Method for preparing β-silyl azoaromatic compounds by catalysis of chitosan Schiff base copper-based functional materials

Abstract

The invention discloses a method for preparing β-silyl azaaromatic compounds by catalysis of chitosan Schiff base copper-based functional materials. The chitosan Schiff base copper-based functional material is to use salicylaldehyde / 5-bromosalicylaldehyde / 3,5-di-tert-butyl salicylaldehyde to exchange aldehyde groups and amino groups with chitosan in an acidic ethanol solution, and then wash and dry the chitosan Schiff base multiple times, and the chitosan Schiff base is exchanged and adsorbed with a soluble divalent copper salt solution multiple times to obtain the chitosan Schiff base copper-based functional material. Using the above prepared catalytic material, alkenyl-substituted azaaromatic compounds and (dimethylphenylsilyl) boric acid pinacol ester are used as template substrates to prepare corresponding β-silyl azaaromatic compounds. This scheme has the advantages of simple operation, mild reaction conditions, low cost, high catalytic activity, high product yield, etc.; the yield of the obtained target product is more than 80%.

Description

Technical Field

[0001] The invention relates to organic chemistry, and in particular to a method for preparing beta-silyl azaaromatic compounds by catalysis of chitosan Schiff base copper-based functional materials. Background Art

[0002] Organosilicon compounds are an important class of functional molecules that play a very important role in the synthesis of drug molecules, natural products and materials science. They can also participate in chemical reactions as ligands or catalytic materials, increasing the selectivity of the reaction. Azoaromatic compounds are an important class of active intermediates, drug molecules and natural product molecules. Currently, modification of azoaromatic compounds is still one of the main ways to obtain functionalized heterocyclic aromatic compounds. β-Silyl azoaromatic compounds are an important class of organic synthesis intermediates that can be used for coupling reactions and oxidation reactions, etc., and are key intermediates in the synthesis of drug molecules and natural products. For example, silyl groups can be converted into hydroxyl and ester groups under certain conditions. So far, the exploration of β-silyl azoaromatic compounds obtained by silicon addition reaction of alkenyl-substituted azoaromatic compounds has been extremely limited. Recently, the literature (Chem. Commun., 2020, 56, 1693–1696.) used (dimethylphenylsilyl)boronic acid pinacol ester as a silicon source and alkenyl-substituted nitrogen heteroaromatic compounds as substrates for asymmetric conjugate addition reactions to synthesize various chiral alkenyl-substituted nitrogen heteroaromatic silicon addition products. The experimental results show that at room temperature, when Cu(MeCN)4PF6 is used as a catalyst, chiral dinaphthyl diphenylphosphine complex B2 is used as a ligand, the solvent is tetrahydrofuran, sodium tert-butoxide is used as a base additive, and methanol is used as a proton source for 12 hours, excellent results are obtained. However, the highly toxic chemical catalyst Cu(MeCN)4PF6 is used in this literature report, which is very harmful to the human body, cumbersome to operate, and cannot be recycled, which will cause environmental pollution.

[0003] Therefore, it is necessary to develop a new method that is low-cost, simple to operate, mild under synthetic conditions, recyclable, and does not cause environmental pollution, and can efficiently and greenly convert alkenyl-substituted nitrogen aromatic compounds into β-silyl nitrogen aromatic compounds.

[0004] Chitosan is the second largest renewable resource in nature. It is environmentally friendly and has a strong chelating effect on metals. It has the characteristics of biocompatibility, degradability and antibacterial properties. Modifying chitosan with Schiff base can not only retain the biocompatibility, degradability and antibacterial properties of chitosan, but also improve the physical and chemical properties of chitosan, and improve its stability and solubility. In the prior art, Chinese patent application CN202110108981.1 discloses a method of preparing chitosan Schiff base material by modifying chitosan with vanillin, and chelating metal zinc to obtain a new type of sustained-release agent. Chitosan Schiff base material contains a large number of imine groups, which are easy to coordinate with transition metals. Therefore, it is widely used in the fields of sustained-release agents, industrial adsorption and catalysis. For example, it is reported (Tetrahedron Lett., 2015, 56, 4135–4142.) that chitosan Schiff base material is prepared by modifying chitosan with salicylaldehyde, and Cu is adsorbed. 2+ Catalyze Chan-Lam CN coupling reaction. However, there are few reports on chitosan Schiff base copper-based functional materials in building C-Si bonds. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of high cost, complicated operation, environmental pollution and difficulty in recycling catalytic materials in the synthesis of β-silyl nitrogen heteroaromatic compounds in the above-mentioned background technology, and to provide a preparation method of chitosan Schiff base copper-based functional materials, and to provide a method for preparing β-silyl nitrogen heteroaromatic compounds by converting alkenyl substituted nitrogen heteroaromatic compounds using the material.

[0006] The technical principle of the present invention is to utilize the biocompatibility and strong coordination ability of chitosan Schiff base copper-based functional materials to promote its catalytic activity to be higher; the chitosan Schiff base itself also contains a large number of imine groups, and the catalytic reaction can be achieved without adding any base, and the catalytic material is recyclable, which is in line with the concept of green chemistry and has broad prospects for industrial application.

