Electrochemical oxidation of cycloalkanes to form cycloalkanone compounds

Abstract

The invention relates to a process for preparing unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation of unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbons by electrochemical oxidation in the presence of an organic nitrate salt in an electrolytic cell in a reaction medium in the presence of oxygen.

Description

[0001] Electrochemical oxidation of cycloalkanes to cycloalkanone compounds

[0002] The invention relates to a process for the preparation of unsubstituted or at least mono-substituted cycloalkanones by electrochemical oxidation of unsubstituted or at least mono-substituted saturated cycloaliphatic hydrocarbons by electrochemical oxidation in the presence of an inorganic or organic nitrate salt in an electrolysis cell in a reaction medium in the presence of oxygen.

[0003] Cycloalkanone and cycloalkanol compounds are important intermediates in a variety of industrial manufacturing processes. The oxidation of saturated, non-functionalized cycloaliphatic hydrocarbons (and thus non-activated CH bonds) to corresponding ketones or alcohols requires special reaction conditions to selectively convert these unreactive substances into monofunctional derivatives while preserving the ring structure.

[0004] There are several processes that rely on transition-metal-catalyzed reactions and oxygen, or on the use of chemical oxidants such as peroxides. The use of expensive transition metals and chemical oxidants not only increases costs but also generates reagent waste, some of which requires complex disposal.

[0005] One example is the production of polyamide 12 from laurolactam, which currently mainly proceeds via cyclododecanone as an intermediate. This is first converted into the peroxide using air. To ensure a largely selective subsequent reaction, boron oxide is used, which reacts with the peroxide to form boric acid esters and oxygen. The resulting alcohol is then oxidized to cyclododecanone using a CuCr catalyst. The disadvantage of this reaction route lies primarily in the use of boron oxide, which is now being discussed as a substance of particular interest because it is suspected of affecting fertility and harming the unborn child.

[0006] In the publication by Yamanaka (J. Chem. Commun. 2000, 2209-2210) it is described that the anodic oxidation of alkanes in aqueous medium at low current densities of <0.1 mA / cm 2to CO2. In non-aqueous media, the oxidation of adamantane was observed at voltages >2 V and current densities <4 mA / cm 2 observed, with the activation of oxygen occurring at the cathode. It was shown that, particularly with an Ir(acac)2 / carbon fiber anode, the formation rate of cycloaliphatic ketones (cyclohexanone) and the current efficiency could be significantly increased. The oxygen comes from water. Organic solvents have an influence; for example, no conversion of cyclohexane occurred in acetonitrile.

[0007] In the publication by Kawamata (J. Am. Chem. Soc. 2017 (139), 7448-7551), it was shown that the electrochemical oxidation of non-activated CH bonds in functionalized aliphatic and cycloaliphatic species is possible at reduced potentials when a mediator such as quinuclidine (tertiary amine, toxic) is used in combination with HFIP (hexafluoroisopropanol, organ-damaging, teratogenic). Me4N-BF4 was used as the supporting electrolyte. It was determined that the introduced oxygen originated from the gas phase. No reaction occurred under argon.

[0008] It is an object of the invention to provide a sustainable and resource-saving process which converts unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbons as selectively as possible into the corresponding ketones as main products.

[0009] This problem was solved by the subject matter of the patent claims and the description.

[0010] The present invention relates to a process for the preparation of unsubstituted or at least mono-substituted cycloalkanones by electrochemical oxidation of unsubstituted or at least mono-substituted, saturated cycloaliphatic hydrocarbons, comprising the process steps

[0011] (a) providing at least one unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon;

[0012] (b) providing at least one organic nitrate salt;

[0013] (c) electrochemical oxidation of the unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon provided in step (a) in the presence of the organic nitrate salt provided in step (b) in an electrolysis cell in a reaction medium in the presence of oxygen.

[0014] The process according to the invention is characterized in particular by high selectivity, low use of auxiliary chemicals, the use of electric current as an oxidizing agent and, associated with this, by a reduced generation of waste products.

[0015] It has surprisingly been found that, with the aid of the inventive process for electrochemical oxidation, atmospheric oxygen can be used to introduce the oxygen function into cycloaliphatic hydrocarbons. This eliminates the need for chemical oxidants, such as reactive peroxides, and expensive catalysts with complex ligand systems. At the same time, the use of toxic and / or potentially carcinogenic reagents can be reduced or even completely avoided. The developed method represents a cost-effective and environmentally friendly alternative to existing syntheses. Due to the simple and safe process conditions, large quantities of the desired compounds can be produced without great effort. Thus, the present invention significantly optimizes previously cost- and time-intensive processes.

[0016] It was also surprisingly found that the process according to the invention enables the use of electricity to produce cycloalkanone compounds from unsubstituted cycloalkanes using nitrate salts, which act both as a supporting salt and as an electrochemical mediator. If byproducts arise during the process according to the invention, in particular cycloaliphatic alcohols of the same ring size, this is unproblematic, since they can be converted into the corresponding ketones by established downstream processes.

[0017] It has also been surprisingly found that the process according to the invention can be carried out under ambient pressure and ambient temperature, which likewise has an advantageous effect on energy efficiency and thus also on environmental compatibility. Unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbons that are monocyclic or polycyclic can be used in the process according to the invention. Monocyclic or bicyclic cycloaliphatic hydrocarbons are preferably used. Monocyclic cycloaliphatic hydrocarbons are particularly preferably used in the process according to the invention.

[0018] The monocyclic or polycyclic, in particular monocyclic or bicyclic, saturated cycloaliphatic hydrocarbons used in the process according to the invention can preferably have 5 to 18 C atoms in the ring system. These cycloaliphatic hydrocarbons can each be unsubstituted or mono- or polysubstituted. If they are mono- or polysubstituted, they are preferably substituted by 1, 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl. The phenyl or benzyl substituents can themselves each be unsubstituted or mono- or polysubstituted by 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO2.If the cycloaliphatic hydrocarbons or their substituents used according to the invention have alkyl radicals with more than one carbon atom in the side chain, undesirable side reactions occur at these substituents when carrying out the process according to the invention.

[0019] Particularly preferred unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbons used in the process according to the invention are monocyclic saturated hydrocarbons having 6 to 12 carbon atoms in the ring, preferably having 8 to 12 carbon atoms in the ring, which are unsubstituted or mono- or polysubstituted by 1, 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl. Very particularly preferred monocyclic saturated hydrocarbons having 8 to 12 carbon atoms in the ring, which are unsubstituted or mono-, di- or tri-substituted by a methyl group, are used in the process according to the invention.

