One-Pot Cu-Catalyzed C-N Coupling Approach to Pyrido[1,2-a]benzimidazoles

Significance

Reported is the synthesis of pyridobenzimidazoles 3 via a copper-catalyzed one-pot double C-N coupling between 2-haloanilines 1 and 2-halopyridines 2. In general, the iodides gave superior yields of products than the bromides. Both EDGs and EWGs are well tolerated on both coupling partners. Steric effects have a major influence on the reaction since the introduction of a methyl group ortho to the aniline or pyridine nitrogen leads to a significant drop in the yield of 3 (25-39%). One example of a benzimidazo[2,1-b]benzothiazole (4), an unusual heterocyclic system, was prepared in high yield from 2-iodobenzothia­zole.