WO2024261178A1 - Electrochemical oxidation of allylic c-h bonds - Google Patents

Abstract

The present invention relates to a process for the electrochemical oxidation of allylic C-H bonds in specific compounds to obtain specific α,β-unsaturated ketones.

Description

Electrochemical Oxidation of Allylic C-H bonds(I) The present invention relates to a novel process for the electrochemical oxidation of allylic C-H bonds in specific compounds to obtain specific α,β-unsaturated ketones. In this frame, electrochemical processes have emerged as environment-friendly methods and sustainable technologies that offer a different solution to many environmental problems because they are versatile, efficient, cost-effective, easily automatable, and the electrons are a clean reagent (inexpensive and suitable reagent to drive the reaction). Such an electrochemical process is very useful to introduce a carbonyl group into a chemical compound in an excellent yield. The obtained oxidised compounds can be used as such, or they can be used as intermediates in chemical synthesis. To oxidise allylic compound, the prior art discloses a variety of ways such as photochemical process or using strong oxidizing agents. So far, only a few electrochemical or electrocatalytic processes for allylic C-H oxidation are known, wherein the conditions are not ideal and/or the yields are not good. An electrochemical mediator is needed, which makes the reaction mixture even more complex. Therefore, the goal of the present invention, was to find an improved electrochemical process for the oxidation of allylic C-H bonds in specific compounds. Surprisingly it was found when a specific oxidising agent was used it was possible to oxidize allylic C-H bonds of specific compounds without the use of an additional mediator. The specific oxidising agent used, which acts also as mediator, is t-butyl hydroperoxide. The compounds to be oxidized are the compounds of formula (I) , wherein

R1 is H; or a linear or branched C1-C4-alkyl moiety, and R2 is H; a linear or branched C1-C10-alkyl moiety, which can be substituted; a linear or branched C3-C10-alkenyl moiety, which can be substituted; a linear or branched C3- C10-alkenyl moiety with a terminal alkyne group, which can be substituted; a linear or branched C4-C10- alkyne moiety, which can be substituted; a moiety of the following formula ,

A is -CH₂-O-; a linear or branched C₁-C₆-alkylene moiety; or a linear or branched C₂-C₆-alkenylene moiety, and R₈ is a linear or branched C₁-C₄-alkyl moiety; or R₂ is a moiety of the following formula ,

R9 is a linear or branched C1-C4-alkyl moiety; or a linear or branched C2-C6-alkenyl moiety, and R3 is H; -CF3; or linear or branched C1-C4-alkyl moiety, and R4 is H or a linear or branched C1-C10-alkyl moiety, which can be substituted; a linear or branched C3-C10-alkenyl moiety, which can be substituted; a linear or branched C3-C10- alkenyl moiety with a terminal alkyne group, which can be substituted; a linear or branched C4-C10- alkyne moiety, which can be substituted; -CF3; a moiety of the following formula ,

A’ is -CH₂-O-; a linear or branched C₁-C₆-alkylene moiety; or a linear or branched C₂-C₆-alkenylene moiety and R’₈ is a linear or branched C₁-C₄-alkyl moiety; or R₄ is a moiety of the following formula ,

R’9 is a linear or branched C1-C6-alkyl moiety; or a linear or branched C2-C6-alkenyl moiety, or R3 and R4 form a -C=O moiety together with the C atom to which they are attached, and R5 is H; a linear or branched C1-C4-alkyl moiety; a linear or branched C2-C4-alkenyl moiety; or -CF3, and R6 is H; -O(CO)CH3; a linear or branched C1-C4-alkyl moiety; or -CF3, and R7 is H; -CF3; or a linear or branched C1-C4-alkyl moiety, and R’7 is H; -CF3; or a linear or branched C1-C4-alkyl moiety, or R’7 and R3 form a -CH2- bridge. The obtained oxidised compounds (α,β-unsaturated ketones) are those of formula (II) , wherein all substituents

for the compound of formula (I). Therefore, the present invention relates to a process (P) for producing a compound of formula (II) , wherein

R₁ is H; or a linear or branched C₁-C₄-alkyl moiety, and R₂ is H; a linear or branched C₁-C₁₀-alkyl moiety, which can be substituted; a linear or branched C₃-C₁₀-alkenyl moiety, which can be substituted; a linear or branched C₄- C₁₀-alkenyl moiety with a terminal alkyne group, which can be substituted; a linear or branched C₄-C₁₀- alkyne moiety, which can be substituted; a moiety of the following formula ,

wherein A is -CH2-O-; a linear or branched C1-C6-alkylene moiety; or a linear or branched C2-C6-alkenylene moiety, and R8 is a linear or branched C1-C4-alkyl moiety; or R2 is a moiety of the following formula ,

R₉ is a linear or branched C₁-C₄-alkyl moiety; or a linear or branched C₂-C₆-alkenyl moiety, and R₃ is H; -CF₃; or linear or branched C₁-C₄-alkyl moiety, and R₄ is H or a linear or branched C₁-C₁₀-alkyl moiety, which can be substituted; a linear or branched C₃-C₁₀-alkenyl moiety, which can be substituted; a linear or branched C₄-C₁₀-alkenyl moiety with a terminal alkyne group, which can be substituted; a linear or branched C₄-C₁₀-alkyne moiety, which can be substituted; -CF₃; a moiety of the following formula ,

A’ is -CH2-O-; a linear or branched C1-C6-alkylene moiety; or a linear or branched C2-C6-alkenylene moiety and R’8 is a linear or branched C1-C4-alkyl moiety; or R4 is a moiety of the following formula ,

