General procedure for the synthesis of 4-(5-chloro-1H-benzo[d]imidazol-2-yl)aniline from p-aminobenzoic acid and 4-chloro-1,2-benzenediamine: Eaton's reagent (10% v/v (w/v)) was added drop-wise to a mixture of 4-chloro-1,2-benzenediamine (1 equiv) and p-aminobenzoic acid (1 equiv). Subsequently, the reaction mixture was heated at 130 °C for 5-6 h. The reaction process was monitored by TLC and LCMS. After completion of the reaction, the mixture was cooled to room temperature and neutralized with 10% sodium hydroxide solution to pH 6-7. The precipitate formed was collected by filtration and washed repeatedly with water and subsequently dried. Finally, the resulting solid was purified by ethanol recrystallization to afford the target product 4-(5-chloro-1H-benzo[d]imidazol-2-yl)aniline in good yield.
