5-acyl barbituric acid compound containing pyrimidinedione structure, preparation method of 5-acyl barbituric acid compound and application of 5-acyl barbituric acid compound in herbicide

Abstract

The invention relates to a 5-acyl barbituric acid compound containing a pyrimidinedione structure, a preparation method of the 5-acyl barbituric acid compound and application of a herbicide of the 5-acyl barbituric acid compound. The phenoxyalkyl acyl chloride compound containing the pyrimidinedione structure is obtained by taking a nitrophenol compound as a raw material through nucleophilic reaction, hydrogenation reduction reaction, condensation ring closing reaction, hydrolysis reaction and acylating chlorination reaction. The 5-acyl barbituric acid compound containing the pyrimidinedione structure is obtained through an intermolecular condensation reaction with a barbituric acid compound, and a weeding test result shows that the yield of the 5-acyl barbituric acid compound containing the pyrimidinedione structure is increased at the dosage of 150 g / hectare in post-seedling treatment. The compound disclosed by the invention has a good growth inhibition effect on dicotyledonous plants such as rape, piemarker, amaranthus retroflexus and chenopodium album and monocotyledonous plants such as barnyard grass, digitaria sanguinalis, eleusine indica and green bristlegrass, and is a broad-spectrum herbicide with a novel structure and a wide application prospect.

Description

[0001] The invention belongs to the technical field of herbicides, and specifically relates to a 5-acylbarbituric acid compound containing a pyrimidinedione structure, a preparation method and application of the same as a herbicide. Background Art

[0002] Weeds compete with crops for nutrients, water, sunlight and space, promote the occurrence and spread of pests and diseases, and affect the health of humans and animals. So far, the most effective way to control weeds is to apply chemical herbicides. Chemical herbicides have played a huge role in controlling weeds in farmland and ensuring food security. However, the long-term, large-scale and irrational use of chemical herbicides has brought about problems such as environmental pollution, food quality and safety, and weed resistance. Creating new herbicides with high efficiency, low toxicity and unique mode of action is an effective way to solve these problems.

[0003] The present invention uses the previously discovered 5-acylbarbituric acid with good herbicidal activity as a lead structure, introduces the pyrimidinedione structure into the benzene ring part of the 5-acylbarbituric acid through the active substructure splicing method, and designs and synthesizes 5-acylbarbituric acid compounds containing the pyrimidinedione structure for the first time. The herbicidal activity test found that some compounds showed herbicidal activity comparable to or even better than that of the control drug fluazifop-butyl. At present, there are no reports on the synthesis of 5-acylbarbituric acid compounds containing the pyrimidinedione structure and their use in agricultural herbicides. Summary of the invention

[0004] The purpose of the present invention is to provide a synthesis of a 5-acylbarbituric acid compound containing a pyrimidinedione structure and its use in agricultural herbicides; the first aspect of the present invention is to provide a compound represented by formula I, or a stereoisomer thereof, or an agriculturally chemically acceptable salt thereof:

[0005]

[0006] Among them, R 1 , R 2 , R 3 , R 4 Independently selected from the following groups: one of hydrogen, halogen, C1-C6 straight chain or branched chain alkyl, and halogen-substituted C1-C6 straight chain or branched chain alkyl;

[0007] R 5 , R 6 , R 9 Independently selected from the following groups: one of hydrogen, C1-C6 straight chain or branched chain alkyl, and halogen-substituted C1-C6 straight chain or branched chain alkyl;

[0008] R 7 , R 8Independently selected from the following groups: one of hydrogen, C1-C6 straight chain or branched chain alkyl, and halogen-substituted C1-C6 straight chain or branched chain alkyl;

[0009] n is selected from 1, 2, 3 or 4.

[0010] Preferably, the R 1 , R 2 , R 3 , R 4 are independently selected from the following groups: hydrogen or halogen;

[0011] The R 5 , R 6 , R 9 Independently selected from the following groups: one of hydrogen, C1-C6 straight chain or branched chain alkyl or halogen-substituted C1-C6 straight chain or branched chain alkyl;

[0012] The R 7 , R 8 Independently selected from: C1-C6 straight or branched chain alkyl;

[0013] n is selected from 1, 2 or 3;

[0014] Further preferably, the halogen is fluorine, chlorine, bromine or iodine;

[0015] The C1-C6 straight or branched alkyl group is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl or hexyl;

[0016] The halogen-substituted C1-C6 straight or branched alkyl group is: -CFH2, -CF2H, -CF3, -CH3CFH2, -CH3CF2H or -CH3CF3.

