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 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. [Background technology]

[0002] Cycloalkanone and cycloalkanol compounds are important intermediates in many industrial manufacturing processes. The oxidation of saturated non-functionalized alicyclic hydrocarbons (and therefore non-activated C-H bonds) to the corresponding ketones or alcohols requires special reaction conditions to selectively convert these non-reactive materials to monofunctional successor products while maintaining the ring structure.

[0003] There are many processes based on transition metal catalysis and the use of oxygen or chemical oxidants such as peroxides. The use of expensive transition metals and chemical oxidants not only increases costs but also generates reagent waste that sometimes requires cumbersome disposal.

[0004] An example is the production of polyamide 12 from laurolactam. This is currently mainly carried out via cyclododecanone as an intermediate. This is first converted to the peroxide by air. To ensure a highly selective further reaction, boron oxide is used, which reacts with the peroxide to produce a boric acid ester and oxygen. The resulting alcohol is then oxidized to cyclododecanone over a CuCr catalyst. The disadvantage of this reaction route is mainly the use of boron oxide. Boron oxide is currently being discussed as a substance of particular interest due to its suspected effect on fertility and harm to the unborn child.

[0005] In a paper by Yamanaka (J. Chem. Commun. 2000, pp. 2209-2210), the anodic oxidation of alkanes in aqueous media was reported to be achieved at 0.1 mA / cm 2At low current densities below CO 2 In non-aqueous media, oxidation of adamantane is reported to occur at voltages above 2 V and 4 mA / cm 2 The formation rate and current yield of alicyclic ketone (cyclohexanone) were significantly higher than those of Ir(acac) at a current density of less than 1000 s, indicating that oxygen activation occurred at the cathode. 2 It has been shown that the conversion rate is significantly increased by the use of carbon fiber anodes. The oxygen is then generated from the water. Organic solvents have an effect; for example, the conversion of cyclohexane does not occur in acetonitrile.

[0006] Kawamata's paper (J. Am. Chem. Soc. 2017(139), pp. 7448-7551) shows that mediators such as quinuclidine (a tertiary amine, toxic) can be used in combination with HFIP (hexafluoroisopropanol, causing organ damage and teratogenicity) to electrochemically oxidize the inactive C-H bonds of functionalized aliphatic and alicyclic species at low potentials. The conductive salt used was Me 4 N-BF 4 It was confirmed that the oxygen introduced was generated from the gas phase. No reaction occurred 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) Summary of the Invention [Problem to be solved by the invention]

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

[0009] This object has been achieved by the subject matter of the claims and the specification.

[0010] The present invention relates to a process for the preparation of unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation of unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons, comprising the steps of: (a) providing at least one unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon; (b) providing at least one organic nitrate; (c) electrochemically oxidizing the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon provided in step (a) in the presence of the organic nitrate provided in step (b) in an electrolytic cell in a reaction medium in the presence of oxygen. The present invention relates to a method comprising the steps of:

[0011] The process of the present invention has the special features of high selectivity, low usage of auxiliary chemicals, and the use of electric current as an oxidant with the attendant low generation of waste products.

[0012] Surprisingly, it has been found that the electrochemical oxidation method of the present invention can be used to introduce oxygen functional groups into alicyclic hydrocarbons using oxygen from the air. This allows the use of chemical oxidants such as reactive peroxides or expensive catalysts with complex ligand systems to be dispensed with. At the same time, the use of potentially toxic and / or carcinogenic reagents can be reduced or even completely avoided. The developed method is a cheap and environmentally friendly alternative to existing synthetic methods. Simple and safe process conditions allow the production of large quantities of the target compounds without significant costs. Thus, the present invention allows a significant optimization of previously costly and time-consuming processes.

[0013] It has also been surprisingly found that the method of the present invention allows the use of electric current in the production of cycloalkanone compounds from unsubstituted cycloalkanes using nitrates, which act as both conductive salts and electrochemical mediators. The production of by-products during the implementation of the method of the present invention, particularly alicyclic alcohols of the same ring size, is not problematic since they can be converted to the corresponding ketones by further, already established methods.

[0014] It has also surprisingly been found that the process of the invention can be carried out at ambient pressure and temperature, which is likewise advantageous for energy efficiency and therefore environmental compatibility.

[0015] In the process 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 process of the present invention, it is particularly preferred to use monocyclic alicyclic hydrocarbons.

[0016] Preferably, the monocyclic or polycyclic, especially monocyclic or bicyclic, saturated alicyclic hydrocarbons used in the process of the present invention may have 5 to 18 carbon atoms in the ring system. Each of these alicyclic hydrocarbons may be unsubstituted or mono- or polysubstituted. If mono- or polysubstituted, they are preferably substituted with 1, 2, 3, 4 or 5 substituents, each independently selected from the group consisting of methyl, phenyl, or benzyl. The phenyl or benzyl substituents themselves may be unsubstituted or may be substituted with F, Cl, Br, and NO, respectively. 2

[0033] When the alicyclic hydrocarbons or their substituents used according to the present invention contain alkyl groups having more than one carbon atom in the side chain, undesirable side reactions can occur at these substituents when carrying out the process of the present invention.

