A method for electrochemically preparing benzyl alcohol

Abstract

The application discloses a method for electrochemically preparing benzyl alcohol. In a ternary electrolyte system of a supporting electrolyte / water / organic solvent, a benzyl carbon derivative or a benzyl ketone is used as a raw material, and an inert electrode is used to perform electrochemical reaction, so that benzyl alcohol is obtained. The application has the advantages of reusable electrolyte and electrode material, high reaction conversion rate, high selectivity of benzyl alcohol, mild reaction condition, simple operation and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for electrochemically preparing benzyl alcohol, belonging to the field of organic synthesis. BACKGROUND

[0002] Benzyl alcohol is an important chemical raw material in chemical industry, and has a wide range of applications in fine chemical and pharmaceutical fields. For example, fluorenyl alcohol is an important organic synthesis intermediate, and plays an important role in chiral synthesis. Tonitol is an important intermediate for synthesizing metoclopramide, a muscarinic receptor antagonist used to treat peptic ulcer, and a detection agent for urea, amine and other substances. Traditional benzyl alcohol synthesis methods need to use toxic chemical reagents, and have problems such as high synthesis cost and serious environmental pollution.

[0003] Electric energy is a clean energy. Using electrons to replace dangerous and toxic redox reagents for electrochemical synthesis can realize chemical conversion of reactants under mild conditions, and is efficient and environmentally friendly. In electrochemistry, electrolyte plays a crucial role in changing the chemical reaction equilibrium and selectivity. The method realizes high-selectivity one-step synthesis of benzyl alcohol under mild conditions by adjusting the performance of electrolyte. Compared with traditional methods, the method does not need to use oxidants or reducing agents, the reaction system is simple, and the electrolyte system and electrode material can be reused, so the method has a broad application prospect. SUMMARY

[0004] The present application aims to provide a method for electrochemically preparing benzyl alcohol.

[0005] The method for electrochemically preparing benzyl alcohol provided by the present application is as follows: in a supporting electrolyte / water / organic solvent ternary system, a benzyl carbon derivative or a benzyl ketone is used as a raw material to perform electrochemical reaction, so as to obtain benzyl alcohol.

[0006] In the above method, the supporting electrolyte can be one or a mixture of several of 1-alkyl-3-methyl imidazole bromide, 1-alkyl-3-methyl imidazole chloride, 1-alkyl-3-methyl imidazole iodide, 1-alkyl-3-methyl imidazole hydroxide, 1-alkyl-3-methyl imidazole acetate, 1-alkyl-3-methyl imidazole nitrate, 1-alkyl-3-methyl imidazole tetrafluoroborate, 1-alkyl-3-methyl imidazole hexafluorophosphate, tetraalkylammonium hydroxide, tetraalkylammonium acetate, tetraalkylammonium bromide, tetraalkylammonium chloride and tetraalkylammonium iodide, wherein the alkyl group is C2-C 12 linear or branched alkyl group, and specifically can be ethyl, butyl, octyl, C 12 alkyl group;

[0007] The organic solvent can be one or a mixture of several of DMF, DMSO and acetonitrile. The volume ratio of water to organic solvent is 2:100-20:100.

[0008] The mass ratio of the supporting electrolyte to water in the supporting electrolyte / water / organic solvent ternary system is 1:0.5-1:5;

[0009] The benzyl group is a common carbon-containing aromatic ring or nitrogen-containing and oxygen-containing heteroaromatic ring, and the benzyl carbon derivative can be an aromatic ring or a nitrogen-containing or oxygen-containing heterocyclic compound, and specifically can be any one of fluorene, xanthene, 9,10-dihydroanthracene, diphenylmethane, benzylmethane, 3-benzylpyridine, and 2,3-benzodihydrofuran;

[0010] The benzyl ketone can be specifically any one of fluorenone, xanthone, anthrone, benzophenone, phenylacetone, bis(pyridin-3-yl)methanone, and phenyl-2-pyridylmethanone;

[0011] The ratio of the raw material to the electrolyte is 0.1 g:100 mL-7 g:100 mL;

