A method for preparing 2,3-benzofuran in one pot by using furoic acid catalyzed by halogen acid

Abstract

The invention discloses a method for preparing 2,3-benzofuran by a one-pot method using furoic acid catalyzed by a halogen acid. The steps of the method are as follows: 1) adding a solvent and a halogen acid to a high-temperature and high-pressure reactor with stirring and lined with polytetrafluoroethylene, starting stirring, and then adding furoic acid; 2) heating to a reaction temperature of 100 to 150° C., and reacting in a one-pot method for 2 to 24 hours; 3) cooling to room temperature after the reaction to obtain a reaction product, and then separating to obtain a 2,3-benzofuran product. The present invention adopts a one-pot method to prepare 2,3-benzofuran from furoic acid, has a short process route, mild conditions, and a 2,3-benzofuran yield of up to 75.0%, and has a very broad prospect for industrial application.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis reactions in the chemical industry, and specifically relates to a method for preparing 2,3-benzofuran in a one-pot process by catalyzing furoic acid with hydrohalic acid. Background Art

[0002] Biomass resources are inexhaustible and can be used endlessly. The preparation of chemicals and fuels from biomass is an inevitable trend in the future.

[0003] Furoic acid (2-Furoic acid, CAS No.: 88-14-2), also known as 2-furoic acid or 2-furancarboxylic acid, has a molecular formula of C5H4O3. It is mainly obtained by the oxidation of furfural, which is formed by the dehydration and cyclization of pentose under the action of acid. my country is the world's major producer of furfural, with an oversupply, and it is urgent to develop new ways to utilize it at a high value. In addition, furoic acid is produced in many biomass catalytic chemical or thermochemical conversion processes.

[0004] 2,3-Benzofuran (CAS No.: 271-89-6), molecular formula: C8H6O, structural formula as shown below, is an aromatic heterocyclic organic compound. At the same time, benzofuran compounds are widely present in natural products with pharmacological activity.

[0005]

[0006] 2,3-Benzofuran is an important pharmaceutical intermediate (such as used in the manufacture of salicylic acid), pesticide intermediate, fine chemical intermediate, fuel intermediate, and also a monomer for resin synthesis, with very broad application prospects.

[0007] There are four main preparation methods for 2,3-benzofuran, using phenol, salicylaldehyde, 2-ethylphenol and furan as starting materials. The first three methods (phenol, salicylaldehyde and 2-ethylphenol) are petroleum-based routes, with non-green raw materials and serious process pollution; only the method starting from furan is a biomass-based route, with green raw material sources and broad development prospects. The following is a review of the domestic and international progress of this route.

[0008] Kang et al. (S. Kang, J. Fu, Z. Xu, Y. Jiang, Y. Pang, R. Miao, D. Yu. Aluminum (III) chloride-catalyzed transformation of biomass derived furans to Benzo [b] furans, Sustain. Chem. Pharm., 21 (2021), 100445) studied the conversion of furan to 2,3-benzofuran in acetic acid-water medium catalyzed by aluminum chloride. After process optimization, the highest yield of 2,3-benzofuran was only 31%; Hu et al. (X. Hu, S. Jiang, S. Kadarwati, D. Dong, C. Li. Effects of water and alcohols on the polymerization of furan during its acid-catalyzed conversion into benzofuran, RSC Adv., 6 (2016): 40489–40501) studied the effects of different solvents on the polymerization of Amberlyst 70 (a The influence of furan condensation on the preparation of 2,3-benzofuran under the catalysis of furan (acid) was studied. The solvents investigated included water, methanol, ethanol, 1-propanol, 2-propanol, DMSO, etc., which showed that the solvent had a huge impact, but the maximum yield of 2,3-benzofuran was less than 30%; Yu et al. (P Yu, G Sun, L Xiong, B Zheng, T Li, J Jiang, Y Wang, W Yang. Biomass to drugs: Green production of salicylic acid from 2-furoic acid in two steps, Molecular catalysis, 521 (2022): 112187) studied the two-step method for the preparation of salicylic acid from furoic acid. The first step investigated the conversion of furoic acid to 2,3-benzofuran under the catalysis of molecular sieves in a toluene-water two-phase system. After process optimization, the maximum yield of 2,3-benzofuran was only 38.2%, and the reaction temperature was as high as 280°C.

