[N+](C1C=CC(N)=C(N)C=1)([O-])=O.[CH:12]([C:15]1[NH:16][C:17]2[CH:23]=[C:22]([N+:24]([O-])=O)[CH:21]=[CH:20][C:18]=2[N:19]=1)([CH3:14])[CH3:13].[N+](C1NC2C=CC=CC=2N=1)([O-])=O>C(O)(=O)C(C)C.CCOC(C)=O.[Pd]>[CH:12]([C:15]1[NH:16][C:17]2[CH:23]=[C:22]([NH2:24])[CH:21]=[CH:20][C:18]=2[N:19]=1)([CH3:14])[CH3:13]
A solution of 4-nitro-1,2-phenylenediamine (0.9 g, 5.9 mmol) in 5 ml of isobutyric acid was stirred at reflux for 12 h. The reaction mixture was concentrated in vacuo to yield a dark brown residue, which was dissolved in 100 ml of EtOAc and washed with aqueous NaHCO3. Organic layer was dried over MgSO4 and concentrated in vacuo, yielding an oil which was characterized as 2-isopropyl-5-nitrobenzimidazole and subjected to a following reaction without further purification. The nitrobenzimidazole and 50 mg of 10% Pd—C were dissolved in 100 ml of MeOR and stirred for 12 h under H2. The reaction mixture was filtered and concentrated in vacuo, yielding 0.95 g (5.4 mmol, 92%) of the desired product.
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