Method for catalytically synthesizing propiconazole by using ionic liquid

Abstract

The invention belongs to the field of chemical production, and particularly relates to a method for catalytically synthesizing propiconazole by using ionic liquid. And carrying out condensation reaction on the brominated substance 2-bromomethyl-2-(2, 4-dichlorophenyl)-4-propyl-1, 3-dioxopentane and triazole under the catalysis of the ionic liquid to generate propiconazole. The ionic liquid is one of [Emim] BF4, [Emim] PF6, [BMIM] PF6 and [BMIM] OH. According to the invention, the imidazole cation ionic liquid is used as a catalyst and a solvent to catalyze the N-alkylation reaction of 2-bromomethyl-2-(2, 4-dichlorophenyl)-4-propyl-1, 3-dioxopentane and triazole, and the research finds that the alkaline imidazole cation liquid has good catalytic performance, high yield and good selectivity, and can be used as a catalyst for catalyzing the N-alkylation reaction of 2-bromomethyl-2-(2, 4-dichlorophenyl)-4-propyl-1, 3-dioxopentane and triazole. And the reaction conditions are mild, the operation is simple, the ionic liquid is easy to recover, and the catalytic activity is not obviously reduced after being applied for five times.

Description

Technical Field

[0001] The invention belongs to the field of chemical production, and specifically relates to a method for synthesizing propiconazole by catalysis of ionic liquid. Background Art

[0002] Propiconazole is a systemic triazole fungicide with both protective and therapeutic effects. It can effectively prevent and treat diseases caused by most higher fungi. Propiconazole has the characteristics of a wide spectrum of fungicides, high activity, fast fungicidal speed, long lasting effect, and strong systemic conductivity. It has become a representative variety of the world's emerging broad-spectrum triazole fungicides with large tonnage, and is a special fungicide for economic crops. Propiconazole belongs to the triazole fungicide class of sterol inhibitors. Its mechanism of action is to affect the biosynthesis of sterols, destroy the cell membrane function of pathogens, and eventually lead to cell death, thereby achieving the effects of sterilization, disease prevention and treatment.

[0003] The current process mainly uses intermediates 2,4-dichloroacetophenone, pentanediol, bromine, triazole, etc. as main raw materials, and obtains high-purity finished products through cyclization, bromination, condensation, high-vacuum distillation or salt purification. There are four steps in total, with a total yield of about 70%, a technical content of 95%, and a light yellow viscous liquid.

[0004] At present, the existing production methods have the following disadvantages: 1) the reaction time is long when synthesizing triazole salts, the material is sticky, and it is difficult to dehydrate; 2) the condensation reaction time is long, and the by-products cannot be recovered after washing with water after the reaction, resulting in a large amount of wastewater; 3) the reaction conditions are harsh and the product separation is complicated. Therefore, it is very necessary to establish an effective and environmentally friendly synthesis method.

[0005] Chinese patent CN 113444077 A discloses a method for producing propiconazole technical, which uses 2,4-dichloroacetophenone and 1,2-pentanediol for cyclization, then bromination reaction with bromine to generate 2-bromomethyl-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, and then condensation reaction with 1,2,4-triazole in a solvent, alkali and phase transfer catalyst to obtain propiconazole. This method for producing propiconazole uses an organic solvent, which is polluting; alkali is added during the condensation reaction, and the subsequent process needs to recover the by-product, which is complicated.

[0006] Ionic liquids refer to salts composed of organic cations and inorganic anions or organic anions, which are liquid at room temperature or near room temperature, also known as room temperature molten salts. Compared with traditional solvents, ionic liquids have many excellent properties and are considered to be green solvents that can replace volatile organic solvents in many fields; common cations include quaternary ammonium ions, quaternary phosphonium ions, imidazolium ions, pyridinium ions, etc.; anions include halogen ions, tetrafluoroborate ions, hexafluorophosphate ions, etc.; compared with traditional organic solvents, ionic liquids have the following advantages:

