Patent ID: 8097616

Claim:
A process for the preparation of 99.8% pure 4-hydroxy-2-methyl-N-(5-methyl-2-thiazolyl)-2H-1,2-benzothiazine-3-carboxamide-1,1-dioxide (meloxicam) of the Formula (II) free of water-insoluble impurities of the compound of the Formula (V) wherein R is methyl, ethyl or isopropyl, according to one of the following process variants: (a) dissolving meloxicam potassium salt monohydrate of the Formula (I) with the water-insoluble impurities of the Formula (V), in water or in a mixture of water and an organic solvent, removing from the meloxicam potassium salt monohydrate, the water-insoluble impurities of the compound of the Formula (V) and treating the resulting solution with an organic or inorganic acid, and crystallizing 99.8% pure meloxicam; or (b) transforming meloxicam raw product into crystalline meloxicam potassium salt monohydrate of the Formula (I) with the water-insoluble impurities of the compound of the Formula (V), dissolving said meloxicam potassium salt monohydrate of the Formula (I) with the water-insoluble impurities of the Formula (V) in water or in a mixture of water and an organic solvent, removing from the meloxicam potassium salt monohydrate, the water-insoluble impurities of the compound of the Formula (V), and treating the dissolved potassium salt of meloxicam with an organic or inorganic acid, followed by crystallization of 99.8% pure meloxicam of the Formula (II); or (c) (i) reacting a compound of the Formula (III) wherein R is methyl, ethyl or isopropyl with 2-amino-5-methyl-thiazole of the Formula (IV) to form a meloxicam raw product of the Formula (II); (ii) transforming the resulting meloxicam of the Formula (II) into its potassium monohydrate salt along with the water-insoluble impurities of the compound of the Formula (V), (iii) separating the water-insoluble impurities of the compound of the Formula (V) from an aqueous or aqueous-organic solution of said meloxicam potassium salt to form a solution of 99.8% pure meloxicam; and (iv) treating said solution with an organic or inorganic acid and crystallizing 99.8% pure meloxicam.