JPS61109759A - Production of 4-alkoxyaniline - Google Patents

Abstract

PURPOSE:To produce the titled compound useful as an intermediate of dyes, pharmaceuticals, etc., in high yield and purity, without using a catalytic poison, by the catalytic hydrogenation of a nitrobenzene compound in a specific mixed solvent in the presence of a noble metal catalyst. CONSTITUTION:The objective compound can be produced by the catalytic hydrogenation of the nitrobenzene compound of formula (R is H, halogen, lower alkyl or lower alkoxy, when R is other than H, it is substituted to o- or m- position of nitro group; n is 1-2) in a mixed solvent consisting of a lower aliphatic alcohol, sulfuric acid and an aliphatic carboxylic acid or its aqueous solution, in the presence of a catalyst such as platinum, palladium, etc. supported by activated carbon, at 30-60 deg.C. The amounts of the alcohol and sulfuric acid are 20-100mol and 1-10mol per 1mol of the nitrobenzene compound of formula, and the content of the lower aliphatic carboxylic acid in the mixed solvent is preferably 1.5-10wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing 4-alkoxyanilines. Specifically, in the presence of a noble metal catalyst, the following general formula (I) [in formula (I), R means a hydrogen atom, a halogen atom, a lower alkyl group, or a lower alkoxy group; In the case of a substituent, it represents the 0-position and/or the m-position with respect to the nitro group. The basket is an integer of 1 to 2.] The present invention relates to a method for producing 4-alkoxyanilines, which comprises catalytically hydrogenating nitrobenzenes in a mixed solvent consisting of alcohol, sulfuric acid, and an aliphatic carboxylic acid or an aqueous solution thereof.

Conventional technology 4 - Alkoxyanilines are important intermediate raw materials for dyes and pharmaceuticals, etc., and industrially they have traditionally been manufactured from nitrobenzenes through many processes, which is extremely unsatisfactory in terms of overall yield and economic efficiency. On the other hand, from the nitrobenzenes of the above general formula CI)
'Attempts have also been made in recent years to produce 4-alkoxyanilines in one step in a mixed solvent consisting of alcohol and sulfuric acid in the presence of a noble metal catalyst.

For example, Journal of the Chemical Society of Japan (I979 (I1)).

According to [Page 1532], dimethyl sulfoxide (hereinafter referred to as D
The highest yield was 27.8 by adding MSO (abbreviated as MSO)
According to the Journal of the Chemical Society of Japan (I980 (2), p. 245), 2.2 p-anisidine was obtained from the ninitro compound, and starting from the obtained 0-methylnitrobenzene. When used as raw material, D
The highest yield 70, fl (DM
When SO was not added, 2-methyl-4-methoxyaniline was obtained in a yield of 4s, al). Furthermore, the Journal of the Chemical Society of Japan (I982(7), 123)
According to [Page 7], from the corresponding nitro compound, 2.3-
Dimethyl-p-anisidine, 2,6-dimethyl-p-anisidine, 1-amino-4-methoxy-naphthalene, and 1-amino-2-methyl-4-methoxy-naphthalene were each prepared by adding DMSO. Maximum yield 67.4% without adding CDMSO s a, 7
%), 72.1% (also 45.2%), 68%, and 55ts"c.In addition, in the past, p-aniline was obtained from phenylhydroxylamine in a mixed solvent of methanol and sulfuric acid. It is obtained for about 40 cm (
Bar, 311500 (I89B)).

Problems to be Solved by the Invention As described above, there is a known method for producing 4-alkoxyanilines in one step by catalytic hydrogenation from the corresponding nitro compound in the presence of a noble metal catalyst by applying the Bamberger rearrangement reaction. In general, the yield power f is low, and it cannot be called an industrial production method.Therefore, as an improved method, as described above (DMSO is added), a yield that can be used practically has been obtained.

However, the DMSO used in these methods is an extremely strong catalyst poison, and it is virtually impossible to reuse the recovered precious metal catalyst, making the use of DMSO extremely uneconomical from an industrial perspective. It becomes a method.