[0007] The technical solution of the present invention is: a method for preparing β-silyl azoaromatic compounds by catalysis of chitosan Schiff base copper-based functional materials, characterized in that it comprises the following steps:

[0008] 1) placing chitosan and aldehyde compounds in a solvent formed by mixing glacial acetic acid and anhydrous ethanol to react, thereby obtaining a chitosan Schiff base material, and then placing the chitosan Schiff base material in a divalent copper ion solution for adsorption, thereby obtaining a chitosan Schiff base copper-based functional material Schiff-CS@Cu;

[0009] 2) Adding alkenyl-substituted nitrogen heteroaromatic compound I, (dimethylphenylsilyl)boronic acid pinacol ester, and chitosan Schiff base copper-based functional material Schiff-CS@Cu to a mixed solution formed by methanol and water, and stirring at room temperature for 3 to 12 hours, wherein the molar ratio of alkenyl-substituted nitrogen heteroaromatic compound I, (dimethylphenylsilyl)boronic acid pinacol ester, and copper loaded in functional material Schiff-CS@Cu is 1:(1.2 to 2.0):(0.001 to 0.005),

[0010] The chemical reaction equation is as follows:

[0011]

[0012] Wherein, R1 is one of phenyl, p-methylphenyl, p-methoxyphenyl, p-chlorophenyl, p-bromophenyl, and biphenyl;

[0013] 3) After the reaction is completed, the reaction is filtered, and the precipitate is washed, dried, and recovered to obtain the chitosan Schiff base copper-based functional material Schiff-CS@Cu. The filtrate is extracted, dried, and rotary evaporated, and finally separated by column chromatography to obtain the β-silyl nitrogen aromatic compound II.

[0014] Preferably, in step 2), methanol and water are mixed in a volume ratio of 4 to 5:1 to form a mixed solution, and (dimethylphenylsilyl)boronic acid pinacol ester is added to the mixed solution at a concentration of 0.2 to 0.5 mmol / mL.

[0015] Preferably, in step 2), the molar ratio of the alkenyl-substituted nitrogen aromatic compound I, (dimethylphenylsilyl)boronic acid pinacol ester, and the copper loaded in the functional material Schiff-CS@Cu is 1:2.0:0.005.

[0016] Preferably, in step 3), ethyl acetate and petroleum ether are used as a developing solvent in a volume ratio of 1:35 in column chromatography separation.

[0017] Preferably, in step 1), the copper content in the chitosan Schiff base copper-based functional material Schiff-CS@Cu is 0.3-1.6 mmol / g.

[0018] Preferably, in step 1), the preparation of the chitosan Schiff base copper-based functional material Schiff-CS@Cu comprises the following steps:

[0019] a. Add chitosan and an aldehyde compound to a solvent formed by a mixture of glacial acetic acid and anhydrous ethanol, wherein the aldehyde compound is one of salicylaldehyde, 5-bromosalicylaldehyde and 3,5-di-tert-butylsalicylaldehyde, adjust the pH value to 4.0-5.5, stir at 65-85° C. for 12-24 hours, separate, wash and dry to obtain a chitosan Schiff base material;

[0020] b. Add the obtained chitosan Schiff base material into a divalent copper salt aqueous solution and stir for 3 to 9 hours;

[0021] c. After filtering, the precipitate is fully washed with distilled water and anhydrous ethanol, and dried at 45-75° C. to obtain the chitosan Schiff base copper-based functional material Schiff-CS@Cu.

[0022] Preferably, the molar ratio of the amino group in the chitosan, the aldehyde group in the aldehyde compound, and the divalent copper ion in the divalent copper salt aqueous solution is 1:(2-6):(1.03-2).

[0023] Furthermore, the molar ratio of the amino group in the chitosan, the aldehyde group in the aldehyde compound, and the divalent copper ion in the divalent copper salt aqueous solution is 1:4:1.03.

[0024] Preferably, in step a, the anhydrous acidic alcohol solution is obtained by mixing glacial acetic acid and anhydrous ethanol in a volume ratio of 1:7.5.

[0025] Preferably, in step a, stirring is carried out at 75° C. for 12 h.

[0026] Preferably, in step b, the divalent copper salt aqueous solution is formed by dissolving one of copper sulfate, copper acetate and copper bromide in water, and the copper ion concentration in the divalent copper salt aqueous solution is 0.16-0.24 mol / L.

[0027] Preferably, in step c, baking is performed at 45° C. to 50° C. for 12 to 24 hours.