[0007] 1) It has good solubility for inorganic substances, organic substances, and some polymers;

[0008] 2) Room temperature ionic liquids are usually liquid in the range of 300°C;

[0009] 3) Almost no vapor pressure, non-volatile;

[0010] 4) Convenient for recycling;

[0011] 5) Ionic liquids have variable Lewis / Bronsted acidity and alkalinity, and a wide pH adjustment range;

[0012] There are reports that alkaline ionic liquid [BMIM]OH (1-butyl-3-methylimidazole hydroxide) is used in Knoevenagel condensation, Markovnikov and Michael addition, Mannich addition and Perkin reaction. However, there are no reports on the synthesis of propiconazole using ionic liquid as catalyst. Summary of the invention

[0013] The technical problem to be solved by the present invention is to solve the disadvantages of using organic toxic solvents and catalysts in the current process, high reaction temperature, harsh conditions, long reaction time, difficult product separation, etc. The present process uses ionic liquids as solvents and catalysts in the synthesis of propiconazole, which increases the reaction rate, makes the reaction conditions milder, is simple to operate, has a high reaction yield, and reduces production costs.

[0014] In order to realize the catalytic synthesis of propiconazole by ionic liquid, the present invention adopts the following scheme: the bromide 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane and triazole are subjected to condensation reaction under the catalysis of ionic liquid to generate propiconazole.

[0015] Furthermore, the bromide 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane and triazole undergo condensation reaction in the presence of water under the catalysis of ionic liquid to produce propiconazole.

[0016] In the condensation reaction, the ionic liquid is one of [Emim]BF4, [Emim]PF6, [BMIM]PF6, and [BMIM]OH, and the molar ratio of the ionic liquid to 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane is 0.2:1 to 0.8:1.

[0017] Further, the molar ratio of the ionic liquid to 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane is 0.2:1 to 0.4:1.

[0018] In the condensation reaction, the molar ratio of triazole to 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane is 0.90-1.10:1.

[0019] Furthermore, in the condensation reaction, the molar ratio of triazole to 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane is 0.98-1.02:1.

[0020] The condensation reaction temperature is 80-100°C.

[0021] The preparation method of the brominated product 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane is as follows: 2,4-dichloroacetophenone and 1,2-pentanediol are used as raw materials, and a cyclization reaction is carried out in the presence of a solvent A and a solid acid catalyst to generate a cyclized product, and the cyclized product is subjected to a bromination reaction with bromine to generate the brominated product 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane.

[0022] Further, the specific steps are as follows:

[0023] (1) Cyclization reaction: 2,4-dichloroacetophenone and 1,2-pentanediol are subjected to cyclization reaction under reflux at elevated temperature in the presence of solvent A and a solid acid catalyst. After the reaction is completed, the solid acid catalyst is recovered by cooling to obtain a filtrate containing 2-methyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane;

[0024]

[0025] (2) Bromination reaction: Bromine is added dropwise to the filtrate containing the cyclized product to carry out bromination reaction. After the reaction is completed, the reaction solution is washed with alkali and the solvent A is simply evaporated to obtain the brominated product 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane;

[0026]

[0027] (3) Condensation reaction: The bromide 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane is reacted with triazole in the presence of water, catalyzed by an ionic liquid, and heated to 80-100°C for condensation reaction. After the reaction, the mixture is extracted with solvent B, and solvent B is evaporated to obtain propiconazole.

[0028]

[0029] The solid acid catalyst is one of phosphomolybdic acid, phosphotungstic acid and p-toluenesulfonic acid.

[0030] After the reaction is completed, the solid acid catalyst obtained by filtration is washed with water and then recovered.

[0031] The solvent A is one or more of benzene, toluene or cyclohexane; the solvent B is one or more of dichloromethane, dichloroethane, chloroform and tetrahydrofuran.

[0032] In the cyclization reaction, the molar ratio of 2,4-dichloroacetophenone, 1,2-pentanediol and solid acid catalyst is 1:1.05-1.20:0.02-0.04.

