Step 3) Synthesis of 7-(benzyloxy)-4-chloroquinoline: 7-(benzyloxy)quinolin-4-ol (72 g, 287 mmol) was suspended in toluene (134 mL), and phosphorus trichloride (44 g, 287 mmol, source: Tianjin FuChen Chem. Co. Ltd.) was added. The suspension was heated to 120 °C and maintained for 1 hour. After completion of the reaction, the mixture was cooled to 70 °C and diluted with EtOAc (600 mL). The resulting mixture was stirred in an ice bath for 30 min and cooled to 15 °C. Subsequently, the mixture was neutralized with 3M NaOH aqueous solution to pH 7~8, keeping the solution temperature below 20°C during the process. The aqueous layer was separated and the organic layer was extracted with EtOAc. The combined organic layers were washed with brine (200 mL), dried over anhydrous Na2SO4, and concentrated in vacuum to give 7-benzyloxy-4-chloroquinoline as a light yellow solid (70.8 g, 91.6% yield). Mass spectrum (ESI, positive ion mode) m/z: 270.1 [M + 1]; 1H NMR (400 MHz, DMSO-d6) δ: 5.31 (s, 2H), 7.35 (t, 1H), 7.42 (t, J = 7.2Hz, 2H), 7.47 (dd, J = 2.8Hz, J = 9.2Hz, 1H), 7.52 (d, J = 7.6 Hz, 2H), 7.13 (t, J = 4.8 Hz, 2H), 8.11 (d, J = 9.6 Hz, 1H), 8.75 (d, J = 4.8 Hz, 1H).
