JPS6379872A - Production of indoles - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as a perfume, etc., in good yield, by catalytically reacting anilines with 1,2-glycols while heating in the presence of a catalyst containing Re. CONSTITUTION:For example, anilines (e.g. aniline, o-, m- or p-toluidine, etc.) expressed by the formula (R is H, halogen, OH, alkyl or alkoxy) is catalytically reacted with 1,2-glycols to provide indoles. In the above-mentioned production, a catalyst containing Re is used. Effective Re-containing catalyst is halide, nitrate, sulfate, carbonate, etc., of Re. The reaction is carried out while heating in the presence of such catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing indoles. More specifically, the present invention relates to a method for producing indoles by catalytically reacting aniline and 1,2-glycols.

Indoles are known as raw materials for the chemical industry, and indoles in particular have become important substances in recent years as raw materials for fragrances and amino acid synthesis.

(Conventional techniques and problems) There have been many attempts to synthesize indoles in the past, but all of them have problems such as a large number of by-products, expensive raw materials, and complicated processes. was.

Recently, cheap raw materials such as anilines and 1.2-
Catalyst systems that are effective in reactions that synthesize indoles using glycols and in short steps have been discovered. For example, Cu-Cr, Cu-Co+ Pd/Si0g, Pt.
/Si0g, etc., but all catalyst systems suffer from a severe reduction in activity due to reaction and cannot be used as practical catalysts.

(Means for solving the problem) The present inventors conducted various studies on this reaction and found that indoles can be obtained in good yield by using a Re-containing catalyst, which has not been used in this reaction. , the method of the present invention has been achieved.

The method for producing indoles of the present invention comprises: aniline;
．． The method is characterized in that 2-glycols are used as raw materials and heated in the presence of a catalyst containing Re in producing indoles through a catalytic reaction.

The anilines used in the method of the present invention are compounds represented by the following general formula (wherein R represents a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group, or an alkoxy group), such as aniline, o-s - or p-toluidine, O-1 - or p-haloaniline, o-2 - or p-hydroxyaniline, O-1 - or p-
Examples include anisidine.

Examples of 1,2-glycols include ethylene glycol, propylene glycol, 1,2-butanediol, 1,2,4-butanetriol, glycerol, 2.
These include 3-butanediol and diethylene glycol.

Some examples of indoles produced by the method of the invention are: indole by reaction of aniline with ethylene glycol, methylindole by reaction of toluidine with ethylene glycol, methoxyindole by reaction of anisidine with ethylene glycol; Examples include skatole produced by the reaction of aniline and propylene glycol, and tryptopol produced by the reaction of aniline and 1,2,4-butanetriol.

The catalyst used in the method of the invention is a Re-containing catalyst. That is, metal Re, Re oxide or R
It is a catalyst containing e compound, and these can also contain other compounds together for the purpose of improving the performance as a catalyst.

Examples of the Re compound used in the method of the present invention include Re halides, nitrates, sulfates, carbonates, phosphates, organic acid salts, oxides, sulfides, selenides, and hydroxides. .

Other compounds used in combination with Re in Method Q of the present invention include Lf, Na, K, Rh, Cs, Mg,
Ca, Sr.

Ha, 50% Y% Lanthanide element, Ti, Z
rs Hfs V, Nb, τaSCrSMo, W, M
n, Fe, Go, Ni, Cu, Ag, Au%
Zn%CcL Hg, B, ^! , Ga, In, T
l5Si, Ge, Sn, Pb, As, Sb, B
Examples include halides, nitrates, sulfates, carbonates, phosphates, organic acid salts, oxides, sulfides, selenides, hydroxides, and metals of i and Te.

When the Re-containing catalyst is used in the form of a heterogeneous catalyst in the method of the present invention, metal Re, Re oxide or Re compound may be used as the catalyst as it is, but it is usually used in the form of a supported catalyst. Ru. Metal Re, Re oxide,
As the carrier for supporting the Re compound or other compounds to be used in combination with Re, any commonly used carrier can be used. Such materials include diatomaceous earth, pumice, silica-alumina, silica gel, alumina, silica-magnesia, titania-zirconia, silica-zinc oxide, acid clay, activated clay, asbestos, and activated carbon. A commonly used impregnation method is used as a supporting method. Metal Re, Re oxide or Re compound and Re
Other compounds to be used together can be impregnated and supported at the same time, but either one may be supported first.

Furthermore, in the method of the present invention, Re or a Re compound can also be used as a liquid phase homogeneous catalyst, in which case,
A promoter is used if necessary. The term "co-catalyst" as used herein means an additive necessary to help dissolve Re or a Re compound in a reaction solution during the reaction, or to enable the dissolved Re or Re compound to become an active catalyst species.

Such promoters include phosphorus, arsenic, antimony,
At least one basic compound containing at least one member of Group Va of the Periodic Table of Elements such as bismuth and/or at least one halide is used.

In the field of homogeneous catalytic reactions, basic compounds containing many Group Va elements of the Periodic Table of Elements as promoters are known. Any of them can be used in the method of the present invention, but among them, phosphines such as triphenylphosphine and tributylphosphine are particularly preferred. In addition, there are many known halides that can be used as co-catalysts, and any of them can be used, but among them, the following are particularly preferred:
Examples include hydrohalic acids such as hydrochloric acid, hydrobromic acid, and hydriodic acid, and alkali metal halides such as lithium chloride and sodium iodide.

When the method of the present invention uses a heterogeneous catalyst, a gas phase,
It can be carried out in either liquid phase or gas-liquid mixing.

