A new and efficient palladium on carbon catalyzed one-pot intramolecular nitro reduction/cyclization
reaction has been developed for the preparation of a series of substituted benzimidazoles,
including some novel ring-fused [1,2-a]-tricyclic, [1,2-a]-tetracyclic, and chiral benzimidazoles. The main advantages of this method are the
mild and simple reaction conditions, the easy isolation of the products, and the excellent
yields. The reaction has the potential to be used as a general procedure for the preparation
of 7-aminobenzimidazoles in good yields. A plausible mechanism for the reaction is
proposed.
Key words
heterocycles - reductions - cyclizations - catalysis - palladium - one-pot reactions