Electrochemical oxidation of cycloalkanes to produce cycloalkanone compounds

Abstract

The present invention relates to a process for the preparation of unsubstituted or at least monosubstituted cycloalkanones by electrochemically oxidizing unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons in the presence of inorganic or organic nitrates in an electrolytic cell in a reaction medium in the presence of oxygen.

Description

[Technical Field]

[0001] The present invention relates to a method for producing unsubstituted or at least monosubstituted cycloalkanones by electrochemically oxidizing an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon in an electrolytic cell in the presence of an inorganic or organic nitrate in an oxygen-containing reaction medium. [Background technology]

[0002] Cycloalkanones and cycloalkanol compounds are important intermediates in numerous industrial manufacturing processes. Oxidizing saturated, non-functionalized alicyclic hydrocarbons (and therefore, inactive CH bonds) to their corresponding ketones or alcohols requires specific reaction conditions to selectively convert these unreactive substances into monofunctional successor products while maintaining their cyclic structure.

[0003] Numerous processes exist that rely on transition metal catalysts and the use of chemical oxidizing agents such as oxygen or peroxides. The use of expensive transition metals and chemical oxidizing agents not only increases costs but also generates reagent waste that may require cumbersome disposal.

[0004] One example is the production of polyamide 12 from laurolactam. This is currently carried out mainly via cyclododecanone as an intermediate. This is first converted to a peroxide by air. To ensure a more selective further reaction, a boron oxide is used, which reacts with the peroxide to produce a borate ester and oxygen. The resulting alcohol is then oxidized to cyclododecanone on a CuCr catalyst. The main drawback of this reaction pathway is the use of boron oxide. Boron oxide is currently a substance of particular interest because it is suspected of affecting fertility and potentially harming the fetus.

[0005] In Yamanaka's paper (J. Chem. Commun. 2000, pp. 2209-2210), it was found that anodization of alkanes in an aqueous medium yielded a radiation level of 0.1 mA / cm². 2It has been reported that CO2 is generated at low current densities of less than 2V. In non-aqueous media, oxidation of adamantane occurs at voltages exceeding 2V and 4mA / cm². 2 Oxygen activation is observed at current densities below a certain level. The rate of alicyclic ketone (cyclohexanone) formation and current yield have been shown to increase significantly, particularly with an Ir(acac)2 / carbon fiber anode. In this case, oxygen is produced from water. Organic solvents have an effect; for example, cyclohexane conversion does not occur in acetonitrile.

[0006] Kawamata's paper (J.Am.Chem.Soc. 2017 (139), pp. 7448-7551) shows that when mediators such as quinuclidine (a tertiary amine, toxic) are used in combination with HFIP (hexafluoroisopropanol, which causes organ damage and teratogenicity), inactive CH bonds in functionalized aliphatic and alicyclic species can be electrochemically oxidized at low potential. The conductive salt used was Me4N-BF4. It was confirmed that the introduced oxygen was generated from the gas phase. The reaction did not occur under argon. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Yamanaka's paper (J. Chem. Commun. 2000, pp. 2209-2210) [Non-Patent Document 2] Kawamata's paper (J.Am.Chem.Soc. 2017 (139), pp. 7448-7551) [Overview of the project] [Problems that the invention aims to solve]

[0008] The object of the present invention is to provide a sustainable and resource-saving method for converting unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons to the corresponding ketones as the main product, as selectively as possible. [Means for solving the problem]

[0009] This objective was achieved through the subject matter of the claims and the specification.

[0010] The present invention relates to a method for producing unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation of unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons. (a) A step of preparing at least one unsubstituted or at least one monosubstituted saturated alicyclic hydrocarbon, (b) A step of preparing at least one organonitrate, (c) In an electrolysis cell in a reaction medium containing oxygen, electrochemically oxidize the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon prepared in step (a) in the presence of the organic nitrate prepared in step (b). Regarding methods including

[0011] The method of the present invention has special features such as high selectivity, low use of auxiliary chemicals, use of electric current as an oxidizing agent, and consequently low waste generation.

[0012] Remarkably, it has been found that the electrochemical oxidation method of the present invention allows for the introduction of oxygen functional groups into alicyclic hydrocarbons using oxygen from the air. This eliminates the need for chemical oxidizers such as reactive peroxides and expensive catalysts with complex ligand systems. At the same time, it reduces or even completely avoids the use of toxic and / or carcinogenic reagents. The developed method is an inexpensive and environmentally friendly alternative to existing synthesis methods. Simple and safe process conditions allow for the production of large quantities of the target compound without incurring significant costs. Therefore, the present invention can significantly optimize processes that were previously costly and time-consuming.

[0013] Furthermore, surprisingly, it has been found that the method of the present invention also allows the use of electric current when producing cycloalkanone compounds from unsubstituted cycloalkanes using nitrates (which function as both conductive salts and electrochemical mediators). Even if byproducts, particularly alicyclic alcohols of the same ring size, are produced during the implementation of the method of the present invention, this is not a problem as they can be converted to the corresponding ketones by further established methods.

[0014] Even more surprisingly, the method of the present invention has been found to be able to be carried out at atmospheric pressure and room temperature. This is equally advantageous in terms of energy efficiency and, consequently, environmental compatibility.

[0015] In the method of the present invention, monocyclic or polycyclic unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons can be used. Monocyclic or bicyclic alicyclic hydrocarbons are preferred. In the method of the present invention, the use of monocyclic alicyclic hydrocarbons is particularly preferred.

[0016] Preferably, the monocyclic or polycyclic, and especially monocyclic or bicyclic saturated alicyclic hydrocarbons used in the methods of the present invention, may have 5 to 18 carbon atoms in their ring system. Each of these alicyclic hydrocarbons may be unsubstituted, monosubstituted, or polysubstituted. If monosubstituted or polysubstituted, they are preferably substituted with one, two, three, four, or five substituents independently selected from the group consisting of methyl, phenyl, or benzyl. The phenyl or benzyl substituents themselves may be unsubstituted, or monosubstituted or polysubstituted with one, two, or three substituents independently selected from the group consisting of F, Cl, Br, and NO2. If the alicyclic hydrocarbon or its substituents used in accordance with the present invention include alkyl groups having more than one carbon atom in their side chains, undesirable side reactions may occur at these substituents when the methods of the present invention are carried out.

