Oxadiazon intermediate as well as preparation method and application thereof

Abstract

The embodiment of the invention relates to the technical field of organic synthesis, and particularly discloses an oxadiazon intermediate as well as a preparation method and application thereof, the oxadiazon intermediate provided by the embodiment of the invention is prepared by taking 2, 4-dichloro-5-isopropoxy phenylhydrazine and pivalic acid as raw materials and reacting under the conditions of a condensing agent and a catalyst; according to the embodiment of the invention, the trivaleric acid which is cheap, easy to obtain and higher in safety is used as the raw material, and the oxadiazon intermediate can be generated through one-step reaction under the conditions of the condensing agent and the catalyst, so that the problem that the production cost cannot be reduced while the safety is met in the existing 2, 4-dichloro-5-isopropoxy benzene hydrazide synthesis method is solved. Moreover, the preparation method provided by the embodiment of the invention is simple, the raw materials are cheap and easy to obtain, the cost is lower, the operation is simpler and safer, and the market prospect is wide.

Description

Technical Field

[0001] The embodiment of the present invention belongs to the technical field of organic synthesis, and specifically relates to an oxadiazine intermediate and a preparation method and application thereof. The oxadiazine intermediate is 2,4-dichloro-5-isopropoxybenzohydrazide. Background Art

[0002] As a kind of substance used to eliminate or inhibit plant growth, herbicides can be widely used to control weeds, shrubs, trees and other harmful plants in farmland, orchards, flower nurseries, etc., and are widely used in agricultural production and other fields. Among them, oxadiazon is a highly effective broad-spectrum herbicide used to control a variety of annual monocotyledonous and dicotyledonous weeds. It belongs to the category of selective pre-emergence and post-emergence herbicides. It is mainly used for weeding in paddy fields, and is also effective for peanuts, cotton, sugarcane and other dry fields. It has the characteristics of high efficiency, long-term effect, broad spectrum, low dosage, safety to humans, animals and the environment, mild to insect natural enemies and beneficial organisms, and has broad market prospects.

[0003] At present, the industrial synthesis route of oxadiazon mainly uses 2,4-dichlorophenol as raw material, and is obtained through esterification, nitration, hydrolysis, etherification, reduction, diazotization, secondary reduction, alkalization, acylation and cyclization, a total of 10 steps. Among them, the intermediate 2,4-dichloro-5-isopropoxyphenylhydrazine involved in the existing technical route is mainly obtained by using 2,4-dichloro-5-isopropoxyphenylhydrazine and pivaloyl chloride as raw materials, but the raw material pivaloyl chloride has a low flash point and is easy to volatilize and decompose; the drop temperature needs to be controlled during the reaction, and if it is not well controlled, diacylated by-products are easily generated; and pivaloyl chloride is relatively expensive.

[0004] Therefore, the above-mentioned prior art solutions have the following defects: In the prior art, the synthesis method of the oxadiazine intermediate 2,4-dichloro-5-isopropoxybenzohydrazide has the problem of not being able to reduce the production cost while meeting the safety requirements. Therefore, it is of great significance to use cheaper, more readily available and safer raw materials to synthesize the 2,4-dichloro-5-isopropoxybenzohydrazide intermediate. Summary of the invention

[0005] The purpose of the embodiments of the present invention is to provide an oxadiazine intermediate to solve the problem that the existing 2,4-dichloro-5-isopropoxybenzohydrazide synthesis method proposed in the above background technology cannot reduce the production cost while meeting the safety requirements.

[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions: An oxadiazine intermediate is prepared by reacting 2,4-dichloro-5-isopropoxyphenylhydrazine and pivalic acid as raw materials in the presence of a condensing agent and a catalyst; wherein the reaction temperature is 30-100°C.

[0007] Preferably, the condensing agent is selected from any one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, diisopropylcarbodiimide, dicyclohexylcarbodiimide, 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate, and O-benzotriazole-tetramethyluronium hexafluorophosphate.

[0008] Further preferably, the catalyst is selected from any one or two of 1-hydroxybenzotriazole, 1-hydroxy-7-azabenzotriazole, triethylamine, N,N-diisopropylethylamine, sodium bicarbonate, N-methylmorpholine, potassium carbonate, pyridine, and N,N-dimethylformamide.

