JPH02292248A - Production of 2,6-dichlorobenzonitrile - Google Patents

Abstract

PURPOSE:To efficiently obtain the subject compound useful as an intermediate for agricultural chemicals, medicines, etc., in one stage by reacting 2,6- dichlorobenzoic acid with urea of over a specific amount in the presence of an inorganic acid or salt thereof at a prescribed temperature. CONSTITUTION:2,6-Dichlorobenzoic acid is reacted with urea in a molar amount of >=3 times, preferably about 5 to 10 times based on the abovementioned compound in the presence of an inorganic acid (e.g. phosphoric acid) or salt thereof at >=200 deg.C temperature, especially about 230 to 260 deg.C temperature to afford 2,6-dichlorobenzonitrile. The objective compound useful as a synthetic intermediate, etc., for agricultural chemicals, medicines and other organic chemicals is obtained in good yield by one-stage reaction according to the abovementioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improvement in a method for producing 2,6-dichlorobenzonitrile. More specifically, the present invention relates to a method for efficiently producing 2,6-dichlorobenzonitrile in one step using 2,6-dichlorobenzoic acid and easily available urea as raw materials.

[Prior Art] 2,6-dichlorobenzonitrile has been known to be a useful compound as a synthetic intermediate for agricultural chemicals, pharmaceuticals, and other organic drugs.

By the way, one of the methods for producing penzonitrile is
There is a method for producing the corresponding penzonitriles using benzoic acids as raw materials. In this method, aromatic carboxylic acid is generally first heated with a chlorinating agent such as thionyl chloride to convert it into aromatic carboxylic acid chloride, and then this carboxylic acid chloride is reacted with ammonia or aqueous ammonia to form an acid amide. and then add phosphorus oxychloride to this,
A method is used in which a dehydrating agent such as thionyl chloride, phosphorus pentoxide, or phosgene is reacted to produce a nitrile compound.

However, in the above method, since the acid amide is passed through the intermediate, it is necessary to purify and dry the acid amide, and more than an equivalent amount of dehydrating agent is used, so after the reaction, the excess dehydrating agent is decomposed and The drawback is that it requires steps such as waste liquid treatment, making the manufacturing process complicated and expensive.

Therefore, in order to improve these drawbacks, various methods have been attempted to directly derive the corresponding nitrile compound from the aromatic carboxylic acid in a step without separating the aromatic carboxamide.

For example, (1) penzoyl chloride and sulfonamide (
A method for producing aromatic nitriles by reaction with NHzSOzMHz ["Tetrahedron Letter (Tetra
hedron Letter) J Volume 23, No. 150
Page 5 (1982) 1, (2) Method for producing aromatic nitriles by heating benzoic acids, amidosulfuric acid, and fluorine in the presence of phosphoric acid [[Chimia J No. 25]
Vol., No. 3, p. 94 (1971)], (3) A method for producing aromatic nitriles by heating benzoic acids and urea in the presence of an inorganic acid such as phosphoric acid (Japanese Patent Publication No. 1983- 58
Publication No. 99), etc. have been attempted.

However, the method (1) has the disadvantage that the sulfonamide used as an auxiliary raw material is difficult to obtain industrially. In addition, in the method (2), amide sulfur al. This method uses 5 to 2 moles of urea and 1 to 1.5 moles of urea and heats at a temperature in the range of 200 to 250°C.On the other hand, method (3) uses urea of 1 to 3 moles per benzoic acid. This is a method of heating to a temperature of 220°C or higher using multiple molar ratios, but in both cases, only reaction examples using mono-substituted or 2.5-mono-substituted benzoic acids are known. , nothing is known about benzoic acid having a substituent at the 2.6-position.

The present inventors used 2,6-dichlorobenzoic acid as a raw material and applied the methods (2) and (3) above to obtain 2,6-dichlorobenzoic acid.
- Attempts were made to produce dichloropenzonitrile, but due to the influence of the substituent at the 2.6-1 position, all methods had low yields, and method (2) used more than the same mole of amidosulfuric acid. Therefore, there was a problem in that more than an equivalent amount of alkali was required for neutralization.

[Problems to be Solved by the Invention] Under these circumstances, the present invention uses 2.6-dichlorobenzoic acid and easily available urea as raw materials to produce 2.6-dichlorobenzoic acid in a high yield in one step. The purpose of this invention is to provide a method for producing dichlorobenzonitrile.

[Means for Solving the Problems] As a result of intensive research to achieve the above object, the present inventors have found that by using a specific amount or more of urea for 2,6-dichlorobenzoic acid, inorganic It was discovered that the object could be achieved by reacting in the presence of an acid or a salt thereof at a predetermined temperature, and based on this knowledge, the present invention was completed.

That is, in the presence of an inorganic acid or a salt thereof, 2.
6-dichlorobenzoic acid and urea in an amount more than 3 times its mole
The present invention provides a method for producing 2,6-dichlorobenzonitrile, characterized in that the reaction is carried out at a temperature exceeding 00°C.

The present invention will be explained in detail below.

In the method of the present invention, 2,6-dichlorobenzoic acid and urea are used as raw materials, and the amount of urea used is 2.
It is necessary that the amount is 3 times or more by mole relative to 6-dichlorobenzoic acid. If this amount is less than 3 moles, the yield will be low, and if it is too large, it will be economically disadvantageous and the post-treatment will be complicated. The preferred amount of the element to be used is selected within the range of 5 to 10 moles.

In the method of the present invention, the reaction between 2,6-dichlorobenzoic acid and urea is carried out in the presence of an inorganic acid or a salt thereof. Examples of the inorganic acids include phosphoric acid, metaphosphoric acid, boric acid, amidosulfuric acid, and sulfuric acid, and examples of salts of these inorganic acids include ammonium salts and cobalt salts.

These inorganic acids and their salts may be used alone or in combination of two or more, and the amount used is usually 2 or more.
．． The amount is selected within the range of 0.01 to 10 moles relative to 6-dichlorobenzoic acid. If this amount is less than 0.01 moles, the reaction rate will be slow, and if it exceeds 10 moles, the post-treatment will be laborious, which is not preferable. The preferred usage amount is 0.02-5
It is selected within the molar range, and within this range, sublimation of urea is suppressed and stirring becomes easy.

In the method of the present invention, the reaction temperature is 200'C!
higher temperature, preferably higher than 200° and 2
The temperature is selected to be up to 80°C, more preferably in the range 230-260°C. If the reaction temperature is below 200°C, 2,6-dichloropenzamide will be produced as a by-product, and if it is too high, urea will sublimate violently, resulting in poor operability, which is not preferable. The reaction time is usually selected within the range of 1 to 10 hours, preferably 3 to 8 hours.

The 2,6-dichlorobenzonitrile in the reaction-completed liquid thus produced is usually extracted with an organic solvent such as ether or n-hexane, and this extract is treated according to a conventional method.
For example, after neutralization and washing, the solvent can be distilled off after drying to recover white crystals.

[Example] Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

Example 1 2l6-cyclobenzoic acid (D
CBA) 4.789 (25 mmol), urea 9.6 g (
160 mmol), phosphoric acid o. 2 g was added and heated to 250°C using a mantle heater equipped with a pressure regulator. Stirring was continued for about 6 hours, and the reaction was terminated when stirring became difficult. Washing and extraction were carried out with 50 ral of ether from the reactor and cooling tube, and 30 all of water and 30 ml of ether were added.
The contents were washed out and extracted and separated. Next, the ether phase was washed twice with 10 ml of IN sodium hydroxide aqueous solution and twice with 50 I+IQ of distilled water, dried with porcelain salt, and then the ether phase was distilled off and the remaining liquid was dried. .999 was obtained.

As a result of gas chromatograph analysis, this white crystal was found to be
It was confirmed to be 2,6-dichloropenzonitrile (DBN). This DBN (11.58 mmol)
The yield based on DCBA was 46.3%.

Examples 2 to 4, Comparative Example 1 The reaction was carried out in the same manner as in Example 1 using the amounts of DCBA, urea and inorganic acid shown in Table 1 and under the reaction conditions shown in Table 1. The results are shown in the table.

In order to prevent severe sublimation of urea, Example 2 used metaphosphoric acid as the inorganic acid, and Example 3 used phosphoric acid and NH. S.O.
A mixture with H was used. In other cases, only phosphoric acid was used as the inorganic acid.

As can be seen from Table 1, when the reaction temperature was as low as 200°C, 2,6-dichloropenzamide was mainly produced, and the amount of DBH produced was only a trace.

(Left below) Comparative Example 2 The amount of urea was changed to 2,6-dichlorobenzoic acid (25 mmol)
Example 1 except that 37.5 mmol (t.S times mole) and 50 mmol of amidosulfuric acid were used instead of phosphoric acid.
The reaction was carried out under the same conditions as I;.

The yield of DBN for 2,6-dichlorobenzoic acid is 10
．． It was 6%.

Comparative Example 3 A reaction was carried out under the same conditions as in Example 1, except that the amount of urea was 70 mmol (2.8@mol) relative to 2,6-dichlorobenzoic acid. The yield of DBN with respect to 2,6-dichlorobenzoic acid was 13.0%. [Effects of the invention] According to the present invention, it is possible to obtain high efficiency in one step from 2,6-dichlorobenzoic acid and urea. 2,6-dichlorobenzonitrile can be easily produced.

The 2,6-dichlorobenzonitrile is used for agricultural chemicals, pharmaceuticals,
It is also suitably used as a synthetic intermediate for other organic drugs.

Claims (1)

[Claims] 1. A method for producing 2,6-dichlorobenzonitrile, which comprises reacting 2,6-dichlorobenzoic acid and urea in an amount of 3 moles or more at a temperature exceeding 200°C in the presence of an inorganic acid or a salt thereof. .