Methylamine → 5-Methyl-2-nitro-4,5,6,7-tetrahydropyrazolo[1,5-A]pyrazine

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Reaction Steps

A 1-L single-neck round-bottomed flask equipped with a magnetic stirrer and nitrogen inlet was charged with THF (350 mL), 124c (10.0 g, 32.2 mmol), 2M methylamine solution in THF (113 mL, 225 mmol) and stirred at room temperature for 72 h. After this time the reaction was concentrated to dryness under reduced pressure, and the resulting solid was stirred with a mixture of ethyl acetate (75 mL) and 10% aqueous potassium carbonate (75 mL). The aqueous layer was separated and extracted with ethyl acetate (2×75 mL). The combined organic extracts were washed with 10% aqueous potassium carbonate (75 mL), followed by brine (50 mL) and dried over sodium sulfate. The drying agent was removed by filtration, and the filtrate concentrated under reduced pressure to afford 128a in 97% yield (5.70 g) as a yellow solid. 1H NMR (300 MHz, CDCl3) δ 6.62 (s, 1H), 4.28 (t, 2H, J=5.4 Hz), 3.67 (s, 2H), 2.95 (t, 2H, J=5.4 Hz), 2.52 (s, 3H); MS (ESI+) m/z 183.0 (M+H)

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