Synthesis process of p-tert-butylcatechol

Abstract

The invention relates to the technical field of organic synthesis, in particular to a synthesis process of p-tert-butylcatechol. According to the synthesis process, catechol and tert-butyl alcohol react under the protection of nitrogen under the action of a temperature response type catalyst, the product is obtained through cooling separation of the catalyst and distillation rectification, and the catalyst realizes para-position high-selectivity alkylation through long-chain alkyl steric hindrance and can be efficiently recycled and reused through temperature response. The process solves the problems of low selectivity and non-recyclability of the catalyst in the traditional method, and has the advantages of high catechol conversion rate, excellent target product selectivity, high catalyst recovery rate, environmental friendliness and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, in particular to a synthesis process of p-tert-butylcatechol. Background Art

[0002] 4-tert-Butylcatechol (4-TBC), an important organic synthesis intermediate, has key applications in polymer polymerization inhibition, oil and fat antioxidants, and pharmaceutical synthesis. The key challenge in its synthesis lies in achieving highly selective para-alkylation of catechol while balancing catalyst recyclability and environmental friendliness. In current industrial production, the mainstream method still utilizes liquid acid catalysis systems such as sulfuric acid, phosphoric acid, or p-toluenesulfonic acid to prepare it through an electrophilic substitution reaction between catechol and tert-butyl alcohol / isobutylene. However, this type of process has multiple technical bottlenecks: the strong corrosiveness of liquid acid leads to high equipment maintenance costs, and a large amount of alkaline solution is required for neutralization and water washing after the reaction. Each ton of product produces about 3-5 tons of wastewater, which contains phenolic organic matter and sulfates, increasing the end-of-pipe treatment load. More importantly, the liquid acid lacks steric control ability. Both the ortho and para positions of catechol are easily attacked by tert-butyl carbon cations. The formation of by-products such as 3-tert-butylcatechol (3-TBC) and 3,5-di-tert-butylcatechol (3,5-DTBC) is difficult to inhibit. The selectivity of the target product is low and needs to be purified by multi-stage distillation. In addition, the liquid acid and the reaction solution form a homogeneous system that cannot be directly recovered, and the catalyst consumption is large, resulting in waste of resources and increased costs. Patent CN 102643170A discloses a method for synthesizing p-tert-butylcatechol using a mixed acid catalytic system containing an ionic liquid. Using the mixed acid catalyst, the conversion rate of catechol reaches 87.2%, and the selectivity for p-tert-butylcatechol reaches 77.3%. However, the catalyst needs to be recovered by extraction and liquid separation during post-processing. The post-processing process is complicated, the amount of solvent used is large, the selectivity for p-tert-butylcatechol is not high, and a large number of by-products are produced.

[0003] In recent years, solid acid catalysts, such as macroporous cationic resins, Y-type molecular sieves, and montmorillonite, have gradually replaced liquid acids. However, their low acid site density and high mass transfer resistance have resulted in minimal improvements in catechol conversion and limited selectivity, hindering the steric hindrance bottleneck. Patent CN 110041170B discloses a method for synthesizing p-tert-butylcatechol using a solid HMT catalyst. The method achieves a maximum catechol conversion of 55% and a maximum selectivity of 91% for p-tert-butylcatechol. However, the solid catalyst's slow diffusion rate and low catalytic efficiency limit its industrial applicability. Summary of the Invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a synthesis process of p-tert-butylcatechol.

[0005] Based on the above purpose, the present invention provides a synthesis process of tert-butyl catechol, comprising the following steps: S1. Under nitrogen protection, catechol, a temperature-responsive catalyst, and toluene were added to a reactor, heated to 90-100°C, stirred for 20-30 min, and then tert-butanol was added dropwise to the reactor for 2-3 h. After reacting for 3-5 h, a reaction solution was obtained; S2. After the reaction, the reaction solution was cooled to room temperature and allowed to stand for 3-5h, and the precipitated catalyst was separated from the reaction solution by filtration; S3. The separated catalyst was washed three times with toluene and dried under vacuum at 60-70 ° C for 6-8h and then reused; S4. The reaction solution was separated by vacuum distillation to remove toluene, and then distilled to obtain tert-butylcatechol; The preparation of the temperature-responsive catalyst comprises the following steps: (1) Protect from light and under nitrogen, add N-phenylimidazole, dodecane bromide and potassium carbonate to acetonitrile, heat to 75-85°C, stir and react for 8-10 hours, return to room temperature, filter, and remove acetonitrile by vacuum distillation. The product is recrystallized from an ethanol / water mixture and dried to obtain 1-dodecyl-3-phenylimidazole bromide as a white powder. The chemical reaction equation is as follows: Formula (1), the product was characterized by H NMR; (2) 1-Dodecyl-3-phenylimidazolium bromide and p-toluenesulfonic acid were added to acetone and stirred at room temperature for 18-24 hours. After the reaction was completed, the crude product was filtered, washed with deionized water, and dried to obtain a temperature-responsive catalyst in the form of a white powder after recrystallization from acetonitrile. The chemical reaction equation is as follows: The product was characterized by H NMR.