[0017] In the process of the invention, it is particularly preferred to use, as unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons, monocyclic saturated hydrocarbons having 6 to 12 carbon atoms in the ring, preferably 8 to 12 carbon atoms in the ring, which are unsubstituted or mono- or polysubstituted with 1, 2, 3, 4 or 5 substituents each independently selected from the group consisting of methyl, phenyl or benzyl. It is very particularly preferred to use, in the process of the invention, monocyclic saturated hydrocarbons having 8 to 12 carbon atoms in the ring, which are unsubstituted or mono-, di- or tri-substituted with methyl groups.

[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, even more preferably selected from the group consisting of cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane, most preferably the hydrocarbon is cyclododecane.

[0019] According to step (b) of the method according to the invention, at least one organic nitrate is provided, which acts both as a conductive salt and as a mediator in the electrochemical oxidation method according to the invention. + ][NO 3 - It is preferable to use an organic nitrate of the formula:

[0020] [Cation + ]teeth, General structure [R 1 R 2 R 3 R 4 N + ](wherein, R 1 , R 2 , R 3 , R 4 is C 1 ~C 16 Alkyl, especially linear or branched C 1 ~C 8each independently selected from the group consisting of alkyl, General structure (I):

[0021] [ka]

[0022] (In the formula, R 1 and R 2 is a linear or branched chain C 1 ~C 18 Alkyl, especially linear or branched C 1 ~C 8 alkyl; 3 is H and linear or branched chain C 1 ~C 18 Alkyl, especially H and straight or branched chain C 1 ~C 8 alkyl. imidazolium cation, General structure (II):

[0023] [ka]

[0024] (In the formula, R 1 is C 1 ~C 18 Alkyl, especially linear or branched C 1 ~C 8 alkyl; R 2 , R 3 and R 4 is H and linear or branched chain C 1 ~C 18 Alkyl, especially H and straight or branched chain C 1 ~C 8 alkyl. the pyridinium cation, and General structure [R 1a R 2a R 3a R4a P + ](wherein, R 1a , R 2a , R 3a , R 4a is C 1 ~C 16 Alkyl, especially linear or branched C 1 ~C 8 each independently selected from the group consisting of alkyl, is selected from the group consisting of:

[0025] When using organic nitrates based on imidazolium cations in the process of the invention, cations of general formula (I) are preferred, in which R 1 and R 2 is a linear or branched chain C 1 ~C 18 Alkyl, especially linear or branched C 1 ~C 8 alkyl; 3 is hydrogen. Particularly preferred are imidazolium cations of the general formula (I), in which R 1 is methyl, R 2 is ethyl, or R 1 is methyl, R 2 is methyl, or R 1 is methyl, R 2 is butyl, and R 3 is hydrogen in both cases.

[0026] When using nitrates based on pyridinium cations in the process of the invention, cations of general formula (II) are preferred, in which R 1 is a linear or branched chain C 1 ~C 18 Alkyl, especially linear or branched C 1 ~C 8 Particularly preferred are pyridinium cations of the general formula (I), in which R 1 is a linear or branched chain C 1 ~C 18 Alkyl, especially linear or branched C1 ~C 8 is an alkyl radical R 2 , R 3 and R 4 is a linear or branched chain C 1 ~C 8 alkyl, preferably monosubstituted at the 2, 3 or 4 positions, disubstituted at the 2,4, 2,5 or 2,6 positions, or trisubstituted at the 2,4,6 positions.

[0027] In principle, more than one of the abovementioned nitrates can also be used in the process according to the invention. 1 R 2 R 3 R 4 N + ][NO 3 - ], or organic ammonium nitrate of composition [R 1a R 2a R 3a R 4a P + ][NO 3 - It is preferable to use organic phosphonium salts of the composition [R 1 R 2 R 3 R 4 N + ][NO 3 - Preferred are organic ammonium nitrates of the formula:

[0028] Very particularly preferably, the organic ammonium nitrate is tetra-n-butylammonium nitrate or methyltri-n-octylammonium nitrate. Particularly preferably, the organic phosphonium nitrate is 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 process of the present invention is tetra-n-butylammonium nitrate or methyltri-n-octylammonium nitrate.

[0030] The order of providing the components used in the methods of the present invention may be varied, as may the order in which the individual components are contacted with one another or with their respective reaction media.

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

[0032] The reaction medium used in the process according to the invention is liquid under the conditions in which the process is carried out and is capable of partially or completely dissolving the components used, i.e. in particular the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons and the inorganic or organic nitrates. If at least one of these components is used in liquid form, the reaction medium is preferably readily miscible with said components.

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

[0034] In the process according to the invention, when inorganic nitrates, especially potassium nitrate or sodium nitrate, are used, the reaction medium advantageously comprises water, preferably aprotic reaction medium mixed with water.The water content in the reaction medium can vary.The water content is preferably at most 20% by volume, more preferably at most 15% by volume, particularly preferably at most 10% by volume, even more preferably at most 5% by volume, based on the total amount of the reaction medium in each case.