[0017] More preferably, the R 1 , R 2 , R 3 , R 4 are independently selected from: hydrogen, fluorine or chlorine;

[0018] The R 5 , R 6 , R 9 Independently selected from: hydrogen, methyl or -CF3;

[0019] The R 7 , R 8 independently selected from: methyl;

[0020] n is selected from 1 or 3.

[0021] The present invention also provides the specific structure of the compound as follows:

[0022]

[0023]

[0024] The second aspect of the present invention is to provide a method for preparing a compound of formula I, or a stereoisomer thereof, or an agrochemically acceptable salt thereof, which comprises the following steps:

[0025] Step a: dissolving the compound of formula 1 and the compound of formula 2 in a solvent, and preparing a compound of formula 3 under alkaline conditions;

[0026]

[0027] Step b: dissolving the compound of formula 3 in a solvent and reacting under reducing conditions to obtain a compound of formula 5;

[0028]

[0029] Step c: reacting a compound of formula 4 with a compound of formula 5 in an acidic solvent to prepare a compound of formula 6;

[0030]

[0031] Step d: dissolving the compound of formula 6 in a solvent, adding a base and a R6X compound to prepare a compound of formula 7;

[0032]

[0033] Step e: dissolving the compound of formula 7 in a solvent, adding a base to hydrolyze to obtain a compound of formula 8;

[0034]

[0035] Step f and step g: the compound of formula 8 is dissolved in a solvent, and a chlorination agent is added to obtain a compound of formula 9; the compound of formula 9 and

[0036] The compound of formula 10 is dissolved in a solvent, a base is added, and the reaction is performed to prepare a compound of formula I;

[0037]

[0038] Wherein the substituent R in Formulas 1 to 9 and Formula I 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , n is defined as in any of the above, wherein X represents a halogen.

[0039] Preferably, the solvent in step a, step b, step d, step e and step f is selected from one or two of N,N-dimethylformamide, methanol, ethanol, ethyl acetate, dichloromethane, toluene, DMSO, acetone, acetonitrile, methyl tert-butyl ether, diethyl ether and water;

[0040] Preferably, the solvent in step a is selected from N,N-dimethylformamide;

[0041] In the step b, the solvent is selected from ethyl acetate;

[0042] In said step d, the solvent is selected from N,N-dimethylformamide;

[0043] In said step e, the solvent is selected from methanol and water;

[0044] In the step f, the solvent is selected from dichloromethane;

[0045] In the step g, the solvent is selected from dichloromethane;

[0046] And / or, the alkaline conditions of step a, step d, step e, and step g are selected from sodium hydrogen, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, barium hydroxide, N,N-diisopropylethylamine, triethylamine, lithium diisopropylamide, n-(C 1-6 One or both of lithium (alkyl), potassium butoxide or potassium pentoxide;

[0047] Preferably, the alkaline condition in step a is selected from potassium carbonate;

[0048] The alkaline condition in step d is selected from potassium carbonate;

[0049] The alkaline condition in step e is selected from lithium hydroxide;

[0050] The alkaline condition in step g is selected from triethylamine;

[0051] And / or, the reduction conditions of step b are palladium / carbon and hydrogen, iron powder and hydrochloric acid, zinc powder and hydrochloric acid, lithium aluminum tetrahydride or sodium borohydride,

[0052] Preferably, the reduction conditions in step c are palladium / carbon and hydrogen;

[0053] And / or, the acidic solvent in step c is hydrochloric acid, acetic acid or sulfuric acid:

[0054] Preferably, the acidic condition in step c is acetic acid;

[0055] And / or, the chlorination agent in step f is thionyl chloride.

[0056] The third aspect of the present invention provides a pesticide composition, which comprises at least the compound of formula I, or a stereoisomer thereof, or an agrochemically acceptable salt thereof and a carrier; the carrier is in liquid or solid form.

