JPS61130282A - Production of benzofuranyl carbamate - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as an insecticide, without generating ill odor, in high yield, by reacting 2,3-dihydro-2,2-dimethylbenzofuran-7-ol with an alkyl isocyanate in the presence of a catalyst under a specific reaction condition. CONSTITUTION:An N-alkyl-benzofuranyl carbamate is produced by (1) reacting 2,3-dihydro-2,2-dimethylbenzofuran-7-ol with an alkyl isocyanate in the presence of a catalyst in an organic solvent (e.g. toluene) capable of forming an azeotropic mixture with water or having lower boiling point than water, (2) adding water to the mixture after the reaction, (3) heating the mixture to distil out the organic solvent, and (4) precipitating the objective compound from the residual liquid. The objective compound having especially high purity and age-stability can be produced by adjusting the pH to 1-4 with an acid such as sulfuric acid, phosphoric acid, etc. in the heat-treatment stage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing N-alkylbenzofuranyl carbamates useful as insecticides. −
The present invention relates to an improvement in a method for producing a corresponding carbamate by reacting 7-ol and an alkyl isocyanate in the presence of a catalyst.

[Conventional technology]

2.3-dihydroco,cordimethylbenzofuran-7
N-alkylbenzo 7 obtained by reacting -ol with an alkyl isocyanate such as methyl isocyanate
2-Nyl carbamates are useful as insecticides, among them N-methylco, J-dihydro-12, Codimethyl-7
-Benzofuranyl carbamate is an insecticide known by the common name carbofuran.

-1J-dihydro-,2,2-dimethylbenzofuran-
A method for producing carbamate by reacting 7-ol (hereinafter abbreviated as BFL) with an alkyl isocyanate is described, for example, in Japanese Patent Publication No. Sho t/-7co No. 23 and Japanese Patent Publication No. 1/-/93/7.
It is already known as it is described in the No.

Conventional methods usually involve reacting BFL and an alkyl isocyanate in an organic solvent such as ether or ligroin in the presence of a catalyst such as triethylamine, cooling after the reaction, and crystallizing the resulting carbamate, which is then collected from door to door.

[Problem that the invention seeks to solve]

When using the above-mentioned conventional method, the wet cake of carbamate obtained by removing the solvent after the reaction contains an organic solvent. Further, since the alkyl isocyanate is usually used in a slightly excessive amount, it is difficult to completely remove the alkyl inocyanate after the reaction, and a trace amount of the alkyl isocyanate remains in the organic solvent. Therefore, there is a tendency to contaminate the working environment during transit of the solvent or when handling the obtained wet cake, or contaminate the environment due to exhaust gas during drying.

In addition, the solubility of the produced carbamate in organic solvents is relatively high, and depending on the type and amount of solvent used and the cooling temperature, during cooling crystallization, the yield decrease due to dissolution loss in liquid F can reach 3 to 20%. .

[Failure to solve the problem]

The present inventors have found that the above-mentioned problems can be solved by replacing the organic solvent used with water after the reaction.

That is, the gist of the present invention is to combine a co,3-dihydroco,2-dimethylbenzo7ran-7-ol and an alkyl isocyanate in the presence of a catalyst to form an azeotrope with water or to form an azeotrope with water in an organic solvent with a low boiling point. After reacting in
N-alkyl benzo 7-ranil carbide is extracted from the residual liquid.

In a detailed explanation of the present invention, examples of the alkylinocyanate used as a raw material of the present invention include methyl isocyanate, ethyl isocyanate, and n-propylinocyanate. , inglobil isocyanate, n-butyl isocyanate, and other lower alkyl isocyanates.

The amount of alkyl incyanate to be used is slightly in excess of the theoretical amount, that is, 07 to 5 moles of BFL, preferably 3 to 3 moles of BFL.