[0009] Another object of the embodiment of the present invention is to provide a method for preparing an oxadiazon intermediate, the method for preparing an oxadiazon intermediate comprising the following steps: Pivalic acid is added to a solvent and stirred to dissolve, a condensation agent, a catalyst and 2,4-dichloro-5-isopropoxyphenylhydrazine are added at 0-30°C, the mixture is heated to 30-100°C for reaction, and then the mixture is acid-washed, water-washed, and concentrated under reduced pressure to remove the solvent to obtain 2,4-dichloro-5-isopropoxyphenylhydrazine.

[0010] Further preferably, in the method for preparing the oxadiazon intermediate, the solvent is selected from any one of chloroform, dichloromethane, 1,2-dichloroethane, tetrahydrofuran, ethyl acetate, N,N-dimethylformamide, and toluene.

[0011] Another object of an embodiment of the present invention is to provide 2,4-dichloro-5-isopropoxybenzohydrazide prepared by the above-mentioned method for preparing the oxadiazon intermediate.

[0012] Another object of an embodiment of the present invention is to provide a use of the above-mentioned oxadiazon intermediate in the preparation of herbicides.

[0013] Compared with the prior art, the beneficial effects of the embodiments of the present invention are: Compared with the prior art, the oxadiazole intermediate 2,4-dichloro-5-isopropoxyphenylhydrazine provided in the embodiment of the present invention is prepared by reacting 2,4-dichloro-5-isopropoxyphenylhydrazine and pivalic acid as raw materials under the conditions of a condensing agent and a catalyst; by using cheap, easily available, and safer pivalic acid as a raw material, the oxadiazole hydrazide intermediate can be generated by a one-step reaction under the conditions of a condensing agent and a catalyst, which is relatively simple in the operation process, and solves the problem that the existing 2,4-dichloro-5-isopropoxyphenylhydrazine intermediate synthesis method cannot reduce production costs while meeting safety. Moreover, the preparation method provided in the embodiment of the present invention is simple, and is a brand-new method for synthesizing 2,4-dichloro-5-isopropoxyphenylhydrazine. Compared with the prior art, the raw materials are cheap and easily available, the cost is lower, and the operation is simpler and safer, and it has great application value in the industrial development of oxadiazole. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention.

[0015] Figure 1 The present invention provides a flow chart of a method for preparing 2,4-dichloro-5-isopropoxybenzohydrazide according to an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention and the accompanying drawings. Obviously, the following embodiments will help those skilled in the art to further understand the embodiments of the present invention, but do not limit the embodiments of the present invention in any form. It should be pointed out that for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the embodiments of the present invention. These all belong to the protection scope of the embodiments of the present invention.

[0017] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0018] First of all, it should be noted that, currently on the market, oxadiazon, as a selective pre-emergence and post-emergence herbicide variety of protoporphyrinogen oxidase inhibitor, is mainly used to control a variety of annual monocotyledonous and dicotyledonous weeds, mainly used for weeding in paddy fields, and is also effective for peanuts, cotton, sugarcane, etc. in dry fields; it belongs to contact pre-emergence and post-emergence herbicides. It has the characteristics of high efficiency, long-lasting effect, broad spectrum, small dosage, safety to humans, animals and the environment, mild to insect natural enemies and beneficial organisms, and has broad market prospects. In the prior art, the current industrial synthesis route of oxadiazon mainly uses 2,4-dichlorophenol as raw material, and is obtained through esterification, nitration, hydrolysis, etherification, reduction, diazotization, secondary reduction, alkalization, acylation and cyclization, a total of 10 steps. Among them, the intermediate 2,4-dichloro-5-isopropoxyphenylhydrazine in the prior art route is mainly obtained by using 2,4-dichloro-5-isopropoxyphenylhydrazine and pivaloyl chloride as raw materials, and the specific reaction equation is as follows:

[0019] However, the raw material pivaloyl chloride has a low flash point and is easy to volatilize and decompose; the drop temperature needs to be controlled during the reaction. If it is not well controlled, diacylated byproducts are easily generated; and pivaloyl chloride is expensive. Therefore, it is of great significance to use cheaper, more readily available and safer raw materials to synthesize 2,4-dichloro-5-isopropoxyphenylhydrazide intermediates.

