A process for the preparation of a sulfonylurea of the formula (I) and intermediates thereof

Abstract

The present application relates to a kind of preparation method of furan sulfonyl ketone and its intermediate, with 2-chloro-3-methyl-4-methylsulfonyl benzoic acid as raw material, directly bromination is obtained 2-chloro-3-bromomethyl-4-methylsulfonyl benzoic acid;Then 2-chloro-3-bromomethyl-4-methylsulfonyl benzoic acid and tetrahydrofurfuryl alcohol substitution reaction is obtained 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl) methoxy) methyl) benzoic acid;Then intermediate acyl chloride is formed;Acyl chloride intermediate and cyclohexanedione are condensed under the action of triethylamine, finally catalyst acetone cyanohydrin is added and rearrangement reaction is obtained target product furan sulfonyl ketone.Compared with prior art, the present application reduces the esterification protection of raw material 2-chloro-3-methyl-4-methylsulfonyl benzoic acid in the step of preparing furan sulfonyl ketone and the deprotection step in subsequent step, and the bromide removed in the reaction can be recycled and reused, shorten the reaction step, improve the overall yield, more green and environmental protection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical synthesis, and particularly relates to a preparation method of tefuryltrione and intermediates thereof. BACKGROUND

[0002] Tefuryltrione, also known as tefuryl, chemical name: 2-{2-chloro-4-methylsulfonyl-3-[(RS)-tetrahydrofuran-2-ylmethoxymethyl]benzoyl}cyclohexane-1,3-dione, CAS registration number: 473278-76-1, is a benzoylcyclohexanedione herbicide developed by Bayer Company in cooperation with Beixing Chemical and National Federation of Agricultural Cooperatives.

[0003] The original research patent CN1323292A discloses the structure of tefuryltrione in Example 13, which is obtained by esterification of 2-chloro-3-methyl-4-methylsulfonylbenzoic acid to obtain methyl 2-chloro-3-methyl-4-methylsulfonylbenzoate, then brominating the hydrogen on the methyl group on the benzene ring with NBS in carbon tetrachloride solvent to obtain methyl 2-chloro-3-bromomethyl-4-methylsulfonylbenzoate, then reacting with tetrahydrofurfuryl alcohol under alkaline conditions of potassium tert-butoxide to form an ether, then hydrolyzing the ester group, and finally obtaining tefuryltrione through several reaction steps.

[0004] The patent CN109535106B discloses a preparation method of tefuryltrione, which is prepared from 2-chloro-3-methyl-4-methylsulfonylbenzoic acid as a raw material by esterification with methanol to generate methyl 2-chloro-3-methyl-4-methylsulfonylbenzoate; then one hydrogen in the methyl group on the benzene ring is replaced with bromine by reaction with NBS to generate methyl 2-chloro-3-methylbromide-4-methylsulfonylbenzoate; then the product methyl 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoate is synthesized by Williamson synthesis method; then condensation reaction is carried out with cyclohexanedione under the action of ethylenediamine to generate enol ester, and finally tefuryltrione is obtained by adding acetonitrile under the action of ethylenediamine.

[0005] In the preparation process route of tefuryltrione disclosed in the prior art, 2-chloro-3-methyl-4-methylsulfonylbenzoic acid is basically used as a synthetic intermediate, and the carboxyl group needs to be protected by esterification and then removed in the subsequent steps. In the bromination reaction step, NBS which is relatively expensive is used as a bromination reagent. The prior art has problems of long synthesis steps, low overall yield, expensive reagents, poor environmental protection, etc. SUMMARY

[0006] The technical problem solved by the present application is to solve the problems of long synthesis steps, low yield, expensive reagents and environmental protection of furansulfone in the prior art, and to provide a preparation method of furansulfone and intermediates thereof with short steps, high yield, low cost and environmental protection.

