1-Bromo-4-fluorobenzene → 2-(benzyloxy)-5-(4-fluorophenyl)-6,7-dihydropyrazolo[1,5-a]pyrazin-4(5H)-one

Participants

Reaction Conditions

Reaction Steps

Copper (I) iodide (0.74 g, 3.88 mmol) was added to a stirred suspension of 2-(benzyloxy)-6,7-dihydropyrazolo[1,5-a]pyrazin-4(5H)-one (1.5 g, 6.17 mmol), 4-bromofluorobenzene (2.03 mL, 18.5 mmol), N,N-dimethylethylenediamine (0.73 mL, 6.78 mmol) and K2CO3 (2.13 g, 15.42 mmol) in toluene (90 mL). The reaction mixture was stirred at 140° C. for 16 hours. The solvent was evaporated in vacuo. The crude product was purified by flash column chromatography (silica; AcOEt in DCM 0/100 to 30/70). The desired fractions were collected, the solvents evaporated in vacuo and the residue triturated with pentane to yield 2-(benzyloxy)-5-(4-fluorophenyl)-6,7-dihydropyrazolo[1,5-a]pyrazin-4(5H)-one (1.8 g, 86% yield) as a white solid. C19H16FN3O2. 1H NMR (500 MHz, CDCl3) δ ppm 4.07-4.17 (m, 2H), 4.32-4.40 (m, 2H), 5.22 (s, 2H), 6.35 (s, 1H), 7.07-7.16 (m, 2H), 7.27-7.33 (m, 2H), 7.32-7.36 (m, 1H), 7.36-7.42 (m, 2H), 7.45 (d, J=7.2 Hz, 2H).

Provenance & Evidence