JPH0355462B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for obtaining an iodinated aromatic amino compound by oxidizing ammonium iodide in the presence of a copper compound in an aqueous medium and iodizing the aromatic amino compound in the reaction solution. Iodinated aromatic amino compounds are important compounds used as synthetic intermediates for dyes, pigments, pharmaceuticals, aramid resin monomers, etc.
Iodoaniline is important as a raw material for the synthesis of p-phenylenediamine, which is used as a monomer for aramid resins and as an intermediate for azo dyes. Conventionally, a method for producing p-mode aniline has been known as a method for iodinating an aromatic amino compound with ammonium iodide. According to this method, p-
Iodoaniline is produced by reacting aniline with ammonium iodide under oxidizing conditions. This oxidation condition can be brought about, for example, by electrolysis (US Pat. No. 3,975,439), by a method using a cupric compound (JP-A-53-50122), or by oxygen oxidation (JP-A-53-132530). Publication No.) etc. are known. However, since the electrolytic method requires the reaction to be carried out in a dilute solution and requires the use of a diaphragm, it is not necessarily advantageous when carried out industrially, as it requires a large scale equipment and consumes a large amount of electricity. This is not a good method. In addition, the method using a cupric compound described above requires a large amount of cupric compound because the cupric compound does not act as a catalyst and performs a stoichiometric reaction, and is not an industrial method. is disadvantageous. On the other hand, in the method using oxygen oxidation, the steps of oxidizing ammonium iodide to generate iodine in the presence of a copper compound catalyst in an ammonia aqueous solution and reacting the generated iodine with aniline must be carried out in separate reactors. As a result, there are inevitable disadvantages in terms of equipment and operation. The reason why it has to be carried out in two steps is that aromatic amino compounds may dimerize and form azobenzene in the presence of oxygen, copper compounds, and bases (Bull.Chem. Soc.Japan”,
(Vol. 32, p. 780). In the method using oxygen oxidation described above, iodine is produced under ammoniacal alkaline conditions, so hydrogen ions are insufficient and the production rate of iodine is slow. In addition, ammonia is also produced as a by-product with the production of iodine, and its concentration increases. As it increases, the reaction becomes slower. Moreover, in the first step of this method, iodine is handled under ammoniacal alkaline conditions, and under such conditions there is a risk of producing explosive nitrogen iodide (published by Maruzen, "New Experimental Chemistry"). It also has the disadvantage of being dangerous. The present inventors have overcome the drawbacks of the conventional methods as described above, and have succeeded in producing iodinated aromatic amino compounds in a single reactor without producing by-products such as nitrogen iodide and azobenzene. As a result of intensive research to develop an industrial method to obtain a good yield, we found that when aromatic amino compounds are iodized with ammonium iodide, the ammonium iodide is oxidized in an aqueous medium containing a copper compound and a weak acid. By oxidizing with and reacting with an aromatic amino compound,
It was discovered that the object could be achieved without producing by-products such as nitrogen iodide and azobenzenes, and based on this knowledge, the present invention was completed. That is, the present invention provides phosphoric acid,
One or more compounds selected from ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, acetic acid, propionic acid,
This is a method for producing an iodinated aromatic amino compound, which comprises reacting ammonium iodide and oxygen using a copper compound as a catalyst, and iodizing the aromatic amino compound in the reaction solution. In the present invention, the weak acid is a reactive agent that captures ammonia produced by the reaction for producing molecular iodine, and is also a hydrogen atom acceptor (hydrogen iodide scavenger) in the iodination reaction of aromatic amino compounds. )
The iodine anion oxidation reaction and the iodination reaction can proceed smoothly in the same system in the absence of substantially free ammonia in the reaction system. When iodinating aniline in the presence of a copper compound using ammonium dihydrogen phosphate as a weak acid in the method of the present invention, it is thought that the reaction proceeds as shown in the following reaction formula. Cu ⁺ 6+NH ₄ ICuI+NH ₄ ⁺ Cu ²⁺ +2NH ₄ ICuI ₂ +2NH ₄ ⁺ 2CuI+1/2O ₂ +2NH ₄ I+H ₂ O→ 2CuI ₂ +2NH ₄ OH 2CuI ₂ →2CuI+I ₂ 2NH ₄ OH+2NH ₄ H ₂ PO ₄ →2(NH ₄ ) ₂ HPO ₄ +2H ₂ O Thus, in the reaction of the present invention, ammonium hydrogen phosphate produced according to the above reaction formula participates in the reaction as a base as shown in the reaction formula,
