Under a nitrogen atmosphere, oxalyl chloride (3.2 g, 0.025 mole) was added dropwise (slowly) to a stirred and chilled (5°-10° C.) solution of 2-(4-bromophenyl)-3H-imidazo[4,5-b]pyridine-3-acetic acid (8.0 g, 0.024 mole) in anhydrous dimethylformamide (50 ml). The reaction mixture was heated at 55°-60° C. for 4 hrs, cooled to room temperature, and added dropwise to a stirred and chilled (10°-15° C.) solution of 2-chloroaniline (3.2 g, 0.25 mole) and triethylamine (2.5 g, 0.025 mole) in anhydrous dimethylformamide (100 ml). The reaction mixture was stirred at room temperature overnight, filtered, and poured into water (350 ml). The mixture was allowed to precipitate and filtered. The filter cake was twice suspended in water (250 ml) and filtered. The filter cake was air dried and twice recrystallized from tetrahydrofuran to give 4.22 g (40%) of a white solid, mp. 230.5°-232° C.
