Rice hull-based catalyst, and preparation method and application thereof

Abstract

The present application relates to the field of catalytic organic synthesis, and specifically discloses a rice husk-based catalyst and a preparation method and application thereof.The rice husk-based catalyst in the present application is used for catalyzing cross-coupling reaction of terminal alkyne; the rice husk-based catalyst is a Cu 2+ imprinted pre-ligating compound is connected with mesoporous SiO2 through-O-Si- bonds and forms a network structure; the Cu 2+ imprinted pre-ligating compound is a polynuclear Cu 2+ complex.The rice husk-based catalyst in the present application can accelerate cross-coupling reaction of terminal alkyne, accelerate reaction speed of 1,3-diynyl compound, has high conversion rate, and effectively reduces the amount of substrate.The rice husk-based catalyst has high selectivity in catalyzing cross-coupling reaction of terminal alkyne with different substituents, and does not need to add other oxidants and other reaction aids.The rice husk-based catalyst has excellent selectivity in cross-coupling of different substrates, and has a wider application prospect compared with the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalytic organic synthesis, in particular to a rice husk-based catalyst and a preparation method and application thereof. BACKGROUND

[0002] The cross-coupling reaction of terminal alkyne is one of the important reactions in the field of organic synthesis, and has a wide application in the field of drug synthesis and materials. The reaction was first reported by Carl A. Glaser, a German chemist, in 1869, and is also known as Glaser coupling reaction, and has been derived through many years of research.

[0003] Most of the Glaser reactions use transition metal to catalyze the self-coupling reaction of terminal alkyne, and the transition metals used are Cu, Au, Pd, etc. Compared with noble metal catalysts such as Au and Pd, copper catalysts are more economical, and will not pollute the environment due to the use of phosphine ligands or amine ligands. In addition, Jia et al. used CuI / I catalyzed method, which catalyzed the homogeneous coupling reaction of terminal alkyne with good yield. However, the cuprous catalyzed Glaser reaction in CuI / I is extremely sensitive to phosgene or oxygen-containing substrates, which may cause side reactions, affecting the yield and selectivity. In addition, when using cuprous catalyst, it is usually necessary to use excess oxidizing agent and other aids to improve the efficiency and selectivity of the reaction.

[0004] Some non-homogeneous catalysts for Glaser reaction have been developed at present, although high selectivity of asymmetric products is achieved, but due to the low conversion rate, in order to obtain the required product, an excess amount of substrate, i.e. terminal alkyne compound, needs to be added during the reaction process. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a rice husk-based catalyst and a preparation method and application thereof, and the catalytic effect of the rice husk-based catalyst effectively promotes the cross-coupling reaction of terminal alkyne, and the overall reaction conversion rate is high, thereby reducing the amount of substrate.

[0006] To achieve the above purpose, the technical scheme of the present application is as follows.

[0007] The present application provides a rice husk-based catalyst for catalyzing the cross-coupling reaction of terminal alkyne.

[0008] The rice husk-based catalyst is prepared by Cu 2+ The imprint pre-ligating compound is connected to mesoporous SiO2 by-O-Si- bond to form a network structure; and the Cu 2+ In the imprint pre-ligating compound, each nitrogen atom is combined with two Cu 2+ ;

[0009] The rice husk-based catalyst is prepared by the following method:

[0010] The Schiff base is mixed with copper ions, and the nitrogen atoms on the Schiff base are coordinated with the copper ions to form Cu 2+ The imprint pre-ligating compound, Cu 2+ The imprint pre-ligating compound is mixed with mesoporous SiO2, Cu 2+ The ethoxy group on the imprint pre-ligating compound undergoes alcoholysis with the hydroxyl group on the surface of the mesoporous SiO2 to form an -O-Si- bond, thereby obtaining the rice husk-based catalyst; the mesoporous SiO2 is obtained by hydrothermal synthesis using rice husk ash as a silicon source.

[0011] The rice husk-based catalyst in the application can provide more catalytically active sites, thereby improving the catalytic effect, accelerating the cross-coupling reaction of terminal alkynes, effectively improving the conversion rate, and reducing the amount of terminal alkyne compounds. Among them, Cu 2+ In the imprint pre-ligating, each nitrogen atom is combined with two Cu 2+ through coordination bonds, forming a multi-nuclear Cu 2+ complex. The multi-nuclear Cu 2+ complex has more coordination numbers, providing more adsorption active sites for Cu 2+ The imprint pre-ligating compound is loaded on the mesoporous SiO2, and the network structure formed increases the number of catalytically active sites, which can more effectively adsorb and convert substrates, thereby improving the catalytic efficiency and reducing the amount of substrates.

