A method for promoting efficient synthesis of perfluoroketoates using magnetically driven microrotors

Abstract

The present invention discloses a method for promoting the efficient synthesis of perfluoroketoates by a magnetically driven microrotor. The method utilizes the advantage of Janus emulsion droplets having two-phase microregions, dissolving α, β-unsaturated ketone and perfluoroalkyl acid into two independent microregions of the droplets respectively, selectively dispersing hydrophobic ferromagnetic nanoparticles into one of the inner phase microregions, and constructing a Janus emulsion microreactor by a surfactant. The present invention utilizes the asymmetric characteristics of the Janus emulsion droplets to the magnetic response, realizes the droplets to rotate in groups, in a directional and orderly manner under the conditions of an external magnetic field, accelerates the contact of reactants at the droplet liquid-liquid interface, thereby promoting the rate of the α, β-unsaturated ketone and perfluoroalkyl acid oxa-Michael addition reaction, and realizes the efficient synthesis of perfluoroketoates in an emulsion system at room temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis and relates to a method for promoting efficient synthesis of perfluoroketoate by a magnetically driven microrotor. Background Art

[0002] The Oxa-Michael addition reaction is a key organic reaction in organic synthesis that forms carbon-oxygen bonds. The resulting ester compounds serve as important chemical intermediates and are widely used in a variety of fields, including food processing, biopharmaceuticals, and material synthesis. Perfluoroketoesters are widely used in pharmaceutical synthesis and as waterproof and oil-repellent agents. For example, perfluorohexylpropyl acrylate can be used to prepare waterproof and oil-repellent fabrics (CN112898125A), while ethyl trifluoropyruvate can be used to synthesize anti-inflammatory, anticancer, and antiviral drugs (CN109776319A).

[0003] Currently, there are many reports on the oxa-Michael addition reaction of alcohols as nucleophiles with α, β-unsaturated ketones, but there are fewer reports on the oxa-Michael addition reaction of organic acid nucleophiles with α, β-unsaturated ketones. The reasons are as follows: (1) organic acids have low nucleophilicity; (2) the reversibility of the reaction. Existing methods mainly achieve the purpose of catalyzing two-phase reactions by changing the type of catalyst. For example, patent CN111187160A discloses a two-phase reaction using sodium carbonate as a reaction medium to synthesize ester compounds through oxa-Michael addition reaction; patent CN103073454A discloses a two-phase reaction using ionic liquid as a catalyst to achieve oxa-Michael reaction between electron-deficient enone and nucleophile. However, the above methods require high-speed stirring to overcome the difficulty of low reaction efficiency caused by the distribution of reactant molecules in the two phases, and the stirring energy consumption is high, and the improvement of reaction yield and rate is limited.

[0004] Magnetically driven Janus emulsions can accelerate the diffusion and mass transfer rate of reactants in a solvent, thereby synthesizing small organic compounds. Existing technologies are primarily limited to using polymerizable monomers as the oil phase of the emulsion to construct Janus emulsions and prepare polymer materials through photocuring. For example, patent CN105294902A discloses a method for preparing double-sided particles using a double-sided emulsion template method. Furthermore, patents CN111233083A and CN110346251A disclose the use of magnetic fields to induce Janus droplet motion. However, the application of these technologies is limited to accelerating physical processes such as the adsorption, separation, and particle size classification of oil-soluble substances. Furthermore, emulsion systems can increase the interfacial area between oil and oil, as well as between oil and water, increasing the probability of contact between reactants and catalysts, thereby significantly improving reaction efficiency. Existing methods for improving reaction efficiency often employ complex reaction processes and techniques with low oil-oil interface utilization. For example, patent CN109485784A discloses a method for synthesizing a soap-free polyacrylate emulsion using a microreactor, patent CN113149817A discloses a method for synthesizing β-bromohydrin using an anisotropic emulsion microreactor, and patent CN114907210A discloses a method for efficiently synthesizing polyfluoroester compounds under room temperature conditions. However, the synthesis of the above-mentioned compounds does not utilize the group and orderly rotation of droplets to increase the reaction rate. In addition, the reaction of synthesizing perfluoroketoesters from α,β-unsaturated ketones and perfluoroalkyl acids is difficult to contact with each other during the reaction because the two reactants are immiscible, resulting in slow reaction rate and low yield. Therefore, increasing the reaction rate is a difficulty in the synthesis of perfluoroketoesters. Summary of the Invention

[0005] The object of the present invention is to provide a method for promoting the efficient synthesis of perfluoroketoesters by using a magnetically driven microrotor.