[0007] The present application provides a preparation method of furansulfone and intermediates thereof. The preparation method of furansulfone provided by the present application is to use 2-chloro-3-methyl-4-methylsulfonylbenzoic acid as raw material, directly perform bromination to obtain 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid; then 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid and tetrahydrofurfuryl alcohol undergo substitution reaction to obtain 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid; then the intermediate is acylated; the acyl chloride intermediate and cyclohexanedione undergo condensation reaction under the action of triethylamine, and finally the catalyst acetone cyanohydrin is added to perform rearrangement reaction to obtain the target product furansulfone.

[0008]

[0009] Specifically, the preparation method of furansulfone provided by the present application comprises the following steps:

[0010] (1) Synthesis of intermediate 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid: using 2-chloro-3-methyl-4-methylsulfonylbenzoic acid as raw material, bromination reagent is directly used for bromination in the presence of an acid catalyst to obtain 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid;

[0011] (2) Synthesis of intermediate 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid: 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid and tetrahydrofurfuryl alcohol undergo substitution reaction in the presence of a basic reagent to obtain 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid;

[0012] (3) Synthesis of intermediate 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid chloride: 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid is acylated to obtain 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid chloride;

[0013] (4) Synthesis of target product furansulfone: 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid chloride and cyclohexanedione undergo condensation reaction under the action of triethylamine; finally, the catalyst acetone cyanohydrin is added to perform rearrangement reaction to obtain the target product furansulfone.

[0014] More particularly, the preparation method of the sulfonylurea of the present application comprises the following steps:

[0015] (1) Synthesis of intermediate 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid: 2-chloro-3-methyl-4-methylsulfonylbenzoic acid is dissolved in an organic solvent, an acid catalyst is added, and a brominating reagent is slowly added under stirring at 45-70°C; after the reaction is completed, water is added to separate the phases, the organic phase is concentrated and crystallized, and solid-liquid separation is performed to obtain 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid;

[0016] (2) Synthesis of intermediate 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid: tetrahydrofurfuryl alcohol and a basic reagent are added to an organic solvent, and 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid is slowly added under stirring at 40-60°C; after the reaction is completed, the solvent is evaporated under reduced pressure, water is added under stirring, and then acidification is performed to precipitate white solids, which are filtered to obtain 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid; the filtrate is recovered for further processing;

[0017] (3) Synthesis of intermediate 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoyl chloride: 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid is dissolved in an appropriate amount of an organic solvent, thionyl chloride or oxalyl chloride is slowly added at room temperature, and the reaction is stirred at 45-60°C; after the reaction is completed, the solvent is evaporated under reduced pressure to obtain 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoyl chloride;

[0018] (4) Synthesis of the target product sulfonylurea: 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoyl chloride and cyclohexanedione are added to an organic solvent, an appropriate amount of triethylamine is added dropwise at 0-5°C, and the reaction is stirred at 5-10°C to obtain intermediate (3-oxocyclohex-1-en-1-yl)-2-chloro-4-methylsulfonyl-3-((2,2,2-trifluoroethoxy)methyl)benzoate; an appropriate amount of triethylamine and acetone cyanohydrin are added, the reaction is stirred, the reaction is detected to be complete, the organic phase is separated, the organic solvent is evaporated, and recrystallization is performed, followed by filtration and drying to obtain the sulfonylurea.

[0019] Further, the organic solvent in step (1) is carbon tetrachloride, DMF, dichloroethane, dibromoethane, chloroform, etc., and is preferably dichloroethane; the amount of the organic solvent is 3-8 times, and preferably 3-5 times, the weight of the raw material 2-chloro-3-methyl-4-methylsulfonylbenzoic acid.

[0020] Further, the bromination reagent in step (1) is NBS, bromine, bromine water, (hydrogen bromide + hydrogen peroxide) or sodium bromide solution, etc., and bromine is preferred.

[0021] Further, the acid catalyst in step (1) is sulfuric acid, nitric acid, hydrochloric acid, acetic acid, etc., and sulfuric acid is preferred.

