Preparation method of 1, 2, 3, 4-tetramethyl-1, 3-cyclopentadiene
By using an acidic ionic liquid catalyst to carry out the dehydration reaction in an organic solvent, the problems of low purity and yield in the preparation of 1,2,3,4-tetramethyl-1,3-cyclopentadiene in the prior art have been solved. This method achieves a highly selective and efficient preparation method, and the catalyst can be recycled multiple times, thus improving economic and environmental benefits.
Patent Information
- Application Number
- CN202511409523.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-29
- Publication Date
- 2025-12-12
AI Technical Summary
Existing technologies for preparing 1,2,3,4-tetramethyl-1,3-cyclopentadiene result in low product purity and yield, poor environmental performance, and the use of sulfuric acid as a catalyst generates a large amount of byproducts and waste acid water, which is cumbersome to handle and uneconomical.
Acidic ionic liquid catalysts are used to carry out dehydration reactions in organic solvents. Specifically, ionic liquids such as 1-butyl-3-methylimidazolium hydrogen sulfate and pyridine dihydrogen phosphate are used as catalysts. The catalysts are recycled multiple times through the dehydration reaction of 2,3,4,5-tetramethyl-2-cyclopentenol combined with hydrogenation reduction reaction.
It improves product selectivity and yield, and the catalyst is easy to separate and reuse, resulting in good economic and environmental benefits.
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Figure CN121107935A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of chemical synthesis, in particular to a preparation method of 1,2,3,4-tetramethyl-1,3-cyclopentadiene. BACKGROUND
[0002] 1,2,3,4-tetramethyl-1,3-cyclopentadiene is an important conjugated diene, which is used as an intermediate in the fields of catalysis, materials and organic synthesis, etc., especially in the synthesis of metallocene catalysts, the compound is often used as a substrate to synthesize various catalysts (such as CGC catalyst). At present, there are mainly two ways to prepare 1,2,3,4-tetramethyl-1,3-cyclopentadiene in industry: one is through petroleum catalytic cracking process; the other is to use homogeneous catalytic system, taking 2,3,4,5-tetramethyl-2-cyclopentenone as raw material, reducing C=O bond by using NaBH4 or LiAlH4, etc. as reducing agent, and then dehydrating under the action of sulfuric acid as catalyst to obtain the product. In the above preparation method, the former has the problems of difficult separation, low efficiency, poor environmental protection and high cost. The strong acidity of sulfuric acid used in the latter process will increase the production of 1,2,3,4-tetramethyl-1,3-cyclopentadiene dimer and multimer, reduce the yield of the product, and the use of sulfuric acid as a catalyst is not convenient, and the amount of sulfuric acid used is large. As a dehydrating agent, it will also produce a large amount of waste acid water after dilution, and the subsequent treatment is more complicated, which is poor in economy and environmental protection. SUMMARY
[0003] The present application provides a preparation method of 1,2,3,4-tetramethyl-1,3-cyclopentadiene to overcome the problems of low product purity and yield and poor environmental protection in the prior art. The method has the advantages of high product selectivity, easy separation of product, high efficiency and recyclable catalyst.
[0004] To achieve the above-mentioned purpose, the present application provides a preparation method of 1,2,3,4-tetramethyl-1,3-cyclopentadiene, which comprises: under the catalysis of an acidic ionic liquid catalyst, dehydrating 2,3,4,5-tetramethyl-2-cyclopentenol in a first organic solvent, wherein the acidic ionic liquid catalyst is at least one of an acidic ionic liquid, a Lewis acidic ionic liquid and a composite acidic ionic liquid. acidic ionic liquid, Lewis acidic ionic liquid and composite acidic ionic liquid.
[0005] Preferably, the acidic ionic liquid catalyst is at least one of The acidic ionic liquid is at least one of 1-butyl-3-methylimidazolium hydrogen sulfate, pyridine dihydrogen phosphate, sulfonic acid functionalized imidazolium hydrogen sulfate, and sulfonic acid pyridine triflate.
