p-Toluenesulfonic acid → 6-Bromo-1-methyl-1H-benzimidazole

Participants

Reaction Conditions

Reaction Steps

To a suspension of (5-bromo-2-nitro-phenyl)-methyl-amine (1.2 g, 5.19 mmol) in ethanol (25 mL) was added tin(II) chloride (1.97 g, 10.39 mmol). The reaction mixture was stirred at 80° C. for 4 h, then it was concentrated in vacuo. To the residue was added toluene (12 mL), trimethyl orthoformate (0.625 mL, 5.71 mmol), and para-toluenesulfonic acid (49 mg, 0.26 mmol). The reaction mixture was stirred at 110° C. for 15 h, then it was concentrated in vacuo and the residue was adsorbed on silica gel. Purification by flash chromatography on silica gel using a gradient of 0-8% methanol/dichloromethane afforded 482 mg of 6-bromo-1-methyl-1H-benzoimidazole as a dark orange solid (44% yield): 1H NMR (DMSO-d6) δ 3.83 (s, 3H), 7.33 (dd, 1H), 7.59 (d, 1H), 7.86 (d, 1H), 8.21 (s, 1H); MS (m/z) 211, 213 [M+H+]+.

Provenance & Evidence