A Synthetic Process for Hexa(trimethylsilylethynyl)benzene
By improving the temperature control and purification methods in the synthesis process of hexa(trimethylsilylethynyl)benzene, the problems of high energy consumption and low solubility were solved, enabling efficient and low-cost industrial production with stable yield.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG UNIV
- Filing Date
- 2023-12-13
- Publication Date
- 2026-06-30
AI Technical Summary
The existing synthesis process of hexa(trimethylsilylethynyl)benzene has problems such as high energy consumption due to the requirement of extremely low temperature, low solubility of anhydrous zinc chloride, and difficulty in purification, which affect the yield and industrial application.
By controlling the reaction temperature between -10 and -40°C, using an ice-salt bath or a cold solvent bath to control the reaction, directly adding solid zinc chloride or zinc bromide and restoring to room temperature, heating to promote dissolution, and using a mixed solution of alcohol and dichloromethane for recrystallization purification, solvent consumption and purification time are reduced.
It reduces energy consumption, increases yield, simplifies the purification process, is suitable for industrial production, and maintains a stable yield of around 52%.
Smart Images
Figure CN117777179B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of organic synthesis technology, and in particular to a synthesis process for hexa(trimethylsilylethynyl)benzene. Background Technology
[0002] Graphdiyne is a two-dimensional carbon allotrope composed of carbon atoms, which can be viewed as a combination of butyryl and benzene rings. Compared to graphene, graphdiyne possesses richer carbon chemical bonds, a larger conjugated system, a naturally porous structure, and an intrinsic band gap. These characteristics give graphdiyne excellent electron transport properties and chemical reactivity, leading to its widespread application in energy storage, catalysis, and sensors. In energy storage, graphdiyne is used as a negative electrode material in lithium-ion batteries, improving cycle stability and capacity retention. Furthermore, graphdiyne can be used as an electrode material in supercapacitors, offering advantages such as high specific capacitance and long cycle life. In catalysis, graphdiyne is used as a catalyst support, enhancing catalyst activity and stability. In sensors, graphdiyne is used as a gas-sensitive material to detect toxic and greenhouse gases in the air. The application of graphdiyne in the gas-phase photocatalytic synthesis of high-value-added chemical fuels has also attracted considerable attention.
[0003] Hexa(trimethylsilylacetyl)benzene is an essential intermediate in the synthesis of graphynylene. It is an organic compound with broad application prospects and significant industrial value. It plays a crucial role in organic synthesis, and in industrial applications, hexa(trimethylsilylacetyl)benzene has wide-ranging uses; for example, it is an important intermediate in dyes, fluorescent probes, and optoelectronic materials. Therefore, optimizing its synthetic route and its industrial application are of great significance.
[0004] The currently reported synthesis process of hexa(trimethylsilylethynyl)benzene is as follows: Step (1), under inert gas protection and extremely low temperature (-78℃) conditions, n-butyllithium is added dropwise to an anhydrous tetrahydrofuran solution of trimethylsilylethynylene, and the reaction is carried out at this temperature for 5-30 min to obtain a solution A of trimethylsilylethynyllithium; Step (2), under inert gas protection and extremely low temperature (-78℃) conditions, anhydrous zinc chloride is dissolved in a large amount of tetrahydrofuran (at room temperature, generally only a maximum of 1.0 mol / L zinc chloride / tetrahydrofuran solution can be prepared), and this solution is added dropwise to the above solution A, and the temperature is restored to room temperature. The reaction time of 1-3 hours promotes the formation of trimethylsilylethynyl zinc chloride. The solubility of zinc chloride is further reduced at extremely low temperatures. Even at room temperature, a large amount of anhydrous zinc chloride is difficult to dissolve. The literature thus prepared a trimethylsilylethynyl zinc chloride solution B. In step (3), under the protection of an inert gas, anhydrous toluene and catalyst tetra(triphenylphosphine)palladium were added to the reaction solution B and stirred at 80°C for 72 hours. In step (4), after the reaction was completed and the solution was cooled to room temperature, the reaction solution was washed with dilute hydrochloric acid, dried with a drying agent, and distilled to obtain a solid mixture C. The solid was purified by silica gel column chromatography to obtain the final product.
[0005] The above method has the following problems:
[0006] 1. When adding n-butyllithium dropwise, the reaction temperature needs to be lowered to an extremely low temperature of -78°C, which is a very low temperature in industry and requires a large amount of energy.