[0028] The above-mentioned chitosan Schiff base copper-based functional material Schiff-CS@Cu can select chitosan, salicylaldehyde, and water-soluble divalent copper salt as raw materials, and salicylaldehyde can also be replaced by 5-bromosalicylaldehyde and 3,5-di-tert-butyl salicylaldehyde. In the preparation method of the chitosan Schiff base copper-based functional material Schiff-CS@Cu, the anhydrous acidic alcohol solution in step a is conventionally operated in the following manner: using an anhydrous ethanol solution (for example, a volume ratio of 7.5:1) in which an organic acid such as acetic acid (for example, acetic acid, citric acid, etc.) is dissolved, and the main purpose is to promote the dissolution of chitosan and aldehyde compounds at the same time. Therefore, the alcohol solution only needs to use a common anhydrous alcohol solution (such as ethanol), and the acid compound can use a common weak acid soluble in alcohol (such as acetic acid). The adsorption of Cu2+ by chitosan Schiff base is mainly based on imine bond coordination, as shown in the following reaction formula (2), and the main adsorption reactions include:

[0029] Schiff reaction: R′-NH2+RCHO→R′-N=CHR (1)

[0030] Coordination:

[0031] The present invention specifically selects salicylaldehyde, 5-bromosalicylaldehyde and 3,5-di-tert-butyl salicylaldehyde to modify chitosan respectively. The primary amine group (R'-NH2) on chitosan reacts with aldehyde (RHC=O) to generate a chitosan Schiff base material containing an imine group (RHC=NR'-). Although the amination reaction reduces the amino groups on the surface of chitosan, the N atom in the C=N double bond formed by the amination reaction and the O atom adjacent to the hydroxyl group in the chitosan structure and salicylaldehyde are very easy to react with Cu 2+ The material of the present invention uses salicylaldehyde, 5-bromosalicylaldehyde or 3,5-di-tert-butyl salicylaldehyde to modify chitosan, and the obtained chitosan Schiff base material can form a multi-dentate ligand (mostly a bidentate ligand) by complexing copper, and Cu 2+ It is four-coordinated, so the coordination ability is significantly enhanced. The three aldehyde-modified chitosan Schiff base copper-based functional materials Schiff-CS@Cu provided by the present invention are more conducive to the attack of reaction substrates; they not only retain the biocompatibility, degradability and antibacterial properties of chitosan, but also improve the physical and chemical properties of chitosan, and improve its mechanical strength and stability. In the preparation method of the material provided by the present invention, compared with the existing method using methanol as the solvent in step a, the present invention uses ethanol instead, which is safer and has lower cost.

[0032] Compared with the prior art, the chitosan Schiff base copper-based functional material Schiff-CS@Cu finally prepared by the present invention can be very conveniently separated from other components in the reaction system by means of a solid-liquid phase separation method after the reaction is completed, and can be reused after simple regeneration, thereby reducing production costs and significantly reducing various environmental pollution problems.

[0033] The chitosan Schiff base copper-based functional material Schiff-CS@Cu prepared by the present invention is used as a catalytic material to prepare β-silyl nitrogen heteroaromatic compounds using alkenyl-substituted nitrogen heteroaromatic compounds and (dimethylphenylsilyl) boric acid pinacol ester as raw materials. The reaction conditions of the entire preparation process are mild, no need to add any base, a mixed solution of methanol and water is used as a solvent, the reaction is carried out at room temperature, and it is simple and easy to operate; it can be reused after simple regeneration, and the functional material still has a high catalytic activity after recovery, which effectively reduces the production cost and can also significantly reduce various environmental pollution problems. The β-silyl nitrogen heteroaromatic compounds finally obtained have a relatively higher product yield, which is all above 80%, and the yield of some specific β-silyl nitrogen heteroaromatic compounds is as high as 98%.

[0034] Compared with the prior art, the present invention is beneficial in that:

[0035] 1. The present invention provides a chitosan Schiff base copper-based functional material, which has the advantages of high catalytic activity, small amount of catalyst, mild reaction conditions, high product yield, etc.;

[0036] 2. It can be used to catalyze the silicon addition reaction of various types of alkenyl-substituted nitrogen heteroaromatic compounds, and the substrate has a wider application range;

[0037] 3. It has the characteristics of "one-pot" synthesis, using a mixed solution of methanol and water with a volume ratio of 4:1 as the solvent, reacting at room temperature, simple and easy to operate, and the material can be reused many times, which is environmentally friendly and cost-saving, and has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is the H NMR spectrum of the target product in Example 4;

[0039] Figure 2 It is the NMR carbon spectrum of the target product in Example 4. DETAILED DESCRIPTION

[0040] The technical scheme of the present invention will be described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative labor conditions belong to the scope of protection of the present invention. The drugs used in the embodiments are all commercially available products unless otherwise specified, and the methods used are all conventional methods in the field unless otherwise specified.

