Method for synthesizing formanilide and derivatives thereof by catalyzing nitro-aromatic hydrocarbon

Abstract

The invention discloses a method for synthesizing formanilide and derivatives thereof by catalyzing nitro-aromatic hydrocarbon, a mixture of o-aniline, ferric chloride hexahydrate and silicon dioxide sol is used as a precursor, high-temperature pyrolysis is performed, silicon dioxide is removed by etching with an ammonium bifluoride solution, and a nitrogen-doped mesoporous carbon-loaded iron catalyst is obtained. The raw materials are easily available and low in cost. And by taking nitro-aromatic hydrocarbon as a reaction substrate, adding the prepared nitrogen-doped mesoporous carbon loaded iron catalyst, and reacting for 24 hours at the temperature of 60-80 DEG C in a nitrogen atmosphere by taking tetrahydrofuran as a solvent and formic acid as a reducing agent and a formylation reagent to obtain formanilide and derivatives thereof. The reaction conditions are relatively mild, high temperature and high pressure are not needed, additional additives are not needed, resources are saved, the synthesis yield is excellent, and the method is suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid-phase catalytic N-formylation, and in particular relates to a method for catalyzing the synthesis of formanilide and its derivatives from nitroaromatic hydrocarbons. Background Art

[0002] Formanilide (N-formylanilide) is an organic synthesis intermediate used in the synthesis of pharmaceuticals, pesticides, dyes, and fragrances. Its derivatives are widely used in the fine chemical industry due to their structural diversity. Existing catalytic synthesis of formanilides from nitroaromatic hydrocarbons mostly utilizes a tandem nitroaromatic reduction-formylation reaction. This involves first using a catalyst to reduce the nitroaromatic hydrocarbon to aniline, which is then formylated with formic acid (or a formic acid ester). The catalyst is crucial for achieving efficient conversion. Currently used catalysts include precious metals (such as Au and Pd) and non-precious metals (such as Co and Fe). Precious metal catalysts can synthesize formanilides under relatively mild reaction conditions, such as 50-100°C and atmospheric pressure, but their high cost limits their widespread application. Non-precious metal catalysts, while inexpensive, often require demanding reaction conditions, such as high temperature and pressure, or require the addition of alkaline additives to achieve excellent catalytic performance. This not only results in high energy consumption and environmental impact, but also increases operational complexity and safety risks. Summary of the Invention

[0003] The present invention aims to solve the technical problems of the prior art such as high catalyst cost, harsh reaction conditions and complicated operation, and provides a method for catalyzing the synthesis of formanilide and its derivatives from nitroaromatic hydrocarbons.

[0004] The technical solution of the present invention is: a method for catalyzing the synthesis of formanilide and its derivatives from nitroaromatic hydrocarbons, which is carried out according to the following steps: Step 1. Place o-phenylenediamine and silica sol in a flask at a mass ratio of 1:0.5-2.5, add an appropriate amount of anhydrous ethanol, and stir at 60°C to uniformly disperse. Then, add ferric chloride hexahydrate and continue stirring for 20 hours. The mass ratio of o-phenylenediamine to ferric chloride hexahydrate is 1:0.1-0.5. The mixture in the flask is naturally cooled to room temperature, the solvent is evaporated, and then dried to obtain a solid, which is then ground into a powder. Step 2. The obtained powder was placed in a tube furnace, heated to 900°C at a rate of 5°C / min under a nitrogen atmosphere, calcined for 2 h, and cooled to room temperature to obtain a black powder; Step 3. The black powder was acid-leached with ammonium bifluoride solution, stirred at room temperature for 24 h, washed with water until the solution was neutral, dried, and finally dried in an oven to obtain a nitrogen-doped mesoporous carbon-supported iron-based catalyst; Step 4: Using nitroaromatic hydrocarbon as a reaction substrate, adding a nitrogen-doped mesoporous carbon-supported iron-based catalyst, wherein the molar ratio of iron in the nitrogen-doped mesoporous carbon-supported iron-based catalyst to nitroaromatic hydrocarbon is 1:5-20, using tetrahydrofuran as a solvent, using formic acid as a reducing agent and a formylating agent, reacting at a temperature of 60-80°C for 24 hours under a nitrogen atmosphere to obtain formanilide and its derivatives, wherein the molar ratio of formic acid to nitroaromatic hydrocarbon is 2-10:1.

