At present, there are several methods for preparing Cinnamate:
1. It is obtained by reacting ethanol and cinnamaldehyde in anhydrous ether for a long time.
2, adopt hot caustic alkali solution to process natural styrax balsam, peruvian balsam to extract Cinnamate, the cinnamate cost of this method production is higher, and raw material is difficult to obtain, and technique is complicated, and pollutes the environment seriously.
3. CN200810046866.0, the title of the invention “a preparation method of cinnamyl cinnamate” discloses the preparation of cinnamoyl chloride by reacting cinnamic acid with thionyl chloride, and then reacting with cinnamyl alcohol in the presence of an organic solvent to synthesize Cinnamate. Although this synthetic method has a relatively simple process, it has large solvent consumption, many by-products, low yield, and the product is difficult to purify, and the organic solvent N,N-dimethylaniline used in the preparation method has a pungent odor, A heavier taste will eventually lead to a product with a less pure aroma.
4. To prepare cinnamic acid by transesterification of ethyl cinnamate and cinnamic alcohol, the reaction is generally carried out under high pressure. After the reaction is completed, decolorization with activated carbon is used to carry out multiple recrystallizations to obtain the final product. This process has problems such as long reaction period, many by-products, difficult crystallization, serious pollution and low yield.
The preparation method includes the following steps:
In an oil bath, methyl cinnamate, cinnyl alcohol and potassium carbonate are mixed in a mass ratio of 1:1 to 2:0.05 to 0.1, and the resulting mixture is heated to 120 to 160 ° C under stirring, and reacted at this temperature. 1～3h, the methanol produced by the reaction distills out as the temperature rises. When methanol no longer distills out, the heating is stopped and the temperature is lowered to 80°C to obtain a reaction solution containing Cinnamate;
(2) Washing and recycling
Add water and ethyl acetate to the reaction solution containing Cinnamate obtained in step (1), then stir and wash until the water phase is neutral, separate the water phase from the oil phase, remove the water phase, and the oil phase is -0.096MPa in a vacuum The ethyl acetate solvent is removed by heating under the condition of temperature of 45°C, and then vacuum distillation is carried out under the conditions of pressure of 0.1～0.2KPa and temperature of 195～205°C to obtain the crude cinnamic acid ester;
The crude Cinnamate obtained in step (2) is recrystallized in ethanol at a temperature of 0 to -10° C., the crystals are separated, and then dried to obtain a white solid cinnamate.
Compared with the prior art, the synthetic method of Cinnamate of the present invention uses methyl laurate and cinnamyl alcohol as reaction raw materials, and transesterification occurs under the catalysis of potassium carbonate, and in the reaction process, the methanol that is generated is directly distilled off. In order to promote the reaction to proceed in the forward direction, the conversion rate of the reaction is improved, the reaction time is shortened, and the side reaction products caused by the high-pressure reaction are avoided. In the post-processing process, the present invention adopts the technological operation of vacuum distillation to steam out the crude Cinnamate first, which not only has the effect of separation and purification, but also achieves the ideal effect of decolorization. Finally, the product obtained by one recrystallization with ethanol has the advantages of pure aroma, good color and high purity.