R’9 is a linear or branched C1-C6-alkyl moiety; or a linear or branched C2-C6-alkenyl moiety, or R3 and R4 form a -C=O moiety together with the C atom to which they are attached, and R5 is H; a linear or branched C1-C4-alkyl moiety; a linear or branched C2-C4- alkenyl moiety; or -CF3, and R6 is H; -O(CO)CH3; a linear or branched C1-C4-alkyl moiety; or -CF3, and R7 is H; -CF3; or a linear or branched C1-C4-alkyl moiety, and R’7 is H; -CF3; or a linear or branched C1-C4-alkyl moiety, or R’7 and R3 form a -CH2- bridge, by electrochemical oxidation of a compound of formula (I) , wherein all substituents

for the compound of formula (II), in the presence of t-butyl hydroperoxide. Preferably, oxidized are compounds of formula (I), wherein R1 is H or -CH3, and R₂ is H; a linear or branched C₁-C₆-alkyl moiety, which can be substituted; a linear or branched C₃-C₈-alkenyl moiety, which can be substituted; a linear or branched C₄- C₈-alkenyl moiety with a terminal alkyne group, which can be substituted; a moiety of the following formula ,

wherein A is -CH2-O-; a linear or branched C1-C4-alkylene moiety; or a linear or branched C2-C4-alkenylene moiety, and R8 is a linear or branched C1-C4-alkyl moiety; or R2 is a moiety of the following formula ,

R₉ is a linear or branched C₁-C₄-alkyl moiety; or a linear or branched C₂-C₄-alkenyl moiety, and R₃ is H or -CH₃, and R₄ is H or a linear or branched C₁-C₄-alkyl moiety, which can be substituted; a linear or branched C₃-C₈-alkenyl moiety, which can be substituted; a linear or branched C₃-C₈-alkenyl moiety with a terminal alkyne group, which can be substituted; a linear or branched C₃-C₈-alkyne moiety, which can be substituted; a moiety of the following formula ,

A’ is a linear or branched C1-C4-alkylene moiety; or a linear or branched C2-C6- alkenylene moiety and R’8 is a linear or branched C1-C4-alkyl moiety; or R4 is a moiety of the following formula ,

R’9 is a linear or branched C1-C4-alkyl moiety; a linear or branched C1-C6-alkylene moiety; or a linear or branched C2-C6-alkenylene moiety, or R3 and R4 form a -C=O moiety together with the C atom to which they are attached, and R5 is H; a C1-C2-alkyl moiety; or a linear or branched C2-C4-alkylene moiety, and R6 is H; -O(CO)CH3; or a C1-C2-alkyl moiety, and R7 is H; or a C1-C2-alkyl moiety, and R’7 is H; or a C1-C2-alkyl moiety, or R’7 and R3 form a -CH2- bridge, by electrochemical oxidation in the presence of t-butyl hydroperoxide. More preferably, oxidized are compounds of formula (I), wherein R1 is H or -CH3, and R₂ is H; -CH₃; a linear or branched C₄-C₈-alkylene moiety, which is substituted by an -OH group; a linear or branched C₄-C₈-alkylene moiety with a terminal alkyne group, which is substituted by an -OH group; or a moiety of the following formula ,

A is -CH2-O-; or -CH=CH-, and R8 is a C1-C2-alkyl moiety; or R2 is a moiety of the following formula ,

R9 is a linear or branched C2-C4-alkenylene moiety, and R3 is H or -CH3, and R4 is -CH3; a linear or branched C4-C8-alkylene moiety, which is substituted by an - OH group; a linear or branched C4-C8-alkylene moiety with a terminal alkyne group, which is substituted by an -OH group; or a moiety of the following formula ,

A’ is -CH=CH-, and R’₈ is a C₁-C₂-alkyl moiety; or R₄ is a moiety of the following formula ,

R’9 is a linear or branched C2-C4-alkenylene moiety, or R3 and R4 form a -C=O moiety together with the C atom to which they are attached, and R5 is H; -CH3; or a linear or branched C2-C4-alkylene moiety, and R6 is H; -O(CO)CH3; or -CH3, and R7 is H; or a C1-C2-alkyl moiety, and R’7 is H; or a C1-C2-alkyl moiety, or R’7 and R3 form a -CH2- bridge, by electrochemical oxidation in the presence of t-butyl hydroperoxide. Even more preferably, oxidized are compounds of formula (I), wherein R1 is H or -CH3, and R2 is H; -CH3; ; R3 is H or -CH3, and R4 is -CH3;

R3 and R4 form a -C=O moiety together with the C atom to which they are attached, and R5 is H; -CH3; or ,

“*” marks the connecting bond, and R₆ is H; -O(CO)CH₃; or -CH₃, and R₇ is H; or -CH₃, and R’₇ is H; or -CH₃, or R’₇ and R₃ form a -CH₂- bridge, by electrochemical oxidation in the presence of t-butyl hydroperoxide. Most preferably, the following compounds (Ia) to (In) 5 , , ,

, Therefore, the present invention relates to a process (P1), which is process (P), wherein R₁ is H or -CH₃, and R2 is H; a linear or branched C1-C6-alkyl moiety, which can be substituted; a linear or branched C3-C8-alkenyl moiety, which can be substituted; a linear or branched C4- C8-alkenyl moiety with a terminal alkyne group, which can be substituted; a moiety of the following formula ,

