JPH116090A - Preparation of 4,6-diaminoresorcin and its salt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare 4,6-diaminoresorcin and its salt as stock monomers of polybenzobisoxazole by electrolytically reducing 4,6-bis-substd. phenylazoresorcinol. SOLUTION: 4,6-Bis-substd. phenylazoresorcinol represented by the formula [where R<1> and R<2> are individually H, 1-10C alkyl, 1-10C alkoxy, halogen, sulfonic acid, cyano, carboxyl or 2-11C carboalkoxy and (n) and (m) are integers of 0-5] is electrolytically reduced in an acidic solvent or its aq. soln. such as an aq. hydrochloric acid soln. or a mixed solvent consisting of an acidic solvent or its aq. soln. and an org. solvent such as dioxide or ethanol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing 4,6-diaminoresorcin and a salt thereof. More specifically, as represented by the following formula, 4,6-bis-substituted phenylazoresorcinol (hereinafter, abbreviated as BPAR derivative) is converted to 4,4 by an electrolytic reduction reaction in various solvents.
6-diaminoresorcin (hereinafter abbreviated as DAR)
And a method for producing a salt thereof.

[0002]

Embedded image

(R1 and R2 each independently represent a hydrogen atom,
Represents an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a halogen atom, a sulfonic acid group, a cyano group, a carboxyl group, or a carboalkoxy group having 2 to 11 carbon atoms; Is an integer. 4,6-Diaminoresorcinol (DAR) is important as a monomer thereof because polycondensation with terephthalic acid results in polybenzobisoxazole (PBO) having various excellent characteristics.

[0004] PBO is superior to conventional spar fiber in various points such as strength, elastic modulus, heat resistance and chemical resistance, and is expected to be developed as a super-super fiber (Japanese Patent Application Laid-Open No. 61-501452). No.).

[0005]

2. Description of the Related Art Conventionally, as an example of an electrolytic reduction reaction of a substituted azophenyl derivative, H. Lund, Acta Chem. Scand., 13, 249-2
67 (1959), HALaitinen, TJKneip, J. Am. Chem. Soc. 78,
736 (1956), R. Hazard. A. Tallec, Bull. Soc. Chim. Fr., 291
7 (1971), L. Halleck, D. Jannakoudakis, A. Wildenau, Elec
trochim. Acta., 12, 1523 (1967), etc., from a BPAR derivative having extremely low solubility in an aqueous electrolytic solution,
There has been no example of obtaining an extremely unstable diaminobenzene derivative by an electrolytic method.

In US Pat. No. 5,453,542, a DAR is obtained from a BPAR derivative by a catalytic reduction method. However, this method requires use of an expensive noble metal catalyst, and an economical method is required.

[0007]

The present inventors have searched for a practical method for producing DAR from a BPAR derivative by electrolysis, and found that the BPAR derivative was prepared in an acidic solvent or an aqueous solution thereof, or in an acidic solvent or an aqueous solution thereof. It has been found that DAR can be obtained in high yield by reduction in a mixed solvent of an aqueous solution and an organic solvent by an electrolytic reduction reaction.

[0008] An object of the present invention is to provide a BP by electrolytic reduction.
An object of the present invention is to provide an industrially economical production method of DAR from an AR derivative with a high yield.

[0009]

That is, the present invention provides a compound represented by the general formula [1]:

[0010]

Embedded image

(R ¹ and R ² each independently represent a hydrogen atom,
Represents an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a halogen atom, a sulfonic acid group, a cyano group, a carboxyl group, or a carboalkoxy group having 2 to 11 carbon atoms; Is an integer. 4)
Production of 4,6-diaminoresorcin and its salt, characterized in that 6-bis-substituted phenylazoresorcin is reduced by an electrolytic reduction reaction in an acidic solvent or an aqueous solution thereof, or a mixed solvent of an acidic solvent or an aqueous solution thereof and an organic solvent. About the method.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The 4,6-bis-substituted phenylazoresorcin, which is a raw material of the present invention, can be obtained in a high yield by reacting resorcinol with a diazonium salt obtained from an aniline derivative (Japanese Patent Application Nos. 7-309803 and 7-3664).
No. 83). These reaction crude products can be used as raw materials of the present invention as they are.

The aniline derivatives used in the present invention include aniline, toluidine, anisidine, dimethylaniline, ethylaniline, trimethylaniline, propylaniline, butylaniline, fluoroaniline, chloraniline, bromoaniline, anilinebenzoic acid and esters thereof, Examples thereof include cyanoaniline and trifluoromethylaniline, and particularly preferred are aniline and toluidine.