[0007] 2. At room temperature, anhydrous zinc chloride (ZnCl2) has very low solubility in anhydrous tetrahydrofuran (THF), with a maximum solubility of about 1 mol / L. Adding a tetrahydrofuran solution of zinc chloride dropwise to a reaction system at an extremely low reaction temperature (-78℃) will rapidly reduce the solubility of anhydrous zinc chloride. Furthermore, commercially available n-butyllithium is typically a 1.6 mol / L or 2.5 mol / L n-hexane solution. This means that under any synthetic process, the reaction solution will contain n-hexane solvent. However, n-hexane solvent has almost no solubility for anhydrous zinc chloride. Since n-hexane was added during the previous step of adding n-butyllithium, the solubility of anhydrous zinc chloride was further reduced. Therefore, at the extremely low reaction temperature (-78°C) reported in the literature, the prepared zinc chloride tetrahydrofuran solution will inevitably precipitate zinc chloride solid from the solution and will not dissolve. Even if the temperature is restored to room temperature, it will still be difficult to dissolve due to the presence of n-hexane. Since the zinc chloride cannot dissolve, trimethylsilylethynyl zinc chloride cannot be completely generated, and only a suspension containing zinc chloride solid can be obtained, thus affecting the yield of hexa(trimethylsilylethynyl)benzene.
[0008] 3. In the published literature, the final product is a mixture of hexa(trimethylsilylethynyl)benzene and penta(trimethylsilylethynyl)benzene, etc. The two compounds are homologues with similar physicochemical properties and very similar polarities, which makes purification difficult. The literature uses silica gel column chromatography for purification, but this purification method requires a large amount of solvent, generates a large amount of solid silica gel waste, consumes a large amount of organic solvents extracted and refined from petroleum (petroleum ether and dichloromethane, etc.), and takes a long time (often several days).
[0009] Therefore, such a synthesis process poses difficulties for the industrial synthesis of hexa(trimethylsilylethynyl)benzene. Summary of the Invention
[0010] To address the aforementioned technical problems, this invention provides a synthesis process for hexa(trimethylsilylethynyl)benzene, aiming to improve yield, reduce energy consumption, and make it suitable for industrial synthesis.
[0011] To achieve the above objectives, the technical solution of the present invention is as follows:
[0012] A process for synthesizing hexa(trimethylsilylethynyl)benzene includes the following steps:
[0013] Step 1: Trimethylsilylacetylene reacts with alkyllithium to form lithium trimethylsilylacetylene:
[0014] Under inert gas protection and at a temperature of -10 to -40°C, trimethylsilylacetylene is dissolved in an organic solvent, and alkyl lithium is slowly added dropwise while stirring. The reaction is carried out under these conditions for at least 5 minutes (extending the reaction time can make the reaction complete without adversely affecting the reaction results, and generally should not exceed 120 hours) to obtain a solution A of trimethylsilylacetylene lithium.
[0015] Step 2: Trimethylsilylacetylenite reacts with anhydrous zinc chloride or anhydrous zinc bromide to produce trimethylsilylacetylenyl zinc chloride or trimethylsilylacetylenyl zinc bromide.
[0016] Under inert gas protection and at a temperature of -10 to -40°C, anhydrous zinc chloride or anhydrous zinc bromide is slowly added in batches to solution A, the temperature is restored to room temperature, and then raised to 30 to 80°C to obtain solution B of trimethylsilylacetyl zinc chloride or trimethylsilylacetyl zinc bromide.
[0017] Step 3: Trimethylsilylacetyl zinc chloride or trimethylsilylacetyl zinc bromide reacts with hexabromobenzene to produce hexa(trimethylsilylacetyl)benzene.
[0018] Under inert gas protection, hexabromobenzene and palladium catalyst were added to solution B, and the temperature was raised to above 50°C (the temperature was raised to the boiling point of the reaction solution). The reaction was carried out for at least 48 hours (extending the reaction time can make the reaction complete without adversely affecting the reaction results, and generally should not exceed 120 hours). After the reaction was completed, the solution was cooled to room temperature, washed with dilute hydrochloric acid, dried with a desiccant, filtered with a silica gel pad, and distilled to obtain a solid mixture C.
