Acetic Acid → 2-(6-Methyl-2-(4-methylphenyl)imidazo(1,2-a)pyridin-3-yl)acetic acid

Participants

Reaction Conditions

Reaction Steps

A solution of potassium hydroxide (90% titre; 30.3 g; 0.48 mols) in water (225 mL) and ethanol (65 mL) is added with ethyl 2-(4-methylphenyl)-6-methylimidazo[1,2-a]-pyridine-3-glyoxalate (141.5 g; 0.44 mols). The suspension is refluxed to obtain a yellow-orange solution, which is concentrated to reach a temperature of 98-100° C. and added with hydrazine (51.7% titre, 27.5 g; 0.44 mols). The solution is refluxed for 14 hours, then cooled to about 60° C., added with potassium hydroxide (90% titre, 54.9 g; 0.88 mols), then distilled under atmospheric pressure to reach the inner temperature of 122÷124° C., keeping the resulting suspension under reflux until nitrogen evolution ceases. The mixture is cooled to about 100° C., diluted with water (500 mL), cooled at room temperature and filtered through Celite. The resulting clear solution is dropped in about one hour into an acetic acid solution (91 g; 1.52 mols) in methanol (500 mL). The resulting suspension is cooled to 0÷5° C., filtered and the solid is washed with water, then dried at 60° C. under vacuum to obtain 2-(4-methylphenyl)-6-methylimidazo[1,2-a]-pyridine-3-acetic acid (118.4 g, 98.5% titre, K.F. 1.4%, yield 96.5%).

Provenance & Evidence