JPH10316682A - Production of quinoxaline dithiocarbonate or its derivative - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and safely obtain the subject compound useful as an agrochemical, etc., in high yield, without using phosgene gas, by feacting quinoxaline-2,3-dithiol with triphosgene or diphosgene. SOLUTION: This quinoxaline-2,3-dithiocarbonate of formula II or derivative thereof is obtained by reacting a quinoxaline-2,3dithiol of formula I [R is a 1-4C alkyl, alkoxy, etc.; (n) is 0-4] or derivative thereof with a carbonylating agent selected from triphosgene and diphosgene. It is preferable that the quantity of the carbonylating agent is 0.34-5 molar times., for triphosgen, or 0.5-5 molar times., for diphosgen, that of the compound of formula I as the raw material. The above reaction is preferably conducted under basic conditions so as to scavenge hydrochloric acid produced as a by-product. The reaction temperature is preferably -78 to 50 deg.C. The compound of formula I can be easily obtained from a diaminobenzene in high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing quinoxaline-2,3-dithiocarbonate or a derivative thereof, which is useful as a crosslinker for agrochemicals or epoxy polymers.

[0002]

2. Description of the Related Art Conventionally, phosgene gas is generally used as a method for producing quinoxaline-2,3-dithiocarbonate or a derivative thereof. In fact, U.S. Pat.
Series of quinoxalines using phosgene gas
A method for producing a 2,3-dithiocarbonate derivative is described.

[0003]

However, phosgene gas has an allowable concentration of 0.1 ppm and is highly toxic. Therefore, a facility that performs a reaction using phosgene gas must take measures against gas leaks, and also must provide equipment related to safety measures in the event of a leak. In the method using phosgene gas in the above-mentioned US Pat. No. 3,141,886, the yield is 33 to 69%.
And satisfactory values have not been obtained. On the other hand, as a raw material, it is known that dimeric diphosgene or trimer triphosgene can be used as a substitute for phosgene. For example, 4-chloro-2-methylaniline is reacted with triphosgene to produce 4-chloro- The reaction yield for obtaining 2-methylphenylisocyanate is 68% (Angew. Chem., Int.
d. Engl., 1987, 26,894.), 4,5-dimethoxy-1,2
The reaction yield when reacting -bis (N-methylamino) benzene with triphosgene to obtain the corresponding cyclic urea is 34% (J. Am. Chem. Soc., 1992, 114, 774), and the yield is high. Was not enough.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that quinoxaline-2,3-dithio which is a compound extremely useful as a cross-linking agent for agricultural chemicals or epoxy polymers. When the carbonate or its derivative is obtained from quinoxaline-2,3-dithiol or its derivative, it can be easily, safely and efficiently produced by using diphosgene or triphosgene instead of phosgene gas as the carbonylating agent. Heading, the present invention has been completed.

That is, the present invention comprises reacting a quinoxaline-2,3-dithiol represented by the following formula (1) or a derivative thereof with a carbonylating agent selected from triphosgene and diphosgene: The method for producing quinoxaline-2,3-dithiocarbonate or a derivative thereof represented by the following formula:

Embedded image

Embedded image (R represents a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxy group, a nitro group, a carbamoyl group, a carboxyl group, an aminosulfonyl group, and a halogeno group;
Represents an integer. )

According to the present invention, by using a stoichiometric amount of triphosgene or diphosgene, the desired quinoxaline-2,3-dithiocarbonate or a derivative thereof can be obtained almost quantitatively without by-products. Therefore, it can be easily purified and can be said to be an industrially superior method. The highest yield obtained by the conventional method disclosed in U.S. Pat. No. 3,141,886 is 69%, and the amount of phosgene gas used in the synthesis appears to be quite excessive. These facts suggest the usefulness of the present invention.

Further, diphosgene and triphosgene are dimers and trimers of phosgene, respectively, and are trichloromethyl chloroformate and bis (trichloromethyl) carbonate. Although the toxicity of these compounds is not so different from that of phosgene gas, they are very stable unless exposed to moisture, have low vapor pressure, and are very easy to handle, so they are suitable as raw materials. In particular, triphosgene is a solid with a melting point of 81-83 ° C and is soluble in all organic solvents. In addition, there is no report that the substance decomposed at a temperature of 130 ° C. or lower, and the raw material is more preferable than phosgene.

[0008]

Embodiments of the present invention will be described in more detail. The starting material, quinoxaline-2,3-dithiol of the formula (1) or a derivative thereof can be easily produced from diaminobenzenes in a high yield by a known method. R of the substituent is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group,
t-butyl group, alkoxy group such as methoxy group, ethoxy group, isopropoxy group, nitro group, carbamoyl group such as dimethylaminocarbonyl group, diethylaminocarbonyl group, etc., carboxyl group, aminosulfonyl group such as dimethylaminosulfonyl group, diethylaminosulfonyl And a group selected from a halogeno group such as a chloro group and a bromo group. The number of substituents R can be from unsubstituted n = 0 to tetrasubstituted n = 4, and the position to which R is attached is not particularly specified.

