Synthesis method of symmetrical tri-sulfide compound and high-efficiency catalyst used in the method

Abstract

The application belongs to the technical field of organic synthesis, and particularly relates to a high-efficiency synthesis method of symmetrical tri-sulfide compounds. The method for synthesizing tri-sulfide compounds by C-S coupling reaction of halide and elemental sulfur in an alkaline environment has low yield and poor selectivity. In view of the above problems, the application provides a synthesis method of symmetrical tri-sulfide compounds, which is obtained by C-S coupling reaction of halide, elemental sulfur, copper-based supported catalyst, acid binding agent and organic solvent. The copper-based supported catalyst is self-made, and has better selectivity for the target product symmetrical tri-sulfide compound and high product yield.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for synthesizing symmetrical trisulfide compounds and the highly efficient catalyst used therein. Background Technology

[0002] Trisulfide compounds are organosulfur compounds with SSS bonds. Due to their unique structure and diverse biological activities, they play an important role in medicinal chemistry, materials chemistry, and synthetic chemistry. Although trisulfide compounds have high application value, research on their synthetic processes has been relatively slow, resulting in a limited number of reported methods for constructing trisulfide compounds.

[0003] Initially, Na₂S₃ was used as the first nucleophilic sulfur transfer agent to prepare bis(2-hydroxyethyl) trisulfides, but the result was a mixture of disulfides and pentasulfides. In the 1960s, Na₂S was used to construct trisulfide compounds, but the method was extremely inconvenient due to the use of highly toxic formaldehyde as an additive in phosphate buffer, and it required both disulfides and tetrasulfides as reactants. In 2001, David et al. proposed the synthesis of trisulfides from the reaction of triphenylmethanesulfonyl chloride with disulfides (Tetrahedron Lett., 2001, 42, 8607). However, triphenylmethanesulfonyl chloride is unstable at room temperature and readily decomposes in hot chloroform solution, and the preparation of this reagent requires the toxic chemical thioyl chloride. In 2019, Krishna et al. used chloride as a starting material, first reacting it with sodium thiosulfate pentahydrate to generate Bunte salt, which was then reacted with sodium sulfide nonahydrate to obtain trisulfide compounds (Chem. Commun., 2019, 55, 13534). Although this provided a new approach for the construction of trisulfide compounds, the strategy requires two steps in different reaction systems, making the operation cumbersome. Furthermore, this strategy easily generates disulfide byproducts, complicating the separation of trisulfide compounds. In 2022, Nader et al. successfully prepared various trisulfide compounds by reacting commercially available electrophilic sulfur transfer reagent 3,4-dichloro-1,2,5-thiadiazole as a sulfur source with thiols under triethylamine catalysis (J. SulfurChem., 2022, 43, 169). Although thiols can be used as precursors for electrophilic sulfur transfer reagents to synthesize trisulfide compounds, their preparation and use are unpopular due to their toxicity and foul odor. Therefore, methods utilizing nucleophilic sulfur transfer agents and electrophilic halide precursors have become very important.

[0004] The halide sulfidation method refers to the synthesis of organosulfur compounds from electrophilic halides and nucleophilic sulfur sources via a CS coupling reaction. This strategy has been successfully applied to the construction of thioethers and dithioethers. Furthermore, various nucleophilic sulfur sources have been used in the sulfidation of halides. Among them, elemental sulfur (S8) is an ideal sulfur source for constructing trithioethers due to its abundant reserves, low price, high atom economy, environmental friendliness, safety, and lack of odor. However, there are currently no reports of the synthesis of trithioethers via the coupling reaction of halides and elemental sulfur. The main reason is that elemental sulfur is activated in an alkaline environment and splits into sulfur clusters with different numbers of sulfur atoms. These sulfur clusters react with halides to generate thioethers (RS) with different numbers of sulfur atoms. n The separation of these polysulfides after synthesis is very challenging because they have similar polarities. Therefore, it is urgent to develop efficient catalytic systems to improve the yield and selectivity of trisulfides generated by the coupling reaction of halides with elemental sulfur (CS). Summary of the Invention

[0005] The existing technology has the problem that the method for synthesizing trisulfide compounds from halides and elemental sulfur under alkaline conditions via CS coupling reaction has low yield and poor selectivity. To address these problems, this invention provides a method for synthesizing symmetrical trisulfide compounds, involving the following reaction processes:

[0006] R-X+S8→RSSSR

[0007] Wherein, the group R can be any one of alkane, alkene, aromatic hydrocarbon, and heterocyclic aromatic hydrocarbon, and the group X is a halogen;

[0008] The above synthesis method involves a CS coupling reaction of halides, elemental sulfur, copper-based supported catalysts, acid-binding agents, and organic solvents.

