反应详情

温度

50 °C

As described in General Procedure III, 2-bromo-5,6-dichlorobenzimidazole (1.0 g, 3.8 mmol), N,O-bis(trimethylsilyl) acetamide (Aldrich, 1.0 ml, 4.1 mmol), and 1,2-dichloroethane (Aldrich Sure Seal, 25 ml) were combined and refluxed under nitrogen for 0.5 h. The solution was cooled to 50° C. and trimethylsilyl trifluoromethanesulfonate (Aldrich, 0.8 ml, 4.1 mmol) was added. Immediately, 1.4 g (4.4 mmol) solid 1,2,3,4-tetra-O-acetyl-beta-L-xylopyranose was added. The solution was stirred under nitrogen at reflux for 0.25 h, then poured into 7% aqueous sodium bicarbonate and extracted with dichloromethane. The organic layers were dried with magnesium sulfate (anhyd), filtered, and evaporated. The crude residue was crystallized from chloroform and hexane to give 1.11 g (56% yield) of 2-bromo-5,6-dichloro-1-(2,3,4-tri-O-acetyl-beta-L-xylopyranosyl)-1H-benzimidazole. 1H NMR (CDCl3) δ7.80 (s,1H), 7.76 (s, 1H), 5.68-5.64 (m, 1H), 5.55-5.51 (m, 1H), 5.32-5.25 (m, 1H), 4.48-4.43 (dd, 1H), 3.69-3.61 (t, 1H), 2.15 (s, 3H), 2.10 (s, 3H), 1.90 (s, 3H).

1. temperaturerefluxed under nitrogen for 0.5 h
2. temperatureat reflux for 0.25 h
3. extractionextracted with dichloromethane
4. dry with materialThe organic layers were dried with magnesium sulfate (anhyd)
5. filtrationfiltered
6. customevaporated
7. customThe crude residue was crystallized from chloroform and hexane