Bromine → 2,3-Dibromo-4-methylpyridine

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Reaktionsschritte

Bromine (0.35 mL, 6.8 mmol) was added dropwise to a solution of 3-bromo-4-methyl-pyridin-2-ylamine (0.44 g, 2.4 mmol) in 48% HBr (3 mL) at −10° C. to give an orange slurry. After 5 minutes NaNO2 (0.47 g, 6.8 mmol), dissolved in water (1.5 mL), was added dropwise over 5 minutes. The dark brown mixture was slowly warmed to 10° C. over 3.5 h and then cooled to 0° C. and quenched with 10N NaOH until pH˜12. The resulting orange slurry was extracted with CH2Cl2 (3×50 mL), dried (Na2SO4), filtered and concentrated in vacuo to give an orange/brown solid. Purification by column chromatography on silica gel (Hexanes:Et2O, 7:3, v/v) yielded 2,3-dibromo-4-methyl-pyridine (0.28 g, 47%) as a pale yellow solid. 1H NMR (CDCl3) δ 2.48 (s, 3H), 7.11 (d, 1H, J=6.0 Hz), 8.16 (d, 1H, J=6.0 Hz).

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