Cesium carbonate → 2[(2-fluorobenzyl)oxy]-5-(4-fluorophenyl)-6,7-dihydropyrazolo[1,5-a]pyrazin-4(5H)-one

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Reaction Steps

2-Fluorobenzyl bromide (0.049 mL, 0.39 mmol) was added to a stirred suspension of 5-(4-fluorophenyl)-2-hydroxy-6,7-dihydropyrazolo[1,5-a]pyrazin-4(5H)-one (0.092 g, 0.36 mmol) and Cs2CO3 (0.234 g, 0.72 mmol) in ACN (1.85 mL). The mixture was stirred at room temperature for 16 hours. The solvent was evaporated in vacuo. The residue was diluted with water and extracted with AcOEt. The organic layer was separated, washed with a saturated solution of NaCl, dried (Na2SO4), filtered and the solvents evaporated in vacuo. The crude product was purified by flash column chromatography (silica; AcOEt in heptane 0/100 to 50/50). The desired fractions were collected and the solvents evaporated in vacuo to yield 2[(2-fluorobenzyl)oxy]-5-(4-fluorophenyl)-6,7-dihydropyrazolo[1,5-a]pyrazin-4(5H)-one (0.109 g, 85% yield) as a white solid. C19H15F2N3O2. 1H NMR (500 MHz, CDCl3) δ ppm 4.14 (dd, J=6.8, 5.1 Hz, 2H), 4.37 (dd, J=6.9, 5.2 Hz, 2H), 5.30 (s, 2H), 6.37 (s, 1H), 7.04-7.15 (m, 3H), 7.17 (td, J=7.5, 0.9 Hz, 1H), 7.28-7.36 (m, 3H), 7.53 (td, J=7.4, 1.4 Hz, 1H).

Provenance & Evidence