JPH07247236A - Production of p-bromophenols - Google Patents

Abstract

PURPOSE:To provide a method capable of producing a p-bromophenol safely and efficiently without evolving hydrogen bromide. CONSTITUTION:A phenol (e.g. 2-methylphenol) nonsubstituted at p-position and at least one o-position based on a hydroxyl group is brominated by using an N-bromo-substituted imide in a single solvent of dimethyl sulfoxide or a mixed solvent containing >=5-wt.% dimethyl sulfoxide under a mild condition at about -20 to 60 deg.C to produce a p-bromophenol (e.g. 2-methyl-4-bromophenol). 1,3- Dibromo-5,5-dimethylhydantoin, N-bromosuccinimide and N-bromoisocyanuric acid may be cited as the N-bromo-substituted imide as the brominating agent. A solvent to be mixed with dimethyl sulfoxide is not particularly limited and dichloromethane and benzene may be cited. The phenol includes 1-naphthol, 8-hydroxyquinoline, etc., as condensed ring compounds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing para-bromophenols useful as an intermediate raw material for medicines, agricultural chemicals, pigments, flame retardants and the like.

[0002]

BACKGROUND OF THE INVENTION Parabromophenols are usually produced by a method using bromine. That is, when brominating a phenol having at least one para-position and at least one ortho-position with respect to a hydroxyl group with bromine, bromination at the para-position takes precedence and the desired para-bromophenol is obtained in good yield. To be

[0003]

However, this method requires bromine, which is toxic and difficult to handle, and has the following problems due to the by-product of hydrogen bromide. However, it is not always satisfactory in today's demand for safe and efficient manufacturing methods.

1) Since hydrogen bromide is highly corrosive, the material of the reactor is restricted.

2) Since a large amount of hydrogen bromide is contained in the waste liquid, a great deal of labor and cost are required for its treatment.

Further, the method using bromine has a problem that phenols having a multi-bonding substituent such as olefin cannot be used as a raw material. For example, 2-
When bromination of allylphenol is carried out using bromine, the product becomes very complicated because ring bromination and addition reaction at the allyl group occur simultaneously.

The present invention has been made in view of the above problems, and an object thereof is to provide a safe and efficient method for producing parabromophenols, which cannot be satisfied by conventional methods.

[0008]

Means for Solving the Problems As a result of intensive investigations by the present inventors on a method for producing bromophenols, a single solvent of dimethyl sulfoxide (hereinafter abbreviated as DMSO) or a mixed solvent containing 5% by weight or more of DMSO. Among these, by brominating phenols using N-bromo-substituted imides as a brominating agent, it was found that para-bromophenols can be produced by solving conventional problems, and completed the present invention. . That is, the present invention relates to DMSO
In a single solvent or a mixed solvent containing 5% by weight or more of DMSO, N-bromo-substituted imides are used to brominate phenols in which the para-position and at least one ortho-position are unsubstituted with respect to the hydroxyl group. And a method for producing para-bromophenols.

The present invention will be described in detail below.

The raw materials used in the method of the present invention are:
Phenols in which the para position and at least one ortho position are unsubstituted with respect to the hydroxyl group. Phenols in which the para position and at least one ortho position are unsubstituted with respect to the hydroxyl group,
There is no particular limitation as long as it is a phenol having a hydrogen atom as a substituent at the para position and at least one ortho position with respect to the hydroxyl group, and examples thereof include phenol and 2-
Methylphenol, 3-methylphenol, 2-methoxyphenol, 2-allylphenol, etc. are mentioned, and 1
-Fused ring compounds such as naphthol and 8-hydroxyquinoline are also included.

The brominating agent used in the method of the present invention is N
The bromo-substituted imides are not particularly limited, but from the practical point of view, 1,3-dibromo-5,5-
Dimethylhydantoin, N-bromosuccinimide, N
-Bromophthalimide, N-bromoisocyanuric acid and the like are preferable. All of these brominating agents are stable and industrially available substances. The N-bromoisocyanuric acid here means monobromoisocyanuric acid, dibromoisocyanuric acid, tribromoisocyanuric acid or a mixture thereof.

The reaction solvent used in the method of the present invention is D
It is a single solvent of MSO or a mixed solvent containing 5% by weight or more of DMSO. The solvent mixed with DMSO is not particularly limited, but examples thereof include dichloromethane and benzene. When a mixed solvent having a DMSO concentration of less than 5% by weight is used, the product yield is extremely reduced.

By using the above-mentioned raw materials, brominating agent and reaction solvent, it is possible to safely and efficiently produce para-bromophenols without generating hydrogen bromide.

