Preparation method of 3-halo-1,2-benzisothiazole

Abstract

The present invention relates to the technical field of fine chemical engineering, and specifically provides a method for preparing 3-halo-1,2-benzisothiazole, aiming to solve the problems of corrosion of reaction equipment and harsh production conditions existing in the purification of 3-chloro-1,2-benzisothiazole by direct concentration and distillation in the prior art. For this purpose, the preparation method of the present invention includes: S1: reacting 1,2-benzisothiazol-3-one, thionyl halide, a polar aprotic solvent, and a non-polar solvent under preset conditions to obtain a mixture containing 3-halo-1,2-benzisothiazole; S2: cooling the mixture containing 3-halo-1,2-benzisothiazole to -10 to 40 °C and then standing for layering to obtain a non-oil phase and an oil phase; S3: washing and distilling the oil phase in S2 to obtain 3-halo-1,2-benzisothiazole and a non-polar solvent. The present invention controls the proportion of raw materials, cools and layers after the reaction, and the oil phase is purified by first washing with water and then distilling to obtain the target product, thereby effectively improving the production conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemicals, and specifically provides a method for preparing 3-halo-1,2-benzisothiazole. Background Art

[0002] Currently, 3-chloro-1,2-benzisothiazole can be obtained by reacting 1,2-benzisothiazol-3-one, dimethylformamide, and thionyl chloride in a solvent. However, the activity of this reaction is not high, and a large amount of dimethylformamide is required during the reaction. Moreover, the product obtained through the above reaction is usually a mixture including dimethylformamide, the solvent, the remaining thionyl chloride, and the by-products of the reaction (such as hydrogen chloride, sulfur dioxide, etc.). For this mixture, currently, 3-chloro-1,2-benzisothiazole in the mixture is usually purified directly by concentration distillation. However, since the mixture contains a large amount of strong acidic substances such as dimethylformamide, hydrogen chloride, and sulfur dioxide generated by side reactions, it will corrode the reaction equipment during the concentration distillation process, and the production conditions are relatively harsh.

[0003] Correspondingly, a new technical solution is needed in this field to solve the above problems. Summary of the Invention

[0004] The present invention aims to solve the above technical problems, that is, to solve the problems such as corrosion of the reaction equipment and harsh production conditions existing in the prior art when purifying 3-chloro-1,2-benzisothiazole directly by concentration distillation.

[0005] The present invention provides a method for preparing 3-halo-1,2-benzisothiazole, characterized in that the preparation method comprises the following steps:

[0006] S1: React 1,2-benzisothiazol-3-one, thionyl halide, a polar aprotic solvent, and a non-polar solvent under preset conditions to obtain a mixture containing 3-halo-1,2-benzisothiazole, wherein the molar ratio of 1,2-benzisothiazol-3-one to thionyl halide is a first molar ratio, and the range of the first molar ratio is 1:1.6 to 1:1.2, and the molar ratio of 1,2-benzisothiazol-3-one:polar aprotic solvent:non-polar solvent is 1:(1.2 - 4):(1.5 - 8);

[0007] S2: Cool the mixture containing 3-halo-1,2-benzisothiazole to -10 to 40 °C and then let it stand for stratification to obtain a non-oil phase and an oil phase;

[0008] S3: The oil phase in S2 is washed with water and distilled to obtain 3-halo-1,2-benzisothiazole and a non-polar solvent.

[0009] In the case of adopting the above technical solution, by controlling the proportions of the raw materials, after the reaction to obtain a mixture containing 3-halo-1,2-benzisothiazole, the mixture is cooled and allowed to stand, and then it can be separated into an oil phase and a non-oil phase. Then, the oil phase is washed with water and distilled to obtain the final product 3-halo-1,2-benzisothiazole. Since the by-products hydrogen chloride and sulfur dioxide usually enter the non-oil phase and there is very little hydrogen chloride and sulfur dioxide in the oil phase, only a small amount of water is needed to wash the hydrogen chloride and sulfur dioxide in the oil phase basically when washing the oil phase. In this way, the equipment will not be corroded during the distillation of the oil phase, and no irritating gas will be generated, improving the production conditions. At the same time, since only the oil phase needs to be washed with water, the amount of wastewater generated during the water washing process is also small, the pressure of wastewater treatment is not very high, and the required treatment cost is also low.

[0010] In a preferred technical solution of the above preparation method, the preparation method further includes the following steps:

[0011] S4: Add a preset amount of polar aprotic solvent to the non-oil phase in S2 to obtain a mixture containing the polar aprotic solvent;

[0012] S5: Replace the polar aprotic solvent in S1 with the mixture containing the polar aprotic solvent in S4, and make it react with 1,2-benzisothiazol-3-one, thionyl halide and non-polar solvent under the preset conditions in S1 to obtain a new mixture containing 3-halo-1,2-benzisothiazole, wherein the molar ratio of 1,2-benzisothiazol-3-one to thionyl halide is a second molar ratio, and the range of the second molar ratio is 1:1.6 to 1:1.2, and the molar ratio of 1,2-benzisothiazol-3-one to non-polar solvent is 1:(1.5 - 8);

[0013] S6: Cycle S2 to S5.

[0014] In the case of adopting the above technical solution, by adding a small amount of polar aprotic solvent to the non-oil phase to replace the large amount of polar aprotic solvent required in the original reaction process, the residual 1,2-benzisothiazol-3-one, thionyl halide, and polar aprotic solvent in the non-oil phase are fully utilized, especially the polar aprotic solvent. In this way, the amount of polar aprotic solvent can be effectively reduced, the waste of effective raw materials can be effectively avoided, and thus the production cost can be greatly reduced.

[0015] In a preferred technical solution of the above preparation method, the preset amount of the polar aprotic solvent added in S4 is 5% - 10% of the amount of the polar aprotic solvent in S1.

[0016] In the case of adopting the above technical solution, only a small amount of polar aprotic solvent needs to be additionally added, which can replace a large amount of polar aprotic solvent originally required, and fully react with 1,2-benzisothiazol-3-one, thionyl halide and non-polar solvent to obtain the target product 3-halo-1,2-benzisothiazole. Therefore, the usage amount of polar aprotic solvent can be greatly reduced, the utilization efficiency of polar aprotic solvent can be improved, and the production cost of enterprises can be reduced.

