JPH0859515A - Production of monobromomethylated aromatic compound - Google Patents

Abstract

PURPOSE: To provide a practical production process for monobromomethyl- aromatic compound in monobromomethylation in high selectivity in high conversion through bromination of a methyl side-chain in an aromatic compound with bromine in high selectivity in high conversion. CONSTITUTION: In the production of monobromomethylated aromatic compound by bromination of a side-chain methyl group in an aromatic compound with bromine under irradiation with light, a solvent which has high solubility of the starting aromatic compound but low solubility of the monobromomethylated aromatic product is used in the reaction and the monobromomethylated aromatic compound is precipitated in solid particles, as the reaction between the starting aromatic compound and bromine is continued.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a monobrominated monobromomethylated aromatic compound by reacting a methyl-substituted aromatic compound with bromine.

[0002]

2. Description of the Related Art Aromatic compounds in which a methyl group directly bonded to an aromatic ring is monobrominated (hereinafter abbreviated as MBAR)
Is important as a raw material for organic fine chemicals such as dyes and pharmaceuticals, and has been industrially manufactured conventionally. Although MBAR can be produced by various methods, it is often advantageous to produce MBAR from an aromatic compound having a side chain methyl group (hereinafter abbreviated as MAR) and bromine. In this method, the MAR is 100 ° C.
As described above, it is general to react with bromine in the absence of a solvent, but a product in which a side chain methyl group is dibrominated (hereinafter, D
(Abbreviated as BAR) as a by-product. DB
The large amount of AR by-product is caused by the high concentration of MBAR in the reaction solution, and it is necessary to lower the MAR reaction rate in order to suppress the large amount of DBAR by-product by the conventional method. However, when the MAR reaction rate is lowered, the MBAR yield is lowered and the efficiency of the whole process is deteriorated.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing MBAR by reacting MAR with bromine.
It is an object of the present invention to provide a method capable of obtaining MBAR with high selectivity even if the R reaction rate is high.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, in a method for producing a monobromomethylated aromatic compound in which a side chain methyl group of an aromatic compound is brominated with bromine under light irradiation, the solubility of the raw material aromatic compound is large, and monobromomethyl Monobromide characterized by reacting the raw material aromatic compound with bromine while precipitating the resulting monobromomethylated aromatic compound as crystals in the reaction solvent with a solvent having a low solubility of the modified aromatic compound as a reaction solvent. A method for producing a methylated aromatic compound is provided.

The method of the present invention is carried out by reacting MAR with bromine while precipitating the produced MBAR as crystals in a reaction solvent in a solvent in which the raw material MAR has a high solubility and the produced MBAR has a low solubility. To be done. Then, by carrying out the reaction in this manner, the target MBAR can be obtained with high yield and high selectivity. That is, in the method of the present invention, the MBAR produced in the reaction is precipitated as solid crystalline particles insoluble in the reaction solvent.
Since the AR crystal is very difficult to be brominated, even if the raw material MAR is brominated at a high reaction rate, the bromination of the MBAR crystal can be effectively prevented. On the other hand, a part of the dissolved MBAR in the reaction solvent is brominated to be converted into DBAR, but the reaction solvent used in the method of the present invention is difficult to dissolve the MBAR.
A small amount of AR, which is why DBAR produced by bromination
The quantity is also small. For the above reasons, in the method of the present invention, M
Even if AR is brominated, the amount of DBAR by-product is small and MBAR can be obtained with good selectivity. Since the amount of by-product DBAR depends on the solubility of MBAR in the reaction solvent, it is desirable to use a reaction solvent having a solubility as low as possible, preferably one in which MBAR is sparingly soluble or substantially insoluble.

The reaction solvent used in the method of the present invention has a high solubility of the raw material MAR and a low solubility of the produced MBAR.
AR solubility is 20 g or more, preferably 40 g or more. Also, the solubility of MBAR per 100 g of solvent is 3
g or less, preferably 1 g or less. Such reaction solvents include saturated aliphatic hydrocarbons, saturated alicyclic hydrocarbons, saturated aliphatic halogenated hydrocarbons, saturated alicyclic halogenated hydrocarbons, and the like. Of these, use of hydrocarbon solvents is preferred. The reaction solvent will be specifically exemplified below.

