Diisopropylethylamine (435 μl, 2.5 mmol) was added to a dichloromethane (10 ml) solution of 4-amino-6-fluoro-5-hydroxy-2-methyl-biphenyl-3-carbonitrile (I-41) (353 mg, 1.46 mmol), then after cooling with ice, O-acetylsalicyloyl chloride (318 mg, 1.6 mmol) was added, followed by stirring at the same temperature for 30 minutes. With cooling with ice, water was added, followed by extraction with ethyl acetate. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, then the solvent was evaporated away under reduced pressure. In xylene (30 ml) and in the presence of a catalytic amount of p-tosylic acid, the resulting residue was heated under reflux for 2 hours with a Dean-Stark device. After cooling, the solvent was evaporated away, and the resulting residue was dissolved in chloroform, washed with saturated sodium bicarbonate water, then dried over anhydrous sodium sulfate, and the solvent was evaporated away under reduced pressure. The resulting residue was washed with a mixed solvent of isopropyl ether and ethanol, and the solid was collected by nitration to obtain the entitled compound (320 mg, 64%) as a pale yellow solid.
