Phosphorus oxychloride → 5,7-dichloro-4H-imidazo[4,5-b]pyridine

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Reaction Steps

7-Chloro-3H-imidazo[4,5-b]pyridine-4-oxide (15 g, 88.5 mMol) and 300 mL phosphorus oxychloride were heated at 110° C. under a nitrogen atmosphere. After 4 hours the excess phosphorus oxychloride was removed in vacuo. The residue was dissolved in water and the solution was neutralized by the addition of aqueous ammonium hydroxide. The suspension was cooled and the solid isolated. After drying, the product, 5,7-dichloro-3H-imidazo[4,5-b]pyridine, weighed 10.5 g (54.5 mMol, 61.6%); m.p. 263° C.; NMR (DMSO-d6): 8.58 δ (s, 1H, H2); 7.58 (s, 1H, H5).

Provenance & Evidence