JP2696565B2 - Electrolytic production of triphenylmethane dye. - Google Patents

Description

The present invention relates to a method for producing a dye. More particularly, the present invention relates to a method for producing a corresponding triphenylmethane dye by electrolytically oxidizing a triphenylmethane compound (leuco compound) containing no sulfonic acid group.

Conventional technology Conventionally, the synthesis of triphenylmethane dyes is described in "New Dye Chemistry" by Yutaka Hosoda, Gihodo p.266,
A method of oxidizing the leuco body with sodium dichromate, lead peroxide or the like to obtain a desired dye is known. For example
CI No. 42040, 42000 is synthesized from the corresponding leuco body using lead peroxide. However, according to such a synthesis method, as described in JP-A-54-10481,
Chromium hydroxide or lead sulfate is formed, and it is difficult to completely separate the same. As a method not using such heavy metals, Japanese Patent Application Laid-Open No. 54-130481 proposes a synthesis method by electrolytic oxidation. That is, a method of oxidizing the leuco body electrochemically instead of using a metal oxidizing agent is employed.

Japanese Patent Application Laid-Open Nos. 61-238992 and 63-53282 also describe a method for synthesizing a triphenylmethane dye by electrolytic oxidation.
The synthesis method in these methods is the same as the synthesis method of the triphenylmethane dye having a sulfonic acid group as in the above-mentioned JP-A-Showa.

Problems to be Solved by the Invention Heavy metal compounds used as oxidants in the conventional method are subject to strict regulations due to their strong toxicity to living organisms, and require special attention and much effort for their use and waste disposal. I do. Therefore, it is an important technical subject from the viewpoint of environmental protection to synthesize industrially a large amount of triphenylmethane dye having no sulfonic acid group without using a heavy metal oxidizing agent.

On the other hand, the method for synthesizing the triphenylmethane dye by the above-described electrolytic oxidation is limited to those containing a sulfonic acid group, and the synthesis technique for a sulfonic acid group-free dye is unclear. Also, when JP-A-61-238992 is applied to the present invention,
The desired product was obtained only in low yield. The inventor of the present invention has conducted intensive studies to solve these problems, and has come to solve those problems.

Means for Solving the Problems The present invention provides a compound represented by the formula (1) [wherein, X and Y represent a hydrogen atom, a chloro atom or a methyl group, R ₁ and R ₂ represent a lower alkyl group or a hydrogen atom, Ar represents a phenyl group or a naphthyl group which may be substituted by a nitro group, a methyl group, a chloro atom, a diethylamino group, a dimethylamino group, an amino group, a monomethylamino group or a monoethylamino group. Wherein a triphenylmethane compound represented by the following formula (2) is electrolytically oxidized in the presence of an acid and water or an organic solvent miscible with water in an amount of 50% by weight or less in a diaphragm-free electrolytic cell.
[In formula (2), X, Y, R ₁ , R ₂ , and Ar represent the same meaning as in (1). And a method for electrolytically producing a triphenylmethane dye.

Hereinafter, the present invention will be described in detail.

In the method of the present invention, specific examples of the triphenylmethane compound of the formula (1) used as a raw material include C.I.
I.No.42040,42000,42037,42036,42030,42025,42140,421
30,42605,42557,42555,42600,42505,42535,42500,4251
And leuco bodies such as 0,42520,42595,44045. As the supporting salt, inorganic acids, organic acids or salts thereof are used. Specific examples thereof include sulfuric acid, phosphoric acid, hydrochloric acid, hydrobromic acid, perchloric acid, nitric acid, tetrafluoroboric acid, benzenesulfonic acid, and toluene. Sulfonic acid, xylenesulfonic acid, benzenedisulfonic acid, toluenedisulfonic acid, xylenedisulfonic acid, chlorobenzenesulfonic acid, dichlorobenzenesulfonic acid, ethylbenzenesulfonic acid, m-nitrobenzenesulfonic acid, 3-nitro-4-methylbenzenesulfonic acid Α-naphthalene sulfonate, β-naphthalene sulfonic acid, naphthalene-2,7-disulfonic acid,
Naphthalene-2,6-disulfonic acid, naphthalene-1,5-disulfonic acid, naphthalene-1,3,6-trisulfonic acid, methylnaphthalenesulfonic acid, chloronaphthalenesulfonic acid, titaniumsulfonic acid, sulfamic acid, phenolsulfonic acid Phenol disulfonic acid, sulfobenzoic acid, and the like, and their alkali metal salts, alkaline earth metal salts, ammonium salts, and the like, of course, but are not limited thereto. Of these, preferred are hydrochloric acid, sulfuric acid, hydrobromic acid, o-toluenesulfonic acid, p
-Toluenesulfonic acid and its Na, K salts. The amount of use of these supporting salts is 0.1 to 40 times mol based on the reaction substrate.

