Process for the preparation of an aqueous solution comprising n-alkylhydroxylamine

Abstract

The present invention relates to a process for the preparation of an aqueous solution comprising N- Alkylhydroxylamine of formula (I) wherein the process comprises the following steps I) oxidizing a secondary amine of formula (II), II) adding an acid, III) distilling the received mixture of step II) in a distillation apparatus comprising a distillation column by removing a composition comprising water and byproducts at the top of the column until the purity of compound of formula (IIIb) in the residue is 95% or greater, IV) adding a base to the residue of step III), V) filtering the received slightly soluble salt off and VI) receiving the aqueous solution as filtrate. The present invention relates further to the aqueous solution obtainable by the inventive process and comprising water, N- alkylhydroylamine of formula (I) alkali cations, anions of sulfur acid, phosphoric acid, oxalic acid or mixtures thereof, the use of this inventive aqueous solution for the production of building blocks for active pharmaceutical and / or agriculturally compounds like 2-C1-C5-alkyl-4-amino-isoxazolidin-3-one.

Description

[0001] Process for the preparation of an aqueous solution comprising N-Alkylhydroxylami ne

[0002] The present invention relates to a process for the preparation of an aqueous solution comprising N- Alkylhydroxylamines of formula (I) wherein the process comprises the following steps I) oxidizing a secondary amine of formula (II), II) adding an acid, III) distilling the received mixture of step II) in a distillation apparatus comprising a distillation column by removing a composition comprising water and byproducts at the top of the column until the purity of compound of formula (lllb) in the residue is 95% or greater, IV) adding a base to the residue of step III), V) filtering the received slightly soluble salt off and VI) receiving the aqueous solution as filtrate. The present invention relates further to the aqueous solution obtainable by the inventive process and comprising water, N- alkylhydroylamine of formula (I), alkali cations, anions of sulfuric acid, phosphoric acid, oxalic acid or mixtures thereof, the use of this inventive aqueous solution for the production of building blocks for active pharmaceutical and / or agricultural compounds like 2-Ci-C5-alkyl-4-amino-isoxazolidin-3-one.

[0003] Substituted cycloserines are important intermediates in the preparation of agriculturally compounds. N-Alkyl- hydroxylamines are versatile building blocks for the synthesis of 2-N-Alkyl-4-ami no-isoxyzol idin-3-one compounds.

[0004] WO2011 / 067272 A , WO2012 / 163959 A, WO2012 / 163960 A and WO2015 / 166094 A describe the synthesis of active agricultural compounds like insecticides wherein N-alkyl-4-amino-isoxazolidin-3-one compounds are important building blocks. WO2015 / 166094 A describes the synthesis of theses isoxazolidine derivates by reacting N-alkyl-, - haloalkyl, -aryl, -aryl substituted hydroxylamines or the corresponding N-alkyl-, -haloalkyl-, -aryl-, -aryl substituted hydroxylammonium salts with an oxazolidine-2, 5-dione derivate carrying a leaving-group in position 4 of the oxazolidine-2, 5-dione. The synthesis of the N-alkylhydroxylami nes as such or an aqueous solution comprising N- alkylhydroxylamine is not described in any of WO2011 / 067272 A, WO2012 / 163959 A, WO2012 / 163960 A and WO2015 / 166094 A.

[0005] US 5,731 ,462 A describes the synthesis of N-alkylhydroxylammonium salts starting from readily available dialkylamines which are oxidized with hydrogen peroxide to yield the corresponding nitrones. The nitrones are hydroylzed under acidic conditions to the corresponding N-alkylhydroxylammonium salts and different kind of byproducts. The main disadvantage of this synthesis is the purification of the mixture containing all byproducts of the oxidation and the hydrolytic cleavage. US 5,731 ,462 A only describes the isolation of the pure N- alkylhydroxylammonoium salts in laboratory scale.

[0006] As already mentioned in WO 2021 / 110445 A hydroxylamine derivates typically feature very high decomposition energies of more than 900 J / g together with low onset temperatures around 100°C so that they are explosive and not very stable under normal handling conditions. Therefore, WO 2021 / 110445 A describes a process for purification of a mixtures comprising water, N-alkyl-hydroxylammonium salts and byproducts wherein during the whole purification process the mixture contains a water content of 40 wt.% by bringing the mixture in contact with steam. The disadvantage of this purification process is the great amount of steam needed during the whole distillation process. Furthermore, an aqueous solution of the free stable base of the N-alkyl hydroxyl amine is not received by this process but only the aqueous solution of the N-alkylhydroxylammonium salt thereof.

[0007] Therefore, it is an object of the present invention to provide an improved process for the production of an aqueous solution comprising free stable N-alkylhydroxylamine without byproducts, handling the N-alkyl-hydroxylammonium salt in a safe way without any danger of explosion, without using additional great amount of water and wherein at the end the free base in water can be received in a safe, optimized production way which is suitable for commercial processes.

[0008] Surprisingly, the problem will be solved with a process for the preparation of an aqueous solution comprising a) 50 to 90 wt.-% of water, b) 5 to 40 wt.-% of one or a mixture of N-alkylhydroxylami nes of formula (I) wherein R1, R2and R3each independently are selected from the group consisting of H, methyl, ethyl, n-propyl and isopropyl, c) 0 001 to 5 wt.% of a secondary amine of formula (II)

[0009] R\

[0010] N - H

[0011] X

[0012] (ID wherein R4and R5each independently are selected from the group consisting of ethyl, n-propyl, isopropyl, n- butyl, 2-butyl, 2-methyl-propyl, tert-butyl, wherein di-tert-butylamine as compound of formula (II) is disclaimed, d) 0.001 to 5 wt.-% of anions selected from the group consisting of SO42-, HSO4 PO43-, HPO42-, F POzr, C2O2-,

[0013] HC2O4- and any mixture thereof, e) 0.001 to 3 wt.-% of alkali cations and f) 0 to 1 wt.-% of alkaline earth cations based on total weight of the aqueous solution, wherein the process comprises the following steps:

[0014] I) oxidizing a secondary amine of formula (II) with an oxidation agent in the presence of an >C=O containing compound selected from the group consisting of carbon dioxide, hydrogencarbonates and carbonates provided that when carbon dioxide is added as >C=O containing compound the concentration of carbon dioxide in the reaction mixture exceeds the naturally occurring concentration, wherein during oxidation the pH-value is kept equal to or higher than 8 by adding a hydroxide selected from the group consisting of alkali hydroxide, alkaline earth hydroxide, aqueous alkali hydroxide solution, aqueous alkaline earth hydroxide solution, aqueous alkali hydroxide slurry, aqueous alkaline earth hydroxide slurry and any mixture thereof,

