EP2751308B1 - Process for cathodic deoxygenation of amides and esters - Google Patents

Description

The present invention relates to a process for the deoxygenation of carboxylic acid amides and carboxylic acid esters by cathodic reduction of a solution of these compounds.

The reduction of carboxylic acid amides to the corresponding amines according to the reaction equation shown schematically below, hereinafter also referred to as deoxygenation of amides, is a long known but not always easy to control reaction:

The skilled worker is fundamentally aware of various methods for the deoxygenation of amides. In general, (half) metal hydrides, such as borohydrides, for example sodium borohydride, in the presence of activators ( S.-H. Xiang, Synlett 2010, 12, 1829-1832 ) or diborane ( HC Brown, J. Org. Chem. 1973, 38, 912-916 ), and aluminum hydrides, eg lithium aluminum hydride ( N. Assimomytis et al, Synlett 2009, 17, 2777-2782 ) or diisobutylaluminum hydride ( Lizakharkin, IMKhorlina, Tetrahedron Letters 1962, 14, 619-620 ). Although these processes usually give the amines in high yields, the handling of (semi) -metal hydrides is not unproblematic because of their property in the presence of acidic protons in an exothermic reaction to form hydrogen and therefore generally requires extensive safety precautions. In addition, during the workup, oxides or hydroxides are formed whose removal from the desired product is generally complicated and which must be disposed of. These disadvantages are contrary to a use of these reactions on an industrial scale, so that these reactions have so far been found primarily in the production of complex drug molecules or in natural product syntheses application.

Several reports have been made of the catalytic hydrogenation of fatty acid amides to the corresponding fatty amines and copper chromite type catalysts - see US 5,840,985 and US 2007/0191642 , WO 2005/066112 describes the catalytic hydrogenation of amides to amines, eg the hydrogenation of 1-acetylpyrrolidine to 1-ethylpyrrolidine, on bimetallic or trimetallic transition metal contacts. However, these methods are usually limited to volatile amides.

On various occasions, electrochemical processes for the preparation of amines have been described. The WO 2008/003620 and the WO 2006/005531 describe, for example, the preparation of amines by cathodic reduction of oxime derivatives. A disadvantage of these processes is that first the corresponding oxime derivatives have to be generated and furthermore only primary amines and no secondary or tertiary amines are accessible in this way.

The object of the present invention is to provide a widely applicable process for the preparation of amines from the corresponding carboxylic acid amides, which overcomes the disadvantages of the prior art. The process should provide the corresponding amines with high selectivity and high yield.

This object is surprisingly achieved by a process in which subjecting a solution of a carboxylic acid amide in a solvent of a cathodic reduction, hereinafter also called cathodic deoxygenation, wherein the solution contains a salt as an additive, which is selected from quaternary ammonium and phosphonium salts , Surprisingly, this process can be transferred to the deoxygenation of carboxylic acid esters to the corresponding ethers according to the following reaction equation:

The present invention thus relates to a process for the deoxygenation of carboxylic acid amides and carboxylic acid esters by cathodic reduction of a solution of the carboxamide or of the carboxylic acid ester, which is characterized in that the solution used for the cathodic reduction of the carboxylic acid amide or of the carboxylic acid ester contains a salt as an additive, which quaternary ammonium salts is selected.

In the process of the invention, an amide is converted to the corresponding amine or an ester in the corresponding ether. Here, the carbonyl groups of the carboxamide unit of the amide or the carbonyl group of the carboxyl unit of the ester is converted into a CH ₂ group.

The inventive method requires no problematic or expensive reagents, as is used as a reducing agent inexpensive stream. The process allows the selective deoxygenation of the amides used without significantly undesirable side reactions, such as cleavage of the amidic C-N bond occur. Unlike the reduction with (semi) metal hydrides, there are no oxidic or hydroxidic by-products which have to be removed from the reaction mixture and disposed of. In addition, the process according to the invention not only enables the preparation of primary but also secondary and tertiary amines and the preparation of symmetrical and unsymmetrical ethers. In addition, the process of the invention allows the use of starting materials which have functional groups which are attacked in the known deoxygenation or lead to side reaction.

In the context of the present invention, the following terms have the following meanings, as far as they have no clear meaning content for the skilled person.

By a quaternary ammonium group is meant an atomic group having a positively charged nitrogen atom bearing four C-bonded substituents.

By a quaternary phosphonium group is meant an atomic group having a positively charged phosphorous atom bearing four C-bonded substituents.

The prefix C _n -C _m used in connection with organic radicals and organic compounds indicates the possible number of carbon atoms which the respective radical or the respective compound can have.

The term "C ₁ -C ₄ -alkyl" denotes a saturated, linear or branched aliphatic hydrocarbon radical having 1 to 4 carbon atoms, such as, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, isobutyl or tert-butyl.

The term "C ₁ -C ₁₀ -alkyl" denotes a saturated, linear or branched aliphatic hydrocarbon radical having 1 to 10 carbon atoms, for example methyl, ethyl, propyl, isopropyl, n-butyl, 2-butyl, sec-butyl, tert-butyl, n-pentyl, 2-pentyl, 2-methylbutyl, 3-methylbutyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl, 2-hexyl , 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,3-dimethylbutyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, 1 , 1,2-trimethylpropyl, 1,2,2-trimethyl-propyl, 1-ethylbutyl, 2-ethylbutyl, 1-ethyl-2-methylpropyl, n-heptyl, 2-heptyl, 3-heptyl, 2-ethylpentyl, 1-propylbutyl, n-octyl, 2-ethylhexyl, 2-propylheptyl, nonyl, decyl.

The term "haloalkyl" refers to a saturated, linear or branched aliphatic hydrocarbon radical having 1 to 10, especially 1 to 6 or 1 to 4, carbon atoms and wherein at least one or all, e.g. 1, 2, 3, 4, 5, 6 or 7 hydrogen atoms are replaced by halogen, in particular by fluorine, chlorine or bromine, e.g. for trifluoromethyl, chloromethyl, bromomethyl, 1,1-difluoroethyl, 2,2,2-trifluoroethyl, pentafluoroethyl, hexafluoropropyl or heptafluoropropyl.

The term "alkenyl" refers to a linear or branched aliphatic hydrocarbon radical which is monounsaturated or polyunsaturated and which generally has 2 to 10, in particular 2 to 6 or especially 2 to 4, carbon atoms, e.g. Ethenyl, 1-propenyl, 2-propenyl, 1-buten-1-yl, 2-buten-1-yl, 3-buten-1-yl, 1-buten-2-yl, 2-methyl-1-propene 1-yl, 2-methyl-2-propen-1-yl, etc.

The term "alkylene" refers to a branched or unbranched, saturated, divalent aliphatic hydrocarbon radical generally having from 2 to 20, especially from 3 to 10, and especially from 3 to 6 carbon atoms, e.g. Ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, 1-methylethane-1,2-diyl, 1,1-dimethylethane-1,2-diyl, 1-methylpropane 1,3-diyl, 1,1-dimethylpropane-1,3-diyl, 2,2-dimethylpropane-1,3-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1, 7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, dodecane-1,12-diyl, etc.

The term "alkenylene" refers to a branched or unbranched, monounsaturated, divalent aliphatic hydrocarbon radical usually having 2 to 20, especially 3 to 10 and especially 3 to 6 carbon atoms, e.g. 1,2-ethenediyl, propene-1,3-diyl, 2-butene-1,4-diyl, 1-methyl-ethen-1,2-diyl, 1-methyl-1-propene-1,3-diyl, 2- Methyl 1-propen-1,3-diyl, 1-pentene-1,5-diyl, 2-pentene-1,5-diyl, 1-hexene-1,6-diyl, 2-hexene-1,6- diyl, 3-hexene-1,6-diyl, 1-heptene-1,7-diyl, 2-heptene-1,7-diyl, 3-heptene-1,7-diyl, etc.

The term "alkoxy" refers to a branched or unbranched, saturated alkyl radical which is linked via an oxygen atom to the remainder of the molecule. The term "C ₁ -C ₁₀ alkoxy" refers to an alkyl group as previously defined below, having 1 to 10 carbon atoms. The term "C ₁ -C ₄ alkoxy" hereinafter denotes an alkyl radical as defined above which has 1 to 4 carbon atoms, for example methoxy, ethoxy, propyloxy, isopropyloxy, n-butyloxy, 2-butyloxy, sec-butyloxy, tert. Butyloxy, n-pentyloxy, 2-pentyloxy, 2-methylbutyloxy, 3-methylbutyloxy, 1,2-dimethylpropyloxy, 1,1-dimethylpropyloxy, 2,2-dimethylpropyloxy, 1-ethylpropyloxy, n-hexyloxy, 2-hexyloxy, 2-methylpentyloxy, 3-methylpentyloxy, 4-methylpentyloxy, 1,2-dimethylbutyloxy, 1,3-dimethylbutyloxy, 2, 3-dimethylbutyloxy, 1,1-dimethylbutyloxy, 2,2-dimethylbutyloxy, 3,3-dimethylbutyloxy, 1,1,2-trimethylpropyloxy, 1,2,2-trimethyl-propyloxy, 1-ethylbutyloxy, 2-ethylbutyloxy, 1- Ethyl 2-methylpropyloxy, n-heptyloxy, 2-heptyloxy, 3-heptyloxy, 2-ethylpentyloxy, 1-propylbutyloxy, n-octyloxy, 2-ethylhexyloxy, 2-propylheptyloxy, nonyl, decyloxy.

The term _{"C3 -C10} -cycloalkyl" denotes a saturated, mono- or bicyclic hydrocarbon radical containing from 3 to 10 carbon atoms, for example cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, bicyclo [2.2.1] heptyl, bicyclo [3.3.0] octyl, bicyclo [3.2.1] octyl, bicyclo [2.2.2] octyl, etc.

The term "aryl" denotes an aromatic or partially aromatic hydrocarbon radical which is mono- or polycyclic and usually has 6, 9, 10, 13 or 14 carbon atoms and which is preferably phenyl, naphthyl, tetrahydronaphthyl, indenyl, indanyl, fluorenyl, anthracenyl , Phenanthrenyl or naphthacenyl, more preferably phenyl or naphthyl.

The term "hetaryl" refers to an aromatic or partially aromatic heterocyclic radical which is mono- or polycyclic and usually has 5 to 14 ring members which have, in addition to carbon, at least one heteroatom as the ring atom selected from N, O and S, e.g. 1 to 4 N atoms or 1 atom selected from O and S and optionally 1, 2 or 3 further N atoms, and preferably the groups pyridyl, quinolinyl, acridinyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, tetrazinyl, pyrrolyl , Pyrazolyl, isoxazolyl, imidazolyl, oxazolyl, thiazolyl, thienyl, furyl.

The term "5 to 7 membered carbocycle" refers to a saturated or unsaturated hydrocarbon group having 5 to 7 carbon atoms as ring members.

The term "5 to 8 membered heterocycle" denotes a monocyclic or polycyclic, saturated or unsaturated heterocyclic radical having 5 to 8 ring atoms, wherein the ring atoms in addition to carbon, at least one heteroatom, which is preferably selected from nitrogen, sulfur and oxygen, for example pyrrolidinyl , Piperidinyl, morpholinyl, thiomorpholinyl, piperazinyl, hexahydroazepinyl, etc.

The term "poly (oxyethylene)" denotes in a polyether radical which oxyethylene groups (OCH ₂ CH ₂ ) is constructed as a repeating unit and which is bonded via an oxygen atom.

