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With bromine; In ethanol; for 1.5h;Heating / reflux;
To the suspension of imidazo[1,2-a]pyrazine-2-carboxylic acid ethyl ester (0.3 g, 0.0016 mol) in anhydrous ethanol (7 mL), the chilled solution of bromine (0.16 mL, 0.0032 mol) in anhydrous ethanol (7 mL) was added dropwise and the resulting mixture was heated at reflux under continuous nitrogen flow for 1.5 hours. The reaction mixture was concentrated under reduced pressure and treated with the saturated solution of sodium bicarbonate in water (50 mL). The aqueous layer was extracted with ethyl acetate (3x25 mL), the combined organic extracts were dried with magnesium sulfate and concentrated. The residue was suspended in heptane (30 mL) and the precipitate was collected by filtration and dried to yield 5-bromo- imidazo [1,2-a]pyrazine-2-carboxylic acid ethyl ester (0.075 g, 0.00028 mol) as a yellow solid. m/z: (M + H) + 270,272.