[0017] In the method of the present invention, as the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon, it has 6 to 12 carbon atoms in the ring, preferably 8 to 12 carbon atoms in the ring, and is unsubstituted or monosubstituted or polysubstituted with 1, 2, 3, 4 or 5 substituents independently selected from the group consisting of methyl, phenyl or benzyl. It is particularly preferred to use a monocyclic saturated hydrocarbon. In the method of the present invention, it is very particularly preferred to use a monocyclic saturated hydrocarbon having 8 to 12 carbon atoms in the ring and being unsubstituted or monosubstituted or disubstituted or trisubstituted with a methyl group.

[0018] Very particularly preferably, the monocyclic saturated hydrocarbon is unsubstituted and is selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane, and even more preferably is selected from the group consisting of cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane, and most preferably the hydrocarbon is cyclododecane.

[0019] According to step (b) of the method according to the present invention, at least one organic nitrate is provided. This nitrate functions as both a conductive salt and a mediator of the electrochemical oxidation method according to the present invention. It is preferred to use an organic nitrate of the general formula [cation + [NO3 - .

[0020] [cation + is of the general structure [R 1 R 2 R 3 R 4 N + (wherein R 1 , R 2 , R 3 , R 4 are each independently selected from the group consisting of C1 to C 16 alkyl, particularly linear or branched C1 to C8 alkyl). An ammonium ion having General structure (I):

[0021] [ka]

[0022] (In the formula, R 1 and R 2 This refers to linear or branched chains C1-C 18 Alkyls, particularly those consisting of linear or branched C1-C8 alkyls, are independently selected from the group, R 3 H and linear or branched chains C1-C 18 Alkyl groups, particularly those consisting of H and linear or branched C1-C8 alkyl groups, are selected. The imidazolium cation, General structure (II):

[0023] [ka]

[0024] (In the formula, R 1 C1~C 18 Alkyl, particularly selected from the group consisting of linear or branched C1-C8 alkyl groups, R 2 , R 3 and R 4 H and linear or branched chains C1-C 18 Alkyl groups, particularly H, and linear or branched C1-C8 alkyl groups, are independently selected. The pyridinium cation, and General structure [R 1a R 2a R 3a R 4a P + ](where R 1a , R 2a , R 3a , R 4a C1~C 16 A phosphonium ion of alkyl groups, particularly those independently selected from the group consisting of linear or branched C1-C8 alkyl groups. It is selected from the group consisting of the following.

[0025] In the method of the present invention, when using an organic nitrate based on an imidazolium cation, the cation of general formula (I) is preferred, where R 1 and R 2 This refers to linear or branched chains C1-C 18 Alkyls, particularly those consisting of linear or branched C1-C8 alkyls, are independently selected from the group, R 3 is hydrogen. Particularly preferred is the imidazolium cation of general formula (I), where R is 1 is methyl, and R 2 is ethyl, or R 1 is methyl, and R 2 is methyl, or R 1 is methyl, and R 2 It is butyl, and R 3 In both cases, it is hydrogen.

[0026] In the method of the present invention, when a pyridinium cation-based nitrate is used, the cation of general formula (II) is preferred, where R 1 This refers to linear or branched chains C1-C 18 Alkyl, particularly linear or branched C1-C8 alkyl. Particularly preferred is the pyridinium cation of general formula (I), where R 1 This refers to linear or branched chains C1-C 18 Alkyl, particularly linear or branched C1-C8 alkyl, and radical R 2 , R 3 and R 4 Each of these is independently selected from the group consisting of linear or branched C1-C8 alkyl groups, and is preferably a monosubstituted at the 2nd, 3rd, or 4th position, a disubstituted at the 2nd, 4th, 2nd, 5th, or 2nd, 6th positions, or a trisubstituted at the 2nd, 4th, or 6th positions.

[0027] In principle, the method of the present invention may also use two or more of the above-mentioned nitrates. Nitrates according to the present invention, in particular composition [R 1 R 2 R 3 R 4 N + ][NO3- ] Organic ammonium nitrate salts, or composition [R 1a R 2a R 3a R 4a P + ][NO3 - It is preferable to use an organic phosphonium salt of ], and in particular composition [R 1 R 2 R 3 R 4 N + ][NO3 - Organic ammonium nitrate salts of ] are preferred.

[0028] Very preferably, the organic ammonium nitrate is tetra-n-butylammonium nitrate or methyltri-n-octylammonium nitrate. The organic phosphonium nitrate is particularly preferably tetra-n-butylphosphonium nitrate or methyltri-n-octylphosphonium nitrate. The organic imidazolium nitrate is preferably 1-butyl-3-methylimidazolium nitrate.

[0029] Most preferably, the organic nitrate used in the method of the present invention is tetra-n-butylammonium nitrate or methyltri-n-octylammonium nitrate.

[0030] The order in which the components used in the method of the present invention are prepared may vary, as may the order in which the individual components are brought into contact with each other or with their respective reaction media.

[0031] In one embodiment of the method of the present invention, an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon or an organic nitrate is added first, combined with the reaction medium, preferably dissolved at least partially or completely in the reaction medium, or mixed with the reaction medium, and then the other components are added to these two components, respectively. In another embodiment of the method of the present invention, an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon and an organic nitrate are added first, and then combined with the reaction medium, preferably dissolved at least partially or completely in the reaction medium, or mixed with the reaction medium. In the method of the present invention, it is also possible to add an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon and an inorganic or organic nitrate to the reaction medium simultaneously or sequentially, preferably dissolved at least partially or completely in the reaction medium, or mixed with the reaction medium.

[0032] The reaction medium used in the method according to the present invention is a liquid under the conditions under which the method is carried out and can partially or completely dissolve the components used, i.e., particularly unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons and inorganic or organic nitrates. When at least one of these components is used in liquid form, the reaction medium is preferably readily miscible with the above components.

[0033] In the method according to the present invention, it is preferable to use a polar aprotic reaction medium for electrochemical oxidation. This can be used in an anhydrous form, a dry form, or mixed with water.

[0034] In the method according to the present invention, when an inorganic nitrate, particularly potassium nitrate or sodium nitrate, is used, the reaction medium is preferably an aprotic reaction medium containing water and mixed with water. The water content in the reaction medium can vary. In all cases, the water content is preferably up to 20% by volume, more preferably up to 15% by volume, particularly preferably up to 10% by volume, and even more preferably up to 5% by volume, relative to the total amount of the reaction medium.