[0015] II) adding to the received reaction mixture of step I) an acid selected from the group consisting of sulfuric acid, aqueous solution of sulfuric acid, phosphoric acid, aqueous solution of phosphoric acid, oxalic acid, aqueous solution of oxalic acid and any mixtures thereof until the pH-value is 1 or lower,

[0016] III) distilling the received mixture of step II) comprising a) 40 to 90 wt -% of water,

[0017] P) 6 to 49 wt.-% of N-alkylhydroxylamine derivates consisting of nitrones of formula (Illa) and / or the N-alkylhydroylammonium salt of formula (I I lb) wherein

[0018] X is selected from the group consisting of SO4, HSO4, PO4, HPO4, H2PO4, C2O4, HC2O4 or any mixtures thereof, n dependent of the valence of X in water is a natural number selected from the group consisting of 1, 2 and 3 and

[0019] R1, R2, R3and R4are as defined above, y) 0.1 to 24 wt.-% of byproducts comprising the aldehyde and / or ketone both corresponding to the nitrones of formula (Illa) and the oxime corresponding to the N-alkylhydroxylamine of formula (I),

[0020] 6) 0.001 to 5 wt.-% of secondary amine of formula (II),

[0021] E) 0.01 to 10 wt.-% of anions selected from the group consisting of SO42', HSO4', PCV, HPCV, H2PO4', C2O42', HC2O4- or any mixtures thereof,

[0022] Q 0.001 to 3 wt.-% of alkali and / or alkaline earth cations, based on total weight of the received mixture of step II), in a distillation apparatus comprising a distillation column with at least 2 theoretical plates by removing a composition comprising compound a) and y) at the top of the column by distillation until the purity of compound of formula (II lb) in the residue is 95% or greater based on the sum of all compounds in the residue without the sum of amount of compounds a), E) and Q, without adding any further water into the distillation apparatus,

[0023] IV) adding to the residue of step III) a base so that a slightly soluble salt precipitates comprising the anion Xn- of compound of formula (I I lb) and the cation of the base,

[0024] V) filtering off the precipitate received from the slurry of step IV),

[0025] VI) receiving the aqueous solution as filtrate of step V)

[0026] The inventive process will be advantageous, when the distillation temperature during step III) is in the range of 10 to 100 °C and the absolute pressure is in the range of 1 to 1000 mbar.

[0027] The inventive process will be advantageous, when step II) takes place in the distillation apparatus of step III) before the distillation starts.

[0028] The inventive process will be advantageous, when the temperature is in the range of 60 to 80°C in step III).

[0029] The inventive process will be advantageous, when the amount of the added base of step IV) is enough to transfer 90 to 110% of the stoichiometric amount of the anion Xn- in the residue of step III) into a form that forms the slightly soluble salt with the cation of the base of step IV).

[0030] The inventive process will be advantageous, when the base in step IV) is selected from the group consisting of alkaline earth oxides, hydroxides of alkaline earth metal cations and any mixture thereof.

[0031] The inventive process will be advantageous, when the slightly soluble salt precipitating in step IV) has a solubility of < 2,4 g / L at 20°C.

[0032] The inventive process will be advantageous, when the column-feed in step III) is fed into the distillation column of the distillation apparatus using a side draw.

[0033] The inventive process will be advantageous, when R4and R6in formula (II) are identical.

[0034] The inventive process will be advantageous, when the anion Xn- in formula (lllb) is selected from the group consisting of SO42, HSO4 PO43HPO42, H2PO4 or any mixture thereof.

[0035] The inventive process will be advantageous, when the secondary amine of formula (II) is diethylamine and the N- alkylhydroxylamine of formula (I) is N-ethylhydroxylamine.

[0036] A further embodiment of the invention is an aqueous solution obtainable by the inventive process. As for the inventive process the possible used secondary amines of formula (II) do not comprise any methyl group for R4and R5in formula (II). Thus, the resulting aqueous solution cannot include N-methylhydroxylamine as formula (I). Therefore, in the aqueous solution obtainable by the inventive process N-methlyhydroxylamine as compound of formula (I) is disclaimed.

[0037] A further embodiment of the invention is an aqueous solution comprising a) 50 to 90 wt.-% of water b) 5 to 40 wt.-% of one or a mixture of N-alkylhydroxylamines of formula (I) wherein R1, R2and R3each independently are selected from the group consisting of H, methyl, ethyl, n-propyl and isopropyl, wherein N-methylhyroxylamine as compound of formula (I) is disclaimed c) 0.001 to 5 wt.-% of a secondary amine of formula (II) wherein R4and R5each independently are selected from the group of ethyl, n-propyl, isopropyl, n-butyl, 2- butyl, 2-methyl-propyl, tert-butyl, wherein di-tert-butylamine as compound of formula (II) is disclaimed, d) 0.001 to 5 wt.-% anions selected from the group of SCU2-, HSOr, PO ', HPO42', H2PO4 C2O42', HC2O4' and any mixture thereof, e) 0.001 to 3 wt.-% of alkali cations and f) 0 to 1 wt.-% of alkaline earth cations based on total weight of the aqueous solution.

[0038] The inventive aqueous solution will be advantageous, when the secondary amine of formula (II) is diethylamine and the N-alkylhydroxylamine of formula (I) is N-ethylhydroxylamine.

[0039] A further embodiment of the invention is the use of the inventive aqueous solution for the production of building blocks for agriculturally compounds.

[0040] The inventive use of the inventive aqueous solution for the production of 2-Ci-C5-alkyl-4-amino-isoxazolidin-3-one.

[0041] The inventive aqueous solution comprises a) 50 to 90 wt.-% of water, b) 5 to 40 wt.-% of one or a mixture of N-alkylhydroxylamines of formula (I) wherein R1, R2and R3each independently are selected from the group of H, methyl, ethyl, n-propyl and isopropyl, wherein N-methylhyroxylamine as compound of formula (I) is disclaimed c) 0.001 to 5 wt.% of a secondary amine of formula (II) wherein R4and R5each independently are selected from the group consisting of ethyl, n-propyl, isopropyl, n- butyl, 2-butyl, 2-methyl-propyl, tert-butyl, wherein di-tert-butylamine as compound of formula (II) is disclaimed, d) 0.001 to 5 wt.-% of anions selected from the group consisting of SO42', HSC , PO43HPCV, H2PO4', C2O42

[0042] HC2O4- and any mixture thereof, e) 0.001 to 3 wt.-% of alkali cations and f) 0 to 1 wt.-% of alkaline earth cations based on total weight of the aqueous solution.

