Phosphorus oxychloride → 7-Chloro-5-(4-fluorophenyl)thieno[3,2-b]pyridine

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Reaction Steps

A solution of 5-(4-fluorophenyl)-thieno[3,2-b]pyridin-7-ol (1.6 g) in phosphorus oxychloride (50 mL) is refluxed for 3 hours. After the excess phosphorus oxychloride is removed under vacuum, the residue is treated with ethyl acetate (20 mL), and NaOH (2N, 20 mL). The mixture is then extracted with ethyl acetate (3×20 mL). The combined organic layers are washed with brine, dried over MgSO4, and filtered. Evaporation of the solvent gives 7-chloro-5-(4-fluorophenyl)thieno[3,2-b]pyridine (1.5 g, 88% yield) as a white solid, m.p. 119-121° C.

Provenance & Evidence