JPH02132158A - Production of indigos - Google Patents

Abstract

PURPOSE:To obtain indigos at one stage in high yield by heating and reacting specific indoles with percarboxylic acids in the presence of aprotic solvent. CONSTITUTION:Indoles (e.g., 1-methylindole) having no substituent group at 2-position and 3-position is subjected to heat reaction with percarboxylic acids (e.g., peracetic acid or m-chloroperbenzoic acid) in the presence of aprotic solvent (e.g., n-hexane or benzene) at >=60 deg.C, preferably 60-150 deg.C for 0.1-24hr to provide the aimed indigos.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing indigo compounds, which are important compounds as dyes. More specifically, the present invention relates to a method for producing indigo compounds by heating and reacting indoles having no substituents at the 2- and 3-positions with percarboxylic acids in the presence of a specific solvent. (Prior art) Currently, the industrial method for producing indigo is to produce N-phenylglydine salt using aniline and chloroacetic acid or aniline, hydrocyanic acid, and formaldehyde as raw materials, and then melt this in an alkali at high temperature to form an indoxyl compound. After that, a method is adopted in which this is further oxidized in air. However, these methods not only involve multi-step and complicated reaction steps, but also require the use of large amounts of potassium hydroxide and sodium hydroxide, which consumes a large amount of energy when recovering and reusing them. Because special equipment is required, it is desired to switch to a more detailed process.

(Problem to be Solved by the Invention) An object of the present invention is to fundamentally improve such a multi-step and complicated method for producing indigo, and to provide a method for producing indigo that is simpler than these conventional methods. It is. There is an example of reacting indole and perbenzoic acid, a percarboxylic acid, in chloroform as a solvent overnight in a refrigerator after cooling with water (Justus Liebigs Anr+al.
en der Chi+mie, 558 volumes. 91-98
Page, 1947). According to this, many other components were produced in addition to orthoformaminobenzaldehyde, and it is reported that a very small amount of indigo was also obtained. Also,
There is an example of generating peracetic acid, which is a percarboxylic acid neck, in a reaction system using an aqueous hydrogen peroxide solution and acetic acid, and reacting it with indole using acetic acid as a solvent (8ull.Agr.Che+
*. Soc. Japan, vol. 20, pp. 80-83, 1
956). According to this, it is reported that 2,2-diindyl-ψ-indoxyl, which is a trimer with an indole skeleton, was produced as the main product, and at this time, a very small amount of indigo was also produced as a by-product. However, all of these methods are merely examples of investigating the reactivity of indole, and the main products are orthoformaminobenzaldehyde and 2,2-diyndi-ψ-indoquinle, respectively.
Indigo, which is the object of the present inventors, is only one of the by-products that can be obtained in extremely small quantities. (Means for Solving the Problems) The present inventors have intensively studied a method for efficiently producing indigo compounds by reacting indoles and percarboxylic acids, and have surprisingly found that indoles and percarboxylic acids The present invention was achieved by discovering that when an aprotic solvent is present when reacting acids and the reaction is further heated, the formation of indigo necks is significantly increased. That is, the present invention provides indigo compounds, which are characterized in that indoles having no substituents at the 2- and 3-positions and percarboxylic acids are reacted by heating to a temperature of 60°C or higher in the presence of an aprotic solvent. This is the manufacturing method. Indoles having no substituents at the 2- and 3-positions, which are raw materials in the method of the present invention, include, for example, indole, 1-methylindole, 4-methylindole, 5-methylindole, and 5-methylindole.
- Alkylindoles such as methylindole, 6-methylindole, 7-methylindole, 4,5-dimethylindole, 4-chloroindole, 5-chloroindole, 4,5-dichloroindole, 4-bromoindole, 5 - Halogenated indoles such as bromoindole, 4.5-dipromoindole, 4-hydroquinindole, 5-hydroxyindole, 4.5-
Hydroxyindoles such as dihydroxyindole, 4-chloro-5-methylindole, 5-chloro-4-
Halogenated alkylindoles such as methylindole, 4-bromo-5-methylindole, and 5-bromo-4-methylindole; ditroindoles such as 4-nitroindole, 5-nitroindole, and 7-nitroindole; indole; These include indole carboxylic acids such as -5-carboxylic acid and sulfonated indoles, and may have substituents at positions other than the 2- and 3-positions as long as they do not inhibit the reaction. The other raw material in the method of the present invention, percarboxylic acids, is an organic compound having a percarboxyl group (-COOO}l).
)Author 1Organic 7 Beroxide (Organic
Peroxides) Vol. I”. Wi1ey-1nterscienc
e) Published (1970); pp. 401-403 and 436
-445 as listed in the true table.
Among these, perfatty acids such as peracetic acid or perprobionic acid, perbenzoic acid, lin-chloroperbenzoic acid, p
-chloroperbenzoic acid, 0-methylperbenzoic acid or p
- Perbenzoic acid derivatives such as isopropyl perbenzoic acid are preferred. These may be used alone, or two or more kinds may be used simultaneously or in a mixture. In addition, it may be a combination of components that can generate these percarboxylic acids in the reaction system, such as a combination of hydrogen peroxide and carboxylic acid.The amount of percarboxylic acids used is particularly limited. However, the amount is usually in the range of 0.01 to 100 mol per mol of the indole, and preferably 0.01 to 100 mol. The amount ranges from D to 20 moles.

