Method for preparing 1, 4-diacyloxy 1, 4-diphenyl butane compound through electrochemical oxidation

Abstract

The invention relates to a method for electrochemical synthesis of a 1, 4-diacyloxy 1, 4-diphenyl butane compound from aryl olefin and carboxylic acid, and belongs to the technical field of organic synthesis. According to the method, rich and cheap aryl olefin and carboxylic acid are used as initial raw materials, electrochemical reaction is carried out on the initial raw materials, electrolyte and an organic solvent in a diaphragm-free electrolytic tank under mild and environment-friendly conditions, and 1, 4-diacyloxy 1, 4-diphenyl butane and derivatives thereof are directly generated. According to the method disclosed by the invention, the use of transition metal, high temperature, high pressure and dangerous oxidizing agents and reducing agents is avoided, good functional group tolerance is established, a supplementary scheme is provided for synthesizing 1, 4-diacyloxy 1, 4-diphenyl butane and derivatives thereof under mild conditions, and the method has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and relates to an efficient and green synthesis method for the reaction of aryl olefins with carboxylic acids mediated by electrochemistry, through coupling and esterification, to generate 1,4-diacyloxy-1,4-diphenylbutane compounds. Background Art

[0002] C2-symmetric 1,4-diols are important precursors for the synthesis of many chiral auxiliaries or ligands, and are also widely present in many natural products and drugs [Org. Lett. 2022, 24, 7512 - 7516.]. For example, 1,4-diol derivatives are important precursors for the synthesis of 2,5-diaryl tetrahydrofuran derivatives [Eur. J. Med. Chem. 2017, 140, 187 - 199.], BPE ligands [Commun. Chem. 2018, 1, 64.], 2,5-disubstituted pyrrolidines [Synthesis 2003(16), 2507 - 2510.], chiral quaternary phosphonium salts [Chem. Commun. 2006, 2980 - 2982.], etc. Many natural and synthetic compounds contain a tetrahydrofuran ring as a structural subunit and have significant biological activities. The BPE ligand is a novel electron-rich C2-symmetric chiral bisphospholane ligand, and the steric hindrance can be regulated by changing the substituents at the 2,5-positions of the phospholane to improve the stereoselectivity of the reaction. This ligand is widely used in various asymmetric synthesis reactions, such as asymmetric Wittig reactions [Eur. J. Org. Chem. 2014, 6630 - 6633.], asymmetric hydrogenation reactions [J. Am. Chem. Soc. 2020, 142, 5272 - 5281.], and so on. In addition, pyrrole, as an important five-membered nitrogen heterocyclic compound in organic chemistry, is the basic structural unit of many amino acids, alkaloids, and enzymes. Its derivatives play important roles in chlorophyll, heme, vitamin B12, and other natural products, and are also widely used in pharmaceutical and materials chemistry [J. Org. Chem. 2022, 87, 13389 - 13395.]. This wide range of applications gives it high synthetic value, and a great deal of effort has been devoted to obtaining these C2-symmetric 1,4-diols.

[0003] In recent years, many research groups have made great efforts to develop methods for the efficient synthesis of 1,4-diphenylbutane-1,4-diol [(a) Tetrahedron Lett. 2015, 56, 1276 - 1279; (b) Tetrahedron Lett. 60, 2019, 151104; (c) Angew. Chem. Int. Ed. 1998, 37(18), 2459 - 2461.] (as shown in the attachment Figure 1(as shown). Although these methods provide effective solutions, most of the reaction conditions are harsh, requiring the use of oxidants, being sensitive to water and air, and operating under low-temperature conditions, etc. Therefore, it is highly necessary to develop a new and efficient green synthesis method for C2-symmetric 1,4-diols. Among them, the simple hydrolysis of 1,4-diacetoxybutane derivatives is one of the important methods for preparing 1,4-diols, while the efficient, green, and simple synthesis of 1,4-diacetoxybutane derivatives is challenging.

