General procedure for the synthesis of 3,4-bis(difluoromethoxy)benzaldehyde from sodium difluorochloroacetate and 3,4-dihydroxybenzaldehyde: Sodium difluorochloroacetate (88 g, 58 mmol) was added to a DMF (200 mL) containing 3,4-dihydroxybenzaldehyde (20 g, 14 mmol), potassium carbonate (80 g, 58 mmol) and water (10 mL, 58 mmol). mL) in a suspension. The suspension was heated to 80 °C, kept for 16 h, and then cooled to room temperature. The reaction mixture was diluted with water and the aqueous phase was extracted with EtOAc. The combined organic phases were washed sequentially with water and brine, dried and concentrated. The residue was partially purified by column chromatography using 5-10% EtOAc/petroleum ether as eluent to afford 3,4-bis(difluoromethoxy)benzaldehyde (22.5 g, 65%) as a colorless oil. Its NMR hydrogen spectrum (400 MHz, CDCl3) data were: δH 6.60 (t, J = 72 Hz, 1H, OCHF2), 6.64 (t, J = 72 Hz, 1H, OCHF2), 7.42 (d, J = 8.0 Hz, 1H, H5), 7.76-7.78 (m, 2H, H2, H6), 9.96 (s, 1H CHO); NMR carbon spectrum (125 MHz, CDCl3) data were: δC 115.2 (t, J = 259 Hz), 115.4 (t, J = 259 Hz), 121.5, 122.2, 128.5, 134.2, 142.4, 147.0, 189.7; and infrared spectroscopy (cm-1) data were 794, 1038 1381, 1509, 1698. 3,4-bis(difluoromethoxy)benzaldehyde co-eluted with about 10-20% of unidentified colorless oil had NMR hydrogen spectral (400 MHz, CDCl3) data of δH 7.13 (s, 1H), 7.19 (d, J = 8.0 Hz, 1H), 7.30 (s, 1H), 7.59 (d, J = 1.5 Hz, 1H), 7.61 (dd, J = 1.5 Hz, 8.0 Hz, 1H), 9.91 (s, 1H).
