SU1039168A1 - Method of producing 5-oxybenz-2,1,3-thiadiazol - Google Patents

Abstract

METHOD FOR OBTAINING 5-OXIBEN30-2, 1,3-TIADIAZOLA by hydrolysis of 5-aminobenzo-2, 1.3-thiadiazole in the presence of an aqueous solution of sodium salt of sulfur-containing acid while boiling the reaction mixture, characterized in that, in order to increase the yield of the target product and simplify technology of the process, sodium pyrosulfite is used as the sodium salt of sulfur-containing acid, and the process is carried out at a molar ratio between 5-aminobenzo-2,1,3 - thiadiazole and sodium pyrosulfite 1: 3.0-3.5. "5-hydroxybenzo-2,1,3-thiadiazole is separated upon decomposition of the diazonium salt from 5-aminobenzo-2, 1,3-thiadiazole. The disadvantage of this method is low.

Description

I am working on it. It should also be noted that sodium bisulfite exists only in an aqueous solution, the concentration of the solution varies, since sodium pyrosulfum crystallizes out of the solution, so sodium bisulfite solution should be prepared before each synthesis, passing hydrogen sulfide anhydride into an aqueous solution of sodium bicarbonate, which requires extra time. The aim of the invention is to increase the yield of 5-hydroxybenzo-2.1,3-thiadiazole.

This goal is achieved by the method of obtaining 5-hydroxybenzo-2,1,3-thiadiazole, which consists in the interaction of 5-aminobenzo-2,1,3-thiadiazole and sodium pyrosulfite aqueous solution at boiling and the molar ratio between 5-aminobenzo-2 , 1,3-thiadiazole and sodium pyrosulfite 1: 3-3.5.

The use of sodium pyrosulfite is due to the fact that it is cheap, readily available, commercially available, convenient during transportation and storage, and soluble in water in quantities sufficient to guide the process. The selected ratio between 5-aminobenzo-2,1,3-thiadiazole and sodium pyrosulfite provides a high (76-80%) yield of 5-hydroxybenzo-2,1,3-thiadiazole, which is 3035% higher than in the known method, and due to the fact that at the specified ratio between the starting materials, the by-product yield is significantly reduced. .

In addition, boiling of 5-aminobenzo2, 1.3-thiadiazole with an aqueous solution of sodium pyrosulfite lasts 10 hours (and not 15-20 hours, as when boiling with sodium bisulfite). .

Failure to synthesize sodium bisulfite also reduces the time required for the specified synthesis.

The synthesis is carried out according to the following scheme:

H, Nv

EXAMPLE 1: A mixture of 6.25 g (0.041 mol) of 5-aminobenzo-2,1,3-thiadiazole, 150 ml of water and 27.5 g (0.144 mol) of sodium pyrosulfite is boiled for 10 hours, cooled, filtered and the precipitate on the filter e (by-product) is washed with 37.5 ml of water. 125 ml of 10% sodium hydroxide is added to the filtrate and the reaction mixture is boiled until ammonia is completely removed. The mixture is then cooled and a solution of sulfuric acid (75 ml of concentrated sulfuric acid and 225 ml of water) is added to it. The reaction mass is boiled until the sulfur dioxide is removed and not cooled.

0 filtered. The precipitation is filtered off, washed with water, dried. 4.5 g (72.0%) of 5-hydroxybenzo-2,1.3-thiadiazole are obtained, m.p. 156-157 ° C (out of water), non-depressing melting point with 5-hydroxy 5 benzo-2,1,3-thiadiazole prepared by a known method. Rf 0.75 (Silufol, UV 254, acetone-chloroform-hexane system, 2: 1: 2, spots are shown in the ultraviolet), Rf coincides with Rf of substances obtained by a known method.

The filtrate is extracted six times with chloroform, the chloroform extracts are filtered and the solvent is removed. Another 0.5 g (80%) of 5-hydroxybenzo-2,1,3-thiadi azole is obtained, m.p. 156-157 ° С (out of water), non-depressant with previously precipitated sediment. Ri is 0.75 (Silufol, UV-254, acetone-chloroform-hexane system, 2: 1: 2, the spots appear in the ultraviolet), Rf coincides with Rf substances,

0 obtained by a known method, and with a previously selected sediment. The total yield of 5-hydroxybenzo-2, 1,3-thiadiazole 5 g (80%).

