JP2652563B2 - Method for producing aromatic nitriles - Google Patents

Description

The present invention relates to an industrial method for producing aromatic nitriles useful as intermediates for agricultural chemicals, medicines, dyes and other organic compounds.

[Prior Art] Conventionally, several methods for producing aromatic nitriles have been known.

As one method, an aromatic carboxylic acid amide or an aromatic aldoxime is treated with a dehydrating agent such as phosphorus pentoxide, phosphorus pentachloride, phosphorus pentachloride-phosphoryl chloride, phosphoryl chloride or thionyl chloride to react with the compound. There is a method of using aromatic nitriles. As a specific example, see pages 1470 to 1471 of New Experimental Chemistry Course 14 (issued by Maruzen Co., Ltd.)
A method of dehydrating 1,2,4,5-benzenetetracarboxylic amide with thionyl chloride-DMF has been proposed.

Other methods include an ammoxidation method for chlorinated aromatic hydrocarbons, for example, chlorotoluene (see, for example, JP-B-59-49070 and JP-B-57-27104), and the reaction of benzotrichloride with aqueous ammonia. (For example, see Japanese Patent Publication No. 59-35392), a method of reacting benzoic acid with urea (for example, Japanese Patent Publication No. 60-32758).
Reference).

[Problems to be Solved by the Invention] However, the method of causing a dehydrating agent to act on an aromatic carboxylic acid amide or an aromatic aldoxime is difficult to handle, toxicity and cost of the dehydrating agent (because the dehydrating agent is disposable. ) And the yield of the desired product, which are never satisfactory.

The ammoxidation method of chlorotoluene is
Side reactions such as cleavage of aromatic rings and dehalogenation occur, which has the disadvantage of low yield, and is disadvantageous in terms of equipment because it is a gas phase reaction. However, there is still a problem in equipment due to the need for a high-pressure reaction vessel, the efficiency of the kettle is low due to the use of a large amount of ammonia, and the method of reacting benzoic acid and urea requires a side reaction at a high temperature. Occurred and the yield was low.

Further, British Patent No. 323,948 discloses a method of reacting acetic acid amide with benzotrichloride to obtain acetonitrile and benzotrichloride, but this method cannot increase the purity of the obtained nitrile. There is a disadvantage.

[Object of the Invention] An object of the present invention is to solve the above-mentioned disadvantages of the prior art and to provide a production method capable of industrially obtaining aromatic nitriles in high yield. .

Another object of the present invention is to provide a method for producing aromatic nitriles that can effectively utilize aromatic carboxylic acid amides obtained simultaneously with aromatic nitriles.

[Means for Solving the Problems] To achieve the above object, the main constitution employed in the present invention is a compound represented by the general formula (1): (Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, a nitro group or a phenoxy group,
n represents an integer of 1 to 3, and when n is 2 or 3, it means that the same or different Rs are bonded to an appropriate position by the number represented by n. An aromatic carboxylic acid amide represented by the general formula (2): (Wherein R and n have the same meanings as described above), and reacted with a benzotrichloride represented by the following general formula (3): (Wherein, R and n have the same meanings as described above) and an aromatic nitrile represented by the general formula (4): (Wherein, R and n have the same meanings as described above) by reacting with an aromatic carboxylic acid chloride represented by the formula:
The aromatic carboxylic acid amides represented by the general formula (1) and the aromatic nitriles represented by the general formula (3) are separated from each other, or they are separated in an inert solvent by the general formula ( 1) (Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, a nitro group or a phenoxy group,
n represents an integer of 1 to 3, and when n is 2 or 3, it indicates that the same or different Rs are bonded to an appropriate position by the number represented by n. An aromatic carboxylic acid amide represented by the general formula (2): (Wherein R and n have the same meanings as described above), and reacted with a benzotrichloride represented by the following general formula (3): (Wherein, R and n have the same meanings as described above) and an aromatic nitrile represented by the general formula (4): (Wherein, R and n have the same meanings as described above) by reacting with an aromatic carboxylic acid chloride represented by the formula:
These are separated as an aromatic carboxylic acid amide represented by the general formula (1) and an aromatic nitrile represented by the general formula (3), and the aromatic carboxylic acid amide represented by the general formula (1) is converted again into the general formula (1). It is characterized by subjecting it to the above reaction with the benzotrichlorides represented by (2).

That is, according to the present invention, the aromatic nitriles represented by the general formula (3) obtained by the above reaction are easily dissolved in an inert solvent, but the aromatic carboxylic acid amides represented by the general formula (1) are not soluble. These compounds are easily separated by utilizing the property of being hardly dissolved in an active solvent.

In the present invention, the aromatic carboxylic acid amides separated from the aromatic nitriles as described above are again subjected to a reaction with benzotrichlorides represented by the general formula (2). Thus, aromatic nitriles are obtained by repeatedly using aromatic carboxylic acid amides.

 Hereinafter, the present invention will be described in detail.

