Preparation method of 3-acetyl-2, 5-dimethylthiophene

Abstract

The invention provides a preparation method of 3-acetyl-2, 5-dimethylthiophene, and belongs to the technical field of chemical synthesis. The method comprises the following steps: absorbing SO2 gas by using an L-leucine aqueous solution until the SO2 gas is balanced, and then synthesizing 3-acetyl-2, 5-dimethylthiophene through a hydrothermal reaction; the preparation method meets the requirements of green chemistry, preparation conditions are easy to control, the preparation process is simple, powerful scientific support is provided for SO2 environmental governance and resource recycling, and the method has profound social and environmental significance.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and specifically relates to a method for preparing 3-acetyl-2,5-dimethylthiophene. Background Art

[0002] The burning of fossil fuels releases a large amount of sulfur dioxide (SO2), which interacts with nitrogen oxides and water vapor in the atmosphere to form smog, which seriously affects human health and causes respiratory damage, heart disease, cancer and other problems. The unique chemical properties of SO2 provide the possibility for its resource utilization. The method of converting SO2 into high value-added products can achieve a win-win situation for environmental governance and economic benefits.

[0003] 3-Acetyl-2,5-dimethylthiophene is an organic sulfur compound with important biological activity. On the one hand, its structural characteristics allow it to be combined with other functional groups through chemical modification to generate a variety of biologically active derivatives, showing antibacterial, antiviral and antitumor pharmacological activities, and can be used as a key intermediate for the synthesis of new drugs; on the other hand, it can be used as a pesticide intermediate for the synthesis of insecticides and herbicides, thereby helping to increase crop yield and quality while reducing negative impacts on the environment. Therefore, 3-acetyl-2,5-dimethylthiophene has a wide range of potential applications in medicinal chemistry.

[0004] The traditional synthesis method of 3-acetyl-2,5-dimethylthiophene is usually carried out through the condensation reaction of thiophene and methyl ethyl ketone. The commonly used sulfur sources in thiophene synthesis include phosphorus pentasulfide and Lawesson's reagent. However, these sulfur sources are not only expensive, but also highly toxic and corrosive, and have complex reaction pathways. Therefore, the development of new economical, safe and simple synthesis methods has become an important research direction in the field of chemical synthesis. Summary of the invention

[0005] In view of some deficiencies in the prior art, the present invention provides a method for preparing 3-acetyl-2,5-dimethylthiophene; the present invention firstly utilizes an L-leucine aqueous solution to absorb SO2 gas to equilibrium, and then synthesizes 3-acetyl-2,5-dimethylthiophene through a hydrothermal reaction; the preparation method of the present invention meets the requirements of green chemistry, the preparation conditions are easy to control, the preparation process is simple, and it also provides strong scientific support for the environmental management and resource recycling of SO2, and has far-reaching social and environmental significance.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: The preparation method of 3-acetyl-2,5-dimethylthiophene of the present invention comprises: A mixed gas of SO2 and N2 is introduced into a saturated L-leucine aqueous solution until absorption reaches equilibrium to obtain solution a; solution a is subjected to a hydrothermal reaction, and after the reaction is completed, the solution is cooled, extracted, washed, dried, separated and purified to obtain 3-acetyl-2,5-dimethylthiophene.

[0007] Preferably, in the saturated L-leucine aqueous solution, the mass ratio of L-leucine to ultrapure water is 0.0224:1.

[0008] Preferably, the pH of the saturated L-leucine aqueous solution is 11.

[0009] Preferably, during the absorption process, the temperature of the saturated L-leucine aqueous solution is 20-60°C.

[0010] Preferably, in the mixed gas of SO2 and N2, the concentration of SO2 is 2.35% to 5.03%, and the concentration of N2 is 97.65% to 94.97%.

[0011] Preferably, the hydrothermal reaction is carried out at 180-220° C. for 10-14 h.

[0012] Preferably, the steps of extraction, washing, drying, separation and purification are: The product was extracted with ethyl acetate, washed with lithium chloride solution and sodium chloride solution, dried over anhydrous sodium sulfate, and separated and purified by silica gel chromatography to obtain the product 3-acetyl-2,5-dimethylthiophene.

[0013] Preferably, the mass percentage of the lithium chloride solution is 10%.

[0014] Preferably, the mass percentage of the sodium chloride solution is 26.5%.

