A method for electrocatalytic synthesis of n-tert-butyl-2-benzothiazolesulfenamide

Abstract

The application relates to the technical field of organic synthesis, in particular to a method for electrocatalytically synthesizing N-tert-butyl-2-benzothiazolesulfenamide. The method comprises the following steps: dispersing raw material 2-mercaptobenzothiazole, a catalyst, an electrolyte and tert-butylamine in a solvent, uniformly mixing the raw material, the catalyst, the electrolyte and the tert-butylamine, and obtaining a reaction solution; placing the reaction solution in an electrolytic cell, and electrocatalytically oxidizing to obtain N-tert-butyl-2-benzothiazolesulfenamide; wherein the catalyst is a Keggin structure quaternary ammonium salt of phosphotungstic acid or a Keggin structure quaternary ammonium salt of silicotungstic acid. Inorganic ammonium salt is used as the electrolyte, and the Keggin structure quaternary ammonium salt of phosphotungstic acid or the Keggin structure quaternary ammonium salt of silicotungstic acid is used as an electrocatalytic promoter, so that a stable and continuously-operable electrocatalytic synthesis system under low current conditions is constructed, and the reaction rate and the yield of the target product N-tert-butyl-2-benzothiazolesulfenamide are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method for the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide. Background Technology

[0002] N-tert-butyl-2-benzothiazole sulfenamide (NS) is a major product among sulfenamides. It has advantages such as fast vulcanization speed, short vulcanization time, excellent anti-scorch properties and processing safety. It is the most ideal accelerator for styrene-butadiene rubber, butadiene rubber, isoprene rubber and radial tires. It does not produce nitrosamines after decomposition and has no carcinogenic problems. It is known in the industry as an environmentally friendly accelerator.

[0003] Currently, the preparation of N-tert-butyl-2-benzothiazole sulfenamide involves using 2-mercaptobenzothiazole (accelerator M) as a raw material, adding an oxidant to oxidize it to generate an intermediate accelerator DM, and then reacting accelerator DM with tert-butylamine to obtain N-tert-butyl-2-benzothiazole sulfenamide. The mainstream oxidants include sodium hypochlorite, chlorine, sodium nitrite, or hydrogen peroxide. However, this method not only severely corrodes equipment but also generates large amounts of high-salinity wastewater.

[0004] Electrochemical synthesis technology offers a new technological route for the green preparation of N-tert-butyl-2-benzothiazole sulfenamide due to its significant advantages, such as no need for external oxidants, mild reaction conditions, and strong process controllability. However, currently available electrochemical synthesis methods typically require high current densities or long reaction times, increasing industrialization costs. Summary of the Invention

[0005] To overcome the above problems, the present invention provides a method for electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution: A method for the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide includes the following steps: The raw material 2-mercaptobenzothiazole, catalyst, electrolyte and tert-butylamine are dispersed in a solvent and mixed evenly to obtain a reaction solution; The reaction solution was placed in an electrolytic cell and electrocatalytically oxidized to obtain N-tert-butyl-2-benzothiazole sulfenamide; The catalyst is a quaternary ammonium salt of phosphotungstic acid or a quaternary ammonium salt of silicotungstic acid with a Keggin structure.

[0007] In one or more embodiments, the Keggin-structured phosphotungstic acid quaternary ammonium salt or silicotungstic acid quaternary ammonium salt includes TBA3PW. 12 O 40 TEA3PW 12 O40 CTA3PW 12 O 40 TBA4SiW 12 O 40 or TEA4SiW 12 O 40 One of them; wherein, TBA represents tetrabutylammonium cation, TEA represents tetraethylammonium cation, and CTA represents hexadecyltrimethylammonium cation.

[0008] In one or more embodiments, the solvent is methanol.

[0009] In one or more embodiments, the electrolyte is one or more of ammonium chloride, ammonium bromide, ammonium iodide, ammonium fluoride, ammonium sulfate, ammonium nitrate, or ammonium phosphate.

