Homogeneous phase and heterogeneous phase combined photoelectrocatalysis C-C coupling method

Abstract

The invention discloses a homogeneous phase and heterogeneous phase combined photoelectrocatalysis C-C coupling method, which comprises the following steps: in a three-electrode system, mixing unsubstituted or substituent Ra substituted 5-20 membered heteroaromatic hydrocarbon, an organic matter containing C (sp3)-H and an electrolyte containing a metal ion compound, applying illumination and voltage to the mixture, and carrying out C-C coupling reaction. The method is simple, does not need to carry out complex modification on the photo-anode, and can be carried out under the condition of no oxidant. In an acidic environment, transition metal ions (such as copper ions) are introduced into a system to promote the generation of chlorine free radicals and inhibit the interaction of the chlorine free radicals, so that the generation of chlorine is inhibited, the formation of a byproduct chlorocyclohexane is reduced, more organic matters containing C (sp3)-H are used for a C-C coupling reaction, and meanwhile, the stability of the electrode is maintained.

Description

Technical Field

[0001] The invention belongs to the field of photoelectrocatalysis, and in particular relates to a homogeneous and heterogeneous photoelectrocatalytic C-C coupling method. Background Art

[0002] Photoelectrochemistry (PEC) has been widely studied for the conversion of solar energy. Photoelectrocatalytic water splitting to obtain fuel hydrogen has always been of great interest, but it is constrained by the oxygen evolution reaction (OER) with high energy and kinetic requirements. Therefore, organic reactions have begun to be introduced into photoelectrochemistry, which can not only increase the yield of hydrogen, but also convert cheap organic compounds into high value-added products. Currently, photoelectrochemistry has been used in different organic reaction processes, among which the largest proportion is the oxidation of alcohols. In addition, the oxidation of furan substrates has also been widely reported. For example, the oxidation yield and Faradaic efficiency of 5-hydroxymethylfurfural (HFM) under photoelectrocatalysis can reach 100% (Nat. Chem. 2015, 7, 328–333). Photoelectrochemistry has also been used to study the activation of C–H bonds, thus providing more possibilities for photoelectrochemical catalysis of organic reactions. For example, cyclohexanol and cyclohexanone were prepared by activating the C–H bond in cyclohexane, achieving the construction of the CO bond and obtaining a high current utilization rate (Angew. Chem. Int. Ed. 2018, 57, 11238–11241). The construction of carbon-heteroatom bonds (such as CN bonds, CP or C-Cl, etc.) can also be carried out by photoelectrocatalytic C–H activation. The reaction of electron-rich aromatics with azole compounds to generate nitrogen heterocycles with medicinal value has been achieved by photoelectrochemistry, which can obtain different ortho-selectivity from the previous one and has been successfully used for the later functionalization of various drug molecules (Nat. Catal. 2019, 2, 366–373). The construction of C–P bonds has also been achieved by photoelectrochemistry (Chem. Commun. 2019, 55, 10376–10379). Although photoelectrochemistry has achieved the construction of C–P bonds and C–N bonds, this only accounts for a very small part in photoelectrochemistry. Minisci radical coupling reaction can couple heteroaromatic hydrocarbons with alkanes C–C to form functionalized heteroaromatic hydrocarbons, which are widely used in drugs, natural products and functional materials. The generation of alkyl radicals plays an important role in the Minisci radical C–C coupling process. Direct generation of alkane radicals from alkanes by C–H activation is a more direct and sustainable method that can be applied to a wider range of substrates. Titanium dioxide photoanode can directly oxidize chloride ions to obtain chloride radicals and generate alkyl radicals for C–C coupling through a hydrogen atom transfer mechanism, but this process has poor selectivity and stability. Therefore, the development of efficient PEC strategies to achieve C–C coupling reactions still needs to be explored and studied. Summary of the invention

[0003] In order to achieve the above objectives, the present invention provides a method for photoelectrocatalytic C-C coupling combining homogeneous and heterogeneous reactions, wherein the method introduces transition metal ions (such as copper ions) into the reaction system, which helps to regulate the generation of chlorine radicals on the photoanode and can significantly improve the yield and conversion rate of the C-C coupling reaction.

