JP2000044501A - Production of fluorinated aromatic compound and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improved dediazonation photo-decomposition process that can efficiently produce an aromatic fluoride. SOLUTION: A mixed solution of hydrofluoric acid and a base is used as a reaction solvent to diazotize an aromatic amine in the reaction solvent and photodecompose the resultant diazonium salt to effect dediazofluorination whereby an aromatic fluoride is produced. In this process, the progress of the photo- decomposition is detected based on the amount of nitrogen gas liberated by the photodecomposition, and the reaction solution is circulated through the photoreactor and the hydrofluoric acid is distilled and recovered from the reaction solution after the photodecomposition reaction. In the meantime, the objective aromatic fluoride is recovered from the reaction solution in which the concentration of hydrofluoric acid is reduced. Then, hydrofluoric acid and the base is recovered from the residue and the recovered hydrofluoric acid and the base are reused as a part of the reaction solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for producing an aromatic fluorine compound. More specifically, the present invention relates to a method for producing an aromatic fluorinated product by photolysis of an aromatic diazonium salt, which has a high yield and is advantageous in terms of maintenance and management of the device, and a production device therefor.

[0002]

2. Description of the Related Art Aromatic fluorine compounds are useful as intermediates for pharmaceuticals, agricultural chemicals, liquid crystals and the like. As typical methods for producing aromatic fluorine compounds, electrophilic fluorine substitution, dehalofluorination reaction (Halex method), diazotization-dediazofluorination reaction (Balz-Schiemann method) and the like are known. . Electrophilic fluorine substitution is performed using fluorine gas or the like, but has problems in control of the reaction and regioselectivity.
The dehalofluorination reaction requires a strong electron-withdrawing group at the o- or p-position, and the substrate is limited.

The diazotization-dediazofluorination reaction is the most versatile of the above methods, but requires a step of isolating a chemically unstable and toxic diazonium salt. Further, it is difficult to control the thermal decomposition and the reproducibility of the reaction is not good. Further, the yield varies greatly depending on the substrate, and there is a problem that the yield is low particularly for a complex compound having a polar substituent.

[0004] An improved method has been proposed in which after diazotization, dediazofluorination is carried out by light irradiation in the presence of a base such as pyridine (JP-A-63-188631). in this way,
Control of the reaction is relatively easy, and isolation of the diazonium salt is not required. In addition, there is an advantage that the reaction proceeds with high selectivity. However, when the reaction is continued for a long period of time or when the reaction apparatus is used repeatedly, there has been a problem that the coupling body or the tar-like substance adheres to the light transmitting material in contact with the reaction solution, thereby lowering the reaction efficiency.

Therefore, the light irradiation time is reduced by adding hydrofluoric acid to the diazotization reaction solution or diluting the reaction solution by adding hydrofluoric acid having a base concentration lower than the base concentration of the diazotization reaction solution. The present inventors have proposed a manufacturing method for shortening the time and reducing the contamination of the light transmitting material for continuous use for a long time (JP-A-9-20697).

[0006]

DISCLOSURE OF THE INVENTION The present invention solves such a conventional problem and efficiently and industrially carries out a dediazofluorination reaction by photodecomposition of a diazonium salt using hydrofluoric acid or a mixed solution of hydrofluoric acid base. It provides a method that can be implemented. Specifically, the production method of the present invention circulates the reaction solution to the photoreactor and repeats the photodecomposition reaction according to the progress of the reaction, thereby increasing the reaction efficiency and causing contamination of the light transmitting material. The production of hydrofluoric acid or hydrofluoric acid and a base is recovered and used repeatedly, thereby suppressing the generation of by-products and increasing the utility as an industrial production method.

[0007]

That is, the present invention relates to the following manufacturing method. (1) Hydrofluoric acid alone or a mixed solution of hydrofluoric acid and a base is used as a reaction solution, an aromatic amino compound is diazotized in the reaction solution, and the resulting diazonium salt is photolyzed and dediazofluorinated. In the method for producing an aromatic fluorine compound, (a) the progress of photodecomposition is detected by the amount of nitrogen gas generated by photodecomposition, and based on this, the reaction solution is circulated through a photoreaction vessel to advance the photodecomposition reaction,
(B) After the photolysis reaction, the reaction solution is heated to distill and recover the hydrofluoric acid, while (c) the target aromatic fluorine compound is recovered from the reaction solution having a reduced hydrofluoric acid concentration, and (d) from the residue. The present invention relates to a method for producing an aromatic fluorine compound, comprising recovering hydrofluoric acid or hydrofluoric acid and a base, and recycling the recovered hydrofluoric acid or hydrofluoric acid and a base to a part of a reaction solution.

