Indoline Oxidation via Dioxygen Activation

A clean, oven-dried Schlenk tube with previously placed magnetic stir-bar was charged with nitrobenzene (184.7 mg, 1.5 mmol), ^tBuOK (224.5 mg, 2.0 mmol) in dry DMF (5 mL) solvent at room temperature under argon atmosphere. After the reaction mixture was stirred at −30 °C for 10 min, the reaction was evacuated and back filled with O₂ (1.0 atm) and this sequence was repeated for three additional times. After indoline (59.6 mg, 0.5 mmol) was added, the reaction stirred at −30 °C and monitored by TLC. After the complete consumption of indoline, the reaction mixture was quenched with water (5 mL), diluted with ethyl acetate, and extracted with ethyl acetate (25 mL × 3). The combined organic phases were washed with brine (5 mL), dried over Na₂SO₄ and concentrated in vacuo. The residue was purified by neutral Al₂O₃ column chromatography (PE: EtOAc = 40:1, v/v).