[0004] The technical solution of the present invention is as follows:

[0005] A method for combining homogeneous and heterogeneous photoelectrocatalytic C–C coupling, the method comprising:

[0006] In a three-electrode system, unsubstituted or Ra-substituted 5-20-membered heteroaromatic hydrocarbons, C(sp 3 )–H organic matter and an electrolyte containing a metal ion compound are mixed, and light and voltage are applied to the mixture to perform a C–C coupling reaction;

[0007] Wherein the substituent Ra is selected from -C 1-10 Alkyl, halogen, -CN, -CHO, -OC 1-10 Alkyl, -C 6-14 Aryl,

[0008] According to an embodiment of the present invention, the number of the substituent Ra may be 1, 2 or more.

[0009] According to an embodiment of the present invention, the substituent Ra is preferably -C 1-6 Alkyl, -CN, -CHO, chlorine, bromine, -OC 1-6 Alkyl, phenyl, Also preferred are -CN, -CHO, methyl, ethyl, methoxy, chlorine, bromine, phenyl,

[0010] According to an embodiment of the present invention, the 5-20 membered heteroaromatic hydrocarbon is selected from unsubstituted or substituent Ra substituted quinoline, isoquinoline, phenanthridine, pyridine, pyrimidine, benzothiophene, benzothiazole, benzopyrimidine, quinoxaline, pyridazine or purine, and the substituent Ra is defined as above.

[0011] According to an embodiment of the present invention, the 3 )-H is selected from unsubstituted or Rb-substituted C 5-20 Cycloalkanes, unsubstituted or Rb-substituted C 1-12 Alkanes, unsubstituted or Rb-substituted C 6-14 Aromatic hydrocarbons, unsubstituted or Rb-substituted 3-20 membered heterocycloalkanes, or CHD 3 ; The substituent Rb is selected from -OH, -C 1-10Alkyl or -OC 1-10 alkyl.

[0012] According to an embodiment of the present invention, the 3 )-H organic compound is selected from unsubstituted or Rb-substituted C 5-12 Cycloalkanes, unsubstituted or Rb-substituted C 1-6 Alkanes, unsubstituted or Rb-substituted C 6-14 Aromatic hydrocarbons, unsubstituted or Rb-substituted 3-10 membered heterocycloalkanes, or CHD 3 ; The substituent Rb is selected from -OH, -C 1-10 Alkyl or -OC 1-10 alkyl.

[0013] According to an embodiment of the present invention, the substituent Rb is selected from -OH, -C 1-6 Alkyl or -OC 1-6 The alkyl group is preferably -OH, methoxy, ethoxy, methyl, ethyl, propyl, butyl or the like.

[0014] According to an embodiment of the present invention, the C(sp 3 )-H organic compound is selected from cyclopentane, cycloheptane, cyclooctane, dodecacyclic hydrocarbons, 1,4-epoxycyclohexane, CH 3 CH 2 OCH 3 , CH 3 CH 2 OH, methane, CHD 3 , oxacyclohexane, oxacyclopentane, 1-butanol, tetrahydropyran, p-xylene or trimethylbenzene.

[0015] According to an embodiment of the present invention, the unsubstituted or substituent Ra-substituted 5-20 membered heteroaromatic hydrocarbon and the C(sp 3 The molar ratio of the organic matter to )-H is 1:(5-50), preferably 1:(10-35), and for example 1:10.

[0016] According to an embodiment of the present invention, the metal ion compound is selected from copper chloride or manganese chloride.

[0017] According to an embodiment of the present invention, in the electrolyte, the content of metal ions is 20ppm-300ppm, for example, 27ppm-270ppm, for example, 27ppm, 50ppm, 100ppm, 150ppm, 200ppm, 250ppm or 270ppm.