[0008] The manufacturing method of the present invention includes the following aspects. (2) The production method according to (1) above, wherein dediazofluorination is carried out by a photolysis reaction using ultraviolet light having a wavelength of 280 nm to 340 nm. (3) The production method according to the above (1) or (2), wherein a hydrofluoric acid base mixed solution having a base concentration of 0 to 50 wt% is used as a reaction solution;
(4) The concentration of the aromatic amino compound in the solvent is 0.0.
The production method according to the above (1), (2) or (3), wherein the amount is 1 to 5 mmol / g.

Further, the present invention relates to the following manufacturing apparatus suitable for carrying out the above manufacturing method. (5) A vertically long phototube and a vertically long photoreaction tube surrounding the phototube, wherein the phototube or the photoreaction tube has a filter for limiting a wavelength range of irradiation light. On the other hand, the photoreaction tube is formed of a light transmissive material, and is provided with an exhaust pipe and gas measuring means for guiding generated gas to the outside, and further circulates the reaction solution to the photoreaction tube. A photoreactor characterized in that a storage tank is provided. (6) The photoreaction device according to (5), wherein the photoreaction tube is formed of a light transmissive material that restricts the wavelength of the irradiation light, instead of providing a filter that limits the wavelength of the irradiation light. (7) An apparatus used for producing an aromatic fluorine compound, wherein the photoreaction tube is formed of a fluoroolefin polymer tube, and the wavelength of irradiation light is 280.
The photoreactor according to the above (5) or (6), wherein the photoreaction device is limited to an ultraviolet region of nm to 340 nm.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on specific embodiments. FIG. 1 shows an outline of an example of the manufacturing process of the present invention, and FIG. 2 shows an example of the apparatus configuration. As shown in the figure, the production method of the present invention comprises (I) hydrofluoric acid alone or a step of diazotizing an aromatic material as a raw material in a reaction solution of hydrofluoric acid and a base, and (II) photo-decomposition of a generated diazonium salt. (III) heating the reaction solution containing the product to recover hydrofluoric acid, and (IV) recovering the hydrofluoric acid from the reaction solution having a reduced hydrofluoric acid concentration. (V) a step of recovering hydrofluoric acid or a hydrofluoric acid and a base from a recovered residue, (VI)
A step of circulating and recovering the recovered hydrofluoric acid and base to the diazotization step.

The reaction solution prepared in the adjusting tank 1 is led to the reaction tank 2 where the diazotization reaction proceeds and the reaction tank 2
From the storage tank 16 to the photoreactor 10
Supplied to The reaction solution is circulated through the storage tank 16 and the photoreactor 10 according to the degree of the photolysis reaction, and is withdrawn to the outside via the storage tank 16 after the reaction. Hereinafter, each step will be described.

(I) Diazotization Step A diazotization reaction is performed by using a hydrofluoric acid alone or a mixed solution of hydrofluoric acid and a base as a reaction solution and adding an aromatic amino compound as a raw material and a nitrite-providing agent to the reaction solution. Let it do. The raw material aromatic amino compound may be any compound in which an amino group is directly bonded to an aromatic ring, and includes aromatic hydrocarbons and aromatic compounds containing hetero atoms. Examples of aromatic hydrocarbons include benzene, naphthalene, anthracene and the like, and examples of heterocycles include pyridine,
Pyrimidine, pyrazoline, triazine, quinoline, furan, benzofuran pyrrole, thiophene, oxazole, isoxazole, thiazole, imidazole, benzimidazole, oxadiazole, thiadiazole, trizole, indole, naphthidine and the like.

The aromatic amino compound as a raw material may have a substituent in addition to the amino group. The type of the substituent is not limited. The present invention is particularly useful when an aromatic compound having a polar substituent is used as a raw material. That is, in the diazotization-photodecomposition of an aromatic compound having a polar substituent, by-products such as a tar-like compound are likely to be generated. In the method of the present invention, even when such a compound is used as a raw material, a tar-like compound is used. The target compound can be obtained by minimizing by-products. Examples of the polar substituent include halogen such as fluorine, chlorine, bromine and iodine, haloalkyl such as trifluoromethyl, alkoxycarbonyl and alkoxy. One molecule may have a plurality of polar substituents, or may have substituents other than those listed here.

