Synthesis
General procedure for the synthesis of 2-chloro-6-(trifluoromethyl)-1H-benzo[d]imidazol-2(3H)-one from 5-(trifluoromethyl)-1H-benzimidazole:
1. Preparation of Intermediate 1: 5-(trifluoromethyl)-1,3-dihydro-2H-benzimidazol-2-one (Intermediate 2, 3.76 g, 18.6 mmol) was mixed with phosphorus trichloride (56 mL) and reacted at 95 °C for 18 h. The reaction was carried out at 95 °C for 1 hour.
2. Post-treatment: After completion of the reaction, the solvent was removed by distillation under reduced pressure. The residue was washed with toluene (3 x 30 mL) and evaporated to dryness at 50 °C.
3. Purification: The resulting solid was recrystallized with ethyl acetate (EtOAc). The precipitate was collected by filtration, washed with ether (Et2O) and dried to give 2-chloro-6-(trifluoromethyl)-1H-benzimidazole (3.75 g, 17.0 mmol, 91% yield).
4. Characterization: 1H-NMR (400 MHz, DMSO-d6): δ 7.90 (1H, s), 7.72 (1H, d), 7.56 (1H, dd); UPLC-MS: retention time 0.67 min, m/z 221 [M + H]+.
References
[1] Patent: WO2008/129007, 2008, A1. Location in patent: Page/Page column 28-29
[2] Journal of Medicinal Chemistry, 2016, vol. 59, # 15, p. 7188 - 7211
[3] European Journal of Medicinal Chemistry, 2008, vol. 43, # 7, p. 1390 - 1402
[4] Patent: US2003/36652, 2003, A1
[5] Bioorganic and Medicinal Chemistry Letters, 2008, vol. 18, # 18, p. 5010 - 5014