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

[0036] Particularly preferably, the reaction medium is 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 a combination of at least two of these components.

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

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

[0039] Likewise, the reaction medium is very particularly preferably acetonitrile, isobutyronitrile or adiponitrile, optionally mixed with water.

[0040] If one or more of the abovementioned components are used in a mixture with water in the reaction medium, the water content is preferably at most 20% by volume, more preferably at most 15% by volume, particularly preferably at most 10% by volume and even more preferably at most 5% by volume, in each case based on the total amount of the reaction medium.

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

[0042] Examples of solubilizing components are primary alcohols, secondary alcohols, monoketones or dialkyl carbonates, or mixtures of at least two of these components, optionally mixed with water. In the process according to the invention, aliphatic C 1-6 It is preferable to use an 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, optionally mixed with water.

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

[0044] When one or more of these solubilizing components are used in admixture with water, the water content is in each case preferably at most 20% by volume, more preferably at most 15% by volume, particularly preferably at most 10% by volume, and even more preferably at most 5% by volume, based on the total amount of solubilizing components and water.

[0045] The solubilizing components may be added preferably in an amount of 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 in each case.

[0046] In the process of the present invention, the organic nitrate is preferably 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 the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon in each case.

[0047] According to the 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 electrolysis cell in a reaction medium in the presence of oxygen.

[0048] It is advantageous if an oxygen-containing gas atmosphere is provided in spatial communication with the reaction medium.

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

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

[0051] Very particularly preferably, the gas atmosphere is air.

[0052] It is advantageous if gas exchange is carried out between the gas atmosphere and the reaction medium, preferably by introducing a gas atmosphere into the reaction medium or by stirring the liquid phase in the presence of a gas atmosphere.

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

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

[0055] Also preferably, the amount of oxygen dissolved in the reaction medium is at least 10 mmol per litre of reaction medium.

[0056] The process of the present invention for the preparation of unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation of unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons in the presence of inorganic or organic nitrates in a reaction medium in the presence of oxygen can be carried out both in a divided electrolytic cell and in a non-divided electrolytic cell, but is preferably carried out in a non-divided electrolytic cell.

[0057] To avoid undesirable chemical reactions, it may be advantageous to separate the cathode and anode compartments, with charge exchange between the anode and cathode compartments occurring only through a porous diaphragm, which is typically an ion exchange resin.

[0058] The non-split electrolytic cell preferably used according to the present invention comprises at least two electrodes.For this purpose, anodes and cathodes made of conventional materials can be used, for example anodes and cathodes made of glassy carbon, boron-doped diamond (BDD) or graphite.The use of glassy carbon electrodes is preferred.

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

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

[0061] Furthermore, the process of the present invention may be carried out batchwise or continuously, preferably in a non-divided flow-through electrolytic cell.

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

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

[0064] An important advantage of the method according to the invention is that electric current is used as oxidizing agent, which is a particularly environmentally friendly agent when obtained from renewable resources, i.e. in particular from 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 process according to the invention can be carried out at elevated pressure or at reduced pressure. If the process according to the invention is carried out at elevated pressure, pressures up to 16 bar are preferred, pressures up to 6 bar are particularly preferred.

[0067] Likewise, the process according to the invention can preferably be carried out at atmospheric pressure.

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

[0069] The following examples further illustrate the invention but are not intended to limit the scope of the invention. EXAMPLES

[0070] General Information and Methods Chemicals of analytical quality were used as obtained from usual sources (TCI, Aldrich, Acros, etc.) Oxygen was obtained in 2.5 quality from Nippon Gases Deutschland GmbH, Düsseldorf, Germany and used as received.

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

[0072] High performance liquid chromatography was performed on a Shimazu HPLC-MS equipped with a SIL 20A HT autosampler, a 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, Berlin). Eluent: acetonitrile / water / formic acid (1% by volume) (10% ACN to 90% ACN in 10 min + 100% ACN in 10 min). Mass spectrometry measurements were performed on a Shimazu LCMS-2020, 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 undivided Teflon cells used for electrolysis have been described in the literature (a) C. Gutz, B. Klockner, S. R. Waldvogel, Org. Process Res. Dev. 2016, 20, 26-32; b) A. Kirste, G. Schnakenburg, F. Stecker, A. Fischer, S. R. Waldvogel, Angew. Chem. Int. Ed. 2010, 49, 971-975; Angew. Chem. 2010, 122, 983-987. (See SI).) The full range of these cells with stainless steel blocks is also commercially available as IKA Screening Systems (IKA-Werke GmbH & Co. KG, Staufen, Germany). The dimensions of the electrodes were 3 cm × 1 cm × 0.3 cm.