In the aromatic carboxylic acid amides represented by the general formula (1) used in the present invention, R represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, a nitro group or a phenoxy group.

In addition, n represents an integer of 1 to 3, and when n is 2 or 3, it indicates that R is bonded to an appropriate position on the aromatic ring by the number represented by n. In this case, R to be bonded may be the same or different.

Any aromatic carboxylic acid amide satisfying the above conditions can be used in the present invention, but specific examples include o-chlorobenzoic acid amide, o-fluorobenzoic acid amide, 2,3-dichlorobenzoic acid amide, 6-dichlorobenzoic acid amide, o-toluic acid amide, m-chlorobenzoic acid amide, m-fluorobenzoic acid amide, 2,4-dichlorobenzoic acid amide, 3,4-dichlorobenzoic acid amide, 2,4,5 -Trichlorobenzoic acid amide, m-toluic acid amide, p-
Chlorobenzoic acid amide, p-fluorobenzoic acid amide,
2,5-dichlorobenzoic acid amide, 3,5-dichlorobenzoic acid amide, 3,4,5-trichlorobenzoic acid amide, p-toluic acid amide, p-phenoxybenzoic acid amide, o-phenoxybenzoic acid amide, m -Phenoxybenzoic acid amide, benzoic acid amide and the like.

In the benzotrichlorides represented by the general formula (2) used in the present invention, R and n have the same meanings as in the case of the aromatic carboxylic acid amides. Can be used in the present invention. Specific examples include o-chlorobenzotrichloride, o-fluorobenzotrichloride, 2,3-
Dichlorobenzotrichloride, 2,6-dichlorobenzotrichloride, o-methylbenzotrichloride, m
-Chlorobenzotrichloride, m-fluorobenzotrichloride, 2,4-dichlorobenzotrichloride,
3,4-dichlorobenzotrichloride, 2,4,5-trichlorobenzotrichloride, m-methylbenzotrichloride, p-chlorobenzotrichloride, p-fluorobenzotrichloride, 2,5-dichlorobenzotrichloride, 3,5-dichlorobenzotrichloride, 3,4,5-
Trichlorobenzotrichloride, p-methylbenzotrichloride, p-phenoxybenzotrichloride,
Examples thereof include o-phenoxybenzotrichloride, m-phenoxybenzotrichloride, and benzotrichloride.

When the aromatic carboxylic acid amides are repeatedly used in the present invention, the aromatic carboxylic acid amides represented by the general formula (1) and the benzotrichlorides represented by the general formula (2) are The substituents must be the same, and in such a case, the desired aromatic nitrile represented by the general formula (3) can be produced in high yield with few by-products.

Thus, the molar ratio between the aromatic carboxylic acid amide represented by the general formula (1) and the benzotrichloride represented by the general formula (2) used in the present invention is stoichiometrically equal. It is preferably equimolar, and a catalyst is used for the reaction between the aromatic carboxylic acid amides and the benzotrichlorides. As the catalyst, any catalyst that is usually called a Lewis acid may be used. can do. Specific examples of the catalyst include ferric chloride, sulfuric acid, aluminum chloride, zinc chloride, antimony chloride and the like.

On the other hand, the inert solvent used in the present invention means an inert solvent for the reaction between the aromatic carboxylic acid amides and the benzotrichlorides, that is, a solvent that does not undergo a Friedel-Crafts type reaction. Examples include orthochlorotoluene, dichlorobenzene, nitrobenzene, benzotolyl, chlorobenzene, tetrachloroethylene and the like.

In the actual reaction, the amount of the catalyst used is 0.1 to 20% by weight, and preferably 1 to 10% by weight, based on the aromatic carboxylic acid amides. It is sufficient that the amount is sufficient to be able to stir, but usually 1 to 5 times (weight ratio) is preferable.

The reaction is carried out at a temperature of 100 ° C. or higher, preferably 100 to 180 ° C. The reaction product of the aromatic carboxylic acid amide and benzotrichloride is reacted with ammonia gas or aqueous ammonia without isolation. The reaction, preferably using 100-110% stoichiometric ammonia gas or aqueous ammonia, proceeds under mild conditions.

Due to the reaction with the ammonia gas or aqueous ammonia, the reaction system contains an aromatic nitrile represented by the general formula (3) and an aromatic carboxylic acid amide represented by the general formula (1). However, aromatic nitriles are easily dissolved in inert solvents, and aromatic carboxylic acid amides are hardly soluble in inert solvents. The aromatic nitriles can be easily separated by distilling or cooling the remaining inert solvent to obtain the aromatic nitriles. As a result, the aromatic nitriles represented by the general formula (3) It can be produced with high purity and high yield.

If the conditions for R and n described above are satisfied, the separated aromatic carboxylic acid amides can be used repeatedly by reacting them with benzotrochlorides again.