[0006] The technical solutions for achieving the purpose of the present invention are as follows:

[0007] A method for efficiently synthesizing perfluoroketoates by using a magnetically driven microrotor, comprising the following steps:

[0008] (1) dissolving an alkaline catalyst in an aqueous surfactant solution to form an alkaline catalyst / surfactant aqueous solution to obtain an aqueous phase, wherein the surfactant is a mixture of polysorbate 20 (Tween 20) and a fluorosurfactant (FS-30);

[0009] (2) dispersing hydrophobic ferromagnetic nanoparticles in an alkane solution containing an α,β-unsaturated ketone to obtain an oil phase 1;

[0010] (3) dissolving the perfluoroalkyl acid in electronic fluorination liquid (FC-770) to obtain oil phase 2;

[0011] (4) mixing and emulsifying the aqueous phase and the two oil phases to prepare a magnetic Janus emulsion microreactor;

[0012] (5) Perfluoroketoates were synthesized in a magnetic Janus emulsion microreactor at room temperature under an external magnetic field.

[0013] In step (1), the alkaline catalyst is an alkaline catalyst commonly used in Oxa-Michael addition reaction, such as sodium hydroxide or sodium ethoxide. In the specific embodiment of the present invention, sodium hydroxide is used as an example.

[0014] Preferably, in step (1), the concentration of the surfactant in the alkaline catalyst / surfactant aqueous solution is 0.1 wt% to 10.0 wt%.

[0015] Preferably, in step (1), the alkaline catalyst / surfactant aqueous solution is a mixture of 0.43% Tween 20 solution and 0.62% FS-30 solution in a volume ratio of 1:1, and NaOH is added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L.

[0016] In step (2), the alkane is a combination of straight-chain alkanes, branched-chain alkanes and cycloalkanes with a carbon chain length of less than ten, such as n-heptane, cyclohexane, etc.

[0017] Preferably, in step (2), the alkane is an alkane mixture of n-heptane and cyclohexane in a volume ratio of 4:1.

[0018] In step (2), the hydrophobic ferromagnetic nanoparticles are hydrophobic Fe2O3 nanoparticles or hydrophobic Fe3O4 nanoparticles, and the concentration of the hydrophobic ferromagnetic nanoparticles is 1 mg / mL to 10 mg / mL.

[0019] In step (2), the α,β-unsaturated ketone is insoluble in water, and the α,β-unsaturated ketone is selected from β-trifluoromethylated phenenone, methylated phenenone, or methylated enone. The concentration of the α,β-unsaturated ketone is 0.1 mmol / L to 100.0 mmol / L. In a specific embodiment of the present invention, β-trifluoromethylated phenenone is used as an example.

[0020] In step (3), the perfluoroalkyl acid is poorly soluble in alkanes and water, and the perfluoroalkyl acid is selected from perfluoroheptanoic acid, perfluorooctanoic acid, or 2H,2H,3H,3H-heptadecafluoroundecanoic acid. The perfluoroalkyl acid contains a perfluoroheptyl group or a perfluorooctyl group that is identical or similar to the perfluoroheptyl group in the solvent FC-770. Based on the principle of like dissolves like, the perfluoroalkyl acid has good solubility in FC-770. The concentration of the perfluoroalkyl acid is 0.1 mmol / L to 100.0 mmol / L.

[0021] In a specific embodiment of the present invention, perfluoroheptanoic acid is taken as an example.

[0022] In step (4), the magnetic Janus emulsion microreactor is a (O1+O2) / W type Janus emulsion microreactor.

[0023] In step (4), in the magnetic Janus emulsion microreactor, the volume ratio of oil phase 1 to oil phase 2 is 1:10 to 10:1, and the volume ratio of the entire oil phase to the water phase is 1:4 to 4:1.

[0024] Preferably, in step (4), the volume ratio of oil phase 1, oil phase 2 and water phase is 1:1:2.

[0025] In step (4), the emulsification method is vortex mixing.

