JPH08176077A - Production of triphenylamine - Google Patents

Abstract

PURPOSE: To obtain in a single step and in high selectivity the subject compound useful as an intermediate for synthesizing dyes, agrochemicals or rubbers, by reaction between a phenol and an aniline in the presence of a hydrogen transfer catalyst. CONSTITUTION: In the presence of (A) a hydrogen transfer catalyst (e.g. Raney nickel, palladium catalyst) and (B) a catalytic amount of the cyclohexanone corresponding to the phenol, as a reactant, (C) a phenol as hydrogen acceptor is reacted with (D) an aniline, while forming the corresponding cyclohexanone in the system, to obtain the objective compound. A preferable version of the process is as follows: in the presence of the hydrogen transfer catalyst, part of the phenol is converted into the corresponding cyclohexanone under pressure with hydrogen, and the rest as hydrogen acceptor is reacted with the aniline under being charged dropwise while forming the corresponding cyclohexanone in the system.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel method for producing triphenylamines. The triphenylamines obtained by the method of the present invention are compounds useful as intermediates for general chemical industry, particularly as intermediates for producing dyes, agricultural chemicals, rubber drugs and the like.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
As a method for producing triphenylamines, a method of heating a potassium salt of anilines or diphenylamines and bromobenzene by heating, and a method of reacting diphenylamine and aniline in the presence of hydrochloric acid (US Pat.
No. 51123), a method of reacting aniline with phenol in the presence of a copper chromium oxide catalyst (Japanese Patent Publication No. 52-489).
69), a method of reacting diphenylamine with an equimolar amount of cyclohexanone in the presence of a palladium catalyst (US Pat. No. 3,219,704), and the like.

However, these methods have drawbacks such as complicated reaction steps and the need for a large amount of acid and base. In addition, JP-B-52-48969 and US Pat.
The method of No. 219704 was not industrially satisfactory because the yield was extremely low.

It is also known that phenols are used as hydrogen acceptors in the presence of a hydrogen transfer catalyst to react with diphenylamines while producing cyclohexanones in the system to produce triphenylamine.
For example, using a palladium catalyst, diphenylamine and cyclohexanone are reacted in an excess amount of phenol to give triphenylamine in a yield of 68.5% (selectivity 85.1).
%) (JP-A-61-183250). However, the method disclosed in JP-A-61-183250 requires a process for producing the starting diphenylamines, and requires two steps to obtain triphenylamines.

An object of the present invention is to provide an extremely efficient method for obtaining triphenylamines by reacting phenols with anilines in one step.

[0006]

Means for Solving the Problems As a result of earnest studies on a more efficient and advantageous industrial production method of triphenylamines, the present inventors have found that phenols and anilines are reacted in the presence of a hydrogen transfer catalyst. As a result, they have found that they can be obtained in a single step and with high selectivity, and have reached the present invention.

That is, in the method of the present invention, phenols are used as hydrogen acceptors in the presence of a hydrogen transfer catalyst and cyclohexanones corresponding to the phenols used in the reaction in a catalytic amount, and the corresponding cyclohexanones are used in the system. While producing, it is reacted with anilines, or without allowing cyclohexanones to coexist in the reaction system from the beginning, under hydrogen pressure, a part of the phenols is converted to the corresponding cyclohexanones, and then the remaining A method for producing triphenylamines, which comprises using phenols as hydrogen acceptors and reacting with anilines while generating corresponding cyclohexanones in the system.

The present invention will be described in detail below. In the method of the present invention, the hydrogen produced by dehydrogenation of the intermediate cyclohexylideneanilines produced by the reaction of anilines and cyclohexanones is used in the same reaction system for the reduction of phenols, that is, the production of cyclohexanones. Are all used in. Further, diphenylamines produced by dehydrogenation of cyclohexylideneanilines in the same reaction system and cyclohexanones undergo a condensation reaction to give N- (1-cyclohexenyl) -diphenylamines, which are dehydrogenated to give triphenyl Amines are obtained. The hydrogen generated at this time is also an extremely efficient method in which all the hydrogen is utilized for the reduction of phenols in the same reaction system.

