A mixture of 1-fluoro-2-nitro-4-trifluoromethylbenzene 523 mg, ethyl 5-[(E)-2-ethoxycarbonylvinyl]-1H-pyrrole-2-carboxyate 593 mg, potassium carbonate 864 mg and dimethylsulfoxide 10 mL was heated at 100° C. for 3.5 hours. After cooling off the reaction liquid, 100 mL of diethyl ether was added, followed by filtration. To the filtrate 100 mL of water was added to separate the organic layer. The aqueous layer was extracted twice with 50 mL of diethyl ether, and the extract was combined with the organic layer, followed by washing three times with 20 mL of water and once with 20 mL of saturated brine by the order stated. After drying the same over magnesium sulfate, the solvent was distilled off under reduced pressure, leaving 965 mg of a brown, viscous substance. This was dissolved in a liquid mixture of 12 mL of acetic acid and 5 mL of water, and to the solution 1.31 g of sodium hyposulfite was added, followed by heating under reflux for 30 minutes. After cooling off the reaction liquid, 50 mL of water was added and the precipitated crystals were recovered by filtration. The crystals were washed with water and diethyl ether, and dried under heating to provide 600 mg of the title compound.
