Method for preparing thiophene compound by using bifunctional catalyst through one-pot method and used catalyst

Abstract

The invention relates to the field of chemical engineering, and particularly discloses a preparation method of a bifunctional catalyst, which sequentially comprises the following steps: mixing alkali metal salt and activated aluminum oxide, and roasting to obtain a solid super alkali carrier; the preparation method comprises the following steps: adding a solid super alkali carrier, a Pd precursor and a Cu precursor into deionized water, carrying out ultrasonic mixing, carrying out vacuum drying, roasting in an inert gas atmosphere, carrying out a thermal insulation reduction reaction in an H2 atmosphere, washing, and carrying out vacuum drying to obtain the bifunctional catalyst. The invention further provides application of the bifunctional catalyst, the bifunctional catalyst is used for preparing the thiophene compound through a one-pot method, the one-pot method is simpler and more convenient to operate, meanwhile, environmental pollution is reduced, and the production cost is further reduced.

Description

Technical Field

[0001] The invention relates to the field of chemical industry, and in particular to a method for preparing thiophene compounds by using a bifunctional catalyst in a one-pot process. Background Art

[0002] 2,6-Diaryl-substituted dithieno[3,2-b:2',3'-d]thiophene (abbreviated as dithieno[3,2-b:2',3'-d]thiophene), whose structural formula is shown in Formula 1, has good photoelectric properties and has important applications in the fields of organic semiconductors, organic field effect transistors, organic light-emitting diodes, and solar cells.

[0003]

[0004] Wherein R can be any of the following: 4-methylphenyl, 4-ethylphenyl, 4-propylphenyl, 4-butylphenyl, 4-pentylphenyl, 4-hexylphenyl, 4-fluorophenyl, etc.

[0005] The following methods have been reported for the synthesis of dithieno[3,2-b:2',3'-d]thiophene:

[0006] The literature (J.Org.Chem., 1971, 36:1645-1648.) uses 3-bromothiophene, n-butyl lithium, thio reagent (PhSO2)2S, and anhydrous CuCl2 to react to obtain dithieno[3,2-b:2',3'-d]thiophene;

[0007] The literature (Tetrahedron Lett., 2002, 43: 1553-1554.) uses 2,3-dibromothiophene, n-butyl lithium, thio reagent (PhSO2)2S, and anhydrous CuCl2 to react to obtain dithieno[3,2-b:2',3'-d]thiophene;

[0008] The literature (Tetrahedron Lett., 1997, 38: 4581-4582.) was used to brominate α-dithiophene with NBS, and then reacted with Zn powder, n-butyl lithium, and (PhSO2)2S to obtain dithieno[3,2-b:2',3'-d]thiophene;

[0009] The literature (Synthesis 2016, 48: 4126–4130) uses tetraiodothiophene and aromatic terminal alkynes as raw materials, Pd(PPh3)2Cl2, CuI as catalysts, diisopropylamine as organic base for sonogashira coupling, and then adds Na2S to synthesize dithieno[3,2-b:2',3'-d]thiophene. The specific reaction conditions are as follows: tetraiodothiophene (4 g, 6.80 mmol) is added to a solution of CuI (0.0626 g, 0.329 mmol), Pd(PPh3)2Cl2 (0.231 g, 0.329 mmol), 1-hexyne (1.23 g, 14.96 mmol) and diisopropylamine (250 mL). Stir at room temperature for 21 h, then heat under reflux for 1 h. After cooling to room temperature, filter the mixture, wash the solid with CH2Cl2 (3×25 mL), and mix the washes. The solution was dried over anhydrous MgSO4, filtered, and the solvent was removed to obtain a residue which was purified by silica gel chromatography to obtain 2,5-di(hex-1-ynyl)-3,4-diiodothiophene. A mixture of 2,5-di(hex-1-ynyl)-3,4-diiodothiophene (1 g, 2.02 mmol), Na2S·9H2O (2.90 g, 12.12 mmol), CuI (0.0768 g, 0.403 mmol) and TMEDA (0.094 g, 0.806 mmol) was stirred in DMF (30 mL) at 80°C under nitrogen atmosphere for 24 hours. After completion, the reaction mixture was extracted with Et2O (20 mL each time) until no product was observed in the extract, monitored by TLC. The combined extracts were washed with brine and dried over anhydrous MgSO4. After filtration, the solvent was removed and the residue was purified by silica gel chromatography. 2,6-Dibutyldithieno[3,2-b:2',3'-d]thiophene was obtained in a yield of 56%.

