Chloroacetic Acid → 2,6-Dichloroimidazo[1,2-A]pyridine

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Reaction Steps

Chloroacetic acid (9.5 g) is dissolved in 70 ml of acetonitrile, to which 10.1 g of triethylamine is portionwise added and further 12.9 g of 2-amino-5-chloropyrdine is added. The mixture is refluxed for 3 hours. After cooling, the precipitated 2-imino-5-chloro-1,2-dihydropyridin-1-ylacetic acid as crystals is collected by filtration and dried. The crystals are added to 40 ml of phosphorus oxychoride and refluxed for 5 hours. After cooling, the reaction mixture is poured into ice water and neutralized with aqueous ammonia. The precipitate collected by filtration is purified by silica gel chromatography(eluent: ethyl acetate) to give 2.1 g of the title compound as crystals. mp. 155°-156° C.

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