[0043] The water content of the inventive aqueous solution is in the range from 50 to 90 wt.%, preferably in range from 85 to 65, most preferably in the range from 80 to 70 wt.-% based on the total weight of the aqueous solution in order to handle the N-al kylhydroxylami ne under safe conditions.

[0044] R1, R2and R3in the N-alkylhydroxylamine of formula (I) are independently selected from the group consisting of H and any Ci to C-j-alkyl group, wherein N-methylhydroxylamine is disclaimed. The C1-C3 alkyl groups are selected from the group consisting of methyl, ethyl, n-propyl and isopropyl. Preferably R1, R2and R3are independently selected from the group consisting of H, methyl, ethyl, n-propyl and isopropyl wherein at least one group of R1, R2and R3is not identical with one of the others, more preferably R1, R2and R3are independently selected from the group consisting of methyl, ethyl and isopropyl and one group of R1, R2and R3is H, most preferably R1and R2are H and R3is methyl. The most preferred N-alkylhydroxylamine of formula (I) is N-ethylhydroxylamine.

[0045] Compound c) of the inventive solution is a secondary amine of formula (II) Wherein R4and R5are independently selected from the group consisting of C2 to C4- alkyl groups wherein di-tert- butylamine as compound of formula (II) is disclaimed. The C2 to C4alkyl groups for R3and R4are selected from the group consisting of ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, 2-methyl-propyl, tert-butyl. Preferably R4and R5in the secondary amine of formula (II) are independently selected from the group consisting of ethyl, n-propyl, isopropyl, n- butyl, 2-butyl and 2-methyl-propyl, more preferably R4and R5are identical, most preferably R4and R5are ethyl. The most preferred dialkylamine of formula (II) is diethylamine. The amount of compound c) is in the range of 0.001 to 5 wt.%, preferably in the range of 0.01 to 4.5 wt.-%, more preferably 0.5 to 4 wt -%, most preferably 0.6 to 3 wt -% based on the total weight of the aqueous solution.

[0046] The content of compound d) of the inventive aqueous solution is in the range of 0.001 to 5 wt.-%, preferably in the range from 0.005 to 4.5 wt.-%, more preferably 0.007 to 4.0 wt.-%, most preferably in the range from 0.007 to 3.5 wt.- % based on the total weight of the aqueous solution. Compound d) of the aqueous solution is an anion which is selected from the group consisting of SO42-, HSO4-, PO43-, HPO42-, PkPO C2O42-, HC2O4- and any mixture thereof, preferably it is an anion of only one kind of anion group selected from the anion group consisting of SO42HSOrand any mixture thereof or PO43-, HPO42-, H2PO4- and any mixture thereof or C2O42-, HC2O4- and any mixture thereof, more preferably it is an anion of only one kind of anion group selected from the anion group consisting of SO42-, HSO4- and any mixture thereof or PO43-, HPO42’, H2PO4- and any mixture thereof, most preferably it is an anion selected from the anion group consisting of SO42-, HSO4- and any mixture thereof.

[0047] The compound e) of the inventive aqueous solution are alkali cations. Preferably they are selected from the group consisting of Li+, Na+, K+, Cs+, Fr+and any mixture thereof, more preferably they are selected from the group consisting of Na+, K+and any mixture thereof, most preferably there is only one kind of cation like Na+or K+. The content of compound e) in the aqueous solution is in the range from 0.001 to 3 wt.-%, preferably in the range from 0.05 to 3wt.-%, more preferably in the range of 0.1 to 3 wt.%, most preferably in the range of 1 to 3 wt.-% based on the total weight of the aqueous solution.

[0048] The compound f) of the inventive aqueous solution is 0 to 1 wt.-% of alkaline earth cations. Preferably the content of the alkaline earth cations is in the range of 0 to 0.9 wt.-%, more preferably 0 to 0.3wt.-%, much more preferably 0 to 0 05 wt -%, most preferably 0 to 0.009 wt.-% based on the total weight of the aqueous solution. The alkaline earth cations are selected from the group consisting of Be2+, Mg2+, Ca2+, Sr2+, Ba2+, Ra2+and any mixture thereof, preferably they are selected from the group consisting of Mg2+, Ca2+, Sr2+, Ba2+and any mixture thereof, more preferably they are selected from the group consisting of Mg2+, Ca2+and Ba2+.

[0049] The inventive aqueous solution can be received by the inventive process. The inventive process can be divided into six process steps. The first step is the oxidization of the secondary amine of formula (II) with an oxidation agent in the presence of an >C=O containing compound.

[0050] As the secondary amine of formula (II) in step (I) do not carry any methyl group, the received N-alkylhydroxylamine of formula (I), received after the inventive process is finished, cannot be N-methylhydroxylamine. Therefore, the inventive process is a process to prepare an aqueous solution wherein N-methylhydroxylamine as compound of formula (I) is disclaimed.

[0051] For step I) the secondary amine of formula (I) will be mixed with a solvent that comprises water. Beside water every organic solvent can be present that is water-miscible. Preferably the solvent is selected form the group consisting of C1-C4- alcohols, acetonitrile, THF, water and any mixture thereof, more preferably the solvent is water only. The oxidation agent used in step I) of the present inventive process is selected from the group consisting of peroxides, hydroperoxides and peracids, more preferably hydrogen peroxide, tert-butyl hydroperoxide or meta-chloroperbenzoic acid, most preferably is hydrogen peroxide. The oxidation agent is added to the secondary amine of formula (II) preferably as a solution with water with a content of oxidation agent in the range of 5 to 70% by weight, preferably is a 30 to 60% by weight, more preferably a 30 to 55% by weight of an aqueous oxidation agent solution. Most preferred is an aqueous 5 to 70% by weight hydroperoxide solution. The amount of oxidation agent for the process step I) will be in a molar ratio between oxidation agent to secondary amine of formula (II) of 1 to 4, preferably 1.5 to

[0052] 3.5, more preferably 2 to 3, most preferably 2.2 to 2.5.