It is also an extremely efficient reaction, as ammonium iodide and ammonium dihydrogen phosphate are produced again. Usually, in the iodination reaction of aromatic amino compounds, in order to capture the generated hydrogen iodide,
Although it is said that it is necessary to carry out the reaction under weakly alkaline conditions [Organic Synthetic Chemistry I, p. 360, edited by Tetsuji Kametani, Nankodo], surprisingly, in the present invention, the aroma can be produced without any problem even in the presence of weak acids. The reason why the iodination reaction of group amino compounds progresses is thought to be because the ammonium salt of a weak acid generated in the system acts as a base and captures the acid generated in the iodination reaction. Therefore, according to the method of the present invention, it is not necessary to separate the iodine anion oxidation reaction and the iodination reaction, and they can be carried out in the same system. Generally, under alkaline conditions, as mentioned above, not only is the oxidation reaction of iodine anions slow, but depending on the reaction conditions, explosive nitrogen iodide may be produced, and azobenzene etc. are likely to be produced as by-products. In the method of the present invention, the oxidation reaction proceeds rapidly, and there is no fear of producing iodine nitrogen and no azobenzene is produced. In the method of the present invention, it is necessary to use a weak acid, and if a strong acid such as hydrochloric acid or sulfuric acid is used instead of the weak acid, nitrogen iodide will not be produced, but
The nitrogen atom of the aromatic amino compound is quaternized and the iodination reaction is inhibited, and even if the iodination reaction occurs, the reaction does not proceed any further because the generated hydrogen iodide is not captured. Furthermore, ammonium salts of strong acids are formed in this case, which must be disposed of. When using a weak acid,
This problem does not arise because the ammonium salt of the weak acid produced can be decomposed into the weak acid and ammonia by heat. As described above, under alkaline conditions, the oxidation reaction progresses slowly, azobenzenes are likely to be produced by the copper compound and oxygen, and nitrogen iodide may also be produced, so it is difficult to carry out industrially. However, the method of the present invention uses a weak acid to
This is the first time that these problems have been resolved. Most copper compounds can be used as the copper compound used in the method of the present invention, but preferred are cuprous iodide, cuprous chloride, cuprous oxide, cuprous bromide, cuprous cyanide, Copper sulfate, cupric chloride,
These include cupric hydroxide, cupric oxide, cupric bromide, cupric phosphate, copper nitrate, copper carbonate, and copper acetate. These compounds may be used alone or in combination of two or more. There is no particular restriction on the amount used, but in practical terms it is preferably in the range of 3 x 10 ^-4 to 3 x 10 ^-1 mol per 100 g of water. Furthermore, the catalyst may be dissolved or undissolved in the aqueous medium. The aromatic amino compounds used in the method of the present invention include those having no substituent or one or two lower alkyl groups on the aromatic ring, or those having no substituent or one substituent on the nitrogen atom. Alternatively, examples include those having two lower alkyl groups. As the lower alkyl group, a methyl group, an ethyl group, etc. are preferable. Aniline, o-
Toluidine, m-toluidine, p-toluidine,
N-methylaniline, N,N-dimethylaniline, N-methyl-o-toluidine, N,N-dimethyl-o-toluidine, N-methyl-m-toluidine, N-methyl-p-toluidine, N,N- Dimethyl-p-toluidine, α-naphthylamine,
Examples include β-naphthylamine. In particular, aniline is suitable because p-mode aniline, which is important as a raw material for p-phenylenediamine, can be obtained in high yield and high selectivity. In the present invention, these aromatic amine compounds can be supplied into the reaction system at any stage before the oxidation reaction, during the oxidation reaction, or after the oxidation reaction. Furthermore, a supply method combining any of these methods may be used. In either case, the iodinated aromatic amino compound can be obtained in good yield. Therefore, in the method of the present invention, it is possible to freely select the timing of supplying the aromatic amino compound into the reaction system. In addition, especially when it is desired to selectively obtain p-iodoaniline, the purpose can be achieved by cooling the reactor after the oxidation reaction, adding aniline, and reacting with the generated iodine. In general, the rate of the oxidation reaction in the method of the present invention increases as the temperature rises, but if the temperature is too high, the ammonium salt, which is a weak acid, will decompose and the ammonia concentration in the system will increase, slowing down the oxidation reaction. This is not desirable. Usually preferred temperatures range from room temperature to 100°C. Although there are no particular limitations on the amount of ammonium iodide used in the process of the present invention, the higher its concentration in the aqueous medium, the faster the oxidation reaction of the iodide anion is in the rate-limiting step, thus forming the iodinated aromatic amino compound. Therefore, the preferred amount in practice is 100g of water.