[0018] According to an embodiment of the present invention, in the electrolyte, the molar concentration of the metal ion compound is 0.02-0.2 mM, for example, 0.02 mM, 0.04 mM, 0.06 mM, 0.08 mM, 0.1 mM, 0.12 mM, 0.14 mM, 0.16 mM, 0.18 mM or 0.2 mM.

[0019] According to an embodiment of the present invention, the pH of the electrolyte is acidic.

[0020] According to an embodiment of the present invention, the electrolyte further comprises an electrolyte salt, a solvent and hydrochloric acid. In the electrolyte, the molar concentration of the electrolyte salt is 0.05-0.2M; the concentration of the hydrochloric acid is 5-30 μL / mL.

[0021] Exemplarily, the electrolyte includes 0.1 M electrolyte salt and 20 μL / mL hydrochloric acid.

[0022] Preferably, the electrolyte salt is selected from at least one of tetramethylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetrabutylammonium hexafluorophosphate, lithium perchlorate, etc. Preferably, the electrolyte salt is selected from tetraethylammonium tetrafluoroborate.

[0023] Preferably, the solvent is selected from a mixture of an organic solvent and water, and the organic solvent is, for example, at least one selected from acetone, acetonitrile, etc. Preferably, the volume ratio of the organic solvent to water is 10-30:1, for example, 19:1.

[0024] The introduction of hydrochloric acid into the electrolyte of the present invention can provide a chlorine source and an acidic environment.

[0025] According to an embodiment of the present invention, the wavelength of the light is 380-800nm.

[0026] According to an embodiment of the present invention, the time for applying light is 6-30 hours, preferably 10-24 hours.

[0027] According to an embodiment of the present invention, the illumination is applied by, for example, a xenon lamp, for example, a 300W xenon lamp. Preferably, the intensity of the illumination is 100-600mW cm -2 , preferably 200-400 mW cm -2 For example, the light intensity of the xenon lamp is 400 mW cm -2 Preferably, the xenon lamp is equipped with an AM 1.5G filter.

[0028] According to an embodiment of the present invention, the voltage is -0.2-1.6V Ag / AgCl .

[0029] According to an embodiment of the present invention, the voltage is applied for a time of 6-30 h, preferably 10-24 h.

[0030] According to an embodiment of the present invention, the reaction temperature is 20-70° C. Exemplarily, it may be 20, 25, 30, 35, 40, 45, 50, 55, 60, 65 or 70° C.

[0031] According to an embodiment of the present invention, the method is carried out in an air atmosphere or in an inert atmosphere, preferably in an inert atmosphere.

[0032] According to an embodiment of the present invention, the method further comprises a post-treatment step: the product after the reaction is separated, extracted and dried to obtain a coupled product. Preferably, the product after the reaction is separated and purified, the reaction product is extracted with ethyl acetate and water, dried with anhydrous sodium sulfate, the solvent is removed by rotary evaporation, and separated and purified by thin layer chromatography to obtain a coupled product.

[0033] According to an embodiment of the present invention, the three-electrode system comprises a working electrode, a counter electrode and a reference electrode;

[0034] Exemplarily, the working electrode is selected from one of a titanium dioxide photoelectrode, a tungsten trioxide photoelectrode, and the like;

[0035] Exemplarily, the counter electrode is selected from one of nickel foam, Pt or Au, etc.;

[0036] Exemplarily, the reference electrode is saturated silver chloride.

[0037] According to an embodiment of the present invention, the titanium dioxide photoanode may be any anode known in the art.

[0038] According to an embodiment of the present invention, the titanium dioxide photoanode is prepared by a method known in the art. Preferably, the titanium dioxide photoanode is prepared by a hydrothermal-annealing two-step method known in the art.

[0039] Exemplarily, the preparation method of the titanium dioxide photoanode is as follows:

[0040] The substrate is added into a mixed solution containing water, hydrochloric acid and tetrabutyl titanate, and heated to perform a hydrothermal reaction; subsequently, the product after the hydrothermal reaction is taken out and subjected to an annealing reaction to prepare a titanium dioxide photoanode.

[0041] Preferably, the volume ratio of water to hydrochloric acid is 1:1.