The nitrite-providing agent used for the diazotization is commonly referred to as a diazotizing agent, and is preferably nitrous anhydride, sodium nitrite, potassium nitrite or the like. The addition amount of the nitrite-imparting agent must be at least equivalent to the aromatic amine as nitrite.

As the reaction solution, hydrofluoric acid alone or a mixed solution of hydrofluoric acid and a base is used. By using the hydrofluoric acid base mixed solution, the photodecomposition reaction can proceed efficiently and the yield of the target compound can be increased. As the base, a base that forms a complex with hydrofluoric acid, that is, a compound containing oxygen, nitrogen, phosphorus, and sulfur can be used. Specifically, for example, pyridine, amine compounds such as triethylamine, ether compounds such as ether ethers, ketone compounds, aldehyde compounds, ester compounds, and alcohols, carboxylic acids, water, sulfoxides, sulfonamide compounds, amide compounds, Nitriles, isonitriles, phosphines, phosphites, phosphate compounds and the like can be used, and amine compounds and ether compounds are particularly preferable.

When only hydrofluoric acid is used as the reaction solution, it is suitably used in an amount of 10 to 50 times, preferably 15 to 40 times, the mole of the starting amine. When a base is allowed to coexist, the base concentration is suitably up to 50 wt%. If the concentration of the base is higher than this, the yield of the target aromatic fluorine compound will decrease. The concentration of the aromatic amino compound in the reaction solution is suitably 0.01 to 5 mmol / g. 0.
If it is less than 01 mol / g, productivity is poor, and if it is more than 5 mmol / g, undissolved amino compounds are generated, which leads to a decrease in the reaction amount and an increase in by-products, which is not preferable. The reaction temperature is suitably from -150 to 150 ° C, and from -100 to 100 ° C.
C is preferred. The reaction time is about 0.1 to 10 hours, depending on the kind of the aromatic amino compound.

(II) Photoreaction Step The reaction product obtained in the above diazotization step is irradiated with light to photodecompose the diazonium salt, and the desired aromatic fluorine compound is produced by a dediazofluorination reaction. This photoreaction has a wavelength of 280 nm to 340 nm, preferably 280 nm to 340 nm.
It is preferable to use ultraviolet light of 320 nm. When the ultraviolet rays having a wavelength of less than 280 nm are contained, the production of tar-like substances increases and the yield of the target compound decreases. At a wavelength exceeding 340 nm, the reaction speed is significantly reduced. By limiting the wavelength of the irradiation light to the above range, the yield of the target compound and the reaction rate can be increased. In particular, in the photodecomposition reaction of a compound having a halogen as a substituent, the effect of the wavelength is more remarkable as the number of substitutions increases.

The wavelength range can be controlled by an ultraviolet light source and a filter. Generally, a high-pressure mercury lamp or the like is used as a light source.
What is necessary is just to combine an ultraviolet transmission filter of 80 nm or more. Further, the wavelength may be controlled by forming the photoreaction container with a glass material having a filter effect. For example, low expansion borosilicate glass (Pyrex)
What is necessary is just to form a reaction container using such.

There is a problem in that tar-like by-products are produced at the stage of the photolysis reaction, which stains the walls of the photoreactor, hinders light irradiation, and lowers the reaction efficiency. The amount of this tar-like substance varies depending on the amino compound and the base concentration used, but can be reduced by increasing the hydrofluoric acid concentration. In this case, when the concentration of hydrofluoric acid is increased, the concentration of the base is relatively decreased.
As described above, the base concentration in the solution is 10 to 50 wt%.
In this case, the amount of the tar-like substance is small and the yield of the target compound is high.

The reaction temperature for photolysis is suitably from -100 to 200 ° C, preferably from -50 to 100 ° C. The reaction time varies depending on the starting compound, but is suitably 1 to 30 hours.
Nitrogen gas is generated as the diazotization proceeds by the photolysis reaction. By measuring the amount of generated nitrogen gas, the progress of the photodecomposition reaction can be grasped, and the reaction solution is circulated from the storage tank to the photoreaction vessel until the calculated amount of nitrogen gas from the raw material or gas generation is eliminated. To repeat the photolysis reaction.

