At 0°C, 70% m-CPBA (1 mol equivalent) was added in portions to a stirred solution of 5.5-6.7 mmol of 4-phenylpyridine in 2 mL of CHCl3. The resulting mixture was stirred at room temperature for 12 h, during which time the feedstock was observed to be completely consumed by TLC. The reaction mixture was diluted with CHCl3, and solid K2CO3 (4 mol equivalent) was added. The mixture was stirred for another 10 min, the solid was separated by filtration, the filtrate was dried with Na2SO4, and concentrated under reduced pressure to produce 4-phenylpyridine-N-oxide in 86-90% yield.
