The general procedure for the synthesis of 5-iodobenzimidazole from formic acid and 4-iodo-2-nitroaniline is as follows: intermediate Example 12.Synthesis of 5-iodo-1H-benzo[d]imidazole from 5-((trimethylsilyl)ethynyl)-1H-benzo[d]imidazole). 4-Methyl-2-nitroaniline (1 g, 3.7 mmol) was dissolved in formic acid (10 ml), iron powder (2.1 g, 37 mmol) was added, and the reaction mixture was heated and refluxed for 12 h at 90 °C. After completion of the reaction, formic acid was removed by distillation. The crude product was dissolved in ethyl acetate, and the organic layer was washed sequentially with water and saturated brine, and then dried with anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure to afford the target product 5-iodo-1H-benzo[d]imidazole in 68% yield (0.85 g). Product characterization by LC-MS (ES): calculated mass: 243.95; observed mass: 244.8 [M + H]+ (retention time: 0.173 min).