[0017] In the preferred technical solution of the above preparation method, the first molar ratio is greater than the second molar ratio; and / or

[0018] In S6, the number of cycles of S2 to S5 is greater than or equal to 5 times.

[0019] By cycling S2 to S5 several times in this way, the polar aprotic solvent in the non-oil phase can be utilized more fully, the utilization efficiency of the polar aprotic solvent can be better improved, and the waste of effective raw materials can be more effectively avoided.

[0020] In the preferred technical solution of the above preparation method, the reaction temperature in the preset conditions in S1 ranges from 65 to 120 °C, and the reaction time is 2 to 6 hours.

[0021] In the preferred technical solution of the above preparation method, the reaction temperature in S1 ranges from 75 to 100 °C, and the reaction time is 3 to 4 hours.

[0022] By reacting 1,2-benzisothiazol-3-one, thionyl halide, polar aprotic solvent, and non-polar solvent at 75 to 100 °C for 3 to 4 hours, a higher reaction efficiency can be obtained, and then a higher yield of 3-halo-1,2-benzisothiazole can be obtained.

[0023] In the preferred technical solution of the above preparation method, the non-polar solvent is at least one of toluene, chlorobenzene, o-dichlorobenzene, benzene, m-dichlorobenzene, o-xylene, m-xylene, p-xylene, dichloroethane, chlorobutane, bromobutane, pentane.

[0024] In the preferred technical solution of the above preparation method, the non-polar solvent is chlorobenzene, dichlorobenzene or toluene.

[0025] In the preferred technical solution of the above preparation method, the polar aprotic solvent is at least one of dimethylformamide, dimethylacetamide, 1,3-dimethyl-2-imidazolidinone and hexamethylphosphoric triamide.

[0026] In the preferred technical solution of the above preparation method, the polar aprotic solvent is dimethylformamide. Description of the Drawings

[0027] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings, in which:

[0028] Figure 1 is a flowchart of a method for preparing 3-halo-1,2-benzisothiazole according to an embodiment of the present invention;

[0029] Figure 2 is a liquid chromatography spectrum of the target product obtained in the first reaction in Specific Example 1 of the present invention;

[0030] Figure 3 is a liquid chromatography spectrum of the target product obtained in the second reaction in Specific Example 1 of the present invention;

[0031] Figure 4 is a liquid chromatography spectrum of the target product obtained in the reaction in Comparative Example 1 of the present invention. Specific Embodiments

[0032] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principle of the present invention and are not intended to limit the protection scope of the present invention.

[0033] Currently, a large amount of wastewater is generated in the process of preparing 3-chloro-1,2-benzisothiazole using 1,2-benzisothiazol-3-one, dimethylformamide, and thionyl chloride, and the subsequent treatment cost is high. Therefore, in the present invention, after the mixture formed by reacting 1,2-benzisothiazol-3-one, thionyl halide, polar aprotic solvent, and nonpolar solvent is allowed to stand and separate into layers, the target product 3-halo-1,2-benzisothiazole can be obtained only by washing the oil phase with water and distilling it, greatly reducing the amount of wastewater generated, reducing the subsequent treatment cost, and reducing the usage amount of polar aprotic solvent.

[0034] In the present invention, 3-halo-1,2-benzisothiazole is prepared using 1,2-benzisothiazol-3-one, thionyl halide, polar aprotic solvent, and nonpolar solvent as raw materials. The following will be combined with Figure 1 to illustrate the steps of preparing 3-halo-1,2-benzisothiazole:

[0035] S1: React 1,2-benzisothiazol-3-one, thionyl halide, polar aprotic solvent, and nonpolar solvent under preset conditions to obtain a mixture containing 3-halo-1,2-benzisothiazole, wherein the molar ratio of 1,2-benzisothiazol-3-one to thionyl halide is a first molar ratio, and the range of the first molar ratio is 1:1.6 to 1:1.2, and the molar ratio of 1,2-benzisothiazol-3-one:polar aprotic solvent:nonpolar solvent is 1:(1.2 - 4):(1.5 - 8).

[0036] In this embodiment, the chemical formula (1) of 1,2-benzisothiazol-3-one is as follows:

[0037]

[0038] Among them, R 1 represents a hydrogen atom, an alkyl group with 1 to 4 carbon atoms, an alkoxy group with 1 to 4 carbon atoms, an alkoxycarbonyl group with 2 to 5 carbon atoms, a nitro group, or a halogen atom.

[0039] The chemical formula (2) of 3-halo-1,2-benzisothiazole is as follows:

[0040]

[0041] Among them, R 1 represents the same group as R in the aforementioned chemical formula (1), and X represents a halogen atom. 1 In a possible implementation manner, the preset conditions in S1 usually include the reaction temperature and the reaction time. Among them, the range of the reaction temperature is 65 - 120 °C, and the range of the reaction time is 2 - 6 hours.

[0042] Preferably, the range of the reaction temperature is 75 - 100 °C. Within this temperature range, the above-mentioned raw materials can participate in the reaction more fully, with better reaction activity, higher reaction efficiency, and higher yield of the target product 3-halo-1,2-benzisothiazole.

[0043] Preferably, the range of the reaction time is 3 - 4 hours. Within this reaction time, the above-mentioned raw materials can participate in the reaction sufficiently, and more 3-halo-1,2-benzisothiazole can be generated, obtaining a higher yield.

[0044] S2: Cool the mixture containing 3-halo-1,2-benzisothiazole to -10 - 40 °C and then let it stand for stratification to obtain a non-oil phase and an oil phase.

[0045] S3: The oil phase in S2 is washed with water and distilled to obtain 3-halo-1,2-benzisothiazole and the non-polar solvent.