A is -CH2-O-; a linear or branched C1-C4-alkylene moiety; or a linear or branched C₂-C₄-alkenylene moiety, and R₈ is a linear or branched C₁-C₄-alkyl moiety; or R2 is a moiety of the following formula R₉ is a linear or branched C₁-C₄-alkyl moiety; or a linear or branched C₂-C₄-alkenyl moiety, and R₃ is H or -CH₃, and R₄ is H or a linear or branched C₁-C₄-alkyl moiety, which can be substituted; a linear or branched C₃-C₈-alkenyl moiety, which can be substituted; a linear or branched C₃-C₈-alkenyl moiety with a terminal alkyne group, which can be substituted; a linear or branched C₃-C₈-alkyne moiety, which can be substituted; a moiety of the following formula ,

A’ is a linear or branched C1-C4-alkylene moiety; or a linear or branched C2-C6- alkenylene moiety and R’8 is a linear or branched C1-C4-alkyl moiety; or R4 is a moiety of the following formula ,

R’₉ is a linear or branched C₁-C₄-alkyl moiety; a linear or branched C₁-C₆-alkylene moiety; or a linear or branched C₂-C_6-alkenylene moiety, or R₃ and R₄ form a -C=O moiety together with the C atom to which they are attached, and R₅ is H; a C₁-C₂-alkyl moiety; or a linear or branched C₂-C₄-alkylene moiety, and R₆ is H; -O(CO)CH₃; or a C₁-C₂-alkyl moiety, and R₇ is H; or a C₁-C₂-alkyl moiety, and R’7 is H; or a C1-C2-alkyl moiety, or R’7 and R3 form a -CH2- bridge. Therefore, the present invention relates to a process (P2), which is process (P), wherein R1 is H or -CH3, and R2 is H; -CH3; a linear or branched C4-C8-alkylene moiety, which is substituted by an -OH group; a linear or branched C4-C8-alkylene moiety with a terminal alkyne group, which is substituted by an -OH group; or a moiety of the following formula ,

A is -CH₂-O-; or -CH=CH-, and R₈ is a C₁-C₂-alkyl moiety; or R₂ is a moiety of the following formula ,

R9 is a linear or branched C2-C4-alkenylene moiety, and R3 is H or -CH3, and R4 is -CH3; a linear or branched C4-C8-alkylene moiety, which is substituted by an - OH group; a linear or branched C4-C8-alkylene moiety with a terminal alkyne group, which is substituted by an -OH group; or a moiety of the following formula ,

A’ is -CH=CH-, and R’₈ is a C₁-C₂-alkyl moiety; or R4 is a moiety of the following formula ,

R’₉ is a linear or branched C₂-C_4-alkenylene moiety, or R₃ and R₄ form a -C=O moiety together with the C atom to which they are attached, and R₅ is H; -CH₃; or a linear or branched C₂-C₄-alkylene moiety, and R₆ is H; -O(CO)CH₃; or -CH₃, and R₇ is H; or a C₁-C₂-alkyl moiety, and R’₇ is H; or a C₁-C₂-alkyl moiety, or R’₇ and R₃ form a -CH₂- bridge. Therefore, the present invention relates to a process (P3), which is process (P), wherein R₁ is H or -CH₃, and R₂ is H; -CH₃; ;

R3 is H or -CH3, and R4 is -CH3; R₃ and R₄ form a -C=O moiety together with the C atom to which they are attached, and R₅ is H; -CH₃; or ,

“*” marks the connecting bond, and R6 is H; -O(CO)CH3; or -CH3, and R7 is H; or -CH3, and R’7 is H; or -CH3, or R’7 and R3 form a -CH2- bridge. Therefore, the present invention relates to a process (P4), which is process (P), wherein a compound of the following formulae (Ia) to (In) ,