[0012] In the application, the nitrogen atoms in the Schiff base are coordinated with copper ions. The electron-donating ability of nitrogen is affected by the electronic effect of the nitrogen side groups, directly affecting the stability of copper ion coordination. Therefore, the nitrogen atoms in the amine groups of the Schiff base in the application have strong electron-donating properties and can form stable Cu 2+ The imprint pre-ligating compound can synthesize a multi-nuclear Cu 2+ complex by introducing multi-chelating coordination nitrogen atoms and adjusting the distance between the coordination atoms, thereby improving the catalytic effect of the rice husk-based catalyst. Through the surface chemical modification method of ion imprinting, the Cu 2+ The imprint pre-ligating compound is modified on the mesoporous SiO2, and the surface of the obtained rice husk-based catalyst becomes rough and forms a network structure, providing more Cu 2+ adsorption active sites, thereby improving the catalytic effect of the catalyst, accelerating the cross-coupling reaction of terminal alkynes, effectively improving the conversion rate, and reducing the amount of terminal alkyne compounds.

[0013] In another preferred embodiment, the Schiff base is a salicylaldehyde-based Schiff base; the Cu 2+from a copper salt, the copper salt being any one of CuCl2, CuSO4, Cu(NO3)2; preferably, the copper salt is CuCl2, which is prepared to obtain the rice husk-based catalyst with the best catalytic effect and the highest activity. The present application selects salicylaldehyde Schiff base because different types of Schiff base can have different spatial structures and geometrical shapes. For example, the molecular structure of certain Schiff base can have a larger steric effect, limiting its coordination mode or coordination number with metal ions. The more planar or rigid Schiff base can have higher coordination ability and more stable complexes. Therefore, the present application selects salicylaldehyde Schiff base to provide more adsorption active sites for copper ions, thereby improving the catalytic activity, and the Cu 2+ The imprinting pre-coordination compound has good stability.

[0014] In another preferred embodiment, the molar ratio of the Schiff base to the copper ion is 1-2:1; the Cu 2+ The molar mass ratio of the imprinting pre-coordination compound to mesoporous SiO2 is 10 mmol: 1.2-1.3 g.

[0015] The second aspect of the present application provides a preparation method of the rice husk-based catalyst, comprising the following steps:

[0016] Mixing the salicylaldehyde Schiff base with the copper salt, wherein the molar ratio of the salicylaldehyde Schiff base to the copper ion in the copper salt is 1-2:1, and a coordination chelation reaction occurs in an ethanol environment at 35-80°C to obtain the Cu 2+ The initial concentration of the copper salt in the ethanol solution is 0.5-1 mol / L;

[0017] Mixing cetyltrimethylammonium bromide, ammonia water and water to obtain a treatment solution; mixing a silicon source with the treatment solution, adjusting the pH to 10-11, and hydrothermally reacting at 100-120°C for 48-72 h to obtain the mesoporous SiO2; the mass-volume ratio of the silicon source, cetyltrimethylammonium bromide, water and ammonia water is 1 g: 0.4-0.6 g: 15-25 mL: 12-15 mL;

[0018] Mixing the Cu 2+ Mixing the imprinting pre-coordination compound and the mesoporous SiO2 in a mass-volume ratio of 10 mmol: 1.2-1.3 g, and reacting at 70-100°C for 46-48 h to obtain the rice husk-based catalyst.

[0019] In another preferred embodiment, the specific preparation process of the silicon source is as follows:

[0020] Soaking the rice husk powder in a hydrochloric acid solution, filtering, washing to neutral, and heating at 700-750°C for 30-45 min to obtain the rice husk ash;

[0021] The rice husk ash is mixed with an alkali solution at a mass ratio of 1:4-6, extracted at 80-90 DEG C for 4-5 hours, filtered, and the precipitate is removed to obtain a silicon source.

[0022] In another preferred embodiment, the alkali solution is a sodium hydroxide solution with a concentration of 2-3 mol / L.

[0023] The mass percentage of the ammonia water is 25-28%, and the mass percentage of the hydrochloric acid solution is 2-3%.

[0024] The third aspect of the present application provides a rice husk-based catalyst for catalyzing the cross-coupling of terminal alkyne to form 1,3-diynyl compounds.