[0006] Preferably, the temperature-responsive catalyst catalyzes the reaction via the following pathway: The p-toluenesulfonate group in the catalyst structure can dissociate into a proton (H + ), as a strong Bronsted acid site, thereby protonating tert-butanol: (CH3)3COH+H + →(CH3)3C-OH2 + →(CH3)3C + +H2O, the generated tert-butyl carbonium ion (CH3)3C + It is an active intermediate in electrophilic substitution reactions; The oxygen atom of the phenolic hydroxyl group in catechol combines with the imidazole ring of the ionic liquid cation through hydrogen bonding, redistributing the electron cloud density of the benzene ring of catechol. The para-position electron cloud density increases significantly, making it more susceptible to attack by the tert-butyl carbocation, generating para-tert-butylcatechol. At the same time, the long-chain alkyl and phenyl groups of the catalyst form a "microreactor" through hydrophobic interaction, fixing the catechol molecule in a specific conformation: The ortho position (2,3 position) of the phenolic hydroxyl group is wrapped by the alkyl chain, which sterically hinders the attack of the tert-butyl carbonium ion; The para position (4) is exposed to the acidic site and preferentially undergoes electrophilic substitution, achieving directed monoalkylation.

[0007] Preferably, the temperature response mechanism of the temperature-responsive catalyst is derived from the reversible change in the solubility of the catalyst's molecular structure (1-dodecyl-3-phenylimidazole p-toluenesulfonate) in the solvent toluene with temperature. The core mechanism lies in the strong hydrophobicity provided by the long-chain dodecyl and phenyl groups, which forms tension with the inherent polarity of the ion pair (imidazole cation / p-toluenesulfonate). During the high-temperature reaction stage, the molecular thermal motion is intense, and the interaction between the hydrophobic groups is weakened. At the same time, the high temperature improves the compatibility of the non-polar solvent toluene with the hydrophobic groups, so that the catalyst is uniformly dissolved to form a homogeneous system. After the reaction is completed, as the system cools down, the molecular thermal motion weakens, the hydrophobic interaction between the long alkyl chains and the potential π-π stacking effect between the phenyl groups are enhanced, driving the catalyst molecules to spontaneously aggregate to form hydrophobic aggregates or crystallites. At low temperatures, the solubility of toluene for hydrophobic aggregates also decreases simultaneously, ultimately leading to the complete precipitation of the catalyst from the reaction solution. Efficient separation can be achieved by simple standing and filtration. The separated catalyst can be washed and dried for recycling.

[0008] Preferably, the molar ratio of catechol to tert-butanol in S1 is 1:1.2-1.5.

[0009] Preferably, the molar ratio of catechol to the temperature-responsive catalyst in S1 is 1:0.01-0.03.

[0010] Preferably, the weight ratio of catechol to toluene in S1 is 1:5-7.

[0011] Preferably, the molar ratio of N-phenylimidazole, dodecane bromide and potassium carbonate in (1) is 1:1-1.2:1-2.

[0012] Preferably, the weight ratio of N-phenylimidazole to acetonitrile in (1) is 1:8-12.

[0013] Preferably, the ethanol / water mixed solution in (1) refers to ethanol and water in a weight ratio of 4:1.

[0014] Preferably, the molar ratio of 1-dodecyl-3-phenylimidazolium bromide to p-toluenesulfonic acid in (2) is 1:1-1.2.

[0015] Preferably, the weight ratio of 1-dodecyl-3-phenylimidazolium bromide to acetone in (2) is 1:8-12.

[0016] Beneficial effects of the present invention: 1. This invention utilizes a temperature-responsive catalyst, leveraging the synergistic effect of the long-chain dodecyl group and the phenyl group within the catalyst's molecular structure to achieve highly selective alkylation. Specifically, the long-chain dodecyl group forms a "steric barrier" through hydrophobic interaction, physically shielding the ortho-reactive sites of catechol and hindering the attack of the tert-butyl carbenium ion. Simultaneously, the phenyl group and the imidazole ring, through π-π stacking and hydrogen bonding, directionally adsorb the catechol molecule and significantly increase its para-position electron cloud density, preferentially allowing electrophilic substitution reactions. This "directional catalysis" mechanism effectively suppresses the formation of byproducts such as 3-tert-butylcatechol and 3,5-di-tert-butylcatechol, improves the selectivity of the target product toward tert-butylcatechol, and reduces the complexity and energy consumption of subsequent distillation and purification.

