2-nitro-6,7-dihydro-4H-pyrazolo[5,1-c][1,4]oxazine → 6,7-dihydro-4H-pyrazolo(5,1-c)(1,4)oxazin-2-amine

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Reaction Steps

A 500-mL Parr hydrogenation bottle was purged with nitrogen and charged with 129a (1.01 g, 5.92 mmol), 10% palladium on carbon (50% wet, 125 mg dry weight) and ethanol (50 mL). The bottle was evacuated, charged with hydrogen gas to a pressure of 25 psi and shaken for 2 h on a Parr hydrogenation apparatus. The hydrogen was then evacuated and nitrogen charged to the bottle. The catalyst was removed by filtration through a pad of CELITE® 521 and the filtrate concentrated under reduced pressure. The resulting residue was purified by column chromatography using 400 cc of silica gel and eluting with 3% methanol in methylene chloride. The fractions containing 129b were collected to afford, after concentrating under reduced pressure, a 73% yield (601 mg) of 129b as a yellow solid: mp 74-76° C. 1H NMR (300 MHz, CDCl3 δ 5.37 (s, 1H), 4.72 (s, 2H), 4.07 (t, 2H, J=5.1 Hz), 3.98 (t, 2H, J=5.1 Hz), 3.57 (br s, 2H); MS (ESI+) m/z 140.4 (M+H).

Provenance & Evidence