JPH1180133A - Production of s,s-(6-methylquinoxaline-2, 3-diyl) dithiocarbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing the subject compound, by which the compound useful as an agrochemical or a vulcanizing agent for a polymer is economically, readily and safely produced in high yield by forming dimercaptomethylquinoxaline into an alkali metal salt, and reacting the alkali metal salt with phenylchloroformates in the presence of a phase transfer catalyst. SOLUTION: 2,3-Dimercapto-6-methylquinoxaline is reacted with a hydroxide or the like of an alkali metal in water or an alcohol solvent, and an organic solvent such as an aromatic hydrocarbons such as toluene and xylene is added to the reaction mixture. The reaction mixture with the organic solvent is subjected to an azeotropic dehydration and a solvent replacement to form an alkali salt, and the alkali salt is reacted with a compound of the formula (R is H, a halogen, an alkyl or the like) preferably in an amount of 1.0-4.0 molar times in the presence of a phase transfer catalyst (e.g. a quarternary ammonium salt or a pyridinium salt) in an amount of 1-5 mol.% at 0-150 deg.C for 0.5-10 hr to provide the objective compound in the method for producing S,S-(6- methylquinoxaline-2,3-diyl) dithiocarbonate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing S, S- (6-methylquinoxaline-2,3-diyl) dithiocarbonate which is useful as a vulcanizing agent for agricultural chemicals or polymers.

[0002]

2. Description of the Related Art S, S- (6-methylquinoxaline-
(2,3-diyl) dithiocarbonate is a compound widely used as an agricultural chemical, and also a useful compound as a vulcanizing agent for polymers.

The following processes are known for producing this compound. For example, US Pat.
No. 3 describes that the compound can be synthesized from the reaction of 2,3-dimercapto-6-methylquinoxaline with phosgene in the presence of sodium hydroxide as an acid acceptor.

[0004] As an improved method thereof, US Pat.
No. 486 describes a production method in which 2,3-dimercapto-6-methylquinoxaline is reacted with phosgene under anhydrous conditions while removing generated hydrogen chloride as a gas to obtain a high yield.

However, all of these methods require the use of highly toxic phosgene, which is not always satisfactory.

[0006]

An object of the present invention is to solve the above-mentioned problems, that is, a novel S, S- (6-methylquinoxaline-2,3) which does not use highly toxic phosgene.
-Diyl) dithiocarbonate.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above-mentioned object, and as a result, after converting 2,3-dimercapto-6-methylquinoxaline into an alkali metal salt, it was inexpensive. S, S- (6-methylquinoxaline-2,3-diyl) dithiocarbonate can be obtained economically, easily and safely in high yield by reacting phenylchloroformates which are easily available. And completed the present invention.

That is, the present invention relates to 2,3-dimercapto-6
-After converting methylquinoxaline into an alkali metal salt, the general formula

Embedded image (Wherein, R represents hydrogen, halogen, alkyl, alkoxy and nitro group) in the presence of a phase transfer catalyst in the presence of S, S- (6
-Methylquinoxaline-2,3-diyl) dithiocarbonate.

The alkali metal salt of 2,3-dimercapto-6-methylquinoxaline can be easily synthesized by a general formulation. This alkali metal salt may be used as an aqueous solution, as a powder, or as a slurry of an organic solvent in the reaction with phenylchloroformates. Usually, 2,3-dimercapto-
6-methylquinoxaline is reacted with an alkali metal or alkaline earth metal hydroxide and carbonate in water or an alcohol solvent such as methanol, and then aromatic hydrocarbons such as toluene and xylene, or methyl isobutyl ketone and the like. An organic solvent such as a ketone or a halogenated hydrocarbon such as 1,2-dichloroethane is added, and azeotropic dehydration or solvent replacement is performed to obtain a slurry of an alkali metal salt. This product may be filtered and isolated, but can be directly used for the reaction with phenylchloroformates.

As the alkali metal or alkaline earth metal hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide and the like are used. As the carbonate, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, calcium carbonate and the like are used.

Examples of the phase transfer catalyst include quaternary ammonium salts, pyridinium salts, quaternary phosphonium salts and the like. More specifically, tetra-n-butylammonium chloride, trioctylmethylammonium chloride, N- n-octylpyridinium, tetrabutylphosphonium chloride and the like. The amount of the phase transfer catalyst to be used is generally 0.1 to 20 mol%, preferably about 1 to 5 mol%, based on 2,3-dimercapto-6-methylquinoxaline.

