JPS6148506B2 - - 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 represents a halogen atom or a lower alkyl group, and A represents a halogen atom or a hydroxyl group. A 2,3-dicyanopyrazine derivative represented by the following is provided. A group of 2,3-dicyanopyrazine derivatives represented by the above general formula () are novel compounds that have not been described in any literature, and they not only have excellent herbicidal activity, for example, for treating flooded soil in paddy fields, but also The following formula was previously proposed by the present inventors as an active ingredient of herbicides for water and soil treatment, for weed growing season foliage treatment, for upland soil treatment, etc. In the formula, R has the above meaning, R ₁ and R ₂ each represent a hydrogen atom or a lower alkyl group, and also as a synthetic intermediate for 2,3-dicyano-5-alkylamino-6-substituted phenylpyrazines. It has been found to be a very useful compound. In particular, the compound of the above formula () generally tends to form a firm chemical treatment layer on the surface layer of the flooded paddy field in the treatment of flooded paddy soil. It has the ability to effectively control annual weeds. As described above, the 2,3-dicyanopyrazine derivative of the present invention can be used as an active ingredient of pre-emergence and/or post-emergence herbicides, and the 2,3-dicyano-5 of the above formula (), which has even better herbicidal activity. It is a compound that has high utility value as a synthetic intermediate for -alkylamino-6-substituted phenylpyrazine herbicides. The "lower alkyl group" used in the above general formula () and the following description is a saturated aliphatic hydrocarbon group having 5 or less carbon atoms, preferably 3 or less carbon atoms, and is most preferably a methyl group. Also,
"Halogen atoms" include fluorine, chlorine, bromine,
Iodine is included, but in general formula (), when R means a halogen atom, the halogen atom is preferably fluorine, chlorine or bromine, and when A means a halogen atom, the halogen atom is preferably fluorine, chlorine or bromine. is preferably a chlorine atom. Thus, examples of the compounds of formula () provided by the present invention are as follows. 2,3-dicyano-5-hydroxy-6-(3
-chlorophenyl)pyrazine, 2,3-dicyano-5-hydroxy-6-(4
-chlorophenyl)pyrazine, 2,3-dicyano-5-hydroxy-6-(3
-bromophenyl)pyrazine, 2,3-dicyano-5-hydroxy-6-(3
-fluorophenyl) pyrazine, 2,3-dicyano-5-hydroxy-6-(4
-fluorophenyl) pyrazine, 2,3-dicyano-5-hydroxy-6-(3
-methylphenyl)pyrazine, 2,3-dicyano-5-hydroxy-6-(4
-methylphenyl)pyrazine, 2,3-dicyano-5-hydroxy-6-(3
-ethylphenyl)pyrazine, 2,3-dicyano-5-chloro-6-(3-chlorophenyl)pyrazine, 2,3-dicyano-5-chloro-6-(4-chlorophenyl)pyrazine, 2,3-dicyano-5 -Chloro-6-(3-bromophenyl)pyrazine, 2,3-dicyano-5-chloro-6-(3-fluorophenyl)pyrazine, 2,3-dicyano-5-chloro-6-(3-methylphenyl) Pyrazine, 2,3-dicyano-5-chloro-6-(4-methylphenyl)pyrazine, 2,3-dicyano-5-chloro-6-(3-ethylphenyl)pyrazine, 2,3-dicyano-5-bromo- 6-(3-chlorophenyl)pyrazine and the like. According to the present invention, the 2,3-dicyanopyrazine derivative of formula () in which A represents a hydroxyl group is obtained by combining diaminomaleonitrile of the following formula () and substituted phenylglyoxylic acid of the following formula () with the following formula: Reaction formula: In each of the above formulas, R has the above meaning. It can be produced by reacting according to the following. Furthermore, when A represents a halogen atom, the 2,3-dicyanopyrazine derivative of the formula () is a 2,3-dicyano-5-hydroxy-6-substituted phenylpyrazine derivative of the formula () obtained as described above. It can be produced by treatment with a curing agent. Note that the compound of formula () has the formula In the formula, R has the above-mentioned meaning.Although it can also be represented by, in this specification, the compound is represented by the above-mentioned formula (). Diaminomaleonitrile of formula () and formula ()
The condensation reaction of with substituted phenylglyoxylic acid is
This can be carried out by bringing these two compounds into contact in the absence or in a solvent. Examples of such solvents include normally inert solvents such as water; alcohols such as methanol, ethanol, and propanol; ethers such as tetrahydrofuran, dioxane, and methylcellosolve; organic acids such as formic acid and acetic acid; and organic acids such as ethyl acetate and isopropyl acetate. Esters: Nitriles such as acetonitrile and propionitrile can be used.
Further, the above reaction is usually preferably carried out in the presence of a dehydration condensation catalyst, and examples of catalysts for dehydration condensation and ring closure that can be used at that time include inorganic acids such as hydrogen chloride, sulfuric acid, phosphoric acid, and nitric acid; formic acid, acetic acid, etc. or phosphorus halides such as phosphorus pentoxide, phosphorus pentachloride, phosphorus oxychloride, and phosphorus trichloride, preferably hydrogen chloride or acetic acid. The reaction temperature of the above condensation reaction is not critical and can vary widely depending on the reactants used;
Generally, it is preferable to use a temperature condition of 0°C to 200°C, particularly room temperature to 150°C. The proportions of diaminomaleonitrile of formula () and substituted phenylglyoxylic acid of formula () are not particularly restricted and can be varied widely as needed; It is advantageous to use molar ratios to the substituted phenylglyoxylic acids of formula () generally from 0.2 to 5, preferably from 0.7 to 2, and most preferably approximately 1 (ie approximately equimolar). Under such conditions, the reaction can be completed within about 30 minutes to 5 hours, and the pyrazine derivative of formula () produced can be treated by means known per se, such as percolation,
It can be separated and/or purified from the reaction mixture by means such as centrifugation, distillation, extraction, chromatography, and recrystallization. The halogenation of the 2,3-dicyano-5-hydroxy-6-substituted phenylpyrazine of the formula () which can be obtained in this way can be carried out by halogenating the compound of the formula () in the absence of a solvent or in an inert solvent. This can be done by treating with a chemical agent. Suitable inert solvents that can be used include, for example, halogenated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride; aromatic hydrocarbons such as benzene, toluene, and xylene. Furthermore, as the halogenating agent, any of those often used to convert hydroxyl groups into halogen atoms can be used, such as phosphorus pentachloride,
Phosphorus pentahalides such as phosphorus pentabromide; phosphorus oxyhalides such as phosphorus oxychloride and phosphorus oxybromide; thionyl halides such as thionyl chloride are advantageously used. Although the amount of these halogenating agents used is not critical, it is generally advantageous to use them in an excess of at least equivalents, preferably from 1.5 to 20 equivalents, per mole of the compound of formula (). In particular, a halogenating agent that is liquid at room temperature, such as phosphorus oxychloride, may be used in large excess so that it also functions as a solvent. The above halogenation reaction is generally carried out under elevated temperature conditions ranging from room temperature to the reflux temperature of the reaction mixture.
Preferably, it can be carried out at a temperature of 50°C to reflux. 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 the tertiary amine used is not critical, but it can be used in an amount ranging from several percent by weight to approximately equimolar amount relative to the compound of formula (). Under such conditions, the above halogenation reaction usually takes place at 1
It can be completed in about 5 hours. The thus obtained 2,3-dicyano-5-halo-6-substituted phenylpyrazine [compound of formula () when A represents a halogen atom] can be processed by means known per se, such as filtration, centrifugation, distillation, It can be separated and/or purified from the reaction mixture by means such as extraction, chromatography, recrystallization, etc. The compound of formula () provided by the present invention has herbicidal activity and pharmacological activity, and is useful in fields such as agricultural chemicals and medicine. In particular, the compounds of the present invention have the ability to suppress the germination of weed seeds and/or cause the death of weed foliage, and can be used as active ingredients in pre-emergence herbicides and/or post-emergence herbicides in flooded rice fields. It can be used for processing, foliage treatment during weed growing season, field soil treatment, etc., and can exhibit outstanding herbicidal effects. In particular, the compounds of the present invention exhibit excellent herbicidal activity in flooded paddy fields that are rich in water, and can be advantageously used as herbicides for paddy fields. This is thought to be because the 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, and death of the weeds. Furthermore, the compounds of the present invention exhibit selective herbicidal activity and can effectively control noxious weeds. For example, the compound of the present invention has the ability to selectively weed out weeds, which are a typical weed of the same family Poaceae, without causing substantial damage to rice, through paddy field flooding soil treatment. Examples of weeds that can be controlled by the compound of the present invention include the following. (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), Poaceae (e.g. Poaceae, Poaceae, Poaceae), Asperaceae (e.g. Cyperaceae), Solanaceae (Episodes japonica), Cyperaceae (Example: Cyperaceae), etc. . When the compounds of the present invention are used as herbicides, one or more of them may be used in combination with an inert liquid or solid carrier material or diluent commonly used in the herbicide field and, if necessary, After preparing the mixture with additives such as surfactants and formulating it into an appropriate dosage form, it can be used as a pre- and/or post-emergence herbicide, as a treatment for flooded soil in paddy fields or as a treatment for field soil. It can be applied directly to the soil or sprayed directly on weeds as a foliar treatment. In that case, the application amount is not critical;
Although it can vary widely depending on the type of active compound, application time, application method, etc., it is generally at least 100 g, preferably 200 to 2000 g per 10 ares.
Advantageously, the application is such that the active compound is . Furthermore, the compounds of the formula () according to the invention can also be used as intermediates for deriving further valuable and useful compounds, such as compounds of the formula () having very good herbicidal activity. . In order to derive a compound of formula () from a compound of formula () when A represents a halogen atom, for example, the following reaction formula: According to the formula (), a 2,3-dicyano-5-halo-6-substituted phenylpyrazine of formula () is reacted with an amine of formula (). Details of this reaction and the excellent herbicidal activity of the resulting compound of formula () are as shown in Reference Examples 1 to 5 and herbicidal activity test below. Example 1 2,3-dicyano-5-hydroxy-6-(3
Synthesis of -chlorophenyl)-pyrazine 7.77 g of diaminomaleonitrile and 13.26 g of 3-chlorophenyl-glyoxylic acid were added to 100 g of methanol.
After adding 72 ml of 2N hydrochloric acid, the mixture was heated to 65°C and stirred for 3 hours. The reaction solution was cooled to room temperature, and the precipitated crystals were separated and recrystallized from benzene to obtain 14.5 g of 2,3-dicyano-5-hydroxy-6-(3-chlorophenyl)pyrazine. Melting point: 185-189℃ (decomposed). Elemental analysis value C ₁₂ H ₅ N ₄ Calculated value as OCl: C 56.16 H 1.96 N 21.83 Actual value: C 56.30 H 1.87 N 21.64 IR (KBr method maximum absorption cm ^-1 ): 2250, 1670,
1535, 1420, 1310. Example 2 2,3-dicyano-5-hydroxy-6-(3
Synthesis of pyrazine (bromophenyl) 8.02 g of diamino maleonitrile and 17.0 g of 3-bromophenylglyoxylic acid are added to 100 ml of ethanol.
After adding 77 ml of 2N hydrochloric acid and stirring at 20 to 25°C for 3 hours, the precipitated crystals were separated and recrystallized from ethanol to give 18.0 g of 2,3-dicyano-5-hydroxy- 6-(3-bromophenyl)pyrazine was obtained. Melting point: 190-192℃ (decomposed). Elemental analysis value as C ₁₂ H ₅ N ₄ OBr Calculated value: C 47.87 H 1.67 N 18.61 Actual value: C 48.02 H 1.44 N 18.47 IR (KBr method maximum absorption cm ^-1 ): 2250 1660 1530
1415 1305 Examples 3 to 6 The following first
The compounds shown in the table were synthesized.

[Table] Example 7 Synthesis of 2,3-dicyano-5-chloro-6-(3-chlorophenyl)pyrazine 2,3-dicyano-5-hydroxy-6-(3
-Dissolve 14.5 g of pyrazine (chlorophenyl) in 173 g of phosphorus oxychloride, and add triethylamine under ice cooling.
6.2 g was added dropwise over about 10 minutes. Thereafter, the mixture was heated to 106°C and stirred for 2.5 hours, and then excess phosphorus oxychloride was removed under reduced pressure, and the residue was dissolved in 150 ml of chloroform. After washing the chloroform solution twice with 100 ml of water, the solid obtained by distilling off the chloroform was recrystallized from carbon tetrachloride to obtain 12.4 g of 2,3-dicyano-5-chloro-6-(3-chlorophenyl). ) pyrazine was obtained. Melting point: 87-88℃. Elemental analysis value as C ₁₂ H ₄ N ₄ Cl ₂ Calculated value: C 52.39 H 1.47 N 20.37 Actual value: C 52.38 H 1.61 N 20.24 IR (KBr method, maximum absorption cm ^-1 ): 2250, 1570,
1400, 1340, 1155. Example 8 Synthesis of 2,3-dicyano-5-chloro-6-(4-methylphenyl)pyrazine 2,3-dicyano-5-hydroxy-6-(4
- 8.3 g of methylphenyl)pyrazine was dissolved in 108 g of phosphorus oxychloride, and 3.1 g of pyridine was cooled to 10°C.
was added. After the mixture was heated to 80°C and stirred for 2 hours, excess phosphorus oxychloride was removed under reduced pressure, and the residue was dissolved in 150 ml of toluene. After washing the toluene solution three times with 50 ml of water, the solid obtained by distilling off the toluene was recrystallized from carbon tetrachloride to obtain 7.0 g of 2,3-dicyano-5-chloro-6-(4-methylphenyl). ) pyrazine was obtained. Melting point 127-130℃. Elemental analysis value as C ₁₃ H ₇ N ₄ Cl Calculated value: C 61.31 H 2.77 N 22.00 Actual value: C 61.13 H 2.89 N 21.82 IR (KBr method maximum absorption cm ^-1 ): 2250, 1610,
1500, 1400, 1340, 1150. Examples 9 to 12 Compounds shown in Table 2 below were synthesized by methods similar to Examples 7 and 8.

[Table] Reference example 1 2,3-dicyano-5-ethylamino-6-
Synthesis of (3-chlorophenyl)pyrazine 2,3-dicyano-5- produced in the above example
Chloro-6-(3-chlorophenyl)pyrazine 1.0
g was dissolved in 20 ml of tetrahydrofuran, cooled to 0°C, and 0.50 g of 70% ethylamine aqueous solution was added.
Stirred at 0°C for 30 minutes. After the reaction, the solvent was distilled off, 20 ml of water was added to the residue, the precipitated powder solid was separated, and recrystallized from benzene:n-hexane (1:1) to give 0.95 g of 2,3-dicyano- 5-ethylamino-6-(3-chlorophenyl)pyrazine was obtained. Melting point: 117-118℃. Elemental analysis value C ₁₄ H ₁₀ N ₅ Calculated value as Cl: C 59.27 H 3.55 N 24.69 Actual value: C 59.41 H 3.55 N 24.52 IR (KBr method maximum absorption cm ^-1 ): 3390, 2230,
1555, 1425, 1350 NMR (solvent CDCl ₃ δppm): 7.53-7.62
(4H), 5.75-6.1 (1H), 3.56 (quintet 2H),
1.25 (triple line 3H). Reference Examples 2 to 5 Compounds shown in Table 3 below were synthesized by a method similar to Reference Example 1.

