Method for synthesizing dihydronaphthalene-1 (2H)-ketone through oxidation of styrene and derivatives thereof

Abstract

The invention provides a method for oxidatively synthesizing dihydronaphthalene-1 (2H)-ketone from styrene and derivatives thereof, which comprises the following steps: in an electrochemical catalytic reactor, oxidizing styrene and derivatives thereof into 3, 4-dihydronaphthalene-1 (2H)-ketone through electrochemical catalysis; a working electrode of the electrochemical catalytic reactor is a platinum nanoparticle electrode. The reaction does not need harsh temperature and pressure, does not use an additional redox agent, only utilizes the cleanest reaction reagent'electrons', generates the required catalyst or reaction active intermediate in situ, has the advantages of cheap and easily available electrode material, simple process and high repeatability, is an efficient, safe, green and environment-friendly production process, and is suitable for industrial production. The potential industrial application value is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and particularly relates to a method for oxidatively synthesizing dihydronaphthalen-1(2H)-one from styrene and its derivatives. Background Art

[0002] Styrene and its derivatives have unique structural features. In styrene, the electrons of the vinyl group are conjugated with the benzene ring. It is insoluble in water and soluble in most organic solvents such as ethanol and ether. Styrene and its derivatives have a wide range of applications in the field of organic chemical production. For example, they are important monomers for synthesizing polymers such as synthetic resins, ion exchange resins, and synthetic rubbers. They can also be applied to industries such as pharmaceuticals, dyes, pesticides, and mineral processing.

[0003] Industrially, after being oxidized, styrene and its derivatives can produce various industrial products such as benzyl alcohol, benzaldehyde, benzoic acid, styrene oxide, and 1-phenylethane-1,2-diol, which have high added value. In particular, the oxidative coupling of styrene can produce many biological macromolecular structures and is an effective means for extending the carbon chain in molecules. Traditional oxidative coupling methods often require heavy metals or strong oxidants, resulting in high material and energy consumption, serious environmental pollution, and difficult post-treatment in products, which greatly limits their applications. Therefore, environmentally friendly, efficient, and green economic methods for the oxidative coupling of styrene have received increasing attention and emphasis.

[0004] In recent decades, the shape-controlled synthesis of platinum (Pt)-group noble metal nanocrystals has been widely studied in the field of electrocatalysis. Researchers have synthesized various platinum-based noble metal nanocrystals (PtNCs) with different morphologies, compositions, and sizes using different methods and applied them to important electrocatalytic reactions such as the oxygen reduction reaction, hydrogen evolution reaction (HER), and ethanol oxidation reaction (EOR). Among them, platinum nanoparticles (PtNPs) have very wide applications due to their unique chemical and physical properties. As a noble metal, platinum has very excellent electrical conductivity. At the same time, its chemical properties are very stable, with good mechanical properties and corrosion resistance, and high electrocatalytic activity for the iodine / triiodide redox reaction. It is usually used as the counter electrode (CE) of DSSCs. Its optical properties can be used in electronics, catalysis, sensing, and photovoltaic applications.

[0005] Carbon materials are of particular value due to their excellent properties, such as their adjustable shape, size, and porosity, chemical stability, corrosion resistance, low cost, good heat resistance, and electrical conductivity. The combination of all these properties promotes the use of these materials as electrode carriers.

[0006] Due to the high catalytic performance of such materials and the various uses of the products after the oxidation of styrene, the preparation methods of new materials for the oxidation of styrene have received increasing attention. In particular, the use of efficient catalysts or green oxidation methods has become a research hotspot at home and abroad. The methods for the oxidation of styrene reported currently are as follows:

[0007] In 2022, a literature reported the oxidation of styrene to benzaldehyde. Using styrene as the raw material, sodium periodate and ruthenium as co-oxidants to catalytically oxidize styrene to remove one carbon atom to generate benzaldehyde. The raw materials of this kind of reaction are cheap and easily available, and the product yield is high. (Applied organometallic chemistry. 2022, 36(10), e6831). In addition, in 2024, a method for the oxidation of styrene to benzaldehyde by a photo-promoted bimetallic catalytic system was also reported. This method uses Cu-BTC-TiO 2 nanoparticles for catalysis, which greatly improves the catalytic efficiency, but the complex MOF production process also limits its application in industry. (Appl Organomet Chem. 2024; 38e7594.)

[0008]

[0009] In addition, there are also reports on the oxidative coupling of styrene. Such reactions usually use styrene or its derivatives as reactants. In the presence of an external oxygen source, one molecule of styrene is oxidized to generate a reactive intermediate, which then attacks another molecule of styrene to complete the process of oxidative coupling. Such reactions usually synthesize a large molecule from two molecules of styrene, which has high value both in theoretical research and practical applications. For example, in the presence of photocatalytic oxygen and using acetonitrile as the solvent, styrene can be oxidatively coupled to dihydronaphthalen-1(2H)-one or its derivatives. They use light as the direct energy source to oxidize styrene efficiently and greenly, but the expensive acridine-based photocatalysts greatly limit their application.

