Formic Acid → 5-bromo-4-methoxy-1H-benzimidazole

Participants

Reaction Conditions

Reaction Steps

A 1 L four-necked round bottom flask fitted with a magnetic stirrer was dried and cooled under a stream of nitrogen then charged with 4-bromo-3-methoxy-benzene-1,2-diamine (61 g, 0.28 mol, 1.0 equiv.) in formic acid (200 mL). The reaction mixture was heated at 100° C. for 2 h, cooled and quenched with ice water (1 L). The reaction mixture was basified with 10% NaOH solution and extracted with ethyl acetate (2×1000 mL). The separated organic layers were combined, washed with brine solution (750 mL), dried (Na2SO4), filtered and concentrated in vacuo. The crude material was purified by SiO2 chromatography eluting with an EtOAc/hexane gradient (30-50% EtOAc) to afford 6-bromo-7-methoxy-1H-benzoimidazole (36 g, crude) as a brown solid. 1H NMR (300 MHz, DMSO-d6): δ 4.26 (br, 3H), 7.16 (s, 1H), 7.29-7.32 (d, 1H), 8.19 (s, 1H), 12.67 (br, 1H).

Provenance & Evidence