A method for preparing benzamide by oxidative cleavage of aromatic alkynes

Abstract

A method for preparing benzamide by oxidative cleavage of aromatic alkynes. The present invention provides a novel method for preparing benzamide. The method uses aromatic alkynes as substrates, oxygen as an oxygen source, ammonia as an ammonia source, and NH4I as an auxiliary agent. Under the action of OMS-2, the aromatic alkynes undergo oxidative cleavage to generate benzamide. This method has high oxidation efficiency, good selectivity, and high product yield, which is due to the regulation of the oxygen vacancy concentration on the surface of OMS-2; and using oxygen as the oxygen source and ammonia as the ammonia source, not only the atomic utilization rate is greatly improved, but also it is economical and environmentally friendly, and has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and specifically relates to designing a high-efficiency OMS-2 catalyst for use in oxidative cracking of aromatic alkynes to prepare benzamide and a preparation method thereof. Background Art

[0002] Oxygen vacancy defects play a very important role in the catalytic process of metal oxide catalysts and have attracted widespread attention. It is generally believed that oxygen vacancies act as an active site in the reaction process, on which reactants are adsorbed, activated, and desorbed, thereby improving their catalytic activity. The present invention achieves the regulation of oxygen vacancy defects in OMS-2 nanorod catalysts by changing the reaction temperature. And a series of characterization methods are used to illustrate the effect of oxygen vacancy concentration on oxidation catalytic activity.

[0003] Amides are a very important class of compounds in chemistry and biology, and are widely used as intermediates for peptide and protein synthesis, enhancers for fragrances, anti-adhesion agents, color pigments for inks, detergents and lubricants, etc. Therefore, the development of new environmentally friendly amide synthesis methods is a very important topic in modern organic synthesis. The inventors provide a synthesis method for preparing amides by oxidative catalysis of aromatic alkynes using an efficient OMS-2 catalyst. Using aromatic alkynes as substrate molecules, various amide compounds are generated by oxidative cleavage. Summary of the invention

[0004] The invention provides a novel preparation method of benzamide. In the method, aromatic alkynes are used as substrates, oxygen is used as an oxygen source, and ammonia is used as an ammonia source. Under the action of an auxiliary agent and OMS-2, the aromatic alkynes are oxidatively cracked to generate benzamide.

[0005] According to the present invention, in the alkyne molecule, the phenyl group having other substituents on the benzene ring Naphthyl (such as ), (N, O, S) heterocyclic group (such as ) or more than one of the following: the (N, O, S) heterocyclic substituent may be located at the α or β position;

[0006] Other substituents -R1 and -R2 on the benzene ring, wherein the other substituent -R1 is one or more of -CH3, -OCH3, -C(CH3)3, -F, -Cl, -Br, -CF3, and -NO2; the other substituent -R2 is one or more of -CH3, -CH2CH3, and phenyl;

[0007] In alkynes with other substituents on the benzene ring, the positions of the other substituents are ortho, meta or para; in alkynes 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. Oxygen molecules are not active enough, and a catalyst is needed to activate oxygen to form active oxygen. The present invention uses one or more of the OMS-2-T catalysts (T = 70, 90, 180 ° C) as catalysts to activate oxygen molecules, achieve oxidative cleavage of aromatic alkynes, and prepare benzamide.

[0008] 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, an appropriate amount needs to be selected. In order to ensure the activity of the catalyst and reduce the cost of the catalyst, the amount of the catalyst used is in the range of 30-70 mg, preferably in the range of 40-60 mg, and the amount of the substrate (aromatic alkyne) is in the range of 0.3-0.7 mmol, and the preferred amount of the substrate is in the range of 0.4-0.5 mmol.

[0009] According to the present invention, the oxidation effect of alkyne 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 110-160°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 130-150°C, and the reaction time is 12-24h.

[0010] According to the present invention, the reaction needs to be carried out in a solvent, especially for some solid aromatic alkyne 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 oxidation of aromatic alkynes can be one or more of tert-amyl alcohol, 1,4-dioxane, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile, n-heptane, and methanol. The preferred solvent of the present invention is tert-amyl alcohol.

[0011] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Attached Figure 1 are the XRD patterns of different catalysts OMS-180, OMS-90 and OMS-70 in Example 1;

[0013] Figure 2These are TEM and HRTEM images of different catalysts OMS-180 (a, b), OMS-90 (c, d) and OMS-70 (e, f) in Example 1. DETAILED DESCRIPTION

[0014] The following examples will help to understand the present invention, but the present invention is not limited thereto.