[0009] The halide includes any one of 1-chloropropane, 3-chloropropene, chlorobutane, benzyl chloride, 4-methylbenzyl chloride, iodobenzene, 4-methylbromobenzene, and 2-bromobenzothiazole;

[0010] Specifically, the copper-based supported catalyst is prepared by the following steps:

[0011] (1) Dissolve the water-soluble copper salt in deionized water, wherein the concentration of the water-soluble copper salt in the deionized water is 2-4 mg / mL copper salt solution.

[0012] (2) At room temperature, add amino-functionalized polymeric porous organic resin to the above copper salt solution and mix and stir evenly. Then let it stand for 4-6 hours. The mass ratio of the amino-functionalized polymeric porous organic resin to the copper salt in the copper salt solution is 50-100:1. After standing, filter to remove the aqueous solution and dry at 50-70℃ for 5-7 hours. Collect the solid product and place the obtained solid product in a tube furnace for calcination at 300-500℃ for 4-6 hours to obtain the product.

[0013] The amino-functionalized porous organic resin is a macroporous polyamino weakly basic anion exchange resin microsphere.

[0014] Specifically, the macroporous polyamino weakly basic anion exchange resin microspheres include any one of the following: SQD-96 type porous resin microspheres, SLCT-20 type porous resin microspheres, D309 type porous resin microspheres, D311 type porous resin microspheres, and D315 type porous resin microspheres.

[0015] Specifically, the water-soluble copper salt includes one or more of copper sulfate, copper acetate, copper nitrate, copper iodide, copper bromide, and copper chloride.

[0016] Specifically, the acid-binding agent includes any one of cesium carbonate, sodium carbonate, sodium hydroxide, potassium hydroxide, sodium methoxide, and sodium tert-butoxide.

[0017] Specifically, the organic solvent includes one or more of ethanol, tert-butanol, isoamyl alcohol, acetonitrile, and tetrahydrofuran.

[0018] Specifically, the method for synthesizing a symmetrical trisulfide compound includes the following steps:

[0019] The halide, elemental sulfur, copper-based supported catalyst, acid-binding agent, and organic solvent are mixed evenly and stirred at 30-80°C until the trisulfide bonds in the reaction system no longer form. The reaction is then complete. The molar ratio of the halide to elemental sulfur and acid-binding agent is 1:1.5-3.5:1. The amount of copper-based supported catalyst added is 10-20% of the total mass of the halide. The molar volume ratio of the halide to the organic solvent is 20 mmol:30-50 mL. After the reaction is complete, the mixture is separated and purified to obtain symmetrical trisulfide compounds.

[0020] Specifically, the separation and purification steps are as follows:

[0021] After the reaction is complete, deionized water is added to the reaction system, and the volume ratio of the added deionized water to the organic solvent is 4-5:5. The organic phase is then extracted, and the extraction is repeated three times. The organic phase is collected and then washed with saturated brine three times. Finally, it is dried with anhydrous sodium sulfate, filtered, and the solvent is removed. Finally, symmetrical trisulfide compounds are obtained by vacuum distillation or column chromatography.

[0022] Specifically, the solvent used for extraction includes any one of ethyl acetate, methyl tert-butyl ether, and dichloromethane.

[0023] The present invention has the following beneficial effects:

[0024] (1) The present invention successfully synthesized symmetrical trisulfide compounds by CS coupling reaction of elemental sulfur with halides. The reaction has high yield and selectivity, with a yield of over 70% and a purity of over 97%.

[0025] (2) In this invention, the N atoms in the porous resin microsphere structure and the transition metal copper ions are strongly coordinated by the impregnation method, thereby obtaining a copper-based supported catalyst. The porous resin microsphere support forms a strong anchoring effect on the transition metal copper ions, reducing the loss of copper ions during the preparation of the copper-based supported catalyst. The copper loading of the porous resin microsphere is significantly improved, and the copper ions are more uniformly and abundantly distributed on the outer surface and inner surface of the pores of the porous resin microsphere support. Under the combined effect of the self-made copper-based supported catalyst, the preferred acid binding agent, the organic solvent and other preferred components, the activation and splitting tendency of elemental sulfur in the reaction system is reduced, and the yield and purity of symmetrical trisulfide compounds are significantly improved.