[0009] From the above, it can be seen that the yields reported in the literature for preparing 2,3-benzofuran from furoic acid and furan are all lower than 40%, which seriously restricts the industrialization of this route. Summary of the invention

[0010] The reaction pathway for preparing 2,3-benzofuran from furoic acid is shown in the following formula: furoic acid first undergoes decarboxylation to generate furan, which then undergoes Diels-Alder condensation to generate intermediate A. The ether bond of intermediate A is hydrolyzed and cleaved to generate intermediate B, which then removes two molecules of water from the molecule to generate 2,3-benzofuran. This is a four-step reaction including decarboxylation, condensation, hydrolysis, and dehydration.

[0011]

[0012] The overall reaction equation from furoic acid to 2,3-benzofuran is as follows: the oxygen content of the raw material furoic acid is 42.9%, while the oxygen content of the product 2,3-benzofuran is only 13.6%. This shows that this reaction successfully achieves biomass deoxygenation, which is crucial for the high-value utilization of biomass.

[0013]

[0014] The current preparation of 2,3-benzofuran from furoic acid and furan involves many steps and has a low yield. It is of great significance to develop a high-yield, one-pot reaction.

[0015] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for preparing 2,3-benzofuran in a one-pot process by using furoic acid catalyzed by a halogen acid.

[0016] The steps of the method are as follows:

[0017] 1) adding a solvent and a hydrohalic acid into a high-temperature and high-pressure reactor lined with polytetrafluoroethylene with stirring, wherein the mass percentage concentration of the hydrogen halide in the mixed system of the solvent and the hydrohalic acid is 0.2-5.0%; starting stirring, and then adding furoic acid, wherein the mass percentage concentration of furoic acid in the reaction system (the solvent, the hydrohalic acid and the furoic acid constitute the reaction system) is 1-20%;

[0018] 2) heating to a reaction temperature of 100-150°C, and reacting in one pot for 2-24 hours;

[0019] 3) After the reaction is completed, the reaction product is cooled to room temperature to obtain the reaction product, and then separated to obtain the 2,3-benzofuran product.

[0020] As a preferred embodiment of the present invention, the solvent described in step 1) of the present invention is sulfolane, 3-methylsulfolane, methyl phenyl sulfone, diphenyl sulfone, dimethyl sulfone, diethyl sulfone, n-butyl sulfone, 3-cyclobutene sulfone, dimethyl sulfoxide, 1,4-dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-ethyl -3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium hydrogen sulfate, 1-hexyl-3-methylimidazolium hydrogen sulfate, 1-ethyl-3-methylimidazolium methanesulfonate, 1-butyl-3-methylimidazolium methanesulfonate, 1-hexyl-3-methylimidazolium methanesulfonate, 1-ethyl-3-methylimidazolium p-toluenesulfonate, 1-butyl-3-methylimidazolium p-toluenesulfonate, 1-hexyl-3-methylimidazolium p-toluenesulfonate. These solvents can be divided into four categories: sulfur-containing solvents (cyclopentane, 3-methylcyclopentane, methyl phenyl sulfone, diphenyl sulfone, dimethyl sulfone, diethyl sulfone, n-butyl sulfone, 3-cyclobutene sulfone, dimethyl sulfoxide), oxygen-containing solvents (1,4-dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, cyclohexanone), nitrogen-containing solvents (N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone), ionic liquids (1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride) and so on. salt, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium hydrogen sulfate, 1-hexyl-3-methylimidazolium hydrogen sulfate, 1-ethyl-3-methylimidazolium methanesulfonate, 1-butyl-3-methylimidazolium methanesulfonate, 1-hexyl-3-methylimidazolium methanesulfonate, 1-ethyl-3-methylimidazolium p-toluenesulfonate, 1-butyl-3-methylimidazolium p-toluenesulfonate, 1-hexyl-3-methylimidazolium p-toluenesulfonate).

[0021] As a preferred embodiment of the present invention, the hydrohalic acid described in step 1) is hydrochloric acid (hydrochloric acid), hydrobromic acid or hydroiodic acid. The hydrogen halide is hydrogen chloride, hydrogen bromide or hydrogen iodide. The hydrohalic acid is an aqueous solution of hydrogen halide: hydrochloric acid (hydrochloric acid) is an aqueous solution of hydrogen chloride, hydrobromic acid is an aqueous solution of hydrogen bromide, and hydroiodic acid is an aqueous solution of hydrogen iodide. As a preferred embodiment of the present invention, the mass percentage concentration of the hydrogen halide described in step 1) in the mixed system of the solvent and the hydrohalic acid is 1.0 to 4.0%.

