(Diethylamino)sulfur trifluoride → (rac)-7-fluoro-2-phenoxymethyl-6,7-dihydro-5H-pyrazolo[1,5-a]pyrazin-4-one

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Reaction Steps

DAST (0.035 mL, 0.29 mmol) was added to a solution of (rac)-7-hydroxy-2-phenoxymethyl-6,7-dihydro-5H-pyrazolo[1,5-a]pyrazin-4-one (50 mg, 0.19 mmol) in DCM (0.5 mL) at −10° C. The mixture was stirred at room temperature for 15 minutes. Then quenched with a 1N solution of HCl and extracted with DCM. The organic layer was separated, dried (Na2SO4), filtered and the solvent evaporated in vacuo to yield (rac)-7-fluoro-2-phenoxymethyl-6,7-dihydro-5H-pyrazolo[1,5-a]pyrazin-4-one (51 mg, quantitative) as light brown solid that was used without further purification.

Provenance & Evidence