4-Bromo-2-sulfanylbenzoic acid → tert-Butyl 3-[2-(7-bromo-4-oxo-4H-1,3-benzothiazin-2-yl)-4-pyridyl]propanoate

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Reaction Steps

tert-Butyl 3-(2-cyano-4-pyridyl)propanoate (1.3 g, 5.6 mmol) and 4-bromothiosalicylic acid (1.8 g, 8.0 mmol) were dissolved in pyridine (20 ml), and the mixture was refluxed for 18 hrs. The solvent was evaporated, and the residue was subjected to a silica gel column chromatography. The fractions eluted with hexane-ethyl acetate (3:2, v/v) were collected, concentrated and recrystallized from hexane-tetrahydrofuran to give the titled compound (0.63 g, 25%) as white crystals.

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