m-Chloroperbenzoic acid → 2-(4-fluorophenyl)-6-methoxy-3-(2-methanesulfonyl-pyrimidin-4-yl)-6,7-dihydro-5H-pyrazolo[1,2-a]pyrazol-1-one

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Reaction Steps

2-(4-Fluorophenyl)-6-methoxy-3-(2-methylsulfanyl-pyrimidin-4-yl)-6,7-dihydro-5H-pyrazolo[1,2-a]pyrazol-1-one, 49, (1.10 g, 2.95 mmol) is diluted with dichloromethane (60 mL). 3-Chloroperbenzoic acid (662 mg of ˜77% purity, 2.95 mmol) is added all at once to the yellow suspension. After 20 min, additional 3-chloroperbenzoic acid (240 mg, 1.07 mmol) is added. After 10 minutes, the clear, yellow reaction solution is poured in a 10% aqueous solution of sodium bisulfite (60 mL). The layers are separated and the aqueous layer extracted with dichloromethane (2×50 mL). The combined organic layers are washed with a saturated aqueous solution of sodium bicarbonate (2×50 mL), dried over sodium sulfate, filtered and concentrated in vacuo to afford 948 mg of a mixture of the corresponding sulfoxide and sulfone as a yellow solid. Used as is for next step.

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