The term "alkanol" denotes an aliphatic, saturated or unsaturated alcohol which has one or more, for example 1, 2 or 3, in particular a hydroxyl group (s) and which generally has 1 to 10 carbon atoms. Accordingly, an alkanol having from 1 to 10 carbon atoms such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, pentanol, hexanol, heptanol, octanol is meant by C ₁ -C ₁₀ -alkanol , Nonanol and decanol, wherein the last mentioned alkanols may be linear or branched, furthermore glycol, propanediol, butanediol and glycerol.

The term "alkylene carbonate" refers to cyclic carbonates of the corresponding alkylene glycols such as ethylene carbonate (1,3-dioxolan-2-one) and propylene carbonate (4-methyl-1,3-dioxolan-2-one).

The term "alkyl phosphate" refers to an anion of the formula R-OP (O) O ₂ ² - wherein R is alkyl, eg, methyl phosphate.

The term "alkylphosphonate" refers to an anion of the formula RP (O) O ₂ ² - wherein R is alkyl, for example methylphosphonate.

The term "alkyl sulfate" refers to an anion of the formula R-OS (O) ₂ O- wherein R is alkyl, eg, methyl sulfate (= methosulfate) or ethyl sulfate.

The term "aryl sulfate" denotes an anion of the formula R-OS (O) ₂ O- in which R is aryl which optionally carries 1 to 3 alkyl groups, for example phenyl sulfate, toluene sulfate, mesitylene sulfate.

The term "arylsulfonate" denotes an anion of the formula RS (O) ₂ O- in which R is aryl which optionally carries 1 to 3 alkyl groups, for example phenylsulfonate, toluenesulfonate, mesitylene sulfonate.

The term "carboxylate" refers to the anion of an aliphatic or aromatic carboxylic acid, such as formate, acetate, propionate or benzoate.

The term "haloalkylsulfonate" refers to an anion of the formula RS (O) ₂ O- wherein R is haloalkyl, eg trifluoromethyl.

The term "imide" refers to anions of cyclic or acyclic carboxylic imides or sulfonic imides in which the imide nitrogen carries a negative charge.

The term "pseudohalide" for example, the following anions: cyanide (CN), azide (N ₃ -), cyanate (OCN), isocyanate (NCO), fulminate (CNO), thiocyanate (SCN) and isothiocyanate (NCS).

The quaternary ammonium salts used as additives have at least 2, e.g. 2 to 100, preferably 2 to 10 and especially 2 or 3 quaternary ammonium groups.

worin

k

für eine ganze Zahl im Bereich von 1 bis 99, vorzugsweise im Bereich von 1 bis 9, insbesondere für 1, 2, 3 oder 4 und speziell für 1 oder 2 steht,

A

für Stickstoff steht,

Z

für eine C₂-C₁₂-Alkylengruppe steht, worin gegebenenfalls 1, 2 oder 3 CH₂-Gruppen, welche von den Stickstoffatomen A und voneinander durch wenigstens 2 C-Atome getrennt sind, durch Sauerstoffatome ersetzt sein können, bevorzugt für eine Alkylengruppe mit 2 bis 6 Kohlenstoffatomen, worin gegebenenfalls 1 oder 2 CH₂-Gruppen, welche von den Stickstoffatomen und voneinander durch wenigstens 2 C-Atome getrennt sind, durch Sauerstoffatome ersetzt sein können, insbesondere für eine Alkylengruppe mit 2 bis 4 Kohlenstoffatomen, worin gegebenenfalls 1 CH₂-Gruppe, welche von den Stickstoffatomen durch wenigstens 2 C-Atome getrennt ist, durch ein Sauerstoffatom ersetzt sein kann;

R¹, R², R³ und R⁴

jeweils unabhängig von einander für C₁-C₁₀-Alkyl stehen, welches jeweils unsubstituiert ist oder mit 1 oder 2 Substituenten, ausgewählt unter Hydroxy, Alkoxy und Poly(oxyethylen), substituiert sein kann, bevorzugt für C₁-C₆-Alkyl stehen, welches jeweils unsubstituiert ist oder mit 1 oder 2 Substituenten, ausgewählt unter Hydroxy, Alkoxy und Poly(oxyethylen), substituiert sein kann, insbesondere für C₁-C₃-Alkyl stehen, welches jeweils unsubstituiert ist oder mit 1 oder 2 Substituenten, ausgewählt unter Hydroxy, Alkoxy und Poly(oxyethylen), substituiert sein kann, oder

R¹ und R²

zusammen mit dem Stickstoff, an den sie gebunden sind, auch für einen 5 bis 8-gliedrigen Heterocyclus stehen können, der im Ring 1 N-Atom enthält und unsubstituiert ist oder mit 1 bis 4 Substituenten, ausgewählt unter Hydroxy, C₁-C₄-Alkoxy und C₁-C₄-Alkyl, substituiert sein kann,

R⁵ und R⁶

jeweils unabhängig von einander für C₁-C₁₀-Alkyl stehen, welches jeweils unsubstituiert ist oder mit 1 oder 2 Substituenten, ausgewählt unter Hydroxy, Alkoxy und Poly(oxyethylen), substituiert sein kann, bevorzugt für C₁-C₆-Alkyl stehen, welches jeweils unsubstituiert ist oder mit 1 oder 2 Substituenten, ausgewählt unter Hydroxy, Alkoxy und Poly(oxyethylen), insbesondere für C₁-C₃-Alkyl stehen, welches jeweils unsubstituiert ist oder mit 1 oder 2 Substituenten, ausgewählt unter Hydroxy, Alkoxy und Poly(oxyethylen), substituiert sein kann.

The additives used in the process according to the invention are salts whose cation has the formula I

wherein

k

is an integer in the range from 1 to 99, preferably in the range from 1 to 9, in particular 1, 2, 3 or 4 and especially 1 or 2,

A

stands for nitrogen,

Z

is a C ₂ -C ₁₂ alkylene group in which optionally 1, 2 or 3 CH ₂ groups, which are separated from the nitrogen atoms A and from each other by at least 2 C atoms, may be replaced by oxygen atoms, preferably an alkylene group 2 to 6 carbon atoms, wherein optionally 1 or 2 CH ₂ groups, which are separated from the nitrogen atoms and from each other by at least 2 C atoms, may be replaced by oxygen atoms, in particular an alkylene group having 2 to 4 carbon atoms, wherein optionally 1 CH ₂ group which is separated from the nitrogen atom by at least 2 C-atoms may be replaced by an oxygen atom;

R ¹ , R ² , R ³ and R ⁴

each independently of one another are C ₁ -C ₁₀ -alkyl, which is in each case unsubstituted or may be substituted by 1 or 2 substituents selected from hydroxy, alkoxy and poly (oxyethylene), preferably C ₁ -C ₆ -alkyl which is in each case unsubstituted or may be substituted by 1 or 2 substituents selected from hydroxy, alkoxy and poly (oxyethylene), in particular C ₁ -C ₃ -alkyl, each of which is unsubstituted or having 1 or 2 substituents selected may be substituted by hydroxy, alkoxy and poly (oxyethylene), or

R ¹ and R ²

together with the nitrogen to which they are attached may also stand for a 5 to 8-membered heterocycle which contains 1 N-atom in the ring and is unsubstituted or having 1 to 4 substituents selected from hydroxy, C ₁ -C ₄ Alkoxy and C ₁ -C ₄ alkyl, may be substituted,

R ⁵ and R ⁶

each independently of one another are C ₁ -C ₁₀ -alkyl, which is in each case unsubstituted or may be substituted by 1 or 2 substituents selected from hydroxy, alkoxy and poly (oxyethylene), preferably C ₁ -C ₆ -alkyl which is in each case unsubstituted or having 1 or 2 substituents selected from hydroxy, alkoxy and poly (oxyethylene), in particular C ₁ -C ₃ -alkyl, which is in each case unsubstituted or having 1 or 2 substituents selected from hydroxy, alkoxy and poly (oxyethylene), may be substituted.

The variables appearing in the formula I, A, R ^1, R ^2, R ^3, R ^4, R ⁵ and R ⁶ have independently of each other or, preferably, in combination with each other have the following meanings.

The variable k preferably stands for an integer in a range from 1 to 9, in particular for 1, 2, 3 or 4 and especially for 1 or 2.

The variable Z is preferably a linear alkylene group having 2 to 12, especially 2 to 6, especially 2 to 4 carbon atoms.

R ¹ , R ² , R ³ and R ⁴ are each, independently of each other, preferably C ₁ -C ₆ -alkyl, each of which is unsubstituted or substituted by 1 or 2 substituents selected from hydroxy, alkoxy and poly (oxyethylene) can, and in particular are C ₁ -C ₃ alkyl, which is in each case unsubstituted or may be substituted by 1 or 2 substituents selected from hydroxy, alkoxy and poly (oxyethylene).

R ⁵ and R ⁶ are each independently preferably C ₁ -C ₆ -alkyl, each of which is unsubstituted or may be substituted by 1 or 2 substituents selected from hydroxy, alkoxy and poly (oxyethylene), and is preferably unsubstituted, and in particular C ₁ -C ₃ alkyl, each of which is unsubstituted or substituted with 1 or 2 substituents selected from hydroxy, alkoxy, and poly (oxyethylene), may be substituted and is preferably unsubstituted.

In particular, R ² , R ³ , R ⁵ and R ^{6 are} methyl.

In particular, R ¹ and R ^{4 are} C ₁ -C ₄ -alkyl and in particular methyl or ethyl.

k

für eine ganze Zahl in einem Bereich von 1 bis 9, vorzugsweise 1, 2, 3 oder 4 und insbesondere 1 oder 2 steht,

A

für Stickstoff steht,

Z

für eine lineare Alkylengruppe mit 2 bis 12, vorzugsweise mit 2 bis 6, insbesondere 2 bis 4 Kohlenstoffatomen steht;

R¹, R², R³ und R⁴

jeweils unabhängig von einander für C₁-C₆-Alkyl stehen, welches jeweils unsubstituiert ist oder mit 1 oder 2 Substituenten, ausgewählt unter Hydroxy, Alkoxy und Poly(oxyethylen), substituiert sein kann, vorzugsweise für C₁-C₃-Alkyl stehen, welches jeweils unsubstituiert ist oder mit 1 oder 2 Substituenten, ausgewählt unter Hydroxy, Alkoxy und Poly(oxyethylen), substituiert sein kann oder

R⁵ und R⁶

jeweils unabhängig von einander für C₁-C₆-Alkyl und vorzugsweise für C₁-C₄-Alkyl stehen, welches jeweils unsubstituiert ist oder mit 1 oder 2 Substituenten, ausgewählt unter Hydroxy, Alkoxy und Poly(oxyethylen), substituiert sein kann und vorzugsweise unsubstituiert ist.

Particular preference is given to cations of the formula I in which

k

is an integer in a range from 1 to 9, preferably 1, 2, 3 or 4 and in particular 1 or 2,

A

stands for nitrogen,

Z

is a linear alkylene group having from 2 to 12, preferably from 2 to 6, especially 2 to 4 carbon atoms;

R ¹ , R ² , R ³ and R ⁴

C ₁ -C ₆ alkyl, each independently of each other, each of which is unsubstituted or may be substituted with 1 or 2 substituents selected from hydroxy, alkoxy, and poly (oxyethylene), preferably are ₃ alkyl, C ₁ -C which is in each case unsubstituted or may be substituted by 1 or 2 substituents selected from hydroxy, alkoxy and poly (oxyethylene), or

R ⁵ and R ⁶

each independently of one another are C ₁ -C ₆ -alkyl and preferably C ₁ -C ₄ -alkyl, which is in each case unsubstituted or may be substituted by 1 or 2 substituents selected from hydroxy, alkoxy and poly (oxyethylene), and is preferably unsubstituted.

k

für 1 bis 9, vorzugsweise 1, 2, 3 oder 4 und insbesondere 1 oder 2 steht,

A

für Stickstoff steht,

Z

für eine lineare Alkylengruppe mit 2 bis 12 Kohlenstoffatomen, vorzugsweise mit 2 bis 6 Kohlenstoffatomen, insbesondere 2 bis 4 Kohlenstoffatomen steht,

R¹ und R⁴

jeweils unabhängig von einander für C₁-C₄-Alkyl, vorzugsweise Methyl und Ethyl, stehen, und

R², R³, R⁵ und R⁶

für Methyl stehen.

