Radical cyclisation onto imidazoles and benzimidazoles

New synthetic methodology has been developed for the synthesis of [1,2-a]Fu sed imidazoles and benzimidazoles using intramolecular homolytic aromatic s ubstitution. In the intramolecular substitution, N-(omega-alkyl) radicals a re generated using Bu3SnH from N-(omega-phenylselanyl)aIkyl side chains. Ph enylselanyl groups are used as radical leaving groups to avoid problems in the N-alkylation of imidazoles and benzimidazoles. Arylsulfones for imidazo les, and phenylsulfides for benzimidazoles, are used as the leaving groups in the homolytic substitutions. (C) 1999 Elsevier Science Ltd. All rights r eserved.