[0010] There is also a report on the use of TiO 2 photocatalyst. In this method, oxygen acts through the photocatalyst, loses one electron to become a more reactive oxygen radical, thereby initiating the reaction of styrene and generating dimerization, and finally generating dihydronaphthalen-1(2H)-one products. (Green Chem., 2016, 18, 2864 - 2870)(Advanced Synthesis & Catalysis, 2016, 358(23): 3887 - 3896.)(ACS Catal. 2016, 6, 8389 - 8394)

[0011]

[0012] While these reactions can simply and efficiently oxidize styrene or its derivatives with a wide substrate scope, there are still several drawbacks: the use of transition metals or noble metal catalysts causes the loss of noble metals and environmental pollution to a certain extent; the use of strong oxidizing and reducing agents increases the reaction risk to a certain extent and does not meet the requirements of environmentally friendly green synthesis methods; and the use of photocatalysts makes the post-treatment of the reaction difficult, and some reactions require specific equipment and instruments, which limits the application of this reaction. Summary of the Invention

[0013] The object of the present invention is to provide a method for the oxidative synthesis of dihydronaphthalen-1(2H)-one from styrene and its derivatives without the use of transition metals or noble metal catalysts, without the use of strong oxidants, and without photocatalysis.

[0014] To achieve the above object, the present invention provides a method for the oxidative synthesis of dihydronaphthalen-1(2H)-one from styrene and its derivatives, comprising: in an electrochemical catalytic reactor, oxidizing styrene and its derivatives to 3,4-dihydronaphthalen-1(2H)-one by electrochemical catalysis, and the reaction formula is as follows:

[0015]

[0016] Wherein: each R1 is independently selected from one of hydrogen, halogen, substituted or unsubstituted C1-10 alkyl, substituted or unsubstituted aryl, substituted or unsubstituted C1-10 alkoxy, substituted or unsubstituted amino, carboxyl, ester group, acyl group, cyano group, nitro group, hydroxyl group, azide group.

[0017] Further, the electrolyte is one or more of lithium perchlorate, ammonium perchlorate, tetrabutylammonium tetrafluoroborate, tetrabutylammonium hexafluorophosphate, tetraethylammonium benzenesulfonate, tetraethylammonium acetate.

[0018] Further, for the preparation method of the aromatic aldehyde and its derivatives, the oxygen content in the oxygen atmosphere is greater than 0%.

[0019] Further, the platinum electrode catalyzes the synthesis of dihydronaphthalen-1(2H)-one from styrene and its derivatives, and the solvent is one or more of water, methanol, ethanol, acetonitrile, benzene, toluene, tetrahydrofuran, 1,4-dioxane, dimethyl sulfoxide, N,N-dimethylformamide, hexafluoroisopropanol, trifluoroacetic acid, ethylene glycol, polyethylene glycol.

[0020] Further, the platinum electrode catalyzes the synthesis of dihydronaphthalen-1(2H)-one from styrene and its derivatives, and it is characterized in that the counter electrode of the electrochemical catalytic reactor is one or more of a platinum electrode, a nickel electrode, a graphite electrode, a glassy carbon electrode, a copper electrode, a magnesium electrode, a silver electrode, an iron electrode, a gold electrode.

[0021] Further, the platinum electrode catalyzes the synthesis of dihydronaphthalen-1(2H)-one from styrene and its derivatives, and the electrolytic cell of the electrochemical catalytic reactor is one of a two-compartment cell separated by a diaphragm, a single-compartment cell without diaphragm separation, or a continuous-flow electrochemical reaction cell.

[0022] Further, the platinum electrode catalyzes the synthesis of dihydronaphthalen-1(2H)-one from styrene and its derivatives, and the electrolysis mode of the electrochemical catalysis reaction is one of constant current or constant voltage. The constant voltage range is 0 - 30 V, and the constant current range is 0 - 100 mA.

[0023] Further, the platinum electrode catalyzes the synthesis of dihydronaphthalen-1(2H)-one from styrene and its derivatives, the reaction temperature is 0 - 50 °C, and the reaction time is 0 - 36 h.

[0024] Further, the platinum electrode catalyzes the synthesis of dihydronaphthalen-1(2H)-one from styrene and its derivatives, and the concentration of styrene or its derivative in the solvent is 0.001 mol / L - 0.5 mol / L.

[0025] Further, the platinum electrode catalyzes the synthesis of dihydronaphthalen-1(2H)-one from styrene and its derivatives. The reaction solution containing dihydronaphthalen-1(2H)-one obtained by the electrochemical catalytic reaction is concentrated, purified by silica gel column, and freeze-dried to obtain dihydronaphthalen-1(2H)-one.

[0026] Further, it is washed several times with an organic phase and dried with anhydrous magnesium sulfate, and finally the organic phase is concentrated to obtain dihydronaphthalen-1(2H)-one.

[0027] Further, the concentration is carried out by one of atmospheric distillation, vacuum distillation, and rotary evaporation.

[0028] Further, post-treatment can also be carried out by column chromatography purification. The column chromatography uses silica gel with 200 - 300 mesh as the separation resin, and the eluent is selected from at least one of petroleum ether, n-hexane, dichloromethane, water, acetonitrile, methanol, and ethyl acetate.

[0029] The preparation method of the above platinum nanoparticle electrode is: in a deposition solution containing platinum ions, platinum nanoparticles are prepared on a substrate by an equipotential electrodeposition method to obtain a platinum nanoparticle electrode.

[0030] Further, for the preparation of the platinum nanoparticle electrode, the substrate material is one or more of carbon paper, carbon felt, glassy carbon, reticulated glassy carbon, nickel foam, and copper foam.

[0031] Further, for the preparation of the platinum nanoparticle electrode, the source of metallic platinum in the deposition solution can be one of platinum dichloride, chloroplatinic acid, potassium chloroplatinate, and diaminodinitroplatinum, and the concentration of platinum ions can be 0.01 - 100 mmol / L.