Although the reaction temperature is not particularly limited,
In order to suppress bromination of the substituent, it is usually carried out under mild conditions of about -20 to 60 ° C.

[0015]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 5.40 g of 2-methylphenol was placed in a 300 ml four-necked flask equipped with a thermometer, a stirring blade and a cooling tube.
(0.05 mol) was charged, and DMSO 80 ml was added to this.
Was added and dissolved. Subsequently, while maintaining the raw material solution at 20 ° C., 8.90 g (0.05 m) of N-bromosuccinimide
ol) was added little by little over 30 minutes, and then aged at the same temperature for 30 minutes.

After aging, the reaction solution was analyzed by high performance liquid chromatography to find that the conversion of 2-methylphenol was 97.6 mol%. The main product in the reaction was 4-bromo-2-methylphenol, and the selectivity was 92.9 mol%. The reaction conditions and the reaction results are shown in Table 1.

[0018]

[Table 1]

Examples 2 to 5 Bromination of 2-methylphenol was carried out in the same manner as in Example 1 except for the reaction conditions shown in Table 1. The results of conversion rate and selectivity are also shown in Table 1.

Example 6 In a 300 ml four-necked flask equipped with a thermometer, a stirring blade and a cooling tube, 6.71 g of 2-allylphenol was added.
(0.05 mol) was charged, and DMSO 80 ml was added to this.
Was added and dissolved. Subsequently, while maintaining the raw material solution at 20 ° C., 8.90 g (0.05 m) of N-bromosuccinimide
ol) was added little by little over 30 minutes, and then aged at the same temperature for 30 minutes.

After aging, the reaction solution was analyzed by high performance liquid chromatography to find that the conversion rate of 2-allylphenol was 90.6 mol%. The main product in the reaction was 2-allyl-4-bromophenol, and the selectivity was 89.9 mol%. The reaction conditions and the reaction results are also shown in Table 1.

Example 7 In a 300 ml four-necked flask equipped with a thermometer, a stirring blade and a cooling tube, 6.71 g of 2-allylphenol was added.
(0.05 mol) was charged and 20 ml of DMSO was added.
And 60 ml of dichloromethane were added and dissolved (DMSO content in solvent: 21.5% by weight). Next, add 2
While maintaining at 0 ° C., N-bromosuccinimide 8.90
After g (0.05 mol) was added little by little over 30 minutes, the mixture was further aged at the same temperature for 30 minutes.

After aging, the reaction solution was analyzed by high performance liquid chromatography to find that the conversion rate of 2-allylphenol was 91.1 mol%. The main product in the reaction was 2-allyl-4-bromophenol, and the selectivity was 89.7 mol%. The reaction conditions and the reaction results are also shown in Table 1.

Comparative Example 1 2-methylphenol was brominated in the same manner as in Example 1 except that bromine was used as a brominating agent except for the reaction conditions shown in Table 1. At this time, hydrogen bromide was generated. The results of conversion rate and selectivity are also shown in Table 1.

Comparative Examples 2 to 5 Bromination of 2-methylphenol was carried out in the same manner as in Example 1 except for the reaction conditions shown in Table 1. The results of conversion rate and selectivity are also shown in Table 1. As you can see from Table 1, DM
In a single solvent other than SO and a mixed solvent not containing DMSO in an amount of 5% by weight or more, the selectivity of para-bromo compound was significantly reduced.

Comparative Example 6 In a 300 ml four-necked flask equipped with a thermometer, a stirring blade and a cooling tube, 6.71 g of 2-allylphenol was added.
(0.05 mol) was charged, and dichloromethane 8
0 ml was added and dissolved. Subsequently, while maintaining the raw material solution at 20 ° C., 7.99 g (0.05 mol) of bromine was added little by little over 30 minutes, and then aging was performed for 30 minutes at the same temperature.

After aging, the reaction solution was analyzed by high performance liquid chromatography to find that the conversion rate of 2-allylphenol was 97.6 mol%. Also, 2-allyl-4-
The selectivity of bromophenol was only 3.1 mol%, confirming that a complicated product was obtained. The reaction conditions and the reaction results are also shown in Table 1.

[0028]

As is apparent from the above description, according to the method of the present invention, it is possible to safely and efficiently produce parabromophenols without generating hydrogen bromide.

Claims (1)

[Claims] 1. A phenol in which para-position and at least one ortho-position relative to a hydroxyl group are unsubstituted using N-bromo-substituted imides in a single solvent of dimethylsulfoxide or a mixed solvent containing 5% by weight or more of dimethylsulfoxide. A process for producing para-bromophenols, which comprises brominating compounds.