[0026] In step (5), the magnetic field is a permanent magnet that moves in a circular motion around the outside of the magnetic Janus emulsion microreactor, with a rotation speed of 100 to 1000 rpm and a magnetic field strength of 1 mT to 1000 mT, preferably 1 mT to 500 mT. Compared with the prior art, the present invention has the following advantages:

[0027] (1) Surfactant-stabilized emulsion systems can provide large oil-oil and oil-water interfacial areas, resolving the problem of immiscible reactants having difficulty contacting each other and increasing the probability of contact between reactants and between reactants and catalysts, thereby accelerating the reaction rate. In a multiphase system without surfactant, the reaction conversion rate was only 0.03% over 2 hours; in an emulsion microreactor containing surfactant, the reaction conversion rate reached 10.62% over 2 hours.

[0028] (2) Magnetic Janus droplets have asymmetric characteristics of magnetic response. The present invention cleverly uses magnetic Janus droplets as microrotors, and induces the magnetic microrotors to rotate in groups, in a directional and orderly manner by applying a weak external magnetic field. The rotation of the microreactor plays a stirring role, promoting the diffusion and mass transfer of reactant and product molecules, accelerating the contact of reactants at the liquid-liquid interface of the droplets, and thus promoting the forward movement of the reaction. When the reaction time is from 0h to 2h, the slope of the oxa-Michael addition reaction curve increases from 5.54h to 1.0h. -1 Rising to 14.21h -1 When a weak external magnetic field was added to the emulsion microreactor at 2 h, the reaction rate constant increased by 2.56 times, and the reaction conversion rate increased by 20%, solving the high energy consumption problem caused by magnetic stirring in general reactions.

[0029] (3) In the method of the present invention, the reaction can be carried out at room temperature. The recovery rate of ferromagnetic nanoparticles is 81.3% under an external magnetic field with a magnetic field strength of 60 mT. The ferromagnetic nanoparticles can be recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow chart of the preparation method of the present invention.

[0031] Figure 2 Schematic diagram of the magnetic Janus emulsion microreactor reaction system of the present invention.

[0032] Figure 3 The droplet morphologies of the emulsion microreactor prepared by adding different reactants are shown in Figure 1. a) 0 mmol / L; b) 10 mmol / L β-trifluoromethylated phenanthene; c) 20 mmol / L perfluoroheptanoic acid.

[0033] Figure 4 These are the droplet morphologies of the Janus emulsion microreactor prepared with different concentrations of perfluoroheptanoic acid, where a is 0 mmol / L, b is 1.0 mmol / L, c is 20.0 mmol / L, and d is 100.0 mmol / L.

[0034] Figure 5 These are the droplet morphologies of the Janus emulsion microreactor prepared with different concentrations of β-trifluoromethylated phenenone, where a is 0 mmol / L, b is 10.0 mmol / L, c is 50.0 mmol / L, and d is 100.0 mmol / L.

[0035] Figure 6 The droplet size distribution diagram of the Janus emulsion microreactor prepared with different concentrations of β-trifluoromethylated phenenone, which are 0 mmol / L; 10.0 mmol / L; 50.0 mmol / L; and 100.0 mmol / L.

[0036] Figure 7 A screenshot of a video showing the rotation of magnetic Janus emulsion droplets under an external magnetic field.

[0037] Figure 8 This is a photo of ferromagnetic nanoparticles being attracted to one side by a magnet and recovered.

[0038] Figure 9 Graph showing the change in conversion rate of the oxa-Michael addition reaction over time in different experimental groups in Example 7.

[0039] Figure 10 This is a graph showing the change in conversion rate of the oxa-Michael addition reaction over time in different experimental groups in Comparative Example 1. DETAILED DESCRIPTION

[0040] Unless otherwise specified, the terms used in the present invention generally have the meanings commonly understood by those skilled in the art. The present invention will be described in further detail below with reference to specific embodiments and accompanying drawings.

[0041] In the following examples, the preparation of hydrophobic ferromagnetic nanoparticles refers to the literature [Li Chunjin. Preparation of magnetic polymer microspheres loaded with nanogold and nanogold palladium and study on their catalytic properties [D]. Huaqiao University.].

[0042] The synthesis of β-trifluoromethylated phenenone was based on the literature [Stark DG, Morrill LC, Yeh PP, et al. Isothiourea-mediated one-pot synthesis of functionalized pyridines [J]. Angewandte Chemie International Edition, 2013, 125(44): 11856-11860.].

[0043] FC-770 was purchased from 3M Company.

[0044] Example 1

[0045] The solubilities of β-trifluoromethylated phenenone and perfluoroheptanoic acid in a mixed phase of n-heptane and cyclohexane, an FC-770 phase, and an aqueous phase were measured at room temperature. The results are shown in Table 1.

[0046] Table 1

[0047]

[0048] Note: “H” and “F” represent a mixture of n-heptane and cyclohexane saturated with FC-770 and a mixture of n-heptane and cyclohexane saturated with FC-770, respectively. The volume ratio of n-heptane to cyclohexane is 4:1. The units are (wt%).

[0049] As shown in Table 1, β-trifluoromethylated phenenone and perfluoroheptanoic acid selectively dissolve in the n-heptane / cyclohexane mixture and the FC-770 phase, respectively. β-trifluoromethylated phenenone has a solubility greater than 50.0 wt% in the n-heptane / cyclohexane mixture, but is virtually insoluble in the FC-770 phase and the aqueous phase. Perfluoroheptanoic acid has a solubility greater than 50.0 wt% in the FC-770 phase, but is virtually insoluble in the n-heptane / cyclohexane mixture and the aqueous phase.

[0050] Example 2

[0051] (1) n-heptane and cyclohexane were mixed uniformly at a volume ratio of 4:1 to form an alkane mixture. The surfactant Tween 20 was dissolved in water to form a 0.43% Tween 20 solution, and NaOH was added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L. The alkane mixture, FC-770, and NaOH / surfactant aqueous solution were added to a centrifuge tube at a volume ratio of 1:1:2 and emulsified at 3000 rpm for 3 min using a vortex mixer to prepare an emulsion microreactor.

[0052] (2) n-heptane and cyclohexane were mixed uniformly at a volume ratio of 4:1 to form an alkane mixture, and then a certain amount of β-trifluoromethylated phenenone was dissolved in 1 mL of the alkane mixture to form a 10 mmol / L β-trifluoromethylated phenenone oil phase solution. The surfactant Tween 20 was dissolved in water to form a 0.43% Tween 20 solution, and NaOH was added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L. The above-mentioned β-trifluoromethylated phenenone oil phase solution, FC-770, and NaOH / surfactant aqueous solution were measured in a volume ratio of 1:1:2 in a centrifuge tube and emulsified at 3000 rpm for 3 minutes using a vortex mixer to prepare an emulsion microreactor.

[0053] (3) A certain amount of perfluoroheptanoic acid was dissolved in 1 mL of FC-770 to form a 20 mmol / L perfluoroheptanoic acid FC-770 solution. n-Heptane and cyclohexane were mixed uniformly at a volume ratio of 4:1 to form an alkane mixture. The surfactant Tween 20 was dissolved in water to form a 0.43% Tween 20 solution, and NaOH was added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L. The above alkane mixture, perfluoroheptanoic acid FC-770 solution, and NaOH / surfactant aqueous solution were measured in a volume ratio of 1:1:2 in a centrifuge tube and emulsified at 3000 rpm for 3 min using a vortex mixer to prepare an emulsion microreactor.

[0054] Figure 3 Images of droplet morphologies in emulsion microreactors prepared with different reactants. a - 0 mmol / L; b - 10 mmol / L β-trifluoromethylated phenyl ketone; c - 20 mmol / L perfluoroheptanoic acid. It can be seen that the addition of reactants has no effect on droplet morphology.

[0055] Example 3

[0056] A certain amount of perfluoroheptanoic acid was dissolved in 1 mL of FC-770 to form a perfluoroheptanoic acid FC-770 solution. n-Heptane and cyclohexane were mixed in a 4:1 volume ratio to form an alkane mixture. Tween 20, a surfactant, was dissolved in water to form a 0.43% Tween 20 solution, and FS-30, a surfactant, was dissolved in water to form a 0.62% FS-30 solution. The 0.43% Tween 20 solution and the 0.62% FS-30 solution were then mixed in a 1:1 volume ratio. NaOH was added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L. The alkane mixture, perfluoroheptanoic acid FC-770 solution, and NaOH / surfactant aqueous solution were added to a centrifuge tube in a 1:1:2 volume ratio and emulsified using a vortex mixer at 3000 rpm for 3 minutes to prepare a Janus emulsion microreactor. The concentration of perfluoroheptanoic acid in FC-770 was changed as follows: a-0 mmol / L, b-1.0 mmol / L, c-20.0 mmol / L, d-100.0 mmol / L.

[0057] Figure 4 The droplet morphology of the Janus emulsion microreactor prepared with different concentrations of perfluoroheptanoic acid. Figure 4 It can be seen that as the concentration of perfluoroheptanoic acid gradually increases to 100.0mmol / L, the droplets partially break up. When the concentration of perfluoroheptanoic acid is 0mmol / L, 1.0mmol / L, and 20.0mmol / L, the droplet morphology does not change.

[0058] Example 4

[0059] n-heptane and cyclohexane were mixed in a 4:1 volume ratio to form an alkane mixture. A predetermined amount of β-trifluoromethylated phenenone was then dissolved in 1 mL of the alkane mixture to form an oily solution of the β-trifluoromethylated phenenone. Tween 20 and FS-30 surfactants were dissolved in water to form a 0.43% Tween 20 solution and a 0.62% FS-30 solution. The 0.43% Tween 20 and 0.62% FS-30 solutions were then mixed in a 1:1 volume ratio. NaOH was then added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L. The β-trifluoromethylated phenenone oily solution, FC-770, and NaOH / surfactant aqueous solution were then added to a centrifuge tube in a 1:1:2 volume ratio and emulsified using a vortex mixer at 3000 rpm for 3 minutes to prepare a Janus emulsion microreactor. The concentration of β-trifluoromethylated phenenone in the alkane mixture was changed as follows: a-0 mmol / L, b-10.0 mmol / L, c-50.0 mmol / L, d-100.0 mmol / L.

[0060] Figure 5 The droplet morphology of the Janus emulsion microreactor prepared with different concentrations of β-trifluoromethylated phenenone is shown in Figure 2. Figure 6 Figure 2 shows the droplet size distribution of a Janus emulsion microreactor prepared with different concentrations of β-trifluoromethylated phenenone. The figure shows that the addition of β-trifluoromethylated phenenone has no effect on droplet morphology, and the droplet size gradually decreases. At β-trifluoromethylated phenenone concentrations of 0 mmol / L, 10.0 mmol / L, 50.0 mmol / L, and 100.0 mmol / L, the droplet size ranged from 20.0 to 40.0 μm, and the droplet type was an (O1+O2) / W Janus emulsion.

[0061] Example 5

[0062] n-heptane and cyclohexane were mixed in a 4:1 volume ratio to form an alkane mixture. β-Trifluoromethylated phenenone was then dissolved in 1 mL of the alkane mixture to form an oil-phase solution of 0.15 mmol / L β-trifluoromethylated phenenone. 5 mg of hydrophobic Fe₃O₄ was then added and ultrasonically dispersed for 5 minutes to form a hydrophobic Fe₃O₄ / β-trifluoromethylated phenenone oil-phase solution. Perfluoroheptanoic acid was dissolved in 1 mL of FC-770 to form a 0.5 mmol / L perfluoroheptanoic acid / FC-770 solution. Tween 20, a surfactant, was dissolved in water to form a 0.43% Tween 20 solution. FS-30, a surfactant, was dissolved in water to form a 0.62% FS-30 solution. The 0.43% Tween 20 solution and the 0.62% FS-30 solution were then mixed in a 1:1 volume ratio. NaOH was added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L. The hydrophobic Fe3O4 / β-trifluoromethylated phenenone oil phase solution, perfluoroheptanoic acid FC-770 solution and NaOH / surfactant aqueous solution were measured and placed in a centrifuge tube in a volume ratio of 1:1:2, and emulsified at 3000 rpm for 3 min using a vortex mixer to prepare a magnetic Janus emulsion microreactor.

[0063] Figure 7 This is a screenshot of the rotation video of magnetic Janus emulsion droplets under an external magnetic field. Figure 7 It can be seen that the magnetic Janus emulsion droplets act as microrotors. Under the external magnetic field, the magnetic Janus emulsion droplets rotate in groups, in a directional and orderly manner, accelerating the contact of reactants at the liquid-liquid interface of the droplets.