[0010] In one or more embodiments, the molar ratio of 2-mercaptobenzothiazole to the catalyst is (0.8~1):(0.1~0.5), preferably (0.8~1):(0.3~0.5).

[0011] In one or more embodiments, the molar ratio of 2-mercaptobenzothiazole to electrolyte is (16~24):(2.5~3.5), preferably (18~22):3.

[0012] In one or more embodiments, the molar ratio of 2-mercaptobenzothiazole to tert-butylamine is (0.8~1):(3~8), preferably (0.8~1):(5~8).

[0013] In one or more embodiments, the concentration of 2-mercaptobenzothiazole in the solvent is 0.1~0.7 mol / L.

[0014] In one or more embodiments, the anode in the electrolytic cell is a graphite electrode, and the cathode is a stainless steel electrode or an inert electrode.

[0015] In one or more embodiments, the current density during electrocatalytic oxidation is 8~16 mA / cm². 2 .

[0016] In one or more embodiments, the electrocatalytic oxidation reaction time is 1 to 3 hours.

[0017] In one or more embodiments, after the electrocatalytic reaction is completed, the reaction solution is collected, concentrated, cooled and crystallized, and the solid and liquid are separated and collected separately. The solid was washed and dried to obtain N-tert-butyl-2-benzothiazole sulfenamide; The liquid was used directly as the mother liquor in the next electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide.

[0018] The beneficial effects of this invention are as follows: (1) In this invention, inorganic ammonium salts are used as electrolytes, and Keggin-structured phosphotungstic acid quaternary ammonium salts or silicotungstic acid quaternary ammonium salts are used as electrocatalytic promoters to construct a stable and continuously operating electrocatalytic synthesis system under low current conditions, which significantly improves the reaction rate and the yield of the target product N-tert-butyl-2-benzothiazole sulfenamide. The mechanism mainly includes the following aspects: First, inorganic ammonium salts, as electrolytes, can improve the ionic conductivity of the system, reduce the solution resistance, and ensure stable current transmission in the reaction system, thereby maintaining the continuous electrolysis process. Simultaneously, NH4... + The ability to participate in proton transfer at the electrode interface provides a stable source of protons for electrocatalytic reactions, which is beneficial for promoting proton-electron coupling transfer (PCET), reducing reaction overpotential, accelerating the formation and transformation of key active intermediates, and improving overall reaction efficiency. Furthermore, the presence of halogen anions helps maintain ionic balance at the electrode interface, enhancing the electrochemical stability of the system and thus improving the continuous operation of the reaction. On the other hand, Keggin-structured phosphotungstic acid quaternary ammonium salts or silicotungstic acid quaternary ammonium salts possess both electronic regulation and charge transfer functions. Among them, polyoxometalate anions exhibit excellent reversible redox properties, acting as "electron buffers" during electrolysis to achieve reversible electron storage and release, thereby mitigating local potential fluctuations on the electrode surface, inhibiting peroxidation and other side reactions, and improving the selectivity and Faradaic efficiency of the target product. Simultaneously, they form a synergistic effect with the inorganic ammonium salt electrolyte system, further promoting interfacial charge migration and reactant activation, accelerating the reaction kinetics. Therefore, inorganic ammonium salt electrolytes are mainly responsible for improving the conductivity of the system, stabilizing ion transport, and providing a proton transfer environment, while Keggin-structured polyoxometalates mainly play the role of electronic regulation and electrocatalytic promotion. Together, they construct an efficient and stable electrocatalytic synthesis system.