[0042] For example, water and hydrochloric acid are first mixed, and then tetrabutyl titanate is added and mixed to prepare a mixed solution.

[0043] Preferably, the substrate is conductive glass coated with fluorine-doped tin oxide (FTO), for example, the parameters of the substrate are: height 4 cm, length 1 cm, thickness 2.2 mm.

[0044] Preferably, the temperature of the hydrothermal reaction is 120-150° C., and the time of the hydrothermal reaction is 4-10 h.

[0045] Preferably, the annealing temperature is 350-450° C., the heating time is 10-40 min, and the annealing time is preferably 0.5-1.5 h.

[0046] Beneficial effects of the present invention:

[0047] (1) The present invention introduces transition metal ions (such as copper ions) into the electrolyte solution to form a homogeneous system. The introduced transition metal ions interact with the photoanode, and the photoelectrocatalytic C-C coupling reaction is achieved by combining homogeneous and heterogeneous methods. The method of the present invention is simple, does not require complex modification of the photoanode, and can be carried out under oxidant-free conditions. In an acidic environment, the introduction of transition metal ions (such as copper ions) into the system promotes the generation of chlorine free radicals, inhibits the interaction of chlorine free radicals, thereby inhibiting the generation of chlorine gas, reducing the formation of byproduct chlorocyclohexane, and allowing more C(sp 3 )–H organic matter is used for C–C coupling reaction while maintaining the stability of the electrode.

[0048] (2) In an acidic environment, the addition of transition metal ions helps maintain the stability of the electrode, inhibits the polymerization of organic matter on the electrode surface, and prolongs the service life of the electrode. In addition, transition metal ions (such as copper ions) also significantly improve the regioselectivity of the reaction. This provides new ideas for the application of photoelectrocatalysis to more and more complex organic reactions.

[0049] Definition and explanation of terms

[0050] Unless otherwise stated, the terms and descriptions in the context of the present invention have the meanings set out below.

[0051] The term "halogen" refers to fluorine, chlorine, bromine and iodine.

[0052] The term "C 1-10 "Alkyl" means straight chain and branched chain alkyl groups having 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms. 1-6The term "alkyl" refers to straight-chain and branched alkyl groups having 1, 2, 3, 4, 5 or 6 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl or 1,2-dimethylbutyl, or the like or isomers thereof.

[0053] The term "-OC 1-10 "Alkyl" means the above "C 1-10 An alkyl group is a group formed by directly bonding an alkyl group to an oxygen group.

[0054] The term "C 5-20 "Cycloalkane" is understood to mean a saturated monovalent monocyclic, bicyclic hydrocarbon ring or bridged cycloalkane having 5 to 20 carbon atoms, preferably "C 5-12 The term "Cycloalkanes". 5-12 The term "cycloalkane" is understood to mean a saturated monovalent monocyclic, bicyclic hydrocarbon ring or a bridged cycloalkane having 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms. 5-12 The cycloalkane may be a monocyclic alkane, such as cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane or cyclodecane, or a bicyclic hydrocarbon such as decalin.