Next, the amount of triphosgene or diphosgene used in the reaction will be described. In the case of triphosgene, it is preferably at least 0.3 mol, more preferably 0.34 to 5 mol, per mol of the raw material quinoxaline-2,3-dithiol or a derivative thereof. In the case of diphosgene, quinoxaline-2,3-dithiol or its derivative
It is preferably at least 0.5 times mol, particularly preferably 0.5 to 5 times mol. In any case below the lower limit, the raw material quinoxaline-2,3
-Dithiol or its derivative remains, and if it is more than the upper limit, the process becomes complicated such that excess triphosgene or diphosgene must be removed, which is not preferable in terms of economy.

When quinoxaline-2,3-dithiol or a derivative thereof is reacted with triphosgene or diphosgene, it is preferable to carry out the reaction under basic conditions in order to capture hydrochloric acid produced as a by-product. As the base used at this time, hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, calcium hydroxide, triethylamine, pyridine, diisopropylethylamine,
Examples include amine compounds such as N, N-dimethylaniline and diazabicycloundecene; carbonates such as sodium carbonate, potassium carbonate and calcium carbonate; and hydrogen carbonates such as potassium hydrogen carbonate and sodium hydrogen carbonate. When triphosgene is used, the amount of the base used at this time is preferably at least 3 times the molar amount of triphosgene. In the case of diphosgene, the amount of the base used is preferably at least 2 times the molar amount of diphosgene. When the amount of the base is less than the lower limit, highly toxic triphosgene or diphosgene remains, and in some cases, quinoxaline-2,3-dithiol or a derivative thereof as a raw material also remains.

The solvent used in the reaction of the present invention is not particularly restricted but includes water, alcohols such as methyl alcohol and ethyl alcohol, aromatic hydrocarbons such as benzene and toluene, aliphatic hydrocarbons such as hexane, and the like. Chlorine solvents such as chloroform and 1,2-dichloroethane, ether solvents such as dioxane, tetrahydrofuran and t-butyl methyl ether, N, N-dimethylformamide (DM
F), aprotic polar solvents such as dimethyl sulfoxide, ketone solvents such as acetone and methyl isobutyl ketone, ester solvents such as ethyl acetate, tertiary amines such as pyridine, triethylamine and diisopropylethylamine, and mixed solvents thereof. Can be used.

During the reaction, the concentration of the starting material quinoxaline-2,3-dithiol or its derivative is not specified.
The reaction temperature is preferably low, but the reaction proceeds and completes without any problem at -78 to 50 ° C. At 80 ° C. or higher, care must be taken because the yield decreases due to the formation of a dimer of quinoxaline-2,3-dithiol or a derivative thereof.

[0013]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Preparation of 6-methylquinoxaline-2,3-dithiocarbonate 6 g of 6-methylquinoxaline-2,3-dithiol (0.048 mol
l) was dissolved in 100 ml of a 5% aqueous KOH solution, and a solution of 5.6 g (0.019 mol) of triphosgene in dioxane was added dropwise with stirring under ice cooling. After completion of the reaction, the reaction solution was added to 100 ml of water, and the precipitated crystals were washed with water to obtain 10.8 g of a yellow solid. 96% yield. 170-172 ° C.

Example 2 Preparation of 5-methylquinoxaline-2,3-dithiocarbonate 10 g of 5-methylquinoxaline-2,3-dithiol (0.048 mol
l) is dissolved in 100 ml of dioxane, and triethylamine 1
0.7 g (0.106 mol) was added. Under ice cooling, 5.6 g (0.019 mol) of triphosgene was added with stirring. After completion of the reaction, the precipitated triethylamine hydrochloride was filtered off and concentrated. Add ethyl acetate, wash with water, and concentrate to a yellow solid.
10.6 g were obtained. 94% yield. 136-137 ° C.

Example 3 Preparation of 5,7-dimethylquinoxaline-2,3-dithiocarbonate 5,7-dimethylquinoxaline-2,3-dithiol 5 g (0.022
mol) in 50 ml of DMF and 4.8 g of triethylamine.
(0.047 mol) was added. Under ice cooling and stirring, 2.5 g (12.8 mmol) of diphosgene was added. By the same operation as in Example 2, 4.9 g of a yellow solid was obtained. 90% yield. Melting point 177-180 [deg.] C.

Example 4 Preparation of 6,7-dimethylquinoxaline-2,3-dithiocarbonate 5 g of 6,7-dimethylquinoxaline-2,3-dithiol (0.022
mol) was dissolved in 50 ml of DMF, and 6.1 g (0.047 mol) of diisopropylethylamine was added. Under ice cooling, triphosgene 2.5 g (8.5 mmol) was added with stirring. By the same operation as in Example 2, 5.0 g of a yellow solid was obtained. Yield 92%. 206-208 ° C.