[0017] 2. The temperature-responsive dissolution-precipitation characteristics of the catalyst of the present invention significantly simplify the separation process from the reaction solution: during the reaction stage, the catalyst is uniformly dissolved in toluene due to molecular thermal motion to form a homogeneous system, ensuring catalytic efficiency; after the reaction is completed and the temperature is lowered to room temperature, the hydrophobic interaction of the long-chain dodecyl group and the π-π stacking of the phenyl group drive the self-assembly and precipitation of the catalyst, which can be separated by simple standing filtration. After the separated catalyst is washed with toluene and vacuum-dried, the structure and active sites remain intact and can be reused multiple times with limited performance degradation. This characteristic avoids the defect that traditional liquid acid catalysts cannot be recycled, significantly reduces catalyst unit consumption and production costs, while reducing the generation of solid waste and improving process economy and sustainability.

[0018] 3. Compared with the traditional liquid acid catalysis process, the solid acid ionic liquid catalyst used in the present invention is not highly corrosive, which can avoid equipment corrosion problems and reduce equipment maintenance costs. At the same time, the reaction process does not require alkali solution neutralization and large-scale water washing, reducing wastewater discharge from the source, which is in line with the concept of green chemistry. The recycling characteristics of the catalyst further reduce the consumption of chemical reagents and reduce the end-point pollution control load. In addition, toluene as a solvent can be recovered and reused by vacuum distillation, and the entire process system forms a low-pollution, low-loss closed loop, which meets the requirements of modern organic synthesis for environmental friendliness.

[0019] 4. The present invention simplifies the synthesis process by optimizing the reaction parameters and catalyst characteristics: the one-step alkylation reaction under nitrogen protection can be completed within 3-5 hours, and the catalyst separation only requires cooling and standing for 3-5 hours, without the need for complex centrifugation or chromatography operations. The homogeneous-heterogeneous transition characteristics of the temperature-responsive catalyst enable the reaction system to maintain high mass transfer efficiency in the catalytic stage and achieve rapid phase separation in the separation stage, shortening the process cycle. In addition, the stability of the catalyst structure ensures the controllability of the reaction conditions, reduces batch quality fluctuations caused by catalyst loss or side reactions in traditional processes, and improves the stability and automation adaptability of the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The H NMR spectrum of 1-dodecyl-3-phenylimidazolium bromide prepared in Example 2; Figure 2 This is the H NMR spectrum of the temperature-responsive catalyst prepared in Example 2; Figure 3 This is the H NMR spectrum of the temperature-responsive catalyst prepared in Comparative Example 1; Figure 4 This is the H NMR spectrum of the temperature-responsive catalyst prepared in Comparative Example 2; Figure 5 This is the H NMR spectrum of the temperature-responsive catalyst prepared in Comparative Example 3; Figure 6 This is the H NMR spectrum of the temperature-responsive catalyst prepared in Comparative Example 4; Figure 7 This is the H NMR spectrum of the temperature-responsive catalyst prepared in Comparative Example 5. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0022] The sources of the reagents and raw materials used in the examples of the present invention are as follows: Catechol was purchased from Jinan Century Tongda Chemical Co., Ltd. with a purity of 99%; tert-butyl alcohol was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 99%; N-phenylimidazole was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 98%; bromododecane was purchased from Hubei Yushenghe Biotechnology Co., Ltd. with a purity of 98%; p-toluenesulfonic acid was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 99%; 1-bromooctadecane was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 97%; 1-bromohexane was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 99%; and 1-methyl-3-phenyliodonium salt was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. with a purity of 97%.

[0023] Example 1: A specific synthesis method of p-tert-butylcatechol, comprising the following steps: (1) Protect from light and under nitrogen, add 10 g of N-phenylimidazole, 17.29 g of bromododecane and 9.59 g of potassium carbonate to 80 g of acetonitrile, heat to 75 ° C, stir and react for 8 hours, return to room temperature, filter, and remove acetonitrile by vacuum distillation. The product is recrystallized from an ethanol / water mixed solution (ethanol and water are mixed in a weight ratio of 4:1) and dried to obtain 1-dodecyl-3-phenylimidazole bromide; (2) 20 g of 1-dodecyl-3-phenylimidazolium bromide and 8.75 g of p-toluenesulfonic acid were added to 160 g of acetone and stirred at room temperature for 18 h. After the reaction was completed, the crude product was filtered, washed with deionized water, and dried to obtain a crude product, which was then recrystallized from acetonitrile and dried to obtain a temperature-responsive catalyst. (3) Under nitrogen protection, 500 g of catechol, 22.01 g of temperature-responsive catalyst and 2.5 kg of toluene were added to the reactor, heated to 90 °C and stirred for 20 min. Then, 403.89 g of tert-butyl alcohol was added dropwise to the reactor for 2 h. After reacting for 3 h, a reaction solution was obtained. (4) After the reaction is completed, the reaction solution is cooled to room temperature and allowed to stand for 3 h. The precipitated catalyst is separated from the reaction solution by filtration; (5) The separated catalyst was washed three times with toluene, dried under vacuum at 60°C for 6 h, and then reused. (6) The separated reaction liquid is subjected to vacuum distillation to remove toluene, and then subjected to rectification to obtain tert-butylcatechol.