[0041] Example 1

[0042] The chitosan Schiff base copper-based functional material Schiff-CS@Cu provided in this embodiment has a chitosan Schiff base powder as a carrier, and is prepared by reaction in a mixed solution of ethanol and acetic acid with a volume ratio of 15:2 using salicylaldehyde and chitosan as raw materials. Subsequently, copper ions are adsorbed to form the Schiff-CS@Cu material. The specific preparation method is as follows:

[0043] a. Add 1.0 g of chitosan and salicylaldehyde (3028.6 mg, 24.8 mmol) to 85 ml of anhydrous acidic ethanol solution (75 ml of anhydrous ethanol, 10 ml of anhydrous acetic acid) and completely dissolve them. Control the initial pH value to 4.38, stir at 75 ° C for 12 h, filter and recover the solid, wash it thoroughly with anhydrous ethanol and distilled water, and dry it to obtain chitosan Schiff base powder;

[0044] The molecular formula of chitosan provided in this embodiment is (C6H 11NO4)N, 1.0g chitosan contains 6.2mmol amino groups, purchased from San Chemical Technology Co., Ltd. The amino groups in chitosan molecules have good reactivity and can be easily modified and grafted. Chitosan can load metal ions through electrostatic action, coordination and ion exchange. Modification of chitosan with salicylaldehyde (purchased from Tianjin Damao Chemical Reagent Factory) not only retains the biocompatibility, degradability and antibacterial properties of chitosan, but also improves the physical and chemical properties of chitosan and increases its mechanical strength and stability.

[0045] b. Add the chitosan Schiff base powder obtained in step a to a divalent copper salt aqueous solution (30 mL of copper sulfate solution, prepared from 1.6 g of copper sulfate pentahydrate, with a substance amount of 6.4 mmol), and stir for 3-9 h (6 h in this embodiment);

[0046] c. Filtration and recovery of loaded Cu 2+ The chitosan Schiff base powder was fully washed with anhydrous ethanol and distilled water to remove free copper ions, sulfate ions and unreacted salicylaldehyde; and dried in an oven at 50°C for 24 hours to obtain the chitosan Schiff base copper-based functional material Schiff-CS@Cu.

[0047] The chitosan Schiff base copper-based functional material Schiff-CS@Cu prepared in this example has a relative content of active ingredient copper of 8.8×10 -4 mol / g (i.e. 0.88mmol / g).

[0048] Example 2

[0049] The chitosan Schiff base copper-based functional material Schiff-CS@Cu provided in this embodiment is prepared by a method substantially the same as that in Example 1, with the only difference being that salicylaldehyde is replaced by 5-bromosalicylaldehyde (4985.3 mg, 24.8 mmol) (purchased from San Chemical Technology Co., Ltd.).

[0050] The chitosan Schiff base copper-based functional material Schiff-CS@Cu prepared in this example has a relative content of active ingredient copper of 6.6×10 -4 mol / g (i.e. 0.66mmol / g).

[0051] Example 3

[0052] The chitosan Schiff base copper-based functional material Schiff-CS@Cu provided in this embodiment adopts a preparation method that is basically the same as that in Example 1, with the only difference being that salicylaldehyde is replaced by 3,5-di-tert-butyl salicylaldehyde (5811.4 mg, 24.8 mmol) (purchased from San Chemical Technology Co., Ltd.).

[0053] The chitosan Schiff base copper-based functional material Schiff-CS@Cu prepared in this example has a relative content of active ingredient copper of 6.2×10 -4 mol / g (i.e. 0.62mmol / g).

[0054] Example 4

[0055] The method for preparing a β-silyl azoaromatic compound using the chitosan Schiff base copper-based functional material Schiff-CS@Cu obtained in Example 1 as a catalyst comprises the following steps:

[0056] P1, take alkenyl substituted nitrogen heteroaromatic compound I 0.20mmol (2-phenylphenylquinoline, by reference to "Jamal Z, Teo YC Bart-catalyzed direct alkenylation of 2-methylquinolines with aldehydes via C (sp 3 )-H functionalization in water[J].Synlett,2014,25,2049–2053.》Self-prepared), (dimethylphenylsilyl)boronic acid pinacol ester 0.4mmol (purchased from San Chemical Technology Co., Ltd.), chitosan Schiff base copper-based functional material 0.001mmol (Cu 2+ The mixture was added to 2.0 ml of a mixed solution of methanol and water in a volume ratio of 4:1, and stirred at room temperature for 3 h to obtain a silicon addition product; Cu in the chitosan Schiff base copper-based functional material Schiff-CS@Cu 2+ The content is 0.5% of the molar fraction of the raw material alkenyl-substituted nitrogen heteroaromatic compound;

[0057] P2. After the reaction is completed, the entire reaction system is filtered, the precipitate is washed and dried, and the chitosan Schiff base copper-based functional material Schiff-CS@Cu is recovered. The filtrate is extracted with ethyl acetate (3×10 ml) three times, and the organic phase is separated and dried with anhydrous Na2SO4, filtered, and rotary evaporated to remove the organic solvent. Finally, a mixed solvent of ethyl acetate / petroleum ether with a volume ratio of 1:35 is used as a developing solvent, and column chromatography is used for separation and purification to obtain β-silyl nitrogen heteroaromatic compound II (R1 is phenyl), and the product yield is 73% (53.7 mg). The reaction process is:

[0058]

[0059] The NMR hydrogen spectrum and carbon spectrum of the target product are shown below. Figure 1 and Figure 2 .

[0060] 1 H NMR (400MHz, Chloroform-d) δ = 8.00 (d, J = 8.3Hz, 1H), 7.83 (d, J = 8.4Hz, 1H), 7.68–7.60 (m, 2H), 7.49–7.29 (m, 6H) ,7.16–7.05(m,3H),7.05–6.96(m,3H),3.54–3.41(m,2H),3.08(dd,J=11.1,5.5Hz,1H),0.34(s,3H),0.30(s,3H).

