Isopropyl chloroacetate → 1,2-Benzisothiazole-2(3H)-acetic acid, 3-oxo-, 1-methylethyl ester, 1,1-dioxide

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A process for manufacturing 4-hydroxy-2-methyl-N-(2-pyridyl)-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide, of formula I, ##STR6## which comprises the following reaction sequence: reacting saccharin sodium with isopropyl chloroacetate in dimethylformamide to obtain isopropyl 3-oxo-1,2-benzoisothiazoline-2-acetate 1,1-dioxide, of formula II ##STR7## reacting the isopropyl 3-oxo-1,2-benzoisothiazoline-2-acetate 1,1-dioxide of formula II with sodium isopropylate in isopropanol at a temperature between 60° C. and the boiling point of the solvent, for a time between 15 minutes and 3 hours, to produce an intermediate of formula III ##STR8## methylating the intermediate of formula III in an aqueous-alcoholic basic medium with dimethyl sulfate to produce an intermediate compound of formula IV ##STR9## condensing the intermediate compound of formula IV with 2-aminopyridine in xylene to obtain a final product of formula I.

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