(1) Saturated aliphatic hydrocarbons n-pentane, n-hexane, 2-methylpentane, 3
-Methylpentane, 2,2-dimethylbutane, 2,3-
Dimethylbutane, n-heptane, 2-methylhexane,
3-methylhexane, 3-ethylpentane, 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-
Dimethyl pentane, 3,3-dimethyl pentane, 2,
2,3-trimethylbutane, n-octane, 2,2
3,3-tetramethylbutane, n-nonane, n-decane and the like.

(2) Saturated alicyclic hydrocarbons ethylcyclopropane, isopropylcyclopropane,
1,1,2-Trimethylcyclopropane, 1,1-diethylcyclopropane, methylcyclobutane, ethylcyclobutane, 1,1-dimethylcyclobutane, isopropylcyclobutane, isobutylcyclobutane, cyclopentane, ethylcyclopentane, propylcyclopentane, butylcyclo Pentane, cyclohexane, methylcyclohexane, 1,1-dimethylcyclohexane, ethylcyclohexane, n-propylcyclohexane, isopropylcyclohexane, butylcyclohexane, cycloheptane, methylcycloheptane, ethylcycloheptane, propylcycloheptane, cyclooctane, methylcyclooctane, Ethyl cyclooctane etc.

(3) Saturated aliphatic halogenated hydrocarbons Ethyl bromide, n-propyl chloride, n-propyl bromide, isopropyl chloride, isopropyl bromide, n-butyl chloride, n-butyl bromide, isobutyl chloride, isobutyl bromide, s- Butyl chloride, s-butyl bromide, t
-Butyl chloride, t-butyl bromide, n-amyl chloride, n-amyl bromide, n-hexyl chloride, n-heptyl chloride, dichloromethane,
Dibromomethane, dichloroethane, dibromoethane, dichloropropane, dibromopropane, dichlorobutane,
Chloroform, bromoform, carbon tetrachloride, carbon tetrabromide, trichloroethane, tetrachloroethane, pentachloroethane, etc. (4) Saturated alicyclic halogenated hydrocarbons chlorocyclopropane, chlorocyclopentane, bromocyclopentane, chlorocyclohexane, bromocyclohexane, chlorocycloheptane, bromocyclooctane and the like.

The reaction solvent used in the method of the present invention may be used alone or as a mixture of two or more kinds. The amount of the solvent used varies depending on the type of the solvent, but is usually 6 to 6 of the reaction raw material MAR.
It is 1 times by weight, preferably 2.5 to 1.5 times by weight. If the amount of the solvent used is too small, the MAR selectivity decreases, and if it is too large, the solvent recovery cost increases, which is not preferable. The reaction raw material used in the method of the present invention is an aromatic compound having a methyl group in the side chain, and various conventionally known compounds are used. Examples of such reaction raw materials include methylated aromatic hydrocarbons such as toluene, xylene, methylnaphthalene, methylanthracene, and methylbiphenyl. Further, these methylated aromatic hydrocarbons may have a substituent, and examples of the substituent include an alkyl group, a halogen atom, a nitro group, a cyano group, a carboxyl group and a sulfone group. In the method of the present invention, in particular, P-nitrotoluene, m-nitrotoluene, p-chlorotoluene, m-chlorotoluene, p-nitrotoluene.
Bromotoluene, m-bromotoluene, p-fluorotoluene, m-fluorotoluene, 2,6-dichlorotoluene, p-methylbenzoic acid, p-cyanotoluene, 2'-
Carboxy-4-methylbiphenyl, 2'-cyano-4
The use of -methylbiphenyl and the like is preferred.