[0075] The gases were introduced in a controlled manner by two model 5850S ​​mass flow controllers (MFCs) from Brooks Instrument BV, Veenendaal, The Netherlands. This was done using one controller for the introduction of oxygen and one for the introduction of nitrogen. The controllers were controlled by Smart DDE and Matlab R2017b software. The volumetric flow rates were additionally monitored by DK800 float principle flowmeters from Krohne Messtechnik GmbH, Duisburg. In all experiments carried out, the overall volumetric flow rate was constant at 20 mL / min. This is also the maximum achievable volumetric flow rate, limited by the MFCs used. The volumetric flow rate ratio of the two gases was adjusted using the MFCs and the associated software. Gas cylinders from the following suppliers 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 electrolysis cell.

[0076] General Procedure GP1 A non-divided electrolytic cell (100 mL capacity three-neck round bottom flask, NS29 Teflon stopper with electrode holder, magnetic stir bar) was charged with cycloalkane (5.0 mmol) and tetrabutylammonium nitrate (0.5 equiv.) dissolved in acetonitrile (25 mL). The cell was fitted with glassy carbon electrodes (3 cm × 1 cm × 0.3 cm) spaced 0.5 cm apart. The immersed surface area of ​​the electrodes was 1.3 cm. 2 Oxygen was introduced into the gas space of the reaction vessel, if necessary, via an NS14.5 gas inlet adapter. Galvanostatic electrolysis was performed at 20°C to 30°C, with a current density of 10 mA / cm. 2 It was carried out in.

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

[0078] Experimental Example 1: Preparation of cyclohexanone: According to GP1, cyclohexane (0.421 g, 5.0 mmol, 1.0 equiv.) was dissolved in acetonitrile (25 mL) and subjected to constant current electrolysis at 25° C. under oxygen atmosphere by applying 5F. After working up according to GP1, the product was obtained as a colorless liquid (yield: 6%, 30 mg, 0.31 mmol). 1 H NMR (400 MHz, CDCl 3 ) δ [ppm] = 2.36-2.32 (m, 4H), 1.90-1.84 (m, 4H), 1.75-1.70 (m, 2H). Analytical data were in agreement with literature values. For yield determination, the solvent signals present were subtracted from the calculation by integral ratio.

[0079] Experimental Example 2: Preparation of cycloheptanone: According to GP1, cycloheptane (0.491 g, 5.0 mmol, 1.0 equiv.) was dissolved in acetonitrile (25 mL) and electrolyzed at constant current with 4F at 21 °C under ambient air atmosphere. Electrode immersion surface area: 1.5 cm 2 The solvent was then 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 H NMR (400 MHz, CDCl 3 ) δ [ppm] = 2.49-2.47 (m, 4H), 1.69-1.64 (m, 8H). Analytical data were in agreement with literature values.

[0080] Experimental Example 3: Preparation of cyclooctanone: According to GP1, cyclooctane (0.561 g, 5.0 mmol, 1.0 equiv.) was dissolved in acetonitrile (25 mL) and 4F was applied to electrolyze at constant current under oxygen atmosphere at 30°C. After working up 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 H NMR (400 MHz, CDCl 3 ) 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). Analytical data were in agreement with literature values.

[0081] Experimental Example 4: Preparation of cyclodecanone: According to GP1, cyclodecane (0.701 g, 5.0 mmol, 1.0 equiv.) was dissolved in acetonitrile (25 mL), and 5F was applied to perform constant current electrolysis at 30 °C under oxygen atmosphere. The solvent was then removed by distillation under reduced pressure, and the residue was purified by column chromatography (CH / EA = 10:0 to 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 H NMR (300 MHz, CDCl 3 ) 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). Analytical data were in agreement with literature values. For yield determination, the solvent signals present were subtracted from the calculation by integral ratio.

[0082] Experimental Example 5: Preparation of cyclododecanone: According to GP1, cyclododecane (0.842 g, 5.0 mmol, 1.0 equiv.) was dissolved in isobutyronitrile (25 mL), 4F was applied, and constant current electrolysis was performed at 27 °C under oxygen atmosphere. The solvent was then 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 H NMR (400 MHz, CDCl 3 ) δ[ppm] = 2.47-2.44 (m, 4H), 1.72-1.69 (m, 4H), 1.31-1.26 (m, 14H). Analytical data were in agreement with literature values.