3 and 4 show examples of the structure of the photolytic device.
FIG. 3 is a longitudinal sectional view schematically showing a photoreactor used in the present invention, and FIG. 4 is a schematic transverse sectional view thereof. As shown in the figure, a vertically long light source 11 (phototube: for example, a fluorescent tube) is erected at the center of the photodecomposition device 10, and a plurality of photoreaction tubes 13 are erected around the phototube 11. Have been. The phototube 11 is a lamp 1 that irradiates light to the entire side.
1a and a transparent cylindrical case 11b that hermetically accommodates the lamp 11a. The type, wavelength, and output of the lamp 11a are appropriately selected according to the reaction system.
Since the transparent case 11b does not directly contact the reaction solution,
The material is not limited to one having corrosion resistance to the reaction solution, and a light transmitting material such as highly transparent quartz glass or organic glass can be used. The transparent case 11b is provided with a filter (not shown) for limiting the wavelength range of the irradiation light to the above range. Alternatively, the transparent case 11b may be formed of a glass material having a filter function of limiting the wavelength range of the irradiation light to the above range.

The photoreaction tubes 13 are arranged so as to surround the phototube 11 so that light from the phototube 11 is uniformly and efficiently irradiated. In the illustrated example of the apparatus, the light reaction tube 13 is 8
The phototubes 11 are arranged concentrically around the phototube 11 two by two, and the outer photoreaction tube 13 is installed at a position facing the phototube 11 from between the inner adjacent photoreaction tubes 13. Since the photoreaction tube 13 supplies a reaction solution to the inside and causes a photoreaction, a light transmissive material having corrosion resistance to the reaction solution and its product is used.

The photoreaction tube 13 is formed by a vertically long tubular member, and a reaction solution is supplied to the lower end thereof.
A pipe 15 for extracting the reaction solution is connected, and the pipe 15 is connected to an external storage tank 16. The plurality of light reaction tubes 13 communicate with a storage tank 16 through a conduit 15, and a circulation path is formed between the light reaction tubes 13 and the storage tank 16. Further, an exhaust pipe 17 for guiding nitrogen gas generated inside the light reaction tube 13 to the outside is provided at an upper end of the light reaction tube 13.
The exhaust pipe 17 is provided with a nitrogen gas measuring means 19.

The light source 11 and the photoreaction tube 13 are accommodated in a cooling tank 21, and the cooling tank 2 is
Fixed to 1. A cooling medium 24 is stored in the cooling tank 21. As the cooling medium, distilled water or ion-exchanged water is preferable, but other cooling mediums can be used as long as they are transparent and do not significantly hinder light irradiation. The phototube 11 and the plurality of photoreaction tubes 13 are provided with the cooling water 24.
In the illustrated example of the apparatus, the upper ends of the phototube 11 and the photoreaction tube 13 are provided so as to protrude from the surface of the cooling water 24 for electrical connection or degassing. Further, the cooling tank 21 is provided with a cooling pipe 25 for adjusting the temperature of the cooling water 24.

Since the photoreaction device 10 has a structure in which the photoreaction tubes 13 are individually erected in cooling water, the outer periphery of each of the photoreaction tubes 13 is wrapped by the cooling water,
Since the cooling efficiency is high and the structure is vertical,
The reaction gas generated inside the tube easily escapes to the end of the upper tube, the generated gas does not hinder the photoreaction, and the generated gas
By detecting the amount of (nitrogen gas), the progress of the photolysis reaction can be grasped. When it is necessary to raise the reaction temperature, the reaction system can be easily maintained at an appropriate temperature by using warm water having a target temperature in place of the cooling water.

In the manufacturing method of the present invention, since a hydrofluoric acid or a mixed solution of hydrofluoric acid and base is used as a reaction solution, a photoreaction tube formed of ordinary quartz glass or the like has poor durability and is corroded in a short time. On the other hand, those formed of a fluoroolefin polymer represented by Teflon are preferable because of their high transparency and excellent durability against hydrofluoric acid. In addition, since it is cylindrically supported and arranged vertically, the strength is sufficient and there is no need to reinforce with glass or other materials. Furthermore, since the reaction solution having a high concentration of hydrofluoric acid is circulated, there is no fear of direct corrosion of glass due to permeation of hydrofluoric acid, which is inevitable in a fluoroolefin polymer. A method in which a reaction tube formed of this fluoroolefin polymer is detachably provided, a photoreaction tube whose transparency has been reduced due to repeated use is removed, and the mixture is boiled in a fluorine-based inert solvent to recover the transparency and reuse. Have been proposed by the present inventors (Japanese Patent Laid-Open No.
9727).