[0024] Example 2: A specific synthesis method of p-tert-butylcatechol, comprising the following steps: (1) Protect from light and under nitrogen, add 30 g of N-phenylimidazole, 57.04 g of bromododecane and 43.14 g of potassium carbonate to 300 g of acetonitrile, heat to 80°C, stir and react for 9 hours, return to room temperature, filter, and remove acetonitrile by vacuum distillation. The product is recrystallized from an ethanol / water mixed solution (ethanol and water are mixed in a weight ratio of 4:1) and dried to obtain 1-dodecyl-3-phenylimidazole bromide; (2) 45 g of 1-dodecyl-3-phenylimidazolium bromide and 19.70 g of p-toluenesulfonic acid were added to 450 g of acetone and stirred at room temperature for 21 h. After the reaction was completed, the crude product was filtered, washed with deionized water, and dried to obtain a crude product, which was then recrystallized from acetonitrile and dried to obtain a temperature-responsive catalyst. (3) Under nitrogen protection, 500 g of catechol, 44.02 g of temperature-responsive catalyst and 3 kg of toluene were added to the reactor, the temperature was raised to 95 °C, and the mixture was stirred for 25 min. Then, 454.37 g of tert-butyl alcohol was added dropwise to the reactor for 2.5 h. After the reaction was completed for 4 h, a reaction solution was obtained. (4) After the reaction is completed, the reaction solution is cooled to room temperature and allowed to stand for 4 h. The precipitated catalyst is separated from the reaction solution by filtration; (5) The separated catalyst was washed with toluene three times, dried under vacuum at 65°C for 7 h, and then reused. (6) The separated reaction liquid is subjected to vacuum distillation to remove toluene, and then subjected to rectification to obtain tert-butylcatechol.

[0025] Example 3: A specific synthesis method of p-tert-butylcatechol, comprising the following steps: (1) Protect from light and under nitrogen, add 45g of N-phenylimidazole, 93.35g of bromododecane and 86.28g of potassium carbonate to 540g of acetonitrile, heat to 85°C, stir and react for 10h, return to room temperature, filter, and remove acetonitrile by vacuum distillation. The product is recrystallized from an ethanol / water mixed solution (ethanol and water are mixed in a weight ratio of 4:1) and dried to obtain 1-dodecyl-3-phenylimidazole bromide; (2) 60 g of 1-dodecyl-3-phenylimidazolium bromide and 31.52 g of p-toluenesulfonic acid were added to 720 g of acetone and stirred at room temperature for 24 h. After the reaction was completed, the crude product was filtered, washed with deionized water, and dried to obtain a crude product, which was then recrystallized from acetonitrile and dried to obtain a temperature-responsive catalyst. (3) Under nitrogen protection, 500 g of catechol, 66.03 g of temperature-responsive catalyst and 3.5 kg of toluene were added to the reactor, heated to 100 °C and stirred for 30 min. Then, 504.86 g of tert-butyl alcohol was added dropwise to the reactor for 3 h. After reacting for 5 h, a reaction solution was obtained. (4) After the reaction is completed, the reaction solution is cooled to room temperature and allowed to stand for 5 h. The precipitated catalyst is separated from the reaction solution by filtration; (5) The separated catalyst was washed three times with toluene and dried under vacuum at 70°C for 8 h before being reused. (6) The separated reaction liquid is subjected to vacuum distillation to remove toluene, and then subjected to rectification to obtain tert-butylcatechol.

[0026] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that bromododecane is replaced by 1-bromo-octadecane. The specific preparation process is as follows: A specific synthesis method of 4-tert-butylcatechol comprises the following steps: (1) Protect from light and under nitrogen, add 40 g of N-phenylimidazole, 101.75 g of 1-bromooctadecane and 57.52 g of potassium carbonate to 400 g of acetonitrile, heat to 80 ° C, stir and react for 9 hours, return to room temperature, filter, and remove acetonitrile by vacuum distillation. The product is recrystallized from an ethanol / water mixed solution (ethanol and water are mixed in a weight ratio of 4:1) and dried to obtain 1-octadecyl-3-phenylimidazole bromide; (2) 60 g of 1-octadecyl-3-phenylimidazolium bromide and 23.80 g of p-toluenesulfonic acid were added to 600 g of acetone and stirred at room temperature for 21 h. After the reaction was completed, the crude product was filtered, washed with deionized water, and dried to obtain a crude product, which was then recrystallized from acetonitrile and dried to obtain a temperature-responsive catalyst. (3) Under nitrogen protection, 500 g of catechol, 51.66 g of temperature-responsive catalyst and 3 kg of toluene were added to the reactor, the temperature was raised to 95 °C, and the mixture was stirred for 25 min. Then, 454.37 g of tert-butyl alcohol was added dropwise to the reactor for 2.5 h. After the reaction was completed for 4 h, a reaction solution was obtained. (4) After the reaction is completed, the reaction solution is cooled to room temperature and allowed to stand for 4 h. The precipitated catalyst is separated from the reaction solution by filtration; (5) The separated catalyst was washed with toluene three times, dried under vacuum at 65°C for 7 h, and then reused. (6) The separated reaction liquid is subjected to vacuum distillation to remove toluene, and then subjected to rectification to obtain tert-butylcatechol.

