Radical cyclisation onto imidazoles and benzimidazoles

Abstract

New synthetic methodology has been developed for the synthesis of [1,2-a]fused imidazoles and benzimidazoles using intramolecular homolytic aromatic substitution. In the intramolecular substitution, N-( ω-alkyl) radicals are generated using Bu 3SnH from N-( ω-phenylselanyl)alkyl side chains. Phenylselanyl groups are used as radical leaving groups to avoid problems in the N-alkylation of imidazoles and benzimidazoles. Arylsulfones for imidazoles, and phenylsulfides for benzimidazoles, are used as the leaving groups in the homolytic substitutions.