KR100377564B1 - Process for preparing 2,4-disubstituted-2-nitro-2'-hydroxy azobenzene derivatives - Google Patents

Abstract

PURPOSE: Provided is a method for preparing 2,4-disubstituted 2-nitro-2'-hydroxy azobenzene derivatives with higher purity at higher yield compared to conventional methods. CONSTITUTION: The method for preparing azo compounds represented by formula (1) comprises the steps of reacting acidic (pH<2) aqueous solution of 2-nitroaniline diazonium salt represented by formula (3) with a 2,4-disubstituted phenol represented by formula (4), in the presence of a dispersant comprising a C8-C20 alkylarylsulfonic acid and/or a metal salt of a C8-C20 alkylarylsulfonate, and polyacrylic acid, wherein each of R1 and R2 is the same or different C1-C5 lower alkyl; R3 is H or a halogen; and X is a leaving group.

Description

Process for preparing 2,4-disubstituted 2-nitro-2'-hydroxy azobenzene derivatives {Process for preparing 2,4-disubstituted-2-nitro-2'-hydroxy azobenzene derivatives}

The present invention relates to a method for synthesizing an azo compound of formula (1), more specifically 2,4 of formula (4) which is insoluble in a diazonium salt of 2-nitroaniline of formula (3) and an aqueous solution A method for synthesizing an azo compound represented by the following formula (1) comprising reacting a -substituted phenol in an aqueous acid solution.

<Formula 1>

<Formula 3>

<Formula 4>

In each said formula,

R ₁ and R ₂ are the same or different, each being a C _1-5 lower alkyl group,

R ₃ is hydrogen or halogen,

X is a leaving group.

In the preparation of azobenzene derivatives known to date, when using 2,4-disubstituted phenol, the compound has a low solubility in an aqueous solution and an alkaline aqueous solution having a pH of 8-11. Solvent and dispersant must be used together.

Japanese Laid-Open Patent No. 56-115757 discloses a method for producing an azobenzene derivative using methanol as an organic solvent, and Japanese Laid-Open Patent No. 53-37628 discloses chlorobenzene as a solvent and alkylaryl as a dispersant. A method for producing an azobenzene derivative using sodium sulfonate salt is disclosed. However, although the azo coupling method using such an organic solvent and a dispersant has an advantage of obtaining a high yield and a high purity compound, it is not preferable because it is very likely to cause environmental problems due to solvent recovery and wastewater treatment.

On the other hand, US Patent No. 3,998,804 discloses arylsulfonic acid and alkylarylpolyglyes for the effective dispersion of a water-soluble 2-nitroaniline diazonium salt and 2,4-disubstituted phenol in an aqueous acid solution having an pH of 2 or less without using an organic solvent. A method for preparing an azobenzene derivative using a lycol ether and an alkyl arylsulfonate as a dispersant is disclosed, but has a disadvantage in low yield and purity.

U.S. Patent No. 5,436,322 discloses a method of preparing an azobenzene derivative using alkanesulfonic acid or a mixture of alkanesulfonates and polyvinyl alcohol as a dispersant, which significantly reduces the amount of dispersant required for the reaction. , High yield, high purity azo compound is disclosed. Nevertheless, there is a need for a process for preparing azo compounds which is further improved in purity and yield.

Accordingly, it is an object of the present invention to provide an azobenzene derivative of formula (1) which is even higher in purity and yield than in the prior art.

The present inventors earnestly studied the process for preparing a high purity and high yield of azobenzene compound, and as a result, the compound of formula (1) was used as a dispersant using alkylarylsulfonic acid and / or alkylarylsulfonate and polyacrylic acid And unexpectedly discovering that the object of the present invention as described above can be achieved by obtaining in high yield, the present invention has been completed.

Hereinafter, the present invention will be described in more detail.

As used herein, "lower alkyl" refers to saturated straight or branched chain hydrocarbon radicals having 1 to 5 carbon atoms, such as methyl, ethyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, etc. "Halogen" means a halogen atom selected from bromine, chlorine, iodine.

The azobenzene derivative of the formula (1) according to the present invention is prepared by dropwise addition of an aqueous acid solution of the diazonium salt of the formula (3) to the phenol of the formula (4).

