Iodine-Promoted C–H Bond Amination Reaction for the Synthesis of Fused Tricyclic Heteroarenes

Abstract

Fused heterocyclic scaffolds, such as benzimidazoles or larger ring systems containing a benzimidazole fragment, are frequently encountered in pharmaceutical compounds and other biologically active molecules. While there are many examples of N9- and/or C3-substituted 9H-benzo[4,5]imidazo[2,1-c][1,2,4]triazoles, current examples of the regioselective preparation of N1-substituted 1H-benzo[4,5]imidazo[2,1-c][1,2,4]triazoles are limited to N1-aryl substituted compounds, which also contain a C3-substituent. Here, we report an iodine-promoted C–H bond amination reaction that allows the selective preparation of 1H-benzo[4,5]imidazo[2,1-c][1,2,4]triazoles with a variety of aryl and alkyl N1-substituents. Not only do these cyclization reactions allow access to a new substitution pattern on the benzo[4,5]imidazo[2,1-c][1,2,4]triazole scaffold, but they are also tolerant toward a wide range of functional groups, including esters, amides, alcohols, alkynes, and alkenes. Our findings expand the synthetic toolbox for the preparation of nitrogen containing fused heteroarenes.