[0061] 13 C NMR(100MHz,Chloroform-d)δ=162.2,147.8,142.0,137.1,135.8,134.4,129.2,128 .8,128.2,128.0,127.7,127.5,126.7,125.6,124.7,121.2,38.8,36.1,-3.8,-5.0.

[0062] This application example shows that under the catalytic conditions of the chitosan Schiff base copper-based functional material Schiff-CS@Cu provided in Example 1, the conversion rate of 2-phenylvinylquinoline is high, and the yield of its silicon addition product reaches 73%.

[0063] Example 5

[0064] The chitosan Schiff base copper-based functional material Schiff-CS@Cu obtained in Example 2 was used as a catalyst to prepare β-silyl azaaromatic compounds according to the method of Example 4. 2+ The content of Cu is also 0.5% of the molar fraction of the raw material alkenyl-substituted nitrogen heteroaromatic compound, that is, Cu 2+ The amount of substance remains the same as in Example 4.

[0065] This application example shows that under the catalytic conditions of the chitosan Schiff base copper-based functional material Schiff-CS@Cu provided in Example 2, the conversion rate of 2-phenylphenylquinoline is very high, and the yield of its silicon addition product reaches 95%.

[0066] Example 6

[0067] The chitosan Schiff base copper-based functional material Schiff-CS@Cu obtained in Example 3 was used as a catalyst to prepare β-silyl azaaromatic compounds according to the method of Example 4. 2+The content of Cu is also 0.5% of the molar fraction of the raw material alkenyl-substituted nitrogen heteroaromatic compound, that is, Cu 2+ The amount of substance remains the same as in Example 4.

[0068] This application example shows that under the catalytic conditions of the chitosan Schiff base copper-based functional material Schiff-CS@Cu provided in Example 3, the conversion rate of 2-phenylvinylquinoline is very high, and the yield of its silicon addition product reaches 68%.

[0069] Example 7

[0070] The chitosan Schiff base copper-based functional material Schiff-CS@Cu prepared in Example 2 was selected as a catalyst, and the β-silyl azaarene compound was prepared according to the method of Example 4. The only difference is that the alkenyl substituted azaarene compound selected in this application example is 2-(4-methylphenylvinyl)quinoline; the stirring reaction time at room temperature in step P1 is 3 hours. Finally, the β-silyl azaarene compound II (R1 is p-methylphenyl) was obtained, and the product yield was 95% (72.5 mg).

[0071] The reaction process is:

[0072]

[0073] The NMR hydrogen spectrum and carbon spectrum of the target product are shown below:

[0074] 1 H NMR (400MHz, Chloroform-d) δ = 8.00 (dd, J = 8.4, 1.0Hz, 1H), 7.83 (dd, J = 8.6, 0.6Hz, 1H), 7.67–7.60 (m, 2H), 7.50–7.46 (m, 2H), 7.44–7.30 (m,4H),7.09(d,J=8.6Hz,1H),6.96–6.88(m,4H),3.53–3.39(m,2H),3.04(dd,J=11.2,5.4Hz,1H),2.23(s,3H),0.34(s,3H),0.29(s,3H).

[0075] 13 C NMR(100MHz,Chloroform-d)δ=162.3,147.8,138.7,137.3,135.8,134.4,134.0,129.2,12 9.1,128.8,128.7,128.1,127.7,127.5,126.7,125.6,121.1,38.8,35.4,21.0,-3.7,-5.0.

[0076] This application example shows that under the catalytic conditions of the chitosan Schiff base copper-based functional material Schiff-CS@Cu provided in the embodiment of the present invention, the conversion rate of 2-(4-methylphenylvinyl)quinoline is also very high, and the yield of its silicon addition product reaches 95%.

[0077] Example 8

[0078] The chitosan Schiff base copper-based functional material Schiff-CS@Cu prepared in Example 2 was selected as a catalyst, and the β-silyl azaaromatic compound was prepared according to the method of Example 4. The only difference is that the alkenyl-substituted azaaromatic compound selected in this application example is 2-(4-methoxyphenylvinyl)quinoline; the stirring reaction time at room temperature in step P1 is 3 hours. Finally, the β-silyl azaaromatic compound II (R1 is p-methoxyphenyl) was obtained, and the product yield was 98% (77.9 mg).

[0079] The reaction process is:

[0080]

[0081] The NMR hydrogen spectrum and carbon spectrum of the target product are shown below:

[0082] 1 H NMR (400MHz, Chloroform-d) δ = 7.98 (d, J = 8.4Hz, 1H), 7.83 (d, J = 8.6Hz, 1H), 7.68–7.59 (m, 2H), 7.48–7.28 (m, 6H), 7.07 (d, J = 8.6Hz, 1 H), 6.89 (d, J = 8.7Hz, 2H), 6.66 (d, J = 8.7Hz, 2H), 3.70 (s, 3H), 3.41 (d, J = 8.3Hz, 2H), 2.98 (t, J = 8.4Hz, 1H), 0.31 (s, 3H), 0.28 (s, 3H).

