Molecular Iodine-Promoted Transimination for the Synthesis of 6-Phenylpyrido[2′,1′:2,3]imidazo[4,5-c]quinoline and 6-(Pyridin-2-yl)pyrido[2′,1′:2,3]imidazo[4,5-c]quinolines

Abstract

An unprecedented, efficient I2-mediated approach for the synthesis of 6-phenylpyrido[2′,1′:2,3]imidazo[4,5-c]quinoline heterocyclic skeletons has been achieved from the reaction of benzylamines and 2-(imidazo[1,2-a]pyridin-2-yl)anilines. This one-pot protocol proceeds through an oxidation/transimination/cyclization/aromatization reaction sequence under metal-free conditions to result in the formation of N−C and C−C bonds. A variety of benzylamines, including pyridin-2-ylmethanamine, were successfully employed under the optimized conditions as imine precursors in this irreversible transimination reaction with 2-(imidazo[1,2-a]pyridin-2-yl)anilines to give the corresponding imines. The subsequent cyclization step successfully generated the the corresponding 6-phenylpyrido[2′,1′:2,3]imidazo[4,5-c]quinolines.