JPS6241592B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel pyrazine derivative, and more particularly to a 2-cyanopyrazine derivative and a herbicide containing the compound as an active ingredient. According to the invention, the general formula [In the formula, R ₁ represents an ethyl group or n-propyl group, and R ₂ represents a hydrogen atom, a halogen atom, or a methyl group] A 2-cyanopyrazine derivative represented by the following is provided. A group of 2-cyanopyrazine derivatives represented by the formula () are new compounds that have not been described in any literature, and the present inventors have now discovered that these compounds have excellent herbicidal activity as active ingredients of herbicides. It was done. In particular, in paddy field flooded soil treatment and upland soil treatment, the compound of formula () forms a firm chemical treatment layer on the soil surface, is virtually harmless to transplanted rice, and is effective against annual weeds such as field weeds. It was found that it has excellent control ability. Examples of the "halogen atom" used in the general formula () include fluorine, chlorine, sulfur, and iodine, with fluorine or chlorine being preferred. The 2-cyanopyrazine derivative of the present invention is, for example, a compound 2,3-dicyanopyrazine derivative (Japanese Patent Application Laid-Open No. 1983-1990), which is a compound known per se and represented by the following formula ().
106479, JP-A-55-45634) as a starting material, it is produced by hydrolysis reaction, decarboxylation reaction, and dehydration reaction. [In the formula, R ₁ and R ₂ have the above-mentioned meanings] In the hydrolysis reaction of the compound of the above formula (), an alkali metal hydroxide or an alkaline earth metal carbonate is mixed with water and/or an alcohol such as methanol or ethanol. This can be done by acting in a similar environment. Generally, -CN group becomes -CONH ₂ group by hydrolysis, but -CONH ₂ group undergoes further hydrolysis to -CONH 2 group.
Easily generates COOH groups. Therefore, by hydrolyzing the -CN group, one becomes -CONH ₂ group and the other becomes -COOH
In order to hydrolyze these groups, it is necessary to carefully select the reaction conditions, and the alkali metal hydroxides or alkaline earth metal carbonates used include sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and potassium carbonate. can give you
Among them, sodium hydroxide is preferred, and the amount used is generally from 1 mol to 1 mol of the compound of formula ().
Advantageously, 1.5 mol is used. The above hydrolysis reaction can be carried out from room temperature to the reflux temperature of the reaction mixture, preferably at reflux temperature, for a reaction time of usually 1 to 3 hours. The compound of formula () thus obtained can be purified by means known per se, such as recrystallization, extraction or chromatography. [In the formula, R ₁ and R ₂ have the above-mentioned meanings] Next, the decarboxylation reaction of the compound of formula () is carried out using a hydrocarbon such as xylene toluene, chlorobenzene, dichlorobenzene, etc. in an inert solvent. This can be carried out by heating a compound of formula () in a halogenated hydrocarbon such as under reflux conditions or in the absence of a solvent. The compound of formula () thus obtained can be purified by means known per se, such as recrystallization, extraction, chromatography, etc. [In the formula, R ₁ and R ₂ have the above-mentioned meanings] Next, the dehydration reaction of formula () is carried out by treating the compound of formula () with a dehydrating agent in the absence