A mixture of (chloroacetonyl)triphenylphosphonium chloride (190.7 g) and 2-amino-4-methylpyridine (158.9 g) in acetonitrile (1.3 l) was stirred under reflux for 5.5 hours. To the reaction mixture were added water (400 ml) and 3-benzyloxy-4-nitrobenzaldehyde (63.0 g) under ice-cooling. The mixture was adjusted to pH 9.5 with potassium carbonate and stirred for 2.5 hours at ambient temperature under keeping the pH 9.5 to 10.0 with 20% aqueous potassium carbonate. The reaction mixture was adjusted to pH 2.0 with conc. hydrochloric acid and the precipitate was collected by filtration. To a mixture of ethyl acetate, tetrahydrofuran and water was added the above obtained precipitate and the resultant mixture was adjusted to pH 7.0 with 20% aqueous potassium carbonate. The separated organic layer was washed with brine and dried over magnesium sulfate. The solvent was removed in vacuo to give 2-[2-(3-benzyloxy-4-nitrophenyl)vinyl]-7-methylimidazo[1,2-a]pyridine (43.14 g).