It is in the range of 10 to 200g. As the oxygen used in the method of the present invention, not only oxygen gas but also an oxygen-containing gas such as air can be used. There are no particular restrictions on the oxygen partial pressure or pressure, but the higher the pressure, the faster the oxidation of iodine anions and the faster the production of iodinated aromatic amino compounds. Practically preferred pressure conditions are in the range of 0.2 to 10 atmospheres. The weak acids used in the method of the present invention include:
Any substance that releases ammonia by heating the ammonium salt may be used, such as phosphoric acid, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, boron, etc. Examples include inorganic acids such as arsenic acid, chromic acid, telluric acid, and silicic acid, and organic acids such as acetic acid and propionic acid. Preferred among these are phosphoric acid, ammonium dihydrogen phosphate, These are sodium dihydrogen phosphate, potassium dihydrogen phosphate, and acetic acid. In particular, in the case of ammonium dihydrogen phosphate, heating the ammonium salt thereof, ammonium monohydrogen phosphate, releases ammonia quantitatively in a short period of time and becomes ammonium dihydrogen phosphate, which is suitable. In order to recover the weak acid used in the method of the present invention, after the iodination reaction is completed, the aqueous medium containing the ammonium salt of the weak acid produced by the reaction may be taken out and heated. The weak acid recovered here can be used again as a raw material for the iodination reaction without the need to add new acid. The higher the decomposition temperature of the ammonium salt of a weak acid, the faster the decomposition and the better the decomposition rate, and the preferred range is usually 100 to 210°C. The reaction solvent in the method of the present invention is a medium mainly composed of water, but a solvent that is not substantially iodinated in this system, such as benzene or chlorzeneben, can also be used in combination with water. When the aromatic amino compound used as a raw material is a solid, it is advantageous to use a solvent capable of dissolving the aromatic amino compound, such as benzene or clokbenzene, in combination with water. In the reaction method of the present invention, the hydrogen ion concentration of the aqueous medium varies depending on the acid and conditions used, but the pH of the reaction medium is generally from weakly acidic to weakly alkaline. Generally, as the hydrogen ion concentration increases, the oxidation of iodine anions tends to become faster and the production of iodinated aromatic amino compounds also becomes faster. By using a weak acid, the iodinated aromatic amino compound can be produced quickly and in good yield, and it is also possible to obtain the iodinated aromatic amino compound without a step of separating iodine. Furthermore, since the ammonium salt of the weak acid produced as a result of the oxidation reaction acts as a base, there is no need to add a base, which is essential in normal iodination reactions.
Furthermore, azobenzenes and explosive nitrogen iodide are not produced. Furthermore, it is possible to recover and reuse the weak acid if necessary, and it is also possible to recover ammonia generated at the same time when recovering the weak acid and use it for other purposes. Next, the present invention will be explained in more detail with reference to Examples. Note that the yield of the iodinated aromatic amino compound and the recovery rate of the weak acid were determined according to the following formula. Yield (%) = Number of moles of iodinated aromatic amino compound produced/Number of moles of charged weak acid x 100 Recovery rate (%) = Number of moles of ammonia produced/Number of moles of ammonium salt of weak acid produced x 10
0 Example 1 150 g (1.03 mol) of ammonium iodide and 5 g of copper iodide were placed in a 500 ml pressure-resistant glass autoclave.
(0.0262 mol), ammonium dihydrogen phosphate 50g
(0.435 mol), p-toluidine 70g (0.654 mol),
Prepare 250ml of benzene and 100ml of pure water, oxygen pressure 3
The reaction was carried out under stirring conditions at ~8 Kg/cm ² (gauge pressure) and a temperature of 70°C. The pressure of oxygen is 8Kg/cm ²
When the amount was reduced from 3 kg/cm ² to 3 kg/cm 2 , the amount was again supplied to 8 kg/cm ² . After 3 hours, take out the organic layer and extract 83.1 g of 2-iodo-4-methylaniline.
