JP2002154994A - Method for producing dichlorinated aromatic compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a 2,6-dichlorinated aromatic compound in high selectivity by the chlorination reaction of an aromatic hydrocarbon. SOLUTION: Chlorination reaction of an aromatic hydrocarbon is carried out in the presence of a Lewis acid catalyst at <=30 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a dichloroaromatic compound which is useful as a raw material for various organic synthetic chemicals such as pharmaceuticals, agricultural chemicals, and polymer raw materials.

[0002]

2. Description of the Related Art Regarding a method for producing a chlorinated aromatic compound by performing a chlorination reaction of an aromatic compound in the presence of a Lewis acid catalyst such as ferric chloride, antimony chloride, and aluminum chloride, reference is made to literatures. It is widely known in patents and the like. For example, in the chlorination of toluene in the presence of a ferric chloride catalyst, mainly o-chlorotoluene and p-chlorotoluene are produced in a ratio of about 65:35,
In the chlorination of chlorotoluene in the presence of a ferric chloride catalyst, 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, and 2,6-dichlorotoluene each account for about 15%. %, 19%, 35%, 31%
Is generated with a selectivity of

On the other hand, some attempts have been made to change these composition ratios in response to a request from the market. For example, in the chlorination for producing dichlorotoluene, as a catalyst, a metal sulfide having Lewis acidity, or
By using a Lewis acid in the presence of a sulfur compound, 2,5-dichlorotoluene can be converted from toluene or o-chlorotoluene (US Pat. No. 4,031,146, JP-A-51-143627), and the same catalyst can be used. By condition,
A technique for selectively obtaining 3,4-dichlorotoluene from p-chlorotoluene (US Pat. No. 4,031,145), and further, zirconium chloride (US Pat. No. 3,366,698) or antimony chloride (US Pat. No. 4,0061,195) from p-chlorotoluene. Official Gazette) as a catalyst,
Techniques for selectively obtaining 4-dichlorotoluene are known.

[0004]

However, there are very few chlorination techniques with controlled reaction positions for the purpose of producing dichloroaromatic compounds, and a wide range of applications among dichloroaromatic compounds has been developed. Two
Regarding 6-dichloroaromatic compounds, despite the strong market demand, there is no technology for regioselective chlorination reaction, and it has been extremely difficult to realize them.

Accordingly, an object of the present invention is to obtain a 2,6-dichloro aromatic compound in a high yield in a chlorination reaction of an aromatic hydrocarbon.

[0006]

The inventors of the present invention have conducted intensive studies to solve these problems and, surprisingly, have found that aromatic hydrocarbons which can be easily obtained as raw materials are used as Lewis acid catalysts. In the reaction for chlorination in the presence, by performing the reaction at a reaction temperature of 30 ° C. or lower, the chlorine reaction position is controlled, and the chlorination reaction is carried out in a form in which a 2,6-dichloroaromatic compound can be more selectively obtained. They have found that they can do this and have completed the present invention.

That is, the present invention provides the following formula (I)

[0008]

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Wherein R represents a lower alkyl group having 1 to 4 carbon atoms, wherein an aromatic hydrocarbon represented by the following formula (II) is chlorinated in the presence of a Lewis acid catalyst.

[0010]

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The method for producing a dichloroaromatic compound represented by the formula (1), characterized in that the reaction is carried out at a reaction temperature of 30 ° C. or lower.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below.

In the present invention, the aromatic hydrocarbon used as a raw material is a compound represented by the following formula (I):
R represents a lower alkyl group having 1 to 4 carbon atoms);

[0014]

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Specifically, toluene, ethylbenzene,
Examples thereof include propylbenzene and butylbenzene, and preferably include toluene.

In the chlorination reaction of the present invention, various chlorinating agents such as simple chlorine, sulfuryl chloride and t-butyl hypochloride can be used. Usually, simple chlorine is used. At that time, the chlorine may be added as it is, or may be diluted with an inert gas such as nitrogen.

In the present invention, the Lewis acid used as a catalyst includes, in addition to those generally known, those which form a Lewis acid during the chlorination reaction or exhibit a function thereof. Usually, elements such as antimony, iron, aluminum, gallium, boron, tin, titanium, zirconium, tungsten, zinc, niobium, bismuth, and tantalum, or halides, oxyhalides, oxides, sulfides, carbonyl compounds, and organic metals And the like. Among them, preferred are ferric chloride, iron sulfide, aluminum chloride, antimony trichloride, antimony pentachloride, antimony oxychloride, titanium tetrachloride, tin tetrachloride, zirconium tetrachloride, tungsten hexachloride, zinc chloride, and pentachloride. Examples include niobium, bismuth trichloride, and gallium trichloride.

In the present invention, since the Lewis acid used as a catalyst can exert its effect even in a small amount, the amount used can be varied in a wide range. That is, the amount of the Lewis acid used in the present invention is preferably from 0.001 to 10% by weight, more preferably from 0.01 to 3.0% by weight, based on the raw material.