[0015] Preferably, the mobile phase for separation by silica gel column chromatography is dichloromethane and methanol, wherein the volume ratio of dichloromethane to methanol is 60:1 to 15:1.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention innovatively adopts hydrothermal synthesis technology to prepare 3-acetyl-2,5-dimethylthiophene, which greatly simplifies the operation process and abandons the dependence on catalysts. It only needs to adjust the reaction conditions to high temperature and high pressure to achieve the preparation of 3-acetyl-2,5-dimethylthiophene, which greatly reduces the production cost and demonstrates the superiority of green chemistry. The present invention cleverly uses SO2 as a raw material, which not only solves the emission problem of SO2, but also realizes its resource utilization, opening up a new path for environmental governance and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 13-acetyl-2,5-dimethylthiophene 13 C NMR spectrum.

[0018] Figure 2 This is the FT-IR spectrum of 3-acetyl-2,5-dimethylthiophene.

[0019] Figure 3 This is the EI mass spectrum of 3-acetyl-2,5-dimethylthiophene. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto. The experimental methods in the following embodiments are conventional methods unless otherwise specified. The test materials used in the following embodiments are commercially available unless otherwise specified.

[0021] Embodiment 1: (1) Absorption of SO2: An absorption tube filled with 10 mL of saturated L-leucine aqueous solution with an initial pH adjusted to 11 was placed in an electric heating insulation jacket, and the temperature controller was adjusted to maintain it at 20°C. At 0.2 MPa, a mixture of SO2 and N2 with a SO2 concentration of 5.03% was passed into the absorption tube at a rate of 15 mL / min. The absorption of SO2 was determined online by iodine titration until the saturated L-leucine aqueous solution absorbed SO2 to reach equilibrium, thereby obtaining solution a.

[0022] Among them, the principle formula for detecting SO2 content by iodine titration is: SO2 + H2O = HSO3 - HSO3 - + H2O + I2 = HSO4 - +2HI.

[0023] (2) Preparation of 3-acetyl-2,5-dimethylthiophene: Solution a was transferred to a 25 mL hydrothermal autoclave and reacted at 200 °C for 10 h. After the reaction was completed, the hydrothermal autoclave was removed from the heating device and cooled to room temperature. The reaction mixture was distributed between water (10 mL) and ethyl acetate (10 mL). The phases were separated and the aqueous phase was extracted with additional ethyl acetate (3 × 10 mL). The organic phases were combined. The mixture was washed with 10% lithium chloride solution (3 × 10 mL) and saturated sodium chloride solution (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to obtain the reaction product.

[0024] The content of the reaction product was detected under the conditions of chromatographic column: HP-5MS; injection port temperature: 280 ℃; carrier gas: He, flow rate: 1.0 mL / min. The yield was 32.99%.

[0025] The above reaction product was mixed with 200-300 mesh column chromatography silica gel, loaded with 150 g column chromatography silica gel, gradient eluted with dichloromethane:methanol (60:1-15:1), and then dichloromethane:methanol was used as the developing system and iodine was used as the color developer. Thin layer chromatography was used to detect each fraction. According to the thin layer chromatography results, the fractions were sorted and combined, and the product obtained after drying was 3-acetyl-2,5-dimethylthiophene.

[0026] Figure 1 3-acetyl-2,5-dimethylthiophene 13 C NMR spectrum, as can be seen from the figure, 8 different resonance signal peaks were observed in the range of 14.90 to 193.97 ppm, corresponding to 8 carbon atoms in different chemical environments of 3-acetyl-2,5-dimethylthiophene. This shows that 3-acetyl-2,5-dimethylthiophene was successfully prepared.

[0027] Figure 2 This is the FT-IR spectrum of 3-acetyl-2,5-dimethylthiophene. As can be seen from the figure, at 2919 cm -1 The absorption peak observed in the high-frequency region is the stretching vibration of the CH bond of the methyl group. -1 The absorption peak at 1550 cm -1 The skeletal vibrations of the thiophene ring correspond to the 1479 and 1427 cm -1 is the bending vibration of methyl. In the low frequency region, 953, 857, 661, 597 cm -1 The absorption peak at comes from the in-plane bending vibration of the carbon-hydrogen bond of the thiophene ring. This further proves that 3-acetyl-2,5-dimethylthiophene was successfully prepared.

[0028] Figure 3 This is the EI mass spectrum of 3-acetyl-2,5-dimethylthiophene. It can be seen from the figure that fragment peaks appear at m / z = 43, m / z = 67, m / z = 97, m / z = 113, and m / z = 139, and a molecular peak appears at m / z = 154.

