反应详情

2-(4-chloro-phenyl)-7-hydroxy-1H-benzoimidazole-4-carboxylic acid (200 mg, 0.69 mmol) obtained in step 3 was dissolved in 5 ml of methanol, H2SO4 (0.18 ml, 3.45 mmol) was added dropwise thereto and refluxed for 15 hours. The resulting solution was cooled to room temperature, concentrated under a reduced pressure to remove methanol, and the residue was neutralized with 1M NaHCO3. Then, the neutralized residue was extracted with ethyl acetate and concentrated under a reduced pressure to obtain a residue which was purified by silica gel column chromatography (eluent—MeOH/CDCl3=5/95, Merck, Silicagel 60) to obtain the title compound (166 mg, 0.55 mmol) in a yield of 80%.

1. temperaturerefluxed for 15 hours
2. concentrationconcentrated under a reduced pressure
3. customto remove methanol
4. extractionThen, the neutralized residue was extracted with ethyl acetate
5. concentrationconcentrated under a reduced pressure
6. customto obtain a residue which
7. customwas purified by silica gel column chromatography (eluent—MeOH/CDCl3=5/95, Merck, Silicagel 60)