Dithianon and preparation method thereof

Abstract

The invention relates to the technical field of pesticides, and provides dithianon and a preparation method thereof.The dithianon preparation method comprises the steps that firstly, a bis-sodium salt solution used for synthesizing dithianon is provided, the sulfur impurity content in the bis-sodium salt solution is smaller than or equal to 1.5%, then a 1, 4-naphthoquinone and acid mixture is dropwise added into the bis-sodium salt solution, then a hydrogen peroxide aqueous solution is dropwise added into the bis-sodium salt solution, stirring is conducted, and the dithianon is obtained. And finally, adding the cyclized wet product into a dilute nitric acid solution in batches, reacting at the temperature of 90-95 DEG C, cooling, carrying out suction filtration, and leaching with water to obtain a dithianon product. According to the method, the content of sulfur impurities in the preparation process of the disodium salt is optimized to be within a specific range, the yield of the dithianon finished product is remarkably increased, the obtained dithianon finished product has few and small impurities, the purity of the dithianon finished product can reach 98% or above, and the yield of cyclization reaction and nitric acid oxidation can reach 97% or above in terms of 1, 4-naphthoquinone.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticides, and in particular to a dithianon and its preparation method, or a method for synthesizing a dithianon technical material as a protective fungicide. Background Art

[0002] Dithianon, Chinese name dicyanoanthraquinone, Chinese chemical name 2,3-dicyano-1,4-dithioanthraquinone, is a protective fungicide developed by BASF Europe Company, and its structural formula is as follows:

[0003]

[0004] Pure dicyanoanthraquinone is a dark brown crystalline solid. It has multiple action sites, mainly inhibits a series of energy conversion enzymes by reacting with sulfur-containing groups and interfering with cell respiration, and ultimately causes bacteria to die. It has been widely used at home and abroad and has good control effects on various leaf and fruit diseases of fruit trees such as apples, pears, grapes, citrus fruits, cherries, dates, and strawberries. For example, in the vast grape-growing areas of the Australian wine region, dithianon is used to control Plasmopara viticola. Its mechanism of action is to inhibit spore germination and ultimately achieve a protective effect.

[0005] Currently, there are mainly four methods for synthesizing anthraquinone: the naphthoquinone method, in which naphthoquinone and butadiene are catalytically condensed and dehydrogenated in a copper salt to obtain anthraquinone; the oxidation method, extracting anthraquinone from coal tar and oxidizing anthraquinone in the air; the styrene method, in which styrene undergoes a dimerization reaction and oxidative cyclization in an acidic medium to synthesize anthraquinone; the phthalic anhydride method, in which phthalic anhydride and benzene are catalytically condensed, acid hydrolyzed, and dehydrated in the presence of aluminum trichloride to generate anthraquinone. These synthesis methods have high reaction costs, are cumbersome to operate, cause large pollution, and it is difficult to recycle wastewater. How to produce dicyanoanthraquinone simply, efficiently, and environmentally friendly has been highly concerned by enterprises. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides a dicyanoanthraquinone and its preparation method to solve the defect that it is difficult to improve the reaction yield and purity when preparing dicyanoanthraquinone in the prior art.

[0007] The present invention provides a disodium salt solution for synthesizing dicyanoanthraquinone, including: the sulfur impurity content in the disodium salt solution is less than or equal to 1.5%, preferably less than or equal to 0.15%, and further preferably less than or equal to 0.1%.

[0008] The disodium salt is used as the starting material for synthesizing dithianon. In the experiments of the present invention, it is found that the sulfur impurity content therein has a great influence on the yield of dithianon. Among them, the sulfur impurities include elemental sulfur, monosodium salt, and impurities generated by sulfur (see the following reaction formula). The test method for the sulfur impurity content is the liquid phase peak area normalization method, that is, regarding the total sum of all peak areas as 100%, and the percentage of the main peak area in the total area is the peak area normalization method.

[0009]

[0010] According to the disodium salt solution for synthesizing dithianon provided by the present invention, the disodium salt solution is obtained by first complexing sodium cyanide and dimethyl sulfoxide to form a solution containing a complex, then adding carbon disulfide to the solution containing the complex, and then performing hydrolysis.

