JPH0739378B2 - Process for producing N, N-dialkyl-substituted aminophenols - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing N, N-dialkyl-substituted aminophenols. N, N-dialkyl-substituted aminophenols are represented by general formula (IV) It is an industrially extremely important compound as an intermediate for heat-sensitive and pressure-sensitive dyes, xanthene dyes, fluorescent dyes, and the like.

<Prior Art> Conventionally, as a synthetic method of a compound represented by the general formula (IV),
Using nitrobenzene as a starting material, sodium metanilate is obtained, which is alkylated with an alkyl halide and then alkali-fused to obtain the desired product, and an alkali metal compound and / or an alkali as a deoxidizing agent for aminophenols. A method of alkylating an alkyl halide with an earth metal compound is known.

All of these methods generate a large amount of wastewater and a large amount of inorganic salts, have a long process, and have problems such as limited material and safety in handling, and are industrially extremely unattractive methods. Is. Further, in this method, the compound represented by the general formula (II) cannot be synthesized in high yield, and therefore, among the compounds represented by the general formula (IV), asymmetric N, N
It also has the disadvantage that it cannot be synthesized.

As a method for synthesizing the compounds represented by the general formulas (II) and (IV), an aminoaromatic compound or a nitroaromatic compound is used as an alkylating agent for aldehydes in the presence of a palladium catalyst, and N is reduced under hydrogen reduction. There is a method of mono / dialkylation, but it has the following drawbacks as an industrial production method. For example, in J. Chem. Soc., 1342 (1950),
It is reported that dimethylation of orthoaminobenzoic acid in the presence of palladium catalyst can be dimethylated in 13 hours by using a large amount of palladium and a large amount of formaldehyde in a large amount of harsh acid solvent. However, this method is impractical because it uses a large amount of palladium, uses a corrosive strong acid solvent, and requires a long time. Furthermore, when this direction is applied to aminophenols having an -OH group, a condensation reaction mainly occurs, a tar-like substance is produced in a large amount, and a target compound is produced in a small amount.

Further, in JP-A-52-71424, dimethylation is carried out by sequentially supplying formaldehyde to an alkyl aqueous solution of 3-aminobenzoic acid in the presence of a large amount of palladium-carbon. When applied to aminophenols having a -OH group, it is in the presence of an alkali,
As a result, the reactivity of aldehydes with respect to the benzene nucleus is further increased, which is not a practical method and industrially unsuitable.

<Problems to be Solved by the Invention> The present invention has the drawbacks of these conventional techniques, namely, generation of a large amount of drainage and sludge, generation of side reaction, difficulty of separation of products, reaction vessel material due to PH decrease. In addition to attempting to solve problems such as the effect of, asymmetric N, N-dialkyl substitution products, which were difficult to synthesize in the past.

<Means for Solving Problems> The present invention relates to general formula (I) R.CHO (I) (wherein R represents an alkyl group having 1 to 5 carbon atoms) per 1 mol of aminophenols. Aldehydes of 0.8 mol or more and less than 1.5 mol are continuously introduced into the reaction system in the presence of platinum and / or palladium supported on activated carbon, an organic solvent, and hydrogen, and the general formula (II) (In the formula, R has the above-mentioned meaning.) After synthesizing the N-monoalkyl-substituted aminophenol represented by the general formula (III) R ′ · CHO (III) (wherein R ′ is the number of carbon atoms). It represents an alkyl group of 1 to 5, and R and R'are different.

Aldehydes of 0.8 mol or more and less than 2.5 mol are continuously introduced into the reaction system, and the general formula (IV) (In the formula, R and R ′ have the above-mentioned meanings.) A method for producing an N, N-dialkyl-substituted aminophenol.