Means for Solving the Problem The inventors of the present invention have intensively investigated a catalytic hydrogenation method that does not use DMi90 at all and is industrially superior in order to obtain the corresponding target product from nitrobenzenes in high yield. As a result, by using a mixed solvent consisting of alcohol and sulfuric acid, which has been used in the past, and which contains substantially no water, a predetermined amount of water is added, and by using a predetermined amount of alcohol and sulfuric acid, the desired purpose can be achieved. I discovered that this could be achieved and filed the application first.

The present inventors further investigated and found that the same or better effect can be obtained by adding an aliphatic carboxylic acid or an aqueous solution thereof instead of water, and completed the present invention.

That is, the present invention provides high yield and high purity nitrobenzenes by catalytic hydrogenation of nitrobenzenes in a mixed solvent consisting of a predetermined amount of alcohol, sulfuric acid, and an aliphatic carboxylic acid or an aqueous solution thereof in the presence of a noble metal catalyst. A method for producing the corresponding 4-alkoxyanilines is provided.

Alcohol used in the method of the present invention, IfE acid,
There is no problem even if water coexists in the mixed solvent of aliphatic carboxylic acid and aliphatic carboxylic acid, and the aliphatic carboxylic acid may be used as an aqueous solution. Both the aliphatic carboxylic acid and its aqueous solution are used within the range of 1.5 to 20% by weight, but when used as an aqueous solution, the aliphatic carboxylic acid contains at least 1% by weight.
．． It should be present in an amount of 5% by weight or more. The content of aliphatic carboxylic acid is preferably adjusted to a mixed solvent containing 1.5 to 10% by weight. If the content is outside this range, the by-product of 4-hydroxy-anilines and/or anilines will increase, which is not a good idea. The amount of alcohol is 10 moles or more, preferably 20 moles or more, based on the raw material nitrobenzene.
-100 mol, more preferably 30-60 mol. Similarly, the amount of sulfuric acid is 0.5 to 2 for the raw material nitrobenzene.
0 mol, preferably 1 to 10 mol, more preferably 2
~7 mol is good. When the amount of sulfuric acid is outside this range, an increase in anilines and/or unknown tar components is observed. In addition, the amount of these mixed solvents provides a high yield of the target product,
In addition, it is natural that the optimum concentration of raw material nitrobenzene should be selected in consideration of the concentration of the raw material nitrobenzene so as to avoid complication in taking out the product.

As the aliphatic carboxylic acid, lower aliphatic carboxylic acids such as acetic acid, propionic acid, acetic acid, and valeric acid are preferably used. Among these carboxylic acids, acetic acid and propionic acid are preferred, and acetic acid is particularly preferred.

The reaction temperature ranges from 0°C to the boiling point of the mixed solvent.

Preferably, 30 to 60°C is selected.

A practical reaction pressure ranges from atmospheric pressure to 2 to 51/clI gauge pressure. High pressures are unnecessary and tend to increase the ma- of the anilines.

Catalysts that can be used are platinum, palladium, and mixtures thereof. These metal catalysts use inert solids as supports; carbon is preferred as a support. It is preferred to use a catalyst containing 1 to 5% platinum and/or palladium supported on activated carbon, although any catalyst containing 0.1 to 20% of these metals may be used. Also, based on the nitrobenzenes to be reacted, it is 0.01
It is preferred to use a catalytic amount of supported catalyst corresponding to ~0.10% by weight of platinum or palladium.

The type of alcohol includes lower alcohols such as methanol and ethanol, and alcohols with 3 carbon atoms are preferred, but methanol is most preferred because it can obtain the desired product in a particularly high yield. .

After carrying out the hydrogenation reaction under the conditions described above, the product can be taken out, for example, as follows. That is,
The reaction completed liquid is filtered to recover the catalyst.

This catalyst will be reused next time. Subsequently, the alcohol is distilled off, and if necessary, water is added to neutralize to pH 7-8. A suitable organic solvent such as ethyl acetate, benzene, or monochlorobenzene is added to this neutralized solution for extraction, and the oil layer is distilled under reduced pressure to obtain 4-alkoxyanilines.

In this way, the method of the present invention has a high yield, and moreover, DMSO
Since no catalyst poisons are used in catalytic hydrogenation reactions such as .

The present invention will be specifically described below with reference to Examples.