[0019] (2) To address the cost and environmental burden issues caused by the single-use of solvents and electrolytes in existing electrocatalytic systems, this invention focuses on designing a recyclable reaction medium system. After the electrocatalytic reaction, the liquid after separating N-tert-butyl-2-benzothiazole sulfenamide can be used as a mother liquor for the next electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide. By optimizing the electrolyte composition and solvent recovery process, the efficient reuse of the reaction medium is achieved, significantly reducing waste emissions and raw material consumption while maintaining a good reaction yield. This improvement not only enhances the overall atom economy of the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide but also provides a practical process foundation for its transition to more sustainable industrial production.

[0020] (3) The electrocatalytic synthesis method of N-tert-butyl-2-benzothiazole sulfenamide provided by the present invention improves the solid-liquid ratio and shortens the reaction time while ensuring high yield production. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 The image shows the hydrogen spectral density (H2N) spectrum of N-tert-butyl-2-benzothiazole sulfenamide. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] Currently, the preparation of N-tert-butyl-2-benzothiazole sulfenamide involves using 2-mercaptobenzothiazole (accelerator M) as a raw material, adding an oxidant to oxidize it to generate an intermediate accelerator DM, and then reacting accelerator DM with tert-butylamine to obtain N-tert-butyl-2-benzothiazole sulfenamide. The mainstream oxidants include sodium hypochlorite, chlorine, sodium nitrite, or hydrogen peroxide. However, this method not only severely corrodes equipment but also generates large amounts of high-salinity wastewater.

[0026] Electrochemical synthesis technology offers a new technological route for the green preparation of N-tert-butyl-2-benzothiazole sulfenamide due to its significant advantages, such as no need for external oxidants, mild reaction conditions, and strong process controllability. However, currently available electrochemical synthesis methods typically require high current densities or long reaction times, increasing industrialization costs.

[0027] To overcome the above problems, the present invention provides a method for electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide.

[0028] The raw material 2-mercaptobenzothiazole, catalyst, electrolyte and tert-butylamine are dispersed in a solvent and mixed evenly to obtain a reaction solution; The reaction solution was placed in an electrolytic cell and electrocatalytically oxidized to obtain N-tert-butyl-2-benzothiazole sulfenamide; The catalyst is a quaternary ammonium phosphotungstic acid salt or a quaternary ammonium silicotungstic acid salt with a Keggin structure; the electrolyte is one or more of ammonium chloride, ammonium bromide, ammonium iodide, ammonium fluoride, ammonium sulfate, ammonium nitrate, or ammonium phosphate.

[0029] This invention employs inorganic ammonium salts as the electrolyte and Keggin-structured phosphotungstic acid quaternary ammonium salts or silicotungstic acid quaternary ammonium salts as electrocatalytic promoters to construct a stable and continuously operating electrocatalytic synthesis system under low current conditions, significantly improving the reaction rate and the yield of the target product N-tert-butyl-2-benzothiazole sulfenamide. The mechanism mainly includes the following aspects: First, the inorganic ammonium salt, as the electrolyte, can increase the ionic conductivity of the system, reduce the solution resistance, and ensure stable current transmission in the reaction system, thereby maintaining the continuous electrolysis process. Simultaneously, NH4... + The ability to participate in proton transfer at the electrode interface provides a stable source of protons for electrocatalytic reactions, which is beneficial for promoting proton-electron coupling transfer (PCET), reducing reaction overpotential, accelerating the formation and transformation of key active intermediates, and improving overall reaction efficiency. Furthermore, the presence of halogen anions helps maintain ionic balance at the electrode interface, enhancing the electrochemical stability of the system and thus improving the continuous operation of the reaction. On the other hand, Keggin-structured phosphotungstic acid quaternary ammonium salts or silicotungstic acid quaternary ammonium salts possess both electronic regulation and charge transfer functions. Among them, polyoxometalate anions exhibit excellent reversible redox properties, acting as "electron buffers" during electrolysis to achieve reversible electron storage and release, thereby mitigating local potential fluctuations on the electrode surface, inhibiting peroxidation and other side reactions, and improving the selectivity and Faradaic efficiency of the target product. Simultaneously, they form a synergistic effect with the inorganic ammonium salt electrolyte system, further promoting interfacial charge migration and reactant activation, accelerating the reaction kinetics. Therefore, inorganic ammonium salt electrolytes are mainly responsible for improving the conductivity of the system, stabilizing ion transport, and providing a proton transfer environment, while Keggin-structured polyoxometalates mainly play the role of electronic regulation and electrocatalytic promotion. Together, they construct an efficient and stable electrocatalytic synthesis system.