[0033] In the bromination reaction, the molar ratio of bromine to 2,4-dichloroacetophenone is 1:1 to 1.5:1; and the bromination reaction temperature is 20-40°C.

[0034] The present invention uses an ionic liquid of an imidazolium cation as a catalyst and solvent to catalyze the N-alkylation reaction of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane with triazole. Studies have shown that the alkaline imidazolium cation liquid has good catalytic performance, high yield, good selectivity, mild reaction conditions, simple operation, and easy recovery of the ionic liquid. The catalytic activity is not significantly reduced after five applications. Compared with the existing propiconazole synthesis process, the present invention has the following advantages:

[0035] 1) The ionic liquid used in the present invention has high catalytic activity and good selectivity;

[0036] 2) The alkaline ionic liquid used in the present invention is liquid at room temperature, has good solubility in the reaction raw materials, and does not require the addition of organic solvents during the reaction, which is more environmentally friendly;

[0037] 3) The ionic liquid used in the present invention has low vapor pressure and good thermal stability. After the reaction is completed, the product can be separated by simple distillation or extraction, and the ionic liquid catalyst can be recycled. DETAILED DESCRIPTION

[0038] The specific implementation of the technical solution of the present invention is described in detail below in conjunction with embodiments:

[0039] Examples 1 and 2 are the synthesis of brominated products, which specifically require two reactions, cyclization and bromination, and the reaction equations are as follows:

[0040] Cyclization reaction:

[0041]

[0042] Bromination reaction:

[0043]

[0044] Embodiment 1:

[0045] (1) Cyclization reaction: 138.5 g of cyclohexane, 100 g of 2,4-dichloroacetophenone, 59.5 g of 1,2-pentanediol and 2.4 g of p-toluenesulfonic acid were added into a 500 ml four-necked bottle, stirred and heated to reflux for reaction, and when the chromatographic analysis showed that 2,4-dichloroacetophenone was less than 1.0%, the reaction was stopped; the reaction solution was cooled to room temperature, filtered to recover the solid acid, and the obtained filtrate was used for the next step of reaction;

[0046] (2) Bromination reaction: 85 g of bromine was added dropwise to the filtrate obtained by the cyclization reaction at 20-40° C. During the addition process, a sample was taken for chromatographic analysis and the result was that 2-methyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane was less than 1.0%, and the reaction was stopped. The reaction solution was washed with 24% KOH solution to remove the generated HBr until the pH was ≥12. The residual material was simply evaporated under negative pressure on a rotary evaporator to remove the cyclohexane solvent, and 185 g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane was obtained, with a content of 96.4% and a yield of 95.22%.

[0047] Embodiment 2:

[0048] (1) Cyclization reaction: 138.5 g of benzene, 100 g of 2,4-dichloroacetophenone, 59.5 g of 1,2-pentanediol, and 57.6 g of phosphotungstic acid were added into a 500 ml four-necked bottle, stirred, heated and refluxed for reaction, and the sample was taken for chromatographic analysis. If 2,4-dichloroacetophenone was less than 1.0%, the reaction was stopped; the reaction solution was cooled to room temperature, filtered to recover the solid acid, and the obtained filtrate was used for the next step of reaction;

[0049] (2) Bromination reaction: 86 g of bromine was added dropwise to the filtrate obtained by the cyclization reaction at 20-40° C. During the addition process, sampling was performed and chromatographic analysis showed that 2-methyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane was less than 1.0%, and the reaction was stopped. The reaction solution was washed with 24% KOH solution to remove the generated HBr until the pH was ≥12. The residual material was simply evaporated under negative pressure on a rotary evaporator to remove the cyclohexane solvent, to obtain 186 g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, with a content of 97.0% and a yield of 96.33%.

[0050] Examples 3-12 are condensation syntheses, which mainly explore the effects of different types of catalysts on the reaction. The reaction equations are as follows:

[0051] Condensation reaction

[0052]

[0053] Embodiment 3:

[0054] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 5.92g of KOH, and 17.76g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 183.5g of residue, in which the content of propiconazole was 11.20% and the yield was 11.36%.