EXAMPLE 2 A mixture of 25 g (6.165 mol) of 5-aminobenzo-2,1,3-thiadiazole, 600 ml of water and 100 g (0.525 mol) of sodium pyrosulfite is boiled for 10 h, and the filter is cooled to filter (by-product) is washed with 150 ml of water. To the filtrate is added 500 ml of 10% sodium hydroxide solution and

0 The reaction mass is boiled until ammonia is completely removed. The mixture is then cooled and a solution of 300 ml of concentrated: sulfuric acid and 900 ml of water is added to it. The reaction mass is boiled to

5 remove sulfur gas and do not cool, filter. The precipitate is filtered off, washed with water and dried. 18 g (72.0%) of 5-hydroxybenzo-2,1,3-thiadiazole are obtained. m.p. 156-157 ° C (out of water), non-depressing melting point with 5-hydroxybenzo-2 .1,3-thiadiazole, prepared by a known method. Rf 0.75 (Silufol, UV254, system, acetone-chloroform-hexane. 2: 1: 2, spots are developed in the ultraviolet). Rf coincides with Rf of substances obtained by the known method in example 1.

The filtrate is extracted six times with chloroform, the chloroform extracts are filtered and the solvent is removed. Another 1.8 g (7.2%) of 5-oxbenzo-2,1,3-thiadiazole is obtained, m.p. 156-157 ° С (out of water), not giving a depression with a previously separated sediment. Rf 0.75 (Silufol, UF-254. Acetone-chlorof99-hexane system. 2: 1: 2, the spots appear in the ultraviolet), Rf coincides with the Rf substances obtained by a known method, and with the previously isolated precipitate. The total yield of 5-hydroxybenzo-2, 1.3-thiadiazole is 19.8 g (79.2%).

Note 3. A mixture of 6.25 g (0.041 mol) of 5-aminobenzo-2,1.3-thiadiazole. 150 ml of water and 23.5 g (0.123 mol) of sodium pyrosulfite are boiled for 10 hours, cooled, filtered, and the filter cake is washed with 37.5 ml of water. Filtrate Is treated successively with a 10% solution of sodium hydroxide and diluted sulfuric acid, as in Example 1. 4.4 g (70.4%) of 5-hydroxybenzo2, 1.3-thiadiazole are obtained. m.p. 156-157 ° C (out of water), non-depressive depressing temperature with 5-hydroxybenzo-2,1,3-thiadiazole as obtained by a known method. Rf 0.75 (Silufol, UV-254. Acetone-chloroform-hexane system. 2: 1: 2, the spots are shown in the ultraviolet). Rf coincides with Rf substances.

obtained by a known method and in examples 1 and 2.

The filtrate is six times / extracted with chloroform, chloroform extracts

filtered and the solvent removed. Another 0.4 g (6.4%) of 5-hydroxybenzo-2,1.3-thiadiazole is obtained, m.p. 156-157 ° C (out of water), non-depressant with previously excreted sediment. Rf 0.75 (Silufol, UV-254, acetone-chloroform-hexane system. 2: 1: 2, spots developed in the ultraviolet). Rf coincides with Rf of the substances obtained by the known method and in examples 1 and 2. The total yield of 5-hydroxybenzo-2,1,3-thiadiazole is 4.8 g (76.8%).

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The proposed method for the preparation of 5-hydroxybenzo-2, 1,3-thiadiazole is simple, reliable, allows to obtain the target product of high purity with a yield of 76-80%. which is 30-35% higher than in the known method, to intensify the process by eliminating the synthesis of sodium bisulfite and reducing the duration of the I stage of the reaction in question.

Claims (1)

(54X57) METHOD FOR PRODUCING 5-OXIBEN30-2,1,3-THIADIAZOLE by hydrolysis of 5-aminobenzo-2,1,3-thiadiazole in the presence of an aqueous solution of sodium salt of sulfur-containing acid, characterized by the fact that the reaction mixture is boiled. that, in order to increase the yield of the target product and simplify the process technology, sodium pyrosulfite is used as the sodium salt of sulfur-containing acid and the process is carried out at a molar ratio between 5-aminobenzo-2,1.3-.tmadiazole and sodium pyrosulfite 1: 3.0-3, 5.