Intramolecular Aromatic Substitutions of the Imidazol-5-yl Radical to form Tricyclic Imidazo[5,1-a] Heterocycles

Five, six and seven-membered intramolecular aromatic substitutions of imidazol-5-yl radicals are reported using both metal hydride/AIBN and photochemical conditions to give imidazo[5,1-a]isoindole, imidazo[5,1-a]isoquinoline and imidazo[5,1-a]benzazepine. Procedures for the synthesis of 5-bromo-(N-ω- phenylalkyl)imidazole radical precursors using 1,3-dibromo-5,5-dimethylhydantoin (dibromantin) and Nbromosuccinimide (NBS) are given.