[0010] At present, there are several problems in the synthesis of dithieno[3,2-b:2',3'-d]thiophene at home and abroad. For example, using 3-bromothiophene, 2,3-dibromothiophene, and α-dithiophene as raw materials, the reaction steps are cumbersome, the reaction conditions are harsh, and the production yield is low. The synthesis of dithieno[3,2-b:2',3'-d]thiophene using tetraiodothiophene and aromatic terminal alkynes as raw materials has cheap raw materials, but the catalyst is a precious metal catalyst, and the catalyst cannot be effectively recovered (the reason for the ineffective recovery is that the catalyst loss is high during the reaction process and it is difficult to recover), and it has no industrial application value. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a one-pot method for preparing thiophene compounds and a bifunctional catalyst used therein.

[0012] In order to solve the above technical problems, the present invention provides a method for preparing a bifunctional catalyst, which comprises the following steps:

[0013] ①. Preparation of solid superbase carrier;

[0014] ②. Synthesis of bifunctional catalysts supported by solid superbase.

[0015] As an improvement of the preparation method of the bifunctional catalyst of the present invention:

[0016] ① Preparation of solid superbase carrier:

[0017] 0.08-0.09 mol of alkali metal salt and 7.5-8.5 g of activated alumina are mixed into a paste in deionized water, vacuum dried (vacuum dried at 110±10°C for 12±1h), and then heated to 550±20°C for calcination for 6±0.5h to obtain a solid super alkali carrier;

[0018] ②Synthesis of bifunctional catalyst supported by solid superbase:

[0019] The solid superbase carrier obtained in step ①, the Pd precursor and the Cu precursor are added to deionized water and ultrasonically mixed (about 1 to 2 hours), the molar ratio of Pd precursor to Cu precursor is 0.5 to 2:1, and 0.4 to 0.6 g of the solid superbase carrier is used for every 0.1 to 0.15 mmol of Cu precursor;

[0020] The mixture is first dried under vacuum (at 80±10°C for 12±1h), then heated to 500±20°C for 4±0.5h in an inert gas (e.g., N2) atmosphere, and then kept warm in a 10% to 12% (volume %) H2 atmosphere (i.e., 500

[0021] ±20℃) reduction reaction 2±0.2h;

[0022] The product obtained by the reduction reaction was washed with deionized water and ethanol (washed three times), respectively, and then vacuum dried (vacuum dried at 60±10° C. for 12±1 h) to obtain a bifunctional catalyst (solid superbase-supported Pd / Cu alloy catalyst).

[0023] Note: The calcination in this step is carried out in an inert gas (such as N2) atmosphere, and the reaction that occurs is to load a certain amount of precious metal palladium and copper onto the solid superbase carrier.

[0024] As a further improvement of the preparation method of the bifunctional catalyst of the present invention:

[0025] The Pd precursor is PdCl2 or Pd(NO)3, and the Cu precursor is CuCl2 or Cu(NO)3.

[0026] As a further improvement of the preparation method of the bifunctional catalyst of the present invention:

[0027] The alkali metal salt is a carbonate; the alkali metal is any one of the following: K, Na, Cs;

[0028] The activated alumina is γ-Al2O3.

[0029] As a further improvement of the preparation method of the bifunctional catalyst of the present invention:

[0030] The heating rate of step ① is 4-6°C / min;

[0031] The heating rate of step ② is 4-6°C / min.

