JPH0472815B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for obtaining an iodinated aromatic hydroxy compound using ammonium iodide as a raw material. Iodine is used as an intermediate in organic synthesis, as a catalyst, in medicine,
Health drugs, fungicides, livestock feed additives, organic compound stabilizers, dyes, photoengraving, agricultural chemicals, rare metal smelting,
It is a useful compound that is widely used as analytical reagents. Various iodine derivatives are useful compounds that are widely used as synthetic intermediates for dyes, pigments, medicines, agricultural chemicals, and the like. Iodine is commonly obtained from saltpeter, a brine that comes with natural gas. Industrially, many methods are used to oxidize iodide anions contained in salt water with an aqueous solution of copper sulfate () and iron sulfate (). Since this method is usually carried out under strong acidic conditions, salts of strong acids and strong alkalis such as sodium sulfate are produced as by-products, which poses problems in their treatment. Methods for obtaining iodine from ammonium iodide include a method using electrolysis (German Patent No. 2436111) and a method using a cupric compound (Japanese Unexamined Patent Application Publication No. 1983-1989).
50122), a method using oxygen oxidation (Japanese Unexamined Patent Publication No. 1983-
Publication No. 73489). In the method using electrolysis (German Patent No. 2436111), the reaction is carried out in a dilute solution and a diaphragm is required, making the equipment large-scale and consuming a large amount of electricity, making it difficult for industrial use. It cannot be said that it is an advantageous method. Method using cupric compounds (JP-A-Sho
53-50122), since the reaction is stoichiometric, the cupric compound does not act as a catalyst and is disadvantageous for producing a large amount of iodine. In the method using oxygen oxidation (Japanese Unexamined Patent Publication No. 53-73489), ammonium iodide is oxidized with oxygen in an aqueous ammonia solution using a copper compound as a catalyst to obtain iodine. Generally, oxidation of iodine anions requires a strong acid [J.Chim.Phys. 55 , 407 (1958).
JCS, Dalton, 793 (1974)], in this method, the iodine formation reaction is carried out under ammoniacal alkaline conditions, so the rate of iodine production is extremely slow, and ammonia is produced as iodine is produced. It is expected that the reaction will be even slower. Furthermore, under ammoniacal alkaline conditions, explosive nitrogen iodide is likely to be produced, as is clear from the Chemistry Encyclopedia (Kyoritsu Shuppan, Vol. 9, p. 447), and this cannot be said to be industrially advantageous. Further, as a method for producing an iodine derivative using 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. ), method using cupric compound (JP-A-53-50122
(Japanese Patent Application Laid-Open No.
53-132530), 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 is disadvantageous as an industrial method because the cupric compound does not act as a catalyst and performs a stoichiometric reaction, so a large amount of the cupric compound is required. It is. Generally, oxidation of iodine anions requires a strong acid [J.Chim.Phys. 55 , 407 (1958).
JCS, Dalton, 793 (1974)], in the method using oxygen oxidation, the rate of iodine production is slow because iodine is produced under ammoniacal alkaline conditions, and ammonia is also produced as a by-product as iodine is produced. As the concentration of raw perilla 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"). Lectures'', Vol. 14 [1], p. 423], it also has the disadvantage of being dangerous. When the functional group is a hydroxyl group, that is, in the case of phenols, the iodination reaction is generally carried out in an alkaline aqueous solution. However, alkali iodides such as Kl and NaI are produced as by-products, and a process of converting the alkali salt of phenol to phenol is required.
This method cannot necessarily be said to be industrially advantageous because it requires a step of neutralizing the waste water of the reaction aqueous solution. The present inventors have developed an advantageous industrial method that overcomes the drawbacks of such conventional methods and can obtain iodinated aromatic hydroxy compounds in good yields without producing by-products that are difficult to reproduce. As a result of extensive research, we have found that it is possible to obtain iodine by oxidizing ammonium iodide with oxygen in a medium containing a transition metal compound and a weak acid, and by reacting it with an aromatic compound having a functional group. It was discovered that the purpose could be achieved without by-products such as nitrogen iodide and alkali iodide.