[0053] If the oxidation agent is a hydrogen peroxide it is necessary that a >C=O containing compound is present. This >C=O containing compound is preferably introduced to the mixture comprising secondary amine and solvent before the oxidation agent is added to the reaction mixture of step I). The >C=O containing compound is selected from the group consisting of carbon dioxide, hydrogencarbonates and carbonates. Preferably the >C=O containing compound is selected from the group consisting of CO2, HCOa', COa2-, Ci-C4-dialkylcarbonates and mixtures thereof wherein the hydrogencarbonate and carbonates anions are accompanied by ammonium and / or alkali metal cations such as sodium and / or potassium cation. More preferably the >C=O containing compound is selected from the group consisting of CO2, HCOa', COa2-, dimethylcarbonate and mixtures thereof, much more preferably is the>C=O containing compound selected from the group consisting of CO2, HCOa' and COa2' or mixtures thereof, most preferably is the >C=0 containing compound CO2. The molar ratio of the >0=0 containing compounds to the secondary amine of formula (II) is needed in step I) in the range from 0.001 to 1 , preferably in the range from 0.005 to 0.1. In the case CO2 is used the molar ratio of the >C=O containing compound to the secondary amine of formula (II) might be greater as CO2 may be continuously passed through the reaction mixture during the whole oxidation in step I) of the inventive process. As a consequence, the overall amount of CO2 introduced into the reaction mixture over time may exceed the specified ranges but the concentration of dissolved CO2 in the mixture will be within the ranges throughout the total duration of step I).

[0054] Preferably the reaction temperature during step I) of the inventive process is in the range of 20°C to 80°C, more preferably in the range of 40 to 70°C and most preferably in the range from 45 °C to 55°C. During step I) of the inventive process it is preferable to keep the pH-value of the reaction mixture at or above 8, preferably at or above

[0055] 8.5. As during the reaction of step I) the pH-value will be decreasing by adding the oxidation agent it will be kept at or above 8 by adding a hydroxide selected from the group consisting of alkali hydroxide, alkaline earth hydroxide, aqueous alkali hydroxide solution, aqueous alkaline earth hydroxide solution, aqueous alkali hydroxide slurry, aqueous alkaline earth hydroxide slurry and any mixture thereof. Preferably is the hydroxide selected from the group of aqueous alkali hydroxide solution, aqueous alkaline earth hydroxide solution, aqueous alkali hydroxide slurry, aqueous alkaline earth hydroxide slurry and any mixture thereof. The used alkali hydroxide and / or alkaline earth hydroxide either used as solid, as aqueous solution or as slurries are selected from the group consisting of NaOH, KOH, Mg(OH)2, Ca(OH)2 Ba(OH)2, the hydrates of Mg(OH)2, Ca(OH)2, Ba(OH)2 and any mixture thereof. Preferably used are aqueous solution and / or slurries of NaOH, KOH, Ca(OH)2 , Mg(OH)2 and or mixtures thereof, more preferably are aqueous solution and / or slurries of NaOH, KOH and Ca(0H)2, most preferable are aqueous solution of NaOH and KOH. The concentration of the aqueous alkali and / or alkaline earth hydroxide solution and or slurries are in the range from 10 to 90% by weight, preferably 15 to 60 % by weight, most preferably in the range from 20 to 50% by weight Step I) of the inventive process will be completed, if so much oxidation agent is added that the molar ratio between oxidation agent and sec amine of formula (II) is in the preferred ranges, the exothermic reaction has ceased and no more oxidation agent can be detected by commercial available strip tests.

[0056] After step I) is completed, an acid selected from the group consisting of sulfuric acid, aqueous solution of sulfuric acid, phosphoric acid, aqueous solution of phosphoric acid, oxalic acid, aqueous solution of oxalic acid and any mixtures thereof will be added to the received reaction mixture of step I) until the pH-value is 1 or lower in step II) of the inventive process. During the acid is added the mixture is stirred at a temperature in the range from 10 to 70°C, preferably in the range from 15 to 55°C, more preferably in the range from 20 to 50°C, most preferably in the range from 30 to 45 °C. The absolute pressure during the time where the acid is added is in the range from 500 to 1100 mbar, preferably 600 to 1050 mbar, more preferably 700 to 1050 mbar, most preferably in the range from 800 to 1050 mbar. Step II) will be completed if the pH- value is 1 or lower for a time period of 30 min, preferably of 20 min, most preferably of 5 min. Preferably the acid is selected from the group consisting of aqueous solution of sulfuric acid, aqueous solution of phosphoric acid, aqueous solution of oxalic acid and any mixture thereof. More preferably the acid is selected from the group consisting of aqueous solution of sulfuric acid, aqueous solution of phosphoric acid and any mixture thereof. Most preferably the acid is an aqueous solution of sulfuric acid. The concentration of the used acid for step II) of the inventive process is in the range from 20 to 100 wt.-%, preferably in the range from 20 to 98 wt.-%, more preferably in the range from 40 to 86 wt.-%, most preferably in the range from 45 to 55 wt.-%. Step II) of the inventive process can be taken place in the distillation apparatus of step III) before the distillation of step III) has started, in the reaction apparatus of step I) after step I) is completed and before the reaction mixture is transferred in the distillation apparatus of step III), or it takes place in the reaction apparatus of step I) after step I) is completed and afterwards all the apparatus constructions which are not needed for step III) of the inventive process will be changed by the apparatus construction which are needed for step III) without changing the reaction apparatus wherein step II) has taken place. Preferably step II) of the inventive process takes place in the distillation apparatus of step III) before the distillation starts.

[0057] After step II) is completed the received mixture of step II) comprises water, N-alkylhydroxylamine derivates, byproducts, secondary amine of formula (II), anions of the used acid in step II) and alkali and / or alkaline earth cations of the used hydroxide in step I). Preferably the received mixture after step II) is completed comprises ct) 40 to 90 wt.-% of water, p) 6 to 49 wt.-% of N-alkylhydroxylamine derivates consisting of nitrones of formula (Illa) and / or the N-alkylhydroylammonium salt of formul wherein

[0058] X is selected from the group consisting of SO4, HSO4, PO4, HPO4, H2PO4, C2O4, HC2O4 or any mixtures thereof, n dependent of the valence of X in water is a natural number selected from the group consisting of 1 , 2 and 3 and

[0059] R1, R2, R3and R4are as defined above, y) 0 1 to 24 wt.-% of byproducts comprising the aldehyde and / or ketone both corresponding to the nitrones of formula (Illa) and the oxime corresponding to the N-alkylhydroxylamine of formula (I) and

[0060] 5) 0.001 to 5 wt.-% of secondary amine of formula (II)

[0061] E) 0.01 to 10 wt.-% of anions selected from the group consisting of SO42HSO44 PO43, HPO42, H2PO4 , C2O42,

[0062] HC O4- or any mixtures thereof,

[0063] Q 0.001 to 3 wt.-% of alkali and / or alkaline earth cations based on total weight of the received mixture of step II).