[0020] In order to solve the problem that the existing synthesis method of oxadiazole intermediate 2,4-dichloro-5-isopropoxybenzohydrazide cannot reduce production costs while meeting safety. An oxadiazole intermediate (i.e., 2,4-dichloro-5-isopropoxybenzohydrazide) and its preparation method and application are provided in an embodiment of the present invention. Specifically, the 2,4-dichloro-5-isopropoxybenzohydrazide is prepared by reacting 2,4-dichloro-5-isopropoxyphenylhydrazine and pivalic acid as initial raw materials under the conditions of a condensing agent and a catalyst to generate an oxadiazole hydrazide intermediate, wherein the reaction temperature is 30-100°C. In an embodiment of the present invention, by using cheap, easily available, and safer pivalic acid as a raw material, the production cost is effectively reduced, while avoiding the problem of the generation of diacylated byproducts by using raw material pivaloyl chloride, and the product yield can reach 98.4%, which can be used as an oxadiazole intermediate to produce the herbicide oxadiazole, and has broad application prospects.

[0021] Furthermore, the pivalic acid generally refers to trimethylacetic acid. It is colorless crystal. It is easily soluble in ethanol, ether and water. It is used as an intermediate for pesticides, medicines and dyes. With cheap and easy-to-obtain pivalic acid as a raw material, it can be reacted in one step under the conditions of a condensing agent and a catalyst to generate an oxadiazon hydrazide intermediate, and the operation process is relatively simple.

[0022] As another preferred embodiment of the present invention, the condensing agent is selected from any one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI), diisopropylcarbodiimide (DIC), dicyclohexylcarbodiimide (DCC), 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU), and O-benzotriazole-tetramethyluronium hexafluorophosphate (HBTU).

[0023] Preferably, the condensing agent is further preferably EDCI.

[0024] As another preferred embodiment of the present invention, the catalyst is selected from any one or two of 1-hydroxybenzotriazole (HOBt), 1-hydroxy-7-azabenzotriazole (HOAt), triethylamine, N,N-diisopropylethylamine, sodium bicarbonate, N-methylmorpholine, potassium carbonate, pyridine, N,N-dimethylformamide, and 4-dimethylaminopyridine.

[0025] Further preferably, the catalyst is selected from any one or two of HOBt, triethylamine, and N,N-diisopropylethylamine.

[0026] It should be noted that the above products can all use raw materials available in the existing market. For example, O-benzotriazole-tetramethyluronium hexafluorophosphate (HBTU, molecular formula: C11H16N5O.PF6, CAS No.: 94790-37-1) can specifically use benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate products produced by existing manufacturers. Other products are not described in detail.

[0027] It should also be noted that in the prior art, the synthesis method of 2,4-dichloro-5-isopropoxyphenylhydrazine generally requires 2,4-dichloro-5-isopropoxyaniline to be diazotized to form a diazonium salt, and then reduced and alkalized to obtain the product 2,4-dichloro-5-isopropoxyphenylhydrazine. The thermal stability of the diazonium salt in the diazotization process is very poor, and it is very easy to decompose when heated, causing safety risks such as explosion, so the production conditions are relatively harsh. Although, the Chinese invention patent with patent number CN2020116371543 discloses a method for preparing 2,4-dichloro-5-isopropoxyphenylhydrazine, an intermediate of oxadiazon: using a toluene solution of 2,4-dichloro-5-isopropoxyphenylhydrazine as a raw material, stirring it under acidic conditions to form a salt, reacting it with cyanate at a certain temperature to form urea, and then degrading and rearranging it, and adding chloroform to extract it to obtain a chloroform solution of 2,4-dichloro-5-isopropoxyphenylhydrazine. However, cyanate is a general term for salts whose anions are cyanate ions, which have certain toxicity, and the synthesis steps are relatively many, requiring reaction to generate urea, followed by degradation, rearrangement, and extraction with chloroform, which relatively increases the production cost. In the embodiment of the present invention, by using cheap, easily available, and safer pivalic acid as a raw material, the reaction can be carried out under the conditions of a condensing agent and a catalyst, the steps are simple, the production cost is effectively reduced, and the problem of the formation of diacylated byproducts easily existing in the raw material pivaloyl chloride is avoided.

