Preparation of 3-bromophenylhydrazine hydrochloride_Kain Industrial Additive

Background and overview^[1]

As an important organic synthesis intermediate, 3-bromophenylhydrazine hydrochloride is widely used in the pharmaceutical manufacturing industry and has broad market prospects.

Preparation^[1]

The product produced by the existing preparation method of 3-bromophenylhydrazine hydrochloride has high impurity content, low purity, poor stability, and small output, which cannot meet the needs of the market. CN201310280009.8 provides a preparation method of 3-bromophenylhydrazine hydrochloride with high purity, large output and good stability. Adopt the following technical solutions:

A preparation method of 3-bromophenylhydrazine hydrochloride, the steps are as follows:

⑴ Diazotization: Mix 3-bromoaniline and 37% concentrated hydrochloric acid and cool to 0~5°C. Add 35% sodium nitrite aqueous solution while stirring, keep the temperature between 0~5°C and react for 1~ 1.5 hours.

⑵Reduction: Add 37% concentrated hydrochloric acid, water and zinc powder to the reaction solution, keep the temperature between 15~20℃ until the reaction is complete, the reaction solution turns off-white, then add 20~30% sodium hydroxide The solution was adjusted to a pH of 10 and kept at 5°C for 1 to 2 hours to precipitate crystals and filter to obtain crude 3-bromophenylhydrazine.

⑶Purification: Dissolve crude 3-bromophenylhydrazine in water, heat to 60°C to completely dissolve, then add an appropriate amount of activated carbon for decolorization for 20 minutes, hot filter to obtain a colorless filtrate, incubate at 5°C for 1 to 2 hours, and precipitate Crystals were filtered to obtain pure 3-bromophenylhydrazine.

⑷Salt formation: Dissolve pure 3-bromophenylhydrazine in 37% hydrochloric acid, stir at 60-70°C until the reaction solution precipitates and crystallize, cool to 20°C, filter, rinse the filter cake with acetone, and dry Finally, the finished product of 3-bromophenylhydrazine hydrochloride is obtained.

Wherein, the weight and volume ratio of 3-bromoaniline and concentrated hydrochloric acid in step (1) is 1:3, g/ml; the weight ratio of 3-bromoaniline and pure sodium nitrite in the sodium nitrite aqueous solution is 11:5. The volume ratio of concentrated hydrochloric acid to water in step (2) is 1:1, and the weight to volume ratio of zinc powder to concentrated hydrochloric acid is 4:15-16, g/ml. The weight ratio of the crude 3-bromophenylhydrazine and water described in step (3) is 1:20. The weight-to-volume ratio of pure 3-bromophenylhydrazine and hydrochloric acid described in step (4) is 19:10, g/ml.