A process for the preparation of 2,5-dimethyl-N-arylpyrroles

Abstract

This invention discloses a 2,5-dimethyl- N The preparation method of 2,5-arylpyrrole involves reacting 2,5-hexanedione and nitroaromatic hydrocarbons in a hydrogen atmosphere and a reaction solvent under the action of a supported bimetallic bifunctional catalyst to obtain 2,5-dimethyl- N -Arylpyrrole. The supported bimetallic bifunctional catalyst includes a support and an active component supported on the support. The support is one of silica (SiO2), titanium dioxide (TiO2), and activated carbon (AC). The active component includes oxides of nickel and manganese. The method of this invention synthesizes 2,5-dimethyl- N The yield of arylpyrrole is over 90%. This invention features a simple process, recyclable catalyst, high reaction selectivity, and high product yield, offering significant advantages for industrial production.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical and chemical technology, specifically to a method for preparing N-arylpyrrole via a one-pot cascade reaction of 2,5-hexanedione and nitroaromatics. Background Technology

[0002] N-arylpyrroles are an important class of nitrogen-containing heterocyclic compounds with diverse biological activities and significant medicinal value. Therefore, the development of precise synthetic methods for constructing pyrrole rings has attracted widespread interest. Currently, the main synthetic methods for N-arylpyrroles include the Hantzsch method, the Clauson-Kaas method, and the Paal-Knorr method. Among these, the Paal-Knorr method is considered one of the most attractive and efficient synthetic methods. The Paal-Knorr method prepares N-arylpyrroles through a condensation reaction of a 1,4-dicarbonyl compound with an aniline compound. As is well known, anilines can be prepared from corresponding nitroaromatics via catalytic hydrogenation. Therefore, in the Paal-Knorr method for constructing N-arylpyrroles, using a nitroaromatic compound instead of aniline as the starting material, and preparing N-arylpyrroles through a one-pot hydrogenation / condensation cascade reaction of a 1,4-dicarbonyl compound with a nitroaromatic compound, is more economical and environmentally friendly. Another starting material for preparing N-arylpyrrole using this method is the 1,4-dicarbonyl compound 2,5-hexanedione (2,5-HD). 2,5-HD can be obtained from renewable lignocellulose, and using it as a starting material enables the sustainable preparation of N-arylpyrrole, which is more in line with the requirements of green chemistry.

[0003] The key to the precise one-pot cascade reaction of 2,5-HD with nitroaromatics to synthesize N-arylpyrrole lies in the design and preparation of a highly efficient bifunctional catalyst. In the reaction, a metal catalyst is needed to first hydrogenate and reduce the nitroaromatics to aniline compounds; and an acid catalyst is needed to promote the condensation reaction between 2,5-HD and the generated aniline compounds, ultimately yielding N-arylpyrrole.

[0004] The literature (ChemCatChem 2013, 5, 538-549) reports a method using Pd (or Pt) containing both metal active centers and Lewis acids Cr. 3+ Using bifunctional MOF materials at specific sites as catalysts, N-arylpyrrole was synthesized via the reaction of 2,5-HD with nitroaromatics. With toluene as solvent, the reaction was carried out at 110 °C and 0.5 MPa hydrogen pressure for 5 h, yielding 99% of 2,5-dimethyl-N-phenylpyrrole. However, Pd (or Pt) is expensive and scarce, making it unsuitable for large-scale use.

[0005] Literature (Angew.Chem.Int.Ed.2020,59,18679-18685 )This paper reports the preparation of 2,5-dimethyl-N-arylpyrrole via a one-pot cascade reaction of 2,5-HD with nitroaromatics using cobalt / cobalt oxide core-shell particles (Co / NGr-C@SiO2-L) supported on SiO2 as a catalyst. The reaction was carried out at 120 °C and 4 MPa hydrogen pressure for 24 h, with a highest yield of 88% for 2,5-dimethyl-N-arylpyrrole. However, this system requires a relatively high reaction temperature, high H2 pressure, and a low yield.

