A method for photoelectrocatalytic CC coupling combining homogeneous and heterogeneous

Abstract

The present invention discloses a method for photoelectrocatalytic C-C coupling combining homogeneous and heterogeneous reactions, wherein the method comprises the following steps: in a three-electrode system, a 5-20-membered heteroaromatic hydrocarbon which is unsubstituted or substituted with a substituent Ra, a 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 carry out a C–C coupling reaction. 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 the 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.

Description

Technical Field

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

[0002] Photoelectrochemical (PEC) has been widely studied for solar energy conversion. Photoelectrocatalytic water splitting to produce fuel hydrogen has long been of interest, but is constrained by the energetically and kinetically demanding oxygen evolution reaction (OER). Consequently, organic reactions have begun to be incorporated into photoelectrochemical processes, which can both increase hydrogen yields and convert inexpensive organic compounds into high-value-added products. Currently, photoelectrochemical processes have been applied to various organic reactions, with the oxidation of alcohols accounting for the largest proportion. Furthermore, the oxidation of furanic substrates has also been widely reported. For example, the photoelectrocatalytic oxidation of 5-hydroxymethylfurfural (HFM) has achieved a yield and Faradaic efficiency of 100% (Nat. Chem. 2015, 7, 328–333). Photoelectrochemistry has also been used to study C–H bond activation, providing further possibilities for photoelectrochemically catalyzed organic reactions. For example, cyclohexanol and cyclohexanone were prepared by activating the C–H bond in cyclohexane, achieving C–O bond formation and high current efficiency (Angew. Chem. Int. Ed. 2018, 57, 11238–11241). Carbon-heteroatom bonds (such as C–N bonds, C–P bonds, or C–Cl bonds) can also be constructed via photoelectrocatalytic C–H activation. The reaction of electron-rich aromatic hydrocarbons with azole compounds to produce pharmaceutically valuable nitrogen heterocycles has been achieved photoelectrochemically, exhibiting distinct ortho-selectivity and successfully used for the later functionalization of various drug molecules (Nat. Catal. 2019, 2, 366–373). C–P bond formation has also been achieved photoelectrochemically (Chem. Commun. 2019, 55, 10376–10379). Although photoelectrochemical construction of C–P and C–N bonds has been achieved, this represents only a small fraction of photoelectrochemical activity. Minisci radical coupling reactions can couple heteroaromatic hydrocarbons with alkanes to form functionalized heteroaromatic hydrocarbons through C–C coupling, 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. Directly generating alkane radicals from alkanes through 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 requires continuous exploration and research. Summary of the Invention

[0003] To achieve the above objectives, the present invention provides a method for photoelectrocatalytic C–C coupling that combines homogeneous and heterogeneous reactions. 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 significantly improves the yield and conversion rate of the C–C coupling reaction.

[0004] The technical solutions of the present invention are as follows:

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

[0006] In a three-electrode system, unsubstituted or Ra-substituted 5-20 membered heteroaromatic hydrocarbons, C(sp 3 )–H organic matter is mixed with an electrolyte containing a metal ion compound, and light and voltage are applied to the mixture to cause 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 substituents 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 organic compound 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 hydrocarbon, unsubstituted or Rb-substituted 3-20 membered heterocycloalkane, or CHD3; the substituent Rb is selected from -OH, -C 1-10 Alkyl or -OC1-10 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 hydrocarbon, unsubstituted or Rb-substituted 3-10 membered heterocycloalkane, or CHD3; 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, twelve-membered cycloalkane, 1,4-epoxycyclohexane, CH3CH2OCH3, CH3CH2OH, methane, CHD3, oxacyclohexane, oxolane, 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 containing 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, the content of metal ions in the electrolyte 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 0.05-0.2 M; the concentration of the hydrochloric acid is 5-30 μL / mL.

[0021] Illustratively, the electrolyte solution 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 380-800 nm.

[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 100-600 mW 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 hours, preferably 10-24 hours.

[0030] According to an embodiment of the present invention, the reaction temperature is 20-70°C, illustratively, it can 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-processing step: separating, extracting, and drying the reaction product to obtain a coupled product. Preferably, the reaction product is separated and purified by extracting the reaction product with ethyl acetate and water, drying it over anhydrous sodium sulfate, and then removing the solvent by rotary evaporation. The coupled product is then separated and purified by thin-layer chromatography to obtain the 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;

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

[0037] According to an embodiment of the present invention, the titanium dioxide photoanode can 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 two-step hydrothermal-annealing 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 annealed 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, and 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 the 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 by-product 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 complex organic reactions.

