CN108689952B - A kind of preparation method of prothioconazole - Google Patents

Abstract

The invention provides a preparation method of prothioconazole, the preparation method comprising: carrying out a heterogeneous oxidation reaction of the compound shown in formula I and ferric chloride in an aromatic hydrocarbon solvent to obtain the prothioconazole; In the preparation method provided by the present invention, by using a separate aromatic hydrocarbon solvent, the amount of solvent used in the reaction is less, and calculated by mass ratio, the amount used is 1-6 times the mass of the raw material, which is easier for large-scale production, Moreover, the target product with a content of more than 98.0% can be obtained directly through filtration and drying, and processes such as extraction and desolvation are omitted, which is beneficial to industrialized production and reduces production cost.

Description

A kind of preparation method of prothioconazole

technical field

The invention belongs to the field of organic synthesis and relates to a preparation method of prothioconazole.

Background technique

Prothioconazole (2-(1-Chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2,4-triazole- 5-thiocarbonyl-1-yl)-propan-2-ol) is a new type of broad-spectrum triazolethione fungicide developed by Bayer, which is mainly used to control many diseases such as cereals, wheat and beans. Prothioconazole has low toxicity, no teratogenicity, no mutagenicity, no toxicity to embryos, and is safe to humans and the environment. At present, its synthesis methods mainly include the following:

CN1411450A discloses a method for preparing: 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2, 4-triazolidine-5-thiocarbonyl-1-yl)-propan-2-ol reacts with the aqueous hydrochloric acid solution of ferric chloride, and the selected diluent is the one in the mixture of ethyl acetate, ethanol or toluene and ethanol . After the reaction has ended, the reaction mixture is mixed with water, the two phases are separated and the organic phase is washed with water, dried and concentrated. Then it is purified by conventional methods (such as recrystallization) to obtain a higher content of the target substance.

The reaction can be illustrated by the following reaction scheme:

The disadvantages of this method are:

1) Because the reaction process needs the ferric chloride aqueous solution of 2 molar equivalents or more molar equivalents, the corresponding molar equivalent ferrous chloride aqueous solution is generated after the reaction is finished, and no treatment will cause great pollution to the environment, and after-treatment is harmless higher cost. The above-mentioned documents do not mention treatment measures for this by-product. In fact, the treatment method is generally to generate ferrous hydroxide sludge, but the amount of waste is huge, and the waste cannot be used in industry.

2) According to the description of this method, at the end of the oxidation reaction, the system is a two-phase organic phase and an aqueous phase, and there is no undissolved solid. If alcohols such as ethanol are used as diluents, other extractive solvents need to be introduced in post-treatment for washing, crystallization and other operations, which increases the complexity of the process; if esters such as ethyl acetate are used as diluents, the strong acidity of ferric chloride solution The system causes significant decomposition of esters, increasing impurities in both phases.

CN106986838A discloses a preparation method of prothioconazole, compound 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro) -1,2,4-Triazolidine-5-thiocarbonyl-1-yl)-propan-2-ol is reacted in the presence of oxidizing agent and solvent at 20-120°C, and after the reaction is finished, it is obtained by post-treatment Prothioconazole. The oxidant used in this method is hydrogen peroxide or m-chloroperoxybenzoic acid. This method uses a large amount of solvent and has a low yield.

At present, the existing preparation methods all have the defects of low product yield, large amount of solvent, and unreusable oxidant. Therefore, how to develop a new synthesis method is of great significance and value for the industrial production of prothioconazole.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a kind of preparation method of prothioconazole.

For this purpose, the present invention adopts the following technical solutions:

The invention provides a preparation method of prothioconazole, the preparation method comprising: carrying out a heterogeneous oxidation reaction of the compound shown in formula I and ferric chloride in an aromatic hydrocarbon solvent to obtain the prothioconazole, The reaction formula is as follows:

In the preparation method of prothioconazole provided by the present invention, by using a separate aromatic hydrocarbon solvent, the amount of solvent used in the reaction is less, and the amount used is 1-6 times the mass of the raw material according to the mass ratio, and it is easier to large-scale In addition, the target product with a content of more than 98.0% can be obtained directly by filtration and drying, and processes such as extraction and desolvation are omitted.

