Process for producing N,N-disubstituted aminophenol

Details Process for producing N,N-disubstituted aminophenol Process for producing N,N-disubstituted aminophenol

1994-11-15

1995-08-15

Robinson, Allen J.

Organic compounds -- part of the class 532-570 series

Organic compounds

Amino nitrogen containing

564395, 564443, 564468, C07C20902

Patent

active

054421217

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/JP94/00424, filed Mar. 17, 1994.


DETAILED DESCRIPTION OF THE INVENTION

1. Field of the Invention
This invention relates to a process for producing N,N-disubstituted aminophenol and, more specifically, to a process for producing high-purity N,N-disubstituted aminophenol at a high yield by aminating and alkylating a dihydric phenol. N,N-disubstituted aminophenol is a valuable compound as an intermediate for producing dyes for heat-sensitive recording papers and fluorescent dyes.
2. Prior Art
Known prior art processes for producing N,N-disubstituted aminophenol include:
(1) a process which comprises reacting a dihydric phenol with a primary amine in the presence of an acid catalyst (first-stage reaction) and alkylating the resulting N-substituted aminophenol with dialkylsulfuric acid or a halogenated alkyl such as alkyl chloride, alkyl bromide or alkyl iodide (second-stage reaction); and
(2) a process which comprises aminating a dihydric phenol with ammonia to produce an aminophenol, separating and purifying the aminophenol, and adding aldehydes stepwise to the aminophenol in the copresence of a reduction catalyst, an organic carboxylic acid, an organic solvent and hydrogen for reduction alkylation.
However, in the process (1), an inorganic acid by-produced in the second-stage alkylation reaction must be neutralized and, hence, a large volume of waste water is produced. When bromine or iodine is used as a halogen, recovery of these halogens is necessary because they are expensive, and the industrial production process becomes complicated. Further, when dialkylsulfuric acid and a halogenated alkyl are used, alkylation of an OH group takes place and a quaternary salt is by-produced by aminophenol and alkylsulfuric acid, with a consequence that the yield of N,N-disubstituted aminophenol decreases and the purification step becomes complicated.
In the process (2), due to a low yield in the step of aminating the dihydric phenol with ammonia, a large amount of the dihydric phenol as a source material remains in the reaction mixture and as a result a complicated step for separating and purifying the resulting aminophenol is required.
A process for producing N-substituted aminophenol by reacting a dihydric phenol with ammonia, a primary amine or a secondary amine in the absence of a catalyst is disclosed in Japanese Patent Publication No. 5416/1987 and Japanese Patent Laid-open Publication No. 99042/1991.
Further, a process for obtaining N,N-disubstituted aminophenol by a reduction alkylation reaction between N-substituted aminophenol and aldehyde in an organic solvent in the presence of hydrogen and a reduction catalyst is disclosed in Japanese Patent Laid-Open Publication Nos.258346/1987 and 292747/1987. According to this process, there can be separated N,N-disubstituted aminophenol purified by distillation after the reduction catalyst has been separated from the reaction mixture after the reaction. With this process, N,N-disubstituted aminophenol can be obtained at high conversion and at high selectivity as far as high-purity N-substituted aminophenol is used as a source material.
However, when a dihydric phenol is used as a starting material and amination and reduction alkylation reactions are carried out to obtain N,N-disubstituted aminophenol in accordance with the two reactions disclosed in the aforementioned Japanese Patent Publications, the objective N,N-disubstituted aminophenol cannot be obtained at a high yield when the catalyst is used several times because the activity of the reduction catalyst lowers in the reduction alkylation step and the catalyst has a short life.


Problem to Be Solved by the Invention

It is therefore a first object of the invention to provide an industrially advantageous process for obtaining N,N-disubstituted aminophenol at high conversion and at high selectivity in a series of steps for obtaining N,N-disubstituted aminophenol from a dihydric phenol as a starting material.
It is a second object of the invention to provide a process in which the

REFERENCES:
patent: 4588841 (1986-05-01), Morellet et al.
patent: 4757144 (1988-07-01), Okabe et al.
patent: 4960432 (1990-10-01), Junino et al.

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