EP4253605A1 - Electrochemical oxidation of cycloalkenes to alpha, omega-dicarboxylic acids and ketocarboxylic acids - Google Patents

Abstract

The invention relates to a process for producing unsubstituted or at least monosubstituted α,ω-dicarboxylic acids and ketocarboxylic acids by electrochemical oxidation of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkenes by electrochemical oxidation in the presence of an inorganic or organic nitrate salt in an electrolysis cell Reaction medium in the presence of oxygen.

Description

The invention relates to a process for the production of unsubstituted or at least monosubstituted α,ω-dicarboxylic acids and ketocarboxylic acids by electrochemical oxidation of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkenes by electrochemical oxidation in the presence of an inorganic or organic nitrate salt in an electrolysis cell Reaction medium in the presence of oxygen.

α,ω-Dicarboxylic acids and ketocarboxylic acids represent important substrates for organic synthetic chemistry as well as monomer building blocks for polymer synthesis and are therefore highly relevant for industrial applications. The conventional access to these substrates from cycloalkenes is essentially achieved via transition metal-catalyzed reactions and the use of chemical oxidants.

To date, only a few electrochemical processes have been described for the synthesis of dicarboxylic acids from cycloalkenes using direct C=C bond cleavage. The known processes usually work in a mediated manner, also using expensive transition metal catalysts. This usually requires an additional oxidizing agent, which is regenerated electrochemically ( CN101092705A ; U.-St. Bäumer, HJ Schäfer, J. Appl. Electrochem. 2005, 35, 1283-1292 ). Furthermore, toxic transition metals or their oxides are usually used as electrode materials ( S. Torii, T. Inokuchi, R. Oi, J. Org. Chem. 1982, 47, 47-52 ; DD Davis, DL Sullivan, Process for the Preparation of Dodecanedionic Acid, 1991, US 5026461 A ). Divided cells are often used, which results in a more complex cell structure ( CN101092705A ). Known methods that do not require additional transition metal catalysts work potentiostatically, require two-phase mixtures and deliver poor current yields, so that scalability and economic efficiency cannot be guaranteed ( S. Torii, T. Inokuchi, R. Oi, J. Org. Chem. 1982, 47, 47-52 ; U. Baumer, Electrochimica Acta 2003, 48, 489-495 ).

Furthermore, in the methods known from the prior art, only a small substrate spectrum is accessible or prefunctionalization is required. In addition, the prior art predominantly describes the synthesis of the corresponding carboxylic acid esters, so that a further hydrolysis step is required to generate the carboxylic acids, which requires additional time and resources.

The use of expensive transition metals, as electrocatalysts or as electrode materials, as well as the use of chemical oxidizing agents, usually as excess components, lead to increased reagent waste due to the increased use of materials, some of which have to be disposed of or regenerated at great expense.

It is an object of the invention to provide a sustainable and resource-saving process which enables the production of α,ω-dicarboxylic acids and ketocarboxylic acids from cycloalkenes.

This task was solved by the subject matter of the patent claims and the description.

1. (a) Bereitstellung wenigstens eines unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkens;
2. (b) Bereitstellung wenigstens eines anorganischen oder organischen Nitratsalzes;
3. (c) elektrochemische Oxidation des in Schritt (a) bereitgestellten unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkens in Gegenwart des in Schritt (b) bereit gestellten anorganischen oder organischen Nitratsalzes in einer Elektrolysezelle in einem Reaktionsmedium in Gegenwart von Sauerstoff.

The present invention relates to a process for producing unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids by electrochemical oxidation of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkenes, comprising the process steps

1. (a) providing at least one unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene;
2. (b) providing at least one inorganic or organic nitrate salt;
3. (c) electrochemical oxidation of the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene provided in step (a) in the presence of the inorganic or organic nitrate salt provided in step (b) in an electrolysis cell in a reaction medium in the presence of oxygen.

The process according to the invention is characterized in particular by high selectivity, small amounts of auxiliary chemicals used, the use of electric current as an oxidizing agent and, associated with this, by a reduced amount of waste products.

It was surprisingly found that with the aid of the electrochemical oxidation process according to the invention, atmospheric oxygen can be used to introduce the oxygen function into cycloalkenes. The use of chemical oxidizing agents, such as reactive peroxides, and high-priced catalysts with complex ligand systems can be dispensed with. At the same time, the use of toxic and/or potentially carcinogenic substances can be reduced or even completely avoided. The method developed represents a cost-effective and environmentally friendly alternative to existing syntheses. The simple and safe process conditions allow upscaling to an industrial scale, so that larger quantities of the desired products can be produced. Through the present invention, previously cost- and time-intensive processes can be significantly optimized.

It was also surprisingly found that the process according to the invention enables the use of electric current to produce unsubstituted or at least monosubstituted α,ω-dicarboxylic acids and ketocarboxylic acids from cycloalkenes using nitrate salts, which function both as a conductive salt and as an electrochemical mediator.

It was also surprisingly found that the method according to the invention can be carried out under ambient pressure and ambient temperature, which also has an advantageous effect on energy efficiency and thus also environmental compatibility.

Unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkenes that are monocyclic or bicyclic can be used in the process according to the invention. Preferably, unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated monocyclic cycloalkenes are used, with unsubstituted or at least monosubstituted, monounsaturated monocyclic cycloalkenes being particularly preferred. The Cycloalkenes used according to the invention have endocyclic, unsaturated bonds.

The unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated monocyclic cycloalkenes used in the process according to the invention can preferably have 5 to 12 C atoms, particularly preferably 6 to 12 C atoms, very particularly preferably 8 to 12 C atoms in the ring system. These cycloalkenes can be monounsaturated or polyunsaturated, with monounsaturated cycloalkenes being preferred. These cycloalkenes can each be unsubstituted or mono- or poly-substituted. If they are substituted once or multiple times, they are preferably substituted with 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 themselves can each be unsubstituted or mono- or polysubstituted, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO ₂ .

The unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated bicyclic cycloalkenes used in the process according to the invention can preferably have 7 to 18 C atoms, particularly preferably 7 to 12 C atoms, very particularly preferably 7 to 10 C atoms in the ring system. These cycloalkenes can be monounsaturated or polyunsaturated, with monounsaturated cycloalkenes being preferred. These cycloalkenes can each be unsubstituted or mono- or poly-substituted. If they are substituted once or multiple times, they are preferably substituted with 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 themselves can each be unsubstituted or mono- or polysubstituted, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO ₂ .

Very particularly preferably, the monocyclic or bicyclic cycloalkene can be selected from the group consisting of cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cycloundecene, cyclododecene, 1-phenylcyclohex-1-ene, bicylo[2.2.1]hept-2-ene, α-pinene and carene.

mit R¹ und R², unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt, und R³ ausgewählt aus der Gruppe bestehend aus H und C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere aus der Gruppe bestehend aus H und C₁- bis C₈-Alkyl, geradkettig oder verzweigt,According to step (b) of the process according to the invention, at least one inorganic or organic nitrate salt is provided. This nitrate salt acts both as a conductive salt and as a mediator in the electrochemical oxidation process according to the invention. An inorganic or organic nitrate of the general formula is preferred

[Cation ⁺ ][NO ₃ ^- ]

for use, whereby the [cation ⁺ ] is selected from the group consisting of Na ⁺ , K ⁺ , 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 one another, each selected from the group consisting of C ₁ - to C ₁₆ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched, imidazolium cations with the general structure (I)

with R ¹ and R ² , independently of one another, each selected from the group consisting of C ₁ - to C ₁₈ alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched, and R ³ selected from Group consisting of H and C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ -alkyl, straight-chain or branched,

Pyridinium cations with the general structure (II)

mit R¹ ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₈-Alkyl, insbesondere C₁-bis C₈-Alkyl, geradkettig oder verzweigt und R², R³ und R⁴, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus H und C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere aus der Gruppe bestehend aus H und C₁- bis C₈-Alkyl, geradkettig oder verzweigt, und Phosphoniumionen mit der allgemeinen Struktur [R^1aR^2aR^3aR^4aP⁺] mit R^1a, R^2a, R^3a, R^4a, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₆-Alkyl, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt.

with R ¹ selected from the group consisting of C ₁ - to C ₁₈ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched and R ² , R ³ and R ⁴ , independently of one another, each selected from the group consisting from H and C ₁ - to C ₁₈ alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ 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 C ₁ - to C ₁₆ -alkyl, especially C ₁ - to C ₈ -alkyl, straight-chain or branched.

If an organic nitrate based on the imidazolium cations is used in the process according to the invention, preference is given to those 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 C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched and R ³ is hydrogen. Particular preference is given to imidazolium cations of the general formula (I) in which R ¹ is methyl and R ² is ethyl or R ¹ is methyl and R 2 is methyl and ^{R 1 is} methyl and R ² is butyl, as well as R ³ each represents hydrogen.