[0035] Preferably, the polar aprotic reaction medium is selected from the group consisting of aliphatic nitriles, aliphatic ketones, alicyclic ketones, dialkyl carbonates, cyclic carbonates, lactones, aliphatic nitroalkanes, dimethyl sulfoxides, esters and ethers, or at least two combinations of these components.

[0036] Particularly preferred is the reaction medium selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, acetone, dimethyl carbonate, methyl ethyl ketone, 3-pentanone, cyclohexanone, nitromethane, nitropropane, tert-butyl methyl ether, dimethyl sulfoxide, γ-butyrolactone, and ε-caprolactone, or at least two combinations thereof.

[0037] More preferably, the reaction medium is selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, dimethyl carbonate, and acetone, or at least two combinations of these components.

[0038] Very preferably, the reaction medium is acetonitrile, isobutyronitrile, or adiponitrile in dry or anhydrous form.

[0039] Similarly, very preferably, the reaction medium is acetonitrile, isobutyronitrile, or adiponitrile mixed with water as needed.

[0040] When one or more of the above components are used in the reaction medium in a mixture with water, the water content is preferably a maximum of 20% by volume, more preferably a maximum of 15% by volume, particularly preferably a maximum of 10% by volume, and even more preferably a maximum of 5% by volume, relative to the total amount of the reaction medium.

[0041] To carry out the method according to the present invention, it may be advantageous to add further solubilizing components to the reaction medium. Suitable advantageous components can be identified by simple preliminary tests of their dissolution behavior.

[0042] Examples of solubilizing components are primary alcohols, secondary alcohols, monoketones or dialkyl carbonates, or mixtures of at least two of these components, which are used mixed with water as needed. In the method according to the present invention, aliphatic C 1-6 It is preferable to use alcohol. Particularly preferred solubilizing components can be selected from the group consisting of methanol, ethanol, isopropanol, 2-methyl-2-butanol, or a mixture of at least two of these components, and may be used mixed with water as needed.

[0043] As a reaction medium, dimethyl carbonate is reacted with at least one C, particularly selected from the group consisting of methanol, ethanol, isopropanol, and 2-methyl-2-butanol. 1-6 It is particularly advantageous to use it mixed with alcohol as needed, and with water as needed.

[0044] When one or more of these solubilizing components are used in combination with water, the water content is preferably up to 20% by volume, more preferably up to 15% by volume, particularly preferably up to 10% by volume, and even more preferably up to 5% by volume, relative to the total amount of solubilizing components and water.

[0045] In all cases, the solubilizing component may be added in an amount preferably less than 50% by volume, more preferably less than 30% by volume, and particularly preferably less than 10% by volume, relative to the total amount of the reaction medium.

[0046] Preferably, in the method of the present invention, the organic nitrate is used in an amount of 0.1 to 2.0 equivalents, preferably 0.2 to 1.0 equivalents, more preferably 0.3 to 0.8 equivalents, and particularly preferably 0.4 to 0.8 equivalents, relative to the amount of unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons.

[0047] According to the present invention, the electrochemical oxidation of unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons in the presence of inorganic or organic nitrates is carried out in an electrolytic cell in a reaction medium in the presence of oxygen.

[0048] It is advantageous to prepare an oxygen-containing gas atmosphere that is spatially connected to the reaction medium.

[0049] The proportion of oxygen in the gas atmosphere can vary. Preferably, the proportion of oxygen in the gas atmosphere is 10% to 100% by volume, more preferably 15% to 30% by volume, more preferably 15% to 25% by volume, and particularly preferably 18% to 22% by volume.

[0050] In one embodiment, the proportion of oxygen in the gas atmosphere can be 10% to 100% by volume, more preferably 15% to 100% by volume, and more preferably 20% to 100% by volume.

[0051] Very preferably, the gaseous atmosphere is air.

[0052] Preferably, it is advantageous to introduce a gas atmosphere into the reaction medium or to perform gas exchange between the gas atmosphere and the reaction medium by stirring the liquid phase in the presence of the gas atmosphere.

[0053] Gas exchange between the gas atmosphere and the reaction medium, particularly stirring, can be used to control electrochemical oxidation, for example, by adjusting the shape or speed of the stirrer.

[0054] Preferably, the amount of oxygen dissolved in the reaction medium is at least 1 millimoles, more preferably at least 5 millimoles, per liter of reaction medium.

[0055] Similarly, preferably, the amount of oxygen dissolved in the reaction medium is at least 10 millimoles per liter of reaction medium.

[0056] The present invention provides a method for producing unsubstituted or at least monosubstituted cycloalkanones by electrochemically oxidizing an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon in the presence of an inorganic or organic nitrate in a reaction medium containing oxygen. This method can be carried out in both a divided electrolytic cell and a non-divided electrolytic cell, but it is preferable to carry it out in a non-divided electrolytic cell.

[0057] To avoid undesirable chemical reactions, it may be advantageous to separate the cathode chamber and the anode chamber, and to ensure that charge exchange between the anode and cathode chambers occurs only through a porous membrane (generally an ion exchange resin).

[0058] A non-divided electrolytic cell preferably used in accordance with the present invention comprises at least two electrodes. For this purpose, anodes and cathodes made of conventional materials, such as glassy carbon, boron-doped diamond (BDD), or graphite, may be used. The use of glassy carbon electrodes is preferred.

[0059] Preferably, the non-divided electrolytic cell comprises at least one glassy carbon anode or at least one glassy carbon cathode. Preferably, both the anode and cathode are glassy carbon electrodes.

[0060] The distance between electrodes can vary over a specific range. Preferably, the distance is 0.1 mm to 2.0 cm, more preferably 0.1 mm to 1.0 cm, and even more preferably 0.1 mm to 0.5 cm.

[0061] Furthermore, the method of the present invention can preferably be carried out in a batch or continuous manner within a non-divided flow-through electrolytic cell.

[0062] Preferably, the method of the present invention is carried out in any case with a charge of 190C (2F) to 970C (10F), more preferably 320C to 820C, particularly preferably 350C to 800C, even more preferably 380C to 775C, and most preferably 380C to 450C, per millimole of an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon. Preferably, the electrochemical oxidation in the method of the present invention is carried out with a constant current.

[0063] The current density at which the method of the present invention is implemented is preferably at least 5 mA / cm². 2 , or at least 10mA / cm 2 , or at least 15mA / cm 2 , or at least 20mA / cm² 2 , or 20mA / cm 2 ~50mA / cm 2 Therefore, the above surface area represents the geometric area of ​​the electrode.