[0006] Preferably, the Lewis acidic ionic liquid is chloroaluminate-1-butyl-3-methylimidazolium salt and / or ferric chloride-1-ethyl-3-methylimidazolium salt.
[0007] Preferably, the complex acidic ionic liquid is an ionic liquid of sulfonic acid imidazolium salt combined with ZnCl2.
[0008] Preferably, the mass ratio of the 2,3,4,5-tetramethyl-2-cyclopentenol to the acidic ionic liquid catalyst is 100:0.5-2.
[0009] Preferably, the mass-volume ratio of the 2,3,4,5-tetramethyl-2-cyclopentenol to the first organic solvent is (10-50) g:50 mL.
[0010] Preferably, the first organic solvent is at least one of diethyl ether, ethyl acetate, n-pentane, n-hexane, and tetrahydrofuran.
[0011] Preferably, the conditions of the dehydration reaction include a temperature of 20-30°C and a time of 1-12 h.
[0012] Preferably, the method further comprises separating the acidic ionic liquid catalyst from the product of the dehydration reaction and repeatedly using the separated acidic ionic liquid catalyst in the process of the dehydration reaction.
[0013] Preferably, the method further comprises preparing 2,3,4,5-tetramethyl-2-cyclopentenol by performing a hydrogenation reduction reaction of 2,3,4,5-tetramethyl-2-cyclopentenone and lithium aluminum hydride in a second organic solvent under an inert atmosphere.
[0014] Preferably, the molar ratio of the 2,3,4,5-tetramethyl-2-cyclopentenone to the lithium aluminum hydride is 2-4:1.
[0015] Preferably, the molar-volume ratio of the 2,3,4,5-tetramethyl-2-cyclopentenone to the second organic solvent is (0.5-2) mol:200 mL.
[0016] Preferably, the second organic solvent is at least one of diethyl ether, ethyl acetate, n-pentane, n-hexane, and tetrahydrofuran.
[0017] Preferably, the conditions of the hydrogenation reduction reaction include a temperature of 0-30°C and a time of 1-12 h.
[0018] The preparation method of 1,2,3,4-tetramethyl-1,3-cyclopentadiene according to the present application can realize the recycling of the acidic ionic liquid catalyst, and has the advantages of high product selectivity, easy separation of the product, high yield, good economic and environmental benefits, etc. DETAILED DESCRIPTION
[0019] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.
[0020] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges or values should be construed to be roughly around the ranges or values. The endpoints between each range of values, the endpoints and individual values between ranges of values, and the individual values themselves can be combined with one another to create one or more new ranges or values, which are to be considered within the scope of the present disclosure.
[0021] The preparation method of 1,2,3,4-tetramethyl-1,3-cyclopentadiene according to the present application includes: under the catalysis of an acidic ionic liquid catalyst, 2,3,4,5-tetramethyl-2-cyclopentenol is subjected to a dehydration reaction in a first organic solvent, and the acidic ionic liquid catalyst is at least one of an acidic ionic liquid, a Lewis acidic ionic liquid, and a composite acidic ionic liquid.
[0022] In the method according to the present application, preferably, the The acidic ionic liquid is an anion-type ionic liquid and / or a cation-type ionic liquid. The anion part of the anion-type ionic liquid can be hydrogen sulfate (HSO4 - ) and / or p-toluene sulfonate (TsO -). In specific embodiments, the anionic ionic liquid is 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM][HS04]) and / or pyridinium dihydrogen phosphate ([Py][H2P04]). The cationic part of the cationic ionic liquid can be at least one of sulfonic acid functionalized imidazoles, pyridines and quaternary ammonium. In specific embodiments, the cationic ionic liquid is sulfonic acid functionalized imidazolium hydrogen sulfate ([BSO3HMIM][HS04]) and / or sulfonic acid pyridine triflate ([NHSO3H-Py][OTf]). The Lewis acidic ionic liquid is a chloroaluminate type catalyst and / or a metal halide type catalyst. In specific embodiments, the chloroaluminate type catalyst is 1-butyl-3-methylimidazolium chloroaluminate ([BMIM]Cl-AlCl3) and / or 1-ethyl-3-methylimidazolium chloride-iron chloride ([EMIM]Cl-FeCl3). The composite acidic ionic liquid is an ionic liquid of imidazolium sulfonate combined with ZnCl2 ([SO3H-BMIM][ZnCl3]).