[0057] The fourth aspect of the present invention provides an agricultural application, which is the use of the aforementioned compound, or its stereoisomer, or its agrochemically acceptable salt or the pesticide composition in an agricultural herbicide. Preferably, the agricultural herbicide is used to kill weeds, and the weeds are dicotyledons or monocotyledons.

[0058] Further preferably, the weeds are rapeseed, velvetleaf, Amaranthus retroflexus, Leonurus japonicus, barnyard grass, crabgrass, goosegrass or foxtail grass.

[0059] A fifth aspect of the present invention provides a method for controlling or preventing unwanted plant growth, wherein a herbicidally effective amount of a compound as defined in any of the preceding items, or its stereoisomers, or its agrochemically acceptable salts or said pesticide composition is applied to these plants, their parts or their loci.

[0060] The following is an explanation and description of the terms of the present invention:

[0061] The compounds and derivatives provided in the present invention can be named according to the IUPAC (International Union of Pure and Applied Chemistry) or CAS (Chemical Abstracts Service, Columbus, OH) nomenclature system.

[0062] "Substitution" refers to the replacement of a hydrogen atom in a molecule by another different atom or molecule.

[0063] The minimum and maximum carbon atom content of a hydrocarbon group is indicated by a prefix, for example, the prefix C1-b alkyl indicates any alkyl group containing from "a" to "b" carbon atoms. Thus, for example, "C1-4 alkyl" refers to an alkyl group containing 1 to 4 carbon atoms.

[0064] The term "alkyl" refers to a saturated hydrocarbon chain with a specified number of member atoms. For example, C1-6 alkyl refers to an alkyl group with 1 to 6 member atoms, such as 1 to 4 member atoms. The alkyl group can be straight or branched. Representative branched alkyl groups have one, two or three branches. The alkyl group may be optionally substituted with one or more substituents as defined herein. Alkyl includes methyl, ethyl, propyl (n-propyl and isopropyl), butyl (n-butyl, isobutyl and tert-butyl), pentyl (n-pentyl, isopentyl and neopentyl) and hexyl, 2,2-dimethylbutyl and 2,3-dimethylbutyl, etc. The term "C1-C3 alkyl" refers to a straight or branched saturated hydrocarbon group with 1-3 carbon atoms. The alkyl group may also be part of other groups, such as C1-C6 alkoxy.

[0065] The term "halogen" refers to fluorine, chlorine, bromine or iodine.

[0066] The term "halogen-substituted alkyl" or "halogen-substituted C1-C6 straight or branched alkyl" means that the hydrogen atoms in the alkyl group may be substituted by one or more halogen atoms. For example, C1-4 halogen alkyl refers to an alkyl group containing 1 to 4 carbon atoms in which the hydrogen atoms are substituted by one or more halogen atoms, such as: -CFH2, -CF2H, -CF3, -CH3CFH2, -CH3CF2H or -CH3CF 3。

[0067] The term "agronomically acceptable salt" refers to the above-mentioned compound or its stereoisomer, acidic and / or basic salts formed with inorganic and / or organic acids and bases, also including zwitterionic salts (inner salts), and also including quaternary ammonium salts, such as alkylammonium salts. These salts can be directly obtained in the final separation and purification of the compound. It can also be obtained by mixing the above-mentioned compound, or its stereoisomer, with a certain amount of acid or base appropriately (such as equivalent). These salts may form precipitation in the solution and be collected by filtering, or be recovered after solvent evaporation, or be obtained by freeze drying after reaction in an aqueous medium. The salt described in the present invention can be the hydrochloride, sulfate, citrate, benzenesulfonate, hydrobromide, hydrofluoride, phosphate, acetate, propionate, succinate, oxalate, malate, succinate, fumarate, maleate, tartrate or trifluoroacetate of the compound.