[0064] Preferably after step II) is completed the content of compound a) in the received mixture is in the range from 40 to 90 wt.-%, preferably in the range from 45to 75wt.-%, most preferably in the range from 50 to 70 wt.-% based on the total weight amount of the received mixture after step II) is completed.

[0065] Compound p) are N-alkylhydroxylamine derivates which consist of nitrones of formula (Illa) and / or N- alkylhydroxylammoniumsalt of formula (I lib). The nitrone of formula (Illa) is formed during the oxidation step I) which will be partially transformed to N-alkylhydroxylammoniumsalt of formula (lllb) during step II) of the inventive process. This transformation will take time and depends on the temperature. Therefore, the amount of N- alkylhydroxylammonium salt of formula (lllb) of compound p) will be in the range from 0 to 49 wt.-%, preferably in the range from 3 to 30wt.-%, more preferably in the range from 5 to 20wt.-%, most preferably in the range from 5 to 15 wt.-% based on the total weight amount of the received mixture after step II) is completed. The amount of the nitrone of formula (Illa) of compound p) will be in the range from 0 to 49 wt.-%, preferably in the range from 10 to 44 wt.-%, more preferably in the range from 15 to 30 wt.-%, most preferably in the range from 15 to 25 wt.-% in this received mixture after step II) is completed.

[0066] The compound y) of the received mixture after step II) is completed, will be 0.1 to 24 wt.-%, preferably 1 to 20 wt.-%, more preferably 3 to 18 wt.-% and most preferably 5 to 15wt -% of byproducts based on the total weight amount of the received mixture after step II) is completed. The word “byproducts” in this application refers to compounds of the received mixture after step II) is completed that do not belong to compound a), (3), 6), E) and Q. The byproducts comprise the aldehyde and / or ketone both corresponding to the nitrones of formula (Illa) and the oxime corresponding to the N-alkylhydroxylamine of formula (I). The aldehydes and / or ketones belonging to the byproducts are the products after hydrolysis of the nitrones of formula (Illa), while the oximes belonging to the byproducts is the product after oxidation of the N-alkylhydroxylamines of formula (I). In case diethylamine is used as secondary amine of formula (II) byproducts are acetaldehyde and acetaldehyde oxime. In the case diisoproylamine is used as secondary amine of formula (II) byproducts are acetone and acetone oxime. In the case ethylisopropylamine is used as secondary amine of formula (II) byproducts are acetaldehyde, acetone, acetaldehyde oxime and acetone oxime. The compound 5) is optionally included in the received mixture after step II) is completed. Therefore, the amount of compound 6) is in the range from 0 to 5 wt.-%, preferably 0 to 4 wt.-%, more preferably 0 to 3 wt.-%, most preferably 0 to 1 ,5 wt.-% based on the sum of all compounds a) to Q of the received mixture after step II) is completed. The compound 6) is the secondary amine of the formula (II) or any mixture of secondary amines of formula (II) that have not reacted during the process step I) and / or step II) of the inventive reaction.

[0067] The compound E) of the received mixture after step II) of the inventive process is completed are anions which are selected from the group consisting of acids that are used in step II) of the inventive step II). Preferably compound E) is selected from the group consisting of SCh2', HSO , PC3’, HPO42H2PO4 C2O42', HC2O4' or any mixtures thereof. More Preferably compound E) is selected from the group consisting of SC2-, HSCh', PC>43’, HPO42H2PO4' and mixtures thereof, most preferably compound E) is selected from the group consisting of SC>42', HSCk and mixtures thereof. The amount of compound E) is in the range from 0.01 to 10 wt.-%, preferably in the range from 0.2 to 8 wt- %, more preferably in the range from 0.5 to 5 wt.-%, most preferably in the range from 1 to 3 wt.-% based on the total weight amount of the received mixture after step II) is completed.

[0068] The compound Q of the received mixture after step II) is completed are cations which are selected from the group consisting of bases that are used in step I) of the invention. Preferably compound 0 is selected from the group consisting of alkali and / or alkaline earth cations, more preferably compound Q is selected from the group consisting of Na+, K+, Mg2+, Ca2+, Ba2+and mixtures thereof, most preferably compound Q is selected from the group consisting of Na+, K+and mixtures thereof. The amount of compound Q is in the range from 0.001 to 3 wt.-%, preferably in the range from 0.1 to 3 wt.-%, more preferably in the range from 0.5 to 3 wt.-%, most preferably in the range from 1 to 2.5 wt.-% based on the total weight amount of the received mixture after step (II) is completed.

[0069] In step III) of the inventive process the received mixture after step II) is completed is distilled in a distillation apparatus. The distillation apparatus comprises at least 3 parts. The first part is located at the bottom of the distillation apparatus and comprises a device wherein the received mixture of step II) of the invention and / or the residue and any mixture thereof can be heated. Preferably the first part comprises at least one access that allows to take samples of the residue before, during and after step III) of the inventive process. This can be realized via bypass at the bottom of the distillation apparatus. Above the first part is a second part which comprises a distillation column with at least two theoretical plates, preferably at least four theoretical plates, more preferably at least six theoretical plates, most preferably at least eight theoretical plates A theoretical plate is a hypothetical zone or stage in which two phases, such as the liquid and vapor phases of a substance, establish an equilibrium with each other. Such equilibrium stages may also be referred to as an equilibrium stage, ideal stage, or a theoretical tray. The distillation column used in the second part of the distillation apparatus is a distillation column selected from the group consisting of tray distillation columns, packed bed distillation columns with random column filling material, packed distillation columns with structured column filling material, spinning bands distillation columns and any combination of such distillation columns. Preferably is the column selected from the group consisting of tray distillation columns, packed bed distillation columns, packed distillation columns and any combination of such distillation columns thereof. If the received mixture after step III) comprises nitrones of formula (Illa) with R1= -H, R2= -CH3 and R4= ethyl the distillation column comprises 2 to 13, preferably 3 to 12, more preferably 4 to 11, most preferably 5 to 10 theoretical plates. Preferably the second part comprises at least one side draw for feeding the distillation column with the column feed which is selected from the group consisting of the received mixture of step II), the residue and any mixture thereof. The side draw for feeding the distillation column with the column feed is located below the column head, more preferably at the third theoretical plate below the column head, most preferably at the first theoretical plate below the column head. After the second part follows the third part which comprises a receiver to collect the overhead product. Preferably the third part comprises an access for taking samples from the overhead product. This is realized via bypass at the bottom of the receiver in the third part. Preferably none of the accesses or side draws of the distillation apparatus are used for feeding the received mixture of step II) of the invention, the residue any mixture thereof and / or the overhead product with additionally water, water vapor, steam or any mixture thereof before, during or after step III) of the inventive process. Therefore, a distillation apparatus as referred here in the application is a device that separates the received mixture after step II) is completed into a residue and an overhead product of it by evaporating the overhead product via a distillation column with at least two theoretical plates in a receiver.

