JPS6148508B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel pyrazine derivative, and more particularly to a 2,3-dicyanopyrazine derivative, a method for producing the same, and a herbicide containing the compound as an active ingredient. According to the invention, the general formula [In the formula, R ₁ is an unsaturated lower aliphatic hydrocarbon group,

group of [formula] or

represents a group of [Formula], where n is 1 or 2, R ₂ is a halogen atom, -COOH,
-CN, group or formula of formula -OR ₃

A 2,3-dicyanopyrazine derivative represented by the following formula is provided: R ₃ represents a hydrogen atom or a lower alkyl group, and R ₄ represents a lower alkyl group. A group of 2,3-dicyanopyrazine derivatives represented by the above general formula () are new compounds that have not been described in any literature, and the present inventors have now demonstrated that these compounds have excellent herbicidal activity as active ingredients of herbicides. was discovered. In particular, in the treatment of flooded paddy soil, the compound of the above formula () generally tends to form a firm chemical treatment layer on the surface layer of the flooded paddy field, although it depends on the type of substituent. It was found to be harmless to humans, and to have the ability to successfully control annual weeds such as field weeds. The "unsaturated lower aliphatic hydrocarbon group" used in the general formula () and the following description is linear or branched, and has at least one, preferably only one, carbon-carbon double chain in the chain. a hydrocarbon group having up to 6 carbon atoms, preferably up to 4 carbon atoms, having a bond or a triple bond, such as an allyl group, a methallyl group, an allylmethyl group, or a propargyl group. etc., among which allyl group is preferred. Among the "halogen atoms", chlorine atoms or bromine atoms are preferred. In addition, "lower alkyl group" has 1 to 6 carbon atoms.
, preferably 1 to 4 linear or branched saturated aliphatic hydrocarbon groups, such as methyl,
Ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, iso-amine, n-hexyl, etc., most preferably methyl or It is an ethyl group. Thus, the present invention provides the above formula ()
The following compounds can be exemplified as typical examples of the compound represented by, but the present invention is not limited to these. 2,3-dicyano-5-allylamino-6-phenylpyrazine, 2,3-dicyano-5-(2-hydroxy-n
-propylamino)-6-phenylpyrazine, 2,3-dicyano-5-(2-chloroethylamino)-6-phenylpyrazine, 2,3-dicyano-5-(2-bromoethylamino)-6-phenylpyrazine, 2・3-dicyano-5-(2-carboxyethylamino)-6-phenylpyrazine, 2,3-dicyano-5-[2-(diethylamino)ethylamino]-6-phenylpyrazine, 2,3-dicyano-5-( 2-hydroxyethylamino)-6-phenylpyrazine, 2,3-dicyano-5-(2-dianoethylamino)-6-phenylpyrazine, 2,3-dicyano-5-(3-diano-n-propylamino) -6-phenylpyrazine, 2,3-dicyano-5-(2-methoxyethylamino)-6-phenylpyrazine, 2,3-dicyano-5-(2-ethoxyethylamino-6-phenylpyrazine, 2,3-dicyano- 5-(3-carboxy-n
-propylamino)-6-phenylpyrazine, 2,3-dicyano-5-(3-methoxy-n-
propylamino)-6-phenylpyrazine, 2,3-dicyano-5-[3-(diethylamino)-n-propylamino]-6-phenylpyrazine, 2,3-dicyano-5-(3-hydroxy-n
-propylamino)-6-phenylpyrazine, 2,3-dicyano-5-(1-ethoxycarbonylmethylamino)-6-phenylpyrazine, 2,3-dicyano-5-(1-ethoxycarbonylethylamino)-6-phenylpyrazine , 2,3-dicyano-5-(1-ethoxycarbonyl-n-propylamino)-6-phenylpyrazine, and the like. The 2,3-dicyanopyrazine derivative of the present invention is
2,3-dicyano-5- represented by the following formula ()
It can be produced by reacting halo-6-phenylpyrazine with an amine represented by the following formula () according to the following reaction formula. [In the formula, R ₁ has the above-mentioned meaning, and X represents a halogen atom] The 2,3-dicyano-5-halo-6-phenylpyrazine of the formula () used as a starting material can be prepared by a method known per se ( For example, the following formula () manufactured by JP-A No. 50-59379) 2,3-dicyano-5-hydroxy-
It can be produced by treating 6-phenylpyrazine with a halogenating agent in the absence of a solvent or in an inert solvent. Examples of inert solvents that can be used include halogenated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride; benzene;
Aromatic hydrocarbons such as toluene and xylene are suitable. In addition, as the halogenating agent, any agent that is often used to convert a hydroxy group into a halogen atom can be used, such as phosphorus pentahalides such as phosphorus pentachloride and phosphorus pentabromide; Phosphorous oxyhalides such as phosphorus bromide; thionyl halides such as thionyl chloride, etc. are advantageously used. The amount of these halogenating agents used is not critical, but generally at least an equivalent amount per mole of the compound of formula (), preferably
It is advantageous to use an excess of 1.5 to 20 equivalents. In particular, a halogenating agent that is liquid at room temperature, such as phosphorus oxychloride, may be used in large excess so that it can simultaneously serve as a solvent. Although the reaction temperature is not critical, the reaction can generally be carried out at a temperature ranging from room temperature to the reflux temperature of the reaction mixture. Further, the halogenation reaction can be carried out in the presence of a tertiary amine such as pyridine, triethylamine or N.N-dimethylaniline, if necessary, thereby promoting the reaction. The amount of such tertiary amine used is not critical, but it is usually several percent by weight based on the compound of formula ().
It is used in approximately equimolar amounts. Under such conditions, the halogenation reaction can usually be completed in about 1 to 5 hours. The compound of formula () thus obtained can be separated and/or purified, if necessary, by means known per se, such as filtration, distillation, extraction, recrystallization, chromatography, etc., or a combination thereof. . Next, 2,3-dicyano-5-halo- of formula ()
The reaction between 6-phenylpyrazine and amines of formula () is generally carried out in an inert solvent such as acetone, ketones such as methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane; hydrocarbons such as benzene, toluene, and xylene. It can be done with Although the reaction temperature is not critical and can vary widely depending on the type of reactants used, it is generally preferred to use relatively low temperatures of about 50°C or less, especially cooling conditions at or below room temperature. Advantageous to use. The amount of the compound of formula () to be used is also not particularly restricted and can be varied over a wide range; however, it is generally used in an approximately equimolar to slightly excess molar amount relative to 1 mole of the compound of formula (). can. The reaction can be carried out in the presence of an acid binder, for example the amine of formula () itself, an inorganic or organic base such as sodium hydroxide, sodium carbonate, triethylamine. The compound represented by the formula () thus obtained can be prepared by a method known per se, such as percolation,