[0023] In the method of the present application, the mass ratio of the 2,3,4,5-tetramethyl-2-cyclopentenol and the acidic ionic liquid catalyst can be 100:0.5-2, specifically, for example, 100:0.5, 100:0.6, 100:0.7, 100:0.8, 100:0.9, 100:1, 100:1.1, 100:1.2, 100:1.3, 100:1.4, 100:1.5, 100:1.6, 100:1.7, 100:1.8, 100:1.9 or 100:2.
[0024] In the method of the present application, the mass-volume ratio of the 2,3,4,5-tetramethyl-2-cyclopentenol and the first organic solvent can be (10-50) g:50 mL, specifically, for example, 10 g:50 ml, 15 g:50 ml, 20 g:50 ml, 25 g:50 ml, 30 g:50 ml, 35 g:50 ml, 40 g:50 ml, 45 g:50 ml or 50 g:50 ml.
[0025] In the method of the present application, the first organic solvent is selected from at least one of diethyl ether, ethyl acetate, n-pentane, n-hexane and tetrahydrofuran. In the most preferred embodiment, the first organic solvent is selected from diethyl ether.
[0026] In the method of the present application, the conditions of the dehydration reaction can include a temperature of 20-30°C and a time of 1-12 h. In a preferred case, the conditions of the dehydration reaction include a temperature of 22-28°C and a time of 5-12 h. The dehydration reaction can be carried out under stirring at a rate of 300-800 r / min. The completeness of the reaction can be determined by gas chromatography (GC) for 2,3,4,5-tetramethyl-2-cyclopentenol.
[0027] In the method of the present application, the method further comprises separating the acidic ionic liquid catalyst from the product of the dehydration reaction and reusing the separated acidic ionic liquid catalyst in the process of the dehydration reaction. Specifically, the method further comprises separating the product of the dehydration reaction into an upper liquid phase and a lower liquid phase, subjecting the upper liquid phase to rotary evaporation and vacuum distillation to obtain 1,2,3,4-tetramethyl-1,3-cyclopentadiene, and subjecting the lower liquid phase to washing and rotary evaporation to obtain the acidic ionic liquid, which can be reused in the process of the dehydration reaction. The conditions of the rotary evaporation can include a temperature of 30-50°C, a time of 0.5-1 h, and a vacuum degree of 10-100 mbar. The rotary evaporation can be carried out in various conventional rotary evaporators in the art. In a preferred case, the pressure of the vacuum distillation is ≤200 Pa. The distillation range of the vacuum distillation can be 26-35°C. The reagent used in the washing process can be n-hexane. The washing process can be carried out once or multiple times, preferably multiple times. In the present application, the pressure refers to absolute pressure.
[0028] The method of the present application further comprises preparing 2,3,4,5-tetramethyl-2-cyclopentenol according to the following procedure: subjecting 2,3,4,5-tetramethyl-2-cyclopentenone and lithium aluminum hydride to a hydrogenation reduction reaction in a second organic solvent under an inert atmosphere.
[0029] In the method of the present application, the molar ratio of the 2,3,4,5-tetramethyl-2-cyclopentenone to the lithium aluminum hydride can be 2-4:1, and specifically, for example, can be 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, or 4:1.
[0030] In the method of the present application, the molar volume ratio of the 2,3,4,5-tetramethyl-2-cyclopentenone to the second organic solvent can be (0.5-2) mol:200 mL, and preferably (0.8-1.5) g:200 mL.
[0031] In the method of the present application, the second organic solvent is selected from at least one of diethyl ether, ethyl acetate, n-pentane, n-hexane and tetrahydrofuran. In the most preferred embodiment, the second organic solvent is selected from diethyl ether.