[0022] As a preferred embodiment of the present invention, the mass percentage concentration of furoic acid in step 1) in the reaction system is 5-15%.

[0023] As a preferred embodiment of the present invention, the reaction temperature in step 2) is 110-140°C.

[0024] The method for separating the reaction products of the present invention varies depending on the reaction solvent used: for high-boiling point solvents, steam distillation can be used for separation, and the effluent can be condensed and separated from the oil and water to obtain the 2,3-benzofuran product; for low-boiling point solvents, distillation can be used for separation.

[0025] The interior of the high-temperature and high-pressure reactor of the present invention is in a vapor-liquid two-phase state, and the reaction pressure is close to the saturated vapor pressure of the solvent.

[0026] The method proposed by the present invention has at least the following advantages:

[0027] 1) The process route is short and a one-pot process is adopted.

[0028] 2) The conditions are mild and the reaction temperature is below 150°C.

[0029] 3) The yield of the product 2,3-benzofuran is as high as 75.0%.

[0030] Therefore, the invention has green raw materials and green processes, has very broad industrial application prospects, and can provide a new approach for the low-cost and efficient preparation of 2,3-benzofuran. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Attached Figure 1 The present invention is a simplified process flow diagram of preparing 2,3-benzofuran by a one-pot process of furoic acid catalyzed by hydrohalic acid. DETAILED DESCRIPTION

[0032] The present invention uses a high performance liquid chromatography-UV detector (HPLC-UV, Agilent 1260) to analyze furoic acid and the main decomposition products furan and 2,3-benzofuran, and adopts an external standard method for quantification. Chromatographic conditions: the chromatographic column is Agilent EC-C18 100mm×4.6mm; the mobile phase is 60% 5mmol / L sulfuric acid aqueous solution-40% acetonitrile, the flow rate is 1mL / min; the column temperature is 40°C; the injection volume is 20μL; the UV detection wavelength is set to 210nm.

[0033] The calculation formula of furoic acid transformation efficiency of the present invention is as follows:

[0034]

[0035] The yield of furans of the present invention is a molar yield, and the calculation formula is as follows:

[0036]

[0037] The yield of 2,3-benzofuran of the present invention is a molar yield, and the calculation formula is as follows:

[0038]

[0039] In the following examples, hydrochloric acid was purchased from Sinopharm Chemical Reagent Co., Ltd. with a mass fraction of 36-38%, calculated as 37%; hydrobromic acid was purchased from Aladdin Reagent (Shanghai) Co., Ltd. with a mass fraction of 48%; hydroiodic acid was purchased from Aladdin Reagent (Shanghai) Co., Ltd. with a mass fraction of 55-58%, calculated as 56.5%. Example 1 Effect of different halogen acids on the one-pot catalytic conversion of furoic acid to prepare 2,3-benzofuran

[0040] According to Figure 1 As shown in the process flow, 300 g of solvent and an appropriate amount of hydrohalic acid are added in sequence to a 500 mL high-temperature and high-pressure reactor with stirring and lined with polytetrafluoroethylene, and stirring is started. Then, an appropriate amount of furoic acid is added, and the temperature is raised to a set temperature for a one-pot reaction for a set time; after the reaction is completed, the reaction product is cooled to room temperature to obtain a reaction product (after sampling, HPLC-UV analysis is performed to calculate the furoic acid conversion rate, the molar yield of furan and the molar yield of 2,3-benzofuran), and then the 2,3-benzofuran product is obtained by separation.

[0041] The experimental results of one-pot catalytic conversion of furoic acid to 2,3-benzofuran by different hydrohalic acids are shown in Table 1, wherein the reaction solvent is sulfolane, the mass percentage concentration of hydrogen halide in the mixed system consisting of solvent and hydrohalic acid is 3.5%, the mass percentage concentration of furoic acid in the entire reaction system is 2%, the reaction temperature is 130°C, and the reaction time is 6h.

[0042] Table 1

[0043]

[0044] Example 2 Effect of different solvents on the one-pot catalytic conversion of furoic acid to 2,3-benzofuran

[0045] According to Figure 1 As shown in the process flow, 300 g of solvent and an appropriate amount of hydrohalic acid are added in sequence to a 500 mL high-temperature and high-pressure reactor with stirring and lined with polytetrafluoroethylene, and stirring is started. Then, an appropriate amount of furoic acid is added, and the temperature is raised to a set temperature for a one-pot reaction for a set time; after the reaction is completed, the reaction product is cooled to room temperature to obtain a reaction product (after sampling, HPLC-UV analysis is performed to calculate the furoic acid conversion rate, the molar yield of furan and the molar yield of 2,3-benzofuran), and then the 2,3-benzofuran product is obtained by separation.