Particularly preferred is the cation of the formula I in which

k

is 1 to 9, preferably 1, 2, 3 or 4 and in particular 1 or 2,

A

stands for nitrogen,

Z

represents a linear alkylene group having 2 to 12 carbon atoms, preferably having 2 to 6 carbon atoms, in particular 2 to 4 carbon atoms,

R ¹ and R ⁴

each independently of one another are C ₁ -C ₄ -alkyl, preferably methyl and ethyl, and

R ² , R ³ , R ⁵ and R ⁶

stand for methyl.

The type of anion of the salt used as an additive is of minor importance to the process according to the invention. However, it is preferably not necessarily selected from electrochemically inert anions. Examples of suitable anions of the salt used as an additive are sulfate, hydrogensulfate, alkylsulfate, arylsulfate, arylsulfonate, haloalkylsulfonate, halide, pseudohalides such as CN, SCN, OCN and N ₃ , carboxylate, carbonate, imide such as bis (trifluoromethylsulfonyl) imide, phosphate , Alkyl phosphate, nitrate, tetrafluoroborate, hexafluorophosphate and perchlorate. Preference is given to hydrogen sulfate, alkyl sulfate, aryl sulfate, arylsulfonate, haloalkylsulfonate, arylsulfonate, in particular sulfate and alkylsulfate such as ethyl sulfate or methyl sulfate.

In preferred embodiments of the invention, salts are used whose cations of the formula I obey, wherein A is nitrogen and the variables k, Z, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶
have the meanings described in each case in a row of Table 1. Compounds in which A is phosphorus are not within the scope of the present invention. Table 1: connection A k Z R ¹ , R ³ , R ⁵ R ⁶ R ² , R ⁴ 1 N 1 ethanediyl methyl methyl 2 N 1 ethanediyl methyl ethyl 3 N 2 ethanediyl methyl methyl 4 N 2 ethanediyl methyl ethyl 5 N 3 ethanediyl methyl methyl 6 N 3 ethanediyl methyl ethyl 7 N 1 propanediyl methyl methyl 8th N 1 propanediyl methyl ethyl 9 N 2 propanediyl methyl methyl 10 N 2 propanediyl methyl ethyl 11 N 1 butanediyl methyl methyl 12 N 1 butanediyl methyl ethyl connection A k Z R ¹ , R ³ , R ⁵ , R ⁶ R ² , R ⁴ 13 N 1 pentanediyl methyl methyl 14 N 1 pentanediyl methyl ethyl 15 N 1 hexanediyl methyl methyl 16 N 1 hexanediyl methyl ethyl 17 N 1 heptanediyl methyl methyl 18 N 1 heptanediyl methyl ethyl 19 N 1 hexanediyl methyl methyl 20 N 1 octanediyl methyl ethyl 21 N 1 nonanediyl methyl methyl 22 N 1 nonanediyl methyl ethyl 23 N 1 decanediyl methyl methyl 24 N 1 decanediyl methyl ethyl 25 N 1 dodecanediyl methyl methyl 26 N 1 dodecanediyl methyl ethyl 27 P 1 ethanediyl methyl methyl 28 P 1 ethanediyl methyl ethyl 29 P 2 ethanediyl methyl methyl 30 P 2 ethanediyl methyl ethyl 31 P 3 ethanediyl methyl methyl 32 P 3 ethanediyl methyl ethyl 33 P 1 propanediyl methyl methyl 34 P 1 propanediyl methyl ethyl 35 P 2 propanediyl methyl methyl 36 P 2 propanediyl methyl ethyl 37 P 1 butanediyl methyl methyl 38 P 1 butanediyl methyl ethyl 39 P 1 pentanediyl methyl methyl 40 P 1 pentanediyl methyl ethyl 41 P 1 hexanediyl methyl methyl 42 P 1 hexanediyl methyl ethyl 43 P 1 heptanediyl methyl methyl 44 P 1 heptanediyl methyl ethyl 45 P 1 hexanediyl methyl methyl 46 P 1 octanediyl methyl ethyl 47 P 1 nonanediyl methyl methyl 48 P 1 nonanediyl methyl ethyl 49 P 1 decanediyl methyl methyl 50 P 1 decanediyl methyl ethyl 51 P 1 dodecanediyl methyl methyl 52 P 1 dodecanediyl methyl ethyl

Particularly preferred salts are N, N, N, N ', N', N'-hexamethyl-1,3-propanediammonium salts, N, N'-diethyl, N, N ', N', N'-tetramethyl-1, 3-propanediammonium salts, N, N, N, N ', N', N'-hexamethyl-1,6-hexanediammonium salts, N, N'-diethyl, N, N ', N', N'-tetramethyl-1, 6-hexanediammonium salts, N, N'-diethyl, N, N ', N', N'-tetramethyl-1,9-nonanediammonium salts and N, N'-diethyl, N, N ', N', N'- tetramethyl-1,12-dodecane-diammonium salts especially the methosulfates and ethyl sulfates of the aforementioned salts.

The solution of the carboxylic acid amide or the carboxylic acid ester generally contains the quaternary ammonium salt in a concentration in the range of 0.001 to 1000 mmol / l, often in the range of 0.1 to 500 mmol / l, preferably in the range of 1 to 100 mmol / l, in particular in the range of 25 to 75 mmol / l.

The ammonium and phosphonium salts described are known and sometimes commercially available or can be prepared in a conventional manner, starting from the corresponding tertiary amines or the tertiary phosphines. Tertiary amines, if not commercially available, are available, for example, by reacting primary amines with formaldehyde and formic acid (Eschweiler-Clark reaction). Tertiary phosphines in turn can be prepared by reaction of phosphorus trichloride with alkyl Grignard reagents or by conversion of phosphine with alkyl halides. The tertiary amines and / or the tertiary phosphines can be converted with alkylating agents such as dimethyl sulfate, diethyl sulfate or trimethyl phosphate into the corresponding quaternary ammonium or phosphonium salts. The counterions of the salts thus obtainable are derived from the alkylating agents used. If an anion other than counterion is desired, it may easily be added e.g. be replaced by inorganic metathesis.

According to the invention, the substrate used is a carboxylic acid amide or a carboxylic acid ester of the formula II

Y

steht für eine chemische Bindung oder eine Alkylengruppe mit 1 bis 6 Kohlenstoffatomen,

X

steht für Sauerstoff oder N-R⁹,

R⁷

ist ausgewählt ist unter C₁-C₁₀-Alkyl, C₂-C₁₀-Alkenyl, C₁-C₁₀-Alkoxy, C₁-C₁₀-Haloalkyl, C₁-C₁₀-Haloalkoxy, C₃-C₁₀-Cycloalkyl, Aryl und Hetaryl, wobei der Ring in den drei letztgenannten Gruppen unsubstituiert ist oder mit bis zu 6 Substituenten substituiert sein kann, die unter Halogen, Hydroxy, C₁-C₄-Alkyl und C₁-C₄-Alkoxy ausgewählt sind, und

R⁸

ausgewählt ist unter Wasserstoff, C₁-C₁₀-Alkyl, das unsubstituiert ist oder 1 oder 2 Substituenten aufweist, die unter Hydroxy, C₁-C₄-Alkoxy und Aryl ausgewählt sind, C₂-C₁₀-Alkenyl, C₁-C₁₀-Haloalkyl, C₁-C₁₀-Haloalkoxy, C₃-C₁₀-Cycloalkyl, Aryl und Hetaryl, wobei der Ring in den drei letztgenannten Gruppen unsubstituiert ist oder mit bis zu 6 Substituenten substituiert sein kann, die unter Halogen, Hydroxy, C₁-C₄-Alkyl und C₁-C₄-Alkoxy ausgewählt sind,
wobei R⁸ von Wasserstoff verschieden ist, wenn X für O steht,

R⁷ und R⁸

können zusammen für C₃-C₂₀-Alkylen oder C₃-C₂₀-Alkenylen stehen, welches unsubstituiert ist oder mit bis zu 6 Substituenten substituiert ist, die unter Hydroxy, C₁-C₄-Alkyl und C₁-C₄-Alkoxy ausgewählt sind, wobei 2 an benachbarte C-Atome gebundene Substituenten zusammen mit den C-Atomen, an die sie gebunden sind, auch einen 5 bis 7-gliedrigen Carbocyclus bilden können; und

R⁹

für Wasserstoff oder C₁-C₁₀-Alkyl steht, das unsubstituiert ist oder 1 oder 2 Substituenten aufweist, die unter Hydroxy, C₁-C₄-Alkoxy und Aryl ausgewählt sind.

In formulas II and III, the variables X, Y, R ⁷ and R ^{8 have} the following meanings:

Y

represents a chemical bond or an alkylene group having 1 to 6 carbon atoms,

X

is oxygen or NR ⁹ ,

R ⁷

is selected from C ₁ -C ₁₀ -alkyl, C ₂ -C ₁₀ -alkenyl, C ₁ -C ₁₀ -alkoxy, C ₁ -C ₁₀ -haloalkyl, C ₁ -C ₁₀ -haloalkoxy, C ₃ -C ₁₀ - cycloalkyl, aryl and hetaryl, where the ring is unsubstituted in the latter three groups or may be substituted with up to 6 substituents, ₄ -alkoxy are selected from halogen, hydroxy, C ₁ -C ₄ alkyl and C ₁ -C and

R ⁸

is selected from hydrogen, C ₁ -C ₁₀ -alkyl which is unsubstituted or has 1 or 2 substituents selected from hydroxy, C ₁ -C ₄ -alkoxy and aryl, C ₂ -C ₁₀ -alkenyl, C ₁ - C ₁₀ haloalkyl, C ₁ -C ₁₀ haloalkoxy, C ₃ -C ₁₀ cycloalkyl, aryl and hetaryl, where the ring in the latter three groups is unsubstituted or may be substituted by up to 6 substituents which are halogen, hydroxy , C ₁ -C ₄ -alkyl and C ₁ -C ₄ -alkoxy are selected,
where R ^{8 is} different from hydrogen when X is O,

R ⁷ and R ⁸

may together be C ₃ -C ₂₀ -alkylene or C ₃ -C ₂₀ -alkenylene which is unsubstituted or substituted by up to 6 substituents which are selected from hydroxy, C ₁ -C ₄ -alkyl and C ₁ -C ₄ - Alkoxy, wherein 2 substituents attached to adjacent carbon atoms together with the carbon atoms to which they are attached may also form a 5- to 7-membered carbocycle; and

R ⁹

is hydrogen or C ₁ -C ₁₀ -alkyl which is unsubstituted or has 1 or 2 substituents selected from hydroxy, C ₁ -C ₄ -alkoxy and aryl.

Preferably, the variables X, Y, R ⁷ , R ⁸ and R ⁹ in the formulas II and III independently and in combination with one another have the following meanings.

