2-Aminopyridine → Methyl 3-methylimidazo[1,2-a]pyridine-2-carboxylate

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Reaction Steps

Methyl 3-bromo-2-oxobutanoate (6.5 g, 34.3 mmol) was added to a stirred solution of 2-aminopyridine (4.0 g, 42.5 mmol) in acetonitrile (100 ml). The mixture was heated at reflux for 14 h (the reaction was monitored by TLC). The mixture was concentrated in vacuo and the residue was diluted with water and the pH was to 7.5 using sodium bicarbonate solution. The mixture was extracted with EtOAc; the combined organics were dried over sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by flash column chromatography using 8% ethyl acetate in n-hexane and silica gel (230-400 mesh) to afford methyl 3-methylimidazo[1,2-a]pyridine-2-carboxylate (2.0 g, 25.1%) as a pale yellow solid. 1H NMR: 200 MHz, CDCl3: δ 7.95 (d, 1H), 7.7 (d, 1H), 7.25 (t, 1H), 6.8 (t, 1H), 4.0 (s, 3H), 2.8 (s, 3H). MS: [M+H]+: m/z=191.1.

Provenance & Evidence