[0020] Most preferably, the saturated monocyclic 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.

[0021] According to step (b) of the process according to the invention, at least one organic nitrate salt is provided. This nitrate salt functions both as a conductive salt and as a mediator in the electrochemical oxidation process according to the invention. Preferably, an organic nitrate of the general formula [cation + ][NO3'] is used, where the [cation + ] is selected from the group consisting of ammonium ions having the general structure [R 1 R 2 R 3 R 4 N+ ] with R 1 , R 2 , R 3 , R 4 , independently of one another, each selected from the group consisting of Ci- to Ci6-alkyl, in particular Ci- to Cs-alkyl, straight-chain or branched, imidazolium cations having the general structure (I)

[0022] R 1

[0023] R 3 + / >

[0024] R 2 ( |) with R 1 and R 2 , independently of one another, each selected from the group consisting of Ci- to Cis-alkyl, straight-chain or branched, in particular Ci- to Cs-alkyl, straight-chain or branched, and R 3 selected from the group consisting of H and Ci- to Cis-alkyl, straight-chain or branched, in particular from the group consisting of H and Ci- to Cs-alkyl, straight-chain or branched,

[0025] Pyridinium cations with the general structure (II) with R 1selected from the group consisting of Ci- to Cis-alkyl, in particular Ci- to Cs-alkyl, straight-chain or branched and R 2 , R 3 and R 4 , independently of one another, each selected from the group consisting of H and Ci- to Cis-alkyl, straight-chain or branched, in particular from the group consisting of H and Ci- to Cs-alkyl, straight-chain or branched, and

[0026] Phosphonium ions with the general structure [R 1a R 2a R 3a R 4a P + ] with R 1a , R 2a , R 3a , R 4a , independently of one another, each selected from the group consisting of Ci- to Ci6-alkyl, in particular Ci- to Cs-alkyl, straight-chain or branched.

[0027] If an organic nitrate based on the imidazolium cations is used in the process according to the invention, preference is given to cations of the general formula (I) in which R 1 and R 2, independently of one another, are each selected from the group consisting of Ci- to Cis-alkyl, straight-chain or branched, in particular Ci- to Cs-alkyl, straight-chain or branched and R 3 represents hydrogen. Particularly preferred imidazolium cations of the general formula (I) are those in which R 1 for methyl and R 2 represent ethyl or R 1 for methyl and R 2 represents methyl and R 1 for methyl and R 2 stands for butyl, and R 3 each stands for hydrogen.

[0028] If a nitrate based on the pyridinium cations is used in the process according to the invention, preference is given to cations of the general formula (II) in which R 1 represents Ci- to Cis-alkyl, straight-chain or branched, in particular represents Ci- to Cs-alkyl, straight-chain or branched. Particularly preferred are pyridinium cations of the general formula (II) in which R 1represents Ci- to Cis-alkyl, straight-chain or branched, in particular Ci- to Cs-alkyl, straight-chain or branched and the radicals R 2 , R 3 and R 4 , independently of one another, are each selected from the group consisting of Ci- to Cs-alkyl, straight-chain or branched, with a single substitution in the 2-, 3- or 4-position, a double substitution in the 2,4-, 2,5- or 2,6-position or a triple substitution in the 2,4,6-position being preferred.

[0029] In principle, two or more of the above-mentioned nitrate salts can also be used in the process according to the invention. Preferably, one nitrate salt according to the invention is used, in particular an organic ammonium nitrate salt of the composition [R 1 R 2 R 3 R 4 N + ][NO3'] or an organic phosphonium salt of the composition [R 1a R 2a R 3a R 4a P +][NO3'], wherein an organic ammonium nitrate salt of the composition [R 1 R 2 R 3 R 4 N + ][NC>3'] is particularly preferred.

[0030] The organic ammonium nitrate salt is most preferably tetra-n-butylammonium nitrate or methyltri-n-octylammonium nitrate. The organic phosphonium nitrate salt is most preferably tetra-n-butylphosphonium nitrate or methyltri-n-octylphosphonium nitrate. The organic imidazolium nitrate salt is preferably 1-butyl-3-methylimidazolium nitrate.

[0031] Tetra-n-butylammonium nitrate or methyltri-n-octylammonium nitrate is most preferably used as the organic nitrate salt in the process according to the invention.

[0032] The order in which the components used in the process according to the invention are provided may vary, as may the order in which the individual components are brought into contact with one another or with the respective reaction medium.

[0033] In one embodiment of the process according to the invention, the unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon or the organic nitrate salt is initially introduced and brought into contact with the reaction medium, preferably at least partially or completely dissolved in the reaction medium or mixed therewith, and then the other of these two components is added. In a further embodiment of the process according to the invention, the unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon and the organic nitrate salt are initially introduced and then brought into contact with the reaction medium, preferably at least partially or completely dissolved in the reaction medium or mixed therewith.Furthermore, it is also possible for the unsubstituted or at least mono-substituted, saturated cycloaliphatic hydrocarbon and the inorganic or organic nitrate salt to be added to the reaction medium simultaneously or in chronological succession to one another, preferably at least partially or completely dissolved in the reaction medium or mixed therewith. The reaction medium used in the process according to the invention is liquid under the conditions under which the process is carried out and is suitable for partially or completely dissolving the components used, ie in particular the unsubstituted or at least mono-substituted, saturated cycloaliphatic hydrocarbon and the inorganic or organic nitrate salt.If at least one of these components is used in liquid form, the reaction medium is preferably readily miscible with this component(s).

[0034] Preferably, a polar aprotic reaction medium is used in the electrochemical oxidation process according to the invention. This can be used in anhydrous form, in dried form, or in combination with water.

[0035] If an inorganic nitrate salt, in particular potassium nitrate or sodium nitrate, is used in the process according to the invention, the reaction medium advantageously contains water, with an aprotic reaction medium in combination with water being preferred. The water content in the reaction medium can vary. Preferably, the water content is up to 20 vol.%, more preferably up to 15 vol.%, most preferably up to 10 vol.%, and even more preferably up to 5 vol.%, in each case based on the total amount of reaction medium.

[0036] 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, dimethyl sulfoxide, esters and ethers or a combination of at least two of these components.