[0032] As a further improvement of the preparation method of the bifunctional catalyst of the present invention:

[0033] In the step ①, 20±5 mL of deionized water is used for every 0.08-0.09 mol of alkali metal salt;

[0034] In the step ②, 10±2 mL of deionized water is added for every 0.1-0.15 mmol of Cu precursor.

[0035] As a further improvement of the preparation method of the bifunctional catalyst of the present invention:

[0036] In step ①: after vacuum drying, the powder is first crushed into 20-40 mesh particles, and then heated and roasted.

[0037] The present invention also provides a one-pot method for preparing thiophene compounds, wherein the bifunctional catalyst (solid superbase-supported Pd / Cu alloy catalyst) prepared by the above method comprises the following steps:

[0038] 1) Tetraiodine thiophene, aryl terminal alkyne and S8 (sulfur element) are used as starting materials, and the molar ratio of tetraiodine thiophene, aryl terminal alkyne and S8 is 1: (2 ± 0.1): (12 ± 0.1);

[0039] Add the starting material, the organic base and the bifunctional catalyst to a solvent, and stir the reaction in an inert gas (such as N2) atmosphere, the reaction temperature is 80-100°C, and the reaction time is 8-15 hours (for example, 100°C for 12 hours);

[0040] 0.4-0.6 g of catalyst is used for every 1.5 mmol of tetraiodothiophene;

[0041] The molar ratio of the organic base to tetraiodothiophene is 6 to 7:1;

[0042] 2) Post-treating the reaction product obtained in step 1) to obtain a thiophene compound.

[0043] As an improvement of the one-pot method for preparing thiophene compounds of the present invention:

[0044] The aromatic terminal alkyne is any of the following: 4-methylphenylacetylene, 4-ethylphenylacetylene, 4-propylphenylacetylene, 4-butylphenylacetylene, 4-pentylphenylacetylene, 4-hexylphenylacetylene, 4-fluorophenylacetylene;

[0045] The organic base is diisopropylamine;

[0046] The solvent is dimethyl sulfoxide (DMSO).

[0047] As a further improvement of the one-pot method for preparing thiophene compounds of the present invention: the post-treatment of step 2) is:

[0048] The reaction product obtained in step 1) is filtered, and the filter cake is a recyclable bifunctional catalyst. The filtrate is extracted with dichloromethane and water, and the dichloromethane organic phase is separated by column chromatography with petroleum ether as the eluent to obtain a thiophene compound.

[0049] Description: The filter cake obtained by filtration is washed alternately with ethanol and water three times (to remove residual impurities attached to the filter cake), and then vacuum dried (dried at 50-60°C to constant weight); it is used as a bifunctional catalyst for recycling.

[0050] The synthesis formula of the present invention is as follows:

[0051]

[0052] Wherein R is any of the following: 4-methylphenyl, 4-ethylphenyl, 4-propylphenyl, 4-butylphenyl, 4-pentylphenyl, 4-hexylphenyl, 4-fluorophenyl, etc.

[0053] Compared with the existing synthesis method using tetraiodothiophene and aryl terminal alkyne as raw materials, the present invention has the following technical advantages:

[0054] 1. The present invention adopts a specially designed bifunctional catalyst, which can efficiently synthesize thiophene compounds (such as 2,6-diaryl substituted dithieno[3,2-b:2',3'-d]thiophene compounds) with a yield as high as 85%. While showing good catalytic activity, the catalyst can be reused, separation is simpler, and the salt content in the wastewater during the extraction process can be reduced, thereby reducing environmental pollution and conforming to the concept of green chemistry.

[0055] 2. The one-pot preparation method reduces the synthesis cost and the step of adding reactants in the existing process (Synthesis 2016, 48: 4126-4130); the operation is simpler, while reducing environmental pollution and further reducing production costs. DETAILED DESCRIPTION

[0056] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0057] Example 1: Bifunctional catalyst - solid superbase supported Pd / Cu alloy catalyst

[0058] 1) Preparation of solid superbase carrier K2CO3 / γ-Al2O3:

[0059] The alkali metal salt is K2CO3; the carrier is γ-Al2O3;

[0060] 0.082 mol (about 11.5 g) of K2CO3 and 8 g of γ-Al2O3 were mixed into a paste in 20 mL of ionized water. The paste was placed at 110°C for vacuum drying for 12 h, then crushed and sieved into 20-40 mesh particles, and then heated to 550°C at 5°C / min and calcined for 6 h to obtain a solid superbase carrier with an alkali metal content of about 10%.

