EP4626862A1

EP4626862A1 - Process for the preparation of n-hydroxypyridone compounds

Info

Publication number: EP4626862A1
Application number: EP23812931.6A
Authority: EP
Inventors: Dirk Fischer; Peter Klug; Claudia Diemel; Wiebke Mueckenheim; Wolfdieter MUELLER
Original assignee: Clariant International Ltd
Current assignee: Clariant International Ltd
Priority date: 2022-11-28
Filing date: 2023-11-24
Publication date: 2025-10-08
Also published as: WO2024115319A1; CN120225505A

Abstract

The invention relates to a process for the preparation of N-hydroxypyridone compounds (I) from pyrone compounds using a phase transfer catalyst.

Description

Process for the preparation of N-hydroxypyridone compounds The invention relates to a process for the preparation of N-hydroxypyridone compounds from pyrone compounds using a phase transfer catalyst. Preservation of cosmetic formulations and household formulations extends their shelf life and therefore provides greater value for money for consumers. Furthermore, preservatives prevent consumers from distributing microbes around their home or on themselves and hence provide health benefits. Anti-microbial actives are well- described in the art and there are many available that provide excellent performance. Piroctone Olamine, also known as Octopirox® (Clariant) and as piroctone ethanolamine, is a compound used in the treatment of fungal infections. The chemical name for Piroctone Olamine is the monoethanolamine salt of 1 hydroxy-4- methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone. Hence, Piroctone Olamine is the ethanolamine salt of piroctone. Piroctone Olamine is often used in anti-dandruff shampoos as an alternative to the commonly used compound zinc pyrithione. GB1440975, EP0158481, and WO2006/081969 describe the use of Piroctone Olamine as an anti-dandruff agent and/or as a preservative. DE4439029 and DE19517891 disclose processes for the preparation of Piroctone Olamine. Surprisingly, it has now been found that a phase transfer catalyst can be used to prepare N-hydroxypyridone compounds from pyrone compounds in good yields. The present invention relates to a process for the preparation of a compound of Formula (I) (I) wherein R¹ is hydrogen, linear or branched C1-C20-alkyl, linear or branched C2-C20-alkenyl, C3-C8-cycloalkyl, cyclohexyl-(C1-C4)-alkyl, benzyl, or benzyl substituted with 1 to 3 C₁-C₄-alkyl; R² is hydrogen, linear or branched C₁-C₅-alkyl, linear or branched C₂-C₅-alkenyl, linear or branched C2-C5-alkynyl, or benzyl, or R² may form together with either R¹ or R³ and the 2 carbon atoms to which R² and either R¹ or R³ are attached a 5- or 6-membered carbocyclic ring; R³ is hydrogen, linear or branched C1-C5-alkyl, or phenyl; R⁴ is hydrogen, linear or branched C1-C5-alkyl, linear or branched C2-C5-alkenyl, linear or branched C₂-C₅-alkynyl, methoxymethyl, or benzyl; Q⁺ is H⁺, Li⁺, Na⁺, K⁺, ½ Ca⁺⁺, ½ Mg⁺⁺, ½ Zn⁺⁺, 1/3 Al⁺⁺⁺, NH4⁺, hydroxylammonium, [NHR⁵R⁶R⁷]⁺, or combinations thereof; R⁵, R⁶ and R⁷ independently of one another are hydrogen, a linear or branched alkyl group having 1 to 22 carbon atoms, a linear or branched, singularly or multiply unsaturated alkenyl group having 2 to 22 carbon atoms, a C6-C22- alkylamidopropyl group, a linear mono-hydroxyalkyl group having 2 to 10 carbon atoms or a linear or branched dihydroxyalkyl group having 3 to 10 carbon atoms, wherein at least one of the radicals R⁵, R⁶ and R⁷ is not hydrogen; comprising the step of reacting a compound of Formula (II) (II) wherein R¹, R², R³ and R⁴ are as in the compound of Formula (I); with hydroxylamine or a hydroxylammonium compound in the presence of a phase transfer catalyst. Advantageously, a compound of Formula (I) can be used as a phase transfer catalyst for the preparation of a compound of Formula (I). This facilitates the reaction and leads to an improved yield. The process of the invention is a process for the preparation of a compound of Formula (I) wherein R¹ is hydrogen, linear or branched C₁-C₂₀-alkyl, linear or branched C₂-C₂₀-alkenyl, C3-C8-cycloalkyl, cyclohexyl-(C1-C4)-alkyl, benzyl, or benzyl substituted with 1 to 3 C1-C4-alkyl; R² is hydrogen, linear or branched C₁-C₅-alkyl, linear or branched C₂-C₅-alkenyl, linear or branched C₂-C₅-alkynyl, or benzyl, or R² may form together with either R¹ or R³ and the 2 carbon atoms to which R² and either R¹ or R³ are attached a 5- or 6-membered carbocyclic ring; R³ is hydrogen, linear or branched C₁-C₅-alkyl, or phenyl; R⁴ is hydrogen, linear or branched C1-C5-alkyl, linear or branched C2-C5-alkenyl, linear or branched C2-C5-alkynyl, methoxymethyl, or benzyl; Q⁺ is H⁺, Li⁺, Na⁺, K⁺, ½ Ca⁺⁺, ½ Mg⁺⁺, ½ Zn⁺⁺, 1/3 Al⁺⁺⁺, NH₄ ⁺, hydroxylammonium, [NHR⁵R⁶R⁷]⁺, or combinations thereof; R⁵, R⁶ and R⁷ independently of one another are hydrogen, a linear or branched alkyl group having 1 to 22 carbon atoms, a linear or branched, singularly or multiply unsaturated alkenyl group having 2 to 22 carbon atoms, a C₆-C₂₂- alkylamidopropyl group, a linear mono-hydroxyalkyl group having 2 to 10 carbon atoms or a linear or branched dihydroxyalkyl group having 3 to 10 carbon atoms, wherein at least one of the radicals R⁵, R⁶ and R⁷ is not hydrogen. Preferred are compounds of Formula (I) wherein R¹ is hydrogen, linear or branched C₁-C₂₀-alkyl, linear or branched C₂-C₆-alkenyl, C5-C7-cycloalkyl, cyclohexyl-(C1-C4)-alkyl, benzyl, or benzyl substituted with 1 to 3 methyl; R² is hydrogen, linear or branched C₁-C₄-alkyl, or benzyl, or R² may form together with R³ and the 2 carbon atoms to which R² and R³ are attached a 5- or 6- membered carbocyclic ring; R³ is hydrogen, or linear or branched C₁-C₄-alkyl; R⁴ is hydrogen, linear or branched C1-C4-alkyl, or benzyl; Q⁺ is H⁺, Li⁺, Na⁺, K⁺, ½ Ca⁺⁺, ½ Mg⁺⁺, ½ Zn⁺⁺, NH4⁺, hydroxylammonium, [NHR⁵R⁶R⁷]⁺, or combinations thereof; R⁵, R⁶ and R⁷ independently of one another are hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, a linear or branched, singularly or multiply unsaturated alkenyl group having 2 to 12 carbon atoms, a linear mono- hydroxyalkyl group having 2 to 8 carbon atoms or a linear or branched dihydroxyalkyl group having 3 to 8 carbon atoms, wherein at least one of the radicals R⁵, R⁶ and R⁷ is not hydrogen. More preferred are compounds of Formula (I) wherein R¹ is hydrogen, linear or branched C6-C10-alkyl, or cyclohexyl; R² is hydrogen; R³ is hydrogen or methyl; R⁴ is hydrogen; Q⁺ is H⁺, Li⁺, Na⁺, K⁺, ½ Ca⁺⁺, ½ Mg⁺⁺, ½ Zn⁺⁺, NH4⁺, hydroxylammonium, [NHR⁵R⁶R⁷]⁺, or combinations thereof; R⁵, R⁶ and R⁷ independently of one another are hydrogen, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear mono-hydroxyalkyl group having 2 to 6 carbon atoms or a linear or branched dihydroxyalkyl group having 3 to 6 carbon atoms, wherein at least one of the radicals R⁵, R⁶ and R⁷ is not hydrogen. Even more preferred are compounds of Formula (I) wherein R¹ is hydrogen, linear or branched C₆-C₁₀-alkyl, or cyclohexyl; R² is hydrogen; R³ is methyl; R⁴ is hydrogen; Q⁺ is H⁺, Na⁺, K⁺, NH4⁺, hydroxylammonium, [NH3(CH2CH2OH)]⁺, or combinations thereof. Even more preferred are compounds of Formula (I) wherein R¹ is 2,4,4-trimethylpentyl; R² is hydrogen; R³ is methyl; R⁴ is hydrogen; Q⁺ is H⁺, Na⁺, hydroxylammonium, [NH₃(CH₂CH₂OH)]⁺, or combinations thereof. Even more preferred are compounds of Formula (I) wherein R¹ is 2,4,4-trimethylpentyl; R² is hydrogen; R³ is methyl; R⁴ is hydrogen; Q⁺ is H⁺, hydroxylammonium, [NH₃(CH₂CH₂OH)]⁺, or combinations thereof. Particularly preferred are compounds of Formula (I) wherein R¹ is 2,4,4-trimethylpentyl; R² is hydrogen; R³ is methyl; R⁴ is hydrogen; Q⁺ is H⁺, [NH₃(CH₂CH₂OH)]⁺, or combinations thereof. In a preferred embodiment, the compound of Formula (I) is selected from the group 1-hydroxy-6-methyl-pyridin-2-one, 1-hydroxy-4,6-dimethyl-pyridin-2-one, 1-hydroxy- 3,4,6-trimethyl-pyridin-2-one, 1-hydroxy-4-methyl-6-ethyl-pyridin-2-one, 1-hydroxy-4- methyl-6-isopropyl-pyridin-2-one, 1-hydroxy-4-methyl-6-heptyl-pyridin-2-one, 1- hydroxy-4-methyl-6-undecyl-pyridin-2-one, 1-hydroxy-4-methyl-6-heptadecyl-pyridin- 2-one, 1-hydroxy-4-ethyl-5,6-dimethyl-pyridin-2-one, 1-hydroxy-4,5-trimethylen-6- methyl-pyridin-2-one, 1-hydroxy-4-methyl-6-cyclohexyl-pyridin-2-one, 1-hydroxy-4- methyl-6-cyclohexyl-methyl-pyridin-2-one, 1-hydroxy-4-methyl-6-cyclohexyl-ethyl- pyridin-2-one, 1-hydroxy-4-methyl-6-isobutenyl-pyridin-2-one, 1-hydroxy-4,6- dimethyl-5-benzyl-pyridin-2-one, 1-hydroxy-3-benzyl-4,6-dimethyl-pyridin-2-one, 1- hydroxy-4-methyl-6-benzyl-pyridin-2-one, 1-hydroxy-3,4-dimethyl-6-(2,4- dimethylbenzyl)-pyridin-2-one, 1-hydroxy-6-cyclohexyl-pyridin-2-one, 1-hydroxy-4- methyl-6-cyclohexyl-pyridin-2-one, 1-hydroxy-4-ethyl-6-cyclohexyl-pyridin-2-one, 1- hydroxy-4-propyl-6-cyclohexyl-pyridin-2-one, 1-hydroxy-6-(2,4,4-trimethylpentyl)- pyridin-2-one, 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-pyridin-2-one, 1-hydroxy- 4-ethyl-6-(2,4,4-trimethylpentyl)-pyridin-2-one, 1-hydroxy-4-propyl-6-(2,4,4- trimethylpentyl)-pyridin-2-one, and salts thereof. Preferably, the compound of Formula (I) is 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or a salt thereof. Particularly preferably, the compound of Formula (I) is 1-hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyridone or the ethanolamine salt of 1-hydroxy-4- methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone. In a particularly preferred embodiment, the compound of Formula (I) is 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone. In another particularly preferred embodiment, the compound of Formula (I) is the ethanolamine salt of 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone. Compounds of Formula (I) wherein Q⁺ is not H⁺ can be converted into compounds of Formula (I) wherein Q⁺ is H⁺ by treatment with water and/or an acid, e.g. hydrochloric acid or sulfuric acid. For example, compounds of Formula (I) wherein Q⁺ is Na⁺, hydroxylammonium, or combinations thereof can be converted into compounds of Formula (I) wherein Q⁺ is H⁺ by treatment with water and/or an acid, e.g. hydrochloric acid or sulfuric acid. Compounds of Formula (I) wherein Q⁺ is H⁺ can be converted into compounds of Formula (I) wherein Q⁺ is not H⁺ by treatment with a base, e.g. an amine. For example, compounds of Formula (I) wherein Q⁺ is H⁺ can be converted into compounds of Formula (I) wherein Q⁺ is [NH₃(CH₂CH₂OH)]⁺ by treatment with monoethanolamine. The process of the invention comprises the step of reacting a compound of Formula (II) wherein R¹, R², R³ and R⁴ are as in the compound of Formula (I); with hydroxylamine or a hydroxylammonium compound in the presence of a phase transfer catalyst. In preferred compounds of Formula (II) R¹, R², R³ and R⁴ are as in preferred compounds of Formula (I). In more preferred compounds of Formula (II) R¹, R², R³ and R⁴ are as in more preferred compounds of Formula (I). In even more preferred compounds of Formula (II) R¹, R², R³ and R⁴ are as in even more preferred compounds of Formula (I). In particularly preferred compounds of Formula (II) R¹, R², R³ and