55933-94-3

The invention discloses a method for synthesizing 2, 3, 5-trichloropyridine. The method mainly comprises: (1) synthesis of 2, 3, 5-trichloro-6-hydrated hydrazinyl pyridine: adding hydrazine hydrate and a reaction solvent into 2, 3, 5, 6-tetrachloropyridine as a raw material, carrying out a reaction process at a certain temperature for some time and carrying out treatment to obtain 2, 3, 5-trichloro-6-hydrated hydrazinyl pyridine, and (2) reaction of 2, 3, 5-trichloro-6-hydrated hydrazinyl pyridine and a sodium hypochlorite aqueous solution in an alkaline environment at a certain temperature for a certain period of time, then treatment and reduced pressure distillation. The method has the advantages of low reaction raw material price, no high toxic, no irritation, small three waste amount,environmentally friendly processes, relatively thorough reaction, simple process control and high product yield.

The invention discloses a preparation method of 2,3,5-trichloropyridine and aims to solve the problems that the production cost is high and a large quantity of sodium chlorate solutions are required to be consumed in existing patents. In the method, Water is taken as a solvent, sodium carbonate is taken as an acid-binding agent, butanol is taken as a catalysis aid, 2,3,4,5-tetrachloropyridine anda proper amount of hydrazine hydrate are subjected to a refluxing reaction at 90-95 DEG C, and trichloropyridine hydrazine is produced; trichloropyridine hydrazine is not separated and is directly oxidized by 30% hydrogen peroxide under the action of 5% sodium hydroxide and a phase transfer catalyst (the phase transfer catalyst can be benzyl triethyl ammonium chloride, beta-cyclodextrin and tetrabutylammonium bromide, preferably, benzyl triethyl ammonium chloride), and 2,3,5-trichloropyridine is obtained. 2,3,5-trichloropyridine is prepared with a one-pot method, the reaction procedure is concise, and industrialization is facilitated; besides, the water is taken as the solvent, hydrogen peroxide is taken as an oxidizing agent, the preparation process is green and environmentally friendly,the problems of consumption during recovery and excessive consumption of sodium chlorate are effectively solved, and the preparation method has remarkable progressive significance.