If a nitrate based on the pyridinium cations is used in the process according to the invention, preference is given to those cations of the general formula (II) in which R ¹ is C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular C ₁ - until C ₈ alkyl, straight chain or branched. Particular preference is given to pyridinium cations of the general formula (II) in which R ¹ is C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -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 C ₁ - to C ₈ alkyl, straight-chain or branched, where a single substitution in the 2-, 3- or 4-position, a double substitution in 2,4-, 2,5- or 2,6-position or a triple substitution in 2,4,6-position is preferred.

In principle, two or more of the above-mentioned nitrate salts can also be used in the process according to the invention. A nitrate salt according to the invention is preferably used, in particular an organic ammonium nitrate salt of the composition [R ¹ R ² R ³ R ⁴ N ⁺ ][NO ₃ ^- ] or an organic phosphonium salt of the composition [R ^1a R ^2a R ^3a R ^4a P ⁺ ][NO ₃ ^- ], with an organic ammonium nitrate salt of the composition [R ¹ R ² R ³ R ⁴ N ⁺ ][NO ₃ ^- ] being particularly preferred.

The organic ammonium nitrate salt tetra-n-butyl ammonium nitrate or methyl tri-n-octylammonium nitrate is very particularly preferred. The organic phosphonium nitrate salt is very particularly preferred tetra-n-butylphosphonium nitrate or methyltri-n-octylphosphonium nitrate. The organic imidazolium nitrate salt is preferably 1-butyl-3-methylimidazolium nitrate.

Tetra-n-butyl ammonium nitrate or methyl tri-n-octylammonium nitrate is most preferably used as the organic nitrate salt in the process according to the invention.

The order in which the components used in the process according to the invention are provided can vary, as can the order in which the individual components are connected to one another or to the respective reaction medium.

In one embodiment of the process according to the invention, the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene or the inorganic or organic nitrate salt is introduced and brought into contact with the reaction medium, preferably at least partially or completely dissolved in the reaction medium or mixed with it, and then the respective other of these two components are added. In a further embodiment of the process according to the invention, the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and the inorganic or organic nitrate salt are introduced and then brought together with the reaction medium, preferably at least partially or completely dissolved in the reaction medium or mixed with it. Furthermore, it is also possible in the process according to the invention for the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and the inorganic or organic nitrate salt to be added to the reaction medium simultaneously or in succession to one another, preferably at least partially or completely dissolved in the reaction medium or mixed with it.

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, mono- or polyunsaturated cycloalkene and the inorganic or organic Nitrate salt. If at least one of these components is used in liquid form, the reaction medium is preferably easily miscible with this component or these components.

A polar aprotic reaction medium is preferably used in the process according to the invention for electrochemical oxidation. This can be used in anhydrous form, in dried form or in combination with water.

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 aprotic reaction medium in combination with water being preferred. The water content in the reaction medium can vary. The water content is preferably up to 20% by volume, particularly preferably up to 15% by volume, very particularly preferably up to 10% by volume, even more preferably up to 5% by volume, in each case on the total amount of reaction medium.

The polar aprotic reaction medium is preferably selected from the group consisting of aliphatic nitriles, aliphatic ketones, cycloaliphatic ketones, dialkyl carbonates, cyclic carbonates, lactones, aliphatic nitroalkanes, and dimethyl sulfoxide, esters and ethers or a combination of at least two of these components.

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 from at least two of these components.

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.

The reaction medium is very particularly preferably acetonitrile, isobutyronitrile or adiponitrile in dried or anhydrous form.

The reaction medium is also very particularly preferred: acetonitrile, isobutyronitrile or adiponitrile, optionally in combination with water.

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

To carry out the process according to the invention, it may be advantageous to add further solubilizing components to the reaction medium. Suitable advantageous components can be determined through simple preliminary tests on solution behavior.

Suitable solubilizing components include, for example, primary alcohols, secondary alcohols, monoketones or dialkyl carbonates or mixtures of at least two of these components, possibly 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 , if necessary in combination with water.

The use of dimethyl carbonate as a reaction medium can be particularly advantageous, if necessary in combination with at least one C _1-6 alcohol, in particular selected from the group consisting of methanol, ethanol, isopropanol, 2-methyl-2-butanol, if necessary in combination with be water.

If one or more of these solubilizing components is used in combination with water, the water content is preferably up to 20% by volume, particularly preferably up to 15% by volume, very particularly preferably up to 10% by volume more preferably up to 5% by volume, based on the total amount of solubilizing component and water.

The solubilizing components can preferably be in amounts of <50% by volume, particularly preferably <30% by volume and very particularly preferably <10% % by volume are added, based on the total amount of reaction medium.

Preferably, the inorganic or 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, each based on the amount of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene used.

According to the invention, the electrochemical oxidation of the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene 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.

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

The proportion of oxygen in the gas atmosphere can vary. The proportion of oxygen in the gas atmosphere is preferably 10 to 100% by volume, particularly preferably 15 to 30% by volume, particularly preferably 15 to 25% by volume, very particularly preferably 18 to 22% by volume.

In one embodiment, the proportion of oxygen in the gas atmosphere can be 10 to 100% by volume, particularly preferably 15 to 100% by volume, particularly preferably 20 to 100% by volume.

The gas atmosphere is particularly preferably air.

A gas exchange is advantageously forced 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.

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 electrochemical oxidation.

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

The amount of oxygen dissolved in the reaction medium is also preferably at least 10 mmol/L reaction medium.

The process according to the invention for producing unsubstituted or at least monosubstituted α,ω-dicarboxylic acids and ketocarboxylic acids by electrochemical oxidation of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkenes in the presence of an inorganic or organic nitrate salt in a reaction medium in the presence of oxygen can be used both carry out in a divided as well as in an undivided electrolysis cell, with implementation in an undivided electrolysis cell being preferred.

The undivided electrolysis cell which is preferably used according to the invention has at least two electrodes. Anodes and cathodes of common materials can be used here, 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.

The distance between the electrodes can vary over a certain range. The distance is preferably 0.1 mm to 2.0 cm, particularly preferably 0.1 mm to 1.0 cm, particularly preferably 0.1 mm to 0.5 cm.

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

The method according to the invention is preferably carried out with a charge quantity of at least 190 C (2 F) to 970 C (10 F), preferably 290 C (3 F) to 870 C (9 F), particularly preferably 330 C (3.5 F) to 820 C (8.5 F), very particularly preferably 380 C (4 F) to 775 C (8 F), most preferably 380 C (4 F) to 580 C (6 F), each for 1 mmol of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene.

The electrochemical oxidation in the process according to the invention preferably takes place at constant current intensity.

The current density at which the method 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 to 50 mA/ cm ² , whereby the area refers to the geometric area of the electrodes.

A significant advantage of the method 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, i.e. in particular from biomass, solar thermal energy, geothermal energy, hydropower, wind power or photovoltaics.

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, particularly preferably 10 to 40 °C, very particularly preferably 15 to 30 °C.

The process according to the invention can be carried out at increased 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.

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

The products produced by the process according to the invention can be isolated or purified by conventional processes known to those skilled in the art, in particular by extraction, crystallization, centrifugation, precipitation, distillation, evaporation or chromatography.

• Ausführungsform 1: Verfahren zur Herstellung von unsubstituierten oder wenigstens einfach substituierten α,ω-Dicarbonsäuren oder Ketocarbonsäuren durch elektrochemische Oxidation von unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkenen umfassend die Verfahrensschritte
  1. (a) Bereitstellung wenigstens eines unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkens;
  2. (b) Bereitstellung wenigstens eines anorganischen oder organischen Nitratsalzes;
  3. (c) elektrochemische Oxidation des in Schritt (a) bereitgestellten unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkens in Gegenwart des in Schritt (b) bereit gestellten anorganischen oder organischen Nitratsalzes in einer Elektrolysezelle in einem Reaktionsmedium in Gegenwart von Sauerstoff.
• Ausführungsform 2: Verfahren nach Ausführungsform 1, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte Cycloalken monocyclisch oder polycyclisch ist, vorzugweise monocyclisch ist.
• Ausführungsform 3: Verfahren nach Ausführungsform 2, wobei das unsubstituierte oder wenigstens einfach substituierte Cycloalken einfach ungesättigt ist, vorzugsweise einfach ungesättigt und monocyclisch ist.
• Ausführungsform 4: Verfahren nach einer der vorhergehenden Ausführungsformen 2 oder 3, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte monocyclische Cycloalken 5 bis 12 C Atome, besonders bevorzugt 6 bis 12 C Atome, ganz besonders bevorzugt 8 bis 12 C Atome im Ringsystem aufweist und unsubstituiert oder einfach oder mehrfach, vorzugsweise mit 1, 2, 3, 4 oder 5 Substituenten, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus Methyl Phenyl oder Benzyl substituiert ist, wobei die Phenyl- bzw. Benzyl-substituenten selbst jeweils unsubstituiert oder einfach oder mehrfach substituiert sind, mit 1, 2 oder 3 Substituenten, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus F, Cl, Br, und NO₂.
• Ausführungsform 5: Verfahren nach einer der vorhergehenden Ausführungsformen 2 oder 3, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte bicyclische Cycloalken 7 bis 18 C Atome, besonders bevorzugt 7 bis 12 C Atome, ganz besonders bevorzugt 7 bis 10 C Atome im Ringsystem aufweist und unsubstituiert oder einfach oder mehrfach, vorzugsweise mit 1, 2, 3, 4 oder 5 Substituenten, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus Methyl Phenyl oder Benzyl substituiert sind, wobei die Phenyl- bzw. Benzyl-substituenten selbst jeweils unsubstituiert oder einfach oder mehrfach substituiert sind, mit 1, 2 oder 3 Substituenten, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus F, Cl, Br, und NO₂.
• Ausführungsform 6: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das Cycloalken ausgewählt ist aus der Gruppe bestehend aus Cyclohexen, Cyclohepten, Cycloocten, Cyclononen, Cyclodecen, Cycloundecen, Cyclododecen, 1-Phenylcyclohex-1-en, Bicylo[2.2.1]hept-2-en, α-Pinen und Caren.
• Ausführungsform 7: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei als anorganisches oder organisches Nitratsalz ein Nitrat der allgemeinen Formel [Kation⁺][NO₃ ^-] vorliegt, mit [Kation⁺] ausgewählt aus der Gruppe bestehend aus Na⁺, K⁺, Ammoniumionen mit der allgemeinen Struktur [R¹R²R³R⁴N⁺] mit R¹, R², R³, R⁴, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₆-Alkyl, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt, Imidazolium-Kationen mit der allgemeinen Struktur (I)
  