R⁴ are as in particularly preferred compounds of Formula (I). A compound of Formula (II) is reacted with hydroxylamine or a hydroxylammonium compound. In one embodiment, a compound of Formula (II) is reacted with hydroxylamine. Hydroxylamine can, for example, be used in the form of an aqueous solution. Hydroxylamine is, for example, commercially available as a 50% aqueous solution. In a preferred embodiment, a compound of Formula (II) is reacted with a hydroxylammonium compound. Suitable hydroxylammonium compounds are known to a person skilled in the art. Preferred hydroxylammonium compounds are selected from hydroxylammonium sulfate, hydroxylammonium chloride, hydroxylammonium acetate, hydroxylammonium phosphate, hydroxylammonium nitrate, hydroxylammonium perchlorate, hydroxylammonium oxalate, hydroxylammonium hydrogen sulfate, hydroxylammonium 4-methylbenzenesulfonate and hydroxylammonium bromide. More preferred hydroxylammonium compounds are selected from hydroxylammonium sulfate, hydroxylammonium chloride and hydroxylammonium acetate. Even more preferred hydroxylammonium compounds are selected from hydroxylammonium sulfate and hydroxylammonium chloride. A particularly preferred hydroxylammonium compound is hydroxylammonium sulfate. Preferably, the molar ratio of the compound of Formula (II) to hydroxylamine equivalents is from 1.0:1.0 to 1.0:6.0, more preferably from 1.0:1.5 to 1.0:6.0, more preferably from 1.0:2.0 to 1.0:4.0, more preferably from 1.0:2.0 to 1.0:3.5, even more preferably from 1.0:2.0 to 1.0:3.0, also even more preferably from 1.0:2.5 to 1.0:3.5 particularly preferably from 1.0:2.5 to 1.0:3.0. In a preferred embodiment, the molar ratio of the compound of Formula (II) to the hydroxylammonium compound is from 1.0:0.5 to 1.0:3.0, more preferably from 1.0:0.8 to 1.0:3.0, more preferably from 1.0:1.0 to 1.0:2.0, more preferably from 1.0:1.0 to 1.0:1.8, even more preferably from 1.0:1.0 to 1.0:1.5, also even more preferably from 1.0:1.2 to 1.0:1.8 particularly preferably from 1.0:1.2 to 1.0:1.5. Such molar ratios are preferred, for example, when hydroxylammonium sulfate is used as the hydroxylammonium compound. In another preferred embodiment, the molar ratio of the compound of Formula (II) to hydroxylamine or the hydroxylammonium compound is from 1.0:1.0 to 1.0:6.0, more preferably from 1.0:1.5 to 1.0:6.0, more preferably from 1.0:2.0 to 1.0:4.0, more preferably from 1.0:2.0 to 1.0:3.5, even more preferably from 1.0:2.0 to 1.0:3.0, also even more preferably from 1.0:2.5 to 1.0:3.5 particularly preferably from 1.0:2.5 to 1.0:3.0. Such molar ratios are preferred, for example, when hydroxylammonium chloride or hydroxylammonium acetate is used as the hydroxylammonium compound. A compound of Formula (II) is reacted with hydroxylamine or a hydroxylammonium compound in the presence of a phase transfer catalyst. Preferably, the phase transfer catalyst is selected from monocarboxylic acids, salts of monocarboxylic acids, esters of monocarboxylic acids, dicarboxylic acids, salts of dicarboxylic acids, esters of dicarboxylic acids, tricarboxylic acids, salts of tricarboxylic acids, esters of tricarboxylic acids, hydroxamic acids, salts of hydroxamic acids, esters of hydroxamic acids, cyclic hydroxamic acids, salts of cyclic hydroxamic acids, esters of cyclic hydroxamic acids, and mixtures thereof. Preferably, the salts are hydroxylammonium salts. Preferably, the esters are methyl esters. In a preferred embodiment, the phase transfer catalyst is selected from a compound of Formula (Ia) wherein R¹, R², R³ and R⁴ are as in the compound of Formula (I); D⁺ is H⁺, Li⁺, Na⁺, K⁺, ½ Ca⁺⁺, ½ Mg⁺⁺, ½ Zn⁺⁺, 1/3 Al⁺⁺⁺, NH4⁺, hydroxylammonium, [NH3(CH2CH2OH)]⁺, or combinations thereof, and/or O-D⁺ = O(C₁-C₄-alkyl); a compound of Formula (F) wherein R¹, R², R³ and R⁴ are as in the compound of Formula (I); T⁺ is H⁺, Li⁺, Na⁺, K⁺, ½ Ca⁺⁺, ½ Mg⁺⁺, ½ Zn⁺⁺, 1/3 Al⁺⁺⁺, NH₄ ⁺, hydroxylammonium, [NH3(CH2CH2OH)]⁺, or combinations thereof, and/or O-T⁺ = O(C1-C4-alkyl); and mixtures thereof. In preferred compounds of Formula (Ia) R¹, R², R³ and R⁴ are as in preferred compounds of Formula (I). In more preferred compounds of Formula (Ia) R¹, R², R³ and R⁴ are as in more preferred compounds of Formula (I). In even more preferred compounds of Formula (Ia) R¹, R², R³ and R⁴ are as in even more preferred compounds of Formula (I). In particularly preferred compounds of Formula (Ia) R¹, R², R³ and R⁴ are as in particularly preferred compounds of Formula (I). Preferred are compounds of Formula (Ia) wherein D⁺ is H⁺, Li⁺, Na⁺, K⁺, NH4⁺, hydroxylammonium, [NH3(CH2CH2OH)]⁺, or combinations thereof, and/or O-D⁺ = OCH3. More preferred are compounds of Formula (Ia) wherein D⁺ is H⁺, Na⁺, K⁺, hydroxylammonium, or combinations thereof. Even more preferred are compounds of Formula (Ia) wherein D⁺ is H⁺, Na⁺, hydroxylammonium, or combinations thereof. Particularly preferred are compounds of Formula (Ia) wherein D⁺ is H⁺, hydroxylammonium, or combinations thereof. In preferred compounds of Formula (F) R¹, R², R³ and R⁴ are as in preferred compounds of Formula (I). In more preferred compounds of Formula (F) R¹, R², R³ and R⁴ are as in more preferred compounds of Formula (I). In even more preferred compounds of Formula (F) R¹, R², R³ and R⁴ are as in even more preferred compounds of Formula (I). In particularly preferred compounds of Formula (F) R¹, R², R³ and R⁴ are as in particularly preferred compounds of Formula (I). Preferred are compounds of Formula (F) wherein T⁺ is H⁺, Li⁺, Na⁺, K⁺, NH₄ ⁺, hydroxylammonium, [NH₃(CH₂CH₂OH)]⁺, or combinations thereof, and/or O-D⁺ = OCH3. More preferred are compounds of Formula (F) wherein T⁺ is H⁺, Na⁺, K⁺, hydroxylammonium, or combinations thereof. Even more preferred are compounds of Formula (F) wherein T⁺ is H⁺, Na⁺, hydroxylammonium, or combinations thereof. Particularly preferred are compounds of Formula (F) wherein T⁺ is H⁺, hydroxylammonium, or combinations thereof. The compound of Formula (Ia) can, e.g., be obtained in situ when carrying out the process of the present invention, e.g. as a by-product or side product. The compound of Formula (F) can, e.g., be obtained in situ when carrying out the process of the present invention, e.g. as a by-product or side product. In a preferred embodiment, the phase transfer catalyst is selected from benzoic acid, benzoic acid hydroxylammonium salt, 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)- 2(1H)-pyridone, 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, 6-cyclohexyl-1-hydroxy-4-methyl-2(1H)-pyridone, 6- cyclohexyl-1-hydroxy-4-methyl-2(1H)-pyridone hydroxylammonium salt, the compound of Formula (III), the compound of Formula (IV), (IV) the compound of Formula (V), and mixtures thereof. Benzoic acid hydroxylammonium salt can, e.g., be obtained in situ from benzoic acid and hydroxylamine or a hydroxylammonium compound. 1-Hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt can, e.g., be obtained in situ from 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)- pyridone and hydroxylamine or a hydroxylammonium compound. 6-Cyclohexyl-1-hydroxy-4-methyl-2(1H)-pyridone hydroxylammonium salt can, e.g., be obtained in situ from 6-cyclohexyl-1-hydroxy-4-methyl-2(1H)-pyridone and hydroxylamine or a hydroxylammonium compound. The compound of Formula (III) can, e.g., be obtained in situ when carrying out the process of the present invention, e.g. as a by-product or side product. The compound of Formula (IV) can, e.g., be obtained in situ when carrying out the process of the present invention, e.g. as a by-product or side product. The compound of Formula (V) can, e.g., be obtained in situ when carrying out the process of the present invention, e.g. as a by-product or side product. More preferably, the phase transfer catalyst is selected from 1-hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyridone, 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)- 2(1H)-pyridone hydroxylammonium salt, 6-cyclohexyl-1-hydroxy-4-methyl-2(1H)- pyridone, 6-cyclohexyl-1-hydroxy-4-methyl-2(1H)-pyridone hydroxylammonium salt, the compound of Formula (III), the compound of Formula (IV), the compound of Formula (V), and mixtures thereof. Even more preferably, the phase transfer catalyst is selected from 1-hydroxy-4- methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone, 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, the compound of Formula (III), the compound of Formula (IV), (IV) the compound of Formula (V), and mixtures thereof. Particularly preferably, the phase transfer catalyst is selected from 1-hydroxy-4- methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone, 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, the compound of Formula (III), the compound of Formula (IV), and mixtures thereof. In a preferred embodiment, the phase transfer catalyst is a compound of Formula (I) as described herein. In a more preferred embodiment, the phase transfer catalyst is 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or a salt thereof. In an even more preferred embodiment, the phase transfer catalyst is 1-hydroxy-4-methyl- 6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt. In a particularly preferred embodiment, the phase transfer catalyst is 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone. In another particularly preferred embodiment, the phase transfer catalyst is 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt. In a preferred embodiment, the phase transfer catalyst is a compound of Formula (I) as described herein. In preferred processes of the invention, wherein the phase transfer catalyst is a compound of Formula (I) as described herein, the compound of Formula (I) is added as a phase transfer catalyst. Adding as a phase transfer catalyst means, for example, that the phase transfer catalyst is added to the reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound. This applies also to preferred embodiments of the compound of Formula (I) as described herein. In a preferred embodiment, the phase transfer catalyst is a compound of Formula (Ia) as described herein. In preferred processes of the invention, wherein the phase transfer catalyst is a compound of Formula (Ia) as described herein, the compound of Formula (Ia) is added as a phase transfer catalyst. Adding as a phase transfer catalyst means, for example, that the phase transfer catalyst is added to the reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound. This applies also to preferred embodiments of the compound of Formula (Ia) as described herein. The prior art discloses processes wherein a compound of Formula (I) or (Ia) as described herein is the product of the reaction of a compound of Formula (II) with hydroxylamine or a hydroxylammonium compound. However, in the processes disclosed in the prior art, a compound of Formula (I) or (Ia) is not added as a phase transfer catalyst. In the processes disclosed in the prior art, the compound of Formula (I) or (Ia) is generated in situ as the reaction progresses. In a preferred