[0032] In the method of the present application, the conditions of the hydrogenation reduction reaction can include a temperature of 0-30°C and a time of 1-12h. The specific operation process of the hydrogenation reduction reaction can include mixing the 2,3,4,5-tetramethyl-2-cyclopentenone and the second organic solvent, then adding the lithium aluminum hydride dropwise into the resulting mixed solution at 0-5°C and heating to 20-30°C for reaction, then adding deionized water dropwise into the product after reaction, then adding sulfuric acid solution dropwise, separating the upper liquid and the condensed solid, then adding deionized water and sulfuric acid solution alternately into the condensed solid, then adding sodium bisulfate to adjust the pH value to 6-8, then adding diethyl ether for extraction, then combining the resulting extract and the upper liquid, then adding anhydrous sodium sulfate and filtering, and then rotary evaporating the remaining liquid. The dropping speed of the lithium aluminum hydride can be 0.1-0.5g / min. The dropwise adding mode can be implemented by a constant pressure dropping funnel. The 2,3,4,5-tetramethyl-2-cyclopentenone can be detected by gas chromatography (GC) to detect whether the reaction is complete. The rotary evaporation process can be implemented in various conventional rotary evaporators in the art.
[0033] In the method of the present application, the inert atmosphere can be provided by nitrogen and / or argon. In the more preferred embodiment, the inert atmosphere is provided by argon.
[0034] The following examples further illustrate the method for preparing 1,2,3,4-tetramethyl-1,3-cyclopentadiene according to the present application. The examples are implemented on the premise of the technical solutions of the present application, and detailed embodiments and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.
[0035] In the following examples, the experimental methods are the conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are commercially available unless otherwise specified.
[0036] In the following examples and comparative examples, the related parameters of 1,2,3,4-tetramethyl-1,3-cyclopentadiene are detected and calculated according to the following methods:
[0037] Product yield = mass of distilled product / theoretical product mass.
[0038] Product purity: The product purity was determined by nuclear magnetic hydrogen spectrum characterization using an internal standard method; the specific operation steps were as follows: 1,2,3,4-tetramethyl-1,3-cyclopentadiene was uniformly mixed with theoretical equimolar amount of dibromomethane (internal standard), then deuterated reagent CDCl3 was added for dissolution, and then nuclear magnetic hydrogen spectrum characterization was directly performed, and the ratio of the peak area of methylene (-CH2-) in the structure of 1,2,3,4-tetramethyl-1,3-cyclopentadiene to the peak area of the internal standard dibromomethane was the product purity.
[0039] Example 1
[0040] Preparation of 2,3,4,5-tetramethyl-2-cyclopentenol:
[0041] A 1L jacketed reaction kettle was filled with argon, then 1 mol of 2,3,4,5-tetramethyl-2-cyclopentenone (purchased from Shanghai Maikelin Biochemical Technology Co., Ltd., CAS No. 54458-61-6, same below) and 200 mL of ether were added. The jacketed reaction kettle was placed in an ice bath environment, the temperature was controlled to be 0°C, and 400 mmol of lithium aluminum hydride was added dropwise through a constant pressure dropping funnel, and the dropping speed was 0.3 g / min. After the dropping was completed, the jacketed reaction kettle was removed from the ice bath environment and heated to 25°C for reaction, and sampling was performed every 0.5 h, and whether the 2,3,4,5-tetramethyl-2-cyclopentenone raw material had been completely reacted was detected by gas chromatography, and after the reaction was completed, the time was 12 h. In the product after the reaction, 15 mL of deionized water was added dropwise, then 100 mL of a 33 wt% sulfuric acid solution was added dropwise to coagulate the solid, the upper liquid was poured into a 500 mL beaker, 100 mL of deionized water and 100 mL of a 33 wt% sulfuric acid solution were added into the jacketed reaction kettle containing the remaining solid in batches (20 mL / time) to dissolve the solid, then sodium bicarbonate was added to the obtained solution to make the pH value of the mixed solution be 7, then 150 mL of ether was added for extraction, and the extract was added into the 500 mL beaker containing the upper liquid, then 30 g of anhydrous sodium sulfate was added and filtered after standing, and the obtained filtrate was concentrated by rotary evaporation, and the rotary evaporation conditions included that the temperature was 35°C, the time was 1 h, and the vacuum degree was 50 mbar, to obtain 2,3,4,5-tetramethyl-2-cyclopentenol.
