A method for selectively oxidizing benzyl sulfide to synthesize benzyl sulfoxide

Abstract

The application discloses a method for synthesizing benzyl sulfoxide by selectively oxidizing benzyl sulfide, belongs to the technical field of fine organic synthesis, and can solve the problems of a long synthesis process, complex catalyst preparation and long reaction time in the synthesis of benzyl sulfoxide at present. The method uses benzyl sulfide as raw material, uses ozone as an oxidant, introduces tert-butyl alcohol as an inhibitor to control the reaction process, and uses ethyl acetate as a reaction solvent, and benzyl sulfoxide is prepared through selective oxidation. The innovative process has the advantages of mild process conditions, environmental friendliness, no need to add any catalyst and high product yield. The method has great potential and value in the industrial application field.

Description

Technical Field

[0001] This invention belongs to the field of fine organic synthesis technology, specifically relating to a method for the selective oxidation of benzyl sulfide to synthesize benzyl sulfoxide. Background Technology

[0002] Compounds containing sulfoxide structural units are important intermediates in organic synthesis, possessing broad-spectrum biological activity and wide-ranging applications. The selective oxidation of sulfides to prepare sulfoxides is one of the main methods, and commonly used oxidants for this oxidation reaction include metal oxides, inorganic and organic oxidants. These oxidants have drawbacks to varying degrees; for example, some oxidants produce equal amounts of low-valence reduction products during the reaction, which not only increases the difficulty of product separation and purification but also has adverse environmental impacts when disposing of these wastes. Ozone, as an oxidant without secondary pollution, has advantages such as simple post-reaction treatment and water as a byproduct, making this method of further research a focus of particular interest for chemists.

[0003] Patent 201610533582.9 discloses a method for synthesizing cage-like compounds and their applications. These cage-like compounds are obtained by condensing a dipeptide Ni(II)Salen-(R1-R1) ligand with an amine compound via amine-aldehyde condensation to yield Schiff base compounds. The cage-like compounds prepared by this invention can catalyze the selective oxidation of anisole and other compounds to synthesize corresponding sulfoxide compounds with high activity and selectivity. Patent 201710008667.X discloses a porous organic polymer framework material and its preparation method and applications. This method uses 2,7-di-(NA-carbazolyl)-9-glyoxal as the structural unit, with dimethylformaldehyde as the crosslinking agent, to obtain a porous organic polymer framework material linked by methylene groups under the catalysis of a Lewis acid catalyst. This porous organic polymer framework material can be applied to the photocatalytic selective synthesis of imines from organic amines or the photocatalytic selective synthesis of sulfoxides from sulfides. Although this invention has excellent reaction results, the catalyst preparation process is cumbersome, and separation and reuse are difficult. Patent 201910565960.5 discloses a method for synthesizing sulfoxide compounds, belonging to the field of organic compound synthesis technology. The method uses perylene imide as a catalyst to catalyze the reaction of sulfoether compounds with an oxygen-generating agent under light irradiation to obtain sulfoxide compounds. Although this invention achieves the synthesis of sulfoxides by the perylene imide-catalyzed oxidation of sulfoethers, this method requires light irradiation and has a relatively complex catalyst structure and preparation process.

[0004] Current methods for synthesizing benzyl sulfoxide suffer from drawbacks such as cumbersome synthesis steps, complex catalyst preparation, and long reaction times. Therefore, developing a novel method for synthesizing benzyl sulfoxide that features mild process conditions, simple operation, high efficiency, environmental friendliness, no catalyst required, and wide applicability has significant industrial application value. Summary of the Invention

[0005] This invention addresses the shortcomings of current methods for synthesizing benzyl sulfoxide, such as cumbersome synthesis steps, complex catalyst preparation, and long reaction time, by providing a method for the selective oxidation of benzyl sulfide to synthesize benzyl sulfoxide.

[0006] The present invention adopts the following technical solution: A method for selectively oxidizing anisole to synthesize benzyl sulfoxide includes the following steps: The first step is to add benzyl sulfide, tert-butanol, and ethyl acetate to the reaction flask in sequence; The second step is to adjust the pressure reducing valve of the oxygen cylinder and set the partial pressure to 0.1 MPa. After the oxygen enters the ozone generator, it produces ozone mixed gas. The gas flow rate is set to 100 L / h. The ozone mixed gas enters the reaction bottle and reacts with the reactants. The gas phase concentration of ozone is controlled to be 20~100 mg / L. The third step is to introduce the ozone mixture into the reaction bottle and set the reaction liquid temperature to 25°C and the reaction time to 30-60 minutes. The fourth step is to remove the reaction solvent by vacuum distillation after the reaction is complete, and then separate the product, phenyl sulfoxide, by column chromatography.

[0007] Furthermore, the amount of anisole used in the first step is 1-5 mL.

[0008] Furthermore, the amount of tert-butanol used in the first step is 100~500 mg.

[0009] Furthermore, the volume ratio of anisole to ethyl acetate in the first step is 1:50 to 1:100.