  mit R¹ und R², unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt, und R³ ausgewählt aus der Gruppe bestehend aus H und C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere aus der Gruppe bestehend aus H und C₁- bis C₈-Alkyl, geradkettig oder verzweigt,
  Pyridinium-Kationen mit der allgemeinen Struktur (II)
  
  mit R¹ ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₈-Alkyl, insbesondere C₁-bis C₈-Alkyl, geradkettig oder verzweigt und R², R³ und R⁴, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus H und C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere aus der Gruppe bestehend aus H und C₁- bis C₈-Alkyl, geradkettig oder verzweigt, und Phosphoniumionen mit der allgemeinen Struktur [R^1aR^2aR^3aR^4aP⁺] mit R^1a, R^2a, R^3a, R^4a, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₆-Alkyl, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt.
• Ausführungsform 8: Verfahren nach Ausführungsform 7, wobei in den Imidazolium-Kationen der allgemeinen Formel (I) die Reste R¹ und R², unabhängig voneinander, jeweils ausgewählt sind aus der Gruppe bestehend aus C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt und R³ für Wasserstoff steht, vorzugsweise R¹ für Methyl und R² für Ethyl stehen oder R¹ für Methyl und R² für Methyl stehen und R¹ für Methyl und R² für Butyl stehen, sowie R³ jeweils für Wasserstoff steht.
• Ausführungsform 9: Verfahren nach Ausführungsform 7 oder 8, wobei in den Pyridinium-Kationen der allgemeinen Formel (II) der Rest R¹ für C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere für C₁- bis C₈-Alkyl, geradkettig oder verzweigt steht und die Reste R², R³ und R⁴, unabhängig voneinander, jeweils ausgewählt sind aus der Gruppe bestehend aus C₁- bis C₈-Alkyl, geradkettig oder verzweigt, wobei eine einfache Substitution in 2-, 3- oder 4-Position, eine zweifache Substitution in 2,4-, 2,5- oder 2,6-Position oder eine dreifache Substitution in 2,4,6-Position bevorzugt ist.
• Ausführungsform 10: Verfahren nach einer der Ausführungsform 7 bis 9, wobei das organische Nitratsalz ausgewählt ist aus der Gruppe bestehend aus Tetra-n-butyl-ammonium-nitrat, Methyl-tri-n-octyl-ammonium-nitrat, Tetra-n-butyl-phosphonium-nitrat, Methyl-tri-n-octyl-phosphonium-nitrat und 1-Butyl-3-methylimidazoliumnitrat.
• Ausführungsform 11: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte Cycloalken oder das anorganische oder organische Nitratsalz vorgelegt und mit dem Reaktionsmedium zusammengebracht wird, vorzugsweise in dem Reaktionsmedium zumindest teilweise oder vollständig gelöst oder damit gemischt wird, und dann die jeweils andere dieser beiden Komponenten dazugegeben wird.
• Ausführungsform 12: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte Cycloalken und das anorganische oder organische Nitratsalz vorgelegt und dann mit dem Reaktionsmedium zusammengebracht werden, vorzugsweise in dem Reaktionsmedium zumindest teilweise oder vollständig gelöst oder damit gemischt werden.
• Ausführungsform 13: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte Cycloalken und das anorganische oder organische Nitratsalz gleichzeitig oder in zeitlicher Abfolge zueinander in das Reaktionsmedium gegeben werden, vorzugsweise in dem Reaktionsmedium zumindest teilweise oder vollständig gelöst oder damit gemischt werden.
• Ausführungsform 14: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das Reaktionsmedium ein polares aprotisches Reaktionsmedium ist, welches wasserfrei, getrocknet oder in Kombination mit Wasser vorliegen kann.
• Ausführungsform 15: Verfahren nach Ausführungsform 14, wobei der Gehalt an Wasser bis zu 20 Vol.-%, vorzugsweise bis zu 15 Vol.-%, besonders bevorzugt bis zu 10 Vol.-%, ganz besonders bevorzugt bis zu 5 Vol.-%, beträgt, jeweils bezogen auf die Gesamtmenge an Reaktionsmedium.
• Ausführungsform 16: Verfahren nach Ausführungsform 14 oder 15, wobei das polare aprotische Reaktionsmedium ausgewählt ist aus der Gruppe bestehend aus aliphatischen Nitrilen, aliphatischen Ketonen, cycloaliphatischen Ketonen, Dialkylcarbonaten, cyclischen Carbonaten, Lactonen, aliphatischen Nitroalkanen, und Dimethylsulfoxid, Estern und Ethern oder einer Kombination aus wenigstens zwei dieser Komponenten.
• Ausführungsform 17: Verfahren nach Ausführungsform 16, wobei als Reaktionsmedium ein polares aprotisches Reaktionsmedium vorliegt, welches ausgewählt ist aus der Gruppe bestehend aus Acetonitril, Isobutyronitril, Adiponitril, Aceton, Dimethylcarbonat, Methylethylketon, 3-Pentanon, Cyclohexanon, Nitromethan, Nitropropan, tert.-Butylmethylether, Dimethylsulfoxid, gamma-Butyrolacton und epsilon-Caprolacton oder einer Kombination aus wenigstens zwei dieser Komponenten, jeweils ggf. in Kombination mit Wasser.
• Ausführungsform 18: Verfahren nach Ausführungsform 17, wobei ein Reaktionsmedium ausgewählt aus der Gruppe bestehend aus Acetonitril, Isobutyronitril, Adiponitril, Dimethylcarbonat und Aceton oder einer Kombination aus wenigstens zwei dieser Komponenten, ggf. in Kombination mit Wasser, vorliegt.
• Ausführungsform 19: Verfahren nach Ausführungsform 17 oder 18. wobei das Reaktionsmedium Acetonitril, Isobutyronitril oder Adiponitril in getrockneter oder wasserfreier Form ist.
• Ausführungsform 20: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das Reaktionsmedium eine oder mehrere lösungsvermittelnde Komponenten aufweist.
• Ausführungsform 21: Verfahren gemäß Ausführungsform 20, wobei als lösungsvermittelnde Komponenten primäre Alkohole, sekundäre Alkohole, Monoketone oder Dialkylcarbonate oder Mischungen aus wenigstens zwei dieser Komponenten vorliegen, ggf. in Kombination mit Wasser.
• Ausführungsform 22: Verfahren gemäß Ausführungsform 20 oder 21, wobei aliphatische C_1-6-Alkohole als eine oder mehrere lösungsvermittelnde Komponenten vorliegen, vorzugsweise einer oder mehrere Alkohole ausgewählt aus der Gruppe bestehend aus Methanol, Ethanol, Isopropanol, 2-Methyl-2-Butanol und Mischungen aus wenigstens zwei dieser Komponenten, ggf. in Kombination mit Wasser. Ausführungsform 23: Verfahren gemäß einer der vorhergehenden Ausführungsformen, wobei als Reaktionsmedium Dimethylcarbonat, ggf. in Kombination mit wenigstens einem C_1-6-Alkohol, vorzugsweise ausgewählt aus der Gruppe bestehend aus Methanol, Ethanol, Isopropanol, 2-Methyl-2-Butanol vorliegt.
• Ausführungsform 24: Verfahren gemäß Ausführungsform 23, wobei das Reaktionsmedium Wasser aufweist.
• Ausführungsform 25: Verfahren gemäß einer der Ausführungsformen 20 bis 24, wobei eine oder mehrere lösungsvermittelnde Komponenten in einer Menge von < 50 Vol.-%, besonders bevorzugt von < 30 Vol.-% und ganz besonders bevorzugt von < 10 Vol.-% zugegeben werden, jeweils bezogen auf die Gesamtmenge an Reaktionsmedium vorliegen.
• Ausführungsform 26: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das anorganische oder organische Nitratsalz in einer Menge von 0,1 bis 2,0, vorzugsweise 0,2 bis 1,0, besonders bevorzugt 0,3 bis 0,8 und ganz besonders bevorzugt 0,4 bis 0.8 Äquivalenten, jeweils bezogen auf die Menge an eingesetztem unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalken.
• Ausführungsform 27: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei in räumlicher Verbindung mit dem Reaktionsmedium eine Gasatmosphäre enthaltend Sauerstoff bereitgestellt wird.
• Ausführungsform 28: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der Anteil von Sauerstoff an der Gasatmosphäre 10 bis 100 Vol.-%, vorzugsweise 15 bis 30 Vol.-%, besonders bevorzugt 15 bis 25 Vol.-%, ganz besonders bevorzugt 18 bis 22 Vol.-%, beträgt.
• Ausführungsform 29: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der Anteil von Sauerstoff an der Gasatmosphäre 10 bis 100 Vol.-% besonders bevorzugt 15 bis 100 Vol.-%, besonders bevorzugt 20 bis 100 Vol.-% beträgt.
• Ausführungsform 30: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die Gasatmosphäre Luft ist.
• Ausführungsform 31: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei zwischen der Gasatmosphäre und dem Reaktionsmedium ein Gasaustausch erzwungen wird.