[0083] 13 C NMR(100MHz,Chloroform-d)δ=162.4,156.9,137.3,135.8,134.4,133.8,129.2,129.1 ,128.8,127.7,127.7,127.5,126.7,125.6,121.2,113.5,55.2,39.0,35.0,-3.7,-4.9.

[0084] This application example shows that under the catalytic conditions of the chitosan Schiff base copper-based functional material Schiff-CS@Cu provided in the embodiment of the present invention, the conversion rate of 2-(4-methylphenylvinyl)quinoline is also very high, and the yield of its silicon addition product reaches 98%.

[0085] Example 9

[0086] The chitosan Schiff base copper-based functional material Schiff-CS@Cu prepared in Example 2 was selected as a catalyst, and the β-silyl azaaromatic compound was prepared according to the method of Example 4. The only difference is that the alkenyl substituted azaaromatic compound selected in this application example is 2-(4-chlorophenylvinyl)quinoline; the stirring reaction time at room temperature in step P1 is 12 hours. Finally, the β-silyl azaaromatic compound II (R1 is p-chlorophenyl) was obtained, and the product yield was 81% (65.1 mg).

[0087] The reaction process is:

[0088]

[0089] The NMR hydrogen spectrum and carbon spectrum of the target product are shown below:

[0090] 1 H NMR (400MHz, Chloroform-d) δ = 7.96 (d, J = 8.4Hz, 1H), 7.86 (dd, J = 8.5, 0.8Hz, 1H), 7.69–7.60 (m, 2H), 7.46–7.29 (m, 6H) ,7.08–7.02(m,3H),6.88(dd,J=8.4,1.7Hz,2H),3.47–3.34(m,2H),3.06(dd,J=10.5,6.2Hz,1H),0.30(d,J=6.8Hz,6H).

[0091] 13 C NMR(100MHz,Chloroform-d)δ=161.7,147.8,140.6,136.6,136.0,134.4,130.2,129.5, 129.4,129.3,128.8,128.1,127.8,127.6,126.7,125.8,121.1,38.6,35.7,-4.0,-4.9.

[0092] This application example shows that under the catalytic conditions of the chitosan Schiff base copper-based functional material Schiff-CS@Cu provided in the embodiment of the present invention, the conversion rate of 2-(4-chlorophenylvinyl)quinoline is also very high, and the yield of its silicon addition product reaches 81%.

[0093] Example 10

[0094] The chitosan Schiff base copper-based functional material Schiff-CS@Cu prepared in Example 2 was selected as a catalyst, and the β-silyl azaarene compound was prepared according to the method of Example 4. The only difference is that the alkenyl substituted azaarene compound I selected in this application example is 2-(4-bromostyryl)quinoline; the stirring reaction time at room temperature in step P1 is 12 hours. Finally, the β-silyl azaarene compound II (R1 is p-bromophenyl) was obtained, and the product yield was 86% (76.8 mg).

[0095] The reaction process is:

[0096]

[0097] The NMR hydrogen spectrum and carbon spectrum of the target product are shown below:

[0098] 1 H NMR (400MHz, Chloroform-d) δ = 7.97 (d, J = 8.4Hz, 1H), 7.86 (dd, J = 8.6, 0.6Hz, 1H), 7.70–7.60 (m, 2H), 7.47–7.30 (m, 6H), 7.23–7 .17(m,2H),7.05(d,J=8.6Hz,1H),6.87–6.80(m,2H),3.47–3.34(m,2H),3.05(dd,J=10.4,6.4Hz,1H),0.31(s,3H),0.29(s,3H).

[0099] 13 C NMR(100MHz,Chloroform-d)δ=161.7,141.2,136.6,136.0,134.4,131.0,129.9,129 .4,129.4,128.8,127.8,127.6,126.8,125.8,121.1,118.3,38.6,35.8,-3.9,-4.9.

[0100] This application example shows that under the catalytic conditions of the chitosan Schiff base copper-based functional material Schiff-CS@Cu provided in the embodiment of the present invention, the conversion rate of 2-(4-bromostyryl)quinoline is also very high, and the yield of its silicon addition product reaches 86%.

[0101] Embodiment 11

[0102] The chitosan Schiff base copper-based functional material Schiff-CS@Cu prepared in Example 2 was selected as a catalyst, and the β-silyl azaaromatic compound was prepared according to the method of Example 4. The only difference is that the alkenyl substituted azaaromatic compound I selected in this application example is 2-(2-(1,1'-biphenyl)-4-vinyl)quinoline; the stirring reaction time at room temperature in step P1 is 3h. Finally, the β-silyl azaaromatic compound II (R1 is biphenyl) was obtained, and the product yield was 96% (85.2mg).

