Method for synthesizing epsilon-caprolactone

Abstract

A method for synthesizing epsilon-caprolactone comprises the following steps that cyclohexane, aldehyde, a photocatalyst and a chlorine source are mixed and stirred, the molar ratio of the aldehyde to the cyclohexane is 1: 2-1: 10, the molar ratio of the photocatalyst to the aldehyde is 1: 10-1: 100, and the molar ratio of the chlorine source to the cyclohexane can be 1: 5-1: 50; and introducing oxygen, and reacting under the irradiation of visible light at room temperature to obtain epsilon-caprolactone. The method for synthesizing epsilon-caprolactone has extremely high selectivity, the highest selectivity of epsilon-caprolactone can reach 95%, no intermediate products cyclohexanol and cyclohexanone are generated, only a small amount of catalyst aldehyde needs to be added, the production cost can be effectively reduced, generation of by-products is reduced, the product separation and purification difficulty is reduced, the aldehyde can be circularly oxidized under light driving, and the method is suitable for industrial production. Therefore, the addition amount can be greatly reduced, reaction conditions are mild, and the method is green and environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a synthesis method. e - Methods involving caprolactone. Background Technology

[0002] e -caprolactone ( e -CL) is an important cyclic ester monomer, a colorless and transparent liquid at room temperature. Its core application is the ring-opening polymerization to produce polycaprolactone (PCL). This material possesses excellent biocompatibility, flexibility, and controllable degradation properties, and is widely used in medical sutures, orthopedic fixation materials, and drug delivery systems. Furthermore, e -CL can also be used to modify bio-based plastics such as PLA and PBS, improving their toughness and processing properties. In recent years, driven by environmental policies and the development of the medical industry, caprolactone has a promising market prospect.

[0003] Currently, industrial production e The traditional method for producing cyclohexane (-CL) involves two steps: First, cyclohexane is used as a raw material to produce cyclohexanol and cyclohexanone through an oxidation reaction, followed by distillation to obtain cyclohexanone. Then, using cyclohexanone as a starting material, a Baeyer-Villiger oxidation reaction is employed to produce cyclohexanone. e -CL. However, this process not only involves explosion risks but also faces problems such as insufficient product stability and excessive byproducts. If a one-step synthesis from cyclohexane could be achieved... e -CL will significantly reduce intermediate separation steps, thereby reducing energy consumption and costs.

[0004] Although existing literature reports the direct preparation of cyclohexane as a raw material e While methods using the -CL approach exist, they generally suffer from problems such as numerous byproducts, low selectivity, large amounts of catalysts or auxiliaries, complex processes, and high operational difficulty. For example, although Chinese patent CN 103373975A achieves a one-step oxidation of cycloalkanes to lactones, the selectivity of the lactone products is low (< 20%), and there are many byproducts. While Chinese patent CN 109232510A uses cyclic organic nitric oxide radical precursors as catalysts and aldehydes as auxiliaries to obtain lactones with high yields (~85%), it still generates byproducts such as cyclohexanone (typically > 5%) and cyclohexanol (typically > 10%). Furthermore, this method requires an equivalent amount (typically 2 monotonies) of aldehyde as a co-oxidant, which not only increases production costs but also introduces more new products.

[0005] Given the numerous shortcomings of existing processes, this study aims to develop a highly selective, low-by-product, low-pollution, environmentally friendly, and simple process for the direct preparation of cyclohexane by oxidation. e -CL's new process has extremely important practical significance. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a synthetic e The -CL method has extremely high selectivity. e -CL exhibits selectivity up to 95%, with no intermediate products cyclohexanol and cyclohexanone generated. It requires only a small amount of catalyst aldehyde, which can effectively reduce production costs, reduce by-product generation, and simplify product separation and purification. Aldehydes can be cyclically oxidized under light-driven conditions, thus greatly reducing the amount added. The reaction conditions are mild and environmentally friendly.

[0007] This invention provides a synthesis e The -CL method includes the following steps: Cyclohexane, aldehyde, photocatalyst and chlorine source are mixed and stirred, wherein the molar ratio of aldehyde to cyclohexane is 1:2-1:10, the molar ratio of photocatalyst to aldehyde is 1:10-1:100, and the molar ratio of chlorine source to cyclohexane can be 1:5-1:50. Oxygen is introduced, and the reaction is carried out under visible light irradiation and at room temperature to obtain... e -CL.

[0008] In one embodiment, the aldehyde is an aryl aldehyde or an alkyl aldehyde.

[0009] In one embodiment, the aryl aldehyde is one or more of the following: benzaldehyde, o-fluorobenzaldehyde, o-chlorobenzaldehyde, o-trifluoromethylbenzaldehyde, m-fluorobenzaldehyde, m-chlorobenzaldehyde, m-trifluoromethylbenzaldehyde, p-fluorobenzaldehyde, p-chlorobenzaldehyde, and p-trifluoromethylbenzaldehyde.

[0010] In one embodiment, the alkyl aldehyde is one or more of pentanal, 2-methyldecanal, and 2-methylundecanal.

