Compound (100a) (2.0 g), cesium carbonate (3.41 g), and 4-fluoro-3-formylbenzonitrile (1.25 g) were suspended in acetonitrile (23 mL), followed by reflux for 3 hr. The reaction solution was distributed between chloroform and water, and the organic layer was washed with saturated saline. The organic layer after the washing was dried over anhydrous sodium sulfate, and then the solvent was distilled away. The residue was purified by neutral silica gel column chromatography (hexane/ethyl acetate) to obtain compound (125a) (2.00 g, 67%) as a white solid.
