4-Chloro-5-nitro-1,2-benzenediamine (8.34 g, 44.4 mmol) was dissolved in tetrahydrofuran (625 mL) at 0 °C, followed by the addition of N,N'-carbonyl diimidazole (8.65 g, 53.3 mmol). The reaction mixture was slowly warmed to 23 °C and stirred continuously at this temperature for 20 hours. Upon completion of the reaction, the mixture was concentrated to about 300 mL, and then 1 M aqueous hydrochloric acid (500 mL) and water (total volume adjusted to 2 L) were added. The resulting suspension was cooled at 0 °C for 2 h. The precipitate was collected by filtration and dried on a filter. Finally, the precipitate was ground with cold ethyl acetate (20 mL) and rinsed with ethyl acetate (2 x 5 mL) to afford 5-chloro-6-nitro-1H-benzo[d]imidazol-2(3H)-one (7.26 g, 76% yield). Mass spectrometry (ESI/CI) analysis: calculated value C7H4ClN3O3, 213.0; measured value m/z, 214.0 [M + H]+.
![5-Chloro-6-nitro-1H-benzo[d]imidazol-2(3H)-one](/CAS/GIF/60713-78-2.gif)