Warner-lambert Company

Jerome D Genzer

Harold Zinnes

John Shavel, Jr

Arthur C Fabian

Charles Francis Kasulanis

Francisco Carrio Fontsere

This invention relates to a process for the preparation of 1-{[5-(4-hydroxy-2H-1,2-benzothiazin-3-yl)-1,2,4-oxadiazol-3-yl]methyl}eth anone S,S-dioxide (III), a novel intermediate useful in the preparation of the known anti-inflammatory agent, 4-hydroxy-3-(5-methyl-3-isoxazolylcarbamoyl)-2-methyl-2H-1,2-benzothiazine 1,1-dioxide (IV). According to the process of this invention, the saccharin compound, 2,3-dihydro-N-(5-methyl-3-isoxazolyl)-3-oxo-1,2-benzisothiazole-2-acetamid e 1,1-dioxide (I) is reacted with an alkali metal alkoxide of a lower alcohol in an inert solvent at temperatures below 30.degree. C. to form the benzenesulfonylglycineamide, alkyl 2-{[({[(5-methyl-3-isoxazolyl)amino]carbonyl}methyl)amino]sulfonyl}benzoat e (II), which is ring closed and rearranged by reaction with an alkali metal alkoxide of a lower alcohol in an inert solvent at temperatures of from 60.degree. to 70.degree. C. to form the desired oxadiazole compound III.

Composition containing alkyl

A novel process for preparing 4-hydroxy-3-(5-methyl-3-isoxazolylcarbamoyl)-2-methyl-2H-1,2-benzothiazine 1,1-dioxide (I), starting with 3-amino-5-methylisoxazole (II) is disclosed. Compound I exhibits anti-inflammatory properties and is useful for treating inflammation. In the process of the invention an intermediate obtained, 2,3-dihydro-N-(5-methyl-3-isoxazolyl)-3-oxo-1,2-benzisothiazole-2-acetamid e 1,1-dioxide (IV) undergoes rearrangement to provide 1-{[5-(4-hydroxy-2H-1,2-benzothiazin-3-yl)-1,2,4-oxadiazol-3-yl]methyl}eth anone S,S-dioxide (V), which is methylated, according to conventional procedures. The methylated intermediate VI, upon further treatment, undergoes a second rearrangement to obtain the desired anti-inflammatory compound I.

Intermediate composition

An improved process for the preparation of 4-hydroxy-3-(5-methyl-3-isoxazolylcarbamoyl)-2-methyl-2H-1,2-benzothiazine 1,1-dioxide (I), a known anti-inflammatory agent, is described. The process involves the reaction of a solution of alkyl 2,3-dihydro-3-oxo-1,2-benzisothiazole-2-acetate 1,1-dioxide (II) in dimethylformamide, with an alkali metal alkoxide using the specific portions of reactants and carefully controlled reaction conditions. Acidification of the reaction mixture precipitates out alkyl 4-hydroxy-2H-1,2-benzothiazine-3-carboxylate 1,1-dioxide (III) in substantially pure form in high yields, without recrystallization. Product III is methylated on the sulfonamide nitrogen and reacted with 3-amino-5-methylisoxazole to obtain crude I. A further improvement in the process of the invention involves a more efficient method for purifying crude product I by solubilizing in dimethylformamide with heating to 125.degree. C. to 148.degree. C. The hot solution is filtered, and the filtrate is cooled to obtain crystalline product I.

Process for the preparation of

A novel process for preparing 4-hydroxy-3-(5-methyl-3-isoxazolylcarbamoyl)-2-methyl-2H-1,2-benzothiazine 1,1-dioxide (I), starting with 3-amino-5-methylisoxazole (II) is disclosed. Compound I exhibits anti-inflammatory properties and is useful for treating inflammation. In the process of the invention an intermediate obtained, 2,3-dihydro-N-(5-methyl-3-isoxazolyl)-3-oxo-1,2-benzisothiazole-2-actamide 1,1-dioxide (IV) undergoes rearrangement to provide 1-{[5-(4-hydroxy-2H-1,2-benzothiazin-3-yl)-1,2,4-oxadiazol-3-yl]methyl}eth anone, S,S-dioxide (V), which is methylated, according to conventional procedures. The methylated intermediate VI, upon further treatment, undergoes a second rearrangement to obtain the desired anti-inflammatory compound I.