Examples of acidic solvents and aqueous solutions thereof which can be used as a solvent in the electrolysis method of the present invention include sulfuric acid or sulfuric acid aqueous solution, hydrohalic acid aqueous solution, phosphoric acid aqueous solution, tetrafluoroboric acid aqueous solution and perchloric acid aqueous solution. There are inorganic acids and their aqueous solutions, lower fatty acids such as formic acid, acetic acid and propionic acid and their aqueous solutions, and organic acids such as methanesulfonic acid aqueous solution and toluenesulfonic acid aqueous solution and their aqueous solutions. Examples of preferred acidic solvents are aqueous sulfuric acid, aqueous hydrochloric acid and aqueous phosphoric acid. These acidic solvents can be used alone, but usually, it is preferable to use them in a mixed solution with an organic solvent in order to increase the solubility of the raw material BPAR derivative.

Examples of the organic solvent include methanol,
Examples include water-soluble lower alcohols such as ethanol and propanol, aromatic hydrocarbons such as benzene, toluene, xylene and tertiary butylbenzene, and ethers such as dioxane, 1,2-dimethoxyethane and tetrahydrofuran. Among these, particularly preferred are:
Toluene and dioxane.

When the above-mentioned inorganic or organic acid or an aqueous solution thereof is used as the first solvent and the organic solvent is used as the second solvent, the mixing ratio of the first solvent and the second solvent is arbitrarily selected. Preferably, the first solvent: the second solvent = (1:20 to 20: 1) (weight ratio). Raw material BP
The amount of the solvent to be used with respect to the AR derivative is preferably from 5 to 1000 times by weight, particularly preferably from 10 to 100 times by weight.

When the substrate concentration becomes high, the reaction can be carried out in a slurry state. At that time, in order to make the reaction proceed smoothly, a phase transfer catalyst such as tetraethylammonium bromide or tetrabutylammonium bromide, or various sulfosuccinates represented by sodium di (2-ethylhexyl) sulfosuccinate (alias: dioctyl sodium sulfosuccinate) are used. Further, a surfactant such as polyoxyethylene alkyl allyl ether represented by acid salt and polyoxyethylene nonylphenyl ether (trade name: Nonanol 210, manufactured by Toho Chemical Co., Ltd.) can also be added.

The amount of the phase transfer catalyst or surfactant added is 0.5 to 20% by weight based on the reaction substrate. In the electrolytic reaction of the production method of the present invention, an electrode usually used for the electrolytic reaction can be used. An electrode made of a material having a long life and not corroding by the electrolytic reaction of the present invention is desirable. Non-limiting examples of this electrode include palladium, platinum, and a metal oxide (ruthenium oxide and indium oxide) coated on a titanium plate as a positive electrode.
E, carbon or lead or metals and carbon such as stainless steel, copper, nickel and the like.

Preferably, both the anode and the cathode are DSE,
Lead, platinum and / or carbon can be mentioned. The voltage between the electrodes is 0.1 to 30 V, preferably 3 to 15 V.
The current density is 0.5 to 10 A / dm ³ , preferably 1.
The reaction temperature of 0 to 5.00 A / dm ³ does not evaporate so quickly that the above-mentioned solvent adversely affects the operation, the reduction reaction proceeds rapidly and the side reaction does not proceed, and the generated DAR or A temperature within a range where the acid salt can be stably present in the solution without decomposition is desirable. For example, it is in the range of 0 to 110 ° C. When sulfuric acid or hydrochloric acid is used as the solvent, 1
The range is 0 to 90 ° C.

The amount of electricity is 0 to 5 of the theoretical amount of 8 Faraday.
0% excess, for example, 9 to 12 F / mol
And The reaction tank can be either a batch type electrolytic cell or a flow type electrolytic cell. After the completion of the electrolytic reduction reaction, the reaction solution is taken out of the electrolytic cell, concentrated, and then cooled or allowed to cool to precipitate crystals of the DAR acid salt, followed by filtration. The crystals are dissolved in water, the insolubles are removed by, for example, filtration, and the filtrate is recrystallized by adding concentrated hydrochloric acid and cooling. Then, the crystals are collected by filtration and dried to obtain the desired DA.
A purified product of R hydrochloride is obtained.

[0021]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Example 1 Commercially available ceramic diaphragm, 100 equipped with thermometer
Dioxane, ethanol, 1N in a beaker cell
A mixed solvent of hydrochloric acid (2: 1: 1 by weight) is applied
ml and 60 ml on the cathode side, and 5 mmol of 4,6 bisphenylazoresorcinol to the cathode. Using a platinum electrode for the anode and a lead electrode for the cathode, a constant current condition (0.2 A,
(5.7 mA / cm ² ), 8 F / mol of electricity was supplied at room temperature under water cooling with stirring. After energization, a solution obtained by dissolving 3 g of tin dichloride dihydrate in 60 ml of 1N hydrochloric acid was added to the catholyte, and the solvent was removed under reduced pressure to obtain a crude yield of 6.5 g.

As a result of analysis by liquid chromatography, D
It was found that AR.2HCl was produced in a yield of 62%.

Example 2 A reaction was performed under the same conditions as in Example 1 except that the amount of electricity was 12 F / mol. By the same reaction treatment as in Example 1, 6.2 g of a crude product was obtained. As a result of analysis by liquid chromatography, it was found that DAR.2HCl was produced in a yield of 68%.

