JPH0940591A - Production of high quality beta-bromoethylbenzene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain β-bromoethylbenzene in a high purity and in a high production efficiency, capable of producing less α-bromoethylbenzene as a by-product and useful for the synthetic intermediate of a medicine, etc., by reacting styrene with hydrogen bromide while supplying a specific amount of air under irradiation of an ultraviolet radiation. SOLUTION: This method for producing β-bromoethylene is to react (A) styrene with (B) hydrogen bromide under the irradiation of an ultraviolet radiation while supplying (C) 0.3-3.0vol.% air based on the component B. For example, a solution containing 25-50vol.% component A concentration (e.g. using n- heptane, toluene, perchloroethylene, etc., as a solvent), the components B and C are supplied simultaeously and reacted under the irradiation of the ultraviolet radiation, and the solution of the produced objective compound is taken out continuously.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a process for producing β-bromoethylbenzene which is useful as a synthetic intermediate for organic functional products and pharmaceuticals.

[0002]

2. Description of the Related Art Conventionally, β-bromoethylbenzene has been produced by adding hydrogen bromide to styrene in the presence of radicals. As a radical source, oxygen or peroxide (US Pat. No. 3,321,536, US Pat.
935535), azo compounds (JP-A-6-172).
232), ultraviolet rays having a wavelength of 290 to 700 nm or high energy ionizing radiation (Japanese Patent Publication No. 38-1623).
No. gazette) is used.

[0003]

However, when ultraviolet rays are used as a radical source (Japanese Patent Publication No. 38-1623), the styrene concentration is 25 vol even if the amount of light is sufficient.
%, It is difficult to reduce the by-product rate of α-bromoethylbenzene to 0.2 mol% or less, and in order to reduce this by-product rate, a strong light source or a significant extension of the residence time in the reaction tank is required. .

Α-Bromoethylbenzene has a boiling point similar to that of β-bromoethylbenzene and is extremely difficult to separate by distillation, which is a problem when high purity is required, for example, as a raw material for producing an antihypertensive agent.

Further, when oxygen or peroxide is used as a radical source (US Pat. No. 3,321,536, US Pat. No. 2,935,535), the by-product rate of α-bromoethylbenzene is reduced under a condition where the styrene concentration is low. Although it is possible to suppress it, under the condition that the styrene concentration exceeds 25 vol%, not only the conversion rate of the raw material styrene does not rise sufficiently, but also many by-products of α-bromoethylbenzene, and further acetophenone Oxides are significantly increased and the β-bromoethylbenzene purity is below 99%.

Furthermore, when an azo compound is used as a radical source (Japanese Patent Laid-Open No. 6-172232), the purity of β-bromoethylbenzene is 99 mol% or more and α-bromo is obtained even under the condition that the styrene concentration exceeds 25 vol%. It is possible to reduce the by-product rate of ethylbenzene to 0.2 mol% or less, but since the azo compound and its decomposed product remain in the product after the removal of the reaction solvent, the reaction such as ring bromination can be performed using this. If done, problems such as coloring occur.

The present invention has been made in view of the above problems, and an object thereof is a method for producing β-bromoethylbenzene, which is useful as a synthetic intermediate for organic functional products and pharmaceuticals, in high quality and in high yield. Is to provide.

[0008]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors, in a method for producing β-bromoethylbenzene from styrene and hydrogen bromide, by supplying a specific amount of air under UV irradiation. , A by-product of α-bromoethylbenzene was suppressed, and a production method of high-purity β-bromoethylbenzene that can improve the production efficiency was found, and the present invention has been completed.

That is, the present invention provides a method for producing β-bromoethylbenzene from styrene and hydrogen bromide,
0.3-3.0 vol% of hydrogen bromide under UV irradiation
High-quality β characterized by supplying air of
-A method for producing bromoethylbenzene.

Hereinafter, the present invention will be described in detail.

The present invention is a batch reaction in which the reaction vessel is charged with styrene and a solvent in advance and hydrogen bromide is blown therein, or continuous reaction is performed by continuously supplying styrene, solvent and hydrogen bromide. It is possible to carry out by any method of reaction.

