Monobasic potassium phosphate → 2-bromo-5-((2-(trimethylsilyl)ethoxy)methyl)-5H-pyrrolo[2,3-b]pyrazine-7-carboxylic acid

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In a flask 2-bromo-5-(2-trimethylsilanylethoxymethyl)-5H-pyrrolo[2,3-b]pyrazine-7-carbaldehyde (3.11 g, 8.74 mmol) was dissolved in dioxane (120 mL) and H2O (30 mL) and the mixture cooled at 0° C. Sufamic acid (5.09 g, 52.4 mmol) was added, followed by a solution of sodium chlorite (1.28 g, 11.4 mmol) and potassium dihydrogen phosphate (14.3 g, 104.9 mmol) in H2O (75 mL) via an addition funnel over 15 min. The mixture was allowed to warm to room temperature over 2 h. The resulting yellow solid was filtered off, washed with H2O and hexane and dried. The filtrate was then extracted with EtOAc, and the combined organics washed with brine, dried over MgSO4 and concentrated to give additional product. In total 3.71 g of 2-bromo-5-(2-trimethylsilanylethoxymethyl)-5H-pyrrolo[2,3-b]pyrazine-7-carboxylic acid was obtained as a yellow solid. 1H NMR (CDCl3, 400 MHz): δ (ppm) 8.52 (s, 1H), 8.42 (s, 1H), 5.73 (s, 2H), 3.56-3.65 (m, 2H), 0.90-1.02 (m, 2H), 0.00 (s, 9H).

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