[0027] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that brominated dodecane is replaced by brominated n-hexane. The specific preparation process is as follows: A specific synthesis method of p-tert-butylcatechol comprises the following steps: (1) Protect from light and under nitrogen, add 20 g of N-phenylimidazole, 25.19 g of bromohexane and 28.76 g of potassium carbonate to 200 g of acetonitrile, heat to 80 ° C, stir and react for 9 hours, return to room temperature, filter, and remove acetonitrile by vacuum distillation. The product is recrystallized from an ethanol / water mixed solution (ethanol and water are mixed in a weight ratio of 4:1) and dried to obtain 1-hexyl-3-phenylimidazole bromide; (2) 30 g of 1-hexyl-3-phenylimidazolium bromide and 18.38 g of p-toluenesulfonic acid were added to 300 g of acetone and stirred at room temperature for 21 h. After the reaction was completed, the crude product was filtered, washed with deionized water, and dried to obtain a crude product, which was then recrystallized from acetonitrile and dried to obtain a temperature-responsive catalyst. (3) Under nitrogen protection, 500 g of catechol, 36.38 g of temperature-responsive catalyst and 3 kg of toluene were added to the reactor, the temperature was raised to 95 °C, and the mixture was stirred for 25 min. Then, 454.37 g of tert-butyl alcohol was added dropwise to the reactor for 2.5 h. After the reaction was completed for 4 h, a reaction solution was obtained. (4) After the reaction is completed, the reaction solution is cooled to room temperature and allowed to stand for 4 h. The precipitated catalyst is separated from the reaction solution by filtration; (5) The separated catalyst was washed with toluene three times, dried under vacuum at 65°C for 7 h, and then reused. (6) The separated reaction liquid is subjected to vacuum distillation to remove toluene, and then subjected to rectification to obtain tert-butylcatechol.

[0028] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that step (1) is omitted, and 1-methyl-3-phenylimidazolium iodide is used to react with p-toluenesulfonic acid. The specific preparation process is as follows: A specific synthesis method of p-tert-butylcatechol comprises the following steps: (1) 30 g of 1-methyl-3-phenylimidazolium iodide and 19.86 g of p-toluenesulfonic acid were added to 300 g of acetone and stirred at room temperature for 21 h. After the reaction was completed, the mixture was filtered, washed with deionized water, and dried to obtain a crude product, which was then recrystallized from acetonitrile and dried to obtain a temperature-responsive catalyst. (2) Under nitrogen protection, 500 g of catechol, 30.01 g of temperature-responsive catalyst and 3 kg of toluene were added to the reactor, the temperature was raised to 95 ° C, and stirred for 25 min. Then, 454.37 g of tert-butanol was added dropwise to the reactor for 2.5 h. After reacting for 4 h, a reaction solution was obtained; (3) After the reaction is completed, the reaction solution is cooled to room temperature and allowed to stand for 4 hours. The precipitated catalyst is separated from the reaction solution by filtration; (4) The separated catalyst was washed with toluene three times, dried under vacuum at 65°C for 7 h, and then reused. (5) The separated reaction liquid is subjected to vacuum distillation to remove toluene, and then subjected to rectification to obtain tert-butylcatechol.

[0029] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that N-phenylimidazole is replaced by N-methylimidazole. A specific synthesis method of p-tert-butylcatechol comprises the following steps: (1) Protect from light and under nitrogen, add 30 g of N-methylimidazole, 100.17 g of bromododecane and 75.75 g of potassium carbonate to 300 g of acetonitrile, heat to 80 ° C, stir and react for 9 hours, return to room temperature, filter, and remove acetonitrile by vacuum distillation. The product is recrystallized from an ethanol / water mixed solution (ethanol and water are mixed in a weight ratio of 4:1) and dried to obtain 1-dodecyl-3-methylimidazole bromide; (2) 40 g of 1-dodecyl-3-methylimidazolium bromide and 22.87 g of p-toluenesulfonic acid were added to 400 g of acetone and stirred at room temperature for 21 h. After the reaction was completed, the crude product was filtered, washed with deionized water, and dried to obtain a crude product, which was then recrystallized from acetonitrile and dried to obtain a temperature-responsive catalyst. (3) Under nitrogen protection, 500 g of catechol, 38.38 g of temperature-responsive catalyst and 3 kg of toluene were added to the reactor, the temperature was raised to 95 °C, and the mixture was stirred for 25 min. Then, 454.37 g of tert-butyl alcohol was added dropwise to the reactor for 2.5 h. After the reaction was completed for 4 h, a reaction solution was obtained. (4) After the reaction is completed, the reaction solution is cooled to room temperature and allowed to stand for 4 h. The precipitated catalyst is separated from the reaction solution by filtration; (5) The separated catalyst was washed with toluene three times, dried under vacuum at 65°C for 7 h, and then reused. (6) The separated reaction liquid is subjected to vacuum distillation to remove toluene, and then subjected to rectification to obtain tert-butylcatechol.