[0068] Compounds according to the present invention can be used as herbicides in unmodified forms, but they are usually formulated into compositions using formulation adjuvants (such as carriers, solvents and surfactants) in a variety of ways. These formulations can be in different physical forms, for example, in the following forms: dusting agents, gels, wettable powders, water dispersible granules, water dispersible tablets, effervescent compressed tablets, emulsifiable concentrates, micro-emulsifiable concentrates, oil-in-water emulsions, flowable oils, aqueous dispersions, oily dispersions, suspoemulsions, capsule suspensions, emulsifiable granules, soluble liquids, water-soluble concentrates, impregnated polymer films or in known other forms. For water-soluble compounds, preferably soluble liquids, water-soluble concentrates or water-soluble granules. Such formulations can be used directly or can be diluted before use. Can be diluted with, for example, water, liquid fertilizers, micronutrients, biological organisms, oil or solvents.

[0069] These formulations can be prepared, for example, by mixing the active ingredients with formulation adjuvants so as to obtain compositions in the form of finely divided solids, granules, solutions, dispersions or emulsions. The active ingredients can also be formulated together with other adjuvants.

[0070] Obviously, according to the above contents of the present invention, in accordance with common technical knowledge and customary means in the art, without departing from the above basic technical ideas of the present invention, other various forms of modification, replacement or change may be made.

[0071] Beneficial technical effects of the present invention: The present invention provides a 5-acylbarbituric acid compound containing a pyrimidinedione structure, using the 5-acylbarbituric acid with good herbicidal activity found in previous work as a leading structure, introducing the pyrimidinedione structure fragment into the benzene ring part of the 5-acylbarbituric acid through the active substructure splicing method, and designing and synthesizing the 5-acylbarbituric acid compound containing a pyrimidinedione structure for the first time; the 5-acylbarbituric acid compound containing a pyrimidinedione structure provided by the present invention has an excellent inhibitory effect on the growth of weeds such as rape, ramie, Amaranthus retroflexus and Leonurus japonicus at a dosage of 150 g / hectare after post-emergence treatment, and some compounds show herbicidal activity comparable to or even better than that of the control drug fluazifop-butyl. The present invention has important guiding significance for the development of new candidate herbicide molecules of the 5-acylbarbituric acid class containing a pyrimidinedione structure, and provides a new prevention and control strategy for solving the increasingly serious drug resistance of farmland weeds. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 : Target compound I-5 1 HNMR;

[0073] Figure 2 : Target compound I-5 13 CNMR. DETAILED DESCRIPTION

[0074] The present invention is further illustrated by the following examples, but are not intended to limit the present invention.

[0075] Intermediate Preparation Example 1: Synthesis of ethyl 2-chloro-5-nitrophenoxyacetate

[0076]

[0077] 2-Chloro-5-nitrophenol (17.3 g, 100 mmol) was dissolved in 200 mL N, N-dimethylformamide (DMF), and potassium carbonate (20.7 g, 150 mmol) and ethyl chloroacetate (12.2 g, 100 mmol) were added in sequence, and the reaction system was stirred at room temperature for 12 h. Then 500 mL of water was added to the reaction system, extracted twice with ethyl acetate, and the ethyl acetate was combined. The organic phase was washed three times with saturated brine and then dried over anhydrous sodium sulfate. After the solvent was dried under reduced pressure, 23.7 g of brown oil was obtained with a yield of 91.5%.

[0078] Intermediate Preparation Example 2: Synthesis of ethyl 2-chloro-5-aminophenoxyacetate

[0079]

[0080] 2-Chloro-5-nitrophenoxyethyl acetate (23.7 g, 91.5 mmol) was dissolved in 200 mL of ethyl acetate, 5% palladium / carbon (2.4 g) was added, and then hydrogen was introduced, and the reaction system was stirred at room temperature for 24 h. The reaction system was filtered, the filtrate was collected, the solvent was dried under reduced pressure, and the residue was purified by column chromatography to obtain 20.3 g of a light yellow solid, the eluent was petroleum ether: ethyl acetate, the volume ratio was 5:1, and the yield was 96.7%.

[0081] Intermediate Preparation Example 3: Synthesis of ethyl 2-(2-chloro-5-(2,6-dioxo-4-trifluoromethyl-3,6-dihydropyrimidin-1(2H)-yl)phenoxy)acetate

[0082]

[0083] Dissolve ethyl 2-chloro-5-aminophenoxyacetate (4.58 g, 20 mmol) in 50 mL of glacial acetic acid, add ethyl 3-(N,N-dimethylurea)-4,4,4-trifluorobut-2-enoate (5.08 g, 20 mmol), and then heat to 120°C and stir for 12 hours. Cool the reaction system to room temperature, and a white solid precipitates. Filter, wash with water, and vacuum dry to obtain 5.2 g of a white solid with a yield of 66.7%.