[0028] As another preferred embodiment of the present invention, the molar ratio of the 2,4-dichloro-5-isopropoxyphenylhydrazine, pivalic acid, condensation agent and catalyst is 1:0.8-1.5:0.8-1.5:0.2-1.4.

[0029] As another preferred embodiment of the present invention, the molar ratio of the 2,4-dichloro-5-isopropoxyphenylhydrazine, pivalic acid, condensation agent and catalyst is 1:1-1.2:1-1.2:0.3-1.2.

[0030] Further preferably, the molar ratio of the 2,4-dichloro-5-isopropoxyphenylhydrazine, pivalic acid, condensation agent and catalyst is 1:1.2:1.1:0.6-1.1.

[0031] The present invention also provides a method for preparing 2,4-dichloro-5-isopropoxybenzohydrazide, which uses 2,4-dichloro-5-isopropoxyphenylhydrazine and pivalic acid as initial raw materials, and reacts them under the conditions of a condensing agent and a catalyst to generate an oxadiazine hydrazide intermediate. The method for preparing 2,4-dichloro-5-isopropoxybenzohydrazide specifically comprises the following steps: Pivalic acid is added to a solvent and stirred to dissolve, a condensation agent, a catalyst and 2,4-dichloro-5-isopropoxyphenylhydrazine are added at 0-30°C, the raw materials are fully stirred to mix, and then the mixture is heated to 30-100°C for reaction. After the reaction is completed, the mixture is acid-washed, washed with water, and concentrated under reduced pressure to remove the solvent to obtain the 2,4-dichloro-5-isopropoxyphenylhydrazine. The general reaction formula is:

[0032] Since this method uses cheap, easily available and safer pivalic acid as a raw material to synthesize 2,4-dichloro-5-isopropoxybenzohydrazide, compared with the existing technology, the raw materials are cheaper and more readily available, the cost is lower, and the operation is simpler and safer, it has great application value in the industrial development of oxadiazon.

[0033] As another preferred embodiment of the present invention, in the method for preparing 2,4-dichloro-5-isopropoxybenzohydrazide, the reaction temperature of the reaction is further preferably 60-80°C.

[0034] As another preferred embodiment of the present invention, in the preparation method of 2,4-dichloro-5-isopropoxybenzohydrazide, the solvent is selected from any one of chloroform, dichloromethane, 1,2-dichloroethane, tetrahydrofuran, ethyl acetate, N,N-dimethylformamide, and toluene.

[0035] As another preferred embodiment of the present invention, in the method for preparing 2,4-dichloro-5-isopropoxybenzohydrazide, the solvent is preferably any one of chloroform, N,N-dimethylformamide and toluene.

[0036] Preferably, Figure 1 As shown, the preparation method of 2,4-dichloro-5-isopropoxybenzohydrazide mainly includes the steps of raw material mixing, heating reaction, acid washing, water washing, and reduced pressure concentration, wherein: 1) Mixing raw materials: first add 13 g of pivalic acid and 100 ml of toluene solvent into a 250 ml reaction bottle, stir and fully dissolve; add 22.4 g of EDCI and 15.8 g of HOBt at room temperature, stir for 15 minutes, then add 25 g of 2,4-dichloro-5-isopropoxyphenylhydrazine and 15.1 g of N,N-diisopropylethylamine, stir and fully obtain a mixture; 2) Heating reaction: The mixture is heated to 60°C for heat preservation reaction; 3) Acid washing and water washing: After the detection reaction is completed, cool to room temperature, add 25 ml of HCl (1.0M) for washing and extraction, and collect the organic phase; the organic phase is then washed and extracted with 25 ml of brine, and the organic phase is collected; 4) Concentrate under reduced pressure: spin dry the organic phase to obtain 2,4-dichloro-5-isopropoxybenzohydrazide.

