JP2000302704A - Preparation of brominated trifluoromethyl benzenes - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain brominated trifluoromethylbenzene in high yield by coexisting bromine with chlorine in bromination of trifluoromethylbenzene in liquid phase under the presence of an iron-containing catalyst. SOLUTION: This compound of formula II ((m) is 1-3) [e.g. 3,5-bis(trifluoromethyl)bromobenzene or the like] is obtained by brominating (A) the compound of formula I ((n) is 1-2) [e.g. 1,3-bis(trifluoromethyl)benzene or the like] in the presence of (B) the iron-containing catalyst (e.g. ferric chloride, ferric bromide or the like), in liquid phase in (C) the coexistence of bromine with chlorine, preferably at 50-200 deg.C under 1-100 kg/cm2 of pressure in a reactor. In the above reaction, 0.1-100 mole of iron in the component B is preferably used for 100 mole of the component A and 1-2 mole of chlorine is preferably used to 1 mole of bromine in the component C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing brominated trifluoromethylbenzenes, which are intermediates for medical and agricultural chemicals.

[0002]

2. Description of the Related Art It is known that an aromatic compound having a bromine atom in an aromatic ring can be obtained by brominating a corresponding aromatic compound. Bromination of trifluoromethylbenzene includes a method of reacting bromine in the presence of iron powder or iron chloride (JP-A-50-76029, J. Am.
Chem. Soc. 69, 947 (1947))
Or bromination using sulfur tetrafluoride-hydrogen fluoride-bromine (Zh. Org. Khim. 27: 1 (1)).
25), and 3-bromo-trifluoromethylbenzene has been obtained.

[0003] Further, 1,3-bis (trifluoromethyl) benzene is reacted simultaneously with chlorine and bromine in the presence of antimony pentachloride to form 3,5-bis (trifluoromethyl) bromo with a selectivity of 74.1%. Benzene and 24.6% of 3,5-bis (trifluoromethyl) chlorobenzene were obtained (Zh. Prikl. Khim. 46: 9 (1973) 2012), and a catalytic amount of antimony pentachloride was similarly obtained. The reaction of chlorine and bromine simultaneously yields 3,5-bis (trifluoromethyl) bromobenzene with 70% conversion and 90% selectivity (J. Am. Chem. Soc. 72: 1651). Page (1950)) is described in each reference. It is also known that 1,3-bis (trifluoromethyl) benzene is brominated with N-bromoimide in the presence of a strong acid to give 3,5-bis (trifluoromethyl) bromobenzene (particularly). Kaihei 9-3344
04 publication).

[0004]

Since bromine is highly corrosive to metals, the bromination reaction is usually performed in a glass reactor in many cases. However, when brominating an aromatic compound having a trifluoromethyl group, bromination of the benzene nucleus is difficult to occur due to the electron withdrawing property of the trifluoromethyl group, and the reaction conditions are relatively severe. The trifluoromethyl group is decomposed by the Lewis acid catalyst used in the bromination reaction, and hydrogen fluoride is generated in the reaction system. Since this hydrogen fluoride corrodes the glass, bromination of compounds having trifluoromethyl groups cannot be carried out in glass reactors or must be carried out with great care.

[0005] Among the Lewis acid catalysts proposed in the prior patents, antimony pentachloride has high reactivity and satisfactory selectivity, but antimony pentachloride itself is highly corrosive to metals, and antimony compounds are organic substances. Because of its high solubility in water, it is difficult to separate it from the product, and even when separated by washing, it is difficult to treat the washing wastewater.

Accordingly, the present invention provides a process for producing brominated trifluoromethylbenzenes in which trifluoromethylbenzenes are brominated in the liquid phase by allowing bromine and chlorine to coexist, wherein the selectivity and the conversion are high. Further, the present invention provides a reaction system which can be easily separated from a product and has a low corrosiveness to metal and can be reacted in a metal container.

[0007]

The present inventors examined a method for producing brominated trifluoromethylbenzenes, which brominates trifluoromethylbenzenes in the liquid phase in the presence of bromine and chlorine. If a catalyst containing iron as a catalyst, for example, an iron halide, particularly iron chloride, is used, the selectivity and conversion are high, and the catalyst component has low solubility in the product and is produced by a simple operation such as decantation. The catalyst can be separated and removed from the material, and the separated catalyst can be used again as a catalyst, and has characteristics that are desirable as an industrial production method such as being less corrosive to metal and capable of reacting in a metal container. This has led to the present invention.