[0025] The fourth aspect of the present application provides a preparation method of 1,3-diynyl compounds, comprising the following steps:

[0026] The terminal alkyne compound, a solvent, and a base are mixed, and the rice husk-based catalyst is added, and a catalytic oxidation reaction is carried out at 45-55 DEG C for 15-20 hours, centrifuged, the filtrate is taken, purified, and the 1,3-diynyl compound is obtained.

[0027] The molar volume ratio of the rice husk-based catalyst IIP-Cu, the terminal alkyne compound, and the solvent is 0.2-0.5 mmol:1 mmol:2-3 mL.

[0028] The molar amount of the base accounts for 10-35% of the terminal alkyne compound.

[0029] In another preferred embodiment, the solvent is obtained by mixing reagent A with water at a volume ratio of 1:1-7.

[0030] The reagent A is any one of methyl sulfoxide, N,N-dimethylformamide, methanol, tetrahydrofuran, ethanol, 1,4-dioxane, polyethylene glycol, and acetonitrile.

[0031] The base is any one of 1,8-diazabicycloundec-7-ene, potassium carbonate, triethylamine, triethylenediamine, and sodium hydroxide.

[0032] In another preferred embodiment, the specific process of the purification is as follows:

[0033] The filtrate is extracted with dichloromethane, dried with anhydrous Na2SO4, filtered, concentrated, and purified by column chromatography to obtain the 1,3-diynyl compound.

[0034] The eluent used in the column chromatography is a mixed solution of ethyl acetate and petroleum ether at a volume ratio of 50-52:1.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The rice husk-based catalyst in this invention is obtained through Cu 2+ In the imprinted precoordinated compound, each nitrogen atom is bonded to two Cu atoms via coordinate bonds. 2+ This provides more Cu 2+ The active sites for adsorption are used to adsorb more Cu. 2+ Then, through the -O-Si- bond, Cu... 2+ Imprinted pre-coordination compounds loaded on mesoporous SiO2 form a network structure that can effectively increase the number of catalytic active sites, thereby enabling more effective adsorption and conversion of reactants, improving catalytic efficiency, and effectively reducing the amount of substrate required.

[0037] (2) This invention synthesizes polynuclear Cu by coordinating the nitrogen atom in the amino group of the Schiff base with a copper ion, introducing multiple chelated nitrogen atoms and adjusting the distance between the coordinating atoms. 2+ The complex enhances the catalytic effect of the rice husk-based catalyst. Then, the divalent copper ions are loaded onto the surface of mesoporous SiO2 to obtain the rice husk-based catalyst, which can accelerate the cross-coupling reaction of terminal alkynes and speed up the reaction rate of 1,3-diyne compounds. The entire reaction process is mild and does not require the addition of other oxidants or reaction aids. Only oxygen in the air is needed as an oxidant to achieve excellent selectivity and good catalytic effect. The conversion rate is high and the amount of substrate used is effectively reduced.

[0038] (3) This invention provides the application of rice husk-based catalysts in the catalytic cross-coupling of terminal alkynes with different substituents to form 1,3-diyne compounds. The rice husk-based catalyst, terminal alkynes with different substituents, a base, and a solvent are reacted in air to obtain 1,3-diyne compounds in high yield. Its application in the catalytic cross-coupling of terminal alkynes with different substituents to form 1,3-diyne compounds yielded excellent selectivity and yield. This invention uses rice husk material as a support to prepare the catalyst, resulting in low preparation cost, mild reaction conditions, and high catalytic activity. Attached Figure Description

[0039] Figure 1 The figure shows the morphological characteristics of the rice husk-based catalyst. In the figure, RH represents rice husk powder, RH@MCM-41 represents mesoporous SiO2, and IIP-Cu represents the rice husk-based catalyst.

[0040] Figure 2The element composition and chemical state of the rice husk-based catalyst are analyzed by X-ray photoelectron spectrometer technology, wherein a is an element composition analysis result map, b is a high-resolution N1s XPS spectrum of IIP-Cu, and c is a high-resolution Cu 2p XPS spectrum of IIP-Cu.

[0041] Figure 3 The X-ray energy dispersive spectroscopy mapping result map of the rice husk-based catalyst is shown in the figure; wherein a is the X-ray energy dispersive spectroscopy mapping result map of C, b is the X-ray energy dispersive spectroscopy mapping result map of N, c is the X-ray energy dispersive spectroscopy mapping result map of O, d is the X-ray energy dispersive spectroscopy mapping result map of Si, and e is the X-ray energy dispersive spectroscopy mapping result map of Cu. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the technical solutions of the present application and to implement them, the present application will be further described below in conjunction with specific embodiments and drawings, but the embodiments are not limiting to the present application. The following test methods and detection methods are all conventional methods unless otherwise specified; the reagents and raw materials are all commercially available unless otherwise specified.

