阅读说明：本技术 一种基于低共熔溶剂催化剂合成肉桂酸甲酯的方法 (Method for synthesizing methyl cinnamate based on eutectic solvent catalyst ) 是由 曾作祥 唐林茂 郭媛 赵凝瑞 薛为岚 孙莉 于 2021-01-25 设计创作，主要内容包括：本发明公开了一种采用苄基三甲基氯化铵类低共熔溶剂催化合成肉桂酸甲酯的方法,即以酸性低共熔溶剂苄基三甲基氯化铵-对甲苯磺酸(BTAC-PTSA)为催化剂,肉桂酸与甲醇为原料进行酯化反应,并经相分离、中和以及结晶纯化等工艺获得肉桂酸甲酯。本发明运用的低共熔溶剂不仅在制备过程中原子利用率为100%,而且与传统硫酸等催化剂相比具有反应条件温和、对设备腐蚀性小、易回收且能重复利用等优点。(The invention discloses a method for catalytically synthesizing methyl cinnamate by adopting a benzyl trimethyl ammonium chloride eutectic solvent, namely, the method takes an acidic eutectic solvent benzyl trimethyl ammonium chloride-p-toluenesulfonic acid (BTAC-PTSA) as a catalyst, cinnamic acid and methanol as raw materials to carry out esterification reaction, and obtains the methyl cinnamate by processes of phase separation, neutralization, crystallization purification and the like. The eutectic solvent used in the invention not only has an atom utilization rate of 100% in the preparation process, but also has the advantages of mild reaction conditions, small corrosion to equipment, easy recovery, reutilization and the like compared with the traditional sulfuric acid and other catalysts.)

1. A method for synthesizing methyl cinnamate based on a eutectic solvent catalyst is characterized by comprising the following steps:

(1) weighing a proper amount of benzyltrimethylammonium chloride and p-toluenesulfonic acid respectively according to a molar ratio of 1:1, performing vacuum drying on the benzyltrimethylammonium chloride and the p-toluenesulfonic acid at 75 ℃ for 30 min respectively, mixing the benzyltrimethylammonium chloride and the p-toluenesulfonic acid, stirring at 65-80 ℃ to obtain a clear transparent solution, wherein a product obtained by reaction is a eutectic solvent catalyst benzyltrimethylammonium chloride-p-toluenesulfonic acid BTAC-PTSA, and sealing and placing the BTAC-PTSA in a silica gel drying box for later use;

(2) weighing appropriate amount of reactants, namely cinnamic acid and anhydrous methanol, respectively, adding the reactants and the anhydrous methanol into a three-neck flask, stirring and heating to a specified temperature, adding an appropriate amount of the catalyst obtained in the step (1) into the three-neck flask, and reacting for a certain time;

(3) after the reaction is finished, dividing the reaction solution into a water phase and an oil phase by a separating funnel while the reaction solution is hot, and carrying out vacuum drying on the water phase at 50 ℃ to recover the catalyst; pouring the oil phase into a beaker while the oil phase is hot, placing the beaker into a water bath kettle at 40-50 ℃, adding a proper amount of 4% sodium carbonate solution under continuous stirring until the pH value of the mixture is alkalescent (= 7-8), standing for layering, and removing the water phase; adding deionized water with the volume about three times of that of the oil phase at 5 ℃ under continuous stirring to separate out crystals, then carrying out suction filtration, washing with deionized water until the filtrate is neutral to obtain a white or light yellow solid, and drying to obtain the target product methyl cinnamate.

2. The method according to claim 1, characterized in that the molar ratio of the cinnamic acid to the absolute methanol is 1: 2-4, and the mass of the catalyst is 10% -30% of the total mass of the reactants.

3. The method according to claim 1, wherein the esterification reaction temperature in the step (2) is 64-76 ℃ and the reaction time is 2-4 h.

Technical Field

The invention relates to a preparation method of synthetic spice methyl cinnamate, belongs to the field of organic chemical synthesis, and particularly relates to a method for catalytically synthesizing methyl cinnamate by adopting a benzyl trimethyl ammonium chloride eutectic solvent.