[0006] The literature (J. Catal. 2022, 416, 39-46) reports the preparation of 2,5-dimethyl-N-arylpyrrole via a one-pot cascade reaction of 2,5-HD and nitroaromatics using Fe@NSiC as a catalyst and HCOOH as a reducing agent. The highest yield of 2,5-dimethyl-N-arylpyrrole was 87% after reacting at 100 °C for 24 h. However, this system still suffers from the disadvantages of long reaction time and low yield. Summary of the Invention

[0007] To address the aforementioned technical problems in the existing technology, the present invention aims to provide a method for preparing 2,5-dimethyl-N-arylpyrrole. The present invention provides an environmentally friendly method for the precise one-pot cascade reaction of 2,5-hexanedione (2,5-HD) with nitroaromatic hydrocarbons using a supported bimetallic bifunctional catalyst and H2 as a reducing agent to synthesize 2,5-dimethyl-N-arylpyrrole. This method features mild reaction conditions and a high yield of 2,5-dimethyl-N-arylpyrrole.

[0008] A method for preparing 2,5-dimethyl-N-arylpyrrole via a one-pot cascade reaction of 2,5-hexanedione and nitroaromatic hydrocarbons, specifically comprising: using 2,5-HD (Formula I) and nitroaromatic hydrocarbons (Formula II) as starting materials, reacting them in a hydrogen atmosphere and a reaction solvent under the action of a supported bimetallic bifunctional catalyst; and after the reaction, post-treatment to obtain 2,5-dimethyl-N-arylpyrrole (Formula III), as shown in the following reaction formula:

[0009]

[0010] In Formulas II and III, the substituent R is a C1-C4 alkyl, C1-C4 alkoxy, or halogen.

[0011] Furthermore, the supported bimetallic bifunctional catalyst includes a support and an effective active ingredient supported on the support; the support is one of activated carbon, mesoporous carbon, diatomaceous earth, ZSM-5, alumina, silicon dioxide, or titanium dioxide; the effective active ingredient includes oxides of nickel metal and manganese.

[0012] Manganese oxides are mainly MnO xIt indicates a mixture containing MnO, MnO2, Mn2O3 and Mn3O4.

[0013] This invention utilizes nickel as a non-noble metal in the supported bimetallic bifunctional catalyst to provide hydrogenation active sites, and employs manganese oxide to provide sufficient Lewis acid sites, forming a metal-acid bifunctional catalyst. This promotes the hydrogenation reaction of nitroaromatics and the subsequent Paal-Knorr condensation reaction, yielding high-yield 2,5-dimethyl-N-arylpyrrole. Simultaneously, manganese inhibits the polymerization of nickel, resulting in high nickel dispersion, small size, and a large active surface area, thus improving the activity of the bifunctional catalyst. The catalyst of this invention exhibits high activity, good selectivity, good reusability, and high product yield, thereby significantly reducing production costs.

[0014] The support has a large specific surface area and pore volume, which allows nickel and manganese to be uniformly dispersed on the support, thereby improving the activity of the supported bimetallic bifunctional catalyst. The support structure has many pores, which can promote mass transfer diffusion and adsorption of the effective active ingredients.

[0015] The carrier is one of activated carbon, mesoporous carbon, diatomaceous earth, ZSM-5, alumina, silicon dioxide, or titanium dioxide; preferably silicon dioxide, titanium dioxide, or activated carbon.

[0016] In the supported bimetallic bifunctional catalyst, the molar ratio of nickel to manganese is 1:0.1 to 4, preferably 1:0.2 to 0.8.

[0017] A suitable molar ratio of nickel and manganese exhibits a good interaction, resulting in excellent catalytic performance. However, if the nickel content is too low, the concentration of the nickel-based active component for hydrogenation is low, leading to low hydrogenation activity in the catalyst, which is detrimental to the hydrogenation of nitroaromatics. Conversely, if the manganese content is too low, there are insufficient acid-active sites on the catalyst, which will affect the condensation reaction rate.

[0018] The nickel metal loading in the supported bimetallic bifunctional catalyst is 0.5–20 wt%, preferably 1–3 wt%.

[0019] When the nickel-manganese loading in the catalyst is too low, there are insufficient active sites in the catalyst, resulting in incomplete reaction and very low product yield. However, when the nickel-manganese loading is too high, the catalyst cost will increase, and too many active sites in the catalyst will easily lead to over-hydrogenation and other side reactions. In addition, when the nickel-manganese loading is too high, the metal components on the catalyst surface will aggregate, reducing the utilization of metal atoms.

[0020] The mass ratio of the nitroaromatic hydrocarbon to the supported bimetallic bifunctional catalyst is 1:0.01 to 0.6.

