Indium(III)-catalyzed solvent-free multicomponent [2 + 2 + 1 + 1]-annulation to polycyclic functionalized fused pyridines as potential optical chemosensors

An In(III)-catalyzed solvent-free one-pot [2 + 2 + 1 + 1]-annulation for the construction of highly fused polycyclic functionalized pyridines as a novel green approach is described. This unique reaction yields a wide range of polycyclic products bearing dihydrobenzoquinoline, azafluorene, azafluorenone, pyridocoumarin, and benzocycloheptapyridine frameworks. The synthesized compounds exhibit excellent photophysical properties as new fluorophores and metal ion chemosensors.