[0010] The beneficial effects of this invention are as follows: This invention uses anisole as a reactant, ozone as an oxidant, and tert-butanol as an inhibitor. Without the need for any catalyst, it selectively oxidizes anisole to prepare benzyl sulfoxide under normal pressure. This method features mild process conditions, simple operation, high efficiency, environmental friendliness, catalyst-free operation, and wide applicability. Specifically, the reaction process involves ozone first attacking the sulfur atoms in the anisole, then decomposing the more reactive benzyl mercaptan. Ozone and benzyl mercaptan undergo a 1,3-dipolar insertion reaction, decomposing to generate benzyl sulfoxide and other reactive free radicals. Tert-butanol is used for quenching, reducing the deep oxidation of benzyl sulfoxide to benzyl sulfoxide and thus improving the selectivity of benzyl sulfoxide. Attached Figure Description

[0011] Figure 1 The equation for the selective oxidation of anisole to benzyl sulfoxide by ozone oxidation is the present invention. Figure 2 The target product of the present invention1 H NMR spectrum; Figure 3 The target product of the present invention 13 C10 NMR spectrum. Detailed Implementation

[0012] The technical solutions of the present invention will now be clearly and completely described with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] Example 1 Weigh 1 mL of anisole, 100 mL of ethyl acetate, and 200 mg of tert-butanol and place them in a reaction flask. Adjust the pressure reducing valve of the oxygen cylinder to set the partial pressure to 0.1 MPa. After the oxygen enters the ozone generator, an ozone mixture is generated. Set the gas flow rate to 100 L / h and the ozone gas phase concentration to 50 mg / L. After reacting at a reaction temperature of 25 °C for 30 min, remove the reaction solvent by vacuum distillation and then separate the product, sulfoxide, by column chromatography with a yield of 65%.

[0014] 1 H NMR (400 MHz, CDCl3) δ7.67-7.63 (m, 2H), 7.54-7.46 (m, 3H), 2.71 (s, 3H).

[0015] 13 C NMR (100 MHz, CDCl3) δ 145.69, 130.97, 129.30, 123.42, 43.90.

[0016] Example 2 Weigh 5 mL of anisole, 250 mL of ethyl acetate, and 500 mg of tert-butanol into a reaction flask. Adjust the pressure reducing valve of the oxygen cylinder to set the partial pressure to 0.1 MPa. After the oxygen enters the ozone generator, an ozone mixture is produced. Set the gas flow rate to 100 L / h and the ozone gas phase concentration to 100 mg / L. After reacting at 25 °C for 60 min, remove the reaction solvent by vacuum distillation and then separate the product, sulfoxide, by column chromatography with a yield of 78%.

[0017] 1H NMR (400 MHz, CDCl3) δ 7.67-7.63 (m, 2H), 7.54-7.46 (m, 3H), 2.71 (s, 3H).

[0018] 13 C NMR (100 MHz, CDCl3) δ 145.69, 130.97, 129.30, 123.42, 43.90.

[0019] Example 3 Weigh 2 mL of anisole sulfide, 200 mL of ethyl acetate, and 100 mg of tert-butanol into a reaction flask. Adjust the pressure reducing valve of the oxygen cylinder to set the partial pressure to 0.1 MPa. After the oxygen enters the ozone generator, an ozone mixture is produced. Set the gas flow rate to 100 L / h and the ozone gas phase concentration to 60 mg / L. After reacting at 25 °C for 45 min, remove the reaction solvent by vacuum distillation and then separate the product, sulfoxide, by column chromatography with a yield of 68%.

[0020] 1 H NMR (400 MHz, CDCl3) δ 7.67-7.63 (m, 2H), 7.54-7.46 (m, 3H), 2.71 (s, 3H).

[0021] 13 C NMR (100 MHz, CDCl3) δ 145.69, 130.97, 129.30, 123.42, 43.90.

[0022] Example 4 Weigh 3 mL of anisole, 150 mL of ethyl acetate, and 200 mg of tert-butanol and place them in a reaction flask. Adjust the pressure reducing valve of the oxygen cylinder to set the partial pressure to 0.1 MPa. After the oxygen enters the ozone generator, an ozone mixture is produced. Set the gas flow rate to 100 L / h and the ozone gas phase concentration to 80 mg / L. After reacting at 25 °C for 60 min, remove the reaction solvent by vacuum distillation and then separate the product, sulfoxide, by column chromatography with a yield of 72%.

[0023] 1 H NMR (400 MHz, CDCl3) δ 7.67-7.63 (m, 2H), 7.54-7.46 (m, 3H), 2.71 (s, 3H).

[0024] 13 C NMR (100 MHz, CDCl3) δ 145.69, 130.97, 129.30, 123.42, 43.90.

[0025] The above description only illustrates the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and all such changes should be included within the protection scope of the present invention.

Claims

1. A method for the selective oxidation of anisole to synthesize benzyl sulfoxide, characterized in that: Includes the following steps: The first step is to add benzyl sulfide, tert-butanol, and ethyl acetate to the reaction flask in sequence; The second step involves adjusting the pressure reducing valve of the oxygen cylinder to a partial pressure of 0.1 MPa. After the oxygen enters the ozone generator, it produces an ozone mixture. The gas flow rate is set to 100 L / h. The ozone mixture enters the reaction bottle to react with the reactants, and the gas phase concentration of ozone is controlled to be 20~100 mg / L. The amount of tert-butanol used is 100~500 mg. The third step is to introduce the ozone mixture into the reaction bottle and set the reaction liquid temperature to 25°C and the reaction time to 30-60 minutes. The fourth step is to remove the reaction solvent by vacuum distillation after the reaction is complete, and then separate the product, phenyl sulfoxide, by column chromatography.

2. The method for selectively oxidizing anisole to synthesize benzyl sulfoxide according to claim 1, characterized in that: The amount of anisole used in the first step is 1-5 mL.

3. The method for selectively oxidizing anisole to synthesize benzyl sulfoxide according to claim 1, characterized in that: The volume ratio of anisole to ethyl acetate in the first step is 1:50 to 1:100.

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