The method of manufacturing an MBAR according to the present invention uses the MAR
The side chain methyl group of bromine is brominated with bromine to give good selectivity.
Is a method of manufacturing. Therefore, the bromination reaction may be carried out under known reaction conditions as the bromination condition of the side-chain methyl group of the aromatic compound, and bromine may be dropped in a liquid state as it is while irradiating the well-stirred reaction solution with light, Alternatively, the reaction may be performed by a method such as appropriately diluting with a solvent used for the reaction and dropping. In this case, the bromine content is 0.9-
It is preferable to use 1.2 mol, preferably 1.0 to 1.05 mol, and the irradiation light may be electric light, ultraviolet light or sunlight. The reaction temperature is the temperature at which the MBAR crystals are stably present in the reaction solvent. Also, the reaction temperature is 10
When the temperature exceeds 0 ° C, the reaction between the reaction solvent and bromine becomes vigorous, and the MBAR solubility often increases and the MBAR selectivity decreases, so the reaction temperature is 0 to 100 ° C, preferably 35 to 60 ° C. Is desirable. The reaction time is generally 5 to 8 hours, and the reaction pressure may be atmospheric pressure or pressurization, but atmospheric pressure is preferable. It is preferable to add a bromination promoter to the reaction solution in order to promote the bromination of the side chain methyl group.

As the bromination accelerator, known radical generators are used, such as hydrogen peroxide, organic peroxides and azo radical generators. For example, organic peroxides such as performic acid, perbenzoic acid, monoperphthalic acid, trifluoroperacetic acid, and pernitrobenzoic acid; azo-based radical generators such as azobisisobutyronitrile and the following structural formulas Is used (however, Ph represents a phenyl group in the following structural formula). _{CH 3 -N = N-CH 3} Ph-N = N-OH, Ph-N = N-Cl Ph-N = N-OCOCH 3 These brominated promoter be used in alone or in admixture Good, 0.1 to 1 mol of the added MAR
The ratio is 2 mol, preferably 0.3 to 1 mol. Further, the accelerator may be added in the whole amount at the start of the reaction or may be dividedly added after the start of the reaction. After the completion of the bromine addition, the reaction solution was stirred at the reaction temperature until the bromine color disappeared, then cooled to room temperature, and the crystals were separated and recovered to give MBA.
R can be obtained. M from the cooled reaction product
The BAR crystals can be separated more easily than solid-liquid separation methods such as filtration and centrifugation. If necessary, the product may be purified by a recrystallization method in order to remove unreacted substances, by-products and the like, and acetone, ethanol, methylene chloride or the like is used as a recrystallization solvent.

[0013]

EXAMPLES Next, the method of the present invention will be described more specifically by way of examples, but the method of the present invention is not limited to these examples. The analysis of reaction products in the following examples and comparative examples was performed by high performance liquid chromatography. Moreover,% shown below is weight%.

Example 1 Internal volume of 300 m equipped with stirrer, thermometer and dropping funnel
Into a four-necked flask made of hard glass (1), 54.8 g (0.4 mol) of p-nitrotoluene (PNT) and 110 ml (72.6 g) of n-hexane were added, and heated and stirred at 40 to 45 ° C to obtain a uniform liquid. And A 100 W tungsten light bulb was placed about 5 cm away from the flask, and 65.8 g (0.41 mol) of bromine was added to the liquid well stirred at the above temperature for about 6 hours under the irradiation of light by this light bulb. It was dripped at. In addition, during the dropping of bromine, 30% hydrogen peroxide solution 2
2.7 g (0.2 mol) was added to the reaction solution in three portions about every 1.5 hours. In this experiment, p-nitrobenzyl bromide (PN
Crystals of MB) were deposited, and when the reaction was continued for about 2 hours after the end of the dropwise addition of bromine, the bromine color of the reaction liquid disappeared and the end of the reaction was recognized. When a homogeneous liquid obtained by adding 150 ml of dichloromethane to the liquid after the reaction was analyzed, the area ratio of PNT, PNMB, p-nitrobenzal bromide (PNDB) and unknown components in the chart of high performance liquid chromatography was 8.2: It was 85.2: 5.9: 0.7.

Example 2 Instead of PNT, p-methylbenzoic acid was added in an amount of 54.4 g (0.
4 moles) and 120 ml (84.3 g) of n-octane was used instead of n-hexane. An experiment was performed in the same manner as in Example 1, except that p-methylbenzoic acid in the reaction product, p -Bromomethylbenzoic acid, p-dibromomethylbenzoic acid, and the area ratio of unknown components were 8.4: 86.
It was 3: 4.8: 0.5.

Example 3 0.4 mol of p-cyanotoluene was used instead of PNT, and 100 ml of cyclohexane was used instead of n-hexane.
(78.0 g) was used, and an experiment was conducted in the same manner as in Example 1 except that the reaction temperature was 45 to 50 ° C., and in the chart of high performance liquid chromatography, p-cyanotoluene, monobromomethylcyanobenzene, The area ratio of dibromomethyl cyanobenzene and unknown components is 7.
It was 2: 88.0: 4.0: 0.8.