[0019] Step 4: Purification of hexa(trimethylsilylethynyl)benzene:
[0020] Under reflux, alcohol or a mixture of alcohol and dichloromethane (volume ratio v / v, not greater than 500:1 and not less than 10:1) is slowly added in batches to the solid mixture C until the mixture C is just completely dissolved; after cooling to room temperature, white crystals precipitate; after filtration, the solid is washed with cold alcohol to obtain pure hexa(trimethylsilylethynyl)benzene.
[0021] In the above scheme, the method for controlling the reaction temperature in the first and second steps to be between -10 and -40°C is to apply an ice-salt bath or a cold solvent bath to the reaction flask. The ice-salt bath is a mixture of crushed ice and inorganic salts, and the cold solvent bath is obtained by cooling the solvent with a cooling device. The inorganic salts used in the ice-salt bath are one, two, or a mixture of sodium chloride, ammonium chloride, potassium chloride, sodium sulfate, sodium carbonate, and sodium bicarbonate. The solvents used in the cold solvent bath are one, two, or a mixture of water, ethanol, ethylene glycol, propanol, and isopropanol.
[0022] In the above scheme, in the first step, the organic solvent is one of tetrahydrofuran, 2-methyltetrahydrofuran, methyl tert-butyl ether, benzene, or toluene.
[0023] In the above scheme, in the first step, the alkyl lithium is one of tert-butyl lithium, methyl lithium, ethyl lithium, propyl lithium, n-butyl lithium or isobutyl lithium.
[0024] In the above scheme, in the third step, an anhydrous solvent is added to solution B to increase the solubility of hexabromobenzene. The anhydrous solvent is one or more of tetrahydrofuran, benzene, toluene, o-xylene, m-xylene, p-xylene, or trimethylbenzene.
[0025] In the above scheme, the inert gas is nitrogen or argon.
[0026] In the above scheme, in the third step, the palladium catalyst is one of tetra(triphenylphosphine)palladium, bis(triphenylphosphine)palladium dichloride, or 1,1'-bis(diphenylphosphine)ferrocenepalladium chloride.
[0027] In the above scheme, the alcohol in the fourth step is one or more of methanol, ethanol, propanol or isopropanol.
[0028] In the above scheme, if the obtained hexa(trimethylsilylethynyl)benzene is impure in the fourth step, the recrystallization process in the fourth step is repeated at least once until pure hexa(trimethylsilylethynyl)benzene is obtained.
[0029] In the above scheme, the molar ratio of trimethylsilylacetylene, alkyllithium, anhydrous zinc chloride or zinc bromide, and hexabromobenzene is (9-18):(9-18):(9-18):1.
[0030] The synthesis process of hexa(trimethylsilylethynyl)benzene provided by the present invention through the above technical solution has the following beneficial effects:
[0031] 1. In the first step of the reaction, the addition of alkyllithium produces an exothermic reaction. Cooling is intended to control the temperature of the reaction solution from becoming too high. However, through practical operation, we found that using an ice-salt bath (or a cold solvent bath) at -10 to -40°C is sufficient to control the reaction temperature. Temperatures that are too low will lead to incomplete reactions in the next step. Conducting the reaction at -10 to -40°C reduces the energy consumption required for the reaction, which is beneficial for its large-scale and industrial application.
[0032] 2. In the second step of this invention, the reaction is carried out at -10 to -40°C. Solid zinc chloride or zinc bromide is directly added to the reaction system, and the mixture is brought back to room temperature. Heating is used to promote the complete dissolution of zinc chloride or zinc bromide and to accelerate the reaction. Only after the zinc chloride or zinc bromide dissolves will it react with lithium trimethylsilylacetylenide to form trimethylsilylacetylenyl zinc chloride or trimethylsilylacetylenyl zinc bromide. The final product is a clear solution of trimethylsilylacetylenyl zinc chloride or trimethylsilylacetylenyl zinc bromide that does not contain solid zinc chloride or zinc bromide. The amount of solvent used is small and the reaction is more complete, which is beneficial to the next step of the reaction.
[0033] 3. After the reaction is completed, the reaction solution is directly extracted, washed, dried, filtered, and the filtrate is concentrated. The filtrate concentrate is directly recrystallized with methanol and dichloromethane in just a few hours with a stable yield of about 52%. Recrystallization is also a prerequisite for industrial application. Attached Figure Description
[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.