[0005] The nitroaromatic hydrocarbon has one or more halogen atoms, methyl, methoxy, alkynyl, cyano, tert-butyl, alcoholic hydroxyl, or ester groups attached to the benzene ring, and the substituents are located at one or more of the ortho, para, or meta positions of the nitro group.

[0006] The present invention first uses a mixture of o-aniline, ferric chloride hexahydrate and silica sol as a precursor, performs high-temperature pyrolysis, and then uses ammonium bifluoride solution to etch and remove silica to obtain a nitrogen-doped mesoporous carbon-supported iron-based catalyst. The iron-based catalyst is then used to catalyze the reduction of nitroaromatic hydrocarbons to aniline, and then formic acid is used to efficiently and simply synthesize formanilide and its derivatives. The prepared iron-based catalyst is a transition metal catalyst and the precursor is cheap and readily available, which greatly reduces the synthesis cost of formanilide and its derivatives. At the same time, the reaction conditions are relatively mild, do not require high temperature and high pressure, and do not require additional additives, saving resources and having an excellent synthesis yield (83%-100%), which has good application prospects in industrial synthesis. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is an electron microscope image (5 μm) and element mapping analysis diagram of the iron-based catalyst Fe-NC-900 prepared in an embodiment of the present invention.

[0008] Figure 2 This is an electron microscope magnified image (10 nm) and a high-resolution N1s XPS spectrum of the iron-based catalyst Fe-NC-900 prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0009] The technical solution of the present invention is: a method for catalyzing the synthesis of formanilide and its derivatives from nitroaromatic hydrocarbons, which is carried out according to the following steps: Step 1. Place o-phenylenediamine (1.000 g) and silica sol (2.500 g) in a round-bottom flask, add 30 ml of anhydrous ethanol, and place the mixture in a 60°C water bath with stirring at 80 rpm for 1 hour to evenly disperse the raw materials. Then, add ferric chloride hexahydrate (0.135 g) and continue stirring for 20 hours. The mixture in the round-bottom flask was naturally cooled to room temperature. The solvent was evaporated using a rotary evaporator and dried in a vacuum oven to obtain a dark green solid. The solid was scraped off with a spatula and ground in a mortar to obtain a powder. Step 2. The resulting powder (1.000 g) was placed in a porcelain boat and placed in a tube furnace. The temperature was raised to 900°C at a rate of 5°C / min under a nitrogen atmosphere, followed by calcination for 2 h. The mixture was then cooled to room temperature to obtain a black powder. Step 3. The black powder was acid-leached with 8 mL (2 M) ammonium bifluoride solution, stirred at room temperature for 24 h, washed with water until the solution was neutral, and then dried. Finally, it was placed in an oven for drying to obtain a nitrogen-doped mesoporous carbon-supported iron-based catalyst, named Fe-NC-900. Its electron microscope image and mapping element map are shown in Figure 2. Figure 1 、 Figure 2 As shown; Figure 1 The middle left picture is an electron microscope picture (5 μm) of the iron-based catalyst Fe-NC-900 prepared in an embodiment of the present invention, and the right picture is an element mapping analysis picture.

[0010] from Figure 1 It can be seen that C, N, O, and Fe elements are distributed in large quantities and relatively evenly on the surface of the catalyst Fe-NC-900, indicating that N and Fe atoms are successfully incorporated into the carbon skeleton.

[0011] Figure 2 (a) is an electron microscope magnified image (10 nm) of the iron-based catalyst Fe-NC-900 prepared in an example of the present invention, and (b) is a high-resolution N 1s XPS spectrum.