[0026] (3) The synthesis process of this invention is simple and selective, and uses cheap, readily available, tasteless and odorless elemental sulfur as the sulfur source. It has high atom utilization rate, no other waste is generated, and it is environmentally friendly. Detailed implementation method:

[0027] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0028] Example 1

[0029] The preparation method of copper-based supported catalysts is as follows:

[0030] Dissolve 0.15 g of copper sulfate in 50 mL of deionized water, then add 10.0 g of SQD-96 porous resin microspheres. Stir thoroughly at room temperature for 2 h, then let stand for 6 h. Filter and collect the solid product. Place the collected solid product under normal pressure and dry at 50 °C for 6 h. Then calcine the dried solid product in a tube furnace at 300 °C for 5 h to obtain the copper-based supported catalyst Cu@SQD-96 catalyst (approximately 10.05 g).

[0031] The synthesis method of dipropyl trisulfide is as follows:

[0032] To a clean, dry Schlenk tube, 1-chloropropane (1.6 g, 20 mmol), elemental sulfur (1.0 g, 30 mmol), Cu@SQD-96 catalyst (0.16 g, 10 wt%), potassium hydroxide (1.1 g, 20 mmol), and ethanol (50 mL) were added sequentially. The mixture was then stirred at 80 °C, and the reaction was monitored using GC. The mixture was stirred continuously at a constant temperature until the characteristic peak of 1-chloropropane in the chromatogram disappeared, indicating the reaction was complete. After the reaction was complete, the reaction system was cooled to room temperature. Then, 40 mL of ethanol was added to the reaction system. The organic phases were extracted three times with ethyl acetate (20 mL × 3) using mL of deionized water. The combined organic phases were then washed three times with saturated brine (20 mL × 3). The organic phase was dried with anhydrous sodium sulfate (approximately 6.0 g), filtered through a sintered glass funnel, and ethanol and ethyl acetate were removed by rotary evaporation. Finally, the product was purified by vacuum distillation (40 °C, 0.01 MPa), collecting the fraction at 35 °C to obtain 1.6 g of colorless liquid dipropyl trisulfide (yield 88%, purity 98%). The 1H NMR, 1C NMR, and mass spectrometry data of the obtained product are as follows: 1 HNMR (400MHz, CDCl3) δ2.87-2.84 (t, 4H, J = 8.0Hz), 1.79-1.76 (m, 4H), 1.04-1.00 (t, 6H, J = 8.0Hz); 13 C NMR (101MHz, CDCl3) δ41.0, 22.3, 13.3; HRMS (ESI) m / z:calcd.For C6H 15 S3[M+H] + :183.0336,found:183.1126.

[0033] Example 2

[0034] The preparation method of copper-based supported catalysts is as follows:

[0035] Dissolve 0.18 g of copper acetate in 50 mL of deionized water, then add 10.0 g of SLCT-20 type resin microspheres, stir thoroughly at room temperature for 1 h, let stand for 5 h, then filter to remove the aqueous solution, and dry the obtained solid product at atmospheric pressure and 65 °C for 6 h; then calcine the dried solid product in a tube furnace at 400 °C for 5 h to obtain the copper-based supported catalyst Cu@SLCT-20 catalyst (approximately 10.05 g).

[0036] The synthesis method of diallyl trisulfide is as follows:

[0037] Add 3-chloropropene (1.5 g, 20 mmol), elemental sulfur (1.6 g, 50 mmol), Cu@SLCT-20 catalyst (0.23 g, 15 wt%), cesium carbonate (6.5 g, 20 mmol), and tert-butanol (40 mL) to a dry, clean Schlenk tube; then stir the mixture at 60 °C, monitoring the reaction progress with GC. Continue stirring at a constant temperature until the characteristic peak of 3-chloropropene in the chromatogram disappears, indicating the reaction is complete. After the reaction is complete, cool the resulting mixture to room temperature; add 40 mL of deionized water, and... The sample was extracted three times with ethyl acetate (20 mL × 3), and the organic phases (upper layer) were combined. The collected organic phase was then washed three times with saturated brine (20 mL × 3). The organic phase was then dried over anhydrous sodium sulfate (approximately 6.0 g), filtered through a sintered glass funnel, and tert-butanol and ethyl acetate were removed by rotary evaporation. Further purification was achieved by vacuum distillation (38 °C, 0.01 MPa), collecting the fraction at 36 °C to obtain 1.5 g of a yellow liquid diallyl trisulfide (yield 84%, purity 97%). The 1H NMR, 1C NMR, and mass spectrometry data of the obtained product are as follows: 1 HNMR (400MHz, CDCl3) δ5.91-5.85(m,2H),5.25-5.20(m,4H),3.51-3.50(d,4H,J=6.0Hz); 13 C NMR (101MHz, CDCl3) δ132.7,119.1,41.6; HRMS (ESI) m / z:calcd.For C6H 11 S3[M+H] + :179.0023,found:179.0096.

