1,2-Dibromoethane → 1-(4-nitrophenyl)-2,3-dihydro-1H-imidazo[1,2-a]benzimidazole

A mixture of N-(4-nitrophenyl)-1H-benzimidazol-2-amine (1.00 g) in DMF (20 ml) at ambient temperature was treated with a 60% dispersion of sodium hydride in mineral oil (393 mg) then stirred for 5 min. The mixture was treated with a solution of 1,2-dibromoethane (738 mg) in DMF (1 ml) then stirred at ambient temperature for 1 h. After this time, the reaction mixture was quenched with saturated aqueous ammonium chloride (10 mL), diluted with water (80 mL) and extracted with ethyl acetate (2×100 mL). The combined organic layers were washed with 5% aqueous lithium chloride (2×50 mL) then brine (50 mL), dried over sodium sulfate, and filtered and the filtrate was concentrated under reduced pressure. The residue obtained was purified by chromatography (silica, heptane to 1:1 ethyl acetate/heptane) to afford 1-(4-nitrophenyl)-2,3-dihydro-1H-imidazo[1,2-a]benzimidazole (63 mg) as a yellow solid.