2-Amino-4-methylpyridine → 2-(Chloromethyl)-7-methylimidazo[1,2-a]pyridine

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Reaction Steps

A mixture of 2-amino-4-picoline (Aldrich; 500 g), 1,3-dichloroacetone (Aldrich; 5.89 g), and 1,2-dimethoxyethane (Aldrich; 44 mL) is stirred for 25 min at 53° C., at which time ethanol (47.5 mL) is added. After stirring for 2.5 h at reflux, the mixture is concentrated under reduced pressure and the residue is partitioned between dichloromethane and saturated sodium bicarbonate and brine. The organic layers are dried over MgSO4 and concentrated under reduced pressure. The crude material is chromatographed on silica gel using methanol/dichloromethane (1/99 to 2/98) to give, after crystallization from dichloromethane/hexane, 3.06 g of product. A portion of this material is dissolved in dichloromethane and refluxed with activated charcoal for 30 min. The activated charcoal is removed by filtration through a pad of diatomaceous earth and the filtrate is atmospherically concentrated, at which time hexane is added. The resulting solids are filtered, washed with hexane, and vacuum dried to give 0.15 g of 2-(chloromethyl)-7-methylimidazo[1,2-a]pyridine; mp 250° C. (decomp); ms m/z 180, 182; IR (mineral oil) 774, 1649, 1504, 1252, 701 cm-1 ; 1H NMR (CDCl3) δ 2.39, 4.75, 6.63, 7.32, 7.53, 7.95.

Provenance & Evidence