4H-1,4-Benzothiazin-3-one → 3-oxo-3,4-dihydro-2H-1,4-benzothiazine-6-sulfonyl chloride

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Reaction Steps

Powdered 4H benzo[1,4]thiazin-3-one (7.0g) was added cautiously, portionwise (over 20 minutes), to chlorosulfonic acid (15 mL), cooled in ice. After 1 hour, the blue solution was allowed to warm to room temperature and it was heated at 45° C. for 2 hours, cooled and poured into ice. The solid was collected, washed with water, and hexane, and dried in vacuo, to give a white solid (7.0 g): LC-MS (ES) m/e 263 (M)+.

Provenance & Evidence