, s oxidized by electrochemical oxidation in the presence of t-butyl hydroperoxide. The new way to oxidise the compound of formula (I) has great advantages such as • Electricity as a safe and cost-effective oxidizing agent • Simplified method for electrochemical allylic oxidation • Reaction conditions suitable for industry-relevant scaling of the approaches • Dual functionality of oxygen source and mediator • Avoidance of brittle, unwieldy electrode material • Avoidance of potentially explosive conductive salts • Elimination of cost-intensive catalytic converter systems In the present invention, the material of the anode and the cathode is not critical and can be any suitable materials known in the art, such as steel, glassy carbon and platinum. Therefore, the present invention relates to a process (P5), which is process (P), (P1), (P2), (P3) or (P4), wherein the material of the electrode is steel, glassy carbon and/or platinum. The form and size (which also means the surface area) of the electrodes in the present invention are also not critical. They may be in any size and in any form, such as in a form of a wire, a rod, a mesh, a grid, a sponge, or any other design suitable for the electrochemical reactor (cell) used in the process of the present invention. Therefore, the present invention relates to a process (P6), which is process (P), (P1), (P2), (P3). (P4) or (P5), wherein the electrode is in the form of a wire, a rod, a mesh, a grid, a sponge, or any other design suitable for the electrochemical reactor (cell). The cell, also known as voltaic cells or galvanic cells, used in the process according to the present invention can be any one of those known by a person skilled in the art. Usually and preferably it is a single compartment electrochemical flow-cell. Therefore, the present invention relates to a process (P7), which is process (P), (P1), (P2), (P3), (P4), (P5) or (P6), wherein the cell is a two-compartments electrochemical flow-cell. The process according to the present invention is carried out in at least one solvent. In the present invention, the electrochemical oxidation is carried out in a medium which may be water or a non-aqueous solvent or mixture thereof. The examples of the non- aqueous solvent include but are not limited to organic carbonates (such as alkylene carbonates (i.e. propylene carbonate, butylene carbonate) and dimethylcarbonate), polyethylene glycol, N-methyl-2-pyrrolidone, N-butylpyrrolidone (NBP), alcohols (such as methanol, ethanol, hexafluoro-2-propanol and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP)), esters, ketones (such as acetone and 2-butanone), acetic acid, sulpholane, dimethylsulphoxide (DMSO), tetrahydrofuran (THF), 2-methyl-tetrahydrofuran (MeTHF), dimethylformamide (DMF), hexa-methylphosphoramide, acetonitrile (MeCN), dichloromethane (DCM), dimethoxyethane (DME), and mixture thereof. Preferably, the medium used in the present invention is a non-aqueous solvent or mixture thereof. In the context of the present invention, the “non-aqueous solvent” means that no water is included in the solvent on purpose. However, it might be possible that the solvent comprises traces of water (usually below 5 wt%, based on the total weight of the solvent). Therefore, the present invention relates to a process (P8), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6) or (P7), wherein the process is carried out in at least one solvent. Therefore, the present invention relates to a process (P8’), which is process (P8), wherein the at least one solvent chosen from the group consisting of organic carbonates (such as alkylene carbonates (i.e. propylene carbonate, butylene carbonate) and dimethylcarbonate), polyethylene glycol, N-methyl-2-pyrrolidone, N-butylpyrrolidone (NBP), alcohols (such as methanol, ethanol, hexafluoro-2-propanol and 1,1,1,3,3,3- hexafluoroisopropanol (HFIP)), esters, ketones (such as acetone and 2-butanone), acetic acid, sulpholane, dimethylsulphoxide (DMSO), tetrahydrofuran (THF), 2-methyl- tetrahydrofuran (MeTHF), dimethylformamide (DMF), hexa-methylphosphoramide, acetonitrile (MeCN), dichloromethane (DCM), and dimethoxyethane (DME). In the present invention, the medium essentially comprises at least one supporting electrolyte, which may be added to in the form of a salt and/or in form of an acid. Any commonly known and commonly used supporting electrolyte can be used. Examples of the suitable supporting electrolytes include but are not limited to HCl, H2SO4, Na2SO4, NaCl, NaHSO4, alkyl- or arylsulfonic acids (such as methanesulfonic acid and p- toluenesulfonic acid), phosphoric acid, phosphates, and tetraalkylammonium salts (such as tetrabutylammonium acetate (NBu4OAc), tetrabutylammonium tetrafluoroborate and tetrabutylammonium hexafluorophosphate). Preferably, the supporting electrolyte used in the present invention is an acid such as HCl, H2SO4, phosphoric acid or mixture thereof. More preferably, the supporting electrolyte used in the present invention is H2SO4. Due to the process hazards, it is preferred that the supporting electrolyte is not a perchlorate salt. In the present invention, the concentration of the supporting electrolyte in the medium is up to 5 mol/L (M), preferably from 0.01 M to 4 M, more preferably from 0.05 M to 3 M, the most preferably from 0.5 M to 1.5 M. Therefore, the present invention relates to a process (P9), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8) or (P8’), wherein the process is carried in the presence of at least one supporting electrolyte. Therefore, the present invention relates to a process (P9’), which is