To a suspension of 7-(benzyloxy)-4-chloroquinoline (10 g, 37.1 mmol) and 4-nitrophenol (6.2 g, 44.5 mmol) in toluene (10 mL) was added DIPEA (6.2 g, 48.2 mmol). The reaction mixture was refluxed at 115° C. for 12 hours, then cooled down to room temperature. DCM (50 mL) was added to the mixture, and the resulted solution was washed with 1 M NaOH (30 mL each) several times till the water phase was colorless. The organic phase was concentrated in vacuo to afford a brown solid (13.2 g, 95.7%). The solid was stirred in 95% EtOH (30 mL) at room temperature for 12 hours, and filtered to give the title compound as a gray-brown solid (12.1 g, 91.7%).
