Background and overview[1]
4-Ethoxy-3-methoxybenzaldehyde (vanillin ether) can be used as a pharmaceutical synthesis intermediate. Vanillyl alcohol ether, also known as capsicum ether, has a strong curry aroma and is widely used as food flavoring. And due to its significant heating effect, it can accelerate blood circulation in the human body and cause a local feeling of heating. As a heating agent in cosmetics, it is especially suitable for women’s facial cleansing in cold winters, and as a heating agent in plasters, it has the effect of dispelling wind and cold. Among them, vanillyl alcohol butyl ether is the most widely used in food and cosmetics.
In the traditional synthesis method, it is obtained by reacting sodium arophyllate with chlorobutane. However, this method requires the removal of sodium chloride and the separation is complicated. It is a reasonable choice to dehydrate vanillyl alcohol and n-butyl alcohol over an acid catalyst to obtain vanillyl alcohol butyl ether, which only needs to remove water as a by-product. However, acid-catalyzed dehydration systems generally have low yields, require the addition of a water outlet device, and are prone to produce vanillyl alcohol ether and butyl ether by-products. Secondly, vanillyl alcohol is more expensive as raw material, which increases production costs.
It is a good method to use vanillin as raw material, reduce it to vanillyl alcohol through sodium borohydride, and then etherify it with n-butyl alcohol to synthesize vanillyl alcohol butyl ether. However, this method is carried out in two steps, which increases the complexity of the process. At the same time, using sodium borohydride as the reducing agent is not only expensive, but also cannot be reused. Therefore, it is of great industrial application value to develop a process for obtaining vanillyl alcohol ether from vanillin in one step.
Structure
Preparation[1]
The preparation of 4-ethoxy-3-methoxybenzaldehyde is as follows: add 1 kg of vanillin, 6.6 liters of ethanol (the concentration of vanillin is 1mol/L), 0.3 kg of catalyst B and 0.15 in the reaction kettle. Kilogram of catalyst F, and fill it with 1.5MPa hydrogen, heat to 30°C and react for 24 hours. Check that the vanillin reaction is complete, stop heating, filter the catalyst after the reaction kettle is cooled, and dry the catalyst directly before use. The filtrate was rotary evaporated to remove excess ethanol, and 1.36 kg of vanillyl alcohol ether (4-ethoxy-3-methoxybenzaldehyde) was obtained, with a yield of 98% and a purity of >98%.
Main reference materials
[1] CN105622363 One-step process for preparing vanillyl alcohol ether
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