In the process of the present invention, when the target triphenylamines are taken out, the phenols containing cyclohexanones to be separated can be reused as a mixture in the reaction system. Further, in the production of nuclear-substituted triphenylamines, even when it is difficult to obtain a corresponding appropriate cyclohexanone, if there is a phenol, an excess amount of phenol is used in advance in place of cyclohexanone to obtain hydrogen. It has a number of advantages, such as wide application range, since it is sufficient to charge and react while converting a part of the phenols to cyclohexanones.

The aniline used as a raw material in the method of the present invention may be any known one, for example, aniline, 2-methylaniline, 3-methylaniline, 4-ethylaniline, and other alkyl group-substituted anilines,
An alkoxy group-substituted aniline such as 4-methoxyaniline,
Carboxy group-substituted aniline such as 4-carboxyaniline, halogen-substituted aniline such as 4-fluoroaniline,
Examples thereof include nitrile group-substituted aniline and p-phenylaniline. Also, anilines such as 2-methyl-4-chloro-aniline having different functional groups substituted in the nucleus may be used.

Any known phenols may be used as a hydrogen acceptor in the method of the present invention, but examples thereof include phenol, methylphenol, ethylphenol, isopropylphenol, butylphenol, 2,4-dimethylphenol and 2 , Alkylphenols such as 4,6-trimethylphenol, alkoxyphenols such as 3-methoxyphenol and 4-methoxyphenol, 2-fluorophenol, 4-cyclohexylphenol, 4-phenoxyphenol, 2-methoxy-4-cyclohexylphenol, 2 -Methoxy-
4-fluorophenol etc. are mentioned.

The amount of the phenols used in the method of the present invention may be 2 equivalents or more with respect to the anilines when cyclohexanones are coexisted from the beginning, but there is no problem, but the phenols are used in excess as the self-solvent. Since the selectivity tends to be higher, it is preferable to use an excess amount of 3 to 20 mol times, preferably 4 to 10 mol times, relative to the anilines.
When the amount of phenols is small, the amount of N-cyclohexylaniline by-products often increases.

Cyclohexanones corresponding to the above-mentioned phenols are used as the cyclohexanones, and the amount used is not particularly problematic if it is about 0.03 mol times or more of the catalyst amount with respect to the anilines, but preferably 0. 05-1.
00 mol times is good.

When cyclohexanones are not used from the beginning of the reaction, hydrogen is added to phenols in an amount corresponding to the above-mentioned suitable amount of cyclohexanones.
That is, about 0.06 mol times or more, preferably 0.10 to
The reaction may be carried out by heating after being enclosed in a 2.00 molar reactor.

The catalyst used in the method of the present invention is required to be a catalyst having both functions of dehydrogenation reaction and reduction reaction, but usually a suitable hydrogenation reduction reaction catalyst is also suitable for dehydrogenation reaction. Specifically, Raney Nickel,
Reduced nickel or nickel-supported catalyst, Raney cobalt, reduced cobalt or cobalt-supported catalyst, Raney copper, reduced copper or copper-supported catalyst, noble metal catalyst of Group 8 of the periodic table or its noble metal as a carrier, carbon, alumina, barium carbonate, etc. Supported catalysts, rhenium catalysts such as rhenium-carbon, and copper-chromium oxide catalysts. Among these catalysts, palladium is preferable, and a palladium catalyst supported on a carrier such as palladium-carbon, palladium-alumina and palladium-magnesium oxide is particularly preferable. The amount used is usually 0.001 to 0.2 gram atom, preferably 0.004 to 0.1 gram atom, as metal atom, based on the amines.

