Method for preparing CC bond coupling products from enol silyl ether compounds and application of SF6

Abstract

The present invention discloses a method for preparing a C-C bond coupling product from an enol silyl ether compound and the application of SF6, belonging to the technical field of organic photochemistry. In this method, an enol silyl ether compound and sulfur hexafluoride undergo a photochemical reaction at room temperature under the action of a light source and a photocatalyst to form a C-C bond coupling product; wherein the photocatalyst is N-phenylphenothiazine (PTH); and the light source is ultraviolet light with a wavelength of 365nm. Beneficial effects: This method utilizes sulfur hexafluoride to promote C-C bond coupling, and the reaction product is a 1,4-dicarbonyl compound that can be used in the synthesis and production of hybrid compounds such as pyrrole and furan; the reaction conditions are mild, and the raw materials are simple and readily available, thus having potential application value.

Description

Technical Field

[0001] The present invention relates to the technical field of organic photochemistry, and in particular to a method for preparing a C—C bond coupling product from an enol silyl ether compound and application of the same to SF6. Background Art

[0002] Sulfur hexafluoride (SF6) gas is in a gaseous state at room temperature and pressure, with a critical temperature of 45.6°C and a sublimation point of -63.8°C at normal pressure. SF6 also possesses a highly symmetrical octahedral structure centered on sulfur and strong SF bonds, resulting in excellent thermal and chemical stability, making it a key component in cutting-edge scientific research and production. Under the same conditions, SF6's insulation capacity is over 2.5 times that of air and nitrogen, and its arc-extinguishing capability is 100 times that of air, making it widely used in power systems. High-purity electronic-grade SF6 is often used as an electronic etchant in the production of integrated circuits such as chips.

[0003] However, SF6 is a strong greenhouse gas, and its greenhouse gas effect is 23,500 times that of carbon dioxide. It is extremely difficult to degrade naturally, has a lifespan of up to 3,200 years, and has an immeasurable impact on global warming. In 1997, the Kyoto Protocol listed SF6 as a restricted emission gas. Therefore, the resource utilization of SF6 gas, which is used in large quantities, is particularly important. In the current research on the utilization of SF6, metal carbenes or metal ligands are usually used to activate and utilize SF6. This is not only expensive and not economically friendly, but also difficult to industrialize. At present, there are reports on methods of activating and utilizing SF6 through photocatalysis, but there are no reports on research on photocatalytic activation of SF6 gas and its use to promote CC bond coupling. In the utilization of SF6, known methods include using strong alkaline phosphines or nitrogen heterocyclic carbenes to activate and utilize SF6. The specific methods are:

[0004] Method 1: SF6 reacts with alkali metal diphenyl phosphide at room temperature, and the phosphide is oxidized to tetraphenyl or tetracyclohexyl diphosphine. When a large amount of di-tert-butyl phosphide is used, a difluorophosphine intermediate is detected (Chem. Commun. 2021, 57, 7128-7131).

[0005]

[0006] The disadvantage of this method is that the reaction relies on the strong alkalinity of phosphine to activate SF6, so highly active reducing metal potassium is required in the reaction. It has a high risk factor and is air-sensitive, making it difficult to use later.

[0007] Method 2: Using ultraviolet light as the light source, electron-rich nitrogen heterocyclic carbene activated gas SF6 was used at 80 degrees Celsius to obtain 2,2-difluoroimidazoline or 2,2-difluoroimidazolidine and thio derivatives of the carbene precursor (Chem. Commun. 2018, 54, 9753-9756).

[0008]

[0009] The disadvantage of this method is that although SF6 can be activated by photocatalysis during the reaction, avoiding the use of active metals, the nitrogen heterocyclic carbene required is also very expensive, with low economic practicality and difficulty in industrialization.

