1185428-32-3

Step 3. Synthesis of 2-bromo-5H-pyrrolo[2,3-b]pyrazine-7-carbaldehyde. To a suspension of 2-bromo-5H-pyrrolo[2,3-b]pyrazin-7-ylmethanol (127 g, 562 mmol) in acetone (2.5 L), Jones reagent (253 mL, 674 mmol) was slowly added dropwise. After the dropwise addition, the reaction mixture was stirred at room temperature for 50 min, and gradual clarification of the suspension and precipitation of a brown solid was observed.Preparation of Jones' reagent (2.67 M) required the careful addition of concentrated H2SO4 (184 mL) to CrO3 (213.6 g) at less than 10 °C, followed by dilution with H2O up to 800 mL.Upon completion of the reaction, the reaction was quenched with isopropanol ( 60 mL) to quench the reaction and the solid was separated by filtration. The filter cake was washed with acetone (1L x 2), and the filtrates were combined and concentrated to afford the target product 2-bromo-5H-pyrrolo[2,3-b]pyrazine-7-carbaldehyde (320 g, 84.4% yield) as a yellow solid.

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