[0038] Example 3

[0039] The preparation method of copper-based supported catalysts is as follows:

[0040] Dissolve 0.18 g of copper nitrate in 50 mL of deionized water, then add 10.0 g of SLCT-20 resin microspheres. Stir thoroughly at room temperature for 3 h, let stand for 4 h, then filter to remove the aqueous solution, and dry at atmospheric pressure and 70 °C for 4 h. Finally, calcine the dried solid product in a tube furnace at 500 °C for 5 h to obtain the copper-based supported catalyst Cu@SLCT-20 catalyst (approximately 10.06 g).

[0041] The synthesis method of dibutyl trisulfide is as follows:

[0042] Add 1.9 g (20 mmol) of n-butane chloride, 2.2 g (70 mmol) of elemental sulfur, 0.38 g (20 wt%) of Cu@SLCT-20 catalyst, 2.1 g (20 mmol) of sodium carbonate, and 50 mL of isoamyl alcohol to a clean, dry Schlenk tube. The reaction mixture was then stirred at 45 °C, and the reaction progress was monitored by GC. The mixture was stirred at a constant temperature until the characteristic peak of n-butane chloride disappeared from the chromatogram, indicating the reaction was complete. After the reaction was complete, the resulting mixture was cooled to room temperature, and then 40 mL of [unspecified substance] was added to the reaction mixture. The sample was extracted three times with methyl tert-butyl ether (20 mL × 3) using deionized water. The combined organic phases (upper layer) were washed three times with saturated brine (20 mL × 3), dried over anhydrous sodium sulfate (approximately 6.0 g), filtered through a sintered glass funnel, and the solvents isoamyl alcohol and ethyl acetate were removed by rotary evaporation. Finally, the sample was purified by vacuum distillation (45 °C, 0.01 MPa), collecting the fraction at 43 °C to obtain 1.9 g of colorless liquid dibutyl trisulfide (90% yield, 99% purity). The 1H NMR, 1C NMR, and mass spectrometry data of the obtained product are as follows: 1 HNMR (400MHz, CDCl3) δ2.90-2.86(m,4H),1.76-1.69(m,4H),1.47-1.41(m,4H),0.96-0.92(t,6H,J=8.0Hz); 13 CNMR(101MHz, CDCl3)δ38.6,30.9,21.7,13.6; HRMS(ESI)m / z:calcd.for C6H 19 S3[M+H] + :211.0649,found:211.0625.

[0043] Example 4

[0044] The preparation method of copper-based supported catalysts is as follows:

[0045] Dissolve 0.20 g of copper iodide in 50 mL of deionized water, then add 10.0 g of D309 type resin microspheres; stir thoroughly at room temperature for 2 h, let stand for 5 h, filter to remove the aqueous solution in the reaction system, and dry at 65 °C for 6 h under normal pressure. Then, calcine the dried solid product in a tube furnace at 300 °C for 5 h to obtain the copper-based supported catalyst Cu@D309 catalyst (approximately 10.06 g).

[0046] The synthesis method of dibenzyl trisulfide is as follows:

[0047] Add benzyl chloride (2.5 g, 20 mmol), elemental sulfur (1.9 g, 60 mmol), Cu@D309 catalyst (0.45 g, 18 wt%), sodium hydroxide (0.8 g, 20 mmol), and acetonitrile (30 mL) to a clean, dry Schlenk tube. The reaction system was then stirred at 30 °C. The reaction progress was monitored by GC, and the mixture was stirred continuously at a constant temperature until the characteristic peak of benzyl chloride disappeared from the chromatogram, indicating the reaction was complete. After the reaction was complete, the reaction system was cooled to room temperature, 40 mL of deionized water was added, and the mixture was extracted three times with dichloromethane (20 mL × 3). The extracts were then combined. After the organic phase (located in the upper layer) was obtained, the sample was washed three times with saturated brine (20 mL × 3), dried with anhydrous sodium sulfate (approximately 6.0 g), filtered through a sintered glass funnel, and the solvents acetonitrile and ethyl acetate were removed by rotary evaporation. Finally, the sample was purified by column chromatography (silica gel column, pure petroleum ether as eluent, elution flow rate of 20 mL / min). The eluent with Rf = 0.8 (TLC detection, pure petroleum ether as developing solvent) was collected, and the eluent was removed by rotary evaporation to obtain 2.6 g of a pale yellow solid dibenzyl trisulfide (yield 94%, purity 98%). The proton NMR, carbon NMR, and mass spectrometry data of the obtained product are as follows: 1 HNMR(400MHz, CDCl3)δ7.33-7.25(m,10H),4.02(s,4H); 13 CNMR(101MHz, CDCl3)δ136.5,129.4,128.6,127.6,43.1; HRMS(ESI)m / z:calcd.for C 14 H 15 S3[M+H] + :279.0336,found:279.0386.

[0048] Example 5

[0049] The preparation method of copper-based supported catalysts is as follows:

[0050] Dissolve 0.10 g of copper chloride in 50 mL of deionized water, then add 10.0 g of D311 type resin microspheres, stir thoroughly at room temperature for 3 h, let stand for 4 h, filter to remove the aqueous solution from the reaction system, dry the obtained solid product at atmospheric pressure and 65 °C for 6 h, and then calcine the dried solid product in a tube furnace at 500 °C for 5 h to obtain the copper-based supported catalyst Cu@D311 catalyst (approximately 10.04 g).

[0051] The synthesis method of bis(4-methylbenzyl)trisulfide is as follows:

[0052] Add 2.8 g (20 mmol) of 4-methylbenzyl chloride, 1.3 g (40 mmol) of elemental sulfur, 0.45 g (16 wt%) of Cu@D311 catalyst, 1.1 g (20 mmol) of sodium methoxide, and 30 mL of tetrahydrofuran to a clean, dry Schlenk tube. Then, stir the reaction mixture at 40 °C and monitor the reaction progress using GC. Continue stirring at a constant temperature until the characteristic peak of 4-methylbenzyl chloride disappears from the chromatogram, indicating the reaction is complete. After the reaction is complete, cool the reaction mixture to room temperature. Then, add 40 mL of deionized water to the reaction mixture and extract three times with ethyl acetate (20 mL × 3). After completion, the organic phases (located in the upper layer) were combined, then washed three times with saturated brine (20 mL × 3), dried with anhydrous sodium sulfate (approximately 6.0 g), filtered through a sintered glass funnel, and the solvents tetrahydrofuran and ethyl acetate were removed by rotary evaporation. The product was then purified by column chromatography (silica gel column, pure petroleum ether as eluent, elution flow rate of 20 mL / min). The eluent with Rf = 0.9 (TLC detection, pure petroleum ether as developing solvent) was collected. Finally, the eluent was removed by rotary evaporation to obtain 2.6 g of a pale white solid bis(4-methylbenzyl) trisulfide (yield 85%, purity 99%). The proton NMR, carbon NMR, and mass spectrometry data of the obtained product are as follows: 1 HNMR (400MHz, CDCl3) δ7.21-7.19 (d, 2H, J = 4.0Hz), 7.14-7.13 (d, 2H, J = 4.0Hz), 4.01 (s, 4H), 2.33 (s, 6H); 13 C NMR(101MHz, CDCl3)δ137.3,133.4,129.4,129.3,42.9,21.2; HRMS(ESI)m / z:calcd.for C 16 H 18 S3K[M+K] + :345.0208,found:345.0189.

[0053] Example 6

[0054] The preparation method of copper-based supported catalysts is as follows:

[0055] Dissolve 0.20 g of copper bromide in 50 mL of deionized water, then add 10.0 g of D315 type resin microspheres. Stir thoroughly at room temperature for 1 h, let stand for 6 h, filter to remove the aqueous solution in the reaction system, and dry at atmospheric pressure and 65 °C for 6 h. Then, calcine the dried solid product in a tube furnace at 400 °C for 5 h to obtain the copper-based supported catalyst Cu@D315 catalyst (approximately 10.05 g).