[0012] When the benzyl carbon derivative is used as the raw material, the electrochemical reaction is an electrocatalytic oxidation reaction, and the electrocatalytic oxidation reaction is carried out at 1.5-5.0 V vs.Ag / Ag + in a constant-potential single electrolytic cell;

[0013] When the benzyl ketone is used as the raw material, the electrochemical reaction is an electrocatalytic reduction reaction, and the electrocatalytic reduction reaction is carried out at-1.5 V--5.0 V vs.Ag / Ag + in a constant-potential single electrolytic cell or an H-type electrolytic cell;

[0014] The cathode of the electrode used in the electrochemical reaction can be a platinum, carbon, copper, or iron electrode, and the anode can be a platinum electrode or a carbon electrode;

[0015] The electrochemical reaction is carried out under stirring;

[0016] The electrochemical reaction can be carried out for 4-30 h.

[0017] The present application has the advantages of reusable electrolyte and electrode material, high reaction conversion rate, high selectivity of benzyl alcohol, mild reaction conditions, and simple operation. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The figure is a structural diagram of a single electrolytic cell (left) and an H-type electrolytic cell (right) used in the electrochemical reaction in the present application.

[0019] Figure 2 The figure is an H spectrum of a compound before and after oxidation of xanthene to xanthol in Example 1 of the present application, in which a is the H spectrum of xanthene before the reaction, and b is the H spectrum of xanthol after the reaction.

[0020] Figure 3The H spectra of compounds before and after the reduction synthesis of xanthone to xanthanol in Example 2 of the present application are shown in the table below, in which a is the H spectrum of xanthone before the reaction; b, the H spectrum of xanthanol after the reaction.

[0021] Figure 4 The H spectra of compounds before and after the reduction synthesis of 9-fluorenone to 9-hydroxyfluorene in Example 4 of the present application are shown in the table below, in which a is the H spectrum of 9-fluorenone before the reaction; b, the H spectrum of 9-hydroxyfluorene after the reaction. DETAILED DESCRIPTION

[0022] The present application will be further described in conjunction with the specific embodiments. The examples provided below are only for the purpose of illustrating the present application, and are not intended to limit the scope of the present application. The examples provided below can serve as a guide for further improvement by those skilled in the art, and do not in any way constitute a limitation on the present application.

[0023] The experimental methods in the following examples are all conventional methods, and are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained commercially, unless otherwise specified.

[0024] The present application provides a method for electrochemically preparing benzyl alcohol, which comprises: performing an electrochemical reaction in a ternary electrolyte system of supporting electrolyte / water / organic solvent, using a benzyl carbon derivative or benzyl ketone as a raw material, to obtain benzyl alcohol.

[0025] In the above method, the supporting electrolyte can be one or a mixture of several of 1-alkyl-3-methylimidazolium bromide, 1-alkyl-3-methylimidazolium chloride, 1-alkyl-3-methylimidazolium iodide, 1-alkyl-3-methylimidazolium hydroxide, 1-alkyl-3-methylimidazolium acetate, 1-alkyl-3-methylimidazolium nitrate, 1-alkyl-3-methylimidazolium tetrafluoroborate, 1-alkyl-3-methylimidazolium hexafluorophosphate, tetraalkylammonium hydroxide, tetraalkylammonium acetate, tetraalkylammonium bromide, tetraalkylammonium chloride, and tetraalkylammonium iodide, etc., in which the alkyl group is C2-C 12 a straight-chain or branched alkyl group, specifically ethyl, butyl, octyl, C 12 alkyl group;

[0026] The benzyl carbon derivative can be any one of fluorene, xanthene, 9,10-dihydroanthracene, diphenylmethane, phenylmethane, 3,3'-dipyridine-methane, 3-benzylpyridine, and 2,3-benzodihydrofuran.

[0027] The benzyl ketone can be any one of fluorenone, xanthone, anthrone, benzophenone, phenylacetone, bis(pyridin-3-yl)methanone, phenyl-2-pyridylmethanone, and isobenzofuranone.