[0083] Experimental Example 6: In the following experiments, the effect of varying different parameters of the electrochemical oxidation was investigated. These studies were in each case 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, the cell was charged with conductive salt (0.2-1.0 equiv.) and substrate (cyclooctane, 0.5-2.5 mmol), which were dissolved in solvent (5 mL). The cell was equipped with a glassy carbon anode and a glassy carbon cathode, spaced 0.5 cm apart (electrode dimensions: 7 cm × 1 cm × 0.3 cm, immersed surface area 1.8 cm). 2 The cell was fixed to a heatable / coolable stainless steel block and, via an adapter, was charged with the gas mixture under investigation (100% by volume O 2 to 0% by volume O 2 The current density (5 to 60 mA / cm 2Electrolysis was carried out at constant current while varying the flow rate (5-50 °C), temperature (5-50 °C), stirring speed (100-600 rpm), and charge (4-8 F). After application of the charge, two drops of the reaction solution were taken and analyzed by gas chromatography. Then, 1,3,5-trimethoxybenzene (1 equiv.) was added to the solution as an NMR standard, and the solvent was removed by distillation (45 °C, 200 mbar). The yield of the cycloalkanone product was calculated by 1 It was determined by H-NMR analysis. For GC analysis, two drops of the reaction solution were passed through approximately 330 mg of silica gel 60 M and eluted with ethyl acetate. 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 carried out in an undivided 5 mL volume PTFE cell. For this, the cell was charged with conductive salt (0.2-1.0 equiv.) and substrate (cyclooctane, 0.5-2.5 mmol), which were dissolved in solvent (5 mL). The cell was equipped with a glassy carbon anode and a glassy carbon cathode, spaced 0.5 cm apart (electrode dimensions: 7 cm × 1 cm × 0.3 cm, immersed surface area 1.8 cm). 2 The cell was fixed to a stainless steel block that could be heated / cooled and was then filled via an adapter with the gas mixture under investigation (100% by volume O 2 to 0% volume O 2 The current density (5 to 60 mA / cm 2 Electrolysis was carried out at constant current while varying the charge (4-8F), temperature (5-50°C), stirring speed (100-600 rpm), and charge (4-8F). After application of 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 for analysis by gas chromatography and quantification of the products. These were eluted with ethyl acetate through approximately 330 mg of silica gel 60M. 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 described above.

[0086] [ka]

[0087] Further exemplary studies are presented below, grouped according to the parameters that were changed in each case. Charge amount (F relative to cyclooctane 1) ·Current density (mA / cm 2 ) O 2 / N 2 ratio Equivalent (cyclooctane / nitrate) Stirring speed (rpm) ·Temperature (℃) Nitrate as a mediator / conductive salt Reaction medium ·Electrode material Change in nitrate cation

[0088] Unless otherwise stated, experiments were performed at least twice and average values ​​including standard deviation were determined. The reference numbers of compounds 1, 2, 3, and 4 correspond to those in Scheme 1.

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

[0090] [Table 1]

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

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

[0093] [Table 2]

[0094] 60mA / cm 2 It can be seen that the yield of 2 is clearly reduced when the reaction is applied. Instead, cyclooctanol 3 is produced to a comparable extent. A series of tests were performed at 20mA / cm 2 Continued at various atmospheric O 2 The content was investigated.

[0095] Experimental example 6c-20mA / cm 2 O 2 / N 2 ratio First, 20mA / cm 2 Rough O in 2 / N 2 Ratios (100:0, 20:80, 0:100) were investigated. The 20:80 ratio was chosen because it is close to the composition of air. Table 3: 20mA / cm 2 Various O 2 / N 2 Ratio Investigation

[0096] [Table 3]

[0097] Under a pure nitrogen atmosphere (ratio 0:100), no product formation was observed. Therefore, a quantitative explanation for the unreacted substrate fraction or by-products could not be given. However, traces of cyclooctanol 3 were detected in the gas chromatogram. 2 Content at initial standard current density of 10mA / cm 2These were repeated at the stated current densities with smaller step changes (gradations) in content so as to correlate with the

[0098] Experimental example 6d-10mA / cm 2 O 2 / N 2 ratio In addition to the content gradients shown in the table, experiments were also performed under ambient conditions without gas supply (denoted as "air"). Table 4: 10mA / cm 2 Various O 2 / N 2 Ratio Investigation

[0099] [Table 4]

[0100] In the above investigation, the conversion of reactant 1 and the formation of product 2 were observed at an oxygen fraction of 20 vol.% and a current density of 10 mA / cm. 2 In addition, the highest was observed when 2 At lower ratios, the production of cyclooctanol 3 increased slightly.

[0101] Due to the high yield of cyclooctanone 2 and the high proportion of nitrogen, which improved safety, these conditions were selected as comparative conditions for the subsequent reaction (Scheme 2), and other parameters were changed based on these conditions.

[0102] Experimental Example 6e - Molar and equivalent amounts of mediator To investigate different substrate and mediator concentrations in the solvent (acetonitrile, 5 mL), the molar amount of substrate and the number of equivalents of conductive salt / mediator were varied. Table 5: Examination of various molar and equivalent amounts of nitrates.

[0103] [Table 5]

[0104] In general, the conversion of reactant 1 to product 2 was slightly better at lower molar amounts of substrate (<1 mmol, equivalent to 0.2 mol / L) than at higher molar amounts. Varying the mediator concentration above or below 0.5 equivalents relative to substrate only resulted in small differences in the yield of 2, suggesting that the oxygen source for oxo-functionalization is dissolved molecular oxygen.

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

[0106] [Table 6]

[0107] The results in Table 6 show a maximum value around 350 rpm, however the effect of speed depends on the stirrer and cell geometry and should not be taken as a fixed value.

[0108] Experimental Example 6g - Temperature The temperatures stated refer to the temperature of the heating block / cryostat. Prior to the start of electrolysis, the electrolyte was stirred at 5° C. and 50° C. for approximately 30 minutes. Table 7: Various temperature studies

[0109] [Table 7]

[0110] Concerning the formation of the product, a slight decrease in yield can be seen at temperatures above and below 30 °C. Thus, the reaction appears to be only slightly temperature dependent. Furthermore, higher temperatures result in a smaller fraction of unreacted substrate, possibly due to its volatility and the open system of the electrolysis cell.

