Method for preparing ester compound from benzyl bromide compound under photocatalysis condition

Abstract

The invention provides a method for preparing an ester compound from a benzyl bromide compound under a photocatalysis condition. The method comprises the following steps: adding a benzyl bromide compound, an additive and a manganese oxide catalyst into an acetonitrile solvent, putting into a photoreactor, and reacting for 12-24 hours under the irradiation of blue light in an oxygen atmosphere, so as to oxidize and break a carbon-bromine bond into a corresponding ester compound. The system has the advantages that the catalyst activity is high, the method is wide in application range, reaction conditions are easy to control, the catalyst can be recycled, post-treatment is simple and the like, and the system has a good application prospect.

Description

Technical Field

[0001] The invention relates to the field of chemistry and chemical engineering, and is a method for preparing ester compounds from benzyl bromide compounds under photocatalytic conditions. Background Art

[0002] Organic carboxylic acid esters play a very important role in the fields of food, organic synthesis, fragrances, cosmetics, medicine and polymer materials. The traditional synthesis method generally uses acid and alcohol as raw materials, acid as catalyst, and synthesizes the corresponding ester products through esterification reaction under long-term heating. The acid used as a catalyst is usually concentrated sulfuric acid. Although it has high activity, it has problems such as poor selectivity, many side reactions, large environmental pollution and serious corrosion. Some documents and patents point out the use of other acids, such as organic acids or inorganic acids such as benzenesulfonic acid and chlorosulfonic acid as catalysts, but the above problems still exist. With the continuous deepening of research, there are documents and patents reporting the use of solid organic sulfonic acid polymers as catalysts to prepare corresponding esters, but only for small molecule organic alcohols and carboxylic acids for esterification.

[0003] Other ester synthesis methods, such as first making carboxylic acid into highly active intermediates such as acyl chlorides and anhydrides, and then reacting with alcohol to generate corresponding esters, but this method has low economic benefits and also has storage problems and equipment corrosion problems. If aldehyde is used as the starting material to prepare esters, it is necessary to undergo three steps of oxidation, activation and esterification, and these methods usually reduce the yield of esters and require a long reaction time. Subsequently, there are also some documents that use the direct oxidation esterification of aldehydes to synthesize esters in one step, but this type of method often uses excessive strong oxidants, such as active manganese dioxide, potassium persulfate, peroxide, etc., although there is a certain yield, it will cause more serious damage to the environment and increase the cost of post-processing. In addition, esters can also be synthesized in one step by direct oxidation esterification of primary alcohols, but the catalyst used in this method needs to use precious metals such as Au and Pd as active centers, which is costly; some catalytic systems use cobalt-based catalysts supported by carbon materials, but the scope of application is small. Benzyl bromide compounds are aromatic compounds whose aromatic rings are substituted by bromomethyl groups. They can effectively benzylate various heteroatom functional groups under various conditions, thus having a wide range of uses in organic synthesis and can be transformed into a variety of organic chemicals. Through research, it was found that under photoreaction and oxygen-rich conditions, benzyl bromide compounds can be esterified by oxidative cleavage of the carbon-bromine bond to obtain new organic carboxylates. This approach is a new and effective way to transform and utilize benzyl bromide compounds. At present, there is no report on the method of preparing ester compounds from benzyl bromide compounds by oxidation under photoreaction conditions. Therefore, this method provides a new way to prepare organic carboxylates. Compared with other approaches, the reaction conditions are milder and easier to control, the green pollution is small during the reaction, the application range is wide, the catalyst can be recycled, and the post-treatment is simple, and many other advantages have good application prospects. Summary of the invention

[0004] The invention provides a novel method for preparing organic carboxylic acid ester. In the method, benzyl bromide is used as a substrate and oxygen is used as an oxygen source. Under the action of a catalyst and the irradiation of a light source, benzyl bromide undergoes self-coupling to generate organic carboxylic acid ester.

[0005] According to the present invention, the other substituents on the benzene ring are one or more of -CH3, -OCH3, -C(CH3)3, -F, -Cl, -Br, -CF3, -NO2;

[0006] In alkynes with other substituents on the benzene ring, the positions of the other substituents are ortho, meta or para; according to the present invention, environmentally friendly oxygen is used as the oxygen source. The three forms of oxygen molecules are not active enough, and a catalyst is required to activate oxygen to form active oxygen. The present invention uses transition metal Mn oxide as a catalyst to activate oxygen molecules, realize oxidative cleavage of benzyl bromide, and prepare organic carboxylic acid esters.

[0007] According to the present invention, the catalytic performance is related to the amount of the catalyst used. Too low an amount will affect the activity of the catalytic reaction, and too high an amount will increase the cost of the catalyst; therefore, it is necessary to select an appropriate amount. In order to ensure the activity of the catalyst and reduce the cost of the catalyst, the amount of the catalyst used is 30%-150% of the mass of the benzyl bromide compound, preferably 45%-120%.