Suitable materials for the photoreaction tube include tetrafluoroethylene-ethylene copolymer (ETFE) and tetrafluoroethylene-hexafluoropropylene copolymer
(FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride polymer (PVDF), And vinyl fluoride polymer (PVF).

(III) Hydrofluoric acid recovery step If the concentration of hydrofluoric acid is 85 wt% or more at the end of the photoreaction, 5
Hydrofluoric acid can be recovered at a distillation temperature of 0 ° C. or lower. For example, in the case of a 90 wt% hydrofluoric acid and a 10 wt% pyridine reaction solution, the used amount of 50 to 60 wt% hydrofluoric acid has a water content of 200 to 200 wt%.
It can be recovered in the range of 1000ppm. If the distillation temperature is too high, the water content in the recovered hydrofluoric acid increases, which is not preferable. It is preferable to use a Teflon-lined acid-resistant container for the distillation tank. Prior to the recovery of the target compound, hydrofluoric acid is distilled and recovered, and the concentration of hydrofluoric acid in the reaction solution is reduced. Therefore, the target compound can be efficiently recovered in the next step.

(IV) Recovery of Target Compound The target aromatic fluorine compound is recovered from the reaction solution. As a recovery method, solvent extraction can be used. Specifically, for example, in order to recover methyl 2,4-dibromo-5-fluoro-6-methylbenzoate (BFTAM) generated by a photoreaction in a mixed solution of pyridine hydrofluoric acid, dichloromethane (CH ₂ Cl ₂ ). When dichloromethane is added to this reaction solution, BF
TAM is absorbed by dichloromethane, and by the specific gravity difference,
The mixture is separated into an upper pyridine hydrofluoric acid mixed reaction solution and a lower dichloromethane solvent phase. The solvent phase is recovered, washed with water and an alkali, and after removing the mixed hydrofluoric acid by an extraction operation, the mixture is concentrated by distillation to obtain the target compound BFTAM. Further, the recovered dichloromethane can be reused.

(V) Recovery of hydrofluoric acid / base When the reaction residue obtained by recovering the target aromatic fluorine compound is heated to use hydrofluoric acid and a base, the base can be recovered by distillation. At the time of this distillation, it is preferable to perform distillation under reduced pressure according to the hydrofluoric acid concentration. Specifically, distillation is carried out by heating under normal pressure until the distillate disappears, and then distillation is performed while gradually reducing the pressure until a distillate is produced. By such distillation under normal pressure or reduced pressure, hydrofluoric acid and a compound of hydrofluoric acid and a base can be recovered from the reaction residue.

(VI) Recycling of Recovered Hydrofluoric Acid In the step of distilling hydrofluoric acid, by controlling the distillation temperature, high-grade hydrofluoric acid having a small amount of water can be recovered. It can be forwarded to each previous step and reused. When a mixed solvent of hydrofluoric acid and a base, for example, a hydrofluoric acid / pyridine solution is used,
Pyridine is obtained as a hydrofluoric acid salt of pyridine, which also has a low water content and can be reused as a part of the solvent for the diazotization reaction.

According to the production method and production apparatus of the present invention, various aromatic fluorine compounds can be produced efficiently. 5 to 11 show examples of the production. FIG.
FIG. 6 shows a synthesis example of 5-trifluorobromobenzene, FIG. 6 shows a synthesis example of methyl 2-fluoro-4-chlorobenzoate, and FIG.
FIG. 8 shows an example of the synthesis of methyl 4,5-trifluorobenzoate.
Synthesis example of methyl 4-dichloro-5-fluorobenzoate, FIG. 9 shows synthesis example of 2,4,5-trifluorobenzotrifluoride, FIG. 10 shows synthesis example of 4-fluoroisoquinoline, FIG.
Is an example of the synthesis of methyl 2,4-dibromo-5-fluoro-6-methylbenzoate. All of these can obtain the target compound in high yield by the photolysis reaction of the present invention.