[0055] The term "3-20 membered heterocycloalkane" means a saturated monovalent monocyclic, bicyclic hydrocarbon ring or bridged cyclic alkane, which contains 1-5 heteroatoms independently selected from N, O and S, and a total number of ring atoms of 3-20 (such as 3, 4, 5, 6, 7, 8, 9, 10, etc.), preferably a "3-10 membered heterocycloalkane". The term "3-10 membered heterocycloalkane" means a saturated monovalent monocyclic, bicyclic hydrocarbon ring or bridged cyclic alkane, which contains 1-5, preferably 1-3 heteroatoms selected from N, O and S. The heterocycloalkane can be connected to the rest of the molecule through any of the carbon atoms or the nitrogen atom (if present). In particular, the heterocycloalkane may include, but is not limited to, a 4-membered ring such as azetidine, oxetanyl; a 5-membered ring such as tetrahydrofuran, dioxole, pyrrolidine, imidazolidine, pyrazolidine, pyrroline alkane; or a 6-membered ring such as tetrahydropyran, piperidine, morpholine, dithiane, thiomorpholine, piperazine or trithiane; or a 7-membered ring such as diazepane. Optionally, the heterocycle may be benzo-fused. The ring containing the nitrogen atom may be partially unsaturated, i.e., it may contain one or more double bonds, such as, but not limited to, 2,5-dihydro-1H-pyrrole, 4H-[1,3,4]thiadiazine, 4,5-dihydrooxazole or 4H-[1,4]thiazine, or it may be benzo-fused, such as, but not limited to, dihydroisoquinoline. According to the present invention, the heterocycloalkane is non-aromatic. When the 3-20 membered heterocycloalkane is connected with other groups to form the compound of the present invention, the carbon atom on the 3-20 membered heterocyclic ring may be connected with other groups, or the heterocyclic atom on the 3-20 membered heterocyclic ring may be connected with other groups. For example, when the 3-20 membered heterocyclic ring is selected from piperazine, the nitrogen atom on the piperazine may be connected with other groups. Or when the 3-20 membered heterocyclic ring is selected from piperidine, the nitrogen atom on the piperidine ring and the carbon atom at the para position thereof may be connected with other groups.

[0056] The term "C 6-14 The term "aromatic hydrocarbon" is understood to mean preferably a monovalent aromatic or partially aromatic monocyclic, bicyclic or tricyclic hydrocarbon ring ("C 6-14 Aromatic hydrocarbons), especially rings with 6 carbon atoms, such as benzene or biphenyl, or rings with 9 carbon atoms ("C 9 aryl), such as indane or indene, or a ring having 10 carbon atoms ("C 10 Aromatic hydrocarbons”), such as tetralin, dilin or naphthalene, or rings having 13 carbon atoms (“C 13 Aromatic hydrocarbons”), such as fluorene, or rings with 14 carbon atoms (“C 14 Aromatic hydrocarbons”), such as anthracene. When the C 6-20When the aromatic hydrocarbon is substituted, it may be monosubstituted or polysubstituted. Also, there is no limitation on the substitution site, for example, it may be substituted at the ortho, para or meta position.

[0057] The term "5-20 membered heteroaromatic hydrocarbon" is understood as including monovalent monocyclic, bicyclic or tricyclic aromatic ring systems having 5 to 20 ring atoms and containing 1 to 5 heteroatoms independently selected from N, O and S, for example "5-14 membered heteroaromatic hydrocarbons". The term "5-14 membered heteroaromatic hydrocarbon" is understood as including monovalent monocyclic, bicyclic or tricyclic aromatic ring systems having 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 ring atoms, in particular 5 or 6 or 9 or 10 carbon atoms, and containing 1 to 5, preferably 1 to 3 heteroatoms each independently selected from N, O and S and, in addition, in each case may be benzo-fused. In particular, the heteroaromatic hydrocarbon is selected from thiophene, furan, pyrrole, oxazole, thiazole, imidazole, pyrazole, isoxazole, isothiazole, oxadiazole, triazole, thiadiazole, thia-4H-pyrazole, etc. and their benzo derivatives, such as benzofuran, benzothiophene, benzoxazole, benzisoxazole, benzimidazole, benzotriazole, indazole, indole, isoindole, etc.; or pyridine, pyridazine, pyrimidine, pyrazine, triazine, etc., and their benzo derivatives, such as quinoline, quinazoline, isoquinoline, etc.; or azine, indolizine, purine, etc. and their benzo derivatives; or cinnoline, phthalazine, quinazoline, quinoxaline, naphthyridine, pteridine, carbazole, acridine, phenazine, phenothiazine, phenoxazine, etc. When the 5-20 membered heteroaromatic hydrocarbon is connected with other groups to form the compound of the present invention, the carbon atom on the 5-20 membered heteroaromatic hydrocarbon ring may be connected with other groups, or the heteroatom on the 5-20 membered heteroaromatic hydrocarbon ring may be connected with other groups. When the 5-20 membered heteroaromatic hydrocarbon is substituted, it may be monosubstituted or polysubstituted. In addition, there is no restriction on its substitution site, for example, the hydrogen connected to the carbon atom on the heteroaromatic hydrocarbon ring may be substituted, or the hydrogen connected to the heteroatom on the heteroaromatic hydrocarbon ring may be substituted. When the heteroaromatic hydrocarbon contains N atoms, the 5-20 membered heteroaromatic hydrocarbon may also be oxidized to its nitrogen oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is the linear sweep voltammetry curve of the titanium dioxide photoanode in Preparation Example 1 under different test conditions.