[0032] Further, for the preparation of the platinum nanoparticle electrode, the anions in the deposition solution are each independently selected from one or more of fluoride ions, chloride ions, bromide ions, iodide ions, nitrate ions, sulfate ions, perchlorate ions, and p-toluenesulfonate ions, and the concentration of the anions is 0.005 - 0.5 mol / L.

[0033] Further, for the preparation of the platinum nanoparticle electrode, it is characterized in that the electrodeposition method can be underpotential deposition, isopotential deposition or overpotential deposition, and the deposition potential is -0.5 V to -1.2 V. The deposition time is between 10 - 300 seconds.

[0034] The structural formula of the above-mentioned dihydronaphthalen-1(2H)-one is as follows:

[0035]

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] In the present invention, platinum nanoparticles are loaded on the conductive carbon paper, replacing the expensive platinum electrode with an inexpensive carbon-based material, saving the reaction cost and greatly improving the catalytic activity. At the same time, this electrode is used for the catalytic oxidation of styrene and its derivatives to obtain a series of products with higher added value, such as 3,4-dihydronaphthalen-1(2H)-one. This reaction does not require strict temperature and pressure, does not use additional oxidation or reduction reagents, and only uses the cleanest reaction reagent "electron" to in-situ generate the required catalyst or reaction active intermediate. The electrode material is inexpensive and easily available, the process is simple, and the repeatability is high. It is an efficient, safe, and green production process with potential industrial application value. Description of the Drawings

[0038] Figure 1 is the deposition curve of the platinum nanoparticle electrode;

[0039] Figure 2 is the XRD characterization diagram of the platinum nanoparticles;

[0040] Figure 3 is the SEM characterization diagram of the platinum nanoparticles;

[0041] Figure 4 is the SEM energy spectrum diagram of the platinum nanoparticles;

[0042] Figure 5 is for compound 3a in the example1 1H NMR carbon nuclear magnetic resonance spectrum;

[0043] Figure 6 This is the 13 13C NMR carbon nuclear magnetic resonance spectrum of compound 3a in the examples.

[0044] Figure 7 This is the 1 1H NMR carbon nuclear magnetic resonance spectrum;

[0045] Figure 8 This is the 13 13C NMR carbon nuclear magnetic resonance spectrum of compound 3b in the examples.

[0046] Figure 9 This is the 1 1H NMR carbon nuclear magnetic resonance spectrum;

[0047] Figure 10 This is the 13 13C NMR carbon nuclear magnetic resonance spectrum of compound 3c in the examples.

[0048] Figure 11 This is the 1 1H NMR carbon nuclear magnetic resonance spectrum;

[0049] Figure 12 This is the 13 13C NMR carbon nuclear magnetic resonance spectrum of compound 3d in the examples. Detailed implementation manners

[0050] Hereinafter, embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present application more clearly, and therefore are only examples and cannot be used to limit the protection scope of the present application.

[0051] The present invention provides a method for synthesizing dihydronaphthalen-1(2H)-one from styrene and its derivatives. In an electrochemical catalytic reactor, styrene and its derivatives are electrochemically catalytically oxidized to 3,4-dihydronaphthalen-1(2H)-one; the reaction formula is as follows:

[0052]

[0053] Wherein the R groups are each independently selected from one of hydrogen, halogen, substituted or unsubstituted C1-10 alkyl, substituted or unsubstituted aryl, substituted or unsubstituted C1-10 alkoxy, substituted or unsubstituted amino, carboxyl, ester group, acyl group, cyano group, nitro group, hydroxyl group, azide group.

[0054] The working electrode of the electrochemical catalytic reactor adopted by the present invention is a platinum nanoparticle electrode;

[0055] According to the present invention, the electrolyte for electrochemical catalysis is one or more of lithium perchlorate, ammonium perchlorate, tetrabutylammonium tetrafluoroborate, tetrabutylammonium hexafluorophosphate, tetraethylammonium benzenesulfonate, and tetraethylammonium acetate. It should be understood that in the reaction of the present invention, the common feature of the above electrolytes is that they are ammonium salts or lithium salts. In the reaction of the present invention, the above electrolytes can all create the electrolytic conditions for electrochemical catalysis in the reaction of the present invention. Therefore, as long as any one of the above electrolytes is selected, the above reaction of the present application can be achieved. Although only some electrolyte embodiments are given in the specific embodiments of the present invention, those skilled in the art should understand that the embodiments are only used to explain the preferred implementation schemes given by the present invention and are not used to limit the present invention. Those skilled in the art can also obtain the present invention according to other electrolytes given by the present invention under the inspiration of the embodiments.

[0056] According to the present invention, the oxygen content in the oxygen atmosphere is greater than 0%. It should be understood that in the reaction of the present invention, as long as styrene or its derivatives, oxygen, and the reaction conditions for electrochemical catalysis exist, the above reaction can occur. Although only some embodiments of the oxygen content of the parameters are given in the specific embodiments of the present invention, those skilled in the art should understand that the embodiments are only used to explain the preferred implementation schemes given by the present invention and are not used to limit the present invention. Those skilled in the art can also obtain the present invention according to other parameters given by the present invention under the inspiration of the embodiments.