When carried out in gas phase or gas-liquid mixed phase, fixed bed, fluidized bed,
Alternatively, it can be carried out in either a moving bed reactor, and is carried out by heating a gas mixture of anilines and 1,2-glycols in the presence of a Re-containing catalyst.

At this time, various inert gaseous substances can be allowed to coexist with the raw material vapor. Examples of such inert gaseous substances include nitrogen gas, carbon dioxide gas, -carbon oxide, methane, ethane, water vapor, and hydrogen.

Anilines and 1,2-glycols are fed into the reactor at a ratio of 0.05 to 5 moles of 1,2-glycols per mole of aniline, and the liquid hourly space velocity relative to the catalyst is 0.
．． 01-5 t7 is made into a vapor state in advance or sent directly to the reactor in a liquid state so as to be a catalyst/hour.

The reaction temperature is in the range of 200 to 500°C, preferably 2
It is in the range of 50-400″C. Below 200°C,
The reaction hardly progresses, and if the temperature exceeds 500°C, the decomposition reaction becomes intense, which is not preferable.

The reaction pressure may be increased pressure, normal pressure, or reduced pressure.

When the process of the invention is carried out in the liquid phase, it is carried out by heating a mixture of anilines and 1,2-glycols in the presence of a Re-containing catalyst.

At this time, various inert gases and/or inert solvents can be allowed to coexist. As such an inert gas,
Examples include nitrogen gas, carbon dioxide gas, -carbon oxide, and hydrogen. In addition, examples of inert solvents include benzene,
Examples include aromatic hydrocarbons such as toluene and xylene, and aliphatic hydrocarbons such as heptane, hexane, octane, and cyclohexane.

If the reaction is carried out in the presence of a heterogeneous catalyst, it can be carried out in a fixed bed, fluidized bed or moving bed reactor.

The liquid phase reaction is carried out in a batch-type or continuous-type reactor, but there are no particular restrictions.

Anilines used as raw materials in liquid phase reactions and 1.2
- The amount of glycols is 1.0% per mole of aniline Ii.
It is a mixture of 2-glycols in a range of 0.05 to 5 moles, preferably in a range of 0.1 to 1 mole.

The amount of the catalyst used in the liquid phase reaction is not particularly limited, but usually Re is in the range of 0.0001 to 0.5 g atom, preferably o ,ooos to 0.05 gram atom.

When a homogeneous catalyst is used, the reaction temperature of the liquid phase reaction is usually 250°C or less, preferably in the range of 50 to 170°C. If it is less than 50''C, the reaction rate is too low to be practical, and if it exceeds 170°C, side reactions will occur, which is not preferable.

In addition, when a heterogeneous catalyst is used, usually 200 to 50
It is in the range of 0°C, preferably in the range of 250 to 400°C. At temperatures below 200°C, the reaction hardly progresses;
If the temperature exceeds ℃, the decomposition reaction becomes violent, which is not preferable.

The reaction pressure for the liquid phase reaction may be any pressure that allows the reactants to remain in a liquid state under the reaction conditions, and the reaction is usually carried out at elevated pressure or normal pressure.

Indoles can be easily separated and obtained from the reaction products of these various methods by commonly used methods such as distillation, extraction, crystallization, and adsorption.

(Example) Hereinafter, the method of the present invention will be explained in further detail using Examples.

Example 1 A glass reaction tube with an inner diameter of 12 mm was filled with 2 cc of 5wtxRe/activated carbon catalyst (manufactured by Nippon Engelhard), and 10 cc of alumina balls were filled thereon to form a preheating section.

It was heated while flowing hydrogen gas at a rate of 1.31xl/hour, and the temperature of the preheating part and the catalyst layer was set to 305°C. Water was fed into the preheating section at a rate of 0.5 gr/hr. After 30 minutes, a mixture of aniline and ethylene glycol (molar ratio 1
0: 1) to 1. The reaction was carried out by supplying the mixture to the preheating section at a rate of Ogr/hour for 28 hours, and the reaction liquid during the reaction time of 2 to 5 hours was collected and used as reaction liquid A, and the reaction time was 25 to 5 hours. The reaction liquids A and B were collected for 28 hours and used as reaction liquid B. As a result of gas chromatography analysis of reaction liquids A and B, it was found that the yields of indole were 57χ and 56χ, respectively.

Example 2 A reaction was carried out in the same manner as in Example 1 except that the catalyst was changed to 3.5wtX Re/silica gel. The yield of indole was 66x and 64x.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1, except that the catalyst was changed to Cu-Co-diatom ± (manufactured by JGC Chemical Co., Ltd.). The yield of indole was 13χ and 6χ.

Example 3 93.2 gt of aniline and 6.0 gt of ethylene glycol were placed in an SUS autoclave with an internal volume of 300 cc and equipped with a stirrer. Ogr, , 0.59gr of rhenium trichloride,
and 1.2 gr of tri-n-butylphosphine were charged, and the space was replaced with nitrogen gas. The temperature was raised to 180°C while stirring, and the reaction was then continued at 180°C for 1 hour.

After cooling, the contents were taken out and analyzed by gas chromatography. Indole was produced at a yield of 4.2χ.

(Effect of the invention) In Comparative Example 1 above, the yield of indole significantly decreases with the reaction time, but in the method of the present invention, as is clear from Examples 1 and 2, the decrease in yield is slight. Therefore, the effect of the invention is obvious.

Claims (1)

[Claims] 1) A method for producing indoles, which comprises heating in the presence of a catalyst containing Re when producing indoles through a contact reaction between anilines and 1,2-glycols.