In the reaction with phenylchloroformates, water, an organic solvent and a mixed solvent thereof are used as a reaction solvent. Examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene and xylene, halogenated hydrocarbons such as 1,2-dichloroethane and dichloromethane, ethers such as diethyl ether, dioxane and tetrahydrofuran, acetone, methyl isobutyl ketone and the like. And polar solvents such as dimethyl sulfoxide, N, N-dimethylformamide, and acetonitrile.

The amount of phenyl chloroformate used is as follows:
It is in the range of 1.0 to 4.0 mole times with respect to 2,3-dimercapto-6-methylquinoxaline.

[0014] The reaction temperature is usually in the range of -30 to 200 ° C, preferably 0 to 150 ° C. The reaction time is affected by the reaction temperature and cannot always be specified.
The range is 0 hours. The reaction is usually carried out by dropping phenylchloroformates, but the reverse is also possible or simultaneous dropping is also possible.

The desired S, S- from the reaction mixture
The removal of (6-methylquinoxaline-2,3-diyl) dithiocarbonate was performed by filtration, washing, recrystallization,
Or by a common operation such as solvent distillation and recrystallization,
It can be easily isolated and purified.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Example 1 Sodium hydroxide 11.52 was added to methanol 100 ml.
g was dissolved and 2,3-dimercapto-6-methylquinoxaline (30.0 g) was added thereto, followed by stirring at room temperature for 1 hour. Subsequently, 300 ml of toluene was added thereto, and the mixture was concentrated and methanol was completely distilled off, whereby a toluene slurry of sodium salt of 2,3-dimercapto-6-methylquinoxaline was obtained. After cooling, 2.32 g of tetra-n-butylammonium bromide was added, and a solution of 45.07 g of phenylchloroformate in 30 ml of toluene was added at 45 ° C.
In minutes. Thereafter, the mixture was stirred at 45 ° C. for 3 hours.
After the completion of the reaction, the inorganic salt generated at 80 ° C. was filtered while hot, and toluene was distilled off. 130 ml of toluene was added to the residue and dissolved by heating.
Then, the mixture was stirred at room temperature for 2 hours. After further cooling to −10 ° C., stirring for 1 hour, filtering, washing with 60 ml of isopropyl alcohol, drying and 31.27 g of S, S
-(6-Methylquinoxaline-2,3-diyl) dithiocarbonate was obtained. 2,3-dimercapto-6
The isolation yield for methylquinoxaline was 92.8%. Purity analysis of this product by gas chromatography revealed that the purity was 99.5%.

Example 2 In place of the phenyl chloroformate used in Example 1, p
The reaction and after-treatment were carried out in the same manner as in Example 1 except that 58.03 g of -nitrophenyl chloroformate was used, and 29.5 g of S, S- (6-methylquinoxaline-
2,3-Diyl) dithiocarbonate was obtained. The yield was 87.5% and the purity was 96.5%.

Example 3 3.84 g of sodium hydroxide was dissolved in 50 ml of water, and 2,3-dimercapto-6-methylquinoxaline 1 was added thereto.
0.0 g was added and stirred at room temperature for 1 hour. Then, 100 ml of toluene was added, and azeotropic dehydration was performed. After cooling, 0.77 g of tetra-n-butylammonium bromide was added, and phenyl chloroformate 1 was added at 60 to 65 ° C.
5.0 g of a 10 ml solution was added dropwise over 30 minutes. Thereafter, the mixture was stirred at 60 ° C. for 3 hours, and after completion of the reaction, hot filtration was performed at 80 ° C. to remove generated inorganic salts. After distilling off toluene, 230 ml of acetone was added, followed by stirring at room temperature for 2 hours. After stirring at −10 ° C. for 1 hour, the mixture was filtered, washed with 10 ml of acetone, dried, and dried with 9.7 g of S, S-
(6-Methylquinoxaline-2,3-diyl) dithiocarbonate was obtained. Yield 86.4%, purity 9
It was 8.6%.

[0020]

According to the production method of the present invention, S, S- (6
-Methylquinoxaline-2,3-diyl) dithiocarbonate can be produced economically, easily, and safely in a high yield.

Claims (1)

[Claims] 1. After converting 2,3-dimercapto-6-methylquinoxaline into an alkali metal salt, the compound has the general formula: (Wherein, R represents hydrogen, halogen, alkyl, alkoxy and nitro group) in the presence of a phase transfer catalyst in the presence of S, S- (6
-Methylquinoxaline-2,3-diyl) dithiocarbonate production process.