[0011] Preferably, the mass ratio of carbon disulfide to sodium cyanide is 76 - 84:50;

[0012] Preferably, when complexing, the temperature of the reaction system is 55 - 65 °C;

[0013] Preferably, the mass ratio of sodium cyanide to dimethyl sulfoxide is 1:6 - 7;

[0014] Preferably, the solution containing the complex is obtained by adding sodium cyanide to dimethyl sulfoxide, heating to 55 - 65 °C, and stirring for 1.5 - 3 h.

[0015] Preferably, the purity of carbon disulfide is above 99%;

[0016] Preferably, the purity of sodium cyanide is above 99%.

[0017] In the above reaction system of the present invention, the reaction process of sodium cyanide and carbon disulfide is as follows:

[0018]

[0019]

[0020] The overall reaction formula is as follows:

[0021]

[0022] It is found in the experiments that first complexing sodium cyanide and dimethyl sulfoxide can make the reaction of sodium cyanide and carbon disulfide more complete, and significantly improve the yield of the disodium salt.

[0023] According to the disodium salt solution for synthesizing dithianon provided by the present invention, the addition of carbon disulfide is carried out by dropwise addition.

[0024] Preferably, when carbon disulfide is added, the temperature of the solution is 40-45 °C;

[0025] Preferably, the addition of carbon disulfide is carried out by dropping at a rate of 0.4-0.65 g / min;

[0026] Preferably, after the addition of carbon disulfide is completed, the mixture is stirred at a temperature of 40-45 °C for 0.5-1.5 h;

[0027] Preferably, the hydrolysis includes: adding water to the reaction system while controlling the temperature of the reaction system at 20-25 °C;

[0028] Preferably, the water is added dropwise;

[0029] Preferably, the mass ratio of the added water to sodium cyanide is 10-12:1;

[0030] Preferably, the dropping rate of the water is 9-10 g / min;

[0031] Preferably, adding carbon disulfide to the solution and then carrying out hydrolysis includes: adjusting the temperature of the solution containing the complex, dropping carbon disulfide into the solution containing the complex at a temperature of 40-45 °C at a rate of 0.4-0.65 g / min, controlling the temperature at 40-45 °C during the dropping process, after the dropping is completed, controlling the temperature at 40-45 °C and stirring for 0.5-1.5 h; after the stirring is completed, cooling the temperature to 20-25 °C, and continuing to add water to the solution at a rate of 9-10 g / min, maintaining the temperature of the reaction system at 20-25 °C during the dropping process, after the dropping is completed, controlling the temperature at 30-35 °C and stirring for 7.5-8.5 h.

[0032] By controlling the addition rate of carbon disulfide, on the one hand, it helps to reduce the volatilization of carbon disulfide (because the heat release during the dropping process is obvious), so that the raw material sodium cyanide reacts completely, and the reaction yield is improved. On the other hand, it helps to control the temperature, so that the impurities generated due to temperature are reduced.

[0033] According to the double-sodium salt solution for synthesizing dithianon provided by the present invention, the unreacted carbon disulfide in the solution obtained by hydrolysis is removed under negative pressure until the sulfur impurity content is less than or equal to 1.5%, preferably less than or equal to 0.15%, and further preferably less than or equal to 0.1%.

[0034] Preferably, the unreacted carbon disulfide in the solution obtained by hydrolysis is removed at a temperature of 30-35 °C;

[0035] Preferably, the unreacted carbon disulfide in the solution obtained by hydrolysis is removed at 30-35 °C under negative pressure, and the removal time is 1.5-2.5 h.

[0036] After the removal is completed, it includes post-treatment, and the post-treatment includes: filtering the reaction system and rinsing with water. The obtained filtrate is the disodium salt solution, and the obtained filter cake is the generated sulfur.

[0037] By reducing the unreacted carbon disulfide in the reaction system, the precipitation of sulfur during the post-treatment can be increased, thereby reducing the content of sulfur impurities in the disodium salt solution, avoiding the adverse effects brought by sulfur impurities on the subsequent reaction, and further improving the yield of the final product, dicyanoanthraquinone.