[0004] Organic electro-synthesis uses inexpensive, clean, and renewable electricity to replace traditional stoichiometric toxic and dangerous oxidants and reductants for reactions. It is a reagent-free atom oxidation (anode) reduction (cathode), avoiding the addition of external oxidants or reductants and their side effects and by-products [Angew. Chem. Int. Ed. 2017, 56, 15446 - 15450.]. Since the voltage applied to the electrode can be adjusted arbitrarily, the reaction selectivity, reaction rate, and the conversion degree (oxidation state) of the substrate can all be regulated by adjusting the voltage of the external power supply. The reaction can also be terminated or started at any time, making electro-synthesis have flexible and unique controllability, rather than relying on the inherent potential of chemical oxidants or reductants [Chem. Soc. Rev. 2024, 53, 263 - 316.]. In addition, from the perspective of industrial production, electro-synthesis has the unique advantage of being easily scalable and is suitable for industrial production [Chem. Soc. Rev. 2014, 43, 2492 - 2521.]. Summary of the Invention

[0005] In view of this, one of the objectives of the present invention is to provide a method for electrochemically synthesizing 1,4-diacetoxy-1,4-diphenylbutane and its derivatives from aryl olefins and carboxylic acids through a tandem reaction of coupling and esterification.

[0006] To achieve the above objective, the present invention provides the following technical solutions:

[0007] 1. A method for electrochemically synthesizing 1,4-diacetoxy-1,4-diphenylbutane compounds from aryl olefins and carboxylic acids, and the reaction general formula of the method is:

[0008]

[0009] The method is as follows: Place aryl olefins, carboxylic acids, an electrolyte, and an organic solvent in a diaphragm-free electrolytic cell, insert an anode and a cathode, and then stir for 2 - 5 h under the conditions of room temperature, air atmosphere, and constant current to carry out an electrochemical reaction. After the reaction ends, a reaction mixture is obtained. The reaction mixture is successively subjected to desolvation and purification to obtain 1,4-diacetoxy-1,4-diphenylbutane and its derivatives;

[0010] The aryl olefin is p-methoxystyrene; the carboxylic acid is any one of benzoic acid, 2-thiophenecarboxylic acid, 4-methylbenzoic acid, and 3-methylbenzoic acid.

[0011] Preferably, the electrolyte is any one of tetrabutylammonium acetate, tetrabutylammonium bromide, tetrabutylammonium iodide, or a mixed solution formed by sodium iodide and tetrabutylammonium tetrafluoroborate.

[0012] Preferably, the organic solvent is any one of acetonitrile, dichloromethane, dichloroethane, acetone, N,N-dimethylformamide, or nitromethane.

[0013] Preferably, the material of the anode is any one of platinum or carbon; the material of the cathode is any one of carbon or platinum.

[0014] Preferably, the constant current is 5 - 15 mA.

[0015] Preferably, the molar ratio of the aryl olefin to the carboxylic acid is 1:1.0 - 1:3.0; the molar ratio of the aryl olefin to the electrolyte is 1:0.5 - 1:1.5.

[0016] The beneficial effect of the present invention lies in that the present invention discloses a method for directly synthesizing 1,4-diacetoxy-1,4-diphenylbutane and its derivatives by electrochemical-mediated tandem reaction for olefin coupling esterification. It mainly utilizes the advantages of electrolysis. The olefin undergoes anodic oxidation to form a carbon radical cation, which undergoes a radical addition reaction with another molecule of olefin. The carboxylic acid acts as a nucleophile and combines with the generated carbocation to achieve the synthesis of 1,4-diacetoxy-1,4-diphenylbutane with extremely high atom economy.

