Hydrochloric Acid → 3,4-Dihydropyrazino[1,2-a]indol-1(2H)-one

A 500-mL Parr reactor bottle was purged with nitrogen and charged with 10% palladium on carbon (50% wet, 3.47 g dry weight), 102a (8.00 g, 35.0 mmol), 12% hydrochloric acid (17.5 mL, 70 mmol), ethyl acetate (150 mL) and ethanol (100 mL). The bottle was attached to a Parr hydrogenator, evacuated, charged with hydrogen gas to a pressure of 50 psi and shaken for 6 h. After this time, the hydrogen was evacuated, and nitrogen was charged into the bottle. Celite 521 (10.0 g) was added, and the mixture was filtered through a pad of Celite 521. The filter cake was washed with ethanol (2×50 mL), and the combined filtrates were concentrated to dryness under reduced pressure. The residue was partitioned between ethyl acetate (400 mL) and 10% aqueous potassium carbonate (300 mL). The organic layer was separated, and the aqueous layer was extracted with ethyl acetate (3×200 mL). The combined organic layers were dried over sodium sulfate and concentrated under reduced pressure. The residue was triturated with ethanol (5 mL) to afford a 70% yield (4.57 g) of 102b as an off-white solid: mp 228-230° C.; 1H NMR (300 MHz, CDCl3) d 7.73 (d, 1H, J=8.1 Hz), 7.34 (m, 3H), 7.18 (m, 1H), 6.75 (br s, 1H), 4.29 (t, 2H, J=5.4 Hz), 3.84 (m, 2H); MS (ESI+) m/z 187.1 (M+H).

1. customA 500-mL Parr reactor bottle was purged with nitrogen
2. customevacuated
3. additioncharged with hydrogen gas to a pressure of 50 psi
4. customAfter this time, the hydrogen was evacuated
5. additionnitrogen was charged into the bottle
6. additionCelite 521 (10.0 g) was added
7. filtrationthe mixture was filtered through a pad of Celite 521
8. washThe filter cake was washed with ethanol (2×50 mL)
9. concentrationthe combined filtrates were concentrated to dryness under reduced pressure
10. customThe residue was partitioned between ethyl acetate (400 mL) and 10% aqueous potassium carbonate (300 mL)
11. customThe organic layer was separated
12. extractionthe aqueous layer was extracted with ethyl acetate (3×200 mL)
13. dry with materialThe combined organic layers were dried over sodium sulfate
14. concentrationconcentrated under reduced pressure
15. customThe residue was triturated with ethanol (5 mL)

ORD record

ord-ff14e836f3fd41af8772f71f926e4706

Source dataset

uspto-grants-2013_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08618107B2