a) 3-Fluorobenzene-1,2-diamine (0.600 g, 4.76 mmol) was dissolved in tetrahydrofuran (THF, 14.82 mL), and 1,1'-carbonyldiimidazole (0.848 g, 5.23 mmol) was added slowly at room temperature. The reaction mixture was stirred overnight at room temperature and then warmed up to 50 °C to continue the reaction for 24 hours. Upon completion of the reaction, the mixture was cooled to room temperature, a methanol solution of ammonia (1.5 mL) was added and stirring was continued for 30 minutes. Subsequently, the reaction mixture was diluted with water (40 mL), the resulting brown solid was collected by filtration, washed with water and dried under vacuum to afford 4-fluoro-1H-benzo[d]imidazol-2(3H)-one (0.700 g, 97% yield). The product could be used in subsequent steps without further purification.1H NMR (400 MHz, DMSO-d6) δ 6.81 (2H, ddd), 6.88-6.95 (1H, m), 10.82 (1H, s), 11.08 (1H, s); Mass Spectrum (ES-) m/z: 151.19 [M-H]-.