[0056] The synthesis method of diphenyl trisulfide is as follows:

[0057] Iodobenzene (4.1 g, 20 mmol), elemental sulfur (1.0 g, 30 mmol), Cu@D315 catalyst (0.49 g, 12 wt%), sodium tert-butoxide (1.9 g, 20 mmol), and tert-butanol (40 mL) were added to a clean, dry Schlenk tube. The reaction system was then stirred at 60 °C, and the reaction progress was monitored by GC. The mixture was stirred continuously at a constant temperature until the characteristic peak of iodobenzene disappeared from the chromatogram, indicating the reaction was complete. After the reaction was complete, the reaction system was cooled to room temperature. Then, 40 mL of deionized water was added to the reaction system, and the mixture was extracted three times with ethyl acetate (20 mL × 3). After combining the organic phases (located in the upper layer), the mixture was washed three times (20 mL × 3) with saturated brine, then dried with anhydrous sodium sulfate (approximately 6.0 g), filtered through a sintered glass funnel, and the solvents tert-butanol and ethyl acetate were removed by rotary evaporation. The mixture was then purified by column chromatography (silica gel column, pure petroleum ether as eluent, elution flow rate of 20 mL / min; the eluent with Rf = 0.7 (TLC detection, pure petroleum ether as developing solvent) was collected, and finally the eluent was removed by rotary evaporation, yielding 2.0 g of colorless oily diphenyl trisulfide (yield 80%, purity 97%). The proton NMR, carbon NMR, and mass spectrometry data of the obtained product are as follows: 1 HNMR(400MHz, CDCl3)δ7.58-7.53(m,4H),7.33-7.14(m,6H); 13 CNMR(101MHz, CDCl3)δ135.8,131.1,129.2,127.1; HRMS(ESI)m / z:calcd.For C 12 H 10 S3Na[M+Na] + :272.9842,found:272.9846.

[0058] Example 7

[0059] The preparation method of copper-based supported catalysts is as follows:

[0060] Dissolve 0.15 g of copper acetate in 50 mL of deionized water, then add 10.0 g of SQD-96 resin microspheres. The reaction system is then stirred thoroughly at room temperature for 2 h and allowed to stand for 5 h. After standing, the aqueous solution in the reaction system is removed by filtration. The collected solid product is dried at atmospheric pressure and 65 °C for 6 h. The dried solid product is then calcined in a tube furnace at 500 °C for 5 h to obtain the copper-based supported catalyst Cu@SQD-96 catalyst (approximately 10.05 g).

[0061] The synthesis method of bis(4-methylphenyl)trisulfide is as follows:

[0062] Add 3.4 g (20 mmol) of 4-methylbromobenzene, 2.2 g (70 mmol) of elemental sulfur, 0.68 g (20 wt%) of Cu@SQD-96 catalyst, 1.9 g (20 mmol) of sodium tert-butoxide, and 30 mL of tert-butanol to a clean, dry Schlenk tube. Then, stir the reaction mixture at 80 °C and monitor the reaction progress using GC. Continue stirring at a constant temperature until the characteristic peak of 4-methylbromobenzene disappears from the chromatogram. After the reaction is complete, cool the reaction mixture to room temperature, add 40 mL of deionized water, and extract three times with ethyl acetate (20 mL × 3). After the organic phase (located in the upper layer) was added, the sample was washed three times (20 mL × 3) with saturated brine, dried over anhydrous sodium sulfate (approximately 6.0 g), filtered through a sintered glass funnel, and the solvents tert-butanol and ethyl acetate were removed by rotary evaporation. The sample was then purified by column chromatography (silica gel column, pure petroleum ether as eluent, elution flow rate of 20 mL / min). The eluent with Rf = 0.8 (TLC detection, pure petroleum ether as developing solvent) was collected. Finally, the eluent was removed by rotary evaporation to obtain 2.1 g of white solid bis(4-methylphenyl)trisulfide (yield 76%, purity 97%). The 1H NMR, 1C NMR, and mass spectrometry data of the bis(4-methylphenyl)trisulfide are as follows: 1 HNMR(400MHz, CDCl3) δ7.38(d,J=8.0Hz,4H),6.98(d,J=8.0Hz,4H),2.33(s,6H,); 13 CNMR(101MHz, CDCl3)δ137.0,132.7,131.1,130.0,21.2; HRMS(ESI)m / z:calcd.ForC 14 H 14 S3Na[M+Na] + :301.0155,found:301.0160.

