JPS5817191B2 - Benzimidazole-2-carbamin ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new process for producing benzimidazole-2-carbamate esters, which are known as fungicides or fungicide intermediates.

Conventionally, many methods are known for producing benzimidazole-2-carbamate esters. For example, the method described in Journal of the American Chemical Society, Vol. 56, p. shown.

In these formulas, R' represents a methyl group or an ethyl group.

Further, US Pat. No. 3,562,290 describes a method in which ≦the following formula.

The inventor described above when reacting the product obtained by the reaction of dicyandiamide with a chloroalkyl carbonate ester with 0-phenylenediamine.

It has been found that benzimidazole-2-carbamate ester can be produced more easily and in a higher yield than the known method.

The present invention is characterized in that the product obtained by reacting dicyandiamide and a chloroalkyl ester in the presence of an alkaline earth metal carbonate is reacted with 0-phenylenediamine under four acidic conditions. This is a method for producing benzimidazole-2-carbamate ester.

1 In the present invention, as the alkyl chlorocarbonate ester, lower alkyl esters such as methyl ester and -ethyl ester of chlorocarbonate are used.

The reaction between this ester and dicyandiamide is carried out in the presence of an alkaline earth metal carbonate such as calcium carbonate, barium carbonate, etc. Calcium carbonate is advantageously used from the viewpoint of cost.

The molar ratio of the reactants in this reaction is preferably 1.5 to 2 moles of alkyl chlorocarbonate to 1 mole of dicyandiamide, and the carbonate is required in an equivalent molar amount to the alkyl chlorocarbonate.

If the amount of the chloroalkyl carbonate ester used is less than 1.5 mol, the yield will decrease slightly.

It is also possible to use organic solvents such as lower ketones and lower alcohols as the reaction solvent, but even if water is used as the solvent, the desired product can be produced in exactly the same way as in the case of using the above-mentioned organic solvents in terms of yield and purity. You can get things.

Further, this reaction is preferably carried out under acidic conditions, for example, the reaction mixture is made acidic with hydrochloric acid, phosphoric acid, acetic acid, or the like.

The reaction temperature is a temperature up to the reflux temperature of the reaction mixture, but a reaction temperature of 45 to 55°C is desirable in order to obtain a suitable reaction rate.

Dicyandiamide and alkaline earth metal carbonate in the above proportions and the solvent are stirred and mixed, heated to reaction humidity, and then, while maintaining this temperature, the chloroalkyl carbonate ester is gradually added dropwise.

After the addition was completed, the mixture was heated and stirred for about 5 hours to complete the reaction.

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A small amount of unreacted material is present in the resulting reaction product,
The carbonate is present in an undissolved state, and the dicyandiamide is present as a solution.

Insoluble matter can be removed by filtration, but it can be used in the next reaction without being removed.

Jin-ah remains. Diamide also has no adverse effect on the next reaction.

The product of the first stage thus obtained is difficult to separate, for example, it cannot be extracted from an aqueous solution with an organic solvent immiscible with water at pH 3 or less, such as ether, methylene chloride, etc.

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However, this product is stable and 2
Even after being left at room temperature for several days, it does not interfere with the next reaction.

The reaction product and 0-phenylenediamine are then mixed under acidic conditions, preferably to a pH of 3 to 4.

While maintaining the temperature, the mixture is heated to 70°C or higher, preferably 90°C or higher, and reacted for 30 minutes or longer while stirring.

After the reaction is completed, the mixture is cooled to room temperature, the resulting slurry is filtered to collect the product, thoroughly washed with water, and then heated and dried to obtain the target benzimidazo-2-carbamate ester.

Examples of acids suitable for adjusting the pH include hydrochloric acid, phosphoric acid, and acetic acid.

0-phenylenediamine can be subjected to the reaction in the form of an aqueous solution, for example as a salt such as hydrochloric acid, and in this case, the amount of acid for adjusting the pH may be small.

If the pH is outside the range of 3 to 4, the yield will drop significantly.

Also, the lower the reaction temperature, the longer the reaction time will be.
When the temperature is 90°C or higher, the reaction is generally completed within one hour.

The hue of the benzimidazole-2-carbamate ester produced by this method depends on the degree of coloring of the 0-phenylenediamine used, but it is grayish white to pale grayish brown, and the shape is in the form of an amorphous fine powder.

According to this method, benzimidazole carbamate ester can be produced more easily and with higher purity and yield than known methods.

Parts in the following examples mean parts by weight.

Example 1 20.2 parts of dicyandiamide, 30.3 parts of calcium carbonate
50 parts of methyl chlorocarbonate was added dropwise to 120 parts of water at 45 to 55°C with stirring over a period of about 2 hours, and the reaction was continued at this temperature for an additional 5 hours.

After cooling the mixture to room temperature, 21.6 parts of 0-phenylenediamine were added, and 35% hydrochloric acid was added to adjust the pH to 3.
was held at

When the mixture was heated to 90°C, crystals began to precipitate, but the reaction was continued at 95-98°C for an additional hour.

At this time, 35% hydrochloric acid was added to maintain the pH at 3 to 4.

Once the reaction is complete, no pH fluctuations are observed.

After the reaction is completed, the reaction product is cooled to room temperature, taken out of the oven, thoroughly washed with water, and dried at 80°C, resulting in benzimidazole-
27.5 parts (72% of theory) of 2-carbamic acid methyl ester were obtained.

This product had a melting point of 280°C or higher and an infrared absorption spectrum that matched that of the standard product.

Example 2 28.6 parts of ethyl chlorocarbonate was added dropwise to 20.2 parts of dicyandiamide, 59.2 parts of barium carbonate, and 120 parts of water at 45 to 55°C with stirring for about 2 hours, and at this temperature. The reaction continued for 5 hours.

After cooling the mixture to room temperature, 21.6 parts of 0-phenylenediamine were added and treated in the same manner as in Example 1 to obtain 28.7 parts of benzimidazole-2-carbamic acid ethyl ester (theoretical value of 70 parts). %) was obtained.

This product had a melting point of 290°C or higher and an infrared absorption spectrum that matched that of the standard product.

Claims (1)

[Claims] 1. Benzimidazole, which is characterized by reacting a product obtained by reacting dicyandiamide and an alkyl chloride carbonate in the presence of an alkaline earth metal carbonate with 0-phenylenediamine under acidic conditions.
Method for producing 2-carbamate ester.