[0010] C-C coupling plays a crucial role in organic synthesis and is a fundamental pathway for carbon chain growth in organic chemistry. Oxidative C-C coupling is typically carried out using inorganic oxidants or oxygen in the presence of metal catalysts. However, no C-C coupling reaction involving SF6 gas has been reported. To promote the effective utilization of SF6, a C-C coupling method involving SF6 that is low-cost, simple to operate, environmentally friendly, and easily applicable in production is currently needed. Summary of the Invention

[0011] The technical problem to be solved by the present invention is how to solve the problems of complex preparation process, high cost and low yield of existing C-C bond coupling products.

[0012] The present invention solves the above technical problems through the following technical means:

[0013] A method for preparing a C—C bond coupling product from an enol silyl ether compound, comprising the steps of placing an enol silyl ether compound, a photocatalyst, and a solvent in a reaction vessel, filling the reaction vessel with sulfur hexafluoride gas, and reacting the reaction vessel under ultraviolet light to obtain a C—C bond coupling product, wherein the structural formula of the enol silyl ether compound is wherein R1 is hydrogen or an alkyl substituent, and the alkyl substituent is selected from a C1-C10 alkyl group.

[0014] Description: Under photochemical conditions, sulfur hexafluoride gas reacts with enol silyl ether compounds under photocatalysis to generate C—C bond coupling product 1,4-diphenylbutane-1,4-dione; the reaction formula is as follows:

[0015]

[0016] The photocatalyst is N-phenylphenothiazine (PTH); the light source is ultraviolet light with a wavelength of 365 nm; R1 is hydrogen or an alkyl substituent, and the alkyl substituent is selected from a C1-C10 alkyl group.

[0017] Beneficial Effects: The present invention operates at room temperature, uses inexpensive and readily available enol silyl ether compounds as reaction substrates, and activates SF6 gas to achieve C-C coupling in the absence of metals and carbenes, effectively utilizing SF6 at a very low cost and with a simple operation method. Compared to other methods utilizing sulfur hexafluoride gas, the present invention offers mild reaction conditions, uses inexpensive and readily available raw materials, eliminates the need for hazardous metals and expensive nitrogen heterocyclic carbenes, and effectively utilizes SF6 during the C-C coupling reaction, resulting in cost savings, environmental friendliness, and industrial applicability.

[0018] Preferably, the molar ratio of the photocatalyst to the enol silyl ether compound is 0.05-0.15:1, and the preferred molar ratio of the photocatalyst to the enol silyl ether compound is 0.1:1. When the molar ratio of the photocatalyst to the enol silyl ether compound is 0.1:1, the yield of the final product is high.

[0019] Preferably, the photocatalyst is one or more of N-phenylphenothiazine (PTH), tungsten trioxide (WO3), and titanium dioxide (TiO2), and more preferably N-phenylphenothiazine (PTH). When the photocatalyst is N-phenylphenothiazine (PTH), the yield of the final product is high.

[0020] Preferably, the solvent is one or more of acetonitrile, tetrahydrofuran, and dichloromethane, and the preferred solvent is acetonitrile. When the reaction solvent is acetonitrile, the yield of the final product is high.

[0021] Preferably, the wavelength of the ultraviolet light is 365 nm.

[0022] Preferably, the reaction temperature is room temperature, preferably 25°C.

[0023] Preferably, the reaction time is 12 to 36 hours, preferably 15 hours. When the reaction time is 15 hours, the yield of the final product is high.

[0024] Preferably, the molar concentration of the enol silyl ether compound in the solvent is 0.05 to 0.20 mmol / mL, preferably 0.1 mmol / mL. When the molar concentration of the enol silyl ether compound in the solvent is 0.1 mmol / mL, the yield of the final product is high.

[0025] The present invention is carried out in a single organic solvent system; if necessary, other organic solvents may also be present in the system, but from the perspective of reaction yield and simplicity of operation, it is preferably not added with other organic solvents, that is, a single organic solvent is used as the reaction solvent.

[0026] Preferably, after the reaction is completed, the solvent is removed by vacuum, concentrated by rotary evaporation, and then subjected to column chromatography to obtain the product.