[0043] Most of the traditional methods for preparing 1,3-conjugated diacetylene compounds still use transition metal catalysis, although the yield is high, but the use of noble metals greatly limits its subsequent application, and the use of phosphine ligands or amine ligands will pollute the environment. The use of monovalent copper salt instead of noble metal requires a large amount of auxiliary to improve the reaction efficiency and selectivity. Some heterogeneous catalysts for Glaser reaction have been developed, which can achieve high selectivity of asymmetric products, but a large excess of substrate is required and ideal products can be obtained under high temperature conditions, which is contrary to the concept of green chemistry.

[0044] The present application provides a rice husk-based catalyst and its preparation method and application. The rice husk-based catalyst with high catalytic activity is prepared by taking rice husk as the carrier, which is applied to the catalytic synthesis of 1,3-diynyl compounds with terminal alkyne of different substituents, without adding other oxidants and reaction aids, only using oxygen in the air as the oxidant, which can achieve good selectivity and excellent catalytic effect. The copper ion is added into the alcohol solution of salicylaldehyde Schiff base to form a pre-ligating compound, and then the pretreated mesoporous SiO2 is added to obtain the rice husk-based catalyst. The catalyst is prepared by taking waste rice husk as the carrier, which has low preparation cost, mild reaction conditions, and high catalytic activity of the obtained rice husk-based catalyst.

[0045] A rice husk-based catalyst and its preparation method and application are described below.

[0046] Example 1

[0047] A preparation method of a rice husk-based catalyst, comprising the following steps:

[0048] S1, 2.2137g of 3-aminopropyltriethoxysilane, 1.4655g of salicylaldehyde and 20mL of ethanol are mixed, and the temperature is raised to 80 DEG C to reflux for 24h, the reaction is monitored by thin layer chromatography, and after the reaction is completed, an alcohol solution of salicylaldehyde Schiff base is obtained.

[0049] S2, 0.6723g of CuCl2 is dissolved in 10mL of ethanol, and the alcohol solution of salicylaldehyde Schiff base is slowly added dropwise, and a coordination chelation reaction occurs at 25 DEG C to obtain Cu 2+ The alcohol solution of the imprint pre-coordination compound; wherein the molar ratio of Cu 2+ In the CuCl2 to salicylaldehyde Schiff base in the alcohol solution of salicylaldehyde Schiff base is 1:2.

[0050] S3, the rice husk powder is soaked with a hydrochloric acid solution with a mass percentage of 2.5% for 0.5h, suction filtered, washed to neutral, dried, and put into a muffle furnace to be ashed at 700 DEG C for 30min to obtain rice husk ash; then, the rice husk ash is subjected to alkalization extraction with a sodium hydroxide solution with a concentration of 2mol / L at 80 DEG C for 5h, filtered, and the precipitate is taken out and dried to obtain a silicon source; wherein the mass ratio of the ashed rice husk powder to the sodium hydroxide solution is 1:4.

[0051] S4, cetyltrimethylammonium bromide is dissolved in water, and ammonia water with a mass percentage of 26% is added to obtain a treatment liquid; the silicon source is added to the treatment liquid, the pH is adjusted to 10, and hydrothermal reaction is carried out at 120 DEG C for 72h to obtain mesoporous SiO2, and is recorded as RH@MCM-41; wherein the mass-volume ratio of the silicon source, cetyltrimethylammonium bromide, water and ammonia water is 1g:0.58g:20mL:12.8mL.

[0052] S5, the alcohol solution of the imprint pre-coordination compound is mixed with 1.2g of RH@MCM-41, and after the temperature is raised to 80 DEG C and reacted for 48h, it is filtered, washed with anhydrous ethanol for 3 times, and dried at 80 DEG C to obtain a rice husk-based catalyst, wherein the mass fraction of Cu 2+ In the alcohol solution of the imprint pre-coordination compound is 0.5%. 2+ In the alcohol solution of the imprint pre-coordination compound, the mass fraction of Cu 2+ The molar mass of the imprint pre-coordination compound is 10mmol.

