JPH02129267A - Production of indigo - Google Patents

Abstract

PURPOSE:To produce an indigo in a very high yield in one stage by a simple process, by reacting an indole having no substituents in the positions 2 and 3 with a peroxycarboxylic acid in the presence of a specified solvent. CONSTITUTION:An indigo is produced by reacting an indole having no substituents in the positions 2 and 3 (e.g., indole) with a peroxycarboxylic acid (e.g., m-chloroperbenzoic acid) in the presence of an alcohol solvent (e.g., methanol). Although a conventional process for producing indigo comprises producing an N-phenylglycine salt from either aniline and chloroacetic acid, of aniline, cyanic acid and formaldehyde and converting this salt into an indoxyl compound by alkali fusion at high temperatures and oxidizing it with air, this process is complicated and requires a large quanty of energy. According to the process of this invention, it is possible to produce an indigo in a very high yield in one stage by a very simple process.

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 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-phenylglycine 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 consume a large amount of energy when recovered and reused. Since special equipment is required for this purpose, it is desired to switch to a more simple 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 with perbenzoic acid, a percarboxylic acid, using chloroform as a solvent (Justus
Liebigs Annalen der Chim
ie, Vol. 558, p. 9198, 1947), it is reported that many components were produced in addition to orthoformaminobenzaldehyde, and a very small amount of indigo was also obtained. There is an example of generating peracetic acid, which is a percarboxylic acid, in a reaction system using acetic acid and acetic acid, and reacting with indole using acetic acid as a solvent.
ll, Agr, Chen+, 5ocjapan+ 20
According to this, 2,2-diindyl-φ-indoxyl, which is a trimer with an indole skeleton, is produced as the main product, and a small amount of indigo is also produced as a by-product. It is reported that it did. However, these methods are merely examples of investigating the reactivity of indole, and the main products are orthoformaminobenzaldehyde and 2,2-diindyl-ψ-, respectively.
Indoxyl, which is the object of the present inventors, is only one of the by-products that can be obtained in very small amounts.

(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 the presence of an alcohol solvent when reacting acids significantly increases the production of indigo compounds.

That is, the present invention is a method for producing indigo compounds, which is characterized by reacting indoles having no substituents at the 2- and 3-positions with percarboxylic acids in the presence of an alcohol solvent.

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-dibromoindole, 4-hydroxyindole, 5-hydroxyindole, 4.5-
Hydroxyindoles such as dihydroxyindole, 4-chloro-5-methylindole, 5-chloro-4
- Halogenated alkylindoles such as methylindole, 4-bromo-5-, methylindole, 5-bromo-4-methylindole, 4-nitroindole, 5
- Nitroindoles such as nitroindole and 7-nitroindole, indole carboxylic acids such as indole-5-carboxylic acid, and sulfonated indoles, which do not inhibit the reaction at positions other than the 2- and 3-positions. If so, it may have a substituent.

The other raw material in the method of the present invention, percarboxylic acids, refers to organic compounds having a percarboxyl group (-COOOH), such as de Swaan (D,
Swern) 1 Organipuku Peroxide (Org
anic Peroxides) Vol, I” + Willy Interscience
science) (1970); pages 401-403 and 436-445. Among these, perfatty acids such as peracetic acid or perpropionic acid, or perbenzoic acids such as perbenzoic acid, tochloroperbenzoic acid, p-chloroperbenzoic acid, 0-methylperbenzoic acid or p-isopropylperbenzoic acid. Derivatives and the like are preferred, and these may be used alone or in combination or in combination of two or more.For example, when hydrogen peroxide is combined with carboxylic acids, these percarboxylic acids may be used in the reaction system. The amount of percarboxylic acids to be used, which may be a combination of components that can be generated, is not particularly limited, but is usually in the range of 0.01 to 100 mol per mol of the indole, Preferably it is in the range of 0.1 to 20 mol.

The alcohol solvent in the method of the present invention is, for example, an alcohol solvent as exemplified in Terumi Asahara et al.'s "Solvent Handbook" 1st edition, published by Kodansha (1976), pages 327-420, methanol,
Ethanol, 1-propanol, 1-butanol, tertiary-butanol, 1-hexanol, 2-octatool, allyl alcohol, benzyl alcohol, cyclohexanol, 1,2-ethanediol, 1,4-butanediol or glycerin, etc. Can be mentioned. These may be used alone or in combination of two or more.