It was unexpectedly found that, in the present invention, the reaction process does not need to dissolve all the formula I, the reaction can be successfully completed, and no other impurities are found. The prothioconazole generated at the end of the reaction is suspended in the reaction system, directly filtered and dried to obtain prothioconazole of higher purity, which can be directly commercialized. In addition, the filtrate obtained by filtration is divided into an organic phase and an aqueous phase. The organic phase can be directly used as the solvent for the next batch of reactions without any treatment, and a small amount of fresh solvent lost due to filtration can be added without affecting the purity of the product. and yield.

However, in the existing method, such as the method disclosed in CN1411450A, a mixed solvent of toluene and ethanol or an ethyl acetate solvent is used, and the recovery of the solvent system is difficult.

Preferably, the molar ratio of the compound represented by the formula I to ferric chloride is 1:(2.0-5.0), for example, it can be 1:2, 1:2.2, 1:2.5, 1:3, 1:3.6, 1 :4.2, 1:4.5, 1:4.8 or 1:5, preferably 1:(2.0-3.0).

Preferably, the aromatic hydrocarbon solvent includes any one or a combination of at least two of toluene, xylene, trimethylbenzene, chlorobenzene or bromobenzene.

Preferably, the mass ratio of the compound represented by the formula I to the aromatic hydrocarbon solvent is 1:(1-6), for example, it can be 1:1, 1:2, 1:3, 1:4, 1:5 or 1 : 6, preferably 1: (2-3).

In the present invention, because the aromatic hydrocarbon solvent produces a heterogeneous reaction system, the compound of formula I dissolves in the solvent and reacts, and the dissolution of the compound of formula II from the solvent is also unpredictable as a person skilled in the art, and The reactions described in the existing methods are homogeneous systems.

When the amount of the aromatic hydrocarbon solvent is small, it is unfavorable for the reaction to proceed because the dissolved amount of the compound of formula I is small, and when the amount of the solvent is large, the equipment utilization rate is low, and the space-time yield is low. Therefore, the present invention preferably uses 2-3 times the amount of solvent, which neither affects the dissolution of raw materials, but also helps to reduce the loss of products.

Preferably, the temperature of the heterogeneous oxidation reaction is 0-100°C, such as 0°C, 10°C, 15°C, 30°C, 35°C, 40°C, 50°C, 60°C, 70°C, 80°C , 90°C or 100°C, preferably 10-50°C.

Preferably, the time of the heterogeneous oxidation reaction is 5-12h, for example, it can be 5h, 6h, 7h, 8h, 9h, 10h, 11h or 12h.

Preferably, after the heterogeneous oxidation reaction is completed, the organic phase and the aqueous phase are obtained by standing for stratification.

In the present invention, the reaction process is a heterogeneous reaction, the raw materials do not need to be completely dissolved in the reaction process, and the solid obtained after the reaction and the solid directly precipitated in the organic phase are dried to be the product prothioconazole without any purification. The processing steps are beneficial to industrial production. Moreover, the organic phase can be directly reused as the solvent for the next reaction without affecting the purity and yield of the product.

Preferably, the prothioconazole is directly obtained after the organic phase is cooled to 10-20° C., filtered and dried.

Preferably, after the aqueous phase is acidified with an inorganic acid, it is reacted with an oxidant to obtain an aqueous ferric chloride solution for the next batch of reactions.

In the present invention, the ferric chloride obtained by oxidation in the water phase can be reused, no waste is generated in the whole process, and the recycling of the solvent and by-products is realized.

Preferably, the oxidizing agent includes any one of hydrogen peroxide, sodium hypochlorite or potassium permanganate.

