Method for preparing primary amide through oxidative cracking of aromatic ketone
The catalyzed oxidative cracking of aromatic ketones is solved by catalyzing the problem of excessive waste of activator in traditional amide synthesis methods, and efficient, economical and environmentally friendly primary amide preparation is achieved.
Patent Information
- Application Number
- CN202311261802.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-27
- Publication Date
- 2025-03-28
AI Technical Summary
Traditional amide synthesis methods require stoichiometric amounts of activators, resulting in excessive waste, high process costs and great environmental impact.
The OMS-2 catalyst was used to cleave aromatic ketone by oxidation, and oxygen and ammonia were used as oxygen and ammonia sources to produce primary amides. This method optimizes the catalytic reaction conditions by regulating the oxygen vacancies and crystallization temperature of the catalyst.
It achieves high oxidation efficiency, good selectivity and high product yield, reduces atomic utilization, and has economical and environmentally friendly processes, and has good application prospects.
Smart Images
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of catalyst preparation and application, and specifically relates to a simple method for designing a high-efficiency OMS-2 catalyst for catalyzing the oxidative cracking of aromatic ketones to prepare primary amides. Background Art
[0002] Oxygen vacancy defects play a very important role in the catalytic process of metal oxide catalysts and have attracted widespread attention. We developed a new and facile hydrothermal redox reaction method to prepare cryptomanganite-type octahedral molecular sieve (OMS-2) nanorods with tunable oxygen vacancy defect concentration, which demonstrated a huge OVD effect on the catalytic performance of OMS-2.
[0003] We evaluated the oxidation efficiency of the catalyst by catalytic oxidation of aromatic ketone substrates and found that increasing the OVD concentration can significantly increase the activity of lattice oxygen, thereby greatly improving the catalytic activity of aromatic ketone oxidation.
[0004] In addition, amides are one of the most widely used chemical intermediates in the production of fine chemicals, polymers and materials. Primary amides, in particular, are widely present in biologically essential compounds such as pharmaceuticals and agrochemicals. Traditional amide synthesis involves the coupling of carboxylic acids or their derivatives with amines. However, this method often requires the use of stoichiometric amounts of activators, which results in a large amount of excess waste. Therefore, in the past few decades, new methods have been developed to reduce process costs and minimize environmental impact. For example, oxidative amidation of primary alcohols, aldehydes, methyl ketones or methyl aromatics, oxidation of primary amines and hydration of nitriles are all effective methods for preparing amides. Among them, the amidation reaction of alcohols and methyl aromatics is more attractive because these starting materials are inexpensive and easily available from the chemical industry and nature. Therefore, developing a simple and efficient method for preparing primary amides remains our goal. Summary of the invention
[0005] The invention provides a novel preparation method of primary amide. In the method, aromatic acetophenone is used as a model substrate, oxygen is used as an oxygen source, and ammonia is used as an ammonia source. Under the action of OMS-T, the aromatic acetophenone undergoes oxidative cleavage to generate benzamide.
[0006] According to the present invention, in the aromatic ketone molecule, the phenyl group having other substituents on the benzene ring (N, O, S) heterocyclic ring One or more of the following:
[0007] The other substituents -R1 on the benzene ring are one or more of -CH3, -OCH3, -C(CH3)3, -F, -Cl, -Br, -CF3, -NO2; the substituents -R2 are -CH3, -CH(CH3)2, -C(CH3)3, -(CH2) n One or more of CH3 (n=1-10) and phenyl;
[0008] There are other substituents -R1 on the benzene ring of the aromatic ketone, and the positions of other substituents -R1 are ortho, meta or para;
[0009] In the ketone with other substituents on the benzene ring, the number of other substituents is 1, 2, 3, 4 or 5; according to the present invention, environmentally friendly oxygen is used as the oxygen source. The three forms of oxygen molecules are not active enough, and a catalyst is required to activate oxygen to form active oxygen. The present invention uses one or more of the OMS-T catalysts (T = 70, 90, 180 ° C) as catalysts to activate oxygen molecules, achieve oxidative cleavage of aromatic ketones, and prepare corresponding primary amides.
[0010] According to the present invention, the catalytic performance is related to the crystallization temperature of the catalyst. If the crystallization temperature is too high, the activity of the catalytic reaction will be reduced. This may be because the concentration of oxygen vacancies on the catalyst surface is reduced due to the high crystallization temperature, and the catalytic activity is also reduced accordingly. Therefore, it is necessary to select an appropriate crystallization temperature to prepare the catalyst. The crystallization temperature range of the catalyst is 50-180°C, and the preferred range is 70-180°C.
[0011] According to the present invention, the catalytic performance is related to the amount of the catalyst used. Too low an amount will affect the activity of the catalytic reaction, and too high an amount will increase the cost of the catalyst; therefore, it is necessary to select an appropriate amount. In order to ensure the activity of the catalyst while reducing the cost of the catalyst, the molar ratio of the Mn content in the catalyst used to the substrate is in the range of 0.1-20 mol%, preferably in the range of 0.1-10 mol%.
