Method for synthesizing 2-methylthiosemicarbazide

Abstract

The invention discloses a method for synthesizing 2-methylthiosemicarbazide. The method comprises the following steps: adding ammonium thiocyanate and a methylhydrazine aqueous solution into a four-neck flask according to a certain ratio, heating the materials under negative pressure, carrying out refluxing at 60-70 DEG C, collecting ammonia water at 80 DEG C according to a ratio of 8: 1, raisingthe temperature to 100 to 102 DEG C, dropwise adding a certain amount of methylbenzene into the four-neck flask, returning methylbenzene into the four-neck flask by a return pipe, adding the ammonia water into a middle flask, continuously heating the materials to 108-110 DEG C after dropwise adding, keeping the temperature for 2 hours, distilling methylbenzene under reduced pressure, fully evaporating methylbenzene in the four-neck flask, adding a certain amount of purified water into the four-neck flask, carrying out refining, carrying out heating to 90 DEG C, keeping the temperature for 0.5hour, carrying out cooling to 30 DEG C, and performing suction filtration and drying to obtain 2-methylthiosemicarbazide. By adopting the method disclosed by the invention, the conversion rate of methylhydrazine is high, and the yield of 2-methylthiosemicarbazide is as high as 95% or above and is improved by 6-8% compared with that of a traditional process.

Description

technical field [0001] The invention belongs to the technical field of medicine preparation, and in particular relates to a method for synthesizing 2-methylthiosemicarbazide. Background technique [0002] 2-Methylthiosemicarbazide is an important intermediate of ceftriaxone. With the development of the production of cephalosporin antibiotics in China, there is a great demand for the triazine ring in the market. At present, the synthesis process of this product is the reaction of methylhydrazine and thiocyanate, and the product is obtained in one step, and the route is simple. However, methylhydrazine is a highly toxic compound, its chemical properties are lively, the production process is relatively complicated, transportation is difficult, and the price is high, resulting in higher production costs and lower profits for manufacturers who synthesize methylthiosemicarbazide in one step. [0003] In the existing technology, toluene is added to the reaction system at one time,...

AI Technical Summary

Problems solved by technology

However, methylhydrazine is a highly toxic compound, its chemical properties are active, the production process is relatively complicated, transportation is difficult, and the price is high, resulting in higher production costs and lower profits for manufacturers who synthesize methylthiosemicarbazide in one step.

[0003] In the existing technology, toluene is added to the reaction system at one time, and the toluene and water are instantaneously azeotroped, and the temperature suddenly changes, and the content of methylhydrazine in the ammonia water brought out increases, resulting in loss of raw materials, reducing the conversion rate of methylhydrazine, and at the same time Ammonium thiocyanate is caused to be supersaturated, and some solids are precipitated, which is not conducive to the positive reaction, resulting in a very low yield of 2-methylthiosemicarbazide

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