Process for the preparation of diacerein
AssigneeLaboratoire Medidom S.A.
InventorGuido Di Napoli
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Abstract
The present invention relates to a process for the preparation of 1,8-diacetoxy-3-carboxyanthraquinone, also known as diacerein, via aloin acetylation, oxidation of the acetylated product, and purification of the raw diacerein obtained by means of crystallization from 2-methoxyethanol or N,N-dimethylacetamide and optionally by dissolution of the corresponding salt with triethylamine in methylene chloride, followed by removal of the insoluble residue.
Claims30
A process for the preparation of 1,8-diacetoxy-3-carboxyanthraquinone of formula (I) ##STR4## comprising:
- a) acetylation of aloin of formula II (II) ##STR5## by treatment with an acetylating agent in a diluent, in the presence of a base or of an acid as catalyst to obtain the corresponding acetylated product as per formula (III) ##STR6## b) treatment of acetylated product (III) with an oxidizing agent, to give raw diacerein;
- c) purification of raw diacerein,
- wherein purification of raw diacerein comprises at least one crystallization step from a solvent selected from the group consisting of 2-methoxyethanol and N,N-dimethylacetamide, and optionally, a salification step comprising dissolving diacerein in a halogenated hydrocarbon solvent by salifying it with triethylamine, removing the insoluble residue, precipitating diacerein in aqueous acidic medium, recovering and drying the precipitated diacerein.
The process according to 23, wherein anhydrous N,N-dimethylacetamide has a water content lower than 0.2%.
Process for purifying diacerein comprising crystallization of raw diacerein from a solvent selected from the group consisting of 2-methoxyethanol and N,N-dimethylacetamide.
A process for producing diacerein comprising acetylation of aloin to produce a compound of formula (III), ##STR7## and reacting the acetylated compound of formula (III) with an oxidizing agent.
Dependencies are inferred from the claim text.