CN114956978A - Microwave synthesis process of 2-hydroxy-5-methoxyacetophenone - Google Patents
Microwave synthesis process of 2-hydroxy-5-methoxyacetophenone Download PDFInfo
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Abstract
The invention relates to the technical field of fine chemical product synthesis, in particular to a microwave synthesis process of 2-hydroxy-5-methoxyacetophenone, which comprises the following synthesis steps: the phenol ester reacts in an alkaline environment under the action of microwave radiation to generate the o-hydroxyacetophenone. The scheme innovatively adopts a green organic synthesis technology, namely microwave synthesis, avoids using Lewis acid, and solves the environmental protection problem in the chemical production process. The scheme also overcomes the problem that the conventional Fries rearrangement requires high temperature, can react quickly at a lower temperature, and has good selectivity and higher safety. The technical scheme solves the technical problem that the synthesis process of 2-hydroxy-5-methoxy-acetophenone and orthotopic substituted ketone with the advantages of short reaction time, high yield, less side reaction, simple operation, environmental friendliness and the like is lacked in the prior art, and has wide application prospect.
Description
Technical Field
The invention relates to the technical field of fine chemical product synthesis, in particular to a microwave synthesis process of 2-hydroxy-5-methoxyacetophenone.
Background
In the prior art, the synthesis routes of 2-hydroxy-5-alkyl (or alkoxy) -acetophenone are mainly three as follows:
(1) 4-alkyl (or alkoxy) phenol is used as a raw material and reacts with an acylating reagent in the presence of anhydrous aluminum trichloride to generate corresponding ketone. The Chinese patent (CN102731278A) reports the following process flow: ethyl ester is formed by tert-octyl phenol, and then 2-hydroxy-5-methoxy acetophenone (shown in a formula II in detail) is obtained by Fries rearrangement synthesis.
(2) Chinese patent (CN102206148A) reports the following process flow: introducing hydrogen chloride gas into 4-nonylphenol and excessive anhydrous acetonitrile, adding one or more catalysts of aluminium trichloride, boron trichloride, zinc chloride and the like to perform catalytic reaction to obtain nonylphenol ketimine, and hydrolyzing to obtain 2-hydroxy-5-nonaacetophenone (see a formula III in detail).
(3) 4-methoxyphenol is used as a raw material, reacts with magnesium methoxide to produce magnesium salt, and then reacts with paraldehyde to generate corresponding ketone.
The three routes have disadvantages, and the routes (1) and (2) have low operation safety, large waste gas and waste water discharge amount, serious environmental protection hidden trouble and low yield. (3) The magnesium is used for preparing the magnesium methoxide in the route, the preparation of the magnesium methoxide can generate a large amount of hydrogen, and the route is avoided as far as possible because the ignition point and the ignition point of the hydrogen are very low, the explosion limit range is large, and the explosion power is large. With the development of society, the consciousness of safety and environmental protection is strengthened, and the greenization of the chemical industry is a necessary trend of social development. The research and development of a synthetic route of 2-hydroxy-5-methoxy-acetophenone and orthotopic substituted ketone with the advantages of short reaction time, high yield, less side reaction, simple operation, environmental friendliness and the like is urgently needed.
Disclosure of Invention
The invention aims to provide a microwave synthesis process of 2-hydroxy-5-methoxyacetophenone, and aims to solve the technical problem that a synthesis process of 2-hydroxy-5-methoxyacetophenone and co-position substituted ketone which have the advantages of short reaction time, high yield, less side reactions, simplicity in operation, environmental friendliness and the like is lacked in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
the microwave synthesis process of 2-hydroxy-5-methoxyacetophenone includes the following steps: the phenol ester reacts in an alkaline environment under the action of microwave radiation to generate the o-hydroxyacetophenone.
The principle and the advantages of the scheme are as follows:
the method takes phenolic ester as a raw material to synthesize o-hydroxyacetophenone under the action of microwave in an alkaline environment. The scheme innovatively adopts a green organic synthesis technology, namely microwave synthesis, avoids using Lewis acid (such as aluminum trichloride, zinc chloride, ferric chloride, titanium tetrachloride, stannic chloride, trifluoromethanesulfonate and the like), and solves the environmental protection problem in the chemical production process. The scheme also overcomes the problem that the conventional Fries rearrangement requires high temperature, can react quickly at a lower temperature, and has good selectivity and higher safety.