(0.357 mol) was obtained. The yield was 82%. Example 2 A reaction was carried out in the same manner as in Example 1 using the raw materials shown in Table 1. The results obtained are shown in Table 1. Example 3 (1) Iodination reaction A reaction was carried out in the same manner as in Example 1 using the composition shown in Table 1. The results obtained are shown in Table 1. (2) Recovery of weak acid Add 30g of aniline to the water tank after the reaction in (1).
(0.322 mol), add 150 ml of benzene, and heat at 50℃ for 2 hours.
The mixture was stirred under nitrogen atmosphere (N ₂ pressure 2 Kg/cm ² ) for an hour. Next, take out the lower layer and add benzene 100
The aqueous layer was collected by washing with ml. Add 100% pure water to this
10 g (0.108 mol) of aniline and 100 ml of benzene were added again, and the mixture was stirred at 50° C. for 1 hour under a nitrogen atmosphere (N ₂ pressure 2 Kg/cm ² ). Remove the aqueous layer, place it in a 500ml SUS316 autoclave, add 170ml of pure water, fill it with nitrogen gas (pressure 2Kg/cm ² ), and stir while stirring.
Diammonium hydrogen phosphate produced by oxidation reaction was thermally decomposed at 170-210°C. At the same time, ammonia was released along with water vapor from a nozzle installed at the top of the autoclave, and about 300 ml of ammonia water was obtained in one hour through a cooling pipe. The amount of ammonia generated was determined using a 1N aqueous sulfuric acid solution and was found to be 5.17 g (0.304 mol). The recovery rate of ammonium dihydrogen phosphate was 10%. (3) Re-iodination reaction The aqueous solution obtained in (2) was replenished with ammonium iodide in the amount consumed in (1), 44.1 g (0.304 mol),
48 g (0.516 mol) of aniline and 100 ml of benzene were added, and the reaction was carried out with stirring at an oxygen pressure of 2 to 5 Kg/cm ² and a temperature of 50° C., and iodoaniline was obtained in 6 hours with a yield of 38%. Example 4 (1) Iodination reaction 150 g (1.03 mol) of ammonium iodide and 5 copper iodide were placed in a 500 ml pressure-resistant glass autoclave.
g (0.0262 mol), ammonium dihydrogen phosphate
50g (0.435mol), benzene 100ml and pure water 100ml
ml, oxygen pressure 3-8Kg/cm ² (gauge pressure),
Iodine was generated by stirring at a temperature of 70°C. After 3 hours, cool to room temperature and add aniline.
48 g (0.516 mol) was added and stirred at room temperature for 2 hours to react with the generated iodine. After that, remove the organic layer, and from this, iodoaniline
40.0g (0.183mol) was obtained. The yield of iodoaniline was 42%, and the ratio of para and ortho forms was P form/O form = 19. (2) Recovery of weak acid A weak acid was recovered in the same manner as in Example 3 (2). The recovery rate was 100%. (3) Add ammonium iodide (1) to the aqueous solution obtained in re-iodination reaction (2).
The amount consumed in 26.5 g (0.183 mol) was replenished, 100 ml of benzene was added, and iodine was generated at 70°C for 2.5 hours. Thereafter, the mixture was cooled to room temperature, 48 g (0.516 mol) of aniline was added, and the mixture was reacted at room temperature for 2 hours to obtain iodoaniline with a yield of 31%. The ratio of para and ortho bodies is P body/O body
Body = 19. Examples 5 and 6 A reaction was carried out in the same manner as in Example 3 using the raw materials shown in Table 1. The results obtained are shown in Table 1. However, the yield in Example 6 is based on aniline. Comparative Example 1 When a reaction was carried out in the same manner as in Example 1 using the composition shown in Table 1 without using a weak acid, iodoaniline was produced in an amount less than the amount of the catalyst used. Furthermore, the formation of azobenzene was observed. The inside of the reaction system became alkaline due to ammonia produced by the oxidation reaction.

【table】

[Table] ** Nitrogen iodide yield of Examples 1 to 6 = 0%
Examples 7 to 9 Reactions were carried out in the same manner as in Example 4 using the compositions shown in Table 2. The results obtained are shown in Table 2. Examples 10 to 13 A reaction was carried out in the same manner as in Example 1 using the compositions shown in Table 2. The results obtained are shown in Table 2. Examples 14-15 A reaction was carried out in the same manner as in Example 4 (1) using the compositions shown in Table 2. The results obtained are shown in Table 2.

【table】

[Table] ** Nitrogen iodide yield in Examples 7 to 15 = 0
Examples 16 to 21 Reactions were carried out in the same manner as in Example 1 using the compositions and conditions shown in Table 3. The results obtained are shown in Table 3.

【table】

【table】

Claims (1)

[Claims] 1. One or more compounds selected from phosphoric acid, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, acetic acid, propionic acid, ammonium iodide and oxygen in an aqueous medium. 1. A method for producing an iodinated aromatic amino compound, which comprises reacting with a copper compound as a catalyst and iodizing the aromatic amino compound in the reaction solution.