Phosphorus oxychloride → 5-Chloro-2-(2,4-difluorophenoxy)pyrido[3,2-d]pyridazine

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Reaction Conditions

Reaction Steps

A mixture of 2-(2,4-difluorophenoxy)pyrido[3,2-d]pyridazin-5(6H)-one (1.00 g, 3.63 mmol) in POCl3 (8.00 mL, 85.82 mmol) was heated at 95° C. for 4 h. The excess POCl3 was removed under reduced pressure and the crude residue was treated with ice and 1N NaOH. The precipitated solid was filtered, rinsed with 2×5 mL of water followed by 2×5 mL of ether to provide 5-chloro-2-(2,4-difluorophenoxy)pyrido[3,2-d]pyridazine as a tan amorphous solid. MS (ESI, pos.ion) m/z: M+1=294.0

Provenance & Evidence