[0042] Preparation of 1,2,3,4-tetramethyl-1,3-cyclopentadiene:
[0043] 30 g of 2,3,4,5-tetramethyl-2-cyclopentenol was placed in a single-necked flask, then 50 mL of ether solvent and 0.5 g of p-toluenesulfonate (TsO -) Ionic liquid catalyst, the reaction was carried out at 25 °C, the stirring rate was 300 r / min. The sample was taken every 0.5 h for gas chromatography detection, and the 2,3,4,5-tetramethyl-2-cyclopentenol raw material was detected by gas chromatography to determine whether it had reacted completely. After the reaction was completed, the time was 12 h. The product after the reaction was separated to obtain the upper liquid phase and the lower liquid phase. The lower liquid phase was washed with 10 mL of diethyl ether twice, and then rotary evaporation was carried out, the rotary evaporation conditions included: the temperature was 40 °C, the time was 0.5 h, the vacuum degree was 50 mbar, and the p-toluenesulfonate (TsO - ) ionic liquid was recovered. The upper liquid phase was rotary evaporated, the rotary evaporation conditions included: the temperature was 30 °C, the time was 1 h, the vacuum degree was 80 mbar, and then the concentrated liquid was subjected to vacuum distillation under the condition of 200 Pa, the fraction of 26-35 °C was collected, and 1,2,3,4-tetramethyl-1,3-cyclopentadiene A1 was obtained. The recovered p-toluenesulfonate (TsO - ) ionic liquid was used as a catalyst and the above preparation process of 1,2,3,4-tetramethyl-1,3-cyclopentadiene was repeated to obtain 1,2,3,4-tetramethyl-1,3-cyclopentadiene B1.
[0044] After testing and calculation, the purity of 1,2,3,4-tetramethyl-1,3-cyclopentadiene A1 was 92.0%, and the yield was 75%. The purity of 1,2,3,4-tetramethyl-1,3-cyclopentadiene B1 was 91.8%, and the yield was 73%.
[0045]
[0046] Example 2
[0047] Preparation of 2,3,4,5-tetramethyl-2-cyclopentenol:
[0048] A 1 L jacketed reactor was charged with nitrogen, then 1.5 mol of 2,3,4,5-tetramethyl-2-cyclopentenone and 200 mL of ethyl acetate. The jacketed reactor was placed in an ice bath environment, and the temperature was controlled at 0°C. 500 mmol of lithium aluminum hydride was added dropwise through a constant pressure dropping funnel at a rate of 0.4 g / min. After the addition was completed, the jacketed reactor was removed from the ice bath environment and heated to 28°C for reaction. Sampling was performed every 0.5 h to determine whether the 2,3,4,5-tetramethyl-2-cyclopentenone raw material had reacted completely by gas chromatography. When the reaction was complete, the time was 12 h. In the product after the reaction, 15 mL of deionized water was added dropwise, then 100 mL of a 33 wt% sulfuric acid solution was added dropwise to coagulate the solids. The upper liquid was poured into a 500 mL beaker, and 100 mL of deionized water and 100 mL of a 33 wt% sulfuric acid solution were added in batches (20 mL each) to the jacketed reactor containing the remaining solids to dissolve the solids. Sodium bicarbonate was added to the resulting solution to adjust the pH of the mixed solution to 7.5, then 150 mL of ethyl acetate was added for extraction, and the extract was added to the 500 mL beaker containing the upper liquid. Then 30 g of anhydrous sodium sulfate was added and allowed to stand and filter. The resulting filtrate was concentrated by rotary evaporation under the following conditions: temperature 50°C, time 0.5 h, vacuum degree 80 mbar, to obtain 2,3,4,5-tetramethyl-2-cyclopentenol.
