Sodium hydride (0.183 g, a 55% dispersion in paraffin liquid) was added to a solution of compound (1d) (0.940 g) in N,N-dimethylformamide (hereinafter referred to as DMF, 6 mL) at room temperature, followed by stirring for 30 min. Subsequently, 2-bromo-4-fluorobenzonitrile (0.838 g) was added to the reaction solution, followed by stirring at 60° C. for 1 hr. After cooling, water was added to the reaction solution, followed by extraction with ethyl acetate. The organic layer was washed with water and saturated saline in this order and was dried over anhydrous sodium sulfate. After distillation of the solvent, the residue was purified by neutral silica gel column chromatography (chloroform/methanol) to obtain compound (1e) (0.56 g, 38%) as a white solid.