Y is preferably a chemical bond or an alkylene group having 1 to 6 carbon atoms and in particular a chemical bond,
X is preferably NR ⁹ ,
R ⁷ is preferably selected from C ₃ -C ₁₀ cycloalkyl, aryl and hetaryl, where the ring is unsubstituted in the three groups or may be substituted with up to 6 substituents selected from halo, hydroxy, C ₁ -C ₄ alkyl and C ₁ -C ₄ -alkoxy are selected, and in particular selected from aryl, which is unsubstituted or may be substituted by up to 6 substituents which are selected from halogen, hydroxy, C ₁ -C ₄ -alkyl and C ₁ -C ₄ - Alkoxy are selected.

R ⁸ is preferably selected from C ₁ -C ₁₀ -alkyl which is unsubstituted or has 1 or 2 substituents selected from hydroxy, C ₁ -C ₄ -alkoxy and aryl, C ₁ -C ₁₀ -haloalkyl, C ₃ C ₁₀ -cycloalkyl, aryl and hetaryl, wherein the ring in the last three groups is unsubstituted or may be substituted by up to 6 substituents which are halogen, hydroxy, C ₁ -C ₄ -alkyl and C ₁ -C ₄ - Alkoxy are selected, and in particular is selected from C ₁ -C ₁₀ alkyl, which is unsubstituted or having 1 or 2 substituents selected from hydroxy, C ₁ -C ₄ alkoxy and aryl, and aryl, which is unsubstituted or may be substituted with up to 6 substituents selected from halo, hydroxy, C ₁ -C ₄ alkyl and C ₁ -C ₄ alkoxy.

R ⁷ and R ⁸ may preferably together also be C ₃ -C ₂₀ -alkylene.

Y

für eine chemische Bindung oder eine Alkylengruppe mit 1 bis 6 Kohlenstoffatomen steht,

X

für N-R⁹ steht,

R⁷

ausgewählt ist unter C₃-C₁₀-Cycloalkyl, Aryl und Hetaryl, wobei der Ring in den drei Gruppen unsubstituiert ist oder mit bis zu 6 Substituenten substituiert sein kann, die unter Halogen, Hydroxy, C₁-C₄-Alkyl und C₁-C₄-Alkoxy ausgewählt sind, und

R⁸

ausgewählt ist unter C₁-C₁₀-Alkyl, das unsubstituiert ist oder 1 oder 2 Substituenten aufweist, die unter Hydroxy, C₁-C₄-Alkoxy und Aryl ausgewählt sind, C₁-C₁₀-Haloalkyl, C₃-C₁₀-Cycloalkyl, Aryl und Hetaryl, wobei der Ring in den drei letztgenannten Gruppen unsubstituiert ist oder mit bis zu 6 Substituenten substituiert sein kann, die unter Halogen, Hydroxy, C₁-C₄-Alkyl und C₁-C₄-Alkoxy ausgewählt sind,

oder

R⁷ und R⁸

zusammen für C₃-C₂₀-Alkylen stehen; und

R⁹

für Wasserstoff oder C₁-C₁₀-Alkyl steht.

In a preferred embodiment of the process according to the invention, a carboxamide of the formula II is used, in which

Y

represents a chemical bond or an alkylene group having 1 to 6 carbon atoms,

X

stands for NR ⁹ ,

R ⁷

is selected from C ₃ -C ₁₀ -cycloalkyl, aryl and hetaryl, wherein the ring in the three groups is unsubstituted or may be substituted with up to 6 substituents which are halogen, hydroxy, C ₁ -C ₄ -alkyl and C ₁ -C ₄ alkoxy are selected, and

R ⁸

is selected from C ₁ -C ₁₀ -alkyl which is unsubstituted or has 1 or 2 substituents selected from hydroxy, C ₁ -C ₄ -alkoxy and aryl, C ₁ -C ₁₀ -haloalkyl, C ₃ -C ₁₀ -cycloalkyl, aryl and hetaryl, where the ring in the latter three groups is unsubstituted or may be substituted by up to 6 substituents which are halogen, hydroxy, C ₁ -C _4- alkyl and C ₁ -C ₄ -alkoxy are selected,

or

R ⁷ and R ⁸

together represent C ₃ -C ₂₀ -alkylene; and

R ⁹

is hydrogen or C ₁ -C ₁₀ alkyl.

Y

für eine chemische Bindung steht,

X

für eine Gruppe N-R⁹ steht,

R⁷

ausgewählt ist unter Aryl, das unsubstituiert ist oder mit bis zu 6 Substituenten substituiert sein kann, die unter Halogen, Hydroxy, C₁-C₄-Alkyl und C₁-C₄-Alkoxy ausgewählt sind, und

R⁸

ausgewählt ist unter C₁-C₁₀-Alkyl, das unsubstituiert ist oder 1 oder 2 Substituenten aufweist, die unter Hydroxy, C₁-C₄-Alkoxy und Aryl ausgewählt sind, und Aryl, das unsubstituiert ist oder mit bis zu 6 Substituenten substituiert sein kann, die unter Halogen, Hydroxy, C₁-C₄-Alkyl und C₁-C₄-Alkoxy ausgewählt sind;

R⁹

für Wasserstoff oder C₁-C₁₀-Alkyl steht.

In a particularly preferred embodiment of the process according to the invention, a substrate according to the formula II is used, in which

Y

stands for a chemical bond,

X

represents a group NR ⁹ ,

R ⁷

is selected from aryl which is unsubstituted or may be substituted by up to 6 substituents selected from halogen, hydroxy, C ₁ -C ₄ alkyl and C ₁ -C ₄ alkoxy, and

R ⁸

is selected from C ₁ -C ₁₀ -alkyl which is unsubstituted or has 1 or 2 substituents selected from hydroxy, C ₁ -C ₄ -alkoxy and aryl, and aryl which is unsubstituted or substituted with up to 6 substituents which are selected from halogen, hydroxy, C ₁ -C ₄ -alkyl and C ₁ -C ₄ -alkoxy;

R ⁹

is hydrogen or C ₁ -C ₁₀ alkyl.

In preferred embodiments of the process according to the invention, the substrate used is a secondary or tertiary carboxylic acid amide, ie a compound of the formula I in which X is a group NR ⁹ , where R ⁸ and optionally R ^{9 have} a meaning other than hydrogen. In a specific embodiment of the process according to the invention, the substrate used is a secondary carboxylic acid amide, ie a compound of the formula II in which X is a group NR ⁹ , where either R ^{8 has} a meaning other than hydrogen and R ^{9 is} hydrogen. In another specific embodiment of the process according to the invention, the substrate used is a tertiary carboxylic acid amide used, ie a compound of the formula II, wherein X is a group NR ⁹ , wherein R ⁸ and R ⁹ each have a meaning other than hydrogen.

The process according to the invention can be carried out in all electrolysis cells known to the person skilled in the art. The process according to the invention is preferably carried out in a divided electrolysis cell. A divided electrolytic cell is understood to mean a cell arrangement in which the cathode space and the anode space and thus the solution (catholyte) contained in the cathode space are separated from the solution (anolyte) contained in the anode space in a manner which does not transfer charge but does not transfer organic charge Substances between catholyte and anolyte allowed. The separation of cathode space and anode space can be achieved in a conventional manner by suitable separation media. As separation media can ion exchange membranes, microporous membranes, diaphragms, filter fabric of non-electron-conducting materials, glass frits, and porous ceramics are used. Preferably, ion exchange membranes, in particular cation exchange membranes, are used. These conductive membranes are commercially available for example under the trade name Nafion ^® (Fa. ET. DuPont de Nemours and Company) and Gore Select ^® (Messrs. WL Gore & Associates, Inc.).

Preferably, the cathodic reduction of the carboxylic acid amide or carboxylic ester solution is conducted in a divided flow cell. Divided cells, in particular divided flow cells, which have a plane-parallel electrode arrangement, are preferably used.

In the method of the invention, the substrate is cathodically reduced, i. the solution containing the carboxylic acid amide or the carboxylic acid ester is added to the cathode half-space in a divided electrolytic cell when the electrolysis is carried out. The carboxylic acid amide or the carboxylic acid ester are then dissolved in the catholyte.

According to the invention, a solution of the carboxylic acid amide or of the carboxylic acid ester is subjected to a cathodic reduction, ie the substrate is present in dissolved form in an organic solvent. Suitable solvents are in principle all inert organic solvents customary for electrochemical reactions and mixtures thereof with water. Examples of solvents are, in particular, alkanols, for example the abovementioned C ₁ -C ₄ -alkanols, alkylene carbonates, such as ethylene carbonate or propylene carbonate, cyclic and acyclic ethers, for example diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, Tetrahydrofuran, methyltetrahydrofuran, dioxane or pyran, alkylglycols, dialkylglycols, alkyldiglycols and Dialkyl diglycols such as methyl glycol, ethyl glycol, dimethyl glycol, diethyl glycol, methyl diglycol or ethyl diglycol, polyethers such as triethylene glycol or higher polyethylene glycols and their alkyl ethers, and nitriles, such as acetonitrile or propionitrile and mixtures of these solvents. The solution used for cathodic reduction may also contain mixtures of said organic solvents with water or with C ₅ -C ₇ hydrocarbons. Other suitable solvents are described in Kosuke Izutsu, "Electrochemistry in Nonaqueous Solutions", published by Wiley-VCH 2002, chap. 1 , Preferably, the catholyte contains inert solvent chosen from C ₁ -C ₄ -alkanols, dimethyl carbonate, propylene carbonate, tetrahydrofuran, dimethoxyethane, acetonitrile, mixtures thereof and mixtures thereof with water, mixtures of these inert solvent or mixtures of these inert solvent with C ₅ -C ₇ - hydrocarbons.

Particularly preferred are C ₁ -C ₄ -alkanols, tetrahydrofuran, dimethoxyethane or mixtures thereof and mixtures with water. This can form a single- or multi-phase system.

Very particular preference is given to C ₁ -C ₄ -alkanols, which are optionally used in mixtures with one another and / or water. C ₁ -C ₄ alkanols include monools such as methanol, ethanol, n-propanol, i-propanol, n-butanol, sec-butanol, tert-butanol, diols such as glycol and triols such as glycerol. Especially preferred as the solvent is methanol.

When carrying out the method according to the invention in a divided electrolysis cell, the catholyte and the anolyte may contain the same or different solvents.

To ensure sufficient conductivity, the solution of the carboxylic acid amide or of the carboxylic acid ester usually contains a mineral acid or an inert conductive salt, mineral acids being preferred. Preferred mineral acids are hydrochloric acid, sulfuric acid or phosphoric acid, in particular sulfuric acid. When carrying out the process according to the invention in a divided electrolysis cell, the catholyte and the anolyte can contain the same or different electrolyte salts or mineral acids. The catholyte and the anolyte preferably contain, independently of one another, a mineral acid, such as hydrochloric acid, sulfuric acid or phosphoric acid, in particular sulfuric acid.

Preferably, the solution of the carboxylic acid amide or of the carboxylic acid ester (or the catholyte and the anolyte contain, independently of one another) the conductive salt or the mineral acid in a concentration in the range of 0.05 to 5 M (= mol / l), preferably in the range of 0.075 to 1 M, in particular in the range of 0.1 to 0.5 M.

The cathodes used are preferably electrodes in which the cathode surface is formed from a material with a high hydrogen overvoltage. In particular, cathodes are used in which the cathode surface consists of a material which is selected from lead, zinc, tin, nickel, mercury, cadmium, copper, an alloy of these metals or glassy carbon, graphite or diamond. Particularly preferred are cathodes in which the cathode surface consists of lead. Preferably, the cathode is polarized prior to its use.

As anodes, in principle, all conventional anode materials come into consideration. Preference is given to anodes whose surface consists of platinum, lead, zinc, tin, nickel, mercury, cadmium, copper, alloys of these metals, glassy carbon, graphite or diamond. If the anolyte contains a mineral acid, platinum, diamond, glassy carbon or graphite anodes and in particular platinum are preferably used. If the anolyte is basic, preference is given to using nickel and, in particular, platinum.