Background

Methyl cinnamate, also known as beta-methyl phenylacrylate, has a cherry-like aroma that strawberries can produce and release during ripening. GB-2760-2014 in China stipulates that the edible spice is an edible spice which is allowed to be used. Methyl cinnamate can be used as perfume fixative, and can be widely used for preparing oriental flower essence, soap, detergent, etc. Can be used as an organic synthesis intermediate of medicines in the pharmaceutical industry. In addition, the composition can also play a certain role in sunscreen products. With the improvement of living standard of people, the demand of people is believed to be increased continuously.

The traditional synthesis method of methyl cinnamate is to take cinnamic acid and methanol as raw materials to perform esterification reaction under the catalytic action of inorganic acid such as concentrated sulfuric acid, however, the side reactions are more, the yield is low, and the concentrated sulfuric acid can corrode equipment due to strong corrosivity, so a more environment-friendly process is required to be sought. In the current research on the catalyst for synthesizing cinnamate, the venturi et al (synthetic chemistry, 2001, 9(03): 269) uses ammonium ferric sulfate as a catalyst to synthesize cinnamate series esters, and has the advantages of convenient operation, mild reaction and no corrosion to equipment, but large alcohol dosage and long reaction time; wang et al (Bioresource Technology, 2015, 198: 256) catalyzed esterification of cinnamic acid with ethanol to ethyl cinnamate using a lipase TLIM, higher yields could be obtained by using isooctane as the reaction medium, however, industrial application of the enzyme was generally hindered by its poor storage durability, difficulty in recovery and lack of reusability; chinese patent CN102701973A proposes that an ionic liquid is mixed with water to prepare microemulsion, then a palladium chloride solution is dripped to prepare a nano-scale palladium catalyst, and then iodobenzene, methyl acrylate and triethylamine are subjected to HECK reaction to prepare methyl cinnamate.

The eutectic solvent is a eutectic mixture formed by combining choline salt, a complexing agent and the like in a certain stoichiometric ratio, wherein the complexing agent comprises metal salt, metal salt hydrate and other hydrogen bond donors. In recent years, eutectic solvent is continuously appeared in the visual field of people as an excellent reaction system, and the eutectic solvent not only has good reaction performance which is comparable to that of ionic liquid, but also has low price and is green and environment-friendly. It has received a great deal of attention in organic synthetic chemistry (Journal of Chemical & Engineering Data, 2017, 62(4): 1173).

The invention provides a method for preparing the benzyl trimethyl ammonium chloride-p-toluenesulfonic acid eutectic solvent serving as a catalyst and a solvent for the cinnamic acid esterification reaction, and the method is simple, low in corrosion to equipment and mild in reaction conditions. Meanwhile, the eutectic solvent is easy to recover and can be recycled, and the industrial application potential of the eutectic solvent is also shown. All in all, the invention meets the requirements of environmental protection and human sustainable development and has industrial application prospect.

Disclosure of Invention

The invention aims to provide a method for synthesizing methyl cinnamate by using benzyl trimethyl ammonium chloride eutectic solvent to catalyze the defects of the traditional process. The method does not need to add other organic solvents in the reaction process, is simple to operate, and can obtain good reaction effect under certain reaction process conditions.

The method of the invention comprises the following steps:

(1) weighing a proper amount of benzyltrimethylammonium chloride and p-toluenesulfonic acid respectively according to a molar ratio of 1:1, performing vacuum drying on the benzyltrimethylammonium chloride and the p-toluenesulfonic acid at 75 ℃ for 30 min respectively, mixing the benzyltrimethylammonium chloride and the p-toluenesulfonic acid, stirring at 65-80 ℃ to obtain a clear transparent solution, wherein a product obtained by reaction is a eutectic solvent catalyst benzyltrimethylammonium chloride-p-toluenesulfonic acid BTAC-PTSA, and sealing and placing the BTAC-PTSA in a silica gel drying box for later use;