[0061] Alkali metal content calculation formula:

[0062]

[0063] Where X is the mass of K2CO3; M K is the molar mass of potassium; M K2CO3 is the molar mass of K2CO3; M K2O is the molar mass of K2O; Y is the mass of γ-Al2O3.

[0064] 2) Synthesis of solid superbase supported Pd / Cu alloy catalyst:

[0065] The Pd precursor is PdCl2; the Cu precursor is Cu(NO3)2;

[0066] Take 0.5 g of the solid superbase carrier obtained in step 1), add 0.075 mmol (about 0.0132 g) of PdCl2 and 0.15 mmol (about 0.028 g) of Cu(NO3)2 to 10 mL of deionized water, and mix by ultrasonication for 1 h;

[0067] The mixture was dried at 80°C in vacuum for 12h, then heated to 500°C at 5°C / min in a N2 atmosphere for 4h, and then partially replaced with H2 until the H2 content reached 10% (volume %), and then reduced at 500°C for 2h in a 10% H2 atmosphere;

[0068] The product obtained by the reduction reaction was washed three times with deionized water and ethanol respectively, and vacuum dried at 60°C for 12 hours; finally, it was crushed into particles of 20 to 40 meshes to obtain a bifunctional catalyst - a solid superbase-supported Pd / Cu alloy catalyst.

[0069] Example 2: Bifunctional catalyst - solid superbase supported Pd / Cu alloy catalyst

[0070] The following changes were made relative to Example 1: the alkali metal salt in Example 1 was changed from K2CO3 to Na2CO3, and the molar amount remained unchanged at 0.082 mol; the resulting solid superbase carrier had an alkali metal content of approximately 14.4%; the rest was the same as Example 1.

[0071] Example 3: Bifunctional catalyst - solid superbase supported Pd / Cu alloy catalyst

[0072] The following changes were made relative to Example 1: the alkali metal salt in Example 1 was changed from K2CO3 to Cs2CO3, and the molar amount remained unchanged at 0.082 mol; the resulting solid superbase carrier had an alkali metal content of approximately 14.5%; the rest was the same as Example 1.

[0073] Example 4: Bifunctional catalyst - solid superbase supported Pd / Cu alloy catalyst

[0074] The following changes were made relative to Example 1: the Pd precursor in Example 1 was changed from PdCl2 to Pd(NO3)2, and the molar amount remained unchanged at 0.075 mmol; the rest was the same as Example 1.

[0075] Example 5: Bifunctional catalyst - solid superbase supported Pd / Cu alloy catalyst

[0076] The following changes were made relative to Example 1: the Cu precursor in Example 1 was changed from Cu(NO3)2 to CuCl2, and the molar amount remained unchanged at 0.015 mmol; the rest was the same as Example 1.

[0077] Example 6: Bifunctional catalyst - solid superbase supported Pd / Cu alloy catalyst

[0078] The following changes were made relative to Example 1: the alkali metal salt in Example 1 was changed from K2CO3 to Na2CO3, and the molar amount remained unchanged at 0.082 mol; the Pd precursor was changed from PdCl2 to Pd(NO3)2, and the molar amount remained unchanged at 0.075 mmol; the rest was the same as Example 1.

[0079] Example 7: Bifunctional catalyst - solid superbase supported Pd / Cu alloy catalyst

[0080] The following changes were made relative to Example 1: the alkali metal salt in Example 1 was changed from K2CO3 to Cs2CO3, and the molar amount remained unchanged at 0.082 mol; the Pd precursor was changed from PdCl2 to Pd(NO3)2, and the molar amount remained unchanged at 0.075 mmol; the rest was the same as Example 1.

