Sulfuric Acid → Ethyl 6-bromoimidazo[1,2-a]pyridine-3-carboxylate

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Reaction Steps

Add concentrated sulfuric acid (0.56 g, 5.78 mmol) to a suspension of 2-chloro-3-oxo-propionic acid ethyl ester potassium salt (Tetrahedron 2000, 58(40), 7915-7921; 3.27 g, 17.3 mmol) and 2-amino-5-bromopyridine (1.0 g, 5.78 mmol) in ethanol (100 mL). Reflux for 2 h, cool, and carefully dilute with saturated aqueous sodium bicarbonate. Extract in ethyl acetate, combine organic extracts, and concentrate. Flash chromatography using appropriate ethyl acetate/methanol mixtures gives 0.85 g (55%) of the subtitled compound as a white solid. MS ES+m/e 269.0, 271.0 (M+1) bromine isotope. 1H NMR (400 MHz, DMSO-d6) δ 9.32 (m, 1H), 8.28 (s, 1H), 7.79 (d, J=10 Hz, 1H), 7.70 (dd, J=10, 2 Hz, 1H), 4.36 (q, J=7.0 Hz, 2H), 1.33 (t, J=7.0 Hz, 3H).

Provenance & Evidence