[0022] Further, the reaction temperature in step (1) is 55-65°C, and 60°C is preferred.

[0023] Further, the basic reagent in step (2) is K2CO3, NaOH, KOH, Na2CO3, etc., and NaOH or KOH is preferred.

[0024] Further, the organic solvent in step (2) is DMF, dichloroethane, acetonitrile, toluene, etc., and dichloroethane is preferred; the amount of the organic solvent is 3-5 times.

[0025] Further, the organic solvent in step (3) is dichloroethane, dichloromethane, chloroform, DMF, etc., and dichloroethane is preferred.

[0026] Further, the organic solvent in step (4) is dichloroethane, dichloromethane, chloroform, DMF, etc., and dichloroethane is preferred.

[0027] Further, the extraction operation in step (4) is first to add sulfuric acid solution for extraction, separate the organic phase, and then add sodium hypochlorite aqueous solution to the organic phase, and separate the organic phase.

[0028] Further, the solvent for recrystallization in step (4) is methanol, ethanol, acetone, dichloroethane, dichloromethane, chloroform, etc., and methanol is preferred.

[0029] As a further improvement of the present application, the bromide ion in the reaction solution in step (2) of the present application is recovered and reused for the bromination reaction of the raw material 2-chloro-3-methyl-4-methylsulfonylbenzoic acid. - The recovered bromide ion can be reused, and the bromination reaction of the raw material 2-chloro-3-methyl-4-methylsulfonylbenzoic acid can be repeated.

[0030] Specifically, the operation for recovering and reusing the bromide ion is as follows: the filtrate in step (2) is measured for bromide ion concentration by ion chromatography, the filtrate is concentrated, an organic solvent is added, the bromine content is calculated according to the measured bromide ion concentration, an appropriate amount of 2-chloro-3-methyl-4-methylsulfonylbenzoic acid is added, an acid catalyst is added, the temperature is raised to 50-70°C, excess hydrogen peroxide is slowly added dropwise, the temperature is maintained until the reaction is complete, the reaction solution is cooled to room temperature, and the reaction solution is neutralized with sodium sulfite until it is free of oxidizing property, the organic layer is taken, the organic layer is washed with water, concentrated, recrystallized, and the intermediate 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid is obtained.

[0031] Furthermore, the organic solvent used in the bromide ion recovery operation is carbon tetrachloride, DMF, dichloroethane, dibromoethane, chloroform, etc., preferably dichloroethane; the amount of organic solvent used is 3 to 8 times the weight of the raw material 2-chloro-3-methyl-4-methanesulfonylbenzoic acid, preferably 3 to 5 times.

[0032] Furthermore, the acid catalyst used in the bromide ion recovery operation is sulfuric acid, nitric acid, hydrochloric acid, acetic acid, etc., with sulfuric acid being preferred.

[0033] Furthermore, the solvent used for recrystallization in the ion recovery operation is methanol, ethanol, acetone, dichloroethane, dichloromethane, chloroform, etc., with methanol being preferred.

[0034] The beneficial effects achieved by this invention are as follows: Compared with the prior art, this invention reduces the esterification protection of the raw material 2-chloro-3-methyl-4-methanesulfonylbenzoic acid and the deprotection step in the subsequent steps in the preparation of furazolidone. Furthermore, the bromide ions removed in the reaction can be recovered and reused, which shortens the reaction steps, improves the overall yield, and is more environmentally friendly. Detailed Implementation

[0035] The present invention will be described in more detail below with reference to the embodiments.