[0053] The morphology of the IIP-Cu prepared in the above embodiment 1 is characterized, as shown in Figure 1 The infrared spectra of the rice husk before and after pretreatment and the rice husk-based catalyst are compared and analyzed, and it is obtained that in the FT-IR spectrum of RH, 3403cm -1 , 2855cm -1 and 1109cm -1The characteristic peak at 1109 cm⁻¹ is attributed to the bending vibrations of OH, CH, and Si-O-Si bonds. For RH@MCM-41, since no new functional groups are introduced, the position of the characteristic peak does not change significantly compared to RH. However, for IIP-Cu, compared to RH@MCM-41, due to the newly added Si-O-Si bending vibration, the characteristic peak position at 1109 cm⁻¹... -1 A strong absorption peak appeared at 2925 cm⁻¹, proving that Si-OH and Si-OEt were successfully cross-linked with the RH@MCM-41 surface. Furthermore, a strong absorption peak was observed at 2925 cm⁻¹. -1 and 2855cm -1 The characteristic peak of the CH bond at [location] is enhanced compared to that at RH@MCM-41, which is due to the introduction of -CH2 on the functional monomer of the modified group. Furthermore, at 1564 cm⁻¹... -1 The newly added characteristic peak at 3403 cm⁻¹ belongs to the typical bending vibration of the C=N bond. Furthermore, due to the introduction of the -NH₂ group, a peak appears at 3403 cm⁻¹. -1 and 1612cm -1 The absorption band at the point is greatly enhanced, indicating that Schiff base functional groups were successfully introduced into the surface of the RH@MCM-41 composite material, thus demonstrating that IIP-Cu was successfully synthesized.

[0054] The elemental composition and chemical state of the IIP-Cu prepared in Example 1 were analyzed using X-ray photoelectron spectroscopy (XPS). Figure 2 As shown in Figure a, the presence of carbon, silicon, nitrogen, oxygen, chlorine, and copper in the IIP-Cu material, compared to the RH@MCM-41 spectrum, indicates that the functionalized modification groups and copper were successfully introduced into the RH@MCM-41 supported material. The high-resolution N1s XPS spectrum of IIP-Cu, shown in Figure b, can be resolved to CN / C=N and HN bonds, located at 399.58 eV and 401.65 eV respectively, consistent with previous FT-IR analysis results. Furthermore, the peak at binding energy of 402.69 eV can be attributed to a Cu-N bond, indicating that the coordination form of copper ions in the IIP-Cu catalyst is mainly in the form of Cu-N bonds. The high-resolution Cu 2p XPS spectrum of IIP-Cu, shown in Figure c, has peaks at 932.1 eV and 952.0 eV attributed to Cu... + The peaks at 933.2 eV and 953.0 eV are attributed to Cu. 2+ The high-resolution Cu 2p XPS spectrum of IIP-Cu indicates that Cu coexists in IIP-Cu. + and Cu 2+ Furthermore, the presence of Cu-N bonds was still observed in the high-resolution Cu 2p XPS spectrum, which further explains the chemical state and coordination mode of copper ions in IIP-Cu.

[0055] In addition, the X-ray energy dispersive spectroscopy mapping of the rice husk-based catalyst IIP-Cu shows that the elements of C, N, O, Si and Cu are uniformly distributed on the surface of the rice husk-based material, as shown in FIG. 2. From the above description, it can be seen that the copper ions are uniformly dispersed on the surface of the rice husk-based catalyst without agglomeration, which further indicates that we have successfully synthesized the rice husk-based catalyst IIP-Cu with rice husk as the carrier. Figure 3

[0056] Example 2

[0057] Synthesis of 1,3-diynyl compounds

[0058] 1. Selection of reaction solvent

[0059] IIP-Cu in Example 1, 1 mmol of phenylacetylene and 1 mmol of 4-ethynyl anisole were mixed, 2 mL of different solvents and 1,8-diazabicycloundec-7-ene were sequentially added to the reaction bottle, and the reaction was carried out at 50°C under 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the system was centrifuged, and the separated reaction liquid was extracted with dichloromethane, dried with anhydrous Na2SO4, filtered, concentrated and purified by column chromatography to obtain the target product 1,3-conjugated diynyl; wherein the eluent used in column chromatography was a mixed solution of ethyl acetate and petroleum ether with a volume ratio of 50:1; the yield is shown in Table 1. The amount of IIP-Cu added was 2.5 mol% of the percentage of terminal alkyne compounds, and the amount of 1,8-diazabicycloundec-7-ene added was 20 mol% of the percentage of terminal alkyne compounds. The reaction equation is as follows:

[0060]

[0061] Table 1 Conversion rate of 1,3-conjugated diynyl obtained under different solvents

[0062]

[0063]

[0064] Note: DBU refers to 1,8-diazabicycloundec-7-ene, the same below.