In the present invention, by controlling the reaction temperature to 30 ° C. or lower, the chlorine reaction position of the aromatic compound is controlled.
The 6-dichloro aromatic compound can be obtained more selectively. Preferably it is 20 ° C. or lower, more preferably 10 ° C. or lower. In addition, since heat of reaction is generated along with the chlorination reaction, in order to reach a target reaction temperature, a water bath, an ice bath, or a refrigerant cooled to a predetermined temperature in advance by a refrigerator or the like is forcibly cooled from the outside. , Keep warm.

In the present invention, the reaction pressure may be any of normal pressure, increased pressure, and reduced pressure. The reaction may be carried out without using a solvent, or may be carried out using a solvent inert to the chlorination reaction. Specific examples of the solvent inert to the chlorination reaction include dichloromethane, chloroform, carbon tetrachloride, tetrachloroethane and the like. The reaction system is not particularly limited, and may be, for example, a batch system, a semi-batch system or a continuous system, but is usually performed in a batch system.

After completion of the reaction, the method for isolating the desired chlorinated aromatic compound from the reaction mixture is arbitrary, and can be isolated and obtained by a conventional method such as distillation or crystallization.

[0022]

The present invention will now be described more specifically with reference to examples. Note that the present invention is not limited at all by these examples.

Example 1 30 units equipped with a stirrer, thermometer, gas injection pipe and reflux cooling pipe
In a 0 ml four-necked flask, 184 g of toluene (2.0
Mole; Tokyo Chemical Special Grade), antimony pentachloride 1.85 g
(1.0% by weight based on toluene; for Wako Pure Chemical) and 1.56 g / min of chlorine at a reaction temperature of 15 ° C.
The reaction was performed for 3 hours while blowing at a flow rate of (0.22 mol / min). After completion of the reaction, the obtained reaction solution was analyzed by gas chromatography. As a result, the conversion of toluene was 100.0%, the production of chlorotoluene was 25.4%,
The dichlorotoluene production rate was 69.1%, the selectivity of each isomer of dichlorotoluene was 2,6-isomer 23.5%,
2,5-isomer 30.9%, 2,4-isomer 31.7%,
The 2,3-form was 10.2% and the 3,4-form was 3.7%.

Example 2 A reaction was carried out in the same manner as in Example 1 except that the reaction temperature was 1 ° C. As a result, the conversion of toluene was 100.0%,
The production rate of chlorotoluene was 48.2%, the production rate of dichlorotoluene was 48.6%, and the selectivity of each isomer of dichlorotoluene was 23.8% in 2,6-form and 2,5-form. 3
1.3%, 2,4-form 30.8%, 2,3-form 1
0.5% and 3,4-form 3.7%.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1 except that the reaction temperature was changed to 50 ° C. As a result, the conversion of toluene was 100.0%.
%, The yield of chlorotoluene is 26.2%, the yield of dichlorotoluene is 67.3%, the selectivity of each isomer of dichlorotoluene is 21.5% for 2,6-isomer, 2.5% for 2,5 isomer. -Body 30.3%, 2,4-body 33.1%, 2,3-body
10.7% and 3,4-form 4.4%.

Comparative Example 2 A reaction was carried out in the same manner as in Example 1 except that the reaction temperature was changed to 100 ° C. As a result, the conversion of toluene was 100.0%.
%, The production rate of chlorotoluene is 26.9%, the production rate of dichlorotoluene is 65.9%, and the selectivity of each isomer of dichlorotoluene is 19.9% for the 2,6-isomer, 2.5%. -Body 29.3%, 2,4-body 34.2%, 2,3-body
It was 11.2% and 5.4% of the 3,4-form.

[0027]

According to the production method of the present invention, 2,6-dichloroaromatic compounds can be obtained in high yield in the chlorination reaction of aromatic hydrocarbons.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomotake Asawa, 161 Kambara, Kambara-cho, Abara-gun, Shizuoka Prefecture Nippon Light Metal Co., Ltd. Inside the Kambara Factory (72) Inventor Hiroshi Ado 161 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture Nippon Light Metal Co., Ltd. Kambara Factory F-term (reference)

Claims (2)

[Claims] (1) The following formula (I): (Wherein, R represents a lower alkyl group having 1 to 4 carbon atoms)
Is chlorinated in the presence of a Lewis acid catalyst to give an aromatic hydrocarbon represented by the following formula (II): A process for producing a dichloroaromatic compound, wherein the reaction is carried out at a reaction temperature of 30 ° C. or lower. 2. The method according to claim 1, wherein the aromatic hydrocarbon represented by the formula (I) is toluene, and the dichloroaromatic compound represented by the formula (II) is 2,6-dichlorotoluene. For producing dichloroaromatic compounds.