[0037] The reaction medium is particularly preferably 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, gamma-butyrolactone, and epsilon-caprolactone, or a combination of at least two of these components. The reaction medium is most preferably selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, dimethyl carbonate, and acetone, or a combination of at least two of these components.

[0038] The reaction medium is most preferably acetonitrile, isobutyronitrile or adiponitrile in dried or anhydrous form.

[0039] Also particularly preferred is the reaction medium acetonitrile, isobutyronitrile or adiponitrile, optionally in combination with water.

[0040] If one or more of the above-mentioned components are used in the reaction medium in combination with water, the water content is preferably up to 20 vol.%, particularly preferably up to 15 vol.%, very particularly preferably up to 10 vol.%, even more preferably up to 5 vol.%, in each case based on the total amount of reaction medium.

[0041] To carry out the process according to the invention, it may be advantageous to add additional solubilizing components to the reaction medium. Suitable solubilizing components can be determined by simple preliminary tests on the solubility behavior.

[0042] Suitable solubilizing components include, for example, primary alcohols, secondary alcohols, monoketones, or dialkyl carbonates, or mixtures of at least two of these components, optionally in combination with water. Aliphatic C 1-6 alcohols can preferably be used in the process according to the invention, with particularly preferred solubilizing components being selected from the group consisting of methanol, ethanol, isopropanol, 2-methyl-2-butanol, or mixtures of at least two of these components, optionally in combination with water.

[0043] The use of dimethyl carbonate as the reaction medium, optionally in combination with at least one C 1-6 alcohol, in particular selected from the group consisting of methanol, ethanol, isopropanol, and 2-methyl-2-butanol, optionally in combination with water, can be particularly advantageous. If one or more of these solubilizing components is used in combination with water, the water content is preferably up to 20 vol.%, particularly preferably up to 15 vol.%, very particularly preferably up to 10 vol.%, and even more preferably up to 5 vol.%, in each case based on the total amount of solubilizing component and water.

[0044] The solubilizing components can preferably be added in amounts of < 50 vol.%, particularly preferably < 30 vol.% and very particularly preferably < 10 vol.%, in each case based on the total amount of reaction medium.

[0045] Preferably, the organic nitrate salt is used in the process according to the invention in an amount of 0.1 to 2.0, preferably 0.2 to 1.0, particularly preferably 0.3 to 0.8 and very particularly preferably 0.4 to 0.8 equivalents, in each case based on the amount of unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon.

[0046] According to the invention, the electrochemical oxidation of the unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon takes place in the presence of the inorganic or organic nitrate salt in an electrolysis cell in a reaction medium in the presence of oxygen.

[0047] For this purpose, a gas atmosphere containing oxygen is advantageously provided in spatial connection with the reaction medium.

[0048] The proportion of oxygen in the gas atmosphere can vary. The proportion of oxygen in the gas atmosphere is preferably 10 to 100 vol.%, particularly preferably 15 to 30 vol.%, particularly preferably 15 to 25 vol.%, and most preferably 18 to 22 vol.%.

[0049] In one embodiment, the proportion of oxygen in the gas atmosphere can be 10 to 100 vol.%, particularly preferably 15 to 100 vol.%, particularly preferably 20 to 100 vol.%.

[0050] The gas atmosphere is most preferably air. Advantageously, gas exchange is enforced 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 the gas atmosphere.

[0051] The gas exchange between the gas atmosphere and the reaction medium, in particular stirring, for example via the geometry of the stirrer or the stirring speed, can be used to control the electrochemical oxidation.

[0052] Preferably, the amount of oxygen dissolved in the reaction medium is at least 1 mmol / L reaction medium, particularly preferably at least 5 mmol / L reaction medium.

[0053] Also preferably, the amount of oxygen dissolved in the reaction medium is at least 10 mmol / L reaction medium.

[0054] The process according to the invention for preparing unsubstituted or at least mono-substituted cycloalkanones by electrochemical oxidation of unsubstituted or at least mono-substituted, saturated cycloaliphatic hydrocarbons by electrochemical oxidation in the presence of an inorganic or organic nitrate salt in a reaction medium in the presence of oxygen can be carried out in both a divided and an undivided electrolysis cell, with the process being carried out in an undivided electrolysis cell being preferred.

[0055] In order to avoid undesirable chemical reactions, it is sometimes advantageous to separate the cathode compartment and the anode compartment and to allow the charge exchange between the anode and cathode compartments to take place only through a porous diaphragm - often an ion exchange resin.

[0056] The undivided electrolysis cell preferably used according to the invention has at least two electrodes. Anodes and cathodes made of conventional materials can be used, for example, glassy carbon, boron-doped diamond (BDD), or graphite. The use of glassy carbon electrodes is preferred. The undivided electrolysis cell preferably has at least one glassy carbon anode or at least one glassy carbon cathode. Both the anode and the cathode are preferably glassy carbon electrodes.

[0057] The distance between the electrodes can vary within a certain range. The distance is preferably 0.1 mm to 2.0 cm, more preferably 0.1 mm to 1.0 cm, and most preferably 0.1 mm to 0.5 cm.

[0058] Furthermore, the process according to the invention can be carried out batchwise or continuously, preferably in an undivided flow-through electrolysis cell.

[0059] The process according to the invention is preferably carried out with a charge quantity of 190 C (2 F) to 970 C (10 F), particularly preferably 320 C to 820 C, very particularly preferably 350 C to 800 C, even more preferably 380 C to 775 C, most preferably 380 C to 450 C, in each case based on 1 mmol of unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon.

[0060] Preferably, the electrochemical oxidation in the process according to the invention takes place at a constant current intensity.

[0061] The current density at which the process according to the invention is carried out is preferably at least 5 mA / cm 2 or at least 10 mA / cm 2 or at least 15 mA / cm 2 or at least 20 mA / cm 2 or 20 mA / cm 2 up to 50 mA / cm 2 , where the area refers to the geometric area of ​​the electrodes.

[0062] A significant advantage of the process according to the invention is that electric current is used as the oxidizing agent, which is a particularly environmentally friendly agent when it comes from renewable sources, in particular from biomass, solar thermal energy, geothermal energy, hydropower, wind power or photovoltaics.

[0063] The process according to the invention can be carried out over a wide temperature range, for example at a temperature in the range from 0 to 60°C, preferably from 5 to 50°C, more preferably from 10 to 40°C, most preferably from 15 to 30°C. The process according to the invention can be carried out at elevated or reduced pressure. If the process according to the invention is carried out at elevated pressure, a pressure of up to 16 bar is preferred, particularly preferably up to 6 bar.