[0029] In summary, through FT-IR, 13 The comprehensive analysis of C NMR and mass spectra confirmed that the product 3-acetyl-2,5-dimethylthiophene was obtained by the reaction of L-leucine with SO2.

[0030] Embodiment 2: (1) Absorption of SO2: An absorption tube filled with 10 mL of saturated L-leucine aqueous solution with an initial pH adjusted to 11 was placed in an electric heating insulation jacket, and the temperature controller was adjusted to maintain it at 40°C. At 0.2 MPa, a mixture of SO2 and N2 with a SO2 concentration of 5.03% was passed into the absorption tube at a rate of 15 mL / min. The absorption of SO2 was determined online by iodine titration until the saturated L-leucine aqueous solution absorbed SO2 to reach equilibrium, thereby obtaining solution a.

[0031] (2) Preparation of 3-acetyl-2,5-dimethylthiophene: Solution a was transferred to a 25 mL hydrothermal autoclave and reacted at 200 °C for 10 h. After the reaction was completed, the hydrothermal autoclave was removed from the heating device and cooled to room temperature. The reaction mixture was distributed between water (10 mL) and ethyl acetate (10 mL). The phases were separated and the aqueous phase was extracted with additional ethyl acetate (3 × 10 mL). The organic phases were combined. The mixture was washed with 10% lithium chloride solution (3 × 10 mL) and saturated sodium chloride solution (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to obtain the reaction product.

[0032] The content of the reaction product was detected under the conditions of chromatographic column: HP-5MS; injection port temperature: 280 ℃; carrier gas: He, flow rate: 1.0 mL / min. The yield was 29.52%.

[0033] The above reaction product was mixed with 200-300 mesh column chromatography silica gel, loaded with 150 g column chromatography silica gel, gradient eluted with dichloromethane:methanol (60:1-15:1), and then dichloromethane:methanol was used as the developing system and iodine was used as the color developer. Thin layer chromatography was used to detect each fraction. According to the thin layer chromatography results, the fractions were sorted and combined, and the product obtained after drying was 3-acetyl-2,5-dimethylthiophene.

[0034] Embodiment 3: (1) Absorption of SO2: An absorption tube filled with 10 mL of saturated L-leucine aqueous solution with an initial pH adjusted to 11 was placed in an electric heating insulation jacket, and the temperature controller was adjusted to maintain it at 60°C. At 0.2 MPa, a mixture of SO2 and N2 with a SO2 concentration of 5.03% was passed into the absorption tube at a rate of 15 mL / min. The absorption of SO2 was determined online by iodine titration until the saturated L-leucine aqueous solution absorbed SO2 to reach equilibrium, thereby obtaining solution a.

[0035] (2) Preparation of 3-acetyl-2,5-dimethylthiophene: Solution a was transferred to a 25 mL hydrothermal autoclave and reacted at 200 °C for 10 h. After the reaction was completed, the hydrothermal autoclave was removed from the heating device and cooled to room temperature. The reaction mixture was distributed between water (10 mL) and ethyl acetate (10 mL). The phases were separated and the aqueous phase was extracted with additional ethyl acetate (3 × 10 mL). The organic phases were combined. The mixture was washed with 10% lithium chloride solution (3 × 10 mL) and saturated sodium chloride solution (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to obtain the reaction product.

[0036] The content of the reaction product was detected under the conditions of chromatographic column: HP-5MS; injection port temperature: 280 ℃; carrier gas: He, flow rate: 1.0 mL / min. The yield was 18.90%.

[0037] The above reaction product was mixed with 200-300 mesh column chromatography silica gel, loaded with 150 g column chromatography silica gel, gradient eluted with dichloromethane:methanol (60:1-15:1), and then dichloromethane:methanol was used as the developing system and iodine was used as the color developer. Thin layer chromatography was used to detect each fraction. According to the thin layer chromatography results, the fractions were sorted and combined, and the product obtained after drying was 3-acetyl-2,5-dimethylthiophene.

[0038] Embodiment 4: (1) Absorption of SO2: An absorption tube filled with 10 mL of saturated L-leucine aqueous solution with an initial pH adjusted to 11 was placed in an electric heating insulation jacket, and the temperature controller was adjusted to maintain it at 20 °C. At 0.2 MPa, a mixture of SO2 and N2 with a SO2 concentration of 4.97% was passed into the absorption tube at a rate of 15 mL / min. The absorption of SO2 was determined online by iodine titration until the saturated L-leucine aqueous solution absorbed SO2 to reach equilibrium, thereby obtaining solution a.