(2) weighing appropriate amount of reactants, namely cinnamic acid and anhydrous methanol, respectively, adding the reactants and the anhydrous methanol into a three-neck flask, stirring and heating to a specified temperature, adding an appropriate amount of the catalyst obtained in the step (1) into the three-neck flask, and reacting for a certain time;

(3) after the reaction, the reaction solution was separated into water and oil phases by a separatory funnel while it was hot, and the water phase was vacuum-dried at 50 ℃ to recover the catalyst. Pouring the oil phase into a beaker while the oil phase is hot, placing the beaker into a water bath kettle at 40-50 ℃, adding a proper amount of 4% sodium carbonate solution into the beaker under continuous stirring till the mixture is alkalescent (pH = 7-8), standing the beaker for layering, and removing the water phase; adding deionized water with the volume about three times of that of the oil phase at 5 ℃ under continuous stirring to separate out crystals, then carrying out suction filtration, washing with deionized water until the filtrate is neutral to obtain a white or light yellow solid, and drying to obtain the target product methyl cinnamate.

The molar ratio of the cinnamic acid to the anhydrous methanol is 1: 2-4, and the mass of the catalyst is 10% -30% of the total mass of reactants.

The esterification reaction temperature of the step (2) is 64-76 ℃, and the reaction time is 2-4 h.

The invention has the innovation points that the BTAC-PTSA eutectic solvent is used as the catalyst for the esterification reaction, the preparation method is simple, the corrosion to equipment is low, the reaction condition is mild, the BTAC-PTSA eutectic solvent is easy to recover and can be recycled, the requirements of environmental protection and human sustainable development are met, and the BTAC-PTSA eutectic solvent has an application prospect.

Detailed Description

Preparation of eutectic solvent catalyst BTAC-PTSA

Weighing 9.28 g (0.05 mol) of benzyltrimethylammonium chloride and 8.61g (0.05 mol) of p-toluenesulfonic acid, respectively drying the benzyltrimethylammonium chloride and the p-toluenesulfonic acid at 75 ℃ for 30 min in vacuum, mixing the benzyltrimethylammonium chloride and the p-toluenesulfonic acid, heating and stirring to obtain a clear transparent solution at 65-80 ℃, wherein a product obtained by reaction is a eutectic solvent catalyst benzyltrimethylammonium chloride-p-toluenesulfonic acid BTAC-PTSA, and sealing and placing the BTAC-PTSA in a silica gel drying box for later use.

Example 1

7.41g (0.05 mol) of cinnamic acid and 6.40g (0.2 mol) of methanol were weighed out, added to a three-necked flask, stirred and heated to 64 ℃, and then 2.76g (20%) of a catalyst BTAC-PTSA was added to the three-necked flask and reacted at that temperature for 4 hours; after the reaction is finished, dividing the reaction solution into a water phase and an oil phase by a separating funnel while the reaction solution is hot, and carrying out vacuum drying on the water phase at 50 ℃ to recover the catalyst; pouring the oil phase into a beaker while the oil phase is hot, placing the beaker into a 40 ℃ water bath kettle, adding a proper amount of 4% sodium carbonate solution into the beaker under continuous stirring till the mixture is alkalescent (pH = 7-8), standing the beaker for layering, and removing the water phase; adding three times volume of deionized water at 5 ℃ into the oil phase under continuous stirring to separate out crystals, then performing suction filtration and washing with deionized water until the filtrate is neutral to obtain a white or light yellow solid, and drying to obtain the target product methyl cinnamate with the yield of 89.81%.