[0064] The process according to the invention can also preferably be carried out under atmospheric pressure.

[0065] The products prepared by the process according to the invention can be isolated or purified by conventional methods known to the person skilled in the art, in particular by extraction, crystallization, centrifugation, precipitation, distillation, evaporation or chromatography.

[0066] The following examples further illustrate the present invention, but are not to be construed as limiting the scope of the invention.

[0067] General information and methods

[0068] Analytical-grade chemicals were purchased and used from common suppliers (such as TCI, Aldrich, and Acros). Oxygen was purchased in 2.5 grade from NIPPON GASES Deutschland GmbH, Düsseldorf, Germany, and used directly.

[0069] Glassy carbon (SIGRADUR® G, from HTW Hochtemperatur Werkstoffe GmbH, Thierhaupten, Germany) was used as the electrode material.

[0070] High-performance liquid chromatography was performed on a Shimadzu HPLC-MS equipped with a SIL 20A HT autosampler, a CTQ-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 x 4 mm, Knauer, Berlin). Eluent: acetonitrile / water / formic acid (1 vol%) (from 10% ACN to 90% ACN in 10 min + 10 min at 100% ACN). Mass spectrometry measurements were performed on an LCMS-2020 Shimadzu, Japan. NMR spectrometry of 1 H-NMR and 13C-NMR spectra were recorded at 25 °C using a Bruker Avance II 400 (400 MHz, 5 mm BBFO head with z-gradient and ATM, SampleXPress 60 sample changer, Analytische Messtechnik, Karlsruhe, Germany).

[0071] The undivided Teflon cells used for electrolysis are described in the literature (a) C. Gütz, B. Klöckner, SR Waldvogel, Org. Process Res. Dev. 2016, 20, 26-32; b) A. Kirste, G. Schnakenburg, F. Stecker, A. Fischer, SR Waldvogel, Angew. Chem. Int. Ed. 2010, 49, 971-975; Angew. Chem. 2010, 122, 983-987. (see Sl). The complete 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 dimensions of the electrodes were 3 cm x 1 cm x 0.3 cm.

[0072] The gas introduction was controlled by two Model 5850S ​​mass flow controllers (MFCs) from Brooks Instrument BV, Veenendaal, Netherlands. One controller each was used for the oxygen and nitrogen lines. The controllers were controlled using the Smart DDE software and Matlab R2017b. The volume flow was additionally controlled by a DK800 variable area flowmeter from KRÖHNE Messtechnik GmbH, Duisburg. For all experiments, the total volume flow was constant at 20 mL / min, which, limited by the MFCs used, also represents the maximum achievable volume flow. The percentage volume flows of the two gases were adjusted using the MFCs and their software. The gas cylinders used were from the following suppliers: Oxygen 2.5 from NIPPON GASES Deutschland GmbH, Düsseldorf, and Nitrogen 4.8 from Westfalen AG, Münster, or Nitrogen 5.0 from NIPPON GASES Deutschland GmbH, Düsseldorf. The apparatus was equipped with a gas distributor including an adapter and a Teflon cover for the electrolysis cells.

[0073] General Working Instruction AAV1

[0074] The cycloalkane (5.0 mmol) and tetrabutylammonium nitrate (0.5 eq.) were dissolved in acetonitrile (25 mL) in an undivided electrolysis cell (100 mL three-neck round-bottom flask, NS29 Teflon stopper with electrode holders, and magnetic stir bar). The cell was equipped with glassy carbon electrodes (3 cm x 1 cm x 0.3 cm) spaced 0.5 cm apart. The immersion area of ​​the electrodes was 1.3 cm. 2 . Oxygen was introduced into the gas space of the reaction vessel via a NS14.5 core olive. Galvanostatic electrolysis was carried out at a current density of 10 mA / cm 2 at 20 to 30 °C.

[0075] After applying a charge of 4 to 5 °F (1930 °C to 2412 °C) to the cycloalkane, the solvent, along with the unreacted portion of cycloalkane, was removed by distillation under reduced pressure. The residue was taken up with 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.

[0076] Example 1 :

[0077] Production of cyclohexanone:

[0078] According to AAV1, cyclohexane (0.421 g, 5.0 mmol, 1.0 eq.) was dissolved in acetonitrile (25 mL) and electrolyzed galvanostatically at 25 °C under oxygen atmosphere with application of 5 F. After workup according to AAV1, the product was obtained as a colorless liquid (yield: 6%, 30 mg, 0.31 mmol). 1 H-NMR (400 MHz, CDCh) δ [ppm] = 2.36-2.32 (m, 4H), 1.90-1.84 (m, 4H), 1.75-1.70 (m, 2H). The analytical data are consistent with the literature values. For the yield determination, existing solvent signals were eliminated using integral ratios.

[0079] Example 2:

[0080] Production of cycloheptanone:

[0081] According to AAV1, cycloheptane (0.491 g, 5.0 mmol, 1.0 eq.) was dissolved in acetonitrile (25 mL) and electrolyzed galvanostatically at 21 °C under ambient air with the application of 4 F. Electrode immersion area: 1.5 cm 2The 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 removal of 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, CDCh) δ [ppm] = 2.49–2.47 (m, 4H), 1.69–1.64 (m, 8H). The analytical data are consistent with the literature values.

[0082] Example 3:

[0083] Preparation of cyclooctanone: According to AAV1, cyclooctane (0.561 g, 5.0 mmol, 1.0 eq.) was dissolved in acetonitrile (25 mL) and electrolyzed galvanostatically at 30 °C under an oxygen atmosphere with the application of 4 F. After workup according to AAV1, the product was obtained as a colorless liquid (yield: 42%, 0.261 g, 2.07 mmol). Rf (cyclohexane / ethyl acetate = 7:3): 0.66; 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 are consistent with the literature values.

[0084] Example 4:

[0085] Production of cyclodecanone:

[0086] According to AAV1, cyclodecane (0.701 g, 5.0 mmol, 1.0 eq.) was dissolved in acetonitrile (25 mL) and electrolyzed galvanostatically at 30 °C under an oxygen atmosphere with the application of 5 F. The solvent was then removed by distillation under reduced pressure, and the residue was purified by column chromatography (CH / EE = 10:0 to 9:1). After removal of the solvent by distillation and drying under vacuum, the product was obtained as a colorless liquid (yield: 12%, 90 mg, 0.59 mmol). Rf (cyclohexane / ethyl acetate = 95:5): 0.28; 1H-NMR (300 MHz, CDCh) 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 are consistent with the literature values. For the yield determination, existing solvent signals were eliminated using integral ratios.