[0049] 1,2,3,4-tetramethyl-1,3-cyclopentadiene was prepared:
[0050] 30 g of 2,3,4,5-tetramethyl-2-cyclopentenol was placed in a single-necked flask, then 50 mL of ethyl acetate solvent and 0.3 g of a p-toluenesulfonate (TsO - ) ionic liquid catalyst represented by formula (1) were added. The reaction was carried out at 23°C with stirring at a rate of 300 r / min. Sampling was performed every 0.5 h to determine whether the 2,3,4,5-tetramethyl-2-cyclopentenol raw material had reacted completely by gas chromatography. When the reaction was complete, the time was 10 h. The product after the reaction was separated into upper and lower liquid phases. The lower liquid phase was washed twice with 10 mL of ethyl acetate, then rotary evaporation was performed under the following conditions: temperature 35°C, time 0.5 h, vacuum degree 20 mbar, to recover the p-toluenesulfonate (TsO -) ion liquid and can be reused as a catalyst. The upper liquid phase is subjected to rotary evaporation under the following conditions: temperature 45°C, time 1 h, vacuum degree 30 mbar, and then the concentrated liquid is subjected to vacuum distillation under a pressure of 200 Pa, and the fraction of 26-35°C is collected to obtain 1,2,3,4-tetramethyl-1,3-cyclopenta- diene A2. The recovered p-toluenesulfonate (TsO - ) ion liquid and the above-mentioned 1,2,3,4-tetramethyl-1,3-cyclopenta- diene preparation process is repeated to obtain 1,2,3,4-tetramethyl-1,3-cyclopenta- diene B2.
[0051] After testing and calculation, the purity of 1,2,3,4-tetramethyl-1,3-cyclopenta- diene A2 is 90.5% and the yield is 73%. The purity of 1,2,3,4-tetramethyl-1,3-cyclopenta- diene B2 is 88.7% and the yield is 71%.
[0052] Example 3
[0053] Preparation of 2,3,4,5-tetramethyl-2-cyclopentenol:
[0054] A 1 L jacketed reactor is filled with argon, and then 2 mol of 2,3,4,5-tetramethyl- 2-cyclopentenone and 200 mL of tetrahydrofuran are added. The jacketed reactor is placed in an ice bath environment, and the temperature is controlled to be kept at 0°C, and 800 mmol of lithium aluminum hydride is added dropwise through a constant pressure dropping funnel at a speed of 0.3 g / min. After the dropwise addition is completed, the jacketed reactor is removed from the ice bath environment and heated to 25°C for reaction, and sampling is performed every 0.5 h to detect whether the 2,3,4,5-tetramethyl-2-cyclopentenone raw material has been completely reacted by gas chromatography. After the reaction is completed, the time is 8 h. In the product after the reaction, 15 mL of deionized water is added dropwise, and then 100 mL of a 33 wt% sulfuric acid solution is added dropwise to coagulate the solids, and the upper liquid is poured into a 500 mL beaker, and 100 mL of deionized water and 100 mL of a 33 wt% sulfuric acid solution are added in batches (20 mL each) to dissolve the solids in the jacketed reactor, and then sodium bicarbonate is added to the obtained solution to make the pH value of the mixed solution 7, and then 150 mL of ether is added for extraction, and the extract is added to the 500 mL beaker containing the upper liquid, and then 30 g of anhydrous sodium sulfate is added and filtered, and the obtained filtrate is subjected to rotary evaporation concentration under the following conditions: temperature 40°C, time 1 h, vacuum degree 50 mbar, to obtain 2,3,4,5-tetramethyl-2-cyclopentenol.