[0017] The method of the present invention avoids the use of transition metals, high temperature, high pressure, as well as dangerous oxidants and reductants, and establishes good functional group tolerance, providing a supplementary solution for the synthesis of 1,4-diacetoxy-1,4-diphenylbutane and its derivatives under mild conditions, and has good application prospects. In addition, the method of the present invention uses clean energy electric energy as the power source of the reaction, which is green and environmentally friendly while having high atom economy; the method of directly constructing 1,4-diacetoxy-1,4-diphenylbutane by electrocatalysis of olefin and carboxylic acid is the first time. Therefore, the development of the method of the present invention fills the blank of the electrochemical method for the synthesis of 1,4-diacetoxy-1,4-diphenylbutane and its derivatives. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in preferred detail below in conjunction with the drawings, where:

[0019] Figure 1Examples of the reported synthesis of 1,4-diphenylbutane-1,4-diol.

[0020] Figure 2 It is an organic electrochemical experimental device.

[0021] Figure 3 This is the possible reaction mechanism diagram for the electrochemical synthesis of 1,4-diacyloxy-1,4-diphenylbutane compounds from aryl olefins and carboxylic acids in the present invention. Detailed implementation manners

[0022] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following examples only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following examples and the features in the examples can be combined with each other.

[0023] In the following examples, the structural formulas corresponding to compounds 3a - 3d are:

[0024]

[0025] Example 1

[0026] Prepare 1,4-bis(4-methoxyphenyl)butane-1,4-diyl dibenzoate (3a). The specific preparation method is as follows:

[0027] Add 0.2 mmol of p-methoxystyrene (1.0 eq.) and 0.6 mmol of benzoic acid (3.0 eq.) as reactants into an electrochemical device (anode: a carbon rod with a specification of Φ = 0.5 cm, cathode: a platinum sheet of 1.0 cm × 1.0 cm × 0.2 mm). Add 0.2 mmol of electrolyte tetrabutylammonium acetate (nBu4NOAc) and 5 mL of reaction solvent acetonitrile. Electrolyze at a constant current of 10 mA for 3 h at room temperature. After the reaction, separate by silica gel column chromatography to obtain a colorless oil, which is compound 3a.

[0028] dr = 1.5:1. 1 1H NMR (600 MHz, Chloroform-d) δ8.03 (d, J = 8.4 Hz, 4H), 7.53 (t,

[0029] J = 7.4 Hz, 2H), 7.41 (t, J = 7.7 Hz, 4H), 7.32 (m, 4H), 6.81 - 6.89 (m, 4H), 5.97 (t, J = 5.5 Hz, 2H), 3.78 (s, 6H), 2.17 (q, J = 10.5, 9.5 Hz, 1.2H), 2.05 (dd, J = 8.3, 4.3 Hz, 1.6H), 1.89 (dd, J = 13.7, 4.5 Hz, 1.2H); 13 C NMR (151 MHz, Chloroform - d) δ 165.8, 159.4, 132.9, 132.4, 132.3, 130.4, 130.4, 129.7, 128.3, 127.9, 127.9, 114.0, 76.0, 75.9, 55.3, 32.5, 32.3.

[0030] Example 2

[0031] Prepare 1,4 - bis(4 - methoxyphenyl)butane - 1,4 - diyl bis(thiophene - 2 - carboxylate) (3b), and the specific preparation method is as follows:

[0032] Add 0.2 mmol of p - methoxystyrene (1.0 eq.) and 0.6 mmol of 2 - thiophenecarboxylic acid (3.0 eq.) as reactants to an electrochemical device (anode: carbon rod with a specification of Φ = 0.5 cm, cathode: platinum sheet of 1.0 cm × 1.0 cm × 0.2 mm), add 0.2 mmol of electrolyte tetrabutylammonium acetate (nBu4NOAc) and 5 mL of reaction solvent acetonitrile, and conduct an electrolytic reaction at a constant current of 10 mA at room temperature for 2 h. After the reaction, separate by silica gel column chromatography to obtain a colorless oil, which is compound 3b.