[0038] In a second aspect, the present invention also provides a method for preparing the disodium salt solution for synthesizing dicyanoanthraquinone as described above.

[0039] In a third aspect, the present invention also provides a method for preparing dicyanoanthraquinone, including: using the disodium salt solution as described above or the disodium salt solution prepared by the method as described above as a raw material.

[0040] According to the method for preparing dicyanoanthraquinone provided by the present invention, it includes: first dropping 1,4-naphthoquinone and an acid mixture into the disodium salt solution, and then dropping an aqueous hydrogen peroxide solution into it to obtain a wet product of the cyclized compound.

[0041] Preferably, the mass content of the disodium salt in the disodium salt solution is 9-10%.

[0042] The structural formula of the disodium salt in the present invention is as follows:

[0043]

[0044] Preferably, the purity of 1,4-naphthoquinone is above 99%;

[0045] Preferably, the mass concentration of the aqueous hydrogen peroxide solution is 13%-15%;

[0046] Preferably, the mass ratio of the disodium salt to 1,4-naphthoquinone is 18-19:15;

[0047] Preferably, the mass ratio of the disodium salt to hydrogen peroxide is 18-19:3-4;

[0048] Preferably, the dropping rate of 1,4-naphthoquinone and the acid mixture is 1-2 g / min;

[0049] Preferably, during the dropping of 1,4-naphthoquinone and the acid mixture, the temperature of the reaction system is -15 to -10 °C;

[0050] Preferably, after the dropping of 1,4-naphthoquinone and the acid mixture is completed, the reaction system reacts at a temperature of -15 to -10 °C for 0.3-1 h;

[0051] Preferably, the dropping rate of the aqueous hydrogen peroxide solution is 0.5-1.5 g / min;

[0052] Preferably, during the addition of the hydrogen peroxide aqueous solution, the temperature of the reaction system is -15 to -10 °C;

[0053] The room temperature in the present invention refers to 20 to 40 °C.

[0054] Preferably, the preparation process of the wet cyclized product is as follows: First, add 1,4-naphthoquinone and the acid mixture to the disodium salt solution at a temperature of -15 to -10 °C at a rate of 1 to 2 g / min. After the addition is completed, keep the reaction at a constant temperature for 0.3 to 1 h, then add the hydrogen peroxide aqueous solution to it at a rate of 0.5 to 1.5 g / min. After the addition is completed, raise the temperature to room temperature under natural conditions, stir at room temperature for 1.5 to 2.5 h, then filter, wash with water, collect the solid, and obtain the wet cyclized product.

[0055] Before the temperature rise, the reaction system is always controlled at -15 to -10 °C.

[0056] According to the preparation method of the dicyanoanthraquinone provided by the present invention, the 1,4-naphthoquinone and the acid mixture are obtained by mixing 1,4-naphthoquinone and acetic acid.

[0057] The mixture obtained by mixing 1,4-naphthoquinone and acetic acid in the present invention is also called the acetic acid slurry of 1,4-naphthoquinone.

[0058] Preferably, the mass ratio of the 1,4-naphthoquinone to the acetic acid is 15:15 to 18.

[0059] In the above process, the formation mechanism of the cyclized product is as follows:

[0060]

[0061] According to the preparation method of the dicyanoanthraquinone provided by the present invention, it includes: batchwise adding the wet cyclized product to the dilute nitric acid solution, reacting at 90 to 95 °C, then cooling, filtering with suction, and washing with water until the pH value of the filtrate is 6 to 7.

[0062] Preferably, the reaction time at 90 to 95 °C is 1.5 to 2.5 h.

[0063] The interval time for the batchwise addition of the wet cyclized product is 12 to 15 min, and the addition amount for each batch is 1 / 8 of the weight of the wet cyclized product. The batchwise addition is to prevent the accumulation of reaction heat, resulting in a sudden temperature rise, out-of-control reaction, and the risk of material overflow.

[0064] According to the preparation method of the dicyanoanthraquinone provided by the present invention, the total concentration of nitric acid in the reaction system is 11% to 15%.

