Phosphorus oxychloride → 7-Chloropyrazolo[1,5-a]pyrimidin-5-amine

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Reaction Steps

A solution of 5-aminopyrazolo[1,5-a]pyrimidin-7(4H)-one (Z-2) (1.5 g, 10 mmol) in phosphoryl chloride (45 mL) is stirred at reflux overnight. The reaction mixture is allowed to cool to RT and concentrated in vacuo. The residue is then dissolved in ice-water (25 mL) and the resulting mixture is neutralized with aqueous NaOH solution (20%) to adjust the pH to 9-10. The mixture is extracted with ethyl acetate (3×50 mL) after which the combined organic layers are washed with brine (500 mL), dried over anhydrous Na2SO4 and filtered. The filtrate is concentrated in vacuo to afford the crude product which is slurried in a mixture of DCM/MTBE (3 mL/15 mL). The resulting solid is then collected by filtration to afford 7-chloropyrazolo[1,5-a]pyrimidin-5-amine (Z-3).

Provenance & Evidence