[0087] Example 5:

[0088] Production of cyclododecanone

[0089] According to AAV1, cyclododecane (0.842 g, 5.0 mmol, 1.0 eq.) was dissolved in isobutyronitrile (25 mL) and electrolyzed galvanostatically at 27 °C under an oxygen atmosphere with the application of 4 F. 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 removal of the solvent by distillation and drying under vacuum, the product was obtained as a colorless solid (yield: 21%, 0.194 g, 1.06 mmol). Rf

[0090] (Cyclohexane / ethyl acetate = 9:1): 0.48; 1 H-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 are consistent with the literature values. Example 6:

[0091] In the following, various parameters of the electrochemical oxidation were varied to investigate their influence. These investigations were carried out for the electrochemical oxidation of cyclooctane to cyclooctanone.

[0092] General working instruction AAV2a:

[0093] The electrolysis was carried out in an undivided 5 mL PTFE cell. The conducting salt (0.2 to 1.0 eq.) and the substrate (cyclooctane, 0.5–2.5 mmol) were placed in the cell and dissolved in the solvent (5 mL). The cell was equipped with a glassy carbon anode and cathode separated by 0.5 cm (electrode dimensions: 7 cm x 1 cm x 0.3 cm, immersion area 1.8 cm). 2). The cells were fixed in a heatable / coolable stainless steel block and supplied with the gas mixture to be investigated (100 vol.% O2 to 0 vol.% O2) via an adapter. Electrolysis was carried out at a constant current, with the current densities (5-60 mA / cm 2 ), temperatures (5-50 °C), stirring speeds (100-600 rpm), and charge amounts (4-8 °F) were varied. After applying the charge amount, 2 drops of the reaction solution were taken for gas chromatographic analysis. Subsequently, 1,3,5-trimethoxybenzene was added to the solution as an NMR standard (1 eq.), and the solvent was removed by distillation (45 °C, 200 mbar). The yield of the cycloalkanone product was determined via 1 H-NMR analysis.

[0094] For GC analysis: Two drops of the reaction solution were eluted with ethyl acetate over approximately 330 mg of 60 M silica gel. Approximately 1.5 mL of the filtrate was collected in a GC vial, which was analyzed for oxidation products using GC-FID and GC-MS.

[0095] General working instruction AAV2b:

[0096] The electrolysis was carried out in an undivided 5 mL PTFE cell. The conducting salt (0.2–1.0 eq.) and the substrate (cyclooctane, 0.5–2.5 mmol) were placed in the cell and dissolved in the solvent (5 mL). The cell was equipped with a glassy carbon anode and cathode separated by 0.5 cm (electrode dimensions: 7 cm x 1 cm x 0.3 cm, immersion area 1.8 cm). 2). The cells were fixed in a heatable / coolable stainless steel block and supplied with the gas mixture to be investigated (100 vol.% O2 to 0 vol.% O2) via an adapter. Electrolysis was carried out at a constant current, with the current densities (5-60 mA / cm 2 ), temperatures (5-50 °C), stirring speeds (100-600 rpm), and charge amounts (4-8 °F) varied. After applying the charge amount, 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 gas chromatographic analysis and quantification of the product. These were eluted using ethyl acetate over approximately 330 mg of 60 M silica gel. Approximately 1.5 mL of the filtrate was collected in a GC vial, which was analyzed for oxidation products using GC-FID and GC-MS. Quantification was performed by prior calibration of the gas chromatograph.

[0097] The results shown in Scheme 1 below were obtained using the AAV2a described above:

[0098] * 1

[0099] Scheme 1.

[0100] Further exemplary studies are presented below, grouped according to the parameters changed:

[0101] Amount of charge (F with respect to cyclooctane 1)

[0102] Current density (mA / cm 2 )

[0103] O2 / N2 ratio

[0104] Equivalents (with respect to cyclooctane 1 / nitrate salt)

[0105] Stirring speed (rpm)

[0106] Temperature (°C)

[0107] Nitrate salt as mediator / conductive salt

[0108] Reaction medium

[0109] Electrode material

[0110] Cation variation of the nitrate salts. Unless otherwise stated, the experiments were performed at least twice, and a mean value with standard deviation was determined. The designations of compounds 1, 2, 3, and 4 correspond to those in Scheme 1.

[0111] Example 6a - Quantity of charge

[0112] The charge amount was investigated in a range from 4 F to 8 F (corresponding to 386 C to 772 C for 1 mmol of substrate cyclooctane 1). Table 1: Investigation of different charge amounts.

[0113] No change in product and by-product formation was observed in the charge range investigated. Due to the shorter electrolysis time, the experiment was continued with 4 F.

[0114] Example 6b - Current density:

[0115] The current density was in the range of 5 mA / cm 2 up to 60 mA / cm 2 varies.

[0116] The electrode area in the electrolyte solution was 1.8 cm2 .

[0117] Table 2: Investigation of different current densities.

[0118] Using 60 mA / cm 2 a significant reduction in yield of 2 is observed. Cyclooctanol 3 is formed to a comparable extent.

[0119] It was measured at 20 mA / cm 2 continued and investigated various atmospheric Ch contents.

[0120] Example 6c - Ch / IXh ratio at 20 mA / cm 2

[0121] First, rough O2 / N2 ratios were determined at 20 mA / cm 2 (100:0, 20:80, 0:100). The ratio 20:80 was chosen for comparability to the air composition. Table 3: Investigation of various O2 / N2 ratios at 20 mA / cm 2 .

[0122] Under a pure nitrogen atmosphere (ratio 0:100), no product formation was observed. Therefore, no quantitative statements regarding the unreacted substrate content or by-products are possible. However, traces of cyclooctanol 3 were detected in the gas chromatogram. To compare the chlorine content with the initial standard current density of 10 mA / cm 2 In order to be able to draw, these were repeated with smaller gradations at the current density mentioned.

[0123] Example 6d - O2 / N2 ratio at 10 mA / cm 2

[0124] In addition to the gradations shown in the table, tests were also carried out without gas supply under ambient conditions (marked as “air”).

[0125] Table 3: Investigation of different O2 / N2 ratios at 10 mA / cm 2 .

