Phosphorus oxychloride → Ethyl 5-chloropyrazolo(1,5-a)pyrimidine-3-carboxylate

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Reaction Steps

Ethyl 5-hydroxypyrazolo[1,5-a]pyrimidine-3-carboxylate (22.7 g, 110 mmol) was suspended in phosphoryl trichloride (100 mL) and heated to reflux. After heating for 2 hours, the reaction mixture was cooled and concentrated to remove excess POCl3. The residue was diluted in DCM (100 mL) and slowly added to a flask containing ice water. The mixture was separated and the aqueous layer was extracted with DCM (2×200 mL). The combined organic layers were dried (MgSO4), filtered and concentrated to afford ethyl 5-chloropyrazolo[1,5-a]pyrimidine-3-carboxylate as a pale-yellow solid (24.2 g, 97.6% yield). MS (apci) m/z=225.9 (M+H).

Provenance & Evidence