In the method of the present invention, after the target product is separated from the reaction mass after completion of the reaction, it is preferable that the reaction solution is repeatedly and continuously circulated without separating the cyclohexanones, in which case phenols are used. Is advantageously used in excess as the self-solvent. It is not necessary to use any other reaction solvent, but of course there is no problem even if it is used.

The reaction temperature is usually 150 to 350 ° C., preferably 180 to 300 ° C. If the temperature is lower than this, the reaction rate is low, and a large amount of N-cyclohexylaniline and N-cyclohexyldiphenylamine tends to be by-produced.

In the method of the present invention, when the raw materials are charged into the reaction vessel, it is preferable to charge the catalyst and the phenols into the vessel in advance, stir and raise the temperature, and then carry out the reaction while dropping the anilines. It is a mode.

The reaction is advantageously carried out while removing the water formed, and for that purpose a method of separating from the reaction mixture by azeotropic distillation using a solvent such as benzene, toluene or xylene is suitable.

The generated triphenylamines can be obtained by treating the mixture after the reaction according to a conventional method such as distillation, crystallization and extraction. For example, the reaction completed liquid is filtered to separate the catalyst. This recovered catalyst can be reused. The filtrate is concentrated, an excess amount of phenols is recovered while containing cyclohexanones, and the fraction is returned to the reaction system as a mixture. The triphenylamines in the kettle are purified and separated by distillation, crystallization and the like.

[0021]

EXAMPLES The method of the present invention will be described in detail below with reference to examples. Example 1 A stainless steel autoclave having an internal volume of 500 ml was charged with 188.2 g (2.0 mol) of phenol, 3.0 g (0.03 mol) of cyclohexanone and 1.07 g of 5% Pd / C manufactured by NE Chemcat. 27.9 g (0.3 mol) of aniline was charged into the dropping apparatus, the inside of the autoclave was replaced with nitrogen, and then the temperature was raised to 250 ° C. While maintaining the temperature under stirring, aniline in the dropping device was added dropwise over 8 hours. After completion of dropping, stirring was continued for 7 hours while maintaining this temperature. Then, the inside of the reactor was cooled to room temperature, and 5% Pd / C was filtered off from the reaction mixture. When the filtrate was analyzed by gas chromatography, the conversion rate of aniline was 95.6% and the selectivity of triphenylamine was 90.4%.

Examples 2 to 5 In the same manner as in Example 1, various anilines, phenols and cyclohexanones corresponding to phenol were used for the reaction. The results are shown in Table 1.

[0023]

[Table 1]

Example 6 The same operation as in Example 1 was carried out except that cyclohexanone was not initially charged into the autoclave having an internal volume of 500 ml used in Example 1. After replacing the inside of the autoclave with nitrogen, the inside of the autoclave was pressurized to 7 kg / cm ² G with hydrogen. Subsequently, the same heat reaction and treatment as in Example 1 were carried out. as a result,
The conversion of aniline was 90.5% and the selectivity of triphenylamine was 88.2%.

[0025]

EFFECTS OF THE INVENTION According to the method of the present invention, phenols are used as hydrogen acceptors in the presence of a hydrogen transfer catalyst, and by reacting with anilines while forming cyclohexanones in the system, it is extremely efficient. Triphenylamines can be obtained in a single step and in good yield.

Claims (3)

[Claims] 1. In the presence of a hydrogen transfer catalyst and cyclohexanones corresponding to phenols used in a catalytic amount of the reaction,
A method for producing triphenylamines, which comprises using phenols as hydrogen acceptors and reacting with anilines while generating corresponding cyclohexanones in the system. 2. In the presence of a hydrogen transfer catalyst, phenols are converted into corresponding cyclohexanones under hydrogen pressure and a part thereof is converted to the corresponding cyclohexanones, and then the remaining phenols are used as hydrogen acceptors. A method for producing triphenylamines, which comprises reacting with anilines while generating cyclohexanones. 3. The method for producing triphenylamines according to claim 1, wherein the reaction is carried out while charging the anilines dropwise.