[0046] The experimental results of one-pot catalytic conversion of furoic acid to 2,3-benzofuran by different solvents are shown in Table 2, wherein the catalyst is hydrobromic acid, the mass percentage concentration of hydrogen bromide in the mixed system consisting of the solvent and hydrobromic acid is 3.5%, the mass percentage concentration of furoic acid in the entire reaction system is 2%, the reaction temperature is 130°C, and the reaction time is 7h.

[0047]

[0048]

[0049] Example 3 Effect of different process conditions on the one-pot catalytic conversion of furoic acid to 2,3-benzofuran

[0050] According to Figure 1 As shown in the process flow, 300 g of solvent and an appropriate amount of hydrohalic acid are added in sequence to a 500 mL high-temperature and high-pressure reactor with stirring and lined with polytetrafluoroethylene, and stirring is started. Then, an appropriate amount of furoic acid is added, and the temperature is raised to a set temperature for a one-pot reaction for a set time; after the reaction is completed, the reaction product is cooled to room temperature to obtain a reaction product (after sampling, HPLC-UV analysis is performed to calculate the furoic acid conversion rate, the molar yield of furan and the molar yield of 2,3-benzofuran), and then the 2,3-benzofuran product is obtained by separation.

[0051] The experimental results of one-pot catalytic conversion of furoic acid to 2,3-benzofuran under different process conditions are shown in Table 3, wherein the reaction solvent is sulfolane and the catalyst is hydrobromic acid.

[0052] Table 3

[0053]

[0054]

[0055] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing 2,3-benzofuran in a one-pot process using furoic acid catalyzed by halogen acid, characterized in that: The steps of the method are as follows: 1) Adding a solvent and a hydrohalic acid to a high-temperature and high-pressure reactor with stirring and lined with polytetrafluoroethylene, wherein the mass percentage concentration of the hydrogen halide in the mixed system of the solvent and the hydrohalic acid is 0.2-5.0%; starting stirring, and then adding furoic acid, wherein the mass percentage concentration of furoic acid in the reaction system is 1-20%; the hydrohalic acid is hydrochloric acid, hydrobromic acid or hydroiodic acid; the hydrogen halide is hydrogen chloride, hydrogen bromide or hydrogen iodide; 2) Heat to the reaction temperature of 100-150°C and react in one pot for 2-24 hours; 3) After the reaction is completed, the reaction product is cooled to room temperature to obtain the reaction product, and then separated to obtain the 2,3-benzofuran product.

2. The method for preparing 2,3-benzofuran by a one-pot process of furoic acid catalyzed by a halogen acid according to claim 1, characterized in that The solvent described in step 1) is sulfolane, 3-methylsulfolane, methyl phenyl sulfone, diphenyl sulfone, dimethyl sulfone, diethyl sulfone, n-butyl sulfone, 3-cyclobutene sulfone, dimethyl sulfoxide, 1,4-dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium Bromide, 1-butyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium hydrogen sulfate, 1-hexyl-3-methylimidazolium hydrogen sulfate, 1-ethyl-3-methylimidazolium methanesulfonate, 1-butyl-3-methylimidazolium methanesulfonate, 1-hexyl-3-methylimidazolium methanesulfonate, 1-ethyl-3-methylimidazolium p-toluenesulfonate, 1-butyl-3-methylimidazolium p-toluenesulfonate, 1-hexyl-3-methylimidazolium p-toluenesulfonate.

3. A method for preparing 2,3-benzofuran by a one-pot process of furoic acid catalyzed by a halogen acid according to claim 1, characterized in that In step 1), the mass percentage concentration of hydrogen halide in the mixed system of solvent and hydrohalic acid is 1.0-4.0%.

4. The method for preparing 2,3-benzofuran by a one-pot process of furoic acid catalyzed by a halogen acid according to claim 1, characterized in that The mass percentage concentration of furoic acid in step 1) in the reaction system is 5-15%.

5. The method for preparing 2,3-benzofuran by a one-pot process of furoic acid catalyzed by a halogen acid according to claim 1, characterized in that The reaction temperature in step 2) is 110-140°C.

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