[0028] When the benzyl carbon derivative is used as the raw material, the electrochemical reaction is an electrocatalytic oxidation reaction, and the electrocatalytic oxidation reaction is carried out at 1.5 V to 5.0 V vs. Ag / Ag + in a constant potential single electrolytic cell;

[0029] When the benzyl ketone is used as the raw material, the electrochemical reaction is an electrocatalytic reduction reaction, and the electrocatalytic reduction reaction is carried out at -1.5 V to -5.0 V vs. Ag / Ag + in a constant potential single electrolytic cell or an H-type electrolytic cell;

[0030] The electrochemical reaction can be carried out for 4 to 30 hours.

[0031] The present application has the advantages of reusable electrolyte and electrode material, high reaction conversion rate, high selectivity of benzyl alcohol, mild reaction conditions, simple operation, etc.

[0032] Example 1

[0033] At 35℃, a platinum electrode is used as the working electrode and the counter electrode, and an Ag / Ag + reference electrode. Xanthene (98%, Tci X0003, CasNo:92-83-1) is used as the reactant, and a constant potential electrolysis experiment is carried out in 1-ethyl-3-methylimidazolium bromide (EmimBr)-water-DMF using a single electrolytic cell. Among them, EmimBr is 1.6 g, water is 3.2 g, and DMF is 40 mL. 0.1 g of xanthene is added to the electrolyte solution, and the potential is set to 3 V vs. Ag / Ag + The electrochemical reaction is carried out. After 10 hours of reaction, the product is analyzed by nuclear magnetic hydrogen spectrum, and xanthene alcohol (shown in the formula) with a yield of 96% is obtained. Figure 2

[0034] Example 2

[0035] At 35℃, a platinum electrode is used as the working electrode and the counter electrode, and an Ag / Ag + reference electrode. Xanthone (98%, Innochem A91761, CasNo:90-47-1) is used as the reactant, and a constant potential electrolysis experiment is carried out in 1-ethyl-3-methylimidazolium bromide (EmimBr)-water-DMF using a single electrolytic cell. Among them, 1-ethyl-3-methylimidazolium bromide (EmimBr) is 1.6 g, water is 3.2 g, and DMF is 40 mL. 0.1 g of xanthone is added to the electrolyte solution, and the potential is set to -3 V vs. Ag / Ag + The electrochemical reaction is carried out. After 10 hours of reaction, the product is analyzed by nuclear magnetic hydrogen spectrum, and xanthone alcohol (shown in the formula) with a yield of 95% is obtained. Figure 3 ​​

[0036] Example 3

[0037] At 35℃, platinum electrodes were used as working and counter electrodes, and Ag / Ag + Reference electrode. Xanthan was used as the reactant, and a constant potential electrolysis experiment was carried out using a single electrolytic cell in tetrabutylammonium hydroxide-water-DMF. Among them, tetrabutylammonium hydroxide (40% aqueous solution) was 4g, water was 0.8g, and DMF was 40mL. 0.1g of xanthan was added to the electrolyte, and under constant stirring, the potential was set to 3V vs. Ag / Ag+ for electrochemical reaction. After 10 hours of reaction, the product was analyzed by nuclear magnetic hydrogen spectrum to obtain xanthan alcohol with a yield of 93%.

[0038] Example 4

[0039] At 35℃, platinum electrodes were used as working and counter electrodes, and Ag / Ag + Reference electrode. Xanthan was used as the reactant, and a constant potential electrolysis experiment was performed in a single electrolytic cell in 1-ethyl-3-methylimidazolium bromide-water-DMF. Among them, EmimBr was 1.6g, water was 3.2g, and DMF was 40mL. 2.0g of xanthan was added to the electrolyte solution in batches, and the potential was set to 3V vs. Ag / Ag under constant stirring. + After 30 hours of electrochemical reaction, the product was analyzed by H-NMR spectroscopy to obtain xanthanol with a yield of 95%.

[0040] Example 5

[0041] At 35℃, platinum electrodes were used as working and counter electrodes, and Ag / Ag + Reference electrode. 9-Fluorenone (98%, Innochem A82345, CasNo: 486-25-9) was used as the reactant, and a constant potential electrolysis experiment was performed in a single electrolytic cell in 1-ethyl-3-methylimidazolium bromide (EmimBr)-water-DMF. Among them, EmimBr was 1.6g, water was 3.2g, and DMF was 40mL. 0.1g of 9-Fluorenone was added to the electrolyte, and the potential was set to -3V vs. Ag / Ag under continuous stirring. + After 10 hours of reaction, the product was analyzed by nuclear magnetic hydrogen spectrum to obtain 9-hydroxyfluorene ( Figure 4 shown).