Prior to the initiation of the reaction, the phenol of formula (4) should be well dispersed and for this purpose, polyacrylic acid and alkylarylsulfonic acid (including metal salt forms) were added to a mixture of phenol and water and stirred. Stirring is suitable for about 30 minutes, wherein the stirring temperature is 30-80 ℃. The aqueous solution of diazonium salt (3) is slowly added dropwise to the reaction mixture thus obtained, and the reaction temperature is preferably 30-80 ° C, particularly preferably 40-45 ° C. After completion of the dropwise addition of the diazonium salt aqueous solution, the mixed solution is stirred for 1-4 hours, and if necessary, the reaction is terminated by raising the reaction temperature to 40-60 ° C and stirring for an additional 30 minutes.

As the dispersant used in the present invention, alkylarylsulfonates in the form of polyacrylic acid and alkylarylsulfonic acid and / or alkali metal salts may be suitably used.

The alkylarylsulfonic acid which can be used in the present invention is preferably 8 to 20 carbon atoms, and examples thereof include benzene sulfonic acid, dodecylbenzene sulfonic acid, octylbenzene sulfonic acid, 1-naphthalenesulfonic acid, 1-naphthylmethanesulfonic acid, and the like. have. In the present invention, alkylarylsulfonates in the form of metal salts may also be used. Examples of alkylarylsulfonates include benzenesulfonate, dodecylbenzenesulfonate, octylbenzenesulfonate, 1-naphthalenesulfonate, 1-naphthylmethane. Sulfonates, and the like. These compounds are particularly preferred because they play an important role in stabilizing the 2-nitroaniline diazonium salt as well as the dispersant.

Polyacrylic acid that can be used in the present invention can be represented by the following formula (5) as a water-soluble polymer.

[Formula 5]

[-CH ₂ CH (CO ₂ H)-] _n

Generally, the molecular weight of polyacrylic acid used for reaction is suitable in the range of about 1,000-200,000, Especially since polyacrylic acid whose molecular weight is 8,000-12,000 is effective for uniform dispersion, it is especially preferable.

When alkylarylsulfonic acid and / or its corresponding alkylarylsulfonate metal salt is used as the dispersant, the amount thereof is preferably in the range of 0.1 to 10% by weight based on the weight of the phenol of formula (4), and poly Acrylic acid is preferably used in an amount of 0.1-5%. These dispersing agents can be used 1 or more types, It is preferable to use especially the alkyl aryl sulfonic acid and / or its corresponding alkyl aryl sulfonate metal salt, and the said polyacrylic acid in mixture. When such alkylarylsulfonic acid and / or its corresponding alkylarylsulfonate metal salt and polyacrylic acid are used as a dispersant, it is possible to prepare azo compounds with high yield and high purity due to the high dispersing effect.

The aqueous solution of the diazonium salt of nitroaniline of formula (3) used in the present invention can be easily prepared according to a known method, in particular from the substituted nitroaniline of formula (2) in detail in the examples of the present invention. As shown, it can be manufactured easily.

[Formula 2]

In the above formula,

R ₃ is hydrogen or halogen.

The present invention is explained in more detail by the following examples, but the present invention is not limited in any way by these examples.

<Example 1>

2-nitro-4-chloro-2'-hydroxy-3,5'-di-tert-butyl azobenzene

(1) Preparation of Diazonium Salt Aqueous Solution

200 g of water and 172.6 g of 4-chloro-2-nitroaniline were added to a 2 L reaction vessel and stirred for 30 minutes. To this mixture, 309.7 g of 95% sulfuric acid was added to 320 g of ice, and the internal temperature of the reactor was 0-5 ° C. Cooled to. At this time, 176.0 g of 30% nitrite sodium salt was added dropwise for 2 hours to maintain the reactor internal temperature at 0-5 ° C. After completion of the dropwise addition, the reaction was further performed for 30 minutes to obtain a clear dark brown diazonium aqueous solution. Excess nitrite remaining unreacted was deactivated by the addition of 2.4 g of sulfamic acid.

