The reaction was carried out with 4-fluoro-1,2-benzenediamine (10 g, 79.3 mmol) and carbon disulfide (70 ml, 1164 mmol) in methanol (100 ml) with stirring at room temperature for 86 hours and 50 minutes. After completion of the reaction, the reaction mixture was concentrated and the residue was suspended with hexane. The resulting precipitate was collected by filtration and washed with hexane to afford 5-fluoro-1H-benzo[d]imidazole-2(3H)-thione (13.1 g, yield: 98.2%), the product was a brown solid.1H NMR (400 MHz, DMSO-d6) δ ppm: 6.90-6.99 (2H, m), 7.06-7.13 (1H, m). 12.58 (1H, s), 12.61 (1H, s).