[0084] Intermediate Preparation Example 4: Synthesis of ethyl 2-(2-chloro-5-(3-methyl-2,6-dioxo-4-trifluoromethyl-3,6-dihydropyrimidin-1(2H)-yl)phenoxy)acetate

[0085]

[0086] Ethyl 2-(2-chloro-5-(2,6-dioxo-4-trifluoromethyl-3,6-dihydropyrimidin-1(2H)-yl)phenoxy)acetate (3.92 g, 10 mmol) was dissolved in 40 mL of N,N-dimethylformamide, potassium carbonate (2.76 g, 20 mmol) and iodomethane (1.42 g, 10 mmol) were added, and the reaction system was heated to 50 ° C and stirred for 12 h. Then 100 mL of water was added to the reaction system, extracted twice with ethyl acetate, and the ethyl acetate was combined. The organic phase was washed three times with saturated brine and then dried over anhydrous sodium sulfate. After the solvent was dried under reduced pressure, the residue was purified by column chromatography to obtain 3.63 g of a white solid, the eluent was petroleum ether:ethyl acetate, the volume ratio was 10:1, and the yield was 89.4%.

[0087] Intermediate Preparation Example 5: Synthesis of 2-(2-chloro-5-(3-methyl-2,6-dioxo-4-trifluoromethyl-3,6-dihydropyrimidin-1(2H)-yl)phenoxy)acetic acid

[0088]

[0089] Dissolve 2-(2-chloro-5-(3-methyl-2,6-dioxo-4-trifluoromethyl-3,6-dihydropyrimidin-1(2H)-yl)phenoxy)ethyl acetate (2.03 g, 5 mmol) in 20 mL of methanol, add lithium hydroxide (0.48 g, 20 mmol) and 2 mL of water, and stir the reaction system at room temperature for 12 h. The solvent in the reaction system was dried under reduced pressure, and the residue was dissolved in 10 mL of water, and the pH was adjusted to 1 with 1 M hydrochloric acid, and then the aqueous phase was extracted with ethyl acetate twice, and the ethyl acetate was combined. The organic phase was washed with water once, washed with saturated brine three times, and then dried over anhydrous sodium sulfate. After the solvent was dried under reduced pressure, 1.3 g of white solid was obtained, with a yield of 68.4%.

[0090] Example 1: Synthesis of 5-(2-(2-chloro-5-(3-methyl-2,6-dioxo-4-trifluoromethyl-3,6-dihydropyrimidin-1(2H)-yl)phenoxy)-1-hydroxyethylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione

[0091]

[0092] 2-(2-chloro-5-(3-methyl-2,6-dioxo-4-trifluoromethyl-3,6-dihydropyrimidin-1(2H)-yl)phenoxy)acetic acid (1.3 g, 3.4 mmol) was dissolved in 20 mL of dichloromethane (DCM), and then 10 mL of dichlorothionyl (SOCl2) and a drop of DMF were added, and the reaction system was stirred at 60 ° C for 12 h. After the solvent in the reaction system was dried under reduced pressure, the obtained residue was redissolved in 20 mL of dichloromethane, and triethylamine (0.69 g, 6.8 mmol) was added, and the reaction system was stirred at room temperature for 48 h. The reaction system was dried under reduced pressure, and the residue was purified by column chromatography to obtain 0.9 g of white solid, the eluent was petroleum ether: ethyl acetate, the volume ratio was 2: 1, and the yield was 51.4%.

[0093] The derivatives prepared by the preparation methods of Examples 1 to 6 using different raw materials are listed in Table 1. 1 H NMR, 13C NMR (Bruker AV-500 spectrometer using tetramethylsilaneas the internal standard) and melting point data are shown in Table 2. 1 HNMR and 13 CNMR see the attached figure in the specification Figure 1 and Figure 2 .

