Synthesis
The general procedure for the synthesis of 5,6-difluorobenzimidazole from 4,5-difluorophthalimide and formic acid was as follows: 4,5-difluorophthalimide (1.5 g, 10 mmol) was dissolved in formic acid (20 mL) and the reaction was heated for 12 hr at 80 °C. Upon completion of the reaction, the mixture was cooled to 25 °C and subsequently concentrated under reduced pressure to remove the solvent. The resulting residue was purified by recrystallization from a solvent mixture of petroleum ether and ethyl acetate (15:1, v/v) to give the final yellow solid 5,6-difluoro-1H-benzo[d]imidazole (1.4 g, 88% yield). Mass spectrum (ESI) m/z: 155 [M + H]+.
References
[1] Patent: WO2015/100609, 2015, A1. Location in patent: Page/Page column 45
[2] Patent: EP2766359, 2016, B1. Location in patent: Paragraph 0756
[3] New Journal of Chemistry, 2006, vol. 30, # 5, p. 803 - 809
[4] Bioorganic and Medicinal Chemistry Letters, 2006, vol. 16, # 14, p. 3674 - 3678
[5] ChemCatChem, 2018, vol. 10, # 19, p. 4338 - 4345