[0046]

[0047] ​In the prior art, after a reaction occurs among 1,2-benzisothiazol-3-one, thionyl halide, polar aprotic solvent and non-polar solvent to obtain a mixture containing 3-halo-1,2-benzisothiazole, the mixture is usually directly concentrated and distilled to purify 3-halo-1,2-benzisothiazole. However, since the mixture contains a large amount of polar aprotic solvent, by-products hydrogen chloride and sulfur dioxide, and hydrogen chloride and sulfur dioxide are strong acidic substances, they will corrode the reaction equipment during the concentration and distillation process, and the production conditions are relatively harsh. For this reason, in the present invention, by controlling the proportions of each raw material and reaction conditions (specific proportions are described below), the mixture containing 3-halo-1,2-benzisothiazole generated by the reaction in S1 will automatically separate into layers after standing still when cooled to -10 to 40 °C, forming an upper oil phase and a lower non-oil phase. Then, the oil phase and the non-oil phase are separated by liquid separation (for example, using a separating funnel for liquid separation, etc.). The oil phase mainly includes 3-halo-1,2-benzisothiazole and non-polar solvent, and the non-oil phase mainly includes unreacted polar aprotic solvent and thionyl halide, as well as hydrogen chloride and sulfur dioxide generated by side reactions during the reaction process.

[0048] There will also be a small amount of polar aprotic solvent in the oil phase. At the same time, part of the hydrogen chloride and sulfur dioxide will enter the oil phase. Although the amount is not much, it will still have an impact on the equipment and production conditions. For this reason, before distilling the oil phase in the present invention, the oil phase is first washed with a small amount of water. After each water wash, it is allowed to stand and separate into layers to obtain a new oil phase and water phase. Since hydrogen chloride, sulfur dioxide and polar aprotic solvent have higher solubility in water, the content of hydrogen chloride, sulfur dioxide and polar aprotic solvent in the oil phase can be effectively reduced in this way. After the water wash, the vast majority of the polar aprotic solvent, hydrogen chloride and sulfur dioxide can be washed into the water, so that there will be no hydrogen chloride and sulfur dioxide to corrode the reaction equipment during the subsequent distillation of the oil phase, improving the production conditions. The water phase obtained during the water wash mainly includes hydrogen chloride and sulfur dioxide, which is treated as wastewater generated during the production process.

[0049] Preferably, after the oil phase obtained in S2 is washed with water three times, the new oil phase obtained basically only includes 3-halo-1,2-benzisothiazole and non-polar solvent, and is weakly acidic, which is beneficial to subsequent distillation treatment. During the distillation treatment process, it will basically not cause corrosion to the reaction equipment, and the production conditions are well improved. At the same time, the wastewater generated by the three water washes is also less.

[0050] In a possible implementation, vacuum distillation is used for distilling the oil phase. Specifically, during the vacuum distillation process, the vacuum degree is -0.09 MPa to -0.095 MPa. The boiling points of the non-polar solvent and 3-halo-1,2-benzisothiazole are different and belong to fractions in different temperature ranges. Taking the non-polar solvent as chlorobenzene and 3-halo-1,2-benzisothiazole as 3-chloro-1,2-benzisothiazole as an example, distillation is carried out under the condition of a vacuum degree of -0.095 MPa. The fraction between 80 °C and 132 °C is chlorobenzene, and the fraction between 135 °C and 165 °C is 3-chloro-1,2-benzisothiazole. It should be noted that the chlorobenzene obtained during the vacuum distillation process can be used as the non-polar solvent in S1.

[0051] S4: Add a preset amount of polar aprotic solvent to the non-oil phase in S2 to obtain a mixture containing the polar aprotic solvent.

[0052] The non-oil phase obtained in S2 mainly includes the unreacted polar aprotic solvent, thionyl halide, as well as hydrogen chloride and sulfur dioxide generated by side reactions during the reaction. Adding a preset amount of polar aprotic solvent to this non-oil phase, the resulting mixture will also contain a relatively large amount of polar aprotic solvent. It should be noted that this preset amount is much smaller than the amount of polar aprotic solvent required in S1.

[0053] S5: Replace the polar aprotic solvent in S1 with the mixture containing the polar aprotic solvent in S4, and make 1,2-benzisothiazol-3-one, thionyl halide, the mixture containing the polar aprotic solvent, and the non-polar solvent react under the preset conditions in S1 to obtain a new mixture containing 3-halo-1,2-benzisothiazole. Among them, the molar ratio of 1,2-benzisothiazol-3-one to thionyl halide is the second molar ratio, and the range of the second molar ratio is 1:1.6 to 1:1.2, and the molar ratio of 1,2-benzisothiazol-3-one to the polar aprotic solvent remains unchanged.

[0054] The preset conditions (reaction temperature and reaction time) in S5 are the same as those in S1, only changing the source of the polar aprotic solvent and the molar ratio of 1,2-benzisothiazol-3-one to thionyl halide. That is, in S5, the non-oil phase in S2 with a small amount of polar aprotic solvent added is used to replace the large amount of polar aprotic solvent originally required. In this way, the 1,2-benzisothiazol-3-one, thionyl halide, and polar aprotic solvent remaining in the non-oil phase are fully utilized, especially the polar aprotic solvent. There is no need to add a large amount of polar aprotic solvent as in S1, so the amount of polar aprotic solvent can be effectively reduced, avoiding waste of effective raw materials, and thus the production cost can be greatly reduced. It should be noted that the non-polar solvent required for the reaction in S5 can be all or part of the non-polar solvent obtained after distillation in S3, which is fully utilized.

[0055] S6: Cycle S2 to S5.

[0056] After the reaction in S5 to obtain a new mixture containing 3-halo-1,2-benzisothiazole, cycle S2 to S5. That is, the new mixture obtained in S5 is cooled to -10 to 40 °C, then allowed to stand for stratification to obtain a new non-oil phase and a new oil phase. The new oil phase is washed with water and distilled to obtain 3-halo-1,2-benzisothiazole and a non-polar solvent. An appropriate amount of polar aprotic solvent is added to the new non-oil phase, and the resulting mixture reacts again with 1,2-benzisothiazol-3-one, thionyl halide, and the non-polar solvent to obtain a new mixture containing 3-halo-1,2-benzisothiazole. Repeating this several times can more fully utilize the polar aprotic solvent remaining in the non-oil phase, reduce the amount of polar aprotic solvent, and reduce the production cost.

[0057] Preferably, when the number of cycles of S2 to S5 is greater than or equal to 5 times, the polar aprotic solvent in the non-oil phase can be more fully utilized, the utilization efficiency of the polar aprotic solvent can be better improved, it is more beneficial to avoid waste of effective raw materials, and the production cost can be reduced. Obviously, the number of cycles of S2 to S5 can also be less than 5 times.