The organic solvent used in the reaction is not particularly limited as long as it is inert to the alkylinocyanate and is azeotropic with water or has a boiling point lower than water. Specifically, aromatic hydrocarbons such as benzene, toluene, and xylene,
Examples include ethers such as diethyl ether, tetrahydrofuran, and dioxane, aliphatic hydrocarbons such as hexane and heptane, and hydrogenated hydrocarbons such as dichloromethane, chloroform, carbon tetrachloride, and dichloroethane, and toluene is usually preferably used. .

The amount of organic solvent used is usually - for 1 mole of raw material BP'L.
It is 50-1000 trt, preferably 300-5OO-. If the amount of solvent is too large, it will be uneconomical and the reaction rate will decrease, while if it is too small, the slurry concentration during the reaction will become high, which will interfere with the stirring operation.

come.

Examples of catalysts include organic amines such as triethylamine and pyridine, stannous ophtate, tin chloride, iron chloride, aluminum chloride, and zinc chloride, and the amount used is usually BF.
0 for L. /-j Morchi.

The reaction between BFL and incyanate typically involves a predetermined amount of BFL.
and a solvent are charged into a reactor, a catalyst is added, the temperature is raised to the reaction temperature, and the alkyl isocyanate is gradually added dropwise while maintaining the temperature. The reaction temperature depends on the type of solvent used, but is usually selected to be 20°C or higher and lower than the boiling point of the solvent, preferably 0-10°C. If the reaction temperature is too high, more alkyl isocyanate will escape,
Moreover, when the temperature becomes extremely high, undesirable by-products are generated.

On the other hand, if it is too low, the reaction rate will be slow and it is not practical.

In the method of the present invention, after BFL and alkylinocyanate are reacted in this manner, water is added to the reaction mixture and heated to distill off the organic solvent. The amount of water added is determined until the concentration of the carbamate slurry is 10-'4 after distilling off the organic solvent.
It is added to approximately 0%. It may be added at once before distillation, or it may be added gradually depending on the rate of distillation of the organic solvent.

When water is added to the reaction mixture, the liquid phase becomes slightly alkaline, usually due to the presence of a catalyst or an alkyl isocyanate hydrolyzate. If heated as it is, the carbamate will be easily hydrolyzed, so it is desirable to add an acid before heating to adjust the pH of the aqueous phase to the acidic side, preferably to pH/~Hiroshi. The acids to be added are usually sulfuric acid, hydrochloric acid,
Inorganic acids such as phosphoric acid, organic acids such as formic acid, acetic acid, and oxalic acid, or acidic phosphorus esters such as monomethyl phosphate and dimethyl phosphate are used, and sulfuric acid, phosphoric acid, etc. are particularly preferred.

After adding water, the reaction mixture is heated to distill off the organic solvent, but it is preferable to distill off at as low a temperature as possible, since hydrolysis of the carbamate is accelerated as the temperature increases. The temperature depends on the pH value of the aqueous phase, but is usually below 0°C, especially '4'.
Preferably it is carried out at 0-40°C. When the boiling point or azeotropic point of the solvent to be distilled off is high, it is preferable to control the temperature by reducing the pressure. After the organic solvent is distilled off, the pressure is returned to normal pressure in the case of distillation under reduced pressure, and the residual liquid is cooled to below μθ°C, preferably below 30°C, and the precipitated carpa mate is collected by filtration. On the other hand, if the organic solvent separated by distillation contains water, it can be separated to remove water and then reused as a reaction solvent.

In addition, when a relatively large amount of organic solvent or alkyl isocyanate is used in the carbamate production reaction, after the reaction is completed and before adding water, distillation is performed to remove the alkyl isocyanate and solvent.
After removal of 10%, water may be added and the organic solvent may be distilled off according to the method described above. The recovered methyl inocyanate-containing solvent can be reused as it is in the carbamate production reaction.

