Step 2: To a carbon disulfide solution (300 mL) containing AlCl3 (76.4 g, 572.6 mmol) was added 3-(3,4-difluorophenyl)propionyl chloride (33.4 g, 163.6 mmol) to a carbon disulfide solution (120 mL) dropwise over 10 minutes at 0°C. The reaction mixture was stirred at 0°C for 30 minutes and then heated to reflux for 4 hours. After the reaction was completed, it was cooled to room temperature and the reaction solution was carefully poured onto crushed ice. The carbon disulfide layer was separated and the aqueous layer was extracted with ethyl acetate. The organic layers were combined, dried with MgSO4 and concentrated under reduced pressure to remove the solvent. The residue was purified by silica gel column chromatography (eluent: 5-10% ethyl acetate/hexane) to afford 5,6-difluoro-2,3-dihydro-1H-inden-1-one 19.3 g (114.9 mmol, 70% yield) as a white solid.1H NMR (400 MHz, CDCl3) δ ppm: 7.50 (t, 1H, J=8.0 Hz),. 7.24 (t, 1H, J=6.6Hz), 3.09 (t, 2H, J=5.5Hz), 2.72-2.69 (m, 2H).