• Ausführungsform 32: Verfahren nach Ausführungsform 31, wobei der Gasaustausch durch das Einleiten von Gasatmosphäre in das Reaktionsmedium erfolgt.
• Ausführungsform 33: Verfahren nach Ausführungsform 31 oder 32, wobei der Gasaustausch durch Rühren der flüssigen Phase in Gegenwart der Gasatmosphäre erfolgt.
• Ausführungsform 34: Verfahren nach Ausführungsform 33, wobei das Rühren zur Steuerung der elektrochemischen Oxidation verwendet wird.
• Ausführungsform 35: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die im Reaktionsmedium gelöste Menge an Sauerstoff mindestens 1 mmol/L Reaktionsmedium beträgt.
• Ausführungsform 36: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die im Reaktionsmedium gelöste Menge an Sauerstoff mindestens 5 mmol/L Reaktionsmedium beträgt.
• Ausführungsform 37: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die Elektrolysezelle eine ungeteilte Elektrolysezelle ist.
• Ausführungsform 38: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die ungeteilte Elektrolysezelle eine Glaskohlenstoff-Anode, eine Graphit-Anode oder eine BDD-Anode, vorzugsweise eine Glaskohlenstoff-Anode aufweist.
• Ausführungsform 39: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die ungeteilte Elektrolysezelle eine Glaskohlenstoff-Kathode, eine Graphit-Kathode oder eine BDD-Kathode, vorzugsweise eine Glaskohlenstoff-Kathode aufweist.
• Ausführungsform 40:
  Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der Abstand der Elektroden in der Elektrolysezelle 0,1 mm bis 2,0 cm, vorzugsweise 0,1 mm bis 1,0 cm, besonders bevorzugt 0,1 mm bis 0,5 cm beträgt.
• Ausführungsform 41: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die Ladungsmenge mindestens 190 C (2 F) bis 970 C (10 F), vorzugsweise 290 C (3 F) bis 870 C (9 F), besonders bevorzugt 330 C (3,5 F) bis 820 C (8,5 F), ganz besonders bevorzugt 380 C (4 F) bis 775 C (8 F), am meisten bevorzugt 380 C (4 F) bis 580 C (6 F), jeweils für 1 mmol an unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigtem Cycloalken.
• Ausführungsform 42: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die elektrochemische Oxidation bei konstanter Stromstärke erfolgt.
• Ausführungsform 43: Verfahren nach einer der vorhergehenden Ausführungsformen, dadurch gekennzeichnet, dass die Stromdichte wenigstens 5 mA/cm² beträgt, wobei sich die Flächenangabe auf die geometrische Fläche der Elektroden bezieht.
• Ausführungsform 44: Verfahren nach einer der vorhergehenden Ausführungsformen, dadurch gekennzeichnet, dass die Stromdichte wenigstens 10 mA/cm² beträgt, wobei sich die Flächenangabe auf die geometrische Fläche der Elektroden bezieht.
• Ausführungsform 45: Verfahren nach einer der vorhergehenden Ausführungsformen, dadurch gekennzeichnet, dass die Stromdichte wenigstens 15 mA/cm² beträgt, wobei sich die Flächenangabe auf die geometrische Fläche der Elektroden bezieht.
• Ausführungsform 46: Verfahren nach einer der vorhergehenden Ausführungsformen, dadurch gekennzeichnet, dass die Stromdichte wenigstens 20 mA/cm² beträgt, wobei sich die Flächenangabe auf die geometrische Fläche der Elektroden bezieht.
• Ausführungsform 47: Verfahren nach einer der vorhergehenden Ausführungsformen, dadurch gekennzeichnet, dass die Stromdichte wenigstens 20 mA/cm² bis 50 mA/cm² beträgt, wobei sich die Flächenangabe auf die geometrische Fläche der Elektroden bezieht.
• Ausführungsform 48: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der zur elektrochemischen Oxidation eingesetzte Strom aus regenerativen Quellen stammt, insbesondere aus Biomasse, Solarthermie, Geothermie, Wasserkraft, Windkraft oder Photovoltaik.
• Ausführungsform 49: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die elektrochemische Oxidation bei einer Temperatur im Bereich von 0 bis 60 °C, vorzugsweise von 5 bis 50 °C, besonders bevorzugt von 10 bis 40°C, ganz besonders bevorzugt von 15-30°C erfolgt.
• Ausführungsform 50: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei es unter Atmosphärendruck durchgeführt wird.
• Ausführungsform 51: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei es unter Unterdruck durchgeführt wird.
• Ausführungsform 52: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei es unter Überdruck, vorzugsweise bis zu 16 bar, besonders bevorzugt bis zu 6 bar durchgeführt wird.
• Ausführungsform 53: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei es Batch-weise durchgeführt wird.
• Ausführungsform 54: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei es kontinuierlich durchgeführt wird, vorzugsweise in einer ungeteilten Durchfluss-Elektrolysezelle.
• Ausführungsform 55: Verfahren nach einem der vorhergehenden Ausführungsformen, wobei es ohne den Zusatz von Katalysatoren, insbesondere ohne den Zusatz von Übergangsmetallkatalysatoren durchgeführt wird.
• Ausführungsform 56: Verfahren nach einem der vorhergehenden Ausführungsform, wobei neben Sauerstoff oder Luftsauerstoff keine weiteren Oxidationsmittel zugesetzt werden.

Further preferred embodiments of the present invention are the following embodiments:

• Embodiment 1: Process for the production of unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids by electrochemical oxidation of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkenes comprising the process steps
  1. (a) providing at least one unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene;
  2. (b) providing at least one inorganic or organic nitrate salt;
  3. (c) electrochemical oxidation of the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene provided in step (a) in the presence of the inorganic or organic nitrate salt provided in step (b) in an electrolysis cell in a reaction medium in the presence of oxygen.
• Embodiment 2: Process according to Embodiment 1, wherein the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene is monocyclic or polycyclic, preferably monocyclic.
• Embodiment 3: Process according to Embodiment 2, wherein the unsubstituted or at least monosubstituted cycloalkene is monounsaturated, preferably monounsaturated and monocyclic.
• Embodiment 4: Process according to one of the preceding embodiments 2 or 3, wherein the unsubstituted or at least monosubstituted, mono or polyunsaturated monocyclic cycloalkene contains 5 to 12 C atoms, particularly preferably 6 to 12 C atoms, very particularly preferably 8 to 12 C atoms Ring system and is unsubstituted or substituted once or multiple times, preferably with 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 themselves being each are unsubstituted or mono or polysubstituted, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO ₂ .
• Embodiment 5: Method according to one of the preceding embodiments 2 or 3, wherein the unsubstituted or at least monosubstituted, simple or polyunsaturated bicyclic cycloalkene has 7 to 18 C atoms, particularly preferably 7 to 12 C atoms, very particularly preferably 7 to 10 C atoms in the ring system and is unsubstituted or mono or multiple, preferably with 1, 2, 3, 4 or 5 substituents, independently each other, each selected from the group consisting of methyl phenyl or benzyl, the phenyl or benzyl substituents themselves being unsubstituted or mono- or polysubstituted, with 1, 2 or 3 substituents, independently of one another, each selected from the Group consisting of F, Cl, Br, and NO ₂ .
• Embodiment 6: Process according to one of the preceding embodiments, wherein the cycloalkene is selected from the group consisting of cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cycloundecene, cyclododecene, 1-phenylcyclohex-1-ene, bicylo[2.2.1]hept- 2-ene, α-pinene and carene.
• Embodiment 7: Method according to one of the preceding embodiments, wherein the inorganic or organic nitrate salt is a nitrate of the general formula [cation ⁺ ][NO ₃ ^- ], with [cation ⁺ ] selected from the group consisting of Na ⁺ , K ⁺ , 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 one another, each selected from the group consisting of C ₁ - to C ₁₆ -alkyl, in particular C ₁ - to C ₈ alkyl, straight chain or branched, imidazolium cations with the general structure (I)
  