〔Example〕

The present invention will be specifically explained with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

EXAMPLE/ A large round flask equipped with a reflux condenser and a stirrer is charged with 32 tons of BFL and 100 tons of toluene. After adding another 4 g of triethylamine, it was heated in a water bath for about 30 minutes while maintaining the internal temperature at roc.
Drop # of methyl innesia, t-t. After the dropwise addition was completed, the temperature was maintained at the same temperature for about one hour, and then 1 tbsp of water was added and the pH of the aqueous phase was adjusted to 7 with sulfuric acid. Thereafter, the system is heated to an internal temperature of 50 to 60° C., and toluene is distilled off using a co-evaporation ladder while maintaining the inside of the system at reduced pressure (approximately 30 θ mmHg). After the distillation of toluene is finished, the pressure is returned to normal and the temperature is cooled to 25-30°C.
-11ruco, 3-dihydroco, -1dimethyl-7-
Penzofuranyl carbamate wet cake 4c 3
．． I got 91. Wet cake has a purity of 96. % (yield 9 de%), water J as an impurity! %, toluene θ, /
% was detected, and they were odorless white crystals.

The purity after drying was 99.9%.

The reaction was carried out in the same manner as in Comparative Example/Example/without adding reaction water, and the m limb was cooled at 10'C''! and then filtered to obtain a wet cake. Yield: 40 LOFS (4 degrees??) The impurities were 2.5% toluene.The wet cake had a strong pungent odor of toluene and dimethyl isocyanate.

Even after repulping this wet cake with water, the strong odor of toluene did not disappear.

Examples 2 to 3 After adding the same amount of drained water that had reacted in the same manner as in Example/, toluene was distilled off under the conditions shown in Table 1. The following results were obtained. All of the obtained wet cakes were odorless white crystals.0*Dry product Example q The reaction was carried out in the same manner as in Example/, except that the organic solvent was changed to dichloromethane and the reaction temperature was set to 0°C. After adding the same amount of water and adjusting the pH to / with sulfuric acid, dichloromethane was distilled off at normal pressure and filtered at 30°C to obtain N-methyl-2°3-dihydroco, cordimethyl-7-penzo. A wet cake of furanyl carbamate was obtained.

Yield qff, jchi, purity? No impurities could be detected other than 6.9% traces of dichloromethane and 3.7% water, and the wet cake was odorless white crystals. What is the purity after drying?
9.9% b 0 Example j~? It was carried out in the same manner as in Example/ under the conditions shown in Table 2. Both the wet cake and dry cake obtained were white and odorless.

, Table WJ2 [Effects of the Invention] According to the present invention, (1) unreacted methyl isocyanate is hydrolyzed, so the resulting product has no bad odor.

(2) Since carbamate crystals are collected door-to-door from water, the recovery rate of carbamate is high.

(3) If an acid such as sulfuric acid is added during the heat treatment to adjust the pH to 1 to 2, a carbamate with particularly high purity and good stability over time can be recovered.

Sender: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Naga Kagawa - (7 others)

Claims (5)

[Claims] (1) 2,3-dihydro-2,2-dimethylbenzofuran-7-ol and an alkyl isocyanate are reacted in the presence of a catalyst to form an azeotrope with water or in an organic solvent with a boiling point lower than water. A method for producing N-alkyl-benzofuranyl carbamate, which comprises adding water to the reaction mixture, heating it, distilling off the organic solvent, and recovering the precipitate from the residual liquid. (2) When adding water to the reaction mixture and heating it, an acid is added and the N-alkyl-benzofuranyl carbamate according to claim (1) is treated under acidic conditions. Manufacturing method (3) Claim No. (3) characterized in that the treatment is performed under acidic conditions of pH 1 to 4 using sulfuric acid or phosphoric acid as the acid.
2) Method for producing N-alkyl-benzofuranyl carbamate (4) Claim No. 1, characterized in that the organic solvent is distilled off at a temperature of 80°C or less under normal pressure or reduced pressure.
Method for producing N-alkyl-benzofuranyl carbamate described in section ) (5) A method for producing N-alkyl-benzofuranyl carbamate according to claim (1), characterized in that toluene is used as an organic solvent.