Synthesis method of saflufenacil intermediate

Abstract

The invention provides a synthesis method of a saflufenacil intermediate V. The synthesis method comprises the following steps: in the presence of a chlorination reagent and a catalyst, synthesizing a compound V from a compound IV; belongs to the field of pesticide synthesis. According to the method, the adopted initial raw materials are relatively cheap, easy to obtain and low in cost; the reaction steps are simple to operate, the conditions are mild, the reaction can be continuously carried out in the same reaction kettle, and the problems of harsh reaction conditions and high cost in some synthesis processes are solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of pesticide synthesis, and relates to a synthesis method of a pyroxsulam intermediate. BACKGROUND

[0002] As a herbicide, pyroxsulam has wide crop suitability, can effectively kill broadleaf weeds, and can prevent weeds resistant to glyphosate and triazines, and has the characteristics of rapid degradation. Although there are currently processes for synthesizing pyroxsulam, the existing synthesis processes have the problems of long synthesis route, harsh conditions, high risk, low yield of intermediates, low yield of products, large amount of waste, and difficulty in large-scale production.

[0003] Therefore, it has been a research focus and goal in the field to seek an intermediate for synthesizing pyroxsulam or a process for synthesizing pyroxsulam, which has low cost, mild synthesis conditions, easy operation, and high product yield. At present, the synthesis of pyroxsulam mainly uses 2-chloro-4-fluorobenzoic acid as a starting material, and is subjected to esterification, nitration, nitro reduction to obtain 5-amino-2-chloro-4-fluoroethyl benzoate, and then is subjected to acylation, cyclization, methylation, hydrolysis, and acyl chloride to obtain the target compound pyroxsulam by reacting with N-methyl-N-isopropyl sulfonamide. However, the synthesis process has the problems of long synthesis route, low product yield, and difficulty in large-scale production. SUMMARY

[0004] In view of the problems in the existing intermediates for synthesizing pyroxsulam and / or the process for synthesizing pyroxsulam, the present application aims to provide a new preparation process of an intermediate for synthesizing pyroxsulam, which has low cost and a mild synthesis route, and a new process for synthesizing pyroxsulam.

[0005] The present application provides a synthesis method of a pyroxsulam intermediate compound V, which comprises the following steps:

[0006] Step S5: synthesizing compound V from compound IV in the presence of a chlorinating agent and a catalyst;

[0007]

[0008] According to an embodiment of the present application, the chlorinating agent in step S5 is at least one of chlorine gas and sulfuryl chloride.

[0009] According to an embodiment of the present application, the catalyst in step S5 is at least one of ferric chloride, aluminum trichloride, and iron.

[0010] According to embodiments of the present application, the molar ratio of the compound IV to the chlorinating agent in step S5 is 1 : (0.8-20), for example 1 : (1-10), such as 1 :2, 1 :3, 1 :4, 1 :5, 1 :6, 1 :7, 1 :8.

[0011] According to embodiments of the present application, the molar ratio of the compound IV to the catalyst in step S5 is 1 : (0.01-5), for example 1 : (0.01-0.2), such as 1 :0.1, 1 :0.2, 1 :0.5, 1 :1, 1 :1.5, 1 :2.

[0012] According to embodiments of the present application, step S5 is carried out in the presence of an organic solvent. For example, the organic solvent is selected from at least one of tetrahydrofuran, toluene, dichloroethane, dichloromethane, acetonitrile; for example acetonitrile.

[0013] According to embodiments of the present application, the reaction temperature of step S5 is 20-150°C, for example 30-100°C, such as 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C.

[0014] According to embodiments of the present application, the reaction time of step S5 is 2-8h, for example 2h, 3h, 4h, 5h, 6h, 7h, 8h.

[0015] According to embodiments of the present application, the method for preparing the compound IV comprises the following steps:

[0016] Step S4: reacting compound III in the presence of an oxidizing agent and a catalyst to obtain compound IV;

[0017]

[0018] wherein X is selected from halogen, for example from chlorine, bromine, iodine.

[0019] According to embodiments of the present application, the oxidizing agent in step S4 is selected from at least one of hydrogen peroxide, oxygen, meta-chloroperoxybenzoic acid, sodium percarbonate.

