A mixture of 5-(4-fluorophenyl)-4-[4-(methylsulfonyl)phenyl]thiophene-2-acetic acid (4.1 g) and 1,1'-carbonyldiimidazole (1.8 g) in tetrahydrofuran (50 ml) was stirred and refluxed for 1 hour. The mixture was added dropwise to an ice-cooled mixture of ammonia water (28%; 5 ml) and tetrahydrofuran (10 ml). The resulting mixture was stirred overnight, diluted with water, and extracted with ethyl acetate. The extract was washed with an aqueous solution of sodium bicarbonate, water, and dilute hydrochloric acid, successively. The organic layer was dried and concentrated, and the residue was recrystallized from a mixture of chloroform, ethyl acetate and ethanol to give crystals of 5-(4-fluorophenyl)-4-[4-(methylsulfonyl)phenyl]thiophene-2-acetamide (3.2 g).