of a solvent or in an inert solvent. can be done. Suitable inert solvents that can be used include, for example, halogenated hydrocarbons such as chloroform carbon tetrachloride, and aromatic hydrocarbons such as benzene, toluene, and xylene. Further, as a dehydrating agent that can be used for dehydrating the compound of formula (), phosphorus pentoxide, phosphorus pentachloride, phosphorus oxychloride, etc. are advantageously used, and the amount of these dehydrating agents used is generally determined for the compound 1 of formula (). It is advantageous to use a molar excess of at least equivalents, preferably 3 to 10 equivalents. The reaction is generally carried out at room temperature to the reflux temperature of the reaction mixture, preferably at about
It can be carried out under elevated temperature conditions ranging from 50 °C to the reflux temperature of the reaction mixture, and if necessary, pyridine,
The reaction can be carried out in the presence of a base such as triethylamine or dimethylformamide, thereby promoting the reaction. The amount of such a base to be used is usually from several % by weight to twice the molar amount of the compound of formula (). Under such conditions, the dehydration reaction can usually be completed in about 2 to 5 hours. The compound of formula () thus obtained can be separated and/or purified by means known per se, such as recrystallization, extraction, chromatography, etc. Next, the method for producing the compound of formula () will be specifically explained with reference to reference examples and examples. Reference example 1 [2-carbamoyl-3-carboxy-5-n
-Synthesis of propylamino-6-m-chlorophenylpyrazine] 2,3-dicyano-5-n-propylamino-
2.98 g (0.01 mol) of 6-m-chlorophenylpyrazine was placed in 60 ml of 1N sodium hydroxide, stirred at 100°C for 3 hours while blowing nitrogen gas, and the resulting yellow solution was adjusted to pH 2 with 6N hydrochloric acid. It was adjusted.
Collect the precipitated crystals and wash with n-hexane.
2.32 g (75% yield) of product was obtained. Melting point 196-197°C (decomposition). Elemental analysis value C ₁₅ H ₁₅ N ₄ O ₃ Calculated value as Cl: C 53.8 H 4.5 N 16.7 Analysis value: C 54.0 H 4.3 N 16.9 Reference example 2 [2-carbamoyl-5-n-propylamino-6-m- Synthesis of chlorphenylpyrazine] 2-carbamoyl-3-carboxy-5-n-
1.0 g (0.003 mol) of propylamino-6-m-chlorophenylpyrazine was suspended in 10 ml of dichlorobenzene and stirred at 175°C for 1 hour. After the reaction, the red colored solution was left in a refrigerator overnight, and the precipitate was collected, and after washing with water, 0.15 g of product was obtained. Melting point 175-177℃. Elemental analysis value C ₁₄ H ₁₅ N ₄ Calculated value as OCl: C 57.8 H 5.2 N 19.3 Actual value: C 57.7 H 5.5 N 19.5 Example 1 [2-cyano-5-n-propylamino-6-
Synthesis of m-chlorphenylpyrudine] 2-carbamoyl-5-n-propylamino-
6-m-chlorophenylpyrazine 1.0g (0.0034
mol) was placed in 21.1 g (0.138 mol) of phosphorus oxychloride, 0.55 g (0.0069 mol) of pyridine was added at 3 to 4°C, stirred for 45 minutes, and then refluxed for 4 hours.
After the reaction, concentrate, dissolve the residue in 60 ml of chloroform, wash with water, concentrate the chloroform solution, add n-hexane to the resulting red oil, collect the precipitate, and recrystallize from n-hexane. 0.55g of product was obtained. Melting point 83-84℃. Elemental analysis value as C ₁₄ H ₁₃ N ₄ Cl Calculated value: C 61.7 H 4.8 N 20.5 Actual value: C 62.0 H 5.0 N 20.4 IR (KBr method, maximum absorption cm ^-1 ) 3360, 2215, 1560. Examples 2-5 The compounds listed in Table 1 below were obtained by the same method as described in Example 1.