[0020] According to embodiments of the present application, when the oxidizing agent in step S4 is hydrogen peroxide, the hydrogen peroxide is an aqueous solution of hydrogen peroxide, for example with a concentration of 10-50wt%, such as 20wt%, 30wt%, 40wt%.

[0021] According to embodiments of the present application, the catalyst in step S4 is selected from at least one of tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium iodide.

[0022] According to an embodiment of the present application, the molar ratio of compound III to oxidizing agent in step S4 is selected from 1 : (0.5-5), for example 1 : (1-3), such as 1 : 1.5, 1 : 2, 1 : 2.5.

[0023] According to an embodiment of the present application, the molar ratio of compound III to catalyst in step S4 is selected from 1 : (0.01-0.5), for example 1 : (0.05-0.1), such as 1 : 0.05, 0.06, 0.07, 0.08, 0.09.

[0024] According to an embodiment of the present application, the temperature of the reaction in step S4 is from 20°C to 100°C, for example from 30°C to 80°C, such as 30°C, 40°C, 50°C, 60°C or 70°C.

[0025] According to an embodiment of the present application, the time of the reaction in step S4 is from 2h to 12h, for example 2h, 4h, 6h, 8h, 10h, 12h.

[0026] According to an embodiment of the present application, the method for preparing compound III comprises the following steps:

[0027] Step S3: reacting compound II with a halogenating agent to obtain compound III;

[0028]

[0029] wherein X has the definition described above; the halogenating agent is selected from NBS (N-bromosuccinimide), NCS (N-chlorosuccinimide), NIS (N-iodosuccinimide).

[0030] According to an embodiment of the present application, the molar ratio of compound II to the halogenating agent in step S3 is 1 : (0.8-5), for example 1 : (1-2), such as 1 : 1.1, 1 : 1.2, 1 : 1.3, 1 : 1.4, 1 : 1.5.

[0031] According to an embodiment of the present application, the reaction in step S3 is carried out in the presence of a catalyst selected from at least one of azobisisobutyronitrile, azobisisoheptyl nitrile, dimethyl azodicarboxylate, azobiscyclohexylcarbonitrile.

[0032] According to an embodiment of the present application, the molar ratio of compound II to the catalyst in step S3 is 1 : (0.01-5), for example 1 : (0.01-0.2), such as 1 : 0.1, 1 : 0.2, 1 : 0.5, 1 : 1, 1 : 1.5, 1 : 2.

[0033] According to an embodiment of the present application, the reaction of step S3 is carried out in the presence of a solvent selected from at least one of dichloromethane, trichloromethane, carbon tetrachloride, preferably carbon tetrachloride.

[0034] According to an embodiment of the present application, the reaction of step S3 is carried out at a temperature ranging from 20°C to 150°C, for example from 30°C to 100°C, such as 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C.

[0035] According to an embodiment of the present application, the reaction of step S3 is carried out for a time ranging from 2h to 12h, for example 2h, 4h, 6h, 8h, 10h, 12h.

[0036] According to an embodiment of the present application, the process for the preparation of the compound II comprises the following steps:

[0037] Step S2: reaction of compound I with 3-amino-4,4,4-trifluorocrotonic acid ester in the presence of dimethyl sulfate to obtain compound II;

[0038]

[0039] wherein R is selected from C 1-6 alkyl, for example methyl, ethyl, propyl or butyl.

[0040] According to an embodiment of the present application, the 3-amino-4,4,4-trifluorocrotonic acid ester of step S2 is selected from at least one of 3-amino-4,4,4-trifluorocrotonic acid methyl ester, 3-amino-4,4,4-trifluorocrotonic acid ethyl ester.

[0041] According to an embodiment of the present application, the molar ratio of the use of compound I to the 3-amino-4,4,4-trifluorocrotonic acid ester of step S2 is 1 : (0.8-2), for example 1 : (1-1.5), such as 1 : 1.1, 1 : 1.2, 1 : 1.3, 1 : 1.4.

[0042] According to an embodiment of the present application, the molar ratio of the use of compound I to the dimethyl sulfate of step S2 is 1 : (0.5-5), for example 1 : (1-2), such as 1 : 1.1, 1 : 1.2, 1 : 1.3, 1 : 1.4, 1 : 1.5, 1 : 1.6, 1 : 1.7, 1 : 1.8.