[0021] The preferred mass ratio of nitroaromatic hydrocarbon to supported bimetallic bifunctional catalyst is 1:0.02 to 0.5.

[0022] If the amount of catalyst used in the reaction is too low, the reaction will be incomplete; however, if the amount of catalyst used is too high, a large number of by-products will be generated, which is detrimental to the reaction.

[0023] The molar ratio of 2,5-hexanedione to nitroaromatic hydrocarbon is 5:1 to 1:1. Preferably, the molar ratio of 2,5-hexanedione to nitroaromatic hydrocarbon is 3:1 to 1:1.

[0024] The reaction solvent is methanol, ethanol, toluene, water, or tetrahydrofuran, preferably methanol or ethanol.

[0025] The volumetric amount of the solvent used is 2 to 50 mL / g, based on the mass of 2,5-hexanedione.

[0026] The preferred volumetric amount of solvent used is 5 to 30 mL / g based on the mass of 2,5-hexanedione.

[0027] Both excessively small and excessively large volumes of solvent are detrimental to the reaction. If the volume of solvent is too small, the concentrations of 2,5-hexanedione, nitrobenzene, and the reaction products will be too high or they will not dissolve completely, resulting in a long reaction time and a low yield. If the volume of solvent is too large, the solution concentration will decrease, reducing intermolecular collisions, which will slow down the reaction rate and reduce the product yield.

[0028] The hydrogen pressure is 0.2–5 MPa, and the reaction is carried out at 50–180°C for 0.1–15 hours.

[0029] The preferred hydrogen pressure is 0.3–3.0 MPa, the reaction temperature is 70–120 °C, and the reaction time is 8–15 h.

[0030] Excessive hydrogen pressure will produce a large number of byproducts, which is detrimental to the reaction; if the reaction temperature is too low, the reaction rate will slow down, the reaction time will be longer, and the reaction will be incomplete; if the reaction temperature is too high, the target product will be over-hydrogenated, resulting in more byproducts and a decrease in product yield.

[0031] The post-reaction processing method is as follows: the reaction solution is filtered, the filter cake is a supported bifunctional catalyst, which is recovered and reused; the solvent is removed by distillation of the filtrate, and the residue is separated by column chromatography to obtain the product 2,5-dimethyl-N-arylpyrrole.

[0032] The method for preparing the supported bimetallic bifunctional catalyst is as follows: the support is calcined at 300-600℃ for 3-8 hours, the calcined support is completely immersed in a mixed aqueous solution of manganese salt and nickel salt, the impregnation is dried at 80-150℃, and then reduced by passing a reducing gas at 200-800℃ to prepare the supported bifunctional catalyst.

[0033] Nickel-soluble salts are decomposed at high temperature and reduced to elemental nickel by a reducing gas. Manganese-soluble salts are decomposed at high temperature to manganese oxides. Some of the high-valence manganese oxides are reduced to low-valence manganese oxides by the reducing gas, thereby preparing the supported bifunctional catalyst.

[0034] The nickel salt is one of nickel nitrate, nickel acetate, or nickel chloride; the manganese salt is one of manganese acetate or manganese nitrate.

[0035] Compared with the prior art, the beneficial effects of this invention are reflected in:

[0036] 1. The supported bimetallic bifunctional catalyst provided by the present invention, under the synergistic effect of nickel metal and manganese oxide, has excellent catalytic activity and selectivity, and a lower metal loading compared with non-precious metal catalysts in the prior art;

[0037] 2. The supported bimetallic bifunctional catalyst provided by this invention, in the one-pot cascade reaction of 2,5-hexanedione and nitroaromatics to prepare 2,5-dimethyl-N-arylpyrrole, offers mild reaction conditions, simple process, high selectivity, and is environmentally friendly. The yield of 2,5-dimethyl-N-arylpyrrole is above 99%.