The mode of the reaction of the present invention is not particularly limited, and may be batchwise,
Either a semi-batch type or a continuous flow type may be used. For example, a method in which the indoles and percarboxylic acids as raw materials are charged into a reactor together with an alcohol solvent, or they are fed in a continuous manner into a reactor all at once. method, method of continuously or intermittently supplying the other raw material to a mixture of alcohol solvent and one raw material, method of supplying both raw materials to alcohol solvent simultaneously or alternately, continuously or intermittently, etc. can do.

The temperature during the reaction is usually in the range of -10 to 170°C. If the temperature is lower than this lower limit, the reaction will be slow;
Moreover, if it is higher than the upper limit, percarboxylic acids will violently decompose and be dangerous. The zero reaction time is preferably in the range of 10 to 150°C, more preferably in the range of 60 to 150°C, and is usually within 50 hours, preferably in the range of 0.1 to 24 hours. It 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 can also 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.Normally, most of the indigo compounds produced after the completion of the reaction are precipitated, and are separated by filtration, centrifugation, etc. Alternatively, it can be easily taken out as a solid by ordinary solid-liquid separation operations such as decanting. When the amount of precipitated indigo compounds 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 I Equipped with stirrer, thermometer, addition funnel and cooling tube,
1.0 g (8.5 mmol) of indole and 17 ml (14 g) of methanol were placed in a 4-bottle flask with an internal volume of 100 ml. This liquid was heated in an oil bath and heated under reflux of methanol at 66°C. A solution prepared by dissolving 2.95 grams (17.1 mmol) of metachloroperbenzoic acid, a percarboxylic acid, in 58 milliliters (46 grams) of methanol was added dropwise over 1.5 hours from the dropping funnel while stirring. The reaction was continued for 3.5 hours. As the reaction progressed, a blue solid was gradually precipitated. After the reaction was completed, the reaction solution was filtered, and the solid was thoroughly washed with methanol (indigo is almost insoluble in methanol. After drying under reduced pressure at 50°C, 188 mg of a blue solid was obtained. This solid was indigo according to the results of elemental and IR analysis. Molar yield of isolated indigo relative to charged indole (hereinafter simply referred to as indigo isolated yield)
was 16.8%.

Comparative Example 1 Instead of the methanol used in Example 1, 17 milliliters (18 grams) and 58 milliliters (61 grams) of acetic acid were used to dissolve indole and metachloroperbenzoic acid, respectively, and the reaction temperature was set to 66°C. When the reaction and post-treatment were carried out in the same manner as in Example 1, except for the same conditions, 35 milligrams of indigo was obtained. The isolated indigo yield was 3.1%.

Example 2 Instead of the methanol used in Example 1, 17 ml and 5 ml of tertiary-butanol were added for dissolving indole and for dissolving metachloroperbenzoic acid, respectively.
Using 8ml, the amount of metachloroperbenzoic acid was 1.
77 grams (10.3 mmol) and the reaction temperature was 80
The reaction and post-treatment were carried out in the same manner as in Example 1 except that the temperature was changed to .degree. C., and 296 milligrams of indigo was obtained. The isolated indigo yield was 26.4%.

Example 3 Indole 1.0 was added to the 470 flask in Example 1.
(8.5 mmol) and 35 ml of methanol were heated in an oil bath.
From the dropping funnel while stirring under reflux of methanol, add 40
After 1.95 g of a wt% peracetic acid solution (10.3 mmol in terms of peracetic acid) was added dropwise over 15 minutes, the reaction was continued for 5 hours.

When post-processing was carried out in the same manner as in Example 1, indigo was reduced to 1
16 milligrams were obtained. Indigo isolation yield is 10.4
%Met.

Example 4 The reaction and post-treatment were carried out in the same manner as in Example 3, except that 35 ml of ethanol was used instead of the methanol charged in Example 3 and the reaction temperature was 80°C. As a result, the indigo isolation yield was was 18.3%.

Comparative Example 2 The reaction and post-treatment were carried out in the same manner as in Example 3 except that 35 ml of acetic acid was used instead of the methanol charged in Example 3 and the reaction temperature was 80°C. As a result, the indigo isolated yield is 3.0%.

(Effects of the Invention) According to the present invention, an extremely convenient method of reacting an indole having no substituents at the 2-position and the 3-position with a percarboxylic acid in the presence of an alcohol solvent is used. It is possible to produce indigo compounds in a much higher yield than the above-mentioned methods.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A method for producing indigo compounds, which comprises reacting indoles having no substituents at the 2- and 3-positions with percarboxylic acids in the presence of an alcohol solvent.