【table】

[Table] 2 represented by the formula () provided by the present invention
- As mentioned above, cyanopyrazine derivatives exhibit very excellent selective herbicidal activity in the treatment of flooded paddy soil, foliage treatment during the weed growing season, field soil treatment, etc., and are extremely suitable as active ingredients in herbicides. Thus, according to the present invention, a herbicide containing a 2-cyanopyrazine derivative represented by the formula () as an active ingredient is provided. The herbicide of the present invention has the ability to suppress the germination of weed seeds and/or kill the foliage of weeds, and can be used as a pre-emergence herbicide and/or a post-emergence herbicide in paddy field flooding soil treatment, during the weed growth period. It exhibits excellent herbicidal effects in foliage treatment, field soil treatment, etc. In particular, the herbicide of the present invention exhibits excellent herbicidal activity in flooded paddy fields that are rich in water, and can be advantageously used as a herbicide for paddy fields.
This is thought to be because the active compound of the present invention dissolves in water and is easily absorbed from the seeds, roots, and leaves of weeds in water, and directly acts on the germination inhibition, growth inhibition, withering, etc. of the weeds. The herbicide containing the compound of the present invention as an active ingredient has the effect of selectively bleaching and killing weeds that germinate from the surface layer of the soil. It is substantially harmless to economic crops and can selectively control bleaching of weeds that occur in cultivated areas such as rice. Examples of weeds that can be controlled by the herbicide of the present invention include the following, but the following list is merely an example, and the herbicide of the present invention is effective against other weeds. It should be understood that it also exhibits excellent herbicidal effects as well. (1) Examples of rice field weeds include Asteraceae (e.g., Asteraceae), Lythraceae (e.g., Siberian capsicum, Aphrodisia spp., Azetian capsicum, Azeena), Lythraceae (e.g., Lythrum japonica, Lythrum japonica, Lythrum), Lythraceae (e.g. Lythrum japonica) , Polygonaceae, (e.g., water chickweed), Polygonaceae (e.g., Polygonaceae), Polygonaceae (e.g., willow knotweed), Chrysophyllaceae (e.g., Coccinaceae), Asteraceae (e.g., Asteraceae, Cannabis), Lemnaceae (e.g., Duckweed) , Hinjimo, Lemna), Cyperaceae (e.g., Hyderico, Firefly, Lamina, Cyperaceae), Poaceae (e.g., Poaceae, Noviaceae), Cyperaceae (e.g., Sagittarius, Lemna), Cyperaceae (e.g., Helaomodacaceae), Adifoliaceae (e.g. Adifoliaceae), Porphyridaceae (e.g. Aimidoro), etc. (2) Upland weeds include, for example, Chenopodiaceae (e.g., Coaxiaceae), Brassicaceae (e.g., shepherd's purse, Japanese radish, wild mustard), Amaranthaceae (e.g., Amaranthaceae),
Polygonaceae (e.g., Physcomyceae), Rubiaceae (e.g., Caryophyllaceae), Caryophyllaceae (e.g., Pygmyensis, Psyllidaceae, Caryophyllaceae), Psyllidaceae (e.g., Pyropianum), Asteraceae (e.g., P. elegans, Artemisia elegans, Dandelion), Convolvulaceae (e.g. Convolvulaceae), Oxalis (e.g. Oxalis), Poaceae (e.g. Poaceae, Poaceae), Euphorbiaceae (e.g. Convolvulus), Solanaceae (e.g. Cyperaceae), Cyperaceae (e.g. Cyperaceae) )Such. When the compound of the present invention is used as an active ingredient of a herbicide, one or a combination of two or more of the active compounds represented by the above formula () may be used in an inert liquid or an inert liquid commonly used in the herbicide field. It can be mixed with a solid carrier material or diluent and, if necessary, additives such as a surfactant, and formulated into a suitable dosage form. As the carrier material or diluent that can be used in the herbicide of the present invention, any carrier material or diluent commonly used in the field can be used. Examples of the solid carrier material or diluent include kaolin, diatomaceous earth, talc, and bentonite. , montmorillonite,
Examples include silica, clay, vermiculite, white carbon, mica, gypsum, calcium carbonate, starch, vegetable flour, etc., and liquid carrier materials or diluents include, for example, water, ethanol,
Cyclohexane, xylene, toluene, benzene, methylnaphthalene, kerosene, acetone, methylenalketone, cyclohexanone, isophorone, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, dioxane,
Examples include ethylene glycol ethyl ether and liquefied tetrafluoroethane. The herbicide of the present invention may contain a surfactant in a conventional amount depending on its dosage form, and examples of such surfactants include, for example, alkylbenzene sulfonate, lignin sulfonate, naphthalene sulfonate, formalin Condensate, dialkyl sulfosuccinate sodium salt, fatty acid salt, alkyl sulfate, higher alcohol sulfate ester, sorbitan fatty acid ester, polyalkylene glycol, polyoxyalkylene monoalkyl ether, polyoxyalkylene alkylaryl ether, polyoxyalkylene fatty acid ester, Polyoxyalkylene alkylmerkabutane ether, quaternary ammonium salts, and the like can be used alone or in combination of two or more. Therefore, the herbicide of the present invention generally contains the active compound of the formula (), although it depends on its dosage form.
At least 0.5% by weight, preferably 1 to 99%, more preferably 2% by weight, based on the weight of the herbicide.
