CN103524319A - A kind of synthetic method of benzoin - Google Patents

Abstract

The invention relates to a method for preparing benzoin from benzaldehyde, in particular to a method for synthesizing benzoin under the catalysis of VB1 by using strong base and weak acid salt as basic reagent. The method utilizes cheap sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate and other strong base and weak acid salts as alkaline reagents, and synthesizes benzoin through the benzoin condensation reaction of benzaldehyde under the catalysis of VB1, which is different from traditional Compared with strong bases such as sodium hydroxide and potassium hydroxide as alkaline reagents, the price is low, the catalyst VB1 has high stability, the reaction is easy to control, and the reproducibility is good. There is no possibility of Cannizzaro side reactions. It is a kind of preparation of benzoin easy-to-use method.

Description

A kind of synthetic method of benzoin

technical field

The invention relates to a method for preparing benzoin from benzaldehyde, in particular to a method for synthesizing benzoin under the catalysis of VB1 by using cheap strong base and weak acid salt as basic reagent.

Background technique

Benzoin is an important organic chemical raw material formed by the condensation coupling of two molecules of benzaldehyde through benzoin. Diphenylethanone, benzoylbenzyl alcohol, α-hydroxy-α-phenylacetophenone, α-hydroxybenzyl benzophenone, etc., are widely used as photosensitizers for photosensitive resins and anti-cratering agents for powder coatings. At the same time, it is also an important synthetic intermediate of drugs, insecticides, and other photosensitive materials. For example, benzoin is the raw material of diphenylhydantoin, an antiepileptic drug, and the reaction raw material of benzyl and benzoin ethers used in photosensitizers in the printing and coating industries.

The benzoin condensation reaction first used highly toxic sodium cyanide or potassium cyanide as a catalyst, but with the continuous improvement of people's awareness of environmental protection, the benzoin condensation reaction catalyzed by VB1 with a thiazole ring structure has attracted widespread attention. The benzoin condensation reaction method under VB1 catalysis includes VB1 catalysis method, phase transfer catalysis-VB1 method, ultrasonic-VB1 method, microwave-VB1 method. He Qiangfang et al. (University Chemistry, 2010, 25(3): 58-61) dissolved VB1 in water, added 95% ethanol and freshly distilled benzaldehyde, then added dropwise 10% NaOH aqueous solution to pH 9~10, at 65°C After 120 min of reaction, furodioin was obtained; Du Zhiyun et al. (Guangdong Chemical Industry, 2006, 33(11): 27-30) prepared thienioin by using VB1 as catalyst and triethylamine as basic reagent. Jia Xiaohong et al. (Natural Science Edition, Journal of Hubei University for Nationalities, 2008, 26(2): 206-208) synthesized benzene in a sodium hydroxide-VB1 catalytic system by adding dodecyldimethylbenzyl ammonium as a phase transfer catalyst. Even marriage; Liu Xiaoling et al. (Journal of Jiaying University, 2006, 26 (3); 43-56.) In the sodium hydroxide-VB1 catalytic system, adding PEG-6000 as a phase transfer catalyst synthesized diphenyloxyethanone (benzene benzoin); in addition, Chen Qiang et al. (Shanghai Chemical Industry, 2005, 30(2): 19-21) studied the method of preparing benzoin by ultrasonic radiation in the sodium hydroxide-VB1 catalytic system, Wang Shouxin et al. (Qufu Normal University University Journal, 2008, 34(3): 93-95) studied the method of synthesizing 2-pyridoin by microwave radiation method in sodium hydroxide-VB1 catalytic system.

Most of the benzoin condensation reactions catalyzed by VB1 use sodium hydroxide as the basic reagent, and a few use triethylamine as the basic reagent. Although sodium hydroxide is used as an alkaline reagent, the yield is high, but the VB1 structure is easily destroyed, the reaction is unstable, and the reproducibility is low, while triethylamine is used as an alkaline reagent, the post-treatment is complicated, and the yield is low.

Contents of the invention

The invention provides a method for preparing benzoin from benzaldehyde, which is characterized in that it uses cheap sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate and other strong bases and weak acid salts as alkaline reagents, under the catalysis of VB1 , Synthesis of benzoin by heating. The use of strong acid and weak base salt is not only beneficial to the structural stability of VB1, but also makes the reaction operation more convenient and reproducible. At the same time, it effectively reduces the possibility of benzaldehyde undergoing Cannizzaro reaction, and its yield is close to that of sodium hydroxide. The reagent is a simple and easy preparation method of benzoin.

The synthesis of benzoin of the present invention comprises the following contents:

Benzaldehyde is newly distilled benzaldehyde, and ethanol is absolute ethanol or 95% ethanol;

Strong base and weak acid salts are sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate, etc., with a concentration of 2% to saturated solution;

The dosage of VB1 is to add 0.5~3.0 g for every 10.5 g of benzaldehyde;

The amount of solvent is to add 1.5 mL~12.5 mL water and 2.0 mL~18.5 mL absolute ethanol or 95% ethanol for every 10.5 g benzaldehyde;

The reaction pH range is 8~11;

The reaction temperature is between 50°C and 100°C, and the reaction time is between 0.5 and 5 hours;

The reaction mode is direct heating reaction.

Dissolve VB1 in ethanol aqueous solution mixed according to a certain ratio, add strong base and weak acid salt to adjust the pH value of the solution, make VB1 generate carbanions, add freshly distilled benzaldehyde and heat for several hours. The reaction product was fully cooled, filtered and dried to obtain crude benzoin with a maximum yield of 63.5%. The crude benzoin product was recrystallized with 95% ethanol to obtain white needle-like crystals. The melting point was 134.3~135.1°C measured by a digital melting point analyzer (the temperature was not corrected), which was consistent with the literature value.