[0037] The preparation method of 2,4-dichloro-5-isopropoxybenzohydrazide provided in the embodiment of the present invention has the advantages of safe and simple operation and cheap and readily available raw materials, and has application value in industrial production.

[0038] The embodiment of the present invention also provides an oxadiazine intermediate 2,4-dichloro-5-isopropoxybenzohydrazide prepared by the above-mentioned preparation method of 2,4-dichloro-5-isopropoxybenzohydrazide.

[0039] The embodiment of the present invention also provides a use of the above-mentioned 2,4-dichloro-5-isopropoxybenzohydrazide in preparing a herbicide.

[0040] The technical effects of the preparation method of the embodiment of the present invention are further described below by listing specific embodiments.

[0041] Example 1 A method for preparing 2,4-dichloro-5-isopropoxyphenylhydrazine comprises taking 2,4-dichloro-5-isopropoxyphenylhydrazine and pivalic acid as initial raw materials, reacting them in the presence of a condensing agent and a catalyst to generate an oxadiazon hydrazide intermediate.

[0042] In this embodiment, the preparation method of 2,4-dichloro-5-isopropoxybenzohydrazide is as follows: In a 250 ml reaction bottle, first add 13 g of pivalic acid and 100 ml of toluene solvent, stir to fully dissolve; add 22.4 g of EDCI and 15.8 g of HOBt at room temperature, stir for 15 minutes, then add 25 g of 2,4-dichloro-5-isopropoxyphenylhydrazine and 15.1 g of N,N-diisopropylethylamine, stir well and heat to 60°C for insulation reaction; after the reaction is detected, cool to room temperature, add 25 ml of HCl (1.0 M) for washing and extraction, and collect the organic phase; the organic phase is then washed and extracted with 25 ml of brine, the organic phase is collected, and the solvent is spin-dried to obtain 2,4-dichloro-5-isopropoxyphenylhydrazine, with a product yield of 98.4%.

[0043] Example 2 A method for preparing 2,4-dichloro-5-isopropoxyphenylhydrazine comprises taking 2,4-dichloro-5-isopropoxyphenylhydrazine and pivalic acid as initial raw materials, reacting them in the presence of a condensing agent and a catalyst to generate an oxadiazon hydrazide intermediate.

[0044] In this embodiment, the preparation method of 2,4-dichloro-5-isopropoxybenzohydrazide is as follows: In a 250 ml reaction bottle, first add 13 g of pivalic acid and 100 ml of chloroform solvent, stir to fully dissolve; add 24.5 g of EDCI and 15.8 g of HOBt at room temperature, stir for 15 minutes, then add 25 g of 2,4-dichloro-5-isopropoxyphenylhydrazine and 12.9 g of triethylamine, stir well and heat to 50 ° C for insulation reaction; after the reaction is detected, cool to room temperature, add 25 ml of HCl (1.0 M) for washing and extraction, and collect the organic phase; the organic phase is then washed and extracted with 25 ml of brine, the organic phase is collected, and the solvent is spin-dried to obtain 2,4-dichloro-5-isopropoxyphenylhydrazine, with a product yield of 92.3%.

[0045] Example 3 A method for preparing 2,4-dichloro-5-isopropoxyphenylhydrazine comprises taking 2,4-dichloro-5-isopropoxyphenylhydrazine and pivalic acid as initial raw materials, reacting them in the presence of a condensing agent and a catalyst to generate an oxadiazon hydrazide intermediate.

[0046] In this embodiment, the preparation method of 2,4-dichloro-5-isopropoxybenzohydrazide is as follows: In a 250 ml reaction bottle, first add 13 g of pivalic acid and 100 ml of tetrahydrofuran solvent, stir to fully dissolve; add 22.4 g of diisopropylcarbodiimide and 15.8 g of 1-hydroxy-7-azabenzotriazole at room temperature, stir for 15 minutes, then add 25 g of 2,4-dichloro-5-isopropoxyphenylhydrazine and 15.1 g of pyridine, stir well and heat to 80°C for insulation reaction; after the reaction is detected, cool to room temperature, add 25 ml of HCl (1.0 M) for washing and extraction, and collect the organic phase; the organic phase is then washed and extracted with 25 ml of brine, the organic phase is collected, and the solvent is spin-dried to obtain 2,4-dichloro-5-isopropoxyphenylhydrazine.