Preferably, the preparation method of prothioconazole specifically comprises: carrying out a heterogeneous oxidation reaction of the compound shown in formula I and ferric chloride in an aromatic hydrocarbon solvent at 0-100° C. for 5-12 hours, and standing to obtain an organic phase and water phase, wherein after the water phase is acidified by inorganic acid, it reacts with oxidant to obtain ferric chloride again, and the organic phase is cooled to 10-20 DEG C to directly obtain the prothioconazole.

Compared with the prior art, the present invention has the following beneficial effects:

In the preparation method of prothioconazole provided by the present invention, by using a separate aromatic hydrocarbon solvent, the amount of solvent used in the reaction is less, and the amount used is 1-6 times the mass of the raw material according to the mass ratio, and it is easier to large-scale In addition, the target product with a content of more than 98.0% can be obtained directly through filtration and drying, and processes such as extraction and desolvation are omitted, which is beneficial to industrial production.

According to the preparation method provided by the present invention, the materials generated after the reaction can be reused directly or after conversion, the organic phase can be directly used as the solvent for the next batch without the recovery operation of distillation or fractionation, and the auxiliary substances in the aqueous phase can be used directly. The product ferrous chloride can be re-converted into ferric chloride after oxidation treatment to realize recycling. Compared with the existing technology, the whole preparation process is more energy-saving, saves material consumption, production equipment and staffing, and solves the problem of by-product ferrous chloride treatment. The problem is that the production process is more environmentally friendly. By comprehensive comparison, the present invention provides a process method for preparing prothioconazole from the compound shown in formula I with high efficiency, environmental protection, easy operation and low cost.

Detailed ways

The technical solutions of the present invention are further described below through specific embodiments. It should be understood by those skilled in the art that the embodiments are only for helping the understanding of the present invention, and should not be regarded as a specific limitation of the present invention.

Example 1

At room temperature, 10.0 g (99.4% purity, 28.7 mmol) 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-di Hydrogen-1,2,4-triazolidine-5-thiocarbonyl-1-yl)-propan-2-ol, 30g toluene and 35.0g (66.0mmol) ferric chloride aqueous solution were added into a 250mL four-neck flask and stirred well , then the temperature was raised to 30-40 °C, and the reaction progress was monitored by HPLC. After the reaction was completed, the temperature was lowered to 10-20° C., and 8.5 g of solid was obtained after suction filtration and drying. HPLC analysis indicated that the solid contained 98.1% 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2, 4-Triazol-5-thiocarbonyl-1-yl)-propan-2-ol. Therefore, the calculated yield is 83.9% of the theoretical value (this yield is the yield after the first batch of reaction, and after the organic phase is reused, the yield is 99%). The filtrate was separated to obtain 22.5 g of the organic phase and 33.5 g of the aqueous phase. The organic phase can be used directly as the solvent for the next batch of oxidation reactions.

A small amount of concentrated hydrochloric acid was added under the stirring condition of the aqueous phase, the temperature was controlled at 30-40° C., and 3.8 g (concentration of 27.0%, 30 mmol) aqueous hydrogen peroxide solution was slowly added. Then the system is heated to about 85°C and kept for 2 hours, then the appropriate amount of water is removed under reduced pressure, and a small amount of fresh ferric chloride is added according to the actual measured ferric chloride concentration, so that the total weight of the ferric chloride solution is maintained at about 35g, and the total molar The number was kept around 66.0 mmol and then used for the next batch of oxidation reactions.

Example 2

At room temperature, 10.0 g (99.4% purity, 28.7 mmol) 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-di Hydrogen-1,2,4-triazolidine-5-thiocarbonyl-1-yl)-propan-2-ol, 22.5 g organic phase recovered in previous batch Example 1, 7.5 g fresh toluene and 35.0 g (66.0 g mmol) aforesaid regenerated ferric chloride aqueous solution, add in a 250mL four-necked flask and stir evenly, then heat up to between 30-40°C, and HPLC monitors the reaction progress. After the reaction, the temperature was lowered to 10-20° C., suction filtration, and drying to obtain 9.94 g of solid. HPLC analysis showed that the solid contained 98.5% 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2, 4-Triazol-5-thiocarbonyl-1-yl)-propan-2-ol. Therefore, the yield was calculated to be 99.0% of the theoretical value. The filtrate was separated to obtain 23.0 g of an organic phase and 35.0 g of an aqueous phase. The organic phase can be used directly as the solvent for the next batch of oxidation reactions.