[0126] In the above investigations, the conversion of reactant 1 and the formation of product 2 was at an oxygen content of 20 vol.% and a current density of 10 mA / cm 2 highest. Furthermore, the formation of cyclooctanol 3 was slightly increased at low O2 levels.

[0127] Due to the higher yield of cyclooctanone 2 and the improved safety aspect due to the higher nitrogen content, these conditions were chosen as comparison conditions in the following reactions (Scheme 2), and the other parameters were changed based on these conditions.

[0128] Example 6e - Amount of Substance and Mediator Equivalents To investigate different substrate and mediator concentrations in the solvent (acetonitrile, 5 mL), the substrate amount and the equivalents of conducting salt / mediator were varied. Table 5: Investigation of different amounts of substance and nitrate equivalents.

[0129] In general, the conversion of reactant 1 to product 2 was somewhat better at lower substrate amounts (< 1 mmol, corresponding to 0.2 mol / L) than at higher amounts. When varying the mediator concentration relative to the substrate, above and below 0.5 equivalents, the yields of 2 differed only slightly, so it can be assumed that the oxygen source for the oxo functionalization is molecular dissolved oxygen.

[0130] Example 6f - Stirring speed

[0131] Since the oxygen source for ketone synthesis comes from the atmosphere, the stirring speed is expected to have a significant influence on the reaction process. Table 4: Investigation of different stirring speeds

[0132] The results in Table 6 show a maximum in the range around 350 rpm. However, the influence of the speed depends on the stirrer and cell geometry and should therefore not be considered as a fixed value.

[0133] Example 6g - Temperature

[0134] The temperatures indicated refer to heating block or

[0135] Cryostat temperatures. The electrolyte solutions were stirred at 5 °C and 50 °C for approximately half an hour before the start of electrolysis.

[0136] Table 5: Investigation of different temperatures.

[0137] Regarding product formation, a slight decrease in yield can be observed at both temperatures higher and lower than 30 °C. The reaction therefore appears to be only slightly temperature-dependent. At higher temperatures, a lower proportion of unreacted substrate can also be detected, which is presumably due to its volatility and the open system of the electrolysis cells.

[0138] Example 6h - Conductive salt / Mediator

[0139] To investigate whether nitrate, as the anion of the conducting salt, also has a mediating effect on the reaction, the standard tetrabutylammonium nitrate was compared with other common conducting salts. The cationic component was kept the same. The non-standard conducting salts were each tested only once in an electrolysis run, so no average was calculated.

[0140] Table 6: Investigation of various conducting salts.

[0141] The results in Table 8 illustrate the dependence of the reaction on the nitrate anion. Product 2 is formed only to a very small extent with other conducting salt anions.

[0142] The examples 6-AAV2a-09, 6-AAV2a-28, 6-AAV2a-29, 6-AAV2a-30 are

[0143] Comparison examples

[0144] Example 6i - Solvent Table 7: Investigation of various solvents.

[0145] The reaction proceeded comparably well in the solvents mentioned. In addition, a higher proportion of unreacted substrate remained in acetone.

[0146] The reaction was also carried out in 3-pentanone, but due to the superposition of the solvent signals with the product signals, no 1 H-NMR yield can be determined. However, gas chromatographic analysis also confirms the selective formation of product 2.

[0147] Since it was previously assumed that isobutyronitrile would have better O2 solubility than acetonitrile, a comparison was also made under a 100% O2 atmosphere (Table 10). Table 8: Investigation of various solvents at 100 vol.% O2.

[0148] The results using acetonitrile and isobutyronitrile are comparable. While a significant increase in the yield of 2 was not achieved using isobutyronitrile, the proportion of unreacted 1 is significantly higher, which is considered an advantage. The reaction was subsequently carried out in nitropropane at 100% C atmosphere, demonstrating that nitrated alkanes can also serve as solvents.

[0149] Example 6j - Electrode material

[0150] Electrolysis tests were conducted using various carbon-based electrode materials. Electrode materials deviating from the GK standard were each tested only once in an electrolysis test, so no average values ​​were calculated.

[0151] Table 9: Investigation of different electrode materials.

[0152] The reaction takes place on all electrode materials used and product 2 is formed. On graphite electrodes, a slight detachment of the electrode material in the form of black particles is observed after electrolysis, which is due to their lower stability.

[0153] Example 6k - Cation variation of the conducting salt / mediator

[0154] Various cations other than standard tetrabutylammonium were investigated. The following were used:

[0155] • Hexadecyltrimethylammonium nitrate ([C19H42N NO3])

[0156] • 1-Butyl-3-methylimidazolium nitrate ([CsHis^HNCh])

[0157] • Methyltrioctylammonium nitrate ([C25H54N NO3])

[0158] • Tetrabutylphosphonium nitrate (PBU4NO3) The anionic nitrate component was left unchanged. The conducting salts deviating from the standard were each tested only once in an electrolysis run, so no average was determined. Table 12: Investigation of various cations.

[0159] It can be seen that the oxidation of the cycloalkane to the ketone works primarily with the nitrate as an anion component (see Example 6h). Long-chain alkyl radicals on the ammonium cations lead to slightly higher yields compared to the tetrabutylammonium cation under the same conditions. The reaction also works with / V-alkylated nitrogen heteroaromatics as cations, as well as with tetraalkylphosphonium cations.

[0160] Example 6I: Oxygen solubility in acetonitrile / NBU4NO3 at 25°C and atmospheric pressure:

[0161] Table 13: Dissolved oxygen concentration in MeCN / NBiuNCh as a function of atmospheric oxygen content.

[0162] General working instruction AAV3:

[0163] In an undivided 25 mL beaker cell with a gas inlet, the cycloalkane (5.0 mmol) and tetrabutylammonium nitrate (0.5 eq.) were dissolved in acetonitrile (25 mL). The cell was equipped with glassy carbon electrodes (7 cm x 1 cm x 0.3 cm) spaced 0.5 to 1.0 cm apart. The immersion area of ​​the electrodes was 1.3 cm. 2 Galvanostatic electrolysis was carried out at a current density of 10 mA / cm 2at 20-30 °C. After applying a charge of 4 F to the cycloalkane, the solvent, along with the unreacted portion of cycloalkane, was removed by distillation under reduced pressure. The residue was taken up with 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.