[0036] Example 1

[0037] This embodiment relates to the preparation of 2-chloro-3-bromomethyl-4-methanesulfonylbenzoic acid, a synthetic intermediate for furazolidone, and the specific steps are as follows:

[0038] 20 g (0.08 mol) of 2-chloro-3-methyl-4-methanesulfonylbenzoic acid, 70 ml of dichloroethane solvent, and catalyst were added to a 500 ml three-necked flask. The temperature was raised to 60 °C, and the brominating reagent was slowly added while maintaining the temperature at 60 °C. After the brominating reagent was added, the reaction was continued at 60 °C for 0.5 h. The temperature was then cooled to 30 °C and neutralized with excess sodium sulfite until no oxidizing agent was present. The aqueous layer was separated, and the organic layer was washed once with an appropriate amount of water. The aqueous phase was separated, and the organic phase was concentrated to obtain crude 3-bromomethyl-2-chloro-4-methanesulfonylbenzoic acid. The crude product was slurried with 40 g of methanol, filtered to obtain a solid, and the content of the target intermediate in the solid was analyzed to calculate the reaction yield.

[0039] Table 1 below shows the effect of different catalysts and brominating agents on the reaction yield.

[0040] Table 1 Effect of catalyst and brominating agent on reaction yield

[0041]

[0042] Example 2

[0043] This example relates to the preparation of furametpyr, which is prepared according to the following steps:

[0044] (1) Into a 500ml three-necked flask, add 2-chloro-3-methyl-4-methanesulfonylbenzoic acid 20g (0.08mol), dichloroethane 70ml and concentrated sulfuric acid 3.94g (0.04mol), heat to 60°C, start to add bromine 14.06g (0.088mol) slowly, control the temperature at 60°C, then continue to heat at 60°C for 0.5h until the reaction is complete, cool to 30°C and neutralize with excess sodium sulfite until no oxidation, separate the water layer, continue to wash the organic layer with 10ml of clean water once, separate the water phase, concentrate the organic phase to get 3-bromomethyl-2-chloro-4-methanesulfonylbenzoic acid crude product, slurry the crude product with 40g of methanol, and filter to get 30.0g of solid, with a product content of 85.0%.

[0045] (2) At 25°C, add dichloroethane 100g, tetrahydrofurfuryl alcohol 20.0g (0.2mol), sodium hydroxide 4.0g (0.1mol) to a 500ml three-necked flask, slowly add 3-bromomethyl-2-chloro-4-methanesulfonylbenzoic acid 30.0g (85%, 0.0778mol) obtained in step (1), control the temperature at 60°C, react for 1h, then take a sample to detect the completion of the reaction, evaporate the organic phase, add 60g of water and stir to dissolve, slowly add hydrochloric acid solution (31%) at 25°C, white solid precipitates, drop for 20min, continue to stir for 0.5h, filter and dry (filtrate 72g, to be recycled for bromide ions), get 26.9g of solid, with a product content of 97.2%.

[0046] (3) Into a dry 500ml reaction flask, add 2-chloro-4-methanesulfonyl-3-((2,2,2-trifluoroethoxy)methyl)benzoic acid (26.9g / 97.2%, 0.075mol), dichloroethane 80g, stir and heat to 50°C, slowly add thionyl chloride (11.75g, 0.098mol), after dropping, heat for 2h until the reaction is complete, evaporate the solvent under reduced pressure to get 2-chloro-4-(methanesulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoyl chloride 27.9g (content not measured).

[0047] (4) In 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl) benzoyl chloride 27.9 g, dichloroethane 60 g and 1,3-cyclohexanedione 9 g (0.078 mol) were added, and the temperature was controlled at 0°C. Triethylamine (23 g, 0.22 mol) was added dropwise. After the dropwise addition was completed, the reaction was maintained at 5°C for 30 min to obtain intermediate (3-oxocyclohex-1-en-1-yl)-2-chloro-4-methylsulfonyl-3-((2,2,2-trifluoroethoxy)methyl)benzoate. Then, triethylamine 18.9 g (0.18 mol) and acetone cyanohydrin 1 g (0.012 mol) were added, and the reaction was maintained at 10°C for 2 h. After the reaction was detected to be complete, 30 g (20%) of sulfuric acid solution was added, and the mixture was stirred for 30 min. The organic phase was separated. Then, 15 g of 2% sodium hypochlorite aqueous solution was added, and the mixture was stirred for 15 min. The organic phase was separated, dichloroethane was distilled off, 30 g of methanol was added, and the mixture was recrystallized by stirring. After 30 min, the temperature was lowered to 5°C. The mixture was filtered and dried to obtain 31.2 g of white solid, with a content of 98.5%. The total yield of furametpyra- zole was calculated to be 86.7%.

