Phosphorus oxychloride → 4-Chloro-5-fluoro-1H-pyrrolo(2,3-b)pyridine

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Reaction Steps

A solution of 1.7 g of 5-fluoro-1H-pyrrolo[2,3-b]pyridine-7-oxide in 10 cm3 of phosphorus oxychloride is maintained at the reflux point of the POCl3 for 8 hours. After distilling off the POCl3 under vacuum, the residue is treated with 50 g of ice, and the pH of the solution obtained is brought in the region of 8-9 by addition of sodium hydrogen carbonate. The aqueous phase is extracted with five times 80 cm3 of ethyl acetate. The combined organic phases are then dried over magnesium sulfate, filtered and concentrated to dryness under reduced pressure (13 kPa). 1.3 g of 4-chloro-5-fluoro-1H-pyrrolo[2,3-b]pyridine are thus obtained in the form of a solid, the characteristics of which are as follows:

Provenance & Evidence