[0065] As shown in the experimental results of Table 1, when methanol and water with a volume ratio of 1:1 are selected as the solvent, the reaction conversion rate is the highest, so the mixed solution of methanol and water is used as the solvent of the reaction system, and further optimization adjustment is carried out.

[0066] 2. Selection of different proportions of reaction solvent

[0067] ​The preparation method in 1 was used, and different proportions of methanol and water were selected for reaction, and the conversion rate was shown in Table 2.

[0068] Table 2 Influence of different proportions of methanol and water on reaction conversion rate

[0069]

[0070] As shown in the experimental results in Table 2, when the ratio of methanol and water reaches 3:17, the reaction conversion rate is the highest. Under this reaction condition, the conversion rate increases first and then decreases with the increase of water content. The experimental results show that due to the intervention of the surface modification group of the carrier, the hydrophilicity of the catalyst material is greatly enhanced, so that it can catalyze the reaction in the mixed solvent containing water. However, under the condition of pure water, the conversion rate decreases significantly, because under the condition of pure water, the catalyst material cannot be well dispersed in the reaction system, and there is a phenomenon of agglomeration and adhesion, which leads to the decrease of catalyst utilization rate. In addition, the solubility of the raw materials in water is poor, and many factors lead to the trend of a large decrease in conversion rate when the water content exceeds 90%. Therefore, the ratio of methanol and water is finally determined as 3:17 as the reaction solvent.

[0071] 3. Selection of base type

[0072] The preparation method in 1 was used, and different bases were selected for reaction, and the conversion rate was shown in Table 3.

[0073] Table 3 Influence of different bases on reaction conversion rate

[0074]

[0075] Note: "-" means not containing this item.

[0076] As shown in the experimental results in Table 3, the influence of base on the cross-coupling reaction of terminal alkyne was studied. As can be seen from the table, under the condition of not adding any base, there is still a yield of 15%, but the selected inorganic bases in the reaction have a conversion rate of not more than 20%, which shows that the presence of inorganic base does not bring positive benefits to the reaction, and the addition of NaOH even inhibits the reaction. This is because the inorganic base has strong basicity, which destroys the structure of copper ions dispersed on the surface of the catalyst material, resulting in a decrease in conversion rate. The selected organic base system all reaches a yield of more than 20%, and the introduction of DBU makes the reaction yield reach 84%. Although DBU is a strong basic reagent, it is a weak nucleophile, which makes it more prone to combine with protons rather than carbon atoms. At the same time, DBU has a certain reducing property, which can reduce the divalent copper on the surface of the catalyst to monovalent, thereby accelerating the start of the terminal alkyne coupling reaction and greatly improving the reaction conversion rate. Therefore, DBU is selected as the base used in the reaction system.

[0077] 4. Selection of catalyst amount

[0078] The preparation method in 1 was used to select different catalyst amounts for the reaction, and the conversion rate is shown in Table 4.

[0079] Table 4 Effect of different catalyst amounts on reaction conversion rate

[0080]

[0081]

[0082] As shown in the experimental results in Table 4, the effect of catalyst amount on reaction conversion rate was investigated. The experimental results showed that when the catalyst content was low, the reaction was difficult to reach a high conversion rate within 15h, when the catalyst content reached 2.5mol%, the reaction could reach a high conversion rate within 15h. With the continued increase of catalyst addition amount, the conversion rate reached the highest. Therefore, the use amount of catalyst was fixed at 2.5mol%.

[0083] 5. Selection of gas

[0084] The preparation method in 1 was used to select different gases for the reaction, and the conversion rate is shown in Table 5.

[0085] Table 5 Effect of different gases on reaction conversion rate

[0086]

[0087] As shown in the experimental results in Table 5, under the optimal reaction conditions obtained, filling nitrogen in the reaction system, no reaction occurred at all, due to the lack of oxidant oxygen oxidation, the copper alkyne intermediate was difficult to convert into the corresponding coupling product. Further indicating that the oxygen in the air participates in the reaction, the copper alkyne intermediate is oxidized by oxygen into the corresponding target product, releasing copper ions on the surface of IIP-Cu, which can enter the next cycle process, thereby verifying the catalytic mechanism of the reaction.

[0088] 6. Selection of different substrate amounts

[0089] The preparation method in 1 was used to select different substrate amounts for the reaction, and the conversion rate is shown in Table 6.