Each of the anode and the cathode may each consist entirely of the previously written materials or may consist of a carrier material coated with the described cathode material. Suitable support materials for such coated electrodes are electrically conductive materials such as niobium, silicon, tungsten, titanium, silicon carbide, tantalum, copper, gold, nickel, iron, graphite, ceramic supports such as titanium suboxide or silver-containing alloys. Preferred supports are metals, in particular metals with a lower standard potential such as, for example, iron, copper, nickel or niobium.

It is preferred to use electrodes in the form of expanded metals, nets or sheets, the electrodes in particular containing the aforementioned materials. In particular, it is preferable to use a polarized lead sheet as the cathode.

The anodic reaction depends in a manner known per se on the composition of the anolyte. As a rule, the solvent used is oxidized. When using methanol as a solvent, for example, methyl formate, formaldehyde dimethyl acetal and / or dimethyl carbonate is formed. When using mixtures of methanol and N, N-dimethylformamide as a solvent, for example N-methoxymethyl-N-methylformamide is formed.

During the deoxygenation process according to the invention, an amount of charge of 4 to 12 F / mol, preferably 6 to 10 F / mol, in particular 7 to 9 F / mol is generally transferred.

The current densities at which the process is carried out are generally from 1 to 1000 mA / cm ² , preferably from 10 to 100 mA / cm ² and in particular from 25 to 75 mA / cm ² .

The electrolysis according to the process of the invention is usually carried out at a temperature in a range of 0 to 100 ° C, preferably above 20 ° C, e.g. in the range of 25 to 100 ° C, in particular in the range of 25 to 80 ° C or preferably in the range of 15 to 100 ° C, in particular in the range of 15 to 80 ° C or in the range of 15 to 55 ° C, especially in Range of 25 to 55 ° C, worked.

In general, working at atmospheric pressure. Higher pressures are preferably used when operating at higher temperatures to avoid boiling of the starting compounds or solvents.

The total duration of the electrolysis naturally depends on the electrolysis cell, the substrate, the optionally added solvent, the electrodes used and the current density. An optimum duration can be determined by the skilled person by routine tests, e.g. by sampling during electrolysis.

In a preferred embodiment of the invention, the contents of the electrolytic cell is mixed. For this thorough mixing of the cell contents, any mechanical stirrer known to those skilled in the art can be used. The use of other mixing methods such as the use of dynamic mixers such as Ultraturrax or liquid pumps, ultrasound or jet nozzles is also preferred.

The electrolyte solution can be worked up after completion of the reaction (batch process) or continuously during the electrolysis by general separation methods. The catholyte can first be distilled and the individual compounds can be obtained separately in the form of different fractions. Suitable distillation processes are processes known to the person skilled in the art, such as direct-current distillation, countercurrent distillation, short-path distillation or steam distillation.

Alternatively, the product obtained can also be obtained by continuous or discontinuous extraction from the catholyte. In the case of discontinuous extraction it is advantageous to work at pHs where the recovered amine is present as an uncharged species. Thus, pH values ≥ 9, preferably pH values ≥ 11, are preferred for the extraction. Particularly suitable extractants are organic solvents known to the person skilled in the art which are immiscible with water, for example hydrocarbons having 5 to 12 carbon atoms, such as hexane or octane Hydrocarbons having 1 to 10 carbon atoms such as dichloromethane or chloroform, aliphatic ethers having 2 to 10 carbon atoms such as diethyl ether or diisopropyl ether, cyclic ethers such as tetrahydrofuran or aliphatic esters such as ethyl acetate or butyl acetate. Further purification after the extraction can be carried out, for example, by crystallization, distillation or by chromatography.

In addition to the products produced by cathodic reduction and unreacted substrate can be separated after completion of the reaction. This re-insulated substrate can be reused in a new electrolysis cycle. An advantage of this repeated use is that repeated amines or ethers can be recovered. Thus, the yield is significantly increased based on the amount of substrate originally used and thus increases the efficiency of the overall process. Furthermore, the repeated use of the reisolated substrate, the concentration of any sensitive products in the electrolyte per reduction process can be kept so low that the undesirable side reactions can be effectively suppressed, while the overall yield over the entire process (multiple electrolysis cycles) increases.

The process according to the invention can be carried out both on a laboratory scale and on an industrial scale. Furthermore, it is possible to carry out the process continuously or discontinuously. Corresponding electrolysis cells are known to the person skilled in the art. All embodiments of this invention relate to both the laboratory and industrial scale.

On an industrial scale, it is preferred to carry out the process continuously.

The following examples describe the invention in more detail and are not intended to be limiting.

Examples I. Preparation of the starting materials 1. Preparation of quaternary ammonium salts 1.1 Preparation of N, N, N, N ', N', N'-hexamethyl-1,3-propanediammonium di (methylsulfate) (1) 1.1.1 Preparation of N, N, N ', N'-tetramethyl-1,3-propanediamine

15.02 g (0.20 mol) of 1,3-propanediamine was added dropwise with stirring to 45.0 ml of 90% formic acid. Subsequently, 24.8 ml of 37% formalin solution were added. After the CO ₂ evolution had ceased, the reaction solution was refluxed until complete conversion. In the boiling heat, the reaction mixture was then mixed with concentrated sulfuric acid. Excess water, formaldehyde and formic acid were removed by distillation after the addition of sulfuric acid. The residue was brought to a pH of ≥ 9 with 50% sodium hydroxide solution. Thereafter, the solution was extracted three times with 60 ml of tert-butyl methyl ether. The combined organic phases were freed from the solvent under reduced pressure and then dried over NaOH.
Yield 21.83 g (0.17 mol, 83%)
¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.49-1.60 (m, 2H, 2-H); 2.13 (s, 12 H, NCH _3); 2.17-2.22 (m, 4H, 1-H).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 26.1 (C-2); 45.5 (NCH ₃ ); 57.9 (C-1).
MS (ESI +)
m / z (int.) = 131.7 (100), [M + H] +,

1.1.2 Quaternization of N, N, N ', N'-tetramethyl-1,3-propanediamine

m/z(Int.)=

271,20 (13), [C₁₀H₂₇N₂O₄S]⁺/[Kation+Anion]⁺, 653,38 (100), [C₂₁H₅₇N₄O₁₂S₃]⁺/[2xKation+3xAnion]⁺.

2.00 g (0.02 mol) of N, N, N ', N'-tetramethyl-1,3-propanediamine were dissolved in 20 ml of dichloromethane. At 0 ° C 4.4 ml (0.05 mol) of dimethyl sulfate were added dropwise with stirring. The reaction mixture was stirred at room temperature for 4 hours after completion of the addition. Unreacted starting materials and solvents were then removed under reduced pressure. The obtained crude product was recrystallized with methanol and ethyl acetate.
Yield 3.93 g (0.01 mol, 69%)
¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 2.31-2.42 (m, 2H, 2-H); 3.19 (s, 18 H, NCH _3); 3.39 - 3.45 (m, 4H, 1-H); 3.74 (s, 6 H, OCH _3).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 17.1 (C-2); 52.9 (NCH ₃ ); 55.2 _(OCH3); 62.2 (C-1).
MS (ESI +)

m / z (Int.) =

271.20 (13), [C ₁₀ H ₂₇ N ₂ O ₄ S] ⁺ / [cation + anion] ⁺ , 653.38 (100), [C ₂₁ H ₅₇ N ₄ O ₁₂ S ₃ ] ⁺ / [2x cation + 3xAnion] ⁺ .

The ammonium salts listed below under 1.2 to 1.20 were prepared in analogy to the method described in 1.1.

1.2 N, N'-diethyl-N, N, N ', N'-tetramethyl-1,3-propanediammonium di (methylsulfate) (2)

¹H-NMR (300 MHz, D₂O)
δ (ppm): 1,37 (t, 6 H, 2'-H, ³J=7.3 Hz)); 2,20 - 2,35 (m, 2 H, 2-H); 3,10 (s, 12 H, NCH₃), 3,34 - 3,40 (m, 4 H, 1-H); 3,45 (q, 4-H, 1'-H, ³J=7.4 Hz); 3,73 (s, 5 H, OCH₃).
¹³C-NMR (75 MHz, D₂O)
δ (ppm): 7,2 (C-2'); 16.2 (C-2), 49,8 (NCH₃); 55,2 (OCH₃); 59,2 (C-1'); 60,2 (C-1).
MS (ESI+)

m/z(Int.)=

299,23 (37), [C₁₂H₃₁N₂O₄S]⁺/[Kation+Anion]⁺, 709,45 (100), [C₂₅H₆₅N₄O₁₂S₃]⁺/[2xKation+3xAnion]⁺.

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.37 (t, 6 H, 2'-H, ³ J = 7.3 Hz)); 2.20 - 2.35 (m, 2H, 2H); 3.10 (s, 12 H, NCH _3), 3.34 to 3.40 (m, 4 H, 1-H); 3.45 (q, 4-H, 1'-H, ³ J = 7.4 Hz); 3.73 (s, 5H, OCH ₃ ).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 7.2 (C-2 '); 16.2 (C-2), 49.8 (NCH ₃ ); 55.2 (OCH ₃ ); 59.2 (C-1 '); 60.2 (C-1).
MS (ESI +)

m / z (Int.) =

299.23 (37), [C ₁₂ H ₃₁ N ₂ O ₄ S] ⁺ / [cation + anion] ⁺ , 709.45 (100), [C ₂₅ H ₆₅ N ₄ O ₁₂ S ₃ ] ⁺ / [2x cation + 3xAnion] ⁺ .

1.3 N, N, N, N ', N', N'-hexamethyl-1,4-butanediammonium di (methylsulfate) (3)

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.84-1.92 (m, 4H, 2-H); 3.13 (s, 18 H, NCH _3); 3.36 - 3.45 (m, 4H, 1-H); 3.73 (s, 6H, OCH ₃ ).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 19.2 (C-2); 52.7 (NCH ₃ ); 55.2 (OCH ₃ ); 65.2 (C-1).
MS (ESI +)
m / z (Int.) = 681.41 (100) [C ₂₃ H ₆₁ N ₄ O ₁₂ S _3] ⁺ / [2xKation + 3xAnion] ^+.

1.4 N, N'-diethyl-N, N, N ', N'-tetramethyl-1,4-butanediammonum di (ethylsulfate) (4)

¹H-NMR (300 MHz, D₂O)
δ (ppm): 1,30 - 1,36 (m, 6 H, 2'-H); 1,78 - 1,90 (m, 4 H, 2-H); 3,04 (s, 12 H, NCH₃); 3,27 - 3,44 (m, 8 H, 1-H, 1'-H); 3,74 (s, 4 H, OCH₃).
¹³C-NMR (75 MHz, D₂O)
δ (ppm): 7,2 (C-2); 18,8 (C-2); 49,7 (NCH₃); 55,2 (OCH₃); 59,6 (C-1'); 62,1 (C-1).
MS (ESI+) m/z(Int.)= 313,22 (53), [C₁₃H₃₃N₂O₄S]⁺/[Kation+Anion]⁺, 737,47 (100), [C₂₇H₆₉N₄O₁₂S₃]⁺/[2xKation+3xAnion]⁺.

