Tert-butyl 4-hydroxymethyl-benzimidazole-1-carboxylate (Intermediate AG, 330 mg, 1.329 mmol) was used as starting material, which was dissolved in ether (5 mL) under argon protection and cooled to 0 °C. Subsequently, phosphorus tribromide (1M solution in dichloromethane, 1.462 mL, 1.462 mmol) was slowly added dropwise, and a thick precipitate was immediately formed in the reaction mixture. The reaction was kept at 0°C for 5 min and then slowly warmed up to room temperature. After 1 hour of reaction, phosphorus tribromide (1M solution in dichloromethane, 0.133 mL, 0.133 mmol) was added again dropwise and diluted with dichloromethane (2 mL). After continuing the reaction for 1 hour at room temperature, the reaction was carefully quenched with saturated sodium bicarbonate solution (20 mL) (note the vigorous release of carbon dioxide) and extracted with ethyl acetate (3 x 15 mL). The organic phases were combined, dried with anhydrous sodium sulfate and concentrated under reduced pressure to give a clarified oil. Purification by silica gel column chromatography using gradient elution (eluent A: heptane/dichloromethane=1/1; eluent B: ethyl acetate/dichloromethane/heptane=1/2/2) from 0% to 100% of eluent B afforded the target product 4-(bromomethyl)-1H-benzo[d]imidazole-1-carboxylic acid tert-butyl ester as a colorless oil (153 mg, 37% yield) . The product was analyzed by HPLC/MS (Method A) with retention time tR = 1.70 min and molecular ion peak [M+H]+ of 310.9-312.9.1H NMR (DMSO-d6) δ ppm: 1.69 (s, 9H), 4.95 (s, 2H), 7.38 (m, 2H), 7.94 (d, 1H), 8.49 (s, 1H).
![tert-Butyl 4-(bromomethyl)-1H-benzo[d]imidazole-1-carboxylate](/CAS/20180702/GIF/132873-77-9.gif)