The present invention obtains technical progress:

In the process of VB1 catalyzed preparation of benzoin, the present invention uses strong base and weak acid salt instead of sodium hydroxide as alkaline reagent, which ensures the structural stability of VB1, improves the reproducibility of the reaction, and avoids the Cannizzaro side reaction. ;

Sodium hydroxide is in the "List of Dangerous Goods" (GB 12268-90) of the People's Republic of China, and it belongs to the second alkaline corrosive product in the eighth category of dangerous goods corrosive products. Sodium carbonate, sodium bicarbonate, etc. used in this method Strong base and weak salts do not belong to hazardous chemicals, so the present invention utilizes strong base and weak salts such as sodium carbonate instead of sodium hydroxide to synthesize benzoin, which improves the safety of synthesis;

Compared with sodium hydroxide used as an alkaline reagent, the present invention can greatly accelerate the dropping speed, save operation time, and make the synthesis process of benzoin simpler and easier because the alkalinity of strong base and weak acid salt is weaker.

Detailed ways

Example 1:

Dissolve 1.75 g (0.005 mol) of VB1 in 5 mL of distilled water, add 15 mL of 95% ethanol and shake well, add 10% NaHCO ₃ aqueous solution dropwise to adjust the pH to 9-10, install a reflux condenser, and place in a 70°C water bath for reaction 2.0 h. After the reaction was completed, the product was fully cooled to precipitate a solid benzoin, filtered under reduced pressure, washed with a small amount of cold 95% ethanol, and dried to obtain 1.55 g of benzoin with a yield of 14.76%. In the NaHCO ₃ -VB1 catalytic system, because the alkalinity of NaHCO ₃ is very weak, it is not conducive to VB1 to generate carbanions, so that VB1 cannot effectively catalyze the benzoin condensation reaction; on the other hand, a large amount of alkali solution needs to be added to make the benzaldehyde and alkali solution Separation, so the yield of benzoin is very low.

Example 2:

Dissolve 1.75 g (0.005 mol) of VB1 in 3.5 mL of distilled water, add 16.5 mL of 95% ethanol and shake well, add 10% Na ₂ CO ₃ aqueous solution dropwise to adjust the pH to 9-10, install a reflux condenser, and place in a 70°C water bath React in medium for 2.0 h. After the reaction was completed, the product was fully cooled to precipitate a benzoin solid, filtered under reduced pressure, washed with a small amount of cold 95% ethanol, and dried to obtain 5.36 g of benzoin with a yield of 51.05%. In the Na ₂ CO ₃ -VB1 catalytic system, the basicity of Na ₂ CO ₃ is stronger than that of NaHCO ₃ , which helps VB1 to generate carbanion, so the yield is higher than that of NaHCO ₃ as basic reagent.

Example 3:

Dissolve 1.75 g (0.005 mol) of VB1 in 6 mL of distilled water, add 15 mL of 95% ethanol and shake well, add 20% Na ₂ CO ₃ aqueous solution dropwise to adjust the pH to 9-10, install a reflux condenser, and place in a 75 °C water bath React for 1.5 h. After the reaction was finished, the product was fully cooled to precipitate a benzoin solid, filtered under reduced pressure, washed with a small amount of cold 95% ethanol, and dried to obtain 6.87 g of benzoin with a yield of 65.40%.

Example 4:

Dissolve 1.75 g (0.005 mol) of VB1 in 5 mL of distilled water, add 15 mL of 95% ethanol and shake well, add 20% Na ₂ CO ₃ aqueous solution dropwise to adjust the pH to 9-10, install a reflux condenser, and place in a 75°C water bath React in medium for 2.0 h. After the reaction was finished, the product was fully cooled to precipitate a benzoin solid, filtered under reduced pressure, washed with a small amount of cold 95% ethanol, and dried to obtain 6.15 g of benzoin with a yield of 58.57%.

Claims (10)

1. A method for preparing benzoin by benzaldehyde, especially with cheap strong base weak salt as alkaline reagent, the synthetic method of benzoin under VB1 catalysis, is characterized in that: VB1 is dissolved in water , adding an appropriate amount of ethanol, adjusting the pH value to be alkaline by using a strong base and a weak acid salt, adding benzaldehyde, and preparing benzoin by heating and reacting for a certain period of time. 2. strong base weak acid salt according to claims 1 refers to sodium carbonate, salt of wormwood, sodium bicarbonate and potassium bicarbonate etc. 3. the benzaldehyde according to claims 1 is newly distilled benzaldehyde. 4. strong base weak acid salt according to claim 2, its concentration is at 2% to saturated solution. 5. according to the consumption of the VB1 described in claim 1 of the claims, add 0.5～3.0 g for every 10 mL (10.5 g) benzaldehyde. 6. the ethanol according to claim 1 refers to absolute ethanol or 95% ethanol. 7. The amount of water and ethanol according to claim 1 in the claims is to add 1.5 mL to 12.5 mL of water and 2.0 mL to 18.5 mL of absolute ethanol or 95% ethanol for every 10 mL (10.5 g) of benzaldehyde. 8. The range of adjusting the pH value according to claim 1 is 8 to 11. 9. The heating reaction temperature according to claim 1 is between 50°C and 100°C, and the reaction time is between 0.5 and 5 h. 10. The heating reaction method according to claim 1 is direct heating reaction.