Example 1 Into a 51-volume glass reactor equipped with a stirrer, a thermometer, and a hydrogen inlet tube, 137.1 g (1,0 mol) of 0-nitrotoluene and 264.5 g (2,5 mol) of 98-thiosulfuric acid were added. , glacial acetic acid 68.6.9. 1518.0 g (47.4 mol) of methanol and 0.41 g of tricarbon carrier platinum catalyst were charged.

The reaction was carried out at 50°C with addition of hydrogen at 20-30 CI.
! This was done under slight pressure maintained in the water column.

The reaction time required 300 minutes and ended with 52.51 hydrogen absorbed. At that point, almost no 0-nitrotoluene remained in the reaction solution.

Subsequently, the reaction solution was filtered to separate the catalyst.

After distilling off the methanol in liquid F, add 500 g of distilled water,
It was neutralized with 28% ammonia water to a pH of 7.2.

200 g of toluene was added to the neutralized solution, extracted, the separated toluene layer was washed with dilute caustic water, and the toluene layer was concentrated.
Distillation under reduced pressure yielded zl, 51 o-toluzine as the first distillate and 99.5 g (yield 72.0 g) of 2-methyl-4-methoxy-aniline (boiling point 136 ~ 1
38° C./20 μHg) was obtained. The purity of the main fraction by gas chromatography was 99.2%.

Calculated value (ch) 70.0 8.08 10.2
Example 2゜Example 1. In the same reactor used in Example 1, 137.1 g (I, 0 mol) of 0-nitrotoluene, 264.5 jl (2,5 mol) of 98-thiosulfuric acid, and glacial acetic acid ss, s11 were added. ．． Methanol 1518.0II (47,
4 mol), and catalyst C recovered from Example 1, SSg
(including water) was prepared.

The reaction was carried out in the same manner as in Example 1. The reaction time required 310 minutes, 52. The hydrogen from OJ was absorbed and the process ended.

Subsequently, treatment was carried out in the same manner as in Example 1, and 0-toluidine 20
．． 119 and 2-methyl-4-methoxy-aniline to
2.0 Jil (yield: 73.8 Jil) was obtained. 2-methyl-
The purity of 4-methoxy-aniline by gas chromatography was 99.2 cs.

Example 3 Similar to Example 2 without adding further catalyst.
The reduction catalytic reaction was carried out three more times. The times required for the reactions were 310 minutes, 320 minutes, and 320 minutes, respectively, and the yields of 2-methyl-4-methoxy-aniline were 73.6 and 74.6 minutes, respectively. It was low and 73.8 chi.

Example 4 A reduction reaction was carried out as in Example 2 by adding 0.139 of the new catalyst used in Example 1 to the catalyst recovered from the fifth reaction. The reaction took 290 minutes and ended after absorbing 53 and 54 hydrogen atoms. Treated as in Example 1 to give 0-toluidine 2
0.8Ii and 2-methyl-4-methoxy-aniline x
oo, sl (yield 73.2*) was obtained. 2-methyl-4
- The purity of methoxyaniline by gas chromatography was 99.4%.

Example 5 A reduction reaction was carried out in the same manner as in Example 1 except that 68.6 JI (0.5 mol) of 0-nitrotoluene was used.

The reaction took 220 minutes and was completed with 26.41 hydrogen absorbed. Treated in the same manner as in Example 1, 0-toluidine 9
．． 0.9 and 2-methyl-4-methoxyaniline 53.1
．． 9 (yield 76.6%) was obtained. The purity of 2-methyl-4-methoxyaniline by gas chromatography is 9
It was 9.0%.

Comparative Example A reduction reaction was carried out in the same manner as in Example 1 except that glacial acetic acid was not charged. The reaction took 1100 minutes, 57. The hydrogen of Ol was absorbed and the process was completed. The treatment was carried out in the same manner as in Example 1, but 0-
Only 4.3 JF of toluidine j and 72.5 J+ of 2-methyl-4-methoxyaniline (yield 52.51) were obtained. The purity of 2-methyl-4-methoxyaniline by gas chromatography was 99.3%.