  with R ¹ and R ² , independently of one another, each selected from the group consisting of C ₁ - to C ₁₈ alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched, and R ³ selected from Group consisting of H and C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ -alkyl, straight-chain or branched,
  Pyridinium cations with the general structure (II)
  
  with R ¹ selected from the group consisting of C ₁ - to C ₁₈ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched and R ² , R ³ and R ⁴ , independently of one another, each selected from the group consisting from H and C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ -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 C ₁ - to C ₁₆ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched .
• Embodiment 8: Process according to Embodiment 7, wherein in the imidazolium cations of the general formula (I), the radicals R ¹ and R ² , independently of one another, are each selected from the group consisting of C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular C ₁ - to C ₈ alkyl, straight-chain or branched and R ³ is hydrogen, preferably R ¹ is methyl and R ² is ethyl or R 1 is methyl and R ² is methyl and R ^{1 is} methyl and R ² represents butyl and R ³ each represents hydrogen.
• Embodiment 9: Process according to embodiment 7 or 8, wherein in the pyridinium cations of the general formula (II) the radical R ¹ is C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -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 C ₁ - to C ₈ -alkyl, straight-chain or branched, with a simple substitution in 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.
• Embodiment 10: Method according to one of embodiments 7 to 9, wherein the organic nitrate salt is selected from the group consisting of tetra-n-butyl ammonium nitrate, methyl tri- n -octyl ammonium nitrate, tetra-n-butyl -phosphonium nitrate, methyl tri-n-octyl phosphonium nitrate and 1-butyl-3-methylimidazolium nitrate.
• Embodiment 11: Process according to one of the preceding embodiments, wherein the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene or the inorganic or organic nitrate salt is initially introduced and is brought together with the reaction medium, preferably at least partially or completely dissolved in the reaction medium or mixed with it, and then the other of these two components is added.
• Embodiment 12: Process according to one of the preceding embodiments, wherein the unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene and the inorganic or organic nitrate salt are introduced and then brought together with the reaction medium, preferably at least partially or completely dissolved in the reaction medium or mixed with it become.
• Embodiment 13: Process according to one of the preceding embodiments, wherein the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and the inorganic or organic nitrate salt are added to the reaction medium simultaneously or in succession to one another, preferably at least partially or completely dissolved in the reaction medium or mixed with it.
• Embodiment 14: Method according to one of the preceding embodiments, wherein the reaction medium is a polar aprotic reaction medium, which can be anhydrous, dried or in combination with water.
• Embodiment 15: Process according to embodiment 14, wherein the water content is up to 20% by volume, preferably up to 15% by volume, particularly preferably up to 10% by volume, very particularly preferably up to 5% by volume. , is based on the total amount of reaction medium.
• Embodiment 16: Process according to Embodiment 14 or 15, wherein 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, and dimethyl sulfoxide, esters and ethers or a combination from at least two of these components.
• Embodiment 17: Process according to Embodiment 16, wherein the reaction medium is a polar aprotic reaction medium which 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, gamma-butyrolactone and epsilon-caprolactone or a combination of at least two of these components, each optionally in combination with water.
• Embodiment 18: Process according to Embodiment 17, 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.
• Embodiment 19: Process according to Embodiment 17 or 18, wherein the reaction medium is acetonitrile, isobutyronitrile or adiponitrile in dried or anhydrous form.
• Embodiment 20: Method according to one of the preceding embodiments, wherein the reaction medium has one or more solubilizing components.
• Embodiment 21: Process according to Embodiment 20, 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.
• Embodiment 22: Method according to embodiment 20 or 21, wherein aliphatic C _1-6 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, possibly in combination with water. Embodiment 23: Process according to one of the preceding embodiments, wherein the reaction medium is dimethyl carbonate, optionally in combination with at least one C _1-6 alcohol, preferably selected from the group consisting of methanol, ethanol, isopropanol, 2-methyl-2-butanol .
• Embodiment 24: Method according to Embodiment 23, wherein the reaction medium comprises water.
• Embodiment 25: Method according to one of embodiments 20 to 24, wherein one or more solubilizing components are added in an amount of <50% by volume, particularly preferably <30% by volume and most preferably <10% by volume are present, based on the total amount of reaction medium.
• Embodiment 26: Method according to one of the preceding embodiments, wherein the inorganic or organic nitrate salt is 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, each based on the amount of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene used.
• Embodiment 27: Method according to one of the preceding embodiments, wherein a gas atmosphere containing oxygen is provided in spatial connection with the reaction medium.
• Embodiment 28: Method according to one of the preceding embodiments, wherein the proportion of oxygen in the gas atmosphere is 10 to 100 vol.%, preferably 15 to 30 vol.%, particularly preferably 15 to 25 vol.%, very particularly preferably 18 to 22% by volume.
• Embodiment 29: Method according to one of the preceding embodiments, wherein the proportion of oxygen in the gas atmosphere is 10 to 100% by volume, particularly preferably 15 to 100% by volume, particularly preferably 20 to 100% by volume.
• Embodiment 30: Method according to one of the preceding embodiments, wherein the gas atmosphere is air.
• Embodiment 31: Method according to one of the preceding embodiments, wherein a gas exchange is forced between the gas atmosphere and the reaction medium.
• Embodiment 32: Method according to Embodiment 31, wherein the gas exchange takes place by introducing a gas atmosphere into the reaction medium.
• Embodiment 33: Method according to embodiment 31 or 32, wherein the gas exchange takes place by stirring the liquid phase in the presence of the gas atmosphere.
• Embodiment 34: The method according to Embodiment 33, wherein stirring is used to control electrochemical oxidation.
• Embodiment 35: Method according to one of the preceding embodiments, wherein the amount of oxygen dissolved in the reaction medium is at least 1 mmol/L reaction medium.
• Embodiment 36: Method according to one of the preceding embodiments, wherein the amount of oxygen dissolved in the reaction medium is at least 5 mmol/L reaction medium.
• Embodiment 37: Method according to one of the preceding embodiments, wherein the electrolytic cell is an undivided electrolytic cell.
• Embodiment 38: Method according to one of the preceding embodiments, wherein the undivided electrolysis cell has a glassy carbon anode, a graphite anode or a BDD anode, preferably a glassy carbon anode.
• Embodiment 39: Method according to one of the preceding embodiments, wherein the undivided electrolysis cell is a glassy carbon cathode, a graphite cathode or a BDD cathode, preferably a glassy carbon cathode.
• Embodiment 40:
  Method according to one of the preceding embodiments, 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.
• Embodiment 41: Method according to one of the preceding embodiments, wherein the amount of charge is at least 190 C (2 F) to 970 C (10 F), preferably 290 C (3 F) to 870 C (9 F), particularly preferably 330 C (3. 5 F) to 820 C (8.5 F), most preferably 380 C (4 F) to 775 C (8 F), most preferably 380 C (4 F) to 580 C (6 F), each for 1 mmol of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene.
• Embodiment 42: Method according to one of the preceding embodiments, wherein the electrochemical oxidation takes place at constant current intensity.
• Embodiment 43: Method according to one of the preceding embodiments, characterized in that the current density is at least 5 mA/cm ² , the area information referring to the geometric area of the electrodes.
• Embodiment 44: Method according to one of the preceding embodiments, characterized in that the current density is at least 10 mA/cm ² , the area information relating to the geometric area of the electrodes.
• Embodiment 45: Method according to one of the preceding embodiments, characterized in that the current density is at least 15 mA/cm ² , the area information relating to the geometric area of the electrodes.
• Embodiment 46: Method according to one of the preceding embodiments, characterized in that the current density is at least 20 mA/cm ² , the area information relating to the geometric area of the electrodes.
• Embodiment 47: Method according to one of the preceding embodiments, characterized in that the current density is at least 20 mA/cm ² to 50 mA/cm ² , the area information relating to the geometric area of the electrodes.
• Embodiment 48: Method according to one of the preceding embodiments, wherein the electricity used for electrochemical oxidation comes from renewable sources, in particular from biomass, solar thermal energy, geothermal energy, hydropower, wind power or photovoltaics.
• Embodiment 49: Method according to one of the preceding embodiments, wherein the electrochemical oxidation takes place at a temperature in the range from 0 to 60 ° C, preferably from 5 to 50 ° C, particularly preferably from 10 to 40 ° C, very particularly preferably from 15-30 ° C.
• Embodiment 50: Method according to one of the preceding embodiments, wherein it is carried out under atmospheric pressure.
• Embodiment 51: Method according to one of the preceding embodiments, wherein it is carried out under negative pressure.
• Embodiment 52: Method according to one of the preceding embodiments, wherein it is carried out under excess pressure, preferably up to 16 bar, particularly preferably up to 6 bar.
• Embodiment 53: Method according to one of the preceding embodiments, wherein it is carried out in batches.
• Embodiment 54: Method according to one of the preceding embodiments, wherein it is carried out continuously, preferably in an undivided flow electrolysis cell.
• Embodiment 55: Process according to one of the preceding embodiments, wherein it is carried out without the addition of catalysts, in particular without the addition of transition metal catalysts.
• Embodiment 56: Method according to one of the preceding embodiments, wherein no further oxidizing agents are added in addition to oxygen or atmospheric oxygen.