[0057] According to the present invention, the solvent is one or more of water, methanol, ethanol, acetonitrile, benzene, toluene, tetrahydrofuran, 1,4-dioxane, dimethyl sulfoxide, N,N-dimethylformamide, hexafluoroisopropanol, trifluoroacetic acid, ethylene glycol, and polyethylene glycol. It should be understood that in the reaction of the present invention, the use of the above solvents is only for dissolving the reactants, and the solvents themselves do not participate in the reaction. Therefore, as long as a solvent that can dissolve the reactants is selected, the above reaction of the present application can be achieved. Although only some of the above solvents are given as reaction solvent embodiments in the specific embodiments of the present invention, those skilled in the art should understand that the embodiments are only used to explain the preferred implementation schemes given by the present invention and are not used to limit the present invention. Those skilled in the art can also obtain the present invention according to other solvents given by the present invention under the inspiration of the embodiments.

[0058] According to the present invention, the counter electrode of the electrochemical catalytic reactor is one or more of a platinum electrode, a nickel electrode, a graphite electrode, a glassy carbon electrode, a copper electrode, a magnesium electrode, a silver electrode, an iron electrode, and a gold electrode. The electrolytic cell of the electrochemical catalytic reactor is a two-compartment cell separated by a diaphragm, a single-compartment cell without diaphragm separation, or a continuous flow electrochemical reaction cell. The electrolysis mode of the electrochemical catalytic reaction is one of the two modes of constant current or constant voltage. The constant voltage range is 0 to 30 V, and the constant current range is 0 to 100 mA. It should be understood that in the reaction of the present invention, the above-mentioned counter electrode is used to provide a conductive environment for the electrolytic cell, and the counter electrode itself does not participate in the reaction. The type of electrolytic cell is a unique device for the electrolysis reaction. Therefore, as long as a suitable counter electrode and electrolytic cell are selected, the above-mentioned reaction of the present application can be realized. Although only the preferred embodiments of the reaction in the above-mentioned partial devices are given in the specific embodiments of the present invention, those skilled in the art should understand that the embodiments are only used to explain the preferred implementation schemes given by the present invention and are not used to limit the present invention. Those skilled in the art can also obtain the present invention according to other solvents given by the present invention under the inspiration of the embodiments.

[0059] According to the present invention, the reaction solution containing dihydronaphthalen-1(2H)-one obtained by using the prepared platinum nanoelectrode for the catalytic reaction of styrene is concentrated, purified by silica gel column, and freeze-dried to obtain dihydronaphthalen-1(2H)-one.

[0060] In addition, the preparation method of the platinum nanoparticle electrode in the present invention is as follows: in a deposition solution containing platinum ions, platinum nanoparticles are prepared on a substrate by an equipotential electrodeposition method to obtain a platinum nanoparticle electrode.

[0061] According to the present invention, the substrate material is one or more of carbon paper, carbon felt, glassy carbon, reticulated glassy carbon, nickel foam, and copper foam. It should be understood that in the reaction of the present invention, the common feature of the above-mentioned substrates is a conductive material. In the reaction of the present invention, the above-mentioned substrate materials can all create the preparation conditions for platinum nanoparticles. Therefore, as long as the above-mentioned substrate materials are selected, the above-mentioned reaction of the present application can be realized. Although only the embodiments of some substrate materials are given in the specific embodiments of the present invention, those skilled in the art should understand that the embodiments are only used to explain the preferred implementation schemes given by the present invention and are not used to limit the present invention. Those skilled in the art can also obtain the present invention according to other electrolytes given by the present invention under the inspiration of the embodiments.

[0062] According to the present invention, the source of platinum metal in the deposition solution can be one of platinum dichloride, chloroplatinic acid, potassium chloroplatinate, and diaminodinitroplatinum, and the concentration of platinum ions can be 0.01 - 100 mmol / L. The anions in the deposition solution are each independently selected from one or more of fluoride ions, chloride ions, bromide ions, iodide ions, nitrate ions, sulfate ions, perchlorate ions, and p-toluenesulfonate ions, and the concentration of the anions is 0.005 - 0.5 mol / L. It should be understood that in the reaction of the present invention, the above-mentioned sources of platinum ions are all platinum-containing salts and have good solubility in aqueous solutions. The above-mentioned anions can all provide a good conductive environment for the solution and have an effect on the shape of platinum ions during the deposition process. Therefore, as long as the above-mentioned platinum salts and anions are selected, the above-mentioned reaction of the present application can be achieved. Although only some examples of platinum salts and anions are given in the specific embodiments of the present invention, those skilled in the art should understand that the examples are only used to explain the preferred implementation schemes given by the present invention and are not used to limit the present invention. Those skilled in the art can also obtain the present invention according to other platinum salts and anions given by the present invention under the inspiration of the examples.

[0063] According to the present invention, the electrodeposition method can be selected as underpotential deposition, isopotential deposition, or overpotential deposition, and the deposition potential is -0.5V to -1.2V. The deposition time is between 10 - 300 seconds. It should be understood that in the reaction of the present invention, as long as the potential for platinum ion deposition is reached, the platinum ion deposition reaction can occur. Although only some parameter implementation methods of deposition potential and deposition time are given in the specific embodiments of the present invention, those skilled in the art should understand that the examples are only used to explain the preferred implementation schemes given by the present invention and are not used to limit the present invention. Those skilled in the art can also obtain the present invention according to other parameters given by the present invention under the inspiration of the examples.

[0064] The following further illustrates the technical solutions and technical effects of the present invention through specific examples.

[0065] Preparation Example of Platinum Nanoparticle Electrode:

[0066] Preparation of the substrate (carbon paper)

[0067] Cut the entire carbon paper into a rectangle of 15 mm × 10 mm, and polish the four sides smoothly. Clean it in a 50W ultrasonic cleaner with 3M hydrochloric acid, absolute ethanol, acetone, and deionized water for 15 minutes respectively, and then dry it in an oven at 80°C for 2 hours.

