Photocatalyst for efficient catalytic synthesis of aryl halide as well as preparation method and application of photocatalyst

Abstract

The invention belongs to the field of novel photocatalytic materials, and particularly relates to a photocatalyst for efficient catalytic synthesis of aryl halide as well as a preparation method and application of the photocatalyst. The photocatalyst prepared by the invention comprises titanium dioxide and a 1, 4-dihydropyridine compound loaded on the surface of the titanium dioxide; wherein the mass ratio of the 1, 4-dihydropyridine compound to the titanium dioxide is that the mass ratio of the 1, 4-dihydropyridine compound to the titanium dioxide is 1: (1-100); according to the present invention, the visible light source is adopted to induce the photocatalytic reaction to generate the aryl halide, the adopted scheme has characteristics of greenness, safety and high atom utilization rate, the use of the toxic solvent is avoided, the energy consumption is reduced through the room temperature reaction, the catalyst can be repeatedly recycled, and the cost is reduced.

Description

Technical Field

[0001] The invention belongs to the field of novel photocatalytic materials, and particularly relates to a photocatalyst for efficiently catalyzing and synthesizing halogenated aromatic hydrocarbons, and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Halogenated aromatics have important applications in pharmaceutical research and development. They are key intermediates for the synthesis of a variety of drugs and can be functionalized through a variety of reactions to synthesize biologically active compounds. At the same time, halogenated aromatics are very important in organic chemistry. They not only serve as precursors for the synthesis of a variety of compounds, but also have extensive applications and research value in green synthesis, environmental governance, and materials science. At present, the synthesis of halogenated aromatics can be achieved through a variety of methods, including electrophilic halogenation, which is a classic aromatic functionalization process that can generate halogenated aromatics that are of great significance in chemical synthesis and pharmaceutical research and development. In addition, halogenated aromatics can also be synthesized by electrochemical methods, using electrical energy to drive chemical reactions to achieve green synthesis technology.

[0004] At present, halogenated aromatics are widely used in organic synthesis. They can be used as starting materials for cross-coupling reactions to form new carbon-carbon bonds (for example, the palladium-catalyzed Ullmann coupling reaction is an important method for constructing carbon-carbon bonds using halogenated aromatics). They can also be converted into corresponding hydrides through hydrogenolysis dehalogenation reactions, which is not only an important synthetic strategy but also has the potential to become an important method for detoxification of toxic halides.

[0005] In terms of environmental governance, the microbial degradation of halogenated aromatic hydrocarbons has received extensive attention. Microorganisms can convert halogenated aromatic hydrocarbons into harmless or less toxic substances through their metabolic pathways, which is of great significance to environmental protection. At the same time, the use of halogenated organic pollutants as halogen sources to achieve the reuse of different halogenated organic pollutants not only helps to reduce environmental pollution, but also can synthesize high value-added products, which has become a hot topic of current research.

[0006] The traditional Wohl-Ziegler bromination reaction usually uses carbon tetrachloride (CCl 4 ) as solvent (Ziegler, K.; Spath, A.; Schaaf, E.; Schumann, W.; Winkelmann, E. Justus Liebigs Ann. Chem. 1942, 551, 80-119), but CCl 4It is a Class 2B carcinogen and has a destructive effect on the ozone layer. Its use has been restricted by international conventions. The classic world Ziegler bromination uses bromosuccinimide (NBS), carbon tetrachloride as a solvent reflux, and a high-energy initiator such as benzoyl peroxide (Veisi, H.; Ghorbani-Vaghei, R.; Zolfigol, MA Org. Prep. Proced. Int. 2011, 43, 489-540.), and this type of alternative method is still often chosen. (Haberhauer, G.; Tepper, C.; Wolper, C.; Blaser, D. Eur. J. Org. Chem. 2013, 2325-2333.).

[0007] Although NBS is a relatively safe and user-friendly brominating agent compared to liquid bromine (bromine), the Wohl-Ziegler bromination protocol similarly uses the toxic and ozone-depleting solvent carbon tetrachloride. Over the past few years, researchers have been working hard to develop green bromination procedures, mainly focusing on replacing hazardous carbon tetrachloride with more benign solvents. Several bromination protocols using non-chlorinated solvents such as methyl acetate, ethyl acetate and valerate, trifluoromethylbenzene, acetonitrile have been developed. Alternative brominating agents have also been studied, as well as different activation methods, especially UV- or visible-light-induced bromination reactions to avoid the use of hazardous and potentially explosive free radical initiators such as benzoyl peroxide. Therefore, designing a catalyst with green, safe, and high atom utilization characteristics is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0008] In order to solve the above technical problems, the purpose of the present invention is to provide a photocatalyst for the efficient catalytic synthesis of halogenated aromatics, as well as a preparation method and application. The photocatalyst prepared by the present invention generates halogenated aromatics by inducing a photocatalytic reaction using a visible light source, and the scheme used has the characteristics of being green and safe; at the same time, the use of toxic solvents is avoided, and the reaction is carried out at room temperature, which greatly reduces energy consumption, and the catalyst can be recycled and reused many times, greatly reducing the cost.

