Chloroacetaldehyde → 7-Methylimidazo(1,2-a)pyridine

Participants

Reaction Steps

A solution of 2-amino-4-methylpyridine (21.6 g, 0.2 mol) in ethanol (300 ml) was treated with sodium hydrogencarbonate (33.6 g, 0.4 mol) then with chloroacetaldehyde (42.4 ml of a 45 wt % solution in water, 0.3 mol) and this mixture was heated at reflux for 16 hours. The reaction was cooled then pre-adsorbed directly on to silica (200 g). Purification by dry flash chromatography, eluting with dichloromethane/methanol/conc. ammonia (95:4.5:0.5) gave 7-methylimidazo[1,2-α]pyridine as an oil (26.4 g, 100%) which crystallised on standing. 1H NMR (400 MHz, CDCl3) δH 2.39 (3H, s), 6.62 (1H, d, J 7), 7.37 (1H, s), 7.49 (1H, s), 7.55 (1H, s), 8.00 (1H, d, J 7); m/z (ES+) 132 (M++H).

Provenance & Evidence