[0049] Definitions and Explanations 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 alkyl groups having 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms, "C 1-6 The 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" represents the above "C 1-10 An alkyl group is a group formed by directly connecting to oxygen.

[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 Cycloalkanes". The term "C 5-12 "Cycloalkane" is understood to mean a saturated monovalent monocyclic, bicyclic hydrocarbon ring or 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 containing 1-5 heteroatoms independently selected from N, O and S, and a non-aromatic cyclic alkane having a total ring number of 3-20 (e.g., 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 containing 1-5, preferably 1-3, heteroatoms selected from N, O and S. The heterocycloalkane may be attached to the rest of the molecule via any of the carbon atoms or the nitrogen atom (if present). In particular, the heterocycloalkanes may include, but are not limited to, 4-membered rings such as azetidine, oxetanyl; 5-membered rings such as tetrahydrofuran, dioxole, pyrrolidine, imidazolidine, pyrazolidine, pyrrolinane; or 6-membered rings such as tetrahydropyran, piperidine, morpholine, dithiane, thiomorpholine, piperazine, or trithiane; or 7-membered rings such as diazepane. Optionally, the heterocycle may be benzo-fused. The nitrogen-containing ring 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 heterocycloalkanes are non-aromatic. When the 3-20 membered heterocycloalkane is linked to other groups to form the compound of the present invention, the linking may be to a carbon atom on the 3-20 membered heterocyclic ring or to a heteroatom on the 3-20 membered heterocyclic ring. For example, when the 3-20 membered heterocyclic ring is selected from piperazine, the linking may be to a nitrogen atom on the piperazine ring and to the other group. Alternatively, when the 3-20 membered heterocyclic ring is selected from piperidine, the linking may be to a nitrogen atom on the piperidine ring and to a carbon atom at the para position thereof.

[0056] The term "C 6-14"Aromatic hydrocarbon" is understood to mean preferably a monovalent aromatic or partially aromatic monocyclic, bicyclic or tricyclic hydrocarbon ring ("C 6-14 arenes), in particular rings with 6 carbon atoms, such as benzene or biphenyl, or rings with 9 carbon atoms ("C9 aryl"), such as indane or indene, or rings with 10 carbon atoms ("C 10 arenes”), such as tetralin, dilin or naphthalene, or a ring having 13 carbon atoms (“C 13 Arenes"), such as fluorene, or a ring with 14 carbon atoms ("C 14 Arenes”), such as anthracene. When the C 6-20 When the aromatic hydrocarbon is substituted, it may be monosubstituted or polysubstituted. Furthermore, there is no limitation on the substitution site, and for example, substitution may be at the ortho, para, or meta position.

[0057] The term “5-20 membered heteroarenes” is understood to include 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 heteroarenes”. The term “5-14 membered heteroarenes” is understood to include 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 to other groups to form the compound of the present invention, the carbon atom on the 5-20 membered heteroaromatic hydrocarbon ring can be connected to the other groups, or the heteroatom on the 5-20 membered heteroaromatic hydrocarbon ring can be connected to the other groups. When the 5-20 membered heteroaromatic hydrocarbon is substituted, it can be monosubstituted or polysubstituted. In addition, there is no restriction on the substitution site, for example, the hydrogen attached to the carbon atom on the heteroaromatic hydrocarbon ring can be substituted, or the hydrogen attached to the heteroatom on the heteroaromatic hydrocarbon ring can be substituted. When the heteroaromatic hydrocarbon contains an N atom, the 5-20 membered heteroaromatic hydrocarbon can also be oxidized to its nitrogen oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 The linear sweep voltammetry curves 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 4 These are the X-ray diffraction patterns of the titanium dioxide photoanode before reaction in Example 2 and the X-ray diffraction patterns 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 solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative 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 encompassed within the scope of protection 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 to a 100 mL beaker, add 25 mL of hydrochloric acid, mix and stir, and cool to room temperature.

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

[0068] 1.3 Add 7.2 mL of tetrabutyl titanate mixed solution to the reactor lining, followed by clean FTO glass. Place the reactor in an oven and heat at 150°C for 10 h.

[0069] After hydrothermal treatment, the FTO glass was removed, rinsed with deionized water, and dried with nitrogen. The glass was then placed in a muffle furnace and heated to 450°C over 40 minutes. Annealed at 450°C for 1.5 hours and allowed to cool naturally to room temperature to yield a titanium dioxide photoanode.

[0070] Figure 1The linear sweep voltammetric curves of the titanium dioxide photoanode prepared in Preparation Example 1 under different test conditions are shown in the figure. 2+ Representatives of the test were tested by adding copper ions to a 0.1M tetraethylammonium tetrafluoroborate solution (as electrolyte), without Cu 2+ "Light" indicates that the test was conducted without adding copper ions to a 0.1 M tetraethylammonium tetrafluoroborate solution. "Dark" indicates that no light was applied during the test.