Example 4 Instead of PNT, 64.4 g of 2,6-dichlorotoluene
(0.4 mol), an experiment was conducted in the same manner as in Example 1 except that 110 ml (140.8 g) of ethylene dichloride was used instead of n-hexane. As a result, in the chart of high performance liquid chromatography, 2,6- Dichlorotoluene, 2,6-dichlorobenzyl bromide, 2,
The area ratio of 6-dichlorobenzal bromide and the unknown component was 8.7: 83.8: 6.5: 1.0.

Comparative Example 1 The four-necked flask used in Example 1 was charged with PNT137.
0 g (1.0 mol) was added and the mixture was heated and melted at 125 to 130 ° C. While stirring this solution, bromine 160 g (1.0
Mol) in 6 hours, and 125 to 130 even after the dropping is completed.
Stirring was continued for 1 hour at ° C. After completion of the reaction, the reaction product was cooled and analyzed. As a result, in the chart of high performance liquid chromatography, the area ratio of PNT, PNMB, PNDB and the unknown component was 13.3: 68.0: 18.4: 0.3.
Met.

Comparative Example 2 Instead of PNT, 136.0 g of p-methylbenzoic acid (1.
0 mol) was used and the experiment was conducted in the same manner as in Comparative Example 1 except that the reaction temperature was 115 to 120 ° C., and in the chart of high performance liquid chromatography, p-methylbenzoic acid and p-bromomethylbenzoic acid were obtained. , P-dibromomethylbenzoic acid and the area ratio of unknown components are 18.2: 6.
It was 6.7: 14.3: 0.8.

Comparative Example 3 117 g (1.0 g) of p-cyanotoluene was used instead of PNT.
Mol) was used and the experiment was conducted in the same manner as in Comparative Example 1 except that the reaction temperature was 135 to 140 ° C., and in the chart of high performance liquid chromatography, p-cyanotoluene, monobromocyanobenzene and dibromocyanobenzene were used. And the area ratio of unknown components is 13.5: 67.0:
It was 19.1: 0.4.

Comparative Example 4 2,6-dichlorotoluene was replaced with 161.0 instead of PNT.
g (1.0 mol) and the reaction temperature is 135 to 140 ° C.
An experiment was carried out in the same manner as in Comparative Example 1 except that, in the chart of high performance liquid chromatography,
The area ratio of 2,6-dichlorotoluene, 2,6-dichlorobenzyl bromide, 2,6-dichlorobenzal bromide and unknown components is 13.0: 65.0: 20.8:
It was 1.2.

[0022]

EFFECTS OF THE INVENTION According to the method for producing a monobromomethylated aromatic compound of the present invention, the target compound can be produced with a high selectivity and a high yield as compared with the conventional method. Therefore,
The amount of aromatic compounds and bromine used as raw materials can be significantly reduced as compared with the conventional method, and the purification cost of the reaction product can be reduced. The side chain methyl group can be monobrominated.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C07C 51/363 63/70 201/12 205/12 253/30 255/50

Claims (3)

[Claims] 1. A method for producing a monobromomethylated aromatic compound in which a side-chain methyl group of an aromatic compound is brominated with bromine under light irradiation, wherein the raw material aromatic compound has high solubility and is monobromomethylated aromatic compound. Is used as a reaction solvent, and the monobromomethylated aromatic compound is reacted with bromine while precipitating the resulting monobromomethylated aromatic compound as crystals in the reaction solvent. Method for producing compound. 2. The reaction solvent is at least one selected from the group consisting of saturated aliphatic hydrocarbons, saturated alicyclic hydrocarbons, saturated aliphatic halogenated hydrocarbons, and saturated alicyclic halogenated hydrocarbons. The method for producing a monobromomethylated aromatic compound according to claim 1, which is a compound of 3. The monobromomethyl according to claim 1, wherein the bromination reaction is carried out at a reaction temperature of 30 to 100 ° C. in the presence of a side chain methyl group bromination promoter. For producing a fluorinated aromatic compound.