A small amount of concentrated hydrochloric acid was added under the stirring condition of the aqueous phase, the temperature was controlled at 30-40° C., and 3.8 g (concentration of 27.0%, 30 mmol) aqueous hydrogen peroxide solution was slowly added. Then the system is heated to about 85°C and kept for 2 hours, then the appropriate amount of water is removed under reduced pressure, and a small amount of fresh ferric chloride is added according to the actual measured ferric chloride concentration, so that the total weight of the ferric chloride solution is maintained at about 35g, and the total molar The number was kept around 66.0 mmol and then used for the next batch of oxidation reactions.

Example 3

At room temperature, 10.0 g (99.4% purity, 28.7 mmol) 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-di Hydrogen-1,2,4-triazolidine-5-thiocarbonyl-1-yl)-propan-2-ol, 25.0g chlorobenzene and 35.0g (66.0mmol) ferric chloride aqueous solution were added to a 250mL four-neck flask Stir well, then heat up to 30-40°C, and monitor the progress of the reaction by HPLC. After the reaction was completed, the temperature was lowered to 10-20° C., and 8.7 g of solid was obtained after suction filtration and drying. HPLC analysis indicated that the solid contained 98.0% 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2, 4-Triazol-5-thiocarbonyl-1-yl)-propan-2-ol. Therefore, the yield was calculated to be 86.3% of the theoretical value. The filtrate was separated to obtain 22.0 g of an organic phase and 34.5 g of an aqueous phase. The organic phase can be used directly as the solvent for the next batch of oxidation reactions.

A small amount of concentrated hydrochloric acid was added under the stirring condition of the aqueous phase, the temperature was controlled at 30-40° C., and 3.8 g (concentration of 27.0%, 30 mmol) aqueous hydrogen peroxide solution was slowly added. Then the system is heated to about 85°C and kept for 2 hours, then the appropriate amount of water is removed under reduced pressure, and a small amount of fresh ferric chloride is added according to the actual measured ferric chloride concentration, so that the total weight of the ferric chloride solution is maintained at about 35g, and the total molar The number was kept around 66.0 mmol and then used for the next batch of oxidation reactions.

Example 4

At room temperature, 10.0 g (99.4% purity, 28.7 mmol) 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-di Hydrogen-1,2,4-triazolidine-5-thiocarbonyl-1-yl)-propan-2-ol, 22.0 g of the organic phase recovered in Example 3 of the previous batch, 3.0 g of fresh chlorobenzene and 35.0 g ( 66.0 mmol) the aforementioned regenerated ferric chloride aqueous solution, added to a 250 mL four-necked flask and stirred evenly, then heated to between 30-40° C., and the reaction progress was monitored by HPLC. After the reaction was completed, the temperature was lowered to 10-20° C., and 9.96 g of solid was obtained after suction filtration and drying. HPLC analysis showed that the solid contained 98.3% 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2, 4-Triazol-5-thiocarbonyl-1-yl)-propan-2-ol. Therefore, the yield was calculated to be 99.1% of the theoretical value. The filtrate was separated to obtain 23.0 g of an organic phase and 35.0 g of an aqueous phase. The organic phase can be used directly as the solvent for the next batch of oxidation reactions. The water phase was regenerated according to the regeneration scheme of ferric chloride in Example 1 and used for the next batch of oxidation reactions.