[0064] A key advantage of the method according to the present invention is that electric current is used as an oxidizing agent, which is particularly environmentally friendly when obtained from renewable resources, i.e., biomass, solar thermal energy, geothermal energy, hydroelectric power, wind power, or photovoltaic power.

[0065] The method according to the present invention can be carried out over a wide temperature range, for example, at temperatures within the range of 0°C to 60°C, preferably 5°C to 50°C, more preferably 10°C to 40°C, and particularly preferably 15°C to 30°C.

[0066] The method according to the present invention can be carried out under high or low pressure. When the method according to the present invention is carried out under high pressure, a pressure of up to 16 bar is preferred, and a pressure of up to 6 bar is particularly preferred.

[0067] Similarly, preferably, the method according to the present invention can be carried out at atmospheric pressure.

[0068] The products produced by the method of the present invention can be isolated and purified by conventional methods known to those skilled in the art, particularly by extraction, crystallization, centrifugation, precipitation, distillation, evaporation, or chromatography.

[0069] The following embodiments further illustrate the present invention, but are not intended to limit the scope of the invention. [Examples]

[0070] General information and methods Chemicals of analytical quality were obtained and used from regular suppliers (TCI, Aldrich, Acros, etc.). Oxygen was obtained as is from Nippon Gases Deutschland GmbH in Düsseldorf, Germany, at quality 2.5, and used without modification.

[0071] The electrode material used was glassy carbon (Sigradur® G, manufactured by HTW Hochtemperatur Werkstoffe GmbH in Tierhaupten, Germany).

[0072] High-performance liquid chromatography (LP chromatography) was performed using a Shimazu HPLC-MS equipped with a SIL 20A HT autosampler, CTO-20AC column oven, two LC-20AD pump modules for eluent gradient adjustment, an SPD-M20A diode array detector, a CBM-20A system controller, and a Eurospher II 100-5 C18 column (150 × 4 mm, Knauer GmbH, Berlin). Eluent: acetonitrile / water / formic acid (1 vol%) (from 10% ACN to 90% ACN in 10 minutes + 100% ACN in 10 minutes). Mass spectrometry was performed using a Shimazu LCMS-2020 from Shimazu, Japan.

[0073] ¹H-NMR and ¹³C-NMR spectra were recorded at 25°C using a Bruker Avance II 400 (400 MHz, 5 mm BBFO probe with Z gradient and ATM, SampleXPress 60 autosampler, Analytische Messtechnik, Karlsruhe, Germany).

[0074] The non-divided Teflon® cells used in electrolysis are described in the following references: (a) C. Gutz, B. Klockner, SRWaldvogel, Org. Process Res. Dev. 2016, pp. 20, 26-32; b) A. Kirste, G. Schnakenburg, F. Stecker, A. Fischer, SRWaldvogel, Angew. Chem. Int. Ed. 2010, pp. 49, 971-975; Angew. Chem. 2010, pp. 122, 983-987. (See SI).) A full range of these cells with stainless steel blocks is also commercially available as the IKA Screening System (IKA-Werke GmbH&Co.KG, Staufen, Germany). The electrode dimensions were 3cm × 1cm × 0.3cm.

[0075] The gases were introduced in a controlled manner using two Brooks Instrument BV Model 5850S ​​mass flow controllers (MFCs) in Wienendaal, Netherlands. One controller was used for oxygen introduction, and the other for nitrogen introduction. The controllers were controlled by Smart DDE and Matlab R2017b software. Volumetric flow rates were additionally monitored using a DK800 float principle flow meter from Krohne Messtechnik GmbH in Duisburg. In all experiments conducted, the overall volumetric flow rate remained constant at 20 mL / min. This is also the maximum achievable volumetric flow rate, although limited by the MFCs used. The volumetric flow rate ratio of the two gases was adjusted using the MFCs and associated software. The following gas cylinders were used: oxygen 2.5 (Nippon Gases Deutschland GmbH, Düsseldorf), nitrogen 4.8 (Westfalen AG, Münster), or nitrogen 5.0 (Nippon Gases Deutschland GmbH, Düsseldorf). For this purpose, the apparatus was equipped with a gas distributor (including a gas adapter) and a Teflon® lid for the electrolytic cell.

[0076] General Procedure GP1 A non-divisible electrolytic cell (100 mL capacity three-neck round-bottom flask, NS29 Teflon® stopper with electrode holder, magnetic stirrer bar) was filled with cycloalkane (5.0 mmol) and tetrabutylammonium nitrate (0.5 equivalents), and dissolved in acetonitrile (25 mL). Glassy carbon electrodes (3 cm × 1 cm × 0.3 cm) were attached to the cell at 0.5 cm intervals. The immersion surface area of ​​the electrodes was 1.3 cm². 2 Oxygen was introduced into the gas space of the reaction vessel via an NS14.5 gas inlet adapter as needed. Constant current electrolysis was performed at 20°C to 30°C with a current density of 10 mA / cm². 2 It was implemented there.

[0077] A charge of 4–5°F (1930°C–2412°C) was applied to the cycloalkane, and the solvent and unreacted portion of the cycloalkane were removed by distillation under reduced pressure. The residue was added to cyclohexane and water (20 mL each). After phase separation, the aqueous phase was extracted with cyclohexane (20 mL). The organic phases were combined and dried over sodium sulfate or magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The product remained as a residue of this distillation.

[0078] Experimental Example 1: Preparation of cyclohexanone: According to GP1, cyclohexane (0.421 g, 5.0 mmol, 1.0 equivalent) was dissolved in acetonitrile (25 mL), and constant current electrolysis was performed at 25°C under an oxygen atmosphere using 5F. After treatment according to GP1, the product was obtained as a colorless liquid (yield: 6%, 30 mg, 0.31 mmol). 1 ¹H NMR (400 MHz, CDCl3) δ[ppm] = 2.36–2.32 (m, 4H), 1.90–1.84 (m, 4H), 1.75–1.70 (m, 2H). The analytical data were consistent with literature values. In yield measurement, the presence of solvent signals was subtracted from the calculation by integration ratio.

