Step 1: Synthesis of pyrazine-2-hydrazine from 2-chloropyrazine. 2-Chloropyrazine (2.0 g, 17.5 mmol) was slowly added dropwise to 35% aqueous hydrazine hydrate (25.8 g, 97.8 mmol) at 63-65°C, and the rate of acceleration of the dropwise addition was strictly controlled so as to maintain the temperature of the reaction not exceeding 65°C. After the dropwise addition was completed, the reaction mixture was heated further up to 65°C and kept at this temperature. The reaction mixture was stirred overnight and cooled to room temperature. The solvent was removed by distillation under reduced pressure to give the product pyrazine-2-hydrazine (1.5 g, 75% yield) as a yellow powder. Mass spectrometry (ESI) analysis: calculated value C4H6N4[M]: 110.1; measured value: 111.4 [M+H]+.1H NMR (400 MHz, CD3OD) δ 8.10 (d, J=1.6 Hz, 1H), 8.00 (dd, J=3.2,1.6 Hz, 1H), 7.73 (d, J=3.2 Hz, 1H).