[0039] (2) Preparation of 3-acetyl-2,5-dimethylthiophene: Solution a was transferred to a 25 mL hydrothermal autoclave and reacted at 180 °C for 10 h. After the reaction was completed, the hydrothermal autoclave was removed from the heating device and cooled to room temperature. The reaction mixture was distributed between water (10 mL) and ethyl acetate (10 mL). The phases were separated and the aqueous phase was extracted with additional ethyl acetate (3 × 10 mL). The organic phases were combined. The mixture was washed with 10% lithium chloride solution (3 × 10 mL) and saturated sodium chloride solution (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to obtain the reaction product.

[0040] The content of the reaction product was detected under the conditions of chromatographic column: HP-5MS; injection port temperature: 280°C; carrier gas: He, flow rate: 1.0 mL / min. The yield was 24.14%.

[0041] The above reaction product was mixed with 200-300 mesh column chromatography silica gel, loaded with 150 g column chromatography silica gel, gradient eluted with dichloromethane:methanol (60:1-15:1), and then dichloromethane:methanol was used as the developing system and iodine was used as the color developer. Thin layer chromatography was used to detect each fraction. According to the thin layer chromatography results, the fractions were sorted and combined, and the product obtained after drying was 3-acetyl-2,5-dimethylthiophene.

[0042] Embodiment 5: (1) Absorption of SO2: An absorption tube filled with 10 mL of saturated L-leucine aqueous solution with an initial pH adjusted to 11 was placed in an electric heating insulation jacket, and the temperature controller was adjusted to maintain it at 20°C. At 0.2 MPa, a mixture of SO2 and N2 with a SO2 concentration of 5.03% was passed into the absorption tube at a rate of 15 mL / min. The absorption of SO2 was determined online by iodine titration until the saturated L-leucine aqueous solution absorbed SO2 to reach equilibrium, thereby obtaining solution a.

[0043] (2) Preparation of 3-acetyl-2,5-dimethylthiophene: Solution a was transferred to a 25 mL hydrothermal autoclave and reacted at 220 °C for 10 h. After the reaction was completed, the hydrothermal autoclave was removed from the heating device and cooled to room temperature. The reaction mixture was distributed between water (10 mL) and ethyl acetate (10 mL). The phases were separated and the aqueous phase was extracted with additional ethyl acetate (3 × 10 mL). The organic phases were combined. The mixture was washed with 10% lithium chloride solution (3 × 10 mL) and saturated sodium chloride solution (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to obtain the reaction product.

[0044] The content of the reaction product was detected under the conditions of chromatographic column: HP-5MS; injection port temperature: 280°C; carrier gas: He, flow rate: 1.0 mL / min. The yield was 19.32%.

[0045] The above reaction product was mixed with 200-300 mesh column chromatography silica gel, loaded with 150 g column chromatography silica gel, gradient eluted with dichloromethane:methanol (60:1-15:1), and then dichloromethane:methanol was used as the developing system and iodine was used as the color developer. Thin layer chromatography was used to detect each fraction. According to the thin layer chromatography results, the fractions were sorted and combined, and the product obtained after drying was 3-acetyl-2,5-dimethylthiophene.

[0046] Embodiment 6: (1) Absorption of SO2: An absorption tube filled with 10 mL of saturated L-leucine aqueous solution with an initial pH adjusted to 11 was placed in an electric heating insulation jacket, and the temperature controller was adjusted to maintain it at 20°C. At 0.2 MPa, a mixture of SO2 and N2 with a SO2 concentration of 5.03% was passed into the absorption tube at a rate of 15 mL / min. The absorption of SO2 was determined online by iodine titration until the saturated L-leucine aqueous solution absorbed SO2 to reach equilibrium, thereby obtaining solution a.

[0047] (2) Preparation of 3-acetyl-2,5-dimethylthiophene: Solution a was transferred to a 25 mL hydrothermal autoclave and reacted at 200 °C for 12 h. After the reaction was completed, the hydrothermal autoclave was removed from the heating device and cooled to room temperature. The reaction mixture was distributed between water (10 mL) and ethyl acetate (10 mL). The phases were separated and the aqueous phase was extracted with additional ethyl acetate (3 × 10 mL). The organic phases were combined. The mixture was washed with 10% lithium chloride solution (3 × 10 mL) and saturated sodium chloride solution (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to obtain the reaction product.

