71924-62-4

Step 1: Preparation of 3,4-dimethoxyfluorobenzene

10.0 g (65.4 mmol) of 3,4-dimethoxyaniline was dissolved in 40.0 mL of HBF₄ (aq 41%) and 40 mL of CH3OH. The solution was cooled to -5 °C in an ice-salt bath. 10.0 mL of n-butyl nitrite was added dropwise under electromagnetic stirring. After stirring for 90 minutes, 200 mL of cold diethyl ether was added. The solution was allowed to stand at 0 °C for 2 hours, and a solid precipitated out. The solution was filtered, washed with 50 mL of cold diethyl ether, and dried under vacuum to obtain 15.0 g (59.8 mmol) of a light purple solid, with a yield of 90%.

20.4 g (81.3 mmol) of the above solid was placed in a 250 mL round-bottom flask, connected to a receiving flask with a U-tube, and cooled in a CaCl2- ice bath. The bottom of the flask was heated with a gas lamp until the solid was completely decomposed, yielding a brown oily liquid. 10 mL of diethyl ether was added to dissolve the liquid, and it was washed once with 5 mL of 10% NaOH solution and once with 5 mL of water. The aqueous layer was extracted twice with 10 mL of diethyl ether. The organic layers were combined, dried over excess anhydrous sodium sulfate, filtered, and the solvent was removed by rotary evaporation. The liquid was purified by vacuum distillation to obtain 5.2 g of a pale yellow oily liquid, with a yield of 42%.

Step 2: Preparation of 2-fluoro-4,5-dimethoxybenzaldehyde.

5.70 g (36.5 mmol)