The electrolytic reaction of the present invention is preferably carried out in an acidic condition, preferably in the range of pH 1 to 4, in order to suppress side reactions and improve the yield. Adjustment to the above pH is achieved by adding the acids mentioned above. Further, since the pH of the reaction system changes to the acidic side as the electrolysis proceeds, it is preferable to adjust the pH by adding a suitable alkali, preferably a hydroxide of the above-mentioned alkali metal.

As a reaction solvent, for example, water, acetone, acetonitrile, DMF, DMA, DMSO, N-methylpyrrolidone, methanol,
Ethanol, 1-propanol, 2-propanol, te
rt-butanol, n-butanol, ethylene glycol, propylene glycol, methylcellosolve, and the like can be used. Among them, particularly preferred are water, methanol, ethanol and iso-propanol. The above-mentioned solvents can be used in a mixed system.

When the present invention is performed in a diaphragm-free electrolytic cell as described below,
It is desirable to carry out the reaction in water or a mixed solvent containing preferably 50% by weight or less of water. The amount of the solvent to be used is usually 1 to 100 times, preferably 3 to 50 times the amount of the reaction substrate. The electrolysis reaction is usually carried out at a temperature lower than the boiling point of the solvent used, for example, at 0 to 50 ° C., preferably at room temperature, but is not particularly limited by this. The amount of electricity required for electrolysis is 2 to 5 F / mol, but in practice, HPLC
The reaction is followed by (high performance liquid chromatography) or the like, and the end point of the reaction is determined by supplying a necessary amount of electricity. The current density is usually 1 to 100 mA / cm ² , preferably 5 to 50 mA / cm ² .

The electrolytic cell used in the present invention is a non-diaphragm type device capable of reducing equipment costs. That is, when the electrolytic reaction is carried out using a supporting salt such as sodium p-toluenesulfonate in an aqueous solvent, the reaction at the cathode does not adversely affect, and the desired product can be obtained in good yield.

Next, the electrode material will be described. An anode having corrosion resistance under electrolysis conditions is usually used. For example, Pt, Au,
Graphite, lead oxide, Ni, Pt / Ti, IrO 2 / Ti, RuO 2 / Ti, RuO
₂ / TiO ₂ / Ti, but is not limited to these.

The target substance after the completion of the electrolytic reaction can be separated from the reaction solution by a usual method. One of the methods is to remove most of the solvent or organic solvent used and make it alkaline in an aqueous solvent, thereby precipitating it as a hydrol form, or as a salt such as oxalic acid, hydrochloric acid, or sulfuric acid. Can be taken away.

Examples The present invention will be described in more detail with reference to Examples.

Example 1. 200 mg of a leuco compound of CI No. 42000 of the following formula (3), 1.0 g of p-toluenesulfonic acid monohydrate and 10 g of water were added to a 20-ml branched test tube, and the mixture was stirred to completely dissolve the leuco compound. . Thereafter, a 20 wt / v% NaOH aqueous solution was added to adjust the pH to about 3, and 1.
Soak two 5 x 2 cm platinum plates (anode and cathode) in the solution and apply 40 mA
(Voltage between terminals is 2 to 3.5 V) and an electric quantity of 3 F / mol flows. During this time, the pH of the reaction solution was adjusted to 2.2 to 3.8 using a 20 wt / v% NaOH aqueous solution. After the completion of the reaction, add a 20 wt / v% NaOH aqueous solution and adjust the pH.
Stir to 13-14 for 30 minutes. This gives equation (4)
A hydrol body of CI No. 42000 was precipitated. The crystals were washed with water to give 201 mg of the desired product. It had sufficient purity as a dye. The dye obtained by acid treatment had a λmax of 620 nm (H ₂ O), which was consistent with the structure of CI No. 42000 (malachite green) represented by the formula (5).

Examples 2 to 5 Example 2 to Example 5 were prepared under various reaction conditions using CI No. 4
The following table shows the results of electrolytic oxidation of 2000 leuco bodies.

Effect of the Invention Without using an oxidizing agent such as dichromate and lead peroxide, a sulfonic acid group-free triphenylmethane dye can be produced from a corresponding leuco body by an electrolytic reaction using a diaphragmless electrolytic cell. It became so.

Claims (1)

(57) [Claims] A compound of the formula (1) wherein X and Y are hydrogen atoms,
A chlorine atom or a methyl group, R ₁ and R ₂ are a lower alkyl group or a hydrogen atom, Ar is a nitro group, a methyl group, a chloro atom,
Represents a phenyl group or a naphthyl group which may be substituted by a diethylamino group, a dimethylamino group, an amino group, a monomethylamino group or a monoethylamino group. Wherein the triphenylmethane compound of formula (2) is electrolytically oxidized in the presence of 50% by weight or less of acid and water or an organic solvent miscible with water in a diaphragm-free electrolytic cell.
[In formula (2), X, Y, R ₁ , R ₂ , and Ar represent the same meaning as in (1). Method for electrolytic production of triphenylmethane dye