[0059] Figure 2 This is a comparison chart of the yields of the products of Example 2 and Comparative Example 5 under the condition of repeated use of titanium dioxide photoanode.

[0060] Figure 3 These are the scanning electron microscope images of the titanium dioxide photoanode before reaction in Example 2 and the scanning electron microscope images of the titanium dioxide photoanode after the 9th cycle experiment.

[0061] Figure 41 and 2. The X-ray diffraction pattern of the titanium dioxide photoanode before reaction in Example 2 and the X-ray diffraction pattern of the titanium dioxide photoanode after the 9th cycle experiment.

[0062] Figure 5 This is the H NMR spectrum of product 3A in Example 2. DETAILED DESCRIPTION

[0063] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0064] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0065] Preparation Example 1

[0066] 1.1 Add 25 mL of deionized water and 25 mL of hydrochloric acid to a 100 mL beaker, mix and stir, and cool to room temperature.

[0067] 1.2 Add 1 mL of tetrabutyl titanate to the cooled hydrochloric acid solution and stir for half an hour.

[0068] 1.3 Add 7.2 mL of tetrabutyl titanate mixed solution into the reactor lining, then add clear and clean FTO glass. Put the reactor into an oven and heat it at 150°C for 10 hours.

[0069] 1.4 After hydrothermal treatment, the FTO glass was taken out, rinsed with deionized water and dried with nitrogen. Then, it was placed in a muffle furnace, heated to 450°C for 40 minutes, annealed at 450°C for 1.5 hours, and finally cooled naturally to room temperature to obtain a titanium dioxide photoanode.

[0070] Figure 1 The linear sweep voltammetric curves of the titanium dioxide photoanode prepared in Preparation Example 1 under different test conditions. 2+ Representatives of the test were added to a 0.1M tetraethylammonium tetrafluoroborate solution (as electrolyte) with copper ions, without Cu 2+ "Light" means that light is applied during the test; "dark" means that no light is applied during the test.

[0071] from Figure 1 It can be seen that the photocurrent of the titanium dioxide photoanode gradually increases with the increase of potential, and the addition of copper ions has no significant effect on the photocurrent.

[0072] Example 1

[0073]

[0074] A coupling reaction of the compounds shown in 1A and 2A above, specifically:

[0075] The titanium dioxide photoanode in Preparation Example 1 was used as the working electrode, nickel foam was used as the counter electrode, saturated silver chloride was used as the reference electrode, and the light source was a 300W xenon lamp equipped with AM 1.5G and 380-800nm ​​filters. The light intensity was measured by a light intensity meter and was 400mW cm -2 .

[0076] Under nitrogen atmosphere, compound 1A (0.1 mmol), compound 2A (0.3 mL) and electrolyte were added to a 10 mL electrolytic cell in sequence, wherein the electrolyte included 0.1 mM copper chloride, 0.1 M tetraethylammonium tetrafluoroborate (TEATFB), acetone, water (5 mL of acetone and water, the volume ratio of acetone to water was 19:1) and hydrochloric acid (the content of hydrochloric acid and the concentration of copper ions in copper chloride are shown in Table 1 below), the device was placed under 380-800 nm light, and voltage was applied to perform coupling reaction. The coupling reaction conditions were:

[0077] The illumination and voltage application time were both 13 h, and the reaction temperature was 40 °C;

[0078] The voltage was applied by linear sweep voltammetry with a scan range of -0.2 to 1.6 V. Ag / AgCl , scan rate 50mV s -1 .