[0038] 3. The supported bimetallic bifunctional catalyst described above is recyclable and reusable, requires a small amount of catalyst, reduces costs, and is suitable for industrial production. Detailed Implementation

[0039] The technical solution of the present invention will be described below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0040] Blank example 1:

[0041] The method for preparing the supported bifunctional catalyst of the present invention uses Ni-MnO with a Ni metal loading of 2wt% x Taking a SiO2 catalyst (Ni:Mn molar ratio of 2:1) as an example, it was prepared as follows: 1g of 120-mesh SiO2 was weighed and placed in a crucible, and calcined at 500℃ for 5 hours. 0.1g of Ni(NO3)2·6H2O was weighed and placed in another crucible, and 0.5g of deionized water was added and completely dissolved. 0.04g of C4H6MnO4·4H2O was weighed and added to a nickel nitrate solution, ensuring thorough mixing of nickel nitrate and manganese acetate. The solution was then sonicated to ensure complete dissolution. SiO2 was added while stirring, and the mixture was impregnated at room temperature for 24 hours. It was then dried at 110℃ for 12 hours and reduced at 500℃ under a hydrogen atmosphere for 3 hours to obtain Ni-MnO with a Ni metal loading of 2wt% and a manganese metal loading of 0.9wt%. x / SiO2 catalyst.

[0042] Using the same method described above, bimetallic bifunctional catalysts with different metal molar ratios or different supports can be prepared by changing the molar ratio of the two metals or the type of support.

[0043] Blank example 2:

[0044] Ni-MnO with a Ni metal loading of 2wt% and a Ni:Mn molar ratio of 4:1, 1:1, or 1:2. x The SiO2 catalyst was prepared by repeating the method in Blank Example 1, except that the amount of C4H6MnO4·4H2O was changed, and the corresponding catalyst was finally obtained.

[0045] Blank example 3:

[0046] Co-MnO with similar properties to Ni was prepared using the same method as Ni-Mn / SiO2 catalyst. x / SiO2 catalyst:

[0047] Co-MnO with a Co metal loading of 2wt% x The SiO2 catalyst (with a Co:Mn molar ratio of 2:1, 1:1, or 1:2) was prepared using the same method as in Blank Example 1, with the only differences being the following two points:

[0048] 1) Replace “0.1g Ni(NO3)2·6H2O” in blank example 1 with the same mass of cobalt nitrate hexahydrate;

[0049] 2) By changing the amount of "C4H6MnO4·4H2O", the corresponding catalyst can be obtained.

[0050] The catalysts prepared in blank examples 1-3 were used in the following examples and control examples.

[0051] Example 1:

[0052] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.04 g of Ni-MnO with a Ni metal loading of 2 wt%. x Using a SiO2 catalyst (Ni:Mn molar ratio of 2:1), the mixture was purged five times with nitrogen gas. The reaction temperature was 70℃, the hydrogen pressure was 1.0MPa, and the reaction time was 14 hours. 2,5-hexanedione was 100% converted to 2,5-dimethyl-N-phenylpyrrole, with a yield of 99.9% before post-treatment.

[0053] Example 2:

[0054] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.04 g of Ni-MnO with a Ni metal loading of 2 wt%. x Using a SiO2 catalyst (Ni:Mn molar ratio of 2:1), the mixture was purged five times with nitrogen gas, reacted at 80°C, and with a hydrogen pressure of 1.0 MPa for 12 hours. 2,5-Hexanedione was 100% converted to 2,5-dimethyl-N-phenylpyrrole, with a yield of 95.4% before post-treatment.

[0055] Example 3:

[0056] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.005 g of Ni-MnO with a Ni metal loading of 2 wt%. x Using a SiO2 catalyst (Ni:Mn molar ratio of 2:1), the mixture was purged five times with nitrogen gas. The reaction temperature was 110℃, the hydrogen pressure was 1.0MPa, and the reaction time was 10 hours. 2,5-hexanedione was 100% converted to 2,5-dimethyl-N-phenylpyrrole, with a yield of 99.9% before post-treatment.

[0057] Example 4:

[0058] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.005 g of Ni-MnO with a Ni metal loading of 2 wt%. x Using a SiO2 catalyst (Ni:Mn molar ratio of 2:1), the mixture was purged with nitrogen five times, the reaction temperature was 110℃, the hydrogen pressure was 1.0MPa, and the reaction time was 8 hours. The conversion rate of 2,5-hexanedione was 97.1%, and 2,5-dimethyl-N-phenylpyrrole was obtained. The yield before post-treatment was 97.1%.

[0059] Example 5:

[0060] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.005 g of Ni-MnO with a Ni metal loading of 2 wt%. xUsing a SiO2 catalyst (Ni:Mn molar ratio of 2:1), the mixture was purged five times with nitrogen gas, reacted at 80°C, and with a hydrogen pressure of 1.0 MPa for 10 hours. The conversion rate of 2,5-hexanedione was 67.8%, and 2,5-dimethyl-N-phenylpyrrole was obtained. The yield before post-treatment was 39.7%.