[0009] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0010] In a first aspect, the present invention provides a photocatalyst, the photocatalyst comprising titanium dioxide and a 1,4-dihydropyridine compound supported on the surface of the titanium dioxide; the mass ratio of the 1,4-dihydropyridine compound to the titanium dioxide is 1:1 to 100;

[0011] Wherein, the 1,4-dihydropyridine compound is selected from one of 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine (DPAD), 1,4-dihydro-4-(4-hydroxyphenyl)-2,6-dimethyl-3,5-pyridinedicarboxylic acid diethyl ester, 1,4-dihydro-2,6-dimethyl-4-phenyl-3,5-pyridinedicarboxylic acid diethyl ester, 1,4-dihydro-4-(4-methoxyphenyl)-2,6-dimethyl-3,5-pyridinedicarboxylic acid diethyl ester, 3,5-diethyl 4-(4-fluorophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate, and 3,5-diethyl 4-(4-nitrophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate.

[0012] In a second aspect, the present invention provides a method for preparing the above-mentioned photocatalyst, comprising: mixing 1,4-dihydropyridine compounds and titanium dioxide, dissolving them in an organic solvent, and performing a hydrothermal reaction to generate the photocatalyst.

[0013] Preferably, the organic solvent is selected from one or more of N,N-dimethylformamide (DMF), dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), acetonitrile, methanol, anhydrous ethanol, isopropanol, n-butanol, isobutanol, water, and tetrahydrofuran.

[0014] Preferably, the crystal form of the titanium dioxide is anatase type, including nanometer and micrometer levels.

[0015] Preferably, the temperature of the hydrothermal reaction is 100 to 380° C., and the time is 5 to 15 hours.

[0016] Preferably, the product after the hydrothermal reaction is filtered and dried in sequence; further preferably, the filtering method is vacuum filtration.

[0017] The third aspect of the present invention provides a method for catalytically synthesizing halogenated aromatic products, comprising: under the irradiation of a visible light source, using the photocatalyst described in the first aspect to catalyze the reaction of an aromatic substrate with a halogenating agent to generate a halogenated aromatic product.

[0018] Preferably, the photocatalyst is added in an amount of 1% to 20% of the total mass of the aromatic hydrocarbon substrate and the halogenation reagent.

[0019] Preferably, the molar ratio of the aromatic hydrocarbon substrate to the halogenating agent is 1:1-3.

[0020] Preferably, the aromatic hydrocarbon substrate has a structure shown in Formula I:

[0021]

[0022] Among them, R1 is a substituent on the parent benzene ring selected from hydrogen, alkyl, substituted alkyl, and halogen;

[0023] R 2 Selected from hydrogen, alkyl, substituted alkyl, amino, carboxyl, ester, acyl, halogen, aryl, and substituted aryl.

[0024] Preferably, R 1 The substitution position is selected from the 4th or 6th position on the benzene ring;

[0025] Preferably, R 1 is selected from hydrogen, trifluoromethyl, fluorine, chlorine, bromine, and iodine;

[0026] Preferably, R 2 Selected from hydrogen, amino, carboxyl, C 1 ~C 6 Alkyl, C 1 ~C 6 Ester group, C 1 ~C 6 Acyl, fluorine, chlorine, bromine, iodine, phenyl, substituted phenyl; wherein the substituted phenyl is selected from C 1 ~C 6 Alkyl, C 1 ~C 6 Ester group, C 1 ~C 6 Acyl, halogen;

[0027] Preferably, R 2 Selected from hydrogen, C 1 ~C 3 Alkyl, methyl group, carboxyl group.

[0028] Preferably, the halogenating agent is selected from one or more of concentrated hydrochloric acid, hydrobromic acid, hydrofluoric acid, iodic acid, elemental fluorine, chlorine, bromine, iodine, N-bromosuccinimide (NBS), N-chlorosuccinimide (NCS) and N-iodosuccinimide (NIS).

[0029] Preferably, the aromatic hydrocarbon substrate is first dissolved in an organic solvent, and then a halogenating agent is added to react; further preferably, the organic solvent is selected from one or more of toluene, DMF, DMA, acetonitrile, tetrahydrofuran, pyridine, methanol, anhydrous ethanol, dichloromethane, dichloroethane, ethyl acetate, and ethyl formate.

[0030] Preferably, the visible light source is selected from one or more of a xenon light source with a power of 50 to 500 W and an LED light source with a power of 50 to 500 W.

[0031] Preferably, after the reaction, the product is concentrated, extracted, dried, and subjected to column chromatography.

[0032] Preferably, the extraction agent used in the extraction is selected from one or more of DMF, DMA, acetonitrile, tetrahydrofuran, pyridine, methanol, anhydrous ethanol, dichloromethane, dichloroethane, ethyl acetate, and ethyl formate; the drying agent used is anhydrous sodium sulfate; and the eluent of the column chromatography is a petroleum ether / ethyl acetate elution system with a volume ratio of 9:1 to 5:1.

[0033] Preferably, the solid obtained after filtration is dried, soaked in a solvent and then dried to obtain a reusable photocatalyst; preferably, the solvent is selected from methanol. 、 One or more of water and DMF.

[0034] The fourth aspect of the present invention provides a use of the photocatalyst described in the first aspect in catalytic synthesis of halogenated aromatic hydrocarbon products.