[Herbicidal activity test]

In the following test, a hydrating powder prepared by the following method was used. Note that "parts" are parts by weight. 40 parts of the active compound was mixed with 55 parts of a 2:1 mixture of Zeekrite (trade name: manufactured by Zeeklite Kagaku Kogyo Co., Ltd.) and Kunilite (trade name: manufactured by Kunimine Kogyo Co., Ltd.) as a carrier material, and as a surfactant. Solbol 800A [Product name: Toho Chemical Industry Co., Ltd.] 5
40% wettable powder is obtained. Test example (testing effectiveness of flooded soil treatment) Fill a 1/5000 are polyethylene pot with paddy soil (planting soil), sow seeds of wild grass, broad-leaved weeds, and scallops in a 2cm 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 the hydrating agent containing the active compound 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 4 below. The numerical values in the table in the test examples indicate the degree of paddy rice damage and herbicidal effect, and are specifically as follows.

【table】

【table】

【table】

Claims (1)

[Claims] 1. General formula In the formula, R represents a halogen atom or a lower alkyl group, and A represents a halogen atom or a hydroxyl group. However, when A represents a halogen atom, R represents a halogen atom. -dicyanopyrazine derivative. 2 General formula for diaminoreonitrile In the formula, R represents a halogen atom or a lower alkyl group; 2,3-dicyano-5-hydroxy-, in which R has the above-mentioned meaning;
Method for producing 6-substituted phenylpyrazine. 3 General formula In the formula, R' represents a halogen atom, 2,3-dicyano-5-hydroxy-
General formula characterized by halogenating 6-substituted phenylpyrazine In the formula, R' has the above-mentioned meaning, and X represents a halogen atom, 2,3-dicyano-5-hydroxy-
Method for producing 6-substituted phenylpyrazine. 4 General formula A herbicide containing a 2,3-dicyanopyrazine derivative as an active ingredient, wherein R' represents a halogen atom, and A' represents a halogen atom.