Telescoping synthesis of 2-methoxymethyl-p-phenylenediamine
View Patent ↗A telescoping process for the preparation of 2-methoxymethyl-p-phenylenediamine, a cosmetically acceptable salt thereof, or mixture thereof. The process according to the present invention is a particularly cost effective process in that it avoids sophisticated chemical steps which requires special equipment or expensive catalysts and in that it comprises a recycling step of one of the starting materials, namely 2-methoxymethylaniline.
1. A telescoping process for the preparation of 2-methoxymethyl-p-phenylenediamine (I), a cosmetically acceptable salt thereof, or mixture thereof comprising the steps of:
a) synthesizing the intermediate 2-(methoxymethyl)-4-{3-[2-(methoxymethyl)phenyl]triaz-1-en-1-yl}aniline (IV) via diazotation using 2-methoxymethylaniline (II) to obtain the intermediate of formula (III) followed by diazo coupling between the intermediate of formula (III) and 2-methoxymethylaniline (II):
b) synthesizing the intermediate 2-(methoxymethyl)-4-{(E)-[2-(methoxymethyl)phenyl]diazenyl}aniline (V) via rearrangement of the intermediate 2-(methoxymethyl)-4-{3-[2-(methoxymethyl)phenyl]triaz-1-en-1-yl} aniline (IV) obtained in step a:
c) synthesizing 2-methoxymethyl-p-phenylenediamine (I) and 2-methoxymethylaniline (II) via hydrogenation of the compound of formula (V):
2. The process according to claim 1 , wherein the process further comprises the step of converting 2-methoxymethyl-p-phenylenediamine (I) into a cosmetically acceptable salt.
3. The process according to claim 2 , wherein the cosmetically acceptable salt is selected from chloride, sulfate, hydrogensulfate or malonate salt.
4. The process according to claim 1 , wherein step a) is carried out in the presence of at least one nitrosation agent.
5. The process according to claim 4 , wherein the nitrosation agent is selected from the group consisting of sodium nitrite, potassium nitrite, dinitrogen pentoxide, nitrosylsulfuric acid and mixtures thereof.
6. The process according to claim 1 , wherein step a) is carried out in the presence of at least one radical scavenger.
7. The process according to claim 1 , wherein step a) or b) carried out in the presence of at least one mineral or organic acid.
8. The process according to claim 7 , wherein the mineral or organic acid is selected from the group consisting of hydrogen chloride, trifluoroacetic acid, sulfuric acid, sulfurous acid, carbonic acid, nitric acid, acetic acid, propionic acid, phosphoric acid and mixtures thereof.
9. The process according to claim 1 , wherein the solvent used in step a) or b) is selected from the group consisting of 1,2-dimethoxyethane, pentane, cyclopentane, hexane, cyclohexane, benzene, toluene, 1,4-dioxane, diethyl ether, tetrahydrofuran, methyl-tetrahydrofuran, n-pentanol, n-butanol, acetic acid, propionic acid, oxalic acid, malonic acid, sulphuric acid, phosphoric acid, iso-pentanol, t-butanol, isopropanol, n-propanol, ethanol, methanol, glycols, hydrogen chloride, water and mixtures thereof.
10. The process according to claim 1 , wherein step c) is carried out in the presence of a hydrogen source selected from hydrazine or H 2 with a metal catalyst selected from the group consisting of Fe, Pd/C, Pd/(OH) 2 , Raney-Ni, Pt/C, PtO 2 and mixtures thereof.
11. The process according to claim 1 , wherein the solvent used in step c) is selected from the group consisting of 1,2-dimethoxyethane, pentane, cyclopentane, hexane, cyclohexane, benzene, toluene, methylacetate, ethylacetate, n-propylacetate, iso-propylacetate, n-butylacetate, methylpropionate, ethylpropionate, n-propylpropionate, iso-propylpropionate, n-butylpropionate, 1,4-dioxane, diethyl ether, tetrahydrofuran, methyl-tetrahydrofuran, n-butanol, isopropanol, n-propanol, ethanol, methanol, water and mixtures thereof.
12. The process according to claim 1 , wherein 2-methoxymethyl-aniline (II) is prepared via methylation of 2-nitro-benzyl alcohol (VI) to obtain the intermediate 2-nitro-methoxymethyl-benzene (VII) followed by hydrogenation of the intermediate 2-nitro-methoxymethyl-benzene
13. The process according to claim 12 , wherein the methylation agent is selected from the group consisting of chloromethane, bromomethane, methyl iodide, dimethyl sulfate and mixtures thereof.
14. The process according to claim 12 , wherein the methylation is carried out using at least one phase transfer catalyst selected from the group consisting of benzyl trialkyl ammonium salts.
15. The process according to claim 12 , wherein the methylation is carried out using at least one phase transfer catalyst selected from the group consisting of chloride, bromide or sulfate salts of benzyl trimethyl ammonium, benzyl triethyl ammonium, benzyl tripropyl ammonium, benzyl tributyl ammonium and mixtures thereof.
16. The process according to claim 12 , wherein the methylation is carried out using a solvent selected from the group consisting of 1,2-dimethoxyethane, pentane, cyclopentane, hexane, cyclohexane, benzene, toluene, 1,4-dioxane, diethyl ether, tetrahydrofuran, methyl-tetrahydrofuran, n-pentanol, iso-pentanol, t-butanol, isopropanol, n-propanol, ethanol, methanol, water, glycols and mixtures thereof.
17. The process according to claim 12 , wherein hydrogenation of the intermediate 2-nitro-methoxymethyl-benzene (VII) is carried out using a solvent selected from the group consisting of 1,2-dimethoxyethane, pentane, cyclopentane, hexane, cyclohexane, benzene, toluene, methylacetate, ethylacetate, n-propylacetate, iso-propylacetate, n-butylacetate, methylpropionate, ethylpropionate, n-propylpropionate, iso-propylpropionate, n-butylpropionate, 1,4-dioxane, diethyl ether, tetrahydrofuran, methyl-tetrahydrofuran, n-butanol, isopropanol, n-propanol, ethanol, methanol, water and mixtures thereof.
18. The process according to claim 1 , wherein 2-methoxymethylaniline (II) is prepared via methoxylation of 2-bromomethyl-nitrobenzene (VIII) to obtain the intermediate 2-nitro-methoxymethyl-benzene (VII) followed by hydrogenation of the intermediate 2-nitro-methoxymethyl-benzene (VII):
19. The process according to claim 18 , wherein the methoxylating agent is selected from the group consisting of methanol, sodium methylate and mixtures thereof.
20. The process according to claim 18 , wherein the methoxylation is carried out using a solvent selected from the group consisting of 1,2-dimethoxyethane, pentane, cyclopentane, hexane, cyclohexane, benzene, toluene, 1,4-dioxane, diethyl ether, tetrahydrofuran, methyl-tetrahydrofuran, n-pentanol, iso-pentanol, t-butanol, isopropanol, n-propanol, ethanol, methanol, water, glycols and mixtures thereof.