[0058] In a possible implementation, the preset amount of the polar aprotic solvent added in S4 is 5% to 10% of the amount of the polar aprotic solvent in S1. In this way, only a small amount of the polar aprotic solvent needs to be additionally added to fully react with 1,2-benzisothiazol-3-one, thionyl halide, and the nonpolar solvent to obtain the target product 3-halo-1,2-benzisothiazole. Moreover, in the case of only adding a small amount of the polar aprotic solvent, the yield of the 3-halo-1,2-benzisothiazole obtained by the reaction is slightly higher than the yield when directly using the polar aprotic solvent as a raw material (please refer to the specific examples 1-6 below for details). This also indicates that the polar aprotic solvent in the non-oil phase in S2 is fully utilized, thereby greatly reducing the usage amount of the polar aprotic solvent, improving the utilization efficiency of the polar aprotic solvent, and reducing the production cost of the enterprise.

[0059] It should be noted that the preset amount of the polar aprotic solvent added in S4 can also be a smaller amount such as 3%, 4%, etc. of the amount of the polar aprotic solvent, or other larger amounts such as 13%, 18%, etc.

[0060] In a possible implementation, the molar ratio of 1,2-benzisothiazol-3-one:polar aprotic solvent:nonpolar solvent in S1 is 1:(1.2 - 4):(1.5 - 8). The ranges of the first molar ratio of 1,2-benzisothiazol-3-one to thionyl halide in S1 and the second molar ratio in S5 are both 1:1.6 - 1:1.2, and the molar ratio of 1,2-benzisothiazol-3-one:nonpolar solvent in S5 is still 1:(1.5 - 8). Under such raw material ratios, after the reaction of 1,2-benzisothiazol-3-one, thionyl halide, polar aprotic solvent, and nonpolar solvent in S1 and S5 to obtain a mixture containing 3-halo-1,2-benzisothiazole, when cooled to -10 - 40°C, layering can be achieved by static settling, forming a non-oil phase and an oil phase. This is because the inventors found that when the mixture after reaction under the above raw material ratios and the above reaction conditions is cooled to -10 - 40°C, some by-products hydrogen chloride and sulfur dioxide react with the weakly basic polar aprotic solvent (such as dimethylformamide, etc.) to form strong acid-weak base salts, achieving an acid-base balance. This will also cause the polar aprotic solvent, thionyl halide, and hydrogen chloride and sulfur dioxide to form a new phase, that is, the non-oil phase, which is no longer miscible with the nonpolar solvent and 3-halo-1,2-benzisothiazole, thus forming two immiscible phases and achieving layering. That is to say, by controlling the ratio of the raw materials in the present invention, the mixture obtained from the reaction in S1 and S5 above can be layered up and down by static settling after cooling to -10 - 40°C, separating the main target product 3-halo-1,2-benzisothiazole from the unreacted raw materials and reaction by-products, which can reduce the treatment amount of the oil phase that needs to be washed and distilled subsequently and simplify the production process.

[0061] When replacing the original polar aprotic solvent in S1 with the non-oil phase added with a polar aprotic solvent in S5 and carrying out the reaction as in S1, since the reaction temperature is much higher than the above cooling temperature of -10 - 40°C, the above acid-base balance is destroyed, and the polar aprotic solvent dissociates from hydrogen chloride and sulfur dioxide and participates in the reaction as a raw material. New hydrogen chloride and sulfur dioxide will be generated during the reaction. When cooled to -10°C - 40°C after the reaction is completed, hydrogen chloride and sulfur dioxide will react with the weakly basic polar aprotic solvent (such as dimethylformamide, etc.) again to reach an acid-base balance, and then two phases are formed.

[0062] In a possible implementation, the first molar ratio is less than or equal to the second molar ratio. That is to say, when the amount of the raw material 1,2-benzisothiazol-3-one is the same and the amount of the obtained target product is the same, compared with S1, the amount of thionyl halide required in S5 can be less (see specific Examples 1-6 below for details). This also indicates that the non-oil phase in S2 also contains thionyl halide and is reused in S5, thus realizing the recycling of thionyl halide in the non-oil phase, reducing the consumption of the raw material thionyl halide, and improving the utilization rate of the raw material. Obviously, the first molar ratio can also be greater than the second molar ratio.

[0063] In a possible implementation, the non-polar solvent is at least one of toluene, chlorobenzene, o-dichlorobenzene, benzene, m-dichlorobenzene, o-xylene, m-xylene, p-xylene, dichloroethane, chlorobutane, bromobutane, and pentane.

[0064] Preferably, the non-polar solvent is chlorobenzene, dichlorobenzene or toluene.

[0065] In a possible implementation, the polar aprotic solvent is at least one of dimethylformamide, dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, and hexamethylphosphoric triamide.

[0066] Preferably, the polar aprotic solvent is dimethylformamide.

[0067] In this example, the halogen atom X in the chemical formula (2) of 3-halo-1,2-benzisothiazole can be a fluorine atom, a chlorine atom, a bromine atom, etc.

[0068] Taking the repetition of steps S2 to S5 once with X in the chemical formula (2) being a chlorine atom as an example, corresponding examples are listed below to specifically illustrate the possible implementation manners of the preparation method of the present invention. Correspondingly, when X is a chlorine atom, the thionyl halide is thionyl chloride.

[0069] Example 1

[0070] Add 2.665 mol of chlorobenzene and 1.09 mol of dimethylformamide (abbreviation: DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviation: BIT). Heat the mixture to 75 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the dropwise addition of thionyl chloride, control the temperature between 75 - 80 °C. After the dropwise addition is completed, control the temperature between 80 - 85 °C. After BIT, chlorobenzene, DMF, and thionyl chloride react for 4 h, cool to about 20 °C, and then let it stand and separate into layers.

[0071] Add 50 g of water to the upper-layer oil phase for water washing, then let it stand and separate layers. The obtained oil phase is washed with water two more times, with 50 g of water used each time. The oil phase washed three times is subjected to vacuum distillation. During the vacuum distillation process, the vacuum degree is -0.095 MPa, and two fractions of chlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. Among them, there are 99 g of the target product 3-chloro-1,2-benzisothiazole, and the purity of this 3-chloro-1,2-benzisothiazole is determined to be 99.36% by liquid chromatography analysis.