[0164] Alternative quantification: 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 for gas chromatographic analysis and quantification of the product. These were eluted using ethyl acetate over approximately 330 mg of 60 M silica gel. Approximately 1.5 mL of the filtrate was collected in a GC vial, which was analyzed for oxidation products using GC-FID and GC-MS. Quantification was performed by prior calibration of the gas chromatograph. Example 7:

[0165] The influence of the electrode distance was investigated below.

[0166] Table 14: Investigation of different electrode distances.

[0167] The examples in Table 14 show that the conversion of the starting material to product 2 is better with a smaller electrode distance.

Claims

Process for the production of unsubstituted or at least singly substituted cycloalkanones by electrochemical oxidation of unsubstituted or at least singly substituted saturated cycloaliphatic hydrocarbons comprising the process steps (a) Provision of at least one unsubstituted or at least one simply substituted saturated cycloaliphatic hydrocarbon; (b) Provision of at least one organic nitrate salt; (c) Electrochemical oxidation of the unsubstituted or at least singly substituted saturated cycloaliphatic hydrocarbon provided in step (a) in the presence of the organic nitrate salt provided in step (b) in an electrolysis cell in a reaction medium in the presence of oxygen, wherein the substituents of the saturated cycloaliphatic hydrocarbons are each selected independently from the group consisting of methyl, phenyl or benzyl, wherein phenyl or benzyl may each be unsubstituted or singly or multiply substituted, with 1, 2 or 3 substituents, each selected independently from the group consisting of F, CI, Br, and NO2. Method according to claim 1, wherein the unsubstituted or at least singly substituted saturated cycloaliphatic hydrocarbon is monocyclic or bicyclic, preferably monocyclic.The method of claim 1, wherein the monocyclic or bicyclic saturated cycloaliphatic hydrocarbon has 5 to 18 carbon atoms in the ring system and is unsubstituted or singly or multiply substituted with 1, 2, 3, 4, or 5 substituents. The method of any one of the preceding claims, wherein the unsubstituted or at least singly substituted saturated cycloaliphatic hydrocarbon is a monocyclic saturated hydrocarbon with 6 to 12 carbon atoms in the ring, preferably with 8 to 12 carbon atoms in the ring, wherein this cycloaliphatic hydrocarbon is unsubstituted or singly or multiply substituted with 1, 2, 3, 4, or 5 substituents, independently. from each other, each selected from the group consisting of methyl, phenyl, or benzyl, particularly preferably a monocyclic saturated hydrocarbon with 8-12 carbon atoms in the ring, wherein this cycloaliphatic hydrocarbon is unsubstituted or singly, doubly, or triply substituted with methyl. A process according to any one of the preceding claims, wherein the saturated cycloaliphatic hydrocarbon is unsubstituted and selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cycloononane, cyclodecane, cycloundecane, and cyclododecane, preferably selected from the group consisting of cyclooctane, cycloononane, cyclodecane, cycloundecane, and cyclododecane, particularly preferably cyclododecane. A process according to any one of the preceding claims, wherein the organic nitrate salt is a nitrate of the general formula [cation + ][NO3'] is present, with [cation +] selected from the group consisting of ammonium ions with the general structure [R 1 R 2 R 3 R 4 N + ] with R 1 , R 2 , R 3 , R 4 , independently of each other, each selected from the group consisting of Ci- to Cie-alkyl, in particular Ci- to Cs-alkyl, straight-chain or branched, imidazolium cations with the general structure (I) with R 1 and R 2 , independently of each other, each selected from the group consisting of Ci- to Cis-alkyl, straight-chain or branched, in particular Ci- to Cs-alkyl, straight-chain or branched, and R 3 selected from the group consisting of H and Ci- to Cis-alkyl, straight-chain or branched, in particular from the group consisting of H and Ci- to Cs-alkyl, straight-chain or branched, pyridinium cations with the general structure (II) with R 1selected from the group consisting of Ci- to Cis-alkyl, in particular Ci- to Cs-alkyl, straight-chain or branched, and R 2 , R 3 and R 4 , independently of each other, each selected from the group consisting of H and Ci- to Cis-alkyl, straight-chain or branched, in particular from the group consisting of H and Ci- to Cs-alkyl, straight-chain or branched, and phosphonium ions with the general structure [R 1a R 2a R 3a R 4a P + ] with R 1a , R 2a , R 3a , R 4a, independently of one another, each selected from the group consisting of Ci- to Cis-alkyl, in particular Ci- to Cs-alkyl, straight-chain or branched. A method according to claim 6, wherein in the imidazolium cations of general formula (I) the residues R1 and R2 are, independently of one another, each selected from the group consisting of C1- to C18-alkyl, straight-chain or branched, in particular C1- to C8-alkyl, straight-chain or branched, and R3 represents hydrogen, preferably R1 represents methyl and R2 represents ethyl, or R1 represents methyl and R2 represents methyl, and R1 represents methyl and R2 represents butyl, and R3 represents hydrogen.The method of claim 6, wherein in the pyridinium cations of general formula (II) the residue R1 represents C1 to C18 alkyl, straight-chain or branched, in particular C1 to C8 alkyl, straight-chain or branched, and the residues R2, R3 and R4 are each selected independently from the group consisting of C1 to C8 alkyl, straight-chain or branched, wherein a simple substitution in the 2-, 3- or 4-position, a double substitution in the 2,4-, 2,5- or 2,6-position or a triple substitution in the 2,4,6-position is preferred. The method of claim 6, wherein the organic nitrate salt is selected from the group consisting of tetra-n-butylammonium nitrate, methyl-tri-n-octylammonium nitrate, tetra-n-butylphosphonium nitrate, methyl-tri-n-octylphosphonium nitrate and 1-butyl-3-methylimidazolium nitrate. A method according to any one of the preceding claims, wherein the unsubstituted or at least singly substituted saturated cycloaliphatic hydrocarbon or the inorganic or organic nitrate salt is presented and brought together with the reaction medium, preferably at least partially or completely dissolved or mixed with the reaction medium, and then the other of these two components is added. A method according to any one of the preceding claims, wherein the unsubstituted or at least singly substituted saturated cycloaliphatic hydrocarbon and the inorganic or organic nitrate salt are presented and then brought together with the reaction medium, preferably at least partially or completely dissolved or mixed with the reaction medium.A method according to any one of the preceding claims, wherein the unsubstituted or at least singly substituted saturated cycloaliphatic hydrocarbon and the inorganic or organic nitrate salt are added to the reaction medium simultaneously or sequentially, preferably dissolved or mixed at least partially or completely in the reaction medium. A method according to any one of the preceding claims, wherein the reaction medium is a polar aprotic reaction medium which is anhydrous, dried, or optionally...in combination with water, wherein a polar aprotic reaction medium 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, wherein, when combined with water, the water content is preferably up to 20 vol.%, particularly preferably up to 15 vol.%, most preferably up to 10 vol.%, and even more preferably up to 5 vol.%, in each case based on the total amount of reaction medium. The process according to claim 13, wherein the reaction medium is a polar aprotic reaction medium selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, acetone, dimethyl carbonate, and methyl ethyl ketone. 3-Pentanone, cyclohexanone, nitromethane, nitropropane, tert-butyl methyl ether, dimethyl sulfoxide, gamma-butyrolactone, and epsilon-caprolactone, or a combination of at least two of these components, optionally in combination with water. A process according to claim 13 or 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 in combination with water, is present. A process according to any one of claims 13 to 15, wherein the reaction medium is acetonitrile, isobutyronitrile, or adiponitrile in dried or anhydrous form. A process according to any one of the preceding claims, wherein the reaction medium comprises one or more solubilizing components.A process according to claim 17, wherein the solubilizing components are primary alcohols, secondary alcohols, monoketones, or dialkyl carbonates, or mixtures of at least two of these components, optionally in combination with water. A process according to claim 16 or 17, wherein aliphatic Ci-6 alcohols are present as one or more solubilizing components, preferably one or more alcohols selected from the group consisting of methanol, ethanol, isopropanol, 2-methyl-2-butanol, and mixtures of at least two of these components, optionally in combination with water. A process according to any of the preceding claims, wherein the reaction medium is dimethyl carbonate, optionally in combination with at least one Ci-6 alcohol, preferably selected from the group consisting of methanol, ethanol, isopropanol, and 2-methyl-2-butanol. A process according to claim 20, wherein the reaction medium comprises water.