With the development of society, the consciousness of safety and environmental protection is strengthened, and the greenization of the chemical industry is a necessary trend of social development. As for 2-hydroxy-5-methoxyacetophenone, the synthetic routes in the prior art have the problems of safety and environmental protection, and the inventors have studied a great deal of Fries rearrangement catalysts (containing ionic liquid), solvents and synthetic lines, and the effects are poor. In the study and research of green chemical synthesis technology, the inventor knows that the purposes of shortening reaction time, improving reaction yield and reducing energy consumption and pollution can be achieved by using a novel synthesis means, particularly by using means of sound, light, electricity, magnetism and the like to carry out organic synthesis, and finally successfully develops a technical route for synthesizing 2-hydroxy-5-methoxyacetophenone by microwave through continuous experiments.
Microwaves are electromagnetic waves with a frequency of 300MHz-300GHz, which are located between infrared radiation and radio waves of the electromagnetic spectrum. Microwave synthesis refers to a technology applied to modern organic/inorganic synthesis research by utilizing the advantages of rapid heating, homogenization, selectivity and the like under the condition of microwaves. Although the microwave reaction has the characteristics of short reaction time, high yield, less side reaction, simple operation, environmental friendliness and the like, how to apply the microwave reaction to the synthesis practice of o-hydroxyacetophenone is a problem which can not be referred to in the prior art. Through a large amount of groceries on experimental conditions, the o-hydroxyacetophenone can be successfully synthesized in an alkali environment, and a process route is established.
Further, the chemical formula of the phenolic ester is shown as a formula I;
wherein R is 1 When the alkyl is alkoxy, the number of carbon atoms is 1-8; r 1 When the alkyl is adopted, the number of carbon atoms is 1-8; r 2 Is alkyl with 1-4 carbon atoms.
The o-hydroxyacetophenone can be synthesized by adopting the phenolic ester with the structural formula as a raw material through the process.
Further, the solvent of the reaction is a nonpolar solvent, and the nonpolar solvent comprises at least one of normal hexane, benzene, chloroform and petroleum ether; the solvent also contains alkali, and the alkali comprises at least one of potassium hydroxide, sodium hydroxide, potassium carbonate and sodium carbonate. The above-mentioned several alkalis can ensure the forward reaction, but different alkalis are used, and the effect of microwave reaction is different. Sodium hydroxide and potassium hydroxide are too alkaline and generate side reactions, so that the content and the yield are low; the sodium bicarbonate has weak alkalinity, low yield, no alkali and very low reaction efficiency. The potassium carbonate and the sodium carbonate can obtain good yield and content, the yield of the potassium carbonate is higher than that of the sodium carbonate, the content of the potassium carbonate is slightly lower than that of the sodium carbonate, and the potassium carbonate is more suitable in comprehensive consideration. Since sodium hydroxide is in the form of flakes and does not couple to microwaves to a sufficient degree, longer heating times and more power are required to complete the reaction. Therefore, the choice of the reaction base is crucial, and only medium and strong bases can be selected, such as: sodium carbonate or potassium carbonate.
Further, the reaction solvent also contains an auxiliary solvent, wherein the auxiliary solvent comprises at least one of water, methanol, ethanol, acetone, ethyl acetate, dimethylformamide and acetic acid. When the n-hexane solvent is used, a small amount of auxiliary solvent is added, so that the coupling of the solvent and the microwave can be enhanced, and the heating speed is increased. The heating and reaction speed, yield, quality and yield can be improved by adding a small amount of solvent including ethyl acetate.
Further, the reaction solvent also contains potassium chloride. When the normal hexane solvent is used, a small amount of salt is added, so that the coupling of the solvent and the microwave can be enhanced, the heating speed is increased, and the heating and reaction speed is increased.
Further, the base includes at least one of potassium hydroxide, sodium hydroxide potassium carbonate, sodium carbonate, and sodium bicarbonate.
Furthermore, the power of microwave radiation is 150-275W, and the reaction time is 10-35 min. The microwave conditions can promote the reaction to be carried out, wherein the microwave radiation power is preferably 175-250, more preferably 200, under the same experimental conditions, when the heating power is less than or equal to 175W, the product yield and content are lower, and when the power is more than or equal to 250W, the product content and yield are reduced, and the color is deepened.