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

General information and methods

Analytical grade chemicals were purchased and used from mainstream suppliers (such as TCI, Aldrich, and Acros). The oxygen was purchased in 2.5 quality from NIPPON GASES Deutschland GmbH, Düsseldorf, Germany and used directly.

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

High performance liquid chromatography was performed on a Shimadzu HPLC-MS with a SIL 20A HT autosampler, a CTO-20AC column oven, two LC-20AD Pump modules for gradient adjustment of the eluent, a diode array detector SPD-M20A, 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 100% ACN). Mass spectrometric measurements were carried out on an LCMS-2020 Shimadzu, Japan.

NMR spectrometry of 1H-NMR and 13C-NMR spectra were recorded at 25 °C with a Bruker Avance II 400 (400 MHz, 5 mm BBFO head with z-gradient and ATM, SampleXPress 60 sample changer, Analytische Messtechnik, Karlsruhe, Germany) recorded.

Gas introduction for AAV1/AAV2/AAV3:

The gas introduction was controlled via two mass flow controllers (MFC) model 5850S from Brooks Instrument B.V., Veenendaal, Netherlands. A regulator was used for the oxygen and nitrogen lines. The controllers were controlled using the Smart DDE and Matlab R2017b software. The volume flow control was also carried out using a DK800 variable area flowmeter from KROHNE Messtechnik GmbH, Duisburg. For all experiments carried out, the total volume flow was a constant 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 set using the MFCs and their software. The gas bottles were used from the following suppliers: oxygen 2.5 from NIPPON GASES Deutschland GmbH, Düsseldorf, and nitrogen 4.8 from Westfalen AG, Münster and nitrogen 5.0 from NIPPON GASES Deutschland GmbH, Düsseldorf. For this purpose, the apparatus was equipped with a gas distributor including an adapter and a Teflon cover for the electrolytic cells.

General working instructions AAV1

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 SI).) The complete range of these cells with stainless steel block is also commercially available as the IKA Screening System (IKA-Werke GmbH & Co. KG, Staufen, Germany). The dimensions of the electrodes were 7 cm x 1 cm x 0.3 cm.

The cycloalkene (1.0 mmol) and tetrabutylammonium nitrate (0.5 eq.) were placed in an undivided 5 mL Teflon pot cell and dissolved in acetonitrile (5 mL). The cell was equipped with glassy carbon electrodes at a distance of 0.5 cm. The immersion area of the electrodes was 1.8 cm ² . After the cell was fixed in a stainless steel block, galvanostatic electrolysis was performed at a current density of 10 mA/cm ² at 5 °C.

After applying a charge amount of 4 to 8 F to the cycloalkene, the solvent was first removed by distillation. The conductive salt was then removed extractively using 10 mL ethyl acetate and 10 mL water. The organic phase was mixed with an aqueous NaOH solution. (1 M, 10 mL). The aqueous phase was then mixed with an aqueous HCl solution. (1 M) adjusted to pH 1 and extracted from this with 2 x 10 mL ethyl acetate. After drying the organic phase over calcium chloride and removing the solvent by distillation, the product obtained was dried under high vacuum. If there are deviations from this AAV1, for example with regard to the solvent, this can be seen in the following examples.

General working instructions AAV2

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 SI).) The complete range of these cells with stainless steel block is also commercially available as the IKA Screening System (IKA-Werke GmbH & Co. KG, Staufen, Germany). The dimensions of the electrodes were 7 cm x 1 cm x 0.3 cm.

The cycloalkene (0.1-1.0 mmol) and tetrabutylammonium nitrate (0.5-2.0 eq.) were placed in an undivided 5 mL Teflon pot cell and dissolved in acetonitrile (5 mL) or isobutyronitrile (5 mL). The cell was equipped with glassy carbon electrodes at a distance of 0.5 cm. The immersion area of the electrodes was 1.8 cm ² . After the cell was fixed in a stainless steel block, galvanostatic electrolysis was carried out at a current density of 5-10 mA/cm ² at 5-50 °C.

After applying a charge amount of 4 to 8 F to the cycloalkene, the solvent was first removed by distillation. The conductive salt was then prepared using 10 mL of ethyl acetate and 10 mL of an aqueous HCl solution. (0.1 M) removed extractively. The solvent of the organic phase is removed by distillation and the residue is mixed with an aqueous NaOH solution. (1 M, 10 mL) and washed with 10 mL diethyl ether or 10 mL n-pentane. The aqueous phase was then adjusted dropwise to pH 1 with concentrated aqueous HCl solution and extracted from this with 2 × 10 mL ethyl acetate. After drying the organic phase over magnesium sulfate and removing the solvent by distillation, the product obtained was dried under high vacuum. If there are deviations from this AAV1, for example with regard to the solvent, this can be seen in the following examples.

General working instructions AAV3

The electrolysis was carried out in an undivided flow cell (IKA, electrode area: 2 cm x 6 cm). For this purpose, the cycloalkene (0.5-5 mmol) and the conductive salt (0.4 to 1.0 eq.) are dissolved in the solvent (5-10 mL) in a reservoir (20 mL snap-top glass). The temperature of the reservoir was 20-50 °C. The reaction solution was transported using a peristatic pump at a flow rate of 5-18 mL/min into a Y-piece or T-piece, into which oxygen gas (100 vol.%) was added at a flow rate of 10-20 mL/min became. This segmented flow was carried further into the cell (electrode distance: 0.05 cm). After flowing through the cell, the reaction solution was returned to the reservoir, where it was sucked in again. The electrolysis was carried out with a constant current intensity (5-20 mA/cm ² ) and a charge amount of 2-4 F based on the substrate. After electrolysis, 1,3,5-trimethoxybenzene was added to the reaction solution as a GC standard (previously: external calibration of the substrate to be analyzed). 3 drops of the reaction solution were eluted using ethyl acetate over approx. 330 mg of 60 M silica gel. Approximately 1.5 mL of the filtrate was collected in a GC vial, which was examined for remaining educt residues using GC-FID. The yield of the dicarboxylic acid was determined via extractive isolation: the solvent in the organic phase was removed by distillation and the residue was washed with an aqueous NaOH solution. (1 M, 10 mL) and washed with 10 mL diethyl ether or 10 mL n-pentane. The aqueous phase was then adjusted dropwise to pH 1 with concentrated aqueous HCl solution and from this with 2 x 10 mL Ethyl acetate extracted. After drying the organic phase over magnesium sulfate and removing the solvent by distillation, the product obtained was dried under high vacuum

Example 1: Preparation of 1,6-hexanedioic acid

According to AAV1, cyclohexene (0.082 g, 1.0 mmol, 1.0 eq.) was electrolyzed galvanostatically under an oxygen atmosphere (100%) and application of 8 F. After removing the solvent by distillation and drying in a high vacuum, the product was obtained as a colorless solid (yield: 16%, 0.023 g, 0.16 mmol). ¹ H-NMR (400 MHz, DMSO-d6) δ [ppm] = 12.00 (s, 2H); 2.22-2.18 (m, 4H); 1.51-1.47 (m, 4H). The analytical data agree with the literature values.

Example 2: Production of 1,8-octanedioic acid

According to AAV1, cyclooctene (0.110 g, 1.0 mmol, 1.0 eq.) was electrolyzed galvanostatically under an oxygen atmosphere (100%) and application of 4 F. After removing the solvent by distillation and drying in a high vacuum, the product was obtained as a colorless solid (yield: 47%, 0.082 g, 0.47 mmol). ¹ H-NMR (400 MHz, DMSO-d6) δ [ppm] = 11.98 (s, 2H); 2.18 (t, J = 7.4 Hz, 4H); 1.49-1.46 (m, 4H); 1.27-1.24 (m, 4H). The analytical data agree with the literature values.