[0094] Table 1 Structures of target compounds

[0095]

[0096]

[0097] Table 2 NMR and melting point data of some target compounds

[0098]

[0099]

[0100]

[0101] Effect Example 1

[0102] The compounds provided by the present invention are used to test the herbicidal activity in greenhouse potted plants. The test objects are dicotyledonous plants (rapeseed, velvetleaf, Amaranthus retroflexus, Chenopodium album) and monocotyledonous plants (barnyard grass, crabgrass, goosegrass, Setaria viridis), and the test method is the fresh weight inhibition method.

[0103] The test method is as follows:

[0104] Place 150g of sandy clay in a small plastic cup with a diameter of 8cm and moisten it with water. Then plant 15 germinated seeds to a depth of 1-2cm and place them in a greenhouse. When the seedlings grow to the two-leaf and one-heart stage, spray the stems and leaves. Spray the solution of the compound on the stems and leaves of the plants at a dosage of 150g / hectare at a dosage of 1000 liters of water / hectare, and use the untreated seedlings as the control group. Set up three parallels for each experimental group. After 3 weeks, weigh the fresh weight of the aboveground part of each potted plant after cutting it from the boundary between the root and seedling, and express the efficacy as the percentage of fresh weight inhibition. The inhibition rate calculation formula is: Inhibition rate (%) = (fresh weight of blank control grass - fresh weight of treated pot grass) / fresh weight of blank control grass × 100%.

[0105] The test results of the above greenhouse potted herbicidal activity are shown in Table 3:

[0106] Table 3 Inhibition rate of greenhouse potted herbicidal activity of some target compounds (%)

[0107]

[0108]

[0109] The results of greenhouse potted herbicidal activity showed that some target compounds showed excellent herbicidal activity. For example, the inhibition rate of compound I-8 on dicotyledonous plants rape, velvetleaf, Amaranthus retroflexus and Chenopodium album and monocotyledonous plants barnyard grass, crabgrass, goosegrass and foxtail grass was 100%, indicating that this class of compounds has broad-spectrum herbicidal activity.

[0110] In addition, through structure-activity relationship studies, it was found that the number of side chain carbons of the target compound has a certain effect on the herbicidal activity. When n=3, the herbicidal activity of the compound is generally higher than that of the compound n=1. The substituents on the benzene ring of the target compound also have a great influence on the herbicidal activity of the compound. When R3 of the compound is a fluorine atom and R1 is a chlorine atom, the herbicidal activity of compound I-8 is the best. The above results show that the compounds currently provided have application potential in the selective control of farmland weeds.

[0111] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A compound of formula I, or a stereoisomer thereof, or an agrochemically acceptable salt thereof: in, R 1 , R 2 , R 3 , R 4 Independently selected from the following groups: one of hydrogen, halogen, C1-C6 straight chain or branched chain alkyl, and halogen-substituted C1-C6 straight chain or branched chain alkyl; R 5 , R 6 , R 9 Independently selected from the following groups: one of hydrogen, C1-C6 straight chain or branched chain alkyl, and halogen-substituted C1-C6 straight chain or branched chain alkyl; R 7 , R 8 Independently selected from the following groups: one of hydrogen, C1-C6 straight chain or branched chain alkyl, and halogen-substituted C1-C6 straight chain or branched chain alkyl; n is selected from 1, 2, 3 or 4.

2. The compound according to claim 1, or its stereoisomer, or its agrochemically acceptable salt, characterized in that: The R 1 , R 2 , R 3 , R 4 are independently selected from the following groups: hydrogen or halogen; The R 5 , R 6 , R 9 Independently selected from the following groups: one of hydrogen, C1-C6 straight chain or branched chain alkyl or halogen-substituted C1-C6 straight chain or branched chain alkyl; The R 7 , R 8 Independently selected from: C1-C6 straight or branched chain alkyl; n is selected from 1, 2 or 3; Preferably, the halogen is fluorine, chlorine, bromine or iodine; The C1-C6 straight or branched alkyl group is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl or hexyl; The halogen-substituted C1-C6 straight or branched alkyl group is: -CFH2, -CF2H, -CF3, -CH3CFH2, -CH3CF2H or -CH3CF3.

3. The compound according to any one of claims 1 to 4, or its stereoisomer, or its agrochemically acceptable salt, characterized in that: The R 1 , R 2 , R 3 , R 4 are independently selected from: hydrogen, fluorine or chlorine; The R 5 , R 6 , R 9 Independently selected from: hydrogen, methyl or -CF3; The R 7 , R 8 independently selected from: methyl; n is selected from 1 or 3.