Distillation, extraction, recrystallization, chromatography, etc.
Or they can be separated and/or purified by a combination thereof. Next, reference examples and examples are given and the above formula ()
The method for producing the compound () and () will be explained in more detail. Reference example 7.0 g (0.0315 mol) of 2,3-dicyano-5-hydroxy-6-phenylpyrazine, 40.0 g (0.26 mol) of phosphorus oxychloride, and 2.77 g of pyridine
(0.035 mol) were mixed, and after stirring and refluxing for 4 hours, excess phosphorus oxychloride was distilled off under reduced pressure. The resulting black and colored residue was extracted with 150 ml of chloroform, insoluble materials were removed separately, and the chloroform solution was washed twice with 50 ml of water, dried over anhydrous calcium chloride overnight, and the solvent was distilled off to give a yellow A white solid was obtained. This solid was recrystallized from benzene and 6.1g of 2.
3-dicyano-5-chloro-6-phenylpyrazine was obtained. Melting point 139-141℃. Elemental analysis value as C ₁₂ H ₅ N ₄ Cl Calculated value: C 59.89 H 2.09 N 23.28 Actual value: C 59.80 H 2.20 N 23.41 Example 1 2,3-dicyano-5-chloro-6-phenylpyrazine 1.20 g (0.005 mol) ) in 20 ml of acetone, cooled to 5°C, and added 10 ml of acetone with stirring.
Allylamine 0.57g (0.010mol) dissolved in ml
was added dropwise over 10 minutes. After the dropwise addition was completed, the mixture was stirred at 10°C for 30 minutes. After the reaction, the precipitate precipitated was separated and removed, and the liquid was concentrated under reduced pressure to obtain a yellowish white solid. This yellowish white solid was washed with water, dried and recrystallized from benzene to produce 2,3-dicyano-5-allylamino-
0.95 g of 6-phenylpyrazine was obtained. Melting point 125~
126℃. Elemental analysis value C ₁₅ H ₁₁ N ₅ Calculated value: C 68.95 H 4.24 N 26.80 Actual value: C 69.03 H 4.05 N 26.93 Example 2 2,3-dicyano-5-chloro-6-phenylpyrazine 1.20 g (0.005 mol) was dissolved in 30 ml of tetrahydrofuran, cooled to 0 to 5°C, and while stirring, 0.75 ml of 2-hydroxy-n-propylamine was added.
g (0.01 mol) was added dropwise over 5 minutes. After the dropwise addition was completed, the mixture was stirred at 5 to 10°C for 30 minutes, the precipitate separated, and the liquid was concentrated under reduced pressure. The resulting solid was washed with water, dried, and then recrystallized from benzene to obtain 2,3-dicyano-5. 0.87 g of -(2-hydroxy-n-propylamino)-6-phenylpyrazine was obtained. melting point
127-129℃. Elemental analysis value Calculated value as C ₁₅ H ₁₃ N ₅ O: C 64.50 H 4.69 N 25.07 Actual value: C 64.70 H 4.76 N 24.95 Example 3 2,3-dicyano-5-chloro-6-phenylpyrazine 1.20 g (0.005 mol) ) was dissolved in 30 ml of acetone, cooled to 0°C, and while stirring, a solution prepared from 1.16 g (0.01 mol) of 2-chloroethylamine hydrochloride, 0.40 g (0.01 mol) of sodium hydroxide, and 10 ml of water was added for 10 minutes. dripped. After the dropwise addition was completed, the mixture was stirred at 0 to 5°C for 30 minutes. After the reaction, the reaction solution was concentrated under reduced pressure to obtain a yellowish white solid. This yellow-white solid was washed with water, dried, and then dissolved in THF, and hexane was added to obtain 0.68 g of 2,3-dicyano-5-(2-chloroethylamino)-6-phenylpyrazine as a precipitate. Melting point 153-156℃. Elemental analysis value C ₁₄ H ₁₀ N ₅ Calculated value as Cl: C 59.27 H 3.55 N 24.68 Actual value: C 59.05 H 3.43 N 24.79 Example 4 2.40 g (0.01 mol) of 2,3-dicyano-5-chloro-6-phenylpyrazine ) in 30 ml of acetone, cooled to 0-5°C, and mixed with 0.89 g (0.01 mol) of β-alanine and 0.80 g of sodium hydroxide while stirring.
(0.01 mol) and 20 ml of water.
It was dripped in minutes. After the dropwise addition was completed, the mixture was stirred at 0 to 10°C for 30 minutes. After the reaction was completed, 1.8 ml of concentrated hydrochloric acid was added to the reaction solution while cooling the reaction container with ice water, and the mixture was extracted with 120 ml of benzene. After washing the extracted benzene layer twice with 50 ml of a saturated aqueous sodium chloride solution, the solvent was concentrated under reduced pressure to obtain a yellow-white solid. This solid was recrystallized from benzene to give 2,3-dicyano-5-(2-carboxyethylamino)-6-phenylpyrazine.
0.83g was obtained. Melting point 155-162°C (decomposition). Elemental analysis value as C ₁₅ H ₁₁ N ₅ O ₂ Calculated value: C 61.43 H 3.78 N 23.88 Actual value: C 61.49 H 3.89 N 23.64 Example 5 2.40 g (0.01 1.16 g (0.01 mol) of 2-(diethylamino)ethylamine was added dropwise to the solution over 5 minutes while cooling to 5° C. and stirring. Subsequently, 10 ml of 2N aqueous sodium hydroxide solution was added dropwise over 5 minutes. After the dropwise addition was completed, the mixture was stirred at 5 to 10°C for 30 minutes. After the reaction is complete,
The benzene layer and the aqueous layer were separated, and the benzene solution was concentrated under reduced pressure to obtain a yellow-white solid. Wash this solid with water,
After drying, recrystallization from benzene yields 2,3-dicyano-5-[2-(diethylamino)ethylamino]
2.21 g of -6r phenylpyrazine was obtained. Melting point 96~
97.5℃. Elemental analysis value C ₁₈ H ₂₀ N ₆ Calculated value: C 67.48 H 6.29 N 26.23 Actual value: C 67.67 H 6.29 N 26.04 Example 6 2.40 g (0.01 mol) of 2,3-dicyano-5-chloro-6-phenylpyrazine was dissolved in 30 ml of tetrahydrofuran, cooled to 0 to 5°C, and while stirring, 2.62 g of DL-α-aminobutyric acid ethyl ester was added.
A solution prepared from (0.02 mol) and 10 ml of tetrahydrofuran was added dropwise over 30 minutes. After completion of dripping, 0~
Stirred at 10°C for 30 minutes. After the reaction was completed, the mixture was concentrated under reduced pressure to obtain a colored oil. This oil was extracted with benzene, the benzene solution was washed twice with 50 ml of water, and the solvent was distilled off to obtain a yellowish white solid. This solid was recrystallized from benzene and 2,3-dicyano-5-(1-
Ethoxycarbonyl-n-propylamino)-6
-0.63 g of phenylpyrazine was obtained. Melting point 82-84
℃. Elemental analysis value as C ₁₈ H ₁₇ N ₅ O ₂ Calculated value: C 64.47 H 5.11 N 20.88 Actual value: C 64.73 H 5.01 N 20.64 Examples 7 to 15 The following The compounds listed in Table 1 were obtained.

