Cyclic Guanidines; IV.¹Intramolecular Nucleophilic Aromatic Substitution of Hydrogen in (3-Nitrophenyl)guanidines

Abstract

Cyclization of substituted (3-nitrophenyl)guanidines is achieved in basic medium by nucleophilic displacement of hydrogen. The reaction offers a new route to benzimidazoles as well as to tricyclic imidazo-, pyrimido- and diazepino-benzimidazoles with uncommon substitution patterns. The mechanism of the redox process is investigated and the regioselectivity is discussed in terms of substrate structure and reaction conditions. An outline is given on the scope of the ring closure.