p-Toluenesulfonic acid → Ethyl 2-(imidazo[1,2-a]pyridin-3-yl)acetate

Participants

Reaction Steps

Heat a mixture of 4,4-dimethoxy-but-2-enoic acid ethyl ester (43.5 g, 250 mmol) and p-toluenesulfonic acid (4.75 g, 25 mmol) in acetonitrile (240 mL) and water (15 mL) at reflux for 2 hours. Cool the reaction mixture to room temperature and add 2-aminopyridine (18.8 g, 200 mmol). Heat the mixture at reflux for 16 hours then cool to room temperature. Dilute the reaction mixture with ethyl acetate (1200 mL) and wash sequentially with saturated aqueous sodium bicarbonate (600 mL×3) and saturated aqueous sodium chloride (600 mL×2). Dry the organic phase over sodium sulfate and concentrate under reduced pressure to provide the desired compound as a brown oil (30 g, 73%).

Provenance & Evidence