(2) azo coupling

308.0 g of water, 2.9 g of 25% polyacrylic acid (molecular weight: 8,000-12,000 wako) and 3.20 g of sodium dodecylbenzenesulfonate were added to the 2L reaction vessel, and the mixture was stirred at 25 ° C for 10 minutes to obtain a clear aqueous solution. To this was added 210.5 g of 2,4-di-tert-butyl-phenol and heated to 60 ° C. for 30 minutes with rapid stirring to dissolve the 2,4-di-tert-butyl-phenol, while simultaneously dispersing well with water. A mixture was obtained (coupler solution). The temperature of this coupler solution was cooled to 45 ° C, and the diazonium salt aqueous solution prepared in step (1) was added dropwise over 4 hours while maintaining the reactor internal temperature at 43 ° C-45 ° C.

After all of the diazonium salt solution was added dropwise, the mixture was stirred at 45 DEG C for 1 hour, and if the reaction was not completed, the reaction was further heated to 50 DEG C for 1 hour to complete the reaction and the reaction was filtered. After filtration, the resultant was first washed with 600 g of water at 50 ° C. and secondly washed with 200 g of water, followed by vacuum drying to obtain 386.8 g of 2-nitro-4-chloro-2′-hydroxy-3 ′, 5′-. Di-tert-butylazobenzene was obtained. The product had a purity of 94.0% (HPLC), a yield of 93.2% and a melting point of 196-210 ° C.

<Example 2>

2-nitro-4-chloro-2'-hydroxy-3'-tert-butyl-5'-methylazobenzene

Diazonium salt aqueous solution was prepared in the same manner as in step (1) of Example 1.

308.0 g of water, 3.2 g of 25% polyacrylic acid (molecular weight: 8,000-12,000; manufactured by Wako), and 6.9 g of sodium dodecylbenzenesulfonate were added to a 2L reaction vessel, and the mixture was stirred for 10 minutes to obtain a clear aqueous solution. 167.5 g of 2-tert-butyl-4-methylphenol was added thereto, and the mixture was heated to 50 ° C. for 30 minutes with rapid stirring to dissolve 2-tert-butyl-4-methylphenol, and the mixture was well dispersed with water by a dispersant. Was obtained (coupler solution). The previously prepared diazonium salt aqueous solution is added dropwise to the well dispersed coupler solution for a constant 4 hours while maintaining the reaction temperature at 34-36 ° C. After all of the diazonium salt aqueous solution was added dropwise, the mixture was further stirred at 35 ° C for 1 hour, then heated to 50 ° C, and stirred for 1 hour to complete the reaction. After completion of the reaction, the reaction was filtered, washed with 400 g of 0 ° C. water and dried in vacuo to give 335.5 g of 2-nitro-4-chloro-2'-hydroxy-3'-tert-butyl-5'-methylazobenzene Got. The product had a purity of 92.8% (HPLC), a yield of 89.6% and a melting point of 162-181 ° C.

According to the present invention, it is possible to prepare a high purity azo compound in high yield by using an alkylarylsulfonic acid and / or its corresponding alkylarylsulfonate metal salt and polyacrylic acid as a dispersant to increase the dispersing effect.

Claims (4)

To to the presence of a dispersing agent for the diazonium salt aqueous acid solution (pH <2) of 2-nitro-aniline of formula (III) include C ₈ -C ₂₀ alkyl aryl sulfonate and (or) an alkyl aryl sulfonate salt and a polyacrylic acid A process for preparing an azo compound of formula (1), characterized by reacting with 2,4-substituted phenols of formula (VI). <Formula 1> <Formula 3> <Formula 4> In each said formula, R ₁ and R ₂ are the same or different, each being a C _1-5 lower alkyl group, R ₃ is hydrogen or halogen, X is a leaving group. The method of claim 1 wherein the polyacrylic acid has a molecular weight of 1,000-200,000. 2. An alkylarylsulfonic acid and / or its corresponding alkylarylsulfonate metal salt thereof as a dispersant is used in an amount of 0.1-10% based on the weight of the phenol of formula (4), and polyacrylic acid is used in a weight ratio of 0.1-. Used in an amount of 5%. The process of claim 1 wherein the reaction temperature is in the range of 30 to 80 ° C.