embodiment, the phase transfer catalyst is a mixture of C1) a compound of Formula (Ia) as described herein, and C2) a compound of Formula (F) as described herein or a salt thereof. In another preferred embodiment, the phase transfer catalyst is a mixture of C1) a compound of Formula (I) as described herein, and C2) a compound of Formula (III) as described herein or a salt thereof. In a more preferred embodiment, the phase transfer catalyst is a mixture of C1) 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or a salt thereof, and C2) a compound of Formula (III) as described herein or a salt thereof. In an even more preferred embodiment, the phase transfer catalyst is a mixture of C1) 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or 1-hydroxy-4- methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, and C2) a compound of Formula (III) as described herein or a compound of Formula (IV) as described herein. In a particularly preferred embodiment, the phase transfer catalyst is a mixture of C1) 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone, and C2) a compound of Formula (III) as described herein. In another particularly preferred embodiment, the phase transfer catalyst is a mixture of C1) 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, and C2) a compound of Formula (IV) as described herein. Preferably, the weight ratio of C2 to C1 is from 1:1 to 1:20, more preferably from 1:2 to 1:15, even more preferably from 1:3 to 1:12, particularly preferably from 1:5 to 1:10. Preferably, the phase transfer catalyst is used in an amount of from 0.1 to 30 mol-%, more preferably from 1 to 20 mol-%, particularly preferably from 5 to 15 mol-%, based on the amount of the compound of Formula (II). Preferably, the phase transfer catalyst is used in an amount of from 0.5 mg to 500 mg per 1 g of the reaction mixture. In preferred embodiments, the compound of Formula (I), preferably 1-hydroxy-4- methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or a salt thereof, particularly preferably 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or 1-hydroxy- 4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, is recirculated from a previous process as described herein. In preferred embodiments, the phase transfer catalyst used in the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is at least a part of a reaction mixture obtained by a previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound. Preferably, said reaction mixture is washed with water before being used. In one embodiment, said reaction mixture is washed with water and/or an acid (e.g. hydrochloric acid or sulfuric acid) before being used. In a preferred embodiment, the reaction mixture obtained by said previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound, after being washed with water, comprises from 16 to 65 wt.-%, preferably from 22 to 55 wt.-%, more preferably from 28 to 47 wt.-%, particularly preferably from 33 to 41 wt.-%, based on the total weight of said reaction mixture, of the phase transfer catalyst. In a preferred embodiment, the reaction mixture obtained by said previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound comprises M1) a compound of Formula (Ia) as described herein, M2) a compound of Formula (F) as described herein or a salt thereof, and M3) optionally a compound of Formula (II) as described herein. In another preferred embodiment, the reaction mixture obtained by said previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound comprises M1) a compound of Formula (I) as described herein, M2) a compound of Formula (III) as described herein or a salt thereof, and M3) optionally a compound of Formula (II) as described herein. In a more preferred embodiment, the reaction mixture obtained by said previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound comprises M1) 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or a salt thereof, M2) a compound of Formula (III) as described herein or a salt thereof, and M3) optionally 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyrone. In an even more preferred embodiment, the reaction mixture obtained by said previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound comprises M1) 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or 1-hydroxy-4- methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, M2) a compound of Formula (III) as described herein or a compound of Formula (IV) as described herein, and M3) optionally 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyrone. In a particularly preferred embodiment, the reaction mixture obtained by said previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound, after being washed with water, comprises M1) from 15 to 50 wt.-%, preferably from 20 to 45 wt.-%, more preferably from 25 to 40 wt.-%, particularly preferably from 30 to 36 wt.-%, based on the total weight of said reaction mixture, of 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone or 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, M2) from 1 to 15 wt.-%, preferably from 2 to 10 wt.-%, more preferably from 3 to 7 wt.-%, particularly preferably from 3 to 5 wt.-%, based on the total weight of said reaction mixture, of a compound of Formula (III) as described herein or a compound of Formula (IV) as described herein, and M3) optionally from 0.1 to 10 wt.-%, preferably from 0.3 to 5 wt.-%, more preferably from 0.5 to 3 wt.-%, particularly preferably from 0.7 to 2 wt.-%, based on the total weight of said reaction mixture, of 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyrone. Typically, the reaction mixture obtained by said previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound comprises solvent, particularly preferably heptane or toluene. Further examples of preferred solvents are described further below. Preferred embodiments of said previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound correspond to the preferred embodiments described herein for the process of the present invention. The preferred embodiments described herein for the process of the present invention apply to said previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound as well. In preferred embodiments, at least a part of a reaction mixture obtained by the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is used as a phase transfer catalyst in a next reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound. Preferably, said reaction mixture is washed with water before being used. In one embodiment, said reaction mixture is washed with water and/or an acid (e.g. hydrochloric acid or sulfuric acid) before being used. In a preferred embodiment, the reaction mixture obtained by said reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound, after being washed with water, comprises from 16 to 65 wt.-%, preferably from 22 to 55 wt.-%, more preferably from 28 to 47 wt.-%, particularly preferably from 33 to 41 wt.-%, based on the total weight of said reaction mixture, of the phase transfer catalyst. In a preferred embodiment, the reaction mixture obtained by said reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound comprises M1) a compound of Formula (Ia) as described herein, M2) a compound of Formula (F) as described herein or a salt thereof, and M3) optionally a compound of Formula (II) as described herein. In another preferred embodiment, the reaction mixture obtained by said reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound comprises M1) a compound of Formula (I) as described herein, M2) a compound of Formula (III) as described herein or a salt thereof, and M3) optionally a compound of Formula (II) as described herein. In a more preferred embodiment, the reaction mixture obtained by said reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound comprises M1) 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or a salt thereof, M2) a compound of Formula (III) as described herein or a salt thereof, and M3) optionally 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyrone. In an even more preferred embodiment, the reaction mixture obtained by said reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound comprises M1) 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or 1-hydroxy-4- methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, M2) a compound of Formula (III) as described herein or a compound of Formula (IV) as described herein, and M3) optionally 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyrone. In a particularly preferred embodiment, the reaction mixture obtained by said reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound, after being washed with water, comprises M1) from 15 to 50 wt.-%, preferably from 20 to 45 wt.-%, more preferably from 25 to 40 wt.-%, particularly preferably from 30 to 36 wt.-%, based on the total weight of said reaction mixture, of 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone or 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, M2) from 1 to 15 wt.-%, preferably from 2 to 10 wt.-%, more preferably from 3 to 7 wt.-%, particularly preferably from 3 to 5 wt.-%, based on the total weight of said reaction mixture, of a compound of Formula (III) as described herein or a compound of Formula (IV) as described herein, and M3) optionally from 0.1 to 10 wt.-%, preferably from 0.3 to 5 wt.-%, more preferably from 0.5 to 3 wt.-%, particularly preferably from 0.7 to 2 wt.