[0068] Preparation of the deposition solution

[0069] Weigh the platinum salt K 2 PtCl 6(240 mg) and sodium chloride (290 mg) as electrolyte were dissolved in 50 ml of deionized water and oscillated in a 50 W ultrasonic cleaner for 30 minutes to ensure complete dissolution of all solids.

[0070] Determine the reduction potential of Pt nanoparticles

[0071] Take 10 ml of the prepared solution, clamp the working electrode (carbon paper), counter electrode (platinum sheet), and reference electrode (Ag / AgCl) on the electrode clamp, set the cyclic voltammetry parameters: initial potential 0 V, upper limit potential 0.1 V, lower limit potential -1.2 V, scan rate 50 mV / s, sensitivity 1.0e-004, and find the Pt reduction potential in the cyclic voltammogram;

[0072] Electrodeposit platinum nanoparticles

[0073] Use i-t amperometry to perform electrodeposition at the Pt reduction potential. The initial potential is the reduction potential of platinum, run for 40 s, and deposit three electrode sheets in parallel at one time.

[0074] Figure 1 Deposit curve of platinum nanoparticles electrode in the preparation example of platinum nanoparticles electrode;

[0075] Figure 2 XRD characterization diagram of platinum nanoparticles in the preparation example of platinum nanoparticles electrode;

[0076] Figure 3 SEM characterization diagram of platinum nanoparticles in the preparation example of platinum nanoparticles electrode;

[0077] Figure 4 SEM energy spectrum diagram of platinum nanoparticles in the preparation example of platinum nanoparticles electrode;

[0078] Using the electrochemical catalytic reactor of the platinum nanoparticle electrode obtained from the above preparation example for the synthesis of styrene and its derivatives into 2,3-dihydronaphthalen-1(2H)-one Example: Example of Synthesizing 2,3-Dihydronaphthalen-1(2H)-one from Styrene and Its Derivatives Using the Electrochemical Catalytic Reactor of the Platinum Nanoparticle Electrode Obtained from the Above Preparation Example:

[0079] Example 1

[0080] Electrochemical catalytic synthesis of dihydronaphthalen-1(2H)-one 3a from styrene derivative 1a. Its structure and preparation method are as follows:

[0081]

[0082] 4-Phenylstyrene (0.2 mmol), tetrabutylammonium hexafluorophosphate (0.4 mmol), acetonitrile (5 mL), and water (0.5 mL) were added to a 10 mL reactor. A magnetic stir bar was added. Using the prepared platinum electrode as the anode and the platinum sheet electrode as the cathode, a constant current electrolysis (7.5 mA) was carried out for 10 hours. The reaction was monitored by TLC. After the reaction was completed, 10 mL of saturated brine was added to the system, and the reaction was quenched by stirring. The mixture was extracted with ethyl acetate (10 mL × 3), and the organic phases were combined. The solvent was removed using a rotary evaporator to obtain the crude product. The crude product was loaded onto silica gel, and column chromatography purification was carried out using a eluent with a volume ratio of petroleum ether:ethyl acetate = 95:5 to obtain 4-([1,1'-biphenyl]-4-yl)-7-phenyl-3,4-dihydronaphthalen-1(2H)-one, a white solid, with a separation yield of 93%.

[0083] Structure identification of compound 3a:

[0084] Nuclear magnetic resonance data:

[0085] 1 H NMR (500 MHz, Chloroform-d) δ 8.21 (d, J = 8.2 Hz, 1H), 7.59 (dddd, J = 13.6, 12.4, 7.3, 1.9 Hz, 5H), 7.53–7.49 (m, 2H), 7.45–7.38 (m, 4H), 7.36–7.32 (m, 2H), 7.28 (d, J = 1.9 Hz, 1H), 7.24–7.21 (m, 2H), 4.43 (dd, J = 7.6, 4.6 Hz, 1H), 2.81–2.75 (m, 1H), 2.67 (ddd, J = 17.2, 8.7, 4.4 Hz, 1H), 2.56 (ddt, J = 13.2, 8.9, 4.5 Hz, 1H), 2.41–2.34 (m, 1H). 13 C NMR (126 MHz, Chloroform-d) δ 197.84, 146.54, 146.31, 142.64, 140.66, 131.75, 129.04, 128.87, 128.81, 128.24, 128.12, 127.87, 127.41, 127.32, 127.29, 127.03, 126.02, 45.11, 36.52, 31.91.

[0086] High-resolution mass spectrometry data

[0087] HRMS (ESI) m / z: [M+H]+ calcd for C 14 H 14 O: 374.1671 found: 375.1737

[0088] of Compound 3a 1 H NMR, 13 C NMR are as Figure 5 and as Figure 6 shown. The analysis results indicate that the obtained target product is correct.

[0089] Example 2

[0090] Electrochemical catalytic oxidation synthesis of dihydronaphthalen-1(2H)-one derivative 3b from styrene derivative 1b, its structure and preparation method are as follows:

[0091]

[0092] 4-Methylstyrene (0.2 mmol), tetrabutylammonium hexafluorophosphate (0.4 mmol), acetonitrile (5 mL), and water (0.5 mL) were added to a 10 mL reactor, a magnetic stirrer was added, the prepared graphite electrode was used as the anode, and the platinum plate electrode was used as the cathode. The reaction was carried out by constant current electrolysis (7.5 mA) for 10 hours. The reaction was monitored by TLC. After the reaction was completed, 10 mL of saturated brine was added to the system, and the reaction was quenched by stirring; the mixture was extracted with ethyl acetate (10 mL × 3), the organic phases were combined, and the solvent was removed by a rotary evaporator to obtain the crude product; the crude product was loaded on silica gel, and column chromatography purification was carried out with an eluent of petroleum ether:ethyl acetate = 95:5 (volume ratio) to obtain 7-methyl-4-(p-tolyl)-3,4-dihydronaphthalen-1(2H)-one, a colorless viscous liquid, with a separation yield of 90%.