[0055] Preparation of 1,2,3,4-tetramethyl-1,3-cyclopenta-diene:
[0056] 30 g of 2,3,4,5-tetramethyl-2-cyclopentenol was placed in a single-necked flask, followed by the addition of 50 mL of ethyl ether solvent and 0.5 g of p-toluenesulfonate (TsO - ) ionic liquid catalyst. The reaction was carried out at 25°C with a stirring rate of 300 r / min. Samples were taken every 0.5 h for gas chromatography detection to determine whether the 2,3,4,5-tetramethyl-2-cyclopentenol raw material had reacted completely. After the reaction was complete, the time was 12 h. The product after the reaction was separated into upper and lower liquid phases. The lower liquid phase was washed twice with 10 mL of ethyl ether, followed by rotary evaporation under the following conditions: temperature of 45°C, time of 0.5 h, vacuum degree of 40 mbar, and recovery of p-toluenesulfonate (TsO - ) ionic liquid, which can be reused as a catalyst. The upper liquid phase was rotary evaporated under the following conditions: temperature of 40°C, time of 1 h, vacuum degree of 50 mbar, and then the concentrated liquid was subjected to vacuum distillation at a pressure of 200 Pa to collect a fraction of 26-35°C to obtain 1,2,3,4-tetramethyl-1,3-cyclopentadiene A3. The recovered p-toluenesulfonate (TsO - ) ionic liquid was reused as a catalyst to prepare 1,2,3,4-tetramethyl-1,3-cyclopentadiene B3.
[0057] After testing and calculation, the purity of 1,2,3,4-tetramethyl-1,3-cyclopentadiene A3 was 86.4% and the yield was 70%. The purity of 1,2,3,4-tetramethyl-1,3-cyclopentadiene B3 was 85.1% and the yield was 67%.
[0058] Example 4
[0059] 1,2,3,4-tetramethyl-1,3-cyclopentadiene was prepared according to the method of Example 1, except that the p-toluenesulfonate (TsO - ) ionic liquid catalyst shown in formula (1) was replaced by a sulfonic acid functionalized imidazole ionic liquid catalyst shown in formula 2 to obtain 1,2,3,4-tetramethyl-1,3-cyclopentadiene A4 and 1,2,3,4-tetramethyl-1,3-cyclopentadiene B4.
[0060] After testing and calculation, the purity of 1,2,3,4-tetramethyl-1,3-cyclopentadiene A4 was 89.2% and the yield was 72%. The purity of 1,2,3,4-tetramethyl-1,3-cyclopentadiene B4 was 87.4% and the yield was 68%.
[0061]
[0062] Example 5
[0063] 1,2,3,4-tetramethyl-1,3-cyclopentadiene was prepared according to the method of Example 1, except that the p-toluenesulfonate (TsO - ) ionic liquid catalyst shown in formula (1) was replaced by the chloroaluminate ionic liquid catalyst shown in formula (3), to obtain 1,2,3,4-tetramethyl-1,3-cyclopentadiene A5 and 1,2,3,4-tetramethyl-1,3-cyclopentadiene B5.
[0064] After testing and calculation, the purity of 1,2,3,4-tetramethyl-1,3-cyclopentadiene A5 was 85.8%, and the yield was 75%. The purity of 1,2,3,4-tetramethyl-1,3-cyclopentadiene B5 was 83.7%, and the yield was 71%.
[0065]
[0066] Example 6
[0067] 1,2,3,4-tetramethyl-1,3-cyclopentadiene was prepared according to the method of Example 1, except that the p-toluenesulfonate (TsO - ) ionic liquid catalyst shown in formula (1) was replaced by the ionic liquid catalyst of the combination of imidazole sulfonic acid salt and ZnCl2 shown in formula 4, to obtain 1,2,3,4-tetramethyl-1,3-cyclopentadiene A6 and 1,2,3,4-tetramethyl-1,3-cyclopentadiene B6.
[0068] After testing and calculation, the purity of 1,2,3,4-tetramethyl-1,3-cyclopentadiene A6 was 90.4%, and the yield was 72%. The purity of 1,2,3,4-tetramethyl-1,3-cyclopentadiene B6 was 89.5%, and the yield was 69%.