[0063] Example 8

[0064] The preparation method of copper-based supported catalysts is as follows:

[0065] Dissolve 0.14 g of copper sulfate in 50 mL of deionized water, then add 10.0 g of D315 type resin microspheres. Stir thoroughly at room temperature for 2 h, let stand for 4 h, then filter to remove the aqueous solution from the reaction system. Dry the solid product at atmospheric pressure and 65 °C for 6 h, and then calcine the dried solid product in a tube furnace at 300 °C for 5 h to obtain the copper-based supported catalyst Cu@D315 catalyst (approximately 10.05 g).

[0066] The synthesis method of bis(1,3-benzothiazole)-2,2'-trisulfide is as follows:

[0067] Add 2-bromobenzothiazole (4.3 g, 20 mmol), elemental sulfur (1.9 g, 60 mmol), Cu@D315 catalyst (0.43 g, 10 wt%), potassium hydroxide (1.1 g, 20 mmol), and ethanol (50 mL) to a clean, dry Schlenk tube. Then, stir the reaction mixture at 40 °C and monitor the reaction progress using GC. Continue stirring at a constant temperature until the absorption peak of 2-bromobenzothiazole disappears in the chromatogram, indicating the reaction is complete. After the reaction is complete, cool the reaction mixture to room temperature, add 40 mL of deionized water, and extract three times with ethyl acetate (20 mL × 3). Combine the organic phases (the upper layer). After washing three times with saturated saline (20 mL × 3), it was dried with anhydrous sodium sulfate (approximately 6.0 g), filtered through a sintered glass funnel, and the solvents ethanol and ethyl acetate were removed by rotary evaporation. Then, it was purified by column chromatography (silica gel column, pure petroleum ether as eluent, elution flow rate of 20 mL / min). The eluent with Rf = 0.5 (TLC detection, pure petroleum ether as developing solvent) was collected. Finally, the eluent was removed by rotary evaporation, yielding 2.6 g of a grayish-white solid bis(1,3-benzothiazole)-2,2'-trisulfide (yield 72%, purity 98%). The 1H NMR, 1C NMR, and mass spectrometry data of the bis(1,3-benzothiazole)-2,2'-trisulfide are as follows: 1 HNMR (400MHz, CDCl3) δ7.95(d,J=8.2Hz,2H),7.78(d,J=8.0Hz,2H),7.47(dd,J=7.2,8.4Hz,2H),7.36(dd,J=7.2,8.2Hz,2H); 13 C NMR(101MHz, CDCl3)δ168.1,154.6,136.3,126.8,125.5,122.8,121.5; HRMS(ESI)m / z:calcd.For C 14 H8N2NaS5[M+Na]+ :386.9189,found:386.9180.

[0068] Comparative Example 1 is the same as Example 4, except that Comparative Example 1 uses an equimolar amount of sodium thiosulfate pentahydrate instead of elemental sulfur in Example 4. The yield of dibenzyl trisulfide obtained in Comparative Example 1 was tested to be 32%.

[0069] Comparative Example 2 is the same as Example 4, except that Comparative Example 2 uses an equimolar amount of sodium sulfide nonahydrate instead of elemental sulfur in Example 4. The yield of dibenzyl trisulfide obtained in Comparative Example 2 was tested to be 38%.

[0070] Comparative Example 3 is the same as Example 4, except that in the preparation of dibenzyl trisulfide in Comparative Example 3, 30 mmol of sodium thiosulfate pentahydrate was first added to the reaction system, and the reaction was stirred at a constant temperature until the sodium thiosulfate pentahydrate was completely consumed. Then, 30 mmol of sodium sulfide nonahydrate was added to the reaction system and stirred at a constant temperature (Comparative Example 3 adopted the sulfur source and feeding method provided by Krishna, see reference Zhang L, Qu Y, Huang J, et al. Memory-effect-induced electrochemical oscillation of an Al-doped Li4Ti5O12 composite in Li-ion batteries (vol 55, pg1279, 2019) [J]. Chemical communications, 2019(64):55.). The yield of dibenzyl trisulfide obtained in Comparative Example 2 was 41%.

[0071] Comparative Example 4 is the same as Example 6, except that Comparative Example 4 uses the same mass of copper bromide instead of the Cu@D315 catalyst in Example 6. The yield of diphenyl trisulfide obtained in Comparative Example 4 was tested to be 45%.

[0072] Comparative Example 5 is the same as Example 6, except that the same mass of triethylamine was used in Comparative Example 5 instead of the Cu@D315 catalyst in Example 6. The yield of diphenyl trisulfide obtained in Comparative Example 5 was tested to be 10%.