[Actions and Effects of the Invention] The present invention first comprises reacting an aromatic carboxylic acid amide represented by the general formula (1) with a benzotrichloride represented by the general formula (2) in an inert solvent. An aromatic nitrile represented by the formula (3) and an aromatic carboxylic chloride represented by the general formula (4) are produced.
The aromatic nitriles and aromatic carboxylic acid chlorides obtained as a result of this reaction are generally difficult to separate by distillation or the like since their boiling points are close to each other. Instead of reacting with ammonia or aqueous ammonia to lead to aromatic nitriles and aromatic carboxylic acid amides. The aromatic nitriles represented by the general formula (3) are easily dissolved in an inert solvent, The aromatic carboxylic acid amides represented by 1) are separated by utilizing the property that they are hardly dissolved in an inert solvent.

That is, since the aromatic carboxylic acid amides represented by the general formula (1) are hardly dissolved in an inert solvent, they can be easily recovered by filtration or the like, while the remaining inert solvents include the general formula (3) Since the aromatic nitrile represented by the formula is dissolved, the aromatic nitrile can be easily produced with high purity and high yield by crystallization and isolation by distillation or cooling. .

Further, the recovered aromatic carboxylic acid amide represented by the general formula (1) can be used repeatedly by reacting with the benzotrichloride represented by the general formula (2). You only need to prepare benzotrichlorides, so if you do this,
The present invention can be said to be a method for producing aromatic nitriles substantially using benzotrichlorides and ammonia as raw materials.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples.

Example 1 (Production of p-chlorobenzonitrile) In a four-necked flask equipped with a stirrer, a thermometer, and a condenser,
p-chlorobenzamide 31.1 g (0.2 mol), concentrated sulfuric acid 0.93
g (3 wt%) and 120 g of o-chlorotoluene,
° C and then p-chlorobenzotrichloride 46.0
g (0.2 mol) was added dropwise over 2 hours. After the completion of the dropwise addition, the reaction was further continued for 4 hours. After cooling the reaction solution to 30 ° C., 7.5 g (0.44 mol) of ammonia gas was slowly blown into the reaction system.

The precipitated crystals were collected by filtration to obtain 30.5 g of p-chlorobenzamide as white crystals having a melting point of 178 to 180 ° C. The yield is 97.
9%.

The filtrate was subjected to distillation to obtain p-chlorobenzenezonitrile as a fraction having a boiling point of 125 ° C./40 mmHg. The yield was 91.5% based on the p-chlorobenzamide used.

Example 2 (Repeated use of p-chlorobenzonitrile) The same procedure was performed as in Example 1 except that p-chlorobenzamide obtained in Example 1 was used.

As a result, p-chlorobenzamide was obtained in a yield of 98.1%,
p-Chlorobenzonitrile was obtained in a yield of 90.9% based on p-chlorobenzamide.

Examples 3 to 9 The same procedures as in Example 1 were carried out except that the aromatic carboxylic acid amides, benzotrichlorides, inert solvent and catalyst were changed.

 The results are shown below.

Comparative Examples The boiling points of aromatic nitriles and aromatic carboxylic acid chlorides separately synthesized are exemplified below. These figures show that it is difficult to separate the aromatic nitriles and aromatic carboxylic acid chlorides obtained by the reaction by distillation.

As described above, the present invention is excellent as a method for producing aromatic nitriles.

Claims (2)

(57) [Claims] (1) In an inert solvent, a compound represented by the general formula (1) (Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, a nitro group or a phenoxy group,
n represents an integer of 1 to 3, and when n is 2 or 3, it means that the same or different Rs are bonded to an appropriate position by the number represented by n. An aromatic carboxylic acid amide represented by the general formula (2): (Wherein R and n have the same meanings as described above), and reacted with a benzotrichloride represented by the following general formula (3): (Wherein, R and n have the same meanings as described above) and an aromatic nitrile represented by the general formula (4): (Wherein, R and n have the same meanings as described above.) By reacting with an aromatic carboxylic acid chloride represented by the following formula:
A method for producing aromatic nitriles, comprising separating an aromatic carboxylic acid amide represented by the general formula (1) and an aromatic nitrile represented by the general formula (3). 2. The compound of the formula (1) in an inert solvent. (Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, a nitro group or a phenoxy group,
n represents an integer of 1 to 3, and when n is 2 or 3, it means that the same or different Rs are bonded to an appropriate position by the number represented by n. An aromatic carboxylic acid amide represented by the general formula (2): (Wherein R and n have the same meanings as described above), and reacted with a benzotrichloride represented by the following general formula (3): (Wherein, R and n have the same meanings as described above) and an aromatic nitrile represented by the general formula (4): (Wherein, R and n have the same meanings as described above.) By reacting with an aromatic carboxylic acid chloride represented by the following formula:
These are separated as an aromatic carboxylic acid amide represented by the general formula (1) and an aromatic nitrile represented by the general formula (3), and the aromatic carboxylic acid amide represented by the general formula (1) is converted again into the general formula (1). A method for producing an aromatic nitrile, which is subjected to the above reaction with the benzotrichloride represented by (2).