[0035] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0036] (1) The photocatalyst prepared by the present invention generates halogenated aromatic hydrocarbons by inducing a photocatalytic reaction using a visible light source, and the scheme used is green and safe.

[0037] (2) The photocatalyst prepared by the present invention avoids the use of toxic solvents and reacts at room temperature, which greatly reduces energy consumption. In addition, the catalyst can be recycled and reused multiple times, which greatly reduces costs and has practical application value.

[0038] (3) The present invention loads 1,4-dihydropyridine compounds with titanium dioxide and combines them through organic bonds, so that the catalyst has good reusability. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 X-ray photoelectron spectrum of the photocatalyst prepared in Example 1 of the present invention, wherein (a) is 0.1DPAD-TiO 2 -380 full spectrum, (b) 0.1DPAD-TiO 2 -180 full spectrum, (c) 0.1DPAD-TiO 2 -380 C1s spectrum, (d) 0.1DPAD-TiO 2 -380 O1s spectrum, (e) 0.1DPAD-TiO 2 -380 Ti2p spectrum, (f) is 0.1DPAD-TiO 2 -180 C1s spectrum, (g) 0.1DPAD-TiO 2 -180 O1s spectrum, (h) 0.1DPAD-TiO 2 -180 Ti2p spectrum;

[0040] Figure 2 The UV-visible diffuse reflectance spectrum of the photocatalyst prepared in Example 1 of the present invention;

[0041] Figure 3 The Fourier transform infrared spectrum of the photocatalyst prepared in Example 1 of the present invention;

[0042] Figure 4 The hydrogen nuclear magnetic resonance spectrum of 1-bromoethylbenzene catalytically synthesized in Application Example 1 of the present invention;

[0043] Figure 5 The hydrogen nuclear magnetic resonance spectrum of methyl bromophenylacetate catalytically synthesized in Application Example 2 of the present invention;

[0044] Figure 6 The hydrogen nuclear magnetic resonance spectrum of 4-fluorophenethyl bromide catalytically synthesized in Application Example 3 of the present invention;

[0045] Figure 7 This is the hydrogen nuclear magnetic resonance spectrum of the catalytic synthesis of 1-(1-bromoethyl)-4-(trifluoromethyl)benzene in Application Example 4 of the present invention;

[0046] Figure 8 This is the hydrogen nuclear magnetic resonance spectrum of α-bromophenylacetic acid catalytically synthesized in Application Example 5 of the present invention;

[0047] Fig. 9 The hydrogen nuclear magnetic resonance spectrum of α-bromo-2-chlorophenylacetic acid catalytically synthesized in Application Example 7 of the present invention;

[0048] Fig.10 This is a TLC thin layer chromatography spot plate monitoring diagram of the catalytic synthesis of 1-bromoethylbenzene in Comparative Example 1 of the present invention;

[0049] Fig.11 This is a cycle performance test of the photocatalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0050] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0051] The raw materials and reagents used in the present invention are as follows:

[0052] Table 1 Main raw materials and reagents

[0053]

[0054]

[0055] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0056] Example 1 :This embodiment provides a photocatalyst for the efficient catalytic synthesis of halogenated aromatic hydrocarbons and a preparation method thereof

[0057] (1) Preparation of 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine:

[0058] 100mL of ethylene tar was reacted at 400℃ and 4 MPa for 6h, and then cooled to obtain 20g of petroleum coke product. 40mL of 36% concentrated hydrochloric acid was used to soak the petroleum coke product in a 250mL beaker. After stirring at room temperature for 24h, 100mL of water was added, and the 20g solid was dried for standby use, namely, petroleum coke catalyst. 262mL of ethyl acetoacetate, 137g of p-dimethylaminobenzaldehyde and 81g of ammonium acetate were added to a 500mL three-necked flask, and 20g of petroleum coke catalyst was added thereto. The reaction was stirred at room temperature for 24h. After the reaction was completed, a large amount of solid was obtained. The solid was filtered, and the obtained solid product was redissolved in 50mL of anhydrous ethanol, filtered and separated to obtain a black petroleum coke catalyst. The remaining filtrate was allowed to stand for crystallization to obtain 301g of a yellow solid compound, namely 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine (DPAD).

[0059] (2) 0.2 g of 30 nm-sized anatase titanium dioxide and 0.02 g of 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine were stirred in 20 g of DMA solvent at room temperature for 12 h, and the mixed solution was subjected to hydrothermal reaction at 180 ° C for 12 h. After the reaction was completed, the filter cake was washed with methanol, and the obtained solid was dried to obtain a photocatalyst (0.1 DPAD-TiO 2 -180).

[0060] Example 2 :This embodiment provides a photocatalyst for the efficient catalytic synthesis of halogenated aromatic hydrocarbons and a preparation method thereof

[0061] (1) Preparation of 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine:

[0062] 100mL of ethylene tar was reacted at 400℃ and 4 MPa for 6h, and then cooled to obtain 20g of petroleum coke product. 40mL of 36% concentrated hydrochloric acid was used to soak the petroleum coke product in a 250mL beaker. After stirring at room temperature for 24h, 100mL of water was added, and the 20g solid was dried for standby use, namely, petroleum coke catalyst. 262mL of ethyl acetoacetate, 137g of p-dimethylaminobenzaldehyde and 81g of ammonium acetate were added to a 500mL three-necked flask, and 20g of petroleum coke catalyst was added thereto. The reaction was stirred at room temperature for 24h. After the reaction was completed, a large amount of solid was obtained. The solid was filtered, and the obtained solid product was redissolved in 50mL of anhydrous ethanol, filtered and separated to obtain a black petroleum coke catalyst. The remaining filtrate was allowed to stand for crystallization to obtain 301g of a yellow solid compound, namely 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine (DPAD).

