JPS6242655B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a catalyst for nuclear chlorination that has excellent selectivity for the p-position of alkylbenzene. Nuclear chlorinated compounds of alkylbenzenes are used in pharmaceuticals,
It is useful as a raw material for various organic synthetic chemicals including agricultural chemicals, but in particular p-chloro-alkylbenzene,
For example, there is a large demand for p-chlorotoluene. However, in the conventional nuclear chlorination reaction, in which chlorine is chlorinated with chlorine gas using a Lewis acid such as antimony chloride, ferric chloride, or aluminum chloride as a catalyst, o-chloroalkylbenzene is mainly produced. Furthermore, m-chloro derivatives, polychlorinated derivatives, etc. were also produced as by-products, making it impossible to produce p-chloroalkylbenzene with a yield of 40% or higher. Therefore, various catalysts have been developed to produce p-chloroalkylbenzene in good yield. For example, in a method using Lewis acid and sulfur or selenium as a catalyst, p-chloro form accounts for 45-52%.
In the method using a Lewis acid and thianthrene as a catalyst, the p-chloro form is obtained with a yield of 55 to
It was obtained with a yield of 60% (Japanese Unexamined Patent Publication No. 19630/1983). This method using a Lewis acid and thianthrene as a catalyst can be said to have very good selectivity toward the p-position, but this thianthrene compound is oxidized in the presence of water, resulting in 5.5-
After converting into dioxythianthrenes, they turn into diphenyl sulfides, which causes problems such as a decrease in catalytic activity when used repeatedly and the production of chlorinated side chain alkyl groups as by-products. The present inventors have conducted intensive research to develop a catalyst that has excellent selectivity for the p-position and does not have the problems of thianthrene compounds. As a result, we have found that when a Lewis acid and a phenoxatine compound are used as a catalyst, the p-position In addition to its excellent selectivity to It was discovered that this does not occur, and based on this finding, the present invention was accomplished. That is, the present invention provides (A) a Lewis acid and (B) a general formula (In the formula, X ₁ , X ₂ , X ₃ and X ₄ each represent the same or different hydrogen atom, electron-withdrawing group or electron-donating group) The present invention provides a catalyst for chemical conversion. In the present invention, the Lewis acid includes not only a Lewis acid in the usual sense but also a metal or a compound that forms a Lewis acid during a nuclear chlorination reaction or functions as a Lewis acid, for example. Examples include metals such as antimony, iron, tin, lead, aluminum, molybdenum, and tellurium, and their halides, oxides, sulfides, and carbonyl compounds. Particularly preferred examples include antimony trichloride, antimony pentachloride, and antimony chloride. aluminum,
antimony trifluoride, ferrous chloride, ferric chloride,
Antimony oxychloride, antimony trioxide, antimony tetroxide, antimony pentate, tellurium tetrachloride,
Examples include ferric oxide, lead sulfide, ferrous sulfide, iron disulfide, molybdenum hexacarbonyl, and iron pentacarbonyl. Furthermore, in the phenoxatine compound represented by the general formula (), X ₁ , X ₂ , X _{3 and} They can be different. Here, the electron-withdrawing group includes a halogen atom such as a chlorine atom, a bromine atom, and a fluorine atom, an alkanoyl group such as an acetyl group, an aroyl group such as a benzoyl group, a nitro group, a sulfonyl group, a cyano group, Examples of the electron donating group include a trifluoromethyl group, and examples of the electron donating group include an alkyl group and an alkoxy group.
Such phenoxatin compounds may be used alone or in combination. As this phenoxatin compound, those having a degree of halogen substitution of 2.0 or more are particularly suitable, but even if the degree of substitution is lower than that, nuclear substitution will proceed due to the halogen while being used in the halogenation reaction. However, the final degree of substitution is 2.0 or higher, so it is fully usable. In the present invention, the Lewis acid and the phenoxatin compound have a molar ratio of 0.1 to 10:1, preferably 0.25 to 10:1.
A ratio of 4:1 is used. In order to carry out the core temperature hydrogenation of alkylbenzene using the catalyst of the present invention, the catalyst is present in a proportion of 0.001 to 5.0% by weight, preferably 0.01 to 1.0% by weight of the amount of alkylbenzene, based on the total amount of Lewis acid and phenoxatin compound, and the reaction is performed. Chlorine gas is introduced at a temperature below the boiling point of the mixture. If the temperature is too high, the amount of polychlorinated products produced increases and the yield of p-chloro compound decreases, which is not preferable. On the other hand, the reaction proceeds even at a low temperature of minus several tens of degrees Celsius or lower, and the selectivity for the p-chloro compound is high, but the reaction rate is slow and uneconomical, so it is usually carried out at a temperature of 0 to 80 degrees Celsius. is 20～
A temperature of 70°C is suitable. The pressure of the chlorine gas may be normal pressure, increased pressure, or reduced pressure, but the reaction is usually carried out under normal pressure. Examples of alkylbenzenes to be nuclear chlorinated using the catalyst of the present invention include benzenes monosubstituted with various straight-chain and branched-chain alkyls, especially those with an alkyl group having 1 to 4 carbon atoms. preferable. By using the catalyst of the present invention, it is possible to suppress the chlorination of the o-position of alkylbenzene and efficiently chlorinate the p-position, and the production of m-chloro and polychlorinated products is extremely small. In addition, the catalyst of the present invention does not lose its activity even after repeated use and has excellent durability, and is suitable for the production of alkylbenzenes such as toluene.
- Suitable for industrial production of chloroforms,
Its industrial value is high. Next, the present invention will be explained in more detail with reference to Examples. Example 1 480 g of cumene, 2 g of antimony trichloride, and 2 g of phenoxatin were placed in a 1-4 neck flask equipped with a stirrer, thermometer, gas blowing tube, and reflux condenser, and heated to about 50°C in a water bath while stirring. After heating to a constant temperature,
Chlorine gas is introduced at a rate of 300 ml/min, and the reaction temperature is maintained at 50-55°C with a water bath. The reaction was stopped by introducing chlorine gas for 5 hours, and the reaction solution was analyzed by gas chromatography. As a result, the composition of the monochlorocumene produced was 2-chlorocumene/4-chlorocumene ratio (o/p) = 0.57. Example 2 A reaction was carried out under the same conditions as in Example 1, except that 424 g of ethylbenzene was used instead of cumene.
As a result of analysis by gas chromatography, the composition of the reaction solution was 2-chloroethylbenzene/4-chloroethylbenzene ratio (o/p) = 0.68. Example 3 Halogenation was carried out under exactly the same conditions as in Example 1, except that toluene was used instead of cumene and the type and amount of catalyst added were changed. The 2-chlorotoluene/4-chlorotoluene ratio (o/p) in the product thus obtained is shown in Table 1.

