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

Participants

Reaction Steps

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).

Provenance & Evidence