22. Method according to one of claims 19 to 23, wherein one or more solubilizing components are added in an amount of < 50 vol.%, particularly preferably < 30 vol.% and most preferably < 10 vol.%, in each case based on the total amount of reaction medium.

23. A process according to any one of the preceding claims, wherein the organic nitrate salt is present in an amount of 0.1 to 2.0, preferably 0.2 to 1.0, particularly preferably 0.3 to 0.8, and most preferably 0.4 to 0.8 equivalents, in each case based on the amount of unsubstituted or at least singly substituted saturated cycloaliphatic hydrocarbon used. A process according to any one of the preceding claims, wherein a gas atmosphere containing oxygen is provided in spatial connection with the reaction medium, wherein the proportion of oxygen in the gas atmosphere is preferably 10 to 100 vol.%, particularly preferably 15 to 30 vol.%, most preferably 15 to 25 vol.%, and most preferably 18 to 22 vol.%.

25. Method according to claim 24, wherein a gas exchange is forced between the gas atmosphere and the reaction medium, preferably by introducing gas atmosphere into the reaction medium or by stirring the reaction medium in the presence of the gas atmosphere.

26. Method according to any of the preceding claims, wherein the gas atmosphere is air.

27. Method according to one of the preceding claims, wherein a gas exchange is forced between the gas atmosphere and the reaction medium.

28. Method according to claim 27, wherein the gas exchange is carried out by introducing a gas atmosphere into the reaction medium.

29. Method according to one of claims 27 or 28, wherein the gas exchange is carried out by stirring the liquid phase in the presence of the gas atmosphere.

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

31. Method according to any of the preceding claims, wherein the amount of oxygen dissolved in the reaction medium is at least 1 mmol / L, preferably 5 mmol / L, more preferably 10 mmol / L reaction medium.

32. Method according to any of the preceding claims, wherein the electrolysis cell is an undivided electrolysis cell.

33. Method according to any of the preceding claims, wherein the undivided electrolysis cell comprises a glassy carbon anode, a graphite anode or a BDD anode, preferably a glassy carbon anode.

34. Method according to any of the preceding claims, wherein the undivided electrolysis cell comprises a glassy carbon cathode, a graphite cathode or a BDD cathode, preferably a glassy carbon cathode.

35. Method according to one of the preceding claims, wherein the distance between the electrodes in the electrolysis cell is 0.1 mm to 2.0 cm, preferably 0.1 mm to 1.0 cm, particularly preferably 0.1 mm to 0.5 cm.

36. Method according to any of the preceding claims, wherein the charge quantity is at least 190°C (2°F) to 970°C (10°F), preferably 320°C to 820°C, particularly preferably 350°C to 800°C, most preferably 380°C to 775°C, most preferably 380°C to 450°C, in each case for 1 mmol of unsubstituted or at least singly substituted saturated cycloaliphatic hydrocarbon.

37. Method according to any of the preceding claims, wherein the current density is at least 5 mA / cm² 2 , preferably 10 mA / cm 2 , preferably 15 mA / cm 2 , especially preferably 20 mA / cm 2 , where the area specification refers to the geometric area of ​​the electrodes.

38. Method according to one of the preceding embodiments, characterized in that the current density is at least 20 mA / cm² 2 up to 50 mA / cm 2 The area specified refers to the geometric area of ​​the electrodes. A method according to any one of the preceding claims, wherein it is carried out in an undivided cell. A method according to any one of the preceding claims, wherein the current used for electrochemical oxidation is derived from renewable sources, in particular from biomass, solar thermal energy, geothermal energy, hydropower, wind power, or photovoltaics. A method according to any one of the preceding claims, wherein the electrochemical oxidation is carried out at a temperature in the range of 0 to 60 °C, preferably from 5 to 50 °C, particularly preferably from 10 to 40 °C, and most preferably from 15 to 30 °C. A method according to any one of the preceding claims, wherein it is carried out under atmospheric pressure. A method according to any one of the preceding claims, wherein it is carried out under vacuum.A method according to any one of the preceding claims, wherein it is carried out under overpressure, preferably up to 16 bar, particularly preferably up to 6 bar. A method according to any one of the preceding claims, wherein it is carried out batchwise. A method according to any one of the preceding claims, wherein it is carried out continuously, preferably continuously in an undivided flow-through electrolysis cell. A method according to any one of the preceding claims, wherein it is carried out without the addition of catalysts, in particular without the addition of transition metal catalysts.

48. A method according to any of the preceding claims, wherein no further oxidizing agents are added besides oxygen or atmospheric oxygen.

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