Further, the dosage ratio of the phenolic ester, the alkali and the nonpolar solvent is as follows: 0.2mol:0.1-0.15mol:150-300 mL. By adopting the dosage ratio, the phenolic ester can be fully reacted to form a target product.
Further, the dosage ratio of the phenolic ester, the potassium chloride and the ethyl acetate is as follows: 0.2mol:0.05-0.08mol:15-45 ml. The addition of appropriate amounts of salt and solvent positively promotes increased heating and reaction rates, but the addition of too much ethyl acetate or salt is not significant for increased heating and rates.
Further, the auxiliary solvent is ethyl acetate; the alkali is potassium carbonate and/or sodium carbonate; the power of the microwave radiation is 200W; the phenolic ester is p-methoxyphenol ethyl ester; the o-hydroxyacetophenone is 2-hydroxy-5-methoxyacetophenone; the dosage ratio of the phenolic ester, the potassium chloride and the ethyl acetate is as follows: 0.2mol:0.05mol:15 ml. The optimal process conditions can ensure the reaction efficiency, and the obtained product has higher purity and yield.
Further, the process also comprises the post-treatment step: filtering to obtain filtrate, and adjusting the pH of the filtrate to 1-2; after phase separation, taking an organic phase, washing the organic phase with water until the pH value of the organic phase is 6, and then removing water in the organic phase; then filtering, concentrating, crystallizing, filtering and drying to obtain a powdery finished product. The pH value of the filtrate is adjusted to facilitate the enrichment of the target component 2-hydroxy-5-methoxyacetophenone in the organic phase during the phase separation process. And washing with water to remove impurities, thereby improving the quality of the finished product. The finished product is yellow crystalline powder, and the content of the 2-hydroxy-5-methoxyacetophenone can reach more than 99%.
Drawings
FIG. 1 is an HPLC image of the product of example 1 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise indicated, the following techniques are conventional and well known to those skilled in the art: the materials, reagents and the like used are all commercially available.
Example (b):
(1) a250 ml three-necked flask was charged with 33.2g (0.2mol) of ethyl p-methoxyphenol, 15.2g (0.11mol) of potassium carbonate, 3.7g (0.05mol) of potassium chloride, 150ml of n-hexane, and 15ml of ETOAC, and stirred at 20 to 30 ℃ for 30 min. In addition, the n-hexane may be replaced with other nonpolar solvents including at least one of n-hexane, benzene, chloroform, and petroleum ether. The amount ratio of the phenol ester (e.g. p-methoxyphenol ethyl ester), the base and the non-polar solvent is 0.2mol:0.1-0.15mol:150-300mL, which can ensure the smooth progress of the reaction.
(2) Carrying out 225W microwave treatment under stirring (80r/min), wherein in the embodiment, the frequency is 2450MHz, the wavelength is 122 mm (the selectable range is 2.45-6.9GHz, and the wavelength is 7.69-1.22cm), and the radiation time is 15 min;
(3) filtering the reactant, adding a small amount of n-hexane to wash a filter cake, and filtering;
(4) adding 2N HCl dropwise into the filtrate while stirring until the pH value is 1-2;
(5) the aqueous phase was separated, the organic phase was washed with deionized water to pH 6 and dried over anhydrous sodium sulfate;
(6) filtering, vacuum concentrating the filtrate, crystallizing, filtering, and drying to obtain yellow crystalline powder with 2-hydroxy-5-methoxyacetophenone content > 99% and yield > 89%. The HPLC is adopted to detect the product, the HPLC map of the product is shown in figure 1, and the retention time of the peak of the product 2-hydroxy-5-methoxyacetophenone is consistent with that of the peak of the standard product.
The reaction equation of this example is shown in formula IV.
Experimental example 1: testing for a particular selected type of base
The procedure of this example is essentially the same as in example 1, except that the base is selected and no salt or auxiliary solvent is added, as specified in Table 1.