Example 3: Preparation of 1,12-dodecanedioic acid

According to AAV1, cyclododecene (0.166 g, 1.0 mmol, 1.0 eq.) was electrolyzed galvanostatically under an oxygen atmosphere (100%) and application of 8 F. Isobutyronitrile (5 mL) was used as solvent. After removing the solvent by distillation and drying in a high vacuum, the product was obtained as a colorless solid (yield: 53%, 0.121 g, 0.53 mmol). ¹ H-NMR (400 MHz, DMSO-d6) δ [ppm] = 11.98 (s, 2H); 2.18 (t, J = 7.6 Hz, 4H); 1.51-1.46 (m, 4H); 1.24 (s, 12H). The analytical data agree with the literature values.

Example 4: Preparation of 6-oxo-6-phenylhexanoic acid

According to AAV1, 1-phenylcyclohex-1-ene (0.158 g, 1.0 mmol, 1.0 eq.) was electrolyzed galvanostatically under an oxygen atmosphere (100%) and application of 4 F. After removing the solvent by distillation and drying in a high vacuum, the product was obtained as a colorless solid (yield: 16%, 0.034 g, 0.16 mmol). ¹ H-NMR (400 MHz, DMSO-d6) δ [ppm] = 12.17 (s, 1H); 7.98-7.93 (m, 2H); 7.65-7.60 (m, 1H); 7.53-7.50 (m, 2H); 3.03 (t, J = 7.0 Hz, 2H); 2.25 (t, J = 7.0 Hz, 2H); 1.66-1.52 (m, 4H). The analytical data agree with the literature values.

Example 5: 1,3-Cyclopentanedioic acid

According to AAV1, bicylo[2.2.1]hept-2-ene (0.094 g, 1.0 mmol, 1.0 eq.) was electrolyzed galvanostatically under an oxygen atmosphere (100%) and application of 4 F. After removing the solvent by distillation and drying in a high vacuum, the product was obtained as a colorless, highly viscous liquid (yield: 20%, 0.031 g, 0.20 mmol).

¹ H-NMR (400 MHz, DMSO-d6) δ [ppm] = 12.14 (s, 2H); 2.78-2.62 (m, 2H); 2.13-2.06 (m, 1H); 1.88-1.72 (m, 5H). 13C-NMR (101 MHz, DMSO-d6) δ [ppm] = 176.4; 43.3; 32.8; 28.9.

Example 6:

Tabelle 1: Zusätzliche 1,8-Octandisäure-Synthesen. Beispiel-Nr. Abweichung von den Standardbedingungen^[a] 1 / % (unumgesetzt, GC) 2 / % (isoliert) 6-AAV1-01 Keine k.A. 40 6-AAV1-02 100% N₂-Atm., 4 F k.A. 0 6-AAV2-03 35 °C, 1 (0,25 mmol), 4 F, 5 mA/cm² 20 41 6-AAV2-04 35 °C, 1 (0,25 mmol), 6 F, 5 mA/cm² 18 44 6-AAV2-05 35 °C, 1 (0,25 mmol), 8 F, 5 mA/cm² 12 39 6-AAV2-06 35 °C, 1 (0,25 mmol), 8 F, 5 mA/cm², Isobutyronitril (5 mL) 13 46 [a] Standardbedingungen: GK∥GK, Acetonitril (5 mL), NBu₄NO₃ (0,5 Äq.), 5 °C, 350 rpm, 1 (1 mmol), 100% O₂-Atm., 5 F, 10 mA/cm². The following examples describe additional syntheses of 1,8-octanedioic acid according to Scheme 1 using AAV1 and AAV2, respectively.

<b>Table 1</b>: Additional 1,8-octanedioic acid syntheses. Example no. Deviation from standard conditions ^[a] 1 / % (unreacted, GC) 2 / % (isolated) 6-AAV1-01 No n/a 40 6-AAV1-02 100% N ₂ atm., 4 F n/a 0 6-AAV2-03 35 °C, 1 (0.25 mmol), 4 F, 5 mA/cm ² 20 41 6-AAV2-04 35 °C, 1 (0.25 mmol), 6 F, 5 mA/cm ² 18 44 6-AAV2-05 35 °C, 1 (0.25 mmol), 8 F, 5 mA/cm ² 12 39 6-AAV2-06 35 °C, 1 (0.25 mmol), 8 F, 5 mA/cm ² , isobutyronitrile (5 mL) 13 46 [a] Standard conditions: GK∥GK, acetonitrile (5 mL), NBu ₄ NO ₃ (0.5 eq.), 5 °C, 350 rpm, 1 (1 mmol), 100% O ₂ atm., 5 F , 10 mA/cm ² .

Example 7:

Tabelle 2: Zusätzliche 1,12-Dodecandisäure-Synthesen im Batch. Beispiel-Nr. Abweichung von den Standard bedi ngu ngen^[a] 3/% (unumgesetzt, GC) 4/% (isoliert) 7-AAV1-01 Keine k.A. 33 7-AAV2-02 22 °C, 3 (0,5 mmol), NBu₄NO₃ (1 Äq.), 8 F 0 61 7-AAV2-03 22 °C, 3 (0,5 mmol), NBu₄NO₃ (2 Äq.), 8 F 0 71 7-AAV2-04 22 °C, 3 (0,5 mmol), NBu₄NO₃ (1 Äq.), 8 F, 5 mA/cm² 0 69 7-AAV2-05 22 °C, 3 (0,5 mmol), 8 F 0 69 7-AAV2-06 22 °C, 3 (0,5 mmol), NBu₄NO₃ (1 Äq.), 6 F, 5 mA/cm² 1 66 7-AAV2-07 22 °C, 3 (0,375 mmol), NBu₄NO₃ (1,3 Äq.), 8 F 0 73 7-AAV2-08 22 °C, 3 (0,5 mmol), NBu₄NO₃ (1 Äq.), 5 mA/cm² 0 68 7-AAV2-09 22 °C, 3 (0,5 mmol), 6 F, 5 mA/cm² 0 70 7-AAV2-10 22 °C, 3 (0,25 mmol), NBu₄NO₃ (2 Äq.), 8 F 0 76 7-AAV2-11 22 °C, 3 (0,25 mmol), 5 mA/cm² 0 75 7-AAV2-12 22 °C, 3 (0,25 mmol) 0 73 7-AAV2-13 22 °C, 3 (0,25 mmol), 2 F 7 63 7-AAV2-14 22 °C, 3 (0,25 mmol), kein Strom 95 0 7-AAV-15 35 °C, 3 (0,25 mmol), 5 mA/cm² 0 78 7-AAV-16 50 °C, 3 (0,25 mmol), 5 mA/cm² 6 57 7-AAV-17 5 °C, 3 (0,25 mmol), 5 mA/cm² 0 71 7-AAV-18 35 °C, 3 (0,25 mmol), 5 mA/cm², 200 rpm 0 63 7-AAV-19 35 °C, 3 (0,25 mmol), 5 mA/cm², 500 rpm 0 59 7-AAV-20 35 °C, 3 (0,1 mmol), 5 mA/cm² k.A. 61 [a] Standardbedingungen: GK∥GK, Isobutyronitril (5 mL), NBu₄NO₃ (0,5 Äq.), 5 °C, 350 rpm, 3 (1 mmol), 100% O₂-Atm., 4 F, 10 mA/cm². The following examples describe additional syntheses of 1,12-dodecanedioic acid according to Scheme 2 using AAV1 and AAV2, respectively.

<b>Table 2</b>: Additional 1,12-dodecanedioic acid syntheses in batch. Example no. Deviation from standard conditions ^[a] 3/% (unreacted, GC) 4/% (isolated) 7-AAV1-01 No n/a 33 7-AAV2-02 22 °C, 3 (0.5 mmol), NBu ₄ NO ₃ (1 eq.), 8 F 0 61 7-AAV2-03 22 °C, 3 (0.5 mmol), NBu ₄ NO ₃ (2 eq.), 8 F 0 71 7-AAV2-04 22 °C, 3 (0.5 mmol), NBu ₄ NO ₃ (1 eq.), 8 F, 5 mA/cm ² 0 69 7-AAV2-05 22 °C, 3 (0.5 mmol), 8 F 0 69 7-AAV2-06 22 °C, 3 (0.5 mmol), NBu ₄ NO ₃ (1 eq.), 6 F, 5 mA/cm ² 1 66 7-AAV2-07 22 °C, 3 (0.375 mmol), NBu ₄ NO ₃ (1.3 eq.), 8 F 0 73 7-AAV2-08 22 °C, 3 (0.5 mmol), NBu ₄ NO ₃ (1 eq.), 5 mA/cm ² 0 68 7-AAV2-09 22 °C, 3 (0.5 mmol), 6 F, 5 mA/cm ² 0 70 7-AAV2-10 22 °C, 3 (0.25 mmol), NBu ₄ NO ₃ (2 eq.), 8 F 0 76 7-AAV2-11 22 °C, 3 (0.25 mmol), 5 mA/cm ² 0 75 7-AAV2-12 22 °C, 3 (0.25 mmol) 0 73 7-AAV2-13 22 °C, 3 (0.25 mmol), 2 F 7 63 7-AAV2-14 22 °C, 3 (0.25 mmol), no power 95 0 7-AAV-15 35 °C, 3 (0.25 mmol), 5 mA/cm ² 0 78 7-AAV-16 50 °C, 3 (0.25 mmol), 5 mA/cm ² 6 57 7-AAV-17 5 °C, 3 (0.25 mmol), 5 mA/cm ² 0 71 7-AAV-18 35 °C, 3 (0.25 mmol), 5 mA/cm ² , 200 rpm 0 63 7-AAV-19 35 °C, 3 (0.25 mmol), 5 mA/cm ² , 500 rpm 0 59 7-AAV-20 35 °C, 3 (0.1 mmol), 5 mA/cm ² n/a 61 [a] Standard conditions: GK∥GK, isobutyronitrile (5 mL), NBu ₄ NO ₃ (0.5 eq.), 5 °C, 350 rpm, 3 (1 mmol), 100% O ₂ atm., 4 F , 10 mA/cm ² .