-%, based on the total weight of said reaction mixture, of 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyrone. Typically, the reaction mixture obtained by said reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound comprises solvent, particularly preferably heptane or toluene. Further examples of preferred solvents are described further below. Preferred embodiments of said next reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound correspond to the preferred embodiments described herein for the process of the present invention. The preferred embodiments described herein for the process of the present invention apply to said next reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound as well. In preferred embodiments, the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is carried out in the presence of a base. In one embodiment, the compound of Formula (II) is reacted with hydroxylamine in the presence of a base. In another embodiment, the compound of Formula (II) is reacted with hydroxylamine in the absence of a base. In a preferred embodiment, the compound of Formula (II) is reacted with the hydroxylammonium compound in the presence of a base. Suitable bases are known to a person skilled in the art. Examples of suitable bases are metal carbonates, metal hydrogen carbonates, or metal hydroxides. Preferred bases are selected from alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydrogen carbonates, alkaline earth metal hydrogen carbonates, alkali metal hydroxides, alkaline earth metal hydroxides, and mixtures thereof. More preferred bases are selected from alkali metal carbonates, alkali metal hydrogen carbonates, alkali metal hydroxides, and mixtures thereof. Even more preferred bases are selected from alkali metal carbonates, alkali metal hydrogen carbonates, and mixtures thereof. Particularly preferred bases are selected from alkali metal carbonates. Examples of suitable bases are lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, cesium hydrogen carbonate, lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium carbonate, magnesium carbonate, barium carbonate, nickel carbonate, zirconium carbonate, calcium hydroxide, magnesium hydroxide, barium hydroxide, nickel hydroxide, or zirconium hydroxide. Preferred bases are selected from lithium carbonate, sodium carbonate, potassium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium hydroxide, potassium hydroxide, and mixtures thereof. More preferred bases are selected from lithium carbonate, sodium carbonate, potassium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and mixtures thereof. Even more preferred bases are selected from lithium carbonate, sodium carbonate, potassium carbonate, and mixtures thereof. Also even more preferred bases are selected from sodium carbonate, sodium hydrogen carbonate, and mixtures thereof. A particularly preferred base is sodium carbonate. Preferably, the molar ratio of base equivalents to hydroxylamine equivalents is from 1.0:0.5 to 1.0:3.0, more preferably from 1.0:0.8 to 1.0:2.0, even more preferably from 1.0:1.0 to 1.0:1.5, even more preferably from 1.0:1.0 to 1.0:1.2, particularly preferably from 1.0:1.0 to 1.0:1.1. In a preferred embodiment, the molar ratio of the base to the hydroxylammonium compound is from 1.0:0.5 to 1.0:3.0, more preferably from 1.0:0.8 to 1.0:2.0, even more preferably from 1.0:1.0 to 1.0:1.5, even more preferably from 1.0:1.0 to 1.0:1.2, particularly preferably from 1.0:1.0 to 1.0:1.1. Such molar ratios are preferred, for example, when hydroxylammonium sulfate is used as the hydroxylammonium compound and an alkali metal carbonate (for example sodium carbonate) is used as the base. In preferred embodiments, the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is carried out in the presence of a solvent. Suitable solvents are known to a person skilled in the art. Preferred solvents are selected from organic solvents, water, and mixtures thereof. More preferred solvents are selected from heptane, hexane, cyclohexane, methylcyclohexane, dimethylcyclohexane, toluene, benzene, 1,2-dimethylbenzene, 1,3-dimethylbenzene, 1,4-dimethylbenzene, methylene chloride, methanol, ethanol, isopropanol, tert-butanol, tert-amyl alcohol, dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, acetonitrile, 2-aminopyridine, glycol monoethyl ether (e.g. ethylene glycol monoethyl ether), water, and mixtures thereof. Even more preferred solvents are selected from hexane, cyclohexane, methylcyclohexane, heptane, benzene, 1,2- dimethylbenzene, 1,3-dimethylbenzene, 1,4-dimethylbenzene, toluene, glycol monoethyl ether (e.g. ethylene glycol monoethyl ether), water, and mixtures thereof. Particularly preferred solvents are selected from heptane, toluene, water, and mixtures thereof. In a preferred embodiment, the solvent comprises at least 80 wt.-%, preferably at least 90 wt.-%, more preferably at least 95 wt.-%, particularly preferably at least 98 wt.-%, based on the total weight of the solvent, of heptane or toluene. In a preferred embodiment, the solvent comprises from 80 to 100 wt.-%, preferably from 90 to 100 wt.-%, more preferably from 95 to 100 wt.-%, particularly preferably from 98 to 100 wt.-%, based on the total weight of the solvent, of heptane or toluene, and from 0 to 20 wt.-%, preferably from 0 to 10 wt.-%, more preferably from 0 to 5 wt.-%, particularly preferably from 0 to 2 wt.-%, based on the total weight of the solvent, of water. In a preferred embodiment, the solvent comprises from 80 to 99.8 wt.-%, preferably from 90 to 99.7 wt.-%, more preferably from 95 to 99.6 wt.-%, particularly preferably from 98 to 99.5 wt.-%, based on the total weight of the solvent, of heptane or toluene, and from 0.2 to 20 wt.-%, preferably from 0.3 to 10 wt.-%, more preferably from 0.4 to 5 wt.-%, particularly preferably from 0.5 to 2 wt.-%, based on the total weight of the solvent, of water. In a preferred embodiment, the solvent comprises at least 80 wt.-%, preferably at least 90 wt.-%, more preferably at least 95 wt.-%, particularly preferably at least 98 wt.-%, based on the total weight of the solvent, of heptane. In a preferred embodiment, the solvent comprises from 80 to 100 wt.-%, preferably from 90 to 100 wt.-%, more preferably from 95 to 100 wt.-%, particularly preferably from 98 to 100 wt.-%, based on the total weight of the solvent, of heptane, and from 0 to 20 wt.-%, preferably from 0 to 10 wt.-%, more preferably from 0 to 5 wt.-%, particularly preferably from 0 to 2 wt.-%, based on the total weight of the solvent, of water. In a preferred embodiment, the solvent comprises from 80 to 99.8 wt.-%, preferably from 90 to 99.7 wt.-%, more preferably from 95 to 99.6 wt.-%, particularly preferably from 98 to 99.5 wt.-%, based on the total weight of the solvent, of heptane, and from 0.2 to 20 wt.-%, preferably from 0.3 to 10 wt.-%, more preferably from 0.4 to 5 wt.-%, particularly preferably from 0.5 to 2 wt.-%, based on the total weight of the solvent, of water. In a preferred embodiment, the solvent comprises at least 80 wt.-%, preferably at least 90 wt.-%, more preferably at least 95 wt.-%, particularly preferably at least 98 wt.-%, based on the total weight of the solvent, of toluene. In a preferred embodiment, the solvent comprises from 80 to 100 wt.-%, preferably from 90 to 100 wt.-%, more preferably from 95 to 100 wt.-%, particularly preferably from 98 to 100 wt.-%, based on the total weight of the solvent, of toluene, and from 0 to 20 wt.-%, preferably from 0 to 10 wt.-%, more preferably from 0 to 5 wt.-%, particularly preferably from 0 to 2 wt.-%, based on the total weight of the solvent, of water. In a preferred embodiment, the solvent comprises from 80 to 99.8 wt.-%, preferably from 90 to 99.7 wt.-%, more preferably from 95 to 99.6 wt.-%, particularly preferably from 98 to 99.5 wt.-%, based on the total weight of the solvent, of toluene, and from 0.2 to 20 wt.-%, preferably from 0.3 to 10 wt.-%, more preferably from 0.4 to 5 wt.-%, particularly preferably from 0.5 to 2 wt.-%, based on the total weight of the solvent, of water. In preferred embodiments, the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is carried out at a temperature of from 60 to 120 °C, preferably from 70 to 110 °C, more preferably from 75 to 105 °C, particularly preferably from 75 to 85 °C, also particularly preferably from 95 to 105 °C. Preferably, the compound of Formula (II) is reacted with hydroxylamine or the hydroxylammonium compound for at least 8 hours, more preferably at least 12 hours, even more preferably at least 16 hours, particularly preferably at least 20 hours. For example, the compound of Formula (II) is reacted with hydroxylamine or the hydroxylammonium compound for 8 to 36 hours, preferably 12 to 32 hours, more preferably 16 to 28 hours, particularly preferably 20 to 24 hours. The reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound can be worked up in a usual manner, for example as described in the Examples. In a preferred embodiment, the process of the invention is a process for the preparation of a compound of Formula (I) wherein R¹ is 2,4,4-trimethylpentyl; R² is hydrogen; R³ is methyl; R⁴ is hydrogen; Q⁺ is H⁺, [NH₃(CH₂CH₂OH)]⁺, or combinations thereof; comprising the step of reacting a compound of Formula (II) wherein R¹, R², R³ and R⁴ are as in the compound of Formula (I); with hydroxylamine or a hydroxylammonium compound in the presence of a phase transfer catalyst, wherein the phase transfer catalyst is selected from 1-hydroxy-4- methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone, 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, the compound of Formula (III), the compound of Formula (IV), and mixtures thereof. In a preferred embodiment, the process of the invention is a process for the preparation of a compound of Formula (I) wherein R¹ is 2,4,4-trimethylpentyl; R² is hydrogen; R³ is methyl; R⁴ is hydrogen; Q⁺ is H⁺, [NH3(CH2CH2OH)]⁺, or combinations thereof; comprising the step of reacting a compound of Formula (II) (II) wherein R¹, R², R³ and R⁴ are as in the compound of Formula (I); with hydroxylamine or a hydroxylammonium compound in the presence of a phase transfer catalyst, wherein the phase transfer catalyst is 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone or 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)- 2(1H)-pyridone hydroxylammonium salt. Optionally, the phase transfer catalyst used in the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is at least a part of a reaction mixture obtained by a previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound. Optionally, at least a part of a reaction mixture obtained by the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is used as a phase transfer catalyst in a next reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound. Optionally, the process further comprises treating the compound of Formula (I) wherein Q⁺ is H⁺ with monoethanolamine to obtain the compound of Formula (I) wherein Q⁺ is [NH3(CH2CH2OH)]⁺. The treatment of the compound of Formula (I) wherein Q⁺ is H⁺ with monoethanolamine can be carried out in a solvent, which is preferably selected from ethyl acetate, methyl tert-butyl ether, ethanol, isopropanol, and mixtures thereof, more preferably selected from ethyl acetate, methyl tert-butyl ether, and mixtures thereof, particularly preferably the solvent is ethyl acetate. The compound of Formula (I) wherein Q⁺ is [NH₃(CH₂CH₂OH)]⁺ can be precipitated from said solvent. In a preferred embodiment, the process of the invention is a process for the preparation of a compound of Formula (I) wherein R¹ is 2,4,4-trimethylpentyl; R² is hydrogen; R³ is methyl; R⁴ is hydrogen; Q⁺ is H⁺, [NH3(CH2CH2OH)]⁺, or combinations thereof; comprising the steps of i) reacting a compound of Formula (II) wherein R¹, R², R³ and R⁴ are as in the compound of Formula (I); with hydroxylamine or a hydroxylammonium compound in the presence of a phase transfer catalyst, wherein the phase transfer catalyst is selected from 1-hydroxy-4- methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone, 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, the compound of Formula (III), (III) the compound of Formula (IV), and mixtures thereof; to obtain the compound of Formula (I) wherein Q⁺ is H⁺; ii) optionally reacting the compound of Formula (I) wherein Q⁺ is H⁺ with monoethanolamine to obtain the compound of Formula (I) wherein Q⁺ is [NH3(CH2CH2OH)]⁺. In a preferred embodiment, the process of the invention is a process for the preparation of a compound of Formula (I) wherein R¹ is 2,4,4-trimethylpentyl; R² is hydrogen; R³ is methyl; R⁴ is hydrogen; Q⁺ is