole, 1-methyl-6-methoxyindole, 1-methyl-6-fluoroindole, 1-methyl-6-chloroindole, 1,7-dimethylindole, 1-methyl-7-methoxyindole, 1-methyl-7-fluoroindole, 1-H-indole, 1-ethylindole, 1-n-propylindole, and 1-benzylindole.

[0024] Preferably, in the synthesis method of the present invention, the monovalent copper salt has the general formula of Formula III:

[0025] Cu(I) n = 1 or 2 X (X = Cl, Br, I, O, S, SCN, CN)

[0026] III

[0027] Preferably, in the synthesis method of the present invention, the monovalent copper salt is selected from one or more of cuprous chloride, cuprous bromide, cuprous iodide, cuprous oxide, cuprous sulfide, cuprous thiocyanate, and cuprous cyanide.

[0028] Preferably, in the synthesis method of the present invention, the reaction atmosphere is: air atmosphere; the molar ratio of indole compound to elemental sulfur to monovalent copper salt catalyst is 4.0-10 : 8-40 : 0.1-1.0; simultaneously, the reaction temperature is 140-160℃, and the reaction time is 2h-24h; the organic solvent is one or more of toluene, ethylbenzene, o-xylene, m-xylene, p-xylene, mesitylene, 1,4-dioxane, chlorobenzene, and o-dichlorobenzene, and the molar concentration of the reaction system is 0.1-0.3 mol / L (the molar concentration is based on the amount of indole compound).

[0029] The purification steps after the reaction are as follows: After the reaction is completed, the mixture is cooled to room temperature and diluted with dichloromethane until the reaction solution is clear. The diluted solution is filtered through diatomaceous earth and the filtrate is collected. Then, the volatiles in the filtrate are removed by rotary evaporation under reduced pressure. The remaining residue is purified by silica gel column chromatography (petroleum ether: dichloromethane = 10-5:1) to obtain the target product.

[0030] This invention also includes the application of the above-mentioned polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole and its derivatives in lithium-sulfur batteries, as detailed below:

[0031] These polysulfide indole derivatives are electrochemically active and can undergo reversible electrochemical reactions based on lithium-sulfur bonds. They can be used as cathode materials for lithium-sulfur batteries and assembled with lithium metal to form half-cells.

[0032] The beneficial effects of this invention compared to the prior art are as follows:

[0033] (I) The present invention provides a technical solution for converting indole compounds and elemental sulfur into a novel polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole under the catalysis of monovalent copper salt, with elemental sulfur providing the "S4" synthetic building block, in an air atmosphere, thereby obtaining a novel polysulfide indole product and its by-products with excellent chemical properties;

[0034] (II) Under the catalysis of monovalent copper salt, elemental sulfur provides the "S4" synthesis building block. In an air atmosphere, indole compounds and elemental sulfur are converted into a polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole. The reaction raw materials are inexpensive and readily available, and no pretreatment is required. The reaction has high atom economy.

[0035] (III) Under the catalysis of monovalent copper salt, elemental sulfur provides the "S4" synthesis building block. In an air atmosphere, indole compounds and elemental sulfur are converted into a polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole. The reaction does not require the use of ligands or additives such as strong acids or strong bases, which saves raw materials and reduces reaction costs.

[0036] (IV) Under the catalysis of monovalent copper salt, elemental sulfur provides the "S4" synthesis building block. In an air atmosphere, indole compounds and elemental sulfur are converted into a polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole. The target product is synthesized directly in a "one-pot" process, saving research and development time and production cycle.

[0037] (V) Under the catalysis of monovalent copper salt, elemental sulfur provides the "S4" synthesis building block. In an air atmosphere, indole compounds and elemental sulfur are converted into a polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole. This technical solution overcomes the difficulties of providing sulfur source with elemental sulfur, low sulfur atom introduction rate, and difficulty in controlling the number of introduced atoms. It enables the actual application of the product to be brought forward and creates the basic conditions for industrial production.

[0038] (VI) Under the catalysis of monovalent copper salt, elemental sulfur provides the "S4" synthesis building block. In an air atmosphere, a technical solution is used to convert indole compounds and elemental sulfur into a polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole. This solution is scientific, reasonable, easy to operate, has few reaction steps, requires few equipment, and has simple post-processing.

[0039] (VII) Under the catalysis of monovalent copper salt, elemental sulfur provides the "S4" synthesis building block. In an air atmosphere, indole compounds and elemental sulfur are converted into a polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole. It has the characteristics of wide availability of raw materials, low input, high output, easy to further mass production and popularization, high product utilization value, and predictable market commercialization prospects.