[0008] According to the present invention, the benzyl bromide oxidation effect is related to the reaction atmosphere, reaction light source and time, wherein the reaction atmosphere is oxygen-enriched air and / or oxygen atmosphere, preferably oxygen atmosphere, the light source is one of visible violet light (390nm-435nm), visible blue light (435nm-490nm), and visible green light (490nm-560nm), preferably visible blue light (435nm-490nm). The reaction time is 12-48h, preferably 16-24h.

[0009] According to the present invention, the reaction needs to be carried out in a solvent, especially for some solid benzyl bromide substrate molecules, which need to be dissolved in a solvent to be evenly dispersed, which is conducive to contact with the catalyst. The solvent used for benzyl bromide oxidation is one or more of toluene, tert-amyl alcohol, 1,4-dioxane, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile, n-heptane, methanol, and ethanol.

[0010] The preparation method of the γ-MnO2 catalyst is as follows: weigh a certain amount of manganese sulfate, and then configure it into 50 ml of a manganese sulfate solution with a mass fraction of 1.00%-30.00% (preferably 10.00%-20.00%), which is recorded as solution A; weigh a certain amount of potassium permanganate, and then configure it into 500 ml of a potassium permanganate solution with a mass fraction of 0.50%-4.50% (preferably 2.00%-4.00%), which is recorded as solution B. In a 50-60°C water bath, solution A is added dropwise to solution B. After the addition is completed, the mixture is stirred at room temperature for 1-3 hours, then allowed to stand for precipitation for 12-24 hours, filtered, washed with deionized water until the filtrate is neutral, and dried to obtain the target catalyst γ-MnO2;

[0011] The system of the present invention has many advantages such as high catalyst activity, wide application range of the method, easy control of reaction conditions, recyclable catalyst, simple post-treatment, etc., and has good application prospects. DETAILED DESCRIPTION

[0012] The specific implementation steps of the present invention are described in detail below through some embodiments, but these embodiments should not be regarded as limiting the scope of the present invention.

[0013] The preparation method of the γ-MnO2 catalyst is as follows: a certain amount of manganese sulfate is weighed, and then configured into 50 ml of a manganese sulfate solution with a mass fraction of 15.00%, which is recorded as solution A; a certain amount of potassium permanganate is weighed, and then configured into 500 ml of a potassium permanganate solution with a mass fraction of 3.50%, which is recorded as solution B. In a 60°C water bath, solution A is added dropwise to solution B. After the addition is completed, the mixture is stirred at room temperature for 2 hours, then allowed to stand for 18 hours, filtered, washed with deionized water until the filtrate is neutral, and dried to obtain the target catalyst γ-MnO2;

[0014] Example 1

[0015] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Blue Light

[0016]

[0017] γ-MnO2 (40 mg), benzyl bromide (0.5 mmol), Na2CO3 (1 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.6 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under blue light (435 nm-490 nm) for 24 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 20.4%.

[0018] Example 2

[0019] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Violet Light

[0020]

[0021] γ-MnO2 (40 mg), benzyl bromide (0.5 mmol), Na2CO3 (1 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.5 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under purple light (390 nm-435 nm) for 24 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 18.1%.

[0022] Example 3

[0023] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Green Light

[0024]

[0025] γ-MnO2 (40 mg), benzyl bromide (0.5 mmol), Na2CO3 (1 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.4 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under green light (490 nm-560 nm) for 24 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 10.6%.

[0026] Example 4

[0027] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Blue Light

[0028]

[0029] γ-MnO2 (40 mg), benzyl bromide (0.5 mmol), Na2CO3 (0.5 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.8 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under blue light (435 nm-490 nm) for 24 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 10.2%.

[0030] Example 5

[0031] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Blue Light

[0032]

[0033] γ-MnO2 (40 mg), benzyl bromide (0.5 mmol), Na2CO3 (0.25 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.6 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under blue light (435 nm-490 nm) for 24 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 5.4%.

[0034] Example 6

[0035] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Blue Light

[0036]

[0037] γ-MnO2 (20 mg), benzyl bromide (0.5 mmol), Na2CO3 (0.25 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.6 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under blue light (435 nm-490 nm) for 24 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 10.8%.

[0038] Example 7

[0039] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Blue Light

[0040]

[0041] γ-MnO2 (60 mg), benzyl bromide (0.5 mmol), Na2CO3 (0.25 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.6 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under blue light (435 nm-490 nm) for 24 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 14.4%.