[0111] Example 6h - Conductive salts / mediators To determine whether nitrate as the anion of the conductive salt also has a mediator effect on the reaction, standard tetrabutylammonium nitrate was compared with other common conductive salts. The cation composition was not changed. The conductive salts different from the standard were each tested in the electrolysis only once, so average values ​​are not recorded. Table 8: Survey of various conductive salts

[0112] [Table 8]

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

[0114] [Table 9]

[0115] The reaction proceeded relatively well in the solvents listed. Acetone resulted in a higher percentage of unreacted substrate.

[0116] The reaction was also carried out in 3-pentanone, but the solvent and product signals overlapped, 1 It was not possible to measure the yield by H NMR, but analysis by gas chromatography confirmed that product 2 was again selectively produced.

[0117] Initially, O 2 was assumed to be more soluble in isobutyronitrile than in acetonitrile, so 100% O 2A comparison of atmosphere was also made in a similar manner (Table 10). Table 10: 100% by volume O 2 Investigation of various solvents in

[0118] [Table 10]

[0119] The results using acetonitrile and isobutyronitrile are comparable. Specifically, no clear increase in the yield of 2 was achieved by using isobutyronitrile. On the other hand, the proportion of unreacted 1 was significantly higher, which may be an advantage. The reaction with nitropropane was then run in 100% O 2 The reaction was carried out under atmospheric pressure, and it was confirmed that nitrated alkanes could also be used as solvents.

[0120] Experimental Example 6j - Electrode material Electrolysis was performed with a variety of carbon-based electrode materials. Average values ​​are not reported because the different electrode materials from the GC standards were each tested in the electrolysis only once. Table 11: Survey of different electrode materials

[0121] [Table 11]

[0122] The reaction took place in all electrode materials used to produce product 2. For the graphite electrode, slight exfoliation of the electrode material in the form of black particles was observed after electrolysis, which is attributed to its low stability.

[0123] Example 6k-Changing the cation of the conductive salt / mediator A variety of cations other than the standard tetrabutylammonium were investigated. The following were used: Hexadecyltrimethylammonium nitrate ([C 19 H 42 N][NO 3 ]) 1-Butyl-3-methylimidazolium nitrate ([C 8 H 15 N 2 ][NO 3 ]) Methyltrioctylammonium nitrate ([C 25 H 54 N][NO 3 ]) Tetrabutylphosphonium nitrate (PBu 4 NO 3 ) The anionic nitrate content was not changed. The different conductive salts from the standard were each tested in the electrolysis only once, so no average values ​​were recorded. Table 12: Survey of various cations

[0124] [Table 12]

[0125] The oxidation of cycloalkanes to ketones is found to work primarily with nitrates as the anion component (see Example 6h). Long chain alkyl groups on the ammonium cation give slightly higher yields compared to the tetrabutylammonium cation under the same conditions. The reaction also works with N-alkylated nitrogen heteroaromatic compounds and with tetraalkylphosphonium cations as the cations.

[0126] Experiment 6l: Acetonitrile / NBu at 25°C and standard pressure 4 NO 3 Oxygen solubility in: Table 13: MeCN / NBu as a function of atmospheric oxygen content 4 NO 3 Dissolved oxygen concentration

[0127] [Table 13]

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

[0129] Alternative quantification: After applying the charge, about 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 for analysis by gas chromatography and quantification of the products. These were eluted with ethyl acetate through about 330 mg of silica gel 60M. About 1.5 mL of the filtrate was collected in a GC vial and investigated for oxidation products by GC-FID and GC-MS. Quantification was achieved by pre-calibration of the gas chromatograph.

[0130] Experiment 7: Next, the effect of the distance between the electrodes was investigated. Table 14: Investigation of different distances between electrodes

[0131] [Table 14]

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

Claims

1. 1. A process for producing unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation of unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons, comprising the steps of: (a) providing at least one unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon; (b) providing at least one organic nitrate; (c) electrochemically oxidizing the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon provided in step (a) in the presence of the organic nitrate provided in step (b) in an electrolytic cell in a reaction medium in the presence of oxygen. Including, The substituents of the saturated alicyclic hydrocarbon are each independently selected from the group consisting of methyl, phenyl, or benzyl, each of which is unsubstituted or selected from F, Cl, Br, and NO. ２ wherein the alkyl group is optionally mono- or polysubstituted with one, two or three substituents each independently selected from the group consisting of:

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

3. 2. The method of claim 1, wherein the monocyclic or bicyclic saturated alicyclic hydrocarbon has 5 to 18 carbon atoms in the ring system and is unsubstituted or mono- or polysubstituted with 1, 2, 3, 4 or 5 substituents.