Example 3 A reaction was carried out under the same conditions as in Example 1 except that the amount of electricity was 16 F / mol. By the same reaction treatment as in Example 1, 6.0 g of a crude product was obtained. As a result of analysis by liquid chromatography, it was found that DAR.2HCl was produced in a yield of 74%.

Example 4 Under the same conditions as in Example 1, the current density was 2.9 mA / cm.
^The reaction was carried out at a current flow rate of 8 F / mol. By the same reaction treatment as in Example 1, 6.3 g of a crude product was obtained. As a result of analysis by liquid chromatography, DAR-2
It was found that HCl was produced in a yield of 54%.

Example 5 Under the same conditions as in Example 1, the current density was 8.6 mA / cm.
^The reaction was carried out at a current flow rate of 8 F / mol. By the same reaction treatment as in Example 1, 7.0 g of a crude product was obtained. As a result of analysis by liquid chromatography, DAR-2
It was found that HCl was produced in a yield of 73%.

Example 6 Under the same conditions as in Example 1, the current density was 11.4 mA / c.
m ^2, and the reaction was carried out at a current flow rate of 8 F / mol.
By the same reaction treatment as in Example 1, 5.7 g of a crude product was obtained. As a result of analysis by liquid chromatography, DAR-2
It was found that HCl was produced in a yield of 81%.

Example 7 Under the same conditions as in Example 1, 10 mmol of 4,6 bisphenylazoresorcin was added, and the reaction was carried out at a current flow rate of 8 F / mol. By the same reaction treatment as in Example 1, 7.7 g of a crude product was obtained. As a result of analysis by liquid chromatography, it was found that DAR.2HCl was produced in a yield of 66%.

Example 8 Under the same conditions as in Example 1, the current density was 8.6 mA / cm.
^The reaction was carried out at a current flow rate of 9 F / mol. By the same reaction treatment as in Example 1, 6.3 g of a crude product was obtained. As a result of analysis by liquid chromatography, DAR-2
It was found that HCl was produced in a yield of 79%.

Example 9 Under the same conditions as in Example 1, the current density was 8.6 mA / cm.
^The reaction was performed at a current flow rate of 10 F / mol.
By the same reaction treatment as in Example 1, 7.5 g of a crude product was obtained. As a result of analysis by liquid chromatography, DAR-2
It was found that HCl was produced in a yield of 83%. Example 10 Under the same conditions as in Example 1, the current density was set to 8.6 mA / cm.
^The reaction was carried out under ice-cooling and the amount of electricity was 10 F / mol. 4. A crude product obtained by the same reaction treatment as in Example 1.
7 g were obtained.

As a result of analysis by liquid chromatography, D
It was found that AR.2HCl was produced in a yield of 78%.

[0032]

The compound of formula [1] is electrolytically reduced in an acidic solvent or an aqueous solution thereof or in a mixed solvent of an acidic solvent or an aqueous solution thereof and an organic solvent, whereby 4,6-diaminoresorcin is converted to an expensive reduction catalyst. Can be obtained in a high yield without using any of the above.

Claims (8)

[Claims] 1. A compound of the general formula [1] (R ¹ and R ² each independently represent a hydrogen atom,
0 alkyl group, alkoxy group having 1 to 10 carbon atoms, halogen atom, sulfonic acid group, cyano group, carboxyl group,
Represents a carboalkoxy group having 2 to 11 carbon atoms, n and m
Is an integer of 0 to 5. Wherein the 4,6-bis-substituted phenylazoresorcin represented by the formula (1) is reduced by an electrolytic reduction reaction in an acidic solvent or an aqueous solution thereof, or a mixed solvent of an acidic solvent or an aqueous solution thereof and an organic solvent. -A method for producing diaminoresorcin and salts thereof. 2. The method for producing 4,6-diaminoresorcin and a salt thereof according to claim 1, wherein the acidic solvent is an inorganic acid or an organic acid. 3. The method for producing 4,6-diaminoresorcin and a salt thereof according to claim 2, wherein the inorganic acid is hydrochloric acid, sulfuric acid or phosphoric acid. 4. The organic acid is formic acid, acetic acid, propionic acid, metasulfonic acid or ethanesulfonic acid.
The method for producing 4,6-diaminoresorcin and the salt thereof described above. 5. An organic solvent comprising an aromatic hydrocarbon, an ether,
The method for producing 4,6-diaminoresorcinol and a salt thereof according to claim 1, which is an aliphatic alcohol. 6. The method for producing 4,6-diaminoresorcin and a salt thereof according to claim 5, wherein the aromatic hydrocarbon is toluene or xylene. 7. The method for producing 4,6-diaminoresorcin and a salt thereof according to claim 5, wherein the ether is dioxane or 1,2-dimethoxyethane. 8. The method for producing 4,6-diaminoresorcin and a salt thereof according to claim 5, wherein the aliphatic alcohol is methanol or ethanol.