[0048] The content of the reaction product was detected under the conditions of chromatographic column: HP-5MS; injection port temperature: 280°C; carrier gas: He, flow rate: 1.0 mL / min. The yield was 27.20%.

[0049] The above reaction product was mixed with 200-300 mesh column chromatography silica gel, loaded with 150 g column chromatography silica gel, gradient eluted with dichloromethane:methanol (60:1-15:1), and then dichloromethane:methanol was used as the developing system and iodine was used as the color developer. Thin layer chromatography was used to detect each fraction. According to the thin layer chromatography results, the fractions were sorted and combined, and the product obtained after drying was 3-acetyl-2,5-dimethylthiophene.

[0050] Embodiment 7: (1) Absorption of SO2: An absorption tube filled with 10 mL of saturated L-leucine aqueous solution with an initial pH adjusted to 11 was placed in an electric heating insulation jacket, and the temperature controller was adjusted to maintain it at 20°C. At 0.2 MPa, a mixture of SO2 and N2 with a SO2 concentration of 5.03% was passed into the absorption tube at a rate of 15 mL / min. The absorption of SO2 was determined online by iodine titration until the saturated L-leucine aqueous solution absorbed SO2 to reach equilibrium, thereby obtaining solution a.

[0051] (2) Preparation of 3-acetyl-2,5-dimethylthiophene: Solution a was transferred to a 25 mL hydrothermal autoclave and reacted at 200 °C for 14 h. After the reaction was completed, the hydrothermal autoclave was removed from the heating device and cooled to room temperature. The reaction mixture was distributed between water (10 mL) and ethyl acetate (10 mL). The phases were separated and the aqueous phase was extracted with additional ethyl acetate (3 × 10 mL). The organic phases were combined. The mixture was washed with 10% lithium chloride solution (3 × 10 mL) and saturated sodium chloride solution (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to obtain the reaction product.

[0052] The content of the reaction product was detected under the conditions of chromatographic column: HP-5MS; injection port temperature: 280°C; carrier gas: He, flow rate: 1.0 mL / min. The yield was 23.58%.

[0053] The above reaction product was mixed with 200-300 mesh column chromatography silica gel, loaded with 150 g column chromatography silica gel, gradient eluted with dichloromethane:methanol (60:1-15:1), and then dichloromethane:methanol was used as the developing system and iodine was used as the color developer. Thin layer chromatography was used to detect each fraction. According to the thin layer chromatography results, the fractions were sorted and combined, and the product obtained after drying was 3-acetyl-2,5-dimethylthiophene.

[0054] Embodiment 8: (1) Absorption of SO2: An absorption tube filled with 10 mL of saturated L-leucine aqueous solution with an initial pH adjusted to 5 was placed in an electric heating insulation jacket, and the temperature controller was adjusted to maintain it at 20°C. At 0.2 MPa, a mixture of SO2 and N2 with a SO2 concentration of 5.03% was passed into the absorption tube at a rate of 15 mL / min. The absorption of SO2 was determined online by iodine titration until the saturated L-leucine aqueous solution absorbed SO2 to reach equilibrium, thereby obtaining solution a.

[0055] (2) Preparation of 3-acetyl-2,5-dimethylthiophene: Solution a was transferred to a 25 mL hydrothermal autoclave and reacted at 200 °C for 10 h. After the reaction was completed, the hydrothermal autoclave was removed from the heating device and cooled to room temperature. The reaction mixture was distributed between water (10 mL) and ethyl acetate (10 mL). The phases were separated and the aqueous phase was extracted with additional ethyl acetate (3 × 10 mL). The organic phases were combined. The mixture was washed with 10% lithium chloride solution (3 × 10 mL) and saturated sodium chloride solution (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to obtain the reaction product.

[0056] The content of the reaction product was detected under the conditions of chromatographic column: HP-5MS; injection port temperature: 280°C; carrier gas: He, flow rate: 1.0 mL / min. The yield was 10.83%.