Example 2

7.41g (0.05 mol) of cinnamic acid and 4.81g (0.15 mol) of methanol were weighed, added to a three-necked flask, stirred and heated to 76 ℃, then 1.23g (10%) of a catalyst BTAC-PTSA was added to the three-necked flask, and a heating reflux reaction was carried out at that temperature for 2 hours; after the reaction is finished, dividing the reaction solution into a water phase and an oil phase by a separating funnel while the reaction solution is hot, and carrying out vacuum drying on the water phase at 50 ℃ to recover the catalyst; pouring the oil phase into a beaker while the oil phase is hot, placing the beaker into a 50 ℃ water bath kettle, adding a proper amount of 4% sodium carbonate solution into the beaker under continuous stirring till the mixture is alkalescent (pH = 7-8), standing the beaker for layering, and removing the water phase; adding three times volume of deionized water at 5 ℃ into the oil phase under continuous stirring to separate out crystals, then performing suction filtration and washing with deionized water until the filtrate is neutral to obtain a white or light yellow solid, and drying to obtain the target product methyl cinnamate with the yield of 79.07%.

Example 3

7.41g (0.05 mol) of cinnamic acid and 4.81g (0.15 mol) of methanol were weighed, added to a three-necked flask, stirred and heated to 76 ℃, then 3.66g (30%) of a catalyst BTAC-PTSA was added to the three-necked flask and heated under reflux at that temperature for 3 hours; after the reaction is finished, dividing the reaction solution into a water phase and an oil phase by a separating funnel while the reaction solution is hot, and carrying out vacuum drying on the water phase at 50 ℃ to recover the catalyst; pouring the oil phase into a beaker while the oil phase is hot, placing the beaker into a 45 ℃ water bath kettle, adding a proper amount of 4% sodium carbonate solution into the beaker under continuous stirring till the mixture is alkalescent (pH = 7-8), standing the beaker for layering, and removing the water phase; adding three times volume of deionized water at 5 ℃ into the oil phase under continuous stirring to separate out crystals, then performing suction filtration and washing with deionized water until the filtrate is neutral to obtain a white or light yellow solid, and drying to obtain the target product methyl cinnamate with the yield of 93.07%.

Example 4

7.41g (0.05 mol) of cinnamic acid and 3.21g (0.1 mol) of methanol were weighed, added to a three-necked flask, stirred and heated to 70 ℃, then 2.12g (20%) of a catalyst BTAC-PTSA was added to the three-necked flask and heated under reflux at that temperature for 4 hours; after the reaction is finished, dividing the reaction solution into a water phase and an oil phase by a separating funnel while the reaction solution is hot, and carrying out vacuum drying on the water phase at 50 ℃ to recover the catalyst; pouring the oil phase into a beaker while the oil phase is hot, placing the beaker into a 50 ℃ water bath kettle, adding a proper amount of 4% sodium carbonate solution into the beaker under continuous stirring till the mixture is alkalescent (pH = 7-8), standing the beaker for layering, and removing the water phase; adding three times volume of deionized water at 5 ℃ into the oil phase under continuous stirring to separate out crystals, then performing suction filtration and washing with deionized water until the filtrate is neutral to obtain a white or light yellow solid, and drying to obtain the target product methyl cinnamate with the yield of 80.84%.

Example 5

7.41g (0.05 mol) of cinnamic acid and 4.81g (0.15 mol) of methanol were weighed, and the two were put into a three-necked flask, and after heating to 70 ℃ with stirring, the catalyst BTAC-PTSA recovered in example 3 was further added into the three-necked flask and a heating reflux reaction was carried out at that temperature for 4 hours; after the reaction is finished, dividing the reaction solution into a water phase and an oil phase by a separating funnel while the reaction solution is hot, and carrying out vacuum drying on the water phase at 50 ℃ to recover the catalyst; pouring the oil phase into a beaker while the oil phase is hot, placing the beaker into a 40 ℃ water bath kettle, adding a proper amount of 4% sodium carbonate solution into the beaker under continuous stirring till the mixture is alkalescent (pH = 7-8), standing the beaker for layering, and removing the water phase; adding three times volume of deionized water at 5 ℃ into the oil phase under continuous stirring to separate out crystals, then performing suction filtration and washing with deionized water until the filtrate is neutral to obtain a white or light yellow solid, and drying to obtain the target product methyl cinnamate with the yield of 91.92%.