JPH0322374B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method for chlorinating the side chains of aromatic compounds having lower alkyl groups as side chains, such as toluene, chlorotoluene, ethylbenzene, xylene, etc., using chlorine and under light irradiation. This type of chlorination reaction is usually carried out by introducing chlorine into a liquid phase reaction system in a glass reaction vessel while irradiating it with light. however,
At this time, the reaction solution often becomes colored, impairing light transmission, or deflagration occurs in the gas phase. When light transmittance deteriorates, side reactions take priority and nuclear chlorides and dehydrochlorination condensates are produced as by-products, reducing the purity and yield of side chain chlorides, which are the desired products. . It has been found that the main cause of this undesirable phenomenon is the presence of metal components such as iron as impurities in the reaction system, and therefore the influence of impurity metal components must be reduced or eliminated as much as possible. Various technologies have been developed to date. Conventional techniques effective for this purpose include substances that have the effect of trapping metal components, that is, urea as a stabilizer for photochlorination reactions, acid amides (US Pat. No. 2,695,872), and hexamethylenetetramine (US Pat. No. 2,695,872). 2817632) into the reaction solution, or a method in which chlorination is carried out in the presence of an N-lower alkyl substituted acid amide such as dimethylformamide (Japanese Patent Application Laid-Open No. 76825/1983). . However, urea is undesirable because it is either dissolvable or insoluble in the reaction solution and adheres to the walls of the reaction vessel during the chlorination reaction, impeding the transmission of light. On the other hand, hexamethylenetetramine,
Acid amides, dimethylformamide, etc. are soluble in the reaction solution, but even if purified products are used, particles that appear to be crystals are generated in the reaction solution during the chlorination reaction, and if severe, the reaction solution becomes cloudy. This prevents light from passing into the reaction system. The present invention was made for the purpose of providing a new and improved side chain chlorination method that eliminates the drawbacks of the conventional methods as described above, and effectively removes impurity metal components present in the reaction system. captured in
Moreover, this invention is based on the discovery of a new metal component scavenger that does not have a negative effect on the chlorination reaction, that is, a stabilizer for the photochlorination reaction. That is, in the present invention, when photochlorinating the side chain of an aromatic compound having a lower alkyl group as a side chain, the following general formula (),
This is a method for chlorinating the side chain of an aromatic compound, which is characterized by using one or more types of carbamate ester derivatives represented by () or (). General formula () (In the formula, R ₁ is an alkyl group that is unsubstituted or substituted with alkoxy or alkylthio, or a phenyl group that is unsubstituted or substituted with alkyl, halogen, or alkoxy, and R ₂ and R ₃ are unsubstituted alkyl groups. (X is an oxygen atom or a sulfur atom.) General formula () (In the formula, R ₁ is an alkyl group that is unsubstituted or substituted with an alkoxy or phenyl group, X is as defined in the general formula (), R ₄ is a hydrogen atom or a lower alkyl group, and n is It is an integer from 4 to 6.) General formula () (wherein R ₁ is unsubstituted or an alkyl group substituted with alkoxy, phenyl group, halogen or phenyl group having alkyl, Y is an unsubstituted or alkyl-substituted morpholine, piperazine or phthalimide residue, X is as defined in the general formula ().) Aromatic compounds to be subjected to side chain chlorination according to the present invention include aromatic compound hydrocarbons such as toluene, xylene, and ethylbenzene, as well as these aromatic compounds. A halogen group was introduced into the nucleus or side chain of the group compound. Examples include aromatic halogenated hydrocarbon compounds such as o-chlorotoluene, p-chlorotoluene, 2,4-dichlorotoluene, 3,4-dichlorotoluene, and o-dichloromethylbenzotrifluoride. The present invention can be carried out either in the presence or absence of a reaction solvent, but if the substance to be chlorinated is liquid at room temperature, it can be used as it is as a reaction solution without the need for a particular solvent. In addition, in the case of a compound that is solid at room temperature, or if it is necessary to carry out the reaction in the presence of a solvent, there is no particular restriction on the solvent as long as it is inert to the chlorination reaction, and carbon tetrachloride is usually used. Polychlorinated compounds such as , chloroform and dichlorobenzene are used, with carbon tetrachloride being particularly preferred. Furthermore, according to the present invention, side reactions can be suppressed and by-product impurities can be reduced. Thereby, it is also possible to use the reaction-finished liquid as it is as a starting material in the next reaction step without going through the step of recovering and purifying the target product from the obtained reaction-finished liquid. The carbamate ester derivatives in the present invention include not only carbamates but also thiol carbamate, dithiocarbamate, and thion carbamate derivatives. The alkyl group which may have a non-dissociable substituent represented by R ₁ , R ₂ and R ₃ has 1 to 8 carbon atoms and includes a cycloalkyl group. Examples of the non-dissociable substituent include halogeno, alkoxy, alkylthio and alkoxycarbonyl groups. Examples of the substituent of the phenyl group which may have a non-dissociable substituent include alkyl, halogeno, halogenoalkyl, and alkoxy groups. Examples of the substituted phenyl group include benzyl and substituted benzyl groups. Substituents for this substituted benzyl group include alkyl, halogeno, halogenoalkyl, and alkoxy groups. Each of the phthalimide, piperazine, and morpholine residues may have a lower alkyl group as a substituent. As such carbamate esters,
Examples are listed in Table 1-a, -b, and -c.