process (P9), wherein the at least one supporting electrolyte is chosen from the group consisting of HCl, H₂SO₄, Na₂SO₄, NaCl, NaHSO₄, alkyl- or arylsulfonic acids (such as methanesulfonic acid and p- toluenesulfonic acid), phosphoric acid, phosphates, and tetraalkylammonium salts (such as tetrabutylammonium acetate (NBu4OAc), tetrabutylammonium tetrafluoroborate and tetrabutylammonium hexafluorophosphate). Therefore, the present invention relates to a process (P9’’), which is process (P9), wherein the at least one supporting electrolyte is chosen from the group consisting of HCl, H2SO4 and phosphoric acid. Therefore, the present invention relates to a process (P9’’), which is process (P9), wherein the concentration of the supporting electrolyte is up to 5 mol/L. Therefore, the present invention relates to a process (P9’’’’), which is process (P98), wherein the concentration of the supporting electrolyte is from 0.01 M to 4 M. Therefore, the present invention relates to a process (P9’’’’’), which is process (P9), wherein the concentration of the supporting electrolyte is from 0.05 M to 3 M. Therefore, the present invention relates to a process (P9’’’’’’), which is process (P9), wherein the concentration of the supporting electrolyte is from 0.5 M to 1.5 M. In the present invention, t-butyl hydroperoxide (which is also used as oxygen source) is included in the medium in an amount of from 0.1 vol% to 20 vol%, preferably from 0.5 vol% to 15.0 vol%, more preferably from 1.0 vol% to 10 vol%, such as 1 vol%, 2 vol%, 3 vol%, 3.5 vol%, 4 vol%, 4.5 vol%, 5 vol%, 5.5 vol%, 6 vol%, 6.5 vol%, 7 vol%, 7.5 vol%, 8 vol%, 8.5 vol%, 9 vol%, 9.5 vol% and 10 vol%. In one preferable embodiment of the present invention, the t-butyl hydroperoxide is included in the medium in an amount of from 1.0 vol% to 10 vol%, preferably from 2.0 vol% to 7.5 vol%, more preferably from 4.0 vol% to 6.0 vol% such as 4.0 vol%, 4.5 vol% and 5.0 vol%. Therefore, the present invention relates to a process (P10), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’) or (P9’’’’’’), wherein the concentration of t-butyl hydroperoxide is 0.1 vol% to 20 vol%. Therefore, the present invention relates to a process (P10’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’) or (P9’’’’’’), wherein the concentration of t-butyl hydroperoxide is 0.5 vol% to 15.0 vol%. Therefore, the present invention relates to a process (P10’’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’) or (P9’’’’’’), wherein the concentration of t-butyl hydroperoxide is 1.0 vol% to 10 vol%. Therefore, the present invention relates to a process (P10’’’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’) or (P9’’’’’’), wherein the concentration of t-butyl hydroperoxide is 2.0 vol% to 7.5 vol%. Therefore, the present invention relates to a process (P10’’’’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’) or (P9’’’’’’), wherein the concentration of t-butyl hydroperoxide is 4.0 vol% to 6.0 vol%. Optionally, another additional oxygen source (in combination with t-butyl hydroperoxide) could be used, but it is not needed. Furthermore, it has been found that said process is preferably performed in the presence of a base, particularly in the presence of an organic base, most preferably in the presence of pyridine. It is preferred that the molar ratio of pyridine/compound of formula (II) is in the range of 1:1 to 10:1, more preferably 1.1:1 to 8:1, even more preferably 1.5:1 to 5:1. It is most preferred that of molar ratio of pyridine/compound of formula (II) is 2.5:1 to 3.5:1. Therefore, the present invention relates to a process (P11), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’) or (P10’’’’), wherein the process is carried out in the presence of at least one base. Therefore, the present invention relates to a process (P11’), which is process (P11), wherein the at least one base is an organic base. Therefore, the present invention relates to a process (P11’’), which is process (P11), wherein the base is pyridine. Therefore, the present invention relates to a process (P11’’’), which is process (P11), (P11’) or (P11’’), wherein the molar ratio of pyridine/compound of formula (II) is in the range of 1:1 to 10:1. Therefore, the present invention relates to a process (P11’’’’), which is process (P11), (P11’) or (P11’’), wherein the molar ratio of pyridine/compound of formula (II) is in the range of 1.1:1 to 8:1. Therefore, the present invention relates to a process (P11’’’’’), which is process (P11), (P11’) or (P11’’), wherein the molar ratio of pyridine/compound of formula (II) is in the range of 1.5:1 to 5:1. Therefore, the present invention relates to a process (P11’’’’’’), which is process (P11), (P11’) or (P11’’), wherein the molar ratio of pyridine/compound of formula (II) is in the range of 2.5:1 to 3.5:1. It is a particular advantage that the above process can be performed without an additional mediator, i.e., without any mediator which is not t- butyl hydroperoxide. Particularly advantageous is, that the above process can be performed in the absence of any N-oxide derivatives, such as TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl) or N- hydroxyphthalimide derivatives. These compounds have significant hazard properties and particularly the use of N-hydroxyphthalimide is highly controversial and, therefore, for example banned in Europe. Therefore, the present invention relates to a process (P12), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), , (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), , wherein the process is carried without any additional mediator.