Table 1: the type of alkali and experimental results
In Table 1, at least three replicates were conducted for each experimental group, and the product weight (g), content (%) and yield (%) in the tables were average values of the replicates. The target component content and yield of the products of experiments 3 and 4 were significantly higher than that of the product of experiment 1/2/5 (t-test, p < 0.05)). From the experimental data of table 1, it can be seen that:
(1) different alkalis are used, the results are different greatly in the microwave reaction, and sodium hydroxide and potassium hydroxide have too strong alkalinity, so that side reaction occurs, the content and the yield are low, and the content and the yield are both statistically and obviously different from the results of experiment 3 or experiment 4. The sodium bicarbonate is too weak in alkalinity, low in yield, basically has no reaction under the condition of no alkali, and has a statistically significant difference from the results of experiment 3 or experiment 4.
(2) The potassium carbonate and the sodium carbonate can obtain good yield and content, the yield of the potassium carbonate is higher than that of the sodium carbonate, the content of the potassium carbonate is slightly lower than that of the sodium carbonate, and the potassium carbonate is more suitable in comprehensive consideration.
(3) Since sodium hydroxide is in the form of flakes and does not couple to microwaves to a sufficient degree, longer heating times and more power are required to complete the reaction.
Therefore, the choice of the reaction base is crucial, and only medium and strong bases can be selected, such as: sodium carbonate or potassium carbonate.
Experimental example 2: study of the Effect of auxiliary solvents and salts on reaction efficiency
The process of this example is substantially the same as that of example 1, except that the auxiliary solvent and salt are selected, as shown in Table 2.
Table 2: results of investigation of the Effect of auxiliary solvents and salts on the reaction
In Table 2, at least three parallel tests were carried out for each experimental group, and the product weight (g), content (%) and yield (%) in the table were average values of the parallel tests. In the products of experiments 1 to 7, the contents of 2-hydroxy-5-methoxy-acetophenone are not significantly different, but different treatment modes have certain influence on the yield of the products. The product yield of experiment 1 was low, with statistically significant differences from the product yields of experiments 2-4 (p < 0.05 by t-test). This demonstrates that the addition of a small amount (10%) of an auxiliary solvent can achieve an increase in heating and reaction rates as well as yield, quality and yield. However, the addition of excessive ethyl acetate is helpful for increasing the heating rate and the heating speed, but the improvement effect is limited. In experiments 5-7, the heating and reaction speed can also be improved by adding a small amount of salt, and the heating and reaction speed is not obviously improved by adding excessive salt, and the optimal amount is about 3.7 g. In conclusion, a small amount of polar solvent ethyl acetate and salt are added into the nonpolar solvent, so that the solvent can enhance the coupling with the microwave, and the heating and reaction speed is improved.
The auxiliary solvent includes at least one of water, methanol, ethanol, acetone, dimethylformamide, and acetic acid, in addition to ethyl acetate. Wherein, ethyl acetate is the best choice, ethyl acetate and n-hexane are mutually soluble and are insoluble in water, and the water phase has no product loss in the water washing process and can well ensure the yield. If the auxiliary solvent is selected from alcohols, acetone, DMF, acetic acid and the like, the phenomenon that the product 2-hydroxy-5-methoxyacetophenone enters a small amount into a water phase and is difficult to completely recover can be caused, and the yield is reduced. If the auxiliary solvent is water, the auxiliary solvent is not dissolved in n-hexane, and the reaction effect is not good enough.
Experimental example 3: study on the influence of microwave power on the quality of products
The process of this example is substantially the same as example 1, except that the microwave power and the treatment time are selected, as shown in table 3.
Table 3: research result of microwave power on product quality
In Table 3, at least three replicates were conducted for each experimental group, and the product weight (g), content (%) and yield (%) in the tables were average values of the replicates. Experiment 3 is the optimal process condition, and experiments are carried out for 4 times, so the microwave power is preferably 200-225W. The product of experiment 4 also had statistically significant differences in yield (t-test, p < 0.05) relative to the product of experiment 3, indicating that the optimal choice of microwave power was 200W. The products of experiment 1, experiment 2, experiment 5 and experiment 6 were also statistically significantly different in yield (t test, p < 0.05) from the product of experiment 3, respectively; in particular, the products of experiments 1, 5 and 6, respectively, also differ statistically significantly in their content with respect to the product of experiment 3 (t-test, p < 0.05). This shows that under the same experimental conditions, the product yield and content are lower when the heating power is less than or equal to 175W, and the product content and yield are reduced and the color deepens when the power is more than or equal to 250W. Therefore, the most suitable heating power is 200W.