The present inventors have diligently studied the reductive alkylation reaction of aminophenols with aldehydes and hydrogen instead of alkyl halides. As a result, aminophenols,
First, in a system charged with an organic solvent, hydrogen, and a catalyst, the amount of the aldehyde represented by the general formula (I) is 0.8 mol or more and less than 1.5 mol per 0.1 mol / aminophenol,
N-represented by the general formula (II) when introduced at a speed of less than a minute
After synthesizing mono-substituted aminophenols,
Aldehydes represented by the general formula (III) are 0.8 mol or more,
By introducing less than 2.5 at a rate of 0.1 mol / min or less, the compound represented by the general formula (IV) can be obtained with high selectivity.

In the present invention, the amount of aldehydes to be subjected to the reaction is such that the aldehydes represented by the general formula (I) are 0.8 mol or more and less than 1.5 mol, preferably 0.9 mol or more, 1.2 mol per 1 mol of aminophenols. If the molar ratio is less than 0.8 mol and the molar ratio is less than 0.8 mol, the conversion rate of the aminophenols is low, the yield of the target product is low, and it is not a good idea. It is not preferable because by-products such as N, N-dialkyl compounds based on the represented aldehydes increase. Further, regarding the aldehydes represented by the general formula (III) to be introduced, 0.
8 mol or more and less than 2.5 mol, preferably 0.9 mol or more and less than 2 mol are used, and if the molar ratio is less than 0.8 mol, the yield of the target product decreases and it is not a good idea. The N, N-dialkyl-substituted aminophenols and aldehydes are further condensed to form a resinous product, which reduces the yield of the target product, which is not preferable.

Specific examples of the aldehydes represented by the general formulas (I) and (III) used in the present invention include acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, pentyl aldehyde and hexyl aldehyde. Be done. As aminophenols, m-aminophenol, p-aminophenol, etc. are shown.

A feature of the present invention is to continuously introduce aldehydes into a system charged with aminophenols, an organic solvent, hydrogen, and a catalyst. The introduction rate of aldehydes is an important factor of the present invention, and it is desirable that the introduction rate be equal to or lower than the hydrogen absorption rate. More specifically, it is desirable to introduce aldehydes at a rate of 0.1 mol / min or less per mol of aminophenols. When aldehydes are introduced at a rate exceeding 0.1 mol / min, the amount of resinous substances is increased and the selectivity of the target compounds of the general formulas (II) and (IV) is remarkably lowered.

The present invention is also characterized in that an organic solvent is used, and as the usable organic solvent, any organic solvent can be used as long as it is stable in the reaction system. Taking into consideration the solubility of general formulas (II) and (IV), etc., aliphatic alcohols are selected.
Further, preferably, an aliphatic alcohol having 1 to 6 carbon atoms is desired. The amount of organic solvent used varies depending on the type of organic solvent used.
A range of 1 to 20 parts by weight is desired with respect to parts by weight.
If the amount of the organic solvent used is less than 1 part by weight with respect to 1 part by weight of the aminophenol, the selectivity of the N-monoalkyl compound, which is the target product, decreases. On the other hand, if the amount exceeds 20 parts by weight, the volumetric efficiency is significantly reduced. Further, a part of the organic solvent may be mixed with aldehydes and continuously introduced into the reaction system.

Platinum and / or palladium used in the present invention are those supported on activated carbon, and the amount used is 0.000% by weight per 1 part by weight of aminophenols.
5 to 0.05 parts by weight is selected. The reaction temperature in the present invention is
0-80 ° C is selected. If the temperature is lower than 0 ° C, the reaction rate is extremely slow, while if it exceeds 80 ° C, a resinous product is formed and a nuclear hydrogenation product is generated, and the selectivity of the target N-monoalkyl compound is lowered, which is not preferable. .

Further, the hydrogen pressure in the present invention is selected to be ^{2 to} 30 kg / cm ² G. When the hydrogen pressure is less than ² Kg / cm ² G, the reaction rate is slow and resin-like formation increases, while when it exceeds 30 Kg / cm ² G, the nuclear hydrogenation product increases and the selectivity of the target compound decreases. , Not desirable.