Therefore, the present invention relates to a process (P13), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), ,

Furthermore, the process according to the present invention can be performed in the absence of any transition metals salts. This is very advantageous as transition metals, particularly soluble transition metals are difficult to recycle from the reaction mixture and/or are disadvantageous in view of ecological point of view. Therefore, the present invention relates to a process (P14), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12) or (P13), wherein the process is carried in the absence of any transition metals salts. In the present invention, the compound of formula (I) may be added into the medium in an amount of from 0.1 mmol/L (mM) to 100 mM, preferably from 0.2 mM to 75 mM, more preferably from 0.2 mM to 50 mM. Therefore, the present invention relates to a process (P15), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), ,

Therefore, the present invention relates to a process (P15’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), ,

Therefore, the present invention relates to a process (P15’’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), ,

In the present invention, the transferred charge for the electrochemical oxidation may be 10 Faraday (F) or less. A suitable range is 1-15 F, preferred is 1.5-10 F; more preferred is 1.5-9 F; most preferred is 1.5-8 F such as 2, 3, 4, 5, 6, 7 and 8 F. Therefore, the present invention relates to a process (P16), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’) or (P15’’), wherein the transferred charge for the electrochemical oxidation is 10 Faraday (F) or less. Therefore, the present invention relates to a process (P16’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’) or (P15’’), wherein the transferred charge for the electrochemical oxidation is 1.5 -15 F. Therefore, the present invention relates to a process (P16’’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’) or (P15’’), wherein the transferred charge for the electrochemical is 1.5-10 F. Therefore, the present invention relates to a process (P16’’’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’) or (P15’’), wherein the transferred charge for the electrochemical is 1.5-9 F. Therefore, the present invention relates to a process (P16’’’’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’) or (P15’’), wherein the transferred charge for the electrochemical is 1.5-8 F. In the present invention, the current density used in the electrochemical oxidation may be from 0.1 mA/cm² to 100 mA/cm², preferably from 0.3 mA/cm² to 50 mA/cm², preferably from 0.5 mA/cm² to 20 mA/cm². Therefore, the present invention relates to a process (P17), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’) or (P16’’’’), wherein the current density used in the electrochemical oxidation is from 0.1 mA/cm² to 100 mA/cm². Therefore, the present invention relates to a process (P17’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’) or (P16’’’’), wherein the current density used in the electrochemical oxidation is from 0.3 mA/cm² to 50 mA/cm². Therefore, the present invention relates to a process (P17’’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’) or (P16’’’’), wherein the current density used in the electrochemical oxidation is from 0.5 mA/cm² to 20 mA/cm². The electrochemical oxidation according to the present invention can be carried out in galvanostatic or potentiostatic mode. Depending on the cell, the electrochemical oxidation according to the present invention can be carried out batch-wise, semi-batch-wise, or in a continuous way, preferably in a continuous way. Therefore, the present invention relates to a process (P18), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’), (P16’’’’), (P17), (P17’) or (P17’’), wherein the electrochemical oxidation is carried out in galvanostatic mode. Therefore, the present invention relates to a process (P19), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’), (P16’’’’), (P17), (P17’) or (P17’’), wherein the electrochemical oxidation is carried out in potentiostatic mode. Therefore, the present invention relates to a process (P20), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’), (P16’’’’), (P17), (P17’), (P17’’), (P18) or (P19), wherein the electrochemical oxidation is carried out batch-wise. Therefore, the present invention relates to a process (P21), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’), (P16’’’’), (P17), (P17’), (P17’’), (P18) or (P19), wherein the electrochemical oxidation is carried out semi-batch-wise. Therefore, the present invention relates to a process (P22), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’), (P16’’’’), (P17), (P17’), (P17’’), (P18) or (P19), wherein the electrochemical oxidation is carried out in a continuous way. The electrochemical oxidation according to the present invention is carried out at a temperature range of from 0 °C to 75 °C, preferably from 5 °C to 60 °C, more preferably 10 – 50°C, most preferably at ambient temperature. Therefore, the present invention relates to a process (P23), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’), (P16’’’’), (P17), (P17’), (P17’’), (P18), (P19), (P20), (P21) or (P22), wherein the electrochemical oxidation is carried out at a temperature range of from 0 °C to 75 °C. Therefore, the present invention relates to a process (P23’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’), (P16’’’’), (P17), (P17’), (P17’’), (P18), (P19), (P20), (P21) or (P22), wherein the electrochemical oxidation is carried out at a temperature range of from 5 °C to 60 °C. Therefore, the present invention relates to a process (P23’’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’), (P16’’’’), (P17), (P17’), (P17’’), (P18), (P19), (P20), (P21) or (P22), wherein the electrochemical oxidation is carried out at a temperature range of from 10 °C to 50 °C. Therefore, the present invention relates to a process (P23’’’), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’), (P16’’’’), (P17), (P17’), (P17’’), (P18), (P19), (P20), (P21) or (P22), wherein the electrochemical oxidation is carried out at ambient temperature. The electrochemical oxidation according to the present invention is usually carried out at ambient pressure. Therefore, the present invention relates to a process (P24), which is process (P), (P1), (P2), (P3), (P4), (P5), (P6), (P7), (P8), (P8’), (P9), (P9’), (P9’’), (P9’’’), (P9’’’’), (P9’’’’’), (P9’’’’’’), (P10), (P10’), (P10’’), (P10’’’), (P10’’’’), (P11), (P11’), (P11’’), (P11’’’), (P11’’’’), (P11’’’’’), (P11’’’’’’), (P12), (P13), (P14), (P15), (P15’), (P15’’), (P16), (P16’), (P16’’), (P16’’’), (P16’’’’), (P17), (P17’), (P17’’), (P18), (P19), (P20), (P21), (P22), (P23), (P23’), (P23’’) or (P23’’’), wherein the electrochemical oxidation is carried out at ambient pressure. The obtained compound of formula (II) according to the present invention can be isolated from the reaction medium using commonly methods. The following examples serve to illustrate the invention. If not otherwise stated all parts are given are related to the weight and the temperature is given in °C.

The examples (summarized in the following tables) are carried as outlined in the following general examples 1 and 2. All reaction conditions which are deviating from the general examples are listed in the tables. GENERAL EXAMPLE 1 The undivided Teflon cells used for electrolysis were purchased from IKA (IKA-Werke GmbH & Co. KG, Staufen, Germany). The dimensions of the electrodes are 7 cm x 1 cm x 0.3 cm. In an undivided 7 mL Teflon pot cell, the appropriate solvent (5 mL) is presented and then sodium tetrafluoroborate (0.02 M), t-BuOOH (3.5 equiv.), pyridine (2.0 equiv.), and a compound of formula (I) (0.5 mmol) are dissolved. The cell is equipped with vitreous carbon electrodes at a distance of 0.5 cm. The immersion area of the electrodes is 1.8 cm². After the cell is fixed in a stainless-steel block, galvanostatic electrolysis is performed with a current density of 1.1 mA/cm² at 23 °C. After completion of the reaction, the reaction was processed with a saturated, aqueous NaCl solution and extracted three times with ethyl acetate. The organic layer was dried over sodium sulfate, filtered and removed under reduced pressure. Subsequently, the corresponding product was obtained after column chromatographic purification. GENERAL EXAMPLE 2 The undivided flow cell used for electrolysis was purchased from IKA (IKA-Werke GmbH & Co. KG, Staufen, Germany). The dimensions of the electrodes are 12 cm x 2 cm x 0.3 cm. In a reservoir, the appropriate solvent (5 mL) is presented and then sodium tetrafluoroborate (0.02 M), t-BuOOH (3.5 equiv.), pyridine (2.0 equiv.) and a compound of formula (I) (0.5 mmol) are dissolved. The solution is cyclically passed through the 34622-WO-PCT undivided flow cell, which is equipped with vitreous carbon electrodes with a spacing of 0.25 mm, at a speed of 20 mL/min. At a constant flow velocity, galvanostatic electrolysis is carried out with a current density of 0.5 mA/cm² at 23°C. After completion of the reaction, the reaction was processed with a saturated, aqueous NaCl solution and extracted three times with ethyl acetate. The organic phase was dried over sodium sulfate, filtered and removed under reduced pressure. Subsequently, the corresponding product was obtained after column chromatographic purification. Examples 1 - 3 Compound of formula (If) is oxidized according to general example 1