Example 8:

Tabelle 3: Zusätzliche 1,12-Dodecandisäure-Synthesen im Durchflussreaktor. Beispiel-Nr. Abweichung von den Standard bedi ngu ngen^[a] 3/% (unumgesetzt, GC) 4/% (isoliert) 8-AAV3-01 Keine 0 76 8-AAV3-02 Dimethylcarbonat (4,5 mL), Flussrate O₂: 20 mL/min, 3 (2,5 mmol), 2 F, 10 mA/cm² 21 35 8-AAV3-03 Dimethylcarbonat (4,3 mL) + Methanol (5 Vol-%, 0,25 mL), Flussrate Elektrolyt: 5 mL/min, 3 (2,5 mmol), NBu₄NO₃ (0,4 Äq.), 2 F 23 33 8-AAV3-04 Dimethylcarbonat (4,3 mL) + Isopropanol (5 Vol-%, 0,25 mL), Flussrate Elektrolyt: 18 mL/min, Flussrate O₂: 20 mL/min, 3 (2,5 mmol), NBu₄NO₃ (1 Äq.), 2 F, 20 mA/cm² 9 38 8-AAV3-05 Dimethylcarbonat (8,2 mL) + Isopropanol (10 Vol-%, 0,92 mL), 50 °C, Flussrate Elektrolyt: 18 mL/min, Flussrate O₂: 20 mL/min, 3 (5 mmol), NBu₄NO₃ (1 Äq.), 2 F, 20 mA/cm² 13 52 [a] Standardbedingungen: GK∥GK, Isobutyronitril (10 mL), NBu₄NO₃ (0,5 Äq.), 20 °C, Flussrate Elektrolyt: 10 mL/min, Flussrate 100% O₂: 10 mL/min, 3 (0,5 mmol), 4 F, 5 mA/cm². The following examples describe additional syntheses of 1,12-dodecanedioic acid according to Scheme 3 using AAV3, which were carried out in an electrochemical flow reactor.

<b>Table 3</b>: Additional 1,12-dodecanedioic acid syntheses in the flow reactor. Example no. Deviation from standard conditions ^[a] 3/% (unreacted, GC) 4/% (isolated) 8-AAV3-01 No 0 76 8-AAV3-02 Dimethyl carbonate (4.5 mL), flow rate O ₂ : 20 mL/min, 3 (2.5 mmol), 2 F, 10 mA/cm ² 21 35 8-AAV3-03 Dimethyl carbonate (4.3 mL) + methanol (5 vol%, 0.25 mL), electrolyte flow rate: 5 mL/min, 3 (2.5 mmol), NBu ₄ NO ₃ (0.4 eq.), 2 F 23 33 8-AAV3-04 Dimethyl carbonate (4.3 mL) + isopropanol (5 vol%, 0.25 mL), electrolyte flow rate: 18 mL/min, O ₂ flow rate: 20 mL/min, 3 (2.5 mmol), NBu ₄ NO ₃ (1 eq.), 2 F, 20 mA/ ^cm2 9 38 8-AAV3-05 Dimethyl carbonate (8.2 mL) + isopropanol (10% by volume, 0.92 mL), 50 °C, electrolyte flow rate: 18 mL/min, O ₂ flow rate: 20 mL/min, 3 (5 mmol), NBu ₄ NO ₃ (1 eq.), 2 F, 20 mA/cm ² 13 52 [a] Standard conditions: GK∥GK, isobutyronitrile (10 mL), NBu ₄ NO ₃ (0.5 eq.), 20 °C, electrolyte flow rate: 10 mL/min, flow rate 100% O ₂ : 10 mL/min, 3 (0.5 mmol), 4 F, 5 mA/cm ² .

Claims (15)

Process for the preparation of unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids by electrochemical oxidation of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkenes, comprising the process steps (a) providing at least one unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene; (b) providing at least one inorganic or organic nitrate salt; (c) electrochemical oxidation of the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene provided in step (a) in the presence of the inorganic or organic nitrate salt provided in step (b) in an electrolysis cell in a reaction medium in the presence of oxygen. The method according to claim 1, wherein the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene is monocyclic or polycyclic, preferably monocyclic, particularly preferably monounsaturated and monocyclic. The method according to claim 2, wherein the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated monocyclic cycloalkene has 5 to 12 C atoms, particularly preferably 6 to 12 C atoms, very particularly preferably 8 to 12 C atoms in the ring system and is unsubstituted or mono or multiple , preferably substituted with 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 themselves being unsubstituted or mono- or poly-substituted , with 1, 2 or 3 substituents, independently of each other, each selected from the group consisting of F, Cl, Br, and NO2. The method according to claim 2, wherein the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated bicyclic cycloalkene has 7 to 18 C atoms, particularly preferably 7 to 12 C atoms, very particularly preferably 7 to 10 C atoms in the ring system and are unsubstituted or substituted once or multiple times, preferably with 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 themselves are each unsubstituted or mono- or polysubstituted, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO2. Method according to one of the preceding claims, wherein the cycloalkene is selected from the group consisting of cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cycloundecene, cyclododecene, 1-phenylcyclohex-1-ene, bicylo[2.2.1]hept-2-ene , α-pinene and carene. Method according to one of the preceding claims, wherein the inorganic or organic nitrate salt is a nitrate of the general formula [cation+][NO3-], with [cation+] selected from the group consisting of Na+, K+, ammonium ions with the general structure [R1R2R3R4N+]. R1, R2, R3, R4, independently of one another, each selected from the group consisting of C1 to _C16 alkyl, in particular C1 to C8 alkyl, straight-chain or branched, imidazolium cations with the general structure (I)

with R ¹ and R ² , independently of one another, each selected from the group consisting of C ₁ - to C ₁₈ alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched, and R ³ selected from Group consisting of H and C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ -alkyl, straight-chain or branched, Pyridinium cations with the general structure (II)

with R ¹ selected from the group consisting of C ₁ - to C ₁₈ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched and R ² , R ³ and R ⁴ , independently of one another, each selected from the group consisting from H and C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ -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 C ₁ - to C ₁₆ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched . Method according to one of the preceding claims, wherein the reaction medium is a polar aprotic reaction medium, optionally in combination with water, whereby in the combination with water the water content is preferably up to 20% by volume, particularly preferably up to 15% by volume. %, very particularly preferably up to 10% by volume, even more preferably up to 5% by volume, based in each case on the total amount of reaction medium. The method according to claim 7, wherein the reaction medium is a polar aprotic reaction medium which is selected from the group consisting of aliphatic nitriles, aliphatic ketones, cycloaliphatic ketones, dialkyl carbonates, cyclic carbonates, lactones, aliphatic nitroalkanes, and dimethyl sulfoxide, esters and ethers or a combination from at least two of these components, preferably 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 one Combination of at least two of these components, each possibly in combination with water. Method according to one of the preceding claims, wherein the inorganic or organic nitrate salt is 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, each based on the amount of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene. Method according to one of the preceding claims, wherein a gas atmosphere containing oxygen is provided in spatial connection with the reaction medium, the proportion of oxygen in the gas atmosphere preferably being 10 to 100% by volume, particularly preferably 15 to 100% by volume, very particularly preferably 18 to 100% by volume, most preferably 20 to 100% by volume. A method according to claim 10, 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. Method according to one of the preceding claims, wherein the amount of charge is at least 190 C (2 F) to 970 C (10 F), preferably 290 C (3 F) to 870 C (9 F), particularly preferably 330 C (3.5 F) to 820 C (8.5 F), very particularly preferably 380 C (4 F) to 775 C (8 F), most preferably 380 C (4 F) to 580 C (6 F), each for 1 mmol of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene. Method according to one of the preceding claims, wherein the current density is at least 5 mA/cm2, the area information relating to the geometric area of the electrodes. Method according to one of the preceding claims, wherein it is carried out in an undivided cell. Method according to one of the preceding claims, wherein it is carried out batchwise or continuously, preferably continuously in an undivided flow electrolysis cell.