[0048] Example 3

[0049] This example relates to the preparation of furametpyrazole, and the preparation steps are as follows:

[0050] The preparation of furametpyrazole was carried out according to the steps and solvent amounts, and various parameters of Example 2. The difference between this example and Example 2 is that KOH was used instead of NaOH in step (2), and oxalyl chloride was used instead of thionyl chloride in step (3).

[0051] As a result, 27.6 g of the target product furametpyrazole was obtained, with a content of 97.2%. The total yield of furametpyrazole was calculated to be 75.7%.

[0052] Example 4

[0053] This example relates to the recycling of bromide ions, and the specific operation is as follows:

[0054] In the process of preparing 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid in step (2) of the above embodiment 2, after the 72 g filtrate was determined by ion chromatography, the concentration of bromide ion was calculated to be 0.97 mmol / g. According to the concentration of bromide ion, the corresponding material ratio in the bromination in example 1 was calculated. The filtrate was concentrated, and then 27.8 ml of dichloroethane was added to the concentrated filtrate. 7.95 g (0.03 mol) of 2-chloro-3-methyl-4-methylsulfonylbenzoic acid and 1.56 g (0.015 mol) of concentrated sulfuric acid were added. The temperature was raised to 60°C, and 4.74 g (0.04 mol) of 27% hydrogen peroxide was slowly added dropwise. The dropwise addition was performed for 5 h, and then the reaction was continued at 60°C for 30 min until the reaction was complete. The reaction solution was cooled to room temperature, and then neutralized with excess sodium sulfite until no oxidation occurred. The aqueous layer was separated, and the organic layer was washed with an appropriate amount of water once. The water phase was separated, and the organic phase was concentrated to obtain 3-bromomethyl-2-chloro-4-methylsulfonylbenzoic acid. The crude product was slurried with 16 g of methanol, and then filtered to obtain 12.40 g of solid with a content of 80.0% and a yield of 98.1%.

[0055] It was calculated that the equivalent amount of 3-bromomethyl-2-chloro-4-methylsulfonylbenzoic acid had a bromide ion recovery rate of 89.7%, and could be reused in the bromination of the raw material 2-chloro-3-methyl-4-methylsulfonylbenzoic acid.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can modify the technical solutions described in the above embodiments, or make equivalent substitutions for part or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solution to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing furazolidone, characterized in that, The method comprises the following steps: (1) synthesis of intermediate 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid: 2-chloro-3-methyl-4-methylsulfonylbenzoic acid is used as raw material, and bromination is directly performed on the 2-chloro-3-methyl-4-methylsulfonylbenzoic acid in the presence of an acid catalyst to obtain 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid; the acid catalyst is sulfuric acid, and the bromination reagent is bromine; (2) synthesis of intermediate 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid: 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid and tetrahydrofurfuryl alcohol are subjected to substitution reaction in the presence of a basic reagent to obtain 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid; (3) synthesis of intermediate 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoyl chloride: 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid is subjected to acyl chloride treatment to obtain 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoyl chloride; (4) synthesis of target product furanilide: 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoyl chloride is subjected to condensation reaction with cyclohexanedione in the presence of triethylamine; finally, a catalyst, acetone cyanohydrin, is added to perform rearrangement reaction, and the target product furanilide is obtained.