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.30-1.36 (m, 6H, 2'-H); 1.78-1.90 (m, 4H, 2-H); 3.04 (s, 12 H, NCH _3); 3.27-3.44 (m, 8H, 1-H, 1'-H); 3.74 (s, 4H, OCH ₃ ).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 7.2 (C-2); 18.8 (C-2); 49.7 (NCH ₃ ); 55.2 (OCH ₃ ); 59.6 (C-1 '); 62.1 (C-1).
MS (ESI +) m / z (Int.) = 313.22 (53) [C ₁₃ H ₃₃ N ₂ O ₄ S] ⁺ / [+ cation anion] ^+, 737.47 (100) [C ₂₇ H ₆₉ N ₄ O ₁₂ S _3] ⁺ / [2xKation + 3xAnion] ^+.

1.5 N, N, N, N ', N', N'-hexamethyl-1,5-pentanediammonium di (methylsulfate) (5)

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.36-1.46 (m, 2H, 3-H); 1.82-1.85 (m, 4H, 2H); 3.09 (s, 18 H, NCH _3); 3.29-3.35 (m, 4H, 1-H); 3.72 (s, 3H, OCH ₃ ).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 21.8 (C-3): 22.2 (C-2); 52.6 (NCH ₃ ); 55.2 (OCH ₃ ); 65.9 (C-1).
MS (ESI +) m / z (Int.) = 299.21 (100) [C ₁₂ H ₃₁ N ₂ O ₄ S] ⁺ / [+ cation anion] ^+, 709.45 (8), [C ₂₅ H ₆₅ N ₄ O ₁₂ S ₃ ] ⁺ / [2x cation + 3x anion] ⁺ .

1.6 N, N'-diethyl-N, N, N ', N'-tetramethyl-1,5-pentanediammonium di (ethylsulfate) (6)

¹H-NMR (300 MHz, D₂O)
δ (ppm): 1,32 - 1,37 (m, 6 H, 2'-H); 1,42 - 1,45 (m, 2 H, 3-H); 1,81 - 1,86 (m, 4 H, 2-H); 3,03 (s, 12 H, NCH₃); 3,25 - 3,32 (m, 4 H, 1-H); 3,37 (q, 4-H, 1'-H, ³J=7,3 Hz).
¹³C-NMR (75 MHz, D₂O)
δ (ppm): 7,2 (C-2'); 14,0 (C-2"); 21,36 (C-3); 22,3 (C-2); 49,7 (NCH₃); 59,5 (C-1'); 62,7 (C-1 "); 65,5 (C-1).
MS (ESI+)

m/z(Int.)=

341,27 (100) [C₁₂H₃₁N₂O₄S]⁺/[Kation+Anion]⁺, 709,45 (8), [C₃₂H₇₉N₄O₁₂S₃]⁺/[2xKation+3xAnion]⁺.

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.32-1.37 (m, 6H, 2'-H); 1.42-1.45 (m, 2H, 3-H); 1.81-1.86 (m, 4H, 2H); 3.03 (s, 12 H, NCH _3); 3.25-3.32 (m, 4H, 1-H); 3.37 (q, 4-H, 1'-H, ³ J = 7.3 Hz).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 7.2 (C-2 '); 14.0 (C-2 "), 21.36 (C-3), 22.3 (C-2), 49.7 (NCH ₃ ), 59.5 (C-1 '), 62.7 ( C-1 "); 65.5 (C-1).
MS (ESI +)

m / z (Int.) =

341.27 (100) [C ₁₂ H ₃₁ N ₂ O ₄ S] ⁺ / [cation + anion] ⁺ , 709.45 (8), [C ₃₂ H ₇₉ N ₄ O ₁₂ S ₃ ] ⁺ / [2x cation + 3xAnion] ⁺ .

1.7 N, N, N, N ', N', N'-hexamethyl-1,6-hexanediammonium di (methylsulfate) (7)

m/z(Int.)=

313,22 (100), [C₁₃H₃₃N₂O₄S]⁺/[Kation+Anion]⁺, 737,47 (99), [C₂₇H₆₉N₄O₁₂S₃]⁺/[2xKation+3xAnion]⁺.

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.43 - 1.52 (m, 4H, 3-H); 1.78-1.91 (m, 4H, 2H); 3.14 (s, 18 H, NCH _3); 3.31-3.39 (m, 4H, 1-H); 3.75 (s, 6H, OCH ₃ ).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 21.9 (C-1); 24.8 (C-2); 52.6 (NCH ₃ ); 55.2 (OCH ₃ ); 66.2 (C-3).
MS (ESI +)

m / z (Int.) =

313.22 (100), [C ₁₃ H ₃₃ N ₂ O ₄ S] ⁺ / [cation + anion] ⁺ , 737.47 (99), [C ₂₇ H ₆₉ N ₄ O ₁₂ S ₃ ] ⁺ / [2x cation + 3xAnion] ⁺ .

1.8 N, N'-diethyl-N, N, N ', N'-tetramethyl-1,6-hexanediammonium di (ethylsulfate) (8)

¹H-NMR (300 MHz, D₂O)
δ (ppm): 1,31 - 1,36 (m, 6 H, 2'-H); 1,37 - 1,47 (m, 4 H, 3-H); 1,72 - 1,83 (m, 4 H, 2-H); 3,02 (s, 12 H, NCH₃); 3,21 - 3,31 (m, 4 H, 1-H); 3,32 - 3,43 (m, 4 H, 1'-H).
¹³C-NMR (75 MHz, D₂O)
δ (ppm): 7,2 (C-2'), 14,0 (C-2"); 22,0 (C-3); 25,0 (C-2), 50,0 (NCH₃); 59,4 (C-1'); 63,0 (C-1 "); 65,5 (C-5).
HRMS (ESI+) m/z für C₁₆H₃₉N₂O₄S⁺: berechnet: 355,2631 gefunden: 355,2628 Elementaranalyse
% für C₁₈H₄₄N₂O₈S₂ (480,68 g/mol): Berechnet: C 44,98 H 9,32 N 5,83 S 13,34 Gefunden: C 44,67 H 8,77 N 5,86 S 12,93.

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.31-1.36 (m, 6H, 2'-H); 1.37-1.47 (m, 4H, 3H); 1.72-1.83 (m, 4H, 2H); 3.02 (s, 12 H, NCH _3); 3.21-3.31 (m, 4H, 1-H); 3.32 - 3.43 (m, 4H, 1'H).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 7.2 (C-2 '), 14.0 (C-2 "), 22.0 (C-3), 25.0 (C-2), 50.0 (NCH ₃ ) 59.4 (C-1 '); 63.0 (C-1 "); 65.5 (C-5).
HRMS (ESI +) m / z for C ₁₆ H ₃₉ N ₂ O ₄ S ^+: calculated: 355.2631 found: 355,2628 Elemental analysis
% For C ₁₈ H ₄₄ N ₂ O ₈ S ₂ (480.68 g / mol): Calculated: C 44,98 H 9,32 N 5.83 P 13,34 Found: C 44.67 H 8,77 N 5.86 S 12,93.

1.9 N, N, N, N ', N', N'-hexamethyl-1,7-heptanediammonium di (methylsulfate) (9)

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.33-1.35 (m, 6H, 3-H, 4-H); 1.70-1.86 (m, 4H, 2H); 3.08 (s, 18 H, NCH _3); 3.25-3.34 (m, 4H, 1-H); 3.72 (s, 3H, OCH ₃ ).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 21.9 (C-4); 25.0 (C-3), 27.5 (C-2), 52.5 (NCH ₃ ); 66.4 (C-1).
HRMS (ESI +) m / z for C ₁₄ H ₃₅ N ₂ O ₄ S ⁺ : calculated: 327.2318 found: 327,2332

1.10 N, N'-diethyl-N, N, N ', N'-tetramethyl-1,7-heptanediammonium di (methylsulfate) (10)

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.31-1.41 (m, 12 H, 2'-H, 3-H, 4-H); 1.66-1.82 (m, 4H, 2H); 3.01 (s, 12 H, NCH _3); 3.21-3.30 (m, 4H, 1-H); 3.36 (q, 4 H, 1'-H, ³ J = 7.3 Hz).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 7.2 (C-2 '), 21.5 (C-4); 25.1 (C-3); 27.5 (C-2), 49.6 (NCH ₃ ); 55.2 (OCH ₃ ); 59.3 (C-1 '); 63.2 (C-1).
HRMS (ESI +) m / z for C ₁₆ H ₃₉ N ₂ O ₄ S ⁺ : calculated: 355.2631 found: 355.2619 Elemental analysis
% For C ₁₈ H ₄₄ N ₂ O ₈ S ₂ (480.68 g / mol): Calculated: C 43,75 H 9.07 N 5.83 P 13,34 Found: C 43,25 H 8,79 N 6,22 P 13:46.

1.11 N, N, N, N ', N', N'-hexamethyl-1,8-octanediammonium di (methylsulfate) (11)

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.31-1.38 (m, 8 H, 4-H, 3-H); 1.71-1.82 (m, 4H, 2H); 3.08 (s, 18 H, NCH _3); 3.25-3.32 (m, 4H, 1-H); 3.72 (s, 3H, OCH ₃ ).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 22.0 (C-4); 25.1 (C-3); 27.7 (C-2); 52.5 (NCH ₃ ); 55.2 (OCH ₃ ); 66.5 (C-1).
HRMS (ESI +) m / z for C ₁₅ H ₃₇ N ₂ O ₄ S ⁺ : calculated: 341,2474 found: 341,2472 Elemental analysis
% For C ₁₆ H ₄₀ N ₂ O ₈ S ₂ (452.63 g / mol): Calculated: C 42.46 H 8,91 N 6.19 S 14,17 Found: C 42,22 H 8,48 N 5.95 S 14.46.

1.12 N, N'-diethyl-N, N, N ', N', - tetramethyl-1,8-octanediammonium di (methylsulfate) (12)

¹H-NMR (300 MHz, D₂O)
δ (ppm): 1,30 - 1,40 (m, 14 H, 2'-H, 4-H, 3-H); 1,67 - 1,79 (m, 4 H, 2-H); 3,00 (s, 12 H, NCH₃); 3,19 - 3,27 (m, 4 H, 1-H); 3,34 (q, 4 H, 1'-H, ³J=7,3 Hz); 3,72 (s, 3 H, OCH₃).
¹³C-NMR (75 MHz, D₂O)
δ (ppm): 7,2 (C-2'); 21,5 (C-4); 24,1 (C-3); 27,7 (C-2); 49,6 (NCH₃); 59,3 (OCH₃); 63,2 (C-1).
HRMS (ESI+) m/z für C₁₄H₃₅N₂O₄S⁺: berechnet: 383,2944 gefunden: 383,2946

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.30-1.40 (m, 14 H, 2'-H, 4-H, 3-H); 1.67-1.79 (m, 4H, 2H); 3.00 (s, 12 H, NCH _3); 3.19-3.27 (m, 4H, 1-H); 3.34 (q, 4 H, 1'-H, ³ J = 7.3 Hz); 3.72 (s, 3H, OCH ₃ ).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 7.2 (C-2 '); 21.5 (C-4); 24.1 (C-3); 27.7 (C-2); 49.6 (NCH ₃ ); 59.3 (OCH ₃ ); 63.2 (C-1).
HRMS (ESI +) m / z for C ₁₄ H ₃₅ N ₂ O ₄ S ⁺ : calculated: 383.2944 found: 383.2946

1.13 N, N, N, N ', N', N'-hexamethyl-1,9-nonanediammonium di (methylsulfate) (13)

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.31-1.40 (m, 10H, 5H, 4H, 3H); 1.72-1.85 (m, 4H, 2H); 3.09 (s, 18 H, NCH _3); 3.24-3.33 (m, 4H, 1-H); 3.74 (s, 6 H, OCH _3).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 22.0 (C-5); 25.2 (C-4); 27.8 (C-3); 27.9 (C-2); 52.5 (NCH ₃ ); 55.2 (OCH ₃ ); 66.5 (C-1).
HRMS (ESI +) m / z for C ₁₆ H ₃₉ N ₂ O ₄ S ⁺ : calculated: 355.2631 found: 355.2619 Elemental analysis
% For C ₁₆ H ₃₉ N ₂ O ₈ S ₂ (451.63 g / mol): Calculated: C 43,75 H 9.07 N 6,00 S 13,74 Found: C 43.68 H 9.05 N 6.06 S 14.04.