[0033] dr = 1:1. 1 H NMR (600 MHz, Chloroform - d) δ 7.78 (m, 2H), 7.53 (m, 2H), 7.30

[0034] (m, 4H), 7.07 (m, 2H), 6.86 (m, 4H), 5.92 (t, J = 6.1 Hz, 2H), 3.779 (s, 3H), 3.776 (s, 3H), 2.15 (m, 1H), 2.03 (m, 2H), 1.87 (m, 1H); 13 C NMR (151 MHz, Chloroform - d) δ 161.5, 159.4, 134.0, 133.5, 132.4, 132.1, 132.1, 128.0, 127.9, 127.8, 114.0, 113.9, 76.3, 76.1, 55.3, 32.4, 32.2.

[0035] Example 3

[0036] To prepare 1,4-bis(4-methoxyphenyl)butane-1,4-diyl bis(4-methylbenzoate) (3c), the specific preparation method is as follows:

[0037] 0.2 mmol of p-methoxystyrene (1.0 eq.) and 0.6 mmol of 4-methylbenzoic acid (3.0 eq.) were added as reactants to an electrochemical device (anode: carbon rod with a specification of Φ = 0.5 cm, cathode: platinum sheet of 1.0 cm × 1.0 cm × 0.2 mm). 0.2 mmol of electrolyte tetrabutylammonium acetate (nBu4NOAc) and 5 mL of reaction solvent acetonitrile were added. The reaction was carried out by passing an electric current of 10 mA at room temperature for 2 h. After the reaction, a colorless oil was obtained by silica gel column chromatography separation, which was compound 3c.

[0038] dr = 1:1. 1 H NMR (600 MHz, Chloroform-d) δ 7.92 (m, 4H), 7.31 (m, 4H), 7.21

[0039] (m, 4H), 6.85 (m, 4H), 5.95 (m, 2H), 3.769 (s, 3H), 3.767 (s, 3H), 2.38 (s, 6H), 2.15 (m, 1H), 2.04 (m, 2H), 1.88 (m, 1H); 13 C NMR (151 MHz, Chloroform-d) δ 165.9, 159.3, 143.6, 132.5, 132.5, 129.7, 129.1, 127.9, 127.9, 127.7, 127.7, 113.9, 75.8, 75.7, 55.3, 32.5, 32.4, 21.7.

[0040] Example 4

[0041] To prepare 1,4-bis(4-methoxyphenyl)butane-1,4-diyl bis(3-methylbenzoate) (3d), the specific preparation method is as follows:

[0042] 0.2 mmol of p-methoxystyrene (1.0 eq.) and 0.6 mmol of 3-methylbenzoic acid (3.0 eq.) were added as reactants to an electrochemical device (anode: a carbon rod with a specification of Φ = 0.5 cm, cathode: a platinum sheet of 1.0 cm × 1.0 cm × 0.2 mm). 0.2 mmol of the electrolyte tetrabutylammonium acetate (nBu4NOAc) and 5 mL of the reaction solvent acetonitrile were added. The reaction was carried out by passing an electric current of 10 mA at room temperature for 2 h. After the reaction, a colorless oil was obtained by silica gel column chromatography separation, which was compound 3d.

[0043] dr = 1:1. 1 H NMR (600 MHz, Chloroform-d) δ 7.85 (m, 4H), 7.34 (m, 8H), 6.87

[0044] (m, 4H), 5.99 (m, 2H), 3.790 (s, 3H), 3.788 (s, 3H), 2.40 (s, 6H), 2.19 (m, 1H), 2.08 (m, 2H), 1.92 (m, 1H); 13 C NMR (151 MHz, Chloroform-d) δ 166.0, 159.4, 138.1, 133.7, 132.5, 132.4, 130.4, 130.2, 128.3, 128.0, 127.9, 126.8, 114.0, 75.9, 75.8, 55.3, 32.5, 32.3, 21.3.