2. The process for the preparation of the funfracloxpyr according to claim 1, characterized in that, The specific operation of step (1) is as follows: 2-chloro-3-methyl-4-methylsulfonylbenzoic acid is dissolved in an organic solvent, a concentrated sulfuric acid catalyst is added, bromine is slowly added under stirring at 45-70 DEG C, and after the reaction is completed, water is added to separate the phases, the organic phase is concentrated and crystallized, and solid-liquid separation is performed to obtain 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid; The specific operation of step (2) is as follows: tetrahydrofurfuryl alcohol and a basic reagent are added to an organic solvent, 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid is slowly added, stirring is performed at 40-60 DEG C, after the reaction is completed, the solvent is distilled off under reduced pressure, water is added to dissolve the clear solution, then acidification treatment is performed, white solids are precipitated, filtration is performed to obtain 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid, and the filtrate is recovered for treatment; The specific operation of step (3) is as follows: 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoic acid is dissolved in an appropriate amount of an organic solvent, thionyl chloride or oxalyl chloride is slowly added at room temperature, stirring is performed under heating to 45-60 DEG C, after the reaction is completed, the solvent is distilled off under reduced pressure, and 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl)benzoyl chloride is obtained; And / or the specific operation of the step (4) is: 2-chloro-4-(methylsulfonyl)-3-(((tetrahydrofuran-2-yl)methoxy)methyl) benzoyl chloride and cyclohexanedione are added into an organic solvent, an appropriate amount of triethylamine is added dropwise at 0-5 °C, and the reaction is stirred at 5-10 °C to obtain an intermediate (3-oxocyclohex-1-en-1-yl)-2-chloro-4-methylsulfonyl-3-((2,2,2-trifluoroethoxy)methyl) benzoate; then an appropriate amount of triethylamine and acetone cyanohydrin are added and stirred to react, the reaction is detected to be complete, the organic phase is extracted and separated, the organic solvent is distilled off, and recrystallization is performed, and the solid is dried by suction filtration to obtain furan sulfonyl ketone.

3. The method for preparing furazolidone as described in claim 1 or 2, characterized in that, The basic reagent in the step (2) is NaOH or KOH.

4. The process for the preparation of the funfracloxpyr according to claim 2, characterized in that, The extraction operation in the step (4) is first to add a sulfuric acid solution for extraction, and then sodium hypochlorite aqueous solution is added to the organic phase, and the organic phase is separated.

5. The method of preparing the funfrxloxyfop of claim 1 or 2, characterized in that, The organic solvent used in the reactions of the steps (1)-(4) is dichloroethane.

6. A process for the preparation of the intermediate of the furan carboxamide, 2-chloro-3-bromomethyl-4-methanesulfonylbenzoic acid, according to claim 1 or 2, characterized in that: 2-chloro-3-methyl-4-methylsulfonylbenzoic acid is dissolved in an organic solvent, sulfuric acid is added as a catalyst, and bromine is slowly added and stirred at 45-70 °C; after the reaction is complete, water is washed to separate the phases, the organic phase is concentrated and crystallized, and solid-liquid separation is performed to obtain 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid.

7. The method for recovering bromide ions in the filtrate as claimed in step (2) of claim 2, characterized by: After the filtrate in the step (2) is determined for bromide ion concentration by ion chromatography, the filtrate is concentrated, dichloromethane is added as an organic solvent, the bromine content is calculated according to the determined bromide ion concentration, an appropriate amount of 2-chloro-3-methyl-4-methylsulfonylbenzoic acid is added, sulfuric acid is added as a catalyst, the temperature is increased to 50-70 °C, and excess hydrogen peroxide is slowly added dropwise, the temperature is maintained until the reaction is complete, the temperature is cooled to room temperature, the reaction solution is neutralized with sodium sulfite until it is not oxidizing, the organic layer is taken, the organic layer is washed with water, concentrated, and recrystallized to obtain the intermediate 2-chloro-3-bromomethyl-4-methylsulfonylbenzoic acid.

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