H⁺, [NH₃(CH₂CH₂OH)]⁺, or combinations thereof; comprising the steps of i) reacting a compound of Formula (II) wherein R¹, R², R³ and R⁴ are as in the compound of Formula (I); with hydroxylamine or a hydroxylammonium compound in the presence of a phase transfer catalyst, wherein the phase transfer catalyst is 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone or 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)- 2(1H)-pyridone hydroxylammonium salt; to obtain the compound of Formula (I) wherein Q⁺ is H⁺; ii) optionally reacting the compound of Formula (I) wherein Q⁺ is H⁺ with monoethanolamine to obtain the compound of Formula (I) wherein Q⁺ is [NH₃(CH₂CH₂OH)]⁺. The present invention also relates to the use of a compound of Formula (I) of the present invention or a phase transfer catalyst as described herein as a phase transfer catalyst for the preparation of a compound of Formula (I) of the present invention. Preferred embodiments of the use of the present invention correspond to the preferred embodiments described herein for the process of the present invention. The preferred embodiments described herein for the process of the present invention apply to the use of the present invention as well. The compound of Formula (I), in particular piroctone or piroctone olamine, can be used as an anti-dandruff agent or as a preservative. Preferably, the dandruff is caused by dandruff-causing organisms, more preferably Malassezia species, particularly preferably Malassezia furfur and/or Malassezia globosa. The compound of Formula (I), in particular piroctone or piroctone olamine, can be incorporated into a cosmetic composition. Preferably, the cosmetic composition is a hair care composition, scalp care composition or skin care composition. For example, the cosmetic composition may be selected from the group consisting of shampoo, hair conditioner, hair tonic, cream rinse, body wash, bubble bath, bath oil, facial cleanser, cleansing mask, cleansing milk, micellar water, make-up remover, cleansing wipes, perfume, soaps, shaving soaps, shaving foams, cleansing foams, face mask, face cream, hand cream and body lotion. In a preferred embodiment, the cosmetic composition is a shampoo composition or hair conditioner composition. In a particularly preferred embodiment, the cosmetic composition is an anti-dandruff shampoo composition. Preferably, the cosmetic composition comprises from 0.01 to 10 wt.-%, more preferably from 0.05 to 5 wt.-%, even more preferably from 0.1 to 2.0 wt.-%, particularly preferably from 0.1 to 1.0 wt.-%, for example from 0.1 to 0.5 wt.-% or from 0.5 to 1.0 wt.-%, of a compound of Formula (I), in particular piroctone or piroctone olamine, based on the total weight of the cosmetic composition. The present invention is illustrated by the following examples without being limited thereby. Examples Used Phase Transfer catalyst. A) Piroctone (CAS: 50650-76-5) (237.34g/mol) also known as: ^ 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)pyridin-2-one ^ 1-Hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone ^ 1-Hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridinone ^ 2(1H)-Pyridinone, 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)- ^ 1-Hydroxy-methyl-6-(2,4,4-trimethylpentyl)-2-(1H)-pyridone B) Liquid Phase Transfer catalyst according to Example 1 or Example 2 Example 1: Synthesis of the Phase Transfer catalyst / Heptane based solvent system. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 255g/1,56mol hydroxyl ammonium sulfate, 160g/1,5mol sodium carbonate, 3g/0,17mol water and 300g heptane will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx. 70 to 75°C. This is indicated by visible foam formation and a CO2 emission. The strength of the CO2 emission increases continuously and induces a drop of the reaction temperature to approx. 60-70°C. After complete hydroxylamine release, the CO₂ flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.80-82°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated, and the organic phase is separated into 120g portions. Example 2: Synthesis of the Phase Transfer catalyst / Toluene based solvent system. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 255g/1,56mol hydroxyl ammonium sulfate, 160g/1,5mol sodium carbonate, 3g/0,17mol water and 310g toluene will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx.70 to 75°C. This is indicated by visible foam formation and a CO₂ emission. The strength of the CO₂ emission increases continuously and induces a drop of the reaction temperature to approx.60-70°C. After complete hydroxylamine release, the CO2 flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.98-103°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated, and the organic phase is separated into 120g portions. Example 3: Heptane based solvent system / with Piroctone as Phase transfer catalyst. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 35g/0,15mol Piroctone, 255g/1,56mol hydroxyl ammonium sulfate, 160g/1,5mol sodium carbonate, 3g/0,17mol water and 300g heptane will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx. 70 to 75°C. This is indicated by visible foam formation and a CO₂ emission. The strength of the CO2 emission increases continuously and induces a drop of the reaction temperature to approx.60-70°C. After complete hydroxylamine release, the CO2 flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.80-82°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated, and the organic phase is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and heptane is removed by distillation. The organic residue is taken up in ethyl acetate (approx.30°C) for piroctone olamine precipitation. The organic phase in ethyl acetate is tempered to an internal temperature of 62°C. In a dropping funnel, 88g of mono ethanol amine and 4.5g of water are weighed and added to the reaction solution within 10 minutes. The internal temperature should not rise above 65°C during addition. Stirring is continued for 30 minutes at 65°C. The reaction mixture is then cooled to 0°C. Piroctone olamine precipitates as needle- shaped white crystals. Piroctone olamine is removed with a filter chute and washed in portions with ice-cooled ethyl acetate. The precipitate is dried overnight at 50°C in a vacuum drying oven (80mbar). Yield 264,99g / 57,4% Piroctone Olamine (99,3% by HPLC) Example 4: Heptane based solvent system / with Piroctone as Phase transfer catalyst. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 35g/0,15mol Piroctone, 305g/1,86mol hydroxyl ammonium sulfate, 190g/1,8mol sodium carbonate, 3g/0,17mol water and 300g heptane will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx. 70 to 75°C. This is indicated by visible foam formation and a CO2 emission. The strength of the CO2 emission increases continuously and induces a drop of the reaction temperature to approx.60-70°C. After complete hydroxylamine release, the CO₂ flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.80-82°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated, and the organic phase is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and heptane is removed by distillation. The organic residue is taken up in ethyl acetate (approx.30°C) for piroctone olamine precipitation. The organic phase in ethyl acetate is tempered to an internal temperature of 62°C. In a dropping funnel, 110g of mono ethanol amine and 4.5g of water are weighed and added to the reaction solution within 10 minutes. The internal temperature should not rise above 65°C during addition. Stirring is continued for 30 minutes at 65°C. The reaction mixture is then cooled to 0°C. Piroctone olamine precipitates as needle- shaped white crystals. Piroctone olamine is removed with a filter chute and washed in portions with ice-cooled ethyl acetate. The precipitate is dried overnight at 50°C in a vacuum drying oven (80mbar). Yield 302,8g / 65,6% Piroctone Olamine (97,8% by HPLC) Example 5: Toluene based solvent system / with Piroctone as Phase transfer catalyst. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 35g/0,15mol Piroctone, 305g/1,86mol hydroxyl ammonium sulfate, 190g/1,8mol sodium carbonate, 3g/0,17mol water and 300g toluene will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx. 70 to 75°C. This is indicated by visible foam formation and a CO₂ emission. The strength of the CO₂ emission increases continuously and induces a drop of the reaction temperature to approx.60-70°C. After complete hydroxylamine release, the CO2 flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.98-103°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated, and the organic phase is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and Toluene is removed by distillation. The organic residue is taken up in ethyl acetate (approx.30°C) for piroctone olamine precipitation. The organic phase in ethyl acetate is tempered to an internal temperature of 62°C. In a dropping funnel, 110g of mono ethanol amine and 4.5g of water are weighed and added to the reaction solution within 10 minutes. The internal temperature should not rise above 65°C during addition. Stirring is continued for 30 minutes at 65°C. The reaction mixture is then cooled to 0°C. Piroctone olamine precipitates as needle- shaped white crystals. Piroctone olamine is removed with a filter chute and washed in portions with ice-cooled ethyl acetate. The precipitate is dried overnight at 50°C in a vacuum drying oven (80mbar). Yield 313g / 67,8% Piroctone Olamine (98,9% by HPLC) Example 6: Toluene based solvent system / with Piroctone as Phase transfer catalyst. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 35g/0,15mol Piroctone, 255g/1,56mol hydroxyl ammonium sulfate, 160g/1,5mol sodium carbonate, 3g/0,17mol water and 300g toluene will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx. 70 to 75°C. This is indicated by visible foam formation and a CO2 emission. The strength of the CO2 emission increases continuously and induces a drop of the reaction temperature to approx.60-70°C. After complete hydroxylamine release, the CO₂ flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.98-103°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated, and the organic phase is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and Toluene is removed by distillation. The organic residue is taken up in ethyl acetate (approx.30°C) for piroctone olamine precipitation. The organic phase in ethyl acetate is tempered to an internal temperature of 62°C. In a dropping funnel, 88g of mono ethanol amine and 4.5g of water are weighed and added to the reaction solution within 10 minutes. The internal temperature should not rise above 65°C during addition. Stirring is continued for 30 minutes at 65°C. The reaction mixture is then cooled to 0°C. Piroctone olamine precipitates as needle- shaped white crystals. Piroctone olamine is removed with a filter chute and washed in portions with ice-cooled ethyl acetate. The precipitate is dried overnight at 50°C in a vacuum drying oven (80mbar). Yield 269,14g / 58,3% Piroctone Olamine (99,5% by HPLC) Example 7: Heptane based solvent system / liquid Phase transfer catalyst. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 120g reaction solution from example 1, 305g/1,86mol hydroxyl ammonium sulfate, 190g/1,8mol sodium carbonate, and 300g heptane will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx. 70 to 75°C. This is indicated by visible foam formation and a CO2 emission. The strength of the CO₂ emission increases continuously and induces a drop of the reaction temperature to approx.60-70°C. After complete hydroxylamine release, the CO2 flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.80-82°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated, and a 120g sample of the reaction mixture is taken as liquid phase transfer catalyst for following experiments. The remaining reaction solution is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and heptane is removed by distillation. The organic residue is taken up in ethyl acetate (approx.30°C) for piroctone olamine precipitation. The organic phase in ethyl acetate is tempered to an internal temperature of 62°C. In a dropping funnel, 98g of mono ethanol amine and 4.5g of water are weighed and added to the reaction solution within 10 minutes. The internal temperature should not rise above 65°C during addition. Stirring is continued for 30 minutes at 65°C. The reaction mixture is then cooled to 0°C. Piroctone olamine precipitates as needle- shaped white crystals. Piroctone olamine is removed with a filter chute and washed in portions with ice-cooled ethyl acetate. The precipitate is dried overnight at 50°C in a vacuum drying oven (80mbar). Yield 251g / 60,3% Piroctone Olamine (99,8% by HPLC) Example 8: Heptane based solvent system / liquid Phase transfer catalyst. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 120g reaction solution from example 1, 256g/1,55mol hydroxyl ammonium sulfate, 160g/1,5mol sodium carbonate, and 300g heptane will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx. 70 to 75°C. This is indicated by visible foam formation and a CO₂ emission. The strength of the CO2 emission increases continuously and induces a drop of the reaction temperature to approx.60-70°C. After complete hydroxylamine release, the CO2 flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.80-82°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated, and a 120g sample of the reaction mixture is taken as liquid phase transfer catalyst for following experiments. The remaining reaction solution is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and heptane is removed by distillation. The organic residue is taken up in ethyl acetate (approx.30°C) for piroctone olamine precipitation. The organic phase in ethyl acetate is tempered to an internal temperature of 62°C. In a dropping funnel, 92g of mono ethanol amine and 4.5g of water are weighed and added to the reaction solution within 10 minutes. The internal temperature should not rise above 65°C during addition. Stirring is continued for 30 minutes at 65°C. The reaction mixture is then cooled to 0°C. Piroctone olamine precipitates as needle- shaped white crystals. Piroctone olamine is removed with a filter chute and washed in portions with ice-cooled ethyl acetate. The precipitate is dried overnight at 50°C in a vacuum drying oven (80mbar). Yield 240g / 57,1% Piroctone Olamine (99,6% by HPLC) Example 9: Heptane based solvent system / liquid Phase transfer catalyst. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 122g reaction solution from example 8, 305g/1,9mol hydroxyl ammonium sulfate, 190g/1,8mol sodium carbonate, and 310g heptane will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx. 70 to 75°C. This is indicated by visible foam formation and a CO2 emission. The strength of the CO2 emission increases continuously and induces a drop of the reaction temperature to approx.60-70°C. After complete hydroxylamine release, the CO₂ flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.80-82°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated. The remaining reaction solution is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and heptane is removed by distillation. The organic residue is taken up in ethyl acetate (approx.30°C) for piroctone olamine precipitation. The organic phase in ethyl acetate is tempered to an internal temperature of 62°C. In a dropping funnel, 110g of mono ethanol amine and 4.5g of water are weighed and added to the reaction solution within 10 minutes. The internal temperature should not rise above 65°C during addition. Stirring is continued for 30 minutes at 65°C. The reaction mixture is then cooled to 0°C. Piroctone olamine precipitates as needle- shaped white crystals. Piroctone olamine is removed with a filter chute and washed in portions with ice-cooled ethyl acetate. The precipitate is dried overnight at 50°C in a vacuum drying oven (80mbar). Yield 297g / 63,2% Piroctone Olamine (98,9% by HPLC) Example 10: Toluene based solvent system / liquid Phase transfer catalyst. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 120g reaction solution from example 2, 305g/1,86mol hydroxyl ammonium sulfate, 190g/1,8mol sodium carbonate and 300g toluene will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx. 70 to 75°C. This is indicated by visible foam formation and a CO2 emission. The strength of the CO₂ emission increases continuously and induces a drop of the reaction temperature to approx.60-70°C. After complete hydroxylamine release, the CO₂ flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.98-103°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated, and the organic phase is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and a 120g sample of the reaction mixture is taken as liquid phase transfer catalyst for following experiments. The remaining reaction solution is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and heptane is removed by distillation. The organic residue is taken up in ethyl acetate (approx.30°C) for piroctone olamine precipitation. The organic phase in ethyl acetate is tempered to an internal temperature of 62°C. In a dropping funnel, 95g of mono ethanol amine and 4.5g of water are weighed and added to the reaction solution within 10 minutes. The internal temperature should not rise above 65°C during addition. Stirring is continued for 30 minutes at 65°C. The reaction mixture is then cooled to 0°C. Piroctone olamine precipitates as needle- shaped white crystals. Piroctone olamine is removed with a filter chute and washed in portions with ice-cooled ethyl acetate. The precipitate is dried overnight at 50°C in a vacuum drying oven (80mbar). Yield 265,6g / 64,4% Piroctone Olamine (99,7% by HPLC) Example 11: Toluene based solvent system / liquid Phase transfer catalyst. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 120g reaction solution from example 10, 255g/1,56mol hydroxyl ammonium sulfate, 160g/1,5mol sodium carbonate, and 300g toluene will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx. 70 to 75°C. This is indicated by visible foam formation and a CO2 emission. The strength of the CO₂ emission increases continuously and induces a drop of the reaction temperature to approx.60-70°C. After complete hydroxylamine release, the CO₂ flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.98-103°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated, and the organic phase is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and a 120g sample of the reaction mixture is taken as liquid phase transfer catalyst for following experiments. The remaining reaction solution is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and heptane is removed by distillation. The organic residue is taken up in ethyl acetate (approx.30°C) for piroctone olamine precipitation. The organic phase in ethyl acetate is tempered to an internal temperature of 62°C. In a dropping funnel, 95g of mono ethanol amine and 4.5g of water are weighed and added to the reaction solution within 10 minutes. The internal temperature should not rise above 65°C during addition. Stirring is continued for 30 minutes at 65°C. The reaction mixture is then cooled to 0°C. Piroctone olamine precipitates as needle- shaped white crystals. Piroctone olamine is removed with a filter chute and washed in portions with ice-cooled ethyl acetate. The precipitate is dried overnight at 50°C in a vacuum drying oven (80mbar). Yield 243g / 57,8% Piroctone Olamine (99,8% by HPLC) Example 12: Toluene based solvent system / liquid Phase transfer catalyst. In a 2L double jacket reactor with anchor stirrer, Claisen attachment, reflux condenser and an internal thermometer a mixture of 320g/1,4mol pyrone (1-Hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyrone), 120g reaction solution from example 2, 305g/1,86mol hydroxyl ammonium sulfate, 190g/1,8mol sodium carbonate and 300g toluene will be suspended under stirring (50 U/min). The reaction mixture is continuously heated up to 70 to 75°C during 15-60 Minutes and agitation is increased to 300 rpm during this process. The start of the reaction can be observed at approx. 70 to 75°C. This is indicated by visible foam formation and a CO2 emission. The strength of the CO₂ emission increases continuously and induces a drop of the reaction temperature to approx.60-70°C. After complete hydroxylamine release, the CO₂ flow decreases measurably, and the reaction temperature increases again. Once this point is reached, the reaction mixture is heated up to reflux temperature (approx.98-103°C). The reaction mixture is kept at reflux for 20h. The reaction mixture is cooled down to 60°C.615g of water at a temperature of 60°C is added. The reaction mixture is stirred at 340U/min for 1h. After this reaction time, the stirring is stopped. Phase separation follows in the reactor. The aqueous phase is separated, and the organic phase is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and a 120g sample of the reaction mixture is taken as liquid phase transfer catalyst for following experiments. The remaining reaction solution is treated with 8g sulfuric acid (48-50%). The reaction mixture is stirred a second time at 340U/min for 1h. The aqueous phase is separated, and heptane is removed by distillation. The organic residue is taken up in ethyl acetate (approx.30°C) for piroctone olamine precipitation. The organic phase in ethyl acetate is tempered to an internal temperature of 62°C. In a dropping funnel, 115g of mono ethanol amine and 4.5g of water are weighed and added to the reaction solution within 10 minutes. The internal temperature should not rise above 65°C during addition. Stirring is continued for 30 minutes at 65°C. The reaction mixture is then cooled to 0°C. Piroctone olamine precipitates as needle- shaped white crystals. Piroctone olamine is removed with a filter chute and washed in portions with ice-cooled ethyl acetate. The precipitate is dried overnight at 50°C in a vacuum drying oven (80mbar). Yield 300g / 65% Piroctone Olamine (99,2% by HPLC)