Example 6 157.1C of 0-chloronitrobenzene was used instead of 137.111C of 0-nitrotoluene (1.0 mol). s I (I
, 0 mol) and a 50% acetic acid aqueous solution was used instead of glacial acetic acid. The reaction took 480 minutes, 53. (Hydrogen of I' was absorbed and the process was completed. After treatment in the same manner as in Example 1, 8.5 g of 0-chloroaniline was used as the first distillate and 103 g of 0-chloroaniline was used as the main fraction.
．． 7Ii (yield: 65.5 h) of 2-chloro-4-methoxyaniline (boiling point: 141-143°C, 720 mHg)
I got it. The purity of the main fraction by gas chromatography was 99.5%.

Calculation II [(ch) 53.3 5.12 8.
89 22.5 Measured value (chi”) 53.2 5,
09 8.84 22.2 Example 7 0-Nitrotoluene 1a7. l,? A reduction reaction was carried out in the same manner as in Example 1 except that 123.1 g (1 mol) of nitrobenzene was used instead of (t, o mol). The reaction took 280 minutes and was completed with the absorption of 55.51% of hydrogen. After that, the reaction was continued in the same manner as in Example 1, and 28.0II of hydrogen was absorbed as the first distillate.
A mixture of P-anisidine and O-anisidine was obtained with aniline as the main fraction and 21c (yield: 53.0 h).

The purity of the main fraction by gas chromatography is 99.3
It's %.

Example 8 2-Methoxy-nitrobenzene 153.1 instead of 0-nitrotoluene (137.11 IC 1.0 mol) IJl(I
The reduction reaction was carried out in the same manner as in Example 1 except that 0 mol) was used. The reaction took 250 minutes and ended with 62.01 hydrogen absorbed. Subsequently, after treatment in the same manner as in Example 1, 50.3 g of 0-anisidine was added as the first fraction and 50.3 g of 0-anisidine as the main fraction.
5.9 g (yield 43.0%) of a mixture of 2.4-dimethoxy-aniline and 2.6-simethoxyaniline was obtained.

Example 9 151.2 g of 2-6-dimethyl-nitrobenzene (137.111 C1.0 mol) of 0-nitrotoluene
The reduction reaction was carried out in the same manner as in Example 1 except that 1,0 mol) was used. The reaction took 290 minutes and ended with 53.01 hydrogen absorbed. Continue to carry out [after treatment in the same way as pH,
23.3I of 2,6-dimethylaniline as the first fraction and IXt as the main fraction, 3g (yield 73.4ti) of 2,
6-dimethyl-4-2 toxic aniline was obtained. The purity of the main fraction by gas chromatography is 99.7%.
Met.

Example 1O A reduction reaction was carried out in the same manner as in Example 1 except that propionic acid was used instead of glacial acetic acid. The reaction was completed in 320 minutes. In the same manner as in Example 1, 22.01F 〇-toluidine and 2-
Methyl-4-methoxy-aniline 98.3# (yield 71
．． 1) was obtained.

Patent ratio - people Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1 Formula (I)▲There are mathematical formulas, chemical formulas, tables, etc.▼(I
) [In formula (I), R means a hydrogen atom, a halogen atom, a lower alkyl group, or a lower alkoxy group, and when R is a substituent other than a hydrogen atom, it is at the o-position or/and m-position with respect to the nitro group. represents rank. n is an integer of 1 to 2] A nitrobenzene represented by the following is mixed with a lower aliphatic alcohol, sulfuric acid, and a lower aliphatic carboxylic acid or an aqueous solution thereof.
In a mixed solvent containing 5 to 20% by weight, using at least 10 times more alcohol and at least 0.5 times more sulfuric acid by mole than nitrobenzene, in the presence of a noble metal catalyst,
A method for producing 4-alkoxyanilines, which comprises carrying out a catalytic hydrogenation reaction. 2 Alcohol to nitrobenzene, 20 to 10
The method according to claim 1, which uses 0 times the mole amount. 3. The method according to claim 1, in which sulfuric acid is used in an amount of 1 to 10 times the amount of nitrobenzene by mole. 4. The method according to claim 1, wherein the lower aliphatic alcohol is methanol. 5. The method according to claim 1, wherein the lower aliphatic carboxylic acid is acetic acid. 6 The lower aliphatic carboxylic acid in the mixed solvent is 1.5 to 10
% by weight.