That is, the present invention provides a compound represented by the general formula (1):

[0009]

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(Wherein, n represents an integer of 1 to 2) and brominates trifluoromethylbenzenes in the liquid phase in the presence of an iron-containing catalyst in the presence of bromine and chlorine. General formula (2),

[0011]

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(Wherein, n represents an integer of 1 to 2 and m represents an integer of 1 to 3).

General formula (1)

[0014]

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In the compound represented by the formula, n is an integer of 1 to 2, and specifically, trifluoromethylbenzene,
1,4-bis (trifluoromethyl) benzene, 1,3
-Bis (trifluoromethyl) benzene and 1,2-bis (trifluoromethyl) benzene. The trifluoromethylbenzenes used in the present invention may be obtained by any production method.

The amount of bromine and chlorine to be used depends on the intended brominated trifluoromethylbenzene represented by the general formula (2), but is 0.5 times or more m times. For example, the case where the target substance is a monobromo compound is described in detail.
It is at least 0.5 mol, preferably 0.5 to 1 mol, more preferably 0.5 to 0.75 mol. When the target compound is a monobromo compound, 0.5 mol of bromine is required for 1 mol of trifluoromethylbenzene, so usually 0.5 mol or more of bromine is used. If it is not desired to increase the production of the polybromo compound, 0.5 mol or less of bromine can be used.

Here, chlorine is used in an amount of 1 mol or more per 1 mol of bromine, but it is enough to use about 1 to 2 mol.
The reaction can be controlled to about 1 to 1.2 mol by controlling the reaction. If the amount of chlorine is less than 1 mol, the conversion rate of bromine decreases, which is not preferable. If it is used more than necessary, the production of chlorinated trifluoromethylbenzenes is promoted and the yield of brominated trifluoromethylbenzenes is reduced. It is not preferred because it lowers the temperature, and it is difficult to treat chlorine in the reaction step.

Usually, chlorine may be charged all at once, but it is preferable to add it continuously or divided appropriately and sequentially. It is preferable to always make the amount of bromine in the reaction system excessive with respect to chlorine, because by-products of chlorinated products can be suppressed. Therefore, it is generally preferable to gradually add chlorine as the reaction proceeds. When purging the by-produced hydrogen chloride to keep the reaction pressure constant,
By installing a reflux device at the reactor outlet and refluxing chlorine and bromine chloride to the reactor, loss of unreacted chlorine and bromine chloride can be reduced. In the addition of chlorine, a device for promoting gas-liquid contact, for example, a stirrer, a blowing pipe, a sparger, or the like can be appropriately used.

In the present invention, an iron halide is used as the catalyst containing iron. The catalyst may be a halide in the reaction state, and at the time of charging, it may be metal iron or an alloy or compound containing iron, but usually, easily available ferric chloride, ferric bromide, etc. It is preferred to use. The amount of the catalyst to be added is 0.1 to 100 mol, preferably 1 to 50 mol, more preferably 5 to 30 mol, as iron, per 100 mol of trifluoromethylbenzenes. When the amount of the catalyst is less than 0.1 mol, the reaction rate becomes slow.
This is not preferable because the operation becomes complicated.

The process of the present invention may be carried out using an inert solvent as a solvent. Examples of such a solvent include a chlorinated solvent, and examples thereof include, but are not limited to, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, tetrachloroethane, pentachloroethane, trichloroethylene, and tetrachloroethylene.

The reaction of the present invention is carried out at about 50 to 200 ° C.
150 ° C is preferred, and 100 to 130 ° C is more preferred. If the reaction temperature is lower than 50 ° C., the reaction is slow, and 200 ° C.
If the temperature is higher than this, the selectivity decreases, which is not preferable. In particular, when a monobromo compound is obtained, the reaction is preferably performed at 150 ° C. or lower. Reactor pressure is 1-100kg
/ Cm ² (0.1 to 10 MPa), 6 to 50 kg
/ Cm ² (0.6 to 5 MPa).

The method of the present invention can be carried out using a metal container made of stainless steel, Hastelloy, Monel or the like.

