1,1-Dichloroacetone → 4,5-Difluoro-2-methoxybenzaldehyde

7.29 ml (66.3 mmol) of titanium tetrachloride were added while stirring to a solution, cooled to 0°, of 5.73 g (39.8 mmol) of 3,4-difluoroanisole in 30 ml of anhydrous dichloromethane. Subsequently, the mixture was treated dropwise over 10 minutes with 3.51 ml (39.6 mmol) of 1,1-dichloromethyl methyl ketone and stirred at room temperature for one hour. The mixture was poured into 100 ml of ice-water, extracted twice with 150 ml of dichloromethane each time and the combined organic phases were washed once with 100 ml of water and once with 100 ml of saturated sodium chloride solution. After drying over magnesium sulfate concentration was carried out in a vacuum. The crude product obtained was purified by column chromatography on silica gel (hexane/ethyl acetate 4:1). There were obtained 5.8 g (84%) of 4,5-difluoro-2-methoxybenzaldehyde as a white solid with m.p. 74°.