[0079] Experimental Example 2: Preparation of cycloheptanone: Following GP1, cycloheptane (0.491 g, 5.0 mmol, 1.0 equivalent) was dissolved in acetonitrile (25 mL), and constant current electrolysis was performed at 21°C under ambient air conditions using 4F. Electrode immersion surface area: 1.5 cm² 2 Next, the solvent was removed by distillation under reduced pressure, and the residue was purified by column chromatography (cyclohexane / ethyl acetate = 10:0 to 7:3). After removing the solvent by distillation, the product was obtained as a colorless liquid (yield: 20%, 0.112 g, 1.00 mmol). 1 ¹H NMR (400 MHz, CDCl3) δ[ppm] = 2.49–2.47 (m, 4H), 1.69–1.64 (m, 8H). The analytical data was consistent with the literature values.

[0080] Experimental Example 3: Preparation of cyclooctanone: According to GP1, cyclooctane (0.561 g, 5.0 mmol, 1.0 equivalent) was dissolved in acetonitrile (25 mL), and constant current electrolysis was performed at 30°C under an oxygen atmosphere with 4F applied. After treatment according to GP1, the product was obtained as a colorless liquid (yield: 42%, 0.261 g, 2.07 mmol). Rf (cyclohexane / ethyl acetate = 7:3): 0.66. 1 ¹H NMR (400 MHz, CDCl3) δ[ppm] = 2.39–2.36 (m, 4H), 1.87–1.81 (m, 4H), 1.54–1.48 (m, 4H), 1.36–1.32 (m, 2H). The analytical data were consistent with the literature values.

[0081] Experimental Example 4: Preparation of cyclodecanone: According to GP1, cyclodecane (0.701 g, 5.0 mmol, 1.0 equivalent) was dissolved in acetonitrile (25 mL), and constant current electrolysis was performed at 30°C under an oxygen atmosphere with 5F applied. Next, the solvent was removed by distillation under reduced pressure, and the residue was purified by column chromatography (CH / EA = 10:0-9:1). After removing the solvent by distillation and drying under reduced pressure, the product was obtained as a colorless liquid (yield: 12%, 90 mg, 0.59 mmol). Rf (cyclohexane / ethyl acetate = 95:5): 0.28; 1 ¹H NMR (300 MHz, CDCl3) δ[ppm] = 2.49–2.45 (m, 4H), 1.85–1.76 (m, 4H), 1.47–1.43 (m, 4H), 1.32–1.29 (m, 6H). The analytical data were consistent with literature values. In yield measurement, the presence of solvent signals was subtracted from the calculation by integration ratio.

[0082] Experimental Example 5: Preparation of cyclododecanone: According to GP1, cyclododecane (0.842 g, 5.0 mmol, 1.0 equivalent) was dissolved in isobutyronitrile (25 mL), 4F was applied, and constant current electrolysis was carried out at 27 °C under an oxygen atmosphere. Next, the solvent was removed by distillation under reduced pressure, and the residue was purified by column chromatography (cyclohexane / ethyl acetate = 10:0 to 9:1). After removing the solvent by distillation and drying under reduced pressure, the product was obtained as a colorless solid (yield: 21%, 0.194 g, 1.06 mmol). Rf (cyclohexane / ethyl acetate = 9:1): 0.48. 1 1H NMR (400 MHz, CDCl3) δ [ppm] = 2.47 - 2.44 (m, 4H), 1.72 - 1.69 (m, 4H), 1.31 - 1.26 (m, 14H). The analytical data was consistent with the literature values.

[0083] Experimental Example 6: In the following experiments, various parameters of electrochemical oxidation were changed to investigate their effects. These investigations were all carried out on the electrochemical oxidation of cyclooctane to cyclooctanone.

[0084] General Procedure GP2a: Electrolysis was carried out in an undivided 5 mL volume PTFE cell. For this purpose, a conductive salt (0.2 - 1.0 equivalent) and a substrate (cyclooctane, 0.5 - 2.5 mmol) were placed in the cell and dissolved in a solvent (5 mL). The cell was equipped with a vitreous carbon anode and a vitreous carbon cathode at a 0.5 cm interval (electrode dimensions: 7 cm × 1 cm × 0.3 cm, immersion surface area 1.8 cm 2 ). The cell was fixed to a heatable / coolable stainless steel block, and the gas mixture under investigation (from 100% by volume of O2 to 0% by volume of O2) was supplied via an adapter. The current density (5 - 60 mA / cm 2Electrolysis was carried out at a constant current while varying the temperature (5-50°C), stirring speed (100-600 rpm), and charge (4-8 F). After applying the charge, two drops of the reaction solution were taken and analyzed by gas chromatography. Next, 1,3,5-trimethoxybenzene (1 equivalent) was added to the solution as an NMR standard, and the solvent was removed by distillation (45°C, 200 mg bar). The yield of the cycloalkanone product was determined. 1 It was measured by 1H-NMR analysis. In GC analysis, two drops of the reaction solution were eluted with ethyl acetate through approximately 330 mg of 60M silica gel. Approximately 1.5 mL of the filtrate was collected in a GC vial, and the oxidation products were examined by GC-FID and GC-MS.

[0085] General procedure GP2b: Electrolysis was performed in a single 5 mL PTFE cell. For this purpose, a conductive salt (0.2–1.0 equivalent) and a substrate (cyclooctane, 0.5–2.5 mmol) were placed in the cell and dissolved in a solvent (5 mL). The cell was equipped with a glassy carbon anode and a glassy carbon cathode at 0.5 cm intervals (electrode dimensions: 7 cm × 1 cm × 0.3 cm, immersion surface area: 1.8 cm²). 2 The cell was fixed to a heat / coolable stainless steel block and supplied with the gas mixture under investigation (100% volume O2 to 0% volume O2) via an adapter. Current density (5-60 mA / cm²) 2 Electrolysis was performed at a constant current while varying the temperature (5-50°C), stirring speed (100-600 rpm), and charge (4-8 F). After applying the charge, 10 mg of 1,3,5-trimethoxybenzene was added to the reaction solution as an internal standard. Three drops of the reaction solution were taken and analyzed by gas chromatography, and the products were quantified. These were eluted with ethyl acetate through approximately 330 mg of 60 M silica gel. Approximately 1.5 mL of the filtrate was collected in a GC vial, and the oxidation products were examined by GC-FID and GC-MS. Quantification was performed by pre-calibration of the gas chromatograph. The results shown in Scheme 1 below were obtained using GP2a as described above.