[0103] The reaction process is:

[0104]

[0105] The NMR hydrogen spectrum and carbon spectrum of the target product are shown below:

[0106] 1 H NMR (400MHz, Chloroform-d) δ = 7.98 (d, J = 8.6Hz, 1H), 7.85 (d, J = 8.6Hz, 1H), 7.68–7.59 (m, 2H), 7.55–7.49 (m, 2H), 7.48–7.28 (m,11H),7.11(d,J=8.4Hz,1H),7.07–7.01(m,2H),3.55–3.40(m,2H),3.10(dd,J=11.2,5.4Hz,1H),0.35(s,3H),0.30(s,3H).

[0107] 13 C NMR(100MHz,Chloroform-d)δ=162.2,141.2,141.0,137.3,137.1,136.0,134.4,129.3,128 .8,128.6,127.8,127.5,126.9,126.8,126.7,126.6,125.7,121.2,38.7,35.9,-3.7,-4.9.

[0108] This application example shows that under the catalytic conditions of the chitosan Schiff base copper-based functional material Schiff-CS@Cu provided in the embodiment of the present invention, the conversion rate of 2-(2-(1,1'-biphenyl)-4-vinyl)quinoline is also very high, and the yield of its silicon addition product reaches 96%.

[0109] It can be seen from the above Examples 7-11 that by using the chitosan Schiff base copper-based functional material Schiff-CS@Cu provided by the present invention, various alkenyl-substituted azaaromatic compounds can be used to prepare corresponding β-silyl azaaromatic compounds.

[0110] Comparative Example 1

[0111] Compared with Examples 1-3, the chitosan Schiff base copper-based functional material CS@Cu provided in this comparative example does not use salicylaldehyde / 5-bromosalicylaldehyde / 3,5-di-tert-butylsalicylaldehyde to participate in the reaction, but directly uses chitosan powder to adsorb Cu 2+ The CS@Cu material is made into finished product. The specific preparation method is as follows:

[0112] (1) Chitosan powder (1.0 g) was added to 30 ml of copper sulfate solution (prepared from 1.6 g of copper sulfate pentahydrate, about 6.4 mmol) and stirred at room temperature for 12 h.

[0113] (2) Separation of loaded Cu by filtration 2+ The powder was washed with anhydrous ethanol and distilled water to remove free Cu 2+ and SO4 2- Finally, the chitosan copper material (CS@Cu) without Schiff modification was dried in an oven at 50 °C for 24 h to obtain the final CS@Cu material. The relative content of the active ingredient copper in the CS@Cu material was 1.75×10 -3 mol / g.

[0114] After analysis, the reason why the copper loading of the single chitosan-loaded copper material is higher is that the steric hindrance between the coordinated atoms of the modified chitosan becomes larger, while the steric hindrance of the single chitosan is relatively small, and it adsorbs more. However, after the Schiff base provided in the embodiment of the present invention is complexed with copper, most of them form bidentate ligands or tridentate ligands, while the single chitosan-loaded copper in the above comparative example 1 is mostly monodentate ligands and bidentate ligands. 2+ It is a four-coordinate structure, so the chitosan Schiff base copper-based functional material structure formed in the embodiment of the present invention is more conducive to the attack of the reaction substrate.

[0115] Comparative Example 2

[0116] This application example uses the CS@Cu material prepared in Comparative Example 1, and uses a method substantially the same as that in Example 4 to prepare a β-silyl azoarene compound. 2+ The content of Cu is also 0.5% of the molar fraction of the raw material alkenyl-substituted nitrogen heteroaromatic compound, that is, Cu 2+ The amount of the substance remains the same as in Application Example 1.

[0117] This application example shows that under the catalysis of the Schiff-CS@Cu material provided in Comparative Example 1, 2-phenylphenylquinoline is converted into the target product at a relatively low conversion rate, and the yield of the silicon addition product is only 55%.

[0118] It can be seen from the above Comparative Example 2 and Examples 4 to 6 that more -NH2 in the Schiff-CS@Cu material does not improve the catalytic efficiency. The catalytic activity of directly loading copper on chitosan (Comparative Example 1) is lower than that of copper immobilized on chitosan using aldehyde (Examples 1-3). After analysis, this may be because during the reaction, (dimethylphenylsilyl) boric acid pinacol ester breaks the Si-B bond under the catalysis of the active copper in the material, and reacts with Cu 2+ The reaction generates a copper silyl complex intermediate and a by-product Bpin-OH. The intermediate undergoes conjugate addition with an alkenyl-substituted nitrogen heteroaromatic compound under the guidance of the imine group, in which copper is coordinated with the heteroatom of the raw alkenyl-substituted nitrogen heteroaromatic compound. After the chitosan Schiff base complexes copper, most of them form bidentate or tridentate ligands, and the divalent copper is a tetracoordinate structure. The chitosan Schiff base copper-based functional material structure formed is more conducive to the attack of the reaction substrate. The catalytic activity of the Schiff-CS@Cu material obtained by modifying chitosan with salicylaldehyde and 3,5-di-tert-butyl salicylaldehyde is lower than that of the Schiff-CS@Cu material obtained by modifying chitosan with 5-bromo salicylaldehyde. After analysis, this may be because the electron-withdrawing group of aldehyde compounds containing salicylaldehyde structure has better catalytic activity than the electron-donating group.