[Table] 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, It exhibits excellent herbicidal effects in foliage treatment during the weed growing season, field soil treatment, etc. In particular, the herbicide of the present invention exhibits excellent herbicidal activity in flooded paddy fields that can withstand abundant 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 herbicidal activity of the compound of the present invention varies depending on the type of amine substituent at the 5-position of the 2,3-dicyano-6-phenylpyrazine represented by the above general formula (), and in particular, the herbicidal activity of the compound of the present invention varies depending on the type of amine substituent at the 5-position of the 2,3-dicyano-6-phenylpyrazine represented by the above general formula (). 2・3
-Dicyano-5-allylamino-6-phenylpyrazine exhibits a remarkable herbicidal effect. Moreover, herbicides containing this compound as an active ingredient have the effect of selectively bleaching and killing weeds that germinate from the surface layer of paddy soil, and even when used for foliage treatment in fields, they are effective against rice, etc. The present invention is substantially harmless to important economic crops, and can selectively control weeds that occur in cultivated fields such as rice by bleaching. 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) Paddy field weeds, such as Asteraceae (e.g. Asteraceae), Asperaceae (e.g. Capsicum spp.
Lythraceae (e.g., Lythrum, Lythrum, Lythrum), Lythraceae (e.g., Lythrum), Lythraceae (e.g., Lythrum), Polygonaceae (e.g., Polygonum), Polygonaceae (e.g., Polygonum) , Chrysophyllaceae (e.g., Asperaceae), Lemnaceae (e.g., Lemnaceae, Poaceae), Lemnaceae (e.g., Duckweed, Hinjimo, Lemnaeus), Cyperaceae (e.g., Hyderico, Firefly, Cyperus japonica, Poaceae), Poaceae (e.g.: Phyllophoridae (e.g., Phyllanthus vulgaris, Noviera), Alocatidae (e.g., Subarnatidae, Sargassum), Omodacaceae (e.g., Helaomodacaceae), Amanidaceae (e.g., Amanitaceae), Amanidae (e.g., Aomidae), 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., Kishigigi, Hurtaceae), Rubiaceae (e.g., Caryophyllaceae), Caryophyllaceae (e.g., Caryophyllaceae, Chrysanthemum chinensis, Caryophyllaceae), Phosphoraceae (e.g., Prunus japonicus), Asteraceae (e.g., Harjiyon, Mugwort, Porphyra), Convolvulaceae (e.g. Convolvulaceae), Oxalis (e.g. Oxalis), Canidae (e.g. Sparrow-tail, Passerium spp., Cucifera), 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,
Silica, clay, vermiculite, Zeeklite (product name: Zeeklite Chemical Co., Ltd.), white carbon, mica, gypsum, calcium carbonate,
Examples include starch, vegetable flour, etc., and liquid carrier materials or diluents include, for example, water, ethanol, cyclohexane, xylene, toluene, benzene, methylnaphthalene, kerosene, acetone,
Methyl ethyl ketone, cyclohexane, 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 alkyl mercaptan ethers, 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 forms such as powders, granules, wettable powders, solutions, emulsions, and sprays, 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 the crop, or spraying it with the seeds at the time of sowing the crop. A method such as spraying is 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 Sieglite (trade name: Sieglite 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 (Water-flooded soil treatment method) A 1/5000 are polyethylene pot was filled with paddy soil (planting soil), seeds of wild grass, broad-leaved weeds, and scallops were sown in a 2-cm layer on the surface.
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 weed control effect, and are specifically as follows.