4. The unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon is a monocyclic saturated hydrocarbon having 6 to 12, preferably 8 to 12, carbon atoms in the ring, the alicyclic hydrocarbon being unsubstituted or mono- or polysubstituted with 1, 2, 3, 4 or 5 substituents each independently selected from the group consisting of methyl, phenyl or benzyl; The process according to any one of claims 1 to 3, wherein the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon is more preferably a monocyclic saturated hydrocarbon having from 8 to 12 carbon atoms in the ring, the alicyclic hydrocarbon being unsubstituted or mono-, di- or tri-substituted with methyl.

5. The process according to any one of claims 1 to 4, wherein the saturated alicyclic hydrocarbon is unsubstituted and is selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane, preferably selected from the group consisting of cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane, more preferably cyclododecane.

6. The organic nitrate present has the general formula: ＋ ][NO ３ － ], wherein [the cation ＋ ]teeth, General structure [R １ R ２ R ３ R ４ N ＋ ] (wherein, R １ , R ２ , R ３ , R ４ is C １ ~C １６ Alkyl, especially linear or branched C １ ~C ８ each independently selected from the group consisting of alkyl, General structure (I): 【Chemistry 1】 (In the formula, R １ and R ２ is a linear or branched chain C １ ~C １８ Alkyl, especially linear or branched C １ ~C ８ alkyl; R ３ is H and linear or branched chain C １ ~C １８ Alkyl, especially H and linear or branched C １ ~C ８ is selected from the group consisting of alkyl. imidazolium cation, General structure (II): 【Chemistry 2】 (In the formula, R １ is C １ ~C １８ Alkyl, especially linear or branched C １ ~C ８ alkyl; R ２ , R ３ and R ４ is H and linear or branched chain C １ ~C １８ Alkyl, especially H and linear or branched C １ ~C ８ alkyl. the pyridinium cation, and General structure [R １ａ R ２ａ R ３ａ R ４ａ P ＋ ] (wherein, R １ａ , R ２ａ , R ３ａ , R ４ａ is C １ ~C １６ Alkyl, especially linear or branched C １ ~C ８ each independently selected from the group consisting of alkyl, The method according to any one of claims 1 to 5, wherein the compound is selected from the group consisting of:

7. In the imidazolium cation of general formula (I), the radical R １ and R ２ is a linear or branched chain C １ ~C １８ Alkyl, especially linear or branched C １ ~C ８ alkyl; R ３ is hydrogen, preferably R １ is methyl, R ２ is ethyl, or R １ is methyl, R ２ is methyl, or R １ is methyl, R ２ is butyl, R ３ The method of claim 6, wherein each occurrence of is hydrogen.

8. In the pyridinium cation of the general formula (II), the radical R １ is a linear or branched chain C １ ~C １８ Alkyl, especially linear or branched C １ ~C ８ is an alkyl radical R ２ , R ３ and R ４ is a linear or branched chain C １ ~C ８ 7. The method of claim 6, wherein each of the alkyl groups is independently selected from the group consisting of alkyl, preferably monosubstituted at the 2, 3 or 4 positions, disubstituted at the 2,4, 2,5 or 2,6 positions, or trisubstituted at the 2,4,6 positions.

9. 7. The method of 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. 10. The process according to any one of claims 1 to 9, wherein the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon or the inorganic or organic nitrate is charged first and combined with the reaction medium, preferably at least partially or completely dissolved in the reaction medium or mixed in the reaction medium, and then the other component is added to these two components, respectively.

11. 11. The process according to any one of claims 1 to 10, wherein the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon and the inorganic or organic nitrate are charged first and then combined with the reaction medium, preferably at least partially or completely dissolved in or mixed with the reaction medium.

12. A process according to any one of claims 1 to 11, wherein the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon and the inorganic or organic nitrate are added simultaneously or sequentially to the reaction medium, preferably at least partially or completely dissolved in or mixed with the reaction medium.

13. 13. The process according to any one of claims 1 to 12, wherein the reaction medium is a polar aprotic reaction medium which is present in anhydrous or dried form or optionally mixed with water, which is selected from the group consisting of aliphatic nitriles, aliphatic ketones, cycloaliphatic ketones, dialkyl carbonates, cyclic carbonates, lactones, aliphatic nitroalkanes, dimethyl sulfoxide, esters and ethers or a combination of at least two of these components, and in which, if mixed with water, the water content is preferably at most 20% by volume, more preferably at most 15% by volume, particularly preferably at most 10% by volume and even more preferably at most 5% by volume, in each case relative to the total amount of the reaction medium.

14. 14. The process according to claim 13, in which 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 a combination of at least two of these components, in each case optionally mixed with water, is present as said reaction medium.

15. 15. The process of claim 13 or claim 14, wherein a reaction medium selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, dimethyl carbonate and acetone, or a combination of at least two of these components, optionally mixed with water, is present.

16. 16. The process according to any one of claims 13 to 15, wherein the reaction medium is acetonitrile, isobutyronitrile or adiponitrile in dry or anhydrous form.

17. The method of any one of claims 1 to 16, wherein the reaction medium comprises one or more solubilizing components.

18. 18. The method of 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, optionally mixed with water, is present as a solubilizing component.