[0057] The above reaction product was mixed with 200-300 mesh column chromatography silica gel, loaded with 150 g column chromatography silica gel, gradient eluted with dichloromethane:methanol (60:1-15:1), and then dichloromethane:methanol was used as the developing system and iodine was used as the color developer. Thin layer chromatography was used to detect each fraction. According to the thin layer chromatography results, the fractions were sorted and combined, and the product obtained after drying was 3-acetyl-2,5-dimethylthiophene.

[0058] Embodiment 9: (1) Absorption of SO2: An absorption tube filled with 10 mL of saturated L-leucine aqueous solution with an initial pH adjusted to 7 was placed in an electric heating insulation jacket, and the temperature controller was adjusted to maintain it at 20°C. At 0.2 MPa, a mixture of SO2 and N2 with a SO2 concentration of 5.03% was passed into the absorption tube at a rate of 15 mL / min. The absorption of SO2 was determined online by iodine titration until the saturated L-leucine aqueous solution absorbed SO2 to reach equilibrium, thereby obtaining solution a.

[0059] (2) Preparation of 3-acetyl-2,5-dimethylthiophene: Solution a was transferred to a 25 mL hydrothermal autoclave and reacted at 200 °C for 10 h. After the reaction was completed, the hydrothermal autoclave was removed from the heating device and cooled to room temperature. The reaction mixture was distributed between water (10 mL) and ethyl acetate (10 mL). The phases were separated and the aqueous phase was extracted with additional ethyl acetate (3 × 10 mL). The organic phases were combined. The mixture was washed with 10% lithium chloride solution (3 × 10 mL) and saturated sodium chloride solution (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to obtain the reaction product.

[0060] The content of the reaction product was detected under the conditions of chromatographic column: HP-5MS; injection port temperature: 280°C; carrier gas: He, flow rate: 1.0 mL / min. The yield was 17.98%.

[0061] The above reaction product was mixed with 200-300 mesh column chromatography silica gel, loaded with 150 g column chromatography silica gel, gradient eluted with dichloromethane:methanol (60:1-15:1), and then dichloromethane:methanol was used as the developing system and iodine was used as the color developer. Thin layer chromatography was used to detect each fraction. According to the thin layer chromatography results, the fractions were sorted and combined, and the product obtained after drying was 3-acetyl-2,5-dimethylthiophene.

[0062] Embodiment 10: (1) Absorption of SO2: An absorption tube filled with 10 mL of saturated L-leucine aqueous solution with an initial pH adjusted to 11 was placed in an electric heating insulation jacket, and the temperature controller was adjusted to maintain it at 20°C. At 0.2 MPa, a mixture of SO2 and N2 with a SO2 concentration of 3.35% was passed into the absorption tube at a rate of 15 mL / min. The absorption of SO2 was determined online by iodine titration until the saturated L-leucine aqueous solution absorbed SO2 to reach equilibrium, thereby obtaining solution a.

[0063] (2) Preparation of 3-acetyl-2,5-dimethylthiophene: Solution a was transferred to a 25 mL hydrothermal autoclave and reacted at 200 °C for 10 h. After the reaction was completed, the hydrothermal autoclave was removed from the heating device and cooled to room temperature. The reaction mixture was distributed between water (10 mL) and ethyl acetate (10 mL). The phases were separated and the aqueous phase was extracted with additional ethyl acetate (3 × 10 mL). The organic phases were combined. The mixture was washed with 10% lithium chloride solution (3 × 10 mL) and saturated sodium chloride solution (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to obtain the reaction product.

[0064] The content of the reaction product was detected under the conditions of chromatographic column: HP-5MS; injection port temperature: 280°C; carrier gas: He, flow rate: 1.0 mL / min. The yield was 26.74%.

[0065] The above reaction product was mixed with 200-300 mesh column chromatography silica gel, loaded with 150 g column chromatography silica gel, gradient eluted with dichloromethane:methanol (60:1-15:1), and then dichloromethane:methanol was used as the developing system and iodine was used as the color developer. Thin layer chromatography was used to detect each fraction. According to the thin layer chromatography results, the fractions were sorted and combined, and the product obtained after drying was 3-acetyl-2,5-dimethylthiophene.

[0066] Embodiment 11: (1) Absorption of SO2: An absorption tube filled with 10 mL of saturated L-leucine aqueous solution with an initial pH adjusted to 11 was placed in an electric heating insulation jacket, and the temperature controller was adjusted to maintain it at 20°C. At 0.2 MPa, a mixture of SO2 and N2 with a SO2 concentration of 2.35% was passed into the absorption tube at a rate of 15 mL / min. The absorption of SO2 was determined online by iodine titration until the saturated L-leucine aqueous solution absorbed SO2 to reach equilibrium, thereby obtaining solution a.