[0064] Example 6

[0065] n-heptane and cyclohexane were mixed in a 4:1 volume ratio to form an alkane mixture. β-Trifluoromethylated phenenone was then dissolved in 1 mL of the alkane mixture to form an oil-phase solution of 0.15 mmol / L β-trifluoromethylated phenenone. 2 mg of hydrophobic Fe₃O₄ was then added and ultrasonically dispersed for 5 minutes to form a hydrophobic Fe₃O₄ / β-trifluoromethylated phenenone oil-phase solution. Perfluoroheptanoic acid was dissolved in 1 mL of FC-770 to form a 0.5 mmol / L perfluoroheptanoic acid / FC-770 solution. Tween 20, a surfactant, was dissolved in water to form a 0.43% Tween 20 solution. FS-30, a surfactant, was dissolved in water to form a 0.62% FS-30 solution. The 0.43% Tween 20 solution and the 0.62% FS-30 solution were then mixed in a 1:1 volume ratio. NaOH was added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L. The hydrophobic Fe₃O₄ / β-trifluoromethylated phenanthene oil solution, perfluoroheptanoic acid FC-770 solution, and NaOH / surfactant aqueous solution were added to a centrifuge tube in a 1:1:2 volume ratio. The mixture was emulsified using a vortex mixer at 3000 rpm for 3 minutes to prepare a magnetic Janus emulsion microreactor. Under these conditions, a permanent magnet was added to allow the ferromagnetic nanoparticles to be recycled.

[0066] from Figure 8 It can be seen that at a hydrophobic Fe3O4 concentration of 2 mg / mL, the ferromagnetic nanoparticles were attracted to one side by a permanent magnet with a magnetic field strength of 60 mT and recovered.

[0067] Example 7

[0068] (1) Three-phase experimental group: n-heptane and cyclohexane were mixed uniformly at a volume ratio of 4:1 to form an alkane mixture. β-trifluoromethylated phenenone was then dissolved in 1 mL of the alkane mixture to form an oil phase solution of β-trifluoromethylated phenenone with a concentration of 0.15 mmol / L. Perfluoroheptanoic acid was dissolved in 1 mL of FC-770 to form a FC-770 solution of perfluoroheptanoic acid with a concentration of 0.5 mmol / L. A 0.2 mol / L aqueous solution of NaOH was prepared. The oil phase solution of β-trifluoromethylated phenenone, the FC-770 solution of perfluoroheptanoic acid, and the aqueous solution of NaOH were measured in a centrifuge tube at a volume ratio of 1:1:2. The mixture was allowed to stand at room temperature. Samples were taken every hour and analyzed by high performance liquid chromatography.

[0069] (2) Microreactor experimental group: n-heptane and cyclohexane were mixed uniformly at a volume ratio of 4:1 to form an alkane mixture, and then β-trifluoromethylated phenenone was dissolved in 1 mL of the alkane mixture to form an oil phase solution of β-trifluoromethylated phenenone with a concentration of 0.15 mmol / L. Perfluoroheptanoic acid was dissolved in 1 mL of FC-770 to form an FC-770 solution of perfluoroheptanoic acid with a concentration of 0.5 mmol / L. The surfactant Tween 20 was dissolved in water to form a 0.43% Tween 20 solution, and the surfactant FS-30 was dissolved in water to form a 0.62% FS-30 solution. The 0.43% Tween 20 solution and the 0.62% FS-30 solution were then mixed uniformly at a volume ratio of 1:1, and NaOH was added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L. The β-trifluoromethylated phenenone oil phase solution, perfluoroheptanoic acid FC-770 solution, and NaOH / surfactant aqueous solution were added to a centrifuge tube in a volume ratio of 1:1:2. The mixture was emulsified using a vortex mixer at 3000 rpm for 3 minutes to prepare a Janus emulsion microreactor. The mixture was allowed to stand at room temperature. Samples were taken every 0.5 hours and analyzed by high-performance liquid chromatography.

[0070] (3) Microrotor experiment group: n-heptane and cyclohexane were mixed at a volume ratio of 4:1 to form an alkane mixture. β-Trifluoromethylated phenenone was then dissolved in 1 mL of the alkane mixture to form an oily solution of β-trifluoromethylated phenenone with a concentration of 0.15 mmol / L. 5 mg of hydrophobic Fe₃O₄ was then added and ultrasonically dispersed for 5 min to obtain an oily solution of hydrophobic Fe₃O₄ / β-trifluoromethylated phenenone. Perfluoroheptanoic acid was dissolved in 1 mL of FC-770 to form a 0.5 mmol / L perfluoroheptanoic acid in FC-770 solution. The surfactant Tween 20 was dissolved in water to form a 0.43% Tween 20 solution, and the surfactant FS-30 was dissolved in water to form a 0.62% FS-30 solution. The 0.43% Tween 20 solution and the 0.62% FS-30 solution were then mixed in a 1:1 volume ratio. NaOH was then added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L. The hydrophobic Fe₃O₄ / β-trifluoromethylated phenenone oil phase solution, the perfluoroheptanoic acid FC-770 solution, and the NaOH / surfactant aqueous solution were added to a centrifuge tube in a 1:1:2 volume ratio and emulsified using a vortex mixer at 3000 rpm for 3 minutes to prepare a magnetic Janus emulsion microreactor. A permanent magnet was placed in a circular motion around the centrifuge tube with a magnetic field strength of 30 mT. Samples were collected every 0.5 hours and analyzed by high-performance liquid chromatography.