[0070] The received mixture after step II) is completed will be distilled in step III) of the inventive process. Thus, the received mixture after step II) is completed is either transferred into the distillation apparatus of step III) or the received mixture of step I) is transferred into the distillation apparatus of step III) and before the distillation starts step II) takes place in the first part of the distillation apparatus. Another possible way to transfer the received mixture of step II) into the distillation apparatus is to change the apparatus construction above the reaction apparatus of step II), which are not used for step III) of the inventive process, by the second and third part of the distillation apparatus of step III) Preferably is the transfer of the received mixture of step I) or step II) of the inventive process into the distillation apparatus of step III). More preferably is to transfer the received mixture of step II) into the distillation apparatus of step III). For continuous production it is preferable to transfer the received mixture of step II) into the distillation apparatus of step III). More preferably the side draw of the distillation column in the second part of the distillation apparatus is used for the transfer of the received mixture of step II).

[0071] During the distillation of the received mixture after step II) is completed, the composition of the residue changes constantly. However, it will refer in this application to the evaporated part as "overhead product” and to the non- evaporated part, whatever the composition of the non-evaporated part is - as the “residue”. In the context of this application wt.-% always refers to the weight percentage of the relevant component as referred to the entire composition, which can be the received mixture after step I) or after step II) is completed, the residue or the overhead product. The overhead product comprises water, byproducts and impurities. The word “impurities” in this application refer to all compounds in the overhead product that are not compound a) and compound y).

[0072] The temperature during the distillation of step III) of the invention will be in the range from 10 to 100°C, preferably in the range from 40 to 95 °C, more preferably in the range from 50 to 85 °C, most preferably in the range from 60 to 80 °C. The absolute pressure during step III) will be in the range from 1 to 1000 mbar, preferably in the range from 100 to 800 mbar, more preferably in the range from 200 to 600 mbar, most preferably in the range from 300 to 400 mbar. Preferably the absolute pressure will be in the range from 1 to 1000 mbar if the temperature during step (III) is in the range from 10 to 100°C.

[0073] The received mixture after step II) is completed is fed into the distillation apparatus. The received mixture after step II) is completed can either be heated before entering the distillation apparatus or in the first part of the distillation apparatus to the respective distillation temperature. The vapor of the received mixture will be separated in the distillation column of the second part of the distillation apparatus and the overhead product will be collected in the receiver of the third part of the distillation apparatus. Preferably the received mixture of step II), a part of the received mixture of step II), the residues or any mixture thereof is continuously fed into the distillation column in the second part of the distillation apparatus via the side draw until the purity of 95 % or greater of compound of formula (I I lb) in the residue is reached. During the whole distillation of step III) no additional water, water vapor or steam is fed to the residue, the received mixture of step II) or any mixture thereof. Step III) of the inventive process is completed when the purity of the compound of formula (I I lb) in the residue of the distillation apparatus is 95 % or greater based on the sum of all compounds in the residue without the sum of amounts of compounds a), E) and Q.

[0074] To the residue after step III) is completed a base is added in step IV) of the inventive process so that a slightly soluble salt precipitates comprising the anion Xn- of compound of formula (I I lb) and the cation of the base. The base that is used in step IV) of the inventive process is selected from the group consisting of alkaline earth oxides, hydroxides and / or slurries of alkaline earth metal cations and any mixture thereof. Preferably the base of step IV) is selected from the group consisting of MgO, CaO, BaO, Mg(OH)2, Ca(OH)2.Ba(OH)2, the hydrates of Mg(OH)2, Ca(OH)2, Ba(OH)2 and any mixture thereof. Preferably the base of step IV) is selected from the group consisting of CaO, Ca(OH)2, BaO, Ba(OH)2, the hydrates of Ca(OH)2 and Ba(OH)2 and any mixture thereof, if Xn- is selected from the group consisting of SO42' , HSO4' and any mixture thereof If Xn- is selected from the group consisting of C2O42HC2O4; PO43, HPO42, H2PO4 and any mixture thereof the base is preferably selected from the group consisting of MgO, CaO, BaO, Mg(OH)2, Ca(OH)2.Ba(OH)2, the hydrates of Mg(OH)2, Ca(OH)2, Ba(OH)2 and any mixture thereof. The amount of the base that is added in step IV) to the residue of step III) is enough to transfer 90 to 110%, preferably 90 to 100%, more preferably 92 to 98 %, most preferably 92 to 95 % of the stoichiometric amount of the anion Xn- in the residue of step III) into a form that forms the slightly soluble salt with the cation of the base of step IV). This means that every H+ion of the added acid in step II) will be replaced by the cation of the added base in step IV). Adding the base to the residue after step III) is completed is an exothermic reaction. Therefore, it is preferable to cool down the residue and to add the base carefully in portions so that the temperature of the residue will not be higher than 70 °C, preferably not higher than 60°C, more preferably not higher than 55°C, most preferably not higher than 45°C.

[0075] The addition of base is completed, when the pH-value is in the range of 5.0 to 9.5, preferably in the range from 5.5 to 85, more preferably from 5.5 to 8.0, most preferably from 6.0 to 8.0.