[0093] Structure identification of Compound 3b:

[0094] Nuclear magnetic resonance data:

[0095] 1 H NMR (500 MHz, Chloroform-d) δ 8.06 (d, J = 8.0 Hz, 1H), 7.18 (t, J = 8.8 Hz, 3H), 7.04 (d, J = 7.9 Hz, 2H), 6.85 (s, 1H), 4.27 (dd, J = 7.7, 4.6 Hz, 1H), 2.73 (ddd, J = 17.1, 8.6, 4.3 Hz, 1H), 2.61 (ddd, J = 17.1, 8.7, 4.4 Hz, 1H), 2.47 (ddd, J = 13.6, 8.9, 4.6 Hz, 1H), 2.39 (s, 3H), 2.32 (s, 3H), 2.27 (td, J = 8.2, 4.1 Hz, 1H). 1313C NMR (126 MHz, Chloroform-d) δ 198.00, 146.48, 144.50, 140.76, 136.33, 130.64, 129.96, 129.35, 128.52, 128.08, 127.24, 44.86, 36.51, 31.98, 21.80, 21.07.

[0096] High-resolution mass spectrometry data

[0097] HRMS (ESI) m / z: [M+H]+ calcd for C 14 H 14 O: 250.1358 found: 251.1362

[0098] For compound 3b 1 1H NMR, 13 13C NMR are as Figure 7 、as Figure 8 shown. The analysis results indicate that the obtained target product is correct.

[0099] Example 3

[0100] Electrochemical catalytic oxidation of styrene derivative 1c to synthesize dihydronaphthalen-1(2H)-one derivative 3c. Its structure and preparation method are as follows:

[0101]

[0102] 4-Methoxystyrene (0.2 mmol), tetrabutylammonium hexafluorophosphate (0.4 mmol), acetonitrile (5 mL), and water (0.5 mL) were added to a 10 mL reactor. A magnetic stirrer was added. The prepared graphite electrode was used as the anode and the platinum plate electrode was used as the cathode. The reaction was carried out under constant current electrolysis (7.5 mA) for 10 hours. The reaction was monitored by TLC. After the reaction was completed, 10 mL of saturated brine was added to the system, and the reaction was quenched by stirring. The mixture was extracted with ethyl acetate (10 mL × 3). The organic phases were combined and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was loaded on silica gel, and column chromatography purification was carried out using a eluent with a volume ratio of petroleum ether:ethyl acetate = 95:5 to obtain 7-methoxy-4-(p-methoxyphenyl)-3,4-dihydronaphthalen-1(2H)-one, a white solid, with a separation yield of 91%.

[0103] Structure identification of compound 3c:

[0104] Nuclear magnetic resonance data:

[0105] 11H NMR (500 MHz, Chloroform-d) δ 8.11 (d, J = 8.7 Hz, 1H), 7.10–7.00 (m, 2H), 6.88 (dd, J = 8.9, 2.4 Hz, 3H), 6.46 (d, J = 2.5 Hz, 1H), 4.22 (dd, J = 8.1, 4.4 Hz, 1H), 3.82 (s, 3H), 3.76 (s, 3H), 2.69 (ddd, J = 17.2, 8.1, 4.4 Hz, 1H), 2.58 (ddd, J = 17.2, 9.0, 4.5 Hz, 1H), 2.43 (ddt, J = 12.7, 8.5, 4.4 Hz, 1H), 2.26 (dtd, J = 13.2, 8.6, 4.4 Hz, 1H). 13 13C NMR (126 MHz, Chloroform-d) δ 197.04, 163.74, 158.42, 149.17, 135.52, 129.63, 129.53, 126.54, 114.04, 113.69, 113.24, 55.37, 55.28, 44.85, 36.47, 31.99.

[0106] High-resolution mass spectrometry data

[0107] HRMS (ESI) m / z: [M+H]+ calcd for C 14 H 14 O: 278.1671 found: 279.1687

[0108] For compound 3c 1 1H NMR, 13 13C NMR are as Figure 9 、as Figure 10 shown. The analysis results indicate that the obtained target product is correct.

[0109] Example 4

[0110] Electrochemical catalytic oxidation synthesis of dihydronaphthalen-1(2H)-one derivative 3d from styrene derivative 1d, its structure and preparation method are as follows:

[0111]

[0112] 2-Methylstyrene (0.2 mmol), tetrabutylammonium hexafluorophosphate (0.4 mmol), acetonitrile (5 mL), and water (0.5 mL) were added to a 10 mL reactor. A magnetic stir bar was added. The prepared graphite electrode was used as the anode and the platinum sheet electrode was used as the cathode. The system was sealed and purged with oxygen three times. Constant current electrolysis (7.5 mA) was carried out for 10 hours. The reaction was monitored by TLC. After the reaction was completed, 10 mL of saturated brine was added to the system, and the reaction was quenched by stirring. The mixture was extracted with ethyl acetate (10 mL×3), and the organic phases were combined. The solvent was removed using a rotary evaporator to obtain the crude product. The crude product was loaded onto silica gel, and column chromatography purification was carried out using a eluent with a volume ratio of petroleum ether:ethyl acetate = 95:5 to obtain 8-methyl-4-(o-tolyl)-3,4-dihydronaphthalen-1(2H)-one, a colorless viscous liquid, with a separation yield of 83%.