[0033]

EXAMPLES The present invention will be specifically illustrated by examples. Example 1 33.6 g of a pyridine hydrofluoric acid solution (hydrofluoric acid 70 wt%) prepared in a fluororesin container containing a magnet rotor was charged with methyl 2,4-dichloro-5-aminobenzoate.
38 g (purity: about 100%, about 19.9 mmol) was added and dissolved at room temperature. Then, the mixture was cooled to -15 ° C and sodium nitrite 1.5
2 g (22 mmol) were added over 6 minutes (maximum temperature -9 ° C). Then, the temperature was gradually raised and aged at 10 ° C. for 1 hour. The reaction solution was cooled to −20 ° C., and 67 g of hydrofluoric acid was added over 5 minutes with stirring. A 1 kw water-cooled high-pressure mercury lamp equipped with a Pyrex cooling tube (UVL-100 manufactured by Riko Kagaku Sangyo Co., Ltd.) equipped with a Pyrex cooling tube in a water bath maintained at 20 ° C.
0HC) for 22 hours. During the light irradiation, the generation of nitrogen gas was monitored to monitor the progress of the reaction. It was confirmed that the generation of nitrogen gas had stopped, and the irradiation of light was terminated. Next, a connecting pipe made of fluororesin, a cooler, and a receiver were connected to the container, and hydrofluoric acid was recovered on a 50 ° C. oil bath until no distilling was observed. Next, the remaining reaction solution was cooled with ice water, and 60 ml of methylene chloride was extracted in three portions. The combined extracts were washed with 100 ml of water and then neutralized by adding 10% potassium carbonate to 100 ml of water (pH = 7). It was further washed with 100 ml of water, dried over anhydrous sodium sulfate, evaporated and concentrated to give 4.29 g of a crude product. The main component was confirmed to be methyl 2,4-dichloro-5-fluoro-benzoate by GC-MS and NMR analysis (substantially 93% yield). The purity by gas chromatography was 96.41%. On the other hand, the reaction solution after the extraction was transferred to a pressure-resistant fluororesin container and distilled to further recover hydrofluoric acid, a solvent and pyridine.
Table 1 shows the recovered amount and composition.

[0034]

[Table 1]

Example 2 The reaction was carried out in the same manner as in Example 1 except that 3.75 g of methyl 2,4-difluoro-5-aminobenzoate was used as a starting material, and 2,4,5-trifluorobenzoic acid was used. The methyl acid salt was obtained in a yield of 96%.

Example 3 Using 4.44 g of 2,4-dichloro-5-aminobenzotrifluoride as a raw material, a pyridine hydrofluoric acid solution (pyridine 2
The reaction was carried out in the same manner as in Example 1 except that 101.8 g of (0 wt%) was used. As a result, 3,4,5-trifluorobromobenzene was obtained in a yield of 96%.

Example 4 A reaction was carried out in the same manner as in Example 1 except that 4.01 g of 2,4-difluoro-5-aminobenzotrifluoride was used as a starting material, and 2,4,5-trifluorobromo was used. Benzene was obtained with a yield of 89%.

Example 5 As a starting material, methyl 3-amino-4-chlorobenzoate 3.76
The reaction was carried out in the same manner as in Example 3 except that g was used. As a result, methyl 2-fluoro-4-chlorobenzoate was obtained in a yield of 75.
%.

Comparative Example 1 In the same experiment as in Example 1, the same operation was performed except that the cooling tube of the high-pressure mercury lamp was changed to quartz.
As the irradiation time becomes longer in the light irradiation, an increase in contamination of the container is observed, and the yield of methyl 2,4-dichloro-5-fluorobenzoate when the reaction is terminated when the generation of nitrogen gas stops is as follows. 42%, indicating not only a decrease in yield but also an increase in by-products.

[0040]

According to the production method of the present invention, the progress of the photodecomposition reaction is detected based on the amount of nitrogen gas generated, and photodecomposition is repeated in accordance with the detected degree. Therefore, the production method is more efficient than the conventional diazotization-photodecomposition method. Thus, the target compound can be obtained. Furthermore, since the mixed solution of hydrofluoric acid base used as the reaction solvent is recovered and reused, it is economically excellent. In addition, the reaction proceeds with high selectivity, and there is almost no by-produced de-diazo hydride which is difficult to separate from the target substance, and the yield of the compound having a polar substituent is high, and the reaction can be easily controlled. It has such advantages. Further, in a preferred embodiment of the present invention, since ultraviolet light having a specific wavelength is used for the photodecomposition reaction, almost no tar-like substance is generated, and contamination of the reaction vessel can be prevented. And the maintenance of the device is easy.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an outline of a production method of the present invention.

