Method for preparing pesticide mefenacet from benzothiazolone and 2-halo-N-methyl-N-phenylacetamide

Abstract

The invention provides a method for preparing mefenacet from benzothiazolone and 2-halo-N-methyl-N-phenylacetamide. The method comprises the following steps: firstly, synthesizing benzothiazolone by taking CO2 as a carbonylation reagent, then reacting the benzothiazolone with alkali liquor to obtain a salt solution of benzothiazolone, and finally reacting the salt solution of benzothiazolone with2-halo-N-methyl-N-phenylacetamide to obtain the mefenacet. A new path is provided for industrial production of mefenacet, the synthesis route of a traditional method is shortened, chemical utilizationof CO2 is achieved, energy conservation and emission reduction are facilitated, and the method better conforms to the concept of green chemistry.

Description

technical field

[0001] The invention relates to the technical field of herbicides, in particular to a method for preparing the pesticide mefenacet by using benzothiazolone and 2-halogenated-N-methyl-N-phenylacetamide. Background technique

[0002] Benfenacet is a herbicide with high efficiency and low toxicity. It has good removal effect on gramineous plants, and the drug has little effect on the growth of rice and has high safety. Mefenacet has a good dispersion effect in the water layer, and has the characteristics of long application period and low dosage. Mefenacet belongs to benzothiazolone derivatives. Currently, there are two main methods for synthesizing mefenacet. One is the 2-chlorobenzothiazole method, which uses the intermediate N-methyl-N-phenyl -2-hydroxyacetamide and 2-chlorobenzothiazole generate mefenacet through condensation reaction; or intermediate N-methyl-N-phenyl-2-acetoxyacetanilide and 2-chlorobenzothiazole Benfenacet is generated through hydrolysi...

Examples

Embodiment 1

[0024] (1) Preparation of benzothiazolone:

[0025] Weigh 124.2mg o-aminothiophenol and 288.2mgNa 2 S·9H 2 O to mix, add 3 mL of NMP (N-methylpyrrolidone) as solvent, then fill with CO 2 to a pressure of 5MPa, stirred and reacted at 60°C for 24 hours, cooled to room temperature, extracted with ethyl acetate, washed with saturated brine to obtain an organic layer, dried the organic layer and removed the solvent under reduced pressure to obtain a crude product; the crude product Benzothiazolone was obtained by recrystallization or column chromatography (200-300 mesh silica gel, petroleum ether and ethyl acetate as eluent);

[0026] (2) preparation of mefenacet:

[0027] First, add 151.2 mg (1.0 mmol) of benzothiazolone solid powder into 15% aqueous sodium hydroxide solution (the amount of sodium hydroxide is 80 mg, 2.0 mmol), and stir until the benzothiazolone powder is completely dissolved to obtain benzothiazolone Thiazolone sodium solution, the reaction formula is as foll...

Embodiment 2

[0037] The difference between Example 2 and Example 1 is only that in the process of preparing mefenacet, different organic solvents are used to dissolve 2-chloro-N-methyl-N-phenylacetamide; the rest are basically the same as in Example 1. same.

[0038] Table 1 shows the yield data of dissolving 2-chloro-N-methyl-N-phenylacetamide in different organic solvents in Example 2.

[0039] Table 1: Yields of 2-chloro-N-methyl-N-phenylacetamide dissolved in different solvents

[0040]

[0041] Comparing the crystallization process of Example 1 and Example 2, it is found that when using DMF as a solvent, there are more crystals and larger crystal shapes; 1,4-dioxane, N-methylpyrrolidone, DMSO, methanol are used as solvents There are fewer crystals and more irregular crystal forms; therefore, DMF is preferably used as a solvent in industrial production.

Embodiment 3

[0043] The difference between Example 3 and Example 1 is only that: the temperature and time of the heating and reflux reaction in the process of preparing mefenacet are different; the rest are basically the same as Example 1.

[0044] The temperature and time list of heating reflux reaction in embodiment 3 are shown in Table 2:

[0045] Table 2: Different temperatures and times for heating to reflux reactions

[0046]

[0047] As can be seen from Table 2, too high temperature is not conducive to the synthesis of mefenacet, and the by-products generated when the temperature is too high; as can be seen from Comparative Example 1, when the reaction temperature is 50°C, the productive rate is higher, and the reaction The by-products generated in the process are less and the reaction is more complete.

technical field

[0001] The invention relates to the technical field of herbicides, in particular to a method for preparing the pesticide mefenacet by using benzothiazolone and 2-halogenated-N-methyl-N-phenylacetamide. Background technique

[0002] Benfenacet is a herbicide with high efficiency and low toxicity. It has good removal effect on gramineous plants, and the drug has little effect on the growth of rice and has high safety. Mefenacet has a good dispersion effect in the water layer, and has the characteristics of long application period and low dosage. Mefenacet belongs to benzothiazolone derivatives. Currently, there are two main methods for synthesizing mefenacet. One is the 2-chlorobenzothiazole method, which uses the intermediate N-methyl-N-phenyl -2-hydroxyacetamide and 2-chlorobenzothiazole generate mefenacet through condensation reaction; or intermediate N-methyl-N-phenyl-2-acetoxyacetanilide and 2-chlorobenzothiazole Benfenacet is generated through hydrolysi...

Examples

Embodiment 1

[0024] (1) Preparation of benzothiazolone:

[0025] Weigh 124.2mg o-aminothiophenol and 288.2mgNa 2 S·9H 2 O to mix, add 3 mL of NMP (N-methylpyrrolidone) as solvent, then fill with CO 2 to a pressure of 5MPa, stirred and reacted at 60°C for 24 hours, cooled to room temperature, extracted with ethyl acetate, washed with saturated brine to obtain an organic layer, dried the organic layer and removed the solvent under reduced pressure to obtain a crude product; the crude product Benzothiazolone was obtained by recrystallization or column chromatography (200-300 mesh silica gel, petroleum ether and ethyl acetate as eluent);

[0026] (2) preparation of mefenacet:

[0027] First, add 151.2 mg (1.0 mmol) of benzothiazolone solid powder into 15% aqueous sodium hydroxide solution (the amount of sodium hydroxide is 80 mg, 2.0 mmol), and stir until the benzothiazolone powder is completely dissolved to obtain benzothiazolone Thiazolone sodium solution, the reaction formula is as foll...

Embodiment 2

[0037] The difference between Example 2 and Example 1 is only that in the process of preparing mefenacet, different organic solvents are used to dissolve 2-chloro-N-methyl-N-phenylacetamide; the rest are basically the same as in Example 1. same.

[0038] Table 1 shows the yield data of dissolving 2-chloro-N-methyl-N-phenylacetamide in different organic solvents in Example 2.

[0039] Table 1: Yields of 2-chloro-N-methyl-N-phenylacetamide dissolved in different solvents

[0040]

[0041] Comparing the crystallization process of Example 1 and Example 2, it is found that when using DMF as a solvent, there are more crystals and larger crystal shapes; 1,4-dioxane, N-methylpyrrolidone, DMSO, methanol are used as solvents There are fewer crystals and more irregular crystal forms; therefore, DMF is preferably used as a solvent in industrial production.

Embodiment 3

[0043] The difference between Example 3 and Example 1 is only that: the temperature and time of the heating and reflux reaction in the process of preparing mefenacet are different; the rest are basically the same as Example 1.

[0044] The temperature and time list of heating reflux reaction in embodiment 3 are shown in Table 2:

[0045] Table 2: Different temperatures and times for heating to reflux reactions

[0046]

[0047] As can be seen from Table 2, too high temperature is not conducive to the synthesis of mefenacet, and the by-products generated when the temperature is too high; as can be seen from Comparative Example 1, when the reaction temperature is 50°C, the productive rate is higher, and the reaction The by-products generated in the process are less and the reaction is more complete.

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