[0061] Example 6:

[0062] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.01 g of Ni-MnO with a Ni metal loading of 2 wt%. x Using a SiO2 catalyst (Ni:Mn molar ratio of 4:1), the mixture was purged five times with nitrogen gas. The reaction temperature was 110℃, the hydrogen pressure was 1.0MPa, and the reaction time was 10 hours. The conversion rate of 2,5-hexanedione was 56.5%, and 2,5-dimethyl-N-phenylpyrrole was obtained. The yield before post-treatment was 56.5%.

[0063] Example 7:

[0064] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.01 g of Ni-MnO with a Ni metal loading of 2 wt%. x Using a SiO2 catalyst (Ni and Mn in a 1:1 molar ratio), the mixture was purged five times with nitrogen gas. The reaction temperature was 110℃, the hydrogen pressure was 1.0 MPa, and the reaction time was 10 hours. The conversion rate of 2,5-hexanedione was 91.8%, and 2,5-dimethyl-N-phenylpyrrole was obtained. The yield before post-treatment was 91.4%.

[0065] Example 8:

[0066] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.01 g of Ni-MnO with a Ni metal loading of 2 wt%. x Using a SiO2 catalyst (Ni:Mn molar ratio of 1:2), the mixture was purged five times with nitrogen gas. The reaction temperature was 110℃, the hydrogen pressure was 1.0MPa, and the reaction time was 10 hours. The conversion rate of 2,5-hexanedione was 60.8%, and 2,5-dimethyl-N-phenylpyrrole was obtained. The yield before post-treatment was 59.1%.

[0067] Examples 9-11:

[0068] Other operations are the same as in Example 3, except that the amount of catalyst is changed, and the following reaction results are obtained (Table 1):

[0069] Table 1

[0070]

[0071] Examples 11-12:

[0072] The other operations are the same as in Example 2, except that the solvent type is changed, and the following reaction results are obtained (Table 2):

[0073] Table 2

[0074]

[0075]

[0076] Examples 13-17:

[0077] Other operations are the same as in Example 1, except that the catalyst is recycled (after each reaction, the reaction solution is filtered, and the filter cake is a supported bifunctional catalyst, which is recovered and reused), and the following reaction results are obtained (Table 3):

[0078] Table 3

[0079] Example Catalyst repetition count 2,5-Dimethyl-N-phenylpyrrole yield (%) 13 1 100 14 2 99.0 15 3 98.3 16 4 96.52 17 5 95.5

[0080] Examples 22-26:

[0081] Other operations are the same as in Example 1, except that the nitroaromatic reaction substrate is changed, and the following reaction results are obtained (Table 4):

[0082] Table 4

[0083]

[0084] Compare with Example 1:

[0085] Co-MnO with similar properties to Ni was prepared using the same method as Ni-Mn / SiO2 catalyst. x / SiO2 catalyst.

[0086] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.04 g of Co-MnO with a Co metal loading of 2 wt%. xUsing a SiO2 catalyst (Co:Mn in a molar ratio of 2:1), the mixture was purged five times with nitrogen gas. The reaction temperature was 80℃, the hydrogen pressure was 1.0 MPa, and the reaction time was 12 hours. The conversion rate of 2,5-hexanedione was 85.6%, and 2,5-dimethyl-N-phenylpyrrole was obtained. The yield before post-treatment was 83.4%.

[0087] Compare with Example 2:

[0088] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.04 g of Co-MnO with a Co metal loading of 2 wt%. x Using a SiO2 catalyst (Co and Mn in a 1:1 molar ratio), the reaction was purged five times with nitrogen gas at a temperature of 80°C and a hydrogen pressure of 1.0 MPa for 12 hours. The conversion rate of 2,5-hexanedione was 79.2%, and 2,5-dimethyl-N-phenylpyrrole was obtained. The yield before post-treatment was 78.1%.

[0089] Compare with Example 3:

[0090] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.04 g of Co-MnO with a Co metal loading of 2 wt%. x Using a SiO2 catalyst (Co:Mn molar ratio of 1:2), the mixture was purged five times with nitrogen gas. The reaction temperature was 80℃, the hydrogen pressure was 1.0MPa, and the reaction time was 12 hours. The conversion rate of 2,5-hexanedione was 89.4%, and 2,5-dimethyl-N-phenylpyrrole was obtained. The yield before post-treatment was 34.9%.