[0073] Comparative Example 6 is the same as Example 6, except that sodium tert-butoxide, an acid-binding agent, was not added during the preparation of diphenyl trisulfide in Comparative Example 6. Testing showed that Comparative Example 6 could not obtain the target product, diphenyl trisulfide.

[0074] Comparative Example 7 is the same as Example 4, except that Comparative Example 7 uses the same molar amount of potassium carbonate instead of sodium hydroxide in Example 4. The yield of diphenyl trisulfide obtained in Comparative Example 7 was tested to be 51%.

[0075] Comparative Example 8 is the same as Example 4, except that Comparative Example 8 uses the same volume of DMSO instead of the organic solvent acetonitrile in Example 4. The yield of diphenyl trisulfide obtained in Comparative Example 8 was tested to be 32%.

[0076] 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 method for synthesizing symmetrical trisulfide compounds, characterized in that, It is obtained by CS coupling reaction of halides, elemental sulfur, copper-based supported catalyst, acid-binding agent and organic solvent; The halide includes any one of 1-chloropropane, 3-chloropropene, chlorobutane, benzyl chloride, 4-methylbenzyl chloride, iodobenzene, 4-methylbromobenzene, and 2-bromobenzothiazole; The copper-based supported catalyst is prepared by the following steps: (1) Dissolve water-soluble copper salt in deionized water, wherein the concentration of water-soluble copper salt in deionized water is 2-4 mg / mL copper salt solution; (2) At room temperature, add amino-functionalized polymeric porous organic resin to the above copper salt solution and mix and stir evenly. Then let it stand for 4-6 hours. The mass ratio of the amino-functionalized polymeric porous organic resin to the copper salt in the copper salt solution is (50-100):

1. After standing, filter to remove the aqueous solution and dry at 50-70℃ for 5-7 hours. Collect the solid product and place the obtained solid product in a tube furnace for calcination at 300-500℃ for 4-6 hours to obtain the product. The amino-functionalized polymeric porous organic resin is a macroporous polyamino weakly basic anion exchange resin microsphere. The macroporous polyamino weakly basic anion exchange resin microspheres include any one of the following: SQD-96 type porous resin microspheres, SLCT-20 type porous resin microspheres, D309 type porous resin microspheres, D311 type porous resin microspheres, and D315 type porous resin microspheres. The acid-binding agent includes any one of cesium carbonate, sodium carbonate, sodium hydroxide, potassium hydroxide, sodium methoxide, and sodium tert-butoxide. The organic solvent includes one or more of ethanol, tert-butanol, isoamyl alcohol, acetonitrile, and tetrahydrofuran.

2. The method for synthesizing a symmetrical trisulfide compound according to claim 1, characterized in that, The water-soluble copper salt includes one or more of copper sulfate, copper acetate, copper nitrate, copper iodide, copper bromide, and copper chloride.

3. The method for synthesizing a symmetrical trisulfide compound according to any one of claims 1-2, characterized in that, The preparation method includes the following steps: The halide, elemental sulfur, copper-based supported catalyst, acid-binding agent, and organic solvent are mixed evenly and stirred at 30-80℃ until the trisulfide bonds in the reaction system no longer form. The reaction is then complete. The molar ratio of the halide to elemental sulfur and acid-binding agent is 1:(1.5-3.5):

1. The amount of copper-based supported catalyst added is 10-20% of the total mass of the halide. The molar volume ratio of the halide to the organic solvent is 20 mmol:(30-50) mL. After the reaction is complete, the mixture is separated and purified to obtain symmetrical trisulfide compounds.

4. The method for synthesizing a symmetrical trisulfide compound according to claim 3, characterized in that, The separation and purification steps include the following steps: After the reaction is completed, deionized water is added to the reaction system. The volume ratio of the added deionized water to the organic solvent in claim 3 is (4-5):

5. The organic phase is then extracted, and the extraction is repeated three times. The organic phase is collected and then washed with saturated brine three times. Finally, the phase is dried, filtered, and the solvent is removed. Finally, the symmetrical trisulfide compounds are obtained by vacuum distillation or column chromatography.

5. The method for synthesizing a symmetrical trisulfide compound according to claim 4, characterized in that, The solvent used for extraction includes any one of ethyl acetate, methyl tert-butyl ether, and dichloromethane.

6. The method for synthesizing a symmetrical trisulfide compound according to claim 4, characterized in that, The drying agent used is anhydrous sodium sulfate.