阅读说明：本技术 一种高效光催化氧化苯甲胺制备n-苄烯丁胺的方法 (Method for preparing N-benzyl enamine by efficiently photo-catalytically oxidizing benzylamine ) 是由 郭慧敏 邱阳 雷志文 张翔宇 刘新 于 2021-08-25 设计创作，主要内容包括：本发明属于光催化氧化技术领域,具体涉及一种高效光催化氧化苯甲胺制备N-苄烯丁胺的方法。以黄素光敏剂作为催化剂,在光照作用下,一步法制备N-苄烯丁胺；所述制备方法具体包括以下步骤：(1)取黄素光敏剂、苄胺溶于有机溶剂中；(2)在室温和常压下,将步骤(1)得到的混合溶液中通入空气,光照,得到N-苄烯丁胺。本发明制备工艺简单,制备的条件较为温和,制备过程中没有使用重金属,环境友好,成本低廉；本发明提供的方法能够在常温常压的条件下制备N-苄烯丁胺,能耗低且方法简单易操作,可用于大规模生产。(The invention belongs to the technical field of photocatalytic oxidation, and particularly relates to a method for preparing N-benzyl enamine by efficiently carrying out photocatalytic oxidation on benzylamine. Taking a flavin photosensitizer as a catalyst, and preparing N-benzyl enamine by a one-step method under the action of illumination; the preparation method specifically comprises the following steps: (1) dissolving a flavin photosensitizer and benzylamine in an organic solvent; (2) and (2) introducing air into the mixed solution obtained in the step (1) at room temperature and normal pressure, and irradiating to obtain the N-benzyl enamine. The preparation method is simple in preparation process, mild in preparation conditions, free of heavy metal in the preparation process, environment-friendly and low in cost; the method provided by the invention can be used for preparing the N-benzyl enamine under the conditions of normal temperature and normal pressure, has low energy consumption, is simple and easy to operate, and can be used for large-scale production.)

1. A method for preparing N-benzyl enamine by photo-catalytic oxidation of benzylamine is characterized in that a flavin photosensitizer is used as a catalyst, and N-benzyl enamine is prepared by a one-step method under the action of illumination; the preparation method specifically comprises the following steps:

(1) dissolving a flavin photosensitizer and benzylamine in an organic solvent;

(2) and (2) introducing air into the mixed solution obtained in the step (1) at room temperature and normal pressure, and irradiating to obtain the N-benzyl enamine.

2. The process according to claim 1, wherein the molar ratio of the flavin photosensitizer to benzylamine in the step (1) is in the range of 1: (50-500).

3. The method according to claim 1, wherein the concentration of benzylamine in the mixed solution obtained in the step (1) is 0.01 to 1 mol/L.

4. The preparation method according to claim 1, wherein the irradiation time in the step (2) is 1-9 h.

5. The method according to claim 1, wherein the light source used in step (2) has a wavelength of 350 to 480 nm.

6. The preparation method according to claim 1, wherein the organic solvent in the step (1) comprises any one of toluene, acetonitrile, dichloromethane, a mixed solution of toluene and methanol, a mixed solution of acetonitrile and methanol, a mixed solution of dichloromethane and methanol, and a mixed solution of acetonitrile and water.

7. The method of claim 1, wherein the flavin photosensitizer is an aromatic organic compound of pteridine-2, 4(1H, 3H) -dione or pteridine-2, 4(3H, 8H) -dione structural fragment and derivatives thereof.

8. The method according to claim 1, wherein the flavin photosensitizer comprises any one of riboflavin, riboflavin tetraacetate, 10-octylbenzo [ g ] pteridine-2, 4(3H,10H) -dione.

Technical Field

The invention belongs to the technical field of photocatalytic oxidation, and particularly relates to a method for preparing N-benzyl enamine by efficiently carrying out photocatalytic oxidation on benzylamine.