[0040] This invention relates to polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole and its derivatives, as well as their synthetic methods, which can be applied to the field of lithium-sulfur batteries; it is particularly suitable for the research and development of one-pot synthesis of polysubstituted -9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole compounds. Attached Figure Description

[0041] To demonstrate the product of this invention, the present invention provides 1H NMR and 1C NMR spectra of some embodiments.

[0042] Figure 1a and 1b NMR spectrum of the product of Example 1;

[0043] Figure 2a and 2b NMR spectrum of the product in Example 3;

[0044] Figure 3a and 3b NMR spectrum of the product in Example 4;

[0045] Figure 4a and 4b NMR spectrum of the product in Example 5;

[0046] Figure 5a and 5b NMR spectrum of the product in Example 6;

[0047] Figure 6a and 6b NMR spectrum of the product in Example 9;

[0048] Figure 7a and 7b NMR spectrum of the product in Example 10;

[0049] Figure 8a and 8b NMR spectrum of the product in Example 13;

[0050] Figure 9a and 9b NMR spectrum of the product in Example 17;

[0051] Figure 10a and 10b NMR spectrum of the product in Example 18;

[0052] Where a is the proton spectrum and b is the carbon spectrum. Detailed Implementation

[0053] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0054] The reaction equation is:

[0055]

[0056] Step 1: Add indole compounds (specific substances are shown in Table 1), elemental sulfur, copper(I) salt (specific substances are shown in Table 1) and organic solvent to the reaction vessel. The molar concentration of the reaction system is 0.2 mol / L (the molar concentration is based on the molar amount of the indole compound). Specific substances are shown in Table 1.

[0057] Step 2: Heat and stir the reaction vessel uniformly (e.g., in an oil bath) to the temperature described in Table 1. The indole compound and elemental sulfur react in the solvent for the time described in Table 1.

[0058] Step 3: After the reaction is complete, cool to room temperature, dilute with dichloromethane until the reaction solution is clear, filter the diluted solution through diatomaceous earth and collect the filtrate, then remove the volatiles in the filtrate by rotary evaporation under reduced pressure, and purify the remaining residue by silica gel column chromatography to obtain the target compound.

[0059] Table 1: Molar ratios of indole compounds, copper(I) salts, organic solvents, (indole compounds, elemental sulfur, and copper(I) salts), reaction temperatures, and reaction times in Examples 1-19

[0060]

[0061]

[0062] * indicates the molar ratio of indole compounds, elemental sulfur, and copper(I) salts.

[0063] In the reactions described above, the monovalent copper salt induces a self-coupling reaction at the C2 and C3 positions of two indole molecules, generating a 2,3'-biindole intermediate in situ. Elemental sulfur, under the influence of copper salt and heating, provides an "S4" fragment through ring-opening and bond breaking. Subsequently, under the catalysis of monovalent copper, the 2,3'-biindole intermediate and the "S4" fragment undergo a [4+4] cycloaddition reaction to synthesize 9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole.

[0064] The conversion rate of the substances in the reaction vessel after step 3 was detected, and nuclear magnetic resonance and high-resolution mass spectrometry tests were performed. The results of some embodiments are as follows:

[0065] The NMR and high-resolution mass spectrometry data of the product of Example 1 are as follows:

[0066] 1 ¹H NMR (500 MHz, CDCl₃, ppm) d 7.92 (d, J = 7.9 Hz, 1H), 7.48 – 7.35 (m,4H), 7.36 – 7.29 (m, 2H), 7.22 – 7.15 (m,1H), 4.02 (s, 3H), 3.65 (s, 3H).; 13 CNMR (126 MHz, CDCl3, ppm) d 142.7, 137.8, 137.3, 131.7, 129.3, 126.4, 124.8,123.4, 121.5, 121.4, 120.7, 119.7, 114.9, 110.8, 109.8, 108.7, 31.9, 30.8;HRMS calcd. for C 18 H 15 N2S4 + (M+H) + 387.0113, found 387.0117.

