JPS6158460B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing an iodinated aromatic amino compound in high yield, and more specifically, a method for producing an iodinated aromatic amino compound by reacting an aromatic amino compound with ammonium iodide. It's about how to get it. 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 uses aramid resin monomers and azo dyes as intermediates. As a conventional method for iodizing aromatic amino compounds with ammonium iodide, for example, a method for producing p-iodoaniline is known. According to this method, p-iodoaniline is produced by reacting aniline with ammonium iodide under oxidizing conditions. ),
A method using a cupric compound (Japanese Unexamined Patent Publication No. 53-50122) or a method using oxygen oxidation (Japanese Unexamined Patent Publication No. 53-50122)
132530) 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 the cupric compound described above requires a large amount of the cupric compound because the cupric compound does not act as a catalyst and performs a stoichiometric reaction.
This is disadvantageous as an industrial method. On the other hand, the method using oxygen oxidation includes the steps of oxidizing ammonium iodide to generate iodine in the presence of a copper compound catalyst in an ammonia aqueous solution;
Since the step of reacting the generated iodine with aniline must be carried out in a separate reactor, there are inevitable disadvantages in terms of equipment and operation. The reason why this process must be carried out in two steps is that in the presence of oxygen, copper compounds, and bases, aromatic amino compounds may dimerize to form azobenzene (Bull.Chem.Soc .Japan”,
(Vol. 32, p. 780). Additionally, hydrogen ions are generally required for the oxidation of iodine anions (J.Chim.Phys. 55 , 407
(1958)), in the above method, iodine is produced under ammoniacal alkaline conditions, so hydrogen ions are insufficient and the rate of iodine production is slow, and ammonia is also produced as a by-product as iodine is produced. As the concentration 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 Structure"). It also has the disadvantage of being dangerous. The present inventors have conducted extensive research in order to overcome the drawbacks of such conventional methods and develop an industrial method for obtaining iodinated aromatic amino compounds in a single reactor and in good yield. As a result, when iodinating an aromatic amino compound with ammonium iodide, in an aqueous medium containing a vanadium compound and a weak acid, by oxidizing the ammonium iodide with oxygen and reacting with the 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, in producing an iodinated aromatic amino compound by reacting an aromatic amino compound with ammonium iodide, the present invention involves oxidizing the ammonium iodide with oxygen in an aqueous medium containing a vanadium compound and a weak acid. The present invention provides a method for producing an iodinated aromatic amino compound, which is characterized by reacting the iodinated aromatic amino compound with an aromatic amino compound. The reaction in the method of the present invention is estimated to proceed as shown in the following reaction formulas (1) to (4) when a vanadium compound, ammonium dihydrogen phosphate, and aniline are used, for example. 2I ^- +V ⁵⁺ →I ₂ +V ³⁺ (1) V ³⁺ +1/2O ₂ +H ₂ O→V ⁵⁺ +2OH ^- (2) 2NH ₄ H ₂ PO ₄ +2OH ^- +2NH ₄ I→2(NH ₄ ) ₂ HPO ₄ +2I ^- +2H ₂ O (3) As described above, in the reaction of the present invention, diammonium hydrogen phosphate produced by the above reaction formula (3) acts as a base as shown in reaction formula (4), and diammonium iodide and dihydrogen phosphate are formed. This is an extremely efficient reaction in which ammonium hydrogen is produced again. Usually, in the iodination reaction of aromatic amino compounds, in order to capture the generated hydrogen iodide,
It is said that it is necessary to carry out the reaction under weakly alkaline conditions [Organic Synthetic Chemistry 1, p. 360, edited by Tetsuji Kameya, Nankodo], but surprisingly, in the present invention, the aroma can be produced without any problem even in the presence of weak acids. The iodination reaction of group amino compounds proceeds. This is thought to be because ammonium salts of weak acids produced within the system function as bases. 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. In general, 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 when copper is used, azobenzene However, in the method of the present invention, the oxidation reaction proceeds rapidly, and there is no fear that nitrogen iodide will be produced, and azobenzene will not be produced. In the method of the present invention, it is necessary to use a weak acid. If a strong acid such as hydrochloric acid or sulfuric acid is used, nitrogen iodide will not be produced, but the nitrogen atom of the aromatic amino compound will be quaternized and iodinated. The reaction is inhibited, and even if the iodination reaction occurs, the generated hydrogen iodide is not captured, so the reaction does not proceed any further. Furthermore, in this case, an ammonium salt of a strong acid is generated and must be disposed of, but when a weak acid is used, the ammonium salt of a weak acid generated can be decomposed by heat into a weak acid and ammonia. Such problems do not occur. As described above, the oxidation reaction progresses slowly under alkaline conditions, and when copper compounds are used, azobenzenes are likely to be produced in the presence of oxygen, and nitrogen iodide may also be produced.