[0063] (2) 0.2 g of 30 nm-sized anatase titanium dioxide and 0.02 g of 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine were stirred in 20 g of DMA solvent at room temperature for 12 h, and the mixed solution was subjected to hydrothermal reaction at 380 ° C for 12 h. After the reaction was completed, the filter cake was washed with methanol, and the obtained solid was dried to obtain a photocatalyst (0.1 DPAD-TiO 2 -380).

[0064] Example 3 :This embodiment provides a photocatalyst for the efficient catalytic synthesis of halogenated aromatic hydrocarbons and a preparation method thereof

[0065] (1) Preparation of 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine:

[0066] 100mL of ethylene tar was reacted at 400℃ and 4 MPa for 6h, and then cooled to obtain 20g of petroleum coke product. 40mL of 36% concentrated hydrochloric acid was used to soak the petroleum coke product in a 250mL beaker. After stirring at room temperature for 24h, 100mL of water was added, and the 20g solid was dried for standby use, namely, petroleum coke catalyst. 262mL of ethyl acetoacetate, 137g of p-dimethylaminobenzaldehyde and 81g of ammonium acetate were added to a 500mL three-necked flask, and 20g of petroleum coke catalyst was added thereto. The reaction was stirred at room temperature for 24h. After the reaction was completed, a large amount of solid was obtained. The solid was filtered, and the obtained solid product was redissolved in 50mL of anhydrous ethanol, filtered and separated to obtain a black petroleum coke catalyst. The remaining filtrate was allowed to stand for crystallization to obtain 301g of a yellow solid compound, namely 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine (DPAD).

[0067] (2) 0.2 g of 30 nm-sized anatase titanium dioxide and 0.01 g of 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine were stirred in 20 g of DMA solvent at room temperature for 12 h, and the mixed solution was subjected to hydrothermal reaction at 180 ° C for 12 h. After the reaction was completed, the filter cake was washed with methanol, and the obtained solid was dried to obtain a photocatalyst (0.05 DPAD-TiO 2 ).

[0068] Example 4 :This embodiment provides a photocatalyst for the efficient catalytic synthesis of halogenated aromatic hydrocarbons and a preparation method thereof

[0069] (1) Preparation of 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine:

[0070] 100mL of ethylene tar was reacted at 400℃ and 4 MPa for 6h, and then cooled to obtain 20g of petroleum coke product. 40mL of 36% concentrated hydrochloric acid was used to soak the petroleum coke product in a 250mL beaker. After stirring at room temperature for 24h, 100mL of water was added, and the 20g solid was dried for standby use, namely, petroleum coke catalyst. 262mL of ethyl acetoacetate, 137g of p-dimethylaminobenzaldehyde and 81g of ammonium acetate were added to a 500mL three-necked flask, and 20g of petroleum coke catalyst was added thereto. The reaction was stirred at room temperature for 24h. After the reaction was completed, a large amount of solid was obtained. The solid was filtered, and the obtained solid product was redissolved in 50mL of anhydrous ethanol, filtered and separated to obtain a black petroleum coke catalyst. The remaining filtrate was allowed to stand for crystallization to obtain 301g of a yellow solid compound, namely 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine (DPAD).

[0071] (2) 0.2 g of 30 nm-sized anatase titanium dioxide and 0.04 g of 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine were stirred in 20 g of DMA solvent at room temperature for 12 h, and the mixed solution was subjected to hydrothermal reaction at 180 ° C for 12 h. After the reaction was completed, the filter cake was washed with methanol, and the obtained solid was dried to obtain a photocatalyst (0.2DPAD-TiO 2 ).

[0072] Example 5 :This embodiment provides a photocatalyst for the efficient catalytic synthesis of halogenated aromatic hydrocarbons and a preparation method thereof

[0073] 0.2 g of 30 nm-scale anatase titanium dioxide and 0.02 g of 1,4-dihydro-4-(4-hydroxyphenyl)-2,6-dimethyl-3,5-pyridinedicarboxylic acid diethyl ester were stirred in 20 g of DMF solvent at room temperature for 6 h, and the mixed solution was hydrothermally reacted at 220 ° C for 12 h. After the reaction was completed, it was filtered under reduced pressure, the filter cake was washed with methanol, and the obtained solid was dried to obtain a photocatalyst.

[0074] Example 6 :This embodiment provides a photocatalyst for the efficient catalytic synthesis of halogenated aromatic hydrocarbons and a preparation method thereof

[0075] 0.2 g of 30 nm-scale anatase titanium dioxide and 0.02 g of 1,4-dihydro-2,6-dimethyl-4-phenyl-3,5-pyridinedicarboxylic acid diethyl ester were stirred in 20 g of methanol solvent at room temperature for 12 h, and the mixed solution was hydrothermally reacted at 150° C. for 12 h. After the reaction was completed, the vacuum was filtered, the filter cake was washed with methanol, and the obtained solid was dried to obtain a photocatalyst.