[0065] In the above process, the reaction process of the cyclized product is as follows:

[0066]

[0067] In summary, the specific steps of the preparation method of the dithianon of the present invention are as follows:

[0068] (1) Sodium cyanide is added to dimethyl sulfoxide, and the temperature is raised to prepare a complex, then carbon disulfide is added dropwise to prepare a monosodium salt, and a certain amount of water is slowly added dropwise. After the addition is completed, stirring is carried out. Then, the excess carbon disulfide is removed under negative pressure, and the reaction solution is filtered. The filtrate is the disodium salt solution.

[0069] (2) The disodium salt solution prepared in step (1) is cooled, and a mixture of 1,4-naphthoquinone and an acid is slowly added dropwise. After the addition is completed, the reaction is carried out under heat preservation; hydrogen peroxide is continuously added dropwise at this temperature. After the addition is completed, the temperature is naturally raised to room temperature, and stirring is carried out at room temperature. After the reaction, filtration is carried out to obtain a wet product of the cyclized product.

[0070] (3) The dilute nitric acid solution is heated to 80-85 °C; the wet product of the cyclized product obtained in step (2) is added in batches; after the addition is completed, the temperature is raised to 90-95 °C, and the reaction is carried out under heat preservation. Then, the temperature is lowered and suction filtration is carried out. The filter cake is washed with water until it is slightly neutral, and the product dithianon is obtained.

[0071] Fourthly, the present invention also provides dithianon prepared by the preparation method of dithianon as described above.

[0072] A dithianon and a preparation method thereof provided by the present invention, as Figure 1 shown, starting from the disodium salt, the starting material for preparing dithianon, sodium cyanide is first complexed with DMSO, then carbon disulfide is added, and it reacts with sodium cyanide to synthesize a monosodium salt, and then water is added for hydrolysis, desulfurization, filtration, and washing with water to separate sulfur to obtain a disodium salt solution; the obtained disodium salt undergoes a cyclization reaction with 1,4-naphthoquinone under the action of acetic acid and hydrogen peroxide, followed by filtration and washing with water to obtain a cyclized product; then the obtained cyclized product is oxidized by nitric acid, filtered, and washed with water to obtain dithianon (also known as dithianon), and the product is dried to obtain the finished product. In this preparation process, the present invention optimizes the sulfur impurity content in the preparation process of the disodium salt within a specific range, significantly improving the yield of the dithianon finished product. Among them, the impurities in the obtained dithianon finished product are few and small, and the purity of the dithianon finished product can reach more than 98%. Based on 1,4-naphthoquinone, the yields of the cyclization reaction and nitric acid oxidation can reach more than 97%.

[0073] Specifically, the present invention uses dimethyl sulfoxide as a solvent to prepare a disodium salt solution, and then, under the acidic condition provided only by acetic acid, uses 1,4-naphthoquinone as a raw material to synthesize a cyclic compound. Dilute nitric acid is used as an oxidant, and the oxidation is carried out in a batch feeding manner. The whole process does not require purification of intermediates until the product is obtained. The operation is simple, no additional catalyst is needed, the raw materials are easily available, the product quality is high, and the gas (NO2) generated during the oxidation process can be absorbed and used to prepare dilute nitric acid, which is green and environmentally friendly. It solves the problems of complex preparation process, high preparation cost, low purity, and environmental pollution, and has important significance for the above industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0075] Figure 1 is a schematic flow chart of the preparation method of dithianon provided by the present invention;

[0076] Figure 2 is a liquid chromatogram of the product obtained in Example 1B provided by the present invention;

[0077] Figure 3 is the data statistics of the liquid chromatogram of the product obtained in Example 1B provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0078] To make the objectives, technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention with reference to the drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present invention belong to the scope of protection of the present invention.

[0079] The following will be combined with Figures 1 - 3 to describe dithianon and its preparation method of the present invention.

[0080] For those not specifying specific techniques or conditions in the embodiments, they shall be carried out according to the techniques or conditions described in the literature in the field or according to the product specifications. For the reagents or instruments not indicating the manufacturer, they are all conventional products that can be obtained through regular channels.