[0047] Example 4 A method for preparing 2,4-dichloro-5-isopropoxyphenylhydrazine comprises taking 2,4-dichloro-5-isopropoxyphenylhydrazine and pivalic acid as initial raw materials, reacting them in the presence of a condensing agent and a catalyst to generate an oxadiazon hydrazide intermediate.

[0048] In this embodiment, the preparation method of 2,4-dichloro-5-isopropoxybenzohydrazide is as follows: In a 250 ml reaction bottle, first add 13 g of pivalic acid and 100 ml of dichloromethane solvent, stir to fully dissolve; add 22.4 g of HATU and 15.8 g of N-methylmorpholine at room temperature, stir for 15 minutes, then add 25 g of 2,4-dichloro-5-isopropoxyphenylhydrazine and 15.1 g of N,N-diisopropylethylamine, stir well and heat to 30°C for insulation reaction; after the reaction is detected, cool to room temperature, add 25 ml of HCl (1.0 M) for washing and extraction, and collect the organic phase; the organic phase is then washed and extracted with 25 ml of brine, the organic phase is collected, and the solvent is spin-dried to obtain 2,4-dichloro-5-isopropoxyphenylhydrazine.

[0049] Example 5 A method for preparing 2,4-dichloro-5-isopropoxyphenylhydrazine comprises taking 2,4-dichloro-5-isopropoxyphenylhydrazine and pivalic acid as initial raw materials, reacting them in the presence of a condensing agent and a catalyst to generate an oxadiazon hydrazide intermediate.

[0050] In this embodiment, the preparation method of 2,4-dichloro-5-isopropoxybenzohydrazide is as follows: In a 250 ml reaction bottle, first add 13 g of pivalic acid and 100 ml of ethyl acetate solvent, stir to fully dissolve; add 22.4 g of EDCI and 15.8 g of HOBt at room temperature, stir for 15 minutes, then add 25 g of 2,4-dichloro-5-isopropoxyphenylhydrazine and 15.1 g of N,N-diisopropylethylamine, stir well and heat to 100 °C for insulation reaction; after the reaction is detected, cool to room temperature, add 25 ml of HCl (1.0 M) for washing and extraction, and collect the organic phase; the organic phase is then washed and extracted with 25 ml of brine, the organic phase is collected, and the solvent is spin-dried to obtain 2,4-dichloro-5-isopropoxyphenylhydrazine.

[0051] Comparative Example 1 Compared with Example 2, except that the solvent used is N,N-dimethylformamide and the temperature is raised to 80°C for the reaction, the other operations are the same as those in Example 2. In addition, the other operation processes are the same as those in Example 2 and are not described here. The yield of the obtained hydrazide product is 96.8%.

[0052] Comparative Example 2 Compared with Example 2, except that the solvent used is N,N-dimethylformamide and the temperature is raised to 70°C for the reaction, the other operations are the same as those in Example 2. In addition, the other operation processes are the same as those in Example 2 and are not described here. The yield of the obtained hydrazide product is 95.2%.

[0053] Comparative Example 3 Compared with Example 2, except that the solvent used is toluene and the temperature is raised to 60°C for the reaction, the other operations are the same as those in Example 2. In addition, the other operation processes are the same as those in Example 2 and are not described in detail here. The yield of the obtained hydrazide product is 97.2%.

[0054] Comparative Example 4 Compared with Example 1, except that the amount of the catalyst HOBt used was 11.5 g, the other processes were the same as those in Example 1. In addition, the other operation processes were the same as those in Example 1 and are not described here. The yield of the obtained hydrazide product was 98.2%.

[0055] Comparative Example 5 Compared with Example 1, except that the amount of the catalyst HOBt used was 8.63 g, the other processes were the same as those in Example 1. In addition, the other operation processes were the same as those in Example 1 and are not described here. The yield of the obtained hydrazide product was 97.5%.