[0067] Example 1 1 H NMR In the atlas d = The singlet at 4.02 (s, 3H) is at position 14. N The -CH3 hydrogen signal peak indicates that the methyl hydrogen is spatially close to the hydrogen at position 13. The two hydrogen atoms exhibit a van der Waals effect, causing the chemical shift to move to a lower field, resulting in a chemical shift greater than that at position 9. N -CH3 contains hydrogen. 13The C10 NMR spectrum yielded 18 carbon signal peaks, including 16 aromatic carbons and 2 alkyl carbons, indicating that the structure lacks symmetry and that all carbons in the compound have different chemical environments. HR-MS data further confirm that Example 1, after protonation, has an elemental composition of C10. 18 H 15 N2S4 + The measured molecular weight of the compound was 387.0117, which is consistent with the theoretical value of 387.0113.

[0068] In summary, the structure of Example 1 is 9,14-dimethyl-9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole.

[0069] The NMR and high-resolution mass spectrometry data of the product in Example 3 are as follows:

[0070] 1 ¹H NMR (500 MHz, CDCl₃, ppm) d 7.43 – 7.40 (m, 1H), 7.35 – 7.30 (m,1H), 7.24 – 7.17 (m, 2H), 7.15 (t, J = 6.0 Hz, 1H), 6.58 (d, J = 4.1 Hz, 1H), 3.88 (s, 3H), 3.54 (s, 3H); 13 C NMR (126 MHz, CDCl3, ppm) d 138.4, 138.0, 135.9,131.1, 126.0, 125.9, 125.7, 125.0, 122.9, 121.8, 121.0, 113.7, 111.1, 108.5,105.4, 101.7, 33.3, 31.1.; HRMS calcd. for C 18 H 13 Cl2N2S4 + (M+H) + 454.9333, found 454.9333.

[0071] The NMR and high-resolution mass spectrometry data of the product in Example 4 are as follows:

[0072] 1 H NMR (500 MHz, Chloroform- d ) δ 7.70 (s, 1H), 7.32 (t, J= 7.8 Hz,2H), 7.23 – 7.17 (m, 2H), 7.08 (s, 1H), 3.98 (s, 3H), 3.63 (s, 3H), 2.54 (s,3H), 2.40 (s, 3H); 13 C NMR (126 MHz, CDCl3) δ 142.9, 136.2, 135.8, 131.5,131.1, 130.9, 129.5, 126.7, 126.7, 124.9, 120.0, 119.4, 114.5, 110.5, 109.5,108.1, 32.0, 30.8, 21.6, 21.4; HRMS calcd. for C 20 H 18 KN2S4 + (M+K) + 452.9984, found 452.9989.

[0073] The NMR and high-resolution mass spectrometry data of the product in Example 5 are as follows:

[0074] 1 H NMR (500 MHz, Chloroform- d ) δ 7.38 – 7.29 (m, 3H), 7.08 – 6.99 (m,2H), 6.66 (s, 1H), 3.98 (s, 3H), 3.94 (s, 3H), 3.74 (s, 3H), 3.63 (s, 3H); 13 CNMR (126 MHz, CDCl3) δ 155.7, 155.5, 143.1, 132.9, 132.6, 131.8, 130.0,126.8, 116.1, 114.4, 113.8, 111.8, 110.7, 108.2, 101.1, 101.0, 56.0, 55.9,31.9, 30.9; HRMS calcd. for C 20 H 18 N2NaO2S4 + (M+Na) + 469.0143, found 469.0151.

[0075] The NMR and high-resolution mass spectrometry data of the product in Example 6 are as follows:

[0076] 1¹H NMR (500 MHz, CDCl₃, ppm) d 7.52 (d, J = 7.5 Hz, 2H), 7.47 (s, 1H),7.44 – 7.28 (m, 10H), 7.17 – 7.07 (m, 2H), 6.73 (s, 1H), 5.27 – 5.12 (m, 2H),5.00 (q, J = 11.8 Hz, 2H), 3.98 (s, 3H), 3.47 (s, 3H); 13 C NMR (126MHz, ppm) d 154.8, 154.4, 143.1, 137.4, 137.1, 133.1, 132.7, 131.7, 130.0, 128.5, 128.5,127.9, 127.8, 127.7, 127.4, 126.6, 116.7, 114.5, 114.4, 111.8, 110.7, 108.1,102.8, 102.7, 70.9, 70.7, 31.8, 30.9; HRMS calcd. for C 32 H 27 N2O2S4 + (M+H) + 599.0950, found 599.0948.

