阅读说明：本技术 一种负载手性杂多酸中空介孔纳米微球的制备方法及其产品和应用 (Preparation method of supported chiral heteropolyacid hollow mesoporous nano-microsphere, product and application thereof ) 是由 谢广新 周贤菊 李丽 罗小兵 江莎 唐笑 李艳虹 曹中民 凌发令 姚璐 于 2020-08-13 设计创作，主要内容包括：本发明涉及一种负载手性杂多酸中空介孔纳米微球的制备方法及其产品和应用,属于功能材料制备技术领域。本发明公开了一种负载手性杂多酸中空介孔纳米微球的制备方法,以Boc-L-脯氨酸为原料,经包裹聚苯乙烯/丙烯酸内核与钨酸钠溶液共沉淀得到核壳结构,再经过脱-Boc、去除内核与介孔模板等步骤,制备负载手性杂多酸中空介孔纳米微球,制备方法简单、容易操作,制备得到的负载手性杂多酸中空介孔纳米微球可用于催化双迈克尔不对称串联反应,提高反应的产率以及选择性,且反应结束后通过简单的离心即可对纳米微球进行回收再利用。(The invention relates to a preparation method of a supported chiral heteropoly acid hollow mesoporous nano microsphere, a product and application thereof, belonging to the technical field of functional material preparation. The invention discloses a preparation method of a supported chiral heteropoly acid hollow mesoporous nano microsphere, which takes Boc-L-proline as a raw material, obtains a core-shell structure by wrapping a polystyrene/acrylic acid core and coprecipitating with a sodium tungstate solution, and prepares the supported chiral heteropoly acid hollow mesoporous nano microsphere through the steps of removing-Boc, removing the core and a mesoporous template and the like.)

1. A preparation method of a supported chiral heteropoly acid hollow mesoporous nano microsphere is characterized by comprising the following steps:

(1) mixing Boc-L-proline, hexadecyl trimethyl ammonium bromide and polystyrene/acrylic acid inner core, adding water, mixing and stirring at 70-85 ℃ for 15-25 min to fully disperse the mixture, and adding NaWO at the speed of 1-3 drops/min₂Carrying out a reaction on the aqueous solution by constant-temperature sedimentation, and after the reaction is finished, carrying out centrifugal separation, washing and drying to obtain white powder, namely the Boc-a core shell;

(2) adding KOH and CH into the Boc-a core shell in the step (1)₃OH and DMSO react for 12-16 h at 60-70 ℃, water is added for quenching, and white powder, namely a core shell, is obtained through centrifugal separation, washing and drying;

(3) and (3) washing the core shell prepared in the step (2) to remove the inner layer template and the pore template, so as to obtain the loaded chiral heteropolyacid hollow mesoporous nano microsphere.

2. The method of claim 1, wherein the Boc-L-proline, the polystyrene/acrylic acid core and NaWO in step (1)₂The molar mass ratio of (a) is 1-8: 100: 0.1-2, mol: g: mol;

the mass ratio of the hexadecyl trimethyl ammonium bromide to the polystyrene/acrylic acid inner core is 13.6: 100.

3. The method according to claim 1, wherein the NaWO is contained in the step (1)₂NaWO in aqueous solution₂The concentration of (2) was 0.625 mol/L.

4. The method of claim 1, wherein the Boc-a core-shell, KOH, CH in step (2)₃The mass-volume ratio of OH to DMSO is 0.5: 0.8-1.2: 5-15: 15-25, and g: g: mL: mL.

5. The method according to claim 1, wherein in the step (1) and the step (2), the washing is carried out by washing with pure water 4 times and then with ethanol 2 times; the rotating speed of the centrifugal separation is 11000-13500 r/min.

6. The method of claim 1, wherein the polystyrene/acrylic core is prepared as follows:

(1) adding styrene, acrylic acid and deionized water into potassium persulfate under the condition of vacuumizing and introducing argon, and heating and stirring for reaction;

(2) and after stirring, adding water for dilution, stirring, centrifuging, washing with deionized water and ethanol in sequence, drying in vacuum, and grinding to obtain the polystyrene/acrylic acid core.

7. The method according to claim 1, wherein the washing in step (3) is carried out in a manner that: washing with any one of acetic acid/tetrahydrofuran mixed solvent, N-dimethylformamide or toluene at a volume ratio of 1:3 until the inner layer template and the pore template are removed.

8. The supported chiral heteropolyacid hollow mesoporous nanospheres prepared by the preparation method according to any one of claims 1-7.

9. The use of the supported chiral heteropolyacid hollow mesoporous nanospheres in catalysis of asymmetric double michael series reactions as claimed in claim 8.

10. Use according to claim 9, wherein the reactants in the asymmetric double michael cascade are nitroenes and unsaturated ketones.

Technical Field

The invention belongs to the technical field of functional material preparation, and particularly relates to a preparation method of a supported chiral heteropolyacid hollow mesoporous nano microsphere, and a product and application thereof.

Background

In recent years, asymmetric organic catalysis has shown excellent catalytic performance in the synthesis of pharmaceutical intermediates, natural products, bioactive molecules, and the like. The proline catalyst is an asymmetric organic catalytic star catalyst due to high reaction activity and high stereoselectivity in asymmetric reactions such as Aldol, Michael, Henry, Michael/Michael and the like. However, because

The Hayashi catalyst presents the following problems in catalytic reactions: 1) the dosage is large (20-30 mol%); 2) the addition of an acid as a co-catalyst is required, which makes it difficult to separate, recover and reuse proline as a catalyst after the reaction is completed.

Based on the idea of green chemistry,the strategy of supported recovery of Hayashi catalysts and their cocatalysts is receiving increasing attention. There is therefore a need to develop a new asymmetric organic catalyst which is capable of catalyzing asymmetric organic reactions while being easily separated and recycled.