[0027] The advantages of the present invention are:

[0028] 1. The present invention operates at room temperature, uses inexpensive and readily available enol silyl ether compounds as reaction substrates, and activates SF6 gas to achieve C-C coupling in the absence of metals and carbenes, effectively utilizing SF6 at extremely low cost and with a simple operation method. Compared to other methods utilizing sulfur hexafluoride gas, the present invention features mild reaction conditions, uses inexpensive and readily available raw materials, eliminates the need for hazardous metals and expensive nitrogen heterocyclic carbenes, and effectively utilizes SF6 during the C-C coupling reaction, resulting in cost savings, environmental friendliness, and industrial applicability.

[0029] 2. The present invention provides a route for CC bond coupling involving photocatalytic SF6 gas. After the reaction is completed, the solvent is removed by vacuum, and 1,4-diphenylbutane-1,4-dione is obtained by rotary evaporation and column chromatography.

[0030] 3. Sulfur hexafluoride is used to promote C-C bond coupling. The reaction conditions are mild and the raw materials are simple and easily available, which has potential application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the H NMR spectrum of 1,4-diphenylbutane-1,4-dione described in Example 1;

[0032] Figure 2 This is the C-NMR spectrum of 1,4-diphenylbutane-1,4-dione described in Example 1;

[0033] Figure 3 This is the H NMR spectrum of 1,4-di-p-tolylbutane-1,4-dione described in Example 2. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0035] In the present invention, "silyl enol ether compounds" have the meaning commonly understood by those skilled in the art, i.e., a class of compounds in which the group on the oxygen atom in the enol ether is substituted with a silicon group, such as triisopropyl((1-phenylvinyl)oxy)silane and its various derivatives.

[0036] The raw materials used in the following specific examples can all be purchased commercially, and each reagent was purified by means known in the art before use when necessary. 1 H NMR, 13 C NMR and were measured using a Bruker Avance 400 spectrometer. The test temperature was room temperature, the solvent was deuterated chloroform, and the reference was selected: 1 H NMR: CHCl3 7.260 ppm; 13 CNMR: CHCl3 is 77.000 ppm.

[0037] Example 1: Synthesis of 1,4-diphenylbutane-1,4-dione

[0038] In an 8 mL vial equipped with a magnetic stirrer, triisopropyl((1-phenylvinyl)oxy)silane (110.0 mg, 0.2 mmol), the photocatalyst N-phenylphenothiazine (PTH) (11.0 mg, 0.02 mmol), and acetonitrile (MeCN) (4.0 mL) were added to dissolve the triisopropyl((1-phenylvinyl)oxy)silane and PTH solution, and the vial was capped. The solution was bubbled with SF6 gas for 5 minutes and then irradiated with a 365 nm UV lamp for 15 hours with stirring at room temperature. After completion of the reaction, the solvent was removed in vacuo, and the mixture was concentrated by rotary evaporation and then subjected to column chromatography to obtain 76.3 mg of 1,4-diphenylbutane-1,4-dione in a 32% yield.

[0039] Product 1,4-diphenylbutane-1,4-dione: 1 H NMR (400MHz, CDCl3) δ8.08-8.01(m,4H),7.64-7.54(m,2H),7.52-7.44(m,4H),3.47(s,4H)ppm. 13 C NMR (101MHz, CDCl3) δ198.7,136.7,133.2,128.6,128.1,32.6ppm.

[0040] Table 1 Yield of 1,4-diphenylbutane-1,4-dione under different conditions

[0041]

[0042] Standard conditions: 1 0.4 mmol, photocatalyst 10 mmol%, solvent 4.0 mL, time 15 h, room temperature. Isolated yields were given. THF = tetrahydrofuran; MeCN = acetonitrile; DCM = dichloromethane; DCE = dichloroethane. Example 2: Synthesis of 1,4-di-p-tolylbutane-1,4-dione

[0043] In an 8 mL vial equipped with a magnetic stirrer, triisopropyl((1-(p-tolyl)vinyl)oxy)silane (116.2 mg, 0.2 mmol), the photocatalyst N-phenylphenothiazine (PTH) (11.0 mg, 0.02 mmol), and acetonitrile (MeCN) (4.0 mL) were added to form a solution of triisopropyl((1-(p-tolyl)vinyl)oxy)silane and PTH. The vial was capped. The solution was bubbled with a balloon filled with SF6 gas for 5 minutes. After stirring at room temperature, it was irradiated with a 365 nm UV lamp for 15 hours. After completion of the reaction, the solvent was removed in vacuo. The product was concentrated by rotary evaporation and then subjected to column chromatography to obtain 79.9 mg of 1,4-di-p-tolylbutane-1,4-dione in a 30% yield.