[0071] from Figure 9It can be seen that in the three-phase system without surfactant, the reaction conversion rate of 2h is only 0.03%; in the emulsion microreactor with surfactant, the reaction conversion rate of 2h is as high as 10.62%. When the reaction time is from 0h to 2h, the slope of the oxa-Michael addition reaction curve increases from 5.54h to 1.04h. -1 Rising to 14.21h -1 At 2 h, the addition of a weak external magnetic field to the emulsion microreactor increased the reaction rate constant by 2.56 times, and the reaction conversion rate increased by 20%. The reaction rate accelerated with the addition of a magnetic field. This indicates that magnetic Janus emulsion droplets, when used as microrotors, have a significant effect on accelerating the oxa-Michael addition reaction.

[0072] Comparative Example 1

[0073] (1) n-heptane and cyclohexane were mixed uniformly at a volume ratio of 4:1 to form an alkane mixture, and then β-trifluoromethylated phenenone was dissolved in 1 mL of the alkane mixture to form an oil phase solution of β-trifluoromethylated phenenone with a concentration of 0.15 mmol / L. Perfluoroheptanoic acid was dissolved in 1 mL of FC-770 to form a FC-770 solution of perfluoroheptanoic acid with a concentration of 0.5 mmol / L. The surfactant Tween 20 was dissolved in water to form a 0.43% Tween 20 solution, and NaOH was added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L. The above-mentioned oil phase solution of β-trifluoromethylated phenenone, the FC-770 solution of perfluoroheptanoic acid, and the NaOH / surfactant aqueous solution were measured in a volume ratio of 1:1:2 in a centrifuge tube and emulsified at a speed of 3000 rpm for 3 minutes using a vortex mixer to prepare a Janus emulsion microreactor. The mixture was allowed to stand at room temperature. Samples were taken every 0.5 h and detected by high performance liquid chromatography.

[0074] (2) n-heptane and cyclohexane were mixed uniformly at a volume ratio of 4:1 to form an alkane mixture, and then β-trifluoromethylated phenenone was dissolved in 1 mL of the alkane mixture to form an oil phase solution of β-trifluoromethylated phenenone with a concentration of 0.15 mmol / L. 5 mg of hydrophobic Fe3O4 was then added and ultrasonically dispersed for 5 minutes to obtain an oil phase solution of hydrophobic Fe3O4 / β-trifluoromethylated phenenone. Perfluoroheptanoic acid was dissolved in 1 mL of FC-770 to form an FC-770 solution of perfluoroheptanoic acid with a concentration of 0.5 mmol / L. The surfactant Tween 20 was dissolved in water to form a 0.43% Tween 20 solution, and NaOH was added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L. A magnetic Janus emulsion microreactor was prepared by adding the aforementioned hydrophobic Fe₃O₄ / β-trifluoromethylated phenenone oil phase solution, perfluoroheptanoic acid FC-770 solution, and NaOH / surfactant aqueous solution to a centrifuge tube in a volume ratio of 1:1:2. The mixture was emulsified using a vortex mixer at 3000 rpm for 3 minutes. A permanent magnet was placed in a circular motion around the centrifuge tube at a magnetic field strength of 30 mT. Samples were collected every 0.5 hours and analyzed by high-performance liquid chromatography.

[0075] from Figure 10 As can be seen, in the emulsion microreactor containing the surfactant Tween 20, the reaction conversion rate was 11.7% after 2 hours. When the reaction time increased from 0 to 2 hours, the reaction conversion rate in the emulsion microreactor with the addition of a 30 mT external magnetic field only increased by 4.9%. This indicates that the addition of only Tween 20 as a surfactant does not significantly improve the reaction conversion rate, even when synthesizing perfluoroketoates using a magnetic Janus emulsion microreactor.

