A charge of 134.6 g (0.500 mol) of 2,5-dichloro-4′-fluorobenzophenone, 50.3 g (0.750 mol) of pyrrole, 76.0 g (0.550 mol) of potassium carbonate and 840 mL of dehydrated N,N′-dimethylacetamide was weighed into a 2-L three-neck flask equipped with a stirrer, a thermometer, a cooling tube and a nitrogen gas introducing tube. The reaction solution was heated under nitrogen atmosphere to 100° C. for 3 hours using an oil bath. After the disappearance of raw materials was confirmed by thin layer chromatography, the reaction solution was left to cool to room temperature. The reaction solution was then gradually added to 3 L of water to coagulate a product, which was filtered. The product obtained by filtration was dissolved in 2.5 L of toluene, which was washed with brine using a separating funnel until an aqueous layer became neutral. After the organic layer was dried over magnesium sulfate, the solvent was removed by an evaporator. A crude yield was 133.3 g. A mixed solvent of hexane and ethyl acetate was used for recrystallization to yield 125.3 g (0.396 mol) of a purified product targeted in 79.3% yield.