Although it is difficult to carry out industrially, and on the other hand, it is difficult to carry out under strong acidic conditions because the iodination reaction is hindered, the method of the present invention uses a weak acid and vanadium. This solves the problem. As shown in the reaction formula above, the vanadium compound used as a catalyst is considered to be simply a source of vanadium ions, and the type of anion side of the vanadium compound is not related to the essence of the reaction and there are no special restrictions. . Therefore, there are no particular limitations on the vanadium compound, and most vanadium compounds can be used, but vanadium monoxide, vanadium hydroxide (), vanadium dichloride, vanadium sulfate (), and K ₄ [V(CN) ₆ ],
Divanadium trioxide, vanadium hydroxide (),
Vanadium trifluoride, M ₂ VF ₅ (M=Na, K,
NH ₄ ), vanadium trichloride, vanadium tribromide,
Vanadium triiodide, vanadium sulfate (), MV
(SO ₄ ) ₂ (M=Na, K, NH ₄ ), K ₃ [V(CN) ₆ ],
Vanadium dioxide, M ₂ V ₄ O ₉ (M=Na, K,
NH ₄ ), vanadium tetrafluoride, M ₂ [VOF ₄ (OH) ₂ ]
(M=Na, K, NH ₄ ), vanadium tetrachloride, vanadium oxydichloride, vanadyl sulfate, M ₂ [VO
(SO ₄ ) ₂ ] (M=Na, K, NH ₄ ), vanadium pentoxide, sodium metavanadate, potassium metavanadate, ammonium metavanadate,
Sodium orthovanadate, potassium orthovanadate, ammonium orthovanadate, sodium pyrovanadate, potassium pyrovanadate, ammonium pyrovanadate,
Sodium pentavanadate, potassium pentavanadate, ammonium pentavanadate, vanadium pentafluoride, MVF ₆ (M=Na, K, NH ₄ ), vanadium oxytrifluoride, vanadium oxytrichloride, vanadium oxytribromide, Such as VO ₂ Cl. 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. Examples of the aromatic amino compounds used in the method of the present invention include those having no substituent on the aromatic ring or those having one or two lower alkyl groups;
Or those with no substituent on the nitrogen atom or 1
Examples include those having one or two lower alkyl groups. As the lower alkyl group, a methyl group, an ethyl group, etc. are preferable. Specific examples of these include 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·N-dimethyl-m-toluidine, N-methyl-p-toluidine, N·N-dimethyl-p-toluidine, α
-naphthylamine, β-naphthylamine, etc. In particular, aniline is suitable because p-iodoaniline, 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 amino 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. Generally speaking, the rate of the oxidation reaction in the method of the present invention increases as the temperature increases, but if the temperature is too high, the ammonium salt of the weak acid will decompose and the ammonia concentration in the system will increase, slowing down the oxidation reaction. Undesirable. 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. In the method of the present invention, the weak acid is used to suppress the production of ammonia by suppressing the pH within the system, promote the oxidation of ammonium iodide, and prevent the production of nitrogen iodide and azobenzenes. Furthermore, the presence of a weak acid ammonium salt plays a role in scavenging hydrogen iodide generated in the iodination reaction. Further, in the method of the present invention, it is advantageous to thermally decompose the ammonium salt of the weak acid produced to recover the weak acid and reuse it in the production of the iodinated aromatic amino compound. 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, silicic acid, and vanadic acid, and organic acids such as acetic acid and propionic acid. Among these, preferred are phosphoric acid and diphosphoric acid. Ammonium hydrogen, sodium dihydrogen phosphate, potassium dihydrogen phosphate, or an organic acid. In particular, in the case of ammonium dihydrogen phosphate, heating the ammonium salt, ammonium phosphate-hydrogen, 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, the aqueous medium may be taken out and heated after the iodination reaction is completed. 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 substances that are not substantially iodinated in this system, such as benzene and chlorobenzene, 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 chlorobenzene, in combination with water. The appropriate hydrogen ion concentration in an aqueous medium is
Although it varies depending on the acid and conditions used and cannot be limited, in general, as the hydrogen ion concentration increases, the oxidation of iodine anions becomes faster and the production of iodinated aromatic amino compounds tends to become faster. According to the method of the present invention, by using a weak acid, iodinated aromatic amino compounds can be produced quickly;
Moreover, the yield is good, and it becomes possible to obtain an iodinated aromatic amino compound without a step of separating iodine. Furthermore, since the ammonium salt of a 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, and in addition, azobenzenes and explosive nitrogen iodide are not produced. do not. In addition, the weak acid can be recovered and reused if necessary, and the ammonia generated at the same time as the weak acid is recovered and used 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 100 Example 1 (1) Iodination reaction In a 500 ml pressure-resistant glass autoclave, 75 g (0.517 mol) of ammonium iodide, 2.4 g (0.0132 mol) of vanadium pentoxide, 25 g (0.217 mol) of ammonium dihydrogen phosphate, 100 ml of benzene, and pure 50 ml of water was charged and stirred at an oxygen pressure of 2 to 8 Kg/cm ² (gauge pressure) and a temperature of 70°C to generate iodine. After 4.5 hours, the mixture was cooled to room temperature, 24 g (0.258 mol) of aniline was added, and the mixture was stirred at room temperature for 2 hours to react with the generated iodine. Thereafter, the organic layer was taken out, and 15.2 g (0.0700 mol) of iodoaniline was obtained from this. The yield of iodoaniline was 32%, and the ratio of para and ortho forms was P form/O form = 19. (2) Recovery of weak acid Add 15g of aniline to the aqueous layer after the reaction in (1).