[0043] According to an embodiment of the present application, the reaction of step S2 is carried out in the presence of an inorganic base selected from at least one of potassium carbonate, sodium carbonate, cesium carbonate.

[0044] According to an embodiment of the present application, the molar ratio of the use of compound I to the inorganic base of step S2 is 1 : (0.5-8), for example 1 : (1-5), such as 1 : 1.5, 1 : 2, 1 : 2.5, 1 : 3, 1 : 3.5, 1 : 4, 1 : 4.5.

[0045] According to an embodiment of the present application, the reaction of step S2 is carried out in the presence of a polar aprotic solvent selected from at least one of N,N- dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone.

[0046] According to an embodiment of the present application, the temperature of the reaction of step S2 is comprised between 80°C and 150°C, for example between 120°C and 230°C, such as 90°C, 100°C, 110°C, 120°C, 130°C, 140°C.

[0047] According to an embodiment of the present application, the time of the reaction of step S2 is comprised between 2h and 18h, for example 4h, 6h, 8h, 10h, 12h.

[0048] According to an embodiment of the present application, the process for the preparation of compound I comprises the following steps:

[0049] Step S1 : 4-fluoro-3-aminotoluene is reacted with to give compound I;

[0050]

[0051] wherein L is selected from halogen, for example Br, CI; R has the definition described above.

[0052] According to an embodiment of the present application, the reaction of step S1 is carried out in the presence of a polar solvent selected from at least one of dichloroethane, toluene, chlorobenzene and xylene.

[0053] According to an embodiment of the present application, the reaction of step S1 is carried out in the presence of at least one of methyl chloroformate, ethyl chloroformate, propyl chloroformate, butyl chloroformate.

[0054] According to an embodiment of the present application, the molar ratio of the use of 4-fluoro-3- aminotoluene to is 1 : (0.8-5), for example 1 : (1-2), such as 1 : 1.1, 1 : 1.2, 1 : 1.3, 1 : 1.4, 1 : 1.5.

[0055] According to an embodiment of the present application, the temperature of the reaction of step S1 is comprised between 40°C and 150°C, for example between 60°C and 120°C, such as 70°C, 80°C, 90°C, 100°C, 110°C, 120°C.

[0056] According to an embodiment of the present application, the reaction of step S1 is carried out for a time of 2h-18h, for example 4h, 6h, 8h, 10h, 12h.

[0057] According to an embodiment of the present application, the synthesis process comprises the following steps:

[0058] (1) reacting 4-fluoro-3-aminotoluene with a chloroformate selected from at least one of methyl chloroformate, ethyl chloroformate, propyl chloroformate, butyl chloroformate in a polar solvent at 40-120°C to obtain compound I;

[0059] (2) reacting compound I with 3-amino-4,4,4-trifluorocrotonic acid ester in the presence of an inorganic base in a polar aprotic solvent at 120-230°C to obtain an intermediate, and further adding dimethyl sulfate to obtain compound II;

[0060] (3) reacting compound II with NCS in the presence of carbon tetrachloride as a solvent and azobisisobutyronitrile at 20-100°C to obtain compound III;

[0061] (4) oxidizing compound III in the presence of hydrogen peroxide and tetrabutylammonium bromide at 20-100°C to obtain compound IV;

[0062] (5) reacting compound IV with a chlorinating agent in the presence of ferric chloride to obtain compound V.

[0063] The present application provides a new process for synthesizing pyroxsulam, which comprises a synthesis process of the intermediate compound V.

[0064] Advantages

[0065] By the above technical scheme of the present application, the present application at least overcomes some deficiencies in the prior art process for synthesizing pyroxsulam, and a new process for preparing intermediate IV more suitable for industrialized production of pyroxsulam is obtained.

[0066] Compared with the prior art process for preparing intermediate IV, the present application uses relatively inexpensive starting materials that are easy to obtain, and has low cost; the reaction steps S1-S5 are simple to operate and have mild conditions, and can be continuously carried out in the same reaction kettle, overcoming the problems of harsh reaction conditions and high cost in some synthesis processes. This synthesis route has reduced danger, less three-waste discharge, high yield of intermediate and target product, and is more conducive to industrialized production. Moreover, the aprotic polar solvent used in the process can be recycled and reused without pollution. DETAILED DESCRIPTION

[0067] The technical solutions of the present disclosure will be further described in detail below in combination with specific embodiments. It should be understood that the following embodiments are only illustratively described and explained, and should not be interpreted as limiting the scope of protection of the present disclosure. Any technology realized based on the above description of the present disclosure is covered within the scope intended to be protected by the present disclosure.