[0044] Product 1,4-diphenylbutane-1,4-dione: 1 H NMR (400MHz, CDCl3) δ7.85-7.69(m,4H),7.33-7.26(m,4H),4.85(s,4H),2.43(s,6H).ppm. 13 C NMR (101MHz, CDCl3) δ197.9,145.3,130.8,129.6,127.8,29.7,21.8ppm.

[0045]

[0046]

[0047] As can be seen from Examples 1-2, the method of the present invention is to synthesize C—C bond coupled 1,4-dicarbonyl products by utilizing sulfur hexafluoride gas under photochemical conditions from cheap and readily available enol silyl ether compounds.

[0048] Comparative Example 1:

[0049] The difference between Comparative Example 1 and Example 1 is that SF6 is not added, and the other steps are the same as Example 1.

[0050] Comparative Example 2:

[0051] The difference between Comparative Example 2 and Example 1 is that no photocatalyst is added, and the other steps are the same as Example 1.

[0052] Comparative Example 3:

[0053] The difference between Comparative Example 3 and Example 1 is that ordinary fluorescent light is used instead of ultraviolet light, and the other steps are the same as Example 1.

[0054] The experimental results of Comparative Examples 1-3 are shown in the following table:

[0055]

[0056] According to the control experiments, the target product cannot be obtained without SF6; the target product cannot be obtained without adding photocatalyst; and the target product cannot be obtained without ultraviolet light irradiation.

[0057] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing C—C bond coupling products from enol silyl ether compounds, characterized in that: The method comprises the following steps: placing an enol silyl ether compound, a photocatalyst and a solvent in a reaction vessel, filling with sulfur hexafluoride gas, and reacting under ultraviolet light to obtain a C—C bond coupling product, wherein the structural formula of the enol silyl ether compound is , wherein R1 is hydrogen or an alkyl substituent, and the alkyl substituent is selected from C1-C10 alkyl; and the photocatalyst is N-phenylphenothiazine (PTH).

2. The method for preparing a C-C bond coupling product from an enol silyl ether compound according to claim 1, wherein: The molar ratio of the photocatalyst to the enol silyl ether compound is 0.05-0.15:

1.

3. The method for preparing a C-C bond coupling product from an enol silyl ether compound according to claim 2, wherein: The molar ratio of the photocatalyst to the enol silyl ether compound is 0.05:

1.

4. The method for preparing a C-C bond coupling product from an enol silyl ether compound according to claim 1, wherein: The solvent is one or more of acetonitrile, tetrahydrofuran, and dichloromethane.

5. The method for preparing a C-C bond coupling product from an enol silyl ether compound according to claim 1, wherein: The wavelength of the ultraviolet light is 365 nm.

6. The method for preparing a C-C bond coupling product from an enol silyl ether compound according to claim 1, characterized in that: The reaction time is 12 to 36 hours.

7. The method for preparing a C-C bond coupling product from an enol silyl ether compound according to claim 1, wherein: The molar concentration of the enol silyl ether compound in the solvent is 0.05-0.20 mmol / mL.

8. The method for preparing a C-C bond coupling product from an enol silyl ether compound according to claim 2, wherein: The molar ratio of the photocatalyst to the enol silyl ether compound is 0.1:

1.

9. The method for preparing a C-C bond coupling product from an enol silyl ether compound according to claim 1, wherein: After the reaction was complete, the solvent was removed in vacuo, concentrated by rotary evaporation, and then subjected to column chromatography to obtain the product.

10. Application of sulfur hexafluoride gas in promoting the formation of C—C bond coupling products of enol silyl ether compounds.

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