[0011] In one embodiment, the photocatalyst is a nitrile aromatic hydrocarbon, benzophenone and quinone, pyran and thiaran, quinoline, acridine, rhodamine, or thiophene.

[0012] In one embodiment, the chlorine source is one or more of hydrogen chloride, sodium chloride, potassium chloride, ammonium chloride, and tetrabutylammonium chloride.

[0013] In one embodiment, the visible light wavelength range is 380~440nm.

[0014] The synthesis provided by this invention e The -CL method has extremely high selectivity. e-CL exhibits selectivity up to 95%, with no intermediate products cyclohexanol and cyclohexanone generated. It requires only a small amount of catalyst aldehyde, which can effectively reduce production costs, reduce by-product generation, and simplify product separation and purification. Aldehydes can be cyclically oxidized under light-driven conditions, thus greatly reducing the amount added. The reaction conditions are mild and environmentally friendly. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 Synthesis provided by the present invention e - CL method flowchart. Detailed Implementation

[0017] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. Based on the description of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0018] In the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0019] The terms “upper,” “lower,” “left,” “right,” “front,” “back,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of description and simplification, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0020] The terms “first,” “second,” “third,” etc., are used merely to distinguish elements with similar properties, not to indicate or imply relative importance or a specific order.

[0021] The terms “include,” “comprising,” or any other variation thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed. Example 1

[0022] Please see Figure 1 The synthesis provided in this embodiment e The -CL method includes the following steps: A 10 mL glass reactor was used, and cyclohexane (2.2 mL, 20 mmol), benzaldehyde (0.42 g, 4.0 mmol), the photocatalyst 10-methyl-9-trimethylammonium acridine perchlorate (0.16 g, 0.4 mmol), and a 1,4-dioxane (1.0 M) solution of hydrogen chloride (2 mL, 2.0 mmol) were added sequentially. The glass reactor was connected to an oxygen balloon and placed under a 32W blue LED light source. The reaction was carried out at room temperature with stirring for 24 hours. After the reaction, the contents of the raw materials and products were detected by gas chromatography-mass spectrometry (GC-MS), and the conversion rate of cyclohexane and the selectivity of the major products were calculated. The experimental results are shown in Table 1.

[0023] Comparative Example 1 This comparative example provides a synthesis e The -CL method, with reaction conditions basically the same as in Example 1, differs in that benzaldehyde is not added. Experimental results are shown in Table 1.

[0024] Comparative Example 2 The reaction conditions for this comparative example were basically the same as those in Example 1, except that no photocatalyst was added and the amount of benzaldehyde added was increased to 4.24 g (40 mmol). The experimental results are shown in Table 1.

[0025] Comparative Example 3 The reaction conditions for this comparative example were basically the same as those in Example 1, except that no chlorine source was added and the amount of benzaldehyde added was increased to 4.24 g (40 mmol). The experimental results are shown in Table 1.

[0026] Comparative Example 4 The reaction conditions were basically the same as in Example 1, except that the reaction was carried out in the dark and the amount of benzaldehyde added was increased to 4.24 g (40 mmol). The experimental results are shown in Table 1. Example 2

[0027] The synthesis provided in this embodiment e The -CL method includes the following steps: A 10 mL glass reactor was used, and cyclohexane (2.2 mL, 20 mmol), p-fluorobenzaldehyde (0.50 g, 4.0 mmol), the photocatalyst 10-methyl-9-trimethylammonium acridine perchlorate (0.16 g, 0.4 mmol), and a 1,4-dioxane (1.0 M) solution of hydrogen chloride (2 mL, 2.0 mmol) were added sequentially. The glass reactor was connected to an oxygen balloon and placed under a 32W blue LED light source. The reaction was carried out at room temperature with stirring for 24 hours. After the reaction, the contents of the raw materials and products were detected by gas chromatography-mass spectrometry (GC-MS), and the conversion rate of cyclohexane and the selectivity of the major products were calculated. The experimental results are shown in Table 1. Example 3

[0028] The synthesis provided in this embodiment e The -CL method includes the following steps: A 10 mL glass reactor was used, and cyclohexane (2.2 mL, 20 mmol), benzaldehyde (0.42 g, 4.0 mmol), the photocatalyst 10-methyl-9-phenylacridine perchlorate (0.15 g, 0.4 mmol), and a 1,4-dioxane (1.0 M) solution of hydrogen chloride (2 mL, 2.0 mmol) were added sequentially. The glass reactor was connected to an oxygen balloon and placed under a 32 W blue LED light source. The reaction was carried out at room temperature with stirring for 24 hours. After the reaction, the contents of the raw materials and products were detected by gas chromatography-mass spectrometry (GC-MS), and the conversion rate of cyclohexane and the selectivity of the major products were calculated. The experimental results are shown in Table 1. Example 4