[0113] Structure identification of compound 3w:

[0114] Nuclear magnetic resonance data:

[0115] 1H NMR (500 MHz, Chloroform-d) δ 7.29–7.25 (m, 2H), 7.19–7.12 (m, 3H), 6.84 (d, J = 7.6 Hz, 1H), 6.79 (d, J = 7.7 Hz, 1H), 4.54 (dd, J = 8.0, 4.8 Hz, 1H), 2.82–2.75 (m, 1H), 2.74 (s, 3H), 2.66 (ddd, J = 16.7, 9.2, 4.7 Hz, 1H), 2.45 (s, 3H), 2.39–2.36 (m, 1H), 2.29–2.22 (m, 1H). 13C NMR (126 MHz, Chloroform-d) δ 200.28, 147.78, 142.20, 141.19, 135.96, 132.46, 131.82, 130.79, 130.69, 128.69, 127.44, 126.60, 126.26, 42.45, 38.68, 29.43, 23.45, 19.65.

[0116] High-resolution mass spectrometry data

[0117] HRMS (ESI) m / z: [M+H]+ calcd for C 14 H 14 O: 278.1671 found: 279.1687

[0118] For compound 3d 1 1H NMR, 13 13C NMR are as Figure 7 、as Figure 8As shown, the analysis results indicate that the obtained target product is correct.

[0119] The present invention also synthesized compounds 3e - 3i by the same method as in Example 1. The nuclear magnetic resonance data of compounds 3e - 3i are as follows. For the structural formulas, yields, etc. of compounds 3e - 3i, please refer to Table 1.

[0120] Table 1 Structural Formulas, Yields, and Nuclear Magnetic Resonance Data of Synthesized Compounds

[0121]

[0122]

[0123]

[0124] Comparative Example 1:

[0125] The difference between Comparative Example 1 and Example 1 is that the electrodes used for electrochemical catalytic oxidation in Comparative Example 1 are: graphite electrodes.

[0126]

[0127] 4 - Phenylstyrene (0.2 mmol), tetrabutylammonium hexafluorophosphate (0.4 mmol), acetonitrile (5 mL), and water (0.5 mL) were added to a 10 mL reactor, and a magnetic stirrer was added. Graphite electrodes were used as the anode and the cathode, and constant - current electrolysis (7.5 mA) was carried out for 10 hours. The reaction was monitored by TLC. After the reaction was completed, 10 mL of saturated brine was added to the system, and the reaction was quenched by stirring; the mixture was extracted with ethyl acetate (10 mL × 3), and the organic phases were combined. The solvent was removed by a rotary evaporator to obtain a crude product; the crude product was loaded on silica gel, and column chromatography purification was carried out using a eluent with a volume ratio of petroleum ether:ethyl acetate = 95:5 to obtain 4 - ([1,1'-biphenyl]-4 - yl)-7 - phenyl - 3,4 - dihydronaphthalen - 1(2H)-one, a white solid, with a separation yield of 21%.

[0128] Comparative Example 2:

[0129] The difference between Comparative Example 2 and Example 1 is that the electrodes used for electrochemical catalytic oxidation in Comparative Example 2 are: platinum sheet electrodes.

[0130]

[0131] 4-Phenylstyrene (0.2 mmol), tetrabutylammonium hexafluorophosphate (0.4 mmol), acetonitrile (5 mL), and water (0.5 mL) were added to a 10 mL reactor. A magnetic stir bar was added. Using a platinum sheet electrode as the anode and a graphite electrode as the cathode, a constant current electrolysis (7.5 mA) was carried out for 10 hours. The reaction was monitored by TLC. After the reaction was completed, 10 mL of saturated brine was added to the system, and the reaction was quenched by stirring. The mixture was extracted with ethyl acetate (10 mL × 3), and the organic phases were combined. The solvent was removed using a rotary evaporator to obtain the crude product. The crude product was loaded onto silica gel, and column chromatography purification was carried out using a eluent with a volume ratio of petroleum ether:ethyl acetate = 95:5 to obtain 4-([1,1'-biphenyl]-4-yl)-7-phenyl-3,4-dihydronaphthalen-1(2H)-one, a white solid, with a separation yield of 44%.

[0132] Comparative Example 3:

[0133] The difference between Comparative Example 3 and Example 1 is that the electrode used for electrocatalytic oxidation in Comparative Example 3 was a metal copper sheet electrode.

[0134]

[0135] 4-Phenylstyrene (0.2 mmol), tetrabutylammonium hexafluorophosphate (0.4 mmol), acetonitrile (5 mL), and water (0.5 mL) were added to a 10 mL reactor. A magnetic stir bar was added. Using a copper sheet electrode as the anode and a graphite electrode as the cathode, a constant current electrolysis (7.5 mA) was carried out for 10 hours. The reaction was monitored by TLC. As the reaction proceeded, TLC showed that no product was formed. The conclusion of Comparative Example 3 was that the metal copper sheet electrode could not catalyze styrene to produce 3,4-dihydronaphthalen-1(2H)-one compounds.

[0136] Comparative Example 4:

[0137] The difference between Comparative Example 4 and Example 1 is that the electrode used for electrocatalytic oxidation in Comparative Example 4 was a platinum nanoparticle electrode with a deposition time of 30 s.

