Phosphorus oxychloride → 3,4,5-Trichloropyridazine

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Reaktionsschritte

A solution of 4,5-dichloropyridazin-3(2H)-one (2 g, 12 mmol) in 20 mL of phosphoryl trichloride was heated to reflux for 2 hrs. The solvent was removed under reduce pressure. The residue was poured into water with stirring and extracted with dichloromathene (50 mL*3). The organic layer was washed with brine, dried over Na2SO4, evaporated to give the crude product (U.S. Pat. Appl. Publ. U.S. Pat. No. 6,800,758 (Egis Gyogyszergyar Rt., Hung., Oct. 5, 2004). The crude product was recrystallized with acetone/water to give the product (2 g, 83%). 1H NMR (300 MHz, CDCl3): 9.09 (s, 1H); LC-MS: m/z=182.9 [M+H]+.

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