[0081] Example 8: Bifunctional catalyst - solid superbase supported Pd / Cu alloy catalyst

[0082] The following changes were made relative to Example 1: the alkali metal salt in Example 1 was changed from K2CO3 to Na2CO3, and the molar amount remained unchanged at 0.082 mol; the Cu precursor was changed from Cu(NO3)2 to CuCl2, and the molar amount remained unchanged at 0.015 mmol; the rest was the same as Example 1.

[0083] Example 9: Bifunctional catalyst - solid superbase supported Pd / Cu alloy catalyst

[0084] The alkali metal salt in Example 1 was changed from K2CO3 to Na2CO3, and the molar amount remained unchanged at 0.082 mol; the Pd precursor was changed from PdCl2 to Pd(NO3)2, and the molar amount remained unchanged at 0.075 mmol; the Cu precursor was changed from Cu(NO3)2 to CuCl2, and the molar amount remained unchanged at 0.015 mmol; the rest was the same as Example 1.

[0085] Example 10: Bifunctional catalyst - solid superbase supported Pd / Cu alloy catalyst

[0086] The alkali metal salt in Example 1 was changed from K2CO3 to Cs2CO3, and the molar amount remained unchanged at 0.082 mol; the Pd precursor was changed from PdCl2 to Pd(NO3)2, and the molar amount remained unchanged at 0.075 mmol; the Cu precursor was changed from Cu(NO3)2 to CuCl2, and the molar amount remained unchanged at 0.015 mmol; the rest was the same as Example 1.

[0087] Example 1: A method for preparing thiophene compounds using a bifunctional catalyst in one pot, comprising the following steps:

[0088] 1) 1.5 mmol tetraiodothiophene, 3 mmol 4-methylphenylacetylene, 9.6 mmol diisopropylamine, 18 mmol S8, 25 ml DMSO, and 0.5 g of the catalyst obtained in Example 1 were added to a reaction tube, nitrogen was introduced to replace the pressure to normal pressure, and stirred at 100° C. for 12 h;

[0089] 2) After the reaction is completed, the filter cake is filtered and the obtained filter cake is a recyclable bifunctional catalyst. Specifically, the filter cake obtained by filtration is washed three times with ethanol and water alternately (to remove residual impurities attached to the filter cake), and then vacuum dried (vacuum dried at 50°C to constant weight); as a recycled bifunctional catalyst (about 0.4g).

[0090] The filtrate obtained by suction filtration was extracted with water and dichloromethane (100 mL of water, 200 mL of dichloromethane), and the dichloromethane organic phase was taken, 4 g of 200-300 mesh silica gel was added, and the mixture was dried by rotation at 45°C. Dry loading was performed, column chromatography was performed, petroleum ether was used as the eluent, and the amount of petroleum ether was 1 L. All the eluents were collected and the collected eluents were subjected to rotary evaporation. Finally, 0.48 g of 2,6-bis(4-methylphenyl)-dithieno[3,2-b:2',3'-d]thiophene was obtained, and the yield was 85%.

[0091]

[0092] Embodiment 2 to Embodiment 10, a method for preparing thiophene compounds using a bifunctional catalyst in one pot,

[0093] With respect to Example 1, the catalyst obtained in Example 1 is replaced with the catalyst obtained in Example 2 to the catalyst obtained in Example 10, respectively, and the rest is the same as Example 1; thus, Examples 2 to 10 are obtained correspondingly.

[0094] The results are shown in Table 1 below.

