ClC1C(N)=C([N+]([O-])=O)C=C([N+]([O-])=O)C=1.C(O)=O.[Cl:18][C:19]1[C:27]2[NH:26][CH:25]=[N:24][C:23]=2[CH:22]=[C:21]([NH:28]C=O)[CH:20]=1.C(N)=O>C(OC(=O)C)(=O)C.Cl.[Pd].CCO>[Cl:18][C:19]1[C:27]2[NH:26][CH:25]=[N:24][C:23]=2[CH:22]=[C:21]([NH2:28])[CH:20]=1Methanolic solution of 6-chloro-2,4-dinitroaniline (2.4 g, 11 mmol) was stirred overnight with 100 mg of 10% Pd/C under H2. Reaction mixture was filtered and concentrated in vacuo to provide an oil which was dissolved in 10 ml of acetic anhydride and 10 ml of formic acid and stirred at reflux for 12 h. The reaction mixture was concentrated in vacuo, yielding a brown oil which was characterized as 4-chloro-6-foramidylbenzimidazole in NMR analysis. The formamide was dissolved in 20 ml of HCl sat'd EtOH and stirred for 3h at 25° C. The reaction mixture was purified in column chromatography (5% MeOH/EtOAc) to provide 0.89 g (5.3 mmol, 48% overall) of the desired product.
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