General procedure for the synthesis of 3-chloro-2-methyl-5-nitropyridine from 2,3-dichloro-5-nitropyridine and methylboronic acid: Cesium carbonate (338 mg, 1.04 mmol), methylboronic acid (47 mg, 0.78 mmol) and tetrakis(triphenylphosphine)palladium (60 mg, 0.052 mmol) were sequentially added to a solution of 1,4-dioxane (3 mL) containing 2,3-dichloro-5-nitropyridine (191 mg, 1.00 mmol), protected by argon gas. -5-nitropyridine (191 mg, 1.00 mmol) to a solution of 1,4-dioxane (3 mL). The reaction mixture was stirred at 100 °C for 6 hours. Upon completion of the reaction, the reaction solution was cooled to room temperature, water (10 mL) was added and extracted with ethyl acetate (3 × 10 mL). The organic phases were combined, washed with saturated saline (10 mL) and dried over anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure to give the crude product. Purification by column chromatography (eluent: petroleum ether/ethyl acetate = 5:1) afforded 3-chloro-2-methyl-5-nitropyridine (344 mg, 90% yield) as a pale yellow solid.
