Dimethyl Sulfate → Isopropyl-4-hydroxy-2-methyl-2H-1,2-benzothiazine-3-carboxylate-1,1-dioxide

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Reaction Steps

1,425 ml (15 mol) of dimethyl sulfate are added at between 10° and 15° C. to a solution of 2,833 g (10 mol) of isopropyl 4-hydroxy-2H-1,2-benzothiazine-3-carboxylate 1,1-dioxide and 440 g (11 mol) of sodium hydroxide in 4 l of water and 11.3 l of isopropanol. The mixture is maintained with stirring for 4 hours at room temperature, diluted with 28 l of water and cooled to 0°-5° C. The precipitate obtained is centrifuged, washed with cold water and dried, 2.675 g (90%) of a white or slightly pink solid, m.p. 102°-3° C. (104°-5° C. from methanol), being obtained.

Provenance & Evidence