3,5-Dibromo-4-hydroxybenzoic acid → Ethyl 5-(3,5-dibromo-4-hydroxyphenyl)-1,2,4-oxadiazole-3-carboxylate

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Reaction Steps

N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (1.32 g, 10 mmol) was added in one portion to a stirred solution of ethyl 2-amino-2-(hydroxyimino)acetate (1.32 g, 10 mmol) plus 3,5-dibromo-4-hydroxybenzoic acid (2.95 g, 10 mmol) in pyridine (20 mL), the resulting solution was stirred at room temperature for 2 h and then at 90° C. for 5 h. After standing at room temperature overnight the pyridine was evaporated in vacuo and the residue was purified by flash chromatography (silica gel, 10% ethyl acetate/dichloromethane) to give the title compound (0.48 g, 12%) as a colourless solid. 1H NMR δ (ppm) (DMSO-d6): 1.48 (3H, t), 4.47 (2H, d), 8.13 (2H, s), 11.54 (1H, s, br).

Provenance & Evidence