[0095] Table 1

[0096] Catalyst used Production volume Yield Example 1 Example 1 Preparation 0.48g 85％ Example 2 Example 2 Preparation 0.45g 80％ Example 3 Example 3 Preparation 0.4g 71％ Example 4 Example 4 Preparation 0.46g 81％ Example 5 Example 5 Preparation 0.44g 78.7％ Example 6 Example 6 Preparation 0.42g 75.2％ Example 7 Example 7 Preparation 0.41g 73％ Example 8 Example 8 Preparation 0.43g 76.9％ Example 9 Example 9 Preparation 0.417g 74％ Example 10 Example 10 Preparation 0.439g 78％

[0097] Example 11: Catalyst recycling

[0098] First recycling: The catalyst recycled from Example 1 (about 0.4 g) was added with the catalyst prepared in Example 1 until the total weight was 0.5 g (i.e., the same amount of catalyst as in Example 1), thereby replacing the catalyst used in Example 1, and the rest was the same as in Example 1; the yield was 79%.

[0099] According to the above recycling method, after the fourth recycling, the yield can still reach 68%.

[0100] Embodiment 12

[0101] The "4-methylphenylacetylene" in Example 1 was replaced with "4-ethylphenylacetylene", and the rest was the same as Example 1, thereby obtaining the corresponding product 2,6-bis(4-ethylphenyl)-dithieno[3,2-b:2',3'-d]thiophene with a yield of 78%.

[0102] Embodiment 13

[0103] The "4-methylphenylacetylene" in Example 1 was replaced with "4-propylphenylacetylene", and the rest was the same as Example 1, thereby obtaining the corresponding product 2,6-bis(4-propylphenyl)-dithieno[3,2-b:2',3'-d]thiophene with a yield of 75%.

[0104] Embodiment 14

[0105] The "4-methylphenylacetylene" in Example 1 was replaced with "4-butylphenylacetylene", and the rest was the same as Example 1, thereby obtaining the corresponding product 2,6-bis(4-butylphenyl)-dithieno[3,2-b:2',3'-d]thiophene with a yield of 78%.

[0106] Embodiment 15

[0107] The "4-methylphenylacetylene" in Example 1 was replaced by "4-pentylphenylacetylene", and the rest was the same as Example 1, thereby obtaining the corresponding product 2,6-bis(4-pentylphenyl)-dithieno[3,2-b:2',3'-d]thiophene with a yield of 73%.

[0108] Example 16

[0109] The "4-methylphenylacetylene" in Example 1 was replaced by "4-hexylphenylacetylene", and the rest was the same as Example 1, thereby obtaining the corresponding product 2,6-bis(4-hexylphenyl)-dithieno[3,2-b:2',3'-d]thiophene with a yield of 74%.

[0110] Embodiment 17

[0111] The "4-methylphenylacetylene" in Example 1 was replaced by "4-fluorophenylacetylene", and the rest was the same as Example 1, thereby obtaining the corresponding product 2,6-bis(4-fluorophenyl)-dithieno[3,2-b:2',3'-d]thiophene with a yield of 60%.

[0112] Note: All products of the present invention have been verified by conventional NMR to be correct.

[0113] Example 18, Comparative Example 1,

[0114] The molar amounts of PdCl2 and Cu(NO3)2 in Example 1 were changed to those shown in Table 2 below, and the rest were the same as in Example 1. The catalyst obtained by replacing the catalyst obtained in Example 1 was used, and the amount remained unchanged, still 0.5 g, and the rest were the same as in Example 1. The yield of the obtained product was compared with that of Example 1 as shown in Table 2 below.

[0115] Table 2

[0116]

[0117] Comparative Example 2

[0118] Preparation method of Pd / Cu / Al2O3 alloy catalyst: relative to Example 1, the following changes are made: omit the preparation of the solid superbase in step 1); change step 2) "take 0.5g of the solid superbase carrier obtained in step 1)" to "take 0.5g of γ-Al2O3", and the rest is the same as Example 1. The obtained catalyst is named Pd / Cu / Al2O3 alloy catalyst.

[0119] The catalyst "solid superbase supported Pd / Cu alloy catalyst" in Example 1 was changed to "Pd / Cu / Al2O3 alloy catalyst", and the rest was the same as Example 1. The result was: the yield was only 13%.

