Copper-Catalyzed Alkynylation/Cyclization/Isomerization Cascade for Synthesis of 1,2-Dihydrobenzofuro[3,2‑b]pyridines and Benzofuro[3,2‑b]pyridines

An efficient copper-catalyzed cascade alkynylation/cyclization/isomerization reaction of aurone-derived azadienes with terminal alkynes has been developed, giving a series of 1,2-dihydrobenzofuro­[3,2-b]­pyridines with excellent yields. The obtained 1,2-dihydrobenzofuro­[3,2-b]­pyridines can be conveniently transformed into the corresponding benzofuro­[3,2-b]­pyridines under basic conditions. Additionally, benzofuro­[3,2-b]­pyridines can also be prepared from azadienes and terminal alkynes in a one-pot reaction. The synthetic utility was demonstrated by the synthesis of three bioactive molecules with potent topoisomerase inhibition in high yields. This strategy provides a facile approach to 1,2-dihydrobenzofuro­[3,2-b]­pyridines and benzofuro­[3,2-b]­pyridines.