Preparation method of piperic acid

Abstract

The invention relates to a preparation method of piperic acid, which belongs to the technical field of organic synthesis, and comprises the following steps: step 1, adding heliotropin into hot water, adding a catalyst, closing a reaction kettle, heating to 120-140 DEG C, introducing pure oxygen, intermittently dropwise adding liquid caustic soda in the reaction process to control the pH value to 8.5-9.5, controlling the reaction temperature to 120-140 DEG C, cooling after the reaction is finished, filtering, washing, and drying to obtain piperic acid; adjusting the pH value to 1-1.5 by using hydrochloric acid, and filtering to obtain a crude piperic acid product; and 2, adding the crude piperic acid product into absolute ethyl alcohol, heating to 95-105 DEG C, filtering, cooling and filtering the filtrate, and drying to obtain a finished piperic acid product. The pepper acid finished product prepared by the preparation method disclosed by the invention is high in purity and high in yield, and the preparation method does not generate secondary pollution and achieves clean production.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a method for preparing piperic acid. Background Art

[0002] Piperic acid is an important pharmaceutical intermediate. In many synthetic reactions, we often use this compound to introduce piperonyl. It is the main raw material for preparing piperine and piperonyl ester series. In recent years, scholars have continuously confirmed through research that piperine and its derivatives have a variety of biological activities, such as hypolipidemic effects, antioxidant activity, anticonvulsant effects, anti-tumor effects, etc. The content of piperine in pepper is very low, and the lipid-lowering effect is not obvious. It can be chemically modified to become a piperonyl ester with obvious effects.

[0003] The common methods of piperic acid at this stage are as follows:

[0004] Method 1: After isomerization of safrole, it is oxidized with chromic acid to obtain piperic acid. This method has the disadvantages of high energy consumption and serious environmental pollution.

[0005] Method 2: Using piperonal as raw material and glacial acetic acid as solvent, air is introduced, and a large amount of pure water is added for crystallization after the reaction is completed. This reaction has the disadvantages of high pressure and large amount of wastewater.

[0006] In order to overcome the above shortcomings and meet the continuous development requirements of piperic acid, clean production of piperic acid is of great significance. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing piperic acid, which does not generate secondary pollutants and achieves clean production.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] Step 1: Take piperonal and add it to 50-70°C hot water, add a catalyst, close the reactor, heat it to 120-140°C and then introduce pure oxygen, add liquid alkali (such as liquid sodium hydroxide) intermittently during the reaction to control the pH to 8.5-9.5, control the reaction temperature to 120-140°C, complete the reaction in 1.5-3.5h, filter, cool to 5-20°C, use hydrochloric acid to adjust the pH to 1-1.5, and filter to obtain crude piperic acid.

[0010] Step 2: adding the crude piperic acid to anhydrous ethanol, heating and filtering, cooling the filtrate, filtering and drying to obtain the finished piperic acid product.

[0011] Preferably, the mass ratio of piperonal to hot water is 1:(3-4).

[0012] Preferably, the mass ratio of piperonal, copper molybdate, sodium phosphate and sodium carbonate is 100:(0.4-0.6):(0.7-0.9):(0.5-1).

[0013] Preferably, after the oxygen is introduced, the stirring speed is controlled to 750-1000 r / min.

[0014] Preferably, the reaction pressure is controlled at 0.4-0.6 MPa.

[0015] Preferably, the crystallization temperature in step 1 is 5-10°C.

[0016] Preferably, in step 2, the mass ratio of the crude piperic acid to anhydrous ethanol is 1:(6-8).

[0017] Preferably, in step 2, the dissolving temperature is raised to 95-105°C.

[0018] Preferably, the filtering temperature in step 2 is 95-105°C.

[0019] Preferably, in step 2, the crystallization temperature is lowered by 5-10°C.

[0020] The beneficial effects of the present invention are:

[0021] The traditional synthesis uses jasminaldehyde to prepare piperic acid through phase transfer catalytic oxidation, which has the problems of low molar yield, complicated operation, high labor intensity and great environmental impact. The scheme of the present invention uses water as solvent, reduces environmental pollution, improves product yield, simplifies operation, does not introduce organic solvents during the operation process, improves product quality, and avoids VOC raw material emissions. DETAILED DESCRIPTION

[0022] Example 1

[0023] Take 100g of piperonal and add it to 300g of 50℃ hot water, add catalyst (0.4g of copper molybdate, 0.8g of sodium phosphate, 1g of sodium carbonate), close the reactor, replace with oxygen 3 times, adjust the stirring speed to 750r / min, and introduce pure oxygen after heating to 130℃. The reactor pressure is controlled at 0.5Mpa, react for 2h, and keep warm for 1h after the reaction is completed. Liquid alkali is added dropwise during the oxidation process to control the pH to 8.6-8.7. After the reaction is completed, cool to 60℃, use 30% hydrochloric acid to adjust the pH to 1.0, continue to cool to 8℃, filter and dry to obtain 108.4g of crude piperic acid.