[0079] The product after the reaction is separated and purified. The reaction product is extracted with ethyl acetate and water, dried over anhydrous sodium sulfate, and then the solvent is removed by rotary evaporation. The product is separated and purified by thin layer chromatography to obtain a coupling compound.

[0080] The reaction was stopped after 13 h of photoelectrolysis, and the yield of compound 3A was determined by adding 1,3,5-trimethoxybenzene as an internal standard.

[0081] Example 2

[0082] The difference between Example 2 and Example 1 is that the voltage application method is changed to the chronoamperometry method, and the applied voltage is set to 1.2V. Ag / AgCl , the test time was set to 13h and recorded as the first cycle experiment.

[0083] The titanium dioxide photoanode after the first experiment was used to repeat the coupling reaction, which was recorded as the second cycle experiment. The above experiment was repeated 9 times in total. The product yield after each experiment was measured, and the test results were as follows: Figure 2 shown.

[0084] Figure 2 The figure is a comparison chart of the yields of the products of Example 2 and Comparative Example 5 under the condition of repeated use of titanium dioxide photoanode, wherein blue represents Example 2 and red represents Comparative Example 5. Figure 2 It can be seen that when copper ions are not present (i.e., comparative example 5), the yield is unstable. In comparative example 5, a yield of 70% can be obtained only when the new electrode is used for the first time, while the yield drops to 50% in the second experiment, and the lowest is 43%; Figure 2 Since the yield was poor in the 7th cycle, the 8th and 9th cycle experiments were not carried out in Comparative Example 5.

[0085] It can be seen that the introduction of copper ions in the method of the present invention can increase the product yield to as high as about 84%, and the product yield has good stability.

[0086] Figure 3 These are the scanning electron microscope images of the titanium dioxide photoanode before reaction in Example 2 and the scanning electron microscope images of the titanium dioxide photoanode after the 9th cycle experiment.

[0087] Figure 4 1 and 2. The X-ray diffraction pattern of the titanium dioxide photoanode before reaction in Example 2 and the X-ray diffraction pattern of the titanium dioxide photoanode after the 9th cycle experiment.

[0088] Comparative Example 1

[0089] The difference between Comparative Example 1 and Example 2 is that no electrolyte salt tetraethylammonium tetrafluoroborate (TEATFB) is added.

[0090] Comparative Example 2

[0091] The difference between Comparative Example 2 and Example 2 is that hydrochloric acid is not added.

[0092] Comparative Example 3

[0093] The difference between Comparative Example 3 and Example 2 is that no light was applied, that is, the reaction was carried out in the dark.

[0094] Comparative Example 4

[0095] The difference between Comparative Example 4 and Example 2 is that no voltage is applied.

[0096] Comparative Example 5

[0097] The difference between Comparative Example 5 and Example 2 is that no copper compound is added.

[0098] The experiment was repeated 7 times using the method of Example 2. The product yield after each experiment was measured. The test results are as follows: Figure 2 shown.

[0099] The conversion rate and yield of the reaction system of Examples 1-2 and Comparative Examples 1-5 were tested, wherein the conversion rate and yield were calculated as follows:

[0100] Conversion rate: 1,3,5-trimethoxybenzene was used as internal standard. 1 Determined by H NMR analysis.

[0101] The yield was calculated by using 1,3,5-trimethoxybenzene as internal standard. 1 Determined by H NMR analysis.

[0102] Table 1

[0103]

[0104]

[0105] In Table 1, “[Cu]” refers to the concentration of copper ions in the electrolyte.

[0106] Example 3

[0107] The difference between Example 3 and Example 1 is that the following raw materials 4A-18A are used to replace 2A, and the reaction results are as follows:

[0108]

[0109] Among them, raw material 7A is solid, and its molar content is 10 times the molar content of raw material 1A.

[0110] The reaction temperature of raw material 7A is 50 degrees Celsius and the reaction time is 24 hours.