[0076] By adding the base to the residue after step III) is completed a slightly soluble salt precipitates in step IV). The slightly soluble salt comprises the anion Xn' of compound of formula (lllb) and the cation of the base and have a solubility in water of 2,7 g / L at 20°C, preferably 2,6 g / L at 20°C, more preferably 2,5 g / L at 20°C, most preferably 2,4 g / L at 20°C. Preferably during adding the base and precipitation of the slightly soluble salt the received suspension is continuously stirred. The precipitation is completed, when the pH-value of the received suspension is in the range from 6.0 to 9.5, preferably in the range from 6.5 to 9.0, more preferably in the range from 6.5 to 8.5, most preferably in the range from 7.0 to 8.5.

[0077] After the precipitation of slightly soluble salt precipitates is completed, it will be filtered off in step V) of the inventive process. For the filtration every kind of filter is possible that will be able to keep the precipitate completely on the filter. Preferably such filter is selected from the group consisting of nutsche filters, filter presses and centrifuges more preferably the filter is selected from the group consisting of nutsche filters and centrifuges, most preferably the filter is a nutsche filter. The received filtrate of step VI) of the inventive process will be the inventive aqueous solution.

[0078] It is preferable to wash the filter cake with water. The filtrates comprising the compound of formula (I) will be collected and combined. To add such collected and combined filtrates with the aqueous solution received after step VI) of the invention will increase the yield of compound of formula (I) in inventive aqueous solution. Preferably the amount of water which is used for washing the filter cake is in the range from 0 to 2000g water, preferably 0 to 1500 g water, more preferably 500 to 1500 g water, most preferably 500 to 1200 g water per 1000 mL of filter cake.

[0079] The collected and combined filtrates comprising the compound of formula (I) after washing can be combined with the inventive aqueous solution received after step VI) of the inventive process and will also the inventive aqueous solution if the content of compound of formula (I) is not outside the range of 5 to 40wt.-% based on the sum of all combined filtrates comprising the compound of formula (I) and the aqueous solution received after step VI) of the invention.

[0080] The inventive aqueous solution can be used for the production of building blocks for active pharmaceutical and / or agriculturally compounds. The used building block are 1 ,2-oxazolidin-3-on derivates as it is used in cycloserine which is used as active pharmaceutical compound against tuberculosis. Furthermore, the inventive active solution can be used for the production of the building block 2-Ci-C5-alkyl-4-amino-isoxazolidin-3-one that is used in many insecticides as mentioned in WO2015 / 166094 A.

[0081] With the inventive process it is possible to receive an aqueous solution comprising the free base of N- alkylhydroxylamines in an easy and safety way in handling and avoids the problem with the isolation of the pure N- alkylhydroxylammonium salt. Furthermore, the inventive process provides an aqueous solution that can be used for the production of important building blocks for active pharmaceutical an agriculturally compounds without any further purification or isolation steps as the aqueous solution can be used to produce the important 1,2-oxazolidin-3-on derivates and / or 2-Ci-C5-alkyl-4-amino-isoxazolidin-3-one compounds. Additionally with the inventive process the free base N-alkylhydroxylamine in water can be received in a safe, optimized production way which is suitable for commercial processes as the starting products as well as the further used ingredients are all easily to get around the world and are safe in handling as well as the isolated byproducts and slightly soluble salt can be disposed on safely and easily.

[0082] Examples

[0083] Examples 1) Production of an aqueous solution of N-Ethylhydroxylamine (NEHA) a) Preparation of nitrone-solution by oxidation of diethylamine with hydrogen peroxide

[0084] A 1 .6 L double walled glass reactor with 3-blade cross bar stirrer, baffles, pH control connected to a pH controlled pump (Prominent Dulcometer; for NaOH-supply), NaOH supply (Teflon® tube connected to NaOH reservoir via the Prominent Dulcometer), CO2 supply (frit fitted glass tube connected to a CO2 3.0 line fed from pressured gas bottle, via flow control), H2O2 supply (Teflon® tube connected to H2O2 reservoir (glass) via a Fink Ritmo R5 pump), N2 overlay (heads only, connected to a 8 bar N2 line via flow control) and reflux condenser (water at 15 °C) was charged with 207 g of diethylamine (2.83 mol, 292 mL) and 200 g of water. The mixture was stirred at 500 rpm and heated to 50 °C with an N2 overlay of 1.0 L / h. The pH of the mixture was 12.8 as indicated by the pH measurement. CO2 was fed through the solution at a flow of 10 L / h until the pH of the mixture had decreased to 11 .0 (approx. 20 min). The CO2 flow was reduced to 0.25 L / h and the H2O2 feed was started at a feed rate of 1 8 mL / min. The internal temperature was kept at 50 °C by external cooling. In the course of the CO2 feed, the pH of the solution decreased to 9 0 within approx. 3 h. As a consequence, NaOH was fed in small portions to keep the pH at or above 9 0. After a total feed time of 4 hours and 15 min., H2O2 feed was stopped. The mixture was kept at 50 °C until the exotherm of the reaction had ceased and no peroxide could be detected in the mixture anymore (test strip). In total 442 g 50 wt- % H2O2 (6.50 mol, 2.30 equiv.) and 39.0 g 50 wt.-% NaOH were dosed. The mixture was analyzed by quantitative1H NMR and transferred to step b). Yield based on the molar amount of reacted diethyl amine: Nitrone: 81%, acetaldehyde oxime: 13% (sum of isomers), res. diethyl amine: 1.5%. b) Acidic hydrolysis and removal of side products b)1. Acidification with H2SO4

[0085] The reactor used in step a) was modified as follows: NaOH-supply, CO2 supply, N2 overlay and reflux condenser were removed and a packed column (3x3 mm glass Raschig rings, 25 cm height) connected to a distillation bridge (water, 15 °C) with vacuum adapter (connected via a dry ice cooled cold trap to a vacuubrand PC3001 membrane pump with vacuubrand CVC 3000 controller) and a 500 mL glass flask which was immersed in an ice bath was added. The HPLC-pump was disconnected from the H2O2 reservoir, rinsed with water and connected to a H2SO4 (50 wt.-%) reservoir. The crude reaction mixture from step a) was heated to 40 °C, stirred (500 rpm) and a slight vacuum was applied (850 mbar). 345 g 50 wt.-% H2SO4 were added slowly to the mixture and the final pH of the mixture was 0 7. The pressure was then lowered to 330 mbar and the sump temperature was increased to 75 °C and stirring was continued for 14 hours. A mixture (183 g) of acetaldehyde (54 wt.-%), water (32 wt.-%) and impurities (13 wt.-%, thereof 10 wt.-% acetaldehyde oxime and 3 % others) was collected as the head product. The mixture was cooled down to room temperature and the vacuum was released. The mixture was analyzed by quantitative1H NMR and was transferred to step c). The mixture contained 136 g N-Ethylhydroxylammonium sulfate (79% yield based used amount of diethylamine). c) Neutralization c)1 .1. Neutralization of Sulfate-Salt with Ca(OH)2

