反应详情

In a round bottomed flask are added K2CO3 (9.34 g, 67.7 mmol), 2-chlorobenzimidazole (5.16 g, 33.8 mmol) and tert-butyl bromoacetate (6.6 g, 5 ml, 33.8 mmol) in acetone (100 ml). The resulting suspension is refluxed for 1 h. The crude mixture is filtered through a filter paper and water (100 ml) is added. The resulting aqueous phase is extracted three times with Et2O. The combined organic phases are washed with brine and dried over MgSO4. The solvent is evaporated under reduced pressure yielding the title compound (7.98 g) in 88% as a white powder: tR=2.20 min (LC-2), ESI-MS (pos.): m/z 267.2 [M+H]+; 1H-NMR (CDCl3): δ (ppm) 1.48 (s, 9H, tBu), 4.92 (s, 2H, CH2CO2), 7.24-7.40 (m, 3Harom), 7.76-7.80 (m, 1Harom). Intermediate 2-IIa and 2-IIb tert-Butyl (2-chloro-5-nitro-benzoimidazol-1-yl)-acetate and its 6-nitro regioisomer are prepared according to the same procedure (yield 93%): tR=6.68 min (LC-1), ESI-MS (pos.): m/z 312.08 [M+H]+, 310.28 [M−H]+; 1H-NMR (CDCl3): δ (ppm) 1.50 (s, 9H, tBu), 1.52 (s, 9H, tBu), 5.04 and 5.06 (s, 2H, CH2CO2), 7.38 (d, 1Harom), 7.86 (d, 1 Harom), 8.32-8.40 (m, 3Harom), 8.96 (m, 1Harom).

1. temperatureThe resulting suspension is refluxed for 1 h
2. filtrationThe crude mixture is filtered through a filter paper and water (100 ml)
3. additionis added
4. extractionThe resulting aqueous phase is extracted three times with Et2O
5. washThe combined organic phases are washed with brine
6. dry with materialdried over MgSO4
7. customThe solvent is evaporated under reduced pressure