JPS6334869B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing 1,3-dimethyl-4-substituted benzoyl-5-hydroxypyrazoles or salts thereof.

The above pyrazole derivatives, salts thereof and organic acid esters thereof are used as herbicides, and it is disclosed in Japanese Patent Application Laid-Open No. 1973-1999 that this pyrazole derivative is produced by reacting 1,3-dimethyl-5-pyrazolone with a substituted benzoyl halide. It is described in Publication No. 126830. However, in general, when 5-pyrazolone is directly reacted with an acylating agent, a C-acyl compound in which an acyl group is introduced into the 4-position of the pyrazole nucleus and an O-acyl compound in which an acyl group is introduced into the 5-position are generated. The ratio of both varies depending on the type of reaction solvent and base, but
Even under conditions where calcium oxide is used as a catalyst in dioxane, which is considered to be the best condition for C-acylation, the yield of C-acylated product is about 70%, and it is about 15%.
(Khimya)
Geterotsiklicheskikh Soedinenii No.6, pp.799−
804, 1972), especially when 2,4-dichlorobenzoic acid chloride is used in this method, C-acylation is difficult to proceed and the yield is less than 50%, and a large amount of 2,4-dichlorobenzoic acid is produced. was released.

The present inventors researched the conditions under which C-acyl compounds could be selectively produced in the above method, and conducted an acylation reaction using acetonitrile as a reaction solvent. It was possible to obtain a C-acyl compound.

That is, the method of the present invention uses 1,3-dimethyl-5
-Pyrazolone and formula (In the formula, X represents a halogen atom, a nitro group or a lower alkyl group, n represents 1, 2 or 3, and n
is 2 or 3, X may be the same or different.
Y represents a halogen atom. ) with benzoic acid halide to form the formula (In the formula, X and n have the same meanings as described above.) A method for producing a pyrazole derivative or a salt thereof, characterized in that the reaction is carried out in acetonitrile in the presence of a base.

As the base used, alkali metal basic salts such as potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate are preferably used, but alkali metal alkoxides such as potassium t-butoxide and triethylamine are also used. Organic bases such as are also used. The amount used is at least equimolar to the raw material, preferably 1.2 to 5 moles.

Acetonitrile can also be used in combination with a solvent such as toluene or dichlormethane. The reaction is carried out at room temperature to the reflux temperature of the solvent.

After the reaction is completed, the target product of the present invention is collected from the reaction mixture by a conventional method. For example, by distilling off the solvent from the reaction mixture, the desired product can be obtained as a salt of the base used. To obtain the free target product, an acid may be added to the reaction mixture to neutralize it. In addition, when further producing the organic acid ester, after cooling the mixture containing the alkali metal salt of the target product, a halide of the desired organic acid is added and reacted, neutralized with acid, and the solvent is distilled off. Then, the desired ester compound can be collected as crystals.

In this way, according to the method of the present invention, the target C-acylated product is selectively produced in high yield,
We were able to significantly increase production efficiency.

Example 1 1.12 g of 1,3-dimethyl-5-pyrazolone and 2.76 g of potassium carbonate were added to 20 ml of acetonitrile, and after stirring at room temperature for 30 minutes, 2.1 g of 2,4-dichlorobenzoyl chloride was added and heated under reflux for 3 hours. did. The solvent was distilled off from the reaction mixture, the residue was dissolved in water, the pH was adjusted to 3.0 with 2N hydrochloric acid, and the precipitated crystals were collected and washed with water to obtain the desired 4-(2,4-dichlorobenzoyl). 2.68 g (yield 94%) of -1,3-dimethyl-5-hydroxypyrazole was obtained.

Example 2 1.12 g of 1,3-dimethyl-5-pyrazolone was dissolved in 10 ml of acetonitrile and 3.03 g of triethylamine, and 2.1 g of 2,4-dichlorobenzoyl chloride was added dropwise thereto, followed by heating under reflux for 2.5 hours with stirring. The solvent of the reaction mixture was distilled off under reduced pressure, 10 ml of water was added to the residue, extracted with toluene, and the aqueous layer was diluted with 2N
The mixture was made acidic with hydrochloric acid and extracted with chloroform. After washing the organic layer with water and drying, the solvent was distilled off and the desired 4-
(2,4-dichlorobenzoyl)-1,3-dimethyl-5-hydroxypyrazole 2.23g (harvested
78.2%).

According to the method of Example 1 above, the following compounds were all produced with a yield of 80% or more.

1,3-dimethyl-4-(4-nitrobenzoyl)-5-hydroxypyrazole (mp234-235
℃) 1,3-dimethyl-4-(2-chloro-4-nitrobenzoyl)-5-hydroxypyrazole (mp, 197-197.5℃) 1,3-dimethyl-4-(2-nitro-5-methylbenzoyl )-5-hydroxypyrazole (mp, 257-258°C).

Claims (1)

[Claims] 1 1,3-dimethyl-5-pyrazolone and the formula (In the formula, X represents a halogen atom, a nitro group or a lower alkyl group, n represents 1, 2 or 3, and n
is 2 or 3, X may be the same or different.
Y represents a halogen atom. ) with benzoic acid halide to form the formula A method for producing a pyrazole derivative or a salt thereof (wherein X and n have the same meanings as defined above), characterized in that the pyrazole derivative or its salt is reacted in acetonitrile in the presence of a base. Salt manufacturing method.