Based on this knowledge, we have completed the present invention. That is, the present invention involves oxidizing ammonium iodide with oxygen or an oxygen-containing gas in a medium containing a copper compound or a vanadium compound and a weak acid, and at least a portion of which is water, and then reacting the ammonium iodide with an aromatic hydroxy compound. This is a characteristic method for producing an iodized aromatic hydroxy compound. In particular, the present invention uses a weak acid to obtain a sufficient iodine production rate, and then extracts the generated iodine or consumes it in an appropriate reaction. By thermally decomposing the ammonium salt of a weak acid, recovering the weak acid, and reusing it in the iodine production reaction,
The present invention provides a highly efficient method for obtaining iodine and iodinated aromatic hydroxy compounds. Using the reaction of the present invention using a copper compound and ammonium dihydrogen phosphate as an example, it is estimated that iodine is produced by the following reaction mechanism. Cu ⁺ +NH ₄ ICuI+NH ₄ ⁺ Cu ²⁺ +2NH ₄ ICuI ₂ +2NH ₄ ⁺ (1) 2CuI+1/2O ₂ +2NH ₄ I+H ₂ O→2CuI ₂ +2NH ₄ OH
(2) 2CuI ₂ →2CuI＋I ₂ (3) 2NH ₄ OH＋2NH ₄ H ₂ PO ₄ →2(NH) ₄ HPO ₄ ＋
2H ₂ O (4) Furthermore, the reaction with phenol will proceed as follows. Thus, in the reaction of the present invention, ammonium hydrogen phosphate produced by the above reaction formula (4) acts as a base as shown in reaction formula (5), and forms ammonium iodide and dihydrogen phosphate. This is an extremely efficient reaction in which ammonium is produced again. Normally, in the iodination reaction of aromatic compounds, it is necessary to carry out the reaction under weakly alkaline or alkaline conditions in order to capture the hydrogen iodide produced [Organic Synthetic Chemistry 1, 360 pages, edited by Tetsuji Kametani, Nankodo. Experimental Chemistry Course 14, Synthesis and Reactions of Organic Chemistry [], p. 423, Maruzen] Surprisingly, in the present invention, the iodination reaction of aromatic compounds proceeds without any problem even in the presence of a weak acid. 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. Generally, under alkaline conditions, as mentioned above, the oxidation reaction of iodine anions is slow, producing alkali iodide that is difficult to reuse, and especially under ammoniacal alkaline conditions, explosive nitrogen iodide may be produced. However, in the method of the present invention,
The oxidation reaction proceeds rapidly, and there is no risk of producing nitrogen iodide. In the method of the present invention, it is necessary to use a weak acid. If a strong acid such as an acid salt or sulfuric acid is used, nitrogen iodide will not be produced, but an ammonium salt of the strong acid will be produced, which must be disposed of. It won't happen. When a weak acid is used, such a problem does not occur because the generated ammonium salt of the weak acid can be recovered by decomposing the weak acid and ammonia by heat. As described above, under alkaline conditions, the oxidation reaction progresses slowly, and under ammoniacal alkaline conditions, nitrogen iodide may be produced, making it difficult to carry out industrially. Industrial implementation is difficult because ammonium salts of strong acids are produced even under low temperatures. In the method of the present invention, these problems can be solved by using a weak acid and a transition metal compound. Any transition metal compound that is generally used as a catalyst for oxidation reactions can be used, such as Cu, Ag, V, Fe, Co, Ni, Cr,
Examples include compounds such as Mo and W. Among these, copper compounds and vanadium compounds are iodide ions (I
) has a fast oxidation rate, so in the present invention,
It is necessary to select and use at least one of the above copper compounds or vanadium compounds. As shown in the above reaction formula, the metal compound used as a catalyst is considered to be simply a source of metal ions, and the type of anion side of the metal compound is considered to be unrelated to the essence of the reaction and there are no special restrictions. .
There are no particular limitations on the copper compound, and most copper compounds can be used, including cuprous iodide, cuprous chloride, cuprous oxide, cuprous bromide, cuprous cyanide,
Cuprous sulfate, cupric sulfate, cupric chloride, cupric hydroxide, cupric oxide, cupric bromide, cupric phosphate, cuprous nitrate, cupric nitrate, copper carbonate, Cuprous acetate, cupric acetate, and the like are preferred. Among them, especially CuCl,
CuCl ₂ , CuBr, CuBr ₂ , CuI, CuO, CU ₂ O,
CuSO ₄ and Cu(OCOCH ₃ ) ₂ are suitable because they are easily available. There are no particular limitations on the vanadium compound, and most vanadium compounds can be used, including vanadium monoxide, vanadium hydroxide (), vanadium dichloride, vanadium sulfate (), 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 ), vanadium dioxide, M ₂ V ₄ O ₉ (M=Na, K, NH ₄ ), vanadium tetrafluoride, M ₂ [VoF ₄ (OH) ₂ ] (M=Na, K,
_NH4 ), vanadium tetrachloride, vanadium oxydichloride, vanadyl sulfate, _M2 [Vo( _SO4 ) ₂ ] (M=Na,
