Trifluoroacetic acid → Benzimidazole, 4-bromo-6-nitro-2-(trifluoromethyl)-

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Reaction Conditions

Reaction Steps

In a 250 mL round-bottom flask a mixture of 3-bromo-5-nitrobenzene-1,2-diamine (10 g, 43.1 mmol) and TFA (23.24 mL, 302 mmol) was heated to 85° C. for 17 hours. The mixture was allowed to cool to RT, and then was concentrated in vacuo to remove the excess TFA. The residue was partitioned between water (100 mL) and ether (100 mL; not soluble in dichloromethane). The phases were separated, and the organic layer was dried over Na2SO4, then filtered and concentrated in vacuo to provide 4-bromo-6-nitro-2-(trifluoromethyl)-1H-benzo[d]imidazole (7.1 g, 22.90 mmol, 53.1% yield) as a brown solid. LCMS and NMR are consistent with structure (NMR contains a trace of ether). MS (ES+) m/e: 308.9, 310.1 [M+H]+; 1H NMR (400 MHz, DMSO-d6) δ ppm 15.09 (br. s., 1H) 8.49-8.66 (m, 1H) 8.36-8.48 (m, 1H)

Provenance & Evidence