[0030] To address the cost and environmental burden issues caused by the single-use of solvents and electrolytes in existing electrocatalytic systems, this invention focuses on designing a recyclable reaction medium system. After the electrocatalytic reaction, the liquid remaining after separating N-tert-butyl-2-benzothiazole sulfenamide can be used as a mother liquor for the next electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide. By optimizing the catalyst composition and solvent recovery process, efficient reuse of the reaction medium is achieved, significantly reducing waste emissions and raw material consumption while maintaining good reaction yield. This improvement not only enhances the overall atom economy of the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide but also provides a practical process foundation for its transition to more sustainable industrial production.

[0031] Furthermore, the electrocatalytic synthesis method for N-tert-butyl-2-benzothiazole sulfenamide provided by this invention improves the solid-liquid ratio and shortens the reaction time while ensuring high yield production.

[0032] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0033] In the following examples, yield = mass of N-tert-butyl-2-benzothiazole sulfenamide product / (molecular weight of N-tert-butyl-2-benzothiazole sulfenamide × molar amount of 2-mercaptobenzothiazole) × 100.

[0034] Example 1 A method for the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide includes the following steps: (1) At room temperature and pressure, 2 mmol of 2-mercaptobenzothiazole, 8 mmol of tert-butylamine, 0.3 mol of ammonium chloride, and 0.4 mmol of TBA3PW were added. 12 O 40 Disperse in 4 mL of methanol, mix well, and obtain the reaction solution.

[0035] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 10 mA / cm². 2 The electrocatalytic oxidation reaction time was 3 h.

[0036] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 77% based on 2-mercaptobenzothiazole.

[0037] Example 2 A method for the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide includes the following steps: (1) At room temperature and pressure, 2 mmol of 2-mercaptobenzothiazole, 14 mmol of tert-butylamine, 0.3 mol of ammonium chloride, and 0.8 mmol of TEA3PW were added. 12 O 40 Disperse in 4 mL of methanol, mix well, and obtain the reaction solution.

[0038] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 16 mA / cm². 2 The electrocatalytic oxidation reaction time was 1 h.

[0039] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 85% based on 2-mercaptobenzothiazole.

[0040] Example 3 A method for the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide includes the following steps: (1) At room temperature and pressure, 2 mmol of 2-mercaptobenzothiazole, 10 mmol of tert-butylamine, 0.3 mol of ammonium chloride, and 0.5 mmol of CTA3PW were added. 12 O 40 Disperse in 8 mL of methanol, mix well, and obtain the reaction solution.

[0041] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 12 mA / cm². 2 The electrocatalytic oxidation reaction time was 2.5 h.

[0042] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 88% based on 2-mercaptobenzothiazole.

[0043] Example 4 A method for the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide includes the following steps: (1) At room temperature and pressure, 2 mmol of 2-mercaptobenzothiazole, 14 mmol of tert-butylamine, 0.3 mol of ammonium chloride, and 0.6 mmol of TBA4SiW were added. 12 O 40Disperse in 8 mL of methanol, mix well, and obtain the reaction solution.

[0044] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 15 mA / cm². 2 The electrocatalytic oxidation reaction time was 1 h.

[0045] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 91% based on 2-mercaptobenzothiazole.