Disclosure of Invention

In view of the above, one of the objectives of the present invention is to provide a method for preparing a supported chiral heteropolyacid hollow mesoporous nanosphere; the second purpose of the invention is to provide a hollow mesoporous nano microsphere loaded with chiral heteropoly acid; the invention also aims to provide application of the supported chiral heteropolyacid hollow mesoporous nanospheres in catalysis of asymmetric double Michael tandem reaction.

In order to achieve the purpose, the invention provides the following technical scheme:

1. a preparation method of a supported chiral heteropoly acid hollow mesoporous nano microsphere comprises the following steps:

(1) mixing Boc-L-proline, Cetyl Trimethyl Ammonium Bromide (CTAB) and polystyrene/acrylic acid inner core (PS/AA), adding water, mixing and stirring at 70-85 ℃ for 15-25 min to fully disperse the mixture, and adding NaWO at the speed of 1-3 drops/min₂Carrying out a reaction on the aqueous solution by constant-temperature sedimentation, and after the reaction is finished, carrying out centrifugal separation, washing and drying to obtain white powder, namely the Boc-a core shell;

(2) adding KOH and CH into the Boc-a core shell in the step (1)₃OH and DMSO react for 12-16 h at 60-70 ℃, water is added for quenching, and white powder, namely a core shell, is obtained through centrifugal separation, washing and drying;

(3) and (3) washing the core shell prepared in the step (2) to remove an inner layer template (PS/AA) and a pore template (CTAB) to obtain the supported chiral heteropolyacid hollow mesoporous nanospheres.

Preferably, the Boc-L-proline in step (1), polystyrene/acrylic acid core and NaWO₂The molar mass ratio of (a) is 1-8: 100: 0.1-2, mol: g: mol;

the mass ratio of cetyltrimethylammonium bromide (CTAB) to polystyrene/acrylic acid core (PS/AA) was 13.6: 100.

Preferably, the NaWO described in step (1)₂NaWO in aqueous solution₂The concentration of (2) was 0.625 mol/L.

Preferably, the Boc-a core-shell, KOH, CH in step (2)₃The mass-volume ratio of OH to DMSO is 0.5: 0.8-1.2: 5-15: 15-25, and g: g: mL: mL.

Preferably, in the step (1) and the step (2), the washing is firstly 4 times of washing with pure water and then 2 times of washing with ethanol; the rotating speed of the centrifugal separation is 11000-13500 r/min.

Preferably, the polystyrene/acrylic acid core (PS/AA) is prepared as follows:

(1) adding styrene, acrylic acid and deionized water into potassium persulfate according to the molar volume ratio of 0.19:4.4:14.6:100 mol: mol: mol: L under the condition of vacuumizing and introducing argon, and heating and stirring for reaction;

(2) and after stirring, adding water for dilution, stirring, centrifuging, washing with deionized water and ethanol in sequence, drying in vacuum, and grinding to obtain the polystyrene/acrylic acid core.

Preferably, the molar volume ratio of the potassium persulfate to the styrene to the acrylic acid to the deionized water is 0.19:4.4:14.6:100, mol: mol: L.

Preferably, the temperature-rising stirring is specifically stirring at the rotation speed of 800rpm for 24 hours when the temperature rises to 80 ℃.

Preferably, the volume ratio of the solution after the reaction by heating and stirring in the process of diluting with water to water is 1:1.

Preferably, the stirring centrifugation is specifically stirring centrifugation at 11800rpm for 8 min.

Preferably, the vacuum drying is vacuum drying at 50 ℃ for 12 h.

Preferably, the washing manner in step (3) is specifically: washing with any one of acetic acid/tetrahydrofuran mixed solvent, N-dimethylformamide or toluene at a volume ratio of 1:3 until removing inner layer template (PS/AA) and pore template Cetyl Trimethyl Ammonium Bromide (CTAB).

2. The supported chiral heteropolyacid hollow mesoporous nanospheres prepared by the preparation method.

3. The supported chiral heteropolyacid hollow mesoporous nanospheres are applied to catalysis of asymmetric double Michael series reaction.

Preferably, the reactants in the asymmetric double Michael tandem reaction are nitroene and unsaturated ketone.

The invention has the beneficial effects that: the invention discloses a preparation method of a supported chiral heteropoly acid hollow mesoporous nano microsphere, which takes Boc-L-proline as a raw material, obtains a core-shell structure by wrapping a polystyrene/acrylic acid inner core and coprecipitating with a sodium tungstate solution, and prepares the supported chiral heteropoly acid hollow mesoporous nano microsphere through the steps of removing-Boc, removing the inner core and a mesoporous template and the like.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.

Drawings

For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a flow chart of preparation of a supported chiral heteropolyacid hollow mesoporous nanosphere;

FIG. 2 is an SEM image of the nanospheres prepared in example 2;

FIG. 3 is a TEM image of the nanospheres prepared in example 2;

FIG. 4 is a distribution diagram of the particle size of the nanospheres prepared in examples 2-5, wherein a, b, c and d represent the nanospheres prepared in examples 2, 3, 4 and 5, respectively;

FIG. 5 is an infrared spectrum of the nanospheres prepared in examples 2-5, wherein a, b, c and d represent the nanospheres prepared in examples 2, 3, 4 and 5, respectively;

FIG. 6 is an SEM image of the nanospheres prepared in examples 2-5, wherein a, b, c and d represent the nanospheres prepared in example 2, example 3, example 4 and example 5, respectively;

FIG. 7 shows the HPLC test results after the nanospheres prepared in example 1 catalyze asymmetric double Michael tandem reaction.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that, in the following embodiments, features in the embodiments may be combined with each other without conflict.