JPH0128031B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention deals with the production of 2,3-dicyano-1,4-dithia-
A novel method for producing 9,10-anthraquinone. 2,3-dicyano-1,4-dithia-9,10-
Anthraquinone (hereinafter abbreviated as DDAQ) is used as a dithianone agent as a fungicide that is effective against a wide range of diseases such as leaf blight of rice and fruit trees and vegetables. A promising method for producing DDAQ is to use 1,4-naphthoquinone as a starting material. Method of reacting 1,2-dimercaptoethene with a dialkali metal salt (Japanese Patent Publication No. 37-13082) 2 A suspension of 1,4-naphthoquinone in water is reacted with 1,
A method is known in which 2-dicyano-1,2-dimercaptoethene is added to an aqueous solution of a dialkali metal salt and reacted while maintaining the pH at 5 (Japanese Patent Publication No. 11730/1973). Since method 1) uses an organic solvent, it is more disadvantageous than method 2), which is carried out in an aqueous medium. Regarding method 2), the present inventors manufactured DDAQ based on the example, but the obtained
The purity and yield of DDAQ were low, and desired results could not be obtained. The present inventors conducted detailed studies to improve the purity and yield of method 2), and found that
The present invention was completed based on the discovery that purity and yield can be significantly improved by strictly maintaining the pH between 5.2 and 5.4. The present invention discloses a di-alkali metal salt of 1,4-naphthoquinone and 1,2-dicyano-1,2-dimercaptoethene suspended in an aqueous medium at a pH of
5.2 to 5.4, followed by treatment with a dehydrogenating agent. The 1,4-naphthoquinone used in the present invention is preferably a finely divided product having a particle size of 32 messules, preferably 60 messles. If the particle size is large, the reaction rate will be slow and side reactions will occur, which is not preferable. In the present invention, 1,2-dicyano-1,2-
The alkali metal salt of dimercaptoethene is selected from lithium, sodium or potassium salts, and sodium salts are usually used. Although its manufacturing method is already known, it can be easily synthesized using carbon disulfide and sodium cyanide as raw materials. The alkali metal salt of 1,2-dicyano-1,2-dimercaptoethene is used in an amount equal to or more than the mole of 1,4-naphthoquinone, preferably 1.05 to 1.3 times the mole. In the present invention, the aqueous medium refers to a medium containing water as a main component, and even if other solvents, such as those used in the synthesis of 1,2-dicyano-1,2-dimercaptoethene, are mixed in, there will be no problem. do not become. In the present invention, the pH during the reaction is 5.1-
5.8, preferably 5.2 to 5.4, more preferably about 5.3
It is desirable to keep the As shown in Table 1 and Figure 1, high values of both purity and yield are guaranteed when the pH is in the range of 5.1 to 5.8, and this is especially noticeable in the range of 5.2 to 5.4.
Its highest value is about 5.3. If the pH is too low or too high, the decomposition rate of 1,4-naphthoquinone will increase and the yield will decrease. This tendency holds true even for 1,4-naphthoquinone containing impurities. In the present invention, the reaction temperature is preferably 0 to 10°C, preferably 0 to 5°C. The invention generally operates as follows. A mixed solution of dimethyl sulfoxide (hereinafter abbreviated as DMSO) of disodium salt of 1,2-dicyano-1,2-dimercaptoethene and water was added to
The 1,4-
Add a mixed suspension of naphthoquinone, acetic acid and water,
Keep pH between 5.2 and 5.4. As the reaction progresses, the pH
increases, so add an acid, for example, an aqueous solution of acetic acid.
Keep PH between 5.2 and 5.4. In addition to acetic acid, carboxylic acids such as formic acid, benzoic acid, and phthalic acid, and inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid can also be used as acids for pH adjustment. The 1,4-naphthoquinone gradually dissolves into a homogeneous aqueous solution, and then gradually becomes a heterogeneous solution. 10 to 60 minutes after adding 1,4-naphthoquinone, usually 15 to 40 minutes, when hydrogen peroxide solution is added in an amount of 1 to 1.2 times the mole of 1,4-naphthoquinone, a blackish brown precipitate (DDAQ and its quinhydrone, which is an intermolecular compound with hydroquinone, which is a reduced form)
is precipitated. After 1 hour, separate the blackish brown precipitate,
The obtained precipitate was suspended in an aqueous solution of ferric chloride.
Light brown DDAQ by oxidation at 50-60℃
is obtained. Next, the present invention will be explained in detail with reference to Examples. Example 1 1.6g (31.3mmol) of sodium cyanide
2.5 g of carbon disulfide suspended in 7.8 g of DMSO
(32.8 mmol) is gradually added. Keep it at 30℃ for 1 hour, keep it at 40℃ for 1.5 hours, then add 20ml of water to bring it to 50℃. After keeping at that temperature for 1.5 hours,
Cooling. The liberated sulfur is filtered off, and the reddish brown liquid containing the disodium salt of 1,2-dicyano-1,2-dimercaptoethene is placed in a 100 ml four-necked flask and kept at 0-2°C. While stirring well,
2.33 g of 1,4-naphthoquinone (99.0% purity)
A suspension of 14.6 mmol (equivalent to 0.93 times the mole of disodium salt of 1,2-dicyano-1,2-dimercaptoethene) in a mixed solution of 20 ml of water and 1.0 g of acetic acid is added at once. Stir well until the pH reaches 5.3, and when the pH reaches 5.3, maintain it using an acetic acid aqueous solution. After 30 minutes, add 1.5 g (15.4 mmol) of hydrogen peroxide (35%) and 10 g of water in about 5 minutes.
Gradually add the aqueous solution with ml. As the pH increases, maintain it at 5.3 with an acetic acid aqueous solution. After 1 hour, the reaction temperature is gradually increased from 0-2°C to 10-15°C. At that time, keep the pH at 5.3.
After the reaction, the blackish brown precipitate is separated, the resulting precipitate is suspended in an aqueous solution in which 7.0 g (26.0 mmol) of ferric chloride is dissolved, and stirred well at 50° C. for 2 hours. The light brown solid obtained is separated, thoroughly washed with water, and then dried. 2,3-dicyano-1,4-dithia-9,10-
4.14 g (purity: 98.7%; yield: 95.8%) of anthraquinone was obtained. Example 2 The same method as in Example 1 was carried out except that the pH was varied from 3.8 to 5.8, and the results shown in Table 1 were obtained.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 shows the relationship between the yield of 2,3-dicyano-1,4-dithia-9,10-anthraquinone and the pH during the reaction. The vertical axis represents the production rate (%), and the horizontal axis represents the PH value.

Claims (1)

[Claims] 1. 1,4-naphthoquinone suspended in an aqueous medium and an alkali metal salt of 1,2-dicyano-1,2-dimercaptoethene are reacted at a pH of 5.2 to 5.4 in an aqueous medium. 2,3-dicyano-1,4-dithia-9, which is then treated with a dehydrogenating agent.
10-Production of anthraquinone. 2. The method according to claim 1, wherein the reaction temperature is 0 to 10°C.