[0042] Example 6

[0043] At 35℃, platinum electrodes were used as working and counter electrodes, and Ag / Ag +Reference electrode. The constant potential electrolysis experiment was carried out in a single electrolytic cell with xanthone as reactant in 1-ethyl-3-methyl imidazole bromide (EmimBr)-water-DMF. Among them, EmimBr was 1.6 g, water was 3.2 g, and DMF was 40 mL. 2.0 g of xanthone was added into the electrolyte in batches, and the potential was set to -3 V vs. Ag / Ag + The electrochemical reaction was carried out. After 30 hours of reaction, the product was analyzed by nuclear magnetic hydrogen spectrum, and the yield of xanthanol was 94%.

[0044] The above has been described in detail. For those skilled in the art, without departing from the purpose and scope of the present application, and without unnecessary experiments, the present application can be implemented in a wide range under the same parameters, concentrations and conditions. Although the present application gives a special example, it should be understood that the present application can be further improved. In short, according to the principle of the present application, this application intends to include any change, use or improvement of the present application, including the change made by the conventional technology known in the art, which is out of the range disclosed in this application. Some basic features can be applied according to the scope of the following attached claims.

Claims

1. A method for electrochemically preparing benzyl alcohol, which comprises: carrying out electrochemical reaction on a benzyl carbon derivative or a benzyl ketone as a raw material in a supporting electrolyte / water / organic solvent ternary system to obtain benzyl alcohol. The supporting electrolyte is one or a mixture of several of 1-alkyl-3-methylimidazolium bromide, 1-alkyl-3-methylimidazolium chloride, 1-alkyl-3-methylimidazolium iodide, 1-alkyl-3-methylimidazolium hydroxide, 1-alkyl-3-methylimidazolium acetate, 1-alkyl-3-methylimidazolium nitrate, 1-alkyl-3-methylimidazolium tetrafluoroborate, 1-alkyl-3-methylimidazolium hexafluorophosphate, tetraalkylammonium hydroxide, tetraalkylammonium acetate, tetraalkylammonium bromide, tetraalkylammonium chloride and tetraalkylammonium iodide, wherein, said alkyl is C2-C 12 straight-chain or branched alkyl; The benzyl carbon derivative is any one of fluorene, xanthene, 9,10-dihydroanthracene, diphenylmethane, benzylmethane, 2,3-benzodihydrofuran, 3-benzylpyridine, or 2,3-benzodihydrofuran. The benzyl ketone is any one of fluorenone, xanthone, anthracene ketone, benzophenone, phenylacetone, 2,3-benzodihydrofuran, 3-benzylpyridine, or 2,3-benzodihydrofuran.

2. The method of claim 1, wherein: The organic solvent is a mixture of one or more of DMF, acetonitrile, ethanol, and DMSO, and the volume ratio of water to the organic solvent is 2:100 to 20:

100. In the supporting electrolyte / water / organic solvent ternary system, the mass ratio of the supporting electrolyte to water is 1:0.5 to 1:

5.

3. The method of claim 1, wherein: The mass / volume ratio of the raw material to the electrolyte is 0.1 g:100 mL to 7 g:100 mL.

4. The method of claim 1, wherein: The electrochemical reaction is an electrocatalytic oxidation reaction, which is carried out at 1.5 V to 5.0 V vs. Ag / Ag + in a constant-potential single electrolytic cell.

5. The method of claim 1, wherein: When benzyl ketone is used as the starting material, the electrochemical reaction is an electrocatalytic reduction reaction, which is carried out at -1.5 V to -5.0 V vs. Ag / Ag + In a constant-potential single electrolytic cell or H-type electrolytic cell.

6. The method of claim 1, wherein: The cathode of the electrochemical reaction is a platinum, carbon, copper, or iron electrode, and the anode is a platinum or carbon electrode. The electrochemical reaction is carried out under stirring.

7. The method of claim 1, wherein: The electrochemical reaction is carried out for 4 to 30 hours.

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