[0012] According to the present invention, the oxidative cleavage effect of aromatic ketone is related to oxygen pressure, ammonia pressure, reaction temperature and time, wherein the oxygen partial pressure is 0.2-0.8MPa; the ammonia partial pressure is 0.2-0.8MPa; the reaction temperature is 120-160°C; the reaction time is 6-24h; preferably, the oxygen partial pressure is 0.4-0.6MPa; the ammonia partial pressure is 0.4-0.6MPa; the reaction temperature is 140-160°C and the reaction time is 8-16h.
[0013] According to the present invention, the reaction needs to be carried out in a solvent, especially for some solid aromatic ketone substrate molecules, which need to be dissolved in a solvent to be uniformly dispersed and facilitate contact with the catalyst. The solvent used for the oxidative cleavage of aromatic ketone is one or more of tert-amyl alcohol, 1,4-dioxane, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile, n-heptane, and N-methylpyrrolidone (NMP). The mass concentration range of the aromatic ketone in the solvent is 1-20wt%, preferably 1-10wt%.
[0014] This method has high oxidation efficiency, good selectivity, and high product yield, thanks to the regulation of the oxygen vacancy concentration on the surface of OMS-2. In addition, using oxygen as the oxygen source and ammonia as the ammonia source not only greatly improves the atomic utilization rate, but is also economical and environmentally friendly, and has good application prospects. DETAILED DESCRIPTION
[0015] The following examples will help to understand the present invention, but the present invention is not limited thereto.
[0016] Example 1
[0017] Preparation of catalyst: The preparation of OMS-T nanorods is carried out by a mild hydrothermal redox reaction of Mn(NO3)2 and KMnO4 at different temperatures. The specific preparation steps are as follows: 3.52g Mn(NO3)2 (50wt%) is dissolved in 40mL distilled water, and then 3.16g KMnO4 is quickly added to the above solution of Mn(NO3)2, and stirred under a magnetic stirrer until KMnO4 is completely dissolved; the above solution is transferred to a 100mL polytetrafluoroethylene liner and placed in a stainless steel reactor; the reactor is placed in an electric oven and reacted at 70, 90 and 180℃ for 24h respectively; after the reaction is completed, the reactor is taken out and cooled to room temperature; the product after the reaction is filtered, repeatedly washed with distilled water, and then dried under an infrared lamp. The samples obtained above are marked as OMS-70, OMS-90 and OMS-180 respectively.
[0018] Example 2
[0019] OMS-70 catalyst (60 mg), acetophenone (0.5 mmol), and tert-amyl alcohol (2 mL) were added to a 5 mL reaction tube, and then transferred to a stainless steel autoclave; NH3 (0.5 MPa) and O2 (0.5 MPa) were then added, and then placed in a 150°C oil bath, stirred at 500 rpm for 12 hours, and the pressure was kept constant during the reaction. The reaction product was analyzed using GC / GC-MS, and the acetophenone conversion rate was 100%, and the benzamide product selectivity / yield was 91%.
[0020] Example 3-20
[0021] Except for the different catalyst types, solvent types, temperature and reaction time, the catalyst activity evaluation is the same as that of Example 2. The reaction conditions and catalytic reaction results are shown in Table 1. As can be seen from Table 1: 1) Different types of catalysts (Examples 3-9) have a great influence on the reaction, such as different crystallization temperatures of the catalysts (Examples 3-5), which have a great influence on the activity of the reaction, and commercial manganese oxides (Examples 6-9) have unsatisfactory catalytic effects; 2) Different types of solvents (Examples 10-16) have a great influence on the reaction system, and tert-amyl alcohol is found to have the best catalytic effect on the reaction system; 3) Different reaction temperatures (Examples 17-20) have a great influence on the conversion rate and yield of the reaction; 4) Different reaction times (Examples 3 and 10) have a certain influence on the conversion of the intermediate nitrile to amide. In short, different catalyst types, solvent types, reaction temperatures and reaction times will affect the efficiency of the oxidation and cleavage of aromatic ketones to amides.
[0022] Table 1 Screening of conditions for oxidative cleavage of acetophenone to generate primary amides
[0023]
[0024] Embodiment 21-78
[0025] Except for the difference in substrate, the evaluation of catalyst activity is the same as that in Example 1. The reaction conditions and catalytic reaction results are shown in Table 2. Aromatic ketone substrates with different substituent groups can undergo oxidative cleavage to generate corresponding primary amide compounds.
[0026] Table 2 Oxidative cleavage of different aromatic ketone substrates to generate primary amides
[0027]
[0028]
[0029]
[0030]
[0031]
[0032] Except for the difference in substrate, the evaluation of catalyst activity was the same as in Example 1. The reaction conditions and catalytic reaction results are shown in Table 3. In addition, through the steric hindrance effect of the ortho-substituent, some aromatic ketones with ortho-substituents were oxidatively cleaved to generate corresponding benzonitrile compounds.
[0033] Table 3 Oxidative cleavage of different aromatic ketone substrates to generate aromatic nitriles
[0034]
[0035]
[0036] The invention has high oxidation efficiency, good selectivity and high product yield; it uses oxygen as an oxygen source, is economical and environmentally friendly, and has good application prospects.
