Carbene Insertion and Furyl Migration Cascade Toward Benzofurans.

Divergent access to complex molecular skeletons from the same set of readily available raw materials has been a primary goal of chemical synthesis, owing to their widespread application in drug research. In this study, a copper-catalyzed insertion reaction of a disubstituted carbene into an unsaturated imine has been developed to form β,γ-unsaturated carbonyl compounds with an α-quaternary carbon center, which subsequently undergo an unprecedented forward 1,2-/backward 1,4-furyl migration cascade, ultimately affording a highly substituted benzofuran. A formal 1,3-furan migration is involved in this multistep cascade sequence, broadening the substrate scope under mild reaction conditions.