[0072] Add 0.109 mol of DMF to the lower non-oil phase to react with 0.66 mol of BIT, 2.665 mol of chlorobenzene, and 0.85 mol of thionyl chloride. The addition method of each raw material is the same as described above, and a new mixture containing 3-chloro-1,2-benzisothiazole is obtained. Cool this new mixture to about 20 °C, then let it stand and separate layers. The upper-layer oil phase obtained is roughly similar to the previous upper-layer oil phase in the treatment process and has the same treatment conditions. After being washed with water three times, it is subjected to vacuum distillation, and 103 g of the target product 3-chloro-1,2-benzisothiazole can be obtained. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 98.92% by liquid chromatography analysis.

[0073] Comparative Example 1

[0074] Add 2.665 mol of chlorobenzene and 1.09 mol of dimethylformamide (abbreviated as DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviated as BIT). Heat the mixture to 75 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the dropwise addition of thionyl chloride, control the temperature between 75 - 80 °C. After the dropwise addition is completed, control the temperature between 80 - 85 °C. After BIT, chlorobenzene, DMF, and thionyl chloride react for 4 h, add 400 g of water to the mixture for water washing, then let it stand and separate layers. The obtained oil phase is washed with water two more times, with 400 g of water used each time. The oil phase washed three times is subjected to vacuum distillation. During the vacuum distillation process, the vacuum degree is -0.095 MPa, and two fractions of chlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. 90 g of the target product 3-chloro-1,2-benzisothiazole can be obtained, and the purity of this 3-chloro-1,2-benzisothiazole is determined to be 98.42% by liquid chromatography analysis.

[0075] Example 2

[0076] Add 1.36 mol of dichlorobenzene and 1.09 mol of dimethylformamide (abbreviated as DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviated as BIT). Heat the mixture to 75 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the addition of thionyl chloride, control the temperature between 75 - 80 °C. After the addition is complete, control the temperature between 80 - 85 °C. Let BIT, chlorobenzene, DMF, and thionyl chloride react for 4 h, and then cool to about 20 °C. Then let it stand and separate into layers.

[0077] Add 50 g of water to the upper oil phase for washing, then let it stand and separate into layers. The obtained oil phase is washed two more times, with 50 g of water used each time. Subject the oil phase washed three times to vacuum distillation. During the vacuum distillation, the vacuum degree is -0.095 MPa, and two fractions of dichlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. Among them, there are 95 g of the target product 3-chloro-1,2-benzisothiazole. Determine the purity of this 3-chloro-1,2-benzisothiazole to be 99.4% by liquid chromatography analysis.

[0078] Add 0.109 mol of DMF to the lower non-oil phase to react with 0.66 mol of BIT, 1.36 mol of dichlorobenzene, and 0.85 mol of thionyl chloride. The addition method of each raw material is the same as the previous one to obtain a new mixture containing 3-chloro-1,2-benzisothiazole. Cool this new mixture to about 20 °C, and then let it stand and separate into layers. The obtained upper oil phase is roughly similar to and has the same treatment conditions as the previous upper oil phase. After being washed three times, it is subjected to vacuum distillation to obtain 105 g of the target product 3-chloro-1,2-benzisothiazole. Determine the purity of this 3-chloro-1,2-benzisothiazole to be 99.1% by liquid chromatography analysis.

[0079] Comparative Example 2

[0080] Add 1.36 mol of dichlorobenzene and 1.09 mol of dimethylformamide (abbreviated as DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviated as BIT). Heat the mixture to 75 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the addition of thionyl chloride, control the temperature between 75 - 80 °C. After the addition is complete, control the temperature between 80 - 85 °C. After the reaction of BIT, chlorobenzene, DMF, and thionyl chloride for 4 h, add 400 g of water to the mixture for water washing, then let it stand and separate layers. The obtained oil phase is washed with water two more times, with 400 g of water used each time. Subject the oil phase washed three times to vacuum distillation. During the vacuum distillation, the vacuum degree is -0.095 MPa, and two fractions of dichlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. 92 g of the target product 3-chloro-1,2-benzisothiazole can be obtained. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 98.6% by liquid chromatography analysis.

[0081] Example 3

[0082] Add 3.256 mol of toluene and 1.09 mol of dimethylformamide (abbreviated as DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviated as BIT). Heat the mixture to 75 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the addition of thionyl chloride, control the temperature between 75 - 80 °C. After the addition is complete, control the temperature between 80 - 85 °C. After the reaction of BIT, chlorobenzene, DMF, and thionyl chloride for 4 h, cool it to about 20 °C. Then let it stand and separate layers.

[0083] Add 50 g of water to the upper oil phase for water washing, then let it stand and separate layers. The obtained oil phase is washed with water two more times, with 50 g of water used each time. Subject the oil phase washed three times to vacuum distillation. During the vacuum distillation, the vacuum degree is -0.095 MPa, and two fractions of dichlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. Among them, 98 g of the target product 3-chloro-1,2-benzisothiazole is obtained. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 99.28% by liquid chromatography analysis.

[0084] Add 0.054 mol of DMF to the lower non-oil phase to react with 0.66 mol of BIT, 3.256 mol of toluene, and 0.85 mol of thionyl chloride. The addition method of each raw material is the same as described above to obtain a new mixture containing 3-chloro-1,2-benzisothiazole. Cool the new mixture to about 20 °C, then let it stand and separate layers. The upper oil phase obtained is roughly similar to and has the same treatment conditions as the upper oil phase described above. After being washed with water three times, vacuum distillation is carried out to obtain 103 g of the target product 3-chloro-1,2-benzisothiazole. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 99.1% by liquid chromatography analysis.

[0085] Comparative Example 3

[0086] Add 3.256 mol of toluene and 1.09 mol of dimethylformamide (abbreviation: DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviation: BIT). Heat the mixture to 75 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the dropwise addition of thionyl chloride, control the temperature between 75 - 80 °C. After the dropwise addition is completed, control the temperature between 80 - 85 °C. After BIT, chlorobenzene, DMF, and thionyl chloride react for 4 h, add 400 g of water to the mixture for washing with water, then let it stand and separate layers. The obtained oil phase is washed with water two more times, with 400 g of water used each time. Carry out vacuum distillation on the oil phase washed three times. During the vacuum distillation process, the vacuum degree is -0.095 MPa, and two fractions of dichlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. 91 g of the target product 3-chloro-1,2-benzisothiazole can be obtained. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 98.6% by liquid chromatography analysis.