[0120] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A method for preparing a bifunctional catalyst, characterized in that Follow these steps in order: ①. Preparation of solid superbase carrier; ②. Synthesis of bifunctional catalysts supported by solid superbase.

2. The method for preparing a bifunctional catalyst according to claim 1, characterized in that: ①. Preparation of solid superbase carrier: 0.08-0.09 mol of alkali metal salt and 7.5-8.5 g of activated alumina are mixed into a paste in deionized water, dried under vacuum, and then heated to 550±20° C. and calcined for 6±0.5 h to obtain a solid super alkali carrier; ②Synthesis of bifunctional catalyst supported by solid superbase: The solid superbase carrier obtained in step ①, the Pd precursor and the Cu precursor are added to deionized water and ultrasonically mixed, the molar ratio of Pd precursor to Cu precursor is 0.5 to 2:1, and 0.4 to 0.6 g of the solid superbase carrier is used for every 0.1 to 0.15 mmol of Cu precursor; The mixture is first dried in vacuum, then heated to 500±20°C for calcination for 4±0.5h in an inert gas atmosphere, and then kept at this temperature for reduction reaction for 2±0.2h in a 10-12% H2 atmosphere; The product obtained by the reduction reaction is washed with deionized water and ethanol respectively, and then dried in vacuum to obtain a bifunctional catalyst.

3. The method for preparing a bifunctional catalyst according to claim 2, characterized in that: The Pd precursor is PdCl2 or Pd(NO)3, and the Cu precursor is CuCl2 or Cu(NO)3.

4. The method for preparing a bifunctional catalyst according to claim 3, characterized in that: The alkali metal salt is a carbonate; the alkali metal is any one of the following: K, Na, Cs; The activated alumina is γ-Al2O3.

5. The method for preparing a bifunctional catalyst according to claim 4, characterized in that: The heating rate of step ① is 4-6°C / min; The heating rate of step ② is 4-6°C / min.

6. A method for preparing a bifunctional catalyst according to any one of claims 2 to 5, characterized in that: In the step ①, 20±5 mL of deionized water is used for every 0.08-0.09 mol of alkali metal salt; In the step ②, 10±2 mL of deionized water is added for every 0.1-0.15 mmol of Cu precursor.

7. The method for preparing a bifunctional catalyst according to claim 6, characterized in that In the step ①: after vacuum drying, the powder is first crushed into particles of 20 to 40 meshes, and then heated and roasted.

8. A one-pot method for preparing thiophene compounds, characterized in that: The bifunctional catalyst prepared by the method according to any one of claims 1 to 7 comprises the following steps: 1) Tetraiodothiophene, aryl-terminal alkyne and S8 are used as starting materials, wherein the molar ratio of tetraiodothiophene, aryl-terminal alkyne and S8 is 1:(2±0.1):(12±0.1); Add the starting material, organic base and bifunctional catalyst into the solvent, stir and react under an inert gas atmosphere, the reaction temperature is 80-100° C., and the reaction time is 8-15 hours; 0.4-0.6 g of catalyst is used for every 1.5 mmol of tetraiodothiophene; The molar ratio of the organic base to tetraiodothiophene is 6 to 7:1; 2) Post-treating the reaction product obtained in step 1) to obtain a thiophene compound.

9. The one-pot method for preparing thiophene compounds according to claim 8, characterized in that: The aromatic terminal alkyne is any of the following: 4-methylphenylacetylene, 4-ethylphenylacetylene, 4-propylphenylacetylene, 4-butylphenylacetylene, 4-pentylphenylacetylene, 4-hexylphenylacetylene, 4-fluorophenylacetylene; The organic base is diisopropylamine; The solvent is dimethyl sulfoxide.

10. The one-pot method for preparing thiophene compounds according to claim 8 or 9, characterized in that: The post-processing of step 2) is: The reaction product obtained in step 1) is filtered, and the filter cake is a recyclable bifunctional catalyst. The filtrate is extracted with dichloromethane and water, and the dichloromethane organic phase is separated by column chromatography with petroleum ether as the eluent to obtain a thiophene compound.

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