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0 °C

A 250-mL single-neck round-bottomed flask equipped with a magnetic stirrer was purged with nitrogen, charged with ethyl 4-nitrophenylpyruvate (5.00 g, 22.4 mmol) and anhydrous methanol (112 mL). The resulting solution was cooled to 0° C. with an ice bath, and N-methylethylenediamine (1.66 g, 22.4 mmol) was added dropwise. After addition was complete, the bath was removed and the reaction was stirred at room temperature for 18 h. After this time the reaction was concentrated under reduced pressure. The residue was purified by column chromatography to afford 1-methyl-3-(4-nitrophenyl)-5,6-dihydropyrazin-2(1H)-one (102h) in 20% yield (1.02 g) as a yellow solid: mp 191-192° C.; 1H NMR (300 MHz, DMSO-d6) δ 8.26 (d, 2H, J=6.9 Hz), 8.05 (d, 2H, J=7.2 Hz), 3.94 (t, 2H, J=6.3 Hz), 3.55 (t, 2H, J=6.3 Hz), 3.02 (s, 3H); MS (ESI+) m/z 234.1 (M+H).

1. customA 250-mL single-neck round-bottomed flask equipped with a magnetic stirrer
2. customwas purged with nitrogen
3. additionAfter addition
4. customthe bath was removed
5. concentrationAfter this time the reaction was concentrated under reduced pressure
6. customThe residue was purified by column chromatography