1416740-16-3

24241-18-7

1416740-16-3

Step 3: Synthesis of 2-bromo-7-nitro-5H-pyrrolo[2,3-b]pyrazine 2-Bromo-5H-pyrrolo[2,3-b]pyrazine (20 g, 101.0 mmol) was dissolved in pre-cooled concentrated sulfuric acid (140.0 mL) to form a bright orange solution. Concentrated nitric acid (12.73 g, 8.470 mL, 202.0 mmol) was slowly added dropwise over a period of 30 min under stirring conditions and ensuring that the temperature of the reaction was maintained below 10 °C (the color of the solution gradually changed to a clear red). After the dropwise addition was completed, the reaction mixture was removed from the ice bath and allowed to warm up slowly to room temperature, and stirring was continued at room temperature for 1 hour. Subsequently, the reaction mixture was slowly poured into crushed ice and a yellow solid was precipitated. The solid product was collected by filtration and washed well with cold water to afford 2-bromo-7-nitro-5H-pyrrolo[2,3-b]pyrazine as a yellow solid (21.76 g, 88.7% yield). Mass spectrometry analysis (ES+): m/z 244.87.