Phosphorus oxychloride → 4-chloro-6-ethylthieno[2,3-d]pyrimidine

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Reaction Steps

To a solution of 6-ethylthieno[2,3-d]pyrimidin-4-ol (10 g, 55.49 mmol, 1.00 equiv) in 1,2-dioxane (100 mL) was added POCl3 (30 mL) and heated to reflux for 4 hr. After completion of the reaction, the reaction mixture was concentrated under vacuum and then quenched with water/ice. The resulting solution was extracted with 3×200 mL of ethyl acetate: The combined organic layers were washed with brine, dried over anhydrous sodium sulfateand concentrated under vacuum. The residue was purified on a silica gel column with ethyl acetate/petroleum ether (1/10) to give 7 g (64%) of 4-chloro-6-ethylthieno[2,3-d]pyrimidine as a yellow solid. MS (ES, m/z): 382 (M+H+).

Provenance & Evidence