[0086] [ka]

[0087] Further illustrative studies, grouped according to the parameters modified in each case, are shown below. • Charge quantity (F for cyclooctane 1) ·Current density (mA / cm 2 ) ·O2 / N2 ratio • Equivalent (1 / 2 nitrate of cyclooctane) • Stirring speed (rpm) ·Temperature (℃) • Nitrates as mediators / conductive salts • Reaction medium ·Electrode material Changes in nitrate cations

[0088] Unless otherwise specified, experiments were performed at least twice, and the mean value, including the standard deviation, was measured. The reference numbers for compounds 1, 2, 3, and 4 correspond to the reference numbers in Scheme 1.

[0089] Experimental Example 6a - Charge Quantity The charge was investigated in the range of 4F to 8F (corresponding to 386C to 772C for 1 mmol of the substrate cyclooctane 1). Table 1: Investigation of various charge quantities

[0090] [Table 1]

[0091] Within the range of charge values ​​investigated, no changes were observed in the formation of products and by-products. Due to the short electrolysis time, the series of tests was continued at 4F.

[0092] Experimental Example 6b - Current Density: The current density is 5 mA / cm². 2 ~60mA / cm 2 It was changed within the range. The electrode surface area in the electrolyte was 1.8 cm 2 . Table 2: Investigation of various current densities

[0093]

Table 2

[0094] When 60 mA / cm 2 is applied, it can be seen that the yield of 2 clearly decreases. Instead, cyclo-octanol 3 is produced to an equivalent extent. A series of tests was continued at 20 mA / cm 2 and various atmospheric O2 contents were investigated.

[0095] Experimental Example 6c - 20 mA / cm 2 O2 / N2 ratio at First, the approximate O2 / N2 ratios (100:0, 20:80, 0:100) at 20 mA / cm 2 were investigated. The ratio 20:80 was selected because it is close to the composition of air. Table 3: Investigation of various O2 / N2 ratios at 20 mA / cm 2

[0096]

Table 3

[0097] In a pure nitrogen atmosphere (ratio 0:100), no product formation was observed. Therefore, no quantitative explanation could be given for the unreacted substrate fraction or by-products. However, traces of cyclo-octanol 3 were detected in the gas chromatogram. As the O2 content was associated with the initial standard current density of 10 mA / cm 2 , these were repeated at the stated current density with smaller stepwise changes (gradations) in the content.

[0098] Experimental Example 6d - 10 mA / cm 2 O2 / N2 ratio at In addition to the gradual changes in content (gradation) shown in the table, experiments were also conducted under ambient conditions without gas supply (labeled "air"). Table 4: 10mA / cm 2 Investigation of various O2 / N2 ratios

[0099] [Table 4]

[0100] The above investigation showed that the conversion of reactant 1 and the formation of product 2 occurred when the oxygen content was 20% by volume and the current density was 10 mA / cm². 2 The highest levels were observed at this time. In addition, a lower proportion of O2 slightly increased the production of cyclooctanol 3.

[0101] Because these conditions resulted in a high yield of cyclooctanone 2 and improved safety due to the higher nitrogen content, these conditions were selected as the comparative conditions for the subsequent reaction (Scheme 2), and other parameters were modified based on these conditions.

[0102] Experimental Example 6: Molar amount and equivalent amount of e-mediator To investigate the concentrations of various substrates and mediators in a solvent (acetonitrile, 5 mL), the molar amount of the substrate and the equivalent ratio of the conductive salt to the mediator were varied. Table 5: Investigation of various molar and equivalent amounts of nitrates

[0103] [Table 5]

[0104] Generally, the conversion from reactant 1 to product 2 was slightly better when the molar amount of substrate was low (less than 1 mmol, equivalent to 0.2 mol / L) than when the molar amount was high. Since changing the mediator concentration relative to the substrate above or below 0.5 equivalents only slightly affected the yield of product 2, it can be inferred that the oxygen source for oxo-functionalization is dissolved molecular oxygen.

[0105] Experimental Example 6f - Stirring Speed Since the oxygen source for ketone synthesis is obtained from the atmosphere, the stirring rate is expected to have a significant impact on the course of the reaction. Table 6: Investigation of various stirring speeds

[0106] [Table 6]

[0107] The results in Table 6 show the maximum value at around 350 rpm. However, the effect of speed is influenced by the shape of the stirrer and cell, so it should not be considered a fixed value.

[0108] Experimental example: 6g - temperature The temperatures mentioned relate to the temperature of the heating block / cryostat. Before starting electrolysis, the electrolyte was stirred at 5°C and 50°C for approximately 30 minutes. Table 7: Survey of various temperatures

[0109] [Table 7]

[0110] Regarding product formation, it can be observed that the yield decreases slightly at temperatures above and below 30°C. Therefore, the reaction appears to be only slightly affected by temperature. Furthermore, at higher temperatures, the fraction of unreacted substrate decreases, which is likely due to its volatility and the open system of the electrolytic cell.

[0111] Experimental Example 6h - Conductive Salt / Mediator To investigate whether nitrate, acting as an anion in conductive salts, also exerts a mediator effect on the reaction, standard tetrabutylammonium nitrate was compared with other common conductive salts. The cation components were not altered. Since each conductive salt different from the standard was tested only once by electrolysis, average values ​​were not recorded. Table 8: Investigation of various conductive salts

[0112] [Table 8]

[0113] The results in Table 8 show that the reaction is dependent on the nitrate anion. Product 2 was produced in very small amounts with different conductive salt anions. Experimental examples 6-GP2a-09, 6-GP2a-28, 6-GP2a-29, and 6-GP2a-30 are comparative examples. Experimental Example 6i - Solvent Table 9: Investigation of various solvents

[0114] [Table 9]

[0115] The reaction proceeded relatively well in the listed solvents. In acetone, the proportion of unreacted substrate was even higher.

[0116] The reaction was also carried out with 3-pentanone, but the solvent signal and product signal overlapped, 1 The yield could not be measured by 1H NMR. However, analysis by gas chromatography confirmed that product 2 was selectively formed in this case as well.

[0117] Initially, it was assumed that O2 was more soluble in isobutyronitrile than in acetonitrile, so a comparison was also performed in a 100% O2 atmosphere (Table 10). Table 10: Investigation of various solvents in 100% by volume O2

[0118] [Table 10]

[0119] The results obtained using acetonitrile and isobutyronitrile were comparable. Specifically, no significant increase in yield of compound 2 was achieved with the use of isobutyronitrile. On the other hand, the proportion of unreacted compound 1 was significantly higher, which is considered an advantage. Subsequently, the reaction with nitropropane was carried out under a 100% O2 atmosphere, confirming that nitrated alkanes can also be used as solvents.