Background

The Schiff base compounds can be used as intermediates for synthesizing fine chemicals and drug molecules, so that the study on the synthesis of the Schiff base compounds is very valuable. In recent years, with the continuous development of science and technology, more and more methods for preparing schiff base compounds are provided. The Schiff base compound is generally obtained by dehydration condensation reaction of an amine compound and a carbonyl compound, but the method has the defect that the nucleophilic addition reaction between the two substances is not easy to control. In addition, there are various methods for synthesizing schiff base compounds under the catalytic action of catalysts, for example, the synthesis is performed by a method of condensing a hydroxyl compound and an amine compound, coupling a primary amine, dehydrogenating a secondary amine, and the like, but the currently reported methods have high synthesis cost and environmental pollution due to the use of a noble metal catalyst because the catalyst used is generally an expensive noble metal catalyst.

Disclosure of Invention

The invention aims to provide a method for preparing N-benzyl enamine by efficiently carrying out photocatalytic oxidation on benzylamine, and the method adopted by the invention has the characteristics of greenness, low cost, simple preparation method, mild experimental conditions and the like.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a method for preparing N-benzyl enamine by photo-catalytic oxidation of benzylamine comprises the steps of taking a flavin photosensitizer as a catalyst, and preparing N-benzyl enamine by a one-step method under the action of illumination; the preparation method specifically comprises the following steps:

(1) dissolving a flavin photosensitizer and benzylamine in an organic solvent;

(2) and (2) introducing air into the mixed solution obtained in the step (1) at room temperature and normal pressure, and irradiating to obtain the N-benzyl enamine.

Preferably, the molar ratio of the flavin photosensitizer to benzylamine in step (1) is 1: (50-500).

Preferably, the concentration of benzylamine in the mixed solution obtained in the step (1) is 0.01-1 mol/L.

Preferably, the illumination time in the step (2) is 1-9 h.

Preferably, the wavelength of the light source irradiated in the step (2) is 350-480 nm.

Preferably, the organic solvent in step (1) is selected according to the solubility of the substrate and the catalyst, and includes any one of toluene, acetonitrile, dichloromethane, a mixed solution of toluene and methanol, a mixed solution of acetonitrile and methanol, a mixed solution of dichloromethane and methanol, and a mixed solution of acetonitrile/water.

Preferably, the flavin photosensitizer is an aromatic organic compound of pteridine-2, 4(1H, 3H) -dione or pteridine-2, 4(3H, 8H) -dione structural fragment and derivatives thereof.

Preferably, the flavin photosensitizer comprises any one of riboflavin, riboflavin tetraacetate, 10-octylbenzo [ g ] pteridine-2, 4(3H,10H) -dione.

The invention has the beneficial effects that:

(1) the preparation method is simple in preparation process, mild in preparation conditions, free of heavy metal in the preparation process, environment-friendly and low in cost;

(2) the method provided by the invention can be used for preparing the N-benzyl enamine under the conditions of normal temperature and normal pressure, has low energy consumption, is simple and easy to operate, and can be used for large-scale production.

Drawings

FIG. 1 is a chromatogram of a standard product of N-benzylbutylamine according to the present invention.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention in conjunction with the following examples, but it will be understood that the description is intended to illustrate the features and advantages of the invention further and is not intended to limit the invention.

Example 1

The invention provides a method for preparing N-benzyl enamine by photocatalytic oxidation of benzylamine with a flavin photosensitizer, which comprises the following steps:

(1) 3ml of an organic solvent was added to a 10ml reaction flask, followed by 0.2mmol of benzylamine and 0.001mmol of flavin photosensitizer;

(2) under the atmosphere of atmospheric air, the light intensity is 1240W/m²Irradiating the mixed solution by an LED lamp with the wavelength of 451nm for 1-9 h, and introducing circulating water to ensure that the reaction condition is carried out at normal temperature;

(3) the progress of the reaction was monitored using thin layer chromatography and the light was stopped when the substrate reaction was complete or no longer changing.

The product is qualitatively analyzed by a gas chromatography-mass spectrometer and a liquid chromatography-mass spectrometer, and quantitatively analyzed by a gas chromatograph (GC2012, a hydrogen flame ionizer detector, produced by Agilent, USA), and the product obtained by catalytic oxidation of benzylamine is N-benzyl enamine.

Example 2

Under the condition of keeping other experimental conditions consistent in the embodiment 1, the self-synthesized 10-octylbenzo [ g ] with acetonitrile as organic solvent, benzylamine as substrate and flavin photosensitizer]Pteridine-2, 4(3H,10H) -dione flavin of formula C₁₈H₂₂N₄O₂Discussing the influence of different light reaction time on the reactant yield, the prepared product labels are sample-1, sample-2, sample-3, sample-4 and sample-5 respectively.