【table】

【table】

【table】

Claims (1)

[Claims] 1. General formula [In the formula, R ₁ represents an unsaturated lower aliphatic hydrocarbon group, a group of the formula [formula] or a group of the formula [formula], where n is 1 or 2, and R ₂ is a halogen atom, - COOH,
-CN, a group of the formula -OR ₃ or a group of the formula [formula], R ₃ represents a hydrogen atom or a lower alkyl group, and R ₄ represents a lower alkyl group] 2,3-didianopyrazine represented by derivative. 2 General formula [In _{the formula ,} represents a group, a group of formula [formula] or a group of formula [formula], where n is 1 or 2, and R ₂ is a halogen atom, -COOH,
−CN, a group of the formula −OR ₃ or a group of the formula [formula], R ₃ represents a hydrogen atom or a lower alkyl group, and R ₄ represents a lower alkyl group] General formula for [In the formula, R ₁ has the above-mentioned meaning] A method for producing a 2,3-dicyanopyrazine derivative represented by the following. 3 General formula [In the formula, R ₁₁ represents an allyl group, a group of the formula -CH ₂ CH ₂ -R ₂₁ , a group of the formula [formula] or a group of the formula [formula], and R ₂₁ represents a halogen atom, -CN, a lower alkoxy group or a di(lower alkyl)amino group, and R ₃₁ and R ₄ each represent a lower alkyl group.] A herbicide containing a 2,3-dicyanopyrazine derivative as an active ingredient.