Step 3 - Preparation of 2-chloro-4,5-difluorobenzaldehyde (110): (2-chloro-4,5-difluorophenyl)-methanol (120,240 g, 0.0134 mol) was dissolved in dichloromethane (40 mL) and Dess-Martin periodinane (6.84 g, 0.0161 mol) was added. The reaction mixture was stirred at room temperature for 10 minutes. After completion of the reaction, the mixture was poured into aqueous potassium carbonate solution and extracted with ethyl acetate. The organic layers were combined, dried with anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure, and the resulting crude product was purified by silica gel column chromatography, using a 30% hexane solution of ethyl acetate as eluent, to give the white solid product 2-chloro-4,5-difluorobenzaldehyde (110, 1.7 g, 71.6% yield).