[0035] Figure 1 The image shows the NMR mass spectrum of hexa(trimethylsilylethynyl)benzene prepared in Example 1 of this invention. Detailed Implementation
[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
[0037] Based on previous literature reports, this invention effectively improves the synthesis efficiency of the product hexa(trimethylsilylethynyl)benzene by improving the process, such as temperature, operation steps, and purification methods, and reduces the consumption of fossil energy such as solvents, thus providing feasibility for industrial production.
[0038] In the following examples, the proportions of all other reactants are based on hexabromobenzene, with the molar amount of hexabromobenzene set at 1.0 equivalent (1.0 eq.). The equivalent of any other reagent refers to its molar amount being a multiple of that of hexabromobenzene. For example, in Example 1, the molar ratios of the five reagents are: trimethylsilylacetylene (12.5 eq.), n-butyllithium (12.0 eq.), anhydrous zinc chloride (12.0 eq.), hexabromobenzene (1.0 eq.), and tetra(triphenylphosphine)palladium (0.05 eq.), which is 12.5:12.0:12.0:1:0.05.
[0039] The synthesis route is as follows:
[0040]
[0041] Example 1
[0042] (1) Connect the three-necked reaction flask to the condenser and introduce argon gas to keep the inside of the reaction flask in an inert atmosphere. Place the reaction flask in an ice / ammonium chloride bath (about -15°C). Add anhydrous tetrahydrofuran (100 mL) and trimethylsilylacetylene (27.0 mL, 12.5 eq.) to the flask in sequence, stir, and at the same time slowly add 2.5 M n-butyllithium (73.36 mL, 183.4 mmol, 12.0 eq.) to the flask. After the addition is complete, continue stirring for 15 minutes under the same conditions to obtain a solution A of trimethylsilylacetylene.
[0043] (2) Under argon protection inside the reaction flask and cooling with an ice / ammonium chloride bath outside, anhydrous zinc chloride (25g, 183.4mmol, 12.0eq.) was slowly added in batches to solution A in the reaction flask. Zinc chloride or zinc bromide is hygroscopic, so care should be taken to avoid contact with air during the addition process. An exothermic phenomenon occurred during the addition. After adding zinc chloride, the ice / ammonium chloride bath was removed, and the mixture was allowed to return to room temperature. Then, the reaction flask was placed in a heater, stirred, and heated to 50°C and stirred for 0.5 hours. During the heating process, solid zinc chloride was observed to slowly dissolve, yielding solution B of trimethylsilylethynyl zinc chloride.
[0044] (3) Under argon protection at room temperature, anhydrous p-xylene (100 mL), hexabromobenzene (8.42 g, 15.28 mmol, 1.0 eq.), and tetra(triphenylphosphine)palladium (883 mg, 0.05 eq.) were added to solution B in the reaction flask. The mixture was heated to 80 °C and stirred for 48 hours under argon protection. After the reaction was completed and the reaction solution was cooled to room temperature, the reaction solution was washed twice with 2 M dilute hydrochloric acid, dried with anhydrous sodium sulfate, filtered through a 5 cm thick silica gel pad, and distilled to obtain a solid mixture C.
[0045] (4) Add the above solid mixture C to a 500 mL single-necked round-bottom flask. Under reflux, slowly add a methanol / dichloromethane mixture (volume ratio v / v = 200:1) until mixture C is just completely dissolved. Cool to room temperature and let stand for 2 hours; white crystals precipitate. Filter and wash the solid with cold methanol (10 mL). Repeat the above recrystallization process three times to obtain 5.25 g of high-purity hexa(trimethylsilylethynyl)benzene, yield: 52.4%. NMR mass spectrometry is as follows: Figure 1 As shown, 1 ¹H NMR (600MHz, CDCl₃) δ (ppm) 0.27, consistent with literature records.
[0046] Example 2
[0047] (1) Connect the three-necked reaction flask to the condenser and introduce argon gas to keep the inside of the reaction flask in an inert atmosphere. Place the reaction flask in an ice / ammonium chloride bath (about -15°C). Add anhydrous tetrahydrofuran (100 mL) and trimethylsilylacetylene (27.0 mL, 12.5 eq.) to the flask in sequence, stir, and at the same time slowly add 1.6 M n-butyllithium (114.6 mL, 183.4 mmol, 12.0 eq.) to the flask. After the addition is complete, continue stirring for 15 minutes under the same conditions to obtain a solution A of trimethylsilylacetylene.
