Synthesis of Unsymmetrical 1,1’‐Bibenzimidazoles via an N‐Amination Reaction Forming the Key N‐N Bond

Abstract

The novel synthesis of unsymmetrical 1,1’‐bibenzimidazoles is described. The key N−N bond was introduced on 1H‐benzimidazole or 1H‐benzimidazole‐2‐sulfonic acid by N‐amination with hydroxylamine‐O‐sulfonic acid (HASA). The precursors, 1‐[(2‐nitrophenyl)amino]‐1H‐benzimidazoles, were prepared by nucleophilic aromatic substitution of 1‐fluoro‐2‐nitrobenzene with 1H‐benzimidazole‐1‐amines. The synthesis was demonstrated on 11 novel 1,1’‐bibenzimidazoles, which were prepared in the final step by one‐pot reduction/cyclization with DMF or DMA acetals under mild acidic conditions in good overall yields.