K, NH ₄ ), vanadium pentoxide, sodium metavanadate, potassium metavanadinate, ammonium metavanadate, sodium orthovanadate, potassium orthovanadate, ammonium orthovanadate, sodium pyrovanadate, potassium pyrovanadate, pyro Ammonium vanadate, sodium pentavanadate, potassium pentavanadate, ammonium pentavanadate, vanadium pentafluoride, MVF ₆ (M=
Preferable examples include vanadium oxytrifluoride _, vanadium oxytrichloride, vanadium oxytribromide, and VO ₂ Cl. Among them, especially V ₂ O ₅ ,
VOSO ₄ , VOCl ₃ , VOCl ₂ , VCl ₃ , NaVO ₃ ,
NH ₄ VO ₃ and NaVO ₄ are particularly suitable because they are easily available. These transition metal compounds may be used alone or in combination of two or more. The amount of the transition metal compound used is not particularly limited, but in practice it is preferably 3 x 10 ^-4 to 0.3 mol per 100 g of water.
Furthermore, the transition metal compound may or may not be dissolved in the aqueous medium. The amount of ammonium iodide used is not particularly limited, but the higher the concentration in the aqueous medium, the faster the rate of iodine production tends to be. Practically preferred is 10 to 200 g per 100 g of water. As for the oxygen used, not only oxygen gas but also air can be used to achieve the purpose of the present invention. There are no particular limitations on oxygen pressure or partial pressure, but
The rate of iodine production tends to be faster at higher pressures. In practical terms, it is preferably 0.2 to 10 atm. The higher the temperature, the faster the oxidation reaction, but if the temperature is too high, the ammonium salt of the weak acid will decompose, increasing the ammonia concentration in the system and slowing down the oxidation. Usually, preferably from 20°C to 100°C. The weak acid is used to react with ammonia produced by the iodine production reaction, keep the pH in the system low, accelerate the oxidation reaction rate, and prevent the production of nitrogen iodide. In addition, when an ammonium salt of a weak acid is present, it plays a role in capturing hydrogen iodide generated in the iodination reaction. Further, it is preferable to thermally decompose the ammonium salt of the weak acid produced as necessary, recover the weak acid, and reuse it in the iodine generation reaction. The weak acids used may be those that release ammonia when the ammonium salt is heated, such as ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, boric acid, arsenic acid, chromic acid, telluric acid. , inorganic acids such as silicic acid and vanadate, and organic acids such as acetic acid and propionic acid. Preferred are phosphoric acid, ammonium dihydrogen phosphate, and organic acids. In addition, ammonium dihydrogen phosphate, sodium dihydrogen phosphate,
In the case of potassium hydrogen phosphate, heating its ammonium salt, phosphoric acid-hydrogen salt, releases ammonia quantitatively in a short period of time and returns to dihydrogen phosphate, which is particularly preferred. In order to recover the weak acid in the present invention, the generated iodine is extracted from the system by extraction with an organic solvent such as ether or an appropriate iodine consumption reaction, and then the aqueous medium containing the generated ammonium salt of the weak acid is heated. do it. The weak acid recovered here can be used again as a raw material for the iodine production reaction, and there is no particular need to add new acid for iodine production. The higher the decomposition temperature of the ammonium salt of a weak acid, the better the decomposition rate and decomposition rate, and is preferably 100 to 210°C. At least a portion of the medium in the present invention is water, but a medium such as benzene or chlorobenzene, which does not substantially react with iodine in this system, can be used in combination with water. The hydrogen ion concentration in water is not limited as it varies depending on the acid used and conditions, but the hydrogen ion concentration is high,
The rate of iodine production tends to be fast. In order to obtain the iodinated aromatic hydroxy compound of the present invention, a compound that reacts with iodine, such as an aromatic hydroxy compound, may be added to the medium. The aromatic hydroxy compound used in the present invention is an aromatic compound having an electron-donating functional group. Among them, Hammett's substituent constant (δ _p ) is −0.25.
The following are preferred. Examples of such aromatic hydroxy compounds include phenol, o-cresol, m-cresol, p-cresol,
2,3-xylenol, 2,4-xylenol,
2,5-xylenol, 2,6-xylenol,
3,4-xylenol, 3,5-xylenol,
Examples include 3,6-xylenol and α-naphthol. These aromatic hydroxy compounds can be supplied into the reaction system at any stage before the oxidation reaction, during the oxidation reaction, or after the oxidation reaction, and any combination of these methods can be used. Although it may be used, in the present invention, it is more suitable to supply the aromatic hydroxy compound into the reaction system after the iodine generation reaction. If the oxidation reaction and iodination reaction are carried out simultaneously, the phenol will be oxidized and many by-products will be produced. Generally, the lower the iodination temperature, the better the regioselectivity, and the iodination temperature is preferably between 0°C and 100°C. According to the invention, by using a weak acid,