Claims

1. A method for preparing β-silyl azoarene compounds by catalysis of chitosan Schiff base copper-based functional materials, characterized in that: The following steps are involved: 1) Chitosan and an aldehyde compound are placed in a solvent formed by a mixture of glacial acetic acid and anhydrous ethanol to react to obtain a chitosan Schiff base material, wherein the aldehyde compound is one of salicylaldehyde, 5-bromosalicylaldehyde, and 3,5-di-tert-butylsalicylaldehyde. The chitosan Schiff base material is then placed in a divalent copper salt aqueous solution for adsorption to obtain a chitosan Schiff base copper-based functional material Schiff-CS@Cu; 2) Add alkenyl-substituted nitrogen heteroaromatic compound I, (dimethylphenylsilyl)boronic acid pinacol ester, and chitosan Schiff base copper-based functional material Schiff-CS@Cu to a mixed solution of methanol and water, and stir at room temperature for 3-12 h, wherein the molar ratio of alkenyl-substituted nitrogen heteroaromatic compound I, (dimethylphenylsilyl)boronic acid pinacol ester, and copper loaded in functional material Schiff-CS@Cu is 1:(1.2-2.0):(0.001-0.005), The chemical reaction equation is as follows: Wherein, R1 is one of phenyl, p-methylphenyl, p-methoxyphenyl, p-chlorophenyl, p-bromophenyl, and biphenyl; 3) After the reaction is completed, the reaction is filtered, and the precipitate is washed, dried, and recovered to obtain the chitosan Schiff base copper-based functional material Schiff-CS@Cu. The filtrate is extracted, dried, and rotary evaporated, and finally separated by column chromatography to obtain the β-silyl nitrogen aromatic compound II.

2. The method for preparing β-silyl azaaromatic compounds catalyzed by chitosan Schiff base copper-based functional materials according to claim 1, characterized in that: In step 2), methanol and water are mixed in a volume ratio of 4 to 5:1 to form a mixed solution, and (dimethylphenylsilyl)boronic acid pinacol ester is added to the mixed solution at a concentration of 0.2 to 0.5 mmol / mL.

3. The method for preparing β-silyl azaaromatic compounds catalyzed by chitosan Schiff base copper-based functional materials according to claim 1, characterized in that: In step 2), the molar ratio of the alkenyl-substituted nitrogen aromatic compound I, (dimethylphenylsilyl)boronic acid pinacol ester, and the copper loaded in the functional material Schiff-CS@Cu is 1: 2.0: 0.

005.

4. The method for preparing β-silylazaaromatic compounds by catalysis of chitosan Schiff base copper-based functional materials according to claim 1, characterized in that: In step 3), ethyl acetate and petroleum ether are prepared as a developing solvent in a volume ratio of 1:35 in column chromatography separation.

5. The method for preparing β-silyl azaaromatic compounds by catalysis of chitosan Schiff base copper-based functional materials according to claim 1, characterized in that: In step 1), the preparation of chitosan Schiff base copper-based functional material Schiff-CS@Cu includes the following steps: a. Add chitosan and aldehyde compounds to a solvent formed by mixing glacial acetic acid and anhydrous ethanol, adjust the pH value to 4.0-5.5, stir at 65-85°C for 12-24 hours, separate, wash and dry to obtain chitosan Schiff base material; b. Add the obtained chitosan Schiff base material into a divalent copper salt aqueous solution and stir for 3 to 9 hours; c. After filtering, the precipitate was fully washed with distilled water and anhydrous ethanol, and dried at 45-75 °C to obtain the chitosan Schiff base copper-based functional material Schiff-CS@Cu.

6. The method for preparing β-silylazaaromatic compounds catalyzed by chitosan Schiff base copper-based functional materials as claimed in claim 5, characterized in that: The molar ratio of the amino group in the chitosan, the aldehyde group in the aldehyde compound, and the divalent copper ion in the divalent copper salt aqueous solution is 1:(2-6):(1.03~2).

7. The method for preparing β-silyl azaaromatic compounds catalyzed by chitosan Schiff base copper-based functional materials as claimed in claim 5, characterized in that: In step a, glacial acetic acid and anhydrous ethanol are mixed in a volume ratio of 1:7.5 to form a solvent.

8. The method for preparing β-silyl azaaromatic compounds catalyzed by chitosan Schiff base copper-based functional materials as claimed in claim 5, characterized in that: In step a, stir at 75 °C for 12 h.

9. The method for preparing β-silyl azaaromatic compounds catalyzed by chitosan Schiff base copper-based functional materials as claimed in claim 5, characterized in that: In step b, the divalent copper salt aqueous solution is formed by dissolving one of copper sulfate, copper acetate and copper bromide in water, and the copper ion concentration in the divalent copper salt aqueous solution is 0.16-0.24 mol / L.

10. The method for preparing β-silyl azaaromatic compounds catalyzed by chitosan Schiff base copper-based functional materials as claimed in claim 5, characterized in that: In step c, bake at 45-50°C for 12-24 hours.

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