[0055] Embodiment 4:

[0056] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 12.92N,N-dimethylpyridine, and 38.77g of water were added, and the mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane, and the extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 182.4g of residue, in which the content of propiconazole was 0.48%, and the residue was basically unreactive.

[0057] Embodiment 5:

[0058] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 17.61g of tetraethylammonium chloride, and 52.82g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 186.4g of residue. The content of propiconazole in the residue was 0.15%, which was basically unreactive.

[0059] Embodiment 6:

[0060] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 34.09g of tetrabutylammonium bromide, and 102.27g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 184.2g of residue. The content of propiconazole in the residue was 0.89%, which was basically unreactive.

[0061] Embodiment 7:

[0062] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 24.91g of [BMIM]HSO4, and 74.73g of water were added, and the mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane, and the extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 184.3g of residue, in which the content of propiconazole was 15.2% and the yield was 15.48%.

[0063] Embodiment 8:

[0064] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 18.54g of [BMIM]Cl, and 55.63g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 182.4g of residue, in which the content of propiconazole was 18.4% and the yield was 18.55%.

[0065] Embodiment 9:

[0066] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 23.23g of [BMIM]Br, and 69.68g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 181.4g of residue, in which the content of propiconazole was 20.4%, and the yield was 20.45%.

[0067] Embodiment 10:

[0068] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 16.48g of [BMIM]OH, and 49.45g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 186.5g of residue. The content of propiconazole in the residue was 94.05%, and the yield was 96.95%.

[0069] Embodiment 11:

[0070] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 29.97g of [BMIM]PF6, and 89.90g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 182.4g of residue. The content of propiconazole in the residue was 46.14%, and the yield was 46.52%.

[0071] Embodiment 12:

[0072] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 20.98g of [Emim] BF4, and 62.93g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 182.4g of residue, in which the content of propiconazole was 48.42% and the yield was 48.82%.

[0073] Based on the above experiments, the effects of different catalysts on reaction activity and yield are shown in Table 1:

[0074] Table 1: Reaction of different catalysts in Examples 3-12

[0075]

[0076] From the results, the alkaline ionic liquid [BMIM]OH has the highest catalytic activity and the highest yield for the N-alkylation of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane with triazole. However, inorganic ionic alkaline liquids and acidic and neutral ionic liquids have low or almost no catalytic activity for this reaction.

[0077] Examples 13-16 are exploratory experiments on the effect of the amount of catalyst on the reaction during the synthesis of propiconazole:

[0078] Embodiment 13:

[0079] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 8.25g of [BMIM]OH, and 24.75g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 182.4g of residue, in which the content of propiconazole was 62.14% and the reaction yield was 62.65%.

[0080] Embodiment 14:

[0081] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 16.50g of [BMIM]OH, and 49.50g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 186.0g of residue, in which the content of propiconazole was 94.11% and the reaction yield was 96.75%.

[0082] Embodiment 15:

[0083] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 41.26g of [BMIM]OH, and 123.78g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 185.2g of residue. The content of propiconazole in the residue was 94.13%, and the reaction yield was 96.36%.

[0084] Embodiment 16:

[0085] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 66.02g of [BMIM]OH, and 198.06g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 185.8g of residue. The content of propiconazole in the residue was 94.24%, and the reaction yield was 96.78%.

[0086] Based on the above experiments, the effects of different catalyst amounts on reaction activity and yield are shown in Table 2:

[0087] Table 2 Effect of different catalyst amounts on reaction activity and yield

[0088]

[0089] It can be seen from the data in Table 2 that when the molar ratio of catalyst to bromide is in the range of 0.2 to 0.8, a very good catalytic effect can be achieved.

