Method for preparing 2-hydrazinobenzoic acid hydrochloride

Abstract

The invention relates to a method for preparing 2-carboxyl phenyl hydrazine, which comprises the following steps: (1) 2-aminobenzoic acid is used as starting material, and benzene diazonium chloride is prepared through diazo reaction; (2) benzene diazonium chloride obtained from the step (1) is utilized to further prepare reduction products through the reduction reaction under the action of a reducing agent; (3) the reduction products obtained from the step (2) undergoes the hydrolysis reaction under the action of hydrochloric acid to generate 2-carboxyl phenyl hydrazine, more particularly, sodium metabisulfite is used as the reducing agent in the reduction reaction in the step (2), and the reaction is performed under the condition that the temperature is 15 to 25 DEG C and the pH value is 7 to 9. The method has higher yield, and can shorten the production period and reduce the manufacture cost at the same time.

Description

technical field [0001] The invention relates to a preparation method of phenylhydrazine hydrochloride, in particular to a preparation method of 2-carboxyphenylhydrazine hydrochloride. Background technique [0002] 2-Carboxylphenylhydrazine hydrochloride is an important intermediate, which is mainly used to prepare indole and pyrazolone derivatives, and can also be used to prepare other chemical products. The traditional preparation process of 2-carboxyphenylhydrazine hydrochloride includes a two-step process of diazotization of aniline and reduction of benzenediazonium chloride, wherein the diazotization of aniline is mostly in hydrochloric acid medium, under the condition of pH equal to 2, at 0~ Add sodium nitrite to react at a low temperature of 5°C to generate benzenediazonium chloride. Sodium sulfite and sodium bisulfite are generally used as reducing agents for the reduction of diazobenzene chloride, and ammonium bisulfite and ammonium hydroxide are also used as reduci...

AI Technical Summary

Problems solved by technology

The synthetic method of this traditional phenylhydrazine hydrochloride, the reaction time is as long as 3~4 hours, and the yield is only between 63-72%. In addition, when the reducing agent used is sodium sulfite and sodium bisulfite, the cost Higher, increase production cost; and when ammonium bisulfite and ammonium hydroxide are used as reducing agents, because they are liquid, it is not easy to transport and store

In addition, reduction kettle, pressure filter and acid analysis kettle are used in this process, which requires a lot of equipment and large investment.