Example 5

At room temperature, 10.0 g (99.4% purity, 28.7 mmol) 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-di Hydrogen-1,2,4-triazolidine-5-thiocarbonyl-1-yl)-propan-2-ol, 30g xylene and 30.4g (57.4mmol) ferric chloride aqueous solution were added into a 250mL four-necked flask and stirred Homogeneous, then the temperature was raised to between 30-40 °C, and the progress of the reaction was monitored by HPLC. After the reaction was completed, the temperature was lowered to 10-20° C., and 8.4 g of solid was obtained after suction filtration and drying. HPLC analysis indicated that the solid contained 98.0% 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2, 4-Triazol-5-thiocarbonyl-1-yl)-propan-2-ol. Therefore, the yield was calculated to be 83.3% of the theoretical value. The filtrate was separated to obtain 25.0 g of the organic phase and 34.5 g of the aqueous phase. The organic phase can be used directly as the solvent for the next batch of oxidation reactions.

A small amount of concentrated hydrochloric acid was added under the stirring condition of the aqueous phase, the temperature was controlled at 30-40° C., and 3.8 g (concentration of 27.0%, 30 mmol) aqueous hydrogen peroxide solution was slowly added. Then the system is warmed up to about 85 ° C and kept for 2 hours, then the appropriate amount of water is removed under reduced pressure, and a small amount of fresh ferric chloride is added according to the actual measured ferric chloride (concentration, so that the total weight of the ferric chloride solution is maintained at about 35g, and the total The moles were kept around 66.0 mmol and then used for the next oxidation batch.

Example 6

At room temperature, 10.0 g (99.4% purity, 28.7 mmol) 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-di Hydrogen-1,2,4-triazolidine-5-thiocarbonyl-1-yl)-propan-2-ol, 22.5g organic phase recovered in previous batch Example 5, 5.0g fresh xylene and 35.0g ( 66.0 mmol) the aforementioned regenerated ferric chloride aqueous solution, added into a 250 mL four-necked flask and stirred evenly, then heated to between 80-100° C., and the reaction progress was monitored by HPLC. After the reaction was completed, the temperature was lowered to 10-20° C., and 9.95 g of solid was obtained after suction filtration and drying. HPLC analysis showed that the solid contained 98.4% 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2, 4-Triazol-5-thiocarbonyl-1-yl)-propan-2-ol. Therefore, the yield was calculated to be 99.1% of the theoretical value. The filtrate was separated to obtain 22.7 g of the organic phase and 35.5 g of the aqueous phase. The organic phase can be used directly as the solvent for the next batch of oxidation reactions. The water phase was regenerated according to the regeneration scheme of ferric chloride in Example 1 and used for the next batch of oxidation reactions.

Example 7

The difference between this example and Example 1 is only that the mass of toluene is 45 g, and prothioconazole is prepared. The yield of prothioconazole was 75.0%.

Example 8

The difference between this example and Example 1 is only that the mass of toluene is 10 g, and prothioconazole is prepared. The yield of prothioconazole was 72.0%.

Comparative Example 1

At room temperature, 1.8 g (0.005 mol) of 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2 ,4-triazolidine-5-thiocarbonyl-1-yl)-propan-2-ol, 40 mL of toluene and 10 mL of ethanol were stirred with 20 mL of ferric chloride with a concentration of 0.5 mol/L that had been slightly acidified with hydrochloric acid. Aqueous solution mix. The reaction mixture was stirred at room temperature for 6 hours, then the two phases were separated. The organic phase was washed twice with water and saturated aqueous sodium chloride solution, dried over sodium sulfate and concentrated under reduced pressure. This yielded 1.8 g of a solid which, by HPLC analysis, contained 94.8% of 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-di Hydrogen-1,2,4-triazol-5-thiocarbonyl-1-yl)-propan-2-ol. Therefore, the yield was calculated to be 99.2% of the theoretical value.