[0087] Example 4

[0088] Add 2.665 mol of chlorobenzene and 1.36 mol of dimethylformamide (abbreviation: DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviation: BIT). Heat the mixture to 75 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the dropwise addition of thionyl chloride, control the temperature between 75 - 80 °C. After the dropwise addition is completed, control the temperature between 80 - 85 °C. After BIT, chlorobenzene, DMF, and thionyl chloride react for 4 h, cool it to about 25 °C. Then let it stand and separate layers.

[0089] Add 50 g of water to the upper-layer oil phase for water washing, then let it stand and separate layers. The obtained oil phase is washed with water two more times, with 50 g of water used each time. The oil phase that has been washed three times is subjected to vacuum distillation. During the vacuum distillation process, the vacuum degree is -0.095 MPa, and two fractions of chlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. Among them, there is 100 g of the target product 3-chloro-1,2-benzisothiazole. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 99.38% by liquid chromatography analysis.

[0090] Add 0.136 mol of DMF to the lower-layer non-oil phase, and make it react with 0.66 mol of BIT, 2.665 mol of chlorobenzene, and 0.85 mol of thionyl chloride. The addition method of each raw material is the same as described above, and a new mixture containing 3-chloro-1,2-benzisothiazole is obtained. Cool this new mixture to about 25 °C, then let it stand and separate layers. The upper-layer oil phase obtained is roughly similar to the previous upper-layer oil phase in the treatment process and has the same treatment conditions. After being washed with water three times, it is subjected to vacuum distillation, and 104 g of the target product 3-chloro-1,2-benzisothiazole can be obtained. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 99.06% by liquid chromatography analysis.

[0091] Comparative Example 4

[0092] Add 2.665 mol of chlorobenzene and 1.09 mol of dimethylformamide (abbreviation: DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviation: BIT). Heat the mixture to 75 °C, and then slowly drop in 0.92 mol of thionyl chloride. During the dropping process of thionyl chloride, control the temperature between 75 - 80 °C. After the dropping is completed, control the temperature between 80 - 85 °C. After BIT, chlorobenzene, DMF, and thionyl chloride react for 4 h, add 400 g of water to the mixture for water washing, then let it stand and separate layers. The obtained oil phase is washed with water two more times, with 400 g of water used each time. The oil phase that has been washed three times is subjected to vacuum distillation. During the vacuum distillation process, the vacuum degree is -0.095 MPa, and two fractions of chlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. 93 g of the target product 3-chloro-1,2-benzisothiazole can be obtained. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 98.6% by liquid chromatography analysis.

[0093] Example 5

[0094] Add 2.665 mol of chlorobenzene and 1.09 mol of dimethylformamide (abbreviated as DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviated as BIT). Heat the mixture to 75 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the dropwise addition of thionyl chloride, control the temperature between 75 - 80 °C. After the dropwise addition is completed, control the temperature between 80 - 85 °C. After the reaction of BIT, chlorobenzene, DMF, and thionyl chloride for 4 h, cool to about 30 °C. Then let it stand and separate layers.

[0095] Add 50 g of water to the upper oil phase for washing, then let it stand and separate layers. The obtained oil phase is washed two more times, with 50 g of water used each time. Subject the oil phase washed three times to vacuum distillation. During the vacuum distillation, the vacuum degree is -0.095 MPa, and two fractions of chlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. Among them, there is 100 g of the target product 3-chloro-1,2-benzisothiazole. Determine the purity of this 3-chloro-1,2-benzisothiazole to be 99.45% by liquid chromatography analysis.

[0096] Add 0.054 mol of DMF to the lower non-oil phase to react with 0.66 mol of BIT, 2.665 mol of chlorobenzene, and 0.85 mol of thionyl chloride. The addition method of each raw material is the same as the previous one, and a new mixture containing 3-chloro-1,2-benzisothiazole is obtained. Cool this new mixture to about 20 °C, then let it stand and separate layers. The obtained upper oil phase is roughly similar to and has the same treatment conditions as the previous upper oil phase. After being washed three times, it is subjected to vacuum distillation, and 102 g of the target product 3-chloro-1,2-benzisothiazole can be obtained. Determine the purity of this 3-chloro-1,2-benzisothiazole to be 99.12% by liquid chromatography analysis.

[0097] Comparative Example 5

[0098] Add 2.665 mol of chlorobenzene and 1.09 mol of dimethylformamide (abbreviated as DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviated as BIT). Heat the mixture to 75 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the dropwise addition of thionyl chloride, control the temperature between 75 - 80 °C. After the dropwise addition is completed, control the temperature between 80 - 85 °C. After the reaction of BIT, chlorobenzene, DMF, and thionyl chloride for 4 h, add 400 g of water to the mixture for washing, then let it stand and separate layers. The obtained oil phase is washed twice more with 400 g of water each time. Subject the oil phase washed three times to vacuum distillation. During the vacuum distillation, the vacuum degree is -0.095 MPa, and two fractions of chlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. 90 g of the target product 3-chloro-1,2-benzisothiazole can be obtained, and the purity of this 3-chloro-1,2-benzisothiazole is determined to be 98.7% by liquid chromatography analysis.

[0099] Example 6

[0100] Add 0.906 mol of dichlorobenzene and 1.09 mol of dimethylformamide (abbreviated as DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviated as BIT). Heat the mixture to 80 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the dropwise addition of thionyl chloride, control the temperature between 80 - 85 °C. After the dropwise addition is completed, control the temperature between 85 - 90 °C. After the reaction of BIT, chlorobenzene, DMF, and thionyl chloride for 3 h, cool it to about 20 °C. Then let it stand and separate layers.

[0101] Add 50 g of water to the upper oil phase for washing, then let it stand and separate layers. The obtained oil phase is washed twice more with 50 g of water each time. Subject the oil phase washed three times to vacuum distillation. During the vacuum distillation, the vacuum degree is -0.095 MPa, and two fractions of chlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. Among them, there is 101 g of the target product 3-chloro-1,2-benzisothiazole, and the purity of this 3-chloro-1,2-benzisothiazole is determined to be 99.6% by liquid chromatography analysis.