Claims

Claims 1. A process for the preparation of a compound of Formula (I) wherein R¹ is hydrogen, linear or branched C₁-C₂₀-alkyl, linear or branched C₂-C₂₀- alkenyl, C3-C8-cycloalkyl, cyclohexyl-(C1-C4)-alkyl, benzyl, or benzyl substituted with 1 to 3 C₁-C₄-alkyl; R² is hydrogen, linear or branched C1-C5-alkyl, linear or branched C2-C5- alkenyl, linear or branched C2-C5-alkynyl, or benzyl, or R² may form together with either R¹ or R³ and the 2 carbon atoms to which R² and either R¹ or R³ are attached a 5- or 6-membered carbocyclic ring; R³ is hydrogen, linear or branched C1-C5-alkyl, or phenyl; R⁴ is hydrogen, linear or branched C₁-C₅-alkyl, linear or branched C₂-C₅- alkenyl, linear or branched C₂-C₅-alkynyl, methoxymethyl, or benzyl; Q⁺ is H⁺, Li⁺, Na⁺, K⁺, ½ Ca⁺⁺, ½ Mg⁺⁺, ½ Zn⁺⁺, 1/3 Al⁺⁺⁺, NH4⁺, hydroxylammonium, [NHR⁵R⁶R⁷]⁺, or combinations thereof; R⁵, R⁶ and R⁷ independently of one another are hydrogen, a linear or branched alkyl group having 1 to 22 carbon atoms, a linear or branched, singularly or multiply unsaturated alkenyl group having 2 to 22 carbon atoms, a C₆-C₂₂-alkylamidopropyl group, a linear mono- hydroxyalkyl group having 2 to 10 carbon atoms or a linear or branched dihydroxyalkyl group having 3 to 10 carbon atoms, wherein at least one of the radicals R⁵, R⁶ and R⁷ is not hydrogen; comprising the step of reacting a compound of Formula (II) (II) wherein R¹, R², R³ and R⁴ are as in the compound of Formula (I); with hydroxylamine or a hydroxylammonium compound in the presence of a phase transfer catalyst.