[0086] The mixture obtained in step b)1 . was transferred into a 2-liter round bottom 4-neck flask with thermometer, pH- sensor and mechanical stirring and stirred mechanically. The flask was immersed in an ice bath. 123.9 g of Ca(OH)2 were added to the mixture in small portions (approx. 3 g per portion). The internal temperature was kept below 30

[0087] °C. By the end of the addition, the pH indicated by the pH-sensor was 7.5. Stirring was continued for 1 hour. During this time span, the pH of the mixture increased to 8.1 . Consequently, the flask was removed from the ice bath and the reaction mixture was filtered through a glass filter funnel (2000 mL, 15-40 micron). The filter cake was washed with 300 mL of water. The filtrates were collected (1089 g) and analyzed by 1 H NMR and elemental analysis. The mixture contained 96 g NEHA (55% total yield), 2.8 g diethylamine, 10.1 g Na+, 0.06 g Ca2+, 11.1 g SO42- and 959 g water.

Claims

Claims1) Process for the preparation of an aqueous solution comprising a) 50 to 90 wt.-% of water, b) 5 to 40 wt.-% of one or a mixture of N-al ky I hydroxy I am i nes of formula (I)wherein R1, R2and R3each independently are selected from the group consisting of H, methyl, ethyl, n- propyl and isopropyl, c) 0.001 to 5 wt.% of a secondary amine of formula (II)wherein R4and R5each independently are selected from the group consisting of ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, 2-methyl-propyl, tert-butyl, wherein di-tert-butylamine as compound of formula (II) is disclaimed, d) 0.001 to 5 wt.-% of anions selected from the group consisting of SO42, HSO4 , PO43HPO42H2PO4C2O42', HC2O4- and any mixture thereof, e) 0.001 to 3 wt.-% of alkali cations and f) 0 to 1 wt.-% of alkaline earth cations based on total weight of the aqueous solution, wherein the process comprises the following steps:I) oxidizing a secondary amine of formula (II) with an oxidation agent in the presence of an >C=O containing compound consisting of carbon dioxide, hydrogencarbonates and carbonates provided that when carbon dioxide is added as >C=O containing compound the concentration of carbon dioxide in the reaction mixture exceeds the naturally occurring concentration, wherein during oxidation the pH-value is kept equal to or higher than 8 by adding a hydroxide selected from the group consisting of alkali hydroxide, alkaline earth hydroxide, aqueous alkali hydroxide solution, aqueous alkaline earth hydroxide solution, aqueous alkali hydroxide slurry, aqueous alkaline earth hydroxide slurry and any mixture thereof,II) adding to the received reaction mixture of step (I) an acid selected from the group of sulfuric acid, aqueous solution of sulfuric acid, phosphoric acid, aqueous solution of phosphoric acid, oxalic acid, aqueous solution of oxalic acid and any mixtures thereof until the pH-value is 1 or lower,III) distilling the received mixture of step (II) comprising a) 40 to 90 wt -% of waterP) 6 to 49 wt.-% of N-alkylhydroxylamine derivates consisting of nitrones of formula (Illa)and / or the N-alkylhydroylammonium salt of formula (lllb)whereinX is selected from the group consisting of SO4, HSO4, PO4, HPO4, H2PO4, C2O4, HC2O4 or any mixtures thereof, n dependent of the valence of X in water is a natural number selected from the group consisting of 1, 2 and 3 andR1, R2, R3and R4are as defined above, y) 0.1 to 24 wt.-% of byproducts comprising the aldehyde and / or ketone both corresponding to the nitrones of formula (Illa) and the oxime corresponding to the N-alkylhydroxylamine of formula (I) and6) 0.001 to 5 wt.-% of secondary amine of formula (II)E) 0.01 to 10 wt.-% of anions selected from the group consisting of SO42', HSC ', PO43HPC2', H2PO4', C2O42', HC2O4- or any mixtures thereof,0 0.001 to 3 wt.-% of alkali and / or alkaline earth cations, based on total weight of the received mixture of step II), in a distillation apparatus comprising a distillation column with at least 2 theoretical plates by removing a composition comprising compound a) and y) at the top of the column by distillation until the purity of compound of formula (lllb) in the residue is 95% or greater based on the sum of all compounds in the residue without the sum of amount of compounds a), E) and Q, without adding any further water into the distillation apparatus,IV) adding to the residue of step III) a base so that a slightly soluble salt precipitates comprising the anion Xn- of compound of formula (lllb) and the cation of the base,V) filtering off the precipitate received from the slurry of step IV),VI) receiving the aqueous solution as filtrate of step V).2) The process according to claim 1 , wherein the distillation temperature during step III) is in the range of 10 to100 °C and the absolute pressure is in the range of 1 to 1000 mbar.3) The process according to any of claim 1 to 2, wherein step II) takes place in the distillation apparatus of step III) before the distillation starts.4) The process according to any claim of 1 to 3, wherein the temperature is in the range of 60 to 80°C in step III).5) The process according to any claim of 1 to 4, wherein the amount of the added base of step IV) is enough to transfer 90 to 110% of the stoichiometric amount to the anion Xn- in the residue of step III) into a form that forms the lightly soluble salt with the cation of the base of step IV).6) The process according to any claim of 1 to 5, wherein the base in step IV) is selected from the group consisting of alkaline earth oxides, hydroxides of alkaline earth metal cations and any mixture thereof.7) The process according to any claim of 1 to 6, wherein the slightly soluble salt precipitating in step IV) has a solubility in water of < 2,4 g / L at 20°C.8) The process according to any of claim 1 to 7, wherein, the column-feed in step III) is fed into the column of the distillation apparatus using a side draw.9) The process according to any of claim of 1 to 8, wherein R4and R5in formula (II) are identical10) The process according to any of claim 1 to 9, wherein the anion Xn- in formula (lllb) is selected from the group consisting of SO42; HSOf, PCV3', HPO42', F PCV' or any mixture thereof11) The process according to any of claim 1 to 10, wherein the secondary amine of formula (II) is diethylamine and the N-alkylhydroxylamine of formula (I) is N-ethylhydroxylamine.12) An aqueous solution obtainable by the process of claim 1

Images