FIG. 2 is an explanatory diagram illustrating a configuration example of a manufacturing apparatus that implements the present invention.

FIG. 3 is a longitudinal sectional view schematically showing a photolysis device used in the method of the present invention.

FIG. 4 is a cross-sectional view schematically showing the photolysis device of FIG.

FIG. 5 is a reaction formula showing an example of the synthesis of 3,4,5-trifluorobromobenzene.

FIG. 6 is a reaction formula showing an example of the synthesis of methyl 2-fluoro-4-chlorobenzoate.

FIG. 7 is a reaction scheme showing an example of the synthesis of methyl 2,4,5-trifluorobenzoate.

FIG. 8 is a reaction scheme showing an example of the synthesis of methyl 2,4-dichloro-5-fluorobenzoate.

FIG. 9 is a reaction formula showing an example of the synthesis of 2,4,5-trifluorobenzotrifluoride.

FIG. 10 is a reaction formula showing an example of the synthesis of 4-fluoroisoquinoline.

FIG. 11 is a reaction scheme showing an example of the synthesis of methyl 2,4-dibromo-5-fluoro-6-methylbenzoate.

[Explanation of symbols]

1-preparation tank, 2-reaction tank, 10-photoreactor, 11-
Photocell, 13-photoreaction tube, 15-line, 16-reservoir,
19-gas metering means, 21-cooling bath, 23-support,
24-cooling water, 25-cooling pipe

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C07C 69/78 C07C 69/78 (72) Inventor Hiroshi Koshiyama 3-6-1 Ibarjima, Akita-shi, Akita Stock (72) Inventor: Toshiaki Sumiyama 3-6-1, Ibarjima, Akita City, Akita Prefecture F-term (reference) 4H006 AA02 AA04 AC30 AC59 AD11 AD13 BA95 BB19 BB20 BB21 BB22 BB23 BB26 BC10 BC31 BC36 BD33 BD81 BD83 BE01 BE44 BJ50 BM30 BM71 FE73 FE74

Claims (7)

[Claims] 1. A hydrofluoric acid alone or a mixed solution of hydrofluoric acid and a base is used as a reaction solution, an aromatic amino compound is diazotized in the reaction solution, and the generated diazonium salt is photodecomposed and dediazofluorinated. In the method for producing an aromatic fluorine compound by this, (a) the progress of photodecomposition is detected by the amount of nitrogen gas generated by photodecomposition, and based on this, the reaction solution is circulated to the photoreaction vessel to advance the photodecomposition reaction (B) After the photolysis reaction, the reaction solution is heated to distill and recover hydrofluoric acid, while (c) the target aromatic fluorine compound is recovered from the reaction solution having a reduced hydrofluoric acid concentration, and (d) the residue A method for producing an aromatic fluorine compound, comprising recovering hydrofluoric acid or hydrofluoric acid and a base from water and recycling the recovered hydrofluoric acid or hydrofluoric acid and a base to a part of a reaction solution. 2. The method according to claim 1, wherein dediafluorination by photolysis is carried out using ultraviolet light having a wavelength of 280 nm to 340 nm. 3. The method according to claim 1, wherein a hydrofluoric acid base mixed solution having a base concentration of 0 to 50 wt% is used as a reaction solution. 4. The method according to claim 1, wherein the concentration of the aromatic amino compound in the solvent is 0.01 to 5 mmol / g. 5. A phototube having a vertically elongated shape and a vertically elongated photoreaction tube which is arranged to surround the phototube, and the phototube or the photoreaction tube limits a wavelength range of irradiation light. A filter is mounted, while the photoreaction tube is formed of a light transmissive material, and an exhaust pipe and a gas measuring means for guiding generated gas to the outside are provided. A photoreactor characterized in that a storage tank that circulates the water is provided. 6. The photoreaction apparatus according to claim 5, wherein instead of providing a filter for limiting the wavelength of the irradiation light, the photoreaction tube is formed of a light-transmitting material for limiting the wavelength of the irradiation light. 7. An apparatus used for producing an aromatic fluorine compound, wherein the photoreaction tube is formed by a fluoroolefin polymer tube, and the wavelength of the irradiation light is further limited to an ultraviolet region of 280 nm to 340 nm. The photoreactor according to claim 5 or 6, wherein: