Green, low-cost and solvent-free method for synthesizing isoeugenol

Abstract

The invention provides a green, low-cost and solvent-free method for synthesizing isoeugenol, which comprises the following steps: heating and stirring a catalyst base and a phase transfer catalyst at a certain temperature, so that the catalyst base is completely dissolved in the phase transfer catalyst to form a complex; the method comprises the following steps: under a nitrogen protection environment, dropwise adding eugenol into a mixture of a catalyst alkali and a phase transfer catalyst, heating for reaction, and adjusting the pH value after the reaction to obtain a head product; and extracting the initial product with ethyl acetate, and then carrying out rotary evaporation to obtain isoeugenol. The phase transfer catalyst can dissolve eugenol and catalyst base at the same time, so that on one hand, a homogeneous catalysis environment is provided, and the catalysis efficiency is improved; on the other hand, anions are exposed after the catalyst alkali enters the phase transfer catalyst, so that the alkalinity of the alkali is enhanced; therefore, reaction conditions become mild, and a very high conversion rate is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis, and particularly relates to a green low-cost solvent-free method for synthesizing isoeugenol. BACKGROUND

[0002] Isoeugenol (4-propenyl-2-methoxyphenol) is a light yellow slightly thick liquid, insoluble in water and glycerol, soluble in ethanol, ethyl acetate and other organic solvents; has soft sweet spicy, has sweet clove, lilac flower fragrance; is mainly used for preparing essence and vanillin, and can be used for preparing essence of ylang, nutmeg and the like; can also be used for preparing edible essence of raspberry, peach, spicy type and clove type; is also a raw material for semi-synthetic vanillin.

[0003] Currently, the traditional base catalysis method is used for preparing isoeugenol in industry, excessive potassium hydroxide is added, and isomerization reaction is carried out under high temperature and high pressure, a large amount of solvent is used to promote the reaction, a large amount of acid needs to be neutralized after the isomerization reaction, and extraction of organic solvent toluene is also needed, so the cost is large, the isomerization effect is poor, the yield is low, the purification is difficult, and the cost is large. The process requires toluene as a solvent, which has high process requirement and does not meet the requirement of green chemical preparation; some processes currently use transition metal complexes as catalysts, which have high catalytic activity, but the cost is high, separation is difficult, and industrialization is difficult to realize.

[0004]

[0005] In summary, it is urgent to seek a more efficient and low-cost isoeugenol synthesis method, which can reduce the cost of industrial production and reduce the discharge of waste liquid in the reaction process. SUMMARY

[0006] The technical problem to be solved by the application is to provide a green low-cost solvent-free method for synthesizing isoeugenol in view of the above-mentioned deficiencies of the prior art, the synthesis method effectively reduces the temperature and pressure of isomerization reaction, shortens the reaction time, and the phase transfer catalyst has low cost, is non-toxic and harmless, and can be used and recycled in industry.

[0007] To solve the above technical problems, the technical scheme adopted by the application is as follows: a green low-cost solvent-free method for synthesizing isoeugenol, which comprises the following steps:

[0008] S1, heating and stirring the base and the phase transfer catalyst at a certain temperature to obtain a complex;

[0009] S2, under the protection of nitrogen, drop eugenol into the complex obtained in S1, and heat to react, and then adjust the pH value to obtain a primary product; extract the primary product with ethyl acetate, and then spin to obtain isoeugenol.

[0010] Preferably, the base in S1 is potassium carbonate or potassium hydroxide; the phase transfer catalyst is 18-crown-6, quaternary ammonium salt or polyethylene glycol; the temperature of the heating and stirring is 80-160℃, and the time is 5-10 min.

[0011] Preferably, the molecular weight of the polyethylene glycol is 400, 600, 800, 1000 or 1500.

[0012] Preferably, the molar ratio of eugenol, the base and the phase transfer catalyst in S2 is 1:3:3.

[0013] Preferably, the drop speed of eugenol in S2 is 1-3 drops / min, the temperature of the heating reaction is 80-160℃, and the time is 2.5 h; the pH value is adjusted to 4-6 with hydrochloric acid, and the concentration of the hydrochloric acid is 2 mol / L.

[0014] Preferably, the extraction with ethyl acetate is performed 2-3 times; the temperature of the spin is 80℃, and the time is 30 min.

[0015] The principle of the present application is that the long chain on the surface of the phase transfer catalyst still has a certain degree of freedom, and when the temperature reaches 80-160℃, the phase transfer catalyst folds into a spiral free sliding chain, at this time the -OH chemical group on the long chain of the phase transfer catalyst can wrap K + in the base to form a complex, when K + is wrapped by the phase transfer catalyst, OH - ion is exposed. Since OH - is exposed, the opportunity of contact between eugenol and OH - is enhanced. The free OH - can react with the α-H in the allyl group in eugenol in the presence of the phase transfer catalyst (which usually needs a strong base). Therefore, this makes the reaction condition mild, and the reaction temperature is usually about 180℃, but under the action of the phase transfer catalyst, the reaction can be carried out at a lower temperature, and a higher conversion rate is obtained, and the yield of isoeugenol methyl ether is greatly improved.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] 1. The present application improves the process route, the existing process route uses eugenol and alkaline catalyst to stir at high temperature and high pressure to generate isoeugenol, the present process uses the way of dropping to add eugenol into the complex of catalyst base and phase transfer catalyst. On the one hand, the use amount of alkaline catalyst is greatly reduced, and the disadvantages of large use amount of alkaline catalyst and inhibition of reaction of eugenol and base salt are avoided.

[0018] 2. The present application effectively improves the conversion rate of eugenol, so that the conversion rate of eugenol reaches 100%; improves the industrialization conditions, reduces the reaction temperature by about 60℃, the phase transfer catalyst is low in price and can be reused. The implementation of industrial production reduces the cost and improves the yield.

[0019] 3. The present application introduces the phase transfer catalyst, and finds that the complex of phase transfer catalyst and potassium hydroxide has good catalysis effect on isomerization of eugenol, and effectively solves the inhibition effect of phenolic hydroxyl on reaction after salt formation of base catalyst; the catalyst can significantly reduce the reaction temperature, and for industrial production, the damage of high temperature to instruments can be effectively reduced, and the energy consumption can be reduced.

[0020] 4. The phase transfer catalyst (PEG) used in the present application can form a complex with base at a certain temperature, and eugenol has a certain solubility in the complex, thereby providing a homogeneous catalysis environment and improving the catalytic efficiency on the one hand; on the other hand, since the catalyst base is added to PEG, the long chain structure of PEG can wrap the cation, so that the anion is exposed, and the alkalinity of the base is enhanced; therefore, the reaction condition becomes mild and a high yield is obtained. At the same time, since the long chain of PEG-X has many hydroxyl groups (-OH), this makes eugenol can be completely dissolved in PEG-X, forming a homogeneous reaction system of inorganic salt catalyst base, eugenol and PEG-X. Under the catalysis of base, the hydrogen on the active methylene group of eugenol is abstracted to form allyl carbon anion, then the double bond is transferred and combined with proton, and finally the stable propenyl isomer is generated.

[0021] The present application will be further described in combination with examples. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0023] The test method in the following examples is: eugenol, isoeugenol is analyzed by GC-9800 chromatograph, and the chromatographic conditions are: initial temperature 120°C, keeping for 2 min, programmed temperature rising to 220°C at a rate of 5°C / min, keeping for 5 min, injection port temperature 260°C, detector temperature 260°C; FID detection, injection 0.8 microliters.

[0024] Example 1

[0025] The present embodiment provides a green low-cost solvent-free method for synthesizing isoeugenol, and the method comprises the following steps:

[0026] S1, 0.84g of potassium hydroxide (KOH) and 6g of polyethylene glycol-400 (PEG-400) are placed in a three-necked flask, a rotor is added, and heating and stirring are carried out at a temperature of 120°C for 5 min to obtain a complex;

[0027] S2, under the protection of nitrogen, eugenol is placed in a normal pressure separatory funnel, then 0.82g of eugenol is added to the complex obtained in S1 at a speed of 1-3 drops / min, and heating is carried out under normal pressure and at a temperature of 120°C for 2.5h, after the reaction, the pH is adjusted to 4-6 by using hydrochloric acid with a concentration of 2mol / L, to obtain a primary product; the primary product is extracted with ethyl acetate for 3 times, and then rotary evaporation is carried out at a temperature of 80°C for 30 min to obtain isoeugenol;

[0028] The molar ratio of eugenol in S2, KOH in S1 and PEG-400 is 1:3:3.

[0029] The conversion rate and trans-selectivity data of isoeugenol obtained in the present embodiment are calculated as follows after analysis:

[0030] Temperature / °C Conversion of eugenol / % Selectivity of trans-isoeugenol / % 120 100 60.86

[0031] Example 2

[0032] The present embodiment provides a green low-cost solvent-free method for synthesizing isoeugenol, and the preparation method comprises the following steps:

[0033] S1, 0.84g of potassium hydroxide (KOH) and 6g of polyethylene glycol-400 (PEG-400) are placed in a three-necked flask, a rotor is added, and heating and stirring are carried out at a temperature of 120°C for 5 min to obtain a complex;

[0034] S2, under the protection of nitrogen, eugenol is placed in a normal pressure separatory funnel, then 0.82 g of eugenol is added into the complex obtained in S1 at a speed of 1-3 drops / min, and the reaction is carried out under the conditions of normal pressure and 120°C for 2.5 h, after the reaction, the pH is adjusted to 4-6 by using hydrochloric acid with a concentration of 2 mol / L, to obtain a primary product; the primary product is extracted by ethyl acetate for 3 times, and then rotary evaporation is carried out at a temperature of 80°C for 30 min, to obtain isoeugenol;

[0035] The molar ratio of the eugenol in S2, the KOH in S1 and the PEG-600 is 1:3:3.

[0036] The conversion rate and trans-selectivity data of isoeugenol obtained in this example are as follows after analysis:

[0037] Temperature / °C Conversion of eugenol / % Selectivity of trans-isoeugenol / % 120 100 63.73

[0038] Example 3

[0039] This example provides a method for synthesizing isoeugenol by a green low-cost solvent-free method, which comprises the following steps:

[0040] S1, 0.84 g of potassium hydroxide (KOH) and 12 g of polyethylene glycol-800 (PEG-800) are placed in a three-necked flask, a rotor is added, and stirring is carried out under the condition of a temperature of 120°C for 5 min, to obtain a complex;

[0041] S2, under the protection of nitrogen, eugenol is placed in a normal pressure separatory funnel, then 0.82 g of eugenol is added into the complex obtained in S1 at a speed of 1-3 drops / min, and the reaction is carried out under the conditions of normal pressure and 120°C for 2.5 h, after the reaction, the pH is adjusted to 4-6 by using hydrochloric acid with a concentration of 2 mol / L, to obtain a primary product; the primary product is extracted by ethyl acetate for 3 times, and then rotary evaporation is carried out at a temperature of 80°C for 30 min, to obtain isoeugenol;

[0042] The molar ratio of the eugenol in S2, the KOH in S1 and the PEG-800 is 1:3:3.

[0043] The conversion rate and trans-selectivity data of isoeugenol obtained in this example are as follows after analysis:

[0044] Temperature / °C Conversion of eugenol / % Selectivity of trans-isoeugenol / % 120 100 78.05

[0045] Example 4

[0046] This example provides a method for synthesizing isoeugenol by a green low-cost solvent-free method, which comprises the following steps:

[0047] S1, 0.84 g of potassium hydroxide (KOH) and 15 g of polyethylene glycol-1000 (PEG-1000) were placed in a three-necked flask, a rotor was added, and stirring was performed at a temperature of 120°C for 5 min to obtain a complex;

[0048] S2, under a nitrogen atmosphere, eugenol was placed in a normal-pressure separatory funnel, and then 0.82 g of eugenol was added dropwise into the complex obtained in S1 at a rate of 1-3 drops / min, and reaction was performed under normal pressure and at a temperature of 120°C for 2.5 h. After the reaction, the pH was adjusted to 4-6 using hydrochloric acid with a concentration of 2 mol / L to obtain a primary product. The primary product was extracted twice with ethyl acetate, and then rotary evaporation was performed at a temperature of 80°C for 30 min to obtain isoeugenol.

[0049] The molar ratio of eugenol in S2, the KOH in S1, and the PEG-1000 was 1:3:3.

[0050] The conversion rate and trans-selectivity data of isoeugenol obtained in this example were calculated after analysis as follows:

[0051] Temperature / °C Conversion of eugenol / % Selectivity of trans-isoeugenol / % Temperature / °C Conversion of eugenol / % Selectivity of trans-isoeugenol / % 120 100 70.23

[0052] Comparative Example 1

[0053] The synthesis method of conventional isoeugenol in this comparative example included the following steps:

[0054] Excess NaOH or KOH was added to eugenol, and reaction was performed at a high pressure of 180-220°C using NaOH / KOH as a catalyst to obtain isoeugenol. The conversion rate of eugenol in this synthesis method was about 78%.

[0055] Example 5

[0056] This example provides a green, low-cost, and solvent-free method for synthesizing isoeugenol, which includes the following steps:

[0057] S1, potassium carbonate and 18-crown-6 were placed in a three-necked flask, a rotor was added, and stirring was performed at a temperature of 140°C for 6 min to obtain a complex;

[0058] S2, under a nitrogen atmosphere, eugenol was placed in a normal-pressure separatory funnel, and then eugenol was added dropwise into the complex obtained in S1 at a rate of 1-3 drops / min, and reaction was performed under normal pressure and at a temperature of 140°C for 2.5 h. After the reaction, the pH was adjusted to 4-6 using hydrochloric acid with a concentration of 2 mol / L to obtain a primary product. The primary product was extracted three times with ethyl acetate, and then rotary evaporation was performed at a temperature of 80°C for 30 min to obtain isoeugenol.

[0059] The molar ratio of the eugenol in S2, the potassium carbonate in S1 and the 18-crown-6 is 1:3:3.

[0060] The temperature of the heating and stirring in S1 can also be 80℃, 82℃, 85℃, 88℃, 90℃, 95℃, 97℃, 99℃, 100℃, 105℃, 110℃, 115℃, 119℃, 123℃, 125℃, 130℃, 135℃, 138℃, 142℃, 144℃, 150℃, 155℃, 156℃, 157℃, 158℃, 159℃ or 160℃, and the time can also be 5.5min, 7min, 8min, 9min or 10min; the phase transfer catalyst can also be PEG-1500, and the base can also be a quaternary ammonium salt; the temperature of the heating reaction in S2 can also be 80℃, 82℃, 85℃, 88℃, 90℃, 95℃, 97℃, 99℃, 100℃, 105℃, 110℃, 115℃, 119℃, 123℃, 125℃, 130℃, 135℃, 138℃, 142℃, 144℃, 150℃, 155℃, 156℃, 157℃, 158℃, 159℃ or 160℃.

[0061] The above is only the preferred embodiments of the present application, and does not limit the present application in any way. Any simple modification, change and equivalent change of the above embodiments according to the technical essence of the present application are still within the protection scope of the technical solutions of the present application.

Claims

1. A green, low-cost, solvent-free method for synthesizing isoeugenol, characterized in that: The method comprises the following steps: S1, heating and stirring the base and the phase transfer catalyst at a certain temperature to obtain a complex; S2. Under nitrogen protection, eugenol is added dropwise to the complex obtained in S1, and the mixture is heated for reaction. After the reaction, the pH value is adjusted to obtain a primary product; the primary product is extracted with ethyl acetate, and then subjected to rotary evaporation to obtain isoeugenol.

2. A green, low-cost, solvent-free method for synthesizing isoeugenol according to claim 1, characterized in that: The base in S1 is potassium carbonate or potassium hydroxide; the phase transfer catalyst is 18-crown ether-6, a quaternary ammonium salt or polyethylene glycol; the heating and stirring temperature is 80 to 160° C., and the time is 5 to 10 minutes.

3. A green, low-cost, solvent-free method for synthesizing isoeugenol according to claim 2, characterized in that: The molecular weight of the polyethylene glycol is 400, 600, 800, 1000 or 1500.

4. A green, low-cost, solvent-free method for synthesizing isoeugenol according to claim 3, characterized in that: The molar ratio of the eugenol in S2, the base in S1 and the phase transfer catalyst is 1:3:

3.

5. A green, low-cost, solvent-free method for synthesizing isoeugenol according to claim 4, characterized in that: The dripping rate of the eugenol in S2 is 1 to 3 drops / min, the temperature of the heating reaction is 80 to 160° C., and the time is 2.5 hours; the pH value is adjusted to 4 to 6 with hydrochloric acid, and the concentration of the hydrochloric acid is 2 mol / L.

6. The method for synthesizing isoeugenol by a green, low-cost, solvent-free method according to claim 5, wherein: The ethyl acetate extraction was performed 2 to 3 times; the rotary evaporation temperature was 80° C. and the time was 30 minutes.

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