General procedure for the synthesis of 2-bromo-5-cyano-3-methylpyridine from 4-toluenesulfonyl cyanide: n-butyllithium (2.5 M hexane solution, 2.59 mL, 6.48 mmol) was added dropwise to an ether solution (65 mL) of 2,5-dibromo-3-methylpyridine (1.48 g, 5.89 mmol) at -78 °C. After 40 min of reaction, p-toluenesulfonyl cyanide (1.17 g, 6.49 mmol) was added, followed by slow warming of the reaction mixture to 0 °C. After completion of the reaction, the reaction was quenched with saturated aqueous NaHCO3 (50 mL) and extracted with CHCl3 (100 mL). The organic layer was dried with Na2S2O5 and concentrated to give the crude product. The crude product was purified by fast column chromatography (EtOAc/hexane as eluent) to give 310 mg (27% yield) of 2-bromo-5-cyano-3-methylpyridine as a white solid.