Exp. solvent Current density Yield [mA/cm²] [%] 1 MeCN 1.1 22 2 Ethyl acetate 1.1 25 3 MeCN 0.55 27 When O2 or H2O2 is used as oxygen source instead of t-BuOOH, no product is achieved. 34622-WO-PCT Example 4 Compound of formula (If) is oxidized according to general example 2

Exp. solvent Current density Yield [mA/cm²] [%] 4 MeCN 0.5 15 Example 5 Compound of formula (Ia) is oxidized according to general example 1

Exp. solvent Current density Yield [mA/cm²] [%] 5 MeCN 1.1 50 34622-WO-PCT Example 6 Compound of formula (Ib) is oxidized according to general example 1

Exp. solvent Current density Yield [mA/cm²] [%] 6 MeCN 1.1 8 Example 7 Compound of formula (Ic) is oxidized according to general example 1

[mA/cm²] [%] 7 MeCN 1.1 28 34622-WO-PCT Example 8 Compound of formula (Id) is oxidized according to general example 1

Example 9 Compound of formula (Ie) is oxidized according to general example 1

[mA/cm²] [%] 9 MeCN 1.1 41

34622-WO-PCT Example 10 Compound of formula (If) is oxidized according to general example 1

[mA/cm²] [%] 10 MeCN 1.1 55 Example 11 Compound of formula (Ig) is oxidized according to general example 1

[mA/cm²] [%] 11 MeCN 1.1 50

34622-WO-PCT Example 12 Compound of formula (Ih) is oxidized according to general example 1

[mA/cm²] [%] 12 MeCN 1.1 37 Example 13 Compound of formula (I’i) is oxidized according to general example 1

Exp. solvent Current density Yield [mA/cm²] [%] 13 MeCN 1.1 26 34622-WO-PCT Example 14 Compound of formula (Il) is oxidized according to general example 1

Exp. solvent Current density Yield [mA/cm²] [%] 14 MeCN 1.1 35 Example 15 Compound of formula (I’m) is oxidized according to general example 1

Yield [mA/cm²] [%] 15 MeCN 1.1 30 34622-WO-PCT Example 16 Compound of formula (I’n) is oxidized according to general example 1

Yield [mA/cm²] [%] 16 MeCN 1.1 18 Example 17 Compound of formula (I’n) is oxidized according to general example 1

[mA/cm²] [%] 17 MeCN 1.1 40

Claims

Claims 1. Process for producing a compound of formula (II) , wherein

R₁ is H; or a linear or branched C₁-C₄-alkyl moiety, and R₂ is H; a linear or branched C₁-C₁₀-alkyl moiety, which can be substituted; a linear or branched C₃-C₁₀-alkenyl moiety, which can be substituted; a linear or branched C₄- C₁₀-alkenyl moiety with a terminal alkyne group, which can be substituted; a linear or branched C₄-C₁₀- alkyne moiety, which can be substituted; a moiety of the following formula ,

A is -CH2-O-; a linear or branched C1-C6-alkylene moiety; or a linear or branched C2-C6-alkenylene moiety, and R8 is a linear or branched C1-C4-alkyl moiety; or R2 is a moiety of the following formula ,

R9 is a linear or branched C1-C4-alkyl moiety; or a linear or branched C2-C6-alkenyl moiety, and R3 is H; -CF3; or linear or branched C1-C4-alkyl moiety, and R4 is H or a linear or branched C1-C10-alkyl moiety, which can be substituted; a linear or branched C3-C10-alkenyl moiety, which can be substituted; a linear or branched C4-C10-alkenyl moiety with a terminal alkyne group, which can be substituted; a linear or branched C4-C10-alkyne moiety, which can be substituted; -CF3; a moiety of the following formula ,

A’ is -CH₂-O-; a linear or branched C₁-C₆-alkylene moiety; or a linear or branched C₂-C₆-alkenylene moiety and R’₈ is a linear or branched C₁-C₄-alkyl moiety; or R₄ is a moiety of the following formula ,

R’9 is a linear or branched C1-C6-alkyl moiety; or a linear or branched C2-C6-alkenyl moiety, or R3 and R4 form a -C=O moiety together with the C atom to which they are attached, and R5 is H; a linear or branched C1-C4-alkyl moiety; a linear or branched C2-C4- alkenyl moiety; or -CF3, and R6 is H; -O(CO)CH3; a linear or branched C1-C4-alkyl moiety; or -CF3, and R7 is H; -CF3; or a linear or branched C1-C4-alkyl moiety, and R’7 is H; -CF3; or a linear or branched C1-C4-alkyl moiety, or R’7 and R3 form a -CH2- bridge, by electrochemical oxidation of a compound of formula (I) , wherein all substituents for the compound of formula (II), in the presence of t-butyl hydroperoxide. 2. Process according to claim 1, wherein R1 is H or -CH3, and R2 is H; a linear or branched C1-C6-alkyl moiety, which can be substituted; a linear or branched C3-C8-alkenyl moiety, which can be substituted; a linear or branched C4- C8-alkenyl moiety with a terminal alkyne group, which can be substituted; a moiety of the following formula ,