[0024] Take 108.4 g of crude piperic acid and add it to 660 g of anhydrous ethanol. Stir and dissolve, heat to 104°C, filter under pressure at 105°C, cool the filtrate to 5°C for crystallization, filter, and dry to obtain 103.6 g of piperic acid with a piperic acid content of 99.90% and a molar yield of 93.59%.

[0025] Example 2

[0026] Take 100g of piperonal and add it to 350g of 50℃ hot water, add catalyst (0.4g of copper molybdate, 0.8g of sodium phosphate, 0.5g of sodium carbonate), close the reactor, replace with oxygen 3 times, adjust the stirring speed to 850r / min, and introduce pure oxygen after heating to 120℃. The reactor pressure is controlled at 0.4Mpa, react for 2h, and keep warm for 1h after the reaction is completed. Liquid alkali is added dropwise during the oxidation process to control the pH to 9.0-9.1. After the reaction is completed, cool to 60℃, use 30% hydrochloric acid to adjust the pH to 1.5, continue to cool to 8℃, filter and dry to obtain 107.9g of crude piperic acid.

[0027] Take 107.9 g of crude piperic acid and add it to 750 g of anhydrous ethanol. Stir and dissolve, heat to 101°C, filter under pressure at 105°C, cool the filtrate to 5 degrees for crystallization, filter, and dry to obtain 102.7 g of piperic acid with a piperic acid content of 99.91% and a molar yield of 92.77%.

[0028] Example 3

[0029] Take 100g of piperonal and add it to 400g of 50℃ hot water, add catalyst (0.4g of copper molybdate, 0.8g of sodium phosphate, 0.5g of sodium carbonate), close the reactor, replace with oxygen 3 times, adjust the stirring speed to 950r / min, and introduce pure oxygen after heating to 140℃. The reactor pressure is controlled at 0.6Mpa, react for 2h, and keep warm for 1h after the reaction is completed. Liquid alkali is added dropwise during the oxidation process to control the pH to 9.4-9.5. After the reaction is completed, cool to 60℃, use 30% hydrochloric acid to adjust the pH to 1.5, continue to cool to 8℃, filter and dry to obtain 107.4g of crude piperic acid.

[0030] Take 107.4 g of crude piperic acid and add it to 850 g of anhydrous ethanol, stir and dissolve, heat to 95° C., filter under pressure at 95° C., cool the filtrate to 5° C. for crystallization, filter, and dry to obtain 101.9 g of piperic acid with a piperic acid content of 99.93% and a molar yield of 92.05%.

[0031] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing piperic acid, characterized in that: The following steps are involved: Step 1: Take piperonal and add it to 50-70°C hot water, add a catalyst, close the reactor, heat it to 120-140°C, then introduce pure oxygen, intermittently add liquid alkali during the reaction to control the pH to 8.5-9.5, control the reaction temperature to 120-140°C, filter and cool after the reaction is completed, adjust the pH to 1-1.5 with hydrochloric acid, and filter to obtain crude piperic acid; Step 2: Take the crude piperic acid and add it to anhydrous ethanol, heat it to 95-105° C., filter it, cool the filtrate, filter it, and dry it to obtain the finished piperic acid.

2. The method for preparing piperic acid according to claim 1, wherein The mass ratio of piperonal to hot water in step 1 is 1:(3-4).

3. The method for preparing piperic acid according to claim 1, wherein The catalyst in step 1 is copper molybdate, sodium phosphate and sodium carbonate.

4. The method for preparing piperic acid according to claim 3, wherein: The mass ratio of piperonal, copper molybdate, sodium phosphate and sodium carbonate is 100:(0.4-0.6):(0.7-0.9):(0.5-1).

5. The method for preparing piperic acid according to claim 1, wherein During the reaction of step 1, the reaction pressure is controlled to be 0.4-0.6 MPa.

6. The method for preparing piperic acid according to claim 1, wherein: The mass ratio of the crude piperic acid to anhydrous ethanol in step 2 is 1:(6-8).