[0090] Table 6 Effect of different substrate amounts on reaction conversion rate

[0091]

[0092]

[0093] Since the addition ratio of two different substrates has a certain influence on the selectivity of the cross-coupling reaction of terminal alkyne, the addition ratio of two different substrates was studied, and the results are shown in Table 6. When the ratio is controlled at 1:1, the yield of the target product is 84%. When the reaction ratio is controlled at 1:1.1 and 1:1.2, it can be found that the yield of the cross-coupling corresponding product does not have obvious improvement compared with the ratio of 1:1. Excess p-methoxyphenylacetylene will gradually convert into the corresponding product of p-methoxyphenylacetylene self-coupling after the consumption of phenylacetylene with the increase of reaction time, thereby causing waste. Although the reaction yield is the highest at the ratio of 1:1.2, considering that the yield improvement is limited and a relatively large amount of raw materials is required, therefore, in combination with the concept of green chemistry, the reaction ratio of 1:1 is selected as the feeding ratio for the subsequent substrate exploration after the cross-coupling of terminal alkyne, and subsequent research is carried out.

[0094] Now taking the rice husk-based catalyst IIP-Cu prepared in Example 1 and the above-mentioned 1-6 optimized reaction conditions as an example, the application effect thereof in the catalytic synthesis of 1,3-diynyl compounds is explored.

[0095] Application Example 1

[0096] 40 mg of rice husk-based catalyst IIP-Cu, 1.0 mmol of substrate A / 1.1 mmol of substrate B, 0.2 mmol of D DBU and 2 ml of methanol / H2O (3:17) were sequentially added to the reaction bottle, and the reaction was carried out at 50°C under 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the system was centrifuged, the separated reaction liquid was extracted, dried with anhydrous Na2SO4, filtered, concentrated, and column chromatography was used for separation to obtain the target product 1,3-conjugated diyne. The specific results are shown in Table 7. The reaction equation is as follows:

[0097]

[0098] Table 7 1,3-diynyl compounds obtained by cross-coupling reaction of terminal alkyne compounds with different substituents

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105] From the results in Table 7, it can be seen that based on the optimized reaction conditions, the substrate scope of terminal alkyne with different substituents is expanded. The results show that among the tested substrates, the aryl ethynes containing electron-withdrawing substituents F, CI, Br, CF3; electron-rich substituents alkyl, propionyl, methoxy can all successfully undergo cross-coupling reaction to generate the corresponding asymmetric aryl-containing 1,3-diynes products, such as products a ~ h, and have a high yield of 81% ~ 86%.

[0106] The phenyl acetylene with -NH2 group can also be used under this condition to provide asymmetric 1,3-diyne target products, such as products i ~ l, with a yield of 80 ~ 86%. At the same time, aryl terminal alkyne containing electron-rich substituents can undergo cross-coupling reaction with 2-methyl-3-butyne-2-ol to obtain 1,3-diyne compounds with aryl and alkyl at both ends, such as products m ~ q. Halogen-substituted aromatic alkynes, -CI such as products r and s, -Br such as product t, -F such as product u, and even strong electron-withdrawing group -CF3 such as product v can also react and produce the desired asymmetric 1,3-diyne with a good yield.

[0107] In addition, under standard conditions, 4-methoxyphenyl acetylene can undergo cross-coupling reaction with 1-ethynyl-1-cyclohexene, such as product w, with a yield of 86%. More importantly, aliphatic alkyne compounds also have good reactivity, such as product x.

[0108] It can be proved that the prepared rice husk-based catalyst IIP-Cu has good reaction activity, reaction selectivity and universality, and can catalyze most of the cross-coupling reactions containing terminal alkyne, and all can achieve good actual separation yield.

[0109] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A rice hull-based catalyst, characterized by, The rice husk-based catalyst is used for catalyzing cross-coupling reaction of terminal alkyne; the rice husk-based catalyst is prepared by Cu 2+ The imprint pre-ligating compound is connected with mesoporous SiO2 through -O-Si- bond to form a network structure; the Cu 2+ In the imprint pre-ligating compound, each nitrogen atom is combined with two Cu 2+ ; The rice husk-based catalyst is prepared according to the following method: The Schiff base is mixed with copper ions, the nitrogen atom in the amine group of the Schiff base coordinates with the copper ions to form Cu 2+ The imprint pre-ligating compound is mixed with mesoporous SiO2, and Cu 2+ The imprint pre-ligating compound is mixed with mesoporous SiO2, and Cu 2+ The ethoxy group on the imprint pre-ligating compound and the hydroxyl group on the surface of mesoporous SiO2 undergo alcoholysis reaction to form an -O-Si- bond, thereby obtaining the rice husk-based catalyst; the mesoporous SiO2 is obtained by hydrothermal synthesis method using rice husk ash as a silicon source; and the Schiff base is a salicylaldehyde-based Schiff base.