[0030] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that p-toluenesulfonic acid is replaced by benzenesulfonic acid. A specific synthesis method of p-tert-butylcatechol comprises the following steps: (1) Protect from light and under nitrogen, add 30 g of N-phenylimidazole, 57.05 g of bromododecane and 43.14 g of potassium carbonate to 300 g of acetonitrile, heat to 80 ° C, stir and react for 9 hours, return to room temperature, filter, and remove acetonitrile by vacuum distillation. The product is recrystallized from an ethanol / water mixed solution (ethanol and water are mixed in a weight ratio of 4:1) and dried to obtain 1-dodecyl-3-phenylimidazole bromide; (2) 40 g of 1-dodecyl-3-phenylimidazolium bromide and 19.26 g of benzenesulfonic acid were added to 400 g of acetone and stirred at room temperature for 21 h. After the reaction was completed, the crude product was filtered, washed with deionized water, and dried to obtain a crude product, which was then recrystallized from acetonitrile and dried to obtain a temperature-responsive catalyst. (3) Under nitrogen protection, 500 g of catechol, 42.74 g of temperature-responsive catalyst and 3 kg of toluene were added to the reactor, the temperature was raised to 95 ° C, and stirred for 25 min. Then, 454.37 g of tert-butanol was dropped into the reactor for 2.5 h. After the reaction was completed for 4 h, a reaction solution was obtained. (4) After the reaction is completed, the reaction solution is cooled to room temperature and allowed to stand for 4 h. The precipitated catalyst is separated from the reaction solution by filtration; (5) The separated catalyst was washed with toluene three times, dried under vacuum at 65°C for 7 h, and then reused. (6) The separated reaction liquid is subjected to vacuum distillation to remove toluene, and then subjected to rectification to obtain tert-butylcatechol.

[0031] Performance testing: 1. Catechol Conversion and Selectivity for p-tert-Butylcatechol: Gas chromatography was used to detect the components in the reaction solutions of Examples 1-3 and Comparative Examples 1-5, and the catechol conversion and selectivity for p-tert-butylcatechol were calculated. The test results are shown in Table 1.

[0032] 2. Yield and purity of tert-butylcatechol: Calculate theoretical yield , and then weigh the p-tert-butylcatechol obtained by distillation of Example 1-3 and Comparative Example 1-5 to calculate the yield; using high performance liquid chromatography, the purity of the p-tert-butylcatechol obtained after recrystallization of Example 1-3 and Comparative Example 1-5 was tested. The experimental results are shown in Table 1.

[0033] 3. Catalyst Recovery Rate and Reuse Efficiency Test: The catalysts used in Examples 1-3 and Comparative Examples 1-5 were weighed after the first recovery, and the recovery rate was calculated as recovered weight / initial weight × 100%. The catalysts were then dried without being replenished to the weight before the first use and put into the next reaction. The reuse efficiency test was performed five times. The reuse efficiency was calculated as follows: the yield of p-tert-butylcatechol after the nth reaction / the yield of p-tert-butylcatechol after the first reaction × 100%. The experimental results are shown in Table 2.

[0034] Table 1 Catechol conversion, selectivity, yield and purity of p-tert-butylcatechol

[0035] Table 2 Catalyst recovery rate and reuse efficiency

[0036] Performance Analysis: As can be seen from the experimental data in Tables 1 and 2, in the process of synthesizing p-tert-butylcatechol using the synthesis process of the present invention in Examples 1-3, the raw material catechol has a high conversion rate, the selectivity of p-tert-butylcatechol in the product is also high, and the generation of by-products is relatively low, thereby resulting in a high yield of the obtained product. At the same time, the specially designed catalyst not only has good catalytic performance, but also can be precipitated by cooling after the reaction is completed, facilitating separation. The separated catalyst only needs to be simply rinsed and dried before it can be reused. The catalytic efficiency retention rate is high and the performance is stable during reuse. Among them, the comprehensive performance of Example 2 is the best.