Claims
1. A method for preparing primary amides by oxidative cleavage of aromatic ketones, characterized in that: Using aromatic ketone as a model substrate, oxygen as an oxygen source, and ammonia as an ammonia source, the aromatic ketone molecules undergo oxidative cleavage under the action of the catalyst OMS-T to generate primary amide compounds; The preparation method of the catalyst: The preparation of OMS-T nanorods is carried out by a hydrothermal redox reaction between a low-valent manganese salt and KMnO4; the specific preparation steps are as follows: the low-valent manganese salt is dissolved in water, and then KMnO4 is added to the above solution of the low-valent manganese salt, and stirred until the KMnO4 is completely dissolved; the above solution is transferred to a reactor for reaction; after the reaction is completed, the reactor is taken out and cooled to room temperature; the product after the reaction is filtered, the solid is washed with water, and then dried to obtain the catalyst, which is marked as OMS-T; The low-valent manganese salt is one or more of manganese acetate, manganese nitrate and manganese sulfate; The dosage range of the low-valent manganese salt and KMnO4 is 10-30 mmol, the optimal concentration range is 0.25-0.75 mol / L, the preferred dosage range is 15-25 mmol, and the optimal concentration range is 0.375-0.625 mol / L The reaction time ranges from 12 to 36 hours, preferably from 20 to 30 hours; The reaction temperature T is in the range of 50-180°C, preferably in the range of 70-180°C.
2. The method for preparing primary amides by oxidative cleavage of aromatic ketones according to claim 1, characterized in that: The system is a heterogeneous system, and the catalyst can be recycled and reused for more than 5 times with high activity. In addition, the yield of gram-scale reaction can be as high as 89%.
3. The method for preparing primary amides by oxidative cleavage of aromatic ketones according to claim 1, characterized in that: The oxidation of the aromatic ketone uses oxygen as the oxygen source and ammonia as the ammonia source, wherein the oxygen partial pressure is 0.2-0.8MPa; the ammonia partial pressure is 0.2-0.8MPa; the reaction temperature is 120-160°C; and the reaction time is 6-24h; preferably, the oxygen partial pressure is 0.4-0.6MPa; the ammonia partial pressure is 0.4-0.6MPa; the reaction temperature is 140-160°C and the reaction time is 8-16h.
4. The method for preparing primary amides by oxidative cleavage of aromatic ketones according to claims 1 and 3, characterized in that: The formation of products can be regulated by the steric effect of the substrate. Aromatic ketones with substituents at the ortho position can be effectively oxidized and broken down to obtain corresponding aromatic nitrile compounds when acetonitrile is used as the solvent.
5. The method for preparing primary amides by oxidative cleavage of aromatic ketones according to claim 1, characterized in that: The catalytic performance is related to the amount of catalyst used. Too low an amount will affect the activity of the catalytic reaction, while too high an amount will increase the cost of the catalyst. Therefore, it is necessary to select an appropriate amount. In order to ensure the activity of the catalyst while reducing the cost of the catalyst, the molar ratio of the Mn content in the catalyst used to the substrate is in the range of 0.1-20 mol%, and the preferred molar ratio is in the range of 0.1-10 mol%.
6. The method for preparing primary amides by oxidative cleavage of aromatic ketones according to claim 1, characterized in that: The catalytic performance is related to the crystallization temperature of the catalyst. If the crystallization temperature is too high, the activity of the catalytic reaction will be reduced. This may be because when the crystallization temperature is too high, the concentration of oxygen vacancies on the catalyst surface decreases, and the catalytic activity also decreases accordingly. Therefore, it is necessary to select an appropriate crystallization temperature to prepare the catalyst. The crystallization temperature range of the catalyst is 50-180°C, and the preferred range is 70-180°C.
7. The method for preparing primary amides by oxidative cleavage of aromatic ketones according to claim 1, characterized in that: The reaction needs to be carried out in a solvent, especially for some solid aromatic ketone substrate molecules, which need to be dissolved in the solvent to be evenly dispersed, which is conducive to contact with the catalyst; the solvent used for the oxidative cleavage of the aromatic ketone is one or more of tert-amyl alcohol, 1,4-dioxane, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile, n-heptane, and N-methylpyrrolidone (NMP); the mass concentration range of the aromatic ketone in the solvent is 1-20wt%, preferably 1-10wt%.
8. The method for preparing benzamide by oxidative cleavage of aromatic ketone according to claim 1, 5 or 6, characterized in that: In the aromatic ketone molecule, the phenyl group on the benzene ring has other substituents. (N, O, S) Heterocyclic One or more of the following: The other substituents -R1 on the benzene ring or heterocyclic ring are one or more of -CH3, -OCH3, -C(CH3)3, -F, -Cl, -Br, -CF3, -NO2; the substituents -R2 are -CH3, -CH(CH3)2, -C(CH3)3, -(CH2) n One or more of CH3 (n=1-10) and phenyl; There are other substituents -R1 on the benzene ring of the aromatic ketone, and the positions of other substituents -R1 are ortho, meta or para; In ketones having other substituents on the benzene ring, the number of other substituents is 1, 2, 3, 4 or 5.