Yield:76537-18-3 87%

Reaction Conditions:

with N-Bromosuccinimide in dichloromethane at 20; for 0.25 h;

Steps:

Preparation of 2-amino-3-bromo-5-chloropyrazine(18a)

17 (1.1 g, 8.5 mmol) was dissolved in dichloromethane (25 mL) followed by the addition of NBS (1.52 g, 8.5 mmol) in batches over a period of 15 min at room temperature. When the reaction was completed, saturated aqueous Na2CO3 solution (10 mL) was added. After stirring for 10 min, the mixture was partitioned between dichloromethane (100 mL) and water (100 mL). The organic layer was dried over anhydrous Na2SO4, decolorized with activated charcoal (0.5 g), and concentrated to give a yellow solid (1.53 g, yield 87%). 2-Amino-3-bromo-5-chloropyrazine (18a) Yield: 87%, yellow solid, M.p.: 108-110 °C. 1H NMR(400 MHz, CDCl3): δ 7.97 (s, 1H), 5.08 (s, 2H). 1H NMR(400 MHz, DMSO-d6): δ 8.10 (s, 1H), 6.99 (s, 2H). 13CNMR (125 MHz, CDCl3):δ 151.66, 140.26, 134.75, 123.27. EI-MS m/z: 207 (M+, Cl35, Br79,76), 209 (M+, Cl37,Br79 and Cl35,Br81,100), 211 (M+, Cl37, Br 81,26), 128 (M+,Cl35,-Br, 75), 130 (M+, Cl37,-Br, 25), 101 (M+, Cl35,-Br,-HCN, 30), 103 (M+, Cl37,-Br, -HCN, 10).

References:

Guo, Qi;Xu, Mingshuo;Guo, Shuang;Zhu, Fuqiang;Xie, Yuanchao;Shen, Jingshan [Chemical Papers,2019,vol. 73,# 5,p. 1043 - 1051]