In this reaction, ultraviolet rays are used to cause radical cleavage of hydrogen bromide, but ultraviolet rays having a wavelength of 290 nm or less promote the polymerization reaction of styrene and cause a decrease in β-BEB yield, which is not preferable. Therefore, it is preferable to shield the ultraviolet rays of 290 nm or less by a method such as using a high pressure mercury lamp as the light source and further using Pyrex glass as the material of the lamp cooling tube.

There is no particular regulation on the intensity of the light source. Although it depends on the shape of the reaction tank, normally, in order to obtain 1 mol / hr or more per 1 L of the reaction tank in a β-bromoethylbenzene yield of 99 mol% or more, the number of photons per reaction tank unit volume of the light source is 0.005 eins. / L · h
It is preferable to use a light source of r or more.

Regarding the organic solvent used in this reaction, n-
Hexane, n-heptane, n-octane and other aliphatic hydrocarbons, benzene, toluene, xylene and other aromatic hydrocarbons, perchlorethylene, carbon tetrachloride, 1,1,1
Halogenated hydrocarbons such as trichloroethane are illustrated as suitable.

The present invention enables a reaction under a high concentration of styrene concentration of 25 vol% or more, which has been problematic in the conventional method using a radical source of air (oxygen) or the method of using an ultraviolet ray as a radical source. In particular, it has one characteristic.
The method of the present invention is usually carried out with a styrene concentration of 25 to 50 v.
It is carried out by simultaneously supplying an ol% solution, hydrogen bromide and air to react with each other, and continuously extracting the produced β-bromoethylbenzene solution.

Hydrogen bromide may be supplied in an equimolar amount or more with respect to 1 mol of styrene, and preferably 1.05 to 1.30 times mol.

The amount of air added is 0.3 to hydrogen bromide.
It is 3.0 vol%. When it is less than 0.3 vol%,
Not only is the suppression of the by-product α-bromoethylbenzene insufficient due to the lack of the air amount, but also improvement in production efficiency cannot be seen. On the other hand, when it exceeds 3.0 vol%, the amount of by-produced oxides such as acetophenone is remarkably increased and the quality is degraded.

The reaction temperature is not particularly limited, but in order to improve the reaction rate, it is preferably in the range of 50 to 90 ° C, particularly preferably in the range of 60 to 80 ° C.

The reaction time in the batch reaction and the residence time of the reaction solution in the reactor in the continuous reaction are not particularly limited, and are appropriately determined depending on the conditions such as the intensity of the light source, the shape of the reactor and the styrene concentration.

According to the method of the present invention, when a suitable light source is used and a suitable residence time is set, the β-bromoethylbenzene yield is 99 mol% or more and the α-bromoethylbenzene by-product rate is 0.2 mol% or less. Of high quality β-bromoethylbenzene is obtained.

[0021]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited to the examples.

In the following examples, a styrene solution supply pipe, a reaction liquid take-out pipe (the reaction liquid is taken out while overflowing), a hydrogen bromide supply pipe, an air supply pipe, a high pressure mercury lamp (0.
The reaction was carried out in a reactor having a reaction tank equipped with 1 kW and a photon number of 0.0112 eins / hr) of 1.24 L. The stirring in the reaction vessel was carried out only by the retention caused by blowing hydrogen bromide.

Example 1 n-heptane was charged into a reaction vessel, the temperature inside the vessel was set to 65 ° C., and 35 vol% of styrene and 65 vol% of n-heptane.
The solution (1) was supplied under the conditions (1,860 ml / hr) such that the residence time in the reaction tank was 40 minutes. At the same time, hydrogen bromide was supplied under the condition that the supply amount of styrene per unit time into the reaction tank was 1.15 times mol (2.44).
The reaction was carried out while blowing air at 1.0 vol% (30 ml / min) with respect to hydrogen bromide. After the reaction reached a steady state (about 3 hours after the start of the reaction), sampling was carried out from the reaction liquid extraction tube, and the components were analyzed by gas chromatography. As a result, β-bromoethylbenzene was 99.5 mol%,
α-bromoethylbenzene 0.13 mol%, unreacted styrene 0.04 mol%, acetophenone 0.1
It was 8 mol%. The results are shown in Table 1.