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[Table] Examples of thiol carbamate ester derivatives are shown in Table 1, -d, -e, and -f.

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[Table] As dithiocarbamate ester derivatives,
Examples such as -g, -h, and -i can be given in Table 1.

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[Table] As thione carbamate ester derivatives,
Examples can be given as shown in Table 1.

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[Table] The amount of these carbamate ester derivatives added can be changed as appropriate depending on the content of impurity metal components present in the reaction system and the type of carbamate ester derivative used, but it is usually 1 ppm based on the weight of the reaction solution. ~1%, preferably 2ppm ~ 1000ppm,
More preferably, it is effective to add 100 to 1000 ppm. When carrying out the present invention, an aromatic compound to be side-chain chlorinated and the above-mentioned carbamate ester derivative are placed in a transparent reaction vessel such as glass, and chlorine is introduced into the reaction vessel while irradiating light. Allow the chain chlorination reaction to proceed. As chlorine, crude chlorine gas or dehydrated chlorine gas generated from an electrolytic tank, or liquid chlorine can be used. As the light source, sunlight, discharge lamps, incandescent lamps, etc. can be used, and indium lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, etc. are particularly advantageous industrially. The temperature of the chlorination reaction may be any temperature at which the reaction solution can exist in a liquid state, but industrially preferred is 50°C or higher. The reaction time varies depending on the degree of chlorination, but is usually about 10 minutes to 100 hours. Dissolved chlorine, hydrogen chloride, etc. are expelled from the obtained reaction-completed liquid by a conventional method, and then the target product is recovered and purified by distillation and crystallization, if necessary. Alternatively, as described above, the target product may be used as it is in the next reaction step without being recovered or purified from the reaction-completed liquid. As is clear from the above explanation, according to the present invention, even if impurity metal components exist in the reaction system, the influence of the impurity metal components can be prevented, and the phenomenon that prevents the transmission of light into the reaction system can be prevented by chlorine. Since the amount of by-products can be reduced by suppressing the progress of side reactions, the desired product can be obtained in high yield and purity. The present invention will be explained below with reference to Examples. Examples 1 to 48 A vertical glass reactor with an inner diameter of 3 cm and a height of 40 cm was equipped with a chlorine introduction tube, a reflux condenser, and a thermometer.
174 g of toluene (approximately 200 g) containing 5 ppm ferric chloride
ml) and 85 mg of the carbamate ester derivative listed in the table below as a photoreaction stabilizer, and while irradiating with a 400 W indium lamp from a distance of 15 cm from the side of the reactor, the reaction solution was kept at 90°C and chlorine was added. Gas was introduced at a rate of 0.60 g/min. After reacting for about 4 hours until the degree of chlorination of toluene reached around 1.1, unreacted dissolved chlorine and generated hydrochloric acid gas were expelled through nitrogen gas, and the reaction solution was cooled to see the effect of the photoreaction stabilizer. APHA value (JIS
K4101-1980, 13 color number measurement method) was measured. The results are shown in Table 1. For comparison, a chlorination reaction was carried out using the same reactor and reaction conditions as above without adding a stabilizer, but the reaction solution was significantly colored and it was impossible to measure the color number as it was. Comparative Example 1 was calculated by multiplying the dilution ratio by toluene.