[0081] Example 1A Disodium Salt Solution

[0082] A method for preparing a disodium salt solution comprises the following steps:

[0083] Weigh 49.5 g (99%) of sodium cyanide and add it to 315 g of dimethyl sulfoxide at one time. Heat the mixture to 60 °C, stir for 2 h, and then cool it down. When the temperature drops to 40 °C, add 81 g of carbon disulfide (99.5%) dropwise over 2 h while controlling the temperature at 40 - 45 °C. After the dropwise addition is completed, keep the temperature at this level and stir for 1 h.

[0084] After the heat preservation is completed, cool the mixture to 20 °C, slowly add 550 g of water dropwise over 1 h while maintaining the temperature at 20 - 25 °C. After the dropwise addition is completed, heat the mixture to 30 - 35 °C and keep it warm and stir for 8 h.

[0085] After the heat preservation ends, remove the excess carbon disulfide under negative pressure (pressure is -0.09 MPa) at this temperature for 2 h. After the operation is completed, filter the reaction solution and wash it with 40 g of water. The filter cake is the generated sulfur (45.5 g wet weight); the filtrate is the disodium salt solution. After quantification (930 g, content 9.83%, yield 98.2%, sulfur-containing impurities 0.09%), it is directly used for the next cyclization step.

[0086] Example 2A Disodium Salt Solution

[0087] A method for preparing a disodium salt solution is as follows:

[0088] Weigh 49.5 g (99%) of sodium cyanide and add it to 315 g of dimethyl sulfoxide at one time to obtain a solution. Immediately, add 81 g of carbon disulfide (99.5%) dropwise to this solution at a temperature of 40 °C over 2 h while controlling the temperature at 40 - 45 °C. After the dropwise addition is completed, keep the temperature at this level and stir for 1 h.

[0089] After the heat preservation is completed, cool the mixture to 20 °C, slowly add 550 g of water dropwise over 1 h while maintaining the temperature at 20 - 25 °C. After the dropwise addition is completed, heat the mixture to 30 - 35 °C and keep it warm and stir for 8 h.

[0090] After the heat preservation ends, remove the excess carbon disulfide under negative pressure (pressure is -0.09 MPa) at this temperature for 2 h. After the operation is completed, filter the reaction solution and wash it with 40 g of water. The filter cake is the generated sulfur (45.5 g wet weight); the filtrate is the disodium salt solution. After quantification, it is 928 g, with a content of 9.4%, a yield of 93.6%, and sulfur-containing impurities of 1.5%.

[0091] Example 3A Disodium Salt Solution

[0092] It is basically the same as Example 1A, except that: in Example 1A, the removal time of the excess carbon disulfide is only 1 h. The obtained disodium salt solution is quantified to be 931 g, with a content of 9.8%, a yield of 97.9%, and sulfur-containing impurities of 0.7%.

[0093] Example 1B Dithianon

[0094] A preparation method of dithianon, the steps are as follows:

[0095] (1) Take the disodium salt solution (186.7 g, 9.83%) prepared in Example 1A and add it to a 500 ml four-necked flask. Stir and cool to -13°C, and slowly add dropwise the slurry of 1,4-naphthoquinone (15 g, 99%) in acetic acid (17.1 g). The dropping time is 30 min. After the dropping is completed, keep the temperature for reaction for 30 min; at this temperature, add dropwise hydrogen peroxide (23.32 g, 13.7%). Similarly, the dropping time is 30 min. After the dropping is completed, turn off the cold bath and let it warm up to room temperature naturally. Stir at room temperature for 2 h and then filter. Wash the filter cake with water twice, collect the solid, and obtain the wet product of the cyclized product (40 g).

[0096] (2) Weigh 22.4 g (66%) of nitric acid and add it to a four-necked flask containing 70.1 g of water. Stir to prepare a dilute nitric acid solution and heat up to 80 - 85°C; at this temperature, add the wet cyclized product obtained in the previous step (5 g per batch) in 8 batches, a total of 40 g. The interval time between each batch is 15 min. After the feeding is completed (at this time, the total mass concentration of nitric acid in the reaction system is 14.4%), heat up to 90 - 95°C and keep the temperature for reaction for 2 h. Cool down to 40°C, carry out suction filtration, wash the filter cake with water until it is slightly neutral, with a pH value of 6 - 7, collect the solid, and dry it to obtain 27.66 g of the product with a purity of 98.04%. Calculated based on 1,4-naphthoquinone, the yields of steps (1) and (2) are 97.5%.