[0102] Add 0.067 mol of DMF to the lower non-oil phase to react with 0.66 mol of BIT, 0.906 mol of dichlorobenzene, and 0.85 mol of thionyl chloride. The addition method of each raw material is the same as described above to obtain a new mixture containing 3-chloro-1,2-benzisothiazole. Cool this new mixture to about 20 °C, then let it stand and separate layers. The upper oil phase obtained is roughly similar to the previous upper oil phase in the treatment process and has the same treatment conditions. After being washed with water 3 times, vacuum distillation is carried out to obtain 105 g of the target product 3-chloro-1,2-benzisothiazole. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 99.4% by liquid chromatography analysis.

[0103] Comparative Example 6

[0104] Add 0.906 mol of dichlorobenzene and 1.09 mol of dimethylformamide (abbreviation: DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviation: BIT). Heat the mixture to 80 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the dropwise addition of thionyl chloride, control the temperature between 80 - 85 °C. After the dropwise addition is completed, control the temperature between 85 - 90 °C. After BIT, chlorobenzene, DMF, and thionyl chloride react for 3 h, add 400 g of water to the mixture for washing with water, then let it stand and separate layers. The obtained oil phase is washed with water two more times, with 400 g of water used each time. The oil phase washed 3 times with water is subjected to vacuum distillation. During the vacuum distillation, the vacuum degree is -0.095 MPa, and two fractions of dichlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively, and 92 g of the target product 3-chloro-1,2-benzisothiazole can be obtained. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 99.1% by liquid chromatography analysis.

[0105] Example 7

[0106] Add 2.665 mol of chlorobenzene and 1.09 mol of dimethylformamide (abbreviation: DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviation: BIT). Heat the mixture to 75 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the dropwise addition of thionyl chloride, control the temperature between 75 - 80 °C. After the dropwise addition is completed, control the temperature between 80 - 85 °C. After BIT, chlorobenzene, DMF, and thionyl chloride react for 4 h, cool to 40 °C, then let it stand and separate layers.

[0107] Add 50 g of water to the upper-layer oil phase for water washing, then let it stand and separate layers. The obtained oil phase is washed with water two more times, with 50 g of water used each time. The oil phase washed three times is subjected to vacuum distillation. During the vacuum distillation process, the vacuum degree is -0.095 MPa, and two fractions of chlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. Among them, there are 98 g of the target product 3-chloro-1,2-benzisothiazole, and the purity of this 3-chloro-1,2-benzisothiazole is determined to be 99.40% by liquid chromatography analysis.

[0108] Add 0.109 mol of DMF to the lower-layer non-oil phase to react with 0.66 mol of BIT, 2.665 mol of chlorobenzene, and 0.85 mol of thionyl chloride. The addition method of each raw material is the same as described above, and a new mixture containing 3-chloro-1,2-benzisothiazole is obtained. Cool this new mixture to 40 °C, then let it stand and separate layers. The upper-layer oil phase obtained is roughly similar to the previous upper-layer oil phase in the treatment process and has the same treatment conditions. After being washed with water three times, it is subjected to vacuum distillation, and 102 g of the target product 3-chloro-1,2-benzisothiazole can be obtained. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 98.82% by liquid chromatography analysis.

[0109] Example 8

[0110] Add 2.665 mol of chlorobenzene and 1.09 mol of dimethylformamide (abbreviation: DMF) to 0.66 mol of 1,2-benzisothiazol-3-one (abbreviation: BIT). Heat the mixture to 75 °C, and then slowly dropwise add 0.92 mol of thionyl chloride. During the dropwise addition of thionyl chloride, control the temperature between 75 - 80 °C. After the dropwise addition is completed, control the temperature between 80 - 85 °C. After BIT, chlorobenzene, DMF, and thionyl chloride react for 4 h, cool it to -10 °C, then let it stand and separate layers.

[0111] Add 50 g of water to the upper-layer oil phase for water washing, then let it stand and separate layers. The obtained oil phase is washed with water two more times, with 50 g of water used each time. The oil phase washed three times is subjected to vacuum distillation. During the vacuum distillation process, the vacuum degree is -0.095 MPa, and two fractions of chlorobenzene and the target product 3-chloro-1,2-benzisothiazole are obtained respectively. Among them, there are 100 g of the target product 3-chloro-1,2-benzisothiazole, and the purity of this 3-chloro-1,2-benzisothiazole is determined to be 99.28% by liquid chromatography analysis.

[0112] Add 0.109 mol of DMF to the lower non-oil phase to react with 0.66 mol of BIT, 2.665 mol of chlorobenzene, and 0.85 mol of thionyl chloride. The addition method of each raw material is the same as described above to obtain a new mixture containing 3-chloro-1,2-benzisothiazole. Cool this new mixture to -10 °C, then let it stand and separate layers. The upper oil phase obtained is roughly similar to the upper oil phase described above in the treatment process and has the same treatment conditions. After being washed with water three times, vacuum distillation is carried out to obtain 101 g of the target product 3-chloro-1,2-benzisothiazole. The purity of this 3-chloro-1,2-benzisothiazole is determined to be 98.92% by liquid chromatography analysis.

[0113] Based on the above Examples 1-8 and Comparative Examples 1-6, it can be seen that in the Examples, the non-oil phase containing a small amount of polar aprotic solvents (chlorobenzene, dichlorobenzene, toluene) is used to replace a large amount of polar aprotic solvents originally participating in the reaction, and the dosage of thionyl chloride is reduced in the reaction, that is, the second reaction in the Examples. The yield of the target product 3-chloro-1,2-benzisothiazole obtained is comparable to the yield of the first reaction, and even slightly higher than the yield of the first reaction. This indicates that the polar aprotic solvents and thionyl chloride in the non-oil phase are fully utilized during the second reaction process. In this way, the utilization efficiency of raw materials is improved, and the production cost of the enterprise is reduced. In addition, it can be seen from Examples 1 to 8 and Comparative Examples 1 to 6 that the amount of water used for washing before distilling the oil phase in each Example is less than that used in each Comparative Example. That is to say, the amount of wastewater generated during the preparation of the target product 3-chloro-1,2-benzisothiazole by using the method of the present invention is less, and the amount of wastewater to be treated is also less.

[0114] In this Example, the purity of the target product 3-chloro-1,2-benzisothiazole obtained in the above Examples 1 to 8 and Comparative Examples 1 to 6 is analyzed by liquid chromatography analysis.