[0046] Example 5 A method for the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide includes the following steps: (1) At room temperature and pressure, 2 mmol of 2-mercaptobenzothiazole, 14 mmol of tert-butylamine, 0.3 mol of ammonium bromide, and 0.6 mmol of TBA4SiW were added. 12 O 40 Disperse in 8 mL of methanol, mix well, and obtain the reaction solution.

[0047] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 15 mA / cm². 2 The electrocatalytic oxidation reaction time was 1 h.

[0048] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 85% based on 2-mercaptobenzothiazole.

[0049] Example 6 A method for the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide includes the following steps: (1) At room temperature and pressure, 2 mmol of 2-mercaptobenzothiazole, 14 mmol of tert-butylamine, 0.3 mol of ammonium iodide, and 0.6 mmol of TBA4SiW were added. 12 O 40 Disperse in 8 mL of methanol, mix well, and obtain the reaction solution.

[0050] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 15 mA / cm². 2 The electrocatalytic oxidation reaction time was 1 h.

[0051] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 76% based on 2-mercaptobenzothiazole.

[0052] Example 7 A method for the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide includes the following steps: (1) At room temperature and pressure, 2 mmol of 2-mercaptobenzothiazole, 14 mmol of tert-butylamine, 0.3 mol of ammonium sulfate, and 0.6 mmol of TBA4SiW were added. 12 O 40 Disperse in 8 mL of methanol, mix well, and obtain the reaction solution.

[0053] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 15 mA / cm². 2 The electrocatalytic oxidation reaction time was 1 h.

[0054] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 82% based on 2-mercaptobenzothiazole.

[0055] Example 8 A method for the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide includes the following steps: (1) At room temperature and pressure, 2 mmol of 2-mercaptobenzothiazole, 10 mmol of tert-butylamine, 0.3 mol of ammonium chloride, and 0.6 mmol of TEA4SiW were added. 12 O 40 Disperse in 10 mL of methanol, mix well, and obtain the reaction solution.

[0056] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 13 mA / cm². 2 The electrocatalytic oxidation reaction time was 2 h.

[0057] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 86% based on 2-mercaptobenzothiazole.

[0058] Figure 1 The image shows the hydrogen spectral density (H2N) of N-tert-butyl-2-benzothiazole sulfenamide collected in this embodiment.

[0059] Comparative Example 1 Compared to Example 8, no electrolyte inorganic ammonium salt was added. Without the inorganic ammonium salt, the resistance is too high, it does not conduct electricity, and the reaction cannot be completed.

[0060] Example 9 (1) Combine the liquid collected after cooling and crystallization in step (3) of Example 1 with the methanol removed by vacuum distillation as the first mother liquor; add 2 mmol of 2-mercaptobenzothiazole to the first mother liquor, adjust the pH to 10.84 with tert-butylamine, and make up the volume of the reaction solution to 9.5 mL with methanol as the reaction solution.

[0061] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 16 mA / cm². 2 The electrocatalytic oxidation reaction time was 1 h.

[0062] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 85% based on 2-mercaptobenzothiazole.

[0063] Example 10 (1) Combine the liquid collected after cooling and crystallization in step (3) of Example 9 with the methanol removed by vacuum distillation as the second mother liquor; add 2 mmol of 2-mercaptobenzothiazole to the first mother liquor, adjust the pH to 10.84 with tert-butylamine, and bring the reaction solution to a final volume of 9.5 mL with methanol as the reaction solution.

[0064] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 16 mA / cm². 2 The electrocatalytic oxidation reaction time was 1 h.

[0065] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 90% based on 2-mercaptobenzothiazole.

[0066] Example 11 (1) Combine the liquid collected after cooling and crystallization in step (3) of Example 10 with the methanol removed by vacuum distillation as the third mother liquor; add 2 mmol of 2-mercaptobenzothiazole to the first mother liquor, adjust the pH to 10.84 with tert-butylamine, and bring the reaction solution to a final volume of 9.5 mL with methanol as the reaction solution.

[0067] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 16 mA / cm². 2 The electrocatalytic oxidation reaction time was 1 h.