[0071] from Figure 1 It can be seen from the figure 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 prepared in Example 1 was used as the working electrode, nickel foam as the counter electrode, and saturated silver chloride as the reference electrode. The light source was a 300W xenon lamp equipped with an AM 1.5G and 380-800nm ​​filter. The light intensity was measured by a light intensity meter to be 400mW cm -2 .

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

[0077] The duration of light irradiation and voltage application was 13 h, and the reaction temperature was 40 °C;

[0078] The voltage was applied using 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 chronoamperometry, and the applied voltage is set to 1.2V. Ag / AgCl , the test time was set to 13 h 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 graph is a comparison 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 As can be seen, when copper ions are not present (i.e., Comparative Example 5), the yield is unstable. In Comparative Example 5, a 70% yield can be achieved only when the new electrode is used for the first time, while the yield drops to 50% in the second experiment and reaches a minimum of 43%. Figure 2 Since the yield deteriorated 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 These are the X-ray diffraction patterns of the titanium dioxide photoanode before reaction in Example 2 and the X-ray diffraction patterns 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 the electrolyte salt tetraethylammonium tetrafluoroborate (TEATFB) is not added.

[0090] Comparative Example 2

[0091] The difference between Comparative Example 2 and Example 2 is that hydrochloric acid was 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 determined, and the test results were as follows: Figure 2 shown.

[0099] The conversion rate and yield of the reaction systems 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 Determination by H NMR analysis.

[0101] The yield was calculated by using 1,3,5-trimethoxybenzene as internal standard. 1 Determination 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] The raw material 7A is solid, and its molar content is 10 times that of the 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 shown below:

[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 scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art within the spirit and principles of the present invention shall be included in the scope of protection 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 the three-electrode system, unsubstituted or Ra-substituted 5-20 membered heteroaromatic hydrocarbons, sp 3 The hybrid C–H organic matter is mixed with an electrolyte containing a metal ion compound, and light and voltage are applied to the mixture to perform a C–C coupling reaction; the metal ion compound is selected from copper chloride; Wherein the substituent Ra is selected from -C 1-10 Alkyl, halogen, -CN, -CHO, -OC 1-10 Alkyl, -C 6-14 Aryl, or ; The electrolyte also includes an electrolyte salt, a solvent and hydrochloric acid; The three-electrode system includes a working electrode, a counter electrode and a reference electrode, wherein the working electrode is selected from a titanium dioxide photoelectrode; The wavelength of the light is 380-800 nm; the intensity of the light is 100-600 mW cm -2 ; The voltage is -0.2-1.6 V Ag / AgCl .

2. The method according to claim 1, characterized in that The 5-20 membered heteroaromatic hydrocarbon is selected from quinoline, isoquinoline, phenanthridine, pyridine, pyrimidine, benzothiophene, benzothiazole, benzopyrimidine, quinoxaline, pyridazine or purine, which is unsubstituted or substituted with a substituent Ra, and the substituent Ra is selected from -C 1-10 Alkyl, halogen, -CN, -CHO, -OC 1-10 Alkyl, -C 6-14 Aryl, or .

3. The method according to claim 1, characterized in that The sp 3 The hybrid C–H organic compound 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 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.

4. The method according to claim 1, wherein The counter electrode is selected from one of foamed nickel, Pt or Au.

5. The method according to claim 1, characterized in that The reference electrode is saturated silver chloride.

6. The method according to claim 1, characterized in that The content of metal ions in the electrolyte is 20ppm-300ppm.

7. The method according to claim 1, characterized in that In the electrolyte, the molar concentration of the metal ion compound is 0.02-0.2 mM.

8. The method according to claim 1, characterized in that The pH of the electrolyte is acidic.

9. The method according to claim 1, characterized in that In the electrolyte, the molar concentration of the electrolyte salt is 0.05-0.2M; the concentration of hydrochloric acid is 5-30 L / mL.

10. The method according to claim 1, characterized in that The solvent is selected from a mixture of an organic solvent and water, and the organic solvent is selected from at least one of acetone and acetonitrile.

11. The method according to claim 1, characterized in that The light exposure time is 6-30h.

12. The method according to claim 1, characterized in that The voltage is applied for 6-30 hours.

13. The method according to claim 1, wherein The temperature of the reaction is 20-70°C.

14. The method according to any one of claims 1 to 13, characterized in that The method is carried out in an air atmosphere or in an inert atmosphere.

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