1.14 N, N'-diethyl-N, N, N ', N'-tetramethyl-1,9-nonanediammonium di (sulfate) (14)

¹H-NMR (300 MHz, D₂O)
δ (ppm): 1,30 - 1,41 (m, 16 H, 2'-H, 5-H, 4-H, 3-H); 1,67 - 1,79 (m, 4 H, 2-H); 3,01 (s, 12 H, NCH₃); 3,20 - 3,28 (m, 4 H, 1-H); 3,35 (q, 4 H, 1'-H, ³J=7,3 Hz); 3,73 (s, 6 H, OCH₃).
¹³C-NMR (75 MHz, D₂O)
δ (ppm): 7,2 (C-2'), 21,5 (C-5); 25,2 (C-4); 27,8 (C-3); 28,0 (C-2); 49,6 (NCH₃); 55,2 (OCH₃); 59,2 (1'-C); 63,3 (C-1).
HRMS (ESI+) m/z für C₁₈H₄₃N₂O₄S⁺: berechnet: 383,2944 gefunden: 383,2936 Elementaranalyse
% für C₁₉H₄₆N₂O₈S₂ (494,72 g/mol): Berechnet: C 46,13 H 9,37 N 5,66 S 12,96 Gefunden: C 45,68 H 9,05 N 5,64 S 12,84.

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.30-1.41 (m, 16 H, 2'-H, 5-H, 4-H, 3-H); 1.67-1.79 (m, 4H, 2H); 3.01 (s, 12 H, NCH _3); 3.20-3.28 (m, 4H, 1-H); 3.35 (q, 4 H, 1'-H, ³ J = 7.3 Hz); 3.73 (s, 6H, OCH ₃ ).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 7.2 (C-2 '), 21.5 (C-5); 25.2 (C-4); 27.8 (C-3); 28.0 (C-2); 49.6 (NCH ₃ ); 55.2 (OCH ₃ ); 59.2 (1'-C); 63.3 (C-1).
HRMS (ESI +) m / z for C ₁₈ H ₄₃ N ₂ O ₄ S ⁺ : calculated: 383.2944 found: 383.2936 Elemental analysis
% For C ₁₉ H ₄₆ N ₂ O ₈ S ₂ (494.72 g / mol): Calculated: C 46,13 H 9,37 N 5.66 S 12,96 Found: C 45.68 H 9.05 N 5.64 S 12,84.

1.15 N, N, N, N ', N', N'-hexamethyl-1,10-decanediammonium di (methylsulfate) (15)

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.29-1.37 (m, 12 H, 5-H, 4-H, 3-H); 1.71-1.82 (m, 4H, 2H); 3.08 (s, 18 H, NCH _3); 3.23-3.34 (m, 4H, 1-H).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 22.0 (C-5); 25.2 (C-4); 27.9 (C-3); 28.0 (C-2); 52.5 (NCH ₃ ); 55.2 (OCH ₃ ); 66.5 (C-1).
HRMS (ESI +) m / z for C ₁₇ H ₄₁ N ₂ O ₄ S ⁺ : calculated: 369.2787 found: 369.2800 Elemental analysis
% for C ₁₇ H ₄₁ N ₂ O ₈ S ₂ (465.65 g / mol): Calculated: C 44,98 H 9,23 N 5.83 P 13,34 Found: C 45,32 H 9,18 N 5.67 S 12,97.

1.16 N, N'-diethyl-N, N, N ', N'-tetramethyl-1,10-decanediammonium di (ethylsulfate) (16)

¹H-NMR (300 MHz, D₂O)
δ (ppm): 1,28 - 1,40 (m, 18 H, 2'-H, 5-H, 4-H, 3-H); 1,66 - 1,78 (m, 4 H, 2-H); 2,99 (s, 12 H, NCH₃); 3,18 - 3,26 (m, 4 H, 1-H); 3,33 (q, 4 H, 1'-H, ³J=7,3 Hz).
¹³C-NMR (75 MHz, D₂O)
δ (ppm): 7,2 (C-2'); 21,5 (C-5); 25,2 (C-4); 27,9 (C-3); 28,1 (C-2); 49,6 (NCH₃); 55,1 (OCH₃); 59,2 (C-1'); 63,3 (C-1).
HRMS (ESI+) m/z für C₂₀H₄₇N₂O₄S⁺: berechnet: 411,3257 gefunden: 411,3269 Elementaranalyse
% für C₂₁H₅₀N₂O₈S₂ (522,77 g/mol): Berechnet: C 48,25 H 9,64 N 5,36 S 12,27 Gefunden: C 47,98 H 9,34 N 5,30 S 12,24.

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.28-1.40 (m, 18 H, 2'-H, 5-H, 4-H, 3-H); 1.66-1.78 (m, 4H, 2H); 2.99 (s, 12 H, NCH _3); 3.18-3.26 (m, 4H, 1-H); 3.33 (q, 4 H, 1'-H, ³ J = 7.3 Hz).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 7.2 (C-2 '); 21.5 (C-5); 25.2 (C-4); 27.9 (C-3); 28.1 (C-2); 49.6 (NCH ₃ ); 55.1 (OCH ₃ ); 59.2 (C-1 '); 63.3 (C-1).
HRMS (ESI +) m / z for C ₂₀ H ₄₇ N ₂ O ₄ S ⁺ : calculated: 411,3257 found: 411,3269 Elemental analysis
% For C ₂₁ H ₅₀ N ₂ O ₈ S ₂ (522.77 g / mol): Calculated: C 48,25 H 9,64 N 5.36 S 12,27 Found: C 47,98 H 9,34 N 5.30 S 12,24.

1.17 N, N, N, N ', N', N'-hexamethyl-1,12-dodecanediammonium di (methylsulfate) (17)

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.28-1.39 (m, 16H, 6H, 5H, 4H, 3H); 1.72-1.84 (m, 4H, 2H); 3.10 (s, 18 H, NCH _3); 3.25-3.34 (m, 4H, 1-H); 3.74 (s, 6 H, OCH _3).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 22.0 (C-6); 25.2 (C-5); 27.9 (C-4); 28.2 (C-3); 28.4 (C-2); 52.5 (NCH ₃ ); 55.2 (OCH ₃ ); 66.6 (C-1).
HRMS (ESI +) m / z for C ₁₉ H ₄₅ N ₂ O ₄ S ⁺ : calculated: 397,3100 found: 397.3087 Elemental analysis
% for C ₂₀ H ₄₈ N ₂ O ₈ S ₂ (508.73 g / mol): Calculated: C 48,25 H 9,64 N 5.36 S 12,27 Found: C 47,98 H 9,34 N 5.30 S 12,24.

1.18 N, N'-diethyl-N, N, N ', N'-tetramethyl-1,12-dodecanediammonium di (ethylsulfate) (18)

¹H-NMR (300 MHz, D₂O)
δ (ppm): 1,29 - 1,40 (m, 22 H, 2'-H, 6-H, 5-H, 4-H, 3-H); 1,66 - 1,79 (m, 4 H, 2-H); 3,00 (s, 12 H, NCH₃); 3,20 - 3,28 (m, 4 H, 1-H); 3,35 (q, 4 H, 1'-H₂, ³J=7,3 Hz).
¹³C-NMR (75 MHz, D₂O)
δ (ppm): 7,2 (C-2'); 14,0 (C-2"); 21,5 (C-6); 25,3 (C-5); 28,0 (C-4); 28,2 (C-3); 28,4 (C-2); 49,7 (NCH₃); 59,2 (C-1'); 63,3 (C-1"); 65,5 (C-1).
HRMS (ESI+) m/z für C₂₀H₄₇N₂O₄S⁺: berechnet: 439,3570 gefunden: 411,3572.

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.29-1.40 (m, 22H, 2'-H, 6H, 5H, 4H, 3H); 1.66-1.79 (m, 4H, 2H); 3.00 (s, 12 H, NCH _3); 3.20-3.28 (m, 4H, 1-H); 3.35 (q, 4 H, 1'-H ₂ , ³ J = 7.3 Hz).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 7.2 (C-2 '); 14.0 (C-2 "); 21.5 (C-6); 25.3 (C-5); 28.0 (C-4); 28.2 (C-3); 28.4 ( C-2); 49.7 (NCH ₃ ); 59.2 (C-1 '); 63.3 (C-1 "); 65.5 (C-1).
HRMS (ESI +) m / z for C ₂₀ H ₄₇ N ₂ O ₄ S ⁺ : calculated: 439.3570 found: 411.3572.

1.19 N, N, N, N ', N', N ", N", N "-octamethyl (diethylenetriamine) tri (methylsulfate) (19)

¹H-NMR (300 MHz, D₂O)
δ (ppm): 3,28 (s, 18 H, 1'-H); 3,34 (s, 6 H, 2'-H); 3,70 (s, 9 H, OCH₃); 4,07 (m, 8 H, 2-H, 1-H).
¹³C-NMR (75 MHz, D₂O)
δ (ppm): 51,1 (C-2'); 53,7 (C-1'); 55,2 (OCH₃); 57,1 (C-2); 57,9 (C-1).
HRMS (ESI+) m/z (Int.)= 440,22 (100) [C₁₄H₃₈N₃O₈S₂]⁺/[Kation+2xAnion]⁺

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 3.28 (s, 18H, 1'-H); 3.34 (s, 6H, 2'-H); 3.70 (s, 9H, OCH ₃ ); 4.07 (m, 8H, 2H, 1H).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 51.1 (C-2 '); 53.7 (C-1 '); 55.2 (OCH ₃ ); 57.1 (C-2); 57.9 (C-1).
HRMS (ESI +) m / z (int.) = 440.22 (100) [C ₁₄ H ₃₈ N ₃ O ₈ S ₂ ] ⁺ / [cation + 2x anion] ⁺

1.20 N, N ', N "-triethyl-N, N, N', N", N "-pentamethyl (diethylene) tri (ethylsulfate) (20)

¹H-NMR (300 MHz, D₂O)
δ (ppm): 1,29 - 1,52 (m, 18 H, 2'-H, 2"-H, 2"'-H); 3,03 - 3,09 (m, 4 H, 1'-H); 3,11 (s, 12 H, 3'-H); 3,23 (s, 6 H, 1"'-H); 3,35 (m, 2 H, 1"-H); 3,40 - 3,57 (m, 11 H, 3"-H, 2-H, 1-H).
¹³C-NMR (75 MHz, D₂O)
δ (ppm): 7,3 (C-2'); 7,4 (C-2"); 14,0 (C-2"'); 45,3 (C-3"); 50,1 (C-3'); 54,5 (C-1"); 59,1 (C-1'); 60,3 (C-2); 61,4 (C-1); 65,5 (C-1'").
HRMS (ESI+)

m/z (Int.)=

510,33 (15) [C₁₉H₄₈N₃O₈S₂]⁺/[Kation+2xAnion]⁺

¹ H-NMR (300 MHz, D ₂ O)
δ (ppm): 1.29 - 1.52 (m, 18 H, 2'-H, 2 "-H, 2"'-H); 3.03 - 3.09 (m, 4H, 1'H); 3.11 (s, 12H, 3'H); 3.23 (s, 6H, 1 "'- H); 3.35 (m, 2H, 1"-H); 3.40 - 3.57 (m, 11H, 3 "-H, 2H, 1H).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 7.3 (C-2 '); 7.4 (C-2 "); 14.0 (C-2"'); 45.3 (C-3 "); 50.1 (C-3 '); 54.5 (C-1"); 59.1 (C-1 '); 60.3 (C-2); 61.4 (C-1); 65.5 (C-1 '").
HRMS (ESI +)

m / z (int.) =

510.33 (15) [C ₁₉ H ₄₈ N ₃ O ₈ S _2] ⁺ / [+ cation 2xAnion] ⁺

2. Preparation of N- (2-ethylhexyl) benzoic acid amide

m/z (Int.)=

256,16 (100) [M+ Na]⁺.