[0068] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 92% based on 2-mercaptobenzothiazole.

[0069] Example 12 (1) Combine the liquid collected after cooling and crystallization in step (3) of Example 11 with the methanol removed by vacuum distillation as the fourth mother liquor; add 2 mmol of 2-mercaptobenzothiazole to the first mother liquor, adjust the pH to 10.84 with tert-butylamine, and bring the reaction solution to a final volume of 9.5 mL with methanol as the reaction solution.

[0070] (2) The reaction solution was placed in an electrolytic cell, with a graphite electrode as the anode and a stainless steel electrode as the cathode, and electrocatalytic oxidation was carried out by passing an electric current at a current density of 16 mA / cm². 2 The electrocatalytic oxidation reaction time was 1 h.

[0071] (3) Collect the reaction solution, remove methanol by vacuum distillation, cool and crystallize, collect the solid, wash with water and petroleum ether respectively, and dry to obtain N-tert-butyl-2-benzothiazole sulfenamide, with a yield of 96% based on 2-mercaptobenzothiazole.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for the electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide, characterized in that, The steps include the following: The raw material 2-mercaptobenzothiazole, catalyst, electrolyte and tert-butylamine are dispersed in a solvent and mixed evenly to obtain a reaction solution; The reaction solution was placed in an electrolytic cell and electrocatalytically oxidized to obtain N-tert-butyl-2-benzothiazole sulfenamide; The catalyst is a quaternary ammonium salt of phosphotungstic acid or a quaternary ammonium salt of silicotungstic acid with a Keggin structure.

2. The method as described in claim 1, characterized in that, The Keggin-structured phosphotungstic acid quaternary ammonium salt or silicotungstic acid quaternary ammonium salt includes TBA3PW. 12 O 40 TEA3PW 12 O 40 CTA3PW 12 O 40 TBA4SiW 12 O 40 or TEA4SiW 12 O 40 One of them; wherein, TBA represents tetrabutylammonium cation, TEA represents tetraethylammonium cation, and CTA represents hexadecyltrimethylammonium cation.

3. The method as described in claim 1, characterized in that, The solvent is methanol; Alternatively, the electrolyte may be one or more of ammonium chloride, ammonium bromide, ammonium iodide, ammonium fluoride, ammonium sulfate, ammonium nitrate, or ammonium phosphate.

4. The method as described in claim 1, characterized in that, The molar ratio of 2-mercaptobenzothiazole to the catalyst is (0.8~1):(0.1~0.5), preferably (0.8~1):(0.3~0.5). Alternatively, the molar ratio of 2-mercaptobenzothiazole to electrolyte is (16~24):(2.5~3.5), preferably (18~22):

3.

5. The method as described in claim 1, characterized in that, The molar ratio of 2-mercaptobenzothiazole to tert-butylamine is (0.8~1):(3~8), preferably (0.8~1):(5~8).

6. The method as described in claim 1, characterized in that, The concentration of 2-mercaptobenzothiazole in the solvent is 0.1~0.7 mol / L.

7. The method as described in claim 1, characterized in that, In the electrolytic cell, the anode is a graphite electrode, and the cathode is a stainless steel electrode or an inert electrode.

8. The method as described in claim 1, characterized in that, During electrocatalytic oxidation, the current density is 8~16 mA / cm². 2 .

9. The method as described in claim 1, characterized in that, During the electrocatalytic oxidation process, the reaction time is 1~3 h.

10. The method as described in claim 1, characterized in that, After the electrocatalytic reaction is completed, the reaction solution is collected, concentrated, cooled and crystallized, and the solid and liquid are separated and collected separately. The solid was washed and dried to obtain N-tert-butyl-2-benzothiazole sulfenamide; The liquid was used directly as the mother liquor in the next electrocatalytic synthesis of N-tert-butyl-2-benzothiazole sulfenamide.

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