[0048] (2) Under argon protection inside the reaction flask and cooling with an ice / ammonium chloride bath outside, anhydrous zinc chloride (25 g, 183.4 mmol, 12.0 eq.) was slowly added in batches to solution A in the reaction flask. Exothermic reaction was observed during the addition. After the zinc chloride was added, the ice / ammonium chloride bath was removed, and the mixture was allowed to return to room temperature. The reaction flask was then placed in a heater, stirred, and heated to 50°C for 0.5 hours. During the heating process, solid zinc chloride was observed to slowly dissolve, yielding a solution B of trimethylsilylethynyl zinc chloride.
[0049] (3) Under argon protection at room temperature, anhydrous p-xylene (100 mL), hexabromobenzene (8.42 g, 15.28 mmol, 1.0 eq.), and tetra(triphenylphosphine)palladium (883 mg, 0.05 eq.) were added to solution B in the reaction flask. The mixture was heated to 80 °C and stirred for 48 hours under argon protection. After the reaction was completed and the reaction solution was cooled to room temperature, the reaction solution was washed twice with 2 M dilute hydrochloric acid, dried with anhydrous sodium sulfate, filtered through a 5 cm thick silica gel pad, and distilled to obtain a solid mixture C.
[0050] (4) Add the above solid mixture C to a 500 mL single-necked round-bottom flask. Under reflux, slowly add a methanol / dichloromethane mixture (volume ratio v / v = 200:1) until mixture C is just completely dissolved. Cool to room temperature and let stand for 2 hours; white crystals precipitate. Filter and wash the solid with cold methanol (10 mL). Repeat the above recrystallization process three times to obtain 5.31 g of high-purity hexa(trimethylsilylethynyl)benzene, yield: 53.0%.
[0051] Example 3
[0052] (1) Connect the three-necked reaction flask to the condenser and introduce argon gas to keep the inside of the reaction flask in an inert atmosphere. Place the reaction flask in an ice / ammonium chloride bath (about -15°C). Add anhydrous tetrahydrofuran (100 mL) and trimethylsilylacetylene (27.0 mL, 12.5 eq.) to the flask in sequence, stir, and at the same time slowly add 2.5 M n-butyllithium (73.36 mL, 183.4 mmol, 12.0 eq.) to the flask. After the addition is complete, continue stirring for 15 minutes under the same conditions to obtain a solution A of trimethylsilylacetylene.
[0053] (2) Under argon protection inside the reaction flask and cooling with an ice / ammonium chloride bath outside, anhydrous zinc bromide (41.3 g, 183.4 mmol, 12.0 eq.) was slowly added in portions to solution A in the reaction flask. Exothermic reaction was observed during the addition. After the zinc bromide was added, the ice / ammonium chloride bath was removed, and the mixture was allowed to return to room temperature. The reaction flask was then placed in a heater, stirred, and heated to 50°C. Stirring continued for 0.5 hours. During the heating process, solid zinc bromide was observed to slowly dissolve, yielding solution B of trimethylsilylethynyl zinc bromide.
[0054] (3) Under argon protection at room temperature, anhydrous p-xylene (100 mL), hexabromobenzene (8.42 g, 15.28 mmol, 1.0 eq.), and tetra(triphenylphosphine)palladium (883 mg, 0.05 eq.) were added to solution B in the reaction flask. The mixture was heated to 80 °C and stirred for 48 hours under argon protection. After the reaction was completed and the reaction solution was cooled to room temperature, the reaction solution was washed twice with 2 M dilute hydrochloric acid, dried with anhydrous sodium sulfate, filtered through a 5 cm thick silica gel pad, and distilled to obtain a solid mixture C.
[0055] (4) Add the above solid mixture C to a 500 mL single-necked round-bottom flask. Under reflux, slowly add a methanol / dichloromethane mixture (volume ratio v / v = 200:1) until mixture C is just completely dissolved. Cool to room temperature and let stand for 2 hours; white crystals precipitate. Filter by suction, and wash the solid with cold methanol (10 mL). Repeat the above recrystallization process three times to obtain 5.16 g of high-purity hexa(trimethylsilylethynyl)benzene, yield: 51.5%.