[0076] Example 7 :This embodiment provides a photocatalyst for the efficient catalytic synthesis of halogenated aromatic hydrocarbons and a preparation method thereof

[0077] 0.2 g of 30 nm rutile titanium dioxide and 0.02 g of 1,4-dihydro-4-(4-methoxyphenyl)-2,6-dimethyl-3,5-pyridinedicarboxylic acid diethyl ester were stirred in 30 g of DMSO solvent at room temperature for 12 h, and the mixed solution was hydrothermally reacted at 250 ° C for 8 h. After the reaction was completed, the vacuum was filtered, the filter cake was washed with methanol, and the obtained solid was dried to obtain a photocatalyst.

[0078] Example 8 :This embodiment provides a photocatalyst for the efficient catalytic synthesis of halogenated aromatic hydrocarbons and a preparation method thereof

[0079] 0.2 g of 30 nm rutile titanium dioxide and 0.02 g of 3,5-diethyl 4-(4-fluorophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate were stirred in 40 g of anhydrous ethanol solvent at room temperature for 12 h, and the mixed solution was hydrothermally reacted at 200 ° C for 12 h. After the reaction was completed, the vacuum was filtered, the filter cake was washed with methanol, and the obtained solid was dried to obtain a photocatalyst.

[0080] Example 9 :This embodiment provides a photocatalyst for the efficient catalytic synthesis of halogenated aromatic hydrocarbons and a preparation method thereof

[0081] 0.2 g of 30 nm rutile titanium dioxide and 0.02 g of 3,5-diethyl 4-(4-nitrophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate were stirred in 20 g of methanol solvent at room temperature for 12 h, and the mixed solution was hydrothermally reacted at 160 ° C for 12 h. After the reaction was completed, the vacuum was filtered, the filter cake was washed with methanol, and the obtained solid was dried to obtain a photocatalyst.

[0082] Example 10 : In this example, the photocatalysts prepared in Examples 1 and 2 were subjected to X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectroscopy analysis.

[0083] like Figure 1 As shown, the photocatalysts prepared in Example 1 and Example 2 were subjected to XPS qualitative analysis. It can be seen from the figure that the peaks of C, N, O, and Ti can be clearly shown in the full spectrum of (a) and (b), proving that DPAD and TiO 2After the thermal reaction, they are combined with each other; (c), (d), and (e) are the C1s, O1s, and Ti2p spectra of 0.1DPAD-TiO2-380, respectively; it can be clearly seen that C1s is fitted into four peaks, and it can be seen that CC, C=C, COC, and -CC=O exist, which are located at 284.81, 283.94, 285.71, and 288.51 eV, respectively. From O1s, it can be seen that there are three peaks, and Ti-O, C=O, and CO exist, which are located at 529.91, 531.65, and 533 eV, respectively. From the Ti2p spectrum, there are obvious Ti2p orbital characteristic peaks at 458.78 and 464.35 eV, indicating that Ti 4+ Existence; (f), (g), (h) are 0.1DPAD-TiO 2 -180 C1s, O1s and Ti2p spectra; it can be clearly seen that C1s is fitted into three peaks, and it can be seen that CC, COC, -CC=O exist, which are located at 284.81, 285.2, and 288.8 eV respectively. From O1s, it can be seen that Ti-O, C=O, and CO exist, which are located at 529.85, 531.7, and 533.5 eV respectively. From the Ti2p spectrum, there are obvious Ti2p orbital characteristic peaks at 458.65 and 464.38 eV, indicating that Ti 4+ exists; in summary, it can be fully explained that the organic matter is loaded on titanium dioxide through chemical bonds.

[0084] like Figure 2 As shown, in TiO 2 、0.1DPAD-TiO 2 -380 and 0.1DPAD-TiO 2 It can be seen from the UV diffuse reflectance spectrum at -180 that a single TiO 2 There is basically no absorption in the visible light region, but there is strong absorption in the ultraviolet absorption region after combining with DPAD. Therefore, it can be seen from the figure that DPAD has a strong effect on TiO 2 The modification effectively improved the absorption of the catalyst at 400-600 nm, indicating that the modification of DPAD effectively improved the catalyst's utilization of visible light.

[0085] Embodiment 11 : This example uses Fourier transform infrared spectroscopy to analyze the photocatalysts prepared in Example 1 and Examples 3 to 4.

[0086] like Figure 3 As shown in the figure, the Fourier transform infrared spectroscopy results show that the organic DPAD has a peak at 3352 cm -1 There is a strong NH absorption peak at 1615 cm -1There is the bending vibration of the NH of the primary amine, 1510~1480cm -1 The skeletal vibration of the benzene ring is 1697 cm -1 The peak is C=O, which is due to the C=C-CO-OR environment causing the absorption to shift to a lower wave number; 1646cm -1 The stretching vibration of C=C is 1206cm -1 is the stretching vibration of the CO bond, 1370cm -1 Then -CH 3 The deformation vibration of the bond. 2 After doping, 3400~3200cm -1 The peak of TiO 2 The -OH peak is covered by the -OH peak, so the NH peak is not visible. At the same time, the catalyst increases with the concentration of DPAD and TiO 2 In contrast, the characteristic peak intensity of DPAD increased.