[0045] Example 5

[0046] According to the preparation method in Example 1, 0.2 mmol of p-methoxystyrene (1.0 eq.) and 0.6 mmol of benzoic acid (3.0 eq.) were added as reactants to an electrochemical device (anode: a carbon rod with a specification of Φ = 0.5 cm, cathode: a platinum sheet of 1.0 cm × 1.0 cm × 0.2 mm). 0.2 mmol of the electrolyte tetrabutylammonium acetate (nBu4NOAc) and 5 mL of the reaction solvent acetonitrile were added. The reaction was carried out by passing an electric current of 7 mA at room temperature for 3 h. After the reaction, a colorless oil was obtained by silica gel column chromatography separation, which was compound 3a.

[0047] 1. Influence of different electrode materials in the electrochemical device on the yield of 1,4-diacetoxybutane derivative 3a:

[0048] Replace the electrode materials in the electrochemical device in the above reaction (anode: a carbon rod with Φ = 0.5 cm, cathode: a platinum sheet with a specification of 1 cm × 1 cm × 0.2 mm), and the yield of compound 3a under the same conditions was obtained. The results are shown in Table 1.

[0049] Table 1 Influence of Different Electrode Materials in the Electrochemical Device on the Yield of Compound 3a

[0050]

[0051] a Reaction conditions: 1a (0.2 mmol, 1.0 eq.), 2a (0.6 mmol, 3.0 eq.), electrolyte nBu4NOAc (0.1 mmol, 0.5 eq.), solvent MeCN (5 mL), at room temperature, open to air in a diaphragm-free electrolytic cell under a constant current of 7 mA.

[0052] It can be seen that in the electrochemical method for preparing 1,4-diacetoxybutane derivative 3a in the present invention, when the anode material of the electrochemical device is a carbon rod and the cathode material is a platinum sheet, the yield of the target product is the best.

[0053] 2. Influence of Different Electrolytes on the Yield of 1,4-Diacetoxybutane Derivative 3a:

[0054] The electrolyte tetrabutylammonium acetate (nBu4NOAc) in the above reaction was replaced with tetrabutylammonium tetrafluoroborate (nBu4NBF4), tetrabutylammonium bromide (nBu4NBr), tetrabutylammonium iodide (nBu4NI), tetrabutylammonium perchlorate (nBu4NClO4), lithium tetrafluoroborate (LiBF4), and sodium iodide (NaI, 0.5 eq.) mixed with tetrabutylammonium tetrafluoroborate (nBu4NBF4, 1.0 eq.) to obtain the yield of compound 3a under different electrolyte reactions, and the results are shown in Table 2.

[0055] Table 2 Influence of Different Electrolytes on the Yield of Compound 3a

[0056]

[0057] a Reaction conditions: 1a (0.2 mmol, 1.0 eq.), 2a (0.6 mmol, 3.0 eq.), electrolyte (0.1 mmol, 0.5 eq.), solvent MeCN (5 mL), at room temperature, open to air in a diaphragm-free electrolytic cell under a constant current of 7 mA.

[0058] It can be seen that in the electrochemical method for preparing 1,4-diacetoxybutane derivative 3a in the present invention, any one of tetrabutylammonium acetate, tetrabutylammonium bromide, tetrabutylammonium iodide, or a mixture of sodium iodide and tetrabutylammonium tetrafluoroborate can be used as the electrolyte for the reaction, and the target product can be prepared by reaction. However, when using tetrabutylammonium acetate, the yield of the target product is the best.

[0059] 3. Influence of different substrate feeding ratios on the yield of 1,4-diacetoxybutane derivative 3a:

[0060] The substrate feeding ratio in the above reaction was replaced by 1:1 and 1:2 respectively instead of 1:3, and the yields of compound 3a under different substrate feeding ratios were obtained. The results are shown in Table 3.

[0061] Table 3 Influence of different substrate feeding ratios on the yield of compound 3a

[0062]

[0063] a Reaction conditions: 1a (0.2 mmol, 1.0 eq.), 2a (x eq.), electrolyte nBu4NOAc (0.1 mmol, 0.5 eq.), solvent MeCN (5 mL), at room temperature, open to air in a diaphragm-free electrolytic cell under a constant current of 7 mA.

