Sodium Hydroxide → 3-Oxo-3,4-dihydro-2H-pyrido[3,2-b][1,4]thiazine-6-carboxylic acid

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Reaction Steps

0.5 M NaOH solution (8 mL, 4 mmole) was added dropwise over 2 hr to a solution of methyl 3-oxo-3,4-dihydro-2H-pyrido[3,2-b][1,4]thiazine-6-carboxylate (788 mg, 3.52 mmole) in dioxane (120 mL) and water (30 mL). The reaction was stirred overnight then was concentrated to about 3 mL. Water (5 mL) was added and the pH was adjusted to 4 with 2 M HCl. The precipitated solid was collected, washed with a small volume of water and dried under vacuum to give the title compound (636 mg, 86%) as a solid: MS (APCI−) m/e 209 (M−H)−, 165 (M-COOH)−.

Provenance & Evidence