[0068] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0069] In the present disclosure, room temperature refers to 20-30℃ unless otherwise specified.

[0070] In the synthetic route of the present disclosure, the content (purity) of the intermediate and target product is measured by liquid chromatography (Agilent HPLC 1260). The conversion rate and selectivity of the reaction are calculated by the following formula:

[0071] Conversion rate = (molar amount of raw material input - molar amount of raw material remaining in product) / molar amount of raw material input x 100%.

[0072] Yield = actual molar amount of target product / theoretical molar amount of target product x 100%.

[0073] Example 1

[0074]

[0075] Step 1: Preparation of compound I-1

[0076] Into a 1L four-necked flask equipped with mechanical stirring, thermometer, condenser, 0.1 mol of raw material 4-fluoro-3-aminotoluene and 500g of dichloromethane were sequentially added, heated to 70-80℃, and then 0.11 mol of methyl chloroformate was added dropwise. After the dropwise addition was completed, the reaction was continued for 11h with stirring;

[0077] The reaction progress was detected by high performance liquid chromatography (HPLC) analysis. After the area percentage of the raw material in all peak areas was <0.2%, the stirring was stopped, the temperature was lowered to room temperature, and the reaction was terminated. The solvent was removed under reduced pressure to obtain compound I-1.

[0078] Based on the raw material compound 4-fluoro-3-aminotoluene, the yield of compound I-1 was calculated to be 80% with a purity of 98%.

[0079] Step 2: Preparation of compound II

[0080] In a four-necked flask equipped with mechanical stirring, thermometer, condenser, 0.1 mol of compound I-1, 100 g of DMF, 0.3 mol of potassium carbonate were added, heated to 120-140°C, reflux, dropwise addition of 0.12 mol of 3-amino-4,4,4-trifluoromethyl crotonate, after dropwise addition, reflux reaction for 10 h;

[0081] After the liquid phase was qualified, it was cooled to room temperature, 0.15 mol of dimethyl sulfate was added dropwise, and after dropwise addition, it was reacted at room temperature for 5 h;

[0082] Using high performance liquid chromatography (HPLC) analysis, the reaction progress was detected, and after the area percentage of the raw material to the total peak area was <0.2%, the stirring was stopped, the mother liquor was removed by filtration, and the DMF was removed to obtain compound II.

[0083] Based on compound I-1, the yield of compound II was calculated to be 95% with a purity of 98%.

[0084] Step 3: Preparation of compound III-1

[0085] In a four-necked flask equipped with mechanical stirring, thermometer, condenser, 0.1 mol of compound II, 100 g of carbon tetrachloride were added, heated to 40°C, 0.11 mol of NCS (N-chlorosuccinimide) and 0.01 mol of azobisisobutyronitrile were added dropwise, after dropwise addition, 40°C reaction for 10 h;

[0086] Using high performance liquid chromatography (HPLC) analysis, the reaction progress was detected, and after the area percentage of the raw material to the total peak area was <0.2%, the stirring was stopped, 100 g of water was added, separated, and the solvent was removed to obtain compound III-1. 1 H NMR (500 MHz, DMSO) δ 7.81 (d, J = 7.6 Hz, 1H), 7.70-7.56 (m, 2H), 6.60 (s, 1H), 4.86 (s, 2H), 3.42 (s, 3H).

[0087] Based on compound II, the yield of compound III-1 was calculated to be 90% with a purity of 98%.

[0088] Step 4: Preparation of compound IV

[0089] In a four-necked flask equipped with mechanical stirring, thermometer, condenser, 0.1 mol of compound III-1, 0.2 mol of hydrogen peroxide, acetonitrile as solvent, 2 g of tetrabutylammonium bromide were added, heated to 70°C and reacted for 10 h;

[0090] The reaction progress was detected by HPLC analysis. When the area percentage of the raw material in all peak areas was less than 0.2%, the stirring was stopped, 100 g of water was added, and 200 g of dichloromethane was added for extraction. After the layers were separated and the solvent was removed, compound V was obtained. 1 H NMR (500 MHz, DMSO) δ 9.98 (s, 1H), 8.04 (d, J = 7.6 Hz, 1H), 7.49-7.65 (m, 2H), 6.60 (s, 1H), 3.42 (s, 3H).

[0091] The yield of compound III-1 was 97% and the purity was 98% based on compound III-1.

[0092] Step 5: Preparation of compound V

[0093] In a four-necked flask equipped with mechanical stirring, thermometer, condenser, 0.1 mol of compound IV, 100 g of acetonitrile were added and heated to 60°C. 0.01 mol of iron chloride was added, and then 0.25 mol of sulfuryl chloride was added dropwise. After the dropwise addition was completed, the reaction was carried out at 60°C for 10 h.

[0094] The reaction progress was detected by HPLC analysis. When the area percentage of the raw material in all peak areas was less than 0.2%, the stirring was stopped, 100 g of water was added, and 200 g of dichloromethane was added for extraction. After the layers were separated and the solvent was removed, compound V was obtained. 1 H NMR (500 MHz, DMSO) δ 9.98 (s, 1H), 8.04 (d, J = 7.6 Hz, 1H), 7.49-7.65 (m, 2H), 6.60 (s, 1H), 3.42 (s, 3H).

[0095] The yield of compound V was 95% and the purity was 98% based on compound IV.

[0096] The above describes exemplary embodiments of the technical solutions of the present disclosure. It should be understood that the protection scope of the present disclosure is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principles of the present disclosure shall be included in the protection scope of the claims of the present application.

Claims

1. A method for synthesizing a compound V, an intermediate of pyrimisulfuron, comprising the following steps: Step S5: In the presence of a chlorinating agent and a catalyst, compound V is synthesized from compound IV; Preferably, the chlorinating agent in step S5 is selected from at least one of chlorine gas and sulfonyl chloride; Preferably, the catalyst in step S5 is selected from at least one of ferric chloride, aluminum trichloride, and iron.

2. The method according to claim 1, characterized in that, The molar ratio of compound IV to the chlorinating agent in step S5 is 1:(0.8-20), for example 1:(1-10); Preferably, the molar ratio of compound IV to the catalyst in step S5 is 1:(0.01-5), for example 1:(0.01-0.2); Preferably, step S5 is carried out in the presence of an organic solvent; for example, the organic solvent is selected from at least one of tetrahydrofuran, toluene, dichloroethane, dichloromethane, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and acetonitrile. Preferably, the reaction temperature in step S5 is 20℃-150℃, for example 30℃-100℃; Preferably, the reaction time for step S5 is 2h-8h.

3. The method according to claim 1 or 2, characterized in that, The preparation method of compound IV includes the following steps: Step S4: Compound III is hydrolyzed in the presence of an oxidant and a catalyst to give compound IV; Wherein, X is selected from halogens, such as chlorine, bromine, and iodine; Preferably, the oxidant in step S4 is selected from at least one of hydrogen peroxide, oxygen, m-chlorobenzoic acid peroxide, and sodium percarbonate; Preferably, in step S4, when the oxidant is hydrogen peroxide, the hydrogen peroxide is an aqueous solution with a concentration of, for example, 10wt%-50wt%. Preferably, the catalyst in step S4 is selected from at least one of tetrabutylammonium bromide, tetrabutylammonium chloride, and tetrabutylammonium iodide; Preferably, the molar ratio of compound III to oxidant in step S4 is selected from 1:(0.5 to 5), for example 1:(1-3); Preferably, the molar ratio of compound III to the catalyst in step S4 is selected from 1:(0.01-0.5), for example 1:(0.05-0.1); Preferably, the reaction temperature in step S4 is 20℃-100℃, for example 30℃-80℃; Preferably, the reaction time in step S4 is 2h-12h.

4. The method according to any one of claims 1-3, characterized in that, The preparation method of compound III includes the following steps: Step S3: Compound II reacts with a halogenating agent to give compound III; Wherein, X has the definition described above; the halogenating reagent is selected from NBS (N-bromosuccinimide), NCS (N-chlorosuccinimide), and NIS (N-iodosuccinimide); Preferably, the molar ratio of compound II to the halogenated reagent in step S3 is 1:(0.8-5), for example 1:(1-2); Preferably, the reaction in step S3 is carried out in the presence of a catalyst, wherein the catalyst is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, and azobiscyclohexylformitrile; Preferably, the molar ratio of compound II to the catalyst in step S3 is 1:(0.01-5), for example 1:(0.01-0.2); Preferably, the reaction in step S3 is carried out in the presence of a solvent, wherein the solvent is selected from at least one of dichloromethane, trichloromethane, and carbon tetrachloride, preferably carbon tetrachloride; Preferably, the reaction temperature in step S3 is 20℃-150℃, for example 30℃-100℃; Preferably, the reaction time in step S3 is 2h-12h.

5. The method according to any one of claims 1-4, characterized in that, The preparation method of compound II includes the following steps: Step S2: Compound I reacts with 3-amino-4,4,4-trifluorocrotonate in the presence of dimethyl sulfate to give compound II; Wherein, R is selected from C 1-6 Alkyl groups, such as methyl, ethyl, propyl, or butyl; Preferably, the 3-amino-4,4,4-trifluorocrotonic acid ester in step S2 is selected from at least one of methyl 3-amino-4,4,4-trifluorocrotonic acid and ethyl 3-amino-4,4,4-trifluorocrotonic acid. Preferably, the molar ratio of compound I in step S2 to the 3-amino-4,4,4-trifluorocrotonate is 1:(0.8-2), for example 1:(1-1.5); Preferably, the molar ratio of compound I to dimethyl sulfate in step S2 is 1:(0.5-5), for example 1:(1-2).

6. The method according to claim 5, characterized in that, The reaction described in step S2 is carried out in the presence of an inorganic base, wherein the inorganic base is selected from at least one of potassium carbonate, sodium carbonate, and cesium carbonate; Preferably, the molar ratio of compound I to the inorganic base in step S2 is 1:(0.5-8), for example 1:(1-5); Preferably, the reaction in step S2 is carried out in the presence of a polar aprotic solvent, wherein the polar aprotic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone; Preferably, the reaction temperature in step S2 is 80℃-150℃, for example 120℃-230℃; Preferably, the reaction time in step S2 is 2h-18h.

7. The method according to any one of claims 1-6, characterized in that, The preparation method of compound I includes the following steps: Step S1: 4-Fluoro-3-aminotoluene and The reaction yields compound I; Wherein, L is selected from halogens, such as Br and Cl; R has the definition as described in any one of claims 1-6; Preferably, the reaction in step S1 is carried out in the presence of a polar solvent, wherein the polar solvent is selected from at least one of dichloroethane, toluene, chlorobenzene and xylene; Preferably, the step S1 described It is selected from at least one of methyl chloroformate, ethyl chloroformate, propyl chloroformate, and butyl chloroformate.

8. The method according to claim 7, characterized in that, The 4-fluoro-3-aminotoluene and The molar ratio of the dosage is 1:(0.8-5), for example 1:(1-2); Preferably, the reaction temperature in step S1 is 40℃-150℃, for example 60℃-120℃; Preferably, the reaction time in step S1 is 2h-18h.

9. The method according to any one of claims 1-8, characterized in that, The synthesis method includes the following steps: (1) 4-fluoro-3-aminotoluene is reacted with chloroformate in a polar solvent at 40-120°C to obtain compound I; wherein the chloroformate is selected from at least one of methyl chloroformate, ethyl chloroformate, propyl chloroformate, and butyl chloroformate. (2) At 120-230℃, in the presence of an inorganic base, in a polar aprotic solvent, compound I reacts with 3-amino-4,4,4-trifluorocrotonate to give an intermediate product, and then further reacts with dimethyl sulfate to give compound II. (3) Compound II reacts with NCS at 20-100℃ in the presence of carbon tetrachloride as solvent and azobisisobutyronitrile to obtain compound III; (4) Compound III was oxidized at 20-100℃ in the presence of hydrogen peroxide and tetrabutylammonium bromide to give compound IV; (5) In the presence of ferric chloride, compound IV reacts with a chlorinating agent to give compound V.

10. A process for synthesizing bensulfuron-methyl, comprising the method for synthesizing the bensulfuron-methyl intermediate compound V as described in any one of claims 1-9.

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