[0111] The amount of hydrochloric acid added to the raw material 15A was 25 μL.

[0112] The percentage values ​​in the above raw materials refer to the yield of the generated product. Taking raw material 4A as an example, "53%" means that the yield of the generated product is 53%.

[0113] Example 4

[0114] The difference between Example 4 and Example 1 is that the following raw materials 19A-38A are used to replace 1A, respectively. The reaction results are as follows:

[0115]

[0116] The percentage values ​​in the above raw materials refer to the yield of the generated product. Taking raw material 19A as an example, "82%" means that the yield of the generated product is 82%.

[0117] The above is an exemplary description of the embodiments of the present invention. However, the protection scope of the present invention is not limited to the above embodiments. Any modification, equivalent substitution, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for photoelectrocatalytic C–C coupling combining homogeneous and heterogeneous reactions, characterized in that: The method comprises: In a three-electrode system, unsubstituted or Ra-substituted 5-20-membered heteroaromatic hydrocarbons, C(sp 3 )–H organic matter and an electrolyte containing a metal ion compound are mixed, and light and voltage are applied to the mixture to perform a C–C coupling reaction; Wherein the substituent Ra is selected from -C 1-10 Alkyl, halogen, -CN, -CHO, -OC 1-10 Alkyl, -C 6-14 Aryl, 2. The method according to claim 1, characterized in that: The 5-20 membered heteroaromatic hydrocarbon is selected from unsubstituted or substituent Ra substituted quinoline, isoquinoline, phenanthridine, pyridine, pyrimidine, benzothiophene, benzothiazole, benzopyrimidine, quinoxaline, pyridazine or purine, and the substituent Ra is selected from -C 1-10 Alkyl, halogen, -CN, -CHO, -OC 1-10 Alkyl, -C 6-14 Aryl, Preferably, the 3 )-H is selected from unsubstituted or Rb-substituted C 5-20 Cycloalkanes, unsubstituted or substituted with Rb 1-12 Alkanes, unsubstituted or Rb-substituted C 6-14 Aromatic hydrocarbon, unsubstituted or Rb-substituted 3-20 membered heterocycloalkane, or CHD3; the substituent Rb is selected from -OH, -C 1-10 Alkyl or -OC 1-10 alkyl.

3. The method according to claim 1 or 2, characterized in that: The three-electrode system includes a working electrode, a counter electrode and a reference electrode; The working electrode is selected from one of a titanium dioxide photoelectrode and a tungsten trioxide photoelectrode; Preferably, the counter electrode is selected from one of nickel foam, Pt or Au; Preferably, the reference electrode is saturated silver chloride.

4. The method according to any one of claims 1 to 3, characterized in that: The metal ion compound is selected from copper chloride or manganese chloride. Preferably, the content of metal ions in the electrolyte is 20ppm-300ppm.

5. The method according to any one of claims 1 to 4, characterized in that: In the electrolyte, the molar concentration of the metal ion compound is 0.02-0.2 mM. Preferably, the pH of the electrolyte is acidic. Preferably, the electrolyte further comprises an electrolyte salt, a solvent and hydrochloric acid. In the electrolyte, the molar concentration of the electrolyte salt is 0.05-0.2 M; the concentration of the hydrochloric acid is 5-30 μL / mL.

6. The method according to claim 5, characterized in that The solvent is selected from a mixture of an organic solvent and water, and the organic solvent is, for example, selected from at least one of acetone and acetonitrile.

7. The method according to any one of claims 1 to 6, characterized in that: The wavelength of the light is 380-800nm. Preferably, the illumination is applied for 6-30 hours. Preferably, the intensity of the illumination is 100-600 mW cm -2 .

8. The method according to any one of claims 1 to 7, characterized in that: The voltage is -0.2-1.6V Ag / AgCl . Preferably, the voltage is applied for 6-30 hours.

9. The method according to any one of claims 1 to 8, characterized in that: The reaction temperature is 20-70°C.

10. The method according to any one of claims 1 to 9, characterized in that: The method is carried out in an air atmosphere or in an inert atmosphere.

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