[0024]

[Table 1]

Examples 2 to 9 Using the reactor of Example 1, the reaction was carried out under the conditions shown in Table 1. The results are shown in Table 1.

Comparative Example 1 and Comparative Example 2 Increasing / decreasing amount of air The amount of air added was 0.2 and 5.0 v with respect to hydrogen bromide.
The reaction was performed in the same manner as in Example 1 except that the amount was changed to ol%. After the reaction reached a steady state, component analysis was performed. The results are also shown in Table 1.

Comparative Example 3 Reaction with light alone, vs. Example 1 The reaction was carried out in the same manner as in Example 1 except that air was not added, and the components were analyzed. As a result, β-bromoethylbenzene was 98.4 mol%, α-bromoethylbenzene was 0.90 mol%, and unreacted styrene was 0.62.
mol% and acetophenone were 0.02 mol%. The results are shown in Table 1.

Comparative Example 4 Reaction with light alone, vs. Example 5 Reaction was carried out in the same manner as in Example 5 except that air was not added,
Component analysis was performed. As a result, β-bromoethylbenzene 99.2 mol%, α-bromoethylbenzene 0.4
It was 7 mol%, unreacted styrene 0.24 mol% and acetophenone 0.04 mol%. The results are shown in Table 1.

Comparative Example 5 Reaction with air alone, vs. Example 1 The reaction was carried out in the same manner as in Example 1 except that the high pressure mercury lamp was not turned on (ultraviolet irradiation), and the component analysis was carried out. As a result, β-bromoethylbenzene 74.5 mol%, α
-Bromoethylbenzene 2.11 mol%, unreacted styrene 21.4 mol%, acetophenone 0.15 mol
%Met. The results are shown in Table 1.

Reference Example 1 Reaction with Air Alone At a temperature of 65 ° C. in a tank, a solution of 20 vol% of styrene and 80 vol% of heptane was retained in the reaction tank for 40 hours.
The supply was carried out under the condition that the minute (1,860 ml / min) was obtained. At the same time, hydrogen bromide was added to 1.1 mol of styrene to 1.1.
Blow under the condition of 5 mol (1.79 L / min), and further, air is 1.0 vol% with respect to hydrogen bromide.
The reaction was carried out while blowing (18 ml / min). After the reaction reached a steady state, sampling was carried out from the reaction liquid take-out tube, and the components were analyzed by gas chromatography. As a result, β-bromoethylbenzene 99.1 m
ol%, α-bromoethylbenzene 0.09 mol%,
Unreacted styrene 0.14 mol%, acetophenone 0.
It was 06 mol%. The results are shown in Table 1.

[0031]

According to the production method of the present invention, the amount of α-bromoethylbenzene by-product, which is difficult to separate by distillation, can be reduced, and high-quality β-bromoethylbenzene can be provided. Furthermore, as compared with the conventional method using only ultraviolet irradiation or only adding air, the reaction under a high concentration or the residence time in the reaction tank can be shortened, and the production efficiency is improved.

Claims (3)

[Claims] 1. A method for producing β-bromoethylbenzene from styrene and hydrogen bromide, wherein the reaction is carried out by irradiating with ultraviolet rays and supplying 0.3 to 3.0 vol% of air to hydrogen bromide. And a method for producing high-quality β-bromoethylbenzene. 2. The method according to claim 1, wherein a solution having a styrene concentration of 25 to 50 vol%, hydrogen bromide and air are simultaneously supplied to react with each other, and the produced β-bromoethylbenzene solution is continuously withdrawn. Production method. 3. The β-bromoethylbenzene produced has a purity of 99 mol% or more, and the α-bromoethylbenzene produced as a by-product is 0.2 mol% or less. Manufacturing method.