[0115] Among them, the manufacturer of the liquid chromatography is Shanghai Wufeng Scientific Instrument Co., Ltd., and the model is LC100. The manufacturer of the chromatographic column is Akzo Nobel Company of Sweden, the model is Kromasil100A C18 7μm, and the size is 250 mm × 4.6 mm. The detection wavelength is 254 nm, the mobile phase is methanol and water, the molar ratio of methanol: water is 3:1, the flow rate is 0.8 ml / min, and the temperature of the chromatographic column is 25 °C.

[0116] Take 0.1 g of the target product 3-chloro-1,2-benzisothiazole and dissolve it in 4 ml of methanol. Place it in an ultrasonic instrument and shake and mix for several minutes (such as 6 minutes, etc.) to prepare a test solution. Inject 2 μl of the test solution into the liquid chromatography and measure it according to the high performance liquid chromatography method under the above conditions. Record the chromatogram, and then calculate the content of each component in the chromatogram by the area normalization method.

[0117] Specifically, in order to clearly illustrate the purity of the target product, the liquid chromatography spectra and analysis results of 3-chloro-1,2-benzisothiazole obtained in Example 1 and Comparative Example 1 above are listed in the Figures 2 to 4 appendix of the specification respectively.

[0118] From Figures 2 to 4 the spectra shown in it, it can be seen that the main component in the test solution is 3-chloro-1,2-benzisothiazole. Among them, the content of 3-chloro-1,2-benzisothiazole in the target product obtained from the first reaction in Example 1 is 99.36%, and the content of 3-chloro-1,2-benzisothiazole in the target product obtained from the second reaction is 98.92%. The content of 3-chloro-1,2-benzisothiazole in the target product obtained from the reaction in Comparative Example 1 is 98.42%.

[0119] Thus, it can be seen that in Example 1 of the present invention, after the reaction, it is first allowed to stand and layer, and the oil phase is washed with water and distilled to obtain a target product with a high purity. The purity of the target product obtained by using a non-oil phase containing a small amount of polar aprotic solvent to replace a large amount of polar aprotic solvent to participate in the reaction is roughly equivalent to the purity of the target product obtained in Comparative Example 1. This also shows that the non-oil phase containing a small amount of polar aprotic solvent can effectively replace the pure polar aprotic solvent, so that on the basis of ensuring the purity of the target product, the polar aprotic solvent in the non-oil phase can be fully utilized, which is more conducive to the popularization and application of the technology.

[0120] In summary, in the preferred technical solution of the present invention, the mixture obtained by reacting 1,2-benzisothiazol-3-one, thionyl halide, polar aprotic solvent, and non-polar solvent is cooled to -10 to 40 °C and then allowed to stand and layer. The oil phase is washed with water and distilled to obtain a target product. A small amount of polar aprotic solvent is added to the non-oil phase and then reacted with 1,2-benzisothiazol-3-one, thionyl halide, and non-polar solvent to obtain a new mixture. The new mixture is cooled and allowed to stand and layer to obtain a new oil phase and non-oil phase, and the oil phase and non-oil phase are respectively treated according to the foregoing treatment methods, and so on. In this way, the polar aprotic solvent in the non-oil phase can be reused, the amount of polar aprotic solvent is reduced, and thus the production cost is reduced. At the same time, the oil phase is washed with water and then distilled, effectively improving the production conditions. And because only the oil phase needs to be washed with water, the waste water generated during the water washing process is less, and the subsequent treatment cost is also lower.

[0121] In the above embodiments, although the various steps are described in the above order, those skilled in the art can understand that, in order to achieve the effects of this embodiment, the different steps do not have to be executed in such an order, and they can be executed simultaneously (in parallel) or in a reversed order, and these simple changes are all within the protection scope of this application.

[0122] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. A method for preparing 3-halo-1,2-benzisothiazole, characterized in that, the preparation method comprises the following steps: S1: React 1,2-benzisothiazol-3-one, thionyl halide, polar aprotic solvent, and non-polar solvent under preset conditions to obtain a mixture containing 3-halo-1,2-benzisothiazole, wherein the molar ratio of 1,2-benzisothiazol-3-one to thionyl halide is a first molar ratio, and the range of the first molar ratio is 1:1.6 to 1:1.2, and the molar ratio of 1,2-benzisothiazol-3-one:polar aprotic solvent:non-polar solvent is 1:(1.2 - 4):(1.5 - 8); S2: Cool the mixture containing 3-halo-1,2-benzisothiazole to -10 to 40 °C and then let it stand for layering to obtain a non-oil phase and an oil phase; S3: Wash and distill the oil phase in S2 to obtain 3-halo-1,2-benzisothiazole and non-polar solvent; S4: Add a preset amount of polar aprotic solvent to the non-oil phase in S2 to obtain a mixture containing polar aprotic solvent; S5: Replace the polar aprotic solvent in S1 with the mixture containing polar aprotic solvent in S4, and react it with 1,2-benzisothiazol-3-one, thionyl halide, and non-polar solvent under the preset conditions in S1 to obtain a new mixture containing 3-halo-1,2-benzisothiazole, wherein the molar ratio of 1,2-benzisothiazol-3-one to thionyl halide is a second molar ratio, and the range of the second molar ratio is 1:1.6 to 1:1.2, and the molar ratio of 1,2-benzisothiazol-3-one to non-polar solvent is 1:(1.5 - 8); S6: Cycle S2 to S5; wherein the non-polar solvent is chlorobenzene, dichlorobenzene or toluene, and the polar aprotic solvent is dimethylformamide.

2. The preparation method according to claim 1, characterized in that, the preset amount of the polar aprotic solvent added in S4 is 5% - 10% of the amount of the polar aprotic solvent in S1.

3. The preparation method according to claim 1, characterized in that, the first molar ratio is less than or equal to the second molar ratio; and / or the number of cycles of S2 to S5 in S6 is greater than or equal to 5 times.

4. The preparation method according to claim 1, characterized in that, the range of the reaction temperature in the preset conditions in S1 is 65 - 120 °C, and the reaction time is 2 - 6 hours.

5. The preparation method according to claim 4, characterized in that, the range of the reaction temperature in S1 is 75 - 100 °C, and the reaction time is 3 - 4 hours.

Images