[0037] From the perspective of the conversion rate of catechol, this may be because the core structure of the temperature-responsive catalyst in Example 2 is 1-dodecyl-3-phenylimidazole p-toluenesulfonate, and the length of its dodecyl chain forms a key advantage in the high-temperature reaction stage. The long-chain hydrophobic group overcomes the interaction through molecular thermal motion and is uniformly dissolved in the toluene solvent to form a homogeneous system, so that the proton of the p-toluenesulfonate group can be efficiently dissociated, fully contacted with tert-butanol and protonated to form tert-butyl carbon cations. The concentration of the active intermediate is high and the mass transfer efficiency is significantly improved, which promotes the reaction of catechol. However, due to the long carbon chain of Comparative Example 1, the intermolecular van der Waals force is significantly enhanced. Although the solubility is excellent at high temperature, the excessively long carbon chain wraps the acidic site of the catalyst, resulting in a decrease in catalytic efficiency, which in turn leads to a decrease in the conversion rate of catechol. 2. The carbon chain is short, and the hydrophobic effect is not enough to support the catalyst to form a stable homogeneous system at high temperature. The mass transfer resistance increases in the heterogeneous state, and the protonation efficiency of tert-butanol is low, resulting in a decrease in the conversion rate. Comparative Example 3 has no long-chain alkyl group, and it is difficult to dissolve in toluene relying solely on the π-π stacking effect of the phenyl group. The reaction system is solid-liquid heterogeneous, and the acid site is not fully exposed, resulting in a decrease in the conversion rate. Comparative Example 4 loses the π-π stacking effect because the imidazole ring substituent is changed from phenyl to methyl, and the catechol molecule cannot be directionally adsorbed on the catalyst surface through hydrogen bonds, and the electron donating ability of the methyl group is weaker than that of the phenyl group, resulting in a decrease in the sulfonate proton supply efficiency, resulting in a decrease in the conversion rate. Comparative Example 5 replaces the acid component with benzenesulfonic acid, which is weaker than p-toluenesulfonic acid. The protonation rate of tert-butanol slows down, and the conversion of catechol is not complete, resulting in a decrease in the conversion rate.

[0038] From the perspective of the selectivity of tert-butylcatechol, this may be due to the dual functional design of the catalyst molecular structure of Example 2. The dodecyl chain forms a "steric barrier" through hydrophobic action, self-assembles around the catechol molecule to form a specific conformation, tightly wraps the ortho position of the phenolic hydroxyl group, and physically hinders the attack of the tert-butyl carbon cation; at the same time, the phenyl and imidazole rings redistribute the electron cloud density of the catechol benzene ring through π-π stacking and hydrogen bonding, and the para electron cloud density is significantly increased, becoming the preferred attack site of the tert-butyl carbon cation, achieving directional monoalkylation, and effectively inhibiting the formation of by-products such as 3-tert-butylcatechol and 3,5-di-tert-butylcatechol; while the octadecyl chain of Comparative Example 1 is too long, resulting in increased chain flexibility, decreased rigidity of the steric barrier, and reduced accuracy of the ortho-shielding, and the tert-butyl carbon cation may The selectivity decreases by attacking the ortho position through the interchain gap. The hexyl chain in comparative example 2 is not long enough to form a complete steric barrier, and the ortho position is highly exposed. The probability of the tert-butyl carbon cation attacking the ortho position increases significantly, and the selectivity decreases. Comparative example 3 has no long-chain alkyl group and completely lacks a steric barrier. The ortho and para positions of catechol are both unprotected, and the tert-butyl carbon cation attacks randomly, resulting in the lowest selectivity. Comparative example 4 cannot directionally adsorb catechol molecules due to the lack of the π-π stacking effect of the phenyl group, the hydrogen bond between the phenolic hydroxyl group and the imidazole ring is weakened, the electron cloud distribution regulation mechanism fails, and the selectivity decreases. The electron-withdrawing effect of the sulfonate group in comparative example 5 is enhanced, resulting in the sulfonate group's ability to dissociate protons slightly lower than that of p-toluenesulfonic acid, the generation rate of the tert-butyl carbon cation slows down, and catechol may undergo side reactions due to the long residence time, resulting in a decrease in selectivity.

[0039] From the recovery rate of the catalyst, this may be due to the temperature response separation characteristics of the catalyst in Example 2 due to the synergistic effect of the dodecyl chain and the phenyl group. In the high-temperature reaction stage, the molecular thermal motion is intense, the interaction between the hydrophobic groups is weakened, and the catalyst is uniformly dissolved in toluene. When the reaction is completed and the temperature is cooled to room temperature, the molecular thermal motion is weakened, the hydrophobic interaction between the dodecyl chains and the π-π stacking effect between the phenyl groups are enhanced, driving the catalyst molecules to self-assemble to form hydrophobic aggregates or crystallites. At the same time, the solubility of toluene for hydrophobic aggregates at low temperatures is significantly reduced, and efficient separation can be achieved by simply standing and filtering. However, the octadecyl chain of Comparative Example 1 has too strong a hydrophobic effect, and the dispersion force between the toluene molecules still dominates at low temperatures. The catalyst is difficult to precipitate from the solution, with a recovery rate of only 5.3%. The hydrophobic effect of the short carbon chain hexyl chain in Examples 2 and 3 is weak, and the catalyst only forms weak aggregations through the π-π stacking effect of the phenyl group. Its precipitation behavior is essentially a self-assembly process based on physical insolubility rather than temperature response. Although the recovery rate is very high, it deviates from the homogeneous reaction-low temperature precipitation mechanism of the process design and is an invalid separation. In Example 4, the intermolecular π-π stacking effect is reduced due to the substitution of the imidazole ring methyl group, the self-assembly ability decreases, and the recovery rate decreases. The ion pair force formed by the acid radical and the imidazole ring in Example 5 is strong, but the synergistic effect between the hydrophobic phenyl group of benzenesulfonic acid and the dodecyl chain is insufficient. The self-assembly efficiency at low temperature is lower than that of p-toluenesulfonic acid, and the recovery rate is insufficient.