4. The compound according to any one of claims 1 to 3, or its stereoisomer, or its agrochemically acceptable salt, characterized in that: The specific structure of the compound is 5. A method for preparing the compound of formula I according to any one of claims 1 to 4, or its stereoisomers, or its agrochemically acceptable salts, characterized in that: It includes the following steps: Step a: dissolving the compound of formula 1 and the compound of formula 2 in a solvent, and preparing a compound of formula 3 under alkaline conditions; Step b: dissolving the compound of formula 3 in a solvent and reacting under reducing conditions to obtain a compound of formula 5; Step c: reacting a compound of formula 4 with a compound of formula 5 in an acidic solvent to obtain a compound of formula 6; Step d: dissolving the compound of formula 6 in a solvent, adding a base and a R6X compound to prepare a compound of formula 7; Step e: dissolving the compound of formula 7 in a solvent, adding a base to hydrolyze to obtain a compound of formula 8; Step f and step g: the compound of formula 8 is dissolved in a solvent, and a chlorination agent is added to obtain a compound of formula 9; the compound of formula 9 and the compound of formula 10 are dissolved in a solvent, and a base is added to react to obtain a compound of formula I; Wherein the substituent R in Formulas 1 to 9 and Formula I 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , n is as defined in any one of claims 1 to 4, wherein X represents a halogen.

6. The preparation method according to claim 5, characterized in that: The solvent in step a, step b, step d, step e and step f is selected from one or two of N,N-dimethylformamide, methanol, ethanol, ethyl acetate, dichloromethane, toluene, DMSO, acetone, acetonitrile, methyl tert-butyl ether, diethyl ether and water; Preferably, the solvent in step a is selected from N,N-dimethylformamide; In the step b, the solvent is selected from ethyl acetate; In said step d, the solvent is selected from N,N-dimethylformamide; In said step e, the solvent is selected from methanol and water; In the step f, the solvent is selected from dichloromethane; In the step g, the solvent is selected from dichloromethane; And / or, the alkaline conditions of step a, step d, step e, and step g are selected from sodium hydrogen, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, barium hydroxide, N,N-diisopropylethylamine, triethylamine, lithium diisopropylamide, n-(C 1-6 One or both of lithium (alkyl), potassium butoxide or potassium pentoxide; Preferably, the alkaline condition in step a is selected from potassium carbonate; The alkaline condition in step d is selected from potassium carbonate; The alkaline condition in step e is selected from lithium hydroxide; The alkaline condition in step g is selected from triethylamine; And / or, the reduction conditions of step b are palladium / carbon and hydrogen, iron powder and hydrochloric acid, zinc powder and hydrochloric acid, lithium aluminum tetrahydride or sodium borohydride, Preferably, the reduction conditions in step c are palladium / carbon and hydrogen; And / or, the acidic solvent in step c is hydrochloric acid, acetic acid or sulfuric acid: Preferably, the acidic condition in step c is acetic acid; And / or, the chlorination agent in step f is thionyl chloride.

7. A pesticide composition comprising at least one compound of formula I according to any one of claims 1 to 4, or a stereoisomer thereof, or an agrochemically acceptable salt thereof and a carrier; the carrier is in liquid or solid form.

8. Use of the compound according to any one of claims 1 to 4, or its stereoisomer, or its agrochemically acceptable salt, or the pesticide composition according to claim 7 in an agricultural herbicide, preferably, the agricultural herbicide is used to kill weeds, and the weeds are dicotyledons or monocotyledons.

9. The use according to claim 8, wherein the weeds are rape, velvetleaf, Amaranthus retroflexus, Leonurus japonicus, Echinochloa crusgalli, Digitaria sanguinea, Goosegrass or Setaria viridis.

10. A method for controlling or preventing unwanted plant growth, wherein a herbicidally effective amount of a compound as defined in any one of claims 1 to 4, or a stereoisomer thereof, or an agrochemically acceptable salt thereof, or a pesticidal composition as claimed in claim 7 is applied to these plants, parts thereof or the locus thereof.

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