Solvent/Base-CocontrolledRegiodivergent Synthesisof 5-Arylnaphtho[1′,2′:4,5]imidazo[1,2- a ]pyridines and 3-Substituted 2-Arylimidazo[1,2- a ]pyridines from 2-Arylimidazo[1,2- a ]pyridines and α-Cl Ketones via a Rh(III)-CatalyzedC–H Activation Strategy

A solvent/base-cocontrolled regiodivergent synthesis via a rhodium(III)-catalyzed C–H annulation and functionalization of 2-arylimidazo[1,2-a]pyridines with α-Cl ketones is disclosed. When using polar solvent 1,1,1,3,3,3-hexafluoro-2-propane (HFIP) with K2CO3, the C–H annulation selectively delivered 5-arylnaphtho[1′,2′:4,5]imidazo[1,2-a]pyridine. In contrast, a system with nonpolar solvent p-xylene with NaOAc predominately afforded 3-substituted 2-arylimidazo[1,2-a]pyridines via C3–H functionalization. The developed reaction methodology features a wide substrate scope and ideal functional group tolerance. It is also operationally simple and scalable. Furthermore, the photophysical properties of annulation products and further derivatizations of C3–H functional products demonstrate that this method has potential applications in photoelectric materials and organic synthesis. Through a combined computational and experimental mechanistic study, we delineate the distinct roles of the solvent and base.