It can be included in concentrations of ~80% by weight. Furthermore, the herbicide of the present invention can be formulated into any conventional dosage form such as a powder, granule, wettable powder, solvent, emulsion, or spray, depending on the method of application. The formulation can be carried out by methods known per se in the art. For example, powders, granules and wettable powders can be prepared by mixing and grinding at least one active compound of formula () with at least one of the solid carrier materials or diluents mentioned above, adding an appropriate amount of surfactant; They can be mixed uniformly and formulated into a formulation. Solutions or emulsions can also be prepared by dissolving or dispersing at least one active compound of formula () in at least one of the above liquid carrier materials or diluents, and optionally adding a surfactant. can be converted into Thus, in the case of powders and granules, from 2 to 80% by weight of active compound, based on the weight of the herbicide.
5 for wettable powders, solutions and emulsions.
It can be included at a concentration of ~60% by weight. Furthermore, the herbicide of the present invention can contain fungicides, insecticides, nematicides, fertilizers, plant growth regulators, etc. commonly used in the agricultural field, and can also be used in combination with other herbicides. can. As mentioned above, the herbicide of the present invention can be applied as a pre-emergence and/or post-emergence herbicide to direct soil as a paddy field flooded soil treatment or upland soil treatment, or directly sprayed on weeds as a foliar treatment. can do. The amount applied is not critical and can vary widely depending on the type of active compound, time of application, method of application, etc.
It is generally advantageous to apply at least 25 g, preferably from 50 to 2000 g of active compound per 10 are. However, the above application amount is just a standard, and it is of course possible to use less or more than the above amount depending on the condition of the crop, the infestation of weeds, etc. In addition, any conventional method can be used for its application, such as applying it from the ground or in the air to the area to be controlled before or after sowing or transplanting crops, or applying it together with seeds when sowing crops. Methods such as spraying on the ground are used. Alternatively, the germination of weed seeds contained in crop seeds can be inhibited by soaking the crop seeds in an aqueous solution containing the active compound of the present invention before sowing the crop seeds. is also possible. Next, specific examples of herbicide formulations and herbicidal activity provided by the present invention will be further explained using the following formulation examples. In the formulation examples, "parts" are parts by weight. Formulation Example 1 (Wettable powder) 40 parts of the active compound of the present invention was mixed with Zeeklite (trade name: Zeeklite Chemical Co., Ltd.) as a carrier material.
[manufactured by Kunimine Kogyo Co., Ltd.] and Kunilite [product name: manufactured by Kunimine Kogyo Co., Ltd.]
55 parts of a 2:1 mixture of
40% wettable powder is obtained. Formulation Example 2 (Emulsion) 15 parts of active compound of the invention, tetrahydrofuran
Mix and dissolve 80 parts and 5 parts of a surfactant (Sorbol 800A) to obtain a 15% emulsion. Formulation Example 3 (Granules) 10 parts of the active compound of the present invention, 50 parts of bentonite,
35 parts of Kunilite and surfactant (Solbol
After mixing and pulverizing 5 parts of 800A), add 10 parts of water, stir evenly, extrude through a sieve hole with a diameter of 0.7 mm, dry, and cut into appropriate lengths to obtain 10% granules. Next, plant test results of the herbicide according to the present invention will be shown to clarify the method of use of the present invention and its effects. Test Example 1 (Paddy field flooded soil treatment method) Fill a 1/5000 are polyethylene pot with paddy soil (planting soil), sow seeds of wild grass, broad-leaved weeds, and firefly to a surface layer of 2 cm.
The stock was transplanted. At the same time, two 3-leaf stage paddy rice plants were planted, transplanted to a depth of 2 cm, and flooded to a depth of 3 cm. At the same time as weed germination, a predetermined amount of a wettable powder containing the active compound of the present invention was weighed out, diluted to 10 ml of water per pot, and dropped onto the water surface. Thereafter, the plants were grown in a glass room, and three weeks after the treatment, the herbicidal effect and the effect on paddy rice were investigated. The results are shown in Table 2 below. In addition, the numerical values in the table in the test examples indicate the degree of paddy rice phytotoxicity and herbicidal effect, and are specifically as follows.

【table】

【table】

【table】

Claims (1)

[Claims] 1. General formula [In the formula, R ₁ represents an ethyl group or n-propyl group, and R ₂ represents a hydrogen atom, a halogen atom, or a methyl group] A 2-cyanopyrazine derivative represented by the following formula. 2 General formula [In the formula, R ₁ represents an ethyl group or n-propyl group, and R ₂ represents a hydrogen atom, a halogen atom, or a methyl group] A herbicide containing a 2-cyanopyrazine derivative as an active ingredient.