A is -CH₂-O-; a linear or branched C₁-C₄-alkylene moiety; or a linear or branched C₂-C₄-alkenylene moiety, and R₈ is a linear or branched C₁-C₄-alkyl moiety; or R₂ is a moiety of the following formula ,

R9 is a linear or branched C1-C4-alkyl moiety; or a linear or branched C2-C4-alkenyl moiety, and R3 is H or -CH3, and R4 is H or a linear or branched C1-C4-alkyl moiety, which can be substituted; a linear or branched C3-C8-alkenyl moiety, which can be substituted; a linear or branched C3-C8-alkenyl moiety with a terminal alkyne group, which can be substituted; a linear or branched C3-C8-alkyne moiety, which can be substituted; a moiety of the following formula ,

A’ is a linear or branched C₁-C₄-alkylene moiety; or a linear or branched C₂-C₆- alkenylene moiety and R’₈ is a linear or branched C₁-C₄-alkyl moiety; or R₄ is a moiety of the following formula ,

R’9 is a linear or branched C1-C4-alkyl moiety; a linear or branched C1-C6-alkylene moiety; or a linear or branched C2-C6-alkenylene moiety, or R3 and R4 form a -C=O moiety together with the C atom to which they are attached, and R5 is H; a C1-C2-alkyl moiety; or a linear or branched C2-C4-alkylene moiety, and R6 is H; -O(CO)CH3; or a C1-C2-alkyl moiety, and R7 is H; or a C1-C2-alkyl moiety, and R’7 is H; or a C1-C2-alkyl moiety, or R’7 and R3 form a -CH2- bridge. 3. Process according to claim 1, wherein R1 is H or -CH3, and R2 is H; -CH3; a linear or branched C4-C8-alkylene moiety, which is substituted by an -OH group; a linear or branched C4-C8-alkylene moiety with a terminal alkyne group, which is substituted by an -OH group; or a moiety of the following formula ,

A is -CH₂-O-; or -CH=CH-, and R₈ is a C₁-C₂-alkyl moiety; or R₂ is a moiety of the following formula ,

R9 is a linear or branched C2-C4-alkenylene moiety, and R3 is H or -CH3, and R4 is -CH3; a linear or branched C4-C8-alkylene moiety, which is substituted by an - OH group; a linear or branched C4-C8-alkylene moiety with a terminal alkyne group, which is substituted by an -OH group; or a moiety of the following formula ,

A’ is -CH=CH-, and R’₈ is a C₁-C₂-alkyl moiety; or R₄ is a moiety of the following formula ,

R’9 is a linear or branched C2-C4-alkenylene moiety, or R3 and R4 form a -C=O moiety together with the C atom to which they are attached, and R5 is H; -CH3; or a linear or branched C2-C4-alkylene moiety, and R6 is H; -O(CO)CH3; or -CH3, and R7 is H; or a C1-C2-alkyl moiety, and R’7 is H; or a C1-C2-alkyl moiety, or R’7 and R3 form a -CH2- bridge. 4. Process according to claim 1, wherein a compound of the following formulae (Ia) to (In) , ,

, is oxidized. 5. Process according to any of the preceding claims, wherein the anode and the cathode are made from steel, glassy carbon and/or platinum. 6. Process according to any of the preceding claims, wherein the anode and cathode are in the form of a wire, a rod, a mesh, a grid, a sponge, or any other design suitable for the electrochemical reactor cell. 7. Process according to any of the preceding claims, wherein the process is carried out in at least one solvent. 8. Process according to claim 7, wherein the solvent is water or at least one non- aqueous solvent. 9. Process according to claim 7, wherein the at least one non-aqueous solvent is chosen from the group consisting of consisting of organic carbonates, polyethylene glycol, N-methyl-2-pyrrolidone, N-butylpyrrolidone, alcohols, esters, ketones, acetic acid, sulpholane, dimethylsulphoxide, tetrahydrofuran, 2-methyl-tetrahydrofuran, dimethylformamide, hexa-methylphosphoramide, acetonitrile, dichloromethane, and dimethoxyethane. 10. Process according to any of the preceding claims, wherein the process is carried out in the presence of at least one supporting electrolyte. 11. Process according to claim 10, wherein the at least one supporting electrolyte is chosen from the group consisting of HCl, H₂SO₄, Na₂SO₄, NaCl, NaHSO₄, alkyl- or arylsulfonic acids, phosphoric acid, phosphates and tetraalkylammonium salts. 12. Process according to claim 10 or 11, wherein the concentration of the at least supporting electrolyte is up to 5 mol/L. 13. Process according to any of the preceding claims, wherein the process is carried out in the presence of at least one base. 14. Process according to any of the preceding claims, wherein t-butyl hydroperoxide is present in an amount of from 0.1 vol% to 20 vol%. 15. Process according to any of the preceding claims, wherein the compound of formula (I) is added into the medium in an amount of from 0.1 mmol/L (mM) to 100 mM. 16. Process according to any of the preceding claims, wherein the current density used in the electrochemical oxidation is from 0.1 mA/cm² to 100 mA/cm².