Next, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to these.

To <Example> SUS steel 200c.c autoclave with Example -1 stirrer, meta-aminophenol 10.9gr (0.10 mol) of methanol were charged 121gr, 5% platinum on activated carbon catalyst 0.27Gr, hydrogen pressure of 10 Kg / cm ² G
Keep constant and acetaldehyde 4.85gr (0.11mol) at 40 ℃
Was continuously introduced for 2 hours. After the introduction of acetaldehyde was completed, the temperature was kept at the same temperature for 20 minutes, and then n
-Butyraldehyde 7.93 gr (0.11 mol) was continuously introduced over 4 hours to continue the reaction. After the completion of the introduction, the mixture was kept for another 20 minutes and then cooled, and the catalyst was overseparated to obtain a reaction solution. As a result of gas chromatography (GC), liquid chromatography (LC), and GPC (gel permeation chromatography) analysis, the conversion rate of meta-aminophenol was 100% and that of N-ethyl-N-butyl-metaaminophenol was 100%. The selectivity was 88.4%.

Examples-2 to 4 According to the combination of aldehydes described in Table-1, reaction and analysis were performed under the same conditions and operations as in Example-1, and Table-
The reaction results described in 1 were obtained.

Examples-5 to 7 In place of metaaminophenol, para-aminophenol was used, and according to the combination of aldehydes shown in Table-2, the reaction and analysis were carried out under the same conditions and operations as in Example-1, and Table-2. The reaction results described were obtained.

<Effects of the Invention> In the method of obtaining an asymmetric N, N-dialkyl-substituted compound by subjecting an aminophenol to an N-alkylation reaction with an aldehyde and hydrogen in the presence of a catalyst, First, the aldehydes to be pre-introduced are used at a specific molar ratio, and are continuously introduced into the reaction system at a specific rate to synthesize N-monoalkyl-substituted aminophenols, and then,
Aldehydes to be introduced later are also used in a specific molar ratio, and by continuously introducing them into the reaction system at a specific rate, the corresponding N, N-dialkyl-substituted aminophenols can be obtained with high selectivity, and the material It has the advantage of being able to produce N, N-dialkyl-substituted aminophenols, which is extremely industrially advantageous in that there is no problem of upper corrosion.

Claims (5)

[Claims] 1. An aldehyde represented by the general formula (I) R.CHO (I) (wherein R represents an alkyl group having 1 to 5 carbon atoms), relative to 1 mol of aminophenol, 0.8 mol or more. , 1.5 mol or less, is continuously introduced into the reaction system in the presence of platinum supported on activated carbon and / or a palladium catalyst, an organic solvent, and hydrogen, and the general formula (II) formula (II) (In the formula, R has the above-mentioned meaning.) After synthesizing N-monoalkyl-substituted aminophenols represented by the following formula, general formula (III) R'.CHO (III) (in the formula, R ' Represents an alkyl group having 1 to 5 carbon atoms, R
And R'are different. ) The aldehydes represented by) are continuously introduced into the reaction system in an amount of 0.8 mol or more and less than 2.5 mol. (In the formula, R and R ′ have the above-mentioned meanings.) A method for producing an N, N-dialkyl-substituted aminophenol. 2. The introduction rate of aldehydes is 0.1 mol / min or less per 1 mol of aminophenols and / or N-monoalkyl-substituted aminophenols. ) The method for producing an N, N-dialkyl-substituted aminophenol according to the above item. 3. The method for producing N, N-dialkyl-substituted aminophenols according to claim 1, wherein the organic solvent is an aliphatic alcohol. 4. The method for producing N, N-dialkyl-substituted aminophenols according to claim 1, wherein the aminophenols are m-aminophenol and p-aminophenol. 5. The N, N- according to claim 3, wherein the aliphatic alcohol has 1 to 6 carbon atoms.
Process for producing dialkyl-substituted aminophenols.