[0015] Example 1

[0016] Preparation of catalyst: The preparation of OMS-2 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% Mn(NO3)2 aqueous solution) 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 were marked as OMS-70, OMS-90 and OMS-180, and the grain sizes of the three samples OMS-180, OMS-90 and OMS-70 were calculated to be 20.5nm, 16.7nm and 8.5nm respectively at 2θ=12.60 (corresponding to the {110} plane of OMS-2) by the Scherrer formula (L=0.89λ / βcosθ).

[0017] Specifically, the BET specific surface areas of the three samples OMS-70, OMS-90, and OMS-180 were calculated by the Brunauer-Emmett-Teller model to be 75.1 m 2 g -1 、56.2m 2 g -1 and 30.2m 2 g -1 The micropore volumes of three samples of OMS-2 nanorods were calculated by the Dubinin-Radushkevich model, and the calculation results are shown in Table 1. As can be seen from Table 1, the micropore volume of OMS-2 is very low, because the kinetic diameter of the N2 molecule is Difficult to diffuse into the pores of OMS-2 In addition, K +The presence of ions in the OMS-2 pores also makes the pore space narrower, resulting in a further decrease in the pore volume. In addition, careful observation by electron microscopy revealed that (see Appendix Figure 2 ), their surfaces are not complete. Compared with OMS-90 and OMS-180 nanorods, the crystal structure surface of OMS-70 nanorods is more incomplete, indicating that there are more oxygen vacancy defects on the surface of OMS-70 nanorods. In addition, XPS, Raman spectroscopy, DFT theoretical calculations and other methods are used to further analyze and prove it.

[0018] Table 1 Surface area and atomic ratio of OMS-2 nanorod samples

[0019]

[0020] The present invention regulates the content of oxygen vacancy defects (OVDs) in a MnO2-based catalyst by regulating the crystallization temperature of the catalyst to improve the catalyst activity; the catalyst is described as OMS-2-T (T is the crystallization temperature of the catalyst), and the crystallization temperature T ranges from 50 to 180°C, preferably in the range of 60 to 80°C.

[0021] Example 2

[0022] 0.05 g of OMS-70 catalyst prepared in Example 1, 0.5 mmol of phenylacetylene, 0.25 mmol of NH4I and 1 mL of tert-amyl alcohol were added to a 10 mL reaction bottle in sequence, and then transferred to a stainless steel autoclave, filled with 0.5 MPa of O2 and 0.5 MPa of NH3, placed in a 130° C. oil bath, stirred for reaction for 24 h, and the pressure was kept constant during the reaction. The reaction product was analyzed using GC / GC-MS, and the phenylacetylene conversion rate was 100%, and the benzamide product selectivity was 84%.

[0023] Example 3-20

[0024] Except for the catalyst and the amount, solvent, temperature, pressure, and reaction time, the catalyst activity evaluation is the same as in Example 2. The reaction conditions and catalytic reaction results are shown in Table 2. As can be seen from Table 2, the type of catalyst (Examples 3, 9, 10, 11, 12, 13) and the amount of catalyst (Examples 4, 7, 8), solvent (Examples 16, 17, 18, 19, 20, 21, 22), oxygen and ammonia pressure (Examples 6, 14, 15), reaction temperature (Examples 3, 4, 5) and reaction time (Examples 4 and 6) have a more obvious effect on the catalytic effect.

[0025] Table 2 Preparation of benzamide by oxidative cleavage of phenylacetylene

[0026]

[0027] Embodiment 23-41

[0028] Except for the different amounts of substrate and solvent, the evaluation of catalyst activity was the same as in Example 2. The reaction conditions and catalytic reaction results are shown in Table 3. Phenyl acetylene substrates with different substituent groups can undergo oxidative cleavage to generate corresponding benzamide compounds.

