General procedure for the synthesis of 2-amino-3-methylaminopyrazine from 2-amino-3-chloropyrazine (5.20 g, 40.1 mmol) and monomethylamine: 2-amino-3-chloropyrazine (5.20 g, 40.1 mmol) and CuSO4 (640 mg, 4.01 mmol) in 12 M aqueous methylamine solution (40.0 mL, 480 mmol) were The mixture was placed in a microwave reactor and the reaction was stirred at 120 °C for 3 hours. Upon completion of the reaction, the reaction mixture was cooled to room temperature and concentrated under reduced pressure to remove the solvent. The residue was purified by fast column chromatography (silica gel as stationary phase and chloroform solution with 0-5% methanol as eluent) to afford the target product 2-amino-3-methylaminopyrazine (3.99 g, 80% yield) as a yellow solid. The structure of the product was confirmed by 1H NMR (DMSO-d6) and mass spectrometry (ESI): 1H NMR (DMSO-d6) δ 2.81 (d, 3H, J=4.7 Hz), 5.84 (s, 2H), 6.13 (q, 1H, J=4.7 Hz), 7.09 (d, 1H, J=3.1 Hz), 7.23 (d, 1H, J=3.1 Hz ); MS (ESI) m/z 125 [M+H]+.
