Tert-butyl 4-methyl-2-(4-nitrophenyl)-3-oxopiperazine-1-carboxylate → Tert-butyl 2-(4-aminophenyl)-4-methyl-3-oxopiperazine-1-carboxylate

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Reaction Steps

A 250-mL Parr hydrogenation bottle was purged with nitrogen and charged with 10% palladium on carbon (50% wet, 10 mg dry weight) followed by a solution of tert-butyl 4-methyl-2-(4-nitrophenyl)-3-oxopiperazine-1-carboxylate (102i) (1.00 g, 2.99 mmol) in ethanol (40 mL). The bottle was evacuated, then charged with hydrogen gas to a pressure of 50 psi and shaken at 50 psi for 18 h at room temperature on a Parr hydrogenation apparatus. After this time the hydrogen was evacuated and nitrogen charged into the bottle. The resulting suspension was filtered through a pad of Celite 521. The filter cake was washed with ethanol (2×20 mL), and the filtrate was evaporated to dryness under reduced pressure to afford a 99% yield (904 mg) of tert-butyl 2-(4-aminophenyl)-4-methyl-3-oxopiperazine-1-carboxylate 102j as a yellow syrup: 1H NMR (300 MHz, DMSO-d6) δ 6.93 (d, 2H, J=8.4 Hz), 6.51 (d, 2H, J=8.4 Hz), 5.27 (bs, 1H), 5.09 (s, 1H), 3.83 (d, 1H, J=10.8 Hz), 3.44 (m, 1H), 3.24 (m, 2H), 2.84 (s, 3H), 1.40 (s, 9H); MS (ESI+) m/z 306.2 (M+H).

Provenance & Evidence