The production of iodine is fast and the yields of iodine and iodinated aromatic hydroxy compounds are also good, and the iodinated aromatic hydroxy compounds can be obtained 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. Alkaline iodides etc. are not generated. In addition, the present invention allows weak acids to be recovered and reused as needed, and ammonia generated at the same time as weak acids can be recovered and used for other purposes, thereby reducing the generation of industrial waste. This is an extremely advantageous method for producing iodinated aromatic hydroxy compounds. The present invention will be explained in more detail with reference to Examples below. In the following examples, the oxidation reaction is performed using a weak acid.
When ammonium dihydrogen phosphate was used, the yield of iodine was determined from equation (2), assuming that the following equation (1) was followed. 1/2O ₂ +2NH ₄ I+2NH ₄ H ₂ PO _4Transition metal compound――――――――――→ I ₂ +2(NH ₄ ) ₂ HPO ₄ +H ₂ O
...(1) Iodine yield (%) = Number of moles of iodine generated/Number of moles of weak acid charged x 1/2 x 100...
(2) Also, assuming that the thermal decomposition of a weak acid follows equation (3) when ammonium dihydrogen phosphate is used as the weak acid,
The recovery rate of weak acid was determined from equation (4). (NH ₄ ) ₂ HPO ₄ →NH ₄ H ₂ PO ₄ +NH ₃ ...(3) Recovery rate (%) = Number of moles of ammonia generated/Number of moles of ammonium salt of weak acid produced x 100...(4) Iodine The yield of the aromatic hydroxy compound was determined according to the following formula. Yield (%) = Number of moles of iodinated aromatic hydroxy compound produced/Number of moles of charged weak acid x 100...(5) The reaction was assumed to follow equation (6). Ar+1/2O ₂ +NH ₄ I+NH ₄ H ₂ PO ₄ →Arl+(NH ₄ ) ₂ HPO ₄ +H ₂ O ……(6) (Ar+1/2O ₂ +2NH ₄ I+2NH ₄ H ₂ PO ₄ → ArI+(NH ₄ ) ₂ HPO ₄ +NH ₄ H ₂ PO ₄ +NH ₄ I+
H ₂ O) Calculations were also performed using equations (2) and (4) when other weak acids were used. Reference example 1 (1) Generation of iodine 300 g (2.07 mol) of ammonium iodide and 5 g of copper iodide in a 500 ml pressure-resistant glass autoclave.
(0.0263mol), ammonium dihydrogen phosphate 100g,
(0.870mol), 200ml of pure water, oxygen pressure 2-5
The reaction was carried out with stirring under conditions of Kg/cm ² (gauge pressure) and a temperature of 50°C. Oxygen has a pressure of 5Kg/ ^cm2 to 2Kg/cm2.
When the amount was reduced to 5 kg/cm ² , the amount was again supplied to 5 kg/cm ² .
After 7 hours, the amount of iodine generated was determined using 0.1N sodium thiosulfate aqueous solution and found to be 77.3g.
(0.305 mol). The yield of iodine was 70%. (2) Recovery of weak acid After adding 600 ml of pure water to the iodine aqueous solution obtained in (1), iodine was extracted three times with diethyl ether from 1, and almost all of the generated iodine could be recovered. Furthermore, a trace amount of iodine remaining in the aqueous solution was reduced with sodium thiosulfate to obtain an aqueous solution containing no molecular iodine. Add this aqueous solution to 1
It was charged into a SUS316 autoclave, heated and stirred at 170 to 210°C under a nitrogen atmosphere, and ammonia was released along with water vapor from a nozzle installed at the top of the autoclave. Approximately 600 c.c of ammonia water was obtained in 2 hours through a cooling pipe. . The generated ammonia is 1N
10.4g (0.612mol) when determined with sulfuric acid aqueous solution
It was hot. The ammonia recovery rate was 100%. (3) Add 88 g (0.607 mol) of ammonium iodide equivalent to the consumed ammonium to the aqueous solution obtained in reoxidation (2), and add 2 to 5 Kg/cm ² (gauge pressure) of oxygen using a pressure-resistant glass autoclave. When the oxidation reaction was carried out again under the conditions of pressurization and temperature of 50°C, iodine was obtained with a yield of 50% in 4 hours. Reference Examples 2 to 4 Reactions were carried out in the same manner as in Reference Example 1 using the compositions shown in Table 1. The results obtained are shown in Table 1. Reference Examples 5 and 6 When the oxidation reaction was carried out in the same manner as in Reference Example 1 (1) with the composition shown in Table 1 without using a weak acid, the amount of iodine was less than or equal to the amount of the catalyst used. It did not occur. At the start of the reaction, the system was neutral, but as iodine was produced, it became alkaline. Further, in Reference Example 6, nitrogen iodide was produced, and when dried, it exploded upon a slight impact.

