Preparation method of 3-bromo-4-hydroxybenzaldehyde

Abstract

The invention discloses a preparation method of 3-bromo-4-hydroxybenzaldehyde. The preparation method comprises the following steps: (1) carrying out a bromination reaction on p-hydroxybenzene methylal and bromine to obtain 3-bromo-4-hydroxybenzene methylal; and (2) carrying out a hydrolysis reaction on the 3-bromo-4-hydroxybenzene methylal obtained in the step (1), and carrying out post-treatmentafter the reaction is finished to obtain the 3-bromo-4-hydroxybenzaldehyde. According to the preparation method, aldehyde is replaced with acetal for the bromination reaction, so that generation of adibromo product is effectively avoided, the yield and purity of a monobromo product are improved, and industrialization is facilitated.

Description

technical field [0001] The invention belongs to the field of fine chemicals, in particular to a preparation method of 3-bromo-4-hydroxybenzaldehyde. Background technique [0002] 3-Bromo-4-hydroxybenzaldehyde (hereinafter referred to as monobromoaldehyde) is an important chemical raw material and an important intermediate for the synthesis of vanillin and trimethoprim. In the existing synthesis method of vanillin, p-hydroxybenzaldehyde is generally used as a raw material, and bromine is added to brominate it. After the reaction is completed, the solvent is recovered under reduced pressure, and the raffinate is recrystallized in hot water for separation to obtain monobromoaldehyde. [0003] The Chinese patent application whose publication number is CN 1406918A discloses a preparation method of 3-bromo-4-hydroxybenzaldehyde. The preparation method uses p-hydroxybenzaldehyde as a starting material and methyl chloride solvent as a reaction solvent, and then adds A certain amoun...

AI Technical Summary

Problems solved by technology

[0004] Qiu Guorong reported a preparation method of 3-bromo-4-hydroxybenzaldehyde (Journal of Weifang University, Volume 3, No. 4, page 26). Compared with the above preparation method, no cosolvent ethyl acetate is used, other The conditions are basically similar, and the reported yield is 94.5%, but the product has only tested the melting point, and the purity has not been tested by HPLC. Therefore, it is difficult to determine the impurities contained

[0005] This shows that, when adopting said method to prepare monobromoaldehyde, there are following disadvantages: (1) the solubility of p-hydroxybenzaldehyde in halogenated alkanes is low, the required solvent amount is large, and the recovery energy consumption is high; (2) p-hydroxybenzaldehyde The hydroxyl group in formaldehyde is the ortho-para positioning group, and the aldehyde is the meta-positioning group, which leads to the abnormal activity of the two ortho positions of the p-hydroxybenzaldehyde hydroxyl group with a small gap, and the bromination reaction is easy to generate 3,5-dibromo- 4-hydroxybenzaldehyde (hereinafter referred to as dibromoaldehyde), makes the selectivity of reaction low, and yield is low and separation difficulty, has limited industrial application

Images