[0087] As mentioned above, by treating the raw materials DPAD, TiO 2 The generated catalyst (DPAD-TiO 2 )'s X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy analysis clearly show that the organic substance DPAD is successfully bonded to titanium dioxide through a chemical bond.

[0088] Application Example 1 This application example uses the photocatalyst prepared in Example 1 to catalyze the synthesis of 1-bromoethylbenzene, comprising the following steps:

[0089] S1. Add 10 mL of benzyl alcohol into a 100 mL beaker with a jacket, add 30 mL of dichloromethane, add 0.3 g of the prepared photocatalyst, add 16.41 g of N-bromosuccinimide (NBS), react under 200 W xenon lamp light source, and stop the reaction after 15 min.

[0090] S2, filtering the reaction solution, drying the obtained solid, soaking it in 30 mL of methanol, evaporating the solvent to obtain a dried solid, which is a reusable photocatalyst;

[0091] S3. The reaction solution after filtration was concentrated, 15 mL of water was added, and the solution was extracted with 20 mL of ethyl acetate. The ethyl acetate layer was collected by repeated extraction three times, and the layer was dried over anhydrous sodium sulfate. The organic layer was concentrated and separated by column chromatography using petroleum ether: ethyl acetate = 9:1 to 5:1 to obtain an oily liquid product with a yield of 85%.

[0092] like Figure 4 As shown, the data characterization: 1H NMR (400 MHz, CDCl 3 )δ7.43(d,J=7.6Hz,2H),7.33(t,J=7.7Hz,2H),7.28(d,J=7.2Hz,1H),5.21(q,J=7.2Hz,1H),2.04(d,J=7.0Hz,3H).

[0093] Application Example 2 This application example uses the photocatalyst prepared in Example 2 to catalyze the synthesis of methyl bromophenylacetate, comprising the following steps:

[0094] S1. Add 10 mL of DL-methyl mandelate into a 100 mL beaker with a jacket, add 30 mL of dichloromethane, add 10.71 g of NBS, and add 0.5 g of the prepared photocatalyst, react under 100 W xenon lamp light source, and stop the reaction after 25 min.

[0095] S2, filtering the reaction solution, drying the obtained solid, soaking it in 30 mL of methanol, evaporating the solvent to obtain a dried solid, which is a reusable photocatalyst;

[0096] S3. The reaction solution after filtration was concentrated, 25 mL of water was added, and the solution was extracted with 40 mL of ethyl acetate. The ethyl acetate layer was collected by repeated extraction three times, and the layer was dried over anhydrous sodium sulfate. The organic layer was concentrated and separated by column chromatography using petroleum ether: ethyl acetate = 9:1 to 5:1 to obtain an oily liquid product with a yield of 90%.

[0097] like Figure 5 As shown, the data characterization: 1 H NMR (400 MHz, CDCl 3 )δ7.61-7.42(m,2H),7.41-7.32(m,3H),5.36(d,J=2.7Hz,1H),3.78(d,J=2.8Hz,3H).

[0098] Application Example 3 This application example uses the photocatalyst prepared in Example 3 to catalyze the synthesis of 4-fluorophenethyl bromide, comprising the following steps:

[0099] S1, 20mL of 1-(4-fluorophenyl)-1-anhydrous ethanol was added to a 100mL beaker with a jacket, 40mL of dichloromethane was added thereto, 25.39g of NBS was added thereto, and 1.5g of the prepared photocatalyst was added thereto, and the reaction was carried out under irradiation with a 200W xenon lamp light source, and the reaction was stopped after 30min;

[0100] S2, filtering the reaction solution, drying the obtained solid, soaking it in 30 mL of methanol, evaporating the solvent to obtain a dried solid, which is a reusable photocatalyst;

[0101] S3. The reaction solution after filtration was concentrated, 40 mL of water was added, and the solution was extracted with 40 mL of ethyl acetate. The ethyl acetate layer was collected by repeated extraction three times, and the layer was dried over anhydrous sodium sulfate. The organic layer was concentrated and separated by column chromatography using petroleum ether: ethyl acetate = 9:1 to 5:1 to obtain an oily liquid product with a yield of 75%.

[0102] like Figure 6 As shown, the data characterization: 1 H NMR (400 MHz, CDCl 3 )δ7.40(dd,J=8.5,5.1Hz,2H),7.01(t,J=8.7Hz,2H),5.19(q,J=7.2Hz,1H),2.02(d,J=6.9Hz,3H).

[0103] Application Example 4 : This application example uses the photocatalyst prepared in Example 4 to catalyze the synthesis of 1-(1-bromoethyl)-4-(trifluoromethyl)benzene, comprising the following steps:

[0104] S1. Add 20 mL of α-methyl-4-(trifluoromethyl)benzyl alcohol into a 100 mL beaker with a jacket, add 50 mL of dichloromethane, add 2 g of the prepared photocatalyst, add 26.41 g of N-bromosuccinimide (NBS), react under irradiation with a 200 W xenon lamp light source, and stop the reaction after 15 min.