[0056] Comparative Example 6 Compared with Example 1, except that the amount of the catalyst HOBt used was 0 g, the other processes were the same as those in Example 1. In addition, the other operation processes were the same as those in Example 1 and are not described in detail herein. The yield of the obtained hydrazide product was 87.5%.

[0057] Comparative Example 7 Compared with Example 1, except that the catalyst used was 8.25 g of N,N-diisopropylethylamine, the other processes were the same as those in Example 1. In addition, the other operation processes were the same as those in Example 1 and are not described in detail herein. The yield of the obtained hydrazide product was 88.0%.

[0058] According to the above results, it can be seen that the beneficial effects of the embodiments of the present invention are as follows: the embodiments of the present invention provide a new method for synthesizing the oxadiazon intermediate 2,4-dichloro-5-isopropoxybenzohydrazide, which has a cheap and readily available raw material, lower cost, simpler and safer operation than the prior art, and has great application value in the industrial development of oxadiazon.

[0059] The above is a detailed description of the preferred embodiments of the present invention, describing the basic principles, main features and advantages of the present invention. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention. Those skilled in the art who are familiar with the profession can make some changes, modifications and evolutions of the technical contents disclosed above without departing from the spirit and scope of the present invention, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention. It is not necessary and impossible to list all the embodiments here. The obvious changes or modifications derived from this are still within the scope of protection of the embodiments of the present invention.

Claims

1. An oxadiazon intermediate, characterized in that: The oxadiazine intermediate is prepared by reacting 2,4-dichloro-5-isopropoxyphenylhydrazine and pivalic acid as raw materials in the presence of a condensing agent and a catalyst; wherein the reaction temperature is 30-100°C.

2. The oxadiazon intermediate according to claim 1, characterized in that The condensing agent is selected from any one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, diisopropylcarbodiimide, dicyclohexylcarbodiimide, 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate, and O-benzotriazole-tetramethyluronium hexafluorophosphate.

3. The oxadiazon intermediate according to claim 2, characterized in that The catalyst is selected from any one or two of 1-hydroxybenzotriazole, 1-hydroxy-7-azabenzotriazole, triethylamine, N,N-diisopropylethylamine, sodium bicarbonate, N-methylmorpholine, potassium carbonate, pyridine, and N,N-dimethylformamide.

4. The oxadiazon intermediate according to claim 3, characterized in that The molar ratio of the 2,4-dichloro-5-isopropoxyphenylhydrazine, pivalic acid, condensation agent and catalyst is 1:1-1.2:1-1.2:0.3-1.

2.

5. The oxadiazon intermediate according to claim 4, characterized in that The molar ratio of the 2,4-dichloro-5-isopropoxyphenylhydrazine, pivalic acid, condensation agent and catalyst is 1:1.2:1.1:0.6-1.

1.

6. A method for preparing the oxadiazon intermediate according to any one of claims 1 to 5, characterized in that: The following steps are involved: Pivalic acid is added to a solvent and stirred to dissolve, a condensation agent, a catalyst and 2,4-dichloro-5-isopropoxyphenylhydrazine are added at 0-30°C, the mixture is heated to 30-100°C for reaction, and then the mixture is acid-washed, water-washed, and concentrated under reduced pressure to remove the solvent to obtain an oxadiazon intermediate.

7. The method for preparing an oxadiazon intermediate according to claim 6, characterized in that: In the method for preparing the oxadiazon intermediate, the reaction is carried out at a temperature of 60-80°C.

8. The method for preparing an oxadiazon intermediate according to claim 6, characterized in that: In the preparation method of the oxadiazon intermediate, the solvent is selected from any one of chloroform, dichloromethane, 1,2-dichloroethane, tetrahydrofuran, ethyl acetate, N,N-dimethylformamide, and toluene.

9. An oxadiazon intermediate obtained by the method for preparing an oxadiazon intermediate according to claim 6.

10. Use of the oxadiazon intermediate as claimed in claim 1, 2, 3, 4, 5 or 9 in the preparation of a herbicide.

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