The synthesis of fluorescent benzofuro[2,3-c]pyridines via palladium-catalyzed heteroaromatic C-H addition and sequential tandem cyclization

A Pd-catalyzed tandem reaction of 2-(cyanomethoxy)chalcones with thiophenes through direct C-H addition and sequential intramolecular conjugate addition/cyclization/aromatization provides a diverse range of 3-aryl-1-(thiophen-2-yl)benzofuro[2,3-c]pyridines. A representative product was assessed as a ratiometric fluorescent probe for Hg2+. This chemistry could also be applied to the synthesis of other fused ring systems.