[0064] It can be seen that in the electrochemical method for preparing 1,4-diacetoxybutane derivative 3a of the present invention, the target product has the best yield when the substrate feeding ratio is 1:3.

[0065] 4. Influence of different reaction solvents on the yield of 1,4-diacetoxybutane derivative 3a:

[0066] The reaction solvent acetonitrile in the above reaction was replaced by dichloromethane, dichloroethane, acetone, a mixture of ethyl acetate and 20 μL of water, a mixture of tetrahydrofuran and 20 μL of water, methanol, N,N-dimethylformamide, dimethyl sulfoxide, and nitromethane respectively, and the yields of compound 3a under different reaction solvents were obtained. The results are shown in Table 4.

[0067] Table 4 Influence of different reaction solvents on the yield of compound 3a

[0068]

[0069]

[0070] a Reaction conditions: 1a (0.2 mmol, 1.0 eq.), 2a (0.6 mmol, 3.0 eq.), electrolyte nBu4NOAc (0.1 mmol, 0.5 eq.), solvent (5 mL), at room temperature, open to air in a diaphragm-free electrolytic cell under a constant current of 7 mA.

[0071] It can be seen that in the electrochemical method for preparing 1,4-diacetoxybutane derivative 3a of the present invention, any one of solvents such as acetonitrile, dichloromethane, dichloroethane, acetone, N,N-dimethylformamide or nitromethane can be used as the reaction solvent, and 1,4-diacetoxybutane derivative can be prepared by reaction. However, the yield of the target product is the best when acetonitrile is used as the solvent.

[0072] 5. Influence of electrolytes with different addition amounts on the yield of 1,4-diacetoxybutane derivative 3a:

[0073] The addition amount of the electrolyte tetrabutylammonium acetate (nBu4NOAc) in the above reaction was respectively replaced by 1.0 eq. and 1.5 eq., and the yields of compound 3a under the reactions with different addition amounts of electrolytes were obtained. The results are shown in Table 5.

[0074] Table 5 Influence of reactions with different addition amounts of electrolytes on the yield of compound 3a

[0075]

[0076] a Reaction conditions: 1a (0.2 mmol, 1.0 eq.), 2a (0.6 mmol, 3.0 eq.), electrolyte nBu4NOAc (x eq.), solvent MeCN (5 mL), room temperature, open to air in a diaphragm-free electrolytic cell under a constant current of 7 mA.

[0077] It can be seen that in the electrochemical method for preparing 1,4-diacetoxybutane derivative 3a of the present invention, the yield of the target product is the best when the addition amount of the electrolyte is 1.0 eq.

[0078] 6. Influence of the magnitude of the applied current during the reaction on the yield of 1,4-diacetoxybutane derivative 3a:

[0079] The current during the power-on process of the above reaction was respectively replaced by 5 mA, 10 mA, 12 mA and 15 mA, and the yields of compound 3a under different currents were obtained. The results are shown in Table 6.

[0080] Table 6 Influence of reactions with different currents on the yield of compound 3a

[0081]

[0082] a Reaction conditions: 1a (0.2 mmol, 1.0 eq.), 2a (0.6 mmol, 3.0 eq.), electrolyte nBu4NOAc (0.2 mmol, 1.0 eq.), solvent MeCN (5 mL), room temperature, open to air in a diaphragm-free electrolytic cell under a constant current of x mA.

[0083] It can be seen that in the electrochemical method for preparing 1,4-diacetoxybutane derivative 3a of the present invention, the current can react to prepare the corresponding target product within the range of 5-15 mA, but the yield of the target product is the best when the current is 10 mA.