[0069]
[0070] Comparative Example 1
[0071] 1,2,3,4-tetramethyl-1,3-cyclopentadiene was prepared according to the method of Example 1, except that the p-toluenesulfonate (TsO - ) ionic liquid catalyst shown in formula (1) was replaced by 30 mL of a sulfuric acid solution with a concentration of 33% by weight, to obtain 1,2,3,4-tetramethyl-1,3-cyclopentadiene D1.
[0072] After testing and calculation, the purity of 1,2,3,4-tetramethyl-1,3-cyclopentadiene D1 was 83.4%, and the yield was 50%.
[0073] The yield and purity of the products of the above examples and comparative examples are shown in Table 1 below.
[0074] Table 1
[0075]
[0076] As can be seen from the results of Table 1, 1,2,3,4-tetramethyl-1,3-cyclopentadiene prepared according to the method of the present application has significantly higher yield and purity.
[0077] The above describes the preferred embodiments of the present application in detail, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.
Claims
1. A method for preparing 1,2,3,4-tetramethyl-1,3-cyclopentadiene, characterized in that, The method includes: dehydrating 2,3,4,5-tetramethyl-2-cyclopentenol in a first organic solvent under the catalysis of an acidic ionic liquid catalyst, wherein the acidic ionic liquid catalyst is... At least one of acidic ionic liquids, Lewis acidic ionic liquids, and composite acidic ionic liquids.
2. The method according to claim 1, characterized in that, The The acidic ionic liquid is at least one of 1-butyl-3-methylimidazolium hydrogen sulfate, pyridine dihydrogen phosphate, sulfonic acid-functionalized imidazolium hydrogen sulfate, and sulfonic acid pyridine trifluoromethanesulfonate; and / or, The Lewis acidic ionic liquid is 1-butyl-3-methylimidazolium chloroaluminate and / or 1-ethyl-3-methylimidazolium ferric chloride; and / or, The composite acidic ionic liquid is an ionic liquid composed of sulfonate imidazole salt and ZnCl2.
3. The method according to claim 1 or 2, characterized in that, The mass ratio of the 2,3,4,5-tetramethyl-2-cyclopentenol to the acidic ionic liquid catalyst is 100:0.5-2.
4. The method according to any one of claims 1-3, characterized in that, The mass-to-volume ratio of 2,3,4,5-tetramethyl-2-cyclopentenol to the first organic solvent is (10-50) g: 50 mL.
5. The method according to claim 1 or 4, characterized in that, The first organic solvent is selected from at least one of diethyl ether, ethyl acetate, n-pentane, n-hexane, and tetrahydrofuran.
6. The method according to any one of claims 1-5, characterized in that, The conditions for the dehydration reaction include: a temperature of 20-30℃ and a time of 1-12h.
7. The method according to any one of claims 1-6, characterized in that, The method further includes: separating the acidic ionic liquid catalyst from the product of the dehydration reaction, and reusing the separated acidic ionic liquid catalyst in the dehydration reaction process.
8. The method according to claim 1 or 7, characterized in that, The method further includes preparing 2,3,4,5-tetramethyl-2-cyclopentenol according to the following steps: Under an inert atmosphere, 2,3,4,5-tetramethyl-2-cyclopentenone and lithium aluminum hydride were subjected to a hydrogenation reduction reaction in a second organic solvent.
9. The method according to claim 8, characterized in that, The molar ratio of the 2,3,4,5-tetramethyl-2-cyclopentenone to the lithium aluminum hydride is 2-4:1; and / or, The molar volume ratio of 2,3,4,5-tetramethyl-2-cyclopentenone to the second organic solvent is (0.5-2) mol: 200 mL; and / or, The second organic solvent is selected from at least one of diethyl ether, ethyl acetate, n-pentane, n-hexane, and tetrahydrofuran.
10. The method according to claim 8 or 9, characterized in that, The conditions for the hydrogenation reduction reaction include: a temperature of 0-30℃ and a time of 1-12h.