[0056] Example 4
[0057] (1) Connect the three-necked reaction flask to the condenser and introduce argon gas to keep the inside of the reaction flask in an inert atmosphere. Place the reaction flask in an ice / ammonium chloride bath (about -15°C). Add anhydrous tetrahydrofuran (50 mL) and trimethylsilylacetylene (14.4 mL, 9.9 eq.) to the flask in sequence, stir, and at the same time slowly add 2.5 M n-butyllithium (36.7 mL, 91.7 mmol, 9.0 eq.) to the flask. Continue stirring for 15 minutes under these conditions to obtain a solution A of trimethylsilylacetylene.
[0058] (2) Under argon protection inside the reaction flask and cooling with an ice / ammonium chloride bath outside, anhydrous zinc chloride (12.5 g, 91.7 mmol, 9.0 eq.) was slowly added in batches to solution A in the reaction flask. Exothermic reaction was observed during the addition. After the zinc chloride was added, the ice / ammonium chloride bath was removed, and the mixture was allowed to return to room temperature. The reaction flask was then placed in a heater, stirred, and heated to 50°C for 0.5 hours. During the heating process, solid zinc chloride was observed to slowly dissolve, yielding a solution B of trimethylsilylethynyl zinc chloride.
[0059] (3) Under argon protection at room temperature, anhydrous p-xylene (100 mL), hexabromobenzene (5.62 g, 10.19 mmol, 1.0 eq.), and tetra(triphenylphosphine)palladium (588 mg, 0.05 eq.) were added to solution B in the reaction flask. The temperature was raised to 80 °C, and the mixture was stirred for 48 hours under argon protection. After the reaction was completed and the reaction solution was cooled to room temperature, the reaction solution was washed twice with 2 M dilute hydrochloric acid, dried with anhydrous sodium sulfate, filtered through a 5 cm thick silica gel pad, and distilled to obtain a solid mixture C.
[0060] (4) Add the above solid mixture C to a 250 mL single-necked round-bottom flask. Under reflux, slowly add a methanol / dichloromethane mixture (volume ratio v / v = 200:1) until mixture C is just completely dissolved. Cool to room temperature and let stand for 2 hours; white crystals precipitate. Filter by suction, and wash the solid with cold methanol (10 mL). Repeat the above recrystallization process three times to obtain 3.50 g of high-purity hexa(trimethylsilylethynyl)benzene, yield: 35%.
[0061] Comparative Example
[0062] (1) Connect the three-necked reaction flask to the condenser and introduce argon gas to keep the inside of the reaction flask in an inert atmosphere. Place the reaction flask in an ice / ammonium chloride bath (about -15°C). Add anhydrous tetrahydrofuran (50 mL) and trimethylsilylacetylene (14.3 mL, 8.25 eq.) to the flask in sequence, stir, and at the same time slowly add 2.5 M n-butyllithium (36.7 mL, 91.7 mmol, 7.5 eq.) to the flask. Continue stirring for 15 minutes under these conditions to obtain a solution A of trimethylsilylacetylene.
[0063] (2) Under argon protection inside the reaction flask and cooling with an ice / ammonium chloride bath outside, anhydrous zinc chloride (12.5 g, 91.7 mmol, 7.5 eq.) was slowly added in batches to solution A in the reaction flask. Exothermic reaction was observed during the addition. After the zinc chloride was added, the ice / ammonium chloride bath was removed, and the mixture was allowed to return to room temperature. The reaction flask was then placed in a heater, stirred, and heated to 50°C for 0.5 hours. During the heating process, solid zinc chloride was observed to slowly dissolve, yielding a trimethylsilylethynyl zinc chloride solution B.
[0064] (3) Under argon protection at room temperature, anhydrous p-xylene (100 mL), hexabromobenzene (6.74 g, 12.23 mmol, 1.0 eq.), and tetra(triphenylphosphine)palladium (706 mg, 0.05 eq.) were added to solution B in the reaction flask. The temperature was raised to 80 °C, and the mixture was stirred for 48 hours under argon protection. After the reaction was completed and the reaction solution was cooled to room temperature, the reaction solution was washed twice with 2 M dilute hydrochloric acid, dried with anhydrous sodium sulfate, filtered through a 5 cm thick silica gel pad, and distilled to obtain a solid mixture C.
[0065] (4) The product content in the solid mixture C is too low, and recrystallization failed according to the previous method.