[0091] Compare with Example 4:

[0092] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.01 g of Ni-MnO with a Ni metal loading of 2 wt%. x Using a TiO2 catalyst (Ni:Mn molar ratio of 2:1), the mixture was purged five times with nitrogen gas, reacted at 110℃, and with a hydrogen pressure of 1.0 MPa for 10 hours. The conversion rate of 2,5-hexanedione was 87.4%, and 2,5-dimethyl-N-phenylpyrrole was obtained. The yield before post-treatment was 87.4%.

[0093] Compare with Example 5:

[0094] Take 0.228 g (2 mmol) of 2,5-hexanedione and 0.246 g (2 mmol) of nitrobenzene and place them in a beaker. Add 2 mL of methanol to dissolve them. Add the solution to a 25 mL high-pressure reactor and add 0.01 g of Ni-MnO with a Ni metal loading of 2 wt%. x With AC catalyst (Ni:Mn molar ratio of 2:1), nitrogen was purged five times, the reaction temperature was 110℃, the hydrogen pressure was 1.0MPa, and the reaction time was 10 hours. The conversion rate of 2,5-hexanedione was 90.5%, and 2,5-dimethyl-N-phenylpyrrole was obtained. The yield before post-treatment was 90.5%.

Claims

1. A 2,5-dimethyl- N The method for preparing -arylpyrrole is characterized by, Using 2,5-hexanedione and nitroaromatics as raw materials, 2,5-dimethyl- N -Arylpyrrole; The supported bimetallic bifunctional catalyst includes a support and an active component supported on the support; the support is one of alumina, silica, or titanium dioxide; the active component includes oxides of nickel metal and manganese. In the supported bimetallic bifunctional catalyst, the molar ratio of nickel to manganese is 1:1 or 2:

1. The nickel metal loading in the supported bimetallic bifunctional catalyst is 1-3 wt%. The mass ratio of the nitroaromatic hydrocarbon to the supported bimetallic bifunctional catalyst is 1:0.01~0.6; The reaction solvent is methanol, ethanol, toluene, water or tetrahydrofuran, and the volume of the solvent used is 2 to 50 mL / g based on the mass of 2,5-hexanedione.

2. The 2,5-dimethyl- according to claim 1 N The method for preparing -arylpyrrole is characterized by, The mass ratio of the nitroaromatic hydrocarbon to the supported bimetallic bifunctional catalyst is 1:0.02~0.

5.

3. A 2,5-dimethyl- N The method for preparing -arylpyrrole is characterized by, The molar ratio of 2,5-hexanedione to nitroaromatic hydrocarbon is 3:1 to 1:

1.

4. A 2,5-dimethyl- N The method for preparing -arylpyrrole is characterized by, The volume of the solvent used is 5~30 mL / g based on the mass of 2,5-hexanedione.

5. A 2,5-dimethyl- N The method for preparing -arylpyrrole is characterized by, The reaction conditions are: hydrogen pressure of 0.2~5 MPa, reaction temperature of 50~180 ℃ for 0.1~15 h.

6. A 2,5-dimethyl- N The method for preparing -arylpyrrole is characterized by, The reaction conditions are: hydrogen pressure of 0.3~3.0 MPa, reaction temperature of 70~120℃, and reaction time of 8~15 h.

7. A 2,5-dimethyl- N The method for preparing -arylpyrrole is characterized by, After the reaction, a post-processing step was performed: the reaction solution was filtered, and the filter cake, which was a supported bifunctional catalyst, was recovered and reused; the solvent in the filtrate was removed by distillation, and the residue was separated by column chromatography to obtain the product 2,5-dimethyl- N -Arylpyrrole.

8. A 2,5-dimethyl- N The method for preparing -arylpyrrole is characterized by, The preparation method of the supported bimetallic bifunctional catalyst is as follows: the support is calcined at 300~600℃ for 3~8 hours, the calcined support is completely immersed in a mixed aqueous solution of manganese salt and nickel salt, the impregnation is dried at 80~150℃, and then reduced by passing a reducing gas at 200~800℃ to prepare the supported bimetallic bifunctional catalyst.

9. A 2,5-dimethyl- N The method for preparing -arylpyrrole is characterized by, The nickel salt is one of nickel nitrate, nickel acetate, or nickel chloride; the manganese salt is one of manganese acetate or manganese nitrate.

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