[0077] The NMR and high-resolution mass spectrometry data of the product in Example 9 are as follows:

[0078] 1 H NMR (500 MHz, Chloroform- d ) d 7.78 (d, J = 8.1 Hz, 1H), 7.22 (d, J = 7.4Hz, 2H), 7.16 (dd, J = 17.7, 8.8 Hz, 2H), 7.02 – 7.00 (m, 1H), 3.95 (s, 3H), 3.60 (s, 3H), 2.54 (s, 3H), 2.51 (s, 3H); 13 C NMR (126 MHz, CDCl3) d142.3,138.1, 137.6, 135.0, 133.3, 130.8, 127.1, 124.4, 123.4, 123.0, 120.3, 119.3,115.0, 110.5, 109.7, 108.3, 31.8, 30.6, 26.9, 22.0; HRMS calcd. for C 20 H 18 KN2S4 + (M+K) + 452.9984, found 452.9989.

[0079] The NMR and high-resolution mass spectrometry data of the product of Example 10 are as follows:

[0080] 1 ¹H NMR (500 MHz, CDCl₃, ppm) d 7.78 (d, J = 8.6 Hz, 1H), 7.20 (d, J = 8.6Hz, 1H), 6.99 – 6.93 (m, 1H), 6.88 – 6.83 (m, 3H), 3.96 (s, 3H), 3.92 (s, 3H), 3.91 (s, 3H), 3.60 (s, 3H).; 13 C NMR (126 MHz, ppm) d 158.6, 157.6, 141.8,138.5, 138.3, 130.0, 123.5, 121.6, 120.9, 120.4, 115.6, 112.3, 111.0, 108.4,93.5, 93.2, 55.9, 55.7, 31.9, 30.7; HRMS calcd. for C 20 H 18 N2NaO2S4 + (M+Na) + 469.0143, found 469.0151.

[0081] The NMR and high-resolution mass spectrometry data of the product in Example 13 are as follows:

[0082] 1 ¹H NMR (500 MHz, CDCl₃, ppm) d 7.76 (d, J= 7.9 Hz, 1H), 7.19 – 7.12 (m,2H), 7.09 – 7.01 (m, 3H), 4.31 (s, 3H), 3.88 (s, 3H), 2.86 (s, 3H), 2.83 (s,3H); 13 C NMR (126 MHz, ppm) d 143.7, 136.7, 136.5, 132.4, 130.1, 127.6, 127.3,126.3, 122.3, 121.6, 121.5, 121.3, 118.8, 117.9, 115.7, 109.0, 35.31, 33.9,20.4, 20.1; HRMS calcd. for C 20 H 18 KN2S4 + (M+K) + 452.9984, found 452.9989.

[0083] The NMR and high-resolution mass spectrometry data of the product in Example 17 are as follows:

[0084] 1 ¹H NMR (500 MHz, CDCl₃, ppm) d 7.93 (d, J = 7.4 Hz, 1H), 7.50 – 7.43 (m,2H), 7.40 – 7.35 (m, 3H), 7.34 – 7.29 (m, 1H), 7.17 (t, J = 7.5 Hz, 1H), 4.69 –4.43 (m, 2H), 4.27 – 4.00 (m, 2H), 1.51 (t, J = 7.2 Hz, 3H), 1.14 (t, J = 7.2 Hz, 3H); 13 C NMR (126 MHz, ppm) d 141.9, 136.6, 136.3, 131.5, 129.6, 126.5, 124.7,123.3, 121.3, 121.2, 120.7, 119.8, 115.0, 110.7, 110.0, 109.5, 40.2, 39.2,15.6, 15.6; HRMS calcd. for C 20 H 18 N2NaS4+ (M+Na) + 437.0245, found 437.0248.

[0085] The NMR and high-resolution mass spectrometry data of the product in Example 18 are as follows:

[0086] 1 ¹H NMR (500 MHz, CDCl₃, ppm) d 7.92 (d, J = 7.1 Hz, 1H), 7.52 – 7.42 (m,2H), 7.39 – 7.29 (m, 4H), 7.16 (t, J = 7.5 Hz, 1H), 4.55 – 4.37 (m, 2H), 4.24 –3.87 (m, 2H), 1.95 (q, J = 7.5 Hz, 2H), 1.58 (q, J = 7.4 Hz, 2H), 1.01 (t, J = 7.4Hz, 3H), 0.61 (t, J = 7.4 Hz, 3H); 13 C NMR (126 MHz, ppm) d 142.3, 136.9, 136.6,132.0, 129.6, 126.3, 124.6, 123.2, 121.3, 121.8, 120.6, 119.8, 115.1, 111.0,110.2, 109.4, 46.8, 45.9, 23.7, 23.0, 11.5, 11.3; HRMS calcd. for C 22 H 23 N2S4 + (M+H) + 443.0739, found 443.0746.