(0.161 mol), add 75 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. Then, the lower layer was taken out, washed with 50 ml of benzene, and the aqueous layer was collected. Add 50ml of pure water to this and add 5g of aniline (0.0538mol) and benzene.
50 ml was added and stirred at 50° C. for 1 hour under nitrogen atmosphere (N ₂ pressure 2 Kg/cm ² ). Take out the aqueous layer, put it in a 500ml SUS316 autoclave, add 85ml of pure water, fill it with nitrogen gas (pressure 2Kg/cm ² ), and stir it until the temperature is 170~216.
Diammonium hydrogen phosphate produced by an oxidation reaction at °C was thermally decomposed. At the same time, ammonia was released along with water vapor from a nozzle installed at the top of the autoclave, and about 150 ml of ammonia water was obtained in one hour through a cooling pipe. When the generated ammonia was quantified with 1N sulfuric acid aqueous solution, it was 1.18.
g (0.0700 mol). The recovery rate of ammonium dihydrogen phosphate was 100%. (3) Add ammonium iodide (1) to the aqueous solution obtained in re-iodination reaction (2).
The amount consumed in 10.2 g (0.0700 mol) was replenished, 50 ml of benzene was added, and iodine was generated at 70°C for 4.5 hours. Thereafter, the mixture was cooled to room temperature, 24 g (0.258 mol) of aniline was added, and the mixture was reacted at room temperature for 2 hours to obtain iodoaniline with a yield of 30%. The ratio of para and ortho isomers is P isomer/O isomer
Body = 19. Examples 2 to 4 A reaction was carried out in the same manner as in Example 1 using the compositions shown in Table 1. The results obtained are shown in Table 1. Example 5 (1) Iodination reaction 75 g (0.517 mol) of ammonium iodide, 4.2 g (0.0267 mol) of vanadium trichloride, 25 g (0.217 mol) of ammonium dihydrogen phosphate, and 24 g of aniline in a 500 ml pressure-resistant glass autoclave.
(0.258 mol), 100 ml of benzene and 50 ml of pure water, oxygen pressure 2-8 Kg/cm ² (gauge pressure), temperature 70
The reaction was carried out at ℃ while stirring. 8.0
After a period of time, the organic layer was taken out, and 28.6 g (0.130 mol) of iodoaniline was obtained from the organic layer. The yield is
It was 60%. (2) Recovery of weak acid A weak acid was recovered in the same manner as in (2) of Example 1. The recovery rate was 100%. (3) Re-iodination reaction The aqueous solution obtained in (2) was supplemented with 18.9 g (0.130 mol) of ammonium iodide, the amount consumed in (1), and 24 g (0.258 mol) of aniline and 100 g of benzene were added.
ml was added and the reaction was carried out with stirring at an oxygen pressure of 2 to 8 Kg/cm ² and a temperature of 70°C.
Iodoaniline was obtained with a yield of %. Examples 6 to 8 Reactions were carried out in the same manner as in Example 5 using the compositions shown in Table 1. The results obtained are shown in Table 1. Examples 9 to 11 A reaction was carried out in the same manner as in Example 5 (1) using the compositions shown in Table 1. The results obtained are shown in Table 1. 【table】

Claims (1)

[Claims] 1. In producing an iodinated aromatic amino compound by reacting an aromatic amino compound with ammonium iodide, the ammonium iodide is oxidized with oxygen in an aqueous medium containing a vanadium compound and a weak acid. 1. A method for producing an iodinated aromatic amino compound, which comprises reacting the iodinated aromatic amino compound with an aromatic amino compound. 2. The method according to claim 1, wherein at least a portion of the weak acid is obtained by thermal decomposition of an ammonium salt of a weak acid produced in an oxidation reaction.