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[Table] From the comparison between Comparative Example 1 and the above-mentioned Examples, it can be seen that the effect of adding the carbamate ester derivative of the present invention is remarkable and that it is extremely excellent as a photoreaction stabilizer. Example 49 A vertical glass reactor with an inner diameter of 4.5 cm and a height of 60 cm was equipped with a chlorine introduction tube, a reflux condenser, and a thermometer.
430g p-xylene containing 10ppm ferric chloride
(500 ml) and 215 mg of benzyl N,N-dimethylcarbamate were charged. The reaction temperature was maintained at 100 to 130° C. while irradiating with a 400 W indium lamp, and chlorine gas was introduced at a rate of 2.5 g/min for 14 hours. The degree of chlorination of p-xylene was 5.98. However, the reaction solution remained transparent without any turbidity or precipitate until the end of the reaction, and the reaction was not inhibited at all. The APHA value of the reaction solution after aeration was 150 at 135°C. Further, as a result of analyzing the reaction solution by gas chromatography, 1,4-ditrichloromethylbenzene with a purity of 98.2% was obtained with a theoretical yield of 98.0%. For comparison, a chlorination reaction was carried out using the same reactor and reaction conditions as above, but with the addition of 430 mg of urea instead of benzyl N,N-dimethylcarbamate. As a result, urea remained insoluble at the start of the reaction. It was suspended in water, but as the reaction progressed, it melted and adhered to the walls of the reactor, blocking light transmission. The reaction at this time required 17 hours, and the APHA value measured in the same manner was 500. The purity of the target 1,4-ditrichloromethylbenzene obtained was 93.8% as analyzed by gas chromatography. Example 50 Using the same reactor as in Example 49, 530 g (about 600 ml) of o-xylene containing 2 ppm ferric chloride and N,
Benzyl N-diethylthiolcarbamate 110
mg was charged into the same reactor as in Example 59, and chlorine was introduced at a rate of 2.5 g/min in the same manner as in Example 59, and photochlorination was carried out for 13 hours. The degree of chlorination of o-xylene was 4.98.
The reaction proceeded without turbidity or precipitation, and the reaction solution remained slightly yellow and transparent at the end of the reaction, and the APHA value measured at 60° C. in the same manner as in the above example was 80. Furthermore, when the reaction solution was analyzed by gas chromatography, the purity of the target product, o-dichloromethylbenzotrichloride, was 98.7%, and the yield was 98.7%.
Obtained 97.9% result. Example 51 In a glass vertical reactor with an inner diameter of 3.5 cm and a height of 45 cm.
3,4 with a purity of 99.2% containing 0.9 mg/Fe content
- 313 g (250 ml) of dichlorotoluene and 35 mg of N,N-diethylthiol methyl carbamate were charged. Irradiate with a 400W indium lamp from a distance of 15cm from the side of the reactor, and reduce the reaction temperature to 120°C with chlorine in the first half.
It was introduced for 6 hours at a rate of 1.15 g/min and at a rate of 0.45 g/min in the second half. The degree of chlorination of 4-dichlorotoluene at this time was 4.95. The color number of the reaction completed solution is APHA90
There is no turbidity or insoluble matter formed during the reaction.
The purity of 3,4-dichlorobenzotrichloride is
A result of 98.3% and yield of 98.0% was obtained.

Claims (1)

[Claims] 1. When photochlorinating the side chain of an aromatic compound having a lower alkyl group as a side chain, the following general formula (), (), or () is added to the reaction system as a stabilizer.
1. A method for chlorinating the side chain of an aromatic compound, the method comprising using one or more of the following carbamate ester derivatives. General formula () (In the formula, R ₁ is an alkyl group that is unsubstituted or substituted with alkoxy or alkylthio, or a phenyl group that is unsubstituted or substituted with alkyl, halogen, or alkoxy, and R ₂ and R ₃ are unsubstituted alkyl groups. (X is an oxygen atom or a sulfur atom.) General formula () (In the formula, R ₁ is an alkyl group that is unsubstituted or substituted with an alkoxy or phenyl group, X is as defined in the general formula (), R ₄ is a hydrogen atom or a lower alkyl group, and n is It is an integer from 4 to 6.) General formula () (wherein R ₁ is unsubstituted or an alkyl group substituted with alkoxy, phenyl group, halogen or phenyl group having alkyl, Y is unsubstituted or alkyl-substituted morpholine, piperazine or phthalimide residue, is as defined in the general formula ().)