[0120] Experimental Example 6: J-Electrode Material Electrolysis was performed using various carbon-based electrode materials. Since each electrode material, which differed from the GC standard, was tested only once by electrolysis, average values ​​were not recorded. Table 11: Investigation of various electrode materials

[0121] [Table 11]

[0122] The reaction occurred with all electrode materials used, producing product 2. With the graphite electrode, slight exfoliation of the electrode material in the form of black particles was observed after electrolysis. This is attributed to its low stability.

[0123] Experimental Example: Changing the Cation of 6K Conductive Salt / Mediator We investigated various cations other than the standard tetrabutylammonium. The following were used: ·Hexadecyltrimethylammonium nitrate ([C 19 H 42 N][NO3]) · 1-Butyl-3-methylimidazolium nitrate ([C8H 15 [N2][NO3]) Methyltrioctylammonium nitrate ([C 25 H 54 N][NO3]) • Tetrabutylphosphonium nitrate (PBu4NO3) The anionic nitrate components were not changed. Since each conductive salt different from the standard was tested only once by electrolysis, average values ​​were not recorded. Table 12: Investigation of various cations

[0124] [Table 12]

[0125] The oxidation of cycloalkanes to ketones is primarily carried out with nitrates acting as the anionic component (see Experiment 6h). Long-chain alkyl groups on ammonium cations yield slightly higher yields under the same conditions compared to tetrabutylammonium cations. This reaction also works with N-alkylated nitrogen heteroaromatic compounds and tetraalkylphosphonium cations as cations.

[0126] Experimental example 6l: Oxygen solubility in acetonitrile / NBu4NO3 at 25°C and standard pressure: Table 13: Dissolved oxygen concentration of MeCN / NBu4NO3 as a function of atmospheric oxygen content

[0127] [Table 13]

[0128] General Procedure GP3: In a 25 mL non-divided beaker cell with a gas inlet attachment, cycloalkane (5.0 mmol) and tetrabutylammonium nitrate (0.5 equivalents) were dissolved in acetonitrile (25 mL). The cell was equipped with glassy carbon electrodes (7 cm × 1 cm × 0.3 cm) at intervals of 0.5 to 1.0 cm. The immersion surface area of ​​the electrodes was 1.3 cm². 2 The constant current electrolysis was performed at 20-30°C with a current density of 10 mA / cm². 2The experiment was carried out as follows: After applying a charge of 4F to the cycloalkane, the solvent and the unreacted portion of the cycloalkane were removed by distillation under reduced pressure. The residue was added to cyclohexane and water (20 mL each). After phase separation, the aqueous phase was extracted with cyclohexane (20 mL). The organic phases were combined and dried over sodium sulfate or magnesium sulfate, and the solvent was removed by vacuum distillation. The product remained as the residue of this distillation.

[0129] Another quantification method: After applying the charge, approximately 50 mg of 1,3,5-trimethoxybenzene was added to the reaction solution as an internal standard. Three drops of the reaction solution were taken and analyzed by gas chromatography, and the products were quantified. These were eluted with ethyl acetate through approximately 330 mg of 60M silica gel. Approximately 1.5 mL of the filtrate was collected in a GC vial, and the oxidation products were investigated by GC-FID and GC-MS. Quantification was performed by pre-calibration of the gas chromatograph.

[0130] Experimental Example 7: Next, we investigated the effect of the distance between electrodes. Table 14: Investigation of various distances between electrodes

[0131] [Table 14]

[0132] The experimental examples in Table 14 show that the shorter the distance between electrodes, the better the conversion from the starting material to product 2 proceeds.

Claims

1. A method for producing unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation of unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons, (a) A step of preparing at least one unsubstituted or at least one monosubstituted saturated alicyclic hydrocarbon, (b) A step of preparing at least one inorganic or organic nitrate, (c) electrochemically oxidizing the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon prepared in step (a) in the presence of the inorganic or organic nitrate prepared in step (b) in a reaction medium containing oxygen in an electrolysis cell. Includes, The substituents of the saturated alicyclic hydrocarbon are independently selected from the group consisting of methyl, phenyl, or benzyl, and phenyl or benzyl are either unsubstituted or F, Cl, Br, and NO, respectively. ２ A method in which the substituents may be monosubstituted or polysubstituted, each independently selected from the group consisting of the above.

2. The method according to claim 1, wherein the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon is monocyclic or bicyclic.

3. The method according to claim 1, wherein the monocyclic or bicyclic saturated alicyclic hydrocarbon has 5 to 18 carbon atoms in its ring system and is unsubstituted or monosubstituted or polysubstituted with substituents.

4. The method according to claim 1, wherein the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon is a monocyclic saturated hydrocarbon having 6 to 12 carbon atoms in the ring, and the alicyclic hydrocarbon is unsubstituted or monosubstituted or polysubstituted with substituents independently selected from the group consisting of methyl, phenyl, or benzyl.

5. The method according to claim 1, wherein the saturated alicyclic hydrocarbon is unsubstituted and selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, and cyclododecane.

6. The existing organic nitrate is a nitrate of the general formula [cation ＋ [NO ３ － , where [cation ＋ has the general structure [R １ R ２ R ３ R ４ N ＋ (where R １ , R ２ , R ３ , R ４ are each independently selected from the group consisting of C １ to C １６ alkyl). It is an ammonium ion having General structure (I): 【Chemistry 1】 (In the formula, R １ and R ２ C is a straight-chain or branched-chain C １ ~C １８ Each is independently selected from the group consisting of alkyls, R ３ H and linear or branched C １ ~C １８ (Selected from the group consisting of alkyl groups.) The imidazolium cation, General structure (II): 【Chemistry 2】 (In the formula, R １ C １ ~C １８ Selected from the group consisting of alkyl groups, R ２ , R ３ and R ４ H and linear or branched C １ ~C １８ Each element is independently selected from the group consisting of alkyl groups. The pyridinium cation, and General structure [R １ａ R ２ａ R ３ａ R ４ａ P ＋ ] (wherein, R １ａ , R ２ａ , R ３ａ , R ４ａ C １ ~C １６ The phosphonium ion (each independently selected from the group consisting of alkyl groups). The method according to claim 1, selected from the group consisting of the following.