[0084] Main reagents and instruments

[0085] Unless otherwise specified, all reagents were purchased from commercial suppliers and did not require further purification. All electrochemical reactions were carried out in a diaphragm-free electrolytic cell. The electrolyzer used was a product of an adjustable DC regulated power supply (MS-150V 100 mA) (Dongguan Maihao Electronic Technology Co., Ltd.). The electrodes used in this experiment were all purchased from Tianjin Gaoxu Optoelectronic Technology Co., Ltd. The specifications of the platinum plate electrode and the graphite electrode were 1.0 cm × 1.0 cm × 0.2 mm, and the C-shaped rod was Φ = 0.5 cm. Ocean GF 254 silica gel plates (Qingdao Ocean Chemical Industry Co., Ltd., Qingdao, China) were used for thin-layer chromatography, and UV light and phosphomolybdic acid were used as color developers. Flash column chromatography was carried out under pressure using 200-300 mesh silica gel. Nuclear magnetic resonance spectrometer (600 MHz, with TMS as the internal standard, Bruker Instruments Co., Ltd.).

[0086] The experimental device consisted of a carbon rod electrode (Φ = 0.5 cm), a platinum plate (1 cm × 1 cm × 0.2 mm), a magnetic stir bar, a test tube (10 mL) with a perforated rubber stopper, an adjustable DC regulated power supply (MS-150V 100 mA), and a magnetic stirrer (as shown in the appendix Figure 2 ).

[0087] Mechanism analysis

[0088] Taking the reaction in Example 1 above as an example, through mechanism exploration experiments, a possible reaction mechanism was proposed: First, the substrate p-methoxystyrene 1a undergoes single-electron oxidation at the anode to generate a radical cation, which then undergoes radical addition with another molecule of alkene to form a new C-C bond, obtaining a new cation intermediate. Benzoic acid in the solution attacks the cation center as a nucleophile, releasing a proton simultaneously to form an intermediate containing an ester group. This intermediate is further oxidized by a single electron at the anode and loses another proton to generate a highly reactive cation intermediate. This cation intermediate undergoes a nucleophilic reaction with benzoic acid again, ultimately generating the target product containing two ester groups. At the cathode, a reduction reaction occurs. Protons in the solution gain electrons on the cathode surface, undergo a reduction reaction, generate hydrogen gas, and escape from the system (as shown in the appendix Figure 3 ).

Claims

1. A method for electrochemically synthesizing 1,4-diacetoxy-1,4-diphenylbutane compounds from aryl olefins and carboxylic acids, characterized in that, The method is as follows: An aryl olefin, a carboxylic acid, an electrolyte and an organic solvent are placed in a diaphragmless electrolytic cell, an anode and a cathode are inserted, and then the mixture is stirred for 2 to 5 h under the conditions of room temperature, air atmosphere and constant current to carry out an electrochemical reaction. After the reaction is completed, a reaction mixture is obtained. The reaction mixture can be obtained 1,4-diacetoxy-1,4-diphenylbutane and its derivatives after desolvation and purification in sequence; The aryl olefin is p-methoxystyrene; the carboxylic acid is any one of benzoic acid, 2-thiophenecarboxylic acid, 4-methylbenzoic acid, 3-methylbenzoic acid.

2. The method according to claim 1, characterized in that: The electrolyte is any one of tetrabutylammonium acetate, tetrabutylammonium bromide, tetrabutylammonium iodide or a mixed solution formed by sodium iodide and tetrabutylammonium tetrafluoroborate.

3. The method according to claim 1, wherein: The organic solvent is any one of acetonitrile, dichloromethane, dichloroethane, acetone, methanol, N , N N,N-dimethylformamide, dimethyl sulfoxide or nitromethane.

4. The method according to claim 1, wherein: The material of the anode is any one of platinum or carbon; the material of the cathode is any one of carbon or platinum.

5. The method according to claim 1, characterized in that: The constant current is 5 to 15 mA.

6. The method according to claim 1, characterized in that: The molar ratio of the aryl olefin to the carboxylic acid is 1:1.0 to 1:3.0; the molar ratio of the aryl olefin to the electrolyte is 1:0.5 to 1:1.5.

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