[0090] Example 17 is an exploratory experiment on the effect of the number of times the ionic liquid catalyst is applied on the reaction:

[0091] Embodiment 17:

[0092] In a 1000ml four-necked bottle, 187.3g of 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane, 36.5g of triazole, 16.5g of [BMIM]OH, and 49.5g of water were added. The mixture was stirred and heated to 80°C for 4 hours. The reaction solution was extracted three times with 360g of dichloroethane. The extracts were combined and dichloroethane was simply evaporated under negative pressure on a rotary evaporator to obtain 185.9g of residue. The content of propiconazole in the residue was 94.15%, and the reaction yield was 96.74%.

[0093] The raffinate is added with 48% potassium hydroxide to adjust the pH to 9-11, and a large amount of water is removed by negative pressure. The temperature is continued to be raised to air-drain the water until there is basically no gasification, and the solid salt is filtered out at a lower temperature. The filtrate is an ionic liquid and is reused. The experiment verified that the ionic liquid still has good reaction activity for the N-alkylation reaction after five applications; as shown in Table 3:

[0094] Table 3 Effect of catalyst recycling on reaction activity and yield

[0095]

[0096] It can be seen from the above cycle experiment that the alkaline ionic liquid catalyst of the present application can still achieve a yield of 96.42% when recycled for 5 times, and the activity of the catalyst is basically not affected.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing propiconazole using ionic liquid catalysis, characterized in that: The bromide 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane and triazole undergo condensation reaction under the catalysis of ionic liquid to produce propiconazole.

2. The method according to claim 1, characterized in that In the condensation reaction, the ionic liquid is one of [Emim]BF4, [Emim]PF6, [BMIM]PF6, and [BMIM]OH, and the molar ratio of the ionic liquid to 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane is 0.2:1 to 0.8:

1.

3. The method according to claim 1, characterized in that: In the condensation reaction, the molar ratio of triazole to 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane is 0.90-1.10:

1.

4. The method according to claim 1, characterized in that The condensation reaction temperature is 80-100°C.

5. The method according to claim 1, characterized in that The preparation method of the brominated product 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane is as follows: 2,4-dichloroacetophenone and 1,2-pentanediol are used as raw materials, and a cyclization reaction is carried out in the presence of a solvent A and a solid acid catalyst to generate a cyclized product, and the cyclized product is subjected to a bromination reaction with bromine to generate the brominated product 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane.

6. The method according to claim 1, characterized in that The specific steps are as follows: (1) Cyclization reaction: 2,4-dichloroacetophenone and 1,2-pentanediol are subjected to cyclization reaction under reflux at elevated temperature in the presence of solvent A and a solid acid catalyst. After the reaction is completed, the solid acid catalyst is recovered by cooling to obtain a filtrate containing 2-methyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane; (2) Bromination reaction: Bromine is added dropwise to the filtrate containing the cyclized product to carry out bromination reaction. After the reaction is completed, the reaction solution is washed with alkali and the solvent A is simply evaporated to obtain the brominated product 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane; (3) Condensation reaction: The bromide 2-bromomethyl-2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolane is reacted with triazole in the presence of water, catalyzed by an ionic liquid, and heated to 80-100°C for condensation reaction. After the reaction, the mixture is extracted with solvent B, and solvent B is evaporated to obtain propiconazole.

7. The method according to claim 6, characterized in that: The solid acid catalyst is one of phosphomolybdic acid, phosphotungstic acid and p-toluenesulfonic acid.

8. The method according to claim 6, characterized in that: The solvent A is one or more of benzene, toluene or cyclohexane; the solvent B is one or more of dichloromethane, dichloroethane, chloroform and tetrahydrofuran.

9. The method according to claim 6, characterized in that: In the cyclization reaction, the molar ratio of 2,4-dichloroacetophenone, 1,2-pentanediol and solid acid catalyst is 1:1.05-1.20:0.02-0.

04.

10. The method according to claim 2, characterized in that: In the bromination reaction, the molar ratio of bromine to 2,4-dichloroacetophenone is 1:1 to 1.5:1; and the bromination reaction temperature is 20-40°C.

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