6-Nitro-2-(trifluoromethyl)-1H-benzimidazole → 5-Amino-2-(trifluoromethyl)benzimidazole

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Reaction Steps

A solution of 4-nitro-1,2-phenylenediamine (3.0 g, 20 mmol) in 15 ml of trifluoroacetic acid was stirred at reflux for 12 h. The reaction mixture was concentrated in vacuo to yield a oily residue, which was dissolved in 100 ml of EtOAc and washed with aqueous NaHCO3. The organic layer was dried over MgSO4 and concentrated in vacuo to provide an oil which was characterized as 2-trifluromethyl-5-nitrobenzimidazole and subjected to the following reaction without further purification. The nitrobenzimidazole and 500 mg of 10% Pd-C were dissolved in 100 ml of MeOH and stirred for 12 h under H2. The reaction mixture was filtered and concentrated in vacuo, yielding 3.2 g (16 mmol, 80%) of the desired product.

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