[0066] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A process for synthesizing hexa(trimethylsilylethynyl)benzene, characterized in that, Includes the following steps: Step 1: Trimethylsilylacetylene reacts with alkyllithium to form lithium trimethylsilylacetylene: Under inert gas protection and at a temperature of -10 to -40°C, trimethylsilylacetylene was dissolved in an organic solvent, and alkyl lithium was slowly added dropwise while stirring. The reaction was carried out under these conditions for at least 5 minutes to obtain a solution A of lithium trimethylsilylacetylene. Step 2: Trimethylsilylacetylenite reacts with anhydrous zinc chloride or anhydrous zinc bromide to produce trimethylsilylacetylenyl zinc chloride or trimethylsilylacetylenyl zinc bromide. Under inert gas protection and at a temperature of -10 to -40°C, anhydrous zinc chloride or anhydrous zinc bromide is slowly added in batches to solution A, the temperature is restored to room temperature, and then raised to 30 to 80°C to obtain solution B of trimethylsilylacetyl zinc chloride or trimethylsilylacetyl zinc bromide. Step 3: Trimethylsilylacetyl zinc chloride or trimethylsilylacetyl zinc bromide reacts with hexabromobenzene to produce hexa(trimethylsilylacetyl)benzene. Under inert gas protection, hexabromobenzene and palladium catalyst were added to solution B, and the temperature was raised to above 50°C for 48 hours. After the reaction was completed, the solution was cooled to room temperature, washed with dilute hydrochloric acid, dried with a desiccant, filtered with a silica gel pad, and distilled to obtain solid mixture C. Step 4: Purification of hexa(trimethylsilylethynyl)benzene: Under reflux, a mixture of alcohol and dichloromethane was slowly added in portions to the solid mixture C until mixture C was just completely dissolved; after cooling to room temperature, white crystals precipitated. The solid was filtered and washed with cold alcohol to give pure hexa(trimethylsilylethynyl)benzene; The molar ratio of the trimethylsilylacetylene, alkyllithium, anhydrous zinc chloride or zinc bromide, and hexabromobenzene is (12.5-18):(12.0-18):(12.0-18):
1.
2. The synthesis process of hexa(trimethylsilylethynyl)benzene according to claim 1, characterized in that, In the first and second steps, the method to control the reaction temperature between -10 and -40°C is to apply an ice-salt bath or a cold solvent bath to the reaction flask. The ice-salt bath is a mixture of crushed ice and inorganic salts, and the cold solvent bath is obtained by cooling the solvent using a cooling device. The inorganic salts used in the ice-salt bath are one, two, or a mixture of sodium chloride, ammonium chloride, potassium chloride, sodium sulfate, sodium carbonate, and sodium bicarbonate. The solvents used in the cold solvent bath are one, two, or a mixture of water, ethanol, ethylene glycol, propanol, and isopropanol.
3. The synthesis process of hexa(trimethylsilylethynyl)benzene according to claim 1, characterized in that, In the first step, the organic solvent is one of tetrahydrofuran, 2-methyltetrahydrofuran, methyl tert-butyl ether, benzene, or toluene.
4. The synthesis process of hexa(trimethylsilylethynyl)benzene according to claim 1, characterized in that, In the first step, the alkyl lithium is one of tert-butyllithium, methyllithium, ethyllithium, propyllithium, n-butyllithium, or isobutyllithium.
5. The synthesis process of hexa(trimethylsilylethynyl)benzene according to claim 1, characterized in that, In the third step, an anhydrous solvent is added to solution B. The anhydrous solvent is one or more of tetrahydrofuran, benzene, toluene, o-xylene, m-xylene, p-xylene, or trimethylbenzene.
6. The synthesis process of hexa(trimethylsilylethynyl)benzene according to claim 1, characterized in that, The inert gas is nitrogen or argon.
7. The synthesis process of hexa(trimethylsilylethynyl)benzene according to claim 1, characterized in that, In the third step, the palladium catalyst is one of tetra(triphenylphosphine)palladium, bis(triphenylphosphine)palladium dichloride, or 1,1'-bis(diphenylphosphine)ferrocenepalladium chloride.
8. The synthesis process of hexa(trimethylsilylethynyl)benzene according to claim 1, characterized in that, The alcohol in the fourth step is one or more of methanol, ethanol, propanol, or isopropanol.
9. The synthesis process of hexa(trimethylsilylethynyl)benzene according to claim 1, characterized in that, In step four, if the resulting hexa(trimethylsilylethynyl)benzene is impure, the recrystallization process in step four is repeated at least once until pure hexa(trimethylsilylethynyl)benzene is obtained.