[0042] Example 8

[0043] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Blue Light

[0044]

[0045] γ-MnO2 (80 mg), benzyl bromide (0.5 mmol), Na2CO3 (0.25 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.9 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under blue light (435 nm-490 nm) for 24 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 12.5%.

[0046] Example 9

[0047] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Blue Light

[0048]

[0049] γ-MnO2 (100 mg), benzyl bromide (0.5 mmol), Na2CO3 (0.25 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 1.0 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under blue light (435 nm-490 nm) for 24 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 11.2%.

[0050] Example 10

[0051] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Blue Light

[0052]

[0053] γ-MnO2 (40 mg), benzyl bromide (0.5 mmol), Na2CO3 (0.25 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.6 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under blue light (435 nm-490 nm) for 12 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 10.3%.

[0054] Embodiment 11

[0055] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Blue Light

[0056]

[0057] γ-MnO2 (40 mg), benzyl bromide (0.5 mmol), Na2CO3 (0.25 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.6 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under blue light (435 nm-490 nm) for 16 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 13.3%.

[0058] Example 12

[0059] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Blue Light

[0060]

[0061] γ-MnO2 (40 mg), benzyl bromide (0.5 mmol), Na2CO3 (0.25 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.6 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under blue light (435 nm-490 nm) for 36 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 20.8%.

[0062] Example 13

[0063] Preparation of Benzyl Benzoate from Benzyl Bromide under Visible Blue Light

[0064]

[0065] γ-MnO2 (40 mg), benzyl bromide (0.5 mmol), Na2CO3 (0.25 mmol), and 4 mL of acetonitrile were added to a 10 mL photoreaction tube in sequence, and the oxygen was replaced three times. 0.6 MPa of oxygen was filled in, and the photoreaction tube was placed in a photoreactor. The reaction was stirred at 500 rpm under blue light (435 nm-490 nm) for 48 h. After the reaction was completed, the reactor was cooled to room temperature, the reactor was opened, and internal standard naphthalene (64 mg) was added. The product was qualitatively detected by gas chromatography-mass spectrometry, and the product yield was 21.4%.

[0066] The invention has high oxidation efficiency, good selectivity and high product yield; it uses oxygen as an oxygen source, is economical and environmentally friendly, and has good application prospects.

[0067] The above embodiments are partial implementation processes of the present invention, but the implementation methods of the present invention are not limited to the above embodiments. Any other changes, substitutions, combinations, and simplifications that violate the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing ester compounds from benzyl bromide under photocatalytic conditions, characterized in that: The benzyl bromide compound, additives and γ-MnO2 catalyst are added to an acetonitrile solvent, placed in a sealed photoreactor, and reacted under light irradiation in an oxygen-rich atmosphere for 12 to 48 hours to oxidatively break the carbon-bromine bond into the corresponding ester compound.

2. The method for preparing ester compounds from benzyl bromide compounds under photocatalytic conditions according to claim 1, characterized in that: The amount of the catalyst used is 30%-150% of the mass of the benzyl bromide compound, preferably 45%-120%.

3. The method for preparing ester compounds from benzyl bromide compounds under photocatalytic conditions according to claim 1, characterized in that: The additive is an alkaline inorganic compound, including one or more of potassium hydroxide, potassium carbonate, sodium carbonate, cesium carbonate and potassium phosphate.

4. The method for preparing ester compounds from benzyl bromide under photocatalytic conditions according to claim 1 or 3, characterized in that: The additive is 100mol%-500mol%, preferably 150mol%-300mol% of the benzyl bromide compound.

5. The method for preparing ester compounds from benzyl bromide compounds under photocatalytic conditions according to claim 1, characterized in that: The acetonitrile solvent is an anhydrous solvent.

6. The method for preparing ester compounds from benzyl bromide compounds under photocatalytic conditions according to claim 1, characterized in that: The light source is one or more of visible violet light (390nm-435nm), visible blue light (435nm-490nm), and visible green light (490nm-560nm), preferably a visible blue light (435nm-490nm).

7. The method for preparing ester compounds from benzyl bromide under photocatalytic conditions according to claim 1, characterized in that: The gas atmosphere is an oxygen-enriched atmosphere (oxygen-enriched air or oxygen), the oxygen volume concentration is 80%-100%; the pressure is 0.2-2MPa.

8. The method for preparing ester compounds from benzyl bromide compounds under photocatalytic conditions according to claim 1, characterized in that: The reaction time is 12-24 hours, preferably 16-18 hours.

9. The method for preparing ester compounds from benzyl bromide under photocatalytic conditions according to claim 1 or 2, characterized in that: The general structural formula of the benzyl bromide compound is as follows: The substituent -R may be one or more of H, -CH3, -OCH3, -C(CH3)3, -F, -Cl, -Br, -CF3, -NO2, and the position of the substituent -R is ortho, meta or para.

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