【table】

[Table] Example 4 The conditions were exactly the same as in Example 1, except that 0.10 g of antimony trichloride and 0.135 g of 2,3,7,8-tetrachlorophenoxatin were used to clarify the effect of repeated use of the catalyst. I did the reaction. After the completion of this reaction, the nuclear chloride of toluene was isolated by distillation, toluene was further added to the residue, and the catalyst was repeatedly used. The results are shown in Table 2. As can be seen from this table, repeated use of catalyst6
The reaction proceeded normally for the second time, and the O/P ratio was 0.88 to 0.87.
No branch chlorinated products were observed. 2, 3, 7, 8- in the residue after 6 more repetitions
When tetrachlorophenoxatin was analyzed by gas chromatography, it was found to be 2,3,7,8-tetrachlorophenoxatin and 10-oxy2,3,7,8-
It was a mixture of tetrachlorophenoxatin, of which 52% was 2,3,7,8-tetrachlorophenoxatin. Further, the total amount was equivalent to the amount of 2,3,7,8-tetrachlorophenoxatin that was added initially.

[Table] Comparative Example Chlorination reaction was carried out under the same conditions as in Example 4, except that 0.142 g of 2,3,7,8-tetrachlorothianethrene was used instead of 2,3,7,8-tetrachlorophenoxatin. I went there. The results are shown in Table 3.

【table】

Claims (1)

[Claims] 1 (A) Lewis acid and (B) general formula (In the formula, X ₁ , X ₂ , X ₃ and X ₄ each represent the same or different hydrogen atom, electron-withdrawing group or electron-donating group) catalyst for chemical conversion.