The foregoing is merely an example of the present invention and common general knowledge in the art of designing and/or characterizing particular aspects and/or features is not described in any greater detail herein. It should be noted that, for those skilled in the art, without departing from the technical solution of the present invention, several variations and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.
Claims (10)
- The microwave synthesis process of 2-hydroxy-5-methoxyacetophenone is characterized by comprising the following synthesis steps: the phenol ester reacts in an alkaline environment under the action of microwave radiation to generate the o-hydroxyacetophenone.
- 2. The microwave synthesis process of 2-hydroxy-5-methoxyacetophenone according to claim 1, wherein the phenolic ester has a chemical formula shown in formula I;
wherein R is 1 When the alkyl is alkoxy, the number of carbon atoms is 1-8; r 1 When the alkyl is adopted, the number of carbon atoms is 1-8; r 2 Is alkyl with 1-4 carbon atoms. - 3. The microwave synthesis process of 2-hydroxy-5-methoxyacetophenone according to claim 2, characterized in that the solvent for the reaction is a nonpolar solvent comprising at least one of n-hexane, benzene, chloroform and petroleum ether; the solvent also contains alkali, and the alkali comprises at least one of potassium hydroxide, sodium hydroxide, potassium carbonate and sodium carbonate.
- 4. The microwave synthesis process of 2-hydroxy-5-methoxyacetophenone according to claim 3, characterized in that the reaction solvent further contains an auxiliary solvent, which comprises at least one of water, methanol, ethanol, acetone, ethyl acetate, dimethylformamide and acetic acid.
- 5. The microwave synthesis process of 2-hydroxy-5-methoxyacetophenone according to claim 4, characterized in that the reaction solvent also contains potassium chloride.
- 6. The microwave synthesis process of 2-hydroxy-5-methoxyacetophenone as claimed in claim 5, characterized in that the power of microwave radiation is 150-275W, the frequency is 2.45-6.9GHz, the wavelength is 1.22-7.69cm, and the reaction time is 10-35 min.
- 7. The microwave synthesis process of 2-hydroxy-5-methoxyacetophenone according to claim 6, characterized in that the ratio of the amounts of the phenolic ester, the base and the non-polar solvent is: 0.2mol:0.1-0.15mol:150-300 mL.
- 8. The microwave synthesis process of 2-hydroxy-5-methoxyacetophenone according to claim 7, characterized in that the ratio of the amounts of phenol ester, potassium chloride and ethyl acetate is: 0.2mol:0.05-0.08mol:15-45 ml.
- 9. The microwave synthesis process of 2-hydroxy-5-methoxyacetophenone according to claim 8, wherein the auxiliary solvent is ethyl acetate; the alkali is potassium carbonate and/or sodium carbonate; the power of the microwave radiation is 200W; the phenolic ester is p-methoxyphenol ethyl ester; the o-hydroxyacetophenone is 2-hydroxy-5-methoxyacetophenone; the dosage ratio of the phenolic ester, the potassium chloride and the ethyl acetate is as follows: 0.2mol:0.05mol:15 ml.
- 10. The microwave synthesis process of 2-hydroxy-5-methoxyacetophenone according to claim 9, further comprising a post-treatment step: filtering to obtain filtrate, and adjusting the pH of the filtrate to 1-2; after phase separation, taking an organic phase, washing the organic phase with water until the pH value of the organic phase is 6, and then removing water in the organic phase; then filtering, concentrating, crystallizing, filtering and drying to obtain a powdery finished product.
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| CN112250597A (en) * | 2020-11-02 | 2021-01-22 | 安徽绿色谷创客空间股份有限公司 | Green synthesis method of 2-hydroxy-5-nonyl acetophenone oxime |
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| CN112250597A (en) * | 2020-11-02 | 2021-01-22 | 安徽绿色谷创客空间股份有限公司 | Green synthesis method of 2-hydroxy-5-nonyl acetophenone oxime |
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| JAYASHRI N.ANGAITKAR等: "Synthesis of 3-Aroyl Flavanones by Using Microwave Irradiation and Study of Its Antibacterial Activity", JCBPS; SECTION A * |
| 刘现国等: "微波加热三氯化铝催化合成邻羟基苯乙酮", 辽宁化工 * |
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