Example 5 Preparation of quinoxaline-2,3-dithiocarbonate 10 g (0.053 mol) of quinoxaline-2,3-dithiol was dissolved in 100 ml of dioxane, and 11.8 g of triethylamine was dissolved.
(0.117 mol) was added. 6.5 g (0.021 mol) of triphosgene was added with stirring under ice cooling. By the same operation as in Example 2, 11.1 g of a yellow solid was obtained. 95% yield. 183-185 ° C.

Example 6 Preparation of 6-butylquinoxaline-2,3-dithiocarbonate 5 g of 6-butylquinoxaline-2,3-dithiol (0.019 mo
l) in 50 ml of dioxane and triethylamine 4.
2 g (0.042 mol) were added. Under ice cooling, triphosgene 2.2 g (7.5 mmol) was added with stirring. By the same operation as in Example 2, 5.0 g of a yellow solid was obtained. Yield 92%.
165-168 ° C.

Example 7 Preparation of 6-methoxyquinoxaline-2,3-dithiocarbonate 5 g of 6-methoxyquinoxaline-2,3-dithiol (0.022 m
ol) was dissolved in 50 ml of pyridine, and 2.5 g (8.5 mmol) of triphosgene was added with stirring under ice cooling. Example 2
By the same operation as described above, 5.1 g of a yellow solid was obtained. Yield 93
%. 166-168 ° C.

Example 8 Preparation of 5,7-dichloroquinoxaline-2,3-dithiocarbonate 5,7-dichloroquinoxaline-2,3-dithiol 5 g (0.020
mol) in 50 ml of DMF and 4.4 g of triethylamine.
(0.043 mol) was added. Under ice cooling, 2.3 g (7.8 mmol) of triphosgene was added with stirring. By the same operation as in Example 2, 5.0 g of a yellow solid was obtained. 90% yield. Melting point 191-192 [deg.] C.

Example 9 Preparation of 6-nitroquinoxaline-2,3-dithiocarbonate 5 g of 6-nitroquinoxaline-2,3-dithiol (0.021 mo
l) in 50 ml of DMF and 4.6 g of triethylamine
(0.045 mol) was added. Under ice cooling and stirring, 2.4 g (8.2 mmol) of triphosgene was added. By the same operation as in Example 2, 5.0 g of a yellow solid was obtained. Yield 89%. Melting point
188-189 ° C.

Example 10 6- (N, N-Dimethylaminosulfonyl) quinoxaline-
Preparation of 2,3-dithiocarbonate 6- (N, N-dimethylaminosulfonyl) quinoxaline-
5 g (0.017 mol) of 2,3-dithiol was dissolved in 50 ml of DMF, and 3.8 g (0.038 mol) of triethylamine was added. Under ice cooling, triphosgene 2 g (6.8 mmol) was added with stirring. By the same operation as in Example 2, 4.6 g of a yellow solid
I got 82% yield. 183-184 ° C.

Example 11 6- (N, N-Dimethylcarbamoyl) quinoxaline-2,3-
Preparation of dithiocarbonate 6- (N, N-dimethylcarbamoyl) quinoxaline-2,3-
Dissolve 5 g (0.019 mol) of dithiol in 50 ml of DMF,
4.2 g (0.042 mol) of triethylamine were added. Under ice cooling, triphosgene 2.2 g (7.5 mmol) was added with stirring. By the same operation as in Example 2, 4.7 g of a yellow solid
I got 85% yield. 173-175 ° C.

Example 12 Preparation of 6-carboxyquinoxaline-2,3-dithiocarbonate 5 g of 6-carboxyquinoxaline-2,3-dithiol (0.021
was dissolved in 100 ml of a 5% aqueous KOH solution, and a dioxane solution of 2.4 g (8.2 mmol) of triphosgene was added dropwise with stirring under ice-cooling. By the same operation as in Example 1, 4.5 g of a yellow solid was obtained. Yield 81%. Melting point 300 ° C or higher.

[0026]

According to the present invention, quinoxaline-2,3-dithiocarbonate or a derivative thereof can be produced safely and in a high yield without generating phosgene gas by an easy method.

Claims (3)

[Claims] 1. A quinoxaline represented by the following formula (1):
Quinoxaline-2,3 represented by the following formula (2), wherein 2,3-dithiol or a derivative thereof is reacted with a carbonylating agent selected from triphosgene and diphosgene.
-A method for producing dithiocarbonate or a derivative thereof. Embedded image Embedded image (R represents a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxy group, a nitro group, a carbamoyl group, a carboxyl group, an aminosulfonyl group, and a halogeno group;
Represents an integer. ) 2. The method for producing quinoxaline-2,3-dithiocarbonate or a derivative thereof according to claim 1, wherein the carbonylating agent is triphosgene. 3. The method for producing quinoxaline-2,3-dithiocarbonate or a derivative thereof according to claim 1, wherein R in Formula 1 is a methyl group at the 6-position.