Step 1 (MW-Si): sodium borohydride (5.3 g, 140.84 mmol) was slowly added to a methanolic solution (200 mL) of 2,3-difluorobenzaldehyde (20 g, 140.84 mmol) in three batches (each batch was separated by more than 25 min) at 0 °C. The temperature rose to 50°C due to exothermic during the reaction. The reaction mixture was continued to be stirred for 1 hour and then the solvent was removed by distillation under reduced pressure. Subsequently, the residue was extracted by adding ethyl acetate and saturated ammonium chloride solution to the residue. After separation of the organic layer, the aqueous layer was extracted again with ethyl acetate. All organic layers were combined, washed sequentially with water and saturated brine, and then dried with anhydrous sodium sulfate. Finally, 20 g of MW-Si (2,3-difluorobenzyl alcohol) was obtained by vacuum concentration as a colorless liquid, which could be used in subsequent steps without further purification.