The aprotic solvent used in the method of the present invention is referred to in “Solvent Handbook” edited by Terumi Asahara et al., 1st edition published by Kodansha (19
76), p. 25, as aprotic solvents, including but not limited to those exemplified in the same book, such as n-hexane, 2-methylpentane, n-octane, Aliphatic or alicyclic hydrocarbons such as isooctane, cyclohexane, bicyclohexyl, p-menthane, aromatic hydrocarbons such as benzene, toluene, xylene, cumene, p-cymene, naphthalene, chloroform, carbon tetrachloride, 1. Aliphatic or aromatic halogen compounds such as 2-cycloethane, chlorobenzene, bromobenzene, chlorotoluene, and dichlorobenzene, ethers such as dipropyl ether, diphenyl ether, tetrahydrofuran, ethylene glycol diethyl ether, and phenetol, ethyl methyl ketone, Ketone necks such as 2-hexanone, acetonylacetone, and acetophenone, esters such as probyl acetate, ethyl propionate, methyl benzoate, and dimethyl phthalate, carbonates such as diethyl carbonate and propylene carbonate, nitroethane and nitrobenzene, etc. Examples include aliphatic or aromatic nitro compounds The, nitriles such as acetonitrile and penzonitrile, and the like. These may be used alone or in combination of two or more. The reaction method of the present invention is not particularly limited, and may be a batch method, a semi-batch method, or a continuous flow method. For example, a method in which the indoles and percarboxylic acids as raw materials are charged into a reactor together with an aprotic solvent, a method in which they are continuously fed all at once into a reactor, or a mixture of an aprotic solvent and one of the raw materials. A method of supplying the other raw material to the aprotic solvent continuously or intermittently, a method of supplying both raw materials to the aprotic solvent simultaneously or alternately, continuously or intermittently, etc. can be used. The reaction temperature is important in the method of the invention;
Heat to above ゛C to react. If the temperature is lower than this, not only will the reaction be slow, but the production of indigo will be extremely suppressed. Preferably, the temperature is always maintained at 60°C or higher from the start of the reaction to the end of the reaction, and more preferably in the range of 60 to 150°C. Reaction time is usually 50
within hours, preferably in the range of 0.1 to 24 hours. The reaction can be carried out under reduced pressure, normal pressure or increased pressure.

Further, in the method of the present invention, the reaction may be carried out under an inert gas atmosphere, but may also be carried out in the presence of molecular oxygen such as air.

