Step 1-A: Under dry conditions, 2,5-diiodofluorobenzene (804 mg, 2.31 mmol) was dissolved in tetrahydrofuran (8 mL) and the solution was cooled to -78°C (using an external cooling bath). Subsequently, a tetrahydrofuran solution of 2.0 M isopropylmagnesium chloride (1.44 mL, 2.89 mmol) was slowly added via syringe. The reaction mixture was stirred at -78 °C for 30 min, during which time the cooling bath temperature was allowed to naturally rise to -50 °C. Afterwards, the reaction mixture was transferred to an ice/water bath to cool to 0 °C and anhydrous N,N-dimethylformamide (425 μL, 5.78 mmol) was added dropwise. After addition, the reaction mixture was continued to be stirred at 0 °C for 10 min, and then raised to room temperature and stirred for 5 min. The progress of the reaction was monitored by thin-layer chromatography (TLC) and after confirming the completion of the reaction, the reaction was quenched with saturated aqueous ammonium chloride solution (8 mL). The aqueous phase was extracted with diethyl ether (2 x 20 mL) and the organic layers were combined and dried over anhydrous sodium sulfate. The organic phase was concentrated under reduced pressure and the resulting crude product was purified by silica gel column chromatography, eluting with a gradient of 0 to 15% v/v ethyl acetate/hexane to afford 2-fluoro-4-iodobenzaldehyde as a white fluffy solid (389 mg, 67% yield).