Comparative Example 2

At room temperature, 1.8 g (0.005 mol) of 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2 , 4-triazolidine-5-thiocarbonyl-1-yl)-propan-2-ol and 50 mL of ethanol were mixed with 20 mL of 0.5 mol/L ferric chloride aqueous solution slightly acidified with hydrochloric acid under stirring and cooling . The reaction mixture was stirred at room temperature for a further 2 hours, then poured into ice water and extracted with ethyl acetate. The organic phase was washed twice with water and saturated aqueous sodium chloride solution, dried over sodium sulfate and concentrated under reduced pressure. This yielded 1.74 g of a solid which, by HPLC analysis, contained 97.1% of 2-(1-chloro-cyclopropan-1-yl)-1-(2-chloro-phenyl)-3-(4,5- Dihydro-1,2,4-triazol-5-thiocarbonyl-1-yl)-propan-2-ol. Therefore, the yield was calculated to be 98.2% of the theoretical value.

From the comparison between Examples 7-8 and Example 1, it can be seen that too much solvent directly increases the dissolved amount of prothioconazole in the organic phase and reduces the primary yield; while too little solvent also reduces the final yield.

It can be seen from the comparison between Comparative Example 1 and Example 1 that the mixed solvent of ethanol and toluene in the comparative example can be used for the regeneration of ferrous chloride after separation, and the whole recovery process is relatively complicated; The ferrous chloride solution obtained by layering is regenerated.

From the comparison between Comparative Example 2 and Example 2, it can be seen that the use of esters as a solvent will cause a certain loss of decomposition of the esters, and the target substance in solid form can be obtained only after the solvent needs to be removed. To obtain the target substance with a content of more than 98%, the operation is more convenient.

The applicant declares that the present invention illustrates the preparation method of prothioconazole of the present invention through the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed method, that is, it does not mean that the present invention must rely on the above-mentioned detailed method to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims (8)

1. a preparation method of prothioconazole, is characterized in that, described preparation method comprises: compound shown in formula I and ferric chloride are carried out heterogeneous oxidation reaction in independent aromatic hydrocarbon solvent, leave standstill layering The organic phase and the water phase are obtained, and the organic phase is cooled to 10-20° C., filtered and dried to directly obtain the prothioconazole. The reaction formula is as follows:

The mass ratio of compound shown in described formula I and aromatic hydrocarbon solvent is 1:(2-3); Described aromatic hydrocarbon solvent is any one or the combination of at least two in toluene, xylene, trimethylbenzene, chlorobenzene or bromobenzene; The temperature of the heterogeneous oxidation reaction is 30-100°C. 2. preparation method according to claim 1, is characterized in that, the mol ratio of compound shown in described formula I and ferric chloride is 1:(2.0-5.0). 3. preparation method according to claim 1 is characterized in that, the mol ratio of compound shown in described formula I and ferric chloride is 1:(2.0-3.0). 4 . The preparation method according to claim 1 , wherein the temperature of the heterogeneous oxidation reaction is 30-50° C. 5 . 5. preparation method according to claim 1 is characterized in that, the time of described heterogeneous oxidation reaction is 5-12h. 6 . The preparation method according to claim 1 , wherein the water phase reacts with an oxidant to obtain ferric chloride after being acidified by an inorganic acid. 7 . 7. The preparation method according to claim 6, wherein the oxidant comprises any one of hydrogen peroxide, sodium hypochlorite or potassium permanganate. 8. preparation method according to any one of claim 1-7, is characterized in that, described preparation method comprises: compound shown in formula I and ferric chloride are in independent aromatic hydrocarbon solvent, in 30-100 Heterogeneous oxidation reaction is carried out at ℃ for 5-12h, and the organic phase and aqueous phase are obtained by standing. The aqueous phase is acidified with inorganic acid, and then reacted with the oxidant to obtain ferric chloride again. The organic phase is cooled to 10-20 ℃, filtered and dried. Then directly obtain the prothioconazole; the aromatic hydrocarbon solvent is any one or a combination of at least two of toluene, xylene, trimethylbenzene, chlorobenzene or bromobenzene.