[0076] In summary, the present invention uses surfactants to construct a magnetic Janus emulsion microreactor, making full use of the orderly rotation of the Janus emulsion droplet group under an external magnetic field to achieve the purpose of accelerating the contact of reactants at the liquid-liquid interface of the droplets, and can achieve efficient synthesis of perfluoroketoates in an emulsion system at room temperature. On the one hand, the unique advantage of the Janus droplet composition being two phases and the large contact area between the two phases is utilized to significantly increase the collision probability between the reactant molecules; at the same time, ferromagnetic nanoparticles can be selectively dispersed in one phase of the droplet, thereby giving the droplet microreactor a magnetic anisotropy characteristic. The external magnetic field is used to induce the magnetic microrotor group to rotate in a directional and orderly manner, which plays a stirring role during the reaction process and promotes the diffusion and mass transfer of reactant and product molecules. The above two advantages work together to significantly promote the rate of the oxa-Michael addition reaction. Compared to existing magnetically stirred oil-water two-phase reaction systems, the magnetically driven microrotor solves the problem of high energy consumption associated with magnetic stirring. The surfactant-stabilized emulsion system provides a large oil-oil and oil-water interface area, eliminating the difficulty in contact between immiscible reactants. This increases the chances of contact between reactants and between reactants and the catalyst, thereby improving reaction efficiency. This invention ultimately achieves an increase in oxa-Michael reaction conversion within a range of 10.0-30.0% within 2 hours.

Claims

1. A method for promoting efficient synthesis of perfluoroketoates using a magnetically driven microrotor, characterized in that: The specific steps are as follows: (1) dissolving an alkaline catalyst in a surfactant aqueous solution to form an alkaline catalyst / surfactant aqueous solution to obtain an aqueous phase, wherein the surfactant is a mixture of Tween 20 and FS-30; (2) Dispersing hydrophobic ferromagnetic nanoparticles in α，β -unsaturated ketone alkane solution, to obtain oil phase 1, the α，β - unsaturated ketones selected from β-trifluoromethylated phenenones or methylated phenenones, α，β - the concentration of the unsaturated ketone is 0.1 mmol / L to 100.0 mmol / L, and the alkane is a combination of straight-chain alkanes, branched-chain alkanes, and cycloalkanes with a carbon chain length of less than ten; (3) dissolving a perfluoroalkyl acid in FC-770 to obtain an oil phase 2, wherein the perfluoroalkyl acid is selected from perfluoroheptanoic acid, perfluorooctanoic acid or 2H,2H,3H,3H-heptadecafluoroundecanoic acid, and the concentration of the perfluoroalkyl acid is 0.1 mmol / L to 100.0 mmol / L; (4) The aqueous phase and the two oil phases were mixed and emulsified to prepare a magnetic Janus emulsion microreactor; (5) Perfluoroketoates were synthesized in a magnetic Janus emulsion microreactor at room temperature under an external magnetic field.

2. The method according to claim 1, characterized in that In step (1), the alkaline catalyst is sodium hydroxide or sodium ethoxide; and the concentration of the surfactant in the alkaline catalyst / surfactant aqueous solution is 0.1 wt% to 10.0 wt%.

3. The method according to claim 1, wherein In step (1), the alkaline catalyst / surfactant aqueous solution is a mixture of 0.43 wt% Tween 20 solution and 0.62 wt% FS-30 solution in a volume ratio of 1:1, and NaOH is added to form a NaOH / surfactant aqueous solution with a NaOH concentration of 0.2 mol / L.

4. The method according to claim 1, wherein In step (2), the alkane is an alkane mixture of n-heptane and cyclohexane in a volume ratio of 4:

1.

5. The method according to claim 1, wherein In step (2), the hydrophobic ferromagnetic nanoparticles are hydrophobic Fe2O3 nanoparticles or hydrophobic Fe3O4 nanoparticles, and the concentration of the hydrophobic ferromagnetic nanoparticles is 1 mg / mL to 10 mg / mL.

6. The method according to claim 1, characterized in that In step (4), in the magnetic Janus emulsion microreactor, the volume ratio of oil phase 1 to oil phase 2 is 1:10-10:1, and the overall volume ratio of oil phase to water phase is 1:4-4:

1.

7. The method according to claim 1, characterized in that In step (4), the volume ratio of oil phase 1, oil phase 2 and water phase is 1:1:

2.

8. The method according to claim 1, wherein In step (4), the emulsification method is vortex mixing; in step (5), the magnetic field is a permanent magnet that performs circular motion around the outside of the magnetic Janus emulsion microreactor, with a rotation speed of 100~1000 rpm and a magnetic field strength of 1mT~1000 mT.

9. The method according to claim 8, characterized in that The magnetic field strength is 1mT~500mT.

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