2,3-Dihydro-N-(5-methyl-3-isoxazolyl)-3-oxo-1,2-

This invention relates to a process for the preparation of 1-{[5-(4-hydroxy-2H-1,2-benzothiazin-3-yl)-1,2,4-oxadiazol-3-yl]methyl}eth anone S,S-dioxide (III), a novel intermediate useful in the preparation of the known anti-inflammatory agent, 4-hydroxy-3-(5-methyl-3-isoxazolylcarbamoyl)-2-methyl-2H-1,2-benzothiazine 1,1-dioxide (IV). According to the process of this invention, the saccharin compound, 2,3-dihydro-N-(5-methyl-3-isoxazolyl)-3-oxo-1,2-benzisothiazole-2-acetamid e 1,1-dioxide (I) is reacted with an alkali metal alkoxide of a lower alcohol in an inert solvent at temperatures below 30.degree. C. to form the benzenesulfonylglycineamide, alkyl 2-{[({[(5-methyl-3-isoxazolyl)amino]carbonyl}methyl)amino]sulfonyl}benzoat e (II), which is ring closed and rearranged by reaction with an alkali metal alkoxide of a lower alcohol in an inert solvent at temperatures of from 60.degree. C. to 70.degree. C. to form the desired oxadiazole compound III.

A novel process for preparing 4-hydroxy-3-(5-methyl-3-isoxazolylcarbamoyl)-2-methyl-2H-1,2-benzothiazine 1,1-dioxide (I), starting with 3-amino-5-methylisoxazole (II) is disclosed. Compound I exhibits anti-inflammatory properties and is useful for treating inflammation. In the process of the invention an intermediate obtained, 2,3-dihydro-N-(5-methyl-3-isoxazolyl)-3-oxo-1,2-benzisothiazole-2-acetamid e 1,1-dioxide (IV) undergoes rearrangement to provide 1-{[5-(4-hydroxy-2H-1,2-benzothiazin-3-yl)-1,2,4-oxadiazol-3-yl]methyl}eth anone S,S-dioxide (V), which is methylated, according to conventional procedures. The methylated intermediates VI, upon further treatment, undergoes a second rearrangement to obtain the desired anti-inflammatory compound I.

3-(Chlorocetamido)-5-methyl isoxazole

An improved process for the preparation of 4-hydroxy-3-(5-methyl-3-isoxazolylcarbamoyl)-2-methyl-2H-1,2-benzothiazine 1,1-dioxide (I), a known anti-inflammatory agent, requires the use of specific proportions of reactants and carefully controlled reaction conditions. An alkali metal alkoxide, suspended in dimethylformamide is combined, with stirring, as rapidly as possible with a solution of alkyl 2,3-dihydro-3-oxo-1,2-benzisothiazole-2-acetate 1,1-dioxide (II) in dimethylformamide, while maining the internal reaction temperature within 15.degree.-30.degree.C. More than two but less than six moles of the alkoxide are used per mole of the alkyl 2,3-dihydro-3-oxo-1,2-benzisothiazole-2-acetate 1,1-dioxide (II). After all reactants have been combined, stirring is continued for a specific period of time and then the reaction mixture is acidified. Total elapsed time from initial combination of reactants to acidification is from 30 to 50 minutes. Acidification of the reaction mixture precipitates out alkyl 4-hydroxy-2H-1,2-benzothiazine-3-carboxylate 1,1-dioxide (III) in substantially pure form in high yields, without recrystallization. Product III is methylated on the sulfonamide nitrogen and reacted with 3-amino-5-methyl-isoxazole to obtain crude I. A further improvement in the process of the invention involves a more efficient method for purifying crude product I: the need for large quantities of dioxane solvent is obviated. After slurrying and washing, product I is solubilized in dilute alkali, and decolorized. After filtration and acidification pure product I in high yield is obtained. In addition to preparing the known anti-inflammatory agent (I), the initial reaction step of the invention wherein 2,3-dihydro-3-oxo-1,2-benzisothiazole-2-acetate, 1,1-dioxide (II) is rearranged to form alkyl 4-hydroxy-2H-1,2-benzothiazine-3-carboxylate 1,1-dioxide (III), may be used with particular advantage for the preparation of other useful benzothiazine derivatives.

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Livingston, NJ, United States of America

Jerome D Genzer