[0138]

[0139] 4-Phenylstyrene (0.2 mmol), tetrabutylammonium hexafluorophosphate (0.4 mmol), acetonitrile (5 mL), and water (0.5 mL) were added to a 10 mL reactor. A magnetic stir bar was added. Using a platinum nanoparticle electrode as the anode and a graphite electrode as the cathode, a constant current electrolysis (7.5 mA) reaction was carried out for 10 hours. The reaction was monitored by TLC. After the reaction was completed, 10 mL of saturated brine was added to the system, and the reaction was quenched by stirring; the mixture was extracted with ethyl acetate (10 mL × 3), the organic phases were combined, and the solvent was removed using a rotary evaporator to obtain a crude product; the crude product was loaded on silica gel, and column chromatography purification was carried out using a eluent with a volume ratio of petroleum ether:ethyl acetate = 95:5 to obtain 4-([1,1'-biphenyl]-4-yl)-7-phenyl-3,4-dihydronaphthalen-1(2H)-one, a white solid, with a separation yield of 32%.

[0140] Comparative Example 5:

[0141] The difference between Comparative Example 5 and Example 1 was that the electrode used for electrocatalytic oxidation in Comparative Example 5 was a platinum nanoparticle electrode with a deposition time of 150 s.

[0142]

[0143] 4-Phenylstyrene (0.2 mmol), tetrabutylammonium hexafluorophosphate (0.4 mmol), acetonitrile (5 mL), and water (0.5 mL) were added to a 10 mL reactor. A magnetic stir bar was added. Using a platinum nanoparticle electrode as the anode and a graphite electrode as the cathode, a constant current electrolysis (7.5 mA) reaction was carried out for 10 hours. The reaction was monitored by TLC. After the reaction was completed, 10 mL of saturated brine was added to the system, and the reaction was quenched by stirring; the mixture was extracted with ethyl acetate (10 mL × 3), the organic phases were combined, and the solvent was removed using a rotary evaporator to obtain a crude product; the crude product was loaded on silica gel, and column chromatography purification was carried out using a eluent with a volume ratio of petroleum ether:ethyl acetate = 95:5 to obtain 4-([1,1'-biphenyl]-4-yl)-7-phenyl-3,4-dihydronaphthalen-1(2H)-one, a white solid, with a separation yield of 70%.

[0144] From Comparative Examples 1, 2, 3, 4, 5 and Example 1, it can be seen that by using the platinum nanoparticle electrode of the present invention and when the morphology and size of the nanoparticles with an appropriate deposition time reach suitable catalytic conditions, a better catalytic oxidation reaction of styrene derivatives can be achieved.

[0145] Finally, it should be noted that the above comparative examples are actually comparative embodiments, and some of the comparative embodiments can also be used as the basis for the technical solutions protected by the claims of the present invention. In addition, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for synthesizing dihydronaphthalene-1(2H)-one by oxidizing styrene and its derivatives, characterized in that: include: In an electrochemical catalytic reactor, styrene and its derivatives are electrochemically catalytically oxidized to 3,4-dihydronaphthalene-1(2H)-one, and the reaction formula is as follows: The working electrode of the electrochemical catalytic reactor is a platinum nanoparticle electrode; In the reaction formula, R is independently selected from one of hydrogen, halogen, substituted or unsubstituted C1-10 alkyl, substituted or unsubstituted aryl, substituted or unsubstituted C1-10 alkoxy, substituted or unsubstituted amino, carboxyl, ester, acyl, cyano, nitro, hydroxyl and azido.

2. The method according to claim 1, characterized in that The electrolyte of the electrochemical catalytic reactor is an ammonium salt electrolyte or a lithium salt electrolyte.

3. The method according to claim 1, characterized in that The electrolysis mode of the electrochemical catalytic reaction is one of constant current and constant voltage, the constant voltage range is 0 to 30 V, and the constant current range is 0 to 100 mA.

4. The method according to claim 1, characterized in that: The concentration of styrene or a styrene derivative in the solvent is 0.001 mol / L to 0.5 mol / L.

5. The method according to claim 1, characterized in that: The reaction solution containing dihydronaphthalene-1(2H)-one obtained by the electrochemical catalytic reaction is concentrated, purified by a silica gel column, and freeze-dried to obtain dihydronaphthalene-1(2H)-one.

6. The method according to claim 1, characterized in that The preparation method of the platinum nanoparticle electrode is: In a deposition solution containing platinum ions, platinum nanoparticles are prepared on a substrate by an isopotential electrodeposition method to obtain a platinum nanoparticle electrode.

7. The method according to claim 6, characterized in that The material of the substrate is one or more of carbon paper, carbon felt, glassy carbon, meshed glassy carbon, foamed nickel, and foamed copper.

8. The method according to claim 6, characterized in that The source of the metal platinum in the deposition solution is one of platinum dichloride, chloroplatinic acid, potassium chloroplatinate, and dinitrosodiammineplatinum; preferably, the concentration of the platinum ions is 0.01-100 mmol / L.

9. The method according to claim 6, characterized in that The anions in the deposition solution are independently selected from one or more of fluoride ion, chloride ion, bromide ion, iodide ion, nitrate ion, sulfate ion, perchlorate ion, and p-toluenesulfonate ion. Preferably, the concentration of the anions is 0.005-0.5 mol / L.

10. The method according to claim 6, characterized in that The electrodeposition method is selected from underpotential deposition, isopotential deposition or overpotential deposition. Preferably, the potential of the electrodeposition is -0.5V to -1.2V, and the deposition time is between 10 and 300 seconds.

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