In the method of the present invention, additives, catalysts, and the like may be used to further improve the yield, selectivity, or production rate of indigo compounds. In the method of the present invention, indigo compounds can be obtained by treating the reaction product after the completion of the reaction according to a conventional method. Usually, most of the indigo compounds produced after the reaction is precipitated and can be easily removed as a solid by ordinary solid-liquid separation operations such as filtration, centrifugation, or decantation. If the amount of precipitated indigo is insufficient, the reaction solution can be concentrated and then taken out in order to precipitate more. (Example) Next, the present invention will be explained in more detail with reference to Examples. Example 1 Equipped with a stirrer, thermometer, dropping funnel and cooling tube,
In a 100 ml four-tube flask, add 1.0 g (8.5 mmol) of indole and 1 ml of toluene.
I prepared 7ml (15g). This liquid was heated to 80°C in an oil bath, and 2.0% metachloroperbenzoic acid, which is percarboxylic acid, was added from the dropping funnel while stirring.
A solution prepared by dissolving 95 grams (17.1 mmol) in 58 milliliters (50 grams) of toluene was added dropwise over 1.5 hours, and the mixture was allowed to react for 3.5 hours. As the reaction progressed, a blue solid gradually precipitated. After the reaction was completed, the reaction solution was filtered, the solid was thoroughly washed with methanol (indigo is almost insoluble in methanol), and then dried under reduced pressure at 50'C to obtain 604 mg of a blue solid. This solid was indigo according to the results of elemental analysis and IR analysis. The molar yield of isolated indigo relative to the charged indole (hereinafter simply referred to as indigo isolated yield) was 54.0%. Comparative Example 1 The reaction was carried out in the same manner as in Example 1 except that the reaction temperature in Example 1 was changed to 5°C by water cooling. As the toluene solution of metachloroperbenzoic acid was added dropwise, a white solid precipitated out, and by the end of the addition it had become a Qi liquid. This solution was allowed to react as it was for 3.5 hours, but no indigo was formed, so the reaction was allowed to proceed for an additional 20 hours. After the reaction was completed, it was filtered and the solid was thoroughly washed with methanol, but all the white solid was dissolved and no indigo was obtained. Example 2 Using 1.77 g (10.3 mmol) of methacroperbenzoic acid in Example 1 and 40 ml (35 g) of toluene in which it was dissolved, the dropping time and subsequent reaction time were set to 1.77 g (10.3 mmol), respectively. 0 hour question and 4
．． When the reaction and post-treatment were carried out in the same manner as in Example 1 except that the time was 0 hours, 404 mg of indigo was obtained. Analysis of the reaction solution by gas chromatography revealed that 4 unreacted indoles were present in the reaction solution.
62 milligrams (3.9 mmol) remained. Indole conversion rate is 53.8%, indigo isolation yield is 36.1
%, and the molar yield of indigo to converted indole (indigo selectivity) was 67.1%. Example 3 The four solo flasks in Example 1 were charged with 1.0 grams (8.5 mmol) of indole and 35 milliliters (30 grams) of toluene. This liquid was heated to 80°C in an oil bath, and poured from the dropping funnel while stirring.
Acetic acid solution of 401% peracetic acid (simply referred to as peracetic acid solution) 1.95 grams (lO.3 in terms of peracetic acid)
mmol) was added dropwise over 15 minutes, and the mixture was allowed to react for 5 hours. Post-treatment was carried out in the same manner as in Example 1.
363 mg of indigo was obtained. As a result of analysis conducted in the same manner as in Example 2, the indole conversion rate was 79.9%,
The indigo isolation yield was 32.4%, and the indigo selectivity was 40.6%. Comparative Example 2 The reaction, post-treatment, and analysis were carried out in the same manner as in Example 3, except that the reaction temperature in Example 3 was changed to 5°C by water cooling. The indole conversion rate was 58.3%, and the indigo isolated yield was rate is 0.1% and indigo selectivity is 0.2
%Met. Comparative Example 3 The reaction, post-treatment and analysis were carried out in the same manner as in Example 3, except that 35 ml of acetic acid was used instead of toluene in Example 3, and the indole conversion rate was 10.
0.0%, the indigo isolation yield was 3.0%, and the indigo selectivity was 3.0%. Example 4 The reaction and post-treatment were carried out in the same manner as in Example 3, except that 35 ml of orthodic benzene was used instead of toluene in Example 3, and the reaction temperature was changed to 65°C. As a result, the indigo isolated yield was was 27.9%. Example 5 Example 3 except that the amount of peracetic acid solution used in Example 3 was changed to 8.12 grams (42.7 mmol in terms of peracetic acid) and 35 ml of diphenyl ether was used instead of toluene. When the reaction and post-treatment were carried out in the same manner as above, the indigo isolation yield was 23.4%.

Example 6 Instead of toluene used in Example 3, 1.2-
The reaction and post-treatment were carried out in the same manner as in Example 3, except that 50 milliliter of dichloroethane was used, and the indigo isolation yield was 30.7%. (Effects of the Invention) According to the method of the present invention, indoles having no substituents at the 2- and 3-positions and percarboxylic acids are reacted by heating in the presence of an aprotic solvent. Indigo compounds can be produced in a single step and in a much higher yield than the prior art method described above.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. Indoles and percarboxylic acids that do not have substituents at the 2- and 3-positions are heated at 60°C in the presence of an aprotic solvent.
1. A method for producing indigo compounds, which comprises heating to a higher temperature to cause a reaction.