反应详情

4-Hydroxymethyl-2-(2-nitrophenyl)-benzimidazole 3 (2.69 g, 10 mmol) was dissolved in a mixture of CH3CN/CH2Cl2 (500 mL, v/v=4:1), and then manganese dioxide (10 g, 120 mmol) was added. The solution was stirred at room temperature and monitored by TLC. Once the reaction was complete, the reaction mixture was filtered through a pad of celite. The filtrate was washed with NaHCO3, and the water phase was extracted with CH2Cl2. The combined organic layer was washed with brine and dried over Na2SO4. Concentration by rotary evaporation and subsequent column chromatography on silica gel using hexane/ethyl acetate (1:1) as the eluent afforded 2-(2-nitrophenyl)-benzimidazole-4-carboxaldehyde (2.2 g, 82%) as a light-yellow solid. Rf=0.38 (hexane/ethyl acetate=1:1); 1H NMR (200 MHz, CDCl3) δ 7.47 (t, J=7.6 Hz, 1H), 7.63-7.82 (m, 3H), 7.94 (d, J,=7.5 Hz, J2=1.5 Hz, 1H), 8.05 (d, J1=7.7 Hz, J2=1.6 Hz, 1H), 8.10 (d, J=8.1 Hz, 1H), 10.11 (s, 1H), 11.21 (broad s, 1H); HRMS: Calcd. for C14H9N3O3 267.0644, found 267.0648.

1. filtrationthe reaction mixture was filtered through a pad of celite
2. washThe filtrate was washed with NaHCO3
3. extractionthe water phase was extracted with CH2Cl2
4. washThe combined organic layer was washed with brine
5. dry with materialdried over Na2SO4
6. concentrationConcentration
7. customby rotary evaporation and subsequent column chromatography on silica gel