[Table] Reference Examples 7 to 10 A reaction was carried out in the same manner as in Reference Example 1 using the compositions shown in Table 2. The results obtained are shown in Table 2. Reference Examples 11 to 15 Using the compositions shown in Table 2, a reaction was carried out in the same manner as in Reference Example 1 (1). The results obtained are shown in Table 2.

【table】

[Table] Reference Examples 16 to 22 A reaction was carried out in the same manner as in Reference Example 1 using the compositions shown in Table 3. The results obtained are shown in Table 3. Reference Examples 23 to 26 Using the compositions shown in Table 3, a reaction was carried out in the same manner as in Reference Example 1 (1). The results obtained are shown in Table 3. Reference Examples 27 to 29 A reaction was carried out in the same manner as in Reference Example 1 using the compositions shown in Table 4. The results obtained are shown in Table 4. Reference Examples 30 to 33 A reaction was carried out in the same manner as in Reference Example 1 (1) using the compositions shown in Table 4. The results obtained are shown in Table 4.

【table】

【table】

[Table] Example 1 (1) Iodination reaction Ammonium iodide 75 (0.515 mol) and copper iodide 2.5 g were placed in a 500 ml pressure-resistant glass autoclave.
(0.0131 mol), ammonium dihydrogen phosphate 25 g
(0.2175 mol), benzene 100 ml and pure water 50 ml, oxygen pressure 2-8 Kg/cm ² (gauge pressure), temperature 70
Iodine was generated by stirring at ℃. After 3 hours, the mixture was cooled to room temperature, 24 g of phenol was added, and the mixture was stirred at room temperature for 3 hours to react with the generated iodine. Thereafter, the organic layer was taken out, and 19.1 g (0.087 mol) of iodophenol was obtained from this.
The yield of iodophenol was 40%, and the ratio of para and ortho forms was P form/O form = 0.4. (2) Recovery of weak acid Add 30g of phenol to the aqueous layer after the reaction in (1).
(0.322 mol) and 150 ml of benzene were added and stirred at 50°C for 3 hours under a nitrogen atmosphere (N ₂ pressure 2 Kg/cm ² ). Then, the lower layer was taken out, washed with 100 ml of benzene, and the aqueous layer was collected. Add 100ml of pure water to this, add 10g of phenol (0.108mol), and 100ml of benzene.
ml and stirred at 50° C. for 2 hours under nitrogen atmosphere (N ₂ pressure 2 Kg/cm ² ). Remove the aqueous layer and place it in a 500ml SUS316 autoclave.
Add 170ml of pure water and fill with nitrogen gas (pressure 2
Kg/cm ² ), and while stirring, diammonium hydrogen phosphate produced by the oxidation reaction was thermally decomposed at 170 to 210°C. At the same time, ammonia is released along with water vapor from a nozzle installed at the top of the autoclave, and the ammonia water is released in one hour through a cooling pipe.
Obtained 200ml. The amount of ammonia generated was determined using a 1N aqueous sulfuric acid solution and was found to be 1.48 g (0.087 mol). Recovery rate of ammonium dihydrogen phosphate is 100%
It was hot. (3) Re-iodination reaction The aqueous solution obtained in (2) was supplemented with ammonium iodide in the amount consumed in (1), 12.6 g (0.087 mol),
100 ml of benzene was added and iodine was generated at 70°C for 3 hours. After that, cool to room temperature and extract the phenol.
When 24g was added and reacted at room temperature for 3 hours, 39
Iodophenol was obtained with a yield of %. The ratio of para-isomer and ortho-isomer was P-isomer/O-isomer = 0.4. Examples 2 to 7 Reactions were carried out in the same manner as in Example 1 (1) using the raw materials shown in Table 5. The results obtained are shown in Table 5.

【table】

【table】

Claims (1)

[Claims] 1. Ammonium iodide is oxidized with oxygen or an oxygen-containing gas in a medium containing a copper compound or vanadium compound and a weak acid and at least partially water, and then reacted with an aromatic hydroxy compound. A method for producing an iodinated aromatic hydroxy compound, characterized by: 2. The method for producing an iodinated aromatic hydroxy compound according to claim 1, wherein at least a part of the weak acid is obtained by thermal decomposition of an ammonium salt of a weak acid generated in an oxidation reaction.