[0029] Table 3 Oxidative cleavage of different phenylacetylene substrates

[0030]

[0031]

[0032]

[0033] 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 aromatic formamide by oxidative cleavage of aromatic alkynes, characterized in that: With aromatic alkynes as substrates, oxygen as oxygen source, and ammonia as ammonia source, under the action of auxiliary agents and OMS-2 catalyst, aromatic alkynes molecules undergo C≡C bond oxidative cleavage to generate aromatic formamide compounds; The auxiliary agent is NH4I; The OMS-2 catalyst is obtained by a hydrothermal redox reaction between a low-valent manganese salt and KMnO4; the specific preparation steps are as follows: dissolving the low-valent manganese salt in water, then adding KMnO4 to the above solution of the low-valent manganese salt, and stirring until the KMnO4 is completely dissolved; transferring the above solution to a reactor for reaction; after the reaction is completed, taking out the reactor and cooling it to room temperature; filtering the product after the reaction, washing the solid with water, and then drying; the above product is marked as OMS-2; The low-valent manganese salt is one or more of manganese acetate, manganese nitrate and manganese sulfate; The reaction time of the OMS-2 catalyst ranges from 12 to 36 h; The reaction temperature T of the OMS-2 catalyst is in the range of 50-180 °C; The amount of catalyst used ranged from 30 to 70 mg, and the amount of substrate aromatic alkyne ranged from 0.3 to 0.7 mmol; The aromatic alkyne molecule is , , One or more of the following: Said The heteroatom S can be replaced by N or O; The aromatic ring contains no or other substituents -R1 and -R2, wherein the other substituents -R1 are one or more of -CH3, -OCH3, -C(CH3)3, -F, -Cl, -Br, -CF3, and -NO2; the other substituents -R2 are one of -CH3, -CH2CH3, and phenyl; In alkynes with other substituents on the aromatic ring, the position of the other substituent -R1 is ortho, meta or para; In alkynes with other substituents on the aromatic ring, the number of other substituents -R1 is 1, 2, 3, 4 or 5; The solvent used for the oxidative cleavage of aromatic alkynes is tert-amyl alcohol; The reaction temperature for the oxidative cleavage of aromatic alkynes to prepare aromatic formamides is 110-160 °C.

2. The method for preparing aromatic formamide by oxidative cleavage of aromatic alkynes according to claim 1, characterized in that: The reaction time of the OMS-2 catalyst ranges from 20 to 30 h; The reaction temperature T of the OMS-2 catalyst is in the range of 60-80°C; The amount of catalyst used ranged from 40 to 60 mg, and the amount of substrate aromatic alkyne used ranged from 0.4 to 0.5 mmol.

3. The method for preparing aromatic formamide by oxidative cleavage of aromatic alkynes according to claim 1, characterized in that: The system is a heterogeneous system, and the catalyst can be recycled for more than 8 times; The concentration range of the low-valent manganese salt and KMnO4 is 0.25-0.75 mol / L.

4. The method for preparing aromatic formamide by oxidative cleavage of aromatic alkynes according to claim 3, characterized in that: The concentration range of the low-valent manganese salt and KMnO4 is 0.375-0.625 mol / L.

5. The method for preparing aromatic formamide by oxidative cleavage of aromatic alkynes according to claim 1, characterized in that: The oxidation of the aromatic alkyne uses oxygen as an oxygen source and ammonia as an ammonia source, wherein the oxygen partial pressure is 0.2-0.8 MPa, the ammonia partial pressure is 0.2-0.8 MPa, and the reaction time is 6-24 hours.

6. The method for preparing aromatic formamide by oxidative cleavage of aromatic alkynes according to claim 1 or 5, characterized in that: The oxygen partial pressure is 0.4-0.6 MPa, the ammonia partial pressure is 0.4-0.6 MPa, the reaction temperature is 130-160°C, and the reaction time is 12-24h.

7. The method for preparing aromatic formamide by oxidative cleavage of aromatic alkynes according to claim 1 or 5, characterized in that: The amount of the auxiliary agent relative to the amount of aromatic alkyne used is 0.3-0.6 equiv.

8. The method for preparing aromatic formamide by oxidative cleavage of aromatic alkynes according to claim 7, characterized in that: The amount of the auxiliary agent relative to the amount of aromatic alkyne used is 0.4-0.6 equiv.

9. The method for preparing aromatic formamide by oxidative cleavage of aromatic alkynes according to claim 1, characterized in that: The amount of the substrate aromatic alkyne used ranges from 0.3 to 0.7 mmol; the amount of the solvent used ranges from 0.5 to 3.0 mL.

10. The method for preparing aromatic formamide by oxidative cleavage of aromatic alkynes according to claim 9, characterized in that: The amount of substrate aromatic alkyne used ranges from 0.4 to 0.5 mmol; the amount of solvent used ranges from 1 to 2 mL.

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