The method of the present invention can be in any embodiment. To illustrate the case of producing a monobromide by a method of successively adding chlorine, for example, a predetermined amount of trifluoromethylbenzenes, bromine and iron halide are added to a reactor in an arbitrary amount. After the temperature of the reaction solution is raised to a predetermined temperature while stirring and stirring, the remaining chlorine gas is blown into the reaction solution at an appropriate number of times as the reaction proceeds. The hydrogen chloride formed in the reaction is purged sequentially to keep the reaction pressure constant. The reaction is continued in this manner, and the reaction is stopped when the composition of the brominated trifluoromethylbenzenes reaches a predetermined value.

After the reaction, the stirring is stopped and the mixture is settled, the catalyst (iron halide) is settled, and the supernatant of the reaction solution is taken out of the reactor. Most of the iron halide can also be left in the reactor by removing the supernatant. This remaining iron halide can be used repeatedly as a catalyst.

The brominated trifluoromethylbenzene represented by the general formula (2) produced by the method of the present invention is a trifluoromethylbenzene of the trifluoromethylbenzene represented by the general formula (1) which is a starting material. The group is unchanged, and is a bromide in which one of the hydrogen atoms on the benzene ring has been replaced with a bromine atom. The position where the bromine atom is preferentially substituted is determined by trifluoromethylbenzenes represented by the general formula (1). For example, in trifluoromethylbenzene, 3-bromo-trifluoromethylbenzene is obtained.
For 1,3-bis (trifluoromethyl) benzene,
5-bis (trifluoromethyl) bromobenzene, 1,4-bis (trifluoromethyl) benzene, 2,5-bis (trifluoromethyl) bromobenzene, and 1,2-bis (trifluoromethyl) benzene 3,4-bis (trifluoromethyl) bromobenzene is obtained as the main product.

The reaction product taken out of the reactor can be purified by various methods. In the reaction liquid, bromine, chlorine, and iron halide remain in addition to organic substances. Of these, iron halides can be separated by decantation or filtration as insoluble components, and other unnecessary components can be easily removed by washing with an aqueous sodium sulfite solution or aqueous sodium hydroxide solution, or by flash distillation. The crude brominated trifluoromethylbenzene from which bromine, chlorine and iron halide have been removed in this manner can be converted to high-purity brominated trifluoromethylbenzene by distillation.

The thus obtained product containing brominated trifluoromethylbenzenes as a main component can be used as it is as various reaction raw materials. For example, a product containing brominated trifluoromethylbenzenes as a main component can be reacted with carbon monoxide using a catalyst having a metal such as palladium as an active species to form bis (trifluoromethyl) Benzoic acid, benzoic acid ester, bis (trifluoromethyl) benzamide and the like can be derived.

[0028]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these embodiments. The reaction pressure in the examples is represented by gauge pressure, and “%” represents “area%” unless otherwise noted.

Example 1 1,3-bis (trifluoromethyl) benzene 770 was placed in a 1 L stainless steel autoclave reactor equipped with a stirrer, a reflux tower, and a thermometer protection tube.
g, bromine 288 g, chlorine 15 g, anhydrous ferric chloride 58 g
And heated in an oil bath until the internal temperature reached 110 ° C. Chlorine was introduced in 9 divided portions of 15 g every hour. Hydrogen chloride generated in the reaction system was sequentially purged, and the reaction pressure was maintained at 6-7 kg / cm ² . When the reaction was performed for 9.5 hours while maintaining the reaction temperature at 110 to 115 ° C., the reaction was completed.

After completion of the reaction, the reactor is cooled and settled.
The contents were taken out and washed with an aqueous solution of sodium sulfite and then with an aqueous solution of sodium hydroxide to recover 997 g of organic matter. When the collected organic matter was analyzed by gas chromatography, 70.5% of 3,5-bis (trifluoromethyl) bromobenzene and 3,5-bis (trifluoromethyl)
1,2-bromobenzene was 1.2% and unreacted 1,3-bis (trifluoromethyl) benzene was 19.5%.

Example 2 After taking out the contents of the reactor in Example 1, the reactor in which ferric chloride and some reaction products remained remained in 1,3-bis (tri). Fluoromethyl) benzene (770 g), bromine (288 g) and chlorine (15 g) were charged.
The temperature was raised to ° C. Chlorine was introduced in 9 divided portions of 15 g every hour. Hydrogen chloride generated in the reaction system was sequentially purged, and the reaction pressure was maintained at 6-7 kg / cm ² .
When the reaction was performed for 9.5 hours while maintaining the reaction temperature at 110 to 115 ° C., the reaction was completed.

