Preparation method for methyl p-methoxycinnamate

Abstract

The invention discloses a preparation method for methyl p-methoxycinnamate. The preparation method comprises the following steps: adding methyl acetate, methanol, sodium methoxide and cyclic ether areinto a condensation reactor and performing a reaction at a reflux temperature; then adding p-methoxybenzaldehyde, and allowing a reaction solution to cyclically pass through a catalyst-loaded reaction bed at the same time; and after completion of the addition of p-methoxybenzaldehyde, carrying out reflux treatment, continuing the reaction under a heat preservation condition, and separating and removing water formed in the reaction. According to the invention, the use amount of a catalyst can be reduced to a low level by adding methanol and cyclic ether and removing the formed water; as the reaction solution cyclically passes through the reaction bed loaded with a metal oxide catalyst, 3-methoxy-3-p-methoxyphenylpropionate generated in the process of the reaction is timely converted into methyl p-methoxycinnamate, so the purity and yield of the product methyl p-methoxycinnamate is improve; meanwhile, the process of acid-base neutralization is not needed, so unwanted waste water and other solid waste are not produced; and compared with traditional processes, the preparation method of the invention has the advantages of higher conversion rate and selectivity, lower production cost and better environmental protection performance.

Description

technical field [0001] The invention belongs to the field of chemical industry, and relates to a preparation method of p-methoxycinnamate, in particular to a preparation method of methyl p-methoxycinnamate. Background technique [0002] P-methoxycinnamate, especially the higher ester of p-methoxycinnamate is an excellent ultraviolet absorber and can be used as a chemical sunscreen. Methyl p-methoxycinnamate is the raw material for the synthesis of higher esters of p-methoxycinnamate, and it also has important applications in the pharmaceutical field. [0003] At present, the preparation method of the mainstream p-methoxycinnamate in the industry is that p-methoxybenzaldehyde is prepared by the Claisen-Schmidt reaction route as raw material: [0004] P-methoxybenzaldehyde and methyl acetate are reacted in a conventional hydrocarbon solvent with a strong base such as sodium methoxide as a catalyst, and the resulting mixture is reacted at 40-65°C for 2-6 hours, and the corresp...

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Problems solved by technology

[0011] In order to improve the yield and purity of methyl p-methoxycinnamate, the method adopted in patent JP617236 is to separate 3-methoxy-3-methyl p-methoxyphenylpropionate, which will reduce the reaction yield , the method adopted by the patent JP283462 is to treat the reaction solution containing 3-methoxy-3-p-methoxyphenyl propionate methyl ester with liquid acid after the reaction, and 3-methoxy-3-p-methoxy Methyl phenylpropionate is converted into methyl p-methoxycinnamate. Although this method improves the reaction yield, it involves multiple acid-base neutralization processes and increases the amount of saline wastewater. The method adopted in patent EP0165521 is to After the reaction, the reaction solution containing 3-methoxyl-3-p-methoxyphenylpropionic acid methyl ester is treated with alkaline hydroxide, and 3-methoxyl-3-p-methoxyphenylpropionic acid methyl Ester is converted to methyl p-methoxycinnamate, which has the same problem as the patent JP283462

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