7. In the imidazolium cation of the general formula (I), the radical R １ and R ２ C is a straight-chain or branched-chain C １ ~C １８ Each is independently selected from the group consisting of alkyls, R ３ The method according to claim 6, wherein is hydrogen.

8. In the pyridinium cation of the general formula (II) described above, the radical R1 is a linear or branched chain C １ ~C １８ It is alkyl, and radical R ２ , R ３ and R ４ C is a straight-chain or branched-chain C １ ~C ８ The method according to claim 6, wherein each is independently selected from the group consisting of alkyl groups.

9. The method according to claim 6, wherein the organic nitrate is selected from the group consisting of tetra-n-butylammonium nitrate, methyltri-n-octylammonium nitrate, tetra-n-butylphosphonium nitrate, methyltri-n-octylphosphonium nitrate, and 1-butyl-3-methylimidazolium nitrate.

10. The method according to claim 1, wherein the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon or the inorganic or organic nitrate is added first and combined with the reaction medium, and then, if the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon was added first, the inorganic or organic nitrate is added, and if the inorganic or organic nitrate was added first, the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon is added.

11. The method according to claim 1, wherein the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon and the inorganic or organic nitrate are first added, and then combined with the reaction medium.

12. The method according to claim 1, wherein the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon and the inorganic or organic nitrate are added to the reaction medium simultaneously or sequentially.

13. The method according to claim 1, wherein the reaction medium is a polar aprotic reaction medium that exists in a dry form or mixed with water, and the polar aprotic reaction medium is selected from the group consisting of aliphatic nitriles, aliphatic ketones, alicyclic ketones, dialkyl carbonates, cyclic carbonates, lactones, aliphatic nitroalkanes, dimethyl sulfoxides, esters and ethers, or at least two combinations thereof.

14. The method according to claim 13, wherein a polar aprotic reaction medium selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, acetone, dimethyl carbonate, methyl ethyl ketone, 3-pentanone, cyclohexanone, nitromethane, nitropropane, tert-butyl methyl ether, dimethyl sulfoxide, γ-butyrolactone, and ε-caprolactone, or at least two combinations thereof, is mixed with water and present as the reaction medium.

15. The method according to claim 13, wherein a reaction medium selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, dimethyl carbonate, and acetone, or at least two combinations thereof, is present in mixture with water.

16. The method according to claim 13, wherein the reaction medium is acetonitrile, isobutyronitrile, or adiponitrile in a dry form.

17. The method according to claim 1, wherein the reaction medium includes a solubilizing component that enables one or more other substances to dissolve.

18. The method according to claim 17, wherein a primary alcohol, a secondary alcohol, a monoketone, or a dialkyl carbonate, or a mixture of at least two of these components, is mixed with water and present as a solubilizing component.

19. aliphatic C １－６ The method according to claim 17, wherein one or more alcohols selected from the group consisting of alcohols are mixed with water and present as one or more solubilizing components.

20. Dimethyl carbonate contains at least one C １－６ At least one C selected from the group consisting of alcohols １－６ The method according to claim 1, wherein the alcohol is mixed with the reaction medium.

21. The method according to claim 20, wherein the reaction medium includes water.

22. The method according to claim 17, wherein one or more solubilizing components are added in an amount less than 50% by volume relative to the total amount of the reaction medium present.

23. The method according to claim 1, wherein the organic nitrate is used in an amount of 0.1 to 2.0 equivalents relative to the amount of the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon used.

24. The method according to claim 1, wherein an oxygen-containing gas atmosphere is prepared that is spatially in communication with the reaction medium.

25. The method according to claim 24, wherein gas exchange between the oxygen-containing gas atmosphere and the reaction medium is performed by introducing the oxygen-containing gas atmosphere into the reaction medium or by stirring the reaction medium in the presence of the oxygen-containing gas atmosphere.

26. The method according to claim 24, wherein the oxygen-containing gas atmosphere is air.

27. ​​The method according to claim 26, wherein gas exchange is performed between the oxygen-containing gas atmosphere and the reaction medium by introducing the oxygen-containing gas atmosphere into the reaction medium or by stirring the reaction medium in the presence of the oxygen-containing gas atmosphere.

28. The method according to claim 27, wherein gas exchange is performed by introducing the gas atmosphere into the reaction medium.

29. The method according to claim 27, wherein gas exchange is performed by stirring the liquid phase in the presence of the aforementioned gas atmosphere.

30. The method according to claim 29, wherein stirring is used to control the electrochemical oxidation.

31. The method according to claim 1, wherein the amount of oxygen dissolved in the reaction medium is at least 1 millimoles per liter of the reaction medium.

32. The method according to claim 1, wherein the electrolytic cell is a non-divided electrolytic cell in which the anode and cathode are arranged in the same compartment without being separated.

33. The method according to claim 1, wherein the non-divided electrolytic cell comprises a glassy carbon anode, a graphite anode, or a BDD anode.

34. The method according to claim 1, wherein the non-divided electrolytic cell comprises a glassy carbon cathode, a graphite cathode, or a BDD cathode.

35. The method according to claim 1, wherein the distance between electrodes in the electrolytic cell is 0.1 mm to 2.0 cm.

36. The method according to claim 1, wherein the amount of charge used for the electrochemical oxidation is at least 190 C (2 F (F: Faraday constant)) to 970 C (10 F (F: Faraday constant)) per millimole of the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon.

37. The current density is at least 5 mA / cm². ２ The method according to any one of claims 1 to 36, wherein the surface area represents the geometric area of ​​the electrode.

38. Current density of at least 20 mA / cm² ２ ~50 mA / cm ２ The method according to claim 1, wherein the surface area represents the geometric area of ​​the electrode.

39. The method according to claim 1, performed within a non-divided cell.

40. The method according to claim 1, wherein the current used for the electrochemical oxidation is obtained from renewable resources.

41. The method according to claim 1, wherein the electrochemical oxidation is performed at a temperature in the range of 0°C to 60°C.

42. The method according to claim 1, performed under atmospheric pressure.

43. The method according to claim 1, carried out under reduced pressure, which is lower than atmospheric pressure.

44. The method according to claim 1, which is carried out under high pressure, which is higher than atmospheric pressure.

45. The method according to claim 1, performed in a batch manner.

46. The method according to claim 1, which is carried out in a continuous manner.

47. The method according to claim 1, which is carried out without adding a catalyst.

48. The method according to claim 1, wherein no further oxidizing agent other than oxygen or oxygen in the air is added.

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