I₂/CuI-mediated C-H Functionalization For The Construction Imidazo [1,2-a] Pyridine And Indole Skeletons

Imidazo[1,2-a]pyridines and indoles are two classes of important heterocyclic compounds,and their skeletons are widely distributed in a broad variety of natural products and biologically active synthetic molecules.Therefore,considerable efforts have been made for the synthesis of their derivatives.In recent years,significant progress was made in transition metal-catalyzed and/or hypervalent iodine-mediated C-H functionaliztion reactions,with many elegant synthetic methods developed.On the other hand,molecular iodine,as an inexpensive and less-toxic oxidant,has been extensively used in organic synthesis.In this dissertation,employing iodine as the sole oxidant,we have established a copper?I?iodide?CuI?-catalyzed intramolecular sp² C-H functionalization reaction for the construction of imidazo[1,2-a]pyridine and indole frameworks.The present synthetic approach is ligand-free,operationally simple,and environmentally friendly,and the substrate scope is broad.Under the optimal reaction conditions thirty imidazo[1,2-a]pyridines and thirteen indoles were successfully synthesized in 43-95% yields from readily accessible N-aryl enamine substrates via I₂/Cu I-mediated oxidative C-N and C-C bond formation,respectively.