52.4 ml (0.32 mol) of 2-ethylhexylamine and 82.8 ml (0.64 mol) of triethylamine were dissolved in 320 ml of dichloromethane. Then, at 0 ° C., 37.2 ml (0.32 mol) of benzoyl chloride dissolved in 320 ml of dichloromethane were added dropwise. The reaction mixture was stirred at room temperature for 12 h and then washed with saturated sodium bicarbonate solution (2 × 80 ml) and with saturated brine (2 × 80 ml). Excess solvent was removed under reduced pressure. The pure product was obtained by short path distillation (9.7 x 10 ^-3 mbar, 142 ° C).
Yield: 68.17 g (0.29 mol, 91%)
¹ H NMR (300 MHz, D ₂ O)
δ (ppm): 0.87 (t, 3 H, 6-H, ³ J = 7.5 Hz); 0.91 (3 H, 8-H t, ³ J = 6.8 Hz); 1.22-1.41 (m, 8H, 7H, 5H, 4H, 3H, 2H); 1.49 - 1.52 (m, 2H, 2H); 3.28- 3.46 (m, 2H, 1-H); 6.10 (s, 1H, NH); 7.35-7.52 (m, 3H, 4'-H, 5'-H); 7.68 - 7.80 (m, 2H, 3'H).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 10.9 (C-6); 14.0 (C-8); 23.0 (C-5); 24.4 (C-4); 28.9 (C-3); 31.1 (C-7); 39.5 (C-2); 42.9 (C-1); 126.8 (C-5 '); 128.5 (C-4 '); 131.3 (C-3 '); 135.0 (C-2 '); 167.6 (C-1 ').
MS (ESI (+))

m / z (int.) =

256.16 (100) [M + Na] ^+.

II Cathodic deoxygenation of N- (2-ethylhexyl) benzoic acid amide to N-benzyl-N- (2-ethylhexyl) amine Example 1: Electrochemical reduction of N- (2-ethylhexyl) benzoic acid amide in the presence of N, N, N, N ', N', N'-hexamethyl-1,3-propanediammonium di (methylsulfate) (1)

m/z(Int.)=

220,21 (100)[M + H]⁺.

The cathode and the anode compartment of a divided half by a Nafion 324 ^® membrane electrolysis cells were respectively mixed with 50 ml of a 2 wt .-% methanolic sulfuric acid solution filled. In the cathode half-space, 397 mg (1.70 mmol) of N- (2-ethylhexyl) benzoic acid amide were dissolved and 325 mg (0.85 mmol) of N, N, N, N ', N', N'-hexamethyl-1, 3-propanediammonium di (methyl sulfate) added. The cathode used was a lead foil, which was polarized before immersion, and the anode used was a platinum sheet. At 45 ° C, the electrolysis was carried out galvanostatically with a current density of 55.55 mA / cm ² . After successful transfer of a charge of 1312 C (8 F), the reaction solution was removed from the cathode compartment and rinsed with methanol (40 mL). The methanol used for rinsing was combined with the reaction solution and the resulting mixture (cathode outlet) was brought to pH≥11 with 1 N NaOH and extracted with diethyl ether (3 x 65 ml). The combined organic phases were extracted with 10% HCl (3 x 50 ml) to give the product. In order to reisolate unreacted educt, the organic phase was dried over Na ₂ SO ₄ and freed from the solvent under reduced pressure. To recover the product, the HCl phase was brought to pH≥11 with aqueous NaOH and the amine was extracted with diethyl ether (3 × 60 ml). The combined organic phases were dried over MgSO ₄ , the solvent removed in vacuo. Yield: 205 mg (0.93 mmol, 55%); Current yield: 23%; Reisoliertes educt: 70 mg (0.30 mol, 18%); ¹ H NMR (300 MHz, D ₂ O)
δ (ppm): 0.83 (t, 3 H, 6-H, ³ J = 7.3 Hz); 0.87 (3 H, 8-H t, ³ J = 6.6 Hz); 1.07-1.45 (m, 11H, 7H, 5H, 4H, 3H, 2H, NH); 2.50 (d, 2 H, 1-H, ³ J = 6.0 Hz); 3.76 (s, 2H, 9-H); 7.13-7.48 (m, 5H, 11H, 12H, 13H).
¹³ C-NMR (75 MHz, D ₂ O)
δ (ppm): 11.0 (C-6); 14.3 (C-8); 23.3 (C-5); 24.6 (C-4); 29.1 (C-3); 31.4 (C-7); 39.3 (C-2); 42.4 (C-1); 54.2 (C-9); 127.3 (C-11); 128.6 (C-12); 140.0 (C-13); 140.8 (C-10).
MS (ESI (+))

m / z (Int.) =

220.21 (100) [M + H] ^+.

Examples 2 to 7:

N- (2-ethylhexyl) benzoic acid amide was deoxygenated analogously to Example 1 in the presence of the salts described in Table A to give N-benzyl-N- (2-ethylhexyl) amine. The electrolysis conditions were as follows: Electrolyte: 50 ml 2% H ₂ SO ₄ in methanol, Q = 8 F / mol, T = 45 ° C, n (additive) = 1.7 mmol, j = 44.1 mA / cm ² Table A: example salt Yield [%] ¹⁾ Current efficiency [%] ²⁾ Reisolated educt [%] ¹⁾ V1 no salt additive 24 12 49 1 1 55 27 18 2 2 38 19 30 3 7 40 20 26 4 14 40 20 22 6 18 32 16 10 1) based on the reactant used
2) based on the amount of charge used

Claims (12)

1. Process for deoxygenation of carboxamides and carboxylic esters by cathodic reduction of a solution of the carboxamide or the carboxylic ester, characterized in that the solution comprises a salt as additive which is selected from among quaternary ammonium salts and the cation of the salt has the formula I

   

   where

   k is an integer in a range from 1 to 99 and is in particular 1 or 2,

   A is nitrogen

   Z is an alkylene group having 2 to 12 carbon atoms, wherein optionally 1, 2 or 3 CH₂ groups, which are separated from the nitrogen atoms A and from each other by at least 2 carbon atoms, may be replaced by oxygen atoms,

   R¹, R², R³ and R⁴ are each independently C₁-C₁₀-alkyl, which in each case is unsubstituted or may be substituted with 1 or 2 substituents selected from hydroxyl, alkoxy and poly(oxyethylene), or

   R¹ and R², together with the nitrogen atom to which they are bonded, may also be a 5- to 8-membered heterocycle which comprises 1 nitrogen atom in the ring and is unsubstituted or may be substituted with 1 to 4 substituents selected from hydroxyl, C₁-C₄-alkoxy and C₁-C₄-alkyl,

   R⁵ and R⁶ are each independently C₁-C₁₀-alkyl, which in each case is unsubstituted or may be substituted with 1 or 2 substituents selected from hydroxyl, alkoxy and poly(oxyethylene), and

   a carboxamide or a carboxylic ester of the formula II is used,

   

   where

   Y is a chemical bond or an alkylene group having 1 to 6 carbon atoms,

   X is oxygen or N-R⁹,

   R⁷ is selected from C₁-C₁₀-alkyl, C₂-C₁₀-alkenyl, C₁-C₁₀-alkoxy, C₁-C₁₀-haloalkyl, C₁-C₁₀-haloalkoxy, C₃-C₁₀-cycloalkyl, aryl and hetaryl, wherein the ring in the latter three groups mentioned is unsubstituted or may be substituted with up to 6 substituents selected from halogen, hydroxyl, C₁-C₄-alkyl and C₁-C₄-alkoxy, and

   R⁸ is selected from hydrogen, C₁-C₁₀-alkyl, which is unsubstituted or has 1 or 2 substituents selected from hydroxyl, C₁-C₄-alkoxy and aryl, C₂-C₁₀-alkenyl, C₁-C₁₀-haloalkyl, C₁-C₁₀-haloalkoxy, C₃-C₁₀-cycloalkyl, aryl and hetaryl, wherein the ring in the latter three groups mentioned is unsubstituted or may be substituted with up to 6 substituents selected from halogen, hydroxyl, C₁-C₄-alkyl and C₁-C₄-alkoxy,
   where R⁸ is different from hydrogen if X is 0,

   R⁷ and R⁸ may together be C₃-C₂₀-alkylene or C₃-C₂₀-alkenylene, which is unsubstituted or is substituted with up to 6 substituents selected from hydroxyl, C₁-C₄-alkyl and C₁-C₄-alkoxy, wherein 2 substituents bonded to adjacent carbon atoms, together with the carbon atoms to which they are attached, may also form a 5- to 7-membered carbocycle; and

   R⁹ is hydrogen or C₁-C₁₀-alkyl, which is unsubstituted or has 1 or 2 substituents selected from hydroxyl, C₁-C₄-alkoxy and aryl.
2. Process according to Claim 1, characterized in that the anions of the salt are selected from among sulphate, hydrogen sulphate, alkyl sulphate, aryl sulphate, aryl sulphonate, haloalkyl sulphonate, halide, pseudohalide, carboxylate, carbonate, imide, phosphate, alkyl phosphate, nitrate, tetrafluoroborate, hexafluorophosphate and perchlorate.
3. Process according to any of the preceding claims, characterized in that the solution of the carboxamide or carboxylic ester comprises the salt at a concentration in a range from 0.001 to 1000 mmol/l, especially in the range from 0.1 to 500 mmol/l.
4. Process according to any of the preceding claims, characterized in that the substrate used is a secondary or tertiary carboxamide.
5. Process according to any of the preceding claims, characterized in that the cathodic reduction of a solution of the carboxamide or carboxylic ester is carried out in a divided flow cell.
6. Process according to any of the preceding claims, characterized in that the cathodic reduction of the solution of the carboxamide or carboxylic ester is carried out in an inert solvent selected from C₁-C₄-alkanols, dimethyl carbonate, propylene carbonate, tetrahydrofuran, dimethoxyethane, acetonitrile and water, mixtures of these inert solvents or mixtures of these inert solvents with C₅-C₇-hydrocarbons.
7. Process according to any of the preceding claims, characterized in that the solution of the carboxamide or carboxylic ester comprises a mineral acid.
8. Process according to Claim 7, characterized in that the solution of the carboxamide or carboxylic ester comprises the mineral acid at a concentration in a range from 0.05 to 5 mol/l.
9. Process according to any of Claims 6 to 8, characterized in that the cathodic reduction of the solution of the carboxamide or carboxylic ester is carried out in an inert solvent thereof selected from C₁-C₄-alkanols or mixtures of C₁-C₄-alkanols and comprising a mineral acid, especially sulphuric acid.
10. Process according to any of the preceding claims, characterized in that the cathode used is an electrode whose surface consists of lead.
11. Process according to any of the preceding claims, characterized in that the anode used is an electrode whose surface consists of platinum, lead, zinc, tin, nickel, mercury, cadmium, copper, alloys of these metals, glassy carbon, graphite or diamond.
12. Process according to any of the preceding claims, characterized in that the electrolysis is carried out at a temperature in the range of 25 to 100°C.