[0105] S2, filtering the reaction solution, drying the obtained solid, soaking it in 30 mL of methanol, evaporating the solvent to obtain a dried solid, which is a reusable photocatalyst;

[0106] S3. The reaction solution after filtration was concentrated, 15 mL of water was added, and the solution was extracted with 20 mL of ethyl acetate. The ethyl acetate layer was collected by repeated extraction three times, and the layer was dried over anhydrous sodium sulfate. The organic layer was concentrated and separated by column chromatography using petroleum ether: ethyl acetate = 9:1 to 5:1 to obtain an oily liquid product with a yield of 85%.

[0107] like Figure 7 As shown, the data characterization: 1 H NMR (400 MHz, CDCl 3)δ7.68(s,1H),7.63(d,J=7.9Hz,1H),7.55(d,J=8Hz,1H),7.46(t,J=8.1Hz,1H),5.26-5.15(m,1H),2.05(dd,J=6.9,2.7Hz,3H).

[0108] Application Example 5 This application example uses the photocatalyst prepared in Example 5 to catalyze the synthesis of α-bromophenylacetic acid, comprising the following steps:

[0109] S1. Add 10 mL of DL-mandelic acid into a 100 mL beaker with a jacket, add 30 mL of dichloromethane, add 0.8 g of the prepared photocatalyst, add 14.1 g of N-bromosuccinimide (NBS), react under 200 W xenon lamp light source, and stop the reaction after 15 min.

[0110] S2, filtering the reaction solution, drying the obtained solid, soaking it in 30 mL of methanol, evaporating the solvent to obtain a dried solid, which is a reusable photocatalyst;

[0111] S3. The reaction solution after filtration was concentrated, 15 mL of water was added, and the solution was extracted with 20 mL of ethyl acetate. The ethyl acetate layer was collected by repeated extraction three times, and the layer was dried over anhydrous sodium sulfate. The organic layer was concentrated and separated by column chromatography using petroleum ether: ethyl acetate = 9:1 to 5:1 to obtain an oily liquid product with a yield of 85%.

[0112] like Figure 8 As shown, the data characterization: 1 H NMR (400 MHz, CDCl 3 )δ10.72(s,1H),10.39(s,1H),7.58-7.52(m,4H),7.40-7.34(m,6H),5.35(s,2H).

[0113] Application Example 6 This application example uses the photocatalyst prepared in Example 6 to catalyze the synthesis of α-bromo-2-chlorophenylacetic acid, comprising the following steps:

[0114] S1. Add 10 mL of 2-chloromandelic acid into a 100 mL beaker with a jacket, add 30 mL of dichloromethane, add 1.1 g of the prepared photocatalyst, add 15.2 g of N-bromosuccinimide (NBS), react under 200 W xenon lamp light source, and stop the reaction after 15 min.

[0115] S2, filtering the reaction solution, drying the obtained solid, soaking it in 30 mL of methanol, evaporating the solvent to obtain a dried solid, which is a reusable photocatalyst;

[0116] S3. The reaction solution after filtration was concentrated, 15 mL of water was added, and the solution was extracted with 20 mL of ethyl acetate. The ethyl acetate layer was collected by repeated extraction three times, and the layer was dried over anhydrous sodium sulfate. The organic layer was concentrated and separated by column chromatography using petroleum ether: ethyl acetate = 9:1 to 5:1 to obtain an oily liquid product with a yield of 85%.

[0117] like Fig. 9 As shown, the data characterization: 1 H NMR (400 MHz, CDCl 3 )δ9.47(s,2H),7.81-7.74(m,1H),7.39(d,J=7.0Hz,1H),7.32(d,J=8.2Hz,2H),5.95(d,J=3.2Hz,1H).

[0118] Comparative Example 1 : This comparative example catalyzes the synthesis of 1-bromoethylbenzene using a single DPAD compound, comprising the following steps:

[0119] S1. Add 10 mL of benzyl alcohol into a 100 mL beaker with a jacket, add 30 mL of dichloromethane, add 0.3 g of DPAD, add 16.41 g of N-bromosuccinimide (NBS), react under 200 W xenon lamp light source, and stop the reaction after 15 min.

[0120] S2. Filter the reaction solution, rinse the filter cake with 30 mL of methanol, dry and weigh the filter cake to obtain 0.3 g of yellow solid;

[0121] S3. The filtered reaction solution is monitored using a TLC thin layer chromatography plate.

[0122] The results are as follows Fig.10 As shown: Through thin layer chromatography analysis, the main reaction raw materials, benzyl alcohol, NBS bromination reagent and target product were spotted. As shown in the figure, the reaction liquid point after filtration was spotted on the far right, and it was found that no target product point appeared in the reaction liquid. This shows that the single DPAD organic substance does not have any ability to catalyze the reaction.

[0123] Test Example 1 :This test example tests the cycle performance of the photocatalyst prepared in Example 1

[0124] Experimental process: Benzyl alcohol was used as the reactant, and the yield of the generated bromination product was used as the performance evaluation index of the catalyst reusability (the catalytic synthesis process of Application Example 1). Fig.11It can be seen that after five repeated experiments, the yield of the product did not show a significant decrease (difference: 1.2~2), indicating that the catalyst has good reusability.

