Sodium Hydroxide → 2-methyl-3-oxo-3,4-dihydro-2H-1,4-benzothiazine-2-carboxylic acid

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Reaction Steps

Ethyl-2-methyl-3,4-dihydro-3-oxo-2H-1,4-benzothiazine-2-carboxylate (0.251 g, 1 mmole) and 1N NaOH (2.2 ml, 2.2 mmoles) were stirred in dioxan (5 ml) for 48 hours at room temperature. The solvent was evaporated, water (5 ml) was added to the residue and it was acidified with 20% HCl to pH=2. The crystals which separated were filtered off by suction and recrystallized from absolute ethanol. Thus there were obtained 0.234 g (98.0%) of the title product in the form of white crystals, m.p. 164-°165° C.

Provenance & Evidence