Phosphorus tribromide → 2,5-Dibromo-3-chloropyridine

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Reaction Steps

36.0 g (172.7 mmol) of 5-bromo-3-chloro-2-hydroxypyridine are stirred at 160° C. for 6 hours in 320 ml of phosphorus tribromide. The reaction mixture is cooled to room temperature and poured carefully into ice water. After 2 hours, the mixture is extracted three times with 500 ml of dichloromethane in each case. The combined organic phases are washed with sodium bicarbonate solution until neutral, dried over Na2SO4 and filtered, and the filtrate is evaporated to dryness. Chromatographic purification (silica gel/dichloromethane) gives 20.53 g of 3-chloro-2,5-dibromopyridine. ##STR14## m.p.: 40°-41° C.

Provenance & Evidence