Sodium pyrazolo[1,5-a]pyrimidin-5-olate → pyrazolo[1,5-c]pyrimidin-5(4H)-one

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Reaction Steps

Sodium pyrazolo[1,5-a]pyrimidin-5-olate (13.47 g) was dissolved in 500 mL of acetic acid and 100 mL of water, stirred 15 minutes then evaporated to dryness under vacuum. The residue was suspended in 300 mL of 9:1 dichloromethane:methanol and vacuum filtered through silica gel to remove sodium acetate. The silica gel pad was washed with 700 mL of additional dichloromethane:methanol solution. The combined dichloromethane:methanol solution was concentrated to dryness. The solid product was suspended in 1:1 hexane:dichloromethane and filtered to yield 9.9 g (85%) pyrazolo[1,5-c]pyrimidin-5(4H)-one. LCMS (ESI) m+H=136.0; 1H NMR (400 MHz, DMSO-d6) δ: 12.1 (s broad exchangeable, 1H), 8.47 (d, 1H, J=7.9), 7.75 (d, 1H, J=1.9), 5.94 (d, 1H, J=7.5), 5.81 (d, 1H, J=1.7).

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