[0097] Test the product obtained in Example 1B, and the test results are as Figures 2 - 3 shown.

[0098] Dithianon of Example 2B

[0099] It is basically the same as Example 1B, the only difference being that: the disodium salt solution prepared in Example 1A is replaced with the disodium salt solution prepared in Example 2A.

[0100] The final product obtained is 26.9 g with a purity of 95.5%. Calculated based on 1,4-naphthoquinone, the yields of steps (1) and (2) are 92.3%.

[0101] Dithianon of Example 3B

[0102] It is basically the same as Example 1B, the only difference being that: the disodium salt solution prepared in Example 1A is replaced with the disodium salt solution prepared in Example 3A.

[0103] The final product obtained is 27.6 g with a purity of 97.0%. Calculated based on 1,4-naphthoquinone, the yields of steps (1) and (2) are 96.2%.

[0104] Example 4B Dithianon

[0105] It is basically the same as Example 1B, except for step (1), as follows:

[0106] (1) Take the disodium salt solution (186.7 g, 9.83%) prepared in Example 1A and add it to a 500 ml four-necked flask. Stir and cool to -13°C, and slowly add dropwise a slurry of 1,4-naphthoquinone (15 g, 99%) in acetic acid (17.1 g). The dropping time is 30 min. After the dropping is completed, keep the temperature for reaction for 30 min; raise the temperature to 0°C, and add dropwise hydrogen peroxide (23.32 g, 13.7%). Similarly, the dropping time is 30 min. After the dropping is completed, continue to naturally raise the temperature to room temperature. After stirring at room temperature for 2 h, filter. The filter cake is rinsed with water twice, and the solid is collected to obtain the wet product of the cyclized compound (40 g).

[0107] The final product obtained is 27.0 g, with a purity of 96%. Calculated based on 1,4-naphthoquinone, the yields of steps (1) and (2) are 93.17%.

[0108] Example 5B Dithianon

[0109] It is basically the same as Example 1B, except that the slurry of 1,4-naphthoquinone (15 g, 99%) in acetic acid (17.1 g) is replaced with a slurry of 1,4-naphthoquinone (15 g, 99%) in hydrochloric acid (27.7 g).

[0110] The product obtained is 27.1 g, with a purity of 96.1%. Calculated based on 1,4-naphthoquinone, the yields of steps (1) and (2) are 93.6%.

[0111] Example 6B Dithianon

[0112] It is basically the same as Example 1B, except for step (2), as follows:.

[0113] (2) Weigh 22.4 g (66%) of nitric acid and add it to a four-necked flask containing 70.1 g of water. Stir to prepare a dilute nitric acid solution and raise the temperature to 80 - 85°C; at this temperature, add the wet cyclized compound obtained in the previous step (5 g per batch) in 8 batches, a total of 40 g. The interval time between each batch is 15 min. After the feeding is completed, raise the temperature to 75°C and keep the temperature for reaction for 2 h. Cool down to 40°C, filter by suction. The filter cake is rinsed with water until it is slightly neutral, with a pH value of 6 - 7. The solid is collected and dried to obtain 27.2 g of the product, with a purity of 96.2%. Calculated based on 1,4-naphthoquinone, the yields of steps (1) and (2) are 94.0%.

[0114] Example 7B Dithianon

[0115] It is basically the same as Example 1B, except for step (2), as follows:.

