3-Nitrobenzaldehyde → N-benzyl-1H-1,3-benzodiazol-2-amine

Participants

Reaction Conditions

Reaction Steps

A 100 mL flask was charged with 1.0 g 2-aminobenzimidazole (7.51 mmol, 1.0 equiv), 1.13 g 3-nitrobenzaldehyde (7.51 mmol, 1.0 equiv), and 25 mL toluene. The flask was equipped with a Dean-Stark trap and reflux condenser and placed in a 110° C. bath. The solution was refluxed for 15.5 h, followed by the addition of 3 mL MeOH and 3 mL diisopropylethylamine. After refluxing an additional 29 h, the flask was removed, and the volatiles were removed under reduced pressure at 70° C. The remaining material was diluted with 50 mL MeOH, and cooled to 0° C. followed by the addition of 426 mg (11.27 mmol, 1.5 equiv) NaBH4. After stirring for 3 h, the solution was concentrated under reduced pressure, and the residue was applied directly to a SiO2 column (preflushed with 10% MeOH/CH2Cl2). The column was eluted with 10% MeOH/CH2Cl2 to give the product as an orange solid 320 mg (1.19 mmol). 1H NMR (DMSO-d6, 400 MHz) δ 11.0 (broad s, 1H), 8.25 (s, 1H), 8.11 (d, J=8.2 Hz, 1H), 7.85 (d, J=7.5 Hz, 1H), 7.62 (t, J=8.0 Hz, 1H), 7.34 (m, 1H), 7.13 (t, J=3.7 Hz, 2 H), 6.86 (s, 2H), 4.64 (d, J=5.8 Hz, 2H); MS: ESI(+) m/z 269.2 (M+H+).

Provenance & Evidence