[0087] Table 2: Conversion rates and product diagrams of reactions in Examples 1-19

[0088]

[0089]

[0090] The compound from Example 1 was used to assemble a half-cell with lithium metal. The results showed that the reversible specific capacity exceeded 500 mA / g and effectively reduced the "shuttle effect" caused by lithium polysulfides (LiPSs), demonstrating its potential application value in the field of energy storage.

[0091] Based on Example 1, with other conditions unchanged, the molar ratio of indole to sulfur was screened. See the comparative examples in Table 3. When the indole:sulfur ratio was 4:8, the conversion rate was approximately 63%, indicating that some indole was not completely reacted. When the indole:sulfur ratio was 4:16, the conversion rate was approximately 83%, and further excess sulfur did not significantly change the yield. If indole was in excess and sulfur was present in a quantified amount, the conversion rate decreased significantly, reaching approximately 37% when the indole:sulfur ratio was 8:8 (as shown in Table 3).

[0092] Table 3

[0093]

[0094] The conversion rates for the examples and comparative examples 1-2 in Tables 2 and 3 are calculated based on the amount of indole compound. The calculation formula is as follows:

[0095]

[0096] The conversion rate for Comparative Example 3 was calculated based on the amount of elemental sulfur. The calculation formula is as follows:

[0097]

[0098] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A 9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole compound, characterized in that, Its general formula is Formula I: I in R 1 Selected from: hydrogen atoms; C1-C10 straight-chain alkyl and branched-chain alkyl groups; unsubstituted C6-C20 aryl groups; halogens, methoxy groups, and benzyloxy groups; R 2 Selected from: hydrogen atoms; C1-C10 straight-chain alkyl and branched-chain alkyl groups; unsubstituted C6-C20 aryl groups.

2. The method for synthesizing the 9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole compound according to claim 1, characterized in that, The steps are as follows: (1) Add indole compounds, elemental sulfur, monovalent copper salts and organic solvents; (2) Mix the reactants thoroughly and heat to react; The indole compounds have the general formula II: II。 3. The synthesis method according to claim 2, characterized in that, It also includes a purification step (3), which is as follows: After the reaction is completed, the mixture is cooled to room temperature and diluted with dichloromethane until the reaction solution is clear. The diluted solution is filtered through diatomaceous earth and the filtrate is collected. Then, the volatiles in the filtrate are removed by rotary evaporation under reduced pressure. The remaining residue is purified by silica gel column chromatography.

4. The synthesis method according to claim 2, characterized in that, The indole compounds are selected from: 1-methylindole, 1,4-dimethylindole, 1-methyl-4-chloroindole, 1,5-dimethylindole, 1-methyl-5-methoxyindole, 1-methyl-5-benzyloxyindole, 1-methyl-5-fluoroindole, 1-methyl-5-chloroindole, 1-methyl-5-bromoindole, 1,6-dimethylindole, 1-methyl-6-methoxyindole, 1-methyl-6-fluoroindole, 1-methyl-6-chloroindole, 1,7-dimethylindole, 1-methyl-7-methoxyindole, 1-methyl-7-fluoroindole, 1-H-indole, 1-ethylindole, or 1-n-propylindole.

5. The synthesis method according to claim 2, characterized in that, The monovalent copper salt has the general formula III: ， III The X is selected from Cl, Br, I, O, S, SCN or CN.

6. The synthesis method according to any one of claims 2-5, characterized in that, The monovalent copper salt is selected from one or more of cuprous chloride, cuprous bromide, cuprous iodide, cuprous oxide, cuprous sulfide, cuprous thiocyanate, and cuprous cyanide.

7. The synthesis method according to any one of claims 2-5, characterized in that, The molar ratio of the indole compound to elemental sulfur to monovalent copper salt catalyst is 4.0-10 : 8-40 : 0.1-1.

0.

8. The synthesis method according to any one of claims 2-5, characterized in that, The reaction temperature is 140-160℃; the reaction time is 2h-24h.

9. The synthesis method according to any one of claims 2-5, characterized in that, The organic solvent is one or more of toluene, ethylbenzene, o-xylene, m-xylene, p-xylene, mesitylene, 1,4-dioxane, chlorobenzene, and o-dichlorobenzene.

10. The application of the 9,14-dihydro[1,2,3,4]tetrathio[5,6-b:7,8-b']diindole compound of claim 1 in lithium-sulfur batteries.

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