[0067] (2) Preparation of 3-acetyl-2,5-dimethylthiophene: Solution a was transferred to a 25 mL hydrothermal autoclave and reacted at 200 °C for 10 h. After the reaction was completed, the hydrothermal autoclave was removed from the heating device and cooled to room temperature. The reaction mixture was distributed between water (10 mL) and ethyl acetate (10 mL). The phases were separated and the aqueous phase was extracted with additional ethyl acetate (3 × 10 mL). The organic phases were combined. The mixture was washed with 10% lithium chloride solution (3 × 10 mL) and saturated sodium chloride solution (10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to obtain the reaction product.

[0068] The content of the reaction product was detected under the conditions of chromatographic column: HP-5MS; injection port temperature: 280°C; carrier gas: He, flow rate: 1.0 mL / min. The yield was 10.52%.

[0069] The above reaction product was mixed with 200-300 mesh column chromatography silica gel, loaded with 150 g column chromatography silica gel, gradient eluted with dichloromethane:methanol (60:1-15:1), and then dichloromethane:methanol was used as the developing system and iodine was used as the color developer. Thin layer chromatography was used to detect each fraction. According to the thin layer chromatography results, the fractions were sorted and combined, and the product obtained after drying was 3-acetyl-2,5-dimethylthiophene.

[0070] In summary, the present invention innovatively adopts hydrothermal synthesis technology to prepare 3-acetyl-2,5-dimethylthiophene, greatly simplifies the operation process, abandons the dependence on catalysts, greatly reduces production costs, and demonstrates the superiority of green chemistry. The preparation method of the present invention meets the requirements of green chemistry, the preparation conditions are easy to control, the preparation process is simple, and it also provides strong scientific support for the environmental governance and resource recycling of SO2, which has far-reaching social and environmental significance.

[0071] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A method for preparing 3-acetyl-2,5-dimethylthiophene, characterized in that: The method comprises: A mixed gas of SO2 and N2 is introduced into a saturated L-leucine aqueous solution until absorption reaches equilibrium to obtain solution a; solution a is subjected to a hydrothermal reaction, and after the reaction is completed, the solution is cooled, extracted, washed, dried, separated and purified to obtain 3-acetyl-2,5-dimethylthiophene.

2. The method for preparing 3-acetyl-2,5-dimethylthiophene according to claim 1, characterized in that: In the saturated L-leucine aqueous solution, the mass ratio of L-leucine to ultrapure water is 0.0224:

1.

3. The method for preparing 3-acetyl-2,5-dimethylthiophene according to claim 1, characterized in that: The pH of the saturated L-leucine aqueous solution is 11.

4. The method for preparing 3-acetyl-2,5-dimethylthiophene according to claim 1, characterized in that: During the absorption process, the temperature of the saturated L-leucine aqueous solution is 20-60°C.

5. The method for preparing 3-acetyl-2,5-dimethylthiophene according to claim 1, characterized in that: In the mixed gas of SO2 and N2, the concentration of SO2 is 2.35%~5.03%, and the concentration of N2 is 97.65%~94.97%.

6. The method for preparing 3-acetyl-2,5-dimethylthiophene according to claim 1, characterized in that: The conditions of the hydrothermal reaction are: reacting at 180-220° C. for 10-14 h.

7. The method for preparing 3-acetyl-2,5-dimethylthiophene according to claim 1, characterized in that: The steps of extraction, washing, drying, separation and purification are: The product was extracted with ethyl acetate, washed with lithium chloride solution and sodium chloride solution, dried over anhydrous sodium sulfate, and separated and purified by silica gel chromatography to obtain the product 3-acetyl-2,5-dimethylthiophene.

8. The method for preparing 3-acetyl-2,5-dimethylthiophene according to claim 1, characterized in that: The mass percentage of the lithium chloride solution is 10%.

9. The method for preparing 3-acetyl-2,5-dimethylthiophene according to claim 1, characterized in that: The mass percentage of the sodium chloride solution is 26.5%.

10. The method for preparing 3-acetyl-2,5-dimethylthiophene according to claim 1, characterized in that: The mobile phases for separation by silica gel column chromatography are dichloromethane and methanol, wherein the volume ratio of dichloromethane to methanol is 60:1 to 15:1.

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