Example 3 Synthesis of 3-aminopyrazine-2-carbonitrile (Intermediate 2): Intermediate 1 (3-aminopyrazine-2-carboxamide, 3.5 g, 25 mmol) was dissolved in DMF (40 mL) at room temperature, followed by slow dropwise addition of POCl3 (4.5 mL, 49 mmol). The reaction mixture was heated at 80 °C with stirring for 15 min, after which it was cooled to room temperature. The reaction mixture was slowly poured into ice water and the pH was adjusted to neutral with 10% NaOH solution. The precipitated solid was collected by filtration and redissolved in 5% HCl solution. The acidic solution was heated at 70 °C for 30 min, followed by filtration to separate the solid product. The target compound 3-aminopyrazine-2-carbonitrile was obtained as a brown solid (1.7 g, 56% yield) after sufficient washing with water. The product was characterized by 1H NMR (500 MHz, DMSO-d6): δ 8.28 (d, J=2.4 Hz, 1H), 7.90 (d, J=2.4 Hz, 1H), 7.32 (br s, 2H). Mass spectrum (ES+): m/z 121 ([M+H]+).
