JPS603296B2 - Manufacturing method of indoles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing indoles, and more particularly to a method for producing indoles by reacting ethanolanilines in a gas phase.

Conventionally, there have been various proposals regarding methods for producing indole.

For example, there is a method in which ortho-toluidine is reacted with formic acid to produce ortho-methyl-N-formyl-aniline, which is then melted with potassium hydroxide. In this synthesis method, it is usually not possible to selectively produce only the ortho form of ortho toluidine used as a starting material, and the para form is produced in an amount equal to or more than the ortho form. Therefore, the processing of creatively co-produced isomers is
This poses a major problem during industrial production. Furthermore, the handling of solids, such as alkali melting, is complicated, and it is difficult to say that it is suitable for industrial production. An object of the present invention is to provide a method for producing indoles that eliminates the drawbacks of the secondary method as described above.

The present inventors have focused on ethanolanilines as a starting material that does not have the problem of ortho-para isomers, and have conducted various studies on methods for converting ethanolanilines into indoles without requiring complicated treatments such as alkali melting. As a result, the inventors discovered that indoles can be produced from ethanolanilines in a single reaction operation by reacting ethanolanilines in the gas phase in the presence of a silver-containing catalyst, leading to the completion of the present invention.

That is, in the method of the present invention, ethanolanilines represented by the general formula (R represents a hydrogen atom or a lower alkyl group) are reacted in a gas phase in the presence of a catalyst containing silver, and a direct one-stage reaction is carried out. Indoles represented by the general formula (R has the same meaning as above) are produced.

According to the method of the present invention, indoles can be industrially advantageously produced without the problem of isomer co-production and without the need for complicated operations such as handling of molten salts and solids. The stoichiometric formula of the method of the present invention is shown in formula [1'], and most of the side reaction products that occur together are R・C6day4NH2
Therefore, it can be recycled and used as a starting material.

- The starting material ethanolaniline used in the method of the present invention can be obtained by the reaction of the '2} formula.

Therefore, ethanolanilines are compounds that can be obtained industrially in large quantities at low cost. In addition, as mentioned above, the side reaction product R・C6day4NH2 is reacted with ethylene oxide again as shown in equation '2} to convert it into ethanolanilines and reuse it as a raw material for the synthesis of indoles. . The catalyst used in the method of the present invention contains silver, and is, for example, a silver-alkali metal-fused alumina catalyst used in the synthesis of ethylene oxide, or a catalyst used in the synthesis of formalin. , metallic silver catalyst, etc. are used. Alternatively, a catalyst prepared by supporting an aqueous solution of a silver salt on a carrier and pyrolyzing it by calcination may be used. As the catalyst carrier for supporting silver, Q-alumina represented by fused alumina, silica gel, silica magnesia, pumice, activated carbon, magnesia, silicon carbide, or the like is used. Activated alumina and y-alumina are not preferred because they promote side reactions. The amount of silver supported on the carrier is 2
A range of 2 to 2 skin t%, especially 5 to 1 skin t% is suitable. The catalyst is usually prepared by drying a carrier impregnated with silver salt at room temperature to 120° C. and then heating it at 300° to 60,000° C. in an air atmosphere for several hours.

The process of the present invention is usually carried out in a gas phase, but the catalyst bed type is often a fixed bed or a fluidized bed.

The temperature of the catalyst bed when carrying out the reaction is 200-450°C
In particular, a range of 250 to 35,000 is suitable. Although normal pressure is often used as the reaction pressure, the reaction can also be carried out under reduced pressure or increased pressure. The raw material ethanolaniline is heated and vaporized in a vaporizer, and the flow rate is made to flow through a heated catalyst bed, and the contact time is in the range of 0.1 to 30 seconds. The raw material ethanolaniline may be reacted alone, but the reaction may also be carried out by diluting the reactant with benzene, nitrogen, methane, hydrogen, or the like. The reactants passed through the catalyst bed are
It is collected in a cooled trap, and the target product is separated by a conventional method, for example, distillation, and the unreacted raw materials and the side reaction product R.C6day4NH2 are recycled and reused.

Indoles obtained by the method of the present invention can be used for fragrances, dyes,
It is a useful compound as a raw material for alkaloids, tryptophan, etc. The present invention will be explained below with reference to Examples.

Example 1 Silica gel (surface area 250〆/unit, average pongee pore diameter 100A
) was soaked with silver nitrate, then treated with an aqueous potassium carbonate solution, dried at 10,000 ℃, and calcined at 500° C. for 3 hours in an air atmosphere to prepare a catalyst.

The approximate amount of silver is 8wt%. The above catalyst (particle weight 1.5~
2.5 m/skin) in a glass reaction tube with an inner diameter of 15/desk.
0 and heated from the outside to 320:00 in an electric furnace.

Meta-methyl-ethanolaniline at a liquid hourly space velocity of 0.
At a rate of -1, it was vaporized in a vaporizer and hydrogen gas was introduced into the catalyst bed as a carrier (100 cc/min).

The reaction liquid flowing out of the reaction tube was collected in an ice-cooled trap and quantified by gas chromatography. As a result, the reaction liquid contained 3 t% of 4-methyl-indole and 42 wt% of metatoluidine.
, metamethyl-ethanolaniline 1 t% per skin.

Example 2 Inner lo
w/The enemy's glass reaction tube is filled, and the catalyst bed is exposed from the outside.
0000.

Ethanol aniline at a liquid hourly space velocity of 0. supplied in set r1;
The reaction was carried out with a carrier of hydrogen gas (50 min). When the reaction tube effluent was collected and analyzed in the same manner as in Example 1, it was found that indole was 4% by weight, aniline was 45% by weight, and ethanol-aniline was 12% by weight. Example 3 Fused alumina (Noreon S.
A-101) was crushed to a particle size of 0.8 to 1.2 and was used as a carrier.

Silver acetate and barium acetate were dissolved in ethanolamine, immersed in the above carrier, and heated at 100 oo for 1 hour under air circulation for 1 hour.
After drying at 50 qo for 1 hour, the catalyst was calcined again at 400 qo for 3 hours to prepare a catalyst. As a result of analyzing this catalyst, the losses of silver and barium were 11 wt% and 0.37 wt%, respectively. This catalyst has an inner diameter of 15 / skin? 12 in a glass reactor
It was filled with water and heated to 340°C from the outside in an electric furnace.
Ethanol aniline was fed to the catalyst bed at a liquid hourly space velocity of 0.3 r-1 and hydrogen (50'/min) was reacted as a carrier gas. When the reaction tube effluent was cooled and collected and analyzed, it was found that indole was 39wt% and aniline was 43wt%.
%, and ethanol aniline was 15 wt%.

Claims (1)

[Scope of Claims] 1 Ethanolanilines represented by the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (R represents a hydrogen atom or a lower alkyl group) are reacted in a gas phase, and the general formula ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼ A method for producing indoles, which is characterized by reacting in the presence of a silver-containing catalyst when producing indoles represented by (R indicates the same meaning as above) .