[0116] (2) 22.4 g (66%) of nitric acid was weighed and added to a four-necked flask containing 115.24 g of water. The solution was stirred to prepare a dilute nitric acid solution and heated to 80-85°C. At this temperature, 40 g of the wet cyclized product obtained in the previous step (5 g per batch) was added in 8 batches with an interval of 15 minutes. After the addition was completed (the total mass concentration of nitric acid in the reaction system was 10%), the temperature was raised to 90-95°C and the reaction was kept warm for 2 hours. The temperature was lowered to 40°C, filtered, and the filter cake was rinsed with water until it was slightly neutral and had a pH of 6-7. The solid was collected and dried to obtain 27.2 g of the product with a purity of 98.0%. The yield of steps (1) and (2) was 95.8% based on 1,4-naphthoquinone.

[0117] Comparative Example 1 Disodium salt solution

[0118] The reaction mixture was basically the same as Example 1A, except that carbon disulfide was added all at once in Example 1A, and after the addition was complete, the mixture was stirred at 40-45° C. for 3 h. The resulting disodium salt solution was quantitatively 925 g, with a content of 8.6%, a yield of 85.5%, and 4.5% sulfur impurities.

[0119] Comparative Example 2 Dicyanoanthraquinone

[0120] The method is basically the same as Example 1B, except that the disodium salt solution prepared in Example 1A is replaced by the disodium salt solution prepared in Comparative Example 2.

[0121] The final product obtained was 26 g with a purity of 93.0%. Calculated based on 1,4-naphthoquinone, the yield of step (1) and step (2) was 86.9%.

[0122] Comparative Example 3 Dicyanoanthraquinone

[0123] The process is basically the same as Example 1B, except that step (1) is as follows:

[0124] (1) A slurry of 1,4-naphthoquinone (15 g, 99%) in acetic acid (17.1 g) was added to a 500 ml four-necked flask, and the disodium salt solution (186.7 g, 9.83%) prepared in Example 1A at -13°C was slowly added dropwise for 30 min. After the addition was complete, the mixture was kept warm for 30 min. At the same temperature, hydrogen peroxide (23.32 g, 13.7%) was added dropwise for 30 min. After the addition was complete, the cooling bath was turned off, and the mixture was naturally warmed to room temperature. After stirring at room temperature for 2 h, the mixture was filtered, and the filter cake was rinsed with water twice. The solid was collected to obtain a wet product of the cyclized product (40 g).

[0125] The final product obtained was 26.5 g with a purity of 93.1%. Calculated based on 1,4-naphthoquinone, the yield of step (1) and step (2) was 88.7%.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. And these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A disodium salt solution for synthesizing dithianon, characterized in that, Comprising: The sulfur impurity content in the disodium salt solution is less than or equal to 1.5%.

2. The disodium salt solution for synthesizing dithianon according to claim 1, characterized in that The disodium salt solution is obtained by first complexing sodium cyanide and dimethyl sulfoxide to form a solution containing a complex, then adding carbon disulfide to the solution containing the complex, and then performing hydrolysis.

3. The disodium salt solution for synthesizing dithianon according to claim 2, characterized in that, The addition of carbon disulfide is carried out by dropwise addition.

4. The preparation method of the disodium salt solution for synthesizing dicyanoanthraquinone according to any one of claims 1 to 3.

5. A preparation method of dithianon, characterized in that, Comprising: Using the disodium salt solution according to any one of claims 1 to 3 or the disodium salt solution prepared by the preparation method according to claim 4 as a raw material.

6. The preparation method of dithianon according to claim 5, wherein, Comprising: First, dropwise add 1,4-naphthoquinone and an acid mixture to the disodium salt solution, and then dropwise add an aqueous hydrogen peroxide solution to obtain a wet product of the cyclized compound.

7. The preparation method of dithianon according to claim 6, characterized in that, The 1,4-naphthoquinone and acid mixture is obtained by mixing 1,4-naphthoquinone and acetic acid.

8. The preparation method of dithianon according to claim 6 or 7, characterized in that Comprising: Batchwise add the wet product of the cyclized compound to a dilute nitric acid solution, react at 90 - 95 °C, then cool down, filter by suction, and wash with water until the pH value of the filtrate is 6 - 7.

9. The preparation method of dithianon according to claim 8, wherein, The total concentration of nitric acid in the reaction system is 11% - 15%.

10. Dicyanoanthraquinone prepared by the preparation method of dicyanoanthraquinone according to any one of claims 5 to 9.

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