Hydrochloric Acid → 2-Methylimidazo[1,2-a]pyridine-8-carbaldehyde

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Reaction Steps

A mixture of 2-aminonicotinaldehyde (92.8 g, 0.76 mol) and bromoacetone (114.5 g, 0.84 mol) in dimethoxyethane (980 ml) is stirred for 2 hr. at room temperature and then heated at 65° with stirring for 14 hr. The solid which separates is isolated by filtration, dissolved in 800 ml absolute ethanol and heated under reflux for 6 hrs. The ethanol solvent isremoved under reduced pressure and the residue treated with 138 ml 6 N hydrochloric acid in 750 ml water for 0.5 hr. The acidic aqueous layer is washed with ether (2×300 ml) and basified with cooling (78 ml 50% sodium hydroxide and 25 g sodium bicarbonate). The aqueous layer is extracted with dichloromethane. The extracts are combined and dried over anhydrous sodium sulfate. Following filtration, the solvent is removed under reduced pressure to afford 2-methyl-8-formylimidazo[1,2-a]pyridine, mp 136°-139.5° C.

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