2. The process according to claim 1, wherein R¹ is hydrogen, linear or branched C1-C20-alkyl, linear or branched C2-C6- alkenyl, C₅-C₇-cycloalkyl, cyclohexyl-(C₁-C₄)-alkyl, benzyl, or benzyl substituted with 1 to 3 methyl; R² is hydrogen, linear or branched C1-C4-alkyl, or benzyl, or R² may form together with R³ and the 2 carbon atoms to which R² and R³ are attached a 5- or 6-membered carbocyclic ring; R³ is hydrogen, or linear or branched C1-C4-alkyl; R⁴ is hydrogen, linear or branched C1-C4-alkyl, or benzyl; Q⁺ is H⁺, Li⁺, Na⁺, K⁺, ½ Ca⁺⁺, ½ Mg⁺⁺, ½ Zn⁺⁺, NH₄ ⁺, hydroxylammonium, [NHR⁵R⁶R⁷]⁺, or combinations thereof; R⁵, R⁶ and R⁷ independently of one another are hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, a linear or branched, singularly or multiply unsaturated alkenyl group having 2 to 12 carbon atoms, a linear mono-hydroxyalkyl group having 2 to 8 carbon atoms or a linear or branched dihydroxyalkyl group having 3 to 8 carbon atoms, wherein at least one of the radicals R⁵, R⁶ and R⁷ is not hydrogen.

3. The process according to claim 1 or 2, wherein the compound of Formula (I) is selected from the group 1-hydroxy-6-methyl-pyridin-2-one, 1-hydroxy-4,6- dimethyl-pyridin-2-one, 1-hydroxy-3,4,6-trimethyl-pyridin-2-one, 1-hydroxy-4- methyl-6-ethyl-pyridin-2-one, 1-hydroxy-4-methyl-6-isopropyl-pyridin-2-one, 1- hydroxy-4-methyl-6-heptyl-pyridin-2-one, 1-hydroxy-4-methyl-6-undecyl- pyridin-2-one, 1-hydroxy-4-methyl-6-heptadecyl-pyridin-2-one, 1-hydroxy-4- ethyl-5,6-dimethyl-pyridin-2-one, 1-hydroxy-4,5-trimethylen-6-methyl-pyridin-2- one, 1-hydroxy-4-methyl-6-cyclohexyl-pyridin-2-one, 1-hydroxy-4-methyl-6- cyclohexyl-methyl-pyridin-2-one, 1-hydroxy-4-methyl-6-cyclohexyl-ethyl- pyridin-2-one, 1-hydroxy-4-methyl-6-isobutenyl-pyridin-2-one, 1-hydroxy-4,6- dimethyl-5-benzyl-pyridin-2-one, 1-hydroxy-3-benzyl-4,6-dimethyl-pyridin-2- one, 1-hydroxy-4-methyl-6-benzyl-pyridin-2-one, 1-hydroxy-3,4-dimethyl-6- (2,4-dimethylbenzyl)-pyridin-2-one, 1-hydroxy-6-cyclohexyl-pyridin-2-one, 1- hydroxy-4-methyl-6-cyclohexyl-pyridin-2-one, 1-hydroxy-4-ethyl-6-cyclohexyl- pyridin-2-one, 1-hydroxy-4-propyl-6-cyclohexyl-pyridin-2-one, 1-hydroxy-6- (2,4,4-trimethylpentyl)-pyridin-2-one, 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-pyridin-2-one, 1-hydroxy-4-ethyl-6-(2,4,4-trimethylpentyl)- pyridin-2-one, 1-hydroxy-4-propyl-6-(2,4,4-trimethylpentyl)-pyridin-2-one, and salts thereof, preferably the compound of Formula (I) is 1-hydroxy-4-methyl-6- (2,4,4-trimethylpentyl)-2(1H)-pyridone or a salt thereof, particularly preferably 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or the ethanolamine salt of 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)- pyridone.

4. The process according to any of claims 1 to 3, wherein the phase transfer catalyst is selected from monocarboxylic acids, salts of monocarboxylic acids, esters of monocarboxylic acids, dicarboxylic acids, salts of dicarboxylic acids, esters of dicarboxylic acids, tricarboxylic acids, salts of tricarboxylic acids, esters of tricarboxylic acids, hydroxamic acids, salts of hydroxamic acids, esters of hydroxamic acids, cyclic hydroxamic acids, salts of cyclic hydroxamic acids, esters of cyclic hydroxamic acids, and mixtures thereof, wherein the salts are preferably hydroxylammonium salts and/or wherein the esters are preferably methyl esters.

5. The process according to any of claims 1 to 4, wherein the phase transfer catalyst is selected from a compound of Formula (Ia) wherein R¹, R², R³ and R⁴ are as in the compound of Formula (I); D⁺ is H⁺, Li⁺, Na⁺, K⁺, ½ Ca⁺⁺, ½ Mg⁺⁺, ½ Zn⁺⁺, 1/3 Al⁺⁺⁺, NH₄ ⁺, hydroxylammonium, [NH3(CH2CH2OH)]⁺, or combinations thereof, and/or O-D⁺ = O(C1-C4-alkyl); a compound of Formula (F) wherein R¹, R², R³ and R⁴ are as in the compound of Formula (I); T⁺ is H⁺, Li⁺, Na⁺, K⁺, ½ Ca⁺⁺, ½ Mg⁺⁺, ½ Zn⁺⁺, 1/3 Al⁺⁺⁺, NH4⁺, hydroxylammonium, [NH₃(CH₂CH₂OH)]⁺, or combinations thereof, and/or O-T⁺ = O(C₁-C₄-alkyl); and mixtures thereof. 6. The process according to any of claims 1 to 5, wherein the phase transfer catalyst is selected from 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)- pyridone, 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, 6-cyclohexyl-1-hydroxy-4-methyl-2(1H)-pyridone,

6- cyclohexyl-1-hydroxy-4-methyl-2(1H)-pyridone hydroxylammonium salt, the compound of Formula (III), (III) the compound of Formula (IV), (IV) the compound of Formula (V), (V) and mixtures thereof.

7. The process according to any of claims 1 to 6, wherein the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is carried out in the presence of a solvent, wherein the solvent is preferably selected from hexane, cyclohexane, methylcyclohexane, heptane, benzene, 1,2-dimethylbenzene, 1,3-dimethylbenzene, 1,4-dimethylbenzene, toluene, glycol monoethyl ether, water, and mixtures thereof, more preferably the solvent is selected from heptane, toluene, water, and mixtures thereof.

8. The process according to any of claims 1 to 7, wherein the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is carried out in the presence of a base, wherein the base is preferably selected from alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydrogen carbonates, alkaline earth metal hydrogen carbonates, alkali metal hydroxides, alkaline earth metal hydroxides, and mixtures thereof.

9. The process according to any of claims 1 to 8, wherein the molar ratio of the compound of Formula (II) to hydroxylamine equivalents is from 1.0:1.0 to 1.0:6.0, preferably from 1.0:1.5 to 1.0:6.0, more preferably from 1.0:2.0 to 1.0:4.0, more preferably from 1.0:2.0 to 1.0:3.5, even more preferably from 1.0:2.0 to 1.0:3.0, also even more preferably from 1.0:2.5 to 1.0:3.5, particularly preferably from 1.0:2.5 to 1.0:3.0.

10. The process according to any of claims 1 to 9, wherein the phase transfer catalyst is used in an amount of from 0.1 to 30 mol-%, preferably from 1 to 20 mol-%, more preferably from 5 to 15 mol-%, based on the amount of the compound of Formula (II).

11. The process according to any of claims 1 to 10, wherein the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is carried out at a temperature of from 60 to 120 °C, preferably from 70 to 110 °C, more preferably from 75 to 105 °C, particularly preferably from 75 to 85 °C, also particularly preferably from 95 to 105 °C.

12. The process according to any of claims 1 to 11, wherein the phase transfer catalyst is a compound of Formula (I) as defined in any of claims 1 to 3, preferably the phase transfer catalyst is 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone or a salt thereof, particularly preferably 1- hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or 1-hydroxy-4- methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt.

13. The process according to claim 12, wherein the compound of Formula (I), preferably 1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridone or a salt thereof, particularly preferably 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone or 1-hydroxy-4-methyl-6-(2,4,4- trimethylpentyl)-2(1H)-pyridone hydroxylammonium salt, is recirculated from a previous process as defined in any of claims 1 to 12.

14. The process according to any of claims 1 to 13, wherein the phase transfer catalyst used in the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is at least a part of a reaction mixture obtained by a previous reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound.

15. The process according to any of claims 1 to 14, wherein at least a part of a reaction mixture obtained by the reaction of the compound of Formula (II) with hydroxylamine or the hydroxylammonium compound is used as a phase transfer catalyst in a next reaction of the compound of Formula (II) with hydroxylamine or a hydroxylammonium compound.

16. Use of a compound of Formula (I) as defined in any of claims 1 to 3 or a phase transfer catalyst as defined in any of claims 4 to 6 as a phase transfer catalyst for the preparation of a compound of Formula (I) as defined in any of claims 1 to 3.