4-Methoxyphenol → 3-Bromo-5-(4-methoxyphenoxy)pyridine

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Reaction Steps

To a stirred suspension of sodium hydride (3.0 g of 80% in mineral oil, 100 mmol) in DMF (95 mL) in an ice water bath, 4-methoxyphenol (12.2 g, 96 mmol) was added slowly under a nitrogen atmosphere. The resulting mixture was warmed to ambient temperature and stirred for 1 h. 3,5-Dibromopyridine (15.6 g of 98%, 65 mmol) was added and the mixture was then heated at 85° C. (bath temperature) for 32 h. The mixture was cooled, diluted with water (120 mL), poured into 5N sodium hydroxide (15 mL), and extracted with ether (3×150 mL). The combined ether extracts were dried (Na2SO4), filtered and concentrated by rotary evaporation, to give a light-yellow oil (21.9 g). The oil was diluted with ethanol and rotary evaporated (twice) to remove residual DMF and then diluted with ether (50 mL) and suction filtered to remove un-reacted 3,5-dibromopyridine. Rotary evaporation and high vacuum treatment left a lard-like product weighing 12.8 g. The product was 94% pure by GC-MS analysis (66% yield) and was sometimes used, without further purification, in subsequent reactions. When desired, further purification (to 99.4%) was accomplished by column chromatography on silica gel, using 85:5:5:4.5:0.5 hexane/chloroform/ethyl acetate/methanol/aqueous ammonia as eluent.

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