The preparation method comprises the following steps:

(1) 3ml acetonitrile was added to a 10ml reaction flask followed by 0.2mmol benzylamine and 0.001mmol 10-octylbenzo [ g ] pteridine-2, 4(3H,10H) -dione;

(2) under the atmosphere of atmospheric air, the light intensity is 1240W/m²The mixed solution is irradiated by an LED lamp with the wavelength of 451nm for 1h, 3h, 5h, 7h and 9h respectively, and circulating water is introduced to ensure that the reaction condition is carried out at normal temperature;

(3) the progress of the reaction was monitored using thin layer chromatography and the light was stopped when the substrate reaction was complete or no longer changing.

The product was qualitatively analyzed by a gas chromatograph-mass spectrometer and a liquid chromatograph-mass spectrometer, and quantitatively analyzed by a gas chromatograph (GC2012, hydrogen flame ionizer detector, Agilent company, usa), and the analysis results obtained are shown in table 1.

TABLE 1 yield of N-benzyl enamine by different reaction time

As shown in Table 1, the yield of N-benzyl butylamine increases with the increase of the reaction time, and after 9h of reaction, the yield reaches 83.2%, and the yield is not increased significantly by continuously prolonging the light irradiation time, so that the optimal reaction time is 9 h.

Example 3

In keeping with the other experimental conditions in example 1, the substrate used was benzylamine and the flavin photosensitizer was 10-octylbenzo [ g ]]Pteridine-2, 4(3H,10H) -diketone (molecular formula is C)₁₈H₂₂N₄O₂) The fixed reaction time is 9h, and the prepared samples are respectively labeled as sample-5, sample-6 and sample-7 for discussing the influence of different organic solvents on the yield of reactants.

The preparation method comprises the following steps:

(1) to a 10ml reaction flask was added 3ml of organic solvent followed by 0.2mmol of benzylamine and 0.001mmol of 10-octylbenzo [ g ] pteridine-2, 4(3H,10H) -dione;

(2) under the atmosphere of atmospheric air, the light intensity is 1240W/m²Irradiating the mixed solution by an LED lamp with the wavelength of 451nm for 9 hours, and introducing circulating water to ensure that the reaction condition is carried out at normal temperature;

(3) the progress of the reaction was monitored using thin layer chromatography and the light was stopped when the substrate reaction was complete or no longer changing.

The product was qualitatively analyzed by a gas chromatograph-mass spectrometer and a liquid chromatograph-mass spectrometer, and quantitatively analyzed by a gas chromatograph (GC2012, hydrogen flame ionizer detector, Agilent company, usa), and the analysis results obtained are shown in table 2.

TABLE 2 yield of N-benzyl enamine by different organic solvents

As can be seen from Table 2, different reaction solvents had an effect on the yield of N-benzylbutylamine at the same reaction time, which was found to be the highest in acetonitrile.

Example 4

Under the condition of keeping other experimental conditions consistent in the embodiment 1, the fixed reaction time is 9h, the fixed reaction solvent is acetonitrile, the influence of different substrates on the yield is discussed, and the prepared samples are respectively marked as sample-5, sample-8 to sample-13.

TABLE 3 yield of N-benzyl enamine by different substrate preparation

As shown in Table 3, under the same reaction conditions, different reaction substrates have influence on the yield of N-benzyl enamine, and compared with the findings that the presence of an electron-withdrawing group on a benzene ring causes the yield of the reaction to be reduced, and the presence of an electron-withdrawing group on the benzene ring causes the yield to be improved.

It can be seen from the above examples that the method of the present invention uses a flavin photosensitizer to photocatalytically oxidize benzylamine to synthesize N-benzyl enamine, and uses oxygen in the air as an oxidant, thereby realizing the high efficiency preparation of N-benzyl amine butene at normal temperature and pressure.

While specific examples have been set forth herein to illustrate embodiments of the invention, the foregoing examples are presented only to aid in understanding the method of the invention, and it will be appreciated by those skilled in the art that various modifications and adaptations of the invention may be made without departing from the principles of the method of the invention and are intended to be within the scope of the claims appended hereto.