19. aliphatic C １－６ 19. The process according to claim 17 or claim 18, wherein one or more alcohols, preferably selected from the group consisting of methanol, ethanol, isopropanol, 2-methyl-2-butanol or a mixture of at least two of these components, are present as one or more solubilizing components, optionally mixed with water.

20. Dimethyl carbonate optionally contains at least one C １－６ Alcohol, preferably at least one C selected from the group consisting of methanol, ethanol, isopropanol and 2-methyl-2-butanol １－６ 20. The process of any one of claims 1 to 19, wherein the alcohol is present as the reaction medium in admixture with the alcohol.

21. 21. The method of claim 20, wherein the reaction medium comprises water.

22. 20. The process according to any one of claims 17 to 19, wherein the solubilizing component or components are added in an amount of less than 50% by volume, more preferably less than 30% by volume, particularly preferably less than 10% by volume, relative to the total amount of reaction medium present in each case.

23. 23. The process according to claim 1, wherein the organic nitrate is used in each case 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, particularly preferably 0.4 to 0.8 equivalents, based on the amount of the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon used.

24. 24. The process according to any one of claims 1 to 23, wherein an oxygen-containing gas atmosphere is provided in spatial communication with the reaction medium, the proportion of oxygen in the gas atmosphere being preferably 10% by volume to 100% by volume, more preferably 15% by volume to 30% by volume, particularly preferably 15% by volume to 25% by volume, most preferably 18% by volume to 22% by volume.

25. 25. The process according to claim 24, wherein the gas exchange between the gas atmosphere and the reaction medium is preferably carried out by introducing the gas atmosphere into the reaction medium or by stirring the reaction medium in the presence of the gas atmosphere.

26. The method of any one of claims 1 to 25, wherein the gas atmosphere is air.

27. The method according to any one of the preceding claims, further comprising a gas exchange between the gas atmosphere and the reaction medium.

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

29. 29. A process according to claim 27 or claim 28, wherein the gas exchange is carried out by stirring the liquid phase in the presence of said gas atmosphere.

30. 30. The method of claim 29, wherein agitation is used to control the electrochemical oxidation.

31. 31. The process of any one of claims 1 to 30, wherein the amount of oxygen dissolved in the reaction medium is at least 1 mmol / L of reaction medium, preferably at least 5 mmol / L, more preferably at least 10 mmol / L of reaction medium.

32. The method of any one of claims 1 to 31, wherein the electrolytic cell is a non-divided electrolytic cell.

33. A method according to any one of the preceding claims, wherein the undivided electrolytic cell comprises a glassy carbon anode, a graphite anode or a BDD anode, preferably a glassy carbon anode.

34. A method according to any one of the preceding claims, wherein the undivided electrolytic cell comprises a glassy carbon cathode, a graphite cathode or a BDD cathode, preferably a glassy carbon cathode.

35. A process according to any one of the preceding claims, wherein the distance between the electrodes in the electrolysis cell is from 0.1 mm to 2.0 cm, preferably from 0.1 mm to 1.0 cm, more preferably from 0.1 mm to 0.5 cm.

36. 36. The process according to any one of claims 1 to 35, wherein the charge amount is in each case at least 190C (2F) to 970C (10F), preferably 320C to 820C, more preferably 350C to 800C, particularly preferably 380C to 775C, most preferably 380C to 450C per mmol of unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon.

37. The current density is at least 5 mA / cm ２ , preferably 10 mA / cm ２ , more preferably 15 mA / cm ２ , particularly preferably 20 mA / cm ２ and the surface area represents the geometric area of ​​the electrode.

38. A current density of at least 20 mA / cm ２ ~50mA / cm ２ and the surface area represents the geometric area of ​​the electrode.

39. The method of any one of claims 1 to 38, carried out in a non-divided cell.

40. 40. The method according to any one of claims 1 to 39, wherein the current used for the electrochemical oxidation is obtained from a renewable resource, in particular biomass, solar thermal energy, geothermal energy, hydroelectric power, wind power or photovoltaic power.

41. The method according to any one of claims 1 to 40, wherein the electrochemical oxidation is carried out at a temperature in the range of 0°C to 60°C, preferably 5°C to 50°C, more preferably 10°C to 40°C, particularly preferably 15°C to 30°C.

42. The process of any one of claims 1 to 41, carried out at atmospheric pressure.

43. The process of any one of claims 1 to 42, which is carried out under reduced pressure.

44. A process according to any one of the preceding claims, which is carried out under high pressure, preferably up to 16 bar, more preferably up to 6 bar.

45. The process of any one of claims 1 to 44, which is carried out batchwise.

46. The process according to any one of claims 1 to 45, which is carried out continuously, preferably in a non-divided flow-through electrolytic cell.

47. 47. The process according to any one of claims 1 to 46, which is carried out without added catalyst, in particular without added transition metal catalyst.

48. 48. The method of any one of claims 1 to 47, wherein no further oxidizing agent other than oxygen or the oxygen in air is added.

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