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

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, CDCl3δ 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).

1. customA 500-mL Parr hydrogenation bottle was purged with nitrogen
2. customThe bottle was evacuated
3. additioncharged with hydrogen gas to a pressure of 25 psi
4. customThe hydrogen was then evacuated
5. additionnitrogen charged to the bottle
6. customThe catalyst was removed by filtration through a pad of CELITE® 521
7. concentrationthe filtrate concentrated under reduced pressure
8. customThe resulting residue was purified by column chromatography
9. washeluting with 3% methanol in methylene chloride
10. additionThe fractions containing 129b
11. customwere collected
12. customto afford
13. concentrationafter concentrating under reduced pressure

ORD record

ord-69264b79f72d495b9c20b111c66079fa

Source dataset

uspto-grants-2016_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09238655B2