[0125] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A photocatalyst, characterized in that: The photocatalyst comprises titanium dioxide and a 1,4-dihydropyridine compound supported on the surface of the titanium dioxide; the mass ratio of the 1,4-dihydropyridine compound to the titanium dioxide is 1:1 to 100; Wherein, the 1,4-dihydropyridine compound is selected from one of 4-(4-(dimethylamino)phenyl)-2,6-dimethyl-3,5-dicarboxylic acid diethyl ester-1,4-dihydropyridine (DPAD), 1,4-dihydro-4-(4-hydroxyphenyl)-2,6-dimethyl-3,5-pyridinedicarboxylic acid diethyl ester, 1,4-dihydro-2,6-dimethyl-4-phenyl-3,5-pyridinedicarboxylic acid diethyl ester, 1,4-dihydro-4-(4-methoxyphenyl)-2,6-dimethyl-3,5-pyridinedicarboxylic acid diethyl ester, 3,5-diethyl 4-(4-fluorophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate, and 3,5-diethyl 4-(4-nitrophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate.

2. A method for preparing a photocatalyst as claimed in claim 1, characterized in that: include: The 1,4-dihydropyridine compound and titanium dioxide are mixed and dissolved in an organic solvent, and a photocatalyst is generated by a hydrothermal reaction.

3. The preparation method according to claim 2, characterized in that: The organic solvent is selected from one or more of N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetonitrile, methanol, anhydrous ethanol, isopropanol, n-butanol, isobutanol, water, and tetrahydrofuran; Preferably, the crystal form of the titanium dioxide belongs to anatase type, including nanometer and micrometer scales; Preferably, the temperature of the hydrothermal reaction is 100 to 380° C. and the time is 5 to 15 hours; Preferably, the product after the hydrothermal reaction is filtered and dried in sequence; further preferably, the filtering method is vacuum filtration.

4. A method for catalytically synthesizing halogenated aromatic products, characterized in that: include: Under the irradiation of visible light source, the photocatalyst according to claim 1 is used to carry out a catalytic reaction between an aromatic hydrocarbon substrate and a halogenating agent to generate a halogenated aromatic hydrocarbon product.

5. The method according to claim 4, characterized in that The amount of the photocatalyst added is 1%-20% of the total mass of the aromatic hydrocarbon substrate and the halogenating agent, and the molar ratio of the aromatic hydrocarbon substrate to the halogenating agent is 1:1-3.

6. The method according to claim 4, characterized in that The aromatic hydrocarbon substrate has a structure shown in Formula I: Among them, R 1 is a substituent on the parent benzene ring selected from hydrogen, alkyl, substituted alkyl, and halogen; R 2 Selected from hydrogen, alkyl, substituted alkyl, amino, carboxyl, ester, acyl, halogen, aryl, and substituted aryl.

7. The method according to claim 6, characterized in that The R 1 The substitution position is selected from the 4-position or the 6-position on the benzene ring; Preferably, R 1 is selected from hydrogen, trifluoromethyl, fluorine, chlorine, bromine, and iodine; Preferably, R 2 is selected from hydrogen, amino, carboxyl, C1-C6 alkyl, C1-C6 ester, C1-C6 acyl, fluorine, chlorine, bromine, iodine, phenyl, substituted phenyl; wherein the substituted phenyl is selected from C1-C6 alkyl, C1-C6 ester, C1-C6 acyl, halogen; Preferably, R 2 Selected from hydrogen, C1-C3 alkyl, methyl ester group, carboxyl group.

8. The method according to claim 4, characterized in that The halogenating agent is selected from one or more of concentrated hydrochloric acid, hydrobromic acid, hydrofluoric acid, iodic acid, elemental fluorine, chlorine, bromine, iodine, N-bromosuccinimide, N-chlorosuccinimide and N-iodosuccinimide; Preferably, the aromatic hydrocarbon substrate is first dissolved in an organic solvent, and then a halogenating agent is added to react; further preferably, the organic solvent is selected from one or more of toluene, DMF, DMA, acetonitrile, tetrahydrofuran, pyridine, methanol, anhydrous ethanol, dichloromethane, dichloroethane, ethyl acetate, and ethyl formate.

9. The method according to claim 4, characterized in that The visible light source is selected from one or more of a xenon light source with a power of 50 to 500w and an LED light source with a power of 50 to 500w; Preferably, after the reaction, the product is concentrated, extracted, dried, and subjected to column chromatography; Preferably, the extraction agent used in the extraction is selected from one or more of DMF, DMA, acetonitrile, tetrahydrofuran, pyridine, methanol, anhydrous ethanol, dichloromethane, dichloroethane, ethyl acetate, and ethyl formate; the drying agent used is anhydrous sodium sulfate; the eluent of the column chromatography is a petroleum ether / ethyl acetate elution system with a volume ratio of 9:1 to 5:1; Preferably, the solid obtained after filtration is dried, soaked in a solvent and then dried to obtain a reusable photocatalyst; preferably, the solvent is selected from methanol. 、 One or more of water and DMF.

10. Use of the photocatalyst according to claim 1 in catalytic synthesis of halogenated aromatic products.

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