2. The rice hull-based catalyst of claim 1, wherein, The Cu 2+ from a copper salt, the copper salt being any one of CuCl2, CuSO4, Cu(NO3)2.

3. The rice hull-based catalyst of claim 2, wherein, The molar ratio of the Schiff base to the copper ion is 1-2:1; the Cu 2+ The molar mass ratio of the imprint pre-ligating compound to the mesoporous SiO2 is 10 mmol: 1.2 g-1.3 g.

4. A process for the preparation of the rice hull-based catalyst of claim 3, characterized in that, The method comprises the following steps: The salicylaldehyde Schiff base is mixed with a copper salt, wherein the molar ratio of the salicylaldehyde Schiff base to copper ions in the copper salt is 1-2:1, and a coordination chelation reaction occurs in an ethanol environment at 35-80 DEG C to obtain Cu 2+ The imprint pre-coordination compound is obtained by mixing the salicylaldehyde Schiff base with the copper salt in ethanol, wherein the initial concentration of the copper salt in ethanol is 0.5-1 mol / L; The cetyltrimethylammonium bromide, ammonia water and water are mixed to obtain a treatment solution; the silica source is mixed with the treatment solution, the pH is adjusted to 10-11, and the hydrothermal reaction is carried out at 100-120 DEG C for 48-72 hours to obtain the mesoporous SiO2; the mass-volume ratio of the silica source, cetyltrimethylammonium bromide, water and ammonia water is 1g: 0.4-0.6g: 15-25ml: 12-15ml; Cu 2+ The imprint pre-ligating compound is mixed with mesoporous SiO2in a molar mass ratio of 10 mmol: 1.2 g ~ 1.3 g, and reacted at 70 °C ~ 100 °C for 46 h ~ 48 h to obtain a rice husk-based catalyst.

5. The method for preparing the rice husk-based catalyst according to claim 4, characterized in that, The specific preparation process of the silica source is as follows: The rice husk powder is soaked in a hydrochloric acid solution, filtered, washed to neutral, heated at 700-750 DEG C for 30-45 minutes to obtain rice husk ash; The rice husk ash is mixed with an alkali solution according to a mass ratio of 1:4-6, extracted at 80-90 DEG C for 4-5 hours, filtered, and the precipitate is obtained to obtain the silica source.

6. The method of claim 5, wherein the rice hull-based catalyst is prepared by the steps of: The alkali solution is a sodium hydroxide solution with a concentration of 2-3 mol / L; The mass percentage of the ammonia water is 25-28%, and the mass percentage of the hydrochloric acid solution is 2-3%.

7. The rice husk-based catalyst of claim 3 is used for catalyzing the cross-coupling of terminal alkyne to form 1,3-diynyl compounds.

8. A method for preparing a 1,3-diyn compound, characterized by, The method comprises the following steps: The terminal alkyne compound, the solvent and the base reagent are mixed, the rice husk-based catalyst of claim 3 is added, and the catalytic oxidation reaction is carried out at 45-55 DEG C for 15-20 hours; centrifugation, taking the supernatant, purification, obtaining the 1,3-diynyl compound; wherein the molar volume ratio of the terminal alkyne compound, the rice husk-based catalyst and the solvent is 1mmol: 0.2-0.5mmol: 2-3ml; The molar amount of the base reagent accounts for 10-35% of the molar amount of the terminal alkyne compound.

9. The method of claim 8, wherein the 1,3-diynene compound is prepared by the reaction of a 1,3-diynene compound of formula (2) with a compound of formula (3) in the presence of a base. The solvent is obtained by mixing reagent A with water according to a volume ratio of 1:1-7; The reagent A is any one of methyl sulfoxide, N,N-dimethylformamide, methanol, tetrahydrofuran, ethanol, 1,4-dioxane, polyethylene glycol and acetonitrile; The base reagent is any one of 1,8-diazabicycloundec-7-ene, potassium carbonate, triethylamine, triethylenediamine and sodium hydroxide.

10. The method for preparing the 1,3-diyne compound according to claim 8, characterized in that, The specific process of the purification is as follows: The filtrate is extracted with dichloromethane, dried with anhydrous Na2SO4, filtered, concentrated, and the 1,3-diynyl compound is obtained after column chromatography purification; The eluent used in the column chromatography is a mixed solution of ethyl acetate and petroleum ether with a volume ratio of 50-52:1.

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