[0029] The synthesis provided in this embodiment e The -CL method includes the following steps: A 10 mL glass reactor was used, and cyclohexane (2.2 mL, 20 mmol), benzaldehyde (0.42 g, 4.0 mmol), rhodamine B photocatalyst (0.19 g, 0.4 mmol), and a 1,4-dioxane (1.0 M) solution of hydrogen chloride (2 mL, 2.0 mmol) were added sequentially. The glass reactor was connected to an oxygen balloon and placed under a 32W blue LED light source. The reaction was carried out at room temperature with stirring for 24 hours. After the reaction, the contents of the raw materials and products were detected by gas chromatography-mass spectrometry (GC-MS), and the conversion rate of cyclohexane and the selectivity of the major products were calculated. The experimental results are shown in Table 1. Example 5

[0030] The synthesis provided in this embodiment e The -CL method includes the following steps: A 10 mL glass reactor was used, and cyclohexane (2.2 mL, 20 mmol), benzaldehyde (0.42 g, 4.0 mmol), the photocatalyst 10-methyl-9-mesinetrimethylacridine perchlorate (0.16 g, 0.4 mmol), and sodium chloride (1.11 g, 4.0 mmol) were added sequentially. The glass reactor was connected to an oxygen balloon and placed under a 32W blue LED light source. The reaction was carried out at room temperature with stirring for 24 hours. After the reaction, the contents of the raw materials and products were detected by gas chromatography-mass spectrometry (GC-MS), and the conversion rate of cyclohexane and the selectivity of the major products were calculated. The experimental results are shown in Table 1. Example 6

[0031] The synthesis provided in this embodiment e The -CL method includes the following steps: A 10 mL glass reactor was used, and cyclohexane (2.2 mL, 20 mmol), benzaldehyde (0.42 g, 4.0 mmol), the photocatalyst 10-methyl-9-mesinetrimethylacridine perchlorate (0.16 g, 0.4 mmol), and tetrabutylammonium chloride (0.23 g, 4.0 mmol) were added sequentially. The glass reactor was connected to an oxygen balloon and placed under 32W blue LED light illumination, with stirring at room temperature for 24 hours. After the reaction, the contents of the raw materials and products were detected using gas chromatography-mass spectrometry (GC-MS), and the conversion rate of cyclohexane and the selectivity of the major products were calculated. The experimental results are shown in Table 1.

[0032] Table 1

[0033] According to the data in Table 1, when the reaction is carried out using the technical route provided by this invention, it can generate [product / product] with extremely high selectivity (over 92%, up to 95%). e -CL. This technology requires only the addition of a small amount of catalyst aldehyde (up to 20 mol%) to achieve catalytic cycling with aldehyde as a co-oxidant. This not only significantly reduces costs but also effectively reduces the generation of byproducts. Furthermore, under the specific reaction conditions of this invention, the formation of some oxidation products such as cyclohexanol and cyclohexanone is avoided, further reducing byproducts and simplifying the target product. e -CL separation and purification process. Comparative data show that the addition of aldehydes promotes the conversion of cyclohexanone and cyclohexanol to... e The conversion of chlorine (-CL) is a process that cannot occur without any of the following conditions: photocatalyst, chlorine source, or light. This clearly demonstrates that the conversion process is the result of the combined action of photocatalysis and aldehyde catalysis.

[0034] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A process for the synthesis of epsilon - caprolactone, characterized in that, comprising the following steps: mixing and stirring cyclohexane, aldehyde, photocatalyst and chlorine source, wherein the molar ratio of the aldehyde to cyclohexane is 1:2-1:10, the molar ratio of the photocatalyst to aldehyde is 1:10-1:100, and the molar ratio of the chlorine source to the cyclohexane can be 1:5-1:50; The reaction is carried out under irradiation with visible light and at room temperature, with the admission of oxygen, to obtain epsilon - caprolactone.

2. The synthesis of claim 1 epsilon - process for the production of caprolactone, characterized in that, The aldehyde is an aryl aldehyde or an alkyl aldehyde.

3. The synthesis of claim 2 epsilon - process for the production of caprolactone, characterized in that, The aryl aldehyde is one or more of benzaldehyde, o-fluorobenzaldehyde, o-chlorobenzaldehyde, o-trifluoromethylbenzaldehyde, m-fluorobenzaldehyde, m-chlorobenzaldehyde, m-trifluoromethylbenzaldehyde, p-fluorobenzaldehyde, p-chlorobenzaldehyde, and p-trifluoromethylbenzaldehyde.

4. The synthesis of claim 2 epsilon - process for the production of caprolactone, characterized in that, The alkyl aldehyde is one or more of tert-pentanal, 2-methyldecanal, and 2-methylundecanal.

5. The synthesis of claim 1 epsilon - process for the production of caprolactone, characterized in that, The photocatalyst is one or more of cyanophenylarenes, benzophenone and quinones, pyran and thiopyran, quinoline, acridine, rhodamine, or thienazine.

6. The synthesis of claim 1 epsilon - process for the production of caprolactone, characterized in that, The chlorine source is one or more of hydrogen chloride, sodium chloride, potassium chloride, ammonium chloride, and tetrabutylammonium chloride.

7. The synthesis of claim 1 epsilon - process for the production of caprolactone, characterized in that, The wavelength range of the visible light is 380-440 nm.

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