[0040] From the perspective of catalyst reuse efficiency, during the recovery process of the catalyst in Example 2, the synergistic effect of the dodecyl chain and the phenyl group ensures the integrity of the molecular structure. The toluene washing only removes physically adsorbed reactants and by-products. The vacuum drying does not destroy the ion pair structure of the imidazole ring and the sulfonate group and the steric hindrance function of the long chain. Therefore, when reused, it can still effectively form a "microreactor" to directionally adsorb catechol and provide acidic sites. The efficiency of five reuses remains at a high level. However, due to the extremely low recovery rate of Comparative Example 1 and the lack of sufficient catalyst for repeated reactions, the performance data is not reflected. The short carbon chain of Comparative Example 2 causes the catalyst to be After the first recovery, the conformational stability decreased, the steric barrier gradually failed, and the ortho-side reactions increased, resulting in a decrease in the reuse efficiency. In comparative example 3, there was no long-chain steric hindrance, and the polyalkylated by-products generated in the reaction were easily adsorbed on the catalyst surface, blocking the sulfonate acid sites. The efficiency dropped significantly for the fifth time. In comparative example 4, due to the lack of phenyl π-π stacking, the binding force between the imidazole ring and catechol was weakened, and the active sites were easily lost with the solution during the washing process, resulting in a decrease in the reuse efficiency. In comparative example 5, the proton supply capacity of the acid group was slightly lower than that of p-toluenesulfonic acid. After each reaction, the proton consumption of the active sites of the catalyst was not fully restored, resulting in a decrease in the reuse efficiency. In summary, the optimization of the dodecyl chain length is the core factor for achieving high recovery and stable reuse of the catalyst, and the balance between solubility, steric effect, and self-assembly ability is the key to the overall superior performance of Example 2 over the comparative example.

[0041] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A process for synthesizing tert-butyl catechol, characterized in that: The following steps are involved: S1. Under nitrogen protection, catechol, a temperature-responsive catalyst, and toluene were added to a reactor, heated to 90-100°C, stirred for 20-30 min, and then tert-butanol was added dropwise to the reactor for 2-3 h. After reacting for 3-5 h, a reaction solution was obtained; S2. After the reaction, the reaction solution was cooled to room temperature and allowed to stand for 3-5h, and the precipitated catalyst was separated from the reaction solution by filtration; S3. The separated catalyst was washed three times with toluene and dried under vacuum at 60-70 ° C for 6-8h and then reused; S4. The reaction solution was separated by vacuum distillation to remove toluene, and then distilled to obtain tert-butylcatechol; The preparation of the temperature-responsive catalyst comprises the following steps: (1) Protect from light and under nitrogen, add N-phenylimidazole, dodecane bromide and potassium carbonate to acetonitrile, heat to 75-85°C, stir and react for 8-10 hours, return to room temperature, filter, and remove acetonitrile by vacuum distillation. The product is recrystallized from an ethanol / water mixture and dried to obtain 1-dodecyl-3-phenylimidazole bromide; (2) 1-Dodecyl-3-phenylimidazolium bromide and p-toluenesulfonic acid are added to acetone and stirred at room temperature for 18-24 hours. After the reaction is completed, the crude product is filtered, washed with deionized water, and dried to obtain a crude product, which is then recrystallized from acetonitrile and dried to obtain a temperature-responsive catalyst.

2. The synthesis process of p-tert-butylcatechol according to claim 1, wherein The molar ratio of catechol to tert-butyl alcohol in S1 is 1:1.2-1.

5.

3. The synthesis process of p-tert-butylcatechol according to claim 1, wherein The molar ratio of catechol to the temperature-responsive catalyst in S1 is 1:0.01-0.

03.

4. The synthesis process of p-tert-butylcatechol according to claim 1, wherein The weight ratio of catechol to toluene in S1 is 1:5-7.

5. The synthesis process of p-tert-butylcatechol according to claim 1, wherein The molar ratio of N-phenylimidazole, dodecane bromide and potassium carbonate in (1) is 1:1-1.2:1-2.

6. The synthesis process of p-tert-butylcatechol according to claim 1, wherein The weight ratio of N-phenylimidazole to acetonitrile in (1) is 1:8-12.

7. The synthesis process of p-tert-butylcatechol according to claim 1, wherein The ethanol / water mixed solution in (1) refers to ethanol and water in a weight ratio of 4:

1.

8. The synthesis process of p-tert-butylcatechol according to claim 1, wherein The molar ratio of 1-dodecyl-3-phenylimidazolium bromide and p-toluenesulfonic acid in (2) is 1:1-1.

2.

9. The synthesis process of p-tert-butylcatechol according to claim 1, wherein The weight ratio of 1-dodecyl-3-phenylimidazolium bromide to acetone in (2) is 1:8-12.

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