After the completion of the reaction, the reactor is cooled and settled,
The contents were taken out and washed with an aqueous solution of sodium sulfite and then with an aqueous solution of caustic soda to collect 972 g of organic matter. When the collected organic matter was analyzed by gas chromatography, 71.9% of 3,5-bis (trifluoromethyl) bromobenzene, 1.2% of 3,5-bis (trifluoromethyl) 1,2-bromobenzene, Unreacted 1,3-
Bis (trifluoromethyl) benzene was 18.2%.

Example 3 In the same manner as described above, the reaction was carried out again without changing the ferric chloride as the catalyst, and 978 g of the obtained contents were obtained by washing with an aqueous solution of sodium sulfite and then with an aqueous solution of caustic soda. The reaction product of was analyzed by gas chromatography to find that 3,5-bis (trifluoromethyl) bromobenzene 69.1%, 3,5-bis (trifluoromethyl) bromobenzene
Bis (trifluoromethyl) 1,2-bromobenzene 1.1%, unreacted 1,3-bis (trifluoromethyl)
Benzene was 20.9%.

Although some clouding was observed in the reactor with regard to the corrosion of the reactor, it was remarkably reduced from that expected from the corrosiveness of bromine, and the allowable range for continuous use as a reactor was observed. Was within.

The reaction products recovered in Examples 1 to 3 were washed with an aqueous sodium sulfite solution and an aqueous sodium hydroxide solution.
Purification by distillation gave 663 g of 3,5-bis (trifluoromethyl) bromobenzene having a purity of 99%.

Finally, the catalyst ferric chloride and a small amount of the reaction product remaining in the lower portion of the reactor were soluble in acetone and easily taken out of the reactor.

Example 4 146 g of trifluoromethylbenzene and 81 g of bromine were placed in a 0.5 L stainless steel autoclave reactor equipped with a stirrer, a reflux tower, and a thermometer protection tube.
36 g of chlorine and 32 g of anhydrous ferric chloride were charged and heated in an oil bath until the internal temperature reached 110 ° C. Reaction pressure 17-19.5 kg / cm ² , reaction temperature 110 ° C
The reaction was terminated when the reaction was carried out for 7.0 h while maintaining the temperature.

After completion of the reaction, the reactor was cooled and settled.
The contents were taken out and washed with an aqueous solution of sodium sulfite and then with an aqueous solution of sodium hydroxide to collect 197 g of organic matter. The collected organic matter was analyzed by gas chromatography to find that 3-bromo-trifluoromethylbenzene 6
2.0%, unreacted trifluoromethylbenzene
It was 0%.

[0039]

The method of the present invention can convert trifluoromethylbenzenes into brominated trifluoromethylbenzenes with a high conversion and a high selectivity because the catalyst containing iron has a high activity in the bromination reaction. In addition, since the solubility in the product is small and the removal of the dissolved metal from the product is practically not required, the process can be simplified and the catalyst can be used repeatedly. Play.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shozo Kaneda 2805 Imafukunakadai, Kawagoe-shi, Saitama Central Research Institute of Glass Co., Ltd. (72) Inventor Satoshi Naruzuka 2805 Imafukunakadai, Kawagoe-shi, Saitama Inside the Chemical Laboratory of Glass Co., Ltd.

Claims (2)

[Claims] 1. A compound of the general formula (1) (Wherein, n represents an integer of 1 to 2). A general formula comprising brominating trifluoromethylbenzenes in the liquid phase in the presence of an iron-containing catalyst in the presence of bromine and chlorine. 2), embedded image (In the formula, n represents an integer of 1-2, and m represents an integer of 1-3.)
A method for producing a brominated trifluoromethylbenzene represented by the formula: 2. A method for producing 3,5-bis (trifluoromethyl) bromobenzene, which comprises brominating 1,3-bis (trifluoromethyl) benzene in the presence of iron chloride in the presence of bromine and chlorine in the presence of iron chloride. A method for producing bromine /
1,3-bis (trifluoromethyl) benzene molar ratio 0.5-2, chlorine / bromine molar ratio 1-2, reaction temperature 50
3,5-bis (trifluoromethyl) at ~ 200 ° C
A method for producing bromobenzene.