[0012] from Figure 2 (a) It can be seen that the iron-based nanoparticles are loaded on the nitrogen-doped carbon carrier. The particle size distribution histogram shows that the Fe nanoparticles are distributed in the range of 1.5-3.0 nm, concentrated between 2-2.5 nm, indicating that the particle size of the iron-based nanoparticles is relatively uniform. Figure 2 (b) It can be seen that there is an Fe-Nx peak, which indicates the interaction between Fe atoms and N atoms, that is, in addition to iron-based nanoparticles, single-atom or sub-nanometer-scale iron species also exist in the catalyst.

[0013] Step 4: Commercially available nitroaromatic hydrocarbons (0.250 mmol) substituted with different substituents are used as reaction substrates. The nitroaromatic hydrocarbons have one or more halogen atoms, methyl, methoxy, alkynyl, cyano, tert-butyl, alcoholic hydroxyl, or ester groups attached to the benzene ring, and the substituents are located at one or more of the ortho, para, and meta positions of the nitro group. 80 mg (0.03 mmol) of iron-based catalyst Fe-NC-900, formic acid (2.5 mmol), and tetrahydrofuran (2 mL) are added to a Schlenk reaction tube. After nitrogen replacement, the tube is sealed and placed in an 80°C oil bath with heating and stirring at 80 r / min for 24 h to obtain N-formanilide and its derivatives.

[0014] After the reaction is completed, tetrahydrofuran and an internal standard are added to the reaction solution, and then the reaction solution is transferred to a centrifuge tube and centrifuged multiple times to obtain the supernatant. The resulting product is quantified by gas chromatography. The N-formanilide, derivatives, and yields obtained in the specific embodiment of the present invention are shown in Table 1.

[0015] Table 1

Claims

1. A method for catalyzing the synthesis of formanilide and its derivatives from nitroaromatic hydrocarbons, characterized in that Follow these steps: Step 1. Place o-phenylenediamine and silica sol in a flask at a mass ratio of 1:0.5-2.5, add an appropriate amount of anhydrous ethanol, and stir at 60°C to uniformly disperse. Then, add ferric chloride hexahydrate and continue stirring for 20 hours. The mass ratio of o-phenylenediamine to ferric chloride hexahydrate is 1:0.1-0.

5. The mixture in the flask is naturally cooled to room temperature, the solvent is evaporated, and then dried to obtain a solid, which is then ground into a powder. Step 2. The obtained powder was placed in a tube furnace, heated to 900°C at a rate of 5°C / min under a nitrogen atmosphere, calcined for 2 h, and cooled to room temperature to obtain a black powder; Step 3. The black powder was acid-leached with ammonium bifluoride solution, stirred at room temperature for 24 h, washed with water until the solution was neutral, and then dried to obtain a nitrogen-doped mesoporous carbon-supported iron-based catalyst; Step 4: Using nitroaromatic hydrocarbon as a reaction substrate, adding a nitrogen-doped mesoporous carbon-supported iron-based catalyst, wherein the molar ratio of iron in the nitrogen-doped mesoporous carbon-supported iron-based catalyst to nitroaromatic hydrocarbon is 1:5-20, using tetrahydrofuran as a solvent, using formic acid as a reducing agent and a formylating agent, reacting at a temperature of 60-80°C for 24 hours under a nitrogen atmosphere to obtain formanilide and its derivatives, wherein the molar ratio of formic acid to nitroaromatic hydrocarbon is 2-10:

1.

2. The method for catalyzing the synthesis of formanilide and its derivatives from nitroaromatic hydrocarbons according to claim 1, characterized in that: The nitroaromatic hydrocarbon has one or more halogen atoms, methyl, methoxy, alkynyl, cyano, tert-butyl, alcoholic hydroxyl, or ester groups attached to the benzene ring, and the substituents are located at one or more of the ortho, para, or meta positions of the nitro group.

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